Archival data from the Cassini mission have unveiled the most detailed set of organic compounds from Enceladus’ ocean to date. During a flyby in 2008, the spacecraft passed through plumes of icy particles and collected samples that were ejected from beneath the surface mere minutes before. This “fresh” material enabled the first detection of organic types never before recorded in the satellite’s emissions.
Particular focus was given to the composition of the icy particles ejected from fractures near Enceladus’ south pole, known as “tiger stripes.” These plumes, composed of water ice and other substances, erupt from the satellite’s subsurface ocean. Analysis revealed the presence of not only known organic compounds but also new, previously undetected molecules. Such compounds may play a crucial role in the chemical and biochemical processes potentially occurring in Enceladus’ ocean.
The key achievement of the study is the discovery of new classes of complex organic molecules, including organic compounds such as aliphatic and cyclic ethers, complex esters, and molecules with double bonds. These structures are vital “building blocks” of organic chemistry: they can participate in reactions on Earth that lead to the formation of amino acids, lipids, and other key biochemistry components.
Previously, Cassini found organics in particles from Saturn’s ring, but these ice grains were long exposed to the radiation environment and could have altered. Now, scientists have evidence that complex organics are formed directly in Enceladus’ ocean, not arising later due to space conditions. “These compounds are a direct product of the under-ice ocean,” noted Nozair Khawaja, the author of the study.
An additional crucial detail is that particles struck the Cosmic Dust Analyzer at speeds around 11,185 mph (18 km/s), and their ionized fragments were analyzed using a mass spectrometer. This allowed for capturing molecules smaller than a thousandth of a millimeter – a level of detail previously unattainable. The identified set of organics includes several types of molecules linked to chemical pathways forming more complex structures, reinforcing the case for active and rich chemistry in the satellite’s ocean.
Recent advances show that in addition to water, salts, and simple organics, Enceladus’ subsurface ocean contains complex molecules that may be precursors to biochemical processes. With mounting evidence of complex chemistry beneath the icy crust, interest in missions for direct ocean exploration of Enceladus is significantly increasing.
Recent projects such as the Enceladus Life Finder or concepts for future missions to probe deeper into these plumes are gaining traction, aiming to further unravel the mysteries of this ocean world.
