New cloud activity on Uranus in 2004: First detection of a southern feature at 2.2 μm

On 4 July 2004 UT, we detected one of Uranusʹ southern hemispheric cloud features at K′ (2.12 μm); this is the first such detection in half a decade of adaptive optics imaging of Uranus at the Keck 10-m telescope. When we observed again on 8 July UT the featureʹs bright core had faded. By 9 July UT it was not seen at K′ and barely detectable at H. The detection and subsequent disappearance of the feature indicates rapid dynamical processes in the localized vertical aerosol structure.