How much larger, or more dense, would Mars have to be, to enable the retention of a breathable atmosphere? Not sea level, obviously, but some high elevation (Andes? Everest?) atmosphere levels.
Thanks again!
This is not a simple question. Earth, obviously, retains a breathable atmosphere, though it was certainly thicker in the past. Venus, which is a close approximation of Earth’s size and mass, has a lethally-thicker atmosphere. Jupiter’s moon Titan, which is smaller than Mars and has about half the density, retains a substantial atmosphere (though it’s not breathable by any standard). It’s possible that Mars could retain–at least, temporarily–a much thicker atmosphere with a substantial oxygen content if there were some way to generate it; it’s possible that it could even have a reinforcing feedback that would maintain such an atmosphere. There are a lot of factors in place as to why the Earth has a life-supporting oxygen-rich atmosphere and Mars does not, including the strong magnetic field of the Earth (and virtually nonexistent one of Mars), the proximity to the Sun, the presense of high albedo oceans, et cetera, and it would be charitable to say that we currently have even a basic comprehenisve understanding of atmosphere mechanics.
Stranger
Ah. I had hoped there would be a fairly simple answer. I should have known better… hehehe…
Thank you sir!
I thought current theory was that Mars suffered having most of it’s primordial atmosphere blasted off by planetesmal collisions near the end of it’s accretion phase. In other words, that it’s atmosphere is thinner then would be expected from considerations of gravity alone.