Saturn’s moon Enceladus is more habitable than previously thought

New research has presented evidence for a key component of life in the subterranean ocean of Saturn’s moon Enceladus. Models indicate that Enceladus’ ocean is relatively rich in dissolved phosphorus, which is an essential ingredient for life.

A research article documenting the study has been published in Proceedings of the National Academy of Sciences.

“Enceladus is one of the main targets in humanity’s search for life in our solar system. In the years since NASA’s Cassini spacecraft visited the Saturn system, we have been repeatedly amazed at the discoveries made possible by the data collected,” Christopher Glein, a co-author of the paper, said in a press release. Glein is an expert in extraterrestrial oceanography.

NASA’s Cassini spacecraft discovered liquid water beneath the surface of Enceladus and analyzed samples of plumes of ice grains and water vapor that erupted into space from cracks in the planet’s icy surface.

“What we have learned is that the pen contains almost all the basic requirements for life as we know it. While the bioessential element phosphorus has yet to be directly identified, our team discovered evidence of its availability in the ocean beneath the moon’s icy crust,” added Glein.

Worlds with oceans under an ice cap are not uncommon in our solar system. The icy satellites of giant planets, such as Europa, Titan, and Enceladus, fall into this category. Even Pluto has a similar icy underground ocean. For oceans to exist on the surface like on Earth, they must be within a narrow range of distance from their star to maintain a temperature where the water does not freeze or boil. But inner ocean worlds can exist over a much wider range of distances.

“The search for extraterrestrial habitability in the solar system has shifted focus, as we now search for the building blocks for life, including organic molecules, ammonia, sulfur-containing compounds, and the chemical energy needed to support life. Phosphorus presents an interesting case because previous work suggested that it might be scarce in Enceladus’ ocean, dimming the prospects for life,” explained Glein.

Phosphorus in the form of phosphates is essential for the creation of several important organic components, from RNA and DNA to energy-carrying molecules and cell membranes to bones and teeth.

Based on data about the ocean system on Enceladus from Cassini, members of the research team created thermodynamic and kinetic models that simulate the geochemistry of phosphorus. They found that phosphate minerals would be unusually soluble there. According to Klein, the underlying geochemistry makes the presence of dissolved phosphorus unavoidable.