For the first time, phosphorus – the rarest of the six elements on which life as we know it depends – has been found on a small, ocean-bound moon in our solar system.
Scientists comb through data sent home by NASA Cassini spacecraft Nearly 15 years ago they said they found abundant phosphorous in geysers that routinely erupt into space from Enceladusa small moon from Saturn And one of the most likely places in Solar System Where life might exist.
Enceladus is an ice-covered moon that harbors a vast ocean of liquid water under an icy crust. Scientists have previously found other building blocks for life in the lunar ocean including carbon, hydrogen, nitrogen, sulfur and oxygen. However, phosphorus, which combines with sugars to form a skeleton for DNA molecules and also helps repair and maintain cell membranes, has so far eluded detection.
Related: Saturn’s moon Enceladus erupts a 6,000-mile-high plume of water. Could life be lurking beneath its icy crust?
The intriguing new findings estimate that phosphorus concentrations on Enceladus are at least 500 times higher than the highest known concentrations on Earth. Landoceans. The discovery, announced in a research paper published Wednesday (June 14), shows that the icy moon, already one of the top candidates in the search for alien life, now meets “the most stringent requirements for habitability.”
“We didn’t find life or even something life created,” Frank Postberg, a professor of planetary sciences at Freie Universität Berlin in Germany who led the research, told Space.com. He added, “We just found signs of something that indicates life could very well be forming there. It’s just a habitability indicator, a very good and important indicator.”
For the past five years, Postberg and his colleagues have been studying data collected by Cassini in 2008, when the spacecraft flew by and “tasted” the geysers that Enceladus had. ejected into space. These powerful water jets are likely triggered when gas giant Saturn’s gravity presses against the moon, warming its rocky interior. The pressurized water then flows through cracks in the ice crust, blasting through space at 79 gallons (360 liters) per second, fast enough to fill an Olympic-sized swimming pool in just two hours. While most of the plume material falls as snow on the surface of the moon, some of it is also fed away SaturnRing E, a faint halo of tiny ice particles. It was these particles that collided with Cassini’s instruments during its flyby.
while previous search Based on computer models concluding that there may be phosphorus on Enceladus, this is the first time that the elemental component has been directly observed in material from Enceladus’ geysers.
“The only indirect thing is that the phosphate salts were found in Saturn’s E ring, not in the pole itself,” Christopher Glenn, a planetary scientist and geochemist at Southwest Research Institute in Texas and one of the new study’s authors, tells Space.com. “But we do know that the Enceladus plume feeds into the E ring. There is no mystery there,” he added.
While browsing the measurements of more than 300 ice grains sampled by the Cassini spacecraft and the data reproduced in the lab for validation purposes, the team behind the new study discovered nine grains that contained a clear fingerprint of phosphate, the only form of phosphorus that It can absorb living organisms And they are used by them for growth.
“It was a baffling moment when I first realized that these spectra most likely show phosphates,” Postberg said, adding that his team was neutral while analyzing the data. “I admit that phosphates are probably the best thing we could find, but we weren’t specifically looking for them.”
Scientists are divided over the presence of phosphorus on Enceladus. a Study 2018 Typical phosphorus concentrations on the Moon have inferred that the crucial element will be depleted in the Moon’s oceans and thus unavailable for potential life. However, the new study “flips my findings from my previous model,” Manasvi Lingam, who led the 2018 research but was not part of the new study, told Space.com. “In science, it is common for old theories to be replaced by newer theories and improved data—in fact, this is how the field is progressing.”
The results of the latest study are consistent with what a team of scientists including Glenn found in 2022. Using updated geochemical models, the team was able to estimated That orthophosphate would in fact dissolve at a much higher rate than previously expected in the waters of Enceladus, resulting in an ocean that could be 1,000 times richer in phosphorus than Earth’s.
The new study also concludes that orthophosphate is “readily available” in Enceladus’ oceans, with the best estimate of the abundance of this phosphate being 1,000 times more abundant than in Earth’s oceans. On Earth, phosphorus is released by rocks during erosion and weathering of dry land, which Enceladus does not have. Instead, scientists believe that interactions between the waters of the moon’s ocean and the rocks that make up its core dissolve large amounts of phosphorus into the ocean.
“Nobody would be surprised if there are phosphates in the Enceladus rock. There are phosphates on comets…it’s no big deal,” Postberg said. “The important thing is that it dissolves into the ocean however [it’s] readily available for the potential formation of life.”
This discovery has implications beyond the corner of Enceladus in the solar system. Phosphorus is very scarce in natural waters because it readily reacts with positively charged atoms such as calcium to form calcium phosphate, which traps the phosphorus and thus renders it unfit for life forms. But Enceladus is able to host such large amounts of dissolved phosphorus because it contains what scientists call a soda ocean.
Soda oceans or soda lakes are rich in carbonates – minerals that contain carbon dioxide and form easily in the water. Carbonates bind to other elements, such as calcium, leaving phosphorus available for life’s use. This process can be seen at Land also. Mono Lake in California, soda lakes in Nevada, and Borax Lake in Oregon are just a few examples of soda lakes where rich ecosystems can survive. Elsewhere in the world, Africa, Asia and Europe are known to have similar soda lakes.
In the solar system, celestial bodies that host oceans beyond the frost line—the arbitrary point in the system between the asteroid belt and Jupiter’s orbit beyond which carbon and ice begin to condense into solid ices—will inevitably have a soda ocean, according to a new study.
Postberg and his team found large amounts of carbonates in the ice grains that Cassini sampled, indicating that ocean worlds like Enceladus–like the four largest of Uranus’ moons that were recently Found to host buried oceans – All these “soda oceans should be and should have an easy time dissolving the phosphates from the rock,” Postberg said.
The planetary building blocks from which all the planets and moons of the solar system are formed are rich in carbonates, so any celestial body in the outer solar system that has an ocean in contact with rocks could host a soda lake that could harbor abundant amounts of phosphates.
“These carbonates, this is something common in the outer solar system,” Postberg said. “This applies not only to Enceladus but to all ocean worlds in the outer solar system.”
So while the exact amount of phosphorus in Enceladus’ ocean is still an estimate — the researchers say local concentrations could remain higher or lower since we don’t yet know everything about the moon’s functioning — the debate over whether phosphorus itself is a critical component for life, Existing on the surface of the moon seems to have finally been settled.
“It’s habitable — obviously, it’s hard to argue against that — but we don’t know if it’s inhabited,” Postberg said.
Researchers know little, if any, of what happens to ocean water on Enceladus as it travels out of the ocean, through the ice crust, and out into space. Elucidating how this transfer process works will give us a better understanding of moon habitability assessments from spacecraft measurements, according to Glenn.
“I think we’re up for the challenge!” He said.
The new research is described in A paper Published Wednesday (June 14) in the journal Nature.
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