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In the not too distant future, mankind has established several mining bases on Ceres. There are a lot of spaceships which come and go. Large mining machines are chewing up the interior for resources. Ceres has become a busy frontier trading station, with most colonists living and working underground.

My question is, what will the atmosphere above the mining towns, and around Ceres as a whole, possibly look like?

Despite the obvious very low pressure of any atmosphere, I expect a lot of dust from mining activities will remain floating about, due to the very weak gravity. In addition to dust, there will be exhaust gasses from spaceship engines and thrusters, colony waste dumps, and leakages, all swirling around in the near zero-g environment. What might this actually look like?

A good answer will help me relate the amount of fog and dust hanging around to the size of settlements, if this dust cloud will spread far, last a long time, have any thermal effects, and most critically, what impacts it may have on visibility. I am interested to know if it will all just dissipate quickly, or if it will hang around like smog, will it be invisible, a mild haze or an impenetrable fog, and so on. Rigorous math is not required, but realistic guesstimates are greatly appreciated.

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  • $\begingroup$ My napkin calculation says thruster gas would exceed escape velocity, so any thruster impacting on the surface has the potential to throw up dust to any speed under escape velocity of 500m/s. That's a flight time for the dust particle of 1hr (straight up/down). So for a spaceport with flights more often than that, there could be a constant dust hanging around... I assume also that every time something launches from the surface there'll be dust kicked up into orbit. How dense and how long for this stuff to lose enough energy to fall back down? $\endgroup$ – Innovine May 3 '19 at 13:31
  • $\begingroup$ Dust does not stay dust for very long is space, especially if it is being stirred in a hard vacuum. vacuum cementing fuses it together. So at least dust can't build up much. $\endgroup$ – John May 3 '19 at 13:36
  • $\begingroup$ @john orbital dust would remain in space until it collides with other dust, loses some energy, and goes into a lower orbit, eventually impacting the surface. This could take millions of years. The question is if it is noticable or not. The moons atmosphere has been noted, but isn't causing any practical impact on spaceships. But around ceres, I wonder if the dust could get much more dense, eventually causing drag, micrometeorite damage, dirty windows, etc $\endgroup$ – Innovine May 7 '19 at 7:04
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Gravity

Ceres is really tiny. Like, it's only 0.00015 times the size of earth that's... puny. It has only .029 g's of gravity. So for our atmospheric considerations, let's use something a little closer to what Ceres is--Mercury, which clocks in at .038 g's. Not the same, but similar ballpark and there's more research, so let's go from there.

Mercury used to have an atmosphere, but it lost it. Venus, Mars, and Earth also lost theirs at one point, but gasses from the interior of the planet came out and reformed it. That didn't happen to Mercury though, because its gravity wasn't quite strong enough to hold onto those gasses so they continually trail off into space. Technically there is an atmosphere, but it's more the beginnings of an exhaust trail then anything. For Ceres, pretty much all your gasses would leave immediately. This is especially true for industrial gasses, because hot gasses are more prone to escaping gravity (because temperature is velocity, so hot gasses are more likely to exceed escape velocity.)

That means you're going to have almost no problems with stray gasses floating around, but that's a problem because frankly atmosphere is important to way more than just breathing. Atmosphere helps shield a planet's surface from harsh radiation from the Sun and it moderates the amount of energy lost to space from the planet's interior. An atmosphere also makes it possible for liquid to exist on a planet's surface by supplying the pressure needed to keep the liquid from boiling away to space. All of those things make industry... difficult.

Obviously you have creative licence to come up with solutions to those problems. I'd solve it with a nice set of domes over any above-ground mining sites, and some good infrastructure underground, but that's just me.

Dust

This one's a little harder and involves Actual Science (tm) as opposed to fun facts about Mercury. When you throw a rock up, it comes down. Mining dust is very small rocks. Now, the reason those don't come down so fast is because they're supported in part by the air. As size goes down, the relation of mass to surface area changes, and with a higher relative surface area comes more resistance.

Since Ceres isn't overly burdened by air, that's not a problem outside or in mines with no atmosphere, but if your mines are indoors it's a really really big one. Air quality in mines is probably the most essential bit of staying alive there, and while dangerous chemicals (As a side note you might want to look into Ceres' water composition--the water makes it a good option for a station, but there might be some Weird Shit in there. I feel like I read the word Ammonia at some point) are a thing, so are particulates, and you have a particulate problem.

This is compounded by the lack of gravity. Again, how much dust floats is a ratio of weight to surface area to air pressure, and as time progresses in the mine your air pressure will increase a bit unless it's free to escape into the general lack-of-atmosphere (good thing for mining. Makes stuff like liquid cooling and combustion possible). Your particulates are really small, and the lower gravity actually makes them lighter, so... dusty hellhole, if it's properly indoors.

In the end, you have two options. Ceres itself isn't going to have an atmosphere, but you get to choose whether your mines do. If they do, that's a hell of a lot easier to deal with mining wise (you wont need airlocks everywhere) and you get your cool dusty hellhole aesthetic. (Note: your people still can't breath there. It would be a dusty hellhole with breathing apparatus and chemical showers upon going inside, and you need to separate the mines very very completely from your colony thing). The other option is to have them airless, use the same technology you'd use for full asteroid mining, and be dust free, since there's no atmosphere to support it.

That's a choice you get to make, but there's actually a smidgen of a thing that you need to consider before completely throwing out Ceres as a place with air, if you're really deeply trying for smog and filth: Artificial Gravity. I don't know if that's a thing in your universe, but if it isn't your people have a lot of health problems besides inhaling dust. Not judging, but if you do have artificial gravity in the living spaces or mines you need to remember that it pulls down air just as much as it does people. Hypothetically, you could pop an artificial gravity device on the surface of Ceres and end up with a bubble of actual atmosphere a few years down the line. It wouldn't be breathable, but still.

If you do decide to gravity it up, then the same rules apply as an earth mining operation as far as air and dust is concerned. The only difference is that you're starting with nothing, so the only atmosphere is the shitty industrial one you put there. That's where your true smoggy landscape would come from, an indoor mine with artificial gravity and a dusty imported atmosphere.

Even if you do that, the air there isn't going to go in your living areas. You're scrubbing this air in some way if you want to breathe it, and while that might not happen in the mine, it will happen in the house, and scrubbing usually includes most particulates. No dust there. Just filthy humans and poor hygiene to make that gross.

Cheers, and have fun with your mining operation.

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  • $\begingroup$ What about heavier molecules at low temperatures (acc. to wikipedia max. temperature on Ceres estimated −38 °C at noon)? I can imagine if mining/refining produces large amounts of sulfur dioxide, couldn't it cool down or partially condense, accumulate and create a corrosive haze thick enough to cause trouble? $\endgroup$ – Juraj May 5 '19 at 20:36
  • $\begingroup$ I still think launching spaceships can blast dust up to orbital speed quite easily. So yep, the dust doesn't float, but it would circle around and some would remain in orbit. I guess the question is more about how much dust is needed before this becomes significant to operating spaceships, and if that level of dust is possible at all. Underground, sure, its going to be a foggy hell when mining $\endgroup$ – Innovine May 7 '19 at 7:10
  • $\begingroup$ I was not considering a pressurized atmosphere, just dust moving around in a near vacuum. $\endgroup$ – Innovine May 7 '19 at 7:12

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