First life may have arisen above serpentine rock, researchers say

Sep 23, 2011 By Max McClure
A photomicrograph of a thin section of serpentinite rock. Photos by Emily Pope

(PhysOrg.com) -- About 3.8 billion years ago, Earth was teeming with unicellular life. A little more than 4.5 billion years ago, the Earth was a ball of vaporous rock. And somewhere in between, the first organisms spontaneously arose. Pinpointing exactly when and how that shift happened has proven a difficult bit of interdisciplinary detective work.

A team of Stanford geologists hasn't quite solved the problem, but they've come closer. By examining the and environment of the , the researchers demonstrate the plausibility of one theory: that life originated above serpentinite rock on the . Because the necessary conditions only existed for a few million years, the findings provide a potential timestamp for the appearance of the Earth's first organism.

The paper, authored by geophysics professor Norm Sleep, geological and environmental sciences professor Dennis Bird, and former graduate student Emily Pope, appears in this week's B.

Serpentinite under the sea

Greenish-colored serpentinite is common enough in California to be the official state rock. But geologists are more interested in deep-sea serpentinite deposits, where the mineral forms "white smoker chimneys" – hydrothermal vents – in which alkaline vent fluids interact with more acidic seawater.

The resulting reaction can form microscopic "pore spaces" in the chimney stone. This honeycombed rock acts as a percolator for white smoker fluid, concentrating dissolved substances inside the tiny spaces. Because the nucleic acids that make up RNA may have occurred naturally in vent fluids, this process increased the probability of spontaneously forming complete RNA strands. The tiny pores could have even allowed the resultant to survive without cell membranes, using the rock itself for structure and protection.

The pH difference between the vent fluids and the ocean also could have provided an important energy supply for early organisms. When serpentinite is oxidized by seawater, hydrogen is formed. Microbes can react hydrogen with carbon dioxide to form methane or acetate, both of which serve as sources of chemical energy.

An outcrop of serpentinite from the Isua Supracrustal sequence of West Greenland, at the western margin of the Greenland Icecap. Under the West Greenland ice fields, the researchers have identified serpentinite among some of the oldest rocks yet found.

"These same conditions exist wherever water comes out of serpentine in the Bay Area," explained Sleep. "If you look, you can see hydrogen bubbling out of the ground."

But this model of life's origins is only feasible under very specific conditions. Serpentinite, a cool Earth, and an acidic ocean all must have coexisted for a time.

Serpentinite was likely present when life arose. Unfortunately, the geological record only reliably goes back approximately 3.8 billion years, making a definitive statement impossible. Still, under the West Greenland ice fields, Bird and Pope have recently identified serpentinite among some of the oldest rocks yet found.

The temperature of the Earth was also habitable at the time in question. A few hundred million years after its formation, the planet had cooled below 120°C – hot by human standards, but livable for certain microorganisms.

Acid enough?

The single most time-restricted requirement for early life would have been the acidity of the ocean. In order for early life to make use of a pH gradient between hydrothermal vents and seawater, the oceans must have been 100 times as acidic as they are today – a state of affairs that overlapped with a cool Earth for only a few million years.

The early oceans would have remained acidic as long as the early earth's atmosphere remained high in carbon dioxide. Much of the gas was eventually trapped in the earth's mantle by subducting continental plates.

"This leaves a relatively brief window for the origin of life, at least by this mechanism," said Sleep.

Smoking-gun evidence in support of the origin-of-life theory remains hard to come by. are currently looking deep in the Earth's crust for ancient white smoker structures. And the search continues for a modern-day version of membrane-less rock-living microbes.

"It's conceivable that a biologist might get lucky," Sleep said. "But I'm not holding my breath."

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User comments : 10

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Deesky
5 / 5 (17) Sep 23, 2011
Kevin, you're a total idiot.
RealScience
5 / 5 (14) Sep 23, 2011
Kevin - Mars has sufficient water even now, locked up as icecaps and sub-surface ice, and its rocks show that it had more in the past.
The moon has no atmosphere, so any water exposed to sun evaporates and escapes almost immediately.
Venus is enough hotter that water vapor rose high enough in the atmosphere to be split by UV, and the hydrogen was light enough to escape (Venus's atmosphere is ~100x richer in heavy hydrogen than earth's, evidence that huge amounts of light hydrogen have escaped.)
The sun temp was lower then but the atmosphere had more CO2 and CH4, so the earth was warm enough.
RNA has already been observed to be stable and even to be concentrated by pores in 'white smokers' (which still exist today but are rarer).
Amino acids found in meteorites have been found to be enriched in the same chirality that life on earth uses.

These answers can be found in previous Phyorg articles and/or Wikipedia.
Please read, think, read more, and then post if you still have questions.
omatumr
1.3 / 5 (12) Sep 23, 2011
Life evolved as Earth's climate changed, and continues to evolve, because the Sun itself has evolved and now emits less "toxic" high-energy radiation [1].

[1] "Origin and Evolution of Life Constraints on the Solar Model", Journal of Modern Physics 2, 587-594 (2011)

http://dl.dropbox...5079.pdf

With kind regards,
Oliver K. Manuel
Parsec
4.2 / 5 (10) Sep 23, 2011
Life evolved as Earth's climate changed, and continues to evolve, because the Sun itself has evolved and now emits less "toxic" high-energy radiation [1].

[1] "Origin and Evolution of Life Constraints on the Solar Model", Journal of Modern Physics 2, 587-594 (2011)

http://dl.dropbox...5079.pdf

With kind regards,
Oliver K. Manuel

I thought life arose from neutron repulsion?
Adam
5 / 5 (3) Sep 24, 2011
Kevin, clearly you can imagine the intellect involved, so how is beyond what we can imagine? If It caused Life, then what caused It? Mind implies complexity, yet somehow all the complexity you have inside your skull sprang from a single cell and a coil of DNA with, at most, about 300 MB of data on it. Hmmm. Seems "complexity" can spring from simpler systems, thanks to recursion and learning from the surrounding environment. Life's complexity could equally have sprung from recursion - regularities in biomolecules and their surrounding matrix, as well as from interaction with their wider environment. No Intellect needed. Or perhaps the Intellect is implicit in the ordering of the Cosmos, rather than as a detachable extra on the "Outside".
Ethelred
4.5 / 5 (8) Sep 24, 2011
Kevin has all those questions answered before. Some just the other day. Instead of opposing the answers he runs away and asks the same questions again.

If you don't like the answers. Kevin show some guts for once and DISCUSS things.

And we about as much chance for Kevin not running away as we do for Oliver engaging in a reasoned discussion. Oliver ran away again just like Kevin. So since I have started reporting Oliver as the spam it is I suppose I should treat Kevin the same.

Ethelred
omatumr
1 / 5 (7) Sep 24, 2011
Thanks, Ethelred,

Those unable to comprehend the conclusions or the experimental observations reported and discussed by PhD scientists have a problem.

They usually identify themselves.

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
jsdarkdestruction
5 / 5 (4) Sep 25, 2011
Yes, you sure do oliver.....we can all tell by the way you act.
Ethelred
4.3 / 5 (6) Sep 25, 2011
Anytime you want to discuss this Oliver instead of repeat yourself I will stop reporting your posts. Repetition like that will get it reported as that is about all you ever do. Repeat the same crap over and over and over and spam and spam and not so wonderful spam.

I do identify myself. I sign every set of posts. My online identity is Ethelred, EthLred, or Ethelred Hardrede. I am the person that has been disproving you for two years straight without you being able to show evidence to support yourself. Clearly my skills trump a Phd.

Deal with what I say. Nearly any Crank can tell you that it is the ideas that count. Yours are wrong and it doesn't matter what your credentials are. However I have taken more astronomy than you AND I clearly am far better at discussion than you. You seem to have been unaware of the PEP, the math showing black holes MUST form is there is enough mass, and you didn't even read the letter you posted a link to that was supposed to show perfidy.

Ethelred
Birger
not rated yet Sep 26, 2011
Kevin and Oliver
If you want to discuss your reservations about the standard explanations about how life evolved, why don't you go to the open thread (episode CCLVI and onwards) at Pharyngula at Freethoughtblogs ?