It’s thought that at least a handful of undiscovered worlds across the Universe became home to extraterrestrials by a similar process.
Dr Akihiko Yamagishi, principal investigator of Tanpopo, said: «The origin of life on Earth is the biggest mystery of human beings.
«Scientists can have totally different points of view on the matter. Some think life is very rare and happened only once in the universe, while others think life can happen on every suitable planet.
«If panspermia is possible, life must exist much more often than we previously thought.»
The finding is based on «exposure panels» of a type of bacteria called Deinococcus that were placed outside the ISS.
Tests took place from 2015 to 2018 on the exterior of the researchers’ craft called Kibo — 250 miles above Earth.
Researchers showed that colonies at least 0.5mm thick – thinner than a piece of paper – are resistant to the extreme cold and high radiation levels.
Only those at the surface did – forming a protective layer for others underneath, which survived for up to three years, explained the team.
Using the data at each year of exposure, it is estimated a pellet thicker than 0.5 mm would have survived for up to 45 years on the ISS.
It means microbes could travel between planets like Earth and Mars by gathering into «aggregates» of particles.
Microscopic organisms could spark life by multiplying again after finding suitable conditions at the other side of the universe.
Dr Yamagishi, of the University of Tokyo, added: «The results suggest radio-resistant Deinococcus could survive during the travel from Earth to Mars and vice versa — which is several months or years in the shortest orbit.»