这个发现不仅解释了火星为啥红，还暗示了火星曾经可能是个“水灵灵”的星球。因为水合铁矿物是在有水、温度较低的环境中形成的，而赤铁矿则是在干燥、温暖的环境中形成的。这意味着，火星在几十亿年前可能有过液态水，甚至可能适合生命存在！

Mars is the Red Planet, but turns out the moon has the makings of a reddish cast, too. Yes, scientists have found rust on the moon. The question is: why?

Iron, a key material in steel and other applications, is most often found in hematite and magnetite ores, though goethite, limonite and siderite ores are also common sources of iron ore.