To scientists' disappointment, a meteorite that fell on a frozen Canadian lake has been found to contain none of the organic ingredients believed necessary to have initiated life on Earth.
Many scientists believe that simple life arose on Earth more than 4 billion years ago after meteorites crashed through the atmosphere, carrying amino acids and other biochemical compounds from outer space.
The fragments of a 220-ton meteorite that were sprinkled on Tagish Lake in British Columbia in January 2000 had generated considerable scientific excitement because they are of a rare, carbon-rich variety.
However, tests in the United States and England show the pristine bits contain different organic compounds than previously studied meteorites.
It raises the possibility that the debris comes from a very old celestial body that originated in the most distant reaches of the solar system's asteroid belt -- a first in meteorite studies.
''We thought we would get all the answers that we wanted,'' said Arizona State University exobiologist Sandra Pizzarello. ''It turned out to be totally opposite of what we were expecting. It has a suite of its own organics.''
The Tagish Lake fragments were compared with results from meteorites such as an amino acid-rich rock discovered in Australia in 1969.
While the Canadian samples contain nearly no amino acids, Pizzarello said they contain high concentrations of hydrocarbon molecules, stardust grains and clays that form in the presence of liquid water.
The meteorite fragments were collected by an amateur geologist. He stored them in a freezer so their volatile chemical contents would not evaporate as the fragments thawed.
A tiny portion was divided between ASU and a lab at the Open University in England.
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