"Planetary scientists revealed their bad habit of hydrobioscopy again this week. They reasoned, Saturn’s little moon Enceladus has water; it has methane; it could have life! Why is that their focus? Why are
Methane in the Plumes of Saturn’s Moon Enceladus: Possible Signs of Life? (University of Arizona). Writer Dan Stolte in the press office titillates readers with the L-word life in his suggestive headline. “A study published in Nature Astronomy concludes that known geochemical processes can’t explain the levels of methane measured by the Cassini spacecraft on Saturn’s icy moon.” If it can’t be explained abiotically, then there’s only one other conclusion. Maybe it’s alive! (hope, hope, hope).
“Obviously, we are not concluding that life exists in Enceladus’ ocean,” Ferrière said. “Rather, we wanted to understand how likely it would be that Enceladus’ hydrothermal vents could be habitable to Earthlike microorganisms. Very likely, the Cassini data tell us, according to our models.
And biological methanogenesis appears to be compatible with the data. In other words, we can’t discard the ‘life hypothesis’ as highly improbable. To reject the life hypothesis, we need more data from future missions,” he added.
In order to avoid charges of unscientific thinking, the scientists at U of Arizona clarify their wording. They say that life under Enceladus is “consistent” with the observations:
The authors applied new mathematical models that combine geochemistry and microbial ecology to analyze Cassini plume data and model the possible processes that would best explain the observations. They conclude that Cassini’s data are consistent either with microbial hydrothermal vent activity, or with processes that don’t involve life forms but are different from the ones known to occur on Earth.
Two models are consistent with the observed methane output: life, or non-life. The conclusion hinges on that word “likely.”
“It partly boils down to how probable we believe different hypotheses are to begin with,” he said. “For example, if we deem the probability of life in Enceladus to be extremely low, then such alternative abiotic mechanisms become much more likely, even if they are very alien compared to what we know here on Earth.”
While the epistemic modesty in that statement is commendable, Régis Ferrière (associate professor in the University of Arizona Department of Ecology and Evolutionary Biology) must surely be wishing for some evidence of “evolutionary biology” to show up. Astrobiology (better described as bio-astrology) remains a science without a subject. Ferrière ran some tests on biotic vs abiotic models (not using actual organisms), and concluded that the vents at Enceladus are “very likely” to be habitable to Earthlike organisms.
---But wait. It’s one thing to say that Earthlike microorganisms could live out there, if they were transported from Earth to Enceladus on spaceships and dropped off.