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Mars rover finds evidence of water

Posted on: Wednesday, 3 March 2004, 06:00 CST

Mars rover finds evidence of water

Discoveries from Opportunity suggest that planet was habitable at one time

By KENNETH CHANG New York Times

Wednesday, March 3, 2004

Washington -- Water is the elixir of life, and scientists reported almost certain evidence on Tuesday that the tiny crater that holds the Mars rover Opportunity was once soaked in it.

The finding greatly increases the likelihood that Mars was a much more hospitable planet early in its history, possibly even amenable to the rise of life.

The scientists do not know what kind of wet environment existed at the Opportunity landing site: perhaps groundwater percolating up through volcanic ash, perhaps a lake bed that dried up, perhaps something else.

Nevertheless, "we believe at this place on Mars for some period in time, it was a habitable environment," said Steven W. Squyres, a professor of astronomy at Cornell and the principal investigator for the mission.

"This is the kind of place that would have been suitable for life," he went on, but quickly added: "Now that doesn't mean life was there. We don't know that."

Squyres said he could not say when the area had been wet or how long it remained that way, except that the period was not recent. While ice still exists near the poles, most of Mars, including the equatorial region where the Opportunity set down, is devoid of water, liquid or frozen.

To highlight the significance of the findings, NASA did not hold Tuesday's news conference at the Jet Propulsion Laboratory in Pasadena, Calif., where the scientists have been working, but instead flew them to NASA headquarters in Washington.

"Our ultimate quest at Mars is to answer the age-old question, 'Was there life, is there life on Mars?' " Edward J. Weiler, NASA's associate administrator for space science, said at the news conference Tuesday afternoon. "Today's results are a giant leap toward achieving that long-term goal."

The surface of Mars is cold and arid, but persistent speculation, based on huge canyons and channels carved in parts of the surface, is that the atmosphere was once thick and warm enough to allow liquid water to exist on the surface. Another possibility is that Mars has always been cold, except for brief episodes of torrential rains after volcanic eruptions or meteor impacts.

The mission of the two rovers that NASA landed on Mars in January is to search for signs of past water. At least in a small crater on the flat plains of Meridiani Planum, the landing site of the Opportunity, scientists have succeeded.

Suggestive hints in rock

Since its arrival on Jan. 25, the Opportunity has spotted suggestive hints of past water -- fine layers in bedrock that might be sedimentary rock deposited at the bottom of a lake or sea and an iron mineral that usually forms in the presence of water. In both cases, however, there are plausible alternative explanations: The layers could be volcanic ash or sediments carried by wind, or the iron could have formed directly from lava.

But close examination of the bedrock, exposed along the rim of the crater that the Opportunity has been scooting around in, provided four lines of evidence.

The most compelling is large quantities of jarosite, a mineral that contains iron, sulfur and trapped water. "This is a mineral that you've got to have water around to make it," Squyres said.

Instruments also measured high levels of sulfur in the rocks, probably in the form of sulfur salts. "The only way you can form such large concentrations of salt on Earth normally is to dissolve it in water and have the water evaporate," said Benton C. Clark III, chief scientist of space exploration at Lockheed Martin Space Systems and a member of the science team.

Photographs also show holes in the rocks roughly the shape and size of pennies. The scientists believe these are places where minerals carried by water formed crystals that subsequently dissolved or fell out.

The final evidence is found in the curious round pebbles, nicknamed blueberries, that are scattered around the surface and are also embedded in the bedrock. The blueberries, the scientists said, are objects known as concretions that form within sedimentary rocks.

The scientists do not yet know whether the rocks formed in water, but as to whether water later altered the minerals in the rocks, "the answer to that we believe, definitively, is yes," Squyres said.

Promoting coming missions

NASA officials used their announcement to promote coming missions and the initiative that President Bush proposed in January to send astronauts back to the moon and eventually to Mars.

"These results from Mars are already laying the foundation for the new vision of robotic and human exploration of the solar system and beyond that was announced by our president from this very stage just six weeks ago," Weiler said.

The discoveries make Meridiani Planum a promising candidate for a future robotic mission, at least a decade away, that would bring pieces of Mars back to Earth for closer examination.

Christopher Chyba, an astrobiologist at the SETI Institute in Mountain View, Calif., who is not involved in the mission, said it was exciting to have solid evidence that liquid water once flowed on Mars.

"People have been talking about wet Mars for a long time," he said. "There's nothing like actually having data. It's one thing to talk about it based on models and photographs. It's another thing to be on the surface and have evidence on the surface that Mars was wet. That's an exciting step."

Next, the Opportunity will cozy up to a section of the bedrock nicknamed Big Bend where scientists may find evidence that the rocks not only sat in water but also formed in water.

Louis Friedman, president of the Planetary Society, a space advocacy group, said evidence of water on Mars was one more piece in a giant puzzle for understanding life and its origins.

"This reminds us again why Mars is always interesting and a focus of our attention," Friedman said.

DISCOVERY MARS WAS ONCE WET

Microscopic examination by the rover Opportunity of an exposed slice of bedrock in the Meridiani Planum has revealed evidence of water.

(FOR GRAPHIC SEE MICROFILM OR BOUND FILE)

Source: NASA

Associated Press

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