How to make metals from Martian dirt
66 comments
·September 7, 2025bruce511
HPsquared
Cooling a large nuclear power reactor would be a challenge on Mars. Probably you'd want something compact that runs at high temperature, like a molten salt design, to make heat rejection easier.
Edit: side benefit would be you could use the heat directly for processes like this metallurgy thing.
owenversteeg
Nuclear and solar are actually pretty competitive here at MW scale, optimistic projections for both are in the ballpark of 100 tons per MW including associated power electronics. That's to say, if Starship continues on the trajectory it's on, putting aside a few MW on Mars to operate a smelter is within the realm of possibility.
On a larger scale (GW) the answer is likely nuclear, unless we can come up with a realistic way to produce solar panels on Mars. Mass-wise, nuclear scales very well, but solar is nearly linear.
There's also some possibility we come up with a creative way to produce methane or another fuel.
bruce511
Solar is likely what will power anything we put there, in the short term at least. But Mars only gets 43% of the solar energy that earth gets. So you need at least twice the panels. Not to mention the batteries.
This is fine for "residential", but perhaps not suited to industrial scale.
Yes, I expect nuclear is the best choice of a list of 1, but it will be substantially harder to build one on Mars than here. For starters the lack of water, and the lack of atmosphere density would result in substantial cooling challenges.
However you slice it, energy on Mars is completely dependent on earth. Panels, batteries, uranium- none of it can be made on Mars, and all have "short" lifespans.
chii
> the lack of atmosphere density would result in substantial cooling challenges.
heat exchange(s) such that the human settlement(s) are warmed by this "waste" heat? Mars is cold, and likely need to have many pipes to generate heat for human settlement, so why not build it in via this need?
roygbiv2
I find it pretty amazing that it only gets 43% of the solar energy as Earth,with it being our neighbour.
stevage
Could always build a helioplex - a gigantic solar concentrator.
strken
Can't you eventually mine and enrich uranium on Mars itself?
bruce511
It's possible, although unlikely, that there are mineable deposits of uranium on Mars. There are trace amounts, but its unlikely that minable deposits formed.
chii
why is there unlikely to be mine-able uranium deposits? It's not like there's some geological process on mars that strips it away (presumably).
metalman
cooling can be done with radiators pointed north, into the permanently black sky,with essentialy no convective heat gain or loss, build for noon in mid summer, and forget about it lots of things work on mars that dont work here, Thin film prevoskerite solar ,which is sensitive to water and oxygen and therefor difficult here, can be sprayed on whatever is handy on mars(oversimplification, but), and the same goes for a smelter that is electric, where one of the byproducts is oxygen driven off, hand that, and that high quality metal and castings will be possible as the lack of atmospheric oxygen and low pressure will de gass metals, also metals wont corode after bieng made. given the very low night time temperatures, it should be quite easy to liquify martian "air" and use it for day time cooling where needed and also the exraction of trace gasses other than CO², which is the bulk.
none of that maters without a good supply of water to crack for fuel and air and general living, and as there is a whole world to work with, it is likely that there are a few areas that will have a fortuitous convergence of ALL the things possible, in one spot, kind of like early settlers finding a stand of trees, felled by beavers, bark stripped and pre notched for assembly into a cabin, next to a pond with fish and medows all around
to put things in perspective
pure gold would be good for use as sheet metal, as it's ductility and ease of refinement would make it the cheapest alternative
it's doable, but only just, and only if we get our shit together and decide that an impossible, ultra long term project to become an interplanitary species is a better way to use our excess capacity than whatever the fuck it is we are doing now
gsf_emergency_2
You can get regolith simulant from Amazon, please do try this at home
https://www.themartiangarden.com/ https://www.amazon.com/Regolith-Simulant-Authentic-Martian-R...
ChuckMcM
Pretty neat. This would certainly make for an interesting Mars mission should SpaceX want to try it, land a lander, have the lander process regolith into iron chunks, create a pile of chunks. All good threshold goals.
What ever happened the asteroid mining folks? They have a similar problem, albeit with very little gravity and no atmosphere, but their metals are in theory worth a lot more (platinum, gold, silver, Etc.)
There was a similar idea/proposal for extracting aluminum from Lunar regolith, also a good space mission for private interests.
Once you've got basic metals you can make more interesting things, with iron you can make reinforced concrete which would be an interesting building material on Mars I suspect.
jacquesm
Asteroids are hit-and-miss composition wise (though you can determine quite a bit by observing them), but when they are a hit they tend to be really valuable. The problem then is that you need to get to them and then the next problem is that you need to get back to where you came from.
Both of these can hurt your ROI considerably assuming you can solve for them at all with the masses involved. They're also usually moving at a pretty good clip and are bad to set up long term for. I think until we have a long term presence in the asteroid belt that this is mostly going to be SF rather than that it will actually happen.
lstodd
delta-V happened to asteroid folks.
there are no realistic proposals for asteroid drives ala https://en.wikipedia.org/wiki/K240
PaulHoule
The product I have in mind is solar sails to be delivered to the Earth-Sun L1 point to counteract climate change. A carbonaceous chondrite asteroid is rich in volatiles to make plastic films as well as metals and stones to coat them with. The pros are:
- solar sails transport themselves without using reaction mass
- you're not competing with cheap resources on Earth to be used on Earth, rather resources from Earth transported past LEO
eliminating many of the fundamental objections to scenarios where ISRU materials get transported somewhere.
Cons are:
- a good sunshade and a good solar sail are different things
- plastic + metal solar sails seem to get corroded badly over time
- if you think the turnaround time between Earth and Mars is bad, you are talking half a decade or more to round trip parts plus a 45 minute communication delay at some times; you either need to send people with all the problems that entails or have advanced autonomy and a manned simulation platform somewhere in near-Earth or cislunar space.
I've got a good picture of what parts of the "head end" that consumes asteroid materials and turns them into reasonable chemical feedstocks looks like with the exception of how to devolatize the asteroid to begin with and where to get the storage tanks to store early offgassing before the metals line comes online. (Storage tanks are an interesting question for manufacturing since the chemical factory needs plenty of them.) I also have some idea of what the "shipyard" that builds the actual sails look like. Trouble is you probably need a Drexler machine to make spare parts and also make customized parts given that you don't really know what you're up against when it comes to the "head end" (though upper pyramid parts of the chemical factory and the shipyard can be simulated close to Earth) ... and Drexler's concept for a Drexler machine doesn't work.
teiferer
> to counteract climate change
Seems way easier to get our act together on earth. It's all solved from a technological angle.
lstodd
If you so very want some mylar over carbon fiber put up in L1, and not ever launch that from Earth then Luna is the most obviously cheap and abundant source of whatever. No need for asteroids at all. Also the comms delay is 1.25s IIRC.
I personally consider this a folly.
On the other hand, no comprehensive survey of Luna was ever done, and we target Mars or even asteroids why? I'd like some at least plausible reason for this.
It is true that Luna is halfway to Mars in dV on hohmanns. But not in time spent. Never will be.
rkagerer
Apropos of nothing, was the PC version/successor Fragile Allegiance as good/better than K240?
MangoToupe
Why can't you just use a mass driver? Just mine bits of the asteroid and fling them. The biggest problem would be fueling this, and nuclear is probably quite cost effective. (Shout out to KSR's fantastic mars trilogy for this idea.)
Sure, this would be slow. But I think it'd be viable. You could move them into earth's orbit or even slam it into the moon.
m4rtink
A mass driver would run off a capacitor bank most likely - can't you just charge that by a solar array ? Unless you really need to send huge amounts, this should be much less hassle than lugging a nuclear reactor around. And for near-Earth asteroids, you should get the same power per square meter, but better (no atmosphere & clouds to get in the way) at least half of the time (considering the asteroid rotates - and even that could be handled by clever engineering/tethered array).
cyberax
Uhh... Why? Getting stuff from an asteroid orbit to Earth needs a delta-v of around 1 km/s. You can even get to circularize the orbit if you're comfortable with doing a couple of gravitational assists.
You won't be moving the whole asteroids, but a few hundred tons of extracted platinum-group metals? Certainly doable.
thaumasiotes
> There was a similar idea/proposal for extracting aluminum from Lunar regolith, also a good space mission for private interests.
With the asteroids, I assume the idea is to bring enough platinum and gold back to Earth to offset the costs of getting them from space. That doesn't sound especially realistic, but in the right circumstances I guess it could be.
With aluminum on the moon or iron on Mars, that will never happen. You'd have to want to use those materials on location.
So what would the value be of producing aluminum on the moon?
jacquesm
> So what would the value be of producing aluminum on the moon?
Building more rockets? Interesting detail: there isn't enough oxygen there to cause aluminum to immediately be covered with a skin of aluminum oxide. I wonder what the energy cost of an extraction process for aluminum on the moon would be. At the same time I would hate to see the moon mined, that's one piece of common property that we should maybe try to preserve unless we have no other alternative, not just for commerce.
PaulHoule
The idea you see in O'Neill and other science fiction that iron is rare on the moon is bunk. There is Hematite
https://www.jpl.nasa.gov/news/the-moon-is-rusting-and-resear...
and Apollo astronauts brought back perfectly good Iron ore. It's true that there is lot of aluminum and titanium on the moon and a lunar economy might use that but there is enough iron that if loonies wanted to make things out of iron they could make things out of iron.
wewtyflakes
Why preserve the current landscape of the moon? It harbors no life, and its surface is scarred by billions years of space collisions.
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pstuart
24/7 solar furnaces harvesting asteroids seems like a huge industry once it's figured out. The big problem is that it would take a billionaire to make it happen.
aj7
I have a fairly generic reaction to this.
Make metals at the top of Everest. Then we’ll talk.
adastra22
You’re right, that is a generic reaction. And completely ignorant of the different chemistry, environment, and context.
wiml
Really? Seems like building a manufacturing capability on Everest or Antarctica or a Saharan dune sea would be easier in every single way.
margalabargala
You're right, it would be easier in every single way.
It would also be different enough that it's not a useful or meaningful comparison. You might as well say "bake a cake while standing on stilts, then we'll talk".
By the way, humans have been mining, and on-and-off purifying, iron from the Saharan dune sea for a thousand years. https://en.m.wikipedia.org/wiki/Zou%C3%A9rat
adastra22
While there is a lot that could be said about this at the object level, the correct answer is “so what?”
teleforce
>Swinburne and CSIRO researchers have successfully made iron under Mars-like conditions, opening the door to off-world metal production.
Not trying to be pedantic but really curious, it should be off-earth not off-world, right?
Off-world meaning that the iron production is made by alien not human.
zokier
Google defines (citing Oxford Languages) offworld as:
* away from earth or (in science fiction) from a place treated as the native world.
* involving, located in, or coming from a place outside one's native world or planet.
While Wiktionary defines it as:
* (chiefly science fiction) Not on Earth.
* (chiefly science fiction) Away from Earth.
https://en.wiktionary.org/wiki/offworld
To me that sounds like Mars would qualify
comechao
On the topic, the ANTHROFUTURISM YouTube channel is excellent for learning about building on the Moon using regolith: https://www.youtube.com/@Anthrofuturism
nine_k
In short: they just heated some (simulated) Martian dirt, and this alone was sufficient to produce liquid iron, and then liquid iron-silicon alloy. No huge quantities of carbon were required. This is quite surprising to me.
Making steel, with controlled carbon content, would be quite another challenge. Carbon is readily available on Mars, but only in the form of CO2.
PaulHoule
Steel has between 2% and 0.05% carbon, that's not really a lot, particularly when you consider martian colonists will want materials like sugar and polyester that have a much higher carbon content. [1]
There are numerous ways to fix carbon from CO2. If you can grow plants you can make a char out of them which what people used to use to reduce iron and add carbon as an alloying elements. There is a huge amount of research on turning CO2 into CO so that it can be mixed with H2 (then they call it syngas) and then build up larger molecules such as methane, methanol, gasoline, fats, etc.
https://news.mit.edu/2024/engineers-find-new-way-convert-car...
It's not a question of being able to do it but instead doing it better, cheaper, harder, faster, ...
The funny thing about reduction of iron (and many metals) is that it can be done with either of the two ingredients of syngas, CO [2] or H2 and either way you get the oxide CO2 or H2O as a byproduct. If space colonists think that volatiles are precious they'll practice chemical cycling, turning those back into reactive CO or H. On the moon or asteroids I'm pretty sure people would think either C or H2 is precious and wouldn't waste it, I am not sure about Martians (e.g. if you can get CO2 out of the atmosphere it might not seem like a crime to vent it)
[1] people think "technology" and they think "metals" but actually a lot of what you want is made of carbon, hydrogen, oxygen and nitrogen (CHON)
[2] what a blast furnace uses
nine_k
Yes, the problem is likely not in getting enough carbon (though a kiloton of steel would require several tons of it), but rather having a mass production process advanced enough to precisely control it. Almost all heavy equipment would have to be bootstrapped on Mars, mostly from the inevitably subpar local materials, and ith access to energy that's worse than on Earth: no fossil fuels, no hydro-energy, much less sunlight.
PaulHoule
Everyone who's seriously considered space colonization has come to the same conclusion that Eric Drexler did -- you need to have some kind of system that can make absolutely everything with as small a population supporting it as possible.
You've got the problem that there's nothing that could manufactured on Mars that would be worth bringing back to Earth. If a Martian colony was dependent on Earth for anything it would expect to get its resources cut off at any time, and even if you can get spare parts and stuff from Earth the turn-around time counting the synodic period and transit time will always be several years. See
https://en.wikipedia.org/wiki/The_Martian_Way
I think it could be possible with some combination of synthetic biology, fermentation, flow chemistry, 3-d printing and such. It's a good northstar for research into "advanced manufacturing" which could come in handy here on Earth.
cindyllm
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staticautomatic
Iron would be fine since there’s basically no atmosphere to oxidize it right?
dmurray
No, steels have 4-6x higher tensile strength (and better performance in other related properties) than raw iron. [0] They're not just preferred over iron for their corrosion resistance.
And note that even what we call "cast iron" - a material that reasonably could be preferred to steel for some industrial purposes - is an iron-carbon alloy that in fact has more carbon than steel[1].
[0] https://www.texasironandmetal.com/strength-of-steel-compares...
rolph
oxidation is a chemical process, [LEO says GER] that which Loses Electrons is Oxidized, that which Gains Electrons is Reduced.
it isnt always oxygen that does this, a difference of RedOx potential allowing redistribution of electrons is all you need.
mars has a perchlorate problem thus carbon compounds are converted to carbonate via Oxidation when encountering ubiquitous perchloate mineral deposits.
its toxic to carbon based biochemical forms, and destructive to carbon materials, such as carbon fibre; carbon nanotubes; carbon steel; even a lot of keypads.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Pesky Perchlorates All Over Mars:
XorNot
We learned it as OILRIG: oxidation is loss, reduction is gain
Yoric
Isn't steel also much stronger?
foota
Iron is a lot heavier than steel and probably weaker too (IINAMS, ask your material scientist)
adrian_b
By "iron", I assume that you mean "cast iron", as pure iron is hardly used for anything.
Cast iron is lighter than steel, not heavier, because of its higher carbon content.
However, objects made of cast iron are indeed heavier than similar objects made of steel, and this is what you must have in mind, because the objects made of cast iron are always made thicker, both because cast iron is weaker, which requires greater thickness for the same strength, and because it is harder to make thinner objects by casting than by forging.
ACCount37
It's a given that if you're taking space exploration seriously, you need ISRU. You can't ship everything to Moon or Mars from Earth - you need to learn how to process and refine local materials.
This is the key advantage of going to Mars or Moon surface, as opposed to operating a space station. A space station exists in a vacuum. Surface bases have access to local materials.
Sadly, very few planned space missions have this kind of ambition. That recent proposal US had about putting a nuclear reactor on the Moon was at least a step in the right direction - if you're bringing an entire reactor, that means you're establishing a permanent base, complete with an industry that would generate the demand for power.
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mcrider
There’s a good recent book series about this by Daniel Suarez called Delta V (in the first book they process regolith from an asteroid; in the second book its on the moon; presumably the unreleased third book is on Mars).
There is the small detail of heating the regolith to 1400c. It's not very clear where that energy comes from (at least not at scale).
Burning fuels seems to be out. So I guess nuclear or solar?
Mars solar is weaker than earth, but I guess let's of panels plus lots of batteries could work. Sorta. Not sure it produces "tons" of material very quickly.
Nuclear is the other option. But would rely on fuel from earth. Not to mention that building a reactor big enough to sustain a colony, plus industry, would be challenging. And of course landing fresh uranium on Mars would be risky. (It's heavy, and any accident would render a chunk of Mars radioactive for quite some time.)
Oh, and the reactor would need to be air-cooled not water-cooled.
But, I guess, yay regolith?