This animation and still image of comet C/2013 A1 Siding Spring were taken by the Mast Camera (Mastcam) on NASA's Curiosity Mars rover as the comet passed near the red planet on Oct. 19, 2014.
The animation consists of 10 exposures of 25 seconds each, taken between 2:33 p.m. PDT (5:33 EDT) and 3:54 p.m. PDT (6:34 EDT) on Oct. 19. The exposures are projected onto a celestial frame. The still is an image from the animation. Most of the specks are electronic noise. The short, straight streaks are stars.
In the still image, comet Siding Spring is visible as a faint smear just above and to the right of the brightest streak. In the animation, the comet moves across the image from right to left above the brightest streak.