The Martian moons Phobos and Deimos, appear to be in motion in this animation created from 19 images taken by the Mars Odyssey orbiter’s Thermal Emission Imaging System, or THEMIS, camera. The images were taken in visible-wavelength light. THEMIS also recorded thermal-infrared imagery in the same scan.
The apparent motion is due to progression of the camera’s pointing during the 17-second span of the 15 February 2018, observation, not from motion of the two moons. This was the second observation of Phobos by Mars Odyssey; the first was on 29 September 2017. Researchers have been using THEMIS to examine Mars since early 2002, but the maneuver turning the orbiter around to point the camera at Phobos was developed only recently.
The distance to Phobos from Odyssey during the observation was about 5,615 kilometers (3,489 miles). The distance to Deimos from Odyssey during the observation was about 19,670 kilometers (12,222 miles).