Purdue News

August 2, 1984 Purdue Researchers Find Changes In Solar Bodies Surrounding Earth ALBUQUERQUE, N.M. — Purdue University researchers presented evidence of recent changes in the nature of extraterrestrial materials orbiting the earth, during the 47th annual meeting today of the Meteoritical Society. "It appears that we now have different types of debris from different solar-system bodies or regions falling on the earth than we did several hundred thousand years ago," said Michael E. Lipschutz, professor of cosmochemistry at Purdue. The research team at Purdue found differences in the chemical composition of H5 chondrites (meteorites) found in the Antarctic and H5 chondrites discovered in other parts of the world. Lipschutz pointed out that while meteorites from the Antarctic came to earth 100,000 to 700,000 years ago, the other meteorites used in the study have fallen within the last 100 years. "While 100,000 years sounds like a long time to most people, it is a very short period on a solar-time scale. To think that our sample of solar-bodies have changed that much in a few hundred thousand years is astounding," said Lipschutz. He added that the findings especially enhance the significance of meteorites discovered in the Antarctic. "Because the meteoroid complex near earth has changed, the Antarctic collection provides a snapshot in time and is even more valuable than thought," said Lipschutz. "The 7,000 fragments collected from the Antarctic to date now represent about 700 new meteorites with characteristics and information that cannot be obtained from our other samplings." The discovery is based on comparison of trace element contents in 17 Antarctic and 16 non-Antarctic H5 chondrites, one of the most common types of meteorites found on earth, Lipschutz explained. "Even if weathering effects are considered, distributions of 9 elements differ significantly in the two sample populations, implying that it is highly improbable that they came from the same parent source," he said. Trace elements and ultratrace elements — those found in part per million and part per billion — can yield particularly important genetic information on a meteorite because the composition levels are so low that even the smallest change induced by a physical or chemical transformation is magnified into a relatively large change, said Lipschutz. The trace element studies at Purdue involve a technique known as neutron-activation analysis. Meteorites are placed in a very powerful reactor and bombarded with uncharged particles, making them radioactive. Researchers then measure the radioactivity to specify trace element content. Purdue has the only research team in the world studying these particular elements. The research project at Purdue is funded by the National Science Foundation and the National Aeronautics and Space Administration. Research findings were presented at the meeting by Jane Dennison, a graduate student in chemistry working under the direction of Lipschutz. Purdue News Service: (765) 494-2096; purduenews@purdue.edu