Microbes may be our miners on asteroids, moons and other planets

Originally published on November 21, 2020.

Microbes could be put to use in future human space settlements extracting metals and rare elements from rocks, according to a researcher who designed the world's first mining experiment in space. 

"You can think of microbes as miniature miners, if you like, going into rocks and getting all that good stuff that we need to build a civilization," said Professor Charles Cockell, an astrobiologist from the University of Edinburgh.

If humans are ever going to settle in space or on other planets, they'll likely need to find ways to efficiently find and harvest resources in alien environments. Mining will be a key technology in that effort.

Cockell told Quirks & Quarks host Bob McDonald that microbes are currently used on Earth to extract materials of value from rock

"If those rocks happen to contain gold or copper, then we can use the microbes to break down those materials," he said.

That straightforward result was very exciting because that was the first demonstration of mining beyond the earth.- Prof. Charles Cockell, University of Edinburgh

Human miners crush the rocks and add liquid — usually water — to activate microbes dormant in the ore.

The microbes then use chemical processes to break down rocks — essentially digesting them — to access nutrients like phosphorus and nitrogen. Valuable metals and minerals can be a bacterial waste product.

"The leachate, which is the liquid that comes out of the rocks, contains the elements that you want to get hold of," added Cockell. Those elements can then be easily extracted from the leachate for use.

On Earth, mining companies use bacteria to extract about 20 per cent of the world's copper and five per cent of our planet's gold.

Potential complicating factors in low gravity

Cockell wanted to see whether microbes would do the same job in space. In 2019 he was able to send an experiment to the International Space Station to test this. He just published the results of his study in the journal Nature Communications. 

The issue he was particularly concerned with was whether the micro-gravity environment of the space station would cause the microbial cells to behave any differently in processing minerals in space than they do on Earth. 

His concern in particular was whether the lack of gravity would mean the bacterial cells couldn't move to the right places in the rock and water slurry, or if it would disrupt the normal circulation processes that on Earth cause mixing of fluids around the rock particles, which allows the microbes to access them. Whether the rock-eating microbes would thrive and reproduce in space was also an issue.

"Many people have shown that gravity does affect microbial growth in space," said Cockell. "So we were simply testing whether Martian gravity and micro-gravity, for example, and asteroids would change the way in which bio-mining occurred."

Mining experiment aboard the ISS

In their space station experiment they tested three different bacterial species in different gravity conditions to mimic gravity on an asteroid or on Mars. 

"We spent several years designing a miniature biomining reactor. And this is essentially a small piece of kit in which you put your pieces of rock, in our case, basalt and your dried microbes," described Cockell.

The basalt rock they used in the experiment is similar to what's found on the moon or Mars.

Italian astronaut, Luca Parmitano, put the biomining reactor into a miniature centrifuge that spun the samples around to simulate different gravity conditions.

The microbes were then left to grow and feed for 21 days. Samples were then flown back to Earth for analysis.

One of the bacterial species they tested is called Sphingomonas desiccabilis, and naturally lives in salt and rock crusts in deserts. Cockell said it "did successfully extract rare earth elements out of the rock."

"That straightforward result was very exciting because that was the first demonstration of mining beyond the earth."

He said what was even more interesting though, was how the microbes managed to overcome the problem of different gravity conditions — perhaps by changing their rate of growth — to eventually reach the same concentration of bacterial cells in the reduced gravity conditions as in the Earth's gravity.

"What our experiment suggests is that you can do biomining on asteroids or Mars, just as you can do on the Earth," he said. "These different gravity effects should not change our ability to do biomining."

A step toward self-sustainability in space

Cockell said he envisions settlements on the moon or Mars, or bases on an asteroid, and nearby, there could be a giant processing facility where microbes could be used to help break down rocks to extract desirable elements.

One concern with this technology, however, would be potential bacterial contamination of places like Mars where scientists are searching for signs of Indigenous life. 

"There's clearly a trade off there. And there's clearly a discussion to be had about whether you want to use biomining or other types of mining," said Cockell who added there is a lot more research to do before we reach that point.

He has another experiment called "BioAsteroid," which is scheduled to fly in a few weeks time. in which astronauts will conduct the same biomining experiment, but using a crushed up meteorite instead of Mars-like rock.

Produced and written by Sonya Buyting