Scientists Discover Phosphorus on Enceladus

A international team of scientists has made a groundbreaking discovery, finding phosphorus, an essential chemical element for life, locked inside salt-rich ice grains ejected into space from Saturn's moon Enceladus.

Using data collected by NASA’s Cassini mission, The findings shed light on the potential habitability of the small moon and have significant implications for the search for life beyond Earth.

Enceladus is known to harbor a subsurface ocean, with water erupting through cracks in its icy crust as geysers at the moon's south pole, creating a plume that feeds Saturn's E ring with icy particles.

Credit: NASA

Cassini had the opportunity to fly through the plume and E ring multiple times during its 13 year mission starting in 2004. During these flybys, scientists discovered that Enceladus' ice grains contain a diverse array of minerals and organic compounds, including the building blocks for amino acids associated with life as we know it.

However, phosphorus, which is crucial for biological processes and a fundamental component of DNA and energy-carrying molecules, had not been detected until now. This element is present in the bones of mammals, cell membranes, and ocean-dwelling plankton, making it a vital ingredient for life on Earth.

The recent study, led by Frank Postberg, a planetary scientist at Freie Universität Berlin, Germany, and published in the journal Nature, revealed the presence of substantial amounts of phosphorus salts within the icy particles ejected by Enceladus' plume.

This is the first time phosphorus has been discovered in an ocean beyond Earth.

Previous analyses of Enceladus' ice grains had already revealed concentrations of sodium, potassium, chlorine, and carbonate-containing compounds, as well as computer modeling suggesting habitable conditions in the subsurface ocean.

The new findings further support the notion that Enceladus may be capable of sustaining life.

To conduct the study, the scientists accessed data from NASA's Planetary Data System, a long-term archive of digital data products from the agency's planetary missions. By focusing on data collected by Cassini's Cosmic Dust Analyzer instrument when it sampled icy particles from Enceladus in Saturn's E ring, the team was able to analyze a larger number of compositional signals. This analysis led to the discovery of high concentrations of sodium phosphates within some of the ice grains.

To validate their findings, co-authors from Europe and Japan carried out laboratory experiments demonstrating that Enceladus' ocean contains phosphorus in various water-soluble forms of phosphate, with concentrations at least 100 times higher than those found in Earth's oceans. Geochemical modeling by the team also suggested that other icy ocean worlds in the outer solar system, particularly those formed from primordial ice containing carbon dioxide, may harbor abundant phosphate.

Christopher Glein, a planetary scientist and geochemist at Southwest Research Institute in San Antonio, Texas, who was involved in the study, highlighted the significance of the discovery, stating that high phosphate concentrations on Enceladus are a result of interactions between carbonate-rich liquid water and rocky minerals on the moon's ocean floor. He added that similar conditions may exist on other ocean worlds, making this a stunning finding for astrobiology.

While the presence of phosphorus and other building blocks for life on Enceladus is promising, the scientists emphasized that the discovery does not confirm the existence of life on the moon or any other extraterrestrial environment. The presence of the necessary ingredients is a prerequisite, but other factors are also critical for the development and sustenance of life.

The question of whether life could have originated in Enceladus' ocean remains unanswered.

Although Cassini's mission concluded in 2017 when the spacecraft burned up in Saturn's atmosphere, the wealth of data it gathered will continue to be a valuable resource for decades to come.

Initially designed to explore Saturn, its rings, and moons, Cassini made numerous unexpected discoveries that have far-reaching implications beyond planetary science.