Sperm get lost in space, Australian research into microgravity impacts suggests | Space

Sperm in space are likely to become disoriented and lost as they struggle to find their way to an egg, according to a new study.

When exposed to microgravity in experiments, sperm lash out like an untethered astronaut, according to researchers at the University of Adelaide.

“It causes them to turn around, turn upside down…they don’t really know which way is up or down,” said researcher Dr. Nicole McPherson.

Australia is part of NASA’s planned Artemis mission to the Moon and Mars, while private companies including Elon Musk’s SpaceX plan to build human habitats on Mars. As a result, there is growing interest in how humans might reproduce and raise animals in extraterrestrial habitats.

Adelaide researchers used a machine to mimic microgravity – the same type of astronauts freefall or weightlessness during the International Space Station experiment. The clinostat “keeps the cells from really understanding or knowing which direction they’re going,” McPherson said.

“With recent advances in space travel and international interest in deep space exploration, colonization of Mars, and mining of the Moon, it is essential to study the effect of microgravity on early fertilization events, not only to create viable food sources, but also to maintain human colonies in space, without the need for continuous repopulation from Earth,” they noted in a paper published in the journal Communications Biology.

McPherson said microgravity research also benefits the science of terrestrial reproduction.

Researchers at the university’s Robinson Research Institute used sperm samples from humans, mice and pigs.

They placed them in a 3D clinostat machine, which rotates to cancel out the effect of gravity, and then into a maze that was a simulation of the female reproductive system – although in the case of human sperm, no eggs were placed at the end for ethical reasons.

Sperm exposed to microgravity had difficulty making their way through the maze, they found.

There was an approximately 40% reduction in the number of human sperm exposed to microgravity that survived compared to the control group.

Microgravity also affected the development of pig and mouse embryos.

McPherson, the lead author, said this was the first time they had demonstrated that gravity was an important factor in the navigation ability of sperm and that, although it had a negative effect, healthy embryos were still able to form.

“This gives us hope that reproduction in space will one day be possible,” she said.

“We want to understand not only the effects of zero g, but also the different gravitational forces, the things we might see on the Moon or Mars, because we know there is a long-term plan for humans to settle there.

“While this may sound like science fiction…we are actually gaining fundamental knowledge about how sperm navigate and pass through the female reproductive tract.”

The researchers collaborated with the university’s Andy Thomas Center for Space Resources.

“As we progress towards a space-faring or multi-planetary species, it is essential to understand how microgravity affects early stages of reproduction,” said center director Associate Professor John Culton.

Adding progesterone helped overcome sperm disorientation, which researchers believe is because eggs also release it and can help guide sperm.

McPherson said radiation, which bombards astronauts when they leave Earth’s protective atmosphere, also affects sperm.

There is a long history of studying reproduction in space.

The University of Adelaide paper references a 1987 investigation into Cosmos 1887, which found that “rats exposed to space had reduced testicular mass”, and experiments on mouse embryos on the space shuttle Columbia in 1998.

In 2018, NASA sent human sperm as part of the Micro-11 mission to the ISS to study the effects of weightlessness. The US space agency also runs an ongoing developmental, reproductive and evolutionary biology program.

In 2024, the New York Times reported that Musk had offered his sperm to help seed a colony on Mars, a claim he denied.

In February, scientists called for more research into reproductive health in space, saying international collaboration was “urgently needed” to fill knowledge gaps on the effects of microgravity and radiation and establish ethical guidelines.