A chunk of ancient Mars

摘要

NASA's decadal survey for planetary science concludes that returning samples of the ancient crust of Mars to Earth ranks among its highest priorities for exploring the Solar System. In this issue, Humayun et al. (page 513) describe a Martian meteorite sample already on Earth, albeit without the geological context that samples collected on Mars would have. Nonetheless, it is a revealing discovery. The meteorite, which is called NWA 7533 (Fig. 1; NWA is an acronym for northwest Africa, where it was found), was part of a celestial rock that broke up during its passage through the atmosphere, producing at least five recovered stones.%这篇论文发现，来自非洲西北地区的NWA 7533陨石是在陨石中所发现的第一例火星高地岩石。Munir Humayun和本文共同作者发现，NWA 7533的组成表明它含有火星高地角砾岩。它还含有44亿多年前的锆石，这说明火星上的早期壳层分化发生在其历史的最初1亿年里，与月球和地球上最早的壳层形成时间相同。