このエントリーをはてなブックマークに追加
ID 48717
本文ファイル
著者
Okazaki, Ryuji
Noguchi, Takaaki
Tsujimoto, Shin-ichi
Tobimatsu, Yu
Nakamura, Tomoki
Ebihara, Mitsuru
Itoh, Shoichi
Nagahara, Hiroko
Tachibana, Shogo
Terada, Kentaro
キーワード
Antarctic micrometeorites
Noble gas
Transmission electron microscopy
Atmospheric entry heating
Solar energetic particles
抄録(英)
We have investigated seven micrometeorites (MMs) from Antarctic snow collected in 2003 and 2010 by means of electron microscopy, X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy (TEM) observation, and noble-gas isotope analysis. Isotopic ratios of He and Ne indicate that the noble gases in these MMs are mostly of solar wind (SW). Based on the release patterns of SW 4He, which should reflect the degree of heating during atmospheric entry, the seven MMs were classified into three types including two least heated, three moderately heated, and two severely heated MMs. The heating degrees are well correlated to their mineralogical features determined by TEM observation. One of the least heated MMs is composed of phyllosilicates, whereas the other consists of anhydrous minerals within which solar flare tracks were observed. The two severely heated MMs show clear evidence of atmospheric heating such as partial melt of the uppermost surface layer in one and abundant patches of dendritic magnetite and Si-rich glass within an olivine grain in the other. It is noteworthy that a moderately heated MM composed of a single crystal of olivine has a 3He/4He ratio of 8.44 × 10−4, which is higher than the SW value of 4.64 × 10−4, but does not show a cosmogenic 21Ne signature such as 20Ne/21Ne/22Ne = 12.83/0.0284/1. The isotopic compositions of He and Ne in this sample cannot be explained by mixing of a galactic cosmic ray (GCR)-produced component and SW gases. The high 3He/4He ratio without cosmogenic 21Ne signature likely indicates the presence of a 3He-enriched component derived from solar energetic particles.
内容記述
This work was supported by Grant-in-Aid for Scientific Research (S) (No. 22224010, PI: H. Nagahara) and partly by a Grant-in-Aid for Young Scientists (A) (No. 23684046, PI: R. Okazaki).
掲載誌名
Earth, Planets and Space
67巻
開始ページ
90
出版年月日
2015-06-17
出版者
Springer Open
ISSN
1880-5981
出版者DOI
言語
英語
NII資源タイプ
学術雑誌論文
広大資料タイプ
学術雑誌論文
DCMIタイプ
text
フォーマット
application/pdf
著者版フラグ
publisher
権利情報
© 2015 Okazaki et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.
関連情報URL
部局名
理学研究科