Abstract The detection of CO 2 on the Jovian satellite Europa by Galileo/NIMS and recent mapping of the leading side by JWST has revealed that it is most concentrated in geologically young terrains, and its ν 3 asymmetric stretch appears as a spectral doublet centered at 4.25 and 4.27 μ m. Since crystalline CO 2 is unstable at Europan surface conditions, this observation implies an active source and a trapping medium, which may be separate. To this end, several hypotheses have been proposed, but no laboratory work has successfully reproduced the spectral features of CO 2 on Europa so far. Radiolyzed carbonates have also been discussed as plausible precursors and host materials for CO 2 , though their role has not been experimentally validated in a Europa-like environment. Here, we report the first laboratory experiments investigating CO 2 production from carbonate salts exposed to 10 keV electron irradiation at 50, 100, and 120 K in ultrahigh vacuum. Using diffuse reflectance FTIR spectroscopy, we observe the emergence, growth, and saturation of an absorption doublet centered near 4.25 and 4.27 μ m, consistent with the CO 2 ν 3 band. Postirradiation thermal desorption studies using residual gas analysis reveal that the radiolytically formed CO 2 is stable at temperatures beyond Europa’s surface. This work provides the first experimental evidence that low-energy electron irradiation of carbonates in cryogenic, vacuum conditions can produce and retain CO 2 , and suggests that carbonates can serve as endogenous reservoirs of CO 2 on irradiated icy bodies in the outer solar system.
Pandya et al. (Wed,) studied this question.