Free Astronomy Magazine November-December 2017

NOVEMBER-DECEMBER 2017 SATURN This free NASA e-Book celebrates Saturn as seen through the eyes of the Cassini spacecraft. https://saturn.jpl.nasa.gov/ resources/7777/?cate- gory=images This high-resolution Cassini mosaic shows that Hype- rion truly has a surface different from any other in the Saturn system. Features within the dark terrain, in- cluding a 200-meter-wide impact crater surrounded by rays to the right of center and numerous bright- rimmed craters, indicate that the dark material may be only tens of meters thick with brighter material be- neath. [NASA/JPL/Space Science Institute] The Cassini spacecraft looks at Saturn's highly ir- regular moon Hyperion in this view from the space- craft's flyby of the moon on Aug. 25, 2011. Hyperion, 270 kilometers across, has an irregular shape, and it tumbles through its orbit: that is, it does not spin at a constant rate or in a constant orientation. [NASA/JPL/Space Science Institute] HYPERION The Cassini spacecraft captures a rare family photo of three of Saturn's moons that couldn't be more different from each other! As the largest of the three, Tethys (image center) is round and has a variety of terrains across its surface. Meanwhile, 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 sculpting the F ring. [NASA/JPL/Space Science Institute] !