Three Moons


3MoonsThe Cassini spacecraft has sent us this family photo of three of Saturn’s moons that are different from each other. The largest of the three, Tethys is round and has a variety of terrains across its surface. Hyperion (to the upper-left of Tethys) is the “wild one” with a chaotic spin, and Prometheus (lower-left) is a tiny moon that busies itself shepherding the F ring.

Image Credit: NASA

That’s No Space Station. It’s a Moon!


TethysSaturn’s moon Tethys’s trailing side shows two terrains that tell a story of a rough past. To the north (up in this picture) is older, rougher terrain, while to the south is new material dubbed “smooth plains” by scientists. The smooth plains are roughly antipodal to the large impact crater Odysseus. Odysseus, which is on the far side of Tethys, is out of view. The leading theory is that the impact that created Odysseus also created the smooth plains, although exactly how this happened is not yet clear.

Image Credit: NASA

Pan and Zoom


Pan in the gap
Pan_zoomSaturn’s moon Pan, named for the Greek god of shepherds, rules over quite a different domain—the Encke gap in Saturn’s rings. See the inset at left for a zoomed in view. Pan (28 km across) keeps the Encke gap open through its gravitational influence on the ring particles nearby.

This view looks toward the sunlit side of the rings from about 48 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Christmas Day, 2013, from a distance of approximately 2.3 million km from Pan. The image scale is about 14 km) per pixel.

Image Credit: NASA