An Energetic Eruption With Associated SO 1.707 Micron Emissions at Io's Kanehekili Fluctus and a Brightening Event at Loki Patera Observed by JWST

摘要

We observed Io with the James Webb Space Telescope (JWST) while the satellite was in eclipse, and detected thermal emission from several volcanoes. The data were taken as part of our JWST-ERS program #1373 on 15 November 2022. Kanehekili Fluctus was exceptionally bright, and Loki Patera had most likely entered a new brightening phase. Spectra were taken with NIRSpec/IFU at a resolving power R similar to 2,700 between 1.65 and 5.3 mu m. The spectra were matched by a combination of blackbody curves that showed that the highest temperature, similar to 1,200 K, for Kanehekili Fluctus originated from an area similar to 0.25 km(2) in size, and for Loki Patera this high temperature was confined to an area of similar to 0.06 km(2). Lower temperatures, down to 300 K, cover areas of similar to 2,000 km(2) for Kanehekili Fluctus, and similar to 5,000 km(2) for Loki Patera. We further detected the a(1) Delta X-3 Sigma(-)1.707 mu m rovibronic forbidden SO emission band complex over the southern hemisphere, which peaked at the location of Kanehekili Fluctus. This is the first time this emission has been seen above an active volcano, and suggests that the origin of such emissions is ejection of SO molecules directly from the vent in an excited state, after having been equilibrated at temperatures of similar to(1),500 K below the surface, as was previously hypothesized. Plain Language Summary We observed Io with JWST in November 2022 while the satellite was in Jupiter's shadow, and glowing volcanoes show up without being (partially) obscured by reflected sunlight. We detected the volcanoes Loki Patera and Kanehekili Fluctus; the latter was exceptionally bright, and Loki Patera had likely entered a new brightening phase. Both volcanoes show erupting lavas at temperatures of at least 1,200 K, originating at a vent of similar to 0.25 km(2) in size for Kanehekili Fluctus and <0.1 km(2) for Loki Patera. In addition to lava, Kanehekili Fluctus spews out gases, and we detected, for the first time, SO emission at 1.707 mu m right over the volcano. This is the first time this emission has been seen above an active volcano, and suggests that such emissions are produced by SO molecules immediately upon leaving the vent.