Using data collected from the expedition Cassini her NASAan international team of scientists discovered phosphorus – an essential chemical element for life – locked inside salt-rich ice grains blasted into space by Enceladus.

The small moon is known to have a subsurface ocean, and water from this ocean erupts through cracks in Enceladus’ icy crust as geysers at its south pole, creating a plume. The plume then feeds Saturn’s E ring (a faint ring outside the brighter main rings) with icy particles.

During its mission to the gas giant from 2004 to 2017, Cassini flew through the plume and E ring several times. Scientists have found that Enceladus’ ice grains contain a rich array of minerals and organic compounds—including the building blocks for amino acids—relevant to life as we know it.

Phosphorus, the least abundant of the elements necessary for biological processes, had not been detected until now. The element is a building block for DNA, which forms chromosomes and carries genetic information, and is found in mammalian bones, cell membranes and ocean-dwelling plankton. Phosphorus is also a fundamental part of the energy-carrying molecules present in all life on Earth. Life would not be possible without it.

“We previously found that Enceladus’ ocean is rich in a variety of organic compounds,” said Frank Postberg, a planetary scientist at Freie Universität Berlin in Germany, who led the new study, published Wednesday, June 14, in the journal Nature. “But now, this new result reveals the clear chemical signature of significant amounts of phosphorus salts within icy particles ejected into space from the small moon’s plume. It is the first time this key element has been discovered in an ocean beyond Earth.”

Previous analysis of Enceladus’ ice grains revealed concentrations of sodium, potassium, chlorine and carbonate-containing compounds, and computer modeling suggested the subsurface ocean is moderately alkaline – all factors favoring habitable conditions.

For this latest study, the authors accessed the data through NASA’s Planetary Data System, a long-term archive of digital data products from the agency’s planetary missions. The archive is actively managed by planetary scientists to ensure its usefulness and usability by the global planetary science community.

The authors focused on data collected by Cassini’s Cosmic Dust Analyzer instrument after sampling icy particles from Enceladus in Saturn’s E ring. Many more ice particles were analyzed when Cassini flew through the E ring than when it passed through the plume alone, so scientists were able to examine a much larger number of compositional signals there. In doing so, they discovered high concentrations of sodium phosphates—molecules of chemically bound sodium, oxygen, hydrogen, and phosphorus—inside some of these grains.

Co-authors in Europe and Japan then conducted laboratory experiments to show that Enceladus’ ocean has phosphorus, bound in different water-soluble forms of phosphate, in concentrations at least 100 times that of our planet’s oceans. Further geochemical modeling by the team showed that an abundance of phosphates may also be possible on other icy oceanic worlds in the outer solar system, particularly those that formed from primordial ices containing carbon dioxide and where liquid water has easy access to the rocks .

“High phosphate concentrations are the result of interactions between carbonate-rich liquid water and rocky minerals on the ocean floor of Enceladus, and may also occur on many other ocean worlds,” said co-investigator Christopher Glein, a planetary scientist and geochemist. at Southwest Research Institute, San Antonio, Texas. “This key ingredient could be abundant enough to potentially support life in Enceladus’ ocean. this is an amazing discovery for astrobiology.”

Although the science team is excited that Enceladus has the building blocks for life, Glein stressed that no life has been found on the moon – or anywhere else in the solar system besides Earth: “Having the ingredients is essential , but it may not be enough for an alien environment to host life. Whether life could have originated in Enceladus’ ocean remains an open question.”

Cassini’s mission ended in 2017, but the treasure trove of data it collected will continue to be a rich resource for decades to come. When it was launched, Cassini’s mission was to explore Saturn, its rings and moons. He ended up making discoveries that continue to greatly influence planetary science.

“This latest discovery of phosphorus in Enceladus’ subsurface ocean has set the stage for what the habitability potential may be on other icy ocean worlds throughout the solar system,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory. in Southern California. who did not participate in the study. “Now that we know there are so many ingredients for life out there, the question is: Is there life beyond Earth, perhaps in our own solar system? I feel that Cassini’s lasting legacy will inspire future missions that could ultimately answer this very question.”