As the northern hemisphere of Saturn moves into summer, the shadow the planet casts on its rings grows shorter due to the tilt of its axis of rotation compared to the plane of its orbit around the Sun.
A year on Saturn (one full orbit around the Sun) takes about 30 years on Earth. This May will see the summer solstice in Saturn’s north, after which the shadow on the rings will begin to grow longer again.
This picture was taken by the Cassini probe in February. Read more at NASA.