Galileo takes close-up snapshots of Io.

Swooping within 671 kilometers of the hottest volcano known in the solar system, the Galileo spacecraft has recorded the sharpest images ever taken of Jupiter's moon Io.

These images are all the more remarkable because Galileo had to fly through Jupiter's belts of intense radiation, which shut down the craft just hours before the observations. Researchers revived it in the nick of time.

One of the close-up portraits, taken Oct. 10 and released by NASA late last week, reveals features as small as 9 meters across in the lava field surrounding the volcano, called Pillan. That's a resolution 50 times higher than that of the previous record holder, Io pictures taken by the Voyager spacecraft 20 years ago.

Io is the solar system's only volcanically active moon, and in 1997, Galileo caught Pillan in the act of erupting. The fresh lava had a temperature of 1,900 kelvins, several hundred degrees higher than any known eruption on Earth during the past 2 billion years.

Intrigued by the findings, scientists selected Pillan for one of the close-up studies the craft is now conducting. The single image of the Pillan lava field presents several puzzles, says Laszlo Keszthelyi of the University of Arizona in Tucson.

One puzzle concerns a zigzag depression that could represent a preexisting channel on Io's surface through which lava flowed. Alternatively, it could be a sinkhole, created when sulfur dioxide gas spewed by Pillan condensed as snow on Io's chilly surface, became buried under other material, and then evaporated.

On Nov. 25, Galileo will attempt the next close-ups, flying 300 km above Io. If it survives, the craft will have a last glimpse of Io next year about the same time that the Saturn-bound Cassini craft takes a fleeting look.