Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 µm, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-µm-sized craters but also a large number of sub-µm- to several-µm-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-µm-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10-9 to 104 meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.
@article{20120224095412-627-620,
author = "Nakamura, Eizo and Makishima, Akio and Moriguti, Takuya and Kobayashi, Katsura and Tanaka, Ryoji and Kunihiro, Tak and Tsujimori, Tatsuki and Sakaguchi, Chie and Kitagawa, Hiroshi and Ota, Tsutomu and Yachi, Yusuke and Yada, Toru and Abe, Masanao and Fujimura, Akio and Ueno, Munetaka and Mukai, Toshifumi and Yoshikawa, Makoto and Kawaguchi, Jun'ichiro",
title = "Space environment of an asteroid preserved on micrograins returned by the Hayabusa spacecraft",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
year = "2012",
volume = "101",
pages = "E624-E629",
doi = "10.1073/pnas.1116236109",
}
name | coordinate | global-id | ||
---|---|---|---|---|
755 pub | (6.91, 17.87) | 20120224170037-167-576 | ||
10 pub | (12.97, 28.48) | 20120224170419-427-622 | ||
9 pub | (20.18, 32.52) | 20120224170343-608-908 | ||
8 pub | (4.84, 21.16) | 20120224170312-470-199 | ||
756 pub | (-4.09, 27.33) | 20120224170110-609-443 | ||
765 pub | (20.05, 35.58) | 20120224170145-076-332 | ||
7 pub | (-5.89, 24.62) | 20120224170234-393-316 |
name | coordinate | global-id | ||
---|---|---|---|---|
720 pub | (10.66, 37.93) | 20120223194311-653-163 | ||
721 pub | (9.92, 20.01) | 20120223193931-048-650 | ||
723 pub | (-0.10, 23.42) | 20120223194050-662-192 | ||
2 pub | (9.27, 32.64) | 20120224162122-595-904 | ||
3 pub | (-0.67, 28.35) | 20120224162233-253-084 | ||
694 pub | (3.44, 31.60) | 20120224162007-252-238 | ||
6 pub | (18.74, 27.27) | 20120224162519-744-911 | ||
5 pub | (15.25, 41.62) | 20120224162410-450-591 | ||
4 pub | (16.59, 36.08) | 20120224162313-125-109 |
caption | ID | rowname | stone | ||
---|---|---|---|---|---|
Table S7. Chemical compositions of the Itokawa grains determined using the Cameca ims-5f ion microprobe pub | 20181219120001-182930 | major-trace by 5f (Itokawa TableS7) | 13 | ||
Table S1.Major element compositions of the Itokawa grains pub | 20181219094303-294307 | major by EMPA (Itokawa Table S1) | 8 | ||
Table S5. Geochemical properties of the reference glasses and minerals pub | 20181225094629-405342 | major-trace of ref (Itokawa TableS5) | 21 | ||
Table S9. Major element compositions of the merrillite in the PIC pub | 20181220105859-969128 | major by FE-SEM-EDS (Itokawa Table S9) | 8 | ||
Table S3. Results of in-situ O isotope analyses pub | 20181219110039-527168 | oxygen (Itokawa Table S3) | 10 | ||