Indeed, they all should be studied. At least 2 of the 4 moons of Jupiter discovered by Galileo. Io with its rocky surface and volcanos, nearest neighbor Europa with its smooth icy surface is about as opposite as you can get for moons orbiting the same planet. Much can be learned from the two alone and a lot of scientist are thinking strongly about finding life under the ice of Europa. Io though the most active and seemingly alive should not be ignored.

No mention of how high the plume rised on this eruption. Did Galileo ever fly through a volcanic plume over the north pole of Io? I remember reading about a plume a 180 plus miles high or so last year and a chacne of a fly through.

SteveS