This colorized mosaic from NASA's Cassini mission shows an infrared view of the Saturn system, backlit by the sun, from July 19, 2013. The image, made from data obtained by Cassini's visual and infrared mapping spectrometer, covers a swath of Saturn and its rings about 340,000 miles (540,000 kilometers) across that includes the planet and its rings out to the diffuse E ring, Saturn's second most distant ring. The mosaic covers an area about 9,800 miles (16,000 kilometers) from top to bottom.
When Saturn is blocking the direct light of the sun, scientists can get a better look at the fainter rings. When small particles are lit from behind, they show up like fog in the headlights of an oncoming vehicle. Conversely, a ring that is easily seen from Earth because it is densely packed with chunks of bright water ice looks dark in these images because it is so thick that it blocks almost all of the sunlight shining behind it.
Looking at Saturn in the infrared spectrum can tell scientists more about the sizes of the particles in the fainter rings, and how these sizes vary with location in the rings. Infrared data also provide clues to ring particles' chemical composition.
Looking at the Saturn system in infrared light also shows thermal, or heat, radiation, so while a visible-light image from this vantage point would simply show the face of the planet as dimly lit by sunlight reflected off the rings, Saturn glows brightly in this view with the heat from Saturn's interior.
The visual and infrared spectrometer team colorized the image by assigning blue to radiation detected in the 1.5-to-1.19-micron range, green to radiation detected in the 1.9-to-2.1-micron range and red to the radiation detected in the 4.88-to-5.06-micron range.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington. The California Institute of Technology in Pasadena manages JPL for NASA. The VIMS team is based at the University of Arizona in Tucson.