ヴェレデフォート隕石クレーターの古磁気現象と火星上のクレーターへの影響

Laurent Carporzen¹, Stuart A Gilder, Rodger J Hart

¹Institut de Physique du Globe, Laboratoire de Paléomagnétisme, 75252 Paris Cedex 05, France.

Nature

|May 13, 2005

まとめ

火星のクレーターには磁場が少ないが,ヴレデフォートクレーターの岩は磁気力が強い. 衝突イベントはランダム化して磁気化を強め,クレーター上の低い磁場を説明する.

科学分野:

地質物理学地質物理学とは地質物理学です.
惑星科学惑星科学
ミネラル物理学ミネラル物理学

背景:

HellasやArgyreのような火星の衝突クレーターは,周囲の地域よりも磁場強度が低いことを示している.
この現象は,グローバル磁場がない状況で,ショックによる圧力去磁化に起因することが多い.

研究の目的:

ヴェレデフォルト隕石クレーター内の岩石の磁気特性を調査するために.
衝突事故がクレーターで観測された磁気異常を説明できるかどうかを判断する.

主な方法:

ヴェレデフォルトクレーター岩の磁気強度と古磁気方向の分析.
マグネチット粒子の結晶化と向きの顕微鏡検査.

主要な成果:

ヴェレデフォートクレーター内の岩石は,地球上の同等の石質学よりもはるかに高い磁気強度を示しています.
古磁気方向はセンチメートルスケールでランダムに指向され,衝撃誘発磁化を示しています.
マグネタイトの粒子は衝突時の結晶化を示し,磁化と衝突を結びつける.

結論:

クレーター内の強烈でランダムな磁気化は,効果的にキャンセルされ,高い高度から低い磁場の幻想を生み出します.
隕石クレーターの磁気異常は,衝突時に惑星の内部磁場が存在しない証拠として解釈されるべきではありません.

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