Assessing the Preservation of Polysaccharides from a Sea-Ice Bacterium Through Analog Icy Moon Plume Ejection.

Detection of complex organics emitted from Saturn's moon Enceladus has intensified the search for biosignatures accessible to future missions. Extracellular polysaccharides (EPSs) from sea-ice bacteria such as Colwellia psychrerythraea are promising analogs for potential biosignatures due to their prevalence in cold, saline environments analogous to the subsurface oceans on icy worlds. Here, we investigate experimentally the effect of a direct transition from liquid to vacuum environments on the detectability and composition of EPSs from C. psychrerythraea 34H using gas chromatography-mass spectrometry. EPSs from the bacterium were isolated and resuspended in solutions prepared with 1 wt. % NaCl and pH 9 to match properties inferred from enceladan plume grains. The primary monomers detected, including fatty acid methyl esters and sugars such as glucuronic acid, galacturonic acid, and glucosamine, remained detectable after injection into the vacuum, with slight shifts in relative abundances. These findings support the potential for EPS detection in icy moon plume samples. Our analytical approach is comparable to that of gas chromatograph-mass spectrometer payloads planned for the exploration of Enceladus and Europa, which aim to characterize organic material in plume or surface ice. These findings highlight microbial EPSs as potentially viable biosignature candidates and inform the interpretation of future in situ organic detections on ocean worlds.