NASA uses the Hubble Space Telescope for all sorts of missions that have to do with observing the galaxy. Earlier this month NASA announced that it has used Hubble to spot five planets that are likely to have water outside of our solar system. NASA has announced that Hubble has discovered evidence of water vapor on one of Jupiter's moons.
Hubble has observed water vapor above the south polar region of the icy Jovian moon Europa. This discovery provides the first strong evidence that water plumes are erupting on the ice surface of Europa. NASA notes that previous findings had suggested that there might be an ocean under the icy surface of Europa.
NASA isn’t ready to confirm just yet that the water vapor in the air over the surface of Europa is caused by water plumes, but the scientists say this is the most likely cause. Further observations are planned and if the water plume theory is confirmed Europa will become the second moon in the solar system known to have water vapor plumes.
The other moon in our solar system known to have water vapor plumes is Saturn's moon Enceladus. The plumes on its surface were discovered by the Cassini orbiter in 2005. Spectroscopic observation of Europa in December of 2012 first gave evidence to suggest water plumes were present. Scientists say that excited atomic oxygen and hydrogen provide a variable auroral glow and leave hints that indicate water molecules are being broken apart by electrons along the magnetic field lines. Scientists believe that the long cracks on Europa's surface might be venting water vapor into space.