The evolution of oxygen-producing organisms has been pushed back another 270 million years through the discovery of well-preserved fossils in Western Australia's Pilbara region.
The discovery is the earliest evidence yet for the point at which the Earth's current atmosphere began to form, described as one of the defining moments in the Earth's history.
David Flannery, who presented his discovery today at the Fifth International Archean Symposium in Perth, Western Australia, argues the find is the earliest sign of oxygenic photosynthesis yet found.
Flannery, a doctoral student at the University of New South Wales Australian Centre for Astrobiology, says signs of the presence of oxygen-producing organisms were found in the rock formation known as the Tumbiana, which stretches about 680 kilometres in the Pilbara to south of Marble Bar.
He says the fossils, which include stromatolites, microbially induced sediment structures and biomarkers, the molecules created when oxygen is made, were well preserved.
The fossils showed indications of the presence of cyanobacteria , commonly known as blue-green algae, which are single-cell life forms that can photosynthesise oxygen, says Flannery
"There is a debate in the literature as to when the first oxygen-producing organisms evolved," he says, adding that the accepted evidence is that this happened about 2.5 billion years ago.
"There are some however who see evidence up to a billion years earlier than that."
The earliest published evidence for these organisms to date had been 2.45 billion years ago.
First signs of oxygen
The work of Flannery and his colleagues places the presence of oxygen-producing cyanobacteria on the Earth at 2.72 billion years ago, some 270 million years earlier than previously thought.
He says the finding not only has implications for how long it took the Earth's atmosphere to oxygenate, but also helps in the search for life on other planets.
Flannery says solving the mystery of the oxygenation of the atmosphere will help exoplanet hunters to better target which planets may support life.
"If for example, we find it takes a billion years for the atmosphere to oxygenate, then we know it is not worth looking at stars less than a billion years old," he says.
Author: Dani Cooper | Source: ABC [September 08, 2010]