Since the Cassini spacecraft began orbiting Saturn in 2004, its nearly two dozen flybys of Enceladus have offered up a series of increasingly tantalizing observations of the icy Saturnine moon. (See the article by John Spencer, Physics Today, November 2011, page 38.) At the moon’s south pole, four parallel cracks, dubbed “tiger stripes,” appear anomalously warm in IR images, and they spew jets of salty ice and water vapor into space. Taken together, those signs point to a liquid water ocean, similar to the one on Jupiter’s moon Europa, beneath the moon’s frozen outer shell and in contact with its rocky core. Enceladus is thus on the short list of the best places in the solar system to look for extraterrestrial life.
Now Alice Le Gall (LATMOS/University of Versailles–Saint Quentin in Yvelines, France) and her collaborators have found that the Enceladean ocean may be closer to the surface...