Glycine Partitioning in Frozen Putative Europan Brines

Europa is a prime candidate in the search for extraterrestrial life due to its potential habitability, which is supported by a sustained energy source, the availability of essential biocritical elements, and an extensive subsurface ocean of liquid water. This study examines the behavior of glycine, an amino acid, in simulated Europan brines subjected to various freezing processes to understand its potential distribution and preservation on Europa. Equimolar brines containing 0.1 M of Na+, Cl-, Mg2+, SO₄2-, and glycine (C₂H₅NO₂) were exposed to flash- and slow-freezing conditions to simulate different emplacement processes onto Europa’s icy surface environment. Analyses using micro-Raman imaging revealed that glycine preferentially associates with salt phases rather than water-ice, where the freezing mechanism (i.e., cooling rate) influences both the species of salt that precipitates and their spatial distribution. These findings suggest that salt-rich ice particles could be valuable targets for remote and in situ detection of organic molecules and potential biosignatures in future explorations. Notably, solid CO₂ was observed in isolated inclusions within slow-frozen samples, suggesting a glycine-driven mechanism for CO₂ entrapment during freezing. Diffuse reflectance infrared measurement of the observed CO2 showed some consistencies but did not produce an identical match of the recent JWST spectra of CO2 on Europa’s surface (Trumbo et al., 2023), implying that this mechanism is unlikely to be the pathway for CO2 production on this icy body.