Identification of a primordial asteroid family constrains the original planetesimal population.

PubMed

Delbo', Marco; Walsh, Kevin; Bolin, Bryce; Avdellidou, Chrysa; Morbidelli, Alessandro

2017-09-08

A quarter of known asteroids is associated with more than 100 distinct asteroid families, meaning that these asteroids originate as impact fragments from the family parent bodies. The determination of which asteroids of the remaining population are members of undiscovered families, or accreted as planetesimals from the protoplanetary disk, would constrain a critical phase of planetary formation by unveiling the unknown planetesimal size distribution. We discovered a 4-billion-year-old asteroid family extending across the entire inner part of the main belt whose members include most of the dark asteroids previously unlinked to families. This allows us to identify some original planetesimals, which are all larger than 35 kilometers, supporting the view of asteroids being born big. Their number matches the known distinct meteorite parent bodies. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

THE SCHULHOF FAMILY: SOLVING THE AGE PUZZLE

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

Vokrouhlický, David; Ďurech, Josef; Pravec, Petr

The Schulhof family, a tight cluster of small asteroids around the central main belt body (2384) Schulhof, belongs to a so far rare class of very young families (estimated ages less than 1 Myr). Characterization of these asteroid clusters may provide important insights into the physics of the catastrophic disruption of their parent body. The case of the Schulhof family has been up to now complicated by the existence of two proposed epochs of its origin. In this paper, we first use our own photometric observations, as well as archival data, to determine the rotation rate and spin axis orientation ofmore » the largest fragment (2384) Schulhof. Our data also allow us to better constrain the absolute magnitude of this asteroid, and thus also improve the determination of its geometric albedo. Next, using the up-to-date catalog of asteroid orbits, we perform a new search of smaller members in the Schulhof family, increasing their number by 50%. Finally, the available data are used to access Schulhof's family age anew. We now find that the younger of the previously proposed two ages of this family is not correct, resulting from a large orbital uncertainty of single-opposition members. Our new runs reveal a single age solution of about 800 kyr with a realistic uncertainty of 200 kyr.« less

The Schulhof Family: Solving the Age Puzzle

NASA Astrophysics Data System (ADS)

Vokrouhlický, David; Ďurech, Josef; Pravec, Petr; Kušnirák, Peter; Hornoch, Kamil; Vraštil, Jan; Krugly, Yurij N.; Inasaridze, Raguli Ya.; Ayvasian, Vova; Zhuzhunadze, Vasili; Molotov, Igor E.; Pray, Donald; Husárik, Marek; Pollock, Joseph T.; Nesvorný, David

2016-03-01

The Schulhof family, a tight cluster of small asteroids around the central main belt body (2384) Schulhof, belongs to a so far rare class of very young families (estimated ages less than 1 Myr). Characterization of these asteroid clusters may provide important insights into the physics of the catastrophic disruption of their parent body. The case of the Schulhof family has been up to now complicated by the existence of two proposed epochs of its origin. In this paper, we first use our own photometric observations, as well as archival data, to determine the rotation rate and spin axis orientation of the largest fragment (2384) Schulhof. Our data also allow us to better constrain the absolute magnitude of this asteroid, and thus also improve the determination of its geometric albedo. Next, using the up-to-date catalog of asteroid orbits, we perform a new search of smaller members in the Schulhof family, increasing their number by 50%. Finally, the available data are used to access Schulhof's family age anew. We now find that the younger of the previously proposed two ages of this family is not correct, resulting from a large orbital uncertainty of single-opposition members. Our new runs reveal a single age solution of about 800 kyr with a realistic uncertainty of 200 kyr.

Search for a Differentiated Asteroid Family

NASA Astrophysics Data System (ADS)

Thomas, Cristina A.; Lim, Lucy F.; Trilling, David E.; Moskovitz, Nicholas

2014-08-01

Dynamical asteroid families resulting from catastrophic disruptions represent the interiors of their former parent bodies. Differentiation of a large initially chondritic parent body is expected to produce an ``onion shell" object with a metal core, a thick olivine-rich mantle, and a thin basaltic crust. However, instead of the mineralogical diversity expected from the disruption of a differentiated parent body, most asteroid families tend to show similar spectra among the members. Moreover, spectra of metal-like materials and olivine-dominated assemblages have not been detected in asteroid families in the Main Belt and the expected mantle material is missing from the meteorite record. The deficit of olivine-rich mantle material in the meteorite record and in asteroid observations is known as the ``Missing Mantle" problem. For years the best explanation for the lack of mantle material has been the ``battered to bits" hypothesis that states that all differentiated parent bodies (aside from Vesta) were disrupted very early in the solar system and the resulting olivine-rich material was collisionally broken down until the object diameters fell below our observational limits. However, in a new, competing, hypothesis, Elkins-Tanton et al. (2013) has suggested that previous work has overestimated the amount of olivine produced by the differentiation of a chondritic parent body. We propose to obtain visible spectra of asteroids within the Massalia, Merxia, and Agnia S-type families to search for compositional variations that are indicators of differentiation and to quantitatively constrain the two competing ``Missing Mantle" hypotheses.

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.

Origin of igneous meteorites and differentiated asteroids

NASA Astrophysics Data System (ADS)

Scott, E.; Goldstein, J.; Asphaug, E.; Bottke, W.; Moskovitz, N.; Keil, K.

2014-07-01

Introduction: Igneously formed meteorites and asteroids provide major challenges to our understanding of the formation and evolution of the asteroid belt. The numbers and types of differentiated meteorites and non-chondritic asteroids appear to be incompatible with an origin by fragmentation of numerous Vesta-like bodies by hypervelocity impacts in the asteroid belt over 4 Gyr. We lack asteroids and achondrites from the olivine-rich mantles of the parent bodies of the 12 groups of iron meteorites and the ˜70 ungrouped irons, the 2 groups of pallasites and the 4--6 ungrouped pallasites. We lack mantle and core samples from the parent asteroids of the basaltic achondrites that do not come from Vesta, viz., angrites and the ungrouped eucrites like NWA 011 and Ibitira. How could core samples have been extracted from numerous differentiated bodies when Vesta's basaltic crust was preserved? Where is the missing Psyche family of differentiated asteroids including the complementary mantle and crustal asteroids [1]? Why are meteorites derived from far more differentiated parent bodies than chondritic parent bodies even though C and S class chondritic asteroids dominate the asteroid belt? New paradigm. Our studies of meteorites, impact modeling, and dynamical studies suggest a new paradigm in which differentiated asteroids accreted at 1--2 au less than 2 Myr after CAI formation [2]. They were rapidly melted by 26Al and disrupted by hit-and-run impacts [3] while still molten or semi-molten when planetary embryos were accreting. Metallic Fe-Ni bodies derived from core material cooled rapidly with little or no silicate insulation less than 4 Myr after CAI formation [4]. Fragments of differentiated planetesimals were subsequently tossed into the asteroid belt. Meteorite evidence for early disruption of differentiated asteroids. If iron meteorites were samples of Fe-Ni cores of bodies that cooled slowly inside silicate mantles over ˜50--100 Myr, irons from each core would have almost indistinguishable cooling rates as thermal gradients across cores would have been minimal. Irons in groups IIIAB, IVA, and IVB have chemical crystallization trends showing that they cooled in three separate bodies. However, each shows a wide range of cooling rates [4]. Group IVA irons cooled through 500°C at 6600--100 °C/Myr in a metallic body of radius 150 ± 50 km with scarcely any silicate insulation [5]. The Pb-Pb age of 4565.3 ± 0.1 Myr for a IVA iron [6] confirms that these irons cooled to ˜300°C only 2--3 Myr after CAI formation. Multiple hit-and-run impacts may have separated core and mantle material during accretion [7] as hypervelocity impacts do not efficiently separate cores from mantles. Thermal histories and magnetic properties of main group pallasites also require early catastrophic disruption of their primary parent body [8,9]. Conclusions. The anomalous properties of differentiated asteroids and meteorites cannot be explained by concealing differentiated planetesimals under chondritic crusts [10] as meteorite breccias and the apparent compositional homogeneity of asteroid families are inconsistent with this model. Like Burbine et al. [11], we attribute the lack of olivine mantle meteorites and asteroids to collisional grinding of weaker silicate and the preferential survival of stronger metallic Fe,Ni fragments. But we infer that asteroid break up occurred very early inside 2 au, not in the asteroid belt over 4 Gyr. Vesta may have preserved its crust due to early ejection into the asteroid belt. It is the smallest terrestrial planet --- not an archetypal differentiated asteroid.

Evolution of the inner asteroid belt: Paradigms and paradoxes from spectral studies

NASA Technical Reports Server (NTRS)

Gaffey, Michael J.

1987-01-01

Recent years have witnessed a significant increase in the sophistication of asteroidal surface material characterizations derived from spectral data. An extensive data base of moderate to high spectral resolution, visible and near-infrared asteroid spectra is now available. Interpretive methodologies and calibrations were developed to determine phase abundance and composition in olivine-pyroxene assemblages and to estimate NiFe metal abundance from such spectra. A modified version of the asteroid classifications system more closely parallels the mineralogic variations of the major inner belt asteroid types. These improvements permit several general conclusions to be drawn concerning the nature of inner belt objects; their history, and that of the inner solar system; and the relationship between the asteroids and meteorites. Essentially all large belt asteroids have or are fragments of parent bodies which have undergone strong post-accretionary heating, varying degrees of melting and magmatic differentiation, and subsequent collisional disruption. These asteroids show a systematic, but not yet well characterized, mineralogic variation with semi-major axis. This suggests that the S-type asteroid families represent relatively recent collisions onto the cores of previously disrupted parent bodies.

Near-infrared reflectance spectra-applications to problems in asteroid-meteorite relationships

NASA Technical Reports Server (NTRS)

Mcfadden, Lucy A.; Chamberlin, Alan; Vilas, Faith

1991-01-01

Near-infrared spectral reflectance data were collected at the Infrared Telescope Facility (IRTF) at Mauna Kea Observatories in 1985 and 1986 for the purpose of searching the region near the 3:1 Kirkwood gap for asteroids with the spectral signatures of ordinary chondrite parent bodies. Twelve reflectance spectra are observed. The presence of ordinary chondrite parent bodies among this specific set of observed asteroids is not obvious, though the sample is biased towards the larger asteroids in the region due to limitations imposed by detector sensitivity. The data set, which was acquired with the same instrumentation used for the 52-color asteroid survey (Bell et al., 1987), also presents some additional findings. The range of spectral characteristics that exist among asteroids of the same taxonomic type is noted. Conclusions based on the findings are discussed.

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.

The oxygen isotope composition of Almahata Sitta

NASA Astrophysics Data System (ADS)

Rumble, Douglas; Zolensky, Michael E.; Friedrich, Jon M.; Jenniskens, Peter; Shaddad, Muawia H.

2010-10-01

Eleven fragments of the meteorite Almahata Sitta (AHS) have been analyzed for oxygen isotopes. The fragments were separately collected as individual stones from the meteorite's linear strewn field in the Nubian Desert. Each of the fragments represents a sample of a different and distinct portion of asteroid 2008 TC3. Ten of the fragments span the same range of values of δ18O, δ17O, and Δ17O, and follow the same trend along the carbonaceous chondrite anhydrous minerals (CCAM) line as monomict and polymict members of the ureilite family of meteorites. The oxygen isotope composition of fragment #25 is consistent with its resemblance petrographically to an H5 ordinary chondrite. Our results demonstrate that a single small asteroidal parent body, asteroid 2008 TC3, only 4 m in length, encompassed the entire range of variation in oxygen isotope compositions measured for monomict and polymict ureilites.

Searching for a Differentiated Asteroid Family: A Spectral Survey of the Massalia, Merxia, and Agnia Families

NASA Astrophysics Data System (ADS)

Thomas, Cristina A.; Moskovitz, Nicholas; Lim, Lucy F.; Trilling, David E.

2017-10-01

Asteroid families were formed by catastrophic collisions or large cratering events that caused fragmentation of the parent body and ejection of asteroidal fragments with velocities sufficient to prevent re-accretion. Due to these formation processes, asteroid families provide us with the opportunity to probe the interiors of the former parent bodies. Differentiation of a large initially chondritic parent body is expected to result in an “onion shell" object with an iron-nickel core, a thick olivine-dominated mantle, and a thin plagioclase/pyroxene crust. However, most asteroid families tend to show similar spectra (and therefore composition) among the members. Spectroscopic studies have observed a paucity of metal-like materials and olivine-dominated assemblages within Main Belt asteroid families.The deficit of olivine-rich mantle material in the meteorite record and in asteroid observations is known as the “Missing Mantle" problem. For years the best explanation has been the “battered to bits" hypothesis: differentiated parent bodies (aside from Vesta) were disrupted very early in the Solar System and the olivine-rich material was collisionally broken down over time. Alternatively, Elkins-Tanton et al. (2013) have suggested that previous work has overestimated the amount of olivine produced by the differentiation of a chondritic parent body.We have completed a visible and near-infrared wavelength spectral survey of asteroids in the Massalia, Merxia, and Agnia S-type Main Belt asteroid families. These families were carefully chosen for the spectroscopic survey because they have compositions most closely associated with a history of thermal metamorphism and because they represent a range of collisional formation scenarios. Additionally, members of the Merxia and Agnia families were identified as products of differentiation by Sunshine et al. (2004).Our spectral analyses suggest that the observed families contain products of partial differentiation. We will present results from our spectral survey of these three families and discuss any evidence of differentiation among the family members. We will discuss our band parameter analyses and compositional results from the Modified Gaussian Model (MGM).

Searching for a Differentiated Asteroid Family: A Spectral Survey of the Massalia, Merxia, and Agnia Families

NASA Astrophysics Data System (ADS)

Thomas, Cristina A.; Lim, Lucy; Moskovitz, Nicholas; Trilling, David

2015-11-01

Asteroid families were formed by catastrophic collisions or large cratering events that caused fragmentation of the parent body and ejection of asteroidal fragments with velocities sufficient to prevent re-accretion. Due to these formation processes, asteroid families should provide us with the opportunity to probe the interiors of the former parent bodies. Differentiation of a large initially chondritic parent body is expected to result in an "onion shell" object with an iron-nickel core, a thick olivine-dominated mantle, and a thin plagioclase/pyroxene crust. However, most asteroid families tend to show similar spectra (and therefore composition) among the members. Spectroscopic studies have observed a paucity of metal-like materials and olivine-dominated assemblages within the Main Belt asteroid families.The deficit of olivine-rich mantle material in the meteorite record and in asteroid observations is known as the "Missing Mantle" problem. For years the best explanation has been the "battered to bits" hypothesis: that all differentiated parent bodies (aside from Vesta) were disrupted very early in the Solar System and the resulting olivine-rich material was collisionally broken down over time until the object diameters fell below our observational limits. In a competing hypothesis, Elkins-Tanton et al. (2013) have suggested that previous work has overestimated the amount of olivine produced by the differentiation of a chondritic parent body.We are conducting a visible and near-infrared wavelength spectral survey of asteroids in the Massalia, Merxia, and Agnia S-type Main Belt asteroid families. These families were carefully chosen for the proposed spectroscopic survey because they have compositions most closely associated with a history of thermal metamorphism and because they represent a range of collisional formation scenarios. In addition, the relatively young ages (under 400 Myr) of these families permit testing of the “battering to bits'' timescale. We will present initial results from our ongoing spectral survey of these three Main Belt families and discuss evidence for differentiation among the family members.We acknowledge funding support from the NASA Planetary Astronomy program.

Asteroid surface processes: Experimental studies of the solar wind on reflectance and optical properties of asteroids

NASA Technical Reports Server (NTRS)

Mcfadden, Lucy-Ann

1991-01-01

The effect of the solar wind on the optical properties of meteorites was studied to determine whether the solar wind can alter the properties of ordinary chondrite parent bodies resulting in the spectral properties of S-type asteroids. The existing database of optical properties of asteroids was analyzed to determine the effect of solar wind in altering asteroid surface properties.

Meteorite Dunite Breccia MIL 03443: A Probable Crustal Cumulate Closely Related to Diogenites from the HED Parent Asteroid

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.

2008-01-01

There are numerous types of differentiated meteorites, but most represent either the crusts or cores of their parent asteroids. Ureilites, olivine-pyroxene-graphite rocks, are exceptions; they are mantle restites [1]. Dunite is expected to be a common mantle lithology in differentiated asteroids. In particular, models of the eucrite parent asteroid contain large volumes of dunite mantle [2-4]. Yet dunites are very rare among meteorites, and none are known associated with the howardite, eucrite, diogenite (HED) suite. Spectroscopic measurements of 4 Vesta, the probable HED parent asteroid, show one region with an olivine signature [5] although the surface is dominated by basaltic and orthopyroxenitic material equated with eucrites and diogenites [6]. One might expect that a small number of dunitic or olivine-rich meteorites might be delivered along with the HED suite. The 46 gram meteoritic dunite MIL 03443 (Fig. 1) was recovered from the Miller Range ice field of Antarctica. This meteorite was tentatively classified as a mesosiderite because large, dunitic clasts are found in this type of meteorite, but it was noted that MIL 03443 could represent a dunite sample of the HED suite [7]. Here I will present a preliminary petrologic study of two thin sections of this meteorite.

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.

Forging Asteroid-Meteorite Relationships Through Reflectance Spectroscopy

NASA Technical Reports Server (NTRS)

Burbine, T. H.; Binzel, R. P.; Bus, S. J.; Buchanan, P. C.; Hinrichs, J. L.; Meibom, A.; Hiroi, T.; Sunshine, J. M.

2000-01-01

Near-infrared spectra were obtained for 196 asteroids as part of SMASSIR. SMASSIR focused on observing asteroids assumed to be one of the following: (1) olivine-rich, (2) objects with "Vesta-like spectra" (the "Vestoids"), and (3) postulated meteorite parent bodies.

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).

Geography of the asteroid belt

NASA Technical Reports Server (NTRS)

Zellner, B. H.

1978-01-01

The CSM classification serves as the starting point on the geography of the asteroid belt. Raw data on asteroid types are corrected for observational biases (against dark objects, for instance) to derive the distribution of types throughout the belt. Recent work on family members indicates that dynamical families have a true physical relationship, presumably indicating common origin in the breakup of a parent asteroid.

Identification of families among highly inclined asteroids

NASA Astrophysics Data System (ADS)

Gil-Hutton, R.

2006-07-01

A dataset of 3652 high-inclination numbered asteroids was analyzed to search for dynamical families. A fully automated multivariate data analysis technique was applied to identify the groupings. Thirteen dynamical families and twenty-two clumps were found. When taxonomic information is available, the families show cosmochemical consistency and support an interpretation based on a common origin from a single parent body. Four families and three clumps found in this work show a size distribution which is compatible with a formation due to a cratering event on the largest member of the family, and also three families have B- or related taxonomic types members, which represents a 14% of the B-types classified by Bus and Binzel [2002. Icarus 158, 146-177].

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.

Simulations of Collisional Disruption at the Catastrophic Impact Energy Threshold: Effect of the Target's Internal Structure and Diameter

NASA Astrophysics Data System (ADS)

Michel, P.; Benz, W.; Richardson, D. C.

2005-08-01

Recent simulations of asteroid break-ups, including both the fragmentation of the parent body and the gravitational interactions of the fragments, have allowed to reproduced successfully the main properties of asteroid families formed in different regimes of impact energy. Here, using the same kind of simulations, we concentrate on a single regime of impact energy, the so-called catastrophic threshold usually designated by Qcrit, which results in the escape of half of the target's mass. Considering a wide range of diameter values and two kinds of internal structures of the parent body, monolithic and pre-shattered, we analyse their potential influences on the value of Qcrit and on the collisional outcome limited here to the fragment size and ejection speed distributions, which are the main outcome properties used by collisional models to study the evolutions of the different populations of small bodies. For all the considered diameters and the two internal structures of the parent body, we confirm that the process of gravitational reaccumulation is at the origin of the largest remnant's mass. We then find that, for a given diameter of the parent body, the impact energy corresponding to the catastrophic disruption threshold is highly dependent on the internal structure of the parent body. In particular, a pre-shattered parent body containing only damaged zones but no macroscopic voids is easier to disrupt than a monolithic parent body. Other kinds of internal properties that can also characterize small bodies in real populations will be investigated in a future work.

Identification of a Common R-Chondrite Impactor on the Ureilite Parent Body

NASA Technical Reports Server (NTRS)

Downes, H.; Mittlefehldt, D. W.

2006-01-01

Polymict ureilites are brecciated ultramafic meteorites that contain a variety of single mineral and lithic clasts. They represent the surface debris from a small, differentiated asteroid. We are continuing a detailed petrological study of several polymict ureilites including EET 87720, EET 83309 and FRO93008 (from Antarctica), North Haig, Nilpena (Australia), DaG 976, DaG 999, DaG 1000 and DaG 1023 (Libya). The latter four stones are probably paired. Clast sizes can be 10 mm in diameter, so a thin-section can consist of a single lithic clast.

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.

The Probable Ages of Asteroid Families

NASA Technical Reports Server (NTRS)

Harris, A. W.

1993-01-01

There has been considerable debate recently over the ages of the Hirayama families, and in particular if some of the families are very oung(u) It is a straightforward task to estimate the characteristic time of a collision between a body of a given diameter, d_o, by another body of diameter greater of equal to d_1. What is less straightforward is to estimate the critical diameter ratio, d_1/d_o, above which catastrophic disruption occurs, from which one could infer probable ages of the Hirayama families, by knowing the diameter of the parent body, d_o. One can gain some insight into the probable value of d_1/d_o, and of the likely ages of existing families, from the plot below. I have computed the characteristic time between collisions in the asteroid belt of a size ratio greater of equal to d_1/d_o, for 4 sizes of target asteroids, d_o. The solid curves to the lower right are the characteristic times for a single object...

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.

Petrology of Anomalous Mafic Achondrite Polymict Breccia Pasamonte

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Berger, E. L.; Le, L.

2017-01-01

The most common asteroidal igneous meteorites are eucrite-type basalts and gabbros - rocks composed of ferroan pigeonite and augite, calcic plagioclase, silica, ilmenite, troilite, Ca-phosphate, chromite and Fe-metal [1]. These rocks are thought to have formed on a single asteroid, widely considered to be 4 Vesta, along with howardites and diogenites [1, 2]. High precision O-isotopic analyses have shown that some eucrites have small, well-resolved O-isotopic differences from the group mean [3-5]. These Oanomalous eucrites are thought to hail from asteroidal parents that are distinct from that of eucrites [5]. Three O-anomalous eucrites are PCA 82502, PCA 91007 (paired) and Pasamonte, all of which have the same O-isotopic composition [5, 6]. Our petrologic studies have shown that PCA 82502 and PCA 91007 have well-resolved anomalies in low-Ca pyroxene Fe/Mn compared to eucrites [6]. Divalent Mn and Fe are homologous species that do not greatly fractionate during igneous processes; mafic mineral Fe/Mn can be used to fingerprint parent object sources [7]. Previous petrological studies of Pasamonte [8-10] have not yielded sufficiently precise Fe/Mn ratios to allow distinction of anomalies of the scale of those found for the PCA basalts. We have begun petrological study of Pasamonte for comparison with our results on normal and anomalous eucrites [6], and to constrain its origin.

Compositional study of asteroids in the Erigone collisional family using visible spectroscopy at the 10.4m GTC

NASA Astrophysics Data System (ADS)

Morate, David; de León, Julia; De Prá, Mário; Licandro, Javier; Cabrera-Lavers, Antonio; Campins, Humberto; Pinilla-Alonso, Noemí; Alí-Lagoa, Víctor

2015-11-01

Asteroid families are formed by the fragments produced by the disruption of a common parent body (Bendjoya & Zappalà 2002). Primitive asteroids in the solar system are believed to have undergone less thermal processing than the S-complex asteroids. Thus, study of primitive asteroid families provides information about the solar system formation period. The Erigone collisional family, together with other three families (Polana, Clarissa and Sulamitis), are believed to be the origin of the two primitive Near-Earth asteroids that are the main targets of the NASA’s OSIRIS-REx ((101955) Bennu) and JAXA’s Hayabusa 2 ((162173) 1999 JU3) missions (Campins et al. 2010; Campins et al. 2013; Lauretta et al. 2010; Tsuda et al. 2013). These spacecrafts will visit the asteroids, and a sample of their surface material will be returned to Earth. Understanding of the families that are considered potential sources will enhance the scientific return of the missions. The main goal of the work presented here is to characterize the Erigone collisional family. Asteroid (163) Erigone has been classified as a primitive object (Bus 1999; Bus & Binzel 2002), and we expect the members of this family to be consistent with the spectral type of the parent body. We have obtained visible spectra (0.5-0.9 μm) for 101 members of the Erigone family, using the OSIRIS instrument at the 10.4m Gran Telescopio Canarias. We performed a taxonomical classification of these asteroids, finding that the number of primitive objects in our sample is in agreement with the hypothesis of a common parent body. In addition, we have found a significant fraction of asteroids in our sample that present evidences of aqueous alteration. Study of aqueous alterations is important, as it can give information on the heating processes of the early Solar System, and for the associated astrobiological implications (it has been suggested that the Earth’s present water supply was brought here by asteroids, instead of comets, in opposition to previous explanations (Morbidelli et al. 2000).

Lunar and Planetary Science XXXV: Asteroids, Meteors, Comets

NASA Technical Reports Server (NTRS)

2004-01-01

The session Asteroids, Meteors, Comets includes the following topics: 1) Where Some Asteroid Parent Bodies; 2) The Collisional Evolution of the Main Belt Population; 3) On Origin of Ecliptic Families of Periodic Comets; 4) Mineralogy and Petrology of Laser Irradiated Carbonaceous Chondrite Mighei; and 5) Interaction of the Gould Belt and the Earth.

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.

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.

A Most Incredible Asteroid: The Break-Up of P/2013 R3

NASA Astrophysics Data System (ADS)

Jewitt, David; Agarwal, Jessica; Li, Jing; Weaver, Harold A.; Mutchler, Maximilian J.; Larson, Stephen M.

2017-10-01

We present a comprehensive study of the actively disintegrating asteroid P/2013 R3. Using the Hubble and Keck telescopes, we identified thirteen discrete components separating with a mean, pair-wise velocity dispersion of v = 0.33+/-0.03 m/s. Their separation times are staggered over an interval of 5 months. Combined, the components of P/2013 R3 would form a single spherical body with radius 400 m, which is our best estimate of the size of the precursor object. Dust enveloping the system has, in the first observations, a cross-section 30 sq. km but fades monotonically at a rate consistent with the action of radiation pressure sweeping. The individual components exhibit comet-like morphologies and also fade except where secondary fragmentation is accompanied by the release of additional dust. Upper limits to the radii of any embedded solid nuclei are typically 100 to 200 m (geometric albedo 0.05 assumed). The observations are consistent with rotational disruption of a weak (cohesive strength 50 to 100 Pa) parent body, 400 m in radius. Estimated radiation (YORP) spin-up times of this parent are less than 1 Myr, shorter than the collisional lifetime. If present, water ice sublimating at as little as 1 g/s could generate a torque on the parent body rivaling the YORP torque. Under conservative assumptions about the frequency of similar disruptions, the inferred asteroid debris production rate is 1000 kg/s, which is at least 4 percent of the rate needed to maintain the Zodiacal Cloud.The work has been recently published: D. Jewitt, J. Agarwal, J. Li, H. Weaver, M. Mutchler, S. Larson (2017). The Astronomical Journal, 153:223(17pp)

Anatomy of an Asteroid Breakup: The Case of P/2013 R3

NASA Astrophysics Data System (ADS)

Jewitt, David; Agarwal, Jessica; Li, Jing; Weaver, Harold; Mutchler, Max; Larson, Stephen

2017-05-01

We present an analysis of new and published data on P/2013 R3, the first asteroid detected while disintegrating. Thirteen discrete components are measured in the interval between UT 2013 October 01 and 2014 February 13. We determine a mean, pair-wise velocity dispersion among these components of Δv = 0.33 ± 0.03 m s-1 and find that their separation times are staggered over an interval of ˜5 months. Dust enveloping the system has, in the first observations, a cross-section of ˜30 km2 but fades monotonically at a rate consistent with the action of radiation pressure sweeping. The individual components exhibit comet-like morphologies and also fade except where secondary fragmentation is accompanied by the release of additional dust. We find only upper limits to the radii of any embedded solid nuclei, typically ˜100-200 m (geometric albedo 0.05 assumed). Combined, the components of P/2013 R3 would form a single spherical body with a radius of ≲ 400 m, which is our best estimate of the size of the precursor object. The observations are consistent with rotational disruption of a weak (cohesive strength of ˜50 to 100 N m-2) parent body, ˜400 m in radius. Estimated radiation (YORP) spin-up times of this parent are ≲ 1 {Myr}, shorter than the collisional lifetime. If present, water ice sublimating at as little as 10-3 kg s-1 could generate a torque on the parent body rivaling the YORP torque. Under conservative assumptions about the frequency of similar disruptions, the inferred asteroid debris production rate is ≳103 kg s-1, which is at least 4% of the rate needed to maintain the Zodiacal Cloud.

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.

Photometric geodesy of main-belt asteroids. III - Additional lightcurves

NASA Technical Reports Server (NTRS)

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

1990-01-01

A total of 107 complete or partial lightcurves are presented for 59 different asteroids over the 1982-1989 period. Unusual lightcurves with unequal minima and maxima at large amplitudes are preferentially seen for M-type asteroids. Some asteroids, such as 16 Psyche and 201 Penelope, exhibit lightcurves combining large amplitude with very unequal brightness for both maxima and both minima, even at small phase angles. An M-type asteroid is believed to consist of a metal core of a differentiated parent body that has had its rocky mantle completely removed by one or more large impacts.

The nature of C-class asteroids from 3-micron spectrophotometry

NASA Technical Reports Server (NTRS)

Feierberg, M. A.; Lebofsky, L. A.; Tholen, D. J.

1985-01-01

Narrowband spectrophotometry between 2.3 and 3.5 micrometers is presented for 14 main-belt C asteroids greater than 100 km in diameter. Absorption features at 3 micrometers due to water of hydration are present in the spectra of nine of the asteroids, with intensities ranging from 6 to 23 percent. The other five asteroids have no such absorption greater than 2 percent in intensity. The present C-asteroid population may be fragments of larger parent bodies with anhydrous C3-like cores and hydrated C1I- or C2M-like mantles.

Photometric geodesy of main-belt asteroids. III. Additional lightcurves

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

Weidenschilling, S.J.; Chapman, C.R.; Davis, D.R.

1990-08-01

A total of 107 complete or partial lightcurves are presented for 59 different asteroids over the 1982-1989 period. Unusual lightcurves with unequal minima and maxima at large amplitudes are preferentially seen for M-type asteroids. Some asteroids, such as 16 Psyche and 201 Penelope, exhibit lightcurves combining large amplitude with very unequal brightness for both maxima and both minima, even at small phase angles. An M-type asteroid is believed to consist of a metal core of a differentiated parent body that has had its rocky mantle completely removed by one or more large impacts. 39 refs.

Original structures, and fragmentation and reassembly histories of asteroids - Evidence from meteorites

NASA Technical Reports Server (NTRS)

Taylor, G. Jeffrey; Maggiore, Peter; Scott, Edward R. D.; Rubin, Alan E.; Keil, Klaus

1987-01-01

The validity of an onion shell model (OSM) for chondrite parent asteroids was assessed using metallographic cooling rates (MCR) derived from the compositions of metallic Fe-Ni grains. The hypothesis evaluated was that the hottest materials in chondrites would have been buried the deepest and cooled the slowest. The survey covered breccia from regolith and 13 different chondrites. The MCRs agreed well with cooling rates predicted by fission-track thermometry and Ar-40/Ar-39 ages. The OSM predicts an inverse correlation between the cooling rate and the petrographic type. Low correlations found between the MCRs and petrographic type indicate that chondrite parent asteroids were not assembled with onion shell structures.

Photometric constraints on binary asteroid dynamics

NASA Astrophysics Data System (ADS)

Scheirich, Peter

2015-08-01

To date, about 50 binary NEAs, 20 Mars-crossing and 80 small MB asteroids are known. We observe also a population of about 200 unbound asteroid systems (asteroid pairs). I will review the photometric observational data we have for the best observed cases and compare them with theories of binary and paired asteroids evolution.The observed characteristics of asteroid systems suggest their formation by rotational fission of parent rubble-pile asteroids after being spun up by the YORP effect. The angular momentum content of binary asteroids is close to critical. The orientations of satellite orbits of observed binary systems are non-random; the orbital poles concentrate near the obliquities of 0 and 180 degrees, i.e., near the YORP asymptotic states.Recently, a significant excess of retrograde satellite orbits was detected, which is not yet explained characteristic.An evolution of binary system depend heavily on the BYORP effect. If BYORP is contractive, the primary and secondary could end in a tidal-BYORP equilibrium. Observations of mutual events between binary components in at least four apparitions are needed for BYORP to be revealed by detecting a quadratic drift in mean anomaly of the satellite. I will show the observational evidence of single-synchronous binary asteroid with tidally locked satellite (175706 1996 FG3), i.e, with the quadratic drift equal to zero, and binary asteroid with contracting orbit (88710 2001 SL9), with positive value of the quadratic drift (the solution for the quadratic drift is ambiguous so far, with possible values of 5 and 8 deg/yr2).The spin configuration of the satellite play a crucial role in the evolution of the system under the influence of the BYORP effect. I will show that the rotational lightcurves of the satellites show that most of them have small libration amplitudes (up to 20 deg.), with a few interesting exceptions.Acknowledgements: This work has been supported by the Grant Agency of the Czech Republic, Grant P209/12/0229, and by the Ministry of Education of the Czech Republic, Grant LG12001.

Compositional Homogeneity of CM Parent Bodies

NASA Astrophysics Data System (ADS)

Vernazza, P.; Marsset, M.; Beck, P.; Binzel, R. P.; Birlan, M.; Cloutis, E. A.; DeMeo, F. E.; Dumas, C.; Hiroi, T.

2016-09-01

CM chondrites are the most common type of hydrated meteorites, making up ˜1.5% of all falls. Whereas most CM chondrites experienced only low-temperature (˜0°C-120°C) aqueous alteration, the existence of a small fraction of CM chondrites that suffered both hydration and heating complicates our understanding of the early thermal evolution of the CM parent body(ies). Here, we provide new constraints on the collisional and thermal history of CM-like bodies from a comparison between newly acquired spectral measurements of main-belt Ch/Cgh-type asteroids (70 objects) and existing laboratory spectral measurements of CM chondrites. It first appears that the spectral variation observed among CM-like bodies is essentially due to variations in the average regolith grain size. Second, the spectral properties of the vast majority (unheated) of CM chondrites resemble both the surfaces and the interiors of CM-like bodies, implying a “low” temperature (<300°C) thermal evolution of the CM parent body(ies). It follows that an impact origin is the likely explanation for the existence of heated CM chondrites. Finally, similarly to S-type asteroids and (2) Pallas, the surfaces of large (D > 100 km)—supposedly primordial—Ch/Cgh-type main-belt asteroids likely expose the interiors of the primordial CM parent bodies, a possible consequence of impacts by small asteroids (D < 10 km) in the early solar system.

Young asteroid mixing revealed in ordinary chondrites: The case of NWA 5764, a polymict LL breccia with L clasts

NASA Astrophysics Data System (ADS)

Gattacceca, Jérome; Krzesińska, Agata M.; Marrocchi, Yves; Meier, Matthias M. M.; Bourot-Denise, Michèle; Lenssen, Rob

2017-11-01

Polymict chondritic breccias—rocks composed of fragments originating from different chondritic parent bodies—are of particular interest because they give insights into the mixing of asteroids in the main asteroid belt (occurrence, encounter velocity, transfer time). We describe Northwest Africa (NWA) 5764, a brecciated LL6 chondrite that contains a >16 cm3 L4 clast. The L clast was incorporated in the breccia through a nondestructive, low-velocity impact. Identical cosmic-ray exposure ages of the L clast and the LL host (36.6 ± 5.8 Myr), suggest a short transfer time of the L meteoroid to the LL parent body of 0.1 ± 8.1 Myr, if that meteoroid was no larger than a few meters. NWA 5764 (together with St. Mesmin, Dimmitt, and Glanerbrug) shows that effective mixing is possible between ordinary chondrite parent bodies. In NWA 5764 this mixing occurred after the peak of thermal metamorphism on the LL parent body, i.e., at least several tens of Myr after the formation of the solar system. The U,Th-He ages of the L clast and LL host, identical at about 2.9 Ga, might date the final assembly of the breccia, indicating relatively young mixing in the main asteroid belt as previously evidenced in St. Mesmin.

Water Transport and the Evolution of CM Parent Bodies

NASA Technical Reports Server (NTRS)

Coker, R.; Cohen, B.

2014-01-01

Extraterrestrial water-bearing minerals are of great importance both for understanding the formation and evolution of the solar system and for supporting future human activities in space. Asteroids are the primary source of meteorites, many of which show evidence of an early heating episode and varying degrees of aqueous alteration. The origin and characterization of hydrated minerals (minerals containing H2O or OH) among both the main-belt and near-earth asteroids is important for understanding a wide range of solar system formation and evolutionary processes, as well as for planning for human exploration. Current hypotheses postulate asteroids began as mixtures of water ice and anhydrous silicates. A heating event early in solar system history was then responsible for melting the ice and driving aqueous alteration. The link between asteroids and meteorites is forged by reflectance spectra, which show 3-µm bands indicative of bound OH or H2O on the C-class asteroids, which are believed to be the parent bodies of the carbonaceous chondrites in our collections. The conditions at which aqueous alteration occurred in the parent bodies of carbonaceous chondrites are thought to be well-constrained: at 0-25 C for less than 15 Myr after asteroid formation. In previous models, many scenarios exhibit peak temperatures of the rock and co-existing liquid water in more than 75 percent of the asteroid's volume rising to 150 C and higher, due to the exothermic hydration reactions triggering a thermal runaway effect. However, even in a high porosity, water-saturated asteroid very limited liquid water flow is predicted (distances of 100's nm at most). This contradiction has yet to be resolved. Still, it may be possible for water to become liquid even in the near-surface environment, for a long enough time to drive aqueous alteration before vaporizing or freezing then subliming. Thus, we are using physics- and chemistry-based models that include thermal and fluid transport as well as the effects of relevant chemical reactions, to investigate whether formation of hydrated minerals can occur in the surface and near-surface environments of carbonaceous type asteroids. These models will elucidate how the conditions within the parent body that cause internal aqueous alteration play themselves out at the asteroid's surface. We are using our models to determine whether the heat budget of 20-100-km bodies is sufficient to bring liquid water to the near-surface and cause mineral alteration, or whether additional heat input at the surface (i.e, by impacts) is needed to provide a transient liquid water source for mineral hydration without large- scale liquid water transport.

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.

Ibitira: A basaltic achondrite from a distinct parent asteroid

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.

2004-01-01

I have done detailed petrologic study of Ibitira, nominally classified as a basaltic eucrite. The Fe/Mn ratio of Ibitira pyroxenes with <10 mole % wollastonite component is 36.4 0.4, and is well-resolved from those of five basaltic eucrites studied for comparison; 31.2-32.2. Data for the latter completely overlap. Ibitira pyroxenes have lower Fe/Mg than the basaltic eucrite pyroxenes. Thus, the higher Fe/Mn ratio does not reflect a simple difference in oxidation state. Ibitira also has an oxygen isotopic composition, alkali element contents and a Ti/Hf ratio that distinguish it from basaltic eucrites. These differences support derivation from a distinct parent asteroid. Ibitira is the first recognized representative of the fifth known asteroidal basaltic crust.

Workshop on Oxygen in Asteroids and Meteorites

NASA Technical Reports Server (NTRS)

2005-01-01

Contents include the following: Constraints on the detection of solar nebula's oxidation state through asteroid observation. Oxidation/Reduction Processes in Primitive Achondrites. Low-Temperature Chemical Processing on Asteroids. On the Formation Location of Asteroids and Meteorites. The Spectral Properties of Angritic Basalts. Correlation Between Chemical and Oxygen Isotopic Compositions in Chondrites. Effect of In-Situ Aqueous Alteration on Thermal Model Heat Budgets. Oxidation-Reduction in Meteorites: The Case of High-Ni Irons. Ureilite Atmospherics: Coming up for Air on a Parent Body. High Temperature Effects Including Oxygen Fugacity, in Pre-Planetary and Planetary Meteorites and Asteroids. Oxygen Isotopic Variation of Asteroidal Materials. High-Temperature Chemical Processing on Asteroids: An Oxygen Isotope Perspective. Oxygen Isotopes and Origin of Opaque Assemblages from the Ningqiang Carbonaceous Chondrite. Water Distribution in the Asteroid Belt. Comparative Planetary Mineralogy: V Systematics in Planetary Pyroxenes and fo 2 Estimates for Basalts from Vesta.

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.

Lunar and Planetary Science XXXV: Concerning Chondrites

NASA Technical Reports Server (NTRS)

2004-01-01

The Lunar and Planetary Science XXXV session entitled "Concerning Chondrites" includes the following topics: 1) Petrology and Raman Spectroscopy of Shocked Phases in the Gujba CB Chondrite and the Shock History of the CB Parent Body; 2) The Relationship Between CK and CV Chondrites: A Single Parent Body Source? 3) Samples of Asteroid Surface Ponded Deposits in Chondritic Meteorites; 4) Composition and Origin of SiO2-rich Objects in Carbonaceous and Ordinary Chondrites; 5) Re-Os Systematics and HSE distribution in Tieschitz (H3.6); Two Isochrons for One Meteorite; 6) Loss of Chromium from Olivine During the Metamorphism of Chondrites; 7) Very Short Delivery Times of Meteorites After the L-Chondrite Parent Body Break-Up 480 Myr Ago; and 8) The Complex Exposure History of a Very Large L/LL5 Chondrite Shower: Queen Alexandra Range 90201.

Hungaria Asteroid Region Telescopic Spectral Survey (HARTSS) II: Spectral Homogeneity Among Hungaria Family Asteroids

NASA Astrophysics Data System (ADS)

Lucas, Michael P.; Emery, Joshua; Pinilla-Alonso, Noemi; Lindsay, Sean S.; MacLennan, Eric M.; Cartwright, Richard; Reddy, Vishnu; Sanchez, Juan A.; Thomas, Cristina A.; Lorenzi, Vania

2017-10-01

Spectral observations of asteroid family members provide valuable information regarding parent body interiors, the source regions of near-Earth asteroids, and the link between meteorites and their parent bodies. Hungaria family asteroids constitute the closest samples to the Earth from a collisional family (~1.94 AU), permitting observations of smaller fragments than accessible for Main Belt families. We have carried out a ground-based observational campaign - Hungaria Asteroid Region Telescopic Spectral Survey (HARTSS) - to record reflectance spectra of these preserved samples from the inner-most primordial asteroid belt. During HARTSS phase one (Lucas et al. [2017]. Icarus 291, 268-287) we found that ~80% of the background population is comprised of stony S-complex asteroids that exhibit considerable spectral and mineralogical diversity. In HARTSS phase two, we turn our attention to family members and hypothesize that the Hungaria collisional family is homogeneous. We test this hypothesis through taxonomic classification, albedo estimates, and spectral properties.During phase two of HARTSS we acquired near-infrared (NIR) spectra of 50 new Hungarias (19 family; 31 background) with SpeX/IRTF and NICS/TNG. We analyzed X-type family spectra for NIR color indices (0.85-J J-K), and a subtle ~0.9 µm absorption feature that may be attributed to Fe-poor orthopyroxene. Surviving fragments of an asteroid collisional family typically exhibit similar taxonomies, albedos, and spectral properties. Spectral analysis of X-type Hungaria family members and independently calculated WISE albedo determinations for 428 Hungaria asteroids is consistent with this scenario. Furthermore, ~1/4 of the background population exhibit similar spectral properties and albedos to family X-types.Spectral observations of 92 Hungaria region asteroids acquired during both phases of HARTSS uncover a compositionally heterogeneous background and spectral homogeneity down to ~2 km for collisional family members. Taxonomy, albedos, and spectral properties reveal that the Hungaria family progenitor was an igneous body that formed under reduced conditions, and was compositionally consistent with the enstatite achondrite (i.e., aubrite) meteorite group.

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.

CM and CO chondrites: A common parent body or asteroidal neighbors? Insights from chondrule silicates

NASA Astrophysics Data System (ADS)

Schrader, Devin L.; Davidson, Jemma

2017-10-01

By investigating the petrology and chemical composition of type II (FeO-rich) chondrules in the Mighei-like carbonaceous (CM) chondrites we constrain their thermal histories and relationship to the Ornans-like carbonaceous (CO) chondrites. We identified FeO-rich relict grains in type II chondrules by their Fe/Mn ratios; their presence indicates chondrule recycling among type II chondrules. The majority of relict grains in type II chondrules are FeO-poor olivine grains. Consistent with previous studies, chemical similarities between CM and CO chondrite chondrules indicate that they had similar formation conditions and that their parent bodies probably formed in a common region within the protoplanetary disk. However, important differences such as mean chondrule size and the lower abundance of FeO-poor relicts in CM chondrite type II chondrules than in CO chondrites suggest CM and CO chondrules did not form together and they likely originate from distinct parent asteroids. Despite being aqueously altered, many CM chondrites contain pre-accretionary anhydrous minerals (i.e., olivine) that are among the least thermally metamorphosed materials in chondrites according to the Cr2O3 content of their ferroan olivine. The presence of these minimally altered pre-accretionary chondrule silicates suggests that samples to be returned from aqueously altered asteroids by the Hayabusa2 and OSIRIS-REx asteroid sample return missions, even highly hydrated, may contain silicates that can provide information about the pre-accretionary histories and conditions of asteroids Ryugu and Bennu, respectively.

Shock fabrics in fine-grained micrometeorites

NASA Astrophysics Data System (ADS)

Suttle, M. D.; Genge, M. J.; Russell, S. S.

2017-10-01

The orientations of dehydration cracks and fracture networks in fine-grained, unmelted micrometeorites were analyzed using rose diagrams and entropy calculations. As cracks exploit pre-existing anisotropies, analysis of their orientation provides a mechanism with which to study the subtle petrofabrics preserved within fine-grained and amorphous materials. Both uniaxial and biaxial fabrics are discovered, often with a relatively wide spread in orientations (40°-60°). Brittle deformation cataclasis and rotated olivine grains are reported from a single micrometeorite. This paper provides the first evidence for impact-induced shock deformation in fine-grained micrometeorites. The presence of pervasive, low-grade shock features in CM chondrites and CM-like dust, anomalously low-density measurements for C-type asteroids, and impact experiments which suggest CM chondrites are highly prone to disruption all imply that CM parent bodies are unlikely to have remained intact and instead exist as a collection of loosely aggregated rubble-pile asteroids, composed of primitive shocked clasts.

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.

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.

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.

Epsilon Eridani Inner Asteroid Belt

NASA Image and Video Library

2017-09-14

SCI2017_0004: Artist's illustration of the Epsilon Eridani system showing Epsilon Eridani b, right foreground, a Jupiter-mass planet orbiting its parent star at the outside edge of an asteroid belt. In the background can be seen another narrow asteroid or comet belt plus an outermost belt similar in size to our solar system's Kuiper Belt. The similarity of the structure of the Epsilon Eridani system to our solar system is remarkable, although Epsilon Eridani is much younger than our sun. SOFIA observations confirmed the existence of the asteroid belt adjacent to the orbit of the Jovian planet. Credit: NASA/SOFIA/Lynette Cook

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.

CM chondrites exhibit the complete petrologic range from type 2 to 1. [Abstract only

NASA Technical Reports Server (NTRS)

Zolensky, M. E.; Browning, L. B.

1994-01-01

Recognition and characterization of the different CM lithologies as components in all meteorites could reveal details of the nature and chronology of alteration and brecciation events on hydrous asteroids. The CM chondrites are of particular interest, as they are the most common carbonaceous chondrites and are found as clasts within other types of meteorites, which suggests that the CM parent asteroids are (or were) widespread in the sections of the asteroid belt providing samples to Earth. Some CM2s, including EET 90047, ALH 83100, and Y 82042, are more 'extensively' altered, and are distinguished by a high proportion of Mg-rich phyllosilicates and Ca-Mg carbonates, frequently in rounded aggregates, and near absence of olivine or pyroxene. 'Completely' altered CMs, called CM1s, essentially lack olivine or pyroxene; these include EET 83334, ALH 88045, and the CM1 clasts in Kaidun. Cold Bokkeveld and EET 84034, both highly brecciated CMs, consist of both extensively and completely altered lithologies. We describe how these lithologies further cosntrain physicochemical conditions on hydrous asteroids. We conclude that CM chondrites exhibit the petrologic range 2 through 1, and that progressive alteration on the parent hydrous asteroid(s) was accompanied by significant increases in temperature (to a peak of approximately 450 C), fO2, water-rock ratio, and (locally) degree of chemical leaching, all well beyond the conditions recorded by CM2s.

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.

Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey.

PubMed

Marchis, F; Kaasalainen, M; Hom, E F Y; Berthier, J; Enriquez, J; Hestroffer, D; Le Mignant, D; de Pater, I

2006-11-01

This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (∼5% of the primary size) suggesting that they are fragments captured after a disruptive collision of a parent body or captured ejecta due to an impact. For each asteroid, we have estimated the minimum size of a moonlet that can positively detected within the Hill sphere of the system by estimating and modeling a 2-σ detection profile: in average on the data set, a moonlet located at 2/100 × R(Hill) (1/4 × R(Hill)) with a diameter larger than 6 km (4 km) would have been unambiguously seen. The apparent size and shape of each asteroid was estimated after deconvolution using a new algorithm called AIDA. The mean diameter for the majority of asteroids is in good agreement with IRAS radiometric measurements, though for asteroids with a D < 200 km, it is underestimated on average by 6-8%. Most asteroids had a size ratio that was very close to those determined by lightcurve measurements. One observation of 104 Klymene suggests it has a bifurcated shape. The bi-lobed shape of 121 Hermione described in Marchis et al. [Marchis, F., Hestroffer, D., Descamps, P., Berthier, J., Laver, C., de Pater, I., 2005c. Icarus 178, 450-464] was confirmed after deconvolution. The ratio of contact binaries in our survey, which is limited to asteroids larger than 40 km, is surprisingly high (∼6%), suggesting that a non-single configuration is common in the main-belt. Several asteroids have been analyzed with lightcurve inversions. We compared lightcurve inversion models for plane-of-sky predictions with the observed images (9 Metis, 52 Europa, 87 Sylvia, 130 Elektra, 192 Nausikaa, and 423 Diotima, 511 Davida). The AO images allowed us to determine a unique photometric mirror pole solution, which is normally ambiguous for asteroids moving close to the plane of the ecliptic (e.g., 192 Nausikaa and 52 Europa). The photometric inversion models agree well with the AO images, thus confirming the validity of both the lightcurve inversion method and the AO image reduction technique.

ASTEROID SIZING BY RADIOGALAXY OCCULTATION AT 5 GHZ

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

Lehtinen, K.; Muinonen, K.; Poutanen, M.

Stellar occultations by asteroids observed at visual wavelengths have been an important tool for studying the size and shape of asteroids and for revising the orbital parameters of asteroids. At radio frequencies, a shadow of an asteroid on the Earth is dominated by diffraction effects. Here, we show, for the first time, that a single observation of an occultation of a compact radio source at a frequency of 5 GHz can be used to derive the effective size of the occulting object and to derive the distance between the observer and the center of the occultation path on the Earth.more » The derived diameter of the occulting object, asteroid (115) Thyra, is 75 ± 6 km. The observed occultation profile shows features that cannot be explained by diffraction of a single asteroid.« less

Discovery of a basaltic asteroid in the outer main belt

PubMed

Lazzaro; Michtchenko; Carvano; Binzel; Bus; Burbine; Mothe-Diniz; Florczak; Angeli; Harris

2000-06-16

Visible and near-infrared spectroscopic observations of the asteroid 1459 Magnya indicate that it has a basaltic surface. Magnya is at 3. 15 astronomical units (AU) from the sun and has no known dynamical link to any family, to any nearby large asteroid, or to asteroid 4 Vesta at 2.36 AU, which is the only other known large basaltic asteroid. We show that the region of the belt around Magnya is densely filled by mean-motion resonances, generating slow orbital diffusion processes and providing a potential mechanism for removing other basaltic fragments that may have been created on the same parent body as Magnya. Magnya may represent a rare surviving fragment from a larger, differentiated planetesimal that was disrupted long ago.

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.

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

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

Do Mesosiderites Reside on 4 VESTA? an Assessment Based on Dawn Grand Data

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Prettyman, T. H.; Reedy, R. C.; Beck, A. W.; Blewett, D. T.; Gaffey, M. J.; Lawrence, D. J.; McCoy, T. J.; McSween, H. Y., Jr.; Toplis, J. J.

2012-01-01

Almost a century ago, simple petrographic observations were used to suggest a close genetic link between eucrites and the silicates in mesosiderites [1]. Mesosiderites are composed of roughly equal proportions of silicates that are very similar in mineralogy and texture to howardites, and Fe, Ni metal (Fig. 1) [2]. This similarity has led some to conclude that mesosiderites come from the howardite, eucrite and diogenite (HED) parent asteroid [3, 4]. Subsequent petrologic study demonstrated a number of differences between mesosiderite silicates and HEDs that are more plausibly explained as requiring separate parent asteroids [5]. However, HEDs and mesosiderites are identical in oxygen isotopic composition, and this has been used to argue for a common parent 4 Vesta [6].

The relationship between CK and CV chondrites

NASA Astrophysics Data System (ADS)

Greenwood, R. C.; Franchi, I. A.; Kearsley, A. T.; Alard, O.

2010-03-01

CK chondrites are highly oxidized meteorites containing abundant magnetite and trace amounts of Fe,Ni metal. Although the group is predominately composed of equilibrated meteorites (types 4-6), in recent years a significant number of new samples have been classified as being either CK3 or CK3-anomalous. These unequilibrated CKs often display a close affinity with members of the CV oxidized subgroup. CKs and CVs (oxidized subgroup) may therefore form a continuum and by implication could be derived from a single common parent body. To investigate the relationship between these two groups a detailed study of the oxygen isotope composition, opaque mineralogy and major and trace element geochemistry of a suite of CV and CK chondrites has been undertaken. The results of oxygen isotope analysis confirm the close affinity between CV and CK chondrites, while excluding the possibility of a linkage between the CO and CK groups. Magnetites in both CV and CK chondrites show significant compositional similarities, but high Ti contents are a diagnostic feature of the latter group. The results of major and trace element analysis demonstrate that both CV and CK chondrites show overlapping variation. Supporting evidence for a single common source for both groups comes from their similar cosmic-ray exposure age distributions. Recent reflectance spectral analysis is consistent with both the CVs and CKs being derived from Eos family asteroids, which are believed to have formed by the catastrophic disruption of a single large asteroid. Thus, a range of evidence appears to be consistent with CV and CK chondrites representing samples from a single thermally stratified parent body. In view of the close similarity between CV and CK chondrites some modification of the present classification scheme may be warranted, possibly involving integration of the two groups. One means of achieving this would be to reassigned CK chondrites to a subgroup of the oxidized CVs. It is recognized that a full evaluation of this proposal may require further study of the still poorly understood CK3 chondrites.

Dynamical Evolution of Asteroids and Meteoroids Using the Yarkovsky Effect

NASA Technical Reports Server (NTRS)

Bottke, William F., Jr.; Vokrouhlicky, David; Rubincam, David P.; Broz, Miroslav; Smith, David E. (Technical Monitor)

2001-01-01

The Yarkovsky effect is a thermal radiation force which causes objects to undergo semimajor axis drift and spin up/down as a function of their spin, orbit, and material properties. This mechanism can be used to (i) deliver asteroids (and meteoroids) with diameter D < 20 km from their parent bodies in the main belt to chaotic resonance zones capable of transporting this material to Earth-crossing orbits, (ii) disperse asteroid families, with drifting bodies jumping or becoming trapped in mean-motion and secular resonances within the main belt, and (iii) modify the rotation rates of asteroids a few km in diameter or smaller enough to explain the excessive number of very fast and very slow rotators among the small asteroids. Accordingly, we suggest that nongravitational forces, which produce small but meaningful effects on asteroid orbits and rotation rates over long timescales, should now be considered as important as collisions and gravitational perturbations to our overall understanding of asteroid evolution.

Modeling close encounters with massive asteroids: a Markovian approach. An application to the Vesta family

NASA Astrophysics Data System (ADS)

Carruba, V.; Roig, F.; Michtchenko, T. A.; Ferraz-Mello, S.; Nesvorný, D.

2007-04-01

Context: Nearly all members of the Vesta family cross the orbits of (4) Vesta, one of the most massive asteroids in the main belt, and some of them approach it closely. When mutual velocities during such close encounters are low, the trajectory of the small body can be gravitationally deflected, consequently changing its heliocentric orbital elements. While the effect of a single close encounter may be small, repeated close encounters may significantly change the proper element distribution of members of asteroid families. Aims: We develop a model of the long-term effect of close encounters with massive asteroids, so as to be able to predict how far former members of the Vesta family could have drifted away from the family. Methods: We first developed a new symplectic integrator that simulates both the effects of close encounters and the Yarkovsky effect. We analyzed the results of a simulation involving a fictitious Vesta family, and propagated the asteroid proper element distribution using the probability density function (pdf hereafter), i.e. the function that describes the probability of having an encounter that modifies a proper element x by Δx, for all the possible values of Δx. Given any asteroids' proper element distribution at time t, the distribution at time t+T may be predicted if the pdf is known (Bachelier 1900, Théorie de la spéculation; Hughes 1995, Random Walks and Random Environments, Vol. I). Results: We applied our new method to the problem of V-type asteroids outside the Vesta family (i.e., the 31 currently known asteroids in the inner asteroid belt that have the same spectral type of members as the Vesta family, but that are outside the limits of the dynamical family) and determined that at least ten objects have a significant diffusion probability over the minimum estimated age of the Vesta family of 1.2 Gyr (Carruba et al. 2005, A&A, 441, 819). These objects can therefore be explained in the framework of diffusion via repeated close encounters with (4) Vesta of asteroids originally closer to the parent body. Conclusions: We computed diffusion probabilities at the location of four of these asteroids for various initial conditions, parametrized by values of initial ejection velocity V_ej. Based on our results, we believe the Vesta family age is (1200 ± 700) Myr old, with an initial ejection velocity of (240 ± 60) m/s. Appendices are only available in electronic form at http://www.aanda.org

Chondritic Meteorites: Nebular and Parent-Body Formation Processes

NASA Technical Reports Server (NTRS)

Rubin, Alan E.; Lindstrom, David (Technical Monitor)

2002-01-01

It is important to identify features in chondrites that formed as a result of parent-body modification in order to disentangle nebular and asteroidal processes. However, this task is difficult because unmetamorphosed chondritic meteorites are mixtures of diverse components including various types of chondrules, chondrule fragments, refractory and mafic inclusions, metal-sulfide grains and fine-grained matrix material. Shocked chondrites can contain melt pockets, silicate-darkened material, metal veins, silicate melt veins, and impact-melt-rock clasts. This grant paid for several studies that went far in helping to distinguish primitive nebular features from those produced during asteroidal modification processes.

Asteroid family dynamics in the inner main belt

NASA Astrophysics Data System (ADS)

Dykhuis, Melissa Joy

The inner main asteroid belt is an important source of near-Earth objects and terrestrial planet impactors; however, the dynamics and history of this region are challenging to understand, due to its high population density and the presence of multiple orbital resonances. This dissertation explores the properties of two of the most populous inner main belt family groups --- the Flora family and the Nysa-Polana complex --- investigating their memberships, ages, spin properties, collision dynamics, and range in orbital and reflectance parameters. Though diffuse, the family associated with asteroid (8) Flora dominates the inner main belt in terms of the extent of its members in orbital parameter space, resulting in its significant overlap with multiple neighboring families. This dissertation introduces a new method for membership determination (the core sample method) which enables the distinction of the Flora family from the background, permitting its further analysis. The Flora family is shown to have a signature in plots of semimajor axis vs. size consistent with that expected for a collisional family dispersed as a result of the Yarkovsky radiation effect. The family's age is determined from the Yarkovsky dispersion to be 950 My. Furthermore, a survey of the spin sense of 21 Flora-region asteroids, accomplished via a time-efficient modification of the epoch method for spin sense determination, confirms the single-collision Yarkovsky-dispersed model for the family's origin. The neighboring Nysa-Polana complex is the likely source region for many of the carbonaceous near-Earth asteroids, several of which are important targets for spacecraft reconnaissance and sample return missions. Family identification in the Nysa-Polana complex via the core sample method reveals two families associated with asteroid (135) Hertha, both with distinct age and reflectance properties. The larger of these two families demonstrates a correlation in semimajor axis and eccentricity indicating that its family-forming collision occurred near the parent body's aphelion. In addition, the Eulalia family is connected with a possible second component, suggesting an anisotropic distribution of ejecta from its collision event.

Space Weathering of Ordinary Chondrite Parent Bodies, Its Impact on the Method of Distinguishing H, L, and LL Types and Implications for Itokawa Samples Returned by the Hayabusa Mission

NASA Technical Reports Server (NTRS)

Hiroi, T.; Sasaki, S.; Noble, S. K.; Pieters, C. M.

2011-01-01

As the most abundance meteorites in our collections, ordinary chondrites potentially have very important implications on the origin and formation of our Solar System. In order to map the distribution of ordinary chondrite-like asteroids through remote sensing, the space weathering effects of ordinary chondrite parent bodies must be addressed through experiments and modeling. Of particular importance is the impact on distinguishing different types (H/L/LL) of ordinary chondrites. In addition, samples of asteroid Itokawa returned by the Hayabusa spacecraft may re veal the mechanism of space weathering on an LLchondrite parent body. Results of space weathering simulations on ordinary chondrites and implications for Itokawa samples are presented here.

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.

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.

Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey

PubMed Central

Marchis, F.; Kaasalainen, M.; Hom, E.F.Y.; Berthier, J.; Enriquez, J.; Hestroffer, D.; Le Mignant, D.; de Pater, I.

2008-01-01

This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (∼5% of the primary size) suggesting that they are fragments captured after a disruptive collision of a parent body or captured ejecta due to an impact. For each asteroid, we have estimated the minimum size of a moonlet that can positively detected within the Hill sphere of the system by estimating and modeling a 2-σ detection profile: in average on the data set, a moonlet located at 2/100 × RHill (1/4 × RHill) with a diameter larger than 6 km (4 km) would have been unambiguously seen. The apparent size and shape of each asteroid was estimated after deconvolution using a new algorithm called AIDA. The mean diameter for the majority of asteroids is in good agreement with IRAS radiometric measurements, though for asteroids with a D < 200 km, it is underestimated on average by 6–8%. Most asteroids had a size ratio that was very close to those determined by lightcurve measurements. One observation of 104 Klymene suggests it has a bifurcated shape. The bi-lobed shape of 121 Hermione described in Marchis et al. [Marchis, F., Hestroffer, D., Descamps, P., Berthier, J., Laver, C., de Pater, I., 2005c. Icarus 178, 450–464] was confirmed after deconvolution. The ratio of contact binaries in our survey, which is limited to asteroids larger than 40 km, is surprisingly high (∼6%), suggesting that a non-single configuration is common in the main-belt. Several asteroids have been analyzed with lightcurve inversions. We compared lightcurve inversion models for plane-of-sky predictions with the observed images (9 Metis, 52 Europa, 87 Sylvia, 130 Elektra, 192 Nausikaa, and 423 Diotima, 511 Davida). The AO images allowed us to determine a unique photometric mirror pole solution, which is normally ambiguous for asteroids moving close to the plane of the ecliptic (e.g., 192 Nausikaa and 52 Europa). The photometric inversion models agree well with the AO images, thus confirming the validity of both the lightcurve inversion method and the AO image reduction technique. PMID:19081813

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.

Secular Resonance Sweeping of the Main Asteroid Belt During Planet Migration

NASA Astrophysics Data System (ADS)

Minton, David A.; Malhotra, Renu

2011-05-01

We calculate the eccentricity excitation of asteroids produced by the sweeping ν6 secular resonance during the epoch of planetesimal-driven giant planet migration in the early history of the solar system. We derive analytical expressions for the magnitude of the eccentricity change and its dependence on the sweep rate and on planetary parameters; the ν6 sweeping leads to either an increase or a decrease of eccentricity depending on an asteroid's initial orbit. Based on the slowest rate of ν6 sweeping that allows a remnant asteroid belt to survive, we derive a lower limit on Saturn's migration speed of ~0.15 AU Myr-1 during the era that the ν6 resonance swept through the inner asteroid belt (semimajor axis range 2.1-2.8 AU). This rate limit is for Saturn's current eccentricity and scales with the square of its eccentricity; the limit on Saturn's migration rate could be lower if its eccentricity were lower during its migration. Applied to an ensemble of fictitious asteroids, our calculations show that a prior single-peaked distribution of asteroid eccentricities would be transformed into a double-peaked distribution due to the sweeping of the ν6 resonance. Examination of the orbital data of main belt asteroids reveals that the proper eccentricities of the known bright (H <= 10.8) asteroids may be consistent with a double-peaked distribution. If so, our theoretical analysis then yields two possible solutions for the migration rate of Saturn and for the dynamical states of the pre-migration asteroid belt: a dynamically cold state (single-peaked eccentricity distribution with mean of ~0.05) linked with Saturn's migration speed ~4 AU Myr-1 or a dynamically hot state (single-peaked eccentricity distribution with mean of ~0.3) linked with Saturn's migration speed ~0.8 AU Myr-1.

The Asteroid Veritas: An intruder in a family named after it?

NASA Astrophysics Data System (ADS)

Michel, Patrick; Jutzi, Martin; Richardson, Derek C.; Benz, Willy

2011-01-01

The Veritas family is located in the outer main belt and is named after its apparent largest constituent, Asteroid (490) Veritas. The family age has been estimated by two independent studies to be quite young, around 8 Myr. Therefore, current properties of the family may retain signatures of the catastrophic disruption event that formed the family. In this paper, we report on our investigation of the formation of the Veritas family via numerical simulations of catastrophic disruption of a 140-km-diameter parent body, which was considered to be made of either porous or non-porous material, and a projectile impacting at 3 or 5 km/s with an impact angle of 0° or 45°. Not one of these simulations was able to produce satisfactorily the estimated size distribution of real family members. Based on previous studies devoted to either the dynamics or the spectral properties of the Veritas family, which already treated (490) Veritas as a special object that may be disconnected from the family, we simulated the formation of a family consisting of all members except that asteroid. For that case, the parent body was smaller (112 km in diameter), and we found a remarkable match between the simulation outcome, using a porous parent body, and the real family. Both the size distribution and the velocity dispersion of the real reduced family are very well reproduced. On the other hand, the disruption of a non-porous parent body does not reproduce the observed properties very well. This is consistent with the spectral C-type of family members, which suggests that the parent body was porous and shows the importance of modeling the effect of this porosity in the fragmentation process, even if the largest members are produced by gravitational reaccumulation during the subsequent gravitational phase. As a result of our investigations, we conclude that it is very likely that the Asteroid (490) Veritas and probably several other small members do not belong to the family as originally defined, and that the definition of this family should be revised. Further investigations will be performed to better constrain the definitions and properties of other asteroid families of different types, using the appropriate model of fragmentation. The identification of very young families in turn will continue to serve as a tool to check the validity of numerical models.

An age-colour relationship for main-belt S-complex asteroids.

PubMed

Jedicke, Robert; Nesvorný, David; Whiteley, Robert; Ivezić Z, Zeljko; Jurić, Mario

2004-05-20

Asteroid collisions in the main belt eject fragments that may eventually land on Earth as meteorites. It has therefore been a long-standing puzzle in planetary science that laboratory spectra of the most populous class of meteorite (ordinary chondrites, OC) do not match the remotely observed surface spectra of their presumed (S-complex) asteroidal parent bodies. One of the proposed solutions to this perplexing observation is that 'space weathering' modifies the exposed planetary surfaces over time through a variety of processes (such as solar and cosmic ray bombardment, micro-meteorite bombardment, and so on). Space weathering has been observed on lunar samples, in Earth-based laboratory experiments, and there is good evidence from spacecraft data that the process is active on asteroid surfaces. Here, we present a measurement of the rate of space weathering on S-complex main-belt asteroids using a relationship between the ages of asteroid families and their colours. Extrapolating this age-colour relationship to very young ages yields a good match to the colour of freshly cut OC meteorite samples, lending strong support to a genetic relationship between them and the S-complex asteroids.

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

Yang Bin; Jewitt, David, E-mail: yangbin@ifa.hawaii.ed, E-mail: jewitt@ucla.ed

Spectrally blue (B-type) asteroids are rare, with the second discovered asteroid, Pallas, being the largest and most famous example. We conducted a focused, infrared spectroscopic survey of B-type asteroids to search for water-related features in these objects. Our results show that the negative optical spectral slope of some B-type asteroids is due to the presence of a broad absorption band centered near 1.0 {mu}m. The 1 {mu}m band can be matched in position and shape using magnetite (Fe{sub 3}O{sub 4}), which is an important indicator of past aqueous alteration in the parent body. Furthermore, our observations of B-type asteroid (335)more » Roberta in the 3 {mu}m region reveal an absorption feature centered at 2.9 {mu}m, which is consistent with the absorption due to phyllosilicates (another hydration product) observed in CI chondrites. The new observations suggest that at least some B-type asteroids are likely to have incorporated significant amounts of water ice and to have experienced intensive aqueous alteration.« less

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.

FORMING CHONDRITES IN A SOLAR NEBULA WITH MAGNETICALLY INDUCED TURBULENCE

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

Hasegawa, Yasuhiro; Turner, Neal J.; Masiero, Joseph

Chondritic meteorites provide valuable opportunities to investigate the origins of the solar system. We explore impact jetting as a mechanism of chondrule formation and subsequent pebble accretion as a mechanism of accreting chondrules onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is ≤5 times more massive than the minimum-mass solar nebula at a ≃ 2–3 au and parent bodies of chondrites are ≤10{sup 24} g (≤500 km in radius) in the solar nebula, impact jetting and subsequent pebble accretion can reproduce a number ofmore » properties of the meteoritic data. The properties include the present asteroid belt mass, the formation timescale of chondrules, and the magnetic field strength of the nebula derived from chondrules in Semarkona. Since this scenario requires a first generation of planetesimals that trigger impact jetting and serve as parent bodies to accrete chondrules, the upper limit of parent bodies’ masses leads to the following implications: primordial asteroids that were originally ≥10{sup 24} g in mass were unlikely to contain chondrules, while less massive primordial asteroids likely had a chondrule-rich surface layer. The scenario developed from impact jetting and pebble accretion can therefore provide new insights into the origins of the solar system.« less

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.

Water in the early solar system: Mid-infrared studies of aqueous alteration on asteroids.

NASA Astrophysics Data System (ADS)

McAdam, Margaret M.; Sunshine, Jessica M.; Kelley, Michael S.; Trilling, David E.

2017-10-01

This work investigates the distribution of water in the early Solar System by connecting asteroids to carbonaceous chondrite meteorites using spectroscopy. Aqueous alteration or the chemical reaction between liquid water and silicates on the parent asteroid, has extensively affected several groups of carbonaceous chondrites. The degree of alteration or amount of hydrated minerals produced depends on a number of factors including the abundance of coaccreted water-ice, the internal distribution of water in the parent body and the setting of alteration (e.g., open vs. closed setting). Despite this complexity which is still under investigation, the mineralogical changes produced by aqueous alteration are well understood (e.g., Howard et al., 2015). The mid-infrared spectral region has been shown to be a tool for estimating the degree of alteration of asteroids and meteorites remotely (McAdam et al., 2015). Specifically, mid-infrared spectral features changes continuously with degree of alteration. In this region meteorites can be categorized into four groups based on their spectral characteristics: anhydrous, less altered, intermediately altered and highly altered. We present the estimated degrees of alteration for 73 main belt asteroids using these results. Hydrated minerals appear to be widespread in the main belt and asteroids have variable degrees of alteration. There does not appear to be any relationship between the estimated degree of alteration and size, albedo or heliocentric distance. This indicates that water-ice must have been a significant component of the solar nebula in the 2-5 AU region during the time of carbonaceous chondrite accretion (~2.7-4 Ma post-CAI formation; Sugiura and Fujiya, 2014). The snow-line therefore must have been in this region during this epoch. Furthermore, local heterogeneities of water-ice were likely common since asteroids of all sizes and heliocentric distances may exhibit any degree from anhydrous to highly altered. Additionally, asteroids that have been shown to have water-ice on their surfaces (e.g., Takir and Emery, 2012) appear to have hydrated minerals. This indicates that while these asteroids have water-ice, its presence did not prevent aqueous alteration.

Pairs of Asteroids Probably of a Common Origin

NASA Astrophysics Data System (ADS)

Vokrouhlický, David; Nesvorný, David

2008-07-01

We report the first observational evidence for pairs of main-belt asteroids with bodies in each pair having nearly identical orbits. The existence of ~60 pairs identified here cannot be reconciled with random fluctuations of the asteroid orbit density and rather suggests a common origin of the paired objects. We propose that the identified pairs formed by (i) collisional disruptions of km-sized and larger parent asteroids, (ii) Yarkovsky-O'Keefe-Radzievski-Paddack (YORP)-induced spin-up and rotational fission of fast-rotating objects, and/or (iii) splitting of unstable asteroid binaries. In case (i), the pairs would be parts of compact collisional families with many km- and sub-km-size members that should be found by future asteroid surveys. Our dynamical analysis suggests that most identified pairs formed within the past lsim1 Myr, in several cases even much more recently. For example, paired asteroids (6070) Rheinland and (54827) 2001 NQ8 probably separated from their common ancestor only 16.5-19 kyr ago. Given their putatively very recent formation, the identified objects are prime candidates for astronomical observations. The title paraphrases that of Hirayama's 1918 paper "Groups of asteroids probably of a common origin," where the first evidence was given for groups of asteroid fragments produced by disruptive collisions.

Near-infrared spectroscopy of 3:1 Kirkwood Gap asteroids III

NASA Astrophysics Data System (ADS)

Fieber-Beyer, Sherry K.; Gaffey, Michael J.

2015-09-01

The research is an integrated effort beginning with telescopic observations and extending through detailed mineralogical characterizations to provide constraints on the composition and meteorite affinities of a subset of fourteen asteroids in/near the 3:1 Kirkwood Gap. Eight asteroids were identified as having either one or two absorption features, while six were deemed featureless. The compositional analysis of Asteroids (355) Gabriella and (1447) Utra reveal Fs and Fa values which are consistent with values for the L-type ordinary chondrites (Fs19-22 and Fa22-26). The location of these two bodies with respect to each other and to the previously identified L-chondrite parent body Asteroid (1722) Goffin, suggests a small L-chondrite genetic family. These results support the model that the L-chondrites come from an asteroid family rather than from a single object. Asteroids (1368) Numidia, (1587) Kahrstadt, (1854) Skvortsov, (2497) Kulikovskij, and (5676) Voltaire were analyzed and determined to have "basaltic" silicate mineralogies similar to those of the HED (howardite-eucrite-diogenite) meteorite group. In particular, we found that the compositions of (1368), (1587) and (1854) are consistent with olivine-orthopyroxenitic diogenites, while (2497) and (5676)'s compositions are consistent with harzburgitic diogenites. The Band I and Band II absorption feature depths are much shallower than seen in diogenite spectra, typically ∼70% depth (Burbine, T.H. et al. [2000]. Forging asteroid-meteorite relationships through reflectance spectroscopy. Lunar Planet. Sci. XXXI. Abstract 1844). The nature of the weak features seen in the asteroid spectra when compared to measured band depths of in situ diogenite samples indicate an additional mechanism(s) acting to weaken the features, most likely space weathering. The aforementioned five asteroids are plausible sources for the olivine-orthopyroxenitic diogenites and harzburgitic diogenites, and very well may be fragments of Vesta. Asteroid (46) Hestia is an interesting object whose surface minerals may be consistent with a CR2 chondrite; however, the unique spectrum deserves further study in the future. Featureless Asteroids (248) Lameia, (1960) Guisan, (3345) Tarkovskij and (6212) 1993 MS1 surface materials are likely organic assemblages consistent with the Type 1 or 2 carbonaceous chondrite meteorite class; however specific terrestrial meteorite analog could not be identified. The spectra of Asteroids (3228) Pire and (3999) Aristarchus are consistent with each other and have been assigned to the Eulalia by Walsh et al. (Walsh, K.J. et al. [2013]. Icarus 225, 283-297). Spectrally they are similar to (495) in terms of blue-slope and albedo (Fieber-Beyer, S.K., et al. [2012]. Icarus 221, 593-602), thus increasing our confidence the three bodies are truly related dynamically and genetically. By extrapolation and due to their location adjacent to the 3:1 Kirkwood Gap, (3228) and (3999) are plausible sources of the CV3OXB carbonaceous chondrites.

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

Asteroidal Differentiation - The Record in Meteorites

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.

2010-01-01

Early in solar system history, an intense energy source modified the small rocky bodies that had accreted from nebular condensates. The consensus view is that this energy source was the decay of short-lived 26Al, perhaps with a contribution from short-lived 60Fe. Differentiated meteorites and primitive achondrites preserve records of the states of asteroids as differentiation was ending. Reading these records provides clues to the nature of the energy source and the mechanisms of differentiation. I will examine the records from the acapulcoite-lordanite clan, ureilites, main-group pallasites, magmatic iron meteorite groups, brachinites and howardite-eucrite-diogenite (HED) clan meteorites. The acapulcoite-lodranite clan and the ureilites contain evidence that their parent asteroids reached temperatures where basaltic melts were produced. The mineralogies of lodranites and ureilites are dominantly olivine and low-Ca pyroxene, and these meteorites are highly depleted in incompatible lithophile elements. The acapulcoite-lodranite and ureilite parent bodies were heated to the point where on the order of 20-30% melting had taken place, but there is no evidence for more extensive melting. Assuming a 26Al energy source, the implication is that transport of the Al-rich basalt out of the mantle outpaced radiogenic heating, and thus shut down further differentiation. Main-group pallasites, magmatic iron meteorites and HED clan meteorites, on the other hand, provide evidence for total or near total melting of asteroids. The silicate phase of pallasites is magnesian olivine; their minor and trace element contents suggest that they are refractory melting residues. The degree of melting was high, perhaps on the order of 80%. The compositions of the most Ir-rich magmatic irons suggest near total melting of the metallic phase, and thus high degrees of melting on their parent asteroids. The compositions of basaltic eucrites are most consistent with them being residues from the crystallization of a largely molten asteroid. For these meteorite groups, the rate of heating outpaced the rate at which the melt could be extracted from the interiors, again, assuming 26Al was the energy source. The nature of the heat engine and asteroidal differentiation processes will be discussed as they can be inferred from the petrology and composition of achondrites, irons and stony irons.

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.

Dynamics of rotationally fissioned asteroids: Source of observed small asteroid systems

NASA Astrophysics Data System (ADS)

Jacobson, Seth A.; Scheeres, Daniel J.

2011-07-01

We present a model of near-Earth asteroid (NEA) rotational fission and ensuing dynamics that describes the creation of synchronous binaries and all other observed NEA systems including: doubly synchronous binaries, high- e binaries, ternary systems, and contact binaries. Our model only presupposes the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, "rubble pile" asteroid geophysics, and gravitational interactions. The YORP effect torques a "rubble pile" asteroid until the asteroid reaches its fission spin limit and the components enter orbit about each other (Scheeres, D.J. [2007]. Icarus 189, 370-385). Non-spherical gravitational potentials couple the spin states to the orbit state and chaotically drive the system towards the observed asteroid classes along two evolutionary tracks primarily distinguished by mass ratio. Related to this is a new binary process termed secondary fission - the secondary asteroid of the binary system is rotationally accelerated via gravitational torques until it fissions, thus creating a chaotic ternary system. The initially chaotic binary can be stabilized to create a synchronous binary by components of the fissioned secondary asteroid impacting the primary asteroid, solar gravitational perturbations, and mutual body tides. These results emphasize the importance of the initial component size distribution and configuration within the parent asteroid. NEAs may go through multiple binary cycles and many YORP-induced rotational fissions during their approximately 10 Myr lifetime in the inner Solar System. Rotational fission and the ensuing dynamics are responsible for all NEA systems including the most commonly observed synchronous binaries.

Mineralogy of Pyroxene and Olivine in the Almahata Sitta Ureilite

NASA Technical Reports Server (NTRS)

Mikouchi, T.; Zolensky, M.; Takeda, H.; Hagiya, K.; Ohsumi, K; Satake, W.; Kurihara, T.; Dept. of Physics; Shaddad, M. H.

2010-01-01

The Almahata Sitta meteorite (hereafter "Alma") is the first example of a recovered asteroidal sample that fell to earth after detection still in the orbit (2008TC3 asteroid), and thus is critical to understand the relationship between meteorites and their asteroidal parent bodies [1]. Alma is a polymict ureilite showing a fine-grained brecciated texture with variable lithologies from black, porous to denser, white stones [1]. It is an anomalous ureilite because of wide compositional ranges of silicates with abundant pores often coated by vapor-deposit crystals [1]. Nevertheless, Alma has general similarities to all ureilites because of reduction textures of silicates suggestive of rapid cooling from high temperature as well as heterogeneous oxygen isotope compositions [e.g., 1-5]. Alma is especially unique because it spans the compositional range of known ureilites [1]. In this abstract we report detailed mineralogical and crystallographic investigations of two different fragments to further constrain its thermal history with regards to the nature of the ureilite parent body.

Core Formation and Evolution of Asteroid 4 Vesta

NASA Technical Reports Server (NTRS)

Kiefer, Walter S.; Mittlefehldt, David W.

2014-01-01

The howardites, eucrites, and diogenites (HEDs) are a suite of related meteorite types that formed by igneous and impact processes on the same parent body. Multiple lines of evidence, including infrared spectroscopy of the asteroid belt and the petrology and geochemistry of the HEDs, suggest that the asteroid 4 Vesta is the parent body for the HEDs. Observations by NASA's Dawn spacecraft mission strongly support the conclusion that the HEDs are from Vesta. The abundances of the moderately siderophile elements Ni, Co, Mo, W, and P in eucrites require that most or all of the metallic phase in Vesta segregated to form a core prior to eucrite solidification. These observations place important constraints on the mode and timescale of core formation on Vesta. Possible core formation mechanisms include porous flow, which potentially could occur prior to initiation of silicate melting, and metallic rain in a largely molten silicate magma ocean. Once the core forms, convection within the core could possible sustain a magnetic dynamo for a period of time. We consider each process in turn.

Asteroidal companions in the visible: HST data

NASA Astrophysics Data System (ADS)

Storrs, Alex; Vilas, Faith; Landis, Rob; Gaffey, Michael J.; Makhoul, Khaldoun; Davis, MIke; Richmond, Mike

2016-01-01

We present a reanalysis of HST images of five asteroids with known companions (45 Eugenia, 87 Sylvia, 93 Minerva, 107 Camilla, 121 Hermione). It is remarkable that all of these companion bodies are much redder in the visible region than their primary bodies. Storrs et al. (2009, BAAS vol. 41, no. 4, p 189) attributed this to space weathering, however, all of these bodies belong to dark C- or X-type groups. Current modeling of space weathering effects are limited to bright asteroids (e.g. Cloutis et al., Icarus 252, pp. 39-82, 2015) and show little change on the scale reported here. We suggest that the interaction of dark, possibly organic-rich surfaces with the solar wind produces reddening on a much greater scale than is observed in bright, silica-rich surfaces, and that this effect is easily reset by collisions. Thus, while both the parent and companion object accumulate the effects, the parent is much more likely to be "reset" by small collisions than the companion, due to the differences in their cross-sections.

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.

From asteroid clusters to families: A proposal for a new nomenclature

NASA Technical Reports Server (NTRS)

Farinella, Paolo; Davis, Donald R.; Cellino, Alberto; Zappala, Vincenzo

1992-01-01

Some confusion on the number, reliability, and characteristics of asteroid families is the result of using the single word 'family' for naming asteroid groupings identified in very different ways. Here we propose a new terminology which in our opinion would alleviate this problem.

Mineralogy and petrography of C asteroid regolith: The Sutter's Mill CM meteorite

NASA Astrophysics Data System (ADS)

Zolensky, Michael; Mikouchi, Takashi; Fries, Marc; Bodnar, Robert; Jenniskens, Peter; Yin, Qing-zhu; Hagiya, Kenji; Ohsumi, Kazumasa; Komatsu, Mutsumi; Colbert, Matthew; Hanna, Romy; Maisano, Jessie; Ketcham, Richard; Kebukawa, Yoko; Nakamura, Tomoki; Matsuoka, Moe; Sasaki, Sho; Tsuchiyama, Akira; Gounelle, Matthieu; Le, Loan; Martinez, James; Ross, Kent; Rahman, Zia

2014-11-01

Based upon our characterization of three separate stones by electron and X-ray beam analyses, computed X-ray microtomography, Raman microspectrometry, and visible-IR spectrometry, Sutter's Mill is a unique regolith breccia consisting mainly of various CM lithologies. Most samples resemble existing available CM2 chondrites, consisting of chondrules and calcium-aluminum-rich inclusion (CAI) set within phyllosilicate-dominated matrix (mainly serpentine), pyrrhotite, pentlandite, tochilinite, and variable amounts of Ca-Mg-Fe carbonates. Some lithologies have witnessed sufficient thermal metamorphism to transform phyllosilicates into fine-grained olivine, tochilinite into troilite, and destroy carbonates. One finely comminuted lithology contains xenolithic materials (enstatite, Fe-Cr phosphides) suggesting impact of a reduced asteroid (E or M class) onto the main Sutter's Mill parent asteroid, which was probably a C class asteroid. One can use Sutter's Mill to help predict what will be found on the surfaces of C class asteroids such as Ceres and the target asteroids of the OSIRIS-REx and Hayabusa 2 sample return missions (which will visit predominantly primitive asteroids). C class asteroid regolith may well contain a mixture of hydrated and thermally dehydrated indigenous materials as well as a significant admixture of exogenous material would be essential to the successful interpretation of mineralogical and bulk compositional data.

A New Equilibrium State for Singly Synchronous Binary Asteroids

NASA Astrophysics Data System (ADS)

Golubov, Oleksiy; Unukovych, Vladyslav; Scheeres, Daniel J.

2018-04-01

The evolution of rotation states of small asteroids is governed by the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, nonetheless some asteroids can stop their YORP evolution by attaining a stable equilibrium. The same is true for binary asteroids subjected to the binary YORP (BYORP) effect. Here we discuss a new type of equilibrium that combines these two, which is possible in a singly synchronous binary system. This equilibrium occurs when the normal YORP, the tangential YORP, and the BYORP compensate each other, and tidal torques distribute the angular momentum between the components of the system and dissipate energy. If unperturbed, such a system would remain singly synchronous in perpetuity with constant spin and orbit rates, as the tidal torques dissipate the incoming energy from impinging sunlight at the same rate. The probability of the existence of this kind of equilibrium in a binary system is found to be on the order of a few percent.

Asteroid/meteorite streams

NASA Astrophysics Data System (ADS)

Drummond, J.

The independent discovery of the same three streams (named alpha, beta, and gamma) among 139 Earth approaching asteroids and among 89 meteorite producing fireballs presents the possibility of matching specific meteorites to specific asteroids, or at least to asteroids in the same stream and, therefore, presumably of the same composition. Although perhaps of limited practical value, the three meteorites with known orbits are all ordinary chondrites. To identify, in general, the taxonomic type of the parent asteroid, however, would be of great scientific interest since these most abundant meteorite types cannot be unambiguously spectrally matched to an asteroid type. The H5 Pribram meteorite and asteroid 4486 (unclassified) are not part of a stream, but travel in fairly similar orbits. The LL5 Innisfree meteorite is orbitally similar to asteroid 1989DA (unclassified), and both are members of a fourth stream (delta) defined by five meteorite-dropping fireballs and this one asteroid. The H5 Lost City meteorite is orbitally similar to 1980AA (S type), which is a member of stream gamma defined by four asteroids and four fireballs. Another asteroid in this stream is classified as an S type, another is QU, and the fourth is unclassified. This stream suggests that ordinary chondrites should be associated with S (and/or Q) asteroids. Two of the known four V type asteroids belong to another stream, beta, defined by five asteroids and four meteorite-dropping (but unrecovered) fireballs, making it the most probable source of the eucrites. The final stream, alpha, defined by five asteroids and three fireballs is of unknown composition since no meteorites have been recovered and only one asteroid has an ambiguous classification of QRS. If this stream, or any other as yet undiscovered ones, were found to be composed of a more practical material (e.g., water or metalrich), then recovery of the associated meteorites would provide an opportunity for in-hand analysis of a potential near-Earth resource.

Asteroid/meteorite streams

NASA Technical Reports Server (NTRS)

Drummond, J.

1991-01-01

The independent discovery of the same three streams (named alpha, beta, and gamma) among 139 Earth approaching asteroids and among 89 meteorite producing fireballs presents the possibility of matching specific meteorites to specific asteroids, or at least to asteroids in the same stream and, therefore, presumably of the same composition. Although perhaps of limited practical value, the three meteorites with known orbits are all ordinary chondrites. To identify, in general, the taxonomic type of the parent asteroid, however, would be of great scientific interest since these most abundant meteorite types cannot be unambiguously spectrally matched to an asteroid type. The H5 Pribram meteorite and asteroid 4486 (unclassified) are not part of a stream, but travel in fairly similar orbits. The LL5 Innisfree meteorite is orbitally similar to asteroid 1989DA (unclassified), and both are members of a fourth stream (delta) defined by five meteorite-dropping fireballs and this one asteroid. The H5 Lost City meteorite is orbitally similar to 1980AA (S type), which is a member of stream gamma defined by four asteroids and four fireballs. Another asteroid in this stream is classified as an S type, another is QU, and the fourth is unclassified. This stream suggests that ordinary chondrites should be associated with S (and/or Q) asteroids. Two of the known four V type asteroids belong to another stream, beta, defined by five asteroids and four meteorite-dropping (but unrecovered) fireballs, making it the most probable source of the eucrites. The final stream, alpha, defined by five asteroids and three fireballs is of unknown composition since no meteorites have been recovered and only one asteroid has an ambiguous classification of QRS. If this stream, or any other as yet undiscovered ones, were found to be composed of a more practical material (e.g., water or metalrich), then recovery of the associated meteorites would provide an opportunity for in-hand analysis of a potential near-Earth resource.

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.

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.

Re-accumulation of Asteroids to Equilibrium Figures

NASA Astrophysics Data System (ADS)

Hestroffer, D.; Tanga, P.; Richardson, D. C.; Berthier, J.; Cellino, A.; Durech, J.; Michel, P.

2008-09-01

Since their formation, asteroids since their formation have experienced little physical, geological or thermal evolution. Like comets they are thought to be among the most pristine remnants of the early solar system. One physical process, however, has played a major role since the ancient times: collisions. Dynamical families were produced by catastrophic collisions involving large enough energy to break the parent body. Other lines of evidence suggest that catastrophic collisions can also produce rubble-piles, i.e., loosely bound of post-collisional aggregates that re-accumulate to form a single body, and are kept together by gravity. The main objective of this work is to understand if—and under what conditions—Jacobi ellipsoids or other equilibrium figures can be obtained naturally by this way. This is done by performing numerical experiments simulating the re-accumulation process, and by performing high-angular resolution observations in order to better constrain the shape and density of the targets. It is shown that the outcomes of reaccumulation events tend to produce a rather narrow variety of possible shapes, and in some cases also binary systems.

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.

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

Pigeonholing planetary meteorites: The lessons of misclassification of EET87521 and ALH84001

NASA Technical Reports Server (NTRS)

Lindstrom, M. M.; Treiman, A. H.; Mittlefehldt, D. W.

1994-01-01

The last few years have provided two noteworthy examples of misclassifications of achondritic meteorites because the samples were new kinds of meteorites from planetary rather than asteroidal parent bodies. Basaltic lunar meteorite EET87521 was misclassified as a eucrite and SNC (martian) orthopyroxenite ALH84001 was misclassified as a diogenite. In classifying meteorites we find what we expect: we pigeonhole meteorites into known categories most of which were derived from the more common asteroidal meteorites. But the examples of EET8752 and ALH84001 remind us that planets are more complex than asteroids and exhibit a wider variety of rock types. We should expect variety in planetary meteorites and we need to know how to recognize them when we have them. Our intent here is to show that our asteroidal perspective is inappropriate for planetary meteorites.

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.

Analytical solution for the normal emission portion of the averaged Yarkovsky-O'Keefe-Radzvieskii-Paddack coefficient for a single facet

NASA Astrophysics Data System (ADS)

Albuja, Antonella A.; Scheeres, Daniel J.

2015-02-01

The Yarkovsky-O'Keefe-Radzvieskii-Paddack (YORP) effect has been well studied for asteroids. This paper develops an analytic solution to find the normal emission YORP component for a single facet. The solution presented here does not account for self-shadowing or self-heating. The YORP coefficient for all facets can be summed together to find the total coefficient of the asteroid. The normal emission component of YORP has been shown to be the most important for asteroids and it directly affects the rate of change of the asteroid's spin period. The analytical solution found is a sole function of the facet's geometry and the obliquity of the asteroid. This solution is universal for any facet and its orientation. The behaviour of the coefficient is analysed with this analytical solution. The closed-form solution is used to find the total YORP coefficient for the asteroids Apollo and 1998 ML14 whose shape models are composed of different numbers of facets. The results are then compared to published results and those obtained through numerical quadrature for validation.

Origin and history of ureilitic material in the solar system: The view from asteroid 2008 TC3 and the Almahata Sitta meteorite

NASA Astrophysics Data System (ADS)

Goodrich, Cyrena Anne; Hartmann, William K.; O'Brien, David P.; Weidenschilling, Stuart J.; Wilson, Lionel; Michel, Patrick; Jutzi, Martin

2015-04-01

Asteroid 2008 TC3 (approximately 4 m diameter) was tracked and studied in space for approximately 19 h before it impacted Earth's atmosphere, shattering at 44-36 km altitude. The recovered samples (>680 individual rocks) comprise the meteorite Almahata Sitta (AhS). Approximately 50-70% of these are ureilites (ultramafic achondrites). The rest are chondrites, mainly enstatite, ordinary, and Rumuruti types. The goal of this work is to understand how fragments of so many different types of parent bodies became mixed in the same asteroid. Almahata Sitta has been classified as a polymict ureilite with an anomalously high component of foreign clasts. However, we calculate that the mass of fallen material was ≤0.1% of the pre-atmospheric mass of the asteroid. Based on published data for the reflectance spectrum of the asteroid and laboratory spectra of the samples, we infer that the lost material was mostly ureilitic. Therefore, 2008 TC3 probably contained only a few percent nonureilitic materials, similar to other polymict ureilites except less well consolidated. From available data for the AhS meteorite fragments, we conclude that 2008 TC3 samples essentially the same range of types of ureilitic and nonureilitic materials as other polymict ureilites. We therefore suggest that the immediate parent of 2008 TC3 was the immediate parent of all ureilitic material sampled on Earth. We trace critical stages in the evolution of that material through solar system history. Based on various types of new modeling and re-evaluation of published data, we propose the following scenario. (1) The ureilite parent body (UPB) accreted 0.5-0.6 Ma after formation of calcium-aluminum-rich inclusions (CAI), beyond the ice line (outer asteroid belt). Differentiation began approximately 1 Ma after CAI. (2) The UPB was catastrophically disrupted by a major impact approximately 5 Ma after CAI, with selective subsets of the fragments reassembling into daughter bodies. (3) Either the UPB (before breakup), or one of its daughters (after breakup), migrated to the inner belt due to scattering by massive embryos. (4) One daughter (after forming in or migrating to the inner belt) became the parent of 2008 TC3. It developed a regolith, mostly ≥3.8 Ga ago. Clasts of enstatite, ordinary, and Rumuruti-type chondrites were implanted by low-velocity collisions. (5) Recently, the daughter was disrupted. Fragments were injected or drifted into Earth-crossing orbits. 2008 TC3 comes from outer layers of regolith, other polymict ureilites from deeper regolith, and main group ureilites from the interior of this body. In contrast to other models that have been proposed, this model invokes a stochastic history to explain the unique diversity of foreign materials in 2008 TC3 and other polymict ureilites.

Brachinite-Like Clast in the Kaidun Meteorite: First Report of Primitive Achondrite Material

NASA Technical Reports Server (NTRS)

Higashi, K.; Hasegawa, H.; Mikouchi, T.; Zolensky, M. E.

2017-01-01

Kaidun is a brecciated meteorite containing many different types of meteorites. It is composed of carbonaceous, enstatite, ordinary and R chondrites with smaller amounts of basaltic achondrites, impact melt products and unknown [1, 2]. Because of the multiple components and high abundance of carbonaceous chondrites, the Kaidun parent body was probably a large C-type asteroid in order to have accumulated clasts of many unrelated asteroids, and thus Kaidun contains previously unknown materials[1]. It has been suggested that the Kaidun parent body trawled through different regions of the solar system [3], but the formation of Kaidun meteorite is still uncertain. In this abstract, we report the first discovery of a brachinite-like clast in Kaidun.

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

Metamorphosed CM and CI Carbonaceous Chondrites Could Be from the Breakup of the Same Earth-crossing Asteroid

NASA Technical Reports Server (NTRS)

Zolensky, Michael; Abell, Paul; Tonui, Eric

2005-01-01

Far from being the relatively unprocessed materials they were once believed to be, we now know that a significant number of carbonaceous chondrites were thermally metamorphosed on their parent asteroid(s). Numerous studies indicate that 7 "CM" and 2 "CI" chondrites have been naturally heated, variously, at from 400 to over 700 C on their parent asteroid(s). Petrographic textures reveal that this thermal metamorphism occurred after the dominant aqueous alteration phase, although some meteorites show evidence of a heating event between two aqueous alteration episodes, i.e. pro- and retrograde aqueous alteration. Aside from the issues of the identification of the transient heat source, timing of metamorphism, and the relation of these materials (if any) to conventional CM and CI chondrites, there is also a mystery related to their recovery. All of these meteorites have been recovered from the Antarctic; none are falls or finds from anyplace else. Indeed, the majority have been collected by the Japanese NIPR field parties in the Yamato Mountains. In fact, one estimate is that these meteorites account for approx. 64 wt% of the CM carbonaceous chondrites at the NIPR. The reasons for this are unclear and might be due in part to simple sampling bias. However we suggest that this recovery difference is related to the particular age of the Yamato Mountains meteorite recovery surfaces, and differences in meteoroid fluxes between the Yamato meteorites and recent falls and substantially older Antarctic meteorites. Additional information is included in the original extended abstract.

Workshop on Parent-Body and Nebular Modification of Chondritic Materials

NASA Technical Reports Server (NTRS)

Zolensky, M. E. (Editor); Krot, A. N. (Editor); Scott, E. R. D. (Editor)

1997-01-01

Topics considered include: thermal Metamorphosed Antarctic CM and CI Carbonaceous Chondrites in Japanese Collections, and Transformation Processes of Phyllosilicates; use of Oxygen Isotopes to Constrain the Nebular and Asteroidal Modification of Chondritic Materials; effect of Revised Nebular Water Distribution on Enstatite Chondrite Formation; interstellar Hydroxyls in Meteoritic Chondrules: Implications for the Origin of Water in the Inner Solar System; theoretical Models and Experimental Studies of Gas-Grain Chemistry in the Solar Nebula; chemical Alteration of Chondrules on Parent Bodies; thermal Quenching of Silicate Grains in Protostellar Sources; an Experimental Study of Magnetite Formation in the Solar Nebula; the Kaidun Meteorite: Evidence for Pre- and Postaccretionary Aqueous Alteration; a Transmission Electron Microscope Study of the Matrix Mineralogy of the Leoville CV3 (Reduced-Group) Carbonaceous Chondrite: Nebular and Parent-Body Features; rubidium-Strontium Isotopic Systematic of Chondrules from the Antarctic CV Chondrites Yamato 86751 and Yamato 86009: Additional Evidence for Late Parent-Body Modification; oxygen-Fugacity Indicators in Carbonaceous Chondrites: Parent-Body Alteration or High-Temperature Nebular Oxidation; thermodynamic Modeling of Aqueous Alteration in CV Chondrites; asteroidal Modification of C and O Chondrites: Myths and Models; oxygen Fugacity in the Solar Nebular; and the History of Metal and Sulfides in Chondrites.

A radar survey of M- and X-class asteroids

NASA Astrophysics Data System (ADS)

Shepard, Michael K.; Clark, Beth Ellen; Nolan, Michael C.; Howell, Ellen S.; Magri, Christopher; Giorgini, Jon D.; Benner, Lance A. M.; Ostro, Steven J.; Harris, Alan W.; Warner, Brian; Pray, Donald; Pravec, Petr; Fauerbach, Michael; Bennett, Thomas; Klotz, Alain; Behrend, Raoul; Correia, Horacio; Coloma, Josep; Casulli, Silvano; Rivkin, Andrew

2008-05-01

We observed ten M- and X-class main-belt asteroids with the Arecibo Observatory's S-band (12.6 cm) radar. The X-class asteroids were targeted based on their albedos or other properties which suggested they might be M-class. This work brings the total number of main-belt M-class asteroids observed with radar to 14. We find that three of these asteroids have rotation rates significantly different from what was previously reported. Based on their high radar albedo, we find that only four of the fourteen—16 Psyche, 216 Kleopatra, 758 Mancunia, and 785 Zwetana—are almost certainly metallic. 129 Antigone has a moderately high radar albedo and we suggest it may be a CH/CB/Bencubbinite parent body. Three other asteroids, 97 Klotho, 224 Oceana, and 796 Sarita have radar albedos significantly higher than the average main belt asteroid and we cannot rule out a significant metal content for them. Five of our target asteroids, 16 Psyche, 129 Antigone, 135 Hertha, 758 Mancunia, and 785 Zwetana, show variations in their radar albedo with rotation. We can rule out shape and composition in most cases, leaving variations in thickness, porosity, or surface roughness of the regolith to be the most likely causes. With the exception of 129 Antigone, we find no hydrated M-class asteroids (W-class; Rivkin, A.S., Howell, E.S., Lebofsky, L.A., Clark, B.E., Britt, D.T., 2000. Icarus 145, 351-368) to have high radar albedos.

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.

The 2014 KCG Meteor Outburst: Clues to a Parent Body

NASA Technical Reports Server (NTRS)

Moorhead, Althea V.; Brown, Peter G.; Spurny, Pavel; Cooke, William J.

2015-01-01

The Kappa Cygnid (KCG) meteor shower exhibited unusually high activity in 2014, producing ten times the typical number of meteors. The shower was detected in both radar and optical systems and meteoroids associated with the outburst spanned at least five decades in mass. In total, the Canadian Meteor Orbit Radar, European Network, and NASA All Sky and Southern Ontario Meteor Network produced thousands of KCG meteor trajectories. Using these data, we have undertaken a new and improved characterization of the dynamics of this little-studied, variable meteor shower. The Cygnids have a di use radiant and a significant spread in orbital characteristics, with multiple resonances appearing to play a role in the shower dynamics. We conducted a new search for parent bodies and found that several known asteroids are orbitally similar to the KCGs. N-body simulations show that the two best parent body candidates readily transfer meteoroids to the Earth in recent centuries, but neither produces an exact match to the KCG radiant, velocity, and solar longitude. We nevertheless identify asteroid 2001 MG1 as a promising parent body candidate.

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.

Diogenites: Cumulates from Asteroid 4 Vesta: Insights from Orthopyroxene and Spinel Chemistry

NASA Technical Reports Server (NTRS)

Papike, James J.; Bowman, L. E.; Spilde, M. N.; Fowler, G. W.; Shearer, C. K.

1996-01-01

Cumulate rocks are important planetary lithologies, but they can be difficult to interpret. Important clues to the nature of their parental melts may still be present in the interiors of cumulus phases. However, in some cases, even the cores of the cumulus grains may have been modified by postcrystallization reactions with trapped melt and other cumulus phases. We have previously studied the major-, minor-, and trace-element chemistry of orthopyroxene from a suite of diogenites and concluded that their chemical attributes can best be explained by crystallization from parental melts that were derived from a depleted mantle source that had already experienced eucrite removal. However, we and others have had difficulty explaining the great range in concentration of minor elements (Al, Ti) and trace elements (REE, Y, Zr) if all diogenites were derived from a single magmatic system. Therefore, we have investigated the chemistry of diogenitic spinels to see if they still held clues to the diogenite parental melt compositions. Although spinel is low in abundance in diogenites (<5 vol%) it still may hold clues to the maomatic and metamorphic history of these rocks.

Thermodynamic Models for Aqueous Alteration Coupled with Volume and Pressure Changes in Asteroids

NASA Technical Reports Server (NTRS)

Mironenko, M. V.; Zolotov, M. Y.

2005-01-01

All major classes of chondrites show signs of alteration on their parent bodies (asteroids). The prevalence of oxidation and hydration in alteration pathways implies that water was the major reactant. Sublimation and melting of water ice, generation of gases, formation of aqueous solutions, alteration of primary minerals and glasses and formation of secondary solids in interior parts of asteroids was likely to be driven by heat from the radioactive decay of short-lived radionuclides. Progress of alteration reactions should have affected masses and volumes of solids, and aqueous and gas phases. In turn, pressure evolution should have been controlled by changes in volumes and temperatures, escape processes, and production/ consumption of gases.

The Steward Observatory asteroid relational database

NASA Technical Reports Server (NTRS)

Sykes, Mark V.; Alvarezdelcastillo, Elizabeth M.

1991-01-01

The Steward Observatory Asteroid Relational Database (SOARD) was created as a flexible tool for undertaking studies of asteroid populations and sub-populations, to probe the biases intrinsic to asteroid databases, to ascertain the completeness of data pertaining to specific problems, to aid in the development of observational programs, and to develop pedagogical materials. To date, SOARD has compiled an extensive list of data available on asteroids and made it accessible through a single menu-driven database program. Users may obtain tailored lists of asteroid properties for any subset of asteroids or output files which are suitable for plotting spectral data on individual asteroids. The program has online help as well as user and programmer documentation manuals. The SOARD already has provided data to fulfill requests by members of the astronomical community. The SOARD continues to grow as data is added to the database and new features are added to the program.

Methods of determination of periods in the motion of asteroids

NASA Astrophysics Data System (ADS)

Bien, R.; Schubart, J.

Numerical techniques for the analysis of fundamental periods in asteroidal motion are evaluated. The specific techniques evaluated were: the periodogram analysis procedure of Wundt (1980); Stumpff's (1937) system of algebraic transformations; and Labrouste's procedure. It is shown that the Labrouste procedure permitted sufficient isolation of single oscillations from the quasi-periodic process of asteroidal motion. The procedure was applied to the analysis of resonance in the motion of Trojan-type and Hilda-type asteroids, and some preliminary results are discussed.

An asteroid breakup 160 Myr ago as the probable source of the K/T impactor.

PubMed

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

2007-09-06

The terrestrial and lunar cratering rate is often assumed to have been nearly constant over the past 3 Gyr. Different lines of evidence, however, suggest that the impact flux from kilometre-sized bodies increased by at least a factor of two over the long-term average during the past approximately 100 Myr. Here we argue that this apparent surge was triggered by the catastrophic disruption of the parent body of the asteroid Baptistina, which we infer was a approximately 170-km-diameter body (carbonaceous-chondrite-like) that broke up 160(-20)+30Myr ago in the inner main asteroid belt. Fragments produced by the collision were slowly delivered by dynamical processes to orbits where they could strike the terrestrial planets. We find that this asteroid shower is the most likely source (>90 per cent probability) of the Chicxulub impactor that produced the Cretaceous/Tertiary (K/T) mass extinction event 65 Myr ago.

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.

Discovery of the triple asteroidal system 87 Sylvia.

PubMed

Marchis, Franck; Descamps, Pascal; Hestroffer, Daniel; Berthier, Jérome

2005-08-11

After decades of speculation, the existence of binary asteroids has been observationally confirmed, with examples in all minor planet populations. However, no triple systems have hitherto been discovered. Here we report the unambiguous detection of a triple asteroidal system in the main belt, composed of a 280-km primary (87 Sylvia) and two small moonlets orbiting at 710 and 1,360 km. We estimate their orbital elements and use them to refine the shape of the primary body. Both orbits are equatorial, circular and prograde, suggesting a common origin. Using the orbital information to estimate its mass and density, 87 Sylvia appears to have a rubble-pile structure with a porosity of 25-60 per cent. The system was most probably formed through the disruptive collision of a parent asteroid, with the new primary resulting from accretion of fragments, while the moonlets are formed from the debris, as has been predicted previously.

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].

Constraints on the Detection of the Solar Nebula's Oxidation State Through Asteroid Observations

NASA Technical Reports Server (NTRS)

Abell, P. A.; Gaffey, M. J.; Hardersen, P. S.

2005-01-01

Introduction: Asteroids represent the only in situ surviving population of planetesimals from the formation of the inner solar system and therefore include materials from the very earliest stages of solar system formation. Hence, these bodies can provide constraints on the processes and conditions that were present during this epoch and can be used to test current models and theories describing the late solar nebula, the early solar system and subsequent planetary accretion. From detailed knowledge of asteroid mineralogic compositions the probable starting materials, thermal histories, and oxidation states of asteroid parent bodies can be inferred. If such data can be obtained from specific mainbelt source regions, then this information can be used to map out the formation conditions of the late solar nebula within the inner solar system and possibly distinguish any trends in oxidation state that may be present.

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

NASA Astrophysics Data System (ADS)

Ševeček, P.; Brož, M.; Nesvorný, D.; Enke, B.; Durda, D.; Walsh, K.; Richardson, D. C.

2017-11-01

We report on our study of asteroidal breakups, i.e. fragmentations of targets, subsequent gravitational reaccumulation and formation of small asteroid families. We focused on parent bodies with diameters Dpb = 10km . Simulations were performed with a smoothed-particle hydrodynamics (SPH) code combined with an efficient N-body integrator. We assumed various projectile sizes, impact velocities and impact angles (125 runs in total). Resulting size-frequency distributions are significantly different from scaled-down simulations with Dpb = 100km targets (Durda et al., 2007). 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 for N-body simulations of small asteroid families. Finally, we discuss a number of uncertainties related to SPH simulations.

The Steward Observatory asteroid relational database

NASA Technical Reports Server (NTRS)

Sykes, Mark V.; Alvarezdelcastillo, Elizabeth M.

1992-01-01

The Steward Observatory Asteroid Relational Database (SOARD) was created as a flexible tool for undertaking studies of asteroid populations and sub-populations, to probe the biases intrinsic to asteroid databases, to ascertain the completeness of data pertaining to specific problems, to aid in the development of observational programs, and to develop pedagogical materials. To date SOARD has compiled an extensive list of data available on asteroids and made it accessible through a single menu-driven database program. Users may obtain tailored lists of asteroid properties for any subset of asteroids or output files which are suitable for plotting spectral data on individual asteroids. A browse capability allows the user to explore the contents of any data file. SOARD offers, also, an asteroid bibliography containing about 13,000 references. The program has online help as well as user and programmer documentation manuals. SOARD continues to provide data to fulfill requests by members of the astronomical community and will continue to grow as data is added to the database and new features are added to the program.

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.

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.

COMPASS Final Report: Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER)

NASA Technical Reports Server (NTRS)

Oleson, Steven R.; McGuire, Melissa L.

2009-01-01

In this study, the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team completed a design for a multi-asteroid (Nereus and 1996 FG3) sample return capable spacecraft for the NASA In-Space Propulsion Office. The objective of the study was to support technology development and assess the relative benefits of different electric propulsion systems on asteroid sample return design. The design uses a single, heritage Orion solar array (SA) (approx.6.5 kW at 1 AU) to power a single NASA Evolutionary Xenon Thruster ((NEXT) a spare NEXT is carried) to propel a lander to two near Earth asteroids. After landing and gathering science samples, the Solar Electric Propulsion (SEP) vehicle spirals back to Earth where it drops off the first sample s return capsule and performs an Earth flyby to assist the craft in rendezvousing with a second asteroid, which is then sampled. The second sample is returned in a similar fashion. The vehicle, dubbed Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER), easily fits in an Atlas 401 launcher and its cost estimates put the mission in the New Frontier s (NF's) class mission.

On possible parent bodies of Innisfree, Lost City and Prgibram meteorites.

NASA Astrophysics Data System (ADS)

Rozaev, A. E.

1994-12-01

Minor planets 1981 ET3 and Seleucus are possible parent bodies of Innisfree and Lost City meteorites, asteroid Mithra is the most probable source of Prgibram meteorite. The conclusions are based on the Southworth - Hawkins criterion with taking into account of the motion constants (Tisserand coefficient, etc.) and minimal distances between orbits at present time.

Oxygen isotope variation in stony-iron meteorites.

PubMed

Greenwood, R C; Franchi, I A; Jambon, A; Barrat, J A; Burbine, T H

2006-09-22

Asteroidal material, delivered to Earth as meteorites, preserves a record of the earliest stages of planetary formation. High-precision oxygen isotope analyses for the two major groups of stony-iron meteorites (main-group pallasites and mesosiderites) demonstrate that each group is from a distinct asteroidal source. Mesosiderites are isotopically identical to the howardite-eucrite-diogenite clan and, like them, are probably derived from the asteroid 4 Vesta. Main-group pallasites represent intermixed core-mantle material from a single disrupted asteroid and have no known equivalents among the basaltic meteorites. The stony-iron meteorites demonstrate that intense asteroidal deformation accompanied planetary accretion in the early Solar System.

Asteroid detection using a single multi-wavelength CCD scan

NASA Astrophysics Data System (ADS)

Melton, Jonathan

2016-09-01

Asteroid detection is a topic of great interest due to the possibility of diverting possibly dangerous asteroids or mining potentially lucrative ones. Currently, asteroid detection is generally performed by taking multiple images of the same patch of sky separated by 10-15 minutes, then subtracting the images to find movement. However, this is time consuming because of the need to revisit the same area multiple times per night. This paper describes an algorithm that can detect asteroids using a single CCD camera scan, thus cutting down on the time and cost of an asteroid survey. The algorithm is based on the fact that some telescopes scan the sky at multiple wavelengths with a small time separation between the wavelength components. As a result, an object moving with sufficient speed will appear in different places in different wavelength components of the same image. Using image processing techniques we detect the centroids of points of light in the first component and compare these positions to the centroids in the other components using a nearest neighbor algorithm. The algorithm was used on a test set of 49 images obtained from the Sloan telescope in New Mexico and found 100% of known asteroids with only 3 false positives. This algorithm has the advantage of decreasing the amount of time required to perform an asteroid scan, thus allowing more sky to be scanned in the same amount of time or freeing a telescope for other pursuits.

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.

Meteorite-asteroid spectral comparison - The effects of comminution, melting, and recrystallization

NASA Technical Reports Server (NTRS)

Clark, Beth E.; Fanale, Fraser P.; Salisbury, John W.

1992-01-01

The present laboratory simulation of possible spectral-alteration effects on the optical surface of ordinary chondrite parent bodies duplicated regolith processes through comminution of the samples to finer rain sizes. After reflectance spectra characterization, the comminuted samples were melted, crystallized, recomminuted, and again characterized. While individual spectral characteristics could be significantly changed by these processes, no combination of the alteration procedures appeared capable of affecting all relevant parameters in a way that improved the match between chondritic meteorites and S-class asteroids.

A Breccia of Ureilitic and C2 Carbonaceous Chondrite Materials from Almahata Sitta: Implications for the Regolith of Urelitic Asteroids

NASA Technical Reports Server (NTRS)

Goodrich, C. A.; Fioretti, A. M.; Zolensky, M.; Fries, M.; Shaddad, M.; Kohl, I.; Young, E.; Jenniskens, P.

2017-01-01

The Almahata Sitta (AhS) polymict ureilite is the first meteorite to originate from a spectrally classified asteroid (2008 TC3) [1-3], and provides an unprecedented opportunity to correlate properties of meteorites with those of their parent asteroid. AhS is also unique because its fragments comprise a wide variety of meteorite types. Of approximately140 stones studied to-date, 70% are ureilites (carbon-rich ultramafic achondrites) and 30% are various types of chondrites [4,5]. None of these show contacts between ureilitic and chondritic lithologies. It has been inferred that 2008 TC3 was loosely aggregated, so that it disintegrated in the atmosphere and only its most coherent clasts fell as individual stones [1,3,5]. Understanding the structure and composition of this asteroid is critical for missions to sample asteroid surfaces. We are studying [6] the University of Khartoum collection of AhS [3] to test hypotheses for the nature of 2008 TC3. We describe a sample that consists of both ureilitic and chondritic materials.

On the concept of material strength and first simulations of asteroid disruption with explicit formation of spinning aggregates in the gravity regime

NASA Astrophysics Data System (ADS)

Michel, P.; Richardson, D. C.

2007-08-01

During their evolutions, the small bodies of our Solar System are affected by several mechanisms which can modify their properties. While dynamical mechanisms are at the origin of their orbital variations, there are other mechanisms which can change their shape, spin, and even their size when their strength threshold is reached, resulting in their disruption. Such mechanisms have been identified and studied, both by analytical and numerical tools. The main mechanisms that can result in the disruption of a small body are collisional events, tidal perturbations, and spin-ups. However, the efficiency of these mechanisms depends on the strength of the material constituing the small body, which also plays a role in its possible equilibrium shape. We will present several important aspects of material strength that are believed to be adapted to Solar System small bodies and briefly review the most recent studies of the different mechanisms that can be at the origin of the disruption of these bodies. In particular, we have recently made a major improvement in the simulations of asteroid disruption by computing explicitly the formation of aggregates during the gravitational reaccumulation of small fragments, allowing us to obtain information on their spin, the number of boulders composing them or lying on their surface, and their shape.We will present the first and preliminary results of this process taking as examples some asteroid families that we reproduced successfully with our previous simulations (Michel et al. 2001, 2002, 2003, 2004a,b), and their possible implications on the properties of asteroids generated by a disruption. Such information 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 fragment of a larger parent body. It is also clear that future space missions to small bodies devoted to precise in-situ analysis and sample return will allow us to improve our understanding on the physical properties of these objects, and to check whether our theoretical and numerical works are valid. References Michel P., BenzW., Tanga P., Richardson D.C. 2001. Collisions and gravitational reaccumulation: forming asteroid families and satellites. Science 294 1696-1700 (+cover of the journal). Michel P., Benz W., Tanga P., Richardson D.C. 2002. Formation of asteroid families by catastrophic disruption: simulations with fragmentation and gravitational reaccumulation. Icarus 160, 10-23. Michel P., Benz W., Richardson D.C. 2003. Fragmented parent bodies as the origin of asteroid families. Nature 421, 608-611 (+cover of the journal). Michel P., BenzW., Richardson D.C. 2004a. Disruption of pre-shattered parent bodies. Icarus 168, 420-432. Michel P., Benz W., Richardson D.C. 2004b. Catastrophic disruptions and family formation: a review of numerical simulations including both fragmentation and gravitational reaccumulations. Planet. Space. Sci. 52, 1109-1117.

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.

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.

Asteroid Spectroscopy: A Declaration of Independence

NASA Astrophysics Data System (ADS)

Bell, J. F.

1995-09-01

One of the shibboleths of asteroid spectroscopy for the past 25 years has been that a detailed knowledge of meteoritics is essential for proper interpretation of asteroid spectra. In fact, several recent spectroscopic discoveries have overturned long-standing models based on popular interpretations of meteorite data. A case can be made that spectroscopists could have made much faster progress if they had worked in total isolation from meteoritics. Consider the first three spectral classes identified in the 1970s: Vesta: The very first asteroid spectrum was unambigously basaltic, yet some meteoriticists have persistently resisted the obvious conclusion that the HED clan comes from Vesta, because A) Vesta is "impossibly" far from the known dynamical escape hatches; and B) the HED O-isotope data "establishes" a lirlk with pallasites and IIIAB irons, suggesting that their parent was some other completely disrupted asteroid. The discovery of a "dynamically impossible" extended family of basaltic fragments extending from Vesta to the 3:1 resonance [1] makes it clear that HEDs must originate on Vesta, and that dynamical, physical and isotopic arguments all led in the wrong direction. Stony: In the early 1970s meteorite fall statistics led to an expectation that many of the larger asteroids would be ordinary chondrites. When the most common class of asteroids proved to have silicate absorption bands, many concluded that these objects were the expected ordinary chondrite parent asteroids. The later discovery that S-type spectra do not actually resemble OCs was rationalized with imaginary "space weathering" processes (which have never been observed or simulated despite 20 years of wasted effort). Now that the real weathering trends in S asteroids have been resolved [2] and asteroids which actually do look like OCs discovered [3], it is clear that the eDhre controversy over S asteroid composition was a blind alley that could have been avoided by taking the spectra at face value. Carbonaceous: These asteroids were interpreted as "carbonaceous chondrites", due to a superficial resemblance in spectral shape and their lesser abundance than S-types. Later it was shown that the most common CCs, COs and CVs, actually fall into the classical S class (now broken off as a separate K class). But Cs and the related G, B, and F classes have been persistently interpreted as CM/CI analogs even though their only resolvable spectral feature is much shallower than that of the CM/CI meteontes. This difference has been rationalized with more "space weathering" processes. However, recently rare highly metamorphosed CCs have been shown to match the C-G-B-F asteroid without "weathering"[4], suggesting that CIs and CMs come from some small, undiscovered class of outer belt asteroids analagous to Qs in the inner belt. These examples demonstrate an evolution of our thinking from belief in a close relationship between the meteorite population and the asteroids (with any discordant results from the telescope explained away by ad hoc mechanisms), toward a model in which the gigantic meteorite data set is seen as highly biased and non-representative of the asteroid belt, and in many cases useless due to the multiple possible interpretations of the same data. It is time for a more balanced approach to asteroid science, in which meteoritics plays a supplementary role to direct studies of asteroids, rather that the dominant one it has to date. References: [1] Binzel et al. (1993) Science, 260, 186-191. [2] Gaffey M. J. et. al. (1994) Icarus, 106, 573-602. [3] Binzel R. P. et al. (1994) Science, 262, 1541-1543. [4] Hiroi T. et al. (1993) LPS XXIV, 659-660.

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.

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.

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.

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.

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.

Size scales over which ordinary chondrites and their parent asteroids are homogeneous in oxidation state and oxygen-isotopic composition

NASA Astrophysics Data System (ADS)

Rubin, Alan E.; Ziegler, Karen; Young, Edward D.

2008-02-01

Literature data demonstrate that on a global, asteroid-wide scale (plausibly on the order of 100 km), ordinary chondrites (OC) have heterogeneous oxidation states and O-isotopic compositions (represented, respectively, by the mean olivine Fa and bulk Δ 17O compositions of equilibrated samples). Samples analyzed here include: (a) two H5 chondrite Antarctic finds (ALHA79046 and TIL 82415) that have the same cosmic-ray exposure age (7.6 Ma) and were probably within ˜1 km of each other when they were excavated from the H-chondrite parent body, (b) different individual stones from the Holbrook L/LL6 fall that were probably within ˜1 m of each other when their parent meteoroid penetrated the Earth's atmosphere, and (c) drill cores from a large slab of the Estacado H6 find located within a few tens of centimeters of each other. Our results indicate that OC are heterogeneous in their bulk oxidation state and O-isotopic composition on 100-km-size scales, but homogeneous on meter-, decimeter- and centimeter-size scales. (On kilometer size scales, oxidation state is heterogeneous, but O isotopes appear to be homogeneous.) The asteroid-wide heterogeneity in oxidation state and O-isotopic composition was inherited from the solar nebula. The homogeneity on small size scales was probably caused in part by fluid-assisted metamorphism and mainly by impact-gardening processes (which are most effective at mixing target materials on scales of ⩽1 m).

Photoelectric and CCD observations of 10 asteroids

NASA Astrophysics Data System (ADS)

de Sanctis, M. C.; Barucci, M. A.; Angeli, C. A.; Fulchignoni, M.; Burchi, R.; Angelini, P.

1994-10-01

A program of physical studies of asteroids has been carried out using two types of detectors: photoelectric photometer and CCD camera. In this paper we report the results of photometric observations of 10 asteroids. We have obtained a total of 35 single night lightcurves and we have determined rotational periods for the asteroids 1520 Imatra (P = 5.23 h), 1534 Nasi (P = 9.75 h), 2078 Nanking (P = 6.473 h), 2241 Alcathous (P = 9.41 h), 3103 1982 BB (P = 5.709 h), 3139 Shantou (P = 8.33 h), 3259 Brownlee (P = 9.24 h), 4455 Ruriko (P = 4.23 h).

Near infrared reflectance spectra: Applications to problems in asteroid-meteorite relationships

NASA Technical Reports Server (NTRS)

Mcfadden, Lucy A.; Chamberlin, Alan B.

1992-01-01

An observing program designed to search for evidence of ordinary chondrite parent bodies near the 3:1 Kirkwood Gap was carried out in 1985 and 1986. Studies by Wisdom (1985), Wetherill (1985), and subsequent work by Milani et al. (1989) indicate that the 3:1 Kirkwood gap is the most probable source region for the majority of ordinary chondrite meteorites. The diversity of the reflectance spectra among this small data set is surprising. Early work by Gaffey and McCord (1978) showed that the inner region of the main asteroid belt is dominated by high albedo objects with mafic silicate surfaces. One would expect to see mostly spectra with 1- and 2-micron absorption bands based on this earlier work. Only 5 (of 12) spectra have these expected features. The distribution of taxonomic types presented by Gradie and Tedesco (1982) is in most cases a useful simplification of the compositional structure of the asteroid belt. The range of spectral characteristics seen with higher resolution in the near-IR has not been previously reported and is not represented in the standard asteroid taxonomy. Near-IR spectra contain valuable mineralogical information which enhances knowledge of the composition and structure of asteroids.

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.

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.

Speckle interferometry applied to asteroids and other solar system objects

NASA Technical Reports Server (NTRS)

Drummond, J. D.; Hege, E. K.

1986-01-01

Speckle interferometry is a high angular resolution technique that allows study of resolved asteroids. By following the changing size, shape, and orientation of minor planets, and with a few general assumptions (e.g., geometric scattering, triaxial ellipsoid figures, no albedo features), it is possible to directly measure an asteroid's true dimensions and the direction of its spin axis in one or two nights. A particular subset of triaxial ellipsoid figures are equilibrium shapes, and would imply that some asteroids are thoroughly fractured. Such shapes if they exist among the asteroids would allow a determination of bulk density since there is a unique relation among spin period, size, shape, and density. The discovery of even a single rubble pile, (just as the finding of even one binary asteroid by speckle interferometric techniques) would drastically alter the notion of asteroids as small solid planets. The Pluto/Charon system was studied to aid in improving the orbital elements necessary to predict the eclipse/occultation season currently in progress. Four asteroids were reduced to their size, shape, and pole direction: 433 Eros, 532 Herculina, 511 Davida, and 2 Pallas.

The Origin of Asteroid 101955 (1999 RQ36)

NASA Astrophysics Data System (ADS)

Campins, Humberto; Morbidelli, A.; de León, J.; Tsiganis, K.; Licandro, J.

2010-10-01

Near-Earth asteroid 101955 (1999 RQ36; henceforth RQ36) is particularly interesting. It's especially accessible to spacecraft and is the primary target of NASA's OSIRIS-REx sample return mission; it's also a potentially hazardous asteroid (Milani et al. 2009). We combine dynamical and spectral information to identify the most likely main-belt origin of RQ36 and conclude that it is the Polana family, located at a semi-major axis of about 2.42 AU (our approach is similar to that used by de León et al. (2010) to link 3200 Phaethon, parent body of the Geminids, to 2 Pallas). Our conclusion is based on the following results. a) Dynamical evidence favors strongly an inner-belt, low-inclination (2.15 AU < a < 2.5 AU and i < 10 degrees) origin, suggesting the ν6 resonance as the preferred (95% probability) delivery route. b) This region is dominated by the Nysa and Polana families (families are favored over single objects because small fragments have already been produced). c) The Polana family is characterized by low albedos and B-class spectra or colors (Bus and Binzel 2002), which is the same spectral class, and albedo, as RQ36. d) The SDSS colors show that the Polana family is the branch of the Nysa-Polana complex that extends toward the ν6 resonance; furthermore, Polana has delivered objects the size of RQ36 and larger into the ν6 resonance. e) RQ36 is retrograde, consistent with the Yarkovsky effect having moved it inward from Polana into the ν6. f) A quantitative comparison of visible and near-infrared spectra does not yield a unique match for RQ36; however, it is consistent with a compositional link between RQ36 and the Polana family. Finally, the Polana Family is likely the most important inner-belt source of low albedo Near-Earth asteroids. This work was supported by NASA and NSF.

Understanding asteroid collisional history through experimental and numerical studies

NASA Technical Reports Server (NTRS)

Davis, Donald R.; Ryan, Eileen V.; Weidenschilling, S. J.

1991-01-01

Asteroids can lose angular momentum due to so called splash effect, the analog to the drain effect for cratering impacts. Numerical code with the splash effect incorporated was applied to study the simultaneous evolution of asteroid sized and spins. Results are presented on the spin changes of asteroids due to various physical effects that are incorporated in the described model. The goal was to understand the interplay between the evolution of sizes and spins over a wide and plausible range of model parameters. A single starting population was used both for size distribution and the spin distribution of asteroids and the changes in the spins were calculated over solar system history for different model parameters. It is shown that there is a strong coupling between the size and spin evolution, that the observed relative spindown of asteroids approximately 100 km diameter is likely to be the result of the angular momentum splash effect.

Understanding asteroid collisional history through experimental and numerical studies

NASA Astrophysics Data System (ADS)

Davis, Donald R.; Ryan, Eileen V.; Weidenschilling, S. J.

1991-06-01

Asteroids can lose angular momentum due to so called splash effect, the analog to the drain effect for cratering impacts. Numerical code with the splash effect incorporated was applied to study the simultaneous evolution of asteroid sized and spins. Results are presented on the spin changes of asteroids due to various physical effects that are incorporated in the described model. The goal was to understand the interplay between the evolution of sizes and spins over a wide and plausible range of model parameters. A single starting population was used both for size distribution and the spin distribution of asteroids and the changes in the spins were calculated over solar system history for different model parameters. It is shown that there is a strong coupling between the size and spin evolution, that the observed relative spindown of asteroids approximately 100 km diameter is likely to be the result of the angular momentum splash effect.

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.

The Origin of Chondrites: Metal-Silicate Separation Experiments Under Microgravity Conditions, Experiment 2

NASA Technical Reports Server (NTRS)

Moore, S. R.; Franzen, M.; Benoit, P. H.; Sears, D. W. G.; Holley, A.; Myers, M.; Godsey, R.; Czlapinski, J.

2003-01-01

Chondrites are categorized into different groups by several properties, including the metal-to-silicate ratio. Various processes have been suggested to produce distinct metal/silicate ratios, some based on sorting in the early solar nebular and others occurring after accretion on the parent body. Huang et al. suggested that a weak gravitational field accompanied by degassing, could result in metal/silicate separation on parent bodies. We suggest that asteroids were volatile-rich, at least early in their histories. Spectroscopic evidence from asteroid surfaces indicates that one-third of all asteroids maybe rich in clays and hydrated minerals, similar to carbonaceous chondrites. Internal and/or external heating could have caused volatiles to evaporate and pass through a surface dust layer. Spacecraft images of asteroids show they have a thick regoliths. Housen, and Asphaug and Nolan proposed that even a 10 km diameter asteroid could potentially have a significant regolith. Grain size and grain density sorting could occur in the unconsolidated layer by the process known as fluidization. This process occurs when an upward stream of gas is passed through a bed of particles which are lifted against a gravitational force. Fluidization is commonly used commercially to sort particulates. This type of behavior is based upon the bed, as a whole, and differs from aerodynamic sorting. Two sets of reduced gravity experiments were conducted during parabolic flights aboard NASA's KC-135 aircraft. The first experiment employed 310 tubes of 2.5 cm diameter, containing mixtures of sand and metal grains. A gas source was used to fluidize the mixture at reduced gravity conditions and mixtures were analyzed after the flight. However, this experiment did not allow a description of the fluidization as a function of gravity. A second experiment was conducted on the KC-135 aircraft in the summer of 2001, consisting of two Plexiglas cylinders containing a metal/silicate mixture, and video cameras to record the experiment on tape. Here we summarize this experiment and discusses the implications for metalsilicate separation on asteroid bodies.

A Mudball Model for the Evolution of Carbonaceous Asteroids

NASA Astrophysics Data System (ADS)

Travis, B. J.; Bland, P. A.

2018-05-01

We simulation the evolution of carbonaceous chondrite parent bodies from initially unconsolidated aggregations of rock grains and ice crystals. Application of the numerical model MAGHNUM to evolution of CM type planetesimals and Ceres is described.

Primordial heating of asteroidal parent bodies

NASA Technical Reports Server (NTRS)

Sonett, C. P.; Reynolds, R. T.

1979-01-01

Most meteorites show evidence of thermal processing either because of metamorphic changes or as a result of melting and differentiation. Proposed mechanisms for supplying this energy generally rely upon short-lived radioisotopes or electrical induction, though accretion is sometimes mentioned, and more exotic models have been discussed. Interest in isotopic heating has been heightened by the discovery of Al-26 in Allende inclusions and also by the proposal that a lunar core and dynamo resulted from the radioactive decay of superheavy elements during the early solar system. Electrical induction as a heat source can be scaled to a broad range of solar system conditions, but corroborative evidence for these conditions is inconclusive. The accretion mechanism is probably not viable for the asteroidal and meteorite parent bodies, because the high kinetic energy requirement is inconsistent with the formation of the objects and their regoliths in the presence of a weak gravitational field.

A preliminary assessment of asteroid shapes produced by impact disruption and re-creation: Application to the AIDA target.

NASA Astrophysics Data System (ADS)

Barnouin, Olivier; Michel, Patrick; Richardson, Derek

2016-04-01

In order to understand the origin of the 65803 Didymos, the target of the Asteroid Impact and Deflection Assessment mission, and gain insights on the origin and evolution of the asteroid's162173 Ryugu and 101955 Bennu, we investigate systematically the shapes of all re-accumulated fragments produced by the catastrophic disruption of a parent body that is 1 km in diameter or larger. These new fragments eventually become new asteroids of the size that current sample-return missions plan to explore. We choose a range of impact conditions by varying the parent bodies' strength, size and porosity, and the velocity and size of the projectile. Impact conditions range from near the catastrophic threshold, usually designated by Q*, where half of the target's mass escapes, to far greater values above this threshold. Our numerical investigations of the catastrophic disruption, which are undertaken using an SPH hydrocode, include a model of fragmentation for porous materials. The gravitationally dominated phase of reaccumulation of our asteroids is computed using the N-body code pkdgrav. At sufficiently slow impact speeds in the N-body model, particles are permitted to stick, forming irregular, competent pieces that can gather into non-idealized rubble piles as a result of re-accumulation. Shape and spin information of re-accumulated bodies are thus preserved. Due to numerical expense, this first study uses what we call a hard-sphere model, rather than a soft-sphere spring and dashpot model. This latter model is more commonly used in granular flow simulations for which detailed treatment of the multicontact physics is needed, which is not the case here, and comes at the expense of much smaller timesteps. With the hard-sphere model, there are three supported collision outcomes for bonded aggregates: sticking on contact (to grow the aggregate); bouncing (computed for these generally non-central impacts); and fragmentation (wherein the particles involved become detached from their respective aggregates and proceed to bounce as rigid spheres, possibly releasing more particles). We adjusted the strength of the forming aggregates to the measured strength of materials in the lab, scaled to the aggregate size, by using strength size scaling rules. In the future we expect to compare our hard-sphere models to a few soft-sphere for reasonable granular materials to best characterize differences between the two approaches, if any. Our results indicate that while 25143 Itokawa-like potato-shaped asteroids are typically the outcome of disruption, often more spherical or "top-shaped" asteroids can also be produced. Our results confirm what others have already noted, namely that a "top-shaped" or diamond shaped asteroid is not necessarily the result of the formation of YORP spin-up. Other criteria besides just shape need to be developed to determine whether or not the evolution of an asteroid and its surface geology have been dominated by YORP-related processes or by impact-derived re-accretion.

Angrites: A Volatile-rich Variety of Asteroidal Basalt (Except for Alkalis and Gallium!)

NASA Astrophysics Data System (ADS)

Warren, P. H.; Kallemeyn, G. W.

1995-09-01

Angrites are commonly viewed as extremely volatile-depleted, and a related notion is that they formed by differentiation of a very CAI-rich material [e.g., 1]. Partial melting experiments reportedly reproduce the bulk compositions (although not fassaite-rich mineralogy) of angrites with Allende as starting material [2], but highly CAI-rich parent materials are difficult to reconcile with isotopic and REE data [3,4]. Mittlefehldt and Lindstrom [5] inferred from the low Na/Al ratios of angrites that outgassing, and thus primordial magmatism, was more intense on their parent body than on the eucrite parent asteroid. Of seven elements that (a) have been adequately determined in angrites, and (b) are far more volatile (solar-nebula 50% condensation T [6] = 690-430 K) than the alkalis (1000-910 K), four are enriched, and none is significantly depleted, in average angrite compared to average eucrite or low-Ti mare basalt (Figure). Gallium, which is of intermediate volatility (830 K), is depleted to roughly the same extent as Na and K. Results for A881371 [3] are incomplete (Zn, 6 micrograms/g, is near INAA detection limit), but even based only on AdoR and the two LEW angrites, this pattern seems firmly established. Apparent gas cavities in A881371 [7] also suggest that volatiles are far from uniformly depleted. The only elements known to be depleted, as volatiles, by clearly significant factors in angrites versus eucrites or lunar basalts, are alkalis plus gallium. Besides being moderately volatile, a noteworthy characteristic shared among Ga and alkalis (and not shared with elements such as Br, Se, and Zn) is that these elements probably tend to partition into crustal feldspar during gross differentiation of small (low-pressure) bodies. If gallium + alkalis were depleted by a single process starting from "normal" chondritic material, that process would seem to require selective exposure of a feldspar-enriched region (i.e., crust) to extremely high temperature. Igneous crystallization of the angrites occurred when the solar system was still extremely young, and apparently <=2 Ma after the volatile-depletion process [4]. The data of [4] eliminate 26Al as a potential heat source for magmatism. The angrite volatile pattern may be the product of heating by an intense, short-lived heat source that melted and partially vaporized the crust of an asteroid(s) (not necessarily the final angrite asteroid), without much affecting the deep interior(s), which later (through mixing and/or magmatism) replenished the angritic materials in most volatiles, but not alkalis and Ga. Exogenic heating, as in the often-conjectured (but hard to test) hypothesis that a major early heat source was enhanced solar luminosity (as in FU-Orionis cycles), would seem to be required. LEW 87051 and A881371 are rich in compositionally diverse olivine xenocrysts, and A881371 contains a possible FeS xenocryst [7]. These, and the angrites' great siderophile diversity [3], tend to suggest that magmatism and intensely disruptive cratering (with mixing of precursor materials) were contemporaneous. This scenario is admittedly speculative, but the volatile-depletion pattern is difficult to rationalize with any other model. References: [1] Prinz M. and Weisberg M. (1995) Antarct. Meteorites, XX, 207-210. [2] Jurewicz A. et al. (1993) GCA, 57, 2123-2139. [3] Warren P. et al. (1995) Antarct. Meteorites, XX, 261-264. [4] Lugmair G. and Galer S. 1992) GCA, 56, 1673-1694. [5] Mittlefehldt D. and Lindstrom M. (1990) GCA, 54, 3209-3218. [6] Wasson J. (1985) Meteorites. [7] Warren P. and Davis A. (1995) Antarct. Meteorites, XX, 257-260.

Colorimetry and magnitudes of asteroids

NASA Technical Reports Server (NTRS)

Bowell, E.; Lumme, K.

1979-01-01

In the present paper, 1500 UBV observations are analyzed by a new rather general multiple scattering theory which provided clear insight into previously poorly-recognized optical nature of asteroid surfaces. Thus, phase curves are shown to consist of a surface-texture controlled component, due to singly scattered light, and a component due to multiple scattering. Phase curve shapes can be characterized by a single parameter, the multiple scattering factor, Q. As Q increases, the relative importance of the opposition effect diminishes. Asteroid surfaces are particulate and strikingly similar to texture, being moderately porous and moderately rough on a scale greater than the wavelength of light. In concequence, Q (and also the phase coefficient) correlate well with geometric albedo, and there exists a purely photometric means of determining albedos and diameters.

Mission Concepts and Operations for Asteroid Mitigation Involving Multiple Gravity Tractors

NASA Technical Reports Server (NTRS)

Foster, Cyrus; Bellerose, Julie; Jaroux, Belgacem; Mauro, David

2012-01-01

The gravity tractor concept is a proposed method to deflect an imminent asteroid impact through gravitational tugging over a time scale of years. In this study, we present mission scenarios and operational considerations for asteroid mitigation efforts involving multiple gravity tractors. We quantify the deflection performance improvement provided by a multiple gravity tractor campaign and assess its sensitivity to staggered launches. We next explore several proximity operation strategies to accommodate multiple gravity tractors at a single asteroid including formation-flying and mechanically-docked configurations. Finally, we utilize 99942 Apophis as an illustrative example to assess the performance of a multiple gravity tractor campaign.

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

Identifying the Parent Body of the Tagish Lake Meteorite and Characterizing its Internal Heating History and Surface Processes

NASA Technical Reports Server (NTRS)

Hiroi, Takahiro

2004-01-01

This short (1-year) funded research encompassed laboratory measurements of the Tagish Lake meteorite samples, experiments of simulated space weathering on them, and comparison with D, T, and P asteroids in reflectance spectrum. In spite of its limited funding and period, we have performed said experiments here at Brown University and at University of Tokyo. Some of the major results were reported at the Lunar and Planetary Science Conference held in Houston in March, 2004. The Tagish Lake meteorite shows a unique visible reflectance spectrum identical to that of the D and T type asteroids. After the present heating experiments at even the lowest temperature of 100 C, the characteristic spectral slope of the Tagish Lake meteorite sample increased. On the other hand, after irradiating its pellet sample with pulse laser, the slope decreased. As the result, the Tagish Lake meteorite and its processed samples have come to cover a wide range of visible reflectance spectra in slope from the C-type asteroids to some extreme T/D-type asteroids, including the P-type asteroids in between. Therefore, logically speaking, our initial affirmation that the Tagish Lake meteorite must have come from one of the D-type asteroids can be wrong if such a meteoritic material is hidden under a space-weathered surface regolith of a C-type asteroid. However, such a case is likely to have a small probability in general. Other major hits of this research includes the first spectral fitting of the P-type asteroids using reflectance spectra derived from the present research. This topic needs more experiments and analysis to be addressed uniquely, and thus further efforts will be proposed.

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.

Iron meteorites as remnants of planetesimals formed in the terrestrial planet region.

PubMed

Bottke, William F; Nesvorný, David; Grimm, Robert E; Morbidelli, Alessandro; O'Brien, David P

2006-02-16

Iron meteorites are core fragments from differentiated and subsequently disrupted planetesimals. The parent bodies are usually assumed to have formed in the main asteroid belt, which is the source of most meteorites. Observational evidence, however, does not indicate that differentiated bodies or their fragments were ever common there. This view is also difficult to reconcile with the fact that the parent bodies of iron meteorites were as small as 20 km in diameter and that they formed 1-2 Myr earlier than the parent bodies of the ordinary chondrites. Here we show that the iron-meteorite parent bodies most probably formed in the terrestrial planet region. Fast accretion times there allowed small planetesimals to melt early in Solar System history by the decay of short-lived radionuclides (such as 26Al, 60Fe). The protoplanets emerging from this population not only induced collisional evolution among the remaining planetesimals but also scattered some of the survivors into the main belt, where they stayed for billions of years before escaping via a combination of collisions, Yarkovsky thermal forces, and resonances. We predict that some asteroids are main-belt interlopers (such as (4) Vesta). A select few may even be remnants of the long-lost precursor material that formed the Earth.

Interpretations of family size distributions: The Datura example

NASA Astrophysics Data System (ADS)

Henych, Tomáš; Holsapple, Keith A.

2018-04-01

Young asteroid families are unique sources of information about fragmentation physics and the structure of their parent bodies, since their physical properties have not changed much since their birth. Families have different properties such as age, size, taxonomy, collision severity and others, and understanding the effect of those properties on our observations of the size-frequency distribution (SFD) of family fragments can give us important insights into the hypervelocity collision processes at scales we cannot achieve in our laboratories. Here we take as an example the very young Datura family, with a small 8-km parent body, and compare its size distribution to other families, with both large and small parent bodies, and created by both catastrophic and cratering formation events. We conclude that most likely explanation for the shallower size distribution compared to larger families is a more pronounced observational bias because of its small size. Its size distribution is perfectly normal when its parent body size is taken into account. We also discuss some other possibilities. In addition, we study another common feature: an offset or "bump" in the distribution occurring for a few of the larger elements. We hypothesize that it can be explained by a newly described regime of cratering, "spall cratering", which controls the majority of impact craters on the surface of small asteroids like Datura.

Mesosiderites on Vesta: A Hyperspectral VIS-NIR Investigation

NASA Technical Reports Server (NTRS)

Palomba, E.; Longobardo, A.; DeSanctis, M. C.; Mittlefehldt, D. W.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Frigeri, A.; Tosi, F.; Zambon, F.;

J6 Himalia: New Compositional Evidence and Interpretations for the Origin of Jupiter's Small Satellites

NASA Technical Reports Server (NTRS)

Vilas, Faith; Jarvis, K.; Larson, S.; Gaffey, M.

1999-01-01

New narrowband spectrophotometric data of J6 Himalia, some of which are spatially resolved, support its C-type classification. The new spectra confirm the presence of a weak absorption feature centered near 0.7 micron attributed to oxidized iron in phyllosilicates, products of aqueous alteration, which varies in depth on opposite sides of the satellite. Evaluation of older UBV photometry of J6 and J7 Elara compared to UBV photometry of C-class (and subclass) asteroids showing spectral evidence of the 0.7-microns absorption feature suggests that J6 Himalia is an F-class asteroid. We propose that the parent body of the prograde Jovian satellites originated as part of the Nysa asteroid family. Evolutionary models of the Jovian system are used to address the capture and dispersal of the irregular satellites.

Chelyabinsk meteorite explains unusual spectral properties of Baptistina Asteroid Family

NASA Astrophysics Data System (ADS)

Reddy, Vishnu; Sanchez, Juan A.; Bottke, William F.; Cloutis, Edward A.; Izawa, Matthew R. M.; O'Brien, David P.; Mann, Paul; Cuddy, Matthew; Le Corre, Lucille; Gaffey, Michael J.; Fujihara, Gary

2014-07-01

We investigated the spectral and compositional properties of Chelyabinsk meteorite to identify its possible parent body in the main asteroid belt. Our analysis shows that the meteorite contains two spectrally distinct but compositionally indistinguishable components of LL5 chondrite and shock blackened/impact melt material. Our X-ray diffraction analysis confirms that the two lithologies of the Chelyabinsk meteorite are extremely similar in modal mineralogy. The meteorite is compositionally similar to LL chondrite and its most probable parent asteroid in the main belt is a member of the Flora family. Our work confirms previous studies (e.g., Vernazza et al. [2008]. Nature 454, 858-860; de León, J., Licandro, J., Serra-Ricart, M., Pinilla-Alonso, N., Campins, H. [2010]. Astron. Astrophys. 517, A23; Dunn, T.L., Burbine, T.H., Bottke, W.F., Clark, J.P. [2013]. Icarus 222, 273-282), linking LL chondrites to the Flora family. Intimate mixture of LL5 chondrite and shock blackened/impact melt material from Chelyabinsk provides a spectral match with (8) Flora, the largest asteroid in the Flora family. The Baptistina family and Flora family overlap each other in dynamical space. Mineralogical analysis of (298) Baptistina and 11 small family members shows that their surface compositions are similar to LL chondrites, although their absorption bands are subdued and albedos lower when compared to typical S-type asteroids. A range of intimate mixtures of LL5 chondrite and shock blackened/impact melt material from Chelyabinsk provides spectral matches for all these BAF members. We suggest that the presence of a significant shock/impact melt component in the surface regolith of BAF members could be the cause of lower albedo and subdued absorption bands. The conceptual problem with part of this scenario is that impact melts are very rare within ordinary chondrites. Of the ∼42,000 ordinary chondrites, less than 0.5% (203) of them contain impact melts. A major reason that impact melts are rare in meteorites is that high impact velocities (V > 10 km/s) are needed to generate the necessary shock pressures and temperatures (e.g., Pierazzo, E., Melosh, H.J. [1998]. Hydrocode modeling of oblique impacts: The fate of the projectile. In: Origin of the Earth and Moon, Proceedings of the Conference. LPI Contribution No. 957) unless the target material is highly porous. Nearly all asteroid impacts within the main belt are at ∼5 km/s (Bottke, W.F., Nolan, M.C., Greenberg, R., Kolvoord, R.A. [1994]. Collisional lifetimes and impact statistics of near-Earth asteroids. In: Tucson, Gehrels T. (Ed.), Hazards Due to Comets and Asteroids. The University of Arizona Press, Arizona, pp. 337-357), which prevents them from producing much impact melt unless they are highly porous. However, shock darkening is an equally efficient process that takes place at much lower impact velocities (∼2 km/s) and can cause the observed spectral effects. Spectral effects of shock darkening and impact melt are identical. The parent asteroid of BAF was either a member of the Flora family or had the same basic composition as the Floras (LL Chondrite). The shock pressures produced during the impact event generated enough impact melt or shock blackening to alter the spectral properties of BAF, but keep the BAF composition largely unchanged. Collisional mixing of shock blackened/impact melt and LL5 chondritic material could have created the Baptistina Asteroid Family with composition identical to those of the Floras, but with subdued absorption bands. Shock darkening and impact melt play an important role in altering the spectral and albedo properties of ordinary chondrites and our work confirms earlier work by Britt and Pieters (Britt, D.T., Pieters, C.M. [1994]. Geochimica et Cosmochimica Acta 58, 3905-3919).

Nuclear cycler: An incremental approach to the deflection of asteroids

NASA Astrophysics Data System (ADS)

Vasile, Massimiliano; Thiry, Nicolas

2016-04-01

This paper introduces a novel deflection approach based on nuclear explosions: the nuclear cycler. The idea is to combine the effectiveness of nuclear explosions with the controllability and redundancy offered by slow push methods within an incremental deflection strategy. The paper will present an extended model for single nuclear stand-off explosions in the proximity of elongated ellipsoidal asteroids, and a family of natural formation orbits that allows the spacecraft to deploy multiple bombs while being shielded by the asteroid during the detonation.

Recent Asteroid Disruptions in the WISE Dataset - Constraining Asteroid Surface Properties Using Solar System Dust Bands

NASA Astrophysics Data System (ADS)

Kehoe, A. E.; Shaw, C.; Kehoe, T. J. J.

2017-12-01

Zodiacal dust bands are a fine-structure feature of the mid-IR emission profile of the zodiacal cloud. The dust bands have been studied for many years dating back to the InfraRed Astronomical Satellite (IRAS) data of the 1980's. The recent discovery and modeling (Espy et al., 2009; 2010; Espy Kehoe et al., 2015) of a very young, still-forming dust band structure has shown that, in the early stages following an asteroid disruption, much information on the dust parameters of the original disruption is retained in the band. Partial dust bands allow a never-before-seen observational look at the size distribution and cross-sectional area of dust produced in an asteroidal disruption, before it has been lost or significantly altered by orbital and collisional decay. The study of these partial band structures reveals information on the way asteroids disrupt and allow us to reconstruct the surface properties of the parent asteroid, including the depth of the surface regolith and the size distribution of particles composing the regolith. Using the greatly increased sensitivity of the Wide-field Infrared Survey Explorer (WISE), we can now detect much fainter (and thus younger) dust bands. The WISE data also reveals much better longitudinal resolution of the bands, allowing a better constraint on the source and age of the disruption. We will present our newest results from the WISE dataset, including detection of faint partial dust bands, improved models of more prominent bands, and our constraints on the asteroid surface properties from modeling these structures.

Accretion, Differentiation, and Impact Processes on the Ureilite Parent Body

NASA Technical Reports Server (NTRS)

Downes, Hilary; Herrin, J. S.; Hudon, P.; Mittlefehldt, D.W.

2007-01-01

Ureilites are primitive ultramafic achondrites composed largely of olivine and pigeonite, with minor augite, orthopyroxene, carbon, sulphide and metal. They represent very early material in the history of the Solar System and (in common with lodranites and acapulcoites) form a bridge between undifferentiated chondrites and fully differentiated asteroidal bodies. They show an intriguing mixture of chemical characteristics, some of which are considered to be nebula-derived (e.g. variations in Delta(sup 17)O and mg#) whereas others have been imposed by asteroidal differentiation (e.g. core formation, silicate partial melting, removal of basalt).

Water Transport and the Evolution of CM Parent Bodies

NASA Technical Reports Server (NTRS)

Coker, Rob; Cohen, Barbara

2014-01-01

Meteorites have amino acids and hydrated minerals which constrain the peak temperature ranges they have experienced. CMs in particular have a narrow range (273-325K). Bulk fluid motion during hydration constrained to small scales (less than mm). Some asteroids are known to have hydrated minerals on their surfaces. It is presumed these two facts may be related. Problem: hydration only occurs (significantly) with liquid water; melting water only occurs early on in nebula (1-10 Myrs ANC); in nebula asteroid surface temperature very cold (approximately 150K). Can indigenous alteration produce CMs and/or surface hydration?

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.

Space Weathering in Olivine and the Mineralogy of (Some) M-Class Asteroids

NASA Astrophysics Data System (ADS)

Britt, Daniel; Kohout, Tomas; Schelling, Patrick; Consolmagno, Guy J.

2014-11-01

One aspect of space weathering of airless bodies is the production of nanophase iron (npFe0) from Fe bearing silicate minerals. The combined effects of low oxygen fugacity and solar-wind implanted H tend to result in strongly-reduced surfaces that can be chemically activated by heating due to micrometeorite impacts. The mineral kinetics of olivine makes it particularly vulnerable to reduction, decomposition, and npFe0 production. Kohout et al. has recently developed a new method of controlled npFe0 production on olivine powder grains that mimics the essential features of this weathering process and was developed to quantitatively evaluate spectral changes related to space weathering and presence of npFe0. Compared to fresh olivine the treated samples exhibit spectral characteristics of space weathering including spectral darkening, shallowing and attenuation of 1 µm olivine absorption band, and reddening. The attenuation of the 1 µm band significantly shrinks the band FWHM and shifts the much reduced band center to shorter wavelengths around 0.95 µm. These spectral changes are related to increasing amounts of npFe0 and the disruption of the crystal structure of the parent olivine. Significantly, the darkened, reddened, and band attenuated olivine spectra are a close match to a number of M-class asteroids. What is particularly interesting is the match with the weak absorption band near 0.95 µm seen in many M-class asteroids (i.e. 16 Psyche, 22 Kalliope, 55 Pandora to name a few). One of the major issues in asteroid science is the relative scarcity of olivine asteroids (the ”Great Dunite Shortage” coined by Bell et al in Asteroids II). One possibility worth further study is that asteroidal olivine may be hidden by the relative ease with which it weathers. The surface chemical and micrometeorite environment in the asteroid belt may produce over time a spectrum for an olivine-rich surface that is remarkably similar to that of an M-class asteroid.

The formation of jupiter, the jovian early bombardment and the delivery of water to the asteroid belt: the case of (4) vesta.

PubMed

Turrini, Diego; Svetsov, Vladimir

2014-01-28

The asteroid (4) Vesta, parent body of the Howardite-Eucrite-Diogenite meteorites, is one of the first bodies that formed, mostly from volatile-depleted material, in the Solar System. The Dawn mission recently provided evidence that hydrated material was delivered to Vesta, possibly in a continuous way, over the last 4 Ga, while the study of the eucritic meteorites revealed a few samples that crystallized in presence of water and volatile elements. The formation of Jupiter and probably its migration occurred in the period when eucrites crystallized, and triggered a phase of bombardment that caused icy planetesimals to cross the asteroid belt. In this work, we study the flux of icy planetesimals on Vesta during the Jovian Early Bombardment and, using hydrodynamic simulations, the outcome of their collisions with the asteroid. We explore how the migration of the giant planet would affect the delivery of water and volatile materials to the asteroid and we discuss our results in the context of the geophysical and collisional evolution of Vesta. In particular, we argue that the observational data are best reproduced if the bulk of the impactors was represented by 1-2 km wide planetesimals and if Jupiter underwent a limited (a fraction of au) displacement.

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.

The Formation of Jupiter, the Jovian Early Bombardment and the Delivery of Water to the Asteroid Belt: The Case of (4) Vesta

PubMed Central

Turrini, Diego; Svetsov, Vladimir

2014-01-01

The asteroid (4) Vesta, parent body of the Howardite-Eucrite-Diogenite meteorites, is one of the first bodies that formed, mostly from volatile-depleted material, in the Solar System. The Dawn mission recently provided evidence that hydrated material was delivered to Vesta, possibly in a continuous way, over the last 4 Ga, while the study of the eucritic meteorites revealed a few samples that crystallized in presence of water and volatile elements. The formation of Jupiter and probably its migration occurred in the period when eucrites crystallized, and triggered a phase of bombardment that caused icy planetesimals to cross the asteroid belt. In this work, we study the flux of icy planetesimals on Vesta during the Jovian Early Bombardment and, using hydrodynamic simulations, the outcome of their collisions with the asteroid. We explore how the migration of the giant planet would affect the delivery of water and volatile materials to the asteroid and we discuss our results in the context of the geophysical and collisional evolution of Vesta. In particular, we argue that the observational data are best reproduced if the bulk of the impactors was represented by 1–2 km wide planetesimals and if Jupiter underwent a limited (a fraction of au) displacement. PMID:25370027

Aqueous Alteration of Carbonaceous Chondrites: New Insights from Comparative Studies of Two Unbrecciated CM2 Chondrites, Y 791198 and ALH 81002

NASA Technical Reports Server (NTRS)

Chizmadia, L. J.; Brearley, A. J.

2004-01-01

Carbonaceous chondrites are an important resource for understanding the physical and chemical conditions in the early solar system. In particular, a long-standing question concerns the role of water in the cosmochemical evolution of carbonaceous chondrites. It is well established that extensive hydration of primary nebular phases occurred in the CM and CI chondrites, but the location where this alteration occurred remains controversial. In the CM2 chondrites, hydration formed secondary phases such as serpentine, tochilinite, pentlandite, carbonate and PCP. There are several textural observations which suggest that alteration occurred before the accretion of the final CM parent asteroid, i.e. preaccretionary alteration. Conversely, there is a significant body of evidence that supports parent-body alteration. In order to test these two competing hypotheses further, we studied two CM chondrites, Y-791198 and ALH81002, two meteorites that exhibit widely differing degrees of aqueous alteration. In addition, both meteorites have primary accretionary textures, i.e. experienced minimal asteroidal brecciation. Brecciation significantly complicates the task of unraveling alteration histories, mixing components that have been altered to different degrees from different locations on the same asteroidal parent body. Alteration in Y-791198 is mostly confined to chondrule mesostases, FeNi metal and fine-grained matrix and rims. In comparison, the primary chondrule silicates in ALH81002 have undergone extensive replacement by secondary hydrous phases. This study focuses on compositional and textural relationships between chondrule mesostasis and the associated rim materials. Our hypothesis is: both these components are highly susceptible to aqueous alteration and should be sensitive recorders of the alteration process. For parent body alteration, we expect systematic coupled mineralogical and compositional changes in rims and altered mesostasis, as elemental exchange between these components occurs. Conversely, for preaccretionary alteration, there should be no clear relationships between the rims and mesostases.

The Almahata Sitta Polymict Ureilite from the University of Khartoum Collection: Classification, Distribution of Clast Types in the Strewn Field, New Meteorite Types, and Implications for the Structure of Asteroid 2008 TC3

NASA Technical Reports Server (NTRS)

Goodrich, C. A.; Fioretti, A. M.; Zolensky, M.; Ross, Daniel K.; Shaddad, M.; Ross, D. K.; Kohl, I.; Young, E.; Kita, N.; Hiroi, T.;

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.

Thermal History and Fragmentation of Ureilitic Asteroids: Insights from the Almahata Sitta Fall

NASA Technical Reports Server (NTRS)

Herrin, J. S.; Ito, M.; Zolensky, M. E.; Mittlefehldt, D. M.; Jenniskens, P. M.; Shaddad, M. H.

2010-01-01

Prior to recovery the Almahata Sitta fall was observed as the asteroid 2008 TC3 on an Earth-bound trajectory, providing a unique link between spectral data and ureilite composition. The event has also provided insight into the nature of ureilitic objects in space. In particular, the large size (4 m3) and low density (2.2 g/cm3) of the object combined with near-complete disintegration upon entry suggest a porous and loosely-consolidated body [1]. Accordingly, recovered fragments are small in size (1.5-283g) and represent several different ureilite lithologies. Some recovered fragments appear brecciated while others do not. We use chemical and mineralogic data to dissect the thermal history of this new ureilite, then use this information to compare the inferred size of fragments within the asteroid to those initially dislodged from a common ureilite parent body (UPB).

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.

The Regolith of 4 Vesta - Inferences from Howardites

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Herrin, J. S.; Cartwright, J. A.

2011-01-01

Asteroid 4 Vesta is quite likely the parent asteroid of the howardite, eucrite and diogenite meteorites - the HED clan. Eucrites and diogenites are the products of igneous processes; the former are basaltic composition rocks from flows, and shallow and deep intrusive bodies, whilst the latter are cumulate orthopyroxenites thought to have formed deep in the crust. Impact processes have excavated these materials and mixed them into a suite of polymict breccias. Howardites are polymict breccias composed mostly of clasts and mineral fragments of eucritic and diogenitic parentage, with neither end-member comprising more than 90% of the rock. Early work interpreted howardites as representing the lithified regolith of their parent asteroid. Recently, howardites have been divided into two subtypes; fragmental howardites, being a type of non-regolithic polymict breccia, and regolithic howardites, being lithified remnants of the active regolith of 4 Vesta. We are in the thralls of a collaborative investigation of the record of impact mixing contained within howardites, which includes studies of their mineralogy, petrology, bulk rock compositions, and bulk rock and clast noble gas contents. One goal of our investigation is to test the hypothesis that some howardites represent breccias formed from an ancient, well-mixed regolith on Vesta. Another is to use our results to further understand regolith processing on differentiated asteroids as compared to what has been learned from the Moon. We have made petrographic observations and electron microprobe analyses on 21 howardites and 3 polymict eucrites. We have done bulk rock analyses using X-ray fluorescence spectrometry and are completing inductively coupled plasma mass spectrometry analyses. Here, we discuss our petrologic and bulk compositional results in the context of regolith formation. Companion presentations describe the noble gas results and compositional studies of low-Ca pyroxene clasts.

Comparing Results of SPH/N-body Impact Simulations Using Both Solid and Rubble-pile Target Asteroids

NASA Astrophysics Data System (ADS)

Durda, Daniel D.; Bottke, W. F.; Enke, B. L.; Nesvorný, D.; Asphaug, E.; Richardson, D. C.

2006-09-01

We have been investigating the properties of satellites and the morphology of size-frequency distributions (SFDs) resulting from a suite of 160 SPH/N-body simulations of impacts into 100-km diameter parent asteroids (Durda et al. 2004, Icarus 170, 243-257; Durda et al. 2006, Icarus, in press). These simulations have produced many valuable insights into the outcomes of cratering and disruptive impacts but were limited to monolithic basalt targets. As a natural consequence of collisional evolution, however, many asteroids have undergone a series of battering impacts that likely have left their interiors substantially fractured, if not completely rubblized. In light of this, we have re-mapped the matrix of simulations using rubble-pile target objects. We constructed the rubble-pile targets by filling the interior of the 100-km diameter spherical shell (the target envelope) with randomly sized solid spheres in mutual contact. We then assigned full damage (which reduces tensile and shear stresses to zero) to SPH particles in the contacts between the components; the remaining volume is void space. The internal spherical components have a power-law distribution of sizes simulating fragments of a pre-shattered parent object. First-look analysis of the rubble-pile results indicate some general similarities to the simulations with the monolithic targets (e.g., similar trends in the number of small, gravitationally bound satellite systems as a function of impact conditions) and some significant differences (e.g., size of largest remnants and smaller debris affecting size frequency distributions of resulting families). We will report details of a more thorough analysis and the implications for collisional models of the main asteroid belt. This work is supported by the National Science Foundation, grant number AST0407045.

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.

Metamorphism and partial melting of ordinary chondrites: Calculated phase equilibria

NASA Astrophysics Data System (ADS)

Johnson, T. E.; Benedix, G. K.; Bland, P. A.

2016-01-01

Constraining the metamorphic pressures (P) and temperatures (T) recorded by meteorites is key to understanding the size and thermal history of their asteroid parent bodies. New thermodynamic models calibrated to very low P for minerals and melt in terrestrial mantle peridotite permit quantitative investigation of high-T metamorphism in ordinary chondrites using phase equilibria modelling. Isochemical P-T phase diagrams based on the average composition of H, L and LL chondrite falls and contoured for the composition and abundance of olivine, ortho- and clinopyroxene, plagioclase and chromite provide a good match with values measured in so-called equilibrated (petrologic type 4-6) samples. Some compositional variables, in particular Al in orthopyroxene and Na in clinopyroxene, exhibit a strong pressure dependence when considered over a range of several kilobars, providing a means of recognising meteorites derived from the cores of asteroids with radii of several hundred kilometres, if such bodies existed at that time. At the low pressures (<1 kbar) that typify thermal metamorphism, several compositional variables are good thermometers. Although those based on Fe-Mg exchange are likely to have been reset during slow cooling, those based on coupled substitution, in particular Ca and Al in orthopyroxene and Na in clinopyroxene, are less susceptible to retrograde diffusion and are potentially more faithful recorders of peak conditions. The intersection of isopleths of these variables may allow pressures to be quantified, even at low P, permitting constraints on the minimum size of parent asteroid bodies. The phase diagrams predict the onset of partial melting at 1050-1100 °C by incongruent reactions consuming plagioclase, clinopyroxene and orthopyroxene, whose compositions change abruptly as melting proceeds. These predictions match natural observations well and support the view that type 7 chondrites represent a suprasolidus continuation of the established petrologic types at the extremes of thermal metamorphism. The results suggest phase equilibria modelling has potential as a powerful quantitative tool in investigating, for example, progressive oxidation during metamorphism, the degree of melting and melt loss or accumulation required to produce the spectrum of differentiated meteorites, and whether the onion shell or rubble pile model best explains the metamorphic evolution of asteroid parent bodies in the early solar system.

Possible Thermal Metamorphism on the C Asteroids Seen from the 3-micrometer Hydration Band in Comparison with Heated CI/CM Meteorites

NASA Astrophysics Data System (ADS)

Hiroi, T.; Pieters, C. M.; Zolensky, M. E.; Lipschutz, M. E.

1995-09-01

Thermal metamorphism study of the C (including G, B, and F) asteroids [1] is revisited using their selected reflectance spectra (0.3-3.6 micrometers) [2]. Laboratory spectra of some carbonaceous chondrites and heated Murchison samples [3] have been also measured for comparison. Both CI1 and CM2 meteorites have a characteristic 3-micrometer hydration band [4] at various strengths, and most CM2 meteorites also have 0.7, 0.9, and 1.1-micrometer bands due to ferric/ferrous Fe in septechlorites (Fig. 1). The unusual CI/CM meteorites (Y-86720, B-7904, Y-82162, etc.) that have evidence of thermal metamorphism have no 0.7-micrometer band but still have a weak 3-micrometer band. The 3-micrometer band of heated Murchison samples is gradually reduced for samples heated up to 500 degrees C and gone around 600 degrees C. The 0.7-micrometer band is gone even before 400 degrees C. The 3-micrometer band strengths of the unusual CI/CM meteorites correspond to the heating temperature between 500 and 600 degrees C if the process was similar to the Murchison heating experiment. None of the C asteroids have both the 3-micrometer band strength and overall spectral profile comparable to the common CI/CM meteorites studied here. Among the seven selected asteroids, only two have a meteorite counterpart over this wavelength range. Asteroid 511 Davida and B-7904 are the best counterparts in both spectral shape and brightness (Fig. 1). Existence of the unusual CI/CM meteorites suggests that there were their parent bodies that contained water (ice) at appropriate temperatures over sufficient time to induce aqueous alteration and were subsequently heated up to 500-600 degrees C. It has been recently suggested that some dark inclusions of Vigarano (CV3) experienced extensive aqueous alteration followed by complete dehydration and recrystallization [5]. Since dark inclusions are common in all CV3 meteorites, aqueous alteration and late-stage heating may have been widespread on the CV3 parent bodies. Because common CI/CM meteorites are spectrally different from any of the observed asteroids, those meteorites must have come from another asteroid population, assuming the asteroid surfaces are not significantly altered by space weathering. CI/CM meteorites may have come from smaller unobservable asteroids or the lost outer portions of asteroids, which escaped extensive heating events. Acknowledgments: Antarctic meteorites were loaned from National Institute of Polar Research and Meteorite Working Group. Laboratory reflectance spectra were measured at RELAB operated under NASA grant NAGW-748. Asteroidal 3-micrometer reflectance spectra were taken from SOARD database. This research was supported in part by NASA grant NAG 9-48 to M. L. and the NASA Origins of Solar Systems Program to M. Z. References: [1] Hiroi T. et al. (1993) Science, 261, 1016-1018; Hiroi T. et al. (1994) Proc. NIPR Symp. Antarct. Meteorites, 7, 230-243. [2] Zellner B. et al. (1985) Icarus, 61, 355-416; Bell J. F. et al. (1988) LPS XIX, 57-58; Jones T. D. et al. (1990) Icarus, 88, 172-192. [3] Matza S. D. and Lipschutz M. E. (1977) Proc. LSC 8th, 161-176. [4] Miyamoto M. and Zolensky M. E. (1994) Meteoritics, 29, 849-853. [5] Kojima H. et al. (1993) Meteoritics, 28, 649-658.

Enhanced Gravity Tractor Derived from the Asteroid Redirect Mission for Deflecting Hypothetical Asteroid 2017 PDC

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Reeves, David M.; Abell, Paul A.; Shen, Haijun; Qu, Min

2017-01-01

The Asteroid Redirect Mission (ARM) concept would robotically visit a hazardous-size near-Earth asteroid (NEA) with a rendezvous spacecraft, collect a multi-ton boulder and regolith samples from its surface, demonstrate an innovative planetary defense technique known as the Enhanced Gravity Tractor (EGT), and return the asteroidal material to a stable orbit around the Moon, allowing astronauts to explore the returned material in the mid-2020s. Launch of the robotic vehicle to rendezvous with the ARM reference target, NEA (341843) 2008 EV5, would occur in late 2021 [1,2]. The robotic segment of the ARM concept uses a 40 kW Solar Electric Propulsion (SEP) system with a specific impulse (Isp) of 2600 s, and would provide the first ever demonstration of the EGT technique on a hazardous-size asteroid and validate one method of collecting mass in-situ. The power, propellant, and thrust capability of the ARM robotic spacecraft can be scaled from a 40 kW system to 150 kW and 300 kW, which represent a likely future power level progression. The gravity tractor technique uses the gravitational attraction of a station-keeping spacecraft with the asteroid to provide a velocity change and gradually alter the trajectory of the asteroid. EGT utilizes a spacecraft with a high-efficiency propulsion system, such as Solar Electric Propulsion (SEP), along with mass collected in-situ to augment the mass of the spacecraft, thereby increasing the gravitational force between the objects [3]. As long as the spacecraft has sufficient thrust and propellant capability, the EGT force is only limited by the amount of in-situ mass collected and can be increased several orders of magnitude compared to the traditional gravity tractor technique in which only the spacecraft mass is used to generate the gravitational attraction force. This increase in available force greatly reduces the required deflection time. The collected material can be a single boulder, multiple boulders, regolith, or a combination of different material types using a variety of collection techniques. The EGT concept assumes that the ability to efficiently collect asteroid mass in-situ from a wide variety of asteroid types and environments is a future capability that will be developed and perfected in the future by the asteroid mining community. Additionally, it is anticipated that the mass collection would likely be performed by a single or multiple separable spacecraft to allow the SEP spacecraft to operate at safe distance from the asteroid.

Binaries and triples among asteroid pairs

NASA Astrophysics Data System (ADS)

Pravec, Petr; Scheirich, Peter; Kušnirák, Peter; Hornoch, Kamil; Galád, Adrián

2015-08-01

Despite major achievements obtained during the past two decades, our knowledge of the population and properties of small binary and multiple asteroid systems is still far from advanced. There is a numerous indirect evidence for that most small asteroid systems were formed by rotational fission of cohesionless parent asteroids that were spun up to the critical frequency presumably by YORP, but details of the process are lacking. Furthermore, as we proceed with observations of more and more binary and paired asteroids, we reveal new facts that substantially refine and sometimes change our understanding of the asteroid systems. One significant new finding we have recently obtained is that primaries of many asteroid pairs are actually binary or triple systems. The first such case found is (3749) Balam (Vokrouhlický, ApJL 706, L37, 2009). We have found 9 more binary systems among asteroid pairs within our ongoing NEOSource photometric project since October 2012. They are (6369) 1983 UC, (8306) Shoko, (9783) Tensho-kan, (10123) Fideoja, (21436) Chaoyichi, (43008) 1999 UD31, (44620) 1999 RS43, (46829) 1998 OS14 and (80218) 1999 VO123. We will review their characteristics. These paired binaries as we call them are mostly similar to binaries in the general ("background") population (of unpaired asteroids), but there are a few trends. The paired binaries tend to have larger secondaries with D_2/D_1 = 0.3 to 0.5 and they also tend to be wider systems with 8 of the 10 having orbital periods between 30 and 81 hours, than average among binaries in the general population. There may be also a larger fraction of triples; (3749) Balam is a confirmed triple, having a larger close and a smaller distant satellite, and (8306) Shoko and (10123) Fideoja are suspect triples as they show additional rotational lightcurve components with periods of 61 and 38.8 h that differ from the orbital period of 36.2 and 56.5 h, respectively. The unbound secondaries tend to be of the same size or smaller (with one exception) than the bound orbiting secondaries. I will compare the observed properties of the paired binaries to predictions from theories of formation of asteroid binaries and pairs.

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].

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.

Evolutionary Pathways for Asteroid Satellites

NASA Astrophysics Data System (ADS)

Jacobson, Seth Andrew

2015-08-01

The YORP-induced rotational fission hypothesis is a proposed mechanism for the creation of small asteroid binaries, which make up approximately 1/6-th of the near-Earth asteroid and small Main Belt asteroid populations. The YORP effect is a radiative torque that rotationally accelerates asteroids on timescales of thousands to millions of years. As asteroids rotationally accelerate, centrifugal accelerations on material within the body can match gravitational accelerations holding that material in place. When this occurs, that material goes into orbit. Once in orbit that material coalesces into a companion that undergoes continued dynamical evolution.Observations with radar, photometric and direct imaging techniques reveal a diverse array of small asteroid satellites. These systems can be sorted into a number of morphologies according to size, multiplicity of members, dynamical orbit and spin states, and member shapes. For instance, singly synchronous binaries have short separation distances between the two members, rapidly rotating oblate primary members, and tidally locked prolate secondary members. Other confirmed binary morphologies include doubly synchronous, tight asynchronous and wide asynchronous binaries. Related to these binary morphologies are unbound paired asteroid systems and bi-lobate contact binaries.A critical test for the YORP-induced rotational fission hypothesis is whether the binary asteroids produced evolve to the observed binary and related systems. In this talk I will review how this evolution is believed to occur according to gravitational dynamics, mutual body tides and the binary YORP effect.

Cosmic Ray Exposure Ages, Ar-Ar Ages, and the Origin and History of Eucrites

NASA Technical Reports Server (NTRS)

Wakefield, Kelli; Bogard, Donald; Garrison, Daniel

2004-01-01

HED meteorites likely formed at different depths on the large asteroid 4-Vesta, but passed through Vesta-derived, km-sized intermediary bodies (Vestoids), before arriving at Earth. Most eucrites and diogenites (and all howardites) are brecciated, and impact heating disturbed or reset the K-Ar ages (and some Rb-Sr ages) of most eucrites in the time period of approx. 3.4 - 4.1 Gyr ago. Some basaltic eucrites and most cumulate eucrites, however, are not brecciated. We recently showed that the Ar-39 - Ar-40 ages for several of these eucrites tightly cluster about a value of 4.48 +/- 0.02 Gyr, and we argue that this time likely represents a single large impact event on Vesta, which ejected these objects from depth and quenched their temperatures. A different parent body has been suggested for cumulate eucrites, although the Ar-Ar ages argue for a common parent. Similarities in the cosmic-ray (space) exposure ages for basaltic eucrites and diogenites also have been used to infer a common parent body for some HEDs. Here we present CRE ages of several cumulate and unbrecciated basaltic (UB) eucrites and compare these with CRE ages of other HEDs. This comparison also has some interesting implications for the relative locations of various HED types on Vesta and/or the Vestoids.

A six-part collisional model of the main asteroid belt

NASA Astrophysics Data System (ADS)

Cibulková, H.; Brož, M.; Benavidez, P. G.

2014-10-01

In this work, we construct a new model for the collisional evolution of the main asteroid belt. Our goals are to test the scaling law of Benz and Asphaug (Benz, W., Asphaug, E. [1999]. Icarus, 142, 5-20) and ascertain if it can be used for the whole belt. We want to find initial size-frequency distributions (SFDs) for the considered six parts of the belt (inner, middle, “pristine”, outer, Cybele zone, high-inclination region) and to verify if the number of synthetic asteroid families created during the simulation matches the number of observed families as well. We used new observational data from the WISE satellite (Masiero et al., 2011) to construct the observed SFDs. We simulate mutual collisions of asteroids with a modified version of the Boulder code (Morbidelli, A., et al. [2009]. Icarus, 204, 558-573), where the results of hydrodynamic (SPH) simulations of Durda et al. (Durda, D.D., et al. [2007]. Icarus, 498-516) and Benavidez et al. (Benavidez, P.G., et al. [2012]. 219, 57-76) are included. Because material characteristics can significantly affect breakups, we created two models - for monolithic asteroids and for rubble-piles. To explain the observed SFDs in the size range D=1 to 10 km we have to also account for dynamical depletion due to the Yarkovsky effect. The assumption of (purely) rubble-pile asteroids leads to a significantly worse fit to the observed data, so that we can conclude that majority of main-belt asteroids are rather monolithic. Our work may also serve as a motivation for further SPH simulations of disruptions of smaller targets (with a parent body size of the order of 1 km).

Heliocentric zoning of the asteroid belt by aluminum-26 heating

NASA Technical Reports Server (NTRS)

Grimm, R. E.; Mcsween, H. Y., Jr.

1993-01-01

Variations in petrology among meteorites attest to a strong heating event early in solar system history, but the heat source has remained unresolved. Aluminum-26 has been considered the most likely high-energy, short-lived radionuclide (half-life 0.72 million years) since the discovery of its decay product - excess Mg-26 - in Allende CAI's. Furthermore, observation of relict Mg-26 in an achondritic clast and in feldspars within ordinary chondrites (3,4) provided strong evidence for live Al-26 in meteorite parent bodies and not just in refractory nebular condensates. The inferred amount of Al-26 is consistent with constraints on the thermal evolution of both ordinary and carbonaceous chondrite parent objects up to a few hundred kilometers in diameter. Meteorites can constrain the early thermal evolution of their parent body locations, provided that a link can be established between asteroid spectrophotometric signature and meteorite class. Asteroid compositions are heliocentrically distributed: objects thought to have experienced high metamorphic or even melting temperatures are located closer to the sun, whereas apparently unaltered or mildly heated asteroids are located farther away. Heliocentric zoning could be the result of Al-26 heating if the initial amount of the radionuclide incorporated into planetesimals was controlled by accretion time, which in turn varies with semimajor axis. Analytic expressions for planetary accretion may be integrated to given the time, tau, required for a planetesimal to grow to a specified radius: tau varies as a(sup n), where n = 1.5 to 3 depending on the assumptions about variations in the surface density of the planetesimal swarm. Numerical simulations of planetesimal accretion at fixed semimajor axis demonstrate that variations in accretion time among small planetesimals can be strongly nonlinear depending on the initial conditions and model assumptions. The general relationship with semimajor axis remains valid because it depends only on the initial orbit properties and distribution of the planesimal swarm. In order to demonstrate the basic dependence of thermal evolution on semimajor axis, we parameterized accretion time across the asteroid belt according to tau varies as a(sup n) and calculated the subsequent thermal history. Objects at a specified semimajor axis were assumed to have the same accretion time, regardless of size. We set the initial Al-26/Al-27 ratio = 6 x 10(exp -5) and treated n and tau(sub 0) at a(sub 0) = 3 AU as adjustable parameters. The thermal model included temperature-dependent properties of ice and rock (CM chondrite analog) and the thermodynamic effects of phase transitions.

Impact simulation in the gravity regime: Exploring the effects of parent body size and internal structure

NASA Astrophysics Data System (ADS)

Benavidez, P. G.; Durda, D. D.; Enke, B.; Campo Bagatin, A.; Richardson, D. C.; Asphaug, E.; Bottke, W. F.

2018-04-01

In this work we extend the systematic investigation of impact outcomes of 100-km-diameter targets started by Durda et al. (2007) and Benavidez et al. (2012) to targets of D = 400 km using the same range of impact conditions and two internal structures: monolithic and rubble-pile. We performed a new set of simulations in the gravity regime for targets of 400 km in diameter using these same internal structures. This provides a large set of 600 simulations performed in a systematic way that permits a thorough analysis of the impact outcomes and evaluation of the main features of the size frequency distribution due mostly to self-gravity. In addition, we use the impact outcomes to attempt to constrain the impact conditions of the asteroid belt where known asteroid families with a large expected parent body were formed. We have found fairly good matches for the Eunomia and Hygiea families. In addition, we identified a potential acceptable match to the Vesta family from a monolithic parent body of 468 km. The impact conditions of the best matches suggest that these families were formed in a dynamically excited belt. The results also suggest that the parent body of the Eunomia family could be a monolithic body of 382 km diameter, while the one for Hygiea could have a rubble-pile internal structure of 416 km diameter.

The thermal history of interplanetary dust particles collected in the Earth's stratosphere

NASA Technical Reports Server (NTRS)

Nier, A. O.; Schlutter, D. J.

1993-01-01

Fragments of 24 individual interplanetary dust particles (IDPs) collected in the Earth's stratosphere were obtained from NASA's Johnson Space Center collection and subjected to pulse-heating sequences to extract He and Ne and to learn about the thermal history of the particles. A motivation for the investigation was to see if the procedure would help distinguish between IDPs of asteroidal and cometary origin. The use of a sequence of short-duration heat pulses to perform the extractions is an improvement over the employment of a step-heating sequence, as was used in a previous investigation. The particles studied were fragments of larger parent IDPs, other fragments of which, in coordinated experiments, are undergoing studies of elemental and mineralogical composition in other laboratories. While the present investigation will provide useful temperature history data for the particles, the relatively large size of the parent IDPs (approximately 40 micrometers in diameter) resulted in high entry deceleration temperatures. This limited the usefulness of the study for distinguishing between particles of asteroidal and cometary origin.

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.

Lunar and Planetary Science XXXVI, Part 22

NASA Technical Reports Server (NTRS)

2005-01-01

The Lunar and Planetary Science XXXVI, Part 22 is presented. The topics include: 1) Pressure Histories from Thin and Thick Shock-induced Melt Veins in Meteorites; 2) Nano-structured Minerals as Signature of Microbial Activity; 3) The Insoluble Carbonaceous Material of CM Chondrites as Possible Source of Discrete Organics During the Asteroidal Aqueous Phase; 4) Discovery of Abundant Presolar Silicates in Subgroups of Antarctic Micrometeorites; 5) Characteristics of a Seismometer for the LUNAR-A Penetrator; 6) Heating Experiments of the HaH 262 Eucrite and Implication for the Metamorphic History of Highly Metamorphosed Eucrites; 7) Measurements of Ejecta Velocity Distribution by a High-Speed Video Camera; 8) Petrological Comparison of Mongolian Jalanash Ureilite and Twelve Antarctic Ureilites; 9) Metallographic Cooling Rate of IVA Irons Revisited; 10) Inhomogeneous Temperature Distribution in Chondrules in Shock-Wave Heating Model; 11) Subsurface Weathering of Rocks and Soils at Gusev Crater; 12) Extinct Radioactivities in the Early Solar System and the Mean Age of the Galaxy; 13) Correlation of Rock Spectra with Quantitative Morphologic Indices: Evidence for a Single Rock Type at the Mars Pathfinder Landing Site; 14) Silicon Isotopic Ratios of Presolar Grains from Supernovae; 15) Current Status and Readiness on In-Situ Exploration of Asteroid Surface by MINERVA Rover in Hayabusa Mission; 16) Long Formation Period of Single CAI: Combination of O and Mg Isotope Distribution; 17) Supra-Canonical Initial 26Al/27Al Indicate a 105 Year Residence Time for CAIs in the Solar Proto-Planetary Disk; 18) Evolution of Mercury's Obliquity; 19) First Results from the Huygens Surface Science Package; 20) Polyhedral Serpentine Grains in CM Chondrites; 21) Mountainous Units in the Martian Gusev Highland Region: Volcanic, Tectonic, or Impact Related? 22) Petrography of Lunar Meteorite MET 01210, A New Basaltic Regolith Breccia; 23) Earth-Moon Impacts at 300 Ma and 500 Ma Ago; 24) Chemical and Isotopic Analyses of Apollo 16 Glasses: An Integrated Approach; 25) Measuring the Surfaces on Mars; 26) Melting in Martian Snowbanks; 27) The Effect of Ni on Fe-FeS Phase Relations: Implications for the Chemistry of the Martian Core; 28) Shorelines in the Western United States as Analogs for Hypothesized Shoreline Features on Mars; 29) Al and Ti Isotopic Ratios of Presolar SiC Grains of Type Z; 30) Physicochemical Conditions of Clinopyroxene Crystallization in the Parental Bodies of Ordinary Chondrites; 31) Metamorphosed CM and CI Carbonaceous Chondrites Could be from the Breakup of the Same Earth-crossing Asteroid; 32) Aqueous Alteration and Hydrogen Generation on Parent Bodies of Unequilibrated Ordinary Chondrites: Thermodynamic Modeling for the Semarkona Composition; and 33) Preliminary Analysis of Relative Abundances of Hydrothermal Alteration Products in the C1-N10, Y6-N19, and Yax-1_863.51 Impact Melt Samples, Chicxulub Structure, Mexico

A new 6-part collisional model of the Main Asteroid Belt

NASA Astrophysics Data System (ADS)

Broz, Miroslav; Cibulkova, H.

2013-10-01

In this work, we constructed a new model for the collisional evolution of the Main Asteroid Belt. Our goals are to test the scaling law from the work of Benz & Asphaug (1999) and ascertain if it can be used for the whole belt. We want to find initial size-frequency distributions (SFDs) for the considered six parts of the belt, and to verify if the number of asteroid families created during the simulation matches the number of observed families as well. We used new observational data from the WISE satellite (Masiero et al., 2011) to construct the observed SFDs. We simulated mutual collisions of asteroids with a modified Boulder code (Morbidelli et al., 2009), in which the results of hydrodynamic (SPH) simulations from the work of Durda et al. (2007) are included. Because material characteristics can affect breakups, we created two models - for monolithic asteroids and for rubble-piles (Benavidez et al., 2012). To explain the observed SFDs in the size range D = 1 to 10 km we have to also account for dynamical depletion due to the Yarkovsky effect. Our work may also serve as a motivation for further SPH simulations of disruptions of smaller targets (parent body size of the order of 1 km). The work of MB was supported by grant GACR 13-013085 of the Czech Science Foundation and the Research Programme MSM0021620860 of the Czech Ministry of Education.

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

Chondritic Asteroids--When Did Aqueous Alteration Happen?

NASA Astrophysics Data System (ADS)

Doyle, P. M.

2015-06-01

Using a synthesized fayalite (Fe2SiO4) standard for improved 53Mn-53Cr radiometric age dating, Patricia Doyle (previously at the University of Hawaii and now at the University of Cape Town, South Africa) and coauthors from Hawaii, the National Astronomical Observatory of Japan, University of Chicago, and Lawrence Livermore National Laboratory in California, analyzed aqueously formed fayalite in the ordinary chondrite Elephant Moraine 90161 (L3.05) and in the carbonaceous chondrites Asuka 881317 (CV3) and MacAlpine Hills 88107 (CO3-like) from Antarctica. The data obtained indicate that liquid water existed - and aqueous alteration started - on the chondritic parent bodies about three million years earlier than previously determined. This discovery has implications for understanding when and where the asteroids accreted. The 53Mn-53Cr chronology of chondrite aqueous alteration, combined with thermodynamic calculations and physical modeling, signifies that hydrated asteroids, at least those sampled by meteorites, accreted in the inner Solar System (2-4 AU) near the main asteroid belt 2-4 million years after the beginning of the Solar System, rather than migrating inward after forming in the Solar System's colder, outer regions beyond Jupiter's present orbit (5-15 AU).

Compositional study of asteroids in the Erigone collisional family using visible spectroscopy at the 10.4 m GTC

NASA Astrophysics Data System (ADS)

Morate, David; de León, Julia; De Prá, Mário; Licandro, Javier; Cabrera-Lavers, Antonio; Campins, Humberto; Pinilla-Alonso, Noemí; Alí-Lagoa, Víctor

2016-02-01

Two primitive near-Earth asteroids, (101955) Bennu and (162173) Ryugu, will be visited by a spacecraft with the aim of returning samples back to Earth. Since these objects are believed to originate in the inner main belt primitive collisional families (Erigone, Polana, Clarissa, and Sulamitis) or in the background of asteroids outside these families, the characterization of these primitive populations will enhance the scientific return of the missions. The main goal of this work is to shed light on the composition of the Erigone collisional family by means of visible spectroscopy. Asteroid (163) Erigone has been classified as a primitive object, and we expect the members of this family to be consistent with the spectral type of the parent body. We have obtained visible spectra (0.5-0.9 μm) for 101 members of the Erigone family, using the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias. We found that 87% of the objects have typically primitive visible spectra consistent with that of (163) Erigone. In addition, we found that a significant fraction of these objects (~50%) present evidence of aqueous alteration.

A unique basaltic micrometeorite expands the inventory of solar system planetary crusts

PubMed Central

Gounelle, Matthieu; Chaussidon, Marc; Morbidelli, Alessandro; Barrat, Jean-Alix; Engrand, Cécile; Zolensky, Michael E.; McKeegan, Kevin D.

2009-01-01

Micrometeorites with diameter ≈100–200 μm dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission. PMID:19366660

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.

Link between the potentially hazardous Asteroid (86039) 1999 NC43 and the Chelyabinsk meteoroid tenuous

NASA Astrophysics Data System (ADS)

Reddy, Vishnu; Vokrouhlický, David; Bottke, William F.; Pravec, Petr; Sanchez, Juan A.; Gary, Bruce L.; Klima, Rachel; Cloutis, Edward A.; Galád, Adrián; Guan, Tan Thiam; Hornoch, Kamil; Izawa, Matthew R. M.; Kušnirák, Peter; Le Corre, Lucille; Mann, Paul; Moskovitz, Nicholas; Skiff, Brian; Vraštil, Jan

2015-05-01

We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous Asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Borovička et al. (Borovička, J., et al. [2013]. Nature 503, 235-237). First, using a slightly more detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to the Asteroid 1999 NC43. We find ∼(1-3) × 10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the ∼(10-3-10-2) level. Secondly, we note that efforts to conclusively prove separation of the Chelyabinsk meteoroid from (86039) 1999 NC43 in the past needs to meet severe criteria: relative velocity ≃1-10 m/s or smaller, and ≃100 km distance (i.e. about the Hill sphere distance from the parent body). We conclude that, unless the separation event was an extremely recent event, these criteria present an insurmountable difficulty due to the combination of strong orbital chaoticity, orbit uncertainty and incompleteness of the dynamical model with respect to thermal accelerations. This situation leaves the link of the two bodies unresolved and calls for additional analyses. With that goal, we revisit the presumed compositional link between (86039) 1999 NC43 and the Chelyabinsk body. Borovička et al. (Borovička, J., et al. [2013]. Nature 503, 235-237) noted that given its Q-type taxonomic classification, 1999 NC43 may pass this test. However, here we find that while the Q-type classification of 1999 NC43 is accurate, assuming that all Q-types are LL chondrites is not. Our experiment shows that not all ordinary chondrites fall under Q-taxonomic type and not all LL chondrites are Q-types. Spectral curve matching between laboratory spectra of Chelyabinsk and 1999 NC43 spectrum shows that the spectra do not match. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8) Flora (the largest member of the presumed LL chondrite parent family) shows that their olivine and pyroxene chemistries are similar to LL chondrites. Similar analysis of 1999 NC43 shows that its olivine and pyroxene chemistries are more similar to L chondrites than LL chondrites (like Chelyabinsk). Analysis of the spectrum using Modified Gaussian Model (MGM) suggests 1999 NC43 is similar to LL or L chondrite although we suspect this ambiguity is due to lack of temperature and phase angle corrections in the model. While some asteroid pairs show differences in spectral slope, there is no evidence for L and LL chondrite type objects fissioning out from the same parent body. We also took photometric observations of 1999 NC43 over 54 nights during two apparitions (2000, 2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of tumblers in Short-Axis Mode (SAM) with the mean wobbling angle 20°-30°. The very slow rotation of 1999 NC43 could be a result of slow-down by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. While, a mechanism of the non-principal axis rotation excitation is unclear, we can rule out the formation of asteroid in disruption of its parent body as a plausible cause, as it is unlikely that the rotation of an asteroid fragment from catastrophic disruption would be nearly completely halted. Considering all these facts, we find the proposed link between the Chelyabinsk meteoroid and the Asteroid 1999 NC43 to be unlikely.

Impact Melting of Ordinary Chondrite Regoliths and the Production of Fine-grained Fe(sup 0)

NASA Technical Reports Server (NTRS)

Hoerz, Friedrich; Cintala, Mark J.; See, Thomas H.

2003-01-01

The detailed study of individual lunar soil grains provides evidence that the major optical properties of the lunar surface are primarily related to the production of fine-grained (< 20 nm, super-paramagnetic) Fe-particles in agglutinitic impact melts and to iron-rich vapor deposits on the surfaces of individual grains. These Fe-rich materials are derived from oxidized species due to high post-shock temperatures in the presence of solar-wind derived H2; part of the Fe-rich grain surfaces may also be due to sputtering processes. Identical processes were recently suggested for the optical maturation of S-type asteroid surfaces, the parent objects of ordinary chondrites (OCs). OCs, however, do not contain impact-produced soil melts, and should thus also be devoid of impact-triggered vapor condensates. The seeming disparity can only be understood if all OCs resemble relatively immature impact debris, akin to numerous lunar highland breccias. It is possible to assess this scenario by evaluating experimentally whether impact velocities of 5- 6 km/s, typical for the present day asteroid belt, suffice to produce both impact melts and fine-grained metallic iron. We used 125-250 m powders of the L6 chondrite ALH85017. These powders were aliquots from fines that were produced by collisionally disrupting a single, large (461g) chunk of this meteorite during nine impacts and by subjecting the resulting rubble to an additional 50 impacts. As a consequence, the present shock-recovery experiments employ target materials of exceptional fidelity (i.e., a real chondrite that was impact pulverized). The target powders were packed into tungsten-alloy containers to allow for the potential investigation of freshly produced, fine-grained iron and impacted by stainless-steel and tungsten flyer plates; the packing density varied between 38 and 45% porosity. Peak pressures ranged from 14.5 to 67 GPa and were attained after multiple reverberations of the shock wave at the interface of the silicate powder and metal container. Pressures in the 50 to 70 GPa range should be fairly typical for asteroid impacts at approx. 5-6 km/s, yet we note that these pressures refer to those at the projectile/target interface only and that most crater ejecta on OC parent-bodies will have experienced much lower stresses.

Meteorites

NASA Astrophysics Data System (ADS)

Jenniskens, Peter

2015-08-01

Meteorites have long been known to offer a unique window into planetary formation processes at the time of solar system formation and into the materials that rained down on Earth at the time of the origin of life. Their material properties determine the impact hazard of Near Earth Asteroids. Some insight into how future laboratory studies of meteorites and laboratory astrophysics simulations of relevant physical processes can help address open questions in these areas and generate new astronomical observations, comes from what was learned from the recent laboratory studies of freshly fallen meteorites. The rapid recovery of Almahata Sitta (a polymict Ureilite), Sutter's Mill (a CM chondrite regolith breccia), Novato (an L6 chondrite), and Chelyabinsk (an LL5 chondrite) each were followed by the creation of a meteorite consortium, which grew to over 50 researchers in the case of Chelyabinsk. New technologies were used to probe the organic content of the meteorites as well as their magnetic signatures, isotopic abundances, trapped noble gasses, and cosmogenic radio nucleides, amongst others. This has resulted in fascinating insight into the nature of the Ureilite parent body, the likely source region of the CM chondrites in the main asteroid belt, and the collisional environment of the CM parent body. This work has encouraged follow-up in the hope of catching more unique materials. Rapid response efforts are being developed that aim to recover meteorites as pristinely as possible from falls for which the approach orbit was measured. A significant increase in the number of known approach orbits for different meteorite types will help tie meteorite types to their asteroid family source regions. Work so far suggests that future laboratory studies may recognize multiple source regions for iron-rich ordinary chondrites, for example. Hope is that these source regions will give insight into the material properties of impacting asteroids. At least some future laboratory astrophysics experiments are expected to focus on clarifying the physical conditions during small asteroid impacts such as the one responsible for the Chelyabinsk airburst and the over 1200 injured who needed medical attention.

Chemical studies of differentiated meteorites. I - Labile trace elements in Antarctic and non-Antarctic eucrites

NASA Technical Reports Server (NTRS)

Paul, Rick L.; Lipschutz, Michael E.

1990-01-01

Element contents of Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U, and Zn were analyzed, using RNAA, in 25 Antarctic and nine non-Antarctic eucrites to determine whether these two populations differ significantly in thermal history and derive from the same or different eucrite parent body. Data for these 15 elements indicate that basaltic Antarctic and non-Antarctic eucrite populations reflect the same genetic processes and, hence, come from the same parent asteroid.

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

NASA Technical Reports Server (NTRS)

Yen, Chen-Wan L.

1989-01-01

An extensive investigation of the ways to rendezvous with diverse groups of asteroids residing between 2.0 and 5.0 AU is made, and the extent of achievable missions using the STS upper-stage launch vehicles (IUS 2-Stage/Star-48 or NASA Centaur) is examined. With judicious use of earth, Mars, and Jupiter gravity assists, rendezvous with some asteroids in all regions of space is possible. It is also shown that the STS upper stages are capable of carrying out missions beyond a single rendezvous, namely with several flybys and/or multiple rendezvous.

Petrologic and Oxygen-Isotopic Investigations of Eucritic and Anomalous Mafic Achondrites

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Greenwood, R. C.; Peng, Z. X.; Ross, D. K.; Berger, E. L.; Barrett, T. J.

2016-01-01

The most common asteroidal igneous meteorites are eucrite-type basalts and gabbros rocks composed of ferroan pigeonite and augite, calcic plagioclase, silica, ilmenite, troilite, Ca-phosphate, chromite and Fe-metal. These rocks are thought to have formed on a single asteroid along with howardites and diogenites (HEDs). However, Northwest Africa (NWA) 011 is mineralogically identical to eucrites, but has an O-isotopic composition distinct from them and was derived from a different asteroid. Modern analyses with higher precision have shown that some eucrites have smaller O-isotopic differences that are nevertheless well-resolved from the group mean.

Volume and mass distribution in selected families of asteroids

NASA Astrophysics Data System (ADS)

Wlodarczyk, I.; Leliwa-Kopystynski, J.

2014-07-01

Members of five asteroid families (Vesta, Eos, Eunomia, Koronis, and Themis) were identified using the Hierarchical Clustering Method (HCM) for a data set containing 292,003 numbered asteroids. The influence of the choice of the best value of the parameter v_{cut} that controls the distances of asteroids in the proper elements space a, e, i was investigated with a step as small as 1 m/s. Results are given in a set of figures showing the families on the planes (a, e), (a, i), (e, i). Another form for the presentation of results is related to the secular resonances in the asteroids' motion with the giant planets, mostly with Saturn. Relations among asteroid radius, albedo, and absolute magnitude allow us to calculate the volumes of individual members of an asteroid family. After summation, the volumes of the parent bodies of the families were found. This paper presents the possibility and the first results of using a combined method for asteroid family identifications based on the following items: (i) Parameter v_{cut} is established with precision as high as 1 m/s; (ii) the albedo (if available) of the potential members is considered for approving or rejecting the family membership; (iii) a color classification is used for the same purpose as well. Searching for the most reliable parameter values for the family populations was performed by means of a consecutive application of the HCM with increasing parameter v_{cut}. The results are illustrated in the figure. Increasing v_{cut} in steps as small as 1 m/s allowed to observe the computational strength of the HCM: the critical value of the parameter v_{cut} (see the breaking-points of the plots in the figure) separates the assemblage of potential family members from 'an ocean' of background asteroids that are not related to the family. The critical values of v_{cut} vary from 57 m/s for the Vesta family to 92 m/s for the Eos family. If the parameter v_{cut} surpasses its critical value, the number of HCM-discovered family members increases enormously and without any physical reason.

PHYS: Division of Physical Chemistry 258 - Properties and Origins of Cometary and Asteroidal Organic Matter Delivered to the Early Earth

NASA Technical Reports Server (NTRS)

Messenger, Scott; Nguyen, Ann

2017-01-01

Comets and asteroids may have contributed much of the Earth's water and organic matter. The Earth accretes approximately 4x10(exp 7) Kg of dust and meteorites from these sources every year. The least altered meteorites contain complex assemblages of organic compounds and abundant hydrated minerals. These carbonaceous chondrite meteorites probably derive from asteroids that underwent hydrothermal processing within the first few million years after their accretion. Meteorite organics show isotopic and chemical signatures of low-T ion-molecule and grain-surface chemistry and photolysis of icy grains that occurred in cold molecular clouds and the outer protoplanetary disk. These signatures have been overprinted by aqueously mediated chemistry in asteroid parent bodies, forming amino acids and other prebiotic molecules. Comets are much richer in organic matter but it is less well characterized. Comet dust collected in the stratosphere shows larger H and N isotopic anomalies than most meteorites, suggesting better preservation of primordial organics. Rosetta studies of comet 67P coma dust find complex organic matter that may be related to the macromolecular material that dominates the organic inventory of primitive meteorites. The exogenous organic material accreting on Earth throughout its history is made up of thousands of molecular species formed in diverse processes ranging from circumstellar outflows to chemistry at near absolute zero in dark cloud cores and the formative environment within minor planets. NASA and JAXA are currently flying sample return missions to primitive, potentially organic-rich asteroids. The OSIRIS-REx and Hayabusa2 missions will map their target asteroids, Bennu and Ryugu, in detail and return regolith samples to Earth. Laboratory analyses of these pristine asteroid samples will provide unprecedented views of asteroidal organic matter relatively free of terrestrial contamination within well determined geological context. Studies of extraterrestrial materials and returned samples are essential to understand the origins of Solar System organic material and the roles of comets and asteroids to providing the starting materials for the emergence of life.

Paris vs. Murchison: Impact of hydrothermal alteration on organic matter in CM chondrites

NASA Astrophysics Data System (ADS)

Vinogradoff, V.; Le Guillou, C.; Bernard, S.; Binet, L.; Cartigny, P.; Brearley, A. J.; Remusat, L.

2017-09-01

Unravelling the origin of organic compounds that were accreted into asteroids requires better constraining the impact of asteroidal hydrothermal alteration on their isotopic signatures, molecular structures, and spatial distribution. Here, we conducted a multi-scale/multi-technique comparative study of the organic matter (OM) from two CM chondrites (that originate from the same parent body or from identical parent bodies that accreted the same mixture of precursors) and underwent a different degree of hydrothermal alteration: Paris (a weakly altered CM chondrite - CM 2.8) and Murchison (a more altered one - CM 2.5). The Paris insoluble organic matter (IOM) shows a higher aliphatic/aromatic carbon ratio, a higher radical abundance and a lower oxygen content than the Murchison IOM. Analysis of the OM in situ shows that two texturally distinct populations of organic compounds are present within the Paris matrix: sub-micrometric individual OM particles and diffuse OM finely distributed within phyllosilicates and amorphous silicates. These results indicate that hydrothermal alteration on the CM parent body induced aromatization and oxidation of the IOM, as well as a decrease in radical and nitrogen contents. Some of these observations were also reported by studies of variably altered fragment of Tagish Lake (C2), although the hydrothermal alteration of the OM in Tagish Lake was apparently much more severe. Finally, comparison with data available in the literature suggests that the parent bodies of other chondrite petrologic groups could have accreted a mixture of organic precursors different from that accreted by the parent body of CMs.

Shadow mechanism and the opposition effect of brightness of atmosphereless celestial bodies

NASA Astrophysics Data System (ADS)

Morozhenko, A. V.; Vidmachenko, A. P.

2013-09-01

We consider the Irvine-Yanovistkii modification of the shadow model developed by Hapke for the opposition effect of brightness. The relation between the single scattering albedo ω and the transparency coefficient of particles κ is suggested to be used in the form κ = (1 - ω) n, which allows the number of unknowns in the model to be reduced to two parameters (the packing density of particles g and ω) and the single-scattering phase function Ξ(α). The analysis of spectrophotometric measurements of the moon and Mars showed that the data on the observed opposition effect and the changes in the color index with the phase angle α well agree if the values of n = 0.25 and g = 0.4 (the moon) and 0.6 (Mars) are assumed in calculations. When being applied to asteroids of several types, this method also yielded a satisfactory agreement. For the E-type asteroids, the sets of parameters are [g = 0.6, ω = 0.6, A g = 0.21, and q = 0.83] or [g = 0.3, ω = 0.4, A g = 0.15, and q = 0.71] under the Martian single-scattering phase function; for the M-type asteroids, it is [g = 0.4, ω ≤ 0.1, A g ≤ 0.075, and q ≤ 0.42] under the lunar single-scattering phase function; for the S-type asteroids, it is [g = 0.4, ω = 0.4, A g = 0.28, and q = 0.49] under the lunar single-scattering phase function; and for the C-type asteroids, it is [g = 0.6, ω ≤ 0.1, A g ≤ 0.075, and q = 0.43] under the modified lunar single-scattering phase function. The polarization measurements fulfilled by Gehrels et al. (1964) for the bright feature on the lunar surface, Copernicus (L = -20°08', φ = +10°11'), at a phase angle α = 1.6° revealed the deviations in the position of the polarization plane from that typical for the negative branch. They were 22° and 12° in the G and I filters, respectively. At the same time, the deviation was within the error (±3° in the U filter and for the dark feature Plato (L = -10°32', φ = +51°25'), which can be caused by the coherent mechanism of the formation of the polarization peak.

Enhancing the Scientific Return from HST Imaging of Debris Disks

NASA Astrophysics Data System (ADS)

Weinberger, Alycia

2016-10-01

We propose realistic modeling of scattering of light by small aggregate dust grains that will enable us to interpret visible to near-infrared imaging of debris disks. We will determine if disk colors, phase functions, and polarizations place unique constraints on the composition of debris dust. Ongoing collisions of planetesimals generate dust; therefore, the dust provides unique information on compositions of the parent bodies. These exosolar analogs of asteroids and comets can bear clues to the history of a planetary system including migration and thermal processing. Because directly imaged debris disks are cold, they have no solid state emission features. Grain scattering properties as a function of wavelength are our only tool to reveal their compositions. Solar system interplanetary dust particles are fluffy aggregates, but most previous work on debris disk composition relied on Mie theory, i.e. assumed compact spherical grains. Mie calculations do not reproduce the observed colors and phase functions observed from debris disks. The few more complex calculations that exist do not explore the range of compositions and sizes relevant to debris disk dust. In particular, we expect porosity to help distinguish between cometary-like parent bodies, which are fluffy due to high volatile content and low collisional velocities, and asteroidal-like parent bodies that are compacted.

Reduced and unstratified crust in CV chondrite parent body.

PubMed

Ganino, Clément; Libourel, Guy

2017-08-15

Early Solar System planetesimal thermal models predict the heating of the chondritic protolith and the preservation of a chondritic crust on differentiated parent bodies. Petrological and geochemical analyses of chondrites have suggested that secondary alteration phases formed at low temperatures (<300 °C) by fluid-rock interaction where reduced and oxidized Vigarano type Carbonaceous (CV) chondrites witness different physicochemical conditions. From a thermodynamical survey of Ca-Fe-rich secondary phases in CV3 chondrites including silica activity (aSiO 2 ), here we show that the classical distinction between reduced and oxidized chondrites is no longer valid and that their Ca-Fe-rich secondary phases formed in similar reduced conditions near the iron-magnetite redox buffer at low aSiO 2 (log(aSiO 2 ) <-1) and moderate temperature (210-610 °C). The various lithologies in CV3 chondrites are inferred to be fragments of an asteroid percolated heterogeneously via porous flow of hydrothermal fluid. Putative 'onion shell' structures are not anymore a requirement for the CV parent body crust.Meteorites may unlock the history of the early solar system. Here, the authors find, through Ca-Fe-rich secondary phases, that the distinction between reduced and oxidized CV chondrites is invalid; therefore, CV3 chondrites are asteroid fragments that percolated heterogeneously via porous flow of hydrothermal fluid.

Spacecraft Mission Design for the Mitigation of the 2017 PDC Hypothetical Asteroid Threat

NASA Technical Reports Server (NTRS)

Barbee, Brent W.; Sarli, Bruno V.; Lyzhoft, Josh; Chodas, Paul W.; Englander, Jacob A.

2017-01-01

This paper presents a detailed mission design analysis results for the 2017 Planetary Defense Conference (PDC) Hypothetical Asteroid Impact Scenario, documented at https:cneos.jpl.nasa.govpdcspdc17. The mission design includes campaigns for both reconnaissance (flyby or rendezvous) of the asteroid (to characterize it and the nature of the threat it poses to Earth) and mitigation of the asteroid, via kinetic impactor deflection, nuclear explosive device (NED) deflection, or NED disruption. Relevant scenario parameters are varied to assess the sensitivity of the design outcome, such as asteroid bulk density, asteroid diameter, momentum enhancement factor, spacecraft launch vehicle, and mitigation system type. Different trajectory types are evaluated in the mission design process from purely ballistic to those involving optimal midcourse maneuvers, planetary gravity assists, and/or low-thrust solar electric propulsion. The trajectory optimization is targeted around peak deflection points that were found through a novel linear numerical technique method. The optimization process includes constrain parameters, such as Earth departure date, launch declination, spacecraft, asteroid relative velocity and solar phase angle, spacecraft dry mass, minimum/maximum spacecraft distances from Sun and Earth, and Earth-spacecraft communications line of sight. Results show that one of the best options for the 2017 PDC deflection is solar electric propelled rendezvous mission with a single spacecraft using NED for the deflection.

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.

Workshop on evolution of igneous asteroids: Focus on Vesta and the HED meteorites

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W. (Editor); Papike, J. J. (Editor)

1996-01-01

Recently, the geology of the surface of Vesta has been coming to light. In 1983 Gaffey first began showing maps of the surface geology of Vesta constructed from numerous spectra obtained at different times as the asteroid rotated. By noting the details of spectral variation with rotation, he was able to develop two possible gross-scale geologic maps of Vesta showing the distributions of mafic and ultramafic materials. These maps were published in 1997. Finally, the capabilities of the Hubble Space Telescope were brought to bear on Vesta and images with a resolution of about 50 km were obtained using four different filters by Binzel and co-workers. Maps produced by this team published in 1997 began to reveal the geology of Vesta in sufficient detail that crude interpretations of the geologic history of the asteroid could be attempted. Additionally, in 1993 Binzel and Xu published a study of small asteroids in the region near Vesta in orbital-element space. In this study, they showed that there are a number of asteroids a few kilometers in size with reflectance spectra like that of Vesta that form a trail in orbital-element space from near Vesta to near resonances that can more easily supply material to near-Earth space. Binzel and Xu thus concluded that these small asteroids were spells of Vesta ejected by impact and that some of their brethren had been perturbed to Earth-approaching orbits. They suggested that these latter were the immediate parents of HED meteorites. This seemed to remove a long-standing dynamical objection to Vesta as the HED parent body, as discussed by Wasson and Wetherill in 1979. Within the last few years, NASA has initiated the Discovery program of low-cost, rapid-timescale development, exploration missions. Vesta has been proposed as an object worthy of study by a Discovery mission, although a Vesta mission has not yet been selected. With all the recent activity aimed at studying Vesta and the HED meteorites, and the possibility of a space mission to Vesta, we felt that time was ripe to convene a workshop bringing together astronomers, meteoriticists, and planetary geologists to focus on what could be learned about the geologic evolution of Vesta through integrating astronomical and HED meteorite studies. This, of course, assumes that the HED meteorites are from Vesta, and this issue was specifically addressed (but not resolved) in the workshop. Indeed, it seems likely that this issue can only be resolved by returning samples from Vesta for detailed study on Earth. The workshop was held at the LPI on October 16-18,1996, and was attended by some 70 scientists. Sessions included a set of talks on Earth- and space-based astronomical observations of Vesta plus the evidence pro and con for Vesta being the HED parent body, talks on the petrology and geochemistry of HED meteorites, talks on the formation and dynamics of ejecta from Vesta, talks on the thermal history of asteroids and HED meteorites, volcanic processes and differentiation history, and a short session devoted to possible missions to Vestal By all accounts, the workshop was considered a great success, although this is the opinion of a biased set of observers.

The tumbling rotational state of 1I/`Oumuamua

NASA Astrophysics Data System (ADS)

Fraser, Wesley C.; Pravec, Petr; Fitzsimmons, Alan; Lacerda, Pedro; Bannister, Michele T.; Snodgrass, Colin; Smolić, Igor

2018-05-01

The discovery1 of 1I/2017 U1 (1I/`Oumuamua) has provided the first glimpse of a planetesimal born in another planetary system. This interloper exhibits a variable colour within a range that is broadly consistent with local small bodies, such as the P- and D-type asteroids, Jupiter Trojans and dynamically excited Kuiper belt objects2-7. 1I/`Oumuamua appears unusually elongated in shape, with an axial ratio exceeding 5:1 (refs 1,4,5,8). Rotation period estimates are inconsistent and varied, with reported values between 6.9 and 8.3 h (refs 4-6,9). Here, we analyse all the available optical photometry data reported to date. No single rotation period can explain the exhibited brightness variations. Rather, 1I/`Oumuamua appears to be in an excited rotational state undergoing non-principal axis rotation, or tumbling. A satisfactory solution has apparent lightcurve frequencies of 0.135 and 0.126 h-1 and implies a longest-to-shortest axis ratio of ≳5:1, although the available data are insufficient to uniquely constrain the true frequencies and shape. Assuming a body that responds to non-principal axis rotation in a similar manner to Solar System asteroids and comets, the timescale to damp 1I/`Oumuamua's tumbling is at least one billion years. 1I/`Oumuamua was probably set tumbling within its parent planetary system and will remain tumbling well after it has left ours.

Oxygen Isotope Evidence for the Relationship between CM and CO Chondrites: Could they Both Coexist on a Single Asteroid

NASA Technical Reports Server (NTRS)

Greenwood, R. C.; Howard, K. T.; Franchi, I. A.; Zolensky, M. E.; Buchanan, P. C.; Gibson, J. M.

2014-01-01

Water played a critical role in the early evolution of asteroids and planets, as well as being an essential ingredient for life on Earth. However, despite its importance, the source of water in the inner solar system remains controversial. Delivery of water to Earth via comets is inconsistent with their relatively elevated D/H ratios, whereas carbonaceous chondrites (CCs) have more terrestrial-like D/H ratios [1]. Of the eight groups into which the CCs are divided, only three (CI, CM, CR) show evidence of extensive aqueous alteration. Of these, the CMs form the single most important group, representing 34% of all CC falls and a similar percentage of finds (Met. Bull. Database). CM material also dominates the population of CC clasts in extraterrestrial samples [2, 3]. The Antarctic micrometeorites population is also dominated by CM and CI-like material and similar particles may have transported water and volatiles to the early Earth [4]. CCs, and CMs in particular, offer the best opportunity for investigating the evolution of water reservoirs in the early solar system. An important aspect of this problem involves identifying the anhydrous silicate component which co-accreted with ice in the CM parent body. A genetic relationship between the essentially anhydrous CO group and the CMs was proposed on the basis of oxygen isotope evidence [5]. However, previous CM whole-rock oxygen isotope data scattered about a line of approximately 0.5 that did not intersect the field of CO chondrites [5]. Here we discuss new oxygen isotope data which provides additional constraints on the relationship between CO and CM chondrites.

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.

Non-equilibrium effects on the chemistry of nebular condensates - Implications for the planets and asteroids

NASA Technical Reports Server (NTRS)

Blander, M.

1979-01-01

Kinetic effects, for example nucleation constraints and slow reactions, should have been important in nebular condensation. Consideration of these effects leads to the prediction of pressure-dependent compositions and physical properties of nebular condensates which is consistent with (1) the differences between different classes of chondritic meteorites, (2) some of the differences between planets, and (3) the presence of oxidized iron on the moon and in the eucrite parent body (presumably an asteroid) despite the low abundance of volatiles. Diffusion effects appear to be important for understanding oxygen isotope anomalies in refractory inclusions in Allende. The consideration of kinetic effects leads to more information concerning nebular processes than if equilibrium is assumed.

The Impact Ejecta Environment of Near Earth Asteroids

NASA Astrophysics Data System (ADS)

Szalay, Jamey R.; Horányi, Mihály

2016-10-01

Impact ejecta production is a ubiquitous process that occurs on all airless bodies throughout the solar system. Unlike the Moon, which retains a large fraction of its ejecta, asteroids primarily shed their ejecta into the interplanetary dust population. These grains carry valuable information about the chemical compositions of their parent bodies that can be measured via in situ dust detection. Here, we use recent Lunar Atmosphere and Dust Environment Explorer/Lunar Dust Experiment measurements of the lunar dust cloud to calculate the dust ejecta distribution for any airless body near 1 au. We expect this dust distribution to be highly asymmetric, due to non-isotropic impacting fluxes. We predict that flybys near these asteroids would collect many times more dust impacts by transiting the apex side of the body compared to its anti-apex side. While these results are valid for bodies at 1 au, they can be used to qualitatively infer the ejecta environment for all solar-orbiting airless bodies.

Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification.

PubMed

Lindskog, A; Costa, M M; Rasmussen, C M Ø; Connelly, J N; Eriksson, M E

2017-01-24

The catastrophic disruption of the L chondrite parent body in the asteroid belt c. 470 Ma initiated a prolonged meteorite bombardment of Earth that started in the Ordovician and continues today. Abundant L chondrite meteorites in Middle Ordovician strata have been interpreted to be the consequence of the asteroid breakup event. Here we report a zircon U-Pb date of 467.50±0.28 Ma from a distinct bed within the meteorite-bearing interval of southern Sweden that, combined with published cosmic-ray exposure ages of co-occurring meteoritic material, provides a precise age for the L chondrite breakup at 468.0±0.3 Ma. The new zircon date requires significant revision of the Ordovician timescale that has implications for the understanding of the astrogeobiologic development during this period. It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated.

Aggregates: The Fundamental Building Blocks of Planetesimals?

NASA Technical Reports Server (NTRS)

Cuzzi, J. N.; Hartlep, T.; Simon, J. I.; Cato, M. J.

2017-01-01

The initial accretion of primitive asteroids (meteorite parent bodies) from freely-floating nebula particles remains problematic. Traditional growth-by-sticking models in turbulent nebulae encounter a formidable "meter-size barrier" due to both drift and destruction, or even a mmtocmsize "bouncing" barrier. Even if growth by sticking could somehow breach these barriers (perhaps if the actual sticking or strength is larger than current estimates, which are based on pure ice or pure silicate), turbulent nebulae present further obstacles through the 1-10km size range. On the other hand, nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids. Thus, the intensity of nebula turbulence (or "alpha ") is critical to the entire process. Theoretical understanding of nebula turbulence continues to evolve; while recent models of MRI (magneticallydriven) turbulence favor lowornoturbulence environments, purely hydrodynamic turbulence is making a comeback with three recently discovered mechanisms generating turbulence of moderate which do not rely on magnetic fields at all.

Planetesimals Born Big by Clustering Instability?

NASA Technical Reports Server (NTRS)

Cuzzi, Jeffrey N.; Hartlep, Thomas; Simon, Justin I.; Estrada, Paul R.

2017-01-01

Roughly 100km diameter primitive bodies (today's asteroids and TNOs; [1]) are thought to be the end product of so-called "primary accretion". They dominated the initial mass function of planetesimals, and precipitated the onset of a subsequent stage, characterized by runaway gravitational effects, which proceeded onwards to planetary mass objects, some of which accreted massive gas envelopes. Asteroids are the parents of primitive meteorites; meteorite data suggest that asteroids initially formed directly from freelyfloating nebula particles in the mm-size range. Unfortunately, the process by which these primary 100km diameter planetesimals formed remains problematic. We review the most diagnostic primitive parent body observations, highlight critical aspects of the nebula context, and describe the issues facing various primary accretion models. We suggest a path forward that combines current scenarios of "turbulent concentration" (TC) and "streaming instabilities" (SI) into a triggered formation process we call clustering instability (CI). Under expected conditions of nebula turbulence, the success of these processes at forming terrestrial region (mostly silicate) planetesimals requires growth by sticking into aggregates in the several cm size range, at least, which is orders of magnitude more massive than allowed by current growth-by-sticking models using current experimental sticking parameters [2-4]. The situation is not as dire in the ice-rich outer solar system; however, growth outside of the snowline has important effects on growth inside of it [4] and at least one aspect of outer solar system planetesimals (high binary fraction) supports some kind of clustering instability.

Planetesimals Born Big by Clustering Instability?

NASA Technical Reports Server (NTRS)

Cuzzi, Jeffrey N.; Hartlep, Thomas; Simon, Justin I.; Estrada, Paul R.

2017-01-01

Roughly 100km diameter primitive bodies (today's asteroids and TNOs; [1]) are thought to be the end product of so-called "primary accretion". They dominated the initial mass function of planetesimals, and precipitated the onset of a subsequent stage, characterized by runaway gravitational effects, which proceeded onwards to planetary mass objects, some of which accreted massive gas envelopes. Asteroids are the parents of primitive meteorites; meteorite data suggest that asteroids initially formed directly from freelyfloating nebula particles in the mm-size range. Unfortunately, the process by which these primary 100km diameter planetesimals formed remains problematic. We review the most diagnostic primitive parent body observations, highlight critical aspects of the nebula context, and describe the issues facing various primary accretion models. We suggest a path forward that combines current scenarios of "turbulent concentration" (TC) and "streaming instabilities" (SI) into a triggered formation process we call clustering instability (CI). Under expected conditions of nebula turbulence, the success of these processes at forming terrestrial region (mostly silicate) planetesimals requires growth by sticking into aggregates in the several cm size range, at least, which is orders of magnitude more massive than allowed by current growth-by-sticking models using current experimental sticking parameters [2-4]. The situation is not as dire in the ice-rich outer solar system; however, growth outside of the snowline has important effects on growth inside of it [4] and at least one aspect of outer solar system planetesimals (high binary fraction) supports some kind of clustering instability

Spectral evidence for amorphous silicates in least-processed CO meteorites and their parent bodies

NASA Astrophysics Data System (ADS)

McAdam, Margaret M.; Sunshine, Jessica M.; Howard, Kieren T.; Alexander, Conel M.; McCoy, Timothy J.; Bus, Schelte J.

2018-05-01

Least-processed carbonaceous chondrites (carbonaceous chondrites that have experienced minimal aqueous alteration and thermal metamorphism) are characterized by their predominately amorphous iron-rich silicate interchondrule matrices and chondrule rims. This material is highly susceptible to destruction by the parent body processes of thermal metamorphism or aqueous alteration. The presence of abundant amorphous material in a meteorite indicates that the parent body, or at least a region of the parent body, experienced minimal processing since the time of accretion. The CO chemical group of carbonaceous chondrites has a significant number of these least-processed samples. We present visible/near-infrared and mid-infrared spectra of eight least-processed CO meteorites (petrologic type 3.0-3.1). In the visible/near-infrared, these COs are characterized by a broad weak feature that was first observed by Cloutis et al. (2012) to be at 1.3-μm and attributed to iron-rich amorphous silicate matrix materials. This feature is observed to be centered at 1.4-μm for terrestrially unweathered, least-processed CO meteorites. At mid-infrared wavelengths, a 21-μm feature, consistent with Si-O vibrations of amorphous materials and glasses, is also present. The spectral features of iron-rich amorphous silicate matrix are absent in both the near- and mid-infrared spectra of higher metamorphic grade COs because this material has recrystallized as crystalline olivine. Furthermore, spectra of least-processed primitive meteorites from other chemical groups (CRs, MET 00426 and QUE 99177, and C2-ungrouped Acfer 094), also exhibit a 21-μm feature. Thus, we conclude that the 1.4- and 21-μm features are characteristic of primitive least-processed meteorites from all chemical groups of carbonaceous chondrites. Finally, we present an IRTF + SPeX observation of asteroid (93) Minerva that has spectral similarities in the visible/near-infrared to the least-processed CO carbonaceous chondrites. While Minerva is not the only CO-like asteroid (e.g., Burbine et al., 2001), Minerva is likely the least-processed CO-like asteroid observed to date.

Velocity distributions among colliding asteroids

NASA Technical Reports Server (NTRS)

Bottke, William F., Jr.; Nolan, Michael C.; Greenberg, Richard; Kolvoord, Robert A.

1994-01-01

The probability distribution for impact velocities between two given asteroids is wide, non-Gaussian, and often contains spikes according to our new method of analysis in which each possible orbital geometry for collision is weighted according to its probability. An average value would give a good representation only if the distribution were smooth and narrow. Therefore, the complete velocity distribution we obtain for various asteroid populations differs significantly from published histograms of average velocities. For all pairs among the 682 asteroids in the main-belt with D greater than 50 km, we find that our computed velocity distribution is much wider than previously computed histograms of average velocities. In this case, the most probable impact velocity is approximately 4.4 km/sec, compared with the mean impact velocity of 5.3 km/sec. For cases of a single asteroid (e.g., Gaspra or Ida) relative to an impacting population, the distribution we find yields lower velocities than previously reported by others. The width of these velocity distributions implies that mean impact velocities must be used with caution when calculating asteroid collisional lifetimes or crater-size distributions. Since the most probable impact velocities are lower than the mean, disruption events may occur less frequently than previously estimated. However, this disruption rate may be balanced somewhat by an apparent increase in the frequency of high-velocity impacts between asteroids. These results have implications for issues such as asteroidal disruption rates, the amount/type of impact ejecta available for meteoritical delivery to the Earth, and the geology and evolution of specific asteroids like Gaspra.

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.

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.

Investigation of Shapes and Spins of Reaccumulated Remnants from Asteroid Disruption Simulations

NASA Astrophysics Data System (ADS)

Michel, Patrick; Ballouz, R.; Richardson, D. C.; Schwartz, S. R.

2012-10-01

Evidence that asteroids larger than a few hundred meters diameter can be gravitational aggregates of smaller, cohesive pieces comes, for instance, from images returned by the Hayabusa spacecraft of asteroid 25143 Itokawa (Fujiwara et al., 2006, Science 312, 1330). These images show an irregular 500-meter-long body with a boulder-strewn surface, as might be expected from reaccumulation following catastrophic disruption of a larger parent asteroid (Michel et al., 2001, Science 294, 1696). However, numerical simulations of this process to date essentially focus on the size/mass and velocity distributions of reaccumulated fragments, matching asteroid families. Reaccumulation was simplified by merging the objects into growing spheres. However, understanding shapes, spins and surface properties of gravitational aggregates formed by reaccumulation is required to interpret information from ground-based observations and space missions. E.g., do boulders on Itokawa originate from reaccumulation of material ejected from a catastrophic impact or from other processes (such as the Brazil-nut effect)? How does reaccumulation affect the observed shapes? A model was developed (Richardson et al., 2009, Planet. Space Sci. 57, 183) to preserve shape and spin information of reaccumulated bodies in simulations of asteroid disruption, by allowing fragments to stick on contact (and optionally bounce or fragment further, depending on user-selectable parameters). Such treatments are computationally expensive, and we could only recently start to explore the parameter space. Preliminary results will be presented, showing that some observed surface and shape features may be explained by how fragments produced by a disruption reaccumulate. Simulations of rubble pile collisions without particle cohesion, and an investigation of the influence of initial target rotation on the outcome will also be shown. We acknowledge the National Science Foundation (AST1009579) and NASA (NNX08AM39G).

Investigating the Geological History of Asteroid 101955 Bennu Through Remote Sensing and Returned Sample Analyses

NASA Technical Reports Server (NTRS)

Messenger, S.; Connolly, H. C., Jr.; Lauretta, D. S.; Bottke, W. F.

2014-01-01

The NASA New Frontiers Mission OSRIS-REx will return surface regolith samples from near-Earth asteroid 101955 Bennu in September 2023. This target is classified as a B-type asteroid and is spectrally similar to CI and CM chondrite meteorites [1]. The returned samples are thus expected to contain primitive ancient Solar System materials that formed in planetary, nebular, interstellar, and circumstellar environments. Laboratory studies of primitive astromaterials have yielded detailed constraints on the origins, properties, and evolutionary histories of a wide range of Solar System bodies. Yet, the parent bodies of meteorites and cosmic dust are generally unknown, genetic and evolutionary relationships among asteroids and comets are unsettled, and links between laboratory and remote observations remain tenuous. The OSIRIS-REx mission will offer the opportunity to coordinate detailed laboratory analyses of asteroidal materials with known and well characterized geological context from which the samples originated. A primary goal of the OSIRIS-REx mission will be to provide detailed constraints on the origin and geological and dynamical history of Bennu through coordinated analytical studies of the returned samples. These microanalytical studies will be placed in geological context through an extensive orbital remote sensing campaign that will characterize the global geological features and chemical diversity of Bennu. The first views of the asteroid surface and of the returned samples will undoubtedly bring remarkable surprises. However, a wealth of laboratory studies of meteorites and spacecraft encounters with primitive bodies provides a useful framework to formulate priority scientific questions and effective analytical approaches well before the samples are returned. Here we summarize our approach to unraveling the geological history of Bennu through returned sample analyses.

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

Metal-silicate fractionation in the surface dust layers of accreting planetesimals: Implications for the formation of ordinary chondrites and the nature of asteroid surfaces

NASA Astrophysics Data System (ADS)

Huang, Shaoxiong; Akridge, Glen; Sears, Derek W. G.

Some of the most primitive solar system materials available for study in the laboratory are the ordinary chondrites, the largest meteorite class. The size and distribution of the chondrules (silicate beads) and metal, which leads to the definition of the H, L, and LL classes, suggest sorting before or during aggregation. We suggest that meteorite parent bodies (probably asteroids) had thick dusty surfaces during their early evolution that were easily mobilized by gases evolving from their interiors. Density and size sorting would have occurred in the surface layers as the upward drag forces of the gases (mainly water) acted against the downward force of gravity. The process is analogous to the industrially important process of fluidization and sorting in pyroclastic volcanics. We calculate that gas flow velocities and gas fluxes for the regolith of an asteroid-sized object heated by the impact of accreting objects or by 26Al would have been sufficient for fluidization. It can also explain, quantitatively in some cases, the observed metal-silicate sorting of ordinary chondrites, which has long been ascribed to processes occurring in the primordial solar nebula. Formation of the chondrites in the thick dynamic regolith is consistent with the major properties of chondritic meteorites (i.e., redox state, petrologic type, cooling rate, matrix abundance). These ideas have implications for the nature of asteroid surfaces and the virtual lack of asteroids with ordinary chondrite-like surfaces.

Oxygen Isotope Compositions of the Kaidun Meteorite - Indications for Aqeuous Alteration of E-Chondrites

NASA Technical Reports Server (NTRS)

Ziegler, K.; Zolensky, M.; Young, E. D.; Ivanov, A.

2012-01-01

The Kaidun microbreccia is a unique meteorite due to the diversity of its constituent clasts. Fragments of various types of carbonaceous (CI, CM, CV, CR), enstatite (EH, EL), and ordinary chondrites, basaltic achondrites, and impact melt products have been described, and also several unknown clasts [1, and references therein]. The small mm-sized clasts represent material from different places and times in the early solar system, involving a large variety of parent bodies [2]; meteorites are of key importance to the study of the origin and evolution of the solar system, and Kaidun is a collection of a range of bodies evidently representing samples from across the asteroid belt. The parent-body on which Kaidun was assembled is believed to be a C-type asteroid, and 1-Ceres and the martian moon Phobos have been proposed [1-4]. Both carbonaceous (most oxidized) and enstatite (most reduced) chondrite clasts in Kaidun show signs of aqueous alterations that vary in type and degree and are most likely of pre-Kaidun origin [1, 4].

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.

Thermal Infrared Imager on Hayabusa2: Science and Development

NASA Astrophysics Data System (ADS)

Okada, Tatsuaki

2015-04-01

Thermal Infrared Imager TIR was developed and calibrated for Haya-busa2 asteroid explorer, aiming at the investigation of thermo-physical properties of C-class near-Earth sub-km sized asteroid (162173) 1999JU3. TIR is based on the 2D micro-bolometer array with germani-um lens to image the surface of asteroid in 8 to 12 μm wavelength (1), measuring the thermal emission off the asteroid surface. Its field of view is 16° x 12° with 328 x 248 pixels. At least 40 (up to 100) images will be taken during asteroid rotation once a week, mainly from the Home Position which is about 20km sunward from asteroid surface. Therefore TIR will image the whole asteroid with spatial resolution of < 20m per pixel, and the temperature profile of each site on the asteroid will be traced from dawn to dusk regions by asteroid rotation. The scien-tific objectives of TIR include the mapping of asteroid surface condi-tions (regional distribution of thermal inertia), since the surface physical conditions are strongly correlated with thermal inertia. It is so informa-tive on understanding the re-accretion or surface sedimentation process-es of the asteroid to be the current form. TIR data will be used for searching for those sites having the typical particle size of 1mm for best sample collection, and within the proper thermal condition for space-craft safe operation. After launch of Hayabusa2, TIR has been tested successfully, covering from -100 to 150 °C using a single parameter settings (2). This implies that TIR is actually able to map the surface other than the sunlit areas. Performance of TIR was found basically the same as those in the pre-launch test, when the temperature of TIR is well controlled. References: (1) Fukuhara T. et al., (2011) Earth Planet. Space 63, 1009-1018; (2) Okada T. et al., (2015) Lunar Planet. Sci. Conf. 46, #1331.

Equatorial cavities on asteroids, an evidence of fission events

NASA Astrophysics Data System (ADS)

Tardivel, Simon; Sánchez, Paul; Scheeres, Daniel J.

2018-04-01

This paper investigates the equatorial cavities found on asteroids 2008 EV5 and 2000 DP107 Alpha. As the likelihood of these cavities being impact craters is demonstrated to be low, the paper presents a fission mechanism that explains their existence as a scar of past fission events. The dynamical environment of "top-shaped" asteroids is such that, at high spin rates, an identifiable equatorial region enters into tension before the rest of the body. We propose hypothetical past shapes for 2008 EV5 and 2000 DP107, with mass added within the cavity to recreate a smoother equatorial ridge. The dynamical environment of these hypothetical parent bodies reveal that this modified region is indeed set in tension when spin is increased. The fission process requires tensile strength at the interface between the ejecta and the remaining body, at the moment of fission, between 0 and 2 Pa for 2008 EV5 and between 0 and 15 Pa for 2000 DP107, depending on the precise fission scenario considered. Going back to the spin-up deformation phase of the asteroids, the paper examines how kinetic sieving can form predominantly rocky equators, whose tensile strength could be much lower than that of the rest of the body. This process could explain the low cohesion values implied for this fission mechanism.

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.

Spatial Mapping of NEO 2008 EV5 Using Small Satellite Formation Flying and Steresoscopic Technology

NASA Astrophysics Data System (ADS)

Gonzalez, Juan; Singh Derewa, Chrishma

2016-10-01

NASA is currently developing the first-ever robotic Asteroid Redirect Robotic Mission (ARRM) to the near-Earth asteroid 2008 EV5 with the objective to capture a multi-ton boulder from the asteroids surface and use its mass to redirect its parent into a CIS lunar orbit where astronauts will study its physical and chemical composition.A critical step towards achieving this mission is to effectively map the target asteroid, identify the candidate boulder for retrieval and characterize its critical parameters. Currently, ARRM utilizes a laser altimeter to characterize the height of the boulders and mapping for final autonomous control of the capture. The proposed Lava-Kusha mission provides the increased of stereoscopic imaging and mapping, not only the Earthward side of the asteroid which has been observed for possible landing sites, but mapping the whole asteroid. LKM will enhance the fidelity of the data collected by the laser altimeter and gather improved topographic data for future Orion missions to 2008 EV5 once in cis lunar space.LKM consists of two low cost small satellites (6U) as a part of the ARRM. They will launch with ARRM as an integrated part of the system. Once at the target, this formation of pathfinder satellites will image the mission critical boulder to ensure the system design can support its removal. LKM will conduct a series of flybys prior to ARRM's rendezvous. LKMs stereoscopic cameras will provide detailed surveys of the boulder's terrain and environment to ensure ARRM can operate safely, reach the location and interface with the boulder. The LKM attitude control and cold gas propulsion system will enable formation maintenance maneuvers for global mapping of asteroid 2008 EV5 at an altitude of 100 km to a high-spatial resolution imaging altitude of 5 km.LKM will demonstrate formation flying in deep space and the reliability of stereoscopic cameras to precisely identify a specific target and provide physical characterization of an asteroid. An assessment of the off-the-shelf technology used at JPL will be provided also with technology readiness descriptions, mission architecture, cost analysis and future work required to make the proposed LKM mission a partner to ARRM.

Spacecraft Mission Design for the Mitigation of the 2017 PDC Hypothetical Asteroid Threat

NASA Technical Reports Server (NTRS)

Barbee, Brent W.; Sarli, Bruno V.; Lyzhoft, Joshua; Chodas, Paul W.; Englander, Jacob A.

2017-01-01

This paper presents a detailed mission design analysis results for the 2017 Planetary Defense Conference (PDC) Hypothetical Asteroid Impact Scenario, documented at https://cneos.jpl.nasa.gov/ pd/cs/pdc17/. The mission design includes campaigns for both reconnaissance (flyby or rendezvous) of the asteroid (to characterize it and the nature of the threat it poses to Earth) and mitigation of the asteroid, via kinetic impactor deflection, nuclear explosive device (NED) deflection, or NED disruption. Relevant scenario parameters are varied to assess the sensitivity of the design outcome, such as asteroid bulk density, asteroid diameter, momentum enhancement factor, spacecraft launch vehicle, and mitigation system type. Different trajectory types are evaluated in the mission design process from purely ballistic to those involving optimal midcourse maneuvers, planetary gravity assists, and/or lowthrust solar electric propulsion. The trajectory optimization is targeted around peak deflection points that were found through a novel linear numerical technique method. The optimization process includes constrain parameters, such as Earth departure date, launch declination, spacecraft/asteroid relative velocity and solar phase angle, spacecraft dry mass, minimum/maximum spacecraft distances from Sun and Earth, and Earth/spacecraft communications line of sight. Results show that one of the best options for the 2017 PDC deflection is solar electric propelled rendezvous mission with a single spacecraft using NED for the deflection

Comet nucleus and asteroid sample return missions

NASA Technical Reports Server (NTRS)

Melton, Robert G.; Thompson, Roger C.; Starchville, Thomas F., Jr.; Adams, C.; Aldo, A.; Dobson, K.; Flotta, C.; Gagliardino, J.; Lear, M.; Mcmillan, C.

1992-01-01

During the 1991-92 academic year, the Pennsylvania State University has developed three sample return missions: one to the nucleus of comet Wild 2, one to the asteroid Eros, and one to three asteroids located in the Main Belt. The primary objective of the comet nucleus sample return mission is to rendezvous with a short period comet and acquire a 10 kg sample for return to Earth. Upon rendezvous with the comet, a tethered coring and sampler drill will contact the surface and extract a two-meter core sample from the target site. Before the spacecraft returns to Earth, a monitoring penetrator containing scientific instruments will be deployed for gathering long-term data about the comet. A single asteroid sample return mission to the asteroid 433 Eros (chosen for proximity and launch opportunities) will extract a sample from the asteroid surface for return to Earth. To limit overall mission cost, most of the mission design uses current technologies, except the sampler drill design. The multiple asteroid sample return mission could best be characterized through its use of future technology including an optical communications system, a nuclear power reactor, and a low-thrust propulsion system. A low-thrust trajectory optimization code (QuickTop 2) obtained from the NASA LeRC helped in planning the size of major subsystem components, as well as the trajectory between targets.

Reduction of photographic observations of asteroids to the reference frame of a single catalog

NASA Astrophysics Data System (ADS)

Chernetenko, Yu. A.

2008-04-01

In 2000, the last international program of photographic observations of selected asteroids aimed at the determination of the mutual orientation of the dynamic and stellar coordinate systems came to an end. The Institute of Applied Astronomy of the Russian Academy of Sciences collected more than 25 000 observations for 15 asteroids spanning from 1949 through 1995. These observations were reduced to the reference frame of the Hipparcos catalog using dependencies published along with observations. The accuracy of observations of selected asteroids was 0.30 arcsec, which is comparable to that of modern CCD observations of minor planets. The observations are available at ftp://quasar.ipa.nw.ru/pub/SMP . An important advantage of these observations is that they are already reduced to the reference frame of a single catalog. Our criteria for the quality of the reduction methods and the accuracy of the observations are based on estimating the parameters of the orientation of the reference frames of the PPM and Hipparcos catalogs with respect to DE200/LE200. The most reliable results are those obtained when reducing old optical observations along with modern ground-based and space-borne observations.

Asteroid families in the Cybele and Hungaria groups

NASA Astrophysics Data System (ADS)

Vinogradova, T.; Shor, V.

2014-07-01

Asteroid families are fragments of some disrupted parent bodies. Planetary perturbations force the primarily close orbits to evolve. One of the main features of the orbit evolution is the long-period variation of the osculating elements, such as the inclination and eccentricity. Proper elements are computed by elimination of short- and long-period perturbations, and, practically, they do not change with time. Therefore, proper elements are important for family-identification procedures. The techniques of proper-element computation have improved over time. More and more accurate dynamical theories are developed. Contrastingly, in this work, an empirical method is proposed for proper-element calculations. The long-term variations of osculating elements manifest themselves very clearly in the distributions of pairs: inclination and longitude of ascending node; eccentricity and longitude of perihelion in the corresponding planes. Both of these dependencies have a nearly sinusoidal form for most asteroid orbits with regular motion of node and perihelion. If these angular parameters librate, then the sinusoids transform to some closed curve. Hence, it is possible to obtain forced elements, as parameters of curves specified above. The proper elements can be calculated by an elimination of the forced ones. The method allows to obtain the proper elements in any region, if there is a sufficient number of asteroids. This fact and the simplicity of the calculations are advantages of the empirical method. The derived proper elements include the short-period perturbations, but their accuracy is sufficient to search for asteroid families. The special techniques have been developed for the identification of the families, but over a long time large discrepancies took place between the lists of families derived by different authors. As late as 1980, a list of 30 reliable families was formed. And now the list by D. Nesvorny includes about 80 robust families. To date, only two families have been found in the most outer part of the main asteroid belt or the Cybele group: Sylvia and Ulla. And the Hungaria group in the most inner part of the belt has always been considered as one family. In this work, the proper elements were calculated by the empirical method for all multi-opposition asteroids in these two zones. As the source of the initial osculating elements, the MPC catalogue (version Feb. 2014) was used. Due to the large set of proper elements used in our work, the families are apparent more clearly. An approach similar to the hierarchical clustering method (HCM) was used for the identification of the families. As a result, five additional families have been found in the Cybele region, associated with (121) Hermione, (643) Scheherezade, (1028) Lydina, (3141) Buchar, and (522) Helga. The small Helga family, including 15 members, is the family in the main belt (3.6--3.7 au) most distant from the Sun. Due to the isolation of this family, its identification is very reliable. As to the Hungaria region, two low-density families have been found additionally: (1453) Fennia and (3854) George. They have inclinations slightly greater than that of the Hungaria family (from 24 to 26 degrees). In contradiction to the predominant C-type of the Hungaria family asteroids, the taxonomy of these families is represented mainly by the S and L types. Most likely, these families are two parts of a single ancient family.

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.

Target selection for a hypervelocity asteroid intercept vehicle flight validation mission

NASA Astrophysics Data System (ADS)

Wagner, Sam; Wie, Bong; Barbee, Brent W.

2015-02-01

Asteroids and comets have collided with the Earth in the past and will do so again in the future. Throughout Earth's history these collisions have played a significant role in shaping Earth's biological and geological histories. The planetary defense community has been examining a variety of options for mitigating the impact threat of asteroids and comets that approach or cross Earth's orbit, known as near-Earth objects (NEOs). This paper discusses the preliminary study results of selecting small (100-m class) NEO targets and mission analysis and design trade-offs for validating the effectiveness of a Hypervelocity Asteroid Intercept Vehicle (HAIV) concept, currently being investigated for a NIAC (NASA Advanced Innovative Concepts) Phase 2 study. In particular this paper will focus on the mission analysis and design for single spacecraft direct impact trajectories, as well as several mission types that enable a secondary rendezvous spacecraft to observe the HAIV impact and evaluate it's effectiveness.

Aqueous alteration on main belt primitive asteroids: Results from visible spectroscopy

NASA Astrophysics Data System (ADS)

Fornasier, S.; Lantz, C.; Barucci, M. A.; Lazzarin, M.

2014-05-01

This work focuses on the study of the aqueous alteration process which acted in the main belt and produced hydrated minerals on the altered asteroids. Hydrated minerals have been found mainly on Mars surface, on main belt primitive asteroids and possibly also on few TNOs. These materials have been produced by hydration of pristine anhydrous silicates during the aqueous alteration process, that, to be active, needed the presence of liquid water under low temperature conditions (below 320 K) to chemically alter the minerals. The aqueous alteration is particularly important for unraveling the processes occurring during the earliest times of the Solar System history, as it can give information both on the asteroids thermal evolution and on the localization of water sources in the asteroid belt. To investigate this process, we present reflected light spectral observations in the visible region (0.4-0.94 μm) of 80 asteroids belonging to the primitive classes C (prevalently), G, F, B and P, following the Tholen (Tholen, D.J. [1984]. Ph.D. Dissertation, University of Arizona, Tucson). classification scheme. We find that about 65% of the C-type and all the G-type asteroids investigated reveal features suggesting the presence of hydrous materials, mainly a band centered around 0.7 μm, while we do not find evidence of hydrated materials in the other low albedo asteroids (B, F, and P) investigated. We combine the present observations with the visible spectra of asteroids available in the literature for a total of 600 primitive main belt asteroids. We analyze 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. 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 aqueous altered, strengthening thus the results previously obtained by Vilas (Vilas, F. [1994]. Icarus 111, 456-467). Around 50% of the observed C-type asteroids show absorption feature in the visible range due to hydrated silicates, implying that more than ∼70% of them will have a 3 μm absorption band and thus hydrated minerals on their surfaces, based on correlations between those two absorptions (Howell, E.S. et al. [2011]. EPSC-DPS Joint Meeting 2011, vol. 6. Abstracts, 637). 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. (Vilas, F., Hatch, E.C., Larson, S.M., Sawyer, S.R., Gaffey, M.J. [1993]. Icarus 102, 225-231). The percentage of hydrated asteroids is strongly correlated with their size. 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 asteroids albedo or orbital elements. Comparing the ∼0.7 μm band parameters of hydrated silicates and CM2 carbonaceous chondrites, the meteorites that have aqueous altered asteroids as parent bodies, we see that the band center of meteorites is at longer wavelengths than that of asteroids. This difference on center positions may be attributed to different minerals abundances, and to the fact that CM2 available on Earth might not be representative of the whole aqueous altered asteroids population.

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.

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.

Visualising Astronomy: Using Impact to Inform

NASA Astrophysics Data System (ADS)

Wyatt, R.

2013-04-01

Pop culture has visualised asteroids in a way that has made a far greater impact in the public domain than the outreach community can ever hope to achieve. Films such as Meteor (1979), Armageddon (1997) and Deep Impact (1997) may score poorly on scientific accuracy, but they have influenced our collective consciousness. (Perhaps in a fit of pre-millennial anxiety, the late 1990s saw a host of films featuring an asteroid or comet on a collision course with Earth1.) In addition to the destruction of Earth's cities, the Millennium Falcon dodging giant tumbling boulders in The Empire Strikes Back has probably influenced more people's mental image of an asteroid belt than any other single visual.

Precise Distances for Main-belt Asteroids in Only Two Nights

NASA Astrophysics Data System (ADS)

Heinze, Aren N.; Metchev, Stanimir

2015-10-01

We present a method for calculating precise distances to asteroids using only two nights of data from a single location—far too little for an orbit—by exploiting the angular reflex motion of the asteroids due to Earth’s axial rotation. We refer to this as the rotational reflex velocity method. While the concept is simple and well-known, it has not been previously exploited for surveys of main belt asteroids (MBAs). We offer a mathematical development, estimates of the errors of the approximation, and a demonstration using a sample of 197 asteroids observed for two nights with a small, 0.9-m telescope. This demonstration used digital tracking to enhance detection sensitivity for faint asteroids, but our distance determination works with any detection method. Forty-eight asteroids in our sample had known orbits prior to our observations, and for these we demonstrate a mean fractional error of only 1.6% between the distances we calculate and those given in ephemerides from the Minor Planet Center. In contrast to our two-night results, distance determination by fitting approximate orbits requires observations spanning 7-10 nights. Once an asteroid’s distance is known, its absolute magnitude and size (given a statistically estimated albedo) may immediately be calculated. Our method will therefore greatly enhance the efficiency with which 4m and larger telescopes can probe the size distribution of small (e.g., 100 m) MBAs. This distribution remains poorly known, yet encodes information about the collisional evolution of the asteroid belt—and hence the history of the Solar System.

Organic matter in extraterrestrial water-bearing salt crystals

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

Chan, Queenie H. S.; Zolensky, Michael E.; Kebukawa, Yoko

Direct evidence of complex prebiotic chemistry from a water-rich world in the outer solar system is provided by the 4.5-billion-year-old halite crystals hosted in the Zag and Monahans (1998) meteorites. This study offers the first comprehensive organic analysis of the soluble and insoluble organic compounds found in the millimeter-sized halite crystals containing brine inclusions and sheds light on the nature and activity of aqueous fluids on a primitive parent body. Associated with these trapped brines are organic compounds exhibiting wide chemical variations representing organic precursors, intermediates, and reaction products that make up life’s precursor molecules such as amino acids. Themore » organic compounds also contain a mixture of C-, O-, and N-bearing macromolecular carbon materials exhibiting a wide range of structural order, as well as aromatic, ketone, imine, and/or imidazole compounds. The enrichment in 15N is comparable to the organic matter in pristine Renazzo-type carbonaceous chondrites, which reflects the sources of interstellar 15N, such as ammonia and amino acids. The amino acid content of the Zag halite deviates from the meteorite matrix, supporting an exogenic origin of the halite, and therefore, the Zag meteorite contains organics synthesized on two distinct parent bodies. Lastly, our study suggests that the asteroidal parent body where the halite precipitated, potentially asteroid 1 Ceres, shows evidence for a complex combination of biologically and prebiologically relevant molecules.« less

Organic matter in extraterrestrial water-bearing salt crystals

PubMed Central

Chan, Queenie H. S.; Zolensky, Michael E.; Kebukawa, Yoko; Fries, Marc; Ito, Motoo; Steele, Andrew; Rahman, Zia; Nakato, Aiko; Kilcoyne, A. L. David; Suga, Hiroki; Takahashi, Yoshio; Takeichi, Yasuo; Mase, Kazuhiko

2018-01-01

Direct evidence of complex prebiotic chemistry from a water-rich world in the outer solar system is provided by the 4.5-billion-year-old halite crystals hosted in the Zag and Monahans (1998) meteorites. This study offers the first comprehensive organic analysis of the soluble and insoluble organic compounds found in the millimeter-sized halite crystals containing brine inclusions and sheds light on the nature and activity of aqueous fluids on a primitive parent body. Associated with these trapped brines are organic compounds exhibiting wide chemical variations representing organic precursors, intermediates, and reaction products that make up life’s precursor molecules such as amino acids. The organic compounds also contain a mixture of C-, O-, and N-bearing macromolecular carbon materials exhibiting a wide range of structural order, as well as aromatic, ketone, imine, and/or imidazole compounds. The enrichment in 15N is comparable to the organic matter in pristine Renazzo-type carbonaceous chondrites, which reflects the sources of interstellar 15N, such as ammonia and amino acids. The amino acid content of the Zag halite deviates from the meteorite matrix, supporting an exogenic origin of the halite, and therefore, the Zag meteorite contains organics synthesized on two distinct parent bodies. Our study suggests that the asteroidal parent body where the halite precipitated, potentially asteroid 1 Ceres, shows evidence for a complex combination of biologically and prebiologically relevant molecules. PMID:29349297

Organic matter in extraterrestrial water-bearing salt crystals

DOE PAGES

Chan, Queenie H. S.; Zolensky, Michael E.; Kebukawa, Yoko; ...

2018-01-10

Direct evidence of complex prebiotic chemistry from a water-rich world in the outer solar system is provided by the 4.5-billion-year-old halite crystals hosted in the Zag and Monahans (1998) meteorites. This study offers the first comprehensive organic analysis of the soluble and insoluble organic compounds found in the millimeter-sized halite crystals containing brine inclusions and sheds light on the nature and activity of aqueous fluids on a primitive parent body. Associated with these trapped brines are organic compounds exhibiting wide chemical variations representing organic precursors, intermediates, and reaction products that make up life’s precursor molecules such as amino acids. Themore » organic compounds also contain a mixture of C-, O-, and N-bearing macromolecular carbon materials exhibiting a wide range of structural order, as well as aromatic, ketone, imine, and/or imidazole compounds. The enrichment in 15N is comparable to the organic matter in pristine Renazzo-type carbonaceous chondrites, which reflects the sources of interstellar 15N, such as ammonia and amino acids. The amino acid content of the Zag halite deviates from the meteorite matrix, supporting an exogenic origin of the halite, and therefore, the Zag meteorite contains organics synthesized on two distinct parent bodies. Lastly, our study suggests that the asteroidal parent body where the halite precipitated, potentially asteroid 1 Ceres, shows evidence for a complex combination of biologically and prebiologically relevant molecules.« less

Organic matter in extraterrestrial water-bearing salt crystals.

PubMed

Chan, Queenie H S; Zolensky, Michael E; Kebukawa, Yoko; Fries, Marc; Ito, Motoo; Steele, Andrew; Rahman, Zia; Nakato, Aiko; Kilcoyne, A L David; Suga, Hiroki; Takahashi, Yoshio; Takeichi, Yasuo; Mase, Kazuhiko

2018-01-01

Direct evidence of complex prebiotic chemistry from a water-rich world in the outer solar system is provided by the 4.5-billion-year-old halite crystals hosted in the Zag and Monahans (1998) meteorites. This study offers the first comprehensive organic analysis of the soluble and insoluble organic compounds found in the millimeter-sized halite crystals containing brine inclusions and sheds light on the nature and activity of aqueous fluids on a primitive parent body. Associated with these trapped brines are organic compounds exhibiting wide chemical variations representing organic precursors, intermediates, and reaction products that make up life's precursor molecules such as amino acids. The organic compounds also contain a mixture of C-, O-, and N-bearing macromolecular carbon materials exhibiting a wide range of structural order, as well as aromatic, ketone, imine, and/or imidazole compounds. The enrichment in 15 N is comparable to the organic matter in pristine Renazzo-type carbonaceous chondrites, which reflects the sources of interstellar 15 N, such as ammonia and amino acids. The amino acid content of the Zag halite deviates from the meteorite matrix, supporting an exogenic origin of the halite, and therefore, the Zag meteorite contains organics synthesized on two distinct parent bodies. Our study suggests that the asteroidal parent body where the halite precipitated, potentially asteroid 1 Ceres, shows evidence for a complex combination of biologically and prebiologically relevant molecules.

The Detection of Collisional and Scattering Processes in the Asteroid-Meteoroid Continuum

NASA Astrophysics Data System (ADS)

Lai, H. R.; Connos, M. A.; Russell, C. T.; Wei, H. Y.

2014-04-01

Optical and radar observations have enabled the compilation of a useful inventory of near-Earth objects down to a diameter of approximately 500m, but at smaller diameters the catalogue is sparse. This is unacceptable for several reasons. First, the most hazardous size range based on damage per impact on Earth times expected impact rate is near 50m and second, we do not know if either the spatial distribution of objects or their behavior is similar to that of the larger objects. We have reason to believe they are importantly different. Near Earth Objects evolve due to collisions with other objects. Disruptive collisions of large objects say 200m in diameter are rare because such objects are "rare" and the impactors that could disrupt a 200m class object are rare. However, near the Earth, collisions are expected to occur at relative velocities of near 20 km/sec and such a speed could disrupt a body 106 times more massive (100 times larger diameter). Our studies show that collisions that can produce objects in the range 10 to 100m in diameter are "frequent" in near-Earth space. Our studies of the asteroid 2201 Oljato at Venus and asteroid 138175 near Earth indicates that both asteroids have coorbital debris clouds presumably caused by a past non-disruptive but debris-producing collision. This has the effect of spreading the hazardous material out of the known orbit so that a false sense of security is had when the parent body is safely past the Earth. We can detect a subset of the debris trail by their destructive impacts because they create a cloud of charged nanoscale dust which in turn creates a magnetic "cloud" that enables the dust cloud to be weighed and its location roughly identified. This shows spreading in longitude, latitude, and heliocentric radius from the parent on a time scale of decades. This is much faster than some modelers have expected and over a broader range, suggesting that the debris trail receives more of the impactor momentum than anticipated. This possibly depends on the elasticity of the target asteroid. In any event, we now have a new qualitative method of tracking debris tails of hazardous materials using existing assets in space

Gas Phase Chemistry and Molecular Complexity: How Far Do They Go?

NASA Astrophysics Data System (ADS)

Balucani, Nadia

2016-07-01

The accumulation of organic molecules of increasing complexity is believed to be an important step toward the emergence of life. But how massive organic synthesis could occur in primitive Earth, i.e. a water-dominated environment, is a matter of debate. Two alternative theories have been suggested so far: endogenous and exogenous synthesis. In the first theory, the synthesis of simple organic molecules having a strong prebiotic potential (simple prebiotic molecules SPMs, such as H2CO, HCN, HC3N, NH2CHO) occurred directly on our planet starting from simple parent molecules of the atmosphere, liquid water and various energy sources. Miller's experiment was a milestone in this theory, but it was later recognized that the complexity of a planet cannot be reproduced in a single laboratory experiment. Some SPMs have been identified in the N2-dominated atmosphere of Titan (a massive moon of Saturn), which is believed to be reminiscent of the primitive terrestrial atmosphere. As such, the atmosphere of Titan represents a planetary scale laboratory for the comprehension of SPM formation in an environment close enough to primitive Earth and is the current frontier in the endogenous theory exploration. In the exogenous theory, SPMs came from space, the carriers being comets, asteroids and meteorites. The rationale behind this suggestion is that plenty of SPMs have been observed in interstellar clouds (ISCs), including star-forming regions, and in small bodies like comets, asteroids and meteorites. Therefore, the basic idea is that SPMs were formed in the solar nebula, preserved during the early phases of the Solar System formation in the body of comets/asteroids/meteorites and finally delivered to Earth by cometary and meteoritic falls. In this contribution, the status of our knowledge on how SPMs can be formed in the gas phase, either in the primitive terrestrial atmosphere or in the cold nebula from which the Solar System originated, will be presented. Particular attention will be given to neutral-neutral reactions.

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.

Investigating the binary nature of active asteroid 288P/300163

NASA Astrophysics Data System (ADS)

Agarwal, Jessica

2016-10-01

We propose to study the suspected binary nature of active asteroid 288P/300163. We aim to confirm or disprove the existence of a binary nucleus, and - if confirmed - to measure the mutual orbital period and orbit orientation of the compoents, and their sizes. We request 5 orbits of WFC3 imaging, spaced at intervals of 8-12 days. 288P belongs to the recently discovered group of active asteroids, and is particularly remarkable as HST images obtained during its last close approach to Earth in 2011 are consistent with a barely resolved binary system. If confirmed, 288P would be the first known active binary asteroid. For the first time, we would see two important consequences of rotational break-up in a single object: binary formation and dust ejection, highlighting the importance of the YORP-effect in re-shaping the asteroid belt. Confirming 288P as a binary would be a key step towards understanding the evolutionary processes underlying asteroid activity. In order to resolve the two components we need 288P at a geocentric distance comparable to or less than we had in 2011 December (1.85 AU). This condition will be fulfilled for the first time since 2011, between mid-July and mid-November of 2016. The next opportunity to carry out such observations will be in 2021.

Petrologic evolution of CM chondrites: The difficulty of discriminating between nebular and parent-body effects

NASA Astrophysics Data System (ADS)

Kerridge, J. F.; McSween, H. Y., Jr.; Bunch, T. E.

1994-07-01

We wish to draw attention to a major controversy that has arisen in the area of CM-chondrite petrology. The problem is important because its resolution will have profound implications for ideas concerning nebular dynamics, gas-solid interactions in the nebula, and accretionary processes in the nebula, among other issues. On the one hand, cogent arguments have been presented that 'accretionary dust mantles,' were formed in the solar nebula prior to accretion of the CM parent asteroid(s). On the other hand, no-less-powerful arguments have been advanced that a significant fraction of the CM lithology is secondary, produced by aqueous alteration in the near-surface regions of an asteroid-sized object. Because most, if not all, CM chondrites are breccias, these two views could coexist harmoniously, were it not for the fact that some of the coarse-grained lithologies surrounded by 'accretion dust mantles' are themselves of apparently secondary origin. Such an observation must clearly force a reassessment of one or both of the present schools of thought. Our objective here is to stimulate such a reassessment. Four possible resolutions of this conflict may be postulated. First, perhaps nature found a way of permitting such secondary alteration to take place in the nebula. Second, maybe dust mantles could form in a regolith, rather than a nebular, environment. Third, it is possible that dust mantles around secondary lithologies are different from those around primary lithologies. Finally, perhaps formation of CM chondrites involved a more complex sequence of events than visualized so far, so that some apparently 'primary' processes postdated certain 'secondary' processes.

Amino acid compositions in heated carbonaceous chondrites and their compound-specific nitrogen isotopic ratios

NASA Astrophysics Data System (ADS)

Chan, Queenie Hoi Shan; Chikaraishi, Yoshito; Takano, Yoshinori; Ogawa, Nanako O.; Ohkouchi, Naohiko

2016-01-01

A novel method has been developed for compound-specific nitrogen isotope compositions with an achiral column which was previously shown to offer high precision for nitrogen isotopic analysis. We applied the method to determine the amino acid contents and stable nitrogen isotopic compositions of individual amino acids from the thermally metamorphosed (above 500 °C) Antarctic carbonaceous chondrites Ivuna-like (CI)1 (or CI-like) Yamato (Y) 980115 and Ornans-like (CO)3.5 Allan Hills (ALH) A77003 with the use of gas chromatography/combustion/isotope ratio mass spectrometry. ALHA77003 was deprived of amino acids due to its extended thermal alteration history. Amino acids were unambiguously identified in Y-980115, and the δ15N values of selected amino acids (glycine +144.8 ‰; α-alanine +121.2 ‰) are clearly extraterrestrial. Y-980115 has experienced an extended period of aqueous alteration as indicated by the presence of hydrous mineral phases. It has also been exposed to at least one post-hydration short-lived thermal metamorphism. Glycine and alanine were possibly produced shortly after the accretion event of the asteroid parent body during the course of an extensive aqueous alteration event and have abstained from the short-term post-aqueous alteration heating due to the heterogeneity of the parent body composition and porosity. These carbonaceous chondrite samples are good analogs that offer important insights into the target asteroid Ryugu of the Hayabusa-2 mission, which is a C-type asteroid likely composed of heterogeneous materials including hydrated and dehydrated minerals.

Probing the internal structure of the asteriod Didymoon with a passive seismic investigation

NASA Astrophysics Data System (ADS)

Murdoch, N.; Hempel, S.; Pou, L.; Cadu, A.; Garcia, R. F.; Mimoun, D.; Margerin, L.; Karatekin, O.

2017-09-01

Understanding the internal structure of an asteroid has important implications for interpreting its evolutionary history, for understanding its continuing geological evolution, and also for asteroid deflection and in-situ space resource utilisation. Given the strong evidence that asteroids are seismically active, an in-situ passive seismic experiment could provide information about the asteroid surface and interior properties. Here, we discuss the natural seismic activity that may be present on Didymoon, the secondary component of asteroid (65803) Didymos. Our analysis of the tidal stresses in Didymoon shows that tidal quakes are likely to occur if the secondary has an eccentric orbit. Failure occurs most easily at the asteroid poles and close to the surface for both homogeneous and layered internal structures. Simulations of seismic wave propagation in Didymoon show that the seismic moment of even small meteoroid impacts can generate clearly observable body and surface waves if the asteroid's internal structure is homogeneous. The presence of a regolith layer over a consolidated core can result in the seismic energy becoming trapped in the regolith due to the strong impedance contrast at the regolith-core boundary. The inclusion of macro-porosity (voids) further complexifies the wavefield due to increased scattering. The most prominent seismic waves are always found to be those traveling along the surface of the asteroid and those focusing in the antipodal point of the seismic source. We find also that the waveforms and ground acceleration spectra allow discrimination between the different internal structure models. Although the science return of a passive seismic experiment would be enhanced by having multiple seismic stations, one single seismic station can already vastly improve our knowledge about the seismic environment and sub-surface structure of an asteroid. We describe several seismic measurement techniques that could be applied in order to study the asteroid internal structure with one three-component seismic station.

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

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.

Cratering rates on the Galilean satellites.

PubMed

Zahnle, K; Dones, L; Levison, H F

1998-12-01

We exploit recent theoretical advances toward the origin and orbital evolution of comets and asteroids to obtain revised estimates for cratering rates in the jovian system. We find that most, probably more than 90%, of the craters on the Galilean satellites are caused by the impact of Jupiter-family comets (JFCs). These are comets with short periods, in generally low-inclination orbits, whose dynamics are dominated by Jupiter. Nearly isotropic comets (long period and Halley-type) contribute at the 1-10% level. Trojan asteroids might also be important at the 1-10% level; if they are important, they would be especially important for smaller craters. Main belt asteroids are currently unimportant, as each 20-km crater made on Ganymede implies the disruption of a 200-km diameter parental asteroid, a destruction rate far beyond the resources of today's asteroid belt. Twenty-kilometer diameter craters are made by kilometer-size impactors; such events occur on a Galilean satellite about once in a million years. The paucity of 20-km craters on Europa indicates that its surface is of order 10 Ma. Lightly cratered surfaces on Ganymede are nominally of order 0.5-1.0 Ga. The uncertainty in these estimates is about a factor of five. Callisto is old, probably more than 4 Ga. It is too heavily cratered to be accounted for by the current flux of JFCs. The lack of pronounced apex-antapex asymmetries on Ganymede may be compatible with crater equilibrium, but it is more easily understood as evidence for nonsynchronous rotation of an icy carapace. c 1998 Academic Press.

Hundred lightcurves of sub-km main-belt asteroids

NASA Astrophysics Data System (ADS)

Yoshida, F.; Souami, D.; Bouquillon, S.; Nakamura, T.; Dermawan, B.; Yagi, M.; Souchay, J.

2014-07-01

We observed a single sky field near opposition and near the ecliptic plane using the Subaru telescope equipped with the Suprime-Cam. Taking advantage of the wide field of view (FOV) for the Suprime-Cam, the plan was to obtain 100 lightcurves of asteroids at the same time. The total observing time interval was about 8 hours on September 2, 2002, with 2-min exposures. We detected 147 moving objects in the single FOV (34'×27') on the Suprime-Cam (see Figure). Of those, 112 detections corresponded to different objects. We used the R filter during almost the entire observing run, but we took a few images with the B filter at the beginning, the middle, and the end of the run. We classified main-belt asteroids into S- and C-complexes with the B-R color of the object (Yoshida & Nakamura 2007). Although we carefully avoided regions of bright stars, the sky in the images taken by Suprime-Cam were actually crowded with faint objects. Therefore, the asteroids overlapped with background stars very often. Thus, it was very difficult to get lightcurves with high accuracy. We modified the GAIA-GBOT (Ground Based Optical Tracking) PIPELINE to measure the position and brightness of each object (Bouquillon et al. 2012). Once the objects were identified and their positions measured in pixel coordinates, the pipeline proceeded to the astrometric calibration and then to the photometric calibrations with the Guide Star Catalog II (Lasker et al. 2008). The pipeline produced time series of photometry for each object. The average brightness of each lightcurve ranged between 19--24 mag. We then estimated the rotational period from the lightcurve of each object. In our presentation, we will show the spin-period distribution of sub- km main-belt asteroids and compare it with that of large main-belt asteroids obtained from the lightcurve catalogue.

BENNU’S JOURNEY

NASA Image and Video Library

2017-12-08

This large asteroid, a proto-star undergoes fusion and our sun is born. This is the parent of Asteroid Bennu. Today, a NASA Spacecraft has the chance to retrieve a sample from Bennu to reveal the history of our solar system. OSIRIRS-REx is a NASA sample return mission to visit Asteroid Bennu. We plan to grab a piece of Bennu, because it’s a time capsule that can tell us about the origins of our planet and our entire solar system. Watch the full video: youtu.be/gtUgarROs08 Learn more about NASA’s OSIRIS-REx mission and the making of Bennu’s Journey: www.nasa.gov/content/goddard/bennus-journey/ More information on the OSIRIS-REx mission is available at: www.nasa.gov/mission_pages/osiris-rex/index.html www.asteroidmission.org NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Anisotropic distribution of orbit poles of binary asteroids

NASA Astrophysics Data System (ADS)

Pravec, P.; Scheirich, P.; Vokrouhlický, D.; Harris, A. W.; Kusnirak, P.; Hornoch, K.; Pray, D. P.; Higgins, D.; Galád, A.; Világi, J.; Gajdos, S.; Kornos, L.; Oey, J.; Husárik, M.; Cooney, W. R.; Gross, J.; Terrell, D.; Durkee, R.; Pollock, J.; Reichart, D.; Ivarsen, K.; Haislip, J.; Lacluyze, A.; Krugly, Y. N.; Gaftonyuk, N.; Dyvig, R.; Reddy, V.; Stephens, R. D.; Chiorny, V.; Vaduvescu, O.; Longa, P.; Tudorica, A.; Warner, B. D.; Masi, G.; Brinsfield, J.; Gonçalves, R.; Brown, P.; Krzeminski, Z.; Gerashchenko, O.; Marchis, F.

2011-10-01

Our photometric observations of 18 mainbelt binary systems in more than one apparition revealed a strikingly high number of 15 having positively re-observed mutual events in the return apparitions. Our simulations of the survey showed that the data strongly suggest that poles of mutual orbits between components of binary asteroids are not distributed randomly: The null hypothesis of the isotropic distribution of orbit poles is rejected at a confidence level greater than 99.99%. Binary orbit poles concentrate at high ecliptic latitudes, within 30° of the poles of the ecliptic. We propose that the binary orbit poles oriented preferentially up/down-right are due to formation of small binary systems by rotational fission of critically spinning parent bodies with poles near the YORP asymptotic states with obliquities near 0 and 180°. An alternative process of elimination of binaries with poles closer to the ecliptic by the Kozai dynamics of gravitational perturbations from the sun does not explain the observed orbit pole concentration as in the close asteroid binary systems the J2 perturbation due to the primary dominates the solar-tide effect.

On the age of the Nele asteroid family

NASA Astrophysics Data System (ADS)

Carruba, V.; Vokrouhlický, D.; Nesvorný, D.; Aljbaae, S.

2018-06-01

The Nele group, formerly known as the Iannini family, is one of the youngest asteroid families in the main belt. Previously, it has been noted that the pericentre longitudes ϖ and nodal longitudes Ω of its largest member asteroids are clustered at the present time, therefore suggesting that the collisional break-up of parent body must have happened recently. Here, we verify this conclusion by detailed orbit-propagation of a synthetic Nele family and show that the current level of clustering of secular angles of the largest Nele family members requires an approximate age limit of 4.5 Myr. Additionally, we make use of an updated and largely extended Nele membership to obtain, for the first time, an age estimate of this family using the backward integration method. Convergence of the secular angles in a purely gravitational model and in a model including the non-gravitational forces caused by the Yarkovsky effect are both compatible with an age younger than 7 Myr. More accurate determination of the Nele family age would require additional data about the spin state of its members.

The kilometer-sized Main Belt asteroid population revealed by Spitzer

NASA Astrophysics Data System (ADS)

Ryan, E. L.; Mizuno, D. R.; Shenoy, S. S.; Woodward, C. E.; Carey, S. J.; Noriega-Crespo, A.; Kraemer, K. E.; Price, S. D.

2015-06-01

Aims: Multi-epoch Spitzer Space Telescope 24 μm data is utilized from the MIPSGAL and Taurus Legacy surveys to detect asteroids based on their relative motion. Methods: Infrared detections are matched to known asteroids and average diameters and albedos are derived using the near Earth asteroid thermal model (NEATM) for 1865 asteroids ranging in size from 0.2 to 169 km. A small subsample of these objects was also detected by IRAS or MSX and the single wavelength albedo and diameter fits derived from these data are within the uncertainties of the IRAS and/or MSX derived albedos and diameters and available occultation diameters, which demonstrates the robustness of our technique. Results: The mean geometric albedo of the small Main Belt asteroids in this sample is pV = 0.134 with a sample standard deviation of 0.106. The albedo distribution of this sample is far more diverse than the IRAS or MSX samples. The cumulative size-frequency distribution of asteroids in the Main Belt at small diameters is directly derived and a 3σ deviation from the fitted size-frequency distribution slope is found near 8 km. Completeness limits of the optical and infrared surveys are discussed. Tables 1-3 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/578/A42

Performance Evaluation of an Expanded Range XIPS Ion Thruster System for NASA Science Missions

NASA Technical Reports Server (NTRS)

Oh, David Y.; Goebel, Dan M.

2006-01-01

This paper examines the benefit that a solar electric propulsion (SEP) system based on the 5 kW Xenon Ion Propulsion System (XIPS) could have for NASA's Discovery class deep space missions. The relative cost and performance of the commercial heritage XIPS system is compared to NSTAR ion thruster based systems on three Discovery class reference missions: 1) a Near Earth Asteroid Sample Return, 2) a Comet Rendezvous and 3) a Main Belt Asteroid Rendezvous. It is found that systems utilizing a single operating XIPS thruster provides significant performance advantages over a single operating NSTAR thruster. In fact, XIPS performs as well as systems utilizing two operating NSTAR thrusters, and still costs less than the NSTAR system with a single operating thruster. This makes XIPS based SEP a competitive and attractive candidate for Discovery class science missions.

Origin and Evolution of Prebiotic Organic Matter as Inferred from the Tagish Lake Meteorite

NASA Technical Reports Server (NTRS)

Herd, Christopher D.; Blinova, Alexandra; Simkus, Danielle N.; Huang, Yongsong; Tarozo, Rafael; Alexander, Conel M.; Gyngard, Frank; Nittler, Larry R.; Cody, George D.; Fogel, Marilyn L.;

The potentially hazardous asteroid 2007CA19 as the parent of the η-Virginids meteoroid stream

NASA Astrophysics Data System (ADS)

Babadzhanov, P. B.; Kokhirova, G. I.; Obrubov, Yu. V.

2015-07-01

The orbit of the potentially hazardous near-Earth asteroid 2007CA19 is classified as comet-like according to the Tisserand parameter with a value of Tj = 2.8, therefore the object can be empirically considered as an extinct or dormant Jupiter-family comet. If 2007CA19 is really a former comet, it could have formed a meteoroid stream in the past in the period of its cometary activity. Investigation of the asteroid's orbital evolution shows that 2007CA19 is a quadruple-crosser of the Earth's orbit. Consequently, the meteoroid stream that is supposedly associated with the object can produce four meteor showers if, as expected, the perihelia arguments of the meteoroids are very distributed over the orbit. Theoretical radiants of the predicted showers were calculated using elements of the 2007CA19 osculating orbit that correspond to the positions of intersections with the Earth's orbit. A search for the predicted night-time showers has shown that the Northern and Southern η-Virginids can be associated to 2007CA19. Using the MOID IAU database, we identify two other daytime showers that can be associated with this asteroid. Thus, we confirm that 2007CA19 has an associated meteoroid stream that produces four active meteor showers in the Earth's atmosphere. This relationship supports the dynamical classification of the object and also points to the possibility of its cometary origin.

Nanoscale Analysis of Space-Weathering Features in Soils from Itokawa

NASA Technical Reports Server (NTRS)

Thompson, M. S.; Christoffersen, R.; Zega, T. J.; Keller, L. P.

2014-01-01

Space weathering alters the spectral properties of airless body surface materials by redden-ing and darkening their spectra and attenuating characteristic absorption bands, making it challenging to characterize them remotely [1,2]. It also causes a discrepency between laboratory analysis of meteorites and remotely sensed spectra from asteroids, making it difficult to associate meteorites with their parent bodies. The mechanisms driving space weathering include mi-crometeorite impacts and the interaction of surface materials with solar energetic ions, particularly the solar wind. These processes continuously alter the microchemical and structural characteristics of exposed grains on airless bodies. The change of these properties is caused predominantly by the vapor deposition of reduced Fe and FeS nanoparticles (npFe(sup 0) and npFeS respectively) onto the rims of surface grains [3]. Sample-based analysis of space weathering has tra-ditionally been limited to lunar soils and select asteroidal and lunar regolith breccias [3-5]. With the return of samples from the Hayabusa mission to asteroid Itoka-wa [6], for the first time we are able to compare space-weathering features on returned surface soils from a known asteroidal body. Analysis of these samples will contribute to a more comprehensive model for how space weathering varies across the inner solar system. Here we report detailed microchemical and microstructal analysis of surface grains from Itokawa.

COMPOSITION OF POTENTIALLY HAZARDOUS ASTEROID (214869) 2007 PA8: AN H CHONDRITE FROM THE OUTER ASTEROID BELT

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

Sanchez, Juan A.; Reddy, Vishnu; Corre, Lucille Le

Potentially hazardous asteroids (PHAs) represent a unique opportunity for physical characterization during their close approaches to Earth. The proximity of these asteroids makes them accessible for sample-return and manned missions, but could also represent a risk for life on Earth in the event of collision. Therefore, a detailed mineralogical analysis is a key component in planning future exploration missions and developing appropriate mitigation strategies. In this study we present near-infrared spectra (∼0.7–2.55 μm) of PHA (214869) 2007 PA8 obtained with the NASA Infrared Telescope Facility during its close approach to Earth on 2012 November. The mineralogical analysis of this asteroidmore » revealed a surface composition consistent with H ordinary chondrites. In particular, we found that the olivine and pyroxene chemistries of 2007 PA8 are Fa{sub 18}(Fo{sub 82}) and Fs{sub 16}, respectively. The olivine–pyroxene abundance ratio was estimated to be 47%. This low olivine abundance and the measured band parameters, close to the H4 and H5 chondrites, suggest that the parent body of 2007 PA8 experienced thermal metamorphism before being catastrophically disrupted. Based on the compositional affinity, proximity to the J5:2 resonance, and estimated flux of resonant objects we determined that the Koronis family is the most likely source region for 2007 PA8.« less

On the Contribution of Asteroid Disruptions to the Interplanetary Dust Flux

NASA Astrophysics Data System (ADS)

Kehoe, T. J. J.; Kehoe, A. E.

2017-12-01

Recent modeling has shown the significant contribution of micron- to millimeter-sized particles released by the disruption of main-belt asteroids (MBAs) to the interplanetary dust particle (IDP) flux (e.g., Dermott et al., 2002; Nesvorný et al., 2003; Espy Kehoe et al., 2015). In this paper, we present the results of a study that indicates that the dust injected into the zodiacal cloud due to the catastrophic disruption of an asteroid is dominated by the release of its surface regolith particles. Our research suggests that disrupting a single asteroid with diameter O(100 km) will be enough to regenerate the entire zodiacal cloud. The breakup of smaller asteroids with diameters O(10 km) will likely produce more moderate, but still significant, changes in the dust environment of the inner solar system. As collisional disruptions of asteroids in this size range occur more frequently, it is important that we develop a better understanding of the injection of asteroidal material into the zodiacal cloud as a result of these type of events in order to determine the temporal evolution of the interplanetary dust flux. The results presented in this paper will lead to a better understanding of the threat to exploration activities due to the enhanced IDP flux resulting from the disruption of asteroidal regoliths. These findings can be employed to improve engineering models, for example, the NASA Meteoroid Engineering Model (MEM) that is widely utilized to assess the impact hazard to space hardware and activities in the inner solar system due to the natural meteoroid environment (McNamara et al., 2004). This is an important area of concern for current and future mission development purposes.

KSC-07pd2592

NASA Image and Video Library

2007-09-27

KENNEDY SPACE CENTER, FLA. -- Nearly enveloped by the smoke after ignition, the Delta II rocket carrying NASA's Dawn spacecraft rises from the smoke and fire on the launch pad to begin its 1.7-billion-mile journey through the inner solar system to study a pair of asteroids. Liftoff was at 7:34 a.m. EDT from Pad 17-B at Cape Canaveral Air Force Station. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Sandra Joseph & Rafael Hernandez

GPU-accelerated computational tool for studying the effectiveness of asteroid disruption techniques

NASA Astrophysics Data System (ADS)

Zimmerman, Ben J.; Wie, Bong

2016-10-01

This paper presents the development of a new Graphics Processing Unit (GPU) accelerated computational tool for asteroid disruption techniques. Numerical simulations are completed using the high-order spectral difference (SD) method. Due to the compact nature of the SD method, it is well suited for implementation with the GPU architecture, hence solutions are generated at orders of magnitude faster than the Central Processing Unit (CPU) counterpart. A multiphase model integrated with the SD method is introduced, and several asteroid disruption simulations are conducted, including kinetic-energy impactors, multi-kinetic energy impactor systems, and nuclear options. Results illustrate the benefits of using multi-kinetic energy impactor systems when compared to a single impactor system. In addition, the effectiveness of nuclear options is observed.

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.

Northwest Africa 1401: A Polymict Cumulate Eucrite with a Unique Ferroan Heteradcumulate Mafic Clast

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.; Killgore, Marvin

2003-01-01

The howardite, eucrite and diogenite (HED) clan is the largest suite of achondrites available for study. The suite gives us a unique view of the magmatism that affected some asteroids early in solar system history. One problem with mining the HED clan for petrogenetic information is that there is only limited petrologic diversity among the rock types. Thus, discovering unusual HED materials holds the potential for revealing new insights into the petrologic evolution of the HED parent asteroid. Here we report on petrologic study of an unusual, 27 gram polymict eucrite, Northwest Africa (NWA) 1401. The thin section studied (approx. 20 x 10 mm) contains one large, ferroan clast described separately. The remainder of the rock, including mineral fragments and other, smaller lithic clasts, forms the host breccia.

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).

High Resolution Asteroid Profile by Multi Chord Occultation Observations

NASA Astrophysics Data System (ADS)

Degenhardt, Scott

2009-05-01

For millennia man has observed celestial objects occulting other bodies and distant stars. We have used these celestial synchronicities to measure the properties of objects. On January 1, 1801 Italian astronomer Giusappe Piazzi discovered the first asteroid that would soon be named Ceres. To date 190,000 of these objects have been catalogued, but only a fraction of these have accurate measurements of their true size and shape. The International Occultation Timing Association (IOTA) currently facilitates the prediction and reduction of asteroidal occultations. By measuring the shadow cast on the earth by an asteroid during a stellar occultation one can directly measure the physical size, shape, and position in space of this body to accuracies orders of magnitudes better than the best ground based adaptive optics telescope and can provide verification to 3D inverted reflective lightcurve prediction models. Recent novel methods developed by IOTA involving an individual making multiple observations through unattended remote observing stations have made way for numerous chords of occultation measurement through a single body yielding high resolution profiles of asteroid bodies. Methodology of how observing stations are deployed will be demonstrated, results of some of these observations are presented as comparisons to their inverted lightcurve are shown.

3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites

NASA Astrophysics Data System (ADS)

Marsset, M.; Carry, B.; Dumas, C.; Hanuš, J.; Viikinkoski, M.; Vernazza, P.; Müller, T. G.; Delbo, M.; Jehin, E.; Gillon, M.; Grice, J.; Yang, B.; Fusco, T.; Berthier, J.; Sonnett, S.; Kugel, F.; Caron, J.; Behrend, R.

2017-08-01

Context. The high-angular-resolution capability of the new-generation ground-based adaptive-optics camera SPHERE at ESO VLT allows us to assess, for the very first time, the cratering record of medium-sized (D 100-200 km) asteroids from the ground, opening the prospect of a new era of investigation of the asteroid belt's collisional history. Aims: We investigate here the collisional history of asteroid (6) Hebe and challenge the idea that Hebe may be the parent body of ordinary H chondrites, the most common type of meteorites found on Earth ( 34% of the falls). Methods: We observed Hebe with SPHERE as part of the science verification of the instrument. Combined with earlier adaptive-optics images and optical light curves, we model the spin and three-dimensional (3D) shape of Hebe and check the consistency of the derived model against available stellar occultations and thermal measurements. Results: Our 3D shape model fits the images with sub-pixel residuals and the light curves to 0.02 mag. The rotation period (7.274 47 h), spin (ECJ2000 λ, β of 343°, +47°), and volume-equivalent diameter (193 ± 6 km) are consistent with previous determinations and thermophysical modeling. Hebe's inferred density is 3.48 ± 0.64 g cm-3, in agreement with an intact interior based on its H-chondrite composition. Using the 3D shape model to derive the volume of the largest depression (likely impact crater), it appears that the latter is significantly smaller than the total volume of close-by S-type H-chondrite-like asteroid families. Conclusions: Our results imply that (6) Hebe is not the most likely source of H chondrites. Over the coming years, our team will collect similar high-precision shape measurements with VLT/SPHERE for 40 asteroids covering the main compositional classes, thus providing an unprecedented dataset to investigate the origin and collisional evolution of the asteroid belt. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 60.A-9379 and 086.C-0785.

The NEOTωIST mission (Near-Earth Object Transfer of angular momentum spin test)

NASA Astrophysics Data System (ADS)

Drube, Line; Harris, Alan W.; Engel, Kilian; Falke, Albert; Johann, Ulrich; Eggl, Siegfried; Cano, Juan L.; Ávila, Javier Martín; Schwartz, Stephen R.; Michel, Patrick

2016-10-01

We present a concept for a kinetic impactor demonstration mission, which intends to change the spin rate of a previously-visited asteroid, in this case 25143 Itokawa. The mission would determine the efficiency of momentum transfer during an impact, and help mature the technology required for a kinetic impactor mission, both of which are important precursors for a future space mission to deflect an asteroid by collisional means in an emergency situation. Most demonstration mission concepts to date are based on changing an asteroid's heliocentric orbit and require a reconnaissance spacecraft to measure the very small orbital perturbation due to the impact. Our concept is a low-cost alternative, requiring only a single launch. Taking Itokawa as an example, an estimate of the order of magnitude of the change in the spin period, δP, with such a mission results in δP of 4 min (0.5%), which could be detectable by Earth-based observatories. Our preliminary study found that a mission concept in which an impactor produces a change in an asteroid's spin rate could provide valuable information for the assessment of the viability of the kinetic-impactor asteroid deflection concept. Furthermore, the data gained from the mission would be of great benefit for our understanding of the collisional evolution of asteroids and the physics behind crater and ejecta-cloud development.

Analysis of laser radar measurements of the asteroid 433 Eros

NASA Astrophysics Data System (ADS)

Cole, Timothy D.; Zuber, Maria T.; Neuman, Greg; Cheng, Andrew F.; Reiter, R. Alan; Guo, Yanping; Smith, David E.

2001-09-01

After a 5-year mission, a 4-year transit followed by a one-year mission orbiting the asteroid 433 Eros, the Near-Earth Asteroid Rendezvous-Shoemaker (NEAR) spacecraft made a controlled landing onto the asteroid's surface on 12 February 2001. Onboard the spacecraft, the NEAR Laser Rangefinder (NLR) facility instrument had gathered over 11 million measurements, providing a spatially dense, high-resolution, topographical map of Eros. This topographic data, combined with Doppler tracking data for the spacecraft, enabled the determination of the asteroid's shape, mass, and density thereby contributing to understanding the internal structure and collisional evolution of Eros. NLR data indicate that Eros is a consolidated body with a complex shape dominated by collisions. The offset between the asteroid's center of mass and center of figure indicates a small deviation from a homogeneous internal structure that is most simply explained by variations in mechanical structure. Regional-scale relief and slope distributions show evidence for control of some topography by a competent substrate. It was found that pulse dilation was the major source of uncertainty in single-shot range measurements from the NLR, and that this uncertainty remains consistent with the overall 6-m range measurement system accuracy for NEAR. Analysis of NLR data fully quantified the geodynamic nature of this planetesimal, ergo, illustrating the utility of laser altimetry for remote sensing.

Dynamical properties of the Watsonia asteroid family

NASA Astrophysics Data System (ADS)

Tsirvoulis, G.; Novakovic, B.; Knezevic, Z.; Cellino, A.

2014-07-01

Introduction: In recent years, a rare class of asteroids has been discovered [1], with its distinguishing characteristic being the anomalous polarimetric properties of its members. Named Barbarians, after (234) Barbara, the prototype of the class, these asteroids show negative polarization at unusually high phase-angles compared to normal asteroids. Motivated by the fact that some of the few discovered Barbarians seemed to be related to the Watsonia asteroid family, Cellino et al. [2] performed a search for more Barbarians among its members. A positive result of this search led to the conclusion that Watsonia is indeed an important repository of Barbarian asteroids. Based on these findings, we decided to analyze this family in detail. Basic information: According to available data, Watsonia is an L-type asteroid family, located in the middle of the main asteroid belt (2.68 < a_{p} < 2.82 au), with low to moderate orbital eccentricities (0.1 < e_{p} < 0.15) and relatively high inclinations (16.5^{o} < i_{p} < 18^{o}). Methodology: The first step in our study is to derive a reliable list of Watsonia family members. To that purpose, we first calculate the synthetic proper elements [3] of an extended catalogue including numbered, as well as multi and single opposition asteroids, in a wide region around the family. To this catalogue we apply the Hierarchical Clustering Method (HCM)[4] to determine the membership of the family, coinciding with the requirement that all confirmed neighboring Barbarians are included (see figure). To detect potential interlopers and refine the membership list, additional data such as the SDSS colors and WISE albedos are used. Moreover, we identify all relevant resonances and analyze the dynamical characteristics of the region occupied by the family. Then we estimate the age of the family, and finally, we perform numerical integrations of test particles to investigate possible dynamical links to other known Barbarians and to the near-Earth region.

Scientific Packages on Small Bodies, a Deployment Strategy for New Missions

NASA Astrophysics Data System (ADS)

Tardivel, Simon; Scheeres, D. J.; Michel, P.

2013-10-01

The exploration of asteroids is currently a topic of high priority for the space agencies. JAXA will launch its second asteroid explorer, aimed at 1999 JU3, in the second half of 2014. NASA has selected OSIRIS-REx to go to asteroid Bennu, and it will launch in 2016. ESA is currently performing the assessment study of the MarcoPolo-R space mission, in the framework of the M3 (medium) competition of its Cosmic Vision Program, whose objective is now 2008 EV5. In the continuity of these missions, landing for an extended period of time on the ground to perform measurements seems a logical next step to asteroid exploration. Yet, the surface behavior of an asteroid is not well known and landing the whole spacecraft on it could be hazardous, and pose other mission operations problems such as ensuring communication with Earth. Hence, we propose a new approach to asteroid surface exploration. Using a mothership spacecraft, we will present how multiple landers could be deployed to the surface of an asteroid using ballistic trajectories. Combining a detailed simulation of the bouncing and contact dynamics on the surface with numerical and mathematical analysis of the flight dynamics near an asteroid, we show how landing pods could be distributed at the surface of a body. The strategy has the advantages that the mothership always maintains a safe distance from the surface and the landers do not need any GNC (guidance, navigation and control system) or landing apparatus. Thus, it allows for simple operations and for the design of lightweight landers with minimum platform overhead and maximum payload. These pods could then be used as a single measurement apparatus (e.g. seismometers) or as independent and different instruments, using their widespread distribution to gain both global and local knowledge on the asteroid.

Asteroid Return Mission Feasibility Study

NASA Technical Reports Server (NTRS)

Brophy, John R.; Gershman, Robert; Landau, Damon; Polk, James; Porter, Chris; Yeomans, Don; Allen, Carlton; Williams, Willie; Asphaug, Erik

2011-01-01

This paper describes an investigation into the technological feasibility of finding, characterizing, robotically capturing, and returning an entire Near-Earth Asteroid (NEA) to the International Space Station (ISS) for scientific investigation, evaluation of its resource potential, determination of its internal structure and other aspects important for planetary defense activities, and to serve as a testbed for human operations in the vicinity of an asteroid. Reasonable projections suggest that several dozen candidates NEAs in the size range of interest (approximately 2-m diameter) will be known before the end of the decade from which a suitable target could be selected. The conceptual mission objective is to return an approximately 10,000-kg asteroid to the ISS in a total flight time of approximately 5 years using a single Evolved Expendable Launch Vehicle. Preliminary calculations indicate that this could be accomplished using a solar electric propulsion (SEP) system with high-power Hall thrusters and a maximum power into the propulsion system of approximately 40 kW. The SEP system would be used to provide all of the post-launch delta V. The asteroid would have an unrestricted Earth return Planetary Protection categorization, and would be curated at the ISS where numerous scientific and resource utilization experiments would be conducted. Asteroid material brought to the ground would be curated at the NASA Johnson Space Center. This preliminary study identified several areas where additional work is required, but no show stoppers were identified for the approach that would return an entire 10,000-kg asteroid to the ISS in a mission that could be launched by the end of this decade.

The σ-Capricornids complex of near-Earth objects

NASA Astrophysics Data System (ADS)

Babadzhanov, P. B.; Kokhirova, G. I.; Khamroev, U. Kh.

2015-04-01

The Earth-crossing asteroids 2008BO16, 2011EC41, and 2013CT36 have very similar orbits according to the Southworth and Hawkins DSH criterion. Their orbits are additionally classified as comet-like based on using the Tisserand parameter which is a standard tool used to distinction between asteroids and comets. The orbital evolution research shows that they cross the Earth's orbit four times over one cycle of the perihelion argument variations. Consequently, a meteoroid stream, possibly associated with them, may produce four meteor showers. Theoretic parameters of the predicted showers were calculated and identified with the observable nighttime σ-Capricornids and χ-Sagittariids, and daytime χ-Capricornids and Capricornids-Sagittariids meteor showers. The similar comet-like orbits and the linkage with the same meteoroid stream producing four active showers provide strong evidence that these asteroids have a common cometary origin. Earlier, it was demonstrated that the Earth-crossing asteroids (2101) Adonis and 1995CS, being a potentially hazardous asteroid (PHA), were recognized as dormant comets because of their linkage with the σ-Capricornids meteoroid stream. Thus, a conclusion was made, that either the considered objects are large pieces of the Adonis, or all five objects are extinct or dormant fragments of a larger comet that was the parent body of the σ-Capricornids meteoroid stream, and whose break-up occurred several tens of thousands years ago. During 2010-2011, three σ-Capricornids fireballs were captured by the Tajikistan fireball network. Taking into account the observations in Canada and the USA, the dynamic and physical properties of the σ-Capricornid meteoroids were identified. According to the estimated meteoroids bulk density a non-homogeneous compound of the σ-Capricornids shower comet-progenitor was suggested.

A Search for Variation in the Surface Mineralogical Composition of J VI Himalia

NASA Astrophysics Data System (ADS)

Jarvis, K. S.; Vilas, F.; Larson, S. M.; Gaffey, M. J.

1996-09-01

Diverse spectral data exist for Jupiter's moon J VI Himalia. The overall spectral shape suggests that it has the same mineralogical composition as a C-class asteroid, lending credibility to the theory that Himalia was a C-class asteroid that formed in or near the main asteroid belt and was ejected and captured into orbit around Jupiter. Using an algorithm developed earlier, ECAS photometry (Tholen and Zellner, 1984) of Himalia taken on one date only have tested positively for the presence of a 0.7- mu m feature attributed to an Fe(2+) -> Fe(3+) charge transfer transition in oxidized iron in phyllosilicates. The presence of this feature was confirmed by narrowband spectrophotometry obtained on one date in April, 1995. Narrowband spectrophotometry of Luu (1991) does not cover the full spectral range defined by the 0.7-mu m absorption feature, but is in good agreement with the ECAS photometry. However, no 3.0-mu m water of hydration absorption feature was observed in IR radiometry (A. S., Rivkin, per. comm.). Correlation between the 0.7-mu m feature and the 3.0-mu m feature has been demonstrated in spectra of low-albedo asteroids, and suggests that it should be present. A rough rotational period for Himalia of 9.2 - 9.8 hrs is known. Himalia could represent the junction of two different compositional units, produced when an impact fragmented Himalia's parent body. The presence of iron-bearing phyllosilicates on part of Himalia's surface supports the hypothesis that Himalia is a captured C-class asteroid. Rotationally-resolved spectra of Himalia could confirm a variation in composition; we have started a program to collect these data.

Magnetism and mineralogy of Almahata Sitta polymict ureilite (= asteroid 2008 TC3): Implications for the ureilite parent body magnetic field

NASA Astrophysics Data System (ADS)

Hoffmann, Viktor H.; Hochleitner, Rupert; Torii, Masayuki; Funaki, Minoru; Mikouchi, Takashi; Kaliwoda, Melanie; Jenniskens, Peter; Shaddad, Muawia H.

2011-10-01

The Almahata Sitta meteorite is the first case of recovered extraterrestrial material originating from an asteroid that was detected in near Earth space shortly before entering and exploding in the high atmosphere. The aims of our project within the 2008 TC3 consortium were investigating Almahata Sitta's (AS) magnetic signature, phase composition and mineralogy, focussing on the opaque minerals, and gaining new insights into the magnetism of the ureilite parent body (UPB). We report on the general magnetic properties and behavior of Almahata Sitta and try to place the results in context with the existing data set on ureilites and ureilite parent body models. The magnetic signature of AS is dominated by a set of low-Ni kamacites with large grain sizes. Additional contributions come from micron-sized kamacites, suessite, (Cr) troilite, and daubreelite, mainly found in the olivine grains adjacent to carbon-rich veins. Our results show that the paleomagnetic signal is of extraterrestrial origin as can be seen by comparing with laboratory produced magnetic records (IRM). Four types of kamacite (I-IV) have been recognized in the sample. The elemental composition of the ureilite vein metal Kamacite I (particularly Co) clearly differs from the other kamacites (II-IV), which are considered to be indigenous. Element ratios of kamacite I indicate that it was introduced into the UPB by an impactor, supporting the conclusions of Gabriel and Pack (2009).

Granular media in the context of small bodies

NASA Astrophysics Data System (ADS)

Tancredi, G.

2014-07-01

Granular materials of different particle sizes are present on the surface and the interior of several atmosphereless Solar System bodies. The presence of very fine particles on the surface of the Moon, the so-called regolith, was confirmed by the Apollo astronauts. From the polarimetric observations and phase angle curves, it is possible to indirectly infer the presence of fine particles on the surfaces of asteroids and planetary satellites. More recently, the visit of spacecraft to several asteroids and comets has provided us with close pictures of the surface, where particles of a wide size range from cm to hundreds of meters have been directly observed. The presence of even finer particles on the visited bodies can also be inferred from image analysis. Solar System bodies smaller than a few hundred km may have a variety of internal structures: monolithic single bodies, objects with internal fractures, rubble piles maintained as a single object by self-gravity, etc. After the visit of the small asteroid Itokawa, it has been speculated that ''some small asteroids appear to be clumps of gravel glued by a very weak gravity field'' (Asphaug 2007). We still do not know the internal structure of these rubble piles and the size distribution of the interior constituents, but these clumps could have several million meter-sized boulders inside. There are several pieces of evidence that many asteroids are agglomerates of small components, like: - Rotation periods for small asteroids - Tidal disruption of asteroids and comets when they enter the Roche's limit of a massive object - The existence of crater chains like the ones observed in Ganymede - Low density estimates (< 2 gr/cm^3) for many asteroids like Mathilde It has been proposed that several typical processes of granular materials (such as: the size segregation of boulders on Itokawa, the displacement of boulders on Eros, the ejection of dust clouds after impacts) can explain some features observed on these bodies. We review the numerical and experimental studies on granular materials with relevance to the understanding of the physical processes on the interior and the surfaces of minor bodies of the Solar System. In particular, we compare the different codes in use to perform numerical simulations of the physical evolution of these objects. We highlight results of these simulations. Some groups have been involved in laboratory experiments on granular material trying to reproduce the conditions in space: vacuum and low gravity. We describe the experimental set-ups and some results of these experiments. Some open problems and future line of work in this field will be presented.

Petrologic evolution of CM chondrites: The difficulty of discriminating between nebular and parent-body effects. [Abstract only

NASA Technical Reports Server (NTRS)

Kerridge, J. F.; Mcsween, H. Y., Jr.; Bunch, T. E.

1994-01-01

We wish to draw attention to a major controversy that has arisen in the area of CM-chondrite petrology. The problem is important because its resolution will have profound implications for ideas concerning nebular dynamics, gas-solid interactions in the nebula, and accretionary processes in the nebula, among other issues. On the one hand, cogent arguments have been presented that 'accretionary dust mantles,' were formed in the solar nebula prior to accretion of the CM parent asteroid(s). On the other hand, no-less-powerful arguments have been advanced that a significant fraction of the CM lithology is secondary, produced by aqueous alteration in the near-surface regions of an asteroid-sized object. Because most, if not all, CM chondrites are breccias, these two views could coexist harmoniously, were it not for the fact that some of the coarse-grained lithologies surrounded by 'accretion dust mantles' are themselves of apparently secondary origin. Such an observation must clearly force a reassessment of one or both of the present schools of thought. Our objective here is to stimulate such a reassessment. Four possible resolutions of this conflict may be postulated. First, perhaps nature found a way of permitting such secondary alteration to take place in the nebula. Second, maybe dust mantles could form in a regolith, rather than a nebular, environment. Third, it is possible that dust mantles around secondary lithologies are different from those around primary lithologies. Finally, perhaps formation of CM chondrites involved a more complex sequence of events than visualized so far, so that some apparently 'primary' processes postdated certain 'secondary' processes.

Petrology of Anomalous Eucrites

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Peng, Z. X.; Ross, D. K.

2015-01-01

Most mafic achondrites can be broadly categorized as being "eucritic", that is, they are composed of a ferroan low-Ca clinopyroxene, high-Ca plagioclase and a silica phase. They are petrologically distinct from angritic basalts, which are composed of high-Ca, Al-Ti-rich clinopyroxene, Carich olivine, nearly pure anorthite and kirschsteinite, or from what might be called brachinitic basalts, which are composed of ferroan orthopyroxene and high-Ca clinopyroxene, intermediate-Ca plagioclase and ferroan olivine. Because of their similar mineralogy and composition, eucrite-like mafic achondrites formed on compositionally similar asteroids under similar conditions of temperature, pressure and oxygen fugacity. Some of them have distinctive isotopic compositions and petrologic characteristics that demonstrate formation on asteroids different from the parent of the HED clan (e.g., Ibitira, Northwest Africa (NWA) 011). Others show smaller oxygen isotopic distinctions but are otherwise petrologically and compositionally indistinguishable from basaltic eucrites (e.g., Pasamonte, Pecora Escarpment (PCA) 91007). The degree of uniformity in delta O-17 of eucrites and diogenites is one piece of evidence considered to favor of a magma-ocean scenario for their petrogenesis. Given that the O isotopic differences separating Pasamonte and PCA 91007 from other eucrites are small, and that there is an absence of other distinguishing characteristics, a legitimate question is: Did the HED parent asteroid fail to homogenize via a magma-ocean stage, thus explaining outliers like Pasamonte? We are initiating a program of study of anomalous eucrite-like achondrites as one part of our effort to seek a resolution of this issue. Here we present preliminary petrologic information on Asuka (A-) 881394, Elephant Moraine (EET) 87520 and EET 87542. We will have studied several more by conference time.

Extraterrestrial Amino Acids in the Almahata Sitta Meteorite

NASA Technical Reports Server (NTRS)

Glavin, Daniel P.; Aubrey, Andrew D.; Callahan, Michael P.; Dworkin, Jason P.; Elsila, Jamie E.; Parker, Eric T.; Bada, Jeffrey L.

2010-01-01

Amino acid analysis of a meteorite fragment of asteroid 2008 TC3 called Almahata Sitta was carried out using reverse-phase liquid chromatography coupled with UV fluorescence detection and time-of-flight mass spectrometry (LC-FD/ToF-MS) as part of a sample analysis consortium. LC-FD/ToF-MS analyses of hot-water extracts from the meteorite revealed a complex distribution of two- to seven-carbon aliphatic amino acids and one- to three-carbon amines with abundances ranging from 0.5 to 149 parts-per-billion (ppb). The enantiomeric ratios of the amino acids alanine, R-amino-n-butyric acid (beta-ABA), 2-amino-2-methylbutanoic acid (isovaline), and 2-aminopentanoic acid (norvaline) in the meteorite were racemic (D/L approximately 1), indicating that these amino acids are indigenous to the meteorite and not terrestrial contaminants. Several other non-protein amino acids were also identified in the meteorite above background levels including alpha-aminoisobutyric acid (alpha-AIB), 4-amino-2- methylbutanoic acid, 4-amino-3-methylbutanoic acid, and 3-, 4-, and 5-aminopentanoic acid. The total abundances of isovaline and alpha-AIB in Almahata Sitta are 1000 times lower than the abundances of these amino acids found in the CM carbonaceous chondrite Murchison. The extremely low abundances and unusual distribution of five carbon amino acids in Almahata Sitta compared to Cl, CM, and CR carbonaceous chondrites may reflect extensive thermal alteration of amino acids on the parent asteroid by partial melting during formation or subsequent impact shock heating. It is also possible that amino acids were synthesized by catalytic reactions on the parent body after asteroid 2008 TC3 cooled to lower temperatures.

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.

KSC-07pd2591

NASA Image and Video Library

2007-09-27

KENNEDY SPACE CENTER, FLA. -- Against a backdrop of clouds on the horizon, the Delta II rocket carrying NASA's Dawn spacecraft rises from the smoke and fire on the launch pad to begin its 1.7-billion-mile journey through the inner solar system to study a pair of asteroids. Liftoff was at 7:34 a.m. EDT from Pad 17-B at Cape Canaveral Air Force Station. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Sandra Joseph & Rafael Hernandez

Dawn at Vesta: testing the protoplanetary paradigm

USGS Publications Warehouse

Russell, C.T.; Raymond, C.A.; Coradini, A.; McSween, H.Y.; Zuber, M.T.; Nathues, A.; DeSanctis, Maria-Cristina; Jaumann, R.; Konopliv, A.S.; Preusker, F.; Asmar, S.W.; Park, R.S.; Gaskell, R.; Keller, H.U.; Mottola, S.; Roatsch, T.; Scully, J.E.C.; Smith, D.E.; Tricarico, P.; Toplis, M.J.; Christensen, U.R.; Feldman, W.C.; Lawrence, D.J.; McCoy, T.J.; Prettyman, T.H.; Reedy, R.C.; Sykes, M.E.; Titus, T.N.

2012-01-01

The Dawn spacecraft targeted 4 Vesta, believed to be a remnant intact protoplanet from the earliest epoch of solar system formation, based on analyses of howardite-eucrite-diogenite (HED) meteorites that indicate a differentiated parent body. Dawn observations reveal a giant basin at Vesta's south pole, whose excavation was sufficient to produce Vesta-family asteroids (Vestoids) and HED meteorites. The spatially resolved mineralogy of the surface reflects the composition of the HED meteorites, confirming the formation of Vesta's crust by melting of a chondritic parent body. Vesta's mass, volume, and gravitational field are consistent with a core having an average radius of 107 to 113 kilometers, indicating sufficient internal melting to segregate iron. Dawn's results confirm predictions that Vesta differentiated and support its identification as the parent body of the HEDs.

Radar-Enabled Recovery of the Sutters Mill Meteorite, a Carbonaceous Chondrite Regolith Breccia

NASA Technical Reports Server (NTRS)

Jenniskens, Petrus M.; Fries, Marc D.; Yin, Qing-Zhu; Zolensky, Michael E.; Krot, Alexander N.; Sandford, Scott A.; Sears, Derek; Beauford, Robert; Ebel, Denton S.; Friedrich, Jon M.;

Vesta Evolution from Surface Mineralogy: Mafic and Ultramafic Mineral Distribution

NASA Technical Reports Server (NTRS)

DeSanctis, M. C.; Ammannito, E.; Palomba, E.; Longobardo, A.; Mittlefehldt, D. W.; McSween, H. Y; Marchi, S.; Capria, M. T.; Capaccioni, F.; Frigeri, A.;

A dual origin for water in carbonaceous asteroids revealed by CM chondrites

NASA Astrophysics Data System (ADS)

Piani, Laurette; Yurimoto, Hisayoshi; Remusat, Laurent

2018-04-01

Carbonaceous asteroids represent the principal source of water in the inner Solar System and might correspond to the main contributors for the delivery of water to Earth. Hydrogen isotopes in water-bearing primitive meteorites, for example carbonaceous chondrites, constitute a unique tool for deciphering the sources of water reservoirs at the time of asteroid formation. However, fine-scale isotopic measurements are required to unravel the effects of parent-body processes on the pre-accretion isotopic distributions. Here, we report in situ micrometre-scale analyses of hydrogen isotopes in six CM-type carbonaceous chondrites, revealing a dominant deuterium-poor water component (δD = -350 ± 40‰) mixed with deuterium-rich organic matter. We suggest that this deuterium-poor water corresponds to a ubiquitous water reservoir in the inner protoplanetary disk. A deuterium-rich water signature has been preserved in the least altered part of the Paris chondrite (δDParis ≥ -69 ± 163‰) in hydrated phases possibly present in the CM rock before alteration. The presence of the deuterium-enriched water signature in Paris might indicate that transfers of ice from the outer to the inner Solar System were significant within the first million years of the history of the Solar System.

Rotation-induced YORP break-up of small bodies to produce post-main-sequence debris

NASA Astrophysics Data System (ADS)

Veras, D.; Jacobson, S. A.; Gänsicke, B. T.

2017-09-01

We hypothesize that the in situ break-up of small bodies such as asteroids spun to fission during the giant branch phases of stellar evolution provides an important contribution to the debris orbiting and ultimately polluting white dwarfs. The YORP (Yarkovsky-O'Keefe-Radviesvki-Paddock) effect, which arises from radiation pressure, accelerates the spin rate of asymmetric asteroids, which can eventually shear themselves apart. This pressure is maintained and enhanced around dying stars because the outward push of an asteroid due to stellar mass loss is insignificant compared to the resulting stellar luminosity increase. Consequently, giant star radiation will destroy nearly all bodies with radii in the range 100 m-10 km that survive their parent star's main-sequence lifetime within a distance of about 7 au; smaller bodies are spun apart to their strongest, competent components. This estimate is conservative and would increase for highly asymmetric shapes or incorporation of the inward drag due to giant star stellar wind. The resulting debris field, which could extend to thousands of au, may be perturbed by remnant planetary systems to reproduce the observed dusty and gaseous discs which accompany polluted white dwarfs.

Optical effects of regolith processes on S asteroids as simulated by laser impulse alteration of ordinary chondrite

NASA Technical Reports Server (NTRS)

Moroz, L. V.; Fisenko, A. V.; Semjonova, L. F.; Pieters, C. M.

1993-01-01

The spectral properties of some powdered chondrites and minerals altered by Isser impulse are studied in order to estimate possible optical effects of regolith processes (micrometeoritic bombardment). Gradual reduction of overall reflectance and spectral contrast, the increase of continuum slope, the increase of spectrally derived olivine/pyroxene ratio and Fs content of orthopyroxene with increasing alteration degree show that regolith processes could affect optical properties of surface material more heavily than has been previously appreciated. Ordinary chondrites (OC's) are known to account for 80 percent of observed meteorite falls, but so far no main belt parent bodies have been identified for these meteorites. S-asteroids resemble OC's spectrally, but are characterized by a steeper red continuum unlike that of OC's and their spectrally derived mineralogies are far outside OC range. Attempts were made to explain the spectral mismatch between OC's and S asteroids by some process, which alters optical properties of uppermost regolith. However, the spectral studies of shocked (black) OC's, gas-rich OC's, melted OC's and synthetic metal-rich regoliths derived from OC's demonstrate that such altered OC materials darken, but do not redden.

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.

DIRBE Comet Trails

NASA Technical Reports Server (NTRS)

Arendt, Richard G.

2015-01-01

Re-examination of the COBE DIRBE data reveals the thermal emission of several comet dust trails.The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported.The known trails of 2P/Encke, and 73P/Schwassmann-Wachmann 3 are also seen. The dust trails have 12 and 25 microns surface brightnesses of <0.1 and <0.15 MJy/sr, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals one additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

Barbarians in the Watsonia family: Interpretation and open problems

NASA Astrophysics Data System (ADS)

Cellino, A.; Bagnulo, S.; Tanga, P.; Novakovic, B.; Delbó, M.

2014-07-01

The so-called Barbarian asteroids, which take their name from the prototype of their class, asteroid (234) Barbara, are characterized by anomalous polarimetric properties. They exhibit a so-called ''negative polarization branch'' which is much wider than usual. This behavior is strikingly different with respect to that exhibited by the vast majority of asteroids. Barbarians are relatively rare. Before the results of the investigation described in this work, only 6 Barbarians were known to exist. A couple of them (980 Anacostia and 387 Aquitania) were known to be within or very close to the Watsonia dynamical family, thought to consist of fragments coming from the collisional disruption of a high-inclination parent body (Novakovic et al., 2011). We have therefore carried out a campaign of spectroscopic observations of members of the Watsonia family using the ESO VLT. The results are striking: 7 out of 9 targets have been found to be Barbarians. This result not only more than doubles the inventory of known Barbarians, but it shows that the Barbarian behavior is due to properties which are not simply due to mere surface properties, but characterize also the overall composition of the interior of the bodies. In this respect, the fact that a number of Barbarians have been found to have also anomalous abundances of the spinel mineral on their surfaces opens exciting lines of investigation, since it is possible that these asteroids could be extremely primitive. Their rarity remains also to be explained.

Experimental study on impact-induced seismic wave propagating through quartz sand simulating asteroid regolith

NASA Astrophysics Data System (ADS)

Matsue, Kazuma; Arakawa, Masahiko; Yasui, Minami; Matsumoto, Rie; Tsujido, Sayaka; Takano, Shota; Hasegawa, Sunao

2015-08-01

Introduction: Recent spacecraft surveys clarified that asteroid surfaces were covered with regolith made of boulders and pebbles such as that found on the asteroid Itokawa. It was also found that surface morphologies of asteroids formed on the regolith layer were modified. For example, the high-resolution images of the asteroid Eros revealed the evidence of the downslope movement of the regolith layer, then it could cause the degradation and the erasure of small impact crater. One possible process to explain these observations is the regolith layer collapse caused by seismic vibration after projectile impacts. The impact-induced seismic wave might be an important physical process affecting the morphology change of regolith layer on asteroid surfaces. Therefore, it is significant for us to know the relationship between the impact energy and the impact-induced seismic wave. So in this study, we carried out impact cratering experiments in order to observe the seismic wave propagating through the target far from the impact crater.Experimental method: Impact cratering experiments were conducted by using a single stage vertical gas gun set at Kobe Univ and a two-stage vertical gas gun set at ISAS. We used quartz sands with the particle diameter of 500μm, and the bulk density of 1.48g/cm3. The projectile was a ball made of polycarbonate with the diameter of 4.75mm and aluminum, titan, zirconia, stainless steel, cupper, tungsten carbide projectile with the diameter of 2mm. These projectiles were launched at the impact velocity from 0.2 to 7km/s. The target was set in a vacuum chamber evacuated below 10 Pa. We measured the seismic wave by using a piezoelectric uniaxial accelerometer.Result: The impact-induced seismic wave was measured to show a large single peak and found to attenuate with the propagation distance. The maximum acceleration of the seismic wave was recognized to have a good relationship with the normalized distance x/R, where x is the propagation distance and R is the crater radius, irrespective of the impact velocities: gmax = 160(x/R)-2.98.

The trajectory, structure and origin of the Chelyabinsk asteroidal impactor

NASA Astrophysics Data System (ADS)

Borovička, Jiří; Spurný, Pavel; Brown, Peter; Wiegert, Paul; Kalenda, Pavel; Clark, David; Shrbený, Lukáš

2013-11-01

Earth is continuously colliding with fragments of asteroids and comets of various sizes. The largest encounter in historical times occurred over the Tunguska river in Siberia in 1908, producing an airburst of energy equivalent to 5-15 megatons of trinitrotoluene (1 kiloton of trinitrotoluene represents an energy of 4.185 × 1012 joules). Until recently, the next most energetic airburst events occurred over Indonesia in 2009 and near the Marshall Islands in 1994, both with energies of several tens of kilotons. Here we report an analysis of selected video records of the Chelyabinsk superbolide of 15 February 2013, with energy equivalent to 500 kilotons of trinitrotoluene, and details of its atmospheric passage. We found that its orbit was similar to the orbit of the two-kilometre-diameter asteroid 86039 (1999 NC43), to a degree of statistical significance sufficient to suggest that the two were once part of the same object. The bulk strength--the ability to resist breakage--of the Chelyabinsk asteroid, of about one megapascal, was similar to that of smaller meteoroids and corresponds to a heavily fractured single stone. The asteroid broke into small pieces between the altitudes of 45 and 30 kilometres, preventing more-serious damage on the ground. The total mass of surviving fragments larger than 100 grams was lower than expected.

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.

When Worlds Collide

NASA Astrophysics Data System (ADS)

Schultz, P. H.

1997-07-01

Although considerable attention has been paid to the catastrophic fragmentation of small planetary bodies following hypervelocity collisions, laboratory experiments at the NASA Ames Vertical Gun Range allow documenting the fate of the impactor. Of particular interest is the effect of oblique impacts on curved planetary surfaces, i.e., when the size of the impactor approaches 20% of the size of the target. Such experiments reveal that the shock created at first contact disrupts and decouples the impactor before it penetrates the target for 5-6 km/s impact velocities. This process has five important consequences. First, relatively large impactor fragments can survive the collision with minimal damage (5-6 largest sizes = 10% of the impactor mass). Moreover, surface curvature ensures escape of larger impactor debris exhibiting a wide range of shocked states. Second, these fragments follow different trajectories depending on their style of failure (spallation or shear) and provenance (their location in the impactor). Third, a low impedance veneer (regolith) reduces the degree of impactor fragmentation. Fourth, the process significantly decreases the energy (peak pressure) in the target and allows its survival even for collisions with large specific energies. Nevertheless, significant residual mafic melts result through frictional heating. And fifth, nominal oblique trajectories (30 deg) become equivalent to much lower angle events (< 10 deg) as the impactor:target ratio approaches 1:4. This process can be scaled (to first order) to asteroid-size events and could provide a mechanism to produce different meteor streams and asteroid families from a single event while leaving behind an intact but mafic scar on the parent body.

Looking a gift horse in the mouth: Evaluation of wide-field asteroid photometric surveys

NASA Astrophysics Data System (ADS)

Harris, Alan W.; Pravec, Petr; Warner, Brian D.

2012-09-01

It has recently become possible to do a photometric survey of many asteroids at once, rather than observing single asteroids one (or occasionally a couple) at a time. We evaluate two such surveys. Dermawan et al. (Dermawan et al. [2011]. Publ. Astron. Soc. Jpn. 63, S555-S576) observed one night on the Subaru 8.2 m telescope, and Masiero et al. (Masiero, J., Jedicke, R., Durech, J., Gwen, S., Denneau, L., Larsen, J. [2009]. Icarus 204, 145-171) observed six nights over 2 weeks with the 3.6 m CFHT. Dermawan claimed 83 rotation periods from 127 detected asteroids; Masiero et al. claimed 218 rotation periods from 828 detections. Both teams claim a number of super-fast rotators (P < 2.2 h) among main belt asteroids larger than 250 m diameter, some up to several km in diameter. This would imply that the spin rate distribution of main belt asteroids differs from like-sized NEAs, that there are larger super-fast rotators (monolithic asteroids) in the main belt than among NEAs. Here we evaluate these survey results, applying the same criteria for reliability of results that we apply to all results listed in our Lightcurve Database (Warner, B.D., Harris, A.W., Pravec, P. [2009a]. Icarus 202, 134-146). In doing so, we assigned reliability estimates judged sufficient for inclusion in statistical studies for only 27 out of 83 (33%) periods claimed by Dermawan, and only 87 out of 218 (40%) periods reported by Masiero et al.; none of the super-fast rotators larger than about 250 m diameter claimed by either survey received a reliability rating judged sufficient for analysis. We find no reliable basis for the claim of different rotation properties between main belt and near-Earth asteroids. Our analysis presents a cautionary message for future surveys.

New Hypervelocity Terminal Intercept Guidance Systems for Deflecting/Disrupting Hazardous Asteroids

NASA Astrophysics Data System (ADS)

Lyzhoft, Joshua Richard

Computational modeling and simulations of visual and infrared (IR) sensors are investigated for a new hypervelocity terminal guidance system of intercepting small asteroids (50 to 150 meters in diameter). Computational software tools for signal-to-noise ratio estimation of visual and IR sensors, estimation of minimum and maximum ranges of target detection, and GPU (Graphics Processing Units)-accelerated simulations of the IR-based terminal intercept guidance systems are developed. Scaled polyhedron models of known objects, such as the Rosetta mission's Comet 67P/C-G, NASA's OSIRIS-REx Bennu, and asteroid 433 Eros, are utilized in developing a GPU-based simulation tool for the IR-based terminal intercept guidance systems. A parallelized-ray tracing algorithm for simulating realistic surface-to-surface shadowing of irregular-shaped asteroids or comets is developed. Polyhedron solid-angle approximation is also considered. Using these computational models, digital image processing is investigated to determine single or multiple impact locations to assess the technical feasibility of new planetary defense mission concepts of utilizing a Hypervelocity Asteroid Intercept Vehicle (HAIV) or a Multiple Kinetic-energy Interceptor Vehicle (MKIV). Study results indicate that the IR-based guidance system outperforms the visual-based system in asteroid detection and tracking. When using an IR sensor, predicting impact locations from filtered images resulted in less jittery spacecraft control accelerations than conducting missions with a visual sensor. Infrared sensors have also the possibility to detect asteroids at greater distances, and if properly used, can aid in terminal phase guidance for proper impact location determination for the MKIV system. Emerging new topics of the Minimum Orbit Intersection Distance (MOID) estimation and the Full-Two-Body Problem (F2BP) formulation are also investigated to assess a potential near-Earth object collision risk and the proximity gravity effects of an irregular-shaped binary-asteroid target on a standoff nuclear explosion mission.

Multi-Objective Hybrid Optimal Control for Multiple-Flyby Interplanetary Mission Design Using Chemical Propulsion

NASA Technical Reports Server (NTRS)

Englander, Jacob; Vavrina, Matthew

2015-01-01

The customer (scientist or project manager) most often does not want just one point solution to the mission design problem Instead, an exploration of a multi-objective trade space is required. For a typical main-belt asteroid mission the customer might wish to see the trade-space of: Launch date vs. Flight time vs. Deliverable mass, while varying the destination asteroid, planetary flybys, launch year, etcetera. To address this question we use a multi-objective discrete outer-loop which defines many single objective real-valued inner-loop problems.

Origin of felsic achondrites Graves Nunataks 06128 and 06129, and ultramafic brachinites and brachinite-like achondrites by partial melting of volatile-rich primitive parent bodies

NASA Astrophysics Data System (ADS)

Day, James M. D.; Walker, Richard J.; Ash, Richard D.; Liu, Yang; Rumble, Douglas; Irving, Anthony J.; Goodrich, Cyrena A.; Tait, Kimberly; McDonough, William F.; Taylor, Lawrence A.

2012-03-01

New major- and trace-element abundances, highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances, and oxygen and rhenium-osmium isotope data are reported for oligoclase-rich meteorites Graves Nunataks 06128 and 06129 (GRA 06128/9), six brachinites (Brachina; Elephant Morraine 99402/7; Northwest Africa (NWA) 1500; NWA 3151; NWA 4872; NWA 4882) and three olivine-rich achondrites, which are referred to here as brachinite-like achondrites (NWA 5400; NWA 6077; Zag (b)). GRA 06128/9 represent examples of felsic and highly-sodic melt products from an asteroid that may provide a differentiation complement to brachinites and/or brachinite-like achondrites. The new data, together with our petrological observations, are consistent with derivation of GRA 06128/9, brachinites and the three brachinite-like achondrites from nominally volatile-rich and oxidised 'chondritic' precursor sources within their respective parent bodies. Furthermore, the range of Δ17O values (˜0‰ to -0.3‰) among the meteorites indicates generation from isotopically heterogeneous sources that never completely melted, or isotopically homogenised. It is possible to generate major- and trace-element compositions similar to brachinites and the three studied brachinite-like achondrites as residues of moderate degrees (13-30%) of partial melting of primitive chondritic sources. This process was coupled with inefficient removal of silica-saturated, high Fe/Mg felsic melts with compositions similar to GRA 06128/9. Melting of the parent bodies of GRA 06128/9, brachinites and brachinite-like achondrites halted well before extensive differentiation, possibly due to the exhaustion of the short-lived radionuclide 26Al by felsic melt segregation. This mechanism provides a potential explanation for the cessation of run-away melting in asteroids to preserve achondrites such as GRA 06128/9, brachinites, brachinite-like achondrites, acapulcoite-lodranites, ureilites and aubrites. Moderate degrees of partial melting of chondritic material and generation of Fe-Ni-S-bearing melts are generally consistent with HSE abundances that are within factors of ˜2-10 × CI-chondrite abundances for GRA 06128/9, brachinites and the three brachinite-like achondrites. However, in detail, brachinite-like achondrites NWA 5400, NWA 6077 and Zag (b) are interpreted to have witnessed single-stage S-rich metal segregation, whereas HSE in GRA 06128/9 and brachinites have more complex heritages. The HSE compositions of GRA 06128/9 and brachinites require either: (1) multiple phases in the residue (e.g., metal and sulphide); (2) fractionation after generation of an initial melt, again involving multiple phases; (3) fractional fusion, or; (4) a parent body with non-chondritic relative HSE abundances. Petrological and geochemical observations permit genetic links (i.e., same parent body) between GRA 06128/9 and brachinites and similar formation mechanisms for brachinites and brachinite-like achondrites.

VizieR Online Data Catalog: NIR albedos of main-belt asteroids (Masiero+, 2014)

NASA Astrophysics Data System (ADS)

Masiero, J. R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; Sonnett, S.

2017-04-01

To fit for NIR albedos of main-belt asteroids, we use data from the WISE/NEOWISE all-sky single exposure source table, which are available for download from the Infrared Science Archive (IRSA, http://irsa.ipac.caltech.edu ; Cutri et al. 2012, xplanatory Supplement to the WISE All-Sky Data Release Products, http://wise2.ipac.caltech.edu/docs/release/allsky/expsup/index.html). We extract photometric measurements of all asteroids observed by WISE following the technique described in Masiero et al. (2011, J/ApJ/741/68) and Mainzer et al. (2011ApJ...731...53M). In particular, we use the NEOWISE observations reported to the MPC and included in the MPC's minor planet observation database as the final validated list of reliable NEOWISE detections of solar system objects. (1 data file).

Linking the collisional history of the main asteroid belt to its dynamical excitation and depletion

NASA Astrophysics Data System (ADS)

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

2005-12-01

The main belt is believed to have originally contained an Earth mass or more of material, enough to allow the asteroids to accrete on relatively short timescales. The present-day main belt, however, only contains ˜5×10 Earth masses. Numerical simulations suggest that this mass loss can be explained by the dynamical depletion of main belt material via gravitational perturbations from planetary embryos and a newly-formed Jupiter. To explore this scenario, we combined dynamical results from Petit et al. [Petit, J. Morbidelli, A., Chambers, J., 2001. The primordial excitation and clearing of the asteroid belt. Icarus 153, 338-347] with a collisional evolution code capable of tracking how the main belt undergoes comminution and dynamical depletion over 4.6 Gyr [Bottke, W.F., Durda, D., Nesvorny, D., Jedicke, R., Morbidelli, A., Vokrouhlický, D., Levison, H., 2005. The fossilized size distribution of the main asteroid belt. Icarus 175, 111-140]. Our results were constrained by the main belt's size-frequency distribution, the number of asteroid families produced by disruption events from diameter D>100 km parent bodies over the last 3-4 Gyr, the presence of a single large impact crater on Vesta's intact basaltic crust, and the relatively constant lunar and terrestrial impactor flux over the last 3 Gyr. We used our model to set limits on the initial size of the main belt as well as Jupiter's formation time. We find the most likely formation time for Jupiter was 3.3±2.6 Myr after the onset of fragmentation in the main belt. These results are consistent with the estimated mean disk lifetime of 3 Myr predicted by Haisch et al. [Haisch, K.E., Lada, E.A., Lada, C.J., 2001. Disk frequencies and lifetimes in young clusters. Astrophys. J. 553, L153-L156]. The post-accretion main belt population, in the form of diameter D≲1000 km planetesimals, was likely to have been 160±40 times the current main belt's mass. This corresponds to 0.06-0.1 Earth masses, only a small fraction of the total mass thought to have existed in the main belt zone during planet formation. The remaining mass was most likely taken up by planetary embryos formed in the same region. Our results suggest that numerous D>200 km planetesimals disrupted early in Solar System history, but only a small fraction of their fragments survived the dynamical depletion event described above. We believe this may explain the limited presence of iron-rich M-type, olivine-rich A-type, and non-Vesta V-type asteroids in the main belt today. The collisional lifetimes determined for main belt asteroids agree with the cosmic ray exposure ages of stony meteorites and are consistent with the limited collisional evolution detected among large Koronis family members. Using the same model, we investigated the near-Earth object (NEO) population. We show the shape of the NEO size distribution is a reflection of the main belt population, with main belt asteroids driven to resonances by Yarkovsky thermal forces. We used our model of the NEO population over the last 3 Gyr, which is consistent with the current population determined by telescopic and satellite data, to explore whether the majority of small craters ( D<0.1-1 km) formed on Mercury, the Moon, and Mars were produced by primary impacts or by secondary impacts generated by ejecta from large craters. Our results suggest that most small craters formed on these worlds were a by-product of secondary rather than primary impacts.

Density of very small meteoroids

NASA Astrophysics Data System (ADS)

Kikwaya Eluo, Jean-Baptiste

2015-08-01

Knowing the density of meteoroids helps to determine the physical structure and gives insight into the composition of their parent bodies. The density of meteoroids can provide clues to their origins, whether cometary or asteroidal. Density helps also to characterize the risk meteoroids may pose to artificial satellites.Ceplecha (1968) calculated the density of small meteoroids based on a parameter KB (meteoroid beginning height) and classified them in four categories (A,B,C,D) with densities going from 2700 to 180 kgm-3.Babadzhanov(2002) applied a model based on quasi-continuous fragmentation (QCF) on 413 photographic Super-Schmidt meteors by solely fitting their light curves. Their densities range from 400 to 7800 kgm-3. Bellot Rubio et al. (2002) analyzed the same 413 photographic meteors assuming the single body theory based on meteoroid dynamical properties and found densities ranging from 400 to 4800 kgm-3. A thermal erosion model was used by Borovicka et al. (2007) to analyze, simultaneously, the observed decelerations and light curves of six Draconid meteors. The density was found to be 300 kgm-3, consistent with the fact that the Draconid meteors are porous aggregates of grains associated with the Jupiter-family-comet 21P/Giacobini-Zinner (Jacchia, L.G., 1950).We used the Campbell-Brown and Koschny (2004) model of meteoroid ablation to determine the density of faint meteoroids from the analysis of both observed decelerations and light curves of meteoroids (Kikwaya et al., 2009; Kikwaya et al., 2011). Our work was based on a collection of six and ninety-two sporadic meteors. The grain masses used in the modeling ranged from 10-12 Kg to 10-9 Kg. We computed the orbit of each meteoroid and determined its Tisserand parameter. We found that meteoroids with asteroidal orbits have bulk densities ranging from 3000-5000 kgm-3. Meteoroids consistent with HTC/NIC parents have bulk densities from 400 kgm-3 to 1600 kg m-3. JFC meteoroids were found to have surprisingly chondritic-like bulk densities, suggesting either the sintering of the meteoroids through evolutionary processes, or the original radial transportation of chondritic materials up to the Kuiper Belt region.

Earth-Moon Impacts at 300 Ma and 500 Ma Ago

NASA Technical Reports Server (NTRS)

Zellner, N. E. B.; Delano, J. W.; Swindle, T. D.; Barra, F.; Whittet, D. C. B.; Spudis, P. D.

2005-01-01

Impact events have played an important role in the evolution of planets and small bodies in the Solar System. Meteorites, lunar melt rocks, and lunar impact glasses provide important information about the geology of the parent body and the age of the impacting episodes. Over 2400 impact glasses from 4 Apollo regolith samples have been geochemically analyzed and a subset has been dated by the (40)Ar/(39)Ar method. New results, consistent with 2 break-ups in the Asteroid Belt, are presented here. Our previous study reported that (40)Ar/(39)Ar ages from 9 impact glasses showed that the Moon experienced significant impacts at approx. 800 Ma and at approx. 3800 Ma ago, somewhere in the vicinity of the Apollo 16 landing site. Additionally, reported on Apollo 12 samples with ages around 800 Ma, together implying global bombardment events. New data on 7 glasses from regolith sample 66041,127 show that the Moon also experienced impact events at approx. 300 Ma and > 500 Ma ago, which may coincide with the break-ups in the Asteroid Belt of the L- and H-chrondrite parent bodies. Since meteoritic evidence for these breakups has been found on Earth, it follows that evidence should be found in lunar samples as well. Additional information is included in the original extended abstract.

Cosmic history and a candidate parent asteroid for the quasicrystal-bearing meteorite Khatyrka

NASA Astrophysics Data System (ADS)

Meier, Matthias M. M.; Bindi, Luca; Heck, Philipp R.; Neander, April I.; Spring, Nicole H.; Riebe, My E. I.; Maden, Colin; Baur, Heinrich; Steinhardt, Paul J.; Wieler, Rainer; Busemann, Henner

2018-05-01

The unique CV-type meteorite Khatyrka is the only natural sample in which "quasicrystals" and associated crystalline Cu, Al-alloys, including khatyrkite and cupalite, have been found. They are suspected to have formed in the early Solar System. To better understand the origin of these exotic phases, and the relationship of Khatyrka to other CV chondrites, we have measured He and Ne in six individual, ∼40-μm-sized olivine grains from Khatyrka. We find a cosmic-ray exposure age of about 2-4 Ma (if the meteoroid was <3 m in diameter, more if it was larger). The U, Th-He ages of the olivine grains suggest that Khatyrka experienced a relatively recent (<600 Ma) shock event, which created pressure and temperature conditions sufficient to form both the quasicrystals and the high-pressure phases found in the meteorite. We propose that the parent body of Khatyrka is the large K-type asteroid 89 Julia, based on its peculiar, but matching reflectance spectrum, evidence for an impact/shock event within the last few 100 Ma (which formed the Julia family), and its location close to strong orbital resonances, so that the Khatyrka meteoroid could plausibly have reached Earth within its rather short cosmic-ray exposure age.

Excluding interlopers from asteroid families

NASA Astrophysics Data System (ADS)

Novakovic, B.; Radovic, V.

2014-07-01

Introduction: Asteroid families are believed to have originated from catastrophic collisions among asteroids. They are a very important subject of Solar System investigation, because practically any research topic carried out in asteroid-related science sooner or later encounters problems pertaining to asteroid families. One basic problem encountered when dealing with families is to determine reliably the list of its members, i.e. to reduce the number of interlopers as much as possible. This is an important problem, because many conclusions derived from analyses of the physical properties of family members must be necessarily based on firm and well established membership. However, as the number of known asteroids increases fast it becomes more and more difficult to obtain robust list of members of an asteroid family. To cope with these challenges we are proposing a new approach that may help to significantly reduce presence of interlopers among the family members. This method should be particularly useful once additional information become available, including primarily spectro-photometric data. This is exactly the kind of information that will be provided by Gaia. Metodology: Families (and their members) have been commonly identified by analysing the distribution of asteroids in the space of proper orbital elements, using the Hierarchical Clustering Method (HCM) [1]. A well-known drawback of the HCM based on the single linkage rule is the so-called chaining phenomenon: first concentrations naturally tend to incorporate nearby groups, forming a kind of 'chain'. Thus, any family membership obtained by the pure HCM must unavoidably include some interlopers. The method we are proposing here could be used to identify these interlopers, with its main advantage being an ability to significantly reduce the chaining effect. The method consists of three main steps. First we determine an asteroid family members by applying the HCM to the catalogue of proper elements obtained from AstDys database. Next, all family members that do not meet adopted criteria (based on physical and spectral characteristics) are excluded from the initial catalogue. Finally, the HCM analysis is performed again using the improved catalogue. Results: We apply this approach to the Themis family. In the first step the HCM links 3061 asteroids to the family. Among them we identify 113 potential interlopers. After removing interlopers, in the second run of the HCM, the total number of members has decreased to 2847. Thus, 101 extra objects have been excluded from the membership list (see Figure).

Micrometer-scale U-Pb age domains in eucrite zircons, impact re-setting, and the thermal history of the HED parent body

NASA Astrophysics Data System (ADS)

Hopkins, M. D.; Mojzsis, S. J.; Bottke, W. F.; Abramov, O.

2015-01-01

Meteoritic zircons are rare, but some are documented to occur in asteroidal meteorites, including those of the howardite-eucrite-diogenite (HED) achondrite clan (Rubin, A. [1997]. Meteorit. Planet. Sci. 32, 231-247). The HEDs are widely considered to originate from the Asteroid 4 Vesta. Vesta and the other large main belt asteroids record an early bombardment history. To explore this record, we describe sub-micrometer distributions of trace elements (U, Th) and 235,238U-207,206Pb ages from four zircons (>7-40 μm ∅) separated from bulk samples of the brecciated eucrite Millbillillie. Ultra-high resolution (∼100 nm) ion microprobe depth profiles reveal different zircon age domains correlative to mineral chemistry and to possible impact scenarios. Our new U-Pb zircon geochronology shows that Vesta's crust solidified within a few million years of Solar System formation (4561 ± 13 Ma), in good agreement with previous work (e.g. Carlson, R.W., Lugmair, G.W. [2000]. Timescales of planetesimal formation and differentiation based on extinct and extant radioisotopes. In: Canup, R., Righter, K. (Eds.), Origin of the Earth and Moon. University of Arizona Press, Tucson, pp. 25-44). Younger zircon age domains (ca. 4530 Ma) also record crustal processes, but these are interpreted to be exogenous because they are well after the effective extinction of 26Al (t1/2 = 0.72 Myr). An origin via impact-resetting was evaluated with a suite of analytical impact models. Output shows that if a single impactor was responsible for the ca. 4530 Ma zircon ages, it had to have been ⩾10 km in diameter and at high enough velocity (>5 km s-1) to account for the thermal field required to re-set U-Pb ages. Such an impact would have penetrated at least 10 km into Vesta's crust. Later events at ca. 4200 Ma are documented in HED apatite 235,238U-207,206Pb ages (Zhou, Q. et al. [2011]. Early basaltic volcanism and Late Heavy Bombardment on Vesta: U-Pb ages of small zircons and phosphates in eucrites. Lunar Planet. Sci. 42. Abstract #2575) and 40-39Ar age spectra (Bogard, D.D. [2011]. Chem. Erde 71, 207-226). Yet younger ages, including those coincident with the Late Heavy Bombardment (LHB; ca. 3900 Ma), are absent from Millbillillie zircon. This is attributable to primordial changes to the velocity distributions of impactors in the asteroid belt, and differences in mineral closure temperatures (Tc zircon ≫ apatite).

Micrometer-scale U–Pb age domains in eucrite zircons, impact re-setting, and the thermal history of the HED parent body

USGS Publications Warehouse

Hopkins, M.D.; Mojzsis, S.J.; Bottke, W.F.; Abramov, Oleg

2015-01-01

Meteoritic zircons are rare, but some are documented to occur in asteroidal meteorites, including those of the howardite–eucrite–diogenite (HED) achondrite clan (Rubin, A. [1997]. Meteorit. Planet. Sci. 32, 231–247). The HEDs are widely considered to originate from the Asteroid 4 Vesta. Vesta and the other large main belt asteroids record an early bombardment history. To explore this record, we describe sub-micrometer distributions of trace elements (U, Th) and 235,238U–207,206Pb ages from four zircons (>7–40 μm ∅) separated from bulk samples of the brecciated eucrite Millbillillie. Ultra-high resolution (∼100 nm) ion microprobe depth profiles reveal different zircon age domains correlative to mineral chemistry and to possible impact scenarios. Our new U–Pb zircon geochronology shows that Vesta’s crust solidified within a few million years of Solar System formation (4561 ± 13 Ma), in good agreement with previous work (e.g. Carlson, R.W., Lugmair, G.W. [2000]. Timescales of planetesimal formation and differentiation based on extinct and extant radioisotopes. In: Canup, R., Righter, K. (Eds.), Origin of the Earth and Moon. University of Arizona Press, Tucson, pp. 25–44). Younger zircon age domains (ca. 4530 Ma) also record crustal processes, but these are interpreted to be exogenous because they are well after the effective extinction of 26Al (t1/2 = 0.72 Myr). An origin via impact-resetting was evaluated with a suite of analytical impact models. Output shows that if a single impactor was responsible for the ca. 4530 Ma zircon ages, it had to have been ⩾10 km in diameter and at high enough velocity (>5 km s−1) to account for the thermal field required to re-set U–Pb ages. Such an impact would have penetrated at least 10 km into Vesta’s crust. Later events at ca. 4200 Ma are documented in HED apatite 235,238U–207,206Pb ages (Zhou, Q. et al. [2011]. Early basaltic volcanism and Late Heavy Bombardment on Vesta: U–Pb ages of small zircons and phosphates in eucrites. Lunar Planet. Sci. 42. Abstract #2575) and 40–39Ar age spectra (Bogard, D.D. [2011]. Chem. Erde 71, 207–226). Yet younger ages, including those coincident with the Late Heavy Bombardment (LHB; ca. 3900 Ma), are absent from Millbillillie zircon. This is attributable to primordial changes to the velocity distributions of impactors in the asteroid belt, and differences in mineral closure temperatures (Tc zircon ≫ apatite).

Igneous history of the aubrite parent asteroid - Evidence from the Norton County enstatite achondrite

NASA Technical Reports Server (NTRS)

Okada, Akihiko; Keil, Klaus; Taylor, G. Jeffrey; Newsom, Horton

1988-01-01

Numerous specimens of the Norton County enstatite achondrite (aubrite) were studied by optical microscopy, electron microprobe, and neutron-activation analysis. Norton County is found to be a fragmental impact breccia, consisting of a clastic matrix made mostly of crushed enstatite, into which are embedded a variety of mineral and lithic clasts of both igneous and impact melt origin. The Norton County precursor materials were igneous rocks, mostly plutonic orthopyroxenites, not grains formed by condensation from the solar nebula. The Mg-silicate-rich aubrite parent body experienced extensive melting and igneous differentiation, causing formation of diverse lithologies including dunites, plutonic orthopyroxenites, plutonic pyroxenites, and plagioclase-silica rocks. The presence of impact melt breccias (the microporphyritic clasts and the diopside-plagioclase-silica clast) of still different compositions further attests to the lithologic diversity of the aubrite parent body.

Interplanetary Dust Particles

NASA Astrophysics Data System (ADS)

Bradley, J. P.

2003-12-01

One of the fundamental goals of the study of meteorites is to understand how the solar system and planetary systems around other stars formed. It is known that the solar system formed from pre-existing (presolar) interstellar dust grains and gas. The grains originally formed in the circumstellar outflows of other stars. They were modified to various degrees, ranging from negligible modification to complete destruction and reformation during their ˜108 yr lifetimes in the interstellar medium (ISM) (Seab, 1987; Mathis, 1993). Finally, they were incorporated into the solar system. Submicrometer-sized silicates and carbonaceous material are believed to be the most common grains in the ISM ( Mathis, 1993; Sandford, 1996), but it is not known how much of this presolar particulate matter was incorporated into the solar system, to what extent it has survived, and how it might be distinguished from solar system grains. In order to better understand the process of solar system formation, it is important to identify and analyze these solid grains. Since all of the alteration processes that modified solids in the solar nebula presumably had strong radial gradients, the logical place to find presolar grains is in small primitive bodies like comets and asteroids that have undergone little, if any, parent-body alteration.Trace quantities of refractory presolar grains (e.g., SiC and Al2O3) survive in the matrices of the most primitive carbon-rich chondritic meteorites (Anders and Zinner, 1993; Bernatowicz and Zinner, 1996; Bernatowicz and Walker, 1997; Hoppe and Zinner, 2000; see Chapter 1.02). Chondritic meteorites are believed to be from the asteroid belt, a narrow region between 2.5 and 3.5 astronomical units (AU) that marks the transition from the terrestrial planets to the giant gas-rich planets. The spectral properties of the asteroids suggest a gradation in properties with some inner and main belt C and S asteroids (the source region of most meteorites and polar micrometeorites) containing layer silicates indicative of parent-body aqueous alteration and the more distant anhydrous P and D asteroids exhibiting no evidence of (aqueous) alteration (Gradie and Tedesco, 1982). This gradation in spectral properties presumably extends several hundred AU out to the Kuiper belt, the source region of most short-period comets, where the distinction between comets and outer asteroids may simply be one of the orbital parameters ( Luu, 1993; Brownlee, 1994; Jessberger et al., 2001). The mineralogy and petrography of meteorites provides direct confirmation of aqueous alteration, melting, fractionation, and thermal metamorphism among the inner asteroids ( Zolensky and McSween, 1988; Farinella et al., 1993; Brearley and Jones, 1998). Because the most common grains in the ISM (silicates and carbonaceous matter) are not as refractory as those found in meteorites, it is unlikely that they have survived in significant quantities in meteorites. Despite a prolonged search, not a single presolar silicate grain has yet been identified in any meteorite.Interplanetary dust particles (IDPs) are the smallest and most fine-grained meteoritic objects available for laboratory investigation (Figure 1). In contrast to meteorites, IDPs are derived from a broad range of dust-producing bodies extending from the inner main belt of the asteroids to the Kuiper belt (Flynn, 1996, 1990; Dermott et al., 1994; Liou et al., 1996). After release from their asteroidal or cometary parent bodies the orbits of IDPs evolve by Poynting-Robertson (PR) drag (the combined influence of light pressure and radiation drag) ( Dermott et al., 2001). Irrespective of the location of their parent bodies nearly all IDPs under the influence of PR drag can eventually reach Earth-crossing orbits. IDPs are collected in the stratosphere at 20-25 km altitude using NASA ER2 aircraft ( Sandford, 1987; Warren and Zolensky, 1994). Laboratory measurements of implanted rare gases, solar flare tracks ( Figure 2), and isotope abundances have confirmed that the collected particles are indeed extraterrestrial and that, prior to atmospheric entry, they spent 104-105 yr as small particles orbiting the Sun (Rajan et al., 1977; Hudson et al., 1981; Bradley et al., 1984a; McKeegan et al., 1985; Messenger, 2000). (21K)Figure 1. (a)-(c) Secondary electron images. (a) Anhydrous CP IDP. (b) Hydrated CS IDP (RB12A44). (c) Single-mineral forsterite grain with adhering chondritic material. (d) Optical micrograph (transmitted light) of giant cluster IDP (U220GCA) in silicone oil on ER2 collection flag. (14K)Figure 2. Darkfield transmission electron micrographs. (a) Solar-wind sputtered rim on exterior surface plus implanted solar flare tracks in chondritic IDP U220A19 (from Bradley and Brownlee, 1986). (b) Solar flare tracks in a forsterite crystal in chondritic IDP U220B11 (from Bradley et al., 1984a). The track densities in both IDPs are ˜1010-1011 cm2 corresponding to an orbital exposure age of ˜104yr. During atmospheric entry most IDPs are frictionally heated to within 100 °C of their peak heating temperature for ˜1 s and, to a first-order approximation, the smallest particles are the least strongly heated. Although some IDPs may experience thermal pulses in excess of 1,000 °C for up to 10 s (depending on particle size, mass, entry angle, and speed) (Love and Brownlee, 1991, 1996), the presence of solar flare tracks in an IDP establishes that it was not heated above ˜650 °C ( Bradley et al., 1984a). Since IDPs decelerate from cosmic velocities at altitudes >90 km, where the maximum aerodynamic ram pressure is a factor of ˜103 less than that exerted on conventional meteorites, extremely fragile meteoritic materials that cannot survive as large objects can survive as small IDPs (Figure 1(a)) ( Brownlee, 1994). Such fragile materials are suspected to be among the most primitive objects and potentially the most informative regarding early solar system and presolar processes. (Conventional meteorites penetrate deep into the atmosphere such that only relatively well-indurated rocks can survive.) Collected IDPs are briefly exposed to the terrestrial environment but since their residence time in the stratosphere is short (˜2 weeks), they are not subjected to longer-term weathering that affects the surfaces of most meteorites (Flynn, 1994a).This chapter examines the compositions, mineralogy, sources, and geochemical significance of IDPs. Additional reading can be found in reviews by Fraundorf (1981), Brownlee (1985), Sandford (1987), Bradley et al. (1988), Jessberger et al. (2001), Rietmeijer (1998), and the book edited by Zolensky et al. (1994). Despite their micrometer-scale dimensions and nanogram masses it is now possible, primarily as a result of advances in small particle handling techniques and analytical instrumentation, to examine IDPs at close to atomic-scale resolution. The most widely used instruments for IDP studies are presently the analytical electron microscope, synchrotron facilities, and the ion microprobe. These laboratory analytical techniques are providing fundamental insights about IDP origins, mechanisms of formation, and grain processing phenomena that were important in the early solar system and presolar environments. At the same time, laboratory data from IDPs are being compared with astronomical data from dust in comets, circumstellar disks, and the ISM. The direct comparison of grains in the laboratory with grains in astronomical environments defines the new discipline of "astromineralogy" ( Jaeger et al., 1998; Bradley et al., 1999a, b; Molster et al., 2001; Keller et al., 2001; Flynn et al., 2002). ,

Radar-Enabled Recovery of the Sutter’s Mill Meteorite, a Carbonaceous Chondrite Regolith Breccia

NASA Astrophysics Data System (ADS)

Jenniskens, Peter; Fries, Marc D.; Yin, Qing-Zhu; Zolensky, Michael; Krot, Alexander N.; Sandford, Scott A.; Sears, Derek; Beauford, Robert; Ebel, Denton S.; Friedrich, Jon M.; Nagashima, Kazuhide; Wimpenny, Josh; Yamakawa, Akane; Nishiizumi, Kunihiko; Hamajima, Yasunori; Caffee, Marc W.; Welten, Kees C.; Laubenstein, Matthias; Davis, Andrew M.; Simon, Steven B.; Heck, Philipp R.; Young, Edward D.; Kohl, Issaku E.; Thiemens, Mark H.; Nunn, Morgan H.; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Cahill, Thomas A.; Lawton, Jonathan A.; Barnes, David; Steele, Andrew; Rochette, Pierre; Verosub, Kenneth L.; Gattacceca, Jérôme; Cooper, George; Glavin, Daniel P.; Burton, Aaron S.; Dworkin, Jason P.; Elsila, Jamie E.; Pizzarello, Sandra; Ogliore, Ryan; Schmitt-Kopplin, Phillipe; Harir, Mourad; Hertkorn, Norbert; Verchovsky, Alexander; Grady, Monica; Nagao, Keisuke; Okazaki, Ryuji; Takechi, Hiroyuki; Hiroi, Takahiro; Smith, Ken; Silber, Elizabeth A.; Brown, Peter G.; Albers, Jim; Klotz, Doug; Hankey, Mike; Matson, Robert; Fries, Jeffrey A.; Walker, Richard J.; Puchtel, Igor; Lee, Cin-Ty A.; Erdman, Monica E.; Eppich, Gary R.; Roeske, Sarah; Gabelica, Zelimir; Lerche, Michael; Nuevo, Michel; Girten, Beverly; Worden, Simon P.

2012-12-01

Doppler weather radar imaging enabled the rapid recovery of the Sutter’s Mill meteorite after a rare 4-kiloton of TNT-equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand’s parameter = 2.8 ± 0.3). Sutter’s Mill is a regolith breccia composed of CM (Mighei)-type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted.

Comets: Data, problems, and objectives

NASA Technical Reports Server (NTRS)

Whipple, F. L.

1977-01-01

A highly abridged review of new relevant results from the observations of Comet Kohoutek is followed by an outline summary of our basic knowledge concerning comets, both subjects being confined to data related to the nature and origin of comets rather than the phenomena (for example, plasma phenomena are omitted). The discussion then centers on two likely places of cometary origin in the developing solar system, the proto-Uranus-Neptune region versus the much more distant fragmented interstellar cloud region, now frequented by comets of the Opik-Oort cloud. The Comet Kohoutek results add new insights, particularly with regard to the parent molecules and the nature of meteoric solids in comets, to restrict the range of the physical circumstances of comet formation. A few fundamental and outstanding questions are asked, and a plea made for unmanned missions to comets and asteroids in order to provide definitive answers as to the nature and origin of comets, asteroids, and the solar system generally.

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

Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.

We present preliminary diameters and albedos for 13511 Main Belt asteroids (MBAs) that were observed during the 3-Band Cryo phase of the Wide-field Infrared Survey Explorer (WISE; after the outer cryogen tank was exhausted) and as part of the NEOWISE Post-Cryo Survey (after the inner cryogen tank was exhausted). With a reduced or complete loss of sensitivity in the two long wavelength channels of WISE, the uncertainty in our fitted diameters and albedos is increased to {approx}20% for diameter and {approx}40% for albedo. Diameter fits using only the 3.4 and 4.6 {mu}m channels are shown to be dependent on themore » literature optical H absolute magnitudes. These data allow us to increase the number of size estimates for large MBAs which have been identified as members of dynamical families. We present thermal fits for 14 asteroids previously identified as the parents of a dynamical family that were not observed during the fully cryogenic mission.« less

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.

Alien Sunset Artist Concept

NASA Image and Video Library

2007-03-29

Observations from NASA Spitzer Space Telescope have revealed that mature planetary systems -- dusty disks of asteroids, comets and possibly planets -- are more frequent around close-knit twin, or binary, stars than single stars like our sun.

The trajectory, structure and origin of the Chelyabinsk asteroidal impactor.

PubMed

Borovička, Jiří; Spurný, Pavel; Brown, Peter; Wiegert, Paul; Kalenda, Pavel; Clark, David; Shrbený, Lukáš

2013-11-14

Earth is continuously colliding with fragments of asteroids and comets of various sizes. The largest encounter in historical times occurred over the Tunguska river in Siberia in 1908, producing an airburst of energy equivalent to 5-15 megatons of trinitrotoluene (1 kiloton of trinitrotoluene represents an energy of 4.185 × 10(12) joules). Until recently, the next most energetic airburst events occurred over Indonesia in 2009 and near the Marshall Islands in 1994, both with energies of several tens of kilotons. Here we report an analysis of selected video records of the Chelyabinsk superbolide of 15 February 2013, with energy equivalent to 500 kilotons of trinitrotoluene, and details of its atmospheric passage. We found that its orbit was similar to the orbit of the two-kilometre-diameter asteroid 86039 (1999 NC43), to a degree of statistical significance sufficient to suggest that the two were once part of the same object. The bulk strength--the ability to resist breakage--of the Chelyabinsk asteroid, of about one megapascal, was similar to that of smaller meteoroids and corresponds to a heavily fractured single stone. The asteroid broke into small pieces between the altitudes of 45 and 30 kilometres, preventing more-serious damage on the ground. The total mass of surviving fragments larger than 100 grams was lower than expected.

Comet nucleus and asteroid sample return missions

NASA Technical Reports Server (NTRS)

1992-01-01

Three Advanced Design Projects have been completed this academic year at Penn State. At the beginning of the fall semester the students were organized into eight groups and given their choice of either a comet nucleus or an asteroid sample return mission. Once a mission had been chosen, the students developed conceptual designs. These were evaluated at the end of the fall semester and combined into three separate mission plans, including a comet nucleus same return (CNSR), a single asteroid sample return (SASR), and a multiple asteroid sample return (MASR). To facilitate the work required for each mission, the class was reorganized in the spring semester by combining groups to form three mission teams. An integration team consisting of two members from each group was formed for each mission so that communication and information exchange would be easier among the groups. The types of projects designed by the students evolved from numerous discussions with Penn State faculty and mission planners at the Johnson Space Center Human/Robotic Spacecraft Office. Robotic sample return missions are widely considered valuable precursors to manned missions in that they can provide details about a site's environment and scientific value. For example, a sample return from an asteroid might reveal valuable resources that, once mined, could be utilized for propulsion. These missions are also more adaptable when considering the risk to humans visiting unknown and potentially dangerous locations, such as a comet nucleus.

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.

(3749) BALAM: A VERY YOUNG MULTIPLE ASTEROID SYSTEM

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

Vokrouhlicky, David, E-mail: vokrouhl@cesnet.c

2009-11-20

Binaries and multiple systems among small bodies in the solar system have received wide attention over the past decade. This is because their observations provide a wealth of data otherwise inaccessible for single objects. We use numerical integration to prove that the multiple asteroid system (3749) Balam is very young, in contrast to its previously assumed age of 0.5-1 Gyr related to the formation of the Flora family. This work is enabled by a fortuitous discovery of a paired component to (3749) Balam. We first show that the proximity of the (3749) Balam and 2009 BR60 orbits is not amore » statistical fluke of otherwise quasi-uniform distribution. Numerical integrations then strengthen the case and allow us to prove that 2009 BR60 separated from the Balam system less than a million years ago. This is the first time the age of a binary asteroid can be estimated with such accuracy.« less

The bering small vehicle asteroid mission concept.

PubMed

Michelsen, Rene; Andersen, Anja; Haack, Henning; Jørgensen, John L; Betto, Maurizio; Jørgensen, Peter S

2004-05-01

The study of asteroids is traditionally performed by means of large Earth based telescopes, by means of which orbital elements and spectral properties are acquired. Space borne research, has so far been limited to a few occasional flybys and a couple of dedicated flights to a single selected target. Although the telescope based research offers precise orbital information, it is limited to the brighter, larger objects, and taxonomy as well as morphology resolution is limited. Conversely, dedicated missions offer detailed surface mapping in radar, visual, and prompt gamma, but only for a few selected targets. The dilemma obviously being the resolution versus distance and the statistics versus DeltaV requirements. Using advanced instrumentation and onboard autonomy, we have developed a space mission concept whose goal is to map the flux, size, and taxonomy distributions of asteroids. The main focus is on main belt objects, but the mission profile will enable mapping of objects inside the Earth orbit as well.

P/2006 VW139: a main-belt comet born in an asteroid collision?

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Hsieh, Henry H.; Cellino, Alberto

2012-08-01

In this paper, we apply different methods to examine the possibility that a small group of 24 asteroids dynamically linked to a main-belt comet P/2006 VW139, recently discovered by the Pan-STARRS1 survey telescope, shares a common physical origin. By applying the hierarchical clustering and backward integration methods, we find strong evidence that 11 of these asteroids form a sub-group which likely originated in a recent collision event, and that this group includes P/2006 VW139. The objects not found to be part of the 11-member sub-group, which we designate as the P/2006 VW139 family, were either found to be dynamically unstable or are likely interlopers which should be expected due to the close proximity of the Themis family. As we demonstrated, statistical significance of the P/2006 VW139 family is >99 per cent. We determine the age of the family to be 7.5 ± 0.3 Myr, and estimate the diameter of the parent body to be ˜11 km. Results show that the family is produced by an impact which can be best characterized as a transition from the catastrophic to the cratering regime. The dynamical environment of this family is studied as well, including the identification of the most influential mean motion and secular resonances in the region. Our findings now make P/2006 VW139 the second main-belt comet to be dynamically associated with a young asteroid family, a fact with important implications for the origin and activation mechanism of such objects.

Evolution of interstellar organic compounds under asteroidal hydrothermal conditions

NASA Astrophysics Data System (ADS)

Vinogradoff, V.; Bernard, S.; Le Guillou, C.; Remusat, L.

2018-05-01

Carbonaceous chondrites (CC) contain a diversity of organic compounds. No definitive evidence for a genetic relationship between these complex organic molecules and the simple organic molecules detected in the interstellar medium (ISM) has yet been reported. One of the many difficulties arises from the transformations of organic compounds during accretion and hydrothermal alteration on asteroids. Here, we report results of hydrothermal alteration experiments conducted on a common constituent of interstellar ice analogs, Hexamethylenetetramine (HMT - C6H12N4). We submitted HMT to asteroidal hydrothermal conditions at 150 °C, for various durations (up to 31 days) and under alkaline pH. Organic products were characterized by gas chromatography mass spectrometry, infrared spectroscopy and synchrotron-based X-ray absorption near edge structure spectroscopy. Results show that, within a few days, HMT has evolved into (1) a very diverse suite of soluble compounds dominated by N-bearing aromatic compounds (> 150 species after 31 days), including for instance formamide, pyridine, pyrrole and their polymers (2) an aromatic and N-rich insoluble material that forms after only 7 days of experiment and then remains stable through time. The reaction pathways leading to the soluble compounds likely include HMT dissociation, formose and Maillard-type reactions, e.g. reactions of sugar derivatives with amines. The present study demonstrates that, if interstellar organic compounds such as HMT had been accreted by chondrite parent bodies, they would have undergone chemical transformations during hydrothermal alteration, potentially leading to the formation of high molecular weight insoluble organic molecules. Some of the diversity of soluble and insoluble organic compounds found in CC may thus result from asteroidal hydrothermal alteration.

Noble Gases in the Chelyabinsk Meteorites

NASA Technical Reports Server (NTRS)

Haba, Makiko K.; Sumino, Hirochika; Nagao, Keisuke; Mikouchi, Takashi; Komatsu, Mutsumi; Zolensky, Michael E.

2014-01-01

The Chelyabinsk meteorite fell in Russia on February 15, 2013 and was classified as LL5 chondrite. The diameter before it entered the atmosphere has been estimated to be about 20 m [1]. Up to now, numerous fragments weighing much greater than 100 kg in total have been collected. In this study, all noble gases were measured for 13 fragments to investigate the exposure history of the Chelyabinsk meteorite and the thermal history of its parent asteroid.

Post-main-sequence planetary system evolution.

PubMed

Veras, Dimitri

2016-02-01

The fates of planetary systems provide unassailable insights into their formation and represent rich cross-disciplinary dynamical laboratories. Mounting observations of post-main-sequence planetary systems necessitate a complementary level of theoretical scrutiny. Here, I review the diverse dynamical processes which affect planets, asteroids, comets and pebbles as their parent stars evolve into giant branch, white dwarf and neutron stars. This reference provides a foundation for the interpretation and modelling of currently known systems and upcoming discoveries.

Mineralogical Variation of Chelyabinsk with Depth from the Surface of the Parent Meteoroid

NASA Technical Reports Server (NTRS)

Yoshida, S.; Mikouchi, T.; Nagao, K.; Haba, M. K.; Hasegawa, H.; Komatsu, M.; Zolensky, M. E.

2014-01-01

The Chelyabinsk meteorite, which passed over the Chelyabinsk Oblast, Russia on Feb. 15th, 2013, brought serious damage by the shock wave and airburst. The diameter of the parent meteoroid is estimated to be approximately 20 m in diameter [1]. It was reported that the impact by this meteorite shower was 4,000 times as large as the TNT explosive and this was the largest airburst on Earth since the asteroid impact in Tunguska, Russia in 1908. The mineralogy and geochemical study of the recovered samples shows that Chelyabinsk is an LL5 chondrite [1]. In this study we analyzed several fragments of Chelyabinsk whose noble gas compositions have been measured and depths from the surface of the parent meteoroid were estimated [2]. We examined how mineralogical characteristics change with depth from the surface. This kind of study has never been performed and thus may be able to offer significant information about the evolution of meteorite parent bodies.

MarcoPolo-R: Mission and Spacecraft Design

NASA Astrophysics Data System (ADS)

Peacocke, L.; Kemble, S.; Chapuy, M.; Scheer, H.

2013-09-01

The MarcoPolo-R mission is a candidate for the European Space Agency's medium-class Cosmic Vision programme, with the aim to obtain a 100 g sample of asteroid surface material and return it safely to the Earth. Astrium is one of two industrial contractors currently studying the mission to Phase A level, and the team has been working on the mission and spacecraft design since January 2012. Asteroids are some of the most primitive bodies in our solar system and are key to understanding the formation of the Earth, Sun and other planetary bodies. A returned sample would allow extensive analyses in the large laboratory-sized instruments here on Earth that are not possible with in-situ instruments. This analysis would also increase our understanding of the composition and structure of asteroids, and aid in plans for asteroid deflection techniques. In addition, the mission would be a valuable precursor for missions such as Mars Sample Return, demonstrating a high speed Earth re-entry and hard landing of an entry capsule. Following extensive mission analysis of both the baseline asteroid target 1996 FG3 and alternatives, a particularly favourable trajectory was found to the asteroid 2008 EV5 resulting in a mission duration of 4.5 to 6 years. In October 2012, the MarcoPolo-R baseline target was changed to 2008 EV5 due to its extremely primitive nature, which may pre-date the Sun. This change has a number of advantages: reduced DeltaV requirements, an orbit with a more benign thermal environment, reduced communications distances, and a reduced complexity propulsion system - all of which simplify the spacecraft design significantly. The single spacecraft would launch between 2022 and 2024 on a Soyuz-Fregat launch vehicle from Kourou. Solar electric propulsion is necessary for the outward and return transfers due to the DeltaV requirements, to minimise propellant mass. Once rendezvous with the asteroid is achieved, an observation campaign will begin to characterise the asteroid properties and map the surface in detail. Five potential sampling sites will be selected and closely observed in a local characterisation phase, leading to a single preferred sampling site being identified. The baseline instruments are a Narrow Angle Camera, a Mid-Infrared Spectrometer, a Visible Near-Infrared Spectrometer, a Radio Science Experiment, and a Close-up Camera. For the sampling phase, the spacecraft will perform a touch-and-go manoeuvre. A boom with a sampling mechanism at the end will be deployed, and the spacecraft will descend using visual navigation to touch the asteroid for some seconds. The rotary brush sampling mechanism will be activated on touchdown to obtain a good quality sample comprising regolith dust and pebbles. Low touchdown velocities and collision avoidance are critical at this point to prevent damage to the spacecraft and solar arrays. The spacecraft will then move away, returning to a safe orbit, and the sample will be transferred to an Earth Re-entry Capsule. After a final post-sampling characterisation campaign, the spacecraft will perform the return transfer to Earth. The Earth Re-entry Capsule will be released to directly enter the Earth's atmosphere, and is designed to survive a hard landing with no parachute deceleration. Once recovered, the asteroid sample would be extracted in a sample curation facility in preparation for the full analysis campaign. This presentation will describe Astrium's MarcoPolo-R mission and spacecraft design, with a focus on the innovative aspects of the design.

KSC-07pd2583

NASA Image and Video Library

2007-09-27

KENNEDY SPACE CENTER, FLA. -- Rising above a cloud-filled horizon, the Delta II rocket carrying the Dawn spacecraft roars into the sky. Liftoff was at 7:34 a.m. EDT from Pad 17-B at Cape Canaveral Air Force Station. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Kim Shiflett

KSC-07pd1654

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- NASA's Dawn spacecraft moves out of the Astrotech facility in Titusville, Fla., for transportation to Launch Pad 17-B at Cape Canaveral Air Force Station, and mate to the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd2584

NASA Image and Video Library

2007-09-27

KENNEDY SPACE CENTER, FLA. -- The Delta II rocket with the Dawn spacecraft on top waits in the early morning light for launch. Liftoff was at 7:34 a.m. EDT from Pad 17-B at Cape Canaveral Air Force Station. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Kim Shiflett

KSC-07pd2585

NASA Image and Video Library

2007-09-27

KENNEDY SPACE CENTER, FLA. -- Rising into billowing clouds above the horizon, the Delta II rocket carrying the Dawn spacecraft roars into the sky. Liftoff was at 7:34 a.m. EDT from Pad 17-B at Cape Canaveral Air Force Station. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/George Shelton

KSC-07pd1661

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At the top of Launch Pad 17-B, at Cape Canaveral Air Force Station, workers help to guide NASA’s Dawn spacecraft into position for stacking with the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd2586

NASA Image and Video Library

2007-09-27

KENNEDY SPACE CENTER, FLA. -- Leaving the clouds behind, the Delta II rocket carrying the Dawn spacecraft arcs through the blue sky over the Atlantic Ocean. Liftoff was at 7:34 a.m. EDT from Pad 17-B at Cape Canaveral Air Force Station. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/George Shelton

KSC-07pd1663

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B, at Cape Canaveral Air Force Station, workers position NASA's Dawn spacecraft to mate it with the Delta II launch vehicle below. Launch is scheduled for July 7. Dawn is the ninth mission in NASA’s Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd1659

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B, at Cape Canaveral Air Force Station, NASA's Dawn spacecraft is hoisted up on the pad in preparation for stacking with the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd1662

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B, at Cape Canaveral Air Force Station, workers position NASA’s Dawn spacecraft to lower it toward the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd1660

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At the top of Launch Pad 17-B, at Cape Canaveral Air Force Station, workers help to guide NASA’s Dawn spacecraft into position for stacking with the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

First Galileo image of asteroid 243 Ida

NASA Technical Reports Server (NTRS)

Chapman, C. R.; Belton, M. J. S.; Veverka, J.; Neukum, G.; Head, J.; Greeley, Ronald; Klaasen, K.; Morrison, D.

1994-01-01

The second spacecraft encounter with an asteroid has yielded an unprecedentedly high resolution portrait of 243 Ida. On 28 Aug. 1993, Galileo obtained an extensive data set on this small member of the Koronis family. Most of the data recorded on the tape recorder will be returned to Earth in spring 1994. A five-frame mosaic of Ida was acquired with good illumination geometry a few minutes before closest approach; it has a resolution of 31 to 38 m/pixel amd was played back during Sept. 1993. Preliminary analyses of this single view of Ida are summarized.

The shapes of fragments in hypervelocity impact experiments ranging from cratering to catastrophic disruption

NASA Astrophysics Data System (ADS)

Michikami, T.; Hagermann, A.; Kadokawa, T.; Yoshida, A.; Shimada, A.; Hasegawa, S.; Tsuchiyama, A.

2015-12-01

Laboratory impact experiments have found that the shapes of impact fragments as defined by axes a, b and c, these being the maximum dimensions of the fragment in three mutually orthogonal planes (a ≥ b ≥ c) are distributed around mean values of the axial ratios b/a ~0.7 and c/a ~0.5, i.e., corresponding to a : b: c in the simple proportion 2: √2: 1. The shape distributions of some boulders on asteroid Eros, the small- and fast-rotating asteroids (diameter < 200 m and rotation period < 1 h), and asteroids in young families, are similar to those of laboratory fragments in catastrophic disruption. However, the shapes of laboratory fragments were obtained from the experiments that　resulted in catastrophic disruption, a process that is different from impact cratering. In order to systematically investigate the shapes of fragments in the range from impact cratering to catastrophic disruption, impact experiments for basalt targets 5 to 15 cm in size were performed. A total of 28 impact experiments were carried out by a spherical nylon projectile (diameter 7.14 mm) perpendicularly into the target surface at velocities of 1.6 to 7.0 km/s. More than 13,000 fragments with b ≥ 4 mm generated in the impact experiments were measured. In the experiments, the mean value of c/a in each impact decreases with decreasing impact energy per unit target mass. For instance, the mean value of c/a in an impact cratering event is nearly 0.2, which is less than that c/a in a catastrophic disruption (~0.5). To apply the experimental results to real collisions on asteroids, we investigated the shapes of 21 arbitrarily selected boulders (> 8 m) on asteroid Itokawa. The mean value of c/a of these boulders is 0.46, which is similar to the value for catastrophic disruption. This implies that the parent body of Itokawa could have experienced a catastrophic disruption.

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.

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.

Reanalysis of asteroid families structure through visible spectroscopy

NASA Astrophysics Data System (ADS)

Mothé-Diniz, T.; Roig, F.; Carvano, J. M.

2005-03-01

The taxonomic properties of the main asteroid families are analyzed and discussed in the light of an updated definition of the families using a large proper elements database and the asteroids taxonomy derived from reflectance spectra recently obtained by two large visible spectroscopic surveys: the SMASS II and the S3OS2. Our analysis indicates that most families are quite homogeneous taxonomically and mineralogically—whenever there exists a mineralogical constraint—, being probably originated from homogeneous parent bodies. The exceptions are the Nysa family, that should likely be considered a clan, and the Eos family that encompasses a broad range of taxonomies, whose mineralogical relations cannot be completely ruled out. Only in a few cases the families may be taxonomically distinguished from the background population. That is the case of the Minerva/Gefion, Adeona, Dora, Merxia, Hoffmeister, Koronis, Eos, and Veritas families. Some of the families presented in this work show a larger spectral diversity than previously reported, as it is the case for the Maria and Koronis families. On the other hand, the Veritas family is found to be homogeneous, in sharp contrast with previous works. Mineralogical relations are reported whenever they could be found in the literature and we examine the possible constraints posed by the presence of different taxonomies in certain families.

Post-main-sequence debris from rotation-induced YORP break-up of small bodies

NASA Astrophysics Data System (ADS)

Veras, Dimitri; Jacobson, Seth A.; Gänsicke, Boris T.

2014-12-01

Although discs of dust and gas have been observed orbiting white dwarfs, the origin of this circumstellar matter is uncertain. We hypothesize that the in situ break-up of small bodies such as asteroids spun to fission during the giant branch phases of stellar evolution provides an important contribution to this debris. The YORP (Yarkovsky-O'Keefe-Radviesvki-Paddock) effect, which arises from radiation pressure, accelerates the spin rate of asymmetric asteroids, which can eventually shear themselves apart. This pressure is maintained and enhanced around dying stars because the outward push of an asteroid due to stellar mass loss is insignificant compared to the resulting stellar luminosity increase. Consequently, giant star radiation will destroy nearly all bodies with radii in the range 100 m-10 km that survive their parent star's main-sequence lifetime within a distance of about 7 au; smaller bodies are spun apart to their strongest, competent components. This estimate is conservative and would increase for highly asymmetric shapes or incorporation of the inward drag due to giant star stellar wind. The resulting debris field, which could extend to thousands of au, may be perturbed by remnant planetary systems to reproduce the observed dusty and gaseous discs which accompany polluted white dwarfs.

The Relationship Between Cosmic-Ray Exposure Ages And Mixing Of CM Chondrite Lithologies

NASA Technical Reports Server (NTRS)

Zolensky, M. E.; Takenouchi, A.; Gregory, T.; Nishiizumi, K.; Caffee, M.; Velbel, M. A.; Ross, K.; Zolensky, A.; Le, L.; Imae, N.;

Relationships Between HED's, Mesosiderites, and Ungrouped Achondrites: Trace Element Analyses of Mesosiderite RKPA 79015 and Ungrouped Achondrite QUE 93148

NASA Technical Reports Server (NTRS)

Righter, M.; Lapen, T.; Righter, K.

2008-01-01

Achondritic meteorites are a diverse group of meteorites that formed by igneous activity in asteroids. These meteorites can provide important information about early differentiation processes on asteroidal bodies. The howardite-eucrite-diogenite (HED) meteorites, the largest group of achondrites, are the only group of meteorites for which a potential parent body has been identified (4 Vesta) [e.g., 1]. Mesosiderites are stony-iron meteorites composed of roughly equal amounts of metal and silicates and silicates are broadly similar to HED meteorites [2]. They may have been formed by impact-mixing of crustal and core materials of differentiated meteorite parent bodies. Chemical and oxygen isotopic compositional data suggest that the HED meteorites and silicate portions of mesosiderites originated on the same or closely related parent bodies. Pallasites and IIIAB irons also have similar oxygen isotope compositions and have been thought to be related to the HEDs [3,4]. However, recent high resolution analyses have shown that pallasites and HED's have different oxygen isotopic values, but mesosiderites and HED s have the same isotope compositions implying a close connection [5]. QUE 93148 is a small (1.1g) olivine-rich (mg 86) achondrite that contains variable amounts of orthopyroxenene (mg 87) and kamacite (6.7 wt% Ni), with minor augite [6]. This meteorite was originally classified as a lodranite [7], but it s oxygen isotopic composition precludes a genetic relationship to the acapulcoites and lodranites. And also this meteorite has a lower Mn/Mg ratio than any major group of primitive or evolved achondrites and suggested that QUE 93148 may be a piece of the deep mantle of the HED parent body [6]. To better understand the relationship between HED s, mesosiderites and related achondrites, we have measured trace elements in the individual metallic and silicate phases. In this study, abundances of a suite of elements were measured for the unusual mesosiderite RKPA 79015 and a ungrouped achondrite QUE93148.

OrbitMaster: An Online Tool for Investigating Solar System Dynamics and Visualizing Orbital Uncertainties in the Undergraduate Classroom

NASA Astrophysics Data System (ADS)

Puckett, Andrew W.; Rector, Travis A.; Baalke, Ron; Ajiki, Osamu

2016-01-01

OrbitMaster is a 3-D orbit visualization tool designed for the undergraduate astronomy classroom. It has been adapted from AstroArts' interactive OrbitViewer applet under the GNU General Public License, as part of the Research-Based Science Education for Undergraduates (RBSEU) curriculum. New features allow the user to alter an asteroid's orbital parameters using slider controls, and to monitor its changing position and speed relative to both Sun and Earth. It detects close approaches and collisions with Earth, and calculates revised distances and impact speeds due to Earth's gravitational attraction. It can also display many asteroid orbits at once, with direct application to visualizing the uncertainty in a single asteroid's orbital parameters. When paired with Project Pluto's Find_Orb orbit determination software and a source of asteroid astrometry, this enables monitoring of changes in orbital uncertainties with time and/or additional observational data. See http://facstaff.columbusstate.edu/puckett_andrew/orbitmaster.html.A series of undergraduate labs using the OrbitMaster applet are available as part of the RBSEU curriculum. In the first lab, students gain hands-on experience with the mechanics of asteroid orbits and confirm Kepler's laws of planetary motion. In the second, they study the orbits of Potentially Hazardous Asteroids as they build their own "Killer Asteroids" and investigate the minimum and maximum speed limits that apply to Earth-impacting objects. In the third and fourth labs, they discover the kinetic energy-crater size relationship, engage in their own Crater Scene Investigation (C.S.I.) to estimate impactor size, and understand the regional consequences of impacts. These labs may be used separately, or in support of a further seven-week sequence culminating in an authentic research project in which students submit measurements to the Minor Planet Center to refine a real asteroid's orbit. As with all RBSE projects, the overarching goal is for students to learn science by actually doing science, and to retain knowledge learned in-context. For more information, see http://rbseu.uaa.alaska.edu.

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.

ASTEROID LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY SURVEY: ROTATION PERIODS AND PHASE FUNCTIONS FROM SPARSE PHOTOMETRY

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

Waszczak, Adam; Chang, Chan-Kao; Cheng, Yu-Chi

We fit 54,296 sparsely sampled asteroid light curves in the Palomar Transient Factory survey to a combined rotation plus phase-function model. Each light curve consists of 20 or more observations acquired in a single opposition. Using 805 asteroids in our sample that have reference periods in the literature, we find that the reliability of our fitted periods is a complicated function of the period, amplitude, apparent magnitude, and other light-curve attributes. Using the 805-asteroid ground-truth sample, we train an automated classifier to estimate (along with manual inspection) the validity of the remaining ∼53,000 fitted periods. By this method we findmore » that 9033 of our light curves (of ∼8300 unique asteroids) have “reliable” periods. Subsequent consideration of asteroids with multiple light-curve fits indicates a 4% contamination in these “reliable” periods. For 3902 light curves with sufficient phase-angle coverage and either a reliable fit period or low amplitude, we examine the distribution of several phase-function parameters, none of which are bimodal though all correlate with the bond albedo and with visible-band colors. Comparing the theoretical maximal spin rate of a fluid body with our amplitude versus spin-rate distribution suggests that, if held together only by self-gravity, most asteroids are in general less dense than ∼2 g cm{sup −3}, while C types have a lower limit of between 1 and 2 g cm{sup −3}. These results are in agreement with previous density estimates. For 5–20 km diameters, S types rotate faster and have lower amplitudes than C types. If both populations share the same angular momentum, this may indicate the two types’ differing ability to deform under rotational stress. Lastly, we compare our absolute magnitudes (and apparent-magnitude residuals) to those of the Minor Planet Center’s nominal (G = 0.15, rotation-neglecting) model; our phase-function plus Fourier-series fitting reduces asteroid photometric rms scatter by a factor of ∼3.« less

Testing the Prediction of Iron Alteration Minerals on Low Albedo Asteroids

NASA Technical Reports Server (NTRS)

Jarvis, K. S.; Vilas, Faith; Howell, E.; Kelley, M.; Cochran, A.

1999-01-01

Absorption features centered near 0.60 - 0.65 and 0.80 - 0.90 micron were identified in the spectra of three low-albedo main-belt (165, 368, 877) and two low-albedo outer-belt (225, 334) asteroids (Vilas et al., Icarus, v. 109,274,1994). The absorption features were attributed to charge transfer transitions in iron alteration minerals such as goethite, hematite, and jarosite, all products of aqueous alteration. Concurrently, Jarvis et al. (LPSC XXIV, 715, 1993) presented additional spectra of low-albedo asteroids that had absorption features centered near 0.60 - 0.65 micron without the longer wavelength feature. Since these two features in iron oxides originate from the same ground state, and the longer wavelength feature requires less energy to exist, the single shorter wavelength feature cannot be caused by the iron alteration minerals. In addition, spectra of minerals such as hematite and goethite show a rapid increase in reflectance beginning near 0.5 micron absent in the low-albedo asteroid spectra. The absence of this rise has been attributed to its suppresion from opaques in the surface material. Spectra on more than one night were available for only one of these five asteroids, 225 Henrietta, and showed good repeatability of the 0.65-micron feature. We have acquired additional spectra of all five asteroids in order to test the repeatability of the 0.65-micron feature, and the presence and repeatability of the features centered near 0.8 - 0.9 micron. We specifically will test the possibility that longer wavelength features could be caused by incomplete removal of telluric water. Asteroid 877 Walkure is a member of the Nysa-Hertha family, and will be compared to spectra of other members of that family. Data were acquired in 1996 and 1999 on the 2.1-m telescope with a facility cassegrain spectrograph, McDonald Observatory, Univ. Of Texas, and the 1.5-m telescope with facility cassegrain spectrograph at CTIO. This research is supported by the NASA Planetary Astronomy Program.

Interplanetary dust particles collected in the stratosphere: observations of atmospheric heating and constraints on their interrelationships and sources.

PubMed

Sandford, S A; Bradley, J P

1989-01-01

The majority of the interplanetary dust particles (IDPs) collected in the stratosphere belong to one of three major classes, the first two dominated by the anhydrous minerals olivine and pyroxene, and the third by hydrous layer-lattice silicates. Infrared spectroscopy and transmission electron microscopy studies show that the different IDP classes represent different types of dust that exist as individual particles in interplanetary space. The majority of the collected IDPs smaller than 30 micrometers in diameter in the layer-lattice silicate and pyroxene classes appear not to have been heated to temperatures above 600 degrees C during atmospheric entry. The relatively low maximum temperatures experienced by these IDPs during atmospheric entry imply that they arrive at the top of the atmosphere with low geocentric encounter velocities. This limits the possible encounter trajectories for these particles to relatively circular, prograde orbits. As a result, it is unlikely that these IDPs are from Earth-crossing comets or asteroids. Asteroids, and comets having low inclinations and perihelia outside 1.2 AU, appear to be the best candidates for the parent bodies of the pyroxene and layer-lattice silicate particles. Chemical and mineralogical information suggests that the pyroxene-rich IDPs are from comets and the layer-lattice silicate-rich IDPs are from asteroids. The collected IDPs dominated by olivine appear to include a larger fraction of particles heating above 600 degrees C, suggesting that these particles were captured from more eccentric orbits. This, and the observation of the infrared spectral features of olivine in several comets suggest these particles have a cometary origin. Since much of the collected dust has apparently been captured from nearly circular, prograde orbits and since there are no appropriate parent bodies presently in such orbits, these results provide an experimental confirmation that the Poynting-Robertson effect exists as a nongravitational force important in the orbital evolution of dust in the Solar System.

Heterogeneous Distributions of Amino Acids Provide Evidence of Multiple Sources Within the Almahata Sitta Parent Body, Asteroid 2008 TC(sub 3)

NASA Technical Reports Server (NTRS)

Burton, Aaron S.; Glavin, Daniel P.; Callahan, Michael P.; Dworkin, Jason P.; Jenniskens, Peter; Shaddad, Muawia H.

2011-01-01

Two new fragments of the Almahata Sitta meteorite and a sample of sand from the related strewn field in the Nubian Desert, Sudan, were analyzed for two to six carbon aliphatic primary amino acids by ultrahigh performance liquid chromatography with UV-fluorescence detection and time-of-flight mass spectrometry (LC-FT/ToF-MS). The distribution of amino acids in fragment #25, an H5 ordinary chondrite, and fragment #27, a polymict ureilite, were compared with results from the previously analyzed fragment #4, also a polymict ureilite. All three meteorite fragments contain 180-270 parts-per-billion (ppb) of amino acids, roughly 1000-fold lower than the total amino acid abundance of the Murchison carbonaceous chondrite. All of the Almahata Sitta fragments analyzed have amino acid distributions that differ from the Nubian Desert sand, which primarily contains L-alpha-amino acids. In addition, the meteorites contain several amino acids that were not detected in the sand, indicating that many of the amino acids are extraterrestrial in origin. Despite their petrological differences, meteorite fragments #25 and #27 contain similar amino acid compositions; however, the distribution of amino acids in fragment #27 was distinct from those in fragment #4, even though both arc polymict ureilites from the same parent body. Unlike in CM2 and CR2/3 meteorites, there are low relative abundances of alpha-amino acids in the Almahata Sitta meteorite fragments, which suggest that Strecker-type chemistry was not a significant amino acid formation mechanism. Given the high temperatures that asteroid 2008 TC3 appears to have experienced and lack of evidence for aqueous alteration on the asteroid, it is possible that the extraterrestrial amino acids detected in Almahata Sitta were formed by Fischer-Tropsch/Haber-Bosch type gas-grain reactions at elevated temperatures.

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

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.

Oxygen isotopic composition of chondritic interplanetary dust particles: A genetic link between carbonaceous chondrites and comets

NASA Astrophysics Data System (ADS)

Aléon, J.; Engrand, C.; Leshin, L. A.; McKeegan, K. D.

2009-08-01

Oxygen isotopes were measured in four chondritic hydrated interplanetary dust particles (IDPs) and five chondritic anhydrous IDPs including two GEMS-rich particles (Glass embedded with metal and sulfides) by a combination of high precision and high lateral resolution ion microprobe techniques. All IDPs have isotopic compositions tightly clustered around that of solar system planetary materials. Hydrated IDPs have mass-fractionated oxygen isotopic compositions similar to those of CI and CM carbonaceous chondrites, consistent with hydration of initially anhydrous protosolar dust. Anhydrous IDPs have small 16O excesses and depletions similar to those of carbonaceous chondrites, the largest 16O variations being hosted by the two GEMS-rich IDPs. Coarse-grained forsteritic olivine and enstatite in anhydrous IDPs are isotopically similar to their counterparts in comet Wild 2 and in chondrules suggesting a high temperature inner solar system origin. The small variations in the 16O content of GEMS-rich IDPs suggest that most GEMS either do not preserve a record of interstellar processes or the initial interstellar dust is not 16O-rich as expected by self-shielding models, although a larger dataset is required to verify these conclusions. Together with other chemical and mineralogical indicators, O isotopes show that the parent-bodies of carbonaceous chondrites, of chondritic IDPs, of most Antarctic micrometeorites, and comet Wild 2 belong to a single family of objects of carbonaceous chondrite chemical affinity as distinct from ordinary, enstatite, K- and R-chondrites. Comparison with astronomical observations thus suggests a chemical continuum of objects including main belt and outer solar system asteroids such as C-type, P-type and D-type asteroids, Trojans and Centaurs as well as short-period comets and other Kuiper Belt Objects.

Lunar and Planetary Science XXXVI, Part 6

NASA Technical Reports Server (NTRS)

2005-01-01

Contents include the following: A Model for Multiple Populations of Presolar Diamonds. Characterization of Martian North Polar Geologic Units Using Mars Odyssey THEMIS Data. Effect of Flow on the Internal Structure of the Martian North Polar Layered Deposits. Elemental Abundance Distributions in Basalt Clays and Meteorites: Is It a Biosignature? Early Results on the Saturn System from the Composite Infrared Spectrometer. NanoSIMS D/H Imaging of Isotopically Primitive Interplanetary Dust Particles. Presolar (Circumstellar and Interstellar) Phases in Renazzo: The Effects of Parent Body Processing. Catastrophic Disruption of Hydrated Targets: Implications for the Hydrated Asteroids and for the Production of Interplanetary Dust Particles. Chemical and Mineralogical Analyses of Particles from the Stratospheric Collections Coinciding with the 2002 Leonid Storm and the 2003 Comet Grigg-Skjellerup Trail Passage. An Analysis of the Solvus in the CaS-MnS System. ESA s SMART-1 Mission at the Moon: First Results, Status and Next Steps. Europa Analog Ice-splitting Measurements and Experiments with Ice-Hunveyor on the Frozen Balaton-Lake, Hungary. Chromium on Eros: Further Evidence of Ordinary Chondrite Composition. Dust Devil Tracks on Mars: Observation and Analysis from Orbit and the Surface. Spatial Variation of Methane and Other Trace Gases Detected on Mars: Interpretation with a General Circulation Model. Mars Water Ice and Carbon Dioxide Seasonal Polar Caps: GCM Modeling and Comparison with Mars Express Omega Observations. Component Separation of OMEGA Spectra with ICA. Clathrate Formation in the Near-Surface Environment of Titan. Space Weathering: A Proposed Laboratory Approach to Explaining the Sulfur Depletion on Eros. Sample Collection from Small Airless Bodies: Examination of Temperature Constraints for the TGIP. Sample Collector for the Hera Near-Earth Asteroid Sample Return Mission. A Rugged Miniature Mass-Spectrometer for Measuring Aqueous Geochemistry on Mars. Martian and Lunar Pyroxene Microstructures Studied by Single-Crystal X-Ray Diffraction.

In Situ Mapping of the Organic Matter in Carbonaceous Chondrites and Mineral Relationships

NASA Technical Reports Server (NTRS)

Clemett, Simon J.; Messenger, S.; Thomas-Keprta, K. L.; Ross, D. K.

2012-01-01

Carbonaceous chondrite organic matter represents a fossil record of reactions that occurred in a range of physically, spatially and temporally distinct environments, from the interstellar medium to asteroid parent bodies. While bulk chemical analysis has provided a detailed view of the nature and diversity of this organic matter, almost nothing is known about its spatial distribution and mineralogical relationships. Such information is nevertheless critical to deciphering its formation processes and evolutionary history.

Post-main-sequence planetary system evolution

PubMed Central

Veras, Dimitri

2016-01-01

The fates of planetary systems provide unassailable insights into their formation and represent rich cross-disciplinary dynamical laboratories. Mounting observations of post-main-sequence planetary systems necessitate a complementary level of theoretical scrutiny. Here, I review the diverse dynamical processes which affect planets, asteroids, comets and pebbles as their parent stars evolve into giant branch, white dwarf and neutron stars. This reference provides a foundation for the interpretation and modelling of currently known systems and upcoming discoveries. PMID:26998326

Applicability of meteor radiant determination methods depending on orbit type. II. Low-eccentric orbits

NASA Astrophysics Data System (ADS)

Svoren, J.; Neslusan, L.; Porubcan, V.

1994-08-01

All known parent bodies of meteor showers belong to bodies moving in high-eccentricity orbits (e => 0.5). Recently, asteroids in low-eccentricity orbits (e < 0.5) approaching the Earth's orbit, were suggested as another population of possible parent bodies of meteor streams. This paper deals with the problem of calculation of meteor radiants connected with the bodies in low-eccentricity orbits from the point of view of optimal results depending on the method applied. The paper is a continuation of our previous analysis of high-eccentricity orbits (Svoren, J., Neslusan, L., Porubcan, V.: 1993, Contrib. Astron. Obs. Skalnate Pleso 23, 23). Some additional methods resulting from mathematical modelling are presented and discussed together with Porter's, Steel-Baggaley's and Hasegawa's methods. In order to be able to compare how suitable the application of the individual radiant determination methods is, it is necessary to determine the accuracy with which they approximate real meteor orbits. To verify the accuracy with which the orbit of a meteoroid with at least one node at 1 AU fits the original orbit of the parent body, the Southworth-Hawkins D-criterion (Southworth, R.B., Hawkins, G.S.: 1963, Smithson. Contr. Astrophys. 7, 261) was applied. D <= 0.1 indicates a very good fit of orbits, 0.1 < D <= 0.2 is considered for a good fit and D > 0.2 means that the fit is rather poor and the change of orbit unrealistic. The optimal method, i.e. the one which results in the smallest D values for the population of low-eccentricity orbits, is that of adjusting the orbit by varying both the eccentricity and perihelion distance. A comparison of theoretical radiants obtained by various methods was made for typical representatives from each group of the NEA (near-Earth asteroids) objects.

A Cabonaceous Chondrite Dominated Lithology from the HED Parent; PRA 04401

NASA Technical Reports Server (NTRS)

Herrin, Jason S.; Zolensky, M. E.; Mittlefehldt, David W.

2010-01-01

The paired howardite breccias Mt. Pratt (PRA) 04401 and PRA 04402 are notable for their high proportion of carbonaceous chondrite clasts [1]. They consist predominantly of coarse (0.1-7 mm) diogenite (orthopyroxene), eucrite (plagioclase + pyroxene), and carbonaceous chondrite clasts set in a finer grained matrix of these same materials. Coarse C-chondrite clasts up to 7 mm are composed mainly of fine-grained phyllosilicates with lesser sulfides and high-mg# anhydrous magnesian silicates. Most of these clasts appear to be texturally consistent with CM2 classification [1] and some contain relict chondrules. The clasts are angular and reaction or alteration textures are not apparent in the surrounding matrix. PRA 04401 contains about 70 modal% C-chondrite clasts while PRA 04402 contains about 7%. Although many howardites are known to contain abundant C-chondrite clasts [2,3,4], PRA 04401 is, to our knowledge, the most chondrite-rich howardite lithology identified to date. Low EPMA totals from CM2-type clasts in other howardites suggest that they frequently contain 10 wt% or more water [2], a figure consistent with their mineralogy. PRA 04401, therefore, demonstrates the potential for hydrous lithologies with greater than 5 wt% water to occur locally within the nominally anhydrous HED parent body. Since the origin of this water is xenogenic, it might therefore be concentrated in portions of the asteroid surface where it would be more readily observable by remote sensing techniques. We plan to further examine C-chondrite clasts in PRA 04401/2 with the intent of establishing firm chemical classification, estimating water content, and evaluating their relationship with the host breccia. To help place them in context of the HED parent, we will also compare these breccias with other howardites to evaluate which lithologies are likely to be more prevalent on the asteroid surface.

SIMULTANEOUS LINEAR AND CIRCULAR OPTICAL POLARIMETRY OF ASTEROID (4) VESTA

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

Wiktorowicz, Sloane J.; Nofi, Larissa A., E-mail: sloanew@ucolick.org

From a single 3.8 hr observation of the asteroid (4) Vesta at 13.°7 phase angle with the POlarimeter at Lick for Inclination Studies of Hot jupiters 2 (POLISH2) at the Lick Observatory Shane 3 m telescope, we confirm rotational modulation of linear polarization in the B and V bands. We measure the peak-to-peak modulation in the degree of linear polarization to be ΔP = (294 ± 35) × 10{sup −6} (ppm) and time-averaged ΔP/P = 0.0575 ± 0.0069. After rotating the plane of linear polarization to the scattering plane, asteroidal rotational modulation is detected with 12σ confidence and observed solelymore » in Stokes Q/I. POLISH2 simultaneously measures Stokes I, Q, U (linear polarization), and V (circular polarization), but we detect no significant circular polarization with a 1σ upper limit of 78 ppm in the B band. Circular polarization is expected to arise from multiple scattering of sunlight by rough surfaces, and it has previously been detected in nearly all other classes of solar system bodies except for asteroids. Subsequent observations may be compared with surface albedo maps from the Dawn Mission, which may allow the identification of compositional variation across the asteroidal surface. These results demonstrate the high accuracy achieved by POLISH2 at the Lick 3 m telescope, which is designed to directly detect scattered light from spatially unresolvable exoplanets.« less

Can the Single Parent Parent As Well?

ERIC Educational Resources Information Center

Flanzer, Jerry P.

The question of whether single parents are able to parent as well as those in two-parent families, as well as the differences between attitudes and practices of single mothers and fathers toward child rearing, were investigated. Members (N=179) of the Southeastern Wisconsin Parents Without Partners group completed the Single Parent Questionnaire,…

DRBE comet trails

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

Arendt, Richard G., E-mail: Richard.G.Arendt@nasa.gov

2014-12-01

Re-examination of the Cosmic Background Explorer Diffuse Infrared Background Experiment (DIRBE) data reveals the thermal emission of several comet dust trails. The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported. The known trails of 2P/Encke and 73P/Schwassmann–Wachmann 3 are also seen. The dust trails have 12 and 25 μm surface brightnesses of <0.1 and <0.15 MJy sr{sup −1}, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBEmore » data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.« less

Gas-drag-assisted capture of Himalia's family

NASA Astrophysics Data System (ADS)

Ćuk, Matija; Burns, Joseph A.

2004-02-01

To elucidate the capture of Jupiter's outer moons, we reverse-evolve satellites from their present orbits to their original heliocentric paths in the presence of Jupiter's primordial circumplanetary disk (Lubow et al., 1999, Astrophys. J. 526, 1001-1012; Canup and Ward, 2003, Astron. J. 124, 3404-3423). Our orbital histories use a symplectic integrator that allows dissipation. We assume that the present satellites Himalia, Elara, Lysithea, Leda, and S/2000 J11 are collisional fragments of a single parent. Our simulations show that this "prograde-cluster progenitor" (PCP) could be derived from objects with heliocentric orbits like those of the Hilda asteroid group. We show analytically that this capture is energetically possible. We also compare the spectroscopic characteristics of the prograde cluster members (Grav et al., 2003, Icarus, submitted for publication) with those of the Hildas, and conclude that the surface color of the prograde-cluster progenitor is consistent with an origin within the Hilda group. Accordingly, gas drag in the primordial jovian nebula is found to offer a plausible explanation for the origin of the prograde cluster. A similar capture mechanism is proposed for Saturn's Phoebe.

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.

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.

Ar-39-Ar-40 Ages of Euerites and the Thermal History of Asteroid 4-Vesta

NASA Technical Reports Server (NTRS)

Bogard, Donald D.; Garrison, Daniel H.

2002-01-01

Eucrite meteorites are igneous rocks that derive from a large asteroid, probably 4 Vesta. Prior studies have shown that after eucrites formed, most were subsequently metamorphosed to temperatures up to equal to or greater than 800 C, and much later many were brecciated and heated by large impacts into the parent body surface. The uncommon basaltic, unbrecciated eucrites also formed near the surface but presumably escaped later brecciation, whereas the cumulate eucrites formed at depth where metamorphism may have persisted for a considerable period. To further understand the complex HED parent body thermal history, we determined new Ar-39-Ar-40 ages for nine eucrites classified as basaltic but unbrecciated, six eucrites classified as cumulate, and several basaltic-brecciated eucrites. Relatively precise Ar-Ar ages of two cumulate eucrites (Moama and EET87520) and four unbrecciated eucrites give a tight cluster at 4.48 +/1 0.01 Gyr. Ar-Ar ages of six additional unbrecciated eucrites are consistent with this age, within their larger age uncertainties. In contrast, available literature data on Pb-Pb isochron ages of four cumulate eucrites and one unbrecciated eucrite vary over 4.4-4.515 Gyr, and Sm-147 - Nd-143 isochron ages of four cumulate and three unbrecciated eucrites vary over 4.41-4.55 Gyr. Similar Ar-Ar ages for cumulate and unbrecciated eucrites imply that cumulate eucrites do not have a younger formation age than basaltic eucrites, as previously proposed. Rather, we suggest that these cumulate and unbrecciated eucrites resided at depth where parent body temperatures were sufficiently high to cause the K-Ar and some other chronometers to remain open diffusion systems. From the strong clustering of Ar-Ar ages at approximately 4.48 Gyr, we propose that these meteorites were excavated from depth in a single large impact event approximately 4.48 Gyr ago, which quickly cooled the samples and started the K-Ar chronometer. A large (approximately 460 km) crater postulated to exist on Vesta may be the source of these eucrites and of many smaller asteroids thought to be spectrally or physically associated with Vesta. Some Pb-Pb and Sm-Nd ages of cumulate and unbrecciated eucrites are consistent with the 4.48 Gyr Ar-Ar age, and the few older Pb-Pb and Sm-Nd ages may reflect isotopic closure prior to the large cratering event. One cumulate eucrite gives an Ar-Ar age of 4.25 Gyr; three additional cumulate eucrites give Ar-Ar ages of 3.4-3.7 Gyr; and two unbrecciated eucrites give Ar-Ar ages of approximately 3.55 Gyr. We attribute these younger ages to later impact heating. In addition, we find Ar-Ar impact-reset ages of several brecciated eucrites and eucritic clasts in howardites to fall in the range of 3.5-4.1 Gyr. Among these, Piplia Kalan, the first eucrite to show evidence for extinct 26 Al, was strongly impact heated approximately3.5 Gyr ago. When these data are combined with eucrite Ar-Ar ages in the literature, they confirm the previous suggestion that several large impact heating events occurred on Vesta over the time period approximately 4.1-3.4 Gyr ago. The onset of major impact heating may have occurred at similar times for both Vesta and the Moon, but impact heating appears to have persisted to a somewhat later time on Vesta compared to the Moon.

KSC-07pd1664

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B, at Cape Canaveral Air Force Station, the Delta II launch vehicle with NASA’s Dawn spacecraft mission logo can be seen as it is moved into position for stacking with the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd1656

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B, at Cape Canaveral Air Force Station, workers attach a crane to NASA's Dawn spacecraft. It will be lifted into the mobile service tower for mating to the Delta II launch vehicle.Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd2062

NASA Image and Video Library

2007-07-22

KENNEDY SPACE CENTER, FLA. — Sitting on a transporter, the Dawn spacecraft arrives at the Astrotech payload processing facility. Dawn was returned from Launch Pad 17-B at Cape Canaveral Air Force Station to Astrotech to await a new launch date. The launch opportunity extends from Sept. 7 to Oct. 15. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. NASA/Charisse Nahser

KSC-07pd1655

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- NASA's Dawn spacecraft, mated to the Delta II upper stage booster, arrives at Launch Pad 17-B at Cape Canaveral Air Force Station. It will be lifted into the mobile service tower for mating to the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd2063

NASA Image and Video Library

2007-07-22

KENNEDY SPACE CENTER, FLA. — The Dawn spacecraft is moved inside the Astrotech payload processing facility. Dawn was returned from Launch Pad 17-B at Cape Canaveral Air Force Station to Astrotech to await a new launch date. The launch opportunity extends from Sept. 7 to Oct. 15. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. NASA/Charisse Nahser

KSC-07pd1653

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- Inside the Astrotech Facility in Titusville, Fla., NASA’s Dawn spacecraft is ready to be transported to Launch Pad 17-B at Cape Canaveral Air Force Station, for mate to the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd1658

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B, at Cape Canaveral Air Force Station, workers prepare NASA's Dawn spacecraft mated to the Delta II upper stage booster, for hoisting up into the mobile service tower. Dawn will be mated with the Delta II launch vehicle. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

KSC-07pd1657

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B, at Cape Canaveral Air Force Station, workers attach a crane to NASA's Dawn spacecraft mated to the Delta II upper stage booster, in preparation for stacking with the Delta II launch vehicle. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Troy Cryder.

Petrology of eucrites, howardites and mesosiderites

USGS Publications Warehouse

Duke, M.B.; Silver, L.T.

1967-01-01

The eucrite and howardite calcium-rich achondrites and many mesosiderites are considered as a coherent meteorite assemblage, their silicates consisting essentially of calciumpoor monoclinic and orthorhombic pyroxenes and calcium-rich plagioclase feldspar. The achondrites can be grouped according to their brecciated structure as follows: eucrites-unbrecciated and monomict brecciated achondrites; howardites-polymict brecciated achondrites. Many mesosiderites contain brecciated structures; they are distinguished from the achondrites by their large metallic fraction. The structure and composition of rock fragments in the breccias indicate a complicated sequence of events including magmatic differentiation, brecciation, recrystallization and refragmentation, and ejection from the parent body. Detailed mineralogical and chemical data suggest that the magmatic differentiation proceeded primarily by the separation of pyroxene from an ultrabasic parent material that had a much lower alkali content than ordinary chondrites. Magmatic crystallization took place in environments ranging from extrusive to deep-seated intrusive. Polymict breccias contain fragments with a wide variety of magmatic and recrystallization textures, which suggests that the breccias were formed either in very large or repeated fragmentation events. Monomict breccias contain fragments with a small range of similar magmatic textures, which suggests that these breccias were formed by small or single events. Petrographic evidence suggests that many of the breccias are impact breccias. Either in their original magmatic crystallization sites or in the sites of breccia accumulation, most of these meteorites apparently had a near-surface location prior to ejection from the parent body. Evidence obtained from eucrites, howardites and mesosiderites forms an important part of our understanding of the early evolution of the surface regions of their parent body. Chemical and oxidation conditions were different from those presently found in the Earth's crust and upper mantle, but the necessary conditions may have been present in the early history of the Earth. A lunar origin for eucrites, howardites and mesosiderites is proposed, but an asteroidal origin can not be presently excluded. ?? 1967.

The NEAR laser ranging investigation

NASA Astrophysics Data System (ADS)

Zuber, M. T.; Smith, D. E.; Cheng, A. F.; Cole, T. D.

1997-10-01

The objective of the NEAR-Earth Asteriod Rendezvous (NEAR) laser ranging investigation is to obtain high integrity profiles and grids of topography for use in geophysical, geodetic and geological studies of asteroid 433 Eros. The NEAR laser rangefinder (NLR) will determine the slant range of the NEAR spacecraft to the asteroid surface by measuring precisely the round trip time of flight of individual laser pulses. Ranges will be converted to planetary radii measured with respect to the asteroid center of mass by subtracting the spacecraft orbit determined from X band Doppler tracking. The principal components of the NLR include a 1064 nm Cr:Nd:YAG laser, a gold-coated aluminum Dall-Kirkham Cassegrain telescope, an enhanced silicon avalanche photodiode hybrid detector, a 480-MHz crystal oscillator, and a digital processing unit. The instrument has a continuous in-flight calibration capability using a fiber-optic delay assembly. The single shot vertical resolution of the NLR is <6m, and the absolute accuracy of the global grid will be ~10m with respect to the asteroid center of mass. For the current mission orbital scenario, the laser spot size on the surface of Eros will vary from ~4-11m, and the along-track resolution for the nominal pulse repetition rate of 1 Hz will be approximately comparable to the spot size, resulting in contiguous along-track profiles. The across-track resolution will depend on the orbital mapping scenario, but will likely be <500m, which will define the spatial resolution of the global topographic model. Planned science investigations include global-scale analyses related to collisional and impact history and internal density distribution that utilize topographic grids as well as spherical harmonic topographic models that will be analyzed jointly with gravity at commensurate resolution. Attempts will be made to detect possible subtle time variations in internal structure that may be present if Eros is not a single coherent body, by analysis of low degree and order spherical harmonic coefficients. Local- to regional-scale analyses will utilize high-resolution three-dimensional topographic maps of specific surface structures to address surface geologic processes. Results from the NLR investigation will contribute significantly to understanding the origin, structure, and evolution of Eros and other asteroidal bodies.

Meeting the Needs of Single-Parent Families.

ERIC Educational Resources Information Center

Olson, Myrna R.; Haynes, Judith A.

1992-01-01

Schools can better meet the needs of single-parent families in the following ways: (1) acknowledge the diversity of single-parent families; (2) avoid assumptions about single-parent families; (3) provide educators with information about differing family structures; and (4) facilitate the connection between single parents and schools. (11…

A collisional family of icy objects in the Kuiper belt.

PubMed

Brown, Michael E; Barkume, Kristina M; Ragozzine, Darin; Schaller, Emily L

2007-03-15

The small bodies in the Solar System are thought to have been highly affected by collisions and erosion. In the asteroid belt, direct evidence of the effects of large collisions can be seen in the existence of separate families of asteroids--a family consists of many asteroids with similar orbits and, frequently, similar surface properties, with each family being the remnant of a single catastrophic impact. In the region beyond Neptune, in contrast, no collisionally created families have hitherto been found. The third largest known Kuiper belt object, 2003 EL61, however, is thought to have experienced a giant impact that created its multiple satellite system, stripped away much of an overlying ice mantle, and left it with a rapid rotation. Here we report the discovery of a family of Kuiper belt objects with surface properties and orbits that are nearly identical to those of 2003 EL61. This family appears to be fragments of the ejected ice mantle of 2003 EL61.

The nucleus of 19/P Borrelly as revealed by deep space 1

USGS Publications Warehouse

Buratti, B.; Hicks, M.; Soderblom, L.; Britt, D.; Boice, D.; Brown, R.; Nelson, R.; Oberst, J.; Owen, Timothy W.; Sandel, B.; Stern, S.A.; Thomas, N.; Yelle, R.

2002-01-01

The Deep Space 1 encounter with comet 19/P Borrelly offered the first close-up view of a comet unobscured by dust. The geometric albedo of the comet is 0.029±0.006 (with a size of 8.0 × 3.15 km), comparable to the low-albedo hemisphere of Iapetus, the lowest albedo C-type asteroids, and the Uranian rings. Albedo variegations on the body are substantial, far greater than on the handful of asteroids so far scrutinized by spacecraft. The Bond albedo of Borrelly is 0.009 ± 0.002, the lowest of any object in the Solar System. The physical photometric parameters of the comet are similar to asteroids, but the optically active portion of its regolith may be fluffier. Differences in macroscopic roughness exist on its surface: the older regions appear to be slightly less rough, as if low-lying regions are infilled with native dust. Regional differences in the single particle phase function exist, with small regions exhibiting almost isotropic functions.

Rockballer Sample Acquisition Tool

NASA Technical Reports Server (NTRS)

Giersch, Louis R.; Cook, Brant T.

2013-01-01

It would be desirable to acquire rock and/or ice samples that extend below the surface of the parent rock or ice in extraterrestrial environments such as the Moon, Mars, comets, and asteroids. Such samples would allow measurements to be made further back into the geologic history of the rock, providing critical insight into the history of the local environment and the solar system. Such samples could also be necessary for sample return mission architectures that would acquire samples from extraterrestrial environments for return to Earth for more detailed scientific investigation.

Could the Geminid meteoroid stream be the result of long-term thermal fracture?

NASA Astrophysics Data System (ADS)

Ryabova, G. O.

2015-10-01

The previous models by Ryabova have shown that the Geminid meteoroid stream has cometary origin, so asteroid (3200) Phaethon (the Geminid's parent body) is probably a dead comet. Recently (in 2009 and 2012) some week activity was observed (see Jewitt & Li, 2010, AJ, 140), but it was not the cometary activity. Recurrent brightening of Phaethon in perihelion could be the result of thermal fracture and decomposition. In this study we model the longterm dust release from Phaethon based on this mechanism.

Boulders on asteroid Toutatis as observed by Chang’e-2

PubMed Central

Jiang, Yun; Ji, Jianghui; Huang, Jiangchuan; Marchi, Simone; Li, Yuan; Ip, Wing-Huen

2015-01-01

Boulders are ubiquitously found on the surfaces of small rocky bodies in the inner solar system and their spatial and size distributions give insight into the geological evolution and collisional history of the parent bodies. Using images acquired by the Chang’e-2 spacecraft, more than 200 boulders have been identified over the imaged area of the near-Earth asteroid Toutatis. The cumulative boulder size frequency distribution (SFD) shows a steep slope of −4.4 ± 0.1, which is indicative of a high degree of fragmentation. Similar to Itokawa, Toutatis probably has a rubble-pile structure, as most boulders on its surface cannot solely be explained by impact cratering. The significantly steeper slope for Toutatis’ boulder SFD compared to Itokawa may imply a different preservation state or diverse formation scenarios. In addition, the cumulative crater SFD has been used to estimate a surface crater retention age of approximately 1.6 ± 0.3 Gyr. PMID:26522880

Getting to Know Vesta

NASA Astrophysics Data System (ADS)

Martel, L. M. V.

2007-11-01

The howardite-eucrite-diogenite class of meteorites (called the HEDs) are rocks formed from basaltic magmas. What makes them special is that the HEDs have reflectance spectra in the visible and near-infrared that match spectra from asteroid 4 Vesta, implying Vesta is their parent body. We will soon have new data from Vesta from NASA's Dawn orbiting spacecraft, which carries a gamma ray and neutron detector, dubbed the GRaND instrument. GRaND will orbit asteroid 4 Vesta and dwarf planet Ceres and map the near-surface abundances of major and minor elements, and volatiles found in ices (in the case of Ceres) such as hydrogen, carbon, nitrogen, and oxygen. Tomohiro Usui and Harry Y. (Hap) McSween, Jr. (University of Tennessee) have proposed a way to interpret the upcoming GRaND data from Vesta based on well-analyzed samples of HED meteorites and a mixing model they devised that uses element ratios of the three expected rock types. In turn, the new data from Vesta may help scientists better understand the geologic context for HED meteorites.

The Themis-Beagle families: Investigation of space-weathering processes on primitive surfaces

NASA Astrophysics Data System (ADS)

Fornasier, S.; Perna, D.; Lantz, C.; Barucci, M.

2014-07-01

In the past 20 years, enormous progress has been reached in the study of space-weathering (SW) effects on silicates and silicate asteroids. The so-called ordinary chondrite paradox, that is, lack of asteroids similar to the ordinary chondrites, which represent 80 % of meteorite falls, has been solved. These meteorites are now clearly related to S-type asteroids, as proved also by the direct measurements of the NEAR and HAYABUSA missions on the near-Earth asteroids Eros and Itokawa. Spectral differences between S-type asteroids and ordinary chondrites are caused by space-weathering effects, which produce a darkening in the albedo, a reddening of the spectra, and diminish the silicate absorption bands on the asteroids surfaces, exposed to cosmic radiation and solar wind. On the other hand, our understanding of space-weathering effects on primitive asteroids is still poor. Only few laboratory experiments have been devoted to the investigation of SW effects on dark carbonaceous chondrites and on complex organic materials. Irradiation of transparent organic materials produces firstly redder and darker materials that upon further processing turn flatter-bluish and darker (Kanuchova et al. 2012; Moroz et al. 2004). The Themis family is a natural laboratory to study primitive asteroids and space-weathering effects. The Themis family is located between 3.05 and 3.24 au, beyond the snow line, and it is composed of primitive asteroids. Themis is one of the most statistically reliable families in the asteroid belt. First discovered by Hirayama (1918), it has been identified as a family in all subsequent works, and it has 550 members as determined by Zappalà et al. (1995) and more than 4000 as determined by Nesvorny et al. (2010). The family formed probably about 2.3 Gyr ago as a result of a large-scale catastrophic disruption event of a parent asteroid 400 km in diameter colliding with a 190-km projectile (Marzari et al. 1995). Several Themis family members show absorption features associated to hydrated silicates, and, recently, water-ice and organics features have been detected on the surface of (24) Themis (Campins et al. 2010, Rivkin & Emery 2010). Hydrated silicates are produced by the aqueous-alteration process, which require low temperature (< 320 K) and the presence of liquid water in the past. The Themis family may be an important reservoir of water ice. Moreover, the main-belt comets 133P, 238P, and 176P seem to be related to the Themis family because of orbital proximities and spectral properties analogies. Within the old Themis family members, a young sub-family, Beagle, formed less than 10 Myr ago, has been identified. This sub-family has 65 members up to 2 km of diameter (Nesvorny et al. 2008). So, the Themis family is very important to shed light on the asteroid-comet continuum, to constrain the abundances of water ices in the outer part of the main belt, and to probe space-weathering effects on old Themis and young Beagle families' members. To investigate all these aspects, we carried out a spectroscopic survey in the visible and near-infrared range at the 3.6-m Italian telescope TNG (La Palma, Spain) during 6 nights in February and December 2012. We got new spectra of 8 Beagle and 22 Themis members using the DOLORES (with the LR-R and LR-B grisms) and the NICS (with the Amici prism) instruments. To look for possible coma around the targets, we also performed deep imaging in the R filter. Data are currently under analysis, and the results will be presented at the ACM meeting. None of the investigated spectra show water-ice absorption features at 1.5 and 2 microns, while few Themis members have visible absorption bands associated with hydrated silicates. The best meteoritic analogues to both Themis and Beagle members are the carbonaceous chondrites, especially CM2. The spectra of Beagle and Themis asteroids show significant differences: 'old' Themis members exhibit a wide range of spectra, including asteroids with blue/neutral and moderately red spectra (relative to the Sun), while the young Beagle members investigated are bluer and brighter than the Themis ones. These preliminary results seem to indicate that the SW effects on primitive asteroids are similar to those observed on silicate asteroids, that is, they produce reddening of the spectra and moderate darkening of the surface.

A Look at the Single Parent Family: Implications for the School Psychologist.

ERIC Educational Resources Information Center

Burns, Christine W.; Brassard, Marla R.

1982-01-01

Reviews the effects on parents and children of living in a single parent family, and suggests ways in which school psychologists can aid schools and single parent families. Presents school-based interventions for children and parents. Suggests changes in administrative policies to meet the needs of single parent families. (Author)

Investigating the Origin of Bright Materials on Vesta: Synthesis, Conclusions, and Implications

NASA Technical Reports Server (NTRS)

Li, Jian-Yang; Mittlefehldt, D. W.; Pieters, C. M.; De Sanctis, M. C.; Schroder, S. E.; Hiesinger, H.; Blewett, D. T.; Russell, C. T.; Raymond, C. A.; Keller, H. U.

2012-01-01

The Dawn spacecraft started orbiting the second largest asteroid (4) Vesta in August 2011, revealing the details of its surface at an unprecedented pixel scale as small as approx.70 m in Framing Camera (FC) clear and color filter images and approx.180 m in the Visible and Infrared Spectrometer (VIR) data in its first two science orbits, the Survey Orbit and the High Altitude Mapping Orbit (HAMO) [1]. The surface of Vesta displays the greatest diversity in terms of geology and mineralogy of all asteroids studied in detail [2, 3]. While the albedo of Vesta of approx.0.38 in the visible wavelengths [4, 5] is one of the highest among all asteroids, the surface of Vesta shows the largest variation of albedos found on a single asteroid, with geometric albedos ranging at least from approx.0.10 to approx.0.67 in HAMO images [5]. There are many distinctively bright and dark areas observed on Vesta, associated with various geological features and showing remarkably different forms. Here we report our initial attempt to understand the origin of the areas that are distinctively brighter than their surroundings. The dark materials on Vesta clearly are different in origin from bright materials and are reported in a companion paper [6].

Developing Software for NASA Missions in the New Millennia

NASA Technical Reports Server (NTRS)

Truszkowski, Walt; Rash, James; Rouff, Christopher; Hinchey, Mike

2004-01-01

NASA is working on new mission concepts for exploration of the solar system. The concepts for these missions include swarms of hundreds of cooperating intelligent spacecraft which will be able to work in teams and gather more data than current single spacecraft missions. These spacecraft will not only have to operate independently for long periods of time on their own and in teams, but will also need to have autonomic properties of self healing, self configuring, self optimizing and self protecting for them to survive in the harsh space environment. Software for these types of missions has never been developed before and represents some of the challenges of software development in the new millennia. The Autonomous Nano Technology Swarm (ANTS) mission is an example of one of the swarm missions NASA is considering. The ANTS mission will use a swarm of one thousand pico-spacecraft that weigh less than five pounds. Using an insect colony analog, ANTS will explore the asteroid belt and catalog the mass, density, morphology, and chemical composition of the asteroids. Due to the size of the spacecraft, each will only carry a single miniaturized science instrument which will require them to cooperate in searching for asteroids that are of scientific interest. This article also discusses the ANTS mission, the properties the spacecraft will need and how that will effect future software development.

Sex Differences in Parenting Behaviors in Single-Mother and Single-Father Households

ERIC Educational Resources Information Center

Dufur, Mikaela J.; Howell, Nyssa C.; Downey, Douglas B.; Ainsworth, James W.; Lapray, Alice J.

2010-01-01

Research on family structure has led some to claim that sex-based parenting differences exist. But if such differences exist in single-parent families, the absence of a second parent rather than specific sex-typed parenting might explain them. We examine differences in mothering and fathering behavior in single-parent households, where number of…

Near Earth asteroids associated with the Sigma-Capricornids meteoroid stream

NASA Astrophysics Data System (ADS)

Gulchekhra, Kokhirova; Pulat, Babadzhanov; Umed, Khamroev

The Near Earth Asteroids (NEAs) 2008BO16, 2011EC41, and 2013CT36 (http://newton.dm.\\unipi.it/neodys, 2013) have very similar orbits according to the D_{SH} criterion of Southworth, Hawkins (1963). Additionally, their orbits are classed as comet-like by the Tisserand invariant values (Kresak 1982; Kosai 1992). The orbital evolution investigation shows, that during one cycle of variations of the argument of perihelion omega, the asteroids cross the Earth’s orbit four times. Consequently, a developed meteoroid stream, possible associated with them, might produce four meteor showers (Babadzhanov, Obrubov 1992). Theoretical parameters of the predicted showers were calculated and identified with the observable nighttime sigma-Capricornids (Sekanina 1973; Jenniskens 2006) and chi-Sagittarids (Sekanina 1976), and daytime chi-Capricornids (Sekanina 1976) and Capricornids-Sagittarids (Sekanina 1973) meteor showers. The similar and comet-like orbits and association with the meteoroid stream producing four active showers are strong indications that these asteroids have a common cometary origin. Earlier the NEAs (2101) Adonis and 1995CS, which additionally is potentially hazardous asteroid (PHA), were recognized as dormant comets because of their link with the same meteoroid stream (Babadzhanov 2003). So, a conclusion was made, that either the considered NEAs are large sized splinters of the Adonis, or all five objects are fragments of a larger comet that was the parent body of the sigma-Capricornids meteoroid stream, and whose break-up occurred several tens of thousands years ago. During 2010-2011 years three fireballs were photographed by the Tajikistan fireball network (Babadzhanov, Kokhirova 2009), belonging to the sigma-Capricornids meteor shower. Taking into account the observations else six fireballs of this shower in the Canada and USA (Halliday et al. 1996; McCrosky et al. 1978), the mean radiant coordinates, the period of activity, as well as the mean daily radiant drift of the sigma-Capricornids were determined. Further to the PE criterion (Ceplecha, McCrosky 1976), the values of bulk density of the nine fireball producing meteoroids are in the range 0.2-3.5 g cm(-3) that suggests a non-homogeneous compound of the comet-progenitor of the sigma-Capricornids fireball shower. size{ References Babadzhanov, P.B., 2003, A&A,397, 319 Babadzhanov, P.B., Kokhirova, G.I., 2009, Izv. Ak. Nauk Resp. Taj.,2(135),46 Babadzhanov, P.B., Obrubov, Yu.V., 1992, Cel. Mech.& Dyn. Astron., v.54, p.111 Ceplecha, Z., McCrosky, R.E.J., 1976, J. Geophys. Res., 81, 6257 Halliday, I., Griffin, A.A., Blackwell, A.T., 1996, Met.& Planet. Sci., 31, 185 Jenniskens, P., 2006, Meteor showers and their parent comets, New- York: Cambridge Univ. Press, p. 790 Kosai, H., 1992, Cel. Mech. & Dyn. Astron., 54, 237 Kresak, L., 1982, BAC, 33, 104 McCrosky, R.E., Shao, C.Y., Posen, A., 1978, Meteoritika, 37, 44 Sekanina Z., 1973, Icarus, 18, 253 Sekanina Z., 1976, Icarus, 27, 265 Southworth, R.B., Hawkins, G.S., 1963, Smith. Cont. Aph. 7, 261}

Enhanced Gravity Tractor Technique for Planetary Defense

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Reeves, David M.; Hopkins, Joshua B.; Wade, Darren W.; Tantardini, Marco; Shen, Haijun

2015-01-01

Given sufficient warning time, Earth-impacting asteroids and comets can be deflected with a variety of different "slow push/pull" techniques. The gravity tractor is one technique that uses the gravitational attraction of a rendezvous spacecraft to the impactor and a low-thrust, high-efficiency propulsion system to provide a gradual velocity change and alter its trajectory. An innovation to this technique, known as the Enhanced Gravity Tractor (EGT), uses mass collected in-situ to augment the mass of the spacecraft, thereby greatly increasing the gravitational force between the objects. The collected material can be a single boulder, multiple boulders, regolith or a combination of different sources. The collected mass would likely range from tens to hundreds of metric tons depending on the size of the impactor and warning time available. Depending on the propulsion system's capability and the mass collected, the EGT approach can reduce the deflection times by a factor of 10 to 50 or more, thus reducing the deflection times of several decades to years or less and overcoming the main criticism of the traditional gravity tractor approach. Additionally, multiple spacecraft can orbit the target in formation to provide the necessary velocity change and further reduce the time needed by the EGT technique to divert hazardous asteroids and comets. The robotic segment of NASA's Asteroid Redirect Mission (ARM) will collect a multi-ton boulder from the surface of a large Near-Earth Asteroid (NEA) and will provide the first ever demonstration of the EGT technique and validate one method of collecting in-situ mass on an asteroid of hazardous size.

Gender differences in the mental health of single parents: New Zealand evidence from a household panel survey.

PubMed

Collings, Sunny; Jenkin, Gabrielle; Carter, Kristie; Signal, Louise

2014-05-01

In many countries single parents report poorer mental health than partnered parents. This study investigates whether there are gender differences in the mental health of single parents in New Zealand (and whether any gender difference varies with that among partnered parents), and examines key social and demographic mediators that may account for this difference. We used data on 905 single parents and 4,860 partnered parents from a New Zealand household panel survey that included the Kessler-10 measure of psychological distress. Linear regression analyses were used to investigate both interactions of gender and parental status, and confounding or mediation by other covariates. High/very high levels of psychological distress were reported by 15.7 % of single mothers and 9.1 % of single fathers, and 6.1 % of partnered mothers and 4.1 % of partnered fathers. In an Ordinary Least Squares regression of continuous K10 scores on gender, parental status and the interaction of both (plus adjustment for ethnicity, number of children and age), female single parents had a 1.46 higher K10 score than male single parents (95 % CI 0.48-2.44; 1.46). This difference was 0.98 (95 % CI -0.04 to 1.99) points greater than the gender difference among partnered parents. After controlling for further confounding or mediating covariates (educational level, labour force status and socioeconomic deprivation) both the gender difference among single parents (0.38, -0.56 to 1.31) and the interaction of gender and parental status (0.28 greater gender difference among single parents, -0.69 to 1.65) greatly reduced in magnitude and became non-significant, mainly due to adjustment for individual socioeconomic deprivation. The poorer mental health of single parents remains an important epidemiological phenomenon. Although research has produced mixed findings of the nature of gender differences in the mental health of single parents, our research adds to the increasing evidence that it is single mothers who have worse mental health. Our findings on the potential explanations of the gender difference in sole parent mental health suggest that socioeconomic deprivation is a key contributor.

A Research Project on Successful Single-Parent Families.

ERIC Educational Resources Information Center

Barry, Ann

1979-01-01

Studies variables associated with successful single-parent families. Single parents volunteered to share their positive family experiences. Information was sought on ages of family members and length of single-parent family status, education level and income, relations with absent parent, and relations with children. A hypothesis and counseling…

Family stressors and postdeployment mental health in single versus partnered parents deployed in support of the wars in Afghanistan and Iraq.

PubMed

Vaughn-Coaxum, Rachel; Smith, Brian N; Iverson, Katherine M; Vogt, Dawne

2015-08-01

Little is known about the family-related stress and postdeployment adjustment of single versus partnered parents deployed in support of the wars in Iraq and Afghanistan. This study examined exposure to family-related stressors during and after deployment, as well as postdeployment psychological symptoms in a national sample of 318 single (n = 74) and partnered (n = 244) parent veterans of Operation Enduring Freedom and Operation Iraqi Freedom. Results demonstrated that single parents experienced higher levels of concern about life and family disruptions during deployment, lower levels of social support during and after deployment, and poorer postdeployment family functioning than partnered parents. Single parents also reported higher posttraumatic stress symptom severity, but not depression or anxiety symptom severity, compared with partnered parents. Family-related stressors demonstrated different associations with mental health for single and partnered parents, suggesting that some stressor-symptom relations may be more salient for single parents, and others may be more salient for partnered parents. Findings suggest that the deployment and postdeployment experiences of parents differ based on their partnered status, which has implications for the design and provision of services to single and partnered parents. (c) 2015 APA, all rights reserved).

Binary asteroid population. 3. Secondary rotations and elongations

NASA Astrophysics Data System (ADS)

Pravec, P.; Scheirich, P.; Kušnirák, P.; Hornoch, K.; Galád, A.; Naidu, S. P.; Pray, D. P.; Világi, J.; Gajdoš, Š.; Kornoš, L.; Krugly, Yu. N.; Cooney, W. R.; Gross, J.; Terrell, D.; Gaftonyuk, N.; Pollock, J.; Husárik, M.; Chiorny, V.; Stephens, R. D.; Durkee, R.; Reddy, V.; Dyvig, R.; Vraštil, J.; Žižka, J.; Mottola, S.; Hellmich, S.; Oey, J.; Benishek, V.; Kryszczyńska, A.; Higgins, D.; Ries, J.; Marchis, F.; Baek, M.; Macomber, B.; Inasaridze, R.; Kvaratskhelia, O.; Ayvazian, V.; Rumyantsev, V.; Masi, G.; Colas, F.; Lecacheux, J.; Montaigut, R.; Leroy, A.; Brown, P.; Krzeminski, Z.; Molotov, I.; Reichart, D.; Haislip, J.; LaCluyze, A.

2016-03-01

We collected data on rotations and elongations of 46 secondaries of binary and triple systems among near-Earth, Mars-crossing and small main belt asteroids. 24 were found or are strongly suspected to be synchronous (in 1:1 spin-orbit resonance), and the other 22, generally on more distant and/or eccentric orbits, were found or are suggested to have asynchronous rotations. For 18 of the synchronous secondaries, we constrained their librational angles, finding that their long axes pointed to within 20° of the primary on most epochs. The observed anti-correlation of secondary synchroneity with orbital eccentricity and the limited librational angles agree with the theories by Ćuk and Nesvorný (Ćuk, M., Nesvorný, D. [2010]. Icarus 207, 732-743) and Naidu and Margot (Naidu, S.P., Margot, J.-L. [2015]. Astron. J. 149, 80). A reason for the asynchronous secondaries being on wider orbits than synchronous ones may be longer tidal circularization time scales at larger semi-major axes. The asynchronous secondaries show relatively fast spins; their rotation periods are typically < 10 h. An intriguing observation is a paucity of chaotic secondary rotations; with an exception of (35107) 1991 VH, the secondary rotations are single-periodic with no signs of chaotic rotation and their periods are constant on timescales from weeks to years. The secondary equatorial elongations show an upper limit of a2 /b2 ∼ 1.5 . The lack of synchronous secondaries with greater elongations appears consistent, considering uncertainties of the axis ratio estimates, with the theory by Ćuk and Nesvorný that predicts large regions of chaotic rotation in the phase space for a2 /b2 ≳√{ 2 } . Alternatively, secondaries may not form or stay very elongated in gravitational (tidal) field of the primary. It could be due to the secondary fission mechanism suggested by Jacobson and Scheeres (Jacobson, S.A., Scheeres, D.J. [2011]. Icarus 214, 161-178), as its efficiency is correlated with the secondary elongation. Sharma (Sharma, I. [2014]. Icarus 229, 278-294) found that rubble-pile satellites with a2 /b2 ≲ 1.5 are more stable to finite structural perturbations than more elongated ones. It appears that more elongated secondaries, if they originally formed in spin fission of parent asteroid, are less likely to survive intact and they more frequently fail or fission.

Photometric analysis of Asteroid (21) Lutetia from Rosetta-OSIRIS images

NASA Astrophysics Data System (ADS)

Masoumzadeh, N.; Boehnhardt, H.; Li, Jian-Yang; Vincent, J.-B.

2015-09-01

We analyzed the photometric properties of Asteroid (21) Lutetia based on images captured by Rosetta during its flyby. We utilized the images recorded in the F17 filter (λ = 631.6 nm) of the Wide Angle Camera (WAC) and in the F82 & F22 filters (λ = 649.2 nm) of the Narrow Angle Camera (NAC) of the OSIRIS imaging system onboard the spacecraft. We present the results of Hapke and Minnaert modeling using disk-integrated and disk-resolved data derived from the surface of the asteroid. At 631.6 nm and 649.2 nm, the geometric albedo of Lutetia is 0.194 ± 0.002. The Bond albedo is 0.076 ± 0.002 at 649.2 nm, and 0.079 ± 0.002 at 631.6 nm. The roughness parameter is 28 ° ± 1 ° , the opposition surge parameters B0 and h are 1.79 ± 0.08 and 0.041 ± 0.003, respectively, and the asymmetry factor of the phase function is -0.28 ± 0.01. The single-scattering albedo is 0.226 ± 0.002 at 631.6 and 649.2 nm. The modeled Hapke parameters of Asteroid Lutetia are close to those of typical S-type asteroids. The Minnaert k parameter of Lutetia at opposition (0.526 ± 0.002) is comparable with other asteroids and comets. Albedo ratio images indicate no significant variation across the surface of Lutetia, apart from the so called NPCC region on Lutetia where a pronounced variation is seen at large phase angle. The small width of the albedo distribution of the surface (∼7% at half maximum) and the similarity between phase ratio maps derived from the measurements and from the modeling suggests that the light scattering property over the whole visible and illuminated surface of the asteroid is widely uniform. The comparison between the reflectance measurement of Lutetia and the available laboratory samples suggests that the regolith on Lutetia is concrete with possible grain size distribution of150 μm or larger.

Thermal alteration in carbonaceous chondrites and implications for sublimation in rock comets

NASA Astrophysics Data System (ADS)

Springmann, Alessondra; Lauretta, Dante S.; Steckloff, Jordan K.

2015-11-01

Rock comets are small solar system bodies in Sun-skirting orbits (perihelion q < ~0.15 AU) that form comae rich in mineral sublimation products, but lack typical cometary ice sublimation products (H2O, CO2, etc.). B-class asteroid (3200) Phaethon, considered to be the parent body of the Geminid meteor shower, is the only rock comet currently known to periodically eject dust and form a coma. Thermal fracturing or thermal decomposition of surface materials may be driving Phaethon’s cometary activity (Li & Jewitt, 2013). Phaethon-like asteroids have dynamically unstable orbits, and their perihelia can change rapidly over their ~10 Myr lifetimes (de León et al., 2010), raising the possibility that other asteroids may have been rock comets in the past. Here, we propose using spectroscopic observations of mercury (Hg) as a tracer of an asteroid’s thermal metamorphic history, and therefore as a constraint on its minimum achieved perihelion distance.B-class asteroids such as Phaethon have an initial composition similar to aqueously altered primitive meteorites such as CI- or CM-type meteorites (Clark et al., 2010). Laboratory heating experiments of ~mm sized samples of carbonaceous chondrite meteorites from 300K to 1200K at a rate of 15K/minute show mobilization and volatilization of various labile elements at temperatures that could be reached by Mercury-crossing asteroids. Samples became rapidly depleted in labile elements and, in particular, lost ~75% of their Hg content when heated from ~500-700 K, which corresponds to heliocentric distances of ~0.15-0.3 au, consistent with our thermal models. Mercury has strong emission lines in the UV (~ 185 nm) and thus its presence (or absence) relative to carbonaceous chondrite abundances would indicate if these bodies had perihelia in their dynamical histories inside of 0.15 AU, and therefore may have previously been Phaethon-like rock comets. Future space telescopes or balloon-borne observing platforms equipped with a UV spectrometer could potentially detect the presence or absence of strong ultraviolet mercury lines on rock comets or rock comet candidates.

Understanding Asteroid Disruptions Using Very Young Dust Bands

NASA Astrophysics Data System (ADS)

Espy Kehoe, Ashley J.; Kehoe, T. J.; Colwell, J. E.; Dermott, S. F.

2013-10-01

Zodiacal dust bands are structures that result from the dynamical sculpting of the dust particles released in the catastrophic disruption of an asteroid. Partial dust bands are the recently discovered younger siblings of the dust bands, ones that are still forming and due to very recent disruptions within the last few hundred thousand years. During the early stages of formation, these structures retain information on the original catastrophic disruptions that produced them (since the dust has not yet been lost or significantly altered by orbital or collisional decay). The first partial dust band, at about 17 degrees latitude, was revealed using a very precise method of co-adding the IRAS data set. We have shown that these partial dust bands exhibit structure consistent with a forming band, can be used to constrain the original size distribution of the dust produced in the catastrophic disruption of an asteroid, and these very young structures also allow a much better estimate of the total amount of dust released in the disruption. In order to interpret the observations and constrain the parameters of the dust injected into the cloud following an asteroid disruption, we have developed detailed models of the dynamical evolution of the dust that makes up the band. We model the dust velocity distribution resulting from the initial impact and then track the orbital evolution of the dust under the effects of gravitational perturbations from all the planets as well as radiative forces of Poynting-Robertson drag, solar wind drag and radiation pressure and use these results to produce maps of the thermal emission. Through the comparison of our newly completed dynamical evolution models with the coadded observations, we can put constraints on the parameters of dust producing the band. We confirm the source of the band as the very young Emilkowalski cluster ( <250,000 years; Nesvorny et al., 2003) and present our most recent estimates of the size-distribution and cross-sectional area of material in the band and discuss the implications of these constraints on the temporal evolution of the zodiacal cloud and to the structure of the parent asteroid.

The Mental Health Status of Single-Parent Community College Students in California.

PubMed

Shenoy, Divya P; Lee, Christine; Trieu, Sang Leng

2016-01-01

Single-parenting students face unique challenges that may adversely affect their mental health, which have not been explored in community college settings. The authors conducted secondary analysis of Spring 2013 data from the American College Health Association-National College Health Assessment to examine difficulties facing single-parent community college students and the association between single parenting and negative mental health (depression, self-injury, suicide attempt). Participants were 6,832 California community college students, of whom 309 were single parents. Demographic and mental health data were characterized using univariate descriptive analyses. Bivariate analyses determined whether single parents differed from other students regarding negative mental health or traumatic/difficult events. Finances, family, and relationship difficulties disproportionally affected single parents, who reported nearly twice as many suicide attempts as their counterparts (5.3% vs. 2.7%; p < .0001). Single-parenting students face a higher prevalence of mental health stressors than other community college students.

KSC-07pd2061

NASA Image and Video Library

2007-07-22

KENNEDY SPACE CENTER, FLA. — On Pad 17-B at Cape Canaveral Air Force Station, the Dawn spacecraft is safely secured on a transporter for its trip to Astrotech. Dawn is being returned to the Astrotech payload processing facility to await a new launch date. The launch opportunity extends from Sept. 7 to Oct. 15. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. NASA/George Shelton

KSC-07pd2058

NASA Image and Video Library

2007-07-22

KENNEDY SPACE CENTER, FLA. — On Pad 17-B at Cape Canaveral Air Force Station, the Dawn spacecraft is lowered from the mobile service tower to the ground. Dawn is being returned to the Astrotech payload processing facility to await a new launch date. The launch opportunity extends from Sept. 7 to Oct. 15. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. NASA/George Shelton

KSC-07pd2059

NASA Image and Video Library

2007-07-22

KENNEDY SPACE CENTER, FLA. — On Pad 17-B at Cape Canaveral Air Force Station, the Dawn spacecraft is lowered from the mobile service tower to the ground. Dawn is being returned to the Astrotech payload processing facility to await a new launch date. The launch opportunity extends from Sept. 7 to Oct. 15. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. NASA/George Shelton

Fragment properties at the catastrophic disruption threshold: The effect of the parent body’s internal structure

NASA Astrophysics Data System (ADS)

Jutzi, Martin; Michel, Patrick; Benz, Willy; Richardson, Derek C.

2010-05-01

Numerical simulations of asteroid breakups, including both the fragmentation of the parent body and the gravitational interactions between the fragments, have allowed us to reproduce successfully the main properties of asteroid families formed in different regimes of impact energy, starting from a non-porous parent body. In this paper, using the same approach, we concentrate on a single regime of impact energy, the so-called catastrophic threshold usually designated by QD*, which results in the escape of half of the target's mass. Thanks to our recent implementation of a model of fragmentation of porous materials, we can characterize QD* for both porous and non-porous targets with a wide range of diameters. We can then analyze the potential influence of porosity on the value of QD*, and by computing the gravitational phase of the collision in the gravity regime, we can characterize the collisional outcome in terms of the fragment size and ejection speed distributions, which are the main outcome properties used by collisional models to study the evolutions of the different populations of small bodies. We also check the dependency of QD* on the impact speed of the projectile. In the strength regime, which corresponds to target sizes below a few hundreds of meters, we find that porous targets are more difficult to disrupt than non-porous ones. In the gravity regime, the outcome is controlled purely by gravity and porosity in the case of porous targets. In the case of non-porous targets, the outcome also depends on strength. Indeed, decreasing the strength of non-porous targets make them easier to disrupt in this regime, while increasing the strength of porous targets has much less influence on the value of QD*. Therefore, one cannot say that non-porous targets are systematically easier or more difficult to disrupt than porous ones, as the outcome highly depends on the assumed strength values. In the gravity regime, we also confirm that the process of gravitational reaccumulation is at the origin of the largest remnant's mass in both cases. We then propose some power-law relationships between QD* and both target's size and impact speed that can be used in collisional evolution models. The resulting fragment size distributions can also be reasonably fitted by a power-law whose exponent ranges between -2.2 and -2.7 for all target diameters in both cases and independently on the impact velocity (at least in the small range investigated between 3 and 5 km/s). Then, although ejection velocities in the gravity regime tend to be higher from porous targets, they remain on the same order as the ones from non-porous targets.

Habitation Concepts and Tools for Asteroid Missions and Commercial Applications

NASA Technical Reports Server (NTRS)

Smitherman, David

2010-01-01

In 2009 studies were initiated in response to the Augustine Commission s review of the Human Spaceflight Program to examine the feasibility of additional options for space exploration beyond the lunar missions planned in the Constellation Program. One approach called a Flexible Path option included possible human missions to near-Earth asteroids. This paper presents an overview of possible asteroid missions with emphasis on the habitation options and vehicle configurations conceived for the crew excursion vehicles. One launch vehicle concept investigated for the Flexible Path option was to use a dual launch architecture that could serve a wide variety of exploration goals. The dual launch concept used two medium sized heavy lift launch vehicles for lunar missions as opposed to the single Saturn V architecture used for the Apollo Program, or the one-and-a-half vehicle Ares I / Ares V architecture proposed for the Constellation Program. This dual launch approach was studied as a Flexible Path option for lunar missions and for possible excursions to other destinations like geosynchronous earth orbiting satellites, Lagrange points, and as presented in this paper, asteroid rendezvous. New habitation and exploration systems for the crew are presented that permit crew sizes from 2 to 4, and mission durations from 100 to 360 days. Vehicle configurations are presented that include habitation systems and tools derived from International Space Station (ISS) experience and new extra-vehicular activity tools for asteroid exploration, Figure 1. Findings from these studies and as presented in this paper indicate that missions to near-Earth asteroids appear feasible in the near future using the dual launch architecture, the technologies under development from the Constellation Program, and systems derived from the current ISS Program. In addition, the capabilities derived from this approach that are particularly beneficial to the commercial sector include human access to geosynchronous orbit and the Lagrange points with new tools for satellite servicing and in-space assembly.

New Research by CCD Scanning for Comets and Asteroids

NASA Technical Reports Server (NTRS)

Gehrels, Tom

1997-01-01

Spacewatch was begun in 1980; its purpose is to explore the various populations of small objects within the solar system. Spacewatch provides data for studies of comets and asteroids, finds potential targets for space missions, and provides information on the environmental problem of possible impacts. Moving objects are discovered by scanning the sky with charge-coupled devices (CCDS) on the 0.9-meter Spacewatch Telescope of the University of Arizona on Kitt Peak. Each Spacewatch scan consists of three drift scan passes over an area of sky using a CCD filtered to a bandpass of 0.5-1.0 pm (approximately V+R+I with peak sensitivity at 0.7 pm). The effective exposure time for each pass is 143 seconds multiplied by the secant of the declination. The area covered by each scan is 32 arcminutes in declination by about 28 minutes of time in right ascension. The image scale is 1.05 arcseconds per pixel. Three passes take about 1.5 hours to complete and show motions of individual objects over a one hour time baseline. The limiting magnitude is about 21.5 in single scans. CCD scanning was developed by Spacewatch in the early 1980s, with improvements still being made - particularly by bringing a new 1.8-m Spacewatch Telescope on line. In the meantime, we have been finding some 30,000 new asteroids per year and applying their statistics to the study of the collisional history of the solar system. Spacewatch had found a total of 150 Near-Earth Asteroids (NEAS) and 8 new comets, and had recovered one lost comet (P/Spitaler in 1993). Spacewatch is also efficient in recovery of known comets and has detected and reported positions for more than 137,000 asteroids, mostly new ones in the main belt, including more than 10,882 asteroids designated by the Minor Planet Center (MPC).

A new type of solar-system material recovered from Ordovician marine limestone

PubMed Central

Schmitz, B.; Yin, Q. -Z.; Sanborn, M. E.; Tassinari, M.; Caplan, C. E.; Huss, G. R.

2016-01-01

From mid-Ordovician ∼470 Myr-old limestone >100 fossil L-chondritic meteorites have been recovered, representing the markedly enhanced flux of meteorites to Earth following the breakup of the L-chondrite parent body. Recently one anomalous meteorite, Österplana 065 (Öst 65), was found in the same beds that yield L chondrites. The cosmic-ray exposure age of Öst 65 shows that it may be a fragment of the impactor that broke up the L-chondrite parent body. Here we show that in a chromium versus oxygen-isotope plot Öst 65 falls outside all fields encompassing the known meteorite types. This may be the first documented example of an ‘extinct' meteorite, that is, a meteorite type that does not fall on Earth today because its parent body has been consumed by collisions. The meteorites found on Earth today apparently do not give a full representation of the kind of bodies in the asteroid belt ∼500 Myr ago. PMID:27299793

A new type of solar-system material recovered from Ordovician marine limestone.

PubMed

Schmitz, B; Yin, Q-Z; Sanborn, M E; Tassinari, M; Caplan, C E; Huss, G R

2016-06-14

From mid-Ordovician ∼470 Myr-old limestone >100 fossil L-chondritic meteorites have been recovered, representing the markedly enhanced flux of meteorites to Earth following the breakup of the L-chondrite parent body. Recently one anomalous meteorite, Österplana 065 (Öst 65), was found in the same beds that yield L chondrites. The cosmic-ray exposure age of Öst 65 shows that it may be a fragment of the impactor that broke up the L-chondrite parent body. Here we show that in a chromium versus oxygen-isotope plot Öst 65 falls outside all fields encompassing the known meteorite types. This may be the first documented example of an 'extinct' meteorite, that is, a meteorite type that does not fall on Earth today because its parent body has been consumed by collisions. The meteorites found on Earth today apparently do not give a full representation of the kind of bodies in the asteroid belt ∼500 Myr ago.

Single Parents and the Work Setting: The Impact of Multiple Job and Homelife Responsibilities.

ERIC Educational Resources Information Center

Burden, Dianne S.

1986-01-01

Examines the impact of combined work/family responsibilities on single-parent employees. Results indicated that parent employees, but particularly single female parents, were at risk for high job-family role strain and reduced levels of well-being. In spite of increased strain, however, single parents exhibited high levels of job satisfaction and…

A geochemical study of the winonaites: Evidence for limited partial melting and constraints on the precursor composition

NASA Astrophysics Data System (ADS)

Hunt, Alison C.; Benedix, Gretchen K.; Hammond, Samantha J.; Bland, Philip A.; Rehkämper, Mark; Kreissig, Katharina; Strekopytov, Stanislav

2017-02-01

The winonaites are primitive achondrites which are associated with the IAB iron meteorites. Textural evidence implies heating to at least the Fe, Ni-FeS cotectic, but previous geochemical studies are ambiguous about the extent of silicate melting in these samples. Oxygen isotope evidence indicates that the precursor material may be related to the carbonaceous chondrites. Here we analysed a suite of winonaites for modal mineralogy and bulk major- and trace-element chemistry in order to assess the extent of thermal processing as well as constrain the precursor composition of the winonaite-IAB parent asteroid. Modal mineralogy and geochemical data are presented for eight winonaites. Textural analysis reveals that, for our sub-set of samples, all except the most primitive winonaite (Northwest Africa 1463) reached the Fe, Ni-FeS cotectic. However, only one (Tierra Blanca) shows geochemical evidence for silicate melting processes. Tierra Blanca is interpreted as a residue of small-degree silicate melting. Our sample of Winona shows geochemical evidence for extensive terrestrial weathering. All other winonaites studied here (Fortuna, Queen Alexander Range 94535, Hammadah al Hamra 193, Pontlyfni and NWA 1463) have chondritic major-element ratios and flat CI-normalised bulk rare-earth element patterns, suggesting that most of the winonaites did not reach the silicate melting temperature. The majority of winonaites were therefore heated to a narrow temperature range of between ∼1220 (the Fe, Ni-FeS cotectic temperature) and ∼1370 K (the basaltic partial melting temperature). Silicate inclusions in the IAB irons demonstrate partial melting did occur in some parts of the parent body (Ruzicka and Hutson, 2010), thereby implying heterogeneous heat distribution within this asteroid. Together, this indicates that melting was the result of internal heating by short-lived radionuclides. The brecciated nature of the winonaites suggests that the parent body was later disrupted by a catastrophic impact, which allowed the preservation of the largely unmelted winonaites. Despite major-element similarities to both ordinary and enstatite chondrites, trace-element analysis suggests the winonaite parent body had a carbonaceous chondrite-like precursor composition. The parent body of the winonaites was volatile-depleted relative to CI, but enriched compared to the other carbonaceous classes. The closest match are the CM chondrites; however, the specific precursor is not sampled in current meteorite collections.

Perceptions of Parent School Collaboration within Single Parent Households

ERIC Educational Resources Information Center

Josafat, Jason Marc

2015-01-01

Little is known regarding the involvement levels of single parents in their child's education or what schools can do to support the collaborative involvement with single parents. This is important, because parent involvement is crucial for student success, and schools play an important part in garnering this role towards parent involvement; single…

Single-Parent Families in Rural Communities

ERIC Educational Resources Information Center

Lewis, Ken

1978-01-01

Presenting national statistics on single-parent families, this article illustrates the need for serious study of this phenomenon, suggesting that changing divorce laws, increased single-parent adoptions, and an increase in the number of supportive services for single-parent families are contingencies having significant bearing upon the…

Variation of mineralogy and organic material during the early stages of aqueous activity recorded in Antarctic micrometeorites

NASA Astrophysics Data System (ADS)

Noguchi, T.; Yabuta, H.; Itoh, S.; Sakamoto, N.; Mitsunari, T.; Okubo, A.; Okazaki, R.; Nakamura, T.; Tachibana, S.; Terada, K.; Ebihara, M.; Imae, N.; Kimura, M.; Nagahara, H.

2017-07-01

Micrometeorites (MMs) recovered from surface snow near the Dome Fuji Station, Antarctica are almost free from terrestrial weathering and contain very primitive materials, and are suitable for investigation of the evolution and interaction of inorganic and organic materials in the early solar system. We carried out a comprehensive study on seven porous and fluffy MMs [four Chondritic porous (CP) MMs and three fluffy fine-grained (Fluffy Fg) MMs] and one fine-grained type 1 (Fg C1) MM for comparison with scanning electron microscope, transmission electron microscope, X-ray absorption near-edge structure analysis, and secondary ion mass spectrometer. They show a variety of early aqueous activities. Four out of the seven CP MMs contain glass with embedded metal and sulfide (GEMS) and enstatite whiskers/platelets and do not have hydrated minerals. Despite the same mineralogy, organic chemistry of the CP MMs shows diversity. Two of them contain considerable amounts of organic materials with high carboxyl functionality, and one of them contains nitrile (Ctbnd N) and/or nitrogen heterocyclic groups with D and 15N enrichments, suggesting formation in the molecular cloud or a very low temperature region of the outer solar system. Another two CP MMs are poorer in organic materials than the above-mentioned MMs. Organic material in one of them is richer in aromatic C than the CP MMs mentioned above, being indistinguishable from those of hydrated carbonaceous chondrites. In addition, bulk chemical compositions of GEMS in the latter organic poor CP MMs are more homogeneous and have higher Fe/(Si + Mg + Fe) ratios than those of GEMS in the former organic-rich CP MMs. Functional group of the organic materials and amorphous silicate in GEMS in the organic-poor CP MMs may have transformed in the earliest stage of aqueous alteration, which did not form hydrated minerals. Three Fluffy Fg MMs contain abundant phyllosilicates, showing a clear evidence of aqueous alteration. Phyllosilicates in thee MMs are richer in Fe than those in hydrated IDPs, typical fine-grained hydrated (Fg C1) MMs, and hydrated carbonaceous chondrites. One of the Fluffy Fg MMs contains amorphous silicate, which is richer in Fe than GEMS and contains little or no nanophase Fe metal but contains Fe sulfide. Because the chemical compositions of the amorphous silicate are within the compositional field of GEMS in CP IDPs, the amorphous silicate may be alteration products of GEMS. The entire compositional field of GEMS in the CP MMs and the amorphous silicate in the Fluffy Fg MM matches that of the previously reported total compositional range of GEMS in IDPs. One Fluffy Fg MM contains Mg-rich phyllosilicate along with Fe-rich phyllosilicate and Mg-Fe carbonate. Mg-rich phyllosilicate and Mg-Fe carbonate may have been formed through the reaction of Fe-rich phyllosilicate, Mg-rich olivine and pyroxene, and water with C-bearing chemical species. These data indicate that CP MMs and Fluffy Fg MMs recovered from Antarctic surface snow contain materials that throw a light on the earliest stages of aqueous alteration on very primitive solar system bodies. Because mineralogy and isotopic and structural features of organic materials in D10IB009 are comparable with isotopically primitive IDPs, its parent body could be comets or icy asteroids showing mass ejection (active asteroids). By contrast, organic-poor CP MMs may have experienced the earliest stage of aqueous alteration and Fluffy Fg MMs experienced weak aqueous alteration. The precursor materials of the parent bodies of Fluffy Fg MMs probably contained abundant GEMS or GEMS-like materials like CP IDPs, which is common to fine-grained matrices of very primitive carbonaceous chondrites such as CR3s. However, highly porous nature of organic-poor CP MMs and Fluffy Fg MMs suggests that parent bodies of these MMs must have been much more porous than the parent bodies of primitive carbonaceous chondrites. Given no phyllosilicate among the returned samples of 81P/Wild 2 comet, the MMs may have been derived from porous icy asteroids such as active asteroids as well as P- and D-type asteroids rather than comets.

CCD observations: rotational properties of 13 small asteroids

NASA Astrophysics Data System (ADS)

Angeli, C. A.; Barucci, M. A.

1996-03-01

About 10 years ago our group in the Meudon Observatory started an observational program on small asteroids (diameter ⩽ 50 km) in order to enlarge the knowledge of this size range objects. The results of three observational runs are reported, carried out in January 1993, August 1993 and August 1994, with the 1.2 m telescope of the Haute-Provence Observatory and with the 2.0 m telescope of the Pic du Midi Observatory, both in France. Thirteen asteroids were observed; for 9 of them the rotational period was determined with different quality codes and the composite lightcurves obtained are presented. For four asteroids (3017 Petrovic ( Psyn = 4.069±0.006 h), 4045 1953RG ( Psyn = 9.764±0.003 h), 4483 Petofi ( Psyn = 4.480±0.013 h) and 4628 Laplace ( Psyn = 9.011±0.005 h)) an unambiguous period is determined. For three of them (4224 Susa ( Psyn = 7.78±0.01 h), 4423 1949GH ( Psyn = 10.51±0.01 h), and 5104 1986RU5 ( Psyn = 6.14±0.01) a reasonably secure result is obtained. For two (3485 Barucci ( Psyn = 14.65±0.06 h) and 3909 Gladys ( Psyn = 6.83±0.01 h)) a tentative result is given. For the others (1783 Albitskij, 4164 Shilov, 4232 1977CD, and 4867 Polites) the single-night lightcurves are reported.

Family Structure and Family Processes in Mexican American Families

PubMed Central

Zeiders, Katharine H.; Roosa, Mark W.; Tein, Jenn-Yun

2010-01-01

Despite increases in single-parent families among Mexican Americans (MA), few studies have examined the association of family structure and family adjustment. Utilizing a diverse sample of 738 Mexican American families (21.7% single parent), the current study examined differences across family structure on early adolescent outcomes, family functioning, and parent-child relationship variables. Results revealed that early adolescents in single parent families reported greater school misconduct, CD/ODD and MDD symptoms, and greater parent-child conflict than their counterparts in two parent families. Single parent mothers reported greater economic hardship, depression and family stress. Family stress and parent-child conflict emerged as significant mediators of the association between family structure and early adolescent outcomes, suggesting important processes linking MA single parent families and adolescent adjustment. PMID:21361925

Incremental laser space weathering of Allende reveals non-lunar like space weathering effects

NASA Astrophysics Data System (ADS)

Gillis-Davis, Jeffrey J.; Lucey, Paul G.; Bradley, John P.; Ishii, Hope A.; Kaluna, Heather M.; Misra, Anumpam; Connolly, Harold C.

2017-04-01

We report findings from a series of laser-simulated space weathering experiments on Allende, a CV3 carbonaceous chondrite. The purpose of these experiments is to understand how spectra of anhydrous C-complex asteroids might vary as a function of micrometeorite bombardment. Four 0.5-gram aliquots of powdered, unpacked Allende meteorite were incrementally laser weathered with 30 mJ pulses while under vacuum. Radiative transfer modeling of the spectra and Scanning Transmission Electron Microscope (STEM) analyses of the samples show lunar-like similarities and differences in response to laser-simulated space weathering. For instance, laser weathered Allende exhibited lunar-like spectral changes. The overall spectra from visible to near infrared (Vis-NIR) redden and darken, and characteristic absorption bands weaken as a function of laser exposure. Unlike lunar weathering, however, the continuum slope between 450-550 nm does not vary monotonically with laser irradiation. Initially, spectra in this region redden with laser irradiation; then, the visible continua become less red and eventually spectrally bluer. STEM analyses of less mature samples confirm submicroscopic iron metal (SMFe) and micron sized sulfides. More mature samples reveal increased dispersal of Fe-Ni sulfides by the laser, which we infer to be the cause for the non-lunar-like changes in spectral behavior. Spectra of laser weathered Allende are a reasonable match to T- or possibly K-type asteroids; though the spectral match with a parent body is not exact. The key take away is, laser weathered Allende looks spectrally different (i.e., darker, and redder or bluer depending on the wavelength region) than its unweathered spectrum. Consequently, connecting meteorites to asteroids using unweathered spectra of meteorites would result in a different parent body than one matched on the basis of weathered spectra. Further, spectra for these laser weathering experiments may provide an explanation for inconsistencies observed in both laboratory (e.g., Hiroi et al., 2003, 2001; Lazzarin et al., 2006; Moroz et al., 2004, 1996; Shingareva et al., 2004) and telescopic data (Lazzarin et al., 2006; Marchi et al., 2006; Nesvorný et al., 2005).

Asteroid mining

NASA Astrophysics Data System (ADS)

Gertsch, Richard E.

The earliest studies of asteroid mining proposed retrieving a main belt asteroid. Because of the very long travel times to the main asteroid belt, attention has shifted to the asteroids whose orbits bring them fairly close to the Earth. In these schemes, the asteroids would be bagged and then processed during the return trip, with the asteroid itself providing the reaction mass to propel the mission homeward. A mission to one of these near-Earth asteroids would be shorter, involve less weight, and require a somewhat lower change in velocity. Since these asteroids apparently contain a wide range of potentially useful materials, our study group considered only them. The topics covered include asteroid materials and properties, asteroid mission selection, manned versus automated missions, mining in zero gravity, and a conceptual mining method.

Asteroid mining

NASA Technical Reports Server (NTRS)

Gertsch, Richard E.

1992-01-01

The earliest studies of asteroid mining proposed retrieving a main belt asteroid. Because of the very long travel times to the main asteroid belt, attention has shifted to the asteroids whose orbits bring them fairly close to the Earth. In these schemes, the asteroids would be bagged and then processed during the return trip, with the asteroid itself providing the reaction mass to propel the mission homeward. A mission to one of these near-Earth asteroids would be shorter, involve less weight, and require a somewhat lower change in velocity. Since these asteroids apparently contain a wide range of potentially useful materials, our study group considered only them. The topics covered include asteroid materials and properties, asteroid mission selection, manned versus automated missions, mining in zero gravity, and a conceptual mining method.

The Origin of Apollo Objects

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

Perlmutter, Saul

1984-03-29

The source of the Earth-orbit-crossing asteroids has been much debated. (This class of asteroidal bodies includes the Apollo, Aten, and some Amor objects, each with its own orbital characteristics; we shall use the term Apollo objects to mean all Earth-crossers.) It is difficult to find a mechanism which would create new Apollo objects at a sufficient rate to balance the loss due to collision with planets and ejection from the solar system, and thus explain the estimated steady-state number. A likely source is the main asteroid belt, since it has similar photometric characteristics. There are gaps in the main beltmore » which correspond to orbits resonant with the orbits of Jupiter and Saturn, and it has been shown that the resonances can perturb a body into an Earth-crossing orbit. Apollo objects could thus be generated when random collisions between asteroids in the main belt sent fragments into these resonant orbits. Calculations of the creation rate from these random collisions, however, yielcl numbers too low by a factor of four. This rate could be significantly lower given the uncertainty in the efficiency of the resonance mechanism. As an alternative, it was suggested that the evaporation of a comet's volatile mantle as it passes near the sun could provide enough non-gravitational force to move the comet into an orbit with aphelion inside of Jupiter's orbit, and thus safe from ejection from the solar system. The probability of such an event occurring is unknown, although the recent discovery of the 'asteroid' 1983 TB, with an orbit matching that of the Geminid meteor shower, suggests that such a mechanism has occurred at least once. New evidence from paleontology and geophysics, however, suggests a better solution to the problem of the source of the Apollos. M. Davis, P. Hut, and R. A. Muller recently proposed that an unseen companion to the sun passes through the Oort cloud every 28 million years, sending a shower of comets to the Earth; this provides an explanation for the periodicity of the fossil record of extinctions found by D. M. Raup and J. J. Sepkoski. W. Alvarez and R. A. Muller have shown that the craters on the earth have an age distribution with a periodicity and phase consistent with this hypothesis. These periodic comet showers would of course pass through the entire solar system, colliding with other bodies besides the earth. When the target is the asteroid belt, many small comets will have sufficient kinetic energy to disrupt large asteroids. This will generate many more fragments in the resonant orbits than would be generated by random collisions of asteroids with each other, and hence more Apollo objects. In this report, we shall calculate approximately (A) the number of comets per shower which cross the asteroid belt, (B) the probability of collisions with a single asteroid per shower, (C) the number of fragments with radius > 0.5 km which reach Apollo orbits, and (D) the current expected number of Apollos derived from comet/asteroid collisions. Given conservative assumptions, the calculated number is in agreement with observations.« less

Impact of caring for a child with cancer on single parents compared with parents from two-parent families.

PubMed

Klassen, Anne F; Dix, David; Papsdorf, Michael; Klaassen, Robert J; Yanofsky, Rochelle; Sung, Lillian

2012-01-01

It is currently unknown how the intensive and often prolonged treatment of childhood cancer impacts on the lives of single parents. Our aims were to determine whether single parents differ from parents from two-parent families in terms of caregiver demand (the time and effort involved in caregiving), and health-related quality of life (HRQL). Forty single parents and 275 parents from two-parent families were recruited between November 2004 and February 2007 from five pediatric oncology centers in Canada. Parents were asked to complete a questionnaire booklet composed of items and scales to measure caregiver demand and HRQL (SF-36). The booklet also measured the following constructs: background and context factors, child factors, caregiving strain, intrapsychic factors, and coping factors. Single parents did not differ from parents from two-parent families in caregiving demand and physical and psychosocial HRQL. Compared with Canadian population norms for the SF-36, both groups reported clinically important differences (i.e., worse health) in psychosocial HRQL (effect size ≥ -2.00), while scores for physical HRQL were within one standard deviation of population norms. Our findings suggest that the impact of caregiving on single parents, in terms of caregiving demand and HRQL is similar to that of parents from two-parent families. Copyright © 2011 Wiley Periodicals, Inc.

Larger classification allows a new interpretation of the Vesta Family

NASA Astrophysics Data System (ADS)

Spoto, Federica; Milani, A.; Cellino, A.; Knezević, Z.; Novaković, B.

2013-10-01

A new classification of asteroids into dynamical families, with a total of 86743 members, has been obtained from 336219 synthetic proper elements sets (http://hamilton.dm.unipi.it/astdys2/index.php?pc=5). From the very fine details of the family structures it is possible to investigate individual collisional events contributing to the formation of the families we now detect as statistical entities. One of the largest is the family of (4) Vesta, with 7865 members. Only fragments with diameter <8 km are in the family. Projected on the proper a-e plane, the dynamical family shows a complex structure, not be the outcome of a single cratering event. The low proper a boundary of the family is defined by the 7/2 mean motion resonance with Jupiter, the high a boundary by the 3/1 resonance. The 1/2 resonance with Mars (at 2.417) cuts across the family, the boundary of the low proper e portion of the family has a very regular shape, suggesting a single cratering event. If we define a subgroup of the family with a<2.417 and e<0.102 we have 5324 members. By assuming all have thesame albedo as Vesta, we can estimate the total volume of the asteroids in the subgroup at 20900 km^3, while the total volume of the family is 32600 km^3. The Rheasilvia crater has a total volume of at least 2 million km^3, indicating that the family formed with the crater was much larger than the current family. Although the age of the cratering generating the subgroup has a significant uncertainty, there is no way it could be more than 500 Myr. The family generated with Rheasilvia must be much older, to have had time to dissipate, with most small asteroids reaching the 3/1 and the g g6 resonances by Yarkovsky effect, others escaping through mean motion resonances. The diffusion processes over time scales of Gyr can be assessed by the asteroids which are likely to be vestoids. For a<2.5 there are 1199 numbered asteroids rated vestoids and not in the (4) family, 504 in the family. Even accounting for false positive in the vestoid criterion, the vestoids outside of the family are more than twice the ones in the family. These should be fragments from previous craterizations.

Pursuing a historical meteor shower

NASA Astrophysics Data System (ADS)

Watanabe, Jun-Ichi; Sato, Mikiya; Kasuga, Toshihiro

2006-11-01

The strong outburst of the Phoenicids was witnessed by people in a Japanese expedition ship, Soya, in 1956. After that, this meteor shower has never been observed at this activity level. Although its parent comet has not been strictly identified, the possible candidate was the comet D/1819W1 (Blanpain) which appeared only once in 1819. A newly discovered asteroid 2003WY25 becomes a clue to the mystery of this meteor shower. We introduce our result on the investigation of this meteor shower on the basis of the dust trail theory.

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.

Near Earth Asteroid Solar Sail Engineering Development Unit Test Program

NASA Technical Reports Server (NTRS)

Lockett, Tiffany Russell; Few, Alexander; Wilson, Richard

2017-01-01

The Near Earth Asteroid (NEA) Scout project is a 30x20x10cm (6U) cubesat reconnaissance mission to investigate a near Earth asteroid utilizing an 86m2 solar sail as the primary propulsion system. This will be the largest solar sail NASA will launch to date. NEA Scout is a secondary payload currently manifested on the maiden voyage of the Space Launch System in 2018. In development of the solar sail subsystem, design challenges were identified and investigated for packaging within a 6U form factor and deployment in cis-lunar space. Analysis furthered understanding of thermal, stress, and dynamics of the stowed system and matured an integrated sail membrane model for deployed flight dynamics. This paper will address design, fabrication, and lessons learned from the NEA Scout solar sail subsystem engineering development unit. From optical properties of the sail material to folding and spooling the single 86m2 sail, the team has developed a robust deployment system for the solar sail. This paper will also address expected and received test results from ascent vent, random vibration, and deployment tests.

New Variable Stars Discovered by Data Mining Images Taken during Recent Asteroid Photometric Observations. II. Results from July 2015 through December 2016

NASA Astrophysics Data System (ADS)

Papini, R.; Marchini, A.; Salvaggio, F.; Agnetti, D.; Bacci, P.; Banfi, M.; Bianciardi, G.; Collina, M.; Franco, L.; Galli, G.; Milani, M. G. A.; Lopresti, C.; Marino, G.; Rizzuti, L.; Ruocco, N.; Quadri, U.

2017-12-01

This paper follows the previous publication of new variables discovered at Astronomical Observatory, DSFTA, University of Siena, while observing asteroids in order to determine their rotational periods. Usually, this task requires time series images acquisition on a single field for as long as possible on a few nights not necessarily consecutive. Checking continually this "goldmine" allowed us to discover 57 variable stars not yet listed in catalogues or databases. While most of the new variables are eclipsing binaries, a few belong to the RR Lyrae or delta Scuti class. Since asteroid work is definitely a time-consuming activity, coordinated campaigns of follow-up with other observatories have been fundamental in order to determine the elements of the ephemeris and sometimes the right subclass of variability. Further observations of these new variables are therefore strongly encouraged in order to better characterize these stars, especially pulsating ones whose data combined with those taken during professional surveys seem to suggest the presence of light curve amplitude and period variations.

Habitat Concepts for Deep Space Exploration

NASA Technical Reports Server (NTRS)

Smitherman, David; Griffin, Brand N.

2014-01-01

Future missions under consideration requiring human habitation beyond the International Space Station (ISS) include deep space habitats in the lunar vicinity to support asteroid retrieval missions, human and robotic lunar missions, satellite servicing, and Mars vehicle servicing missions. Habitat designs are also under consideration for missions beyond the Earth-Moon system, including transfers to near-Earth asteroids and Mars orbital destinations. A variety of habitat layouts have been considered, including those derived from the existing ISS designs and those that could be fabricated from the Space Launch System (SLS) propellant tanks. This paper presents a comparison showing several options for asteroid, lunar, and Mars mission habitats using ISS derived and SLS derived modules and identifies some of the advantages and disadvantages inherent in each. Key findings indicate that the larger SLS diameter modules offer built-in compatibility with the launch vehicle, single launch capability without on-orbit assembly, improved radiation protection, lighter structures per unit volume, and sufficient volume to accommodate consumables for long duration missions without resupply. The information provided with the findings includes mass and volume comparison data that should be helpful to future exploration mission planning efforts.

Single-Parent Family Forms and Children's Educational Performance in a Comparative Perspective: Effects of School's Share of Single-Parent Families

ERIC Educational Resources Information Center

de Lange, Marloes; Dronkers, Jaap; Wolbers, Maarten H. J.

2014-01-01

Living in a single-parent family is negatively related with children's educational performance compared to living with 2 biological parents. In this article, we aim to find out to what extent the context of the school's share of single-parent families affects this negative relationship. We use pooled data from the Organisation for Economic…

76 FR 55066 - Agency Information Collection Request. 30-Day Public Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-06

... Survey of Single Parent Caregivers--OMB No. 0990-NEW-OWH; HHS, Office on Women's Health. Abstract: The National Survey of Single Parent Caregivers will measure the size, characteristics, and unmet needs of single parents providing care for an adult family member or friend. Single parent caregivers provide...

Parental Divorce, Parental Religious Characteristics, and Religious Outcomes in Adulthood.

PubMed

Uecker, Jeremy E; Ellison, Christopher G

2012-12-01

Parental divorce has been linked to religious outcomes in adulthood. Previous research has not adequately accounted for parental religious characteristics or subsequent family context, namely whether one's custodial parent remarries. Using pooled data from three waves of the General Social Survey, we examine the relationships among parental divorce, subsequent family structure, and religiosity in adulthood. Growing up in a single-parent family-but not a stepparent family-is positively associated with religious disaffiliation and religious switching and negatively associated with regular religious attendance. Accounting for parental religious characteristics, however, explains sizable proportions of these relationships. Accounting for parental religious affiliation and attendance, growing up with a single parent does not significantly affect religious attendance. Parental religiosity also moderates the relationship between growing up with a single parent and religious attendance: being raised in a single-parent home has a negative effect on religious attendance among adults who had two religiously involved parents.

Parental Divorce, Parental Religious Characteristics, and Religious Outcomes in Adulthood

PubMed Central

Uecker, Jeremy E.; Ellison, Christopher G.

2013-01-01

Parental divorce has been linked to religious outcomes in adulthood. Previous research has not adequately accounted for parental religious characteristics or subsequent family context, namely whether one’s custodial parent remarries. Using pooled data from three waves of the General Social Survey, we examine the relationships among parental divorce, subsequent family structure, and religiosity in adulthood. Growing up in a single-parent family—but not a stepparent family—is positively associated with religious disaffiliation and religious switching and negatively associated with regular religious attendance. Accounting for parental religious characteristics, however, explains sizable proportions of these relationships. Accounting for parental religious affiliation and attendance, growing up with a single parent does not significantly affect religious attendance. Parental religiosity also moderates the relationship between growing up with a single parent and religious attendance: being raised in a single-parent home has a negative effect on religious attendance among adults who had two religiously involved parents. PMID:23357965

A Comprehensive Study of Chelyabinsk Meteorite: Physical, Mineralogical, Spectral Properties and Solar System Orbit

NASA Astrophysics Data System (ADS)

Gritsevich, Maria; Kohout, T.; Grokhovsky, V.; Yakovlev, G.; Lyytinen, E.; Vinnikov, V.; Haloda, J.; Halodova, P.; Michallik, R.; Penttilä, A.; Muinonen, K.; Peltoniemi, J.; Lupovka, V.; Dmitriev, V.

2013-10-01

On February 15, 2013, at 9:22 am, an exceptionally bright and long duration fireball was observed by many eyewitnesses in the Chelyabinsk region, Russia. A strong shock wave associated with the fireball caused significant damage such as destroyed windows and parts of buildings in Chelyabinsk and the surrounding territories. A number of video records of the event are available and have been used to reconstruct atmospheric trajectory, velocity, deceleration rate, and parent asteroid Apollo-type orbit in the Solar System. Two types of meteorite material are present among recovered fragments of the Chelyabinsk meteorite. These are described as the light-colored and dark-colored lithology. Both types are of LL5 composition with the dark-colored one being an impact-melt shocked to a higher level. Based on the magnetic susceptibility measurements, the Chelyabinsk meteorite is richer in metallic iron as compared to other LL chondrites. The measured bulk and grain densities and the porosity closely resemble other LL chondrites. Shock darkening does not have a significant effect on the material physical properties, but causes a decrease of reflectance and decrease in silicate absorption bands in the reflectance spectra. This is similar to the space weathering effects observed on asteroids. However, no spectral slope change similar to space weathering is observed as a result of shock-darkening. Thus, it is possible that some dark asteroids with invisible silicate absorption bands may be composed of relatively fresh shock darkened chondritic material.

Amino Acids in the Asteroidal Water-Bearing Salt Crystals Hosted in the Zag Meteorite

NASA Technical Reports Server (NTRS)

Chan, Q. H. S.; Zolensky, M. E.; Burton, A. S.; Locke, D. R.

2016-01-01

Solid evidence of liquid water in primitive meteorites is given by the ordinary chondrites H5 Monahans (1998) and H3-6 Zag. Aqueous fluid inclusion-bearing halite (NaCl) crystals were shown to be common in Zag. These striking blue/purple crystals (Figure 1), which gained the coloration from electron-trapping in the Cl-vacancies through exposure to ionizing radiation, were determined to be over 4.0-4.7 billion years old by I-Xe dating. The halite grains are present as discrete grains within an H-chondrite matrix with no evidence for aqueous alteration that indicates a xenogenic source, possibly ancient cryovolcanism. They were proposed to be formed from the cryovolcanic plumes on icy C-type asteroids (possibly Ceres), and were transferred and incorporated into the H chondrite parent asteroid following the eruption event(s). A unique aspect of these halites is that they contain abundant solid inclusions hosted within the halites alongside the water inclusions. The solid inclusions were suggested to be entrained within the fluid erupted from the cryovolcanic event(s), and were shown to be comprised of abundant organics. Spectrofluorometric study and Raman imaging of the halites have identified macromolecular carbon and aliphatic carbon compounds. In order to investigate the type of organics present in Zag and in particular within the fluid-bearing halites, we studied for the first time the amino acid contents of a selected mineral (halite) phase in a meteorite sample.

Binary asteroid population. 2. Anisotropic distribution of orbit poles of small, inner main-belt binaries

NASA Astrophysics Data System (ADS)

Pravec, P.; Scheirich, P.; Vokrouhlický, D.; Harris, A. W.; Kušnirák, P.; Hornoch, K.; Pray, D. P.; Higgins, D.; Galád, A.; Világi, J.; Gajdoš, Š.; Kornoš, L.; Oey, J.; Husárik, M.; Cooney, W. R.; Gross, J.; Terrell, D.; Durkee, R.; Pollock, J.; Reichart, D. E.; Ivarsen, K.; Haislip, J.; LaCluyze, A.; Krugly, Yu. N.; Gaftonyuk, N.; Stephens, R. D.; Dyvig, R.; Reddy, V.; Chiorny, V.; Vaduvescu, O.; Longa-Peña, P.; Tudorica, A.; Warner, B. D.; Masi, G.; Brinsfield, J.; Gonçalves, R.; Brown, P.; Krzeminski, Z.; Gerashchenko, O.; Shevchenko, V.; Molotov, I.; Marchis, F.

2012-03-01

Our photometric observations of 18 main-belt binary systems in more than one apparition revealed a strikingly high number of 15 having positively re-observed mutual events in the return apparitions. Our simulations of the survey showed that it cannot be due to an observational selection effect and that the data strongly suggest that poles of mutual orbits between components of binary asteroids in the primary size range 3-8 km are not distributed randomly: The null hypothesis of an isotropic distribution of the orbit poles is rejected at a confidence level greater than 99.99%. Binary orbit poles concentrate at high ecliptic latitudes, within 30° of the poles of the ecliptic. We propose that the binary orbit poles oriented preferentially up/down-right are due to either of the two processes: (i) the YORP tilt of spin axes of their parent bodies toward the asymptotic states near obliquities 0° and 180° (pre-formation mechanism) or (ii) the YORP tilt of spin axes of the primary components of already formed binary systems toward the asymptotic states near obliquities 0° and 180° (post-formation mechanism). The alternative process of elimination of binaries with poles closer to the ecliptic by dynamical instability, such as the Kozai effect due to gravitational perturbations from the Sun, does not explain the observed orbit pole concentration. This is because for close binary asteroid systems, the gravitational effects of primary’s irregular shape dominate the solar-tide effect.

Organic Compounds Produced by Photolysis of Realistic Interstellar and Cometary Ice Analogs Containing Methanol

NASA Technical Reports Server (NTRS)

Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Chang, Sherwood; Scharberg, Maureen A.

1995-01-01

The InfraRed (IR) spectra of UltraViolet (UV) and thermally processed, methanol-containing interstellar / cometary ice analogs at temperatures from 12 to 300 K are presented. Infrared spectroscopy, H-1 and C-13 Nuclear Magnetic Resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry indicate that CO (carbon monoxide), CO2 (carbon dioxide), CH4 (methane), HCO (the formyl radical), H2CO (formaldehyde), CH3CH2OH (ethanol), HC([double bond]O)NH2 (formamide), CH3C([double bond]O)NH2 (acetamide), and R[single bond]C[triple bond]N (nitriles) are formed. In addition, the organic materials remaining after photolyzed ice analogs have been warmed to room temperature contain (in rough order of decreasing abundance), (1) hexamethylenetetramine (HMT, C6H12N4), (2) ethers, alcohols, and compounds related to PolyOxyMethylene (POM, ([single bond]CH2O[single bond](sub n)), and (3) ketones (R[single bond]C([double bond]O)[single bond]R') and amides (H2NC([double bond]O)[single bond]R). Most of the carbon in these residues is thought to come from the methanol in the original ice. Deuterium and C-13 isotopic labeling demonstrates that methanol is definitely the source of carbon in HMT. High concentrations of HMT in interstellar and cometary ices could have important astrophysical consequences. The ultraviolet photolysis of HMT frozen in H2O ice readily produces the 'XCN' band observed in the spectra of protostellar objects and laboratory ices, as well as other nitriles. Thus, HMT may be a precursor of XCN and a source of CN in comets and the interstellar medium. Also, HMT is known to hydrolyze under acidic conditions to yield ammonia, formaldehyde, and amino acids. Thus, HMT may be a significant source of prebiogenic compounds on asteroidal parent bodies. A potential mechanism for the radiative formation of HMT in cosmic ices is outlined.

Linear structures on the small inner satellites of Saturn

NASA Technical Reports Server (NTRS)

Stooke, Philip J.

1993-01-01

Shape modelling methods developed for non-spherical worlds were applied to four satellites of Saturn: Prometheus, Pandora, Janus, and Epimetheus. This results in the first detailed shaded relief maps of their surfaces. Ridges and valleys are described with their implications for satellite history and asteroid 951 Gaspra. They probably result from fracturing during break-up of parent bodies and/or later large impacts. Prometheus and perhaps Gaspra may be coated with debris from parent body fragmentation as well as more recent regolith. These four satellites are covered by relatively few useful images, so the shapes are imperfectly known and positions of features on maps may be wrong by up to a few tens of degrees in some areas (worst where a feature is seen only near a limb). Nevertheless, these shape models are more useful than the previous triaxial ellipsoid models.

Cretaceous-Tertiary findings, paradigms and problems

NASA Technical Reports Server (NTRS)

Officer, C. B.; Drake, C. L.

1988-01-01

The asteroid hypothesis has stimulated numerous studies of the paleontological record at Cretaceous/Tertiary time as well as of geological indicators of environmental crisis preserved in the rock record. Both extinctions and geological anomalies often occur at times that do not appear to be synchronous or instantaneous. The record includes paleontological indicators of dinosaurs, terrestrial flora, marine planktonic organisms, and shallow water marine macrofauna and geological phenomena include occurrences of iridium and other platinum metals, trace elements, clay mineralogy, shocked minerals, soot, microspherules, and isotopes of osmium, strontium and carbon. These findings are reviewed in the context of the alternate hypotheses of an exogenic cause, involving either a single asteroid impact or multiple commentary impacts, and an endogenic cause, involving intense global volcanism and major sea level regression.

KSC-07pd2066

NASA Image and Video Library

2007-07-22

KENNEDY SPACE CENTER, FLA. — At the Astrotech payload processing facility, workers guide the movement of the upper canister being lifted from the Dawn spacecraft, seen encased in a protective cover. Dawn was returned from Launch Pad 17-B at Cape Canaveral Air Force Station to Astrotech to await a new launch date. The launch opportunity extends from Sept. 7 to Oct. 15. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA’s first purely scientific mission powered by three solar electric ion propulsion engines. NASA/Charisse Nahser

KSC-07pd1673

NASA Image and Video Library

2007-06-27

KENNEDY SPACE CENTER, FLA. -- On Launch Pad 17-B at Cape Canaveral Air Force Station, workers supervise the lowering of NASA's Dawn spacecraft in the mobile service tower. The spacecraft is clad in a shipping canister for its transport from Astrotech in Titusville, Fla. The canister will be removed and the spacecraft prepared for launch. Launch is scheduled for July 7. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines. Photo credit: NASA/Cory Huston

Cosmic-Ray-Exposure Ages of Diogenites and the Collisional History of the HED Parent Body or Bodies

NASA Technical Reports Server (NTRS)

Welten, K. C.; Lindner, L.; vanderBorg, K.; Loeken, T.; Scherer, P.; Schultz, L.

1996-01-01

Cosmic-ray-exposure ages of meteorites provide information on the collisional history of their parent bodies and the delivery mechanism of meteorites to Earth. The exposure-age distributions of ordinary chondrites show distinct patterns for H, L, and LL types, consistent with their origin on different parent bodies. The exposure-age distributions of howardites, eucrites. and diogenites (HEDS) show a common pattern with major peaks at 22 Ma and 38 Ma This provides additional evidence for a common origin of the HED meteorites, possibly 4 Vesta, although orbital dynamics calculations showed that the delivery of meteorites from Vesta to Earth is difficult. However, the discovery of several kilometer-sized Vesta-like asteroids in the region between Vesta and the 3:1 resonance suggested that these seem more likely parent bodies of the HEDs than Vesta itself. This implies that the exposure-age clusters may represent samples of several parent bodies. Therefore, the near-absence of diogenites with ages <20 Ma might be of interest for the composition of these kilometer-sized fragments of Vesta. Here we present cosmic-ray-exposure ages of 20 diogenites, including 9 new meteorites. In addition, we calculate the probability for each peak to occur by chance, assuming a constant production rate of HED fragments.

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.

Asteroid mass estimation using Markov-chain Monte Carlo

NASA Astrophysics Data System (ADS)

Siltala, Lauri; Granvik, Mikael

2017-11-01

Estimates for asteroid masses are based on their gravitational perturbations on the orbits of other objects such as Mars, spacecraft, or other asteroids and/or their satellites. In the case of asteroid-asteroid perturbations, this leads to an inverse problem in at least 13 dimensions where the aim is to derive the mass of the perturbing asteroid(s) and six orbital elements for both the perturbing asteroid(s) and the test asteroid(s) based on astrometric observations. We have developed and implemented three different mass estimation algorithms utilizing asteroid-asteroid perturbations: the very rough 'marching' approximation, in which the asteroids' orbital elements are not fitted, thereby reducing the problem to a one-dimensional estimation of the mass, an implementation of the Nelder-Mead simplex method, and most significantly, a Markov-chain Monte Carlo (MCMC) approach. We describe each of these algorithms with particular focus on the MCMC algorithm, and present example results using both synthetic and real data. Our results agree with the published mass estimates, but suggest that the published uncertainties may be misleading as a consequence of using linearized mass-estimation methods. Finally, we discuss remaining challenges with the algorithms as well as future plans.

Self-organizing control strategy for asteroid intelligent detection swarm based on attraction and repulsion

NASA Astrophysics Data System (ADS)

An, Meiyan; Wang, Zhaokui; Zhang, Yulin

2017-01-01

The self-organizing control strategy for asteroid intelligent detection swarm, which is considered as a space application instance of intelligent swarm, is developed. The leader-follower model for the asteroid intelligent detection swarm is established, and the further analysis is conducted for massive asteroid and small asteroid. For a massive asteroid, the leader spacecraft flies under the gravity field of the asteroid. For a small asteroid, the asteroid gravity is negligible, and a trajectory planning method is proposed based on elliptic cavity virtual potential field. The self-organizing control strategy for the follower spacecraft is developed based on a mechanism of velocity planning and velocity tracking. The simulation results show that the self-organizing control strategy is valid for both massive asteroid and small asteroid, and the exploration swarm forms a stable configuration.

Amino acids in the Tagish Lake Meteorite

NASA Technical Reports Server (NTRS)

Kminek, G.; Botta, O.; Glavin, D. P.; Bada, J. L.

2002-01-01

High-performance liquid chromatography (HPLC) based amino acid analysis of a Tagish Lake meteorite sample recovered 3 months after the meteorite fell to Earth have revealed that the amino acid composition of Tagish Lake is strikingly different from that of the CM and CI carbonaceous chondrites. We found that the Tagish Lake meteorite contains only trace levels of amino acids (total abundance = 880 ppb), which is much lower than the total abundance of amino acids in the CI Orgueil (4100 ppb) and the CM Murchison (16 900 ppb). Because most of the same amino acids found in the Tagish Lake meteorite are also present in the Tagish Lake ice melt water, we conclude that the amino acids detected in the meteorite are terrestrial contamination. We found that the exposure of a sample of Murchison to cold water lead to a substantial reduction over a period of several weeks in the amount of amino acids that are not strongly bound to the meteorite matrix. However, strongly bound amino acids that are extracted by direct HCl hydrolysis are not affected by the leaching process. Thus even if there had been leaching of amino acids from our Tagish Lake meteorite sample during its 3 month residence in Tagish Lake ice and melt water, a Murchison type abundance of endogenous amino acids in the meteorite would have still been readily detectable. The low amino acid content of Tagish Lake indicates that this meteorite originated fiom a different type of parent body than the CM and CI chondrites. The parent body was apparently devoid of the reagents such as aldehyldes/ketones, HCN and ammonia needed for the effective abiotic synthesis of amino acids. Based on reflectance spectral measurements, Tagish Lake has been associated with P- or D-type asteroids. If the Tagish Lake meteorite was indeed derived fiom these types of parent bodies, our understanding of these primitive asteroids needs to be reevaluated with respect to their potential inventory of biologically important organic compounds.

BILLIARDS: Baseline Instrumented Lithology Lander, Inspector and Asteroid Redirection Demonstration System

NASA Technical Reports Server (NTRS)

Marcus, Matthew; Sloane, Joshua; Ortiz, Oliver; Barbee, Brent

2015-01-01

BILLIARDS Baseline Instrumented Lithology Lander, Inspector, and Asteroid Redirection Demonstration System Proposed demonstration mission for Billiard-Ball concept Select asteroid pair with natural close approach to minimize cost and complexity Primary Objectives Rendezvous with a small (10m), near Earth (alpha) asteroid Maneuver the alpha asteroid to a collision with a 100m (beta) asteroid Produce a detectable deflection or disruption of the beta asteroid Secondary objectives Contribute knowledge of asteroid composition and characteristics Contribute knowledge of small-body formation Opportunity for international collaboration

Single Parent and Homemaker Projects Resource Notebook (Working Copy).

ERIC Educational Resources Information Center

Ohio State Dept. of Education, Columbus. Div. of Vocational and Career Education.

This guide is intended to assist developers and providers of programs for single parents and homemakers. The first section discusses the special needs of single parents and homemakers, the provisions of the Carl D. Perkins Vocational Education Act of 1984, and Ohio's single parent and homemaker projects. Section 2 covers the the following aspects…

Asteroid team

NASA Technical Reports Server (NTRS)

Matson, D. L.

1988-01-01

The purpose of this task is to support asteroid research and the operation of an Asteroid Team within the Earth and Space Sciences Division at the Jet Propulsion Laboratory (JPL). The Asteroid Team carries out original research on asteroids in order to discover, better characterize and define asteroid properties. This information is needed for the planning and design of NASA asteroid flyby and rendezvous missions. The asteroid Team also provides scientific and technical advice to NASA and JPL on asteroid related programs. Work on asteroid classification continued and the discovery of two Earth-approaching M asteroids was published. In the asteroid photometry program researchers obtained N or Q photometry for more than 50 asteroids, including the two M-earth-crossers. Compositional analysis of infrared spectra (0.8 to 2.6 micrometer) of asteroids is continuing. Over the next year the work on asteroid classification and composition will continue with the analysis of the 60 reduced infrared spectra which we now have at hand. The radiometry program will continue with the reduction of the N and Q bandpass data for the 57 asteroids in order to obtain albedos and diameters. This year the emphasis will shift to IRAS follow-up observations; which includes objects not observed by IRAS and objects with poor or peculiar IRAS data. As in previous year, we plan to give top priority to any opportunities for observing near-Earth asteroids and the support (through radiometric lightcurve observations from the IRTF) of any stellar occultations by asteroids for which occultation observation expeditions are fielded. Support of preparing of IRAS data for publication and of D. Matson for his participation in the NASA Planetary Astronomy Management and Operations Working Group will continue.

International Asteroid Mission (IAM)

NASA Astrophysics Data System (ADS)

Yamaguchi, Ryuuji

1991-07-01

International Asteroid Mission (IAM) is a program aimed at developing resources of asteroids abundantly existing near the earth. This report describes the research results of design project of the International Space University (ISU) held in 1990 at Tront-York University. ISU research and asteroid survey results, and the manned asteroid mining mission are outlined. Classification of asteroids existing near the earth and asteroid resource processing and use analyses are conducted. Asteroid selection flow charts are introduced, and the 1982HR-Orpheus is selected as a candidate asteroid because it takes an approaching orbit toward the earth, requires small delta V, and possesses abundant carbonaceous chondrites. Characteristics of 1982HR-Orpheus are presented. Mission requirements, mission outlines, transportation systems, and mining and processing systems for manned asteroid mining missions are presented.

Serra Pelada: the first Amazonian Meteorite fall is a Eucrite (basalt) from Asteroid 4-Vesta.

PubMed

Zucolotto, Maria Elizabeth; Tosi, Amanda A; Villaça, Caio V N; Moutinho, André L R; Andrade, Diana P P; Faulstich, Fabiano; Gomes, Angelo M S; Rios, Debora C; Rocha, Marcilio C

2018-01-01

Serra Pelada is the newest Brazilian eucrite and the first recovered fall from Amazonia (State of Pará, Brazil, June 29th 2017). In this paper, we report on its petrography, chemistry, mineralogy and its magnetic properties. Study of four thin sections reveals that the meteorite is brecciated, containing basaltic and gabbroic clasts, as well of recrystallized impact melt, embedded into a fine-medium grained matrix. Chemical analyses suggest that Serra Pelada is a monomict basaltic eucritic breccia, and that the meteorite is a normal member of the HED suite. Our results provide additional geological and compositional information on the lithological diversity of its parent body. The mineralogy of Serra Pelada consists basically of low-Ca pyroxene and high-Ca plagioclase with accessory minerals such as quartz, sulphide (troilite), chromite - ulvöspinel and ilmenite. These data are consistent with the meteorite being an eucrite, a basaltic achondrite and a member of the howardite-eucrite-diogenite (HED) clan of meteorites which most likely are from the crust asteroid 4 Vesta.

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.

Single Mother Parenting and Adolescent Psychopathology.

PubMed

Daryanani, Issar; Hamilton, Jessica L; Abramson, Lyn Y; Alloy, Lauren B

2016-10-01

Children raised in single-mother families are at increased risk for psychopathology, but the mechanisms that help explain this relationship are understudied. In a community sample of diverse adolescents (N = 385, 52 % female, 48 % Caucasian) and their mothers, we hypothesized that single mothers would be more likely than cohabitating mothers to engage in negative parenting behaviors, which would predict adolescent psychopathology prospectively. Single mothers were more likely to engage in psychologically controlling behaviors, which predicted to their adolescent offspring experiencing higher rates of depressive symptoms and externalizing disorders. Girls were more susceptible to depressive symptoms via psychologically controlling parenting than boys in single-mother families. Further, single mothers were more likely to engage in rejecting parenting behaviors, which predicted to a higher prevalence of adolescent externalizing disorders. Surprisingly, rejection in single-mother families predicted to less severe anxiety symptoms in adolescents relative to two-parent families. It is likely that single mothers are not inherently inferior parents relative to cohabitating mothers; rather, their parenting practices are often compromised by a myriad of demands and stressors. Consistent with this postulate, low socioeconomic status was associated with single motherhood and negative parenting behaviors. Clinical implications and study limitations are discussed.

Single Mother Parenting and Adolescent Psychopathology

PubMed Central

Daryanai, Issar; Hamilton, Jessica L.; Abramson, Lyn Y.; Alloy, Lauren B.

2017-01-01

Children raised in single-mother families are at increased risk for psychopathology, but the mechanisms that help explain this relationship are understudied. In a community sample of diverse adolescents (N= 385, 52% female, 48% Caucasian) and their mothers, we hypothesized that single mothers would be more likely than cohabitating mothers to engage in negative parenting behaviors, which would predict adolescent psychopathology prospectively. Single mothers were more likely to engage in psychologically controlling behaviors, which predicted to their adolescent offspring experiencing higher rates of depressive symptoms and externalizing disorders. Girls were more susceptible to depressive symptoms via psychologically controlling parenting than boys in single-mother families. Further, single mothers were more likely to engage in rejecting parenting behaviors, which predicted to a higher prevalence of adolescent externalizing disorders. Surprisingly, rejection in single-mother families predicted to less severe anxiety symptoms in adolescents relative to two-parent families. It is likely that single mothers are not inherently inferior parents relative to cohabitating mothers; rather, their parenting practices are often compromised by a myriad of demands and stressors. Consistent with this postulate, low socioeconomic status was associated with single motherhood and negative parenting behaviors. Clinical implications and study limitations are discussed. PMID:26767832

Wet, Carbonaceous Asteroids: Altering Minerals, Changing Amino Acids

NASA Astrophysics Data System (ADS)

Taylor, G. J.

2011-04-01

Many carbonaceous chondrites contain alteration products from water-rock interactions at low temperature and organic compounds. A fascinating fact known for decades is the presence in some of them of an assortment of organic compounds, including amino acids, sometimes called the building blocks of life. Murchison and other CM carbonaceous chondrites contain hundreds of amino acids. Early measurements indicated that the amino acids in carbonaceous chondrites had equal proportions of L- and D-structures, a situation called racemic. This was in sharp contrast to life on Earth, which heavily favors L- forms. However, beginning in 1997, John Cronin and Sandra Pizzarello (Arizona State University) found L- excesses in isovaline and several other amino acids in the Murchison carbonaceous chondrite. In 2009, Daniel Glavin and Jason Dworkin (Astrobiology Analytical Lab, Goddard Space Flight Center) reported the first independent confirmation of L-isovaline excesses in Murchison using a different analytical technique than employed by Cronin and Pizzarello. Inspired by this work, Daniel Glavin, Michael Callahan, Jason Dworkin, and Jamie Elsila (Astrobiology Analytical Lab, Goddard Space Flight Center), have done an extensive study of the abundance and symmetry of amino acids in carbonaceous chondrites that experienced a range of alteration by water in their parent asteroids. The results show that amino acids are more abundant in the less altered meteorites, implying that aqueous processing changes the mix of amino acids. They also confirmed the enrichment in L-structures of some amino acids, especially isovaline, confirming earlier work. The authors suggest that aqueously-altered planetesimals might have seeded the early Earth with nonracemic amino acids, perhaps explaining why life from microorganisms to people use only L- forms to make proteins. The initial imbalance caused by non-biologic processes in wet asteroids might have been amplified by life on Earth. Alternatively, the same processes that produced the L-amino acid excesses in carbonaceous asteroids also operated on the early Earth.

Re-accumulation Scenarios Governing Final Global Shapes of Rubble-Pile Asteroids

NASA Astrophysics Data System (ADS)

Hestroffer, Daniel; Tanga, P.; Comito, C.; Paolicchi, P.; Walsh, K.; Richardson, D. C.; Cellino, A.

2009-05-01

Asteroids, since the formation of the solar system, are known to have experienced catastrophic collisions, which---depending on the impact energy---can produce a major disruption of the parent body and possibly give birth to asteroid families or binaries [1]. We present a general study of the final shape and dynamical state of asteroids produced by the re-accumulation process following a catastrophic disruption. Starting from a cloud of massive particles (mono-disperse spheres) with given density and velocity distributions, we analyse the final shape, spin state, and angular momentum of the system from numerical integration of a N-body gravitational system (code pkdgrav [2]). The re-accumulation process itself is relatively fast, with a dynamical time corresponding to the spin-period of the final body (several hours). The final global shapes---which are described as tri-axial ellipsoids---exhibit slopes consistent with a degree of shear stress sustained by interlocking particles. We point out a few results: -the final shapes are close to those of hydrostatic equilibrium for incompressible fluids, preferably Maclaurin spheroid rather than Jacobi ellipsoids -for bodies closest to the sequence of hydrostatic equilibrium, there is a direct relation between spin, density and outer shape, suggesting that the outer surface is nearly equipotential -the evolution of the shape during the process follows a track along a gradient of potential energy, without necessarily reaching its minimum -the loose random packing of the particles implies low friction angle and hence fluid-like behaviour, which extends the results of [3]. Future steps of our analysis will include feature refinements of the model initial conditions and re-accumulation process, including impact shakings, realistic velocity distributions, and non equal-sized elementary spheres. References [1] Michel P. et al. 2001. Science 294, 1696 [2] Leinhardt Z.M. et al. 2000. Icarus 146, 133 [3] Richardson D.C. et al. 2005. Icarus 173, 349

Yarkovsky footprints in the Eos family

NASA Astrophysics Data System (ADS)

Vokrouhlický, D.; Brož, M.; Morbidelli, A.; Bottke, W. F.; Nesvorný, D.; Lazzaro, D.; Rivkin, A. S.

2006-05-01

The Eos asteroid family is the third most populous, after Themis and Koronis, and one of the largest non-random groups of asteroids in the main belt. It has been known and studied for decades, but its structure and history still presented difficulties to understand. We first revise the Eos family identification as a statistical cluster in the space of proper elements. Using the most to-date catalogue of proper elements we determine a nominal Eos family, defined by us using the hierarchical-clustering method with the cut-off velocity of 55 m/s, contains some 4400 members. This unforeseen increase in known Eos asteroids allows us to perform a much more detailed study than was possible so far. We show, in particular, that most of the previously thought peculiar features are explained within the following model: (i) collisional disruption of the parent body leads to formation of a compact family in the proper element space (with characteristic escape velocities of the observed asteroids of tens of meters per second, compatible with hydrocode simulations), and (ii) as time goes, the family dynamically evolves due to a combination of the thermal effects and planetary perturbations. This model allows us to explain sharp termination of the family at the J7/3 mean motion resonance with Jupiter, uneven distribution of family members about the J9/4 mean motion resonance with Jupiter, semimajor axis distribution of large vs small members in the family and anomalous residence of Eos members inside the high-order secular resonance z. Our dynamical method also allows us to estimate Eos family age to 1.3-0.2+0.15 Gyr. Several formal members of the Eos family are in conflict with our model and these are suspected interlopers. We use spectroscopic observations, whose results are also reported here, and results of 5-color wide-band Sloan Digital Sky Survey photometry to prove some of them are indeed spectrally incompatible with the family.

Mature and Fresh Surfaces on New-Born Asteroid Karin

NASA Astrophysics Data System (ADS)

Sasaki, S.; Sasaki, T.; Watanabe, J.; Sekiguchi, T.; Yoshida, F.; Ito, T.; Kawakita, H.; Fuse, T.; Takato, N.; Dermawan, B.

2004-11-01

We report a near-infrared (J, H, and K bands) spectroscopy of the brightest asteroid 832 Karin among the Karin cluster group, which was formed by collisional breakup only 5.8 million years ago. The spectroscopic observation was performed by the Subaru telescope with Cooled Infrared Spectrograph and Camera for OHS (CISCO) on 2003 September 14. To obtain a wide range spectrum, grisms named zJ (0.88-1.40 micron), JH (1.06-1.82 micron), and wK (1.85-2.51 micron) were used. We obtained 3 sets of spectra corresponding to the rotational phase 0.30-0.34, 0.35-0.38, and 0.45-0.50 in comparison with lightcurve observations. Near infrared (0.9-1.4micron) reflectance slope of the 1st set was twice as steep as that of later spectra. The range, where the most significant spectral change was detected, was observed both by zJ and JH bands. Gradual change of the spectral slope is detected through zJ(1st) - JH(1st) - zJ(2nd) - JH(2nd) data . We verified that spectra of a reference star SAO165395 (zJ) were not changed before the 1st set and after the 2nd set of Karin observation, which should remove the possibility that the spectral change was caused by instrumental or atmospheric (and hour angle) effect through the observation of the 1st set and the 2nd set of Karin. For different rotational phases of Karin, we derived different spectra such as a reddened spectrum like that of S-type asteroid and an un-reddened spectrum like that of ordinary chondrite. Karin would be an impact fragment which not only has new surface but also preserves old surface. Probably it would be one of cone-shaped fragments at low-velocity impact forming Karin cluster group. Our result supports the idea that S-type asteroids are parent bodies of ordinary chondrites.

Planetary Defense: Are we currently looking for our keys under the lamp post?

NASA Astrophysics Data System (ADS)

Nuth, J. A., III; Barbee, B.; Leung, R. Y.

2016-12-01

Planetary Defense is a serious and important endeavor and the approach taken to date is a sensible beginning. Finding and cataloging all potentially hazardous asteroids and supporting research into relevant topics required to divert such a threat to our home planet is a necessary, but far from sufficient set of activities required to ensure the survival of our species. Concentrating our efforts on the asteroid threat is relatively easy. Most asteroids move in near-circular orbits, are relatively close to the ecliptic plane and are likely to be detected as hazards many decades in advance of a potential impact. The single most likely problem that will be encountered in deflecting such a threat will be developing the political will to fund the project while there is still ample time for multiple deflection techniques to be applied successfully. While asteroid threats can be mitigated, comets are the invisible danger lurking in the vast, dark parking lot that is the outer solar system. Very few comets falling into the inner solar system will be detected more than two years before their arrival: refinement of a new comet's trajectory requires months of observation before its hazard potential can be realistically assessed and knowledge of the composition, mass and shape of the body cannot be refined sufficiently to design a deflection campaign without much more observational effort. To make matters worse, because of the highly elliptical orbits of most new comets, some of which can be far out of the ecliptic plane while a few can even be in retrograde orbits, the impact velocity of a typical comet will be significantly higher than that of an asteroid. If this increase is only a factor of two, then a typical comet carries four times the impact energy of an asteroid of similar size, though much higher multipliers are possible. The distribution of meteor stream velocities can be examined to place bounds on this threat. Finally, the time required to assemble and launch an asteroid deflection mission starting from scratch and with a high probability of success could exceed three years from mission approval. Based on the recent passage of Comet Siding Spring one must therefore conclude that a successful comet deflection mission must begin well before a hazardous comet is even detected, much less characterized as a significant threat.

34 CFR 403.82 - In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women Program...

Code of Federal Regulations, 2011 CFR

2011-07-01

... Homemakers, and Single Pregnant Women Program be offered? 403.82 Section 403.82 Education Regulations of the... Secretary Assist Under the Basic Programs? Single Parents, Displaced Homemakers, and Single Pregnant Women Program § 403.82 In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women...

34 CFR 403.82 - In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women Program...

Code of Federal Regulations, 2013 CFR

2013-07-01

... Homemakers, and Single Pregnant Women Program be offered? 403.82 Section 403.82 Education Regulations of the... Secretary Assist Under the Basic Programs? Single Parents, Displaced Homemakers, and Single Pregnant Women Program § 403.82 In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women...

34 CFR 403.82 - In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women Program...

Code of Federal Regulations, 2012 CFR

2012-07-01

... Homemakers, and Single Pregnant Women Program be offered? 403.82 Section 403.82 Education Regulations of the... Secretary Assist Under the Basic Programs? Single Parents, Displaced Homemakers, and Single Pregnant Women Program § 403.82 In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women...

34 CFR 403.82 - In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women Program...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Homemakers, and Single Pregnant Women Program be offered? 403.82 Section 403.82 Education Regulations of the... Secretary Assist Under the Basic Programs? Single Parents, Displaced Homemakers, and Single Pregnant Women Program § 403.82 In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women...

34 CFR 403.82 - In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women Program...

Code of Federal Regulations, 2010 CFR

2010-07-01

... Homemakers, and Single Pregnant Women Program be offered? 403.82 Section 403.82 Education Regulations of the... Secretary Assist Under the Basic Programs? Single Parents, Displaced Homemakers, and Single Pregnant Women Program § 403.82 In what settings may the Single Parents, Displaced Homemakers, and Single Pregnant Women...