A survey of possible impact structures on 25143 Itokawa |
| |
| Authors: | Naru Hirata Olivier S Barnouin-Jha Chikatoshi Honda Ryosuke Nakamura Hideaki Miyamoto Sho Sasaki Hirohide Demura Akiko M Nakamura Tatsuhiro Michikami Robert W Gaskell Jun Saito |
| |
| Institution: | aDepartment of Computer Software, The University of Aizu, Ikki-machi, Aizu-Wakamatsu, Fukushima 965-8580, Japan;bThe Johns Hopkins University Applied Physics Laboratory, Johns Hopkins Road, Laurel, MD 20723-6099, USA;cInstitute of Space and Astronautical Sciences, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 229-8510, Japan;dNational Institute of Advanced Science and Technology, Tsukuba 305-8568, Japan;eThe University Museum, University of Tokyo, Tokyo 113-0033, Japan;fRISE Project Office, Mizusawa Astrogeodynamic Observatory, National Astronomical Observatory of Japan, Mizusawa, Oshu 023-0861, Japan;gGraduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan;hFukushima National College of Technology, Iwaki, Fukushima 970-8034, Japan;iPlanetary Science Institute, PO Box 135, Altadena, CA 91003, USA;jDepartment of Architecture, School of Engineering, Tokai University, Kitakaname, Hiratuska, Kanagawa 259-1292, Japan |
| |
| Abstract: | We determined the morphologies and dimensions of possible impact craters on the surface of Asteroid 25143 Itokawa from images taken by the Hayabusa spacecraft. Circular depressions, circular features with flat floors or convex floors, and circular features with smooth surfaces were identified as possible craters. The survey identified 38 candidates with widely varying morphologies including rough, smooth and saddle-shaped floors, a lack of raised rims and fresh material exposures. The average depth/diameter ratio was 0.08±0.03: these craters are very shallow relative to craters observed on other asteroids. These shallow craters are a result of (1) target curvature influencing the cratering process, (2) raised rim not being generated by this process, and (3) fines infilling the craters. As many of the crater candidates have an unusual appearance, we used a classification scheme that reflects the likelihood of an observed candidate's formation by a hypervelocity impact. We considered a variety of alternative interpretations while developing this scheme, including inherited features from a proto-Itokawa, spall scars created by the disruption of the proto-Itokawa, spall scars following the formation of a large crater on Itokawa itself, and apparent depressions due to random arrangements of boulders. The size-frequency distribution of the crater candidates was close to the empirical saturation line at the largest diameter, and then decline with decreasing diameter. |
| |
| Keywords: | Asteroids Asteroid Itokawa Impact processes Cratering |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
