Conceiving of a moon with a similar ecology and atmosphere to Earth, but with a gravity level equivalent to the moon. This is essentially a terraformed analogue to Earth's moon in terms of size and orbit along with a rotation of 60 hour days. My question is what would rain storms look like on this world? Would it be more like mist? Or would it just be similar to Earth.

the idea for this came from an article i will post below. Does not go into a few things, among them, how rain behaves on a terraformed moon, so was trying to get an idea how rain storms would work.


  • $\begingroup$ Since gravity is a direct function of mass, you're not conceiving a world, you're conceiving a moon. We're flexible so long as we understand our constraints. Do you want us to ignore the fact that your "world" is a terraformed version of Earth's moon, or do you want us to address the issues of a terraformed Luna? (Please update your answer with the criteria. Thanks!) $\endgroup$ – JBH Oct 18 '17 at 22:54
  • $\begingroup$ From just a first-level guess, it would not look like mist. In order for the droplets to fall, they would have to be much larger than on the Earth. They would still fall at their terminal velocity. $\endgroup$ – Phiteros Oct 18 '17 at 22:55
  • $\begingroup$ @JBH just because a world is lighter doesn't mean its a moon... $\endgroup$ – A. C. A. C. Oct 18 '17 at 22:56
  • $\begingroup$ Low gravity comparable to the moon, kind of feel like Jeans Escape or something would prevent it from raining at all if it was warm enough to support Human life. $\endgroup$ – Ferret Civilization Oct 18 '17 at 23:04
  • $\begingroup$ @A.C.A.C. a world-sized object with the gravity of the moon is gaseous. Mass=gravity. It's not magic. $\endgroup$ – JBH Oct 18 '17 at 23:39

I'd guess drops would be larger, as they fall more slowly and have more time to accrete and grow.

The speed of rain depends on drops' terminal velocity, which depend on air density and gravity. Density depends on the overall quantity of air together with gravity, so you can have an atmosphere as dense as Earth's. No changes there.

The density gradient would be gentler. So I suspect clouds would tend to form at a higher altitude and also be taller in general. On the other hand, they might be less dense since the same quantity of water vapour would be diffused on a larger volume. Rain frequency might then be different from Earth, you might even not have rain at all -- but I'm already far outside the boundaries of my meteorological knowledge.

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    $\begingroup$ Terminal velocity will also depend on the surface area of the raindrop. Larger surface area will mean lower terminal velocity. $\endgroup$ – Phiteros Oct 18 '17 at 22:56
  • $\begingroup$ So it would probably be pretty similar to how rain works on earth (accounting for differences due to lower gravity). $\endgroup$ – mental_maelstorm Oct 19 '17 at 2:25

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