In the 1898 novel Edison’s Conquest  of Mars, astronauts travel to the Moon and find, among other things, some mountains made out of diamond-like “moon jewels.” According to the narrator, these  mountains could provide, quote, “an inexhaustible mine of wealth”.

And over the past two centuries,  the idea of a lunar mine… as well as mines on asteroids and  comets…has gained a lot of traction. Not to extract moon jewels of course, but water, oxygen, helium-3,  and a ton of different metals.

There’s a whole heap of challenges,  but a lot of interested parties are working on ways to access  those precious, precious resources. For example, to collect certain metals, we may wind up launching a  crew of microscopic miners. [♪ INTRO] Our moon contains a ton of  different types of metals, everything from boring old  aluminum and iron to the rare earth elements that are critical  components in a lot of modern technology. People might want to ship some  of those metals back to Earth.

And some, they might want to keep  up in space so they don’t have to waste a bunch of money and rocket  fuel launching materials from Earth. But wherever these metals end up, scientists are trying to work  out exactly how to mine them. That includes one particularly  nifty technique called biomining.

While we often think of mining as a  huge operation involving pickaxes, explosives, and power tools, mining  at its core is just any method by which we extract metals from the ground. And as the name implies, biomining relies on biological organisms, like microbes and fungi. It might seem far-fetched, but biomining  is actually being used on Earth right now!

Not in random R&D labs, but actual industry. It’s estimated that about 1/5 of  copper production comes from biomining, and biomining has also been used to extract other metals like uranium, nickel, and gold. But why would microbes even want to mine metals?

Well, as much as microbes  want to do anything, anyway. It turns out they care less about the metal, and more about the electrons  in all those metallic atoms. Certain types of microbes and fungi  gain energy from a chemical reaction called oxidation, which causes a  chemical compound to lose electrons.

Those lost electrons don’t just  disappear, they simply go somewhere else. And that going means the microbe or  fungus has a form of energy transport and leaves behind a chemically-altered  version of the metal that humans can use. When a metal becomes oxidized, it can take  on some radically different properties.

The classic example is iron becoming rust. But for biomining, we mostly  care that some oxidized metals will become more soluble. In other words, they’ll dissolve way easier.

What are they dissolving into? Probably an acid. The species that we use for  biomining tend to thrive in acidic environments, so that’s  the set-up they get to live in.

Now, there are a few different kinds of biomining, but all of them involve getting  ores in acid at some point. For example, a technique called  heap leaching involves crushing up your chunks of ore, stacking  layers of all that crushed ore onto an impermeable sheet, and then  pouring acid over the whole thing. But what all of these set-ups  have in common is that after the metals get oxidized by the microbes, either directly or indirectly, they slip out  of the rocks and minerals and into the acid.

That acid then gets collected, and put into a bioreactor so the metals can get extracted. There are a lot of different  extraction techniques and they all involve chemical reactions  that turn the metals insoluble again. And being insoluble means they’ll  settle out of the solution, turning into little grains or  flakes of a metallic compound.

From there, a process called  electrowinning is used to make the flakes settle onto a  plate, forming a coating that can then be collected and  used for whatever you want. Compared to more traditional mining  methods, biomining has a few perks. For example, the microbes we use can do their little miner jobs at  a cool 50 degrees Celsius.

Which yes, is not a temperature you  or I would ever want to work in. But compare that to the  furnaces we use to smelt metals, which can regularly reach  temperatures of 1000 degrees Celsius. Since biomining can be  operated at lower temperatures, and without using so many toxic solvents, it reduces the pollution  associated with traditional mining.

It’s also a lot less  energy-intensive, meaning that it’s not as expensive as traditional  mining, and can be used to process low-grade ores which would be a waste of  money to tackle using normal tools. And it requires much less equipment than  traditional mining … at least on Earth. But this episode isn’t about biomining on Earth.

It’s about biomining on the Moon,  and moon-adjacent objects in space. How feasible is this plan? Before we can answer that  question, here’s a quick ad.

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Our outer space treaties aren’t  particularly robust at the moment, which leaves room for exploitation. And there are enough examples  from history that if there’s a loophole anywhere in legislation,  someone will walk through it. But even if everyone got along  and promised not to stripmine the solar system for profit,  would biomining even work?

Well, in contrast to all those perks I mentioned, biomining does have its downsides. It takes far longer than  traditional mining techniques, and requires very specific  temperature conditions to function, which would be hard to maintain in space. For example, over the course  of the 4-week-long lunar day, the surface at the Moon’s  equator can swing between about -130 degrees all the  way up to 120 degrees Celsius.

Biomining reactions are also usually aerobic, meaning that they require oxygen gas. And the Moon is not exactly  known for having a lot of that. On Earth, biomining is considered a complement to traditional mining, not a replacement.

So it’s going to take time  to scale up this technology so it can be used on its own in  an entirely different environment. That said, initial tests have been promising. Two successful biomining  experiments have been conducted on the International Space Station.

And one of them was done using  actual chunks of asteroid, instead of rocks from Earth  that were a close enough match. Another study showed that you can  take rocks similar to those on Mars and the Moon and then  extract iron that can then be 3D printed into structural materials. In other words, astronauts  might be able to build out their Mars base with Martian iron.

And even more research has found that  at least one biomining fungus species isn’t hindered by the Moon’s lower gravity. So that’s promising, too. But there are still a few kinks to work out.

Lunar dust is super fine, super  clingy, and super abrasive, which can be murder on machines. And while biomining on Earth requires  less equipment than traditional methods, biomining on the Moon is going to need more, since those microbes won’t survive  when exposed to an airless world that swings hundreds of degrees  over the course of a day. Proponents of biomining say that  these are just “technical challenges” that will eventually be  overcome with new technology.

But it remains to be seen whether biomining would be an effective use of anyone’s time. Still, the science seems to show  that biomining could be possible. And with as much power and money  behind it as it seems to have, we could be getting some of our rare  metals from space sooner than we think. [♪ OUTRO]