Enceladus, Saturn’s moon, constantly emits ice grains and gas plumes from its subterranean seas through fissures near the Antarctic region. A research team from the University of Stuttgart and the University of Berlin Fly utilized data from NASA’s Cassini spacecraft to chemically analyze newly emitted particles originating from Enceladus’ ocean. They successfully identified intermediates of organic molecules that may have biological significance (including aliphatic and (hetero)cyclic esters/alkenes, ethers/ethyl, and tentatively, nitrogen and oxygen-containing compounds), marking the first discovery of such compounds among ice particles in extraterrestrial oceans.
Artist’s impression of NASA’s Cassini spacecraft navigating through the plumes erupting from Enceladus’ Antarctic region. These plumes resemble geysers and release a mix of water vapor, ice grains, salt, methane, and various organic molecules. Image credit: NASA/JPL-Caltech.
Enceladus has a diameter of approximately 500 km, and its surface is covered by ice shells that are about 25-30 km thick on average.
Cassini made the first revelation of a hidden ocean beneath Enceladus’ surface back in 2005.
A current emerges from a fissure near the moon’s Antarctic, sending ice grains into space.
Some ice particles, smaller than grains of sand, settle on the moon’s surface, while others escape, forming a ring that orbits Enceladus around Saturn.
“Cassini consistently detected samples from Enceladus while passing through Saturn’s E ring,” noted Nozail Kawaja, a researcher at the Free University of Berlin and the lead author of the study.
“Many organic molecules have already been identified within these ice grains, including precursors to amino acids.”
The ice grains in the ring may be hundreds of years old and could have undergone changes due to strong cosmic radiation.
Scientists aimed to analyze the recently released grains to enhance their understanding of the dynamics within Enceladus’ seas.
Fortunately, they already had the relevant data. In 2008, Cassini flew directly through the ice sprays. The released primitive particles were emitted just minutes before they interacted with the spacecraft’s Cosmic Dust Analyzer (CDA) at speeds of approximately 18 km/sec. These represented not only the most recent ice grains Cassini has detected but also the fastest.
“Ice grains encompass not just frozen water, but also other molecules containing organic matter,” Dr. Kawaja stated.
“Lower impact speeds can break the ice, leading to signals from water molecule clusters that may obscure signals from certain organic molecules.”
“However, when ice grains strike the CDA at high speeds, the water molecules do not cluster, allowing previously hidden signals to emerge.”
Years of data from previous flybys were necessary to interpret this information.
This time, the authors successfully identified the molecules contained in the freshly released ice grains.
The analysis showed that certain organic molecules known to be present in the E rings were also found in the fresh ice grains, affirming their formation within Enceladus’ seas.
Furthermore, they discovered a completely new molecule that had never before been observed in Enceladus’ ice grains.
Chemical analyses revealed that the newly detected molecular fragments consisted of aliphatic, (hetero)cyclic esters/alkenes, ethers/ethyl, and potentially nitrogen and oxygen-containing compounds.
On Earth, these same compounds participate in a series of chemical reactions that ultimately yield more complex molecules essential for life.
“Numerous pathways from the organic molecules detected in Cassini’s data to potentially biologically relevant compounds exist, enhancing the possibility of habitability on the moon,” Dr. Kawaja mentioned.
“We have more data currently under review, so we anticipate further discoveries soon.”
“The molecules we identified in the newly released materials indicate that the complex organic molecules Cassini detected within Saturn’s E ring are not merely a result of prolonged exposure to space; they are readily found within Enceladus’ ocean,” added co-author Dr. Frank Postberg, also from the Free University of Berlin.
For more details, refer to the study featured in this month’s edition of Natural Astronomy.
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N. Kawaja et al. Detection of organic compounds in newly released ice grains from the Enceladus ocean. Nat Astron Published online on October 1, 2025. doi: 10.1038/s41550-025-02655-y
Source: www.sci.news
