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The bacterial exposure experiment took place from 2015 to 2018 using the Exposed Facility located on the exterior of Kibo, the Japanese Experimental Module of the International Space Station.

https://www.zmescience.com/science/news-science/bacteria-can-survive-interplanetary-travel-between-earth-and-mars/

Dr. Yamagishi and his team came to this conclusion by placing dried Deinococcus colonies on display panels outside the ISS. Samples of various thicknesses were exposed to the space environment for one, two, or three years, and then tested for their survival. Three years later, the researchers found that all colonies larger than 0.5 mm had partially survived in space. Observations show that although the bacteria on the surface of the aggregate died, it created a protective layer for the bacteria underneath, ensuring the survival of the colony. Using survival data after one, two, and three years of exposure, the researchers calculated that a granule greater than 0.5 mm thick could live 15 to 45 years on the ISS, thus proving the possibility of natural interplanetary transfer of microbial life that would otherwise called panspermia.