created by nip_dip on 09/07/2023 at 02:25 UTC*
27 upvotes, 1 top-level comments (showing 1)
From what I know, whether or not a celestial object can hold a certain gas in its atmosphere is dependent on three factors - its escape velocity, its temperature, and the gas in question. Due to gas laws, lower temperatures and higher escape velocities make it easier to hold on to gases, and heavier gases are easier for a planet to hold on to than lighter ones. When compared to Titan, Jupiter's moon Ganymede has a slightly higher temperature, which should hinder its ability to hold on to an atmosphere, but it also has a slightly higher escape velocity due to its higher mass and density which nearly cancels that out. So, similar to Titan, Ganymede should be able to support an atmosphere of heavy gases like carbon dioxide, and maybe some nitrogen and oxygen. However, Ganymede is almost completely devoid of any atmosphere, while Titan's atmosphere completely obscures the surface underneath and is more massive than even the Earth's. So why does Ganymede have no atmosphere while Titan has one?
Comment by TearsFallWithoutTain at 10/07/2023 at 02:55 UTC
6 upvotes, 1 direct replies
It was a lot hotter around Jupiter when it was forming and that presumably drove off a lot of the atmospheres of its moons. Meanwhile it was a lot colder around Saturn since it's so much further away from the Sun as well as being a smaller planet. If Saturn had other large moons, they could conceivably have atmospheres as well.