Because of Amalthea's close proximity to Jupiter, it is exposed to the intense Jovian radiation field. It continuously receives high doses of energetic ions , protons, and electrons produced by the Jovian magnetosphere . In addition it is bombarded with micrometeorites, and heavy sulfur, oxygen, and sodium ions that have been striped away from Io. This image of Amalthea was acquired by the Voyager 1 spacecraft on March 5, 1979. 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. 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. It emphasizes the presence of surface materials that are intrinsically brighter or darker than their surroundings.