astronomy people?

Question

how a planets gravity affects the kind of atmosphere it can have, and the origin and evolution of planetary atmospheres?

Answer 1

The gravity of a planet does not alter its atmosphere's chemical composition that much, but bigger planets will have thicker atmospheres. However, smaller planets like Earth cannot hold hydrogen in thier atmospheres, it is too light.

What is more important is how close a planet is to the sun: a gas giant brought too close to the sun will lose its atmosphere as it heats up.