UC Riverside engineers have developed a catalyst to remove a dangerous chemical from water on Earth that could also make Martian soil safer for agriculture and help produce oxygen for human Mars explorers.
Perchlorate, a negative ion consisting of one chlorine atom bonded to four oxygen atoms, occurs naturally in some soils on Earth, and is especially abundant in Martian soil. As a powerful oxidizer, perchlorate is also manufactured and used in solid rocket fuel, fireworks, munitions, airbag initiators for vehicles, matches and signal flares. It is a byproduct in some disinfectants and herbicides.
Because of its ubiquity in both soil and industrial goods, perchlorate is a common water contaminant that causes certain thyroid disorders. Perchlorate bioaccumulates in plant tissues and a large amount of perchlorate found in Martian soil could make food grown there unsafe to eat, limiting the potential for human settlements on Mars. Perchlorate in Martian dust could also be hazardous to explorers. Current methods of removing perchlorate from water require either harsh conditions or a multistep enzymatic process to lower the oxidation state of the chlorine element into the harmless chloride ion.
Changxu Ren and Jinyong Liu noted anaerobic microbes use molybdenum in their enzymes to reduce perchlorate and harvest energy in oxygen-starved environments.
“Previous efforts in constructing a chemical molybdenum catalyst for perchlorate reduction have not been successful,” Liu said. “Many other metal catalysts either require harsh conditions or are not compatible with water.”
“This catalyst is much more active than any other chemical catalyst reported to date and reduces more than 99.99% of the perchlorate into chloride regardless of the initial perchlorate concentration,” Ren said.
The new catalyst reduces perchlorate in a wide concentration range, from less than 1 milligram per liter to 10 grams per liter. This makes it suitable for use in various scenarios, including remediating contaminated groundwater, treating heavily contaminated wastewater from explosives manufacturing, and making Mars habitable.
Abstract
Perchlorate (ClO4–) is a pervasive, harmful, and inert anion on both Earth and Mars. Current technologies for ClO4– reduction entail either harsh conditions or multicomponent enzymatic processes. Herein, we report a heterogeneous (L)Mo–Pd/C catalyst directly prepared from Na2MoO4, a bidentate nitrogen ligand (L), and Pd/C to reduce aqueous ClO4– into Cl– with 1 atm of H2 at room temperature. A suite of instrument characterizations and probing reactions suggest that the MoVI precursor and L at the optimal 1:1 ratio are transformed in situ into oligomeric MoIV active sites at the carbon–water interface. For each Mo site, the initial turnover frequency (TOF0) for oxygen atom transfer from ClOx– substrates reached 165 h–1. The turnover number (TON) reached 3840 after a single batch reduction of 100 mM ClO4–. This study provides a water-compatible, efficient, and robust catalyst to degrade and utilize ClO4– for water purification and space exploration.
SOURCES- Journal of American Chemical Society, UC Riverside
Written by Brian Wang, Nextbigfuture.com
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While it wouldn't have been healthy for him, it's not clear it would have killed him all that fast. Probably a lot slower than starving to death…
Also, one abstract I skimmed regarding perchlorate bioaccumulation in plants mentioned that it tended to happen substantially more in the above-ground portions of plants. Potatoes of course grow below ground… so maybe that'd reduce his dose? Article wasn't about potatoes, so that's purely speculation.
It's behind a paywall but similar articles make it pretty clear they would have removed the perchlorates beforehand.
https://blogs.scientificamerican.com/observations/how-to-grow-vegetables-on-mars/
I've done some comparison previously and came up with 0.01 hectares/person (100 square meters), but that was with more traditional agriculture, and including chickens for natural meat and eggs.
Dust would be a minor issue for sunlight, IMO. Natural light on Mars is like a cloudy day here. Use some mirrors to boost that, and sweep them off after a dust storm, you're fine.
Or use solar panels and LED lighting. It will probably be a mix. Red LEDs in the hydroponic labs for maximum food production, but for mental health you'll want some green plants, including flowers, scattered around the living quarters, with either natural sunlight or something with a spectrum that looks like that.
For political reasons, I think your uranium proposal is a non-starter. Fortunately the uranium ore on Mars should be plentiful and untouched.
I've put some time as an engineer into trying to envision how you'd actually build a Mars colony, if you were going to be practical.
Martian levels of sunlight aren't idea for Earth plants, but that could be dealt with using reflectors or concentrators. But given issues with dust, the higher meteor flux, and radiation, you'd probably just bury everything. If the living space was constructed of balloons under a layer of sand bags, you could just have a layer of hydroponics over the living space, and it would work out to a reasonable amount of space for the people, about 20 square meters per person is the minimum to feed them hydroponically.
It's not so bad. For one thing, the planet shields 50% of cosmic radiation (can't go thru the ground underneath you). Live in a valley or canyon and that can go to 60% or 70% shielding. That's just standing on the surface, add your structure, which hopefully has its own radiation shielding, especially if underground.
Nice blog, I might have to check out some more entries
I don't think it was explicitly brought up, but in the movie he was clearly getting some radiation, he was literally using a radioisotope generator for warmth at one point.
Martian surface radiation levels aren't acutely dangerous, just chronically. Elevated risk of cancer, for instance.
Technically, I suppose Xenon isn't *really* inert. It's just kind of shy. The only genuinely inert elements (Under normal Earth conditions, nothing would be inert at the core of Jupiter, for instance.) are Helium and Neon. The rest of them can be coxed into forming compounds, just not easily.
But, yes, elements can be toxic without having to undergo chemical reactions. Just as compounds can.
Right. He basically admitted that in an interview someplace. He tried to keep science and math in there as much as possible, but some things had to be bent for purposes of the story. Then when the book was made into a movie, things like plastic rippling in the "wind" were added for visual clues to the audience as to what was happening. A static bulge would not have been as obvious.
Also radiation shielding was never brought up, and that would definitely be an issue for someone spending that much time at the surface.
Near vacuum would be more of a short term issue.
Solving radiation is easy. Just live underground.
Hydroponics would be the way to go. Big greenhouses take up too much in the way of resources to make and natural sunlight isn't as good at producing food on Mars because it is weaker.
People will definitely want reclaimed sod for green spaces, just not for mass food production. You do that underground in the tunnels.
I'd imagine that sourcing Molybdenum from Earth would be easy. I fancy that when a family migrates to Mars that they bring a kilogram of Uranium fuel salt with them as a way of making a down payment on all the energy they will use.
Either way Mars is untouched and whatever valuable materials are on the surface are literally there for the picking.
Radiation on Mars is not as bad as you think. It's equivalent to Ramsar, Iran, where people are just fine.
https://caseyhandmer.wordpress.com/2019/10/20/omg-space-is-full-of-radiation-and-why-im-not-worried/
Thanks for the explanation, and also for the bit about Xenon — I had never heard about that.
https://www.nationalgeographic.com/science/article/mars-soil-earthworm-agriculture-science-spd
what about the magnetic field? until we figure that out no plants or animals could survive
Yes, the very first plot hole in the movie: The Martian atmosphere is too thin to have threatened that rocket in the first place, let alone to have carried debris at potentially lethal speeds.
I gather the author was aware of this, and some of the other problems, but just had to bite the bullet on some points for dramatic purposes.
Copy and paste of the original paper's mistake. It's a stable anion, but not inert.
Oh, but inert elements CAN be toxic; Xenon works as an anesthesia, for instance. Because it dissolves in lipid bilayers and alters cell behavior without chemically reacting.
Not the case for Perchlorate, though. It's just stable, not inert.
Yar, clearly it wasn't duct tape as we would buy down at the corner store. Probably carbon fiber stuff with some sort of adhesive that works even in space and even in super-cold places. All the same, that plastic was probably holding back 30 tons or more of pressure. Even allowing for "space" plastic and a perfectly balanced installation, that's a lot. Also, why was it snapping in and out like a sail in the wind? All the pressure was on the inside. The Martian atmospheric pressure and wind would have been negligible compared with that.
Well, he might not have been aware of it but Perchlorates are reactive chemicals first detected in arctic Martian soil by NASA's Phoenix lander that plopped down on Mars in May 2008.
The book was published in 2011, and the movie came out in 2015.
There were also hints going back as far as 1976 (though it would be ridiculous to think anyone should have deduced it from that). But there was further corroborating evidence in 2012 by the Curiosity rover when it found them in Gale crater. Plenty of time to fix it in the story before the movie came out, at least.
I still like the movie a lot.
I don't know about that "minimal" bit. Sure, the catalyst itself likely won't be inactivated, but that's not a lot of consolation if you can't get it back out of the soil after the remediation.
I really do wonder if there's enough Mo in the Martian soil that you could use engineered bacteria?
The abstract begins: "Perchlorate (ClO4–) is a pervasive, harmful, and inert anion . . .".
How can something be both harmful and inert? Am I overlooking something obvious? Am I misunderstanding the statement?
When Andy Weir wrote The Martian the presence of perchlorates in Mars was not yet known!
The book was written at the best of the knowledge of the time.
There are two sorts of audience members. Those who really wanted there to be another 12 hours of detailed, technically accurate, engineering. And those who wanted far less engineering, no duck tape, nothing with calculations, and maybe a romance.
I wanted the detailed calculations.
But the studio is to be congratulated for giving us as much as they did.
The Mo is just a catalyst, so you only have to provide it once, then you can keep reusing it (there will be loses of course, but these should be minimal).
Good movie, but some enormous plot holes. Closing off the blown airlock with plastic film and duct tape made this mechanical engineer a bit upset.
Since the catalyst in question is inspired by a natural bacterial enzyme, I suppose the bacteria he added with the stored wastes *might* have helped. But probably not, based on current research.
Yep. This was one of the big plot holes in The Martian. Matt Damon could not have survived by growing potatoes in Martian dirt.
Actually, it was probably an oversight, they did try to be somewhat scientifically accurate (compare it with Ad Astra). Although it would have been a major PITA for the protagonist, Matt Damon, and required a lot of energy, Matt could have gotten it out, and it probably would have been included as another major challenge for the survival-bent scientist to overcome.
In any event, this new method is cool, even though whipping up the catalyst might not have been practical for a stranded man on Mars.
edit: This is what I get for reading right after I wake- you need to bring your on H2.
So send fleets if rovers to spray this stuff all over. Lol
I mean, it's nice to say this would provide colonists oxygen, and that's technically true. But unless the colonists are going to depend on imported food, they'll need local agriculture, and that will quite automatically generate the appropriate amount of oxygen.
But, yes, technically true, because the perchlorates have to be neutralized to use Martian soil. Maybe not if the colonists rely on hydroponics, though.
Molybdenum, though: Not the most common of elements; How much would the colonists have to bring, to pull this off? Be a while before they were sourcing it locally.
If it's just trace levels, maybe engineered microbes could get it from the soil itself?
Pretty cool stuff!