These
four images of Jupiter's moon, Amalthea, were taken by Galileo's solid state
imaging system at various times between February and June 1997. North is
approximately up in all cases. Amalthea, whose longest dimension is approximately
247 kilometers across, is tidally locked so that the same side of the satellite
always points towards Jupiter, similar to how the near side of our own Moon
always points toward Earth. 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 two images. |
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The
opposite side of Amalthea, 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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