Why does Titan has a denser atmosphere than Ganymede moon and the other moons?
The amount of atmosphere that can be retained is not just a function of mass, but it can also be affected by the distance from the sun. At its size, Ganymede might be close enough to the sun that all the gases were “blown” away by the solar wind. Titan would be less affected by that. Also, Titan is colder and its atmosphere could be the result of temperatur e characteristics of methane (mostly) and the fact that it would be denser at the lower temp. This could allow for just enough of a greenhouse effect that a sizeable atmosphere could accumulate. Remember, the slightest differences in conditions can be responsible for huge variations between the moons and planets. Look at Venus and Earth.
