Martian Rock Shows Planet is More Like Earth Than Scientists Had Believed

PASADENA, Calif. (July 9, 1997 1:21 p.m. EDT) -- The first chemical analysis of a rock on Mars suggests the dusty world may have had abundant water at the time it formed -- a vital requirement if the red planet was to develop life as Earth did.

Geologists already know that water once existed on Mars. On Monday, Pathfinder scientists presented evidence of massive floods 1 billion to 3 billion years ago. But the latest evidence hints that water may have existed there more than 4 billion years ago, the same era when life began on Earth.

The findings radioed to scientists from the Mars Pathfinder spacecraft and released Tuesday suggested the rock -- a football-sized specimen nicknamed "Barnacle Bill" -- may be andesite. That's a type of volcanic rock named for Earth's Andes Mountains, where it is common.

Such a rock could have been brought to the surface by volcanic activity or a meteorite impact.

It is too early to tell for certain that Barnacle Bill is andesite. But because some types of the rock only form in the presence of water, the new results may eventually lead to the demonstration that early Mars had water in its interior, said Allan Treiman, a planetary scientist at the Lunar and Planetary Institute in Houston.

"It completely changes most people's views of Mars. Mars becomes a place that had water from the beginning and the water was very active in the planet," Treiman said in a telephone interview just as scientists were finishing a news conference at NASA's Jet Propulsion Laboratory.

After the Sojourner rover spent 10 hours with a small instrument pressed up against Barnacle Bill, scientists said it appears to contain the mineral quartz.

"This is a real surprise. We were not expecting a rock of this composition," said Hap McSween, a University of Tennessee specialist in meteorites who is working with the Pathfinder team.

Barnacle Bill is more Earthlike than scientists had expected, suggesting that Mars' rocks were heated and reheated many times in the planet's early history. But Pathfinder scientists were reluctant to make assumptions about water or life on Mars.

The chemical analysis of Barnacle Bill also strengthens scientists' belief that 12 meteorites found on Earth and thought to come from Mars, including the famous Antarctic meteorites where some scientists think they see signs of life, are indeed martian.

Because scientists haven't yet had a chance to closely examine the rock's texture, McSween said it was too early to be sure whether it is andesite or a mix of other types of rocks, like granite and basalt, the most commonly found lava on Earth.

In any case, Mars seems to have undergone a process of successive melting and cooling, which is needed to form these types of rocks.

The rover's alpha proton X-ray spectrometer also returned data showing that soil on the martian surface at the landing site in Ares Vallis, an ancient flood plain, was remarkably similar to that of both landing sites of the two Viking spacecraft in 1976. The implication is that all those soils formed in the same way.

Scientists said the latest weather report from Mars showed that at 11:57 p.m. PDT Monday, it was just 5 degrees Fahrenheit outside, with weak winds out of the northwest.

The lack of winds was confirmed by shots showing the wind socks on the atmospheric mast hanging limply.

"The weather on Mars at this season is pretty boring," said Jeffrey Barnes, an Oregon State University scientist working with Pathfinder's atmospheric instruments.

He said Pathfinder also found that dust in the atmosphere is deeply distributed, extending up to 18 to 25 miles from the surface.

"The dust is deep and the dust is in a lot of places around the planet, not just Ares Vallis," he said. But he said it was no thicker in the atmosphere than an average smoggy day in Los Angeles.

Project scientist Matthew Golombek said photographs indicate that Sojourner has now executed "the first wheelie on Mars," when it turned and a middle wheel was rotated while the others were still.

--By JANE E. ALLEN, AP science writer