Atmospheres for Galilean moons?

[JackHiggins]

After about 45 seconds research last night, I found several sites with information on the very thin atmospheres of Europa, Ganymede & Io.

Triton has an atmosphere too, but I'm not sure are the Galilean moons' atmospheres as thick as that...?

It'd be nice to see this small addition to solarsys.ssc, it would increase the realism ever so slightly!

All 3 are very, very thin, but:
Io's atmosphere is mostly sodium (Na)... (I think)
Europa is mostly molecular oxygen (O2)
Ganymede is mostly Ozone (O3) caused by the solar wind interacting with oxygen at the surface.
Dunno about Callisto, but probably something similar to Ganymede?

What colours would these atmospheres be?

[granthutchison]

What colours would these atmospheres be?

Black, I reckon.
Io's atmosphere has a pressure less than a millionth of Earth's - there's no detectable dimming as a star passes behind its limb, which means no appreciable scattering of light. If that's the best that Io can do, with all those bloomin' volcanoes and its gas torus to help replenish the atmosphere, I'd guess that the other Galileans are much worse off .

Grant

[JackHiggins]

Oh well... Actually Io's is sulphur dioxide & callisto's is carbon dioxide, but at least now I know...!

In that case, is triton's atmosphere accurate in Celestia?
// added later
Triton is a tad smaller than europa, and even though it has those geysers, there probably isn't enough gravity to hold any permanent "atmosphere" to speak of...?

[granthutchison]

More info:
Europa and Ganymede have atmospheric pressures of around 10 to the minus 11th atmospheres - pretty hard vacuum.
Triton comes in around a hundred-thousandth of an atmosphere, which is equivalent to ~100km up on Earth, where the sky is pretty much black. There's a "very thin" haze layer at 13km. So I reckon Triton might be better modelled with no atmosphere and a diffuse patchy "cloud" layer so transparent you can only glimpse it edge on (as Voyager did).

Grant

[JackHiggins]

Ok so i'm convinced theres no point putting any atmospheres on Jupiter's moons...

I'll get to work on a Triton cloud layer instead so....! (pretty easy since it'll be 95% transparent...)

[Rassilon]

I actually made a triton cloud map almost a year ago if anyones interested...

http://www.shatters.net/~rassilon/triton-clouds.zip

[granthutchison]

Sorry Rass, should have remembered - that sort of thing, yes indeed. I'd vote for even more transparent, but I've absolutely nothing to back that up with, apart from a feeling that 10-to-the-minus-five atmospheres shouldn't be able to keep much of an aerosol aloft - the absolutely highest clouds on Earth are 10km lower than that pressure level.

Grant