Martian Water

Water is overwhelmingly abundant on Mars and mainly occurs in two forms: (1) as ice in the polar caps and buried underground at high latitudes, and (2) in hydrated minerals including sulfates and clays. The locations of both have been mapped with satellite data to fairly high confidence, but ground-based exploration will still be needed to fully prove the deposit quality and demonstrate an end-to-end pilot extraction operation. The majority of martian water will be split apart into hydrogen and oxygen for rocket propellant and other products, with only a small amount being used for life support. There is no economic reason to export water from Mars, for example to use in cislunar transportation networks.

If solar power is the only power supply on the martian surface, there is a direct trade-off between the amount of power available and the confidence that ice will be found just beneath the surface. This leads to a narrow band of latitudes around 40° that provide an acceptable compromise. On the other hand, hydrated sulfate deposits extend right to the equator and allow for maximal solar power, but have lower water concentrations than subsurface ice deposits and therefore require more energy to mine.

The northern hemisphere of Mars has lower elevations and has been favored for human landing sites because large landers need a lot of atmosphere to slow down. But an unappreciated factor is that the next 3+ launch windows in 2026, 2029, and 2031 will all land on Mars heading into northern winter, which is also peak dust storm season. This may make current humans to Mars plans non-viable even if crews are not sent during these windows, and plans should be re-assessed to include sulfates as a water source, or quickly mature nuclear fission technology at scale.