Showing papers by "Paul Sánchez published in 2019"
University of Colorado Boulder1, California Institute of Technology2, Goddard Space Flight Center3, The Aerospace Corporation4, University of Tennessee5, Open University6, Auburn University7, Colorado Center for Astrodynamics Research8, Japan Aerospace Exploration Agency9, Planetary Science Institute10, University of Arizona11, University of British Columbia12, Johns Hopkins University Applied Physics Laboratory13, York University14, Southwest Research Institute15, National Museum of Natural History16, Lockheed Martin Space Systems17, Centre national de la recherche scientifique18, Rowan University19
TL;DR: Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, a notable transition is found in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface.
Abstract: The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu’s surface has been most recently migrating towards its equator (given Bennu’s increasing spin rate), we infer that Bennu’s surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennu’s top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennu’s top-shape morphology and its link to the formation of binary asteroids.
144 citations
Paris Observatory1, University of Colorado Boulder2, University of Paris3, University of Alicante4, University of Washington5, University of Maryland, College Park6, Institut supérieur de l'aéronautique et de l'espace7, University of Liège8, University of Montpellier9, Centre national de la recherche scientifique10, University of Arizona11, École normale supérieure de Lyon12
TL;DR: A review of the multi-disciplinary research carried out by these different scientific communities in an effort to study SSSBs can be found in this paper, where the authors present a review of their work.
Abstract: Asteroids and other Small Solar System Bodies (SSSBs) are of high general and scientific interest in many aspects. The origin, formation, and evolution of our Solar System (and other planetary systems) can be better understood by analysing the constitution and physical properties of small bodies in the Solar System. Currently, two space missions (Hayabusa2, OSIRIS-REx) have recently arrived at their respective targets and will bring a sample of the asteroids back to Earth. Other small body missions have also been selected by, or proposed to, space agencies. The threat posed to our planet by near-Earth objects (NEOs) is also considered at the international level, and this has prompted dedicated research on possible mitigation techniques. The DART mission, for example, will test the kinetic impact technique. Even ideas for industrial exploitation have risen during the last years. Lastly, the origin of water and life on Earth appears to be connected to asteroids. Hence, future space mission projects will undoubtedly target some asteroids or other SSSBs. In all these cases and research topics, specific knowledge of the structure and mechanical behaviour of the surface as well as the bulk of those celestial bodies is crucial. In contrast to large telluric planets and dwarf planets, a large proportion of such small bodies is believed to consist of gravitational aggregates (‘rubble piles’) with no—or low—internal cohesion, with varying macro-porosity and surface properties (from smooth regolith covered terrain, to very rough collection of boulders), and varying topography (craters, depressions, ridges). Bodies with such structure can sustain some plastic deformation without being disrupted in contrast to the classical visco-elastic models that are generally valid for planets, dwarf planets, and large satellites. These SSSBs are hence better described through granular mechanics theories, which have been a subject of intense theoretical, experimental, and numerical research over the last four decades. This being the case, it has been necessary to use the theoretical, numerical and experimental tools developed within soil mechanics, granular dynamics, celestial mechanics, chemistry, condensed matter physics, planetary and computer sciences, to name the main ones, in order to understand the data collected and analysed by observational astronomy (visible, thermal, and radio), and different space missions. In this paper, we present a review of the multi-disciplinary research carried out by these different scientific communities in an effort to study SSSBs.
27 citations
TL;DR: In asteroids with diameter less than 1 km, a regime where rare energetic impactors can excite seismic waves with frequencies near those of the asteroid's slowest normal modes is identified, where the distribution of seismic reverberation is not evenly distributed across the body surface.
20 citations
Paris Observatory1, University of Colorado Boulder2, University of Paris3, University of Alicante4, University of Washington5, University of Maryland, College Park6, Institut supérieur de l'aéronautique et de l'espace7, University of Liège8, University of Montpellier9, Centre national de la recherche scientifique10, University of Arizona11, École normale supérieure de Lyon12
TL;DR: Asteroids and other Small Solar System Bodies (SSSBs) are of high general and scientific interest in many aspects as mentioned in this paper, and future space mission projects will undoubtedly target some asteroids or other SSSBs.
Abstract: Asteroids and other Small Solar System Bodies (SSSBs) are of high general and scientific interest in many aspects. The origin, formation, and evolution of our Solar System (and other planetary systems) can be better understood by analysing the constitution and physical properties of small bodies in the Solar System. Currently, two space missions (Hayabusa2, OSIRIS-REx) have recently arrived at their respective targets and will bring a sample of the asteroids back to Earth. Other small body missions have also been selected by, or proposed to, space agencies. The threat posed to our planet by near-Earth objects (NEOs) is also considered at the international level, and this has prompted dedicated research on possible mitigation techniques. The DART mission, for example, will test the kinetic impact technique. Even ideas for industrial exploitation have risen during the last years. Lastly, the origin of water and life on Earth appears to be connected to asteroids. Hence, future space mission projects will undoubtedly target some asteroids or other SSSBs. In all these cases and research topics, specific knowledge of the structure and mechanical behaviour of the surface as well as the bulk of those celestial bodies is crucial. In contrast to large telluric planets and dwarf planets, a large proportion of such small bodies is believed to consist of gravitational aggregates ('rubble piles') with no -- or low -- internal cohesion, with varying macro-porosity and surface properties (from smooth regolith covered terrain, to very rough collection of boulders), and varying topography (craters, depressions, ridges) [...].
17 citations
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TL;DR: In this paper, the authors studied the migration of cohesive regolith on the surface of an otherwise monolithic or strong asteroid using theoretical and simulation models and derived a scaling law that can be used to determine whether observed asteroids could retain surface regolith grains of a given size.
Abstract: The migration of cohesive regolith on the surface of an otherwise monolithic or strong asteroid is studied using theoretical and simulation models. The theory and simulations show that under an increasing spin rate (such as due to the YORP effect), the regolith covering is preferentially lost across certain regions of the body. For regolith with little or no cohesive strength, failure occurs by landsliding from the mid latitudes of the body at high enough spin rates. As the cohesive strength of the regolith increases, failure occurs by fission of grains (or coherent chunks of grains) across a greater extent of latitudes and eventually will first occur at the equator. As the spin rate is further increased, failure regions migrate from the first failure point to higher and lower latitudes. Eventually failure will encompass the equatorial region, however there always remains a region of high latitudes (around the poles) that will not undergo failure for arbitrarily high spin rates (unless disturbed by some other phenomenon). With these results a scaling law is derived that can be used to determine whether observed asteroids could retain surface regolith grains of a given size. The implications of this for the interpretation of spectral observations of small asteroids and boulder migration on large asteroids are discussed.
9 citations
TL;DR: Simulations of nearly spherical but wobbling bodies with hard and soft cores show that the energy dissipation rate is more sensitive to the material properties in the core than near the surface.
Abstract: Using a damped mass-spring model, we simulate wobble of spinning homogeneous viscoelastic ellipsoids undergoing non-principal axis rotation. Energy damping rates are measured for oblate and prolate bodies with different spin rates, spin states, viscoelastic relaxation timescales, axis ratios, and strengths. Analytical models using a quality factor by Breiter et al. (2012) and for the Maxwell rheology by Frouard & Efroimsky (2018) match our numerical measurements of the energy dissipation rate after we modify their predictions for the numerically simulated Kelvin-Voigt rheology. Simulations of nearly spherical but wobbling bodies with hard and soft cores show that the energy dissipation rate is more sensitive to the material properties in the core than near the surface.
8 citations