Center for Lunar Science and Exploration, Lunar and Planetary Institute, Universities Space Research Association, 3600 Bay Area Boulevard, Houston, TX 77058, USA.
Science. 2012 Jun 15;336(6087):1426-9. doi: 10.1126/science.1219633. Epub 2012 May 17.
The lunar surface, a key proxy for the early Earth, contains relics of asteroids and comets that have pummeled terrestrial planetary surfaces. Surviving fragments of projectiles in the lunar regolith provide a direct measure of the types and thus the sources of exogenous material delivered to the Earth-Moon system. In ancient [>3.4 billion years ago (Ga)] regolith breccias from the Apollo 16 landing site, we located mineral and lithologic relics of magnesian chondrules from chondritic impactors. These ancient impactor fragments are not nearly as diverse as those found in younger (3.4 Ga to today) regolith breccias and soils from the Moon or that presently fall as meteorites to Earth. This suggests that primitive chondritic asteroids, originating from a similar source region, were common Earth-Moon-crossing impactors during the latter stages of the basin-forming epoch.
月球表面是早期地球的一个关键示踪物，其中包含了撞击地球行星表面的小行星和彗星的残骸。月球风化层中幸存的弹体碎片直接反映了输送至地月系统的外源物质的类型，进而反映了其来源。在古老的（>34 亿年前）月海玄武岩中的阿波罗 16 着陆点的角砾岩中，我们发现了来自球粒陨石撞击体的镁质球粒陨石碎屑的矿物和岩屑遗迹。这些古老的撞击体碎片远没有年轻的（34 亿年至今天）月海玄武岩角砾岩和土壤以及目前降落在地球上的陨石中发现的那些撞击体碎片那样多样。这表明，原始的球粒陨石小行星，源自相似的源区，在盆地形成阶段的后期是常见的穿越地球和月球的撞击体。
