Enceladus: Does Saturn's ocean moon hold chemicals necessary for life?

Scientists are still probing Enceladus, Saturn's ocean moon, as they think there's more to what we already know on planet Earth. They are trying to find life on another planet, and in the past decade, the search and research have picked pace, with increased attention on Enceladus.

So far, what we know about Enceladus is that it's an ice-covered ocean. The information comes from the Cassini mission, a space-research mission by NASA, the European Space Agency, and the Italian Space Agency to study Saturn and its system, including its rings and natural satellites.

The mission ended its exploration of the Saturn system in 2017. However, scientists are still working through its data to find out more. Cassini discovered geyser-like plumes of water erupting through Enceladus' icy shell during its mission.

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It performed a close-proximity flyby in 2008 and analysed the plumes with its Cosmic Dust Analyzer (CDA), which showed that the water in the plumes contained a surprising mix of volatiles, including carbon dioxide, water vapour, and carbon monoxide.

The mission also found trace amounts of molecular nitrogen, simple hydrocarbons, and complex organic chemicals. Scientists are still analysing data from Cassini, which was destroyed in Saturn's atmosphere.

A new paper, titled "Observations of Elemental Composition of Enceladus Consistent with Generalized Models of Theoretical Ecosystems", has unveiled new findings.

For the latest finding, the researchers have used ecological and metabolic theory and modelling to understand how ammonia and inorganic phosphorous in Enceladus' ocean could make the moon favourable for life.

The authors explain: "Apart from speculating about threshold concentrations of bioactive compounds to support ecosystems, metabolic and ecological theory can provide a powerful interpretative lens to assess whether extraterrestrial environments are compatible with living ecosystems."

The analysis could be related to the Redfield ratio which is the consistent atomic ratio of carbon, nitrogen and phosphorus found in marine phytoplankton and throughout the deep oceans.

The theory is given by American oceanographer Alfred Redfield, who said in his study in 1934 that the ratio of carbon to nitrogen to phosphorous (C:N:P) was remarkably consistent across ocean biomass at 106:16:1.

The authors of the new paper say: "Because of this seeming ubiquity, the Redfield ratio has been considered a target signature for astrobiological life detection, especially on ocean worlds such as Europa and Enceladus."

The study has noted that the analysis of Cassini's data from Enceladus' plumes shows a high level of inorganic phosphate in the ocean.

The authors have said that these reports of "phosphorus follow on the tails of previous work identifying numerous elemental constituents of terrestrial life (C, N, H, O) from the Enceladus plume".

Hence, Enceladus' ocean has a rich chemistry, and many chemicals reflect life's chemical makeup.

(With inputs from agencies)