Quite an interesting idea! Would love to see planet or moon with this concept. Imagine atmosphere being only in lowlands or craters, and no atmosphere in hilly or mountainous areas. Maybe the atmosphere got blasted away by solar winds and it only remains in lower reaches of a planet/moon. One planet looked like it only had atmosphere in craters (I think it was Charr), so that gave me the idea of atmosphere only existing in lower parts of the planet/moon.