Purdue News

February 18, 1982 Meteorite Studies Advance Knowledge Of Solar System WEST LAFAYETTE, Ind. — Analysis of a "puzzling" meteorite may establish a new chemical group for one of its components — the newest such group identified in a century and a half of study, says an authority on space chemistry. He is Michael E. Lipschutz, professor of chemistry at Purdue University, who heads a research group currently studying material embedded in a meteorite recovered near Cumberland Falls, Ky. It is a chondrite, the kind of stony meteorite recovered most often on earth. Chondrites are named for chondrules, the round, stony spheres they contain. "The hundreds of other chondrites that have been found over the years always fit into five standard chemical groups," Lipschutz points out. But a look at the mineral composition of the new chondritic sample told Lipschutz's researchers that this one was different. Lipschutz thinks the Cumberland Falls material is a strong candidate for a sixth group of chondrites, called forsterite chondrites. Forsterite chondrites will become the newest such group recognized as "a new type of primitive solar-system matter — matter that dates back to the beginning of the solar system, 4.65 billion years ago," Lipschutz says. "It appears that the forsterite chondrites came from a larger object that collided with another body which provided the host material of the Cumberland Falls meteorite," he says. Lipschutz and a former student, Charles W. Neal, reported on the mineralogy of the forsterite chondrites in late 1981 in Geochimica et Cosmochimica Acta, the official journal of two international scientific societies, the Meteoritical Society and the Geochemical Society. Neal received his Ph.D. from Purdue in 1980 and is now at Procter & Gamble. All potential forsterite chondrites are being analyzed extensively. R. Michael Verkouteren, a Ph.D. student at Purdue, "is doing the chemistry on the forsterite chondrite," Lipschutz says. "Mineralogy is run first," Verkouteren explains. "After that, the elemental abundances have to be looked at." The phrase "elemental abundances" Verkouteren used refers to the amounts of chemical elements a meteorite contains. Lipschutz and his Purdue research team specialize in the study of elements which show up in extremely small amounts — so-called trace elements. "A part per million is a trace element," Lipschutz says. "We work down from there." Researchers in his laboratory may work with elements in evidence at a part per trillion — one part of the element surrounded by a trillion times as much other material. That's comparable to a teaspoonful of water out of more than a billion gallons. Trace elements, whose chemical characteristics, Lipschutz says, are often quite different from the same elements in bulk, are good indicators of what a meteorite has gone through in time. "The kinds of elements we concentrate on, such as bismuth, tellurium, thallium and indium, are elements we know are sensitive to thermal episodes — to heat," he says. "We use techniques that give us the maximum information from the smallest possible samples," the professor continues. One such technique, neutron activation, involves the use of a research reactor at the University of Missouri at Columbia. Fractions of a gram of the meteorite sample are irradiated in the reactor. Comparison with a control sample, equally irradiated, reveals the original chemical composition of the rock, Lipschutz says. If that composition differs from known compositions — as the Cumberland Falls chondritic group does — "we know more than we knew before about how the solar system was formed," the cosmochemist says. Later, this solar-system material will be studied by other scientists using other techniques to learn more about it. "We're trying to reconstruct the primitive solar system from little pieces of rock in other pieces of rock," Lipschutz summarizes. "It's like trying to put together a jigsaw puzzle with 99 percent of the pieces missing." At the same time, students like Verkouteren learn how to do trace element analysis. "My students learn to think like trace elements," a talent that takes them on to careers not necessarily in space science, Lipschutz says, but in places like the electronics and oil industries as well. Electrical properties of solid-state devices such as computer chips are affected by elements at the trace level. Also, certain trace elements are geochemical markers for the occurrence of oil, he explains. Purdue News Service: (765) 494-2096; purduenews@purdue.edu