3.7-Billion-Year-Old Rock Might Not Hold Evidence Of Life After All

A few years back some scientists found an ancient rock in Greenland that was about 3.7 billion years old. This ancient rock had roughly triangular-shaped objects inside it that scientists originally thought were microbial fossils. Those structures led the scientists to proclaim that this rock had the oldest evidence of life ever discovered.

A new analysis published this week is casting doubt on those original claims. According to the second group of examiners, the structures within the rocks that the original scientists believed to be communities of single-celled microbes are mineral structures. The new researchers say the shape of those structures, originally thought to be signs of life, are easier to explain in geological terms.

The structures, which are shaped like a Toblerone candy bar, appear to be created when the rocks were squeezed and deformed under tectonic pressures says the new research. One scientist on the new study, Abigail Allwood of the Jet Propulsion Laboratory, and lead author of the new analysis says of the chances that the structures were created by ancient microbes, "I don't think there's much chance at all."

The oldest widely accepted proof of ancient microbial life is 3.5 billion years old and was found in Western Australia. Allwood was part of the team that found those ancient structures in the Australian rock. She says that the finding preservation in rocks some 200 million years older, such as the Greenland rock, "seemed incredible" going on to say that "it wasn't credible."

Allwood and her colleagues tested samples of the Greenland rock in the lab using a tool called PIXL that will be sent to Mars in 2020. That tool found that the Greenland rock structures lack the distinctive lamination seen when microbes build up materials like a stack of pancakes. She says that the study revealed that the rock structure formed, and other minerals later seeped into the structure from the outside. Naturally, the team who found the Greenland rock dispute the new findings.