It is a well-known fact that humanity must bring Earth’s environment with it if it wants to explore space and live and work on other planets. These include life support systems that utilize biological processes – also known as: bioregenerative life support systems (BLSS) – but also the many types of microbes that are essential to living systems. Humans already bring microbes with them when they travel into space, particularly to the International Space Station (ISS). These microbes become part of the natural environment, sticking to surfaces, growing in nooks and crannies, and getting into everything.
Given their constant presence, it is paramount that we understand how they survive in space. Additionally, they have potential uses that could enable greater self-sufficiency in space. For example, certain species of bacteria and fungi extract minerals from rocks as a source of nutrients. In a recent study aboard the ISS, researchers from Cornell and the University of Edinburgh examined how these species could be used to extract platinum from a meteorite under microgravity conditions. Their results suggest that this could be an effective method for extracting mineral resources in space and reducing dependence on Earth.
The study was led by Rosa Santomartino, an assistant professor of biological and environmental engineering at Cornell’s College of Agriculture and Life Sciences (CALS), and Alessandro Stirpe, a research fellow in microbiology at Cornell and the School of Biological Sciences at the University of Edinburgh. They were joined by researchers from the Medical University of Graz in Austria, Rice University, Cancer Research UK, the UK Center for Astrobiology at the University of Edinburgh, Kayser Space Ltd and Kayser Italia. Their study was published January 30 in npj Microgravity.
*A bioreactor manufactured by the BioAsteroid project at the University of Edinburgh. Photo credit: University of Edinburgh*
The work was part of the BioAsteroid project, a collaborative initiative between the University of Edinburgh and the European Space Agency (ESA). This project is led by Charles Cockell, a professor of astrobiology at the University of Edinburgh and senior author of the study. Cockell and his colleagues developed “biomining reactors” that were deployed on the ISS in late 2020/early 2021 to study how gravity affects the interaction between microbes and rocks in microgravity.
These reactors contained samples of an L-chondrite asteroid that were treated with the bacterium Sphingomonas desiccabilis and the fungus Penicillium simplicissimum. These microbes are promising for raw material extraction because they produce carboxylic acids that bind to minerals and release them from rocks. However, there is still uncertainty about how this mechanism works. To this end, the experiment also included a metabolomic analysis, in which part of the liquid culture was extracted and analyzed for biomolecules and secondary metabolites. As Santomartino said in a Cornell Chronicle press release:
This is likely the first experiment of its kind on the International Space Station [a] Meteorite. We wanted to keep the approach individual but also general to increase its impact. These are two completely different species, and they will extract different things. So we wanted to understand what and how, but keep the results relevant for a broader perspective, since not much is known about the mechanisms that influence microbial behavior in space.
The experiment was conducted aboard the ISS by NASA astronaut Michael Scott Hopkins, while the researchers conducted their own control version in the laboratory. This allowed them to examine how the experiment would work in weightlessness compared to Earth’s gravity. Santomartino and Stirpe then analyzed the experiment data and showed that of the 44 different elements, 18 were extracted through biological processes. Stirpe said:
We broke the analysis down to the individual element and asked ourselves, “Okay, does extraction behave differently in space than on Earth?” Are these elements more extracted if we have a bacteria or a fungus or if we have both? Is this just noise, or can we see something that might make a little sense? We don’t see any major differences, but there are some very interesting ones.
NASA astronaut Michael Scott Hopkins installs the experimental containers in KUBIK (left) and the six hardware units inserted into the KUBIK on board the ISS (right). Image credit: ESA/NASA/
Their analysis found that the microbes produced consistent results in both Earth gravity and microgravity. However, there were also clear changes in microbial metabolism, particularly in the fungal samples. In microgravity, the fungus increased its production of carboxylic acids and other molecules, leading to the extraction of more palladium, platinum and other elements. Meanwhile, the non-biological leaching experiment proved less effective in zero gravity than on Earth. Santomartino said:
In these cases, the microbe does not improve the extraction itself, but rather ensures that the extraction remains at a constant level regardless of gravity. And this applies not only to palladium, but to various types of metals, although not all. Another complex but very interesting result, in my opinion, is that the extraction rate varies greatly depending on the metal you are considering and the microbial and gravity conditions.
This experiment successfully demonstrated the potential of “biomining” that future astronauts could use to explore the Moon and Mars. In addition to life support systems that rely on cyanobacteria and other photosynthetic organisms to purify the air and produce edible algae, microbes and fungi could be used to leach minerals from the local regolith. These, in turn, could be used to produce building materials for structures and tools, reducing the amount of supplies that need to be sent from Earth.
Additionally, biomining has potential applications here on Earth, providing a biological method for extracting metals in resource-limited environments or from mining waste. This technology could also lead to biotechnologies that facilitate the emergence of a waste-free circular economy. However, the team cautions that more research is needed because there are many variables and uncertainties surrounding the effects of space on microbes.
“Depending on the type of microbe, depending on the space conditions, depending on the method the researchers use, everything changes,” Santomartino said. “Bacteria and fungi are all so different and space conditions are so complex that there is currently no single answer. So maybe we need to dig more. I don’t want to be too poetic, but for me that’s a bit [of] the beauty of it. It’s very complex. And I like it.”
Further reading: Cornell Chronicle, npj Microgravity.
