Detection of HCN and diverse redox chemistry in the plume of Enceladus

The Cassini spacecraft observed that Saturn's moon Enceladus has a series of jets erupting from its South Polar Terrain. Previous studies of in situ data collected by Cassini's Ion and Neutral Mass Spectrometer (INMS) have identified H2O, CO2, CH4, NH3 and H2 within the plume of ejected material. Identification of minor species in the plume remains an ongoing challenge, owing to the large number of possible combinations that can be used to fit the INMS data. Here we present the detection of several additional compounds of strong importance to the habitability of Enceladus, including HCN, C2H2, C3H6 and C2H6. Our analyses of the low-velocity INMS data, coupled with our detailed statistical framework, enable discrimination between previously ambiguous species in the plume by alleviating the effects of high-dimensional model fitting. Together with plausible mineralogical catalysts and redox gradients derived from surface radiolysis, these compounds could potentially support extant microbial communities or drive complex organic synthesis leading to the origin of life. An information-theory-inspired re-analysis of Cassini mass spectrometry data reveals the presence of HCN and partially oxidized organics within the plume of Enceladus. Ongoing redox chemistry may create a habitable environment.

Automated summary

The Cassini spacecraft observed jets erupting from Saturn's moon Enceladus, containing compounds such as H2O, CO2, CH4, NH3, and H2. By using statistical analysis and low-velocity INMS data, additional compounds like HCN, C2H2, C3H6, and C2H6 were detected. These compounds, along with mineral catalysts and redox gradients, could support microbial communities and organic synthesis leading to the origin of life.