Images Confirm Mars Flood

Published Tuesday, July 8, 1997, in the San Jose Mercury News

Images confirm Mars flood The big question remains: Where did the water go?

BY ROBERT S. BOYD Mercury News Washington Bureau

PASADENA -- A flood of biblical proportions -- enough to equal the Mediterranean Sea -- gushed down from the highlands of Mars a billion or so years ago, the latest pictures from the Pathfinder spacecraft confirmed Monday.

The images, taken in 12 colors and from a higher perspective than earlier pictures, revealed a series of 12-foot-high ridges and valleys near Pathfinder's landing site that scientists believe were carved out by the thunderous force of the deluge.

The amount of water must have been thousands of times greater than the flood that washed over Grand Forks, N.D., this spring, said Michael Malin, a geologist who has studied floods on Earth for 20 years.

Malin, head of Malin Space Science Systems in La Jolla, estimated that the deluge was hundreds of miles wide and hundreds of feet deep, and flowed for thousands of miles. ``This was huge,'' he said, ``but we don't know where the water went.''

From the shapes and colors of the rocks, surface textures and undulating low ridges and valleys, scientists inferred Monday that the plain of Ares Vallis, where the spacecraft landed, had been scoured by liquid. The tilt of rocks and tails of debris behind pebbles suggested that the flood came from the southwest. Crustal splotches indicate that puddles left by the flood slowly evaporated, leaving what appear to be salty residues.

Since the Viking missions to Mars in the 1970s, scientists have believed that the face of Mars was scoured by mighty waters. But the fresh pictures from Pathfinder provide the most convincing evidence yet.

In addition, the Martian inundation left traces of dried-up channels and puddles, similar to what happens after a flood on Earth, showing that some liquid remained on the surface for a while before evaporating. This is strong evidence that, for a time at least, Mars was warm enough to keep its water from freezing.

``The implications are enormous, since liquid water is the key ingredient for life,'' said Matthew Golombek, Pathfinder's chief scientist.

The Ares Vallis site was chosen because pictures from previous missions showed that it was probably a floodplain scattered with rocks washed down from ancient highlands nearby.

Scientists think the highlands are 4.5 billion to 3.6 billion years old, which is the same period during which life emerged on Earth. The early evidence indicates that the most recent flood at the landing site occurred 1 billion to 3 billion years ago.

While Pathfinder was strengthening the case for a wetter, warmer ancient Mars, its roving partner, Sojourner, completed its first two assignments. The robot tested the chemical makeup of the dark red soil at the base of the lander and of a craggy, 10-inch-high rock nicknamed ``Barnacle Bill.''

After ambling down its exit ramp Sunday, the little robotic geologist pirouetted on its six aluminum wheels and then backed up about a yard to Barnacle Bill.

``Once there, she nestled up and kissed affectionately,'' Golombek said. Pathfinder scientists tend to personify their machines, and frequently refer to Sojourner -- named for 19th-century anti-slavery crusader Sojourner Truth -- as ``she.''

The rover cuddled with the rock for 10 hours, examining it with an X-ray spectrometer.

``It's a rare treat for scientists to get a rock on the first day,'' said Golombek.

Sojourner radioed back its chemistry report to NASA's Jet Propulsion Laboratory on Monday, but scientists said they wouldn't finish analyzing it until today.

``We are awash in new things,'' said Golombek delightedly. ``Everything is working perfectly.''

After bidding farewell to Barnacle Bill, Sojourner, which moves about two feet a minute, is to crawl about five yards to a large black rock dubbed ``Yogi,'' because it vaguely resembles a bear. On the way, the rover is to stop and wiggle its wheels so that scientists can study the makeup of the soil. Then it will take a closeup photo of Yogi, and put its spectrometer down on the ground to test the chemistry there.

Also expected today is the ``Monster Pan,'' a full-color, high-resolution, stereoscopic panorama of the horizon. The millions of bits of data making up that portrait will let scientists produce a detailed map of the area around the landing site,and determine the correct size and distance of each object.

The pictures Pathfinder took Monday are quite different from the first images, since the camera is now at the level of a person standing up, not crouching, as before.

``They give us a new perspective,'' said Peter Smith, manager of Pathfinder's camera system. ``Rocks that seemed huge yesterday turn out to be only one foot high. We can now see a channel behind some boulders that we couldn't see yesterday.''

In addition, the camera, which had been taking pictures with three color filters, began using all 12 of its filters, five in visible light and seven in infrared. This greatly increases the richness of the information.

The new photos showed a variety of hues, from dark gray to bright red to almost white. Some rocks are almost black, like those found on the volcanic slopes of the big island of Hawaii.

But the predominant color, as expected, is red -- the result of iron combining with oxygen to form rust.

``The surface of Mars is rusting,'' said James Bell, a Cornell University astronomer on the Pathfinder science team. ``The soil is very rich in iron oxides.''

An unanswered question is what happened to the oxygen that caused the rusting, Bell said. Most of the oxygen on Mars is now tied up in the form of carbon dioxide, which makes up 97 percent of the planet's atmosphere.

Scientists are also unsure where all the Martian water went. Some of it is frozen in the polar ice caps, and vast quantities are believed to be locked up in a mile-thick band of permafrost below the surface. They also think there is an ocean of liquid water deep down, where radioactive processes warm the core of the planet.

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The New York Times contributed to this report.