A Mouse's Six Weeks in Space Showed Up in Her Grandchildren

Twenty female mice rode a SpaceX rocket to the International Space Station, spent 42 days in orbit, came back to Earth and had babies. Those babies had babies. And somewhere in that chain, something went wrong.

The mothers came home in good shape. They got pregnant, and their litters were only slightly smaller than those of mice that never left Earth, a gap small enough to be chance. Their daughters were a different story. They had fewer litters, much smaller ones, and low levels of anti-Müllerian hormone, a marker of how many eggs are left in reserve.

The daughters were also about 15 percent weaker than control mice and more easily stressed. The granddaughters, two generations removed from orbit, still had low levels of the same egg-reserve hormone.

Lane Christenson, a study author at the University of Kansas Medical Center, said the size of the effect from just 42 days caught his team off guard. His working theory is that weightlessness speeds up aging in cells, straining mitochondria, the cell's power plants, which carry their own DNA and pass only from mother to child. That mechanism is still unconfirmed. So is whether any of this happens in people. Female reproductive health in space has barely been studied, even though hormones like estrogen also help keep bones strong.

And the space station gets far less cosmic radiation than deep space does. One outside researcher warns that a trip to Mars could hit harder.

The mice are mammals. So are we.

Read the full story at Live Science, September 21, 2026

Hot Take: One fairly serious wrinkle in humanity's plans to colonize space: a colony that can't produce healthy future generations isn't a colony. It's an outpost with an expiration date.