A new study from the University of Adelaide has found that sperm become disoriented in microgravity, struggling to navigate towards an egg. The research, published in Communications Biology, used a clinostat machine to mimic the weightlessness experienced by astronauts on the International Space Station.
Dr Nicole McPherson, senior author of the study, explained that microgravity causes sperm to flip around and lose their sense of direction. 'They don’t really know which way is up or down,' she said. The team tested sperm from humans, mice and pigs, placing them in a maze simulating the female reproductive tract. Human sperm exposed to microgravity showed a 40% reduction in successfully navigating the maze compared to a control group.
The research is part of growing interest in reproduction in space, as plans for lunar and Martian settlements advance. The study noted that understanding microgravity's effects on fertilisation is critical for creating viable food sources and maintaining human space colonies without constant resupply from Earth.
Despite the negative effects, healthy embryos were still able to form, offering hope that reproduction in space may one day be possible. The researchers also found that adding progesterone, a hormone released by eggs, helped counteract the disorientation. Dr McPherson emphasised that radiation, which bombards astronauts beyond Earth's atmosphere, also affects sperm.
The study builds on earlier investigations, including a 1987 Soviet mission that found reduced testicular mass in space-exposed rats, and NASA's Micro-11 mission in 2018 that sent human sperm to the ISS. In February, scientists called for more international collaboration to address knowledge gaps and establish ethical guidelines for space reproduction.
