Scientists detected more potential signs of life on Enceladus.
A joint team of astrobiologists from the University of Arizona and the University of Science and Literature in Paris has presented a new study analyzing the atmosphere of Enceladus. According to scientists, the existence of methane plumes on Enceladus may be a sign of the existence of life. They hypothesize that an unknown process of methane production may be taking place in the ocean hidden under the ice shell.
In the past, astronomers detected giant “water plumes” on Enceladus, which gave rise to reflections of the existence of a huge ocean that is hidden beneath the icy surface.
Not so long ago, flying through plumes of water and taking samples to analyze their chemical composition, the Cassini spacecraft recorded a relatively high concentration of certain molecules. They turned out to be identical to those molecules that are observed on Earth in hydrothermal vents at the bottom of the oceans.
We are talking about dihydrogen, methane, and carbon dioxide, and the amount of methane found in the Enceladus plumes was unexpectedly large.
Methane on Earth is mainly of biological origin; it is a by-product of the activity of methanogenic microbes. However, Enceladus’s plumes contain so much of it that no known pathway of the abiogenic appearance of methane can explain such an amount.
The key question here is whether this presence could be explained by the existence of terrestrial-life microbes that produce it or the reason is completely different. The best way to know is with a dedicated mission to the ocean on Enceladus but as we all know, this is unlikely to happen.
Therefore, Ferrier and his team created mathematical models. This helped to calculate the probabilities that various processes, including biological methanogenesis, could reliably explain the Cassini data.
As a result, the scientists concluded that the Cassini data are consistent with either microbial hydrothermal activity or processes that are not associated with various life forms, at least with those that are known to us.
In considering the first option, the team examined the results of several chemical and physical processes that are likely to occur in the bowels of Enceladus. Then they created a mathematical analog of the earth’s microbes. By running the model, the researchers were able to assess whether given chemical conditions, such as the concentration of dihydrogen in the hydrothermal source and temperature, could provide a suitable environment for the growth of these microbes.
They also looked at the impact a hypothetical microbial population might have on the environment. These factors include, for example, the rate of leakage of dihydrogen and methane in the Enceladus plumes.
The results showed that even the highest possible methane production without biological assistance, based on known hydrothermal chemistry data, could not explain the high methane concentration in plumes. But adding biological methanogenesis to the abiotic mixture could create conditions under which the “production” of methane at Enceladus would be in line with Cassini’s observations.
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Sources:
• Affholder, A., Guyot, F., Sauterey, B., Ferrière, R., & Mazevet, S. (2021, June 7). Bayesian analysis of Enceladus’s plume data to assess methanogenesis. Nature News.
• EurekAlert! (n.d.). Methane in the plumes of Saturn’s moon Enceladus: Possible signs of life?
• Gamillo, E. (2021, July 8). Could Methane-Spewing Microbes Be Living in the Depths of a Subsurface Ocean on Saturn’s Moon Enceladus? Smithsonian.com.
• Starr, M. (n.d.). Methane Detected on Enceladus Could Actually Be a Sign of Life, Study Shows. ScienceAlert.
• University of Arizona News. (2021, July 7). Methane in the Plumes of Saturn’s Moon Enceladus: Possible Signs of Life?
