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Scientists call Martian rock 'a real surprise'


Mars' geology 'more like Earth than the moon'

July 8, 1997
Web posted at: 7:18 p.m. EDT (2318 GMT)

PASADENA, California (CNN) -- A scientist on the Mars Pathfinder project says that the first chemical analysis of a stone on Mars' surface was "a real surprise" and suggests that the geology of Mars may be "more like the Earth than the moon was."

Hap McSween, a University of Tennessee scientist, told a press conference Tuesday at Cal Tech's Jet Propulsion Laboratory that the rock dubbed Barnacle Bill by scientists had more "free quartz" in it than was expected.

One possible explanation, he said, is that the rock had melted and solidified a number of times underground and was similar to a volcanic rock found on Earth.

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    "We were not expecting to see a rock of this composition," McSween said.


    The data from the Sojourner rover's alpha proton X-ray spectrometer suggests that the football-sized rock may be a kind of andesite, the second most common type of lava on Earth.

    McSween emphasized that there was no confirmation that Barnacle Bill was formed by volcanic action, and said it could either be sedimentary rock or an "impact" rock caused by a meteorite.

    'This is a rock festival'

    But he did say that its composition is different from meteorites from Mars. He also said that scientists hope an analysis of the soil will help them get a better idea of Mars' geology.

    "We sure didn't expect this, but it's very exciting," said McSween. "This is a rock festival."

    Project scientist Matthew Golombek reminded reporters that "we've just landed on Mars and started to look at it. We're seeing real surprises, but it's too early to tell."


    The scientists also revealed that:

    • The dust in the Martian atmosphere is comparable to that of a moderately smoggy day in Los Angeles. Scientist Jeffrey Barnes of Oregon State University said the dust ranges as high as 21 to 24 miles (35-40 km) into the atmosphere.

    • Sunrises and sunsets on Mars are longer and brighter than on Earth, owing to the dust. First light on Mars occurs at 3:15 a.m. A day on Mars is similar in length to a day on Earth.

    • The first observations were made of Deimos, the smaller of Mars' two moons. Thirteen images were beamed back to Earth, and Dr. Nicholas Thomas of the Max Planck Institute in Germany said Deimos would never be more than a "spot" passing over Mars. Phobos, though larger than Deimos, crosses the Martian night sky in four hours, he said.

    "They don't look like our moon at all," Thomas said.

    The weather on Mars is "boring," in the words of Barnes. At 2:45 in the Martian afternoon, the temperature was 5 degrees Fahrenheit, and there was a weak wind from the northwest.

    "It's exactly what we expected," Barnes said. However, he added that during the Martian fall which begins in "50 or 60 days," the weather change will be dramatic.

    Golombek revealed that the Pathfinder lander bounced more than 16 times on its cushion of air bags before coming to rest in the area called Ares Vallis. And since overcoming a communications glitch over the weekend, everything has worked flawlessly.


    "The Pathfinder is in excellent health, the rover's in excellent health and all the instruments are in excellent health," Golombek said with a toothy grin.

    The scientists' muted euphoria has become a regular feature at the briefings, and they make no apologies for it.

    "We're immensely happy with the variety of the surface and the variety of rock types," Golombek said Tuesday. "I could only have hoped it in my wildest dreams..."

    Rover records another first

    Golombek said the instruments will continue to gather data on the soil, rocks and atmosphere. He also said the Hubble Telescope may shoot pictures of Mars from space that would be compared with those shot from the planet's surface.


    Finally, Golombek revealed yet another space first. Two, in fact.

    Among the photos shown at the briefing was one of a shallow depression in the Martian surface caused by the Sojourner rover. Golombek said the middle wheel of the rover was rotated and spun, causing the deformation so that the X-ray spectrometer could analyze the soil.

    "The deformation was caused by the first wheelie on Mars," Golombek said happily. "We picked up our first bogey."

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