Macromolecular organic compounds from the depths of Enceladus

Saturn’s moon Enceladus harbours a global ocean(1), which lies under an ice crust and above a rocky core(2). Through warm cracks in the crust(3) a cryo-volcanic plume ejects ice grains and vapour into space(4–7), providing access to materials originating from the ocean(8,9). Hydrothermal activity is suspected to be occurring deep inside the water-percolated porous core(10–12), powered by tidal dissipation(13). So far only simple organic compounds with molecular masses mostly below 50u have been observed in the plume(6,14,15). Here we report observations of emitted ice grains containing concentrated, complex, macromolecular organic material with molecular masses above 200u. The data provides key constraints on the macromolecular structure and is suggestive of a thin organic-rich film on top of the oceanic water table. There, organic nucleation cores generated by bubble bursting allow probing of Enceladus’ organic inventory in drastically enhanced concentrations.