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Discovery of New Oxygen Aurora on Europa, Ganymede and Callisto

Presentation #513.08 in the session Fire and Ice: Europa and Aurorae.

Published onOct 20, 2022
Discovery of New Oxygen Aurora on Europa, Ganymede and Callisto

The thin atmospheres of Europa, Ganymede and Callisto can be studied remotely through their auroral emissions. Previous studies have focused primarily on the ultraviolet oxygen aurora at 130.4 and 135.6 nm. We observed all three satellites in Jupiter eclipse with Keck/HIRES covering optical wavelengths from 500 to 950 nm. In addition to the red and green auroral lines at 630.0 and 557.7 nm (see presentation by de Kleer et al.), we report the first extraterrestrial detection of oxygen aurora at the 777.4 and 844.6 nm triplets. We detected both triplets on Ganymede on June 8, 2021, and the 777.4 nm triplet on Europa on May 20, 2021. The measurement of new auroral lines allow for more robust constraints on the parent molecule of the emitting oxygen atoms, and these new detections support an O2-dominated atmosphere for both moons. In addition, we present the first detection of magnetospheric-electron-excited aurora on Callisto with a 3-sigma detection of the 630.0 and 636.4 nm doublet on July 4, 2021.

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