Phobos is what scientists call a ‘small irregular body’. Measuring 27 km × 22 km × 19 km, it is one of the least reflective objects in the Solar System, thought to be a captured asteroid or a remnant of the material that formed the planets.
Phobos in 3-D
The HRSC images, which are still under processing, form a bounty for scientists studying Phobos. They are a result of observations carried out over several close fly-bys of the martian moon, performed over the past three weeks. At their best, the pictures have a resolution of 3.7 m/pixel and are taken in five channels to obtain images in 3-D and to perform analyses of the physical properties of the surface.
The images obtained by several other spacecraft so far have either been of a lower resolution, or not available in 3D and have not covered the entire disc of Phobos. This is also the first time that portions of the far-side of the moon have been imaged in such high resolution (Phobos always faces Mars on the same side).
Potential Phobos-Grunt landing site
In observing Phobos, Mars Express benefits from its highly elliptical orbit which takes it from a closest distance of 270 km from the planet to a maximum of