Posts Tagged ‘Colonizing Mars’

How Much Oxygen Can You Pull Out of Martian Perchlorates?

June 2, 2019

(or, how my grandaddy fast-terraformed Mars in 2055)

So, maybe you’ve heard. Martian soil is about 0.5-1.0% perchlorates, that is, ClO4ions, which are supposed to be really bad for human thyroids. Being that it’s an ion, you usually find it paired up with something like sodium or potassium, so really, it’s a salt, but it’ll still kill you.

There are articles online about soil remediation using a variety of methods, because perchlorates are a problem here on Earth, too, residue from such things as fireworks and rocket propellant, and sometimes when the EPA isn’t run by idiots, we try to fix that problem. So there are ways to deal with it, including bioremediation using bacteria.

The question I pose here is; if you have the tools for bioremediation on Mars, how much oxygen could you produce in that process, and would it be a greater volume than the CO2 that’s already there? Could you fast-terraform Mars with the available oxygen?

Let’s figure it out. If you want to skip the “figuring out” part, just skip to THE BOTTOM.

I make a few assumptions that may or may not be reasonable, but let’s start with the idea that we can convert all the ClO4ions into a Cl– atom and two O2 molecules. If you wonder how we’re going to discard the Chlorine atoms, don’t forget that we started with a salt, like NaClO4, or KClO4, and can recombine with the positive ion to make NaCl or KCl, both of which are relatively harmless to humans.

Second assumption is that the 0.5% (by weight) soil contamination only goes down one meter on Mars. Martian soil, as everyone knows, weighs about 1520 kg/m(okay, I looked it up. I’m sure this varies a lot, but it’s the number I used). If 0.5% of that is perchlorate salt, that’s 7.6 kg per cubic meter of Martian surface (or square meter by area, since I speculated on a 1 meter depth).

Mars is 144.8 x 1012 square meters in area, so we get a total of 1.1 x 1015 kg of perchlorate salt. Of that mass, roughly half is oxygen. You can look up molecular weights if you like. I’ll wait.

So, roughly 5.5 x 1014 kg of oxygen! Woo-hoo! That’s a lot of oxygen. Let’s compare that to the CO2that’s on the surface (Googling it now…) Ah, dang, the COis 2.5 x1016 kg. Even at .01 atm, it outweighs the available oxygen from perchlorate remediation by 50 times.

THE BOTTOM; The existing COon Mars is about 50 times heavier than the Oyou could get out of the perchlorates in the soil, assuming my assumptions, which are many. Don’t get me wrong, 5.5 x 1014 kg of oxygen is still a hell of a lot of oxygen and you get to clean up the soil so it doesn’t kill you as you track it into your hab.

But if it isn’t enough to bulk up the atmosphere, is it worth the bother? Well, sure. I’ve been working on an SF story where humans start covering Mars (and the Moon) with tents, tall poles with clear plastic sheets on top, basically, so they’re creating an atmosphere that’s only 3 meters high. It’s well designed science-fiction plastic, so it keeps out gamma rays, the solar wind, and holds 0.5 atm pressure with ease. It’s the future!

If I’ve done my math right, we have 1.7E16 moles of oxygen, so if we’re shooting for room temperature at 0.5 atm, and using PV=nRT, we should have about 7.6E14 cubic meters of gas.  Based on the known square meters of Mars, this should give us a potential tent height of 5 meters over the whole damn surface, full of oxygen at ½ Earth pressure, assuming we can heat it to room temperature (thank goodness for all those orbiting reflectors).

Wow! Plenty of space for those 2-meter tall Earthlings to evolve into 4-meter tall Martians in the low gravity. Maybe even enough for a few giant dome-cities if you add in some nitrogen and water vapor and some carbon dioxide for the plants.

Feel free to check my math, I only ran through it once. Sometimes I make mistakes. But to all the nay-sayers telling us we can’t Terraform Mars, I say; it’s just engineering. You just need to make the top of the atmosphere much lower.

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