Professional astronomers spend their days at the computer or booking time to log radio-waves from a minute portion of the skies, peering into deep time and cosmological secrets. That leaves amateurs and enthusiasts to scan the skies for dramatic changes. They are the ones who first see the new comets, novae, and asteroid strikes. On July 19th something dropped into Jupiter’s atmosphere, leaving a dark disturbance in its wake. Now everybody’s studying it.