How do clouds form on waterless planets?

[Sharkman Briton]

See title. I was thinnking this after I saw Duna with EVE, and Venus has a thick clous covering but any water would've evaporated long ago.

[Rath]

Dust and wind

[Sharkman Briton]

Oooh, I didn't know that, interesting.

[Technical Ben]

Some planets have clouds of nitrogen etc.

[ComradeWolfe]

Clouds can be nearly anything. Even lead could form a cloud if heated enough in a low enough gravity environment. A cloud is basically any dispersion of particles or droplets floating about in a gas.

[Tex_NL]

Some planets have clouds of nitrogen etc.

Exactly. Who says all clouds are water vapour?

Venus is covered with a thick dense cloud layer. It's much too hot for liquid water and the Venusian atmosphere contains only half a percent of the amount of water in Earth's atmosphere.

[MinimumSky5]

Venus's clouds are made of sulphuric acid, Jupiter has clouds of ammonia, ammonium chloride and phosphine, and Pluto has a nitrogen haze in its atmosphere.

[Camacha]

See title. I was thinnking this after I saw Duna with EVE, and Venus has a thick clous covering but any water would've evaporated long ago.

Why would you presume water is required for vapour (and thus clouds)?

[smjjames]

Venus's clouds are made of sulphuric acid, Jupiter has clouds of ammonia, ammonium chloride and phosphine, and Pluto has a nitrogen haze in its atmosphere.

To push it further, Titan and Uranus have methane clouds.

The basic definition of an atmospheric cloud is a collection of liquid droplets and/or ice particles. These liquid droplets and ices don't have to be water, just has to be anything that is able to be in a liquid or frozen state in the atmosphere.

[Camacha]

To push it even further, dust particulates can also form clouds. Sandstorms or other (possibly extreme) weather, explosions, all sorts of things can cause clouds of dust. At the same time, ice can also form clouds in the upper Earth atmosphere. While made of solids, these are still proper clouds. The whispy, feather like clouds (cirrus or cirro*)you sometimes see are made of ice, and generally are much, much higher up in the atmosphere than other clouds.

I would define a cloud as a collection of particulates carried in a gas (maybe with the added requirement that it has to be visible).

[AngelLestat]

Exactly. Who says all clouds are water vapour?

Venus is covered with a thick dense cloud layer. It's much too hot for liquid water and the Venusian atmosphere contains only half a percent of the amount of water in Earth's atmosphere.

Venus atmosphere has the same amount of water than earth atmosphere, which is 15000km3 aprox, the difference with venus is that its atmosphere is 90 times ours.

[Findthepin1]

Venus' clouds are sulphuric acid vapour. Earth's clouds are water vapour. Mars has very little to speak of in clouds, when there are any they will likely be water vapour. Titan's clouds are methane IIRC.

[KerikBalm]

Venus atmosphere has the same amount of water than earth atmosphere, which is 15000km3 aprox, the difference with venus is that its atmosphere is 90 times ours.

Earths atmosphere:

https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Composition

0.4% over the entire atmosphere, so that is an average of 4,000 ppm

Venus'satmosphere:

https://en.wikipedia.org/wiki/Atmosphere_of_Venus

20 ppm

4000/20 = 200x as much...

Sorry, Venus has lesss water vapor than Earth, in absolute terms

[lajoswinkler]

Yeah, Venus lost most of its water when it combined with sulfur oxides to form sulfuric acid. A great deal of water was photolyzed and radiolyzed by the Sun into ions that got blown away into space.

A cloud is simply a bunch of condensed (liquid or solid) dispersed matter in a noncondensed (gas) medium. In terms of colloidal chemistry, a cloud is either smoke or mist.

I'm not sure if a cloud is neccessarily a colloid. Colloids are relatively stable systems and if we have a dust cloud, that's unstable and settles down; it's called a suspension.

Suspensions are heterogeneous mixtures, solutions are homogenous mixtures. Colloids are in between.