A moon’s shadow falls upon ring after ring in this image, taken on April 29 by Cassini.
Varying brightnesses and compositions of ring segments scatter light differently, as shown above. With Saturn’s spring equinox (August 11) getting closer every day, the ringplane – and orbital plane of many of its moons – are approaching a perpendicular position to that of Saturn’s orbital plane. This makes the shadows cast by the moons nearest the rings fall upon the icy dust particles of the rings themselves, offering Cassini – and us – another look at their varied compositions.
The image above is one frame of the animation at right. Here we can see the moon’s shadow – most likely from Epimetheus or Tethys – traversing many ringlets, and in the latter frames actually disappearing in what seems to be thicker (or higher?) ring segments. More info from the Cassini team is needed to explain exactly the process that is seen here…these images are raw data, and not yet calibrated or validated. They won’t be entered into NASA’s Planetary Data System until 2010. Still, they’re a first look at the most recent photos taken by the Cassini orbiter. In many cases seen here the day the data is received on Earth. Stay tuned, folks.
Raw image credits: NASA/JPL/Space Science Institute. GIF animation: J. Major.