There are no grocery stores on Mars, and resupply from Earth is many months away. As much food as future astronauts to the red planet may pack for the trip, inevitably, they’ll have to create some food of their own in an inhospitable environment. Whether they go the fanciful farm-to-table route with locally sourced potatoes, like Matt Damon’s character did in the 2015 film The Martian, remains to be seen. But they may have an even more science-forward option.
Creating protein out of thin air.
That’s the goal of a partnership between the European Space Agency and a company called Solar Foods, formed out of a scientific research program less than a decade ago. Solar Foods opened its first large-scale production facility in 2024.
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The project, dubbed HOBI-WAN (for “hydrogen oxidizing bacteria in weightlessness as a source of nutrition”) in a nod to the Star Wars movies, is an outer space version of a process that Solar Foods has been working on already here on Earth. That effort involves growing bacteria in a vat with water, air and nutrients, and then drying out the bacteria, turning them into a protein powder called Solein for human consumption.
A key next step will be to test Solein production on the International Space Station.
“Providing a sustainable and nutritious food supply which meets the energy requirements of the crew is one of the biggest challenges in human spaceflight exploration beyond low Earth orbit,” ESA said in a blog post. “In cases where pre-deployed food depots or continuous resupply missions from Earth are impractical, resource-heavy, or technically unfeasible, cost-effective alternatives are required.”
Solein starts wet and is dried through a process that includes centrifugal force and spray drying.
From bacteria to protein
The central goal of the HOBI-WAN project is to determine whether production of the protein-rich powder can take place in microgravity conditions.
The process is complex, but essentially it’ll be letting nature take its course.
“Solar Foods produces Solein by a process called gas fermentation,” Arttu Luukanen, the company’s senior vice president of space and defense, tells me. The gas fermentation process, he says, creates single-celled organisms that feed on hydrogen gas and use it to “sequester” carbon. From there, the bacteria are fed “minerals of life” using ammonia as a nitrogen and hydrogen source.
All the ingredients go into a bioreactor along with water and gases that are pumped in “a bit like a big SodaStream,” Luukanen says. This provides the bacteria with the proper environment to reproduce, which they do very quickly. Once the bacteria have reproduced to a sufficient quantity, they’re harvested. Some of it is set aside to seed the next round in the bioreactor, while the rest is thoroughly dried and pasteurized.
These dried and pasteurized bacteria form the Solein product, which is composed of 78% protein, 6% fat (primarily unsaturated), 10% dietary fiber, 2% carbohydrates and 4% mineral nutrients. Luukanen says the powder can be flavored in any number of ways and on its own imparts “a very mild flavor of umami.”
The HOBI-WAN project will be heading to the International Space Station to see if Solein can be made in space.
How to make protein in space
Solein production will be harder to do in space. The weightless environment, plus the limited cargo capacity and reduced space for the bioreactor, add challenges that ESA and Solar Foods believe they can solve.
“[The] main difference for the experiment onboard the ISS is the lack of gravity, which means there is no buoyancy, which alters greatly how liquids and gases behave,” Luukanen says. The other challenge is limited physical space. Solar Foods uses bioreactors that can hold 20,000 liters or more, while the bioreactor heading to the ISS will be significantly smaller — a “few tens of liters.”
Extra steps will be required for gas safety, process monitoring, quality assurance and maintainability, as there won’t be bioprocess engineers on board to babysit the process. The product made in space also won’t be dried into a powder, at least not at the ISS. In the event of a leak, having a cloud of powder floating around in a zero-gravity environment wouldn’t be ideal.
So in space, Solein will likely be served up as a paste.
Soleil in its powder form here on Earth. The space version will be more of a paste.
Recycling in space
The last big factor is the ingredients. They’ll have to be altered to account for the lack of resources available in a long-term space flight. Recycling has long been a key component of living in space, and that’ll be true for Solein production.
That means using CO2 from crew respiration and recycling the hydrogen gas made when the ISS uses electrolysis to turn water into oxygen for the crew. On Earth, making Solein requires a lot of water.
There will also be substitutions, such as using urea instead of ammonia, since ammonia would be dangerous if there were an accident. But that doesn’t mean that astronauts will be using urine like they do for “recycled coffee.”
“On Earth, we use ammonia, but for the ESA project, we’ve decided to use synthetic urea instead, mainly because it is not potentially hazardous like ammonia is if there is a spill,” Luukanen says. “Recovering the urea from urine is in principle possible, but given the small portion of urea needed, it may not make sense, especially if the urea extraction from urine involves complex and heavy equipment.”
Should the HOBI-WAN project be successful, it’ll help unlock long-term space exploration for humans, including a potential trip to Mars.
Feeding astronauts on long-duration missions
A trip to Mars is a much bigger time commitment than an excursion to the moon. NASA’s upcoming Artemis II mission will see astronauts circle the moon for the first time in nearly half a century, but the trip will last only 10 days. In terms of food, it’s not that big a deal. But Mars — eyed by space agencies and Elon Musk alike — is much, much farther away, and travel times will stretch to months and months. Heading to the red planet, astronauts will need to pack more than a picnic.
Should the Solein project prove successful, the amount of food it generates could theoretically feed a team of astronauts for hundreds of days while using much less cargo space than today’s space meals. Luukanen says that, as the project is being designed, the only thing astronauts would need to carry would be mineral salts, and they wouldn’t need that much.
“Even for a five-[person] crew, 900-day mission to Mars, we are talking of [less than]100 kilograms of mineral salts,” he says.
Other technologies may also help recycle nitrogen and minerals, which would allow astronauts to reuse those materials onsite, further extending food supply.
Using the protein powder, astronauts could make all sorts of food with the right additional ingredients. Luukanen says Solar Foods has developed recipes ranging from ice cream to cream cheese ravioli. Some of them were showcased during NASA’s Deep Space Food Challenge, which highlighted methods for long-term food solutions, including a no-light food-growing method called Nolux and a closed ecosystem that can autonomously grow food and maintain insects for use in an astronaut’s diet.
It might not be what you’d expect from a Michelin-starred restaurant or even your neighborhood deli, but it’ll likely be better than a steady diet of Mars-grown baked potatoes.
