衝撃ジェットがコンドルールの起源である
Brandon C Johnson1, David A Minton2, H J Melosh2
1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Nature
|January 17, 2015
まとめ
初期の惑星増殖の時の衝撃は,隕石に含まれるコンドルルを生成することができます. これらの発見は,隕石が惑星形成の副産物であり,残った構成要素ではないことを示唆しています.
科学分野:
- 惑星科学は惑星科学である.
- 宇宙化学 (コスモケミストリー)
- 天体物理学 天体物理学
背景:
- チョンドルル (chondrules) は,以前溶けたほとんどの隕石に含まれるミリメートルスケールの球体です.
- 以前のモデルでは,コンドルールの形成が太陽の星雲で起きたと示唆されていたが,証拠は,衝撃の羽根のような固体豊富な環境を指している.
- 大半のコンドルールの正確な形成メカニズムについては,まだ議論が続いている.
研究 の 目的:
- 原惑星の衝突が,観測されたコンドルールの豊富さを生み出すことができるかどうかを調査する.
- 衝撃がコンドルールを形成する条件を決定する.
- コンドルルの衝突起源が隕石の重要性に及ぼす影響を評価する.
主な方法:
- 材料の放出と融解を分析するために,原惑星の衝突をシミュレートする.
- モンテカルロ増積コードを用いて,コンドルーラ形成の衝撃事件をモデル化しました.
- 射出された滴の冷却速度を決定するために,放射伝送モデルを使用した.
主要な成果:
- 2.5 km/sを超える衝突速度は,高速度で材料を溶かして放出することができます.
- シミュレーションでは,最初の500万年の増殖期間に十分なコンドルル生産が示されています.
- 噴出された溶融滴は,コンドルルに特徴的なサイズと冷却速度に一致します.
結論:
- 原惑星の衝突は,コンドルルの大部分の生存可能な源である.
- コンドルル形成は,太陽星雲だけでなく,衝突によって発生した羽根で発生した可能性が高い.
- 隕石は,原始的な建材ではなく,惑星形成の副産物であるかもしれない.
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