Searching for life beyond Earth. Important discovery regarding the moon of Saturn

“Enceladus is one of the main targets of researchers looking for life in our solar system,” says Dr. Christopher Glein of the Southwest Research Institute. He is the co-author of a study on Enceladus, which appeared in “Proceedings of the National Academy of Sciences” (DOI: 10.1073 / pnas.2201388119). – Since the Cassini spacecraft visited the Saturn system, we have been surprised many times by the discoveries made possible by the data collected at that time – adds the scientist.

Cassini discovered liquid water beneath Enceladus’ surface. She also analyzed her samples as plumes of ice grains and water vapor shot into space from cracks in the moon’s icy surface.

“We learned that these plumes contain almost all the essentials for life, at least as we know it,” explains Glein. “The probe did not identify phosphorus, but our team found evidence of its presence in the ocean under the moon’s icy crust,” he adds.

One of the most interesting discoveries in planetary science over the past 25 years is that worlds with oceans under a thick layer of ice are quite numerous in our solar system. Such worlds include the ice satellites of giant planets such as Europa, Titan, and Enceladus, as well as more distant bodies such as Pluto.

Worlds such as Earth, with surface oceans, must travel within a narrow range of their host stars in order to maintain the temperatures that keep the surface water liquid. However, worlds with subsurface oceans can exist over a much wider range of distances, greatly expanding the number of habitable places.

– The search for habitable extraterrestrial worlds in the solar system has changed. We are currently looking for the building blocks of life, including organic molecules, ammonia, sulfur-containing compounds, as well as the chemical energy needed to support life in our system, says Glein. Previous work has suggested that there may be little phosphorus on Enceladus, which would limit the prospects for life development, he adds.

Phosphorus in the form of phosphates is essential for all forms of life on Earth. It is essential for the formation of DNA and RNA, energy transfer molecules, cell membranes, bones and teeth in humans and animals, and even the marine microbiome and plankton.

Scientists performed thermodynamic and kinetic modeling that simulates the geochemistry of phosphorus based on Cassini’s data about the ocean system on Enceladus. In the course of their research, scientists developed the most detailed geochemical model to date of how seabed minerals dissolve in the Enceladus ocean. Research shows that phosphate minerals dissolve very well in the ocean waters of this moon.

– The geochemistry underlying our research is elegant and simple. It is she who makes the presence of dissolved phosphorus in the ocean of Enceladus inevitable, reaching levels close to or even higher than in Earth’s seawater, explains Glein. “This means for astrobiology that we can be much more certain than before that the ocean of Enceladus is habitable,” he adds.

According to Glein, the next step is clear: we must return to Enceladus to see if the habitable ocean is actually inhabited.

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