HOUSTON -- After seven months of considering the bold claim that a brick-sized rock from Mars contains signs of ancient life on the red planet, the only thing scientists can agree on is that it's too early to tell.
The biggest debate yet on the topic, held March 19 at the 28th Lunar and Planetary Science Conference in Houston, quickly led to impasse. In discussing their findings since last August, when NASA researchers claimed to have found signs of life in a Martian meteorite, researchers soon discovered that they are not much further along now than they were then.
When Kathie Thomas-Keprta of Lockheed Martin Corp. looks at tiny magnetic mineral grains in the Martian meteorite, she sees signs of life. The grains look just like magnetic mineral grains made by terrestrial bacteria.
But when meteorite expert Ralph Harvey looks at the same mineral, magnetite, he sees the same grains as well as others that could only have formed at temperatures above 1,200 degrees Fahrenheit -- far too hot for life.
Ditto for the oxygen in microscopic blobs of carbonate, another mineral said to have been deposited by the Martian microbes. John Valley of the University of Wisconsin in Madison says that the ratio of different types of oxygen demonstrates it formed in a low-temperature environment hospitable to life.
But Laurie Leshin, another expert in the arcane science of determining a mineral's temperature of formation by its chemical composition, draws the exact opposite conclusion.
"Right now our data are not indicating an environment suitable for life," said Leshin, a professor at the University of California, Los Angeles.
NASA planetary scientist Everett Gibson of Johnson Space Center, an author of the paper that first claimed to have found signs of life in the meteorite, said he put the odds at better than 90 percent that his theory would be proven by the massive worldwide research effort currently under way.
Since August he has found more evidence for life, including a film of organic material in the Martian meteorite similar to ones commonly found surrounding bacteria on Earth. Early criticisms that the bacterial fossils were much smaller than anything on Earth have faded away, as researchers have found examples of terrestrial bacteria comparable in size to the tiny blobs in the martian meteorite.
But while the controversy continues over evidence of ancient life on Mars, a Purdue University scientist says Martian meteorites can tell us something about the early life of the planet itself.
Michael Lipschutz, professor of chemistry who has analyzed trace elements in 11 of the 12 known Martian meteorites, says the samples contain a different mix of volatile elements than do rock samples from Earth, indicating that the Red Planet was created from a different nebular womb.
"It looks like the cloud of gas and dust from which Mars was born contained more volatile elements such as thallium, bismuth and cadmium than did the cloud from which Earth was formed," Lipschutz says.
Original file name: CNI - Mars Life Controversy
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