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New Organic Compounds Found in Plumes From Saturn’s Icy Moon Enceladus

Analysis of data from the late, great Cassini spacecraft reveals the moon is spurting oxygen and nitrogen-bearing organic compounds into space

(NASA/JPL/Space Science Institute)
smithsonian.com

Earlier this week, NASA revealed that researchers have detected more organic compounds in the plumes of water jetting from the surface of Enceladus, the icy moon orbiting the planet Saturn. The new molecules include oxygen and nitrogen-bearing organic compounds, or molecules that contain the element carbon.

In 2017, it was revealed that the Cassini space probe detected organic molecules in 2004 and 2008 after flying through plumes of spray from four cracks in the ice near the south pole of Enceladus. Cassini’s instruments determined that 98 percent of the material blown into space was water and ice, while about 1 percent was hydrogen and the rest was composed of carbon dioxide, methane and ammonia.

To dig deeper into the Cassini data, detailed in the journal Monthly Notices of the Royal Astronomical Society, Nozair Khawaja of the Free University of Berlin and his team analyzing data collected by the mass spectrometer on the craft’s Cosmic Dust Analyzer. What they found is evidence of nitrogen and oxygen containing amines, a class of molecules derived from ammonia that are similar to those that combine into amino acids on Earth, reports Ryan F. Mandelbaum at Gizmodo. Amino acids are among the critical building blocks of life as we know it.

Scientists believe Enceladus contains a global subsurface ocean beneath a shell of ice. According to the press release, the plumes may form when hydrothermal vents eject material from the moon’s rocky core. That material mixes with water in the subsurface ocean before it is blasted through the cracks in the surface into space. Some of the water vapor condenses into ice grains, and researchers believe the amines condense on the surface 0f these grains.

The finding raises the possibility that life exists, or could develop in the future, on Enceladus. “If the conditions are right, these molecules coming from the deep ocean of Enceladus could be on the same reaction pathway as we see here on Earth,” Khawaja says. “We don't yet know if amino acids are needed for life beyond Earth, but finding the molecules that form amino acids is an important piece of the puzzle.”

Last year after analyzing the Cassini data the same team found fragments of large, complex organic molecules that they believe were produced by the hydrothermal vents. The researchers hypothesized that large bubbles of gas emanating from the vents in the seafloor could rise through miles of ocean, leaving a thin film of organic molecules on the surface of the sea beneath the moon’s icy shell.

But the amines detected in the new study are even more exciting. “Here we are finding smaller and soluble organic building blocks—potential precursors for amino acids and other ingredients required for life on Earth,” co-author Jon Hillier says in the press release.

Though the Cassini spacecraft met its end during a controlled crash into Saturn in 2017, the massive amount of data it collected during 13 years exploring the Saturn system is still being analyzed. Just last month, data revealed that huge lakes on the surface of Saturn’s moon Titan were likely made by explosions of warming nitrogen. Also this year, post-mortem Cassini data suggested that Saturn’s rings are only between 10 and 100 million years old, helped to establish the length of a day on Saturn and revealed that the five tiny moons orbiting within Saturn’s rings are heavily coated in ring dust.

NASA has no firm plans to return to Enceladus. Instead, the space agency is funding the Dragonfly Mission to Saturn’s larger moon Titan, where a large rotorcraft will explore the planet searching for the building blocks of life.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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