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View Full Version : Lunar tungsten hexaflouride atmosphere



Tom Mazanec
2012-Oct-29, 04:52 PM
Suppose we gave the moon an atmosphere of tungsten hexaflouride (never mind how and why) as dense as Titan's (half again as dense as Earth's, IIRC). How long would it last? Would the water at the poles be enough to react it away? Or would it still be light enough to escape from the Moon?

chornedsnorkack
2012-Oct-29, 04:56 PM
Note that water would react cyclically:
WF6+3H2O=WO3+6HF
CaO+2HF=CaF2+H2O.

Tom Mazanec
2012-Oct-29, 05:48 PM
Would selenium hexaflouride suffer from this water catalys?
I am pretty sure sulfur hexaflouride would not.
So if selenium hexaflouride does not react with water, make the atmosphere out of this.
If it does, make the atmosphere out of sulfur hexaflouride.

kzb
2012-Oct-29, 06:02 PM
Going by the lunar escape velocity and the molecular mass of WF6, it should not escape into space.

It will freeze out during the lunar night, and may exist in the liquid phase in a limited way.

Note that flouride is something to do with ground-up seeds, whereas fluoride is a compound of the element fluorine.

It's one thing it not escaping into space, but putting it on the moon as-is, I think it would react with the regolith in a big way, basically converting everything to a fluoride. I don't think it would need water necessarily to catalyse this either.

Still, you could keep on supplying WF6 until this reaction was complete, then add excess to make your atmosphere. From then on, consumption of atmosphere should be relatively slow, considering the lack of geological activity on the moon. Just the odd meteor to contend with.

chornedsnorkack
2012-Oct-29, 06:19 PM
It will freeze out during the lunar night, and may exist in the liquid phase in a limited way.



It will also freeze on both poles. Until it fills all the craters in polar areas and covers both poles with polar caps thick enough to undergo glacier flow to lower latitudes where it melts and evaporates.

Tom Mazanec
2012-Oct-29, 07:51 PM
Isn't WF6 a greenhouse gas, preventing freezing? I know SF6 is a powerful one.

Noclevername
2012-Oct-29, 08:11 PM
Isn't WF6 a greenhouse gas, preventing freezing? I know SF6 is a powerful one.

A 2 week night, or permanent shadow as at the poles, leaves plenty of time for heat to leak away even with vacuum insulation.

Tom Mazanec
2012-Oct-29, 09:17 PM
I assume similar factors would apply to a WF6 atmosphere for Mercury? Or would the greater heat drive off the atmosphere?

Ara Pacis
2012-Oct-30, 04:45 AM
If you managed to create an atmosphere, would not the atmosphere become a transport system to keep the dark side warm?

kzb
2012-Oct-30, 01:00 PM
If you managed to create an atmosphere, would not the atmosphere become a transport system to keep the dark side warm?

Yes it's interesting to think what are the real consequences of such an atmosphere.

Bearing in mind the boiling point of WF6 is 17 degrees C (at atmospheric pressure), my expection is that it would fall as precipitation as the sun went down. So you would end up with a continuous wind acting to transport gas from the day side to the dark side on one limb, and the other direction on the other limb.

I can't think anyone knows precisely what the resulting climate and weather would be like. Interesting thing for someone to computer-model.