The distribution of CO on Europa indicates an internal source of carbon.

Jupiter's moon Europa has a subsurface ocean, the chemistry of which is largely unknown. Carbon dioxide (CO) 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 mapped the distribution of CO on Europa using observations obtained with the James Webb Space Telescope (JWST). We found a concentration of CO within Tara Regio, a recently resurfaced terrain. This indicates that the CO is derived from an internal carbon source. We propose that the CO formed in the internal ocean, although we cannot rule out formation on the surface through radiolytic conversion of ocean-derived organics or carbonates.