[P-PS04] Regolith Science

[PPS04-03] The size of ejecta particles of the artificial impact crater formed by Hayabusa2 Small Carry-on Impactor

*Koji Wada¹, Ko Ishibashi¹, Hiroshi Kimura¹, Masahiko Arakawa², Hirotaka Sawada³, Kazunori Ogawa^3,2, Kei Shirai², Rie Honda⁴, Yuichi Iijima³, Toshihiko Kadono⁵, Naoya Sakatani³, Yuya Mimasu³, Tomoaki Toda³, Yuri Shimaki³, Satoru Nakazawa³, Hajime Hayakawa³, Takanao Saiki³, Yasuhiko Takagi⁶, Hiroshi Imamura³, Chisato Okamoto², Masahiko Hayakawa³, Naru Hirata⁷, Hajime Yano³ (1.Planetary Exploration Research Center, Chiba Institute of Technology, 2.Kobe University, 3.JAXA, 4.Kochi University, 5.University of Occupational and Environmental Health, 6.Aichi Toho University, 7.The University of Aizu)

Keywords:Hayabusa2, Small Carry-on Impactor, Deployable Camera 3, Ryugu, Impact crater, ejecta

A projectile accelerated by Hayabusa2 Small Carry-on Impactor succeeded in producing an artificial impact crater with a diameter of >10 m on the surface of the asteroid Ryugu on April 5, 2019. At the time of cratering, Deployable Camera 3 (DCAM3) took clear images of ejecta curtain emerged from the crater. Comparing the ejecta curtain images to a theoretical model of ejecta curtain, we infer the size of the particles composing the ejecta curtain. Since almost of the ejecta particles come from the underground, we can discuss about the particle size distribution of the subsurface layer of Ryugu and the evolution process of Ryugu’s surface layer. As a result, the typical size range of the ejecta particles is estimated to be ~cm to several 10 cm, although it depends on the assumed size distribution. This typical size is relatviely small compared to the boulder size on the uppermost surface, suggesting some kind of surface process occured in the past.