A female mouse that spent time aboard China's Tiangong space station last year has birthed her third consecutive healthy litter back on Earth, providing scientists with invaluable data on mammalian reproduction after spaceflight.

Four mice were sent to the Tiangong space station as part of the Shenzhou-21 mission on Oct. 31, 2025, marking China's first small-mammal experiment in orbit. The rodents spent approximately two weeks in a specialized habitat in microgravity conditions before returning to Earth on Nov. 14.

Shortly after their return, one female conceived and delivered her first litter of nine pups on Dec. 10. She has since birthed two additional healthy litters, the second of which resulted in 10 pups and the third in another nine. The size of each litter has exceeded typical terrestrial litters of five to seven pups, China Media Group reported on Saturday.

Researchers at the Chinese Academy of Sciences' Institute of Zoology have observed intriguing behavioral variations across the three litters.

The first exhibited more cautious, "socially anxious" behavior, hiding in sheltered areas frequently. The second showed greater confidence, exploring their environment more readily. By the third litter, the offspring demonstrated progressively improved adaptation to ground living conditions, according to the report.

Overall, each successive litter has shown improved adaptation to ground living conditions compared to the previous one. These subtle changes provide important evidence for the study of space life reproduction, according to the researchers.

Mice have approximately 85 percent genetic similarity to humans and have rapid reproductive cycles, making them ideal models for the study of potential risks to human reproduction during long-term space missions.

Researchers will now monitor these "space pups" closely, tracking growth curves and testing whether they themselves can reproduce normally, searching for potential generational impacts.

What lies ahead is even more exciting. According to the research plan, the scientific team will conduct longer-duration space experiments with mice, mirroring human orbital missions that last over six months to study their physiological responses and spatial adaptability, per the report.

These findings bring scientists closer to answering a fundamental question for the future of humanity in space: Can mammals successfully reproduce beyond Earth?