Researcher helps identify new evidence for habitability in ocean of Saturn's moon Enceladus

SwRI Lead Scientist Dr. Christopher Glein contributed to new findings that phosphorus in the form of orthophosphate (e.g., HPO42-) is likely abundant in the subsurface ocean of Saturn's moon Enceladus. A soda or alkaline ocean (containing NaHCO3 and/or Na2CO3) inside of Enceladus interacts geochemically with a rocky core. Modeling indicates that this interaction promotes the dissolution of phosphate minerals, making orthophosphate readily available to possible life in the ocean. Because phosphorus is an essential ingredient for life, this finding bolster mounting evidence for habitability within this small Saturnian moon. Credit: Southwest Research Institute

Dr. Christopher Glein of the Southwest Research Institute is part of a research team that found fresh evidence for a crucial component of life in the water beneath Saturn's moon Enceladus. New models suggest dissolved phosphorus, a necessary component for life should be relatively abundant in the Enceladus Ocean. This discovery has increased the interest in the quest for alien life.

According to Glein, a world authority on extraterrestrial oceanography, "Enceladus is one of the primary objectives in humanity's hunt for life in our solar system." He is a co-author of a report on this study published in the Proceedings of the National Academy of Sciences. "We have continually been blown away by the discoveries made possible by the collected data in the years after NASA's Cassini probe visited the Saturn system," said Dr. Robert J. Smith.

The Cassini mission found the moon's underlying liquid water and collected samples as ice-grain and water-vapor plumes burst into space from fissures in Enceladus' icy surface.

What we've discovered, according to Glein, is that the plume is almost entirely composed of the essential elements for life as we know it. "Our team found evidence supporting the availability of the bioessential element phosphorous in the ocean beneath the frozen surface of the moon, although it has not yet been directly identified."

The finding that worlds with seas beneath a surface layer of ice are frequent in our solar system during the past 25 years has been one of the most significant ones in planetary research. The ice satellites of large planets like Europa, Titan, and Enceladus, as well as farther-off entities like Pluto, are examples of such worlds. For worlds with surface seas like Earth to sustain temperatures suitable for liquid water on the surface, the planets must be located within a small range of distances from their host stars. However, interior water ocean planets can occur across a far larger range of distances, considerably increasing the potential number of habitable worlds in the galaxy.

"The search for alien habitability in the solar system has switched focus, as we now hunt for the building blocks for life, including organic molecules, ammonia, sulfur-bearing chemicals, and the chemical energy needed to support life," Glein added. "Phosphorus is a fascinating instance since prior research revealed that it may be sparse in the ocean of Enceladus, which would decrease the possibilities for life."

All life on Earth depends on phosphates, which are made up of phosphorus. It is necessary to produce DNA and RNA, energy-carrying molecules, cell membranes, bones, and teeth in humans and animals, as well as the plankton microbiome in the ocean.

Based on knowledge gained from Cassini about the ocean-seafloor system on Enceladus, team members carried out thermodynamic and kinetic modeling that models the geochemistry of phosphorus. Throughout their investigation, they created the most thorough geochemical model of seabed mineral dissolution in the Enceladus Ocean, and they predicted that phosphate minerals would be exceptionally soluble there.

The existence of dissolved phosphorus at quantities comparable to or even higher than those in current Earth saltwater is unavoidable due to the exquisite simplicity of the underlying geochemistry, according to Glein. We can now be more certain than ever that the ocean on Enceladus is livable, which is good news for astrobiologyThe following action is obvious, according to Glein: "We need to return to Enceladus to determine whether a livable ocean is indeed populated."

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