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Astronomy

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    $\begingroup$ Interesting question! Looking for some nice answers. $\endgroup$
    – Infinity Milestone
    Commented Oct 12, 2020 at 2:10
  • $\begingroup$ 1. Yes, 2. 100%. One needs to include in the calculation photo ejection and cosmic ray ejection. But, the ice cube should last a long time in the Oort Cloud, I would think. $\endgroup$
    – eshaya
    Commented Feb 12, 2021 at 18:16
  • $\begingroup$ 1. Yes, but... Ice grains would of course evaporate in any condition where their vapor pressure is less than the atmospheric pressure, but it sounds like you already know this based on your question. The problem is finding a "true" vacuum. As you indicated, the atmospheric pressure estimate of intergalactic space is an order of magnitude higher than the vapor pressure of ice, so you'd either have to find extremely thin area of intergalactic space OR construct a vacuum of your own. $\endgroup$
    – GrasshopperTaji
    Commented Dec 21, 2021 at 21:10
  • $\begingroup$ 2. Given the density of material in space, one could reasonably argue that it is at 100% humidity near the ice cube if sufficient amounts of water have vaporized off the ice cube, however...the ice on the surface of your ice cube wouldn't actually evaporate or condense, it would vaporize. So, space would, quite literally, rip entire H2O molecules off the surface of the ice cube. $\endgroup$
    – GrasshopperTaji
    Commented Dec 21, 2021 at 21:10
  • $\begingroup$ Another detail is that vapor pressure equilibrium depends not on the total pressure in the gas, but the partial pressure of the volatile species. So in space, most of that 10^-16 torr is hydrogen, not water vapor. The partial pressure of water vapor is going to be much lower than the total pressure. $\endgroup$
    – giardia
    Commented Feb 3, 2022 at 6:06