While billionaires like Jeff Bezos and Elon Musk were vying to launch themselves into space, scientists have been busy shuttling freeze-dried mouse sperm through the stars.

In new research published Friday in Science Advances, scientists studying the effects of space radiation on reproduction report that freeze-dried mouse sperm weathered a nearly six-year trip on the International Space Station without any damage and could ultimately last for 200 years in space.

“But as we move from space exploration to things like colony building and long-term living in space, doses from space radiation are going to accumulate and these may manifest as fertility and reproductive decrement,” said Zarana Patel, a senior scientist with the technology and engineering company KBR, Inc., and contractor for NASA’s Human Research Program, who was not involved in the study.

So in 2013, Wakayama and his team sent 12 samples of freeze-dried sperm, which can be stored at room temperature, up to the International Space Station to study the long-term effects of space radiation on reproduction.

The returned sperm were thawed and evaluated for DNA damage before being used to produce two generations of “space pups.” There were slight differences in the preservation of DNA and the rate of offspring produced between the 3-year and 6-year sperm, but they were both small enough that researchers concluded the space radiation did not cause damage.

The International Space Station orbits within Earth’s gravitational field, meaning that radiation isn’t as strong as it would be in deep space or on Mars.

And the sperm is actually strengthened against space radiation in the freeze-drying process, according to the researchers, who also performed experiments on the ground to observe the effects of the freeze-drying process.

“It’s the diversity of the female’s ability to repair sperm damage that is the most important thing,” said Andrew Wyrobek, a senior scientist at Lawrence Berkeley National Laboratory who has studied radiation and the reproductive system since 1975, who was not involved in the study.

In the short term, experts said the study could bring needed attention to the potential dangers of space radiation to the reproductive system.

While more research is needed to learn the true dangers of space radiation for human reproductive systems, Wakayama hopes the new study may prove that if humans do move to Mars someday, other mammals could be brought along through freeze-dried reproduction cells

When the freeze-dried sperm first launched to space in 2013, Wakayama and his team had been working on the proposal and preparation for four years