The Mars Express, which the agency launched in 2003, has begun a series of flybys of Phobos, the largest moon of Mars, that will ultimately set a new record for the closest pass to Phobos, skimming toward the surface at 50 km - or about 31 miles on March 3, the ESA said.
The data collected by the satellite could help unwrap some of the mystery about the moon, the ESA said. The origin of Phobos is a mystery. Three scenarios are possible. The first is that the moon is a captured asteroid. The second is that it formed in situ as Mars formed below it. The third is that Phobos formed later than Mars, out of debris flung into Martian orbit when a large meteorite struck the red planet, according to the ESA.
Mars has two tiny moons--Phobos and Deimos. According to NASA, the larger moon, Phobos, is a cratered, asteroid-like object and orbits so close to Mars that gravitational tidal forces are dragging it down. In 100 million years or so, Phobos likely will be shattered by stress caused by the relentless tidal forces, the debris forming a decaying ring around Mars, according to NASA.
According to the ESA, a heavy emphasis is being placed upon the closest flyby because it is an unprecedented opportunity to map Phobos' gravity field. At that range, Mars Express should feel a difference in the pull from Phobos depending on which part of the moon is closest at the time.
Previous Mars Express flybys have provided the most accurate mass for Phobos, and its High Resolution Stereo Camera (HRSC) has provided the volume. When calculating the density, this gives a surprising figure because it seems that parts of Phobos may be hollow, the ESA stated.
The Mars Express's main mission has been to explore the planet Mars. Some of its goals have been to image the entire surface at high resolution (10 meters/pixel) and selected areas at super resolution (2 meters/pixel) and to produce a map of the mineral composition of the surface at 100 meter resolution.
It also has as a task to image the proposed landing sites for the oft-delayed Russian Mars mission Phobos-Grunt mission, which is now targeted for sometime in 2011.
NASA and the European Space Agency last year signed an agreement to "cooperate on all manner of robotic orbiters, landers and exploration devices for a future trip to Mars."
Specifically, NASA and ESA agreed to consider the establishment of a new joint initiative to define and implement their scientific, programmatic, and technological goals for the exploration of Mars. The program would focus on several launch opportunities with landers and orbiters conducting astrobiological, geological, geophysical, climatological, and other high-priority investigations and aiming at returning samples from Mars in the mid-2020s.
The envisioned program includes the provision that by 2016, ESA will build what it calls an Entry, Descent, and semi-soft Landing System (EDLS) technology demonstrator and a science/relay orbiter. In 2018, the ESA would also deliver its ExoMars rover equipped with drilling capability. NASA's contribution in 2016 includes a trace gas mapping and imaging scientific payload for the orbiter and the launch and, in 2018 a rover, the EDLS, and rockets for the launch.
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