Both the Moon and Mercury have polar cold traps in polar craters, with signs of volatiles. This is of course not as interesting on a moon in the outer Solar System which consists of volatiles anyway. But suppose that there is some use for very cold real estate shielded from the Sun out there.

Which moons are candidates to have eternally shadowed (or eternally sunlit) regions, and wouldn't they be even colder than those on the Moon? Jupiter and Neptune have less than 2 degrees inclination so their moons maybe are good candidates.

  • 2
    $\begingroup$ @barrycarter, you may have mis-read the question. It concerns regions, like the Shakleton crater on the moon, which due to their high latitude, and crater walls, are permanently in shadow. Not to a "dark side" of an moon. $\endgroup$
    – James K
    Jan 15, 2016 at 20:52
  • $\begingroup$ The gas giants can take up a healthy solid angle as viewed from their moons. I imagine the gas giant would be visible from many of the crater floors that are permanently shadowed from the sun. The big planets might be a source of infrared heating the shadowed craters. $\endgroup$
    – HopDavid
    Apr 26, 2016 at 23:23
  • $\begingroup$ @HopDavid I actually meant to delete my comment earlier but forgot. I've now actually deleted it. $\endgroup$
    – user21
    Apr 28, 2016 at 16:40

1 Answer 1


Many of the moons of Jupiter and Saturn are tidally locked and probably move ice from their equatorial regions to their polar regions. Ganymede is the best example where you see bright polar ice caps and a dark equatorial zone. A migration process occurs on all of these moons in which light from the sun gets absorbed by water ice molecules and sends them on random jumps. After a long random walk, they eventually end up near the pole where they stay for a long time even if they are not in a perpetual shadow, and they stay there for nearly forever if they are.

But, if the moon has a very thick coating of ice everywhere, this process may not have dug down deep enough, so it is still covered with ice everywhere, in which case it is hard to see the effect happening.


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