First, on December 11, 2013, the space agency announced the results of analysis of data returned by the Galileo probe that orbited Jupiter for several years studying the planet and its various moons before being plunged into the atmosphere of the solar system’s largest planet.
“A new analysis of data from NASA's Galileo mission has revealed clay-type minerals at the surface of Jupiter's icy moon Europa that appear to have been delivered by a spectacular collision with an asteroid or comet. This is the first time such minerals have been detected on Europa's surface. The types of space rocks that deliver such minerals typically also often carry organic materials.”
This means that sometime in the ancient past a huge asteroid or comet hit Europa at about a 45 degree angle, splashing material across its icy surface.
“NASA’s Hubble Space Telescope has observed water vapor above the frigid south polar region of Jupiter's moon Europa, providing the first strong evidence of water plumes erupting off the moon's surface.
“Previous scientific findings from other sources already point to the existence of an ocean located under Europa's icy crust. Researchers are not yet fully certain whether the detected water vapor is generated by erupting water plumes on the surface, but they are confident this is the most likely explanation.”
A similar phenomenon was been detected on Saturn’s moon Enceladus. If the water plumes are connected in any way to the subsurface ocean thought to exist below Europa’s icy crust, then it means that the ocean, which might be an abode of life, could be accessed by some future expedition without having to drill through the icy crust. Scientists speculate that the action of Jupiter’s gravity opens and closes vents through Europa’s crust, allowing water to escape. The water vapor rises to about 125 miles above the surface of the moon before falling back down.