TERRAPUB Earth, Planets and Space

Earth, Planets Space, Vol. 51 (No. 11), pp. 1163-1171, 1999

Angular momentum transfer in oblique impacts: Implications for 1989ML

Masahisa Yanagisawa and Sunao Hasegawa

University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182-8585, Japan

(Received October 10, 1998; Revised August 6, 1999; Accepted September 23, 1999)

Abstract: We conducted 10 shots of high-velocity oblique impact experiments (1.95–3.52 km/s) using nylon projectiles and spherical mortar targets. Large craters were formed, but these targets were not disrupted by the impacts. We then calculated the efficiencies of momentum transfer from the projectile to the post-impact target for each experiment. The efficiencies of angular momentum transfer from the translational motion of the projectiles to the rotation of the post-impact targets were also derived. A representative efficiency of angular momentum transfer was calculated to be 0.17 for random successive collisions. The efficiency was applied to an equation expressing the precession angle of asteroids. It is shown that 1989ML, target of Japan-US asteroid-sample-return-mission (MUSES-C) would be tumbling.

Corresponding author E-mail: yanagi@ee.uec.ac.jp

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