小さな近地天体の流れが,地球と衝突する
P Brown1, R E Spalding, D O ReVelle
1Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada. pbrown@uwo.ca
Nature
|November 26, 2002
まとめ
小型の小惑星の衝突は,これまで考えられていたよりも頻繁に起こっています. 衛星データは,地球はTNTの5キロトンに相当する年間大気爆発を経験し,トンガスカのようなイベントは1000年ごとに発生することを明らかにしています.
科学分野:
- 惑星科学 惑星科学
- 天文学 天文学
- 地質物理学 地質物理学とは地質物理学です.
背景:
- 小型小惑星 (50~100m) は,通常,地球の大気圏で爆発するので,地面への衝突物として爆発しない.
- 1908年のトゥングースカ爆発のような過去の出来事は,大気中の小惑星の爆発による破壊的可能性を強調しています.
- トングースカ級 (10メガトンTNT) のイベントの推定では,200~300年に1度発生し,年間20キロトンTNTの小さなイベントが起こると示唆されています.
研究 の 目的:
- 大気中の爆発を分析することによって,小さな近地天体の流れをよりよく制限する.
- 新規の観測データを用いて小惑星空爆の発生頻度を調査する.
- 小惑星の小さな集団に対する衝撃の危険性評価を洗練する.
主な方法:
- 衛星で記録された8.5年間のボリデ爆発の分析.
- 小型 (1~10m) の衝突物体と,より大きな (>50m) の衝突物体のサイズ・周波数分布の比較.
- 観測された爆発データを抽出して,異なるエネルギー出力の衝撃周波数を推定する.
主要な成果:
- 直径1~10mの物体の流動は,より大きな物体 (>50m) と同様の力法則分布に従っている.
- 地球は年間平均5キロトンのTNTのエネルギー量を持つ大気爆発を経験しています.
- トングースカのような大気爆発は,およそ1000年に1回発生すると推定されています.
結論:
- 小型小惑星の大気爆発は,地上からの観測に基づいて以前に推定されたより頻繁に発生しています.
- 衛星モニタリングは,小さな近地天体の集団と衝突頻度を理解するためのより包括的なデータセットを提供します.
- この発見は,特に大気中の大きな爆発を起こす可能性のある小惑星の小さな集団について,衝撃の危険性評価を再評価することを必要としています.
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