嫦娥6号サンプルが月衝突フラックスを制約し初期衝突史を解明(Chang’e-6 Samples Constrain Lunar Impact Flux and Illuminate Early Impact History)

2026-02-09 中国科学院(CAS)

中国の嫦娥6号ミッションが月の裏側・南極エイトケン盆地で回収した試料を用い、中国科学院の研究チームは、月面クレーター年代モデルを約半世紀ぶりに改訂した。裏側試料(約28億年前の玄武岩、42.47億年前の衝突溶融起源ノーライト)とリモートセンシングを統合解析した結果、月の表側と裏側で隕石衝突フラックスに有意差はないことを初めて実証。さらに、初期衝突率は時間とともに単調に減少しており、約39億年前に衝突が急増したとする後期重爆撃(LHB)仮説を支持しないことが示された。改訂された全球的クレーター年代関数は、未採取地域の年代推定精度を高め、月および内惑星系初期史の理解を前進させる。

嫦娥6号サンプルが月衝突フラックスを制約し初期衝突史を解明(Chang’e-6 Samples Constrain Lunar Impact Flux and Illuminate Early Impact History)
Topographic map of the lunar farside based on LRO LOLA Data. (Image by YUE Zongyu’s team)

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嫦娥6号の裏側サンプルを用いた月年表モデルと初期衝突史への示唆 Lunar chronology model with the Chang’e-6 farside samples and implications for the early impact history

Zongyu Yue, Sheng Gou, Yexin Wang, Huacheng Li, […] , and Fuyuan Wu
Science Advances  Published:4 Feb 2026
DOI:https://doi.org/10.1126/sciadv.ady9265

Abstract

The radiometric ages of the returned samples are the cornerstone of lunar cratering chronology models. However, all the previous samples were from the lunar nearside and the radiometric ages of those samples that can be associated with particular surfaces are <4.0 billion years. On 25 June 2024, Chang’e-6 successfully returned 1.935-kilogram samples from the lunar farside. The samples included local basalts with an age of 2807 ± 3 million years and the norites with an age of 4247 ± 5 million years likely corresponding to the age of the South Pole–Aitken basin. With these radiometric ages, we refined the lunar chronology function (CF) and verified that it is still consistent with a combination of an exponential decrease and a linear rate. We further derived the impacting rate and found it supports a smooth decay instead of abrupt changes of the impactor flux at early times. The refined lunar CF can be used to obtain more reliable ages for unsampled lunar areas and provide critical constraint for the lunar early impact history.

1702地球物理及び地球化学
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