Time-Evolution and Thermal Mapping of Io's Loki Patera at High Resolution

Observations of Loki Patera with Keck, Gemini N, and the Large Binocular Telescope have yielded a wealth of information in the past several years. Observations with adaptive optics at the Keck and Gemini N telescopes have captured multiple brightening events since 2009. High-cadence observations of the three most recent events place constraints on the thermal properties of the magma and indicate a dependency of the observed intensity on either viewing geometry or mean anomaly. Large Binocular Telescope Interferometer (LBTI) observations during a Europa mutual event have yielded the first-ever temperature map of the entire patera floor at high spatial resolution. M-band (4.7-micron) images were recorded during the event at a cadence of 123 milliseconds, corresponding to a spatial resolution of 10 km across the entire ~200-km patera. This represents a factor of 40 improvement over the spatial resolution achieved by standard adaptive optics imaging with a 10-m telescope at this wavelength. A map of the lava age distribution within the patera is derived from the temperature map using models for cooling basaltic lavas, and the resurfacing rate is calculated. This age distribution, as well as the locations of emission derived from the Keck and Gemini N observations, suggests that resurfacing proceeds in a clockwise direction, contrary to previous findings. All data are consistent with resurfacing by an overturn front on a magma sea, but other resurfacing mechanisms are not ruled out.