It looks like aliens aren’t alien — they may be our ancestors.

It’s possible that microscopic aliens from Mars started life on Earth, scientists have concluded,  after a study on the International Space station found that bacteria can live for years in the vacuum of space.

Tiny cosmic life-forms can survive the trip despite radiation and then find “suitable conditions” and multiply,  a team of Tokyo University scientists said in a press release about the research.

They found that the seeding of life could have also worked the other way, with Earth bacteria heading to Mars.

“If life emerged on Earth, it may have been transferred to Mars. Alternatively, if life emerged on Mars, it may [have been] transferred to Earth … meaning that we are the offspring of Martian life,” said lead researcher, Akihiko Yamagishi of the Tokyo University of Pharmacy and Life Sciences.

For the study, scientists strapped microbes to the outside of the International Space Station and found that many survived for three years — enough time to journey from Mars to Earth, according to a press release from researchers.

The bacterial cell clumps were placed on aluminium plates outside the spacecraft, where researchers took samples each year and sent them back to Earth for testing.  They found many of them survived despite being exposed to radiation.

“Ultraviolet light in space is so strong and was expected to kill bacteria,” Yamagishi said. “We were surprised.”

The discovery backs up a scientific theory called “panspermia,” which argues that microbes have been migrating between planets since the beginning of time.

“This theory implies that bacteria would survive the long journey in outer space, resisting to space vacuum, temperature fluctuations, and space radiations,” the researchers noted.