Glycine Partitioning in Frozen Putative Europan Brines

Abstract Europa is considered a leading target in the search for extraterrestrial life because it may host conditions conducive to habitability, including a persistent energy source, access to biologically critical elements, and a vast subsurface ocean of liquid water. This study examines the behavior of glycine, an amino acid, in simulated Europan brines subjected to various freezing conditions to understand its potential distribution and preservation on Europa. Equimolar brines containing 0.1 M of Na + , Cl − , Mg 2+ , SO 4 2− , and glycine (C 2 H 5 NO 2 ) were exposed to flash- and slow-freezing conditions to simulate different emplacement processes onto Europa’s icy surface environment. Analyses using Raman imaging revealed that glycine preferentially associates with salt phases rather than water ice, where the 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 exploration. Notably, solid CO 2 was observed in isolated inclusions within slow-frozen samples, suggesting a glycine-driven mechanism for CO 2 entrapment during freezing. Diffuse reflectance infrared measurements of the observed CO 2 showed some consistencies but did not produce an identical match of the recent JWST spectra of CO 2 on Europa’s surface, implying that this mechanism is unlikely to be the pathway for CO 2 production on this icy body.