The color 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-kilometer Herschel would likely have destroyed the entire world. The crater is so large that it is surprising that Mimas was not shattered by the impact that caused it. It measures 139 km across, almost 1/3 the diameter of the moon; its walls are approximately 5 km high, parts of its floor are 10 km deep, and its central peak rises 6 km above the crater floor. If there were a crater of an equivalent scale on Earth it would be over 4,000 km in diameter and wider than Canada. The impact that formed Herschel must have nearly disrupted Mimas entirely; fractures can be seen on the opposite side of Mimas that may be due to the shock waves from the impact travelling through the moon’s body.
(Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA)