Significant-Eye4711 t1_isusie1 wrote on October 18, 2022 at 9:15 PM

Reply to comment by StrangeTangerine1525 in The Europa Clipper mission may be as exciting as a manned mars mission and it’s only two years away by Wide-Escape-5618

Well mars once had an atmosphere and liquid water on its surface, if we answer why it doesn’t now we might understand why it’s less suitable than one of the ice moons. Mars is smaller and less dense than earth, it also doesn’t have a magnetosphere. This means that it doesn’t have a protective shield against solar wind which blows away any atmosphere. Also because Mars’s gravity is low it doesn’t hold on to an atmosphere as well as the earth. We could terraform mars but it would still be bombarded by solar winds.

StrangeTangerine1525 t1_iswhjp7 wrote on October 19, 2022 at 5:15 AM

That’s wrong though. Being “blown away by solar winds” doesn’t mean much when it’s only 100 grams per second. At the current rate it would take the age of the solar system just to remove 1 current Martian atmosphere. A magnetosphere isn’t requirement for an atmosphere, mass is however, and that limits the amount of time air does remain on Mars, to hundreds of millions of years down from billions. Air loss is trivial when it comes to terraforming. Earth loses air all the time too, and currently at a rate twice as fast as Mars (0.7 kg/s compared to 1.4, note that modern Mars loses most of its air from interactions with ultraviolet rays) though it doesn’t matter because Earth has life and active outgassing.

Significant-Eye4711 t1_iswnw5g wrote on October 19, 2022 at 6:33 AM

The problem is mars has already lost a lot of its atmosphere, it’s a big job to replace it and we already know it’s a leaky boat. Plus even if it did have an atmosphere everything would be irradiated. We can certainly move about on it’s surface but it’s never going to be like earth.

StrangeTangerine1525 t1_it0gh79 wrote on October 20, 2022 at 1:01 AM

It was a leaky boat three billion years ago when the Sun had a much higher ionizing radiation output and solar flare rate, also why would it’s surface be irradiated if it has a 1 bar atmosphere? With current evidence Mars in theory should have more than a bar of CO2 locked up in its crust, and if we want to make the air breathable we can just import it from some place else.