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Scientists have long seen Saturn’s moon Enceladus, which harbors an ocean beneath its thick icy shell, as one of the best places to search 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 found intriguing evidence that supports the idea of Enceladus as a habitable ocean world.
Enceladus first attracted the attention of scientists in 2005 when plumes of ice grains and water vapor were seen rising through cracks in the moon’s ice shell and escaping into space. The spacecraft flew through and “sampled” the plumes, with data suggesting the presence of organic compounds within the plumes, some of which are vital to life.
The latest data analysis of Cassini’s flybys of Enceladus revealed the detection of a molecule called hydrogen cyanide that is toxic to humans but vital to processes that drive the origin of life. In addition, the team also found evidence to support that Enceladus’ oceans contain 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 Nature Astronomy.
“Our work provides further evidence that Enceladus hosts some of the most important molecules for creating the building blocks of life and sustaining that life through metabolic reactions,” said study author Jonah Peter , a doctoral student in biophysics at Harvard University. , in a statement.
“Not only does Enceladus appear to meet the basic requirements for habitability, we now have an idea of how complex biomolecules might form there, and what kind of chemical pathways might be involved.”
The essential ingredients for life as we know it on Earth include water, energy and chemical elements. The new research provides scientists with chemical blueprints that can be tested in laboratories, Peter said.
Finding building blocks for life
Amino acids are part of the building blocks of life, and hydrogen cyanide is thought to be a versatile molecule that allows amino acids to form, according to the study’s authors.
“The discovery of hydrogen cyanide was very exciting, as it is the starting point for most theories of the origin of life,” said Peter. “The more we tried to poke holes in our findings by testing other models, the stronger the evidence became.
Eventually, it became clear that there is no way to match the composition of the lead without including hydrogen cyanide.”
Previously, molecules such as carbon dioxide, methane, molecular hydrogen, water and ammonia were detected in Enceladus’ plumes, indicating the composition of the ocean beneath the ice shell that generates the plumes.
The combination of these elements together suggested that a process called methanogenesis, or the metabolic creation of methane, could be at work on Enceladus. Scientists suspect that methanogenesis may have also occurred early on Earth, contributing to the origin of life.
But the new research shows that more diverse and powerful sources of chemical energy are occurring within Enceladus’ ocean. In addition to hydrogen cyanide, organic compounds detected in the analysis included acetylene, propylene and ethane along with traces of alcohols such as methanol and molecular oxygen, suggesting that there is more than one way for life to have originated. nurtured within the ocean world.
“If methanogenesis is like a small watch battery, in terms of energy, then our results suggest that the ocean of Enceladus could offer something more like a car battery, which would be able to provide a large amount of energy to any life that ‘could be there,” study co-author Kevin Hand, deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement.
Now, the authors of the study want to investigate how diluted the organic compounds are within the subsurface ocean because the dilution of these compounds could determine whether Enceladus could support life.
In the future, astronomers hope to launch a dedicated mission to investigate Enceladus, which could provide a definitive answer as to whether life exists in the ocean world.
Although the Cassini mission ended six years ago, its data remains 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,” study co-author Tom Nordheim, a planetary scientist at JPL who worked on the Cassini mission, said in a statement.
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