[P-PS03] Regolith Science

[PPS03-P04] Ryugu's surface change formed by SCI forward debris

*Yuri Shimaki¹, Yasuhiro Yokota¹, Rie Honda², Masahiko Arakawa³, Koji Wada⁴, Toshihiko Kadono⁵, Kei Shirai³, Kazunori Ogawa⁶, Naoya Sakatani⁷, Ko Ishibashi⁴, Takanao saiki¹, Hiroshi Imamura¹, Satoru Nakazawa¹, Masahiko Hayakawa¹, Hajime Yano¹, Yasuhiko Takagi⁸, Naru Hirata⁹, Hirotaka Sawada¹, Seiji Sugita¹⁰, Tomokatsu Morota¹⁰, Shingo Kameda⁷, Eri Tatsumi¹¹, Manabu Yamada⁴, Toru Kouyama¹², Yuichiro Cho¹⁰, Moe Matsuoka¹, Kazuo Yoshioka¹⁰, Hidehiko Suzuki¹³, Chikatoshi Honda⁹ (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.Kochi University, 3.Kobe University, 4.Planetary Exploration Research Center, Chiba Institute of Technology, 5.University of Occupational and Environmental Health, 6.JAXA Space Exploration Center, Japan Aerospace Exploration Agency, 7.Rikkyo University, 8.Aichi Toho University, 9.The University of Aizu, 10.The University of Tokyo, 11.Instituto de Astrofisica de Canarias, University of La Laguna, 12.National Institute of Advanced Industrial Science and Technology, 13.Meiji University)

Keywords:Hayabusa2, Crater formation, Asteroid Ryugu

The small carry-on impactor (SCI) on the Hayabusa2 spacecraft is designed to create an artificial crater on an asteroid surface for the collection of sub-surface materials and validation of crater scaling laws [1]. The SCI launches a hollow hemisphere copper liner with a diameter of 13 cm at a velocity of 2 km/s, accompanied by numerous debris [2]. In the ground tests, the SCI forward debris generated concentric damage on the target surface. The SCI successfully created an artificial crater on the surface of Ryugu in 2019 [3]. Besides the artificial crater, surface changes around the crater, such as rim formation, boulder movement, and the emergence of new boulders were observed by the optical navigation camera telescope (ONC-T) [4]. Additionally, concentric surface changes were observed ~70 m distance from the artificial crater, created by the SCI forward debris. Here we report the distribution of the surface changes formed by the SCI forward debris both in the ground test and Ryugu. Based on the SCI detonation position [5], we found that the polar angle of the forward debris in the ground tests is ~11°, whereas that in Ryugu is ~15°, probably due to the absence of ambient pressure.

[1] Arakawa et al. (2017), Space Science Review 208, 187–212. [2] Saiki et al. (2017), Space Science Review 208, 165–186. [3] Arakawa et al. (2020), Science 368, 67-71. [4] Honda et al., submitted to Icarus. [5] Saiki et al. (2020), Astrodynamics 4, 289–308.