The discovery, based on the study of data collected by NASA's Cassini probe, was published Wednesday in the prestigious journal Nature.
The Cassini spacecraft explored Saturn and its rings and moons from 2004 until its destruction in the gas giant planet's atmosphere in 2017.
"This is an incredible discovery for astrobiology," said Christopher Glein of the Southwest Research Institute, one of the paper's co-authors. "We found phosphorus in abundance in samples of ice plume ejected from the subterranean ocean."
The geysers of Enceladus' south pole spew into space very fine particles of ice that feed Saturn's outermost and thinnest E ring.
Scientists had previously discovered minerals and organic compounds in ice particles ejected by Enceladus, but not phosphorus, an essential component of DNA and RNA that is also found in the bones and teeth of humans and animals, and even oceanic plankton.
In fact, life as we know it would not be possible without phosphorus.
Geochemical models predicted the presence of phosphorus in these particles, a prediction published in an earlier paper, but this has yet to be confirmed, Glein said.
"This is the first time that this essential element has been discovered in an ocean outside of Earth," added the study's lead author, Frank Postberg, a planetary scientist at the Freie Universitat in Berlin.
NASA image obtained on June 14, 2023 of the planet Enceladus taken by the Cassini probe in 2005 © HANDOUT / NASA / AFP
For this discovery, the authors combed through the data collected by the Cosmic Dust Analyzer instrument of the Cassini probe. They confirmed the results by conducting laboratory experiments to show that Enceladus' ocean contained phosphorus in various water-soluble forms.
Over the past 25 years, planetary scientists have discovered that worlds with oceans under a layer of surface ice are numerous in our solar system.
For example, there are some on Europa, a moon of Jupiter; on Titan, Saturn's largest moon, and even on the dwarf planet Pluto.
Planets that have, like Earth, surface oceans must be at an adequate distance from their star to maintain temperatures that support life. The discovery of worlds with subterranean oceans increases the number of planets that could be habitable.
"With this discovery, Enceladus' ocean is now known to satisfy what is generally considered to be the first necessary condition for life," Glein said. "The next step is clear – you have to go back to Enceladus to see if the habitable ocean is actually inhabited."
© 2023 AFP