Is there any wind on the moon?, even a negligible amount

Submitted by fixingshitiswhatido t3_10zvsqj in askscience

So, The moon has an atmosphere nothing like the one on earth obviously, but a thin layer of gases that are “attached” to the moon through gravity barring any space weather, impacts and the like. My question is with the extreme temperature changes between the light and dark side of the moon would it not generate wind? I’m not talking about let’s build a windmill wind more something detectable with modern instruments, even theoretically. Or is the density/pressure just too low for the effect to take place?

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rootofallworlds t1_j8avowq wrote

The “atmosphere” of the moon is a surface boundary exosphere. This means molecules are ejected from the surface (by various processes), fly on a ballistic arc, then hit the surface again with almost no chance of encountering another molecule on the way.

Without interaction between molecules, the atmosphere does not behave as a fluid and cannot form winds.

Any object with enough gravity that ejected molecules have a decent chance of falling back, but no denser atmosphere, will form a surface boundary exosphere.

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fixingshitiswhatido OP t1_j8eu8lx wrote

Thanks, I thought this might be case. But just could rule out a small boundary layer that moves very very slightly. We'll explained my good man

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DoctorRisen t1_j89op2k wrote

I don’t believe there is a high enough density of molecules in the “air” on the moon to produce the same thing we call wind on earth. Sure, they’re going to move around a bit, but they’re unlikely to collide with each other often enough to create a detectable trend of common movement, aka wind.

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fixingshitiswhatido OP t1_j8ev1kd wrote

Great article, I suppose this depends on the definition of wind. But vertical movement of molecules due to a decrease in density from temperature changes sounds like wind with more steps to me.

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