Scientists believe they might have identified one of Earth's earliest life forms preserved in sedimentary rock.
Found in the Pilbara district of Western Australia, a research team with the Carnegie Institution for Science found what they described as mound-like deposits that would have been created by photosynthetic bacteria. The rock also included microfossils of bacteria the scientists date at 3.5 billion years old.
A rock surface displaying ‘polygonal oscillation cracks’ in the 3.48 billion years old Dresser Formation, Pilbara region, Western Australia. Such and similar sedimentary structures are of biological origin. They document ancient microorganisms that formed carpet-like microbial mats on the former sediment surface. The Dresser Formation records an ancient playa-like setting – similar environments are occurring on Mars as well. The microbially induced sedimentary structures constitute a novel approach to detect and to understand Earth’s earliest life. (Image source: Nora Noffke/Carnegie Institution for Science)
Identified from samples in the region's Dresser Rock formation, the "microbially induced sedimentary structures" are similar to those found in rock samples in other countries -- only older.
“This work extends the geological record of MISS by almost 300 million years,” investigator and Old Dominion University professor Nora Noffke said in a statement. “Complex mat-forming microbial communities likely existed almost 3.5 billion years ago.”
“The structures give a very clear signal on what the ancient conditions were, and what the bacteria composing the biofilms were able to do,” Noffke said.
David Wallace with the University of Western Australia told the U.K.'s Daily Telegraph there are claims of older evidence of life found in rocks from Greenland, but they are "so deformed that it is very difficult to tell if what you are seeing was actually there in the first place."
The fossil evidence of bacteria found in Australia gives scientists a clearer picture of how the bacteria could have interacted with the sediment on which it lived.
As for the finding's larger implications, Carnegie's news release pointed out that Mars rovers are searching for "microbially induced sedimentary structures" as well.
Wallace told the Telegraph the study published in the journal Astrobiology could help scientists understand when life evolved and what Earth's early environment was like.
"Ultimately, we are looking for when that soup of chemicals became something that could be called life," he said.