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Meteorites may seed life on Earth
Issue date: 4/3/08
No one really knows how life originated on Earth. Scientists have several plausible theories, but one that has gained currency in recent years might surprise you.
Panspermia is the idea that life, or at least the molecules necessary for life, might have come to our planet from other celestial bodies. Thanks to the discovery of organic chemicals on two meteorites, there is new evidence to support this theory.
Amino acids are the essential building blocks of proteins in all Earth-bound organisms, from the simplest bacteria to humans. Proteins, in turn, are key molecules in all of the chemical pathways of life.
It had been thought that amino acids were formed in the early environment of the Earth, thanks to a chemical soup in our seas and atmosphere and the higher temperatures of that time.
Scientists lead by Conel Alexander of the Carnegie Institution of Washington, a private scientific research center, examined three asteroids found in Antarctica in the early 1990s. These chondrites, as they are called, broke off of a larger asteroid formed in the earliest period of our solar system.
The researchers took samples from the chondrites to determine their age and chemical makeup. Although amino acids have been found on meteorites before, these chondrites have a concentration of amino acids over ten times greater than any other found.
Scientists believe that the amino acids were formed in the carbon-containing asteroids in the presence of water and ammonia, a simple nitrogen-containing compound. When the asteroid shattered, amino acids rained down onto neighboring planets.
These amino acids could be related to those that originated life on Earth. Each amino acid can be considered "left-handed" or "right-handed" depending on its shape. Virtually all amino acids on Earth are left-handed, but no one really knows why.
The amino acids found on the Antarctic chondrites were all left-handed, just like the ones found in living cells. Could amino acids from deep space have seeded life on Earth, providing a chemical input necessary for life to begin?
Although no conclusive evidence has been found, this hypothesis is a distinct possibility for the origins of life.
Panspermia is the idea that life, or at least the molecules necessary for life, might have come to our planet from other celestial bodies. Thanks to the discovery of organic chemicals on two meteorites, there is new evidence to support this theory.
Amino acids are the essential building blocks of proteins in all Earth-bound organisms, from the simplest bacteria to humans. Proteins, in turn, are key molecules in all of the chemical pathways of life.
It had been thought that amino acids were formed in the early environment of the Earth, thanks to a chemical soup in our seas and atmosphere and the higher temperatures of that time.
Scientists lead by Conel Alexander of the Carnegie Institution of Washington, a private scientific research center, examined three asteroids found in Antarctica in the early 1990s. These chondrites, as they are called, broke off of a larger asteroid formed in the earliest period of our solar system.
The researchers took samples from the chondrites to determine their age and chemical makeup. Although amino acids have been found on meteorites before, these chondrites have a concentration of amino acids over ten times greater than any other found.
Scientists believe that the amino acids were formed in the carbon-containing asteroids in the presence of water and ammonia, a simple nitrogen-containing compound. When the asteroid shattered, amino acids rained down onto neighboring planets.
These amino acids could be related to those that originated life on Earth. Each amino acid can be considered "left-handed" or "right-handed" depending on its shape. Virtually all amino acids on Earth are left-handed, but no one really knows why.
The amino acids found on the Antarctic chondrites were all left-handed, just like the ones found in living cells. Could amino acids from deep space have seeded life on Earth, providing a chemical input necessary for life to begin?
Although no conclusive evidence has been found, this hypothesis is a distinct possibility for the origins of life.
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Brig Klyce
Brig Klyce
posted 4/05/08 @ 10:46 AM EST
If "the molecules necessary for life" come from space, it's not yet panspermia, but rather, "pseudo-panspermia." But don't ignore the possibility that the left-handed amino acids in meteorites are remnants of prior life. (Continued…)
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