[meteorite-list] 3.5 Billion-Year-Old Bacterial Ecosystems Found In Western Australia

[Ron Baalke]

http://www.news.uwa.edu.au/201311116238/research/pilbara-home-35-billion-year-old-bacterial-ecosystems

Pilbara home to 3.5 billion-year-old bacterial ecosystems
The University of Western Australia
November 11, 2013
 
Evidence of complex microbial ecosystems dating back almost 3.5 billion 
years has been found in Western Australia's Pilbara region by an international 
team including UWA Research Assistant Professor David Wacey.

The research, published this week in the journal Astrobiology has revealed 
the well-preserved remnants of a complex ecosystem in a 3.5 billion-year-old 
sedimentary rock sequence.

Professor Wacey said identifying and reconstructing Earth's earliest biosphere 
was challenging because the oldest sedimentary rocks were not only rare, 
but also almost always changed by hydrothermal and tectonic activity.

"The Pilbara region of Western Australia is one of the rare geological 
regions that provides insight into the early evolution of life on Earth," 
he said.

"Mound-like deposits created by ancient bacteria, called stromatolites, 
and microfossils of bacteria have previously been discovered in this region. 
 However, a phenomenon called microbially induced sedimentary structures, 
or MISS, had not previously been seen in rocks of this great age."

MISS were created by microbial mats as the microbial communities responded 
to changes in physical sediment dynamics, Professor Wacey said.

"A common example would be the binding together of sediment grains by 
microbes to prevent their erosion by water currents," he said.  "The significance 
of MISS is that they not only demonstrate the presence of life, but also 
the presence of whole microbial ecosystems that could co-ordinate with 
one another to respond to changes in their environment."

Professor Wacey, based at the ARC Centre of Excellence for Core to Crust 
Fluid Systems, the Centre for Microscopy, Characterisation and Analysis, 
and the Centre for Exploration Targeting, worked with US colleagues Nora 
Noffke and Daniel Christian of Old Dominion University, and Bob Hazen 
of the Carnegie Institute Washington.

The team described the various MISS from the ancient coastal flats preserved 
in the Dresser Formation and found close similarities in both form and 
preservation style to MISS in younger rocks.

Associate Professor Noffke, lead author of the paper, said the research 
extended the geological record of MISS by almost 300 million years and 
showed that complex mat-forming microbial communities likely existed almost 
3.5 billion years ago.

MISS are among the targets of Mars rovers, which search for similar biological 
signals on that planet's surface.  Hence, the team's findings could be 
significant for studies of life elsewhere in our solar system.

Media references

Assistant Professor David Wacey (Centre for Microscopy, Characterisation 
and Analysis)  (+61 8)  6488 8064
UWA Public Affairs Media Team  (+61 8)  6488 7977  /  (+61 4) 32 637 716