This past week
, scientists found extensive evidence of a magma ocean underneath the surface of Io, a moon of Jupiter. It now looks like all four moons discovered by Galileo in the 1600s -- Io, Europa, Callisto and Ganymede -- could have oceans of some kind, magma or liquid water. Although they may have dramatically different qualities -- from the hellish lava flows of Io to the potentially life-giving sub-surface ocean of Europa -- these oceans are all driven by tidal interactions with Jupiter.
While NASA studied the Jovian moons in detail in the 1990s and early 2000s with the Galileo mission, scientists have been anxious for another visit to Jupiter that would be longer than just a flyby.
NASA's Juno spacecraft
may get distant glimpses of the moons after it arrives in 2016. For a close-up view, space fans will need to wait for a
European mission called JUICE (JUpiter ICy moons Explorer)
, which should launch in 2022 and arrive in 2030.
PHOTOS: The Moons of Jupiter
Starting with the most extreme, Io is a volcanic planet, but what has intrigued scientists for decades is the volcanoes appear to be offset from where computer models predict. A newly released study suggests that a magma ocean -- a great conductor of heat --
could explain why the hotspots are in a different location than expected
. This follows on from research in 2011 from the Galileo spacecraft, showing that there likely is a magma ocean under the moon.