This false-colour image of two density waves in Saturn's A ring was taken by the NASA/ESA/ASI Cassini-Huygens spacecraft at a distance of 6.8 million kilometres from Saturn.
The image was made from the stellar occultation observed by the Cassini-Huygens Ultraviolet Imaging Spectrograph, and shows a section of rings about 724 kilometres across and the smallest features about half a kilometre across. Bright areas indicate the denser regions of the rings. The bright bands in the left part of the image are the 'peaks' of a density wave caused by gravitational stirring of the rings by Saturn's moon Janus.
A smaller density wave in the right half of the image is produced by the moon Pandora. The Ultraviolet Imaging Spectrograph observed the brightness of the star Xi Ceti as the rings passed in front of it, and the flickering of the starlight was converted into the ring density depicted by the image. The Cassini-Huygens mission is a co-operative project of NASA, ESA and ASI, the Italian space agency.