Lunar soil could help us make oxygen in space


A group of Chinese scientists investigated moon pebbles returned to Earth by China's Chang'e-5 mission—the first moon materials returned to Earth since the last Apollo mission in the 1970s.

Experiments in a lab indicated that the new moon rocks contain elements that might be used as catalysts to create fuel and oxygen on the moon. The researchers have proposed an approach for future lunar explorers to employ these catalysts to manufacture crucial resources rather than carrying those supplies, which might reduce the expense of long-term space travel. 

The fact that the team was able to use data from the new moon rocks and “do this sort of calculation, I think is very impressive,” says Jeffrey Hoffman, former NASA astronaut and professor of aeronautics and astronautics at MIT who wasn’t involved with the research.

However, Hoffman claims that the study lacks accurate estimations of how the process might scale up when it comes to the materials and energy required to manufacture fuel and oxygen.
Water, carbon, and chemical catalysts extracted from lunar soil are required for the proposed procedure. These catalysts would aid in the separation of hydrogen and oxygen from water. With the use of catalysts, carbon dioxide and hydrogen could be transformed into a hydrocarbon fuel–methane or methanol–to be burnt with the freshly created oxygen.

However, because carbon isn't found on the moon's surface, the team's proposal calls for collecting it from the air of a crew cabin. Carbon capture is a challenging and energy-intensive approach for mitigating climate change. According to Hoffman, questions about how astronauts would remove carbon dioxide from the air and how much they might gather remain unanswered. Another difficulty is that the procedure would require on water and metals gathered from lunar soil.

A lunar sample used in this study, obtained by the Chang’e-5 mission. Yingfang Yao

The team plans to employ synthetic photosynthesis to power the process, but Hoffman doubts that a modest solar array will be able to provide enough energy to fuel a return voyage.

Hoffman was a member of the team who worked on the MOXIE experiment, designed to generate oxygen from Martian carbon dioxide, onboard the Perseverance rover. The MOXIE experiment needs 300 watts of power—enough to run a small vacuum—“just to make a few grams of oxygen per hour” from carbon dioxide in the atmosphere, Hoffman says.Only a few breaths of oxygen are left in the end.

According to Julie Stopar, a planetary scientist who studies the moon's surface and geology at the Universities Space Research Association's Lunar and Planetary Institute, the new lunar study has some clever ideas, such as using the moon's day-night cycle to heat and cool reactants and drive part of the process.The challenge will be to “find a way to scale up and make it practical,” she adds.

Explorers would have to be able to supply precisely the proper ratios of raw materials and limit waste in the process for a system like this to function on the moon using just local resources, she adds. Finally, it's a lab experiment that has to be scaled up, which might require numerous iterations and adjustments to moon-like circumstances. The team believes astronauts will be able to obtain the water required for this technique from the shadowy sections of lunar craters.

“We have no ground truths there yet,” Hoffman says, regarding how much water there is and how accessible it will be. According to him, the water might be in the form of hydrated minerals or ice crystals, concentrated in clumps or distributed in inconveniently spaced layers. NASA likes flat landing locations away from craters, which are dangerous–but the only spot where water is believed to exist in sufficient amounts.

Even if obtainable water exists, harvesting the ice would entail “a mining operation in really, really cold regions,” Hoffman says: 40 to 60°C above absolute zero. “We right now don’t have equipment that works at those temperatures.”

Stopar adds that using indigenous resources on the moon or Mars would necessitate NASA's "long-term commitment." NASA is currently thinking out concepts for such missions, she said.

Stopar believes that space organizations should begin with smaller alien material objectives, such as creating radiation shelters on the moon out of lunar regolith. Those agencies might then show how to treat lunar dirt for water on a limited scale. Mining on other worlds will be difficult, but MOXIE has previously demonstrated that fuel can be made from the atmosphere of Mars.

In the near future NASA may send all of the oxygen required for a return trip to Mars. However, according to Hoffman, the agency would "pay the price." Shipping fuel instead of producing it on Mars will be less dangerous, but it will cost a few billion dollars more. Hoffman, on the other hand, is confident of one thing: if NASA wants to keep its Mars exploration mission continuing, astronauts will have to start exploiting what they discover far away from Earth sooner or later.