Why we live in a left-handed world! - Flash back three or four billion years: the earth is a hot, dry and lifeless place. Without warning, a meteor slams into this endless desert at over ten thousand miles per hour. We're all terrified that this might happen again and destroy life on earth, but it may have been what planted the seeds of life here in the past.
Scientists have presented evidence 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, which are 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. Scientists used this knowledge to make the popular artificial sweetener "Splenda," which is a right-handed version of the sugar molecule, which the body does not recognize and thus does not absorb.
In order for life to arise, proteins must contain only one form of amino acids, either left or right. Researcher Ronald Breslow says, "If you mix [this] up, a protein's properties change enormously. Life couldn't operate with just random mixtures of stuff/ 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" are 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 destruction of one form of amino acid?either left or right. "Everything that is going on on Earth occurred because the meteorites happened to land here," says Breslow. "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.
"This work is related to the probability that there is life somewhere else." And have they been coming here?
Some meteorites have a smaller impact: in the April 20th edition of the New Zealand Herald, Nicola Shepheard reports that Hawke's Bay resident George Cunningham now has a huge hole in his ceiling. When he discovered the hole, he also saw a piece of rusty iron lying on the floor, but no one recognizes the object. Shepeard writes: "The velocity of its descent suggests it fell from the sky, rather than being thrown." If it wasn't an aircraft part or a piece of a satellite, could it have been a meteorite?
Art credit: gimp-savvy.com
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