Saturday, April 23, 2011

Apex Chert: Microfossils, Microfractures, or Maybe Both

"Most Ancient Fossils Aren't Life, Study Suggests"
Charles Q. Choi, (March 24 , 2011)

"Structures thought of as the oldest known fossils of microbes might actually be microscopic mineral formations not associated with life, suggesting that astrobiologists must be careful calling alien objects 'life' when scientists have trouble telling what is or was alive on Earth.

"More than 20 years ago, microscopic structures uncovered in the roughly 3.5-billion-year-old Apex Chert formation in western Australia were described as the oldest microbial fossils. These structures were interpreted as cyanobacteria, once known as blue-green algae, embedded in a silica-loaded rock formed in a shallow marine setting. These structures were all detected in slices of rock just 300 microns thick, or roughly three times the diameter of a human hair.

"However, the interpretation of the structures has always been controversial, and it is still hotly debated among scientists searching for Earth’s earliest evidence for life. Specimens from the site apparently displayed branching structures that some researchers said were inconsistent with life, while others dismissed such branching as artifacts from photo software...."

One of the more interesting parts of this article, in the Lemming's opinion, may be the date stamp: April 24, 2011. At this moment, it's 10:55 a.m. in North America's Central time zone. That's 3:55 p.m. in the United Kingdom, 9:25 p.m. in Mumbai, (Still Saturday, April 23, 2011), and 12:55 a.m. Sunday morning, April 24, 2011, in Tokyo. And back to 5:55 a.m. April 23, 2011, in Honolulu.

Looks like this article was written by someone living near the western edge of the Pacific Ocean. That's more interesting than microfossils that may not be microfossils? Of living things, anyway? Not really: but nearly-as-interesting. For the Lemming. Your experience may vary.

"A Little More Complex"

"...'We were interested in developing new methods of looking at ancient microfossils, and so we were drawn to the Apex Chert as these putative microfossils are so iconic,' [University of Kansas geospectroscopist Craig] Marshall explained. "However, when we started working on the rocks, we discovered things were a little more complex than we thought they would be.'..."

That phrase, "a little more complex than we thought they would be," sums up quite a bit of what we know, as the Lemming sees it. Particularly in comparatively new fields, like studies of what's happened for the last few billion years on this planet.

The issue with the Apex Chert micro-things seems to be that when you take a close look at them, they look like fossils of living things. When you look closer: not so much. The microbe-things start looking more like fracture-things.

Sort of like the canals of Mars, only going in the other direction in terms of scale.

On the other hand, Marshall and company point out that their closer look may be a closer look at something different from what researchers took a close look at before. Both samples could look like the same thing at 'normal' distances - but not be quite the same thing at all.

So, where's the absolute certainty that scientists have about stuff? The Lemming thinks the sort of scientific triumphalism that was fashionable in some circles a half-century back - isn't quite so fashionable now.

Besides, the Lemming suspects that 'those scientists' never were quite as self-assured as some of their fans wanted to think they were. And that's another topic.

Back to the Apex Chert microfossils that may not be microfossils - or not fossilized organisms, after all. Again.

Apex Chert and the Search for Extraterrestrial Life

"...If the new study is true, the findings are important not only when it comes to evaluating evidence of life in ancient rocks on Earth, but have ramifications for astrobiological prospecting elsewhere in the universe.

" 'If it is really this hard to find convincing evidence for life on early Earth when we know there is life on Earth now, then it becomes clear that we need to be extra cautious interpreting data collected on Mars,' said paleobiogeochemist Alison Olcott Marshall at the University of Kansas, a co-author of the new study.

"The scientists detailed their findings online Feb. 20 in the journal Nature Geoscience."

Being "extra cautious" makes sense, in the Lemming's opinion. Particularly when there's not all that much data to go on, or when studying something new.

So, interpreting the Viking lander's life experiment results as "peculiar chemistry" may have been more sensible caution than insufficient imagination.

On the other hand, if a camera on one of the Mars rovers sent back a picture of something with four arms, eight legs, and tool belt - that hadn't been there a minute before - being "extra cautious" might not be quite so necessary.

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