The distribution of CO$_2$ on Europa indicates an internal source of carbon

Abstract: Jupiter's moon Europa has a subsurface ocean, the chemistry of which is largely unknown. Carbon dioxide (CO$_2$) has previously been detected on the surface of Europa, but it was not possible to determine whether it originated from subsurface ocean chemistry, was delivered by impacts, or was produced on the surface by radiation processing of impact-delivered material. We map the distribution of CO$_2$ on Europa using observations obtained with the James Webb Space Telescope (JWST) and find a concentration of CO$_2$ within Tara Regio, a recently resurfaced terrain. This indicates the CO$_2$ is derived from an internal carbon source. We propose the CO$_2$ formed in the internal ocean, though we cannot rule out formation on the surface by radiolytic conversion of ocean-derived organics or carbonates.

• The paper uses JWST data to map the distribution of CO2 on Europa's surface with high resolution, linking it to recent geological activity.
• The CO2 is primarily found in geologically young chaos terrain, a pattern inconsistent with external sources and strongly suggesting an origin from Europa's interior.
• Finding an internal source for CO2 on Europa implies its subsurface ocean may be more oxidizing than previously thought, which has significant implications for its potential habitability.

Analysis of Carbon Dioxide Distribution on Europa as Indicating an Endogenous Carbon Source

The paper "The distribution of CO on Europa indicates an internal source of carbon" by Samantha K. Trumbo and Michael E. Brown leverages data from the James Webb Space Telescope (JWST) to explore the origins of carbon dioxide (CO₂) observed on the surface of Jupiter's moon Europa. The distribution pattern of CO₂ is crucial in assessing the possible contribution of Europa's subsurface ocean to the moon's surface chemistry, providing insights into the potential habitability of this extraterrestrial environment.

Methodology and Results

The study utilized JWST's Near Infrared Spectrograph (NIRSpec) to map spatial variations of CO₂ on Europa with an impressive resolution (R~2,700). The CO₂ on Europa exhibits a double-peaked structure, with significant absorptive features predominating in the chaos terrain within Tara Regio and to a lesser extent in Powys Regio. These areas are characterized by recent resurfacing, suggesting they interact dynamically with endogenic materials, possibly from subsurface reservoirs.

It is particularly noteworthy that the CO₂ distributions do not align with known exogenic sources observed on other Jovian moons such as Ganymede and Callisto, where CO₂ appears more connected to older, impact-related or magnetospheric processes. Instead, the spatial relationship of CO₂ with geologically young chaos terrains on Europa supports an endogenic origin, implying CO₂ is sourced from Europa’s internal ocean rather than being externally delivered or produced in situ from meteoritic materials.

Implications for Ocean Chemistry

The study implies that Europa's CO₂ likely emanates from its subsurface ocean, which could provide insights into the ocean's chemical profile. Should the observed CO₂ indeed be a representative of carbon species dissolved in this ocean, its presence challenges the hypothesis of a highly reduced ocean chemistry and instead points towards more oxidizing conditions. Such a redox state could be consistent with models predicting the transport of oxidants like O₂ or H₂O₂ through Europa’s icy crust into its ocean, which may have implications for potential biological activity.

The detection marks potential pathways for future research endeavors, encouraging a deeper probe into the oceanic chemistry beneath Europa's icy crust. Given the importance of carbon in biochemical processes, affirming the internal ocean as the source of surface CO₂ contributes meaningfully to the discussiоn on the moon's habitability.

Trapping and Behavior of CO₂

No direct evidence of organic or carbonate precursors was found, suggesting CO₂ reaches the surface primarily in its original oceanic form. The CO₂ appears to be trapped in a manner that does not conform to known mechanisms like adsorption onto water ice or phyllosilicates, raising questions about the materials and processes responsible for this trapping. The paper posits a connection between temperature, ice content, and the observed double-peaked absorption, suggesting a need for laboratory experimentation to resolve these unresolved aspects of CO₂’s molecular behavior on Europa.

Conclusion

Overall, the paper underscores the importance of high-resolution spectral analysis in astrobiological studies, using sophisticated instrumentation to establish relationships between geologic activity and chemical distributions on extremophile planetary landscapes. Future explorations could benefit from targeted investigations into the geochemical interactions at play in Europa’s dynamic surface—ocean interface to further elucidate this intriguing discovery. The study's findings not only advance our understanding of Europa's subsurface processes but also set a foundation for future missions aimed at unraveling the complexities of extraterrestrial ocean worlds.