On Mars, minerals reveal wet past

NASA scientists elated by evidence in rock sampled by rover

`Life could have existed'

March 03, 2004|By Michael Stroh and Dennis O'Brien | Michael Stroh and Dennis O'Brien,SUN STAFF

WASHINGTON - The red planet was once a wet planet.

That was the word from jubilant NASA scientists, who announced yesterday that the rover Opportunity has found the first compelling evidence that liquid water once drenched parts of the Martian surface, creating an environment that could have harbored life.

Only five weeks after it landed, the rover fulfilled the primary goal of the $820 million Mars mission by stumbling on proof of liquid water just a few yards from where it landed near the Martian equator.

It struck scientific gold in the first place it looked: a 16-inch-tall rock dubbed "El Capitan." After drilling into the rock, Opportunity found minerals that could have been formed only if the surface was once much wetter than it is today, scientists said.

"Were these rocks altered by liquid water? We believe definitively, yes," said Steven Squyres, a Cornell University geologist in charge of the rovers' scientific instruments.

Officials of the National Aeronautics and Space Administration said the finding will help the agency refine its exploration plans in the coming years, including a mission to return a rock sample from the planet's surface to Earth.

Others in the scientific community said yesterday's findings make it even more imperative for NASA to send humans to the planet, a goal that President Bush proposed in January.

"We now know there are places on Mars where life in one form or another could have existed. The question is, did it? For that we're going to have to send people there," said Robert Zubrin, an astronautical engineer and director of the Mars Society.

After the existence of life, the question of whether water once flowed on Mars has been a contentious one among planetary scientists.

The first hints that Mars might have had a wet past came in 1971, when NASA's Mariner 9 became the first spacecraft to successfully orbit the planet. It beamed back images showing sculpted channels similar to river-carved valleys on Earth.

NASA's twin Viking missions in 1976 snapped pictures that seem to show not only rivers but also the geological ghosts of lakes and even oceans etched into the dusty surface. More recently, U.S. and European orbiters have found signs of frozen water at the Martian poles.

But lacking direct geological evidence that liquid water once sloshed on the surface, many remained unconvinced. Scientists said yesterday that the data from Opportunity's onboard instruments might finally settle the debate.

One strong hint of liquid water on the surface came from a scattering of strange spheres embedded in a rock outcropping near Opportunity's landing site. The BB-sized objects - which scientists nicknamed "blueberries" - often form on Earth when minerals precipitate out of liquid water.

Another key piece of evidence turned up when Opportunity drilled into El Capitan and found it rich in sulfur-based salts, one of which was similar to the familiar home remedy, Epsom salts. The only way the rock could have become so salty, said NASA scientist Benton Clark, was if water had been involved.

But the clincher came when one of Opportunity's spectrometers detected the presence of a rare mineral called jarosite. "This is a mineral that you've got to have water around to make," Squyres said.

Despite the substantive evidence, scientists stressed that they still don't know the full story of water on Mars, including how much water had been there or how long it lasted. Another mystery: whether the water came in the form of wave-capped lakes and oceans.

Scientists said it's possible that Martian water existed only underground, periodically percolating to the surface and soaking volcanic ash to produce the salts and other minerals that scientists observe today.

Scientists said that in the coming weeks Opportunity is scheduled to study other rocks in the small crater where it landed that might resolve the question of whether water was standing or seeping.

Either scenario raises the possibility that primitive organisms once inhabited the planet. On Earth, at least, water is necessary for life.

"We believe at this place on Mars, for some period of time, it was an inhabitable environment," said Squyres.

That possibility thrilled astronomers and other scientists. "This is very exciting," said Mario Livio, an astronomer at the Space Telescope Science Institute in Baltimore.

Livio, who works with the Hubble Space Telescope, said discoveries of extraterrestrial life might come on several fronts in the years ahead. He noted, for example, that Hubble recently discovered oxygen and carbon - elements also vital to the evolution of life as we know it - on a distant planet tentatively named Osiris, a gas giant orbiting another star.

Zubrin said the discovery of evidence of water on Mars bolsters arguments that NASA should plan manned space flights to the red planet.

The instruments aboard Opportunity and its twin, Spirit, aren't designed to answer questions about the presence of life, said James Garvin, who oversees Mars missions at NASA headquarters.

Garvin said yesterday that it will take future spacecraft, such as the Mars Science Laboratory scheduled for 2009, and a more advanced spacecraft designed to return samples of Martian rocks, to answer this question.

But, he added, "Now we have one example of stuff we really want to bring home to Earth."

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