Vapor plumes on Enceladus, Courtesy Ciclops.org

The Cassini spacecraft has found evidence of geysers on Enceladus, a strange, cold moon of Saturn. This discovery brings the total number of places in the known universe with liquid water to two: there and Earth. (Mars had liquid water long ago, and Jupiters moon Europa is only suspected of having a liquid ocean buried under ice.) Carolyn Porco, the always-enthusiastic Cassini imaging team leader, describes the findings thusly in her e-mail announcement:

What we have discovered about the story of Enceladus is thrilling beyond imagination: more heat emerging from the south polar region, per square meter, than from the Earth and, possibly, subterranean organic-rich bodies of liquid water only tens of meters beneath the south polar terrain. If we did nothing else, these findings alone would have made the Cassini mission worthwhile.

Weve written about Cassini twice in recent years: a preview of the mission as it arrived in July 2004 and an update on its incredible findings in April 2005. Perhaps its time for another look. —Michael Moyer