Re: NEWS: Early Life Survived 'Snowball Earth'


Ye Old One wrote:
Early Life Survived 'Snowball Earth'
By Corey Binns
Special to LiveScience
posted: 07 June 2006
08:40 am ET
http://www.livescience.com/animalworld/060607_snowball_earth.html


Ancient relatives of today's plants and animals may have survived
Earth's oldest, longest winter, when the planet was covered in a deep
*** of ice.

Scientists refer to this chilly period as "Snowball Earth," which
first occurred more than two billion years ago. Some computer models
suggest the planet was encased in a shell of ice at least a half-mile
thick.

Inside rocks collected near Elliot Lake in Ontario, Canada-rocks older
than Snowball Earth-scientists found oil trapped in water droplets, in
the crevices of rock crystals.

Most oil is a residue of tiny organisms that once lived in the ocean.
The oil contains biomarkers, or molecular fossils, that scientists can
use to determine what types of life went into making it.

Alive and kicking

The Ontario oil held answers to age-old questions about when
oxygen-producing bacteria and multi-cellular living organisms, called
eukaryotes, first appeared on Earth.

"We can use these biomarkers to say something about what the early
history of life and the planet was like," said astrobiologist Roger
Buick of the University of Washington. "It gives us another powerful
tool to understanding the evolution of life and Earth."

Buick, and petroleum geochemist Adriana Dutkiewicz of the University
of Sydney in Australia, found evidence in the oil that suggests
eukaryotes and bacteria were alive and kicking 100 million years
before the planet froze over. The finding fits with a study last year
that concluded bacteria actually caused the first snowball scenario by
producing oxygen that destroyed a warm blanket of methane in the
atmosphere.

Details of Buick and Dutkiewicz's study are published in the June
edition of the journal Geology.

The research calls into question the severity of Earth's snowball,
however. The eukaryotes would not have survived a total, global ice
age over a long period of time, according to Buick. "That kind of ice
coverage chokes off photosynthesis, so there's no food for anything,
particularly eukaryotes," he said. "They just couldn't survive," he
said. "But this research shows they did survive."

If they could live through the toughest, coldest models of Snowball
Earth, such hardy microbes could probably make a living on the frozen
moons of Jupiter, he said.

"That's pretty extreme," Buick told LiveScience.

Another interpretation

However, one proponent of the Snowball Earth theory said that Buick's
findings aren't contradictory to the deep-freeze model.

"No matter how thick the ice was, if you had eukaryotes before the
freezing, there are still going to be survivors somehow making a
living-even in complete darkness," said geologist Mark McMenamin of
Mount Holyoke College. "I don't think this tells us whether Snowball
Earth was severe or not because I think eukaryotes would have survived
either way."

This is the second time Buick has found evidence of eukaryotes
existing before Snowball Earth.

Some scientists disputed his initial research on the topic, published
in 1999, suggesting that even a diesel truck driving by the lab could
contaminate his previous samples and results.

This time, the "foolproof" rock crystals protected the oil from any
pollutants, Buick said.

"In a study of this sort, there's always the possibility of
contamination," McMenamin told LiveScience. "They've done a good job
ruling it out."


--
Bob.

My understanding of the snowball earth theory is that the degree of ice
cover has been somewhat exagerated. Current thinking (and I am only
reporting what on a talk on the subject by someone involved in such
research told us) is that ice cover was extensive, but not the 100%
claimed by some scientists.

This is, after all, an event which happened 700 million years ago, and
rocks of that age are pretty rare.

RF

.

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