Unusual Layers on Saturns Moon Phoebe . ... Credit Copyright: Cassini Imaging Team , SSI , JPL , ESA , NASA Explanation: What caused the unusual light and dark layers on Saturn 's moon Phoebe ? The layers were discovered just Friday during the Cassini spacecraft flyby of the small moon. Such layering is particularly evident on the crater just above the image center, where alternating light and dark material makes this crater appear particularly structured. ... NASA Official: Jay Norris. ...