Mars: Dead Again?

WASHINGTON: More bad news for ALH84001. The chunk of 16 million-year-old Martian rock was thrust into the limelight two years ago, when NASA said it held evidence of life on the Red Planet. Friday's issue of Science, however, says that's hogwash. The organic compounds researchers found bear a chemical signature common in Antarctica, where the meteorite was discovered. In other words, this rock was contaminated by distinctly Earth-bound bacteria.

"This is not the first paper that's come out," says TIME science writer Mike Lemonick, "but it's more powerful than anything we've seen before." Indeed, Jeffrey L. Bada of the Scripps Institute of Oceanography, who wrote the Science report, claims to have done the most extensive examination of the Mars rock yet and the amino acids it contains "look just like the ones on Earth." So are the little green bugs dead and buried? NASA says no and there is still some evidence of Martian life on the rock, such as tiny structures in the shape of bacteria, left untouched by Science magazine's assault. "The whole thing's a judgment call," says Lemonick. "Contrary to what we think about science, there are some cases where evidence isn't strong enough one way or the other." Life on Mars: The great debate continues.