In the center of the meteorite, McKays team had found tiny egg-shaped and
tubular structures that looked like fossils of minuscule bacteria. Evidence from
Zares lab provided critical support for the idea that those structures
might once have been alive.
Zare found a unique combination of everyday air pollutants called polycyclic
aromatic hydrocarbons (PAHs) that form when living things die. Because the PAHs
were concentrated in the center of the meteorite, they did not appear to be
contaminants picked up on Earth. The concentrations peaked near the possible
At first, says former grad student Simon Clemett, who worked on the project
with Claude Maechling and Xavier Chillier, no one dared breathe the L
Eventually, though, every test they could devise pointed to the same conclusion:
Several lines of evidence can be explained most simply by the hypothesis that
primitive life existed on Mars about 3.6 billion years ago.
Now that the public clamor has quieted down, the scientists involved
still must test the Martian life hypothesis. Zares lab is looking for
traces of amino acids, the
building blocks of life. Many other researchers are designing experiments,
including some that may ship on spacecraft aimed at Mars.
As intriguing as the Mars findings are, no one is promising solid proof soon.
As Zare says, It is very difficult to prove that life existed 3.6 billion
ago on Earth, let alone on Mars. ST