It’s life, but not as we know it

22 August 2005

in 2005

Billion year old bacteria in NT rocks and bugs from outer space

Researchers from the CSIRO, Sydney University and Colorado State University have developed a means of detecting signs of ancient microbes which may have lived on Earth or come from outer space.

The group already has picked up signs of bacteria more than a billion years old inside rocks from the Northern Territory.

The technique centres around analysing tiny oil droplets-sealed inside rocks as they formed-for traces of chemical compounds known only to be produced by particular types of organisms. The results provide unequivocal evidence of their presence.

“Oil forms from decayed organisms, and therefore contains fatty tracers or biomarkers for the organism from which they came-like the footprint of a dinosaur, but at a molecular level,” says Herbert Volk from CSIRO Petroleum, a member of the research team.

“It’s important that we understand these early organisms, as they were the building blocks for the evolution of the more complex life forms which play an important part in today’s ecosystems.”

The team has managed to extract such biomarkers from oil droplets sealed in Precambrian rocks from the Northern Territory for more than a billion years.

The chemical analysis of the oil indicates that it is derived from single-celled cyanobacteria, the aquatic and photosynthetic bacteria responsible for increasing oxygen levels in the atmosphere. There is also evidence of the presence of more complex strains of life.

“Microscopic evidence of fossilised microbes is very rare in rocks of this age, and if present are often fiercely debated,” Volk says. “Biomarkers have been extracted from rocks of similar age before, but these were not from oil droplets sealed in crystals, so they may have been contaminated by more recent life forms. The new results are free of such doubt.

“And should oil inclusions be found in extraterrestrial rocks such as meteorites or Martian rocks, the molecular signature would be perfectly protected from traces of terrestrial life that could otherwise compromise the information.”

Herbert is one of 13 Fresh Scientists presenting their research to the public for the first time thanks to Fresh Science, a national program hosted by the State Library of Victoria. One of the Fresh Scientists will win a trip to the UK courtesy of the British Council to present his or her work to the Royal Institution.

To view larger image, click on image:  
Remote arid landscape near the drill site in the Roper Superbasin in the Northern Territory, near the Gulf of Carpentaria.
Photo: Dr David Rawlings
The Roper Superbasin is one of the oldest basins known to contain petroleum which is where the researchers look for life.
 This is a thin slice of rock viewed through a microscope with UV light. The oil inclusions are seen fluorescing in bright blue. What the researchers look for are biomarkers of life. Some of the chemical structures they look for are hopanes, derived mainly from hopanols which are fatty alcohols in the cell walls of bacteria.
This is the chemical structure of a hopane molecule.
Herbert Volk (right) and colleague Simon George (left), analysing the oil droplets using a mass spectrometer.

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