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Space Exploration

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  • $\begingroup$ Unless there is a flaw in your answer this seems, like the best. $\endgroup$
    – James Jenkins
    Commented Jan 10, 2017 at 18:52
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    $\begingroup$ @JamesJenkins: There could be effect connected with dynamics of boiling/evaporation. Possibly quite a bit of steam would turn into snow during the initial boil-off; it's hard to predict the actual mechanics and how the very surface would appear immediately afterwards; evaporation rate afterwards would also be related to amount of heat provided from other sources - if the pool is shaded from sunlight, it would be much slower. $\endgroup$
    – SF.
    Commented Jan 10, 2017 at 18:57
  • $\begingroup$ also, the amount of heat that can be drained from water by freezing it, and from the surrounding ground is just a drop comparing to what is needed to evaporate comparable amounts of water, so other sources of heat would play dominant role in evaporation of the ice. $\endgroup$
    – SF.
    Commented Jan 10, 2017 at 18:58
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    $\begingroup$ @TylerH: Observe the graph in Dean McGregor's answer below mine. This depends on pressure primarily - the triple point is at 611 Pa - below it liquid water can't exist. Mars atmosphere is slightly less. As you go down the green area of the graph (liquid) it tapers to a point, the temperature difference between vapor (yellow) and solid (blue) shrinking. As you heat or cool things or pressurize/depressurize, you can move over the field. But each of these black borders should be imagined as a fence/step, skipping which requires extra heat (going or releases extra heat. $\endgroup$
    – SF.
    Commented May 10, 2018 at 15:03
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    $\begingroup$ ...and so, as pressure drops, less pressurized water crosses over to the yellow side - but needs heat, which it sucks out of more pressurized water. Eventually, as all the water (steam too) cools to 0C, the water on the surface (least pressurized) can't suck more heat from liquid water below without pushing it over to become ice. And no more water can become steam, until more heat is extracted - forming more ice, until the layer of ice is thick enough that pressure on its bottom is still "in the green". And the ice surface will evaporate as fast as heat is provided - that is not fast at all. $\endgroup$
    – SF.
    Commented May 10, 2018 at 15:11