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Microbes can be the friends of future colonists living from earth to the Moon, Mars, or elsewhere in the solar system and aiming to establish self-sustaining homes.
Space colonists, like people on Earth, will need so-called rare earth elements, which are essential to modern technologies. These 17 elements, with intimidating names like yttrium, lanthanum, neodymium and gadolinium, are sparsely distributed in the earth’s crust. Without rare earths, we wouldn’t have certain lasers, metal alloys, and strong magnets used in cell phones and electric cars.
But their extraction on Earth today is a difficult process. You have to crush tons of ore and then extract a small amount of these metals using chemicals that leave rivers of toxic wastewater behind.
Experiments on the International Space Station show that a potentially cleaner and more efficient method could work on other worlds: letting bacteria do the complicated job of separating rare earth elements from rocks.
“The idea is that biology essentially catalyzes a reaction that would happen very slowly without biology,” said Charles S. Cockell, professor of astrobiology at the University of Edinburgh.
On Earth, these bio-extraction techniques are already used to produce 10 to 20 percent of the world’s copper and also in some gold mines; scientists have identified microbes that help leach rare earth elements from rocks.
Dr Cockell and his colleagues wanted to know if these microbes would still live and function as efficiently on Mars, where gravity’s pull to the surface is only 38% that of Earth, or even without gravity. So they sent some of them to the International Space Station last year.
The results, published Tuesday in the journal Nature Communications, show that at least one of these bacteria, a species called Sphingomonas desiccabilis, is insensitive to different forces of gravity.
In the experiment, called BioRock, 36 samples were launched into orbit in matchbox-sized containers with slices of basalt (a common rock made from cooled lava). Half of the samples contained one of three types of bacteria; the others contained only basalt.
At the space station, Luca Parmitano, an astronaut with the European Space Agency, placed some of them in a centrifuge launched at speeds to simulate the gravity of Mars or Earth. Other samples have experienced the floating environment of space. Additional control experiments were carried out in the field.
After 21 days, the bacteria were killed and the samples returned to Earth for analysis.
For two of the three types of bacteria, the results were disappointing. But S. desiccabilis increased the amount of rare earth elements extracted from basalt by about a factor of two, even in a zero gravity environment.
“It surprised us,” said Dr Cockell, explaining that without gravity, there is no convection which usually flushes bacteria waste and replenishes nutrients around cells.
“You could then hypothesize that microgravity would prevent microbes from bio-mining or stress them to the point where they wouldn’t do biomining,” he said. “In fact, we didn’t see any effect at all.”
The results were even better for the lower gravity of Mars.
Payam Rasoulnia, a doctoral student at the University of Tampere in Finland who has studied bio-extraction of rare earth elements, called the results of the BioRock experiment interesting, but noted that the yields were “very low even. in ground experiments ”.
Dr Cockell said BioRock was not designed to optimize extraction. “We are really looking at the fundamental process behind biomining,” he said. “But this is certainly not a demonstration of commercial biomining.”
SpaceX’s next cargo mission to the space station, currently scheduled for December, will feature a tracking experiment called BioAsteroid. Instead of basalt, containers the size of a matchbox will hold pieces of meteorites and mushrooms. They, rather than bacteria, will be the agents they will test to break down the rock.
“I think you could possibly evolve that to do it on Mars,” Dr Cockell said.
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