Images from the recent flyby of Phobos, on 7 March 2010, are
released today. The images show Mars' rocky moon in exquisite
detail, with a resolution of just 4.4 metres per pixel. They show
the proposed landing sites for the forthcoming Phobos-Grunt
mission.
ESA's Mars Express spacecraft orbits the Red Planet in a highly
elliptical, polar orbit that brings it close to Phobos every five
months. It is the only spacecraft currently in orbit around Mars
whose orbit reaches far enough from the planet to provide a
close-up view of Phobos.
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. Mars Express did just this on 7, 10 and 13
March 2010. Mars Express also collected data with other
instruments.
Phobos is an irregular body measuring some 27 × 22 ×
19 km. Its origin is debated. It appears to share many surface
characteristics with the class of 'carbonaceous C-type' asteroids,
which suggests it might have been captured from this population.
However, it is difficult to explain either the capture mechanism or
the subsequent evolution of the orbit into the equatorial plane of
Mars. An alternative hypothesis is that it formed around Mars, and
is therefore a remnant from the planetary formation period.
In 2011 Russia will send a mission called Phobos–Grunt
(meaning Phobos Soil) to land on the martian moon, collect a soil
sample and return it to Earth for analysis.
For operational and landing safety reasons, the proposed landing
sites were selected on the far side of Phobos within the area
5°S-5°N, 230-235°E. This region was imaged by the HRSC
high-resolution camera of Mars Express during the July-August 2008
flybys of Phobos. But new HRSC images showing the vicinity of the
landing area under different conditions, such as better
illumination from the Sun, remain highly valuable for mission
planners.
It is expected that Earth-based ESA stations will take part in
controlling Phobos-Grunt, receiving telemetry and making trajectory
measurements, including implementation of very long-baseline
interferometry (VLBI). This cooperation is realized on the basis of
the agreement on collaboration of the Russian Federal Space Agency
and ESA in the framework of the 'Phobos-Grunt' and 'ExoMars'
projects.
Mars Express will continue to encounter Phobos until the end of
March, when the moon will pass out of range. During the remaining
flybys, HRSC and other instruments will continue to collect
data.
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