The ocean on Saturn’s moon Enceladus contains large amounts of phosphorus – a chemical element of great importance in the origin and development of life as it is known on Earth. This is shown by archive data from the space probe Cassiniwhich have now been re-analyzed by an international research team and compared to laboratory experiments on Earth. The scientists write in the science journal that the ocean of Enceladus fulfills even the strictest criteria for classification as “life-friendly”. Nature.
In addition to hydrogen, oxygen and carbon, researchers consider sodium, sulfur and phosphorus to be essential for the existence of life as it evolved on Earth. Phosphorus is not only an important component of the genetic material DNA, but also the central chemical element for energy transport in cells. But “of these six elements, phosphorus is the rarest in the cosmos,” explain Frank Postberg from Freie Universität Berlin and his colleagues.
Higher concentration of phosphorus than in Earth’s oceans
In the search for life in our solar system, scientists have increasingly focused on the icy moons of the planets Jupiter and Saturn in recent years. Because many of them have deep oceans of water under kilometers of ice shells. “But so far, phosphorus has not been detected in any of these oceans,” say the scientists.
Saturn’s moon Enceladus in particular offers a chance for such evidence. It is tectonically active at its south pole and shoots ice particles and water vapor out several thousand kilometers into space from several fountains.
The US spacecraft Cassini, which orbited Saturn from 2004 to 2017, flew through these fountains several times. In the ice particles captured by a special instrument, the Cosmic Dust Analyzer, researchers initially detected organic – i.e. carbon-based – molecules, but no phosphorus. Experts have therefore debated whether Enceladus’ ocean contains sufficient amounts of this element to support life.
Postberg and his colleagues now have data from a total of 345 of Cassini Once again analyzed the trapped ice particles with new methods and improved accuracy and found nine particles that show an unusual composition that differs from the other particles: they contain molecules whose mass corresponds to that of sodium phosphates. In order to estimate how much phosphate the ice particles and thus the ocean of Enceladus contain, the team also carried out a series of laboratory experiments.
‘Our observations and our laboratory experiments suggest that phosphorus is available in the form of phosphates in the Enceladus ocean,’ the researchers conclude in their paper. “And in concentrations a hundred times higher than in the Earth’s oceans.” If the availability of phosphorus was previously considered a hurdle for the livability of Saturn’s moon, this hurdle has now been overcome.
However, the investigations by Postberg and his team go far beyond Enceladus: In their opinion, the chemical conditions in the oceans of other icy moons of Saturn and Jupiter should be similar and phosphorus should therefore also be abundant there. All of these moons could therefore be habitable.