Life On Mars: Just A Theory?

The announcement stunned the world: Scientists had found evidence of life on Mars.

Inside a meteorite from Mars, NASA researchers said, they had discovered the fossilized remains of tiny, bacteria-like animals that may have once thrived on the Red Planet.

The idea seized global attention and gave sudden popular legitimacy to the possibility of extraterrestrial life. President Clinton called for a space summit. Famed scientist Carl Sagan called it "a possible turning point in human history."

"We'll know for sure in two years or so," said NASA researcher Everett Gibson.

Now that two years have passed, excitement and applause have faded to doubt and skepticism.

Hundreds of scientists have poked, probed, crushed, dissolved, and broken parts of the Mars rock known as Allen Hills 84001. So far, no one has found absolute, incontrovertible evidence that the potato-sized chunk ever contained life.

Then again, nobody has proven that the team led by Gibson and David McKay was wrong.

"Everyone was hopeful that it would just take a short period of time to prove," said Richard N. Zare of Stanford University, a key member of the McKay-Gibson team. "We've seen two years go by. I don't know of anyone who has changed their opinion."

Ralph Harvey of Case Western Reserve University, an expert on meteorites, was excited and skeptical when the McKay group made its announcement. Now he is just skeptical and believes most other scientists are, too.

"People in the field either aren't able to confirm the work or don't seem favorable to it," said Harvey.

John Bradley, a professor at Georgia Institute of Technology, is even more blunt: "Early skepticism has evolved into international consensus...that this rock does not contain Martian fossils. I do not know of a single other individual who believes it at this point."

McKay, Gibson, Zare, and other members of the original team have countered each argument, doing lab experiments to reinforce their findings. Gibson has debated scientists in open meetings.

The debate may never be settled, says NASA's Ed Weiler, "until we go [to Mars] and get some samples."

No matter how or when the question is answered, notes Zare, science has been the winner.

"Prior to this study, if you talked about searching for life on another planet, you were considered a nut," he said. "It has now become a huge topic that is attracting the best scientists."

Written by Paul Recer