This animation is comprised of three images acquired by ESA’s Mars Express spacecraft on Sept. 12, 2017 with its High Resolution Stereo Camera (HRSC). It shows parts of the grooved and pitted surface of Phobos, the larger of Mars’ two natural satellites.
The original images were captured in greyscale; I added color based on other images of Phobos taken by NASA’s Mars Reconnaissance Orbiter in March 2008.
Unlike Earth’s relatively enormous Moon, Phobos is a tiny satellite only about 16 miles (26 km) across. It orbits Mars at a very low altitude of 3,721 miles (5,989 km) and travels rapidly, only taking 7 hours and 39 minutes to complete a single orbit.
See more images of Phobos captured by various missions over the years here.
Unlike our Moon which is slowly but steadily moving away from us, little Phobos’ orbit is degrading. Eventually (some estimates say in only about 10 million years) Phobos will either impact Mars or be ripped apart by tidal forces, forming a ring of material that would temporarily turn Mars into a miniature version of Saturn.
And speaking of Saturn, in 2016 Mars Express captured images of Phobos passing in front of the ringed planet, which at 650 million miles distant appeared as a small oval dot in the background blackness. Besides making for fascinating images, such observations are planned to help mission scientists calibrate the positioning of the spacecraft and better determine the precise location and orbit of Mars’ moons. Click here to watch the video and see more images from Mars Express.
Source: ESA. HT to Bill Dunford on Twitter.