The core problem: food, air, and waste in a closed system
A crewed spacecraft or planetary habitat faces a fundamental constraint that no other food system must: complete mass closure. On Earth, food systems can discard waste to the environment. In space, every kilogram of consumable launched from Earth represents an enormous propulsive cost — approximately $54,000 per kilogram to the International Space Station (ISS) orbit in the Space Shuttle era, and still in the range of $1,000–10,000/kg even with commercial launch. A Mars mission, with a transit time of approximately 6–9 months each way plus surface operations, cannot rely on resupply. Every kilogram of food, water, and oxygen must either be launched, recycled, or produced in situ.
This constraint defines the interest in bioregenerative life support: the use of biological systems — photosynthetic organisms, nitrifying bacteria, other microorganisms — to close the loops between human metabolic output (CO₂, urine, faeces) and the inputs needed for survival (O₂, food, potable water). Spirulina, as a photosynthetic microorganism that fixes CO₂ into biomass and releases O₂ while simultaneously producing human-edible protein, carbohydrates, and micronutrients, is a near-ideal first link in a bioregenerative loop.
MELiSSA: ESA’s closed-loop life support programme
The Micro-Ecological Life Support System Alternative (MELiSSA) is an ESA research programme initiated in 1988 and continuing today at the MELiSSA Pilot Plant in Barcelona (at the Universitat Autònoma de Barcelona). The programme’s goal is to develop a fully closed ecosystem that can sustain a crew in space using only sunlight as an external energy input.
MELiSSA is designed as a loop of interconnected bioreactor “compartments”. Compartment I receives raw organic waste (faeces, food scraps, paper) and uses thermophilic anaerobic bacteria to mineralise it into ammonia, CO₂, and water. Compartment II handles volatile fatty acids using photosynthetic anoxygenic bacteria (Rhodospirillum rubrum). Compartment III is a nitrifying bioreactor converting ammonia to nitrate (using Nitrosomonasand Nitrobacter species). Compartment IVa is the spirulina bioreactor — the photoautotrophic compartment in which Arthrospira platensis (the scientific name for spirulina) fixes CO₂ from the upstream compartments, produces O₂, and grows as edible biomass. Compartment IVb uses higher plants (wheat, lettuce, soybeans, rice) to complete food production.
The choice of spirulina for Compartment IVa reflects several properties. Spirulina grows photosynthetically in simple mineral media, tolerates the high CO₂ concentrations that human respiration produces, has a high growth rate (doubling time of approximately 2–4 days under optimal conditions), reaches high biomass densities in flat-panel photobioreactors, and produces biomass that is already consumed by humans. No further processing to isolate an active component is required — the dried biomass is the food.
MELiSSA has produced detailed Life Cycle Assessments and nutritional modelling of spirulina as a crew food source. At the pilot plant level, the spirulina compartment has been operated continuously for years, demonstrating the kind of sustained, reliable production that mission planning requires. ESA has also conducted sensory studies on spirulina-supplemented crew foods and published integration studies for how spirulina-derived protein interacts with the broader MELiSSA menu.
NASA and CELSS: the American programme
NASA’s interest in bioregenerative food production ran in parallel under the CELSS (Controlled Ecological Life Support Systems) programme, initiated in the 1970s. CELSS research examined a range of candidate species — wheat, potato, soybean, rice, lettuce, and various microalgae including spirulina and Chlorella. The microalgae were attractive for the same reasons that attracted ESA: high photosynthetic efficiency per unit area, high protein density, and the capacity for continuous rather than batch production.
A detailed NASA technical report (NASA Technical Memorandum 101535, 1989, by Tadashi Ohya and colleagues) examined spirulina as a CELSS candidate in depth, covering growth conditions in microgravity, bioreactor design considerations, and nutritional composition. Subsequent NASA-sponsored work through the 1990s and 2000s continued evaluating microalgae for the Variable Gravity Research Facility and later International Space Station bioregenerative experiments.
JAXA (Japan Aerospace Exploration Agency) has also studied spirulina in the context of long-duration mission nutrition. Japanese researchers have a long independent tradition of spirulina production and consumption research, and JAXA’s interest in spirulina for space nutrition has led to studies on spirulina stability under storage conditions relevant to spaceflight.
Nutritional density: the numbers
Dried spirulina powder has a caloric density of approximately 290 kcal per 100 g — comparable to other protein-rich dried foods and substantially higher than most vegetables on a per-gram basis. Its macronutrient profile is approximately 60–70% protein, 15–20% carbohydrate, and 5–8% fat by dry weight. This places it among the most protein-dense natural foods known.
For mission planning, the key metric is not just calories per gram but nutritional completeness per kilogram of cargo. A crew of four on a three-year Mars mission requires approximately 2,200–2,800 kcal/person/day, or roughly 3.2 million kcal total (at 2,500 kcal/day). At 290 kcal/100g, spirulina would need to provide approximately 1,103 kg to cover total caloric needs — far too much to launch. The realistic model is spirulina as a component of the food system, not the entire system. MELiSSA modelling suggests spirulina could realistically provide 20–30% of crew protein requirements from bioregenerative production, supplementing higher-plant crops that provide more carbohydrate calories.
Spirulina’s micronutrient profile is particularly strong for a compact food source. It provides: all essential amino acids (though with lower methionine and cysteine content than the WHO reference pattern, which is why it complements grain crops well); iron; vitamins B1, B2, B3, and B12 (though the B12 is primarily pseudocobalamin, which does not function as active B12 in humans — an important qualification for vegan space crew relying on spirulina as a B12 source); beta-carotene (pro-vitamin A); vitamin K; and the essential fatty acid GLA.
The B12 caveat bears emphasis: spirulina contains analogues of vitamin B12 that bind to B12-binding proteins and can produce falsely normal serum B12 readings while functionally blocking active B12. Space crew relying on spirulina as a primary food source would require an alternative B12 source or supplementation. This is a known issue in MELiSSA nutritional modelling.
The radiation protection angle
Beyond nutrition, spirulina has attracted space medicine interest for its potential radiation-protective properties. This is a distinct concern from Earth nutrition. In space, crew are exposed to two primary radiation hazards: Galactic Cosmic Rays (GCRs) — high-energy charged particles from outside the solar system, including protons, helium nuclei, and high-Z high-energy (HZE) ions — and Solar Particle Events (SPEs), which deliver intense but shorter-duration proton radiation from solar flares and coronal mass ejections.
The lifetime effective dose limit for NASA astronauts has historically been set at levels intended to keep excess cancer risk below 3%. For a Mars transit mission, estimated GCR doses are approximately 0.3–0.6 Sievert per year, which approaches or exceeds NASA lifetime limits for female crew members (who have lower limits due to higher radiation sensitivity in breast and ovarian tissue). Shielding can attenuate SPE radiation but is largely ineffective against GCR — the particles are too energetic for practical shielding mass.
Phycocyanin is a free radical scavenger. Its chromophore, phycocyanobilin, structurally resembles bilirubin and biliverdin — endogenous antioxidants — and can quench reactive oxygen species generated by ionising radiation. In cell and animal studies, phycocyanin pretreatment has reduced radiation-induced DNA damage (measured by comet assay and γH2AX foci), reduced micronucleus frequency, and improved survival in total-body irradiation models.
A frequently cited study is that of Bhat and Madyastha (2001) in Biochemical and Biophysical Research Communications, which showed that C-phycocyanin scavenged hydroxyl radicals and peroxyl radicals with high efficiency in cell-free systems. Subsequent animal work by Romay and others demonstrated radioprotective effects in X-irradiated mice.
The critical caveat for space applications: these studies used conventional ionising radiation (X-rays, gamma rays) at doses relevant to medical radiology or nuclear accident scenarios. The HZE ion radiation characteristic of deep space — iron-56 nuclei accelerated to near-relativistic speeds — produces fundamentally different biological damage patterns. HZE ions cause dense ionisation tracks with clustered DNA double-strand breaks that are poorly repaired and not well modelled by conventional radiation experiments. No published study has examined spirulina or phycocyanin in HZE radiation models. The extrapolation from conventional radiation protection to deep space radiation protection is genuinely uncertain, and this should be stated plainly when discussing spirulina’s radiation angle.
Physical form: the advantage of dried powder
One practical advantage spirulina holds for spaceflight is its existing form as a shelf-stable dried powder. Freshly grown spirulina biomass is harvested, filtered, and either spray-dried or drum-dried to produce a powder with water activity below 0.2 — sufficiently low to inhibit microbial growth and enzymatic degradation. Properly packaged (sealed in nitrogen or vacuum), dried spirulina retains nutritional quality for 2–3 years at ambient temperatures.
For a pre-positioned food supply (launched in advance of a crewed mission and waiting on the Martian surface), shelf stability is critical. A 2016 study by Perchonok and colleagues examining space food shelf life for Mars missions found that most conventional foods showed substantial nutrient degradation over 5-year storage periods, with vitamins particularly vulnerable. Dried spirulina’s stable protein fraction and carotenoids fare better than many conventional food components under the same conditions — though more data under spaceflight-relevant conditions (vacuum, radiation, temperature cycling) is needed.
In-situ production (growing spirulina during the mission rather than launching dried powder) is the more mass-efficient approach for long missions. This requires a photobioreactor system with adequate lighting (either solar or LED), temperature control, and CO₂ supply from the crew’s respiration. Mars receives approximately 44% of Earth’s solar irradiance at the surface — sufficient for spirulina growth if photobioreactors can be designed for the Martian environment, though Martian dust storms that reduce sunlight to near-zero periodically are an engineering challenge.
What remains unresolved
The space nutrition case for spirulina is genuine and has been taken seriously by multiple space agencies for decades. What remains unresolved is worth specifying honestly.
The B12 analogue problem is significant if spirulina becomes a major protein source. Microgravity-induced changes in gut microbiome (which are well documented in ISS studies) may alter the bioavailability of spirulina components in ways not predictable from Earth studies. The radiation protection data at doses and radiation types relevant to deep space is largely absent. Long-term consumption of spirulina as a primary protein source (rather than as a supplement at 5–10 g/day) has not been studied in humans over multi-year periods. The sensory acceptability of spirulina-heavy diets is a real constraint for crew morale — studies of food acceptability on ISS consistently find that food quality and variety are significant quality-of-life concerns.
Despite these gaps, spirulina remains one of the best-characterised candidate organisms for bioregenerative space food systems. The 30 years of ESA MELiSSA research in particular represent a serious, sustained scientific investment — and the Compartment IVa spirulina bioreactor at the Barcelona pilot plant has demonstrated the operational reliability that space systems demand. If humans reach Mars, they will almost certainly be farming microalgae to supplement their diet. Whether that microalga looks like the spirulina in your daily supplement is an interesting question — one the bioreactor engineers are actively working to answer.