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StrangeTangerine1525 t1_iwzx08a wrote

Reply to comment by danielravennest in Mars was once covered by 300-meter deep oceans, study shows by magenta_placenta

Should be noted that planets with magnetic fields do still experience air loss, Earth actually loses more air to space per second currently than Mars or Venus does, mostly because our atmosphere is composed of lighter air molecules, and our magnetic field heats up the ionosphere dramatically, making it easier for molecules to escape. One other thing about Mars. It has no plate tectonics and very little volcanic outgassing, so no matter were the air is going, whether into the ground or out into space, its not getting replaced like it is on Earth or Venus.

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danielravennest t1_ix3c4wj wrote

Countering air loss, both Earth and Mars have a flux of meteor/asteroid material coming in. Mars likely gets relatively more because its orbit skims the inner edge of the Asteroid Belt. Some of the incoming objects contain volatiles.

So a full accounting of mass flow needs to consider both loss and gain processes.

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StrangeTangerine1525 t1_ix57p54 wrote

True, but because of Mar's lower gravity its less likely to keep any of those volatiles, and any that do stay are likely to freeze in to the polar caps and crust. Anyway you slice it making Mars ... less Mars is going to be quite hard.

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