Scientists Just Ruled Out An Indicator For Life On Saturn's Moon Enceladus

Artist's impression of the interior of Enceladus, where hydrothermal vents create a chemically active ocean. NASA/JPL-Caltech

The organic molecule methanol was once thought to be a possible indicator there was life under the surface of Saturn's icy moon Enceladus. But we've just found a ton of methanol elsewhere around Saturn – suggesting it is not as important as we thought.

A few months ago, NASA confirmed that under the ice of Enceladus there’s hydrothermal activity that propels complex molecules into space. The Cassini probe detected hydrogen, carbon dioxide, and methanol, among other substances, and now a study indicates that we might have been looking at only part of the picture.

In a study presented at the National Astronomy Meeting at the University of Hull in the UK this week, researchers announced the discovery of a greater amount of methanol in the Saturnian system than the previous detection made by Cassini as it flew through plumes ejected by Enceladus. This suggests that methanol production might be happening away from this icy moon but still driven by the moon itself.

"[O]ur findings suggest that that methanol is being created by further chemical reactions once the plume is ejected into space, making it unlikely it is an indication for life on Enceladus,” Dr. Emily Drabek-Maunder, who is presenting the research, said in a statement.

These observations were conducted by Dr. Jane Greaves of Cardiff University and Dr. Helen Fraser of the Open University, using the IRAM 30-meter radio telescope in Spain.

The plumes of Enceladus fuel materials in the E-ring of Saturn, and in the team's observations, they suddenly found a very bright emission of methanol. The detection of this complex molecule (made of carbon, hydrogen, and oxygen) was not expected, and when they saw such a clear signature, they knew something odd was happening.

This points at two possible explanations for the strong signal. Either the methanol from the plumes penetrates deeper into the E-ring than thought, or a large cloud was trapped by Saturn’s magnetic field. Either option though can’t explain the more abundant methanol unless it’s formed in space.

NASA image of Enceladus within the E-ring in orbit around Saturn. NASA/JPL-Caltech/Space Science Institute

While organic molecules like methanol can be produced by lifeforms, they can be produced by chemical processes too. This research suggests that the latter is more likely to be the case for Enceladus. But the detection is important by itself, both for the method and its implications.

"This observation is incredibly important because it is the first detection of a molecule in Enceladus' vicinity from a ground-based telescope," Dr. Drabek-Maunder told IFLScience.

"The Cassini spacecraft is coming to an end towards the end of the year, and in-situ [direct] observations from future space missions won't be possible for another decade or so. The only way for us to continue studying this environment in the meantime is by using remote telescopes." 

Cassini is now in the last few months of its mission before it takes a final plunge into Saturn at the end of September. A new Saturn mission is currently in the works, but until that happens ground instruments are the best we have. And there's plenty more science that they can do.

"One really interesting thing ground-based observatories can do in the meantime is to study how Enceladus' plumes vary in time," said Dr. Drabek-Maunder. "In past flybys, Cassini found that Enceladus 'huffs and puffs', meaning the plumes appear to be brighter when Enceladus is furthest away from Saturn. However, we don't know if the molecules being ejected from Enceladus vary over time and if variability is also found within the E-ring."

We learned so much about Saturn in the 13 years Cassin explored it. But it seems there's a lot more to learn.

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