NASA has MOXIE, but rivals reckon they can do better for oxygen on Mars Last year, NASA produced oxygen on Mars. Now, scientists experimenting here on Earth may have found a much more efficient method of doing so for future missions. The resulting equipment could be used to produce the necessary materials for human colonization, too. Writing in the Journal of Applied Physics, an international team …
... not a bad volume either...
An adult breathes about 11,000 litres of air/day, about 2,200 litres of O2, which at 1.43 g/l at stp is about 3.1 kg/day or about 130g/hr.
So the quoted 10g/r and 14g/hr for what is essentially experimental equipment is pretty good. Scaling up 10X production normally could be done without requiring 10X increase in equipment mass as well, so achieving a 30kg or less machine that can provide all the O2 requirement of one adult should be quite possible.
So, we'll basically need to send one machine per crew member ?
Either that, or someone will have to stop breathing.
I concur with your science. Seems like a good estimate.
1 mole O2 (roughly 32g) is 22.4l at STP, or about 100 moles per day by your calculations (about 3.2kg by this ballpark calculation).
I was actually thinking that if we could "lasso" a comet (or a big chunk of one) we'd have enough water ice to do quite a bit of O2 and liquid water, as well as HC compounds of various kinds.
Worthy of mention, there is a lot of perchlorate in the soil, which also contains oxygen, as does the oxidized iron that makes the soil reddish. You would probably, need some kind of water chemistry to release it, though if you could extract the perchlorates and make them into oxygen candles, then THAT would work nicely! Washing the soil to enable plants to grow is necessary. Using them for O2 and chloride chemicals may just be a plus side to an otherwise water-intensive process.
We don't absorb/utilize 100% of the oxygen we inhale either, though the rate is highly variable as it is also impacted by the rate of blood transport, in turn tied to metabolic and activity rates, stress, etc.
So in reality, while they need to have a safe margin, it is likely able to keep up with O2 for more than one person.
By converting different molecules directly from the Martian atmosphere
That's very impressive. It's been known for a long time that water ice on the icy bodies in the outer solar system separates out into its hydrogen and oxygen components when exposed to local radiation and that the atomic oxygen recombines into O2, the hydrogen goes off into space. So breaking up CO2 with plasma is reasonable.
Interesting question! I would guess maybe yes, but not as efficient, since the article states Martian atmosphere is ideal for the plasma thingamajig they're using.
In any case it's very low volume, so I guess the power and volume requirements to use such technology to remove CO2 from Earth's atmosphere would be completely disproportional to the utility. Much better to plant a few million trees (or just stop using the land - I've seen examples in Brazil where just leaving the land undisturbed for 5-10 years it will start to re-forest by itself)
I've seen examples in Brazil where just leaving the land undisturbed for 5-10 years it will start to re-forest by itself)
Just stop mowing and driving on it. In most temperate lands, you have woody plants knee-high in a year, head-high in 2 years. Where I cleared-out some 70-foot trees 5 years ago is already (despite shade from the trees I didn't clear) is already head-high and too dense to walk through.
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As the device consumes CO2, could it be used also on Earth?
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Yes, but the reason we got the excess CO2 in the first place was that we borrowed the energy in the very strong carbon-oxygen double bonds to make steel and concrete, run the truck, fly to Ibiza, cool the refrigerator, keep warm and cook dinner. To break the C=O bond takes the same amount of energy as we got when we made it. If we had a source of energy which was free of pollution, cost and everything else that we don't like we could do this as much as we liked. Unfortunately we don't have such a source, so this kind of thing tends to be limited to applications where the product is essential and there's no alternative.
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In that experiment, what does the carbon become?
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I don't understand the question. Are you suggesting some kind of transmutation? It's carbon. Apart from the parts-per-trillion amounts of carbon 14 (which decays to nitrogen with a half-life of thousands of years), it will remain carbon. In the description they talk about carbon monoxide production, so you start with some CO2 and you get some CO and some O. When you've made two atoms of O they tend to combine to make one molecule of O2 unless something else reacts with them first. That will happen a lot if you let it, single atoms of O are very reactive. The CO just hangs around, it's a component of what we used to call coal gas. It's stable enough until e.g. you set light to it in the presence of oxygen, in which case you're back to where you started.
I think the implication is that the CO2 would be converted into something useful like jet fuel. The problem, as you point out, is that this is very inefficient. It only makes sense
1. If there's a a large surplus of sustainable generation over energy transmission and efficient storage,
2. If there's an overriding demand for the fuel, for instance for high priority air travel or defence.
Yes, but the reason we got the excess CO2 in the first place was that we borrowed...
As you say, we haven't that energy source, and even if, it won't be used in a near future. CO2 production will rise in the next years whatever Europe does, so the only solution in a new future is to remove the CO2 from the atmosphere.
I don't understand the question
You're right, I didn't read carefully enough and didn't see CO was produced, something that isn't good enough as CO is toxic to us.
"The resulting equipment could be used to produce the necessary materials for human colonization, too"
As (if I remember right) Larry Niven stated in the '60s:
"The more you control your environment the more hazardous it becomes to live in it".
The thought of relying absolutely and permanently on any machine for my source of oxygen terrifies me, particularly if rescue is so far away. Divers (and even astronauts) do for only limited periods - not for their entire natural lives.
Read up about Bill Stone's rebreathers to get an overview on technology better than NASA, with multiple levels or redundancy. Even with his Mk1, he was doing unsupported 24 hour dives last century. I believe he then went on to consult for NASA.
Rick Stanton and John Volanthan (both of Thai cave rescue fame) and many other cave divers have made their own rebreathers. Cave dive profiles are nothing like open water profiles, some going to extreme depth multiple times between air spaces, something almost impossible to calculate (or support with bottle dumps) in an open-circuit rig.
Admittedly, something that it going to periodically inject a little O2 in the mix is ultimately going to be limited by the O2 tank size/weight, but some of the guys rebreathers designed for tight caves are not much bigger than a couple of drinks bottles.
is one of the harshest possible environments. Surface and even deep open water divers can bug out if they have a gear problem, and others in a group may be able to help.
In a cave, you can lose visibility and orientation in an instant, and if there is a problem, you may be in a restricted space, and have no alternative than to head back out every inch of the way you came in. It is likely that no one can reach you before you die.
So redundancy is pretty essential, especially as you need time to clear a failure in your primary air system. Something else few outside the dive community know is that most of those long endurance rebreathers should be labeled more like "Up to 24 hours*" instead of 24 hours.
That's a real problem if your scrubber tank burns fast 12 hours into the back of a submerged cave. This is why even with long endurance gear they will have piles of bottles stashed along the route. They, as while I love caving, and I like diving, for me they are two great tastes that are best enjoyed separately.
> rebreathers designed for tight caves are not much bigger than a couple of drinks bottles.
By truly habitable you mean habitable by humans without significant life support systems. A bit like some of the warmer parts of the Earth where modern humans enjoy life by occupying a small enclosed space protected from the UV and using copious amounts of energy to have the heat removed. Like Phoenix and Dubai. They don't grow potatoes in their own sewage in Phoenix though, at least I don't think they do. It's only Idaho where they do that.
Then some of the higher latitudes that have a permanent human presence, but people can't really go out of their heated building without considerable amounts of protective clothing.
Arizona for the win!
Reminds me of Mr. Burns' mirror - let me know when it is finished (perhaps 20 years after fusion?). Also, looks like a good potential target for an asteroid, or meteorite, or missile . . .
I can see the point of building underground on the moon as a step out of the potential well (at least it stays more or less constant distance), but Mars is no use for that - so why do we even want to go there?
Clearly you don't, and for perfectly good reasons.
Elon's stated goal is to make humans a multi-planet species so a single large asteroid cannot take us all out at once. There are others who despite some evidence to the contrary consider humanity worth protecting even though there are enormous difficulties.
There are bad reasons to go too. In the words of former US Vice President Dan Quayle:
"Mars is essentially in the same orbit... Mars is somewhat the same distance from the Sun, which is very important. We have seen pictures where there are canals, we believe, and water. If there is water, that means there is oxygen. If oxygen, that means we can breathe."
A Moon base is easier than a Mars base but for a self sustaining colony, Mars is a better choice. If thousands of years from now Mars has a breathable atmosphere and an asteroid takes out the radiation shield then Martians will have thousands more years to put off building a replacement before they would have to retreat back into pressurised habitats.
Surface farming on Mars with a terraformed atmosphere is fine in science fiction, but dumb IRL. The magnetic field problem is more easily solvable then the atmospheric ones, and for your trouble, you just waste that gas you released as it gets slowly blasted off into space.
Trap all the gas and water you can, put it far enough underground to protect the structures and inhabitants, and create a air and water recycling system to preserve the limited and precious resource in the places it's doing something useful.
The surface of a colonized Mars will be solar and wind farms, landing pads, and railroad tracks.
Face it, Mars will be filled with Morlocks.
To keep an atmosphere, Mars needs a magnetic field but also volcanoes. Both imply a molten core+mantle which, I believe, Mars does NOT have (quick research indicates partially molten core, speculative). You could bring the components to Mars, but for long lasting terraforming, the core needs to be melted somehow.
so yeah, a bit beyond 21st century tech, where we still haven't even sent people there.
The perchlorates and rust can be a good feed stock for making Oxygen, but what we breathe on Earth is 80% Nitrogen. To be able to have a habitat/colony/indoor space with breathable air is going to require an inert gas to bring the partial pressure of Oxygen up without winding up with an atmosphere that will sustain vigorous combustion at the slightest spark. Plants also need Nitrogen and more importantly, fixed Nitrogen in the soil. When we can truck in what's needed from Titan, humans can colonize Mars as long as they live underground. Until then, spending billions to make Starships to send people by the hundreds (/s) is a waste of money. There is also the problem of the trip time. Meatsacks don't do that well after 9 months in 0G.
"adding that a cash infusion from a space agency could make the tech mature enough to take to Mars."
In experiments, this looks better than MOXIE but we can't be sure yet as we can't yet even build a proper prototype. If someone will supply the cash, we'll see if we are right or wrong.
That's how science works and is funded :-)
Oxygen is a relatively common element on Mars, at least when compared to hydrogen:
The red planet is red primarily because of iron oxide (rust), so heat the soil hot enough and Oxygen, and other gases, will be released.
Oxygen can as has been done with MOXIE extracted from carbon dioxide in the thin Martian atmosphere.
Oxygen can also be extracted through electrolysis from water that is found in deposits of ice mostly at the frigid poles (−153 °C; 120 K; −243 °F).
Plants could also create Oxygen from carbon dioxide with enough sunlight. But more than about 0.2% and less than 0.025% carbon dioxide will kill most plants.
Even though the atmosphere on Mars has a pressure *155 times lower than is found on Earth, all the elements found in it: carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%) could, with enough energy, be used to synthesise an earth like air (78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide). Looking at the elements present in the Martian atmosphere a simpler atmosphere to synthesise for humans to live in might be 46.09% nitrogen, 20.95% oxygen, 32.92% argon, 0.04% carbon dioxide, but that would probably not be as useful for nitrogen-fixing bacteria for plants as 78.08% nitrogen.
To create water or rocket fuel one element you need is hydrogen.
About ~0.6% of mars regolith (soil) by weight is (water soluble) Perchlorate, and of that roughly 20% is ammonium perchlorate (NH4ClO4) which contains hydrogen. I would be very interested in the process that NASA plan to use to purify and extract Hydrogen from about 0.12% ammonium perchlorate found in the soil of mars to synthesise drinking water and rocket fuel. One problem with processing regolith would be that it requires more energy (collection and transportation) typically than processing the Martian atmosphere.
Another option would be to extract water from the thin Martian atmosphere, where tiny trace amounts (~0.03%) can be found, the simplest way would be to condense it as ice by cooling the Martian atmosphere entering and leaving through a recuperator to minimise the energy used.
* Mars atmospheric pressure (ground level) 652 Pascal 0.00643 atm 0.0945 psi 0.006518 bar
* Earth atmospheric pressure (sea level) 101353 Pascal 1.00000 atm 14.7 psi 1.01353 bar
I suspect that multiple synthesised atmospheres initially could be very useful, one optimised for plants to generate maximise biomass (more N2 and more CO2) and a separate atmosphere with less CO2 and more argon (to increase the nitrogen available for plants) for humans. Both would still be safe for humans to breath.
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