Compositional studies of primitive asteroids

NASA Technical Reports Server (NTRS)

Vilas, Faith

1991-01-01

Primitive asteroids in the solar system (C, P, D class and associated subclasses) are believed to have undergone less thermal processing compared with the differential (S class) asteroids. Telescopic spectra of C class asteroids show effects of aqueous alteration products produced when heating of the asteroids was sufficient to melt surface water, but not strong enough to produce differentiation. Spectrum analysis of P and D class asteroids suggests that aqueous alteration terminated in the outer belt and did not operate at the distance of Jupiter's orbit.

The Violent Collisional History of Asteroid 4 Vesta

NASA Astrophysics Data System (ADS)

Marchi, S.; McSween, H. Y.; O'Brien, D. P.; Schenk, P.; De Sanctis, M. C.; Gaskell, R.; Jaumann, R.; Mottola, S.; Preusker, F.; Raymond, C. A.; Roatsch, T.; Russell, C. T.

2012-05-01

Vesta is a large differentiated rocky body in the main asteroid belt that accreted within the first few million years after the formation of the earliest solar system solids. The Dawn spacecraft extensively imaged Vesta’s surface, revealing a collision-dominated history. Results show that Vesta’s cratering record has a strong north-south dichotomy. Vesta’s northern heavily cratered terrains retain much of their earliest history. The southern hemisphere was reset, however, by two major collisions in more recent times. We estimate that the youngest of these impact structures, about 500 kilometers across, formed about 1 billion years ago, in agreement with estimates of Vesta asteroid family age based on dynamical and collisional constraints, supporting the notion that the Vesta asteroid family was formed during this event.

Spectroscopy of five V-type asteroids in the middle and outer main belt

NASA Astrophysics Data System (ADS)

Migliorini, Alessandra; De Sanctis, M. C.; Lazzaro, D.; Ammannito, E.

2018-03-01

The origin of basaltic asteroids found in the middle and outer main belt is an open question. These asteroids are not dynamically linked to the Vesta collisional family and can be the remnants of other large differentiated asteroids present in the early phases of the main belt but destroyed long ago. Spectroscopic investigation of some V-type asteroids in the middle-outer belt, classified as such by their SLOAN photometric colours (Ivezić et al.) and WISE albedos (Masiero et al.), has revealed that their spectra are more similar to other taxonomic classes, like -Q, R, S, or A (Jasmim et al. and Oszkiewicz et al.). Here, we report about the observation, in the near-infrared spectral range, of five V-type asteroids located beyond 2.5 au. These observations allowed us to infer their taxonomic classification. Two asteroids, (21238) Panarea (observed in a previous campaign but here included for comparison) and (105041) 2000 KO41, confirm their basaltic nature. For asteroids (10800) 1992 OM8 and (15898) Kharasterteam a taxonomic classification is more uncertain, being either Q- or S-type. Asteroid (14390) 1990 QP10 classification is difficult to ascribe to the known taxonomic classes, maybe due to the low-quality spectrum. Further observations are desirable for this asteroid.

Samples from Differentiated Asteroids; Regolithic Achondrites

NASA Technical Reports Server (NTRS)

Herrin J. S.; Ross, A. J.; Cartwright, J. A.; Ross, D. K.; Zolensky, Michael E.; Jenniskens, P.

2011-01-01

Differentiated and partially differentiated asteroids preserve a glimpse of planet formation frozen in time from the early solar system and thus are attractive targets for future exploration. Samples of such asteroids arrive to Earth in the form of achondrite meteorites. Many achondrites, particularly those thought to be most representative of asteroidal regolith, contain a diverse assortment of materials both indigenous and exogenous to the original igneous parent body intermixed at microscopic scales. Remote sensing spacecraft and landers would have difficulty deciphering individual components at these spatial scales, potentially leading to confusing results. Sample return would thus be much more informative than a robotic probe. In this and a companion abstract [1] we consider two regolithic achondrite types, howardites and (polymict) ureilites, in order to evaluate what materials might occur in samples returned from surfaces of differentiated asteroids and what sampling strategies might be prudent.

Asteroid differentiation - Pyroclastic volcanism to magma oceans

NASA Technical Reports Server (NTRS)

Taylor, G. J.; Keil, Klaus; Mccoy, Timothy; Haack, Henning; Scott, Edward R. D.

1993-01-01

A summary is presented of theoretical and speculative research on the physics of igneous processes involved in asteroid differentiation. Partial melting processes, melt migration, and their products are discussed and explosive volcanism is described. Evidence for the existence of asteroidal magma oceans is considered and processes which may have occurred in these oceans are examined. Synthesis and inferences of asteroid heat sources are discussed under the assumption that asteroids are heated mainly by internal processes and that the role of impact heating is small. Inferences of these results for earth-forming planetesimals are suggested.

Variation in Surficial Hydrated Minerals on Large Low-Albedo Asteroids

NASA Astrophysics Data System (ADS)

Rivkin, Andrew S.; Emery, Joshua P.; Howell, Ellen S.

2017-10-01

Observations of asteroids in the 3-µm spectral region, where absorptions diagnostic for hydrated minerals are found, show low-albedo asteroid spectra can be classified into at least 3 groups (Takir et al. 2013, Rivkin et al. 2015). While definitions of these groups vary between authors, they hold in common a group with spectra like what we see for CM/CI meteorites, one group with spectra like that of Ceres, and a group with spectra that have been interpreted as ice frost. The relationship between these groups is not yet clear. One possibility is that the spectrum reflects (no pun intended) the formation location for the asteroids and that a given object is undifferentiated and homogeneous in the composition of its hydrated minerals. However, models of the thermal and chemical evolution of large, low-albedo asteroids suggests that differentiation may be more common than we had thought, and impacts could exhume once-deep layers or expose complicated mixes of salts and silicates (for instance, Castillo-Rogez et al. LPSC 2017 model of Ceres). In this case, we might expect variation in the 3-µm spectral region to be seen on the surfaces of some objects as they rotate. We will present evidence for such variation in the spectrum of two large asteroids, 704 Interamnia (306 km diameter) and 324 Bamberga (220 km diameter). In the first case, Interamnia’s spectrum seems to have a combination of Ceres- and CM/CI-like features and has aspects where one or another component is dominant, while Bamberga’s spectrum is not easily placed in previously-defined groups.

Differentiation of the asteroid Ceres as revealed by its shape.

PubMed

Thomas, P C; Parker, J Wm; McFadden, L A; Russell, C T; Stern, S A; Sykes, M V; Young, E F

2005-09-08

The accretion of bodies in the asteroid belt was halted nearly 4.6 billion years ago by the gravitational influence of the newly formed giant planet Jupiter. The asteroid belt therefore preserves a record of both this earliest epoch of Solar System formation and variation of conditions within the solar nebula. Spectral features in reflected sunlight indicate that some asteroids have experienced sufficient thermal evolution to differentiate into layered structures. The second most massive asteroid--4 Vesta--has differentiated to a crust, mantle and core. 1 Ceres, the largest and most massive asteroid, has in contrast been presumed to be homogeneous, in part because of its low density, low albedo and relatively featureless visible reflectance spectrum, similar to carbonaceous meteorites that have suffered minimal thermal processing. Here we show that Ceres has a shape and smoothness indicative of a gravitationally relaxed object. Its shape is significantly less flattened than that expected for a homogeneous object, but is consistent with a central mass concentration indicative of differentiation. Possible interior configurations include water-ice-rich mantles over a rocky core.

Meteoritic and Asteroidal Constraints on the Identification and Collisional Evolution of Asteroid Families

NASA Technical Reports Server (NTRS)

Gaffey, Michael J.; Kelley, Michael S.; Hardersen, Paul S.

2002-01-01

Studies of meteorites and observations of asteroids can provide important constraints on the formation and evolution of asteroid families. The iron meteorites alone require the disruption of 85 differentiated asteroids, and the potential formation of 85 families. Additional information is contained in the original extended abstract.

NASA's Discovery Mission to (16) Psyche: Visiting a Metal World

NASA Astrophysics Data System (ADS)

Elkins-Tanton, L. T.; Bell, J. F., III

2017-09-01

The Psyche mission is one of NASA's most recent Discovery mission selections. It is designed to explore the large metallic Main Belt asteroid (16) Psyche and test the hypothesis that it is the exposed core of an ancient differentiated planetesimal.

Extreme AO Observations of Two Triple Asteroid Systems with SPHERE

NASA Astrophysics Data System (ADS)

Yang, B.; Wahhaj, Z.; Beauvalet, L.; Marchis, F.; Dumas, C.; Marsset, M.; Nielsen, E. L.; Vachier, F.

2016-04-01

We present the discovery of a new satellite of asteroid (130) Elektra—S/2014 (130) 1—in differential imaging and in integral field spectroscopy data over multiple epochs obtained with Spectro-Polarimetric High-contrast Exoplanet Research/Very Large Telescope. This new (second) moonlet of Elektra is about 2 km across, on an eccentric orbit, and about 500 km away from the primary. For a comparative study, we also observed another triple asteroid system, (93) Minerva. For both systems, component-resolved reflectance spectra of the satellites and primary were obtained simultaneously. No significant spectral difference was observed between the satellites and the primary for either triple system. We find that the moonlets in both systems are more likely to have been created by sub-disruptive impacts as opposed to having been captured.

On Identifying Clusters Within the C-type Asteroids of the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Poole, Renae; Ziffer, J.; Harvell, T.

2012-10-01

We applied AutoClass, a data mining technique based upon Bayesian Classification, to C-group asteroid colors in the Sloan Digital Sky Survey (SDSS). Previous taxonomic studies relied mostly on Principal Component Analysis (PCA) to differentiate asteroids within the C-group (e.g. B, G, F, Ch, Cg and Cb). AutoClass's advantage is that it calculates the most probable classification for us, removing the human factor from this part of the analysis. In our results, AutoClass divided the C-groups into two large classes and six smaller classes. The two large classes (n=4974 and 2033, respectively) display distinct regions with some overlap in color-vs-color plots. Each cluster's average spectrum is compared to 'typical' spectra of the C-group subtypes as defined by Tholen (1989) and each cluster's members are evaluated for consistency with previous taxonomies. Of the 117 asteroids classified as B-type in previous taxonomies, only 12 were found with SDSS colors that matched our criteria of having less than 0.1 magnitude error in u and 0.05 magnitude error in g, r, i, and z colors. Although this is a relatively small group, 11 of the 12 B-types were placed by AutoClass in the same cluster. By determining the C-group sub-classifications in the large SDSS database, this research furthers our understanding of the stratigraphy and composition of the main-belt.

EXTREME AO OBSERVATIONS OF TWO TRIPLE ASTEROID SYSTEMS WITH SPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, B.; Wahhaj, Z.; Dumas, C.

We present the discovery of a new satellite of asteroid (130) Elektra—S/2014 (130) 1—in differential imaging and in integral field spectroscopy data over multiple epochs obtained with Spectro-Polarimetric High-contrast Exoplanet Research/Very Large Telescope. This new (second) moonlet of Elektra is about 2 km across, on an eccentric orbit, and about 500 km away from the primary. For a comparative study, we also observed another triple asteroid system, (93) Minerva. For both systems, component-resolved reflectance spectra of the satellites and primary were obtained simultaneously. No significant spectral difference was observed between the satellites and the primary for either triple system. Wemore » find that the moonlets in both systems are more likely to have been created by sub-disruptive impacts as opposed to having been captured.« less

Low-Degree Partial Melting Experiments of CR and H Chondrite Compositions: Implications for Asteroidal Magmatism Recorded in GRA 06128 and GRA 06129 T

NASA Technical Reports Server (NTRS)

Usui, T.; Jones, John H.; Mittlefehldt, D. W.

2010-01-01

Studies of differentiated meteorites have revealed a diversity of differentiation processes on their parental asteroids; these differentiation mechanisms range from whole-scale melting to partial melting without the core formation [e.g., 1]. Recently discovered paired achondrites GRA 06128 and GRA 06129 (hereafter referred to as GRA) represent unique asteroidal magmatic processes. These meteorites are characterized by high abundances of sodic plagioclase and alkali-rich whole-rock compositions, implying that they could originate from a low-degree partial melt from a volatile-rich oxidized asteroid [e.g., 2, 3, 4]. These conditions are consistent with the high abundances of highly siderophile elements, suggesting that their parent asteroid did not segregate a metallic core [2]. In this study, we test the hypothesis that low-degree partial melts of chondritic precursors under oxidizing conditions can explain the whole-rock and mineral chemistry of GRA based on melting experiments of synthesized CR- and H-chondrite compositions.

Spectroscopic and theoretical constraints on the differentiation of planetesimals

NASA Astrophysics Data System (ADS)

Moskovitz, Nicholas A.

The differentiation of small proto-planetary bodies into metallic cores, silicate mantles and basaltic crusts was a common occurrence in the first few million years of Solar System history. In this thesis, observational and theoretical methods are employed to investigate this process. Particular focus is given to the basaltic, crustal remnants of those differentiated parent bodies. A visible-wavelength spectroscopic survey was designed and performed to constrain the population of basaltic asteroids in the Main Belt. The results of this survey were used to provide statistical constraints on the orbital and size-frequency distributions of these objects. These distributions imply that basaltic material is rare in the Main Belt (particularly beyond the 3:1 mean motion resonance at 2.5 AU), however relic fragments of crust from multiple differentiated parent bodies are likely present. To provide insight on the mineralogical diversity of basaltic asteroids in the Main Belt, we performed a series of near-infrared spectroscopic observations. We find that V-type asteroids in the inner belt have spectroscopic properties consistent with an origin from a single parent body, most likely the asteroid Vesta. Spectroscopic differences (namely band area ratio) between these asteroids and basaltic meteorites here on Earth are best explained by space weathering of the asteroid surfaces. We also report the discovery of unusual spectral properties for asteroid 10537 (1991 RY16), a V-type asteroid in the outer Main Belt that has an ambiguous mineralogical interpretation. We conclude this thesis with a theoretical investigation of the relevant stages in the process of differentiation. We show that if partial silicate melting occurs within the interior of a planetesimal then both core and crust formation could have happened on sub-million year (Myr) time scales. However, it is shown that the high temperatures necessary to facilitate these processes may have been affected by the migration of molten silicates within these planetesimals and by chemical interactions between liquid water and silicate rock. Finally, a 1-dimensional model of heat conduction is used to explore whether differentiation would have occurred for planetesimals across a range of sizes (4-250 km) and times of accretion (0-3 Myr).

UV Spectroscopy of Metallic Asteroid (16) Psyche

NASA Astrophysics Data System (ADS)

Cunningham, N. J.; Becker, T. M.; Retherford, K. D.; Roth, L.; Feaga, L. M.; Wahlund, J.-E.; Elkins-Tanton, L. T.

2017-09-01

Asteroid (16) Psyche is the largest M-type asteroid, and the planned destination of the NASA Discovery mission Psyche and the proposed ESA M5 mission Heavy Metal. Psyche is considered to be the exposed core of a differentiated asteroid, whose mantle has been stripped by collisions; but other histories have been proposed. We observed Psyche with the Space Telescope Imaging Spectrograph (STIS) and Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope, to obtain a full ultraviolet (UV) spectrum of both of Psyche's hemispheres. We seek to test three possible scenarios for Psyche's origin: Is Psyche the exposed core of a differentiated asteroid? Is it an asteroid with high olivine content that has been space-weathered? Or did Psyche accrete as-is in a highly-reducing environment early in the history of the solar system? We will present the UV spectra and their implications for Psyche's history.

Radar Observations of Asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda

NASA Technical Reports Server (NTRS)

Mitchell, David L.; Ostro, Steven J.; Rosema, Keith D.; Hudson, R. Scott; Campbell, Donald B.; Chandler, John F.; Shapiro, Irwin I.

1995-01-01

We report 13-cm wavelength radar observations of the main-belt asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda obtained at Arecibo between 1980 and 1989. The echoes are highly polarized yet broadly distributed in Doppler frequency, indicating that our targets are smooth on decimeter scales but very rough on some scale(s) larger than about I m. The echo spectra are generally consistent with existing size, shape, and spin information based on radiometric, lightcurve, and occultation data. All of our targets possess distinctive radar signatures that reveal large- scale topography. Reflectivity spikes within narrow ranges of rotation phase suggest large flat regions on Iris, Metis, and Zelinda, while bimodal spectra imply nonconvex, possibly bifurcated shapes for Kleopatra and Victoria. Kleopatra has the highest radar albedo yet measured for a main-belt asteroid, indicating a high metal concentration and making Kleopatra the best main-belt candidate for a core remnant of a differentiated and subsequently disrupted parent body. Upon completion of the Arecibo telescope upgrade, there will be several opportunities per year to resolve main-belt asteroids with hundreds of delay-Doppler cells, which can be inverted to provide estimates of both three-dimensional shape and radar scattering properties.

BAOBAB (Big And Outrageously Bold Asteroid Belt) Project

NASA Technical Reports Server (NTRS)

Mcfadden, L. A.; Thomas, C. A; Englander, J. A.; Ruesch, O.; Hosseini, S.; Goossens, S. J.; Mazarico, E. M.; Schmerr, N.

2017-01-01

One of the intriguing results of NASA's Dawn mission is the composition and structure of the Main Asteroid Belt's only known dwarf planet, Ceres [1]. It has a top layer of dehydrated clays and salts [2] and an icy-rocky mantle [3,4]. It is widely known that the asteroid belt failed to accrete as a planet by resonances between the Sun and Jupiter. About 20-30 asteroids >100 km diameter are probably differentiated protoplanets [5]. 1) how many more and which ones are fragments of protoplanets? 2) How many and which ones are primordial rubble piles left over from condensation of the solar nebula? 3) How would we go about gaining better and more complete characterization of the mass, interior structure and composition of the Main Belt asteroid population? 4) What is the relationship between asteroids and ocean worlds? Bulk parameters such as the mass, density, and porosity, are important to characterize the structure of any celestial body, and for asteroids in particular, they can shed light on the conditions in the early solar system. Asteroid density estimates exist but currently they are often based on assumed properties of taxonomic classes, or through astronomical survey data where interactions with asteroids are weak at best resulting in large measurement uncertainty. We only have direct density estimates from spacecraft encounters for a few asteroids at this time. Knowledge of the asteroids is significant not only to understand their role in solar system workings, but also to assess their potential as space resources, as impact hazards on Earth, or even as harboring life forms. And for the distant future, we want to know if the idea put forth in a contest sponsored by Physics Today, to surface the asteroids into highly reflecting, polished surfaces and use them as a massively segmented mirror for astrophysical exploration [6], is feasible.

The Large Super-Fast Rotators and Asteroidal Spin-Rate Distributions With Large Sky-Field Surveys Using iPTF

NASA Astrophysics Data System (ADS)

Chang, Chan-Kao; Lin, Hsing-Wen; Ip, Wing-Huen; iPTF Team

2016-10-01

In order to look for kilometer-sized super-fast rotators (large SFRs) and understand the spin-rate distributions of small (i.e. D of several kilometers) asteroids, we have been conducting asteroid rotation period surveys of large sky area using intermediate Palomar Transient Factory (iPTF) since 2014. So far, we have observed 261 deg2 with 20 min cadence, 188 deg2 with 10 min cadence, and 65 deg2 with 5 min cadence. From these surveys, we found that the spin-rate distributions of small asteroids at different locations in the main-belt are very similar. Moreover, the distributions of asteroids with 3 < D < 15 km show number decrease along with increase of spin rate for frequency > 5 rev/day, and that of asteroids with D < 3 km have a significant number drop at frequency = 5 rev/day. However, we only discover two new large SFRs and 24 candidates. Comparing with the ordinary asteroids, the population of large SFR seems to be far less than the whole asteroid population. This might indicate a peculiar group of asteroid for large SFRs.

Geologic History of Asteroid 4 Vesta

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.

2014-01-01

Some types of meteorites - most irons, stony irons, some achondrites - hail from asteroids that were heated to the point where magmatism occurred within a very few million years of the formation of the earliest solids in the solar system. The largest clan of achondrites, the howardite, eucrite and diogenite (HED) meteorites, represent the crust of their parent asteroid]. Diogenites are cumulate harzburgites and orthopyroxenites from the lower crust whilst eucrites are basalts, diabases and cumulate gabbros from the upper crust. Howardites are impact-engendered breccias mostly of diogenites and eucrites. There remains only one large asteroid with a basaltic crust, 4 Vesta, which is thought to be the source of the HED clan. Differentiation models for Vesta are based on HED compositions. Proto-Vesta consisted of chondritic materials containing Al-26, a potent, short-lived heat source. Inferences from compositional data are that Vesta was melted to high degree (=50%) allowing homogenization of the silicate phase and separation of a metallic core. Convection of the silicate magma ocean allowed equilibrium crystallization, forming a harzburgitic mantle. After convective lockup occurred, melt collected between the mantle and the cool thermal boundary layer and underwent fractional crystallization forming an orthopyroxene-rich (diogenite) lower crust. The initial thermal boundary layer of chondritic material was replaced by a mafic upper crust through impact disruption and foundering. The mafic crust thickened over time as additional residual magma intrudes and penetrates the mafic crust forming plutons, dikes, sills and flows of cumulate and basaltic eucrite composition. This magmatic history may have taken only 2-3 Myr. This magma ocean scenario is at odds with a model of heat and magma transport that indicates that small degrees of melt would be rapidly expelled from source regions, precluding development of a magma ocean. Constraints from radiogenic Mg-26 distibutions suggest that the parent asteroid of HEDs was much smaller than Vesta. Thus, first-order questions regarding asteroid differentiation remain.

Modeling of Giant Impact into a Differentiated Asteroid and Implications for the Large-Scale Troughs on Vesta

NASA Astrophysics Data System (ADS)

Buczkowski, D.; Iyer, K.; Raymond, C. A.; Wyrick, D. Y.; Kahn, E.; Nathues, A.; Gaskell, R. W.; Roatsch, T.; Preusker, F.; Russell, C. T.

2012-12-01

Linear structures have been identified in a concentric orientation around impact craters on several asteroids (e.g. Ida [1], Eros [2], Lutetia [3]) and their formation tied to the impact event [1,2]. Images of Vesta taken by the Dawn spacecraft reveal large-scale linear structural features in a similar orientation around the Rheasilvia and Veneneia basins [4]. However, the dimensions and shape of these features suggest that they are graben similar to those observed on terrestrial planets, not fractures or grooves such as are found on Ida, Eros and Lutetia [5]. Although the fault plane analysis [4] implies that impact may have been responsible for triggering the formation of these features as on the smaller asteroids, we suggest the significantly different morphology implies that some other component must also have been involved in their development. It has been established that Vesta is a differentiated body with a core [6]. This differentiated interior could be a factor in the troughs' resemblance to planetary faults rather than asteroidal fractures, as it is predicted that the stresses resultant from impact would be amplified and reoriented compared to a similar impact on an undifferentiated body. Preliminary CTH hydrocode [7] models of a 530 km sphere composed of a basalt analog with a 220 km iron core [6] show that the impact of a 50 km object results in different patterns of tensile stress and pressure compared to an undifferentiated sphere of the same material and diameter. While these first-order models have yet to fully mimic the observations we've made on Vesta, they do demonstrate that the density contrast in Vesta's differentiated interior affects the stresses resulting from the Rheasilivia and Veneneia impacts. It is this impedance mismatch that we suggest is responsible for the development of Vesta's planet-like troughs. Thus, future identification of planetary-style tectonic features on small solar system bodies may then imply a differentiated interior like Vesta's. The authors gratefully acknowledge the support of the Dawn Instrument, Operations, and Science Teams. This work was funded by the Dawn at Vesta Participating Science Program. [1] Asphaug et al. 1996, Icarus, 120, 158-184. [2] Buczkowski et al. 2008, Icarus, 193, 39-52. [3] Thomas et al. 2011, Planet. Space Sci., doi:10.1016/j.pss.2011.10.003. [4] Jaumann et al. 2012, Science 336, 687-690. [5] Buczkowski et al. 2012, GRL, submitted. [6] Russell et al. 2012, Science 336, 684-686. [7] McGlaun et al. 1990, Int. J. Impact Eng., 10(1-40), 351-360.

Effects of Space Weathering on Reflectance Spectra of Ureilites: First Studies

NASA Technical Reports Server (NTRS)

Goodrich, C. A.; Gillis-Davis, J.; Cloutis, E.; Applin, D.; Takir, D.; Hibbitts, C.; Christoffersen, R.; Fries, M.; Klima, R.; Decker, S.

2018-01-01

Ureilites are differentiated meteorites (ultramafic rocks interpreted to be mantle residues) that contain as much carbon as the most carbon-rich carbonaceous chondrites (CCs). Reflectance spectra of ureilites are similar to those of some CCs. Hence, ureilitic asteroids may accidentally be categorized as primitive because their spectra could resemble those of C-complex asteroids, which are thought to be CC-like. We began spectral studies of progressively laser-weathered ureilites with the goals of predicting UV-VIS-IR spectra of ureilitic asteroids, and identifying features that could distinguish differentiated from primitive dark asteroids. Space weathering has not previously been studied for ureilites, and, based on space weathering studies of CCs and other C-rich materials, it could significantly alter their reflectance spectra.

An ancient core dynamo in asteroid Vesta.

PubMed

Fu, Roger R; Weiss, Benjamin P; Shuster, David L; Gattacceca, Jérôme; Grove, Timothy L; Suavet, Clément; Lima, Eduardo A; Li, Luyao; Kuan, Aaron T

2012-10-12

The asteroid Vesta is the smallest known planetary body that has experienced large-scale igneous differentiation. However, it has been previously uncertain whether Vesta and similarly sized planetesimals formed advecting metallic cores and dynamo magnetic fields. Here we show that remanent magnetization in the eucrite meteorite Allan Hills A81001 formed during cooling on Vesta 3.69 billion years ago in a surface magnetic field of at least 2 microteslas. This field most likely originated from crustal remanence produced by an earlier dynamo, suggesting that Vesta formed an advecting liquid metallic core. Furthermore, the inferred present-day crustal fields can account for the lack of solar wind ion-generated space weathering effects on Vesta.

Asteroid-Meteorite Links: The Vesta Conundrum(s)

NASA Technical Reports Server (NTRS)

Pieters, C. M.; Binzel, R.; Bogard, D.; Hiroi, T.; Mittlefehldt, D. W.; Nyquist, L.; Rivkin, A.; Takeda, H.

2006-01-01

Although a direct link between the HED meteorites and the asteroid 4 Vesta is generally acknowledged, several issues continue to be actively examined that tie Vesta to early processes in the solar system. Vesta is no longer the only basaltic asteroid in the Main belt. In addition to the Vestoids of the Vesta family, the small asteroid Magnya is basaltic but appears to be unrelated to Vesta. Similarly, diversity now identified in the collection of basaltic meteorites requires more than one basaltic parent body, consistent with the abundance of differentiated parent bodies implied by iron meteorites. The timing of the formation of the Vestoids (and presumably the large crater at the south pole of Vesta) is unresolved. Peaks in Ar-Ar dates of eucrites suggest this impact event could be related to a possible late heavy bombardment at least 3.5 Gyr ago. On the other hand, the optically fresh appearance of both Vesta and the Vestoids requires either a relatively recent resurfacing event or that their surfaces do not weather in the same manner thought to occur on other asteroids such as the ordinary chondrite parent body. Diversity across the surface of Vesta has been observed with HST and there are hints of compositional variations (possibly involving minor olivine) in near-infrared spectra.

V-type candidates and Vesta family asteroids in the Moving Objects VISTA (MOVIS) catalogue

NASA Astrophysics Data System (ADS)

Licandro, J.; Popescu, M.; Morate, D.; de León, J.

2017-04-01

Context. Basaltic asteroids (spectrally classified as V-types) are believed to be fragments of large differentiated bodies. The majority of them are found in the inner part of the asteroid belt, and are current or past members of the Vesta family. Recently, some V-type asteroids have been discovered far from the Vesta family supporting the hypothesis of the presence of multiple basaltic asteroids in the early solar system. The discovery of basaltic asteroids in the outer belt challenged the models of the radial extent and the variability of the temperature distribution in the early solar system. Aims: We aim to identify new basaltic V-type asteroids using near-infrared colors of 40 000 asteroids observed by the VHS-VISTA survey and compiled in the MOVIS-C catalogue. We also want to study their near-infrared colors and to study the near-infrared color distribution of the Vesta dynamical family. Methods: We performed a search in the MOVIS-C catalogue of all the asteroids with (Y-J) and (J-Ks) in the range (Y-J) ≥ 0.5 and (J-Ks) ≤ 0.3, associated with V-type asteroids, and studied their color distribution. We have also analyzed the near-infrared color distribution of 273 asteroid members of the Vesta family and compared them with the albedo and visible colors from WISE and SDSS data. We determined the fraction of V-type asteroids in the family. Results: We found 477 V-type candidates in MOVIS-C, 244 of them outside the Vesta dynamical family. We identified 19 V-type asteroids beyond the 3:1 mean motion resonance, 6 of them in the outer main belt, and 16 V-types in the inner main belt with proper inclination Ip ≤ 3.0°, well below the inclination of the Vesta family. We computed that 85% of the members of the Vesta dynamical family are V-type asteroids, and only 1-2% are primitive class asteroids and unlikely members of the family. Conclusions: This work almost doubles the sample of basaltic asteroid candidates in regions outside the Vesta family. Spectroscopic studies in the near-infrared and dynamical studies are needed to confirm their basaltic composition and to determine their origin.

On the metal-rich surfaces of (16) Psyche and other M-type asteroids from interferometric observations in the thermal infrared

NASA Astrophysics Data System (ADS)

Delbo, Marco; Matter, A.; Gundlach, B.; Blum, J.

2013-10-01

Asteroids belonging to the spectroscopic M-type exhibit a quasi featureless and moderately red reflectance spectrum and a geometric visible albedo between 0.1 and 0.3. These asteroids were initially thought to be metallic cores of differentiated asteroids that were exposed to space by a catastrophic disruption by impacts. Later, this view has been challenged by the detection of silicates and hydration spectroscopic bands on these bodies. Unveiling the physical properties of the surfaces of these asteroids, and identifying their meteorite analogs is a challenge from remote-sensing observations. Nevertheless, these are crucial problems, important for estimating the number of asteroids that underwent differentiation in the early phases of the formation of our solar system. The thermal inertia is a sensitive indicator for the presence of metal in the regolith on the surfaces of asteroids. We developed a new thermophysical model that allow us to derive the value of the thermal inertia from interferometric observations in the thermal infrared. We report on our investigation of the thermal inertia of M-type asteroids, including the asteroids (16) Psyche, for which we obtained a thermal inertia value anomalously high compared to the thermal inertia values of other asteroids in the same size range. From the thermal inertia and model of heat conductivity that accounts for different values of the packing fraction (a measure of the degree of compaction of the regolith particles) the regolith grain size is derived.

The hierarchical stability of the seven known large size ratio triple asteroids using the empirical stability parameters.

PubMed

Liu, Xiaodong; Baoyin, Hexi; Marchis, Franck

In this study, the hierarchical stability of the seven known large size ratio triple asteroids is investigated. The effect of the solar gravity and primary's J 2 are considered. The force function is expanded in terms of mass ratios based on the Hill's approximation and the large size ratio property. The empirical stability parameters are used to examine the hierarchical stability of the triple asteroids. It is found that the all the known large size ratio triple asteroid systems are hierarchically stable. This study provides useful information for future evolutions of the triple asteroids.

The thermal evolution of large water-rich asteroids

NASA Astrophysics Data System (ADS)

Schmidt, B. E.; Castillo, J. C.

2009-12-01

Water and heat played a significant role in the formation and evolution of large main belt asteroids, including 1 Ceres, 2 Pallas, and 24 Themis, for which there is now evidence of surficial water ice (Rivkin & Emery, ACM 2008). Shape measurements indicate some differentiation of Ceres’ interior, which, in combination with geophysical modeling, may indicate compositional layering in a core made up of anhydrous and hydrated silicate and a water ice mantle (Castillo-Rogez & McCord, in press, Icarus). We extend these interior models now to other large, possibly water-rich main belt asteroids, namely Pallas, at mean radius 272 km, and the Themis family parent body, at mean radius 150 km. The purpose of this study is to compare geophysical models against available constraints on the physical properties of these objects and to offer constraints on the origin of these objects. Pallas is the largest B-type asteroid. Its surface of hydrated minerals and recent constraint on its density, 2.4-2.8 g/cm3, seems to imply that water strongly affected its evolution (Schmidt et al., in press, Science). 24 Themis is the largest member of the Themis family that now counts about 580 members, including some of the main belt comets. The large member 90 Antiope has a density of about 1.2 g/cm3, while 24 Themis has a density of about 2.7 +/-1.3 g/cm3. The apparent contrast in the densities and spectral properties of the Themis family members may reflect a compositional layering in the original parent body. In the absence of tidal heating and with little accretional heat, the evolution of these small water-rich objects is a function of their initial composition and temperature. The latter depends on the location of formation (in the inner or outer solar system) and most importantly on the time and duration of accretion, which determines the amount of short-lived radioisotopes available for early internal activity. New accretional models suggest that planetesimals grew rapidly throughout the asteroid belt to several hundred kilometers (Morbidelli et al, in press, Icarus), so that even the water-rich asteroids accreted a volume of short-lived radionuclides significant enough to create substantial internal heat. As an alternative to the classical model of formation in the inner solar system, it has been hypothesized that some water-rich asteroids could have formed in the transneptunian region before migration inward. In such a context the accretion timescale for objects 100-300 km radius is several hundred My, limiting the role of 26Al as a major heat source. However, formation in the outer solar system implies a different composition of the volatile and refractory phases, such as the possible accretion of clathrate hydrates, ammonia hydrates, etc. We will quantify the degree of differentiation achieved for the different formation scenarios envisioned for these objects and investigate the endogenic activity (e.g., hydrothermal, core warming) promoted by the accompanying geophysical conditions. Part of this work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology. Government sponsorship acknowledged.

Explorations of Psyche and Callisto Enabled by Ion Propulsion

NASA Technical Reports Server (NTRS)

Wenkert, Daniel D.; Landau, Damon F.; Bills, Bruce G.; Elkins-Tanton, Linda T.

2013-01-01

Recent developments in ion propulsion (specifically solar electric propulsion - SEP) have the potential for dramatically reducing the transportation cost of planetary missions. We examine two representative cases, where these new developments enable missions which, until recently, would have required resouces well beyond those allocated to the Discovery program. The two cases of interest address differentiation of asteroids and large icy satellites

Speckle interferometry of asteroids

NASA Technical Reports Server (NTRS)

Drummond, Jack

1988-01-01

By studying the image two-dimensional power spectra or autocorrelations projected by an asteroid as it rotates, it is possible to locate its rotational pole and derive its three axes dimensions through speckle interferometry under certain assumptions of uniform, geometric scattering, and triaxial ellipsoid shape. However, in cases where images can be reconstructed, the need for making the assumptions is obviated. Furthermore, the ultimate goal for speckle interferometry of image reconstruction will lead to mapping albedo features (if they exist) as impact areas or geological units. The first glimpses of the surface of an asteroid were obtained from images of 4 Vesta reconstructed from speckle interferometric observations. These images reveal that Vesta is quite Moon-like in having large hemispheric-scale albedo features. All of its lightcurves can be produced from a simple model developed from the images. Although undoubtedly more intricate than the model, Vesta's lightcurves can be matched by a model with three dark and four bright spots. The dark areas so dominate one hemisphere that a lightcurve minimum occurs when the maximum cross-section area is visible. The triaxial ellipsoid shape derived for Vesta is not consistent with the notion that the asteroid has an equilibrium shape in spite of its having apparently been differentiated.

Rotational spectral variations of asteroid (8) Flora Implications for the nature of the S-type asteroids and for the parent bodies of the ordinary chondrites

NASA Technical Reports Server (NTRS)

Gaffey, M. J.

1984-01-01

The surface material and the surface material heterogeneities of the asteroid Flora are characterized using the best available data sets and the most sophisticated interpretive calibrations. Five spectrally derived mineralogic and patrologic properties of the surface assemblage of Flora which are relevant to whether this body is a differentiated or undifferentiated object are considered: bulk mineralogy, mafic mineral assemblage, metallic phase, pyroxene composition and structural type, and mineralogic variation. All of these properties indicate that Flora is a differentiated body. Flora is probably the residual core of an intensely heated, thermally evolved, and magnetically differentiated planetesimal which was subsequently disrupted. The present surface sample layers formed at or near the core-mantle boundary in the parent body.

The Main Asteroid Belt: The Crossroads of the Solar System

NASA Astrophysics Data System (ADS)

Michel, Patrick

2015-08-01

Orbiting the Sun between Mars and Jupiter, main belt asteroids are leftover planetary building blocks that never accreted enough material to become planets. They are therefore keys to understanding how the Solar System formed and evolved. They may also provide clues to the origin of life, as similar bodies may have delivered organics and water to the early Earth.Strong associations between asteroids and meteorites emerged thanks to multi-technique observations, modeling, in situ and sample return analyses. Spacecraft images revolutionized our knowledge of these small worlds. Asteroids are stunning in their diversity in terms of physical properties. Their gravity varies by more orders of magnitude than its variation among the terrestrial planets, including the Moon. Each rendezvous with an asteroid thus turned our geological understanding on its head as each asteroid is affected in different ways by a variety of processes such as landslides, faulting, and impact cratering. Composition also varies, from ice-rich to lunar-like to chondritic.Nearly every asteroid we see today, whether of primitive or evolved compositions, is the product of a complex history involving accretion and one or more episodes of catastrophic disruption that sometimes resulted in families of smaller asteroids that have distinct and indicative petrogenic relationships. These families provide the best data to study the impact disruption process at scales far larger than those accessible in laboratory. Tens, perhaps hundreds, of early asteroids grew large enough to thermally differentiate. Their traces are scattered pieces of their metal-rich cores and, more rarely, their mantles and crusts.Asteroids represent stages on the rocky road to planet formation. They have great stories to tell about the formation and evolution of our Solar System as well as other planetary systems: asteroid belts seem common around Sun-like stars. We will review our current knowledge on their properties, their link to other populations in the different parts of the Solar System, and the space missions devoted to these tracers of our origins, which, for a small fraction, are also potentially hazardous.

Dynamical evolution of V-type photometric candidates in the central and outer main belt asteroids

NASA Astrophysics Data System (ADS)

Carruba, V.; Huaman, M.

2014-07-01

V-type asteroids are associated with basaltic composition, and are supposed to be fragments of crust of differentiated objects. Most V-type asteroids in the main belt are found in the inner main belt, and are either current members of the Vesta dynamical family (Vestoids), or past members that drifted away. However, several V-type photometric candidates have been recently identified in the central and outer main belt. The origin of this large population of V-type objects is not well understood, since it seems unlikely that Vestoids crossing the 3:1 and 5:2 mean-motion resonance with Jupiter could account for the whole observed population. In this work, we investigated a possible origin of the bodies from local sources, such as the parent bodies of the Eunomia, Merxia, and Agnia asteroid families in the central main belt, and Dembowska, Eos and Magnya asteroid families in the outer main belt. Our results show that dynamical evolution from the parent bodies of the Eunomia and Merxia/Agnia families on timescales of 2 Gyr or more could be responsible for the current orbital location of most of the V-type photometric candidates in the central main belt. Studies for the outer main belt are currently in progress. by the FAPESP (grant 2011/19863-3) and CAPES (grant 15029-12-3) funding agencies.

Thermophysical characteristics of the large main-belt asteroid (349) Dembowska

NASA Astrophysics Data System (ADS)

Yu, Liang Liang; Yang, Bin; Ji, Jianghui; Ip, Wing-Huen

2017-12-01

(349) Dembowska is a large, bright main-belt asteroid that has a fast rotation and an oblique spin axis. It might have experienced partial melting and differentiation. We constrain Dembowska's thermophysical properties, such as thermal inertia, roughness fraction, geometric albedo and effective diameter within 3σ uncertainty of Γ =20^{+12}_{-7} Jm-2 s-0.5 K-1, f_r=0.25^{+0.60}_{-0.25}, p_v=0.309^{+0.026}_{-0.038} and D_eff=155.8^{+7.5}_{-6.2} km, by utilizing the advanced thermophysical model to analyse four sets of thermal infrared data obtained by the Infrared Astronomy Satellite (IRAS), AKARI, the Wide-field Infrared Survey Explorer (WISE) and the Subaru/Cooled Mid-Infrared Camera and Spectrometer (COMICS) at different epochs. In addition, by modelling the thermal light curve observed by WISE, we obtain the rotational phases of each data set. These rotationally resolved data do not reveal significant variations of thermal inertia and roughness across the surface, indicating that the surface of Dembowska should be covered by a dusty regolith layer with few rocks or boulders. Besides, the low thermal inertia of Dembowska shows no significant difference with other asteroids larger than 100 km, which indicates that the dynamical lives of these large asteroids are long enough to make their surfaces have sufficiently low thermal inertia. Furthermore, based on the derived surface thermophysical properties, as well as the known orbital and rotational parameters, we can simulate Dembowska's surface and subsurface temperatures throughout its orbital period. The surface temperature varies from ∼40 to ∼220 K, showing significant seasonal variation, whereas the subsurface temperature achieves equilibrium temperature about 120-160 K below a depth of 30-50 cm.

A Study Regarding the Possibility of True Polar Wander on the Asteroid Vesta

NASA Astrophysics Data System (ADS)

Karimi, M.; Dombard, A. J.

2014-12-01

The asteroid 4 Vesta, with an average diameter of ~525 km, is the second most massive asteroid in the solar system. Most of our knowledge about this differentiated asteroid comes from the Howardite-Eucrite-Diogenite class of meteorites that originated from Vesta, images provided by Hubble Space Telescope, and data from the Dawn spacecraft that orbited Vesta from July 2011 to September 2012. Notably, these close-range data confirmed what Hubble images suggested: a highly oblate shape in which the equatorial radius is ~60 km greater than the polar radius, a shape consistent with Vesta's short rotational period of ~5.3 hr. These images also revealed the presence of two large impact craters near the asteroid's south pole. Rheasilvia, the younger and larger crater at ~500 km in diameter, is superimposed over Veneneia, ~400 km in diameter. The occurrence of two large impacts near a pole, which possesses a relatively small area (less than 30% of the surface), is highly improbable. Thus, we investigate the possibility of True Polar Wander. We hypothesize that the integrated mass deficit of these two basins applied a torque to the lithosphere to reorient the surface relative to the spin axis and thereby placing these basins near the pole. In order for this phenomenon to occur, however, the lithosphere needs to be pliable enough to allow relaxation of the ancient rotational bulge and concurrent development of the current bulge. We have previously explored whether the lithosphere of Vesta could support the large-scale (~20 vertical km) topography of the basins (short answer: it can). Here, we explore whether this lithosphere could also permit True Polar Wander. We use the Finite Element Method and a viscoelastic rheology to simulate the relaxation of an oblate Vesta under a range of plausible thermal scenarios consistent with Vesta's expected budget of long-lived radiogenic nuclides. Our results indicate that under reasonable thermal conditions, the relaxation of the rotational bulge of Vesta and subsequent True Polar Wander cannot happen. As unlikely as it may be, it seems that both large impacts occurred in the south polar region of Vesta.

An initial perspective of S-asteroid subtypes within asteroid families

NASA Technical Reports Server (NTRS)

Kelley, M. S.; Gaffey, M. J.

1993-01-01

Many main belt asteroids cluster around certain values of semi-major axis (a), inclination (i), and eccentricity (e). Hirayama was the first to notice these concentrations which he interpreted as evidence of disruptions of larger parent bodies. He called these clusters 'asteroid families'. The term 'families' is increasingly reserved for genetic associations to distinguish them from clusters of unknown or purely dynamical origin (e.g. the Phocaea cluster). Members of a genetic asteroid family represent fragments derived from various depths within the original parent planetesimal. Thus, family members offer the potential for direct examination of the interiors of parent bodies which have undergone metamorphism and differentiation similar to that occurring in the inaccessible interiors of terrestrial planets. The differentiation similar to that occurring in the inaccessible interiors of terrestrial planets. The condition that genetic family members represent the fragments of a parent object provides a critical test of whether an association (cluster in proper element space) is a genetic family. Compositions (types and relative abundances of materials) of family members must permit the reconstruction of a compositionally plausible parent body. The compositions of proposed family members can be utilized to test the genetic reality of the family and to determine the type and degree of internal differentiation within the parent planetesimal. The interpretation of the S-class mineralogy provides a preliminary evaluation of family memberships. Detailed mineralogical and petrological analysis was done based on the reflectance spectra of 39 S-type asteroids. The result is a division of the S-asteroid class into seven subtypes based on compositional differences. These subtypes, designated S(I) to S(VII), correspond to surface silicate assemblages ranging from monomineralic olivine (dunites) through olivine-pyroxene mixtures to pure pyroxene or pyroxene-feldspar mixtures (basalts). The most general conclusion is that the S-asteroids cannot be treated as a single group of objects without greatly oversimplifying their properties. Each S-subtype needs to be treated as an independent group with a distinct evolutionary history.

The Big Splash: Tsunami from Large Asteroid and Comet Impacts

NASA Astrophysics Data System (ADS)

Hills, J.; Goda, M.

Asteroid and comet impacts produce a large range of damage. Tsunami may produce most of the economic damage in large asteroid impacts. Large asteroid impacts produce worldwide darkness lasting several months that may kill more people by mass starvation, especially in developing countries, than would tsunami, but the dust should not severely affect economic infrastructure. The tsunami may even kill more people in developed countries with large coastal populations, such as the United States, than the starvation resulting from darkness. We have been determining which regions of Earth are most susceptible to asteroid tsunami by simulating the effect of a large asteroid impact into mid-ocean. We have modeled the effect of midAtlantic and midPacific impacts that produce craters 300 to 150 km in diameter. A KT-size impactor would cause the larger of these craters. We used a computer code that has successfully determined the runup and inundation from historical earthquake-generated tsunami. The code has been progressively improved to eliminate previous problems at the domain boundaries, so it now runs until the tsunami inundation is complete. We find that the larger of these two midAtlantic impacts would engulf the entire Florida Peninsula. The smaller one would inundate the eastern third of the peninsula while a tsunami passing through the Gulf of Cuba would inundate the West Coast of Florida. Impacts at three different sites in the Pacific show the great vulnerability of Tokyo and its surroundings to asteroid tsunami. Mainland Asia is relatively protected from asteroid tsunami. In Europe, the Iberian Peninsula and the Atlantic Providences of France are highly vulnerable to asteroid tsunami.

Magnetic Evidence for a Partially Differentiated Carbonaceous Chondrite Parent Body and Possible Implications for Asteroid 21 Lutetia

NASA Astrophysics Data System (ADS)

Weiss, Benjamin; Carporzen, L.; Elkins-Tanton, L.; Shuster, D. L.; Ebel, D. S.; Gattacceca, J.; Binzel, R. P.

2010-10-01

The origin of remanent magnetization in the CV carbonaceous chondrite Allende has been a longstanding mystery. The possibility of a core dynamo like that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferentiated. Here we report that Allende's magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a > 20 microtesla field 8-9 Ma after solar system formation. This field was present too recently and directionally stable for too long to have been the generated by the protoplanetary disk or young Sun. The field intensity is in the range expected for planetesimal core dynamos (Weiss et al. 2010), suggesting that CV chondrites are derived from the outer, unmelted layer of a partially differentiated body with a convecting metallic core (Elkins-Tanton et al. 2010). This suggests that asteroids with differentiated interiors could be present today but masked under chondritic surfaces. In fact, CV chondrites are spectrally similar to many members of the Eos asteroid family whose spectral diversity has been interpreted as evidence for a partially differentiated parent asteroid (Mothe-Diniz et al. 2008). CV chondrite spectral and polarimetric data also resemble those of asteroid 21 Lutetia (e.g., Belskaya et al. 2010), recently encountered by the Rosetta spacecraft. Ground-based measurements of Lutetia indicate a high density of 2.4-5.1 g cm-3 (Drummond et al. 2010), while radar data seem to rule out a metallic surface composition (Shepard et al. 2008). If Rosetta spacecraft measurements confirm a high density and a CV-like surface composition for Lutetia, then we propose Lutetia may be an example of a partially differentiated carbonaceous chondrite parent body. Regardless, the very existence of primitive achondrites, which contain evidence of both relict chondrules and partial melting, are prima facie evidence for the formation of partially differentiated bodies.

Volcanism on differentiated asteroids (Invited)

NASA Astrophysics Data System (ADS)

Wilson, L.

2013-12-01

The Dawn spacecraft's investigation of 4 Vesta, best-preserved of the early-forming differentiated asteroids, prompts a reappraisal of factors controlling igneous activity on such bodies. Analogy with melt transfer in zones of partial melting on Earth implies that silicate melts moved efficiently within asteroid mantles in complex networks of veins and dikes, so that only a few percent of the mantle consisted of melt at any one time. Thus even in cases where large amounts of mantle melting occurred, the melts did not remain in the mantle to form "magma oceans", but instead migrated to shallow depths. The link between magma flow rate and the stresses needed to keep fractures open and allow flow fast enough to avoid excessive cooling implies that only within asteroids with radii more than ~190-250 km would continuous magma flow from mantle to surface be possible. In all smaller asteroids (including Vesta) magma must have accumulated in sills at the base of the lithosphere (the conductively controlled ~10 km thick thermal boundary layer) or in crustal magma reservoirs near its base. Magma would then have erupted intermittently to the surface from these steadily replenished reservoirs. The average rates of eruption to the surface (or shallow intrusion) should balance the magma production rate, but since magma could accumulate and erupt intermittently from these reservoirs, the instantaneous eruption rates could be hundreds to thousands of cubic m/s, comparable to historic basaltic eruption rates on Earth and very much greater than the average mantle melting rate. The absence of asteroid atmospheres makes explosive eruptions likely even if magmas are volatile-poor. On asteroids with radii less than ~100 km, gases and sub-mm pyroclastic melt droplets would have had speeds exceeding the escape speed assuming a few hundred ppm volatiles, and only cm sized or larger clasts would have been retained. On larger bodies almost all pyroclasts will have returned to the surface after passing through optically dense fire fountains. At low eruption rates and high volatile contents many clasts cooled to form spatter or cinder deposits, but at high eruption rates and low volatile contents most clasts landed hot and coalesced into lava ponds to feed lava flows. Lava flow thickness varies with surface slope, acceleration due to gravity, and lava yield strength induced by cooling. Low gravity on asteroids caused flows to be relatively thick which reduced the effects of cooling, and many flows probably attained lengths of tens of km and stopped as a result of cessation of magma supply from the reservoir rather than cooling. On most asteroids larger than 100 km radius experiencing more than ~30% mantle melting, the erupted volcanic deposits will have buried the original chondritic surface layers of the asteroid to such great depths that they were melted, or at least heavily thermally metamorphosed, leaving no present-day meteoritical evidence of their prior existence. Tidal stresses from close encounters between asteroids and proto-planets may have very briefly increased melting and melt migration speeds in asteroid interiors but only gross structural disruption would have greatly have changed volcanic histories.

A Thermal Model for the Differentiation of Asteroid 4 Vesta, Based on Radiogenic and Collisional Heating

NASA Astrophysics Data System (ADS)

Ghosh, Amitabha

A finite element code has been developed to study the thermal history of asteroid 4 Vesta. This is the first attempt to model the thermal history of a differentiated asteroid, from accretion through core and crust formation and subsequent cooling until geochemical closure is attained. Previous thermal models were simpler formulations aimed at explaining metamorphism and aqueous alteration in unmelted asteroids. The results of the simulation are consistent with chronological measurements of cumulate and noncumulate eucrites, meteorites belonging to the HED suite, believed to have been derived from 4 Vesta. The work solves major problems with the hypothesis of heating by decay of 26Al, an extinct radionuclide, believed to be a plausible heat source in the early solar system. The simulation draws a model chronology of Vesta and predicts the time interval of accretion at 2.85 Myrs, the absolute times (with respect to CAI formation) of core formation at 4.58 Myrs, crust formation at 6.58 Myrs and geochemical closure on Vesta at ~100 Myrs. It is concluded that neither collisional heating nor heating due to the radioactive decay of 60Fe caused any perceptible difference in the whole-body thermal history of Vesta. Further, the thermal model suggested that the olivine-rich spot observed on Vesta may not be excavated mantle material, but may be unmelted near-surface material that escaped the asteroid's differentiation history.

Chemical Mixing Model and K-Th-Ti Systematics and HED Meteorites for the Dawn Mission

NASA Technical Reports Server (NTRS)

Usui, T.; McSween, H. Y., Jr.; Mittlefehldt, D. W.; Prettyman, T. H.

2009-01-01

The Dawn mission will explore 4 Vesta, a large differentiated asteroid believed to be the parent body of the howardite, eucrite and diogenite (HED) meteorite suite. The Dawn spacecraft carries a gamma-ray and neutron detector (GRaND), which will measure the abundances of selected elements on the surface of Vesta. This study provides ways to leverage the large geochemical database on HED meteorites as a tool for interpreting chemical analyses by GRaND of mapped units on the surface of Vesta.

Asteroid Systems: Binaries, Triples, and Pairs

NASA Astrophysics Data System (ADS)

Margot, J.-L.; Pravec, P.; Taylor, P.; Carry, B.; Jacobson, S.

In the past decade, the number of known binary near-Earth asteroids has more than quadrupled and the number of known large main-belt asteroids with satellites has doubled. Half a dozen triple asteroids have been discovered, and the previously unrecognized populations of asteroid pairs and small main-belt binaries have been identified. The current observational evidence confirms that small (≲20 km) binaries form by rotational fission and establishes that the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect powers the spin-up process. A unifying paradigm based on rotational fission and post-fission dynamics can explain the formation of small binaries, triples, and pairs. Large (>~20 km) binaries with small satellites are most likely created during large collisions.

Chondrites, S asteroids, and space weathering: Thumping noises from the coffin?

NASA Technical Reports Server (NTRS)

Fanale, F. P.; Clark, B. E.

1993-01-01

Most of the spectral characteristics of ordinary chondrites and S-asteroids in the visible and infrared can be reduced to three numerical values. These values represent the depth of the absorption band resulting from octahedrally coordinated Fe(sup 2+), the reflectance at 0.56 microns and the slope of the continuum (as measured according to convention). By plotting these three characteristics, it is possible to immediately compare the spectral characteristics of large numbers of ordinary chondrites and S-asteroids. Commonality of spectral characteristics between these populations can thus be evaluated on the basis of overlap in position on three two-coordinate systems: albedo vs. band depth, band depth vs. slope, and slope vs. albedo. In order to establish identity, members of the two populations must overlap on all three of these independent parameter spaces. In this coordinate system, spectra of 23 ordinary chondrites (representing all metamorphic grades), and 39 S-asteroids were compared. It was found that there was no overlap between the two populations in terms of the slope vs. band depth parameters, nor were most chondrites identical to the S-asteroids with respect to the other criteria. However, the controversial question remains: Where are the parent bodies of the chondrites? Perhaps an even more critical question is: Where are our samples of the S-asteroids? Considering the geography of the asteroid belt and the theory that early solar-system electromagnetic induction heating differentiated protoasteroids in the inner portion of the main belt, it was suggested that although S-asteroids and ordinary chondrites have very similar mineralogy, the S-asteroids are mixtures of metallic nickel iron and silicates which resulted from magmatism induced by electromagnetic heating whereas chondrites were only slightly metamorphosed nebular condensates. In this scenario chondrites would have been derived from a population of bodies with thermal lag times so short that they were not subjected to melting during the phase of the electromagnetic induction heating event but only to various degrees of pervasive metamorphism. Furthermore, these objects would then have been too small to be observed and systematically included in the library of asteroidal spectra. It was also suggested that the parametric distribution of S-asteroid spectra could be reproduced by mixing various proportions of NiFe meteorite and achondritic materials. This has also been demonstrated in the laboratory.

Building Blocks of the Terrestrial Planets: Mineralogy of Hungaria Asteroids

NASA Astrophysics Data System (ADS)

Lucas, Michael; Emery, J. P.

2013-10-01

Deciphering the mineralogy of the Hungaria asteroids has the potential to place constraints on the material from which the terrestrial planets accreted. Among asteroids with semi-major axes interior to the main-belt (e.g., Hungarias, Mars-crossers, and near-Earth asteroids), only the Hungarias are located in relatively stable orbital space. Hungaria asteroids have likely resided in this orbital space since the planets completed their migration to their current orbits. The accretion and igneous differentiation of primitive asteroids appears to be a function of chronology and heliocentric distance. However, differentiated bodies that originated in the terrestrial planet region were either accreted or scattered out of this region early in solar system history. Thus, the Hungaria asteroids represent the closest reservoir of in situ material to the terrestrial planet region from early in solar system history. We present VISNIR 0.45-2.45 µm) and NIR spectra 0.65-2.45 µm) spectra of 24 Hungaria group (objects in similar orbital space) asteroids. Our NIR data (17 objects) were acquired using the InfraRed Telescope Facility and was supplemented with available visible data. Spectra of seven objects were obtained from the MIT-UH-IRTF survey. We distinguish our sample between Hungaria family (presumed fragments of parent 434 Hungaria; 2 objects) and Hungaria background (group minus family 22 objects) asteroids using proper orbital elements. The classification of each asteroid is determined using the taxonomy of Bus-DeMeo. We find that S- and S-subtypes are prevalent among the Hungaria background population (17/22). Spectral band parameters measurements (i.e., Band I and Band II centers and depths, and Band Area Ratio) indicate that eight of these S-types are analogous with undifferentiated ordinary chondrites (SIV “boot” of S-subtypes plot). Mafic silicate mineral abundances and compositions derived for these SIV asteroids mainly correlate with L chondrites. However, one object is an SIII subtype (possible ureilite analog), while two asteroids are SVI subtypes (possible primitive achondrite analog). Family member 6447 Terrycole is a Xe-type, consistent with the taxonomic classification of the parent 434 Hungaria.

Asteroid rotation. I - Tabulation and analysis of rates, pole positions and shapes. II - A theory for the collisional evolution of rotation rates

NASA Technical Reports Server (NTRS)

Harris, A. W.; Burns, J. A.

1979-01-01

Rotation properties and shape data for 182 asteroids are compiled and analyzed, and a collisional model for the evolution of the mean rotation rate of asteroids is proposed. Tabulations of asteroid rotation rates, taxonomic types, pole positions, sizes and shapes and plots of rotation frequency and light curve amplitude against size indicate that asteroid rotational frequency increases with decreasing size for all asteroids except those of the C or S classes. Light curve data also indicate that small asteroids are more irregular in shape than large asteroids. The dispersion in rotation rates observed is well represented by a three dimensional Maxwellian distribution, suggestive of collisional encounters between asteroids. In the proposed model, the rotation rate is found to tend toward an equilibrium value, at which spin-up due to infrequent, large collisions is balanced by a drag due to the larger number of small collisions. The lower mean rotation rate of C-type asteroids is attributed to a lower means density of that class, and the increase in rotation rate with decreasing size is interpreted as indicative of a substantial population of strong asteroids.

(abstract) Large-Scale Topography on Main-Belt Asteroids: Evidence from Arecibo Radar Spectra

NASA Technical Reports Server (NTRS)

Mitchell, D. L.; Ostro, S. J.; Rosma, K. D.; Campbell, D. B.; Chandler, J. F.; Shapiro, I. I.; Hudson, R. S.

1994-01-01

Arecibo lambda 13 cm radar spectra of the main belt asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda exhibit evidence for large-scale topography. These asteroids range in diameter from 113 to 200 km and include members of the S,C, and M classes. Radar.

Sensitivity of Asteroid Impact Risk to Uncertainty in Asteroid Properties and Entry Parameters

NASA Astrophysics Data System (ADS)

Wheeler, Lorien; Mathias, Donovan; Dotson, Jessie L.; NASA Asteroid Threat Assessment Project

2017-10-01

A central challenge in assessing the threat posed by asteroids striking Earth is the large amount of uncertainty inherent throughout all aspects of the problem. Many asteroid properties are not well characterized and can range widely from strong, dense, monolithic irons to loosely bound, highly porous rubble piles. Even for an object of known properties, the specific entry velocity, angle, and impact location can swing the potential consequence from no damage to causing millions of casualties. Due to the extreme rarity of large asteroid strikes, there are also large uncertainties in how different types of asteroids will interact with the atmosphere during entry, how readily they may break up or ablate, and how much surface damage will be caused by the resulting airbursts or impacts.In this work, we use our Probabilistic Asteroid Impact Risk (PAIR) model to investigate the sensitivity of asteroid impact damage to uncertainties in key asteroid properties, entry parameters, or modeling assumptions. The PAIR model combines physics-based analytic models of asteroid entry and damage in a probabilistic Monte Carlo framework to assess the risk posed by a wide range of potential impacts. The model samples from uncertainty distributions of asteroid properties and entry parameters to generate millions of specific impact cases, and models the atmospheric entry and damage for each case, including blast overpressure, thermal radiation, tsunami inundation, and global effects. To assess the risk sensitivity, we alternately fix and vary the different input parameters and compare the effect on the resulting range of damage produced. The goal of these studies is to help guide future efforts in asteroid characterization and model refinement by determining which properties most significantly affect the potential risk.

The asteroids - Accretion, differentiation, fragmentation, and irradiation

NASA Technical Reports Server (NTRS)

Wilkening, L. L.

1979-01-01

Various types of meteorites have experienced processes of condensation, accretion, metamorphism, differentiation, brecciation, irradiation and fragmentation. A typical view of meteorite formation has been that the processes following accretion take place in a few asteroidal-sized (approximately 100 km) objects. Discovery of decay products of now extinct Al-26 and Pd-107 in meteorites, discovery of isotopic heterogeneity among meteorite types, re-analysis of meteorite cooling rates, and continuing study of meteoritic compositions have led some meteoriticists to conclude that meteorites obtained their chemical, isotopic, and some textural characteristics in objects initially less than 10 km in diameter. Such a scenario, which is described in this paper, raises the possibility that some of these small planetesimals may have been 'condensation nuclei' for the formation of comets as well as the precursors of asteroids.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baer, James; Chesley, Steven R.; Matson, Robert D., E-mail: jimbaer1@earthlink.net, E-mail: steve.chesley@jpl.nasa.gov

As an application of our recent observational error model, we present the astrometric masses of 26 main-belt asteroids. We also present an integrated ephemeris of 300 large asteroids, which was used in the mass determination algorithm to model significant perturbations from the rest of the main belt. After combining our mass estimates with those of other authors, we study the bulk porosities of over 50 main-belt asteroids and observe that asteroids as large as 300 km in diameter may be loose aggregates. This finding may place specific constraints on models of main-belt collisional evolution. Additionally, we observe that C-group asteroidsmore » tend to have significantly higher macroporosity than S-group asteroids.« less

Ceres In Context: What the Rest of the Asteroid Population Tells Us About Its Largest Member

NASA Astrophysics Data System (ADS)

Rivkin, A.

2015-12-01

Ceres is famously the largest object in the asteroid belt. Over the course of the last 215 years it has been considered everything from a unique protoplanet (or indeed full-fledged "planet") to a large but run-of-the-mill piece of rock. Over the last decade, models of Ceres' thermal history and shape measurements based on HST imagery have led to the recognition that Ceres is a differentiated object, and likely an ice-rich one. In the last year the Dawn spacecraft has provided unprecedented views of Ceres' surface and combined with data from observational facilities like Herschel and countless telescopes it has shown the varied nature of its geology and ongoing processes. Even given these recent results, Ceres remains an inhabitant of the asteroid belt, existing in the ambient environment and affected by impactors, micrometeorites, solar wind, and other factors. While we only have spacecraft imagery from a very small number of targets, we do have a wealth of Earth-based data from the objects that have shared space with Ceres for billions of years. The insights gained from studying these objects can be applied to Ceres to understand its context and nature. Similarly, what we learn at Ceres will be applicable in many ways to other objects, particularly the twenty or so largest asteroids, which tend to be low-albedo, water-rich bodies. I will discuss our current understanding of the asteroids, particularly those that share important characteristics with Ceres, and focus on what we can learn about Ceres from these bodies.

Howardites and Mesosiderites: Contrasting Polymict Breccias from Two Similar Differentiated Asteroids

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.

2014-01-01

Silicates in mesosiderites commonly show anomalous characteristics compared to howardites. These characteristics indicate that many of the mesosiderite lithologies were formed during and/or after metal silicate mixing. Petrologic evidence indicates that impact gardening occurred on the mesosiderite asteroid after metal-silicate mixing. Thus the anomalous materials ought to be widely distributed on that asteroid. The compositions of howardites suggest a well-mixed regolith on Vesta. The lack of distinctive mesosiderite-like materials in howardites favors separate parents for the two meteorite groups.

The Fossilized Size Distribution of the Main Asteroid Belt

NASA Astrophysics Data System (ADS)

Bottke, W. F.; Durda, D.; Nesvorny, D.; Jedicke, R.; Morbidelli, A.

2003-05-01

At present, we do not understand how the main asteroid belt evolved into its current state. During the planet formation epoch, the primordial main belt (PMB) contained several Earth masses of material, enough to allow the asteroids to accrete on relatively short timescales (e.g., Weidenschilling 1977). The present-day main belt, however, only contains 5e-4 Earth masses of material (Petit et al. 2002). Constraints on this evolution come from (i) the observed fragments of differentiated asteroids, (ii) meteorites collected from numerous differentiated parent bodies, (iii) the presence of ˜ 10 prominent asteroid families, (iv) the "wavy" size-frequency distribution of the main belt, which has been shown to be a by-product of substantial collisional evolution (e.g., Durda et al. 1997), and (v) the still-intact crust of (4) Vesta. To explain the contradictions in the above constraints, we suggest the PMB evolved in this fashion: Planetesimals and planetary embryos accreted (and differentiated) in the PMB during the first few Myr of the solar system. Gravitational perturbations from these embryos dynamically stirred the main belt, enough to initiate fragmentation. When Jupiter reached its full size, some 10 Myr after the solar system's birth, its perturbations, together with those of the embryos, dynamically depleted the main belt region of ˜ 99% of its bodies. Much of this material was sent to high (e,i) orbits, where it continued to pummel the surviving main belt bodies at high impact velocities for more than 100 Myr. While some differentiated bodies in the PMB were disrupted, most were instead scattered; only small fragments from this population remain. This period of comminution and dynamical evolution in the PMB created, among other things, the main belt's wavy size distribution, such that it can be considered a "fossil" from this violent early epoch. From this time forward, however, relatively little collisional evolution has taken place in the main belt, consistent with the surprising paucity of prominent asteroid families. Preliminary modeling results of this scenario and implications will be presented.

Effects of YORP-induced rotational fission on the small size end of the Main Belt asteroid size distribution

NASA Astrophysics Data System (ADS)

Rossi, Alessandro; Jacobson, S.; Marzari, F.; Scheeres, D.; Davis, D. R.

2013-10-01

From the results of a comprehensive asteroid population evolution model, we conclude that the YORP-induced rotational fission hypothesis has strong repercussions for the small size end of the Main Belt asteroid size frequency distribution. These results are consistent with observed asteroid population statistics. The foundation of this model is the asteroid rotation model of Marzari et al. (2011), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis (i.e. when the rotation rate exceeds a critical value, erosion and binary formation occur). The YORP effect timescale for large asteroids with diameters D > ~6 km is longer than the collision timescale in the Main Belt, thus the frequency of large asteroids is determined by a collisional equilibrium (e.g. Bottke 2005), but for small asteroids with diameters D < ~6 km, the asteroid population evolution model confirms that YORP-induced rotational fission destroys small asteroids more frequently than collisions. Therefore, the frequency of these small asteroids is determined by an equilibrium between the creation of new asteroids out of the impact debris of larger asteroids and the destruction of these asteroids by YORP-induced rotational fission. By introducing a new source of destruction that varies strongly with size, YORP-induced rotational fission alters the slope of the size frequency distribution. Using the outputs of the asteroid population evolution model and a 1-D collision evolution model, we can generate this new size frequency distribution and it matches the change in slope observed by the SKADS survey (Gladman 2009). This agreement is achieved with both an accretional power-law or a truncated “Asteroids were Born Big” size frequency distribution (Weidenschilling 2010, Morbidelli 2009).

Simulations of hypervelocity impacts for asteroid deflection studies

NASA Astrophysics Data System (ADS)

Heberling, T.; Ferguson, J. M.; Gisler, G. R.; Plesko, C. S.; Weaver, R.

2016-12-01

The possibility of kinetic-impact deflection of threatening near-earth asteroids will be tested for the first time in the proposed AIDA (Asteroid Impact Deflection Assessment) mission, involving two independent spacecraft, NASAs DART (Double Asteroid Redirection Test) and ESAs AIM (Asteroid Impact Mission). The impact of the DART spacecraft onto the secondary of the binary asteroid 65803 Didymos, at a speed of 5 to 7 km/s, is expected to alter the mutual orbit by an observable amount. The velocity imparted to the secondary depends on the geometry and dynamics of the impact, and especially on the momentum enhancement factor, conventionally called beta. We use the Los Alamos hydrocodes Rage and Pagosa to estimate beta in laboratory-scale benchmark experiments and in the large-scale asteroid deflection test. Simulations are performed in two- and three-dimensions, using a variety of equations of state and strength models for both the lab-scale and large-scale cases. This work is being performed as part of a systematic benchmarking study for the AIDA mission that includes other hydrocodes.

The recent breakup of an asteroid in the main-belt region.

PubMed

Nesvorný, David; Bottke, William F; Dones, Luke; Levison, Harold F

2002-06-13

The present population of asteroids in the main belt is largely the result of many past collisions. Ideally, the asteroid fragments resulting from each impact event could help us understand the large-scale collisions that shaped the planets during early epochs. Most known asteroid fragment families, however, are very old and have therefore undergone significant collisional and dynamical evolution since their formation. This evolution has masked the properties of the original collisions. Here we report the discovery of a family of asteroids that formed in a disruption event only 5.8 +/- 0.2 million years ago, and which has subsequently undergone little dynamical and collisional evolution. We identified 39 fragments, two of which are large and comparable in size (diameters of approximately 19 and approximately 14 km), with the remainder exhibiting a continuum of sizes in the range 2-7 km. The low measured ejection velocities suggest that gravitational re-accumulation after a collision may be a common feature of asteroid evolution. Moreover, these data can be used to check numerical models of larger-scale collisions.

Multiple-hopping trajectories near a rotating asteroid

NASA Astrophysics Data System (ADS)

Shen, Hong-Xin; Zhang, Tian-Jiao; Li, Zhao; Li, Heng-Nian

2017-03-01

We present a study of the transfer orbits connecting landing points of irregular-shaped asteroids. The landing points do not touch the surface of the asteroids and are chosen several meters above the surface. The ant colony optimization technique is used to calculate the multiple-hopping trajectories near an arbitrary irregular asteroid. This new method has three steps which are as follows: (1) the search of the maximal clique of candidate target landing points; (2) leg optimization connecting all landing point pairs; and (3) the hopping sequence optimization. In particular this method is applied to asteroids 433 Eros and 216 Kleopatra. We impose a critical constraint on the target landing points to allow for extensive exploration of the asteroid: the relative distance between all the arrived target positions should be larger than a minimum allowed value. Ant colony optimization is applied to find the set and sequence of targets, and the differential evolution algorithm is used to solve for the hopping orbits. The minimum-velocity increment tours of hopping trajectories connecting all the landing positions are obtained by ant colony optimization. The results from different size asteroids indicate that the cost of the minimum velocity-increment tour depends on the size of the asteroids.

Lightcurve Results for Eleven Asteroids

NASA Astrophysics Data System (ADS)

Gartrelle, Gordon M.

2012-04-01

Differential photometry techniques were used to develop lightcurves, rotation periods and amplitudes for eleven main-belt asteroids: 833 Monica, 962 Aslog, 1020 Arcadia, 1082 Pirola, 1097 Vicia, 1122 Lugduna, 1145 Robelmonte, 1253 Frisia, 1256 Normannia, 1525 Savolinna, and 2324 Janice. Ground-based observations from Badlands Observatory (BLO) in Quinn, SD, as well as the University of North Dakota Observatory (UND) in Grand Forks, ND, provided the data for the project. A search of the asteroid lightcurve database (LCDB) did not reveal any previously reported results for seven of the eleven targets in this study.

Mineralogy of dark clasts in primitive versus differentiated meteorites

NASA Technical Reports Server (NTRS)

Zolensky, M. E.; Weisberg, M. K.; Barrett, R. A.; Prinz, M.

1993-01-01

The presence of dark lithic clasts within meteorites can provide information concerning asteroidal regolith processes, the extent of interactions between asteroids, and the relationship between meteorite types, micrometeorites, and interplanetary dust particles. Accordingly, we have been seeking and characterizing dark clasts found within carbonaceous chondrites, unequilibrated ordinary chondrites, howardites, and eucrites. We find that unequilibrated chondrites in this study contain fine-grained, anhydrous unequilibrated inclusions, while the howardites often contain inclusions from geochemically processed, hydrous asteroids (type 1 and 2 carbonaceous chondrites). Eucrites and howardities contain unusual clasts, not easily classified.

THE PUZZLING MUTUAL ORBIT OF THE BINARY TROJAN ASTEROID (624) HEKTOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marchis, F.; Cuk, M.; Durech, J.

Asteroids with satellites are natural laboratories to constrain the formation and evolution of our solar system. The binary Trojan asteroid (624) Hektor is the only known Trojan asteroid to possess a small satellite. Based on W. M. Keck adaptive optics observations, we found a unique and stable orbital solution, which is uncommon in comparison to the orbits of other large multiple asteroid systems studied so far. From lightcurve observations recorded since 1957, we showed that because the large Req = 125 km primary may be made of two joint lobes, the moon could be ejecta of the low-velocity encounter, which formedmore » the system. The inferred density of Hektor's system is comparable to the L5 Trojan doublet (617) Patroclus but due to their difference in physical properties and in reflectance spectra, both captured Trojan asteroids could have a different composition and origin.« less

The nature of Trojan asteroid 624 Hektor

NASA Technical Reports Server (NTRS)

Hartmann, W. K.; Cruikshank, D. P.

1978-01-01

Near-simultaneous visual and thermal IR (20-micron) photometry of the Trojan asteroid 624 Hektor is reported which was performed when the asteroid was observed nearly along its rotation axis. The results confirm and refine the low albedo and large size of this asteroid and confirm the general rotational-pole position and aspect angle predicted by Dunlap and Gehrels (1969). Hektor is found to be a truly extraordinary object in that it is larger and far more irregular in shape than other measured Trojans and far more irregular than other belt asteroids of comparable size. It is proposed that Hektor could be a partially coalesced pair of Trojan asteroids which collided with energy too low to cause complete fragmentation, thus forming a dumbbell-shaped object. A possible scenario is outlined according to which the two pre-Hektor objects were neighboring relatively large primitive spheroidal planetesimals trapped in Jupiter's Lagrangian cloud. Observational and theoretical tests of this model are suggested.

Evidence for the late formation of hydrous asteroids from young meteoritic carbonates.

PubMed

Fujiya, Wataru; Sugiura, Naoji; Hotta, Hideyuki; Ichimura, Koji; Sano, Yuji

2012-01-17

The accretion of small bodies in the Solar System is a fundamental process that was followed by planet formation. Chronological information of meteorites can constrain when asteroids formed. Secondary carbonates show extremely old (53)Mn-(53)Cr radiometric ages, indicating that some hydrous asteroids accreted rapidly. However, previous studies have failed to define accurate Mn/Cr ratios; hence, these old ages could be artefacts. Here we develop a new method for accurate Mn/Cr determination, and report a reliable age of 4,563.4+0.4/-0.5 million years ago for carbonates in carbonaceous chondrites. We find that these carbonates have identical ages, which are younger than those previously estimated. This result suggests the late onset of aqueous activities in the Solar System. The young carbonate age cannot be explained if the parent asteroid accreted within 3 million years after the birth of the Solar System. Thus, we conclude that hydrous asteroids accreted later than differentiated and metamorphosed asteroids.

Direct and indirect capture of near-Earth asteroids in the Earth-Moon system

NASA Astrophysics Data System (ADS)

Tan, Minghu; McInnes, Colin; Ceriotti, Matteo

2017-09-01

Near-Earth asteroids have attracted attention for both scientific and commercial mission applications. Due to the fact that the Earth-Moon L1 and L2 points are candidates for gateway stations for lunar exploration, and an ideal location for space science, capturing asteroids and inserting them into periodic orbits around these points is of significant interest for the future. In this paper, we define a new type of lunar asteroid capture, termed direct capture. In this capture strategy, the candidate asteroid leaves its heliocentric orbit after an initial impulse, with its dynamics modeled using the Sun-Earth-Moon restricted four-body problem until its insertion, with a second impulse, onto the L2 stable manifold in the Earth-Moon circular restricted three-body problem. A Lambert arc in the Sun-asteroid two-body problem is used as an initial guess and a differential corrector used to generate the transfer trajectory from the asteroid's initial obit to the stable manifold associated with Earth-Moon L2 point. Results show that the direct asteroid capture strategy needs a shorter flight time compared to an indirect asteroid capture, which couples capture in the Sun-Earth circular restricted three-body problem and subsequent transfer to the Earth-Moon circular restricted three-body problem. Finally, the direct and indirect asteroid capture strategies are also applied to consider capture of asteroids at the triangular libration points in the Earth-Moon system.

Water and ice in asteroids: Connections between asteroid observations and the chondritic meteorite record

NASA Astrophysics Data System (ADS)

Schmidt, B.; Dyl, K.

2014-07-01

The mid-outer main belt is rich in possible parent bodies for the water-bearing carbonaceous chondrites, given their dark surfaces and frequent presence of hydrated minerals (e.g., Feierberg et al. 1985). Ceres (Thomas et al. 2005) and Pallas (Schmidt et al. 2009) possess shapes that indicate that these bodies have achieved hydrostatic equilibrium and may be differentiated (rock from ice). Dynamical calculations suggest asteroids formed rapidly to large sizes to produce the size frequency distribution within today's main belt (e.g., Morbidelli et al. 2009). Water-ice bound to organics has now been detected on the surface of Themis (Rivkin and Emery 2009, Campins et al. 2009), and indirect evidence for ice on many of the remaining family members, including main-belt comets (Hsieh & Jewitt 2006, Castillo-Rogez & Schmidt 2010), supports the theory that the ''C-class'' asteroids formed early and ice-rich. The carbonaceous chondrites represent a rich history of the thermal and aqueous evolution of early planetesimals (e.g., McSween 1979, Bunch and Chang, 1980, Zolensky and McSween 1988, Clayton 1993, Rowe et al., 1994). The composition of these meteorites reflects the timing and duration of water flow, as well as subsequent mineral alteration and isotopic evolution that can constrain temperature and water-rock ratios in which these systematics were set (e.g., Young et al. 1999, Dyl et al. 2012). Debate exists as to how the chemical and thermal consequences of fluid flow on carbonaceous chondrite parent bodies relate to parent-body characteristics: small, static water bodies (e.g., McSween 1979); small, convecting but homogeneous bodies (e.g., Young et al. 1999, 2003); or larger convecting bodies (e.g., Grimm and McSween 1989, Palguta et al. 2010). Heterogeneous thermal and aqueous evolution on larger asteroids that suggests more than one class of carbonaceous chondrite may be produced on the same body (e.g., Castillo-Rogez & Schmidt 2010, Elkins-Tanton et al. 2011, Schmidt & Castillo-Rogez 2012) if the chemical consequences can be reconciled (e.g., Young 2001, Young et al. 2003). Both models (Schmidt and Castillo-Rogez 2012) and experiments (e.g., Hiroi et al. 1996) suggest that water loss from asteroids is an important factor in interpreting the connections between the C-class asteroids and meteorites. The arrival of the Dawn spacecraft to Ceres will determine its much-debated internal structure and finally answer the following question: did large, icy planetesimals form and thermally evolve in the inner solar system? Even if Ceres is not icy, Dawn observations will shed light on its surface composition, and by extension on the surfaces of objects with similar surface properties. This presentation will focus on tying the observational evidence for water on evolving and contemporary asteroids with detailed studies of the carbonaceous chondrites in an effort to synthesize physical and chemical realities with the observational record, bridging the gap between the asteroid and meteorite communities.

Identification and Calculation of the Three-Dimensional Orbit of an Asteroid

ERIC Educational Resources Information Center

Pereira, Vincent; Millan, Justin; Martin, Emerick

2013-01-01

Asteroids are clumps of rock, the sizes of which range from less than a kilometer to a few hundred kilometers in diameter. They are generally found in the unusually large gap between Mars and Jupiter. There are probably more than 40,000 asteroids in this gap called the "asteroid belt." In this paper we describe our efforts in confirming…

Laser Simulations of the Destructive Impact of Nuclear Explosions on Hazardous Asteroids

NASA Astrophysics Data System (ADS)

Aristova, E. Yu.; Aushev, A. A.; Baranov, V. K.; Belov, I. A.; Bel'kov, S. A.; Voronin, A. Yu.; Voronich, I. N.; Garanin, R. V.; Garanin, S. G.; Gainullin, K. G.; Golubinskii, A. G.; Gorodnichev, A. V.; Denisova, V. A.; Derkach, V. N.; Drozhzhin, V. S.; Ericheva, I. A.; Zhidkov, N. V.; Il'kaev, R. I.; Krayukhin, A. A.; Leonov, A. G.; Litvin, D. N.; Makarov, K. N.; Martynenko, A. S.; Malinov, V. I.; Mis'ko, V. V.; Rogachev, V. G.; Rukavishnikov, A. N.; Salatov, E. A.; Skorochkin, Yu. V.; Smorchkov, G. Yu.; Stadnik, A. L.; Starodubtsev, V. A.; Starodubtsev, P. V.; Sungatullin, R. R.; Suslov, N. A.; Sysoeva, T. I.; Khatunkin, V. Yu.; Tsoi, E. S.; Shubin, O. N.; Yufa, V. N.

2018-01-01

We present the results of preliminary experiments at laser facilities in which the processes of the undeniable destruction of stony asteroids (chondrites) in space by nuclear explosions on the asteroid surface are simulated based on the principle of physical similarity. We present the results of comparative gasdynamic computations of a model nuclear explosion on the surface of a large asteroid and computations of the impact of a laser pulse on a miniature asteroid simulator confirming the similarity of the key processes in the fullscale and model cases. The technology of fabricating miniature mockups with mechanical properties close to those of stony asteroids is described. For mini-mockups 4-10 mm in size differing by the shape and impact conditions, we have made an experimental estimate of the energy threshold for the undeniable destruction of a mockup and investigated the parameters of its fragmentation at a laser energy up to 500 J. The results obtained confirm the possibility of an experimental determination of the criteria for the destruction of asteroids of various types by a nuclear explosion in laser experiments. We show that the undeniable destruction of a large asteroid is possible at attainable nuclear explosion energies on its surface.

Retrograde spins of near-Earth asteroids from the Yarkovsky effect.

PubMed

La Spina, A; Paolicchi, P; Kryszczyńska, A; Pravec, P

2004-03-25

Dynamical resonances in the asteroid belt are the gateway for the production of near-Earth asteroids (NEAs). To generate the observed number of NEAs, however, requires the injection of many asteroids into those resonant regions. Collisional processes have long been claimed as a possible source, but difficulties with that idea have led to the suggestion that orbital drift arising from the Yarkovsky effect dominates the injection process. (The Yarkovsky effect is a force arising from differential heating-the 'afternoon' side of an asteroid is warmer than the 'morning' side.) The two models predict different rotational properties of NEAs: the usual collisional theories are consistent with a nearly isotropic distribution of rotation vectors, whereas the 'Yarkovsky model' predicts an excess of retrograde rotations. Here we report that the spin vectors of NEAs show a strong and statistically significant excess of retrograde rotations, quantitatively consistent with the theoretical expectations of the Yarkovsky model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szabó, R.; Sárneczky, K.; Szabó, Gy. M.

Unlike NASA’s original Kepler Discovery Mission, the renewed K2 Mission will target the plane of the Ecliptic, observing each field for approximately 75 days. This will bring new opportunities and challenges, in particular the presence of a large number of main-belt asteroids that will contaminate the photometry. The large pixel size makes K2 data susceptible to the effects of apparent minor planet encounters. Here, we investigate the effects of asteroid encounters on photometric precision using a subsample of the K2 engineering data taken in 2014 February. We show examples of asteroid contamination to facilitate their recognition and distinguish these eventsmore » from other error sources. We conclude that main-belt asteroids will have considerable effects on K2 photometry of a large number of photometric targets during the Mission that will have to be taken into account. These results will be readily applicable for future space photometric missions applying large-format CCDs, such as TESS and PLATO.« less

A Study of the Effects of Faint Dust Comae on the Spectra of Asteroids

NASA Astrophysics Data System (ADS)

Rondón, E.; Carvano, J.; Lorenz-Martins, S.

2017-09-01

The presence of dust comae on asteroids and centaurs is a phenomenon that became accepted in the last decades and which challenges the traditional definitions of asteroids and comets. A possible way of improving the chances of discovery of Active Asteroids is to use large multi-colour surveys or catalogs, like SDSS Moving Object Catalog. In this work we analyze the effects of faint dust comae on asteroid spectra and then use it to investigate the effects that a faint dust comae would have over the spectrum, magnitude, and radial profile of asteroids.

Calculation methods for estimating the prospects of a space experiment by means of impact by asteroid Apophis on the Moon surface

NASA Astrophysics Data System (ADS)

Ostrik, A. V.; Kazantsev, A. M.

2018-01-01

The problem of principal change of asteroid 99952 (Apophis) orbit is formulated. Aim of this change is the termination of asteroid motion in Solar system. Instead of the passive rescue tactics from asteroid threat, an option is proposed for using the asteroid for setting up a large-scale space experiment on the impact interaction of the asteroid with the Moon. The scientific and methodical apparatus for calculating the possibility of realization, searching and justification the scientific uses of this space experiment is considered.

NASA's Asteroid Redirect Mission (ARM)

NASA Technical Reports Server (NTRS)

Abell, P. A.; Mazanek, D. D.; Reeves, D. M.; Chodas, P. W.; Gates, M. M.; Johnson, L. N.; Ticker, R. L.

2017-01-01

Mission Description and Objectives: NASA's Asteroid Redirect Mission (ARM) consists of two mission segments: 1) the Asteroid Redirect Robotic Mission (ARRM), a robotic mission to visit a large (greater than approximately 100 meters diameter) near-Earth asteroid (NEA), collect a multi-ton boulder from its surface along with regolith samples, and return the asteroidal material to a stable orbit around the Moon; and 2) the Asteroid Redirect Crewed Mission (ARCM), in which astronauts will explore and investigate the boulder and return to Earth with samples. The ARRM is currently planned to launch at the end of 2021 and the ARCM is scheduled for late 2026.

Electromagnetic Scattering Analysis of Large Size Asteroids/Comets for Reflection/Transmission Tomography (RTT)

NASA Technical Reports Server (NTRS)

Deshpande, Manohar

2011-01-01

A precise knowledge of the interior structure of asteroids, comets, and Near Earth Objects (NEO) is important to assess the consequences of their impacts with the Earth and develop efficient mitigation strategies. Knowledge of their interior structure also provides opportunities for extraction of raw materials for future space activities. Low frequency radio sounding is often proposed for investigating interior structures of asteroids and NEOs. For designing and optimizing radio sounding instrument it is advantageous to have an accurate and efficient numerical simulation model of radio reflection and transmission through large size bodies of asteroid shapes. In this presentation we will present electromagnetic (EM) scattering analysis of electrically large size asteroids using (1) a weak form formulation and (2) also a more accurate hybrid finite element method/method of moments (FEM/MOM) to help estimate their internal structures. Assuming the internal structure with known electrical properties of a sample asteroid, we first develop its forward EM scattering model. From the knowledge of EM scattering as a function of frequency and look angle we will then present the inverse scattering procedure to extract its interior structure image. Validity of the inverse scattering procedure will be presented through few simulation examples.

The breakup of a main-belt asteroid 450 thousand years ago.

PubMed

Nesvorný, David; Vokrouhlický, David; Bottke, William F

2006-06-09

Collisions in the asteroid belt frequently lead to catastrophic breakups, where more than half of the target's mass is ejected into space. Several dozen large asteroids have been disrupted by impacts over the past several billion years. These impact events have produced groups of fragments with similar orbits called asteroid families. Here we report the discovery of a very young asteroid family around the object 1270 Datura. Our work takes advantage of a method for identification of recent breakups in the asteroid belt using catalogs of osculating (i.e., instantaneous) asteroid orbits. The very young families show up in these catalogs as clusters in a five-dimensional space of osculating orbital elements.

Qualitative and quantitative behaviour of planetary systems; Proceedings of the 3rd Alexander von Humboldt Colloquium on Celestial Mechanics, Ramsau, Austria, Mar. 29-Apr. 4, 1992

NASA Astrophysics Data System (ADS)

Dvorak, R.; Henrard, J.

1993-06-01

Topics addressed include planetary theories, the Sitnikov problem, asteroids, resonance, general dynamical systems, and chaos and stability. Particular attention is given to recent progress in the theory and application of symplectic integrators, a computer-aided analysis of the Sitnikov problem, the chaotic behavior of trajectories for the asteroidal resonances, and the resonant motion in the restricted three-body problem. Also discussed are the second order long-period motion of Hyperion, meteorites from the asteroid 6 Hebe, and least squares parameter estimation in chaotic differential equations.

Bayesian modeling of the mass and density of asteroids

NASA Astrophysics Data System (ADS)

Dotson, Jessie L.; Mathias, Donovan

2017-10-01

Mass and density are two of the fundamental properties of any object. In the case of near earth asteroids, knowledge about the mass of an asteroid is essential for estimating the risk due to (potential) impact and planning possible mitigation options. The density of an asteroid can illuminate the structure of the asteroid. A low density can be indicative of a rubble pile structure whereas a higher density can imply a monolith and/or higher metal content. The damage resulting from an impact of an asteroid with Earth depends on its interior structure in addition to its total mass, and as a result, density is a key parameter to understanding the risk of asteroid impact. Unfortunately, measuring the mass and density of asteroids is challenging and often results in measurements with large uncertainties. In the absence of mass / density measurements for a specific object, understanding the range and distribution of likely values can facilitate probabilistic assessments of structure and impact risk. Hierarchical Bayesian models have recently been developed to investigate the mass - radius relationship of exoplanets (Wolfgang, Rogers & Ford 2016) and to probabilistically forecast the mass of bodies large enough to establish hydrostatic equilibrium over a range of 9 orders of magnitude in mass (from planemos to main sequence stars; Chen & Kipping 2017). Here, we extend this approach to investigate the mass and densities of asteroids. Several candidate Bayesian models are presented, and their performance is assessed relative to a synthetic asteroid population. In addition, a preliminary Bayesian model for probablistically forecasting masses and densities of asteroids is presented. The forecasting model is conditioned on existing asteroid data and includes observational errors, hyper-parameter uncertainties and intrinsic scatter.

IS THE LARGE CRATER ON THE ASTEROID (2867) STEINS REALLY AN IMPACT CRATER?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, A. J. W.; Price, M. C.; Burchell, M. J., E-mail: m.j.burchell@kent.ac.uk

The large crater on the asteroid (2867) Steins attracted much attention when it was first observed by the Rosetta spacecraft in 2008. Initially, it was widely thought to be unusually large compared to the size of the asteroid. It was quickly realized that this was not the case and there are other examples of similar (or larger) craters on small bodies in the same size range; however, it is still widely accepted that it is a crater arising from an impact onto the body which occurred after its formation. The asteroid (2867) Steins also has an equatorial bulge, usually consideredmore » to have arisen from redistribution of mass due to spin-up of the body caused by the YORP effect. Conversely, it is shown here that, based on catastrophic disruption experiments in laboratory impact studies, a similarly shaped body to the asteroid Steins can arise from the break-up of a parent in a catastrophic disruption event; this includes the presence of a large crater-like feature and equatorial bulge. This suggests that the large crater-like feature on Steins may not be a crater from a subsequent impact, but may have arisen directly from the fragmentation process of a larger, catastrophically disrupted parent.« less

26Al-26Mg systematics in chondrules from Kaba and Yamato 980145 CV3 carbonaceous chondrites

NASA Astrophysics Data System (ADS)

Nagashima, Kazuhide; Krot, Alexander N.; Komatsu, Mutsumi

2017-03-01

We report the mineralogy, petrography, and in situ measured 26Al-26Mg systematics in chondrules from the least metamorphosed CV3 (Vigarano-type) chondrites, Kaba and Yamato (Y) 980145. Two Y 980145 chondrules measured show no resolvable excesses in 26Mg (26Mg∗), a decay product of a short-lived (t1/2 ∼0.7 Ma) radionuclide 26Al. Plagioclase in one of the chondrules is replaced by nepheline, indicative of thermal metamorphism. The lack of 26Mg∗ in the Y 980145 chondrules is most likely due to disturbance of their 26Al-26Mg systematics during the metamorphism. Although Kaba experienced extensive metasomatic alteration (<300 °C), it largely avoided subsequent thermal metamorphism, and the 26Al-26Mg systematics of its chondrules appear to be undisturbed. All eight Kaba chondrules measured show 26Mg∗, corresponding to the initial 26Al/27Al ratios [(26Al/27Al)0] ranging from (2.9 ± 1.7) × 10-6 to (6.3 ± 2.7) × 10-6. If CV parent asteroid accreted rapidly after chondrule formation, the inferred (26Al/27Al)0 ratios in Kaba chondrules provide an upper limit on 26Al available in this asteroid at the time of its accretion. The estimated initial abundance of 26Al in the CV asteroid is too low to melt it and contradicts the existence of a molten core in this body suggested from the paleomagnetic records of Allende [Carporzen et al. (2011) Magnetic evidence for a partially differentiated carbonaceous chondrite parent body. Proc. Natl. Acad. Sci. USA108, 6386-6389] and Kaba [Gattacceca et al. (2013) More evidence for a partially differentiated CV parent body from the meteorite Kaba. Lunar Planet. Sci.44, abstract#1721].

Asteroidal Differentiation Processes Deduced from Ultramafic Achondrite Ureilite Meteorites

NASA Technical Reports Server (NTRS)

Downes, Hilary; Mittlefehldt, David W.; Hudson, Pierre; Romanek, Christopher S.; Franchi, Ian

2006-01-01

Ureilites are the second largest achondrite group. They are ultramafic achondrites that have experienced igneous processing whilst retaining some degree of nebula-derived chemical heterogeneity. They differ from other achondrites in that they contain abundant carbon and their oxygen isotope compositions are very heterogeneous and similar to those of the carbonaceous chondrite anhydrous mineral line. Their carbonaceous nature and some compositional characteristics indicative of nebular origin suggest that they are primitive materials that form a link between nebular processes and early periods of planetesimal accretion. However, despite numerous studies, the exact origin of ureilites remains unclear. Current opinion is that they represent the residual mantle of an asteroid that underwent silicate and Fe-Ni-S partial melting and melt removal. Recent studies of short-lived chronometers indicate that the parent asteroid of the ureilites differentiated very early in the history of the Solar System. Therefore, they contain important information about processes that formed small rocky planetesimals in the early Solar System. In effect, they form a bridge between nebula processes and differentiation in small planetesimals prior to accretion into larger planets and so a correct interpretation of ureilite petrogenesis is essential for understanding this critical step.

The Nature of C Asteroid Regolith from Meteorite Observations

NASA Technical Reports Server (NTRS)

Zolensky, M.; Mikouchi, T.; Hagiya, K.; Ohsumi, K.; Komatsu, M.; Jenniskens, P.; Le, L.; Yin, Q.-Z; Kebukawa, Y.; Fries, M.

2013-01-01

Regolith from C (and related) asteroid bodies are a focus of the current missions Dawn at Ceres, Hayabusa 2 and OSIRIS REx. An asteroid as large as Ceres is expected to be covered by a mature regolith, and as Hayabusa demonstrated, flat and therefore engineeringly-safe ponded deposits will probably be the sampling sites for both Hayabusa 2 and OSIRIS REx. Here we examine what we have learned about the mineralogy of fine-grained asteroid regolith from recent meteorite studies and the examination of the samples harvested from asteroid Itokawa by Hayabusa.

Collision rates and impact velocities in the Main Asteroid Belt

NASA Technical Reports Server (NTRS)

Farinella, Paolo; Davis, Donald R.

1992-01-01

Wetherill's (1967) algorithm is presently used to compute the mutual collision probabilities and impact velocities of a set of 682 asteroids with large-than-50-km radius representative of a bias-free sample of asteroid orbits. While collision probabilities are nearly independent of eccentricities, a significant decrease is associated with larger inclinations. Collisional velocities grow steeply with orbital eccentricity and inclination, but with curiously small variation across the asteroid belt. Family asteroids are noted to undergo collisions with other family members 2-3 times more often than with nonmembers.

Mining the apollo and amor asteroids.

PubMed

O'leary, B

1977-07-22

Earth-approaching asteroids could provide raw materials for space manufacturing. For certain asteroids the total energy per unit mass for the transfer of asteroidal resources to a manufacturing site in high Earth orbit is comparable to that for lunar materials. For logistical reasons the cost may be many times less. Optical studies suggest that these asteroids have compositions corresponding to those of carbonaceous and ordinary chondrites, with some containing large quantities of iron and nickel; others are thought to contain carbon, nitrogen, and hydrogen, elements that appear to be lacking on the moon. The prospect that several new candidate asteroids will be discovered over the next few years increases the likelihood that a variety of asteroidal resource materials can be retrieved on low-energy missions.

Mining the Apollo and Amor asteroids

NASA Technical Reports Server (NTRS)

Oleary, B.

1977-01-01

Earth-approaching asteroids could provide raw materials for space manufacturing. For certain asteroids the total energy per unit mass for the transfer of asteroidal resources to a manufacturing site in high earth orbit is comparable to that for lunar materials. For logistical reasons the cost may be many times less. Optical studies suggest that these asteroids have compositions corresponding to those of carbonaceous and ordinary chondrites, with some containing large quantities of iron and nickel; other are thought to contain carbon, nitrogen, and hydrogen, elements that appear to be lacking on the moon. The prospect that several new candidate asteroids will be discovered over the next few years increases the likelihood that a variety of asteroidal resource materials can be retrieved on low-energy missions.

Photometric geodesy of main-belt asteroids. I - Lightcurves of 26 large, rapid rotators

NASA Technical Reports Server (NTRS)

Weidenschilling, S. J.; Chapman, C. R.; Davis, D. R.; Greenberg, R.; Levy, D. H.

1987-01-01

A 'photometric geodesy' program is selected on the basis of light-curve data from five years' observations of large, rapidly rotating asteroids, where the observing protocol was designed to obtain precise, absolute photometry at a wide variety of orbital longitudes and phase angles. A total of 257 complete or partial light-curves are obtained for 26 asteroids; the data set will allow the future determination of pole positions and shapes, as well as to constrain the geophysical traits of these bodies.

The compositional diversity of non-Vesta basaltic asteroids

NASA Astrophysics Data System (ADS)

Leith, Thomas B.; Moskovitz, Nicholas A.; Mayne, Rhiannon G.; DeMeo, Francesca E.; Takir, Driss; Burt, Brian J.; Binzel, Richard P.; Pefkou, Dimitra

2017-10-01

We present near-infrared (0.78-2.45 μm) reflectance spectra for nine middle and outer main belt (a > 2.5 AU) basaltic asteroids. Three of these objects are spectrally distinct from all classifications in the Bus-DeMeo system and could represent spectral end members in the existing taxonomy or be representatives of a new spectral type. The remainder of the sample are classified as V- or R-type. All of these asteroids are dynamically detached from the Vesta collisional family, but are too small to be intact differentiated parent bodies, implying that they originated from differentiated planetesimals which have since been destroyed or ejected from the solar system. The 1- and 2-μm band centers of all objects, determined using the Modified Gaussian Model (MGM), were compared to those of 47 Vestoids and fifteen HED meteorites of known composition. The HEDs enabled us to determine formulas relating Band 1 and Band 2 centers to pyroxene ferrosilite (Fs) compositions. Using these formulas we present the most comprehensive compositional analysis to date of middle and outer belt basaltic asteroids. We also conduct a careful error analysis of the MGM-derived band centers for implementation in future analyses. The six outer belt V- and R-type asteroids show more dispersion in parameter space than the Vestoids, reflecting greater compositional diversity than Vesta and its associated bodies. The objects analyzed have Fs numbers which are, on average, between five and ten molar percent lower than those of the Vestoids; however, identification and compositional analysis of additional outer belt basaltic asteroids would help to confirm or refute this result. Given the gradient in oxidation state which existed within the solar nebula, these results tentatively suggest that these objects formed at either a different time or location than 4 Vesta.

Dynamical Origin and Terrestrial Impact Flux of Large Near-Earth Asteroids

NASA Astrophysics Data System (ADS)

Nesvorný, David; Roig, Fernando

2018-01-01

Dynamical models of the asteroid delivery from the main belt suggest that the current impact flux of diameter D> 10 km asteroids on the Earth is ≃0.5–1 Gyr‑1. Studies of the Near-Earth Asteroid (NEA) population find a much higher flux, with ≃ 7 D> 10 km asteroid impacts per Gyr. Here we show that this problem is rooted in the application of impact probability of small NEAs (≃1.5 Gyr‑1 per object), whose population is well characterized, to large NEAs. In reality, large NEAs evolve from the main belt by different escape routes, have a different orbital distribution, and lower impact probabilities (0.8 ± 0.3 Gyr‑1 per object) than small NEAs. In addition, we find that the current population of two D> 10 km NEAs (Ganymed and Eros) is a slight fluctuation over the long-term average of 1.1+/- 0.5 D> 10 km NEAs in a steady state. These results have important implications for our understanding of the occurrence of the K/T-scale impacts on the terrestrial worlds.

New Insights on 216 Kleopatra Based on Images Collected with the SPHERE Extreme AO System

NASA Astrophysics Data System (ADS)

Marchis, F.; Vernazza, P.; Hanus, J.; Marsset, M.; Yang, B.; Carry, B.; Santana-Ros, T.; Birlan, M.

2017-12-01

ESO allocated to our Large Asteroid Survey with SPHERE (LASS) program 152 hours of observations over four semesters (PI: Pierre Vernazza, run ID: 199.C-0074) to carry out disk-resolved images of 38 large (D≥100 km) main-belt asteroids (sampling the four main compositional classes) at high angular- resolution with VLT/SPHERE throughout their rotation in order to derive their 3-D shape, the size distribution of the largest craters, and their density. Here we focus on the analysis of SPHERE data taken in July 2017 of the triple asteroid (216) Kleopatra. Two tiny moons (3 & 5 km diameter) were discovered in September 2008 around the large (equivalent radius 67.5±2.9 km) M-type asteroid orbiting very close to the irregularly shaped primary at 300 and 700 km respectively (Descamps et al. 2010). With these additional data, our goals are i) to refine the average density of this interesting M-type asteroid ii) estimate its interior structure by detecting precession effects between the satellites iii) detect the presence of an additional moon which was suspected in W.M. Keck AO observation taken back in 2008. We will present this new data set, their analysis and new conclusion on the origins and formation of this asteroid.

Using ANTS to explore small body populations in the solar system.

NASA Astrophysics Data System (ADS)

Clark, P. E.; Rilee, M.; Truszkowski, W.; Curtis, S.; Marr, G.; Chapman, C.

2001-11-01

ANTS (Autonomous Nano-Technology Swarm), a NASA advanced mission concept, is a large (100 to 1000 member) swarm of pico-class (1 kg) totally autonomous spacecraft that prospect the asteroid belt. Little data is available for asteroids because the vast majority are too small to be observed except in close proximity. Light curves are available for thousands of asteroids, confirmed trajectories for tens of thousands, detailed shape models for approximately ten. Asteroids originated in the transitional region between the inner (rocky) and outer (solidified gases) solar system. Many have remained largely unmodified since formation, and thus have more primitive composition than planetary surfaces. Determination of the systematic distribution of physical and compositional properties within the asteroid population is crucial in the understanding of solar system formation. The traditional exploration approach of using few, large spacecraft for sequential exploration, could be improved. Our far more cost-effective approach utilizes distributed intelligence in a swarm of tiny highly maneuverable spacecraft, each with specialized instrument capability (e.g., advanced computing, imaging, spectrometry). NASA is at the forefront of Intelligent Software Agents (ISAs) research, performing experiments in space and on the ground to advance deliberative and collaborative autonomous control techniques. The advanced development under consideration here is in the use of ISAs at a strategic level, to explore remote frontiers of the solar system, potentially involving a large class of objects such as asteroids. Supervised clusters of spacecraft operate simultaneously within a broadly defined framework of goals to select targets (> 1000) from among available candidates while developing scenarios for studying targets. Swarm members use solar sails to fly directly to asteroids > 1 kilometer in diameter, and then perform maneuvers appropriate for the instrument carried, ranging from hovering to orbiting. Selected members return with data and are replaced as needed.

Vesta and Ceres

NASA Astrophysics Data System (ADS)

Righter, Kevin

2018-04-01

Asteroids 1 Ceres and 4 Vesta are the two largest asteroids in the asteroid belt, with mean diameters of 946 km and 525 km, respectively. Ceres was reclassified as a dwarf planet by the IAU (International Astronomical Union) as a result of their new dwarf planet definition, which is a body that (a) orbits the sun, (b) has enough mass to assume a nearly round shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a moon. Our understanding of these two bodies has been revolutionized in the last decade by the success of the Dawn mission that visited both bodies. Vesta is an example of a small body that has been heated substantially, and differentiated into a metallic core, silicate mantle, and basaltic crust. Ceres is a volatile-rich rocky body that did not experience significant heating and therefore has only partially differentiated. These two contrasting bodies have been instrumental in learning how inner solar system material formed and evolved.

A low-density M-type asteroid in the main belt.

PubMed

Margot, J L; Brown, M E

2003-06-20

The orbital parameters of a satellite revolving around 22 Kalliope indicate that the bulk density of this main-belt asteroid is 2.37 +/- 0.4 grams per cubic centimeter. M-type asteroids such as Kalliope are thought to be the disrupted metallic cores of differentiated bodies. The low-density indicates that Kalliope cannot be predominantly composed of metal and may be composed of chondritic material with approximately 30% porosity. The satellite orbit is circular, suggesting that Kalliope and its satellite have different internal structures and tidal dissipation rates. The satellite may be an aggregate of impact ejecta from an earlier collision with Kalliope.

Exogenous origin of hydration on asteroid (16) Psyche: the role of hydrated asteroid families

NASA Astrophysics Data System (ADS)

Avdellidou, C.; Delbo', M.; Fienga, A.

2018-04-01

Asteroid (16) Psyche, which for a long time was the largest M-type with no detection of hydration features in its spectrum, was recently discovered to have a weak 3-μm band and thus it was eventually added to the group of hydrated asteroids. Its relatively high density, in combination with the high radar albedo, led researchers to classify the asteroid as a metallic object. It is believed that it is possibly a core of a differentiated body, a remnant of `hit-and-run' collisions. The detection of hydration is, in principle, inconsistent with a pure metallic origin for this body. Here, we consider the scenario in which the hydration on its surface is exogenous and was delivered by hydrated impactors. We show that impacting asteroids that belong to families whose members have the 3-μm band can deliver hydrated material to Psyche. We developed a collisional model with which we test all dark carbonaceous asteroid families, which contain hydrated members. We find that the major source of hydrated impactors is the family of Themis, with a total implanted mass on Psyche of the order of ˜1014 kg. However, the hydrated fraction could be only a few per cent of the implanted mass, as the water content in carbonaceous chondrite meteorites, the best analogue for the Themis asteroid family, is typically a few per cent of their mass.

Orbital and Landing Operations at Near-Earth

NASA Technical Reports Server (NTRS)

Scheeres, D. J.

1995-01-01

Orbital and landing operations about near-Earth asteroids are different than classical orbital operations about large bodies. The major differences lie with the small mass of the asteroid, the lower orbital velocities, the larger Solar tide and radiation pressure perturbations, the irregular shape of the asteroid and the potential for non-uniform rotation of the asteroid. These differences change the nature of orbits about an asteroid to where it is often common to find trajectories that evolve from stable, near-circular orbits to crashing or escaping orbits in a matter of days. The understanding and control of such orbits is important if a human or robotic presence at asteroids is to be commonplace in the future.

Meteoritical Implications of the Vesta Asteroid Family

NASA Astrophysics Data System (ADS)

Bell, J. F.

1993-07-01

The discovery of a large dynamical family of basaltic asteroids associated with Vesta and extending to the 3:1 Jupiter resonance [1] provides firm evidence at last that Vesta is the actual parent body of the basaltic achondrite meteorites [2]. This discovery raises several interesting questions. The Vesta family demonstrates that objects as large as ~10km can be ejected from large asteroids at velocities up to 500 m/sec, which is adequate to deliver material to a strong resonance from almost anywhere in the asteroid belt. However, most other asteroid families show a much smaller range of ejection velocities and a more symmetrical distribution of the fragments in orbital element space. These families probably come from complete disruption of parent bodies, which would therefore appear to be the dominant process. Meteoritical evidence is also relevant. There are at least six large dunite (A-class) asteroids, only one of which is providing brachinites to the Earth. Even more striking, the Nysa asteroid family is predominantly composed of the mysterious F-class asteroids, which have no meteorite analog at all. The evidence suggests that the Vesta event is atypical and that there is considerable bias in meteorite delivery. The family is extended in a but narrowly confined in e and i. Curiously, Vesta is not at one end but in the middle. The very narrow sunward leg of the family contains a rare pure-olivine (Class A) asteroid among the many eucrites (Class V) and diogenites (Class J), while in the more diffuse anti-sunward leg no olivine objects have yet been found. This mineral distribution mimics the mineral map of Vesta derived from telescopic spectroscopy [3], in which a small olivine spot is semi-antipodal to a large diogenite patch. This suggests that the sunward leg is direct ejecta from a large crater, while the anti-sunward leg (and the populartion of HEDs reaching Earth) is composed of crustal fragments spalled off by focused shock waves. This mechanism is well-known from lab experiments [4] and probably causes the jumbled terrain antipodal to impact basins on the Moon and Mercury. Finally, it is now clear that the association between the HED clan and the pallasites is coincidental. We may expect many more such false genetic links between meteorite classes as more oxygen isotope data is obtained. References: [1] Binzel R. P. and Xu S. (1993) Science, 260, 186- 191. [2] Gaffey M. J. (1993) Science, 260, 167-168. [3] Gaffey M. J. (1983) LPS XIV, 231-232. [4] Horz F. and Schaal R. B. (1981) Icarus, 46, 337-353.

New Analysis Of The Baptistina Asteroid Family: Implications For Its Link With The K/t Impactor

NASA Astrophysics Data System (ADS)

Delbo, Marco; Nesvorny, D.; Licandro, J.; Ali-Lagoa, V.

2012-10-01

The Baptistina Asteroid Family (BAF) is the result of the breakup of an asteroid roughly 100 million years ago. This family is the source of meteoroids and near-Earth asteroids and likely caused an asteroid shower of impactors on our Earth. Bottke et al. (2007) proposed a link between the BAF and the K/T impactor, based on the favorable timing, large probability of a terrestrial impact of one 10-km BAF asteroid, and the Sloan colors of the BAF members, indicating that the BAF may have composition consistent with the K/T impactor (CM2-type carbonaceous meteorite, as inferred from chromium studies at different K/T boundary sites; Alvarez et al. 1980, Kring et al. 2007). The relationship between the BAF and K/T impactor is now controversial. Masiero et al. (2011) found that the albedo of BAF family members is 0.15, significantly higher than expected for a dark carbonaceous parent body. Also, Reddy et al. (2011) reported the spectroscopic observations of (298) Baptistina and objects in the general neighborhood of the BAF, and suggested the BAF includes a mixture of spectroscopic types that is not very different from the background (mostly S-type asteroids in the background Flora family). Unfortunately, Reddy et al. observed only the large asteroids near (298) Baptistina, and not the K/T-impactor-size BAF members with D 10 km. Using WISE albedos, Sloan colors and newly obtained spectroscopic observations of BAF members, here we show that (1) the large objects in the BAF are mostly BAF interlopers, (2) that BAF has an homogeneous composition consistent with an X-type class. We discuss the implications of the link between the BAF and the K/T impactor.

Multiple Asteroid Systems: Dimensions and Thermal Properties from Spitzer Space Telescope and Ground-based Observations

NASA Technical Reports Server (NTRS)

Marchis, F.; Enriquez, J. E.; Emery, J. P.; Mueller, M.; Baek, M.; Pollock, J.; Assafin, M.; Matins, R. Vieira; Berthier, J.; Vachier, F.;

Both size-frequency distribution and sub-populations of the main-belt asteroid population are consistent with YORP-induced rotational fission

NASA Astrophysics Data System (ADS)

Jacobson, S.; Scheeres, D.; Rossi, A.; Marzari, F.; Davis, D.

2014-07-01

From the results of a comprehensive asteroid-population-evolution model, we conclude that the YORP-induced rotational-fission hypothesis has strong repercussions for the small size end of the main-belt asteroid size-frequency distribution and is consistent with observed asteroid-population statistics and with the observed sub-populations of binary asteroids, asteroid pairs and contact binaries. The foundation of this model is the asteroid-rotation model of Marzari et al. (2011) and Rossi et al. (2009), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis (i.e. when the rotation rate exceeds a critical value, erosion and binary formation occur; Scheeres 2007) and binary-asteroid evolution (Jacobson & Scheeres, 2011). The YORP-effect timescale for large asteroids with diameters D > ˜ 6 km is longer than the collision timescale in the main belt, thus the frequency of large asteroids is determined by a collisional equilibrium (e.g. Bottke 2005), but for small asteroids with diameters D < ˜ 6 km, the asteroid-population evolution model confirms that YORP-induced rotational fission destroys small asteroids more frequently than collisions. Therefore, the frequency of these small asteroids is determined by an equilibrium between the creation of new asteroids out of the impact debris of larger asteroids and the destruction of these asteroids by YORP-induced rotational fission. By introducing a new source of destruction that varies strongly with size, YORP-induced rotational fission alters the slope of the size-frequency distribution. Using the outputs of the asteroid-population evolution model and a 1-D collision evolution model, we can generate this new size-frequency distribution and it matches the change in slope observed by the SKADS survey (Gladman 2009). This agreement is achieved with both an accretional power-law or a truncated ''Asteroids were Born Big'' size-frequency distribution (Weidenschilling 2010, Morbidelli 2009). The binary-asteroid evolution model is highly constrained by the modeling done in Jacobson & Scheeres, and therefore the asteroid-population evolution model has only two significant free parameters: the ratio of low-to-high-mass-ratio binaries formed after rotational fission events and the mean strength of the binary YORP (BYORP) effect. Using this model, we successfully reproduce the observed small-asteroid sub-populations, which orthogonally constrain the two free parameters. We find the outcome of rotational fission most likely produces an initial mass-ratio fraction that is four to eight times as likely to produce high-mass-ratio systems as low-mass-ratio systems, which is consistent with rotational fission creating binary systems in a flat distribution with respect to mass ratio. We also find that the mean of the log-normal BYORP coefficient distribution B ≈ 10^{-2}.

Mineralogy of Inverted Pigeonite and Plagioclase in Cumulate Eucrites Y-980433 and Y-980318 with Reference to Early Crust Formation of the Vesta-Like Body

NASA Technical Reports Server (NTRS)

Takeda, H.; Ohtake, M.; Hiroi, T.; Nyquist, L. E.; Shih, C.-Y.; Yamaguchi, A.; Nagaoka, H.

2011-01-01

On July 16, the Dawn spacecraft became the first probe to enter orbit around asteroid 4 Vesta and will study the asteroid for a year before departing for Ceres. The Vesta-HED link is directly tied to the observed and inferred mineralogy of the asteroid and the mineralogy of the meteorites [1]. Pieters et al. [2] reported reflectance spectra of the Yamato- (Y-)980318 cumulate eucrite as a part of their study on the Asteroid-Meteorite Links in connection with the Dawn Mission. Pyroxenes and calcic plagioclase are the dominant minerals present in HED meteorites and provide multiple clues about how the parent body evolved [1]. The differentiation trends of HED meteorites are much simpler than those of the lunar crust

Analysis of GSC 2475-1587 and GSC 841-277: Two Eclipsing Binary Stars Found During Asteroid Lightcurve Observations

NASA Astrophysics Data System (ADS)

Stephens, R. D.; Warner, B. D.

2006-05-01

When observing asteroids we select from two to five comparison stars for differential photometry, taking the average value of the comparisons for the single value to be subtracted from the value for the asteroid. As a check, the raw data of each comparison star are plotted as is the difference between any single comparison and the average of the remaining stars in the set. On more than one occasion, we have found that at least one of the comparisons was variable. In two instances, we took time away from our asteroid lightcurve work to determine the period of the two binaries and attempted to model the system using David Bradstreet's Binary Maker 3. Unfortunately, neither binary showed a total eclipse. Therefore, our results are not conclusive and present only one of many possibilities.

Large-Scale Experimental Planetary Science Meets Planetary Defense: Deorbiting an Asteroidal Satellite

NASA Technical Reports Server (NTRS)

Cintala, M. J.; Durda, D. D.; Housen, K. R.

2005-01-01

Other than remote-sensing and spacecraft-derived data, the only information that exists regarding the physical and chemical properties of asteroids is that inferred through calculations, numerical simulations, extrapolation of experiments, and meteorite studies. Our understanding of the dynamics of accretion of planetesimals, collisional disruption of asteroids, and the macroscopic, shock-induced modification of the surfaces of such small objects is also, for the most part, founded on similar inferences. While considerable strides have been made in improving the state of asteroid science, too many unknowns remain to assert that we understand the parameters necessary for the more practical problem of deflecting an asteroid or asteroid pair on an Earth-intersecting trajectory. Many of these deficiencies could be reduced or eliminated by intentionally deorbiting an asteroidal satellite and monitoring the resulting collision between it and the primary asteroid, a capability that is well within the limitations of current technology.

Do L chondrites come from the Gefion family?

NASA Astrophysics Data System (ADS)

McGraw, Allison M.; Reddy, Vishnu; Sanchez, Juan A.

2018-05-01

Ordinary chondrites (H, L, and LL chondrites) are the most common type of meteorites comprising 80 per cent of the meteorites that fall on Earth. The source region of these meteorites in the main asteroid belt has been a basis of considerable debate in the small bodies community. L chondrites have been proposed to come from the Gefion asteroid family, based on dynamical models. We present results from our observational campaign to verify a link between the Gefion asteroid family and L chondrite meteorites. Near-infrared spectra of Gefion family asteroids (1839) Ragazza, (2373) Immo, (2386) Nikonov, (2521) Heidi, and (3860) Plovdiv were obtained at the NASA Infrared Telescope Facility (IRTF). Spectral band parameters including band centres and the band area ratio were measured from each spectrum and used to constrain the composition of these asteroids. Based on our results, we found that some members of the Gefion family have surface composition similar to that of H chondrites, primitive achondrites, and basaltic achondrites. No evidence was found for L chondrites among the Gefion family members in our small sample study. The diversity of compositional types observed in the Gefion asteroid family suggests that the original parent body might be partially differentiated or that the three asteroids with non-ordinary chondrite compositions might be interlopers.

Meteoritic and other constraints on the internal structure and impact history of small asteroids

NASA Astrophysics Data System (ADS)

Scott, Edward R. D.; Wilson, Lionel

2005-03-01

Studies of the internal structure of asteroids, which are crucial for understanding their impact history and for hazard mitigation, appear to be in conflict for the S-type asteroids, Eros, Gaspra, and Ida. Spacecraft images and geophysical data show that they are fractured, coherent bodies, whereas models of catastrophic asteroidal impacts, family and satellite formation, and studies of asteroid spin rates, and other diverse properties of asteroids and planetary craters suggest that such asteroids are gravitationally bound aggregates of rubble. These conflicting views may be reconciled if 10-50 km S-type asteroids formed as rubble piles, but were later consolidated into coherent bodies. Many meteorites are breccias that testify to a long history of impact fragmentation and consolidation by alteration, metamorphism, igneous and impact processes. Ordinary chondrites, which are the best analogs for S asteroids, are commonly breccias. Some may have formed in cratering events, but many appear to have formed during disruption and reaccretion of their parent asteroids. Some breccias were lithified during metamorphism, and a few were lithified by injected impact melt, but most are regolith and fragmental breccias that were lithified by mild or moderate shock, like their lunar analogs. Shock experiments show that porous chondritic powders can be consolidated during mild shock by small amounts of silicate melt that glues grains together, and by friction and pressure welding of silicate and metallic Fe,Ni grains. We suggest that the same processes that converted impact debris into meteorite breccias also consolidated asteroidal rubble. Internal voids would be partly filled with regolith by impact-induced seismic shaking. Consolidation of this material beneath large craters would lithify asteroidal rubble to form a more coherent body. Fractures on Ida that were created by antipodal impacts and are concentrated in and near large craters, and small positive gravity anomalies associated with the Psyche and Himeros craters on Eros, are consistent with this concept. Spin data suggest that smaller asteroids 0.6-6 km in size are unconsolidated rubble piles. C-type asteroids, which are more porous than S-types, and their analogs, the volatile-rich carbonaceous chondrites, were probably not lithified by shock.

Main-belt asteroid exploration - Mission options for the 1990s

NASA Technical Reports Server (NTRS)

Yen, C.-W. L.

1982-01-01

Mission configurations, propulsion systems, and target bodies for possible NASA asteroid exploration projects are examined. Noting that an announced delay in the development of a solar electric propulsion system has led to a consideration of chemical rocket systems, asteroid missions are grouped in terms of five potential areas for investigation, each successively further from the sun. The Shuttle-launched IUS is suggested as the prime candidate for boosting probes into trajectories for asteroid rendezvous with a number of the 3000 known asteroids. Planetary swingbys are mentioned as the only suitable method for satisfying the large energy requirements of the asteroid missions. Performance analyses are presented of the IUS 2-stage/Star-48 and Centaur vehicles, and sample missions to Fortuna, Anahita, and Urania in 1990 and further missions to the middle, outer, and Trojans asteroids are outlined.

Search techniques for near-earth asteroids

NASA Technical Reports Server (NTRS)

Helin, E. F.; Dunbar, R. S.

1990-01-01

Knowledge of the near-earth asteroids (Apollo, Amor, and Aten groups) has increased enormously over the last 10 to 15 years. This has been due in large part to the success of programs that have systematically searched for these objects. These programs have been motivated by the apparent relationships of the near-earth asteroids to terrestrial impact cratering, meteorites, and comets, and their relative accessibility for asteroid missions. Discovery of new near-earth asteroids is fundamental to all other studies, from theoretical modeling of their populations to the determination of their physical characteristics by various remote-sensing techniques. The methods that have been used to find these objects are reviewed, and ways in which the search for near-earth asteroids can be expanded are discussed.

Asteroid 4 Vesta: A Fully Differentiated Dwarf Planet

NASA Technical Reports Server (NTRS)

Mittlefehldt, David

2014-01-01

One conclusion derived from the study of meteorites is that some of them - most irons, stony irons, some achondrites - hail from asteroids that were heated to the point where metallic cores and basaltic crusts were formed. Telescopic observations show that there remains only one large asteroid with a basaltic crust, 4 Vesta; present day mean radius 263 km. The largest clan of achondrites, the howardite, eucrite and diogenite (HED) meteorites, represent the crust of their parent asteroid. Diogenites are cumulate harzburgites and orthopyroxenites from the lower crust whilst eucrites are cumulate gabbros, diabases and basalts from the upper crust. Howardites are impact-engendered breccias of diogenites and eucrites. A strong case can be made that HEDs are derived from Vesta. The NASA Dawn spacecraft orbited Vesta for 14 months returning data allowing geological, mineralogical, compositional and geophysical interpretations of Vesta's surface and structure. Combined with geochemical and petrological observations of HED meteorites, differentiation models for Vesta can be developed. Proto-Vesta probably consisted of primitive chondritic materials. Compositional evidence, primarily from basaltic eucrites, indicates that Vesta was melted to high degree (>=50%) which facilitated homogenization of the silicate phase and separation of immiscible Fe,Ni metal plus Fe sulphide into a core. Geophysical models based on Dawn data support a core of 110 km radius. The silicate melt vigorously convected and initially followed a path of equilibrium crystallization forming a harzburgitic mantle, possibly overlying a dunitic restite. Once the fraction of crystals was sufficient to cause convective lockup, the remaining melt collected between the mantle and the cool thermal boundary layer. This melt undergoes fractional crystallization to form a dominantly orthopyroxenite (diogenite) lower crust. The initial thermal boundary layer of primitive chondritic material is gradually replaced by a mafic crust through impact disruption and foundering. The quenched mafic crust thickens over time through magma extrusion/intrusion. Melt from the residual magma ocean intrudes and penetrates the mafic crust forming cumulate eucrite plutons, and dikes, sills and flows of basaltic eucrite composition. The post-differentiation vestan structure is thus not too dissimilar from that of terrestrial planets: (i) a metallic core; (ii) an ultramafic mantle comprised of a lower dunitic layer (if melting was substantially <100%) and an upper cumulate harzburgitic layer; (iii) a lower crust of harzburgitic and orthopyroxenitic cumulates; and (iv) an upper mafic crust of basalts and diabases (melt compositions) with cumulate gabbro intrusions. Impacts have excavated to the lower crust and delivered howardites, eucrites and diogenites to Earth, but there is yet no evidence demonstrating excavation of the vestan mantlle.

Asteroid masses with Gaia from ground and space-based observations

NASA Astrophysics Data System (ADS)

Ivantsov, Anatoliy; Hestroffer, Daniel; Thuillot, William; Bancelin, David

2013-04-01

Determination of masses of large asteroids is one of the expected scientific outputs from the future Gaia astrometric space mission. With the exception of binary asteroids or fly-by with a space probe, the error in mass determination depends on the size of perturbation effect produced on the motion of small asteroids. Considering the 5 years nominal duration of the Gaia mission, there will be mutual close encounters between asteroids occurring either close to the beginning or to the end of the mission. So that the maximum of deflection angle pertained to the perturbation maxima will not be observed directly by Gaia. Since astrometric data of the perturbed body before and after the encounter are mandatory to derive a perturber mass, the precision of mass determinations based solely on the Gaia observations will deteriorate in such cases. The possible way out consists in acquiring ground-based observations of high astrometric precision in time either before or after the Gaia operations, as it was suggested in [1]. By adding such data, it is expected to increase the number of derived asteroids masses [2]. This paper updates earlier predictions of encounters of large asteroids with smaller ones, e.g. [3], in terms of newly discovered asteroids and available ground-based observations. The method used consists in the computation of the offsets in right ascension and declination between the unperturbed and perturbed solutions fitted to the available observations for each small (perturbed) asteroid. For the purpose of decreasing CPU time, a special filter was applied based on the solution of the two-body problem and systematical search for close encounters, e.g. less than 0.1 A.U., of all known asteroids with the large (perturber) ones. The obtained list of asteroids-candidates was used as the input file for the mentioned above accurate calculations. Such a procedure was used for a few asteroids in [2]. The maximum visible offset corresponds to the dates when the complementary ground-based observations will be useful. [1] Hestroffer, D., Thuillot, W., Mouret, S., Colas, F., Tanga, P., Mignard, F., Delbo, M., Carry, B.: Ground-based observations of solar system bodies in complement to Gaia, SF2A-2008: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics, 30 June - 4 July 2008, Paris, France, 2008. [2] Mouret, S., Hestroffer, D., and Mignard, F.: Asteroid masses and Gaia, Astronomy and Astrophysics, Vol. 472, pp. 1017-1027, 2007. [3] Mouret, S.: Investigations on the dynamics of minor planets with GAIA: orbits, masses and fundamental physics, PhD thesis, Paris Observatory, 2007. [4] Hilton, J.L., Seidelmann, P.K., and Middour, J.: Prospects for determining asteroid masses, Astronomical Journal, Vol. 112, pp. 2319-2329, 1996.

Asteroid and comet surfaces

NASA Technical Reports Server (NTRS)

Mcfadden, Lucy-Ann

1988-01-01

Photometric and spectrophotometric studies of asteroids and comets are in progress to address questions about the mineralogical relationship between asteroids near the 3:1 Kirkwood gap and ordinary chondrite meteorites and between cometary nuclei and the surface of asteroids. Progress was made on a method to convert the measured excess UV flux in the spectrum of 2201 Oljato to column abundance of OH and CN. Spectral reflectance measurements of large asteroids near the 3:1 Kirkwood gap, which is expected to be the source of ordinary chondrite meteorites, were briefly examined and show no spectral signatures that are characteristic of ordinary chondrite meteorite powders measured in the lab.

Flavors of Chaos in the Asteroid Belt

NASA Astrophysics Data System (ADS)

Tsiganis, Kleomenis

2016-10-01

The asteroid belt is a natural laboratory for studying chaos, as a large fraction of asteroids actually reside on chaotic orbits. Numerous studies over the past 25 years have unveiled a multitude of dynamical chaos-generating mechanisms, operating on different time-scales and dominating over different regions of the belt. In fact, the distribution of chaotic asteroids in orbital space can be largely understood as the outcome of the combined action of resonant gravitational perturbations and the Yarkovsky effect - two topics on which Paolo Farinella has made an outstanding contribution! - notwithstanding the fact that the different "flavors" of chaos can give rise to a wide range of outcomes, from fast escape (e.g. to NEA space) to slow (~100s My) macroscopic diffusion (e.g. spreading of families) and strange, stable-looking, chaotic orbits (ultra-slow diffusion). In this talk I am going to present an overview of these mechanisms, presenting both analytical and numerical results, and their role in understanding the long-term evolution and stability of individual bodies, asteroid groups and families.

Impact Histories of Vesta and Vestoids inferred from Howardites, Eucrites, and Diogenites

NASA Technical Reports Server (NTRS)

Scott, E. R. D.; Bogard, D. D.; Bottke, W. F.; Taylor, G. J.; Greenwood, R. C.; Franchi, I. A.; Keil, K.; Moskovitz, N. A.; Nesvorny, D.

2009-01-01

The parent body of the howardites, eucrites and diogenites (HEDs) is thought to be asteroid (4) Vesta [1]. However, several eucrites have now been recognized, like NWA 011 and Ibitira, with major element compositions and mineralogy like normal eucrites but with different oxygen isotope compositions and minor element concentrations suggesting they are not from the same body [2, 3]. The discoveries of abnormal eucrites and V-type asteroids that are probably not from Vesta [see 4] raise the question whether the HEDs with normal oxygen isotopes are coming from Vesta [3]. To address this issue and understand more about the evolution of Vesta in preparation for the arrival of the Dawn spacecraft, we integrate fresh insights from Ar-Ar dating and oxygen isotope analyses of HEDs, radiometric dating of differentiated meteorites, as well as dynamical and astronomical studies of Vesta, the Vesta asteroid family (i.e., the Vestoids), and other V-type asteroids.

Galileo support observations of Asteroid 951 Gaspra

NASA Technical Reports Server (NTRS)

Goldader, Jeffrey D.; Tholen, David J.; Cruikshank, Dale P.; Hartmann, William K.

1991-01-01

Observations of 951 Gaspra in support of the Galileo spacecraft encounter are reported. Photometric observations of the asteroid yield a synodic rotational period of 7.042 46 and a slope parameter G of 0.285 + or - 0.005. It is inferred from data obtained on May 18, 1990, that the subearth latitude was higher at that time than it was earlier in the opposition. This places a limit on the possible pole orientation of the asteroid. A slope parameter of 0.25 is proposed on the basis of a comparison of the present result for the slope parameter with that of Barucci et al. (1990). A low-quality 0.8-2.5-micron spectrum of 951 Gaspra suggests a high olivine/pyroxene ratio, which is indicative of a source region in the lower mantle of a differentiated asteroid, and similarities to 8 Flora and particularly 15 Eunomia.

Chromium on Eros: Further Evidence of Ordinary Chondrite Composition

NASA Technical Reports Server (NTRS)

Foley, C. N.; Nittler, L. R.; Brown, M. R. M.; McCoy, T. J.; Lim, L. F.

2005-01-01

The surface major element composition of the near-earth asteroid 433-Eros has been determined by x-ray fluorescence spectroscopy (XRS) on the NEAR-Shoemaker spacecraft [1]. The abundances of Mg, Al, Si, Ca and Fe match those of ordinary chondrites [1]. However, the observation that Eros appears to have a sulfur abundance at least a factor of two lower than ordinary chondrites, suggests either sulfur loss from the surface of Eros by impact and/or radiation processes (space weathering) or that its surface is comprised of a somewhat more differentiated type of material than an ordinary chondrite [1]. A definitive match for an ordinary chondrite parent body has very rarely been made, despite the conundrum that ordinary chondrites are the most prevalent type of meteorite found on Earth. Furthermore, Eros is classified as an S(IV) type asteroid [2] and being an S, it is the second most prevalent type of asteroid in the asteroid belt [3].

Main-belt Asteroids in the K2 Uranus Field

NASA Astrophysics Data System (ADS)

Molnár, L.; Pál, A.; Sárneczky, K.; Szabó, R.; Vinkó, J.; Szabó, Gy. M.; Kiss, Cs.; Hanyecz, O.; Marton, G.; Kiss, L. L.

2018-02-01

We present the K2 light curves of a large sample of untargeted main-belt asteroids (MBAs) detected with the Kepler Space Telescope. The asteroids were observed within the Uranus superstamp, a relatively large, continuous field with a low stellar background designed to cover the planet Uranus and its moons during Campaign 8 of the K2 mission. The superstamp offered the possibility of obtaining precise, uninterrupted light curves of a large number of MBAs and thus determining unambiguous rotation rates for them. We obtained photometry for 608 MBAs, and were able to determine or estimate rotation rates for 90 targets, of which 86 had no known values before. In an additional 16 targets we detected incomplete cycles and/or eclipse-like events. We found the median rotation rate to be significantly longer than that of the ground-based observations, indicating that the latter are biased toward shorter rotation rates. Our study highlights the need and benefits of further continuous photometry of asteroids.

Chang'e-2 spacecraft observations of asteroid 4179 Toutatis

NASA Astrophysics Data System (ADS)

Ji, Jianghui; Jiang, Yun; Zhao, Yuhui; Wang, Su; Yu, Liangliang

2016-01-01

On 13 December 2012, Chang'e-2 completed a successful flyby of the near-Earth asteroid 4179 Toutatis at a closest distance of 770 meters from the asteroid's surface. The observations show that Toutatis has an irregular surface and its shape resembles a ginger-root of a smaller lobe (head) and a larger lobe (body). Such bilobate shape is indicative of a contact binary origin for Toutatis. In addition, the high-resolution images better than 3 meters provide a number of new discoveries about this asteroid, such as an 800-meter depression at the end of the large lobe, a sharply perpendicular silhouette near the neck region, boulders, indicating that Toutatis is probably a rubble-pile asteroid. Chang'e-2 observations have significantly revealed new insights into the geological features and the formation and evolution of this asteroid. In final, we brief the future Chinese asteroid mission concept.

REPEATING FAST RADIO BURSTS FROM HIGHLY MAGNETIZED PULSARS TRAVELING THROUGH ASTEROID BELTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Z. G.; Wang, J. S.; Huang, Y. F.

Very recently, Spitler et al. and Scholz et al. reported their detections of 16 additional bright bursts in the direction of the fast radio burst (FRB) 121102. This repeating FRB is inconsistent with all of the catastrophic event models put forward previously for hypothetically non-repeating FRBs. Here, we propose a different model, in which highly magnetized pulsars travel through the asteroid belts of other stars. We show that a repeating FRB could originate from such a pulsar encountering a large number of asteroids in the belt. During each pulsar-asteroid impact, an electric field induced outside of the asteroid has suchmore » a large component parallel to the stellar magnetic field that electrons are torn off the asteroidal surface and accelerated to ultra-relativistic energies instantaneously. The subsequent movement of these electrons along magnetic field lines will cause coherent curvature radiation, which can account for all of the properties of an FRB. In addition, this model can self-consistently explain the typical duration, luminosity, and repetitive rate of the 17 bursts of FRB 121102. The predicted occurrence rate of repeating FRB sources may imply that our model would be testable in the next few years.« less

Bunburra Rockhole: Exploring the geology of a new differentiated asteroid

NASA Astrophysics Data System (ADS)

Benedix, G. K.; Bland, P. A.; Friedrich, J. M.; Mittlefehldt, D. W.; Sanborn, M. E.; Yin, Q.-Z.; Greenwood, R. C.; Franchi, I. A.; Bevan, A. W. R.; Towner, M. C.; Perrotta, G. C.; Mertzman, S. A.

2017-07-01

Bunburra Rockhole is the first recovered meteorite of the Desert Fireball Network. We expanded a bulk chemical study of the Bunburra Rockhole meteorite to include major, minor and trace element analyses, as well as oxygen and chromium isotopes, in several different pieces of the meteorite. This was to determine the extent of chemical heterogeneity and constrain the origin of the meteorite. Minor and trace element analyses in all pieces are exactly on the basaltic eucrite trend. Major element analyses show a slight deviation from basaltic eucrite compositions, but not in any systematic pattern. New oxygen isotope analyses on 23 pieces of Bunburra Rockhole shows large variation in both δ17O and δ18O, and both are well outside the HED parent body fractionation line. We present the first Cr isotope results of this rock, which are also distinct from HEDs. Detailed computed tomographic scanning and back-scattered electron mapping do not indicate the presence of any other meteoritic contaminant (contamination is also unlikely based on trace element chemistry). We therefore conclude that Bunburra Rockhole represents a sample of a new differentiated asteroid, one that may have more variable oxygen isotopic compositions than 4 Vesta. The fact that Bunburra Rockhole chemistry falls on the eucrite trend perhaps suggests that multiple objects with basaltic crusts accreted in a similar region of the Solar System.

Asteroid Redirect Mission Proximity Operations for Reference Target Asteroid 2008 EV5

NASA Technical Reports Server (NTRS)

Reeves, David M.; Mazanek, Daniel D.; Cichy, Benjamin D.; Broschart, Steve B.; Deweese, Keith D.

2016-01-01

NASA's Asteroid Redirect Mission (ARM) is composed of two segments, the Asteroid Redirect Robotic Mission (ARRM), and the Asteroid Redirect Crewed Mission (ARCM). In March of 2015, NASA selected the Robotic Boulder Capture Option1 as the baseline for the ARRM. This option will capture a multi-ton boulder, (typically 2-4 meters in size) from the surface of a large (greater than approx.100 m diameter) Near-Earth Asteroid (NEA) and return it to cis-lunar space for subsequent human exploration during the ARCM. Further human and robotic missions to the asteroidal material would also be facilitated by its return to cis-lunar space. In addition, prior to departing the asteroid, the Asteroid Redirect Vehicle (ARV) will perform a demonstration of the Enhanced Gravity Tractor (EGT) planetary defense technique2. This paper will discuss the proximity operations which have been broken into three phases: Approach and Characterization, Boulder Capture, and Planetary Defense Demonstration. Each of these phases has been analyzed for the ARRM reference target, 2008 EV5, and a detailed baseline operations concept has been developed.

ON THE EFFECT OF GIANT PLANETS ON THE SCATTERING OF PARENT BODIES OF IRON METEORITE FROM THE TERRESTRIAL PLANET REGION INTO THE ASTEROID BELT: A CONCEPT STUDY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haghighipour, Nader; Scott, Edward R. D., E-mail: nader@ifa.hawaii.edu

2012-04-20

In their model for the origin of the parent bodies of iron meteorites, Bottke et al. proposed differentiated planetesimals, formed in 1-2 AU during the first 1.5 Myr, as the parent bodies, and suggested that these objects and their fragments were scattered into the asteroid belt as a result of interactions with planetary embryos. Although viable, this model does not include the effect of a giant planet that might have existed or been growing in the outer regions. We present the results of a concept study where we have examined the effect of a planetary body in the orbit ofmore » Jupiter on the early scattering of planetesimals from the terrestrial region into the asteroid belt. We integrated the orbits of a large battery of planetesimals in a disk of planetary embryos and studied their evolutions for different values of the mass of the planet. Results indicate that when the mass of the planet is smaller than 10 M{sub Circled-Plus }, its effects on the interactions among planetesimals and planetary embryos are negligible. However, when the planet mass is between 10 and 50 M{sub Circled-Plus }, simulations point to a transitional regime with {approx}50 M{sub Circled-Plus} being the value for which the perturbing effect of the planet can no longer be ignored. Simulations also show that further increase of the mass of the planet strongly reduces the efficiency of the scattering of planetesimals from the terrestrial planet region into the asteroid belt. We present the results of our simulations and discuss their possible implications for the time of giant planet formation.« less

Abodes for life in carbonaceous asteroids?

NASA Astrophysics Data System (ADS)

Abramov, Oleg; Mojzsis, Stephen J.

2011-05-01

Thermal evolution models for carbonaceous asteroids that use new data for permeability, pore volume, and water circulation as input parameters provide a window into what are arguably the earliest habitable environments in the Solar System. Plausible models of the Murchison meteorite (CM) parent body show that to first-order, conditions suitable for the stability of liquid water, and thus pre- or post-biotic chemistry, could have persisted within these asteroids for tens of Myr. In particular, our modeling results indicate that a 200-km carbonaceous asteroid with a 40% initial ice content takes almost 60 Myr to cool completely, with habitable temperatures being maintained for ˜24 Myr in the center. Yet, there are a number of indications that even with the requisite liquid water, thermal energy sources to drive chemical gradients, and abundant organic "building blocks" deemed necessary criteria for life, carbonaceous asteroids were intrinsically unfavorable sites for biopoesis. These controls include different degrees of exothermal mineral hydration reactions that boost internal warming but effectively remove liquid water from the system, rapid (1-10 mm yr -1) inward migration of internal habitable volumes in most models, and limitations imposed by low permeabilities and small pore sizes in primitive undifferentiated carbonaceous asteroids. Our results do not preclude the existence of habitable conditions on larger, possibly differentiated objects such as Ceres and the Themis family asteroids due to presumed longer, more intense heating and possible long-lived water reservoirs.

The Fossilized Size Distribution of the Main Asteroid Belt

NASA Astrophysics Data System (ADS)

Bottke, W. F.; Durda, D.; Nesvorny, D.; Jedicke, R.; Morbidelli, A.

2004-05-01

The main asteroid belt evolved into its current state via two processes: dynamical depletion and collisional evolution. During the planet formation epoch, the primordial main belt (PMB) contained several Earth masses of material, enough to allow the asteroids to accrete on relatively short timescales (e.g., Weidenschilling 1977). The present-day main belt, however, only contains 5e-4 Earth masses of material (Petit et al. 2002). To explain this mass loss, we suggest the PMB evolved in the following manner: Planetesimals and planetary embryos accreted (and differentiated) in the PMB during the first few Myr of the solar system. Gravitational perturbations from these embryos dynamically stirred the main belt, enough to initiate fragmentation. When Jupiter reached its full size, some 10 Myr after the solar system's birth, its perturbations, together with those of the embryos, dynamically depleted the main belt region of > 99% of its bodies. Much of this material was sent to high (e,i) orbits, where it continued to pummel the surviving main belt bodies at high impact velocities for more than 100 Myr. While some differentiated bodies in the PMB were disrupted, most were instead scattered; only small fragments from this population remain. This period of comminution and dynamical evolution in the PMB created, among other things, the main belt's wavy size-frequency distribution, such that it can be considered a "fossil" from this violent early epoch. From this time forward, however, relatively little collisional evolution has taken place in the main belt, consistent with the surprising paucity of prominent asteroid families. We will show that the constraints provided by asteroid families and the shape of the main belt size distribution are essential to obtaining a unique solution from our model's initial conditions. We also use our model results to solve for the asteroid disruption scaling law Q*D, a critical function needed in all planet formation codes that include fragmentation between rocky planetesimals.

Asteroid and comet flux in the neighborhood of the earth

NASA Technical Reports Server (NTRS)

Shoemaker, Eugene M.; Shoemaker, Carolyn S.; Wolfe, Ruth F.

1988-01-01

Significant advances in the knowledge and understanding of the flux of large solid objects in the neighborhood of Earth have occurred. The best estimates of the collision rates with Earth of asteroids and comets and the corresponding production of impact craters are presented. Approximately 80 Earth-crossing asteroids were discovered through May 1988. Among 42 new Earth-crossing asteroids found in the last decade, two-thirds were discovered from observations at Palomar Observatory and 15 were discovered or independently detected in dedicated surveys with the Palomar Observatory and 15 were discovered or independently detected in dedicated surveys with the Palomar 46 cm Schmidt. Probabilities of collision with Earth have been calculated for about two-thirds of the known Earth-crossing asteroids. When multiplied by the estimated population of Earth-crossers, this yields an estimated present rate of collision about 65 pct higher than that previously reported. Spectrophotometric data obtained chiefly in the last decade show that the large majority of obvserved Earth-crossers are similar to asteroids found in the inner part of the main belt. The number of discovered Earth-crossing comets is more than 4 times greater than the number of known Earth-crossing asteroids, but reliable data on the sizes of comet nuclei are sparse. The flux of comets almost certainly was highly variable over late geologic time, owing to the random perturbation of the Oort comet cloud by stars in the solar neighborhood.

Strata-1: An International Space Station Experiment into Fundamental Regolith Processes in Microgravity

NASA Technical Reports Server (NTRS)

Fries, M.; Abell, P.; Brisset, J.; Britt, D.; Colwell, J.; Durda, D.; Dove, A.; Graham, L.; Hartzell, C.; John, K.;

Polarimetric survey of main-belt asteroids. IV. New results from the first epoch of the CASLEO survey

NASA Astrophysics Data System (ADS)

Gil-Hutton, R.; Cellino, A.; Bendjoya, Ph.

2014-09-01

Aims: We present results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained using the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 1995, and until 2012 data on a large sample of asteroids were obtained. We here present and analyze the unpublished results for 129 asteroids of different taxonomic types, 56 which were polarimetrically observed for the first time. We find that the asteroids (402) Chloe and (729) Watsonia are Barbarians, and asteroid (269) Justitia shows a phase - polarization curve that seems to have a small inversion angle. Data obtained in UBVRI colors allow us to sketch an analysis of the wavelength dependence of the degree of linear polarization for 31 asteroids, in spite of some large error bars in some cases. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/569/A122

Scenarios which may lead to the rise of an asteroid-based technical civilisation

NASA Astrophysics Data System (ADS)

Kecskes, Csaba

2002-05-01

In a previous paper, the author described a hypothetical development path of technical civilisations which has the following stages: planet dwellers, asteroid dwellers, interstellar travellers, interstellar space dwellers. In this paper, several scenarios are described which may cause the rise of an asteroid-based technical civilisation. Before such a transition may take place, certain space technologies must be developed fully (now these exist only in very preliminary forms): closed-cycle biological life support systems, space manufacturing systems, electrical propulsion systems. After mastering these technologies, certain events may provide the necessary financial means and social impetus for the foundation of the first asteroid-based colonies. In the first scenario, a rich minority group becomes persecuted and they decide to leave the Earth. In the second scenario, a "cold war"-like situation exists and the leaders of the superpowers order the creation of asteroid-based colonies to show off their empires' technological (and financial) grandiosity. In the third scenario, the basic situation is similar to the second one, but in this case the asteroids are not just occupied by the colonists. With several decades of hard work, an asteroid can be turned into a kinetic energy weapon which can provide the same (or greater) threat as the nuclear arsenal of a present superpower. In the fourth scenario, some military asteroids are moved to Earth-centred orbits and utilised as "solar power satellites" (SPS). This would be a quite economical solution because a "military asteroid" already contains most of the important components of an SPS (large solar collector arrays, power distribution devices, orbit modifying rocket engine), one should add only a large microwave transmitter.

Scenarios which may lead to the rise of an asteroid-based technical civilisation.

PubMed

Kecskes, Csaba

2002-05-01

In a previous paper, the author described a hypothetical development path of technical civilisations which has the following stages: planet dwellers, asteroid dwellers, interstellar travellers, interstellar space dwellers. In this paper, several scenarios are described which may cause the rise of an asteroid-based technical civilisation. Before such a transition may take place, certain space technologies must be developed fully (now these exist only in very preliminary forms): closed-cycle biological life support systems, space manufacturing systems, electrical propulsion systems. After mastering these technologies, certain events may provide the necessary financial means and social impetus for the foundation of the first asteroid-based colonies. In the first scenario, a rich minority group becomes persecuted and they decide to leave the Earth. In the second scenario, a "cold war"-like situation exists and the leaders of the superpowers order the creation of asteroid-based colonies to show off their empires' technological (and financial) grandiosity. In the third scenario, the basic situation is similar to the second one, but in this case the asteroids are not just occupied by the colonists. With several decades of hard work, an asteroid can be turned into a kinetic energy weapon which can provide the same (or greater) threat as the nuclear arsenal of a present superpower. In the fourth scenario, some military asteroids are moved to Earth-centred orbits and utilised as "solar power satellites" (SPS). This would be a quite economical solution because a "military asteroid" already contains most of the important components of an SPS (large solar collector arrays, power distribution devices, orbit modifying rocket engine), one should add only a large microwave transmitter. c2002 Elsevier Science Ltd. All rights reserved.

AsteroidZoo: A New Zooniverse project to detect asteroids and improve asteroid detection algorithms

NASA Astrophysics Data System (ADS)

Beasley, M.; Lewicki, C. A.; Smith, A.; Lintott, C.; Christensen, E.

2013-12-01

We present a new citizen science project: AsteroidZoo. A collaboration between Planetary Resources, Inc., the Zooniverse Team, and the Catalina Sky Survey, we will bring the science of asteroid identification to the citizen scientist. Volunteer astronomers have proved to be a critical asset in identification and characterization of asteroids, especially potentially hazardous objects. These contributions, to date, have required that the volunteer possess a moderate telescope and the ability and willingness to be responsive to observing requests. Our new project will use data collected by the Catalina Sky Survey (CSS), currently the most productive asteroid survey, to be used by anyone with sufficient interest and an internet connection. As previous work by the Zooniverse has demonstrated, the capability of the citizen scientist is superb at classification of objects. Even the best automated searches require human intervention to identify new objects. These searches are optimized to reduce false positive rates and to prevent a single operator from being overloaded with requests. With access to the large number of people in Zooniverse, we will be able to avoid that problem and instead work to produce a complete detection list. Each frame from CSS will be searched in detail, generating a large number of new detections. We will be able to evaluate the completeness of the CSS data set and potentially provide improvements to the automated pipeline. The data corpus produced by AsteroidZoo will be used as a training environment for machine learning challenges in the future. Our goals include a more complete asteroid detection algorithm and a minimum computation program that skims the cream of the data suitable for implemention on small spacecraft. Our goal is to have the site become live in the Fall 2013.

Spectral decomposition of asteroid Itokawa based on principal component analysis

NASA Astrophysics Data System (ADS)

Koga, Sumire C.; Sugita, Seiji; Kamata, Shunichi; Ishiguro, Masateru; Hiroi, Takahiro; Tatsumi, Eri; Sasaki, Sho

2018-01-01

The heliocentric stratification of asteroid spectral types may hold important information on the early evolution of the Solar System. Asteroid spectral taxonomy is based largely on principal component analysis. However, how the surface properties of asteroids, such as the composition and age, are projected in the principal-component (PC) space is not understood well. We decompose multi-band disk-resolved visible spectra of the Itokawa surface with principal component analysis (PCA) in comparison with main-belt asteroids. The obtained distribution of Itokawa spectra projected in the PC space of main-belt asteroids follows a linear trend linking the Q-type and S-type regions and is consistent with the results of space-weathering experiments on ordinary chondrites and olivine, suggesting that this trend may be a space-weathering-induced spectral evolution track for S-type asteroids. Comparison with space-weathering experiments also yield a short average surface age (< a few million years) for Itokawa, consistent with the cosmic-ray-exposure time of returned samples from Itokawa. The Itokawa PC score distribution exhibits asymmetry along the evolution track, strongly suggesting that space weathering has begun saturated on this young asteroid. The freshest spectrum found on Itokawa exhibits a clear sign for space weathering, indicating again that space weathering occurs very rapidly on this body. We also conducted PCA on Itokawa spectra alone and compared the results with space-weathering experiments. The obtained results indicate that the first principal component of Itokawa surface spectra is consistent with spectral change due to space weathering and that the spatial variation in the degree of space weathering is very large (a factor of three in surface age), which would strongly suggest the presence of strong regional/local resurfacing process(es) on this small asteroid.

Peculiar Euphrosyne

NASA Astrophysics Data System (ADS)

Carruba, V.; Aljbaae, S.; Souami, D.

2014-09-01

The asteroid (31) Euphrosyne is the largest body of its namesake family, and it contains more than 99% of the family mass. Among large asteroid families, the Euphrosyne group is peculiar because of its quite steep size-frequency distribution (SFD), significantly depleted in large- and medium-sized asteroids (8 < D < 12 km). The current steep SFD of the Euphrosyne family has been suggested to be the result of a grazing impact in which only the farthest, smallest members failed to accrete. The Euphrosyne family is, however, also very peculiar because of its dynamics: near its center it is crossed by the ν6 = g - g 6 linear secular resonance, and it hosts the largest population (140 bodies) of asteroids in ν6 antialigned librating states (or Tina-like asteroids) in the main belt. In this work we investigated the orbital evolution of newly obtained members of the dynamical family, with an emphasis on its interaction with the ν6 resonance. Because of its unique resonant configuration, large- and medium-sized asteroids tend to migrate away from the family orbital region faster than small-sized objects, which were ejected farther away from the family center. As a consequence, the SFD of the Euphrosyne family becomes steeper in time with a growing depletion in the number of the largest family members. We estimate that the current SFD could be attained from a typical, initial SFD on timescales of 500 Myr, consistent with estimates of the family age obtained with other independent methods.

Asteroid families from cratering: Detection and models

NASA Astrophysics Data System (ADS)

Milani, A.; Cellino, A.; Knežević, Z.; Novaković, B.; Spoto, F.; Paolicchi, P.

2014-07-01

A new asteroid families classification, more efficient in the inclusion of smaller family members, shows how relevant the cratering impacts are on large asteroids. These do not disrupt the target, but just form families with the ejecta from large craters. Of the 12 largest asteroids, 8 have cratering families: number (2), (4), (5), (10), (87), (15), (3), and (31). At least another 7 cratering families can be identified. Of the cratering families identified so far, 7 have >1000 members. This imposes a remarkable change from the focus on fragmentation families of previous classifications. Such a large dataset of asteroids believed to be crater ejecta opens a new challenge: to model the crater and family forming event(s) generating them. The first problem is to identify which cratering families, found by the similarity of proper elements, can be formed at once, with a single collision. We have identified as a likely outcome of multiple collisions the families of (4), (10), (15), and (20). Of the ejecta generated by cratering, only a fraction reaches the escape velocity from the surviving parent body. The distribution of velocities at infinity, giving to the resulting family an initial position and shape in the proper elements space, is highly asymmetric with respect to the parent body. This shape is deformed by the Yarkovsky effect and by the interaction with resonances. All the largest asteroids have been subjected to large cratering events, thus the lack of a family needs to be interpreted. The most interesting case is (1) Ceres, which is not the parent body of the nearby family of (93). Two possible interpretations of the low family forming efficiency are based on either the composition of Ceres with a significant fraction of ice, protected by a thin crust, or with the larger escape velocity of ~500 m/s.

Petrologic evidence for collisional heating of chondritic asteroids

NASA Technical Reports Server (NTRS)

Rubin, Alan E.

1995-01-01

The identification of the mechanism(s) responsible for heating asteroids is among the major problems in planetary science. Because of difficulties with models of electromagnetic induction and the decay of short-lived radionuclides, it is worthwhile to evaluate the evidence for collisional heating. New evidence for localized impact heating comes from the high proportion of relict type-6 material among impact-melt-bearing ordinary chondrites (OC). This relict material was probably metamorphosed by residual heat within large craters. Olivine aggregates composed of faceted crystals with 120 deg triple junctions occur within the melted regions of the Chico and Rose City OC melt rocks; the olivine aggregates formed from shocked, mosaicized olivine grains that underwent contact metamorphism. Large-scale collisional heating is supoorted by the correlation in OC between petrologic type and shock stage; no other heating mechanism can readily account for this correlation. The occurrence of impact-melt-rock clasts in OC that have been metamorphosed along with their whole rocks indicates that some impact events preceded or accompanied thermal metamorphism. Such impacts events, occurring during or shortly after accretion, are probably responsible for substantially melting approximately 0.5% of OC. These events must have heated a larger percentage of OC to subsolidus temperatures sufficient to have caused significant metamorphism. If collisional heating is viable, then OC parent asteroids must have been large; large OC asteroids in the main belt may include those of the S(IV) spectral subtype. Collisional heating is inconsistent with layered ('onion-shell') structures in OC asteroids (wherein the degree of metamorphism increases with depth), but the evidence for such structures is weak. It seems likely that collisional heating played an important role in metamorphosing chondritic asteroids.

Simultaneous Mass Determination for Gravitationally Coupled Asteroids

NASA Astrophysics Data System (ADS)

Baer, James; Chesley, Steven R.

2017-08-01

The conventional least-squares asteroid mass determination algorithm allows us to solve for the mass of a large subject asteroid that is perturbing the trajectory of a smaller test asteroid. However, this algorithm is necessarily a first approximation, ignoring the possibility that the subject asteroid may itself be perturbed by the test asteroid, or that the encounter’s precise geometry may be entangled with encounters involving other asteroids. After reviewing the conventional algorithm, we use it to calculate the masses of 30 main-belt asteroids. Compared to our previous results, we find new mass estimates for eight asteroids (11 Parthenope, 27 Euterpe, 51 Neimausa, 76 Freia, 121 Hermione, 324 Bamberga, 476 Hedwig, and 532 Herculina) and significantly more precise estimates for six others (2 Pallas, 3 Juno, 4 Vesta, 9 Metis, 16 Psyche, and 88 Thisbe). However, we also find that the conventional algorithm yields questionable results in several gravitationally coupled cases. To address such cases, we describe a new algorithm that allows the epoch state vectors of the subject asteroids to be included as solve-for parameters, allowing for the simultaneous solution of the masses and epoch state vectors of multiple subject and test asteroids. We then apply this algorithm to the same 30 main-belt asteroids and conclude that mass determinations resulting from current and future high-precision astrometric sources (such as Gaia) should conduct a thorough search for possible gravitational couplings and account for their effects.

The orbital evolution of the Aten asteroids over 11,550 years (9300 BC to 2250 AD)

NASA Astrophysics Data System (ADS)

Zausaev, A. F.; Pushkarev, A. N.

1991-04-01

The orbital evolution of five Aten asteroids was monitored by the Everhart method in the time interval from 9300 BC to 2250 AD. The closest encounters with large planets in the evolution process are calculated. Four out of five asteroids exhibit stable resonances with earth and Venus over the period from 9300 BC to 2250 AD.

SPHERE Sheds New Light on the Collisional History of Main-belt Asteroids

NASA Astrophysics Data System (ADS)

Marsset, M.; Carry, B.; Pajuelo, M.; Viikinkoski, M.; Hanuš, J.; Vernazza, P.; Dumas, C.; Yang, B.

2017-09-01

The Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument has unveiled unprecedented details of the three-dimensional shape, surface topography and cratering record of four medium-sized ( 200 km) asteroids, opening the prospect of a new era of ground-based exploration of the asteroid belt. Although two of the targets, (130) Elektra and (107) Camilla, have been observed extensively for more than fifteen years by the first-generation adaptive optics imagers, two new moonlets were discovered around these targets, illustrating the unique power of SPHERE. In the next two years SPHERE will continue to collect high- angular-resolution and high-contrast measurements of about 40 asteroids. These observations of a large number of asteroids will provide a unique dataset to better understand the collisional history and multiplicity rate of the asteroid belt.

Chemistry of Diogenites and Evolution of their Parent Asteroid

NASA Technical Reports Server (NTRS)

Mittlefehldt, D.W.; Beck, A.W.; McSween, H.Y.; Lee, C-T A.

2009-01-01

Diogenites are orthopyroxenite meteorites [1]. Most are breccias, but remnant textures indicate they were originally coarse-grained rocks, with grain sizes of order of cm. Their petrography, and major and trace element chemistry support an origin as crustal cumulates from a differentiated asteroid. Diogenites are genetically related to the basaltic and cumulate-gabbro eucrites, and the polymict breccias known as howardites, collectively, the HED suite. Spectroscopic observations, orbit data and dynamical arguments strongly support the hypothesis that asteroid 4 Vesta is the parent object for HED meteorites [2]. Here we discuss our new trace element data for a suite of diogenites and integrate these into the body of literature data. We use the combined data set to discuss the petrologic evolution of diogenites and 4 Vesta.

Physical properties of asteroids in comet-like orbits in the infrared asteroidal survey catalogs

NASA Astrophysics Data System (ADS)

Kim, Y.; Ishiguro, M.; Usui, F.

2014-07-01

Dormant comet and Infrared Asteroidal Survey Catalogs. Comet nucleus is a solid body consisting of dark refractory material and ice. Cometary volatiles sublimate from subsurface layer by solar heating, leaving behind large dust grains on the surface. Eventually, the appearance could turn into asteroidal rather than cometary. It is, therefore, expected that there would be ''dormant comets'' in the list of known asteroids. Over past decade, several ground-based studies have been performed to dig out such dormant comets. One common approach is applying a combination of optical and dynamical properties learned from active comet nucleus to the list of known asteroids. Typical comet nucleus has (i) Tisserand parameter with respect to Jupiter, T_{J}<3, (ii) low geometric albedo, p_{v}<0.1 and (iii) reddish or neutral spectra, similar to P, D, C-type asteroids. Following past ground-based surveys, infrared space missions gave us an opportunity to work on further study of dormant comets. To the present, three infrared asteroidal catalogs taken with IRAS[1], AKARI[2] and WISE[3] are available, providing information of sizes and albedos which are useful to study the physical properties of dormant comets as well as asteroids. Usui et al. (2014) merged three infrared asteroidal catalogs with valid sizes and albedos into single catalog, what they called I-A-W[4]. We applied a huge dataset of asteroids in I-A-W to investigate the physical properties of asteroids in comet-like orbits (ACOs, whose orbits satisfy Q>4.5 au and T_{J}<3). Here we present a study of ACOs in infrared asteroidal catalogs taken with AKARI, IRAS and WISE. In this presentation, we aim to introduce albedo and size properties of ACOs in infrared asteroidal survey catalogs, in combination with orbital and spectral properties from literature. Results and Implications. We summarize our finding and implication as followings: - are 123 ACOs (Q>4.5 au and T_J<3) in I-A-W catalog after rejection of objects with large orbital uncertainties. - Majority (˜80 %) of ACOs have low albedo (p_{v}<0.1), showing similar albedo distribution to active comet nuclei. - Low-albedo ACOs have the cumulative size distribution shallower than that of active comet nuclei. - High-albedo (p_{v}≥0.1) ACOs consist of small (D<3 km) bodies are concentrated in near-Earth space. - We suggest that such high-albedo, small near-Earth asteroids are susceptible to Yarkovsky effect and injected into comet-like orbits.

Lightcurves of the Karin family asteroids

NASA Astrophysics Data System (ADS)

Yoshida, Fumi; Ito, Takashi; Dermawan, Budi; Nakamura, Tsuko; Takahashi, Shigeru; Ibrahimov, Mansur A.; Malhotra, Renu; Ip, Wing-Huen; Chen, Wen-Ping; Sawabe, Yu; Haji, Masashige; Saito, Ryoko; Hirai, Masanori

2016-05-01

The Karin family is a young asteroid family formed by an asteroid breakup 5.8 Myr ago. Since the members of this family probably have not experienced significant orbital or collisional evolution yet, it is possible that they still preserve properties of the original family-forming event in terms of their spin state. We carried out a series of photometric observations of the Karin family asteroids, and here we report on the analysis of the lightcurves including the rotation period of eleven members. The mean rotation rate of the Karin family members turned out to be much lower than those of near-Earth asteroids or small main belt asteroids (diameter D < 12 km), and even lower than that of large main belt asteroids (D > 130 km). We investigated a correlation between the peak-to-trough variation and the rotation period of the eleven Karin family asteroids, and found a possible trend that elongated members have lower spin rates, and less elongated members have higher spin rates. However, this trend has to be confirmed by another series of future observations.

Stochastic YORP On Real Asteroid Shapes

NASA Astrophysics Data System (ADS)

McMahon, Jay W.

2015-05-01

Since its theoretical foundation and subsequent observational verification, the YORP effect has been understood to be a fundamental process that controls the evolution of small asteroids in the inner solar system. In particular, the coupling of the YORP and Yarkovsky effects are hypothesized to be largely responsible for the transport of asteroids from the main belt to the inner solar system populations. Furthermore, the YORP effect is thought to lead to rotational fission of small asteroids, which leads to the creation of multiple asteroid systems, contact binary asteroids, and asteroid pairs. However recent studies have called into question the ability of YORP to produce these results. In particular, the high sensitivity of the YORP coefficients to variations in the shape of an asteroid, combined with the possibility of a changing shape due to YORP accelerated spin rates can combine to create a stochastic YORP coefficient which can arrest or change the evolution of a small asteroid's spin state. In this talk, initial results are presented from new simulations which comprehensively model the stochastic YORP process. Shape change is governed by the surface slopes on radar based asteroid shape models, where the highest slope regions change first. The investigation of the modification of YORP coefficients and subsequent spin state evolution as a result of this dynamically influenced shape change is presented and discussed.

Sending an Instrument to Psyche, the Largest Metal Asteroid in the Solar System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burks, Morgan

In a few years, an instrument designed and built by Lawrence Livermore National Laboratory researchers will be flying hundreds of millions of miles through space to explore a rare, largely metal asteroid. The Livermore gamma ray spectrometer will be built in collaboration with researchers from the Johns Hopkins Applied Physics Laboratory for the first-ever visit to Psyche, the largest metal asteroid in the solar system.

Asteroid Family Physical Properties

NASA Astrophysics Data System (ADS)

Masiero, J. R.; DeMeo, F. E.; Kasuga, T.; Parker, A. H.

An asteroid family is typically formed when a larger parent body undergoes a catastrophic collisional disruption, and as such, family members are expected to show physical properties that closely trace the composition and mineralogical evolution of the parent. Recently a number of new datasets have been released that probe the physical properties of a large number of asteroids, many of which are members of identified families. We review these datasets and the composite properties of asteroid families derived from this plethora of new data. We also discuss the limitations of the current data, as well as the open questions in the field.

Software Development for Asteroid and Variable Star Research

NASA Astrophysics Data System (ADS)

Sweckard, Teaghen; Clason, Timothy; Kenney, Jessica; Wuerker, Wolfgang; Palser, Sage; Giles, Tucker; Linder, Tyler; Sanchez, Richard

2018-01-01

The process of collecting and analyzing light curves from variable stars and asteroids is almost identical. In 2016 a collaboration was created to develop a simple fundamental way to study both asteroids and variable stars using methods that would allow the process to be repeated by middle school and high school students.Using robotic telescopes at Cerro Tololo (Chile), Yerkes Observatory (US), and Stone Edge Observatory (US) data were collected on RV Del and three asteroids. It was discovered that the only available software program which could be easily installed on lab computers was MPO Canopus. However, after six months it was determined that MPO Canopus was not an acceptable option because of the steep learning curve, lack of documentation and technical support.Therefore, the project decided that the best option was to design our own python based software. Using python and python libraries we developed code that can be used for photometry and can be easily changed to the user's needs. We accomplished this by meeting with our mentor astronomer, Tyler Linder, and in the beginning wrote two different programs, one for asteroids and one for variable stars. In the end, though, we chose to combine codes so that the program would be capable of performing photometry for both moving and static objects.The software performs differential photometry by comparing the magnitude of known reference stars to the object being studied. For asteroids, the image timestamps are used to obtain ephemeris of the asteroid from JPL Horizons automatically.

Almahata Sitta and Brecciated Ureilites: Insights into the Heterogeneity of Asteroids and Implications for Sample Return

NASA Technical Reports Server (NTRS)

Ross, A. J.; Herrin, J. S.; Alexander, L.; Downes, H.; Smith, C. L.; Jenniskens, P.

2011-01-01

Analysis of samples returned to terrestrial laboratories enables more precise measurements and a wider range of techniques to be utilized than can be achieved with either remote sensing or rover instruments. Furthermore, returning samples to Earth allows them to be stored and re-examined with future technology. Following the success of the Hayabusa mission, returning samples from asteroids should be a high priority for understanding of early solar system evolution, planetary formation and differentiation. Meteorite falls provide us with materials and insight into asteroidal compositions. Almahata Sitta (AS) was the first meteorite fall from a tracked asteroid (2008 TC3) [1] providing a rare opportunity to compare direct geochemical observations with remote sensing data. Although AS is predominantly ureilitic, multiple chondritic fragments have been associated with this fall [2,3]. This is not unique, with chondritic fragments being found in many howardite samples (as described in a companion abstract [4]) and in brecciated ureilites, some of which are known to represent ureilitic regolith [5-7]. The heterogeneity of ureilite samples, which are thought to all originate from a single asteroidal ureilite parent body (UPB) [5], gives us information about both internal and external asteroidal variations. This has implications both for the planning of potential sample return missions and the interpretation of material returned to Earth. This abstract focuses on multiple fragments of two meteorites: Almahata Sitta (AS); and Dar al Gani (DaG) 1047 (a highly brecciated ureilite, likely representative of ureilite asteroidal regolith).

Simultaneous Mass Determination for Gravitationally Coupled Asteroids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baer, James; Chesley, Steven R., E-mail: jimbaer1@earthlink.net

The conventional least-squares asteroid mass determination algorithm allows us to solve for the mass of a large subject asteroid that is perturbing the trajectory of a smaller test asteroid. However, this algorithm is necessarily a first approximation, ignoring the possibility that the subject asteroid may itself be perturbed by the test asteroid, or that the encounter’s precise geometry may be entangled with encounters involving other asteroids. After reviewing the conventional algorithm, we use it to calculate the masses of 30 main-belt asteroids. Compared to our previous results, we find new mass estimates for eight asteroids (11 Parthenope, 27 Euterpe, 51more » Neimausa, 76 Freia, 121 Hermione, 324 Bamberga, 476 Hedwig, and 532 Herculina) and significantly more precise estimates for six others (2 Pallas, 3 Juno, 4 Vesta, 9 Metis, 16 Psyche, and 88 Thisbe). However, we also find that the conventional algorithm yields questionable results in several gravitationally coupled cases. To address such cases, we describe a new algorithm that allows the epoch state vectors of the subject asteroids to be included as solve-for parameters, allowing for the simultaneous solution of the masses and epoch state vectors of multiple subject and test asteroids. We then apply this algorithm to the same 30 main-belt asteroids and conclude that mass determinations resulting from current and future high-precision astrometric sources (such as Gaia ) should conduct a thorough search for possible gravitational couplings and account for their effects.« less

Hungaria Asteroid Region Telescopic Spectral Survey (HARTSS): Stony Asteroids Abundant in the Background and Family Populations

NASA Astrophysics Data System (ADS)

Lucas, Michael P.; Emery, Joshua P.; Pinilla-Alonso, Noemi; Lindsay, Sean S.; Lorenzi, Vania

2016-10-01

The Hungaria region represents a "purgatory" for the closest, preserved samples of the material from which the terrestrial planets accreted. The Hungaria region harbors a collisional family of Xe-type asteroids, which are situated among a background of predominantly S-complex asteroids. Deciphering their surface composition may provide constraints on the nature of the primordial building blocks of the terrestrial planets. We hypothesize that planetesimals in the inner part of the primordial asteroid belt experienced partial- to full-melting and differentiation, the Hungaria region should retain any petrologically-evolved material that formed there.We have undertaken an observational campaign entitled the Hungaria Asteroid Region Telescopic Spectral Survey (HARTSS) to record near-infrared (NIR) spectra to characterize taxonomy, surface mineralogy, and potential meteorite analogs. We used NIR instruments at two ground-based facilities (NASA IRTF; TNG). Our data set includes spectra of 82 Hungaria asteroids (61 background; 21 family), 65 were observed during HARTSS. We compare S-complex background asteroids to calibrations developed via laboratory analyses of ordinary chondrites, and to our analyses (EPMA, XRD, VIS+NIR spectra) of 11 primitive achondrite (acapulcoite-lodranite clan) meteorites.We find that stony S-complex asteroids dominate the Hungaria background population (~80%). Background objects exhibit considerable spectral diversity, when quantified by spectral band parameter measurements, translates to a variety of surface compositions. Two main meteorite groups are represented within the Hungaria background: unmelted, nebular L chondrites (and/or L chondrites), and partially-melted primitive achondrites. H-chondrite mineralogies appear to be absent from the Hungaria background. Xe-type Hungaria family members exhibit spectral homogeneity, consistent with the hypothesis that the family was derived from the disruption of a parent body analogous to an enstatite achondrite (i.e., aubrite) composition. Hungaria region asteroids exhibit a full range of petrologic evolution, from nebular, unmelted ordinary chondrites, through partially-melted primitive achondrites, to fully-melted igneous aubrite meteorites.

Small main-belt asteroid spectroscopic survey: Initial results

NASA Technical Reports Server (NTRS)

Xu, Shui; Binzel, Richard P.; Burbine, Thomas H.; Bus, Schelte J.

1995-01-01

The spectral characterization of small asteroids is important for understanding the evolution of their compositional and mineralogical properties. We report the results of a CCD spectroscopic survey of small main-belt asteroids which we call the Small Main-belt Asteroid Spectroscopic Survey (SMASS). Spectra of 316 asteroids were obtained, with wavelength coverage ranging from 4000 to 10000 A (0.4 to 1 micrometers). More than half of the objects in our survey have diameters less than 20 km. Survey results include the identification of the first object resembling ordinary chondrite meteorites among the main-belt asteroids (Binzel, R. P., et al, 1993) and observations of more than 20 asteroids showing basaltic achondrite spectral absorption features that strongly link Vesta as the parent body for the basaltic achondrite meteorites (Binzel, R. P., and S. Xu 1993). A potential Mars-crossing asteroid analog to ordinary chondrite meteorites (H chondrites), 2078 Nanking, is reported here. Through a principal component analysis, we have assigned classifications to the members of our sample. The majority of the small main-belt asteroids belong to S and C classes, similar to large asteroids. Our analysis shows that two new classes are justified which we label as J and O. Small asteroids display more diversity in spectral absorption features than the larger ones, which may indicate a greater variation of compositions in the small asteroid population. We found a few candidates for olivine-rich asteroids within the S class. Although the total number of olivine-rich candidates is relatively small, we present evidence suggesting that such objects are more prevalent at smaller sizes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gould, Andrew; Yee, Jennifer C., E-mail: gould@astronomy.ohio-state.edu, E-mail: jyee@astronomy.ohio-state.edu

While of order of a million asteroids have been discovered, the number in rigorously controlled samples that have precise orbits and rotation periods, as well as well-measured colors, is relatively small. In particular, less than a dozen main-belt asteroids with estimated diameters D < 3 km have excellent rotation periods. We show how existing and soon-to-be-acquired microlensing data can yield a large asteroid sample with precise orbits and rotation periods, which will include roughly 6% of all asteroids with maximum brightness I < 18.1 and lying within 10 Degree-Sign of the ecliptic. This sample will be dominated by small andmore » very small asteroids, down to D {approx} 1 km. We also show how asteroid astrometry could turn current narrow-angle OGLE proper motions of bulge stars into wide-angle proper motions. This would enable one to measure the proper-motion gradient across the Galactic bar.« less

Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris

NASA Astrophysics Data System (ADS)

Baer, James; Chesley, Steven R.

2008-01-01

We apply the technique of astrometric mass determination to measure the masses of 21 main-belt asteroids; the masses of 9 Metis (1.03 ± 0.24 × 10-11 M⊙), 17 Thetis (6.17 ± 0.64 × 10-13 M⊙), 19 Fortuna (5.41 ± 0.76 × 10-12 M⊙), and 189 Phthia (1.87 ± 0.64 × 10-14 M⊙) appear to be new. The resulting bulk porosities of 11 Parthenope (12±4%) and 16 Psyche (46±16%) are smaller than previously-reported values. Empirical expressions modeling bulk density as a function of mean radius are presented for the C and S taxonomic classes. To accurately model the forces on these asteroids during the mass determination process, we created an integrated ephemeris of the 300 large asteroids used in preparing the DE-405 planetary ephemeris; this new BC-405 integrated asteroid ephemeris also appears useful in other high-accuracy applications.

Solar System Science with LSST

NASA Astrophysics Data System (ADS)

Jones, R. L.; Chesley, S. R.; Connolly, A. J.; Harris, A. W.; Ivezic, Z.; Knezevic, Z.; Kubica, J.; Milani, A.; Trilling, D. E.

2008-09-01

The Large Synoptic Survey Telescope (LSST) will provide a unique tool to study moving objects throughout the solar system, creating massive catalogs of Near Earth Objects (NEOs), asteroids, Trojans, TransNeptunian Objects (TNOs), comets and planetary satellites with well-measured orbits and high quality, multi-color photometry accurate to 0.005 magnitudes for the brightest objects. In the baseline LSST observing plan, back-to-back 15-second images will reach a limiting magnitude as faint as r=24.7 in each 9.6 square degree image, twice per night; a total of approximately 15,000 square degrees of the sky will be imaged in multiple filters every 3 nights. This time sampling will continue throughout each lunation, creating a huge database of observations. Fig. 1 Sky coverage of LSST over 10 years; separate panels for each of the 6 LSST filters. Color bars indicate number of observations in filter. The catalogs will include more than 80% of the potentially hazardous asteroids larger than 140m in diameter within the first 10 years of LSST operation, millions of main-belt asteroids and perhaps 20,000 Trans-Neptunian Objects. Objects with diameters as small as 100m in the Main Belt and <100km in the Kuiper Belt can be detected in individual images. Specialized `deep drilling' observing sequences will detect KBOs down to 10s of kilometers in diameter. Long period comets will be detected at larger distances than previously possible, constrainting models of the Oort cloud. With the large number of objects expected in the catalogs, it may be possible to observe a pristine comet start outgassing on its first journey into the inner solar system. By observing fields over a wide range of ecliptic longitudes and latitudes, including large separations from the ecliptic plane, not only will these catalogs greatly increase the numbers of known objects, the characterization of the inclination distributions of these populations will be much improved. Derivation of proper elements for main belt and Trojan asteroids will allow ever more resolution of asteroid families and their size-frequency distribution, as well as the study of the long-term dynamics of the individual asteroids and the asteroid belt as a whole. Fig. 2 Orbital parameters of Main Belt Asteroids, color-coded according to ugriz colors measured by SDSS. The figure to the left shows osculating elements, the figure to the right shows proper elements - note the asteroid families visible as clumps in parameter space [1]. By obtaining multi-color ugrizy data for a substantial fraction of objects, relationships between color and dynamical history can be established. This will also enable taxonomic classification of asteroids, provide further links between diverse populations such as irregular satellites and TNOs or planetary Trojans, and enable estimates of asteroid diameter with rms uncertainty of 30%. With the addition of light-curve information, rotation periods and phase curves can be measured for large fractions of each population, leading to new insight on physical characteristics. Photometric variability information, together with sparse lightcurve inversion, will allow spin state and shape estimation for up to two orders of magnitude more objects than presently known. This will leverage physical studies of asteroids by constraining the size-strength relationship, which has important implications for the internal structure (solid, fractured, rubble pile) and in turn the collisional evolution of the asteroid belt. Similar information can be gained for other solar system bodies. [1] Parker, A., Ivezic

An efficient algorithm for global periodic orbits generation near irregular-shaped asteroids

NASA Astrophysics Data System (ADS)

Shang, Haibin; Wu, Xiaoyu; Ren, Yuan; Shan, Jinjun

2017-07-01

Periodic orbits (POs) play an important role in understanding dynamical behaviors around natural celestial bodies. In this study, an efficient algorithm was presented to generate the global POs around irregular-shaped uniformly rotating asteroids. The algorithm was performed in three steps, namely global search, local refinement, and model continuation. First, a mascon model with a low number of particles and optimized mass distribution was constructed to remodel the exterior gravitational potential of the asteroid. Using this model, a multi-start differential evolution enhanced with a deflection strategy with strong global exploration and bypassing abilities was adopted. This algorithm can be regarded as a search engine to find multiple globally optimal regions in which potential POs were located. This was followed by applying a differential correction to locally refine global search solutions and generate the accurate POs in the mascon model in which an analytical Jacobian matrix was derived to improve convergence. Finally, the concept of numerical model continuation was introduced and used to convert the POs from the mascon model into a high-fidelity polyhedron model by sequentially correcting the initial states. The efficiency of the proposed algorithm was substantiated by computing the global POs around an elongated shoe-shaped asteroid 433 Eros. Various global POs with different topological structures in the configuration space were successfully located. Specifically, the proposed algorithm was generic and could be conveniently extended to explore periodic motions in other gravitational systems.

LARGE SUPER-FAST ROTATOR HUNTING USING THE INTERMEDIATE PALOMAR TRANSIENT FACTORY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chan-Kao; Lin, Hsing-Wen; Ip, Wing-Huen

In order to look for large super-fast rotators, in late 2014 and early 2015, five dedicated surveys covering ∼188 deg{sup 2} in the ecliptic plane have been carried out in the R -band, with ∼10 minute cadence using the intermediate Palomar Transient Factory. Among 1029 reliable rotation periods obtained from the surveys, we discovered 1 new large super-fast rotator, (40511) 1999 RE88, and 18 other candidates. (40511) 1999 RE88 is an S-type inner main-belt asteroid with a diameter of D  = 1.9 ± 0.3 km, a rotation period of P  = 1.96 ± 0.01 hr, and a light curve amplitude of Δ m  ∼ 1.0 mag. To maintainmore » such fast rotation, an internal cohesive strength of ∼780 Pa is required. Combining all known large super-fast rotators, their cohesive strengths all fall in the range of 100–1000 Pa of lunar regolith. However, the number of large super-fast rotators seems to be far less than the whole asteroid population. This might indicate a peculiar asteroid group for them. Although the detection efficiency for a long rotation period is greatly reduced due to our two-day observation time span, the spin-rate distributions of this work show consistent results with Chang et al. (2015), after considering the possible observational bias in our surveys. It shows a number decrease with an increase of spin rate for asteroids with a diameter of 3 ⩽  D  ⩽ 15 km, and a number drop at a spin rate of f  = 5 rev day{sup −1} for asteroids with D  ⩽ 3 km.« less

Coupled extremely light Ca and Fe isotopes in peridotites

NASA Astrophysics Data System (ADS)

Zhao, Xinmiao; Zhang, Zhaofeng; Huang, Shichun; Liu, Yufei; Li, Xin; Zhang, Hongfu

2017-07-01

Large metal stable isotopic variations have been observed in both extraterrestrial and terrestrial samples. For example, Ca exhibits large mass-dependent isotopic variation in terrestrial igneous rocks and mantle minerals (on the order of ∼2‰ variation in 44Ca/40Ca). A thorough assessment and understanding of such isotopic variations in peridotites provides important constraints on the evolution and compositon of the Earth's mantle. In order to better understand the Ca and Fe isotopic variations in terrestrial silicate rocks, we report Ca isotopic compositions in a set of peridotitic xenoliths from North China Craton (NCC), which have been studied for Fe isotopes. These NCC peridotites have large Ca and Fe isotopic variations, with δ44/40Ca ranging from -0.08 to 0.92 (delta value relative to SRM915a) and δ57/54Fe (delta value relative to IRMM-014) ranging from -0.61 to 0.16, and these isotopic variations are correlated with large Mg# (100 × Mg/(Mg + Fe) molar ratio) variation, ranging from 80 to 90. Importantly, NCC Fe-rich peridotites have the lowest 44Ca/40Ca and 57Fe/54Fe ratios in all terrestrial silicate rocks. In contrast, although ureilites, mantle rocks from a now broken differentiated asteroid(s), have large Mg# variation, from 70 to 92, they have very limited δ57Fe/54Fe variation (0.03-0.21, delta value relative to IRMM-014). Our model calculations show that the coupled extremely light Ca-Fe isotopic signatures in NCC Fe-rich peridotites most likely reflect kinetic isotopic fractionation during melt-peridotite reaction on a timescale of several to 104 years. In addition, our new data and compiled literature data show a possible compositional effect on the inter-mineral Ca isotopic fractionation between co-existing clinopyroxene and orthopyroxene pairs.

ScienceCast 106: Big Asteroid Flyby

NASA Image and Video Library

2013-05-30

NASA is tracking a large near-Earth asteroid as it passes by the Earth-Moon system on May 31st. Amateur astronomers in the northern hemisphere may be able to see the space rock for themselves during the 1st week of June.

An anomalous basaltic meteorite from the innermost main belt.

PubMed

Bland, Philip A; Spurny, Pavel; Towner, Martin C; Bevan, Alex W R; Singleton, Andrew T; Bottke, William F; Greenwood, Richard C; Chesley, Steven R; Shrbeny, Lukas; Borovicka, Jiri; Ceplecha, Zdenek; McClafferty, Terence P; Vaughan, David; Benedix, Gretchen K; Deacon, Geoff; Howard, Kieren T; Franchi, Ian A; Hough, Robert M

2009-09-18

Triangulated observations of fireballs allow us to determine orbits and fall positions for meteorites. The great majority of basaltic meteorites are derived from the asteroid 4 Vesta. We report on a recent fall that has orbital properties and an oxygen isotope composition that suggest a distinct parent body. Although its orbit was almost entirely contained within Earth's orbit, modeling indicates that it originated from the innermost main belt. Because the meteorite parent body would likely be classified as a V-type asteroid, V-type precursors for basaltic meteorites unrelated to Vesta may reside in the inner main belt. This starting location is in agreement with predictions of a planetesimal evolution model that postulates the formation of differentiated asteroids in the terrestrial planet region, with surviving fragments concentrated in the innermost main belt.

K/TH in Achondrites and Interpretation of Grand Data for the Dawn Mission

NASA Technical Reports Server (NTRS)

Usui, T.; McSween, H. Y., Jr.; Mittlefehldt, D. W.; Prettyman, T. H.

2008-01-01

The Dawn mission will explore 4 Vesta [1], a highly differentiated asteroid believed to be the parent body of the howardite, eucrite and diogenite (HED) meteorite suite [e.g. 2]. The Dawn spacecraft is equipped with a gamma-ray and neutron detector (GRaND), which will enable measurement and mapping of elemental abundances on Vesta s surface [3]. Drawing on HED geochemistry, Usui and McSween [4] proposed a linear mixing model for interpretation of GRaND data. However, the HED suite is not the only achondrite suite representing asteroidal basaltic crusts; others include the mesosiderites, angrites, NWA 011, and possibly Ibitira, each of which is thought to have a distinct parental asteroid [5]. Here we critically examine the variability of GRaND-analyzed elements, K and Th, in HED meteorites, and propose a method based on the K-Th systematics to distinguish between HED and the other differentiated achondrites. Maps of these elements might also recognize incompatible element enriched areas such as mapped locally on the Moon (KREEP) [6], and variations in K/Th ratios might indicate impact volatilization of K. We also propose a new mixing model using elements that will be most reliably measured by GRaND, including K.

Compositional Variegation of Large-Diameter Low-Albedo Asteroids

NASA Astrophysics Data System (ADS)

Vilas, F.; Jarvis, K. S.; Anz-Meador, T. D.; Thibault, C. A.; Sawyer, S. R.; Fitzsimmons, A.

1997-07-01

Asteroids showing signs of aqueous alteration and thermal metamorphism in visible/near IR spectroscopy and photometry (C, G, F, B, and P classes) ranging from 0.37 - 0.90mu m dominate the asteroid population at heliocentric distances of 2.6 - 3.5 AU. Age dating of meteorites indicates that the Solar System was subjected to a major heating event 4.5 Gyr ago. Recent meteoritic research has produced evidence of a carbonaceous chondrite subjected to two separate aqueous alteration events with a metamorphic heating inbetween (Krot et al., 1997, submitted). Models of the effects of heating by electromagnetic induction or decay of short-lived radionuclides combined with models of the early collisional history of the Solar System after Jupiter's formation indicate that asteroids observed today can be divided into two groups by diameter. Those asteroids having diameters greater than 100 km were mixed by multiple collisions but remain as gravitationally bound rubble piles. Asteroids with diameters less than 100 km should show more compositional diversity. Vilas and Sykes (1996, Icarus, v. 124, 483) have shown using ECAS photometry that this compositional difference exists. Those asteroids having diameters greater than 100 km should be individually homogeneous, with spectral differences showing the combined effects of a primordial compositional gradient in the asteroid belt with thermal metamorphism. We address the significance of spatially-resolved spectra of 42 asteroids to the collective origin of these asteroids.

Reconstructing the size distribution of the primordial Main Belt

NASA Astrophysics Data System (ADS)

Tsirvoulis, G.; Morbidelli, A.; Delbo, M.; Tsiganis, K.

2018-04-01

In this work we aim to constrain the slope of the size distribution of main-belt asteroids, at their primordial state. To do so we turn out attention to the part of the main asteroid belt between 2.82 and 2.96 AU, the so-called "pristine zone", which has a low number density of asteroids and few, well separated asteroid families. Exploiting these unique characteristics, and using a modified version of the hierarchical clustering method we are able to remove the majority of asteroid family members from the region. The remaining, background asteroids should be of primordial origin, as the strong 5/2 and 7/3 mean-motion resonances with Jupiter inhibit transfer of asteroids to and from the neighboring regions. The size-frequency distribution of asteroids in the size range 17 < D(km) < 70 has a slope q ≃ - 1 . Using Monte-Carlo methods, we are able to simulate, and compensate for the collisional and dynamical evolution of the asteroid population, and get an upper bound for its size distribution slope q = - 1.43 . In addition, applying the same 'family extraction' method to the neighboring regions, i.e. the middle and outer belts, and comparing the size distributions of the respective background populations, we find statistical evidence that no large asteroid families of primordial origin had formed in the middle or pristine zones.

The global topography of Bennu: altimetry, photoclinometry, and processing

NASA Astrophysics Data System (ADS)

Perry, M. E.; Barnouin, O. S.; Daly, M. G.; Seabrook, J.; Palmer, E. E.; Gaskell, R. W.; Craft, K. L.; Roberts, J. H.; Philpott, L.; Asad, M. Al; Johnson, C. L.; Nair, A. H.; Espiritu, R. C.; Nolan, M. C.; Lauretta, D. S.

2017-09-01

The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission will spend two years observing (101955) Bennu and will then return pristine samples of carbonaceous material from the asteroid [1]. Launched in September 2016, OSIRISREx arrives at Bennu in August 2018, acquires a sample in July 2020, and returns the sample to Earth in September 2023. The instruments onboard OSIRIS-REx will measure the physical and chemical properties of this B-class asteroid, a subclass within the larger group of C-complex asteroids that might be organic-rich. At approximately 500m in average diameter [2], Bennu is sufficiently large to retain substantial regolith and as an Apollo asteroid with a low inclination (6°), it is one of the most accessible primitive near-Earth asteroid.

Revealing Secrets of Triple Asteroid Systems with SPHERE

NASA Astrophysics Data System (ADS)

Yang, Bin; Wahhaj, Zahed; Beauvalet, Laurene; Marchis, Franck; Dumas, Christophe; Marsset, Michaël

2015-11-01

A multiple-asteroid system provides otherwise unattainable information about the intrinsic properties of the system itself as well as its formation and evolution. Comparative spectroscopy and imaging of two large multiple main-belt asteroids: (93) Minerva and (130) Elektra were performed using the newly commissioned Spectro-Polarimetric High-contrast Exoplanet Research instrument (SPHERE) on ESO's 8.2-m VLT. A new moon (S/2014 (130) 1), of the known binary asteroid (130) Elektra, was discovered based on the SPHERE observations, making (130) Elektra the sixth triple system detected in the asteroid belt. We will present the component-resolved near infrared spectra, from 0.9 to 1.6 micron, of the Minerva and the Elektra triple systems. We will also present the orbital solution and the dynamical simulations on the two moons of (130) Elektra.

Calculating the momentum enhancement factor for asteroid deflection studies

DOE PAGES

Heberling, Tamra; Gisler, Galen; Plesko, Catherine; ...

2017-10-17

The possibility of kinetic-impact deflection of threatening near-Earth asteroids will be tested for the first time in the proposed AIDA (Asteroid Impact Deflection Assessment) mission, involving NASAs DART (Double Asteroid Redirection Test). The impact of the DART spacecraft onto the secondary of the binary asteroid 65803 Didymos at a speed of 5 to 7 km/s is expected to alter the mutual orbit by an observable amount. Furthermore, the velocity transferred to the secondary depends largely on the momentum enhancement factor, typically referred to as beta. Here, we use two hydrocodes developed at Los Alamos, RAGE and PAGOSA, to calculate anmore » approximate value for beta in laboratory-scale benchmark experiments. Convergence studies comparing the two codes show the importance of mesh size in estimating this crucial parameter.« less

Calculating the momentum enhancement factor for asteroid deflection studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heberling, Tamra; Gisler, Galen; Plesko, Catherine

The possibility of kinetic-impact deflection of threatening near-Earth asteroids will be tested for the first time in the proposed AIDA (Asteroid Impact Deflection Assessment) mission, involving NASAs DART (Double Asteroid Redirection Test). The impact of the DART spacecraft onto the secondary of the binary asteroid 65803 Didymos at a speed of 5 to 7 km/s is expected to alter the mutual orbit by an observable amount. Furthermore, the velocity transferred to the secondary depends largely on the momentum enhancement factor, typically referred to as beta. Here, we use two hydrocodes developed at Los Alamos, RAGE and PAGOSA, to calculate anmore » approximate value for beta in laboratory-scale benchmark experiments. Convergence studies comparing the two codes show the importance of mesh size in estimating this crucial parameter.« less

Impact simulations on the rubble pile asteroid (2867) Steins

NASA Astrophysics Data System (ADS)

Deller, Jakob; Lowry, Stephen; Snodgrass, Colin; Price, Mark; Sierks, Holger

2015-04-01

Images from the OSIRIS camera system on board the Rosetta spacecraft (Keller et al. 2010) have revealed several interesting features on asteroid (2867) Steins. Its macro porosity of 40%, together with the shape that looks remarkably like a YORP evolved body, both indicate a rubble pile structure. A large crater on the southern pole is evidence for collisional evolution of this rubble pile asteroid. We have developed a new approach for simulating impacts on asteroid bodies that connects formation history to their collisional evolution. This is achieved by representing the interior as a 'rubble pile', created from the gravitational aggregation of spherical 'pebbles' that represent fragments from a major disruption event. These 'pebbles' follow a power-law size function and constitute the building blocks of the rubble pile. This allows us to explicitly model the interior of rubble pile asteroids in hyper-velocity impact simulations in a more realistic way. We present preliminary results of a study validating our approach in a large series of simulated impacts on a typical small main-belt rubble pile asteroid using the Smoothed Particle Hydrodynamics solver in LS-DYNA. We show that this approach allows us to explicitly follow the behavior of a single 'pebble', while preserving the expected properties of the bulk asteroid as known from observations and experiments (Holsapple 2009). On the example of Steins, we use this model to relate surface features like the northern hill at 75/100 degrees lon/lat distance to the largest crater (Jorda et al. 2012), or the catena of depletion pits, to the displacement of large fragments in the interior of the asteroid during the impact. We do this by following the movement of pebbles below the surface feature in simulations that recreate the shape of the impact crater. We show that while it is not straightforward to explain the formation of the hill-like structure, the formation of cracks possibly leading to depletion zones can be observed. References: Keller et al., 2010, Science, 327(5962), pp. 190-193; Jorda et al., 2012, Icarus, vol. 221 (2) pp. 1089-1100; Holsapple, 2009, PSS, 57(2), 127-141.

Impact Simulations on the Rubble Pile Asteroid (2867) Steins

NASA Astrophysics Data System (ADS)

Deller, Jakob; Snodgrass, Colin; Lowry, Stephen C.; Price, Mark C.; Sierks, Holger

2014-11-01

Images from the OSIRIS camera system on board the Rosetta spacecraft (Keller et al. 2010) has revealed several interesting features on asteroid (2867) Steins. Its macro porosity of 40%, together with the shape that looks remarkably like a YORP evolved body, both indicate a rubble pile structure. A large crater on the southern pole is evidence for collisional evolution of this rubble pile asteroid. We have developed a new approach for simulating impacts on asteroid bodies that connects formation history to their collisional evolution. This is achieved by representing the interior as a ‘rubble pile’, created from the gravitational aggregation of spherical ‘pebbles’ that represent fragments from a major disruption event. These ‘pebbles’ follow a power law size function and constitute the building blocks of the rubble pile. This allows us to explicitly model the interior of rubble pile asteroids in hyper-velocity impact simulations in a more realistic way. We present preliminary results of a study validating our approach in a large series of simulated impacts on a typical small main belt rubble pile asteroid using the Smoothed Particle Hydrodynamics solver in Autodyn. We show that this approach allows us to explicitly follow the behavior of a single ‘pebble’, while preserving the expected properties of the bulk asteroid as known from observations and experiments (Holsapple 2009). On the example of Steins, we use this model to investigate if surface features like the northern hill at 75/100 degrees lon/lat distance to the largest crater (Jorda et al. 2012), or the catena of depletion pits, can be explained by the displacement of large fragments in the interior of the asteroid during the impact. We do this by following the movement of pebbles below the surface feature in simulations that recreate the shape of the impact crater.Acknowledgements: Jakob Deller thanks the Planetary Science Institute for a Pierazzo International Student Travel Award that funds his attendance at this conference. References: Keller et al., 2010, Science, 327(5962), pp. 190-193 Jorda et al., 2012, Icarus, vol. 221 (2) pp. 1089-1100; Holsapple, 2009, PSS, 57(2), 127-141.

THE ASTEROID DISTRIBUTION IN THE ECLIPTIC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryan, Erin Lee; Woodward, Charles E.; Dipaolo, Andrea

2009-06-15

We present analysis of the asteroid surface density distribution of main-belt asteroids (mean perihelion {delta} {approx_equal} 2.404 AU) in five ecliptic latitude fields, -17 {approx}> {beta}({sup 0}) {approx}< +15, derived from deep Large Binocular Telescope V-band (85% completeness limit V = 21.3 mag) and Spitzer Space Telescope IRAC 8.0 {mu}m (80% completeness limit {approx}103 {mu}Jy) fields enabling us to probe the 0.5-1.0 km diameter asteroid population. We discovered 58 new asteroids in the optical survey as well as 41 new bodies in the Spitzer fields. The derived power-law slopes of the number of asteroids per square degree are similar withinmore » each {approx}5{sup 0} ecliptic latitude bin with a mean value of -0.111 {+-} 0.077. For the 23 known asteroids detected in all four IRAC channels mean albedos range from 0.24 {+-} 0.07 to 0.10 {+-} 0.05. No low-albedo asteroids (p{sub V} {approx}< 0.1) were detected in the Spitzer FLS fields, whereas in the SWIRE fields they are frequent. The SWIRE data clearly samples asteroids in the middle and outer belts providing the first estimates of these km-sized asteroids' albedos. Our observed asteroid number densities at optical wavelengths are generally consistent with those derived from the Standard Asteroid Model within the ecliptic plane. However, we find an overdensity at {beta} {approx}> 5{sup 0} in our optical fields, while the infrared number densities are underdense by factors of 2 to 3 at all ecliptic latitudes.« less

Basalt or Not? Near-infrared Spectra, Surface Mineralogical Estimates, and Meteorite Analogs for 33 Vp-type Asteroids

NASA Astrophysics Data System (ADS)

Hardersen, Paul S.; Reddy, Vishnu; Cloutis, Edward; Nowinski, Matt; Dievendorf, Margaret; Genet, Russell M.; Becker, Savan; Roberts, Rachel

2018-07-01

Investigations of the main asteroid belt and efforts to constrain that population’s physical characteristics involve the daunting task of studying hundreds of thousands of small bodies. Taxonomic systems are routinely employed to study the large-scale nature of the asteroid belt because they utilize common observational parameters, but asteroid taxonomies only define broadly observable properties and are not compositionally diagnostic. This work builds upon the results of work by Hardersen et al., which has the goal of constraining the abundance and distribution of basaltic asteroids throughout the main asteroid belt. We report on the near-infrared (NIR: 0.7 to 2.5 μm) reflectance spectra, surface mineralogical characterizations, analysis of spectral band parameters, and meteorite analogs for 33 Vp asteroids. NIR reflectance spectroscopy is an effective remote sensing technique to detect most pyroxene group minerals, which are spectrally distinct with two very broad spectral absorptions at ∼0.9 and ∼1.9 μm. Combined with the results from Hardersen et al., we identify basaltic asteroids for ∼95% (39/41) of our inner-belt Vp sample, but only ∼25% (2/8) of the outer-belt Vp sample. Inner-belt basaltic asteroids are most likely associated with (4) Vesta and represent impact fragments ejected from previous collisions. Outer-belt Vp asteroids exhibit disparate spectral, mineralogical, and meteorite analog characteristics and likely originate from diverse parent bodies. The discovery of two additional likely basaltic asteroids provides additional evidence for an outer-belt basaltic asteroid population.

Interplanetary Trajectory Design for the Asteroid Robotic Redirect Mission Alternate Approach Trade Study

NASA Technical Reports Server (NTRS)

Merrill, Raymond Gabriel; Qu, Min; Vavrina, Matthew A.; Englander, Jacob A.; Jones, Christopher A.

2014-01-01

This paper presents mission performance analysis methods and results for the Asteroid Robotic Redirect Mission (ARRM) option to capture a free standing boulder on the surface of a 100 m or larger NEA. It details the optimization and design of heliocentric low-thrust trajectories to asteroid targets for the ARRM solar electric propulsion spacecraft. Extensive searches were conducted to determine asteroid targets with large pick-up mass potential and potential observation opportunities. Interplanetary trajectory approximations were developed in method based tools for Itokawa, Bennu, 1999 JU3, and 2008 EV5 and were validated by end-to-end integrated trajectories.

Catching a Rolling Stone: Dynamics and Control of a Spacecraft and an Asteroid

NASA Technical Reports Server (NTRS)

Roithmayr, Carlos M.; Shen, Haijun; Jesick, Mark C; Cornelius, David M

2013-01-01

In a recent report, a robotic spacecraft mission is proposed for the purpose of collecting a small asteroid, or a small part of a large one, and transporting it to an orbit in the Earth-Moon system. Such an undertaking will require solutions to many of the engineering problems associated with deflection of an asteroid that poses a danger to Earth. In both cases, it may be necessary for a spacecraft to approach an asteroid from a nearby position, hover for some amount of time, move with the same angular velocity as the asteroid, descend, perhaps ascend, and finally arrest the angular velocity of the asteroid. Dynamics and control in each of these activities is analyzed in order to determine the velocity increments and control torque that must be provided by a reaction control system, and the mass of the propellant that will be consumed. Two attitude control algorithms are developed, one to deal with synchronizing the spacecraft s angular velocity with that of the asteroid, and the other to arrest the asteroid s angular velocity. A novel approach is proposed for saving fuel in the latter case.

Characteristics and large bulk density of the C-type main-belt triple asteroid (93) Minerva

NASA Astrophysics Data System (ADS)

Marchis, F.; Vachier, F.; Ďurech, J.; Enriquez, J. E.; Harris, A. W.; Dalba, P. A.; Berthier, J.; Emery, J. P.; Bouy, H.; Melbourne, J.; Stockton, A.; Fassnacht, C. D.; Dupuy, T. J.; Strajnic, J.

2013-05-01

From a set of adaptive optics (AO) observations collected with the W.M. Keck telescope between August and September 2009, we derived the orbital parameters of the most recently discovered satellites of the large C-type asteroid (93) Minerva. The satellites of Minerva, which are approximately 3 and 4 km in diameter, orbit very close to the primary (˜5 and ˜8 × Rp and ˜1% and ˜2% × RHill) in a circular manner, sharing common characteristics with most of the triple asteroid systems in the main-belt. Combining these AO observations with lightcurve data collected since 1980 and two stellar occultations in 2010 and 2011, we removed the ambiguity of the pole solution of Minerva's primary and showed that it has an almost regular shape with an equivalent diameter Deq = 154 ± 6 km in agreement with IRAS observations. The surprisingly high bulk density of 1.75 ± 0.30 g/cm3 for this C-type asteroid, suggests that this taxonomic class is composed of asteroids with different compositions, For instance, Minerva could be made of the same material as dry CR, CO, and CV meteorites. We discuss possible scenarios on the origin of the system and conclude that future observations may shine light on the nature and composition of this fifth known triple main-belt asteroid.

A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2.

PubMed

Snodgrass, Colin; Tubiana, Cecilia; Vincent, Jean-Baptiste; Sierks, Holger; Hviid, Stubbe; Moissl, Richard; Boehnhardt, Hermann; Barbieri, Cesare; Koschny, Detlef; Lamy, Philippe; Rickman, Hans; Rodrigo, Rafael; Carry, Benoît; Lowry, Stephen C; Laird, Ryan J M; Weissman, Paul R; Fitzsimmons, Alan; Marchi, Simone

2010-10-14

The peculiar object P/2010 A2 was discovered in January 2010 and given a cometary designation because of the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized class of main-belt comets. If confirmed, this new object would expand the range in heliocentric distance over which main-belt comets are found. Here we report observations of P/2010 A2 by the Rosetta spacecraft. We conclude that the trail arose from a single event, rather than a period of cometary activity, in agreement with independent results. The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around 10 February 2009.

Tsunami Generation from Asteroid Airburst and Ocean Impact and Van Dorn Effect

NASA Technical Reports Server (NTRS)

Robertson, Darrel

2016-01-01

Airburst - In the simulations explored energy from the airburst couples very weakly with the water making tsunami dangerous over a shorter distance than the blast for asteroid sizes up to the maximum expected size that will still airburst (approx.250MT). Future areas of investigation: - Low entry angle airbursts create more cylindrical blasts and might couple more efficiently - Bursts very close to the ground will increase coupling - Inclusion of thermosphere (>80km altitude) may show some plume collapse effects over a large area although with much less pressure center dot Ocean Impact - Asteroid creates large cavity in ocean. Cavity backfills creating central jet. Oscillation between the cavity and jet sends out tsunami wave packet. - For deep ocean impact waves are deep water waves (Phase speed = 2x Group speed) - If the tsunami propagation and inundation calculations are correct for the small (<250MT) asteroids in these simulations where they impact deep ocean basins, the resulting tsunami is not a significant hazard unless particularly close to vulnerable communities. Future work: - Shallow ocean impact. - Effect of continental shelf and beach profiles - Tsunami vs. blast damage radii for impacts close to populated areas - Larger asteroids below presumed threshold of global effects (Ø200 - 800m).

Finding and characterizing candidate targets for the Asteroid Redirect Mission (ARM)

NASA Astrophysics Data System (ADS)

Chodas, P.

2014-07-01

NASA's proposed Asteroid Redirect Mission (ARM) leverages key on-going activities in Human Exploration and Space Technology to advance NASA's goals in these areas. One primary objective of ARM would be to develop and demonstrate a high-power Solar Electric Propulsion (SEP) vehicle which would have the capability of moving significant amounts of mass around the solar system. SEP would be a key technology for robust future missions to deep space destinations, possibly including human missions to asteroids or to Mars. ARM would use the SEP vehicle to redirect up to hundreds of tons of material from a near-Earth asteroid into a stable lunar orbit, where a crew flying in an Orion vehicle would rendezvous and dock with it. The crew would perform an extra-vehicular activity (EVA), sample the material, and bring it back to the Earth; follow-on visits would also be possible. Two ARM mission concepts are being studied: one is to go to a small 4-10-meter-diameter asteroid, capture the entire asteroid and guide it into lunar orbit; the other is to go to a large 100-500 meter asteroid, remove a 1-10 meter boulder, and bring the boulder back into lunar orbit. A planetary defense demonstration could be included under either concept. Although some candidate targets are already known for both mission concepts, an observation campaign has been organized to identify more mission candidates. This campaign naturally leverages off of NASA's NEO Observations Program. Enhancements to asteroid search capabilities which will come online soon should increase the discovery rates for ARM candidates and hazardous asteroids alike. For the small-asteroid ARM concept, candidate targets must be smaller than about 12 meters, must follow Earth-like orbits and must naturally approach the Earth closely in the early 2020s, providing the opportunity for a low-velocity capture into the Earth/Moon system. About a dozen candidates are known with absolute magnitudes in the right range and with orbits suitable for missions launching no earlier than June 2019; the maximum asteroid return masses for these range from 45 to 800 tons according to the orbit. Unfortunately, many of the currently known candidates have not had their sizes, masses and spin rates adequately constrained in order to provide confidence that they are within the capability of the ARM vehicle to return. Still, three candidates have been characterized well enough, two by the Spitzer Space Telescope, 2009 BD and 2011 MD, and one by radar, 2013 EC_{20}. 2009 BD was not actually detected by Spitzer, indicating it was smaller than expected, about 4 meters; similarly, 2013 EC_{20} turned out to be smaller than desired, less than 3 meters. A fourth candidate, 2008 HU_4, should be characterized with radar in 2016 when it passes near the Earth. In general, physical characterization of these very small asteroids is best performed immediately after discovery, while they are still very near the Earth. Radar is important for characterizing size and rotation state, while long-arc high-precision astrometry can help characterize mass through estimation of the area-to-mass ratio. Rapid-response characterization for an ARM candidate was successfully demonstrated last year for 2013 EC_{20}, mentioned earlier. More candidates for the small-asteroid concept are expected: new potential candidates should be detected at the rate of 3 to 5 per year, based on extrapolations from past discovery rates. For the large-asteroid ARM concept, there is an additional characterization challenge: the surface of the asteroid must be observed with enough resolution that the presence of ˜3-meter boulders can be either directly seen or inferred from high-SNR radar. The maximum size and mass of the returnable boulders depends on the asteroid orbit in much the same way as for the other concept. Asteroid Itokawa is a strong candidate because it has already been well characterized by the Japanese Hayabusa spacecraft. The future targets of the OSIRIS-REx and Hayabusa 2 missions, Bennu and 1999 JU_3, should also become strong candidates in 2018. Also considered a valid candidate is 2008 EV_5: radar detected decameter-scale boulders on its surface, from which the presence of returnable ˜3-meter boulders can be inferred. The characterization rate for large-asteroid concept candidates using high-SNR radar is about 1 per year. NASA plans to choose between the two ARM concepts, capture an entire small asteroid versus pick up a boulder from a large one, within about a year.

The Gulliver Mission: A Short-Cut to Primitive Body and Mars Sample Return

NASA Astrophysics Data System (ADS)

Britt, D. T.

2003-05-01

The Martian moon Deimos has extraordinary potential for future sample return missions. Deimos is spectrally similar to D-type asteroids and may be a captured primitive asteroid that originated in the outer asteroid belt. This capture probably took place in the earliest periods of Martian history, over 4.4 Gyrs ago [1], and Deimos has been accumulating material ejected from the Martian surface ever since. Analysis of Martian ejecta, material accumulation, capture cross-section, regolith over-turn, and Deimos's albedo suggest that Mars material may make up as much as 10% of Deimos's regolith. The Martian material on Deimos would be dominated by ejecta from the ancient crust of Mars, delivered during the Noachian Period of basin-forming impacts and heavy bombardment. Deimos could be a repository of samples from ancient Mars, including the full range of Martian crustal and upper mantle material from the early differentiation and crustal-forming epoch as well as samples from the era of high volatile flux, thick atmosphere, and possible surface water. In addition to Martian ejecta, 90% of the Deimos sample will be spectral type D asteroidal material. D-type asteroids are thought to be highly primitive and are most common in the difficult to access outer asteroid belt and the Jupiter Trojans. The Gulliver Mission proposes to directly collect up to 10 kilograms of Deimos regolith and return it to Earth. This sample may contain up to 1000 grams of Martian material along with up to 9 kilograms of primitive asteroidal material. Because of stochastic processes of regolith mixing over 4.4 Gyrs, the rock fragments and grains will likely sample the diversity of the Martian ancient surface as well as the asteroid. In essence, Gulliver represents two shortcuts, to Mars sample return and to the outer asteroid belt. References: [1] Burns J. A. (1992) Mars (Kieffer H. H. et al., eds), 1283-1302.

Spectroscopic Evidence for the Asteroidal Nature of the July 2009 Jovian Impactor

NASA Astrophysics Data System (ADS)

Lisse, Carey; Orton, Glenn; Yanamandra-Fisher, Padma; Fletcher, Leigh; Depater, Imke; Hammel, Heidi

2010-05-01

The collision of a large object with Jupiter on July 19, 2009, heated its atmosphere, modified its composition and generated a prominent field of deposited particulate debris. Low-resolution 7-24 μm spectroscopy of the impact field obtained using the T-ReCS mid-infrared camera/spectrometer on Gemini/South on 24 July 2009 has revealed an excess 9-μm absorption in the impact debris in addition to that supplied by hot ammonia created in the impact. We have searched for candidate materials that would best fit the spectral feature near 9 μm, and find that the feature cannot be matched with candidate materials in Jupiter's atmosphere. A search through a large suite of gaseous and solid absorption spectra (c.f Lisse et al. 2008, 2009) revealed that the major competent matches were for (a) obsidian, a glassy silica, and (b) quartz and cristobalite, crystalline silicas, kinetic alteration products of primitive body ferromagnesian silicates formed at high pressures and temperatures over 1500 K. There are also weak features at 10 - 11 um consistent with olivine absorptions. While the high temperatures required to create silicas are also high enough to destroy the non-refractory water and organics dominating icy cometary bodies, and thus destroy their spectral signal, there was no detectable absorption due to pyroxene materials, which, along with olivines in roughly equal measure, comprise the majority of refractory silicaceous species found in comets (Lisse et al. 2007). This suggests that the impacting body was not a comet, but an olivine-rich differentiated body similar to asteroids that are abundant in the outer regions of the main asteroid belt (Lodders and Fegley 1998). We speculate that the weak structural strength of bulk cometary material causes a comet impactor to catastrophically disrupt at higher altitudes and lower temperatures than a strong, dense asteroidal body, so that the cometary refractory dust component remains relatively cold and unaltered through blowback and Jovian surface deposition, while asteroidal dust is heated enough to be transformed from silicates to silicas. Ancillary evidence for the asteroidal nature of the impactor arises from the singular nature of the impact site, the existence of asteroidal orbits consistent with the observed geometry (Chodas 2009, Orton et al. 2010), and the differences between the observed 2009 opacity spectra of the debris and the observed debris opacity created in July 1994 by the SL9 fragments. Nicholson et al. (1995) noted the presence of a non-gaseous component of their spectrum of the SL9 R fragment impact, which they fit with the 'astronomical silicate' of Draine (1985). Griffith et al. (1997) also required an opacity source besides NH3 gas in order to explain the spectral continuum associated with debris from the L fragment, inferring that it was most likely the result of a silicate feature similar to those in comets (Hanner et al. 1994). Both of these are consistent with increased opacity in the 10-12 μm region due to a mix of stratospheric debris consisting of olivines and pyroxenes, typically found in comets, without any additional opacity at ~9 um due to silica.

Large ejecta fragments from asteroids. [Abstract only

NASA Technical Reports Server (NTRS)

Asphaug, E.

1994-01-01

The asteroid 4 Vesta, with its unique basaltic crust, remains a key mystery of planetary evolution. A localized olivine feature suggests excavation of subcrustal material in a crater or impact basin comparable in size to the planetary radius (R(sub vesta) is approximately = 280 km). Furthermore, a 'clan' of small asteroids associated with Vesta (by spectral and orbital similarities) may be ejecta from this impact 151 and direct parents of the basaltic achondrites. To escape, these smaller (about 4-7 km) asteroids had to be ejected at speeds greater than the escape velocity, v(sub esc) is approximately = 350 m/s. This evidence that large fragments were ejected at high speed from Vesta has not been reconciled with the present understanding of impact physics. Analytical spallation models predict that an impactor capable of ejecting these 'chips off Vesta' would be almost the size of Vesta! Such an impact would lead to the catastrophic disruption of both bodies. A simpler analysis is outlined, based on comparison with cratering on Mars, and it is shown that Vesta could survive an impact capable of ejecting kilometer-scale fragments at sufficient speed. To what extent does Vesta survive the formation of such a large crater? This is best addressed using a hydrocode such as SALE 2D with centroidal gravity to predict velocities subsequent to impact. The fragmentation outcome and velocity subsequent to the impact described to demonstrate that Vesta survives without large-scale disassembly or overturning of the crust. Vesta and its clan represent a valuable dataset for testing fragmentation hydrocodes such as SALE 2D and SPH 3D at planetary scales. Resolution required to directly model spallation 'chips' on a body 100 times as large is now marginally possible on modern workstations. These boundaries are important in near-surface ejection processes and in large-scale disruption leading to asteroid families and stripped cores.

Finding 'paydirt' on the moon and asteroids

NASA Technical Reports Server (NTRS)

Staehle, R. L.

1983-01-01

Lunar polar region water ice, the Trojan asteroids of the earth, accessible, volatile substance-rich near-earth asteroids, and lunar gas deposits, are theoretically identified extraterrestrial resources for application to space transportation whose existence and economical exploitability could be confirmed by explorations conducted with relatively simple spacecraft. Any of these resources could improve the economics of interorbit transportation, thereby permitting launch vehicle payloads to be devoted to the transport of revenue-generating or services-providing equipment, rather than to the large propellant volumes required for the placing of large payloads on station. Among the verification missions cited is a simple lunar prospector orbiter, carrying a gamma-ray spectrometer and an electromagnetic sounder, which could ascertain the presence of water ice at the lunar poles.

First known terrestrial impact of a binary asteroid from a main belt breakup event.

PubMed

Ormö, Jens; Sturkell, Erik; Alwmark, Carl; Melosh, Jay

2014-10-23

Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt, which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering rate during several millions of years following the event. The 7.5-km wide Lockne crater, central Sweden, is known to be a member of this family. We here provide evidence that Lockne and its nearby companion, the 0.7-km diameter, contemporaneous, Målingen crater, formed by the impact of a binary, presumably 'rubble pile' asteroid. This newly discovered crater doublet provides a unique reference for impacts by combined, and poorly consolidated projectiles, as well as for the development of binary asteroids.

Properties of the moon, Mars, Martian satellites, and near-earth asteroids

NASA Technical Reports Server (NTRS)

Taylor, Jeffrey G.

1989-01-01

Environments and surface properties of the moon, Mars, Martian satellites, and near-earth asteroids are discussed. Topics include gravity, atmospheres, surface properties, surface compositions, seismicity, radiation environment, degradation, use of robotics, and environmental impacts. Gravity fields vary from large fractions of the earth's field such as 1/3 on Mars and 1/6 on the moon to smaller fractions of 0.0004 g on an asteroid 1 km in diameter. Spectral data and the analogy with meteor compositions suggest that near-earth asteroids may contain many resources such as water-rich carbonaceous materials and iron-rich metallic bodies. It is concluded that future mining and materials processing operations from extraterrestrial bodies require an investment now in both (1) missions to the moon, Mars, Phobos, Deimos, and near-earth asteroids and (2) earth-based laboratory research in materials and processing.

The missing large impact craters on Ceres.

PubMed

Marchi, S; Ermakov, A I; Raymond, C A; Fu, R R; O'Brien, D P; Bland, M T; Ammannito, E; De Sanctis, M C; Bowling, T; Schenk, P; Scully, J E C; Buczkowski, D L; Williams, D A; Hiesinger, H; Russell, C T

2016-07-26

Asteroids provide fundamental clues to the formation and evolution of planetesimals. Collisional models based on the depletion of the primordial main belt of asteroids predict 10-15 craters >400 km should have formed on Ceres, the largest object between Mars and Jupiter, over the last 4.55 Gyr. Likewise, an extrapolation from the asteroid Vesta would require at least 6-7 such basins. However, Ceres' surface appears devoid of impact craters >∼280 km. Here, we show a significant depletion of cerean craters down to 100-150 km in diameter. The overall scarcity of recognizable large craters is incompatible with collisional models, even in the case of a late implantation of Ceres in the main belt, a possibility raised by the presence of ammoniated phyllosilicates. Our results indicate that a significant population of large craters has been obliterated, implying that long-wavelength topography viscously relaxed or that Ceres experienced protracted widespread resurfacing.

VLT/SPHERE- and ALMA-based shape reconstruction of asteroid (3) Juno

NASA Astrophysics Data System (ADS)

Viikinkoski, M.; Kaasalainen, M.; Ďurech, J.; Carry, B.; Marsset, M.; Fusco, T.; Dumas, C.; Merline, W. J.; Yang, B.; Berthier, J.; Kervella, P.; Vernazza, P.

2015-09-01

We use the recently released Atacama Large Millimeter Array (ALMA) and VLT/SPHERE science verification data, together with earlier adaptive-optics images, stellar occultation, and lightcurve data to model the 3D shape and spin of the large asteroid (3) Juno with the all-data asteroid modelling (ADAM) procedure. These data set limits on the plausible range of shape models, yielding reconstructions suggesting that, despite its large size, Juno has sizable unrounded features moulded by non-gravitational processes such as impacts. Based on observations collected at the European Southern Observatory, Paranal, Chile (prog. ID: 60.A-9379, 086.C-0785), and at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

The missing large impact craters on Ceres

USGS Publications Warehouse

Marchi, S.; Ermakov, A.; Raymond, C.A.; Fu, R.R.; O'Brien, D.P.; Bland, Michael T.; Ammannito, E.; De Sanctis, M.C.; Bowling, Tim; Schenk, P.; Scully, J.E.C.; Buczkowski, D.L.; Williams, D.A.; Hiesinger, H.; Russell, C.T.

2016-01-01

Asteroids provide fundamental clues to the formation and evolution of planetesimals. Collisional models based on the depletion of the primordial main belt of asteroids predict 10–15 craters >400 km should have formed on Ceres, the largest object between Mars and Jupiter, over the last 4.55 Gyr. Likewise, an extrapolation from the asteroid Vesta would require at least 6–7 such basins. However, Ceres’ surface appears devoid of impact craters >~280 km. Here, we show a significant depletion of cerean craters down to 100–150 km in diameter. The overall scarcity of recognizable large craters is incompatible with collisional models, even in the case of a late implantation of Ceres in the main belt, a possibility raised by the presence of ammoniated phyllosilicates. Our results indicate that a significant population of large craters has been obliterated, implying that long-wavelength topography viscously relaxed or that Ceres experienced protracted widespread resurfacing.

Project RAMA: Reconstructing Asteroids Into Mechanical Automata

NASA Technical Reports Server (NTRS)

Dunn, Jason; Fagin, Max; Snyder, Michael; Joyce, Eric

2017-01-01

Many interesting ideas have been conceived for building space-based infrastructure in cislunar space. From O'Neill's space colonies, to solar power satellite farms, and even prospecting retrieved near earth asteroids. In all the scenarios, one thing remained fixed - the need for space resources at the outpost. To satisfy this need, O'Neill suggested an electromagnetic railgun to deliver resources from the lunar surface, while NASA's Asteroid Redirect Mission called for a solar electric tug to deliver asteroid materials from interplanetary space. At Made In Space, we propose an entirely new concept. One which is scalable, cost effective, and ensures that the abundant material wealth of the inner solar system becomes readily available to humankind in a nearly automated fashion. We propose the RAMA architecture, which turns asteroids into self-contained spacecraft capable of moving themselves back to cislunar space. The RAMA architecture is just as capable of transporting conventional-sized asteroids on the 10-meter length scale as transporting asteroids 100 meters or larger, making it the most versatile asteroid retrieval architecture in terms of retrieved-mass capability. This report describes the results of the Phase I study funded by the NASA NIAC program for Made In Space to establish the concept feasibility of using space manufacturing to convert asteroids into autonomous, mechanical spacecraft. Project RAMA, Reconstituting Asteroids into Mechanical Automata, is designed to leverage the future advances of additive manufacturing (AM), in-situ resource utilization (ISRU) and in-situ manufacturing (ISM) to realize enormous efficiencies in repeated asteroid redirect missions. A team of engineers at Made In Space performed the study work with consultation from the asteroid mining industry, academia, and NASA. Previous studies for asteroid retrieval have been constrained to studying only asteroids that are both large enough to be discovered, and small enough to be captured and transported using Earth-launched propulsion technology. Project RAMA is not forced into this constraint. The mission concept studied involved transporting a much larger approximately 50-meter asteroid to cislunar space. Demonstration of transport of a 50-meter-class asteroid has several ground-breaking advantages. First, the returned material is of an industrial, rather than just scientific, quantity (greater than 10,000 tonnes versus approximately10s of tonnes). Second, the "useless" material in the asteroid is gathered and expended as part of the asteroid's propulsion system, allowing the returned asteroid to be considerably "purer" than a conventional asteroid retrieval mission. Third, the infrastructure used to convert and return the asteroid is reusable, and capable of continually returning asteroids to cislunar space.

Asteroid spectral reflectivities.

NASA Technical Reports Server (NTRS)

Chapman, C. R.; Mccord, T. B.; Johnson, T. V.

1973-01-01

We measured spectral reflectivities (0.3-1.1 micron) for 32 asteroids. There are at least 14 different curve types. Common types are: (a) reddish curves with 10% absorptions near 0.95 micron or beyond 1.0 micron, due to Fe(2+) in minerals such as pyroxenes; (b) flat curves in the visible and near-IR with sharp decreases in the UV and (c) flat curves even into the UV. Several asteroids show probable color variations with rotation, especially 6 Hebe. A sample of 102 asteroids with reliably known colors is derived from the reflectivities and from earlier colorimetry. Several correlations of colors and spectral curve types with orbital and physical parameters are examined: (1) asteroids with large aphelia have flat reflectivities while those with small perihelia are mostly reddish, (2) curve types show evidence for clustering on an a vs e plot, with 0.95 micron bands occuring mainly for Mars-approaching asteroids, (3) no strong correlation exists between color and either proper eccentricity or proper inclination.

Measurement of Cohesion in Asteroid Regolith Materials

NASA Technical Reports Server (NTRS)

Kleinhenz, Julie; Gaier, James; Waters, Deborah; Harvey, Ralph; Zeszut, Zoe; Carreno, Brandon; Shober, Patrick

2017-01-01

There is increasing evidence that a large fraction of asteroids, and even Phobos, have such low densities (<2 g/cu cm) that the are unlikely to be consolidated rocks in space.-Water is unlikely due to close orbits to the sun. Instead, many of these asteroids are thought to be made up of unconsolidated smaller particles of varying size referred to as rubble piles. Images of the asteroid Itokawa reinforce this hypothesis. What holds the rubble piles together? Gravitational forces alone are not strong enough to hold together rubble pile asteroids, at least not those that are rapidly spinning Van der Waals forces and or Electrostatic forces must therefore be responsible for holding them together. Previous work suggests that electrostatic forces, which are orders of magnitude stronger are far more likely. Charge build-up is a likely consequence of the interaction of airless bodies with the solar wind plasma, analogous to what has been proposed to occur on the moon. Objective: Experimentally measure cohesive forces relevant to those holding rubble pile asteroids together

Predictions of asteroid hazard to the Earth for the 21st century

NASA Astrophysics Data System (ADS)

Petrov, Nikita; Sokolov, Leonid; Polyakhova, Elena; Oskina, Kristina

2018-05-01

Early detection and investigation of possible collisions and close approaches of asteroids with the Earth are necessary to exept the asteroid-comet hazard. The difficulty of prediction of close approaches and collisions associated with resonant returns after encounters with the Earth due to loss of precision in these encounters. The main research object is asteroid Apophis (99942), for which we found many possible orbits of impacts associated with resonant returns. It is shown that the early orbit change of Apophis allows to avoid main impacts, associated with resonant returns. Such a change of the orbit, in principle, is feasible. We also study the possible impacts with the Ground asteroid 2015 RN35. We present 21 possible collisions in this century, including 7 collisions with large gaps presented in NASA website. The results of observations by the telescope ZA-320M at Pulkovo Obser-vatory of the three near-Earth asteroids, namely, 7822, 20826, 68216, two of which 7822 and 68216 are potentially hazardous, are presented.

The impact and recovery of asteroid 2008 TC(3).

PubMed

Jenniskens, P; Shaddad, M H; Numan, D; Elsir, S; Kudoda, A M; Zolensky, M E; Le, L; Robinson, G A; Friedrich, J M; Rumble, D; Steele, A; Chesley, S R; Fitzsimmons, A; Duddy, S; Hsieh, H H; Ramsay, G; Brown, P G; Edwards, W N; Tagliaferri, E; Boslough, M B; Spalding, R E; Dantowitz, R; Kozubal, M; Pravec, P; Borovicka, J; Charvat, Z; Vaubaillon, J; Kuiper, J; Albers, J; Bishop, J L; Mancinelli, R L; Sandford, S A; Milam, S N; Nuevo, M; Worden, S P

2009-03-26

In the absence of a firm link between individual meteorites and their asteroidal parent bodies, asteroids are typically characterized only by their light reflection properties, and grouped accordingly into classes. On 6 October 2008, a small asteroid was discovered with a flat reflectance spectrum in the 554-995 nm wavelength range, and designated 2008 TC(3) (refs 4-6). It subsequently hit the Earth. Because it exploded at 37 km altitude, no macroscopic fragments were expected to survive. Here we report that a dedicated search along the approach trajectory recovered 47 meteorites, fragments of a single body named Almahata Sitta, with a total mass of 3.95 kg. Analysis of one of these meteorites shows it to be an achondrite, a polymict ureilite, anomalous in its class: ultra-fine-grained and porous, with large carbonaceous grains. The combined asteroid and meteorite reflectance spectra identify the asteroid as F class, now firmly linked to dark carbon-rich anomalous ureilites, a material so fragile it was not previously represented in meteorite collections.

THE PHYSICAL CHARACTERIZATION OF THE POTENTIALLY HAZARDOUS ASTEROID 2004 BL86: A FRAGMENT OF A DIFFERENTIATED ASTEROID

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, Vishnu; Sanchez, Juan A.; Takir, Driss

The physical characterization of potentially hazardous asteroids (PHAs) is important for impact hazard assessment and evaluating mitigation options. Close flybys of PHAs provide an opportunity to study their surface photometric and spectral properties that enable the identification of their source regions in the main asteroid belt. We observed PHA (357439) 2004 BL86 during a close flyby of the Earth at a distance of 1.2 million km (0.0080 AU) on 2015 January 26, with an array of ground-based telescopes to constrain its photometric and spectral properties. Lightcurve observations showed that the asteroid was a binary and subsequent radar observations confirmed themore » binary nature and gave a primary diameter of 300 m and a secondary diameter of 50–100 m. Our photometric observations were used to derive the phase curve of 2004 BL86 in the V-band. Two different photometric functions were fitted to this phase curve, the IAU H–G model and the Shevchenko model. From the fit of the H–G function we obtained an absolute magnitude of H = 19.51 ± 0.02 and a slope parameter of G = 0.34 ± 0.02. The Shevchenko function yielded an absolute magnitude of H = 19.03 ± 0.07 and a phase coefficient b = 0.0225 ± 0.0006. The phase coefficient was used to calculate the geometric albedo (Ag) using the relationship found by Belskaya and Schevchenko, obtaining a value of Ag = 40% ± 8% in the V-band. With the geometric albedo and the absolute magnitudes derived from the H–G and the Shevchenko functions we calculated the diameter (D) of 2004 BL86, obtaining D = 263 ± 26 and D = 328 ± 35 m, respectively. 2004 BL86 spectral band parameters and pyroxene chemistry are consistent with non-cumulate eucrite meteorites. A majority of these meteorites are derived from Vesta and are analogous with surface lava flows on a differentiated parent body. A non-diagnostic spectral curve match using the Modeling for Asteroids tool yielded a best-match with non-cumulate eucrite Bereba. Three other near-Earth asteroids (1993 VW, 1998 KK17, and 2000 XH44) that were observed by Burbine et al. also have spectral properties similar to 2004 BL86. The presence of eucrites with anomalous oxygen isotope ratios compared to the howardites, eucrites, and diogenites meteorites from Vesta suggests the possible presence of multiple differentiated bodies in the inner main belt or the contamination of Vesta’s surface with exogenic material. The spectral properties of both anomalous and Vestan eucrites are degenerate, making it difficult to identify the parent bodies of anomalous eucrites in the main belt and the NEO population using remote sensing. This makes it difficult to link 2004 BL86 directly to Vesta, although the Vesta family is the largest contributor of V-types to near-Earth space.« less

The 1986 DA and 1986 EB: M-class asteroids in near-Earth orbits

NASA Technical Reports Server (NTRS)

Gradie, Jonathan; Tedesco, Edward

1987-01-01

The Earth-approaching asteroid population is composed of asteroids in orbits with short lifetimes compared with the age of the solar system. These objects which are comprised of Aten, Apollo, and Amor asteroids must be replenished from either cometary or mainbelt asteroid sources since lifetimes against collision with or ejection by a planet are on the order of 10 to 100 million years. The physical study of Earth-approaching asteroids is constrained by the generally long period between favorable apparitions and poorly known orbits. Broadband spectrophotometry on the Johnson UBVR system and the Eight-Color Asteroid Survey system were obtained at Kitt Peak National Observatory and on the Johnson JHK system and at 10 and 20 microns at the NASA Infrared Telescope Facility at Mauna Kea Observatory. These observations were used to determine the absolute visual magnitudes and to derive the visual geometric albedos and diameters on the IRAS system. The spectral reflectance properties and geometric albedos of the M-class asteroids are consistent compositions analogous to the iron nickel meteorites or the enstatite-metal assemblages of the enstatite chondrites. The issue of the source(s) of the near-Earth asteroids population was examined by comparing the classifications on the scheme employed by Gradie and Tedesco of 38 such asteroids. Most of the near-Earth objects is indeed the asteroid belt as the observations suggest, then a method for removing extinct nuclei of short period comets must be found since the rate of production of short period comets from the long period comets is relatively large.

Scale-dependent measurements of meteorite strength: Implications for asteroid fragmentation

NASA Astrophysics Data System (ADS)

Cotto-Figueroa, Desireé; Asphaug, Erik; Garvie, Laurence A. J.; Rai, Ashwin; Johnston, Joel; Borkowski, Luke; Datta, Siddhant; Chattopadhyay, Aditi; Morris, Melissa A.

2016-10-01

Measuring the strengths of asteroidal materials is important for developing mitigation strategies for potential Earth impactors and for understanding properties of in situ materials on asteroids during human and robotic exploration. Studies of asteroid disruption and fragmentation have typically used the strengths determined from terrestrial analog materials, although questions have been raised regarding the suitability of these materials. The few published measurements of meteorite strength are typically significantly greater than those estimated from the stratospheric breakup of meter-sized meteoroids. Given the paucity of relevant strength data, the scale-varying strength properties of meteoritic and asteroidal materials are poorly constrained. Based on our uniaxial failure studies of centimeter-sized cubes of a carbonaceous and ordinary chondrite, we develop the first Weibull failure distribution analysis of meteorites. This Weibull distribution projected to meter scales, overlaps the strengths determined from asteroidal airbursts and can be used to predict properties of to the 100 m scale. In addition, our analysis shows that meter-scale boulders on asteroids are significantly weaker than small pieces of meteorites, while large meteorites surviving on Earth are selected by attrition. Further, the common use of terrestrial analog materials to predict scale-dependent strength properties significantly overestimates the strength of meter-sized asteroidal materials and therefore is unlikely well suited for the modeling of asteroid disruption and fragmentation. Given the strength scale-dependence determined for carbonaceous and ordinary chondrite meteorites, our results suggest that boulders of similar composition on asteroids will have compressive strengths significantly less than typical terrestrial rocks.

Radar investigation of asteroids

NASA Technical Reports Server (NTRS)

Ostro, S. J.

1986-01-01

The number of radar detected asteroids has climbed from 6 to 40 (27 mainbelt plus 13 near-Earth). The dual-circular-polarization radar sample now comprises more than 1% of the numbered asteroids. Radar results for mainbelt asteroids furnish the first available information on the nature of these objects at macroscopic scales. At least one object (2 Pallas) and probably many others are extraordinarily smooth at centimeter-to-meter scales but are extremely rough at some scale between several meters and many kilometers. Pallas has essentially no small-scale structure within the uppermost several meters of the regolith, but the rms slope of this regolith exceeds 20 deg., much larger than typical lunar values (approx. 7 deg.). The origin of these slopes could be the hypervelocity impact cratering process, whose manifestations are likely to be different on low-gravity, low-radius-of-curvature objects from those on the terrestrial planets. The range of mainbelt asteroid radar albedoes is very broad and implies big variations in regolith porosity or metal concentration, or both. The highest albedo estimate, for 16 Psyche, is consistent with a surface having porosities typical of lunar soil and a composition nearly completely metallic. Therefore, Psyche might be the collisionally stripped core of a differentiated small plant, and might resemble mineralogically the parent bodies of iron meteorites.

Lunar and Planetary Science XXXV: Asteroids, Meteors, Comets

NASA Technical Reports Server (NTRS)

2004-01-01

Reports included:Long Term Stability of Mars Trojans; Horseshoe Asteroids and Quasi-satellites in Earth-like Orbits; Effect of Roughness on Visible Reflectance Spectra of Planetary Surface; SUBARU Spectroscopy of Asteroid (832) Karin; Determining Time Scale of Space Weathering; Change of Asteroid Reflectance Spectra by Space Weathering: Pulse Laser Irradiation on Meteorite Samples; Reflectance Spectra of CM2 Chondrite Mighei Irradiated with Pulsed Laser and Implications for Low-Albedo Asteroids and Martian Moons; Meteorite Porosities and Densities: A Review of Trends in the Data; Small Craters in the Inner Solar System: Primaries or Secondaries or Both?; Generation of an Ordinary-Chondrite Regolith by Repetitive Impact; Asteroid Modal Mineralogy Using Hapke Mixing Models: Validation with HED Meteorites; Particle Size Effect in X-Ray Fluorescence at a Large Phase Angle: Importance on Elemental Analysis of Asteroid Eros (433); An Investigation into Solar Wind Depletion of Sulfur in Troilite; Photometric Behaviour Dependent on Solar Phase Angle and Physical Characteristics of Binary Near-Earth-Asteroid (65803) 1996 GT; Spectroscopic Observations of Asteroid 4 Vesta from 1.9 to 3.5 micron: Evidence of Hydrated and/or Hydroxylated Minerals; Multi-Wavelength Observations of Asteroid 2100 Ra-Shalom: Visible, Infrared, and Thermal Spectroscopy Results; New Peculiarities of Cometary Outburst Activity; Preliminary Shape Modeling for the Asteroid (25143) Itokawa, AMICA of Hayabusa Mission; Scientific Capability of MINERVA Rover in Hayabusa Asteroid Mission; Characteristics and Current Status of Near Infrared Spectrometer for Hayabusa Mission; Sampling Strategy and Curation Plan of Hayabusa Asteroid Sample Return Mission; Visible/Near-Infrared Spectral Properties of MUSES C Target Asteroid 25143 Itokawa; Calibration of the NEAR XRS Solar Monitor; Modeling Mosaic Degradation of X-Ray Measurements of 433 Eros by NEAR-Shoemaker; Scattered Light Remediation and Recalibration of near Sheomaker s NIS Global Dataaset at 433 Eros; Evaluation of Preparation and Measuring Techniques for Interplanetary Dust Particles for the MIDAS Experiment on Rosetta; Chiron: a Proposed Remote Sensing Prompt Gamma Ray Activation Analysis Instrument for a Nuclear Powered Prometheus Mission;From Present Surveying to Future Prospecting of the Asteroid Belt; Asteroid Physical Properties Probe Microgravity Testing of a Surface Sampling System for Sample Return from Small Solar System Bodies;and Penetrator Coring Apparatus for Cometary Surfaces.

Evidence for ground-ice occurrence on asteroid Vesta using Dawn bistatic radar observations

NASA Astrophysics Data System (ADS)

Palmer, E. M.; Heggy, E.; Kofman, W. W.

2017-12-01

From 2011 to 2012, the Dawn spacecraft orbited asteroid Vesta, the first of its two targets in the asteroid belt, and conducted the first bistatic radar (BSR) experiment at a small-body, during which Dawn's high-gain communications antenna is used to transmit radar waves that scatter from Vesta's surface toward Earth at high incidence angles just before and after occultation of the spacecraft behind the asteroid. Among the 14 observed mid-latitude forward-scatter reflections, the radar cross section ranges from 84 ± 8 km2 (near Saturnalia Fossae) to 3,588 ± 200 km2 (northwest of Caparronia crater), implying substantial spatial variation in centimeter- to decimeter-scale surface roughness. The compared distributions of surface roughness and subsurface hydrogen concentration [H]—measured using data from Dawn's BSR experiment and Gamma Ray and Neutron Spectrometer (GRaND), respectively—reveal the occurrence of heightened subsurface [H] with smoother terrains that cover tens of square kilometers. Furthermore, unlike on the Moon, we observe no correlation between surface roughness and surface ages on Vesta—whether the latter is derived from lunar or asteroid-flux chronology [Williams et al., 2014]—suggesting that cratering processes alone are insufficient to explain Vesta's surface texture at centimeter-to-decimeter scales. Dawn's BSR observations support the hypothesis of transient melting, runoff and recrystallization of potential ground-ice deposits, which are postulated to flow along fractures after an impact, and provide a mechanism for the smoothing of otherwise rough, fragmented impact ejecta. Potential ground-ice presence within Vesta's subsurface was first proposed by Scully et al. [2014], who identified geomorphological evidence for transient water flow along several of Vesta's crater walls using Dawn Framing Camera images. While airless, differentiated bodies such as Vesta and the Moon are thought to have depleted their initial volatile content during the process of differentiation, evidence to the contrary is continuing to change our understanding of the distribution and preservation of volatiles during planetary formation in the early solar system.

Finding the Parent Body of Anomalous Achondrite NWA 6704 Among V-type Asteroids

NASA Astrophysics Data System (ADS)

McGraw, Allison M.; Reddy, Vishnu; Le Corre, Lucille; Cloutis, Edward

2017-10-01

North West Africa (NWA) 6704 is an unusual, ungrouped basaltic achondrite meteorite that has a striking greenish-yellow color on the inside, and that is also relatively unaltered and un-shocked. The meteorite is coarse-grained with grain sizes around1.5 millimeters, which is highly suggestive of a slow-cooling geologic environment. The meteorite is mostly composed of orthopyroxene (~70%), with a less abundant olivine fraction (~16%), as well as feldspar (~13%). We obtained laboratory spectra of NWA 6704 as chips and <150-micron samples for analysis with XRD and Ramen spectroscopy. Asteroid (4) Vesta has been proposed to be the parent body of the largest basaltic achondrite clan, the HED meteorites. However, NWA 6704 has an 0.625 micrometer absorption band feature attributed to Ni3+ in olivine that has not been detected on Vesta. We plotted the Band I center and Band Area Ratio (BAR) for this meteorite and it plots in the region between S(V) and S(VI) subtype. The S(V) subtype shows strong variations in olivine-feldspar ratios, and becomes difficult to distinguish with large amounts of metal phases. The S(VI) type describes mineralogy that is consistent with olivine-metal assemblage, with a minor pyroxene component. Both of these subtypes are indicative with bodies that have experienced some component of partial differentiation. NWA 6704 could be one of the oldest rocks in the solar system, as multiple distinguished thermal events are revealed through U-Pb dating as well as Ar-Ar dating at ~4.52 Ga and at ~2.67 Ga. We also compared the spectral band parameters of NWA 6704 with V-type asteroids from the literature. Based on this comparison, the best match is an outer main belt V-type asteroid that suffered a catastrophic collision very early on in the Solar System history.

Porphyritic Olivine-Pyroxene Clast in Kaidun: First Discovery of an Ordinary Chondrite Clast?

NASA Technical Reports Server (NTRS)

Mikouchi, T.; Makishima, J.; Koizumi, E.; Zolensky, M. E.

2005-01-01

Kaidun is an enigmatic meteorite showing a micro-brecciated texture composed of variable kinds of lithic clasts and mineral fragments. The constituent components range from primitive chondritic materials to differentiated achondritic materials, and thus believed to have originated from a large parent body accumulating materials from many different bodies in the asteroid belt. One of the interesting observations is that no ordinary chondrite component has been found yet, although C and E chondrites components are abundant. In this abstract, we report mineralogy of the clast (Kaidun #15415- 01.3.13a) showing a porphyritic olivine-pyroxene chondrule-like texture similar to those found in unequilibrated ordinary chondrites.

Spin states of asteroids in the Eos collisional family

NASA Astrophysics Data System (ADS)

Hanuš, J.; Delbo', M.; Alí-Lagoa, V.; Bolin, B.; Jedicke, R.; Ďurech, J.; Cibulková, H.; Pravec, P.; Kušnirák, P.; Behrend, R.; Marchis, F.; Antonini, P.; Arnold, L.; Audejean, M.; Bachschmidt, M.; Bernasconi, L.; Brunetto, L.; Casulli, S.; Dymock, R.; Esseiva, N.; Esteban, M.; Gerteis, O.; de Groot, H.; Gully, H.; Hamanowa, Hiroko; Hamanowa, Hiromi; Krafft, P.; Lehký, M.; Manzini, F.; Michelet, J.; Morelle, E.; Oey, J.; Pilcher, F.; Reignier, F.; Roy, R.; Salom, P. A.; Warner, B. D.

2018-01-01

Eos family was created during a catastrophic impact about 1.3 Gyr ago. Rotation states of individual family members contain information about the history of the whole population. We aim to increase the number of asteroid shape models and rotation states within the Eos collision family, as well as to revise previously published shape models from the literature. Such results can be used to constrain theoretical collisional and evolution models of the family, or to estimate other physical parameters by a thermophysical modeling of the thermal infrared data. We use all available disk-integrated optical data (i.e., classical dense-in-time photometry obtained from public databases and through a large collaboration network as well as sparse-in-time individual measurements from a few sky surveys) as input for the convex inversion method, and derive 3D shape models of asteroids together with their rotation periods and orientations of rotation axes. We present updated shape models for 15 asteroids and new shape model determinations for 16 asteroids. Together with the already published models from the publicly available DAMIT database, we compiled a sample of 56 Eos family members with known shape models that we used in our analysis of physical properties within the family. Rotation states of asteroids smaller than ∼ 20 km are heavily influenced by the YORP effect, whilst the large objects more or less retained their rotation state properties since the family creation. Moreover, we also present a shape model and bulk density of asteroid (423) Diotima, an interloper in the Eos family, based on the disk-resolved data obtained by the Near InfraRed Camera (Nirc2) mounted on the W.M. Keck II telescope.

Origin of Water on Mars

NASA Technical Reports Server (NTRS)

Lunine, J. I.; Morbidelli, A.; Chambers, J. E.

2002-01-01

Dynamical simulations suggest that the Earth's water budget was delivered primarily from the asteroid belt, in the form of large planetary embryos. The same simulations present a very different picture for Mars its water came from a mixture of cometary and small asteroidal bodies. Additional information is contained in the original extended abstract.

Asteroids Search Results in Large Photographic Sky Surveys

NASA Astrophysics Data System (ADS)

Shatokhina, S. V.; Kazantseva, L. V.; Yizhakevych, O. M.; Eglitis, I.; Andruk, V. M.

Photographic observations of XX century contained numerous and varied information about all objects and events of the Universe fixed on plates. The original and interesting observations of small bodies of the Solar system in previous years can be selected and used for various scientific tasks. Existing databases and online services can help make such selection easily and quickly. The observations of chronologically earlier ppositions, photometric evaluation of brightness for long periods of time allow refining the orbits of asteroids and identifying various non-stationaries. Photographic observations of Northern Sky Survey project and observations of clusters in UBVR bands were used for global search for small bodies of Solar system. Total we founded 2486 positions of asteroids and 13 positions of comets. All positions were compared with ephemeris. It was found that 80 positions of asteroids have a moment of observation preceding their discovery, and 19 of them are chronologically the earliest observations of these asteroids in the world.

An interstellar origin for Jupiter's retrograde co-orbital asteroid

NASA Astrophysics Data System (ADS)

Namouni, F.; Morais, M. H. M.

2018-06-01

Asteroid (514107) 2015 BZ509 was discovered recently in Jupiter's co-orbital region with a retrograde motion around the Sun. The known chaotic dynamics of the outer Solar system have so far precluded the identification of its origin. Here, we perform a high-resolution statistical search for stable orbits and show that asteroid (514107) 2015 BZ509 has been in its current orbital state since the formation of the Solar system. This result indicates that (514107) 2015 BZ509 was captured from the interstellar medium 4.5 billion years in the past as planet formation models cannot produce such a primordial large-inclination orbit with the planets on nearly coplanar orbits interacting with a coplanar debris disc that must produce the low-inclination small-body reservoirs of the Solar system such as the asteroid and Kuiper belts. This result also implies that more extrasolar asteroids are currently present in the Solar system on nearly polar orbits.

Chips off of Asteroid 4 Vesta: Evidence for the Parent Body of Basaltic Achondrite Meteorites.

PubMed

Binzel, R P; Xu, S

1993-04-09

For more than two decades, asteroid 4 Vesta has been debated as the source for the eucrite, diogenite, and howardite classes of basaltic achondrite meteorites. Its basaltic achondrite spectral properties are unlike those of other large main-belt asteroids. Telescopic measurements have revealed 20 small (diameters

First known Terrestrial Impact of a Binary Asteroid from a Main Belt Breakup Event

PubMed Central

Ormö, Jens; Sturkell, Erik; Alwmark, Carl; Melosh, Jay

2014-01-01

Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt, which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering rate during several millions of years following the event. The 7.5-km wide Lockne crater, central Sweden, is known to be a member of this family. We here provide evidence that Lockne and its nearby companion, the 0.7-km diameter, contemporaneous, Målingen crater, formed by the impact of a binary, presumably ‘rubble pile’ asteroid. This newly discovered crater doublet provides a unique reference for impacts by combined, and poorly consolidated projectiles, as well as for the development of binary asteroids. PMID:25340551

Albedos of Small Hilda Asteroids

NASA Astrophysics Data System (ADS)

Ryan, Erin L.; Woodward, C. E.

2010-10-01

We present albedo results for 70 small Hilda dynamical family members detected by the Spitzer Space Telescope in multiple archival programs. This Spitzer data samples Hildas with diameters between 2 and 11 kilometers. Our preliminary analysis reveals that the mean geometric albedo for this sample is pv = 0.05, matching the mean albedo derived for large (20 to 160 km) Hilda asteroids observed by IRAS (Ryan and Woodward 2010). This mean albedo is significantly darker than the mean albedo of asteroids in the outer main belt (2.8 AU < a < 3.5 AU), possibly suggesting that these asteroids did not originate from the outer main belt . This is in direct conflict with some dynamical models which suggest that the HIldas are field asteroids trapped from an inward migration of Jupiter (Franklin et al. 2004), and may provide additional observation support for delivery of dark Kuiper Belt contaminants to the inner solar system as per the Nice Model (Levison et al. 2009).

On the post mitigation impact risk assessment of possible targets for an asteroid deflection demonstration mission in the NEOShield project.

NASA Astrophysics Data System (ADS)

Eggl, Siegfried

2014-05-01

Mankind believes to have the capabilities to avert potentially disastrous asteroid impacts. Yet, only the realization of a mitigation demonstration mission can confirm such a claim. The NEOShield project, an international collaboration under European leadership, aims to draw a comprehensive picture of the scientific as well as technical requirements to such an endeavor. One of the top priorities of such a demonstration mission is, of course, that a previously harmless target asteroid shall not be turned into a potentially hazardous object. Given the inherently large uncertainties in an asteroid's physical parameters, as well as the additional uncertainties introduced during the deflection attempt, an in depth analysis of the change in asteroid impact probabilities after a deflection event becomes necessary. We present a post mitigation impact risk analysis of a list of potential deflection test missions and discuss the influence of orbital, physical and mitigation induced uncertainties.

Instabilities in the Sun-Jupiter-Asteroid three body problem

NASA Astrophysics Data System (ADS)

Urschel, John C.; Galante, Joseph R.

2013-03-01

We consider dynamics of a Sun-Jupiter-Asteroid system, and, under some simplifying assumptions, show the existence of instabilities in the motions of an asteroid. In particular, we show that an asteroid whose initial orbit is far from the orbit of Mars can be gradually perturbed into one that crosses Mars' orbit. Properly formulated, the motion of the asteroid can be described as a Hamiltonian system with two degrees of freedom, with the dynamics restricted to a "large" open region of the phase space reduced to an exact area preserving map. Instabilities arise in regions where the map has no invariant curves. The method of MacKay and Percival is used to explicitly rule out the existence of these curves, and results of Mather abstractly guarantee the existence of diffusing orbits. We emphasize that finding such diffusing orbits numerically is quite difficult, and is outside the scope of this paper.

Testing Collisional Scaling Laws: Comparing with Observables

NASA Astrophysics Data System (ADS)

Davis, D. R.; Marzari, F.; Farinella, P.

1999-09-01

How large bodies break up in response to energetic collisions is a problem that has attracted considerable attention in recent years. Ever more sophisticated computation methods have also been developed; prominent among these are hydrocode simulations of collisional disruption by Benz and Asphaug (1999, Icarus, in press), Love and Ahrens (1996, LPSC XXVII, 777-778), and Melosh and Ryan (1997, Icarus 129, 562-564). Durda et al. (1998, Icarus 135, 431-440) used the observed asteroid size distribution to infer a scaling algorithm. The present situation is that there are several proposed scaling laws that differ by as much as two orders of magnitude at particular sizes. We have expanded upon the work of Davis et al. (1994, Goutelas Proceedings) and tested the suite of proposed scaling algorithms against observations of the main-belt asteroids. The effects of collisions among the asteroids produce the following observables: (a) the size distribution has been significantly shaped by collisions, (b) collisions have produced about 25 well recognized asteroid families, and (c) the basaltic crust of Vesta has been largely preserved in the face of about 4.5 Byr of impacts. We will present results from a numerical simulation of asteroid collisional evolution over the age of the solar system using proposed scaling laws and a range of hypothetical initial populations.

Asteroid Redirect Robotic Mission: Robotic Boulder Capture Option Overview

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Merrill, Raymond G.; Belbin, Scott P.; Reeves, David M.; Earle, Kevin D.; Naasz, Bo J.; Abell, Paul A.

2014-01-01

The National Aeronautics and Space Administration (NASA) is currently studying an option for the Asteroid Redirect Robotic Mission (ARRM) that would capture a multi-ton boulder (typically 2-4 meters in size) from the surface of a large (is approximately 100+ meter) Near-Earth Asteroid (NEA) and return it to cislunar space for subsequent human and robotic exploration. This alternative mission approach, designated the Robotic Boulder Capture Option (Option B), has been investigated to determine the mission feasibility and identify potential differences from the initial ARRM concept of capturing an entire small NEA (4-10 meters in size), which has been designated the Small Asteroid Capture Option (Option A). Compared to the initial ARRM concept, Option B allows for centimeter-level characterization over an entire large NEA, the certainty of target NEA composition type, the ability to select the boulder that is captured, numerous opportunities for mission enhancements to support science objectives, additional experience operating at a low-gravity planetary body including extended surface contact, and the ability to demonstrate future planetary defense strategies on a hazardous-size NEA. Option B can leverage precursor missions and existing Agency capabilities to help ensure mission success by targeting wellcharacterized asteroids and can accommodate uncertain programmatic schedules by tailoring the return mass.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steinberg, Elad; Sari, Re’em

The Asteroid Belt and the Kuiper Belt are relics from the formation of our solar system. Understanding the size and spin distribution of the two belts is crucial for a deeper understanding of the formation of our solar system and the dynamical processes that govern it. In this paper, we investigate the effect of collisions on the evolution of the spin distribution of asteroids and KBOs. We find that the power law nature of the impactors’ size distribution leads to a Lévy distribution of the spin rates. This results in a power law tail in the spin distribution, in starkmore » contrast to the usually quoted Maxwellian distribution. We show that for bodies larger than 10 km, collisions alone lead to spin rates peaking at 0.15–0.5 revolutions per day. Comparing that to the observed spin rates of large asteroids (R > 50 km), we find that the spins of large asteroids, peaking at ∼1–2 revolutions per day, are dominated by a primordial component that reflects the formation mechanism of the asteroids. Similarly, the Kuiper Belt has undergone virtually no collisional spin evolution, assuming current densities. Collisions contribute a spin rate of ∼0.01 revolutions per day, thus the observed fast spin rates of KBOs are also primordial in nature.« less

Asteroid Redirect Mission Concept: A Bold Approach for Utilizing Space Resources

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Merrill, Raymond G.; Brophy, John R.; Mueller, Robert P.

2014-01-01

The utilization of natural resources from asteroids is an idea that is older than the Space Age. The technologies are now available to transform this endeavour from an idea into reality. The Asteroid Redirect Mission (ARM) is a mission concept which includes the goal of robotically returning a small Near-Earth Asteroid (NEA) or a multi-ton boulder from a large NEA to cislunar space in the mid 2020's using an advanced Solar Electric Propulsion (SEP) vehicle and currently available technologies. The paradigm shift enabled by the ARM concept would allow in-situ resource utilization (ISRU) to be used at the human mission departure location (i.e., cislunar space) versus exclusively at the deep-space mission destination. This approach drastically reduces the barriers associated with utilizing ISRU for human deep-space missions. The successful testing of ISRU techniques and associated equipment could enable large-scale commercial ISRU operations to become a reality and enable a future space-based economy utilizing processed asteroidal materials. This paper provides an overview of the ARM concept and discusses the mission objectives, key technologies, and capabilities associated with the mission, as well as how the ARM and associated operations would benefit humanity's quest for the exploration and settlement of space.

Rotational breakup as the origin of small binary asteroids.

PubMed

Walsh, Kevin J; Richardson, Derek C; Michel, Patrick

2008-07-10

Asteroids with satellites are observed throughout the Solar System, from subkilometre near-Earth asteroid pairs to systems of large and distant bodies in the Kuiper belt. The smallest and closest systems are found among the near-Earth and small inner main-belt asteroids, which typically have rapidly rotating primaries and close secondaries on circular orbits. About 15 per cent of near-Earth and main-belt asteroids with diameters under 10 km have satellites. The mechanism that forms such similar binaries in these two dynamically different populations was hitherto unclear. Here we show that these binaries are created by the slow spinup of a 'rubble pile' asteroid by means of the thermal YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect. We find that mass shed from the equator of a critically spinning body accretes into a satellite if the material is collisionally dissipative and the primary maintains a low equatorial elongation. The satellite forms mostly from material originating near the primary's surface and enters into a close, low-eccentricity orbit. The properties of binaries produced by our model match those currently observed in the small near-Earth and main-belt asteroid populations, including 1999 KW(4) (refs 3, 4).

Rotational breakup as the origin of small binary asteroids

NASA Astrophysics Data System (ADS)

Walsh, Kevin J.; Richardson, Derek C.; Michel, Patrick

2008-07-01

Asteroids with satellites are observed throughout the Solar System, from subkilometre near-Earth asteroid pairs to systems of large and distant bodies in the Kuiper belt. The smallest and closest systems are found among the near-Earth and small inner main-belt asteroids, which typically have rapidly rotating primaries and close secondaries on circular orbits. About 15 per cent of near-Earth and main-belt asteroids with diameters under 10km have satellites. The mechanism that forms such similar binaries in these two dynamically different populations was hitherto unclear. Here we show that these binaries are created by the slow spinup of a `rubble pile' asteroid by means of the thermal YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect. We find that mass shed from the equator of a critically spinning body accretes into a satellite if the material is collisionally dissipative and the primary maintains a low equatorial elongation. The satellite forms mostly from material originating near the primary's surface and enters into a close, low-eccentricity orbit. The properties of binaries produced by our model match those currently observed in the small near-Earth and main-belt asteroid populations, including 1999KW4 (refs 3, 4).

Basaltic material in the main belt: a tale of two (or more) parent bodies?

NASA Astrophysics Data System (ADS)

Ieva, S.; Dotto, E.; Lazzaro, D.; Fulvio, D.; Perna, D.; Epifani, E. Mazzotta; Medeiros, H.; Fulchignoni, M.

2018-06-01

The majority of basaltic objects in the main belt are dynamically connected to Vesta, the largest differentiated asteroid known. Others, due to their current orbital parameters, cannot be easily dynamically linked to Vesta. This is particularly true for all the basaltic asteroids located beyond 2.5 au, where lies the 3:1 mean motion resonance with Jupiter. In order to investigate the presence of other V-type asteroids in the middle and outer main belt (MOVs) we started an observational campaign to spectroscopically characterize in the visible range MOV candidates. We observed 18 basaltic candidates from TNG and ESO - NTT between 2015 and 2016. We derived spectral parameters using the same approach adopted in our recent statistical analysis and we compared our data with orbital parameters to look for possible clusters of MOVs in the main belt, symptomatic for a new basaltic family. Our analysis seemed to point out that MOVs show different spectral parameters respect to other basaltic bodies in the main belt, which could account for a diverse mineralogy than Vesta; moreover, some of them belong to the Eos family, suggesting the possibility of another basaltic progenitor. This could have strong repercussions on the temperature gradient present in the early Solar System, and on our current understanding of differentiation processes.

Spectral evidence of size dependent space weathering processes on asteroid surfaces

NASA Technical Reports Server (NTRS)

Gaffey, M. J.; Bell, J. F.; Brown, R. H.; Burbine, T. H.; Piatek, J. L.; Reed, K. L.; Chaky, D. A.

1993-01-01

Most compositional characterizations of the minor planets are derived from analysis of visible and near-infrared reflectance spectra. However, such spectra are derived from light which has only interacted with a very thin surface layer. Although regolith processes are assumed to mix all near-surface lithologic units into this layer, it has been proposed that space weathering processes can alter this surface layer to obscure the spectral signature of the bedrock lithology. It has been proposed that these spectral alteration processes are much less pronounced on asteroid surfaces than on the lunar surface, but the possibility of major spectral alteration of asteroidal optical surfaces has been invoked to reconcile S-asteroids with ordinary chondrites. The reflectance spectra of a large subset of the S-asteroid population have been analyzed in a systematic investigation of the mineralogical diversity within the S-class. In this sample, absorption band depth is a strong function of asteroid diameter. The S-asteroid band depths are relatively constant for objects larger than 100 km and increase linearly by factor of two toward smaller sizes (approximately 40 km). Although the S-asteroid surface materials includes a diverse variety of silicate assemblages, ranging from dunites to basalts, all compositional subtypes of the S-asteroids conform to this trend. The A-, R-, and V-type asteroids which are primarily silicate assemblages (as opposed to the metal-silicate mixtures of most S-asteroids) follow a parallel but displaced trend. Some sort of textural or regolith equilibrium appears to have been attained in the optical surfaces of asteroids larger than about 100 km diameter but not on bodies below this size. The relationships between absorption band depth, spectral slope, surface albedo and body size provide an intriguing insight into the nature of the optical surfaces of the S-asteroids and space weathering on these objects.

Discovery of a New Super-Fast Rotator

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-07-01

Recent observations of asteroid (335433) 2005 UW163 have added a new member to the mysterious category of "super-fast rotators" — asteroids that rotate faster than should be possible, given current theories of asteroid composition. Asteroids come in sizes of a few meters to a few hundred kilometers, and can spin at rates from 0.1 to nearly 1000 revolutions per day. Current theories suggest that asteroids smaller than 150m are mostly monolithic (made up of a single rock), whereas asteroids larger than 150m are usually what's known as a "rubble pile" — a collection of rock fragments from past collisions, bound together into a clump by gravity. "Rubble pile" asteroids have an important structural limitation: they can't spin faster than once every 2.2 hours without flying apart as the centripetal force overcomes the force of gravity. Asteroid 2005 UW163 violates this rule: its diameter is 690m, but it rotates once every 1.29 hours. This discovery was made by a team of scientists using telescopes at the Palomar Observatory in California to conduct a large survey of the rotation rates of nearby asteroids. The group, led by Chan-Kao Chang of Taiwan's National Central University, discovered 11 super-fast rotator candidates — of which asteroid 2005 UW163 is the first to have its rotation rate confirmed by additional observations. The category of super-fast rotators poses an interesting problem: how are they able to spin so quickly without flying apart? Either the density of these asteroids is unexpectedly high (roughly four times the density of typical "rubble pile" asteroids), or else there must be additional forces besides gravity at work to help hold the asteroid together, such as bonds between the rocks. Future observations of super-fast rotators will help us better understand the peculiar structure of these rocky neighbors. Citation: Chan-Kao Chang et al. 2014 ApJ 791 L35 doi:10.1088/2041-8205/791/2/L35

Experimental Simulations of Large-Scale Collisions

NASA Technical Reports Server (NTRS)

Housen, Kevin R.

2002-01-01

This report summarizes research on the effects of target porosity on the mechanics of impact cratering. Impact experiments conducted on a centrifuge provide direct simulations of large-scale cratering on porous asteroids. The experiments show that large craters in porous materials form mostly by compaction, with essentially no deposition of material into the ejecta blanket that is a signature of cratering in less-porous materials. The ratio of ejecta mass to crater mass is shown to decrease with increasing crater size or target porosity. These results are consistent with the observation that large closely-packed craters on asteroid Mathilde appear to have formed without degradation to earlier craters.

Specific effects of large asteroids on the orbits of terrestrial planets and the ASETEP database

NASA Astrophysics Data System (ADS)

Aljbaae, S.; Souchay, J.

2012-04-01

The necessity to take into account the perturbations caused by a large number of asteroids on the terrestrial planets is fundamental in the construction of modern numerical ephemeris on the solar system. Therefore about 300 of the largest asteroids were taken into account in recent ephemeris. Yet, the uncertainty on the mass values of the great majority of these asteroids constitutes a crucial and the main limit of accuracy of this ephemeris. Consequently, it is important to conduct a specific and detailed study of their individual effects especially on the terrestrial planets, which are far more affected than the giant planets. This was already done explicitly, but only for Mars and for only two orbital elements (a and λ). We aim both to confirm these previous results and to extend the study to all orbital elements and to the other three terrestrial planets (Mercury, Venus and the Earth), which are priori less affected by asteroid perturbations. Our methodology consists in several steps: we carried out precise computations of the orbital motions of the planets at short (100 y) and longer (1000 y) time scales with numerical integration. For that purpose we included the eight planets and also considered 43 of the most powerful asteroids. These were added to the numerical integrations once separately and once combined to determine their specific effects on the orbital elements of the Earth and the three other terrestrial planets. This procedure also allowed us to assess the spatial geocentric coordinates of the three terrestrial planets. We determined the signal that represents the effects by simple subtraction. Then we systematically analyzed this signal by FFT (fast Fourier transform), and finally we adjusted the signal with a set of sinusoidal components. We analyzed in detail the variations of the six orbital elements a, e, i, Ω, ˜ ω and λ of Mercury, Venus, the Earth-Moon barycenter (EMB) and Mars that are caused by the individual influences of the set of our 43 selected asteroids. We compared our results for Mars with the analytical ones on the semi-major axis and the longitude. The tow studies agree very well. All our results, consisting of 1032 different curves (43 asteroids × 4 planets × 6 orbital elements) and the related tables that provide the fitted Fourier and Poisson components are gathered the ASETEP database (asteroid effect on the terrestrial planets). Moreover, we include in this database the influence of our sample of 43 asteroids on three fundamental parameters: the distance and the bi-dimensional orientation vector (α, δ) from the EMB to each of the other terrestrial planets. This database, which will be regularly updated by taking into account more asteroids with improved mass determinations, constitutes a precious tool for understanding specifically the influence of the large asteroids on the orbital motion of the terrestrial planets, and also for better understanding how modern ephemeris can be improved. Appendices A-C are available in electronic form at http://www.aanda.org

Meteoroid Impact Ejecta Detection by Nanosatellites for Asteroid Surface Characterization

NASA Astrophysics Data System (ADS)

Lee, N.; Close, S.; Goel, A.

2015-12-01

Asteroids are constantly bombarded by much smaller meteoroids at extremely high speeds, which results in erosion of the material on the asteroid surface. Some of this material is vaporized and ionized, forming a plasma that is ejected into the environment around the asteroid where it can be detected by a constellation of closely orbiting nanosatellites. We present a concept to leverage this natural phenomenon and to analyze this excavated material using low-power plasma sensors on nanosatellites in order to determine the composition of the asteroid surface. This concept would enable a constellation of nanosatellites to provide useful data complementing existing techniques such as spectroscopy, which require larger and more power-hungry sensors. Possible mission architectures include precursor exploratory missions using nanosatellites to survey and identify asteroid candidates worthy of further study by a large spacecraft, or simultaneous exploration by a nanosatellite constellation with a larger parent spacecraft to decrease the time required to cover the entire asteroid surface. The use of meteoroid impact plasma to analyze the surface composition of asteroids will not only produce measurements that have not been previously obtained, including the molecular composition of the surface, but will also yield a better measurement of the meteoroid flux in the vicinity of the asteroid. Current meteoroid models are poorly constrained beyond the orbit of Mars, due to scarcity of data. If this technology is used to survey asteroids in the main belt, it will offer a dramatic increase in the availability of meteoroid flux measurements in deep space, identifying previously unknown meteoroid streams and providing additional data to support models of solar system dust dynamics.

A cheaper, faster, better way to detect water of hydration on Solar System bodies

NASA Technical Reports Server (NTRS)

Vilas, Faith

1994-01-01

The 3.0-micrometers water of hydration absorption feature observed in the IR photometry of many low-albedo and some medium-albedo asteroids strongly correlates with the 0.7-micrometers Fe(+2) to Fe(+3) oxidized iron absorption feature observed in narrowband spectrophotometry of these asteroids. Using this relationship, an empirical algorithm for predicting the presence of water of hydration in the surface material of a Solar System body using photometry obtained through the Eight-Color Asteroid Survey nu (0.550 micrometers), w (0.701 micrometers), and x (0.853 micrometers) filters was developed and applied to the ECAS photometry of asteroids and outer planet satellites. The percentage of objects in low-albedo, outer main-belt asteroid classes that test positively for water of hydration increases from P to B to C to G class and correlates linearly with the increasing mean albedos of those objects testing positively. The medium-albedo M-class asteroids do not test positively in large number using this algorithm. Aqueously altered asteroids dominate the Solar System population between heliocentric distances of 2.6 to 3.5 AU, bracketing the Solar System region where the aqueous alteration mechanism operated most strongly. One jovian satellite, J VI Himalia, and one saturnian satellite. Phoebe, tested positively for water of hydration, supporting the hypothesis that these may be captured C-class asteroids from a postaccretional dispersion. The proposed testing technique could be applied to an Earth-based survey of asteroids or a space-probe study of an asteroid's surface characteristic in order to identify a potential water source.

A cheaper, faster, better way to detect water of hydration on Solar System bodies

NASA Astrophysics Data System (ADS)

Vilas, Faith

1994-10-01

The 3.0-micrometers water of hydration absorption feature observed in the IR photometry of many low-albedo and some medium-albedo asteroids strongly correlates with the 0.7-micrometers Fe(+2) to Fe(+3) oxidized iron absorption feature observed in narrowband spectrophotometry of these asteroids. Using this relationship, an empirical algorithm for predicting the presence of water of hydration in the surface material of a Solar System body using photometry obtained through the Eight-Color Asteroid Survey nu (0.550 micrometers), w (0.701 micrometers), and x (0.853 micrometers) filters was developed and applied to the ECAS photometry of asteroids and outer planet satellites. The percentage of objects in low-albedo, outer main-belt asteroid classes that test positively for water of hydration increases from P to B to C to G class and correlates linearly with the increasing mean albedos of those objects testing positively. The medium-albedo M-class asteroids do not test positively in large number using this algorithm. Aqueously altered asteroids dominate the Solar System population between heliocentric distances of 2.6 to 3.5 AU, bracketing the Solar System region where the aqueous alteration mechanism operated most strongly. One jovian satellite, J VI Himalia, and one saturnian satellite. Phoebe, tested positively for water of hydration, supporting the hypothesis that these may be captured C-class asteroids from a postaccretional dispersion. The proposed testing technique could be applied to an Earth-based survey of asteroids or a space-probe study of an asteroid's surface characteristic in order to identify a potential water source.

2014 Summer Series - Rusty Schweickart - Dinosaur Syndrome Avoidance Project: How Gozit?

NASA Image and Video Library

2014-07-17

The 2013 Chelyabinsk meteor demonstrated that grave uncertainties exist pertaining to near-Earth objects (NEOs). Although the impact rate for dangerous asteroids is relatively low, the consequences of such an event are severe. Apollo Astronaut Rusty Schweickart, will talk about our prospects of avoiding the same fate as the dinosaurs. He will review the status of the global efforts to protect life on the planet from the devastation of large asteroid impacts. He will also discuss both the technical and geopolitical components of the challenge of preventing future asteroid impacts.

The bare nucleus of comet Neujmin 1

NASA Technical Reports Server (NTRS)

Campins, Humberto; A'Hearn, Michael F.; Mcfadden, Lucy-Ann

1987-01-01

Simultaneous visible and infrared observations of comet P/Neujmin 1 1984c are presented which show that the comet has a large (mean radius 10 km), dark (geometric albedo 2-3 percent) nucleus with a surface which is mostly inert material but which still shows a low level of gaseous activity. This is the first physical evidence that cometary nuclei can leave behind an inert body after the coma activity ceases. No asteroid or asteroid class has been found to match the reflectance and albedo of this comet except possibly some D asteroids.

Radar investigation of asteroids

NASA Astrophysics Data System (ADS)

Ostro, S. J.

1984-07-01

The initial radar observations of the mainbelt asteroids 9 Metis, 27 Euterpe, and 60 Echo are examined. For each target, data are taken simultaneously in the same sense of circular polarization as transmitted as well as in the opposite (OC) sense. Estimates of the radar cross sections provide estimates of the circular polarization ratio, and the normalized OC radar cross section. The circular polarization ratio, is comparable to values measured for other large S type asteroids and for a few much smaller, Earth approaching objects, most of the echo is due to single reflection backscattering from smooth surface elements.

Radar investigation of asteroids

NASA Technical Reports Server (NTRS)

Ostro, S. J.

1984-01-01

The initial radar observations of the mainbelt asteroids 9 Metis, 27 Euterpe, and 60 Echo are examined. For each target, data are taken simultaneously in the same sense of circular polarization as transmitted as well as in the opposite (OC) sense. Estimates of the radar cross sections provide estimates of the circular polarization ratio, and the normalized OC radar cross section. The circular polarization ratio, is comparable to values measured for other large S type asteroids and for a few much smaller, Earth approaching objects, most of the echo is due to single reflection backscattering from smooth surface elements.

Computer modeling of large asteroid impacts into continental and oceanic sites: Atmospheric, cratering, and ejecta dynamics

NASA Technical Reports Server (NTRS)

Roddy, D. J.; Schuster, S. H.; Rosenblatt, M.; Grant, L. B.; Hassig, P. J.; Kreyenhagen, K. N.

1988-01-01

Numerous impact cratering events have occurred on the Earth during the last several billion years that have seriously affected our planet and its atmosphere. The largest cratering events, which were caused by asteroids and comets with kinetic energies equivalent to tens of millions of megatons of TNT, have distributed substantial quantities of terrestrial and extraterrestrial material over much or all of the Earth. In order to study a large-scale impact event in detail, computer simulations were completed that model the passage of a 10 km-diameter asteroid through the Earth's atmosphere and the subsequent cratering and ejecta dynamics associated with impact of the asteroid into two different targets, i.e., an oceanic site and a continental site. The calcuations were designed to broadly represent giant impact events that have occurred on the Earth since its formation and specifically represent an impact cratering event proposed to have occurred at the end of Cretaceous time. Calculation of the passage of the asteroid through a U.S. Standard Atmosphere showed development of a strong bow shock that expanded radially outward. Behind the shock front was a region of highly shock compressed and intensely heated air. Behind the asteroid, rapid expansion of this shocked air created a large region of very low density that also expanded away from the impact area. Calculations of the cratering events in both the continental and oceanic targets were carried to 120 s. Despite geologic differences, impacts in both targets developed comparable dynamic flow fields, and by approx. 29 s similar-sized transient craters approx. 39 km deep and approx. 62 km across had formed. For all practical purposes, the atmosphere was nearly completely removed from the impact area for tens of seconds, i.e., air pressures were less than fractions of a bar out to ranges of over 50 km. Consequently, much of the asteroid and target materials were ejected upward into a near vacuum. Effects of secondary volcanism and return of the ocean over hot oceanic crater floor could also be expected to add substantial solid and vaporized material to the atmosphere, but these conditions were not studied.

Cat Mountain: A meteoritic sample of an impact-melted chondritic asteroid

NASA Technical Reports Server (NTRS)

Kring, David A.

1993-01-01

Although impact cratering and collisional disruption are the dominant geologic processes affecting asteroids, samples of impact melt breccias comprise less than 1 percent of ordinary chondritic material and none exist among enstatite and carbonaceous chondrite groups. Because the average collisional velocity among asteroids is sufficiently large to produce impact melts, this paucity of impact-melted material is generally believed to be a sampling bias, making it difficult to determine the evolutionary history of chondritic bodies and how impact processes may have affected the physical properties of asteroids (e.g., their structural integrity and reflectance spectra). To help address these and related issues, the first petrographic description of a new chondritic impact melt breccia sample, tentatively named Cat Mountain, is presented.

Direct Characterization of Comets and Asteroids via Cosmic Dust Analysis from the Deep Space Gateway

NASA Technical Reports Server (NTRS)

Fries, M.; Fisher, K.

2018-01-01

The Deep Space Gateway (DSG) may provide a platform for direct sampling of a large number of comets and asteroids, through employment of an instrument for characterizing dust from these bodies. Every year, the Earth traverses through debris streams of dust and small particles from comets and asteroids in Earth-crossing orbits, generating short-lived outbursts of meteor activity commonly known as "meteor showers" (Figure 1). The material in each debris stream originates from a distinct parent body, many of which have been identified. By sampling this material, it is possible to quantitatively analyze the composition of a dozen or more comets and asteroids (See Figure 2, following page) without leaving cislunar space.

NASA's New Discovery Missions

NASA Image and Video Library

2017-01-04

On Jan. 4, 2017 NASA announced the selection of two missions to explore previously unexplored asteroids. The first mission, called Lucy, will study asteroids, known as Trojan asteroids, trapped by Jupiter’s gravity. The Psyche mission will explore a very large and rare object in the solar system’s asteroid belt that’s made of metal, and scientists believe might be the exposed core of a planet that lost its rocky outer layers from a series of violent collisions. Lucy is targeted for launch in 2021 and Psyche in 2023. Both missions have the potential to open new windows on one of the earliest eras in the history of our solar system – a time less than 10 million years after the birth of our sun.

UV Reflectance of Jupiter's Moon Europa and Asteroid (16) Psyche

NASA Astrophysics Data System (ADS)

Becker, T. M.; Retherford, K. D.; Roth, L.; Hendrix, A.; McGrath, M. A.; Cunningham, N.; Feaga, L. M.; Saur, J.; Elkins-Tanton, L. T.; Walhund, J. E.; Molyneux, P.

2017-12-01

Surface reflectance observations of solar system objects in the UV are not only complimentary to longer wavelength observations for identifying surface composition, but can also reveal new and meaningful information about the surfaces of those bodies. On Europa, far-UV (FUV) spectral observations made by the Hubble Space Telescope (HST) show that the surface lacks a strong water ice absorption edge near 165 nm, which is intriguing because such a band has been detected on most icy satellites. This may suggest that radiolytic processing by Jupiter's magnetosphere has altered the surface, causing absorption at wavelengths longward of the H2O edge, masking this feature. Additionally, the FUV spectra are blue (increasing albedo with shorter wavelengths), and regions that are observed to be dark in the visible appear bright in the FUV. This spectral inversion, also observed on the Moon and some asteroids, may provide insight into the properties of the surface material and how they are processed.We also explore the UV reflectance spectra of the main belt asteroid (16) Psyche. This asteroid is believed to be the metallic remnant core of a differentiated asteroid, stripped of its mantle through collisions. However, there is speculation that the asteroid could have formed as-is from highly reduced metal-rich material near the Sun early in the formation of the solar system. Further, spectral observations in the infrared have revealed pyroxene and hydroxyl on the asteroid's surface, complicating the interpretation that (16) Psyche is a pure metallic object. Laboratory studies indicate that there are diagnostic spectral features in the UV that could be useful for determining the surface composition. We obtained HST observations of Psyche from 160 - 300 nm. Preliminary results show a featureless, red-sloped spectrum, inconsistent with significant amounts of pyroxene on the surface. We will present the spectra of Europa and the asteroid (16) Psyche and discuss the unique details unveiled by studies of these objects in the UV.

On protecting the planet against cosmic attack: Ultrafast real-time estimate of the asteroid's radial velocity

NASA Astrophysics Data System (ADS)

Zakharchenko, V. D.; Kovalenko, I. G.

2014-05-01

A new method for the line-of-sight velocity estimation of a high-speed near-Earth object (asteroid, meteorite) is suggested. The method is based on the use of fractional, one-half order derivative of a Doppler signal. The algorithm suggested is much simpler and more economical than the classical one, and it appears preferable for use in orbital weapon systems of threat response. Application of fractional differentiation to quick evaluation of mean frequency location of the reflected Doppler signal is justified. The method allows an assessment of the mean frequency in the time domain without spectral analysis. An algorithm structure for the real-time estimation is presented. The velocity resolution estimates are made for typical asteroids in the X-band. It is shown that the wait time can be shortened by orders of magnitude compared with similar value in the case of a standard spectral processing.

Metal-Silicate Segregation in Asteroidal Meteorites

NASA Technical Reports Server (NTRS)

Herrin, Jason S.; Mittlefehldt, D. W.

2006-01-01

A fundamental process of planetary differentiation is the segregation of metal-sulfide and silicate phases, leading eventually to the formation of a metallic core. Asteroidal meteorites provide a glimpse of this process frozen in time from the early solar system. While chondrites represent starting materials, iron meteorites provide an end product where metal has been completely concentrated in a region of the parent asteroid. A complimentary end product is seen in metal-poor achondrites that have undergone significant igneous processing, such as angrites, HED's and the majority of aubrites. Metal-rich achondrites such as acapulcoite/lodranites, winonaites, ureilites, and metal-rich aubrites may represent intermediate stages in the metal segregation process. Among these, acapulcoite-lodranites and ureilites are examples of primary metal-bearing mantle restites, and therefore provide an opportunity to observe the metal segregation process that was captured in progress. In this study we use bulk trace element compositions of acapulcoites-lodranites and ureilites for this purpose.

Reconnaissance and recovery of the brighter asteroids. Brief summary of the entire project

NASA Technical Reports Server (NTRS)

Edmonson, F. K.; Wood, H. J.

1982-01-01

An inexpensive method of baking large (8- by 10-inch) IIIa-J plates in 2 percent forming gas was found and successfully tested. The large storage capacity and fine grain structure of the emulsion made the sky fog negligible on plates of one-hour exposure at Link. Plates were taken through the end of October 18, 1981 on various asteroids from the recent critical lists published in the Minor Planet Circulars and the Russian Ephemeris of Minor Planets.

Asteroid Impact Risk: Ground Hazard versus Impactor Size

NASA Technical Reports Server (NTRS)

Mathias, Donovan; Wheeler, Lorien; Dotson, Jessie; Aftosmis, Michael; Tarano, Ana

2017-01-01

We utilized a probabilistic asteroid impact risk (PAIR) model to stochastically assess the impact risk due to an ensemble population of Near-Earth Objects (NEOs). Concretely, we present the variation of risk with impactor size. Results suggest that large impactors dominate the average risk, even when only considering the subset of undiscovered NEOs.

Automated Classification of Asteroids into Families at Work

NASA Astrophysics Data System (ADS)

Knežević, Zoran; Milani, Andrea; Cellino, Alberto; Novaković, Bojan; Spoto, Federica; Paolicchi, Paolo

2014-07-01

We have recently proposed a new approach to the asteroid family classification by combining the classical HCM method with an automated procedure to add newly discovered members to existing families. This approach is specifically intended to cope with ever increasing asteroid data sets, and consists of several steps to segment the problem and handle the very large amount of data in an efficient and accurate manner. We briefly present all these steps and show the results from three subsequent updates making use of only the automated step of attributing the newly numbered asteroids to the known families. We describe the changes of the individual families membership, as well as the evolution of the classification due to the newly added intersections between the families, resolved candidate family mergers, and emergence of the new candidates for the mergers. We thus demonstrate how by the new approach the asteroid family classification becomes stable in general terms (converging towards a permanent list of confirmed families), and in the same time evolving in details (to account for the newly discovered asteroids) at each update.

Optimal Asteroid Mass Determination from Planetary Range Observations: A Study of a Simplified Test Model

NASA Technical Reports Server (NTRS)

Kuchynka, P.; Laskar, J.; Fienga, A.

2011-01-01

Mars ranging observations are available over the past 10 years with an accuracy of a few meters. Such precise measurements of the Earth-Mars distance provide valuable constraints on the masses of the asteroids perturbing both planets. Today more than 30 asteroid masses have thus been estimated from planetary ranging data (see [1] and [2]). Obtaining unbiased mass estimations is nevertheless difficult. Various systematic errors can be introduced by imperfect reduction of spacecraft tracking observations to planetary ranging data. The large number of asteroids and the limited a priori knowledge of their masses is also an obstacle for parameter selection. Fitting in a model a mass of a negligible perturber, or on the contrary omitting a significant perturber, will induce important bias in determined asteroid masses. In this communication, we investigate a simplified version of the mass determination problem. Instead of planetary ranging observations from spacecraft or radar data, we consider synthetic ranging observations generated with the INPOP [2] ephemeris for a test model containing 25000 asteroids. We then suggest a method for optimal parameter selection and estimation in this simplified framework.

Compositional Variation in Large-Diameter Low-Albedo asteroids

NASA Astrophysics Data System (ADS)

Vilas, F.; Jarvis, K. S.; Thibault, C. A.; Sawyer, S. R.

2000-12-01

Age dating of meteorites indicates that the Solar System was subjected to a major heating event 4.5 Gyr ago. Models of the effects of heating by electromagnetic induction or decay of short-lived radionuclides combined with models of the early collisional history of the Solar System after Jupiter's formation indicate that asteroids observed today can be divided into two groups by diameter. Those asteroids having diameters greater than 100 km were mixed by multiple collisions but remain as gravitationally bound rubble piles. Asteroids with diameters less than 100 km should show more compositional diversity. Vilas and Sykes (1996, Icarus, 124) have shown using ECAS photometry that this compositional difference exists. The larger diameter group should be individually homogenous, with spectral differences showing the combined effects of a primordial compositional gradient in the asteroid belt with thermal metamorphism. We address the significance of 36 rotationally-resolved spectra of larger-diameter low-albedo asteroids of the C class (and subclasses B, F, G) and P class in the visible and Near-IR spectral regions. This work was supported by the NASA Planetary Astronomy program.

Astrometric Masses of 21 Asteroids, and an Integrated Asteroid Ephemeris

NASA Astrophysics Data System (ADS)

Baer, James J.; Chesley, S. R.

2007-07-01

We apply the technique of astrometric mass determination to measure the masses of 21 main-belt asteroids; the masses of 6 Hebe (7.59 +/- 1.42 x 10-12 SM), 9 Metis (1.03 +/- 0.24 x 10-11 SM), 17 Thetis (6.17 +/- 0.64 x 10-13 SM), 19 Fortuna (5.41 +/- 0.76 x 10-12 SM), and 189 Phthia (1.87 +/- 0.64 x 10-14 SM) appear to be new. The resulting bulk porosities of 11 Parthenope (12%) and 16 Psyche (45%) are smaller than previous values; while the bulk porosities of 52 Europa (41%) and 189 Phthia (64%) are significant. The variations in density within the C- and S-classes are consistent with either heteorogenous mineralogical compositions within each class, significant variations in porosity, or both. To accurately model the forces on these asteroids during the mass determination process, we created an integrated ephemeris of the 300 large asteroids used in preparing the DE-405 planetary ephemeris; this new BC-405 integrated asteroid ephemeris also appears useful in other high-accuracy applications.

Application of a Novel Long-Reach Manipulator Concept to Asteroid Redirect Missions

NASA Technical Reports Server (NTRS)

Dorsey, John T.; Doggett, William R.; Jones, Thomas C.; King, Bruce D.

2015-01-01

A high priority mission currently being formulated by NASA is to capture all or part of an asteroid and return it to cis-lunar space for examination by an astronaut crew. Two major mission architectures are currently being considered: in the first (Mission Concept A), a spacecraft would rendezvous and capture an entire free flying asteroid (up to 14 meters in diameter), and in the second (Mission Concept B), a spacecraft would rendezvous with a large asteroid (which could include one of the Martian moons) and retrieve a boulder (up to 4 meters in diameter). A critical element of the mission is the system that will capture the asteroid or boulder material, enclose it and secure it for the return flight. This paper describes the design concepts, concept of operations, structural sizing and masses of capture systems that are based on a new and novel Tendon- Actuated Lightweight In-Space MANipulator (TALISMAN) general-purpose robotic system. Features of the TALISMAN system are described and the status of its technology development is summarized. TALISMAN-based asteroid material retrieval system concepts and concepts-of-operations are defined for each asteroid mission architecture. The TALISMAN-based capture systems are shown to dramatically increase operational versatility while reducing mission risk. Total masses of TALISMAN-based systems are presented, reinforcing the mission viability of using a manipulator-based approach for the asteroid redirect mission.

New observations of (4179) Toutatis from the Chang'e-2 flyby mission and future Chinese missions to asteroids

NASA Astrophysics Data System (ADS)

Ji, J.

2014-07-01

Primitive asteroids are remnant building blocks in the Solar System formation. They provide key clues for us to reach in-depth understanding of the process of planetary formation, the complex environment of early Solar nebula, and even the occurrence of life on the Earth. On 13 December 2012, Chang'e-2 completed a successful flyby of the near-Earth asteroid (4179) Toutatis at a closest distance of 770 meters from the asteroid's surface. The observations show that Toutatis has an irregular surface and its shape resembles a ginger-root with a smaller lobe (head) and a larger lobe (body). Such bifurcated configuration is indicative of a contact binary origin for Toutatis. In addition, the images with a 3-m resolution or higher provide a number of new discoveries about this asteroid, such as an 800-meter basin at the end of the large lobe, a sharply perpendicular silhouette near the neck region, and direct evidence of boulders and regolith, indicating that Toutatis is probably a rubble-pile asteroid. The Chang'e-2 observations have provided significant new insights into the geological features and the formation and evolution of this asteroid. Moreover, a conceptual introduction to future Chinese missions to asteroids, such as the major scientific objectives, scientific payloads, and potential targets, will be briefly given. The proposed mission will benefit a lot from potential international collaboration in the future.

The missing large impact craters on Ceres

PubMed Central

Marchi, S.; Ermakov, A. I.; Raymond, C. A.; Fu, R. R.; O'Brien, D. P.; Bland, M. T.; Ammannito, E.; De Sanctis, M. C.; Bowling, T.; Schenk, P.; Scully, J. E. C.; Buczkowski, D. L.; Williams, D. A.; Hiesinger, H.; Russell, C. T.

2016-01-01

Asteroids provide fundamental clues to the formation and evolution of planetesimals. Collisional models based on the depletion of the primordial main belt of asteroids predict 10–15 craters >400 km should have formed on Ceres, the largest object between Mars and Jupiter, over the last 4.55 Gyr. Likewise, an extrapolation from the asteroid Vesta would require at least 6–7 such basins. However, Ceres' surface appears devoid of impact craters >∼280 km. Here, we show a significant depletion of cerean craters down to 100–150 km in diameter. The overall scarcity of recognizable large craters is incompatible with collisional models, even in the case of a late implantation of Ceres in the main belt, a possibility raised by the presence of ammoniated phyllosilicates. Our results indicate that a significant population of large craters has been obliterated, implying that long-wavelength topography viscously relaxed or that Ceres experienced protracted widespread resurfacing. PMID:27459197

Dynamical evolution of differentiated asteroid families

NASA Astrophysics Data System (ADS)

Martins-Filho, W. S.; Carvano, J.; Mothe-Diniz, T.; Roig, F.

2014-10-01

The project aims to study the dynamical evolution of a family of asteroids formed from a fully differentiated parent body, considering family members with different physical properties consistent with what is expected from the break up of a body formed by a metallic nucleus surrounded by a rocky mantle. Initially, we study the effects of variations in density, bond albedo, and thermal inertia in the semi-major axis drift caused by the Yarkovsky effect. The Yarkovsky effect is a non-conservative force caused by the thermal re-radiation of the solar radiation by an irregular body. In Solar System bodies, it is known to cause changes in the orbital motions (Peterson, 1976), eventually bringing asteroids into transport routes to near-Earth space, such as some mean motion resonances. We expressed the equations of variation of the semi-major axis directly in terms of physical properties (such as the mean motion, frequency of rotation, conductivity, thermal parameter, specific heat, obliquity and bond albedo). This development was based on the original formalism for the Yarkovsky effect (i.e., Bottke et al., 2006 and references therein). The derivation of above equations allowed us to closely study the variation of the semi-major axis individually for each physical parameter, clearly showing that the changes in semi-major axis for silicate bodies is twice or three times greater than for metal bodies. The next step was to calculate the orbital elements of a synthetic family after the break-up. That was accomplished assuming that the catastrophic disruption energy is given by the formalism described by Stewart and Leinhardt (2009) and assuming an isotropic distribution of velocities for the fragments of the nucleus and the mantle. Finally, the orbital evolution of the fragments is implemented using a simpletic integrator, and the result compared with the distribution of real asteroid families.

ANTS: A New Concept for Very Remote Exploration with Intelligent Software Agents

NASA Astrophysics Data System (ADS)

Clark, P. E.; Curtis, S.; Rilee, M.; Truszkowski, W.; Iyengar, J.; Crawford, H.

2001-12-01

ANTS (Autonomous Nano-Technology Swarm), a NASA advanced mission concept, is a large (100 to 1000 member) swarm of pico-class (1 kg) totally autonomous spacecraft that prospect the asteroid belt. As the capacity and complexity of hardware and software, and the sophistication of technical and scientific goals have increased, greater cost constraints have led to fewer resources and thus, the need to operate spacecraft with less frequent contact. At present, autonomous operation of spacecraft systems allows great capability of spacecraft to 'safe' themselves when conditions threaten spacecraft safety. To further develop spacecraft capability, NASA is at the forefront of Intelligent Software Agent (ISA) research, performing experiments in space and on the ground to advance deliberative and collaborative autonomous control techniques. Selected missions in current planning stages require small groups of spacecraft to cooperate at a tactical level to select and schedule measurements to be made by appropriate instruments to characterize rapidly unfolding real-time events on a routine basis. The next level of development, which we are considering here, is in the use of ISAs at a strategic level, to explore the final, remote frontiers of the solar system, potentially involving a large class of objects with only infrequent contact possible. Obvious mission candidates are mainbelt asteroids, a population consisting of more than a million small bodies. Although a large fraction of solar system objects are asteroids, little data is available for them because the vast majority of them are too small to be observed except in close proximity. Asteroids originated in the transitional region between the inner (rocky) and outer (solidified gases) solar system, have remained largely unmodified since formation, and thus have a more primitive composition which includes higher abundances of siderophile (metallic iron-associated) elements and volatiles than other planetary surfaces. As a result, there has been interest in asteroids as sources of exploitable resources. Far more reconnaissance is required before such a program is undertaken. A traditional mission approach (to explore larger asteroids sequentially) is not adequate for determining the systematic distribution of exploitable material in the asteroid population. Our approach involves the use of distributed intelligence in a swarm of tiny spacecraft, each with specialized instrument capability (e.g., advanced computing, imaging, spectrometry, etc.) to evaluate the resource potential of the entire population. Supervised clusters of spacecraft will operate simultaneously within a broadly defined framework of goals to select targets (>1000) from among available candidates and to develop scenarios for studying targets simultaneously. Spacecraft use solar sails to fly directly to asteroids 1 kilometer or greater in diameter. Selected swarm members return to Earth with data, replacements join the swarm as needed. We would like to acknowledge our students R. Watson, V. Cox, and F. Olukomo for their support of this work.

Iron oxide bands in the visible and near-infrared reflectance spectra of primitive asteroids

NASA Technical Reports Server (NTRS)

Jarvis, Kandy S.; Vilas, Faith; Gaffey, Michael J.

1993-01-01

High resolution reflectance spectra of primitive asteroids (C, P, and D class and associated subclasses) have commonly revealed an absorption feature centered at 0.7 microns attributed to an Fe(2+)-Fe(3+) charge transfer transition in iron oxides and/or oxidized iron in phyllosilicates. A smaller feature identified at 0.43 microns has been attributed to an Fe(3+) spin-forbidden transition in iron oxides. In the spectra of the two main-belt primitive asteroids 368 Haidea (D) and 877 Walkure (F), weak absorption features which were centered near the location of 0.60-0.65 microns and 0.80-0.90 microns prompted a search for features at these wavelengths and an attempt to identify their origin(s). The CCD reflectance spectra obtained between 1982-1992 were reviewed for similar absorption features located near these wavelengths. The spectra of asteroids in which these absorption features have been identified are shown. These spectra are plotted in order of increasing heliocentric distance. No division of the asteroids by class has been attempted here (although the absence of these features in the anhydrous S-class asteroids, many of which have presumably undergone full heating and differentiation should be noted). For this study, each spectrum was treated as a continuum with discrete absorption features superimposed on it. For each object, a linear least squares fit to the data points defined a simple linear continuum. The linear continuum was then divided into each spectrum, thus removing the sloped continuum and permitting the intercomparison of residual spectral features.

Solar system dynamics

NASA Technical Reports Server (NTRS)

Wisdom, Jack

1987-01-01

The rotational dynamics of irregularly shaped satellites and the origin of Kirkwood Gaps are discussed. The chaotic tumbling of Hyperion and the anomalously low eccentricity of Deimos are examined. The Digital Orrery is used to explore the phase space of the ellipic restricted three body problem near the principal commensurabilities (2/1, 5/2, 3/1, and 3/2). The results for the 3/1 commensurability are in close agreement with those found earlier with the algebraic mapping method. Large chaotic zones are associated with the 3/1, 2/1 and 5/2 resonances, where there are gaps in the distribution of asteroids. The region near the 3/2 resonance, where the Hilda group of asteroids is located, is largely devoid of chaotic behavior. Thus, there is a qualitative agreement between the character of the motion and the distribution of asteroids.

Volumes and bulk densities of forty asteroids from ADAM shape modeling

NASA Astrophysics Data System (ADS)

Hanuš, J.; Viikinkoski, M.; Marchis, F.; Ďurech, J.; Kaasalainen, M.; Delbo', M.; Herald, D.; Frappa, E.; Hayamizu, T.; Kerr, S.; Preston, S.; Timerson, B.; Dunham, D.; Talbot, J.

2017-05-01

Context. Disk-integrated photometric data of asteroids do not contain accurate information on shape details or size scale. Additional data such as disk-resolved images or stellar occultation measurements further constrain asteroid shapes and allow size estimates. Aims: We aim to use all the available disk-resolved images of approximately forty asteroids obtained by the Near-InfraRed Camera (Nirc2) mounted on the W.M. Keck II telescope together with the disk-integrated photometry and stellar occultation measurements to determine their volumes. We can then use the volume, in combination with the known mass, to derive the bulk density. Methods: We downloaded and processed all the asteroid disk-resolved images obtained by the Nirc2 that are available in the Keck Observatory Archive (KOA). We combined optical disk-integrated data and stellar occultation profiles with the disk-resolved images and use the All-Data Asteroid Modeling (ADAM) algorithm for the shape and size modeling. Our approach provides constraints on the expected uncertainty in the volume and size as well. Results: We present shape models and volume for 41 asteroids. For 35 of these asteroids, the knowledge of their mass estimates from the literature allowed us to derive their bulk densities. We see a clear trend of lower bulk densities for primitive objects (C-complex) and higher bulk densities for S-complex asteroids. The range of densities in the X-complex is large, suggesting various compositions. We also identified a few objects with rather peculiar bulk densities, which is likely a hint of their poor mass estimates. Asteroid masses determined from the Gaia astrometric observations should further refine most of the density estimates.

Asteroid spin-rate studies using large sky-field surveys

NASA Astrophysics Data System (ADS)

Chang, Chan-Kao; Lin, Hsing-Wen; Ip, Wing-Huen; Prince, Thomas A.; Kulkarni, Shrinivas R.; Levitan, David; Laher, Russ; Surace, Jason

2017-12-01

Eight campaigns to survey asteroid rotation periods have been carried out using the intermediate Palomar Transient Factory in the past 3 years. 2780 reliable rotation periods were obtained, from which we identified two new super-fast rotators (SFRs), (335433) 2005 UW163 and (40511) 1999 RE88, and 23 candidate SFRs. Along with other three known super-fast rotators, there are five known SFRs so far. Contrary to the case of rubble-pile asteroids (i.e., bounded aggregations by gravity only), an internal cohesion, ranging from 100 to 1000 Pa, is required to prevent these five SFRs from flying apart because of their super-fast rotations. This cohesion range is comparable with that of lunar regolith. However, some candidates of several kilometers in size require unusually high cohesion (i.e., a few thousands of Pa). Therefore, the confirmation of these kilometer-sized candidates can provide important information about asteroid interior structure. From the rotation periods we collected, we also found that the spin-rate limit of C-type asteroids, which has a lower bulk density, is lower than for S-type asteroids. This result is in agreement with the general picture of rubble-pile asteroids (i.e., lower bulk density, lower spin-rate limit). Moreover, the spin-rate distributions of asteroids of 3< D < 15 km in size show a steady decrease along frequency for f > 5 rev/day, regardless of the location in the main belt. The YORP effect is indicated to be less efficient in altering asteroid spin rates from our results when compared with the flat distribution found by Pravec et al. (Icarus 197:497-504, 2008. doi: 10.1016/j.icarus.2008.05.012). We also found a significant number drop at f = 5 rev/day in the spin-rate distributions of asteroids of D < 3 km.

Mining The Sdss-moc Database For Main-belt Asteroid Solar Phase Behavior.

NASA Astrophysics Data System (ADS)

Truong, Thien-Tin; Hicks, M. D.

2010-10-01

The 4th Release of the Sloan Digital Sky Survey Moving Object Catalog (SDSS-MOC) contains 471569 moving object detections from 519 observing runs obtained up to March 2007. Of these, 220101 observations were linked with 104449 known small bodies, with 2150 asteroids sampled at least 10 times. It is our goal to mine this database in order to extract solar phase curve information for a large number of main-belt asteroids of different dynamical and taxonomic classes. We found that a simple linear phase curve fit allowed us to reject data contaminated by intrinsic rotational lightcurves and other effects. As expected, a running mean of solar phase coefficient is strongly correlated with orbital elements, with the inner main-belt dominated by bright S-type asteroids and transitioning to darker C and D-type asteroids with steeper solar phase slopes. We shall fit the empirical H-G model to our 2150 multi-sampled asteroids and correlate these parameters with spectral type derived from the SDSS colors and position within the asteroid belt. Our data should also allow us to constrain solar phase reddening for a variety of taxonomic classes. We shall discuss errors induced by the standard "g=0.15" assumption made in absolute magnitude determination, which may slightly affect number-size distribution models.

Effect of yield curves and porous crush on hydrocode simulations of asteroid airburst

NASA Astrophysics Data System (ADS)

Robertson, D. K.; Mathias, D. L.

2017-03-01

Simulations of asteroid airburst are being conducted to obtain best estimates of damage areas and assess sensitivity to variables for asteroid characterization and mitigation efforts. The simulations presented here employed the ALE3D hydrocode to examine the breakup and energy deposition of asteroids entering the Earth's atmosphere, using the Chelyabinsk meteor as a test case. This paper examines the effect of increasingly complex material models on the energy deposition profile. Modeling the meteor as a rock having a single strength can reproduce airburst altitude and energy deposition reasonably well but is not representative of real rock masses (large bodies of material). Accounting for a yield curve that includes different tensile, shear, and compressive strengths shows that shear strength determines the burst altitude. Including yield curves and compaction of porous spaces in the material changes the detailed mechanics of the breakup but only has a limited effect on the burst altitude and energy deposition. Strong asteroids fail and create peak energy deposition close to the altitude at which ram dynamic pressure equals the material strength. Weak asteroids, even though they structurally fail at high altitude, require the increased pressure at lower altitude to disrupt and disperse the rubble. As a result, a wide range of weaker asteroid strengths produce peak energy deposition at a similar altitude.

An ISU study of asteroid mining

NASA Technical Reports Server (NTRS)

Burke, J. D.

1991-01-01

During the 1990 summer session of the International Space University, 59 graduate students from 16 countries carried out a design project on using the resources of near-earth asteroids. The results of the project, whose full report is now available from ISU, are summarized. The student team included people in these fields: architecture, business and management, engineering, life sciences, physical sciences, policy and law, resources and manufacturing, and satellite applications. They designed a project for transporting equipment and personnel to a near-earth asteroid, setting up a mining base there, and hauling products back for use in cislunar space. In addition, they outlined the needed precursor steps, beginning with expansion of present ground-based programs for finding and characterizing near-earth asteroids and continuing with automated flight missions to candidate bodies. (To limit the summer project's scope the actual design of these flight-mission precursors was excluded.) The main conclusions were that asteroid mining may provide an important complement to the future use of lunar resources, with the potential to provide large amounts of water and carbonaceous materials for use off earth. However, the recovery of such materials from presently known asteroids did not show an economic gain under the study assumptions; therefore, asteroid mining cannot yet be considered a prospective business.

The fossilized size distribution of the main asteroid belt

NASA Astrophysics Data System (ADS)

Bottke, William F.; Durda, Daniel D.; Nesvorný, David; Jedicke, Robert; Morbidelli, Alessandro; Vokrouhlický, David; Levison, Hal

2005-05-01

Planet formation models suggest the primordial main belt experienced a short but intense period of collisional evolution shortly after the formation of planetary embryos. This period is believed to have lasted until Jupiter reached its full size, when dynamical processes (e.g., sweeping resonances, excitation via planetary embryos) ejected most planetesimals from the main belt zone. The few planetesimals left behind continued to undergo comminution at a reduced rate until the present day. We investigated how this scenario affects the main belt size distribution over Solar System history using a collisional evolution model (CoEM) that accounts for these events. CoEM does not explicitly include results from dynamical models, but instead treats the unknown size of the primordial main belt and the nature/timing of its dynamical depletion using innovative but approximate methods. Model constraints were provided by the observed size frequency distribution of the asteroid belt, the observed population of asteroid families, the cratered surface of differentiated Asteroid (4) Vesta, and the relatively constant crater production rate of the Earth and Moon over the last 3 Gyr. Using CoEM, we solved for both the shape of the initial main belt size distribution after accretion and the asteroid disruption scaling law QD∗. In contrast to previous efforts, we find our derived QD∗ function is very similar to results produced by numerical hydrocode simulations of asteroid impacts. Our best fit results suggest the asteroid belt experienced as much comminution over its early history as it has since it reached its low-mass state approximately 3.9-4.5 Ga. These results suggest the main belt's wavy-shaped size-frequency distribution is a "fossil" from this violent early epoch. We find that most diameter D≳120 km asteroids are primordial, with their physical properties likely determined during the accretion epoch. Conversely, most smaller asteroids are byproducts of fragmentation events. The observed changes in the asteroid spin rate and lightcurve distributions near D˜100-120 km are likely to be a byproduct of this difference. Estimates based on our results imply the primordial main belt population (in the form of D<1000 km bodies) was 150-250 times larger than it is today, in agreement with recent dynamical simulations.

Accretion timescales and style of asteroidal differentiation in an 26Al-poor protoplanetary disk

PubMed Central

Larsen, K.K.; Schiller, M.; Bizzarro, M.

2016-01-01

The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al−26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ~ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of μ26Mg (μ26Mg*) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg* in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ~250,000 years of solar system formation from a hot (>~500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (~1–2 × 10−5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10−5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These ‘non-carbonaceous’ planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and undifferentiated chondritic crusts. In contrast, individual olivine crystals from Eagle Station pallasites record variable μ26Mg* excesses, suggesting that these crystals captured the 26Mg* evolution of a magmatic reservoir controlled by fractional crystallization processes during the lifespan of 26Al. Similar to previous suggestions based on isotopic evidence, we suggest that Eagle Station pallasites formed from precursor material similar in composition to carbonaceous chondrites from a cool outer protoplanetary disk region characterized by (26Al/27Al)0 ≥ 2.7 × 10−5. Protracted planetesimal accretion timescales at large orbital distances, with onset of accretion 0.3–1 Myr post-CAIs, may have resulted in significant radiative heat loss and thus efficient early interior cooling of slowly accreting ‘carbonaceous’ planetesimals. PMID:27445415

Accretion timescales and style of asteroidal differentiation in an 26Al-poor protoplanetary disk

NASA Astrophysics Data System (ADS)

Larsen, K. K.; Schiller, M.; Bizzarro, M.

2016-03-01

The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al-26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ∼ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of μ26Mg (μ26Mg∗) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg∗ in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ∼250,000 years of solar system formation from a hot (>∼500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (∼1-2 × 10-5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10-5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These 'non-carbonaceous' planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and undifferentiated chondritic crusts. In contrast, individual olivine crystals from Eagle Station pallasites record variable μ26Mg∗ excesses, suggesting that these crystals captured the 26Mg∗ evolution of a magmatic reservoir controlled by fractional crystallization processes during the lifespan of 26Al. Similar to previous suggestions based on isotopic evidence, we suggest that Eagle Station pallasites formed from precursor material similar in composition to carbonaceous chondrites from a cool outer protoplanetary disk region characterized by (26Al/27Al)0 ⩾ 2.7 × 10-5. Protracted planetesimal accretion timescales at large orbital distances, with onset of accretion 0.3-1 Myr post-CAIs, may have resulted in significant radiative heat loss and thus efficient early interior cooling of slowly accreting 'carbonaceous' planetesimals.

Comet deflection by directed energy: a finite element analysis

NASA Astrophysics Data System (ADS)

Madajian, Jonathan; Griswold, Janelle; Gandra, Anush; Hughes, Gary B.; Zhang, Qicheng; Rupert, Nic; Lubin, Philip

2016-09-01

Comets and Asteroids are viable threats to our planet; if these space rocks are smaller than 25 meters, they burn up in the atmosphere, but if they are wider than 25 meters they can cause damage to the impact area. Anything more than one to two kilometers can have worldwide effects, furthermore a mile-wide asteroid travelling at 30,000 miles per hour has the energy equal to a megaton bomb and is very likely to wipe out most of the life on Earth. Residents near Chelyabinsk, Russia experienced the detrimental effects of a collision with a Near-Earth Asteroid (NEA) on 15 February 2013 as a 20 m object penetrated the atmosphere above that city. The effective yield from this object was approximately 1/2 Megaton TNT equivalent (Mt), or that of a large strategic warhead. The 1908 Tunguska event, also over Russia, is estimated to have had a yield of approximately 15 Mt and had the potential to kill millions of people had it come down over a large city1. In the face of such danger a planetary defense system is necessary and this paper proposes a design for such a system. DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) is a phased array laser system that can be used to oblate, deflect and de-spin asteroids and comets.

Spacewatch Survey of the Solar System

NASA Technical Reports Server (NTRS)

McMillan, Robert S.

2000-01-01

The purpose of the Spacewatch project is to explore the various populations of small objects throughout the solar system. Statistics on all classes of small bodies are needed to infer their physical and dynamical evolution. More Earth Approachers need to be found to assess the impact hazard. (We have adopted the term "Earth Approacher", EA, to include all those asteroids, nuclei of extinct short period comets, and short period comets that can approach close to Earth. The adjective "near" carries potential confusion, as we have found in communicating with the media, that the objects are always near Earth, following it like a cloud.) Persistent and voluminous accumulation of astrometry of incidentally observed main belt asteroids MBAs will eventually permit the Minor Planet Center (MPQ to determine the orbits of large numbers (tens of thousands) of asteroids. Such a large body of information will ultimately allow better resolution of orbit classes and the determinations of luminosity functions of the various classes, Comet and asteroid recoveries are essential services to planetary astronomy. Statistics of objects in the outer solar system (Centaurs, scattered-disk objects, and Trans-Neptunian Objects; TNOs) ultimately will tell part of the story of solar system evolution. Spacewatch led the development of sky surveying by electronic means and has acted as a responsible interface to the media and general public on this discipline and on the issue of the hazard from impacts by asteroids and comets.

ATLAS: Finding the Nearest Asteroids

NASA Astrophysics Data System (ADS)

Heinze, Aren; Tonry, John L.; Denneau, Larry; Stalder, Brian

2017-10-01

The Asteroid Terrestrial-impact Last Alert System (ATLAS) became fully operational in June 2017. Our two robotic, 0.5 meter telescopes survey the whole accessible sky every two nights from the Hawaiian mountains of Haleakala and Mauna Loa. With sensitivity to magnitude 19.5 over a field of 30 square degrees, we discover several bright near-Earth objects every month - particularly fast moving asteroids, which can slip by other surveys that scan the sky more slowly. Several important developments in 2017 have enhanced our sensitivity to small, nearby asteroids and potential impactors. We report on these developments - including optical adjustments, automated screening of detections, closer temporal spacing of images, and tolerance for large deviations from Great Circle motion on the sky - and we describe their effect in terms of measuring and discovering real objects.

A preliminary analysis of the orbit of the Mars Trojan asteroid (5261) Eureka

NASA Technical Reports Server (NTRS)

Mikkola, Seppo; Innanen, Kimmo; Muinonen, Karri; Bowell, Edward

1994-01-01

Observations and results of orbit determination of the first known Mars Trojan asteroid (5261) Eureka are presented. We have numerically calculated the evolution of the orbital elements, and have analyzed the behavior of the motion during the next 2 Myr. Strong perturbations by planets other than Mars seem to stabilize the eccentricity of the asteroid by stirring the high order resonances present in the elliptic restricted problem. As a result, the orbit appears stable at least on megayear timescales. The difference of the mean longitudes of Mars and Eureka and the semimajor axis of the asteroid form a pair of variables that essentially behave in an adiabatic manner, while the evolution of the other orbital elements is largely determined by the pertubations due to other planets.

Cosmochemical Studies: Meteorites and their Parent Asteroids

NASA Technical Reports Server (NTRS)

Wasson, John T.

2003-01-01

This a final technical report that focuses on cosmochemical studies of meteorites and their parent asteroids. The topics include: 1) Formation of iron meteorites and other metal rich meteorites; 2) New perspectives on the formation of chondrules; and 3) Consequences of large aerial bursts. Also a list of seven papers that received significant support from this research are included.

Band of Rubble

NASA Technical Reports Server (NTRS)

2005-01-01

This artist's animation illustrates a massive asteroid belt in orbit around a star the same age and size as our Sun. Evidence for this possible belt was discovered by NASA's Spitzer Space Telescope when it spotted warm dust around the star, presumably from asteroids smashing together.

The view starts from outside the belt, where planets like the one shown here might possibly reside, then moves into to the dusty belt itself. A collision between two asteroids is depicted near the end of the movie. Collisions like this replenish the dust in the asteroid belt, making it detectable to Spitzer.

The alien belt circles a faint, nearby star called HD 69830 located 41 light-years away in the constellation Puppis. Compared to our own solar system's asteroid belt, this one is larger and closer to its star - it is 25 times as massive, and lies just inside an orbit equivalent to that of Venus. Our asteroid belt circles between the orbits of Mars and Jupiter.

Because Jupiter acts as an outer wall to our asteroid belt, shepherding its debris into a series of bands, it is possible that an unseen planet is likewise marshalling this belt's rubble. Previous observations using the radial velocity technique did not locate any large gas giant planets, indicating that any planets present in this system would have to be the size of Saturn or smaller.

Asteroids are chunks of rock from 'failed' planets, which never managed to coalesce into full-sized planets. Asteroid belts can be thought of as construction sites that accompany the building of rocky planets.

Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids.

PubMed

Montecino-Latorre, Diego; Eisenlord, Morgan E; Turner, Margaret; Yoshioka, Reyn; Harvell, C Drew; Pattengill-Semmens, Christy V; Nichols, Janna D; Gaydos, Joseph K

2016-01-01

Sea star wasting disease devastated intertidal sea star populations from Mexico to Alaska between 2013-15, but little detail is known about its impacts to subtidal species. We assessed the impacts of sea star wasting disease in the Salish Sea, a Canadian / United States transboundary marine ecosystem, and world-wide hotspot for temperate asteroid species diversity with a high degree of endemism. We analyzed roving diver survey data for the three most common subtidal sea star species collected by trained volunteer scuba divers between 2006-15 in 5 basins and on the outer coast of Washington, as well as scientific strip transect data for 11 common subtidal asteroid taxa collected by scientific divers in the San Juan Islands during the spring/summer of 2014 and 2015. Our findings highlight differential susceptibility and impact of sea star wasting disease among asteroid species populations and lack of differences between basins or on Washington's outer coast. Specifically, severe depletion of sunflower sea stars (Pycnopodia helianthoides) in the Salish Sea support reports of major declines in this species from California to Alaska, raising concern for the conservation of this ecologically important subtidal predator.

Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids

PubMed Central

Montecino-Latorre, Diego; Eisenlord, Morgan E.; Turner, Margaret; Yoshioka, Reyn; Harvell, C. Drew; Pattengill-Semmens, Christy V.; Nichols, Janna D.

2016-01-01

Sea star wasting disease devastated intertidal sea star populations from Mexico to Alaska between 2013–15, but little detail is known about its impacts to subtidal species. We assessed the impacts of sea star wasting disease in the Salish Sea, a Canadian / United States transboundary marine ecosystem, and world-wide hotspot for temperate asteroid species diversity with a high degree of endemism. We analyzed roving diver survey data for the three most common subtidal sea star species collected by trained volunteer scuba divers between 2006–15 in 5 basins and on the outer coast of Washington, as well as scientific strip transect data for 11 common subtidal asteroid taxa collected by scientific divers in the San Juan Islands during the spring/summer of 2014 and 2015. Our findings highlight differential susceptibility and impact of sea star wasting disease among asteroid species populations and lack of differences between basins or on Washington’s outer coast. Specifically, severe depletion of sunflower sea stars (Pycnopodia helianthoides) in the Salish Sea support reports of major declines in this species from California to Alaska, raising concern for the conservation of this ecologically important subtidal predator. PMID:27783620

Localized sources of water vapour on the dwarf planet (1) Ceres.

PubMed

Küppers, Michael; O'Rourke, Laurence; Bockelée-Morvan, Dominique; Zakharov, Vladimir; Lee, Seungwon; von Allmen, Paul; Carry, Benoît; Teyssier, David; Marston, Anthony; Müller, Thomas; Crovisier, Jacques; Barucci, M Antonietta; Moreno, Raphael

2014-01-23

The 'snowline' conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Models suggest that some of the icy bodies may have migrated into the asteroid belt. Recent observations indicate the presence of water ice on the surface of some asteroids, with sublimation a potential reason for the dust activity observed on others. Hydrated minerals have been found on the surface of the largest object in the asteroid belt, the dwarf planet (1) Ceres, which is thought to be differentiated into a silicate core with an icy mantle. The presence of water vapour around Ceres was suggested by a marginal detection of the photodissociation product of water, hydroxyl (ref. 12), but could not be confirmed by later, more sensitive observations. Here we report the detection of water vapour around Ceres, with at least 10(26) molecules being produced per second, originating from localized sources that seem to be linked to mid-latitude regions on the surface. The water evaporation could be due to comet-like sublimation or to cryo-volcanism, in which volcanoes erupt volatiles such as water instead of molten rocks.

Comet or asteroid shower in the late Eocene?

PubMed

Tagle, Roald; Claeys, Philippe

2004-07-23

The passage of a comet shower approximately 35 million years ago is generally advocated to explain the coincidence during Earth's late Eocene of an unusually high flux of interplanetary dust particles and the formation of the two largest craters in the Cenozoic, Popigai and the Chesapeake Bay. However, new platinum-group element analyses indicate that Popigai was formed by the impact of an L-chondrite meteorite. Such an asteroidal projectile is difficult to reconcile with a cometary origin. Perhaps instead the higher delivery rate of extraterrestrial matter, dust, and large objects was caused by a major collision in the asteroid belt.

Asteroid families classification: Exploiting very large datasets

NASA Astrophysics Data System (ADS)

Milani, Andrea; Cellino, Alberto; Knežević, Zoran; Novaković, Bojan; Spoto, Federica; Paolicchi, Paolo

2014-09-01

The number of asteroids with accurately determined orbits increases fast, and this increase is also accelerating. The catalogs of asteroid physical observations have also increased, although the number of objects is still smaller than in the orbital catalogs. Thus it becomes more and more challenging to perform, maintain and update a classification of asteroids into families. To cope with these challenges we developed a new approach to the asteroid family classification by combining the Hierarchical Clustering Method (HCM) with a method to add new members to existing families. This procedure makes use of the much larger amount of information contained in the proper elements catalogs, with respect to classifications using also physical observations for a smaller number of asteroids. Our work is based on a large catalog of high accuracy synthetic proper elements (available from AstDyS), containing data for >330,000 numbered asteroids. By selecting from the catalog a much smaller number of large asteroids, we first identify a number of core families; to these we attribute the next layer of smaller objects. Then, we remove all the family members from the catalog, and reapply the HCM to the rest. This gives both satellite families which extend the core families and new independent families, consisting mainly of small asteroids. These two cases are discriminated by another step of attribution of new members and by merging intersecting families. This leads to a classification with 128 families and currently 87,095 members. The number of members can be increased automatically with each update of the proper elements catalog; changes in the list of families are not automated. By using information from absolute magnitudes, we take advantage of the larger size range in some families to analyze their shape in the proper semimajor axis vs. inverse diameter plane. This leads to a new method to estimate the family age, or ages in cases where we identify internal structures. The analysis of the plot above evidences some open problems but also the possibility of obtaining further information of the geometrical properties of the impact process. The results from the previous steps are then analyzed, using also auxiliary information on physical properties including WISE albedos and SDSS color indexes. This allows to solve some difficult cases of families overlapping in the proper elements space but generated by different collisional events. The families formed by one or more cratering events are found to be more numerous than previously believed because the fragments are smaller. We analyze some examples of cratering families (Massalia, Vesta, Eunomia) which show internal structures, interpreted as multiple collisions. We also discuss why Ceres has no family.

Reanalysis of Asteroid Families Structure Through Visible Spectroscopy

NASA Astrophysics Data System (ADS)

Mothé-Diniz, T.; Carvano, J.; Roig, F.; Lazzaro, D.

In this work we re-analyse the presence of interlopers in asteroid families based on a larger spectral database and on a family determination which makes use of a larger set of proper elements. The asteroid families were defined using the HCM method (Zappalà et al. 1995) on the set of proper elements for 110,000 asteroids available at the Asteroid Dynamic Site (AstDyS http://hamilton.dm.unipi.it/astdys )). The spectroscopic analysis is performed using spectra on the 0.44-0.92 μ m range observed by the SMASS Xu et al. 1995, SMASSII (Bus and Binzel, 2002) and 3OS2 (Lazzaro et al. 2002) surveys, which together total around 2140 asteroids with observed spectra. The asteroid taxonomy used is the Bus taxonomy (Bus et al. 2000). A total of 22 two families were analysed . The families of Vesta, Eunomia, Hoffmeister, Dora, Merxia, Agnia, and Koronis were found to be spectrally homogeneous, which confirms previous studies. The Veritas family, on the other hand, which is quoted in the literature as an heterogeneous family was found to be quite homogeneous in the present work. The Eos family is noteworthy for being at one time spectrally heterogeneous and quite different from the background population. References Bus, S. J., and R. P. Binzel 2002. Phase II of the Small Main-Belt Asteroid Spectroscopic Survey - The Observations. Icarus 158, 106-145. Bus, S. J., R. P. Binzel, and T. H. Burbine 2000. A New Generation of Asteroid Taxonomy. Meteoritics and Planetary Science, vol. 35, Supplement, p.A36 35, 36 +. Lazzaro, D., C. A. Angeli, T. Mothe-Diniz, J. M. Carvano, R. Duffard, and M. Florczak 2002. The superficial characterization of a large sample of asteroids: the S3OS2. Bulletin of the American Astronomical Society 34, 859 +. Xu, S., R. P. Binzel, T. H. Burbine, and S. J. Bus 1995. Small main-belt asteroid spectroscopic survey: Initial results. Icarus 115, 1-35. Zappala, V., P. Bendjoya, A. Cellino, P. Farinella, and C. Froeschle 1995. Asteroid families: Search of a 12,487-asteroid sample using two different clustering techniques. Icarus 116, 291-314.

Phase equilibria of the magnesium sulfate-water system to 4 kbars

NASA Technical Reports Server (NTRS)

Hogenboom, D. L.; Kargel, J. S.; Ganasan, J. P.; Lee, L.

1993-01-01

Magnesium sulfate is the most abundant salt in carbonaceous chondrites, and it may be important in the low-temperature igneous evolution and aqueous differentiation of icy satellites and large chondritic asteroids. Accordingly, we are investigating high-pressure phase equilibria in MgSO4-H2O solutions under pressures up to four kbars. An initial report was presented two years ago. This abstract summarizes our results to date including studies of solutions containing 15.3 percent, 17 percent, and 22 percent MgSO4. Briefly, these results demonstrate that increasing pressure causes the eutectic and peritectic compositions to shift to much lower concentrations of magnesium sulfate, and the existence of a new low-density phase of magnesium sulfate hydrate.

How long will asteroids on retrograde orbits survive?

NASA Astrophysics Data System (ADS)

Kankiewicz, Paweł; Włodarczyk, Ireneusz

2018-05-01

Generally, a common scenario for the origin of minor planets with high orbital inclinations does not exist. This applies especially to objects whose orbital inclinations are much greater than 90° (retrograde asteroids). Since the discovery of Dioretsa in 1999, approximately 100 small bodies now are classified as retrograde asteroids. A small number of them were reclassified as comets, due to cometary activity. There are only 25 multi-opposition retrograde asteroids, with a relatively large number of observations and well-determined orbits. We studied the orbital evolution of numbered and multi-opposition retrograde asteroids by numerical integration up to 1 Gy forward and backward in time. Additionally, we analyzed the propagation of orbital elements with the observational errors, determined dynamical lifetimes and studied their chaotic properties. Conclusively, we obtained quantitative parameters describing the long-term stability of orbits relating to the past and the future. In turn, we were able to estimate their lifetimes and how long these objects will survive in the Solar System.

Psyche: The Science of a Metal World

NASA Astrophysics Data System (ADS)

Elkins-Tanton, L. T.

2016-12-01

(16) Psyche is a large metallic asteroid orbiting in the outer main belt at 3 AU. Psyche's metal composition is indicated by high radar albedo, thermal inertia, and density. Models show that among the accretionary collisions early in the solar system, some destructive "hit and run" impacts could strip the silicate mantle from differentiated bodies. This is the leading hypothesis for Psyche's formation: it is a bare planetesimal core. It is the only one we can explore for substantial information about a metal core (other metallic asteroids are far smaller and not roughly spherical). If our observations indicate that it is not a core, Psyche may instead be highly reduced, primordial metal-rich materials that accreted closer to the Sun, and never melted. Psyche is also a Discovery-class mission, selected for a Step 2 concept study, to investigate this metal body. The Psyche investigation has three broad goals: Understand a previously unexplored building block of planet formation: iron cores. Look inside the terrestrial planets, including Earth, by directly examining the interior of a differentiated body, which otherwise could not be seen. Explore a new type of world. For the first time, examine a world made not of rock, ice, or gas, but of metal. We will meet our science objectives with three domestic high heritage instruments and radio science: Multispectral imagers with clear and seven color filters map surface morphology and reveal the distribution of residual mantle silicates. A gamma-ray and neutron spectrometer determines elemental composition, particularly the concentrations of iron, nickel, silicon, and potassium. Dual fluxgate magnetometers, in a gradiometer configuration, characterize the magnetic field. Radio science maps the gravity field sufficiently to differentiate among core-formation hypotheses. New models for magnetic dynamo generation and solidification of planetesimal cores make testable predictions for geophysical measurements, and lead as well to predictions about tectonics and surface compositions. In this presentation we will show how measurements from these flight instruments can confirm or disprove hypotheses for Psyche's formation and evolution.

Assessing Atmospheric Water Injection from Oceanic Impacts

NASA Technical Reports Server (NTRS)

Pierazzo, E.

2005-01-01

Collisions of asteroids and comets with the Earth s surface are rare events that punctuate the geologic record. Due to the vastness of Earth s oceans, oceanic impacts of asteroids or comets are expected to be about 4 times more frequent than land impacts. The resulting injections of oceanic water into the upper atmosphere can have important repercussions on Earth s climate and atmospheric circulation. However, the duration and overall effect of these large injections are still unconstrained. This work addresses atmospheric injections of large amounts of water in oceanic impacts.

NASA's Asteroid Redirect Mission: The Boulder Capture Option

NASA Technical Reports Server (NTRS)

Abell, Paul A.; Nuth, J.; Mazanek, D.; Merrill, R.; Reeves, D.; Naasz, B.

2014-01-01

NASA is examining two options for the Asteroid Redirect Mission (ARM), which will return asteroid material to a Lunar Distant Retrograde Orbit (LDRO) using a robotic solar-electric-propulsion spacecraft, called the Asteroid Redirect Vehicle (ARV). Once the ARV places the asteroid material into the LDRO, a piloted mission will rendezvous and dock with the ARV. After docking, astronauts will conduct two extravehicular activities (EVAs) to inspect and sample the asteroid material before returning to Earth. One option involves capturing an entire small (approximately 4-10 m diameter) near-Earth asteroid (NEA) inside a large inflatable bag. However, NASA is examining another option that entails retrieving a boulder (approximately 1-5 m) via robotic manipulators from the surface of a larger (approximately 100+ m) pre-characterized NEA. This option can leverage robotic mission data to help ensure success by targeting previously (or soon to be) well-characterized NEAs. For example, the data from the Hayabusa mission has been utilized to develop detailed mission designs that assess options and risks associated with proximity and surface operations. Hayabusa's target NEA, Itokawa, has been identified as a valid target and is known to possess hundreds of appropriately sized boulders on its surface. Further robotic characterization of additional NEAs (e.g., Bennu and 1999 JU3) by NASA's OSIRIS REx and JAXA's Hayabusa 2 missions is planned to begin in 2018. The boulder option is an extremely large sample-return mission with the prospect of bringing back many tons of well-characterized asteroid material to the Earth-Moon system. The candidate boulder from the target NEA can be selected based on inputs from the world-wide science community, ensuring that the most scientifically interesting boulder be returned for subsequent sampling. This boulder option for NASA's ARM can leverage knowledge of previously characterized NEAs from prior robotic missions, which provides more certainty of the target NEA's physical characteristics and reduces mission risk. This increases the return on investment for NASA's future activities with respect to science, human exploration, resource utilization, and planetary defense

Dynamical history of the asteroid belt and implications for terrestrial pla net bombardment

NASA Astrophysics Data System (ADS)

Minton, David Andrew

The main asteroid belt spans ~ 2-4 AU in heliocentric distance and is sparsely populated by rocky debris. The dynamical structure of the main belt records clues to past events in solar system history. Evidence from the structure of the Kuiper belt, an icy debris belt beyond Neptune, suggests that the giant planets were born in a more compact configuration and later experienced planetesimal-driven planet migration. Giant planet migration caused both mean motion and secular resonances to sweep across the main asteroid belt, raising the eccentricity of asteroids into planet-crossing orbits and depleting the belt. I show that the present-day semimajor axis and eccentricity distributions of large main belt asteroids are consistent with excitation and depletion due to resonance sweeping during the epoch of giant planet migration. I also use an analytical model of the sweeping of the n 6 secular resonance, to set limits on the migration speed of Saturn. After planet migration, dynamical chaos became the dominant loss mechanism for asteroids with diameters D [Special characters omitted.] 10 km in the current asteroid belt. I find that the dynamical loss history of test particles from this region is well described with a logarithmic decay law. My model suggests that the rate of impacts from large asteroids may have declined by a factor of three over the last ~ 3 Gy, and that the present-day impact flux of D > 10 km objects on the terrestrial planets is roughly an order of magnitude less than estimates used in crater chronologies and impact hazard risk assessments. Finally, I have quantified the change in the solar wind 6 Li/ 7 Li ratio due to the estimated in-fall of chondritic material and enhanced dust production during the epoch of planetesimal-driven giant planet migration. The solar photosphere is currently highly depleted in lithium relative to chondrites, and 6 Li is expected to be far less abundant in the sun than 7 Li due to the different nuclear reaction rates of the two isotopes. Evidence for a short- lived impact cataclysm that affected the entire inner solar system may be found in the composition of implanted solar wind particles in lunar regolith.

NASA’s Asteroid Redirect Mission: The Boulder Capture Option

NASA Astrophysics Data System (ADS)

Abell, Paul; Nuth, Joseph A.; Mazanek, Dan D.; Merrill, Raymond G.; Reeves, David M.; Naasz, Bo J.

2014-11-01

NASA is examining two options for the Asteroid Redirect Mission (ARM), which will return asteroid material to a Lunar Distant Retrograde Orbit (LDRO) using a robotic solar-electric-propulsion spacecraft, called the Asteroid Redirect Vehicle (ARV). Once the ARV places the asteroid material into the LDRO, a piloted mission will rendezvous and dock with the ARV. After docking, astronauts will conduct two extravehicular activities (EVAs) to inspect and sample the asteroid material before returning to Earth. One option involves capturing an entire small (˜4-10 m diameter) near-Earth asteroid (NEA) inside a large inflatable bag. However, NASA is examining another option that entails retrieving a boulder (˜1-5 m) via robotic manipulators from the surface of a larger (˜100+ m) pre-characterized NEA. This option can leverage robotic mission data to help ensure success by targeting previously (or soon to be) well-characterized NEAs. For example, the data from the Hayabusa mission has been utilized to develop detailed mission designs that assess options and risks associated with proximity and surface operations. Hayabusa’s target NEA, Itokawa, has been identified as a valid target and is known to possess hundreds of appropriately sized boulders on its surface. Further robotic characterization of additional NEAs (e.g., Bennu and 1999 JU3) by NASA’s OSIRIS REx and JAXA’s Hayabusa 2 missions is planned to begin in 2018. The boulder option is an extremely large sample-return mission with the prospect of bringing back many tons of well-characterized asteroid material to the Earth-Moon system. The candidate boulder from the target NEA can be selected based on inputs from the world-wide science community, ensuring that the most scientifically interesting boulder be returned for subsequent sampling. This boulder option for NASA’s ARM can leverage knowledge of previously characterized NEAs from prior robotic missions, which provides more certainty of the target NEA’s physical characteristics and reduces mission risk. This increases the return on investment for NASA’s future activities with respect to science, human exploration, resource utilization, and planetary defense.

The Spherical Brazil Nut Effect and its Significance to Asteroids

NASA Astrophysics Data System (ADS)

Perera, Viranga; Jackson, Alan P.; Asphaug, Erik; Ballouz, Ronald-Louis

2015-11-01

Asteroids are intriguing remnant objects from the early solar system. They can inform us on how planets formed, they could possibly impact the earth in the future, and they likely contain precious metals; for those reasons, there will be future exploration and mining space missions to them. Telescopic observations and spacecraft data have helped us understand basic properties such as their size, mass, spin rate, orbital elements, and their surface properties. However, their interior structures have remained elusive. In order to fully characterize the interiors of these bodies, seismic data will be necessary. However, we can infer their interior structures by combining several key factors that we know about them: 1). Past work has shown that asteroids between 150 m to 10 km in size are rubble-piles that are a collection of particles held together by gravity and possibly cohesion. 2). Asteroid surfaces show cratering that suggests that past impacts would have seismically shaken these bodies. 3). Spacecraft images show that some asteroids have large protruding boulders on their surfaces. A rubble-pile object made of particles of different sizes and that undergoes seismic shaking will experience granular flow. Specifically, a size sorting effect known as the Brazil Nut Effect will lead larger particles to move towards the surface while smaller particles will move downwards. Previous work has suggested that this effect could possibly explain not only why there are large boulders on the surfaces of some asteroids but also might suggest that the interior particles of these bodies would be organized by size. Previous works have conducted computer simulations and lab experiments; however, all the particle configurations used have been either cylindrical or rectangular boxes. In this work we present a spherical configuration of self-gravitating particles that is a better representation of asteroids. Our results indicate that while friction is not necessary for the Brazil Nut Effect to take place, it aids the sorting process after a certain energy threshold is met. Even though we find that the outer layers of asteroids could possibly be size sorted, the inner regions are likely mixed.

ASTEROIDS: Living in the Kingdom of Chaos

NASA Astrophysics Data System (ADS)

Morbidelli, A.

2000-10-01

The existence of chaotic regions in the main asteroid belt, related with the lowest-order mean-motion and secular resonances, has long been known. However, only in the last decade have semi-analytic theories allowed a proper understanding of the chaotic behavior observed in numerical simulations which accurately incorporate the entire planetary system. The most spectacular result has been the discovery that the asteroids in some of these resonance may collide with the Sun on typical time scales of a few million year, their eccentricities being pumped to unity during their chaotic evolution. But the asteroid belt is not simply divided into violent chaotic zones and regular regions. It has been shown that the belt is criss-crossed by a large number of high-order mean-motion resonances with Jupiter or Mars, as well as by `three-body resonances' with Jupiter and Saturn. All these weak resonances cause the slow chaotic drift of the `proper' eccentricities and inclinations. The traces left by this evolution are visible, for example, in the structure of the Eos and Themis asteroid families. Weak chaos may also explain the anomalous dispersion of the eccentricities and inclinations observed in the Flora ``clan." Moreover, due to slow increases in their eccentricities, many asteroids start to cross the orbit of Mars, over a wide range of semimajor axes. The improved knowledge of the asteroid belt's chaotic structure provides, for the first time, an opportunity to build detailed quantitative models of the origin and the orbital distribution of Near-Earth Asteroids and meteorites. In turn, these models seem to imply that the semimajor axes of main-belt asteroids must also slowly evolve with time. For asteroids larger than about 20 km this is due mainly to encounters with Ceres, Pallas, and Vesta, while for smaller bodies the so-called Yarkovsky effect should dominate. Everything moves chaotically in the asteroid belt.

The Double Asteroid Redirection Test (DART)

NASA Astrophysics Data System (ADS)

Rivkin, A.; Cheng, A. F.; Stickle, A. M.; Richardson, D. C.; Barnouin, O. S.; Thomas, C.; Fahnestock, E.

2017-12-01

The Double Asteroid Redirection Test (DART) will be the first space experiment to demonstrate asteroid impact hazard mitigation by using a kinetic impactor. DART is currently in Preliminary Design Phase ("Phase B"), and is part of the Asteroid Impact and Deflection Assessment (AIDA), a joint ESA-NASA cooperative project. The AIDA target is the near-Earth binary asteroid 65803 Didymos, an S-class system that will make a close approach to Earth in fall 2022. The DART spacecraft is designed to impact the Didymos secondary at 6 km/s and demonstrate the ability to modify its trajectory through momentum transfer. The primary goals of AIDA are (1) perform a full-scale demonstration of the spacecraft kinetic impact technique for deflection of an asteroid; (2) measure the resulting asteroid deflection, by targeting the secondary member of a binary NEO and measuring the resulting changes of the binary orbit; and (3) study hyper-velocity collision effects on an asteroid, validating models for momentum transfer in asteroid impacts. The DART impact on the Didymos secondary will change the orbital period of the binary by several minutes, which can be measured by Earth-based optical and radar observations. The baseline DART mission launches in late 2020 to impact the Didymos secondary in 2022 near the time of its close pass of Earth, which enables an array of ground- and space-based observatories to participate in gathering data. The AIDA project will provide the first measurements of momentum transfer efficiency from hyper-velocity kinetic impact at full scale on an asteroid, where the impact conditions of the projectile are known, and physical properties and internal structures of the target asteroid are characterized or constrained. The DART kinetic impact is predicted to make a crater of 6 to 17 meters diameter, depending on target physical properties, but will also release a large volume of particulate ejecta that may be directly observable from Earth or even resolvable as a coma or an ejecta tail by ground-based telescopes.

First results of the seven-color asteroid survey

NASA Astrophysics Data System (ADS)

Clark, Beth E.; Bell, Jeffrey F.; Fanale, Fraser P.; Lucey, Paul G.

1993-03-01

The new Seven-Color infrared filter system (SCAS), designed specifically to capture the essential mineralogical information present in asteroid spectra, is composed of seven broad-band filters which allow for IR observations of objects as faint as 17th magnitude. The first test of the SCAS system occurred in Jul. 1992. In four nights at the IRTF on Mauna Kea, Hawaii, over 67 objects were observed. Five of the observations were to test the new system for accuracy relative to previous observations with the high-resolution 52 Color Infrared Survey and with the Eight-Color Asteroid Survey (ECAS). In three cases, the match with previous data was good. In two cases, the match to previous observations was not as good. In addition, sixty S-Type asteroids were measured with the SCAS system. Forty of those asteroids were also observed with the ECAS system. Among the new observations is infrared data of 371 Bohemia, a main belt asteroid which was classified 'QSV' according to its UBV colors in the taxonomic system of D.J. Tholen. There are no corresponding ECAS data for 371. Q-type asteroids are of special interest as they are proposed to be the elusive parent bodies of the ordinary chondrite meteorites. Most Q-types are Earth-crossing asteroids and have not yet been observed in the infrared (except, perhaps, 371). Positive identification of a large main belt Q-type would be of major importance in the scheme of the geological structure of the asteroid belt. Without visible wavelength data, however, the classification of 371 Bohemia remains ambiguous. An attempt to conjoin Bohemia SCAS data with ECAS data of both a typical Q-Type asteroid and an average S-Type asteroid is shown. This figure thus illustrates the importance of visible wavelength data to the SCAS system. In other words, without ECAS data of 371 Bohemia we cannot use its spectral characteristics to identify it as a possible parent body of ordinary chondrite meteorites.

The Double Asteroid Redirection Test in the AIDA Project

NASA Astrophysics Data System (ADS)

Cheng, Andrew; Rivkin, Andrew; Michel, Patrick

2016-04-01

The Asteroid Impact & Deflection Assessment (AIDA) mission will be the first space experiment to demonstrate asteroid impact hazard mitigation by using a kinetic impactor. AIDA is a joint ESA-NASA cooperative project, that includes the ESA Asteroid Impact Mission (AIM) rendezvous mission and the NASA Double Asteroid Redirection Test (DART) mission. The AIDA target is the near-Earth binary asteroid 65803 Didymos, which will make an unusually close approach to Earth in October, 2022. The ~300-kg DART spacecraft is designed to impact the Didymos secondary at 7 km/s and demonstrate the ability to modify its trajectory through momentum transfer. DART and AIM are currently Phase A studies supported by NASA and ESA respectively. The primary goals of AIDA are (1) perform a full-scale demonstration of the spacecraft kinetic impact technique for deflection of an asteroid, by targeting an object larger than ~100 m and large enough to qualify as a Potentially Hazardous Asteroid; (2) measure the resulting asteroid deflection, by targeting the secondary member of a binary NEO and measuring the period change of the binary orbit; (3) understand the hyper-velocity collision effects on an asteroid, including the long-term dynamics of impact ejecta; and validate models for momentum transfer in asteroid impacts, based on measured physical properties of the asteroid surface and sub-surface. The primary DART objectives are to demonstrate a hyper-velocity impact on the Didymos moon and to determine the resulting deflection from ground-based observatories. The DART impact on the Didymos secondary will cause a measurable change in the orbital period of the binary. Supporting Earth-based optical and radar observations and numerical simulation studies are an integral part of the DART mission. The baseline DART mission launches in December, 2020 to impact the Didymos secondary in September, 2022. There are multiple launch opportunities for DART leading to impact around the 2022 Didymos close approach to Earth. The AIM spacecraft will be launched in Dec. 2020 and arrive at Didymos in spring, 2022, several months before the DART impact. AIM will characterize the Didymos binary system by means of remote sensing and in-situ instruments both before and after the DART impact. The asteroid deflection will be measured to higher accuracy, and additional results of the DART impact, like the impact crater, will be studied in great detail by the AIM mission. The combined DART and AIM missions will provide the first measurements of momentum transfer efficiency β from hyper-velocity kinetic impact at full scale on an asteroid, where the impact conditions of the projectile are known, and physical properties and internal structures of the target asteroid are also characterized. The DART impact on the Didymos secondary is predicted to cause a ~4.4 minute change in the binary orbit period, assuming β=1, and is expected to be observable within a few days. The predicted β would be in the range 1.1 to 1.3 for a porous target material based on a variety of numerical and analytical methods, but may be much larger if the target is non-porous. The DART kinetic impact is predicted to make a crater of ~6 to ~17 meters diameter, depending on target physical properties, but will also release a large volume of particulate ejecta that may be directly observable from Earth or even resolvable as a coma or an ejecta tail by ground-based telescopes.

Synergistic approach of asteroid exploitation and planetary protection

NASA Astrophysics Data System (ADS)

Sanchez, J. P.; McInnes, C. R.

2012-02-01

The asteroid and cometary impact hazard has long been recognised as an important issue requiring risk assessment and contingency planning. At the same time asteroids have also been acknowledged as possible sources of raw materials for future large-scale space engineering ventures. This paper explores possible synergies between these two apparently opposed views; planetary protection and space resource exploitation. In particular, the paper assumes a 5 tonne low-thrust spacecraft as a baseline for asteroid deflection and capture (or resource transport) missions. The system is assumed to land on the asteroid and provide a continuous thrust able to modify the orbit of the asteroid according to the mission objective. The paper analyses the capability of such a near-term system to provide both planetary protection and asteroid resources to Earth. Results show that a 5 tonne spacecraft could provide a high level of protection for modest impact hazards: airburst and local damage events (caused by 15-170 m diameter objects). At the same time, the same spacecraft could also be used to transport to bound Earth orbits significant quantities of material through judicious use of orbital dynamics and passively safe aero-capture manoeuvres or low energy ballistic capture. As will be shown, a 5 tonne low-thrust spacecraft could potentially transport between 12 and 350 times its own mass of asteroid resources by means of ballistic capture or aero-capture trajectories that pose very low dynamical pressures on the object.

Space Weathering Rates in Lunar and Itokawa Samples

NASA Technical Reports Server (NTRS)

Keller, L. P.; Berger, E. L.

2017-01-01

Space weathering alters the chemistry, microstructure, and spectral proper-ties of grains on the surfaces of airless bodies by two major processes: micrometeorite impacts and solar wind interactions. Investigating the nature of space weathering processes both in returned samples and in remote sensing observations provides information fundamental to understanding the evolution of airless body regoliths, improving our ability to determine the surface composition of asteroids, and linking meteorites to specific asteroidal parent bodies. Despite decades of research into space weathering processes and their effects, we still know very little about weathering rates. For example, what is the timescale to alter the reflectance spectrum of an ordinary chondrite meteorite to resemble the overall spectral shape and slope from an S-type asteroid? One approach to answering this question has been to determine ages of asteroid families by dynamical modeling and determine the spectral proper-ties of the daughter fragments. However, large differences exist between inferred space weathering rates and timescales derived from laboratory experiments, analysis of asteroid family spectra and the space weathering styles; estimated timescales range from 5000 years up to 108 years. Vernazza et al. concluded that solar wind interactions dominate asteroid space weathering on rapid timescales of 10(exp 4)-10(exp 6) years. Shestopalov et al. suggested that impact-gardening of regolith particles and asteroid resurfacing counteract the rapid progress of solar wind optical maturation of asteroid surfaces and proposed a space weathering timescale of 10(exp 5)-10(exp 6) years.

The early evolution of the inner solar system: a meteoritic perspective.

PubMed

O'D Alexander, C M; Boss, A P; Carlson, R W

2001-07-06

Formation of the solar system may have been triggered by a stellar wind. From then on, the solar system would have followed a conventional evolutionary path, including the formation of a disk and bipolar jets. The now extinct short-lived radionuclides beryllium-10 and, possibly, manganese-53 that were present in meteorites probably resulted from energetic particle irradiation within the solar system. Calcium-aluminum-rich inclusions (the oldest known solar system solids) and chondrules could have been produced by the bipolar jets, but it is more likely that they formed during localized events in the asteroid belt. The chondritic meteorites formed within the temperature range (100 to 400 kelvin) inferred for the midplane of classical T Tauri disks at 2 to 3 astronomical units from their central stars. However, these meteorites may retain a chemical memory of earlier times when midplane temperatures were much higher. Dissipation of the solar nebula occurred within a few million years of solar system formation, whereas differentiation of asteroidal-sized bodies occurred within 5 to 15 million years. The terrestrial planets took approximately 100 million years to form. Consequently, they would have accreted already differentiated bodies, and their final assembly was not completed until after the solar nebula had dispersed. This implies that water-bearing asteroids and/or icy planetesimals that formed near Jupiter are the likely sources of Earth's water.

Catastrophic Disruption of Asteroids: First Simulations with Explicit Formation of Spinning Rigid and Semi-rigid Aggregates

NASA Astrophysics Data System (ADS)

Michel, Patrick; Richardson, D. C.

2007-10-01

We have made major improvements in simulations of asteroid disruption by computing explicitly aggregate formations during the gravitational reaccumulation of small fragments, allowing us to obtain information on their spin and shape. First results will be presented taking as examples asteroid families that we reproduced successfully with previous less sophisticated simulations. In the last years, we have simulated successfully the formation of asteroid families using a SPH hydrocode to compute the fragmentation following the impact of a projectile on the parent body, and the N-body code pkdgrav to compute the mutual interactions of the fragments. We found that fragments generated by the disruption of a km-size asteroid can have large enough masses to be attracted by each other during their ejection. Consequently, many reaccumulations take place. Eventually most large fragments correspond to gravitational aggregates formed by reaccumulation of smaller ones. Moreover, formation of satellites occurs around the largest and other big remnants. In these previous simulations, when fragments reaccumulate, they merge into a single sphere whose mass is the sum of their masses. Thus, no information is obtained on the actual shape of the aggregates, their spin, ... For the first time, we have now simulated the disruption of a family parent body by computing explicitly the formation of aggregates, along with the above-mentioned properties. Once formed these aggregates can interact and/or collide with each other and break up during their evolution. We will present these first simulations and their possible implications on properties of asteroids generated by disruption. Results can for instance be compared with data provided by the Japanese space mission Hayabusa of the asteroid Itokawa, a body now understood to be a reaccumulated fragment from a larger parent body. Acknowledgments: PM and DCR acknowledge supports from the French Programme National de Planétologie and grants NSF AST0307549&AST0708110.

Processes in Early Planetesimals: Evidence from Ureilite Meteorites

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.; Downes, H.

2007-01-01

Ureilites are primitive ultramafic achondrites composed largely of olivine and pigeonite, with minor augite, carbon, sulphide and metal. They represent very early material in the history of the Solar System and form a bridge between undifferentiated chondrites and fully differentiated asteroids. They show a mixture of chemical characteristics, some of which are considered to be nebula-derived (e.g. a negative correlation between Mg/Fe and Delta O-17 that resembles that of the ordinary chondrites but at lower Delta O-17 values) whereas others have been imposed by asteroidal differentiation. Carbon isotope data show a striking negative correlation of delta C-13 values with mg# in olivine. delta C-13 also correlates positively with Delta O-17, and therefore this isotopic variation was probably also nebula-derived. Thus, oxygen and carbon isotope compositions and Fe-Mg systematics of each monomict ureilite were established before differentiation processes began. Heated by decay of short-lived radioactive isotopes, the ureilite asteroid started to melt. Metal and sulphide would have melted first, forming a Fe-S eutectic liquid, which removed chalcophile elements and incompatible siderophile elements, and basaltic melts that removed Al, Ca and the LREE. Several elements show different abundances and/or correlations with Fo content in olivine, e.g. carbon shows a positive correlation in ferroan ureilites, and a weak or even negative correlation in more magnesian compositions. HSE such as Os and Ir also show different distributions, i.e. ureilites with Fo < 82 have very scattered Os and Ir concentrations, which reach high values, whereas ureilites with Fo > 82 tend to have much less scattered and overall lower Os and Ir abundances. A similar change in elemental behaviour is shown by the Fe-Mn relations in ureilitic olivines: those with Fo contents < 85 show a good negative correlation, whereas those with Fo > 85 show much greater scatter. This suggests that a major change affected the parent body at a time when melting had reached relatively magnesian bulk compositions. We consider that this event may have been a hit and run collision in which the ureilite parent body collided with a larger object. During the collision, the ureilite mantle broke up catastrophically but re-accreted in a jumbled state around the still-intact core. Mg-rich basaltic melts that were in the process of being formed at the time of break-up were retained in part as melt clasts that re-accreted to the regolith and are found in polymict ureilites.

Tides Versus Collisions in the Primordial Main Belt

NASA Astrophysics Data System (ADS)

Asphaug, E.; Bottke, W. F., Jr.; Morbidelli, A.; Petit, J.-M.

2000-10-01

Recent numerical and theoretical developments (e.g. Wetherill 1992; Chambers and Wetherill 1998) suggest that hundreds or thousands of Moon- to Mars-sized planetary embryos may have resided between 0.5 and 4 AU during early solar system accretion, to be scattered by mutual encounters and resonant perturbations with Jupiter and Saturn. At the same time, we lack compelling scenarios leading to the origin of iron meteorites, believed to represent the cores from approximately 85 different primordial planetesimals (Kail et al. 1994). Are M-type asteroids such as Kleopatra the exposed cores of these parent bodies? Early solar system collisions have been called upon to excavate this iron (Haack et al. 1996), although numerical impact models (Asphaug 1997) have found this task difficult to achieve, particularly when it is required to occur many dozens of times, yet not a single time for asteroid Vesta. One possibility, consistent with the unusual shape of Kleopatra, is tidal disassembly of collisionally weakened differentiated planetesimals by close encounters with primordial planetary embryos. Differentiation enhances the efficacy of tidal disassembly, which is probably already comparable (Asphaug and Benz 1996) to the efficacy of collisional disassembly, but only for bodies of very low strength. Tidal disassembly has the further advantage of stripping all material from a given isosurface, whereas collisions partition energy into both fast and slow debris, leaving behind a rock mantle. To further explore this idea, in comparison with the efficacy of collisional breakup of differentiated planetesimals, we determine the minimal encounter distances between evolving asteroids and the embryos as modeled by Petit et al. (2000). We then directly simulate these tidal encounters using a smooth particle hydrocode (SPH; Benz and Asphaug 1995), and compare tidal encounters to collisional encounters using the same code.

Recent collisional jet from a primitive asteroid

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Dell'Oro, Aldo; Cellino, Alberto; Knežević, Zoran

2012-09-01

In this paper we show an example of a young asteroid cluster located in a dynamically stable region, which was produced by partial disruption of a primitive body about 30 km in size. We estimate its age to be only 1.9 ± 0.3 Myr; thus, its post-impact evolution should have been very limited. The large difference in size between the largest object and the other cluster members means that this was a cratering event. The parent body had a large orbital inclination and was subject to collisions with typical impact speeds higher by a factor of 2 than in the most common situations encountered in the main belt. For the first time, we have at our disposal the observable outcome of a very recent event to study high-speed collisions involving primitive asteroids, providing very useful constraints to numerical simulations of these events and to laboratory experiments.

Mars, Phobos, and Deimos Sample Return Enabled by ARRM Alternative Trade Study Spacecraft

NASA Technical Reports Server (NTRS)

Englander, Jacob A.; Vavrina, Matthew; Merrill, Raymond G.; Qu, Min; Naasz, Bo J.

2014-01-01

The Asteroid Robotic Redirect Mission (ARRM) has been the topic of many mission design studies since 2011. The reference ARRM spacecraft uses a powerful solar electric propulsion (SEP) system and a bag device to capture a small asteroid from an Earth-like orbit and redirect it to a distant retrograde orbit (DRO) around the moon. The ARRM Option B spacecraft uses the same propulsion system and multi-Degree of Freedom (DoF) manipulators device to retrieve a very large sample (thousands of kilograms) from a 100+ meter diameter farther-away Near Earth Asteroid (NEA). This study will demonstrate that the ARRM Option B spacecraft design can also be used to return samples from Mars and its moons - either by acquiring a large rock from the surface of Phobos or Deimos, and or by rendezvousing with a sample-return spacecraft launched from the surface of Mars.

Mars, Phobos, and Deimos Sample Return Enabled by ARRM Alternative Trade Study Spacecraft

NASA Technical Reports Server (NTRS)

Englander, Jacob A.; Vavrina, Matthew; Naasz, Bo; Merill, Raymond G.; Qu, Min

2014-01-01

The Asteroid Robotic Redirect Mission (ARRM) has been the topic of many mission design studies since 2011. The reference ARRM spacecraft uses a powerful solar electric propulsion (SEP) system and a bag device to capture a small asteroid from an Earth-like orbit and redirect it to a distant retrograde orbit (DRO) around the moon. The ARRM Option B spacecraft uses the same propulsion system and multi-Degree of Freedom (DoF) manipulators device to retrieve a very large sample (thousands of kilograms) from a 100+ meter diameter farther-away Near Earth Asteroid (NEA). This study will demonstrate that the ARRM Option B spacecraft design can also be used to return samples from Mars and its moons - either by acquiring a large rock from the surface of Phobos or Deimos, and/or by rendezvousing with a sample-return spacecraft launched from the surface of Mars.

Catastrophic Disruption Threshold and Maximum Deflection from Kinetic Impact

NASA Astrophysics Data System (ADS)

Cheng, A. F.

2017-12-01

The use of a kinetic impactor to deflect an asteroid on a collision course with Earth was described in the NASA Near-Earth Object Survey and Deflection Analysis of Alternatives (2007) as the most mature approach for asteroid deflection and mitigation. The NASA DART mission will demonstrate asteroid deflection by kinetic impact at the Potentially Hazardous Asteroid 65803 Didymos in October, 2022. The kinetic impactor approach is considered to be applicable with warning times of 10 years or more and with hazardous asteroid diameters of 400 m or less. In principle, a larger kinetic impactor bringing greater kinetic energy could cause a larger deflection, but input of excessive kinetic energy will cause catastrophic disruption of the target, leaving possibly large fragments still on collision course with Earth. Thus the catastrophic disruption threshold limits the maximum deflection from a kinetic impactor. An often-cited rule of thumb states that the maximum deflection is 0.1 times the escape velocity before the target will be disrupted. It turns out this rule of thumb does not work well. A comparison to numerical simulation results shows that a similar rule applies in the gravity limit, for large targets more than 300 m, where the maximum deflection is roughly the escape velocity at momentum enhancement factor β=2. In the gravity limit, the rule of thumb corresponds to pure momentum coupling (μ=1/3), but simulations find a slightly different scaling μ=0.43. In the smaller target size range that kinetic impactors would apply to, the catastrophic disruption limit is strength-controlled. A DART-like impactor won't disrupt any target asteroid down to significantly smaller size than the 50 m below which a hazardous object would not penetrate the atmosphere in any case unless it is unusually strong.

A New Tool for Classifying Small Solar System Objects

NASA Astrophysics Data System (ADS)

Desfosses, Ryan; Arel, D.; Walker, M. E.; Ziffer, J.; Harvell, T.; Campins, H.; Fernandez, Y. R.

2011-05-01

An artificial intelligence program, AutoClass, which was developed by NASA's Artificial Intelligence Branch, uses Bayesian classification theory to automatically choose the most probable classification distribution to describe a dataset. To investigate its usefulness to the Planetary Science community, we tested its ability to reproduce the taxonomic classes as defined by Tholen and Barucci (1989). Of the 406 asteroids from the Eight Color Asteroid Survey (ECAS) we chose for our test, 346 were firmly classified and all but 3 (<1%) were classified by Autoclass as they had been in the previous classification system (Walker et al., 2011). We are now applying it to larger datasets to improve the taxonomy of currently unclassified objects. Having demonstrated AutoClass's ability to recreate existing classification effectively, we extended this work to investigations of albedo-based classification systems. To determine how predictive albedo can be, we used data from the Infrared Astronomical Satellite (IRAS) database in conjunction with the large Sloan Digital Sky Survey (SDSS), which contains color and position data for over 200,000 classified and unclassified asteroids (Ivesic et al., 2001). To judge our success we compared our results with a similar approach to classifying objects using IRAS albedo and asteroid color by Tedesco et al. (1989). Understanding the distribution of the taxonomic classes is important to understanding the history and evolution of our Solar System. AutoClass's success in categorizing ECAS, IRAS and SDSS asteroidal data highlights its potential to scan large domains for natural classes in small solar system objects. Based upon our AutoClass results, we intend to make testable predictions about asteroids observed with the Wide-field Infrared Survey Explorer (WISE).

Asteroid (2867) Steins: Shape, topography and global physical properties from OSIRIS observations

NASA Astrophysics Data System (ADS)

Jorda, L.; Lamy, P. L.; Gaskell, R. W.; Kaasalainen, M.; Groussin, O.; Besse, S.; Faury, G.

2012-11-01

The Rosetta spacecraft flew by Asteroid (2867) Steins on 5 September 2008, allowing the onboard OSIRIS cameras to collect the first images of an E-type asteroid. We implemented several three-dimensional reconstruction techniques to retrieve its shape. Limb profiles, combined with stereo control points, were used to reconstruct an approximate shape model. This model was refined using a stereophotoclinometry technique to accurately retrieve the topography of the hemisphere observed by OSIRIS. The unseen part of the surface was constrained by the technique of light curves inversion. The global shape resembles a top with dimensions along the principal axes of inertia of 6.83 × 5.70 × 4.42 km. It is conspicuously more regular than other small asteroids like (233) Eros and (25143) Itokawa. Its mean radius is Rm = 2.70 km and its equivalent radius (radius of a sphere of equivalent volume) is Rv = 2.63 km. The north pole is oriented at RA = 99 ± 5° and Dec = -59 ± 5°, which implies a very large obliquity of 172° and a retrograde rotation. Maps of the gravitational field and slopes were calculated for the well-imaged part of the asteroid. Together with the shape, they helped characterizing the most prominent topographic features identified at the surface of (2867) Steins: an equatorial ridge restricted to the extremities of the long axis, a large crater having dimensions of 2100 × 1800 m in the southern hemisphere, and an elongated hill in the northern hemisphere. We conjecture that the equatorial ridge was formed by centrifugal acceleration as the asteroid was spun up by the Yarkovsky-O’Keefe-Radzievskii-Paddack effect.

Roadmap of next generation minor body explorations in Japan

NASA Astrophysics Data System (ADS)

Yano, H.

As of the early 2004, more than 250,000 minor bodies in the solar system have been detected. Among them, several thousands of asteroids are determined orbital elements well and even multi-band spectroscopic observation from ground enables us to classify taxonomy of them in statistically valid numbers. On the other hand, there have been several 10,000s of meteorite and cosmic dust samples already collected in the terrestrial environment. Thus, asteroid studies in statistical manners are practically conducted by ground observation and meteoritic analyses. It is a unique contribution of planetary exploration to provide the ground truth which bridges between abundant database of the ground observation and that of the meteoritic analyses, by bringing samples back to the Earth from a particular asteroid investigated in-situ. In May 2003, JAXA/ISAS successfully launched the Hayabusa (MUSES-C) spacecraft as the first kind of such minor body exploration, which will bring surface samples of an S-type NEO back to the Earth in mid 2007. Many of Japanese planetary scientists hope to advance such sample return strategies as their new expertise in the post-Hayabusa era. Now the ISAS new minor body exploration working group is about to start. Mission candidates include multiple sample returns from known spectra asteroids, in order to complete the asteroid taxonomy-meteoritic connection issue as early as possible (next 10-20 years) with possible international collaborations. One of such ideas is the multiple rendezvous sample return mission to known spectra NEOs of both primitive types (i.e., C, P/D) and differentiated types (e.g., V, M). Another is fly-by investigation and sample collection of multiple asteroids that belong to a single main-belt family. It will provide direct information of the interior as well as collisional history of their parent body, a refractory planetesimal disrupted by mutual collisions in the early stage of the Solar System evolution. One scenario targets the Koronis family including the Ida-Gaspra system, the only family asteroid visited by spacecraft in the past, and its dust band. Another aims the Nysa-Polana Family, which has several spectral types. Also what ISAS is planning is the solar powered sail mission which will make fly-by observations of main belt asteroids as well as Jovian Trojan asteroids, most of which are D-type asteroids with the absence of water absorption lines. Understanding generic connections among the Trojans, short-period cometary nucleus and the outermost D-type asteroids in the main belt may be a clue of how to distinguish between asteroids and comets, depending upon where they originated with respect to heliocentric distance in the early solar system.

Colors and spin period distributions of sub-km main belt asteroids

NASA Astrophysics Data System (ADS)

Yoshida, Fumi; Lin, Hsing-Wen; Chen, Ying-Tung; Souami, Damya; Bouquillon, Sebastien; Ip, Wing-Huen; Chang, Chan-Kao; Nakamura, Tsuko; Dermawan, Budi; Yagi, Masafumi; Souchay, Jean

2014-11-01

The size dependency of space weathering on asteroid’s surface and collisional lifetimes suggest that small asteroids are younger than large asteroids. Therefore, the studies of smaller asteroid provide us new information about asteroid composition on fresh surface and their collisional evolution. We performed a color observation using 4 filters and lightcurve observation using 2 filters on different nights, using the 8.2m Subaru telescope/Suprime-Cam, for investigating the color and spin period distributions of sub-km main-belt asteroids (MBAs) that could not be seen before by middle class telescopes. In a lightcurve observation on Sep. 2, 2002, we kept taking images of a single sky field at near the opposition and near the ecliptic plane. Taking advantage of the wide field view of Suprime-Cam, this observation was planned to obtain lightcurves of 100 asteroids at the same time. Actually, we detected 112 MBAs and obtained their lightcurves by using a modified GAIA-GBOT PIPELINE. For the period analysis, we defined a criterion for judging whether an obtained rotational period is robust or not. Although Dermawan et al. (2011) have suggested that there are many fast rotators (FR) in MBAs, we noticed that many MBAs have long spin periods. Therefore, we could determine the rotation period of only 22 asteroids. We found one FR candidate (P=2.02 hr). We could measure the B-R color of 16 asteroids among the 22 MBAs. We divided them into S-like and C-like asteroids by the B-R color. The average rotational periods of C-like and S-like asteroids are 4.3 hr and 7.6 hr, respectively. C-like asteroids seem to rotate faster than S-like ones. We carried out a multi-color survey on Aug. 9 and 10, 2004 and then detected 154 MBAs. We classified them into several taxonomic types. Then we noticed that there are only very few Q-type candidates (non-weathered S-type) unlike the near Earth asteroid (NEAs) population, in which Q-type is a main component. This may indicate that most of Q-type NEAs did not originated from Q-type MBAs. They are probably objects subjected to resurfacing process (by peeling surface regolith, the outer layer of asteroid changes from S-type to Q-type) due to the tidal effect during their planetary encounters.

Testing the FLI in the region of the Pallas asteroid family

NASA Astrophysics Data System (ADS)

Todorović, N.; Novaković, B.

2015-08-01

Computation of the fast Lyapunov indicator (FLI) is one of the most efficient numerical ways to characterize dynamical nature of motion and to detect phase-space structures in a large variety of dynamical models. Despite its effectiveness, FLI was mainly used for symplectic maps or simple Hamiltonians, but it has never been used to study dynamics of asteroids to a greater extent. This research shows that FLI could also be successfully applied to real (Solar system) dynamics. For this purpose, we focus on the main belt region where the Pallas asteroid family is located. By using the full Solar system model, different sets of initial conditions and different integration times, we managed not only to visualize a large multiplet of resonances located in the region, but also their structures, chaotic boundaries, stability islands therein and the positions of their mutual interaction. In the end, we have identified some of the most dominant resonances present in the region and established a link between these resonances and chaotic areas visible in our maps. We have illustrated that FLI once again has shown its efficiency to detect dynamical structures in the main belt, e.g. in the Pallas asteroid family, with a surprisingly good clarity.

Fast delivery of meteorites to Earth after a major asteroid collision.

PubMed

Heck, Philipp R; Schmitz, Birger; Baur, Heinrich; Halliday, Alex N; Wieler, Rainer

2004-07-15

Very large collisions in the asteroid belt could lead temporarily to a substantial increase in the rate of impacts of meteorites on Earth. Orbital simulations predict that fragments from such events may arrive considerably faster than the typical transit times of meteorites falling today, because in some large impacts part of the debris is transferred directly into a resonant orbit with Jupiter. Such an efficient meteorite delivery track, however, has not been verified. Here we report high-sensitivity measurements of noble gases produced by cosmic rays in chromite grains from a unique suite of fossil meteorites preserved in approximately 480 million year old sediments. The transfer times deduced from the noble gases are as short as approximately 10(5) years, and they increase with stratigraphic height in agreement with the estimated duration of sedimentation. These data provide powerful evidence that this unusual meteorite occurrence was the result of a long-lasting rain of meteorites following the destruction of an asteroid, and show that at least one strong resonance in the main asteroid belt can deliver material into the inner Solar System within the short timescales suggested by dynamical models.

Prospects and challenges of touchless electrostatic detumbling of small bodies

NASA Astrophysics Data System (ADS)

Bennett, Trevor; Stevenson, Daan; Hogan, Erik; Schaub, Hanspeter

2015-08-01

The prospects of touchlessly detumbling a small, multiple meters in size, space object using electrostatic forces are intriguing. Physically capturing an object with a large rotation rate poses significant momentum transfer and collision risks. If the spin rate is reduced to less than 1 deg/s, relative motion sensing and control associated with mechanical docking becomes manageable. In particular, this paper surveys the prospects and challenges of detumbling large debris objects near Geostationary Earth Orbit for active debris remediation, and investigates if such electrostatic tractors are suitable for small asteroids being considered for asteroid retrieval missions. Active charge transfer is used to impart arresting electrostatic torques on such objects, given that they are sufficiently non-spherical. The concept of touchless electrostatic detumbling of space debris is outlined through analysis and experiments and is shown to hold great promise to arrest the rotation within days to weeks. However, even conservatively optimistic simulations of small asteroid detumbling scenarios indicate that such a method could take over a year to arrest the asteroid rotation. The numerical debris detumbling simulation includes a charge transfer model in a space environment, and illustrates how a conducting rocket body could be despun without physical contact.

The structure of the asteroid 4 Vesta as revealed by models of planet-scale collisions.

PubMed

Jutzi, M; Asphaug, E; Gillet, P; Barrat, J-A; Benz, W

2013-02-14

Asteroid 4 Vesta seems to be a major intact protoplanet, with a surface composition similar to that of the HED (howardite-eucrite-diogenite) meteorites. The southern hemisphere is dominated by a giant impact scar, but previous impact models have failed to reproduce the observed topography. The recent discovery that Vesta's southern hemisphere is dominated by two overlapping basins provides an opportunity to model Vesta's topography more accurately. Here we report three-dimensional simulations of Vesta's global evolution under two overlapping planet-scale collisions. We closely reproduce its observed shape, and provide maps of impact excavation and ejecta deposition. Spiral patterns observed in the younger basin Rheasilvia, about one billion years old, are attributed to Coriolis forces during crater collapse. Surface materials exposed in the north come from a depth of about 20 kilometres, according to our models, whereas materials exposed inside the southern double-excavation come from depths of about 60-100 kilometres. If Vesta began as a layered, completely differentiated protoplanet, then our model predicts large areas of pure diogenites and olivine-rich rocks. These are not seen, possibly implying that the outer 100 kilometres or so of Vesta is composed mainly of a basaltic crust (eucrites) with ultramafic intrusions (diogenites).

Accretion of Planetesimals and the Formation of Rocky Planets

NASA Astrophysics Data System (ADS)

Chambers, John E.; O'Brien, David P.; Davis, Andrew M.

2010-02-01

Here we describe the formation of rocky planets and asteroids in the context of the planetesimal hypothesis. Small dust grains in protoplanetary disks readily stick together forming mm-to-cm-sized aggregates, many of which experience brief heating episodes causing melting. Growth to km-sized planetesimals might proceed via continued pairwise sticking, turbulent concentration, or gravitational instability of a thin particle layer. Gravitational interactions between planetesimals lead to rapid runaway and oligarchic growth forming lunar-to-Mars-sized protoplanets in 10^5 to 10^6 years. Giant impacts between protoplanets form Earth-mass planets in 10^7 to 10^8 years, and occasionally lead to the formation of large satellites. Protoplanets may migrate far from their formation locations due to tidal interactions with the surrounding disk. Radioactive decay and impact heating cause melting and differentiation of planetesimals and protoplanets, forming iron-rich cores and silicate mantles, and leading to some loss of volatiles. Dynamical perturbations from giant planets eject most planetesimals and protoplanets from regions near orbital resonances, leading to asteroid-belt formation. Some of this scattered material will collide with growing terrestrial planets, altering their composition as a result. Numerical simulations and radioisotope dating indicate that the terrestrial planets of the Solar System were essentially fully formed in 100-200 million years.

Polygonal Craters on Dwarf-Planet Ceres

NASA Astrophysics Data System (ADS)

Otto, K. A.; Jaumann, R.; Krohn, K.; Buczkowski, D. L.; von der Gathen, I.; Kersten, E.; Mest, S. C.; Preusker, F.; Roatsch, T.; Schenk, P. M.; Schröder, S.; Schulzeck, F.; Scully, J. E. C.; Stepahn, K.; Wagner, R.; Williams, D. A.; Raymond, C. A.; Russell, C. T.

2015-10-01

With approximately 950 km diameter and a mass of #1/3 of the total mass of the asteroid belt, (1) Ceres is the largest and most massive object in the Main Asteroid Belt. As an intact proto-planet, Ceres is key to understanding the origin and evolution of the terrestrialplanets [1]. In particular, the role of water during planet formation is of interest, because the differentiated dwarf-planet is thought to possess a water rich mantle overlying a rocky core [2]. The Dawn space craft arrived at Ceres in March this year after completing its mission at (4) Vesta. At Ceres, the on-board Framing Camera (FC) collected image data which revealed a large variety of impact crater morphologies including polygonal craters (Figure 1). Polygonal craters show straight rim sections aligned to form an angular shape. They are commonly associated with fractures in the target material. Simple polygonal craters develop during the excavation stage when the excavation flow propagates faster along preexisting fractures [3, 5]. Complex polygonal craters adopt their shape during the modification stage when slumping along fractures is favoured [3]. Polygonal craters are known from a variety of planetary bodies including Earth [e.g. 4], the Moon [e.g. 5], Mars [e.g. 6], Mercury [e.g. 7], Venus [e.g. 8] and outer Solar System icy satellites [e.g. 9].

A Classification Table for Achondrites

NASA Technical Reports Server (NTRS)

Chennaoui-Aoudjehane, H.; Larouci, N.; Jambon, A.; Mittlefehldt, D. W.

2014-01-01

Classifying chondrites is relatively easy and the criteria are well documented. It is based on mineral compositions, textural characteristics and more recently, magnetic susceptibility. It can be more difficult to classify achondrites, especially those that are very similar to terrestrial igneous rocks, because mineralogical, textural and compositional properties can be quite variable. Achondrites contain essentially olivine, pyroxenes, plagioclases, oxides, sulphides and accessory minerals. Their origin is attributed to differentiated parents bodies: large asteroids (Vesta); planets (Mars); a satellite (the Moon); and numerous asteroids of unknown size. In most cases, achondrites are not eye witnessed falls and some do not have fusion crust. Because of the mineralogical and magnetic susceptibility similarity with terrestrial igneous rocks for some achondrites, it can be difficult for classifiers to confirm their extra-terrestrial origin. We -as classifiers of meteorites- are confronted with this problem with every suspected achondrite we receive for identification. We are developing a "grid" of classification to provide an easier approach for initial classification. We use simple but reproducible criteria based on mineralogical, petrological and geochemical studies. We presented the classes: acapulcoites, lodranites, winonaites and Martian meteorites (shergottite, chassignites, nakhlites). In this work we are completing the classification table by including the groups: angrites, aubrites, brachinites, ureilites, HED (howardites, eucrites, and diogenites), lunar meteorites, pallasites and mesosiderites. Iron meteorites are not presented in this abstract.

The structure of the asteroid 4 Vesta as revealed by models of planet-scale collisions

NASA Astrophysics Data System (ADS)

Jutzi, M.; Asphaug, E.; Gillet, P.; Barrat, J.-A.; Benz, W.

2013-02-01

Asteroid 4 Vesta seems to be a major intact protoplanet, with a surface composition similar to that of the HED (howardite-eucrite-diogenite) meteorites. The southern hemisphere is dominated by a giant impact scar, but previous impact models have failed to reproduce the observed topography. The recent discovery that Vesta's southern hemisphere is dominated by two overlapping basins provides an opportunity to model Vesta's topography more accurately. Here we report three-dimensional simulations of Vesta's global evolution under two overlapping planet-scale collisions. We closely reproduce its observed shape, and provide maps of impact excavation and ejecta deposition. Spiral patterns observed in the younger basin Rheasilvia, about one billion years old, are attributed to Coriolis forces during crater collapse. Surface materials exposed in the north come from a depth of about 20 kilometres, according to our models, whereas materials exposed inside the southern double-excavation come from depths of about 60-100 kilometres. If Vesta began as a layered, completely differentiated protoplanet, then our model predicts large areas of pure diogenites and olivine-rich rocks. These are not seen, possibly implying that the outer 100 kilometres or so of Vesta is composed mainly of a basaltic crust (eucrites) with ultramafic intrusions (diogenites).

Detection of Rotational Spectral Variation on the M-type Asteroid (16) Psyche

NASA Astrophysics Data System (ADS)

Sanchez, Juan A.; Reddy, Vishnu; Shepard, Michael K.; Thomas, Cristina; Cloutis, Edward A.; Takir, Driss; Conrad, Albert; Kiddell, Cain; Applin, Daniel

2017-01-01

The asteroid (16) Psyche is of scientific interest because it contains ˜1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. However, no comprehensive study that combines multi-wavelength data has been conducted so far. Here we present rotationally resolved NIR spectra (0.7-2.5 μm) of (16) Psyche obtained with the NASA Infrared Telescope Facility. These data have been combined with shape models of the asteroid for each rotation phase. Spectral band parameters extracted from the NIR spectra show that the pyroxene band center varies from ˜0.92 to 0.94 μm. Band center values were used to calculate the pyroxene chemistry of the asteroid, whose average value was found to be Fs30En65Wo5. Variations in the band depth (BD) were also observed, with values ranging from 1.0% to 1.5%. Using a new laboratory spectral calibration method, we estimated an average orthopyroxene content of 6% ± 1%. The mass-deficit region of Psyche, which exhibits the highest radar albedo, also shows the highest value for the spectral slope and the minimum BD. The spectral characteristics of Psyche suggest that its parent body did not have the typical structure expected for a differentiated body or that the sequence of events that led to its current state was more complex than previously thought.

DETECTION OF ROTATIONAL SPECTRAL VARIATION ON THE M-TYPE ASTEROID (16) PSYCHE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanchez, Juan A.; Thomas, Cristina; Reddy, Vishnu

The asteroid (16) Psyche is of scientific interest because it contains ∼1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. However, no comprehensive study that combines multi-wavelength data has been conducted so far. Here we present rotationally resolved NIR spectra (0.7–2.5 μ m) of (16) Psyche obtained with the NASA Infrared Telescope Facility.more » These data have been combined with shape models of the asteroid for each rotation phase. Spectral band parameters extracted from the NIR spectra show that the pyroxene band center varies from ∼0.92 to 0.94 μ m. Band center values were used to calculate the pyroxene chemistry of the asteroid, whose average value was found to be Fs{sub 30}En{sub 65}Wo{sub 5}. Variations in the band depth (BD) were also observed, with values ranging from 1.0% to 1.5%. Using a new laboratory spectral calibration method, we estimated an average orthopyroxene content of 6% ± 1%. The mass-deficit region of Psyche, which exhibits the highest radar albedo, also shows the highest value for the spectral slope and the minimum BD. The spectral characteristics of Psyche suggest that its parent body did not have the typical structure expected for a differentiated body or that the sequence of events that led to its current state was more complex than previously thought.« less

Asteroids@Home

NASA Astrophysics Data System (ADS)

Durech, Josef; Hanus, J.; Vanco, R.

2012-10-01

We present a new project called Asteroids@home (http://asteroidsathome.net/boinc). It is a volunteer-computing project that uses an open-source BOINC (Berkeley Open Infrastructure for Network Computing) software to distribute tasks to volunteers, who provide their computing resources. The project was created at the Astronomical Institute, Charles University in Prague, in cooperation with the Czech National Team. The scientific aim of the project is to solve a time-consuming inverse problem of shape reconstruction of asteroids from sparse-in-time photometry. The time-demanding nature of the problem comes from the fact that with sparse-in-time photometry the rotation period of an asteroid is not apriori known and a huge parameter space must be densely scanned for the best solution. The nature of the problem makes it an ideal task to be solved by distributed computing - the period parameter space can be divided into small bins that can be scanned separately and then joined together to give the globally best solution. In the framework of the the project, we process asteroid photometric data from surveys together with asteroid lightcurves and we derive asteroid shapes and spin states. The algorithm is based on the lightcurve inversion method developed by Kaasalainen et al. (Icarus 153, 37, 2001). The enormous potential of distributed computing will enable us to effectively process also the data from future surveys (Large Synoptic Survey Telescope, Gaia mission, etc.). We also plan to process data of a synthetic asteroid population to reveal biases of the method. In our presentation, we will describe the project, show the first results (new models of asteroids), and discuss the possibilities of its further development. This work has been supported by the grant GACR P209/10/0537 of the Czech Science Foundation and by the Research Program MSM0021620860 of the Ministry of Education of the Czech Republic.

Asteroid Ida and Its Moon

NASA Technical Reports Server (NTRS)

1994-01-01

This is the first full picture showing both asteroid 243 Ida and its newly discovered moon to be transmitted to Earth from the National Aeronautics and Space Administration's (NASA's) Galileo spacecraft--the first conclusive evidence that natural satellites of asteroids exist. Ida, the large object, is about 56 kilometers (35 miles) long. Ida's natural satellite is the small object to the right. This portrait was taken by Galileo's charge-coupled device (CCD) camera on August 28, 1993, about 14 minutes before the Jupiter-bound spacecraft's closest approach to the asteroid, from a range of 10,870 kilometers (6,755 miles). Ida is a heavily cratered, irregularly shaped asteroid in the main asteroid belt between Mars and Jupiter--the 243rd asteroid to be discovered since the first was found at the beginning of the 19th century. Ida is a member of a group of asteroids called the Koronis family. The small satellite, which is about 1.5 kilometers (1 mile) across in this view, has yet to be given a name by astronomers. It has been provisionally designated '1993 (243) 1' by the International Astronomical Union. ('1993' denotes the year the picture was taken, '243' the asteroid number and '1' the fact that it is the first moon of Ida to be found.) Although appearing to be 'next' to Ida, the satellite is actually in the foreground, slightly closer to the spacecraft than Ida is. Combining this image with data from Galileo's near-infrared mapping spectrometer, the science team estimates that the satellite is about 100 kilometers (60 miles) away from the center of Ida. This image, which was taken through a green filter, is one of a six-frame series using different color filters. The spatial resolution in this image is about 100 meters (330 feet) per pixel.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usui, Fumihiko; Hasegawa, Sunao; Matsuhara, Hideo

We present an analysis of the albedo properties of main belt asteroids (MBAs) detected by the All-Sky Survey of the infrared astronomical satellite AKARI. The characteristics of 5120 asteroids detected by the survey, including their sizes and albedos, were cataloged in the Asteroid Catalog Using AKARI (AcuA). Size and albedo measurements were based on the standard thermal model, using inputs of infrared fluxes and absolute magnitudes measured at optical wavelengths. MBAs, which account for 4722 of the 5120 AcuA asteroids, have semimajor axes of 2.06-3.27 AU, except for the near-Earth asteroids. AcuA provides a complete data set of all MBAsmore » brighter than the absolute magnitude of H < 10.3, which corresponds to the diameter of d > 20 km. We confirmed that the albedo distribution of the MBAs is strongly bimodal as was already known from the past observations, and that the bimodal distribution occurs not only in the total population, but also within inner, middle, and outer regions of the main belt. The bimodal distribution in each group consists of low-albedo components in C-type asteroids and high-albedo components in S-type asteroids. We found that the small asteroids have much more variety in albedo than the large asteroids. In spite of the albedo transition process like space weathering, the heliocentric distribution of the mean albedo of asteroids in each taxonomic type is nearly flat. The mean albedo of the total, on the other hand, gradually decreases with an increase in semimajor axis. This can be explained by the compositional ratio of taxonomic types; that is, the proportion of dark asteroids such as C- and D-types increases, while that of bright asteroids such as S-type decreases, with increasing heliocentric distance. The heliocentric distributions of X-subclasses: E-, M-, and P-types, which can be divided based on albedo values, are also examined. P-types, which are the major component in X-types, are distributed throughout the main belt regions, and the abundance of P-types increases beyond 3 AU. This distribution is similar to that of C- or D-types.« less

A new mechanism for the formation of regolith on asteroids

NASA Astrophysics Data System (ADS)

Delbo, Marco; Libourel, Guy; Wilkerson, Justin; Murdoch, Naomi; Michel, Patrick; Ramesh, Kt; Ganino, Clement; Verati, Chrystele; Marchi, Simone

2014-11-01

The soil of asteroids, like that of the Moon, and other rocky, airless bodies in the Solar System, is made of a layer of pebbles, sand, and dust called regolith.Previous works suggested that the regolith on asteroids is made from material ejected from impacts and re-accumulated on the surface and from surface rocks that are broken down by micrometeoroid impacts. However, this regolith formation process has problems to explain the regolith on km-sized and smaller asteroids: it is known that impact fragments can reach escape velocities and breaks free from the gravitational forces of these small asteroids, indicating the impact mechanism is not the dominant process for regolith creation. Other studies also reveal that there is too much regolith on small asteroids’ surfaces to have been deposited there solely by impacts over the millions of years of asteroids’ evolution.We proposed that another process is capable of gently breaking rocks at the surface of asteroids: thermal fatigue by temperature cycling. As asteroids spin about their rotation axes, their surfaces go in and out of shadow resulting in large surface temperature variations. The rapid heating and cooling creates thermal expansion and contraction in the asteroid material, initiating cracking and propagating existing cracks. As the process is repeated over and over, the crack damage increases with time, leading eventually to rock fragmentation (and production of new regolith).To study this process, in the laboratory, we subjected meteorites, used as asteroid material analogs, to 37 days of thermal cycles similar to those occurring on asteroids. We measured cracks widening at an average rate of 0.5 mm/y. Some fragments were also produced, indicating meteorite fragmentation. To scale our results to asteroid lifetime, we incorporated our measurements into a fracture model and we deduced that thermal cycling is more efficient than micrometeorite bombardment at fragmenting rock over millions of years on asteroids (see Delbo et al. 2014. Nature 508, 233-236).This work was supported by the French Agence National de la Recherche (ANR) SHOCKS,

Search for Water in Outer Main Belt Based on AKARI Asteroid Catalog

NASA Astrophysics Data System (ADS)

Usui, Fumihiko

2012-06-01

We propose a program to search water ice on the surface of asteroids in the outer main belt regions, which have high albedo measured with AKARI. The distribution of water in the main belt provides important information to understanding of the formation and evolution of the solar system, because water is a good indicator of temperature in the early solar nebula. The existence of water ice is a hot topic in the solar system studies today. Water ice is recently found in the outer region of the main asteroid belt and some of them are linked to the main belt comets. Brand-new albedo data brought by AKARI opens the possibility of detection of water ice on the C-type asteroids. Here we propose to make the spectroscopic observations with the Subaru telescope in the near-infrared wavelengths to detect water ice on these high-albedo C-type asteroids. Thanks to a large aperture of Subaru telescope and a high altitude of Mauna Kea, it can be only possible to observe a weak signal of the existence of water on the surface of asteroids with a certain S/N. In addition, using the imaging data taken prior to IRCS spectroscopic mode, we intend to seek any comet-like activities by investigating diffuseness of the asteroids, which can be detected by comparing the observed point-spread functions with those of field stars.

Initial velocity V-shapes of young asteroid families

NASA Astrophysics Data System (ADS)

Bolin, Bryce T.; Walsh, Kevin J.; Morbidelli, Alessandro; Delbó, Marco

2018-01-01

Ejection velocity fields of asteroid families are largely unconstrained due to the fact that members disperse relatively quickly on Myr time-scales by secular resonances and the Yarkovsky effect. The spreading of fragments in a by the Yarkovsky effect is indistinguishable from the spreading caused by the initial ejection of fragments. By examining families <20 Myr old, we can use the V-shape identification technique to separate family shapes that are due to the initial ejection velocity field and those that are due to the Yarkovsky effect. Asteroid families that are <20 Myr old provide an opportunity to study the velocity field of family fragments before they become too dispersed. Only the Karin family's initial velocity field has been determined and scales inversely with diameter, D-1. We have applied the V-shape identification technique to constrain young families' initial ejection velocity fields by measuring the curvature of their fragments' V-shape correlation in semimajor axis, a, versus D-1 space. Curvature from a straight line implies a deviation from a scaling of D-1. We measure the V-shape curvature of 11 young asteroid families including the 1993 FY12, Aeolia, Brangane, Brasilia, Clarissa, Iannini, Karin, Konig, Koronis(2), Theobalda and Veritas asteroid families. We find that the majority of asteroid families have initial ejection velocity fields consistent with ∼D-1 supporting laboratory impact experiments and computer simulations of disrupting asteroid parent bodies.

Asteroid approach covariance analysis for the Clementine mission

NASA Technical Reports Server (NTRS)

Ionasescu, Rodica; Sonnabend, David

1993-01-01

The Clementine mission is designed to test Strategic Defense Initiative Organization (SDIO) technology, the Brilliant Pebbles and Brilliant Eyes sensors, by mapping the moon surface and flying by the asteroid Geographos. The capability of two of the instruments available on board the spacecraft, the lidar (laser radar) and the UV/Visible camera is used in the covariance analysis to obtain the spacecraft delivery uncertainties at the asteroid. These uncertainties are due primarily to asteroid ephemeris uncertainties. On board optical navigation reduces the uncertainty in the knowledge of the spacecraft position in the direction perpendicular to the incoming asymptote to a one-sigma value of under 1 km, at the closest approach distance of 100 km. The uncertainty in the knowledge of the encounter time is about 0.1 seconds for a flyby velocity of 10.85 km/s. The magnitude of these uncertainties is due largely to Center Finding Errors (CFE). These systematic errors represent the accuracy expected in locating the center of the asteroid in the optical navigation images, in the absence of a topographic model for the asteroid. The direction of the incoming asymptote cannot be estimated accurately until minutes before the asteroid flyby, and correcting for it would require autonomous navigation. Orbit determination errors dominate over maneuver execution errors, and the final delivery accuracy attained is basically the orbit determination uncertainty before the final maneuver.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, B.; Helou, G.; Noriega-Crespo, A.

The Spitzer Space Telescope routinely detects asteroids in astrophysical observations near the ecliptic plane. For the galactic or extragalactic astronomer, these solar system bodies can introduce appreciable uncertainty into the source identification process. We discuss an infrared color discrimination tool that may be used to distinguish between solar system objects and extrasolar sources. We employ four Spitzer Legacy data sets, the First Look Survey-Ecliptic Plane Component (FLS-EPC), SCOSMOS, SWIRE, and GOODS. We use the Standard Thermal Model to derive FLS-EPC main belt asteroid (MBA) diameters of 1-4 km for the numbered asteroids in our sample and note that several ofmore » our solar system sources may have fainter absolute magnitude values than previously thought. A number of the MBAs are detected at flux densities as low as a few tens of {mu}Jy at 3.6 {mu}m. As the FLS-EPC provides the only 3.6-24.0 {mu}m observations of individual asteroids to date, we are able to use this data set to carry out a detailed study of asteroid color in comparison to astrophysical sources observed by SCOSMOS, SWIRE, and GOODS. Both SCOSMOS and SWIRE have identified a significant number of asteroids in their data, and we investigate the effectiveness of using relative color to distinguish between asteroids and background objects. We find a notable difference in color in the IRAC 3.6-8.0 mm and MIPS 24 {mu}m bands between the majority of MBAs, stars, galaxies, and active galactic nuclei, though this variation is less significant when comparing fluxes in individual bands. We find median colors for the FLS-EPC asteroids to be [F(5.8/3.6), F(8.0/4.5), F(24/8)] = (4.9 {+-} 1.8, 8.9 {+-} 7.4, 6.4 {+-} 2.3). Finally, we consider the utility of this technique for other mid-infrared observations that are sensitive to near-Earth objects, MBAs, and trans-Neptunian objects. We consider the potential of using color to differentiate between solar system and background sources for several space-based observatories, including Warm Spitzer, Herschel, and WISE.« less

3-µm Spectroscopy of Asteroid 16 Psyche

NASA Astrophysics Data System (ADS)

Takir, Driss; Reddy, Vishnu; Sanchez, Juan; Shepard, Michael K.

2016-10-01

Asteroid 16 Psyche, an M-type asteroid, is thought to be one of the most massive exposed iron metal object in the asteroid belt. The high radar albedos of Psyche suggest that this differentiated asteroid is dominantly composed of metal. Psyche was previously found to be featureless in the 3-µm spectral region. However, in our study we found that this asteroid exhibits a 3-µm absorption feature, possibly indicating the presence of hydrated silicates.We have observed Psyche in the 3-µm spectral region, using the long-wavelength cross-dispersed (LXD:1.9-4.2 µm) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). For data reduction, we used the IDL (Interactive Data Language)-based spectral reduction tool Spextool (v4.1). Psyche was observed over the course of three nights with an apparent visual magnitude of ~9.50: 8 December 2015 (3 sets), 9 December 2015 (1 set), and 10 March 2016 (1 set). These observations have revealed that Psyche may exhibit a 3-µm absorption feature, similar to the sharp group in the 2.9-3.3-µm spectral range. Psyche also exhibits an absorption feature similar to the one in Ceres and Ceres-like group in the spectral 3.3-4.0-µm range. These 3-µm observational results revealed that Psyche may not be as featureless as once thought in the 3-µm spectral region.Evidence for the 3-µm band was found on the surfaces of many M-type asteroids and a number of plausible alternative interpretations for the presence of this 3-µm band were previously suggested. These interpretations include the presence of anhydrous silicates containing structural OH, the presence of fluid inclusions, the presence of xenolithic hydrous meteorite components on asteroid surfaces from impacts, solar wind-implanted H, or the presence of troilite. The detection of the Ceres-like feature in the 3.3-4.0-µm spectral range, however, would rule out some of these alternative interpretations, especially the solar wind-implanted H.

NASA's Dawn Mission to Asteroid 4 Vesta

NASA Technical Reports Server (NTRS)

McFadden, Lucyann A.

2011-01-01

NASA's Dawn Mission to asteroid 4 Vesta is part of a 13-year robotic space project designed to reveal the nature of two of the largest asteroids in the Main Asteroid Belt of our Solar System. Ceres and Vesta are two complementary terrestrial protoplanets whose accretion was probably terminated by the formation of Jupiter. They provide a bridge in our understanding between the rocky bodies of the inner solar system and the icy bodies of the outer solar system. Ceres appears to be undifferentiated Vesta has experienced significant heating and likely differentiation. Both formed very early in history of the solar system and while suffering many impacts have remained intact, thereby retaining a record of events and processes from the time of planet formation. Detailed study of the geophysics and geochemistry of these two bodies provides critical benchmarks for early solar system conditions and processes that shaped its subsequent evolution. Dawn provides the missing context for both primitive and evolved meteoritic data, thus playing a central role in understanding terrestrial planet formation and the evolution of the asteroid belt. Dawn is to he launched in 2006 arriving at Vesta in 20l0 and Ceres in 2014, stopping at each to make 11 months of orbital measurements. The spacecraft uses solar electric propulsion, both in cruise and in orbit, to make most efficient use of its xenon propellant. The spacecraft carries a framing camera, visible and infrared mapping spectrometer, gamma ray/neutron magnetometer, and radio science.

Rubble-Pile Minor Planet Sylvia and Her Twins

NASA Astrophysics Data System (ADS)

2005-08-01

VLT NACO Instrument Helps Discover First Triple Asteroid One of the thousands of minor planets orbiting the Sun has been found to have its own mini planetary system. Astronomer Franck Marchis (University of California, Berkeley, USA) and his colleagues at the Observatoire de Paris (France) [1] have discovered the first triple asteroid system - two small asteroids orbiting a larger one known since 1866 as 87 Sylvia [2]. "Since double asteroids seem to be common, people have been looking for multiple asteroid systems for a long time," said Marchis. "I couldn't believe we found one." The discovery was made with Yepun, one of ESO's 8.2-m telescopes of the Very Large Telescope Array at Cerro Paranal (Chile), using the outstanding image' sharpness provided by the adaptive optics NACO instrument. Via the observatory's proven "Service Observing Mode", Marchis and his colleagues were able to obtain sky images of many asteroids over a six-month period without actually having to travel to Chile. ESO PR Photo 25a/05 ESO PR Photo 25a/05 Orbits of Twin Moonlets around 87 Sylvia [Preview - JPEG: 400 x 516 pix - 145k] [Normal - JPEG: 800 x 1032 pix - 350k] ESO PR Photo 25b/05 ESO PR Photo 25b/05 Artist's impression of the triple asteroid system [Preview - JPEG: 420 x 400 pix - 98k] [Normal - JPEG: 849 x 800 pix - 238k] [Full Res - JPEG: 4000 x 3407 pix - 3.7M] [Full Res - TIFF: 4000 x 3000 pix - 36.0M] Caption: ESO PR Photo 25a/05 is a composite image showing the positions of Remus and Romulus around 87 Sylvia on 9 different nights as seen on NACO images. It clearly reveals the orbits of the two moonlets. The inset shows the potato shape of 87 Sylvia. The field of view is 2 arcsec. North is up and East is left. ESO PR Photo 25b/05 is an artist rendering of the triple system: Romulus, Sylvia, and Remus. ESO Video Clip 03/05 ESO Video Clip 03/05 Asteroid Sylvia and Her Twins [Quicktime Movie - 50 sec - 384 x 288 pix - 12.6M] Caption: ESO PR Video Clip 03/05 is an artist rendering of the triple asteroid system showing the large asteroid 87 Sylvia spinning at a rapid rate and surrounded by two smaller asteroids (Remus and Romulus) in orbit around it. This computer animation is also available in broadcast quality to the media (please contact Herbert Zodet). One of these asteroids was 87 Sylvia, which was known to be double since 2001, from observations made by Mike Brown and Jean-Luc Margot with the Keck telescope. The astronomers used NACO to observe Sylvia on 27 occasions, over a two-month period. On each of the images, the known small companion was seen, allowing Marchis and his colleagues to precisely compute its orbit. But on 12 of the images, the astronomers also found a closer and smaller companion. 87 Sylvia is thus not double but triple! Because 87 Sylvia was named after Rhea Sylvia, the mythical mother of the founders of Rome [3], Marchis proposed naming the twin moons after those founders: Romulus and Remus. The International Astronomical Union approved the names. Sylvia's moons are considerably smaller, orbiting in nearly circular orbits and in the same plane and direction. The closest and newly discovered moonlet, orbiting about 710 km from Sylvia, is Remus, a body only 7 km across and circling Sylvia every 33 hours. The second, Romulus, orbits at about 1360 km in 87.6 hours and measures about 18 km across. The asteroid 87 Sylvia is one of the largest known from the asteroid main belt, and is located about 3.5 times further away from the Sun than the Earth, between the orbits of Mars and Jupiter. The wealth of details provided by the NACO images show that 87 Sylvia is shaped like a lumpy potato, measuring 380 x 260 x 230 km (see ESO PR Photo 25a/05). It is spinning at a rapid rate, once every 5 hours and 11 minutes. The observations of the moonlets' orbits allow the astronomers to precisely calculate the mass and density of Sylvia. With a density only 20% higher than the density of water, it is likely composed of water ice and rubble from a primordial asteroid. "It could be up to 60 percent empty space," said co-discoverer Daniel Hestroffer (Observatoire de Paris, France). "It is most probably a "rubble-pile" asteroid", Marchis added. These asteroids are loose aggregations of rock, presumably the result of a collision. Two asteroids smacked into each other and got disrupted. The new rubble-pile asteroid formed later by accumulation of large fragments while the moonlets are probably debris left over from the collision that were captured by the newly formed asteroid and eventually settled into orbits around it. "Because of the way they form, we expect to see more multiple asteroid systems like this." Marchis and his colleagues will report their discovery in the August 11 issue of the journal Nature, simultaneously with an announcement that day at the Asteroid Comet Meteor conference in Armação dos Búzios, Rio de Janeiro state, Brazil.

Hypervelocity impacts on asteroids and momentum transfer I. Numerical simulations using porous targets

NASA Astrophysics Data System (ADS)

Jutzi, Martin; Michel, Patrick

2014-02-01

In this paper, we investigate numerically the momentum transferred by impacts of small (artificial) projectiles on asteroids. The study of the momentum transfer efficiency as a function of impact conditions and of the internal structure of an asteroid is crucial for performance assessment of the kinetic impactor concept of deflecting an asteroid from its trajectory. The momentum transfer is characterized by the so-called momentum multiplication factor β, which has been introduced to define the momentum imparted to an asteroid in terms of the momentum of the impactor. Here we present results of code calculations of the β factor for porous targets, in which porosity takes the form of microporosity and/or macroporosity. The results of our study using a large range of impact conditions indicate that the momentum multiplication factor β is small for porous targets even for very high impact velocities (β<2 for vimp⩽15 km/s), which is consistent with published scaling laws and results of laboratory experiments (Holsapple, K.A., Housen, K.R. [2012]. Icarus 221, 875-887; Holsapple, K.A., Housen, K.R. [2013]. Proceedings of the IAA Planetary Defense Conference 2013, Flagstaff, USA). It is found that both porosity and strength can have a large effect on the amount of transferred momentum and on the scaling of β with impact velocity. On the other hand, the macroporous inhomogeneities considered here do not have a significant effect on β.

Peculiar Euphrosyne

NASA Astrophysics Data System (ADS)

Carruba, V.; Aljbaae, S.; Souami, D.

2014-07-01

(31) Euphrosyne is the largest body of its namesake family, and contains more the 99.35% of the family mass. Among asteroid families, the Euphosyne group is peculiar because of its quite steep size frequency distribution, significantly depleted in large and medium- sized asteroids (8 < D < 12~km). The current steep size frequency distribution of the Euphrosyne family has been suggested to be the result of a grazing impact in which only the farthest, smallest members failed to accrete. The Euphrosyne family is however also very peculiar because of its dynamics: near its center it is crossed by the ν_6 = g -g_6 linear secular resonance, and it hosts the largest population (140 bodies) of asteroids in ν_6 anti-aligned librating states (or Tina-like asteroids) in the main belt. In this work we investigated the orbital evolution of newly obtained members of the dynamical family, with an emphasis on its interaction with the ν_6 resonance. Because of its unique resonant configuration, large and medium sized asteroids tend to migrate away from the family orbital region faster than small-sized objects, that were ejected further away from the family center. As a consequence, the size-frequency distribution of the Euphrosyne family becomes steeper in time, with a growing depletion in the number of the largest family members. We estimate that the current size-frequency distribution could be attained from a typical, initial size-frequency distribution in time-scales of the order of 1~Byr, consistently with estimates of the family age obtained with other, independent, methods.

Impact as a general cause of extinction: A feasibility test

NASA Technical Reports Server (NTRS)

Raup, David M.

1988-01-01

Large body impact has been implicated as the possible cause of several extinction events. This is entirely plausible if one accepts two propositions: (1) that impacts of large comets and asteroids produce environmental effects severe enough to cause significant species extinctions and (2) that the estimates of comet and asteroid flux for the Phanerozoic are approximately correct. A resonable next step is to investigate the possibility that impact could be a significant factor in the broader Phanerozoic extinction record, not limited merely to a few events of mass extinction. Monte Carlo simulation experiments based on existing flux estimates and reasonable predictions of the relationship between bolide diameter and extinction are discussed. The simulation results raise the serious possibility that large body impact may be a more pervasive factor in extinction than has been assumed heretofore. At the very least, the experiments show that the comet and asteroid flux estimates combined with a reasonable kill curve produces a reasonable extinction record, complete with occasional mass extinctions and the irregular, lower intensity extinctions commonly called background extinction.

Necroplanetology: Disrupted Planetary Material Transiting WD 1145+017

NASA Astrophysics Data System (ADS)

Manideep Duvvuri, Girish; Redfield, Seth; Veras, Dimitri

2018-06-01

The WD 1145+017 system shows irregular transit features that are consistent with the tidal disruption of differentiated asteroids with bulk densities < 4 g cm-3 and bulk masses < 1021 kg. We use the open-source N-body code REBOUND to simulate this disruption with different internal structures: varying the core volume fraction, mantle/core density ratio, and the presence/absence of a thin low-density crust. We show that these parameters have observationally distinguishable effects on the transit light curve as the asteroid is disrupted and fit the simulation-generated lightcurves to data. We find that an asteroid with a low core fraction, low mantle/density ratio, and without a crust is most consistent with the A1 feature present for multiple weeks circa April 2017. This combination of observations and simulations to study the interior structure and chemistry of exoplanetary bodies via their destruction in action is an early example of necroplanetology, a field that will hopefully grow with the discovery of other systems like WD 1145+017.

Petrology of Igneous Clasts in Regolithic Howardite EET 87503

NASA Technical Reports Server (NTRS)

Hodges, Z. V.; Mittlefehldt, D. W.

2017-01-01

The howardite, eucrite and diogenite (HED) clan of meteorites is widely considered to originate from asteroid 4 Vesta, as a result of a global magma ocean style of differentiation. A global magmatic stage would allow silicate material to be well mixed, destroying any initial heterogeneity that may have been present resulting in the uniformity of eucrite and diogenite delta(exp 17)O, for example. The Fe/Mn ratio of mafic phases in planetary basalts can be diagnostic of different source bodies as this ratio is little-affected by igneous processes, so long as the oxygen and sulphur fugacities are buffered. Here, pyroxene Fe/Mn ratios in mafic clasts in howardite EET 87503 have been determined to further evaluate whether the HED parent asteroid is uniform. Uniformity would suggest that the parent asteroid was subject to homogenization prior to the formation of HED lithologies, likely through an extensive melting phase. Whereas, distinct differences may point towards heterogeneity of the parent body.

Veritas Asteroid Family Still Holds Secrets?

NASA Astrophysics Data System (ADS)

Novakovic, B.

2012-12-01

Veritas asteroid family has been studied for about two decades. These studies have revealed many secrets, and a respectable knowledge about this family had been collected. Here I will present many of these results and review the current knowledge about the family. However, despite being extensively studied, Veritas family is still a mystery. This will be illustrated through the presentation of the most interesting open problems. Was there a secondary collision within this family? Does asteroid (490) Veritas belong to the family named after it? How large was the parent body of the family? Finally, some possible directions for future studies that aims to address these questions are discussed as well.

Lorre cluster: an outcome of recent asteroid collision

NASA Astrophysics Data System (ADS)

Novakovic, B.; Dell'Oro, A.; Cellino, A.; Knezevic, Z.

2012-09-01

Here we show an example of a young asteroid cluster located in a dynamically stable region, which was produced by partial disruption of a primitive body about 30 km in size. According to our estimation it is only 1.9±0.3 Myr old, thus its post-impact evolution is very limited. The parent body had a large orbital inclination, and was subject to collisions with typical impact speeds higher by a factor of 2 than in the most common situations encountered in the main belt. For the first time we have at disposal the observable outcome of a very recent event to study high-speed collisions involving primitive asteroids.

Investigation of the interior of primordial asteroids and the origin of the Earth's water: The INSIDER space mission

NASA Astrophysics Data System (ADS)

Vernazza, P.; Lamy, P.

2014-07-01

Today's asteroid belt may not only be populated by objects that formed in situ, typically between 2.2 and 3.3 au, but also by bodies that formed over a very large range of heliocentric distances. It is currently proposed that both the early (<5 Myrs after Solar System formation) and late (>700 Myrs after Solar System formation) dynamical evolution of the Solar System was governed by giant planet migrations that led to the insertion of inner (1--3 au) as well as outer (4--13 au) small bodies in the asteroid belt. Taken altogether, the current dynamical models are able to explain many striking features of the asteroid belt including i) its incredible compositional diversity deduced mainly from spectroscopic observations and meteorites measurements, and ii) the evidence of radial mixing experienced by the various asteroid classes (e.g., S-, C-types) after their formation. In a broad stroke, the idea that the asteroid belt is a condensed version of the primordial Solar System is progressively emerging. The asteroid belt therefore presents the double advantage of being easily accessible and of offering crucial tests for the formation models of the Solar System by exploring the building blocks predicted by models of i) the telluric planets, ii) the giant planet cores, iii) the giant planets' satellites, and iv) outer small bodies such TNOs and comets. It also appears as an ideal place to search for the origin of Earth's water. Up to now, only a few asteroid classes (e.g., several S-types) have been visited by spacecraft and the focus of these in situ measurements has been mainly to give a geological context to ground based observations as well as strengthen/validate their interpretation. Most of the tantalizing discoveries of asteroid missions have been realized via images of the objects surfaces. Time has come for asteroid space science to reach a new milestone by extending the reconnaissance of the Belt's diversity and addressing new science questions. The scientific objectives of the INSIDER mission, to be proposed in response to the 2014 ESA call for an M-class mission, require the exploration of diverse primordial asteroids --- possibly the smallest surviving protoplanets of our Solar System --- in order to constrain the earliest stages of planetesimal formation thus avoiding the effect of destructive collisions, which produce extensively processed rubble piles. Our science objectives that justify in situ measurements in the context of an M-class mission and that are expected to lead to significant breakthroughs include: - The exploration of the diversity of the asteroid belt - The first investigation of the internal structure of asteroids - The origin of water on Earth The proposed mission scenario consists in i) successive rendez-vous followed by orbit insertion of two and possibly three large (D>100 km) objects, ii) one or two small landing modules (MASCOT type) to perform cosmochemical measurements (D/H ratio, O isotopes). The potential targets would include 24 Themis and 10 Hygiea. Meeting our science objectives requires instruments (such as radar, seismometers to be dropped to the surface, magnetometer, high resolution laser-desorption-ionization mass spectrometer to analyse the surface samples) not flown so far during past asteroids missions along with the traditional powerhouses, such as cameras and spectrometers.

Mineralogical characterization of asteroid (1951) Lick

NASA Astrophysics Data System (ADS)

de Leon, J.; Duffard, R.; Licandro, J.; Lazzaro, D.

A-type asteroids are usually found in the main asteroid belt and their spectra are very similar to spectra of the silicate mineral olivine (Cruikshank and Hartmann 1984). The existence of olivine-rich asteroids is a result of differentiation, those being the pieces of the mantle of a larger parent body. Extraterrestrial sources of such material must exist because we have meteorites that are nearly pure olivine (dunites). There is a limited number of observed asteroids classified as A-type, all of them belonging to the Main Belt and the study of such objects is crucial to better understand their origin and formation and their relation with dunites. We have obtained visible and near infrared reflectance spectra of asteroid (1951) Lick using the telescopes located at Observatorio del Roque de los Muchachos (Canary Islands, Spain). According to its spectral characteristics in the visible region, this object has been classified as an A-type asteroid by Bus and Binzel (2002). Although considered an Amor object by several authors, according to its orbital parameters (a = 1.390 AU, e = 0.061, i = 39.093 deg, q = 1.304) this object is just in the limit that separates Amors from Mars Crossers (q = 1.3). Whether it is classified as an Amor or a Mars Crosser, (1951) Lick is the first object with such orbital characteristics classified as an A-type asteroid. Here we present a mineralogical analysis of the reflectance spectra obtained for (1951) Lick. We calculate several parameters that are extracted from the spectrum of the asteroid and that give relevant information about its mineralogical composition, using the method defined by Gaffey et al. (1993). We also present results obtained by a preliminary fit to the absorption band associated to the presence of the olivine mineral using the Modified Gaussian Model method (MGM) developed by Sunshine et al.(1990). References Bus, J. S. and Binzel, R. P. 2002. Icarus, 158, 146 Cuikshank, D. P. and Hartmann, W. K. 1984. Science, 223, 281 Gaffey, M. J., Bell, J. F., Brown, R. H., Burbine, T. H., Piatek, J. L., Reed, K. L. and Chaky, D. A. 1993. Icarus, 106, 573 Sunshine, J. M., Pieters, C. M. and Pratt, S. F. 1990. JGR, 95, B5, 6955

Variability in Abundances of Meteorites in the Ordovician

NASA Astrophysics Data System (ADS)

Heck, P. R.; Schmitz, B.; Kita, N.

2017-12-01

The knowledge of the flux of extraterrestrial material throughout Earth's history is of great interest to reconstruct the collisional evolution of the asteroid belt. Here, we present a review of our investigations of the nature of the meteorite flux to Earth in the Ordovician, one of the best-studied time periods for extraterrestrial matter in the geological record [1]. We base our studies on compositions of extraterrestrial chromite and chrome-spinel extracted by acid dissolution from condensed marine limestone from Sweden and Russia [1-3]. By analyzing major and minor elements with EDS and WDS, and three oxygen isotopes with SIMS we classify the recovered meteoritic materials. Today, the L and H chondrites dominate the meteorite and coarse micrometeorite flux. Together with the rarer LL chondrites they have a type abundance of 80%. In the Ordovician it was very different: starting from 466 Ma ago 99% of the flux was comprised of L chondrites [2]. This was a result of the collisional breakup of the parent asteroid. This event occurred close to an orbital resonance in the asteroid belt and showered Earth with >100x more L chondritic material than today during more than 1 Ma. Although the flux is much lower at present, L chondrites are still the dominant type of meteorites that fall today. Before the asteroid breakup event 467 Ma ago the three groups of ordinary chondrites had about similar abundances. Surprisingly, they were possibly surpassed in abundance by achondrites, materials from partially and fully differentiated asteroids [3]. These achondrites include HED meteorites, which are presumably fragments released during the formation of the Rheasilvia impact structure 1 Ga ago on asteroid 4 Vesta. The enhanced abundance of LL chondrites is possibly a result of the Flora asteroid family forming event at 1 Ga ago. The higher abundance of primitive achondrites was likely due to smaller asteroid family forming events that have not been identified yet but that did not generate a supply of fragments that was long-lived enough to be still important today. Our results imply that the composition of the flux of meteorites to Earth is biased by discrete collisional events in the asteroid belt. [1] Schmitz B (2013) Chem Erde 73, 117; [2] Heck PR et al (2016) GCA 177, 120; [3] Heck PR et al (2017) Nat Astron 1, 35, DOI: 10.1038/s41550-016-0035.

The Collisional Evolution of the Main Asteroid Belt

NASA Astrophysics Data System (ADS)

Bottke, W. F.; Brož, M.; O'Brien, D. P.; Campo Bagatin, A.; Morbidelli, A.; Marchi, S.

Collisional and dynamical models of the main asteroid belt allow us to glean insights into planetesimal- and planet-formation scenarios as well as how the main belt reached its current state. Here we discuss many of the processes affecting asteroidal evolution and the constraints that can be used to test collisional model results. We argue the main belt's wavy size-frequency distribution for diameter D < 100-km asteroids is increasingly a byproduct of comminution as one goes to smaller sizes, with its shape a fossil-like remnant of a violent early epoch. Most D > 100-km asteroids, however, are primordial, with their physical properties set by planetesimal formation and accretion processes. The main-belt size distribution as a whole has evolved into a collisional steady state, and it has possibly been in that state for billions of years. Asteroid families provide a critical historical record of main-belt collisions. The heavily depleted and largely dispersed "ghost families," however, may hold the key to understanding what happened in the primordial days of the main belt. New asteroidal fragments are steadily created by both collisions and mass shedding events via YORP spinup processes. A fraction of this population, in the form of D < 30 km fragments, go on to escape the main belt via the Yarkovsky/YORP effects and gravitational resonances, thereby creating a quasi-steady-state population of planet-crossing and near-Earth asteroids. These populations go on to bombard all inner solar system worlds. By carefully interpreting the cratering records they produce, it is possible to constrain how portions of the main-belt population have evolved with time.

Asteroid Deflection: How, Where and When?

NASA Astrophysics Data System (ADS)

Fargion, D.

2008-10-01

To deflect impact-trajectory of massive and spinning km^3 asteroid by a few terrestrial radiuses one need a large momentum exchange. The dragging of huge spinning bodies in space by external engine seems difficult or impossible. Our solution is based on the landing of multi screw-rockets, powered by mini-nuclear engines, on the body, that dig a small fraction of the soil surface to use as an exhaust propeller, ejecting it vertically in phase among themselves. Such a mass ejection increases the momentum exchange, their number redundancy guarantees the stability of the system. The slow landing (below ≃ 40 cm s^{-1}) of each engine-unity at those very low gravity field, may be achieved by safe rolling and bouncing along the surface. The engine array tuned activity, overcomes the asteroid angular velocity. Coherent turning of the jet heads increases the deflection efficiency. A procession along its surface may compensate at best the asteroid spin. A small skin-mass (about 2×10^4 tons) may be ejected by mini-nuclear engines. Such prototypes may also build first safe galleries for humans on the Moon. Conclusive deflecting tests might be performed on remote asteroids. The incoming asteroid 99942 Apophis (just 2% of km^3) may be deflected safely a few Earth radiuses. Its encounter maybe not just a hazard but an opportunity, learning how to land, to dig, to build and also to nest safe human station inside. Asteroids amplified deflections by gravity swing may be driven into longest planetary journeys, beginning i.e. with the preliminary landing of future missions on Mars' moon-asteroid Phobos or Deimos.

Interrelating meteorite and asteroid spectra at UV-Vis-NIR wavelengths using novel multiple-scattering methods

NASA Astrophysics Data System (ADS)

Martikainen, Julia; Penttilä, Antti; Gritsevich, Maria; Muinonen, Karri

2017-10-01

Asteroids have remained mostly the same for the past 4.5 billion years, and provide us information on the origin, evolution and current state of the Solar System. Asteroids and meteorites can be linked by matching their respective reflectance spectra. This is difficult, because spectral features depend strongly on the surface properties, and meteorite surfaces are free of regolith dust present in asteroids. Furthermore, asteroid surfaces experience space weathering which affects their spectral features.We present a novel simulation framework for assessing the spectral properties of meteorites and asteroids and matching their reflectance spectra. The simulations are carried out by utilizing a light-scattering code that takes inhomogeneous waves into account and simulates light scattering by Gaussian-random-sphere particles large compared to the wavelength of the incident light. The code uses incoherent input and computes phase matrices by utilizing incoherent scattering matrices. Reflectance spectra are modeled by combining olivine, pyroxene, and iron, the most common materials that dominate the spectral features of asteroids and meteorites. Space weathering is taken into account by adding nanoiron into the modeled asteroid spectrum. The complex refractive indices needed for the simulations are obtained from existing databases, or derived using an optimization that utilizes our ray-optics code and the measured spectrum of the material.We demonstrate our approach by applying it to the reflectance spectrum of (4) Vesta and the reflectance spectrum of the Johnstown meteorite measured with the University of Helsinki integrating-sphere UV-Vis-NIR spectrometer.Acknowledgments. The research is funded by the ERC Advanced Grant No. 320773 (SAEMPL).

Computer simulation of position and maximum of linear polarization of asteroids

NASA Astrophysics Data System (ADS)

Petrov, Dmitry; Kiselev, Nikolai

2018-01-01

The ground-based observations of near-Earth asteroids at large phase angles have shown some feature: the linear polarization maximum position of the high-albedo E-type asteroids shifted markedly towards smaller phase angles (αmax ≈ 70°) with respect to that for the moderate-albedo S-type asteroids (αmax ≈ 110°), weakly depending on the wavelength. To study this phenomenon, the theoretical approach and the modified T-matrix method (the so-called Sh-matrices method) were used. Theoretical approach was devoted to finding the values of αmax, corresponding to maximal values of positive polarization Pmax. Computer simulations were performed for an ensemble of random Gaussian particles, whose scattering properties were averaged over with different particle orientations and size parameters in the range X = 2.0 ... 21.0, with the power law distribution X - k, where k = 3.6. The real parts of the refractive index mr were 1.5, 1.6 and 1.7. Imaginary part of refractive index varied from mi = 0.0 to mi = 0.5. Both theoretical approach and computer simulation showed that the value of αmax strongly depends on the refractive index. The increase of mi leads to increased αmax and Pmax. In addition, computer simulation shows that the increase of the real part of the refractive index reduces Pmax. Whereas E-type high-albedo asteroids have smaller values of mi, than S -type asteroids, we can conclude, that value of αmax of E-type asteroids should be smaller than for S -type ones. This is in qualitative agreement with the observed effect in asteroids.

Distribution of shape elongations of main belt asteroids derived from Pan-STARRS1 photometry

NASA Astrophysics Data System (ADS)

Cibulková, H.; Nortunen, H.; Ďurech, J.; Kaasalainen, M.; Vereš, P.; Jedicke, R.; Wainscoat, R. J.; Mommert, M.; Trilling, D. E.; Schunová-Lilly, E.; Magnier, E. A.; Waters, C.; Flewelling, H.

2018-04-01

Context. A considerable amount of photometric data is produced by surveys such as Pan-STARRS, LONEOS, WISE, or Catalina. These data are a rich source of information about the physical properties of asteroids. There are several possible approaches for using these data. Light curve inversion is a typical method that works with individual asteroids. Our approach in focusing on large groups of asteroids, such as dynamical families and taxonomic classes, is statistical; the data are not sufficient for individual models. Aim. Our aim is to study the distributions of shape elongation b/a and the spin axis latitude β for various subpopulations of asteroids and to compare our results, based on Pan-STARRS1 survey, with statistics previously carried out using various photometric databases, such as Lowell and WISE. Methods: We used the LEADER algorithm to compare the b/a and β distributions for various subpopulations of asteroids. The algorithm creates a cumulative distributive function (CDF) of observed brightness variations, and computes the b/a and β distributions with analytical basis functions that yield the observed CDF. A variant of LEADER is used to solve the joint distributions for synthetic populations to test the validity of the method. Results: When comparing distributions of shape elongation for groups of asteroids with different diameters D, we found that there are no differences for D < 25 km. We also constructed distributions for asteroids with different rotation periods and revealed that the fastest rotators with P = 0 - 4 h are more spheroidal than the population with P = 4-8 h.

Tidal excitation of elliptical instability in the Martian core: Possible mechanism for generating the core dynamo

NASA Astrophysics Data System (ADS)

Arkani-Hamed, J.; Seyed-Mahmoud, B.; Aldridge, K. D.; Baker, R. E.

2008-06-01

We propose a causal relationship between the creation of the giant impact basins on Mars by a large asteroid, ruptured when it entered the Roche limit, and the excitation of the Martian core dynamo. Our laboratory experiments indicate that the elliptical instability of the Martian core can be excited if the asteroid continually exerts tidal forces on Mars for ~20,000 years. Our numerical experiments suggest that the growth-time of the instability was 5,000-15,000 years when the asteroid was at a distance of 50,000-75,000 km. We demonstrate the stability of the orbital motion of an asteroid captured by Mars at a distance of 100,000 km in the presence of the Sun and Jupiter. We also present our results for the tidal interaction of the asteroid with Mars. An asteroid captured by Mars in prograde fashion can survive and excite the elliptical instability of the core for only a few million years, whereas a captured retrograde asteroid can excite the elliptical instability for hundreds of millions of years before colliding with Mars. The rate at which tidal energy dissipates in Mars during this period is over two orders of magnitude greater than the rate at which magnetic energy dissipates. If only 1% of the tidal energy dissipation is partitioned to the core, sufficient energy would be available to maintain the core dynamo. Accordingly, a retrograde asteroid is quite capable of exciting an elliptical instability in the Martian core, thus providing a candidate process to drive a core dynamo.

KSC-07pd1265

NASA Image and Video Library

2007-05-23

KENNEDY SPACE CENTER, FLA. -- At Astrotech, workers prepare the Dawn spacecraft before test deploying its large solar panels on one side. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. Dawn is scheduled to launch June 30 aboard a Delta II rocket from Launch Complex 17-B at Cape Canaveral Air Force Station. Photo credit: NASA/George Shelton

The Potential of AutoClass as an Asteroidal Data Mining Tool

NASA Astrophysics Data System (ADS)

Walker, Matthew; Ziffer, J.; Harvell, T.; Fernandez, Y. R.; Campins, H.

2011-05-01

AutoClass-C, an artificial intelligence program designed to classify large data sets, was developed by NASA to classify stars based upon their infrared colors. Wanting to investigate its ability to classify asteroidal data, we conducted a preliminary test to determine if it could accurately reproduce the Tholen taxonomy using the data from the Eight Color Asteroid Survey (ECAS). For our initial test, we limited ourselves to those asteroids belonging to S, C, or X classes, and to asteroids with a color difference error of less than +/- 0.05 magnitudes. Of those 406 asteroids, AutoClass was able to confidently classify 85%: identifying the remaining asteroids as belonging to more than one class. Of the 346 asteroids that AutoClass classified, all but 3 (<1%) were classified as they had been in the Tholen classification scheme. Inspired by our initial success, we reran AutoClass, this time including IRAS albedos and limiting the asteroids to those that had also been observed and classified in the Bus taxonomy. Of those 258 objects, AutoClass was able to classify 248 with greater than 75% certainty, and ranked albedo, not color, as the most influential factor. Interestingly, AutoClass consistently put P type objects in with the C class (there were 19 P types and 7 X types mixed in with the other 154 C types), and omitted P types from the group associated with the other X types (which had only one rogue B type in with its other 49 X-types). Autoclass classified the remaining classes with a high accuracy: placing one A and one CU type in with an otherwise perfect S group; placing three P type and one T type in an otherwise perfect D group; and placing the four remaining asteroids (V, A, R, and Q) into a class together.

A Spectroscopic and Mineralogical Study of Multiple Asteroid Systems

NASA Astrophysics Data System (ADS)

Lindsay, Sean S.; Emery, J. P.; Marchis, F.; Enriquez, J.; Assafin, M.

2013-10-01

There are currently ~200 identified multiple asteroid systems (MASs). These systems display a large diversity in heliocentric distance, size/mass ratio, system angular momentum, mutual orbital parameters, and taxonomic class. These characteristics are simplified under the nomenclature of Descamps and Marchis (2008), which divides MASs into four types: Type-1 - large asteroids with small satellites; Type-2 - similar size double asteroids; Type-3 - small asynchronous systems; and Type-4 - contact-binary asteroids. The large MAS diversity suggests multiple formation mechanisms are required to understand their origins. There are currently three broad formation scenarios: 1) ejecta from impacts; 2) catastrophic disruption followed by rotational fission; and 3) tidal disruption. The taxonomic class and mineralogy of the MASs coupled with the average density and system angular momentum provide a potential means to discriminate between proposed formation mechanisms. We present visible and near-infrared (NIR) spectra spanning 0.45 - 2.45 μm for 23 Main Belt MASs. The data were primarily obtained using the Southern Astrophysical Research Telescope (SOAR) Goodman High Throughput Spectrograph (August 2011 - July 2012) for the visible data and the InfraRed Telescope Facility (IRTF) SpeX Spectrograph (August 2008 - May 2013) for the IR data. Our data were supplemented using previously published data when necessary. The asteroids' Bus-DeMeo taxonomic classes are determined using the MIT SMASS online classification routines. Our sample includes 3 C-types, 1 X-type, 1 K-type, 1 L-type, 4 V-types, 10 S-types, 2 Sq- or Q-types, and 1 ambiguous classification. We calculate the 1- and 2-μm band centers, depths, and areas to determine the pyroxene mineralogy (molar Fs and Wo) of the surfaces using empirically derived equations. The NIR band analysis allows us to determine the S-type subclasses, S(I) - S(VII), which roughly tracks olivine-pyroxene chemistry. A comparison of the orbital parameters, physical parameters (size, density, and angular momentum), collisional family membership, and taxonomy is presented in an effort to find correlations, which may give insights to how these MASs formation mechanisms.

Exploring the collisional evolution of the asteroid belt

NASA Astrophysics Data System (ADS)

Bottke, W.; Broz, M.; O'Brien, D.; Campo Bagatin, A.; Morbidelli, A.

2014-07-01

The asteroid belt is a remnant of planet-formation processes. By modeling its collisional and dynamical history, and linking the results to constraints, we can probe how the planets and small bodies formed and evolved. Some key model constraints are: (i) The wavy shape of the main-belt size distribution (SFD), with inflection points near 100-km, 10--20-km, 1 to a few km, and ˜0.1-km diameter; (ii) The number of asteroid families created by the catastrophic breakup of large asteroid bodies over the last ˜ 4 Gy, with the number of disrupted D > 100 km bodies as small as ˜20 or as large as 60; (iii) the flux of small asteroids derived from the main belt that have struck the Moon over the last 3.5 Ga --- crater SFDs on lunar terrains with known ages suggest the D < 0.1 km projectile population has not varied appreciably over this interval; (iv) Vesta has an intact basaltic crust with two very large basins, but only two, on its surface. Fits to these parameters allow us to predict the shape of the initial main-belt SFD after accretion and the approximate asteroid disruption scaling law, with the latter consistent with numerical hydrocode simulations. Overall, we find that the asteroid belt probably experienced the equivalent of ˜6--10 Gy of comminution over its history. This value may seem strange, considering the solar system is only 4.56 Gy old. One way to interpret it is that the main belt once had more mass that was eliminated by early dynamical processes between 4--4.56 Ga. This would allow for more early grinding, and it would suggest the main belt's wavy-shaped SFD is a ''fossil'' from a more violent early epoch. Simulations suggest that most D > 100 km bodies have been significantly battered, but only a fraction have been catastrophically disrupted. Conversely, most small asteroids today are byproducts of fragmentation events. These results are consistent with growing evidence that most of the prominent meteorite classes were produced by young asteroid families. The big question is how to use what we know to determine the main belt's original size and state. This work is ongoing, but dynamical models hint at many possibilities, including both the late arrival and late removal of material from the main belt. In addition, no model has yet properly accounted for the bombardment of the primordial main belt by leftover planetesimals in the terrestrial planet region. It is also possible to use additional constraints, such as the apparent paucity of Vesta-like or V-type objects in the outer main belt, to argue that the primordial main belt at best only 3--4 its current mass at its start. In our talk, we will review what is known, what has been predicted, and some intriguing directions for the future.

Radar Movie of Asteroid 2011 UW158

NASA Image and Video Library

2015-07-23

Scientists using two giant, Earth-based radio telescopes bounced radar signals off passing asteroid 2011 UW158 to create images for this animation showing the rocky body's fast rotation. The passing asteroid made its closest approach to Earth on July 19, 2015 at 7:37 a.m. PST (4:37 a.m. EST) at a distance of about 1.5 million miles (2.4 million kilometers, or 6 times the distance from Earth to the moon). The close proximity during the pass made 2011 UW158 one of the best asteroid flybys of 2015 for imaging from Earth using radar. The radar images reveal that the shape of the asteroid is extremely irregular and quite elongated. Prominent parallel, linear features run along the length of the object that cause a large increase in brightness of the radar images as they rotate into view. Scientists note that the asteroid appears to be fairly unusual. Its fast rotation suggests the object has greater mechanical strength than other asteroids its size. A fast-rotating asteroid with lower mechanical strength would tend to split apart. To obtain the views, researchers paired the 230-foot- (70-meter-) wide Deep Space Network antenna at Goldstone, California, in concert with the National Radio Astronomy Observatory's 330-foot (100-meter) Green Bank Telescope. Using this technique, the Goldstone antenna beams a radar signal at an asteroid and Green Bank receives the reflections. The technique, referred to as a bi-static observation, dramatically improves the amount of detail that can be seen in radar images. The new views obtained with the technique show features as small as about 24 feet (7.5 meters) wide. The 171 individual images used in the movie were generated from data collected on July 18. They show the asteroid is approximately 2000 by 1000 feet (600 by 300 meters) across. The observations also confirm earlier estimates by astronomers that the asteroid rotates quickly, completing one spin in just over half an hour. The movie spans a period of about an hour and 45 minutes. The trajectory of asteroid 2011 UW158 is well understood. This flyby was the closest approach the asteroid will make to Earth for at least the next 93 years. Asteroid 2011 UW158 was discovered on October 25, 2011, by the PanSTARRS 1 telescope, located on the summit of Haleakala on Maui, Hawaii. Managed by the University of Hawaii, the PanSTARRS survey receives NASA funding. Radar is a powerful technique for studying an asteroid's size, shape, rotation state, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than if radar observations weren't available. http://photojournal.jpl.nasa.gov/catalog/PIA19644

Initial Orbit Determination Based on Propagation of Admissible Regions with Differential Algebra

DTIC Science & Technology

2017-01-19

Asteroid close encounter characterization using differential algebra: the case of aphophis. Celestial Mechanics and Dynamical Astronomy , 107(4), 2010...Mechanics and Dynamical Astronomy , 112 (3):331–352, 2012. ISSN 09232958. doi: 10.1007/s10569-012-9400-8. Roberto Armellin, Pierluigi Di Lizia, and Renato... Astronomy , 90(1-2):59–87, 2004. ISSN 09232958. doi: 10.1007/s10569-004-6593-5. 50 DISTRIBUTION A. Approved for public release: distribution unlimited

Nature and evolution of the meteorite parent bodies: Evidence from petrology and metallurgy

NASA Technical Reports Server (NTRS)

Wood, J. A.

1978-01-01

The physical as well as chemical properties of the meteorite parent bodies are reviewed and it is concluded that many differentiated meteorites were likely formed in asteroidal-sized parents. A new model is developed for the formation of pallasites at the interface between an iron core and olivine mantle in differentiated bodies only about 10 km in diameter, which are later incorporated into a second generation of larger (100 km) parent bodies.

First images of asteroid 243 Ida

USGS Publications Warehouse

Belton, M.J.S.; Chapman, C.R.; Veverka, J.; Klaasen, K.P.; Harch, A.; Greeley, R.; Greenberg, R.; Head, J. W.; McEwen, A.; Morrison, D.; Thomas, P.C.; Davies, M.E.; Carr, M.H.; Neukum, G.; Fanale, F.P.; Davis, D.R.; Anger, C.; Gierasch, P.J.; Ingersoll, A.P.; Pilcher, C.B.

1994-01-01

The first images of the asteroid 243 Ida from Galileo show an irregular object measuring 56 kilometers by 24 kilometers by 21 kilometers. Its surface is rich in geologic features, including systems of grooves, blocks, chutes, albedo features, crater chains, and a full range of crater morphologies. The largest blocks may be distributed nonuniformly across the surface; lineaments and dark-floored craters also have preferential locations. Ida is interpreted to have a substantial regolith. The high crater density and size-frequency distribution (-3 differential power-law index) indicate a surface in equilibrium with saturated cratering. A minimum model crater age for Ida - and therefore for the Koronis family to which Ida belongs - is estimated at 1 billion years, older than expected.

A Delta-V map of the known Main Belt Asteroids

NASA Astrophysics Data System (ADS)

Taylor, Anthony; McDowell, Jonathan C.; Elvis, Martin

2018-05-01

With the lowered costs of rocket technology and the commercialization of the space industry, asteroid mining is becoming both feasible and potentially profitable. Although the first targets for mining will be the most accessible near Earth objects (NEOs), the Main Belt contains 106 times more material by mass. The large scale expansion of this new asteroid mining industry is contingent on being able to rendezvous with Main Belt asteroids (MBAs), and so on the velocity change required of mining spacecraft (delta-v). This paper develops two different flight burn schemes, both starting from Low Earth Orbit (LEO) and ending with a successful MBA rendezvous. These methods are then applied to the ∼700,000 asteroids in the Minor Planet Center (MPC) database with well-determined orbits to find low delta-v mining targets among the MBAs. There are 3986 potential MBA targets with a delta-v < 8 km s-1 , but the distribution is steep and reduces to just 4 with delta-v < 7 km s-1. The two burn methods are compared and the orbital parameters of low delta-v MBAs are explored.

Global Statistics of Bolides in the Terrestrial Atmosphere

NASA Astrophysics Data System (ADS)

Chernogor, L. F.; Shevelyov, M. B.

2017-06-01

Purpose: Evaluation and analysis of distribution of the number of meteoroid (mini asteroid) falls as a function of glow energy, velocity, the region of maximum glow altitude, and geographic coordinates. Design/methodology/approach: The satellite database on the glow of 693 mini asteroids, which were decelerated in the terrestrial atmosphere, has been used for evaluating basic meteoroid statistics. Findings: A rapid decrease in the number of asteroids with increasing of their glow energy is confirmed. The average speed of the celestial bodies is equal to about 17.9 km/s. The altitude of maximum glow most often equals to 30-40 km. The distribution law for a number of meteoroids entering the terrestrial atmosphere in longitude and latitude (after excluding the component in latitudinal dependence due to the geometry) is approximately uniform. Conclusions: Using a large enough database of measurements, the meteoroid (mini asteroid) statistics has been evaluated.

Remarkable modification of light curves for shadowing effects on irregular surfaces - The case of the asteroid 37 Fides

NASA Technical Reports Server (NTRS)

Zappala, V.; Di Martino, M.; Scaltriti, F.; Burchi, R.; Milano, L.; Young, J. W.; Wahlgren, G.; Pavlovski, K.

1983-01-01

Photometric observations of the asteroid 37 Fides carried out at four observatories are reported. The data were taken at phase angles ranging from approximately 2-23 deg. A composite of the light curves obtained revealed that, considering a period of 7.33 hr, the full cycle light curve exhibits one maximum and one minimum. An increase in brightness was observed following a primary minimum, a factor that indicated the cyclical appearance and disappearance of a large topographical feature. It is concluded that the 7.33 hr period is the rotational speed of the asteroid, in contrast with a previously held 14.66 hr rotational period. The method is concluded useful for identifying rotational periods of asteroids when only partial light curve data from different sources is available, and when the projections can be checked observationally.

Solar Wind Plasma Interaction with Asteroid 16 Psyche: Implication for Formation Theories

NASA Astrophysics Data System (ADS)

Fatemi, Shahab; Poppe, Andrew R.

2018-01-01

The asteroid 16 Psyche is a primitive metal-rich asteroid that has not yet been visited by spacecraft. Based on remote observations, Psyche is most likely composed of iron and nickel metal; however, the history of its formation and solidification is still unknown. If Psyche is a remnant core of a differentiated planetesimal exposed by collisions, it opens a unique window toward understanding the cores of the terrestrial bodies, including the Earth and Mercury. If not, it is perhaps a reaccreted rubble pile that has never melted. In the former case, Psyche may have a remanent, dipolar magnetic field; in the latter case, Psyche may have no intrinsic field, but nevertheless would be a conductive object in the solar wind. We use Advanced Modeling Infrastructure in Space Simulation (AMITIS), a three-dimensional GPU-based hybrid model of plasma that self-consistently couples the interior electromagnetic response of Psyche (i.e., magnetic diffusion) to its ambient plasma environment in order to quantify the different interactions under these two cases. The model results provide estimates for the electromagnetic environment of Psyche, showing that the magnetized case and the conductive case present very different signatures in the solar wind. These results have implications for an accurate interpretation of magnetic field observations by NASA's Discovery mission (Psyche mission) to the asteroid 16 Psyche.

Limits to Ice on Asteroids (24) Themis and (65) Cybele

NASA Astrophysics Data System (ADS)

Jewitt, David; Guilbert-Lepoutre, Aurelie

2012-01-01

We present optical spectra of (24) Themis and (65) Cybele, two large main-belt asteroids on which exposed water ice has recently been reported. No emission lines, expected from resonance fluorescence in gas sublimated from the ice, were detected. Derived limits to the production rates of water are lsim400 kg s-1 (5σ) for each object, assuming a cometary H2O/CN ratio. We rule out models in which a large fraction of the surface is occupied by high-albedo ("fresh") water ice because the measured albedos of Themis and Cybele are low (~0.05-0.07). We also rule out models in which a large fraction of the surface is occupied by low-albedo ("dirty") water ice because dirty ice would be warm and would sublimate strongly enough for gaseous products to have been detected. If ice exists on these bodies it must be relatively clean (albedo gsim0.3) and confined to a fraction of the Earth-facing surface lsim10%. By analogy with impacted asteroid (596) Scheila, we propose an impact excavation scenario, in which 10 m scale projectiles have exposed buried ice. If the ice is even more reflective (albedo gsim0.6), then the timescale for sublimation of an optically thick layer can rival the ~103 yr interval between impacts with bodies this size. In this sense, exposure by impact may be a quasi steady-state feature of ice-containing asteroids at 3 AU.

Long-term influence of asteroids on planet longitudes and chaotic dynamics of the solar system

NASA Astrophysics Data System (ADS)

Woillez, E.; Bouchet, F.

2017-11-01

Over timescales much longer than an orbital period, the solar system exhibits large-scale chaotic behavior and can thus be viewed as a stochastic dynamical system. The aim of the present paper is to compare different sources of stochasticity in the solar system. More precisely we studied the importance of the long term influence of asteroids on the chaotic dynamics of the solar system. We show that the effects of asteroids on planets is similar to a white noise process, when those effects are considered on a timescale much larger than the correlation time τϕ ≃ 104 yr of asteroid trajectories. We computed the timescale τe after which the effects of the stochastic evolution of the asteroids lead to a loss of information for the initial conditions of the perturbed Laplace-Lagrange secular dynamics. The order of magnitude of this timescale is precisely determined by theoretical argument, and we find that τe ≃ 104 Myr. Although comparable to the full main-sequence lifetime of the sun, this timescale is considerably longer than the Lyapunov time τI ≃ 10 Myr of the solar system without asteroids. This shows that the external sources of chaos arise as a small perturbation in the stochastic secular behavior of the solar system, rather due to intrinsic chaos.

SPH/N-body simulations of small (D = 10 km) monolithic asteroidal breakups and improved parametric relations for Monte-Carlo collisional models

NASA Astrophysics Data System (ADS)

Ševecek, Pavel; Broz, Miroslav; Nesvorny, David; Durda, Daniel D.; Asphaug, Erik; Walsh, Kevin J.; Richardson, Derek C.

2016-10-01

Detailed models of asteroid collisions can yield important constrains for the evolution of the Main Asteroid Belt, but the respective parameter space is large and often unexplored. We thus performed a new set of simulations of asteroidal breakups, i.e. fragmentations of intact targets, subsequent gravitational reaccumulation and formation of small asteroid families, focusing on parent bodies with diameters D = 10 km.Simulations were performed with a smoothed-particle hydrodynamics (SPH) code (Benz & Asphaug 1994), combined with an efficient N-body integrator (Richardson et al. 2000). We assumed a number of projectile sizes, impact velocities and impact angles. The rheology used in the physical model does not include friction nor crushing; this allows for a direct comparison to results of Durda et al. (2007). Resulting size-frequency distributions are significantly different from scaled-down simulations with D = 100 km monolithic targets, although they may be even more different for pre-shattered targets.We derive new parametric relations describing fragment distributions, suitable for Monte-Carlo collisional models. We also characterize velocity fields and angular distributions of fragments, which can be used as initial conditions in N-body simulations of small asteroid families. Finally, we discuss various uncertainties related to SPH simulations.

Spectrophotometric Characterisation of the Trojan Asteroids (624) Hektor et (911) Agamemnon

NASA Astrophysics Data System (ADS)

Doressoundiram, A.; Bott, N.; Perna, D.

2016-12-01

We obtained spectrophotometric observations of (624) Hektor and (911) Agamemnon, two large Trojan asteroids in order to (1) better understand the composition of their surface by means of their visible and infrared spectra, and (2) eventually detect a possible weak cometary activity by means of their images in the visible. We had data at different rotational phases to probe surface variegations. We found that the visible and infrared spectra are very similar to each other. That indicates a relatively homogenous surface for the asteroids, but it does not exclude the presence of localized inhomogeneities. Computation of a high spectral slope confirmed their D-type asteroids classification. No aqueous alteration absorption band was found in the visible spectra of both studied Trojan asteroids. This can be interpreted in two differents ways: either no liquid water flowed on their surface, or the surface is covered with a crust that mask the presence of hydrated minerals. We use a radiative transfer model to investigate the surface composition of these icy and primitive outer solar system bodies. We suggest models composed of mixtures of organic compounds, minerals and lower limits for water ice. Lastly, the analysis of the images of both Trojan asteroids did not reveal any cometary activity.

The Impossible Siblings

NASA Astrophysics Data System (ADS)

2007-03-01

Unique Data Collected on Double Asteroid Antiope Combining precise observations obtained by ESO's Very Large Telescope with those gathered by a network of smaller telescopes, astronomers have described in unprecedented detail the double asteroid Antiope, which is shown to be a pair of rubble-pile chunks of material, of about the same size, whirling around one another in a perpetual pas de deux. The two components are egg-shaped despite their very small sizes. The asteroid (90) Antiope was discovered in 1866 by Robert Luther from Dusseldorf, Germany. The 90th asteroid ever discovered, its name comes from Greek mythology. In 2000, William Merline and his collaborators found that the asteroid was composed of two similarly-sized components, making it a truly 'double' asteroid, one of the very first of this kind in the main belt of asteroids that lies between the orbits of Mars and Jupiter. ESO PR Photo 18a/07 ESO PR Photo 18a/07 The Antiope Doublet "The way double asteroids have formed in the main belt is still unclear," says Pascal Descamps, from the Paris Observatory and lead-author of the paper presenting the new results. "The Antiope system provides us with a unique opportunity to know more about this class of objects and we decided to study it in detail," he adds. Descamps, with colleague Franck Marchis from the University of California at Berkeley, USA, therefore initiated a large campaign of observations for more than two and a half years starting in January 2003. They used the NACO instrument on ESO's Very Large Telescope at Cerro Paranal for the larger part, while using one of the Keck telescopes for some additional observations in 2005. NACO allows the astronomers to perform adaptive optics observations, providing images that are mostly free from the blurring effect of the atmosphere. With these, it was always possible to separate clearly the two components of the Antiope system, thereby obtaining a large set of very precise measurements of their positions. "With this unique set of data, we could determine with utmost precision the course of the two pieces of cosmic rock as they turn around each other," says Marchis. "We found that the two objects are separated by 171 km, and that they perform their celestial dance in 16.5 hours. In fact, we now know this orbital period with a precision of better than half a second." With the orbit determined, the astronomers could derive the total mass of the system: 828 millions million tons, and found the two objects were rotating around their own axes at the same speed as they orbit each other. Thus, in the same way than the Moon does to the Earth, they always present to each other the same side (something astronomers call 'tidal locking'). Moreover, the two asteroids rotate in the same plane as they orbit each other. ESO PR Photo 18b/07 ESO PR Photo 18b/07 Double Asteroid (NACO/VLT) The adaptive optics observations could, however, never resolve the shape of the individual components as they are too small. "But with the new orbit, we could precisely predict that from the end of May to the end of November 2005 the system would present eclipses and occultations," says Marchis. "Such 'mutual events' are unique opportunities to learn a great deal about this double asteroid." The astronomers invited observers around the world to turn their eyes on the asteroid pair to measure the drops in brightness resulting from the predicted events. Over the six-month period, amateurs and professionals from as far afield as Brazil, Chile, France, Réunion Island, South Africa, and the USA, observed repeated occultations as well as shadows passing over one of the pair. With this new data, Descamps, Marchis and their team, found enough evidence that the two mountain-like chunks of material forming the Antiope system have the shape of ellipsoids, that is, slightly deformed spheres, almost similar in size: 93.0 x 87.0 x 83.6 km and 89.4 x 82.8 x 79.6 km, respectively. Each asteroid in the pair is thus roughly the size of a large city. Perhaps the most astonishing result is the fact that the two components have a shape close to the one predicted by the French scientist Edouard Roche in 1849 for self-gravitating, rotating fluid objects orbiting each other and tidally locked. Of course, the asteroids are not gaseous nor liquids, they are solids, but their internal structure must be so loose that their bodies can readjust themselves due to the gravitational influence of the companion. The scientists were also able to derive the density of the objects, only a quarter higher than the density of water. This means the asteroids are very porous, having 30 percent empty space, and thereby suggesting a rubble-pile structure. This structure could explain why it was easier for the asteroids to reach equilibrium shapes, while being so small. "Despite this intensive study, the origin of this unique doublet still remains a mystery," says Descamps. "The formation of such a large double system is an improbable event and represents a formidable challenge to theory. One possibility is that a parent body was spun up so much that it took the shape of an apple core, then split into two similar-sized pieces." More Information This work is reported in a paper published in the journal Icarus ("Figure of the double Asteroid 90 Antiope from adaptive optics and lightcurve observations", by P. Descamps et al.). The team is composed of P. Descamps, F. Marchis, F. Vachier, F. Colas, J. Berthier, D. Hestroffer, R. Viera-Martins, and M. Birlan (Observatoire de Paris, France), T. Michalowski and M. Polinska (Adam Mickiewicz University, Poznan, Poland), M. Assafin (Observatorio do Valongo/UFRJ, Brazil), P.B. Dunckel (Rattlesnake Creek Observatory, USA), W. Pych (Nicolaus Copernicus Astronomical Center, Warsaw, Poland), J.-P. Teng-Chuen-Yu, A. Peyrot, B. Payet, J. Dorseuil, Y. Léonie, and T. Dijoux (Makes Observatory, Réunion Island, France). F. Marchis is also at the University of California at Berkeley, USA.

Pristine Igneous Rocks and the Genesis of Early Planetary Crusts

NASA Technical Reports Server (NTRS)

Warren, Paul H.; Lindstrom, David (Technical Monitor)

2002-01-01

Our studies are highly interdisciplinary, but are focused on the processes and products of early planetary and asteroidal differentiation, especially the genesis of the ancient lunar crust. The compositional diversity that we explore is the residue of process diversity, which has strong relevance for comparative planetology.

Asteroid Satellites

NASA Astrophysics Data System (ADS)

Merline, W. J.

2001-11-01

Discovery and study of small satellites of asteroids or double asteroids can yield valuable information about the intrinsic properties of asteroids themselves and about their history and evolution. Determination of the orbits of these moons can provide precise masses of the primaries, and hence reliable estimates of the fundamental property of bulk density. This reveals much about the composition and structure of the primary and will allow us to make comparisons between, for example, asteroid taxonomic type and our inventory of meteorites. The nature and prevalence of these systems will also give clues as to the collisional environment in which they formed, and have further implications for the role of collisions in shaping our solar system. A decade ago, binary asteroids were more of a theoretical curiosity. In 1993, the Galileo spacecraft allowed the first undeniable detection of an asteroid moon, with the discovery of Dactyl, a small moon of Ida. Since that time, and particularly in the last year, the number of known binaries has risen dramatically. Previously odd-shaped and lobate near-Earth asteroids, observed by radar, have given way to signatures indicating, almost certainly, that at least four NEAs are binary systems. The tell-tale lightcurves of several other NEAs reveal a high likelihood of being double. Indications are that among the NEAs, there may be a binary frequency of several tens of percent. Among the main-belt asteroids, we now know of 6 confirmed binary systems, although their overall frequency is likely to be low, perhaps a few percent. The detections have largely come about because of significant advances in adaptive optics systems on large telescopes, which can now reduce the blurring of the Earth's atmosphere to compete with the spatial resolution of space-based imaging (which itself, via HST, is now contributing valuable observations). Most of these binary systems have similarities, but there are important exceptions. Searches among other dynamical populations such as the Trojans and KBOs are also proving fruitful. Similarities and differences among the detected systems are thus revealing important clues about the possible formation mechanisms. There are several theories seeking to explain the origin of these binary systems, all of them involving collisions of one type or another, either physical or gravitational. It is likely that several of the mechanisms will be required to explain the observations. Now that we have reliable techniques for detection, we have been rewarded with many examples of systems for study. This has in turn spurred new theoretical thinking and numerical simulations, the techniques for which have also improved substantially in recent years.

The DLR AsteroidFinder for NEOs

NASA Astrophysics Data System (ADS)

Mottola, Stefano; Kuehrt, Ekkehard; Michaelis, Harald; Hoffmann, Harald; Spietz, Peter; Jansen, Frank; Thimo Grundmann, Jan; Hahn, Gerhard; Montenegro, Sergio; Findlay, Ross; Boerner, Anko; Messina, Gabriele; Behnke, Thomas; Tschentscher, Matthias; Scheibe, Karsten; Mertens, Volker; Heidecke, Ansgar

Potential Earth-impacting asteroids that spend most of their time interior to Earth's orbit are extremely difficult to be observed from the ground and remain largely undetected. Firstly, they are mostly located at small solar elongations, where the sky brightness and their faintness due to the large phase angle prevents their discovery. Secondly, these objects tend to have very long synodic orbital periods, which makes observation opportunities rare and impact warning times short. Because of these limitations, even the advent of next generation ground-based asteroid surveys is not likely to radically improve the situation (Veres et al. Icarus 203, p472, 2009). On the other hand, a small satellite with a suitable design can observe close to the Sun and detect these objects efficiently against a dark sky background. For this reason, DLR, the German Aerospace Center, has selected AsteroidFinder as the first experiment to be launched under its new compact satellite national program. The primary goal of the mission is to detect and characterize Near Earth Objects (NEOs), with a particular focus on the population of objects completely contained within Earth's orbit (IEOs or Inner Earth Objects). Current dynamical models predict the existence of more than 1000 such objects down to a size of 100m, of which, due to the abovementioned observation difficulties, only 10 have been discovered to date. Benefitting from the vantage point of a Low Earth Orbit (LEO), AsteroidFinder makes use of a small optical telescope to scan those regions of the sky that are close to the Sun, and therefore beyond the reach of ground based observatories. By estimating the population, the size and the orbital distribution of IEOs, AsteroidFinder will contribute to our knowledge of the inner Solar System, and to the assessment of the impact hazard for the Earth. A secondary goal of the mission is to demonstrate techniques that enable the space-based detection of space debris in the cm size range. With these mission goals, AsteroidFinder also addresses the programmatic goals of the ESA SSA initiative, both for the NEO and space debris domain. The AsteroidFinder mission is based on the DLR SSB standard platform, it employs a 400-cm2 clear-aperture, off-axis design telescope and an array of new technology CCDs. AsteroidFinder, which is presently in its Phase-B development stage, is planned to launch in 2013 with a one-year nominal mission duration and the possibility of an extension.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terai, Tsuyoshi; Takahashi, Jun; Itoh, Yoichi, E-mail: tsuyoshi.terai@nao.ac.jp

Main-belt asteroids have been continuously colliding with one another since they were formed. Their size distribution is primarily determined by the size dependence of asteroid strength against catastrophic impacts. The strength scaling law as a function of body size could depend on collision velocity, but the relationship remains unknown, especially under hypervelocity collisions comparable to 10 km s{sup –1}. We present a wide-field imaging survey at an ecliptic latitude of about 25° for investigating the size distribution of small main-belt asteroids that have highly inclined orbits. The analysis technique allowing for efficient asteroid detections and high-accuracy photometric measurements provides sufficientmore » sample data to estimate the size distribution of sub-kilometer asteroids with inclinations larger than 14°. The best-fit power-law slopes of the cumulative size distribution are 1.25 ± 0.03 in the diameter range of 0.6-1.0 km and 1.84 ± 0.27 in 1.0-3.0 km. We provide a simple size distribution model that takes into consideration the oscillations of the power-law slope due to the transition from the gravity-scaled regime to the strength-scaled regime. We find that the high-inclination population has a shallow slope of the primary components of the size distribution compared to the low-inclination populations. The asteroid population exposed to hypervelocity impacts undergoes collisional processes where large bodies have a higher disruptive strength and longer lifespan relative to tiny bodies than the ecliptic asteroids.« less

Consequences of impacts of small asteroids and comets with Earth

NASA Technical Reports Server (NTRS)

Hills, J. G.

1994-01-01

The fragmentation of a small asteroid in the atmosphere greatly increases its cross sections for aerodynamic braking and energy dissipation. At a typical impact velocity of 22 km/s, the atmosphere absorbs more than half the kinetic energy of stony meteoroids with diameters, D(sub m), less than 220 m and iron meteoroids with D(sub m) less than 80 m. The corresponding diameter for comets with impact velocity 50 km/s is D(sub m) less than 1600 m. Most of the atmospheric energy dissipation occurs in a fraction of a scale height, so large meteors appear to 'explode' or 'flare' at the end of their visible paths. This dissipation of energy in the atmosphere protects the earth from direct impact damage (e.g., craters), but it produces a blast wave that can do considerable damage. The area of destruction around the impact point in which the over-pressure in the blast wave exceeds 4 lb/sq in = 2.8 x 10(exp 5) dynes/cu cm, which is enough to knock over trees and destroy buildings, increases rapidly from zero for chondritic meteoroids less than 56 m in diameter (15 megatons) to about 200 sq km for those 80 m in diameter (48 megatons); the probable diameter of the tunguska impactor of 1908 is about 80 m. Crater formation and earthquakes are not significant in land impacts by stony asteroids less than about 200 m in diameter because of the air protection. A tsunami is probably the most devastating type of damage for asteroids 200 m to 1 km in diameter. An impact by an asteroid this size anywhere in the Atlantic would devastate coastal areas on both sides of the ocean. An asteroid a few kilometers across would produce a tsunami that would reach the foothills of the Appalachian Mountains in the upper half of the East Coast of the United States. Most of Florida is protected from a tsunami by the gradual slope of the ocean off its coast, which causes most of the tsunami energy to be reflected back into the Atlantic. The atmosphere plume produced by asteroids with diameters exceeding about 120 m cannot be contained by the atmosphere, so this bubble of high-temperature gas forms a new layer on top of the atmosphere. The dust entrapped in this hot gas is likely to have optical depths exceeding tau = 10 for asteroids with diameters exceeding about 0.5 to 1 km. The optical flux from asteroids 60 m or more in diameter is enough to ignite pine forests. However, the blast wave from an impacting asteroid goes beyond the radius in which the fire starts. The blast wave tends to blow out the fire, so it is likely that the impact will char the forest, as at Tunguska, but the impact will not produce a sustained fire. Because comets dissipate their energy much higher in the atmosphere than asteroids, they illuminate a much larger region and their blast wave is weaker. So they are much more effective in producing large fires. This suggests that the KT impactor was a comet rather than an asteroid.

The Death of the Dinosaurs: 27 Years Later (LBNL Summer Lecture Series)

ScienceCinema

Muller, Rich [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Dept. of Physics

2017-12-15

Summer Lecture Series 2006: Rich Muller, a Berkeley Lab physicist, discusses Nobel laureate Luis Alvarez and colleagues' 1979 discovery that an asteroid impact killed the dinosaurs. He also discusses what scientists have learned in the subsequent 27 years. Alvarez's team detected unusual amounts of iridium in sedimentary layers. They attributed the excess iridium to an impact from a large asteroid. His talk was presented June 30, 2006.

The large-scale structure of the asteroid belt

NASA Technical Reports Server (NTRS)

Zellner, B.; Thirunagari, A.; Bender, D.

1985-01-01

The distributions of 2888 numbered minor planets over orbital inclination, eccentricity, and semimajor axis are examined, and 19 zones believed to adequately isolate the selection biases in survey programs of the physical properties of minor planets are defined. Six numbered asteroids have exceptional orbits and fall into no zone. Attention is called to rather sharp upper limits, which become increasingly stringent at larger heliocentric distances, on orbital inclinations and eccentricity.

KSC-07pd1264

NASA Image and Video Library

2007-05-23

KENNEDY SPACE CENTER, FLA. -- At Astrotech, workers get ready to test deploy the large solar array panels on one side of the Dawn spacecraft. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. Dawn is scheduled to launch June 30 aboard a Delta II rocket from Launch Complex 17-B at Cape Canaveral Air Force Station. Photo credit: NASA/George Shelton

The Death of the Dinosaurs: 27 Years Later (LBNL Summer Lecture Series)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muller, Rich

2006-06-30

Summer Lecture Series 2006: Rich Muller, a Berkeley Lab physicist, discusses Nobel laureate Luis Alvarez and colleagues' 1979 discovery that an asteroid impact killed the dinosaurs. He also discusses what scientists have learned in the subsequent 27 years. Alvarez's team detected unusual amounts of iridium in sedimentary layers. They attributed the excess iridium to an impact from a large asteroid. His talk was presented June 30, 2006.

Space debris, asteroids and satellite orbits; Proceedings of the Fourth and Thirteenth Workshops, Graz, Austria, June 25-July 7, 1984

NASA Technical Reports Server (NTRS)

Kessler, D. J.; Gruen, E.; Sehnal, L.

1985-01-01

The workshops covered a variety of topics relevant to the identification, characterization and monitoring of near-earth solar system debris. Attention was given to man-made and naturally occurring microparticles, their hazards to present and future spacecraft, and ground- and space-based techniques for tracking both large and small debris. The studies are extended to solid fuel particulates in circular space. Asteroid rendezvous missions are discussed, including propulsion and instrumentation options, the possibility of encountering asteroids during Hohman transfer flights to Venus and/or Mars, and the benefits of multiple encounters by one spacecraft. Finally, equipment and analytical models for generating precise satellite orbits are reviewed.

Ellipsoidal geometry in asteroid thermal models - The standard radiometric model

NASA Technical Reports Server (NTRS)

Brown, R. H.

1985-01-01

The major consequences of ellipsoidal geometry in an othewise standard radiometric model for asteroids are explored. It is shown that for small deviations from spherical shape a spherical model of the same projected area gives a reasonable aproximation to the thermal flux from an ellipsoidal body. It is suggested that large departures from spherical shape require that some correction be made for geometry. Systematic differences in the radii of asteroids derived radiometrically at 10 and 20 microns may result partly from nonspherical geometry. It is also suggested that extrapolations of the rotational variation of thermal flux from a nonspherical body based solely on the change in cross-sectional area are in error.

Nanopaleomagnetism of Meteoritic Fe-Ni: the Potential for Time-Resolved Remanence Records within the Cloudy Zone

NASA Astrophysics Data System (ADS)

Harrison, R. J.; Bryson, J. F.; Kasama, T.; Church, N. S.; Herrero Albillos, J.; Kronast, F.; Ghidini, M.; Redfern, S. A.; van der Laan, G.; Tyliszczak, T.

2013-12-01

Paleomagnetic signals recorded by meteorites provide compelling evidence that the liquid cores of differentiated asteroids generated magnetic dynamo fields. Here we argue that magnetic nanostructures unique to meteoritic Fe-Ni metal are capable of carrying a time-resolved record of asteroid dynamo activity, a prospect that could revolutionise our understanding of the thermochemical conditions of differentiated bodies in the early solar system. Using a combination of high-resolution magnetic imaging techniques (including electron holography, magnetic force microscopy, X-ray photoemission electron microscopy and scanning transmission X-ray microscopy) we reveal the origins of the dramatic changes in magnetic properties that are associated with the transition from kamacite - tetrataenite rim - cloudy zone - plessite, typical of Fe-Ni intergrowths. The cloudy zone is comprised of nanoscale islands of tetrataenite (FeNi) coherently intergrown with a hitherto unobserved soft magnetic phase (Fe3Ni). The tetrataenite island diameter decreases with increasing lateral distance from the tetrataenite rim. Exchange coupling between the hard tetrataenite islands and the soft matrix phase leads to an exchange spring effect that lowers the tetrataenite switching field and causes a systematic variation in microcoercivity throughout the cloudy zone. The cloudy zone displays a complex interlocking magnetic domain pattern caused by uniaxial single domain tetrataenite islands with easy axes distributed along all three of the possible <100> crystallographic orientations. The coarse and intermediate cloudy zones contain a random distribution of all three easy axes. The fine cloudy zone, on the other hand, contains one dominant easy axis direction. This easy axis distribution suggests that strong interaction fields (either magnetic or stress) were present in this region at the time of tetrataenite formation, which likely originated from the neighbouring plessite. The easy axis distribution in the coarse and intermediate cloudy zone indicates a lack of interaction fields present at the time of formation, implying that deviations from randomness could be used to detect the presence of an external (e.g. dynamo) field. Zoned metallic grains within chondritic meteorites originating from the top ~5-10% of a differentiated asteroid may have formed their cloudy zones while the core was generating a dynamo field. In this case, as the cloudy zone formed continuously over a period of 10-100 Ma it had the potential to encode sequential information regarding the dynamo field as the spinodal microstructure developed laterally. Thus the local magnetic structure as a function of position throughout the cloudy zone could relate to the time dependence of an asteroid dynamo field. The experimental and analysis methods presented in this study could, in principle, be used to measure the relative strength (proportion of dominant easy axis) and direction (direction of dominant easy axis) of an asteroid dynamo field over ~100 Ma.

Regolith on Super Fast Rotators

NASA Astrophysics Data System (ADS)

Sanchez Lana, Diego Paul; Scheeres, Daniel J.

2017-10-01

The current understanding of small asteroids in the Solar System is that they are gravitational aggregates held together by gravitational, cohesive and adhesive forces. Results from the Hayabusa mission to Itokawa along with in situ, thermal and radar observations of asteroids have shown that they can be covered in a size distribution of grains that spans from microns to tens of meters. Before the Hayabusa mission, it was generally thought that smaller asteroids would likely be “regolith-free,” due to impact seismic shaking removing the loose covering. Given the regolith-rich surface of that body, it is now an open question whether even smaller bodies, down to a few meters in size, could also retain regolith covering. The question is especially compelling for the small-fast rotators, whose surface centripetal accelerations exceed their gravitational attraction. When the physical theory of cohesion is considered, it becomes possible for small-fast rotators to retain regolith.We use a Soft-Sphere discrete element method (SSDEM) code to simulate a longitudinal slice of a spherical monolith covered by cohesive regolith. The simulations are carried out in the body frame. Tensile strength is varied to span the observed strength of asteroids and spin rate is elevated in small steps until the majority of regolith is removed from the surface. The simulations show that under an increasing spin rate (such as due to the YORP effect), the regolith covering on an otherwise monolithic asteroid is preferentially lost across certain regions of the body. In general, regolith from the mid latitudes is the first to fail at high spin rates. This failure happens either by regolith flowing towards the equator or by detachment of large coherent chunks of material depending on the tensile strength of the regolith. Regolith from the equator region fails next, usually by the detachment of large pieces. Regolith from the poles stays in place unless the spin rates are extremely high. With these results we derive a scaling law that can be used to determine whether observed small asteroids could retain surface regolith of a given size. The implications of this for the interpretation of spectral observations of small asteroids are discussed.

Photometry of Main Belt and Trojan asteroids with K2

NASA Astrophysics Data System (ADS)

Szabó, Gyula; Kiss, Csaba; Pal, Andras; Szabo, Robert

2016-10-01

Due to the failure of the second reaction wheel, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 Mission, the telescope is staring at the plane of the Ecliptic, hence thousands of Solar System bodies cross the K2 fields, usually causing extra noise in the highly accurate photometric data.We could measure the first continuous asteroid light curves, covering several days wthout interruption, that has been unprecedented to date. We studied the K2 superstamps covering the M35 and Neptune/Nereid fields observed in the long cadence (29.4-min sampling) mode. Asteroid light curves are generated by applying elongated apertures. We investigated the photometric precision that the K2 Mission can deliver on moving Solar System bodies, and determined the first uninterrupted optical light curves of main-belt and Trojan asteroids. We use thed Lomb-Scargle method to find periodicities due to rotation.We derived K2 light curves of 924 main-belt asteroids in the M35 field, and 96 in the path of Neptune and Nereid. Due to the faintness of the asteroids and the high density of stars in the M35 field, 4.0% of the asteroids with at least 12 data points show clear periodicities or trend signalling a long rotational period, as opposed to 15.9% in the less crowded Neptune field. We found that the duty cycle of the observations had to reach ˜ 60% in order to successfully recover rotational periods.The derived period-amplitude diagram is consistent to the known distribution of Main Belt asteroids. For Trojan asteroids, the contribution of our 56 objects with newly determined precise period and amplitude is in the order of all previously known asteroids. The comparison with earth-based determinations showed a previous bias toward short periods and has also proven that asteroid periods >20 hour can be unreliable in a few cases because of daylight time and diurnal calibrations. These biases are avoided from the space. We present an unbiased sample of rotation periods and identify a higher rate of slow rotators. We also found multiple periods of large asteroids that has not been observed earlier and still needs explanation.

MULTIBAND OPTICAL OBSERVATION OF THE P/2010 A2 DUST TAIL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Junhan; Ishiguro, Masateru; Hanayama, Hidekazu

2012-02-10

An inner main-belt asteroid, P/2010 A2, was discovered on 2010 January 6. Based on its orbital elements, it is considered that the asteroid belongs to the Flora collisional family, where S-type asteroids are common, while showing a comet-like dust tail. Although analysis of images taken by the Hubble Space Telescope and Rosetta spacecraft suggested that the dust tail resulted from a recent head-on collision between asteroids, an alternative idea of ice sublimation was suggested based on the morphological fitting of ground-based images. Here, we report a multiband observation of P/2010 A2 made on 2010 January with a 105 cm telescopemore » at the Ishigakijima Astronomical Observatory. Three broadband filters, g', R{sub c} , and I{sub c} , were employed for the observation. The unique multiband data reveal that the reflectance spectrum of the P/2010 A2 dust tail resembles that of an Sq-type asteroid or that of ordinary chondrites rather than that of an S-type asteroid. Due to the large error of the measurement, the reflectance spectrum also resembles the spectra of C-type asteroids, even though C-type asteroids are uncommon in the Flora family. The reflectances relative to the g' band (470 nm) are 1.096 {+-} 0.046 at the R{sub c} band (650 nm) and 1.131 {+-} 0.061 at the I{sub c} band (800 nm). We hypothesize that the parent body of P/2010 A2 was originally S-type but was then shattered upon collision into scattering fresh chondritic particles from the interior, thus forming the dust tail.« less

The Chelyabinsk superbolide: a fragment of asteroid 2011 EO40?

NASA Astrophysics Data System (ADS)

de la Fuente Marcos, C.; de la Fuente Marcos, R.

2013-11-01

Bright fireballs or bolides are caused by meteoroids entering the Earth's atmosphere at high speed. Some have a cometary origin, a few may have originated within the Venus-Earth-Mars region as a result of massive impacts in the remote past but a relevant fraction is likely the result of the break-up of asteroids. Disrupted asteroids produce clusters of fragments or asteroid families and meteoroid streams. Linking a bolide to a certain asteroid family may help to understand its origin and pre-impact dynamical evolution. On 2013 February 15, a superbolide was observed in the skies near Chelyabinsk, Russia. Such a meteor could be the result of the decay of an asteroid and here we explore this possibility applying a multistep approach. First, we use available data and Monte Carlo optimization (validated using 2008 TC3 as template) to obtain a robust solution for the pre-impact orbit of the Chelyabinsk impactor (a = 1.62 au, e = 0.53, i = 3.82°, Ω = 326.41° and ω = 109.44°). Then, we use this most probable orbit and numerical analysis to single out candidates for membership in, what we call, the Chelyabinsk asteroid family. Finally, we perform N-body simulations to either confirm or reject any dynamical connection between candidates and impactor. We find reliable statistical evidence on the existence of the Chelyabinsk cluster. It appears to include multiple small asteroids and two relatively large members: 2007 BD7 and 2011 EO40. The most probable parent body for the Chelyabinsk superbolide is 2011 EO40. The orbits of these objects are quite perturbed as they experience close encounters not only with the Earth-Moon system but also with Venus, Mars and Ceres. Under such conditions, the cluster cannot be older than about 20-40 kyr.

Detectability of Boulders on Near-Earth Asteroids

NASA Astrophysics Data System (ADS)

Miller, Kevin J.; Taylor, Patrick A.; Magri, Christopher; Nolan, Michael C.; Howell, Ellen S.

2014-11-01

Boulders are seen on spacecraft images of near-Earth asteroids Eros and Itokawa. Radar images often show bright pixels or groups of pixels that travel consistently across the surface as the object rotates, which may be indicative of similar boulders on other near-Earth asteroids. Examples of these bright pixels were found on radar observations of 2005 YU55 and 2006 VV2 (Benner et al. 2014). Nolan et al. (2013) also identify one large possible boulder on the surface of Bennu, target of the OSIRIS-REx sample return mission. We explore the detectability of boulders by adding synthetic features on asteroid models, and then simulating radar images. These synthetic features were added using BLENDER ver. 2.70, a free open-source 3-D animation suite. Starting with the shape model for Bennu (diameter ~500 m), spherical 'boulders' of 10 m, 20 m, and 40 m diameter were placed at latitudes between 0 and 90 deg. Simulated radar observations of these models indicated that spherical boulders smaller than 10 m may not be visible in observations but that larger ones should be readily seen. Boulders near the sub-Earth point can be hidden in the bright region near the leading edge, but as the asteroid's rotation moves them towards the terminator, they become visible again, with no significant dependence on the latitude of the boulder. These simulations suggest that we should detect large boulders under most circumstances in high-quality radar images, and we have a good estimate of the occurrence of such features on near-Earth objects. Results of these simulations will be presented.

Near-Earth asteroid satellite spins under spin-orbit coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naidu, Shantanu P.; Margot, Jean-Luc

We develop a fourth-order numerical integrator to simulate the coupled spin and orbital motions of two rigid bodies having arbitrary mass distributions under the influence of their mutual gravitational potential. We simulate the dynamics of components in well-characterized binary and triple near-Earth asteroid systems and use surface of section plots to map the possible spin configurations of the satellites. For asynchronous satellites, the analysis reveals large regions of phase space where the spin state of the satellite is chaotic. For synchronous satellites, we show that libration amplitudes can reach detectable values even for moderately elongated shapes. The presence of chaoticmore » regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, explain the observed fraction of asychronous binaries, delay BYORP-type evolution, and extend the lifetime of binaries. The variations in spin rate due to large librations also affect the analysis and interpretation of light curve and radar observations.« less

Space Weathering Radiation Environment of the Inner Solar System from the Virtual Energetic Particle Observatory

NASA Astrophysics Data System (ADS)

Cooper, J. F.; Papitashvili, N. E.

2016-12-01

The surfaces of Mercury, the Moon, the moons of Mars, the asteroids, and other small bodies of the inner solar system have been directly weathered for millions to billions of years by solar wind, energetic particle, and solar ultraviolet irradiation. Surface regolith layers to meters in depth are formed by impacts of smaller bodies and micrometeoroids. Sample return missions to small bodies, such as Osiris-REx to the asteroid Bennu, are intended to recover information on the early history of solar system formation, but must contend with the long-term space weathering effects that perturb the original structure and composition of the affected bodies. Solar wind plasma ions at keV energies penetrate only to sub-micron depths, while more energetic solar & heliospheric particles up to MeV energies reach centimeter depths, and higher-energy galactic cosmic rays to GeV energies fully penetrate through the impact regolith. The weathering effects vary with energy and penetration depth from ion implantation and erosive sputtering at solar wind energies to chemical and structural evolution driven by MeV - GeV particles. The energy versus depth dependence of such effects is weighted by the differential flux distributions of the incident particles as measured near the orbits of the affected bodies over long periods of time. Our Virtual Energetic Particle Observatory (http://vepo.gsfc.nasa.gov/) enables simultaneous access to multiple data sets from 1973 through the present in the form of differential flux spectral plots and downloadable data tables. The most continuous VEPO coverage exists for geospace data sources at 1 AU from the Interplanetary Monitoring Platform 8 (IMP-8), launched in 1973, through the present 1-AU constellation including the ACE, WIND, SOHO, and Stereo-A/B spacecraft. Other mission data, e.g. more occasionally from Pioneer-10/11, Helios-1/2, Voyager-1/2, and Ulysses, extend heliospheric coverage from the orbit of Mercury to that of Mars, the asteroid belt, and beyond. Using data from the VEPO services, we show the time-averaged spectra of protons and helium during 1973 - 2016 from Mercury to Mars. The main contributors on solar cycle time scales at keV to MeV energies are large solar flare and ICME events. These time-averaged spectra can then be used for space weathering models of the inner solar system.

PHYSICAL CHARACTERIZATION OF ∼2 m DIAMETER NEAR-EARTH ASTEROID 2015 TC25: A POSSIBLE BOULDER FROM E-TYPE ASTEROID (44) NYSA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, Vishnu; Sanchez, Juan A.; Bottke, William F.

Small near-Earth asteroids (NEAs) (<20 m) are interesting, because they are progenitors for meteorites in our terrestrial collection. The physical characteristics of these small NEAs are crucial to our understanding of the effectiveness of our atmosphere in filtering low-strength impactors. In the past, the characterization of small NEAs has been a challenge, because of the difficulty in detecting them prior to close Earth flyby. In this study, we physically characterized the 2 m diameter NEA 2015 TC25 using ground-based optical, near-infrared and radar assets during a close flyby of the Earth (distance 128,000 km) in 2015 October 12. Our observationsmore » suggest that its surface composition is similar to aubrites, a rare class of high-albedo differentiated meteorites. Aubrites make up only 0.14% of all known meteorites in our terrestrial meteorite collection. 2015 TC25 is also a very fast rotator with a period of 133 ± 6 s. We combined the spectral and dynamical properties of 2015 TC25 and found the best candidate source body in the inner main belt to be the 70 km diameter E-type asteroid (44) Nysa. We attribute the difference in spectral slope between the two objects to the lack of regolith on the surface of 2015 TC25. Using the albedo of E-type asteroids (50%–60%) we refine the diameter of 2015 TC25 to 2 m, making it one of the smallest NEAs ever to be characterized.« less

The Chronology of Asteroid Accretion, Differentiation, and Secondary Mineralization

NASA Technical Reports Server (NTRS)

Nyquist, L. E.; Kleine, T.; Shih, C.-Y.; Reese, Y. D.

2008-01-01

We evaluate initial (Al-26/Al-27)(sub I), (Mn-53/Mn-55)(sub I), (Hf-182/Hf-180)(sub I), and Pb-207/Pb-206 ages for igneous differentiated meteorites and chondrules from ordinary chondrites for consistency with radioactive decay of the parent nuclides within a common, closed isotopic system, i.e., the early solar nebula. We find that the relative abundances of Al-26, Mn-53, and Hf-182, here denoted by I(Al)(sub CAI, I(Mn)(sub CAI) and I(Hf)(sub CAI), are consistent with decay from common initial values for the bulk solar system. I(Mn)(sub CAI) and I(Hf)(sub CAI) = 9.1+/-1.7 x 10(exp -6) and 1.06+/-0.09 x 10(exp -6) respectively, correspond to the canonical value of I(Al)(sub CAI) = 5.1 x 10(exp -5). I(Hf)(sub CAI) thus determined is consistent with I(Hf)(sub CAI) = 1.003+/-0.045 x 10(exp -6) directly determined in separate work. I(Mn)(sub CAI) is within error of the lowest value directly determined for CAI. We suggest that erratically higher values directly determined for CAI in carbonaceous chondrites reflect proton irradiation of unaccreted CAIs by the early Sun after other asteroids destined for melting by Al-26 decay had already accreted. The Mn-53 incorporated within such asteroids would have been shielded from further "local" spallogenic contributions. The relative abundances of the short-lived nuclides are less consistent with the Pb-207/Pb-206 ages of the corresponding materials with the best consistency being obtained between (Hf-182/Hf-180)(sub I) and Pb-207/Pb-206 ages of angrites. (Hf-182/Hf-180)(sub I) decreases with decreasing Pb-207/Pb-206 ages at the rate expected from the 8.90+/-0.09 Ma half-life of Hf-182. However, the model "CAI age" thus determined, T(sub CAI,Mn-W) = 4568.6+/-0.7 Ma, is older than the commonly accepted directly measured value T(sub CAI) = 4567.l+/-0.2 Ma. I(Al)(sub I), and (Mn-53/Mn-55)(sub I) are less consistent with Pb-207/Pb-206 ages, but determine T(sub CAI, Mn-Cr) = 4568.3+/-0.5 Ma relative to I(AI)(sub CAI)= 5.1 x 10(exp -5) and a Pb-207/Pb-206 age of 4558.6 Ma for the LEW86010 angrite. However. the (Mn-53/Mn-55)(sub I) and Pb-207/Pb-206 ages of "intermediate" age D'Orbigny-clan angrites and Asuka 881394 are inconsistent with radioactive decay from CAI values with a Mn-55 half-life of 3.7+/-0.4 Ma. in spite of consistency between (Mn-53/Mn-55)(sub I) and (Al-26/Al-27)(sub I). Nevertheless, it appears that the Mn-Cr method with I(Mn)(sub CAI) = 9.1+/-1.7 x 10(exp -6) can be used to date primary igneous events and also secondary mineralization on asteroid parent bodies. We summarize ages thus determined for igneous events on differentiated asteroids and for carbonate and fayalite formation on carbonaceous asteroids.

Yarkovsky effect and V-shapes: New method to compute family ages

NASA Astrophysics Data System (ADS)

Spoto, F.; Milani, A.; Cellino, A.; Knezevic, Z.; Novakovic, B.; Paolicchi, P.

2014-07-01

The computation of family ages is a high-priority goal. As a matter of principle, it can be achieved by using V-shape plots for the families old enough to have the Yarkovsky effect dominating the spread of the proper a and large enough for a statistically significant analysis of the shape. By performing an asteroid family classification with a very enlarged dataset, the results are not just ''more families'', but there are interesting qualitative changes. These are due to the large-number statistics, but also to the larger fraction of smaller objects contained in recently numbered asteroids. We are convinced that our method is effective in adding many smaller asteroids to the core families. As a result, we have a large number of families with very well defined V-shapes, thus with a good possibility of age estimation. We have developed our method to compute ages, which we believe is better than those used previously because it is more objective. Since there are no models for error in absolute magnitude H and for albedo, we have also developed a model of the error in the inverse of the diameter and then we have performed a weighted least-squares fit. We report at least 5/6 examples of dynamical families for which the computation of the V-shape is possible. These examples show the presence of different internal structure of the families, e.g., in the dynamical family of (4) Vesta, we have found two collisional families. The main problem in estimating the ages is the calibration. The difficulty in the Yarkovsky calibration, due to the need to extrapolate from near-Earth asteroids (NEAs) with measured da/dt to main-belt asteroids, is in most cases the main limitation to the accuracy of the age estimation. We obtain an age estimation by scaling the results for the NEA for which there is the best Yarkovsky effect determination, namely (101955) Bennu.

A Large Program to derive the shape, cratering history and density of the largest main-belt asteroids

NASA Astrophysics Data System (ADS)

Marchis, Franck; Vernazza, Pierre; Marsset, Michael; Hanus, Josef; Carry, Benoit; Birlan, Mirel; Santana-Ros, Toni; Yang, Bin; and the Large Asteroid Survey with SPHERE (LASS)

2017-10-01

Asteroids in our solar system are metallic, rocky and/or icy objects, ranging in size from a few meters to a few hundreds of kilometers. Whereas we now possess constraints for the surface composition, albedo and rotation rate for all D≥100 km main-belt asteroids, the 3-D shape, the crater distribution, and the density have only been measured for a very limited number of these bodies (N≤10 for the first two). Characterizing these physical properties would allow us to address entirely new questions regarding the earliest stages of planetesimal formation and their subsequent collisional and dynamical evolution.ESO allocated to our program 152 hours of observations over 4 semesters to carry out disk-resolved observations of 38 large (D≥100 km) main-belt asteroids (sampling the four main compositional classes) at high angular-resolution with VLT/SPHERE throughout their rotation in order to derive their 3-D shape, the size distribution of the largest craters, and their density (PI: P. Vernazza). These measurements will allow investigating for the first time and for a modest amount of observing time the following fundamental questions: (A) Does the asteroid belt effectively hosts a large population of small bodies formed in the outer solar system? (B) Was the collisional environment in the inner solar system (at 2-3 AU) more intense than in the outer solar system (≥5AU)? (C) What was the shape of planetesimals at the end of the accretion process?We will present the goals and objectives of our program in the context of NASA 2014 Strategic Plan and the NSF decadal survey "Vision and Voyages" as well as the first observations and results collected with the SPHERE Extreme AO system. A detailed analysis of the shape modeling will be presented by Hanuš et al. in this session.

Asteroid Discovery and Characterization with the Large Synoptic Survey Telescope

NASA Astrophysics Data System (ADS)

Jones, R. Lynne; Jurić, Mario; Ivezić, Željko

2016-01-01

The Large Synoptic Survey Telescope (LSST) will be a ground-based, optical, all-sky, rapid cadence survey project with tremendous potential for discovering and characterizing asteroids. With LSST's large 6.5m diameter primary mirror, a wide 9.6 square degree field of view 3.2 Gigapixel camera, and rapid observational cadence, LSST will discover more than 5 million asteroids over its ten year survey lifetime. With a single visit limiting magnitude of 24.5 in r band, LSST will be able to detect asteroids in the Main Belt down to sub-kilometer sizes. The current strawman for the LSST survey strategy is to obtain two visits (each `visit' being a pair of back-to-back 15s exposures) per field, separated by about 30 minutes, covering the entire visible sky every 3-4 days throughout the observing season, for ten years. The catalogs generated by LSST will increase the known number of small bodies in the Solar System by a factor of 10-100 times, among all populations. The median number of observations for Main Belt asteroids will be on the order of 200-300, with Near Earth Objects receiving a median of 90 observations. These observations will be spread among ugrizy bandpasses, providing photometric colors and allow sparse lightcurve inversion to determine rotation periods, spin axes, and shape information. These catalogs will be created using automated detection software, the LSST Moving Object Processing System (MOPS), that will take advantage of the carefully characterized LSST optical system, cosmetically clean camera, and recent improvements in difference imaging. Tests with the prototype MOPS software indicate that linking detections (and thus `discovery') will be possible at LSST depths with our working model for the survey strategy, but evaluation of MOPS and improvements in the survey strategy will continue. All data products and software created by LSST will be publicly available.

Large Subdued and Small Fresh Craters

NASA Image and Video Library

2012-03-27

This image from NASA Dawn spacecraft shows many large subdued craters that have smaller, younger craters on top of them on asteroid Vesta. There are two large subdued craters in the center of the image, which have very degraded and rounded rims.

Polarimetric survey of main-belt asteroids. V. The unusual polarimetric behavior of V-type asteroids

NASA Astrophysics Data System (ADS)

Gil-Hutton, R.; López-Sisterna, C.; Calandra, M. F.

2017-03-01

Aims: We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained using the CASPROF and CASPOL polarimeters at the 2.15 m telescope. The CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation and CASPOL is a polarimeter based on a CCD detector, which allows us to observe fainter objects with better signal-to-noise ratio. Results: The survey began in 1995 and data on a large sample of asteroids were obtained until 2012. A second period began in 2013 using a polarimeter with a more sensitive detector in order to study small asteroids, families, and special taxonomic groups. We obtained 55 polarimetric measurements for 28 V-type main belt asteroids, all of them polarimetrically observed for the first time. The data obtained in this survey let us find polarimetric parameters for (1459) Magnya and for a group of 11 small V-type objects with similar polarimetric behavior. These polarization curves are unusual since they show a shallow minimum and a small inversion angle in comparison with (4) Vesta, although they have a steeper slope at α0. This polarimetric behavior could be explained by differences in the regoliths of these asteroids. The observations of (2579) Spartacus, and perhaps also (3944) Halliday, indicate a inversion angle larger than 24-25°. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

Asteroid Ida and Its Moon

NASA Image and Video Library

1996-02-01

This is the first full picture showing both asteroid 243 Ida and its newly discovered moon to be transmitted to Earth from the National Aeronautics and Space Administration's (NASA's) Galileo spacecraft--the first conclusive evidence that natural satellites of asteroids exist. Ida, the large object, is about 56 kilometers (35 miles) long. Ida's natural satellite is the small object to the right. This portrait was taken by Galileo's charge-coupled device (CCD) camera on August 28, 1993, about 14 minutes before the Jupiter-bound spacecraft's closest approach to the asteroid, from a range of 10,870 kilometers (6,755 miles). Ida is a heavily cratered, irregularly shaped asteroid in the main asteroid belt between Mars and Jupiter -- the 243rd asteroid to be discovered since the first was found at the beginning of the 19th century. Ida is a member of a group of asteroids called the Koronis family. The small satellite, which is about 1.5 kilometers (1 mile) across in this view, has yet to be given a name by astronomers. It has been provisionally designated '1993 (243) 1' by the International Astronomical Union. ('1993' denotes the year the picture was taken, '243' the asteroid number and '1' the fact that it is the first moon of Ida to be found.) Although appearing to be 'next' to Ida, the satellite is actually in the foreground, slightly closer to the spacecraft than Ida is. Combining this image with data from Galileo's near-infrared mapping spectrometer, the science team estimates that the satellite is about 100 kilometers (60 miles) away from the center of Ida. This image, which was taken through a green filter, is one of a six-frame series using different color filters. The spatial resolution in this image is about 100 meters (330 feet) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA00136

HUBBLE: ON THE ASTEROID TRAIL

NASA Technical Reports Server (NTRS)

2002-01-01

Astronomers Karl Stapelfeldt and Robin Evans have tracked down about 100 small asteroids by hunting through more than 28,000 archival images taken by the Hubble Space Telescope's Wide Field and Planetary Camera 2. Here is a sample of what they have found: four archival images that show the curved trails left by asteroids. [Top left]: Hubble captured a bright asteroid, with a visual magnitude of 18.7, roaming in the constellation Centaurus. Background stars are shown in white, while the asteroid trail is depicted in blue at top center. The trail has a length of 19 arc seconds. This asteroid has a diameter of one and one-quarter miles (2 kilometers), and was located 87 million miles from Earth and 156 million miles from the sun. Numerous orange and blue specks in this image and the following two images were created by cosmic rays, energetic subatomic particles that struck the camera's detector. [Top right]: Here is an asteroid with a visual magnitude of 21.8 passing a galaxy in the constellation Leo. The trail is seen in two consecutive exposures, the first shown in blue and the second in red. This asteroid has a diameter of half a mile (0.8 kilometers), and was located 188 million miles from Earth and 233 million miles from the sun. [Lower left]: This asteroid in the constellation Taurus has a visual magnitude of 23, and is one of the faintest seen so far in the Hubble archive. It moves from upper right to lower left in two consecutive exposures; the first trail is shown in blue and the second in red. Because of the asteroid's relatively straight trail, astronomers could not accurately determine its distance. The estimated diameter is half a mile (0.8 kilometers) at an Earth distance of 205 million miles and a sun distance of 298 million miles. [Lower right]: This is a broken asteroid trail crossing the outer regions of galaxy NGC 4548 in Coma Berenices. Five trail segments (shown in white) were extracted from individual exposures and added to a cleaned color image of the galaxy. The asteroid enters the image at top center and moves down toward the lower left. Large gaps in the trail occur because the telescope is orbiting the Earth and cannot continuously observe the galaxy. This asteroid has a visual magnitude of 20.8, a diameter of one mile (1.6 kilometers), and was seen at a distance of 254 million miles from Earth and 292 million miles from the sun. Credit: R. Evans and K. Stapelfeldt (Jet Propulsion Laboratory) and NASA

An Overview of NASA's Asteroid Redirect Mission (ARM) Concept

NASA Technical Reports Server (NTRS)

Abell, P. A.; Mazanek, D. D.; Reeves, D. M.; Chodas, P. W.; Gates, M. M.; Johnson, L. N.; Ticker, R. L.

2016-01-01

The National Aeronautics and Space Administration (NASA) is developing the Asteroid Redirect Mission (ARM) as a capability demonstration for future human exploration, including use of high-power solar electric propulsion, which allows for the efficient movement of large masses through deep space. The ARM will also demonstrate the capability to conduct proximity operations with natural space objects and crewed operations beyond the security of quick Earth return. The Asteroid Redirect Robotic Mission (ARRM), currently in formulation, will visit a large near-Earth asteroid (NEA), collect a multi-ton boulder from its surface, conduct a demonstration of a slow push planetary defense technique, and redirect the multi-ton boulder into a stable orbit around the Moon. Once returned to cislunar space in the mid-2020s, astronauts aboard an Orion spacecraft will dock with the robotic vehicle to explore the boulder and return samples to Earth. The ARM is part of NASA's plan to advance technologies, capabilities, and spaceflight experience needed for a human mission to the Martian system in the 2030s. The ARM and subsequent availability of the asteroidal material in cis-lunar space, provide significant opportunities to advance our knowledge of small bodies in the synergistic areas of science, planetary defense, and in-situ resource utilization (ISRU). NASA established the Formulation Assessment and Support Team (FAST), comprised of scientists, engineers, and technologists, which supported ARRM mission requirements formulation, answered specific questions concerning potential target asteroid physical properties, and produced a publically available report. The ARM Investigation Team is being organized to support ARM implementation and execution. NASA is also open to collaboration with its international partners and welcomes further discussions. An overview of the ARM robotic and crewed segments, including mission requirements, NEA targets, and mission operations, and a discussion of potential opportunities for participation with the ARM will be provided.

Initial Results of a Survey of Earth's L4 Point for Possible Earth Trojan Asteroids

NASA Astrophysics Data System (ADS)

Connors, M.; Veillet, C.; Wiegert, P.; Innanen, K.; Mikkola, S.

2000-10-01

Using the Canada-France-Hawaii 3.6 m telescope and the new CFH12k wide-field CCD imager, a survey of the region near Earth's L4 (morning) Lagrange Point was conducted in May and July/August 2000, in hopes of finding asteroids at or near this point. This survey was motivated by the dynamical interest of a possible Earth Trojan asteroid (ETA) population and by the fact that they would be the easiest asteroids to access from Earth. Recent calculations (Wiegert, Innanen and Mikkola, 2000, Icarus v. 145, 33-43) indicate stability of objects in ETA orbits over a million year timescale and that their on-sky density would be greatest roughly five degrees sunward of the L4 position. An optimized search technique was used, with tracking at the anticipated rate of the target bodies, near real-time scanning of images, and duplication of fields to aid in detection and permit followup. Limited time is available on any given night to search near the Lagrange points, and operations must be conducted at large air mass. Approximately 9 square degrees were efficiently searched and two interesting asteroids were found, NEA 2000 PM8 and our provisionally named CFZ001. CFZ001 cannot be excluded from being an Earth Trojan although that is not the optimal solution for the short arc we observed. This object, of R magnitude 22, was easily detected, suggesting that our search technique worked well. This survey supports the earlier conclusion of Whitely and Tholen (1998, Icarus v. 136, 154-167) that a large population of several hundred meter diameter ETAs does not exist. However, our effective search technique and the discovery of two interesting asteroids suggest the value of completing the survey with approximately 10 more square degrees to be searched near L4 and a comparable search to be done at L5. Funding from Canada's NSERC and HIA and the Academic Research Fund of Athabasca University is gratefully acknowledged.

Multistep method to deal with large datasets in asteroid family classification

NASA Astrophysics Data System (ADS)

Knežević, Z.; Milani, A.; Cellino, A.; Novaković, B.; Spoto, F.; Paolicchi, P.

2014-07-01

A fast increase in the number of asteroids with accurately determined orbits and with known physical properties makes it more and more challenging to perform, maintain, and update a classification of asteroids into families. We have therefore developed a new approach to the family classification by combining the Hierarchical Clustering Method (HCM) [1] to identify the families with an automated method to add members to already known families. This procedure makes use of the maximum available information, in particular, of that contained in the proper elements catalog [2]. The catalog of proper elements and absolute magnitudes used in our study contains 336 319 numbered asteroids with an information content of 16.31 Mb. The WISE catalog of albedos [3] and SDSS catalog of color indexes [4] contain 94 632 and 59 975 entries, respectively, with a total amount of information of 0.93 Mb. Our procedure makes use of the segmentation of the proper elements catalog by semimajor axis, to deal with a manageable number of objects in each zone, and by inclination, to account for lower density of high-inclination objects. By selecting from the catalog a much smaller number of large asteroids, in the first step, we identify a number of core families; to these, in the second step, we attribute the next layer of smaller objects. In the third step, we remove all the family members from the catalog, and reapply the HCM to the rest; this gives both satellite families which extend the core families and new independent families, consisting mainly of small asteroids. These two cases are separated in the fourth step by attribution of another layer of new members and by merging intersecting families. This leads to a classification with 128 families and 87 095 members. The list of members is updated automatically with each update of the proper elements catalog, and this represents the final and repetitive step of the procedure. Changes in the list of families are not automated.

Aftermath of early Hit-and-Run collisions in the Inner Solar System

NASA Astrophysics Data System (ADS)

Sarid, Gal; Stewart, Sarah T.; Leinhardt, zoe M.

2015-08-01

Planet formation epoch, in the terrestrial planet region and the asteroid belt, was characterized by a vigorous dynamical environment that was conducive to giant impacts among planetary embryos and asteroidal parent bodies, leading to diverse outcomes. Among these the greatest potential for producing diverse end-members lies is the erosive Hit-and-Run regime (small mass ratios, off-axis oblique impacts and non-negligible ejected mass), which is also more probable in terms of the early dynamical encounter configuration in the inner solar system. This collision regime has been invoked to explain outstanding issues, such as planetary volatile loss records, origin of the Moon and mantle stripping from Mercury and some of the larger asteroids (Vesta, Psyche).We performed and analyzed a set of simulations of Hit-and-Run events, covering a large range of mass ratios (1-20), impact parameters (0.25-0.96, for near head-on to barely grazing) and impact velocities (~1.5-5 times the mutual escape velocity, as dependent on the mass ratio). We used an SPH code with tabulated EOS and a nominal simlated time >1 day, to track the collisional shock processing and the provenance of material components. of collision debris. Prior to impact runs, all bodies were allowed to initially settle to negligible particle velocities in isolation, within ~20 simulated hrs. The total number of particles involved in each of our collision simulations was between (1-3 x 105). Resulting configurations include stripped mantles, melting/vaporization of rock and/or iron cores and strong variations of asteroid parent bodies fromcanonical chondritic composition.In the context of large planetary formation simulations, velocity and impact angle distributions are necessary to asses impact probabilities. The mass distribution and interaction within planetary embryo and asteroid swarms depends both on gravitational dynamics and the applied fragmentation mechanism. We will present results pertaining to general projectile remnant scaling relations, constitution of ejected unbound material and the composition of variedcollision remnants, which become available to seed the asteroid belt.

Intrepid: Exploring the NEA population with a Fleet of Highly Autonomous SmallSat explorers

NASA Astrophysics Data System (ADS)

Blacksberg, Jordana; Chesley, Steven R.; Ehlmann, Bethany; Raymond, Carol Anne

2017-10-01

The Intrepid mission concept calls for phased deployment of a fleet of small highly autonomous rendezvous spacecraft designed to characterize the evolution, structure and composition of dozens of Near-Earth Asteroids (NEAs). Intrepid represents a marked departure from conventional solar system exploration projects, where a single unique and complex spacecraft is typically directed to explore a single target body. In contrast, Intrepid relies on the deployment of a large number of autonomous spacecraft to provide redundancy and ensure that the project goals are achieved at a small fraction of the cost of typical missions.The Intrepid science goals are threefold: (1) to understand the evolutionary processes that govern asteroid physical, chemical and dynamical histories and relate these results to solar system origins and evolution; (2) to facilitate impactor deflection scenarios for planetary defense by statistically characterizing relevant asteroid physical properties; (3) to quantify the presence and extractability of potentially useful resources on a large sample of asteroids. To achieve these goals, the baseline architecture includes multiple modular instruments including cameras, spectrometers, radar sounders, and projectiles that could interact with the target asteroid. Key questions to be addressed are: what is the total quantity of water in each object? How is the water incorporated? Are organics present? What is the asteroid physical structure? How would the object respond to impact/deflection?We have begun development of a miniature infrared point spectrometer, a cornerstone of the Intrepid payload, covering both shortwave infrared (SWIR) and mid-infrared (MIR) spectral bands. The spectrometer is designed with a compact 2U form-factor, making it both relevant to Intrepid and implementable on a CubeSat. The combination of SWIR and MIR in a single integrated instrument would enable robust compositional interpretations from a single dataset combining both solar reflectance and thermal emission spectroscopy. These measurements would be crucial to determining the quantity and nature of water present.

Palomar Planet-Crossing Asteroid Survey (PCAS): Recent discovery rate

NASA Technical Reports Server (NTRS)

Helin, Eleanor F.

1992-01-01

The discovery rate of Near-Earth Asteroids (NEA's) has increased significantly in the last decade. As greater numbers of NEA's are discovered, worldwide interest has grown leading to new programs. With the introduction of CCD telescopes throughout the world, an increase of 1-2 orders of magnitude in the discovery rate can be anticipated. Nevertheless, it will take several decades of dedicated searching to accomplish a 95 percent completeness, even for large objects.

KSC-07pd1263

NASA Image and Video Library

2007-05-23

KENNEDY SPACE CENTER, FLA. -- At Astrotech, workers fold the large solar array panels on one side of the Dawn spacecraft. The panels will be tested for deployment and stowage. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. Dawn is scheduled to launch June 30 aboard a Delta II rocket from Launch Complex 17-B at Cape Canaveral Air Force Station. Photo credit: NASA/George Shelton

The orbital evolution of the Apollo asteroid group over 11,550 years

NASA Astrophysics Data System (ADS)

Zausaev, A. F.; Pushkarev, A. N.

1992-08-01

The Everhard method was used to monitor the orbital evolution of 20 Apollo asteroids in the time interval from 2250 A.D. to 9300 B.C. The closest encounters with large planets in the evolution process are calculated. Stable resonances with Venus and Earth over the period from 2250 A.D. to 9300 B.C. are obtained. Theoretical coordinates of radiants on initial and final moments of integration are calculated.

Spacecraft Station-Keeping Trajectory and Mission Design Tools

NASA Technical Reports Server (NTRS)

Chung, Min-Kun J.

2009-01-01

Two tools were developed for designing station-keeping trajectories and estimating delta-v requirements for designing missions to a small body such as a comet or asteroid. This innovation uses NPOPT, a non-sparse, general-purpose sequential quadratic programming (SQP) optimizer and the Two-Level Differential Corrector (T-LDC) in LTool (Libration point mission design Tool) to design three kinds of station-keeping scripts: vertical hovering, horizontal hovering, and orbiting. The T-LDC is used to differentially correct several trajectory legs that join hovering points. In a vertical hovering, the maximum and minimum range points must be connected smoothly while maintaining the spacecrafts range from a small body, all within the law of gravity and the solar radiation pressure. The same is true for a horizontal hover. A PatchPoint is an LTool class that denotes a space-time event with some extra information for differential correction, including a set of constraints to be satisfied by T-LDC. Given a set of PatchPoints, each with its own constraint, the T-LDC differentially corrects the entire trajectory by connecting each trajectory leg joined by PatchPoints while satisfying all specified constraints at the same time. Vertical and horizontal hover both are needed to minimize delta-v spent for station keeping. A Python I/F to NPOPT has been written to be used from an LTool script. In vertical hovering, the spacecraft stays along the line joining the Sun and a small body. An instantaneous delta-v toward the anti- Sun direction is applied at the closest approach to the small body for station keeping. For example, the spacecraft hovers between the minimum range (2 km) point and the maximum range (2.5 km) point from the asteroid 1989ML. Horizontal hovering buys more time for a spacecraft to recover if, for any reason, a planned thrust fails, by returning almost to the initial position after some time later via a near elliptical orbit around the small body. The mapping or staging orbit may be similarly generated using T-LDC with a set of constraints. Some delta-v tables are generated for several different asteroid masses.

Early history of Vesta: implications for the surface morphology and composition

NASA Astrophysics Data System (ADS)

Turrini, D.; Coradini, A.; Formisano, M.; Carli, C.; Magni, G.

2011-12-01

The Dawn mission inserted into orbit around Vesta on 15 July 2011 and is presently gathering data on the morphology and the composition of the asteroid. In order to fully exploit the data that the Dawn mission is supplying to probe the ancient past of our Solar System, we need to be able to understand how the present state of Vesta is linked to its origin and its secular evolution. The spectral connection between Vesta and the Howardite-Eurcrite-Diogenite (HED) suite of meteorites suggests that Vesta formed very early in the history of the Solar System and differentiated on a Ma-long timescale due to the decay of short-lived radioactive nuclides (see Keil 2002 and references therein). Short after the differentiation process ended, Vesta started to cool down quickly, so that on a 10 Ma timescale its molten mantle would be topped by a thick solid layer (Formisano et al. 2011). Across the same timespan, Jupiter and the other giant planets would form in the outer Solar System and trigger a primordial phase of bombardment on the other already formed planetary bodies (Turrini et al. 2011, Coradini et al. 2011). Such primordial bombardment is expected to excavate the solid crust of Vesta and to cause local to regional effusive phenomena (Turrini et al. 2011). Moreover, due to the relatively high escape speed from Vesta, most of the excavated material would fall back on the asteroid as an ejecta blanket. Here we discuss the timescale of the formation and evolution of Vesta and the implications for the interpretation of the data that the Dawn mission is collecting while orbiting the asteroid. Bibliography 1. Coradini A., Turrini D., Federico C., Magni G. (2011). Vesta and Ceres: crossing the history of the Solar System. Space Science Reviews, DOI: 10.1007/s11214-011-9792-x. 2. Formisano M., Federico C., Coradini A. (2011). Vesta Thermal Models. EPSC-DPS Joint Meeting 2011, Nantes, France. 3. Keil K. (2002). Geological History of Asteroid 4 Vesta: The Smallest Terrestrial Planet. Asteroids III, Eds. W. F. Bottke Jr., A. Cellino, P. Paolicchi, and R. P. Binzel, University of Arizona Press, Tucson, 573-584. 4. Turrini D., Magni G., Coradini A. (2011). Probing the history of Solar System through the cratering records on Vesta and Ceres. Monthly Notices of the Royal Astronomical Society, DOI: 10.1111/j.1365-2966.2011.18316.x.

Solar wind tans young asteroids

NASA Astrophysics Data System (ADS)

2009-04-01

A new study published in Nature this week reveals that asteroid surfaces age and redden much faster than previously thought -- in less than a million years, the blink of an eye for an asteroid. This study has finally confirmed that the solar wind is the most likely cause of very rapid space weathering in asteroids. This fundamental result will help astronomers relate the appearance of an asteroid to its actual history and identify any after effects of a catastrophic impact with another asteroid. ESO PR Photo 16a/09 Young Asteroids Look Old "Asteroids seem to get a ‘sun tan' very quickly," says lead author Pierre Vernazza. "But not, as for people, from an overdose of the Sun's ultraviolet radiation, but from the effects of its powerful wind." It has long been known that asteroid surfaces alter in appearance with time -- the observed asteroids are much redder than the interior of meteorites found on Earth [1] -- but the actual processes of this "space weathering" and the timescales involved were controversial. Thanks to observations of different families of asteroids [2] using ESO's New Technology Telescope at La Silla and the Very Large Telescope at Paranal, as well as telescopes in Spain and Hawaii, Vernazza's team have now solved the puzzle. When two asteroids collide, they create a family of fragments with "fresh" surfaces. The astronomers found that these newly exposed surfaces are quickly altered and change colour in less than a million years -- a very short time compared to the age of the Solar System. "The charged, fast moving particles in the solar wind damage the asteroid's surface at an amazing rate [3]", says Vernazza. Unlike human skin, which is damaged and aged by repeated overexposure to sunlight, it is, perhaps rather surprisingly, the first moments of exposure (on the timescale considered) -- the first million years -- that causes most of the aging in asteroids. By studying different families of asteroids, the team has also shown that an asteroid's surface composition is an important factor in how red its surface can become. After the first million years, the surface "tans" much more slowly. At that stage, the colour depends more on composition than on age. Moreover, the observations reveal that collisions cannot be the main mechanism behind the high proportion of "fresh" surfaces seen among near-Earth asteroids. Instead, these "fresh-looking" surfaces may be the results of planetary encounters, where the tug of a planet has "shaken" the asteroid, exposing unaltered material. Thanks to these results, astronomers will now be able to understand better how the surface of an asteroid -- which often is the only thing we can observe -- reflects its history. More information This result was presented in a paper published this week in the journal Nature, "Solar wind as the origin of rapid reddening of asteroid surfaces", by P. Vernazza et al. The team is composed of Pierre Vernazza (ESA), Richard Binzel (MIT, Cambridge, USA), Alessandro Rossi (ISTI-CNR, Pisa, Italy), Marcello Fulchignoni (Paris Observatory, France), and Mirel Birlan (IMCCE, CNRS-8028, Paris Observatory, France). A PDF file can be downloaded here. Notes [1] Meteorites are small fragments of asteroids that fall on Earth. While a meteorite enters the Earth's atmosphere its surface can melt and be partially charred by the intense heat. Nevertheless, the meteorite interior remains unaffected, and can be studied in a laboratory, providing a wealth of information on the nature and composition of asteroids. [2] An asteroid family is a group of asteroids that are on similar orbits around the Sun. The members of a given family are believed to be the fragments of a larger asteroid that was destroyed during a collision. [3] The surface of an asteroid is affected by the highly energetic particles forming the solar wind. These particles partially destroy the molecules and crystals on the surface, re-arranging them in other combinations. Over time, these changes give formation of a thin crust or irradiated material with distinct colours and properties.

Petrology and Composition of HED Polymict Breccias

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.; Herrin, J. S.; Mertzman, S. A.; Mertzman, K. R.

2010-01-01

The howardite, eucrite and diogenite (HED) clan of meteorites forms the largest suite of achondrites with over 900 named members. The HEDs are igneous rocks and breccias of igneous rocks from a differentiated asteroid [1]. The consensus view is that these rocks hail from the asteroid 4 Vesta, which will be the first target of NASA's Dawn mission. When Dawn arrives at Vesta, she will begin remote imagery and spectroscopy of the surface. The surface she will observe will be dominated by rocks and soils mixed through impact gardening. To help with the interpretation of the remotely sensed data, we have begun a project on the petrologic and compositional study of a suite of HED polymict breccias. Here we report on the preliminary findings of this project.

An Investigation of the 3-μm Feature in M-Type Asteroids

NASA Astrophysics Data System (ADS)

Landsman, Zoe A.; Campins, H.; Hargrove, K.; Pinilla-Alonso, N.; Emery, J.; Ziffer, J.

2013-10-01

The M-type asteroids had originally been interpreted as the disrupted iron cores of differentiated bodies by spectral analogy with the NiFe meteorites. More detailed studies have since indicated a range of compositions. In particular, the presence of a 3-µm feature, diagnostic of hydration, detected in more than 35% of surveyed M-type asteroids (Jones et al. 1990, Rivkin et al. 1995, 2000) has challenged the notion that these bodies are all metallic. Spectroscopy in the 0.8 - 2.5 µm region has revealed absorption features due to mafic silicates and hydroxides or phyllosilicates (Fornasier et al. 2010, Hardersen et al. 2006, 2010, Ockert-Bell et al. 2010). Radar studies have shown that most M-types are not likely to be iron cores, but they typically have a higher metal content than average (Shepard et al. 2010). Taken together, these results paint a fairly confounding picture of the M-type asteroids. While several interpretations have been suggested, more work is needed to clarify the mineralogy of these bodies. We have started a new spectroscopic study of the M asteroids in the 2 - 4 µm region. We seek to characterize the shape, band center, and band depth of the 3-µm feature where it is present, as these measures are indicative of the type and extent of hydration present on asteroids (Lebofsky et al. 1985, Rivkin et al. 2002, Takir & Emery 2012, Volguardsen et al. 2007). With this work, we hope to shed new light on the origin of hydration on M asteroids and its context within their mineralogy and thermal evolution. In July 2013, we obtained 2 - 4 µm spectra for 69 Hesperia, 136 Austria, and 261 Prymno with the SpeX at NASA’s IRTF, and are in the process of reducing the data. We have also obtained 0.8 - 2.0 µm data for 261 Prymno using the NICS at the TNG in February 2013. We report the presence of an absorption feature near 0.9 µm in Prymno’s spectrum, indicating a partially silicate composition. Based on spectral, physical and orbital similarities to other hydrated M-types, we predict the presence of a 3-μm feature in Prymno’s 2 - 4 μm. More 2 - 4 μm observations of M-type asteroids are planned.

The differentiation of eucrites: The role of in situ crystallization

NASA Astrophysics Data System (ADS)

Barrat, J. A.; Blichert-Toft, J.; Gillet, Ph.; Keller, F.

2000-09-01

We report on major and trace element analyses of 17 eucrites, including three cumulate eucrites (Binda, Moore County, and Serra de Magé), determined by, respectively, ICP-AES and ICP-MS. The results obtained for Binda and Moore County are consistent with the model of Treiman (1997) for the formation of cumulate eucrites, which holds that these meteorites were produced from a eucritic melt. Our sample of Serra de Magé contains unusually large amounts of pyroxene and probably an accessory phase rich in HREEs and is therefore not representative of this eucrite as known from literature data. Our results for the noncumulate eucrites Bereba, Bouvante, Cachari, Caldera, Camel Donga, Ibitira, Jonzac, Juvinas, Lakangaon, Millbillillie, Padvarninkai, Pasamonte, Sioux County and Stannern are in good agreement with literature data. The observed decoupling between major and trace elements for noncumulate eucrites can be explained by in-situ crystallization during the differentiation of an asteroidal magma ocean. This model can further account for both the Nuevo Laredo and the Stannern trends but has as a consequence that none of the analyzed eucrites represents a primary melt.

Composition and evolution of the eucrite parent body - Evidence from rare earth elements. [extraterrestrial basaltic melts

NASA Technical Reports Server (NTRS)

Consolmagno, G. J.; Drake, M. J.

1977-01-01

Quantitative modeling of the evolution of rare earth element (REE) abundances in the eucrites, which are plagioclase-pigeonite basalt achondrites, indicates that the main group of eucrites (e.g., Juvinas) might have been produced by approximately 10% equilibrium partial melting of a single type of source region with initial REE abundances which were chondritic relative and absolute. Since the age of the eucrites is about equal to that of the solar system, extensive chemical differentiation of the eucrite parent body prior to the formation of eucrites seems unlikely. If homogeneous accretion is assumed, the bulk composition of the eucrite parent body can be estimated; two estimates are provided, representing different hypotheses as to the ratio of metal to olivine in the parent body. Since a large number of differentiated olivine meteorites, which would represent material from the interior of the parent body, have not been detected, the eucrite parent body is thought to be intact. It is suggested that the asteroid 4 Vesta is the eucrite parent body.

Detailed Pictures of Multiple Asteroid Systems in the Main-Belt

NASA Astrophysics Data System (ADS)

Marchis, F.; Emery, J. P.; Enriquez, J. E.; Descamps, P.; Berthier, J.; Vachier, F.; Durech, J.

2011-12-01

Since their discovery less than 10 years ago, ~200 known multiple asteroid systems have been studied with a combination of observing techniques, including adaptive optics, lightcurve photometry, and mid-infrared spectrophotometry. Those observations show that ~15 large (D>100km) asteroids that are known to possess km-sized satellite(s) (22 Kalliope, 45 Eugenia, 87 Sylvia, 93 Minerva, 216 Kleopatra, ...) share common orbital characteristics, implying a common formation scenario: e.g. catastrophic disruption or ejection after an oblique impact. More than 70 smaller (10-15km) binary asteroid systems have been detected through anomalies in their lightcurves and are believed to have formed by fission due to the YORP effect. By comparison with meteorite analog densities, mid-IR data reveal that these systems have a significant porosity (larger than 30%) implying a rubble-pile interior. We will review these key results and discuss their implications for the interior of asteroids in the light of recent space mission results. Future explorations using new ground-based facilities and space mission concepts will be also discussed. This work is supported by the NSF grant AAG-0807468 and NASA grant NNX11AD62G

Asteroidal Space Weathering: The Major Role of FeS

NASA Technical Reports Server (NTRS)

Keller, L. P.; Rahman, Z.; Hiroi, T.; Sasaki, S.; Noble, S. K.; Horz, F.; Cintala, M. J.

2013-01-01

Space weathering (SW) effects on the lunar surface are reasonably well-understood from sample analyses, remote-sensing data, and experiments, yet our knowledge of asteroidal SW effects are far less constrained. While the same SW processes are operating on asteroids and the Moon, namely solar wind irradiation, impact vaporization and condensation, and impact melting, their relative rates and efficiencies are poorly known, as are their effects on such vastly different parent materials. Asteroidal SW models based on remote-sensing data and experiments are in wide disagreement over the dominant mechanisms involved and their kinetics. Lunar space weathering effects observed in UVVIS-NIR spectra result from surface- and volume-correlated nanophase Fe metal (npFe(sup 0)) particles. In the lunar case, it is the tiny vapor-deposited npFe(sup 0) that provides much of the spectral reddening, while the coarser (largely melt-derived) npFe(sup 0) produce lowered albedos. Nanophase FeS (npFeS) particles are expected to modify reflectance spectra in much the same way as npFe(sup 0) particles. Here we report the results of experiments designed to explore the efficiency of npFeS production via the main space weathering processes operating in the asteroid belt.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vernazza, P.; Barge, P.; Zanda, B.

Although petrologic, chemical, and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there are several questions that cannot be resolved via laboratory measurements and/or experiments alone. Here, we propose the rationale for several new constraints on the formation and evolution of ordinary chondrite parent bodies (and, by extension, most planetesimals) from newly available spectral measurements and mineralogical analysis of main-belt S-type asteroids (83 objects) and unequilibrated ordinary chondrite meteorites (53 samples). Based on the latter, we suggest that spectral data may be usedmore » to distinguish whether an ordinary chondrite was formed near the surface or in the interior of its parent body. If these constraints are correct, the suggested implications include that: (1) large groups of compositionally similar asteroids are a natural outcome of planetesimal formation and, consequently, meteorites within a given class can originate from multiple parent bodies; (2) the surfaces of large (up to ∼200 km) S-type main-belt asteroids mostly expose the interiors of the primordial bodies, a likely consequence of impacts by small asteroids (D < 10 km) in the early solar system; (3) the duration of accretion of the H chondrite parent bodies was likely short (instantaneous or in less than ∼10{sup 5} yr, but certainly not as long as 1 Myr); (4) LL-like bodies formed closer to the Sun than H-like bodies, a possible consequence of the radial mixing and size sorting of chondrules in the protoplanetary disk prior to accretion.« less

Global environmental effects of impact-generated aerosols: Results from a general circulation model

NASA Technical Reports Server (NTRS)

Covey, C.; Ghan, S. J.; Weissman, Paul R.

1988-01-01

Cooling and darkening at Earth's surface are expected to result from the interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet, according to the one-dimensional radioactive-convective atmospheric model (RCM) of Pollack et al. An analogous three-dimensional general circulation model (GCM) simulation obtains the same basic result as the RCM but there are important differences in detail. In the GCM simulation the heat capacity of the oceans, not included in the RCM, substantially mitigates land surface cooling. On the other hand, the GCM's low heat capacity surface allows surface temperatures to drop much more rapidly than reported by Pollack et al. These two differences between RCM and GCM simulations were noted previously in studies of nuclear winter; GCM results for comet/asteroid winter, however, are much more severe than for nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on Earth. In the simulation the global average of land surface temperature drops to the freezing point in just 4.5 days, one-tenth the time required in the Pollack et al. simulation. In addition to the standard case of Pollack et al., which represents the collision of a 10-km diameter asteroid with Earth, additional scenarios are considered ranging from the statistically more frequent impacts of smaller asteroids to the collision of Halley's comet with Earth. In the latter case the kinetic energy of impact is extremely large due to the head-on collision resulting from Halley's retrograde orbit.

Pristine Igneous Rocks and the Early Differentiation of Planetary Materials

NASA Technical Reports Server (NTRS)

Warren, Paul H.

2005-01-01

Our studies are highly interdisciplinary, but are focused on the processes and products of early planetary and asteroidal differentiation, especially the genesis of the ancient lunar crust. The compositional diversity that we explore is the residue of process diversity, which has strong relevance for comparative planetology. Most of the accessible lunar crust consists of materials hybridized by impact-mixing. Our lunar research concentrates on the rare pristine (unmixed) samples that reflect the original genetic diversity of the early crust. Among HED basalts (eucrites and clasts in howardites), we distinguish as pristine the small minority that escaped the pervasive thermal metamorphism of the parent asteroid's crust. We have found a correlation between metamorphically pristine HED basalts and the similarly small minority of compositionally evolved "Stannern trend" samples, which are enriched in incompatible elements and titanium compared to main group eucrites, and yet have relatively high mg ratios. Other topics under investigation included: lunar and SNC (martian?) meteorites; igneous meteorites in general; impact breccias, especially metal-rich Apollo samples and polymict eucrites; siderophile compositions of the lunar and martian mantles; and planetary bulk compositions and origins.

Modelling the Thermal History of Asteroid 4 Vesta

NASA Technical Reports Server (NTRS)

Solano, James M.; Kiefer, W. S.; Mittlefehldt, D. W.

2012-01-01

The asteroid 4 Vesta is widely thought to be the source of the HED (Howardite, Eucrite and Diogenite) meteorites, with this link supported by spectroscopic and dynamical studies. The availability of the HED meteorites for study and the new data being gained from the Dawn mission provides an excellent opportunity to investigate Vesta s history. In this study, modelling of Vesta has been undertaken to investigate its evolution from an unconsolidated chondritic body to a differentiated body with an iron core. In contrast to previous modelling, both heat and mass transfer are considered as coupled processes. This work draws on models of melt segregation in terrestrial environments to inform the evolution of Vesta into the differentiated body observed today. In order for a core to form in this body, a separation of the metallic iron from the silicates must take place. Temperatures in excess of the solidus temperatures for the Fe-FeS system and the silicates are therefore required. Thermal modelling has shown accretion before 2Myr leads to temperatures in excess of the silicate solidus.

The Physical, Geological, and Dynamical Nature of Asteroid (101955) Bennu - Target of OSIRIS-REx

NASA Astrophysics Data System (ADS)

Lauretta, Dante

2014-11-01

OSIRIS-REx will survey asteroid (101955) Bennu to understand its properties, assess its resource potential, refine the impact hazard, and return a sample to Earth. This mission launches in 2016. Bennu is different from all other near-Earth asteroids previously visited by spacecraft. (433) Eros, target of the NEAR-Shoemaker mission, and (25143) Itokawa, target of Hayabusa, are both high-albedo, S-type asteroids with irregular shapes. In contrast, Bennu has a low albedo, is a B-type asteroid, and has a distinct spheroidal shape. While Eros and Itokawa are similar to ordinary chondrites, Bennu is likely related to carbonaceous chondrites, meteorites that record the history of volatiles and organic compounds in the early Solar System.We performed an extensive campaign to determine the properties of Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. Combining these data with cosmochemical and dynamical models yields a hypothetical timeline for Bennu’s formation and evolution. Bennu is an ancient object that has witnessed over 4.5 Gyr of Solar System history. Its chemistry and mineralogy were established within the first 10 Myr of the Solar System. It likely originated as a discrete asteroid in the main belt ~0.7 - 2 Gyr ago as a fragment from the catastrophic disruption of a large, carbonaceous asteroid. It was delivered to near-Earth space via a combination of Yarkovsky-induced drift and interaction with giant-planet resonances. During its journey, YORP processes and planetary encounters modified Bennu’s spin state, potentially reshaping and resurfacing the asteroid. Bennu is a Potentially Hazardous Asteroids with an ~1-in-2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner Solar System after a close encounter with Jupiter. OSIRIS-REx will return samples from this intriguing asteroid in September 2023.

Inner main belt asteroids in Slivan states?

NASA Astrophysics Data System (ADS)

Vraštil, J.; Vokrouhlický, D.

2015-07-01

Context. The spin state of ten asteroids in the Koronis family has previously been determined. Surprisingly, all four asteroids with prograde rotation were shown to have spin axes nearly parallel in the inertial space. All asteroids with retrograde rotation had large obliquities and rotation periods that were either short or long. The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect has been demonstrated to be able to explain all these peculiar facts. In particular, the effect causes the spin axes of the prograde rotators to be captured in a secular spin-orbit resonance known as Cassini state 2, a configuration dubbed "Slivan state". Aims: It has been proposed based on an analysis of a sample of asteroids in the Flora family that Slivan states might also exist in this region of the main belt. This is surprising because convergence of the proper frequency s and the planetary frequency s6 was assumed to prevent Slivan states in this zone. We therefore investigated the possibility of a long-term stable capture in the Slivan state in the inner part of the main belt and among the asteroids previously observed. Methods: We used the swift integrator to determine the orbital evolution of selected asteroids in the inner part of the main belt. We also implemented our own secular spin propagator into the swift code to efficiently analyze their spin evolution. Results: Our experiments show that the previously suggested Slivan states of the Flora-region asteroids are marginally stable for only a small range of the flattening parameter Δ. Either the observed spins are close to the Slivan state by chance, or additional dynamical effects that were so far not taken into account change their evolution. We find that only the asteroids with very low-inclination orbits (lower than ≃4°, for instance) could follow a similar evolution path as the Koronis members and be captured in their spin state into the Slivan state. A greater number of asteroids in the inner main-belt Massalia family, which are at a slightly larger heliocentric distance and at lower inclination orbits than in the Flora region, may have their spin in the Slivan state.

Preliminary Results in Asteroid Mass Determination

NASA Astrophysics Data System (ADS)

Aslan, Z.; Gumerov, R. I.; Hudkova, L. A.; Ivantsov, A. V.; Khamitov, I.; Pinigin, G. I.

2006-08-01

Asteroid masses are extremely important for the determination of their bulk densities, especially for the discussed relatively high porosities in about 20 to 30% of the studied bodies. The problem will have some coverage in clarifying errors of both mass and volume determinations. We have used lists of encounters for massive and less massive asteroids, prepared by J.L. Hilton, which cover relatively contemporary period of optical observations, 1950-2005. These observations were taken from the MPC database of observations. The model of the motions uses integrations of relativistic equations for perturbing asteroids (Ceres, Pallas, Vesta, and others concerned), perturbed asteroid. Positions and velocities of the Sun and large planets are directly taken from the DE405. The necessary initial conditions were taken from the HORIZONS system. By the adjustment of dynamical model parameters (both initial conditions and perturbing masses for asteroids) there were determined preliminary masses (in 10^-10 of Sun mass) for seven asteroids: (7) Iris 0.090±0.008, (10) Hygiea 0.213±0.030, (24) Themis 0.010±0.024, (45) Eugenia 0.012±0.025, (52) Europa 0.362±0.041, (87) Sylvia 0.180±0.090, (165) Loreley 0.157±0.100. These masses were calculated from difficult cases, where the earlier study by some authors gave negative masses in the unweighted calculations. The values obtained were compared with other estimations. Both the two-fold increase in the number of observations up the present and the active boundary on the determined mass parameter or equivalent logarithm transform should have given physically meaningful values in any case.

NASA's asteroid redirect mission: Robotic boulder capture option

NASA Astrophysics Data System (ADS)

Abell, P.; Nuth, J.; Mazanek, D.; Merrill, R.; Reeves, D.; Naasz, B.

2014-07-01

NASA is examining two options for the Asteroid Redirect Mission (ARM), which will return asteroid material to a Lunar Distant Retrograde Orbit (LDRO) using a robotic solar-electric-propulsion spacecraft, called the Asteroid Redirect Vehicle (ARV). Once the ARV places the asteroid material into the LDRO, a piloted mission will rendezvous and dock with the ARV. After docking, astronauts will conduct two extravehicular activities (EVAs) to inspect and sample the asteroid material before returning to Earth. One option involves capturing an entire small (˜4--10 m diameter) near-Earth asteroid (NEA) inside a large inflatable bag. However, NASA is also examining another option that entails retrieving a boulder (˜1--5 m) via robotic manipulators from the surface of a larger (˜100+ m) pre-characterized NEA. The Robotic Boulder Capture (RBC) option can leverage robotic mission data to help ensure success by targeting previously (or soon to be) well-characterized NEAs. For example, the data from the Japan Aerospace Exploration Agency's (JAXA) Hayabusa mission has been utilized to develop detailed mission designs that assess options and risks associated with proximity and surface operations. Hayabusa's target NEA, Itokawa, has been identified as a valid target and is known to possess hundreds of appropriately sized boulders on its surface. Further robotic characterization of additional NEAs (e.g., Bennu and 1999 JU_3) by NASA's OSIRIS REx and JAXA's Hayabusa 2 missions is planned to begin in 2018. This ARM option reduces mission risk and provides increased benefits for science, human exploration, resource utilization, and planetary defense.

Thermal Intertias of Main-Belt Asteroids from Wise Thermal Infrared Data

NASA Astrophysics Data System (ADS)

Hanus, Josef; Delbo', Marco; Durech, Josef; Alí-Lagoa, Victor

2014-11-01

By means of a modified thermophysical model (TPM) that takes into account asteroid shape and pole uncertainties, we analyze the thermal infrared data acquired by the NASA's Wide-field Infrared Survey Explorer (WISE) of about 300 asteroids with derived convex shape models. We adopt convex shape models from the DAMIT database (Durech et al., 2010, A&A 513, A46) and present new determinations based on optical disk-integrated photometry and the lightcurve inversion method (Kaasalainen & Torppa, 2001, Icarus 153, 37). This work more than double the number of asteroids with determined thermophysical properties. We also discuss cases in which shape uncertainties prevent the determination of reliable thermophysical properties. This is per-se a novel result, as the effect of shape has been often neglected in thermophysical modeling of asteroids.We also present the main results of the statistical study of derived thermophysical parameters within the whole population of MBAs and within few asteroid families. The thermal inertia increases with decreasing size, but a large range of thermal inertia values is observed within the similar size ranges between 10-100 km. Surprisingly, we derive low (<20J m^{-2} s^{-1/2} K^{-1}) thermal inertia values for several asteroids with sizes D>10 km, indicating a very fine and mature regolith on these small bodies. The work of JH and MD was carried under the contract 11-BS56-008 (SHOCKS) of the French Agence National de la Recherche (ANR), and JD has been supported by the grant GACR P209/10/0537 of the Czech Science Foundation.

Differentiation of Asteroid 4 Vesta: Core Formation by Iron Rain in a Silicate Magma Ocean

NASA Technical Reports Server (NTRS)

Kiefer, Walter S.; Mittlefehldt, David W.

2017-01-01

Geochemical observations of the eucrite and diogenite meteorites, together with observations made by NASA's Dawn spacecraft while orbiting asteroid 4 Vesta, suggest that Vesta resembles H chondrites in bulk chemical composition, possible with about 25 percent of a CM-chondrite like composition added in. For this model, the core is 15 percent by mass (or 8 percent by volume) of the asteroid, with a composition of 73.7 percent by weight Fe, 16.0 percent by weight S, and 10.3 percent by weight Ni. The abundances of moderately siderophile elements (Ni, Co, Mo, W, and P) in eucrites require that essentially all of the metallic phase in Vesta segregated to form a core prior to eucrite solidification. The combination of the melting phase relationships for the silicate and metal phases, together with the moderately siderophile element concentrations together require that complete melting of the metal phase occurred (temperature is greater than1350 degrees Centigrade), along with substantial (greater than 40 percent) melting of the silicate material. Thus, core formation on Vesta occurs as iron rain sinking through a silicate magma ocean.

Investigating the Source of Water and/or Hydroxyl on Asteroid (16) Psyche

NASA Astrophysics Data System (ADS)

Takir, D.; Reddy, V.; Sanchez, J. A.; Shepard, M. K.; Emery, J. P.

2017-12-01

Asteroid (16) Psyche will be visited by the Psyche mission, which was selected by NASA and will be launched in 2022 as the 14th Discovery mission. Psyche is thought to be one of the most massive exposed metallic core in the asteroid belt. The high radar albedos, thermal inertia, and density of Psyche revealed that this asteroid is composed of almost entirely of Fe-Ni metal. Psyche is also characterized by moderately red spectra and the presence of weak features (attributed to silicates) in the visible and near-infrared (NIR) region (0.3-2.5 µm). Recent NIR observations also showed rotational spectral variations indicating a possible change in the metal/silicate ratio on the surface of this asteroid. Additionally, we observed Psyche in the 3-µm spectral region using the long-wavelength cross-dispersed (LXD: 1.9-4.2 µm) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). Our observations revealed that Psyche exhibits a 3-µm feature, more likely attributed to water- and/or hydroxyl molecules. While the source of water and/or hydroxyl on Psyche remains unclear, we proposed a few possible mechanisms for their formation: (1) the water/hydroxyl-rich materials detected on Psyche might have been delivered to its surface by carbonaceous impactors (like on Vesta), (2) Psyche may not be entirely exposed metallic, instead, its surface has a core-mantle boundary of a differentiated body that was disrupted by impacts (e.g., Pallasite-like), or (3) the water/hydroxyl-rich materials detected on Psyche is produced by Solar wind implantation (like on the Moon). In this talk we will discuss these three possible mechanisms and hypotheses and how they can be tested prior to the launch of the Psyche spacecraft using predictive laboratory measurements and modeling, and during the spacecraft encounter with the asteroid using the mission main instruments that will include the multispectral imagers, the gamma-ray and neutron spectrometer, and the dual fluxgate magnetometers.

Illumination Conditions at the Asteroid 4 Vesta: Implications for the Presence of Water Ice

NASA Technical Reports Server (NTRS)

Stubbs, Timothy J.; Wang, Yongli

2011-01-01

The mean illumination conditions and surface temperatures over one orbital period are calculated for the Asteroid 4 Vesta using a coarse digital elevation model produced from Hubble Space Telescope images. Even with the anticipated effects of finer-scale topography taken into account, it is unlikely that any significant permanently shadowed regions currently exist on Vesta due to its large axial tilt (approx. = 27deg). However, under present day conditions, it is predicted that about half of Vesta's surface has an average temperature of less than 145 K, which, based on previous thermal modeling of main belt asteroids, suggests that water ice could survive in the top few meters of the vestal regolith on billion-year timescales.

Routing the asteroid surface vehicle with detailed mechanics

NASA Astrophysics Data System (ADS)

Yu, Yang; Baoyin, He-Xi

2014-06-01

The motion of a surface vehicle on/above an irregular object is investigated for a potential interest in the insitu explorations to asteroids of the solar system. A global valid numeric method, including detailed gravity and geomorphology, is developed to mimic the behaviors of the test particles governed by the orbital equations and surface coupling effects. A general discussion on the surface mechanical environment of a specified asteroid, 1620 Geographos, is presented to make a global evaluation of the surface vehicle's working conditions. We show the connections between the natural trajectories near the ground and differential features of the asteroid surface, which describes both the good and bad of typical terrains from the viewpoint of vehicles' dynamic performances. Monte Carlo simulations are performed to take a further look at the trajectories of particles initializing near the surface. The simulations reveal consistent conclusions with the analysis, i.e., the open-field flat ground and slightly concave basins/valleys are the best choices for the vehicles' dynamical security. The dependence of decending trajectories on the releasing height is studied as an application; the results show that the pole direction (where the centrifugal force is zero) is the most stable direction in which the shift of a natural trajectory will be well limited after landing. We present this work as an example for pre-analysis that provides guidance to engineering design of the exploration site and routing the surface vehicles.

Significantly high polarization degree of the very low-albedo asteroid (152679) 1998 KU2

NASA Astrophysics Data System (ADS)

Kuroda, Daisuke; Ishiguro, Masateru; Watanabe, Makoto; Hasegawa, Sunao; Sekiguchi, Tomohiko; Naito, Hiroyuki; Usui, Fumihiko; Imai, Masataka; Sato, Mitsuteru; Kuramoto, Kiyoshi

2018-03-01

We present a unique and significant polarimetric result regarding the near-Earth asteroid (152679) 1998 KU2, which has a very low geometric albedo. From our observations, we find that the linear polarization degrees of 1998 KU2 are 44.6 ± 0.5% in the RC band and 44.0 ± 0.6% in the V band at a solar phase angle of 81.0°. These values are the highest of any known airless body in the solar system (i.e., high-polarization comets, asteroids, and planetary satellites) at similar phase angles. This polarimetric observation is not only the first for primitive asteroids at large phase angles, but also for low-albedo (<0.1) airless bodies. Based on spectroscopic similarities and polarimetric measurements of materials that have been sorted by size in previous studies, we conjecture that 1998 KU2 has a highly microporous regolith structure comprising nano-sized carbon grains on the surface.

Reflectance spectra of 'featureless' materials and the surface mineralogies of M- and E-class asteroids

NASA Technical Reports Server (NTRS)

Cloutis, Edward A.; Smith, Dorian G.; Lambert, Richard St. J.; Gaffey, Michael J.

1990-01-01

In a search for diagnostic spectral parameters which can be used to distinguish different materials on the surface of asteroids and to provide information on the detection limits for mafic silicates, the 0.3- to 2.6-micron reflectance spectra of meteoritic enstatite (nearly pure MgSiO3), iron meteorite metal, magnetite, and amorphous carbon as well as various mixtures of these materials with mafic silicates were examined. Results are presented on the dependence of the spectral detectability of mafic silicates associated with metal, carbon, and magnetite on the particle sizes of the phases, their chemistries, crystal structures, and abundances. It is shown that the observational data for a representative M-class asteroid, (16) Psyche, are largely consistent with a fine-grained metal-rich surface assemblage, whereas data for the E-class asteroid (44) Nysa indicate that its surface is composed of fine-grained material similar to enstatite achondrites, with a small amount of material comparable to the chondritic inclusions found in the Cumberland Falls aubrite.

Asteroid Airbursts: Risk Assessment and Reduction

NASA Astrophysics Data System (ADS)

Boslough, M.

2015-12-01

Airbursts are events in which small (meters to tens-of-meters in diameter) asteroids deposit most of their energy in the atmosphere with a total energy greater than small nuclear explosions (>0.1 kilotons of TNT). The airburst risk is higher than previous assessments for two reasons. First, they are more frequent than previously thought. The Tunguska-class (~40 meters) population estimate has doubled, and Chelyabinsk-class (~20 meters) has increased by a factor of 2.6. Second, asteroid airbursts are significantly more damaging than previously assumed. In most cases, they more efficiently couple energy to the surface than nuclear explosions of the same yield. Past Near-Earth Object (NEO) risk assessments concluded that the largest asteroids (> 1 km) dominated the hazard. Large NEOs represent only a tiny fraction of the population but the potential for global catastrophe means that the contribution from low-probability, high-consequence events is large. Nearly 90% of these objects, none of which is on a collision course, have been catalogued. This has reduced their assessed near-term statistical risk by more than an order of magnitude because completion is highest for the largest and most dangerous. The relative risk from small objects would therefore be increasing even if their absolute assessed risk were not. Uncertainty in the number of small NEOs remains large and can only be reduced by expanded surveys. One strategy would be to count small NEOs making close passes in statistically significant numbers. For example, there are about 25 times as many objects of a given size that pass within the distance of geosynchronous orbit than collide with the earth, and 2000 times as many pass within a lunar distance (accounting for gravitational focusing). An asteroid the size of the Chelyabinsk impactor (~20 m) could potentially be observed within geosynchronous orbit every two years and within lunar orbit nearly once a week. A Tunguska-sized asteroid (~40 m) passes within a lunar distance several times a year. A survey optimized to discover and count these objects would rapidly reduce the uncertainty in their populations. An additional benefit would be early warning of an imminent impact to give authorities time to issue evacuation or take-cover instructions in circumstances for which there would be no time the prevent an impact.

BILLIARDS: A Demonstration Mission for Hundred-Meter Class Near-Earth Asteroid Disruption

NASA Technical Reports Server (NTRS)

Marcus, Matthew; Sloane, Joshua; Ortiz, Oliver; Barbee, Brent William

2015-01-01

Collisions from near-Earth asteroids (NEAs) have the potential to cause widespread harm to life on Earth. The hypervelocity nature of these collisions means that a relatively small asteroid (about a quartermile in diameter) could cause a global disaster. Proposed strategies for deflecting or disrupting such a threatening asteroid include detonation of a nuclear explosive device (NED) in close proximity to the asteroid, as well as intercepting the asteroid with a hypervelocity kinetic impactor. NEDs allow for the delivery of large amounts of energy to a NEA for a given mass launched from the Earth, but have not yet been developed or tested for use in deep space. They also present safety and political complications, and therefore may only be used when absolutely necessary. Kinetic impactors require a relatively simple spacecraft compared to NEDs, but also deliver a much lower energy for a given launch mass. To date, no demonstration mission has been conducted for either case, and such a demonstration mission must be conducted prior to the need to utilize them during an actual scenario to ensure that an established, proven system is available for planetary defense when the need arises. One method that has been proposed to deliver a kinetic impactor with impact energy approaching that of an NED is the "billiard-ball" approach. This approach would involve capturing an asteroid approximately ten meters in diameter with a relatively small spacecraft (compared to the launch mass of an equivalent direct kinetic impactor), and redirecting it into the path of an Earth-threatening asteroid. This would cause an impact which would disrupt the Earth-threatening asteroid or deflect it from its Earth-crossing trajectory. The BILLIARDS Project seeks to perform a demonstration of this mission concept in order to establish a protocol that can be used in the event of an impending Earth/asteroid collision. In order to accomplish this objective, the mission must (1) rendezvous with a small (less than 10m), NEA (hereinafter "Alpha"), (2) maneuver Alpha to a collision with a approx. 100 m NEA (hereinafter "Beta"), and (3) produce a detectable deflection or disruption of Beta. In addition to these primary objectives, the BILLIARDS project will contribute to the scientific understanding of the physical properties and collision dynamics of asteroids, and provide opportunities for international collaboration.

Hungaria asteroid region telescopic spectral survey (HARTSS) I: Stony asteroids abundant in the Hungaria background population

NASA Astrophysics Data System (ADS)

Lucas, Michael P.; Emery, Joshua P.; Pinilla-Alonso, Noemi; Lindsay, Sean S.; Lorenzi, Vania

2017-07-01

The Hungaria asteroids remain as survivors of late giant planet migration that destabilized a now extinct inner portion of the primordial asteroid belt and left in its wake the current resonance structure of the Main Belt. In this scenario, the Hungaria region represents a ;purgatory; for the closest, preserved samples of the asteroidal material from which the terrestrial planets accreted. Deciphering the surface composition of these unique samples may provide constraints on the nature of the primordial building blocks of the terrestrial planets. We have undertaken an observational campaign entitled the Hungaria Asteroid Region Telescopic Spectral Survey (HARTSS) to record near-infrared (NIR) reflectance spectra in order to characterize their taxonomy, surface mineralogy, and potential meteorite analogs. The overall objective of HARTSS is to evaluate the compositional diversity of asteroids located throughout the Hungaria region. This region harbors a collisional family of Xe-type asteroids, which are situated among a background (i.e., non-family) of predominantly S-complex asteroids. In order to assess the compositional diversity of the Hungaria region, we have targeted background objects during Phase I of HARTSS. Collisional family members likely reflect the composition of one original homogeneous parent body, so we have largely avoided them in this phase. We have employed NIR instruments at two ground-based telescope facilities: the NASA Infrared Telescope Facility (IRTF), and the Telescopio Nazionale Galileo (TNG). Our data set includes the NIR spectra of 42 Hungaria asteroids (36 background; 6 family). We find that stony S-complex asteroids dominate the Hungaria background population (29/36 objects; ∼80%). C-complex asteroids are uncommon (2/42; ∼5%) within the Hungaria region. Background S-complex objects exhibit considerable spectral diversity as band parameter measurements of diagnostic absorption features near 1- and 2-μm indicate that several different S-subtypes are represented therein, which translates to a variety of surface compositions. We identify the Gaffey S-subtype (Gaffey et al. [1993]. Icarus 106, 573-602) and potential meteorite analogs for 24 of these S-complex background asteroids. Additionally, we estimate the olivine and orthopyroxene mineralogy for 18 of these objects using spectral band parameter analysis established from laboratory-based studies of ordinary chondrite meteorites. Nine of the asteroids have band parameters that are not consistent with ordinary chondrites. We compared these to the band parameters measured from laboratory VIS+NIR spectra of six primitive achondrite (acapulcoite-lodranite) meteorites. These comparisons suggest that two main meteorite groups are represented among the Hungaria background asteroids: unmelted, nebular L- (and possibly LL-ordinary chondrites), and partially-melted primitive achondrites of the acapulcoite-lodranite meteorite clan. Our results suggest a source region for L chondrite like material from within the Hungarias, with delivery to Earth via leakage from the inner boundary of the Hungaria region. H chondrite like mineralogies appear to be absent from the Hungaria background asteroids. We therefore conclude that the Hungaria region is not a source for H chondrite meteorites. Seven Hungaria background asteroids have spectral band parameters consistent with partially-melted primitive achondrites, but the probable source region of the acapulcoite-lodranite parent body remains inconclusive. If the proposed connection with the Hungaria family to fully-melted enstatite achondrite meteorites (i.e., aubrites) is accurate (Gaffey et al. [1992]. Icarus 100, 95-109; Kelley and Gaffey [2002]. Meteorit. Planet. Sci. 37, 1815-1827), then asteroids in the Hungaria region exhibit a full range of petrologic evolution: from nebular, unmelted ordinary chondrites, through partially-melted primitive achondrites, to fully-melted igneous aubrite meteorites.

Images of an Activated Asteroid

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-08-01

In late April of this year, asteroid P/2016 G1 (PANSTARRS) was discovered streaking through space, a tail of dust extending behind it. What caused this asteroids dust activity?Asteroid or Comet?Images of asteroid P/2016 G1 at three different times: late April, late May, and mid June. The arrow in the center panel points out an asymmetric feature that can be explained if the asteroid initially ejected material in a single direction, perhaps due to an impact. [Moreno et al. 2016]Asteroid P/2016 G1 is an interesting case: though it has the orbital elements of a main-belt asteroid it orbits at just under three times the EarthSun distance, with an eccentricity of e ~ 0.21 its appearance is closer to that of a comet, with a dust tail extending 20 behind it.To better understand the nature and cause of this unusual asteroids activity, a team led by Fernando Moreno (Institute of Astrophysics of Andalusia, in Spain) performed deep observations of P/2016 G1 shortly after its discovery. The team used the 10.4-meter Great Canary Telescope to image the asteroid over the span of roughly a month and a half.A Closer Look at P/2016 G1P/2016 G1 lies in the inner region of the main asteroid belt, so it is unlikely to have any ices that suddenly sublimated, causing the outburst. Instead, Moreno and collaborators suggest that the asteroids tail may have been caused by an impact that disrupted the parent body.To test this idea, the team used computer simulations to model their observations of P/2016 G1s dust tail. Based on their models, they demonstrate that the asteroid was likely activated on February 10 2016 roughly 350 days before it reached perihelion in its orbit and its activity was a short-duration event, lasting only ~24 days. The teams models indicate that over these 24 days, the asteroid lost around 20 million kilograms of dust, and at its maximum activity level, it was ejecting around 8 kg/s!Comparison of the observation from late May (panel a) and two models: one in which the emission is all isotropic (panel b), and one in which the emission is initially directed (panel c). The second model better fits the observations. [Adapted from Moreno et al. 2016]Activation By ImpactTo reproduce the observed asymmetric features in the asteroids tail, Moreno and collaborators show that the ejected material could not have been completely isotropically emitted. Instead, the observations can be reproduced if the material was initially ejected all in the same direction (away from the Sun) at the time of the asteroids activation.These conclusions support the idea that the asteroids parent body was impacted by another object. The initial impact caused a large ejection of material, and the subsequent activity is due to the partial or total disruption of the asteroid as a result of the impact.To further test this model for P/2016 G1, the next step is to obtain higher-resolution and higher-sensitivity imaging (as could be provided by Hubble) of this unusual object. Such images would allow scientists to search for smaller fragments of the parent body that could remain near the dust tail.CitationF. Moreno et al 2016 ApJ 826 L22. doi:10.3847/2041-8205/826/2/L22

Could G Asteroids be the Parent Bodies of the CM Chondrites?

NASA Astrophysics Data System (ADS)

Burbine, T. H.; Binzel, R. P.

1995-09-01

Since almost all meteorites are believed to be derived from asteroidal source bodies, the comparison of asteroid and meteorite spectra should allow for possible meteorite parent bodies to be identified. However only two asteroids with unique spectral characteristics, 4 Vesta with the basaltic achondrites [1] and near-Earth asteroid 3103 Eger with the aubrites [2], have been convincingly linked with any meteorite type. Farinella et al. [3] has done a study of 2355 numbered main-belt asteroids to determine which asteroids have the highest probability of having their fragments injected into the 3:1 mean motion and the nu6 secular resonance regions. Interestingly, asteroids with the third (19 Fortuna), tenth (1 Ceres) and eleventh (13 Egeria) highest theoretical total fragment delivery efficiencies are G-asteroids, a moderately rare type of asteroid with approximately ten known members. (Vesta has the fifth highest theoretical total fragment delivery efficiency.) G-asteroids tend to have the strongest ultraviolet, 0.7 micrometers and 3 micrometers absorption features of all C-type (B, C, F and G) asteroids, appearing to indicate that G-asteroids are at the upper range of the aqueous alteration sequence in the asteroid population. (The 0.7 micrometers feature is apparently due to iron oxides in hydrated silicates and the 3 micrometers feature is apparently due to hydrated minerals.) Meteorites that have reflectance spectra with a 3 micrometers feature of comparable intensity to those of the G-asteroids are the CI, CM and CR chondrites. However, G-asteroids (like all C-types) have ultraviolet absorption features that are weaker than previously measured meteorite spectra. Comparisons of reflectance spectra between Ceres and meteorite samples appear to indicate that Ceres is compositionally different from almost all known carbonaceous chondrites. Both Fortuna and Egeria have an absorption feature centered around 0.7 micrometers [4] that is similar in structure and strength to those found in many CM chondrites. The visible and near-infrared spectrum of Fortuna [5] matches very well the spectra of CM chondrites Murchison (bulk powder) [6] and LEW90500 (particle sizes less than 100 micrometers) [7]. However, the ultraviolet absorption feature is still weaker in Fortuna's spectrum. A spectrum of a bulk powder of LEW90500 does have an ultraviolet feature that matches Fortuna's feature, but this spectrum is substantially bluer than Fortuna in the near-infrared. Egeria's ultraviolet absorption feature also matches very well the ultraviolet feature in LEW90500Us (bulk powder) spectrum, but this spectrum is slightly redder than Egeria [5] in the near-infrared. The question is how unique is any postulated linkage between the CM chondrites and the G-asteroids. The problem is that approximately two-thirds of all C-type asteroids have 3 micrometers absorption features [8] and approximately three-fourths have 0.7 micrometers absorption features [4]. However of all observed C-type asteroids, Fortuna and Egeria appear to be two of the best spectral matches for the CM chondrites. Coupled with the high probability that these two asteroids are injecting large numbers of fragments into meteorite-supplying resonances, G-asteroids Fortuna and Egeria appear to be possible CM chondrite parent bodies. Acknowledgments: This research is supported by NASA Grant Number NAGW-2049. References: [1] Binzel R. P. and Xu S. (1993) Science, 260, 186-191. [2] Gaffey M. J. et al. (1992) Icarus, 100, 95-109. [3] Farinella P. et al. (1993) Icarus, 101, 174-187. [4] Sawyer S. R. (1991) Ph.D. thesis, Univ. of Texas, Austin. [5] Bell J. F. et al. (1988) LPS XIX, 57-58. [6] Gaffey M. J. (1976) JGR, 81, 905-920. [7] Hiroi T. et al. (1993) Science, 261, 1016-1018. [8] Jones T. D. et al. (1990) Icarus, 88,172-192.

The Joint Milli-Arcsecond Pathfinder Survey (JMAPS): Mission Overview and Attitude Sensing Applications

DTIC Science & Technology

2009-01-01

employs a set of reference targets such as asteroids that are relatively numer- ous, more or less uniformly distributed around the Sun, and relatively...point source-like. Just such a population exists—90 km-class asteroids . There are about 100 of these objects with relatively well-know orbits...These are main belt objects that are approximately evenly distributed around the sun. They are large enough to be quasi-spherical in nature, and as a

Asteroid Retrieval Mission Concept - Trailblazing Our Future in Space and Helping to Protect Us from Earth Impactors

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Brohpy, John R.; Merrill, Raymond G.

2013-01-01

The Asteroid Retrieval Mission (ARM) is a robotic mission concept with the goal of returning a small (7 m diameter) near-Earth asteroid (NEA), or part of a large NEA, to a safe, stable orbit in cislunar space using a 50 kW-class solar electric propulsion (SEP) robotic spacecraft (40 kW available to the electric propulsion system) and currently available technologies. The mass of the asteroidal material returned from this mission is anticipated to be up to 1,000 metric tons, depending on the orbit of the target NEA and the thrust-to-weight and control authority of the SEP spacecraft. Even larger masses could be returned in the future as technological capability and operational experience improve. The use of high-power solar electric propulsion is the key enabling technology for this mission concept, and is beneficial or enabling for a variety of space missions and architectures where high-efficiency, low-thrust transfers are applicable. Many of the ARM operations and technologies could also be applicable to, or help inform, planetary defense efforts. These include the operational approaches and systems associated with the NEA approach, rendezvous, and station-keeping mission phases utilizing a low-thrust, high-power SEP spacecraft, along with interacting with, capturing, maneuvering, and processing the massive amounts of material associated with this mission. Additionally, the processed materials themselves (e.g., high-specific impulse chemical propellants) could potentially be used for planetary defense efforts. Finally, a ubiquitous asteroid retrieval and resource extraction infrastructure could provide the foundation of an on call planetary defense system, where a SEP fleet capable of propelling large masses could deliver payloads to deflect or disrupt a confirmed impactor in an efficient and timely manner.

Asteroid families spin and shape models to be supported by the ProjectSoft robotic observatory

NASA Astrophysics Data System (ADS)

Brož, M.; Ďurech, J.; Hanuš, J.; Lehký, M.

2014-07-01

In our recent work (Hanuš et al. 2013), we studied dynamics of asteroid families constrained by the distribution of pole latitudes vs semimajor axis. The model contained the following ingredients: (i) the Yarkovsky semimajor-axis drift; (ii) secular spin evolution due to the YORP effect; (iii) collisional re-orientations; (iv) a simple treatment of spin-orbit resonances; and (v) of mass shedding. We suggest to use a different complementary approach, based on distribution functions of shape parameters. Based on ˜1000 old and new convex-hull shape models, we construct the distributions of suitable quantities (ellipticity, normalized facet areas, etc.) and we discuss a significance of differences among asteroid populations. We check for outlier points which may then serve as a possible identification of (large) interlopers among ''real'' family members. This has also implications for SPH models of asteroid disruptions which can be possibly further constrained by the shape models of resulting fragments. Up to now, the observed size-frequency distribution and velocity field were used as constraints, sometimes allowing for a removal of interlopers (Michel et al. 2011). We also outline an ongoing construction of the ProjectSoft robotic observatory called ''Blue Eye 600'', which will support our efforts to complete the sample of shapes for a substantial fraction of (large) family members. Dense photometry will be targeted in such a way to maximize a possibility to derive a new pole/shape model. Other possible applications of the observatory include: (i) fast resolved observations of fireballs (thanks to a fast-motion capability, tens of degrees per second); or, (ii) an automatic survey of a particular population of objects (main-belt and near-Earth asteroids, variable stars, novae etc.)

The Moon is a Planet Too: Lunar Science and Robotic Exploration

NASA Technical Reports Server (NTRS)

Cohen, Barbara A.

2009-01-01

This slide presentation reviews some of what is known about the moon, and draws parallels between the moon and any other terrestrial planet. The Moon is a cornerstone for all rocky planets The Moon is a terrestrial body, formed and evolved similarly to Earth, Mars, Mercury, Venus, and large asteroids The Moon is a differentiated body, with a layered internal structure (crust, mantle, and core) The Moon is a cratered body, preserving a record of bombardment history in the inner solar system The Moon is an active body, experiencing moonquakes, releasing primordial heat, conducting electricity, sustaining bombardment, and trapping volatile molecules Lunar robotic missions provide early science return to obtain important science and engineering objectives, rebuild a lunar science community, and keep our eyes on the Moon. These lunar missions, both past and future are reviewed.

Simulation-Based Height of Burst Map for Asteroid Airburst Damage Prediction

NASA Technical Reports Server (NTRS)

Aftosmis, Michael J.; Mathias, Donovan L.; Tarano, Ana M.

2017-01-01

Entry and breakup models predict that airburst in the Earth's atmosphere is likely for asteroids up to approximately 200 meters in diameter. Objects of this size can deposit over 250 megatons of energy into the atmosphere. Fast-running ground damage prediction codes for such events rely heavily upon methods developed from nuclear weapons research to estimate the damage potential for an airburst at altitude. (Collins, 2005; Mathias, 2017; Hills and Goda, 1993). In particular, these tools rely upon the powerful yield scaling laws developed for point-source blasts that are used in conjunction with a Height of Burst (HOB) map to predict ground damage for an airburst of a specific energy at a given altitude. While this approach works extremely well for yields as large as tens of megatons, it becomes less accurate as yields increase to the hundreds of megatons potentially released by larger airburst events. This study revisits the assumptions underlying this approach and shows how atmospheric buoyancy becomes important as yield increases beyond a few megatons. We then use large-scale three-dimensional simulations to construct numerically generated height of burst maps that are appropriate at the higher energy levels associated with the entry of asteroids with diameters of hundreds of meters. These numerically generated HOB maps can then be incorporated into engineering methods for damage prediction, significantly improving their accuracy for asteroids with diameters greater than 80-100 m.

Near Earth Asteroid Scout Thrust and Torque Model

NASA Technical Reports Server (NTRS)

Heaton, Andrew; Ahmad, Naeem; Miller, Kyle

2017-01-01

The Near Earth Asteroid (NEA) Scout is a solar sail mission whose objective is to scout at least one Near Earth Asteroid in preparation for manned missions to asteroids. NEA Scout will use a solar sail as the primary means of propulsion. Thus it is important for mission planning to accurately characterize the thrust of the sail. Additionally, the solar sail creates a relatively large solar disturbance torque that must be mitigated. For early mission design studies a flat plate model of the solar sail with a fixed center of pressure was adequate, but as mission concepts and the sail design matured, greater fidelity was required. Here we discuss the progress to a three-dimensional sail model that includes the effects of tension and thermal deformation that has been derived from a large structural Finite Element Model (FEM) developed by the Langley Research Center. We have found that the deformed sail membrane affects torque relatively much more than thrust. We have also found that other than uncertainty over the precise shape, the effect of small (approximately millimeter scale) wrinkles on the diffusivity of the sail is the leading remaining source of uncertainty. We demonstrate that millimeter-scale wrinkles can be modeled analytically as a change in the fraction of specular reflection. Finally we discuss the implications of these results for the NEA Scout mission.

Vesta Surface at High Resolution: Dominated by Impact Craters

NASA Image and Video Library

2012-02-13

This image from NASA Dawn spacecraft shows a large number of craters, formed by collisions into the surface of asteroid Vesta. The relatively large circular depressions in this image are older, heavily degraded impact craters.

Solar Sailing Kinetic Energy Interceptor (KEI) Mission for Impacting/Deflecting Near-Earth Asteroids

NASA Technical Reports Server (NTRS)

Wie, Bong

2005-01-01

A solar sailing mission architecture, which requires a t least ten 160-m, 300-kg solar sail spacecraft with a characteristic acceleration of 0.5 mm/sqs, is proposed as a realistic near- term option for mitigating the threat posed by near-Earth asteroids (NEAs). Its mission feasibility is demonstrated for a fictional asteroid mitigation problem created by AIAA. This problem assumes that a 200-m asteroid, designated 2004WR, was detected on July 4, 2004, and that the expected impact will occur on January 14, 2015. The solar sailing phase of the proposed mission for the AIAA asteroid mitigation problem is comprised of the initial cruise phase from 1 AU t o 0.25 AU (1.5 years), the cranking orbit phase (3.5 years), and the retrograde orbit phase (1 year) prior to impacting the target asteroid at its perihelion (0.75 AU from the sun) on January 1, 2012. The proposed mission will require at least ten kinetic energy interceptor (KEI) solar sail spacecraft. Each KEI sailcraft consists of a 160- m, 150-kg solar sail and a 150-kg microsatellite impactor. The impactor is to be separated from a large solar sail prior to impacting the 200-m target asteroid at its perihelion. Each 150-kg microsatellite impactor, with a relative impact velocity of at least 70 km/s, will cause a conservatively estimated AV of 0.3 cm/s in the trajectory of the 200-m target asteroid, due largely to the impulsive effect of material ejected from the newly-formed crater. The deflection caused by a single impactor will increase the Earth-miss-distance by 0.45Re (where Re denotes the Earth radius of 6,378 km). Therefore, at least ten KEI sailcraft will be required for consecutive impacts, but probably without causing fragmentation, to increase the total Earth-miss-distance by 4.5Re. This miss-distance increase of 29,000 km is outside of a typical uncertainty/error of about 10,000 km in predicting the Earth-miss- distance. A conventional Delta I1 2925 launch vehicle is capable of injecting at least two KEI sailcraft into an Earth escaping orbit. A 40-m solar sail is currently being developed by NASA and industries for a possible flight validation experiment within 10 years, and a 160-m solar sail is expected to be available within 20 years.

ASTEX - a study of a lander and orbiter mission to two near-Earth asteroids

NASA Astrophysics Data System (ADS)

Boehnhardt, Hermann; Nathues, Andreas; Harris, Alan; Astex Study Team

ASTEX stands for a feasibility study of an exploration mission to two near-Earth asteroids. The targets should have different mineralogical constitution, more specifically one asteroid should be of ‘primitive" nature, the other one should be "evolved". The scientific goal of such a mission is to explore the physical, geological and compositional constitution of the asteroids as planetary bodies as well as to provide information and constraints on the formation and evolution history of the objects per se and of the planetary system, here the asteroid belt, as a whole. Two aspects play an important role, i.e. the search and exploration for the origin and evolution of the primordial material for the formation of life in the solar system on one side and the understanding of the processes that have led to mineralogical differentiation of planetary embryos on the other side. The mission scenario consists of an orbiting and landing phase at each target. The immediate aims of the study are (1) to identify potential targets and to develop for selected pairs more detailed mission scenarios including the best possible propulsion systems to be used, (2) to define the scientific payload of the mission, (3) to analyse the requirements and options for the spacecraft bus and the lander system, and (4) to assess and to define requirements for the operational ground segment of the mission.This eight-months study is directed by the MPI for Solar System Research under support grant by DLR Bonn-Oberkassel and is performed in close collaboration between German scientific research institutes and industry. It is considered complementary to mission studies performed elsewhere and focussing on sample return and impact hazards and their remedy from near-Earth objects.

Multi-color lightcurve observation of the asteroid (163249) 2002 GT

NASA Astrophysics Data System (ADS)

Oshima, M.; Abe, S.

2014-07-01

NASA's Deep Impact/EPOXI spacecraft plans to encounter the asteroid (163249) 2002 GT, classified as a PHA (Potentially Hazardous Asteroid), on January 4, 2020. However, the taxonomic type and spin state of 2002 GT remain to be determined. We have carried out ground-based multi-color (B-V-R-I) lightcurve observations taking advantage of the 2002 GT Characterization Campaign by NASA. Multi-color lightcurve measurements allow us to estimate the rotation period and obtain strong constraints on the shape and pole orientation. Here we found that the rotation period of 2002 GT is estimated to be 3.7248 ± 0.1664 h. In mid-2013, 2002 GT passed at 0.015 au from the Earth, resulting an exceptional opportunity for ground-based characterization. Using the 0.81-m telescope of the Tenagra Observatory (110°52'44.8''W, +31°27'44.4''N, 1312 m) in Arizona, USA, and the Johnson-Cousins BVRI filters, we have found lightcurves of 2002 GT (Figure). The Tenagra II 0.81-m telescope is used for research of the Hayabusa2 target Asteroid (162173) 1999 JU_3. The lightcurves (relative magnitude) show that the rotation period of 2002 GT, the target of NASA's Deep Impact/EPOXI spacecraft, is estimated to be 3.7248 ± 0.1664 hr. On June 9, 2013, we had 7 hours of ground-based observations on 2002 GT from 4:00 to 11:00 UTC. The number of comparison stars for differential photometry was 34. Because of tracking the fast-moving asteroid, it was necessary to have the same comparison star among the fields of vision. We have also obtained absolute photometry of 2002 GT on June 13, 2013.

What makes a family reliable?

NASA Technical Reports Server (NTRS)

Williams, James G.

1992-01-01

Asteroid families are clusters of asteroids in proper element space which are thought to be fragments from former collisions. Studies of families promise to improve understanding of large collision events and a large event can open up the interior of a former parent body to view. While a variety of searches for families have found the same heavily populated families, and some searches have found the same families of lower population, there is much apparent disagreement between proposed families of lower population of different investigations. Indicators of reliability, factors compromising reliability, an illustration of the influence of different data samples, and a discussion of how several investigations perceived families in the same region of proper element space are given.

Aqueous alteration on main-belt asteroids

NASA Astrophysics Data System (ADS)

Fornasier, S.; Lantz, C.; Barucci, M.; Lazzarin, M.

2014-07-01

The study of aqueous alteration is particularly important for unraveling the processes occurring during the earliest times in Solar System history, as it can give information both on the thermal processes and on the localization of water sources in the asteroid belt, and for the associated astrobiological implications. The aqueous alteration process produces the low temperature (< 320 K) chemical alteration of materials by liquid water which acts as a solvent and produces materials like phyllosilicates, sulphates, oxides, carbonates, and hydroxides. This means that liquid water was present in the primordial asteroids, produced by the melting of water ice by heating sources, very probably by ^{26}Al decay. Hydrated minerals have been found mainly on Mars surface, on primitive main-belt asteroids (C, G, B, F, and P-type, following the classification scheme by Tholen, 1984) and possibly also on few transneptunian objects. Reflectance spectroscopy of aqueous altered asteroids shows absorption features in the 0.6-0.9 and 2.5-3.5-micron regions, which are diagnostic of, or associated with, hydrated minerals. In this work, we investigate the aqueous alteration process on a large sample of 600 visible spectra of C-complex asteroids available in the literature. We analyzed all these spectra in a similar way to characterize the absorption-band parameters (band center, depth, and width) and spectral slope, and to look for possible correlations between the aqueous alteration process and the asteroids taxonomic classes, orbital elements, heliocentric distances, albedo, and sizes. We find that 4.6 % of P, 7.7 % of F, 9.8 % of B, 50.5 % of C, and 100 % of the G-type asteroids have absorption bands in the visible region due to hydrated silicates. Our analysis shows that the aqueous alteration sequence starts from the P-type objects, practically unaltered, and increases through the P → F → B → C → G asteroids, these last being widely aqueously altered, strengthening thus the results previously obtained by Vilas (1994). We confirm the strong correlation between the 0.7-μm band and the 3-μ m band, the deepest feature associated with hydrated minerals, as 95 % of the asteroids showing the 0.7-μ m band have also the 3-μ m feature. 45 % of the asteroids belonging to the C-complex (the F, B, C, and G classes) have signatures of aqueously altered materials in the visible range. It must be noted that this percentage represents a lower limit in the number of hydrated asteroids, simply because the 3-μ m band, the main absorption feature produced by hydrated silicates, may be present in the spectra of primitive asteroids when no bands are detected in the visible range. All this considered, we estimate that 70 % of the C-complex asteroids might have the 3-μ m signature in the IR range and thus were affected by the aqueous alteration process in the past. We find that the aqueous alteration process dominates in primitive asteroids located between 2.3 and 3.1 au, that is, at smaller heliocentric distances than previously suggested by Vilas et al. (1993). The percentage of hydrated asteroids is strongly correlated with their size (Fornasier et al. 2014). The aqueous alteration process is less effective for bodies smaller than 50 km, while it dominates in the 50-240-km sized primitive asteroids. No correlation is found between the aqueous alteration process and the asteroid albedo or orbital elements. Aqueously altered asteroids are the plausible parent bodies of CM2 meteorites. Nevertheless, we see a systematic difference in the 0.7-μ m band center position, the CM2 meteorites having a band centered at longer wavelengths (0.71-0.75 μ m) compared to that of hydrated asteroids. Moreover, the hydrated asteroids are more clustered in spectral slope and band depth than the CM meteorites. All these spectral differences may be attributed to different mineral abundances (CM2 meteorites being more serpentine rich than the asteroids), and/or to grain-size effects, or simply to the fact the CM2 collected on the Earth might not be representative of the whole population of aqueously altered asteroids.

Three-body affairs in the outer solar system

NASA Astrophysics Data System (ADS)

Funato, Yoko; Makino, Junichiro; Hut, Piet; Kokubo, Eiichiro; Kinoshita, Daisuke

Recent observations have revealed an unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that populate the Kuiper Belt. The TNO binaries are strikingly different from asteroid binaries in four respects: their frequency is an order of magnitude larger, the mass ratio of their components is closer to unity, and their orbits are wider and highly eccentric. Two explanations have been proposed for their formation, one assuming large numbers of massive bodies, and one assuming large numbers of light bodies. We argue that both assumptions are unwarranted, and we show how TNO binaries can be produced from a modest number of intermediate-mass bodies of the type predicted by the gravitational instability theory for the formation of planetesimals. We start with a TNO binary population similar to the asteroid binary population, but subsequently modified by three-body exchange reactions, a process that is far more efficient in the Kuiper belt, because of the much smaller tidal perturbations by the Sun. Our mechanism can naturally account for all four characteristics that distinguish TNO binaries from main-belt asteroid binaries.

Polarimetric survey of main-belt asteroids. VI. New results from the second epoch of the CASLEO survey

NASA Astrophysics Data System (ADS)

Gil-Hutton, R.; García-Migani, E.

2017-11-01

Aims: We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry and to estimate the diversity in the polarimetric properties of asteroids that belong to different taxonomic classes. Methods: The data were obtained using the CASPOL polarimeter at the 2.15 m telescope. CASPOL is a polarimeter based on a CCD detector and a Savart plate. The survey began in 1995 and data on a large sample of asteroids were obtained until 2012. A second period began in 2013 using a polarimeter with a more sensitive detector in order to study small asteroids, families, and special taxonomic groups. Results: We present and analyze the unpublished results for 128 asteroids of different taxonomic types, 55 of them observed for the first time. The observational data allowed us to find probable new cases of Barbarian objects but also two D-type objects, (565) Marbachia and (1481) Tubingia, that seem to have phase-polarization curves with a large inversion angle. The data obtained combined with data from the literature enabled us to find phase-polarization curves for 121 objects of different taxonomic types and to study the relations between several polarimetric and physical parameters. Using an approximation for the phase-polarization curve we found the index of refraction of the surface material and the scatter separation distance for all the objects with known polarimetric parameters. We also found that the inversion angle is a function of the index of refraction of the surface, while the phase angle where the minimum of polarization is produced provides information about the distance between scatter particles or, to some extent, the porosity of the surface. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A103

Prospective very young asteroid pairs

NASA Astrophysics Data System (ADS)

Galád, A.; Vokrouhlický, D.; Zizka, J.

2014-07-01

Several tens of asteroid pairs can be discerned from the background main-belt asteroids. The majority of them are thought to have formed within only the last few 10^6 yr. The youngest recognized pairs have formed more than ≈ 10 kyr ago. As some details of pair formation are still not understood well, the study of young pairs is of great importance. It is mainly because the conditions at the time of the pair formation could be deduced much more reliably for young pairs. For example, space weathering on the surfaces of the components, or changes in their rotational properties (in spin rates, tumbling, coordinates of rotational pole) could be negligible since the formation of young pairs. Also, possible strong perturbations by main-belt bodies on pair formation can be reliably studied only for extremely young pairs. Some pairs can quickly blend in with the background asteroids, so even the frequency of asteroid pair formation could be determined more reliably based on young pairs (though only after a statistically significant sample is at disposal). In our regular search for young pairs in the growing asteroid database, only multiopposition asteroids with very similar orbital and proper elements are investigated. Every pair component is represented by a number of clones within orbital uncertainties and drifting in semimajor axis due to the Yarkovsky effect. We found that, if the previously unrecognized pairs (87887) 2000 SS_{286} - 2002 AT_{49} and (355258) 2007 LY_{4} - 2013AF_{40} formed at the recent very close approach of their components, they could become the youngest known pairs. In both cases, the relative encounter velocities of the components were only ˜ 0.1 m s^{-1}. However, the minimum distances between some clones are too large and a few clones of the latter pair did not encounter recently (within ≈ 10 kyr). The age of some prospective young pairs cannot be determined reliably without improved orbital properties (e.g., the second component of a pair (320025) 2007 DT_{76} - 2007 DP_{16}). It is because some components suffered recently repeated close approaches to Ceres or other large main-belt perturbers. In general, the uncertainties in age estimation can be heavily reduced after the physical properties (e.g., sense of rotation, shape, size, binarity) of the pair components are determined.

The influence of global self-heating on the Yarkovsky and YORP effects

NASA Astrophysics Data System (ADS)

Rozitis, B.; Green, S. F.

2013-07-01

In addition to collisions and gravitational forces, there is a growing amount of evidence that photon recoil forces from the asymmetric reflection and thermal re-radiation of absorbed sunlight are primary mechanisms that are fundamental to the physical and dynamical evolution of small asteroids. The Yarkovsky effect causes orbital drift, and the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect causes changes in the rotation rate and pole orientation. We present an adaptation of the Advanced Thermophysical Model to simultaneously predict the Yarkovsky and YORP effects in the presence of global self-heating that occurs within the large concavities of irregularly shaped asteroids, which has been neglected or dismissed in all previous models. It is also combined with rough surface thermal-infrared beaming effects, which have been previously shown to enhance the Yarkovsky orbital drift and dampen on average the YORP rotational acceleration by orders of several tens of per cent. Tests on all published concave shape models of near-Earth asteroids, and also on 100 Gaussian random spheres, show that the Yarkovsky effect is sensitive to shadowing and global self-heating effects at the few per cent level or less. For simplicity, Yarkovsky models can neglect these effects if the level of accuracy desired is of this order. Unlike the Yarkovsky effect, the YORP effect can be very sensitive to shadowing and global self-heating effects. Its sensitivity increases with decreasing relative strength of the YORP rotational acceleration, and does not appear to depend greatly on the degree of asteroid concavity. Global self-heating tends to produce a vertical offset in an asteroid's YORP-rotational-acceleration versus obliquity curve which is in opposite direction to that produced by shadowing effects. It also ensures that at least one critical obliquity angle exists at which zero YORP rotational acceleration occurs. Global self-heating must be included for accurate predictions of the YORP effect if an asteroid exhibits a large shadowing effect. If global self-heating effects are not included, then it is found in ˜75 per cent of cases that better predictions are produced when shadowing is also not included. Furthermore, global self-heating has implications for reducing the sensitivity of the YORP effect predictions to detailed variations in an asteroid's shape model.

The Rotational Properties of Multi-tailed Asteroid P/2013 P5

NASA Astrophysics Data System (ADS)

Gustafsson, Annika; Moskovitz, Nicholas; Levine, Stephen

2014-11-01

To date, there are twelve known celestial bodies in the Solar System, labeled Main Belt Comets (e.g. Hsieh & Jewitt, 2006) or Active Asteroids (Jewitt, 2012) that exhibit both asteroid and comet-like properties. Among them is P/2013 P5, a comet-asteroid transition object discovered by PAN-STARRS in August 2013. Observations made with the Hubble Space Telescope in September 2013 revealed that P/2013 P5 appears to have six comet-like dust tails. Jewitt et al. (2013) concluded that this extraordinary structure and activity cannot be explained by traditional near-surface ice sublimation or collision events ejecting particles from the asteroid’s surface. Instead, the most likely explanation is that this unusual object has been spun-up by YORP torques to a critical limit that has resulted in the rotational disruption of the asteroid causing the unique six-tail structure. This interpretation predicts that the nucleus of this comet-like asteroid should be in rapid rotation. In November 2013, broadband photometry of P/2013 P5 was obtained with Lowell Observatory’s 4-meter Discovery Channel Telescope using the Large Monolithic Imager to investigate the possibility of rapid rotation. On chip optimal aperture photometry was performed on P/2013 P5. At an apparent magnitude V=22.5 magnitude, we found no significant variability in the light curve at the level of 0.15 magnitudes. General morphology changes in the nucleus-coma system of the asteroid were also investigated. We will present our analysis of this search for variability in both time and spatially across the coma relative to the object’s center of brightness. Hsieh, H. H., & Jewitt, D. 2006, Science, 312, 561Jewitt, D. 2012, AJ, 143, 66Jewitt, D.C., Agarwal, J., Weaver, H., Mutchler, M., & Larson, S. 2013, ApL, 778

Asteroid retrieval missions enabled by invariant manifold dynamics

NASA Astrophysics Data System (ADS)

Sánchez, Joan Pau; García Yárnoz, Daniel

2016-10-01

Near Earth Asteroids are attractive targets for new space missions; firstly, because of their scientific importance, but also because of their impact threat and prospective resources. The asteroid retrieval mission concept has thus arisen as a synergistic approach to tackle these three facets of interest in one single mission. This paper reviews the methodology used by the authors (2013) in a previous search for objects that could be transported from accessible heliocentric orbits into the Earth's neighbourhood at affordable costs (or Easily Retrievable Objects, a.k.a. EROs). This methodology consisted of a heuristic pruning and an impulsive manoeuvre trajectory optimisation. Low thrust propulsion on the other hand clearly enables the transportation of much larger objects due to its higher specific impulse. Hence, in this paper, low thrust retrieval transfers are sought using impulsive trajectories as first guesses to solve the optimal control problem. GPOPS-II is used to transcribe the continuous-time optimal control problem to a nonlinear programming problem (NLP). The latter is solved by IPOPT, an open source software package for large-scale NLPs. Finally, a natural continuation procedure that increases the asteroid mass allows to find out the largest objects that could be retrieved from a given asteroid orbit. If this retrievable mass is larger than the actual mass of the asteroid, the asteroid retrieval mission for this particular object is said to be feasible. The paper concludes with an updated list of 17 EROs, as of April 2016, with their maximum retrievable masses by means of low thrust propulsion. This ranges from 2000 tons for the easiest object to be retrieved to 300 tons for the least accessible of them.

Shape and spin determination of Barbarian asteroids

NASA Astrophysics Data System (ADS)

Devogèle, M.; Tanga, P.; Bendjoya, P.; Rivet, J. P.; Surdej, J.; Hanuš, J.; Abe, L.; Antonini, P.; Artola, R. A.; Audejean, M.; Behrend, R.; Berski, F.; Bosch, J. G.; Bronikowska, M.; Carbognani, A.; Char, F.; Kim, M.-J.; Choi, Y.-J.; Colazo, C. A.; Coloma, J.; Coward, D.; Durkee, R.; Erece, O.; Forne, E.; Hickson, P.; Hirsch, R.; Horbowicz, J.; Kamiński, K.; Kankiewicz, P.; Kaplan, M.; Kwiatkowski, T.; Konstanciak, I.; Kruszewki, A.; Kudak, V.; Manzini, F.; Moon, H.-K.; Marciniak, A.; Murawiecka, M.; Nadolny, J.; Ogłoza, W.; Ortiz, J. L.; Oszkiewicz, D.; Pallares, H.; Peixinho, N.; Poncy, R.; Reyes, F.; de los Reyes, J. A.; Santana-Ros, T.; Sobkowiak, K.; Pastor, S.; Pilcher, F.; Quiñones, M. C.; Trela, P.; Vernet, D.

2017-11-01

Context. The so-called Barbarian asteroids share peculiar, but common polarimetric properties, probably related to both their shape and composition. They are named after (234) Barbara, the first on which such properties were identified. As has been suggested, large scale topographic features could play a role in the polarimetric response, if the shapes of Barbarians are particularly irregular and present a variety of scattering/incidence angles. This idea is supported by the shape of (234) Barbara, that appears to be deeply excavated by wide concave areas revealed by photometry and stellar occultations. Aims: With these motivations, we started an observation campaign to characterise the shape and rotation properties of Small Main-Belt Asteroid Spectroscopic Survey (SMASS) type L and Ld asteroids. As many of them show long rotation periods, we activated a worldwide network of observers to obtain a dense temporal coverage. Methods: We used light-curve inversion technique in order to determine the sidereal rotation periods of 15 asteroids and the convergence to a stable shape and pole coordinates for 8 of them. By using available data from occultations, we are able to scale some shapes to an absolute size. We also study the rotation periods of our sample looking for confirmation of the suspected abundance of asteroids with long rotation periods. Results: Our results show that the shape models of our sample do not seem to have peculiar properties with respect to asteroids with similar size, while an excess of slow rotators is most probably confirmed. The light curves are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A119

Discovery of Spin-Rate-Dependent Asteroid Thermal Inertia

NASA Astrophysics Data System (ADS)

Harris, Alan; Drube, Line

2016-10-01

Knowledge of the surface thermal inertia of an asteroid can provide insight into surface structure: porous material has a lower thermal inertia than rock. Using WISE/NEOWISE data and our new asteroid thermal-inertia estimator we show that the thermal inertia of main-belt asteroids (MBAs) appears to increase with spin period. Similar behavior is found in the case of thermophysically-modeled thermal inertia values of near-Earth objects (NEOs). We interpret our results in terms of rapidly increasing material density and thermal conductivity with depth, and provide evidence that thermal inertia increases by factors of 10 (MBAs) to 20 (NEOs) within a depth of just 10 cm. On the basis of a picture of depth-dependent thermal inertia our results suggest that, in general, thermal inertia values representative of solid rock are reached some tens of centimeters to meters below the surface in the case of MBAs (the median diameter in our dataset = 24 km). In the case of the much smaller (km-sized) NEOs a thinner porous surface layer is indicated, with large pieces of solid rock possibly existing just a meter or less below the surface. These conclusions are consistent with our understanding from in-situ measurements of the surfaces of the Moon, and a few asteroids, and suggest a very general picture of rapidly changing material properties in the topmost regolith layers of asteroids. Our results have important implications for calculations of the Yarkovsky effect, including its perturbation of the orbits of potentially hazardous objects and those of asteroid family members after the break-up event. Evidence of a rapid increase of thermal inertia with depth is also an important result for studies of the ejecta-enhanced momentum transfer of impacting vehicles ("kinetic impactors") in planetary defense.

Assessing the Age of an Asteroid's Surface with Data from the International Rosetta Mission

NASA Technical Reports Server (NTRS)

Lopez, Juan Carlos

2011-01-01

Rosetta is an international mission led by the European Space Agency (ESA) with key support and instrumentation from the National Aeronautics and Space Administration (NASA). Rosetta is currently on a ten-year mission to catch comet 67P/Churyumov-Gerasimenko (C-G); throughout its voyage, the spacecraft has performed flybys of two main belt asteroids (MBA): Steins and Lutetia. Data on the physical, chemical, and geological properties of these asteroids are currently being processed and analyzed. Accurate interpretation of such data is fundamental in the success of Rosetta's mission and overall objectives. Post-flyby data analyses strive to correlate the size, shape, volume, and rotational rate of Lutetia, in addition to interpreting its multi-color imagining, albedo, and spectral mapping. Although advancements in science have contributed to the examination of celestial bodies, methods to analyze asteroids remain largely empirical, not semi-empirical, nor ab initio. This study aims to interpret and document the scientific methods currently utilized in the characterization of asteroid (21) Lutetia in order to render these processes and methods accessible to the public. Examples include a standardized technique for assessing the age of an asteroid surface, complete with clickable reference maps, methodology of grouping surface characteristics together, and a standardized power law equation for the age. Other examples include determining the density of an object. Context for what both density and age mean is a bi-product of this study. Results of the study will aid in the development of pedagogical material on asteroids for public use, and in creation of an academic database for selected targets that might be used as a reference.

Asteroid shape and spin statistics from convex models

NASA Astrophysics Data System (ADS)

Torppa, J.; Hentunen, V.-P.; Pääkkönen, P.; Kehusmaa, P.; Muinonen, K.

2008-11-01

We introduce techniques for characterizing convex shape models of asteroids with a small number of parameters, and apply these techniques to a set of 87 models from convex inversion. We present three different approaches for determining the overall dimensions of an asteroid. With the first technique, we measured the dimensions of the shapes in the direction of the rotation axis and in the equatorial plane and with the two other techniques, we derived the best-fit ellipsoid. We also computed the inertia matrix of the model shape to test how well it represents the target asteroid, i.e., to find indications of possible non-convex features or albedo variegation, which the convex shape model cannot reproduce. We used shape models for 87 asteroids to perform statistical analyses and to study dependencies between shape and rotation period, size, and taxonomic type. We detected correlations, but more data are required, especially on small and large objects, as well as slow and fast rotators, to reach a more thorough understanding about the dependencies. Results show, e.g., that convex models of asteroids are not that far from ellipsoids in root-mean-square sense, even though clearly irregular features are present. We also present new spin and shape solutions for Asteroids (31) Euphrosyne, (54) Alexandra, (79) Eurynome, (93) Minerva, (130) Elektra, (376) Geometria, (471) Papagena, and (776) Berbericia. We used a so-called semi-statistical approach to obtain a set of possible spin state solutions. The number of solutions depends on the abundancy of the data, which for Eurynome, Elektra, and Geometria was extensive enough for determining an unambiguous spin and shape solution. Data of Euphrosyne, on the other hand, provided a wide distribution of possible spin solutions, whereas the rest of the targets have two or three possible solutions.

Observing the variation of asteroid thermal inertia with heliocentric distance

NASA Astrophysics Data System (ADS)

Rozitis, B.; Green, S. F.; MacLennan, E.; Emery, J. P.

2018-06-01

Thermal inertia is a useful property to characterize a planetary surface, since it can be used as a qualitative measure of the regolith grain size. It is expected to vary with heliocentric distance because of its dependence on temperature. However, no previous investigation has conclusively observed a change in thermal inertia for any given planetary body. We have addressed this by using NEOWISE data and the Advanced Thermophysical Model to study the thermophysical properties of the near-Earth asteroids (1036) Ganymed, (1580) Betulia, and (276 049) 2002 CE26 as they moved around their highly eccentric orbits. We confirm that the thermal inertia values of Ganymed and 2002 CE26 do vary with heliocentric distance, although the degree of variation observed depends on the spectral emissivity assumed in the thermophysical modelling. We also confirm that the thermal inertia of Betulia did not change for three different observations obtained at the same heliocentric distance. Depending on the spectral emissivity, the variations for Ganymed and 2002 CE26 are potentially more extreme than that implied by theoretical models of heat transfer within asteroidal regoliths, which might be explained by asteroids having thermal properties that also vary with depth. Accounting for this variation reduces a previously observed trend of decreasing asteroid thermal inertia with increasing size, and suggests that the surfaces of small and large asteroids could be much more similar than previously thought. Furthermore, this variation can affect Yarkovsky orbital drift predictions by a few tens of per cent.

Spin State Equilibria of Asteroids due to YORP Effects

NASA Astrophysics Data System (ADS)

Golubov, Oleksiy; Scheeres, Daniel J.; Lipatova, Veronika

2016-05-01

Spins of small asteroids are controlled by the Yarkovsky--O'Keefe--Radzievskii--Paddack (YORP) effect. The normal version of this effect has two components: the axial component alters the rotation rate, while the obliquity component alters the obliquity. Under this model the rotation state of an asteroid can be described in a phase plane with the rotation rate along the polar radius and the obliquity as the polar angle. The YORP effect induces a phase flow in this plane, which determines the distribution of asteroid rotation rates and obliquities.We study the properties of this phase flow for several typical cases. Some phase flows have stable attractors, while in others all trajectories go to very small or large rotation rates. In the simplest case of zero thermal inertia approximate analytical solutions to dynamics equations are possible. Including thermal inertia and the Tangential YORP effect makes the possible evolutionary scenarios much more diverse. We study possible evolution paths and classify the most general trends. Also we discuss possible implications for the distribution of asteroid rotation rates and obliquities.A special emphasis is put on asteroid (25143) Itokawa, whose shape model is well determined, but who's measured YORP acceleration does not agree with the predictions of normal YORP. We show that Itokawa's rotational state can be explained by the presence of tangential YORP and that it may be in or close to a stable spin state equilibrium. The implications of such states will be discussed.

Candidate Binary Trojan and Hilda Asteroids from Rotational Light Curves

NASA Astrophysics Data System (ADS)

Sonnett, Sarah M.; Mainzer, Amy K.; Grav, Tommy; Masiero, Joseph R.; Bauer, James M.; Kramer, Emily A.

2017-10-01

Jovian Trojans (hereafter, Trojans) are asteroids in stable orbits at Jupiter's L4 and L5 Lagrange points, and Hilda asteroids are inwards of the Trojans in 3:2 mean-motion resonance with Jupiter. Due to their special dynamical properties, observationally constraining the formation location and dynamical histories of Trojans and HIldas offers key input for giant planet migration models. A fundamental parameter in assessing formation location is the bulk density - with low-density objects associated with an ice-rich formation environment in the outer solar system and high-density objects typically linked to the warmer inner solar system. Bulk density can only be directly measured during a close fly-by or by determining the mutual orbits of binary asteroid systems. With the aim of determining densities for a statistically significant sample of Trojans and Hildas, we are undertaking an observational campaign to confirm and characterize candidate binary asteroids published in Sonnett et al. (2015). These objects were flagged as binary candidates because their large NEOWISE brightness variations imply shapes so elongated that they are not likely explained by a singular equilibrium rubble pile and instead may be two elongated, gravitationally bound asteroids. We are obtaining densely sampled rotational light curves of these possible binaries to search for light curve features diagnostic of binarity and to determine the orbital properties of any confirmed binary systems by modeling the light curve. We compare the We present an update on this follow-up campaign and comment on future steps.

Minor planets and related objects. XIX - Shape and pole orientation of /39/ Laetitia

NASA Technical Reports Server (NTRS)

Sather, R. E.

1976-01-01

Results are reported for analyses of UBV photoelectric photometric data and light curves of the asteroid Laetitia. The pole orientation is determined using a technique for reducing the scatter in the magnitude-phase relation. No significant variations in color are found over the surface, and the light curves are found to indicate topographic elements (peaks, scarps, or depressions) approximately 10 km in radius. It is shown that the light-curve amplitudes as well as the wide scatter in observed magnitude and phase relation can be explained by a triaxial ellipsoidal figure with a dimensional ratio of about 15:9:5. It is concluded that the size, shape, and composition of this asteroid are highly suggestive of a major collisional fragment from a substantially more massive differentiated parent body.

Short arc orbit determination and imminent impactors in the Gaia era

NASA Astrophysics Data System (ADS)

Spoto, F.; Del Vigna, A.; Milani, A.; Tommei, G.; Tanga, P.; Mignard, F.; Carry, B.; Thuillot, W.; David, P.

2018-06-01

Short-arc orbit determination is crucial when an asteroid is first discovered. In these cases usually the observations are so few that the differential correction procedure may not converge. We developed an initial orbit computation method, based on systematic ranging, which is an orbit determination technique that systematically explores a raster in the topocentric range and range-rate space region inside the admissible region. We obtained a fully rigorous computation of the probability for the asteroid that could impact the Earth within a few days from the discovery without any a priori assumption. We tested our method on the two past impactors, 2008 TC3 and 2014 AA, on some very well known cases, and on two particular objects observed by the European Space Agency Gaia mission.

Impact Hazard Monitoring: Theory and Implementation

NASA Astrophysics Data System (ADS)

Farnocchia, Davide

2015-08-01

Impact monitoring is a crucial component of the mitigation or elimination of the hazard posed by asteroid impacts. Once an asteroid is discovered, it is important to achieve an early detection and an accurate assessment of the risk posed by future Earth encounters. Here we review the most standard impact monitoring techniques. Linear methods are the fastest approach but their applicability regime is limited because of the chaotic dynamics of near-Earth asteroids, whose orbits are often scattered by planetary encounters. Among nonlinear methods, Monte Carlo algorithms are the most reliable ones. However, the large number of near-Earth asteroids and the computational load required to detect low probability impact events make Monte Carlo approaches impractical in the framework of monitoring all near-Earth asteroids. In the last 15 years, the Line of Variations (LOV) method has been the most successful technique as it strikes a remarkable compromise between computational efficiency and the capability of detecting low probability events deep in the nonlinear regime. As a matter of fact, the LOV method is the engine of JPL’s Sentry and University of Pisa’s NEODyS, which the two fully automated impact monitoring systems that routinely search for potential impactors among known near-Earth asteroids. We also present some more recent techniques developed to deal with the new challenges arising in the impact hazard assessment problem. In particular, we describe how to use keyhole maps to go beyond strongly scattering encounters and push forward in time the impact prediction horizon. In these cases asteroids usually have a very well constrained orbit and we often need to account for the action of nongravitational perturbations, especially the Yarkovsky effect. Finally, we discuss the short-term hazard assessment problem for newly discovered asteroids, when only a short observed arc is available. The limited amount of observational data generally leads to severe degeneracies in the orbit estimation process. We overcome these degeneracies by employing ranging techniques, which scan the poorly constrained space of topocentric range and range rate.

Physical characterization of (333358) 2001 WN1: a large, possibly water-rich, low delta-V near-Earth asteroid.

NASA Astrophysics Data System (ADS)

Hicks, M.; Dombroski, D.

2012-12-01

The near-Earth asteroid (333358) 2001 WN1 was discovered on 2001 November 17 by the LINEAR NEO survey (MPEC 2001-W30). We obtained one night of Bessel BVRI on 2012 November 25 at the JPL Table Mountain Observatory (TMO) 0.6-m telescope. The observational circumstances are summarized in Table 1, with heliocentric, geocentric, solar phase angle, lunar elongation, and expected V magnitude as computed by the JPL HORIZONS ephemeris service.

Elements of planetary protection against asteroid and comet hazard

NASA Astrophysics Data System (ADS)

Steklov, A. F.; Vidmachenko, A. P.; Dashkiev, G. N.; Zhilyaev, B. E.

2018-05-01

The principles of protection against asteroid-comet hazard should constitute the main priority of the modern Proto-cosmic civilization on the planet Earth. Any impact of a fairly large asteroid or cometary nucleus with a size of 1 to 20 or more kilometers will lead to a global catastrophe and, perhaps, to the death of Mankind. Forces in order to withstand such a blow of the cosmic body during large space invasions, we do not have and, most likely, will not be for a long time . We need as soon as possible to create technical facilities and systems for long-term comfortable living of large colonies of people on the Moon, Mars, Venus and Mercury, having arranged there some elements of the biosphere. In these colonies people should live in extraterrestrial space settlements, and should periodically and constantly "outplay" scenarios of reliable and guaranteed re-population of the planet Earth by people. Such periodic "exercises" on the actual modeling of the return to the "post-catastrophic" Earth should ensure the survival of humanity even in the worst versions of the consequences of possible dangerous space invasions. That is, we should always be ready for the repopulation on the Earth by people and for the reconstruction of the basic elements of the man's biosphere.

The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop

NASA Technical Reports Server (NTRS)

Morrison, David (Editor)

1992-01-01

Impacts by Earth-approaching asteroids and comets pose a significant hazard to life and property. Although the annual probability of the Earth being struck by a large asteroid or comet is extremely small, the consequences of such a collision are so catastrophic that it is prudent to assess the nature of the threat and to prepare to deal with it. The first step in any program for the prevention or mitigation of impact catastrophes must involve a comprehensive search for Earth-crossing asteroids and comets and a detailed analysis of their orbits. At the request of the U.S. Congress, NASA has carried out a preliminary study to define a program for dramatically increasing the detection rate of Earth-crossing objects, as documented in this workshop report.

Mitigation of Earth-asteroid collisions via explosive, intense radiation sources

NASA Astrophysics Data System (ADS)

Miles, Aaron; Sanders, James

2005-10-01

The Universe is continually producing astrophysical explosions that generate intense bursts of electromagnetic and particle radiation. Interaction of this radiation with nearby objects can effect significant changes to their dynamics through a variety of processes including ionization, ablation, and shock generation. The next time a large asteroid or comet is found to be approaching the Earth on an impact trajectory, humans may find it prudent to mimic nature by using the most intense radiation sources available to alter the incoming object's trajectory and avert a catastrophic collision. With this in mind, we consider the effect of nuclear explosives on nearby would-be Earth impactors. Neutrons and x-rays produced in the explosion are deposited in a thin layer of the asteroid's surface, resulting in ablation and shock and thereby imparting a deflection velocity. A Monte Carlo code is used for radiation transport and energy deposition, while the subsequent dynamic evolution of the asteroid is followed with the hydrodynamics code CALE. We consider the dependence of the deflection velocity on the source energy and spectrum, the asteroid or comet composition, and the standoff distance between the target and the source. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Waves Generated by Asteroid Impacts and Their Hazard Consequences on The Shorelines

NASA Astrophysics Data System (ADS)

Ezzedine, S. M.; Miller, P. L.; Dearborn, D. S.

2014-12-01

We have performed numerical simulations of a hypothetical asteroid impact onto the ocean in support of an emergency preparedness, planning, and management exercise. We addressed the scenario from asteroid entry; to ocean impact (splash rim); to wave generation, propagation, and interaction with the shoreline. For the analysis we used GEODYN, a hydrocode, to simulate the impact and generate the source wave for the large-scale shallow water wave program, SWWP. Using state-of-the-art, high-performance computing codes we simulated three impact areas — two are located on the West Coast near Los Angeles's shoreline and the San Francisco Bay, respectively, and the third is located in the Gulf of Mexico, with a possible impact location between Texas and Florida. On account of uncertainty in the exact impact location within the asteroid risk corridor, we examined multiple possibilities for impact points within each area. Uncertainty in the asteroid impact location was then convolved and represented as uncertainty in the shoreline flooding zones. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and partially funded by the Laboratory Directed Research and Development Program at LLNL under tracking code 12-ERD-005.

A NEW LARGE SUPER-FAST ROTATOR: (335433) 2005 UW163

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chan-Kao; Lin, Hsing-Wen; Ip, Wing-Huen

2014-08-20

Asteroids of size larger than 150 m generally do not have rotation periods smaller than 2.2 hr. This spin cutoff is believed to be due to the gravitationally bound rubble-pile structures of the asteroids. Rotation with periods exceeding this critical value will cause asteroid breakup. Up until now, only one object, 2001 OE84, has been found to be an exception to this spin cutoff. We report the discovery of a new super-fast rotator, (335433) 2005 UW163, spinning with a period of 1.290 hr and a light curve variation of r' ∼ 0.8 mag from the observations made at the P48 telescope andmore » the P200 telescope of the Palomar Observatory. Its H{sub r{sup ′}}=17.69±0.27 mag and multi-band colors (i.e., g' – r' = 0.68 ± 0.03 mag, r' – i' = 0.19 ± 0.02 mag and SDSS i – z = –0.45 mag) show it is a V-type asteroid with a diameter of 0.6 + 0.3/ – 0.2 km. This indicates (335433) 2005 UW163 is a super-fast rotator beyond the regime of the small monolithic asteroid.« less

The asteroid-meteorite connection: Forging a new link to Vesta as the parent body of basaltic achondrite (HED) meteorites

NASA Technical Reports Server (NTRS)

Binzel, R. P.

1993-01-01

Asteroid 4 Vesta has been at the center of the debate over the identity of the howardite eucrite diogenite (HED) parent body since the early 1970s. Despite its unique (among the 500 largest asteroids) compositional match to HED meteorites, substantial dynamical difficulties in delivering fragments from Vesta to the Earth have precluded any conclusive HED parent body link. These dynamical difficulties arise because Vesta's orbital location is far from known resonances. Consequently, it has been argued as dynamically improbable that meteoroid-sized (1 km) fragments could be excavated from Vesta with sufficient velocities to reach the resonances. Through new astronomical observations, numerous small (4-7 km) asteroids between Vesta and the 3:1 resonance have been discovered to have eucrite and diogenite compositions. Based on similar orbital elements to Vesta, all of these new asteroids are likely large impact fragments excavated from Vesta. Their current orbits imply ejection velocities in excess of 700 m/sec. Smaller (1 km) fragments can therefore be expected to have been ejected with velocities greater than 1 km/sec, sufficient to reach the 3:1 and v6 resonances. Thus it now appears to be dynamically viable for Vesta to be linked as the HED parent body.

Sparse source configurations in radio tomography of asteroids

NASA Astrophysics Data System (ADS)

Pursiainen, S.; Kaasalainen, M.

2014-07-01

Our research targets at progress in non-invasive imaging of asteroids to support future planetary research and extra-terrestrial mining activities. This presentation concerns principally radio tomography in which the permittivity distribution inside an asteroid is to be recovered based on the radio frequency signal transmitted from the asteroid's surface and gathered by an orbiter. The focus will be on a sparse distribution (Pursiainen and Kaasalainen, 2013) of signal sources that can be necessary in the challenging in situ environment and within tight payload limits. The general goal in our recent research has been to approximate the minimal number of source positions needed for robust localization of anomalies caused, for example, by an internal void. Characteristic to the localization problem are the large relative changes in signal speed caused by the high permittivity of typical asteroid minerals (e.g. basalt), meaning that a signal path can include strong refractions and reflections. This presentation introduces results of a laboratory experiment in which real travel time data was inverted using a hierarchical Bayesian approach combined with the iterative alternating sequential (IAS) posterior exploration algorithm. Special interest was paid to robustness of the inverse results regarding changes of the prior model and source positioning. According to our results, strongly refractive anomalies can be detected with three or four sources independently of their positioning.

Circumpulsar Asteroids: Inferences from Nulling Statistics and High Energy Correlations

NASA Astrophysics Data System (ADS)

Shannon, Ryan; Cordes, J. M.

2006-12-01

We have proposed that some classes of radio pulsar variability are associated with the entry of neutral asteroidal material into the pulsar magnetosphere. The region surrounding neutron stars is polluted with supernova fall-back material, which collapses and condenses into an asteroid-bearing disk that is stable for millions of years. Over time, collisional and radiative processes cause the asteroids to migrate inward until they are heated to the point of ionization. For older and cooler pulsars, asteroids ionize within the large magnetospheres and inject a sufficient amount of charged particles to alter the electrodynamics of the gap regions and modulate emission processes. This extrinsic model unifies many observed phenomena of variability that occur on time scales that are disparate with the much shorter time scales associated with pulsars and their magnetospheres. One such type of variability is nulling, in which certain pulsars exhibit episodes of quiescence that for some objects may be as short as a few pulse periods, but, for others, is longer than days. Here, in the context of this model, we examine the nulling phenomenon. We analyze the relationship between in-falling material and the statistics of nulling. In addition, as motivation for further high energy observations, we consider the relationship between the nulling and other magnetospheric processes.

SOFIA + FORCAST Observations of 10 Aqueously Altered Asteroids

NASA Astrophysics Data System (ADS)

McAdam, Margaret; Sunshine, Jessica M.; Kelley, Michael S.; Bus, Schelte J.

2016-10-01

Aqueous alteration, or the reaction of water and minerals to produce hydrated minerals, has affected certain groups of carbonaceous meteorites (e.g., the CM and CI meteorites) and asteroids. In the visible/near-infrared (VNIR), CM/CI meteorites and some dark C-complex asteroids are known to have 0.7-µm absorptions that indicate the presence of hydrated minerals [1, 2, 3]. However, this feature does not provide any information about the amount of hydrated minerals in asteroids or meteorites [1]. In contrast, at mid-infrared (MIR) wavelengths, strong spectral features change continuously with amount of hydrated minerals in a suite of well-characterized CM/CI meteorites [1].Using these results, we analyze the spectra of 10 C-complex asteroids observed by SOFIA + FORCAST. These targets are large objects (>95 km diameter) situated in the mid to outer Main Asteroid Belt (2.4 - 3.4 AU). We present spectra of the following asteroids, spectral types in parentheses: 36 Atalante (C), 38 Leda (Cgh), 62 Erato (Ch), 121 Hermione (Ch), 165 Loreley (Cb), 194 Prokne (C), 203 Pompeja (C), 266 Aline (Ch), 52 Europa (Ch), and 19 Fortuna (Ch). Spectra were obtained in two wavelength regions: 8.5-13.6-μm and 17.6-27.7-μm. In these spectral regions, mineralogical features that are known to change continuously with amount of hydrated minerals appear. Most of these targets are known to have hydrated minerals on their surfaces by the presence of the 0.7-μm feature [e.g. 3, 4] or from observations in the 3-μm region [5]. We interpret the spectral features observed using SOFIA and estimate the abundances of hydrated minerals for each asteroid. Additionally, we compare these observations to Spitzer observations of similar objects. A subset of these asteroids have also been measured in VNIR, which allows us to directly compare the signatures of hydration in both the VNIR and the MIR.[1] McAdam et al., (2015), Icarus, 245, 320-332. [2] Cloutis, et al., (2011), Icarus, 216, 309-346. [3] Vilas and Gaffey (1989), Science, 246, 790-792. [4] Bus and Binzel (2002), Icarus, 158, 146-177. Takir and Emery (2012), Icarus, 219, 641-654.

Evidence from Polymict Ureilite Meteorites for a Single "Rubble-Pile" Ureilite Parent Asteroid Gardened by Several Distinct Impactors

NASA Technical Reports Server (NTRS)

Downes, Hilary; Mittlefehldt, David W.; Kita, Noriko T.; Valley, John W.

2008-01-01

Ureilites are ultramafic achondrite meteorites that have experienced igneous processing whilst retaining heterogeneity in mg# and oxygen isotope ratios. Polymict ureilites represent material derived from the surface of the ureilite parent asteroid(s). Electron microprobe analysis of more than 500 olivine and pyroxene clasts in six polymict ureilites reveals that they cover a statistically identical range of compositions to that shown by all known monomict ureilites. This is considered to be convincing evidence for derivation from a single parent asteroid. Many of the polymict ureilites also contain clasts that have identical compositions to the anomalously high Mn/Mg olivines and pyroxenes from the Hughes 009 monomict ureilite (here termed the Hughes cluster ). Four of the six samples also contain distinctive ferroan lithic clasts that have been derived from oxidized impactors. The presence of several common distinctive lithologies within the polymict ureilites is additional evidence that the ureilites were derived from a single parent asteroid. Olivine in a large lithic clast of augite-bearing ureilitic has an mg# of 97, extending the compositional range of known ureilite material. Our study confirms that ureilitic olivine clasts with mg#s < 85 are much more common than those with mg# > 85, which also show more variable Mn contents, including the melt-inclusion bearing "Hughes cluster" ureilites. We interpret this to indicate that the parent ureilite asteroid was disrupted by a major impact at a time when melt was still present in regions with a bulk mg# > 85, giving rise to the two types of ureilites: common ferroan ones that were already residual after melting and less common magnesian ones that were still partially molten when disruption occurred, some of which are the result of interaction of melts with residual mantle during disruption. A single daughter asteroid re-accreted from the disrupted remnants of the mantle of the proto-ureilite asteroid, giving rise to a "rubble-pile" body that had material of a wide variety of compositions and shock states present on its surface. The analysed polymict ureilite meteorites represent regolith that subsequently formed on this asteroidal surface, including impact-derived material from at least six different meteoritic sources.

Dynamics of Populations of Planetary Systems (IAU C197)

NASA Astrophysics Data System (ADS)

Knezevic, Zoran; Milani, Andrea

2005-05-01

1. Resonances and stability of extra-solar planetary systems C. Beaugé, N. Callegari, S. Ferraz-Mello and T. A. Michtchenko; 2. Formation, migration, and stability of extrasolar planetary systems Fred C. Adams; 3. Dynamical evolution of extrasolar planetary systems Ji-Lin Zhou and Yi-Sui Sun; 4. Dynamics of planetesimals: the role of two-body relaxation Eiichiro Kokubo; 5. Fitting orbits Andrzej J. Maciejewski, Krzysztof Gozdziewski and Szymon Kozlowski; 6. The secular planetary three body problem revisited Jacques Henrard and Anne-Sophie Libert; 7. Dynamics of extrasolar systems at the 5/2 resonance: application to 47 UMa Dionyssia Psychoyos and John D. Hadjidemetriou; 8. Our solar system as model for exosolar planetary systems Rudolf Dvorak, Áron Süli and Florian Freistetter; 9. Planetary motion in double stars: the influence of the secondary Elke Pilat-Lohinger; 10. Planetary orbits in double stars: influence of the binary's orbital eccentricity Daniel Benest and Robert Gonczi; 11. Astrometric observations of 51 Peg and Gliese 623 at Pulkovo observatory with 65 cm refractor N. A. Shakht; 12. Observations of 61 Cyg at Pulkovo Denis L. Gorshanov, N. A. Shakht, A. A. Kisselev and E. V. Poliakow; 13. Formation of the solar system by instability Evgeny Griv and Michael Gedalin; 14. Behaviour of a two-planetary system on a cosmogonic time-scale Konstantin V. Kholshevnikov and Eduard D. Kuznetsov; 15. Boundaries of the habitable zone: unifying dynamics, astrophysics, and astrobiology Milan M. Cirkovic; 16. Asteroid proper elements: recent computational progress Fernando Roig and Cristian Beaugé; 17. Asteroid family classification from very large catalogues Anne Lemaitre; 18. Non-gravitational perturbations and evolution of the asteroid main belt David Vokrouhlicky, M. Broz and W. F. Bottke, D. Nesvorny and A. Morbidelli; 19. Diffusion in the asteroid belt Harry Varvoglis; 20. Accurate model for the Yarkovsky effect David Capek and David Vokrouhlicky; 21. The population of asteroids in the 2:1 mean motion resonance with Jupiter revised Miroslav Broz, D. Vokrouhlicky, F. Roig, D. Nesvorny, W. F. Bottke and A. Morbidelli; 22. On the reliability of computation of maximum Lyapunov Characteristic Exponents for asteroids Zoran Knezevic and Slobodan Ninkovic; 23. Nekhoroshev stability estimates for different models of the Trojan asteroids Christos Efthymiopoulos; 24. The role of the resonant 'stickiness' in the dynamical evolution of Jupiter family comets A. Alvarez-Canda and F. Roig; 25. Regimes of stability and scaling relations for the removal time in the asteroid belt: a simple kinetic model and numerical tests Mihailo Cubrovic; 26. Virtual asteroids and virtual impactors Andrea Milani; 27. Asteroid population models Alessandro Morbidelli; 28. Linking Very Large Telescope asteroid observations M. Granvik, K. Muinonen, J. Virtanen, M. Delbó, L. Saba, G. De Sanctis, R. Morbidelli, A. Cellino and E. Tedesco; 29. Collision orbits and phase transition for 2004 AS1 at discovery Jenni Virtanen, K. Muinonen, M. Granvik and T. Laakso; 30. The size of collision solutions in orbital elements space G. B. Valsecchi, A. Rossi, A. Milani and S. R. Chesley; 31. Very short arc orbit determination: the case of asteroid 2004 FU162 Steven R. Chesley; 32. Nonlinear impact monitoring: 2-dimensional sampling Giacomo Tommei; 33. Searching for gravity assisted trajectories to accessible near-Earth asteroids Stefan Berinde; 34. KLENOT - Near Earth and other unusual objects observations Michal Kocer, Jana Tichá and M. Tichy; 35. Transport of comets to the Inner Solar System Hans Rickman; 36. Nongravitational Accelerations on Comets Steven R. Chesley and Donald K. Yeomans; 37. Interaction of planetesimals with the giant planets and the shaping of the trans-Neptunian belt Harold F. Levison and Alessandro Morbidelli; 38. Transport of comets to the outer p

A radar survey of M- and X-class asteroids II. Summary and synthesis

NASA Astrophysics Data System (ADS)

Shepard, Michael K.; Clark, Beth Ellen; Ockert-Bell, Maureen; Nolan, Michael C.; Howell, Ellen S.; Magri, Christopher; Giorgini, Jon D.; Benner, Lance A. M.; Ostro, Steven J.; Harris, Alan W.; Warner, Brian D.; Stephens, Robert D.; Mueller, Michael

2010-07-01

Using the S-band radar at Arecibo Observatory, we observed six new M-class main-belt asteroids (MBAs), and re-observed one, bringing the total number of Tholen M-class asteroids observed with radar to 19. The mean radar albedo for all our targets is σ=0.28±0.13, significantly higher than the mean radar albedo of every other class (Magri, C., Nolan, M.C., Ostro, S.J., Giorgini, J.D. [2007]. Icarus 186, 126-151). Seven of these objects (Asteroids 16 Psyche, 129 Antigone, 216 Kleopatra, 347 Pariana, 758 Mancunia, 779 Nina, 785 Zwetana) have radar albedos indicative of a very high metal content (meanσ=0.41±0.13), and consistent with a remnant iron/nickel core interpretation (irons) or exotic high metal meteorite types such as CB. We propose designating these high radar albedo objects as Mm. Two asteroids, 110 Lydia and 678 Fredegundis, have more moderate radar albedos (meanσ=0.22), but exhibit high values (σ˜0.35) at some rotation phases suggesting a significant metal content. The remaining 10 objects have moderate radar albedos (σ=0.20±0.06) at all rotation phases. Most of our targets have visible/near-infrared spectra (Hardersen, P.S., Gaffey, M.J., Abell, P.A. [2005]. Icarus 175, 141-158; Fornasier, S., Clark, B.E., Dotto, E., Migliorini, A., Ockert-Bell, M., Barucci, M.A. [2009]. Icarus, submitted for publication) that indicate the presence of at least some silicate phases. All of the non-Mm asteroids show a positive correlation between visual and radar albedo but the reasons for this are not clear. All of the higher radar albedo targets (the 7 Mm asteroids, Lydia, and Fredegundis) show moderate to large variations in radar albedo with rotation phase. We suggest that their high radar reflectivity exaggerates irregularities in the asteroid shape to cause this behavior. One-third of our targets show evidence for asteroid-scale concavities or bifurcation. Based on all the evidence available, we suggest that most Tholen M-class asteroids are not remnant iron cores or enstatite chondrites, but rather collisional composites of silicates and irons with compositions more analogous to stony-iron meteorites and high-iron carbonaceous chondrites.

Solar-phase-angle effects on the taxonomic classification of asteroids

NASA Astrophysics Data System (ADS)

Carvano, J.; Davallos, J.

2014-07-01

Asteroid taxonomy is the effort of grouping asteroids into classes based on similarities of a number of their observational properties. The most used properties include measurements of their spectral reflectance (by means of low-resolution spectra, spectro-photometry, or colors), and geometric albedo. The usefulness of asteroid taxonomic classes derived in this way relies on the assumption that the classes bear some correspondence to the mineralogy of the asteroids, and on the fact that such classification can be made using types of observations that presently are available to a large number of asteroids. Therefore, asteroid taxonomy can be used to infer trends in the distribution of compositions in the main belt and other populations, as an additional parameter in defining asteroid families, and as a selection tool to identify candidates for more detailed observations. However, the fact that the correspondence between taxonomic class and composition is far from perfect is still sometimes overlooked in the literature. Indeed, although a taxonomic classification narrows down the possible mineralogies of a given asteroid, it will seldom point univocally to one particular mineralogy. This happens for a number of reasons, some linked to the intrinsic difficulty involved in the remote characterization of the mineralogy of an asteroid, since it depends on the presence of absorption bands in its reflectance spectrum which may be absent or not completely sampled by the observations used to derive taxonomy. Other problem here is the exposure of the material on the surface of the asteroid to space-weathering effects, such as solar wind implantation and micro-meteorite bombardment, which can change the optical properties of the material. Finally, the overall shape of the reflectance spectrum of an asteroid is also affected by the geometry of the observation, as well as by its shape. In this work, we analyze how the classification of asteroids observed by the Sloan Digital Sky Survey is affected by the solar phase angle of the observation. It is found that the number of observations assigned to several taxonomic classes has a clear dependency on the solar phase angle of the asteroid at the moment of the observation. In order to understand how variations of phase angles affect the reflectance spectra of the individual asteroids listed in the SDSS with multiple observations, we use the reflectance spectra derived from the SDSS colors to define two parameters, which measure the spectral slope in the visible and the depth of the 1-micron band, if present. It is found that most asteroids in the sample tend to be redder at higher phase angles, and that, for the classes showing a 1-μ m band, most show increasing band depth with increasing phase angle. This predominance of positive correlations for both band depth and spectral slope might suffice to explain the offsets in the distribution of classes. However, for both parameters there is a significant fraction in each sample for which there seem to be no correlation at all, and a comparable number seem to display anti-correlation between the parameters and the phase angle. Therefore, although phase-reddening effects, as currently understood in the literature, can account for the offsets in the distribution of taxonomic classes with phase angle, it cannot explain all variability seen in the SDSS data. There is also a dependency on composition and also shape effects involved, which can be reproduced using Hapke reflectance models.

The Midplane of the Main Asteroid Belt and Its Warps

NASA Astrophysics Data System (ADS)

Cambioni, Saverio; Malhotra, Renu

2017-10-01

It has been recognized for a long time that the orbital planes of asteroids are surprisingly highly dispersed about the mean plane of the solar system, and likely memorialize dynamical events over the ancient history of the solar system. But how well do we know the mean plane of the asteroid belt? Since the time of the first measurements of their mean plane (Plummer 1916; Shor & Yagudina 1991), the number of known main belt asteroids (MBAs) has dramatically increased; the large size of this population now allows measuring its mean plane at much higher accuracy than in previous studies and also allows to compare it with theoretical expectations. The theoretically expected mean plane is defined by the forced solution of the secular perturbation theory for the inclinations and nodes (e.g., Murray & Dermott 1999); this forced plane varies with semi-major axis. We measure the mean plane by analyzing the observational data and we compare it with the theoretical prediction. Our observationally nearly complete sample consists of 89,216 numbered, non-collisional family asteroids of absolute magnitude below 15.5. For the population as a whole, we find that the mean plane differs significantly from previous measurements: the mean plane’s inclination is I = 0.929 (+0.042, -0.042) degrees and its longitude of ascending node is Ω = 87.60 (+2.58, -2.58) degrees. When measured in small semi-major axis bins between 2.15 and 3.25 AU, the mean plane is found to be largely consistent with secular perturbation theory predictions, deviating not more than (1-2)-σ from the theoretically expected values. A warp near the inner edge, due to the ν16 secular resonance, is visible in the data. Our analysis reveals the way to a novel method for the computation of the free or “proper” inclinations of the MBAs, by computing asteroid inclinations relative to the measured mean plane at that location in semi-major axis.This study used the catalogs of osculating elements for the minor planets and collisional family membership available on the AstDys-2 website (http://hamilton.dm.unipi.it/astdys/). We are grateful for research funding from NSF (grant AST-1312498).

Psyche's UV Reflectance Spectra: Exploring the origins of the largest exposed-core metallic asteroid

NASA Astrophysics Data System (ADS)

Becker, Tracy

2016-10-01

(16) Psyche is the largest of the M-class asteroids, and is presumed to be the exposed core of a differentiated asteroid stripped of its mantle through hit-and-run collisions. However, other origins for Psyche have been proposed, including that it formed from a highly-reduced, metal rich material in the inner solar system or that its surface is olivine that has been space weathered. If (16) Psyche is an exposed core, then studying its properties enhances our understanding of the cores of all terrestrial planets, including the Earth's. If it accreted in the inner part of the solar system and was later injected into the asteroid belt, then Psyche sheds light on the conditions and subsequent evolution of the early solar system. Lastly, if Psyche is weathered olivine, then olivine may be more abundant in the solar system than currently measured, rectifying the so-called Great Dunite Shortage. Our program to obtain high-resolution UV spectra of Psyche with the COS G140L mode and the STIS NUV MAMA G230L mode to measure spectral signatures between 90 - 315 nm is designed to distinguish between the 3 hypothesized cases. These observations will enable identification of absorption bands, especially Fe-O charge transfer bands and will be sensitive to spectral blueing that occurs at UV wavelengths for space-weathered objects. When combined, the presence of these UV features, or not, provides a novel test of Psyche formation theories.

Computer simulations of large asteroid impacts into oceanic and continental sites--preliminary results on atmospheric, cratering and ejecta dynamics

USGS Publications Warehouse

Roddy, D.J.; Schuster, S.H.; Rosenblatt, M.; Grant, L.B.; Hassig, P.J.; Kreyenhagen, K.N.

1987-01-01

Computer simulations have been completed that describe passage of a 10-km-diameter asteroid through the Earth's atmosphere and the subsequent cratering and ejecta dynamics caused by impact of the asteroid into both oceanic and continental sites. The asteroid was modeled as a spherical body moving vertically at 20 km/s with a kinetic energy of 2.6 ?? 1030 ergs (6.2 ?? 107 Mt ). Detailed material modeling of the asteroid, ocean, crustal units, sedimentary unit, and mantle included effects of strength and fracturing, generic asteroid and rock properties, porosity, saturation, lithostatic stresses, and geothermal contributions, each selected to simulate impact and geologic conditions that were as realistic as possible. Calculation of the passage of the asteroid through a U.S. Standard Atmosphere showed development of a strong bow shock wave followed by a highly shock compressed and heated air mass. Rapid expansion of this shocked air created a large low-density region that also expanded away from the impact area. Shock temperatures in air reached ???20,000 K near the surface of the uplifting crater rim and were as high as ???2000 K at more than 30 km range and 10 km altitude. Calculations to 30 s showed that the shock fronts in the air and in most of the expanding shocked air mass preceded the formation of the crater, ejecta, and rim uplift and did not interact with them. As cratering developed, uplifted rim and target material were ejected into the very low density, shock-heated air immediately above the forming crater, and complex interactions could be expected. Calculations of the impact events showed equally dramatic effects on the oceanic and continental targets through an interval of 120 s. Despite geologic differences in the targets, both cratering events developed comparable dynamic flow fields and by ???29 s had formed similar-sized transient craters ???39 km deep and ???62 km across. Transient-rim uplift of ocean and crust reached a maximum altitude of nearly 40 km at ???30 s and began to decay at velocities of 500 m/s to develop large-tsunami conditions. After ???30 s, strong gravitational rebound drove both craters toward broad flat-floored shapes. At 120 s, transient crater diameters were ???80 km (continental) and ???105 km (oceanic) and transient depths were ???27 km; crater floors consisting of melted and fragmented hot rock were rebounding rapidly upward. By 60 s, the continental crater had ejected ???2 ?? 1014 t, about twice the mass ejected from the oceanic crater. By 120 s, ???70,000 km3 (continental) and ???90,000 km3 (oceanic) target material were excavated (no mantle) and massive ejecta blankets were formed around the craters. We estimate that in excess of ???70% of the ejecta would finally lie within ???3 crater diameters of the impact, and the remaining ejecta (???1013 t), including the vaporized asteroid, would be ejected into the atmosphere to altitudes as high as the ionosphere. Effects of secondary volcanism and return of the ocean over hot oceanic crater floor could also be expected to contribute substantial material to the atmosphere. ?? 1987.

Characterization of Near-Earth Asteroids Using KMTNET-SAAO

NASA Astrophysics Data System (ADS)

Erasmus, N.; Mommert, M.; Trilling, D. E.; Sickafoose, A. A.; van Gend, C.; Hora, J. L.

2017-10-01

We present here VRI spectrophotometry of 39 near-Earth asteroids (NEAs) observed with the Sutherland, South Africa, node of the Korea Microlensing Telescope Network (KMTNet). Of the 39 NEAs, 19 were targeted, but because of KMTNet’s large 2° × 2° field of view, 20 serendipitous NEAs were also captured in the observing fields. Targeted observations were performed within 44 days (median: 16 days, min: 4 days) of each NEA’s discovery date. Our broadband spectrophotometry is reliable enough to distinguish among four asteroid taxonomies and we were able to confidently categorize 31 of the 39 observed targets as either an S-, C-, X-, or D-type asteroid by means of a Machine Learning algorithm approach. Our data suggest that the ratio between “stony” S-type NEAs and “not-stony” (C+X+D)-type NEAs, with H magnitudes between 15 and 25, is roughly 1:1. Additionally, we report ∼1 hr light curve data for each NEA, and of the 39 targets, we were able to resolve the complete rotation period and amplitude for six targets and report lower limits for the remaining targets.

A three-dimensional model of Tangential YORP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golubov, O.; Scheeres, D. J.; Krugly, Yu. N., E-mail: golubov@astron.kharkov.ua

2014-10-10

Tangential YORP, or TYORP, has recently been demonstrated to be an important factor in the evolution of an asteroid's rotation state. It is complementary to normal YORP, or NYORP, which used to be considered previously. While NYORP is produced by non-symmetry in the large-scale geometry of an asteroid, TYORP is due to heat conductivity in stones on the surface of the asteroid. To date, TYORP has been studied only in a simplified one-dimensional model, substituting stones with high long walls. This article for the first time considers TYORP in a realistic three-dimensional model, also including shadowing and self-illumination effects viamore » ray tracing. TYORP is simulated for spherical stones lying on regolith. The model includes only five free parameters and the dependence of the TYORP on each of them is studied. The TYORP torque appears to be smaller than previous estimates from the one-dimensional model, but is still comparable to the NYORP torques. These results can be used to estimate TYORP of different asteroids and also as a basis for more sophisticated models of TYORP.« less

VLT/SPHERE observations and shape reconstruction of asteroid (6) Hebe

NASA Astrophysics Data System (ADS)

Marsset, Michael; Carry, Benoit; Dumas, Christophe; Vernazza, Pierre; Jehin, Emmanuel; Sonnett, Sarah M.; Fusco, Thierry

2016-10-01

(6) Hebe is a large main-belt asteroid, accounting for about half a percent of the mass of the asteroid belt. Its spectral characteristics and close proximity to dynamical resonances within the main-belt (the 3:1 Kirkwood gap and the nu6 resonance) make it a probable parent body of the H-chondrites and IIE iron meteorites found on Earth.We present new AO images of Hebe obtained with the high-contrast imager SPHERE (Beuzit et al. 2008) as part of the science verification of the instrument. Hebe was observed close to its opposition date and throughout its rotation in order to derive its 3-D shape, and to allow a study of its surface craters. Our observations reveal impact zones that witness a severe collisional disruption for this asteroid. When combined to previous AO images and available lightcurves (both from the literature and from recent optical observations by our team), these new observations allow us to derive a reliable shape model using our KOALA algorithm (Carry et al. 2010). We further derive an estimate of Hebe's density based on its known astrometric mass.

Evidence of a metal-rich surface for the Asteroid (16) Psyche from interferometric observations in the thermal infrared

NASA Astrophysics Data System (ADS)

Matter, Alexis; Delbo, Marco; Carry, Benoit; Ligori, Sebastiano

2013-09-01

We describe the first determination of thermal properties and size of the M-type Asteroid (16) Psyche from interferometric observations obtained with the Mid-Infrared Interferometric Instrument (MIDI) of the Very Large Telescope Interferometer. We used a thermophysical model to interpret our interferometric data. Our analysis shows that Psyche has a low macroscopic surface roughness. Using a convex 3-D shape model obtained by Kaasalainen et al. (Kaasalainen, M., Torppa, J., Piironen, J. [2002]. Icarus 159, 369-395), we derived a volume-equivalent diameter for (16) Psyche of 247 ± 25 km or 238 ± 24 km, depending on the possible values of surface roughness. Our corresponding thermal inertia estimates are 133 or 114 J m-2 s-0.5 K-1, with a total uncertainty estimated at 40 J m-2 s-0.5 K-1. They are among the highest thermal inertia values ever measured for an asteroid of this size. We consider this as a new evidence of a metal-rich surface for the Asteroid (16) Psyche.

Asteroid science by Gaia

NASA Astrophysics Data System (ADS)

Muinonen, Karri; Cellino, Alberto; Dell Oro, Aldo; Tanga, Paolo; Delbo, Marco; Mignard, Francois; Thuillot, William; Berthier, Jerome; Carry, Benoit; Hestroffer, Daniel; Granvik, Mikael; Fedorets, Grigori

2016-07-01

Since the start of its regular observing program in summer 2014, the Gaia mission has carried out systematic photometric, spectrometric, and astrometric observations of asteroids. In total, the unique capabilities of Gaia allow for the collection of an extensive and homogeneous data set of some 350,000 asteroids down to the limiting magnitude of G = 20.7 mag. The Gaia performance remains excellent over the entire available brightness range. Starting from 2003, a working group of European asteroid scientists has explored the main capabilities of the mission, defining the expected scientific impact on Solar System science. These results have served as a basis for developing the Gaia data reduction pipeline, within the framework of the Data Processing and Analysis Consortium (DPAC). We describe the distribution of the existing and forecoming Gaia observations in space and time for different categories of objects. We illustrate the peculiar properties of each single observation, as these properties will affect the subsequent exploitation of the mission data. We will review the expected performances of Gaia, basically as a function of magnitude and proper motion of the sources. We will further focus on the areas that will benefit from complementary observational campaigns to improve the scientific return of the mission, and on the involvement of the planetary science community as a whole in the exploitation of the Gaia survey. We will thus describe the current and future opportunities for ground-based observers and forthcoming changes brought by Gaia in some observational approaches, such as stellar occultations by transneptunian objects and asteroids. We will show first results from the daily, short-term processing of Gaia data, all the way from the onboard data acquisition to the ground-based processing. We illustrate the tools developed to compute predictions of asteroid observations, we discuss the procedures implemented by the daily processing, and we illustrate some tests and validations of the processing of the asteroid observations. Overall, our findings are consistent with the expectations from the performances of Gaia and of the subsequent data reduction. As to the long-term processing of Gaia data, we expect to derive masses, sizes, average densities, spin properties, reflectance spectra, albedos, as well as new taxonomic classifications for large numbers of asteroids. In this review, we will describe the prospects for Gaia photometry and spectrophotometry. We will describe inverse methods for sparse photometric data using the so-called Lommel-Seeliger ellipsoids. We will further describe the modeling of Gaia spectra for the compositional studies of asteroids, as well as the prospects for a new Gaia asteroid taxonomy. Gaia data will open a new era in asteroid science, allowing us to answer fundamental questions concerning, for example, the interrelation between asteroid internal structure and surface properties.

The Strata-1 Regolith Dynamics Experiment: Class 1E Science on ISS

NASA Technical Reports Server (NTRS)

Fries, Marc; Graham, Lee; John, Kristen

2016-01-01

The Strata-1 experiment studies the evolution of small body regolith through long-duration exposure of simulant materials to the microgravity environment on the International Space Station (ISS). This study will record segregation and mechanical dynamics of regolith simulants in a microgravity and vibration environment similar to that experienced by regolith on small Solar System bodies. Strata-1 will help us understand regolith dynamics and will inform design and procedures for landing and setting anchors, safely sampling and moving material on asteroidal surfaces, processing large volumes of material for in situ resource utilization (ISRU) purposes, and, in general, predicting the behavior of large and small particles on disturbed asteroid surfaces. This experiment is providing new insights into small body surface evolution.

Evidence for the presence of planetesimal material among the precursors of magnesian chondrules of nebular origin

NASA Astrophysics Data System (ADS)

Libourel, Guy; Krot, Alexander N.

2007-02-01

Chondrules are the major high-temperature components of chondritic meteorites, which are conventionally viewed as the samples from the very first generation of undifferentiated planetesimals. Growing evidences from long- and short-lived radionuclide chronologies indicate however that chondrite parent asteroids accreted after or contemporaneously with igneous activities on differentiated asteroids, questioning the pristine nature of chondrites. Here we report a discovery of metal-bearing olivine aggregates with granoblastic textures inside magnesian porphyritic (Type I) chondrules from the CV carbonaceous chondrite Vigarano. Formation of the granoblastic textures requires sintering and prolonged, high-temperature (> 1000 °C) annealing - conditions which are not expected in the solar nebula during chondrule formation, but could have been achieved on parent bodies of olivine-rich differentiated or thermally metamorphosed meteorites. The mineralogy and petrography of the metal-olivine aggregates thus indicate that they are relict, dunite-like lithic fragments which resulted from fragmentation of such bodies. The very old Pb-Pb absolute ages and Al-Mg relative model ages of bulk CV chondrules suggest that such planetesimals may have formed as early as the currently accepted age of the Solar System (4567.2 ± 0.6 Ma).

Earth Rings for Planetary Environment Control

NASA Astrophysics Data System (ADS)

Pearson, Jerome; Oldson, John; Levin, Eugene; Carroll, Joseph

2002-01-01

For most of its past, large parts of the Earth have experienced subtropical climates, with high sea levels and no polar icecaps. This warmer environment was punctuated 570, 280, and 3 million years ago with periods of glaciation that covered temperate regions with thick ice for millions of years. At the end of the current ice age, a warmer climate could flood coastal cities, even without human-caused global warming. In addition, asteroids bombard the Earth periodically, with impacts large enough to destroy most life on Earth, and the sun is warming inexorably. This paper proposes a concept to solve these problems simultaneously, by creating an artificial planetary ring about the Earth to shade it. Past proposals for space climate control have depended on gigantic engineering structures launched from Earth and placed in Earth orbit or at the Earth-Sun L1 libration point, requiring fabrication, large launch masses and expense, constant control, and repair. Our solution is to begin by using lunar material, and then mine and remove Earth-orbit-crossing asteroids and discard the tailings into Earth orbit, to form a broad, flat ring like those of Saturn. This solution is evaluated and compared with other alternatives. Such ring systems can persist for thousands of years, and can be maintained by shepherding satellites or by continual replenishment from new asteroids to replace the edges of the ring lost by diffusion. An Earth ring at R = 1.3-1.83 RE would shade only the equatorial regions, moderating climate extremes, and could reverse a century of global warming. It could also absorb particles from the radiation belts, making trips to high Earth orbit and GEO safer for humans and for electronics. It would also light the night many times as bright as the full moon. A preliminary design of the ring is developed, including its location, mass, composition, stability, and timescale required. A one-dimensional climate model is used to evaluate the Earth ring performance. Earth, lunar, and asteroidal material sources are evaluated; asteroid retrieval is addressed, along with techniques for processing and forming the ring to the proper thickness and density. The ring could consist of particles, or fabricated satellite structures. Environmental concerns and effects on existing satellites in various Earth orbits are addressed. There are uncertainties in our understanding of climate and its control. But it appears that the Earth ring could control the Earth's temperature and its latitudinal variation, make dangerous asteroids useful, reduce the intensity of the Van Allen radiation belts, provide nighttime illumination without power, and create an artificial ionosphere for radio communication.

Near-infrared colors of minor planets recovered from VISTA-VHS survey (MOVIS)

NASA Astrophysics Data System (ADS)

Popescu, M.; Licandro, J.; Morate, D.; de León, J.; Nedelcu, D. A.; Rebolo, R.; McMahon, R. G.; Gonzalez-Solares, E.; Irwin, M.

2016-06-01

Context. The Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE) provide information about the surface composition of about 100 000 minor planets. The resulting visible colors and albedos enabled us to group them in several major classes, which are a simplified view of the diversity shown by the few existing spectra. A large set of data in the 0.8-2.5 μm, where wide spectral features are expected, is required to refine and complement the global picture of these small bodies of the solar system. Aims: We aim to obtain the near-infrared colors for a large sample of solar system objects using the observations made during the VISTA-VHS survey. Methods: We performed a serendipitous search in VISTA-VHS observations using a pipeline developed to retrieve and process the data that corresponds to solar system objects (SSo). The resulting photometric data is analyzed using color-color plots and by comparison with the known spectral properties of asteroids. Results: The colors and the magnitudes of the minor planets observed by the VISTA survey are compiled into three catalogs that are available online: the detections catalog (MOVIS-D), the magnitudes catalog (MOVIS-M), and the colors catalog (MOVIS-C). They were built using the third data release of the survey (VISTA VHS-DR3). A total of 39 947 objects were detected, including 52 NEAs, 325 Mars Crossers, 515 Hungaria asteroids, 38 428 main-belt asteroids, 146 Cybele asteroids, 147 Hilda asteroids, 270 Trojans, 13 comets, 12 Kuiper Belt objects and Neptune with its four satellites. The colors found for asteroids with known spectral properties reveal well-defined patterns corresponding to different mineralogies. The distributions of MOVIS-C data in color-color plots shows clusters identified with different taxonomic types. All the diagrams that use (Y - J) color separate the spectral classes more effectively than the (J - H) and (H - Ks) plots used until now: even for large color errors (<0.1), the plots (Y - J) vs. (Y - Ks) and (Y - J) vs. (J - Ks) provide the separation between S-complex and C-complex. The end members A, D, R, and V-types occupy well-defined regions. The catalogs are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A115

Environments and extinctions at the K-T boundary in eastern Montana are compatible with an asteroid impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fastovsky, D.E.; Sheehan, P.M.

1992-01-01

In the terrestrial latest Cretaceous Hell Creek (HC) Formation, both non-biotic events and patterns of extinction and survivorship are consistent with an asteroid impact causing the extinctions. Environments through the last 2--3 million-year interval represented by the HC remained relatively constant: an aggrading coastal lowland dissected by meandering rivers. The K-T boundary occurred during an abrupt change to impeded drainage represented by coals and pond deposits formed under low-energy conditions. Because of the close temporal proximity of the sediments of the Paleocene Cannonball Sea to the K-T boundary in South Dakota, impeded drainage in the earliest Paleocene in eastern Montanamore » may be attributable to riverine base-level changes associated with a renewed transgression of the western interior sea during the K-T transition. Patterns within the biota mirror those of the paleoenvironments. The ecological diversity of HC dinosaurs remains statistically unchanged through HC time. Analyses of vertebrates at the species level indicate a differential extinction in which the terrestrial biota underwent far more extinction than its aquatic counterpart. There is no evidence for changing environments in the upper HC, and there is circumstantial evidence that the latest Cretaceous was a time of renewed transgression rather than regression. Likewise, biotic patterns do not accord with gradual, environmentally driven extinctions. While the paleoenvironmental change that marks the K-T transition in eastern Montana accounts for some of the extinctions, the pattern of differential extinction is concordant with an asteroid impact. In this scenario, aquatic ecosystems and some land-based food chains would be buffered by detritus-based feeding. Terrestrial systems, dependent upon primary productivity, would undergo a short-term loss of resources causing extinctions.« less

Rotational Properties of Jupiter Trojan 1173 Anchises

NASA Astrophysics Data System (ADS)

Chatelain, Joseph; Henry, Todd; French, Linda; Trilling, David

2015-11-01

Anchises (1173) is a large Trojan asteroid librating about Jupiter’s L5 Lagrange point. Here we examine its rotational and lightcurve properties by way of data collected over a 3.5 year observing campaign. The length of the campaign means that data were gathered for more than a quarter of Anchises' full orbital revolution which allows for accurate determinations of pole orientation and bulk shape properties for the asteroid that can then be compared to results of previous work (i.e. French 1987, Horner et al. 2012). In addition to light curves, photometric data taken during this campaign could potentially detect color differences between hemispheres as the viewing geometry changes over time. Understanding these details about a prominent member of the Jupiter Trojans may help us better understand the history of this fascinating and important group of asteroids.

Core solidification and dynamo evolution in a mantle-stripped planetesimal

NASA Astrophysics Data System (ADS)

Scheinberg, A.; Elkins-Tanton, L. T.; Schubert, G.; Bercovici, D.

2016-01-01

The physical processes active during the crystallization of a low-pressure, low-gravity planetesimal core are poorly understood but have implications for asteroidal magnetic fields and large-scale asteroidal structure. We consider a core with only a thin silicate shell, which could be analogous to some M-type asteroids including Psyche, and use a parameterized thermal model to predict a solidification timeline and the resulting chemical profile upon complete solidification. We then explore the potential strength and longevity of a dynamo in the planetesimal's early history. We find that cumulate inner core solidification would be capable of sustaining a dynamo during solidification, but less power would be available for a dynamo in an inward dendritic solidification scenario. We also model and suggest limits on crystal settling and compaction of a possible cumulate inner core.

A search for Earth-crossing asteroids, supplement

NASA Technical Reports Server (NTRS)

Taff, L. G.; Sorvari, J. M.; Kostishack, D. F.

1984-01-01

The ground based electro-optical deep space surveillance program involves a network of computer controlled 40 inch 1m telescopes equipped with large format, low light level, television cameras of the intensified silicon diode array type which is to replace the Baker-Nunn photographic camera system for artificial satellite tracking. A prototype observatory was constructed where distant artificial satellites are discriminated from stars in real time on the basis of the satellites' proper motion. Hardware was modified and the technique was used to observe and search for minor planets. Asteroids are now routinely observed and searched. The complete observing cycle, including the 2"-3" measurement of position, requires about four minutes at present. The commonality of asteroids and artificial satellite observing, searching, data reduction, and orbital analysis is stressed. Improvements to the hardware and software as well as operational techniques are considered.

On the oldest asteroid families in the main belt

NASA Astrophysics Data System (ADS)

Carruba, V.; Nesvorný, D.; Aljbaae, S.; Domingos, R. C.; Huaman, M.

2016-06-01

Asteroid families are groups of minor bodies produced by high-velocity collisions. After the initial dispersions of the parent bodies fragments, their orbits evolve because of several gravitational and non-gravitational effects, such as diffusion in mean-motion resonances, Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects, close encounters of collisions, etc. The subsequent dynamical evolution of asteroid family members may cause some of the original fragments to travel beyond the conventional limits of the asteroid family. Eventually, the whole family will dynamically disperse and no longer be recognizable. A natural question that may arise concerns the time-scales for dispersion of large families. In particular, what is the oldest still recognizable family in the main belt? Are there any families that may date from the late stages of the late heavy bombardment and that could provide clues on our understanding of the primitive Solar system? In this work, we investigate the dynamical stability of seven of the allegedly oldest families in the asteroid main belt. Our results show that none of the seven studied families has a nominally mean estimated age older than 2.7 Gyr, assuming standard values for the parameters describing the strength of the Yarkovsky force. Most `paleo-families' that formed between 2.7 and 3.8 Gyr would be characterized by a very shallow size-frequency distribution, and could be recognizable only if located in a dynamically less active region (such as that of the Koronis family). V-type asteroids in the central main belt could be compatible with a formation from a paleo-Eunomia family.

The Double Asteroid Redirection Test in the AIDA Mission

NASA Astrophysics Data System (ADS)

Cheng, Andrew; Reed, Cheryl; Rivkin, Andrew

2016-07-01

The Asteroid Impact & Deflection Assessment (AIDA) mission will be the first space experiment to demonstrate asteroid impact hazard mitigation by using a kinetic impactor. AIDA is a joint ESA-NASA cooperative project, consisting of the ESA Asteroid Impact Mission (AIM) rendezvous mission and the NASA Double Asteroid Redirection Test (DART) mission. The AIDA target is the near-Earth binary asteroid 65803 Didymos, which will make an unusually close approach to Earth in October, 2022. The DART spacecraft is designed to impact the Didymos secondary at 7 km/s and demonstrate the ability to modify its trajectory through momentum transfer. DART and AIM are currently Phase A studies supported by NASA and ESA respectively. The primary goals of AIDA are (1) perform a full-scale demonstration of the spacecraft kinetic impact technique for deflection of an asteroid; (2) measure the resulting asteroid deflection, by targeting the secondary member of a binary NEO and measuring the resulting changes of the binary orbit; and (3) study hyper-velocity collision effects on an asteroid, validating models for momentum transfer in asteroid impacts based on measured physical properties of the asteroid surface and sub-surface, and including long-term dynamics of impact ejecta. The primary DART objectives are to demonstrate a hyper-velocity impact on the Didymos moon and to determine the resulting deflection from ground-based observations. The DART impact on the Didymos secondary will change the orbital period of the binary which can be measured by supporting Earth-based optical and radar observations. The baseline DART mission launches in December, 2020 to impact the Didymos secondary in September,2022. There are multiple launch opportunities for DART leading to impact around the 2022 Didymos close approach to Earth. The AIM spacecraft will be launched in Dec. 2020 and arrive at Didymos in spring, 2022, several months before the DART impact. AIM will characterize the Didymos binary system by means of remote sensing and in-situ instruments both before and after the DART impact. The asteroid deflection will be measured to higher accuracy, and additional results of the DART impact, like the impact crater, will be studied in detail by the AIM mission. The combined DART and AIM missions will provide the first measurements of momentum transfer efficiency from hyper-velocity kinetic impact at full scale on an asteroid, where the impact conditions of the projectile are known, and physical properties and internal structures of the target asteroid are also characterized. The DART impact on the Didymos secondary is predicted to cause a 4.4 minute change in the binary orbit period, assuming unit momentum transfer efficiency. The predicted transfer efficiency would be in the range 1.1 to 1.3 for a porous target material based on a variety of numerical and analytical methods, but may be much larger if the target is non-porous. The DART kinetic impact is predicted to make a crater of 6 to 17 meters diameter, depending on target physical properties, but will also release a large volume of particulate ejecta that may be directly observable from Earth or even resolvable as a coma or an ejecta tail by ground-based telescopes.

Modeling of the Yarkovsky and YORP effects

NASA Astrophysics Data System (ADS)

Rozitis, B.

2014-07-01

The Yarkovsky and YORP effects are now widely regarded to be fundamental mechanisms, in addition to collisions and gravitational forces, which drive the dynamical and physical evolution of small asteroids in the Solar System [1]. They are caused by the net force and torque resulting from the asymmetric reflection and thermal re-radiation of sunlight from an asteroid's surface. The net force (Yarkovsky effect) causes the asteroid's orbit to drift outwards or inwards depending on whether the asteroid is a prograde or retrograde rotator. The first direct measurement of Yarkovsky orbital drift was achieved by sensitive radar-ranging on the near-Earth asteroid (NEA) (6489) Golevka in 2003 [2]. The net torque (YORP effect) changes the asteroid's rotation rate and the direction of its spin axis. It can cause an asteroid to spin faster or slower depending on the shape asymmetry, and the first direct measurement of the YORP rotational acceleration was achieved by lightcurve observations on NEA (54509) YORP in 2007 [3]. Since these first direct detections, the Yarkovsky orbital drift has been detected in several tens of NEAs [4,5], and the YORP rotational acceleration has been detected in four more NEAs [6--9]. Indirect evidence of the action of these two effects has also been seen in the populations of NEAs [10], small main-belt asteroids [11], and asteroid families [12]. Modeling of these effects allows further insights into the properties of detected asteroids to be gained, such as the bulk density, obliquity, and surface thermal properties. Recently, high-precision astrometric observations of the Yarkovsky orbital drift of PHA (101955) Bennu were combined with suitable models informed by thermal-infrared observations to derive a bulk density with an uncertainty comparable to that of in-situ spacecraft investigations [13]. Also, the recent YORP effect detection in (25143) Itokawa was combined with a model utilizing the highly detailed Hayabusa-derived shape model to infer an inhomogeneous internal bulk density distribution [9]. Prediction and interpretation of these two effects are therefore critically dependent on accurate models that describe how asteroids reflect and thermally re-radiate sunlight. Yarkovsky and YORP effect models must take into account an asteroid's size and shape, mass and moment of inertia, surface thermal/reflection/emission properties, rotation state, and its orbit about the Sun. A variety of analytical, numerical, and semi-analytical models have been developed over the past decade to study these effects with different levels of detail. The Yarkovsky effect is driven by a morning-afternoon temperature asymmetry during a rotation (diurnal effect) or orbit (seasonal effect) that arises on asteroids with non-zero thermal inertias. Models show that this temperature asymmetry can be enhanced by surface roughness through thermal-infrared beaming effects [14]. YORP rotation rate changes are driven by shape irregularities where photon torques induced on opposite sides of the body do not cancel out. These rotation rate changes have been shown to be independent of thermal inertia for asteroids larger than the thermal skin depth [15]. The YORP effect has also been shown to be highly sensitive to small-scale shape variations [16], surface roughness [14], and the shape model resolution [17] such that the uncertainty in any prediction could be very large. However, recent work has shown that this sensitivity could be less than previously thought when both shadowing and global self-heating effects are included [18], and/or when the induced YORP rotation rate change is relatively large [19]. Recently, a new model has been developed that can simultaneously interpret thermal-infrared observations and predict the Yarkovsky/YORP effects for the derived properties, and has been verified against observations for NEA (1862) Apollo [20]. Also, a ''tangential-YORP'' model has been proposed to explain why only YORP rotational acceleration has been observed when YORP rotational deceleration should also be observed in equal numbers [21]. In the talk, the latest Yarkovsky and YORP modeling techniques and methods will be reviewed, and the future directions of such modeling efforts will be discussed.

Paradigms and Paradoxes: Dawn at Vesta

NASA Technical Reports Server (NTRS)

Raymond, C. A.; Russell, C. T.; Mittlefehldt, D. W.

2014-01-01

While confirming the popular paradigm of Vesta as the parent body of the HED meteorites, Dawn measurements have discovered many unexpected aspects of the vestan surface. First, an olivine layer was not found in the bottom of the large basin near the south pole of Vesta. In fact, while patches of olivine have been found in the north, it is rare on the surface. Secondly, while Vesta has little gravity and appears to have completely differentiated, it is not completely dry evidence for transient flows and pits resulting from devolatization have been found, implying a substantial amount of accessible water. Thirdly, transport of material to the surface of Vesta from elsewhere in the asteroid belt appears as dark material buried near the top of the crust to Vesta. This may have arrived in a single large impact and been spread around the surface and buried, later to be re-excavated. However, it is not certain that this is the only scenario possible for the source of this material. In short, Dawn's observations of Vesta have been both reassuring but unsettling at the same time.

Solar Power at Play

NASA Astrophysics Data System (ADS)

2007-03-01

For the very first time, astronomers have witnessed the speeding up of an asteroid's rotation, and have shown that it is due to a theoretical effect predicted but never seen before. The international team of scientists used an armada of telescopes to discover that the asteroid's rotation period currently decreases by 1 millisecond every year, as a consequence of the heating of the asteroid's surface by the Sun. Eventually it may spin faster than any known asteroid in the solar system and even break apart. ESO PR Photo 11a/07 ESO PR Photo 11a/07 Asteroid 2000 PH5 "The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is believed to alter the way small bodies in the Solar System rotate," said Stephen Lowry (Queens University Belfast, UK), lead-author of one of the two companion papers in which this work is reported [1, 2]. "The warming caused by sunlight hitting the surfaces of asteroids and meteoroids leads to a gentle recoil effect as the heat is released," he added. "By analogy, if one were to shine light on a propeller over a long enough period, it would start spinning." Although this is an almost immeasurably weak force, its effect over millions of years is far from negligible. Astronomers believe the YORP effect may be responsible for spinning some asteroids up so fast that they break apart, perhaps leading to the formation of double asteroids. Others may be slowed down so that they take many days to complete a full turn. The YORP effect also plays an important role in changing the orbits of asteroids between Mars and Jupiter, including their delivery to planet-crossing orbits, such as those of near-Earth asteroids. Despite its importance, the effect has never been seen acting on a solar system body, until now. Using extensive optical and radar imaging from powerful Earth-based observatories, astronomers have directly observed the YORP effect in action on a small near-Earth asteroid, known as (54509) 2000 PH5. Shortly after its discovery in 2000, it was realised that asteroid 2000 PH5 would be the ideal candidate for such a YORP detection. With a diameter of just 114 metres, it is relatively small and so more susceptible to the effect. Also, it rotates very fast, with one 'day' on the asteroid lasting just over 12 Earth minutes, implying that the YORP effect may have been acting on it for some time. With this in mind, the team of astronomers undertook a long term monitoring campaign of the asteroid with the aim of detecting any tiny changes in its rotation speed. Over a 4-year time span, Stephen Lowry, Alan Fitzsimmons and colleagues took images of the asteroid at a range of telescope sites including ESO's 8.2-m Very Large Telescope array and 3.5-m New Technology Telescope in Chile, the 3.5-m telescope at Calar Alto, Spain, along with a suite of other telescopes from the Czech Republic, the Canary Islands, Hawaii, Spain and Chile. With these facilities the astronomers measured the slight brightness variations as the asteroid rotated. ESO PR Photo 11b/07 ESO PR Photo 11b/07 Radar Images of 2000 PH5 Over the same time period, the radar team led by Patrick Taylor and Jean-Luc Margot of Cornell University employed the unique capabilities of the Arecibo Observatory in Puerto Rico and the Goldstone radar facility in California to observe the asteroid by 'bouncing' a radar pulse off the asteroid and analysing its echo. "With this technique we can reconstruct a 3-D model of the asteroid's shape, with the necessary detail to allow a comparison between the observations and theory," said Taylor. After careful analysis of the optical data, the asteroid's spin rate was seen to steadily increase with time, at a rate that can be explained by the YORP theory. Critically, the effect was observed year after year, for more than 4 years. Furthermore, this number was elegantly supported via analysis of the combined radar and optical data, as it was required that the asteroid is increasing its spin rate at exactly this rate in order for a satisfactory 3-D shape model to be determined. ESO PR Video 11/07 ESO PR Video 11c/07 Watch the Asteroid Move! To predict what will happen to the asteroid in the future, Lowry and his colleagues performed detailed computer simulations using the measured strength of the YORP effect and the detailed shape model. They found that the orbit of the asteroid about the Sun could remain stable for up to the next 35 million years, allowing the rotation period to be reduced by a factor of 36, to just 20 seconds, faster than any asteroid whose rotation has been measured until now. "This exceptionally fast spin-rate could force the asteroid to reshape itself or even split apart, leading to the birth of a new double system," said Lowry.

Thermal Conductive Heat Transfer and Partial Melting of Volatiles in Icy Moons, Asteroids, and Kuiper Belt Objects (Invited)

NASA Astrophysics Data System (ADS)

Kargel, J. S.; Furfaro, R.

2013-12-01

Thermal gradients within conductive layers of icy satellite and asteroids depend partly on heat flow, which is related to the secular decay of radioactive isotopes, to heat released by chemical phase changes, by conversion of gravitational potential energy to heat during differentiation, tidal energy dissipation, and to release of heat stored from prior periods. Thermal gradients are also dependent on the thermal conductivity of materials, which in turn depends on their composition, crystallinity, porosity, crystal fabric anisotropy, and details of their mixture with other materials. Small impurities can produce lattice defects and changes in polymerization, and thereby have a huge influence on thermal conductivity, as can cage-inclusion (clathrate) compounds. Heat flow and thermal gradients can be affected by fluid phase advection of mass and heat (in oceans or sublimating upper crusts), by refraction related to heterogeneities of thermal conductivity due to lateral variations and composition or porosity. Thermal profiles depend also on the surface temperature controlled by albedo and climate, surface relief, and latitude, orbital obliquity and surface insolation, solid state greenhouses, and endogenic heating of the surface. The thermal state of icy moon interiors and thermal gradients can be limited at depth by fluid phase advection of heat (e.g., percolating meteoric methane or gas emission), by the latent heat of phase transitions (melting, solid-state transitions, and sublimation), by solid-state convective or diapiric heat transfer, and by foundering. Rapid burial of thick volatile deposits can also affect thermal gradients. For geologically inactive or simple icy objects, most of these controls on heat flow and thermal gradients are irrelevant, but for many other icy objects they can be important, in some cases causing large lateral and depth variations in thermal gradients, large variations in heat flow, and dynamically evolving thermal states. Many of these processes result in transient thermal states and hence rapid evolution of icy body interiors. Interesting heat-flow phenomena (approximated as steady-state thermal states) have been modeled in volatile-rich main belt asteroids, Io, Europa, Enceladus, Titan, Pluto, and Makemake (2005 FY9). Thermal conditions can activate geologic processes, but the occurrence of geologic activity can fundamentally alter the thermal conductivity and elasticity of icy objects, which then further affects the distribution and type of subsequent geologic activity. For example, cryoclastic volcanism on Enceladus can increase solid-state greenhouse heating of the upper crust, reduce thermal conductivity, and increase retention of heat and spur further cryovolcanism. Sulfur extrusion on Io can produce low-thermal-conductivity flows, high thermal gradients, basal melting of the flows, and lateral extrusion and spreading of the flows or formation of solid-crusted lava lakes. Impact formation of regoliths and fine-grained dust deposits on large asteroids may generate local variations in thermal gradients. Interior heating and geologic activity can either (1) emplace low-conductivity materials on the surface and cause further interior heating, or (2) drive metamorphism, sintering, and volatile loss, and increase thermal conductivity and cool the object. Thus, the type and distribution of present-day geologic activity on icy worlds is dependent on geologic history. Geology begets geology.

Vesta Thermal Models

NASA Astrophysics Data System (ADS)

Formisano, M.; Federico, C.; Coradini, A.; Carli, C.; Turrini, D.

2011-12-01

Vesta is one of the largest Main Belt asteroid, considered the parent of the HED (Howardite - Eucrite - Diogenite) meteorites. Spectroscopic studies in fact show the presence of the 0.9 and 1.9 μm absorption bands for pyroxene in the spectra of Vesta that match those observed in the spectra of HED meteorites (see Gaffey, 1997, Surface Lihologic Heterogeneity of Asteroid 4 Vesta, Icarus, 127). The spectral connection between Vesta and the Howardite-Eurcrite-Diogenite (HED) suite of meteorites suggests that Vesta formed very early in the history of the Solar System and differentiated on a Ma-long timescale due to the decay of short-lived radioactive nuclides (see Keil K., 2002, Geological History of Asteroid 4 Vesta: The Smallest Terrestrial Planet. Asteroids III, and references therein). The importance of studying the thermal evolution of Vesta is therefore linked to the understanding of the processes of core and crust formation in planetary bodies so Vesta can be considered a good model for the primordial stages of the terrestrial planets. Our interest is mainly focused on the study of different energy sources, and how they contribute to differentiation and, more generally, to the thermal history of the body. We analyze not only the contribution of short-lived radionuclides, i.e. 26Al and 60Fe, but also the contribution of long-lived radionuclides, in particular 40K, 232Th, 235U and 238U, and that of accretional heating. The contribution of the long-lived radionuclides does not change the overall thermal history but it only slows down the cooling of the body. We have also observed that the effect of the accretional heating is limited if not negligible: in the most favourable scenarios its contribution only raise the starting temperature of the body but it is not sufficient to start the differentiation process. Vesta thermal and structural evolution is therefore characterized by the contribution of the short-lived radionuclides. The scenarios we considered differ in the time delay Δt. The time delay Δt is a parameter that takes into account not only the uncertainties due to the injection of 26Al in the Solar Nebula, but also the uncertainties linked to the time of the accretional process of Vesta. In all the scenarios we observe the differentiation of the body, i.e. the formation of a metallic core (mainly iron) and a silicatic crust of which we discuss the chemical and physical evolution, in particular by analyzing the link with the Jovian Early Bombardment phase ( D.Turrini, G.Magni, A.Coradini, 2011, Probing the history of Solar System through the cratering records on Vesta and Ceres, MNRAS, DOI: 10.1111/j.1365-2966.2011.18316.x). We also preliminarly discuss the heat released by the impacts during the Jovian Early Bombardment phase and their possible contribution to the thermal history of Vesta.

Near-Earth Asteroid Tracking with the Maui Space Surveillance System (NEAT/MSSS)

NASA Technical Reports Server (NTRS)

Helin, Eleanor F.; Pravdo, Steven H.; Lawrence, Kenneth J.; Hicks, Michael D.

2001-01-01

Over the last year the Jet Propulsion Laboratory's (JPL) Near-Earth Asteroid Tracking (NEAT) program has made significant progress and now consists of two simultaneously-operating, autonomous search systems on the 1.2-m (48") telescopes: on the Maui Space Surveillance System (NEAT/MSSS) and NEAT/Palomar on the Palomar Observatory's Oschin telescope. This paper will focus exclusively on the NEAT/MSSS system. NEAT/MSSS is operated as a partnership between NASA/JPL and the United States Air Force Research Laboratory (AFRL), utilizing the AFRL 1.2-m telescope on the 3000-m summit of Haleakala, Maui, The USAF Space Command (SPCMD) contributed financial support to build and install the 'NEAT focal reducer' on the MSSS 1.2-m telescope giving it a large field of view (2.5 square degrees), suitable for the near-earth object (NEO),both asteroids and comets, survey. This work was completed in February 2000. AFRL has made a commitment to NEAT/MSSS that allows NEAT to operate full time with the understanding that AFRL participate as partners in NEAT/MSSS and have use of the NEAT camera system for high priority satellite observations during bright time (parts of 12 nights each month). Currently, NEAT has discovered 42 NEAs including 12 larger than 1-km, 5 Potentially Hazardous Asteroids (PHAs), 6 comets, and nearly 25,000 asteroid detections since March 2000.

A successful search for hidden Barbarians in the Watsonia asteroid family

NASA Astrophysics Data System (ADS)

Cellino, A.; Bagnulo, S.; Tanga, P.; Novaković, B.; Delbò, M.

2014-03-01

Barbarians, so named after the prototype of this class (234) Barbara, are a rare class of asteroids exhibiting anomalous polarimetric properties. Their very distinctive feature is that they show negative polarization at relatively large phase angles, where all `normal' asteroids show positive polarization. The origin of the Barbarian phenomenon is unclear, but it seems to be correlated with the presence of anomalous abundances of spinel, a mineral usually associated with the so-called calcium-aluminium-rich inclusions (CAIs) on meteorites. Since CAIs are samples of the oldest solid matter identified in our Solar system, Barbarians are very interesting targets for investigations. Inspired by the fact that some of the few known Barbarians are members of, or very close to, the dynamical family of Watsonia, we have checked whether this family is a major repository of Barbarians, in order to obtain some hints about their possible collisional origin. We have measured the linear polarization of a sample of nine asteroids which are members of the Watsonia family within the phase-angle range 17°-21°. We found that seven of them exhibit the peculiar Barbarian polarization signature, and we conclude that the Watsonia family is a repository of Barbarian asteroids. The new Barbarians identified in our analysis will be important to confirm the possible link between the Barbarian phenomenon and the presence of spinel on the surface.

NASA's Asteroid Redirect Mission (ARM)

NASA Astrophysics Data System (ADS)

Abell, Paul; Mazanek, Dan; Reeves, David; Naasz, Bo; Cichy, Benjamin

2015-11-01

The National Aeronautics and Space Administration (NASA) is developing a robotic mission to visit a large near-Earth asteroid (NEA), collect a multi-ton boulder from its surface, and redirect it into a stable orbit around the Moon. Once returned to cislunar space in the mid-2020s, astronauts will explore the boulder and return to Earth with samples. This Asteroid Redirect Mission (ARM) is part of NASA’s plan to advance the technologies, capabilities, and spaceflight experience needed for a human mission to the Martian system in the 2030s. Subsequent human and robotic missions to the asteroidal material would also be facilitated by its return to cislunar space. Although ARM is primarily a capability demonstration mission (i.e., technologies and associated operations), there exist significant opportunities to advance our knowledge of small bodies in the synergistic areas of science, planetary defense, asteroidal resources and in-situ resource utilization (ISRU), and capability and technology demonstrations. In order to maximize the knowledge return from the mission, NASA is organizing an ARM Investigation Team, which is being preceded by the Formulation Assessment and Support Team. These teams will be comprised of scientists, technologists, and other qualified and interested individuals to help plan the implementation and execution of ARM. An overview of robotic and crewed segments of ARM, including the mission requirements, NEA targets, and mission operations, will be provided along with a discussion of the potential opportunities associated with the mission.

The Asteroid Redirect Mission (ARM)

NASA Technical Reports Server (NTRS)

Abell, Paul

2015-01-01

The National Aeronautics and Space Administration (NASA) is developing a robotic mission to visit a large near-Earth asteroid (NEA), collect a multi-ton boulder from its surface, and redirect it into a stable orbit around the Moon. Once returned to cislunar space in the mid-2020s, astronauts will explore the boulder and return to Earth with samples. This Asteroid Redirect Mission (ARM) is part of NASA's plan to advance the technologies, capabilities, and spaceflight experience needed for a human mission to the Martian system in the 2030s. Subsequent human and robotic missions to the asteroidal material would also be facilitated by its return to cislunar space. Although ARM is primarily a capability demonstration mission (i.e., technologies and associated operations), there exist significant opportunities to advance our knowledge of small bodies in the synergistic areas of science, planetary defense, asteroidal resources and in-situ resource utilization (ISRU), and capability and technology demonstrations. In order to maximize the knowledge return from the mission, NASA is organizing an ARM Investigation Team, which is being preceded by the Formulation Assessment and Support Team. These teams will be comprised of scientists, technologists, and other qualified and interested individuals to help plan the implementation and execution of ARM. An overview of robotic and crewed segments of ARM, including the mission requirements, NEA targets, and mission operations, will be provided along with a discussion of the potential opportunities associated with the mission.

Petrologic constraints on the surface processes on asteroid 4 Vesta and on excavation depths of diogenite fragments

NASA Technical Reports Server (NTRS)

Grove, T. L.

1993-01-01

The eucrite-howardite-diogenite meteorite groups are though to be related by magmatic processes. Asteroid 4 Vesta has been proposed as the parent body for these basaltic achondrite meteorites. The similarity of the planetesimal's surface composition to eucrite and diogenite meteorites and the large size of the asteroid (r = 250 km) make it an attractive source, but its position in the asteroid belt far from the known resonances from which meteorites originate make a relation between Vesta and eucrite-howardite-giogenite group problematic. It has been proposed that diogenites are low-Ca pyroxene-rich cumulates that crystallized from a magnesian parent (identified in howardite breccias), and this crystallization process led to evolved eucrite derivative magmas. This eucrite-diogenite genetic relationship places constraints on the physical conditions under which crystallization occurred. Elevated pressure melting experiments on magnesian eucrite parent compositions show that the minimum pressure at which pyroxene crystallization could lead to the observed compositions of main series eucrites is 500 bars, equivalent to a depth of 135 km in a 4 Vesta-sized eucrite parent body. Therefore, the observation of diogenite on the surface of 4 Vesta requires a post-crystallization process that excavates diogenite cumulate from depth. The discovery of diogenite asteroidal fragments is consistent with an impact event on 4 Vesta that penetrated the deep interior of this planetesimal.

Global environmental effects of impact-generated aerosols: Results from a general circulation model

NASA Technical Reports Server (NTRS)

Covey, Curt; Ghan, Steven J.; Walton, John J.; Weissman, Paul R.

1989-01-01

Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to the three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans, not included in the one-dimensional model, substantially mitigates land surface cooling. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stages of cooling than in the one-dimensional model study. GCM-simulated climatic changes in the scenario of asteroid/comet winter are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though of course less severe, climatic changes, according to the GCM. An asteroid or comet impact would not lead to anything approaching complete global freezing, but quite reasonable to assume that impacts would dramatically alter the climate in at least a patchy sense.

Internal state of Lutetia as a function of the macroporosity

NASA Astrophysics Data System (ADS)

Neumann, W.; Breuer, D.; Spohn, T.

2014-07-01

The asteroid (21) Lutetia appears to be an intermediate object between the small near-primordial asteroids and a fully differentiated dwarf planet (4) Vesta. Understanding its evolution is crucial for the understanding of the accretion chain from km-sized planetesimals to full-sized planets and of the possible origin of both differentiated and undifferentiated meteorites. Remarkable is the bulk density value of 3400 kg m^{-3} obtained by the Rosetta flyby in July 2010 [1]. It indicates a relatively high intrinsic density, because the heavily cratered surface suggests a certain macroporosity of this body. Thereby, the macroporosity ϕ_{m} remains an uncertainty. We adopted the numerical model from [2] to consider an enstatite chondritic composition suggested by the spectrum [3], and supplemented it with a radiation boundary condition. Thereby, the nebula temperature is variable in order to simulate the cooling of the protoplanetary nebula with time and the migration of Lutetia from the inner Solar System (where it could have formed) to its present orbit. Assuming a value of ϕ_{m} in the range of 0-25 %, we calculate the intrinsic material properties, such as the density, composition, and radiogenic heat-source abundance. Subsequently, we simulate the accretion of Lutetia from the protoplanetary dust as a porous aggregate. Upon radiogenic heating by the short-lived radionuclides ^{26}Al and ^{60}Fe, compaction of the interior to the consolidated state by hot pressing is modeled using a creep-law-related approach. In the frame of a complex numerical model, a variety of physical processes is taken into account, like the calculation of melting, latent heat consumption and release, magmatic heat transport, melt segregation by porous flow, and the associated approach on differentiation modelling. The equations describing the physical processes like simultaneous growth due to the accretion, shrinkage due to the compaction, and differentiation, are solved simultaneously. The goal is to constrain the present-day macroporosity of the asteroid and its possible internal structure (porous/compacted/differentiated), starting with accretion from a highly porous building material. The evolution scenarios arising from assumptions on the macroporosity ϕ_{m} are examined to derive implications on the compaction of an initially highly porous material and (partial) differentiation. The calculated final structures are compared with the observations of Rosetta in order to derive bounds on the present-day macroporosity and internal structure of Lutetia. We obtain a number of possible compaction and differentiation scenarios consistent with the properties of the present-day Lutetia. The most probable macroporosity for a Lutetia-like body with the observed bulk density of 3400 kg m^{-3} is ϕ_{m} ≥ 0.04. Small changes can be expected if an error of ± 300 kg m^{-3} in the bulk density is considered. Depending on the adopted value of ϕ_{m}, Lutetia may have formed contemporaneously with the calcium-aluminium-rich inclusions (ϕ_{m} = 0.04) or up to 8 Ma later (ϕ_{m}= 0.25). The degree of differentiation varies significantly and the most evolved structure consists of an iron core and a silicate mantle that are covered by an undifferentiated but sintered layer and an undifferentiated and unsintered regolith. We find a differentiated interior, i.e., an iron-rich core and a silicate mantle, only for a rather narrow interval between 0.04 ≤ ϕ_{m} < 0.06 with the formation times between 0 Ma and 1.8 Ma after the CAIs. Regardless of melting and partial differentiation, no melt extrusion through the porous layer is likely -- a finding that is consistent with the lack of basalt at the surface of Lutetia. Thus, although the outside is primordial, it could still have experienced substantial melting, have an iron core and a hidden igneous activity in the past. For ϕ_{m} ≥ 0.6, an iron-silicate differentiation is not possible, but the interior is compacted due to sintering below a porous outer layer. Our results [4] confirm the idea raised theoretically in [2,5] that a small asteroid like Lutetia can be a parent body of undifferentiated (chondritic), partially differentiated (primitive achondritic), and differentiated (achondritic) meteorites. Thus, enstatite chondritic, iron, and primitive achondritic meteorites can, in principle, originate from Lutetia, because it may be partially differentiated and was clearly disturbed by several major impacts. Furthermore, the timing of the occurrence of thermal convection in the metallic core suggests the possibility of an internal dynamo on Lutetia. This could explain the remanent magnetization found in undifferentiated chondritic meteorites.

The Asteroid Redirect Mission (ARM): Exploration of a Former Binary NEA?

NASA Technical Reports Server (NTRS)

Abell, P. A.; Mazanek, D. D.; Reeves, D. M.; Chodas, P. W.; Gates, M. M.; Johnson, L. N.; Ticker, R. L.

2016-01-01

The National Aeronautics and Space Administration (NASA) is developing the Asteroid Redirect Mission (ARM) as a capability demonstration for future human exploration, including use of high-power solar electric propulsion, which allows for the efficient movement of large masses through deep space. The ARM will also demonstrate the capability to conduct proximity operations with natural space objects and crewed operations beyond the security of quick Earth return. The Asteroid Redirect Robotic Mission (ARRM), currently in formulation, will visit a large near-Earth asteroid (NEA), collect a multi-ton boulder from its surface, conduct a demonstration of a slow push planetary defense technique, and redirect the multi-ton boulder into a stable orbit around the Moon. Once returned to cislunar space in the mid-2020s, astronauts aboard an Orion spacecraft will dock with the robotic vehicle to explore the boulder and return samples to Earth. The ARM is part of NASA's plan to advance technologies, capabilities, and spaceflight experience needed for a human mission to the Martian system in the 2030s. The ARM and subsequent availability of the asteroidal material in cis-lunar space, provide significant opportunities to advance our knowledge of small bodies in the synergistic areas of science, planetary defense, and in-situ resource utilization (ISRU). The current reference target for the ARM is NEA (341843) 2008 EV5, which may have been the primary body of a former binary system (Busch et al., 2011; Tardivel et al., 2016). The ARRM will perform several close proximity operations to investigate the NEA and map its surface. A detailed investigation of this object may allow a better understanding of binary NEA physical characteristics and the possible outcomes for their evolution. An overview of the ARM robotic and crewed segments, including mission operations, and a discussion of potential opportunities for participation with the ARM will be provided in this presentation.

A Potpourri of Near-Earth Asteroid Observations

NASA Astrophysics Data System (ADS)

Tholen, David J.; Ramanjooloo, Yudish; Fohring, Dora; Hung, Denise; Micheli, Marco

2016-10-01

Ongoing astrometric follow-up of near-Earth asteroids has yielded a variety of interesting results. In the limited space of a DPS abstract, three recently observed objects are worth mentioning.2008 HU4 is among the most accessible asteroids for a human space flight mission. We successfully recovered this object at a second opposition on 2016 April 26 despite the large ephemeris uncertainty. The small size of this asteroid makes it relatively easy to detect the departure from purely gravitational motion caused by solar radiation pressure, which can be used to estimate the density of the object. At the time of this writing, the object remains bright enough for additional observations, so we expect to improve on our five-sigma detection of a relatively low density (roughly similar to water, indicating a high porosity) between now and the DPS meeting.2016 HO3 is a newly-discovered co-orbital with the Earth. Our 2016 May 10-11 observations extended the observational arc by enough to permit backward extrapolation that led to prediscovery observations by Pan-STARRS in 2015, and then annually back to 2011, and ultimately to Sloan DSS observations in 2004. The 12-year arc is sufficient to examine the dynamical behavior of the object, which shows how it will remain in the vicinity of the Earth for decades, if not centuries. Our observations also revealed a rapid rotation (less than a half hour) with large brightness variation (in excess of 1 magnitude), which helps to explain why this object eluded discovery until this year.2011 YV62 is among the top 20 largest near-Earth asteroids with Earth impact solutions (in 2078 and 2080). At the time of this writing, the object is flagged as being "lost", but a re-examination of observations made in 2013 and 2015 finally yielded a successful recovery at a magnitude fainter than 24. We expect the new observations to eliminate the impact possibilities. The story behind this difficult recovery is fascinating.

The AKARI IRC asteroid flux catalogue: updated diameters and albedos

NASA Astrophysics Data System (ADS)

Alí-Lagoa, V.; Müller, T. G.; Usui, F.; Hasegawa, S.

2018-05-01

The AKARI IRC all-sky survey provided more than twenty thousand thermal infrared observations of over five thousand asteroids. Diameters and albedos were obtained by fitting an empirically calibrated version of the standard thermal model to these data. After the publication of the flux catalogue in October 2016, our aim here is to present the AKARI IRC all-sky survey data and discuss valuable scientific applications in the field of small body physical properties studies. As an example, we update the catalogue of asteroid diameters and albedos based on AKARI using the near-Earth asteroid thermal model (NEATM). We fit the NEATM to derive asteroid diameters and, whenever possible, infrared beaming parameters. We fit groups of observations taken for the same object at different epochs of the survey separately, so we compute more than one diameter for approximately half of the catalogue. We obtained a total of 8097 diameters and albedos for 5170 asteroids, and we fitted the beaming parameter for almost two thousand of them. When it was not possible to fit the beaming parameter, we used a straight line fit to our sample's beaming parameter-versus-phase angle plot to set the default value for each fit individually instead of using a single average value. Our diameters agree with stellar-occultation-based diameters well within the accuracy expected for the model. They also match the previous AKARI-based catalogue at phase angles lower than 50°, but we find a systematic deviation at higher phase angles, at which near-Earth and Mars-crossing asteroids were observed. The AKARI IRC All-sky survey is an essential source of information about asteroids, especially the large ones, since, it provides observations at different observation geometries, rotational coverages and aspect angles. For example, by comparing in more detail a few asteroids for which dimensions were derived from occultations, we discuss how the multiple observations per object may already provide three-dimensional information about elongated objects even based on an idealised model like the NEATM. Finally, we enumerate additional expected applications for more complex models, especially in combination with other catalogues. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A85

Study of the Asteroid Florence

NASA Astrophysics Data System (ADS)

Vodniza, Alberto; Pereira, Mario

2018-06-01

Asteroid Florence was discovered at Siding Spring Observatory in Australia (March 1981). Paul Chodas, manager of CNEOS-JPL said: “Florence is the largest asteroid to pass by our planet this close since the NASA program to detect and track near-Earth asteroids began” [1]. The asteroid passed 7.1 million kilometers away from the earth [2]. The GDSCC-NASA discovered that the asteroid has two small moons. The diameter of Florence is 4.5 kilometers, and the sizes of the two moons are probably between 100 – 300 meters across. The inner moon has a rotation period around Florence of about 8 hours, and the outer moon has a period of about 25 hours [3]. From our Observatory, located in Pasto-Colombia, we captured several pictures, videos and astrometry data during several hours during three days. Our data was published by the Minor Planet Center (MPC) and also appears at the web page of NEODyS [4]. The pictures were captured with the following equipment: CGE PRO 1400 CELESTRON and STL-1001 SBIG camera. Astrometry and photometry was carried out, and we calculated the orbital elements and the rotation period. Summary and conclusions: We obtained the following orbital parameters: eccentricity = 0.422548 +/- 0.000994, semi-major axis = 1.76675 +/- 0.00313 A.U, orbital inclination = 22.128 +/- 0.029 deg, longitude of the ascending node = 336.0960 +/- 0.0013 deg, argument of perihelion = 27.861 +/- 0.016, mean motion = 0.41970 +/- 0.00112 deg/d, perihelion distance = 1.0202151 +/- 5.27e-5 A.U, aphelion distance = 2.51329 +/- 0.00625 A.U, absolute magnitude = 14.4. The parameters were calculated based on 281 observations. Dates: 2017 September 01 to 05 with mean residual = 0.19 arcseconds. The asteroid has an orbital period of 2.35 years (857.74 days). The rotation period of the asteroid is 2.3 hours. Note: Spaceweather published our video on September 1-2017 [5].[1] https://www.nasa.gov/feature/jpl/large-asteroid-to-safely-pass-earth-on-sept-1[2] http://newton.dm.unipi.it/neodys/index.php?pc=1.1.8&n=Florence[3] https://cneos.jpl.nasa.gov/news/news199.html[4] http://newton.dm.unipi.it/neodys/index.php?pc=2.1.2&o=H78&ab=8[5] http://www.spaceweather.com/archive.php?view=1&day=01&month=09&year=2017

Thermophysical modeling of main-belt asteroids from WISE thermal data

NASA Astrophysics Data System (ADS)

Hanuš, J.; Delbo', M.; Ďurech, J.; Alí-Lagoa, V.

2018-07-01

By means of a varied-shape thermophysical model of Hanuš et al. (2015) that takes into account asteroid shape and pole uncertainties, we analyze the thermal infrared data acquired by the NASA's Wide-field Infrared Survey Explorer of about 300 asteroids with derived convex shape models. We utilize publicly available convex shape models and rotation states as input for the thermophysical modeling. For more than one hundred asteroids, the thermophysical modeling gives us an acceptable fit to the thermal infrared data allowing us to report their thermophysical properties such as size, thermal inertia, surface roughness or visible geometric albedo. This work more than doubles the number of asteroids with determined thermophysical properties, especially the thermal inertia. In the remaining cases, the shape model and pole orientation uncertainties, specific rotation or thermophysical properties, poor thermal infrared data or their coverage prevent the determination of reliable thermophysical properties. Finally, we present the main results of the statistical study of derived thermophysical parameters within the whole population of main-belt asteroids and within few asteroid families. Our sizes based on TPM are, in average, consistent with the radiometric sizes reported by Mainzer et al. (2016). The thermal inertia increases with decreasing size, but a large range of thermal inertia values is observed within the similar size ranges between D ∼ 10-100 km. We derived unexpectedly low thermal inertias ( < 20 J m-2 s- 1 / 2 K-1) for several asteroids with sizes 10 < D < 50 km, indicating a very fine and mature regolith on these small bodies. The thermal inertia values seem to be consistent within several collisional families, however, the statistical sample is in all cases rather small. The fast rotators with rotation period P ≲ 4 h tend to have slightly larger thermal inertia values, so probably do not have a fine regolith on the surface. This could be explained, for example, by the loss of the fine regolith due to the centrifugal force, or by the ineffectiveness of the regolith production(e.g., by the thermal cracking mechanism of Delbo' et al. 2014).

Obliquity, precession rate, and nutation coefficients for a set of 100 asteroids

NASA Astrophysics Data System (ADS)

Lhotka, C.; Souchay, J.; Shahsavari, A.

2013-08-01

Context. Thanks to various space missions and the progress of ground-based observational techniques, the knowledge of asteroids has considerably increased in the recent years. Aims: Due to this increasing database that accompanies this evolution, we compute for a set of 100 asteroids their rotational parameters: the moments of inertia along the principal axes of the object, the obliquity of the axis of rotation with respect to the orbital plane, the precession rates, and the nutation coefficients. Methods: We select 100 asteroids for which the parameters for the study are well-known from observations or space missions. For each asteroid, we determine the moments of inertia, assuming an ellipsoidal shape. We calculate their obliquity from their orbit (instead of the ecliptic) and the orientation of the spin-pole. Finally, we calculate the precession rates and the largest nutation components. The number of asteroids concerned leads to some statistical studies of the output. Results: We provide a table of rotational parameters for our set of asteroids. The table includes the obliquity, their axes ratio, their dynamical ellipticity Hd, and the scaling factor K. We compute the precession rate ψ˙ and the leading nutation coefficients Δψ and Δɛ. We observe similar characteristics, as observed by previous authors that is, a significantly larger number of asteroids rotates in the prograde mode (≈ 60%) than in the retrograde one with a bimodal distribution. In particular, there is a deficiency of objects with a polar axis close to the orbit. The precession rates have a mean absolute value of 18″/y, and the leading nutation coefficients have an average absolute amplitude of 5.7″ for Δψ and 5.2″ for Δɛ. At last, we identify and characterize some cases with large precession rates, as seen in 25143 Itokawa, with has a precession rate of about - 475''/y. Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/556/A8

The GTC mid-infrared spectroscopic program of primitive outer-belt asteroids

NASA Astrophysics Data System (ADS)

Licandro, J.; Alvarez-Iglesias, C. Carlos; Cabrera-Lavers, A.; Ali-Lagoa, V.; Pinilla-Alonso, N.; Campins, H.; de Leon, J.; Kelley, M.

2014-07-01

Asteroids in the outer edge of the asteroid belt (Cybeles, Hildas, and Jupiter Trojans) may provide a number of clues to the origin and evolution of the asteroid belt and the formation of our planetary system. They have a pristine composition, experienced little heating and may contain a significant fraction of ice in their interiors. The origin of these populations is still under debate. Levison et al. (2009) suggested that a large fraction of these bodies are transneptunian objects (TNOs) moved to these resonances in an early epoch of the Solar System called the ''Late Heavy Bombardment'' (LHB). To compare the physical properties of these asteroid populations with TNOs and comets is thus a strong test of dynamical models. In mid 2013, we started a mid-infrared photometric and spectroscopic program in the N-band using the CANARICAM camera-spectrograph at the 10.4-m GTC telescope at the ''Roque de los Muchachos'' Obserbatory (Canary Islands, Spain). We aim to study the surface composition and key properties such as radius, albedo, and thermal inertia based on their low-resolution 8--13-micron spectra and N-band photometry. We already obtained the spectra of 5 objects, that of (225) Henrieta is shown as an example in the Figure. The three published spectra of Trojan asteroids (Emery et al. 2006) and of (65) Cybele (Licandro et al. 2011) exhibit clear emissivity features from which the compositional and physical properties can be inferred. The spectra of these objects strongly resemble one another, presenting an emission plateau due to silicates at about 9.1-11.5 microns (the Si-O stretch fundamental). Fine-grained silicates in a very porous (fairly castle) structure, and no other mineral group (Emery et al. 2006, Vernazza et al. 2012), reproduce the major features of the Trojans and Cybele asteroid spectra. In this work, we present the preliminary results of our observational program including the N-band spectra, size, and albedo of the already observed 5 asteroids, and discuss the potential of such observations.

The Asteroid Impact Mission

NASA Astrophysics Data System (ADS)

Carnelli, Ian; Galvez, Andres; Mellab, Karim

2016-04-01

The Asteroid Impact Mission (AIM) is a small and innovative mission of opportunity, currently under study at ESA, intending to demonstrate new technologies for future deep-space missions while addressing planetary defense objectives and performing for the first time detailed investigations of a binary asteroid system. It leverages on a unique opportunity provided by asteroid 65803 Didymos, set for an Earth close-encounter in October 2022, to achieve a fast mission return in only two years after launch in October/November 2020. AIM is also ESA's contribution to an international cooperation between ESA and NASA called Asteroid Impact Deflection Assessment (AIDA), consisting of two mission elements: the NASA Double Asteroid Redirection Test (DART) mission and the AIM rendezvous spacecraft. The primary goals of AIDA are to test our ability to perform a spacecraft impact on a near-Earth asteroid and to measure and characterize the deflection caused by the impact. The two mission components of AIDA, DART and AIM, are each independently valuable but when combined they provide a greatly increased scientific return. The DART hypervelocity impact on the secondary asteroid will alter the binary orbit period, which will also be measured by means of lightcurves observations from Earth-based telescopes. AIM instead will perform before and after detailed characterization shedding light on the dependence of the momentum transfer on the asteroid's bulk density, porosity, surface and internal properties. AIM will gather data describing the fragmentation and restructuring processes as well as the ejection of material, and relate them to parameters that can only be available from ground-based observations. Collisional events are of great importance in the formation and evolution of planetary systems, own Solar System and planetary rings. The AIDA scenario will provide a unique opportunity to observe a collision event directly in space, and simultaneously from ground-based optical and radar facilities. For the first time, an impact experiment at asteroid scale will be performed with accurate knowledge of the precise impact conditions and also the impact outcome, together with information on the physical properties of the target, ultimately validating at appropriate scales our knowledge of the process and impact simulations. AIM's important technology demonstration component includes a deep-space optical communication terminal and inter-satellite network with two CubeSats deployed in the vicinity of the Didymos system and a lander on the surface of the secondary. To achieve a low-cost objective AIM's technology and scientific payload are being combined to support both close-proximity navigation and scientific investigations. AIM will demonstrate the capability to achieve a small spacecraft design with a very large technological and scientific mission return.

Collisional fragmentation of asteroids and its implication on the physical properties of Near-Earth Objects

NASA Astrophysics Data System (ADS)

Michel, P.

Collisions are at the origin of catastrophic disruptions in the asteroid Main Belt. This is witnessed by the observation of asteroid families, each composed of asteroids which originated from a single parent body, broken-up by a collision with another asteroid. Understanding the collisional process and its outcome properties is not only necessary in order to study the collisional evolution of small body population or the planetary formation, it is also strongly required in the context of mitigation strategies aimed at deviating a threatening asteroid. In the last three years, for the first time we have successfully performed numerical simulations of high speed collisions between small bodies which account for the production of gravitationally reaccumulated bodies. More precisely, we have developped a procedure which divides the process into two phases. Using a 3D SPH hydrocode, the fragmentation of the solid target through crack propagation is first computed. Then the simulation of the gravitational evolution and possible piecewise reaccumulation of the parent body is performed using the parallel N-body code pkdgrav. Our first simulations using monolithic parent bodies have succeeded in reproducing fundamental properties of some well-identified asteroid families, showing that gravitational re-accumulations following disruptive collisions are the key process accounting for the existence of asteroid families. Then, we have investigated the effect of the internal structure of the parent body on the outcome properties. We have thus shown that family parent bodies are likely to have already been pre-shattered by small impacts before being disrupted by a major event. We then suggested that the most likely internal structure of large asteroids in the main belt is not monolithic but rather composed of macroscopic fractures and voids. We will make a review of these simulations in three different impact regimes, from highly catastrophic to barely disruptive. In particular we will show the sensitivity of the resulting family characteristics upon the internal structure of the parent body. According to our current understanding, most NEOs are certainly fragments of larger asteroids of the Main Belt, injected either directly or by diffusion into main resonances that transported them to Earth-crossing orbits. According to our simulations, most NEOs with diameter larger than several hundreds of meters should then correspond to gravitational aggregates. Given the crucial role of the internal structure on the impact outcome, this has important implications in the development of efficient mitigation strategies.

Mass extinctions caused by large bolide impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alvarez, L.W.

1987-07-01

Evidence indicates that the collision of Earth and a large piece of Solar System derbris such as a meteoroid, asteroid or comet caused the great extinctions of 65 million years ago, leading to the transition from the age of the dinosaurs to the age of the mammals.