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Four views of Amalthea
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These 4 images of Amalthea were taken by Galileo's Solid State Imaging System at various times between February and June 1997. North is approx. up in all cases. Amalthea, whose longest dimension is about 247 Km (154 miles) across, is tidally locked (like Thebe) so that the same side of the moon always points towards Jupiter. In such a tidally locked state, one side of Amalthea always points in the direction in which Amalthea moves as it orbits about Jupiter. This is called the "leading side" of the moon and is shown in the top 2 images. The opposite side of Amalthea, such as the "trailing side," is shown in the bottom pair of images. The Sun illuminates the surface from the left in the top left image and from the right in the bottom left image. Such lighting geometries, similar to taking a picture from a high altitude at sunrise or sunset, are excellent for viewing the topography of the satellite's surface such as impact craters and hills. In the two images on the right, however, the Sun is almost directly behind the spacecraft. This latter geometry, similar to taking a picture from a high altitude at noon, washes out topographic features and emphasizes Amalthea's albedo (light/dark) patterns. It emphasizes the presence of surface materials that are intrinsically brighter or darker than their surroundings. The bright albedo spot that dominates the top right image is located inside a large south polar crater named Gaea.
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(Dettagli)
