Dust collected in the stratosphere by high-altitude aircraft may actually have its origin in interstellar space, and be billions of years older than the solar system itself, according to research published in this week's volume of the journal "Science." The finding means that scientists may be able to directly analyze in the laboratory the same material that falls together to form stars -- material which may be made of the solar system's earliest building blocks.

GEMS are crystals scarcely larger than one one-thousandth of a millimeter across, and are themselves embedded in tiny dust specks that scientists believe come from comets. The dust grains themselves are smaller than one-fifth the diameter of a human hair.

The cometary particles are among the grains of cosmic dust that NASA collects during aircraft flights at altitudes near 60,000 feet (18 to 20 kilometers).

The GEMS are made of silicates -- the same material that makes up most rocks on Earth -- but their composition is unique, presumably because they have not been transformed by the physical and chemical changes that occur during the evolution of stars and planets.

If Bradley's analysis is correct, the GEMS "would be the source of most of the heavy atoms in the solar system," he said. The finding appears to confirm a suggestion Bradley first published in 1992 that the GEMS are unaltered interstellar particles.

That suggestion could not be proven because of a limitation in the technology of the time, Bradley said. The problem was that it was physically impossible to get an infrared spectrum from the miniscule grains because they were so tiny. What was needed was a very specialized infrared microscope with greater magnification and a much brighter infrared light source than was available.

Then, a few years ago, just such an instrument was assembled at Brookhaven National Laboratory, when scientists there attached an infrared microscope to the lab's synchrotron light source. This light source was 100 to 1,000 times brighter than that of common microscopes, and could be concentrated in an extremely narrow beam.

"For the first time ever, you could exploit that intense brightness to analyze very tiny samples," said Bradley, who credits Brookhaven with making this finding possible. "We couldn't have done this without the Brookhaven facility. If that technology didn't exist, we could never have gotten a decent signal off such tiny particles," he said.

Taking the interplanetary dust to Brookhaven, Bradley and his team arranged GEMS particles on a transparent film and shot the infrared light through them to produce an absorption spectrum for the particles.

That unique fingerprint has not been observed in any material studied in the lab on Earth.

"You kind of have the feeling that what you're looking at is unaltered, primordial, early-solar-system material," said University of Colorado astronomer Theodore Snow, who was brought into Bradley's group a few years ago to provide an astronomer's perspective on the interplanetary dust.

"We've been trying for years to obtain a better understanding of the interstellar dust because we know it's important in star formation and the general physics and chemistry of the interstellar medium. And the thought that we can have in our hands, in the lab, samples of interstellar dust is extremely exciting," Snow said.

The next step in analyzing the GEMS will be to do a very detailed breakdown of their chemical composition. Preliminary analysis shows that the iron-rich crystals contain sodium, magnesium, aluminum, calcium and potassium, but a more specific understanding of the composition would provide another basis for comparing the composition that we infer from the interstellar dust with the composition that we actually measure from the GEMS, Snow said.

That will give astronomers a better profile for comparing the GEMS particles to the substance that makes up the interstellar medium, which in turn will help them to develop a better understanding about how stars and planets form.