Delicious Martian Salt

[Ciber]

I need to know what combination of feedstock, chemical reactions, and filtering are required to produce edible table salt on mars.

[p1t1o]

Do you mean "from martian raw materials" or do you mean what would you have to take with you? Or, do you just mean in general?

[gmalivuk]

I would assume raw materials because if you're bringing stuff just bring salt.

[p1t1o]

Well short of finding a seam of rock salt, it will be more difficult than its worth.

If its nutrition that is the worry, then it doesnt need to be in the form of "table salt", just sodium and chloride contained in various foods.

Thats probably the best way to get dietary salt on mars - grow stuff and eat it. Its how the human body gets most of the salt it needs on Earth.

Otherwise you're stuck with the problem of creating pure(ish) sodium chloride from the minerals contained in martian soil/rock and separating sodium chloride from mixed geological minerals is...effort-intensive. There might be some combination of titrations, precipitations and reactions that might yield some table salt from martian regolith, but thats an awful lot of equipment/reagents to take with, just for salt.

Here's a breakdown of the mineral content of martian soil as an example:



Yeah, try separating table salt out of that on a lab bench.

[Xanthir]

Given that Mars once had seas, tho, presumably there are salt deposits somewhere, right? Iirc, the sea is salty due to weathering rocks producing either salts directly, or producing acids and bases which react to produce salts, and that salt just kinda hanging around and concentrating over the megayears.

[ConMan]

Given that Mars once had seas, tho, presumably there are salt deposits somewhere, right? Iirc, the sea is salty due to weathering rocks producing either salts directly, or producing acids and bases which react to produce salts, and that salt just kinda hanging around and concentrating over the megayears.

I don't think there's any guarantee that the seas were (a) salty, or (b) salty from sodium chloride. There are lots of "salts" that aren't table salt, and very few of them would be particularly good for human consumption (Arsenic Cyanide, anyone?).

[Xanthir]

Sure. I'm not up enough on geology to know if our preponderance of sodium chloride over other salts is an incidental or expected sort of outcome, tho.

[Himself]

One aspect of geochemistry that may be a factor is that on Earth we have continental crust with a roughly granitic composition, which is fairly rich in sodium. Weathering that granite, I figure, is a possible source of sodium for sea salt. Mars, as far as we know, has no granite. Most of its surface materials appear to have a basaltic composition, which would suggest a lower sodium content. That's a bit of an assumption, since basalt-like rock on Mars might not have quite the same composition as it does on Earth.

[gmalivuk]

I mean there is a soil composition graph right up there.

[Pfhorrest]

Am I reading that graph correctly that there is somehow solid elemental chlorine in the Martian soil? How is that even a thing?

[pogrmman]

Am I reading that graph correctly that there is somehow solid elemental chlorine in the Martian soil? How is that even a thing?

It’s gotta be just chloride. Chlorine would probably sublimate, given the low atmospheric pressure. Not to mention reacting with everything else. Because only some minerals are the primary rock building blocks, I think they’re just showing things outside of those “primary building blocks” as the element (so that’d also apply for bromine, zinc, and nickel). The other stuff looks like standard rock building minerals — phosphates, silicates, corundum, sulfates, plus what would be carbonates on earth (CaO, MgO, Na2O, K2O).*

*Note: I know very little about geology, but I’m speculating that because mars has no carbon cycle, you get the alkali/alkaline earth oxides instead of carbonates.