Washington – The best evidence yet for the oldest life on Earth is found in odd-shaped, rock-like mounds in Australia that are actually fossils created by microbes 3.4 billion years ago, researchers report.
“It’s an ancestor of life. If you think that all life arose on this one planet, perhaps this is where it started,” said Abigail Allwood, a researcher at the Australian Centre for Astrobiology and lead author of the new study. It appears today in the journal Nature.
The strange geologic structures, which range from smaller than a fingernail to taller than a man, are exactly the type of early life astrobiologists are looking for on Mars and elsewhere.
They are known as stromatolites. They’re produced layer by layer when dirt sediments mix with carbon dioxide expelled from bacteria, water and minerals – all trapped in the microbes’ sticky mucilage. The theory is that microbes built them a few billion years ago.
Some look like frosting swirls on cupcakes; others look like the inside of an egg carton. Allwood even nicknamed one 6 1/2-foot mound “crocodile back” because of its appearance.
Stromatolites have been studied for a long time, but the big question has been: Were they once teeming with life?
Recently, more scientists have been leaning toward answering yes.
“It is the best bet for the best evidence of the oldest life on Earth,” said Bruce Runnegar, director of the NASA Astrobiology Institute in Moffett Field, Calif. “These are too complicated to be attributed to non-biological processes – but we don’t know that for a fact.”
