エウロパの二次クレーターと,クレーター表面への影響
Edward B Bierhaus1, Clark R Chapman, William J Merline
1Lockheed Martin, Space Exploration Systems, MS S8110, PO Box 179, Denver, Colorado 80201, USA. edward.b.bierhaus@lmco.com
Nature
|October 21, 2005
まとめ
エウロパのような氷の月の小さなクレーターは,主に二次的衝突であり,主要因ではありません. この発見は,太陽系全体のほとんどの小さなクレーターも二次的であることを示唆し,惑星の表面の年代測定に関する以前の仮定に挑戦しています.
科学分野:
- 惑星科学は惑星科学である.
- インパクトクレーター研究
- 太陽系探査 太陽系探査について
背景:
- 惑星の研究では,衝突クレーターの人口は主に小惑星と彗星の直接的な衝突を反映していると伝統的に仮定しています.
- 固体表面上の地質単位の年齢推定は,この主要な衝撃仮定に依存しています.
- クレーター形成記録は,惑星の進化と表面の年齢を理解するために極めて重要です.
研究 の 目的:
- 木星の衛星欧州のクレーター群を分析するために.
- 小型クレーターが主に一次衝突の結果であるという仮定を再評価する.
- 欧州の小さなクレーター (直径<1km) の起源を調査する.
主な方法:
- エウロパの希少なクレーター集団の分析.
- クレーターサイズ分布の統計的調査.
- 観測されたクレーター形成データと衝突モデルの比較.
主要な成果:
- 二次クレーター (より大きな衝突で放出された物質によって形成された) は,ヨーロッパ上の小さなクレーター (直径1km未満) の約95%を占めています.
- これは,大規模な一次衝突が,以前に推定されたよりもはるかに多くの二次クレーターを生成することを示している.
- この研究は,最近,木星系で小さな彗星 (<100 m) の希少性を示唆しています.
結論:
- 小型クレーターが主に直接的な衝突によるものであるという仮定は,ヨーロッパでは正しくありません.
- 月,火星,その他の天体の小さなクレーター集団は,二次衝突によって支配されている可能性が高い.
- クレーターモデルの再考は,正確な年代測定と惑星の表面過程を理解するために必要である.
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