Using two cameras on the Mars Reconnaissance Orbiter (MRO) spacecraft, scientists based at the University of Arizona scoured Mars' surface for fresh meteorite craters. These natural excavations, tens of meters deep and as little as a month old, have revealed something bright and white that looks suspiciously like clean ice. At one crater, astronomers were even able to watch as the freshly exposed ice evaporated away over the course of a few months. The purity of the ice was the biggest surprise. Some believe it could be a relic of an ancient Martian ice age.