Experimental Insights into the Azotosome Hypothesis in Titan’s Lake Fluids

Since the discovery of hydrocarbon lakes and seas on Saturn’s moon Titan, there has been much speculation on whether these could serve as suitable environments to host exotic life. A decade ago, molecular dynamics simulations suggested that amphiphilic cyanide species such as acrylonitrile (CH2CHCN) could self-assemble in these cold, non-polar liquid media to form stable closed membranes known as azotosomes, potentially compartmentalizing complex biochemicals reactions. A subsequent thermodynamic study in 2020, however, concluded that azotosomes cannot exist under Titan’s conditions. Motivated by these incongruent computational results, this work undertakes the first experimental test of the azotosome hypothesis where we characterize acrylonitrile/methane and acrylonitrile/ethane mixtures under simulated Titan conditions using a combination of differential scanning calorimetry and Raman microscopy. The results indicate that acrylonitrile forms a stable molecular co-crystal with ethane, while exhibiting little changes in the presence of liquid methane under experimental timescales. These findings suggest that the acrylonitrile-based azotosome structure would be unlikely to form in Titan’s lake fluids.