The search for life outside Earth. Important discovery about Saturn’s moon

“Enceladus is one of the main targets of researchers searching for life in our solar system,” says Dr. Christopher Glenn 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 several times by the discoveries that were made possible thanks to the data collected at that time – the scientist adds.

Cassini has discovered liquid water under the surface of Enceladus. It also analyzed its samples as plumes of ice grains and water vapor shot out into space from cracks in the moon’s icy surface.

“We’ve learned that these pillars contain nearly all of life’s necessities, at least as we know them,” Glenn explains. “The probe did not identify phosphorous, but our team found evidence of it in the ocean under the moon’s icy crust,” he adds.

One of the most intriguing discoveries in planetary science over the past 25 years is that in our Solar System there are very many worlds with oceans beneath a thick layer of ice. These worlds include icy satellites of giant planets such as Europa, Titan and Enceladus, as well as distant objects such as Pluto.

Worlds like Earth, with surface oceans, must travel within a narrow band of their host stars in order to maintain temperatures that maintain surface water fluids. However, worlds with subterranean oceans can exist over a much wider range of distances, which leads to a significant increase in the number of habitable places.

The search for habitable extraterrestrial worlds in the solar system has changed. We’re currently looking for the building blocks of life, including organic molecules, ammonia, and sulfur-containing compounds, as well as the chemical energy needed to support life in our system, says Glenn. He adds that previous work indicated that there may be little phosphorous on Enceladus, which could limit the possibilities for life to develop.

Phosphorous in the form of phosphate is necessary for all 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 have performed thermodynamic and kinetic modeling that simulates the geochemistry of phosphorous based on Cassini data about the ocean system on Enceladus. In the course of their research, the scientists developed the most detailed geochemical model yet of how seafloor minerals in the ocean of Enceladus are melting. Research shows that phosphate minerals dissolve well in the ocean waters of this moon.

The geochemistry upon which our research is based is elegant and simple. It’s what makes the presence of dissolved phosphorous in Enceladus’ oceans inevitable, reaching levels close to or above seawater on Earth, Glenn explains. “This means for astrobiology that we can be more certain than before that Enceladus’ ocean is habitable,” he adds.

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