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Keywords = rubble-pile asteroids

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21 pages, 13149 KiB  
Article
Experimental and Numerical Simulation of Ejecta Size and Velocity of Hypervelocity Impact Rubble-Pile Asteroid
by Wenjin Liu, Qingming Zhang, Renrong Long, Jiankang Ren, Juncheng Li, Zizheng Gong, Qiang Wu and Siyuan Ren
Aerospace 2024, 11(8), 621; https://doi.org/10.3390/aerospace11080621 - 29 Jul 2024
Cited by 2 | Viewed by 1627
Abstract
Rubble-pile asteroids may be the type of near-Earth object most likely to threaten Earth in a future collision event. Small-scale impact experiments and numerical simulations for large-scale impacts were conducted to clarify the size ratio of the boulder/projectile diameter effects on ejecta size–velocity [...] Read more.
Rubble-pile asteroids may be the type of near-Earth object most likely to threaten Earth in a future collision event. Small-scale impact experiments and numerical simulations for large-scale impacts were conducted to clarify the size ratio of the boulder/projectile diameter effects on ejecta size–velocity distribution. A series of small-scale impact cratering experiments were performed on porous gypsum–basalt targets at velocities of 2.3 to 5.5 km·s−1. Three successive ejection processes were observed by high-speed and ultra-high-speed cameras. The momentum transfer coefficient and cratering size were measured. A three-dimensional numerical model reflecting the random distribution of the interior boulders of the rubble-pile structure asteroid is established. The size ratio (length to diameter) of the boulder size inside the asteroid to the projectile diameter changed from 0.25 to 1.7. We conducted a smoothed particle hydrodynamics numerical simulation in the AUTODYN software to study the boulder size effect on the ejecta size–velocity distribution. Simulation results suggest that the microscopic porosity on regolith affects the propagation of shock waves and reduces the velocity of ejecta. Experiments and numerical simulation results suggest that both excavation flow and spalling ejection mechanism can eject boulders (0.12–0.72 m) out of the rubble-pile asteroid. These experiments and simulation results help us select the potential impact site in a planetary defense scenario and reduce deflection risk. are comprised primarily of boulders of a range of sizes. Full article
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15 pages, 4056 KiB  
Review
The Formation of a Rubble Pile Asteroid: Insights from the Asteroid Ryugu
by Tsutomu Ota, Christian Potiszil, Katsura Kobayashi, Ryoji Tanaka, Hiroshi Kitagawa, Tak Kunihiro, Chie Sakaguchi, Masahiro Yamanaka and Eizo Nakamura
Universe 2023, 9(6), 293; https://doi.org/10.3390/universe9060293 - 16 Jun 2023
Cited by 3 | Viewed by 2572
Abstract
The Hayabusa2 mission returned primitive samples from the C-type asteroid Ryugu to Earth. The C-type asteroids hold clues to the origin of Earth’s water and the building blocks of life. The rubble pile structure of C-type asteroids is a crucial physical feature relating [...] Read more.
The Hayabusa2 mission returned primitive samples from the C-type asteroid Ryugu to Earth. The C-type asteroids hold clues to the origin of Earth’s water and the building blocks of life. The rubble pile structure of C-type asteroids is a crucial physical feature relating to their origin and evolution. A rubble pile asteroid is hypothesized to be bound primarily by self-gravity with a significant void space among irregularly shaped materials after catastrophic impacts between larger asteroids. However, the geological observations from Hayabusa2 and the analyses of the returned sample from Ryugu revealed that the high microporosity was common to various >10 m- to mm-sized materials of Ryugu, which suggests that the asteroid Ryugu is not just a loosely bound agglomeration of massive rocky debris from shattered asteroids. For a better understanding of the origin and evolution of the rubble pile asteroid, the current most accepted hypothesis should be verified by observations and laboratory analyses and improved upon based on this information. Here, the previous models are examined using Hayabusa2’s geological observations of the asteroid and the analytical data from the samples returned from Ryugu’s surface and subsurface material. Incorporating the new findings, a hypothesis for the evolution of the rubble pile asteroid Ryugu from a cometary nucleus through sublimation and subsequent dynamic resurfacing is proposed. The proposed hypothesis is applicable to other rubble-pile asteroids and would provide perspectives for near-Earth objects in general. Full article
(This article belongs to the Special Issue Space Missions to Small Bodies: Results and Future Activities)
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7 pages, 444 KiB  
Article
Inelastic Collision Influencing the Rotational Dynamics of a Non-Rigid Asteroid (of Rubble Pile Type)
by Sergey Ershkov and Dmytro Leshchenko
Mathematics 2023, 11(6), 1491; https://doi.org/10.3390/math11061491 - 18 Mar 2023
Cited by 2 | Viewed by 1785
Abstract
We have considered here a novel particular model for dynamics of a non-rigid asteroid rotation, assuming the added mass model instead of the concept of Viscoelastic Oblate Rotators to describe the physically reasonable response of a ‘rubble pile’ volumetric material of asteroid with [...] Read more.
We have considered here a novel particular model for dynamics of a non-rigid asteroid rotation, assuming the added mass model instead of the concept of Viscoelastic Oblate Rotators to describe the physically reasonable response of a ‘rubble pile’ volumetric material of asteroid with respect to the action of a projectile impacting its surface. In such a model, the response is approximated as an inelastic collision in which the projectile pushes the ‘rubble pile’ parts of the asteroid together to form a mostly solidified plug in the crater during the sudden impact on the asteroid’s surface. Afterwards, the aforementioned ‘solidified plug’ (having no sufficient adhesion inside the after-impact crater) will be pushed outside the asteroid’s surface by centrifugal forces, forming a secondary rotating companion around the asteroid. Thus, according to the fundamental law of angular momentum conservation, the regime of the asteroid’s rotation should be changed properly. Namely, changes in rotational dynamics stem from decreasing the asteroid’s mass (due to the fundamental law of angular momentum conservation). As the main finding, we have presented a new solving procedure for a semi-analytical estimation of the total mass of the aforementioned ‘solidified plug’, considering the final spin state of rotation for the asteroid with minimal kinetic energy reduced during a long time period by the inelastic (mainly, tidal) dissipation. The asteroid is assumed to be rotating mainly along the maximal inertia axis with a proper spin state corresponding to minimal energy with a fixed angular momentum. Full article
(This article belongs to the Special Issue Theoretical Research and Computational Applications in Fluid Dynamics)
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20 pages, 1620 KiB  
Article
The Coupling Orbit–Attitude–Structure Evolution of Rubble-Pile Asteroid with Earth Flyby in the Restricted Three-Body Problem
by Xiangyuan Zeng, Chengfan Feng, Tongge Wen and Qingbo Gan
Aerospace 2022, 9(7), 351; https://doi.org/10.3390/aerospace9070351 - 30 Jun 2022
Cited by 5 | Viewed by 3349
Abstract
Some asteroids flying close to Earth may pose a threat of impact. Among them, the structural and dynamical characteristics of rubble-pile asteroids can be changed because of the tidal force of the Earth in this process. This can provide key information for predicting [...] Read more.
Some asteroids flying close to Earth may pose a threat of impact. Among them, the structural and dynamical characteristics of rubble-pile asteroids can be changed because of the tidal force of the Earth in this process. This can provide key information for predicting the dynamical evolution of potentially hazardous asteroids. In this study, the long-term evolution of the coupling orbit–attitude–structure of these small bodies is presented numerically based on the integration of two models. One is the 3D discrete element method, which models the structure and irregular shape of the rubble-pile asteroid. The other is the dynamical model of the circular restricted three-body problem (CRTBP). This provides a more precise dynamical environment of the asteroid orbital deflection, morphological modification, and attitude angles analysis compared to the frequently adopted two-body problem. Parametric studies on the asteroid evolution were performed focusing on its flyby distance and the bulk porosity. Numerical results indicate that the Earth flyby can form different patterns of modification of asteroids, where the rubble-pile structure can be destructed by considering the bulk porosity. The asteroid orbital deflection and attitude variational trends are also summarized based on the simulations of multi-orbital revolutions. Full article
(This article belongs to the Special Issue Recent Advances in Spacecraft Dynamics and Control)
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25 pages, 26694 KiB  
Article
Particle Size-Frequency Distributions of the OSIRIS-REx Candidate Sample Sites on Asteroid (101955) Bennu
by Keara N. Burke, Daniella N. DellaGiustina, Carina A. Bennett, Kevin J. Walsh, Maurizio Pajola, Edward B. Bierhaus, Michael C. Nolan, William V. Boynton, Juliette I. Brodbeck, Harold C. Connolly, Jasinghege Don Prasanna Deshapriya, Jason P. Dworkin, Catherine M. Elder, Dathon R. Golish, Rachael H. Hoover, Erica R. Jawin, Timothy J. McCoy, Patrick Michel, Jamie L. Molaro, Jennifer O. Nolau, Jacob Padilla, Bashar Rizk, Stuart J. Robbins, Eric M. Sahr, Peter H. Smith, Stephanie J. Stewart, Hannah C. M. Susorney, Heather L. Enos and Dante S. Laurettaadd Show full author list remove Hide full author list
Remote Sens. 2021, 13(7), 1315; https://doi.org/10.3390/rs13071315 - 30 Mar 2021
Cited by 44 | Viewed by 6847
Abstract
We manually mapped particles ranging in longest axis from 0.3 cm to 95 m on (101955) Bennu for the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission. This enabled the mission to identify candidate sample collection sites and [...] Read more.
We manually mapped particles ranging in longest axis from 0.3 cm to 95 m on (101955) Bennu for the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission. This enabled the mission to identify candidate sample collection sites and shed light on the processes that have shaped the surface of this rubble-pile asteroid. Building on a global survey of particles, we used higher-resolution data from regional observations to calculate particle size-frequency distributions (PSFDs) and assess the viability of four candidate sites for sample collection (presence of unobstructed particles ≤ 2 cm). The four candidate sites have common characteristics: each is situated within a crater with a relative abundance of sampleable material. Their PSFDs, however, indicate that each site has experienced different geologic processing. The PSFD power-law slopes range from −3.0 ± 0.2 to −2.3 ± 0.1 across the four sites, based on images with a 0.01-m pixel scale. These values are consistent with, or shallower than, the global survey measurements. At one site, Osprey, the particle packing density appears to reach geometric saturation. We evaluate the uncertainty in these measurements and discuss their implications for other remotely sensed and mapped particles, and their importance to OSIRIS-REx sampling operations. Full article
(This article belongs to the Special Issue Planetary 3D Mapping, Remote Sensing and Machine Learning)
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