In 2025, DLR tested continuous spirulina growth on the ISS for future closed-loop life support; Limnospira indica produced oxygen and edible biomass in microgravity

Scientists on the International Space Station quietly experimented on something that might determine the breakfast of future Mars crews, and it involves the same blue-green algae that can be found in your pantry. According to a 2025 DLR press release, scientists report that they were able to cultivate the cyanobacterium Limnospira indica (aka spirulina) continuously in the space environment on the ISS, where it produced oxygen and harvestable biomass. The (Deutsches Zentrum für Luft- und Raumfahrt) or German Aerospace Center experiment, known as Arthrospira-C, is a crucial step towards growing food and breathable air in space without having to ship all the calories from Earth.

Meet the microbe doing double duty in orbit

While spirulina may not be a novel find in the healthy food section, its role in space is lesser known. It is a photosynthetic organism; it consumes CO₂ and light, and produces oxygen as a byproduct like a plant, but it is also a single-celled microbe that can grow rapidly and provide a high nutritional content. That's the very reason that space agencies are coming back to it: one organism, two jobs, minimal footprint.

The DLR experiment was managed from the Microgravity User Support Center in Cologne. The biology was led by the SCK CEN research center in Belgium, and custom bioreactor hardware was provided by Redwire Space Europe. The point wasn't so much about whether or not spirulina could grow in space, because that had already been answered in the past, as to whether it could grow continuously, in a steady, self-sustaining cycle. That's a much tougher engineering challenge than a one-shot batch demo.

This isn't spirulina's first rodeo up there

This wasn't spirulina's first time showing up on the ISS. In an earlier experiment called Arthrospira-B, batch cultures of the same organism were flown in 2018-2019, and the findings stated that microgravity did not significantly affect its production of oxygen. That previous mission is also documented in a 2021 peer-reviewed research article titled “Photobioreactor Limnospira indica Growth Model: Application From the MELiSSA Plant Pilot Scale to ISS Flight Experiment,” published in the journal Frontiers in Astronomy and Space Sciences, and is worth citing as the actual scientific basis for why agencies chose this particular strain in the first place. Building on that earlier batch success, Arthrospira-C set out to prove something the previous flight never tested: sustained, continuous growth rather than a single short-term burst. That shift, from "can it survive up there" to "can it run indefinitely, like a real life-support system would need to," is exactly the engineering milestone the mission was designed to demonstrate, not a lesser follow-up to it.

The Mars math problem

NASA may not be able to carry enough food for a two- to three-year mission to Mars, and every gram launched there is expensive. That's one reason algae-based, closed-loop life support continues to appear in American aerospace research labs, not just European ones. A NASA-related technical paper titled “Food Production and Gas Exchange System using Blue-green Alga (Spirulina) for CELSS,” delivered at the International Conference on Environmental Systems, spells out why: spirulina's cells have thin walls and are very digestible, which makes it possible to feed it into space without any significant processing, unlike most crops under trial for growing in space.

There are a couple of things to take into account

The DLR press release itself was very careful to call this a “milestone” rather than a completed project. Scaling up a laboratory-scale bioreactor into something that could actually provide enough food for four people for several years is a massive technical challenge that remains unsolved. Flavor, texture, safety concerns, and food fatigue remain unresolved issues. Space organizations have a history of hyping preliminary biological experiments as “leaps forward,” so it’s reasonable to take this as encouraging research rather than a future Mars menu.

This study is not an exercise in futility just because it stayed within Earth's orbit rather than reaching Mars. Recycling waste for oxygen and food is a glimpse at hyper-efficient agriculture, a technology that could be important for disaster relief, submarines, or even for areas on Earth where drought is a concern, before it becomes a necessity on Mars. The next time you throw spirulina in your smoothie, it's worth remembering that back in 2025, on a station orbiting a few hundred kilometers overhead, the same organism had already quietly done a shift as both an air purifier and a food source; a small preview of the life-support systems a future Mars crew may one day depend on to get themselves home.