Enceladus, one of Saturn’s small icy moons, spans just 300 miles (500 kilometers) — yet despite its modest size, it has become a star in the search for life beyond Earth. From cracks near its south pole, the moon blasts towering geysers of water vapor, ice and organic molecules into space, which are tantalizing hints of a hidden ocean that could, in theory, be habitable.
But new research presented this week at a planetary science conference in Finland shows that many of the organic molecules detected in these plumes could also form right on the moon’s surface, driven by relentless radiation from Saturn’s magnetic field. The results cast doubt on whether the plumes truly carry whispers of alien life, or merely echoes of lifeless chemistry on the frozen shell.
“Although this doesn’t rule out the possibility that Enceladus‘ ocean may be habitable, it does mean we need to be cautious in making that assumption just because of the composition of the plumes,” study lead Grace Richards of Italy’s National Institute for Astrophysics said in a statement.
For their experiment, Richards and her colleagues recreated conditions on Enceladus in miniature inside a specialized laboratory in Hungary. Using an ice chamber, the team froze mixtures of water, carbon dioxide, methane and ammonia to a bone-chilling –420 degrees Fahrenheit (-253 degrees Celsius), mimicking frigid conditions near the moon’s surface. The ices were then bombarded with high-energy “water-group ions,” the same charged particles trapped around Saturn that constantly irradiate Enceladus.
To monitor the chemical changes induced by radiation, the researchers used infrared spectroscopy to observe the molecular “fingerprints,” or spectra, of the ices. As radiation interacted with the samples, the spectra shifted, signaling the formation of new molecules.
Each of the five experiments produced carbon monoxide, cyanate, and ammonium — compounds that were detected in Enceladus’ plumes by NASA’s Cassini spacecraft in 2005. When the samples were gently warmed, more complex organics appeared, including carbamic acid, ammonium carbamate and potential amino acid precursors including methanol and ethanol, as well as molecules like acetylene, acetaldehyde and formamide, which are building blocks that could contribute to the chemistry of life.
“Although many of these products have not previously been detected on Enceladus’ surface, some have been detected in Enceladus’ plumes,” Richards and her…
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