In Daylight on the Night Side

rings-in-daylightThe Cassini spacecraft looked down at the rings of Saturn from above the planet’s nightside to take this picture. The darkened globe of Saturn is on the lower right, along with the shadow it casts across the rings. Even on the planet’s night side, part of the rings remain in sunlight, and they reflect sunlight back onto the night side of the planet, making it appear brighter than it would otherwise appear.

Saturn’s small moon Prometheus ( 86 km across) is faintly visible as a speck near upper left. Earlier in the planet’s year, Saturn’s shadow was once long enough to stretch to the orbit of Prometheus, but as northern summer solstice approaches, the shadow no longer reaches that far. Prometheus won’t be in the planet’s shadow until the progression of the seasons again causes the shadow to lengthen.

Image Credit: NASA

Shaping Dione

Dione_TectonicsThis image of Saturn’s moon Dione shows a mixture of features: bright, linear features showing evidence of tectonic movant and impact craters. The tectonic features reveal that Dione has been heated and cooled since its formation, and scientists use those as clues to piece together the moon’s past. The impact craters are evidence of external debris striking the surface and tell about the environment in which the moon has existed over its history.

Image Credit: NASA

Shadow on the Rings

ring shadows 2The changing length of Saturn’s shadow marks the passing of the planet’s seasons. As the planet nears its northern-hemisphere solstice in May, 2017, the shadow will get even shorter. At solstice, the shadow’s edge will be about 45,000 km from the planet’s surface, barely making it past the middle of the B ring.

The white speck in the lower left of the picture isn’t a dust mote on your monitor. It’s the moon Mimas, only a few pixels wide in this image.

Image Credit: NASA