Overview
- Researchers exposed dried Physcomitrium patens sporophyte capsules on the Kibo module’s external facility for 283 days in 2022, launching on Cygnus NG-17 and returning on SpaceX CRS-16 in January 2023.
- Laboratory assays showed that more than 80% of the spores survived and nearly all of those germinated, despite an observed ~20% drop in chlorophyll a.
- Ultraviolet radiation proved the most damaging stressor, and the encased spores exhibited about 1,000 times greater UV tolerance than other moss tissues tested.
- Using the survival data, the team modeled potential viability of up to roughly 5,600 days (about 15 years) under similar conditions, characterizing the figure as a preliminary estimate.
- The study is the first long-term space-exposure demonstration for an early land plant, and the authors note that ISS conditions differ from deep space, with molecular and genomic follow-ups and longer, off-ISS tests planned.