Deflection by kinetic impact: Sensitivity to asteroid properties

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

Bruck Syal, Megan; Michael Owen, J.; Miller, Paul L.

Impacting an asteroid with a spacecraft traveling at high speed delivers an impulsive change in velocity to the body. In certain circumstances, this strategy could be used to deflect a hazardous asteroid, moving its orbital path off of an Earth-impacting course. However, the efficacy of momentum delivery to asteroids by hypervelocity impact is sensitive to both the impact conditions (particularly velocity) and specific characteristics of the target asteroid. We numerically model asteroid response to kinetic impactors under a wide range of initial conditions, using an Adaptive Smoothed Particle Hydrodynamics code. Impact velocities spanning 1–30 km/s were investigated, yielding, for amore » particular set of assumptions about the modeled target material, a power-law dependence consistent with a velocity-scaling exponent of μ = 0.44. Target characteristics including equation of state, strength model, porosity, rotational state, and shape were varied, and corresponding changes in asteroid response were documented. Moreover, the kinetic-impact momentum-multiplication factor, β, decreases with increasing asteroid cohesion and increasing porosity. Although increased porosity lowers β, larger porosities result in greater deflection velocities, as a consequence of reduced target masses for asteroids of fixed size. Porosity also lowers disruption risk for kinetic impacts near the threshold of disruption. Including fast (P = 2.5 h) and very fast (P = 100 s) rotation did not significantly alter β but did affect the risk of disruption by the impact event. Asteroid shape is found to influence the efficiency of momentum delivery, as local slope conditions can change the orientation of the crater ejecta momentum vector. Our results emphasize the need for asteroid characterization studies to bracket the range of target conditions expected at near-Earth asteroids while also highlighting some of the principal uncertainties associated with the kinetic-impact deflection strategy.« less

Deflection by kinetic impact: Sensitivity to asteroid properties

DOE PAGES

Bruck Syal, Megan; Michael Owen, J.; Miller, Paul L.

2016-05-01

Impacting an asteroid with a spacecraft traveling at high speed delivers an impulsive change in velocity to the body. In certain circumstances, this strategy could be used to deflect a hazardous asteroid, moving its orbital path off of an Earth-impacting course. However, the efficacy of momentum delivery to asteroids by hypervelocity impact is sensitive to both the impact conditions (particularly velocity) and specific characteristics of the target asteroid. We numerically model asteroid response to kinetic impactors under a wide range of initial conditions, using an Adaptive Smoothed Particle Hydrodynamics code. Impact velocities spanning 1–30 km/s were investigated, yielding, for amore » particular set of assumptions about the modeled target material, a power-law dependence consistent with a velocity-scaling exponent of μ = 0.44. Target characteristics including equation of state, strength model, porosity, rotational state, and shape were varied, and corresponding changes in asteroid response were documented. Moreover, the kinetic-impact momentum-multiplication factor, β, decreases with increasing asteroid cohesion and increasing porosity. Although increased porosity lowers β, larger porosities result in greater deflection velocities, as a consequence of reduced target masses for asteroids of fixed size. Porosity also lowers disruption risk for kinetic impacts near the threshold of disruption. Including fast (P = 2.5 h) and very fast (P = 100 s) rotation did not significantly alter β but did affect the risk of disruption by the impact event. Asteroid shape is found to influence the efficiency of momentum delivery, as local slope conditions can change the orientation of the crater ejecta momentum vector. Our results emphasize the need for asteroid characterization studies to bracket the range of target conditions expected at near-Earth asteroids while also highlighting some of the principal uncertainties associated with the kinetic-impact deflection strategy.« less

The Asteroid Impact and Deflection Assessment Mission and its Potential Contributions to Human Exploration of Asteroids

NASA Technical Reports Server (NTRS)

Abell, Paul A.; Rivkin, Andy S.

2014-01-01

The joint ESA and NASA Asteroid Impact and Deflection Assessment (AIDA) mission will directly address aspects of NASA's Asteroid Initiative and will contribute to future human exploration. The NASA Asteroid Initiative is comprised of two major components: the Grand Challenge and the Asteroid Mission. The first component, the Grand Challenge, focuses on protecting Earth's population from asteroid impacts by detecting potentially hazardous objects with enough warning time to either prevent them from impacting the planet, or to implement civil defense procedures. The Asteroid Mission, involves sending astronauts to study and sample a near-Earth asteroid (NEA) prior to conducting exploration missions of the Martian system, which includes Phobos and Deimos. AIDA's primary objective is to demonstrate a kinetic impact deflection and characterize the binary NEA Didymos. The science and technical data obtained from AIDA will aid in the planning of future human exploration missions to NEAs and other small bodies. The dual robotic missions of AIDA, ESA's Asteroid Impact Monitor (AIM) and NASA's Double Asteroid Redirection Test (DART), will provide a great deal of technical and engineering data on spacecraft operations for future human space exploration while conducting in-depth scientific examinations of the binary target Didymos both prior to and after the kinetic impact demonstration. The knowledge gained from this mission will help identify asteroidal physical properties in order to maximize operational efficiency and reduce mission risk for future small body missions. The AIDA data will help fill crucial strategic knowledge gaps concerning asteroid physical characteristics that are relevant for human exploration considerations at similar small body destinations.

Rotational and translational considerations in kinetic impact deflection of potentially hazardous asteroids

NASA Astrophysics Data System (ADS)

Zhang, Fei; Xu, Bo; Circi, Christian; Zhang, Lei

2017-04-01

Kinetic impact may be the most reliable and easily implemented method to deflect hazardous asteroids using current technology. Depending on warning time, it can be effective on asteroids with diameters of a few hundred meters. Current impact deflection research often focuses on the orbital dynamics of asteroids. In this paper, we use the ejection outcome of a general oblique impact to calculate how an asteroid's rotational and translational state changes after impact. The results demonstrate how small impactors affect the dynamical state of small asteroids having a diameter of about 100 m. According to these consequences, we propose using several small impactors to hit an asteroid continuously and gently, making the deflection mission relatively flexible. After calculating the rotational variation, we find that the rotational state, especially of slender non-porous asteroids, can be changed significantly. This gives the possibility of using multiple small impactors to mitigate a potentially hazardous asteroid by spinning it up into pieces, or to despin one for future in-situ investigation (e.g., asteroid retrieval or mining).

AIDA: Asteroid Impact & Deflection Assessment

NASA Astrophysics Data System (ADS)

Cheng, Andrew; Michel, Patrick; Ulamec, Stephan; Reed, Cheryl; Galvez, Andres; Carnelli, Ian

On Feb. 15, 2013, an exceptionally close approach to Earth by the small asteroid 2012 DA14 was eagerly awaited by observers, but another small asteroid impacted Earth over Chelyabinsk, Russia the same day without warning, releasing several hundred kilotons TNT of energy and injuring over 1500 people. These dramatic events remind us of the needs to discover hazardous asteroids and to learn how to mitigate them. The AIDA mission is the first demonstration of a mitigation technique to protect the Earth from a potential asteroid impact, by performing a spacecraft kinetic impact on an asteroid to deflect it from its trajectory. We will provide an update on the status of parallel AIDA mission studies supported by ESA and NASA. AIDA is an international collaboration consisting of two independent but mutually supporting missions, one of which is the asteroid kinetic impactor, and the other is the characterization spacecraft which will orbit the asteroid system to monitor the deflection experiment and measure the results. These two missions are the NASA Double Asteroid Redirection Test (DART), which is the kinetic impactor, and the European Space Agency's Asteroid Impact Monitoring (AIM) mission, which is the characterization spacecraft. The target of the AIDA mission will be a binary asteroid, in which DART will target the secondary, smaller member in order to deflect the binary orbit. The resulting period change can be measured to within 10% by ground-based observations. The asteroid deflection will be measured to higher accuracy, and additional results of the DART impact, like the impact crater, will be studied in great detail by the AIM mission. AIDA will return vital data to determine the momentum transfer efficiency of the kinetic impact and key physical properties of the target asteroid. The two mission components of AIDA, DART and AIM, are each independently valuable, but when combined they provide a greatly increased knowledge return. The AIDA mission will combine US and European space experience and expertise to address an international problem, the asteroid impact hazard. AIDA will also be a valuable precursor to human spaceflight to an asteroid, as it would return unique information on an asteroid's strength and internal structure and would be particularly relevant to a human mission for asteroid mitigation. AIDA will furthermore return fundamental new science data on impact cratering, surface properties and interior structure. AIDA will target the binary Near-Earth asteroid Didymos with two independently launched spacecraft, with the deflection experiment to occur in October, 2022.

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.

Impact risk assessment and planetary defense mission planning for asteroid 2015 PDC

NASA Astrophysics Data System (ADS)

Vardaxis, George; Sherman, Peter; Wie, Bong

2016-05-01

In this paper, an integrated utilization of analytic keyhole theory, B-plane mapping, and planetary encounter geometry, augmented by direct numerical simulation, is shown to be useful in determining the impact risk of an asteroid with the Earth on a given encounter, as well on potential future encounters via keyhole passages. The accurate estimation of the impact probability of hazardous asteroids is extremely important for planetary defense mission planning. Asteroids in Earth resonant orbits are particularly troublesome because of the continuous threat they pose in the future. Based on the trajectories of the asteroid and the Earth, feasible mission trajectories can be found to mitigate the impact threat of hazardous asteroids. In order to try to ensure mission success, trajectories are judged based on initial and final mission design parameters that would make the mission easier to complete. Given the potential of a short-warning time scenario, a disruption mission considered in this paper occurs approximately one year prior to the anticipated impact date. Expanding upon the established theory, a computational method is developed to estimate the impact probability of the hazardous asteroid, in order to assess the likelihood of an event, and then investigate the fragmentation of the asteroid due to a disruption mission and analyze its effects on the current and future encounters of the fragments with Earth. A fictional asteroid, designated as 2015 PDC - created as an example asteroid risk exercise for the 2015 Planetary Defence Conference, is used as a reference target asteroid to demonstrate the effectiveness and applicability of computational tools being developed for impact risk assessment and planetary defense mission planning for a hazardous asteroid or comet.

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

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

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.

Guided asteroid deflection by kinetic impact: Mapping keyholes to an asteroid's surface

NASA Astrophysics Data System (ADS)

Chesley, S.; Farnocchia, D.

2014-07-01

The kinetic impactor deflection approach is likely to be the optimal deflection strategy in most real-world cases, given the likelihood of decades of warning time provided by asteroid search programs and the probable small size of the next confirmed asteroid impact that would require deflection. However, despite its straightforward implementation, the kinetic impactor approach can have its effectiveness limited by the astrodynamics that govern the impactor spacecraft trajectory. First, the deflection from an impact is maximized when the asteroid is at perihelion, while an impact near perihelion can in some cases be energetically difficult to implement. Additionally, the asteroid change in velocity Δ V should aligned with the target's heliocentric velocity vector in order to maximize the deflection at a potential impact some years in the future. Thus the relative velocity should be aligned with or against the heliocentric velocity, which implies that the impactor and asteroid orbits should be tangent at the point of impact. However, for natural bodies such as meteorites colliding with the Earth, the relative velocity vectors tend to cluster near the sunward or anti- sunward directions, far from the desired direction. This is because there is generally a significant crossing angle between the orbits of the impactor and target and an impact at tangency is unusual. The point is that hitting the asteroid is not enough, but rather we desire to hit the asteroid at a point when the asteroid and spacecraft orbits are nearly tangent and when the asteroid is near perihelion. However, complicating the analysis is the fact that the impact of a spacecraft on an asteroid would create an ejecta plume that is roughly normal to the surface at the point of impact. This escaping ejecta provides additional momentum transfer that generally adds to the effectiveness of a kinetic deflection. The ratio β between the ejecta momentum and the total momentum (ejecta plus spacecraft) can range from around 1 for a porous, compressible body producing negligible ejecta, to 2 when the ejecta momentum matches the spacecraft momentum, and as high as 5--10 for rocky bodies that produce large, high-velocity ejecta fragments. If the impactor hits the centerpoint of a spherical asteroid the momentum of the escaping ejecta directly adds to the momentum of the impacting asteroid, but if the impact is oblique then the ejecta and spacecraft momenta are added to the asteroid in vector sum. This suggests the possibility that for a given intercept trajectory the asteroid deflection could include guidance by targeting an oblique impact that could steer the asteroid Δ V to a more optimal direction that is different from the relative velocity direction of the spacecraft. An oblique impact decreases the net Δ V magnitude, and yet could significantly increase the net deflection at the time of the threatening Earth encounter. We use asteroid (101955) Bennu, which is the target of the OSIRIS-REx asteroid sample return mission and which has a series of potential Earth impacts in the years from 2175--2196, as an example to demonstrate the effectiveness of the oblique impact. These future potential impacts will occur if the asteroid passes through one of a series of keyholes when the asteroid passes the Earth at roughly the lunar distance from the Earth in 2135. To study the Bennu deflection problem we simulate a hypervelocity spacecraft impact on Bennu in March 2021, after the OSIRIS-REx mission is complete. In our example, the spacecraft arrives from approximately the sunward direction, and targeting ahead or behind the center of the asteroid allows non-negligible transverse accelerations for modest values of β. A given impact location on the asteroid surface yields a given Δ V vector, and our approach starts by mapping the net Δ V components on the surface for an assumed value of β. Knowing the mapping from impact location to Δ V and also the mapping from Δ V to the future Earth miss distance allows us to map the surface locations where a spacecraft impact would lead to an Earth impact 150--200 years later. In effect, we are able to project Earth impact trajectories, or keyholes, onto the asteroid surface and, for a given value of β, we can target our impactor spacecraft for an area on the surface that avoids potential Earth impacts. Of course, at the present time we have little information on what is the appropriate value or range of values for β in the case of asteroid Bennu, or any other asteroid for that matter. However, if this information is made known, either through a precursor mission or better inferences as to its nature we can develop a distribution of β that can be used to better design an impact deflection strategy. Specifically, we can compute a map of Earth impact probability density on the surface of the asteroid based on an assumed probability density function for β. If we target the lowest impact probability density regions then we maximize the chance of a successful deflection. This approach has the potential to allow more efficient kinetic impactor deflection, and therefore the deflection of larger bodies than would otherwise be possible.

Simulations of hypervelocity impacts for asteroid deflection studies

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

Dynamical properties of Watsonia asteroid family

NASA Astrophysics Data System (ADS)

Tsirvoulis, Georgios; Novaković, Bojan; Knežević, Zoran; Cellino, Alberto

2014-07-01

In recent years, a rare class of asteroids has been discovered by Cellino et al. (2006), 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. (2014) 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.

Satellite and Ground System Solutions at Your Fingertips

NASA Technical Reports Server (NTRS)

2005-01-01

In the summer of 1998, the blockbuster action movie Armageddon captivated audiences with a thrilling doomsday plot about a meteor the size of Texas that was racing towards the Earth. Though the premise of the movie was purely fictional, the unfortunate reality is that near-Earth asteroids such as the one portrayed in the film do exist. On December 23, 2004, NASA announced that an asteroid it anticipated to pass near the Earth on April 13, 2029, had been assigned the highest score to date on the universally used Torino Impact Hazard Scale. At first, the flyby distance for the asteroid, dubbed MN4, was uncertain and an Earth impact could not be ruled out. The odds of impact were initially believed to be 1 in 300, high enough to merit special monitoring by astronomers around the world, but were then escalated to 1 in 37 on December 27. NASA officials noted, however, that these odds should not be of public concern, since they were likely to change on a day-to-day basis as new data were received. The officials were correct in their assertion, as any chances of an impact with Earth in 2029 were completely ruled out later that same day. Integral Systems, Inc., a leading provider of satellite ground systems and the first company to offer an integrated suite of commercial-off-the-shelf software products for satellite command and control, is helping NASA keep a careful watch for any close-encountering asteroids with its tracking technology. The company supported the first NASA Discovery mission, the Near Earth Asteroid Rendezvous (NEAR) program, back in 1996, and has expanded its business by building more ground systems for a greater variety of satellites than any other company in the world. (NASA has since launched seven more Discovery missions, with the eighth lifting off earlier this year.) The experience gained from the company s participation in developing satellite command and control ground systems for the NEAR program has bolstered its flagship product line, the EPOCH Integrated Product Suite (IPS), first featured in Spinoff 1997, and led to the creation of its latest product, the Skylight Direct Broadcast Ground Terminal.

The Double Asteroid Redirection Test (DART)

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Composition of 298 Baptistina: Implications for the K/T impactor link

NASA Astrophysics Data System (ADS)

Reddy, V.; Emery, J. P.; Gaffey, M. J.; Bottke, W. F.; Cramer, A.; Kelley, M. S.

2009-01-01

Bottke et al. (2007) suggested that the breakup of the Baptistina asteroid family (BAF) 160+30 /-20 Myr ago produced an “asteroid shower” that increased by a factor of 2-3 the impact flux of kilometer-sized and larger asteroids striking the Earth over the last ~120 Myr. This result led them to propose that the impactor that produced the Cretaceous/Tertiary (K/T) mass extinction event 65 Myr ago also may have come from the BAF. This putative link was based both on collisional/dynamical modeling work and on physical evidence. For the latter, the available broadband color and spectroscopic data on BAF members indicate many are likely to be dark, low albedo asteroids. This is consistent with the carbonaceous chondrite-like nature of a 65 Myr old fossil meteorite (Kyte 1998)and with chromium from K/T boundary sediments with an isotopic signature similar to that from CM2 carbonaceous chondrites. To test elements of this scenario, we obtained near-IR and thermal IR spectroscopic data of asteroid 298 Baptistina using the NASA IRTF in order to determine surface mineralogy and estimate its albedo. We found that the asteroid has moderately strong absorption features due to the presence of olivine and pyroxene, and a moderately high albedo (~20%). These combined properties strongly suggest that the asteroid is more like an S-type rather than Xc-type (Mothé-Diniz et al. 2005). This weakens the case for 298 Baptistina being a CM2 carbonaceous chondrite and its link to the K/T impactor. We also observed several bright (V Mag. ≤16.8) BAF members to determine their composition.

WISE Revises Numbers of Asteroids Near Earth

NASA Image and Video Library

2011-09-29

Data from NASA Wide-field Infrared Survey Explorer has led to revisions in the estimated population of near-Earth asteroids. The most accurate survey to date has allowed new estimates of the total numbers of objects in different size categories.

Evidence for magma oceans on asteroids, the moon, and Earth

NASA Technical Reports Server (NTRS)

Taylor, G. Jeffrey; Norman, Marc D.

1992-01-01

There are sound theoretical reasons to suspect that the terrestrial planets melted when they formed. For Earth, the reasons stem largely from the hypothesis that the moon formed as a result of the impact of a Mars-sized planetesimal with the still accreting Earth. Such a monumental event would have led to widespread heating of the Earth and the materials from which the moon was made. In addition, formation of a dense atmosphere on the Earth (and possibly the Moon) would have led to retention of accretional heat and, thus, widespread melting. In other words, contemporary theory suggests that the primitive Moon and terrestrial planets had magma oceans.

Design of the optical communication system for the asteroid impact mission

NASA Astrophysics Data System (ADS)

Heese, C.; Sodnik, Z.; Carnelli, I.

2017-09-01

The Asteroid Impact Mission (AIM) is part of the joint Asteroid Impact and Deflection Assessment (AIDA) project of ESA, DLR, Observatoire de la Côte d'Ázur, NASA, and Johns Hopkins University Applied Physics Laboratory (JHU/APL).

The Double Asteroid Redirection Test in the AIDA Mission

NASA Astrophysics Data System (ADS)

Cheng, Andrew; Reed, Cheryl; Rivkin, Andrew

2016-07-01

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

The Double Asteroid Redirection Test in the AIDA Project

NASA Astrophysics Data System (ADS)

Cheng, Andrew; Rivkin, Andrew; Michel, Patrick

2016-04-01

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

Thermal fatigue as the origin of regolith on small asteroids.

PubMed

Delbo, Marco; Libourel, Guy; Wilkerson, Justin; Murdoch, Naomi; Michel, Patrick; Ramesh, K T; Ganino, Clément; Verati, Chrystele; Marchi, Simone

2014-04-10

Space missions and thermal infrared observations have shown that small asteroids (kilometre-sized or smaller) are covered by a layer of centimetre-sized or smaller particles, which constitute the regolith. Regolith generation has traditionally been attributed to the fall back of impact ejecta and by the break-up of boulders by micrometeoroid impact. Laboratory experiments and impact models, however, show that crater ejecta velocities are typically greater than several tens of centimetres per second, which corresponds to the gravitational escape velocity of kilometre-sized asteroids. Therefore, impact debris cannot be the main source of regolith on small asteroids. Here we report that thermal fatigue, a mechanism of rock weathering and fragmentation with no subsequent ejection, is the dominant process governing regolith generation on small asteroids. We find that thermal fragmentation induced by the diurnal temperature variations breaks up rocks larger than a few centimetres more quickly than do micrometeoroid impacts. Because thermal fragmentation is independent of asteroid size, this process can also contribute to regolith production on larger asteroids. Production of fresh regolith originating in thermal fatigue fragmentation may be an important process for the rejuvenation of the surfaces of near-Earth asteroids, and may explain the observed lack of low-perihelion, carbonaceous, near-Earth asteroids.

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 Big Splash: Tsunami from Large Asteroid and Comet Impacts

NASA Astrophysics Data System (ADS)

Hills, J.; Goda, M.

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

Observation of asteroid 2013 TV135 supports my idea that a new impaction will come in 20 years

NASA Astrophysics Data System (ADS)

Cao, Dayong

2014-03-01

Asteroid 2013 TV135 who will impact in 2023 was newly discovered by Ukrainian astronomers in 2013. It supports my idea that a new impaction will come in 20 years. http://www.nasa.gov/mission_pages/asteroids/news/asteroid20131017.html, http://meetings.aps.org/link/BAPS.2011.DFD.LA.24, http://meetings.aps.org/link/BAPS.2012.APR.K1.78, http://meetings.aps.org/link/BAPS.2013.APR.S2.14. The Sun's companion-dark hole, which is made of dark matter seasonal took its dark comets belt, dark matter, dark lives, and the pressed asteroids belt to impact near our earth. These impactions and dark matter's killers caused seasonal extinctions and produced new species. By many dark comets and asteroids impacting, the dark impaction model is a high probability impaction model; the impaction would not change the orbit of the invisible dark hole, so that it could keep accurate periodicity impactions. With the space-time center, the dark hole system is a negative Einstein's model by ``mass-energy coordinate.'' Sun and Dark hole build up the balance system. Through studying the model, the rule of the impaction can be calculated. Avoid Earth Extinction Association.

The Double Asteroid Redirection Test (DART) for the AIDA Mission

NASA Astrophysics Data System (ADS)

Stickle, Angela; Cheng, Andy F.; Michel, Patrick; Barnouin, Olivier S.; Campo Bagatin, Adriano; Miller, Paul L.; Pravec, Petr; Richardson, Derek C.; Schwartz, Stephen R.; Tsiganis, Kleomenis; Ulamec, Stephan; AIDA Impact Modeling and Simulation Working Group

2016-10-01

The Asteroid Impact Deflection Assessment (AIDA) mission will be the first space experiment to demonstrate asteroid impact hazard mitigation using a kinetic impactor. AIDA is a joint ESA-NASA cooperative project, consisting of the NASA Double Asteroid Redirection Test (DART) mission, which provides the kinetic impactor, and the ESA Asteroid Impact Mission (AIM) rendezvous spacecraft. DART is a Phase A study supported by NASA, and AIM is a Phase B1 study supported by ESA. The AIDA target is the near-Earth binary asteroid 65803 Didymos, which will make a close approach to Earth in October, 2022. The DART spacecraft is designed to impact the Didymos secondary at ~6 km/s and deflect its trajectory, changing the orbital period of the binary. This change can be measured by Earth-based optical and radar observations. The primary goals of AIDA are to (1) perform a full-scale demonstration of asteroid deflection by kinetic impact; (2) measure the resulting deflection; and (3) validate and improve models for momentum transfer in high-speed impacts on an asteroid. The combined DART and AIM missions will provide the first measurements of momentum transfer efficiency from a kinetic impact at full scale on an asteroid, where the impact conditions of the projectile are known, and physical properties and internal structures of the target asteroid are also characterized. In addition to a predicted 4.4 minute change in the binary orbit period, assuming unit momentum transfer efficiency, the DART kinetic impact is predicted to induce forced librations of the Didymos secondary of possibly several degrees amplitude. Models predict the impact will create a 6-17 meter diameter crater, depending on target physical properties, and it will release a volume of particulate ejecta that may be directly observable from Earth or even resolvable as a coma or an ejecta tail by ground-based telescopes. Current simulations of the DART impact provide predictions for momentum transfer, crater size, and ejecta mass following impact. Additional work benchmarking impact hydrocodes with one another provides a way to bound the uncertainty in these critical simulations, allowing better predictions for the momentum transfer to the moon of Didymos.

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

NASA Technical Reports Server (NTRS)

Yen, C.-W. L.

1982-01-01

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

The Asteroid Impact Mission (AIM): Studying the geophysics of small binaries, measuring asteroid deflection and studying impact physics

NASA Astrophysics Data System (ADS)

Kueppers, Michael; Michel, Patrick; AIM Team

2016-10-01

Binary asteroids and their formation mechanisms are of particular interest for understanding the evolution of the small bodies in the solar system. Also, hazards to Earth from impact of near-Earth asteroids and their mitigation have drawn considerable interest over the last decades.Those subjects are both addressed by ESA's Asteroid Impact mission, which is part of the Asteroid Impact & Deflection Assessment (AIDA) currently under study in collaboration between NASA and ESA. NASA's DART mission will impact a projectile into the minor component of the binary near-Earth asteroid (65803) Didymos in 2022. The basic idea is to demonstrate the effect of the impact on the orbital period of the secondary around the primary. ESA's AIM will monitor the Didymos system for several months around the DART impact time.AIM will be launched in aurumn 2020. It is foreseen to arrive at Didymos in April 2022. The mission takes advantage of a close approach of Didymos to Earth. The next opportunity would arise in 2040 only.AIM will stay near Didymos for approximately 6 months. Most of the time it will be placed on the illuminated side of the system, at distances of approximately 35 km and 10 km. AIM is expected to move away from Didymos for some time around the DART impact.The reference payload for AIM includes two visual imagers, a hyperspectral camera, a lidar, a thermal infrared imager, a monostatic high frequency radar, and a bistatic low frequency radar. In addition, AIM will deploy a small lander on the secondary asteroid, and two cubesats that will be used for additional, more risky investigations close to or on the surface of the asteroid.Major contributions from AIM are expected in the study of the geophysics of small asteroids (including for the first time, radar measurements of an interior structure), the formation of binary asteroids, the momentum enhancement factor from the DART impact (through measuring the mass and the change of orbit of the seondary), and impact physics through observing the outcome of an impact with well known impact conditions. In addition, AIM will test new technologies (Cubesats in interplanetary space, Intersatellite links, optical telecommunication in deep space, infrared navigation).

Momentum transfer in asteroid impacts. I. Theory and scaling

NASA Astrophysics Data System (ADS)

Holsapple, Keith A.; Housen, Kevin R.

2012-11-01

When an asteroid experiences an impact, its path is changed. How much it changes is important to know for both asteroid evolution studies and for attempts to prevent an asteroid from impacting the Earth. In an impact process the total momentum of the material is conserved. However, not all of the material is of interest, but only that remaining with the asteroid. The ratio of the change of momentum of the remaining asteroid to that of the impactor is called the momentum multiplication factor; and is commonly given the symbol β. It has been known for some time that β can be greater than unity, and in some cases far greater. That could be a significant factor in attempts to deflect an asteroid with an impact, and can also be important in the stirring of objects in the asteroid belt due to mutual impacts. The escaping crater ejecta are the source of the momentum multiplication. Housen and Holsapple (Housen, K.R., Holsapple, K.A. [2011a]. Icarus 211, 856-875) have given a recent summary of ejecta characteristics and scaling. Here we use those ejecta results to determine how β depends on the impactor properties, on the asteroid size and composition, and establish the paths and time of flight of all of the ejecta particles. The approach is to add the contribution of each element of ejected mass accounting for its initial velocity, its trajectory and whether it escapes the asteroid. The goal in this paper is to provide a theoretical framework of the fundamental results which can be used as a test of the veracity of experiments and detailed numerical calculations of impacts. A subsequent paper will present direct laboratory results and numerical simulations of momentum multiplication in various geological materials.

Asteroid Impact Mission: relevance to asteroid mining

NASA Astrophysics Data System (ADS)

Michel, P.; Kueppers, M.; Carnelli, I.

2017-09-01

The Asteroid Impact Mission (AIM) is the European (ESA) component of the AIDA mission in collaboration with NASA. The objectives of AIDA are: (1) to perform a test of asteroid deflection using a kinetic impactor with the USA (NASA) component DART, and (2) with AIM, to investigate the binary near-Earth asteroid Didymos, in particular its secondary and target of DART, with data of high value for mining purposes.

AIDA: The Asteroid Impact & Deflection Assessment Mission

NASA Astrophysics Data System (ADS)

Galvez, A.; Carnelli, I.; Michel, P.; Cheng, A. F.; Reed, C.; Ulamec, S.; Biele, J.; Abell, P.; Landis, R.

2013-09-01

The Asteroid Impact and Deflection Assessment (AIDA) mission, a joint effort of ESA, JHU/APL, NASA, OCA, and DLR, is the first demonstration of asteroid deflection and assessment via kinetic impact. AIDA consists of two independent but mutually supporting mission elements, one of which is the asteroid kinetic impactor and the other is the characterization spacecraft. These two missions are, respectively, JHU/APL's Double Asteroid Redirection Test (DART) and the European Space Agency's Asteroid Investigation Mission (AIM) missions. As in the separate DART and AIM studies, the target of this mission is the binary asteroid [65803] Didymos in October, 2022. For a successful joint mission, one spacecraft, DART, would impact the secondary of the Didymos system while AIM would observe and measure any change in the relative orbit. AIM will be the first probe to characterise a binary asteroid, especially from the dynamical point of view, but also considering its interior and subsurface composition. The mission concept focuses on the monitoring aspects i.e., the capability to determine in-situ the key physical properties of a binary asteroid playing a role in the system's dynamic behavior. DART will be the first ever space mission to deflect the trajectory of an asteroid in a measurable way.- It is expected that the deflection can be measured as a change in the relative orbit period with a precision better than 10%. The joint AIDA mission will return vital data to determine the momentum transfer efficiency of the kinetic impact [1,2].

Chemical, thermal and impact processing of asteroids

NASA Technical Reports Server (NTRS)

Scott, E. R. D.; Taylor, G. J.; Newsom, H. E.; Herbert, F.; Zolensky, M.

1989-01-01

The geological effects of impacts, heating, melting, core formation, and aqueous alteration on asteroids are reviewed. A review of possible heat sources appears to favor an important role for electrical induction heating. The effects of each geologic process acting individually and in combination with others, are considered; it is concluded that there is much evidence for impacts during alteration, metamorphism and melting. These interactions vastly increased the geologic diversity of the asteroid belt. Subsequent impacts of cool asteroids did not reduce this diversity. Instead new rock types were created by mixing, brecciation and minor melting.

Double Asteroid Redirection Test (DART) element of AIDA mission

NASA Astrophysics Data System (ADS)

Cheng, A.; Michel, P.; Rivkin, A.; Barnouin, O.; Stickle, A.; Miller, P.; Chesley, S.; Richardson, D.

2017-09-01

The AIDA mission, an international cooperation between NASA and ESA, will be the first demonstration of a kinetic impactor spacecraft to deflect an asteroid. AIDA will perform the first hypervelocity impact on an asteroid where the impact conditions are fully known and the target properties are also characterized. AIDA will reduce risks for any future asteroid hazard mitigation.

AIDA DART asteroid deflection test: Planetary defense and science objectives

NASA Astrophysics Data System (ADS)

Cheng, Andrew F.; Rivkin, Andrew S.; Michel, Patrick; Atchison, Justin; Barnouin, Olivier; Benner, Lance; Chabot, Nancy L.; Ernst, Carolyn; Fahnestock, Eugene G.; Kueppers, Michael; Pravec, Petr; Rainey, Emma; Richardson, Derek C.; Stickle, Angela M.; Thomas, Cristina

2018-08-01

The Asteroid Impact & Deflection Assessment (AIDA) mission is an international cooperation between NASA and ESA. NASA plans to provide the Double Asteroid Redirection Test (DART) mission which will perform a kinetic impactor experiment to demonstrate asteroid impact hazard mitigation. ESA proposes to provide the Hera mission which will rendezvous with the target to monitor the deflection, perform detailed characterizations, and measure the DART impact outcomes and momentum transfer efficiency. The primary goals of AIDA are (i) to demonstrate the kinetic impact technique on a potentially hazardous near-Earth asteroid and (ii) to measure and characterize the deflection caused by the impact. The AIDA target will be the binary asteroid (65803) Didymos, which is of spectral type Sq, with the deflection experiment to occur in October, 2022. The DART impact on the secondary member of the binary at ∼6 km/s changes the orbital speed and the binary orbit period, which can be measured by Earth-based observatories with telescope apertures as small as 1 m. The DART impact will in addition alter the orbital and rotational states of the Didymos binary, leading to excitation of eccentricity and libration that, if measured by Hera, can constrain internal structure of the target asteroid. Measurements of the DART crater diameter and morphology can constrain target properties like cohesion and porosity based on numerical simulations of the DART impact.

Science case for the Asteroid Impact Mission (AIM): A component of the Asteroid Impact & Deflection Assessment (AIDA) mission

NASA Astrophysics Data System (ADS)

Michel, Patrick; Cheng, A.; Küppers, M.; Pravec, P.; Blum, J.; Delbo, M.; Green, S. F.; Rosenblatt, P.; Tsiganis, K.; Vincent, J. B.; Biele, J.; Ciarletti, V.; Hérique, A.; Ulamec, S.; Carnelli, I.; Galvez, A.; Benner, L.; Naidu, S. P.; Barnouin, O. S.; Richardson, D. C.; Rivkin, A.; Scheirich, P.; Moskovitz, N.; Thirouin, A.; Schwartz, S. R.; Campo Bagatin, A.; Yu, Y.

2016-06-01

The Asteroid Impact & Deflection Assessment (AIDA) mission is a joint cooperation between European and US space agencies that consists of two separate and independent spacecraft that will be launched to a binary asteroid system, the near-Earth asteroid Didymos, to test the kinetic impactor technique to deflect an asteroid. The European Asteroid Impact Mission (AIM) is set to rendezvous with the asteroid system to fully characterize the smaller of the two binary components a few months prior to the impact by the US Double Asteroid Redirection Test (DART) spacecraft. AIM is a unique mission as it will be the first time that a spacecraft will investigate the surface, subsurface, and internal properties of a small binary near-Earth asteroid. In addition it will perform various important technology demonstrations that can serve other space missions. The knowledge obtained by this mission will have great implications for our understanding of the history of the Solar System. Having direct information on the surface and internal properties of small asteroids will allow us to understand how the various processes they undergo work and transform these small bodies as well as, for this particular case, how a binary system forms. Making these measurements from up close and comparing them with ground-based data from telescopes will also allow us to calibrate remote observations and improve our data interpretation of other systems. With DART, thanks to the characterization of the target by AIM, the mission will be the first fully documented impact experiment at asteroid scale, which will include the characterization of the target's properties and the outcome of the impact. AIDA will thus offer a great opportunity to test and refine our understanding and models at the actual scale of an asteroid, and to check whether the current extrapolations of material strength from laboratory-scale targets to the scale of AIDA's target are valid. Moreover, it will offer a first check of the validity of the kinetic impactor concept to deflect a small body and lead to improved efficiency for future kinetic impactor designs. This paper focuses on the science return of AIM, the current knowledge of its target from ground-based observations, and the instrumentation planned to get the necessary data.

A Potpourri of Near-Earth Asteroid Observations

NASA Astrophysics Data System (ADS)

Tholen, David J.; Ramanjooloo, Yudish; Fohring, Dora; Hung, Denise; Micheli, Marco

2016-10-01

Ongoing astrometric follow-up of near-Earth asteroids has yielded a variety of interesting results. In the limited space of a DPS abstract, three recently observed objects are worth mentioning.2008 HU4 is among the most accessible asteroids for a human space flight mission. We successfully recovered this object at a second opposition on 2016 April 26 despite the large ephemeris uncertainty. The small size of this asteroid makes it relatively easy to detect the departure from purely gravitational motion caused by solar radiation pressure, which can be used to estimate the density of the object. At the time of this writing, the object remains bright enough for additional observations, so we expect to improve on our five-sigma detection of a relatively low density (roughly similar to water, indicating a high porosity) between now and the DPS meeting.2016 HO3 is a newly-discovered co-orbital with the Earth. Our 2016 May 10-11 observations extended the observational arc by enough to permit backward extrapolation that led to prediscovery observations by Pan-STARRS in 2015, and then annually back to 2011, and ultimately to Sloan DSS observations in 2004. The 12-year arc is sufficient to examine the dynamical behavior of the object, which shows how it will remain in the vicinity of the Earth for decades, if not centuries. Our observations also revealed a rapid rotation (less than a half hour) with large brightness variation (in excess of 1 magnitude), which helps to explain why this object eluded discovery until this year.2011 YV62 is among the top 20 largest near-Earth asteroids with Earth impact solutions (in 2078 and 2080). At the time of this writing, the object is flagged as being "lost", but a re-examination of observations made in 2013 and 2015 finally yielded a successful recovery at a magnitude fainter than 24. We expect the new observations to eliminate the impact possibilities. The story behind this difficult recovery is fascinating.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

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

NASA Technical Reports Server (NTRS)

Kring, David A.

1993-01-01

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

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

PubMed

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

2006-06-09

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

Bayesian modeling of the mass and density of asteroids

NASA Astrophysics Data System (ADS)

Dotson, Jessie L.; Mathias, Donovan

2017-10-01

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

Effective Scenarios for Exploring Asteroid Surfaces

NASA Astrophysics Data System (ADS)

Clark, Pamela E.; Clark, C.; Weisbin, C.

2010-10-01

In response to the proposal that asteroids be the next targets for exploration, we attempt to develop scenarios for exploring previously mapped asteroid 433 Eros, harnessing our recent experience gained planning such activity for return to the lunar surface. The challenges faced in planning Apollo led to the development of a baseline methodology for extraterrestrial field science. What `lessons learned’ can be applied for asteroids? Effective reconnaissance (advanced mapping at <0.5 m, photos with plotted routes as in-field reference maps), training/simulating/planning (highly interactive abundant field time for extended crew), and documentation (hands-free audio and visual systematic description) procedures are still valid. The use of Constant Scale Natural Boundary rather than standard projection maps eases the challenge of navigating and interpreting a highly irregular object. Lunar and asteroid surfaces are dominated by bombardment and space radiation/dust/charged particle/regolith interactions, with similar implications for sampling. Asteroid work stations are selected on the basis of impact-induced exposure of `outcrops’ from prominent ridges (e.g., Himeros, the noses) potentially representing underlying material, supplemented by sampling of areas of especially thin or deep regolith (ponds). Unlike the Moon, an asteroid lacks sufficient gravity and most likely the necessary stability to support `normal’ driving or walking. In fact, the crew delivery vehicle might not even be `tetherable’ and would most likely `station keep’ to maintain a position. The most convenient local mobility mechanism for astronauts/robots would be `hand over hand’ above the surface at a field station supplemented by a `tetherless’ (small rocket-pack) control system for changing station or return to vehicle. Thus, we assume similar mobility constraints (meters to hundreds of meters at a local station, kilometers between stations) as those used for Apollo. We also assume the vehicle could `station keep’ at more than one location separated by tens of kilometers distance.

Probabilistic Asteroid Impact Risk Assessment for the Hypothetical PDC17 Impact Exercise

NASA Technical Reports Server (NTRS)

Wheeler, Lorien; Mathias, Donovan

2017-01-01

Performing impact risk assessment for the 2017 Planetary Defense Conference (PDC17) hypothetical impact exercise, to take place at the PDC17 conference, May 15-20, 2017. Impact scenarios and trajectories are developed and provided by NASA's Near Earth Objects Office at JPL (Paul Chodas). These results represent purely hypothetical impact scenarios, and do not reflect any known asteroid threat. Risk assessment was performed using the Probabilistic Asteroid Impact Risk (PAIR) model developed by the Asteroid Threat Assessment Project (ATAP) at NASA Ames Research Center. This presentation includes sample results that may be presented or used in discussions during the various stages of the impact exercisecenter dot Some cases represent alternate scenario options that may not be used during the actual impact exercise at the PDC17 conference. Updates to these initial assessments and/or additional scenario assessments may be performed throughout the impact exercise as different scenario options unfold.

Collision rates and impact velocities in the Main Asteroid Belt

NASA Technical Reports Server (NTRS)

Farinella, Paolo; Davis, Donald R.

1992-01-01

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

The asteroid impact mission: testing laser communication in deep-space

NASA Astrophysics Data System (ADS)

Carnelli, I.; Mellab, K.; Heese, C.; Sodnik, Z.; Pesquita, V.; Gutierrez, B.

2017-09-01

In October 2022 the binary asteroid system 65803 Didymos will have an exceptionally close approach with the Earth flying by within only 0.088 AU. ESA is planning to leverage on this close encounter to launch a small mission of opportunity called Asteroid Impact Mission (AIM) to explore and demonstrate new technologies for future science and exploration missions while addressing planetary defence and performing asteroid scientific investigations.

AIDA: the Asteroid Impact & Deflection Assessment mission

NASA Astrophysics Data System (ADS)

Vincent, Jean-Baptiste

2016-07-01

The Asteroid Impact & Deflection Assessment (AIDA) mission is a joint cooperation between European and US space agencies that consists of two separate and independent spacecraft that will be launched to a binary asteroid system, the near-Earth asteroid Didymos, to assess the possibility of deflecting an asteroid trajectory by using a kinetic impactor. The European Asteroid Impact Mission (AIM) is under Phase A/B1 study at ESA from March 2015 until summer 2016. AIM is set to rendez-vous with the asteroid system a few months prior to the impact by the US Double Asteroid Redirection Test (DART) spacecraft to fully characterize the smaller of the two binary components. AIM is a unique mission as it will be the first time that a spacecraft will investigate the surface, subsurface, and internal properties of a small binary near Earth asteroid. In addition it will perform various important technology demonstrations that can serve other space missions: AIM will release a set of CubeSats in deep space and a lander on the surface of the smaller asteroid and for the first time, deep-space inter-satellite linking will be demonstrated between the main spacecraft, the CubeSats, and the lander, and data will also be transmitted from interplanetary space to Earth by a laser communication system. The knowledge obtained by this mission will have great implications for our understanding of the history of the Solar System. Small asteroids are believed to result from collisions and other processes (e.g., spinup, shaking) that made them what they are now. Having direct information on their surface and internal properties will allow us to understand how these processes work and transform these small bodies as well as, for this particular case, how a binary system forms. So far, our understanding of the collisional process and the validation of numerical simulations of the impact process rely on impact experiments at laboratory scales. With DART, thanks to the characterization of the target by AIM, the mission will be the first fully documented impact experiment at asteroid scale, which will include the characterization of the target's properties and the outcome of the impact. By comparing our in situ measurements with ground-based data from telescopes, we can calibrate better the remote observations and improve our data interpretation of other systems. Therefore, AIDA offers a unique opportunity to test and refine our understanding and models at the actual scale of an asteroid. This will allow feeding small-body collisional evolution models with more realistic parameters to draw a more reliable story of the Solar System formation and evolution. Moreover, it will offer a first check of the validity of the kinetic impactor concept to deflect a small body trajectory and lead to improved efficiency for future kinetic impactor designs.

A new mechanism for the formation of regolith on asteroids

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

The Miniaturized Moessbauer Spectrometer MIMOS II for the Asteroid Redirect Mission(ARM): Quantative Iron Mineralogy And Oxidation States

NASA Technical Reports Server (NTRS)

Schroeder, C.; Klingelhoefer, G; Morris, R. V.; Yen, A. S.; Renz, F.; Graff, T. G.

2016-01-01

The miniaturized Moessbauer spectrometer MIMOS II is an off-the-shelf instrument with proven flight heritage. It has been successfully deployed during NASA’s Mars Exploration Rover (MER) mission and was on-board the UK-led Beagle 2 Mars lander and the Russian Phobos-Grunt sample return mission. A Moessbauer spectrometer has been suggested for ASTEX, a DLR Near-Earth Asteroid (NEA) mission study, and the potential payload to be hosted by the Asteroid Redirect Mission (ARM). Here we make the case for in situ asteroid characterization with Moessbauer spectroscopy on the ARM employing one of three available fully-qualified flight-spare Moessbauer instruments.

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

NASA Astrophysics Data System (ADS)

Eggl, Siegfried

2014-05-01

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

Penetrator Coring Apparatus for Cometary Surfaces

NASA Technical Reports Server (NTRS)

Braun, David F.; Heinrich, Michael; Ai, Huirong Anita; Ahrens, Thomas J.

2004-01-01

Touch and go impact coring is an attractive technique for sampling cometary nuclei and asteroidal surface on account of the uncertain strength properties and low surface gravities of these objects. Initial coring experiments in low temperature (approx. 153K polycrystalline ice) and porous rock demonstrate that simultaneous with impact coring, measurements of both the penetration strength and constraints on the frictional properties of surface materials can be obtained upon core penetration and core sample extraction. The method of sampling an asteroid, to be deployed, on the now launched MUSES-C mission, employs a small gun device that fires into the asteroid and the resulted impact ejecta is collected for return to Earth. This technique is well suited for initial sampling in a very low gravity environment and deployment depends little on asteroid surface mechanical properties. Since both asteroids and comets are believed to have altered surface properties a simple sampling apparatus that preserves stratigraphic information, such as impact coring is an attractive alternate to impact ejecta collection.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

YORP: Influence on Rotation Rate

NASA Astrophysics Data System (ADS)

Golubov, A. A.; Krugly, Yu. N.

2010-06-01

We have developed a semi-analytical model for calculating angular acceleration of asteroids due to Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. The calculation of the YORP effect has been generalized for the case of elliptic orbits. It has been shown that the acceleration does not depend on thermal inertia of the asteroid's surface. The model was applied to the asteroid 1620 Geographos and led to acceleration 2×10^{-18}s^{-2}. This value is close to the acceleration obtained from photometric observations of Geographos by Durech et al. [1].

Simulation of asteroid impact on ocean surfaces, subsequent wave generation and the effect on US shorelines

DOE PAGES

Ezzedine, Souheil M.; Lomov, Ilya; Miller, Paul L.; ...

2015-05-19

As part of a larger effort involving members of several other organizations, we have conducted numerical simulations in support of emergency-response exercises of postulated asteroid ocean impacts. We have addressed the problem from source (asteroid entry) to ocean impact (splash) to wave generation, propagation and interaction with the U.S. shoreline. We simulated three impact sites. The first site is located off the east coast by Maryland's shoreline. The second site is located off of the West coast, the San Francisco bay. The third set of sites are situated in the Gulf of Mexico. Asteroid impacts on the ocean surface aremore » conducted using LLNL's hydrocode GEODYN to create the impact wave source for the shallow water wave propagation code, SWWP, a shallow depth averaged water wave code.« less

Simulation of asteroid impact on ocean surfaces, subsequent wave generation and the effect on US shorelines

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

Ezzedine, Souheil M.; Lomov, Ilya; Miller, Paul L.

As part of a larger effort involving members of several other organizations, we have conducted numerical simulations in support of emergency-response exercises of postulated asteroid ocean impacts. We have addressed the problem from source (asteroid entry) to ocean impact (splash) to wave generation, propagation and interaction with the U.S. shoreline. We simulated three impact sites. The first site is located off the east coast by Maryland's shoreline. The second site is located off of the West coast, the San Francisco bay. The third set of sites are situated in the Gulf of Mexico. Asteroid impacts on the ocean surface aremore » conducted using LLNL's hydrocode GEODYN to create the impact wave source for the shallow water wave propagation code, SWWP, a shallow depth averaged water wave code.« less

Impact Hazard Monitoring: Theory and Implementation

NASA Astrophysics Data System (ADS)

Farnocchia, Davide

2015-08-01

Impact monitoring is a crucial component of the mitigation or elimination of the hazard posed by asteroid impacts. Once an asteroid is discovered, it is important to achieve an early detection and an accurate assessment of the risk posed by future Earth encounters. Here we review the most standard impact monitoring techniques. Linear methods are the fastest approach but their applicability regime is limited because of the chaotic dynamics of near-Earth asteroids, whose orbits are often scattered by planetary encounters. Among nonlinear methods, Monte Carlo algorithms are the most reliable ones. However, the large number of near-Earth asteroids and the computational load required to detect low probability impact events make Monte Carlo approaches impractical in the framework of monitoring all near-Earth asteroids. In the last 15 years, the Line of Variations (LOV) method has been the most successful technique as it strikes a remarkable compromise between computational efficiency and the capability of detecting low probability events deep in the nonlinear regime. As a matter of fact, the LOV method is the engine of JPL’s Sentry and University of Pisa’s NEODyS, which the two fully automated impact monitoring systems that routinely search for potential impactors among known near-Earth asteroids. We also present some more recent techniques developed to deal with the new challenges arising in the impact hazard assessment problem. In particular, we describe how to use keyhole maps to go beyond strongly scattering encounters and push forward in time the impact prediction horizon. In these cases asteroids usually have a very well constrained orbit and we often need to account for the action of nongravitational perturbations, especially the Yarkovsky effect. Finally, we discuss the short-term hazard assessment problem for newly discovered asteroids, when only a short observed arc is available. The limited amount of observational data generally leads to severe degeneracies in the orbit estimation process. We overcome these degeneracies by employing ranging techniques, which scan the poorly constrained space of topocentric range and range rate.

Calculating the momentum enhancement factor for asteroid deflection studies

DOE PAGES

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

2017-10-17

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

Calculating the momentum enhancement factor for asteroid deflection studies

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

Heberling, Tamra; Gisler, Galen; Plesko, Catherine

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

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

NASA Astrophysics Data System (ADS)

Nesvorný, David; Roig, Fernando

2018-01-01

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

The Asteroid Impact Mission

NASA Astrophysics Data System (ADS)

Carnelli, Ian; Galvez, Andres; Mellab, Karim

2016-04-01

The Asteroid Impact Mission (AIM) is a small and innovative mission of opportunity, currently under study at ESA, intending to demonstrate new technologies for future deep-space missions while addressing planetary defense objectives and performing for the first time detailed investigations of a binary asteroid system. It leverages on a unique opportunity provided by asteroid 65803 Didymos, set for an Earth close-encounter in October 2022, to achieve a fast mission return in only two years after launch in October/November 2020. AIM is also ESA's contribution to an international cooperation between ESA and NASA called Asteroid Impact Deflection Assessment (AIDA), consisting of two mission elements: the NASA Double Asteroid Redirection Test (DART) mission and the AIM rendezvous spacecraft. The primary goals of AIDA are to test our ability to perform a spacecraft impact on a near-Earth asteroid and to measure and characterize the deflection caused by the impact. The two mission components of AIDA, DART and AIM, are each independently valuable but when combined they provide a greatly increased scientific return. The DART hypervelocity impact on the secondary asteroid will alter the binary orbit period, which will also be measured by means of lightcurves observations from Earth-based telescopes. AIM instead will perform before and after detailed characterization shedding light on the dependence of the momentum transfer on the asteroid's bulk density, porosity, surface and internal properties. AIM will gather data describing the fragmentation and restructuring processes as well as the ejection of material, and relate them to parameters that can only be available from ground-based observations. Collisional events are of great importance in the formation and evolution of planetary systems, own Solar System and planetary rings. The AIDA scenario will provide a unique opportunity to observe a collision event directly in space, and simultaneously from ground-based optical and radar facilities. For the first time, an impact experiment at asteroid scale will be performed with accurate knowledge of the precise impact conditions and also the impact outcome, together with information on the physical properties of the target, ultimately validating at appropriate scales our knowledge of the process and impact simulations. AIM's important technology demonstration component includes a deep-space optical communication terminal and inter-satellite network with two CubeSats deployed in the vicinity of the Didymos system and a lander on the surface of the secondary. To achieve a low-cost objective AIM's technology and scientific payload are being combined to support both close-proximity navigation and scientific investigations. AIM will demonstrate the capability to achieve a small spacecraft design with a very large technological and scientific mission return.

Global climate change driven by soot at the K-Pg boundary as the cause of the mass extinction

NASA Astrophysics Data System (ADS)

Kaiho, Kunio; Oshima, Naga; Adachi, Kouji; Adachi, Yukimasa; Mizukami, Takuya; Fujibayashi, Megumu; Saito, Ryosuke

2016-07-01

The mass extinction of life 66 million years ago at the Cretaceous/Paleogene boundary, marked by the extinctions of dinosaurs and shallow marine organisms, is important because it led to the macroevolution of mammals and appearance of humans. The current hypothesis for the extinction is that an asteroid impact in present-day Mexico formed condensed aerosols in the stratosphere, which caused the cessation of photosynthesis and global near-freezing conditions. Here, we show that the stratospheric aerosols did not induce darkness that resulted in milder cooling than previously thought. We propose a new hypothesis that latitude-dependent climate changes caused by massive stratospheric soot explain the known mortality and survival on land and in oceans at the Cretaceous/Paleogene boundary. The stratospheric soot was ejected from the oil-rich area by the asteroid impact and was spread globally. The soot aerosols caused sufficiently colder climates at mid-high latitudes and drought with milder cooling at low latitudes on land, in addition to causing limited cessation of photosynthesis in global oceans within a few months to two years after the impact, followed by surface-water cooling in global oceans in a few years. The rapid climate change induced terrestrial extinctions followed by marine extinctions over several years.

Global climate change driven by soot at the K-Pg boundary as the cause of the mass extinction

PubMed Central

Kaiho, Kunio; Oshima, Naga; Adachi, Kouji; Adachi, Yukimasa; Mizukami, Takuya; Fujibayashi, Megumu; Saito, Ryosuke

2016-01-01

The mass extinction of life 66 million years ago at the Cretaceous/Paleogene boundary, marked by the extinctions of dinosaurs and shallow marine organisms, is important because it led to the macroevolution of mammals and appearance of humans. The current hypothesis for the extinction is that an asteroid impact in present-day Mexico formed condensed aerosols in the stratosphere, which caused the cessation of photosynthesis and global near-freezing conditions. Here, we show that the stratospheric aerosols did not induce darkness that resulted in milder cooling than previously thought. We propose a new hypothesis that latitude-dependent climate changes caused by massive stratospheric soot explain the known mortality and survival on land and in oceans at the Cretaceous/Paleogene boundary. The stratospheric soot was ejected from the oil-rich area by the asteroid impact and was spread globally. The soot aerosols caused sufficiently colder climates at mid–high latitudes and drought with milder cooling at low latitudes on land, in addition to causing limited cessation of photosynthesis in global oceans within a few months to two years after the impact, followed by surface-water cooling in global oceans in a few years. The rapid climate change induced terrestrial extinctions followed by marine extinctions over several years. PMID:27414998

Global climate change driven by soot at the K-Pg boundary as the cause of the mass extinction.

PubMed

Kaiho, Kunio; Oshima, Naga; Adachi, Kouji; Adachi, Yukimasa; Mizukami, Takuya; Fujibayashi, Megumu; Saito, Ryosuke

2016-07-14

The mass extinction of life 66 million years ago at the Cretaceous/Paleogene boundary, marked by the extinctions of dinosaurs and shallow marine organisms, is important because it led to the macroevolution of mammals and appearance of humans. The current hypothesis for the extinction is that an asteroid impact in present-day Mexico formed condensed aerosols in the stratosphere, which caused the cessation of photosynthesis and global near-freezing conditions. Here, we show that the stratospheric aerosols did not induce darkness that resulted in milder cooling than previously thought. We propose a new hypothesis that latitude-dependent climate changes caused by massive stratospheric soot explain the known mortality and survival on land and in oceans at the Cretaceous/Paleogene boundary. The stratospheric soot was ejected from the oil-rich area by the asteroid impact and was spread globally. The soot aerosols caused sufficiently colder climates at mid-high latitudes and drought with milder cooling at low latitudes on land, in addition to causing limited cessation of photosynthesis in global oceans within a few months to two years after the impact, followed by surface-water cooling in global oceans in a few years. The rapid climate change induced terrestrial extinctions followed by marine extinctions over several years.

Dynamical and Physical Properties of 65803 Didymos, the AIDA Mission Target

NASA Astrophysics Data System (ADS)

Campo Bagatin, A.; Richardson, D. C.; Tsiganis, K.; Cheng, A. F.; Michel, P.

2017-09-01

The near-Earth asteroid (NEA) 65803 Didymos is a binary system and is the target of the proposed Asteroid Impact & Deflection Assessment (AIDA) mission, which combines an orbiter (Asteroid Impact Mission, AIM, or the reduced-scope AIM Deflection Demonstration, AIM-D2) [1, 2] and a kinetic impactor experiment (Double Asteroid Redirection Test, DART) planned to impact the secondary of the Didymos binary system in October, 2022 [3]. The Dynamical and Physical Properties of Didymos Working Group supports the AIDA mission by addressing questions related to understanding the dynamical state of the system and inferring the physical properties of the components

TC4 Observing Campaign: An Operational Test of NASA Planetary Defense Network

NASA Astrophysics Data System (ADS)

Reddy, V.; Kelley, M. S.; Landis, R. R.

Impacts due to near-Earth objects ( 90% near-Earth asteroids, or NEAs, and 10% comets) are one of the natural hazards that can pose a great risk to life on Earth, but one that can potentially be mitigated, if the threat is detected with sufficient lead-time. While the probability of such an event is low, the outcome is so catastrophic that we are well justified in investing a modest effort to minimize this threat. Historically, asteroid impacts have altered the course of evolution on the Earth. In 2013 the Chelyabinsk meteor over Russia, which injured over 1600 people and caused $30M in damages, reinforced the importance of detecting and characterizing small NEAs that pose a greater threat than most large NEAs discovered so far. The NASA Planetary Defense Coordination Office (PDCO) was established to ensure the early detection, tracking and characterization of potentially hazardous objects (PHOs) and is the lead office for providing timely and accurate communications and coordination of U.S. Government planning for response to an actual impact threat. In an effort to test the operational readiness of all entities critical to planetary defense, the NASA PDCO is supporting a community-led exercise. The target of this exercise is 2012 TC4, a 20- meter diameter asteroid that is currently expected to pass by the Earth over Antarctica on Oct. 12, 2017 at a distance of only 2.3 Earth radii. The goal of the TC4 Observing Campaign is to recover, track, and characterize 2012 TC4 as a potential impactor in order to exercise the entire Planetary Defense system from observations, modeling, prediction, and communication. The paper will present an overview of the campaign and summarize early results from the exercise.

Asteroid Crewed Segment Mission Lean Development

NASA Technical Reports Server (NTRS)

Gard, Joe; McDonald, Mark; Jermstad, Wayne

2014-01-01

The next generation of human spaceflight missions presents numerous challenges to designers that must be addressed to produce a feasible concept. The specific challenges of designing an exploration mission utilizing the Space Launch System and the Orion spacecraft to carry astronauts beyond earth orbit to explore an asteroid stored in a distant retrograde orbit around the moon will be addressed. Mission designers must carefully balance competing constraints including cost, schedule, risk, and numerous spacecraft performance metrics including launch mass, nominal landed mass, abort landed mass, mission duration, consumable limits and many others. The Asteroid Redirect Crewed Mission will be described along with results from the concurrent mission design trades that led to its formulation. While the trades presented are specific to this mission, the integrated process is applicable to any potential future mission. The following trades were critical in the mission formulation and will be described in detail: 1) crew size, 2) mission duration, 3) trajectory design, 4) docking vs grapple, 5) extravehicular activity tasks, 6) launch mass and integrated vehicle performance, 7) contingency performance, 8) crew consumables including food, clothing, oxygen, nitrogen and water, and 9) mission risk. The additional Orion functionality required to perform the Asteroid Redirect Crewed Mission and how it is incorporated while minimizing cost, schedule and mass impacts will be identified. Existing investments in the NASA technology portfolio were leveraged to provide the added functionality that will be beneficial to future exploration missions. Mission kits are utilized to augment Orion with the necessary functionality without introducing costly new requirements to the mature Orion spacecraft design effort. The Asteroid Redirect Crewed Mission provides an exciting early mission for the Orion and SLS while providing a stepping stone to even more ambitious missions in the future.

ASTEX - a study of a lander and orbiter mission to two near-Earth asteroids

NASA Astrophysics Data System (ADS)

Boehnhardt, Hermann; Nathues, Andreas; Harris, Alan; Astex Study Team

ASTEX stands for a feasibility study of an exploration mission to two near-Earth asteroids. The targets should have different mineralogical constitution, more specifically one asteroid should be of ‘primitive" nature, the other one should be "evolved". The scientific goal of such a mission is to explore the physical, geological and compositional constitution of the asteroids as planetary bodies as well as to provide information and constraints on the formation and evolution history of the objects per se and of the planetary system, here the asteroid belt, as a whole. Two aspects play an important role, i.e. the search and exploration for the origin and evolution of the primordial material for the formation of life in the solar system on one side and the understanding of the processes that have led to mineralogical differentiation of planetary embryos on the other side. The mission scenario consists of an orbiting and landing phase at each target. The immediate aims of the study are (1) to identify potential targets and to develop for selected pairs more detailed mission scenarios including the best possible propulsion systems to be used, (2) to define the scientific payload of the mission, (3) to analyse the requirements and options for the spacecraft bus and the lander system, and (4) to assess and to define requirements for the operational ground segment of the mission.This eight-months study is directed by the MPI for Solar System Research under support grant by DLR Bonn-Oberkassel and is performed in close collaboration between German scientific research institutes and industry. It is considered complementary to mission studies performed elsewhere and focussing on sample return and impact hazards and their remedy from near-Earth objects.

Anatomy of an Asteroid Breakup

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-05-01

A team of scientists has observed the breakup of an asteroid as it orbits the Sun. In a new study, they reveal what theyve learned from their ground- and space-based observations of this disintegration.These Hubble images show the fragments of R3 in higher resolution over the span of October 2013 to February 2014. [Jewitt et al. 2017]Observations of DisintegrationActive asteroids are objects that move on asteroid-like orbits while displaying comet-like behavior. The cause of their activity can vary ranging from outgassing as the asteroid heats up in its solar approach, to expelled debris from a collision, to the entire asteroid flying apart because its spinning too fast.Led by David Jewitt (University of California at Los Angeles), a team of scientists has analyzed observations of the disintegrating asteroid P/2013 R3. The observations span two years and were made by a number of telescopes, including Hubble, Keck (in Hawaii), Magellan (in Chile), and the Very Large Telescope (in Chile).A schematic diagram of the different fragments of R3 and how they relate to each other. Black numbers estimate the fragment separation velocities; red numbers estimate the separation date. [Jewitt et al. 2017]Jewitt and collaborators then used these observations and a bit of modeling to understand what asteroid R3 was like originally, what its pieces are doing now, and what caused it to break up.Cause of the BreakupThe team found that P/2013 R3 broke up into at least 13 pieces, the biggest of which was likely no more than 100-200 meters in size. The original asteroid was probably less than 400 m in radius.By measuring the velocities of the fragments in the various observations, Jewitt and collaborators were able to work backward to determine when each piece broke off. They found that the fragmentation process was spread out over the span of roughly 5 months suggesting that the asteroids breakup wasnt impact-related (otherwise the fragmentation would likely have been all at once rather than gradual).Timeline of the destruction of R3. Calendar dates are in black, day-of-year dates are in red. The letters below the timeline indicate observations. [Jewitt et al. 2017]So if it wasnt an impact, what caused the breakup of R3? Tidal stresses are unlikely; the asteroid wasnt close enough to the Sun or a planet to experience strong pulls. Gas pressure from sublimating ice also falls short of being strong enough to have caused the disruption, according to the authors calculations.The authors conclude that the most plausible cause of R3s breakup was rotational instability. If an asteroid is made up of a collection of rocky material loosely gravitationally bound in whats known as a rubble-pile composition, then it tends to fly apart if the asteroid spins faster than once every 2.2 hours. The authors show that torques from radiation or anisotropic sublimation could have driven R3 to spin this quickly on a relatively short timescale.A Dusty EndZodiacal light, caused by scattering by dust in the Zodiacal Cloud. [ESO]Lastly, Jewitt and collaborators examine the debris cloud released by the breakup of R3. They use these observations to estimate how much debris disrupted asteroids likely contribute to the Zodiacal Cloud, the cloud of dust found in our solar system, primarily between the Sun and Jupiter.The authors estimate that the fractional contribution by asteroids like R3 is roughly 4% consistent with models that suggest that asteroid dust is a measurable, but not dominant, contributor to the Zodiacal Cloud. Future sky surveys will allow us to better examine this contribution.CitationDavid Jewitt et al 2017 AJ 153 223. doi:10.3847/1538-3881/aa6a57

Waves Generated by Asteroid Impacts and Their Hazard Consequences on The Shorelines

NASA Astrophysics Data System (ADS)

Ezzedine, S. M.; Miller, P. L.; Dearborn, D. S.

2014-12-01

We have performed numerical simulations of a hypothetical asteroid impact onto the ocean in support of an emergency preparedness, planning, and management exercise. We addressed the scenario from asteroid entry; to ocean impact (splash rim); to wave generation, propagation, and interaction with the shoreline. For the analysis we used GEODYN, a hydrocode, to simulate the impact and generate the source wave for the large-scale shallow water wave program, SWWP. Using state-of-the-art, high-performance computing codes we simulated three impact areas — two are located on the West Coast near Los Angeles's shoreline and the San Francisco Bay, respectively, and the third is located in the Gulf of Mexico, with a possible impact location between Texas and Florida. On account of uncertainty in the exact impact location within the asteroid risk corridor, we examined multiple possibilities for impact points within each area. Uncertainty in the asteroid impact location was then convolved and represented as uncertainty in the shoreline flooding zones. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and partially funded by the Laboratory Directed Research and Development Program at LLNL under tracking code 12-ERD-005.

Martian cratering. II - Asteroid impact history.

NASA Technical Reports Server (NTRS)

Hartmann, W. K.

1971-01-01

This paper considers the extent to which Martian craters can be explained by considering asteroidal impact. Sections I, II, and III of this paper derive the diameter distribution of hypothetical asteroidal craters on Mars from recent Palomar-Leiden asteroid statistics and show that the observed Martian craters correspond to a bombardment by roughly 100 times the present number of Mars-crossing asteroids. Section IV discusses the early bombardment history of Mars, based on the capture theory of Opik and probable orbital parameters of early planetesimals. These results show that the visible craters and surface of Mars should not be identified with the initial, accreted surface. A backward extrapolation of the impact rates based on surviving Mars-crossing asteroids can account for the majority of Mars craters over an interval of several aeons, indicating that we see back in time no further than part-way into a period of intense bombardment. An early period of erosion and deposition is thus suggested. Section V presents a comparison with results and terminology of other authors.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Rapid short-term cooling following the Chicxulub impact at the Cretaceous–Paleogene boundary

PubMed Central

Vellekoop, Johan; Sluijs, Appy; Smit, Jan; Schouten, Stefan; Weijers, Johan W. H.; Sinninghe Damsté, Jaap S.; Brinkhuis, Henk

2014-01-01

The mass extinction at the Cretaceous–Paleogene boundary, ∼66 Ma, is thought to be caused by the impact of an asteroid at Chicxulub, present-day Mexico. Although the precise mechanisms that led to this mass extinction remain enigmatic, most postulated scenarios involve a short-lived global cooling, a so-called “impact winter” phase. Here we document a major decline in sea surface temperature during the first months to decades following the impact event, using TEX86 paleothermometry of sediments from the Brazos River section, Texas. We interpret this cold spell to reflect, to our knowledge, the first direct evidence for the effects of the formation of dust and aerosols by the impact and their injection in the stratosphere, blocking incoming solar radiation. This impact winter was likely a major driver of mass extinction because of the resulting global decimation of marine and continental photosynthesis. PMID:24821785

Simulations of impacts on rubble-pile asteroids

NASA Astrophysics Data System (ADS)

Deller, J.; Snodgrass, C.; Lowry, S.; Price, M.; Sierks, H.

2014-07-01

Rubble-pile asteroids can contain a high level of macroporosity. For some asteroids, porosities of 40 % or even more have been measured [1]. While little is known about the exact distribution of the voids inside rubble-pile asteroids, assumptions have to be made for the modeling of impact events on these bodies. Most hydrocodes do not distinguish between micro- and macroporosity, instead describing brittle material by a constitutive model as homogeneous. We developed a method to model rubble-pile structures in hypervelocity impact events explicitly. The formation of the asteroid is modelled as a gravitational aggregation of spherical `pebbles', that form the building blocks of our target. This aggregate is then converted into a high-resolution Smoothed Particle Hydrodynamics (SPH) model, which also accounts for macroporosity inside the pebbles. We present results of a study that quantifies the influence of our model parameters on the outcome of a typical impact event of two small main-belt asteroids. The existence of void space in our model increases the resistance against collisional disruption, a behavior observed before [2]. We show that for our model no a priori knowledge of the rubble-pile constituents in the asteroid is needed, as the choice of the corresponding parameters does not directly correlate with the impact outcome. The size distribution of the pebbles used as building blocks in the formation of an asteroid is only poorly constrained. As a starting point, we use a power law N(>r) ∝ r^α to describe the distribution of radii of the pebbles. Reasonable values for the slope α range around α=-2.5, as found in the size distribution of main-belt objects [3,4]. The cut-off values for pebbles, r_{min} and r_{max} are given by practical considerations: In the SPH formalism, properties are represented by weighted averages of particles within their smoothing length h, preventing the resolution of structures below that scale. Using spheres with radius in the range of h results in a practically monolithic body, as well as using spheres of a radius similar to the asteroid itself. We quantify the sensitivity of impact outcomes to the choice of parameters. Propagation of the shock front inside the asteroid depends on the pebble size distribution. While larger pebbles transmit the shock wave further into the structure, resulting in a steeper crater, small pebbles result in a more evenly distributed shock front and a wider crater. Because the shock wave is transmitted only at the small contact area of the pebbles, the shock wave is focused at the contact points and material can be compressed or damaged even at a distance to the impact zone. We create maps of the displacement of pebbles at the surface of the asteroid on the opposing site of the impact event. This can possibly be used to relate surface features on asteroids like Šteins or Itokawa to specific impact events.

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

PubMed

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

2014-10-23

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

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.

Exploration of the Moon and Asteroids by Secondary Students

NASA Astrophysics Data System (ADS)

Shaner, A. J.; Bakerman, M. N.; Buxner, S.

2016-12-01

Since 2014, the Exploration of the Moon and Asteroids by Secondary Students, or ExMASS, program provides an opportunity for students to participate in authentic scientific research. The ExMASS program is an effort managed by the Center for Lunar Science and Exploration (CLSE). Led by the Lunar and Planetary Institute and Johnson Space Center, CLSE is one of nine teams comprising NASA's Solar System Exploration Research Virtual Institute (SSERVI). Over the course of one academic year, 10 teams of U.S. high school students conduct their own scientific investigations of Earth's Moon, or asteroids, with guidance from a scientist advisor. The program includes two elements: 1) two guided-inquiry introductory research activities that builds student knowledge of current lunar/asteroid science and lunar/asteroid data, and 2) an open-inquiry research project in which the students apply their knowledge to a self-defined project. Because the research is student-driven, it is not necessarily original research; original research is therefore not required. However, one team's research has been published in a professional journal. At the end of the school year, teams submit an abstract and research poster which are scored by a panel a judges. The top four scoring teams gather virtually to give short presentations to the judges. After presentations and time for Q&A, the judges choose one team to present in person at the Exploration Science Forum (ESF). The posters of all finalist schools are displayed at the ESF. The ExMASS program is evaluated by collecting data on changes in students' lunar/asteroid content knowledge, student attitudes toward science and science careers, and student perceptions of the processes of science in which their team participated. Exit surveys for teachers, students, and advisors are also distributed at the end of each program year to gather general feedback about the program and its impact. Results of this data from the first two years of the ExMASS program (2014 and 2015) will be discussed.

OBSERVED ASTEROID SURFACE AREA IN THE THERMAL INFRARED

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

Nugent, C. R.; Mainzer, A.; Masiero, J.

The rapid accumulation of thermal infrared observations and shape models of asteroids has led to increased interest in thermophysical modeling. Most of these infrared observations are unresolved. We consider what fraction of an asteroid’s surface area contributes the bulk of the emitted thermal flux for two model asteroids of different shapes over a range of thermal parameters. The resulting observed surface in the infrared is generally more fragmented than the area observed in visible wavelengths, indicating high sensitivity to shape. For objects with low values of the thermal parameter, small fractions of the surface contribute the majority of thermally emittedmore » flux. Calculating observed areas could enable the production of spatially resolved thermal inertia maps from non-resolved observations of asteroids.« less

The Nature of Airbursts and their Contribution to the Impact Hazard (Invited)

NASA Astrophysics Data System (ADS)

Boslough, M. B.

2009-12-01

Ongoing simulations of low-altitude airbursts from hypervelocity asteroid impacts have led to a re-evaluation of the impact hazard that accounts for the enhanced damage potential relative to the standard point-source approximations. Computational models demonstrate that the altitude of maximum energy deposition is not a good estimate of the equivalent height of a point explosion, because the center of mass of an exploding projectile maintains a significant fraction of its initial momentum and is transported downward in the form of a high-temperature jet of expanding gas. This “fireball” descends to a depth well beneath the burst altitude before its velocity becomes subsonic. The time scale of this descent is similar to the time scale of the explosion itself, so the jet simultaneously couples both its translational and its radial kinetic energy to the atmosphere. Because of this downward flow, larger blast waves and stronger thermal radiation pulses are experienced at the surface than would be predicted for a nuclear explosion of the same yield at the same burst height. For impacts with a kinetic energy below some threshold value, the hot jet of vaporized projectile loses its momentum before it can make contact with the Earth's surface. The 1908 Tunguska explosion is the largest observed example of this first type of airburst. For impacts above the threshold, the fireball descends all the way to the ground, where it expands radially, driving supersonic winds and radiating thermal energy at temperatures that can melt silicate surface materials. The Libyan Desert Glass event, 29 million years ago, may be an example of this second, larger, and more destructive type of airburst. The kinetic energy threshold that demarcates these two airburst types depends on asteroid velocity, density, strength, and impact angle. There is no evidence that the Tunguska fireball descended all the way to the surface, suggesting that its yield was about 5 megatons or lower. Better understanding of airbursts, combined with the diminishing number of undiscovered large asteroids, leads to the conclusion that airbursts represent a large and growing fraction of the total impact threat. Sandia is a multiprogram laboratory operated by Sandia Corp, a Lockheed Martin Company, for the US DOE under Contract DE-AC04-94AL85000. At altitude of maximum energy deposition (9 km) for a 15-megaton stony asteroid, its mass continues to descend at 9 km/s (60% of initial velocity).

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

PubMed

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

2004-03-25

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

Consequences of impacts of small asteroids and comets with Earth

NASA Technical Reports Server (NTRS)

Hills, J. G.

1994-01-01

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

Contribution of Asteroid Generated Tsunami to the Impact Hazard

NASA Technical Reports Server (NTRS)

Morrison, David; Venkatapathy, Ethiraj

2017-01-01

The long-standing uncertainty about the importance of asteroid-generated tsunami was addressed at a workshop in August 2016, co-sponsored by NASA and NOAA. Experts from NASA, NOAA, the DoE tri-labs (LLNL, SNL, and LANL), DHS, FEMA, and academia addressed the hazard of tsunami created by asteroid impacts, focusing primarily on NEAs with diameter less than 250m. Participants jointly identified key issues and shared information for nearly a year to coordinate their results for discussion at the workshop. They used modern computational tools to examine 1) Near-field wave generation by the impact; 2) Long-distance wave propagation; 3) Damage from coastal run-up and inundation, and associated hazard. The workshop resulted in broad consensus that the asteroid impact tsunami threat is not as great as previously thought.

Doublet craters and the tidal disruption of binary asteroids

NASA Technical Reports Server (NTRS)

Melosh, H. J.; Stansberry, J. A.

1991-01-01

An evaluation is conducted of the possibility that the tidal disruption of a population of contact binary asteroids can account for terrestrial-impact 'doublet' craters. Detailed orbital integrations indicate that while such asteroids are often disrupted by tidal forces outside the Roche limit, the magnitude of the resulting separations is too small to account for the observed doublet craters. It is hypothesized that an initial population of km-scale earth-crossing objects encompassing 10-20 percent binaries must be responsible for doublet impacts, as may be verified by future observations of earth-approaching asteroids.

Stop hitting yourself: did most terrestrial impactors originate from the terrestrial planets?

NASA Astrophysics Data System (ADS)

Jackson, Alan; Asphaug, Erik; Elkins-Tanton, Linda

2014-11-01

Although the asteroid belt is the main source of impactors in the inner solar system today, it contains only 0.0006 Earth mass, or 0.05 Lunar mass. While the asteroid belt would have been more massive when it formed, it is unlikely to have had greater than 0.5 Lunar mass since the formation of Jupiter and the dissipation of the solar nebula. By comparison, giant impacts onto the terrestrial planets typically release debris equal to several per cent of the planets mass. The Moon-forming impact on Earth and the dichotomy forming impact on Mars, to consider but two of these major events, released 1.3 and 0.3 Lunar mass in debris respectively, many times the mass of the present day asteroid belt. This escaping impact debris is less long lived than the main asteroid belt, as it is injected on unstable, planet-crossing orbits, but this same factor also increases the impact probability with the terrestrial planets and asteroids. We show that as a result terrestrial ejecta played a major role in the impact history of the early inner solar system, and we expect the same is also likely to be true in other planetary systems.

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

NASA Technical Reports Server (NTRS)

Robertson, Darrel

2016-01-01

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

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

PubMed Central

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

2014-01-01

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

Asteroid Impact Mission (aim) & Deflection Assessment: AN Opportunity to Understand Impact Dynamics and Modelling

NASA Astrophysics Data System (ADS)

Galvez, A.; Carnelli, I.; Fontaine, M.; Corral Van Damme, C.

2012-09-01

ESA's Future Preparation and Strategic Studies Office has carried out the Asteroid Impact Mission (AIM) study with the objective of defining an affordable and fully independent mission element that ESA could contribute to an Asteroid Impact Deflection Assessment campaign (AIDA), a joint effort of ESA, JHU/APL, NASA, OCA and DLR. The mission design foresees two independent spacecraft, one impactor (DART) and one rendezvous probe (AIM). The target of this mission is the binary asteroid system (65803) Didymos (1996 GT): one spacecraft, DART, would impact the secondary of the Didymos binary system while AIM would observe and measure any the change in the relative orbit. For this joint project, the timing of the experiment is set (maximum proximity of the target to Earth allowing for ground-based characterisation of the experiment) but the spacecraft are still able to pursue their missions fully independently. This paper describes in particular the AIM rendezvous mission concept.

Meteoroid impacts onto asteroids: A competitor for Yarkovsky and YORP

NASA Astrophysics Data System (ADS)

Wiegert, Paul A.

2015-05-01

The impact of a meteoroid onto an asteroid transfers linear and angular momentum to the larger body, which may affect its orbit and its rotational state. Here we show that the meteoroid environment of our Solar System can have an effect on small asteroids that is comparable to the Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects under certain conditions. The momentum content of the meteoroids themselves is expected to generate an effect much smaller than that of the Yarkovsky effect. However, momentum transport by ejecta may increase the net effective force by one order of magnitude for iron or regolith surfaces, and two orders of magnitude for impacts into bare rock surfaces. The result is sensitive to the extrapolation of laboratory microcratering experiment results to real meteoroid-asteroid collisions and needs further study. If this extrapolation holds, then meteoroid impacts are more important to the dynamics of small rocky asteroids than had previously been considered. Asteroids orbiting on prograde orbits near the Earth encounter an anisotropic meteoroid environment, including a population of particles on retrograde orbits generally accepted to be material from long-period comets spiralling inwards under Poynting-Robertson drag. High relative speed (60 km s-1) impacts by meteoroids provide a small effective drag force that decreases asteroid semimajor axes and which is independent of their rotation pole. If small asteroids are bare instead of regolith covered, as is perhaps to be expected given their rapid rotation rates (Harris, A.W., Pravec, P. [2006]. In: Daniela, L., Sylvio Ferraz, M., Angel, F.J. (Eds.), Asteroids, Comets, Meteors. IAU Symposium, vol. 229, pp. 439-447), this effect may exceed the instantaneous Yarkovsky drift at sizes near and below one meter. Since one meter objects are the most abundant meteorite droppers at the Earth, the delivery of these important objects may be controlled by drag against the meteoroid environment. The rate of reorientation of asteroid spins is also substantially increased when momentum transport by ejecta is included. This has an indirect effect on the net Yarkovsky drift, particularly the diurnal variant, as the sign of the drift it creates depends on its rotational state. The net drift of an asteroid towards a resonance under the diurnal Yarkovsky effect can be slowed by more frequent pole reorientations or induced tumbling. This may make the effect of the meteoroid environment more important than the Yarkovsky effect at sizes even above one meter. Meteoroid impacts also affect asteroid spins at a level comparable to that of YORP at sizes smaller than tens of meters. Here the effect comes primarily from a small number of impacts by centimeter size particles. We conclude that recent measurements of the YORP effect have probably not been compromised, because of the targets' large sizes and because they are known or likely to be regolith-covered rather than bare rock. However, the effect of impacts increases sharply with decreasing size, and will likely become important for asteroids smaller than a few tens of meters in radius.

The Remote Observing Working Group for the Asteroid Impact and Deflection Assessment (AIDA)

NASA Astrophysics Data System (ADS)

Rivkin, A. S.; Pravec, P.; Thomas, C. A.; Thirouin, A.; Snodgrass, C.; Green, S.; Licandro, J.; Sickafoose, A. A.; Erasmus, N.; Howell, E. S.; Osip, D.; Thomas-Osip, J.; Moskovitz, N.; Scheirich, P.; Oszkiewicz, D.; Richardson, D. C.; Polishook, D.; Ryan, W. H.; Busch, M. W.

2017-09-01

The Asteroid Impact and Deflection Assessment (AIDA) is a joint US-European mission concept designed to demonstrate the effectiveness of an kinetic impactor for planetary defense. Ground-based observing is a key component to AIDA and critical for its success. We present the observing campaign we have been conducting of the asteroid Didymos, the AIDA target, and plans for future work.

Ejecta evolutions and fates from the AIDA impact on the secondary of the binary asteroid Didymos: a NEOShield-2 project contribution

NASA Astrophysics Data System (ADS)

Michel, P.; Yu, Y.

2017-09-01

We simulated the evolutions and fates of ejecta produced by the impact of a projectile of the secondary of the binary asteroid Didymos, in the framework of the AIDA space mission project. Our results show how these evolutions and fates depend on the impact location on the secondary and ejection speeds of the ejecta. This information can be used to defined safe positions for an observing spacecraft and to better understand the outcome of an impact in the environment of a binary asteroid.

Evidence of Collisional Histories of Asteroids, Comets and Meteorites: Comparisons with Shocked Minerals

NASA Technical Reports Server (NTRS)

Lederer, Susan M.; Jensen, Elizabeth; Smith, Douglas; Fane, Michael; Whizin, Akbar; Landsman, Zoe A.; Wooden, Diane H.; Lindsay, Sean S.; Cintala, Mark; Keller, Lindsay P.;

Near Earth Asteroid Characterization for Threat Assessment

NASA Technical Reports Server (NTRS)

Dotson, Jessie; Mathias, Donovan; Wheeler, Lorien; Wooden, Diane; Bryson, Kathryn; Ostrowski, Daniel

2017-01-01

Physical characteristics of NEAs are an essential input to modeling behavior during atmospheric entry and to assess the risk of impact but determining these properties requires a non-trivial investment of time and resources. The characteristics relevant to these models include size, density, strength and ablation coefficient. Some of these characteristics cannot be directly measured, but rather must be inferred from related measurements of asteroids and/or meteorites. Furthermore, for the majority of NEAs, only the basic measurements exist so often properties must be inferred from statistics of the population of more completely characterized objects. The Asteroid Threat Assessment Project at NASA Ames Research Center has developed a probabilistic asteroid impact risk (PAIR) model in order to assess the risk of asteroid impact. Our PAIR model and its use to develop probability distributions of impact risk are discussed in other contributions to PDC 2017 (e.g., Mathias et al.). Here we utilize PAIR to investigate which NEA characteristics are important for assessing the impact threat by investigating how changes in these characteristics alter the damage predicted by PAIR. We will also provide an assessment of the current state of knowledge of the NEA characteristics of importance for asteroid threat assessment. The relative importance of different properties as identified using PAIR will be combined with our assessment of the current state of knowledge to identify potential high impact investigations. In addition, we will discuss an ongoing effort to collate the existing measurements of NEA properties of interest to the planetary defense community into a readily accessible database.

The Binary Asteroid in-situ Explorer (BASiX) Mission

NASA Astrophysics Data System (ADS)

Dissly, Richard; Scheeres, D. J.; Nilsen, E.; Roark, S.; Frazier, W.; Bank, T.; Rosing, D.; Jordan, E.; BASiX Science Team

2010-10-01

The Binary Asteroid in-situ Explorer (BASiX) Mission represents the next phase of asteroid exploration, carrying out geophysical experiments by active engagement with an asteroid in a controlled and repeatable manner. BASiX will address new and timely scientific goals that address unresolved issues at the heart of our understanding of these bodies and which serve as barriers to their future exploration. A primary objective of the BASiX Mission is to determine the fundamental mechanical and strength properties of an asteroid through the creation of craters on the asteroid surface using calibrated charges. BASiX also takes advantage of these experiments to further understand the weathering and seismic properties of an asteroid. By carrying out these experiments at a binary Near Earth Asteroid (NEA), BASiX also advances our understanding of these ubiquitous bodies in the small asteroid population. BASiX is an efficient and simple mission concept that can deliver revolutionary science with its threshold mission and adds substantial enhancements with its baseline mission. BASiX assembles an international team of top small body scientists and astronomers and is led by PI Dan Scheeres (University of Colorado). BASiX is managed by JPL, which is also where mission and science operations will be based. The BASiX Spacecraft is built by Ball Aerospace & Technologies Corp. Instruments are built by JPL and Ball with additional contributed instruments from CNES.

ASPECT spectral imaging satellite proposal to AIDA/AIM CubeSat payload

NASA Astrophysics Data System (ADS)

Kohout, Tomas; Näsilä, Antti; Tikka, Tuomas; Penttilä, Antti; Muinonen, Karri; Kestilä, Antti; Granvik, Mikael; Kallio, Esa

2016-04-01

ASPECT (Asteroid Spectral Imaging Mission) is a part of AIDA/AIM project and aims to study the composition of the Didymos binary asteroid and the effects of space weathering and shock metamorphism in order to gain understanding of the formation and evolution of the Solar System. The joint ESA/NASA AIDA (Asteroid Impact & Deflection Assessment) mission to binary asteroid Didymos consists of AIM (Asteroid Impact Mission, ESA) and DART (Double Asteroid Redirection Test, NASA). DART is targeted to impact Didymos secondary component (Didymoon) and serve as a kinetic impactor to demonstrate deflection of potentially hazardous asteroids. AIM will serve as an observational spacecraft to evaluate the effects of the impact and resulting changes in the Didymos dynamic parameters. The AIM mission will also carry two CubeSat miniaturized satellites, released in Didymoon proximity. This arrangement opens up a possibility for secondary scientific experiments. ASPECT is one of the proposed CubeSat payloads. Whereas Didymos is a space-weathered binary asteroid, the DART impactor is expected to produce a crater and excavate fresh material from the secondary component (Didymoon). Spectral comparison of the mature surface to the freshly exposed material will allow to directly deter-mine space weathering effects. It will be also possible to study spectral shock effects within the impact crater. ASPECT will also demonstrate for the first time the joint spacecraft - CubeSat operations in asteroid proximity and miniature spectral imager operation in deep-space environment. Science objectives: 1. Study of the surface composition of the Didymos system. 2. Photometric observations (and modeling) under varying phase angle and distance. 3. Study of space weathering effects on asteroids (comparison of mature / freshly exposed material). 4. Study of shock effects (spectral properties of crater interior). 5. Observations during the DART impact. Engineering objectives: 1. Demonstration of CubeSat semi-autonomous operations in deep space environment. 2. Navigation in the vicinity of a binary asteroid. 3. Demonstration of a satellite survival during impact. 4. Demonstration of joint spacecraft - CubeSat operations. ASPECT is a 3U CubeSat (size of 3 units, Fig. 1) equipped with a spectral imager from 500 nm to 1600 nm (spatial resolution < 2 m, spectral resolution 10 - 30 nm; VIS channel 512 x 512 pixels, NIR channel 256 x 256 pixels), and a non-imaging spectrometer from 1600 - 2500 nm. The design is based on the Aalto-1 CubeSat Spectral Imager heritage. ASPECT will also demonstrate the capabilities of a CubeSat and a miniature spectral imager for the first time in deep-space environment. Acknowledgements: This work is done under Sys-Nova: R&D Studies Competition for Innovation contract with ESA.

Impact Record of a Asteroid Regolith Recorded in a Carbonaceous Chrondrite

NASA Technical Reports Server (NTRS)

Zolensky, Michael; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Komatsu, Mutsumi; Chan, Queenie H. S.; Le, Loan; Kring, David; Cato, Michael; Fagan, Amy L.;

Designing Asteroid Impact Scenario Trajectories

NASA Astrophysics Data System (ADS)

Chodas, Paul

2016-05-01

In order to study some of the technical and geopolitical issues of dealing with an asteroid on impact trajectory, a number of hypothetical impact scenarios have been presented over the last ten years or so. These have been used, for example, at several of the Planetary Defense Conferences (PDCs), as well as in tabletop exercises with the Federal Emergency Management Agency (FEMA), along with other government agencies. The exercise at the 2015 PDC involved most of the attendees, consisted of seven distinct steps (“injects”), and with all the presentations and discussions, took up nearly 10 hours of conference time. The trajectory for the PDC15 scenario was entirely realistic, and was posted ahead of the meeting. It was made available in the NEO Program’s Horizons ephemeris service so that users could , for example, design their own deflection missions. The simulated asteroid and trajectory had to meet numerous very exacting requirements: becoming observable on the very first day of the conference, yet remaining very difficult to observe for the following 7 years, and far enough away from Earth that it was out of reach of radar until just before impact. It had to be undetectable in the past, and yet provide multiple perihelion opportunities for deflection in the future. It had to impact in a very specific region of the Earth, a specific number of years after discovery. When observations of the asteroid are simulated to generate an uncertainty region, that entire region must impact the Earth along an axis that cuts across specific regions of the Earth, the “risk corridor”. This is important because asteroid deflections generally move an asteroid impact point along this corridor. One scenario had a requirement that the asteroid pass through a keyhole several years before impact. The PDC15 scenario had an additional constraint that multiple simulated kinetic impactor missions altered the trajectory at a deflection point midway between discovery and impact. This talk will describe a few recent impact scenarios and outline techniques for finding trajectories that satisfy the complex constraints.

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

NASA Image and Video Library

2014-07-17

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

Vesta Cratered Landscape: Double Crater and Craters with Bright Ejecta

NASA Image and Video Library

2011-11-23

This image from NASA Dawn spacecraft is dominated by a double crater which may have been formed by the simultaneous impact of a binary asteroid. Binary asteroids are asteroids that orbit their mutual center of mass.

Comparison of Damage from Hydrocode Simulations of an Asteroid Airburst or Impact on Land, in Deep, or in Shallow Water

NASA Technical Reports Server (NTRS)

Robertson, Darrel; Wheeler, Lorien; Mathias, Donovan

2017-01-01

If an asteroid is discovered to be on a collision course with Earth and there is insufficient time for a deflection effort to make it miss Earth completely, should it be redirected to a land or ocean impact? While distance from densely populated areas should obviously be maximized, the differing ability of air blast, seismic waves, and tsunami waves to cause damage at distance does not make the choice between land and ocean impacts an immediately obvious one. More broadly this work is a step towards improving damage models from asteroid impacts. This extended abstract follows the hypothetical scenario of the 2017 IAA Planetary Defense Conference where a 100-250m diameter asteroid is on a potential impact course with Earth. A hydrocode was used to simulate impacts into the most sparsely populated areas along the eastern end of the hypothetical impact corridor- specifically in the Gobi Desert, in the shallow waters of the Sea of Japan, and in the deep waters of the Japan Trench in the Pacific Ocean.

Asteroids from a Martian Mega Impact

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-04-01

Like evidence left at a crime scene, the mineral olivine may be the clue that helps scientists piece together Marss possibly violent history. Could a long-ago giant impact have flung pieces of Mars throughout our inner solar system? Two researchers from the Tokyo Institute of Technology in Japan are on the case.A Telltale MineralOlivine, a mineral that is common in Earths subsurface but weathers quickly on the surface. Olivine is a major component of Marss upper mantle. [Wilson44691]Olivine is a major component of the Martian upper mantle, making up 60% of this region by weight. Intriguingly, olivine turns up in other places in our solar system too for instance, in seven out of the nine known Mars Trojans (a group of asteroids of unknown origin that share Marss orbit), and in the rare A-type asteroids orbiting in the main asteroid belt.How did these asteroids form, and why are they so olivine-rich? An interesting explanation has been postulated: perhaps this olivine all came from the same place Mars as the result of a mega impact billions of years ago.Evidence for ImpactMars bears plenty of signs pointing to a giant impact in its past. The northern and sourthern hemispheres of Mars look very different, a phenomenon referred to as the Mars hemisphere dichotomy. The impact of a Pluto-sized body could explain the smooth Borealis Basin that covers the northern 40% of Marss surface.This high-resolution topographic map of Mars reveals the dichotomy between its northern and sourthern hemispheres. The smooth region in the northern hemisphere, the Borealis basin, may have been formed when a giant object impacted Mars billions of years ago. [NASA/JPL/USGS]Other evidence piles up: Marss orbit location, its rotation speed, the presence of its two moons all could be neatly explained by a large impact around 4 billion years ago. Could such an impact have also strewn debris from Marss mantle across the solar system?To test this theory, we need to determine if a mega impact is capable of producing enough ejecta and with the appropriate compositions and orbits to explain the Mars trojans and the A-type asteroids we observe. Tackling this problem, researchers Ryuki Hyodo and Hidenori Genda have performed numerical simulations to explore the ejecta from such a collision.Distributing DebrisHyodo and Genda examine the outcomes of a Mars mega impact using smoothed particle hydrodynamics simulations. They test different impactor masses, impactor speeds, angles of impact, and more to determine how these properties affect the properties of the Martian ejecta that result.Debris ejected in a Mars mega impact, at 20 hours post-impact. Blue particles are from the impactor, red particles are from Mars, yellow particles are clumps of 10 particles. [Hyodo Genda 2018]The authors find that a large amount of debris can be ejected from Mars during such an impact and distributed between 0.53 AU in the solar system. Roughly 2% of this debris could originate from Marss olivine-rich, unmelted upper mantle which could indeed be the source of the olivine-rich Mars Trojan asteroids and rare A-type asteroids.How can we further explorethis picture? Debris from a Mars mega impact would not justhave been the source of new asteroids; the debris likely also collided with pre-existing asteroids or even transferred to early Earth. Signatures of a Mars mega impact may therefore be recorded in main-belt asteroids or in meteorites found on Earth, providing tantalizing targets for future studies in the effort to map out Marss past.CitationRyuki Hyodo and Hidenori Genda 2018 ApJL 856 L36. doi:10.3847/2041-8213/aab7f0

Cosmic impact: What are the odds?

NASA Astrophysics Data System (ADS)

Harris, A. W.

2009-12-01

Firestone et al. (PNAS 104, 16016-16021, 2007) propose that the impact of a ~4 km diameter comet (or multiple bodies making up a similar mass) led to the Younger Dryas cooling and extinction of megafauna in North America, 12,900 years ago. Even more provocatively, Firestone et al. (Cycle of Cosmic Catastrophes, Bear & Co. Books, 2006, 392pp), suggest that a nearby supernova may have produced a comet shower leading to the impact event, either by disturbing the Oort Cloud or by direct injection of 4-km comet-like bodies to the solar neighborhood. Here we show: (a) A supernova shockwave or mass ejection is not capable of triggering a shower of comets from the Oort Cloud. (b) An Oort Cloud shower from whatever cause would take 100,000 years or more for the perturbed comets to arrive in the inner solar system, and the peak flux would persist for some hundreds of thousands more years. (c) Even if all 20 solar masses or so of ejected matter from a SN were in the form of 4-km diameter balls, the probability of even one such ball hitting the Earth from an event 100 light years away would be about 3e-5. (d) A 4-km diameter ball traveling fast enough to get here from 100 LY away in some tens of thousands of years would deliver the energy of a 50 km diameter impactor traveling at typical Earth-impact velocity (~20 km/sec). We review the current impact flux on the Earth from asteroids and comets, and show that the probability of an impact of a 4-km diameter asteroid in an interval of 13,000 years is about one in a thousand, and the probability of a comet impact of that size is a few in a million. An "impact shower" caused by the injection or breakup of comets or asteroids in the inner solar system by whatever means would take tens to hundreds of thousands of years to clear out, thus the population of NEOs we see now with our telescopic surveys is what we’ve had for the last few tens of thousands of years, at least. Faced with such low odds, the evidence that such a large cosmic impact is the cause of the Younger Dryas boundary and cooling, and that there is no other possible cause, needs to be extraordinary indeed.

Observation of freakish-asteroid-discovered-resembles support my idea that many dark comets were arrested and lurked in the solar system after every impaction

NASA Astrophysics Data System (ADS)

Cao, Dayong

2014-03-01

New observations show that some asteroids are looked like comets. http://www.astrowatch.net/2013/11/freakish-asteroid-discovered-resembles.html, http://www.astrowatch.net/2013/11/astronomers-puzzle-over-newfound.html. It supports my idea that ``many dark comets with very special tilted orbits were arrested and lurked in the solar system'' - ``Sun's companion-dark hole seasonal took its dark comets belt and much dark matter to impact near our earth. And some of them probability hit on our earth. So this model kept and triggered periodic mass extinctions on our earth every 25 to 27 million years. After every impaction, many dark comets with very special tilted orbits were arrested and lurked in the solar system. Because some of them picked up many solar matter, so it looked like the asteroids. When the dark hole-Tyche goes near the solar system again, they will impact near planets.'' The idea maybe explains why do the asteroid looks like the comet? Where are the asteroids come from? What relationship do they have with the impactions and extinctions? http://meetings.aps.org/link/BAPS.2011.CAL.C1.7, http://meetings.aps.org/Meeting/CAL12/Event/181168, http://meetings.aps.org/link/BAPS.2013.MAR.H1.267. During 2009 to 2010, I had presented there are many dark comets like dark Asteroids near the orbit of Jupiter in ASP Meetings. In 2010, NASA's WISE found them. http://meetings.aps.org/link/BAPS.2011.APR.K1.17, http://www.nasa.gov/mission_pages/WISE/news/wise20100122.html Avoid Earth Extinction Associ.

Evidence of Collisional Histories of Asteroids, Comets and Meteorites: Comparisons with Shocked Minerals

NASA Astrophysics Data System (ADS)

Lederer, Susan M.; Jensen, Elizabeth; Smith, Douglas; Fane, Michael; Whizin, Akbar; Landsman, Zoe A.; Wooden, Diane H.; Lindsay, Sean S.; Cintala, Mark; Keller, Lindsay P.; Zolensky, Michael

2017-10-01

Evidence of the collisional history of comets and asteroids has been emerging from analyses of cometary forsterite and enstatite returned from Comet Wild 2 by the Stardust mission (Keller et al.Geochim. Cosmochim. Acta 72, 2008; Tomeoka et al. MAPS 43, 2008; Jacobs et al. MAPS 44, 2009). Likewise, shock metamorphism is observed in many meteoritic forsterites and enstatites (McCausland et al. AGU, 2010), suggesting similar collisional histories for asteroids. Further exploration of the effects of collisions is slated for the upcoming Asteroid Impact Mission/Double Asteroid Redirection Test (AIM/DART) mission, expected for launch in 2020. DART will impact Didymoon, the companion of the larger 65803 Didymos (1996 G2) asteroid, and AIM will use its instrumentation to characterize the impact.A suite of relevant impact experiments have been carried out in the Experimental Impact Laboratory at the NASA Johnson Space Center at velocities ranging from ~2.0 - 2.8 km s-1 and temperatures from 25°C to -100°C. Targets include a suite of minerals typically found in cometary dust and in asteroids and meteorites: Mg-rich forsterite (olivine), enstatite (orthopyroxene), diopside (clinopyroxene), magnesite (Mg-rich carbonate), and serpentine (phyllosilicate). Transmission Electron Microscope (TEM) imaging indicates evidence of shock similar to that seen in forsterite and enstatite from Comet Wild 2. Fourier Transform Infrared (FTIR) Spectroscopy will also be used for comparisons with meteorite spectra. A quantitative analysis of the shock pressures required to induce planar dislocations and spectral effects with respect to wavelength will also be presented.Funding provided by the NASA PG&G grant 09-PGG09-0115, NSF grant AST-1010012. Special thanks to NASA EIL staff, F. Cardenas and R. Montes.

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

NASA Technical Reports Server (NTRS)

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

1988-01-01

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

The Impact Imperative: Laser Ablation for Deflecting Asteroids, Meteoroids, and Comets From Impacting the Earth

NASA Technical Reports Server (NTRS)

Campbell, Jonathan W.; Phipps, Claude; Smalley, Larry; Reilly, Jim; Boccis, Dona; Howell, Joe T., Jr. (Technical Monitor)

2002-01-01

Impacting at hypervelocity, an asteroid struck the Earth approximately 65 million years ago in the Yucatan Peninsula area. This triggered the extinction of almost 70% of the species of life on Earth including the dinosaurs. Other impacts prior to this one have caused even greater extinctions. Preventing collisions with the Earth by hypervelocity asteroids, meteoroids, and comets is the most important immediate space challenge facing human civilization. This is the Impact Imperative. We now believe that while there are about 2000 earth orbit crossing rocks greater than 1 kilometer in diameter, there may be as many as 200,000 or more objects in the 100 m size range, Can anything be done about this fundamental existence question facing our civilization? The answer is a resounding yes! By using an intelligent combination of Earth and space based sensors coupled with an infra-structure of high-energy laser stations and other secondary mitigation options, we can deflect inbound asteroids, meteoroids, and comets and prevent them from striking the Earth.

Nanoindenting the Chelyabinsk Meteorite to Learn about Impact Deflection Effects in asteroids

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

Moyano-Cambero, Carles E.; Trigo-Rodríguez, Josep M.; Martínez-Jiménez, Marina

The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids. Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young’s modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce themore » efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and therefore, higher values imply more efficient impacts. In the Chelyabinsk meteorite, the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and therefore increase the momentum multiplication. These results are relevant to the growing interest in missions to test asteroid deflection, such as the recent collaboration between the European Space Agency and NASA, known as the Asteroid Impact and Deflection Assessment mission.« less

Deflection by Kinetic Impact or Nuclear Ablation: Sensitivity to Asteroid Properties

NASA Astrophysics Data System (ADS)

Bruck Syal, M.

2015-12-01

Impulsive deflection of a threatening asteroid can be achieved by deploying either a kinetic impactor or a standoff nuclear device to impart a modest velocity change to the body. Response to each of these methods is sensitive to the individual asteroid's characteristics, some of which may not be well constrained before an actual deflection mission. Numerical simulations of asteroid deflection, using both hypervelocity impacts and nuclear ablation of the asteroid's surface, provide detailed information on asteroid response under a range of initial conditions. Here we present numerical results for the deflection of asteroids by both kinetic and nuclear methods, focusing on the roles of target body composition, strength, porosity, rotational state, shape, and internal structure. These results provide a framework for evaluating the planetary defense-related value of future asteroid characterization missions and capture some of the uncertainty that may be present in a real threat scenario. Part of this work was funded by the Laboratory Directed Research and Development Program at LLNL under project tracking code 12-ERD-005, performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675914.

Fresh Impact Craters on Asteroid Vesta

NASA Image and Video Library

2011-12-06

This image combines two separate views of the giant asteroid Vesta obtained by NASA Dawn spacecraft. The fresh impact craters in this view are located in the south polar region, which has been partly covered by landslides from the adjacent crater.

Tidal stress and failure in the moon of binary asteroid systems: Application to asteroid (65803) Didymos

NASA Astrophysics Data System (ADS)

Sophal Pou, Laurent; Garcia, Raphael F.; Mimoun, David; Murdoch, Naomi; Karatekin, Ozgur

2017-04-01

Rocky remnants left over from the early formation of the Solar System, asteroids are a target of choice for planetary science since much about the history of planetary formation and small body evolution processes can be learnt by studying them. Here we consider the case of the binary asteroid (65803) Didymos, the target of several mission proposals e.g., AIM [1] and DART [2]. A mission to Didymos would be a great opportunity for in-situ geophysical investigation, providing information on the surface and interior of asteroids. Such studies would improve our knowledge of binary asteroid formation and subsequent evolution of asteroids, thus of the history of the Solar System. As Didymos is a binary asteroid [3] with the main 800-meter diameter asteroid named Didymain and a 150-meter sized moon named Didymoon, both are subject to tidal stress. Recent investigations suggest that Didymoon is tidally locked and moves in a retrograde motion around Didymain along an elliptic orbit with a 0.03 eccentricity at most. In the case of an eccentric orbit, the tidal stress varies periodically and may be strong enough to cause tidal quakes on Didymoon at some points of the orbit. For this study, we modelled Didymoon as a spherical, layered body with different internal structures: a homogeneous model, and two models with a 1-meter and 10-meter regolith layer on top of a stronger internal core. Simulations show that, for a cohesionless body with an internal friction angle of 30°, tidal stress is strong enough to cause failure at the surface of Didymoon. A maximal stress is reached around the poles and for a mean anomaly of 90°. These results would mean that if tidal quakes occur on Didymoon, then they are likely to happen at these locations. An extension of these results to an ellipsoidal model of Didymoon is also presented for comparison with the spherical case and for application to other bodies. [1]: P. Michel et al., Science case for the asteroid impact mission (aim): A component of the asteroid impact and deflection assessment (aida) mission, Advances in Space Research 57 (12) (2016) 2529 - 2547. doi:http://dx.doi.org/10.1016/j.asr.2016.03.031. [2]: A. F. Cheng et al., Asteroid Impact & Deflection Assessment mission: Kinetic impactor, Planetary and Space Science 121 (2016) 27-35. doi:10.1016/j.pss.2015.12.004. [3]:"AIM-A Team", ASTEROID IMPACT MISSION: DIDYMOS REFERENCE MODEL v10, ESA document reference: AD3-AIMA.

The Nature of C Asteroid Regolith Revealed from the Jbilet Winselwan CM Chondrite

NASA Technical Reports Server (NTRS)

Zolensky, Michael; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Komatsu, Mutsumi; Chan, Queenie H. S.; Le, Loan; Kring, David; Cato, Michael; Fagan, Amy L.

2016-01-01

C-class asteroids frequently exhibit reflectance spectra consistent with thermally metamorphosed carbonaceous chondrites, or a mixture of phyllosilicate-rich material along with regions where they are absent. One particularly important example appears to be asteroid 162173 Ryugu, the target of the Hayabusa 2 mission, although most spectra of Ryugu are featureless, suggesting a heterogeneous regolith. Here we explore an alternative cause of dehydration of regolith of C-class asteroids - impact shock melting. Impact shock melting has been proposed to ex-plain some mineralogical characteristics of CB chondrites, but has rarely been considered a major process for hydrous carbonaceous chondrites.

Near-field effects of asteroid impacts in deep water

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

Gisler, Galen R; Weaver, Robert P; Gittings, Michael L

2009-06-11

Our previous work has shown that ocean impacts of asteroids below 500 m in diameter do not produce devastating long-distance tsunamis. Nevertheless, a significant portion of the ocean lies close enough to land that near-field effects may prove to be the greatest danger from asteroid impacts in the ocean. Crown splashes and central jets that rise up many kilometres into the atmosphere can produce, upon their collapse, highly non-linear breaking waves that could devastate shorelines within a hundred kilometres of the impact site. We present illustrative calculations, in two and three dimensions, of such impacts for a range of asteroidmore » sizes and impact angles. We find that, as for land impacts, the greatest dangers from oceanic impacts are the short-term near-field, and long-term atmospheric effects.« less

Impact simulations on the rubble pile asteroid (2867) Steins

NASA Astrophysics Data System (ADS)

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

2015-04-01

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

Impact Simulations on the Rubble Pile Asteroid (2867) Steins

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

Sensitivity to Uncertainty in Asteroid Impact Risk Assessment

NASA Astrophysics Data System (ADS)

Mathias, D.; Wheeler, L.; Prabhu, D. K.; Aftosmis, M.; Dotson, J.; Robertson, D. K.

2015-12-01

The Engineering Risk Assessment (ERA) team at NASA Ames Research Center is developing a physics-based impact risk model for probabilistically assessing threats from potential asteroid impacts on Earth. The model integrates probabilistic sampling of asteroid parameter ranges with physics-based analyses of entry, breakup, and impact to estimate damage areas and casualties from various impact scenarios. Assessing these threats is a highly coupled, dynamic problem involving significant uncertainties in the range of expected asteroid characteristics, how those characteristics may affect the level of damage, and the fidelity of various modeling approaches and assumptions. The presented model is used to explore the sensitivity of impact risk estimates to these uncertainties in order to gain insight into what additional data or modeling refinements are most important for producing effective, meaningful risk assessments. In the extreme cases of very small or very large impacts, the results are generally insensitive to many of the characterization and modeling assumptions. However, the nature of the sensitivity can change across moderate-sized impacts. Results will focus on the value of additional information in this critical, mid-size range, and how this additional data can support more robust mitigation decisions.

Momentum Enhancement from Hypervelocity Crater Ejecta: Implications for the AIDA Target

NASA Astrophysics Data System (ADS)

Flynn, G. J.; Durda, D. D.; Patmore, E. B.; Jack, S. J.; Molesky, M. J.; Strait, M. M.; Macke, R. M.

2017-09-01

We performed hypervelocity impact cratering of porous meteorites and terrestrial pumice and found higher values of the momentum enhancement factor due to ejecta than found in hydrocode modeling. This has important implications for kinetic impact deflection of small, hazardous asteroids and on the Asteroid Impact and Deflection Assessment mossion.

Asteroid Impact Risk: Ground Hazard versus Impactor Size

NASA Technical Reports Server (NTRS)

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

2017-01-01

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

The Impact Threat and Public Perception

NASA Technical Reports Server (NTRS)

Chodas, Paul W.

2000-01-01

Recent popular movies have raised public consciousness of the very real possibility of a comet or asteroid collision with the Earth, and a news report last year implying that asteroid 1997 XF11 had a distinct chance of hitting the Earth in the year 2028 further caught the public's eye. The report of possible impact was withdrawn the very next day, and the public perceived either that astronomers had made mistaken calculations, or that the pre-discovery observations found that day had been responsible for the revised prediction. But in fact, the original report of the possibility of impact in 2028 was simply a premature assessment. The XF11 affair has demonstrated the need for clarity and precision in public communications dealing with the possibility of Earth impact, as well as the importance of peer review before results are released to the press. This year, another potentially hazardous asteroid, 1999 AN10, has made the news, and this time there is indeed a remote chance of collision. Although impact is not possible during the asteroid's primary close approach in 2027, the uncertainties allow for a remarkably close passage, and embedded within the encounter's uncertainty region are many narrow "keyholes" which could bring the asteroid back for a close approach in a later year. Three keyholes have been identified which could perturb the asteroid onto trajectories that collide with the Earth in the years 2044, 2046, or 2039. At the time of this writing, the estimated impact probability for 1999 AN10 is on the order of 1 in 500,000, larger than for any other known object, but still significantly less than the probability of an undiscovered asteroid of equivalent size striking the Earth before 2044. Additional astrometric measurements of 1999 AN10 will likely drive its impact probability down to near-zero, but this may not happen for years, testing the public's reaction to a lingering remote possibility of impact. A side effect of the increasing discovery rate for Near Earth objects will be a growing number of cases like 1999 ANIO.

Meteoroid Impacts: A Competitor for Yarkovsky and YORP

NASA Astrophysics Data System (ADS)

Wiegert, Paul

2014-11-01

Meteoroids impacting an asteroid transfer linear and angular momentum to the larger body, which may change its orbit and its rotational state. The meteoroid environment of our Solar System may affect small (few meter sizes and smaller) asteroids at a level that is comparable to the Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects.Asteroids orbiting on prograde orbits near the Earth encounter an anisotropic meteoroid environment, including a population of particles on retrograde orbits generally accepted to be material from long-period comets spiralling inwards under Poynting-Robertson drag. High relative speed (60 km/s) impacts by meteoroids provide a small effective drag force that decreases asteroid semimajor axes and which is independent of their rotation pole. This effect may exceed the Yarkovsky drift at sizes near and below one meter.The momentum content of the meteoroids themselves is small enough to neglect, but it is the momentum transport by ejecta that increases the net effective force by two orders of magnitude for impacts into bare rock surfaces: this brings the effect to a level where it is of order that due to Yarkovsky, at least for small bodies. However, the above results are sensitive to the extrapolation of laboratory microcratering experiment results to real meteoroid-asteroid collisions and need further study.Meteoroid impacts may also affect asteroid spins at a level comparable to that of YORP at sizes smaller than tens of meters. However, we conclude that recent measurements of the YORP effect have probably not been compromised, because of the targets' large sizes and because they are known or likely to be regolith-covered rather than bare rock, which decreases the efficiency of ejecta production. However, the effect of impacts increases sharply with decreasing size, and may be important for asteroids smaller than a few tens of meters in radius.

Asteroid Detection Results Using the Space Surveillance Telescope

DTIC Science & Technology

2015-10-18

Distribution Statement A: Approved for public release, distribution unlimited. Asteroid Detection Results Using the Space Surveillance Telescope...issued a series of directives to the National Air and Space Administration (NASA), setting Near-Earth Asteroid (NEA) search and discovery targets in...order to protect the Earth and its inhabitants from the threat of asteroid impact. The focus of the original 1998 Congressional mandate was to catalog

Asteroid-Generated Tsunami and Impact Risk

NASA Astrophysics Data System (ADS)

Boslough, M.; Aftosmis, M.; Berger, M. J.; Ezzedine, S. M.; Gisler, G.; Jennings, B.; LeVeque, R. J.; Mathias, D.; McCoy, C.; Robertson, D.; Titov, V. V.; Wheeler, L.

2016-12-01

The justification for planetary defense comes from a cost/benefit analysis, which includes risk assessment. The contribution from ocean impacts and airbursts is difficult to quantify and represents a significant uncertainty in our assessment of the overall risk. Our group is currently working toward improved understanding of impact scenarios that can generate dangerous tsunami. The importance of asteroid-generated tsunami research has increased because a new Science Definition Team, at the behest of NASA's Planetary Defense Coordinating Office, is now updating the results of a 2003 study on which our current planetary defense policy is based Our group was formed to address this question on many fronts, including asteroid entry modeling, tsunami generation and propagation simulations, modeling of coastal run-ups, inundation, and consequences, infrastructure damage estimates, and physics-based probabilistic impact risk assessment. We also organized the Second International Workshop on Asteroid Threat Assessment, focused on asteroid-generated tsunami and associated risk (Aug. 23-24, 2016). We will summarize our progress and present the highlights of our workshop, emphasizing its relevance to earth and planetary science. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

Environmental Perturbations Caused by the Impacts of Comets and Asteroids on Earth

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Lawless, James G. (Technical Monitor)

1994-01-01

The extinction mechanisms proposed at the Cretaceous-Tertiary geological boundary are reviewed and related to the impact of asteroids or comets in general. For impact energies below 10(exp 4) Megatons (less than 6 x 10(exp 4) years; asteroid diameter less than 650 m), blast, earthquake, and fire may destroy local areas up to 10(exp 5) square m. Tidal waves could flood a kilometer inland over entire ocean basins. The energy range from 105 to 106 Megatons (less than 2 x 10(exp 6) years; asteroid diameter less than 3 km) is transitional. Dust lifted, sulfur released from within impacting asteroids, and soot from fires started by comets can produce climatologically significant optical depths of 10. At energies beyond 10(exp 7) Megatons, blast and earthquake damage is regional (10(exp 6) square cm). Tsunami cresting to 100 m and flooding 20 km inland will sweep the coastal zones of the world's oceans. Fires will be set globally. Light levels may drop so low from the smoke, dust and sulfate that vision is not possible. At energies approaching 10(exp 9) Megatons the ocean surface waters may be acidified by sulfur. The combination of these effects would be devastating.

Post mitigation impact risk analysis for asteroid deflection demonstration missions

NASA Astrophysics Data System (ADS)

Eggl, Siegfried; Hestroffer, Daniel; Thuillot, William; Bancelin, David; Cano, Juan L.; Cichocki, Filippo

2015-08-01

Even though mankind believes to have the capabilities to avert potentially disastrous asteroid impacts, only the realization of mitigation demonstration missions can validate this claim. Such a deflection demonstration attempt has to be cost effective, easy to validate, and safe in the sense that harmless asteroids must not be turned into potentially hazardous objects. Uncertainties in an asteroid's orbital and physical parameters as well as those additionally introduced during a mitigation attempt necessitate an in depth analysis of deflection mission designs in order to dispel planetary safety concerns. We present a post mitigation impact risk analysis of a list of potential kinetic impactor based deflection demonstration missions proposed in the framework of the NEOShield project. Our results confirm that mitigation induced uncertainties have a significant influence on the deflection outcome. Those cannot be neglected in post deflection impact risk studies. We show, furthermore, that deflection missions have to be assessed on an individual basis in order to ensure that asteroids are not inadvertently transported closer to the Earth at a later date. Finally, we present viable targets and mission designs for a kinetic impactor test to be launched between the years 2025 and 2032.

Flying Through Dust From Asteroids

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-11-01

How can we tell what an asteroid is made of? Until now, weve relied on remote spectral observations, though NASAs recently launched OSIRIS-REx mission may soon change this by landing on an asteroid and returning with a sample.But what if we could learn more about the asteroids near Earth without needing to land on each one? It turns out that we can by flying through their dust.The aerogel dust collector of the Stardust mission. [NASA/JPL/Caltech]Ejected CluesWhen an airless body is impacted by the meteoroids prevalent throughout our solar system, ejecta from the body are flung into the space around it. In the case of small objects like asteroids, their gravitational pull is so weak that most of the ejected material escapes, forming a surrounding cloud of dust.By flying a spacecraft through this cloud, we could perform chemical analysis of the dust, thereby determining the asteroids composition. We could even capture some of the dust during a flyby (for example, by using an aerogel collector like in the Stardust mission) and bring it back home to analyze.So whats the best place to fly a dust-analyzing or -collecting spacecraft? To answer this, we need to know what the typical distribution of dust is around a near-Earth asteroid (NEA) a problem that scientists Jamey Szalay (Southwest Research Institute) and Mihly Hornyi (University of Colorado Boulder) address in a recent study.The colors show the density distribution for dust grains larger than 0.3 m around a body with a 10-km radius. The distribution is asymmetric, with higher densities on the apex side, shown here in the +y direction. [Szalay Hornyi 2016]Moon as a LaboratoryTo determine typical dust distributions around NEAs, Szalay and Hornyi first look at the distribution of dust around our own Moon, caused by the same barrage of meteorites wed expect to impact NEAs. The Moons dust cloud was measured in situ in 2013 and 2014 by the Lunar Dust Experiment (LDEX) on board the Lunar Atmosphere and Dust Environment Explorer mission.From LDEXs measurements of the dust distribution around the Moon, Szalay and Hornyi next calculate how this distribution would change for different grain sizes if the body were instead much smaller i.e., a 10-km asteroid instead of the 1700-km Moon.Optimizing the Geometry for an EncounterThe authors find that the dust ejected from asteroids is distributed in an asymmetric shape around the body, with higher dust densities on the side of the asteroid facing its direction of travel. This is because meteoroid impacts arent isotropic: meteoroid showers tend to be directional, and amajority of meteoroids impact the asteroid from this apex side.Total number of impacts per square meter and predicted dust density for a family of potential trajectories for spacecraft flybys of a 10-km asteroid. [Szalay Hornyi 2016]Szalay and Hornyi therefore conclude that dust-analyzing missions would collect many times more dust impacts by transiting the apex side of the body. The authors evaluate a family of trajectories for a transiting spacecraft to determine the density of dust that the spacecraft will encounter and the impact rates expected from the dust particles.This information can help optimize the encounter geometry of a future mission to maximize the science return while minimizing the hazard due to dust impacts.CitationJamey R. Szalay and Mihly Hornyi 2016 ApJL 830 L29. doi:10.3847/2041-8205/830/2/L29

Exploration of the Moon and Asteroids by Secondary Students (ExMASS): An Authentic, Open-Inquiry Research Experience for High School Students

NASA Astrophysics Data System (ADS)

Shaner, A. J.; Allen, J. S.; Shipp, S. S.; Kramer, G. Y.; Nahm, A.; Balazs, L.; Fuller, J.; Newland, J.; Snyder, R. D.; Kring, D. A.

2014-12-01

The National Research Council (2012) has expressed a need for participatory science experiences for students. Opportunities are needed for students which 1) allow them to understand how scientific knowledge develops and 2) can heighten their curiosity, capture their interest, and motivate their continued study of science. Studies (e.g., Aydeniz et al., 2011) have also recommend educators provide students with opportunities to do science through extracurricular work with scientists. In addition to being given the opportunity to fully participate in the scientific enterprise, students must also be explicitly guided in their attempts to develop a more appropriate understanding of the nature of the scientific enterprise (McDonald, 2010; Rudge & Howe, 2010; Yacoubian & BouJaoude, 2010). Exploration of the Moon and Asteroids by Secondary Students, or ExMASS, provides such an opportunity for students. The ExMASS program is an education effort managed by the LPI/NASA JSC-led Center for Lunar Science and Exploration (CLSE), one of nine teams comprising NASA's Solar System Exploration Research Virtual Institute (SSERVI). Over the course of one academic year, teams of high school students conduct their own scientific investigations of either Earth's Moon or asteroids, with guidance from a scientist mentor. The program includes two elements: 1) a guided inquiry introductory research activity that builds student knowledge of current lunar/asteroid science and lunar/asteroid data, and 2) an open inquiry research project in which the students apply their knowledge to a self-defined project. Evaluation data collected during the predecessor program to ExMASS revealed many successes, but also room for improvement. In response, an Advisory Group consisting of past teachers and mentors was formed to address the gaps revealed in the evaluation data. The ExMASS program will continue to collect similar evaluation data including assessment of changes in students' lunar/asteroid content knowledge, student attitudes toward science and science careers, and views of the nature of science and scientific inquiry. Exit surveys for teachers, students, and mentors will also be used to gather general feedback about the program and its impact.

An Optimal Mitigation Strategy Against the Asteroid Impact Threat with Short Warning Time

NASA Technical Reports Server (NTRS)

Wie, Bong; Barbee, Brent; Pitz, Alan; Kaplinger, Brian; Hawkins, Matt; Winkler, Tim; Premaratne, Pavithra; Vardaxis, George; Lyzhoft, Joshua; Zimmerman, Ben

2015-01-01

To develop an innovative yet practically implementable mitigation technique for the most probable impact threat of an asteroid or comet with short warning time (i.e., when we don't have sufficient warning times for a deflection mission).

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).

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.

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

Asteroid Redirect Mission - Next Major stepping-stone to Human Exploration of NEOs and beyond

NASA Astrophysics Data System (ADS)

Sanchez, Natalia

2016-07-01

In response to NASA's Asteroid Initiative, an Asteroid Redirect and Robotic Mission (ARRM) is being studied by a NASA cohort, led by JPL, to enable the capture a multi-ton boulder from the surface of a Near-Earth Asteroid and return it to cislunar space for subsequent human and robotic exploration. The mission would boost our understanding of NEOs and develop technological capabilities for Planetary Defense, shall a NEO come up on a collision course. The benefits of this mission can extend our capabilities to explore farther into space, as well as create a new commercial sector in Space Mining, which would make materials in Space available for our use. ARRM would leverage and advance current knowledge of higher-efficiency propulsion systems with a new Solar Electric Propulsion demonstration (similar to that on the Dawn spacecraft) to be incorporated into future Mars Missions.

Field evidence of Eros-scale asteroids and impact-forcing of Precambrian geodynamic episodes, Kaapvaal (South Africa) and Pilbara (Western Australia) Cratons

NASA Astrophysics Data System (ADS)

Glikson, Andrew Y.

2008-03-01

The role of asteroid and comet impacts as triggers of mantle-crust processes poses one of the fundamental questions in Earth science. I present direct field evidence for close associations between impact ejecta/fallout units, major unconformities and lithostratigraphic boundaries in Archaean and early Proterozoic terrains, including abrupt changes in the composition of volcanic and sedimentary assemblages across stratigraphic impact boundaries, with implications for the nature and composition of their provenance terrains. As originally observed by D.R. Lowe and G.R. Byerly, in the Barberton Greenstone Belt, eastern Kaapvaal Craton, South Africa, 3.26-3.24 Ga asteroid mega-impact units are closely associated with the abrupt break between an underlying simatic mafic-ultramafic volcanic crust and an overlying association of turbidites, banded iron formations, felsic tuff and conglomerates of continental affinities. Contemporaneous stratigraphic relationships are identified in the Pilbara Craton, Western Australia. Evidence for enrichment of seawater in ferrous iron in the wake of major asteroid impacts reflects emergence of new source terrains, likely dominated by mafic compositions, attributed to impact-triggered oceanic volcanic activity. Relationships between impact and volcanic activity are supported by the onset of major mafic dyke systems associated with ~ 2.48 Ga and possibly the 2.56 Ga mega-impact events.

Consequences of Predicted or Actual Asteroid Impacts

NASA Astrophysics Data System (ADS)

Chapman, C. R.

2003-12-01

Earth impact by an asteroid could have enormous physical and environmental consequences. Impactors larger than 2 km diameter could be so destructive as to threaten civilization. Since such events greatly exceed any other natural or man-made catastrophe, much extrapolation is necessary just to understand environmental implications (e.g. sudden global cooling, tsunami magnitude, toxic effects). Responses of vital elements of the ecosystem (e.g. agriculture) and of human society to such an impact are conjectural. For instance, response to the Blackout of 2003 was restrained, but response to 9/11 terrorism was arguably exaggerated and dysfunctional; would society be fragile or robust in the face of global catastrophe? Even small impacts, or predictions of impacts (accurate or faulty), could generate disproportionate responses, especially if news media reports are hyped or inaccurate or if responsible entities (e.g. military organizations in regions of conflict) are inadequately aware of the phenomenology of small impacts. Asteroid impact is the one geophysical hazard of high potential consequence with which we, fortunately, have essentially no historical experience. It is thus important that decision makers familiarize themselves with the hazard and that society (perhaps using a formal procedure, like a National Academy of Sciences study) evaluate the priority of addressing the hazard by (a) further telescopic searches for dangerous but still-undiscovered asteroids and (b) development of mitigation strategies (including deflection of an oncoming asteroid and on- Earth civil defense). I exemplify these issues by discussing several representative cases that span the range of parameters. Many of the specific physical consequences of impact involve effects like those of other geophysical disasters (flood, fire, earthquake, etc.), but the psychological and sociological aspects of predicted and actual impacts are distinctive. Standard economic cost/benefit analyses may not apply due to the exceptional rarity of major impacts.

Asteroid rotation rates - Distributions and statistics

NASA Technical Reports Server (NTRS)

Binzel, Richard P.; Farinella, Paolo; Zappala, Vincenzo; Cellino, Alberto

1989-01-01

An analysis of asteroid rotation rates and light-curve amplitudes disclosed many significant correlations between these rotation parameters and asteroid diameter, with distinct changes occurring near 125 km, a diameter above which self-gravity may become important. It is suggested that this size range may represent a division between surviving primordial asteroids and collisional fragments. A comparison of rotational parameters between family and nonfamily asteroids showed that the Koronis and Eos families exhibit noticeable differences, considered to be due to different impact conditions and/or to a relatively younger age for the Koronis family.

Asteroid differentiation - Pyroclastic volcanism to magma oceans

NASA Technical Reports Server (NTRS)

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

1993-01-01

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

Delivery of organics to Mars through asteroid and comet impacts

NASA Astrophysics Data System (ADS)

Frantseva, K.; Mueller, M.; van der Tak, F. F. S.; ten Kate, I. L.; Greenstreet, S.

2017-09-01

Preliminary results show that the asteroid-borne organic flux on Mars is comparable to the IPD rate; asteroids certainly cannot be neglected. Comets, on the other hand, contribute only 0.01% of the IDP-borne rate and can be neglected in the process of organic delivery to Mars.

Possible impact solutions of asteroid (99942) Apophis

NASA Astrophysics Data System (ADS)

Wlodarczyk, Ireneusz

2017-07-01

We computed impact solutions of the potentially dangerous asteroid (99942) Apophis based on 4469 optical observations from March 15.10789 UTC, 2004 through January 03.26308 UTC, 2015, and 20 radar observations from January 27.97986 UTC, 2005 through March 15.99931 UTC, 2013. However, we computed possible impact solutions by using the Line Of Variation method out to σ LOV = 5 computing 3000 virtual asteroids (VAs) on both sides of the LOV which gives 6001 VAs and propagated their orbits to JD 2495000.5 TDT=December 24, 2118. We computed the non-gravitational parameter A2=-5.586×10^{-14} au/d^{2} with 1-σ uncertainty 2.965×10^{-14} au/d^{2} and possible impacts until 2096. The possible impact corridor for 2068 is presented.

Design of Spacecraft Missions to Test Kinetic Impact for Asteroid Deflection

NASA Technical Reports Server (NTRS)

Barbee, Brent W.; Hernandez, Sonia

2012-01-01

Earth has previously been struck with devastating force by near-Earth asteroids (NEAs) and will be struck again. Telescopic search programs aim to provide advance warning of such an impact, but no techniques or systems have yet been tested for deflecting an incoming NEA. To begin addressing this problem, we have analyzed the more than 8000 currently known NEAs to identify those that offer opportunities for safe and meaningful near-term tests of the proposed kinetic impact asteroid deflection technique. In this paper we present our methodology and results, including complete mission designs for the best kinetic impactor test mission opportunities.

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.

Asteroid Deflection Mission Design Considering On-Ground Risks

NASA Astrophysics Data System (ADS)

Rumpf, Clemens; Lewis, Hugh G.; Atkinson, Peter

The deflection of an Earth-threatening asteroid requires high transparency of the mission design process. The goal of such a mission is to move the projected point of impact over the face of Earth until the asteroid is on a miss trajectory. During the course of deflection operations, the projected point of impact will match regions that were less affected before alteration of the asteroid’s trajectory. These regions are at risk of sustaining considerable damage if the deflecting spacecraft becomes non-operational. The projected impact point would remain where the deflection mission put it at the time of mission failure. Hence, all regions that are potentially affected by the deflection campaign need to be informed about this risk and should be involved in the mission design process. A mission design compromise will have to be found that is acceptable to all affected parties (Schweickart, 2004). A software tool that assesses the on-ground risk due to deflection missions is under development. It will allow to study the accumulated on-ground risk along the path of the projected impact point. The tool will help determine a deflection mission design that minimizes the on-ground casualty and damage risk due to deflection operations. Currently, the tool is capable of simulating asteroid trajectories through the solar system and considers gravitational forces between solar system bodies. A virtual asteroid may be placed at an arbitrary point in the simulation for analysis and manipulation. Furthermore, the tool determines the asteroid’s point of impact and provides an estimate of the population at risk. Validation has been conducted against the solar system ephemeris catalogue HORIZONS by NASA’s Jet Propulsion Laboratory (JPL). Asteroids that are propagated over a period of 15 years show typical position discrepancies of 0.05 Earth radii relative to HORIZONS’ output. Ultimately, results from this research will aid in the identification of requirements for deflection missions that enable effective, minimum risk asteroid deflection. Schweickart, R. L. (2004). THE REAL DEFLECTION DILEMMA. In 2004 Planetary Defense Conference: Protecting Earth from Asteroids (pp. 1-6). Orange County, California. Retrieved from http://b612foundation.org/wp-content/uploads/2013/02/Real_Deflection_Dilemma.pdf

DAMIT: a database of asteroid models

NASA Astrophysics Data System (ADS)

Durech, J.; Sidorin, V.; Kaasalainen, M.

2010-04-01

Context. Apart from a few targets that were directly imaged by spacecraft, remote sensing techniques are the main source of information about the basic physical properties of asteroids, such as the size, the spin state, or the spectral type. The most widely used observing technique - time-resolved photometry - provides us with data that can be used for deriving asteroid shapes and spin states. In the past decade, inversion of asteroid lightcurves has led to more than a hundred asteroid models. In the next decade, when data from all-sky surveys are available, the number of asteroid models will increase. Combining photometry with, e.g., adaptive optics data produces more detailed models. Aims: We created the Database of Asteroid Models from Inversion Techniques (DAMIT) with the aim of providing the astronomical community access to reliable and up-to-date physical models of asteroids - i.e., their shapes, rotation periods, and spin axis directions. Models from DAMIT can be used for further detailed studies of individual objects, as well as for statistical studies of the whole set. Methods: Most DAMIT models were derived from photometric data by the lightcurve inversion method. Some of them have been further refined or scaled using adaptive optics images, infrared observations, or occultation data. A substantial number of the models were derived also using sparse photometric data from astrometric databases. Results: At present, the database contains models of more than one hundred asteroids. For each asteroid, DAMIT provides the polyhedral shape model, the sidereal rotation period, the spin axis direction, and the photometric data used for the inversion. The database is updated when new models are available or when already published models are updated or refined. We have also released the C source code for the lightcurve inversion and for the direct problem (updates and extensions will follow).

Two cubesat mission to study the Didymos asteroid system

NASA Astrophysics Data System (ADS)

Wahlund, J.-E.; Vinterhav, E.; Trigo-Rodríguez, J. M.; Hallmann, M.; Barabash, S.; Ivchenko, N.

2015-10-01

Among the growing interest about asteroid impact hazard mitigation in our community the Asteroid Impact & Deflection Assessment (AIDA) mission will be the first space experiment to use a kinetic impactor to demonstrate its capability as reliable deflection system [1]. As a part of the AIDA mission, we have proposed a set of two three-axis stabilized 3U CubeSats (with up to 5 science sensors) to simultaneously rendezvous at close range (<500m) with both the primary and the secondary component of the Didymos asteroid system. The CubeSats will be hosted on the ESA component of the AIDA mission, the monitoring satellite AIM (Asteroid Impact Mission). The CubeSats will characterise the magnetization, the main bulk chemical composition and presence of volatiles as well as do superresolution surface imaging of the Didymos components. The CubeSats will also support the plume characterisation resulting from the DART impact (Double Asteroid Redirection Test, a NASA component of the AIDA mission) at much closer range than the AIM main spacecraft, and provide imaging, composition, and temperature of the plume material. At end of the mission, the two CubeSats can optionally land on one of the asteroids for continued science operation. The science sensors consist of a dual fluxgate magnetometer (MAG), one miniaturized volatile composition analyser (VCA), a narrow angle camera (NAC) and a Video Emission Spectrometer (VES) with a diffraction grating for allowing a sequential chemical study of the emission spectra associated with the impact flare and the expanding plume. Consequently, the different envisioned instruments onboard the CubeSats can provide significant insight into the complex response of asteroid materials during impacts that has been theoretically studied using different techniques [2]. The two CubeSats will remain stowed in CubeSat dispensers aboard the main AIM spacecraft. They will be deployed and commissioned before the AIM impactor reaches the secondary and record the impact event from a closer vantage point than the main spacecraft. The two CubeSats are equipped with relative navigation systems capable of estimating the spacecraft position relative to the asteroids and propulsion system that allow them to operate close to the asteroid bodies. The two CubeSats will rely on mapping data relayed via the AIM main spacecraft but operate autonomously and individually based on schedules and navigation maps uploaded from ground. AIDA's target is the binary Apollo asteroid 65803 Didymos that is also catalogued as Potentially Hazardous Asteroid (PHA) because it experiences close approaches to Earth. Didymos' primary has a diameter of ˜800 meters and the secondary is ˜150 m across. Both bodies are separated about 1.1 km [3]. The rotation period and asymmetry of the secondary object is unknown, and it might be tidally locked to the larger primary body. At least the primary body is expected to be associated with ordinary chondrite material, consisting mostly of silicates, and metal, but the earlier made Xk classification suggested a rubble-pile type with large amount of volatile content. The secondary companion spectral class is unknown, but the total mass of the system suggests that the secondary companion could be of similar class. Detailed empirical information on the physical properties of the Didymos asteroid system, in particular the magnetic field, the (mineralogical) surface composition, the internal composition via the bulk density, the ages of surface units through crater counts and other morphological surface features is valuable in order to make progress in the asteroid field of science. Furthermore, the periodic effect of such a close dynamic system in the presence and temporal displacement of the surface regolith is EPSC Abstracts Vol. 10, EPSC2015-698, 2015 European Planetary Science Congress 2015 c Author(s) 2015 EPSC European Planetary Science Congress unknown, and could be followed using close-up video systems provided by the CubeSats. In conclusion, the proposed two CubeSats as part of the AIDA mission can therefore contribute significantly, since they can monitor the Didymos asteroid components at a very close range around hundred meters, and at the same time monitor in-situ an impact plume when it is created.

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

NASA Astrophysics Data System (ADS)

Jutzi, Martin; Michel, Patrick

2014-02-01

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

Impact experiments onto heterogeneous targets and their interpretation in relation with formation of the asteroid families

NASA Astrophysics Data System (ADS)

Leliwa-Kopystynski, J.; Arakawa, M.

2014-07-01

Results of laboratory impact experiments, when extrapolated to the planetary scale of events, are aimed for better understanding of cratering and/or disruption of asteroids, satellites, and cometary nuclei. There is absolutely no reason to assume that these bodies are uniform rocky or icy monoliths. So, we studied reactions of the heterogeneous targets on the impacts. A series of impact experiments onto solid decimeter-sized cylinders made of porous gypsum mixed with approximately one-centimeter-sized pebbles have been performed. The mean density of the material of the targets was 1867 kg m^{-3}, the mean mass ratio (pebbles / gypsum) = 0.856 / 0.144, and the mean volume ratio (pebbles / gypsum / pores) = 0.585 / 0.116 / 0.299. The target densities and their heterogeneous structures could be representative of those of the asteroids Ida, Eros, and many others, because asteroid sub-surface volumes could be composed of consolidated boulders formed by self-compaction and/or by impact compaction. Impact velocities in the experiments ranged from 2.0 km/s to 6.7 km/s (collision velocity in the asteroid main belt is approximately 5 km/s). By means of weighting and counting the post-impact fragments, their distribution function was found. Let Q [J/kg] be the specific energy of impact per unit of the target mass. Of particular interest is the value of impact strength, that is, the specific energy of disruption Q^*, corresponding to the ratio (mass of the largest fragment) / (mass of the target) = m_l/M = 0.5, which is, by convention, the value separating the cratering events from the catastrophic disruption impacts. Mass or size distribution of the post-impact fragments is expressed by the power law N ∝ m^{-p} ∝ r^{-3p}, p=p(Q/Q^{*}) A parameter that can be measured in the laboratory is the exponent p. For the case of a swarm of asteroids forming an asteroid family, the observationally estimated value is not the exponent p but rather the exponent q = 3p, since the sizes r of the family members are better known than their masses m (because then the asteroids' densities should be known). We have found that, for the gypsum/pebbles targets, there is Q^* ≈ 270 J/kg and the exponent q varies linearly with rather high slope: q = (0.705 ± 0.093)(Q/Q^{*}) + (2.7 ± 1.2) for 1 < Q/Q^* < 40, approximately. For comparison, this result differs considerably from that for porous water ice targets with porosity equal to 0.37 and specific energy of disruption Q^* ≈ 39 J/kg (based on the data presented in Fig. 9 of Arakawa et al., 2002). In that case, q has only a slight slope: q = (0.092 ± 0.020)(Q/Q^*) + (1.30 ± 0.22) for 1 < Q/Q^* < 20, approximately. The presence of pebbles strongly influences the impact strength of the target as well as the size distribution of the post-impact fragments. Formulae (2) and (3) indicate that the increase of specific impact energy delivered to the target leads to more efficient comminuting. Comparison with the experimental size distribution within families of asteroids is in progress.

Asteroid Impact Deflection and Assessment (AIDA) mission - Properties of Impact Ejecta

NASA Astrophysics Data System (ADS)

Hamilton, Douglas P.; Fahnestock, Eugene G.; Schwartz, Stephen R.; Murdoch, Naomi; Asphaug, Erik; Cheng, Andrew F.; Housen, Kevin R.; Michel, Patrick; Miller, Paul L.; Stickle, Angela; Tancredi, Gonzalo; Vincent, Jean-Baptiste; Wuennemann, Kai; Yu, Yang; AIDA Impact Simulation Working Group

2016-10-01

The Asteroid Impact Deflection and Assessment (AIDA) mission is composed of NASA's Double Asteroid Redirection Test (DART) mission and ESA's Asteroid Impact Monitor (AIM) rendezvous mission. The DART spacecraft is designed to impact the small satellite of near-Earth asteroid 65803 Didymos in October 2022, while the in-situ AIM spacecraft observes. AIDA's Modeling and Simulation of Impact Outcomes Working Group is tasked with investigating properties of the debris ejected from the impact. The orbital evolution of this ejecta has important implications for observations that the AIM spacecraft will take as well as for the safety of the spacecraft itself. Ejecta properties including particle sizes, bulk densities, and velocities all depend on the poorly-known physical properties of Didymos' moon. The moon's density, internal strength, and especially its porosity have a strong effect on all ejecta properties. Making a range of assumptions, we perform a suite of numerical simulations to determine the fate of the ejected material; we will use simulation predictions to optimize AIM observations and safety. Ultimately, combining AIM's observations of the ejecta with detailed numerical simulations will help constrain key satellite parameters.We use distinct types of numerical tools to explore ejecta properties based on additional target parameters (different forms of friction, cohesion), e.g., the shock physics code iSALE, smoothed particle hydrodynamics codes, and the granular code PKDGRAV. Given the large discrepancy between the 6 km/s impact speed of DART and the moon's 6 cm/s escape speed, a great challenge will be to determine properties of the low-speed ejecta. Very low-speed material relevant to the safety of the AIM spacecraft and its ability to conduct its observations may loft from the crater at late stages of the impact process, or from other locations far from the impact site due to seismic energy propagation. The manner in which seismic waves manifests in asteroid regolith is extremely speculative at present. Through experiment, simulation, and observational strategies, we are working to gain insight into this and related phenomenon and will present the ongoing progress of our working group.

Meteoroid Impact Ejecta Detection by Nanosatellites for Asteroid Surface Characterization

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

A 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.

Short term impact risk assessment for asteroids 2011 AG5

NASA Astrophysics Data System (ADS)

Bancelin, D.; Pravec, P.; Nolan, M.

2013-04-01

Among the potentially hazardous asteroids (PHAs) in orbit around the Earth, some of them can become a real threat. The most famous PHA presently known is asteroid (99942) Apophis which briefly presented an unusually high impact probability (up to 2.3 %) for a collision with the Earth in 2029. It remains the only asteroid to have reached level 4 of the Torino Scale. Even if Apophis is not a threat anymore, other PHAs are still monitored and now, only one asteroid is scaled to 1 with the highest impact probability. Asteroid 2011 AG5 has 1 chance over 500 to hit the Earth on 2040. This asteroid is challenging because it will remain of faint magnitude around 23.0 until its close encounter with the Earth in February 2023. It will come close to the Earth by 0.012 AU. Intensive ground-based (optical and mainly radar measurements) will be performed. Before this date, optical measurements would be possible (provided that large telescopes are used) and orbital refinement could be performed in order to improve the orbital uncertainty of this asteroid. Nevertheless, no physical data can be derived before 2023 and therefore, the influence of non gravitational forces, mainly Yarkovsky effect, can not be precisely determined. This non gravitational effect produces a secular drift da/dt (positive or negative) of the semi-major axis due to the anisotropic re-emission of the incident solar radiation. We propose here a dynamical study of the asteroid 2011 AG5. We discuss first the location of primary and secondary keyholes in the target plane of 2023 as well as the quantification of the impact probability. Secondary keyholes are due to two consecutive close encounters, the second usually happening near a keyhole or a resonant return. Then, we will address how those quantities evolve with future dedicated ground-based measurements. In a second part, we will discuss non gravitational perturbations through Yarkovsky effect. Assuming that this asteroid is a C or S-type, we can statistically derive some maximum intensity of Yarkovsky force, without any assumptions on the physical parameters. This will help to assess the maximum deviation expected on the geocentric distance expressed in the 2023 target plane. This deviation will have a direct consequence on the impact probability. Finally, a deeper study will include a Monte Carlo test on the orbital fit in order to compute virtual asteroids (VA) moving under gravity, relativistic and Yarkovsky perturbations. Using a simple model of Yarkovsky force as a perturbation along the transverse component and inversely proportional to the heliocentric square distance of the asteroid, we include a random deviation da/dt to assess the number of VA becoming virtual impactors (VI). We will compare this number to the one obtained with VA moving only under gravity and relativistic perturbations.

Gemini and Keck Observations of Slowly Rotating, Bilobate Active Asteroid (300163)

NASA Astrophysics Data System (ADS)

Waniak, Waclaw; Drahus, Michal

2016-10-01

One of the most puzzling questions regarding Active Asteroids is the mechanism of their activation. While some Active Asteroids show protracted and often recurrent mass loss, consistent with seasonal ice sublimation, some other eject dust impulsively as a result of a catastrophic disruption (e.g. Jewitt et al. 2015, Asteroids IV, 221). It has been suggested that ice can be excavated from the cold near-surface interior by an impact (Hsieh & Jewitt 2006, Science 312, 561) or, for small objects susceptible to YORP torques, by near-critical spin rate (Sheppard & Trujillo 2014, AJ 149, 44). But impact and rapid spin can also cause a catastrophic disruption (e.g. Jewitt et al. 2015, Asteroids IV, 221). It therefore becomes apparent that the different types of mass loss observed in Active Asteroids can be best classified and understood based on the nucleus spin rates (Drahus et al. 2015, ApJL 802, L8), but unfortunately the rotation periods have been measured for a very limited number of these objects. With this in mind we have initiated a survey of light curves of small Active Asteroids on the largest ground-based optical telescopes. Here we present the results for (300163), also known as 288P and 2006 VW139, which is a small 2.6-km sized asteroid that exhibited a comet-like activity over 100 days in the second half of 2011 (Hsieh et al. 2012, ApJL 748, L15; Licandro et al. 2013, A&A 550, A17; Agarwal et al. 2016, AJ 151, 12). Using Keck/DEIMOS and Gemini/GMOS-S working in tandem on UT 2015 May 21-22 we have detected an inactive nucleus and measured a complete, dense, high-S/N rotational light curve. The light curve has a double-peaked period of 16 hours, an amplitude of 0.4 mag, and moderately narrow minima suggesting a bilobate or contact-binary shape. The long rotation period clearly demonstrates a non-rotational origin of activity of this object, consistent with an impact. Furthermore, among the five small Active Asteroids with known rotation periods (300163) is only the second object with a confirmed slow spin rate, the other three rotating rapidly, near the limit of rotational stability. This suggests that rotation- and impact-driven origin of activity can be comparably common among small asteroids.

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

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.

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.

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.

MASCOT2, a Lander to Characterize the Target of an Asteroid Kinetic Impactor Deflection Test (AIM) Mission

NASA Astrophysics Data System (ADS)

Biele, J.; Ulamec, S.; Krause, C.; Cozzoni, B.; Lange, C.; Grundmann, J. T.; Grimm, C.; Ho, T.-M.; Herique, A.; Plettemeier, D.; Grott, M.; Auster, H.-U.; Hercik, D.; Carnelli, I.; Galvez, A.; Philippe, C.; Küppers, M.; Grieger, B.; Gil Fernandez, J.; Grygorczuk, J.

2017-09-01

In the course of the AIDA/AIM mission studies [1,2] a lander, MASCOT2, has been studied to be deployed on the moon of the binary Near-Earth Asteroid system, (65803) Didymos. The AIDA technology demonstration mission, composed of a kinetic impactor, DART, and an observing spacecraft, AIM, has been designed to deliver vital data to determine the momentum transfer efficiency of the kinetic impact and key physical properties of the target asteroid. This will enable derivation of the impact response of the object as a function of its physical properties, a crucial quantitative point besides the qualitative proof that the asteroid has been deflected at all. A landed asset on the target asteroid greatly supports analyzing its dynamical state, mass, geophysical properties, surface and subsurface structure. The lander's main instrument is a bistatic, low frequency radar (LFR) [3a,b] to sound the interior structure of the asteroid. It is supported by a camera (MasCAM) [4], a radiometer (MARA)[5], an accelerometer (DACC [9]), and, optionally regarding the science case, also a magnetometer (MasMAG)[6].

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.

Implications of theories of asteroid and comet impact for policy options for management of spent nuclear fuel and high-level radioactive wastes

USGS Publications Warehouse

Trask, Newell J.

1994-01-01

Concern with the threat posed by terrestrial asteroid and comet impacts has heightened as the catastrophic consequences of such events have become better appreciated. Although the probabilities of such impacts are very small, a reasonable question for debate is whether such phenomena should be taken into account in deciding policy for the management of spent fuel and high-level radioactive waste. The rate at which asteroid or comet impacts would affect areas of surface storage of radioactive waste is about the same as the estimated rate at which volcanic activity would affect the Yucca Mountain area. The Underground Retrievable Storage (URS) concept could satisfactorily reduce the risk from cosmic impact with its associated uncertainties in addition to providing other benefits described by previous authors.

Design of Spacecraft Missions to Test Kinetic Impact for Asteroid Deflection

NASA Technical Reports Server (NTRS)

Hernandez, Sonia; Barbee, Brent W.

2011-01-01

There are currently over 8,000 known near-Earth asteroids (NEAs), and more are being discovered on a continual basis. More than 1,200 of these are classified as Potentially Hazardous Asteroids (PHAs) because their Minimum Orbit Intersection Distance (MOID) with Earth's orbit is <= 0.05 AU and their estimated diameters are >= 150 m. To date, 178 Earth impact structures have been discovered, indicating that our planet has previously been struck with devastating force by NEAs and will be struck again. Such collisions are aperiodic events and can occur at any time. A variety of techniques have been proposed to defend our planet from NEA impacts by deflecting the incoming asteroid. However, none of these techniques have been tested. Unless rigorous testing is conducted to produce reliable asteroid deflection systems, we will be forced to deploy completely untested -- and therefore unreliable -- deflection missions when a sizable asteroid on a collision course with Earth is discovered. Such missions will have a high probability of failure. We propose to address this problem with a campaign of deflection technology test missions deployed to harmless NEAs. The objective of these missions is to safely evaluate and refine the mission concepts and asteroid deflection system designs. Our current research focuses on the kinetic impactor, one of the simplest proposed asteroid deflection techniques in which a spacecraft is sent to collide with an asteroid at high relative velocity. By deploying test missions in the near future, we can characterize the performance of this deflection technique and resolve any problems inherent to its execution before needing to rely upon it during a true emergency. In this paper we present the methodology and results of our survey, including lists of NEAs for which safe and effective kinetic impactor test missions may be conducted within the next decade. Full mission designs are also presented for the NEAs which offer the best mission opportunities.

Post Deflection Impact Risk Analysis of the Double Asteroid Redirection Test (DART)

NASA Astrophysics Data System (ADS)

Eggl, S.; Hestroffer, D.

2017-09-01

Collisions between potentially hazardous near-Earth objects and our planet are among the few natural disasters that can be avoided by human intervention. The complexity of such an endeavor necessitates an asteroid orbit deflection test mission, however, ensuring all relevant knowledge is present when an asteroid on a collision course with the Earth is indeed discovered. The double asteroid redirection test (DART) mission concept currently investigated by NASA would serve such a purpose. The aim of our research is to make certain that DART does not turn a previously harmless asteroid into a potentially dangerous one.

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.

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.

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.

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.

The ISIS Mission Concept: An Impactor for Surface and Interior Science

NASA Technical Reports Server (NTRS)

Chesley, Steven R.; Elliot, John O.; Abell, Paul A.; Asphaug, Erik; Bhaskaran, Shyam; Lam, Try; Lauretta, Dante S.

2013-01-01

The Impactor for Surface and Interior Science (ISIS) mission concept is a kinetic asteroid impactor mission to the target of NASA's OSIRIS-REx (Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer) asteroid sample return mission. The ISIS mission concept calls for the ISIS spacecraft, an independent and autonomous smart impactor, to guide itself to a hyper-velocity impact with 1999 RQ36 while the OSIRIS-REx spacecraft observes the collision. Later the OSIRIS-REx spacecraft descends to reconnoiter the impact site and measure the momentum imparted to the asteroid through the impact before departing on its journey back to Earth. In this paper we discuss the planetary science, human exploration and impact mitigation drivers for mission, and we describe the current mission concept and flight system design.

A global response roadmap to the asteroid impact threat: The NEOShield perspective

NASA Astrophysics Data System (ADS)

Perna, D.; Barucci, M. A.; Drube, L.; Falke, A.; Fulchignoni, M.; Harris, A. W.; Harris, A. W.; Kanuchova, Z.

2015-12-01

Besides being of great scientific interest, near-Earth objects represent a well-founded threat to life on our planet. Nonetheless, up to now there has been no concerted international plan on how to deal with the impact threat, and how to prepare and implement mitigation measures. The NEOShield project is funded by the European Commission to address such issues, to investigate the feasibility of techniques to prevent a potentially catastrophic impact on Earth by an asteroid or a comet, and to develop detailed designs of appropriate space missions to test deflection techniques. In this work we present and discuss the scientific and strategic aspects of the asteroid impact threat, highlighting the necessary steps so as to be ready to react to future hazardous objects.

Investigating the surface and subsurface properties of the Didymos binary asteroid with a landed CubeSat

NASA Astrophysics Data System (ADS)

Murdoch, Naomi; Cadu, Alexandre; Mimoun, David; Karatekin, Ozgur; Garcia, Raphael; Carrasco, José; Garcia de Quiros, Javier; Vasseur, Hugues; Ritter, Birgit; Eubanks, Marshall; Radley, Charles; Dehant, Veronique

2016-04-01

Despite the successes of recent space missions (e.g., Cheng et al., 1997; Fujiwara et al., 2006), there is still no clear understanding of the asteroid internal structure(s). Depending on their size, evolution and physical properties, many different asteroid internal structure models have been suggested from completely cohesive bodies, through to rubble pile objects. The Asteroid Geophysical Explorer (AGEX), a COPINS payload selected by ESA*, will land geophysical instrument packages on the surface of Didymoon; the secondary object in the (65803) Didymos (1996 GT) binary system (Karatekin et al 2016). The instruments will characterize the asteroid surface mechanical properties and probe, for the first time, the sub-surface structure of an asteroid. AGEX will be deployed from AIM on a ballistic transfer to the asteroid surface, several days before the MASCOT-2 package. We expect that AGEX will bounce multiple times before coming to rest on the surface of the asteroid thus providing a unique opportunity to study the asteroid surface properties, perhaps at several locations, using accelerometers. Once stationary, the seismological surface-monitoring phase, using a three-axis set of geophones, can begin. The high speed DART impact will be a major seismic source on Didymoon. However, the seismic payload may also be able to perform seismological investigations using natural seismic sources such as micrometeoroid impacts (e.g., Garcia et al., 2015), thermal cracks (e.g., Delbo et al., 2014), internal quakes due to tidal forces (e.g., Richardson et al. 1998) and other geophysical processes (see Murdoch et al., 2015). We will present the expected signal characteristics of the landing and also of the natural seismic sources that may occur on Didymoon. An understanding of the amplitude and frequency content of such signals is necessary in order to design the optimal geophysical payload for small body exploration using a CubeSat platform. [1.] Cheng, A. et al., Journal of Geophysical Research, 102, E10 (1997) [2.] Delbo, M., et al., Nature, 508, 233-236 (2014) [3.] Fujiwara, A. et al., Science 312, 1330 (2006) [4.] Garcia, R. F. et al., Icarus, 253, 159-168 (2015) [5.] Murdoch, N. et al., ASTEROIDS IV, University of Arizona Press Space Science Series, edited by P. Michel, F. DeMeo and W. Bottke, (2015) [6.] Richardson, D.C. et al., Icarus, 134, 47-79 (1998) [7.] Karatekin et al., The Asteroid Geophysical Explorer (AGEX); Proposal to explore the Didymos System using Cubesats, EGU (2016) *http://www.esa.int/Our_Activities/Space_Engineering_Technology/Asteroid_Impact_Mission/ CubeSat_companions_for_ESA_s_asteroid_mission

The Physical, Geological, and Dynamical Nature of Asteroid (101955) Bennu - Target of OSIRIS-REx

NASA Astrophysics Data System (ADS)

Lauretta, Dante

2014-11-01

OSIRIS-REx will survey asteroid (101955) Bennu to understand its properties, assess its resource potential, refine the impact hazard, and return a sample to Earth. This mission launches in 2016. Bennu is different from all other near-Earth asteroids previously visited by spacecraft. (433) Eros, target of the NEAR-Shoemaker mission, and (25143) Itokawa, target of Hayabusa, are both high-albedo, S-type asteroids with irregular shapes. In contrast, Bennu has a low albedo, is a B-type asteroid, and has a distinct spheroidal shape. While Eros and Itokawa are similar to ordinary chondrites, Bennu is likely related to carbonaceous chondrites, meteorites that record the history of volatiles and organic compounds in the early Solar System.We performed an extensive campaign to determine the properties of Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. Combining these data with cosmochemical and dynamical models yields a hypothetical timeline for Bennu’s formation and evolution. Bennu is an ancient object that has witnessed over 4.5 Gyr of Solar System history. Its chemistry and mineralogy were established within the first 10 Myr of the Solar System. It likely originated as a discrete asteroid in the main belt ~0.7 - 2 Gyr ago as a fragment from the catastrophic disruption of a large, carbonaceous asteroid. It was delivered to near-Earth space via a combination of Yarkovsky-induced drift and interaction with giant-planet resonances. During its journey, YORP processes and planetary encounters modified Bennu’s spin state, potentially reshaping and resurfacing the asteroid. Bennu is a Potentially Hazardous Asteroids with an ~1-in-2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner Solar System after a close encounter with Jupiter. OSIRIS-REx will return samples from this intriguing asteroid in September 2023.

Comet/Asteroid Protection System (CAPS): A Space-Based System Concept for Revolutionizing Earth Protection and Utilization of Near-Earth Objects

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Roithmayr, Carlos M.; Antol, Jeffrey; Kay-Bunnell, Linda; Werner, Martin R.; Park, Sang-Young; Kumar, Renjith R.

2002-01-01

There exists an infrequent, but significant hazard to life and property due to impacting asteroids and comets. There is currently no specific search for long-period comets, smaller near-Earth asteroids, or smaller short-period comets. These objects represent a threat with potentially little or no warning time using conventional ground-based telescopes. These planetary bodies also represent a significant resource for commercial exploitation, long-term sustained space exploration, and scientific research. The Comet/Asteroid Protection System (CAPS) would expand the current detection effort to include long-period comets, as well as small asteroids and short-period comets capable of regional destruction. A space-based detection system, despite being more costly and complex than Earth-based initiatives, is the most promising way of expanding the range of detectable objects, and surveying the entire celestial sky on a regular basis. CAPS is a future spacebased system concept that provides permanent, continuous asteroid and comet monitoring, and rapid, controlled modification of the orbital trajectories of selected bodies. CAPS would provide an orbit modification system capable of diverting kilometer class objects, and modifying the orbits of smaller asteroids for impact defense and resource utilization. This paper provides a summary of CAPS and discusses several key areas and technologies that are being investigated.

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.

Asteroid Risk Assessment: A Probabilistic Approach.

PubMed

Reinhardt, Jason C; Chen, Xi; Liu, Wenhao; Manchev, Petar; Paté-Cornell, M Elisabeth

2016-02-01

Following the 2013 Chelyabinsk event, the risks posed by asteroids attracted renewed interest, from both the scientific and policy-making communities. It reminded the world that impacts from near-Earth objects (NEOs), while rare, have the potential to cause great damage to cities and populations. Point estimates of the risk (such as mean numbers of casualties) have been proposed, but because of the low-probability, high-consequence nature of asteroid impacts, these averages provide limited actionable information. While more work is needed to further refine its input distributions (e.g., NEO diameters), the probabilistic model presented in this article allows a more complete evaluation of the risk of NEO impacts because the results are distributions that cover the range of potential casualties. This model is based on a modularized simulation that uses probabilistic inputs to estimate probabilistic risk metrics, including those of rare asteroid impacts. Illustrative results of this analysis are presented for a period of 100 years. As part of this demonstration, we assess the effectiveness of civil defense measures in mitigating the risk of human casualties. We find that they are likely to be beneficial but not a panacea. We also compute the probability-but not the consequences-of an impact with global effects ("cataclysm"). We conclude that there is a continued need for NEO observation, and for analyses of the feasibility and risk-reduction effectiveness of space missions designed to deflect or destroy asteroids that threaten the Earth. © 2015 Society for Risk Analysis.

Problems with the Younger Dryas Boundary (YDB) Impact Hypothesis

NASA Astrophysics Data System (ADS)

Boslough, M.

2009-12-01

One breakthrough of 20th-century Earth science was the recognition of impacts as an important geologic process. The most obvious result is a crater. There are more than 170 confirmed terrestrial impact structures with a non-uniform spatial distribution suggesting more to be found. Many have been erased by tectonics and erosion. Deep water impacts do not form craters, and craters in ice sheets disappear when the ice melts. There is growing speculation that such hidden impacts have caused frequent major environmental events of the Holocene, but this is inconsistent with the astronomically-constrained population of Earth-crossing asteroids. Impacts can have consequences much more significant than excavation of a crater. The K/T boundary mass extinction is attributed to the environmental effects of a major impact, and some researchers argue that other extinctions, abrupt climate changes, and even civilization collapses have resulted from impacts. Nuclear winter models suggest that 2-km diameter asteroids exceed a "global catastrophe threshold" by injecting sufficient dust into the stratosphere to cause short-term climate changes, but would not necessarily collapse most natural ecosystems or cause mass extinctions. Globally-catastrophic impacts recur on timescales of about one million years. The 1994 collision of Comet Shoemaker-Levy 9 with Jupiter led us recognize the significance of terrestrial airbursts caused by objects exploding violently in Earth’s atmosphere. We have invoked airbursts to explain rare forms of non-volcanic glasses and melts by using high-resolution computational models to improve our understanding of atmospheric explosions, and have suggested that multiple airbursts from fragmented impactors could be responsible for regional effects. Our models have been cited in support of the widely-publicized YDB impact hypothesis. Proponents claim that a broken comet exploded over North America, with some fragments cratering the Laurentide Ice Sheet. They suggest an abrupt climate change caused by impact-triggered meltwater forcing, along with massive wildfires, resulted in megafaunal extinctions and collapse of the Clovis culture. We argue that the physics of fragmentation, dispersion, and airburst is not consistent with the hypothesis; that observations are no more compatible with impact than with other causes; and that the probability of the scenario is effectively nil. Moreover, millennial-scale climate events are far more frequent than catastrophic impacts, and pose a much greater threat to humanity. Sandia is a multiprogram laboratory operated by Sandia Corp, a Lockheed Martin Company, for the US DOE under Contract DE-AC04-94AL85000. Probability density for largest asteroid impact since Last Glacial Maximum based on power-law size distribution. Comets are orders of magnitude less likely. Grazing trajectory or recent fragmentation further reduces probability.

Search techniques for near-earth asteroids

NASA Technical Reports Server (NTRS)

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

1990-01-01

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

A Parameter Study on the Effect of Impactor Size for NASA’s DART Mission

NASA Astrophysics Data System (ADS)

Truitt, Amanda; Weaver, Robert; Gisler, Galen

2018-06-01

We have modeled the impact of the Double Asteroid Redirection Test (DART) spacecraft into the binary near-Earth asteroid (65803) Didymos. While the primary object is approximately 800 meters across, its secondary body (“moonlet” Didymoon) has a diameter of 150 meters, which is thought to be a much more typical size for the kind of asteroid that would pose a hazard to Earth. DART will be the first demonstration of the kinetic impact technique to change the motion of an asteroid in space, an important consideration for understanding our capabilities in planetary defense of Near-Earth Asteroids. Recent modeling of this impact has used full-density solid aluminum spheres with a mass of approximately 500 kg. Many of the published scaling laws for crater size and diameter as well as ejecta modeling assume this type of impactor, although the actual spacecraft shape being considered for the DART Mission impact is not solid and does not contain a solid dedicated kinetic impactor – rather, the spacecraft itself is considered the impactor. Since the 500 kg hollow spacecraft is significantly larger (~100 x 100 x 200 cm) in size than a solid aluminum sphere (radius ~ 36 cm) the resulting impact dynamics are quite different. Here we have modeled both types of impacts and compare the results of the simulations for crater size, depth, and ejecta for a solid sphere (R = 36 cm) and cylindrical spacecraft (R = 20, 50, and 100 cm), while maintaining a constant mass and material density. This work will allow for a more robust comparison of the momentum enhancement β-factor, which describes the gain in a momentum transfer exerted by the impacting spacecraft on a Near-Earth Object due to ejecta momentum escape. (LA-UR-18-21571)

Performance of Hayabusa2 DCAM3-D Camera for Short-Range Imaging of SCI and Ejecta Curtain Generated from the Artificial Impact Crater Formed on Asteroid 162137 Ryugu (1999 JU3)

NASA Astrophysics Data System (ADS)

Ishibashi, K.; Shirai, K.; Ogawa, K.; Wada, K.; Honda, R.; Arakawa, M.; Sakatani, N.; Ikeda, Y.

2017-07-01

Deployable Camera 3-D (DCAM3-D) is a small high-resolution camera equipped on Deployable Camera 3 (DCAM3), one of the Hayabusa2 instruments. Hayabusa2 will explore asteroid 162137 Ryugu (1999 JU3) and conduct an impact experiment using a liner shooting device called Small Carry-on Impactor (SCI). DCAM3 will be detached from the Hayabusa2 spacecraft and observe the impact experiment. The purposes of the observation are to know the impact conditions, to estimate the surface structure of asteroid Ryugu, and to understand the physics of impact phenomena on low-gravity bodies. DCAM3-D requires high imaging performance because it has to image and detect multiple targets of different scale and radiance, i.e., the faint SCI before the shot from 1-km distance, the bright ejecta generated by the impact, and the asteroid. In this paper we report the evaluation of the performance of the CMOS imaging sensor and the optical system of DCAM3-D. We also describe the calibration of DCAM3-D. We confirmed that the imaging performance of DCAM3-D satisfies the required values to achieve the purposes of the observation.

Origin of asteroids and the missing planet

NASA Technical Reports Server (NTRS)

Opik, E. J.

1977-01-01

Consideration is given to Ovenden's (1972) theory concerning the existence of a planet of 90 earth masses which existed from the beginning of the solar system and then disappeared 16 million years ago, leaving only asteroids. His model for secular perturbations is reviewed along with the principle of least interaction action (1972, 1973, 1975) on which the model is based. It is suggested that the structure of the asteroid belt and the origin of meteorites are associated with the vanished planet. A figure of 0.001 earth masses is proposed as a close estimate of the mass of the asteroidal belt. The hypothesis that the planet was removed through an explosion is discussed, noting the possible origin of asteroids in such a manner. Various effects of the explosion are postulated, including the direct impact of fragments on the earth, their impact on the sun and its decreased radiation, and the direct radiation of the explosion. A model for the disappearance of the planet by ejection in a gravitational encounter with a passing mass is also described.

Scattering of trajectories of hazardous asteroids

NASA Astrophysics Data System (ADS)

Sokolov, Leonid; Petrov, Nikita; Kuteeva, Galina; Vasilyev, Andrey

2018-05-01

Early detection of possible collisions of asteroids with the Earth is necessary to exept the asteroid-comet hazard. Many collisions associate with resonant returns after preceding approaches. The difficulty of collisions prediction is associated with a resonant returns after encounters with the Earth due to loss of precision in these predictions. On the other hand, we can use the fly-by effect to avoid hazardous asteroid from collision. The main research object is the asteroid Apophis (99942), for which we found about 100 orbits of possible impacts with the Earth and more than 10 - with the Moon. It is shown that the early (before 2029) change of the Apophis orbit allows to avoid all main impacts with the Earth in 21st century, associated with resonant returns, and such a change of the orbit, in principle, is feasible. The scattering of possible trajectories of Apophis after 2029 and after 2051, as well as 2015 RN35 and other dangerous objects, is discussed.

ISALE impact simulations in support of AIDA mission

NASA Astrophysics Data System (ADS)

Oklay, Nilda; Vincent, Jean-Baptiste; Michel, Patrick; Schwartz, Stephen

2016-07-01

Introduction: The Asteroid Impact Deflection Assessment (AIDA) mission is a joint project of ESA and NASA with two independent spacecraft. ESA's contribution is an observer satellite called Asteroid Impact Mission (AIM, [1]), and NASA's contribution is a projectile called Double Asteroid Redirection Test (DART, [2]). The target of the mission is a near-Earth binary asteroid system (65803) Didymos. The aim is to study the possibility of deflecting an asteroid by using a kinetic impactor, as well as to characterize the internal properties of the target and test various relevant technologies for other missions. The design is that the DART would impact the secondary of the binary system and AIM would characterize the target asteroid, observe the impact event and measure the changes in the relative orbit after the impact. Impact modeling will be used to interpret the results of the AIDA impact event. There are numerous impact simulation codes, which are planned to be used to understand the AIDA impact results. Therefore an international benchmarking program is ongoing for the comparison of the results of various codes on the defined test cases [3]. We will present the results of the test cases performed by iSALE hydrocode. Modeling: In this work we use the iSALE-2D shock physics code [4], which is based on the SALE hydrocode solution algorithm [5]. To simulate hypervelocity impact processes in solid materials SALE was modified to include an elastoplastic constitutive model, fragmentation models, various EOS, and multiple materials [6, 7]. More recent improvements include a modified strength model [8] and a porosity compaction model [4, 9]. References: [1] Michel P. et al., 2016, ASR, submitted [2] Cheng A. F. et al., (2016) PSS, 121, 27-35 [3] Stickle A. M. et al., (2016). 47th LPSC [4] Wünnemann,K. et al., (2006). Icarus, 180:514-527 [5] Amsden, A., et al., (1980) LANL Report, LA-8095:101p. [6] Melosh, H. J., et al., (1992). J. Geophys. Res., 97(E9):14735-14759 [7] Ivanov, B. A., et al., (1997) Int. J. Imp. Eng., 20:411-430; [8] Collins, G. S., et al., (2004). Met. & Planet. Sci., 39:217-231. [9] Collins, G., et al., (2011) Int. J. Imp. Eng., 38:434-439

Unique View of C Asteriod Regolith from the Jbilet Winselwan CM Chondrite

NASA Technical Reports Server (NTRS)

Zolensky, Michael; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Komatsu, Mutsumi; Chan, Queenie H. S.; Le, Loan; Kring, David; Cato, Michael; Fagan, Amy L.;

Three-Dimensional Simulations of Oblique Asteroid Impacts into Water

NASA Astrophysics Data System (ADS)

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

2016-12-01

Waves generated by impacts into oceans may represent the most significant danger from near-earth asteroids and comets. For impacts near populated shores, the crown splash and subsequent waves, accompanied by sediment lofting and high winds, could be more damaging than storm surges from the strongest hurricanes. For asteroids less than 500 m in diameter that impact into deep water far from shores, the waves produced will be detectable over large distances, but probably not significantly dangerous. We present new three-dimensional simulations of oblique impacts into deep water, with trajectory angles ranging from 20 degrees to 60 degrees (where 90 degrees is vertical). These simulations are performed with the Los Alamos Rage hydrocode, and include atmospheric effects including ablation and airbursts. These oblique impact simulations are specifically performed in order to help determine whether there are additional dangers from the obliquity of impact not covered by previous two-dimensional studies. Water surface elevation profiles, surface pressures, and depth-averaged mass fluxes within the water are prepared for use in propagation studies.

Deflection Missions for Asteroid 2011 AG5

NASA Technical Reports Server (NTRS)

Grebow, Daniel; Landau, Damon; Bhaskaran, Shyam; Chodas, Paul; Chesley, Steven; Yeomans, Don; Petropoulos, Anastassios; Sims, Jon

2012-01-01

The recently discovered asteroid 2011 AG5 currently has a 1-in-500 chance of impacting Earth in 2040. In this paper, we discuss the potential of future observations of the asteroid and their effects on the asteroid's orbital uncertainty. Various kinetic impactor mission scenarios, relying on both conventional chemical as well as solar-electric propulsion, are presented for deflecting the course of the asteroid safely away from Earth. The times for the missions range from pre-keyhole passage (pre-2023), and up to five years prior to the 2040 Earth close approach. We also include a brief discussion on terminal guidance, and contingency options for mission planning.

The origin of planetary impactors in the inner solar system.

PubMed

Strom, Robert G; Malhotra, Renu; Ito, Takashi; Yoshida, Fumi; Kring, David A

2005-09-16

Insights into the history of the inner solar system can be derived from the impact cratering record of the Moon, Mars, Venus, and Mercury and from the size distributions of asteroid populations. Old craters from a unique period of heavy bombardment that ended approximately 3.8 billion years ago were made by asteroids that were dynamically ejected from the main asteroid belt, possibly due to the orbital migration of the giant planets. The impactors of the past approximately 3.8 billion years have a size distribution quite different from that of the main belt asteroids but very similar to that of near-Earth asteroids.

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

NASA Astrophysics Data System (ADS)

Minton, David Andrew

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

Space science: Causes and impacts of cutbacks to NASA's outer solar system exploration missions. Report to the Chairman, Subcommittee on Investigations and Oversight, Committee on Science, Space, and Technology, House of Representatives

NASA Astrophysics Data System (ADS)

Degnan, Frank

1993-12-01

The Comet Rendezvous Asteroid Flyby (CRAF)/Cassini program was first funded by the Congress in fiscal year 1990. Since then, it has encountered difficulties that resulted in the cancellation of CRAF, reduction of Cassini's original scientific capabilities, and extension of its launch date. At the request of the former Chairman of the Investigations and Oversight Subcommittee, House Committee on Science, Space, and Technology, GAO reviewed the program to identify the factors that led to the cancellation of the CRAF project and the prospects for continuation of the Cassini project.

The asteroids - Accretion, differentiation, fragmentation, and irradiation

NASA Technical Reports Server (NTRS)

Wilkening, L. L.

1979-01-01

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

Asteroid impacts on terrestrial planets: the effects of super-Earths and the role of the ν6 resonance

NASA Astrophysics Data System (ADS)

Smallwood, Jeremy L.; Martin, Rebecca G.; Lepp, Stephen; Livio, Mario

2018-01-01

With N-body simulations of a planetary system with an asteroid belt, we investigate how the asteroid impact rate on the Earth is affected by the architecture of the planetary system. We find that the ν6 secular resonance plays an important role in the asteroid collision rate with the Earth. Compared to exoplanetary systems, the Solar system is somewhat special in its lack of a super-Earth mass planet in the inner Solar system. We therefore first consider the effects of the presence of a super-Earth in the terrestrial planet region. We find a significant effect for super-Earths with a mass of around 10 M⊕ and a separation greater than about 0.7 au. For a super-Earth which is interior to the Earth's orbit, the number of asteroids colliding with Earth increases the closer the super-Earth is to the Earth's orbit. This is the result of multiple secular resonance locations causing more asteroids to be perturbed on to Earth-crossing orbits. When the super-Earth is placed exterior to Earth's orbit, the collision rate decreases substantially because the ν6 resonance no longer exists in the asteroid belt region. We also find that changing the semimajor axis of Saturn leads to a significant decrease in the asteroid collision rate, though increasing its mass increases the collision rate. These results may have implications for the habitability of exoplanetary systems.

Synergistic approach of asteroid exploitation and planetary protection

NASA Astrophysics Data System (ADS)

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

2012-02-01

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

Space Weathering Rates in Lunar and Itokawa Samples

NASA Technical Reports Server (NTRS)

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

2017-01-01

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

Meteoritic Evidence for Injection of Trans-Neptunian Objects into the Inner Solar System

NASA Technical Reports Server (NTRS)

Zolensky, M.; Johnson, J.; Ziegler, K.; Chan, Q.; Kebukawa, Y.; Bottke, W.; Fries, M.; Martinez, J.; Le, L.

2018-01-01

There is excellent evidence that a dynamical instability in the early solar system led to gravitational interactions between the giant planets and trans-Neptunian planetesimals. Giant planetary migration triggered by the instability dispersed a disk of primordial trans-Neptunian object (TNOs) and created a number of small body reservoirs (e.g. the Kuiper Belt, scattered disk, irregular satellites, and the Jupiter/Neptune Trojan populations). It also injected numerous bodies into the main asteroid belt, where modeling shows they can successfully reproduce the observed P and D-type asteroid populations.

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.

The 1990 MB: The first Mars Trojan

NASA Technical Reports Server (NTRS)

Innanen, Kimmo A.; Mikkola, Seppo; Bowell, Edward; Muinonen, Karri; Shoemaker, Eugene M.

1991-01-01

Asteroid 1990 MB was discovered by D. H. Levy and H. E. Holt during the course of the Mars and Earth Crossing Asteroid and Comet Survey. An orbit based on a 9 day arc and the asteroid's location near Mars' L5 (trailing Lagrangean) longitude led E. Boswell to speculate that it might be in 1:1 resonance with Mars, analogous to the Trojan asteroids of Jupiter. Subsequent observations strengthened the possibility, and later calculations confirmed it. Thus 1990 MB is the first known asteroid in 1:1 resonance with a planet other than Jupiter. The existence of 1990 MB (a small body most likely between 2 and 4 km in diameter) provides remarkable confirmation of computer simulations. These self consistent n-body simulations demonstrated this sort of stability for Trojans of all the terrestrial planets over at least a 2 million year time base. The discovery of 1990 MB suggests that others of similar or smaller diameter may be found. Using hypothetical populations of Mars Trojans, their possible sky plane distributions were modeled as a first step in undertaking a systematic observational search of Mars' L4 and L5 libration regions.

A Mobile Asteroid Surface Scout for the AIDA Mission

NASA Astrophysics Data System (ADS)

Ho, Tra Mi; Lange, Caroline; Grimm, Christian; Thimo Grundmann, Jan; Rößler, Johannes; Schröder, Silvio; Skoczylas, Thomas; Ziach, Christian; Biele, Jens; Cozzoni, Barbara; Krause, Christian; Küchemann, Oliver; Maibaum, Michael; Ulamec, Stephan; Lange, Michael; Mierheim, Olaf; Maier, Maximilian; Herique, Alain; Mascot Study Team

2016-04-01

The Asteroid Impact Deflection, AIDA, mission is composed of a kinetic impactor, DART and an observer, the Asteroid Impact Monitor, AIM, carrying among other payload a surface package, MASCOT2 (MSC2). Its proposed concept is based on the MASCOT lander onboard the HAYABUSA2 Mission (JAXA) to near-Earth asteroid (162173) Ryugu. MASCOT is a compact platform ('shoe box size') carrying a suite of 4 scientific instruments and has a landed mass of ~10kg. Equipped with a mobility mechanism, the MASCOT lander is able to upright and relocate on the targeted asteroid; thus providing in-situ data at more than one site. In the context of the AIDA Mission, the MASCOT2 lander would be carried by the AIM spacecraft and delivered onto Didymoon, the secondary object in the (65803) Didymos binary near-Earth asteroid system. Since the mission objectives of the AIM mission within the joint AIDA mission concept differ from JAXA's sample return mission HAYABUSA2, several design changes need to be studied and implemented. To support one of the prime objectives of the AIM mission, the characterization of the bulk physical properties of Didymoon, the main scientific payload of MSC2 is a low-frequency radar (LFR) to investigate the internal structure of the asteroid moon. Since the total science payload on MASCOT2 is limited to approximately 2.3 kg, the mass remaining for a suite of other experiments is in the range of 0.1 to 0.5 kg per instrument. Further requirements have a significant impact on the MSC2 design which will be presented. Among these are the much longer required operational lifetime than for MASCOT on HAYABUSA2, and different conditions on the target body such as an extremely low gravity due to its small size of Ø_[Didymoon] ~ 150m.

Planetary geology: Impact processes on asteroids

NASA Technical Reports Server (NTRS)

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

1982-01-01

The fundamental geological and geophysical properties of asteroids were studied by theoretical and simulation studies of their collisional evolution. Numerical simulations incorporating realistic physical models were developed to study the collisional evolution of hypothetical asteroid populations over the age of the solar system. Ideas and models are constrained by the observed distributions of sizes, shapes, and spin rates in the asteroid belt, by properties of Hirayama families, and by experimental studies of cratering and collisional phenomena. It is suggested that many asteroids are gravitationally-bound "rubble piles.' Those that rotate rapidly may have nonspherical quasi-equilibrium shapes, such as ellipsoids or binaries. Through comparison of models with astronomical data, physical properties of these asteroids (including bulk density) are determined, and physical processes that have operated in the solar system in primordial and subsequent epochs are studied.

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.

An Overview of the Chelyabinsk Impact Event (Invited)

NASA Astrophysics Data System (ADS)

Chodas, P. W.; Chesley, S.

2013-12-01

On February 15, 2013, a small asteroid called 2012 DA14 was about to make a much anticipated extremely close flyby of the Earth, when an even smaller asteroid stole the show by impacting into the Earth's atmosphere near Chelyabinsk, Russia, releasing half a megaton of energy and creating a shock wave that reportedly injured more than a thousand people. The passage of a 40-meter asteroid within the ring of geosynchrounous satellites is rare, calculated to be a once-in-40-year event, and yet it was upstaged on the same day by an actual Earth impact of a previously unseen 20-meter asteroid, an event expected to occur only about once per century, on average. Infrasound-based estimates of the released energy from this impact lie in the range of from 450 to 700 kilotons, making the Chelyabinsk fireball the largest impact event since the Tunguska explosion over Siberia in 1908. From the standpoint of acquiring data, it is incredibly fortunate that this impact occurred when and where it did, i.e., near a large city, during the morning commute hours, in a country where continuously operating "dash-cams" are ubiquitous, and in an era when videos can quickly be uploaded and viewed worldwide. There are over 400 videos of the event or its effects catalogued to date, half of them viewing the fireball directly or showing its lightflash. Some of these were available online within an hour of the event, and they enabled a quick scientific assessment of both the size of the fireball and its approximate trajectory. Social media played a key role by providing an early alert to scientists and by calling attention to the online videos. Even a cursory examination of the trajectory of the fireball path revealed that the impactor entered at a very shallow entry angle (later determined to be about 17 deg to the horizontal), and that it entered from the general direction of the Sun. It was clear that the east-to-west trajectory of the Chelyabinsk impactor was very different from the south-to-north path of 2012 DA14. With such clearly different trajectories, we could assure the public with confidence that the two asteroids were unrelated. There have been several detailed analyses of the approach trajectory of the Chelyabinsk impactor, all of them indicating that the asteroid approached the Earth from within 20 degrees of the sunline. Thus, this object could not have been detected on its final approach by any of the asteroid search programs, which optically scan the night sky, well away from direction of the Sun. It is worth noting, however, that the even smaller object 2009 TC3, was discovered by a NASA-funded asteroid survey program on its final plunge to an impact in Sudan in October 2008, but it approached the Earth from the side opposite the Sun. The Chelyabinsk impact event reminds us of the hazard posed by near-Earth asteroids, and validates NASA-funded efforts to find and track as many of these potentially hazardous objects as possible.

Comet/Asteroid Protection System (CAPS): Preliminary Space-Based Concept and Study Results

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Roithmayr, Carlos M.; Antol, Jeffrey; Park, Sang-Young; Koons, Robert H.; Bremer, James C.; Murphy, Douglas G.; Hoffman, James A.; Kumar, Renjith R.; Seywald, Hans

2005-01-01

There exists an infrequent, but significant hazard to life and property due to impacting asteroids and comets. There is currently no specific search for long-period comets, smaller near-Earth asteroids, or smaller short-period comets. These objects represent a threat with potentially little or no warning time using conventional ground-based telescopes. These planetary bodies also represent a significant resource for commercial exploitation, long-term sustained space exploration, and scientific research. The Comet/Asteroid Protection System (CAPS) is a future space-based system concept that provides permanent, continuous asteroid and comet monitoring, and rapid, controlled modification of the orbital trajectories of selected bodies. CAPS would expand the current detection effort to include long-period comets, as well as small asteroids and short-period comets capable of regional destruction. A space-based detection system, despite being more costly and complex than Earth-based initiatives, is the most promising way of expanding the range of detectable objects, and surveying the entire celestial sky on a regular basis. CAPS would provide an orbit modification system capable of diverting kilometer class objects, and modifying the orbits of smaller asteroids for impact defense and resource utilization. This Technical Memorandum provides a compilation of key related topics and analyses performed during the CAPS study, which was performed under the Revolutionary Aerospace Systems Concepts (RASC) program, and discusses technologies that could enable the implementation of this future system.

Environmental Perturbations Caused by the Impacts of Asteroids and Comets

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Zahnle, Kevin; Morrison, David; Turco, Richard; Covey, Curt

1997-01-01

We review the major mechanisms proposed to cause extinctions at the Cretaceous-Tertiary geological boundary following an asteroid impact. We then discuss how the proposed extinction may relate to the impact of asteroids or comets in general. We discuss the limitations of these mechanisms in terms of the spatial scale that may be affected, and the time scale over which the effects may last. Our goal is to provide relatively simple prescriptions for evaluating the importance of colliding objects having a range of energies and compositions. We also identify the many uncertainties concerning the environmental effects of impacts. We conclude that, for impact energies below about 10(exp 4) Mts (megatons of TNT equivalent) - i.e., impact frequencies less than in 6 x 10(exp 4) yr, corresponding to comets and asteroids with diameters smaller than about 400 m and 650 m, respectively - blast damage, earthquakes, and fires should be important on a scale of 10(exp 4) or 10(exp 5) km (exp 2), which corresponds to the area damaged in many natural disasters of recent history. However, tsunami could be more damaging, flooding a kilometer of coastal plane over entire ocean basins. In the energy range of 10(exp 4) to 10 (exp 5) Mts (intervals up to 3 x 10(exp 5) yr; comets and asteroids with sizes up to 800 m and 1.5 km, respectively) water vapor injections and ozone loss become significant on the global scale. In the submicrometer dust injection fraction from the pulverized target material is much higher than is presently thought to be most likely, then dust injection could be important in this energy range.

Terrestrial production vs. extraterrestrial delivery of prebiotic organics to the early Earth

NASA Technical Reports Server (NTRS)

Chyba, C. F.; Sagan, C.; Thomas, P. J.; Brookshaw, L.

1991-01-01

A comprehensive treatment of comet/asteroid interaction with the atmosphere, ensuring surface impact, and resulting organic pyrolysis is required to determine whether more than a negligible fraction of the organics in incident comets and asteroids actually survived collision with Earth. Results of such an investigation, using a smoothed particle hydrodynamic simulation of cometary and asteroidal impacts into both oceans and rock, demonstrate that organics will not survive impacts at velocities approx. greater than 10 km s(exp -1), and that even comets and asteroids as small as 100m in radius cannot be aerobraked to below this velocity in 1 bar atmospheres. However, for plausible dense (10 bar CO2) early atmospheres, there will be sufficient aerobraking during atmospheric passage for some organics to survive the ensuing impact. Combining these results with analytical fits to the lunar impact record shows that 4.5 Gyr ago Earth was accreting at least approx. 10(exp 6) kg yr(exp 1) of intact cometary organics, a flux which thereafter declined with a approx. 100 Myr half-life. The extent to which this influx was augmented by asteroid impacts, as well as the effect of more careful modelling of a variety of conservative approximations, is currently being quantified. These results may be placed in context by comparison with in situ organic production from a variety of terrestrial energy sources, as well as organic delivery by interplanetary dust. Which source dominated the early terrestrial prebiotic inventory is found to depend on the nature of the early terrestrial atmosphere. However, there is an intriguing symmetry: it is exactly those dense CO2 atmospheres where in situ atmospheric production of organic molecules should be the most difficult, in which intact cometary organics would be delivered in large amounts.

Calculations of Asteroid Impacts into Deep and Shallow Water

NASA Astrophysics Data System (ADS)

Gisler, Galen; Weaver, Robert; Gittings, Michael

2011-06-01

Contrary to received opinion, ocean impacts of small (<500 m) asteroids do not produce tsunamis that lead to world-wide devastation. In fact the most dangerous features of ocean impacts, just as for land impacts, are the atmospheric effects. We present illustrative hydrodynamic calculations of impacts into both deep and shallow seas, and draw conclusions from a parameter study in which the size of the impactor and the depth of the sea are varied independently. For vertical impacts at 20 km/s, craters in the seafloor are produced when the water depth is less than about 5-7 times the asteroid diameter. Both the depth and the diameter of the transient crater scale with the asteroid diameter, so the volume of water excavated scales with the asteroid volume. About a third of the crater volume is vaporised, because the kinetic energy per unit mass of the asteroid is much larger than the latent heat of vaporisation of water. The vaporised water carries away a considerable fraction of the impact energy in an explosively expanding blast wave which is responsible for devastating local effects and may affect worldwide climate. Of the remaining energy, a substantial portion is used in the crown splash and the rebound jet that forms as the transient crater collapses. The collapse and rebound cycle leads to a propagating wave with a wavelength considerably shorter than classical tsunamis, being only about twice the diameter of the transient crater. Propagation of this wave is hindered somewhat because its amplitude is so large that it breaks in deep water and is strongly affected by the blast wave's perturbation of the atmosphere. Even if propagation were perfect, however, the volume of water delivered per metre of shoreline is less than was delivered by the Boxing Day 2004 tsunami for any impactor smaller than 500 m diameter in an ocean of 5 km depth or less. Near-field effects are dangerous for impactors of diameter 200 m or greater; hurricane-force winds can extend tens of kilometers from the impact point, and fallout from the initial splash can be extremely violent. There is some indication that near-field effects are more severe if the impact occurs in shallow water.

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

PubMed

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

2016-01-01

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

Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids

PubMed Central

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

2016-01-01

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

Dark Hill on Asteroid Vesta Movie

NASA Image and Video Library

2011-12-06

This still from a movie shows an image taken by NASA Dawn spacecraft layered on a digital terrain model of an unusual hill containing a dark-rayed impact crater and nearby dark deposit on asteroid Vesta.

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.

An Optimal Mitigation Strategy Against the Asteroid Impact Threat with Short Warning Time

NASA Technical Reports Server (NTRS)

Wie, Bong; Barbee, Brent W.

2015-01-01

This paper presents the results of a NASA Innovative Advanced Concept (NIAC) Phase 2 study entitled "An Innovative Solution to NASA's Near-Earth Object (NEO) Impact Threat Mitigation Grand Challenge and Flight Validation Mission Architecture Development." This NIAC Phase 2 study was conducted at the Asteroid Deflection Research Center (ADRC) of Iowa State University in 2012-2014. The study objective was to develop an innovative yet practically implementable mitigation strategy for the most probable impact threat of an asteroid or comet with short warning time (less than 5 years). The mitigation strategy described in this paper is intended to optimally reduce the severity and catastrophic damage of the NEO impact event, especially when we don't have sufficient warning times for non-disruptive deflection of a hazardous NEO. This paper provides an executive summary of the NIAC Phase 2 study results.

Asteroid Redirect Mission: Update on Planetary Defense Demonstration and Small Bodies Benefits and Community Interaction

NASA Astrophysics Data System (ADS)

Reeves, D.; Mazanek, D. D.; Abell, P. A.; Brophy, J. R.; Chodas, P. W.; Cichy, B. D.

2016-12-01

The National Aeronautics and Space Administration (NASA) is developing the Asteroid Redirect Mission (ARM) to robotically visit a large near-Earth asteroid (NEA), collect a multi-ton boulder and regolith samples from its surface, demonstrate the enhanced gravity tractor (EGT) planetary defense technique, return the asteroidal material to a stable orbit around the Moon, and explore the returned material with a crewed mission in the mid-2020s. Recent analysis of the EGT has led to a change in the robotic baseline operations from a halo orbit, to an in-line stand-off. This study took into account the uncertainties in size and mass of the current reference target (2008 EV5), the desire to be able to perform the EGT operations with the collected boulder augmenting the spacecraft mass or with the spacecraft alone, the assumed capability of the ARM solar electric propulsion (SEP) system, and the extensibility to future planetary defense missions. This presentation will cover the findings that led to this change in the baseline, as well as the benefits that this EGT demonstration will provide. ARM is a capability and technology demonstration mission, which will also benefit our understanding of small bodies in the areas of science, planetary defense, and asteroidal resources and in-situ resource utilization (ISRU). The synergistic benefits of both the robotic and crewed segments will be discussed in addition to describing ARM's interaction with communities that are interested in small bodies, including: the Formulation Assessment and Support Team (FAST) effort, the Small Bodies Assessment Group (SBAG) Special Action Team (SAT) effort, and the upcoming Investigation Team (IT). The IT, which is expected to be announced in the spring of 2017, will assist the ARM project in the definition, design, development, and operations phases of the ARRM with the goal of maximizing the probability of mission success and the knowledge return from the mission.

Physical Mechanism of Comet (and Asteroid) Outbursts: The Movie

NASA Astrophysics Data System (ADS)

Hartmann, W. K.

2015-07-01

A film made during impact experiments at NASA Ames illustrates a mechanism in which regolith can become gas charged and then erupt to create outbursts as observed on comets (and "asteroids" such as 2060 Chiron).

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.

Assessing Atmospheric Water Injection from Oceanic Impacts

NASA Technical Reports Server (NTRS)

Pierazzo, E.

2005-01-01

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

Life and Death on Mars and Earth

NASA Technical Reports Server (NTRS)

Zahnle, K. J.; Sleep, N. H.

1999-01-01

Failure to discover life on Mars has led a great many experts to conclude that it must be hiding. Where? The likeliest hiding places are deep beneath the surface, where geothermal heat could permit liquid water. In this the search for life on Mars parallels the search for water on Mars. Liquid water has been, at least on occasion, a geologically significant presence on the surface. Channels were cut and plains dissected. This water is now hidden, in all likelihood having drained to the base of the porous regolith, where it fills possibly frozen aquifers. Presumably any surviving biota has followed the water from the surface to its hiding places in the deep. Accordingly, we have extended our environmental impact assessment of the environmental hazards posed by large asteroid and comet impacts to Mars, and compare its case to Earth's. In particular, we address the continuous habitability of surface and subsurface environments.

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

NASA Astrophysics Data System (ADS)

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

2013-10-01

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

A Probabilistic Asteroid Impact Risk Model

NASA Technical Reports Server (NTRS)

Mathias, Donovan L.; Wheeler, Lorien F.; Dotson, Jessie L.

2016-01-01

Asteroid threat assessment requires the quantification of both the impact likelihood and resulting consequence across the range of possible events. This paper presents a probabilistic asteroid impact risk (PAIR) assessment model developed for this purpose. The model incorporates published impact frequency rates with state-of-the-art consequence assessment tools, applied within a Monte Carlo framework that generates sets of impact scenarios from uncertain parameter distributions. Explicit treatment of atmospheric entry is included to produce energy deposition rates that account for the effects of thermal ablation and object fragmentation. These energy deposition rates are used to model the resulting ground damage, and affected populations are computed for the sampled impact locations. The results for each scenario are aggregated into a distribution of potential outcomes that reflect the range of uncertain impact parameters, population densities, and strike probabilities. As an illustration of the utility of the PAIR model, the results are used to address the question of what minimum size asteroid constitutes a threat to the population. To answer this question, complete distributions of results are combined with a hypothetical risk tolerance posture to provide the minimum size, given sets of initial assumptions. Model outputs demonstrate how such questions can be answered and provide a means for interpreting the effect that input assumptions and uncertainty can have on final risk-based decisions. Model results can be used to prioritize investments to gain knowledge in critical areas or, conversely, to identify areas where additional data has little effect on the metrics of interest.

Survey of Technologies Relevant to Defense From Near-Earth Objects

NASA Technical Reports Server (NTRS)

Adams, R. B.; Alexander, R.; Bonometti, J.; Chapman, J.; Fincher, S.; Hopkins, R.; Kalkstein, M.; Polsgrove, T.; Statham, G.; White, S.

2004-01-01

Several recent near-miss encounters with asteroids and comets have focused attention on the threat of a catastrophic impact with the Earth. This Technical Publication reviews the historical impact record and current understanding of the number and location of near-Earth objects (NEOs) to address their impact probability. Various ongoing projects intended to survey and catalog the NEO population are also reviewed. Details are given of a Marshall Space Flight Center-led study intended to develop and assess various candidate systems for protection of the Earth against NEOs. Details of analytical tools, trajectory tools, and a tool that was created to model both the undeflected inbound path of an NEO as well as the modified, postdeflection path are given. A representative selection of these possible options was modeled and evaluated. It is hoped that this study will raise the level of attention about this very real threat and also demonstrate that successful defense is both possible and practicable, provided appropriate steps are taken.

SPH simulations of high-speed collisions

NASA Astrophysics Data System (ADS)

Rozehnal, Jakub; Broz, Miroslav

2016-10-01

Our work is devoted to a comparison of: i) asteroid-asteroid collisions occurring at lower velocities (about 5 km/s in the Main Belt), and ii) mutual collisions of asteroids and cometary nuclei usually occurring at significantly higher relative velocities (> 10 km/s).We focus on differences in the propagation of the shock wave, ejection of the fragments and possible differences in the resultingsize-frequency distributions of synthetic asteroid families. We also discuss scaling with respect to the "nominal" target diameter D = 100 km, projectile velocity 3-7 km/s, for which a number of simulations were done so far (Durda et al. 2007, Benavidez et al. 2012).In the latter case of asteroid-comet collisions, we simulate the impacts of brittle or pre-damaged impactors onto solid monolithic targets at high velocities, ranging from 10 to 15 km/s. The purpose of this numerical experiment is to better understand impact processes shaping the early Solar System, namely the primordial asteroid belt during during the (late) heavy bombardment (as a continuation of Broz et al. 2013).For all hydrodynamical simulations we use a smoothed-particle hydrodynamics method (SPH), namely the lagrangian SPH3D code (Benz & Asphaug 1994, 1995). The gravitational interactions between fragments (re-accumulation) is simulated with the Pkdgrav tree-code (Richardson et al. 2000).

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.

Space station impact experiments

NASA Technical Reports Server (NTRS)

Schultz, P.; Ahrens, T.; Alexander, W. M.; Cintala, M.; Gault, D.; Greeley, R.; Hawke, B. R.; Housen, K.; Schmidt, R.

1986-01-01

Four processes serve to illustrate potential areas of study and their implications for general problems in planetary science. First, accretional processes reflect the success of collisional aggregation over collisional destruction during the early history of the solar system. Second, both catastrophic and less severe effects of impacts on planetary bodies survivng from the time of the early solar system may be expressed by asteroid/planetary spin rates, spin orientations, asteroid size distributions, and perhaps the origin of the Moon. Third, the surfaces of planetary bodies directly record the effects of impacts in the form of craters; these records have wide-ranging implications. Fourth, regoliths evolution of asteroidal surfaces is a consequence of cumulative impacts, but the absence of a significant gravity term may profoundly affect the retention of shocked fractions and agglutinate build-up, thereby biasing the correct interpretations of spectral reflectance data. An impact facility on the Space Station would provide the controlled conditions necessary to explore such processes either through direct simulation of conditions or indirect simulation of certain parameters.

Asteroid Crew Segment Mission Lean Development

NASA Technical Reports Server (NTRS)

Gard, Joseph; McDonald, Mark

2014-01-01

Asteroid Retrieval Crewed Mission (ARCM) requires a minimum set of Key Capabilities compared in the context of the baseline EM-1/2 Orion and SLS capabilities. These include: Life Support & Human Systems Capabilities; Mission Kit Capabilities; Minimizing the impact to the Orion and SLS development schedules and funding. Leveraging existing technology development efforts to develop the kits adds functionality to Orion while minimizing cost and mass impact.

Perspectives on the Near-Earth Object Impact Hazard After Chelyabinsk

NASA Astrophysics Data System (ADS)

Chapman, C. R.

2013-12-01

Until this year, the NEO impact hazard had been regarded as a theoretical example of a very low probability high consequence natural disaster. There had been no confirmed examples of fatalities directly due to asteroid or meteoroid strikes. (There still aren't.) The several megaton Tunguska event in 1908 was in a remote, unpopulated place. So human beings have been witnessing only the tiniest analogs of asteroid strikes, the night-sky meteors and occasional bolides, which - on rare occasions - yield meteoritic fragments that puncture holes in roofs. Though the NEO impact hazard has occasionally been treated in the natural hazards literature, interest primarily remained in the planetary science and aerospace communities. The Chelyabinsk asteroid impact on 15 February 2013 was a real disaster, occurring near a city with a population exceeding a million. Well over a thousand people were injured, thousands of buildings suffered at least superficial damage (mainly to windows), schools and sports facilities were closed, and emergency responders swarmed across the city and surrounding rural areas. While the consequences were very small compared with larger natural disasters, which kill tens of thousands of people annually worldwide, this specific case - for the first time - has permitted a calibration of the consequences of the rare impacts asteroid astronomers have been predicting. There now are reasons to expect that impacts by bodies tens of meters in diameter are several times more frequent than had been thought and each impact is more damaging than previously estimated. The Chelyabinsk event, produced by a 20 meter diameter asteroid, specifically suggests that asteroids just 15 meters diameter, or even smaller, could be very dangerous and damaging; indeed, a more common steeper impact angle would have produced more consequential damage on the ground. This contrasts with estimates a decade earlier [NASA NEO Science Definition Team report, 2003] that asteroids smaller than 40 to 50 meters diameter would explode harmlessly in the upper atmosphere. Given the observed size-frequency relation for NEOs, this means that dangerous impacts could be many tens of times more frequent than had been thought. New observing campaigns (e.g. ATLAS) oriented towards finding roughly half of the frequent smaller impactors meters to tens of meters in size during their final days to weeks before impact will soon result in warnings every few years of a potentially dangerous impact, perhaps requiring evacuation or instructions to shelter-in-place, even though most will turn out to be essentially harmless events. Warnings may become even more frequent as prudent emergency managers take into account the large uncertainties in sizes and destructive potential of these 'final plungers.' So emergency management officials around the world should at least be aware of the potential for a NEO impact to produce a real, if generally minor and local, natural disaster. Fortunately, success of the Spaceguard search for civilization-threatening large NEOs (> 1 km diameter) over the last 15 years has nearly retired the risk of global calamity by impact. So attention turns to the much smaller impacts that are far less dangerous, but soon will be frequently predicted and so cannot be ignored.

Japanese Studies of Asteroids Following the Discovery of the Hirayama Families

NASA Astrophysics Data System (ADS)

Nakamura, Tsuko

This paper reviews studies relating to asteroids conducted by Japanese astronomers since the discovery of asteroid families by Kiyotsugu Hirayama in 1918. First, the situation is mentioned that it took quite some time for the concept of an `asteroid family' to be understood correctly by the astronomical community worldwide. It is no wonder that some eminent researches on the dynamics of asteroids based on secular perturbation theories appeared in Japan after WWII, as represented by the `Kozai mechanism' (1962), which probably was influenced by Hirayama's monumental discovery. As for studies of the physical nature of asteroids, we must note the pioneering work by M. Kitamura in 1959 when the observed colors of about 40 asteroids were compared with reflectance spectra of several meteorites measured in the laboratory, even though this result unfortunately was not pursued further at the time. Modern impact experiments initiated by A. Fujiwara in 1975 soon became an important means of investigating the origin of asteroid families, and of the ubiquitous craters seen on the surfaces of airless Solar System bodies.

Asteroids and Comets Outreach Compilation

NASA Technical Reports Server (NTRS)

1999-01-01

Contents include various different animations in the area of Asteroids and Comets. Titles of the short animated clips are: STARDUST Mission; Asteroid Castallia Impact Simulation; Castallia, Toutatis and the Earth; Simulation Asteroid Encounter with Earth; Nanorover Technology Task; Near Earth Asteroid Tracking; Champollian Anchor Tests; Early Views of Comets; Exploration of Small Bodies; Ulysses Resource Material from ESA; Ulysses Cometary Plasma Tail Animation; and various discussions on the Hale-Bopp Comet. Animation of the following are seen: the Stardust aerogel collector grid collecting cometary dust particles, comet and interstellar dust analyzer, Wiper-shield and dust flux monitor, a navigation camera, and the return of the sample to Earth; a comparison of the rotation of the Earth to the Castallia and Tautatis Asteroids; an animated land on Tautatis and the view of the motion of the sky from its surface; an Asteroid collision with the Earth; the USAF Station in Hawaii; close-up views of asteroids; automatic drilling of the Moon; exploding Cosmic Particles; and the dropping off of the plasma tail of a comet as it travels near the sun.

Granular impact cratering by liquid drops: Understanding raindrop imprints through an analogy to asteroid strikes

PubMed Central

Zhao, Runchen; Zhang, Qianyun; Tjugito, Hendro; Cheng, Xiang

2015-01-01

When a granular material is impacted by a sphere, its surface deforms like a liquid yet it preserves a circular crater like a solid. Although the mechanism of granular impact cratering by solid spheres is well explored, our knowledge on granular impact cratering by liquid drops is still very limited. Here, by combining high-speed photography with high-precision laser profilometry, we investigate liquid-drop impact dynamics on granular surface and monitor the morphology of resulting impact craters. Surprisingly, we find that despite the enormous energy and length difference, granular impact cratering by liquid drops follows the same energy scaling and reproduces the same crater morphology as that of asteroid impact craters. Inspired by this similarity, we integrate the physical insight from planetary sciences, the liquid marble model from fluid mechanics, and the concept of jamming transition from granular physics into a simple theoretical framework that quantitatively describes all of the main features of liquid-drop imprints in granular media. Our study sheds light on the mechanisms governing raindrop impacts on granular surfaces and reveals a remarkable analogy between familiar phenomena of raining and catastrophic asteroid strikes. PMID:25548187

Optimised low-thrust mission to the Atira asteroids

NASA Astrophysics Data System (ADS)

Di Carlo, Marilena; Romero Martin, Juan Manuel; Ortiz Gomez, Natalia; Vasile, Massimiliano

2017-04-01

Atira asteroids are recently-discovered celestial bodies characterised by orbits lying completely inside the heliocentric orbit of the Earth. The study of these objects is difficult due to the limitations of ground-based observations: objects can only be detected when the Sun is not in the field of view of the telescope. However, many asteroids are expected to exist in the inner region of the Solar System, many of which could pose a significant threat to our planet. In this paper, a small, low-cost, mission to visit the known Atira asteroids and to discover new Near Earth Asteroids (NEA) is proposed. The mission is realised using electric propulsion. The trajectory is optimised to maximise the number of visited asteroids of the Atira group using the minimum propellant consumption. During the tour of the Atira asteroids an opportunistic NEA discovery campaign is proposed to increase our knowledge of the asteroid population. The mission ends with a transfer to an orbit with perihelion equal to Venus's orbit radius. This orbit represents a vantage point to monitor and detect asteroids in the inner part of the Solar System and provide early warning in the case of a potential impact.

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

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

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

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.

Ureilite petrogenesis: A limited role for smelting during anatexis and catastrophic disruption

NASA Astrophysics Data System (ADS)

Warren, Paul H.; Huber, Heinz

2006-06-01

A popular model for ureilites assumes that during anatexis in an asteroidal mantle, pressure-buffered equilibrium smelting (partial reduction coincident with partial melting) engendered their conspicuous mafic-silicate-core mg diversity (75-96 mol%). Several mass-balance problems arise from this hypothesis. Smelting inevitably consumes a large proportion of any plausible initial carbon while generating significant proportions of Fe metal and copious proportions of CO gas. The most serious problem concerns the yield of CO gas. If equilibrium smelting produced the ureilites' entire 21 mol% range in olivine-core mg, the proportion of gas within the asteroidal mantle (assuming plausibly low pressure <˜80 bar) should have reached ≥85 vol%. Based on the remarkably stepwise cooling history inferred from ureilite texture and mineralogy, a runaway, CO-leaky process that can loosely be termed smelting appears to have occurred, probably triggered by a major impact. The runaway scenario appears likely because, by Le Châtelier's principle, CO leakage would tend to accelerate the smelting process. Also, the copious volumes of gas produced by smelting would have led to explosive, mass-leaky eruptions into the vacuum surrounding the asteroid. Loss of mass would mean diminution of interior pressure, which would induce further smelting, leading to further loss of mass (basalt), and so on. Such a disruptive runaway process may have engendered the ureilites' distinctive reduced olivine rims. But the only smelting, according to this scenario, was a short-lived disequilibrium process that reduced only the olivine rims, not the cores; and the ureilites were cooling, not melting, during the abortive "smelting" episode.

Ejecta cloud from the AIDA space project kinetic impact on the secondary of a binary asteroid: I. mechanical environment and dynamical model

NASA Astrophysics Data System (ADS)

Yu, Yang; Michel, Patrick; Schwartz, Stephen R.; Naidu, Shantanu P.; Benner, Lance A. M.

2017-01-01

An understanding of the post-impact dynamics of ejecta clouds are crucial to the planning of a kinetic impact mission to an asteroid, and also has great implications for the history of planetary formation. The purpose of this article is to track the evolution of ejecta produced by AIDA mission, which targets for kinetic impact the secondary of near-Earth binary asteroid (65803) Didymos on 2022, and to feedback essential informations to AIDA's ongoing phase-A study. We present a detailed dynamic model for the simulation of an ejecta cloud from a binary asteroid that synthesizes all relevant forces based on a previous analysis of the mechanical environment. We apply our method to gain insight into the expected response of Didymos to the AIDA impact, including the subsequent evolution of debris and dust. The crater scaling relations from laboratory experiments are employed to approximate the distributions of ejecta mass and launching speed. The size distribution of fragments is modeled with a power law fitted from observations of real asteroid surface. A full-scale demonstration is simulated using parameters specified by the mission. We report the results of the simulation, which include the computed spread of the ejecta cloud and the recorded history of ejecta accretion and escape. The violent period of the ejecta evolution is found to be short, and is followed by a stage where the remaining ejecta is gradually cleared. Solar radiation pressure proves to be efficient in cleaning dust-size ejecta, and the simulation results after two weeks shows that large debris on polar orbits (perpendicular to the binary orbital plane) has a survival advantage over smaller ejecta and ejecta that keeps to low latitudes.

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.

The global impact distribution of Near-Earth objects

NASA Astrophysics Data System (ADS)

Rumpf, Clemens; Lewis, Hugh G.; Atkinson, Peter M.

2016-02-01

Asteroids that could collide with the Earth are listed on the publicly available Near-Earth object (NEO) hazard web sites maintained by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). The impact probability distribution of 69 potentially threatening NEOs from these lists that produce 261 dynamically distinct impact instances, or Virtual Impactors (VIs), were calculated using the Asteroid Risk Mitigation and Optimization Research (ARMOR) tool in conjunction with OrbFit. ARMOR projected the impact probability of each VI onto the surface of the Earth as a spatial probability distribution. The projection considers orbit solution accuracy and the global impact probability. The method of ARMOR is introduced and the tool is validated against two asteroid-Earth collision cases with objects 2008 TC3 and 2014 AA. In the analysis, the natural distribution of impact corridors is contrasted against the impact probability distribution to evaluate the distributions' conformity with the uniform impact distribution assumption. The distribution of impact corridors is based on the NEO population and orbital mechanics. The analysis shows that the distribution of impact corridors matches the common assumption of uniform impact distribution and the result extends the evidence base for the uniform assumption from qualitative analysis of historic impact events into the future in a quantitative way. This finding is confirmed in a parallel analysis of impact points belonging to a synthetic population of 10,006 VIs. Taking into account the impact probabilities introduced significant variation into the results and the impact probability distribution, consequently, deviates markedly from uniformity. The concept of impact probabilities is a product of the asteroid observation and orbit determination technique and, thus, represents a man-made component that is largely disconnected from natural processes. It is important to consider impact probabilities because such information represents the best estimate of where an impact might occur.

A probabilistic asteroid impact risk model: assessment of sub-300 m impacts

NASA Astrophysics Data System (ADS)

Mathias, Donovan L.; Wheeler, Lorien F.; Dotson, Jessie L.

2017-06-01

A comprehensive asteroid threat assessment requires the quantification of both the impact likelihood and resulting consequence across the range of possible events. This paper presents a probabilistic asteroid impact risk (PAIR) assessment model developed for this purpose. The model incorporates published impact frequency rates with state-of-the-art consequence assessment tools, applied within a Monte Carlo framework that generates sets of impact scenarios from uncertain input parameter distributions. Explicit treatment of atmospheric entry is included to produce energy deposition rates that account for the effects of thermal ablation and object fragmentation. These energy deposition rates are used to model the resulting ground damage, and affected populations are computed for the sampled impact locations. The results for each scenario are aggregated into a distribution of potential outcomes that reflect the range of uncertain impact parameters, population densities, and strike probabilities. As an illustration of the utility of the PAIR model, the results are used to address the question of what minimum size asteroid constitutes a threat to the population. To answer this question, complete distributions of results are combined with a hypothetical risk tolerance posture to provide the minimum size, given sets of initial assumptions for objects up to 300 m in diameter. Model outputs demonstrate how such questions can be answered and provide a means for interpreting the effect that input assumptions and uncertainty can have on final risk-based decisions. Model results can be used to prioritize investments to gain knowledge in critical areas or, conversely, to identify areas where additional data have little effect on the metrics of interest.

The Main Asteroid Belt: The Crossroads of the Solar System

NASA Astrophysics Data System (ADS)

Michel, Patrick

2015-08-01

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

Evidence for Impact Shock Melting in CM and CI Chondrite Regolith Samples

NASA Technical Reports Server (NTRS)

Zolensky, Michael; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Komatsu, Mutsumi; Le, Loan

2014-01-01

C class asteroids frequently exhibit reflectance spectra consistent with thermally metamorphosed carbonaceous chondrites, or a mixture of phyllosilicate-rich material along with regions where they are absent. One particularly important example appears to be near-Earth asteroid 1999 JU3, the target of the Hayabusa II sample return mission [1], although not all spectra indicate this. In fact most spectra of 1999 JU3 are featureless, suggesting a heterogeneous regolith. Here we explore an alternative cause of dehydration of regolith of C class asteroids - impact shock melting. Impact shock melting has been proposed to explain some mineralogical characteristics of CB chondrites, but has not been considered a major process for hydrous carbonaceous chondrites. What evidence is there for significant shock melting in the very abundant CMs, or less abundant but still important CI chondrites?

Simulation of the dusty plasma environment of 65803 Didymos for the Asteroid Impact Mission (AIM)

NASA Astrophysics Data System (ADS)

Cipriani, Fabrice; Rodgers, David; Hilgers, Alain; Hess, Sebastien; Carnelli, Ian

2016-10-01

The Asteroid Impact and Deflection Assessment mission (AIDA) is a joint European-US technology demonstrator mission including the DART asteroid impactor (NASA/JHU/APL) and the AIM asteroid rendezvous platform (ESA/DLR/OCA) set to reach Near Earth binary Object 65803 Didymos in October 2022. Besides technology demonstration in the deep space communications domain and the realization of a kinetic impact on the moonlet to study deflection parameters, this asteroid rendezvous mission is an opportunity to carry out in-situ observations of the close environment of a binary system, addressing some fundamental science questions. The MASCOT-2 lander will be released from the AIM platform and operate at the surface of the moonlet of 65803 Didymos, complemented by the ability of the Cubesat Opportunity Payloads (COPINS) to sample the close environment of the binary.In this context, we have developed an model describing the plasma and charged dust components of the near surface environment of the moonlet (170m in diameter), targeted by the MASCOT-2 lander and of the DART impactor. We performed numerical simulations in order to estimate the electrostatic surface potentials at various locations of the surface, resulting from its interaction with the solar wind plasma and solar photons. In addition, we describe charging levels, density profiles, and velocity distribution of regolith grains lifted out from the surface up to about 70m above the surface.

Scientific Objectives of Small Carry-on Impactor (SCI) and Deployable Camera 3 Digital (DCAM3-D): Observation of an Ejecta Curtain and a Crater Formed on the Surface of Ryugu by an Artificial High-Velocity Impact

NASA Astrophysics Data System (ADS)

Arakawa, M.; Wada, K.; Saiki, T.; Kadono, T.; Takagi, Y.; Shirai, K.; Okamoto, C.; Yano, H.; Hayakawa, M.; Nakazawa, S.; Hirata, N.; Kobayashi, M.; Michel, P.; Jutzi, M.; Imamura, H.; Ogawa, K.; Sakatani, N.; Iijima, Y.; Honda, R.; Ishibashi, K.; Hayakawa, H.; Sawada, H.

2017-07-01

The Small Carry-on Impactor (SCI) equipped on Hayabusa2 was developed to produce an artificial impact crater on the primitive Near-Earth Asteroid (NEA) 162173 Ryugu (Ryugu) in order to explore the asteroid subsurface material unaffected by space weathering and thermal alteration by solar radiation. An exposed fresh surface by the impactor and/or the ejecta deposit excavated from the crater will be observed by remote sensing instruments, and a subsurface fresh sample of the asteroid will be collected there. The SCI impact experiment will be observed by a Deployable CAMera 3-D (DCAM3-D) at a distance of ˜1 km from the impact point, and the time evolution of the ejecta curtain will be observed by this camera to confirm the impact point on the asteroid surface. As a result of the observation of the ejecta curtain by DCAM3-D and the crater morphology by onboard cameras, the subsurface structure and the physical properties of the constituting materials will be derived from crater scaling laws. Moreover, the SCI experiment on Ryugu gives us a precious opportunity to clarify effects of microgravity on the cratering process and to validate numerical simulations and models of the cratering process.

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.

Constraining the Bulk Density of 10m-Class Near-Earth Asteroid 2012 LA

NASA Astrophysics Data System (ADS)

Mommert, Michael; Hora, Joseph; Farnocchia, Davide; Trilling, David; Chesley, Steve; Harris, Alan; Mueller, Migo; Smith, Howard

2016-08-01

The physical properties of near-Earth asteroids (NEAs) provide important hints on their origin, as well as their past physical and orbital evolution. Recent observations seem to indicate that small asteroids are different than expected: instead of being monolithic bodies, some of them instead resemble loose conglomerates of smaller rocks, so called 'rubble piles'. This is surprising, since self-gravitation is practically absent in these bodies. Hence, bulk density measurements of small asteroids, from which their internal structure can be estimated, provide unique constraints on asteroid physical models, as well as models for asteroid evolution. We propose Spitzer Space Telescope observations of 10 m-sized NEA 2012 LA, which will allow us to constrain the diameter, albedo, bulk density, macroporosity, and mass of this object. We require 30 hrs of Spitzer time to detect our target with a minimum SNR of 3 in CH2. In order to interpret our observational results, we will use the same analysis technique that we used in our successful observations and analyses of tiny asteroids 2011 MD and 2009 BD. Our science goal, which is the derivation of the target's bulk density and its internal structure, can only be met with Spitzer. Our observations will produce only the third comprehensive physical characterization of an asteroid in the 10m size range (all of which have been carried out by our team, using Spitzer). Knowledge of the physical properties of small NEAs, some of which pose an impact threat to the Earth, is of importance for understanding their evolution and estimating the potential of destruction in case of an impact, as well as for potential manned missions to NEAs for either research or potential commercial uses.

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

ScienceCinema

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

2017-12-15

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

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

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

Muller, Rich

2006-06-30

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

Explaining the Birth of the Martian Moons

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-09-01

A new study examines the possibility that Marss two moons formed after a large body slammed into Mars, creating a disk of debris. This scenario might be the key to reconciling the moons orbital properties with their compositions.Conflicting EvidenceThe different orbital (left) and spectral (right) characteristics of the Martian moons in the three different formation scenarios. Click for a better look! Phobos and Deimoss orbital characteristics are best matched by formation around Mars (b and c), and their physical characteristics are best matched by formation in the outer region of an impact-generated accretion disk (rightmost panel of c). [Ronnet et al. 2016]How were Marss two moons, Phobos and Deimos, formed? There are three standing theories:Two already-formed, small bodies from the outer main asteroid belt were captured by Mars, intact.The bodies formed simultaneously with Mars, by accretion from the same materials.A large impact on Mars created an accretion disk of material from which the two bodies formed.Our observations of the Martian moons, unfortunately, provide conflicting evidence about which of these scenarios is correct. The physical properties of the moons low albedos, low densities are consistent with those of asteroids in our solar system, and are not consistent with Marss properties, suggesting that the co-accretion scenario is unlikely. On the other hand, the moons orbital properties low inclination, low eccentricity, prograde orbits are consistent with bodies that formed around Mars rather than being captured.In a recent study,a team of scientists led by Thomas Ronnet and Pierre Vernazza (Aix-Marseille University, Laboratory of Astrophysics of Marseille) has attempted to reconcile these conflictingobservations by focusing on the third option.Moons After a Large ImpactIn the thirdscenario, an impactor of perhaps a few percent of Marss mass smashed into Mars, forming a debris disk of hot material that encircled Mars. Perturbations in the disk then led to the formation of large clumps, which eventually agglomerated to form Phobos and Deimos.The authors find that Phobos and Deimos most likely formed in the outer regions of the accretion disk that was created by a large impact with Mars. [Adapted from Ronnet et al. 2016]In the study conducted by Ronnet, Vernazza, and collaborators, the authors investigated the composition and texture of the dust that would have crystallized in an impact-generated accretion disk making up Marss moons. They find that Phobos and Deimos could not have formed out of the extremely hot, magma-filled inner regions of such a disk, because this would have resulted in different compositions than we observe.Phobos and Deimos could have formed, however, in the very outer part of an impact-generated accretion disk, where the hot gas condensed directly into small solid grains instead of passing through the magma phase. Accretion of such tiny grains would naturally explain the similarity in physical properties we observe between Marss moons and some main-belt asteroids and yet this picture is also consistent with the moons current orbital parameters.The authors argue that the formation of the Martian moons from the outer regions of an impact-generated accretion disk is therefore a plausible scenario, neatly reconciling the observed physical properties of Phobos and Diemos with their orbital properties.CitationT. Ronnet et al 2016 ApJ 828 109. doi:10.3847/0004-637X/828/2/109

Trajectory-capture cell instrumentation for measurement of dust particle mass, velocity and trajectory, and particle capture

NASA Technical Reports Server (NTRS)

Simpson, J. A.; Tuzzolino, A. J.

1989-01-01

The development of the polyvinylidene fluoride (PVDF) dust detector for space missions--such as the Halley Comet Missions where the impact velocity was very high as well as for missions where the impact velocity is low was extended to include: (1) the capability for impact position determination - i.e., x,y coordinate of impact; and (2) the capability for particle velocity determination using two thin PVDF sensors spaced a given distance apart - i.e., by time-of-flight. These developments have led to space flight instrumentation for recovery-type missions, which will measure the masses (sizes), fluxes and trajectories of incoming dust particles and will capture the dust material in a form suitable for later Earth-based laboratory measurements. These laboratory measurements would determine the elemental, isotopic and mineralogical properties of the captured dust and relate these to possible sources of the dust material (i.e., comets, asteroids), using the trajectory information. The instrumentation described here has the unique advantages of providing both orbital characteristics and physical and chemical properties--as well as possible origin--of incoming dust.

Using Information from Rendezvous Missions For Best-Case Appraisals of Impact Damage to Planet Earth Caused By Natural Objects

NASA Technical Reports Server (NTRS)

Arnold, J. O.; Chodas, P. W.; Ulamec, S.; Mathias, D. L.; Burkhard, C. D.

2017-01-01

The Asteroid Threat Assessment Project (ATAP), a part of NASAs Planetary Defense Coordination Office (PDCO) has the responsibility to appraise the range of surface damage by potential asteroid impacts on land or water. If a threat is realized, the project will provide appraisals to officials empowered to make decisions on potential mitigation actions. This paper describes a scenario for assessment of surface damage when characterization of an asteroid had been accomplished by a rendezvous mission that would be conducted by the international planetary defense community. It is shown that the combination of data from ground and in-situ measurements on an asteroid provides knowledge that can be used to pin-point its impact location and predict the level of devastation it would cause. The hypothetical asteroid 2017 PDC with a size of 160 to 290 m in diameter to be discussed at the PDC 2017 meeting is used as an example. In order of importance for appraising potential damage, information required is: (1) where will the surface impact occur? (2) What is the mass, shape and size of the asteroid and what is its entry state (speed and entry angle) at the 100 km atmospheric pierce point? And (3) is the asteroid a monolith or a rubble pile? If it is a rubble pile, what is its sub and interior structure? Item (1) is of first order importance to determine levels of devastation (loss of life and infrastructure damage) because it varies strongly on the impact location. Items (2) and (3) are used as input for ATAPs simulations to define the level of surface hazards: winds, overpressure, thermal exposure; all created by the deposition of energy during the objects atmospheric flight, andor cratering. Topics presented in this paper include: (i) The devastation predicted by 2017 PDCs impact based on initial observations using ATAPs risk assessment capability, (ii) How information corresponding to items (1) to (3) could be obtained from a rendezvous mission, and (iii) How information from a rendezvous mission could be used, along with that from ground observations and data from the literature, could provide input for an new risk analysis capability that is emerging from ATAPs research. It is concluded that this approach would result in appraisal with the least uncertainty possible (herein called the best-case) using simulation capabilities that are currently available or will be in the future.

Using Information from Rendezvous Missions For Best-Case Appraisals of Impact Damage to Planet Earth Caused By Natural Objects

NASA Technical Reports Server (NTRS)

Arnold, James O.; Chodas, Paul W.; Ulamec, Stephan; Mathias, Donovan L.; Burkhard, Craig D.

2017-01-01

The Asteroid Threat Assessment Project (ATAP), a part of NASAs Planetary Defense Coordination Office (PDCO) has the responsibility to appraise the range of surface damage by potential asteroid impacts on land or water. If a threat is realized, the project will provide appraisals to officials empowered to make decisions on potential mitigation actions. This paper describes a scenario for assessment of surface damage when characterization of an asteroid had been accomplished by a rendezvous mission that would be conducted by the international planetary defense community. It is shown that the combination of data from ground and in-situ measurements on an asteroid provides knowledge that can be used to pin-point its impact location and predict the level of devastation it would cause. The hypothetical asteroid 2017 PDC with a size of 160 to 290 m in diameter to be discussed at the PDC 2017 meeting is used as an example. In order of importance for appraising potential damage, information required is: (1) where will the surface impact occur? (2) What is the mass, shape and size of the asteroid and what is its entry state (speed and entry angle) at the 100 km atmospheric pierce point? And (3) is the asteroid a monolith or a rubble pile? If it is a rubble pile, what is its sub and interior structure? Item (1) is of first order importance to determine levels of devastation (loss of life and infrastructure damage) because it varies strongly on the impact location. Items (2) and (3) are used as input for ATAPs simulations to define the level of surface hazards: winds, overpressure, thermal exposure; all created by the deposition of energy during the objects atmospheric flight, and/or cratering. Topics presented in this paper include: (i) The devastation predicted by 2017 PDCs impact based on initial observations using ATAPs risk assessment capability, (ii) How information corresponding to items (1) to (3) could be obtained from a rendezvous mission, and (iii) How information from a rendezvous mission could be used, along with that from ground observations and data from the literature, could provide input for an new risk analysis capability that is emerging from ATAPs research. It is concluded that this approach would result in appraisal with the least uncertainty possible (herein called the best-case) using simulation capabilities that are currently available or will be in the future.

Using Information from Rendezvous Missions for Best-Case Appraisals of Impact Damage to Planet Earth Caused by Natural Objects

NASA Technical Reports Server (NTRS)

Arnold, James O.; Chodas, Paul W.; Ulamec, Stephan; Mathias, Donovan L.; Burkhard, Craig D.

2017-01-01

The Asteroid Threat Assessment Project (ATAP), a part of NASAs Planetary Defense Coordination Office (PDCO) has the responsibility to appraise the range of surface damage by potential asteroid impacts on land or water. If a threat is realized, the project will provide appraisals to officials empowered to make decisions about potential mitigation actions. This paper describes a scenario for assessment of surface damage when characterization of an asteroid had been accomplished by a rendezvous mission that would be conducted by the international planetary defense community. It is shown that the combination of data from ground and in-situ measurements on an asteroid provides knowledge that can be used to pin-point its impact location and predict the level of devastation it would cause. The hypothetical asteroid 2017 PDC with a size range of 160 to 290 m in diameter to be discussed at the PDC 2017 is used as an example. In order of importance for appraising potential damage, information required is: (1) where will the surface impact occur? (2) what is the mass, shape and size of the asteroid and what is its entry state (speed and entry angle) at the 100 km atmospheric pierce point? And (3) is the asteroid a monolith or a rubble pile? If it is a rubble pile, what is its structure and heterogeneity from the surface and throughout its interior? Item (1) is of first order importance to determine levels of devastation (loss of life and infrastructure damage) because it varies strongly on the impact location. Items (2) and (3) are used as inputs for ATAPs simulations to define the level of surface hazards: winds, overpressure, thermal exposure; all created by the deposition of energy during the objects atmospheric flight, andor cratering. Topics presented in this paper include: (i) the devastation predicted by 2017 PDCs impact on land based on initial observations using ATAPs risk assessment capability, (ii) how information corresponding to items (1) to (3) could be obtained from a rendezvous mission, and (iii) how information from a rendezvous mission could be used, along with that from ground observations and data from the literature to provide input for a new risk analysis capability that is emerging from ATAPs research. It is concluded that this approach would result in the creation of an appraisal of the threat from 2017 PDC with the least uncertainty possible, herein called the best-case.

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.

Understanding the Effects of Collisional Evolution and Spacecraft Impact Experiments on Comets and Asteroids

NASA Technical Reports Server (NTRS)

Lederer, S.M.; Jensen, E.A.; Fane, M.; Smith, D.C.; Holmes, J.; Keller, L.P.; Lindsay, S.S.; Wooden, D.H.; Whizin, A.; Cintala, M.J.;

Waves generated by Asteroid impacts and their effects on US shorelines

NASA Astrophysics Data System (ADS)

Ezzedine, S. M.; Miller, P. L.; Dearborn, D. S.; Dennison, D. S.; Glascoe, L. G.; Antoun, T.

2013-12-01

On February 15, 2013 an undetected ~17-20-m diameter asteroid entered earth's atmosphere and, due to its large entry speed of 18.6 km/s and its shallow entry angle, the asteroid exploded in an airburst over Chelyabinsk, Russia, generating a bright flash, producing many small fragment meteorites and causing a powerful shock wave which released the equivalent of ~440 kt TNT of energy. About 16 hours after the Chelyabinsk asteroid, the elongated ~20m by ~40m (~30 m diameter) NEA 2012 DA14 with an estimated mass of 40 kt neared the earth surface at ~28,100km, ~2.2 earth's diameter. These two consecutive events, which were unrelated and had drastically different orbits, generated considerable attention and awareness from the public, confusion among the local residents, and raised the issue of emergency response and preparedness of local, state and government agencies. LLNL and other government agencies have performed numerical simulations of a postulated asteroid impact onto the ocean and generated data to support an emergency preparedness exercise. We illustrate the exercise through the application of several codes from source (asteroid entry) to ocean impact (splash rim) to wave generation, propagation and interaction with the shoreline. Using state-of-the-art high performance computing codes we simulate three impact sites; one site is located off the eat coat by Maryland's shoreline and two other sites on the west coast: the San Francisco bay and the Los Angeles bay shorelines, respectively. Simulations were conducted not only under deterministic conditions but also under conditions of uncertainty. Uncertainty assessment of flood hazards zones and structural integrity of infrastructures will be presented. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and partially funded by the Laboratory Directed Research and Development Program at LLNL under tracking code 12-ERD-005.

Constraints on the perturbed mutual motion in Didymos due to impact-induced deformation of its primary after the DART impact

NASA Astrophysics Data System (ADS)

Hirabayashi, Masatoshi; Schwartz, Stephen R.; Yu, Yang; Davis, Alex B.; Chesley, Steven R.; Fahnestock, Eugene G.; Michel, Patrick; Richardson, Derek C.; Naidu, Shantanu P.; Scheeres, Daniel J.; Cheng, Andrew F.; Rivkin, Andrew S.; Benner, Lance A. M.

2017-12-01

Binary near-Earth asteroid (65803) Didymos is the target of the proposed NASA Double Asteroid Redirection Test (DART), part of the Asteroid Impact & Deflection Assessment (AIDA) mission concept. In this mission, the DART spacecraft is planned to impact the secondary body of Didymos, perturbing mutual dynamics of the system. The primary body is currently rotating at a spin period close to the spin barrier of asteroids, and materials ejected from the secondary due to the DART impact are likely to reach the primary. These conditions may cause the primary to reshape, due to landslides or internal deformation, changing the permanent gravity field. Here, we propose that if shape deformation of the primary occurs, the mutual orbit of the system would be perturbed due to a change in the gravity field. We use a numerical simulation technique based on the full two-body problem to investigate the shape effect on the mutual dynamics in Didymos after the DART impact. The results show that under constant volume, shape deformation induces strong perturbation in the mutual motion. We find that the deformation process always causes the orbital period of the system to become shorter. If surface layers with a thickness greater than ∼0.4 m on the poles of the primary move down to the equatorial region due to the DART impact, a change in the orbital period of the system and in the spin period of the primary will be detected by ground-based measurement.

Collisional fragmentation of asteroids and its implication on the physical properties of Near-Earth Objects

NASA Astrophysics Data System (ADS)

Michel, P.

Collisions are at the origin of catastrophic disruptions in the asteroid Main Belt. This is witnessed by the observation of asteroid families, each composed of asteroids which originated from a single parent body, broken-up by a collision with another asteroid. Understanding the collisional process and its outcome properties is not only necessary in order to study the collisional evolution of small body population or the planetary formation, it is also strongly required in the context of mitigation strategies aimed at deviating a threatening asteroid. In the last three years, for the first time we have successfully performed numerical simulations of high speed collisions between small bodies which account for the production of gravitationally reaccumulated bodies. More precisely, we have developped a procedure which divides the process into two phases. Using a 3D SPH hydrocode, the fragmentation of the solid target through crack propagation is first computed. Then the simulation of the gravitational evolution and possible piecewise reaccumulation of the parent body is performed using the parallel N-body code pkdgrav. Our first simulations using monolithic parent bodies have succeeded in reproducing fundamental properties of some well-identified asteroid families, showing that gravitational re-accumulations following disruptive collisions are the key process accounting for the existence of asteroid families. Then, we have investigated the effect of the internal structure of the parent body on the outcome properties. We have thus shown that family parent bodies are likely to have already been pre-shattered by small impacts before being disrupted by a major event. We then suggested that the most likely internal structure of large asteroids in the main belt is not monolithic but rather composed of macroscopic fractures and voids. We will make a review of these simulations in three different impact regimes, from highly catastrophic to barely disruptive. In particular we will show the sensitivity of the resulting family characteristics upon the internal structure of the parent body. According to our current understanding, most NEOs are certainly fragments of larger asteroids of the Main Belt, injected either directly or by diffusion into main resonances that transported them to Earth-crossing orbits. According to our simulations, most NEOs with diameter larger than several hundreds of meters should then correspond to gravitational aggregates. Given the crucial role of the internal structure on the impact outcome, this has important implications in the development of efficient mitigation strategies.

Secular evolution of asteroid families: the role of Ceres

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Tsirvoulis, Georgios; Marò, Stefano; Đošović, Vladimir; Maurel, Clara

2016-01-01

We consider the role of the dwarf planet Ceres on the secular dynamics of the asteroid main belt. Specifically, we examine the post impact evolution of asteroid families due to the interaction of their members with the linear nodal secular resonance with Ceres. First, we find the location of this resonance and identify which asteroid families are crossed by its path. Next, we summarize our results for three asteroid families, namely (1726) Hoffmeister, (1128) Astrid and (1521) Seinajoki which have irregular distributions of their members in the proper elements space, indicative of the effect of the resonance. We confirm this by performing a set of numerical simulations, showcasing that the perturbing action of Ceres through its linear nodal secular resonance is essential to reproduce the actual shape of the families.

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.

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.

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.

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.

Survey and Risk Assessment of Near Earth Asteroids

NASA Astrophysics Data System (ADS)

Zhao, H. B.

2010-07-01

In 1994, 21 fragments of comet Shoemaker-Levy 9 impacted Jupiter with a velocity of about 60 km/s, which is the first grand collision between celestial bodies observed by human beings. The impact makes us informed definitely that the earth is faced with the small but serious threat of Near Earth Objects (NEOs). Chinese scientists of Purple Mountain Observatory proposed a plan of Chinese Near Earth Object Survey (CNEOS) in the conference on NEOs held in the building of the World Headquarters of United Nations, New York in 1995. This project started in 1998. During the past 7 years, CNEOS proceeded in selecting observational site, manufacturing telescope and CCD detector, carrying out observation, reducing mass data, and assessing impact risk from NEOs. Will those so-called potential hazardous asteroids be the terminator of mankind? In 2007, NASA proposed the Spaceguard goal to detect, track, catalogue and characterize 90% of the potentially hazardous objects with diameters greater than 140 m. This dissertation reviews the current situation of research on asteroids and NEOs, which will greatly enhance our understanding of the planetary sciences. The project of CNEOS, including selecting observational site, manufacturing telescope and CCD detector, had been put in practice since 1998. The telescope of CNEOS is a 1.04/1.20/1.80 m Schmidt telescope, equipped with a 4096 by 4096 CCD detector which has drift-scanning function. In this dissertation, the advantage and disadvantage of drift-scanning and corresponding observational method are discussed. This dissertation discusses residential district of asteroids and distribution of visual magnitudes of asteroids. As a result, we draw three principles of observational plan. This dissertation also develops algorithms of pretreatment of astronomical image, extracting objects, and cross-identification, then discusses the methods of identifying and classifying of move objects, establishes software to realize the reduction of the mass data. Until November 2007, CNEOS had found 332 new asteroids including an Apollo type NEO and a Jupiter-family periodic comet. The observation quantity of CNEOS ranked the eighth among all 378 asteroid observation plans, and the accuracy of positional reduction was also quite well. The dissertation carries out the research of dynamics of asteroids. A software on orbit determination, differential correction, dynamical evolution and asteroid ephemeris is reconstructed. This dissertation reviews the history of impact prediction theory, and covers the linear techniques for analyzing encounters, consisting of precise orbit determination and propagation followed by target plane analysis. The impact probabilities and risks between three NEOs and the earth in 200 years are calculated. In this dissertation, a set of numerical algorithms are built to discuss the observational prediction of Northern Taurids under the effect of the lunar gravitational assembling in 2011. In addition, the earth satellite measurement, the lunar orbiter measurement and lunar laser ranging measurement are used to constrain the intermediate-range gravity from λ = 1.2×107 ˜ 3.8 × 108 m.

Assessing the Age of an Asteroid's Surface with Data from the International Rosetta Mission

NASA Technical Reports Server (NTRS)

Lopez, Juan Carlos

2011-01-01

Rosetta is an international mission led by the European Space Agency (ESA) with key support and instrumentation from the National Aeronautics and Space Administration (NASA). Rosetta is currently on a ten-year mission to catch comet 67P/Churyumov-Gerasimenko (C-G); throughout its voyage, the spacecraft has performed flybys of two main belt asteroids (MBA): Steins and Lutetia. Data on the physical, chemical, and geological properties of these asteroids are currently being processed and analyzed. Accurate interpretation of such data is fundamental in the success of Rosetta's mission and overall objectives. Post-flyby data analyses strive to correlate the size, shape, volume, and rotational rate of Lutetia, in addition to interpreting its multi-color imagining, albedo, and spectral mapping. Although advancements in science have contributed to the examination of celestial bodies, methods to analyze asteroids remain largely empirical, not semi-empirical, nor ab initio. This study aims to interpret and document the scientific methods currently utilized in the characterization of asteroid (21) Lutetia in order to render these processes and methods accessible to the public. Examples include a standardized technique for assessing the age of an asteroid surface, complete with clickable reference maps, methodology of grouping surface characteristics together, and a standardized power law equation for the age. Other examples include determining the density of an object. Context for what both density and age mean is a bi-product of this study. Results of the study will aid in the development of pedagogical material on asteroids for public use, and in creation of an academic database for selected targets that might be used as a reference.

The impact rate on Earth.

PubMed

Bland, Philip A

2005-12-15

Recent data, and modelling of the interaction between asteroids and the atmosphere, has defined a complete size-frequency distribution for terrestrial impactors, from meteorite-sized objects up to kilometre-sized asteroids, for both the upper atmosphere and the Earth's surface. Although there remain significant uncertainties in the incidence of specific size-fractions of impactors, these estimates allow us to constrain the threat posed by impacts to human populations. It is clear that impacts remain a significant natural hazard, but uniquely, they are a threat that we can accurately predict, and take steps to avoid.

A Unified Model for Repeating and Non-repeating Fast Radio Bursts

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

Bagchi, Manjari, E-mail: manjari@imsc.res.in

The model that fast radio bursts (FRBs) are caused by plunges of asteroids onto neutron stars can explain both repeating and non-repeating bursts. If a neutron star passes through an asteroid belt around another star, there would be a series of bursts caused by a series of asteroid impacts. Moreover, the neutron star would cross the same belt repetitively if it were in a binary with the star hosting the asteroid belt, leading to a repeated series of bursts. I explore the properties of neutron star binaries that could lead to the only known repeating FRB so far (FRB121102). Inmore » this model, the next two epochs of bursts are expected around 2017 February 27 and 2017 December 18. On the other hand, if the asteroid belt is located around the neutron star itself, then a chance fall of an asteroid from that belt onto the neutron star would lead to a non-repeating burst. Even a neutron star grazing an asteroid belt can lead to a non-repeating burst caused by just one asteroid plunge during the grazing. This is possible even when the neutron star is in a binary with the asteroid-hosting star, if the belt and the neutron star orbit are non-coplanar.« less

Impact-generated Tsunamis: An Over-rated Hazard

NASA Technical Reports Server (NTRS)

Melosh, H. J.

2003-01-01

A number of authors have suggested that oceanic waves (tsunami) created by the impact of relatively small asteroids into the Earth's oceans might cause widespread devastation to coastal cities. If correct, this suggests that asteroids > 100 m in diameter may pose a serious hazard to humanity and could require a substantial expansion of the current efforts to identify earth-crossing asteroids > 1 km in diameter. The debate on this hazard was recently altered by the release of a document previously inaccessible to the scientific community. In 1968 the US Office of Naval Research commissioned a summary of several decades of research into the hazard proposed by waves generated by nuclear explosions in the ocean. Authored by tsunami expert William Van Dorn, this 173-page report entitled Handbook of Explosion-Generated Water Waves affords new insight into the process of impact wave formation, propagation, and run up onto the shoreline.

Amor: Investigating The Triple Asteroid System 2001 SN263

NASA Astrophysics Data System (ADS)

Jones, T.; Bellerose, Julie; Lee, P.; Prettyman, T.; Lawrence, D.; Smith, P.; Gaffey, M.; Nolan, M.; Goldsten, J.; Thomas, P.; Veverka, J.; Farquhar, R.; Heldmann, J.; Reddy, V.; Williams, B.; Chartres, J.; DeRosee, R.; Dunham, D.

2010-10-01

The Amor mission will rendezvous and land at the triple Near-Earth Asteroid system (153591) 2001 SN263 and execute detailed, in-situ science investigations. The spacecraft reaches 2001 SN263 by using a two-year ΔVEGA (ΔV-Earth Gravity Assist) trajectory with a relatively low launch C3 of 33.5 km2/s2. Rendezvous will enable reconnaissance activities including global and regional imaging, shape modeling, system dynamics, and compositional mapping. After landing, Amor will conduct in-situ imaging (panoramic to microscopic scale) and compositional measurements to include elemental abundance. The main objectives are to 1) establish in-situ the long-hypothesized link between C-type asteroids and the primitive carbonaceous chondrite (CC) meteorites, 2) investigate the nature, origin and evolution of C-type asteroids, and 3) investigate the origin and evolution of a multiple asteroid system. The mission also addresses the distribution of volatiles and organic materials, impact hazards, and resources for future exploration. Amor is managed by NASA Ames Research Center in partnership with Orbital Sciences, KinetX, MDA, and Draper with heritage instruments provided by Ball Aerospace, JHU/APL, and Firestar Engineering. The science team brings experience from NEAR, Hayabusa, Deep Impact, Dawn, LCROSS, Kepler, and Mars missions. In this paper, we describe the science, mission design, and main operational challenges of performing in-situ science at this triple asteroid system. Challenges include landing on the asteroid components, thermal environment, short day-night cycles, and the operation of deployed instruments in a low gravity (10^-5 g) environment.

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.

Resurfacing asteroids from YORP spin-up and failure

NASA Astrophysics Data System (ADS)

Graves, Kevin J.; Minton, David A.; Hirabayashi, Masatoshi; DeMeo, Francesca E.; Carry, Benoit

2018-04-01

The spectral properties of S and Q-type asteroids can change over time due to interaction with the solar wind and micrometeorite impacts in a process known as 'space weathering.' Space weathering raises the spectral slope and decreases the 1 μm absorption band depth in the spectra of S and Q-type asteroids. Over time, Q-type asteroids, which have very similar spectra to ordinary chondrite meteorites, will change into S-type asteroids. Because there are a significant number of Q-type asteroids, there must be some process which is resurfacing S-type asteroids into Q-types. In this study, we use asteroid data from the Sloan Digital Sky Survey to show a trend between the slope through the g‧, r‧, and i‧ filters, called the gri-slope, and size that holds for all populations of S and Q-type asteroids in the inner solar system, regardless of orbit. We model the evolution of a suite of asteroids in a Monte Carlo YORP rotational evolution and space weathering model. We show that spin-up and failure from YORP is one of the key resurfacing mechanisms that creates the observed weathering trends with size. By varying the non-dimensional YORP coefficient and running time of the present model over the range 475-1425 Myr, we find a range of values for the space weathering timescale, τSW ≈ 19-80 Myr at 2.2 AU. We also estimate the time to weather a newly resurfaced Q-type asteroid into an S-complex asteroid at 1 AU, τQ → S(1AU) ≈ 2-7 Myr.

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.

Impact as a general cause of extinction: A feasibility test

NASA Technical Reports Server (NTRS)

Raup, David M.

1988-01-01

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

Secular resonances with massive asteroids and their impact on the dynamics of small bodies

NASA Astrophysics Data System (ADS)

Tsirvoulis, Georgios; Novaković, Bojan; Djošović, Valdimir

2015-08-01

The quest for understanding the dynamical structure of the main belt has been a long-lasting endeavor. From the discovery of the Kirkwood gaps and the Hirayama families, to the more recent advances in secular perturbation theory, the refinement of the proper elements and the discovery of the three-body mean-motion resonances, only to name a few, the progress has been immense. Dynamical models coupled with the outbursts in computational power and observations have greatly improved our knowledge of the dynamical evolution of the small bodies in the Solar System.While our set of tools for studying the dynamical porperties of the main belt is believed to be sufficiently complete, our assumptions on how to use them seem to have hindered this effort.The concensus has been that, judging by their mass, only the planets, especially the giant ones, can act as efficient perturbers of the orbits of asteroids. Thus a lot of studies have been made on the locations and effects of secular resonances with the giant planets in different parts of the main belt, explaining among other things the presence of gaps in the distribution of asteroids, strange shapes of some asteroid families and transport mechanisms of asteroids to the near-Earth region.Our work is motivated by the first discovery that a secular resonance with the most massive asteroid, Ceres, is the dominant dynamical mechanism responsible for the post-impact evolution of the Hoffmeister family members. Thus the concensus is wrong. Knowing now, that secular resonances with massive asteroids can be effective on asteroid dynamics, we set out to construct a dynamical map of these resonances across the main belt.Our study is focused on the linear and degree four non-linear secular resonances with the two most massive asteroids (1) Ceres and (4) Vesta. First we determine the locations of these secular resonances in the proper elements space, acquiring an understanding of the potentially affected regions, and then we perform numerical simulations to investigate the importance of each secular resonance on the dynamical evolution of asteroid orbits in the different parts of the main belt.

Surface Exposure Ages of Space-Weathered Grains from Asteroid 25143 Itokawa

NASA Technical Reports Server (NTRS)

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

2015-01-01

Space weathering processes such as solar wind ion irradiation and micrometeorite impacts are widely known to alter the properties of regolith materials exposed on airless bodies. The rates of space weathering processes however, are poorly constrained for asteroid regoliths, with recent estimates ranging over many orders of magnitude. The return of surface samples by JAXA's Hayabusa mission to asteroid 25143 Itokawa, and their laboratory analysis provides "ground truth" to anchor the timescales for space weathering processes on airless bodies.

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

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.

2014-01-01

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

Deployable Camera (DCAM3) System for Observation of Hayabusa2 Impact Experiment

NASA Astrophysics Data System (ADS)

Sawada, Hirotaka; Ogawa, Kazunori; Shirai, Kei; Kimura, Shinichi; Hiromori, Yuichi; Mimasu, Yuya

2017-07-01

An asteroid exploration probe "Hayabusa2", that was developed by Japan Aerospace Exploration Agency (JAXA), was launched on December 3rd, 2014 to challenge complicated and accurate operations during the mission phase around the C-type asteroid 162137 Ryugu (1999 JU3) (Tsuda et al. in Acta Astron. 91:356-362, 2013). An impact experiment on a surface of the asteroid will be conducted using the Small Carry-on Impactor (SCI) system, which will be the world's first artificial crater creation experiment on asteroids (Saiki et al. in Proc. International Astronautical Congress, IAC-12.A3.4.8, 2012, Acta Astron. 84:227-236, 2013a; Proc. International Symposium on Space Technology and Science, 2013b). We developed a new micro Deployable CAMera (DCAM3) system for remote observations of the impact phenomenon applying our conventional DCAM technology that is one of the smallest probes in space missions and gained a great success in past Japanese mission IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). DCAM3 is a miniaturized separable unit that contains two cameras and radio communication devices for transmission image data to the mothership "Hayabusa2", and it observes the impact experiment at an unsafe region in where the "Hayabusa2" is difficult to stay because of a risk of exploding and impacting debris hitting. In this paper, we report details of the DCAM3 system and development results as well as our mission plan for the DCAM3 observation during the SCI experiment.

Secular resonances with Ceres and Vesta

NASA Astrophysics Data System (ADS)

Tsirvoulis, Georgios; Novaković, Bojan

2016-12-01

In this work we explore dynamical perturbations induced by the massive asteroids Ceres and Vesta on main-belt asteroids through secular resonances. First we determine the location of the linear secular resonances with Ceres and Vesta in the main belt, using a purely numerical technique. Then we use a set of numerical simulations of fictitious asteroids to investigate the importance of these secular resonances in the orbital evolution of main-belt asteroids. We found, evaluating the magnitude of the perturbations in the proper elements of the test particles, that in some cases the strength of these secular resonances is comparable to that of known non-linear secular resonances with the giant planets. Finally we explore the asteroid families that are crossed by the secular resonances we studied, and identified several cases where the latter seem to play an important role in their post-impact evolution.

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

NASA Technical Reports Server (NTRS)

Taylor, Jeffrey G.

1989-01-01

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

Working Group Reports and Presentations: Asteroids

NASA Technical Reports Server (NTRS)

Lewis, John

2006-01-01

The study and utilization of asteroids will be an economical way to enable exploration of the solar system and extend human presence in space. There are thousands of near-earth objects (NEOs) that we will be able to reach. They offer resources, transportation, and exploration platforms, but also present a potential threat to civilization. Asteroids play a catastrophic role in the history of the Earth. Geological records indicate a regular history of massive impacts, which astronomical observations confirm is likely to continue with potentially devastating consequences. However, study and exploration of near earth asteroids can significantly increase advanced warning of an Earth impact, and potentially lead to the technology necessary to avert such a collision. Efforts to detect and prevent cataclysmic events would tend to foster and likely require international cooperation toward a unified goal of self-preservation. Exploration of asteroids will help us to understand our history and perhaps save our future. Besides the obvious and compelling scientific and security drivers for asteroid research and exploration, there are numerous engineering and industrial applications for near-term asteroid exploration. We have strong evidence that some asteroids are metal rich. Some are water and organic rich. They can be reached with a very low fuel cost compared to other solar system destinations. Once we reach them, there are efficient, simple extraction technologies available that would facilitate utilization. In addition, the costs of returning extracted resources from asteroids will be a fraction of the cost to return similar resources from the moon to Low Earth Orbit (LEO). These raw materials, extracted and shipped at relatively low cost, can be used to manufacture structures, fuel, and products which could be used to foster mankind s further exploration of the solar system. Asteroids also have the potential to offer transport to several destinations in the solar system. In addition to Mars and the Asteroid belt, it is possible to nudge the orbits of NEOs to provide convenient transport to other destinations. Resources to support life on these long voyages may be gathered from the host asteroid itself. As asteroids travel over a wide range of inclinations and ranges, they offer possible platforms to perform scientific investigations. These include unique vantage point observations of the sun and planets. These observations can help us to understand solar activity and space weather. They also afford us an opportunity to see how the earth looks from afar with different perspectives. When we look for planets outside of our solar system, these observations will help us to calibrate our data. Asteroids may also be used as platforms to support very long baseline interferometry with unprecedented angular resolutions.

BILLIARDS: A Demonstration Mission for Hundred-Meter Class Near-Earth Asteroid Disruption

NASA Technical Reports Server (NTRS)

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

2015-01-01

Collisions from near-Earth asteroids (NEAs) have the potential to cause widespread harm to life on Earth. The hypervelocity nature of these collisions means that a relatively small asteroid (about a quartermile in diameter) could cause a global disaster. Proposed strategies for deflecting or disrupting such a threatening asteroid include detonation of a nuclear explosive device (NED) in close proximity to the asteroid, as well as intercepting the asteroid with a hypervelocity kinetic impactor. NEDs allow for the delivery of large amounts of energy to a NEA for a given mass launched from the Earth, but have not yet been developed or tested for use in deep space. They also present safety and political complications, and therefore may only be used when absolutely necessary. Kinetic impactors require a relatively simple spacecraft compared to NEDs, but also deliver a much lower energy for a given launch mass. To date, no demonstration mission has been conducted for either case, and such a demonstration mission must be conducted prior to the need to utilize them during an actual scenario to ensure that an established, proven system is available for planetary defense when the need arises. One method that has been proposed to deliver a kinetic impactor with impact energy approaching that of an NED is the "billiard-ball" approach. This approach would involve capturing an asteroid approximately ten meters in diameter with a relatively small spacecraft (compared to the launch mass of an equivalent direct kinetic impactor), and redirecting it into the path of an Earth-threatening asteroid. This would cause an impact which would disrupt the Earth-threatening asteroid or deflect it from its Earth-crossing trajectory. The BILLIARDS Project seeks to perform a demonstration of this mission concept in order to establish a protocol that can be used in the event of an impending Earth/asteroid collision. In order to accomplish this objective, the mission must (1) rendezvous with a small (less than 10m), NEA (hereinafter "Alpha"), (2) maneuver Alpha to a collision with a approx. 100 m NEA (hereinafter "Beta"), and (3) produce a detectable deflection or disruption of Beta. In addition to these primary objectives, the BILLIARDS project will contribute to the scientific understanding of the physical properties and collision dynamics of asteroids, and provide opportunities for international collaboration.

Impact-induced seismic activity on asteroid 433 Eros: a surface modification process.

PubMed

Richardson, James E; Melosh, H Jay; Greenberg, Richard

2004-11-26

High-resolution images of the surface of asteroid 433 Eros revealed evidence of downslope movement of a loose regolith layer, as well as the degradation and erasure of small impact craters (less than approximately 100 meters in diameter). One hypothesis to explain these observations is seismic reverberation after impact events. We used a combination of seismic and geomorphic modeling to analyze the response of regolith-covered topography, particularly craters, to impact-induced seismic shaking. Applying these results to a stochastic cratering model for the surface of Eros produced good agreement with the observed size-frequency distribution of craters, including the paucity of small craters.

Implantation of Martian Materials in the Inner Solar System by a Mega Impact on Mars

NASA Astrophysics Data System (ADS)

Hyodo, Ryuki; Genda, Hidenori

2018-04-01

Observations and meteorites indicate that the Martian materials are enigmatically distributed within the inner solar system. A mega impact on Mars creating a Martian hemispheric dichotomy and the Martian moons can potentially eject Martian materials. A recent work has shown that the mega-impact-induced debris is potentially captured as the Martian Trojans and implanted in the asteroid belt. However, the amount, distribution, and composition of the debris has not been studied. Here, using hydrodynamic simulations, we report that a large amount of debris (∼1% of Mars’ mass), including Martian crust/mantle and the impactor’s materials (∼20:80), are ejected by a dichotomy-forming impact, and distributed between ∼0.5–3.0 au. Our result indicates that unmelted Martian mantle debris (∼0.02% of Mars’ mass) can be the source of Martian Trojans, olivine-rich asteroids in the Hungarian region and the main asteroid belt, and some even hit the early Earth. The evidence of a mega impact on Mars would be recorded as a spike of 40Ar–39Ar ages in meteorites. A mega impact can naturally implant Martian mantle materials within the inner solar system.

Asteroid Composite Tape

NASA Astrophysics Data System (ADS)

1998-07-01

This is a composite tape showing 10 short segments primarily about asteroids. The segments have short introductory slides, which include brief descriptions about the shots. The segments are: (1) Radar movie of asteroid 1620 Geographos; (2) Animation of the trajectories of Toutatis and Earth (3) Animation of a landing on Toutatis; (4) Simulated encounter of an asteroid with Earth, includes a simulated impact trajectory; (5) An animated overview of the Manrover vehicle; (6) The Near Earth Asteroid Tracking project, includes a photograph of USAF Station in Hawaii, and animation of Earth approaching 4179 Toutatis and the asteroid Gaspara; (7) live video of the anchor tests of the Champoleon anchoring apparatus; (8) a second live video of the Champoleon anchor tests showing anchoring spikes, and collision rings; (9) An animated segment with narration about the Stardust mission with sound, which describes the mission to fly close to a comet, and capture cometary material for return to Earth; (10) live video of the drop test of a Stardust replica from a hot air balloon; this includes sound but is not narrated.

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

PubMed

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

2009-03-26

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

Composition of Impact Melt Debris from the Eltanin Impact Strewn Field, Bellingshausen Sea

NASA Technical Reports Server (NTRS)

Kyte, Frank T.

2002-01-01

The impact of the km-sized Eltanin asteroid into the Bellingshausen Sea produced mm- to cm-sized vesicular impact melt-rock particles found in sediment cores across a large area of the ocean floor. These particles are composed mainly of olivine and glass with minor chromite and traces of NiFe-sulfides. Some particles have inclusions of unmelted mineral and rock fragments from the precursor asteroid. Although all samples of melt rock examined have experienced significant alteration since their deposition in the late Pliocene, a significant portion of these particles have interiors that remain pristine and can be used to estimate the bulk composition of the impact melt. The bulk composition of the melt-rock particles is similar to the composition of basaltic meteorites such as howardites or mesosiderite silicates, with a contribution from seawater salts and a siderophile-rich component. There is no evidence that the Eltanin impact melt contains a significant terrestrial silicate component that might have been incorporated by mixing of the projectile with oceanic crust. If terrestrial silicates were incorporated into the melt, then their contribution must be much less than 10 wt%. Since excess K, Na, and CI are not present in seawater proportions, uptake of these elements into the melt must have been greatest for K and least for CI, producing a K/CI ratio about 4 times that in seawater. After correcting for the seawater component, the bulk composition of the Eltanin impact melt provides the best estimate of the bulk composition of the Eltanin asteroid. Excess Fe in the impact melt, relative to that in howardites, must be from a significant metal phase in the parent asteroid. Although the estimated Fe:Ni:Ir ratios (8:1:4 x 10(exp -5)) are similar to those in mesosiderite metal nodules (10:1:6 x 10(exp -5), excess Co and Au by factors of about 2 and 10 times, respectively, imply a metal component distinct from that in typical mesosiderites. An alternative interpretation, that siderophiles have been highly fractionated from a mesosiderite source, would require loss of about 90% of the original metal from the impact melt and the sediments, and is unsupported by any observational data. More likely, the excess Fe in the melt rocks is 'representative of the amount of metal in the impacting asteroid, which is estimated to be 4+/- 1 wt%.

Constraints on the perturbed mutual motion in Didymos due to impact-induced deformation of its primary after the DART impact

NASA Astrophysics Data System (ADS)

Hirabayashi, M.; Schwartz, S. R.; Yu, Y.; Davis, A. B.; Chesley, S. R.; Fahnestock, E.; Michel, P.; Richardson, D. C.; Naidu, S.; Scheeres, D. J.; Cheng, A. F.; Rivkin, A.; Benner, L.

2017-12-01

(65803) Didymos is a binary near-Earth asteroid that consists of a top-shaped primary body rotating at a spin period of 2.26 hr and a secondary body orbiting around it at an orbital period of 11.92 hr. This asteroid is the target of the proposed NASA Double Asteroid Redirection Test (DART), which is part of the Asteroid Impact & Deflection Assessment (AIDA) mission concept. The goal of DART is to impact the secondary with the spacecraft and measure the momentum transfer by observing the perturbation of the orbital period of the system after the impact. Achieving this goal requires careful accounting for physical uncertainties that prevent accurate measurement of the momentum transfer. Here, we examine a scenario that might affect the momentum transfer measurement and a possible solution to avoiding issues due to this scenario. The primary's spin period is close to the spin barrier of rubble-pile asteroids, i.e., 2.3 hr. Also, some particles ejected from the secondary due to the DART impact may reach the primary and induce landslides or internal deformation of the primary, changing the gravity field. We have developed a numerical simulation technique for investigating how the mutual orbit of the system varies due to symmetric shape deformation of the primary along its spin axis after the DART impact. We find that if the deformation process occurs, the orbital period can change significantly, depending on the magnitude of the shape deformation. The mission currently plans a nearly head-on collision of the DART impactor with the secondary, making the orbital period of the system shorter. Our simulations show that since the deformation process always causes the primary to become more oblate, it shortens the orbital period as well. We also propose precise measurement of the primary's spin state to determine the deformation of the primary. This relies on the fact that any deformation process changes the spin state of the primary consistent with angular momentum conservation. Further investigations on this problem may improve the accuracy of the momentum transfer measurement for the AIDA mission.

The REgolith X-Ray Imaging Spectrometer (REXIS) for OSIRIS-REx: identifying regional elemental enrichment on asteroids

NASA Astrophysics Data System (ADS)

Allen, Branden; Grindlay, Jonathan; Hong, Jaesub; Binzel, Richard P.; Masterson, Rebecca; Inamdar, Niraj K.; Chodas, Mark; Smith, Matthew W.; Bautz, Marshall W.; Kissel, Steven E.; Villasenor, Joel; Oprescu, Miruna; Induni, Nicholas

2013-09-01

The OSIRIS-REx Mission was selected under the NASA New Frontiers program and is scheduled for launch in September of 2016 for a rendezvous with, and collection of a sample from the surface of asteroid Bennu in 2019. 101955 Bennu (previously 1999 RQ36) is an Apollo (near-Earth) asteroid originally discovered by the LINEAR project in 1999 which has since been classified as a potentially hazardous near-Earth object. The REgolith X-Ray Imaging Spectrometer (REXIS) was proposed jointly by MIT and Harvard and was subsequently accepted as a student led instrument for the determination of the elemental composition of the asteroid's surface as well as the surface distribution of select elements through solar induced X-ray fluorescence. REXIS consists of a detector plane that contains 4 X-ray CCDs integrated into a wide field coded aperture telescope with a focal length of 20 em for the detection of regions with enhanced abundance in key elements at 50 m scales. Elemental surface distributions of approximately 50-200 m scales can be detected using the instrument as a simple collimator. An overview of the observation strategy of the REXIS instrument and expected performance are presented here.

Cratering on 4 Vesta - Comparison of Crater Retention Ages and Ar-Ar Ages of HED Meteorites.

NASA Astrophysics Data System (ADS)

Schmedemann, N.; Kneissl, T.; Michael, G.; Neukum, G.; Nathues, A.; Sierks, H.; Wagner, R.; Krohn, K.; Reddy, V.; Hiesinger, H.; Jaumann, R.; Raymond, C. A.; Russell, C. T.

2012-04-01

In July 2011 the Dawn spacecraft entered orbit around the Main Belt asteroid 4 Vesta utilizing three different instruments to map the asteroid [1]. The Main Belt is the source region of most impactors in the inner solar system [2]. We compare the obtained crater size-frequency distribution (CSFD) of Vesta with that of the Moon and other Main Belt asteroids such as 951 Gaspra, 243 Ida, and 21 Lutetia. We also compare our results of crater counting on Vesta with K/Ar-Ar reset ages of HED meteorites, which most likely originated from Vesta [3]. To properly compare the lunar CSFD with that of the asteroids we applied scaling laws [4] to account for various impact velocities, surface gravities as well as material properties between the investigated bodies. We found well defined lunar-like CSFDs of impact craters on all four asteroids. The CSFD of Vesta and Lutetia had to be constructed from several individual measurements following [5]. We were able to derive lunar-like chronologies for each asteroid utilizing intrinsic collision probabilities [6], lunar-like CSFDs and the ground truth-derived lunar chronology. Since the Moon and the Main Belt asteroids share the same main impactor source, it is straightforward to also assume a very similar time-dependent impact rate over the solar system history. Alternative chronologies, which are based on computer models of the LHB [7], result in surface ages >4.5 Ga, which are highly unlikely for Vesta. Our lunar-like chronology for Vesta is able to match three out of four peaks in age probabilities of HED meteorites [3]. We measured the age of the Rheasilvia basin with 3.70 +/-0.02 Ga, which coincides with a wide-spread resurfacing age on Vesta. An underlying older basin, partially obliterated by the Rheasilvia impact was formed 3.81 +/-0.05 Ga ago. Finally the large basins and craters >150 km in diameter and the densest cratered areas on Vesta indicate a global resurfacing event 4.00 +/-0.02 Ga ago. This represents the oldest age we can infer from Vesta by this technique. Acknowledgement: This work has been supported by the German Space Agency (DLR) on behalf of the Federal Ministry of Economics and Technology, grant 50 OW 1101.

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

NASA Astrophysics Data System (ADS)

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

2013-10-01

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

New Research by CCD Scanning for Comets and Asteroids

NASA Technical Reports Server (NTRS)

Gehrels, Tom; McMillan, Robert S.

1997-01-01

The purpose of Spacewatch 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 microns (approximately V+R+I with peak sensitivity at 0.7 micron). The effective exposure time for each pass is 143 seconds multiplied by the secant of the declination. 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. As of the end of the observing run of Nov. 1997, Spacewatch had found a total of 153 Near-Earth Asteroids (NEAs) and 8 new comets since the project began in the 1980s, and had recovered one lost comet. The total number of NEAs found by Spacewatch big enough to be hazardous if they were to impact the Earth is 36. 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 16,000 asteroids designated by the Minor Planet Center (MPC).

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.;

Virtual Impactors: Search and Destroy

NASA Astrophysics Data System (ADS)

Milani, Andrea; Chesley, Steven R.; Boattini, Andrea; Valsecchi, Giovanni B.

2000-05-01

If for an asteroid which has been observed only over a short arc and then lost there are orbits compatible with the observations resulting in collisions, recovery would be desirable to decide if it will actually impact. If recovery is essentially impractical, as is the case for many small asteroids in the 100- to 500-m-diameter range, the next best thing is to make sure that the lost asteroid is not on a collision course. We propose a method for achieving this guarantee, with an observational effort far smaller than the one required for recovery. The procedure involves the computation of an orbit that is compatible with the available observations and, by hypothesis, results in an impact at some later encounter; this we call a virtual impactor (VI). The collision at some future time is a strong constraint; thus the VI has a well determined orbit. We show that it is possible to compute for each given time of observation the skyprint of the VI, that is the set of astrometric positions compatible with an impact (or a near impact). The skyprint needs to be scanned by powerful enough telescopes to perform a negative observation; once this has been done for the skyprints of all VIs, collisions can be excluded even without recovery. We propose to apply this procedure to the case of the lost asteroid 1998 OX 4, for which we have found orbital solutions with impacts in the years 2014, 2038, 2044, and 2046. Suitable observing windows are found when the VI would be close to the Earth in 2001 and in 2003, and the corresponding skyprints are small enough to be covered with very few frames. This procedure might become more and more necessary in the future, as the number of discoveries of small potentially hazardous asteroids increases; we discuss the general principles and the validation procedures that should apply to such a VI removal campaign.

Asteroidal versus cometary meteoroid impacts on the Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

Zook, Herbert A.

1993-01-01

Meteoroids that enter the Earth's atmosphere at low velocities will tend to impact the apex side (that surface facing the spacecraft direction of motion) of a spacecraft at a very high rate compared to the rate with which they will impact an antapex-facing surface. This ratio--apex to antapex impact rates--will become less as meteoroid entry velocities increase. The measured ration, apex to antapex, for 500 micron diameter impact craters in 6061-T6 aluminum on LDEF seems to be about 20 from the work of the meteoroid SIG group and others, that was presented at the first LDEF symposium. Such a ratio is more consistent with the meteoroid velocity distributions derived by Erickson and by Kessler, than it is with others that have been tested. These meteoroid velocity distributions have mean entry velocities into the Earth's atmosphere of 16.5 to 16.9 km/s. Others have numerically simulated the orbital evolution of small dust grains emitted from asteroids and comets. For those asteroidal grains small enough (below about 100 microns diameter) to drift from the asteroid belt to the orbit of the Earth, under P-R and solar wind drag, without suffering collisional destruction, the following results are found: as the ascending or descending nodes cross the Earth's orbit, their orbital eccentricities and inclinations are quite low (e less than 0.3, i less than 20 deg), and their mean velocity with respect to the Earth is about 5 or 6 km/s. When gravitational acceleration of the Earth is taken into account, the corresponding mean velocities relative to the top of the Earth's atmosphere are 12 to 13 km/s. This means that, at best, these small asteroidal particles cannot comprise more than 50 percent of the particles entering the Earth's atmosphere. When gravitational focusing is considered, they cannot comprise more than a few percent of those in heliocentric orbit at 1 AU. The rest are presumably of cometary origin.

The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop

NASA Technical Reports Server (NTRS)

Morrison, David (Editor)

1992-01-01

Impacts by Earth-approaching asteroids and comets pose a significant hazard to life and property. Although the annual probability of the Earth being struck by a large asteroid or comet is extremely small, the consequences of such a collision are so catastrophic that it is prudent to assess the nature of the threat and to prepare to deal with it. The first step in any program for the prevention or mitigation of impact catastrophes must involve a comprehensive search for Earth-crossing asteroids and comets and a detailed analysis of their orbits. At the request of the U.S. Congress, NASA has carried out a preliminary study to define a program for dramatically increasing the detection rate of Earth-crossing objects, as documented in this workshop report.

The DLR AsteroidFinder for NEOs

NASA Astrophysics Data System (ADS)

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

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

Asteroid Secular Dynamics: Ceres’ Fingerprint Identified

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Maurel, Clara; Tsirvoulis, Georgios; Knežević, Zoran

2015-07-01

Here we report on the significant role of a so far overlooked dynamical aspect, namely, a secular resonance between the dwarf planet Ceres and other asteroids. We demonstrate that this type of secular resonance can be the dominant dynamical factor in certain regions of the main asteroid belt. Specifically, we performed a dynamical analysis of the asteroids belonging to the (1726) Hoffmeister family. To identify which dynamical mechanisms are actually at work in this part of the main asteroid belt, i.e., to isolate the main perturber(s), we study the evolution of this family in time. The study is accomplished using numerical integrations of test particles performed within different dynamical models. The obtained results reveal that the post-impact evolution of the Hoffmeister asteroid family is a direct consequence of the nodal secular resonance with Ceres. This leads us to the conclusion that similar effects must exist in other parts of the asteroid belt. In this respect, the obtained results shed light on an important and entirely new aspect of the long-term dynamics of small bodies. Ceres’ fingerprint in asteroid dynamics, expressed through the discovered secular resonance effect, completely changes our understanding of the way in which perturbations by Ceres-like objects affect the orbits of nearby bodies.

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.

Collisional Histories of Comets and Trojan Asteroids: Insights from Forsterite and Enstatite Impact Studies

NASA Technical Reports Server (NTRS)

Lederer. S. M.; Jensen, E. A.; Wooden, D. H.; Lindsay, S. S.; Smith, D. C.; Cintala, M. J.; Nakamura-Messenger, K.; Keller, L. P.

2012-01-01

Impacts into forsterite and orthoenstatite at speeds typically encountered by comets demonstrate that shock imparted by collisions is detectable in the infrared signatures of their dust. The spectral signatures can be traced to physical alterations in their crystalline structures, as observed in TEM imaging and modeled using a dipole approximation. These results yield tantalizing insights into the collisional history of our solar system, as well as the history of individual comets and Trojan asteroids.

Lunar and Planetary Science XXXV: Asteroids, Meteors, Comets

NASA Technical Reports Server (NTRS)

2004-01-01

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

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

Jewitt, David, E-mail: jewitt@ucla.edu; Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1567

Some asteroids eject dust, unexpectedly producing transient, comet-like comae and tails. First ascribed to the sublimation of near-surface water ice, mass-losing asteroids (also called 'main-belt comets') can in fact be driven by a surprising diversity of mechanisms. In this paper, we consider 11 dynamical asteroids losing mass, in nine of which the ejected material is spatially resolved. We address mechanisms for producing mass loss including rotational instability, impact ejection, electrostatic repulsion, radiation pressure sweeping, dehydration stresses, and thermal fracture, in addition to the sublimation of ice. In two objects (133P and 238P) the repetitive nature of the observed activity leavesmore » ice sublimation as the only reasonable explanation, while in a third ((596) Scheila), a recent impact is the cause. Another impact may account for activity in P/2010 A2, but this tiny object can also be explained as having shed mass after reaching rotational instability. Mass loss from (3200) Phaethon is probably due to cracking or dehydration at extreme ({approx}1000 K) perihelion temperatures, perhaps aided by radiation pressure sweeping. For the other bodies, the mass-loss mechanisms remain unidentified, pending the acquisition of more and better data. While the active asteroid sample size remains small, the evidence for an astonishing diversity of mass-loss processes in these bodies is clear.« less

The planet crossing asteroid survey: Progress in the analysis of populations and terrestrial-planet cratering rates

NASA Technical Reports Server (NTRS)

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

1984-01-01

The Planet-Crossing Asteroid Survey (PCAS) is making steady progress toward the accumulation of the data required to make improved estimates of the populations and cratering rates which can be compared with the existing record of impact events. The PCAS is the chief source of new objects on which to base these calculations over the past decade, and is an integral part of the continuing refinement of the estimates used in planetological applications. An adjunct effort to determine albedo statistics from photometry of UCAS plates is being pursued as well, to better define the magnitude frequency distributions of asteroids. This will improve the quality of the population and collision probability calculations. The survey effort continues to discover new asteroids whose orbital characteristics may reveal the origin and evolution mechanisms reponsible for the transport of the planet-crossing asteroids to the inner solar system.

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

Cruise status of Hayabusa2: Round trip mission to asteroid 162173 Ryugu

NASA Astrophysics Data System (ADS)

Tsuda, Yuichi; Watanabe, Sei-ichiro; Saiki, Takanao; Yoshikawa, Makoto; Nakazawa, Satoru

2017-07-01

The Japan Aerospace Exploration Agency launched an asteroid sample return spacecraft "Hayabusa2" on December 3, 2014 by the Japanese H2A launch vehicle. Hayabusa2 aims at the round trip mission to the asteroid 162173 Ryugu. Hayabusa2 successfully conducted the Earth gravity assist on December 3, 2015, and now the spacecraft is flying toward Ryugu with the microwave discharge ion engine as the means of propulsion. As of September 2016, 1346 h of the ion engine operation has been achieved as planned. Three touch downs/sample collections, one kinetic impact/crater generation, four surface rovers deployment and many other in-situ observations are planned in the asteroid proximity phase. The operation team will perform extensive operation practice/rehearsal using a hardware-in-the-loop simulator in the year 2017 to be ready for the asteroid arrival in the summer 2018.

Evidence from Polymict Ureilite Meteorites for a Single "Rubble-Pile" Ureilite Parent Asteroid Gardened by Several Distinct Impactors

NASA Technical Reports Server (NTRS)

Downes, Hilary; Mittlefehldt, David W.; Kita, Noriko T.; Valley, John W.

2008-01-01

Ureilites are ultramafic achondrite meteorites that have experienced igneous processing whilst retaining heterogeneity in mg# and oxygen isotope ratios. Polymict ureilites represent material derived from the surface of the ureilite parent asteroid(s). Electron microprobe analysis of more than 500 olivine and pyroxene clasts in six polymict ureilites reveals that they cover a statistically identical range of compositions to that shown by all known monomict ureilites. This is considered to be convincing evidence for derivation from a single parent asteroid. Many of the polymict ureilites also contain clasts that have identical compositions to the anomalously high Mn/Mg olivines and pyroxenes from the Hughes 009 monomict ureilite (here termed the Hughes cluster ). Four of the six samples also contain distinctive ferroan lithic clasts that have been derived from oxidized impactors. The presence of several common distinctive lithologies within the polymict ureilites is additional evidence that the ureilites were derived from a single parent asteroid. Olivine in a large lithic clast of augite-bearing ureilitic has an mg# of 97, extending the compositional range of known ureilite material. Our study confirms that ureilitic olivine clasts with mg#s < 85 are much more common than those with mg# > 85, which also show more variable Mn contents, including the melt-inclusion bearing "Hughes cluster" ureilites. We interpret this to indicate that the parent ureilite asteroid was disrupted by a major impact at a time when melt was still present in regions with a bulk mg# > 85, giving rise to the two types of ureilites: common ferroan ones that were already residual after melting and less common magnesian ones that were still partially molten when disruption occurred, some of which are the result of interaction of melts with residual mantle during disruption. A single daughter asteroid re-accreted from the disrupted remnants of the mantle of the proto-ureilite asteroid, giving rise to a "rubble-pile" body that had material of a wide variety of compositions and shock states present on its surface. The analysed polymict ureilite meteorites represent regolith that subsequently formed on this asteroidal surface, including impact-derived material from at least six different meteoritic sources.

Tidal Excitation of the Core Dynamo of Mars

NASA Astrophysics Data System (ADS)

Seyed-Mahmoud, B.; Arkani-Hamed, J.; Aldridge, K.

2007-05-01

The lack of magnetic anomalies inside the giant impact basins Hellas, Isidis, Utopia and Argyre, inside the northern low lands, over the Tharsis bulge, and over the Tharsis and Olympus mounts suggests that the core field of Mars ceased to exist by about 4 Gyr ago, almost when the giant basins were formed. On the other hand, the giant basins are located on a great circle, implying that the basins were likely produced by fragments of a large asteroid that broke apart as it entered the Roche limit of Mars. This scenario offers a causative relationship for the apparent coincidence of the formation of the giant basins and the cessation of the core dynamo. We suggest that the core dynamo was excited by tidally driven elliptical instability in the Martian core. The breaking of the asteroid and its final impact on Mars eliminated the excitation and thus killed the dynamo. We show that a retrograde asteroid captured in a Keplerian orbit around Mars at a distance of about 50,000-100,000 km could orbit Mars for several hundreds of millions of years before impacting the planet due to the tidal coupling of the asteroid and Mars. Because of relatively very short growth time of the elliptical instability, less than 50,000 years, the asteroid was capable of retaining the elliptical instability and energizing the core dynamo for a geologically long period prior to 4 Ga. Our laboratory observations of a parametric instability of a rotating incompressible fluid, contained in a flexible-walled spherical cavity, confirm the possibility that an early Martian dynamo could have been powered by tidal straining.

The extinction of the dinosaurs.

PubMed

Brusatte, Stephen L; Butler, Richard J; Barrett, Paul M; Carrano, Matthew T; Evans, David C; Lloyd, Graeme T; Mannion, Philip D; Norell, Mark A; Peppe, Daniel J; Upchurch, Paul; Williamson, Thomas E

2015-05-01

Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult. © 2014 The Authors. Biological Reviews © 2014 Cambridge Philosophical Society.

NASA Double Asteroid Redirection Test (Dart) Trajectory Validation and Robustness

NASA Technical Reports Server (NTRS)

Sarli, Bruno V.; Ozimek, Martin T.; Atchison, Justin A.; Englander, Jacob A.; Barbee, Brent W.

2017-01-01

The Double Asteroid Redirection Test (DART) mission will be the first to test the concept of a kinetic impactor. Several studies have been made on asteroid redirection and impact mitigation, however, to this date no mission tested the proposed concepts. An impact study on a representative body allows the measurement of the effects on the target's orbit and physical structure. With this goal, DART's objective is to verify the effectiveness of the kinetic impact concept for planetary defense. The spacecraft uses solar electric propulsion to escape Earth, flyby (138971) 2001 CB21 for impart rehearsal, and impact the secondary body of the (65803) Didymos system. This work focuses on the interplanetary trajectory design part of the mission with the validation of the baseline trajectory, performance comparison to other mission objectives, and assessment of the baseline robustness to missed thrust events. Results show a good performance of the selected trajectory for different mission objectives: latest possible escape date, maximum kinetic energy on impact, shortest possible time of flight, and use of an Earth swing-by. The baseline trajectory was shown to be robust to a missed thrust with 1% of fuel margin being enough to recover the mission for failures of more than 14 days.

Global environmental effects of impact-generated aerosols: Results from a general circulation model

NASA Technical Reports Server (NTRS)

Covey, Curt; Ghan, Steven J.; Walton, John J.; Weissman, Paul R.

1989-01-01

Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to the three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans, not included in the one-dimensional model, substantially mitigates land surface cooling. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stages of cooling than in the one-dimensional model study. GCM-simulated climatic changes in the scenario of asteroid/comet winter are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though of course less severe, climatic changes, according to the GCM. An asteroid or comet impact would not lead to anything approaching complete global freezing, but quite reasonable to assume that impacts would dramatically alter the climate in at least a patchy sense.

Crystallographic Study of Itokawa Particle, RA-QD02-0127 by Using Energy-Scanning X-Ray Diffraction Method with Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Hagiya, K.; Ohsumi, K.; Komatsu, M.; Mikouchi, T.; Zolensky, M. E.; Hirata, A.; Yamaguchi, S.; Kurokawa, A.

2016-08-01

Crystallographic study of Itokawa particle, RA-QD02-0127 by using new X-ray diffraction method was performed. The purpose of this study is to understand better the metamorphic and impact shock history of asteroid Itokawa, and other S-class asteroids.

Crystallographic Study of Itokawa Particle, RA-QD02-0127 by Using Energy-Scanning X-Ray Diffraction Method with Synchrotron Radiation

NASA Technical Reports Server (NTRS)

Hagiya, K.; Ohsumi, K.; Komatsu, M.; Mikouchi, T.; Zolensky, M. E.; Hirata, A.; Yamaguchi, S.; Kurokawa, A.

2016-01-01

The petrographic study of Itokawa particle, RA-QD02-0127 has been performed by SEM-EDS and optical microscope observations. The purpose of this study is to understand better the metamorphic and impact shock history of asteroid Itokawa, and other S-class asteroids.

Small carry-on impactor of Hayabusa2 mission

NASA Astrophysics Data System (ADS)

Saiki, Takanao; Sawada, Hirotaka; Okamoto, Chisato; Yano, Hajime; Takagi, Yasuhiko; Akahoshi, Yasuhiro; Yoshikawa, Makoto

2013-03-01

A Japanese spacecraft, Hayabusa2, the successor of Hayabusa, which came back from the Asteroid Itokawa with sample materials after its 7-year-interplanetary journeys, is a current mission of Japan Aerospace Exploration Agency (JAXA) and scheduled to be launched in 2014. Although its design basically follows Hayabusa, some new components are planned to be equipped in Hayabusa2 mission. A Small Carry-on Impactor (SCI), a small explosive device, is one of the challenges that were not seen with Hayabusa. An important scientific objective of Hayabusa2 is to investigate chemical and physical properties of the internal materials and structures. SCI creates an artificial crater on the surface of the asteroid and the mother spacecraft observes the crater and tries to get sample materials. High kinetic energy is required to creating a meaningful crater. The SCI would become complicated and heavy if the traditional acceleration devices like thrusters and rocket motors are used to hit the asteroid because the acceleration distance is quite large and guidance system is necessary. In order to make the system simpler, a technology of special type of shaped charge is used for the acceleration of the impact head. By using this technology, it becomes possible to accelerate the impact head very quickly and to hit the asteroid without guidance system. However, the impact operation should be complicated because SCI uses powerful explosive and it scatters high speed debris at the detonation. This paper presents the overview of our new small carry-on impact system and the impact operation of Hayabusa2 mission.

The violent collisional history of asteroid 4 Vesta.

PubMed

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

2012-05-11

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

Can Plume-Forming Asteroid Airbursts Generate Meteotsunami in Deep Water?

NASA Astrophysics Data System (ADS)

Boslough, M.

2015-12-01

Hydrocode simulations suggest that the 1908 Tunguska explosion was a plume-forming airburst analogous to those caused by Comet Shoemaker-Levy 9 (SL9) collisions with Jupiter in 1994. A noctilucent cloud that appeared over Europe following the Tunguska event is similar to post-impact features on Jupiter, consistent with a collapsed plume containing condensation from the vaporized asteroid. Previous workers treated Tunguska as a point explosion and used seismic records, barograms, and extent of fallen trees to determine explosive yield. Estimates were based on scaling laws derived from nuclear weapons data, neglecting directionality, mass, and momentum of the asteroid. This point-source assumption, with other simplifications, led to a significant overestimate. Tunguska seismic data were consistent with ground motion from a vertical point impulse of 7×1018dyn sec caused by the downward blast wave of a 12.5-megaton nuclear explosion at an altitude of 8.5 km for an effective momentum multiplication factor (β) of ~80. However, simulations of a 3-megaton collisional airburst reveal that the upward-directed momentum contained in a ballistic plume can reach this level within the first minute after the explosion (β≈300). The reaction impulse from such an airburst is therefore similar to a much larger non-plume-forming nuclear explosion. Momentum is coupled through the atmosphere to the surface, generating disproportionately large seismic signatures. This result suggests that coupling from an over-water plume-forming airburst could be a more efficient tsunami source mechanism than a collapsing impact cavity or direct air blast because the characteristic time of the plume is closer to that of a long-period wave in deep water. As the plume accelerates upward, it creates a slowly-rising and sustained overpressure with a ramp wave that propagates outward at the speed of sound, generating a tsunami in deep ocean by the same mechanism that yields slower meteotsunami in shallow basins. This hypothesis is consistent with the observation of prominent internal waves observed propagating radially outward from several SL9 impacts, even though the waves were not in Proudman resonance. Because of slow compression, the SL9 waves grew with a Froude number of ~1.6, the same as that of the sound speed in air over ~4.6-km-deep water.

The Impact and Oxidation Survival of Selected Meteoritic Compounds: Signatures of Asteroid Organic Material on Planetary Surfaces

NASA Technical Reports Server (NTRS)

Cooper, George; Horz, Fred; Oleary, Alanna; Chang, Sherwood

2013-01-01

Polar, non-volatile organic compounds may be present on the surfaces (or near surfaces) of multiple Solar System bodies. If found, by current or future missions, it would be desirable to determine the origin(s) of such compounds, e.g., asteroidal or in situ. To test the possible survival of meteoritic compounds both during impacts with planetary surfaces and under subsequent (possibly) harsh ambient conditions, we subjected known meteoritic compounds to relatively high impact-shock pressures and/or to varying oxidizing/corrosive conditions. Tested compounds include sulfonic and phosphonic acids (S&P), polyaromatic hydrocarbons (PAHs) amino acids, keto acids, dicarboxylic acids, deoxy sugar acids, and hydroxy tricarboxylic acids (Table 1). Meteoritic sulfonic acids were found to be relatively abundant in the Murchison meteorite and to possess unusual S-33 isotope anomalies (non mass-dependent isotope fractionations). Combined with distinctive C-S and C-P bonds, the S&P are potential signatures of asteroidal organic material.

Computer simulations of large asteroid impacts into oceanic and continental sites--preliminary results on atmospheric, cratering and ejecta dynamics

USGS Publications Warehouse

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

1987-01-01

Computer simulations have been completed that describe passage of a 10-km-diameter asteroid through the Earth's atmosphere and the subsequent cratering and ejecta dynamics caused by impact of the asteroid into both oceanic and continental sites. The asteroid was modeled as a spherical body moving vertically at 20 km/s with a kinetic energy of 2.6 ?? 1030 ergs (6.2 ?? 107 Mt ). Detailed material modeling of the asteroid, ocean, crustal units, sedimentary unit, and mantle included effects of strength and fracturing, generic asteroid and rock properties, porosity, saturation, lithostatic stresses, and geothermal contributions, each selected to simulate impact and geologic conditions that were as realistic as possible. Calculation of the passage of the asteroid through a U.S. Standard Atmosphere showed development of a strong bow shock wave followed by a highly shock compressed and heated air mass. Rapid expansion of this shocked air created a large low-density region that also expanded away from the impact area. Shock temperatures in air reached ???20,000 K near the surface of the uplifting crater rim and were as high as ???2000 K at more than 30 km range and 10 km altitude. Calculations to 30 s showed that the shock fronts in the air and in most of the expanding shocked air mass preceded the formation of the crater, ejecta, and rim uplift and did not interact with them. As cratering developed, uplifted rim and target material were ejected into the very low density, shock-heated air immediately above the forming crater, and complex interactions could be expected. Calculations of the impact events showed equally dramatic effects on the oceanic and continental targets through an interval of 120 s. Despite geologic differences in the targets, both cratering events developed comparable dynamic flow fields and by ???29 s had formed similar-sized transient craters ???39 km deep and ???62 km across. Transient-rim uplift of ocean and crust reached a maximum altitude of nearly 40 km at ???30 s and began to decay at velocities of 500 m/s to develop large-tsunami conditions. After ???30 s, strong gravitational rebound drove both craters toward broad flat-floored shapes. At 120 s, transient crater diameters were ???80 km (continental) and ???105 km (oceanic) and transient depths were ???27 km; crater floors consisting of melted and fragmented hot rock were rebounding rapidly upward. By 60 s, the continental crater had ejected ???2 ?? 1014 t, about twice the mass ejected from the oceanic crater. By 120 s, ???70,000 km3 (continental) and ???90,000 km3 (oceanic) target material were excavated (no mantle) and massive ejecta blankets were formed around the craters. We estimate that in excess of ???70% of the ejecta would finally lie within ???3 crater diameters of the impact, and the remaining ejecta (???1013 t), including the vaporized asteroid, would be ejected into the atmosphere to altitudes as high as the ionosphere. Effects of secondary volcanism and return of the ocean over hot oceanic crater floor could also be expected to contribute substantial material to the atmosphere. ?? 1987.

A CCD comparison of outer Jovian satellites and Trojan asteroids

NASA Technical Reports Server (NTRS)

Luu, Jane X.

1991-01-01

The eight small outer Jovian satellites are not as well known as the brighter, more illustrious Galilean satellites. They are divided into two groups, each containing four satellites; the inner group travels in prograde orbits while the outer group travels in retrograde orbits. From the distinct orbital characteristics of the two groups, most of the theories of their origin involve the capture and breakup of two planetesimals upon entry into the atmosphere of proto-Jupiter. Their proximity to the Trojans asteroids has led to conjectures of a link between them and the Trojans. However, Tholen and Zellner (1984) found no red spectrum among six of the satellites and postulated that they were all C-type objects; therefore, they were unlikely to be derivatives of the Trojan population. Charge-coupled device (CCD) photometry and spectroscopy of the eight outer Jovian satellites obtained from 1987 to 1989 and a comparison between these eight satellites and the Trojan asteroids are presented.

The OVIRS Visible/IR Spectrometer on the OSIRIS-Rex Mission

NASA Technical Reports Server (NTRS)

Reuter, D. C.; Simon-Miller, A. A.

2012-01-01

The OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security Regolith Explorer) Mission is a planetary science mission to study, and return a sample from, the carbonaceous asteroid 1999 RQ-36. The third mission selected under NASA's New Frontiers Program, it is scheduled to be launched in 2016. It is led by PI Dante Lauretta at the University of Arizona and managed by NASA's Goddard Space Flight Center. The spacecraft and the asteroid sampling mechanism, TAGSAM (Touch-And-Go Sample Acquisition Mechanism) will be provided by Lockheed Martin Space Systems. Instrumentation for studying the asteroid include: OCAMS (the OSIRIS-REx Camera Suite), OLA (the OSIRIS-REx Laser Altimeter, a scanning LIDAR), OTES (The OSIRIS-REx Thermal Emission Spectrometer, a 4-50 micron point spectrometer) and OVIRS (the OSIRIS-REx Visible and IR Spectrometer, a 0.4 to 4.3 micron point spectrometer). The payload also includes REXIS (the Regolith X-ray Imaging Spectrometer) a student provided experiment. This paper presents a description of the OVIRS instrument.

Application of photometric models to asteroids

NASA Technical Reports Server (NTRS)

Bowell, Edward; Hapke, Bruce; Domingue, Deborah; Lumme, Kari; Peltoniemi, Jouni; Harris, Alan W.

1989-01-01

The way an asteroid or other atmosphereless solar system body varies in brightness in response to changing illumination and viewing geometry depends in a very complicated way on the physical and optical properties of its surface and on its overall shape. This paper summarizes the formulation and application of recent photometric models by Hapke (1981, 1984, 1986) and by Lumme and Bowell (1981). In both models, the brightness of a rough and porous surface is parameterized in terms of the optical properties of individual particles, by shadowing between particles, and by the way in which light is scattered among collections of particles. Both models succeed in their goal of fitting the observed photometric behavior of a wide variety of bodies, but neither has led to a very complete understanding of the properties of asteroid regoliths, primarily because, in most cases, the parameters in the present models cannot be adequately constrained by observations of integral brightness alone over a restricted range of phase angles.

Driven by Affect to Explore Asteroids, the Moon, and Science Education

NASA Astrophysics Data System (ADS)

Dingatantrige Perera, Jude Viranga

Affect is a domain of psychology that includes attitudes, emotions, interests, and values. My own affect influenced the choice of topics for my dissertation. After examining asteroid interiors and the Moon's thermal evolution, I discuss the role of affect in online science education. I begin with asteroids, which are collections of smaller objects held together by gravity and possibly cohesion. These "rubble-pile" objects may experience the Brazil Nut Effect (BNE). When a collection of particles of similar densities, but of different sizes, is shaken, smaller particles will move parallel to the local gravity vector while larger objects will do the opposite. Thus, when asteroids are shaken by impacts, they may experience the BNE as possibly evidenced by large boulders seen on their surfaces. I found while the BNE is plausible on asteroids, it is confined to only the outer layers. The Moon, which formed with a Lunar Magma Ocean (LMO), is the next topic of this work. The LMO is due to the Moon forming rapidly after a giant impact between the proto-Earth and another planetary body. The first 80% of the LMO solidified rapidly at which point a floatation crust formed and slowed solidification of the remaining LMO. Impact bombardment during this cooling process, while an important component, has not been studied in detail. Impacts considered here are from debris generated during the formation of the Moon. I developed a thermal model that incorporates impacts and find that impacts may have either expedited or delayed LMO solidification. Finally, I return to affect to consider the differences in attitudes towards science between students enrolled in fully-online degree programs and those enrolled in traditional, in-person degree programs. I analyzed pre- and post-course survey data from the online astrobiology course Habitable Worlds. Unlike their traditional program counterparts, students enrolled in online programs started the course with better attitudes towards science and also further changed towards more positive attitudes during the course. Along with important conclusions in three research fields, this work aims to demonstrate the importance of affect in both scientific research and science education.

Integrated Blowoff and Breakup Calculations for Asteroid Deflection by Nuclear Ablation

NASA Astrophysics Data System (ADS)

Bruck Syal, M.; Owen, M.; Dearborn, D. S.; Miller, P. L.

2016-12-01

When the warning timing is short, hazardous asteroids or comets can only be deflected off of an Earth-impacting trajectory by a nuclear device [1]. Here we model asteroid response to a standoff nuclear explosion, a problem which requires sub-millimeter spatial resolution at the body's surface to fully capture x-ray energy deposition. The first stage of the calculation focuses on modeling blowoff momentum from vaporized material, using a problem domain confined to the uppermost surface of the asteroid. Once the blowoff momentum transfer process is complete, the problem is remapped into a coarser resolution and the remainder of the asteroid body is added to the calculation, so that asteroid response can be tracked over longer timescales. This two-stage approach enables an integrated assessment of both the efficacy of momentum delivery and damage incurred by the bulk of the asteroid. Investigating the degree of post-ablation fracture, fragmentation, and fragment dispersion is necessary for modeling the outcomes of cases intended to fully fragment and disperse the body (disruption), as well as cases where the bulk of the asteroid should remain intact (deflection). We begin with 500-m spherical asteroids but also extend our analysis to radar-derived asteroid shape models. [1] Dearborn, D.S.P., Miller, P.L., 2014. Deflecting or Disrupting a Threatening Object, in: Pelton, J.N., Allahdadi, F. (Eds.), Handbook of Cosmic Hazards and Planetary Defense, Springer. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344. LLNL-ABS-699631.

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

NASA Astrophysics Data System (ADS)

Jewitt, David; Guilbert-Lepoutre, Aurelie

2012-01-01

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

Impact trajectories of the asteroid Apophis in the 21st century

NASA Astrophysics Data System (ADS)

Sokolov, L. L.; Bashakov, A. A.; Borisova, T. P.; Petrov, N. A.; Pitjev, N. P.; Shaidulin, V. S.

2012-07-01

The asteroid Apophis is one of the most hazardous near-Earth asteroids. As a result of the scattering of Apophis' potential trajectories after its close approach in 2029, and its possible approach in 2036, there are many dangerous trajectories including impact trajectories after 2036. The purpose of this study is to identify and investigate these trajectories. We use the Everhart integrator; the DE405, DE423, and EPM2008 ephemerides; and two sets of initial data for Apophis (those collected by NASA in 2006 and by the IAA in 2010). More than 50 possible encounters in this century are presented, including 13 encounters between 2036 and 2050. The minimum geocentric distances obtained using a different ephemeris and initial conditions differ little between themselves. Analogous results in (Yeomans et al., 2009) are consistent with our results.

A Dark Asteroid Family in the Phocaea Region

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Tsirvoulis, Georgios; Granvik, Mikael; Todović, Ana

2017-06-01

We report the discovery of a new asteroid family among the dark asteroids residing in the Phocaea region the Tamara family. We make use of available physical data to separate asteroids in the region according to their surface reflectance properties, and establish the membership of the family. We determine the slope of the cumulative magnitude distribution of the family, and find it to be significantly steeper than the corresponding slope of all the asteroids in the Phocaea region. This implies that subkilometer dark Phocaeas are comparable in number to bright S-type objects, shedding light on an entirely new aspect of the composition of small Phocaea asteroids. We then use the Yarkovsky V-shape based method and estimate the age of the family to be 264 ± 43 Myr. Finally, we carry out numerical simulations of the dynamical evolution of the Tamara family. The results suggest that up to 50 Tamara members with absolute magnitude H< 19.4 may currently be found in the near-Earth region. Despite their relatively small number in the near-Earth space, the rate of Earth impacts by small, dark Phocaeas is non-negligible.

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

PubMed

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

2002-06-13

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

The Explored Asteroids: Science and Exploration in the Space Age

NASA Astrophysics Data System (ADS)

Sears, D. W. G.

2015-11-01

Interest in asteroids is currently high in view of their scientific importance, the impact hazard, and the in situ resource opportunities they offer. They are also a case study of the intimate relationship between science and exploration. A detailed review of the twelve asteroids that have been visited by eight robotic spacecraft is presented here. While the twelve explored asteroids have many features in common, like their heavily cratered and regolith covered surfaces, they are a remarkably diverse group. Some have low-eccentricity orbits in the main belt, while some are potentially hazardous objects. They range from dwarf planets to primary planetesimals to fragments of larger precursor objects to tiny shards. One has a moon. Their surface compositions range from basaltic to various chondrite-like compositions. Here their properties are reviewed and what was confirmed and what was newly learned is discussed, and additionally the explored asteroids are compared with comets and meteorites. Several topics are developed. These topics are the internal structure of asteroids, water distribution in the inner solar system and its role in shaping surfaces, and the meteoritic links.

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

NASA Astrophysics Data System (ADS)

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

2014-07-01

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

NASA Double Asteroid Redirection Test (DART) Trajectory Validation and Robutness

NASA Technical Reports Server (NTRS)

Sarli, Bruno V.; Ozimek, Martin T.; Atchison, Justin A.; Englander, Jacob A.; Barbee, Brent W.

2017-01-01

The Double Asteroid Redirection Test (DART) mission will be the first to test the concept of a kinetic impactor. Several studies have been made on asteroid redirection and impact mitigation, however, to this date no mission tested the proposed concepts. An impact study on a representative body allows the measurement of the effects on the target's orbit and physical structure. With this goal, DART's objective is to verify the effectiveness of the kinetic impact concept for planetary defense. The spacecraft uses solar electric propulsion to escape Earth, fly by (138971) 2001 CB21 for impact rehearsal, and impact Didymos-B, the secondary body of the binary (65803) Didymos system. This work focuses on the heliocentric transfer design part of the mission with the validation of the baseline trajectory, performance comparison to other mission objectives, and assessment of the baseline robustness to missed thrust events. Results show a good performance of the selected trajectory for different mission objectives: latest possible escape date, maximum kinetic energy on impact, shortest possible time of flight, and use of an Earth swing-by. The baseline trajectory was shown to be robust to a missed thrust with 1% of fuel margin being enough to recover the mission for failures of more than 14 days.

The delivery of water by impacts from planetary accretion to present

PubMed Central

2018-01-01

Dynamical models and observational evidence indicate that water-rich asteroids and comets deliver water to objects throughout the solar system, but the mechanisms by which this water is captured have been unclear. New experiments reveal that impact melts and breccias capture up to 30% of the water carried by carbonaceous chondrite–like projectiles under impact conditions typical of the main asteroid belt impact and the early phases of planet formation. This impactor-derived water resides in two distinct reservoirs: in impact melts and projectile survivors. Impact melt hosts the bulk of the delivered water. Entrapment of water within impact glasses and melt-bearing breccias is therefore a plausible source of hydration features associated with craters on the Moon and elsewhere in the solar system and likely contributed to the early accretion of water during planet formation. PMID:29707636

The delivery of water by impacts from planetary accretion to present.

PubMed

Daly, R Terik; Schultz, Peter H

2018-04-01

Dynamical models and observational evidence indicate that water-rich asteroids and comets deliver water to objects throughout the solar system, but the mechanisms by which this water is captured have been unclear. New experiments reveal that impact melts and breccias capture up to 30% of the water carried by carbonaceous chondrite-like projectiles under impact conditions typical of the main asteroid belt impact and the early phases of planet formation. This impactor-derived water resides in two distinct reservoirs: in impact melts and projectile survivors. Impact melt hosts the bulk of the delivered water. Entrapment of water within impact glasses and melt-bearing breccias is therefore a plausible source of hydration features associated with craters on the Moon and elsewhere in the solar system and likely contributed to the early accretion of water during planet formation.

Impact penetrometry of analogue planetary regoliths

NASA Astrophysics Data System (ADS)

Paton, M. D.; Green, S. F.; Ball, A. J.

2013-09-01

Erosion and deposition processes on major and minor planetary bodies generate layers of loose broken up material on the surface. Due to the long period over which these processes have been active, the material in these layers can be, depending on the bodies' size, finely ground into grains similar in size to sand or a finer power such as found on the lunar surface. The subsurface stratigraphy of an asteroid, for example, could help characterise and understand the variety of geological features and granular processes on asteroids, e.g. see [1]. The microstructural properties of the asteroid's surface are also important for understanding the impact history of the asteroid, the interpretation of light scattering observations and thermal modelling. As the surface of an asteroid or planet will most likely be granular and loose it is then easy to penetrate, for example by using a cylindrical body tipped with a conical or other shaped tip. Such a device, fitted with a force sensor, that measures the resistance to penetration, can then be used to infer the physical properties of the target, in a similar way to penetrometers used on Earth. These instruments can be made small enough to be deployed by spacecraft to investigate extraterrestrial surfaces as with the Huygens penetrometer that investigated the surface of Titan [2]. A prototype impact penetrometer (fig. 1), based on a standard instrument used for making such measurements on Earth, is introduced. For detailed characterisation of the local stratigraphy penetrometry is usually conducted on the Earth using such a standardised penetrometer inserted slowly and at constant speed into the subsurface. Consequently there is an established and extensive library of publications available for the interpretation of this type of instrument. Impact penetrometry, as the name suggests, is conducted during the impact of a projectile. This type of penetrometry has not been so well characterised and interpreting the results, in terms of stratigraphy, is made difficult due to dynamic effects such as variation in friction and drag coefficient with speed. Here we investigate speed-dependent effects with depth of penetration (see fig. 2) and compare them with the effects of layered material (see fig. 3). We combine a microstructural model [3] with a macroscale model of penetration (see fig. 6) to investigate the importance of momentum effects with impact speed and grain size relative to penetrometer size.We assess the penetrometer for detection of microstructural properties of the regolith such as particle size (see fig. 5) and mass and make recommendations, building on our previous work, for further refinement of an asteroid penetrometer.

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

Asteroid Impact Deflection and Assessment (AIDA) mission - Full-Scale Modeling and Simulation of Ejecta Evolution and Fates

NASA Astrophysics Data System (ADS)

Fahnestock, Eugene G.; Yu, Yang; Hamilton, Douglas P.; Schwartz, Stephen; Stickle, Angela; Miller, Paul L.; Cheng, Andy F.; Michel, Patrick; AIDA Impact Simulation Working Group

2016-10-01

The proposed Asteroid Impact Deflection and Assessment (AIDA) mission includes NASA's Double Asteroid Redirection Test (DART), whose impact with the secondary of near-Earth binary asteroid 65803 Didymos is expected to liberate large amounts of ejecta. We present efforts within the AIDA Impact Simulation Working Group to comprehensively simulate the behavior of this impact ejecta as it moves through and exits the system. Group members at JPL, OCA, and UMD have been working largely independently, developing their own strategies and methodologies. Ejecta initial conditions may be imported from output of hydrocode impact simulations or generated from crater scaling laws derived from point-source explosion models. We started with the latter approach, using reasonable assumptions for the secondary's density, porosity, surface cohesive strength, and vanishingly small net gravitational/rotational surface acceleration. We adopted DART's planned size, mass, closing velocity, and impact geometry for the cratering event. Using independent N-Body codes, we performed Monte Carlo integration of ejecta particles sampled over reasonable particle size ranges, and over launch locations within the crater footprint. In some cases we scaled the number of integrated particles in various size bins to the estimated number of particles consistent with a realistic size-frequency distribution. Dynamical models used for the particle integration varied, but all included full gravity potential of both primary and secondary, the solar tide, and solar radiation pressure (accounting for shadowing). We present results for the proportions of ejecta reaching ultimate fates of escape, return impact on the secondary, and transfer impact onto the primary. We also present the time history of reaching those outcomes, i.e., ejecta clearing timescales, and the size-frequency distribution of remaining ejecta at given post-impact durations. We find large numbers of particles remain in the system for several weeks after impact. Clearing timescales are nonlinearly dependent on particle size as expected, such that only the largest ejecta persist longest. We find results are strongly dependent on the local surface geometry at the modeled impact locations.

Imaging the interiors of near-earth objects with radio reflection tomography

NASA Technical Reports Server (NTRS)

Safaeinili, A.; Ostro, S. J.

2002-01-01

Scenarios for mitigation of asteroid comet collisions include the use of explosives to deflect or destroythe projectile. However, as demonstrated by Asphaug et al.( 1998), the outcome of explosive energy transfer to an asteroid or comet (via a bomb or a hypervelocity impact) is extremely sensitive to the pre-existing configuration of fractures and voids.

Tactile Earth and Space Science Materials for Students with Visual Impairments: Contours, Craters, Asteroids, and Features of Mars

ERIC Educational Resources Information Center

Rule, Audrey C.

2011-01-01

New tactile curriculum materials for teaching Earth and planetary science lessons on rotation=revolution, silhouettes of objects from different views, contour maps, impact craters, asteroids, and topographic features of Mars to 11 elementary and middle school students with sight impairments at a week-long residential summer camp are presented…

A Martian origin for the Mars Trojan asteroids

NASA Astrophysics Data System (ADS)

Polishook, D.; Jacobson, S. A.; Morbidelli, A.; Aharonson, O.

2017-08-01

Seven of the nine known Mars Trojan asteroids belong to an orbital cluster1,2 named after its largest member, (5261) Eureka. Eureka is probably the progenitor of the whole cluster, which formed at least 1 Gyr ago3. It has been suggested3 that the thermal YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect spun up Eureka, resulting in fragments being ejected by the rotational-fission mechanism. Eureka's spectrum exhibits a broad and deep absorption band around 1 μm, indicating an olivine-rich composition4. Here we show evidence that the Trojan Eureka cluster progenitor could have originated as impact debris excavated from the Martian mantle. We present new near-infrared observations of two Trojans ((311999) 2007 NS2 and (385250) 2001 DH47) and find that both exhibit an olivine-rich reflectance spectrum similar to Eureka's. These measurements confirm that the progenitor of the cluster has an achondritic composition4. Olivine-rich reflectance spectra are rare amongst asteroids5 but are seen around the largest basins on Mars6. They are also consistent with some Martian meteorites (for example, Chassigny7) and with the material comprising much of the Martian mantle8,9. Using numerical simulations, we show that the Mars Trojans are more likely to be impact ejecta from Mars than captured olivine-rich asteroids transported from the main belt. This result directly links specific asteroids to debris from the forming planets.

Melting, vaporization, and energy partitioning for impacts on asteroidal and planetary objects

NASA Technical Reports Server (NTRS)

Smither, Catherine L.; Ahrens, Thomas J.

1992-01-01

A three-dimensional smoothed particle hydrodynamics code was used to model normal and oblique impacts of silicate projectiles on asteroidal and planetary bodies. The energy of the system, initially in the kinetic energy of the impactor, is partitioned after impact into internal and kinetic energy of the impactor and the target body. These simulations show that, unlike the case of impacts onto a half-space, a significant amount of energy remains in the kinetic energy of the impacting body, as parts of it travel past the main planet and escape the system. This effect is greater for more oblique impacts, and for impacts onto the small planets. Melting and vaporization of both bodies were also examined. The amount of the target body melted was much greater in the case of smaller targets than for an impact of a similar scale on a larger body.

Initial Results on the Extraterrestrial Component of New Sediment Cores Containing Deposits of the Eltanin Impact Event

NASA Technical Reports Server (NTRS)

Kyte, Frank T.; Gersonde, Rainer

2003-01-01

Background The impact of the Eltanin asteroid into the Bellingshausen Sea (2.15 Ma) is the only known impact in a deep-ocean (approx. 5 km) basin. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits. Sediments of Eocene age and younger were ripped up and redeposited by the impact. The depositional sequence produced by the impact has three units: a chaotic assemblage of sediment fragments up to 50 cm, followed by laminated sands deposited as a turbulent flow, and finally silts and clays that accumulated from dispersed sediments in the water column. The meteoritic impact ejecta, which is composed of shock-melted asteroidal materials and unmelted meteorites, settled through the water column and concentrated near the top of the laminated sands.

BAOBAB (Big And Outrageously Bold Asteroid Belt) Project

NASA Technical Reports Server (NTRS)

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

2017-01-01

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

The Violent Collisional History of Asteroid 4 Vesta

NASA Astrophysics Data System (ADS)

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

2012-05-01

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

The Role of Near-Earth Asteroids in Long-Term Platinum Supply

NASA Astrophysics Data System (ADS)

Blair, B. R.

2000-01-01

High-grade platinum-group metal concentrations have been identified in an abundant class of near-Earth asteroids known as LL Chondrites. The potential existence of a high-value asteroid-derived mineral product is examined from an economic perspective to assess the possible impacts on long-term precious metal supply. It is hypothesized that extraterrestrial sources of platinum group metals will become available in the global marketplace in a 20-year time frame, based on current trends of growth in technology and increasing levels of human activities in near-Earth space. Current and projected trends in platinum supply and demand are cited from the relevant literature to provide an economic context and provide an example for evaluating the economic potential of future asteroid-derived precious and strategic metals.

ATLAS: Finding the Nearest Asteroids

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

The disposition of impact ejecta resulting from the AIDA-DART mission to binary asteroid 65803 Didymos: an independent investigation

NASA Astrophysics Data System (ADS)

Richardson, James E.; O'Brien, David P.

2016-10-01

If all goes as planned, in the year 2020 a joint ESA and NASA mission will be launched that will rendezvous with the near-Earth binary asteroid system 65803 Didymos in the fall of 2022. The European component, the Asteroid Impact & Deflection Assessment (AIDA) spacecraft will arrive first and characterize the system, which consists of a ~800 m diameter primary and a ~160 m diameter secondary, orbiting a common center of mass at a semi-major axis distance of ~1200 m with a orbital period of 11.9 hr. Following system characterization, the AIDA spacecraft will remove to a safe distance while the NASA component, the 300 kg Double Asteroid Redirection Test (DART) spacecraft collides with the trailing edge of the secondary body (with respect to the binary's retrograde mutual orbit). Meanwhile, the AIDA spacecraft will conduct observations of this impact and its aftermath, specifically looking for changes made to the primary, the secondary, and their mutual orbit as a result of the DART collision. Of particular interest is the ballistic flight and final disposition of the ejecta produced by the impact cratering process, not just from the standpoint of scientific study, but also from the standpoint of AIDA spacecraft safety.In this study, we investigate a series of hypothetical DART impacts utilizing a semi-empirical, numerical impact ejecta plume model originally developed for the Deep Impact mission and designed specifically with impacts on small bodies in mind. The resulting excavated mass is discretized into 7200 individual tracer particles, each representing a unique combination of speed, mass, and ejected direction. The trajectory of each tracer is computed numerically under the gravitational influence of both primary and secondary, along with the effects of solar radiation pressure. Each tracer is followed until it either impacts a body or escapes the system, whereupon tracking is continued in the heliocentric frame using an N-body integrator. Various impact scenarios will be explored, along with a number of ejecta particle sizes, with the aim of characterizing the most likely final ejecta dispositions resulting from the DART impact, and the safest vantages from which the AIDA spacecraft can observe this event.

Catastrophic disruption of asteriods and satellites; Proceedings of the International Workshop, Pisa, Italy, July 30-August 2, 1985

NASA Astrophysics Data System (ADS)

Davis, D. R.; Farinella, P.; Paolicchi, P.; Zappala, V.

Theoretical, numerical, and experimental investigations of the violent disruption of asteroids or planetary satellites are discussed in reviews and reports. Topics examined include acceleration techniques and results of experiments simulating catastrophic fragmentation events; laboratory simulations of catastrophic impact; scaling laws for the catastrophic collisions of asteroids; asteroid collisional history, the origin of the Hirayama families, and disruption of small satellites; and the implications of the inferred compositions of a steroids for their collisional evolution. Diagrams, graphs, tables, and a summary of the discussion at the workshop are provided.

Erosive Hit-and-Run Impact Events: Debris Unbound

NASA Astrophysics Data System (ADS)

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

2016-01-01

Erosive collisions among planetary embryos in the inner solar system can lead to multiple remnant bodies, varied in mass, composition and residual velocity. Some of the smaller, unbound debris may become available to seed the main asteroid belt. The makeup of these collisionally produced bodies is different from the canonical chondritic composition, in terms of rock/iron ratio and may contain further shock-processed material. Having some of the material in the asteroid belt owe its origin from collisions of larger planetary bodies may help in explaining some of the diversity and oddities in composition of different asteroid groups.

Comet or asteroid shower in the late Eocene?

PubMed

Tagle, Roald; Claeys, Philippe

2004-07-23

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

Catastrophic disruption of asteriods and satellites; Proceedings of the International Workshop, Pisa, Italy, July 30-August 2, 1985

NASA Technical Reports Server (NTRS)

Davis, D. R. (Editor); Farinella, P. (Editor); Paolicchi, P. (Editor); Zappala, V. (Editor)

1986-01-01

Theoretical, numerical, and experimental investigations of the violent disruption of asteroids or planetary satellites are discussed in reviews and reports. Topics examined include acceleration techniques and results of experiments simulating catastrophic fragmentation events; laboratory simulations of catastrophic impact; scaling laws for the catastrophic collisions of asteroids; asteroid collisional history, the origin of the Hirayama families, and disruption of small satellites; and the implications of the inferred compositions of a steroids for their collisional evolution. Diagrams, graphs, tables, and a summary of the discussion at the workshop are provided.

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.

Autonomous vision-based navigation for proximity operations around binary asteroids

NASA Astrophysics Data System (ADS)

Gil-Fernandez, Jesus; Ortega-Hernando, Guillermo

2018-02-01

Future missions to small bodies demand higher level of autonomy in the Guidance, Navigation and Control system for higher scientific return and lower operational costs. Different navigation strategies have been assessed for ESA's asteroid impact mission (AIM). The main objective of AIM is the detailed characterization of binary asteroid Didymos. The trajectories for the proximity operations shall be intrinsically safe, i.e., no collision in presence of failures (e.g., spacecraft entering safe mode), perturbations (e.g., non-spherical gravity field), and errors (e.g., maneuver execution error). Hyperbolic arcs with sufficient hyperbolic excess velocity are designed to fulfil the safety, scientific, and operational requirements. The trajectory relative to the asteroid is determined using visual camera images. The ground-based trajectory prediction error at some points is comparable to the camera Field Of View (FOV). Therefore, some images do not contain the entire asteroid. Autonomous navigation can update the state of the spacecraft relative to the asteroid at higher frequency. The objective of the autonomous navigation is to improve the on-board knowledge compared to the ground prediction. The algorithms shall fit in off-the-shelf, space-qualified avionics. This note presents suitable image processing and relative-state filter algorithms for autonomous navigation in proximity operations around binary asteroids.

Asteroid diversion considerations and comparisons of diversion techniques

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

Owen, J. Michael; Miller, Paul; Rovny, Jared

The threat of asteroid impacts on Earth poses a low-probability but high consequence risk, with possible outcomes ranging from regional to global catastrophe. However, unique amongst such global threats we have the capability of averting such disasters. Diversion approaches by either kinetic impactor or nuclear energy deposition are the two most practical technologies for mitigating hazardous near Earth asteroids. One of the greatest challenges in understanding our options is the uncertain response of asteroids to such impulsive techniques, due both to our lack of knowledge of the composition and structure of these objects as well as their highly varied nature.more » Predicting whether we will simply divert or break up a given object is a crucial: the weak self-gravity and inferred weak structure of typical asteroids present the strong possibility the body will fragment for modest impulses. Predictive modeling of failure and fragmentation is one important tool for such studies. In this paper we apply advances in modeling failure and fracture using Adaptive Smoothed Particle Hydrodynamics (ASPH) to understand mega-cratering on asteroids as a validation exercise, and show examples of diverting the near Earth asteroid Bennu using both a kinetic impactor and ablative blow-off due to nuclear energy deposition.« less

Asteroid diversion considerations and comparisons of diversion techniques

DOE PAGES

Owen, J. Michael; Miller, Paul; Rovny, Jared; ...

2015-05-19

The threat of asteroid impacts on Earth poses a low-probability but high consequence risk, with possible outcomes ranging from regional to global catastrophe. However, unique amongst such global threats we have the capability of averting such disasters. Diversion approaches by either kinetic impactor or nuclear energy deposition are the two most practical technologies for mitigating hazardous near Earth asteroids. One of the greatest challenges in understanding our options is the uncertain response of asteroids to such impulsive techniques, due both to our lack of knowledge of the composition and structure of these objects as well as their highly varied nature.more » Predicting whether we will simply divert or break up a given object is a crucial: the weak self-gravity and inferred weak structure of typical asteroids present the strong possibility the body will fragment for modest impulses. Predictive modeling of failure and fragmentation is one important tool for such studies. In this paper we apply advances in modeling failure and fracture using Adaptive Smoothed Particle Hydrodynamics (ASPH) to understand mega-cratering on asteroids as a validation exercise, and show examples of diverting the near Earth asteroid Bennu using both a kinetic impactor and ablative blow-off due to nuclear energy deposition.« less

Autonomous vision-based navigation for proximity operations around binary asteroids

NASA Astrophysics Data System (ADS)

Gil-Fernandez, Jesus; Ortega-Hernando, Guillermo

2018-06-01

Future missions to small bodies demand higher level of autonomy in the Guidance, Navigation and Control system for higher scientific return and lower operational costs. Different navigation strategies have been assessed for ESA's asteroid impact mission (AIM). The main objective of AIM is the detailed characterization of binary asteroid Didymos. The trajectories for the proximity operations shall be intrinsically safe, i.e., no collision in presence of failures (e.g., spacecraft entering safe mode), perturbations (e.g., non-spherical gravity field), and errors (e.g., maneuver execution error). Hyperbolic arcs with sufficient hyperbolic excess velocity are designed to fulfil the safety, scientific, and operational requirements. The trajectory relative to the asteroid is determined using visual camera images. The ground-based trajectory prediction error at some points is comparable to the camera Field Of View (FOV). Therefore, some images do not contain the entire asteroid. Autonomous navigation can update the state of the spacecraft relative to the asteroid at higher frequency. The objective of the autonomous navigation is to improve the on-board knowledge compared to the ground prediction. The algorithms shall fit in off-the-shelf, space-qualified avionics. This note presents suitable image processing and relative-state filter algorithms for autonomous navigation in proximity operations around binary asteroids.

Design concepts and options for the Thermal Infrared Imager (TIRI) as part of ESA's Asteroid Impact Mission.

NASA Astrophysics Data System (ADS)

Bowles, Neil; Calcutt, Simon; Licandro, Javier; Reyes, Marcos; Delbo, Marco; Donaldson Hanna, Kerri; Arnold, Jessica; Howe, Chris

2016-04-01

ESA's Asteroid Impact Mission (AIM) is being studied as part of the joint ESA/NASA AIDA mission for launch in 2020. AIDA's primary mission is to investigate the effect of a kinetic impactor on the secondary component of the binary asteroid 65803 Didymos in late 2022. AIM will characterise the Didymos system and monitor the response of the binary system to the impact. A multi-spectral, thermal-infrared imaging instrument (TIRI) will be an essential component of AIM's remote sensing payload, as it will provide key information on the nature of the surfaces (e.g. presence or absence of materials, degree of compaction, and rock abundance of the regolith) of both components in the Didymos system. The temperature maps provided by TIRI will be important for navigation and spacecraft health and safety for proximity/lander operations. By measuring the asteroids' diurnal thermal responses (thermal inertia) and their surface compositions via spectral signatures, TIRI will provide information on the origin and evolution of the binary system. In this presentation we will discuss possible instrument design for TIRI, exploring options that include imaging spectroscopy to broadband imaging. By using thermal models and compositional analogues of the Didymos system we will show how the performance of each design option compares to the wider scientific goals of the AIDA/AIM mission.

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.

Moving Object Detection Using a Parallax Shift Vector Algorithm

NASA Astrophysics Data System (ADS)

Gural, Peter S.; Otto, Paul R.; Tedesco, Edward F.

2018-07-01

There are various algorithms currently in use to detect asteroids from ground-based observatories, but they are generally restricted to linear or mildly curved movement of the target object across the field of view. Space-based sensors in high inclination, low Earth orbits can induce significant parallax in a collected sequence of images, especially for objects at the typical distances of asteroids in the inner solar system. This results in a highly nonlinear motion pattern of the asteroid across the sensor, which requires a more sophisticated search pattern for detection processing. Both the classical pattern matching used in ground-based asteroid search and the more sensitive matched filtering and synthetic tracking techniques, can be adapted to account for highly complex parallax motion. A new shift vector generation methodology is discussed along with its impacts on commonly used detection algorithms, processing load, and responsiveness to asteroid track reporting. The matched filter, template generator, and pattern matcher source code for the software described herein are available via GitHub.

Arecibo Radar Observations of Near-Earth Asteroids

NASA Astrophysics Data System (ADS)

Rivera-Valentin, Edgard G.; Taylor, Patrick A.; Virkki, Anne; Saran Bhiravarasu, Sriram; Venditti, Flaviane; Zambrano-Marin, Luisa Fernanda; Aponte-Hernandez, Betzaida

2017-10-01

The Arecibo S-Band (2.38 GHz, 12.6 cm; 1 MW) planetary radar system at the 305-m William E. Gordon Telescope in Arecibo, Puerto Rico is the most active, most powerful, and most sensitive planetary radar facility in the world. As such, Arecibo is vital for post-discovery characterization and orbital refinement of near-Earth asteroids. Since August 2016, the program has observed 100 near-Earth asteroids (NEAs), of which 38 are classified as potentially hazardous to Earth and 31 are compliant with the NASA Near-Earth Object Human Space Flight Accessible Targets Study (NHATS). Arecibo observations are critical for identifying NEAs that may be on a collision course with Earth in addition to providing detailed physical characterization of the objects themselves in terms of size, shape, spin, and surface properties, which are valuable for assessing impact mitigation strategies. Here, we will present a sampling of the asteroid zoo observed by Arecibo, including press-noted asteroids 2014 JO25 and the (163693) Atira binary system.

Rapid design and optimization of low-thrust rendezvous/interception trajectory for asteroid deflection missions

NASA Astrophysics Data System (ADS)

Li, Shuang; Zhu, Yongsheng; Wang, Yukai

2014-02-01

Asteroid deflection techniques are essential in order to protect the Earth from catastrophic impacts by hazardous asteroids. Rapid design and optimization of low-thrust rendezvous/interception trajectories is considered as one of the key technologies to successfully deflect potentially hazardous asteroids. In this paper, we address a general framework for the rapid design and optimization of low-thrust rendezvous/interception trajectories for future asteroid deflection missions. The design and optimization process includes three closely associated steps. Firstly, shape-based approaches and genetic algorithm (GA) are adopted to perform preliminary design, which provides a reasonable initial guess for subsequent accurate optimization. Secondly, Radau pseudospectral method is utilized to transcribe the low-thrust trajectory optimization problem into a discrete nonlinear programming (NLP) problem. Finally, sequential quadratic programming (SQP) is used to efficiently solve the nonlinear programming problem and obtain the optimal low-thrust rendezvous/interception trajectories. The rapid design and optimization algorithms developed in this paper are validated by three simulation cases with different performance indexes and boundary constraints.

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.

The missing large impact craters on Ceres.

PubMed

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

2016-07-26

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

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

Harris, Alan W.; Drube, Line, E-mail: alan.harris@dlr.de

The metal content of asteroids is of great interest, not only for theories of their origins and the evolution of the solar system but, in the case of near-Earth objects (NEOs), also for impact mitigation planning and endeavors in the field of planetary resources. However, since the reflection spectra of metallic asteroids are largely featureless, it is difficult to identify them and relatively few are known. We show how data from the Wide-field Infrared Survey Explorer (WISE)/NEOWISE thermal-infrared survey and similar surveys, fitted with a simple thermal model, can reveal objects likely to be metal rich. We provide a listmore » of candidate metal-rich NEOs. Our results imply that future infrared surveys with the appropriate instrumentation could discover many more metal-rich asteroids, providing valuable data for assessment of the impact hazard and the potential of NEOs as reservoirs of vital materials for future interplanetary space activities and, eventually perhaps, for use on Earth.« less

The missing large impact craters on Ceres

USGS Publications Warehouse

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

2016-01-01

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

Asteroids IV

NASA Astrophysics Data System (ADS)

Michel, Patrick; DeMeo, Francesca E.; Bottke, William F.

Asteroids are fascinating worlds. Considered the building blocks of our planets, many of the authors of this book have devoted their scientific careers to exploring them with the tools of our trade: ground- and spacebased observations, in situ space missions, and studies that run the gamut from theoretical modeling efforts to laboratory work. Like fossils for paleontologists, or DNA for geneticists, they allow us to construct a veritable time machine and provide us with tantalizing glimpses of the earliest nature of our solar system. By investigating them, we can probe what our home system was like before life or even the planets existed. The origin and evolution of life on our planet is also intertwined with asteroids in a different way. It is believed that impacts on the primordial Earth may have delivered the basic components for life, with biology favoring attributes that could more easily survive the aftermath of such energetic events. In this fashion, asteroids may have banished many probable avenues for life to relative obscurity. Similarly, they may have also prevented our biosphere from becoming more complex until more recent eras. The full tale of asteroid impacts on the history of our world, and how human life managed to emerge from myriad possibilities, has yet to be fully told. The hazard posed by asteroid impacts to our civilization is low but singular. The design of efficient mitigation strategies strongly relies on asteroid detection by our ground- and spacebased surveys as well as knowledge of their physical properties. A more positive motivation for asteroid discovery is that the proximity of some asteroids to Earth may allow future astronauts to harvest their water and rare mineral resources for use in exploration. A key goal of asteroid science is therefore to learn how humans and robotic probes can interact with asteroids (and extract their materials) in an efficient way. We expect that these adventures may be commonplace in the future. Asteroids, like planets, are driven by a great variety of both dynamical and physical mechanisms. In fact, images sent back by space missions show a collection of small worlds whose characteristics seem designed to overthrow our preconceived notions. Given their wide range of sizes and surface compositions, it is clear that many formed in very different places and at different times within the solar nebula. These characteristics make them an exciting challenge for researchers who crave complex problems. The return of samples from these bodies may ultimately be needed to provide us with solutions. In the book Asteroids IV, the editors and authors have taken major strides in the long journey toward a much deeper understanding of our fascinating planetary ancestors. This book reviews major advances in 43 chapters that have been written and reviewed by a team of more than 200 international authorities in asteroids. It is aimed to be as comprehensive as possible while also remaining accessible to students and researchers who are interested in learning about these small but nonetheless important worlds. We hope this volume will serve as a leading reference on the topic of asteroids for the decade to come. We are deeply indebted to the many authors and referees for their tremendous efforts in helping us create Asteroids IV. We also thank the members of the Asteroids IV scientific organizing committee for helping us shape the structure and content of the book. The conference associated with the book, "Asteroids Comets Meteors 2014" held June 30-July 4, 2014, in Helsinki, Finland, did an outstanding job of demonstrating how much progress we have made in the field over the last decade. We are extremely grateful to our host Karri Muinonnen and his team. The editors are also grateful to the Asteroids IV production staff, namely Renée Dotson and her colleagues at the Lunar and Planetary Institute, for their efforts, their invaluable assistance, and their enthusiasm; they made life as easy and pleasant as possible for the editors, authors, and referees. They also thank Richard Binzel, the General Editor of the Space Science Series, for his strong support and advice during this process, as well as the staff at the University of Arizona Press. Finally, editor Patrick Michel would like to thank his wife Delphine, who married him on June 14, 2013, almost at the birth of the book process. He is grateful that she was willing to put up with him as he spent many of his nights and weekends working on the book. Thanks to her support, their trajectories are as bounded as a perfectly stable asteroid binary system, and this was probably the best way to experience from the start what her life would be like with a researcher! Co-editor Bottke would also like to thank his wife Veronica and his children Kristina-Marie, Laura, and Julie, who make up his own favorite asteroid family. Since Asteroids III, the size distribution of the family members has been steadily changing, and who knows how many tiny new members it will contain by Asteroids V! Co-editor DeMeo would like to thank her husband Alfredo for his support and encouragement throughout the process of creating this book. They met at the beginning of her career in research, becoming an asteroid pair and now continuing on the same orbit in life.

Ruling out Virtual Impactors with Negative Observations

NASA Astrophysics Data System (ADS)

Milani, A.; Chesley, S. R.; Boattini, A.; Valsecchi, G. B.

1999-09-01

If, for an asteroid which has been observed only over a short arc then lost, there are orbits compatible with the observations resulting in collisions, recovery would be desirable to decide if it will actually impact. If recovery is essentially impractical, as is the case for many small asteroids in the 100 m to 500 m diameter range, the next best thing is to make sure that the lost asteroid is not on a collision course. We propose a method to achieve this guarantee, with an observational effort far smaller than the one required for recovery. The procedure involves the computation of an orbit which is compatible with the available observations and, by hypothesis, results in an impact at some later encounter; this we call a Virtual Impactor (VI). The collision at some future time is a strong constraint, thus the VI has a well determined orbit. We show that it is possible to compute for each given time of observation the skyprint of the VI, that is the set of astrometric positions compatible with an impact (or a near impact). The skyprint needs to be scanned by powerful enough telescopes to perform a negative observation; once this has been done for the skyprints of all VIs, collisions can be excluded even without recovery. We propose to apply this procedure to the case of the lost asteroid 1998 OX_4, for which we have found orbital solutions with impacts in the years 2014, 2038, 2044 and 2046. Suitable observing windows are found when the VI would be close to the Earth in 2001 and in 2003, and the corresponding skyprints are small enough to be covered with very few frames. This procedure might become more and more necessary in the future, as the number of discoveries of small potentially hazardous asteroids increases; we discuss the general principles and the validation procedures that should apply to such a VI removal campaign. This research has been funded by the Italian Space Agency (ASI), by a NATO fellowship, by Consiglio Nazionale delle Ricerche (CNR), by the University of Pisa, and by the Spaceguard Foundation.

Asteroidal versus cometary meteoroid impacts on the Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

Zook, Herbert A.

1992-01-01

Meteoroids that enter the Earth's atmosphere at low velocities will tend to impact the apex side (that surface facing the spacecraft direction of motion) of a spacecraft at a very high rate compared to the rate with which they will impact an antapex-facing surface. This ratio -- apex to antapex impact rates -- will become less as meteoroid entry velocities increase. The measured ratio, apex to antapex, for 500 micron diameter impact craters in 6061-T6 aluminum on LDEF seems to be about 20 from the work of the meteoroid SIG group and from the work of Humes that was presented at the first LDEF symposium. Such a ratio is more consistent with the meteoroid velocity distributions derived by Erickson and by Kessler, than it is with others that have been tested. These meteoroid velocity distributions have mean entry velocities into the Earth's atmosphere of 16.5 to 16.9 km/s. Jackson and Zook (in a paper submitted to Icarus) have numerically simulated the orbital evolution of small dust grains emitted from asteroids and comets. For those asteroidal grains small enough (below about 100 microns diameter) to drift from the asteroid belt to the orbit of the Earth, under P-R and solar wind drag, without suffering collisional destruction, the following results are found: as their ascending or descending nodes cross the Earth's orbit (and when they might collide with the Earth), their orbital eccentricities and inclinations are quite low (e less than 0.3, i less than 20 degrees), and their mean velocity with respect to the Earth is about 5 or 6 km/s. When gravitational acceleration of the Earth is taken into account, the corresponding mean velocities relative to the top of the Earth's atmosphere are 12 to 13 km/s. This means that, at best, these small asteroidal particles can not comprise more than 50 percent of the particles entering the Earth's atmosphere. And when gravitational focusing is considered, they cannot comprise more than a few percent of those in heliocentric orbit at 1 AU. The rest are presumably of cometary origin.

The Spherical Brazil Nut Effect and its Significance to Asteroids

NASA Astrophysics Data System (ADS)

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

2015-11-01

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

Yarkovsky-driven Impact Predictions: Apophis and 1950 DA

NASA Astrophysics Data System (ADS)

Farnocchia, Davide; Chesley, S. R.; Chodas, P.; Milani, A.

2013-05-01

Abstract (2,250 Maximum Characters): Orbit determination for Near-Earth Asteroids presents unique technical challenges due to the imperative of early detection and careful assessment of the risk posed by specific Earth close approaches. The occurrence of an Earth impact can be decisively driven by the Yarkovsky effect, which is the most important nongravitational perturbation as it causes asteroids to undergo a secular variation in semimajor axis resulting in a quadratic effect in anomaly. We discuss the cases of (99942) Apophis and (29075) 1950 DA. The relevance of the Yarkovsky effect for Apophis is due to a scattering close approach in 2029 with minimum geocentric distance ~38000 km. For 1950 DA the influence of the Yarkovsky effect in 2880 is due to the long time interval preceding the impact. We use the available information on the asteroids' physical models as a starting point for a Monte Carlo method that allow us to measure how the Yarkovsky effect affects orbital predictions. For Apophis we map onto the 2029 close approach b-plane and analyze the keyholes corresponding to resonant close approaches. For 1950 DA we use the b-plane corresponding to the possible impact in 2880. We finally compute the impact probability from the mapped probability density function on the considered b-plane.

Climatic Effects of Medium-Sized Asteroid Impacts on Land

NASA Astrophysics Data System (ADS)

Bardeen, C.; Garcia, R. R.; Toon, O. B.; Otto-Bliesner, B. L.; Wolf, E. T.

2015-12-01

Using the Community Earth System Model (CESM), a three-dimensional coupled climate model with interactive chemistry, we have simulated the climate response to a medium-sized (1 km) asteroid impact on the land. An impact of this size would cause local fires and may also generate submicron dust particles. Dust aerosols are injected into the upper atmosphere where they persist for ~3 years. Soot aerosols from fires are injected into the troposphere and absorb solar radiation heating the air which helps loft the soot into the stratosphere where it persists for ~10 years. Initially, these aerosols cause a heating of over 240 K in the stratosphere and up to a 70% reduction in downwelling solar radiation at the surface. Global average surface temperature cools by as much as -8.5 K, ocean temperature cools by -4.5 K, precipitation is reduced by 50%, and the ozone column is reduced by 55%. The surface UV Index exceeds 20 in the tropics for several years. These changes represent a significant hazard to life on a global scale. These results extend the work of Pierazzo et al. (2010), also using CESM, which found a significant impact on stratospheric ozone, but little change in surface temperature or precipitation, from a 1 km asteroid impact in the ocean.

Natural and Artificial Satellite Dynamics and Evolution around Near-Earth Asteroids with Solar Radiation Pressure

NASA Astrophysics Data System (ADS)

Rieger, Samantha M.

Natural and artificial satellites are subject to perturbations when orbiting near-Earth asteroids. These perturbations include non-uniform gravity from the asteroid, third-body disturbances from the Sun, and solar radiation pressure. For small natural (1 cm-15 m) and artificial satellites, solar radiation pressure is the primary perturbation that will cause their orbits to go unstable. For the asteroid Bennu, the future target of the spacecraft OSIRIS-REx, the possibility of natural satellites having stable orbits around the asteroid and characterize these stable regions is investigated. It has been found that the main orbital phenomena responsible for the stability or instability of these possible natural satellites are Sun-synchronous orbits, the modified Laplace plane, and the Kozai resonance. These findings are applied to other asteroids as well as to artificial satellites. The re-emission of solar radiation pressure through BYORP is also investigated for binary asteroid systems. Specifically, the BYORP force is combined with the Laplace plane such that BYORP expands the orbit of the binary system along the Laplace surface where the secondary increases in inclination. For obliquities from 68.875° - 111.125° the binary will eventually extend into the Laplace instability region, where the eccentricity of the orbit will increase. A subset of the instability region leads to eccentricities high enough that the secondary will impact the primary. This result inspired the development of a hypothesis of a contact-binary binary cycle described briefly in the following. YORP will increase the spin rate of a contact binary while also driving the spin-pole to an obliquity of 90°. Eventually, the contact binary will fission. The binary will subsequently become double-synchronous, thus allowing the BYORP acceleration to have secular effects on the orbit. The orbit will then expand along the Laplace surface to the Laplace plane instability region eventually leading to an impact and the start of a new cycle with the YORP process.

Collision lifetimes and impact statistics of near-Earth asteroids

NASA Technical Reports Server (NTRS)

Bottke, W. F., Jr.; Nolan, M. C.; Greenberg, R.

1993-01-01

We have examined the lifetimes of Near-Earth asteroids (NEA's) by directly computing the collision probabilities with other asteroids and with the terrestrial planets. We compare these to the dynamical lifetimes, and to collisional lifetimes assumed by other workers. We discuss the implications of the differences. The lifetimes of NEA's are important because, along with the statistics of craters on the Earth and Moon, they help us to compute the number of NEA's and the rate at which new NEA's are brought to the vicinity of the Earth. Assuming that the NEA population is in steady-state, the lifetimes determine the flux of new bodies needed to replenish the population. Earlier estimates of the lifetimes ignored (or incompletely accounted for) the differences in the velocities of asteroids as they move in their orbits, so our results differ from (for example) Greenberg and Chapman (1983, Icarus 55, 455) and Wetherill (1988, Icarus 76, 1) by factors of 2 to 10. We have computed the collision rates and relative velocities of NEA's with each other, the main-belt asteroids, and the terrestrial planets, using the corrected method described by Bottke et. al. (1992, GRL, in press). We find that NEA's typically have shorter collisional lifetimes than do main-belt asteroids of the same size, due to their high eccentricities, which typically give them aphelia in the main belt. Consequently, they spend a great deal of time in the main belt, and are moving much slower than the bodies around them, making them 'sitting ducks' for impacts with other asteroids. They cross the paths of many objects, and their typical collision velocities are much higher (10-15 km/s) than the collision velocities (5 km/s) among objects within the main belt. These factors combine to give them substantially shorter lifetimes than had been previously estimated.

Top 10 astronomy stories of 2005

NASA Astrophysics Data System (ADS)

Reddy, Francis

2006-01-01

Spacecraft explored two planets and touched a comet, while astronomers puzzled over an errant asteroid, larger galaxies, and a titanic explosion in space. (10) Blast from beyond; (9) Exoplanet surprises; (8) An asteroid among us; (7) Return to space; (6) A year at Saturn ... (5) ... and two at Mars; (4) Deep impact; (3) Bigger, better galaxies; (2) The tenth planet; (1) Huygens lands on Titan.

Oxygen Isotope Composition of Almahata Sitta

NASA Technical Reports Server (NTRS)

Rumble, D.; Zolensky, M. E.; Friedrich, J. M.; Jenniskens, P.; Shaddad, M. H.

2010-01-01

The name Almahata Sitta is applied collectively to some hundreds of stones that were found in a linear strewn field in the Nubian Desert coincident with the projected Earth-impacting orbit of the Asteroid 2008 TC3. Fragments of the meteorite were collected in December 2008 and March 2009, 2 to 5 months after the asteroid exploded in Earths atmosphere on 7 October 2008.

The Small Carry-on Impactor (SCI) and the Hayabusa2 Impact Experiment

NASA Astrophysics Data System (ADS)

Saiki, T.; Imamura, H.; Arakawa, M.; Wada, K.; Takagi, Y.; Hayakawa, M.; Shirai, K.; Yano, H.; Okamoto, C.

2017-07-01

Hayabusa2 is a sample return mission of JAXA launched on 3 December 2014. Hayabusa2 is the successor of Hayabusa, which returned samples from the asteroid Itokawa to the Earth. Although the design of Hayabusa2 follows that of Hayabusa, the former is equipped with some new components. The small carry-on impactor (SCI) is one of those components. The SCI is a compact kinetic impactor designed to remove the asteroid surface regolith locally and create an artificial crater. One of the most important scientific objectives of Hayabusa2 is to investigate the chemical and physical properties of the internal materials and structures of the target body, asteroid Ryugu. Hayabusa2 will attempt to observe the resultant crater with some scientific instruments and to get samples from around the crater. High kinetic energy is required to create a meaningful crater, however, the impact system design needs to fit within strict constraints. Complicated functions, such as a guidance and control system, are not permitted. A special type of shaped charge is used for the acceleration of the impactor of the SCI in order to make system simpler. Using this explosion technique makes it possible to accelerate the impactor very quickly and to hit the asteroid without a guidance system. However, the impact operation will be complicated because the explosive is very powerful and it scatters high-speed debris at the detonation. This paper describes an overview of the SCI system, the results of the development testing and an outline of the impact experiment of the Hayabusa2 mission.

Global environmental effects of impact-generated aerosols: Results from a general circulation model

NASA Technical Reports Server (NTRS)

Covey, C.; Ghan, S. J.; Weissman, Paul R.

1988-01-01

Cooling and darkening at Earth's surface are expected to result from the interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet, according to the one-dimensional radioactive-convective atmospheric model (RCM) of Pollack et al. An analogous three-dimensional general circulation model (GCM) simulation obtains the same basic result as the RCM but there are important differences in detail. In the GCM simulation the heat capacity of the oceans, not included in the RCM, substantially mitigates land surface cooling. On the other hand, the GCM's low heat capacity surface allows surface temperatures to drop much more rapidly than reported by Pollack et al. These two differences between RCM and GCM simulations were noted previously in studies of nuclear winter; GCM results for comet/asteroid winter, however, are much more severe than for nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on Earth. In the simulation the global average of land surface temperature drops to the freezing point in just 4.5 days, one-tenth the time required in the Pollack et al. simulation. In addition to the standard case of Pollack et al., which represents the collision of a 10-km diameter asteroid with Earth, additional scenarios are considered ranging from the statistically more frequent impacts of smaller asteroids to the collision of Halley's comet with Earth. In the latter case the kinetic energy of impact is extremely large due to the head-on collision resulting from Halley's retrograde orbit.

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

PubMed

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

2004-07-15

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

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 Gao-Guenie impact melt breccia—Sampling a rapidly cooled impact melt dike on an H chondrite asteroid?

NASA Astrophysics Data System (ADS)

Schmieder, Martin; Kring, David A.; Swindle, Timothy D.; Bond, Jade C.; Moore, Carleton B.

2016-06-01

The Gao-Guenie H5 chondrite that fell on Burkina Faso (March 1960) has portions that were impact-melted on an H chondrite asteroid at ~300 Ma and, through later impact events in space, sent into an Earth-crossing orbit. This article presents a petrographic and electron microprobe analysis of a representative sample of the Gao-Guenie impact melt breccia consisting of a chondritic clast domain, quenched melt in contact with chondritic clasts, and an igneous-textured impact melt domain. Olivine is predominantly Fo80-82. The clast domain contains low-Ca pyroxene. Impact melt-grown pyroxene is commonly zoned from low-Ca pyroxene in cores to pigeonite and augite in rims. Metal-troilite orbs in the impact melt domain measure up to ~2 mm across. The cores of metal orbs in the impact melt domain contain ~7.9 wt% of Ni and are typically surrounded by taenite and Ni-rich troilite. The metallography of metal-troilite droplets suggest a stage I cooling rate of order 10 °C s-1 for the superheated impact melt. The subsolidus stage II cooling rate for the impact melt breccia could not be determined directly, but was presumably fast. An analogy between the Ni rim gradients in metal of the Gao-Guenie impact melt breccia and the impact-melted H6 chondrite Orvinio suggests similar cooling rates, probably on the order of ~5000-40,000 °C yr-1. A simple model of conductive heat transfer shows that the Gao-Guenie impact melt breccia may have formed in a melt injection dike ~0.5-5 m in width, generated during a sizeable impact event on the H chondrite parent asteroid.

Catastrophic Disruption Threshold and Maximum Deflection from Kinetic Impact

NASA Astrophysics Data System (ADS)

Cheng, A. F.

2017-12-01

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

Hazards on Hazards, Ensuring Spacecraft Safety While Sampling Asteroid Surface Materials

NASA Astrophysics Data System (ADS)

Johnson, C. A.; DellaGiustina, D. N.

2016-12-01

The near-Earth object Bennu is a carbonaceous asteroid that is a remnant from the earliest stages of the solar-system formation. It is also a potentially hazardous asteroid with a relatively high probability of impacting Earth late in the 22nd century. While the primary focus of the NASA funded OSIRIS-REx mission is the return of pristine organic material from the asteroid's surface, information about Bennu's physical and chemical properties gleaned throughout operations will be critical for a possible future impact mitigation mission. In order to ensure a regolith sample can be successfully acquired, the sample site and surrounding area must be thoroughly assessed for any potential hazards to the spacecraft. The OSIRIS-REx Image Processing Working Group has been tasked with generating global and site-specific hazard maps using mosaics and a trio of fea­­­ture identification techniques. These techniques include expert-lead manual classification, internet-based amateur classification using the citizen science platform CosmoQuest, and automated classification using machine learning and computer vision tools. Because proximity operations around Bennu do not begin until the end of 2018, we have an opportunity to test t­­­he performance of our software on analogue surfaces of other asteroids from previous NASA and other space agencies missions. The entire pipeline from image processing and mosaicking to hazard identification, analysis and mapping will be performed on asteroids of varying size, shape and surface morphology. As a result, upon arrival at Bennu, we will have the software and processes in place to quickly and confidently produce the hazard maps needed to ensure the success of our mission.

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.

Data Report: A Search for Deposits of the Late Pliocene Impact of the Eltanin Asteroid in Rise Sediments from the Antarctic Peninsula, Site 1096

NASA Technical Reports Server (NTRS)

Kyte, Frank T.

2003-01-01

Concentrations of Ir have been measured in 87 sediment samples from Ocean Drilling Program Site 1096 in search of evidence of fallout from the impact of the Eltanin asteroid, which occurred at 2.15 Ma, approx. 1300 km northwest of the site. An additional six samples were measured from a unique sand layer and adjacent sediments that are dated at approx. 1.6 Ma. These 93 sediment samples are all silts and muds that were deposited on a continental rise drift of the Antarctic Peninsula. No evidence of the Eltanin impact deposit was found in this study.

Asteroid Origins Satellite (AOSAT) I: An On-orbit Centrifuge Science Laboratory

NASA Astrophysics Data System (ADS)

Lightholder, Jack; Thoesen, Andrew; Adamson, Eric; Jakubowski, Jeremy; Nallapu, Ravi; Smallwood, Sarah; Raura, Laksh; Klesh, Andrew; Asphaug, Erik; Thangavelautham, Jekan

2017-04-01

Exploration of asteroids, comets and small moons (small bodies) can answer fundamental questions relating to the formation of the solar system, the availability of resources, and the nature of impact hazards. Near-earth asteroids and the small moons of Mars are potential targets of human exploration. But as illustrated by recent missions, small body surface exploration remains challenging, expensive, and fraught with risk. Despite their small size, they are among the most extreme planetary environments, with low and irregular gravity, loosely bound regolith, extreme temperature variation, and the presence of electrically charged dust. Here we describe the Asteroid Origins Satellite (AOSAT-I), an on-orbit, 3U CubeSat centrifuge using a sandwich-sized bed of crushed meteorite fragments to replicate asteroid surface conditions. Demonstration of this CubeSat will provide a low-cost pathway to physical asteroid model validation, shed light on the origin and geophysics of asteroids, and constrain the design of future landers, rovers, resource extractors, and human missions. AOSAT-I will conduct scientific experiments within its payload chamber while operating in two distinct modes: (1) as a nonrotating microgravity laboratory to investigate primary accretion, and (2) as a rotating centrifuge producing artificial milligravity to simulate surface conditions on asteroids, comets and small moons. AOSAT-I takes advantage of low-cost, off-the-shelf components, modular design, and the rapid assembly and instrumentation of the CubeSat standard, to answer fundamental questions in planetary science and reduce cost and risk of future exploration.

Thermal Tomography of Asteroid Surface Structure

NASA Astrophysics Data System (ADS)

Harris, Alan W.; Drube, Line

2016-12-01

Knowledge of the surface thermal inertia of an asteroid can provide insight into its surface structure: porous material has a lower thermal inertia than rock. We develop a means to estimate thermal inertia values of asteroids and use it to show that thermal inertia appears to increase with spin period in the case of main-belt asteroids (MBAs). Similar behavior is found on the basis of thermophysical modeling for near-Earth objects (NEOs). We interpret our results in terms of rapidly increasing material density and thermal conductivity with depth, and provide evidence that thermal inertia increases by factors of 10 (MBAs) to 20 (NEOs) within a depth of just 10 cm. Our results are consistent with a very general picture of rapidly changing material properties in the topmost regolith layers of asteroids and have important implications for calculations of the Yarkovsky effect, including its perturbation of the orbits of potentially hazardous objects and those of asteroid family members after the break-up event. Evidence of a rapid increase of thermal inertia with depth is also an important result for studies of the ejecta-enhanced momentum transfer of impacting vehicles (“kinetic impactors”) in planetary defense.

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

NASA Technical Reports Server (NTRS)

Deshpande, Manohar

2011-01-01

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

THERMAL TOMOGRAPHY OF ASTEROID SURFACE STRUCTURE

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

Harris, Alan W.; Drube, Line, E-mail: alan.harris@dlr.de

Knowledge of the surface thermal inertia of an asteroid can provide insight into its surface structure: porous material has a lower thermal inertia than rock. We develop a means to estimate thermal inertia values of asteroids and use it to show that thermal inertia appears to increase with spin period in the case of main-belt asteroids (MBAs). Similar behavior is found on the basis of thermophysical modeling for near-Earth objects (NEOs). We interpret our results in terms of rapidly increasing material density and thermal conductivity with depth, and provide evidence that thermal inertia increases by factors of 10 (MBAs) tomore » 20 (NEOs) within a depth of just 10 cm. Our results are consistent with a very general picture of rapidly changing material properties in the topmost regolith layers of asteroids and have important implications for calculations of the Yarkovsky effect, including its perturbation of the orbits of potentially hazardous objects and those of asteroid family members after the break-up event. Evidence of a rapid increase of thermal inertia with depth is also an important result for studies of the ejecta-enhanced momentum transfer of impacting vehicles (“kinetic impactors”) in planetary defense.« less

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

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

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

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

Comparison of the orbital properties of Jupiter Trojan asteroids and Trojan dust

NASA Astrophysics Data System (ADS)

Liu, Xiaodong; Schmidt, Jrgen

2018-06-01

In a previous paper we simulated the orbital evolution of dust particles from the Jupiter Trojan asteroids ejected by the impacts of interplanetary particles, and evaluated their overall configuration in the form of dust arcs. Here we compare the orbital properties of these Trojan dust particles and the Trojan asteroids. Both Trojan asteroids and most of the dust particles are trapped in the Jupiter 1:1 resonance. However, for dust particles, this resonance is modified because of the presence of solar radiation pressure, which reduces the peak value of the semi-major axis distribution. We find also that some particles can be trapped in the Saturn 1:1 resonance and higher order resonances with Jupiter. The distributions of the eccentricity, the longitude of pericenter, and the inclination for Trojans and the dust are compared. For the Trojan asteroids, the peak in the longitude of pericenter distribution is about 60 degrees larger than the longitude of pericenter of Jupiter; in contrast, for Trojan dust this difference is smaller than 60 degrees, and it decreases with decreasing grain size. For the Trojan asteroids and most of the Trojan dust, the Tisserand parameter is distributed in the range of two to three.

The “Main-Belt Comets” are not comets, nor active asteroids; they are temporary shaken asteroids

NASA Astrophysics Data System (ADS)

Tancredi, Gonzalo

2015-08-01

Several objects in asteroidal orbits have presented comaes and tails similar to the ones presented by comets for short period of times. There are at present 16 objects in this group. Several hypotheses have been proposed to explain the activity of this object [Jewitt 2012]. Among them, the most accepted scenario for many objects is the ice sublimation and the ejection of dust, in a similar way as the cometary activity. Therefore several authors have coined these objects “Main Belt Comets” [Hsieh & Jewitt 2006]. Nevertheless, in some cases, some authors have concluded that the ejection of dust must be due to an impact.We propose an alternative model for the formation of the dusty comaes and tails.The impact of a small body against a larger one initially produces a crater and the ejection of dust at high velocity (>100 m/s). The dust is rapidly dispersed and it should be only observable just after the impact. In addition the impact generates a shock wave, which propagates to the body interior. The asteroid is globally shaken. Material is ejected at low velocities from the entire surface, similar to the low escape velocities at the surface. The particles move away from the asteroid due to the solar radiation pressure, forming the thin tails aligned with the orbital plane. These tails could persist for various months, as they have been seen in these objects.In addition, chunks of rock could be ejected in suborbital flights lasting for days; which, at return they would induce a new low-velocity ejection of particles. This process can explain some of the long-lasting events.The recurrence of the activity for some objects could be explained due to the collision with a dense meteor shower present in the main-belt.The so-called “Main Belt Comets” could be explained with a hypothesis that does not require the presence of ice on the surface of these objects. We also do not favor the term “Activated asteroids”, because it implies some kind of endogenous process. The objects are plain asteroids that suffered a recent collision, and the entire body is shaken, ejecting dust from the surface at low velocities.

Near Earth Asteroid redirect missions based on gravity assist maneuver

NASA Astrophysics Data System (ADS)

Ledkov, Anton; Shustov, Boris M.; Eismont, Natan; Boyarsky, Michael; Nazirov, Ravil; Fedyaev, Konstantin

During last years several events attracted world community attention to the hazards of hitting the Earth by sky objects. One of these objects is Apophis asteroid what was expected with nonzero probability to hit the Earth in 2036. Luckily after more precise measurements this event is considered as practically improbable. But the other object has really reached the Earth, entered the atmosphere in the Chelyabinsk area and caused vast damages. After this the hazardous near Earth objects problem received practical confirmation of the necessity to find the methods of its resolution. The methods to prevent collision of the dangerous sky object with the Earth proposed up to now look not practical enough if one mentions such as gravitational tractor or changing the reflectivity of the asteroid surface. Even the method supposing the targeting of the spacecraft to the hazardous object in order to deflect it from initial trajectory by impact does not work because its low mass as compared with the mass of asteroid to be deflected. For example the mass of the Apophis is estimated to be about 40 million tons but the spacecraft which can be launched to intercept the asteroid using contemporary launchers has the mass not more than 5 tons. So the question arises where to find the heavier projectile which is possible to direct to the dangerous object? The answer proposed in our paper is very simple: to search it among small near Earth asteroids. As small ones we suppose those which have the cross section size not more than 12-15 meters and mass not exceeding 1500 -1700 tons. According to contemporary estimates the number of such asteroids is not less than 100000. The other question is how to redirect such asteroid to the dangerous one. In the paper the possibilities are studied to use for that purpose gravity assist maneuvers near Earth. It is shown that even among asteroids included in contemporary catalogue there are the ones which could be directed to the trajectory of the gravity assist maneuver near Earth resulted by following impact with dangerous asteroid. As example of the last one the Apophis was chosen. The required delta-V pulse to be applied to the candidate projectile asteroid to fulfill mentioned change of initial trajectory was confirmed to be comparatively small: not exceeding 10 m/s, and the smallest is about 2 m/s. To fulfilled this maneuver it is necessary to land and to mount on the surface of the asteroid projectile the spacecraft with sufficient amount of propellant onboard. The possible trajectories and demanded maneuvers were explored and it was confirmed that for contemporary space technology it is doable for the small asteroids belonging to the determined by our studies list of candidates supposing some reservations, namely the mass of the found asteroids. This was not considered as decisive obstacle because up to now only about 1% of small enough asteroids are included in catalogue so the list of the appropriate ones is far from to be closed. The studies have been fulfilled aimed to develop the methods to reached required accuracies of asteroid projectile trajectory parameters determination. With existing methods used for the usual spacecraft the limits of achievable accuracies demand the corrections delta-V maneuvers which may exceed the nominal ones. As a result the proposed conception of hazardous asteroids deflection becomes problematic. To overcome this obstacle in the paper new method of trajectory parameters determination is proposed and explored. Practically it is radio interferometer method when one transponder is placed on the asteroid target and two others together with the asteroid projectile form tetrahedron. This system begins to operate in vicinity of target asteroid in autonomous regime and expected to allow reaching the demanded low enough correction maneuver values. Paper gives the estimations of the accuracy of these three bodies relative motion parameters and expected limit values of correction maneuvers needed for hitting the target object. As additional option of planetary defense system construction the idea to redirect small near Earth asteroids onto the orbits resonance with the Earth orbit is explored. It is shown that it is possible to reach it by the use gravity assist maneuvers as it was described above by applying small velocity impulses to the asteroids. At least 11 asteroids were found demanded small enough delta-V for transferring them on such trajectories. After executing these maneuvers one can receive the system of asteroids approaching to the Earth practically each month with a possibility to use them as projectiles or for the purposes of delivering to the Earth their soil samples.

Sky Survey Detected This Small Asteroid

NASA Image and Video Library

2017-06-30

This frame from a sequence of four images taken during one night of observation by NASA's Catalina Sky Survey near Tucson, Arizona, shows the speck of light that moves relative to the background stars is a small asteroid that was, at the time, about as far away as the moon. This asteroid, named 2014 AA, was the second one ever detected on course to impact Earth. It was estimated to be about 6 to 10 feet (2 to 3 meters) in diameter, and it harmlessly hit Earth's atmosphere over the Atlantic Ocean about 20 hours after its discovery in these images. The images were taken Jan. 1, 2014. They provide an example of how asteroids are typically discovered by detection of their motion relative to background stars. An animation is available at https://photojournal.jpl.nasa.gov/catalog/PIA21712

Near Earth Asteroid Characteristics for Asteroid Threat Assessment

NASA Technical Reports Server (NTRS)

Dotson, Jessie

2015-01-01

Information about the physical characteristics of Near Earth Asteroids (NEAs) is needed to model behavior during atmospheric entry, to assess the risk of an impact, and to model possible mitigation techniques. The intrinsic properties of interest to entry and mitigation modelers, however, rarely are directly measureable. Instead we measure other properties and infer the intrinsic physical properties, so determining the complete set of characteristics of interest is far from straightforward. In addition, for the majority of NEAs, only the basic measurements exist so often properties must be inferred from statistics of the population of more completely characterized objects. We will provide an assessment of the current state of knowledge about the physical characteristics of importance to asteroid threat assessment. In addition, an ongoing effort to collate NEA characteristics into a readily accessible database for use by the planetary defense community will be discussed.

Mapping Near-Earth Hazards

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-06-01

How can we hunt down all the near-Earth asteroids that are capable of posing a threat to us? A new study looks at whether the upcoming Large Synoptic Survey Telescope (LSST) is up to the job.Charting Nearby ThreatsLSST is an 8.4-m wide-survey telescope currently being built in Chile. When it goes online in 2022, it will spend the next ten years surveying our sky, mapping tens of billions of stars and galaxies, searching for signatures of dark energy and dark matter, and hunting for transient optical events like novae and supernovae. But in its scanning, LSST will also be looking for asteroids that approach near Earth.Cumulative number of near-Earth asteroids discovered over time, as of June 16, 2016. [NASA/JPL/Chamberlin]Near-Earth objects (NEOs) have the potential to be hazardous if they cross Earths path and are large enough to do significant damage when they impact Earth. Earths history is riddled with dangerous asteroid encounters, including the recent Chelyabinsk airburst in 2013, the encounter that caused the kilometer-sized Meteor Crater in Arizona, and the impact thought to contribute to the extinction of the dinosaurs.Recognizing the potential danger that NEOs can pose to Earth, Congress has tasked NASA with tracking down 90% of NEOs larger than 140 meters in diameter. With our current survey capabilities, we believe weve discovered roughly 25% of these NEOs thus far. Now a new study led by Tommy Grav (Planetary Science Institute) examines whether LSST will be able to complete this task.Absolute magnitude, H, of asynthetic NEO population. Though these NEOs are all larger than 140 m, they have a large spread in albedos. [Grav et al. 2016]Can LSST Help?Based on previous observations of NEOs and resulting predictions for NEO properties and orbits, Grav and collaborators simulate a synthetic population of NEOs all above 140 m in size. With these improved population models, they demonstrate that the common tactic of using an asteroids absolute magnitude as a proxy for its size is a poor approximation, due to asteroids large spread in albedos. Roughly 23% of NEOs larger than 140 m have absolute magnitudes fainter than H = 22 mag, the authors show which is the value usually assumed as the default absolute magnitude of a 140 m NEO.Fraction of NEOs weve detected as a function of time based on the authors simulations of the current surveys (red), LSST plus the current surveys (black), NEOCam plus the current surveys (blue), and the combined result for all surveys (green). [Grav et al. 2016]Taking this into account, Grav and collaborators then use information about the planned LSST survey strategies and detection limits to test what fraction of this synthetic NEO population LSST will be able to detect in its proposed 10-year mission.The authors find that, within 10 years, LSST will likely be able to detect only 63% of NEOs larger than 140 m. Luckily, LSST may not have to work alone; in addition to the current surveys in operation, a proposed infrared space-based survey mission called NEOCam is planned for launch in 2021. If NEOCam is funded, it will complement LSSTs discovery capabilities, potentially allowing the two surveys to jointly achieve the 90% detection goal within a decade.CitationT. Grav et al 2016 AJ 151 172. doi:10.3847/0004-6256/151/6/172

Lightcurve Analysis of 932 Hooveria

NASA Astrophysics Data System (ADS)

Warner, Brian D.; Sada, Pedro V.; Pollock, J.; Reichart, Daniel; Ivarsen, Ivan; Haislip, Josh; Lacluyze, Aaron; Nysewander, Melissa

2010-10-01

CCD observations of the main-belt asteroid 932 Hooveria in 2010 February and March led to a lightcurve with a synodic period of P = 39.15 ± 0.05 h. This contradicted a period of 30 h (Sada, 2004). Re-analysis of the Sada data set gives P = 39.23 ± 0.02 h, putting the two periods in fairly close agreement.

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

NASA Astrophysics Data System (ADS)

Rivkin, A.

2015-12-01

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

Initial Results on the Meteoritic Component of new Sediment Cores Containing Deposits of the Eltanin Impact Event

NASA Technical Reports Server (NTRS)

Kyte, Frank T.; Gersonde, Rainer; Kuhn, Gerhard

2002-01-01

The late Pliocene impact of the Eltanin asteroid is the only known asteroid impact in a deep- ocean (-5 km) basin . This was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta. The latter is composed of shock-melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstern returned to the impact area during expedition ANT XVIIU5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a region of about 80,000 square km. To date we have measured Ir concentrations in sediments from seven of the new cores and preliminary data should be available for a few more by the time of the meeting. Our initial interpretation of these data is that there is a region in the vicinity of the San Martin Seamounts comprising at least 20,000 square km in which the average amount of meteoritic material deposited was more than 1 g per square cm. This alone is enough material to support a 500 m asteroid. Beyond this is a region of about 60,000 square km, mostly to the north and west, where the amount of ejecta probably averages about 0.2 g per square cm. Another 400 km to the east, USNS Eltanin core E10-2 has about 0.05 g per square cm, so we know that ejecta probably occurs across more than a million square km of ocean floor. A key to future exploration of this impact is to find evidence of the ejecta at more sites distant from the seamounts. We currently have almost no data from regions to the west or south of the San Martin seamounts.

Analysis of Potentially Hazardous Asteroids

NASA Technical Reports Server (NTRS)

Arnold, J. O.; Burkhard, C. D.; Dotson, J. L.; Prabhu, D. K.; Mathias, D. L.; Aftosmis, M. J.; Venkatapathy, Ethiraj; Morrison, D. D.; Sears, D. W. G.; Berger, M. J.

2015-01-01

The National Aeronautics and Space Administration initiated a new project focused on Planetary Defense on October 1, 2014. The new project is funded by NASAs Near Earth Object Program (Lindley Johnson, Program Executive). This presentation describes the objectives, functions and plans of four tasks encompassed in the new project and their inter-relations. Additionally, this project provides for outreach to facilitate partnerships with other organizations to help meet the objectives of the planetary defense community. The four tasks are (1) Characterization of Near Earth Asteroids, (2) Physics-Based Modeling of Meteor Entry and Breakup (3) Surface Impact Modeling and (4) Physics-Based Impact Risk Assessment.

Thinking of biology: asteroid impacts, microbes, and the cooling of the atmosphere

NASA Technical Reports Server (NTRS)

Oberbeck, V. R.; Mancinelli, R. L.

1994-01-01

The authors examine the cooling of the Earth's surface from 3.75 to 1 billion years ago. Three effects of the bombardment of Earth by asteroids and comets that may have delayed surface cooling include time to form continents, volatilization of carbonate rocks which released carbon dioxide into the atmosphere, and inability of microbes to inhabit land masses during large impact events. Continental microbes may have helped reduce high temperatures from 3.75 to 3.5 billion years ago. If so, the evolutionary sequence of microbes is proposed to be anaerobic heterotrophs, chemoautotrophs, and then photoautotrophs.

Asteroid proper elements and secular resonances

NASA Technical Reports Server (NTRS)

Knezevic, Zoran; Milani, Andrea

1992-01-01

In a series of papers (e.g., Knezevic, 1991; Milani and Knezevic, 1990; 1991) we reported on the progress we were making in computing asteroid proper elements, both as regards their accuracy and long-term stability. Additionally, we reported on the efficiency and 'intelligence' of our software. At the same time, we studied the associated problems of resonance effects, and we introduced the new class of 'nonlinear' secular resonances; we determined the locations of these secular resonances in proper-element phase space and analyzed their impact on the asteroid family classification. Here we would like to summarize the current status of our work and possible further developments.

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

PubMed

Margot, J L; Brown, M E

2003-06-20

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

Looking into the evolution of granular asteroids in the Solar System

NASA Astrophysics Data System (ADS)

Sánchez, Paul; Scheeres, Daniel; Hirabayashi, Masatoshi; Tardivel, Simon

2017-06-01

By now it has been accepted that most of the small asteroids in the Solar System are granular aggregates kept together by gravitational and possibly, cohesive forces. These aggregates can form, deform and disrupt over millennia subjected to different internal and external factors that would ultimately determine how they evolve over time. Parameters such as porosity, cohesive and tensile strength, angles of friction, particle size distributions, stress states, heterogeneity and yield criteria among others, determine how these granular systems will react when subjected to different, changing, external factors. These external factors include solar photon momentum, gravitational tides, micro- and macro-impacts and are believed to have produced and shaped the current asteroid population. In our research we use a combination of Soil Mechanics theory, Soft-Sphere Discrete Element Method (SSDEM) Simulations and Orbital Mechanics in order to understand how simulated, homogeneous and heterogeneous, ellipsoidal and spherical gravitational aggregates, a crude but useful representation of an asteroid, evolve when rotated to the point of disruption. Then, we compare our results to the shapes of observed asteroids as well as to the disruption patterns of a few active asteroids. Our results lead us to believe that the different shapes of observed asteroids as well as their unique disruption patterns could give us clues about their internal structure, strength and geophysical properties in general.

SEM and TEM Observation of the Surfaces of the Fine-Grained Particles Retrieved from the Muses-C Regio on the Asteroid 25413 Itokawa

NASA Technical Reports Server (NTRS)

Noguchi, T.; Nakamura, T.; Zolensky, Michael E.; Tanaka, M.; Hashimoto, T.; Konno, M.; Nakato, A.; Ogami, T.; Fujimura, A.; Abe, M.;

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

Asteroid and comet flux in the neighborhood of the earth

NASA Technical Reports Server (NTRS)

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

1988-01-01

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

Growth of asteroids, planetary embryos, and Kuiper belt objects by chondrule accretion

PubMed Central

Johansen, Anders; Low, Mordecai-Mark Mac; Lacerda, Pedro; Bizzarro, Martin

2015-01-01

Chondrules are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of chondrules into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag–assisted accretion of chondrules. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of chondrules within ~3 My, forming planetary embryos up to Mars’s size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of chondrules consistent with chondrites. Accretion of millimeter-sized chondrules and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disc lifetime outside of 25 AU. The contribution of direct planetesimal accretion to the growth of both asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion and chondrule accretion play more equal roles in the formation of Moon-sized embryos in the terrestrial planet formation region. These embryos are isolated from each other and accrete planetesimals only at a low rate. However, the continued accretion of chondrules destabilizes the oligarchic configuration and leads to the formation of Mars-sized embryos and terrestrial planets by a combination of direct chondrule accretion and giant impacts. PMID:26601169

Growth of asteroids, planetary embryos, and Kuiper belt objects by chondrule accretion

NASA Astrophysics Data System (ADS)

Johansen, Anders; Mac Low, Mordecai-Mark; Lacerda, Pedro; Bizzarro, Martin

2015-04-01

Chondrules are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of chondrules into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag-assisted accretion of chondrules. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of chondrules within ~3 My, forming planetary embryos up to Mars's size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of chondrules consistent with chondrites. Accretion of millimeter-sized chondrules and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disc lifetime outside of 25 AU. The contribution of direct planetesimal accretion to the growth of both asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion and chondrule accretion play more equal roles in the formation of Moon-sized embryos in the terrestrial planet formation region. These embryos are isolated from each other and accrete planetesimals only at a low rate. However, the continued accretion of chondrules destabilizes the oligarchic configuration and leads to the formation of Mars-sized embryos and terrestrial planets by a combination of direct chondrule accretion and giant impacts.

Growth of asteroids, planetary embryos, and Kuiper belt objects by chondrule accretion.

PubMed

Johansen, Anders; Low, Mordecai-Mark Mac; Lacerda, Pedro; Bizzarro, Martin

2015-04-01

Chondrules are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of chondrules into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag-assisted accretion of chondrules. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of chondrules within ~3 My, forming planetary embryos up to Mars's size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of chondrules consistent with chondrites. Accretion of millimeter-sized chondrules and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disc lifetime outside of 25 AU. The contribution of direct planetesimal accretion to the growth of both asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion and chondrule accretion play more equal roles in the formation of Moon-sized embryos in the terrestrial planet formation region. These embryos are isolated from each other and accrete planetesimals only at a low rate. However, the continued accretion of chondrules destabilizes the oligarchic configuration and leads to the formation of Mars-sized embryos and terrestrial planets by a combination of direct chondrule accretion and giant impacts.

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

NASA Technical Reports Server (NTRS)

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

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.

Deflection and fragmentation of near-earth asteroids

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.; Harris, Alan W.

1992-01-01

The collision with earth of near-earth asteroids or comet nuclei poses a potential threat to mankind. Objects about 100 m in diameter could be diverted from an earth-crossing trajectory by the impact of a rocket-launched mass, but for larger bodies nuclear explosions seem to be the only practical means of deflection. Fragmentation of the body by nuclear charges is less efficient or secure.

Planetary Defense: Options for Deflection of Near Earth Objects

NASA Technical Reports Server (NTRS)

Adams, R. B.; Statham, G.; Hopkins, R.; Chapman, J.; White, S.; Bonometti, J.; Alexander, R.; Fincher, S.; Polsgrove, T.; Kalkstein, M.

2003-01-01

Several recent near-miss encounters with asteroids and comets have focused attention on the threat of a catastrophic impact with the Earth. This document reviews the historical impact record and current understanding of the number and location of Near Earth Objects (NEO's) to address their impact probability. Various ongoing projects intended to survey and catalog the NEO population are also reviewed. Details are then given of an MSFC-led study, intended to develop and assess various candidate systems for protection of the Earth against NEOs. An existing program, used to model the NE0 threat, was extensively modified and is presented here. Details of various analytical tools, developed to evaluate the performance of proposed technologies for protection against the NEO threat, are also presented. Trajectory tools, developed to model the outbound path a vehicle would take to intercept or rendezvous with a target asteroid or comet, are described. Also, details are given of a tool that was created to model both the un-deflected inbound path of an NE0 as well as the modified, post-deflection, path. The number of possible options available for protection against the NE0 threat was too numerous for them to all be addressed within the study; instead, a representative selection were modeled and evaluated. The major output from this work was a novel process by which the relative effectiveness of different threat mitigation concepts can be evaluated during future, more detailed, studies. In addition, several new or modified mathematical models were developed to analyze various proposed protection systems. A summary of the major lessons learned during this study is presented, as are recommendations for future work. It is hoped that this study will serve to raise the level attention about this very real threat and also demonstrate that successful defense is both possible and practicable, provided appropriate steps are taken.

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

NASA Astrophysics Data System (ADS)

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

2010-05-01

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

The detection of impact regions of asteroids' orbits by means of constrained minimization of confidence coefficient. (Russian Title: Выявление областей столкновительных орбит астероидов с помощью условной минимизации доверительного коэффициента)

NASA Astrophysics Data System (ADS)

Baturin, A. P.

2014-12-01

The theme of NEO's impact orbits' regions detecting has been considered. The regions have been detected in the space of initial motion parameters. The detecting has been done by means of constrained minimization of so called "confidence coefficient". This coefficient determines the position of an orbit inside its confidence ellipsoid obtained from a least-square orbit fitting. As a condition the constraining of an asteroid-Earth distance at considered encounter has been used. By means of random variation of initial approximations for the minimization and of the parameter constraining an asteroid-Earth distance it has been demonstrated that impact regions usually have a form of some long tubes in the space of initial motion parameters. The demonstration has been done for the asteroids 2009 FD, 2011 TO and 2012 PB20 at their waited closest encounters to the Earth.

Impacts and evolution: future prospects.

PubMed

Morrison, David

2003-01-01

The discipline of astrobiology includes the dynamics of biological evolution. One of the major ways that the cosmos influences life is through the catastrophic environmental disruptions caused when comets and asteroids collide with a planet. We now recognize that such impacts have caused mass extinctions and played a major role in determining the evolution of life on Earth. The time-averaged impact flux as a function of projectile energy can be derived from lunar cratering statistics as well as the current population of near Earth asteroids (NEAs). Effects of impacts of various energies can be modeled, using data from historic impacts [such as the Cretaceous-Tertiary (KT) impactor 65 million years ago] and the observed 1994 bombardment of Jupiter by fragments of Comet Shoemaker-Levy 9. It is of particular interest to find from such models that the terrestrial environment is highly vulnerable to perturbation from impacts, so that even such a small event as the KT impact (by a projectile 10-15 km in diameter) can lead to a mass extinction. Similar considerations allow us to model the effects of still smaller (and much more likely) impacts, down to the size of the asteroid that exploded over Tunguska in 1908 (energy approximately 10 megatons). Combining the impact flux with estimates of environmental and ecological effects reveals that the greatest contemporary hazard is associated with impactors near 1 million megatons in energy (approximately 2 km in diameter for an asteroid). The current impact hazard is significant relative to other natural hazards, and arguments can be developed to illuminate a variety of public policy issues. The first priority in any plan for defense against impactors is to survey the population of Earth-crossing NEAs and project their orbits forward in time. This is the purpose of the Spaceguard Survey, which has already found more than half of the NEAs >1 km in diameter. If there is an NEA on a collision course with Earth, it can be discovered and the impact predicted with decades or more of warning. It is then possible to consider how to deflect or disrupt the NEA. Unlike other natural hazards, the impact risk can be largely eliminated, given sufficient advanced knowledge to take action against the threatening projectile.

Impacts and evolution: future prospects

NASA Technical Reports Server (NTRS)

Morrison, David

2003-01-01

The discipline of astrobiology includes the dynamics of biological evolution. One of the major ways that the cosmos influences life is through the catastrophic environmental disruptions caused when comets and asteroids collide with a planet. We now recognize that such impacts have caused mass extinctions and played a major role in determining the evolution of life on Earth. The time-averaged impact flux as a function of projectile energy can be derived from lunar cratering statistics as well as the current population of near Earth asteroids (NEAs). Effects of impacts of various energies can be modeled, using data from historic impacts [such as the Cretaceous-Tertiary (KT) impactor 65 million years ago] and the observed 1994 bombardment of Jupiter by fragments of Comet Shoemaker-Levy 9. It is of particular interest to find from such models that the terrestrial environment is highly vulnerable to perturbation from impacts, so that even such a small event as the KT impact (by a projectile 10-15 km in diameter) can lead to a mass extinction. Similar considerations allow us to model the effects of still smaller (and much more likely) impacts, down to the size of the asteroid that exploded over Tunguska in 1908 (energy approximately 10 megatons). Combining the impact flux with estimates of environmental and ecological effects reveals that the greatest contemporary hazard is associated with impactors near 1 million megatons in energy (approximately 2 km in diameter for an asteroid). The current impact hazard is significant relative to other natural hazards, and arguments can be developed to illuminate a variety of public policy issues. The first priority in any plan for defense against impactors is to survey the population of Earth-crossing NEAs and project their orbits forward in time. This is the purpose of the Spaceguard Survey, which has already found more than half of the NEAs >1 km in diameter. If there is an NEA on a collision course with Earth, it can be discovered and the impact predicted with decades or more of warning. It is then possible to consider how to deflect or disrupt the NEA. Unlike other natural hazards, the impact risk can be largely eliminated, given sufficient advanced knowledge to take action against the threatening projectile.

A Unified Theory of Impact Crises and Mass Extinctions: Quantitative Tests

NASA Technical Reports Server (NTRS)

Rampino, Michael R.; Haggerty, Bruce M.; Pagano, Thomas C.

1997-01-01

Several quantitative tests of a general hypothesis linking impacts of large asteroids and comets with mass extinctions of life are possible based on astronomical data, impact dynamics, and geological information. The waiting of large-body impacts on the Earth derive from the flux of Earth-crossing asteroids and comets, and the estimated size of impacts capable of causing large-scale environmental disasters, predict that impacts of objects greater than or equal to 5 km in diameter (greater than or equal to 10 (exp 7) Mt TNT equivalent) could be sufficient to explain the record of approximately 25 extinction pulses in the last 540 Myr, with the 5 recorded major mass extinctions related to impacts of the largest objects of greater than or equal to 10 km in diameter (greater than or equal to 10(exp 8) Mt Events). Smaller impacts (approximately 10 (exp 6) Mt), with significant regional environmental effects, could be responsible for the lesser boundaries in the geologic record.

The hazard of near-Earth asteroid impacts on earth

NASA Astrophysics Data System (ADS)

Chapman, Clark R.

2004-05-01

Near-Earth asteroids (NEAs) have struck the Earth throughout its existence. During epochs when life was gaining a foothold ˜4 Ga, the impact rate was thousands of times what it is today. Even during the Phanerozoic, the numbers of NEAs guarantee that there were other impacts, possibly larger than the Chicxulub event, which was responsible for the Cretaceous-Tertiary extinctions. Astronomers have found over 2500 NEAs of all sizes, including well over half of the estimated 1100 NEAs >1 km diameter. NEAs are mostly collisional fragments from the inner half of the asteroid belt and range in composition from porous, carbonaceous-chondrite-like to metallic. Nearly one-fifth of them have satellites or are double bodies. When the international telescopic Spaceguard Survey, which has a goal of discovering 90% of NEAs >1 km diameter, is completed, perhaps as early as 2008, nearly half of the remaining impact hazard will be from land or ocean impacts by bodies 70-600 m diameter. (Comets are expected to contribute only about 1% of the total risk.) The consequences of impacts for civilization are potentially enormous, but impacts are so rare that worldwide mortality from impacts will have dropped to only about 150 per year (averaged over very long durations) after the Spaceguard goal has, presumably, ruled out near-term impacts by 90% of the most dangerous ones; that is, in the mid-range between very serious causes of death (disease, auto accidents) and minor but frightening ones (like shark attacks). Differences in perception concerning this rather newly recognized hazard dominate evaluation of its significance. The most likely type of impact events we face are hyped or misinterpreted predicted impacts or near-misses involving small NEAs.

Asteroid Deflection: How, Where and When?

NASA Astrophysics Data System (ADS)

Fargion, D.

2008-10-01

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

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

NASA Astrophysics Data System (ADS)

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

2008-06-01

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

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.

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].

A reduced estimate of the number of kilometre-sized near-Earth asteroids.

PubMed

Rabinowitz, D; Helin, E; Lawrence, K; Pravdo, S

2000-01-13

Near-Earth asteroids are small (diameters < 10 km), rocky bodies with orbits that approach that of the Earth (they come within 1.3 AU of the Sun). Most have a chance of approximately 0.5% of colliding with the Earth in the next million years. The total number of such bodies with diameters > 1 km has been estimated to be in the range 1,000-2,000, which translates to an approximately 1% chance of a catastrophic collision with the Earth in the next millennium. These numbers are, however, poorly constrained because of the limitations of previous searches using photographic plates. (One kilometre is below the size of a body whose impact on the Earth would produce global effects.) Here we report an analysis of our survey for near-Earth asteroids that uses improved detection technologies. We find that the total number of asteroids with diameters > 1 km is about half the earlier estimates. At the current rate of discovery of near-Earth asteroids, 90% will probably have been detected within the next 20 years.

Angular momentum transfer in low velocity oblique impacts - Implications for asteroids

NASA Technical Reports Server (NTRS)

Yanagisawa, Masahisa; Eluszkiewicz, Janusz; Ahrens, Thomas J.

1991-01-01

An experimental study has been conducted for the low-velocity oblique impact efficiency of angular momentum transfer, which is defined as that fraction of incident angular momentum that is transferred to the rotation of a target. The results obtained suggest that more energetic impacts are able to transfer angular momentum more efficiently. In the cases of ricochetted projectiles, the fraction of angular momentum carried off by the ejecta was noted to be less than 30 percent. It is suggested that, if asteroid spin rates are due to mutual noncatastrophic collisions and the taxonomic classes are indicative of bulk properties, the differences between corresponding spin rates will be smaller than expected from a consideration of relative strength and density alone.

Simulations of Prebiotic Chemistry under Post-Impact Conditions on Titan.

PubMed

Turse, Carol; Leitner, Johannes; Firneis, Maria; Schulze-Makuch, Dirk

2013-12-17

The problem of how life began can be considered as a matter of basic chemistry. How did the molecules of life arise from non-biological chemistry? Stanley Miller's famous experiment in 1953, in which he produced amino acids under simulated early Earth conditions, was a huge leap forward in our understanding of this problem. Our research first simulated early Earth conditions based on Miller's experiment and we then repeated the experiment using Titan post-impact conditions. We simulated conditions that could have existed on Titan after an asteroid strike. Specifically, we simulated conditions after a potential strike in the subpolar regions of Titan that exhibit vast methane-ethane lakes. If the asteroid or comet was of sufficient size, it would also puncture the icy crust and bring up some of the subsurface liquid ammonia-water mixture. Since, O'Brian, Lorenz and Lunine showed that a liquid water-ammonia body could exist between about 102-104 years on Titan after an asteroid impact we modified our experimental conditions to include an ammonia-water mixture in the reaction medium. Here we report on the resulting amino acids found using the Titan post-impact conditions in a classical Miller experimental reaction set-up and how they differ from the simulated early Earth conditions.

Fugitives from the Hungaria region: Close encounters and impacts with terrestrial planets

NASA Astrophysics Data System (ADS)

Galiazzo, M. A.; Bazsó, Á.; Dvorak, R.

2013-08-01

Hungaria asteroids, whose orbits occupy the region in element space between 1.78

FEMA Asteroid Impact Tabletop Exercise Simulations

DOE PAGES

Boslough, Mark; Jennings, Barbara; Carvey, Brad; ...

2015-05-19

We describe the computational simulations and damage assessments that we provided in support of a tabletop exercise (TTX) at the request of NASA's Near-Earth Objects Program Office. The overall purpose of the exercise was to assess leadership reactions, information requirements, and emergency management responses to a hypothetical asteroid impact with Earth. The scripted exercise consisted of discovery, tracking, and characterization of a hypothetical asteroid; inclusive of mission planning, mitigation, response, impact to population, infrastructure and GDP, and explicit quantification of uncertainty. Participants at the meeting included representatives of NASA, Department of Defense, Department of State, Department of Homeland Security/Federal Emergencymore » Management Agency (FEMA), and the White House. The exercise took place at FEMA headquarters. Sandia's role was to assist the Jet Propulsion Laboratory (JPL) in developing the impact scenario, to predict the physical effects of the impact, and to forecast the infrastructure and economic losses. We ran simulations using Sandia's CTH hydrocode to estimate physical effects on the ground, and to produce contour maps indicating damage assessments that could be used as input for the infrastructure and economic models. We used the FASTMap tool to provide estimates of infrastructure damage over the affected area, and the REAcct tool to estimate the potential economic severity expressed as changes to GDP (by nation, region, or sector) due to damage and short-term business interruptions.« less

Thermal radiation from large bolides and impact plumes

NASA Astrophysics Data System (ADS)

Svetsov, V.; Shuvalov, V.

2017-09-01

Numerical simulations of the impacts of asteroids and comets from 20 m to 3 km in diameter have been carried out and thermal radiation fluxes on the ground and luminous efficiencies of the impacts have been calculated. It was assumed that the cosmic objects have no strength, deform, fragment, and vaporize in the atmosphere. After the impact on the ground, formation of craters and plumes was simulated taking into account internal friction of destroyed rocks and a wake formed in the atmosphere. The equations of radiative transfer, added to the equations of gas dynamics, were used in the approximation of radiative heat diffusion or, if the Rosseland optical depth of a radiating volume of gas and vapor was less than unity, in the approximation of volume emission. Radiation fluxes on the Earth's surface were calculated by integrating the equation of radiative transfer along rays passing through a luminous area. Direct thermal radiation from fireballs and impact plumes produced by asteroids and comets larger than 50 m in diameter is dangerous for people, animals, plants, economic objects. Forest fires can be ignited on the ground within a radius of roughly 1000 times the body's diameter (for diameters of the order or smaller than 1 km), 50-m-diameter bodies can ignite forest fires within a radius of up to 40 km and 3-km asteroids - within 1700 km.

Global environmental effects of impact-generated aerosols: Results from a general circulation model, revision 1

NASA Technical Reports Server (NTRS)

Covey, Curt; Ghan, Steven J.; Walton, John J.; Weissman, Paul R.

1989-01-01

Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to our three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans substantially mitigates land surface cooling, an effect that one-dimensional models cannot quantify. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stage of cooling than in the one-dimensional model study. These two differences between three-dimensional and one-dimensional model simulations were noted previously in studies of nuclear winter; GCM-simulated climatic changes in the Alvarez-inspired scenario of asteroid/comet winter, however, are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though less severe, climatic changes, according to our GCM. Our conclusion is that it is difficult to imagine an asteroid or comet impact leading to anything approaching complete global freezing, but quite reasonable to assume that impacts at the Alvarez level, or even smaller, dramatically alter the climate in at least a patchy sense.

FEMA Asteroid Impact Tabletop Exercise Simulations

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

Boslough, Mark; Jennings, Barbara; Carvey, Brad

We describe the computational simulations and damage assessments that we provided in support of a tabletop exercise (TTX) at the request of NASA's Near-Earth Objects Program Office. The overall purpose of the exercise was to assess leadership reactions, information requirements, and emergency management responses to a hypothetical asteroid impact with Earth. The scripted exercise consisted of discovery, tracking, and characterization of a hypothetical asteroid; inclusive of mission planning, mitigation, response, impact to population, infrastructure and GDP, and explicit quantification of uncertainty. Participants at the meeting included representatives of NASA, Department of Defense, Department of State, Department of Homeland Security/Federal Emergencymore » Management Agency (FEMA), and the White House. The exercise took place at FEMA headquarters. Sandia's role was to assist the Jet Propulsion Laboratory (JPL) in developing the impact scenario, to predict the physical effects of the impact, and to forecast the infrastructure and economic losses. We ran simulations using Sandia's CTH hydrocode to estimate physical effects on the ground, and to produce contour maps indicating damage assessments that could be used as input for the infrastructure and economic models. We used the FASTMap tool to provide estimates of infrastructure damage over the affected area, and the REAcct tool to estimate the potential economic severity expressed as changes to GDP (by nation, region, or sector) due to damage and short-term business interruptions.« less

OSIRIS-REx Asterod Sample Return Mission

NASA Technical Reports Server (NTRS)

Nakamura-Messinger, Keiki; Connolly, Harold C. Jr.; Messenger, Scott; Lauretta, Dante S.

2017-01-01

OSIRIS-REx is NASA's third New Frontiers Program mission, following New Horizons that completed a flyby of Pluto in 2015 and the Juno mission to Jupiter that has just begun science operations. The OSIRIS-REx mission's primary objective is to collect pristine surface samples of a carbonaceous asteroid and return to Earth for analysis. Carbonaceous asteroids and comets are 'primitive' bodies that preserved remnants of the Solar System starting materials and through their study scientists can learn about the origin and the earliest evolution of the Solar System. The OSIRIS-REx spacecraft was successfully launched on September 8, 2016, beginning its seven year journey to asteroid 101955 Bennu. The robotic arm will collect 60-2000 grams of material from the surface of Bennu and will return to Earth in 2023 for worldwide distribution by the Astromaterials Curation Facility at NASA Johnson Space Center. The name OSIRIS-REx embodies the mission objectives (1) Origins: Return and analyze a sample of a carbonaceous asteroid, (2) Spectral Interpretation: Provide ground-truth for remote observation of asteroids, (3) Resource Identification: Determine the mineral and chemical makeup of a near-Earth asteroid (4) Security: Measure the non-gravitational that changes asteroidal orbits and (5) Regolith Explorer: Determine the properties of the material covering an asteroid surface. Asteroid Bennu may preserve remnants of stardust, interstellar materials and the first solids to form in the Solar System and the molecular precursors to the origin of life and the Earth's oceans. Bennu is a potentially hazardous asteroid, with an approximately 1 in 2700 chance of impacting the Earth late in the 22nd century. OSIRIS-REx collects from Bennu will help formulate the types of operations and identify mission activities that astronauts will perform during their expeditions. Such information is crucial in preparing for humanity's next steps beyond low Earthy orbit and on to deep space destinations.

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.

NEOCAM: Near Earth Object Chemical Analysis Mission: Bridging the Gulf between Telescopic Observations and the Chemical and Mineralogical Compositions of Asteroids or Diogenes A: Diagnostic Observation of the Geology of Near Earth Spectrally-Classified Asteroids

NASA Technical Reports Server (NTRS)

Nuth, Joseph A.

2009-01-01

Studies of meteorites have yielded a wealth of scientific information based on highly detailed chemical and isotopic studies possible only in sophisticated terrestrial laboratories. Telescopic studies have revealed an enormous (greater than 10(exp 5)) number of physical objects ranging in size from a few tens of meters to several hundred kilometers, orbiting not only in the traditional asteroid belt between Mars and Jupiter but also throughout the inner solar system. Many of the largest asteroids are classed into taxonomic groups based on their observed spectral properties and are designated as C, D. X, S or V types (as well as a wide range in sub-types). These objects are certainly the sources far the meteorites in our laboratories, but which asteroids are the sources for which meteorites? Spectral classes are nominally correlated to the chemical composition and physical characteristics of the asteroid itself based on studies of the spectral changes induced in meteorites due to exposure to a simulated space environment. While laboratory studies have produced some notable successes (e.g. the identification of the asteroid Vesta as the source of the H, E and D meteorite classes), it is unlikely that we have samples of each asteroidal spectral type in our meteorite collection. The correlation of spectral type and composition for many objects will therefore remain uncertain until we can return samples of specific asteroid types to Earth for analyses. The best candidates for sample return are asteroids that already come close to the Earth. Asteroids in orbit near 1 A.U. have been classified into three groups (Aten, Apollo & Amor) based on their orbital characteristics. These Near Earth Objects (NEOs) contain representatives of virtually all spectral types and sub-types of the asteroid population identified to date. Because of their close proximity to Earth, NEOs are prime targets for asteroid missions such as the NEAR-Shoemaker NASA Discovery Mission to Eros and the Japanese Hyabusa Mission to Itokawa. Also due to their close proximity to Earth, NEOs constitute the most likely set of celestial objects that will impact us in the relatively near future.

Spin Vector and Shape of (6070) Rheinland and Their Implications

NASA Astrophysics Data System (ADS)

Vokrouhlický, David; Ďurech, Josef; Polishook, David; Krugly, Yurij N.; Gaftonyuk, Ninel N.; Burkhonov, Otabek A.; Ehgamberdiev, Shukhrat A.; Karimov, Rivkat; Molotov, Igor E.; Pravec, Petr; Hornoch, Kamil; Kušnirák, Peter; Oey, Julian; Galád, Adrián; Žižka, Jindřich

2011-11-01

Main belt asteroids (6070) Rheinland and (54827) 2001 NQ8 belong to a small population of couples of bodies that reside in very similar heliocentric orbits. Vokrouhlický & Nesvorný promoted the term "asteroid pairs," pointing out their common origin within the past tens to hundreds of kyr. Previous attempts to reconstruct the initial configuration of Rheinland and 2001 NQ8 at the time of their separation have led to the prediction that Rheinland's rotation should be retrograde. Here, we report extensive photometric observations of this asteroid and use the light curve inversion technique to directly determine its rotation state and shape. We confirm the retrograde sense of rotation of Rheinland, with obliquity value constrained to be >=140°. The ecliptic longitude of the pole position is not well constrained as yet. The asymmetric behavior of Rheinland's light curve reflects a sharp, near-planar edge in our convex shape representation of this asteroid. Our calibrated observations in the red filter also allow us to determine HR = 13.68 ± 0.05 and G = 0.31 ± 0.05 values of the H-G system. With the characteristic color index V - R = 0.49 ± 0.05 for S-type asteroids, we thus obtain H = 14.17 ± 0.07 for the absolute magnitude of (6070) Rheinland. This is a significantly larger value than previously obtained from analysis of astrometric survey observations. We next use the obliquity constraint for Rheinland to eliminate some degree of uncertainty in the past propagation of its orbit. This is because the sign of the past secular change of its semimajor axis due to the Yarkovsky effect is now constrained. The determination of the rotation state of the secondary component, asteroid (54827) 2001 NQ8, is the key element in further constraining the age of the pair and its formation process.

A new terminal guidance sensor system for asteroid intercept or rendezvous missions

NASA Astrophysics Data System (ADS)

Lyzhoft, Joshua; Basart, John; Wie, Bong

2016-02-01

This paper presents the initial conceptual study results of a new terminal guidance sensor system for asteroid intercept or rendezvous missions, which explores the use of visual, infrared, and radar devices. As was demonstrated by NASA's Deep Impact mission, visual cameras can be effectively utilized for hypervelocity intercept terminal guidance for a 5 kilometer target. Other systems such as Raytheon's EKV (Exoatmospheric Kill Vehicle) employ a different scheme that utilizes infrared target information to intercept ballistic missiles. Another example that uses infrared information is the NEOWISE telescope, which is used for asteroid detection and tracking. This paper describes the signal-to-noise ratio estimation problem for infrared sensors, minimum and maximum range of detection, and computational validation using GPU accelerated simulations. Small targets (50-100 m in diameter) are considered, and scaled polyhedron models of known objects, such as the Rosetta mission's Comet 67P/Churyumov-Gerasimenko, 101,955 Bennu, target of the OSIRIS-REx mission, and asteroid 433 Eros, are utilized. A parallelized ray tracing algorithm to simulate realistic surface-to-surface shadowing of a given celestial body is developed. By using the simulated models and parameters given from the formulation of the different sensors, impact mission scenarios are used to verify the feasibility for intercepting a small target.

Asteroid astrometry with Gaia: stellar occultations and beyond

NASA Astrophysics Data System (ADS)

Tanga, Paolo; Spoto, Federica; Hestroffer, Daniel; Altmann, Martin; Bouquillon, Sebastien; Desmars, Josselin

2017-10-01

The first data release of star astrometry by Gaia (Sept. 2016) has given an anticipation of the mission capabilities. By providing positions with uncertainties at the level of few milli-arcsec (mas) a new frame to calibrate ground-based observations has immediately become available, thus disclosing a new possibility of exploitation for archive data. We will discuss, in particular, the new role of stellar occulations.Successful observations of occultations have been used in the past to provide accurate shape and size of the targets and to calibrate other size determination methods. Now, a new possibility of exploitation exists, as occultation astrometry provides the possibility of measuring precise asteroid position, at the level of Gaia accuracy. This approach will have an increasing impact, also thanks to the much improved prediction accuracy that Gaia is going to provide, for smaller asteroids and fainter target stars.The scientific goals of improving asteroid astrometry are multiple. For instance, reaching sensitivity to Yarkovsky drift in the Main Belt might become possible, by occultation astrometry performed on smaller asteroids, thanks to future Gaia predictions.The second data release (April 2018) will also contain astrometry of asteroids observed directly by Gaia. The properties of this new data set, that will permit direct orbit improvement, will be illustrated.

Constraining Binary Asteroid Mass Distributions Based On Mutual Motion

NASA Astrophysics Data System (ADS)

Davis, Alex B.; Scheeres, Daniel J.

2017-06-01

The mutual gravitational potential and torques of binary asteroid systems results in a complex coupling of attitude and orbital motion based on the mass distribution of each body. For a doubly-synchronous binary system observations of the mutual motion can be leveraged to identify and measure the unique mass distributions of each body. By implementing arbitrary shape and order computation of the full two-body problem (F2BP) equilibria we study the influence of asteroid asymmetries on separation and orientation of a doubly-synchronous system. Additionally, simulations of binary systems perturbed from doubly-synchronous behavior are studied to understand the effects of mass distribution perturbations on precession and nutation rates such that unique behaviors can be isolated and used to measure asteroid mass distributions. We apply our investigation to the Trojan binary asteroid system 617 Patroclus and Menoetius (1906 VY), which will be the final flyby target of the recently announced LUCY Discovery mission in March 2033. This binary asteroid system is of particular interest due to the results of a recent stellar occultation study (DPS 46, id.506.09) that suggests the system to be doubly-synchronous and consisting of two-similarly sized oblate ellipsoids, in addition to suggesting the presence mass asymmetries resulting from an impact crater on the southern limb of Menoetius.

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

NASA Astrophysics Data System (ADS)

Vernazza, P.; Lamy, P.

2014-07-01

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

Impacts into Coarse-Grained Spheres at Moderate Impact Velocities: Implications for Cratering on Asteroids and Planets

NASA Technical Reports Server (NTRS)

Barnouin, Olivier S.; Daly, R. Terik; Cintala, Mark J.; Crawford, David A.

2018-01-01

The surfaces of many planets and asteroids contain coarsely fragmental material generated by impacts or other geologic processes. The presence of such pre-existing structures may affect subsequent impacts, particularly when the width of the shock is comparable to or smaller than the size of pre-existing structures. Reasonable theoretical predictions and low speed (<300m/s) impact experiments suggest that in such targets the cratering process should be highly dissipative, which would reduce cratering efficiencies and cause a rapid decay in ejection velocity as a function of distance from the impact point. In this study, we assess whether these results apply at higher impact speeds between 0.5 and 2.5 km s-1. This study shows little change in cratering efficiency when 3.18 mm diameter glass beads are launched into targets composed of these same beads. These impacts are very efficient, and ejection velocity decays slowly as function of distance from the impact point. This slow decay in ejection velocity probably indicates a correspondingly slow decay of the shock stresses. However, these experiments reveal that initial interactions between projectile and target strongly influence the cratering process and lead to asymmetries in crater shape and ejection angles, as well as significant variations in ejection velocity at a given launch position. Such effects of asymmetric coupling could be further enhanced by heterogeneity in the initial distribution of grains in the target and by mechanical collisions between grains. These experiments help to explain why so few craters are seen on the rubble-pile asteroid Itokawa: impacts into its coarsely fragmental surface by projectiles comparable to or smaller than the size of these fragments likely yield craters that are not easily recognizable.

Observations and Characterization of Binary Near-Earth Asteroid 65803 Didymos, the Target of the AIDA Mission

NASA Astrophysics Data System (ADS)

Naidu, S.; Benner, L.; Brozovic, M.; Ostro, S. J.; Nolan, M. C.; Margot, J. L.; Giorgini, J. D.; Magri, C.; Pravec, P.; Scheirich, P.; Scheeres, D. J.; Hirabayashi, M.

2016-12-01

Binary near-Earth asteroid 65803 Didymos is the target of the proposed Asteroid Impact and Deflection Assessment (AIDA) space mission. The mission consists of two spacecraft, the Demonstration for Autonomous Rendezvous Technology (DART) spacecraft that will impact the asteroid's satellite and the Asteroid Impact Mission (AIM) spacecraft that will observe the impact. We used radar observations obtained at Arecibo and Goldstone in 2003, and lightcurve data from Pravec et al. (2006) to model the shapes, sizes, and spin states of the components. The primary is top shaped and has an equatorial ridge similar to the one seen on 2000 DP107 (Naidu et al. 2015). A 300 m long flat region is also seen along the equator. The primary has an equivalent diameter of 780 m (+/- 10 %) and its extents along the principal axes are 826 m, 813 m, and 786 m (10% uncertainties). It has a spin period of 2.2600 +/- 0.0001 h. A grid search for the spin pole resulted in the best fit at ecliptic (longitude, latitude) = (296, +71) degrees (+/- 15 degrees). This estimate is consistent with the spin pole being aligned to the binary orbit normal at (310, -84) degrees. Dividing the primary mass of 5.24e11 kg (Fang & Margot 2012) by the model volume we estimate a bulk density of 2100 kg m-3 (+/- 30 %). We summed multiple radar runs to estimate the range and Doppler extents of the satellite. We estimated the motion in successive images and used a shift-and-sum technique to mitigate smearing due to translational motion. This boosted the SNRs and allowed us to obtain size and bandwidth estimates of the satellite. The visible range extent of the satellite is roughly 60-75 m at the 15 m resolution of the Arecibo images. Assuming that the true extent is twice the visible extent, we obtain a diameter estimate of 120-150 m. The bandwidth of the satellite suggests a spin period between 9-12 h that is consistent with the orbit period of 11.9 hours and with synchronous rotation.

The Observing Working Group for the Asteroid Impact & Delfection Assessment (AIDA) Mission

NASA Astrophysics Data System (ADS)

Osip, David J.; Rivkin, Andrew S.; Pravec, Petr; Moskovitz, Nicholas; Thirouin, Audrey; Scheirich, Peter; Oszkiewicz, Dagmara Anna; Richardson, Derek C.; Polishook, David; Ryan, William; Thomas, Cristina; Busch, Michael W.; Cheng, Andrew F.; Michel, Patrick; AIDA Observing Working Group

2016-10-01

The Asteroid Impact & Deflection Assessment (AIDA) mission is a joint ESA-NASA mission concept currently under study. AIDA has two components: the Double Asteroid Redirect Test (DART) is the US component designed to demonstrate a kinetic impactor, while the Asteroid Impact Mission (AIM) spacecraft is on station to do a thorough pre- and post-impact survey of the Didymos system.Members of the DART and AIM Investigation teams have been organized into several joint and independent working groups. While there is overlap in subject matter and membership between the groups, we focus here on the activities of the Observing Working Group.The first work by the group was undertaken during the spring of 2015, before DART entered Phase A. During this period Didymos made an apparition reaching roughly V ~ 20.5 in brightness, and our top priority was constraining which of two very different pole positions for the Didymos system was correct. Several telescopes in the 2-4-m aperture range around the world attempted observations. An observed mutual event allowed the one pole position to be ruled out. Didymos is now thought to be a low-obliquity, retrograde rotator, similar to many other asteroid binary systems and consistent with expectations from a YORP-driven origin for the satellite.We have begun planning for the 2017 apparition, occurring in the first half of the year. Didymos will be ~20% brighter at opposition than the 2015 apparition. Scaling from the successful observations with the 4.3-m Lowell Discovery Channel Telescope indicates that we will need telescopes at least 4 m (or larger, for some of the tasks, or at times longer before or after the opposition) in primary diameter for the advanced characterization in 2017.Currently, we have four goals for this apparition: 1) confirming the preferred retrograde pole position; 2) gathering data to allow BYORP-driven changes in the mutual orbit to potentially be determined by later observations; 3) establishing whether or not the secondary is in synchronous rotation with the primary; and 4) constraining the inclination of the satellite orbit.

Structure and origin of Australian ring and dome features with reference to the search for asteroid impact events

NASA Astrophysics Data System (ADS)

Glikson, Andrew

2018-01-01

Ring, dome and crater features on the Australian continent and shelf include (A) 38 structures of confirmed or probable asteroid and meteorite impact origin and (B) numerous buried and exposed ring, dome and crater features of undefined origin. A large number of the latter include structural and geophysical elements consistent with impact structures, pending test by field investigations and/or drilling. This paper documents and briefly describes 43 ring and dome features with the aim of appraising their similarities and differences from those of impact structures. Discrimination between impact structures and igneous plugs, volcanic caldera and salt domes require field work and/or drilling. Where crater-like morphological patterns intersect pre-existing linear structural features and contain central morphological highs and unique thrust and fault patterns an impact connection needs to tested in the field. Hints of potential buried impact structures may be furnished by single or multi-ring TMI patterns, circular TMI quiet zones, corresponding gravity patterns, low velocity and non-reflective seismic zones.

The missing large impact craters on Ceres

PubMed Central

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

2016-01-01

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

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.

Cohesion of Mm- to Cm-Sized Asteroid Simulant Grains: An Experimental Study

NASA Astrophysics Data System (ADS)

Brisset, Julie; Colwell, Joshua E.; Dove, Adrienne; Jarmak, Stephanie; Anderson, Seamus

2017-10-01

The regolith covering the surfaces of asteroids and planetary satellites is very different from terrestrial soil particles and subject to environmental conditions very different from what is found on Earth. The loose, unconsolidated granular material has angular-shaped grains and a broad size distribution. On small and airless bodies (<10 km), the solar wind leads to a depletion of fine grains (<100µm) on the surface. Ground observations of the two asteroids currently targeted by spacecraft, Ryugu (Hayabusa-2) and Bennu (OSIRIS-REx), indicate that their surfaces could be covered in mm- to cm-sized regolith grains. As these small bodies have surface gravity levels below 10-5g, g being the Earth surface gravity, the cohesion behavior of the regolith grains will dictate the asteroid’s surface morphology and its response to impact or spacecraft contact.Previous laboratory experiments on low-velocity impacts into regolith simulant with grain sizes <250 µm have revealed a transition of the grain behavior from a gravity-dominated regime to a cohesion-dominated regime when the local gravity level reaches values below 10-3g. This is in good agreement with analytical and simulation studies for these grain sizes. From the expected grain sizes at the surfaces of Ryugu and Bennu, we have now focused on larger grain sizes ranging from mm to cm. We have carried out a series of experiments to study the cohesion behavior of such larger grains of asteroid regolith simulant. The simulant used was CI Orgueil of Deep Space Industries. Experiments included laboratory tabletop avalanching, compression and shear force measurements, as well as low-velocity impacts under microgravity.Our goal is to determine if the grain size distribution has an influence on the cohesion behavior of the regolith and if we can validate numerical simulation results with experimental measurements. We will discuss the implications of our results for sample return or landing missions to small bodies such as asteroids or Martian moons.

An Archaean heavy bombardment from a destabilized extension of the asteroid belt.

PubMed

Bottke, William F; Vokrouhlický, David; Minton, David; Nesvorný, David; Morbidelli, Alessandro; Brasser, Ramon; Simonson, Bruce; Levison, Harold F

2012-05-03

The barrage of comets and asteroids that produced many young lunar basins (craters over 300 kilometres in diameter) has frequently been called the Late Heavy Bombardment (LHB). Many assume the LHB ended about 3.7 to 3.8 billion years (Gyr) ago with the formation of Orientale basin. Evidence for LHB-sized blasts on Earth, however, extend into the Archaean and early Proterozoic eons, in the form of impact spherule beds: globally distributed ejecta layers created by Chicxulub-sized or larger cratering events4. At least seven spherule beds have been found that formed between 3.23 and 3.47 Gyr ago, four between 2.49 and 2.63 Gyr ago, and one between 1.7 and 2.1 Gyr ago. Here we report that the LHB lasted much longer than previously thought, with most late impactors coming from the E belt, an extended and now largely extinct portion of the asteroid belt between 1.7 and 2.1 astronomical units from Earth. This region was destabilized by late giant planet migration. E-belt survivors now make up the high-inclination Hungaria asteroids. Scaling from the observed Hungaria asteroids, we find that E-belt projectiles made about ten lunar basins between 3.7 and 4.1 Gyr ago. They also produced about 15 terrestrial basins between 2.5 and 3.7 Gyr ago, as well as around 70 and four Chicxulub-sized or larger craters on the Earth and Moon, respectively, between 1.7 and 3.7 Gyr ago. These rates reproduce impact spherule bed and lunar crater constraints.

Experimental Simulations of Large-Scale Collisions

NASA Technical Reports Server (NTRS)

Housen, Kevin R.

2002-01-01

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

Are we producing PHAs? On the target selection for a proposed mitigation demo-mission within the NEO-Shield project

NASA Astrophysics Data System (ADS)

Eggl, S.; Hestroffer, D.; Thuillot, W.

2013-09-01

The Chelyabinsk event on February 15th, 2013 has shown once again that even small near earth objects (NEOs) can become a real safety concern. Eventhough we believe to have the capabilities to avert larger potentially disastrous asteroid impacts, only the realization of mitigation demonstration missions can confirm this claim. The target selection process for such deflection demonstrations is a demanding task, as physical, dynamical and engineering aspects have to be considered in great detail. One of the top priorities of such a demonstration mission is, of course, that a harmless asteroid should not be turned into a potentially hazardous object (PHO). Given the potentially large uncertainties in the asteroid's physical parameters as well as the additional uncertainties introduced during the deflection attempt, an in depth analysis of the impact probabilities over the next century becomes necessary, in order to exclude an augmentation of potential risks. Assuming worst case scenarios regard- ing the orbital, physical and mitigation induced uncertainties, we provide a keyhole and impact risk analysis of a list of potential targets for the mitigation demomission proposed in the framework of the NEO-Shield project.

When Worlds Collide: Witnessing Planetary-Scale Impacts in the Coming Decades

NASA Astrophysics Data System (ADS)

Masiero, J. R.; Bauer, J. M.; Grav, T.; Mainzer, A. K.

2017-02-01

Asteroid impacts offer a unique opportunity to study the collisional processes that shape planetary systems. In the coming decades, expanded surveys may give us the chance to predict an impact with enough advance warning to observe it in situ.

Nine Galileo Views in Exaggerated Color of Main-Belt Asteroid Ida

NASA Technical Reports Server (NTRS)

1997-01-01

This set of color images of asteroid 243 Ida was taken by the imaging system on the Galileo spacecraft as it approached and raced past the asteroid on August 28, 1993. These images were taken through the 4100-angstrom (violet), 7560-angstrom (infrared) and 9680- angstrom (infrared) filters and have been processed to show Ida in exaggerated color to bring out subtle color contrasts caused by small variations in composition and surface microtexture of the asteroid's soil. In natural color Ida appears gray with slight overtones of red or brown. Stark shadows portray Ida's irregular shape, which changes its silhouetted outline when seen from different angles. More subtle shadings reveal surface topography (such as craters) and differences in the physical state and composition of the soil ('regolith'). Note in particular the color differences associated with the rims and floors of certain impact craters, which may have excavated to layers of slightly differing composition or may have ingested material from impactors of different compositions. Analysis of the images show that Ida is 58 kilometers long and 23 kilometers wide (36 x 14 miles). Ida is the first asteroid discovered to have a natural satellite, Dactyl (not shown here). Ida and Dactyl are heavily cratered by impacts with smaller asteroids and comets, including some of the same populations of small objects that bombard Earth. These data, combined with reflectance spectra from Galileo's near-infrared mapping spectrometer, may allow scientists to determine whether Ida is a relatively unaltered primitive object made of material condensed from the primordial Solar Nebula at the origin of the Solar System or whether it has been altered by strong heating--evidence interpreted so far suggests that Ida is a piece of a larger object that has been severely heated. Whereas heating and melting of large planets is well understood, the cause of heating of small asteroids is more enigmatic--it may have involved exotic processes that occurred only for a short time after the birth of the Sun and its planets.

Solar Power at Play

NASA Astrophysics Data System (ADS)

2007-03-01

For the very first time, astronomers have witnessed the speeding up of an asteroid's rotation, and have shown that it is due to a theoretical effect predicted but never seen before. The international team of scientists used an armada of telescopes to discover that the asteroid's rotation period currently decreases by 1 millisecond every year, as a consequence of the heating of the asteroid's surface by the Sun. Eventually it may spin faster than any known asteroid in the solar system and even break apart. ESO PR Photo 11a/07 ESO PR Photo 11a/07 Asteroid 2000 PH5 "The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is believed to alter the way small bodies in the Solar System rotate," said Stephen Lowry (Queens University Belfast, UK), lead-author of one of the two companion papers in which this work is reported [1, 2]. "The warming caused by sunlight hitting the surfaces of asteroids and meteoroids leads to a gentle recoil effect as the heat is released," he added. "By analogy, if one were to shine light on a propeller over a long enough period, it would start spinning." Although this is an almost immeasurably weak force, its effect over millions of years is far from negligible. Astronomers believe the YORP effect may be responsible for spinning some asteroids up so fast that they break apart, perhaps leading to the formation of double asteroids. Others may be slowed down so that they take many days to complete a full turn. The YORP effect also plays an important role in changing the orbits of asteroids between Mars and Jupiter, including their delivery to planet-crossing orbits, such as those of near-Earth asteroids. Despite its importance, the effect has never been seen acting on a solar system body, until now. Using extensive optical and radar imaging from powerful Earth-based observatories, astronomers have directly observed the YORP effect in action on a small near-Earth asteroid, known as (54509) 2000 PH5. Shortly after its discovery in 2000, it was realised that asteroid 2000 PH5 would be the ideal candidate for such a YORP detection. With a diameter of just 114 metres, it is relatively small and so more susceptible to the effect. Also, it rotates very fast, with one 'day' on the asteroid lasting just over 12 Earth minutes, implying that the YORP effect may have been acting on it for some time. With this in mind, the team of astronomers undertook a long term monitoring campaign of the asteroid with the aim of detecting any tiny changes in its rotation speed. Over a 4-year time span, Stephen Lowry, Alan Fitzsimmons and colleagues took images of the asteroid at a range of telescope sites including ESO's 8.2-m Very Large Telescope array and 3.5-m New Technology Telescope in Chile, the 3.5-m telescope at Calar Alto, Spain, along with a suite of other telescopes from the Czech Republic, the Canary Islands, Hawaii, Spain and Chile. With these facilities the astronomers measured the slight brightness variations as the asteroid rotated. ESO PR Photo 11b/07 ESO PR Photo 11b/07 Radar Images of 2000 PH5 Over the same time period, the radar team led by Patrick Taylor and Jean-Luc Margot of Cornell University employed the unique capabilities of the Arecibo Observatory in Puerto Rico and the Goldstone radar facility in California to observe the asteroid by 'bouncing' a radar pulse off the asteroid and analysing its echo. "With this technique we can reconstruct a 3-D model of the asteroid's shape, with the necessary detail to allow a comparison between the observations and theory," said Taylor. After careful analysis of the optical data, the asteroid's spin rate was seen to steadily increase with time, at a rate that can be explained by the YORP theory. Critically, the effect was observed year after year, for more than 4 years. Furthermore, this number was elegantly supported via analysis of the combined radar and optical data, as it was required that the asteroid is increasing its spin rate at exactly this rate in order for a satisfactory 3-D shape model to be determined. ESO PR Video 11/07 ESO PR Video 11c/07 Watch the Asteroid Move! To predict what will happen to the asteroid in the future, Lowry and his colleagues performed detailed computer simulations using the measured strength of the YORP effect and the detailed shape model. They found that the orbit of the asteroid about the Sun could remain stable for up to the next 35 million years, allowing the rotation period to be reduced by a factor of 36, to just 20 seconds, faster than any asteroid whose rotation has been measured until now. "This exceptionally fast spin-rate could force the asteroid to reshape itself or even split apart, leading to the birth of a new double system," said Lowry.

TRIGGERING SUBLIMATION-DRIVEN ACTIVITY OF MAIN BELT COMETS

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

Haghighipour, N.; Maindl, T. I.; Dvorak, R.

2016-10-10

It has been suggested that the comet-like activity of main belt comets (MBCs) is due to the sublimation of sub-surface water–ice that has been exposed as a result of their surfaces being impacted by meter-sized bodies. We have examined the viability of this scenario by simulating impacts between meter-sized and kilometer-sized objects using a smooth particle hydrodynamics approach. Simulations have been carried out for different values of the impact velocity and impact angle, as well as different target material and water-mass fractions. Results indicate that for the range of impact velocities corresponding to those in the asteroid belt, the depthmore » of an impact crater is slightly larger than 10 m, suggesting that if the activation of MBCs is due to the sublimation of sub-surface water–ice, this ice has to exist no deeper than a few meters from the surface. Results also show that ice exposure occurs in the bottom and on the interior surface of impact craters, as well as on the surface of the target where some of the ejected icy inclusions are re-accreted. While our results demonstrate that the impact scenario is indeed a viable mechanism to expose ice and trigger the activity of MBCs, they also indicate that the activity of the current MBCs is likely due to ice sublimation from multiple impact sites and/or the water contents of these objects (and other asteroids in the outer asteroid belt) is larger than the 5% that is traditionally considered in models of terrestrial planet formation, providing more ice for sublimation. We present the details of our simulations and discuss their results and implications.« less

Yarkovsky-driven Impact Predictions: Apophis and 1950 DA

NASA Astrophysics Data System (ADS)

Chesley, Steven R.; Farnocchia, D.; Chodas, P. W.; Milani, A.

2013-10-01

Orbit determination for Near-Earth Asteroids presents unique technical challenges due to the imperative of early detection and careful assessment of the risk posed by specific Earth close approaches. The occurrence of an Earth impact can be decisively driven by the Yarkovsky effect, which is the most important nongravitational perturbation as it causes asteroids to undergo a secular variation in semimajor axis resulting in a quadratic effect in anomaly. We discuss the cases of (99942) Apophis and (29075) 1950 DA. The relevance of the Yarkovsky effect for Apophis is due to a scattering close approach in 2029 with minimum geocentric distance ~38000 km. For 1950 DA the influence of the Yarkovsky effect in 2880 is due to the long time interval preceding the impact. We use the available information from the astrometry and the asteroids' physical models and dynamical evolution as a starting point for a Monte Carlo method that allows us to measure how the Yarkovsky effect affects orbital predictions. We also find that 1950 DA has a 98% likelihood of being a retrograde rotator. For Apophis we map onto the 2029 close approach b-plane and analyze the keyholes corresponding to resonant close approaches. For 1950 DA we use the b-plane corresponding to the possible impact in 2880. We finally compute the impact probability from the mapped probability density function on the considered b-plane. For Apophis we have 4 in a million chances of an impact in 2068, while the probability of Earth impact in 2880 for 1950 DA is 0.04%.

Impact on Comets and Asteroids

NASA Technical Reports Server (NTRS)

OKeefe, John D.; Stewart, Sarah T.; Ahrens, Thomas J.

2001-01-01

We characterized the impact physics in collisions on porous bodies by various density projectiles and defined different penetration modes (compression, spreading, or breakup) based on transitions between instability regimes. Additional information is contained in the original extended abstract.

An experimental study on low-velocity low-gravity collisions into granular surfaces

NASA Astrophysics Data System (ADS)

Sunday, C.; Murdoch, N.; Mimoun, D.

2014-07-01

The Japanese Space Agency (JAXA) is scheduled to launch the asteroid sample-return mission, Hayabusa-2, to target body 1999 JU_3 in December 2014 [1]. The spacecraft will arrive at the C-type near-Earth asteroid in mid-2018 and deploy several science payloads to its surface. Among these payloads is a 10-kg lander, the Mobile Asteroid Surface Scout (MASCOT), provided by the German Space Agency (DLR) with cooperation from the Centre National d'Etudes Spatiales (CNES). MASCOT will reach the asteroid's surface with an anticipated impact speed of 10--20 cm/s. In addition to housing four instruments for in-situ science investigation, MASCOT contains a mobility mechanism that will correct its orientation and enable it to ''hop'' to various measurement sites [2]. Based on thermal infrared observations [3,4,5] and previous space missions [6,7], it is strongly believed that 1999 JU_3 is covered by loose regolith. The asteroid's granular surface, in combination with the low surface gravity, makes it difficult to predict the lander's collision behavior from existing theoretical models. However, to ensure that MASCOT can successfully fulfill its mission, it is vital to understand the rebound dynamics of the lander in the asteroid surface environment. The objective of this work, derived from the needs of current and future asteroid missions, is to present an experiment designed to study low-velocity, low-gravity collisions into granular surfaces. The experiment measures the amount of energy lost during impact via a projectile's coefficient of restitution and also the acceleration profile of the projectile during collision. The key challenge to designing an asteroid collision experiment is finding a way to simulate reduced gravity conditions on the Earth so that the prevailing forces in micro-gravity collisions can be reflected in the experimental results. The proposed way to achieve this goal is to let a free-falling projectile impact a surface with a constant downward acceleration, or an acceleration less than that of gravity, so that the effective surface acceleration felt by the grains at impact is very small. In reducing the effective surface acceleration of the granular material, the medium's inter-grain cohesion forces will become more important compared to its weight force [8], and the properties of the granular material will become more representative of those on an asteroid's surface. The concept of effective acceleration drives the design of this experiment and results in the following key features: First, the granular surface is given a constant downward acceleration using an Atwood machine, or a system of pulleys and counterweights. Next, the projectile and surface are simultaneously released from rest using a magnetic solenoid and hook assembly. The starting height of the surface container and the initial separation distance between the projectile and surface are variable and chosen to accommodate collision velocities of 10--20 cm/s and effective accelerations of 0.3--1.0 m/s^2. Finally, wireless accelerometers, placed on the surface container and in the projectile, provide acceleration data, while high-speed cameras capable of recording 100,000 frames per second capture the collision and act as secondary data sources. The experiment is built into an existing 6-m drop-tower frame and requires the custom design of all components, including the projectile, surface sample container, release mechanism, and deceleration system. This work will present the detailed design of the asteroid-collision experiment as well as a discussion on the planned experimental trials. The experimental results, once obtained, will be used to create a scaling law that will help predict a projectile's rebound and acceleration behavior during a low-velocity collision into a granular surface in micro-gravity conditions.

X-Ray Micro-Tomography Applied to Nasa's Materials Research: Heat Shields, Parachutes and Asteroids

NASA Technical Reports Server (NTRS)

Panerai, Francesco; Borner, Arnaud; Ferguson, Joseph C.; Mansour, Nagi N.; Stern, Eric C.; Barnard, Harold S.; Macdowell, Alastair A.; Parkinson, Dilworth Y.

2017-01-01

X-ray micro-tomography is used to support the research on materials carried out at NASA Ames Research Center. The technique is applied to a variety of applications, including the ability to characterize heat shield materials for planetary entry, to study the Earth- impacting asteroids, and to improve broadcloths of spacecraft parachutes. From micro-tomography images, relevant morphological and transport properties are determined and validated against experimental data.

The Impact Clan: A Disenchanted Look at Asteroid Impact Monitoring Science

NASA Astrophysics Data System (ADS)

D'Abramo, Germano

2015-11-01

Synopsis: How many times in the last decade have you heard announcements about asteroids with unusually high Earth-collision chances in the near future? Surely more than once, we guess. It is not difficult to find sentences like "this is one of most dangerous asteroids ever found" every now and then in the media. It is probably difficult for the man in the street to reconcile his (ordinary) perception of risk with something that, despite these continuous and alarming announcements, has never happened and is still not happening: how many people have been killed by these nasty asteroids in the history of mankind? Earthquakes, floods, and volcanic eruptions are known to be dangerous because they have already struck with a high death toll. This book is an informed and disenchanted review of the activity of the so-called "Impact Monitoring Systems", which were born in the late 90's. The author happened to be involved in this business right from the outset, when he started his research career. His critique addresses directly the merits of that science, providing the reader with scientific and rigorous arguments against the worth of such an activity, at least in the way in which it is currently being carried out. But this book also brings together the personal and human vicissitudes of the author, experienced during his 16 years spent in Astronomy and Astrophysics research, his views on Science, Life and Society. The book is non-fiction; it is accessible to any (curious) person with a high-school/college level education.

The Unique Geomorphology and Physical Properties of the Vestalia Terra Plateau

NASA Technical Reports Server (NTRS)

Buczkowski, D.L.; Wyrick, D.Y.; Toplis, M.; Yingst, R. A.; Williams, D. A.; Garry, W. B.; Mest, S.; Kneissl, T.; Scully, J. E. C.; Nathues, A.;

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.

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.

Incorporating Uncertainty into Spacecraft Mission and Trajectory Design

NASA Astrophysics Data System (ADS)

Juliana D., Feldhacker

The complex nature of many astrodynamic systems often leads to high computational costs or degraded accuracy in the analysis and design of spacecraft missions, and the incorporation of uncertainty into the trajectory optimization process often becomes intractable. This research applies mathematical modeling techniques to reduce computational cost and improve tractability for design, optimization, uncertainty quantication (UQ) and sensitivity analysis (SA) in astrodynamic systems and develops a method for trajectory optimization under uncertainty (OUU). This thesis demonstrates the use of surrogate regression models and polynomial chaos expansions for the purpose of design and UQ in the complex three-body system. Results are presented for the application of the models to the design of mid-eld rendezvous maneuvers for spacecraft in three-body orbits. The models are shown to provide high accuracy with no a priori knowledge on the sample size required for convergence. Additionally, a method is developed for the direct incorporation of system uncertainties into the design process for the purpose of OUU and robust design; these methods are also applied to the rendezvous problem. It is shown that the models can be used for constrained optimization with orders of magnitude fewer samples than is required for a Monte Carlo approach to the same problem. Finally, this research considers an application for which regression models are not well-suited, namely UQ for the kinetic de ection of potentially hazardous asteroids under the assumptions of real asteroid shape models and uncertainties in the impact trajectory and the surface material properties of the asteroid, which produce a non-smooth system response. An alternate set of models is presented that enables analytic computation of the uncertainties in the imparted momentum from impact. Use of these models for a survey of asteroids allows conclusions to be drawn on the eects of an asteroid's shape on the ability to successfully divert the asteroid via kinetic impactor.

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.

Nasa s near earth object program office

NASA Astrophysics Data System (ADS)

Yeomans, D.; Chamberlin, A.; Chesley, S.; Chodas, P.; Giorgini, J.; Keesey, M.

In 1998, NASA formed the Near-Earth Object Program Office at JPL to provide a focal point for NASA's efforts to discover and monitor the motions of asteroids and comets that can approach the Earth. This office was charged with 1.) facilitating communication between the near-Earth object (NEO) community and the public, 2.) helping coordinate the search efforts for NEOs, 3.) monitoring the progress in finding NEOs at NASA -supported sites, and 4.) monitoring the future motions of all known NEOs and cataloging their orbits. There are far more near-Earth asteroids (NEAs) than near-Earth comets and one of the driving motivations for NASA's NEO Program is the Spaceguard Goal to find 90% of the NEAs larger than one kilometer by 2008. While the total population of NEAs is not clearly established, the consensus opinion seems to be that the total population of NEAs larger than one kilometer is about 1000 (with a range of perhaps 800 - 1200). By April 2002, nearly 60% of the total population of large NEAs had been discovered and while the discovery rate will likely drop off as the easy ones are found, these early discovery efforts are encouraging. The five NASA-supported NEO discovery teams are the Lincoln Laboratory Near-Earth Asteroid Research effort (LINEAR, Grant Stokes, Principal Investigator), the Near-Earth Asteroid Tracking team at JPL (NEAT, Eleanor Helin, P.I.), the Lowell Observatory Near-Earth Object Search (LONEOS, E. Bowell, P.I.), and two discovery teams near Tucson Arizona - the Spacewatch effort (R. McMillan, P.I.) and the Catalina Sky Survey group (S. Larson, P.I.). Mention should also be made of the Japanese Spaceguard discovery site at Bisei Japan (S. Isobe, P.I.). A substantial portion of the critical follow-up observations necessary to secure the orbits of NEOs and provide information on their physical characteristics is provided by a group of very sophisticated amateur astronomers who might better be described as unfunded professionals. After nearly two years in development, the JPL SENTRY system has been brought on line to provide automatic updates of near-Earth asteroid (NEA) orbits and to predict future close Earth approaches along with their associated impact probabilities. For those NEAs that can approach the Earth, a Palermo Scale risk number is computed based upon the object's impact probability at a particular time, the energy upon impact and the time interval before the potential impact. A Palermo Scale number larger than zero implies the predicted impact event has risen above the expected background level of impacts that could occur between now and the predicted time of impact from all NEAs of the same size or larger. Computed Palermo Scale values are used to prioritize automatic Monte Carlo numerical integration runs to determine robust impact probabilities for those NEAs where a future impact cannot be ruled out - usually because of poor orbits and/or close planetary encounters. Our interactive web site at http://neo.jpl.nasa.gov will allow the user access to the latest information on NEOs including coming close Earth approaches, the risk page for poorly determined orbits, the progress toward meeting the Spaceguard Goal, links to the web sites of the NEO search teams, the rationale for studying NEOs, space missions to NEOs, as well as information on the characteristics, future motions, orbits and orbital movies for well over 120,000 comets and asteroids.

Space Radar of Image Aorounga Impact Crater, Chad

NASA Image and Video Library

1999-04-15

The impact of an asteroid or comet several hundred million years ago left scars in the landscape that are still visible in this spaceborne radar image of an area in the Sahara Desert of northern Chad.

Space Radar Image of Possible String of Impact Creaters

NASA Image and Video Library

1999-04-15

The impact of an asteroid or comet several hundred million years ago left scars in the landscape that are still visible in this spaceborne radar image of an area in the Sahara Desert of northern Chad.

Successive Formation of Impact Craters

NASA Image and Video Library

2012-02-16

This image from NASA Dawn spacecraft shows two overlapping impact craters on asteroid Vesta. The rims of the craters are both reasonably fresh but the larger crater must be older because the smaller crater cuts across the larger crater rim.

Vesta Surface at High Resolution: Dominated by Impact Craters

NASA Image and Video Library

2012-02-13

This image from NASA Dawn spacecraft shows a large number of craters, formed by collisions into the surface of asteroid Vesta. The relatively large circular depressions in this image are older, heavily degraded impact craters.

Collisional Histories of Comets and Trojan Asteroids: Diopside, Magnesite, and Fayalite Impact Studies

NASA Technical Reports Server (NTRS)

Lederer, S. M.; Jensen, E. A.; Wooden, D. H.; Lindsay, S. S.; Nakamura-Messenger, K.; Smith, D. C.; Keller, L. P.; Cintala, M. J.; Zolensky, M. E.

2012-01-01

Comets and asteroids have weathered dynamic histories, as evidenced by their rough surfaces. The Nice model describes a violent reshuffling of small bodies during the Late Heavy Bombardment, with collisions acting to grind these planetesimals away. This creates an additional source of impact material that can re-work the surfaces of the larger bodies over the lifetime of the solar system. Here, we investigate the possibility that signatures due to impacts (e.g. from micrometeoroids or meteoroids) could be detected in their spectra, and how that can be explained by the physical manifestation of shock in the crystalline structure of minerals. All impact experiments were conducted in the Johnson Space Center Experimental Impact Laboratory using the vertical gun. Impact speeds ranged from approx.2.0 km/s to approx.2.8 km/s. All experiments were conducted at room temperature. Minerals found in comets and asteroids were chosen as targets, including diopside (MgCaSi2O6, monoclinic pyroxene), magnesite (MgCO3, carbonate), and fayalite (FeSiO4, olivine). Impacted samples were analyzed using a Fourier Transform Infrared Spectrometer (FTIR) and a Transmission Electron Microscope (TEM). Absorbance features in the 8-13 m spectral region demonstrate relative amplitude changes as well as wavelength shifts. Corresponding TEM images exhibit planar shock dislocations in the crystalline structure, attributed to deformation at high strain and low temperatures. Elongating or shortening the axes of the crystalline structure of forsterite (Mg2SiO4, olivine) using a discrete dipole approximation model (Lindsay et al., submitted) yields changes in spectral features similar to those observed in our impacted laboratory minerals.

System Configuration and Operation Plan of Hayabusa2 DCAM3-D Camera System for Scientific Observation During SCI Impact Experiment

NASA Astrophysics Data System (ADS)

Ogawa, Kazunori; Shirai, Kei; Sawada, Hirotaka; Arakawa, Masahiko; Honda, Rie; Wada, Koji; Ishibashi, Ko; Iijima, Yu-ichi; Sakatani, Naoya; Nakazawa, Satoru; Hayakawa, Hajime

2017-07-01

An artificial impact experiment is scheduled for 2018-2019 in which an impactor will collide with asteroid 162137 Ryugu (1999 JU3) during the asteroid rendezvous phase of the Hayabusa2 spacecraft. The small carry-on impactor (SCI) will shoot a 2-kg projectile at 2 km/s to create a crater 1-10 m in diameter with an expected subsequent ejecta curtain of a 100-m scale on an ideal sandy surface. A miniaturized deployable camera (DCAM3) unit will separate from the spacecraft at about 1 km from impact, and simultaneously conduct optical observations of the experiment. We designed and developed a camera system (DCAM3-D) in the DCAM3, specialized for scientific observations of impact phenomenon, in order to clarify the subsurface structure, construct theories of impact applicable in a microgravity environment, and identify the impact point on the asteroid. The DCAM3-D system consists of a miniaturized camera with a wide-angle and high-focusing performance, high-speed radio communication devices, and control units with large data storage on both the DCAM3 unit and the spacecraft. These components were successfully developed under severe constraints of size, mass and power, and the whole DCAM3-D system has passed all tests verifying functions, performance, and environmental tolerance. Results indicated sufficient potential to conduct the scientific observations during the SCI impact experiment. An operation plan was carefully considered along with the configuration and a time schedule of the impact experiment, and pre-programed into the control unit before the launch. In this paper, we describe details of the system design concept, specifications, and the operating plan of the DCAM3-D system, focusing on the feasibility of scientific observations.

A Mobile Asteroid Surface Scout (MASCOT) for the Hayabusa 2 Mission to 1999 JU3: The Scientific Approach

NASA Astrophysics Data System (ADS)

Jaumann, Ralf; Bibring, Jean-Pierre; Glassmeier, Karl-Heinz; Grott, Matthias; Ho, Tra-Mi; Ulamec, Stepahn; Schmitz, Nicole; Auster, Ulrich; Biele, Jens; Kuninaka, Hitoshi; Okada, Tatsuaki; Yoshikawa, Makoto; Watanabe, Sei-ichhiro; Fujimoto, Masaki; Spohn, Tilman; Koncz, Alexander; Michaelis, Harald

2014-05-01

MASCOT, a Mobile Asteroid Surface Scout, will support JAXA's Hayabusa 2 mission to investigate the C-type asteroid 1999 JU3 (1). The German Aer-ospace Center (DLR) develops MASCOT with contributions from CNES (France) (2,3). Main objective is to in-situ map the asteroid's geomorpholo-gy, the intimate structure, texture and composition of the regolith (dust, soil and rocks), and the thermal, mechanical, and magnetic properties of the sur-face in order to provide ground truth for the orbiter remote measurements, support the selection of sampling sites, and provide context information for the returned samples. MASCOT comprises a payload of four scientific in-struments: camera, radiometer, magnetometer and hyperspectral microscope. C- and D-type asteroids hold clues to the origin of the solar system, the for-mation of planets, the origins of water and life on Earth, the protection of Earth from impacts, and resources for future human exploration. C- and D-types are dark and difficult to study from Earth, and have only been glimpsed by spacecraft. While results from recent missions (e.g., Hayabusa, NEAR (4, 5, 6)) have dramatically increased our understanding of asteroids, important questions remain. For example, characterizing the properties of asteroid regolith in-situ would deliver important ground truth for further understanding telescopic and orbital observations and samples of such aster-oids. MASCOT will descend and land on the asteroid and will change its position two times by hopping. This enables measurements during descent, at the landing and hopping positions #1-3, and during hopping. References: (1) Vilas, F., Astronomical J. 1101-1105, 2008; (2) Ulamec, S., et al., Acta Astronautica, Vol. 93, pp. 460-466; (3) Jaumann et al., 45th LPSC, Houston; (4) Special Issue, Science, Vol. 312 no. 5778, 2006; (5) Special Issue Science, Vol. 333 no. 6046, 2011. (6) Bell, L., Mitton, J-., Cambridge Univ. Press, 2002.

A Mobile Asteroid Surface Scout (MASCOT) for the Hayabusa 2 Mission to 1999 JU3: The Scientific Approach

NASA Astrophysics Data System (ADS)

Jaumann, Ralf; Bibring, Jean-Pierre; Glassmeier, Karl-Heinz; Grott, Matthias; Ho, Tra-Mie; Ulamec, Stephan; Schmitz, Nicole; Auster, Hans-Ulrich; Biele, Jens; Kuninaka, Hitoshi; Okada, Tatsuaki; Yoshikawa, Makoto; Watanabe, Sei-ichhiro; Fujimoto, Masaki; Spohn, Tilman

2013-04-01

Mascot, a Mobile Asteroid Surface Scout, will support JAXA's Hayabusa 2 mission to investigate the C-type asteroid 1999 JU3 (1). The German Aero-space Center (DLR) develops Mascot with contributions from CNES (France) (2). Main objective is to in-situ map the asteroid's geomorphology, the intimate structure, texture and composition of the regolith (dust, soil and rocks), and the thermal, mechanical, and magnetic properties of the surface in order to provide ground truth for the orbiter remote measurements, sup-port the selection of sampling sites, and provide context information for the returned samples. Mascot comprises a payload of four scientific instruments: camera, radiometer, magnetometer and hyperspectral microscope. C- and D-type asteroids hold clues to the origin of the solar system, the formation of planets, the origins of water and life on Earth, the protection of Earth from impacts, and resources for future human exploration. C- and D-types are dark and difficult to study from Earth, and have only been glimpsed by spacecraft. While results from recent missions (e.g., Hayabusa, NEAR (3, 4, 5)) have dramatically increased our understanding of asteroids, important questions remain. For example, characterizing the properties of asteroid reg-olith in-situ would deliver important ground truth for further understanding telescopic and orbital observations and samples of such asteroids. Mascot will descend and land on the asteroid and will change its position two times by hopping. This enables measurements during descent, at the landing and hopping positions #1-3, and during hopping. References: (1) Vilas, F., Astronomical J. 1101-1105, 2008; (2) Ulamec, S., et al., COSPAR, General Assembly, Mysore/India, 2012; (3) Special Issue, Science, Vol. 312 no. 5778, 2006; (4) Special Issue Science, Vol. 333 no. 6046, 2011; (5) Bell, L., Mitton, J-., Cambridge Univ. Press, 2002.

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

NASA Astrophysics Data System (ADS)

Britt, D. T.

2003-05-01

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

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.

New Results on Hydration in M-Type Asteroids

NASA Astrophysics Data System (ADS)

Landsman, Zoe A.; Campins, Humberto; Pinilla-Alonso, Noemí; Emery, Joshua P.; Lorenzi, Vania

2014-11-01

The M-type asteroids are a taxonomic group considered to be a candidate source of iron meteorites due to spectral and albedo similarities; however, because the spectra of M-type asteroids lack strong diagnostic absorption features in the near-infrared (NIR), their composition is difficult to constrain. High-resolution NIR spectroscopy and radar studies have shown that a metallic interpretation is unlikely to be valid for the majority of M-types. Many show weak absorption features attributed to mafic silicates (Hardersen et al. 2005, 2011; Ockert-Bell et al. 2010; Fornasier et al. 2010). Radar results show evidence for elevated metal content on the surfaces of most M-type asteroids, but few are likely to be entirely metal (Shepard et al. 2010). Surprisingly, spectrophotometric studies in the 3-μm region have indicated that hydrated minerals are relatively common among the M-type population, confounding interpretations of M-types as highly thermally processed (Rivkin et al. 1995, 2000). The shape of the 3-μm band, diagnostic of hydrated and hydroxylated minerals, is relevant to an asteroid’s thermal history (Rivkin et al. 2002, Takir & Emery 2012). To characterize this region, we have conducted a 2 - 4 μm spectroscopic study of six M-type asteroids using SpeX at NASA’s Infrared Telescope Facility. In its LXD mode, SpeX allows us to investigate the 3-μm band at spectral resolutions unavailable during previously published studies. We report the presence of a 3-μm feature on all six asteroids, indicating hydrated minerals on the asteroids’ surfaces. We have also detected rotational variability of the 3-μm feature in asteroid (216) Kleopatra, which, interestingly, had been interpreted as “dry” in previous work (Rivkin et al. 2000). On all of our target asteroids, the 3-μm band depths are < 10%, and there is apparent variation in the shape of the feature among them. We discuss the impact of our results on interpretations of M-type asteroid composition.

Hydrocode Models of Mitigation of a 170-Meter-Diameter Asteroid Using Energetic Techniques

NASA Astrophysics Data System (ADS)

Plesko, C. S.; Gisler, G. R.; Heberling, T.; Nouanesengsy, B.; Patchett, J.; Sagert, I.; Tarnowsky, T. J.; Weaver, R.

2017-12-01

Binary asteroid 65803 Didymos is the target of the proposed NASA Double Asteroid Redirection Test (DART) mission. The smaller member of the binary pair, S/2003 (65803) Didymos B, is approximately 170 meters in diameter. Didymos A is spectrally similar to H-LL ordinary chondrites and asteroids Eros and Itokawa, so we assume Didymos B is similar. We also assume it to be a rubble pile aggregate of material from Didymos A, and take further guidance on material properties from the AIM Didymos Reference Model V. 10 (P. Michel et al., 2015). We are modeling deflection attempts by kinetic impactor and nuclear stand-off burst against a hypothetical solo Didymos B asteroid as part of the NASA-NNSA inter-agency collaboration on impact hazard mitigation. The collaboration agreed on model initial conditions at our February 2017 Technical Interchange Meeting. The kinetic impactor is a 63.5 cm-diameter aluminum impactor striking at 10 km/s. We model the stand-off nuclear burst according to procedures described in Barbee et al. (Acta A. 2017) and Dearborn et al. (in press). We will present our model predictions and their implications for planetary defense mission design space.

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.

Detailed Pictures of Multiple Asteroid Systems in the Main-Belt

NASA Astrophysics Data System (ADS)

Marchis, F.; Emery, J. P.; Enriquez, J. E.; Descamps, P.; Berthier, J.; Vachier, F.; Durech, J.

2011-12-01

Since their discovery less than 10 years ago, ~200 known multiple asteroid systems have been studied with a combination of observing techniques, including adaptive optics, lightcurve photometry, and mid-infrared spectrophotometry. Those observations show that ~15 large (D>100km) asteroids that are known to possess km-sized satellite(s) (22 Kalliope, 45 Eugenia, 87 Sylvia, 93 Minerva, 216 Kleopatra, ...) share common orbital characteristics, implying a common formation scenario: e.g. catastrophic disruption or ejection after an oblique impact. More than 70 smaller (10-15km) binary asteroid systems have been detected through anomalies in their lightcurves and are believed to have formed by fission due to the YORP effect. By comparison with meteorite analog densities, mid-IR data reveal that these systems have a significant porosity (larger than 30%) implying a rubble-pile interior. We will review these key results and discuss their implications for the interior of asteroids in the light of recent space mission results. Future explorations using new ground-based facilities and space mission concepts will be also discussed. This work is supported by the NSF grant AAG-0807468 and NASA grant NNX11AD62G

Near-Earth asteroid discovery rate review

NASA Technical Reports Server (NTRS)

Helin, Eleanor F.

1991-01-01

Fifteen to twenty years ago the discovery of 1 or 2 Near Earth Asteroids (NEAs) per year was typical from one systematic search program, Palomar Planet Crossing Asteroid Survey (PCAS), and the incidental discovery from a variety of other astronomical program. Sky coverage and magnitude were both limited by slower emulsions, requiring longer exposures. The 1970's sky coverage of 15,000 to 25,000 sq. deg. per year led to about 1 NEA discovery every 13,000 sq. deg. Looking at the years from 1987 through 1990, it was found that by comparing 1987/1988 and 1989/1990, the world discovery rate of NEAs went from 20 to 43. More specifically, PCAS' results when grouped into the two year periods, show an increase from 5 discoveries in the 1st period to 20 in the 2nd period, a fourfold increase. Also, the discoveries went from representing about 25 pct. of the world total to about 50 pct. of discoveries worldwide. The surge of discoveries enjoyed by PCAS in particular is attributed to new fine grain sensitive emulsions, film hypering, more uniformity in the quality of the photograph, more equitable scheduling, better weather, and coordination of efforts. The maximum discoveries seem to have been attained at Palomar Schmidt.

The Survival of Meteorite Organic Compounds with Increasing Impact Pressure

NASA Technical Reports Server (NTRS)

Cooper, George; Horz, Friedrich; Oleary, Alanna; Chang, Sherwood; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

The majority of carbonaceous meteorites studied today are thought to originate in the asteroid belt. Impacts among asteroidal objects generate heat and pressure that may have altered or destroyed pre-existing organic matter in both targets and projectiles to a greater or lesser degree depending upon impact velocities. Very little is known about the shock related chemical evolution of organic matter relevant to this stage of the cosmic history of biogenic elements and compounds. The present work continues our study of the effects of shock impacts on selected classes of organic compounds utilizing laboratory shock facilities. Our approach was to subject mixtures of organic compounds, embedded in a matrix of the Murchison meteorite, to a simulated hypervelocity impact. The molecular compositions of products were then analyzed to determine the degree of survival of the original compounds. Insofar as results associated with velocities < 8 km/sec may be relevant to impacts on planetary surfaces (e.g., oblique impacts, impacts on small outer planet satellites) or grain-grain collisions in the interstellar medium, then our experiments will be applicable to these environments as well.

The Discovery and Analysis of a New Type of Wolf-Rayet Star

NASA Astrophysics Data System (ADS)

Nowinski, Matt Clarke

A massive impact event on (4) Vesta is believed to have created the Vesta family of asteroids (Asphaug, 1997). The rotational characteristics of the Vesta family provide important clues about this event, including its timing, the make-up of the resulting debris, the subsequent migration of members of the family into Earth-crossing orbits, and the deposition of the Howardite-Eucrite-Diogenite meteorites on the Earth's surface. This study conducted lightcurve measurements of ten Vp-type asteroids, drawn from an asteroid taxonomy defined by Carvano et al. (2010) and based on the Sloan Digital Sky Survey (SDSS) Moving Object Catalogue (MOC4). These measurements identified a range of asteroid rotation periods from approximately 2.5 to 9.5 hours, as well as a potential synchronous binary system, (15121) 2000 EN14. The lightcurve results were combined with those of other V/Vp-type asteroids available in LightCurve Database (LCDB; Warner et al., 2009), and matched with both WISE diameter/albedo (J. Masiero et al., 2011) and near-infrared spectroscopic (Hardersen et al., 2014-2018) data. This integrated approach identified a set of Vesta family asteroids with relatively fast spin rates, nearly spherical shapes, and loose aggregate compositions. These findings, combined with the non-Maxwellian shape of this population's spin rate distribution, highlighted the importance of thermal Yarkovsky-YORP effects on the evolution of the Vesta family.

Dynamics of ejecta from a binary asteroid impact in the framework of the AIDA mission: a NEOShield-2 contribution

NASA Astrophysics Data System (ADS)

Yu, Y.; Schwartz, S. R.; Michel, P.; Benner, L. A. M.

2015-10-01

The dynamics of the ejecta cloud that results from a binary asteroid impact is one of the tasks of the NEOShield-2 project, funded by the European Commission in its program Horizon 2020. Results from such an investigation will have great relevance to the Phase-A study of the AIDA space mission, a collaborative effort between ESA and NASA, which aims to perform a kinetic impactor demonstration. Our study presents a multi-scale dynamical model of the ejecta cloud produced by a hypervelocity impact, which enables us to check the behaviors of the ejecta at different spatial and time scales. This model is applied to the impact into the small moon of the binary Near- Earth asteroid (65803) Didymos on October 2022 as considered by the AIDA mission. We attempt to model the process by including as much practical information as possible, e.g., the gravitational environment influenced by the non-spherical shapes of the bodies based on observed shape of the primary), the solar tides, and the solar radiation pressure. Our simulations show the general patterns of motion of the ejecta cloud, which we use to assess the potential hazard to an observing spacecraft. We also look into the grain-scale dynamics of the ejecta during this process, which has influence on the re-accumulation of particles orbiting in the vicinity.

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

Unmelted meteoritic debris in the Late Pliocene iridium anomaly - Evidence for the ocean impact of a nonchondritic asteroid

NASA Technical Reports Server (NTRS)

Kyte, F. T.; Brownlee, D. E.

1985-01-01

Ir-bearing particles have been recovered from two piston cores in the Antarctic Basin in the southeastern Pacific. In core E13-3, the particles closely correspond to the Late Pliocene Ir anomaly and have a fluence of about 100 mg/cm sq. In core E13-4, 120 km to the southwest, the particle fluence is about 4 mg/cm sq. Particles with diameters from 0.5 to 4 mm contain at least 35 percent of the Ir in this horizon. Three types of particles have been identified: (1) vesicular, (2) basaltic, and (3) metal. The vesicular particles appear to be shock-melted debris derived from the oceanic impact of a howarditic asteroid containing a minor metal component. These particles have recrystallized from a melt and impact into the ocean has resulted in the incorporation of Na, K, Cl, and radiogenic Sr from the ocean water target. The basaltic clasts appear to be unmelted fragments of the original asteroid which may have separated from the main body prior to impact. Combined vesicular and basaltic particles are believed to have formed by collisions in the debris cloud. Estimates of the diameter of the projectile range from 100 to 500 m. By many orders of magnitude, this is the most massive achondrite sampled by a single meteorite fall.

KSC-2014-3133

NASA Image and Video Library

2014-07-03

CAPE CANAVERAL, Fla. – Former NASA astronaut Tom Jones discusses the characteristics of asteroids and meteors with a young guest during the grand opening of the Great Balls of Fire exhibit at NASA’s Kennedy Space Center Visitor Complex in Florida. Great Balls of Fire shares the story of the origins of our solar system, asteroids and comets and their possible impacts and risks. The 1,500-square-foot exhibit, located in the East Gallery of the IMAX theatre at the visitor complex, features several interactive displays, real meteorites and replica asteroid models. The exhibit is a production of The Space Science Institute's National Center for Interactive Learning. It is a traveling exhibition that also receives funding from NASA and the National Science Foundation. Photo credit: NASA/Daniel Casper

KSC-2014-3132

NASA Image and Video Library

2014-07-03

CAPE CANAVERAL, Fla. – Former NASA astronaut Tom Jones discusses the characteristics of asteroids and meteors with a young guest during the grand opening of the Great Balls of Fire exhibit at NASA’s Kennedy Space Center Visitor Complex in Florida. Great Balls of Fire shares the story of the origins of our solar system, asteroids and comets and their possible impacts and risks. The 1,500-square-foot exhibit, located in the East Gallery of the IMAX theatre at the visitor complex, features several interactive displays, real meteorites and replica asteroid models. The exhibit is a production of The Space Science Institute's National Center for Interactive Learning. It is a traveling exhibition that also receives funding from NASA and the National Science Foundation. Photo credit: NASA/Daniel Casper

Robotic Missions to Small Bodies and Their Potential Contributions to Human Exploration and Planetary Defense

NASA Technical Reports Server (NTRS)

Abell, Paul A.; Rivkin, Andrew S.

2015-01-01

Introduction: Robotic missions to small bodies will directly address aspects of NASA's Asteroid Initiative and will contribute to future human exploration and planetary defense. The NASA Asteroid Initiative is comprised of two major components: the Grand Challenge and the Asteroid Mission. The first component, the Grand Challenge, focuses on protecting Earth's population from asteroid impacts by detecting potentially hazardous objects with enough warning time to either prevent them from impacting the planet, or to implement civil defense procedures. The Asteroid Mission involves sending astronauts to study and sample a near-Earth asteroid (NEA) prior to conducting exploration missions of the Martian system, which includes Phobos and Deimos. The science and technical data obtained from robotic precursor missions that investigate the surface and interior physical characteristics of an object will help identify the pertinent physical properties that will maximize operational efficiency and reduce mission risk for both robotic assets and crew operating in close proximity to, or at the surface of, a small body. These data will help fill crucial strategic knowledge gaps (SKGs) concerning asteroid physical characteristics that are relevant for human exploration considerations at similar small body destinations. These data can also be applied for gaining an understanding of pertinent small body physical characteristics that would also be beneficial for formulating future impact mitigation procedures. Small Body Strategic Knowledge Gaps: For the past several years NASA has been interested in identifying the key SKGs related to future human destinations. These SKGs highlight the various unknowns and/or data gaps of targets that the science and engineering communities would like to have filled in prior to committing crews to explore the Solar System. An action team from the Small Bodies Assessment Group (SBAG) was formed specifically to identify the small body SKGs under the direction of the Human Exploration and Operations Missions Directorate (HEOMD), given NASA's recent interest in NEAs and the Martian moons as potential human destinations. The action team organized the SKGs into four broad themes: 1) Identify human mission targets; 2) Understand how to work on and interact with the small body surface; 3) Understand the small body environment and its potential risk/benefit to crew, systems, and operational assets; and 4) Understand the small body resource potential. Of these four SKG themes, the first three have significant overlap with planetary defense considerations. The data obtained from investigations of small body physical characteristics under these three themes can be directly applicable to planetary defense initiatives. Conclusions: Missions to investigate small bodies can address small body strategic knowledge gaps and contribute to the overall success for human exploration missions to asteroids and the Martian moons. In addition, such reconnaissance of small bodies can also provide a wealth of information relevant to the science and planetary defense of NEAs.

The impact trajectory of asteroid 2008 TC3

NASA Astrophysics Data System (ADS)

Farnocchia, Davide; Jenniskens, Peter; Robertson, Darrel K.; Chesley, Steven R.; Dimare, Linda; Chodas, Paul W.

2017-09-01

The impact of asteroid 2008 TC3 was an unprecedented event-the first ever predicted impact of a near-Earth object. When it was first detected about 20 h before impact, 2008 TC3 was still farther away than the Moon. Once it was recognized as an impactor and announced as such, 2008 TC3 began to receive considerable attention from astronomical observers. Using the unprecedented dataset of nearly 900 astrometric observations and the latest observation debiasing and weighting techniques, we estimate the precise trajectory of 2008 TC3 and its impact ground track. At the entry point into the atmosphere, the 3-σ formal uncertainty in predicted position is an ellipse only 1.4 km × 0.15 km in size. The locations of the many meteorites recovered from the desert floor mark the asteroid's actual ground track and provide a unique opportunity to validate trajectory models. We find that the second-order zonal harmonics of the Earth gravity field moves the ground track by more than 1 km and the location along the ground track by more than 2 km, while non-zonal and higher order harmonics change the impact prediction by less than 20 m. The contribution of atmospheric drag to the trajectory of 2008 TC3 is similar to the numerical integration error level, a few meters, down to an altitude of 50 km. Integrating forward to lower altitudes and ignoring the break-up of 2008 TC3, atmospheric drag causes an along-track deviation that can be as large as a few kilometers at sea level.

Research of the orbital evolution of asteroid 2012 DA14 (in Russian)

NASA Astrophysics Data System (ADS)

Zausaev, A. F.; Denisov, S. S.; Derevyanka, A. E.

Research of the orbital evolution of asteroid 2012 DA14 on the time interval from 1800 to 2206 is made, an object close approaches with Earth and the Moon are detected, the probability of impact with Earth is calculated. The used mathematical model is consistent with the DE405, the integration was performed using a modified Everhart's method of 27th order, the probability of collision is calculated using the Monte Carlo method.

Asteroids in the service of humanity

NASA Astrophysics Data System (ADS)

Crawford, Ian A.

2013-07-01

There are at least three compelling reasons for the human race to initiate a major programme to explore and better understand the 'minor planets' of the Solar System: (1) Enhancing scientific knowledge; (2) Mitigating the impact hazard; and (3) Utilizing extraterrestrial resources. Strong synergies exist between all three. Moreover, all these activities would benefit from greater international cooperation in space exploration by the World's space agencies, and the recognition that asteroids are important targets for human and robotic exploration.

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.

BENNU’S JOURNEY - Early Earth

NASA Image and Video Library

2017-12-08

This is an artist's concept of the young Earth being bombarded by asteroids. Scientists think these impacts could have delivered significant amounts of organic matter and water to Earth. Image Credit: NASA's Goddard Space Flight Center Conceptual Image Lab The Origins Spectral Interpretation Resource Identification Security -- Regolith Explorer spacecraft (OSIRIS-REx) will travel to a near-Earth asteroid, called Bennu, and bring a sample back to Earth for study. The mission will help scientists investigate how planets formed and how life began, as well as improve our understanding of asteroids that could impact Earth. OSIRIS-REx is scheduled for launch in late 2016. As planned, the spacecraft will reach its asteroid target in 2018 and return a sample to Earth in 2023. 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

A Fragment-Cloud Model for Breakup of Asteroids with Varied Internal Structures

NASA Technical Reports Server (NTRS)

Wheeler, Lorien; Mathias, Donovan; Stokan, Ed; Brown, Peter

2016-01-01

As an asteroid descends toward Earth, it deposits energy in the atmosphere through aerodynamic drag and ablation. Asteroid impact risk assessments rely on energy deposition estimates to predict blast overpressures and ground damage that may result from an airburst, such as the one that occurred over Chelyabinsk, Russia in 2013. The rates and altitudes at which energy is deposited along the entry trajectory depend upon how the bolide fragments, which in turn depends upon its internal structure and composition. In this work, we have developed an analytic asteroid fragmentation model to assess the atmospheric energy deposition of asteroids with a range of structures and compositions. The modeling approach combines successive fragmentation of larger independent pieces with aggregate debris clouds released with each fragmentation event. The model can vary the number and masses of fragments produced, the amount of mass released as debris clouds, the size-strength scaling used to increase the robustness of smaller fragments, and other parameters. The initial asteroid body can be seeded with a distribution of independent fragment sizes amid a remaining debris mass to represent loose rubble pile conglomerations, can be given an outer regolith later, or can be defined as a coherent or fractured monolith. This approach enables the model to represent a range of breakup behaviors and reproduce detailed energy deposition features such as multiple flares due to successive burst events, high-altitude regolith blow-off, or initial disruption of rubble piles followed by more energetic breakup of the constituent boulders. These capabilities provide a means to investigate sensitivities of ground damage to potential variations in asteroid structure.

A Fragment-Cloud Approach for Modeling Atmospheric Breakup of Asteroids with Varied Internal Structures

NASA Astrophysics Data System (ADS)

Wheeler, Lorien; Mathias, Donovan; NASA Engineering Risk Assessment Team, NASA Asteroid Threat Assessment Project

2016-10-01

As an asteroid descends toward Earth, it deposits energy in the atmosphere through aerodynamic drag and ablation. Asteroid impact risk assessments rely on energy deposition estimates to predict blast overpressures and ground damage that may result from an airburst, such as the one that occurred over Chelyabinsk, Russia in 2013. The rates and altitudes at which energy is deposited along the entry trajectory depend upon how the bolide fragments, which in turn depends upon its internal structure and composition. In this work, an analytic asteroid fragmentation model has been developed to model the atmospheric breakup and resulting energy deposition of asteroids with a range of internal structures. The modeling approach combines successive fragmentation of larger independent pieces with aggregate debris clouds released with each fragmentation event. The model can vary the number and masses of fragments produced, the amount of mass released as debris clouds, and the size-strength scaling used to increase the robustness of smaller fragments. The initial asteroid body can be seeded with a distribution of independent fragment sizes amid a remaining debris mass to represent loose rubble pile conglomerations, or can be defined as a monolith with an outer regolith layer. This approach enables the model to represent a range of breakup behaviors and reproduce detailed energy deposition features such as multiple flares due to successive burst events, high-altitude regolith blow-off, or initial disruption of rubble piles followed by more energetic breakup of the constituent boulders. These capabilities provide a means to investigate sensitivities of ground damage to potential variations in asteroid structure.

3D Orbital Stability and Dynamic Environment of Asteroid 216 Kleopatra

NASA Astrophysics Data System (ADS)

Winter, Othon; Chanut, Thierry

A peculiar asteroid that might be the target of future space mission explorations is 216 Kleopatra, which has two small satellites and a peculiar dog-bone shape. Recent data processing showed the existence of a difference that can reach 25% for the dimensions of 216 Kleopatra between the radar observations and the light curves. We rebuild the shape of the asteroid 216 Kleopatra from these new data and estimate certain physical features by using the polyhedral model method. In our computations we use a code that avoids singularities from the line integrals of a homogeneous arbitrary shaped polyhedral source. This code evaluates the gravitational potential function and its first and second order derivatives. Then, we find the location of the and zero velocity curves. Finally, taking the rotation of asteroid 216 Kleopatra into consideration, the aims of this work is to analyze the stability against impact and the dynamics of numerical simulations of 3D initially equatorial and polar orbits near the body.

Detection of water and/or hydroxyl on asteroid (16) Psyche

USGS Publications Warehouse

Takir, Driss; Reddy, Vishnu; Sanchez, Juan A.; Shepard, Michael K.; Emery, Joshua P.

2016-01-01

In order to search for evidence of hydration on M-type asteroid (16) Psyche, we observed this object in the 3 μm spectral region using the long-wavelength cross-dispersed (LXD: 1.9–4.2 μm) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility. Our observations show that Psyche exhibits a 3 μm absorption feature, attributed to water or hydroxyl. The 3 μm absorption feature is consistent with the hydration features found on the surfaces of water-rich asteroids, attributed to OH- and/or H2O-bearing phases (phyllosilicates). The detection of a 3 μm hydration absorption band on Psyche suggests that this asteroid may not be a metallic core, or it could be a metallic core that has been impacted by carbonaceous material over the past 4.5 Gyr. Our results also indicate rotational spectral variations, which we suggest reflect heterogeneity in the metal/silicate ratio on the surface of Psyche.

Detection of Water and/or Hydroxyl on Asteroid (16) Psyche

NASA Astrophysics Data System (ADS)

Takir, Driss; Reddy, Vishnu; Sanchez, Juan A.; Shepard, Michael K.; Emery, Joshua P.

2017-01-01

In order to search for evidence of hydration on M-type asteroid (16) Psyche, we observed this object in the 3 μm spectral region using the long-wavelength cross-dispersed (LXD: 1.9-4.2 μm) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility. Our observations show that Psyche exhibits a 3 μm absorption feature, attributed to water or hydroxyl. The 3 μm absorption feature is consistent with the hydration features found on the surfaces of water-rich asteroids, attributed to OH- and/or H2O-bearing phases (phyllosilicates). The detection of a 3 μm hydration absorption band on Psyche suggests that this asteroid may not be a metallic core, or it could be a metallic core that has been impacted by carbonaceous material over the past 4.5 Gyr. Our results also indicate rotational spectral variations, which we suggest reflect heterogeneity in the metal/silicate ratio on the surface of Psyche.

DETECTION OF WATER AND/OR HYDROXYL ON ASTEROID (16) Psyche

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

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

In order to search for evidence of hydration on M-type asteroid (16) Psyche, we observed this object in the 3 μ m spectral region using the long-wavelength cross-dispersed (LXD: 1.9–4.2 μ m) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility. Our observations show that Psyche exhibits a 3 μ m absorption feature, attributed to water or hydroxyl. The 3 μ m absorption feature is consistent with the hydration features found on the surfaces of water-rich asteroids, attributed to OH- and/or H{sub 2}O-bearing phases (phyllosilicates). The detection of a 3 μ m hydration absorption band on Psyche suggestsmore » that this asteroid may not be a metallic core, or it could be a metallic core that has been impacted by carbonaceous material over the past 4.5 Gyr. Our results also indicate rotational spectral variations, which we suggest reflect heterogeneity in the metal/silicate ratio on the surface of Psyche.« less

Update on an Interstellar Asteroid

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-01-01

Whats the news coming from the research world on the interstellar asteroid visitor, asteroid 1I/Oumuamua? Read on for an update from a few of the latest studies.What is Oumuamua?In lateOctober2017, the discovery of minor planet 1I/Oumuamua was announced. This body which researchers first labeled asa comet and later revised to an asteroid had just zipped around the Sun and was already in the process of speeding away whenwe trained our telescopes on it. Its trajectory, however, marked it as being a visitor from outside our solar system: the first knownvisitorof its kind.Since Oumuamuasdiscovery, scientists have been gathering as many observations of this bodyas possible before it vanishes into the distance. Simultaneously, theorists have leapt at the opportunity to explain its presence and the implications its passage has on our understanding of our surroundings. Here we present just a few of the latest studies that have been published on this first detected interstellar asteroid including several timelystudies published in our new journal, Research Notes of the AAS.The galactic velocity of Oumuamua does not coincide with any of the nearest stars to us. [Mamajek 2018]Where Did Oumuamua Come From?Are we sure Oumuamua didnt originate in our solar system andget scattered into a weird orbit? Jason Wright (The Pennsylvania State University) demonstrates via a series of calculations that no known solar system body could have scattered Oumuamua onto its current orbit nor could any stillunknown object bound to our solar system.Eric Mamajek (Caltech and University of Rochester) showsthat thekinematics of Oumuamua areconsistent with what we might expect of interstellar field objects, though he argues that its kinematics suggest its unlikely to have originated from many of the neareststellar systems.What AreOumuamuas Properties?Oumuamuas light curve. [Bannister et al. 2017]A team of University of Maryland scientists led by Matthew Knight captured a light curve of Oumuamua using Lowell Observatorys 4.3-m Discovery Channel Telescope. The data indicate that the asteroids period is at least 3 hours in length,and most likely more than 5 hours. Assuming the light curves variation is caused by the tumbling asteroids changing cross-section, Oumuamuamust be a minimum of3 times as long as it is wide. Knight and collaborators seeno signs in their images of a coma or tail emitted from Oumuamua, suggesting there isno volatile material sublimating from its surface under the heat of the Sun.No coma is visible around Oumuamua. [Knight et al. 2017]A study of the asteroids photometry, led by Michele Bannister (Queens University Belfast, UK), usedthe Gemini-North telescope in Hawaii and the William Herschel Telescope in Spainto explore the asteroids shape and color. Bannister and collaborators refined the estimate of the asteroids shape to be at least 5.3 times as long as it is wide, which requiresthis body to have significant internal cohesion to hold together as it tumbles. Their measured color for Oumuamua is largely neutral.What Does This Visitor Imply?Masses and semimajor axes of known exoplanets. Colors correspond to the ratio of escape velocity to circular velocity. The presence of Oumuamua implies a vast and cool, stillundetected population of planets. [Laughlin Batygin, 2017]Gregory Laughlinof Yale University and Konstantin Batyginof Caltech(andPlanet Nine fame) explore some of the consequences of Oumuamuas parameters. They arguethat its current passage, if its not a fluke, suggests the presence ofan enormous number (1027) ofsuch objects in our galaxy alone enough to account for two Earth-masses of material for every star in the galaxy. Flinging asteroids like Oumuamuaout into interstellar space isnteasy, though; the necessary multi-body interaction requires the system to containa giant and long-period planet like our Neptune or Jupiter. Taken together, this information suggests that every star in the galaxy may host a Neptune-like planet at a Neptune-like distance.More information on Oumuamua is sure to come in the next few months as scientists continue to process their data from the asteroids swift passage. In the meantime, this interstellar visitor continues to challenge our understanding of our nearbysurroundings and the broader context of thegalaxy around us.CitationJason T. Wright 2017 Res. Notes AAS 1 38. doi:10.3847/2515-5172/aa9f23Eric Mamajek 2017 Res. Notes AAS 1 21. doi:10.3847/2515-5172/aa9bdcMatthew M. Knight et al 2017 ApJL 851 L31.doi:10.3847/2041-8213/aa9d81Michele T. Bannister et al 2017 ApJL 851 L38. doi:10.3847/2041-8213/aaa07cGregory Laughlin and Konstantin Batygin 2017 Res. Notes AAS 1 43. doi:10.3847/2515-5172/aaa02b

Multi-color lightcurve observation of the asteroid (163249) 2002 GT

NASA Astrophysics Data System (ADS)

Oshima, M.; Abe, S.

2014-07-01

NASA's Deep Impact/EPOXI spacecraft plans to encounter the asteroid (163249) 2002 GT, classified as a PHA (Potentially Hazardous Asteroid), on January 4, 2020. However, the taxonomic type and spin state of 2002 GT remain to be determined. We have carried out ground-based multi-color (B-V-R-I) lightcurve observations taking advantage of the 2002 GT Characterization Campaign by NASA. Multi-color lightcurve measurements allow us to estimate the rotation period and obtain strong constraints on the shape and pole orientation. Here we found that the rotation period of 2002 GT is estimated to be 3.7248 ± 0.1664 h. In mid-2013, 2002 GT passed at 0.015 au from the Earth, resulting an exceptional opportunity for ground-based characterization. Using the 0.81-m telescope of the Tenagra Observatory (110°52'44.8''W, +31°27'44.4''N, 1312 m) in Arizona, USA, and the Johnson-Cousins BVRI filters, we have found lightcurves of 2002 GT (Figure). The Tenagra II 0.81-m telescope is used for research of the Hayabusa2 target Asteroid (162173) 1999 JU_3. The lightcurves (relative magnitude) show that the rotation period of 2002 GT, the target of NASA's Deep Impact/EPOXI spacecraft, is estimated to be 3.7248 ± 0.1664 hr. On June 9, 2013, we had 7 hours of ground-based observations on 2002 GT from 4:00 to 11:00 UTC. The number of comparison stars for differential photometry was 34. Because of tracking the fast-moving asteroid, it was necessary to have the same comparison star among the fields of vision. We have also obtained absolute photometry of 2002 GT on June 13, 2013.

Asteroid Shapes Are Always Close To Fluid Equilibrium

NASA Astrophysics Data System (ADS)

Tanga, Paolo; Comito, C.; Hestroffer, D.; Richardson, D. C.

2010-10-01

The simple evidence that asteroid are composed by solid rocks suggests that their shape can be rather far from the theoretical equilibrium for rotating fluid bodies. The possible fragmented ("rubble-pile") nature of most of them has suggested interpretations based on elasto-plastic models (such as the Mohr-Coulomb theory) that take into account the static behavior of a granular structure. However, these approaches did not incorporate explicitly the possible evolution of shapes in time due to external factors such as crater forming impacts or tidal deformations. We revisited the theory of equilibrium shapes for fluids, quantitatively evaluating - by appropriate metrics - the distance of the observed shapes from fluid equilibrium. This distance turns out to be much smaller than previously expected. On the basis of this evidence, we simulated numerically the evolution of gravitational aggregates having a small degree of internal friction, consistent with the theoretical findings. Our results offer a global scenario for the evolution of asteroid shapes under the action of gradual stresses due to minor impacts, tidal forces and seismic shaking. We show that actual asteroid shapes are consistent with the evolution of aggregates tending towards minimum free energy states. We are able to explain the samples of observed shapes obtained by different techniques. Our findings strongly support a highly porous and fragmented nature for most asteroids, at least in an external layer. Reference: Tanga et al. 2009: ApJ Letters, 706, 1, L197-L202 Acknowledgments: PT and CC have been supported by the "Programme Nationale de Planetologie" of France; DCR acknowledges support by the NASA (grant no. NNX08AM39G issued through the Office of Space Science) and by the NSF (grant no. AST0708110).