These experiments suggest that Enceladus has a so-called “soda ocean” rich in carbonates that speed up the dissolution of phosphorus from rocks into the marine environment. To shed light on this mystery, Postberg’s team reconstructed an Enceladus-like environment in laboratory conditions using ocean water simulant and mineral-rich rocks. Their detection of sodium phosphates was “one of the nice surprises we got,” Postberg said, though the high concentrations of the compounds in Cassini’s samples raised the question of how phosphorus came to be so much more abundant in Enceladus’ ocean compared to Earth’s seas. Postberg and his colleagues have spent years poring over data captured by a Cassini’s Cosmic Dust Analyzer (CDA), an instrument that was not equipped to search for life, but could examine the properties and compositions of extremely small particles with a high degree of precision. It's just an ingredient that, at least for Earth, was essential for the emergence of life.” This phosphorus is not something that comes from any lifeform. "Of course, habitable does not mean inhabited. “This was basically the last piece that was needed to finally, now, deem Enceladus’ ocean to be habitable without any doubt,” Postberg said. Phosphorus plays a major role in many life processes, such as the transfer of energy within cells and the stability of DNA and cell membranes, but it is also the most elusive element in life’s toolkit.įor that reason, the discovery of phosphates in Enceladus’ marine environment has satisfied “what is generally considered to be the strictest requirement of habitability” and suggests that “Enceladus’s ocean could be a harbinger of high phosphorus availability in subsurface oceans across most of the outer Solar System,” according to the team’s study, which was published on Wednesday in Nature. Indeed, prior to the new study, scientists had shown that Enceladus’ ocean contains five of the six main elements that are needed for life as we know it-carbon, hydrogen, nitrogen, oxygen, and sulfur-leaving phosphorus as the absent piece of this bioessential puzzle. “That's why phosphorus got a lot of attention, because it was the only element that had not been detected by Cassini, and was considered critical.”
“The missing ingredient was phosphorus,” he continued. There is a rich variety of organic compounds we detected previously in the ice and vapor that is emitted in the plume.” There are very likely hydrothermal vent systems at the bottom of the ocean that would be an energy source, so you don't need sunlight. “The conditions in the ocean seem to be good for life. “Enceladus was already considered a pretty habitable place before this,” Postberg said in a call with Motherboard. Moreover, the team found that phosphate concentrations are 100 times higher in Enceladus’ ocean than in Earth’s marine habitats, suggesting that there is no shortage of this key element in the moon’s subsurface sea. Now, researchers led by Frank Postberg, a planetary scientist at Freie Universität Berlin, have discovered abundant supplies of phosphorus salts, known as sodium phosphates, in ice grains captured by Cassini from Saturn’s outer E-ring, which is primarily fed by the wellspring of Enceladus’ plumes. NASA’s Cassini spacecraft, which ended its mission in 2017, was fortuitously able to scoop up some of this frozen moon juice during its final years in orbit around Saturn, offering an unprecedented look at the contents of an extraterrestrial ocean. Though its marine environment is hidden under the moon’s icy shell, plumes of seawater erupt into space from geysers on the surface. Enceladus is a tiny ice world that measures about 300 miles across, but what it lacks in size it makes up for with its tantalizing subsurface ocean.
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