Between 23 July and 15 September 2008 Mars Express performed a series of eight fly-bys of the martian moon Phobos, at distances ranging between 4500 and 93 km from the centre of the moon, conducting some of the most detailed investigations of the Moon to date. In observing Phobos, Mars Express benefits from its highly elliptical orbit which takes it from a closest Mars approach of 270 km above the surface up to a maximum of 10 000 km distant from the planet's centre, crossing the 9 400 km orbit of the moon. Like our Moon, Phobos always shows the same side to the planet, so it is only by flying outside the orbit that it becomes possible to observe the far side. The other spacecraft presently orbiting Mars do so at much lower altitudes, and therefore only see the planet-facing side of the moon.
This image was obtained by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express on 23 July 2008 (orbit 5851), at a distance of 93 km from the moon’s centre. The image was taken using the camera’s stereo-1 channel, at a resolution of 3.7 m/pixel.
The ellipses show the previously (red) and currently (blue) considered landing sites for the Phobos-Grunt Russian mission: based on Mars Express’ image series, the Russian Federal Space Agency is now considering to move the landing location slightly to the north of the previous one, to a safer area located between 7°-21°S and 214°-233°W.
Phobos-Grunt (meaning Phobos Soil) will land on Phobos, collect a soil sample and return it to Earth for analysis. The landing site has been selected to be on the side of the moon facing away from Mars - a place now only imaged by Mars Express after the Viking orbiters in the 1970s.
