London: Twenty years ago, 3.5-billion-year-old microbes discovered embedded in rock in Australia were described as the oldest fossils on the planet.
However, a new study has claimed that the Apex Chert formation found in Western Australia’s Pilbara region is not biological material at all.
Instead, it has been interpreted as cyanobacteria, once known as blue-green algae.
US scientists said these structures might in fact simply be a series of rock fractures filled with crystals, reports the Daily Mail.
The finding suggests that astrobiologists examining distant planets such as Mars must be careful labelling alien objects ‘life’, when researchers cannot be certain even with the evidence in front of them on Earth.
The claim that the Apex Chert formation was carbon-based life forms has always been controversial, and so geologists from the University of Kansas decided to take another look.
Like previous teams, they cut slices of rock just 300 microns thick - roughly three times the diameter of a human hair - to study under the microscope, but this time added 30 micron sections to allow more light into the sample.
This revealed fractures within the rock that were filled with two unknown materials. Further analysis using a laser identified the mystery minerals were in fact haematite and quartz, neither of which are biological materials.
“It`s one of those funny moments in science when you go out to do one thing and it completely flips 180 on you,” said co-author Craig Marshall.
“We discovered things were a little more complex than we thought they would be,” he added.
The study is published in Nature Geoscience.