1.   As the Jovian moon begins to feel the strongest gravitational tug from Jupiter, the ice starts its first crack.

2.   According to these, it is actually the smallest Jovian moon.

3.   But whether all that water is frozen solid down to the very bottom has long been one of the great unknowns about the Jovian moon.

4.   Callisto would thus join two other Jovian moons, Europa and Ganymede, in being suspected of having a subsurface ocean.

5.   Interest in exploration of the Jovian moon is rapidly growing, Burns said in an interview.

6.   It will also be making close approaches to two other Jovian moons, Europa and Callisto.

7.   More surprising to scientists are the hints that Callisto, the outermost of the largest Jovian moons, may also have a subsurface ocean.

8.   On Monday, scientists reported the best evidence yet of a giant ocean on Europa, a Jovian moon.

9.   Scientists reported evidence of an ocean on the Jovian moon of Ganymede.

10.   Since then, images returned by spacecraft sent to examine Mars and the jovian moon Europa have expanded this list to three.