The first new soil sample from the Moon in decades is helping to lay the groundwork for “extraterrestrial photosynthesis,” a potential pathway toward producing water, oxygen, and fuel using sunlight and the rocky material on the lunar surface, known as regolith, reports a new study.
The concept is part of an array of emerging research into living off the lunar land, as nations such as the United States and China prepare to send humans to the Moon, and potentially beyond, in the coming decades. In anticipation of these missions, scientists are devising new techniques to use the available materials on alien surfaces for life support, fuel, and infrastructure—a process called in-situ resource utilization (ISRU)—instead of hauling supplies from Earth, which would take up valuable space and weight on crewed spacecraft.
Now, researchers led by Yingfang Yao, a scientist at Nanjing University, have tried out one of these methods on real lunar regolith. The team was able to road-test “a potential strategy to build an ISRU system that can accommodate the extreme lunar environment” using soil returned from the Moon by China’s Chang’e-5 mission which, in December 2020, became the first mission to bring lunar samples back to Earth in more than four decades, according to a study published on Thursday in the journal Joule.
“Long-term survival on the Moon shall be the first milestone toward the long march of manned deep space exploration,” the team said in the study. “Maximizing the utilization of in situ lunar resources, including extreme environmental temperature (minus 173°C to 127°C) and strong solar irradiation, could help us build an extraterrestrial base on the Moon for life-supporting and spacecraft launch/manufacture proposes.”
While there are scores of studies focused on ISRU on the Moon, Yao and his colleagues had the relatively rare opportunity to use bonafide lunar samples in their work, as opposed to resorting to simulants, which are fake soils made to imitate extraterrestrial surfaces using Earth’s materials. The team’s study is also unusual in its pursuit of a process that would not rely on any energy sources from Earth, and would run only on resources available on the Moon, which they call a “zero-energy consumption’’ life support system.
To that end, the researchers experimented with extraterrestrial photosynthesis, which is more or less what it sounds like—a means of duplicating the ability of plantlife to convert water, sunlight, and nutrients into oxygen and other useful byproducts.
Water and sunlight can both be harvested from the Moon’s surface, and the soil sample in the experiment also contained traces of iron and titanium that are useful as catalysts for this artificial photosynthetic process. Meanwhile, excess water vapor and carbon dioxide gas could also be sourced from breathing equipment used by astronauts on the Moon. With those basic materials, the team was able to produce a photosynthetic process by electrolyzing water into oxygen and hydrogen, and combining carbon dioxide with hydrogen to make methane fuel, all while only using solar energy as a power source.
While the study offers a promising roadmap to lunar life support, the team cautions that “the current catalytic performance from the Chang’e-5 lunar sample cannot fully satisfy the requirement of extraterrestrial survival,” according to the study. That said, Yao and his colleagues added that “significant improvement could be achieved via structure optimization, morphological modification, and composition engineering of the lunar sample” in the future.
“Compared with catalysts on the Earth, lunar soil or components extracted from lunar soil, as the photocatalysts for splitting water on the Moon, can greatly reduce the load and cost of spacecraft,” the researchers said in the study. “Chang’e-5’s sample provides us a great opportunity to study the lunar soil from the [extraterrestrial photosynthesis] catalytic perspective.”
“Based on this system, we can realize a ‘‘zero-energy consumption’ environment and life support system, and truly support lunar exploration, research, and traveling,” the team concluded.