The study zooms in on data collected by NASA’s Cassini on Saturn’s icy moon and finds evidence of a key ingredient for life and a powerful energy source to power it. Scientists know that the giant cloud of ice grains and water vapor emerging from Saturn’s moon Enceladus is rich in organic compounds, some of which are important for life as we know it. Now, scientists analyzing data from NASA’s Cassini mission are expanding the evidence for life: they have found strong evidence for hydrogen cyanide, a molecule that holds the key to the origin of life.

Researchers also found evidence that the ocean lurking beneath the moon’s icy outer shell and feeding the cloud contains a powerful source of chemical energy. The hitherto unidentified source of energy comes in the form of various organic compounds, some of which serve as fuel for organisms on Earth.

The results were published on: Nature Astronomy, showing that there may be much more chemical energy inside this tiny moon than previously thought. The more energy available, the more likely life is to reproduce and sustain itself.

“Our study provides further evidence that Enceladus is home to some of the most important molecules that both form the building blocks of life and sustain that life through metabolic reactions,” said lead author Jonah Peter, a postdoctoral fellow at Harvard University who conducted much of the research. . The research is being run at NASA’s Jet Propulsion Laboratory in Southern California.

“Not only does Enceladus appear to meet the basic requirements for habitability, but we now have an idea about how complex biomolecules might form there and what chemical pathways might be involved.”

“The discovery of hydrogen cyanide was particularly exciting because it was the starting point for most theories regarding the origin of life,” Petro said. said. Life as we know it requires building blocks such as amino acids, and hydrogen cyanide is one of the most important and versatile molecules needed to form amino acids. Because its molecules can be combined in many different ways, the study authors call hydrogen cyanide the Swiss Army knife of amino acid precursors.

“The more we tried to refine our results by testing alternative models, the stronger the evidence became,” Peter added. “In the end, it became clear that there was no way to reconcile the composition of the smoke without including hydrogen cyanide.”

In 2017, scientists found evidence of chemistry on Enceladus that could help support life in its ocean, if it existed. The combination of carbon dioxide, methane and hydrogen in the smoke indicated methanogenesis, the metabolic process that produces methane. Methanogenesis is common on Earth and may be crucial to the origin of life on our planet.

The new study reveals evidence for additional sources of chemical energy that are much more powerful and diverse than methane production: The authors found a number of organic compounds that were oxidized; This tells scientists that there are many chemical pathways in Enceladus’ subsurface ocean that could potentially support life. . This is because oxidation promotes the release of chemical energy.

“If methanogenesis is like a tiny clock battery in terms of energy, our results suggest that the Enceladus ocean may offer something more like a car battery, capable of providing large amounts of energy to any life that might exist,” said Kevin Hand. JPL is a co-author of the study and principal investigator of the study that led to the new results.

Math is the way

Unlike previous studies that used laboratory experiments and geochemical modeling to replicate the conditions Cassini found on Enceladus, the authors of the new paper relied on detailed statistical analysis. They examined data collected by the Cassini Neutral Ion Mass Spectrometer, which examines gas, ions and ice grains around Saturn.

By measuring the amount of information contained in the data, the authors were able to detect subtle differences between how well different chemical compounds explained Cassini’s signal.

“There are many potential pieces of the puzzle that can be put together when trying to match observed data,” Petro said. “We used mathematical and statistical modeling to determine which combination of puzzle pieces best fit the composition of the cloud and make the best use of the data without over-interpreting the limited data set.”

Scientists are still far from answering the question of whether life began on Enceladus. But as Peter points out, the new work reveals chemical pathways for life that can be tested in the laboratory.

Cassini, meanwhile, is a mission that continues to yield results long after Enceladus was discovered to be an active moon. The mission ended in 2017 when the spacecraft deliberately plunged into Saturn’s atmosphere. “Our study shows that even though Cassini’s mission is over, its observations continue to provide us with new information about Saturn and its moons, including the mysterious Enceladus,” said Tom Nordheim, a JPL planetary scientist and co-author of the study. From the Cassini team.