Enceladus has all the ingredients for life – except maybe time – 06/18/2023 – Sidereal Messenger

Enceladus, Saturn’s small moon with a subsurface ocean that routinely leaks into space in the form of geysers, has all the essential ingredients for life. The revelation came with the detection of the missing piece – phosphorus – in the plumes of water ejected from it. It now remains to be seen whether there was enough time for life to emerge there.

There are six chemical elements absolutely essential to biology, known by the acronym Chonps: carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. Of these, all had already been detected before, except the blessed phosphorus – which happens to be the rarest of them. But that story has just changed.

Frank Postberg, from the Free University of Berlin, and colleagues presented, in the latest issue of the journal Nature, an analysis of ice grains probed by the CDA (Cosmic Dust Analyzer) of the Cassini spacecraft, which operated in orbit around Saturn until 2017, performing several flybys of Enceladus’ plumes.

The data suggest that among these ice grains were sodium phosphates. It is the first time that a phosphorus-containing compound has been detected in an ocean other than the terrestrial one. Yeah, there’s a lot of it over there. Combining the measurements with laboratory experiments, Postberg and his colleagues estimate that phosphorus concentrations in Enceladus’ waters are at least 100 times greater than those present in Earth’s oceans.

The finding reinforces the hypothesis that the global layer of water that exists between a rocky core and an ice crust on the small moon of 504 km in diameter is a potentially favorable environment for life. Future missions to Enceladus could explore more possibilities and try to detect direct evidence of biological activity, such as complex organic molecules.

If we’re lucky, we might not even have to wait that long to perform this quest. Last month, the James Webb Space Telescope was pointed in the direction of Enceladus and detected a huge plume of water ejected from the moon, about 10,000 km long. The instruments weren’t able to detect molecules other than water, but that could change with future observations. And the result, published in Nature Astronomy, confirms that the ejection rate of water on Enceladus has remained intense and constant for decades, at least since the first detections of the plumes by Cassini.

The biggest challenge for the presence of life there, therefore, is perhaps the weather. There is evidence that the moon (as well as Saturn’s famous rings) is of relatively recent formation, something like 100 million years ago. Would this period be sufficient for the emergence of biological forms? There’s no way to be sure, since we don’t even know how long it took to happen here on Earth (although we do know that it happened early, somewhere in the first 500 million years of the 4.5 billion years the planet has today). Models to explain the amounts of methane present in the plumes, published in Nature Astronomy in 2021, suggest that organisms called methanogens may be at work there. But this is something that only a more detailed exploration of Enceladus will corroborate or refute.

This column is published on Mondays in the printed version, in Folha Corrida.

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