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Posted on 06/07/2006 2:46:26 PM PDT by xcamel
WASHINGTON -- The best evidence yet for the oldest life on Earth is found in odd-shaped, rock-like mounds in Australia that are actually fossils created by microbes 3.4 billion years ago, researchers report.
"It's an ancestor of life. If you think that all life arose on this one planet, perhaps this is where it started," said Abigail Allwood, a researcher at the Australian Centre for Astrobiology and lead author of the new study. It appears Thursday in the journal Nature.
The strange geologic structures - which range from smaller than a fingernail to taller than a man - are exactly the type of early life astrobiologists are looking for on Mars and elsewhere.
They are known as stromatolites. They're produced layer by layer when dirt sediments mix with carbon dioxide expelled from bacteria, water, and minerals - all trapped in the microbes' sticky mucilage.
The theory is that these ancient mounds dotting a large swath of western Australia are not merely dirt piles that formed randomly into odd shapes, but that microbes built them a few billion years ago.
Some look like frosting swirls on cupcakes; others look like the inside of an egg carton. Allwood even nicknamed one 6 1/2-foot mound "crocodile back" because of its appearance.
Stromatolites have been studied for a long time, but the big question has been: Were they once teeming with life? Recently, more scientists have been leaning toward answering yes.
Allwood's research included examining thousands of the rocky mounds and grouping them into seven subtypes. It is the most comprehensive and compelling evidence that these are fossils of life, not funny-shaped rocks, according to a top expert not on her team.
"It is the best bet for the best evidence of the oldest life on Earth," said Bruce Runnegar, director of the NASA Astrobiology Institute in Moffett Field, Calif. "These are too complicated to be attributed to non-biological processes - but we don't know that for a fact."
Allwood said her study made the case for life by looking at how the stromatolites fit with the rock formations around them, with each other, and with what would have been happening on Earth at that time. One of the clinchers was categorizing them into seven repeating subtypes, which indicates they weren't random.
"It's just the sheer abundance of material and to be able to put it all in context," Allwood said.
Runnegar who has examined the mounds in western Australia several times said the first time he saw them - some of which jut out from hills at eye-level - he experienced an otherworldly feeling.
In a similar situation 10 years ago, scientists at NASA claimed they found evidence of fossilized microbial life in a Martian meteorite. Those claims have been sharply disputed and are not generally accepted.
One of the chief skeptics of the Martian meteorite claims, Ralph Harvey, a geology professor at Case Western Reserve University in Cleveland, said he is far more inclined to believe that the Australian mounds were once alive.
The key difference is that on Mars, scientists were looking for evidence of life on "a potentially dead planet" and the requirement for proof is extraordinary, Harvey said. Less evidence, he said is needed for Allwood's claims because "we already know that life has been on Earth for a very, very long time; all we're trying to do is push it further back."
Surely this refers to Helen Thomas. :^)
Are these mounds the remnants of bacteria around 'black smokers', from the ancient sea floor? I thought that was where life was supposed to have started.
ping
I may be mistaken, but I thought creationists claimed conditions for life didn’t exist on earth until 160 million years ago.
Creationists? Most young-earth creationists here believe the universe didn't even exist before 6000 years ago.
Evolutionists have found evidence for life in microfossils back to about 3 billion years ago, and there has been debate about these stromatolites' origin for quite a while. These conclusions push the origin of life back even further.
Thanks for the ping, I appreciate it, but this is obviously headed toward another Crevo bloodbath.
nope.. not going that way.
The crevo war is happening on the previous posting of this article.
Early Earth Likely Had Continents, Was Habitable, According To New Study
University of Colorado at Boulder | 2005-11-18 | University of Colorado at Boulder
Posted on 11/18/2005 11:32:59 PM EST by dila813
http://www.freerepublic.com/focus/f-news/1525001/posts
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