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MIXIE, the Mars Oxygen ISRU Experiment is an experiment on the Perseverance rover currently on its way to Mars, that will test solid oxide electrolysis as a way to extract oxygen from atmospheric carbon dioxide.

As such its solid oxide fuel cell (run in regenerative mode, i.e. "backwards" to produce oxygen) will be exposed to the martian atmosphere at least sometimes if not constantly.

But we don't control the weather on Mars, at least not yet!

Question(s):

  1. Will MOXIE get physically clogged or even chemically degraded by martian dust? If so, how quickly? Besides physically covering the surface, I wonder if perchlorate in martian soil and presumably the dust could chemically poison the chemistry.
  2. Is MOXIE's fuel cell's solid oxide material constantly exposed to the Martian atmosphere or is there a little door that opens and closes? Are there at least "dust traps" or other passive devices that keep the dust from clogging the permeable surface of the solid oxide?
uhoh
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2 Answers2

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Little known fact - Martian dust is almost all magnetic. https://physicsworld.com/a/rover-reveals-magnetic-mars/

So some passive magnetic filters will keep the vast majority of dust out.

I strongly suspect perchlorates won't be a problem, as they are locked into the soil. If they weren't, we might have got a bigger hint of their presence when we used spectroscopy on the place - although that is speculative.

(Side note, https://www.sciencedirect.com/science/article/pii/S0032063319301758?via%3Dihub might be a better process. Generates metals and other resources as well as providing oxygen)

user2702772
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  • That's cool, er... hot! Possibly related: How is it proposed to extract oxygen from lunar regolith? and also Demonstrating molten oxide electrolysis on the Moon, what would require the most power, keeping it molten or driving the electrolysis? Please feel free to add an answer to either one if you like. – uhoh Aug 24 '20 at 05:58
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    @uhoh One answered, other requires a clarification and more maths than I can handle at this hour of the day. – user2702772 Aug 24 '20 at 06:43
  • Of course perchlorates will be a problem, they are not locked, they are in the dust ! https://space.com/21554-mars-toxic-perchlorate-chemicals.html – Cornelis Aug 24 '20 at 08:39
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    @Cornelisinspace do you have a good source for airborne perchlorates? Dust suspension depends on mass and particle size. Given that we don't know the formation route of perchlorates on Mars (some good guesses, but not known) we don't know if there is a significant amount in the dust or not. The magnetic traps on Spirit didn't observe an dust that wasn't magnetic. https://www.researchgate.net/publication/8412771_Magnetic_Properties_Experiments_on_the_Mars_Exploration_Rover_Spirit_at_Gusev_Crater – user2702772 Aug 24 '20 at 10:13
  • Why should dust being magnetic exclude the presence of perchlorates in it ? They think the origin of martian dust is the MMF formation, with a high enrichment in sulfur and chlorine. https://hub.jhu.edu/magazine/2018/winter/mars-dust-medusae-fossae-formation/ – Cornelis Aug 24 '20 at 11:11
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    Perchlorates aren't magnetic, given that all the dust observed is magnetic, you'd have to have dust forming (plausibly the source you link) and then for perchlorates getting stuck to the magnetic grains. In which case they'd still be filtered out by magnets. – user2702772 Aug 24 '20 at 12:40
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First, yes, it will degrade - the fuel cell itself will be isolated from dust by a filter, but the filter itself will be gradually clogged. How long? This is one of important things to be determined by this very mission; MOXIE is equipped with a microscope observing that filter, in order to record and measure dust accumulation and profile of the grains so that better filters could be developed. pdf.

The fuel cell itself will not be exposed to "ambient air" at any point, it wouldn't work like that anyway. It has two modes of operation - either fed by a compressor directly, or fed with pressurized CO2 from an accumulation tank where CO2 is gathered over time through cryocooling. It has valves to switch between these two options, and "neither" certainly is an option. It's not going to run all the time anyway - multiple 1-hour runs are planned throughout the mission "intermittently".

SF.
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