BEIJING -- Of the four mice involved in a recent mission aboard China's space station, one female has now successfully birthed healthy offspring on Earth, the Technology and Engineering Center for Space Utilization (CSU) of the Chinese Academy of Sciences (CAS) has announced.

The four mice were sent into space aboard the Shenzhou-21 crewed spaceship on Oct 31, and were housed in a specialized habitat on the space station before returning to Earth on Nov 14.

After their return, one female conceived and later delivered nine pups on Dec 10. Six of the newborns have survived — a rate considered normal. Researchers have noted that the mother is nursing normally and the pups appear active and healthy.

"This mission showed that short-term space travel did not impair the reproductive capability of the mouse," said Wang Hongmei, a researcher at the Institute of Zoology of the CAS. "It also provides invaluable samples for the investigation of how the space environment influences early developmental stages in mammals."

The CSU noted that the mission faced unexpected difficulties after a change in the return schedule of the Shenzhou-20 mission, which was scheduled to carry the mice back to Earth, leading to a food shortage toward the end of the subjects' time in orbit. Ground teams quickly developed countermeasures.

With support from astronauts on the space station, water was supplied to the mice via a dedicated port in their habitat area. Resolving the food shortage presented greater challenges. As the specialized mouse feed could not be replenished in time, scientists evaluated various items from the astronauts' food supplies. Following ground-based tests, soybean milk was chosen as a suitable temporary substitute.

According to the CSU, throughout the period, an AI-powered monitoring system tracked the behavior of the mice, including movement, feeding and sleep patterns, providing critical data to support real-time decision-making.

The CSU stated that this achievement signifies China's first full-cycle realization of a mammalian space experiment, covering pre-launch preparations, in-orbit operations aboard the Chinese space station, and sample recovery.

This milestone lays a solid foundation for larger-scale mammalian space science experiments in the future, the CSU added.

Scientists will continue to study the postnatal development of the mouse pups, monitoring their growth and physiological changes. Further research may also examine whether these offspring can reproduce normally, helping reveal potential multigenerational effects of space exposure on mammals.