The Cassini spacecraft made its final close flyby of Saturn’s icy moon Enceladus in December, releasing its final up-close look at these weird little spots last week. Discovered over a decade again, we’re still trying to work out exactly how these spots formed.
When we think “ancient Mars,” we often picture roaring rivers, warm oceans, and if we’re being optimistic, perhaps some simple life forms. But it’s also possible the Mars of eons past was not a water-covered paradise at all. It may, in fact, have resembled a giant, dirty snowball.