The plume of the giant volcano Tvashtar is brightly backlit by the Sun. On the sunlit limb, there is a bright flash off of the smooth surface of the flat lava flows of Loki Patera; these flows look quite dark when seen with the Sun overhead, but in this lighting geometry the sunlight glances off the smooth surface as off a mirror, producing a flash of light.
Original image data dated on or about March 3, 2007.
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