Seeds of Life Discovered on Interplanetary Dust : Chemistry: Findings boost theories that ‘cosmic schmutz’ might have sparked life on Earth.

In a discovery that is likely to refuel debate over a fundamental issue in science--the origin of life on Earth--scientists in California and Missouri report that they have found organic molecules, potential seeds of life, clinging to interplanetary dust.

The discovery of bits of carbon, oxygen and nitrogen on microscopic specks of dust from space bolsters theories that the dust could have been a significant extraterrestrial source of the complex molecules essential for the creation of life about 3.5 billion years ago.

The scientists, from Stanford University and Washington University in St. Louis, emphasized that they haven’t found life itself on the dust, or anything close to it; what they found are the elemental building blocks used to create the amino acids, simple sugars and DNA bases that are necessary for life.

In addition, the scientists reported seeing evidence of nitrogen in their samples. Nitrogen--an essential component of amino acids, which link in long chains to form proteins--has not been seen on meteorites or other extraterrestrial materials.

One of the scientists, Stanford chemistry professor Richard N. Zare, said the discovery was made possible by new technology that let his team isolate and analyze the “cosmic schmutz” on dust particles so small that tens of thousands could fit on the period at the end of this sentence.

The results were first reported at a conference in Houston in March and will be described in an article to be published Friday in the journal Science.

“It is a very exciting finding,” said UC San Diego chemistry professor Stanley H. Miller, who gained fame as a graduate student in 1953 for demonstrating in the laboratory how elements on Earth could by themselves combine to spontaneously create life.

Miller emphasized that he still believes most--if not all--of the building blocks of life on Earth came from the planet, either injected into the atmosphere by volcanoes or dissolved into the oceans by the erosion of rocks.

Indeed, most scientists still believe Miller’s hypothesis, as he dramatically demonstrated in a famous experiment with his late University of Chicago colleague, Nobel laureate Harold Urey. In a test tube, Miller and Urey re-created the chemistry of Earth’s oceans and atmosphere billions of years ago, then shocked the soup with electricity to simulate lightning. Amino acids formed in the simulated oceans.

However, this orthodox approach has been challenged by such researchers as Michel Maurette of the French national research laboratory in Orsay. They argued that the methane- and ammonia-rich “atmosphere” in the Miller-Urey experiment was unlikely to have been found on a primordial Earth.

This unorthodox scientific camp has long argued that the relatively sudden appearance of life on Earth suggests the process may have been triggered by the arrival of complex organic molecules on comets, meteorites or other extraterrestrial material that collided with Earth.

Miller and other skeptics of this extraterrestrial argument contend that there were too few comets and meteorites to supply a significant amount of organic material, and the material on known extraterrestrial samples lacked such significant elements as nitrogen.

But even the skeptics conceded that if nitrogen-bearing “organic seeds” could arrive in much larger volumes on relatively abundant interplanetary dust particles, the extraterrestrial argument gains considerable currency.

Washington University physics professor Robert M. Walker said he and his colleagues found the extraterrestrial organic materials after studying 17 dust particles gathered by National Aeronautics and Space Administration aircraft flying more than 12 miles above Earth.

Walker, director of the McDonnell Center for the Space Sciences in St. Louis, said eight of the dust particles were identified as extraterrestrial because they had ratios of graphite and silicon carbide isotopes that are not found on Earth. Two of those eight particles had organic material, he said.