The ocean inside Saturn’s moon Enceladus may be enriched in phosphorus, an essential element for life as we know it, new research shows.
Phosphorus is an important part of the biochemistry of life. For example, it combines with sugars to provide a “backbone” for DNA, binding the four nucleobases to the double helix. Phosphorus is also used in cell membranes and bones, and in a molecule called adenosine triphosphate, which carries metabolic energy throughout the body.
However, previous studies had indicated that phosphorus would rarely be present Enceladus. Scientists caught a glimpse of the composition of the ocean through the giant water geysers who squirt out”tiger stripes,” deep openings in the moon’s icy surface. On numerous occasions before the end of the mission in 2017, NASA Cassini spacecraft flew through and “tasted” these geysers and analyzed the chemical components. The spacecraft discovered elements and molecules vital to life as we know it, including organic molecules such as methaneplus ammonia, carbon, nitrogen, oxygen and possibly hydrogen sulfide.
Related: How phosphorus helped oxygenate the Earth’s atmosphere
However, the lack of phosphorus is noteworthy. In 2018, research by Harvard’s Manasvi Lingam and Avi Loeb concluded Phosphorus would be scarce in the ocean of Enceladus because phosphorus in the rocks on the seabed would slowly dissolve into the ocean. On EarthPhosphorus is made available by the weathering of dry land, which Enceladus lacks.
However, a new study led by Jihua Hao, a senior research scientist at the University of Science and Technology of China, contradicts these earlier findings, claiming that the 2018 research used outdated geochemical models of Enceladus’ rocky seafloor.
“While the bioessential element phosphorus has yet to be directly identified, our team has uncovered evidence of its availability in the ocean beneath the moon’s icy crust,” said study co-author Christopher Glein, a senior research scientist at the Southwest Research Institute in San Antonio said in a expression.
Using new models based on the latest available data, Hao and Glein’s group simulated how phosphorus-rich minerals, called phosphates, dissolve into the ocean from Enceladus’ rocky core. In particular, the team found that the rate of dissolution of a mineral called orthophosphate would be much higher than previous studies had suggested and would be able to fill the ocean at a concentration high enough to support life in just tens of thousands of years support. One reason for this high concentration is the presence of bicarbonates in ocean water, whose chemical properties allow phosphates to accumulate in the ocean.
“The underlying geochemistry has an elegant simplicity that makes the presence of dissolved phosphorus inevitable, reaching levels close to or even exceeding those found in modern seawater.” [on Earth]’ said Glein. “For astrobiology, this means we can be more confident than ever that Enceladus’ ocean is habitable.”
Despite the tantalizing possibilities, the results represent a hypothesis; to prove that the ocean of Enceladus contains phosphorus, a future Mission to Enceladus would have to directly detect orthophosphate or another phosphorus-derived mineral in the water geysers that periodically erupt from the moon.
“We need to return to Enceladus to see if a habitable ocean is actually inhabited,” Glein said.
The results were published in the journal on September 19 Proceedings of the National Academy of Sciences.
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