Earth microbes survive simulated conditions of Saturn moon’s ocean — SkimNews
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- Methanogens from hydrothermal vents in the Okinawa trough between Japan and Taiwan grew in a lab-simulated Enceladus ocean at pH 11 — far more alkaline than their known limit — and adapted their metabolism to low carbon dioxide concentrations, according to a paper in Science Advances.
- William Orsi of Ludwig-Maximilian University in Munich and colleagues built the simulation using water, salts, carbonates and powdered rock to recreate the rock-water reactions thought to churn out hydrogen on Enceladus's seafloor.
- A second Science Advances paper by some of the same researchers shows that ice grains in Enceladus's plumes freeze and fragment in a way that concentrates any microbial constituents within a small fraction of particles — "great news" for future detection, said planetary scientist Frank Postberg.
- NASA's Cassini probe first revealed the plumes erupting from Enceladus and evidence of a saltwater ocean under its icy crust, and last year scientists confirmed organic substances in samples Cassini collected as it flew through a plume.
- The European Space Agency's proposed L4 mission would combine a Saturn orbiter with an Enceladus lander touching down at the moon's south pole to hunt for biosignatures in plume material, with a launch proposed for about 2042 and arrival not until the 2050s.
- Orsi cautioned the experiments ran only days, so it remains unclear whether similar microbes could persist for years or geological timescales, and that any native Enceladus life could be "radically different" from Earth's — but planetary geoscientist David Rothery said the result "removes another barrier to the viability of microbial life there."
Why it matters: By surviving pH 11 — roughly the alkalinity of household ammonia — the test microbes erase a key assumed barrier to Enceladus's habitability, and the companion ice-grain paper shows any alien cells in the plumes would be concentrated in a small share of particles, making biosignatures far easier for a future lander to detect.
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