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PASADENA, Calif. — “Barnacle Bill,” the first rock to undergo chemical analysis from NASA’s Mars Pathfinder Mission, may have been formed by a volcano, a University of Tennessee geologist said Tuesday.

 Dr. Hap McSween told reporters at a news conference at NASA’s Jet Propulsion Lab here that the rock seems similar to Earth rocks known as andesites, which are formed by volcanoes in the Andes Mountains of South America.

 The resemblance to andesites, which are quartz- or silica-rich, surprised scientists and could indicate a greater geological diversity on Mars than suspected, McSween said.

“We thought that if it was igneous (fire-formed), it would be primarily basalt, which is a different type of lava-rock,” McSween said.

 “Andesites are very different from the basalt types. This is a real surprise, we were not expecting to see a rock of this composition.”

 “Barnacle Bill,” which was about a foot from the rover after it left the lander, is thought to be about 8- to-10-inches tall. Its very distinctive surface looks almost as if it is covered with barnacle-shaped objects.

McSween said scientists are still studying incoming data to determine the rock’s minerology, and more analysis will be needed to determine if the rock was indeed formed by fire.

 “I lean toward that (igneous) interpretation because it has holes called vessicles, or gas bubbles which usually form in lava,” McSween said. “It looks like Swiss cheese, but there are other ways to explain this texture.”

 McSween said weather conditions, water or even crashing meteorites could give rocks a similar appearance.

 Scientists hope to know more about “Barnacle Bill” and other rocks when higher resolution photos are sent from the Pathfinder lander, he said.

 “This site is really a ‘rock festival,”‘ McSween said. “I sure did not expect (an andesite rock), but it is very exciting. I think we are going to see a real smorgasbord when we get more data.”


 Contact: Dr. Hap McSween(818-354-4321)