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Posted on 04/06/2008 7:15:15 AM PDT by decimon
NEW ORLEANS, April 6, 2008—Flash back three or four billion years — Earth is a hot, dry and lifeless place. All is still. Without warning, a meteor slams into the desert plains at over ten thousand miles per hour. With it, this violent collision may have planted the chemical seeds of life on Earth.
Scientists presented evidence today that desert heat, a little water, and meteorite impacts may have been enough to cook up one of the first prerequisites for life: The dominance of “left-handed” amino acids, the building blocks of life on this planet.
In a report at the 235th national meeting of the American Chemical Society, Ronald Breslow, Ph.D., University Professor, Columbia University, and former ACS President, described how our amino acid signature came from outer space.
Chains of amino acids make up the protein found in people, plants, and all other forms of life on Earth. There are two orientations of amino acids, left and right, which mirror each other in the same way your hands do. This is known as “chirality.” In order for life to arise, proteins must contain only one chiral form of amino acids, left or right, Breslow noted.
“If you mix up chirality, a protein’s properties change enormously. Life couldn’t operate with just random mixtures of stuff,” he said.
With the exception of a few right-handed amino acid-based bacteria, left-handed “L-amino acids” dominate on earth. The Columbia University chemistry professor said that amino acids delivered to Earth by meteorite bombardments left us with those left-handed protein units.
“These meteorites were bringing in what I call the ‘seeds of chirality,’” stated Breslow. “If you have a universe that was just the mirror image of the one we know about, then in fact, presumably it would have right-handed amino acids. That’s why I’m only half kidding when I say there is a guy on the other side of the universe with his heart on the right hand side.”
These amino acids “seeds” formed in interstellar space, possibly on asteroids as they careened through space. At the outset, they have equal amounts of left and right-handed amino acids. But as these rocks soar past neutron stars, their light rays trigger the selective destruction of one form of amino acid. The stars emit circularly polarized light—in one direction, its rays are polarized to the right. 180 degrees in the other direction, the star emits left-polarized light.
All earthbound meteors catch an excess of one of the two polarized rays. Breslow said that previous experiments confirmed that circularly polarized light selectively destroys one chiral form of amino acids over the other. The end result is a five to ten percent excess of one form, in this case, L-amino acids. Evidence of this left-handed excess was found on the surfaces of these meteorites, which have crashed into Earth even within the last hundred years, landing in Australia and Tennessee.
Breslow simulated what occurred after the dust settled following a meteor bombardment, when the amino acids on the meteor mixed with the primordial soup. Under “credible prebiotic conditions”— desert-like temperatures and a little bit of water — he exposed amino acid chemical precursors to those amino acids found on meteorites.
Breslow and Columbia chemistry grad student Mindy Levine found that these cosmic amino acids could directly transfer their chirality to simple amino acids found in living things. Thus far, Breslow’s team is the first to demonstrate that this kind of handedness transfer is possible under these conditions.
On the prebiotic Earth, this transfer left a slight excess of left-handed amino acids, Breslow said. His next experiment replicated the chemistry that led to the amplification and eventual dominance of left-handed amino acids. He started with a five percent excess of one form of amino acid in water and dissolved it.
Breslow found that the left and right-handed amino acids would bind together as they crystallized from water. The left-right bound amino acids left the solution as water evaporated, leaving behind increasing amounts of the left-amino acid in solution. Eventually, the amino acid in excess became ubiquitous as it was used selectively by living organisms.
Other theories have been put forth to explain the dominance of L-amino acids. One, for instance, suggests polarized light from neutron stars traveled all the way to earth to “zap” right-handed amino acids directly. “But the evidence that these materials are being formed out there and brought to us on meteorites is overwhelming,” said Breslow.
The steps afterward that led towards the genesis of life are shrouded in mystery. Breslow hopes to shine more light on prebiotic Earth as he turns his attention to nucleic acids, the chemical units of DNA and its more primitive cousin RNA.
“This work is related to the probability that there is life somewhere else,” said Breslow. “Everything that is going on on Earth occurred because the meteorites happened to land here. But they are obviously landing in other places. If there is another planet that has the water and all of the things that are needed for life, you should be able to get the same process rolling.”
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Please visit http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=222&content_id=WPCP_008688&use_sec=true&sec_url_var=region1 for our press briefings schedule.
The American Chemical Society — the world’s largest scientific society — is a nonprofit organization chartered by the U.S. Congress and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
*Whew* That’s a relief. Guess we don’t need science, or medicine, astronauts, or telescopes anymore. Think of the money I’ll save on my daughters tuition.
Of course you realize; Bill Clinton is a lefty?
You may want to rethink that a bit. :)
Is that handedness or bentedness?
Panspermia is a recent scientific hypothesis, but not really new. The term has been around for thousands of years. The cometary hypothesis is not all that new an idea either, but even so, the comets and asteroids etc are all from the same region of the universe, that is, inside the solar system and would probably have some common characteristics with each other and earth whether they collide or not if the nebular hypothesis of planetary origin is at all valid.
Um, politically, and physically. Well, the parts I can see anyway.
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Panspermia, plus catastrophism/astronomy, plus some other possible digest headers. Thanks decimon. |
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I’m also left-handed.
hey, might that explain why half the population votes for the Left?
YEC INTREP
Not life. Amino acids.
We have seen amino acids come down on meteorites, and form naturally here on earth.
Nothing mysterious about amino acids, but it is interesting that polarizing light in space could preferentially destroys the right handed amino acids rather than the left ones.
But it is a rather weak explanation for the prevalence of left handed amino acids in terrestrial life forms.
“One would have to examine meteors before they become ‘contaminated by the Earth...right now, such a thing is the stuff of science fiction.”
Actually not, see the book “Comet” by Carl Sagan and Ann Druyan. We have sent rockets into the tails of several comets, and have a pretty clear idea of the various chemicals that comets are carrying with them, and can deposit on the earth when they crash.
“If ‘scientists’ are going to push their theories into the realm of faith...well that’s just religion, too.”
These scientists are NOT pushing their theories into the realm of faith. The article is well sprinkled with mays, mights, and by definition, “theory” means they are still exploring the ideas and possible proofs of their statements. Furthermore, near the end the author states that as he does further work on certain aspects of amino acids this may provide additional evidence for the theory. Please do not confuse science and faith. Science seeks answers, faith assumes them.
“inside the solar system”
If you mean within the orbits of the planets, that is not correct. Even if you mean as far away as the ends of the Oort Cloud which extends out about 2 light years and contains about 1 trillion cometary objects, that still may not be correct. See my comment #74 for an interesting source. Some comets may come in from outside the Oort Cloud.
On which day did this happen?
“Science seeks answers, faith assumes them.”
Glib.
And shallow.
You should explore the concept of a philosophical proof sometime. Maybe then you’d be ready to examine the evidence for the existence of God.
That is my definition and is therefore apriori true.
Scientists used to think that metors did not fall from the sky. It was considered folklore, old wives tales etc.
It wasn’t until one fell somewhere in France I think and many of the townspeople were witnesses to this event that this started to change.
The heavenly rock is still on view at the local church in this small town.
Source The History Channel, of course at my age some of the details may be a bit fuzzy.
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