Astronauts in low Earth orbit get a much higher dose of cosmic radiation than folks down Earth, and there have been concerns that this might lead to damage to DNA passed onto offspring. Research in mice provides the strongest clues that this is not the case.
As reported in Science Advances, scientists have compared samples of freeze-dried mouse sperm kept on Earth, with samples that were sent to the International Space Station (ISS). Some of the samples were there for nine months. Another portion was there for two years and nine months. The final part was in orbit for five years and ten months. Different techniques showed that the sperm stored in orbit did not have any DNA damage compared to the one stored on Earth.
“The space radiation did not affect sperm DNA or fertility after preservation on ISS, and many genetically normal offspring were obtained without reducing the success rate compared to the ground-preserved control,” the researchers wrote in the paper’s abstract.
Eight healthy space pups were born from the sperm. The team rehydrated the cells and injected them into fresh ovary cells which were then implanted into female mice. RNA sequencing showed these pups were just as healthy as mice born from the freeze-dried sperm kept on Earth. The same was done for the samples that stayed in space for less time, with similar results.
“These space pups did not show any differences compared to the ground-control pups, and their next generation also had no abnormalities,” the researchers explained in the paper.
The team also bombarded the samples with X-rays to simulate a much longer period of intense cosmic radiation. They estimate that freeze-dried mouse sperm could be kept in low Earth orbit for up to 200 years without accumulating any damage to its genetic material.
The research is clearly important in understanding the impact of cosmic radiation on mammals, but it's important to stress that this cannot be extended to space travel in general. At an average altitude of 400 kilometers (248 miles), the ISS is still well within the Earth’s magnetic field, shielded from a good chunk of cosmic radiation.
We need studies further afield to get this wider picture. Over the next decade, a new space station is expected to be constructed orbiting around the Moon. The Lunar Orbital Platform-Gateway, as it is called, could be the perfect place to test this further in preparation for missions well beyond the Moon. If we are to send humans to explore Mars and the rest of the solar system, the risks to them and maybe their children ought to be as clear as they can possibly be.