A meteorite that fell on Australia in 1969 has been found to contain fatty chemicals that, in the laboratory, spontaneously assembled themselves into membranes that enclosed droplets of water such as chemically similar membranes maintain the integrity of living cells.
The discovery, announced at an international conference on the origin of life last week at the University of California at Berkeley, suggests that similar chemicals could have been present on the primordial Earth and helped make life possible.
Meteorites are chunks of minerals and other substances that formed at the origin of the solar system, 4.6 billion years ago, but missed becoming incorporated into planets and moons and have been drifting essentially unchanged since. Scientists regard them as samples of the chemical mixes that were available on the early Earth.
The Murchison meteorite, named for the Australian town near which it fell, has been a favorite for study because it contains many of the organic compounds that make up living cells. The Murchinson and similar meteorites have proven that many of the early steps of chemical synthesis leading toward life, including the early stages in the formation of proteins, can occur under entirely nonliving conditions.
The meteorite's fatty compounds, also called lipids, "were likely present on the Earth and could contribute to the essential membrane of the first microorganism," said David W. Deamer, a biophysicist at the University of California at Davis. He said, however, that it has not be found whether such a step was "on the main line of evolution to the first cells."
Some form of membrane must have been essential to life's origin because without the selective permeability of such a container it would have been impossible to maintain the concentration of specialized chemicals necessary to life. Other researchers have shown that structures resembling membranes can form spontaneously in the test tube from proteins. A membrane made of lipids and proteins would theoretically be an even better membrane for the first cell.