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Searching for Signs of a Wet Mars

NASA mission hopes to finally answer whether the Red Planet was ever hospitable to life.

June 06, 2003|Usha Lee McFarling | Times Staff Writer

When astronomer Percival Lowell gazed through his mountainside telescope at Mars a century ago, he saw cities, patches of vegetation and an intricate network of canals -- features that seemed to indicate vast quantities of water.

Lowell, of course, was wrong. But the search for water continues today, driven by the belief that where there is water, there is the possibility of life. It is a quest that has thrilled -- and disappointed -- a vast constituency of sci-fi junkies, scientists and ordinary people who have gazed at the Red Planet.

"I would characterize Mars as being a bipolar place," said Jonathan Lunine, a planetary scientist at the University of Arizona. "It creates great excitement and great depression."

After centuries of speculation and decades of conflicting data, NASA scientists hope they will finally be able to answer what is still one of the most contentious questions in planetary science: whether Mars was once "warm and wet" and hospitable to life or has always been a frozen wasteland.

For The Record
Los Angeles Times Thursday June 12, 2003 Home Edition Main News Part A Page 2 National Desk 1 inches; 54 words Type of Material: Correction
Mars rover -- A June 6 article in Section A about the search for water on Mars gave the incorrect name and landing date of the last Mars rover. It was named Sojourner, not Pathfinder, which was the name of the spacecraft that carried it. The rover landed on Mars in 1997, not 1996.

NASA is scheduled to launch on Sunday two massive robots armed with chemical analyzers, rock grinders and microscopic lenses able to detect the faintest evidence that rocks may have formed in a watery environment. While they will not directly search for life or water -- a task that would likely require deep drilling and different instruments -- the Mars Exploration Rovers will be able to look for evidence of what the past was like in the place where such ancient records are best kept: the rocks.

"If we don't find evidence of persistent water then we are either very, very unlucky or we're looking at a dry planet," said Dan McCleese, an atmospheric physicist and chief scientist of the Jet Propulsion Laboratory's Mars exploration program.

Mars has always been a distant tabula rasa: a blank slate to paint with imaginings born of what was known of life on Earth. Lowell dreamed of a dying civilization forced to build canals to survive the desiccation that surrounded them. Other astronomers thought they saw changing seasons and greenish tints from vegetation.

It was not until the mid-1960s, when the string of missions to Mars began, that science started to overwhelm imagination, raising entirely new questions with each swing past the planet. The debate has been a seesawing free-for-all ever since.

"Every time we send a mission to Mars," said Bruce Jakosky, a planetary scientist who directs the Center for Astrobiology at the University of Colorado, "we seem to find a new planet."

The first close-up images of Mars were sent back from Mariner 4 in 1965. Hazy as the images were, they made it clear there were no canals, no civilizations, no vegetation, no oceans, not even a puddle. The only water was frozen in the icecaps.

Hopes soared in 1971 after Mariner 9 sent back images of volcanoes, canyons and what looked to be vast river systems. Though dry, they appeared carved by ancient waters.

But in 1976, the Viking mission put the first robots on the surface of Mars to seek signs of life or organic material. The two landers found nothing of the sort, disappointing scientists and stalling exploration.

In 1996, NASA's interest was reignited with the discovery of a Mars meteorite purported to contain traces of primitive life that had existed on Mars 3.6 billion years ago. The finding, however, was largely dismissed after further analysis. The real explosion of information about Mars has occurred only in the last four years with a flotilla of orbiters photographing and analyzing the chemistry of Mars in unprecedented detail.

Mars Global Surveyor has snapped more than 100,000 detailed pictures of the surface -- the most exciting showing gullies that might have been cut by flowing water very recently.

Another orbiter, called Odyssey, found evidence of vast deposits of ice just beneath the Martian surface -- far more ice and far closer to the frozen surface than scientists had expected.

The find provided a partial answer to the question of where all of that Martian water went. Another instrument detected hematite, a mineral that often forms in warm water, although it also has just found evidence of thick layers of the mineral olivine, which exists only in the driest of places because it decomposes in water.

The prodigious flow of new information, however, has only fueled more debate over water and life. In short, the geology says there was water. The chemistry and the physics still say no.

"We don't know what's going on," said Mike Carr, a U.S. Geological Survey geologist who has participated in nearly every mission to Mars. "The more knowledge we get, the less we understand Mars."

The biggest problem is that basic physics don't easily allow for a warm Mars. The planet is about 50 million miles farther from the sun than Earth. And in the period when some scientists think Mars would have been warm -- about 3 billion years ago -- the sun was about 70% dimmer than it is today.

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