The European Space Agency’s Rosetta spacecraft saw material and gases – including oxygen – erupt off the surface of Comet 67P/Churyumov-Gerasimenko. (Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)

Space is an inhospitable place. For now, when humans go out in space capsules and stations, they need to bring their own air and water — and do without gravity — during their stay. In the future, if humans want to stay in space long-term (and they do), they’ll need t