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THE HEAVENS: VOLCANO ACTIVE ON NEPTUNE MOON

SHARE THE HEAVENS: VOLCANO ACTIVE ON NEPTUNE MOON

A geyserlike volcano blasting nitrogen ice and gas five miles high was photographed on Neptune's moon Triton by Voyager 2 in the craft's last hurrah of its grand solar-system tour.

The discovery, announced Monday as Voyager 2 formally ended its two-month encounter with Neptune, proves Triton is the solar system's third known object with active eruptions, scientists said. The others are Earth and Jupiter's moon Io, which has sulfur-spewing volcanoes and geysers.Photographs radioed to Earth when Voyager flew past Neptune and Triton in August showed dark, plume-shaped deposits of material lying on Triton's south polar ice cap.

At the time, scientists believed the deposits were created by volcanoes spewing gas and ice 12 to 20 miles skyward. They said they believed the volcanoes were active or had been active during the past few centuries.

But it wasn't until late last week that closer examination of pictures taken from 62,000 miles revealed an eruption in progress, said Ellis Miner, deputy Voyager project scientist at NASA's Jet Propulsion Laboratory.

"We caught one in the act!" he said.

A National Aeronautics and Space Administration news release called such eruptions "geyserlike phenomena."

But Voyager's project scientist Edward Stone said, "From the standpoint of a major eruption, one would clearly discuss it as a volcano."

He said a column of dark material rising five miles from the surface can be seen.