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Scientists have long looked to Saturn’s moon Enceladus, which has an ocean beneath its thick, icy shell, as one of the best places to look for life beyond Earth.
Now, a new analysis of data collected by NASA’s Cassini mission, which orbited Saturn and its moons between 2004 and 2017, has revealed intriguing evidence that further supports the idea that Enceladus is a habitable ocean world.
Enceladus initially caught the attention of scientists in 2005 because ice and water vapor were seen rising through cracks in the moon’s ice and escaping into space. The spacecraft flew through the plumes and “sampled” them, data indicating the presence of organic compounds within the plumes, some of which are important for life.
Recent data analysis of Cassini’s flybys of Enceladus revealed the detection of a molecule called hydrogen cyanide, which is toxic to humans but critical to the processes that drive the origin of life. What’s more, the team also found evidence that Enceladus’ ocean contains organic compounds that provide a source of chemical energy that could be used as a powerful fuel for any form of life.
A study detailing the findings was published Thursday in the journal Natural Astronomy.
“Our work provides additional evidence that Enceladus hosts some of the most important molecules for building the building blocks of life and sustaining that life through metabolic reactions,” said Jonah Peters, a doctoral student in biophysics at Harvard University. , in a statement.
“Not only does Enceladus seem to meet the basic requirements for life, but we now have an idea of how complex biomolecules might form there and what kind of chemical pathways might be involved.”
Materials needed for life on Earth include water, energy, and chemical elements. The new research gives scientists chemical maps that can be tested in labs, Peter said.
Amino acids are some of the building blocks of life, and hydrogen cyanide is considered a versatile molecule that allows amino acids to be formed, the study authors report.
“The discovery of hydrogen cyanide was particularly exciting because it is the starting point for most theories about the origin of life,” Peter said. “The more we tried to poke holes in our results by testing alternative models, the stronger the evidence became.
Eventually, it became clear that there was no way to match the bloom composition without adding hydrogen cyanide.
Previously, molecules such as carbon dioxide, methane, molecular hydrogen, water and ammonia were detected in Enceladus’ plumes, reflecting the composition of the ocean beneath the ice.
The combination of these elements suggested a process called methanogenesis, or the metabolic creation of methane, may be at play on Enceladus. Scientists believe methanogenesis may have played a role on early Earth, contributing to the origin of life.
But new research indicates that more diverse and powerful chemical energy sources occur within Enceladus’ ocean. In addition to hydrogen cyanide, the organic compounds found in the analysis included acetylene, propylene and ethane, as well as traces of alcohols such as methanol and molecular oxygen, suggesting there is more than one way to survive in the marine world.
“If methanogenesis is like a small watch battery, in terms of energy, our results suggest that the Enceladus ocean may provide something akin to a car battery, capable of providing more energy to any life.” Kevin Hand, associate program scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement.
Now, the study authors want to investigate how diluted organic compounds are within the subsurface ocean, as this could determine whether the dilution of these compounds could support life on Enceladus.
In the future, astronomers hope to send a dedicated mission to investigate Enceladus, which will provide a definitive answer on whether life exists in the ocean world.
Although the Cassini mission ended six years ago, its data is still a treasure trove of new information.
“(The mission’s) observations continue to give us new insights into Saturn and its moons — including the enigmatic Enceladus,” JPL planetary scientist Tom Nordheim, who worked on the Cassini mission, said in a statement.