Spin rates of fast-rotating asteroids and fragments in impact disruption |
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Authors: | Toshihiko Kadono Masahiko Arakawa Takashi Ito Keiji Ohtsuki |
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Institution: | aCenter for Deep Earth Exploration, Japan Agency for Marine–Earth Science and Technology, Syowa 3173-25, Kanazawa, Yokohama, Kanagawa 236-0001, Japan;bGraduate School of Environmental Studies, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-8601, Japan;cNational Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan;dLaboratory for Atmospheric and Space Physics, University of Colorado, 392 UCB, Boulder, CO 80309-0392, USA |
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Abstract: | We present a new experimental result of fragment spin-rate in impact disruption, using a thin glass plate. A cylindrical projectile impacts on a side (edge) of the plate. Dispersed fragments are observed using a high-speed camera and the spin rates of fragments are measured. We find that the measured fragment spin-rate decreases with increasing size. Assuming that the rotational energy of fragments is supplied from the residual stress, the spin rate ω decreases with increasing fragment size r as ω∼r−1, which explains the above experimental results. This size-dependence is similar to that of the observed spin rates of small fast-rotating asteroids. Our results suggest that spin rates of fragments of small asteroids immediately after disruption may have a similar size-dependence, and can provide constraints on the subsequent spin-state evolution of small asteroids due to thermal torques. |
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Keywords: | Impact processes Asteroids rotation |
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