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Asteroids

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Daniel J Scheeres – 1st expert on this subject based on the ideXlab platform

  • Temporarily Captured Asteroids as a Pathway to Affordable Asteroid Retrieval Missions
    Journal of Guidance Control and Dynamics, 2015
    Co-Authors: Hodei Urrutxua, Daniel J Scheeres, Claudio Bombardelli, Juan Luis Gonzalo, Jesús Peláez

    Abstract:

    The population of “temporarily captured Asteroids” offers attractive candidates for asteroid retrieval missions. Once naturally captured, these Asteroids have lifetimes ranging from a few months up to several years in the vicinity of the Earth. One could potentially extend the duration of such temporary capture phases by acting upon the asteroid with slow deflection techniques that conveniently modify their trajectories, allowing for an affordable access and in situ study. In this paper, a case study on asteroid 2006 RH120 is presented, which was temporarily captured during 2006–2007 and is the single known member of this category to date. Simulations estimate that deflecting the asteroid with 0.27 N for less than six months and a change of velocity, ΔV of barely 32  m/s would have sufficed to extend the capture for over five additional years. The study is extended to another nine virtual Asteroids, showing that low-ΔV (less than 15  m/s) and low-thrust (less than 1 N) deflections initiated a few years in…

  • the strength of regolith and rubble pile Asteroids
    Meteoritics & Planetary Science, 2014
    Co-Authors: Paul Sanchez, Daniel J Scheeres

    Abstract:

    We explore the hypothesis that, due to small van der Waals forces between constituent grains, small rubble pile Asteroids have a small but non-zero cohesive strength. The nature of this model predicts that the cohesive strength should be constant independent of asteroid size, which creates a scale dependence with relative strength increasing as size decreases. This model counters classical theory that rubble pile Asteroids should behave as scale-independent cohesionless collections of rocks. We explore a simple model for asteroid strength that is based on these weak forces, validate it through granular mechanics simulations and comparisons with properties of lunar regolith, and then explore its implications and ability to explain and predict observed properties of small Asteroids in the NEA and Main Belt populations, and in particular of asteroid 2008 TC3. One conclusion is that the population of rapidly rotating Asteroids could consist of both distributions of smaller grains (i.e., rubble piles) and of monolithic boulders.

  • The Fate of Asteroid Ejecta
    , 2002
    Co-Authors: Daniel J Scheeres, Daniel D. Durda, Paul E. Geissler

    Abstract:

    The distribution of regolith on asteroid surfaces has only recently been measured directly by in situ observations from spacecraft. To the surprise of many researchers, most of the classical predictions for the distribution of asteroid impact ejecta have not rung true, with regoliths appearing to be geologically active at small scales on asteroid surfaces. This indicates that significant insight into geological processes on Asteroids may be inferred by detailed studies of the distribution of impact ejecta on Asteroids. This chapter has been written to support these future investigations, by trying to identify and clarify all the important elements for such a study, to point to the recent history of such studies, and to indicate the current gaps in our understanding. The chapter begins with a discussion of the initial conditions of ejecta fields generated from impacts on the asteroid surface. Then the relevant physical laws and forces affecting asteroid ejecta, in orbit and on the surface, are reviewed and the basic dynamical equations of motion for ejecta are stated. Some general results and constraints on the solutions to these equations are given, and a classification scheme for ejecta trajectories is given. Finally, recent studies of asteroid ejecta are reviewed, showing the application of these techniques to asteroid science.

B Carry – 2nd expert on this subject based on the ideXlab platform

  • olivine dominated a type Asteroids in the main belt distribution abundance and relation to families
    Icarus, 2019
    Co-Authors: Francesca E Demeo, Richard P. Binzel, D Polishook, B Carry, Brian Burt, Henry H Hsieh, Nicholas Moskovitz, T H Burbine

    Abstract:

    Abstract Differentiated Asteroids are rare in the main asteroid belt despite evidence for  ∼ 100 distinct differentiated bodies in the meteorite record. We have sought to understand why so few main-belt Asteroids differentiated and where those differentiated bodies or fragments reside. Using the Sloan Digital Sky Survey (SDSS) to search for a needle in a haystack we identify spectral A-type asteroid candidates, olivine-dominated Asteroids that may represent mantle material of differentiated bodies. We have performed a near-infrared spectral survey with SpeX on the NASA IRTF and FIRE on the Magellan Telescope. We report results from having doubled the number of known A-type Asteroids. We deduce a new estimate for the overall abundance and distribution of this class of olivine-dominated Asteroids. We find A-type Asteroids account for less than 0.16% of all main-belt objects larger than 2 km and estimate there are a total of  ∼ 600 A-type Asteroids above that size. They are found rather evenly distributed throughout the main belt, are even detected at the distance of the Cybele region, and have no statistically significant concentration in any asteroid family. We conclude the most likely implication is the few fragments of olivine-dominated material in the main belt did not form locally, but instead were implanted as collisional fragments of bodies that formed elsewhere.

  • Solar System evolution from compositional mapping of the asteroid belt
    Nature, 2014
    Co-Authors: F. E. Demeo, B Carry

    Abstract:

    Advances in the discovery and characterization of Asteroids over the past decade have revealed an unanticipated underlying structure that points to a dramatic early history of the inner Solar System. The Asteroids in the main asteroid belt have been discovered to be more compositionally diverse with size and distance from the Sun than had previously been known. This implies substantial mixing through processes such as planetary migration and the subsequent dynamical processes. The main asteroid belt, once regarded as a sort of dumping ground for the spent remnants of planet formation, has emerged in recent years as a region of dynamic activity that provides a window on the processes that are still shaping our Solar System and the many extrasolar planetary systems across the Universe. Francesca DeMeo and Benoit Carry review recent advances in the discovery and characterization of Asteroids. More than half a million Asteroids have been discovered and mapped since the 1980s, revealing remarkable diversity in size, composition and orbit. New evidence has demonstrated substantial mixing through planetary migration and the subsequent dynamical processes. Next year NASA’s Dawn space probe is due to rendezvous with Ceres, the largest body in asteroid belt and one recently proven to contain water, so many new developments in this field can be expected. Unexpected diversity in the Asteroids in the main asteroid belt holds clues to mixing via planetary migration in the early Solar System.

  • Asteroids physical models from combined dense and sparse photometry and scaling of the yorp effect by the observed obliquity distribution
    Astronomy and Astrophysics, 2013
    Co-Authors: J Hanus, B Carry, J ďurech, M Brož, A Marciniak, Brian D Warner, Frederick Pilcher, Robert D Stephens, R Behrend, D Capek

    Abstract:

    The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt Asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties. We use all available photometric data of Asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all Asteroids with known convex shape models with the simulated pole latitude distributions. We used classical dense photometric lightcurves from several sources and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of Asteroids used in our previous paper. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.

Hutao Cui – 3rd expert on this subject based on the ideXlab platform

  • Proposal for a multiple-asteroid-flyby mission with sample return
    Advances in Space Research, 2012
    Co-Authors: Dong Qiao, Pingyuan Cui, Hutao Cui

    Abstract:

    Asteroid exploration provides a new approach to study the formation of the solar system and the planetary evolution. Choosing a suitable target and designing of feasible profile for asteroid mission are challenging due to constraints such as scientific value and technical feasibility. This paper investigates a feasible mission scenario among the potential candidates of multiple flybys and sample return missions. First, a group of potential candidates are selected by considering the physical properties and accessibility of Asteroids, for the sample return missions. Second, the feasible mission scenarios for multiple flybys and sample return missions to various spectral-type Asteroids are investigated. We present the optimized design of preliminary interplanetary transfer trajectory for two kinds of missions. One is the single sample return mission to Asteroids with various spectral types. The other is the multiple flybys and sample return mission to several Asteroids. In order to find the optimal profiles, the planetary swing-by technique and Differential Evolution algorithm are used. ?? 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.