In a world first, astronomers detect phosphate in an alien ocean

Phosphate, a key building block of life, was detected in archive data from NASA's Cassini spacecraft.
Chris Young
An image of Enceladus captured by Cassini.
An image of Enceladus captured by Cassini.


Astronomers detected phosphate on Saturn's moon Enceladus, marking the first time the chemical compound has ever been detected in an ocean not on Earth.

The findings, published today, June 14, in a new paper in the journal Nature, were made after scientists poured over archive data from Cassini's Cosmic Dust Analyzer, captured before the Cassini probe crashed into Saturn on September 15, 2017.

This is a key discovery as phosphates are one of the main constituents of chromosomes, the carriers of genetic information in which DNA is found. It suggests we may be a step closer to finding alien life in one of the alien ocean worlds orbiting our Sun.

Searching for life on ocean worlds

The new discovery helps to shed new light on ocean worlds beyond Earth. These are a great source of interest among the scientific community as they have the potential to harbor life due to the abundance of water on these moons and planets.

NASA, for example, is sending its Europa Clipper spacecraft to Jupiter's moon, Europa, in a bid to study the celestial body's massive internal oceans and help determine whether the moon might be home to alien life.

Much like Europa, Enceladus is covered by a global ocean hidden beneath an outer icy crust. As it orbited Saturn, the Cassini mission collected a wealth of data on Saturn as well as its family of icy moons, including Enceladus.

According to a press statement, "analysis of ice grains ejected from the moon's subsurface ocean have been analysed here to offer new insights into the elemental composition of this subsurface ocean."

Computer models have previously suggested that presence of phosphorus on Enceladus, but scientists have not been able to agree whether the ocean moon contains large quantities of phosphates.

Investigating Cassini's Cosmic Dust Analyzer data

In their new paper, Frank Postberg, university professor for Planetary Sciences at the Department of Earth sciences at FU Berlin, and colleagues, analyzed data collected by Cassini's Cosmic Dust Analyzer to determine the chemical composition of Enceladus' oceans.

Their measurements showed that phosphorus is present in the form of orthophosphate ions. Not only that, they showed, by combining their findings with laboratory data, that the compound is available at concentration of at least 100 times higher than that of Earth's oceans.

In a world first, astronomers detect phosphate in an alien ocean
An artist's impression of the Cassini spacecraft orbiting Saturn.

Crucially, their models based on the results show that high phosphate levels are likely to be observed in other icy moons with similar environmental conditions.

The new study shows that one of the key components for life is likely abundant in certain types of icy ocean worlds. It's a promising finding, given the fact that NASA and ESA are sending probes to Europa in order to gain a better understanding of the conditions on the worlds. Ultimately, it could be a sign that life is, indeed, present in one of the distant oceans of our solar system.

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