I've been reading this wikipedia article on terraforming mars. One of the major issues with terraforming mars is essential molecules and elements escaping the planet. There have been several proposed solutions to stopping solar wind degradation that seem feasible, however it still leaves the possibility of molecules escape velocity being low enough to leave the planet easily, especially if the planet were to be heated up.

According to this graph, it looks like water vapor would easily escape mars's atmosphere:

enter image description here Source

What could we conceivably do to keep liquid water exposed on the surface of Mars when any evaporation could leak large amounts of water from the planet?

  • $\begingroup$ It's a good question. I've added a few words to the last sentence and to the title to make it clear you mean exposed surface liquid water. I don't think you mean stored in tanks or frozen underground for example. $\endgroup$ – uhoh Apr 23 '19 at 22:24
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    $\begingroup$ The key question is the rate of loss. Does anyone have any reasoned ideas of what that is. I am sure water would escape over millions of years, but I'm not sure how much you'd lose in a few centuries. $\endgroup$ – Steve Linton Apr 23 '19 at 22:29
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    $\begingroup$ Read crowlspace.com/?p=3149 (it relates to @SteveLinton's comment). The contention is that the loss rate pertains to geologic timescales, not human colonization timescales. Not that it answers your question really, but I guess it challenges the motivation (paraphrasing: we must try to counter solar wind and low gravity to avoid any atmospheric loss from a terraformed Mars). $\endgroup$ – ben Apr 23 '19 at 22:53
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    $\begingroup$ @uhoh yes that is exactly what I meant. $\endgroup$ – whn Apr 24 '19 at 1:25
  • $\begingroup$ A different but related question with some interesting answers: How is Martian water lost to space? $\endgroup$ – uhoh Apr 27 '19 at 11:52

The short answer is that ruling out world-building thought experiments to increase mars' escape velocity; nothing can be done to prevent water vapor from escaping which is precisely why it has so little water compared to Earth.

With that said, Mars' water escapes on astronomical timescales while the goal of any type of terraforming activities would be to liquify mars' water on human timescales. Assuming that you could heat up the planet enough to have meaningful quantities of atmospheric water vapor, it would not escape at a rate sufficient to interfere with those efforts and would only become a problem thousands if not millions of years in the future.

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    $\begingroup$ We might not know how much water is on Mars in toto, but it certainly has little to no surface water. $\endgroup$ – uhoh Dec 16 '19 at 4:01
  • $\begingroup$ This answer would do better with sources for its claims. $\endgroup$ – whn Dec 16 '19 at 15:32

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