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2h ago

Moss Spores Survive Nine Months Outside the ISS, Remain Viable on Return

Researchers credit protective spore walls and call for longer trials to determine true longevity in space.

A reddish-brown sporophyte can be seen at the top center of a leafy gametophore.
a photo of the ISS with an inset box showing a close-up of moss
Roughly 80% of the moss spores continued germinating after returning to Earth.
Germinated moss spores after space exposure. (Credit: Dr. Chang-hyun Maeng and Maika Kobayashi)

Overview

  • The iScience study reports that Physcomitrium patens sporophyte spores endured 283 days on the ISS Kibo exterior with more than 80% surviving and reproducing after return.
  • Shielded control groups germinated at roughly 95–97%, while spores exposed to ultraviolet light in space achieved about 86% germination.
  • Samples were launched on Cygnus NG-17 in March 2022, mounted outside the station, and returned to Earth on SpaceX CRS-16 in January 2023 for laboratory assays.
  • Chlorophyll a levels dropped by around 20% in returned spores, a change that did not appear to impair viability in the tests conducted.
  • Using post-flight data, the team modeled a potential survival limit near 5,600 days (about 15 years) under similar conditions, emphasizing this estimate is preliminary and that deeper-space, longer-duration and genomic follow-up studies are needed.