If space colonization is in our future, we’ll have to use the resources available there. But we won’t be able to bring our established industrial methods and processes from Earth into space. Transporting heavy mining machinery to the Moon, Mars, or anywhere else in space is not feasible. And each of those environments is wildly different from Earth. We’ll need novel approaches to solve all of the problems facing us, and the approaches will have to be sustainable.
Terrestrial microbes are the foundation of Earth’s biosphere, and they could play an outsized role in space colonization.
Wherever we go, microbes are along for the ride. They’re on our skin, in our mucous membranes, and in our stomachs. There are as many microbial cells on and in our bodies as there are human cells.
We use microbes to process waste, produce insulin, extract metals from ores, and make concrete. They were nature’s first engineers and changed Earth’s atmosphere over billions of years. They’ve adapted to almost every habitat on Earth.
It makes sense that they’ll play a role in space colonization.
“How can microbial biotechnology enhance the sustainability of long-term deep-space exploration missions and settlements?”
In a new white paper, a team of researchers explains how we can use microbes in sustainable space colonization. The primary author is Rosa Santomartino, a researcher at the UK Centre for Astrobiology, School of Physics and Astronomy, at the University of Edinburgh. The paper is “Biologically Facilitated Processes Towards Sustainable Space Exploration,” and it was submitted to NASA’s Decadal Survey on Biological and Physical Sciences Research in Space 2023-2032.
“Finding sustainable approaches to achieve independence from terrestrial resources will be pivotal to the success of space exploration in the next decade (2023-2032),” the authors write. Microbes have a pivotal role to play in these approaches by performing what’s called biological in-situ resource utilization (bio-ISRU). Bio-ISRU can supply us with life-supporting processes like water recycling and soil-building and also industrial activities like energy production and mineral acquisition.
Santomartino and her colleagues have been working on these approaches for a while. One of the first things they tested was the microbial response to different gravities. The ESA BioRock experiment on the International Space Station grew three types of microbes on a piece of basalt. On Earth, more than 90% of all volcanic rock is basalt, and it’s also common on the Moon and Mars. It’s present on all rocky bodies.
This fluorescent light image shows Sphingomonas desiccabilis growing on basalt. It was one of three strains of microbes tested in the BioRock experiment aboard the ISS. Image Credit: UK Centre for Astrobiology/University of Edinburgh–Rosa Santomartino
Basalt contains important metals and elements and is rich in magnesium and iron. On Earth, we use bio-mining to access these types of minerals. Some microbes can oxidize metals to make them dissolvable in water. Before testing that in space, scientists needed to determine how microbes respond in different gravities. In the BioRock experiment, they tested three strains of microbes in three different simulated gravities: microgravity, Moon gravity (0.38 g) and simulated Earth gravity.
When the cell populations were analyzed back on Earth, researchers found that none of the three suffered any significant adverse effects. Two of the three “ate” as much rock as they do on Earth and produced the same amount of metals as they do on Earth. After this initial taste of success, scientists are setting their sights on the future and how microbes could play a larger role.
The white paper explains the many roles microbes can play in future space colonization efforts. It also lays out, in broad terms, what avenues researchers should follow next.
In order to develop infrastructure in other environments, we’ll need structural materials and chemicals. The weaker gravities on Mars and the Moon mean we might need less of them, but the need will be ongoing. Santomartino and her co-authors suggest that terrestrial bio-mining methods can be adapted to space.
On Earth, bio-mining is especially effective for mining metals like copper, uranium, nickel, and gold. That’s because they’re present in sulphide-bearing minerals, and microbes are especially adept at oxidizing sulphidic minerals. But while Mars is rich in sulphide-bearing minerals, the Moon might require different bio-mining approaches. Its surface is mostly composed of silica-saturated rocks. There are microbes that prefer silica-saturated rocks, though, and this shows how microbes that have evolved in different terrestrial habitats can be preferentially employed on other worlds.
One important group of elements needed to build electronic systems in space is the Rare Earth Elements (REEs.) REEs include things like Vanadium and Silicon. REEs arent’ widespread, but the Moon’s KREEP K (potassium), REE (rare-earth elements) and P (phosphorus) terrain contains some of them in its basaltic rock. As the Bio-Rock experiment showed, microbes can likely play a role in obtaining REEs. The white paper authors say that more work is needed to understand the extent of that role.
The Moon’s Procellarum KREEP Terrane contains rare earth elements needed for advanced manufacturing. It also contains elevated levels of Thorium. It’s the colourful area on the left, on the Moon’s near-side. Image Credit: By NASA – http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Planets&IM_ID=13643, Public Domain, https://commons.wikimedia.org/w/index.php?curid=32868958
The authors also addressed the role microbes can play in waste processing, one of our persistent problems here on Earth. Sewage, crop waste, spent consumable items and expired electronics all require specific solutions. “A closed-loop, or recycling and reuse of materials, is key for sustainable human exploration of space,” the authors write. How can microbes help colonists deal with it?
Microbes can help with everything from sewage to plastic recycling. “Microbiologically supported processes can provide viable and efficient methods for recycling human and consumable (e.g., plastics) wastes, to reclaim water, fixed carbon and nitrogen, and inorganic byproducts (e.g., minerals, volatiles etc.),” the paper states. Microbes are used to treat sewage on Earth, and they process organic waste in the natural environment, in places like the forest floor. On the Moon and Mars, the waste from all these processes can be used as feedstocks in the next iteration of manufacturing.
Oxygen is introduced into sewage to encourage microorganisms processing the organic waste in this Activated Sludge Tank in the UK. Image Credit: By John Rostron, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=14228830
“All the principles and applications mentioned above could be included in regenerative life support systems (LSS),” the authors state, and LSSs are a foundational element of colonization. To that end, the authors say that biologically-driven waste recycling should be a top priority for future experiments. On the International Space Station, human waste is collected in canisters and disposed of during destructive entry into Earth’s atmosphere. But that’s not an option on the surface of another world.
Microbes can also recycle breathing air as part of bio-regenerative life support systems (BLSS.) They can remove CO2 and be part of O2 generation, and the carbon from the CO2 can be used in bio-concrete. Part of BLSS involves creating soil that plants can grow in. Martian soil is laden with too many iron oxides, perchlorates, and hydrogen peroxide. The result is a toxic mix. Martian soil is also, obviously, not suited to terrestrial plants.
MELiSSA (Micro-Ecological Life Support System Alternative) is an ESA closed-loop experiment demonstrating the ideal technologies to recycle waste from space missions into air, water, and food. It uses bio-reactors full of bacteria or microalgae to mimic natural processes and celebrated its ten-year anniversary in 2019. Image Credit: ESA
The authors point out that our understanding of how microbes could remediate soil is limited. That’s why more work is needed. Lunar or Martian soil may never be like soil on Earth, but it could be used as a substrate in hydroponics or other systems, with nutrients provided externally. They describe microbial soil remediation as pivotal for space colonization and say that “The maturation of BLSS and bioremediation technologies is recommended as a top priority.”
Readers may be surprised to find that bio-concrete is already a thing on Earth, though it’s not widespread yet. Bio-concrete has the unique capability of repairing its own cracks. It contains bacteria that can produce limestone to repair the cracks, though only in certain conditions.
The lunar environment is harsh, and so is the Martian environment. Radiation from space bombards the surfaces of both worlds, the temperatures are more extreme than Earth’s, and the dust on both worlds is a hazard. Habitats on both worlds require protective structures, and this is where bio-concrete, also known as Microbiologically Induced Calcite Precipitation (MICP), can play a role. Some microbes can use atmospheric CO2 to heal concrete, and Mars’ atmosphere is 95% CO2. The Lunar atmosphere is exceedingly thin, but it does contain CO2.
Bio-concrete can repair its own cracks with microbes that produce Microbiologically Induced Calcite Precipitation (MICP.) Jakhrani et al. 2019.
“Using appropriate extremophiles for MICP may help in the production and maintenance of bio-concrete,
as well as space conditions-resistant structures on Lunar and planetary surfaces,” the authors write. They recommend more research into how bio-concrete and MICP can be used in the production of “… concrete for (habitable) structures, roads, launch pads, and other key assets on the Lunar surface.”
Santomartino and the other authors also point out how fungi could play a role in structures. This is called Myco-Architecture, and it’s something NASA is already studying. One experiment showed that a certain type of radiation-resistant fungi could create a living radiation shield for astronauts and colonists. Not only that, but a specific fungus actually uses radiation to grow, similar to how plants use photosynthesis. Fungal mycelium, a root-like structure, also has insulative and fire-retardant properties, along with structural properties. The authors point out that there may be untapped potential in fungi, and it should be researched further.
Microbes can also be used to produce energy. Photovoltaics can provide energy on the Moon and Mars, but it has some limitations. This is where microbial fuel cells (MFCs) can play a role. A type of anaerobic bacteria can produce energy while it processes waste, and MFCs could be a part of “… in-situ flow-through waste remediation systems,” the authors say. Microbes could also produce hydrogen fuel from organic waste. These systems are starting to gain a foothold in commercial wastewater treatment systems on Earth.
The bacteria are the easy part of MFCs. Scaling them up to a practical size, and generating usable voltage, are the current engineering challenges. Space-related endeavours have a history of spurring innovations used here on Earth, and this is one area where that synergy could continue.
The authors know what NASA needs to do next to investigate all these potential microbial solutions: build bioreactors and data-acquisition systems. Those systems need extensive testing and development in Earth laboratories and simulation platforms. Those include suborbital flights, ISS experiments, and, eventually, lunar surface experiments.
The authors also point out that developing Bio-ISRU will involve synthetic biology. They emphasize that “… funding should take into account the high cost of genetic engineering and synthetic biology.” NASA, and the US Congress, may have to open their wallets.
For the authors, the future of Bio-ISRU is guided by one overarching question: “How can microbial biotechnology enhance the sustainability of long-term deep-space exploration missions and settlements?” The authors have made their case for the avenues NASA should pursue in their next Decadal Survey on Biological and Physical Research in Space. Expect to see some of their suggestions implemented in the near future.
Nobody yet knows exactly what space colonization will look like. But barring some revolutionary technological development that no one can yet foresee, the rocket equation will rule supreme over our efforts to establish a presence in space. Technologies like space elevators may play a role one day, but we’re nowhere near building one.
The rocket equation is unforgiving, and there’s no possible way we can establish an efficient supply train from Earth to Mars or even from Earth to the Moon using rockets. In-situ resource utilization will be the name of the game.
Why not press nature’s original engineers into service?