For the first time, both Martian moons, Phobos and Deimos, have been captured together in a sequence of high-resolution images. This was made possible by the fact that the two moons were both in the field of view of the High Resolution Stereo Camera (HRSC) camera system onboard the ESA Mars Express probe on 5 November 2009, one behind the other.
The HRSC made 130 individual exposures with its SRC (Super Resolution Channel), 120 of which have been edited into the animated sequence shown here. The exposures were made first at intervals of one second, and speeded up to half-second intervals in the middle of the sequence. For technical reasons – Mars Express is in a polar orbit and travelling from north to south, while the moons are moving perpendicular to it in equatorial orbits – north is to the right of the images in the sequence.
At the time of the exposures, during mission orbit 7492, Phobos, the larger of the two moons and the one whose orbit is closer to planet, was 11,800 kilometres away from the Mars Express, while Deimos was 26,200 kilometres away. Due to these large distances, the Super Resolution Channel of the HRSC was used, a channel which uses an additional lens which, with its field of view of just 0.5°, provides four times the magnification of the HRSC itself. The resolution of the images is around 110 metres per pixel for Phobos and 240 metres per pixel for Deimos, which was twice as far from the camera.
Animation: ESA/DLR/FU Berlin (G. Neukum).