Phobos par MRO

HiRISE acquired two dramatic views of the Martian moon, Phobos, on 23 March 2008. Observation, acquired at a distance of 6,800 kilometers from Phobos, provides surface detail at 6.8 m/pixel scale and a object diameter of about 3,200 pixels. The second observation, providing a closer look at 5,800 km, views the surface at slightly more detail (5.8 m/pixel with an object diameter of about 4,000 pixels). The two images were taken within 10 minutes of each other and show roughly the same features, but from a different angle so that they can be combined to yield a stereo view. (Watch a short clip of both observations: 204KB, QuickTime.) The illuminated part of Phobos visible in the images is about 21 km across. Images from previous spacecraft have been of smaller pixel scale (for example, Mars Global Surveyor got data at 4 m/pixel, because this spacecraft came closer to Phobos), but the HiRISE images have greater signal-to-noise, making the new data some of the best ever for Phobos. The most prominent feature in the images is the large impact crater Stickney, in the lower right. With a diameter of 9 km, it is the largest feature on Phobos. A series of grooves and crater chains is obvious on the other parts of the moon. Although many appear radial to Stickney in the images, previous studies show that the grooves radiate from a different point on Phobos. Hypotheses for their formation vary. Some scientists believe the grooves and crater chains are related to the formation of Stickney, whereas others think they may have formed from ejecta from impacts on Mars that later collided with Phobos. The lineated textures on the walls of Stickney and other large craters are landslides formed from materials falling into the crater interiors in the weak Phobos gravity (less than 1/1000th the gravity on Earth)

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