Illustration of Europa water jet.

Source: http://www.newscientist.com/article/dn24...

An icy moon of Jupiter has been caught spitting into space. For the first time, a towering plume of water vapour has been seen coming from Europa. The discovery strengthens the case that the moon has a liquid ocean beneath its icy crust, and may even offer a way to taste its seas and search for signs of life.

Images from the Galileo spacecraft, which orbited Jupiter from 1995 to 2003, revealed a cracked and chaotic surface dominated by dark ridges and faults. This hinted that Europa has a relatively thin crust in which fissures sometimes open up and let water escape from a subsurface ocean. Similar rifts on Saturn's icy moon Enceladus shoot spectacular water geysers. But the Galileo probe did not spot any plumes in action on Europa, and later efforts also came up empty.

Now images taken by the Hubble Space Telescope have revealed a large cloud of hydrogen and oxygen – most likely in the form of water vapour – extending from the moon's south pole. A model suggests that it is a plume 200 kilometres high that is spouting 3000 kilograms of water per second.

"This is a big discovery," says Cynthia Phillips at the SETI Institute in Mountain View, California, who was not involved in the find but had looked for plumes with Galileo. "If there are plumes erupting, there's got to be liquid water, and it's got to be pretty close to the surface."