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''' *4.65 BILLION YEARS AGO* :
MOTHER EARTH '''
WHAT MAY BE WORLD'S OLDEST FOSSILS have just been found in Greenland.
An expert *on life origins* at Harvard Medical School.
And it bears repeating that because of the importance of the claim made by Dr. Nutman and his colleagues, considerable discussion can be expected before their interpretation is generally accepted.
Certain features are ''fairly credible hallmarks of microbial activity,'' Abigail C. Allwood of the California Institute of Technology's Jet Propulsion Laboratory wrote in a commentary accompanying the article.
They have a few features that make them ''interesting and possibly biological,'' she added in an email.
Another expert in the early Earth's environment, Tanja Bosak of the Massachusetts Institute of Technology, said the structures do resemble modern astromatolites, but their origin ''will be hotly debated.'' given-
There is no sign of certain features that might bolster the case for biological origin, such as crinkling in the layers of sediment.
So several different species of microbes are involved in stramatolite creation. The Isua structures, if indeed stromatolites, would represent fairly evolved organisms.
Dr. Nutman argues that life must therefore have originated even earlier, probably in the late Hadean stage of Earth's history which lasted from 4.65 billion year ago -when the planet formed from debris in orbit around the sun -to 4 billion years ago.
But the Hadean was so called because of the hellish conditions thought to have prevailed, including cataclysmic meteorite impacts that boiled the oceans into steam and-
*Turned Earth's surface into molten lava*.
The largest of these impacts, at 4.5 billions years ago, tore piece from Earth that became the moon.
It is difficult to see how life could have begun under such circumstances.
But some geologists now favor a milder version of the Hadean, with the rain of asteroids quickly tapering off after the moon was formed.
The early sun was much weaker then, and the threat to life, in this view, would not have been molten lava but frozen oceans, a calamity that may have been averted by a surge of greenhouse gases.
''The largest Hadean impacts may have been severe , but not planet sterilizing. Once life has developed to the point that could spread across the planet, it would have been hard to wipe out, said Jack Szotak, an expert of life origins at Harvard Medical School.
*But the chemistry of life favors an origin, not the deep ocean, he said.
Still, even when the Hadean ended, a final rain of large asteroids descended on Earth at the beginning of the ensuing Archaean stage, possibly set loose when-
The great planets Saturn, Uranus and Neptune drifted out into the Kuiper belt of asteroids.
This cataclysm, known as the Late Heavy Bombardment , hit Earth between 3.9 and 3.8 billion years ago.
Dr. Nutman believes life would have survived through the end of the Hadean and the bombardment. Some geologists, he notes, now think the asteroids impacts were spread over time, lessening their effects.
If life on Earth did not begin until after the Late Heavy Bombardment , then it had a more 100 million years in which to evolve to the quite advanced stage seen in the new fossils.
*If so, Dr. Allwood wrote, then 'life is not a fussy, reluctant and unlikely thing.'' It will emerge whenever there's an opportunity*.
But the argument that the life seems to have evolved very early and quickly, so therefore is inherently likely, can be turned around, Dr, Joyce said.
''You could ask why, if life were such a probable event, we don't have evidence of multiple origins,'' he said.
In fact, with trivial variations, there is only one genetic code, for all known forms of life, pointing to a single origin. ,
With respectful dedication to the Scientists, Students, Professors and Teachers of the world. See Ya all on !WOW! -the World Students Society and Twitter-!E-WOW! -the Ecosystem 2011:
''' The Creation '''
Good Night and God Bless
SAM Daily Times - the Voice of the Voiceless
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