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Microbes could be friends of future settlers who live off the earth on the Moon, Mars or elsewhere in the solar system and aim to create self-sufficient homes.
Space settlers, like people on Earth, will need what are known as rare earth elements, which are critical to modern technologies. These 17 elements, with daunting names such as 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 powerful magnets used in cell phones and electric cars.
But extracting them on Earth today is an arduous process. It requires crushing tons of ore and then extracting fragments of these metals using chemicals that leave rivers of toxic wastewater.
Experiments conducted aboard the International Space Station show that a potentially cleaner and more efficient method could work on other worlds: letting bacteria do the messy job of separating rare earth elements from rock.
“The idea is that biology is essentially catalyzing a reaction that would occur very slowly without biology,” said Charles S. Cockell, professor of astrobiology at the University of Edinburgh.
On Earth, such biomining techniques are already used to produce 10 to 20 percent of the world’s copper and even 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 just as effectively on Mars, where gravity’s pull to the surface is only 38 percent of Earth’s, or even when there is no gravity at all. So last year they sent some to the International Space Station.
The results, published Tuesday in the journal Nature Communications, show that at least one of those bacteria, a species called Sphingomonas desiccabilis, is unaffected by the 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 of 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 from the European Space Agency, placed some of them in a centrifuge spinning at speed to simulate the gravity of Mars or Earth. Other champions have experimented with the free environment of space. Further control experiments were conducted on the ground.
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 the zero-gravity environment.
“This surprised us,” said Dr. Cockell, explaining that without gravity, there is no convection that usually carries waste away from bacteria and replenishes nutrients around cells.
“One could therefore speculate that microgravity would prevent the microbes from biomining or stress them to the point where they weren’t biomining,” he said. “In fact, we didn’t see any effect.”
The results were also slightly better for Mars’ lower gravity.
Payam Rasoulnia, a PhD student at the University of Tampere in Finland who has studied biomining of rare earth elements, called the results of the BioRock experiment interesting, but noted that yields were “very low even in ground experiments.” “.
Dr Cockell said BioRock was not designed to optimize extraction. “We are really looking into the fundamental process behind biomining,” he said. “But certainly this isn’t a demonstration of commercial biomination.”
The next SpaceX cargo mission to the space station, currently scheduled for December, will bring a follow-up experiment called BioAsteroid. Instead of basalt, matchbox-sized containers will contain pieces of meteorites and mushrooms. They, rather than the bacteria, will be the agents they test to break down the rock.
“I think eventually, you could scale this to make it to Mars,” said Dr. Cockell
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