Crater depth-to-diameter ratios on asteroid 162173 Ryugu d/D of craters on Ryugu

Rina Noguchi, Naoyuki Hirata, Naru Hirata, Yuri Shimaki, Naoki Nishikawa, Sayuri Tanaka, Takaaki Sugiyama, Tomokatsu Morota, Seiji Sugita, Yuichiro Cho, Rie Honda, Shingo Kameda, Eri Tatsumi, Kazuo Yoshioka, Hirotaka Sawada, Yasuhiro Yokota, Naoya Sakatani, Masahiko Hayakawa, Moe Matsuoka, Manabu YamadaToru Kouyama, Hidehiko Suzuki, Chikatoshi Honda, Kazunori Ogawa, Masanori Kanamaru, Sei ichiro Watanabe

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The near-Earth asteroid 162173 Ryugu, the target of the Hayabusa2 mission, is noted to be a spinning top-shaped rubble-pile. Craters are among the most prominent surface features on Ryugu. Their shapes, particularly their depth-to-diameter ratio (d/D), can provide an important proxy for probing both the internal structure and surface processes of planetary bodies. Here, we report d/D of every impact crater on Ryugu using a shape model derived from stereo-photoclinometry. We found that the average, standard deviation, and observed range of d/D for the entire set of craters are 0.09, 0.02, and 0.03–0.15, respectively. Except for possible pit craters, the maximum d/D of large craters on Ryugu (D > 50 m) is close to 0.13, which is comparable with those of fresh simple craters on rocky asteroids, such as Gaspra and Ida. Conversely, the d/D of small craters (D < 50 m) increases with the crater diameter. This behavior implies that a smaller crater on Ryugu is formed as a shallower crater. As on Itokawa, the surface environment on Ryugu likely inhibits craters becoming deep. This especially affects smaller craters, as their normal small depth decreases in the Ryugu environment and they become still more shallow. As a result, small craters rapidly degrade beyond the point where they can be identified as candidate craters. This is likely responsible for the apparent lack of small craters. The d/D has no reliable relationship with the types of crater classification in Hirata et al. (2020). Examination of latitudinal and longitudinal variation in d/D of craters on Ryugu revealed no statistically significant trends.

Original languageEnglish
Article number114016
JournalIcarus
Volume354
DOIs
Publication statusPublished - 15 Jan 2021

Keywords

  • Asteroids
  • Cratering
  • Impact processes

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