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June 14, 2023
An artist’s rendering of Saturn’s moon Enceladus depicts coastal hydrothermal activity and cracks in the moon’s icy crust. Those ejected particles, traces of the surface ocean, were analyzed by instruments on board the Cassini spacecraft. New analysis finds evidence of phosphates, a key building block for life as we know it.NASA/JPL-Caltech
An international team, including a University of Washington scientist, has discovered that water in one of Saturn’s moons contains phosphates, a key building block for life. A team led by the Freie Universität Berlin has used data from NASA’s Cassini spacecraft to detect evidence of phosphates in particles ejected from the icy global ocean of Saturn’s moon Enceladus.
Phosphorus, in the form of phosphate, is essential for all life on Earth. It forms the backbone of DNA and is part of cell membranes and bones. New studyPublished June 14 in Nature, the first reported direct evidence of phosphorus in an extraterrestrial ocean world.
The team found that Enceladus’ oceans contain at least 100 times more phosphate—and perhaps a thousand times more—than Earth’s oceans.
„By determining the high phosphate concentrations readily available in Enceladus’ ocean, we have now satisfied what is generally considered one of the most stringent requirements for establishing whether celestial bodies are habitable,” said the third author. Fabian Kleiner, a UW postdoctoral researcher in Earth and space sciences. While at the Freie Universität Berlin, Kleiner conducted experiments that revealed high phosphate concentrations in Enceladus’ ocean.
One of the most profound discoveries in planetary science in the last 25 years is that worlds with oceans beneath the surface layer of ice are common in our solar system. These icy bodies include the icy moons of Jupiter and Saturn – including Ganymede, Titan and Enceladus – as well as more distant celestial bodies such as Pluto.
of NASA The Cassini mission From 2004 to 2017 it explored Saturn, its rings and its moons. It first discovered that Enceladus has an ice-covered watery ocean, and studied material blasted through cracks in the moon’s south polar region.
The spacecraft was equipped Cosmic Dust Analyzer. It probed the individual ice masses ejected from Enceladus and transmitted those measurements back to Earth. To determine the chemical composition of the grains, Kleiner used a special system in Berlin that mimics the data generated by the ice hitting the instrument. He tried different chemical compositions and concentrations for his samples to match the unknown signatures in the spacecraft’s observations.
„I prepared different phosphate solutions, did the measurements, and we hit Bulls. It was a perfect match with the data from space,” Kleiner said. „This was the first discovery of phosphorus on an extraterrestrial ocean world.”
Planets with Earth-like surface oceans must reside at a short distance from their host stars (called the „habitable zone”) to maintain temperatures where water does not evaporate or freeze. However, worlds with an internal ocean, such as Enceladus, can occur over a much wider range of distances, greatly expanding the number of potentially habitable worlds across the galaxy.
In previous studies, the team at Freie Universität Berlin found that Enceladus has a „soda ocean” rich in dissolved carbonates that contain a variety of reactive and sometimes complex carbon-containing compounds. The team also found signs of hydrothermal environments on the ocean floor. The new study now shows unmistakable signatures of dissolved phosphates.
„Previous geochemical models have been divided on the question of whether Enceladus’ ocean contains significant amounts of phosphates,” said the lead author. Frank Postberg at the Freie Universität Berlin. „These measurements leave no doubt that seawater contains significant amounts of this essential substance.”
To investigate how the ocean on Enceladus could maintain such high concentrations of phosphate, the geochemical laboratory experiments and modeling included in the new paper were conducted by a second author-led team from Japan. Yasuhito Sekin Tokyo Institute of Technology and an American team led by the fourth author Christopher Klein at the Southwestern Research Institute in San Antonio, Texas. Other authors are from Germany, USA, Japan and Finland.
For more information, contact klenner at [email protected] and Postberg at [email protected].
Adapted from a press release of the Free Universität Berlin.
Tag(s): Astrophysics • College of the Environment • Department of Earth and Space Sciences • Fabian Kleiner • Space Sciences