Traces of 'Microbial Cities' a Record 3.49 Billion Years Old Discovered --"Communicating Via Chemical Signals"
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November 12, 2013

Traces of 'Microbial Cities' a Record 3.49 Billion Years Old Discovered --"Communicating Via Chemical Signals"

 

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Scientists analyzing some of the planet's oldest rocks, located in Western Australia's Pilbara region, have discovered traces of bacteria  that thrived a record-breaking 3.49 billion years ago, only one billion years after Earth formed.. These textures on the surfaces of sandstone thought to be sculpted by once-living organisms that lived in the equivalent of microbial cities. The sandstone hosted thousands of kinds of bacteria, each specialized for a different task and communicating with the others via chemical signals.

These are "our oldest ancestors," said Nora Noffke, a biogeochemist at Old Dominion University, who was part of the group that made the discovery. Similar traces are found today along parts of Tunisia's coast, created by thick mats of bacteria that trap and glue together sand particles. The ancient and pristine Pilbara landscape was once shoreline during the Archean eon, which ended 2.5 billion years ago.

Many of the textures seen in the Australian rocks had already shown up in 2.9 billion-year-old rocks from South Africa, found by Noffke and colleagues in 2007. "But these are the best-preserved sedimentary rocks we know of, the ones most likely to preserve the really tiny structures and chemicals that provide evidence for life," says said Maud Walsh, a biogeologist at Louisiana State University.

In 2012, another team of researcher discovered microscopic fossils in Pilbara's Strelley Pool Formation, about 3.4 billion years old. With this new discovery, Noffke and her colleagues corroborated their story by measuring the organic carbon-13 that accounts for the 1% of microbes that use photosynthesis to make their food. The balance of the carbon is carbon-12, non-living stuff --a lighter version of the element than the carbon-13 that accounts for most of the remaining 1%. Most microbial mats today contain lots of photosynthetic cyanobacteria, which make the food that sustains the other bacteria. Named after the blue-green pigment they use for this process, called phycocyanin, cyanobacteria also make oxygen and are given the credit for creating Earth's atmosphere about 2.4 billion years ago.

 

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Cyanobacteria living in microbial mats nearly 3.5 billion years ago could challenge the history of the evolution of oxygen on Earth as well as pointing to the possibility of ancient life on Mars by NASA's Curiosity rover, which has recently found evidence for ancient waterways.

 

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Remnants of life on the Mars, a planet that's nearly dead geologically and lacks active tectonic activity, might even be better preserved than they are here on Earth," says Harvard University paleontologist Andrew Knoll.

The image at the top of the page shows the Hancock Gorge in Karijini national park, Pilbara, home to some of the planet's most ancient rock formations. 

The Daily Galaxy via University of Western Australia, Washington Post, and The Guardian.com

Image credits: With thanks to http://jordancantelophotography.wordpress.com/tag/karijini/

Comments

Let's try to correlate this with assessments of when the Late Heavy Bombardment Period (LHBP) occurred. If I read this article correctly, it seems to indicate that either complex life emerged on Earth just a few hundred million years after the end of the LHBP or life existed prior to the LHBP, which must have liquefied much of the planet's crust, and survived it. Either one of these options is extremely significant in any assessment of where and under what circumstances life can emerge on other planets. Check out Wikipedia on this -- http://en.wikipedia.org/wiki/Late_Heavy_Bombardment

I think this just goes to show that life is quite robust and adaptable--whether it evolved before or after the Late Heavy Bombardment Period. The chances are quite good that life can exist under very extreme conditions.

The galaxy should be teeming with life.


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