3 ms·

I always wondered what it would be like if Mars and Venus were swapped. Would Mars be warmer, or would it be even more devoid of atmosphere? And would Venus (

I always wondered what it would be like if Mars and Venus were swapped. Would Mars be warmer, or would it be even more devoid of atmosphere? And would Venus (with its greenhouse gas) be a more livable temperature if it was in Mars's orbit? It still wouldn't be survivable due to the atmospheric composition, but I was just wondering about raw climate.

Robotbeat 6y ago
The atmospheric composition is likely driven in part by the higher intensity of the Sun. At Mars, it’d have gotten a quarter of the sunlight. That means more water in its atmosphere (as there’s have been less UV to dissociate the water and less light pressure and less solar wind to blow the hydrogen away), less release of CO2 from carbonates, etc.
jjk166 6y ago
Yes, mars is too small to hold its atmosphere at its current distance from the sun, moving it closer would only make the problem worse. Like our moon, the bright side would be hot during the day, but it would be cold at night with very little atmosphere to retain heat, and even in temperate regions at the poles liquid water would not be stable. We're not really sure what kicked off Venus' runaway greenhouse, so it's possible that would still occur, though it does seem less likely. Without the runaway greenhouse, Venus' atmosphere would likely remain primarily nitrogen. Its atmosphere would still be significantly thicker than Earth's but by a factor of 5 instead of a factor of 100. With the additional atmosphere, it might remain quite temperate even at the greater distance. Of course had Venus and Mars developed in eachother's places, Venus would have developed as a smaller world with a thinner atmosphere (generally more mars-like) and Mars would have been larger with a thicker atmosphere (generally more venus-like), so the whole point is somewhat moot.

3 ms·

I always wondered what it would be like if Mars and Venus were swapped. Would Mars be warmer, or would it be even more devoid of atmosphere? And would Venus (

by derekp7 6y ago

Robotbeat 6y ago
The atmospheric composition is likely driven in part by the higher intensity of the Sun. At Mars, it’d have gotten a quarter of the sunlight. That means more water in its atmosphere (as there’s have been less UV to dissociate the water and less light pressure and less solar wind to blow the hydrogen away), less release of CO2 from carbonates, etc.
jjk166 6y ago
Yes, mars is too small to hold its atmosphere at its current distance from the sun, moving it closer would only make the problem worse. Like our moon, the bright side would be hot during the day, but it would be cold at night with very little atmosphere to retain heat, and even in temperate regions at the poles liquid water would not be stable. We're not really sure what kicked off Venus' runaway greenhouse, so it's possible that would still occur, though it does seem less likely. Without the runaway greenhouse, Venus' atmosphere would likely remain primarily nitrogen. Its atmosphere would still be significantly thicker than Earth's but by a factor of 5 instead of a factor of 100. With the additional atmosphere, it might remain quite temperate even at the greater distance. Of course had Venus and Mars developed in eachother's places, Venus would have developed as a smaller world with a thinner atmosphere (generally more mars-like) and Mars would have been larger with a thicker atmosphere (generally more venus-like), so the whole point is somewhat moot.