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Munching microbes do heavy work in the mining industry, extracting metals such as copper and gold from the earth. They could also mine rare earth elements such as lanthanides, scandium and yttrium, expensive minerals used in electronics and some metal alloys.
Such microbes could also aid in space mining, according to a new study (Ski Adv. 2020, DOI: 10.1038 / s41467-020-19276-w). Experiments conducted on the International Space Station (ISS) have shown that the bacterium Sphingomonas desiccabilis was efficient in extracting 14 different rare earth elements from basalt under conditions of microgravity similar to those on the Moon and Mars, as it is under Earth’s gravity.
This means that a human settlement on the moon or Mars could potentially extract rare earth elements from the surrounding environment for use in the construction of rovers, electronic equipment and other technologies, says Charles Cockell, an astrobiologist at the University of Edinburgh, who led the she studies. “Wherever we go, we will have to mine planetary materials or asteroids to sustain a long-term presence in space,” he says. “Here is a demonstration of a particular approach.”
On the ISS, astronauts added the bacterium and basalt into miniature reactors under microgravity conditions and specially designed incubators that contain centrifuges that can simulate gravity on Mars and Earth. The team chose basalt because it has a high concentration of rare earth metals and is similar to the rock found on the Moon and Mars. Fluids don’t mix as well under microgravity conditions as they do on Earth, so Cockell and his colleagues speculated that microbes might not munch on basalt as effectively. But after 3 weeks, the insects were found to perform equally well in all three gravity conditions. “It was really the first mining experiment in space,” says Cockell.
Some microbes extract the metal from the rock by acidifying the medium, but this was not the case here. Instead, S. desiccabilis expels the polysaccharides that bind to the metals, preferentially grabbing the rare earth metals. Cockell and his colleagues are now studying how microbes absorb metals.
The great thing about the approach is that a tiny vial of cells can self-assemble in a mining operation, says Buz Barstow, a synthetic biologist at Cornell University who wasn’t involved in the study. But rare earth elements are relatively rare, he says, so many microbes would be needed to generate even small amounts of minerals, and those cells would need a lot of sugars to fuel their metabolism. Scientists will need to figure out how to produce enough nutrients in space to support cell growth, he says.
“There are obviously many steps” from this prototype to a biomination system that could be used in space, says Barstow, “but they got off to a great start.”
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