(Inside Science) -- The moons, planets and asteroids of our solar system are full of useful stuff: water to make hydrogen fuel, metals and minerals for construction, even rocks that can be broken down into soil-like material for farming and terraforming.
“Virtually all the raw materials you need to build anything in space is already there,” said Chris Dreyer, a mechanical engineer who studies space resources at the Colorado School of Mines in Golden.
The tricky part is efficiently extracting these precious resources upon reaching another world.
Three bacteria for mining in space
An experiment that launched on July 25, headed for the International Space Station, will test the ability of bacteria to do the job -- a process known as biomining. The experiment consists of 18 small biomining reactors, each of which is about the size of a deck of cards and includes two small reaction chambers.
“They’re the first prototype miniature mining reactors to go to space,” said Charles Cockell, an astrobiologist at the University of Edinburgh who is leading the project.
Within them, three different types of bacteria will be grown on basalt, a common volcanic rock that makes up much of the crusts on the moon and Mars. The three microscopic astronauts are Bacillus subtilis, a common species of bacteria found in soil on Earth as well as inside human guts; Sphingomonas desiccabilis, a species of bacteria that is known for its ability to break down rock; and Cupriavidus metallidurans, a heavy-metal-resistant organism sometimes found in the cooling pond of nuclear reactors. One-third of the reactors aboard the space station will be kept in the normal microgravity of the space station, while another third will be kept in a centrifuge simulating the 0.38 g gravity of Mars, and the final third in a centrifuge simulating Earth's gravity.
When the reactors return to Earth in a few weeks, Cockell and his team will study what metals and minerals the microbes were able to extract from the basalt, and how effective they are as biominers. They will also examine the bacterial biofilms that form on the rocks, and the plastic membranes on the sides of the small blocky reaction chambers within each reactor, to see how the mining activity is affected by varying levels of gravity. “There’s a lot going on in these little one-centimeter-cubed boxes,” said Cockell.
An organic alternative to machines
Most ideas for asteroid mining don't include microbes. They involve capturing an asteroid and heating it up until it melts, to extract the desired materials, said Dreyer. These methods face challenges such as the high temperatures needed to melt the ores and the need for new techniques to separate lighter elements from heavier ones in the absence of gravity. Biomining could circumvent these hurdles.
According to Cockell, biomining is not a new concept, and has been widely used for commercial mining operation on Earth, including about 20% of current copper production.
Some microbes can be highly effective at getting metals and minerals out of rocks, said Dreyer. “There are microbes that have been doing this for millennia,” he said. “Some of the ores that we mine on Earth are actually their byproducts.”
The downside, said Dreyer, is that the microbes will likely work much more slowly. “It will take time for the bacteria to extract useful amounts of material,” he said. For now, he thinks that microbes might be most useful as a way of concentrating the target metals before further processing.
Dreyer expects asteroid mining to become a reality within the next 10 years. The first efforts will probably focus on collecting and processing water to use as propellant. That will make moving around space much less expensive, he said, by removing the need to haul tons of rocket fuel up from Earth. That will allow the next step: mining metals and rocks to build ever larger structures in space.
“Microbes are everywhere on Earth, there’s no escaping them, and when we go to space they follow us,” said Cockell. “Rather than see them as detrimental, why not think about how we can use them?”