How does Venus retain its atmosphere without a magnetosphere? If it can keep its atmosphere in its current orbit does it follow that it can in Mars's orbit? Or are other factors like tidal forces involved?

Venus 's escape velocity is similar to Earth's escape velocity.

Venus atmosphere is made of CO₂ with rest-mass 44.011 u per molecule, and it's slightly more than Earth's O₂ 32 u and N₂ 28 u (accordingly 37.5% and 57% more). i.e. there is needed less energy to eject Earth's molecule from atmosphere than it's needed for Venus's molecule.

 

4 hours ago, Prometheus said:

How does Venus retain its atmosphere without a magnetosphere? If it can keep its atmosphere in its current orbit does it follow that it can in Mars's orbit? Or are other factors like tidal forces involved?

Mars' orbit would seem to be less stressful in all/most cases, wrt it's atmosphere. 

Edited May 23, 20196 yr by dimreepr