Human exploration of Mars is planned after NASA plans to establish a permanent lunar outpost by the end of this decade. But as we establish base camps outside Earth, human space settlers will need to bring with them an ecosystem that includes animals.

After all, animals can help carry out vital tasks: insects that provide pollination, for example, shrimp and fish that can be raised in small spaces and used as a food source, or tiny water bears that can teach us how to resist radiation. So which animals should colonize the Moon and Mars, not just with astronauts?

There is no consensus yet. “Complexly developed ecosystems [за межами Землі] “We’re still very far in the future and more in the realm of science fiction than active scientific research,” David Ketling, an astrobiologist at the University of Washington in Seattle, told LiveScience in an email. However, even without serious research, it is clear that the central force of the universe can be a serious obstacle.

“The big question is reducing gravity,” Christopher McKay, a planetary scientist at NASA’s Ames Research Center, told LiveScience. The gravity of Mars is about one-third that of Earth, and that of the Moon is one-sixth that of Earth. McKay said the habitat can be designed to match the temperature, pressure and atmospheric composition to which Earthlings are accustomed, but gravity cannot be changed.

The best-case scenario is that animals will evolve on Mars and the Moon just as they did on Earth, but the evidence isn’t yet available, McKay said. Changing gravity could affect muscle and bone development, preventing animals on Mars from standing or walking properly. Under those circumstances, small animals, perhaps mice and aquatic animals, would probably be the best choice, he said.

Catling gave a similar answer. Given the challenges of space, “I think simple animals like insects or crustaceans would probably be more durable,” he said.

Space settlements will also require resource conservation and high efficiency.

McKay suggested that because fish and other aquatic animals are powered by buoyancy, changes in gravity probably wouldn’t have much of an effect on their development. Fish could also be successful in space farming because they are more efficient at feeding and produce less waste than their terrestrial counterparts, according to a 2021 review published in the journal Frontiers in Astronomy and Space Sciences. Since 2019, the Lunar Hatch program has been investigating the feasibility of sending fish eggs into space for programmed hatching. If fish can survive launch and spaceflight, they would be a more efficient, high-protein, low-waste food source than land-dwelling animals, according to a 2021 review.

Insects are also valid space animals, according to a 2020 report from the University of South Australia and the International Astronautical University in France. The report states that insects such as crickets (Acheta domesticus) are the most feasible and affordable, offering a good source of protein while using less space and water than traditional protein sources. In a closed life support system, an artificial habitat for humans and animals on Mars, insects could provide important services such as pollination, soil turnover and debris cleanup, and be a backup food source in the event of crop failures, Catling said.

Like insects, crustaceans can be grown in tight spaces as a productive food source. Shrimp can be grown in small tanks and also used as part of a plant-growing aquaponics system, Catling said.

To colonize the Moon, researchers are looking to slow-moving animals often called “water bears.” These tiny hardy creatures have already demonstrated the ability to withstand extreme conditions such as extreme heat, extreme cold, radiation and the vacuum of space. Previous missions have shown that these tiny creatures can still survive after 12 days in the vacuum of space and reproduce without any adverse effects during spaceflight. There are even dehydrated (and possibly dead) walkers on the moon after a crash landing in 2019. Although they do not directly serve the human ecosystem, studying tardigrades in space could reveal how they withstand extreme conditions such as radiation and how we can mimic this trait in other organisms.

“Even without colonization, human exploration will take many years into the future,” Catling said. And even then colonization will be accompanied by many engineering problems. But when that day comes, he said, the animals that join these new habitats will be the animals that sustained the ecosystem of the first human settlers.