Saturn’s moon Enceladus, about 500 kilometers in diameter, continuously ejects ice particles from its subsurface ocean through giant plumes at its south pole. Using data from NASA’s Cassini spacecraft, researchers from the University of Stuttgart and Freie Universität Berlin have chemically analyzed freshly emitted particles from this ocean, revealing organic molecules – some potentially relevant to biological processes. Their findings, published in Nature Astronomy, mark the first detection of such intermediates in ice from an extraterrestrial ocean.

Cassini first discovered the plumes in 2005, and later data confirmed that a global ocean of liquid water lies beneath Enceladus’ 25-30 km thick icy crust. Earlier analyses showed organic molecules in older, space-weathered ice grains, but this new study focused on pristine particles collected when Cassini flew just 21 kilometers above the surface in 2008. The team, led by Dr. Nozair Khawaja, evaluated these measurements with colleagues from Germany, the USA, and Japan.

The researchers confirmed that both simple and complex organics found in Saturn’s E ring originate from Enceladus’ ocean. They suggest these compounds may have formed at hydrothermal vents on the ocean floor, where hot water rises from the moon’s interior – similar to life-supporting systems found on Earth. Among the newly identified molecules were pyrimidines, key components of DNA, also previously detected on asteroids Bennu and Ryugu.

Cassini’s high-speed flyby, traveling at nearly 65,000 km/h, enabled its “Cosmic Dust Analyzer” (CDA) – a sensor operated by the University of Stuttgart – to obtain clearer molecular data. The instrument measures positively charged fragments from ice grain impacts, producing mass spectra that reveal the molecules’ composition. Higher speeds reduce interference, allowing for more reliable analysis.

Although Cassini ended its mission in 2017, its data continue to yield groundbreaking insights into Enceladus’ hidden ocean. Inspired by these discoveries, the European Space Agency (ESA) is preparing a follow-up mission planned for 2040, aiming to analyze Enceladus’ ice in far greater detail. According to Khawaja, these results will play a key role in designing future instruments to search for potential signs of life beneath the icy shell.

For more details, read the full article by Freie Universität Berlin.