Paris, August 1 : Using the High Resolution Stereo Camera (HRSC), ESA's (European Space Agency's) Mars Express has acquired the sharpest images of the Martian moon Phobos.
The images were clicked when Mars Express closed in on Phobos on 23rd July, flying past at 2.96 km/s, only 100 km from the centre of the moon.
Measuring 27 km x 22 km x 19 km, Phobos 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.
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.
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 10 000 km (from the centre of Mars), crossing the 6000 km orbit of the Martian moon.
Mars Express imaged the far-side of Phobos (with respect to Mars) for the first time after NASA's Viking mission in the 1970s, by flying outside the spacecraft's orbit around Mars.
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.
The moon's remarkably grooved surface can be seen in the pictures quite clearly.
The origin of these grooves is still debated. It is not known whether they are produced by ejecta thrown up from impacts on Mars, or if they result from the surface regolith, or soil, slipping into internal fissures.