It was created from radio signals received during a lightning storm on Saturn by the radio and plasma wave science instrument on the Cassini spacecraft. The sounds are similar to the crackles and pops we hear on an AM radio during a thunderstorm on Earth. This Saturnian storm occurred on January 23 and 24, 2006. The clip compresses two hours of observations into about 28 seconds; every second of audio corresponds to about 4 minutes, 18 seconds.
