HUMANS have looked to Mars for signs of life for generations-sometimes with longing and sometimes with apprehension. Last week, the world listened open-mouthed as NASA claimed that a team of researchers had found traces of organisms that lived on the Red Planet billions of years ago.
Not surprisingly, their evidence was nothing as unambiguous as a photograph of little green men striding about the planet, but a few microscopic blobs scattered throughout a potato-sized chunk of rock that fell from Mars.
Now, however, as the details of NASA's study begin to sink in, scepticism is mounting. The debate over the validity of the data is likely to rage for years. "This is a controversial story, and there will be a lot of disagreement," says David McKay of NASA's Johnson Space Center in Houston, who led the team. Yet in their report in this week's issue of