Numerical modelling of medium-speed impacts on a granular surface in a low-gravity environment application to Hayabusa2 sampling mechanism
AffiliationUniv Arizona, Lunar & Planetary Lab
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PublisherOXFORD UNIV PRESS
CitationFlorian Thuillet, Patrick Michel, Shogo Tachibana, Ronald-L Ballouz, Stephen R Schwartz, Numerical modelling of medium-speed impacts on a granular surface in a low-gravity environment application to Hayabusa2 sampling mechanism, Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 1, January 2020, Pages 153–177, https://doi.org/10.1093/mnras/stz3010
RightsCopyright © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
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AbstractEven if craters are very common on Solar System body surfaces, crater formation in granular media such as the ones covering most of visited asteroids still needs to be better understood, above all in low-gravity environments. JAXA's sample return mission Hayabusa2, currently visiting asteroid (162173) Ryugu, is a perfect opportunity for studying medium-speed impacts into granular matter, since its samplingmechanism partly consists of a 300 m s(-1) impact. In this paper, we look at medium-speed impacts, from 50 to 300 m s(-1), into a granular material bed, to better understand crater formation and ejecta characteristics. We then consider the sampler horn of Hayabusa2 sampling mechanism and monitor the distribution of particles inside the horn. We find that the cratering process is much longer under low gravity, and that the crater formation mechanism does not seem to depend on the impact speed, in the considered range. The Z-model seems to rightly represent our velocity field for a steady excavation state. From the impact, less than 10 per cent is transmitted into the target, and grains are ejected mostly with angles between 48 degrees and 54 degrees. Concerning the sampling mechanism, we find that for most of the simulations, the science goal of 100 mg is fulfilled, and that a second impact increases the number of ejecta but not necessarily the number of collected particles.
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