A Japanese research team has found that male mice sent to outer space for more than a month retained their reproductive capabilities and sired healthy offspring, according to findings published Tuesday by Scientific Reports, a British online journal.

Results from what the team says are the world's first findings on the effects of space on mammalian reproductive capability are expected to be useful for humankind's space activities.

For moral and privacy reasons, no reports have been published on studies related to reproductive capability that may have been performed on humans, the research team said.

The team led by Masahito Ikawa, a professor at Osaka University's Research Institute for Microbial Diseases, studied 12 mice that were returned to earth after being raised for 35 days in Japan's experimental module Kibo on the International Space Station.

"We conclude that short-term stays in outer space do not cause overt defects in the physiological function of male reproductive organs, sperm function, and offspring vitality," the authors wrote.

Mice were placed under artificial gravity or microgravity, and were compared with a control group on Earth. Those in orbit were found to have normally functioning male reproductive organs at the molecular level, and produce sperm capable of fertilizing eggs.

Their progenitors showed no overt defects, with normal development and fertility, the team said.

However, the scientists indicated that further analysis would be required to examine longer-term effects of the space environment on the male reproductive system.

As space travel becomes increasingly accessible, studies are "necessary to prevent undesirable effects in the next generation" as humans undergo emotional and physical stresses such as gravity changes and radiation, they wrote.