Hypervelocity impact fragmentation of basalt and shale projectiles

Wickham-Eade, J.E. and Burchell, M.J. and Price, M.C. and Harriss, K.H. (2018) Hypervelocity impact fragmentation of basalt and shale projectiles. Icarus, 311 . pp. 52-68. ISSN 0019-1035. (doi:https://doi.org/10.1016/j.icarus.2018.03.017) (Full text available)

Abstract

Results are presented for the fragmentation of projectiles in laboratory experiments. 1.5?mm cubes and spheres of basalt and shale were impacted onto water at normal incidence and speeds from 0.39 to 6.13?km s?1; corresponding to peak shock pressures 0.7–32?GPa. Projectile fragments were collected and measured (over 100,000 fragments in some impacts, at sizes down to 10?µm). Power laws were fitted to the cumulative fragment size distributions and the evolution of the exponent vs. impact speed and peak shock pressure found. The gradient of each of these power laws increased with increasing impact speed/peak shock pressure. The percentage of the projectiles recovered in the impacts was found and used to estimate projectile remnant survival in different solar system impact scenarios at the mean impact speed appropriate to that scenario. For Pluto, the Moon and in the asteroid belt approximately 55%, 40% and 15%, respectively, of an impactor could survive and be recovered at an impact site. Finally, the catastrophic disruption energy densities of basalt and shale were measured and found to be 24?×?104?J kg?1 and 9?×?104?J kg?1, respectively, a factor of ?2.5 difference. These corresponded to peak shock pressures of 1 to 1.5?GPa (basalt), and 0.8?GPa (shale). This is for near normal-incidence impacts where tensile strength is dominant. For shallow angle impacts we suggest shear effects dominate, resulting in lower critical energy densities and peak shock pressures. We also determine a method to ascertain information about fragment sizes in solar system impact events using a known size of impactor. The results are used to predict projectile fragments sizes for the Veneneia and Rheasilvia crater forming impacts on Vesta, and similar impacts on Ceres.

Item Type: Article
Uncontrolled keywords: Impacts, asteroids, projectile, fragmentation, basalt, shale
Subjects: Q Science > QB Astronomy > QB651 Planets, Minor
Divisions: Faculties > Sciences > School of Physical Sciences
Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Mark Burchell
Date Deposited: 04 Apr 2018 08:05 UTC
Last Modified: 09 Apr 2018 10:11 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/66613 (The current URI for this page, for reference purposes)
Burchell, M.J.: https://orcid.org/0000-0002-2680-8943
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