In the current edition of leading international science journal, Nature, a Macquarie University scientist argues that the oldest evidence of life on Earth is right here in Australia - not just a few fossil remnants, but a large, c. 3.5 billion year-old reef community in fossil form, now entombed in the Pilbara region of Western Australia.

Lead author Abigail Allwood of Macquarie University's Australian Centre for Astrobiology, says the existence - or otherwise - of life on Earth in the Archaean eon (more than 2.5 billion years ago) has long been a matter of heated debate.

"The problem bears upon our understanding of the origins of life on Earth and directly informs the search for evidence of past life on other planets and moons," she says. "Much of the early life debate centres on whether layered sedimentary structures called stromatolites reflect the activities of colonial microorganisms, as is the case today, or betray some non-biological process."

The case for life is boosted by new analysis of a remarkable 10-km long rocky outcrop in Western Australia - part of a rock formation known as the Strelley Pool Chert. The stromatolites here are almost 3.5 billion years old and display a variety of characteristics similar to those found in younger reefs formed by microorganisms.

"This is not a handful of isolated or dubious fossils but an entire microbial reef community in fossil form," argues Allwood. "While stromatolitic structures have been identified previously in the area, no amount of close scrutiny seemed to yield conclusive evidence of a biological origin. However our new study suggests that life not only existed way back then, but it was thriving, just waiting in the wings to flourish as soon as the right conditions emerged. This suggests life probably emerged much earlier, very soon after the planet formed. If life flourished so quickly on Earth, there's a good chance life could also have gained a toehold on Mars, even if it were habitable only briefly."

The other authors of the article are Professor Malcolm Walter and Ian Burch (Macquarie University), Professor Balz Kamber (Laurentian University, Canada), and Dr Craig Marshall (University of Sydney).

More information about the project can be found at:
http://www.nasa.gov/audience/foreducators/9-12/features/F_Field_Trip_Into_Past.html

Images can be found at:
http://pilbara.mq.edu.au/wiki/Images