JpGU-AGU Joint Meeting 2020

Presentation information

[E] Poster

P (Space and Planetary Sciences ) » P-PS Planetary Sciences

[P-PS07] Solar System Small Bodies: Explorations of Ryugu, Bennu, and the Solar System at Large

convener:Taishi Nakamoto(Tokyo Institute of Technology), Tatsuaki Okada(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), Dante S Lauretta(University of Arizona), Masateru Ishiguro(Department of Physics and Astronomy, Seoul National University)

[PPS07-P07] East-west asymmetric crater ejecta on Ryugu

*Naoyuki Hirata1, Noriyuki Namiki2 (1.Kobe University, 2.National Astronomical Observatory of Japan)

Keywords:Ryugu, impact crater, Hayabusa 2

Asteroid 162173 Ryugu is a top-shaped body formed by a prior period of rapid spin. Major craters on Ryugu appears an east–west asymmetric profile of crater rims; their western crater rims are sharp and tall, while their eastern crater rims are rounded and low. Although there are various possible explanations, we theoretically assess the effect of rotation as a possible origin of this east-west asymmetry. It is known that the trajectories and fates of ejecta are affected by the effect of rotation, especially the Coriolis force and the inertial speed of the rotating surface. As a result, we found that east-west asymmetric crater rim can be explained by the effect of a rotation, only if the inertial speed of the rotating surface is nearly equal to the first cosmic velocity of the body. In particular, Urashima, Cendrillon, and Kolobok craters might be formed, when Ryugu was fast rotator with a rotation period of ~3.6 hours. Brabo crater may be relatively younger.