Image: Mars meteorite
A photomicrograph of ALH84001, a meteorite from Mars that landed in Antarctica, shows a wormlike structure that researchers called a "nanofossil." Some doubt that life forms could exist on such a small scale, but recent research argues that they could.
By Alan Boyle Science editor

The main fascination about Mars has to do with the search for life beyond Earth.

“The key reason that we’re in this quest and that reach out there is to find a mirror to ourselves,” said retired astronaut Story Musgrave, who served as a technical consultant to “Mission to Mars.” (He also appears in a cameo role.)

More than a century ago, astronomers could make out channels that cut through the Red Planet’s surface, leading some to speculate that they played a role in supporting creatures or even civilizations.

As time went on, however, scientists progressively lowered their expectations: More than 20 years ago, results from life detection experiments on the Mars Viking landers were ambiguous — and the widely trumpeted 1996 announcement about what appeared to be “nanofossils” within Martian meteorites has ended up in the same scientific limbo.

Most scientists now believe that if life exists on Mars, it won’t be found on the surface: The mainstream view is that the radiation is too intense and that water couldn’t exist for long in liquid form because of Mars’ temperatures and low atmospheric pressure. Liquid water is considered a prerequisite for sustaining life.

At the same time, most scientists also accept evidence that liquid water flowed freely on Mars billions of years ago — and it’s theoretically possible that primitive organisms could still hang on deep beneath the surface, even though the surface has dried up.

Probing those subtle mysteries, however, is beyond the capability of the most intelligent robots on Earth, let alone a rover the size of a breadbox. The task would require the brute force of an oil-drilling operation as well as the scientific delicacy of an autopsy.

Ken Edgett, a geologist at San Diego-based Malin Space Science Systems who analyzes pictures from NASA’s Mars Global Surveyor orbiter, said the images so far raise scientific questions that are virtually impossible to answer remotely.

“Life is hand in hand with these other issues, in terms of why you would send a human to Mars,” he told MSNBC. “It’s just a matter of being able to quickly and efficiently do the work. ... One could imagine that you could do it with robots, but one can also imagine that it would take 100 years.”

Exploring the Red Planet would revolutionize our understanding of life on Earth, Edgett said. He noted that Mars’ geology was likely to preserve a record from a time “when a planet was freshly formed” — a record that no longer exists on our more dynamic world.

“What was the earth like 4 billion years ago?” he asked. “One way to find out is to go to Mars, because it’ll give you clues that you just can’t find on Earth.”

Even if life never arose on Mars, scientists would want to find out “what was different about Mars, that life didn’t start,” he said.

“If life did start, that record would be preserved on Mars, whereas on Earth it’s not,” Edgett said. “So either way, you win.”

More about missions to Mars:

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