Life-Sparking Gas Strengthens Evidence That Enceladus, a Moon of Saturn, Could Be Habitable

Enceladus, an icy moon of Saturn, contains many building blocks needed to support life, including water, carbon dioxide, methane, ammonia and hydrogen gas. In a new study of data collected by the spacecraft Cassini, scientists identified another key molecule that could likely be added to that list: hydrogen cyanide. Despite the gas’s reputation as a poison, it’s thought to play a role in life’s beginnings.

“It’s the starting point for most theories on the origin of life,” Jonah Peter, a biophysicist at Harvard University and lead author of the new study, tells the New York Times’ Kenneth Chang. “It’s sort of the Swiss Army knife of prebiotic chemistry.”

The researchers also found evidence of several other organic compounds, including acetylene, propene and ethane, which also signal the moon’s potential to support life.

Scientists have found no evidence yet of life itself on the moon. But the compounds identified in the new study, published Thursday in the journal Nature Astronomy, have the potential to support microbial life or processes that could kick-start life’s emergence, the authors write.

The findings are a “very exciting” result, Kate Craft, a planetary scientist at Johns Hopkins University who was not involved in the research, says to Scientific American’s Ling Xin. By mixing together, the molecules could theoretically lead to “a habitable environment where life can be supported or might originate,” Craft tells the publication.

Small, cold and very bright, Enceladus contains a vast saltwater ocean beneath its icy surface. Geysers eject ice water and gas from the ocean into space at around 800 miles per hour. Most of the spewed material falls back to the surface, but some ends up in one of Saturn’s rings.

By taking samples from the giant plume, NASA’s Cassini spacecraft was able to provide insight into the chemical makeup of the moon’s ocean. It found not only water vapor, carbon dioxide and methane, but also salts and silica, which is made in warm temperatures and suggests the ocean contains hydrothermal vents.

Earlier this year, scientists also found evidence of phosphorus in the ice grains. Phosphorus was the last of the six elements essential for life to be detected on Enceladus, marking a key milestone in the search for life in our solar system.

For the new study, the researchers used statistical modeling to predict which set of chemical compounds in the geyser plumes would best explain the data collected by Cassini’s Ion and Neutral Mass Spectrometer.

“Searching for compounds in the plume is a bit like putting the pieces of a puzzle back together,” Peter tells Scientific American. “We look for the right combination of molecules that reproduce the observed data.”

Among the handful of molecules the models pointed to, hydrogen cyanide particularly intrigued the researchers.

“We don’t yet have a complete picture of the molecules that are there and that would be necessary for the origin of life—we don’t even know how the origin of life happened on Earth,” Peter tells New Scientist’s Leah Crane. “But we do have a good idea of some of the building blocks that are required for the beginning of life, and hydrogen cyanide is one of those extremely versatile building blocks.”

Hydrogen cyanide is an important molecule for forming amino acids, which are the building blocks of proteins and form components of both DNA and RNA.

The researchers also found organic compounds that were oxidized, meaning they’ve chemically combined with oxygen. This process releases chemical energy that could theoretically fuel life, per NASA. Taken together, the detection of these compounds “indicate the presence of a rich, chemically diverse environment that could support complex organic synthesis and possibly even the origin of life,” the study authors write.

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.