There is no air on the Moon. So how can people breathe in a future Moon base? The answer may be under their feet. About 40 to 45 percent of Moon soil is oxygen. The oxygen is locked inside rocks.

Scientists in Europe and the US have taken oxygen out of fake Moon soil using electricity and heat. This oxygen can also be used for rockets.

Future Moon bases will need oxygen, but carrying it from Earth would be very expensive. Fortunately, about 40 to 45 percent of the Moon's soil, called regolith, is oxygen by weight. It is not a gas, though. It is bonded with elements such as iron and aluminum inside minerals.

In 2020, researchers at the University of Glasgow, working with the European Space Agency, put simulated lunar soil into hot molten salt and passed electricity through it. They removed 96 percent of the oxygen in about 50 hours, and the leftover soil became metal. In 2023, a NASA team used a laser and carbon to extract oxygen in a vacuum chamber. The oxygen could be used for breathing and for rocket propellant.

Any long-term human presence on the Moon will require oxygen, and launching it from Earth would be extremely costly. A promising alternative lies underfoot: oxygen makes up roughly 40 to 45 percent of lunar regolith by weight, making it, according to ESA, the most abundant element in the soil. It exists not as gas but chemically bound in minerals with silicon, iron and aluminum, so extracting it means breaking those bonds.

In 2020, researchers at the University of Glasgow, in collaboration with ESA, used molten salt electrolysis at about 950 degrees Celsius to remove 96 percent of the oxygen from a lunar soil simulant in about 50 hours, leaving behind a metal alloy that could serve as building material. In 2023, a NASA team demonstrated carbothermal reduction, heating simulant with a laser inside a large vacuum chamber, the first such test under vacuum. On the Moon, mirrors could concentrate sunlight instead. The oxygen could supply both breathing air and rocket propellant. However, these tests used simulants on Earth, and real regolith, with its fine, clinging dust and low gravity, has yet to be processed on the Moon.