Tuesday, November 29, 2005
The Plumes of EnceladusCheck the Cassini link on the side bar for the whole story. These are ice geysers spouting material from the moon's southern hemisphere. Inside the moon, water is in a liquid state. On the surface, the ambient temperature is cold enough to freeze earth's air--a few hundred degrees below zero.
Enceladus presents a problem for planetary scientists. Unlike the moons of Jupiter which are sizable enough to generate tides and heat, we didn't expect to see this kind of geological activity on a much smaller moon. Conventional wisdom held that Titan would be interesting because it was large and held a significant atmosphere, but that the small moons would be fairly uninteresting ice balls with impact craters. Dione and Rhea show some evidence of ancient ice resurfacing. They are probably driving internal tides under Enceladus' ice crust.
Lots of questions remain: Why just the south pole region of Enceladus: is this a seasonal effect? (Saturn and its moons are in the middle of southern summer, and it lasts for over seven years out there.) What might be happening on the other moons?
