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Author

Paul Sánchez

Bio: Paul Sánchez is an academic researcher from Colorado Center for Astrodynamics Research. The author has contributed to research in topics: Asteroid & Physics. The author has an hindex of 18, co-authored 51 publications receiving 1428 citations. Previous affiliations of Paul Sánchez include University of Nottingham & University of Colorado Boulder.
Topics: Asteroid, Physics, Regolith, Rubble, Population


Papers
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Journal ArticleDOI
01 Dec 2010-Icarus
TL;DR: In this article, the scaling of physical forces to the extremely low ambient gravitational acceleration regimes found on the surfaces of small asteroids is performed, and it is found that van der Waals cohesive forces between regolith grains on asteroid surfaces should be a dominant force and compete with particle weights and be greater, in general, than electrostatic and solar radiation pressure forces.

294 citations

Journal ArticleDOI
TL;DR: In this article, the authors explore the hypothesis that small rubble pile asteroids have a small but non-zero cohesive strength, which creates a scale dependence with relative strength increasing as size decreases.
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.

198 citations

Journal ArticleDOI
TL;DR: In this paper, the authors explore the hypothesis that small rubble pile asteroids have a small but non-zero cohesive strength, which creates a scale dependence with relative strength increasing as size decreases.
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.

182 citations

Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: In this article, a soft-sphere distinct element method was used to simulate asteroid regolith and rubble piles and then an algorithm to calculate self-gravity was derived and incorporated for full-scale simulations of rubble-pile asteroids using Granular Dynamics techniques.
Abstract: This paper applies a soft-sphere distinct element method Granular Dynamics code to simulate asteroid regolith and rubble piles. Applications to regolith studies in low gravity are also studied. Then an algorithm to calculate self-gravity is derived and incorporated for full-scale simulations of rubble-pile asteroids using Granular Dynamics techniques. To test its validity, the algorithm's results are compared with the exact direct calculation of the gravitational forces. Further avenues to improve the performance of the algorithm are also discussed.

97 citations


Cited by
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Journal ArticleDOI
TL;DR: Zhu et al. as discussed by the authors provided a summary of the studies based on discrete particle simulation in the past two decades or so, with emphasis on the microdynamics including packing/flow structure and particle-particle, particle-fluid and particle wall interaction forces.

1,253 citations

Journal ArticleDOI
TL;DR: The authors show the operational environment of asteroid Bennu, validate its photometric phase function and demonstrate the accelerating rotational rate due to YORP effect using the data acquired during the approach phase of OSIRIS-REx mission.
Abstract: During its approach to asteroid (101955) Bennu, NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft surveyed Bennu’s immediate environment, photometric properties, and rotation state. Discovery of a dusty environment, a natural satellite, or unexpected asteroid characteristics would have had consequences for the mission’s safety and observation strategy. Here we show that spacecraft observations during this period were highly sensitive to satellites (sub-meter scale) but reveal none, although later navigational images indicate that further investigation is needed. We constrain average dust production in September 2018 from Bennu’s surface to an upper limit of 150 g s–1 averaged over 34 min. Bennu’s disk-integrated photometric phase function validates measurements from the pre-encounter astronomical campaign. We demonstrate that Bennu’s rotation rate is accelerating continuously at 3.63 ± 0.52 × 10–6 degrees day–2, likely due to the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, with evolutionary implications.

905 citations