Scientists have used a tiny plastic obstacle course to find out if sperm would struggle to “navigate” during sex in space.
Some particularly resilient sperm did make it through the course, suggesting that conceiving children in space would be possible, according to research published on Thursday.
A bigger problem may be that the development of embryos after fertilisation could be harmed by a lack of gravity, researchers in Australia found.
With hopes of colonising space, scientists have been studying how difficult it would be to procreate. Next week, Nasa hopes to launch its first crewed mission around the moon in half a century.
Nicole McPherson, a researcher at Adelaide University, said: “Sperm need to actively find their way to an egg, and this study is the first to put that ability to the test under space-like conditions.”
Researchers found that a lack of gravity could make reproduction harder than on Earth – Carlos Duarte
The scientists used a plastic chamber that resembles the female reproductive tract to act as a miniature obstacle course, the senior author of the new study said.
Ms McPherson said: “Think of it as a tiny race track … sperm are introduced at one end and have to swim their way through to the other.”
Sperm from humans and mice were sent down the course, which was in a device that uses constant rotation to simulate the lack of gravity in space.
The sperm was about 50 per cent worse at navigating through the course compared with how they performed under Earth’s gravity.
Successful sperm ‘of higher quality’
This worked out to be roughly a 30 per cent drop in successful fertilisation, according to the study published in the journal Communications Biology.
However, the sperm that did make it through seemed to produce higher-quality embryos, which could turn out to be beneficial, Ms McPherson said.
It appeared that the stress of microgravity acted as a filter that effectively cleared the field, “leaving only the most capable sperm in the running”, she explained.
A bigger problem came in the first 24 hours after sperm had fertilised the eggs. She said: “The results reversed sharply, with fewer embryos formed, and those that did were of poorer quality.”
This suggests that microgravity “may not be the deal-breaker we feared, but protecting the embryo from weightlessness in those critical first hours will likely be essential for reproduction in space”.
Some, including Elon Musk, the founder of SpaceX, have ambitious plans to make humans an interplanetary species by establishing settlements on the moon then Mars.
There has been speculation that the first baby conceived somewhere other than on Earth could be the result of a couple having sex on a flight launched by the space tourism industry.
Ms McPherson emphasised that much more research was needed to understand how reproduction works in space, adding that fertilisation was “one small piece of a very long and complex puzzle”.
She added: “We are still a long way from seeing the first space baby.”