Tardigrades survive reversible dormancy during spaceflight: In-orbit revival, post-flight recovery, and transcriptomic responses

Dormant tardigrades (Tardigrada) survived a 64-day International Space Station mission and were revived twice, with ~45% survival.

• Why it matters: Long-duration spaceflight is constrained by limited resources and harsh microgravity and radiation exposure, and dormancy-based transport needs experimental proof in multicellular animals beyond Earth.
• What they did: Dormant tardigrades were exposed to extreme conditions on Earth and then transported to the ISS, where they were revived, returned to dormancy, and revived again after return; transcriptomics compared ISS-exposed survivors.
• The result: Surviving tardigrades endured near-absolute-zero (~12 mK), near-vacuum (10-9 mbar), 3000 Gy ionizing radiation, and desiccation, retained reproductive capacity, and showed upregulated protein folding/stress genes with downregulated energy metabolism and protein synthesis.

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