In a first, freeze-dried sperm stored for over nine months aboard the International Space Station (ISS) has yielded healthy mice offspring, say scientists who suggest that assisted reproduction may be possible for humans living in space in the future.

If humans ever set up space colonies, assisted reproductive technology using preserved sperm samples will be important for producing offspring, researchers said.

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However, radiation on the ISS is more than 100 times stronger than that on Earth, and irradiation causes DNA damage in cells.

This has led to concerns that radiation could kill or mutate sperm and pose serious reproductive problems for those travelling in space for extended periods.

Researchers at the University of Yamanashi in Japan fertilised eggs with sperm that had been kept on the ISS for nine months at minus 95 degrees Celsius.

Although the sperm DNA was slightly damaged during space preservation, it could be repaired by the egg and did not impair the birth rate or normality of the offspring, researchers said.

“Our results demonstrate that generating human or domestic animal offspring from space-preserved spermatozoa is a possibility, which should be useful when the space age arrives,” researchers said in the study published in the journal Proceedings of the National Academy of Sciences.