| Ultimi arrivi - Phobos: the "Doomed" Moon |
PHOBOS-Image031-420-20081008-6042-6-src-02-PhobosSeries_H1.jpgApproaching Phobos (natural colors; credits: Lunexit)58 visiteThis image of Phobos was obtained by the Super Resolution Channel (or SRC, a part of the High Resolution Stereo Camera experiment) on board ESA’s Mars Express on 15 September 2008 (orbit 6042).
The distance from the moon’s centre was 3718 km, and the image resolution is 34 m/pixel.
The original image has been corrected for mirror distortion.
MareKromiumNov 04, 2008
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PHOBOS-Image000-409-20081008-5870-6-nd3-02-PhobosSeries_H1.jpgGeometry of the Phobos fly-by58 visitenessun commentoMareKromiumNov 02, 2008
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PHOBOS-Image001-409-20081008-5870-6-nd3-02-PhobosSeries_H1.jpgPhobos, from Mars Express56 visiteThis image was obtained by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express on 28 July 2008 (orbit 5870), at a distance of 351 Km from the moon’s centre. The image was taken using the camera’s nadir channel, at a resolution of 14 mt/pixel.
The origin of Phobos is debated. While its density, lower than the density of the Martian Surface rocks, make it appear to belong to "D-Class" Asteroids, the moon 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 following evolution of its orbit into the Equatorial Plane of Mars.
An alternative hypothesis is that it formed in its present position, and is therefore a remnant from the planetary formation period.MareKromiumNov 02, 2008
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PHOBOS-Image002-415-20081008-5861-6-src-01-PhobosSeries_H1.jpgPhobos: close-up, from Mars Express58 visiteThis striking close-up image of Phobos was obtained by the Super Resolution Channel (or SRC, a part of the High Resolution Stereo Camera experiment) on board ESA’s Mars Express on 26 July 2008 (orbit 5861). The distance from the moon’s centre was 2295 Km, and the image resolution is 20 mt/pixel.
The Super Resolution Channel (SRC), is an additional camera sharing HRSC’s processing electronics. Unlike HRSC, SRC is a framing camera, taking a complete image during a single exposure like a conventional pocket camera. Its 975 mm Maksutov-Cassegrain telescope gives it a pixel-resolution about four times higher than that of HRSC.
Early in the mission, the thermal conditions of the instrument in space caused a distortion in its precision optics. This resulted in a performance lower than expected, with some blur and ghosting visible in the raw images.
However, a significant part of the degradation has now been compensated for by analysing the effect of the distortion on test images (with point-like stars as target) and applying a corrective processing.MareKromiumNov 02, 2008
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000-PHOBOS-1.jpgMars and Phobos68 visiteMareKromiumNov 02, 2008
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Phobos-MEXP-1-h3909_0000_H.jpgPhobos, the "Doomed Moon", from Mars Express (False Colors; credits: Lunexit)55 visiteCaption ESA:"An image of Phobos by the High-Resolution Stereo Camera on board Mars Express taken on January 22, 2007.
The larger and inner of the two Martian Moons is seen here floating just above the Martian Limb. The image has been enhanced slightly to bring out the detail on the moon".MareKromiumLug 20, 2008
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Phobos-MEXP-2-h3868_0000_H.jpgPhobos, the "Doomed Moon", from Mars Express (MULTISPECTRUM; credits: Lunexit)56 visiteCaption ESA:"An image of Phobos by the High-Resolution Stereo Camera on board Mars Express taken on January 10, 2007.
The larger and inner of the two Martian Moons is seen here floating just above the Martian Limb. The image has been enhanced slightly to bring out the detail on the moon".
MareKromiumLug 20, 2008
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PSP_007769_9015_RED.jpgPhobos (RAW Frame; credits: NASA)54 visitenessun commentoMareKromiumApr 10, 2008
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PSP_007769_9015_MarsShine.jpgIn the Mars-Shine... (credits: NASA)54 visiteThis is a close-up and enhanced part of image PSP_007769_9015. In the original image, detail in the black, un-illuminated portion is not apparent. However, seen in enhanced detail here, craters are clearly visible.
This faint illumination is from reflected light off of Mars (“Marsshine”). This is directly analogous to “Earthshine,” where reflected sunlight from our planet illuminates the dark side of the Moon.
The ability to see features on Phobos illuminated by Marsshine demonstrates the high sensitivity of the HiRISE camera.MareKromiumApr 10, 2008
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PSP_007769_9015_IRB.jpgPhobos (Natural Colors; credits: NASA)54 visitePhobos, and the second Martian moon, Deimos, are interesting for several reasons. Both objects are small, with average diameters of just 22 and 12 Km, respectively.
At this size, their gravity is insufficient (less than 1/1000th of Earth) to pull them into spherical shapes, in contrast to the larger moons and planets in the Solar System.
Both moons are tidally locked to Mars, meaning, like our own moon relative to Earth, they present the same side to Mars all the time. The small size and composition (determined from spectroscopy) of Phobos and Deimos make them very similar to some asteroids.
Most asteroids are located in a belt between Mars and Jupiter, with others having orbits that cross that of Mars. Therefore, it is possible that Phobos and Deimos are captured asteroids.
Other hypotheses are that they formed with Mars in the early Solar System, or are composed of material blasted off of Mars by impacts.MareKromiumApr 10, 2008
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PSP_007769_9010-Stickney-1.jpgStickney Crater (Natural Colors + MULTISPECTRUM; credits: NASA & Lunexit)61 visitenessun commentoMareKromiumApr 10, 2008
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