Scientists at the Carnegie Institution's Department of Terrestrial Magnetism found that asteroids and comets - the parent bodies of meteorites - contain primitive organic matter. The finding provides clues about how organic matter was distributed and processed in the solar system.

"Atoms of different elements come in different forms, or isotopes, and the relative proportions of these depend on the environmental conditions in which their carriers formed, such as the heat encountered, chemical reactions with other elements, and so forth," said lead author Henner Busemann.

"In this study," Busemann continued, "we looked at the relative amounts of different isotopes of hydrogen and nitrogen associated with tiny particles of insoluble organic matter to determine the processes that produced the most pristine type of meteorites known. The insoluble material is very hard to break down chemically and survives even very harsh acid treatments."

Reporting in the May 5 issue of Science, the scientists said they used microscopic imaging to analyze the isotopes contained in insoluble organic matter from six carbonaceous chondrite meteorites - the oldest type known. The relative proportion of isotopes of nitrogen and hydrogen associated with the insoluble organic matter act as fingerprints that can reveal how and when the carbon was formed.

The isotope of nitrogen most often found in nature is 14N, and its rarer and heavier variety is 15N. Differing amounts of 15N, in addition to a heavier form of hydrogen called deuterium, reveal whether a particle remains relatively unaltered from the time when the solar system was forming.

"The tell-tale signs are lots of deuterium and 15N chemically bonded to carbon," said co-author Larry Nittler. "We have known for some time, for instance, that interplanetary dust particles collected from high-flying airplanes in the upper atmosphere contain huge excesses of these isotopes, probably indicating vestiges of organic material that formed in the interstellar medium.

The IDPs exhibit other characteristics suggesting they originated on interplanetary bodies such as comets, Nittler said, that have undergone less severe processing than the asteroids from which meteorites originate.

The scientists found when they examined some meteorite samples at the same tiny scales as interplanetary dust particles, they found similar or even higher abundances of 15N and D than those reported for IDPs.

"It's amazing that pristine organic molecules associated with these isotopes were able to survive the harsh and tumultuous conditions present in the inner solar system when the meteorites that contain them came together," said co-author Conel Alexander.

"It means that the parent bodies - the comets and asteroids - of these seemingly different types of extraterrestrial material are more similar in origin than previously believed."

Busemann said the discovery allows scientists to extract large amounts of the material from meteorites, "which are large and contain several percent of carbon, instead of from IDPs, which are on the order of a million-million times less massive. This advancement has opened up an entirely new window on studying this elusive period of time."

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