TY - JOUR
T1 - Mineralogy and crystallography of some itokawa particles returned by the hayabusa asteroidal sample return mission
AU - Mikouchi, Takashi
AU - Komatsu, Mutsumi
AU - Hagiya, Kenji
AU - Ohsumi, Kazumasa
AU - Zolensky, Michael E.
AU - Hoffmann, Viktor
AU - Martinez, James
AU - Hochleitner, Rupert
AU - Kaliwoda, Melanie
AU - Terada, Yasuko
AU - Yagi, Naoto
AU - Takata, Masaki
AU - Satake, Wataru
AU - Aoyagi, Yuya
AU - Takenouchi, Atsushi
AU - Karouji, Yuzuru
AU - Uesugi, Masayuki
AU - Yada, Toru
N1 - Funding Information:
We thank JAXA for providing us with the Itokawa particles. Advice for the sample preparation and discussion with Dr. T. Nakamura was very helpful. We are grateful for the constructive reviews by Drs. A. Bischoff and T. Nakamura, and editorial handling by Dr. T. Okada. The electron microscopy was performed at the Electron Microbeam Analysis Facility for Mineralogy at the Department of Earth and Planetary Science, University of Tokyo. A part of this study was supported by the Grant-in-Aid for Scientific Research (B) by the Japanese Ministry of Education, Culture, Sports, Science and Technology No. 23360333 (TM). The SR-XRD work was supported by the SPring-8 long-term project (2010B1415) and SR-XANES work was by KEK 2012G652. MEZ was supported by NASA's Muses-C Program.
Publisher Copyright:
© 2014 Mikouchi et al.; licensee Springer.
PY - 2014
Y1 - 2014
N2 - We studied seven Itokawa particles provided by the Japan Aerospace Exploration Agency (JAXA) as first International Announcement of Opportunity (AO) study mainly using electron and synchrotron radiation X-ray beam techniques. All the analyzed particles were collected from the first-touchdown site and composed of olivine and plagioclase with traces of Ca phosphate and chromite, and do not contain pyroxenes. Optical microscopy of these particles shows minor undulatory extinction of olivine and plagioclase, suggesting minor shock metamorphism (shock stage: S2). The electron microprobe analysis shows that olivine is Fo 70-73 and plagioclase is An 13-10 Or 5-7 . The synchrotron radiation X-ray diffraction (SR-XRD) analysis of olivine crystals gives cell dimensions of a = 4.708 to 4.779 Å, b = 10.271 to 10.289 Å, c = 6.017 to 6.024 Å, corresponding to the Fo content of Fo ~70 by Vegard's law. This composition matches the result obtained by the electron microprobe analysis. The olivine compositions of the analyzed particles are consistent with those of LL chondrites. The cell dimensions of two plagioclase crystals (a = 8.180 to 8.194 Å, b = 12.53 to 12.893 Å, c = 7.125 to 7.23 Å, α = 92.6° to 93.00°, β = 116.36° to 116.75°, γ = 90.03° to 90.17°) indicate that their equilibration temperatures are 800°C ± 10°C. This temperature is near the peak metamorphic temperature recorded by equilibrated ordinary chondrites. The size of plagioclase crystals and the homogeneity of olivine compositions indicate that their petrologic type is ≥5. We also analyzed plagioclase by SR iron X-ray absorption near-edge structure (SR-XANES) and found that its Fe 3+ /(Fe 2+ + Fe 3+ ) ratio is approximately 0.5. Such high Fe 3+ abundance indicates the formation under a relatively oxidizing environment. Thus, all these analyses have reconfirmed that the Itokawa particles returned by the Hayabusa spacecraft are very weakly shocked equilibrated LL chondrites, which matches the results of the preliminary examination team.
AB - We studied seven Itokawa particles provided by the Japan Aerospace Exploration Agency (JAXA) as first International Announcement of Opportunity (AO) study mainly using electron and synchrotron radiation X-ray beam techniques. All the analyzed particles were collected from the first-touchdown site and composed of olivine and plagioclase with traces of Ca phosphate and chromite, and do not contain pyroxenes. Optical microscopy of these particles shows minor undulatory extinction of olivine and plagioclase, suggesting minor shock metamorphism (shock stage: S2). The electron microprobe analysis shows that olivine is Fo 70-73 and plagioclase is An 13-10 Or 5-7 . The synchrotron radiation X-ray diffraction (SR-XRD) analysis of olivine crystals gives cell dimensions of a = 4.708 to 4.779 Å, b = 10.271 to 10.289 Å, c = 6.017 to 6.024 Å, corresponding to the Fo content of Fo ~70 by Vegard's law. This composition matches the result obtained by the electron microprobe analysis. The olivine compositions of the analyzed particles are consistent with those of LL chondrites. The cell dimensions of two plagioclase crystals (a = 8.180 to 8.194 Å, b = 12.53 to 12.893 Å, c = 7.125 to 7.23 Å, α = 92.6° to 93.00°, β = 116.36° to 116.75°, γ = 90.03° to 90.17°) indicate that their equilibration temperatures are 800°C ± 10°C. This temperature is near the peak metamorphic temperature recorded by equilibrated ordinary chondrites. The size of plagioclase crystals and the homogeneity of olivine compositions indicate that their petrologic type is ≥5. We also analyzed plagioclase by SR iron X-ray absorption near-edge structure (SR-XANES) and found that its Fe 3+ /(Fe 2+ + Fe 3+ ) ratio is approximately 0.5. Such high Fe 3+ abundance indicates the formation under a relatively oxidizing environment. Thus, all these analyses have reconfirmed that the Itokawa particles returned by the Hayabusa spacecraft are very weakly shocked equilibrated LL chondrites, which matches the results of the preliminary examination team.
KW - Hayabusa
KW - Itokawa
KW - LL chondrites
KW - Olivine
KW - Plagioclase
KW - SR-XANES
KW - SR-XRD
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U2 - 10.1186/1880-5981-66-82
DO - 10.1186/1880-5981-66-82
M3 - Letter
AN - SCOPUS:85015657942
SN - 1343-8832
VL - 66
JO - Earth, Planets and Space
JF - Earth, Planets and Space
IS - 1
M1 - 82
ER -