火星（Mars）的奇特卫星火卫二（Deimos）由撞击形成

最新研究表明，火卫二南极的大型撞击坑及其表面深厚的风化层均源于一次撞击事件。该研究揭示了这颗卫星结构脆弱且多孔，类似于碎石堆型小行星（asteroid）。

Mars' moon Deimos has a large crater on its southern pole. It's also covered by a layer of regolith so deep it buries many other, smaller craters. New research shows that an impact is responsible for both, and that the moon is rather fragile and porous, like a rubble pile asteroid.