Astronomy Picture of the Day

Explanation: Why is this giant crater on Mimas oddly coloured? Mimas, one of the smaller round moons of Saturn, sports Herschel crater, one of the larger impact craters in the entire Solar System. The robotic Cassini spacecraft now orbiting Saturn took the above image of Herschel crater in unprecedented detail while making a 10,000-kilometre record close pass by the icy world just over one month ago. Shown in contrast-enhanced false colour, the above image includes colour information from older Mimas images that together show more clearly that Herschel's landscape is coloured slightly differently from more heavily cratered terrain nearby. The colour difference could yield surface composition clues to the violent history of Mimas. An impact on Mimas much larger than the one that created the 130-kilometre Herschel would likely have destroyed the entire world.