For many years, Enceladus has attracted the attention of scientists as a candidate world to host extraterrestrial life forms. New data reinforce the idea that the ocean hidden under the thick ice layer of this moon of Saturn would be conducive to the development of life.
In search of extraterrestrial life, scientists are particularly interested in the search for new Earth-sized exoplanets and located in the habitable zone of its star. But our best chance of finding living organisms may well lie much closer to us, inside our solar system.
A liquid ocean below the surface of Enceladus
For several decades now, certain moons of JupiterJupiter Y SaturnSaturn indeed attract the attention of scientists and exobiologists due to the presence of a large CortexCortex of water ice on its surface. EnceladusEnceladussmall MoonMoon of Saturn only 500 kilometers in diameter, it has been the subject of very special attention since the passage of the Cassini probe in 2004. If the surface of this moon orbiting around the gas giantgas giant inside the outer ring it seems totally frozen, many observations suggest the presence of water liquidliquid under this thick layer of ice. Several geysersgeysers in fact, they have been observed breaking the surface, suggesting that this internal liquid ocean would be animated by currents of convectionconvection due to the presence of important heat sources.
liquid water and a geological activity that produces heat intensely and continuously, nothing more is needed to raise the hopes of scientists about the potential presence of living organisms under the icy surface of Enceladus. These two criteria that allow the habitability of the small moon it has just been completed by a third. Via modelingmodelingResearchers have found that Enceladus’ hidden ocean is relatively rich in phosphorus, a chemical elementchemical element essential for the development of life. On Earth, phosphorus, in the form of phosphate, is in fact a basic ingredient for buildingbuilding of’DNADNA and of theRNARNAbut it also enters into the composition of many energetic molecules, cell membranescell membranes, bones and teeth. It is also an essential component in the development of simpler organisms, such as the planktonplankton.
Liquid water, heat and organic molecules
During its pass near Enceladus in 2004, the Cassini spacecraft was able to sample and analyze ice grains and steam emitted by geysers erupting on the frozen surface. The data collected later surprised the scientific community by the extraordinary potential of this moon of Saturn. In fact, the samples contained all the basic elements necessary for life, but the presence of phosphorus could not be confirmed. The new hypothesis that the liquid ocean contains a large amount of it therefore only reinforces these earlier results.
To reach this conclusion, the researchers carried out a modeling thermodynamicsthermodynamics and kinetics that simulates the geochemical cycle of phosphorus based on data reported by the Cassini spacecraft. The results, published in the journal PNASwell show how the mineralsminerals forming the solid core of Enceladus dissolve in contact with water alkalinealkaline (containing NaHCO3 and/or natwoCO3). According to their model, the presence of phosphorus in the ocean of Enceladus is therefore unavoidable and even reaches amounts equivalent to, or even higher than, those observed in seawater on Earth.
The clues supporting the habitability of this Saturnian moon’s ocean therefore continue to accumulate. For scientists, the next step can only be sending a new probe intends to validate or not this hypothesis.