@abetterjulie Ganymede's surface gravity is 0.146g, which is plenty to keep whatever is on the ground where it is. 1L of liquid water weighs 146g.

@abetterjulie Regardless of gravity, material in space retains its full inertial mass -- that is, it takes the same amount of energy to move it, minus the gravity you're not working against. So something that weighs 1KG here on Earth, and something that weighs 1KG on Ganymede, will require different amounts of energy input to move.