The crucial chemicals to make life have been discovered in a meteorite, and the steps to explain how these bases of life might have formed in the frigid, airless atmosphere of space have been found, chemists announced at the American Chemical Society meeting in Washington yesterday.
The work makes the formation of life in space seem easier and likelier than scientists had thought.
"The processes we believe might have created life on Earth also go on elsewhere in the universe, may be very common and even may be the preferred ways" that the chemicals like to combine, said Gordon Schlesinger of the University of California at San Diego, one of the scientists involved in the work.
Two groups of scientists have produced four new findings:
* A famous and much-studied meteorite called the Murchison meteorite contains all five of the basic chemicals required to make deoxyribonucleic acid or DNA, the molecule basic to all living things.
* An experiment mimicking early Earth's violent atmospheric chemistry formed all five of the same building blocks of DNA spontaneously. This apparently was the first time all five were made in a single experiment designed to imitate the conditions that created life.
* Another experiment showed the likelihood that during the Murchison meteorite's flight through space, liquid water existed inside the meteorite, again making it a much likelier place for the basic chemicals of life to form.
* Finally, it appears that some of the basic chemicals that combine to create life were formed relatively quickly within the meteorite, possibly over 10,000 years rather than the millions of years once thought necessary.
Cyril Ponnamperuma, director of the University of Maryland's Laboratory of Chemical Evolution, who presented two of the four findings at the chemical society meeting, said yesterday that both the work with the meteorite and the mimickry of the chemistry of the early Earth made it "ever more reasonable and clear" that the first steps toward living cells could have taken place not only spontaneously, but rather quickly.
The work to demonstrate that life could arise spontaneously out of chemistry began in 1953 when Stanley Miller, now leader of one of the groups that reported its findings yesterday, first created an "artificial Earth's atmosphere" in a flask and saw, after shooting electrical energy through it like lightning, the formation of some chemicals critical to life.
Roughly, the steps some scientists believe necessary for the spontaneous formation of life on Earth are the buildup from simple chemical substances of several more complex ones, including the two most fundamental: nucleic acids and amino acids.
A variety of "artificial Earth" experiments have been conducted over the years, and all the amino acids found in living things have been produced in the experiments. The nucleic acids have been created, too, but never before in one experiment.
In 1969, when the Murchison meteorite fell in Australia and quickly was captured and preserved, scientists were astonished to discover that it contained an enormous variety of complex chemicals involved in life.
Ponnamperuma's lab, in cooperation with a lab at the University of Missouri at Columbia, has tested the meteorite and found all five of the nucleic acids which make up DNA and its companion molecule ribonucleic acid, RNA, the two fundamental molecules of life.
Miller and his co-workers in California, also studying the meteorite, have worked out the chemistry of how large molecules that are the precursors of life could be formed in a meteorite.
In space, the meteorite would be cold stone on the outside, warm radioactive material on the inside. The warmth would liquefy the water in its porous rock, and the liquid water, plus some other chemicals, could trigger reactions that make the amino acids and other large molecules found in living things on Earth.