Equatorial CO2 Distribution Suggests Active CO2 Supply on Europa

The James Webb Space Telescope’s (JWST) observation of Europa recently revealed CO₂ accumulation around geologically young chaos terrains Tara Regio and Powys Regio.

The spatial heterogeneity in CO₂ distribution suggests an endogenic source of CO₂ in these terrains, although the timescale of CO₂ supply remains uncertain. Here, we investigate CO₂ distribution on Europa by conducting Monte Carlo simulations considering sublimation, ballistic transport, and loss via photoionization. With a hypothetical CO₂ source at the equator, a CO₂ molecule is transported to the polar regions over a timescale of ∼10 days before being lost via photoionization.

Accordingly, CO₂ accumulates around the poles, with minimal CO₂ around the hypothetical source under steady-state conditions. To achieve a CO₂ distribution similar to that observed by the JWST, an unknown effective loss process of CO₂ on Europa, >100 times faster than photoionization, would be required.

Such a process may include CO₂ dissociation/ionization by irradiation of high-energy particles. Since CO₂ at the equatorial regions would be lost via either transport to the polar regions or dissociation/ionization within tens of days after CO₂ supply, CO₂ at around the equatorial regions observed by the JWST suggests its ongoing supply to the surface.

Further continuous observations of Europa provide insights into the chemistry and dynamics of CO₂.

Difference in CO₂ distribution in a steady state with different loss rates or residence time. In (a) and (b), the CO₂ loss rate (τphoto in Equation (27)) was assumed to be 100 times and 1000 times less than the case shown in Figure 4, respectively. On the other hand, in (c) and (d), the residence time of CO₂ (τ_ice,co2 in Equation (14)) was assumed to be 106 and 107 times larger than the case shown in Figure 4. See Figure 4 for further details. A shorter timescale of CO₂ loss and/or a larger residence time of CO₂ resulted in a higher concentration of CO₂ around the hypothetical source of CO₂, indicated by white diamonds (10°S, 75°W).– The Planetary Science Journal

Equatorial CO2 Distribution Suggests Active CO2 Supply on Europa, The Planetary Science Journal (open access)

Astrobiology