[Graeme]

Meteorites delivered the 'seeds' of Earth's left-hand life

$this->bbcode_second_pass_quote('', 'S')cientists 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.

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.

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 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.

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.

“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.”

[Graeme]

I understand that panspermia is a theory that suggests that life already exists in space and hence seeded life on Earth. This has not been disproven as indicated on the wikipedia site but it is not generally accepted.

However, the authors in the above article have shown that organic elements from space did contribute to life here on Earth. What is surprising to me is that they conclude that life could also exist elsewhere given the right conditions for evolution and survival.

[TheDude]

$this->bbcode_second_pass_quote('Opies', 'I') became shocked and confused when I discovered Golem was not the author of this thread... The stars are lining up after all.