Image: Image: Sam Woolley/Gizmodo, Shutterstock

Lots of people really want to go to Mars. Some of them want to live on that barren litter box forever, which sounds exciting, but would probably suck. The thing about a Martian colony is that people would have to be able to reproduce there in order to keep it going—and luckily for those hopeful pioneers, a team of Japanese scientists have achieved an important first step toward making their pipe dream a reality.

That team has successfully bred mice from sperm kept on board the International Space Station (ISS) for nine months, from August 2013 to May 2014. The freeze-dried sperm were kept in some pretty extreme conditions, receiving roughly 100 times the radiation we do on Earth. That’s enough to damage the sexual cells, called gametes, in our bodies. While other studies have analyzed the effects of microgravity on bird, sea urchin, and even fish reproduction, information on how mammalian reproduction, including human fertility, might respond to spaceflight is scarce.

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“If humans ever start to live permanently in space, assisted reproductive technology using preserved spermatozoa will be important for producing offspring,” the researchers write in their paper published today in Proceedings of the National Academy of Sciences. “However, radiation on the International Space Station (ISS) is more than 100 times stronger than that on Earth, and irradiation causes DNA damage in cells and gametes.”

Image: Screen Shot via PNAS

When the frozen sperm returned to Earth, researchers compared them to control samples from the same mice kept on Earth during the same time period. Analysis showed some damage to the space-preserved sperms’ DNA, but after they were transferred to female mice via in vitro fertilization, the mice moms had healthy pups. Those baby mice suffered no major health complications, grew to adulthood and exhibited normal fertility.

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“The birth rate of offspring from the space sperm samples did not decrease compared with that from ground control sperm samples, even with the apparent increase in DNA damage to the nuclei during space flight,” the team wrote.

Obviously, this one study about mice can’t predict how successful every mammal would be at making space babies. What’s more, the researchers note that 9 months in space might not have been quite long enough for the effects of DNA damage to become obvious, since sex cells have a fairly high capacity for DNA repair. Longer-term experiments are needed to suss out exactly how much damage might occur on, say, an interplanetary voyage.

“If the DNA damage occurring during longterm preservation is found to have a significant effect on offspring, we will need to develop methods to protect sperm samples against space radiation, such as with an ice shield, to enable future animal breeding in this environment,” the researchers write.

Still, this small achievement could help scientists understand how to prepare human sperm for the inevitable baby-making on a place like Mars. Or, you know, the cat colony that I’m trying to convince Elon Musk to build there.

[PNAS]