Narrator: This is Science Today. Using a process similar to DNA fingerprinting, researchers at the University of California, San Diego re-analyzed Martian meteorites and found no chemical trace of a biological process. Mark Thiemens, a professor of chemistry, says it's been thought these meteorites contained clues of ancient life on Mars. But by measuring sulfur isotopes found in these rocks, his group only found an atmospheric influence.
Thiemens: The isotopes give you a very distinctive signature, so one gets a sort of information. It was this laboratory that found this new type of isotope effect that really fingerprints specific processes that we can look at it and say - we know this is not biologic, it's in fact photochemical.
Narrator: But Thiemens says that's not to say there wasn't life on Mars.
Thiemens: Mars was wet. It had an ocean, it was probably warmer. There very likely could have been life on Mars. But the feature that we're seeing in these meteorites is probably not nano-bacteria. The only way to answer this question for sure is a return sample taken from the right areas.
Narrator: For Science Today, I'm Larissa Branin. .