Photo Courtesy Jet Propulsion Lab/ Pasadena, Calif.

This photo taken from the Pathfinder lander shows evidence of water at Ares Vallis, Mars. Scientists examining rocks called Barnicle Bill (lower left), Yogi (upper right) and Whale rock (a log-shaped rock at the top of the photo) find extensive oxidation (rusting) of iron on the rocks' surfaces. Iron oxidation is possible only with water.

ITHACA, N.Y. -- After studying more than 9,500 images taken during the acclaimed Mars Pathfinder mission, scientists report in today's journal Science (Dec. 5) that surface photographs provide strong geological and geochemical evidence that fluid water was once present on the red planet.

"We now have geological evidence from the Martian surface supporting theories based on previous pictures of Mars from orbit that water played an important part in Martian geological history," said James F. Bell, Cornell senior research associate in astronomy and a member of the Mars Pathfinder imaging team.

Bell, along with lead author P. H. Smith of the University of Arizona; Robert J. Sullivan Jr., Cornell research associate in planetary science; and 23 other scientists authored the paper, "Results from the Mars Pathfinder Camera." The report is part of a complete Mars Pathfinder mission report published in Science.

During the first 30 days of the Mars Pathfinder mission, the Imager for Mars Pathfinder (IMP) returned 9,669 pictures of the surface. These pictures appear to confirm that a giant flood left stones, cobbles and rocks throughout Ares Vallis, the Pathfinder landing site. In addition to finding evidence of water, the scientists confirmed that the soils are rich in iron, and that suspended iron-rich dust particles permeate the Martian atmosphere.

Bolstering their evidence for once-present water, the imaging team found evidence for a mineral known as maghemite -- a very magnetic iron oxide. Bell explained that maghemite forms in water-rich environments on Earth and could likely be formed the same way on Mars. Bell explained that reddish rocks like Barnacle Bill, Yogi and Whale rock show evidence of extensive oxidation on their surfaces. He said the oxidation -- or the rusting of the iron -- is possible only if water existed on the surface at some time and played an important role in the geology and geochemistry of the planet.

But, where did all the water go?

"That's the golden question. No one knows," said Bell, explaining that several theories about the disappearing water exist, such as evaporation into space, or seepage into sub-surface ice deposits or liquid aquifers, or storage at the Martian poles. Bell said that robotic missions to Mars early in the next century, including a Cornell-led rover mission to be launched in 2001, will attempt to determine the water's whereabouts, as well as to determine whether the Martian environment may once have been more conducive to life.

Photo Courtesy Jet Propulsion Lab/ Pasadena, Calif.

Pathfinder sent this picture of a rock called Moe. It shows scientists that low-level Martian winds, with iron-rich dust particles, literally sand-blasted the rock over billions of years.

Mars Pathfinder's camera also revealed that Mars' atmosphere is more dusty and dynamic than expected, Bell explained. Surprisingly, the scientists found wispy, blue clouds, possibly composed of carbon dioxide (dry ice), traveling through Mars' salmon-colored sky. White cirrus-like clouds, made of icy water vapor, also circulate throughout the thin Martian atmosphere.

"We were surprised to see such variations in the clouds, particularly since Mars has such a thin atmosphere," Bell said. "We figured the atmosphere would be the same everyday, but there is a lot of real weather occurring there. It's a small atmosphere, but a vigorous one."

Looking at Martian rocks like Yogi, Barnacle Bill and Scooby Doo reveals that the rocks have been sitting on the planet's surface for billions of years, enduring a slow-motion sandblasting from a usually weak, dusty Martian wind. To carve rock with such a weak wind force requires a vast amount of time, Bell explained.

"The slow, persistent weathering and erosion of the rocks is like water torture to the max," he said. "Mars really is an ancient world. We're still trying to sort it all out."