最近の太陽風における窒素同位体の豊富さ

J S Kim¹, Y Kim, K Marti

¹Department of Chemistry 0317, University of California, San Diego, La Jolla 92093-0317, USA.

Nature

|June 1, 1995

まとめ

月面のレゴリットには,主に太陽風からの窒素が含まれており,結晶岩ではない. 新しい測定により,この太陽風の窒素は,地球の大気よりも15N/14Nの比率が高いことが明らかになりました.

科学分野:

月と惑星科学月と惑星科学
地質化学地質化学
宇宙化学 (コスモケミストリー)

背景:

月面の結晶岩は窒素が少ないが,レゴライトのサンプルには窒素濃度がかなり高い (質量の0.012%まで).
月面のレゴリット窒素は,太陽放射線によって埋め込まれた貴気体と相関しており,太陽起源を示唆しています.
レゴリットサンプルにおける窒素同位体比 (15N/14N) の変動は,太陽風の長期的同位体変化を暗示しているが,直接的な太陽風測定は欠けている.

研究の目的:

現代の太陽風の15N/14N比率を決定する.
過去10^5~5x10^7年に月面に埋め込まれた窒素の信頼性の高い同位体シグネチャーを提供するためです.

主な方法:

シンプルで最近の被曝歴のある2つの月球レゴリットサンプルにおける窒素同位体の分析.
植入された窒素における15N/14N比の測定.

主要な成果:

過去10^5~5x10^7年に月面に埋め込まれた窒素は,地球の大気よりも約40%高い15N/14N比を示しています.
この測定された比率は,太陽風の同位体組成に関する以前のほとんどの推定値よりも大幅に低い.

結論:

この研究は,現在の太陽風における15N/14N比の新しい,堅固な測定を提供します.
この発見は,月面のレゴリットに観察された同位体変動を説明するのに役立ち,太陽の組成の長期的な進化の洞察を提供します.

キーワード:

非プログラム的なものです.

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