本期Nature Communications介绍了远古水在其从太空飞驰而过的一个陨石中蒸发过程的最后时刻。这些发现支持以下观点：地球的水来自太空。
陨石是较大小行星的碎块，自太阳系在距今46亿年前形成以来一直在太空中漂浮。它们是从第一批宇宙颗粒形成的，也许含有可用来确定地球上水和生命起源的关键信息。Yuki Kimura及同事研究了2000年在加拿大掉到地球上的一个陨石中的微小晶体的磁性，以揭示曾经在太空中存在的远古水的特征。该研究小组发现，微小磁铁矿颗粒的磁性是这样的：这些晶体只有在最后的水滴干了之后才能形成，留下一个几十亿年之后将被发现的独特水印。（生物谷Bioon.com）
生物谷推荐的英文摘要
Nature Communications doi:10.1038/ncomms3649
Vortex magnetic structure in framboidal magnetite reveals existence of water droplets in an ancient asteroid
Yuki Kimura，Takeshi Sato，Norihiro Nakamura，Jun Nozawa，Tomoki Nakamura，Katsuo Tsukamoto& Kazuo Yamamoto
The majority of water has vanished from modern meteorites， yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important， because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method， applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure， a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid.
