One of the inner group of Jupiter's satellites that was discovered in 1892 by E.E. Barnard and until 1979 was thought to be the innermost satellite. It has been greatly distorted by the gravitational pull of Jupiter, becoming markedly elongated in shape (270 × 166 × 150 km); its long axis points toward Jupiter. Photographs from the Voyager probes show the surface is very red, due probably to sulfur contamination from Io. The albedo is generally low, but the bright rather greenish patches have a reflectivity of up to 20% (albedo 0.2) and may be due to recently exposed material that contains less sulfur-rich glass. Its two main craters are bowl-shaped: Pan is 90 km in diameter and Gaea is 75 km. The Galileo orbiter flew past Amalthea in November 2002 but did not image it. See Table 2, backmatter.
Summary Article: Amalthea
From Collins Dictionary of Astronomy