Jupiter's Liquid Moons

It's that old moon river again. Not content with finding ice on our very own Luna, scientists unveiled evidence in the journal Nature Thursday of entire underground oceans on no less than two of Jupiter's moons. Europa and Callisto were long suspected to bear icy crusts, but at a decidely chilly 483 million miles from the Sun, nobody expected these rocks to be anywhere near tropical enough for the liquid stuff. "If we find out four and a half billion years after the formation of the solar system that there's still enough heat that ice will melt on the interior of these bodies," said Margaret Kivelson, one of the researchers behind the study, "we have to do a little bit of rethinking."

Until we go get our feet wet, there's no way of knowing for sure if the underground oceans actually exist. But when the spacecraft Galileo passed by these moons, it encountered strong disturbances in Jupiter's magnetic field -- too much to come from their cores, but just right for a highly conductive saltwater sea. Something 60 miles below the ice and about six miles deep, assuming they are as salty as their earthbound counterparts. You know, of course, what salt water means. "One could expect life in such oceans," said geophysicist Krishan Khurana, the lead author of the research. Come on in, the water's fine.