The cool part about science is that you can ask questions like what happens if you stick some moss spores on the outside of the International Space Station, and then get funding for answering said question. This was roughly the scope of the experiment that [Chang-hyun Maeng] and colleagues ran back in 2022, with their findings reported in iScience.

Used as moss specimen was Physcomitrium patens, a very common model organism. After previously finding during Earth-based experiments that the spores are the most resilient, these were subsequently transported to the ISS where they found themselves placed in the exposure unit of the Kibo module. Three different exposure scenarios were attempted for the spores, with all exposed to space, but one set kept in the dark, another protected from UV and a third set exposed to the healthy goodness of the all-natural UV that space in LEO has to offer.

After the nine month exposure period, the spores were transported back to Earth, where the spores were allowed to develop into mature P. patens moss. Here it was found that only the spores which had been exposed to significant UV radiation – including UV-C unfiltered by the Earth’s atmosphere – saw a significant reduction in viability. Yet even after nine months of basking in UV-C, these still had a germination rate of 86%, which provides fascinating follow-up questions regarding their survivability mechanisms when exposed to UV-C as well as a deep vacuum, freezing temperatures and so on.