Space Telescope Science
Though it's five times farther from the Sun than Earth, and therefore so cold that ice becomes as hard as rock, Jupiter's moon Europa may be the first place to go to look for extraterrestrial life. Ever since the moon, which superficially resembles a cracked eggshell, was photographed close-up by the Voyager space probe, scientists have been intrigued by its potential as a niche for life.
For over the past 30 years it has been hypothesized that the icy crust covers a subsurface ocean. Where there is water there could be life. Now NASA's Hubble Space Telescope has found something the Jovian probes may have missed, plumes of water vapor leaking off into space near the moon's south pole. Astronomers do not know yet if these gas plumes are connected to subsurface liquid water or not. This venting doesn't seem unique. In 2005, NASA's Cassini orbiter discovered similar water vapor plumes spewing off of the tiny moon Enceladus, 1 billion miles away.