The imaging team for NASA's Galileo mission marked its 81^st and last official meeting on Monday by releasing a small batch of images the aging spacecraft snapped of two of Jupiter's moons.

The meeting capped 21 years of preparatory and actual imaging work on Galileo, which NASA belatedly launched in 1989.

Since its launch, the spacecraft has: discovered for the first time a moon orbiting an asteroid; documented the impact of the comet Shoemaker-Levy 9 into Jupiter; found evidence of a sloshing ocean under the jovian moon Europa and gained further insight into the prolific volcanism on another moon, Io.

The images released Monday shed further light on Io and Europa, the latter of which NASA plans to target with its own mission in the near future.

Europa's Jupiter-facing side

The November 25, 1999 image shows details as small as 1.2 miles (2 kilometers) in size, although massive fractures hundreds of miles (kilometers) long in the surface ice dominate the whole.

Since the moon lies so close to Jupiter, the giant planet's enormous gravitational tug sends what scientists believe is a liquid ocean sloshing about with tidal regularity, fracturing the surface ice.

A pair of images focuses on the tremendous volcanism of Io.

Both combine high-resolution, black-and-white images and lower-resolution color images to underscore the relationship between various surface materials with the underlying geologic structures.

In one image, scientists believe that reddish material around the margin of a caldera known as Monan Patera is a sulfur compound associated with areas where erupting lava spills onto the surface.

Monan Patera

Elsewhere in the same image, a volcanic plume called Amirani deposits sulfur dioxide, leaving a broad circle of billowy whiteness.

Mountains evident in the Monan Patera image cast enormous shadows, which allow scientists to estimate their heights. A peak at the far right of the image reaches 26,000 feet (8 kilometers), while one to the north is about half as high. The terrestrial equivalents would be Nepal's Annapurna and Switzerland's Eiger, respectively.

A composite image of the Zal Patera region of Io shows black flows near the edge of a plateau in the center of the image, along with more reddish sulfur following the base of a mountain. Scientists believe the deposits could be associated with sulfurous gases escaping from faults associated with the formation of the peak.

Zal Patera region of Io

Galileo reached Jupiter in 1995. The $1.4 billion spacecraft is now several months into its second extended mission, which will include a rendezvous with Cassini when that probe reaches Jupiter in December, en route to Saturn.

The mission has been marred by numerous spacecraft glitches, including the failure of its high-gain primary communications antenna.