Without a functional protective magnetic field around itself, a terrestrial planet such as Mars would be extremely vulnerable to harsh solar winds and lose all the water on its surface, making it incapable of sustaining life.

Why does solar wind strip water from the planet? For some reason I thought Mars' smaller size and less gravity was more the reason for it's state.

[–] [email protected] 12 points 1 year ago

Water doesn't exist in liquid form in low-pressure environments. If the atmosphere gets stripped off, so will all non-ice water.

[–] pntha 7 points 1 year ago (1 children)

IAMNAA but I believe it’s because the winds strip the atmosphere and, without a solid atmosphere for containment, the evaporation of water molecules escapes into space

[–] [email protected] 4 points 1 year ago

Yeah something like that, PBS Eons does a good episode on the history of Mars, and PBS Space Time has done a few episodes about Mars too if you’re interested.

[–] brianorca 7 points 1 year ago* (last edited 1 year ago) (1 children)

Those are contributing factors, and the small size could be part of the reason the magnetic field stopped at some point, if the core cools down too fast. But a strong magnetic field like Earth's will block the fastest parts of the solar wind from hitting the atmosphere. Without that, each particle of solar wind that hits a molecule of the atmosphere can send that molecule out into space, (beyond escape velocity) which adds up over thousands or millions of years to remove most of the atmosphere that was originally there.

Without enough pressure, liquid water will boil even at cold temperatures, and will be part of the atmosphere that is stripped away.

[–] GaMEChld 1 points 1 year ago

Thank you! I completely forgot about the importance of atmospheric pressure.