On July 1, a dust cloud emerged from Mars’ Hellas Basin, a crater that ranks as one of the biggest in the solar system. Just 3 days later, the cloud had become 1,800 kilometers wide, roughly one-fourth the Red Planet’s diameter.
Two years ago, a similar cloud from Hellas Basin grew until it circled the entire planet, blurring Mars into a featureless orange ball (SN: 11/10/01, p.