A silver-and-black spacecraft named Voyager 2 today flew by Jupiter and its four large and richly-colored moons that scientists find more fascinating than most planes in the solar system.
Moving at more than 45,000 miles per hour, the 1,800-pound Voyager 2 passed by Jupiter at 7:21 p.m. EDT from a distance of 404,000 miles. Before that, it flew by the dark brown, ice-covered moons Callisto and Ganymede and then passed the yellow moon Europa, which was found to be criss-crossed with hundreds of ice-filled crevices.
Just beyond Jupiter the spacecraft began a 10-hour watch of the red moon Io, where at least six volcnoes were erupting as Voyager 2 began photographing them.
Just before 8 p.m. EDT, Voyager 2 began scanning the moon Io to see if it could find more than the eight active volcanoes it and Voyager 1 before it had already identified.
On each rotation as Io showed a new face to Voyager 2, nothing new appeared in the way of an active volcano.
But as Voyager 2 flew away from the environs of Io and Jupiter, it picked up what clearly were two volcanic plumes pouring ash into space above Io. One plume appeared to be about 100 miles high and the other about 70 miles.
The volcano watch from Voyager 2 was to continue into Tuesday.
"We've seen the youngest, the oldest, the brightest, the darkest, the reddest and the most active bodies in the solar system," Dr. Laurance A. Soderblom of the U.S. Geological Survey said at the Jet Propulsion Laboratory, where Voyager is directed. "We thought we had some idea of what planets were like, but now we've discovered how wrong we were."
The surprise of the day was a closeup picture of the moon Europa, which looked for all the world like the 19th century telescope views of the features of the planet Mars that some astromers long believed to the canals.
Threaded and laced by hundreds of dark cracks in its icy yellow surface, Europa had the appearance of a giant eggshell that had been squeezed and cracked by an invisible hand. The cracks were as wide as 30 miles and as long as 2,000 miles. None of the cracks was deeper than a few hundred feet and some appeared to have a raised look, as if they were protruding from the surface.
"You certainly couldn't call them canyons," Soderblom said. "They have the appearance of gullies of the fracture patterns you get in pack ice in the polar regions of earth."