Celestia Forums

Imagine a planet that is big enough to have a very dense atmosphere. But a small planet had an impact with this world and this world lost all the atmosphere. This world have a big and dense core and the gravity is very high. Would the gravity continue to be the same without the atmosphere, because of the dense core?

It would probably end up like a big Mercury. Dense but with no atmosphere. The gravity change would probably be slight, depending on the size of the big atmosphere.

- Tyrone

Assuming that the planet loses nothing but its atmosphere, and that the atmosphere was uniformly thick, there wouldn't be any change at all in the gravity at the surface. The mass of the atmosphere would have pulled on objects above it in space, though, so that force would diminish slightly because of the loss of the atmosphere.

As a result of the impact's effect on it's lithosphere, it will have a new atmosphere within a short lapse of time.