§5Life support
Water recovery at 98%, oxygen from Martian air proven at gram scale, ice mapped from orbit. And no closed ecological loop that has ever held.
Life support is where the optimistic case has its best evidence and the skeptical case its cleanest counterexample. The physico-chemical systems, recycling water and making oxygen, are maturing on real hardware. The biological system, a closed loop that grows food and regenerates air for years without resupply, has never worked anywhere.
Water and air: the ISS record
§5.1 The ISS reached 98% water recovery in June 2023. Jill Williamson, NASA’s water-subsystems manager: “Before the BPA, our total water recovery was between 93 and 94% overall… We have now demonstrated that we can reach [a] total water recovery of 98%, thanks to the brine processor.” Mars transit requires at least 98%, approaching 99%. Oxygen comes from electrolysis (the Oxygen Generation Assembly, roughly 2.5–4 kg O₂ per day). established
These are physico-chemical systems. They recycle; they do not grow anything.
The loop nobody has closed
§5.2 No closed ecological life-support system has ever been sustained. Biosphere 2 (1991–1993) suffered oxygen crashes and crop failures. ESA’s MELiSSA is a decades-long effort to build a closed loop and remains at component and pilot scale. A settlement that cannot be resupplied from Earth is, by definition, a closed loop, and the report’s scorecard threshold is explicit: ≥98% closed bioregenerative life support at pilot scale would materially strengthen the optimistic case. It has not been shown. contested
Oxygen from Martian air: MOXIE
§5.3 In-situ resource utilization (ISRU) means making what you need from what is there. MOXIE, riding on Perseverance, ran 16 times between April 2021 and August 7, 2023. It generated 122 g of oxygen in total, peaking at 12 g per hour at ≥98% purity, twice its design goal, by solid-oxide electrolysis of CO₂; its final run made 9.8 g. A human-scale system, supplying propellant and breathing air, needs roughly 2–3 kg per hour: a several-hundred-fold scale-up, plus liquefaction and storage.
Water ice
§5.4 The SWIM project (Morgan, Putzig et al., phases through 2025) integrates neutron, radar, thermal, and geomorphic data to map subsurface ice at about 3 km resolution across the mid-latitudes, finding buried ice sometimes below 30° latitude. But accessible ice at latitudes warm enough for humans remains uncertain, which is what motivates the proposed International Mars Ice Mapper mission. established that ice exists and is mapped; unknown whether it is reachable where a base could survive.
Perchlorate
§5.5 Martian regolith contains up to about 0.5–1% perchlorate, toxic to humans (the thyroid) and to most organisms, and synergistically worse under UV and radiation. Bioremediation with perchlorate-reducing bacteria or plants is researched but unproven at scale. Raw regolith is unsuitable for agriculture without nitrogen addition and perchlorate removal.
Power
§5.6 NASA’s Fission Surface Power project targets a 40 kWe (kilowatt-electric) reactor under 6 tons, with a lunar demonstration targeted for the first quarter of FY2030 and Mars application to follow. Multiple contracts are active (Westinghouse, January 2025, among others); solicitations for the flight demo were issued in 2025. Funded and progressing; stated: lunar demo Q1 FY2030.
Expedition or settlement?
§5.7 An expedition can carry its water, make some oxygen, and go home before the loop matters. A settlement is the loop. That is why this chapter’s two best-established results, 98% water recovery and MOXIE, belong to the expedition case, while its single most important absence, a closed bioregenerative system, belongs to the settlement case.