These images of the inner Jovian moons Thebe, Amalthea, and Metis (left to right), taken in January 2000 by the camera onboard NASA's Galileo spacecraft, are the highest-resolution images ever obtained of these small, irregularly shaped satellites.
The images resolve surface features as small as 2 kilometers (about 1.2 miles) across for Thebe; 2.4 kilometers (about 1.5 miles) across for Amalthea, and 3 kilometers (about 1.9 miles) across for Metis. In late 1999 and early 2000, near the end of a two-year mission extension known as the Galileo Europa Mission, the Galileo spacecraft dipped closer to Jupiter than it had been since it first went into orbit around the giant planet in 1995. These maneuvers allowed Galileo to make three flybys of the volcanically active moon Io and also made possible these new high-quality images of Thebe, Amalthea, and Metis, which lie very close to Jupiter, inside the orbit of Io.
The moons are shown in their correct relative sizes, with sunlight coming from the right. We are viewing the side of each moon that faces permanently away from Jupiter, and north is approximately up in all cases. The prominent impact crater on Thebe is about 40 kilometers (about 25 miles) across and has been given the provisional name Zethus. The large white region near the south pole of Amalthea marks the location of the brightest patch of surface material seen anywhere on these three moons. This unusual material, which sits inside a large crater named Gaea, has been greatly overexposed; accordingly, the white area on this image is somewhat larger than the actual bright area on Amalthea. Note also the 'scalloped' or 'sawtooth' shape of Amalthea's terminator (the line between day and night, at the left-hand edge of Amalthea's disk), which indicates that parts of this satellite's surface are very rough, with many small hills and valleys.
The images are, from left to right: Thebe taken January 4, 2000 at a range of 193,00 kilometers (about 120,000 miles); Amalthea taken January 4, 2000 at a range of 238,000 kilometers (about 176,000 miles); Metis taken on January 4, 2000 at a range of 293,000 kilometers (about 182,000 miles).