Wired featured a gorgeous shot of Enceladus as its Space Science image of the week last week:
This face-on colour view of Enceladus was taken by the international Cassini spacecraft on 31 January 2011, from a distance of 81 000 km, and processed by amateur astronomer Gordan Ugarković.
I love that NASA’s imagery is publicly available, and that anybody who wants can download the raw images and play with them on their home computers. Dang, we live in an amazing era.
What Wired’s caption didn’t note, but which immediately drew my eye, are the water plumes clearly visible near Enceladus’ south pole. There is a lot of water vapor geysering out into space from this moon, and a few years back, Cassini flew through them to take samples. Turns out they’re rich in salt, which means it’s very unlikely that they originate from the icy surface of the moon. Salt water that freezes slowly tends to squeeze out the salt grains, leaving pure water ice behind. If the plumes came from the surface, they should have little to no salt in them. But their salty nature indicates that they come from elsewhere…which means there is almost certainly a saltwater ocean beneath that icy mantle.
Enceladus has secrets, and a clue to them is quietly jetting into space, visible to anyone who knows enough to look.
(Click the image to plumify.)