The James Webb Space Telescope has observed Saturn for the first time, completing a family portrait of the Solar Systemโs ringed planets nearly a year after the missionโs first jaw-dropping image release.
Webbโs near-infrared camera took the picture of Saturn on June 25. Scientists added orange color to the monochrome picture to produce the image released Friday.
The picture shows Saturnโs iconic icy rings shining around the disk of the gas giant, which appears much darker in near-infrared due to the absorption of sunlight by methane particles suspended high in the planetโs atmosphere.
Researchers report that water on Enceladus, one of Saturnโs moons, holds phosphates.
The team used data from NASAโs Cassini space mission to detect evidence of phosphates in particles ejected from the moonโs ice-covered global ocean.
Phosphorus, in the form of phosphates, is vital for all life on Earth. It forms the backbone of DNA and is part of cell membranes and bones. The new study in Natureย is the first to report direct evidence of phosphorus on an extraterrestrial ocean world.
The team found that phosphate is present in Enceladusโ ocean at levels at least 100 times higherโand perhaps 1,000 times higherโthan in Earthโs oceans.
โBy determining such high phosphate concentrations readily available in Enceladusโ ocean, we have now satisfied what is generally considered one of the strictest requirements in establishing whether celestial bodies are habitable,โ says third author Fabian Klenner, a postdoctoral researcher in Earth and space sciences at the University of Washington.
โThis is the first finding of phosphorus on an extraterrestrial ocean world.โ
While at Freie Universitรคt Berlin, Klenner did experiments that revealed the high phosphate concentrations present in Enceladusโ ocean.
One of the most profound discoveries in planetary science over the past 25 years is that worlds with oceans beneath a surface layer of ice are common in our solar system. These ice-covered celestial bodies include the icy moons of Jupiter and Saturnโincluding Ganymede, Titan, and Enceladusโas well as even more distant celestial bodies, like Pluto.
NASAโs Cassini mission explored Saturn, its rings and its moons from 2004 to 2017. It first discovered that Enceladusโ harbors an ice-covered watery ocean, and analyzed material that erupted through cracks in the region of the moonโs south pole.
The spacecraft was equipped with the Cosmic Dust Analyzer that analyzed individual ice grains emitted from Enceladus and sent those measurements back to Earth. To determine the chemical composition of the grains, Klenner used a specialized setup in Berlin that mimicked the data generated by an ice grain hitting the instrument. He tried different chemical compositions and concentrations for his samples to try to match the unknown signatures in the spacecraftโs observations.
โI prepared different phosphate solutions, and did the measurements, and we hit the bullseye. This was in perfect match with the data from space,โ Klenner says. โThis is the first finding of phosphorus on an extraterrestrial ocean world.โ
Planets with surface oceans, like Earth, must reside within a narrow range of distances from their host stars (in what is known as the โhabitable zoneโ) to maintain temperatures at which water neither evaporates nor freezes. Worlds with an interior ocean like Enceladus, however, can occur over a much wider range of distances, greatly expanding the number of habitable worlds likely to exist across the galaxy.
In previous studies, the team at the Freie Universitรคt Berlin determined that Enceladus harbors a โsoda ocean,โ rich in dissolved carbonates, that also contains a vast variety of reactive and sometimes complex carbon-containing compounds. The team also found indications of hydrothermal environments on the seafloor.
The new study now shows the unmistakable signatures of dissolved phosphates.
โPrevious geochemical models were divided on the question of whether Enceladusโ ocean contains significant quantities of phosphates at all,โ says lead author Frank Postberg at Freie Universitรคt Berlin. โThese measurements leave no doubt that substantial quantities of this essential substance are present in the ocean water.โ
To investigate how the ocean on Enceladus can maintain such high concentrations of phosphate, geochemical lab experiments and modeling included in the new paper were conducted by a Japan-based team led by second author Yasuhito Sekine at the Tokyo Institute of Technology and a US-based team led by fourth author Christopher Glein at the Southwest Research Institute in San Antonio, Texas.
Source: University of Washington
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