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The Colors of Tethys

28 Sep 2017, 17:00 UTC
The Colors of Tethys
(200 words excerpt, click title or image to see full post)

NASA dixit:
“April 11, 2015. This enhanced-color mosaic of Saturn’s icy moon Tethys shows a range of features on the moon’s trailing hemisphere. Tethys is tidally locked to Saturn, so the trailing hemisphere is the side of the moon that always faces opposite its direction of motion as it orbits the planet. Images taken using clear, green, infrared and ultraviolet spectral filters were combined to create the view, which highlights subtle color differences across Tethys’ surface at wavelengths not visible to human eyes. The moon’s surface is fairly uniform in natural color.
The color of the surface changes conspicuously across the disk, from yellowish hues to nearly white. These broad color changes are affected by a number of external processes. First, Saturn’s diffuse E-ring preferentially bombards Tethys’ leading hemisphere, toward the right side of this image, with ice bright ice grains. At the same time, charged particles from Saturn’s radiation belt bombard the surface on the trailing side, causing color changes due to chemical alteration of the materials there. The albedo — a measure of the surface’s reflectivity — drops by 10 to 15 percent from the moon’s leading side to the trailing side. Similar global color patterns exist on ...

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