Lab Study Suggests Methane-Producing Microbes Could Survive on Enceladus
Laboratory work finds hydrogen-consuming archaea could tolerate Enceladus's seafloor conditions, while separate studies weigh how easily a future mission could detect biosignatures in its plumes.
Laboratory experiments have shown that certain hydrogen-consuming, methane-producing archaea could tolerate conditions thought to exist on the seafloor of Saturn's moon Enceladus, according to a study supervised by William Orsi, professor of geomicrobiology at LMU. His team recreated those conditions in the laboratory and found that the microorganisms seem able to adapt to the environment — a survivability finding, not evidence of life. The result places Enceladus among the few places in the solar system where the conditions for life to emerge could be present.
The setting is forbidding by human standards: icy cold, hardly any oxygen, and, below its icy crust, a global subsurface ocean whose water is described as being as corrosive as a pipe cleaner. Heat at the moon's core-mantle boundary drives hydrothermal activity, a consequence of tidal flexing from Saturn's gravitational pull. NASA's Cassini spacecraft, which arrived at Saturn in 2004, repeatedly flew through the plume of water vapour and tiny ice particles erupting from fractures near the south pole and feeding Saturn's E ring, sampling ocean-derived material without landing or drilling through kilometres of ice.
Between 2004 and 2017, the Cosmic Dust Analyser aboard Cassini measured the composition of individual ice grains in the E ring. An international team including scientists from the Earth-Life Science Institute at the Institute of Science Tokyo has examined how ocean water may be transformed as it travels from the subsurface ocean into those grains. Cassini also detected salts and organic compounds, and evidence of water-rock interactions on the rocky seafloor.
Researchers in Berlin frame the practical question as detectability. The Planetary Sciences and Remote Sensing group at Freie Universität Berlin has published two studies examining the prospects of a dedicated Enceladus mission, concluding that such a mission would have an easier time detecting biosignatures. Scientists hope to send a dedicated mission to explore Enceladus for signs of life; the supplied excerpts do not indicate that any such mission has yet flown.