While Amalthea, the largest of these four tiny moons, was imaged by NASA's two Voyager spacecraft in 1979 with a resolution comparable to what is shown here, the new Galileo observations represent the first time that Metis, Adrastea, and Thebe have been seen as more than points of light. These two images of the Jovian moon Thebe were taken by Galileo's solid state imaging system in November 1996 and June 1997, respectively. North is approximately up in both cases. In such a tidally locked state, one side of Thebe always points in the direction in which Thebe moves as it orbits about Jupiter. 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.
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. 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.