Please use this identifier to cite or link to this item: http://hdl.handle.net/1893/26999
Appears in Collections:Biological and Environmental Sciences Journal Articles
Peer Review Status: Refereed
Title: Fragment shapes in impact experiments ranging from cratering to catastrophic disruption
Author(s): Michikami, Tatsuhiro
Hagermann, Axel
Kadokawa, Tokiyuki
Yoshida, Akifumi
Shimada, Akira
Hasegawa, Sunao
Tsuchiyama, Akira
Keywords: Impact processes
Collisional physics
Asteroids
Asteroid Itokawa
Issue Date: Jan-2016
Citation: Michikami T, Hagermann A, Kadokawa T, Yoshida A, Shimada A, Hasegawa S & Tsuchiyama A (2016) Fragment shapes in impact experiments ranging from cratering to catastrophic disruption, Icarus, 264, pp. 316-330.
Abstract: Laboratory impact experiments have found that impact fragments tend to be elongated. Their shapes, as defined by axes a, b and c, these being the maximum dimensions of the fragment in three mutually orthogonal planes (a≥ b≥ c), are distributed around mean values of the axial ratios b/. a~. 0.7 and c/. a~. 0.5. This corresponds to a:. b:. c in the simple proportion 2:2:1 The shape distributions of some boulders on Asteroid Eros, the small- and fast-rotating asteroids (diameter <200. m and rotation period <1 h), and asteroids in young families, are similar to those of laboratory fragments created in catastrophic disruptions. Catastrophic disruption is, however, a process that is different from impact cratering. In order to systematically investigate the shapes of fragments in the range from impact cratering to catastrophic disruption, impact experiments for basalt targets 5-15. cm in size were performed. A total of 28 impact experiments were carried out by firing a spherical nylon projectile (diameter 7.14. mm) perpendicularly into the target surface at velocities of 1.60-7.13. km/s. More than 12,700 fragments with b≥ 4 mm generated in the impact experiments were measured. We found that the mean value of c/ a in each impact decreases with decreasing impact energy per unit target mass. For instance, the mean value of c/ a in an impact cratering event is nearly 0.2, which is considerably smaller than c/ a in a catastrophic disruption (~0.5). The data presented here can provide important evidence to interpret the shapes of asteroids and boulders on asteroid surfaces, and can constrain current interpretations of asteroid formation. As an example, by applying our experimental results to the boulder shapes on Asteroid Itokawa's surface, we can infer that Itokawa's parent body must have experienced a catastrophic disruption. © 2015 The Authors.
DOI Link: http://dx.doi.org/10.1016/j.icarus.2015.09.038
Rights: Copyright 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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