eli5: Why has Venus’ atmosphere so much more pressure than Earth’s atmosphere?

Question

There must be some factor other than gravity that contributes to an atmosphere’s pressure level because Earth and Venus have almost the same mass.

In: 3

Answer 1

more of venus’ mass is its atmosphere.

it might be more helpful to think of it less as atmosphere and more as an ocean. the pressure on venus is so incredibly high that the carbon dioxide is a supercritical fluid. think something trying to be liquid and gas at the same time. the atmosphere only behaves like a gaseous atmosphere well above the rocky surface.