>>13050322Titan's atmosphere's average molecular weight is actually somewhat lighter than our own (no oxygen present, small amounts of methane, mostly nitrogen).
The reason Titan has an atmosphere at all is because it is very cold. Gas particles physically move faster at warmer temperatures and slower at colder temperatures. Titan's atmosphere is cold enough that the gas particles don't achieve a significant fraction of orbital velocity. However, if you warmed that atmosphere up to Earthlike temperatures, not only would the entire surface melt into a global ocean, the atmosphere itself would begin to escape at a rate of trillions of tons of gas per second, as the fast moving gas particles simply exceeded orbital velocity and were allowed to expand into space to be gently stripped away by solar wind pressure.
This is why any outdoor terraforming concepts for Titan and any other Moon-sized object are all retarded, buy the way. Nothing with an escape velocity that low can physically hold onto an atmosphere at earthlike temperatures, not only on geologic time scales but on human time scales. If you could magically wish for our own Moon to have an atmosphere identical to Earth's it would be completely gone in 100 years or less.
