Akira Tsuchiyama

Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan

The Japanese spacecraft Hayabusa returned samples from the surface of an asteroid (near-Earth S-type asteroid 25143 Itokawa) for the first time in human history. This article describes the results of the initial analysis of the mineralogy, micropetrology, and elemental and isotopic compositions of regolith particles from Itokawa measuring 30–180 μm in diameter. The results show a direct link between ordinary chondrites and S-type asteroids. The regolith particles provide evidence of space-weathering rims and grain abrasion, and the information obtained has elucidated various processes on the airless surface of Itokawa, such as the impact of small objects, grain motion, and irradiation by solar wind.

Reference
Tsuchiyama A (2014) Asteroid Itokawa A Source of Ordinary Chondrites and A Laboratory for Surface Processes. Elements  10:45-50.
[doi:10.2113/gselements.10.1.45]
Copyright: The Mineralogical Society of America

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Harry Y. McSween¹, Maria Cristina De Sanctis², Thomas H. Prettyman³, Dawn Science Team

¹Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
²Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale de Astrofisica, Rome, Italy
³Planetary Science Institute, Tucson, AZ 85719, USA

Most asteroids are collisional rubble from eons past, and few of them have survived intact. Vesta, the second most massive asteroid, is the only differentiated, rocky body in this category. This asteroid provides a unique view of the kinds of planetesimals that accreted to form the terrestrial planets. We know more about this asteroid than any other, thanks to its recently completed exploration by the orbiting Dawn spacecraft and studies of the ~1000 meteorites derived from it. The synergy provided by in situ analyses and samples has allowed an unparalleled understanding of Vesta’s mineralogy, petrology, geochemistry, and geochronology.

Reference
McSween HY, De Sanctis MC, Prettyman TH and Dawn Science Team (2014) Unique, Antique Vesta. Elements  10:39-44.
[doi:10.2113/gselements.10.1.39]
Copyright: The Mineralogical Society of America

Link to Article

Cyrena Goodrich¹, Addi Bischoff² and David P. O’Brien³

¹Planetary Science Institute, 1700 E. Ft. Lowell Drive, Tucson, AZ 85179, USA
²Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³Planetary Science Institute, 1700 E. Ft. Lowell Drive, Tucson, AZ 85179, USA

On October 6, 2008, the small (~4 m) asteroid 2008 TC₃ was discovered and predicted to hit Earth within ~19 hours. Photometric data and a reflectance spectrum were obtained. The asteroid fragmented at ~37 km altitude above Sudan. Approximately 700 centimeter-sized fragments were recovered and constitute the meteorite Almahata Sitta. It is a unique meteorite breccia, consisting of ~50–70% ureilitic materials, plus samples of nearly every major chondrite group. The reflectance spectrum of 2008 TC₃is closest to that of F-class asteroids, not previously associated with any meteorite type. 2008 TC₃/Almahata Sitta records a complex history of fragmentation, migration, and reaccretion of materials in the Solar System.

Reference
Goodrich C, Bischoff A and O’Brien DP (2014) Asteroid 2008 TC3 and the Fall of Almahata Sitta, a Unique Meteorite Breccia. Elements  10:31-37.
[doi:10.2113/gselements.10.1.31]
Copyright: The Mineralogical Society of America

Link to Article