Little Enceladus found a “phosphine” that she could call her own. One group of researchers suggest that the presence of methane in the amounts observed in the water clouds ejected from Saturn’s moon cannot be explained by any known mechanism other than life.
The result is strongly reminiscent of the conclusions of researchers led by Jane Greaves from Cardiff University, Great Britain, who discovered phosphine in the clouds of Venus. They also didn’t believe it was a sign of life, but stated that they didn’t know of any alternative mechanism that could explain the quantities.
The new study, led by Régis Ferrière from the University of Arizona in the US and Stéphane Mazevet from Paris Science & Letters University in France, was published in the journal Nature Astronomy and follows the trail of the Cassini probe results, which caused a sensation in 2017 by traversing the plumes and discovering the presence of molecular hydrogen and methane in them.
It is known that under the frozen crust of Enceladus there is an ocean of liquid water that is in direct contact with a bedrock. From there come the feathers that are ejected from cracks in the ice. On earth, fumaroles from the deep sea are home to many methanogenic forms of life: They consume hydrogen and dump methane. We find both on Saturn’s moon, which has led many to call the subterranean ocean habitable. But from there to inhabited there are another 500. Also because there are other methane production processes that do not involve life forms, such as the interaction of water with certain minerals in the process known as serpentinization.
Model of the inner structure of Enceladus with its global ocean discovered by the Cassini spacecraft (Source: NASA)
The work of Ferrière and Mazevet was to determine the origin of the methane without checking it. Instead, the group mathematically modeled the probability that various processes, including biological methanogenesis, i.e. the production of methane by living things, could explain the result Cassini had collected.
The central question was: Would the amount be compatible with purely geological processes? And the researchers’ answer is “no” – but only as far as we know. They indicate that either one of the two: either methanogenesis is taking place inside Enceladus by microbes, or there is an unknown phenomenon unique to Earth that can create the substance.
When we summarize the results, we can consider the glass half full or half empty. On the one hand, it is exciting that we have already discovered compounds that can signal the presence of life in so many stars (phosphine on Venus, methane on Enceladus and on Mars). On the other hand, the conclusions are more speculative than we’d like so far. Just in case, it is still entirely possible, perhaps probable, that the explanation does not require biological activity. What is missing overall is more observations. It will be necessary to send new probes there if we are to unlock these secrets.
This column is published in Folha Corrida on Mondays.
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