Widespread volcanism and a geologically active surface were descriptions of the planet Venus presented Friday in the first published papers by members of the Magellan Project science team at NASA's Jet Propulsion Laboratory.

In the papers, published in the April 12 issue of Science magazine, Magellan scientists described geologic features of Earth's sister planet as they begin the unprecedented task of mapping an Earth-size planet. The reports describe extensive volcanism, tectonic deformations, mountain belts, and a number of impact craters that indicate a relatively young surface age of a few hundred million years.

Science team members described several types of lava flows, evidence of lava rivers hundreds of miles long and craters created by meteorite impacts that caused surface material to be ejected as far as 600 miles.

"The Magellan spacecraft is producing comprehensive image and altimetry data for the planet Venus," said Project Scientist Stephen Saunders and his co-authors in one of the papers.

The Magellan spacecraft was launched May 4, 1989, and began mapping Sept. 15, 1990. Its primary mission goal of mapping 70 percent of the planet was accomplished April 3. Project officials said that when the first mapping cycle of 243-days -- one Venus rotation beneath the orbiter -- ends on May 15, a total of 84 percent of the planet's surface will have been acquired.

NASA officials announced last week that because of the excellence of the radar images produced by the spacecraft and the excitement they have generated in the science community, a second mapping cycle has been approved.

The first priority of the second cycle, beginning May 16, will be to acquire the remaining 16 percent of the planet's surface in radar imagery, including the south pole which has not been imaged by spacecraft before.

The papers, written by science team members from JPL and other American and foreign institutions, covered the first 21 days of Magellan radar image data.

The Magellan project is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science and Applications, NASA Headquarters, Washington, D.C.

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