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Phobos Pictured in Color and 3DMRO makes fly-by around Mars' largest moon |
By Gabriel Gache, Science News Editor
10th of April 2008, 08:02 GMT
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Mars' largest and closest moon, Phobos, was recently photographed with the help of the HiRISE camera on board the Mars Reconnaissance Orbiter, during a fly-by through its vicinity. 3D color images of the small moon reveal a material rim around its biggest surface structure, the Stickney crater,
measuring 9 kilometers in diameter.
"Phobos is of great interest because it may be rich in water ice and carbon-rich material," says HiRISE principal investigator from the Lunar and Planetary Laboratory at the University of Arizona, Alfred Mc.Ewen.
"The new images will help constrain the origin and evolution of this moon. Based on analogy with material on our own moon, the bluer color could mean that the material is fresher, or hasn't been exposed to space as long as the rest of Phobos' surface has," said Nathan Bridges, Jet Propulsion Laboratory HiRISE team member.
Similarly to our moon, Phobos' dark side is illuminated by 'Marsshine', or by light coming from the Sun, reflected of the surface of Mars towards Phobos, thus revealing surface features such as grooves and crater chains. Another striking similarity between the Moon and Mars' two small asteroid moons, Phobos and Deimos, is that they are also 'tidal locked', meaning they have an orbital period identical to the spin around their axis, and always show the same face towards the planet.
Phobos is only 22 kilometers in diameter, while Deimos is about 12 kilometers in diameter, each with gravitational pulls less than one-thousandth of that of Earth. Because of this, they are not able to shape themselves into spheres, as our Moon did.
In a previous fly-by last year, the Mars Reconnaissance Orbiter made a spectrometric analysis of both moons with the Compact Reconnaissance Imaging Spectrometer. The data collected during the recent fly-by and that of last year will be corroborated, so that researchers can determine the type of minerals and soils present on the two asteroid moons.
The MRO orbits Mars at an altitude from 250 to 316 kilometers, and it reaches speeds up to 4,800 kilometers per hour. During the fly-by, it took two photographs of Phobos, one at a distance of 6,800 kilometers form the moon and the second one at 5,800 kilometers, both with a resolution of 6.8 meters.
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