Aug. 14, 1998 WEST LAFAYETTE, Ind. -- Though scientists can't trace Martian meteorites back to their specific sites on the Red Planet, a Purdue University study shows that the travelers contain more chemical clues to the location and history of their native neighborhoods than originally expected. Michael Lipschutz, professor of chemistry, analyzed the trace element content of the 12 meteorites that are known to have originated from Mars and found that the rocky fragments came from six different regions below the surface of the planet.
He also found that each of the six regions operated as a "closed system," blocking the transfer of materials such as dust and vapor between regions.
"Since even vapor transfer did not occur between the regions, the composition of each Martian meteorite can be considered an accurate reflection of its source region, and therefore can provide detailed information on each region's location and history," Lipschutz says.
The study was published in the July issue of Meteoritics and Planetary Science, which focused on the Martian meteorites. Lipschutz also wrote the chapter on meteorites for the 40-chapter Encyclopedia of the Solar System, which will be available in August.
Based on concentrations of 15 volatile trace elements, which are the chemical elements most likely to condense last as the planet solidified from a cloud of dust and gas, Lipschutz was able to divide the meteorites into six major groups from as many different parent regions.
He then compared the groupings to previous studies that had divided the meteorites into six classifications based upon other chemical contents and markers.
Because the groupings were virtually identical -- a finding that indicated that the trace elements were intact and had escaped contamination from outside influences -- Lipschutz says the volatile chemical contents of the meteorites can serve as reliable markers to assess information on their thermal histories.
"These rocks provide samples from and glimpses into six chambers within the Martian mantle," Lipschutz says. "Each of the 12 Martian meteorites appears to have crystallized in a location deep within the planet, and was excavated only when its chamber was opened by an impact."
Lipschutz says it is unusual to find samples where the chemical markers are so well preserved.
"The amazing thing is that whatever chemical and geological events Mars experienced through time, all of the elements -- volatile or not -- were able to remain intact," Lipschutz says. "This is unlike the situation in other extraterrestrial bodies, such as the Moon and many asteroids, where heating caused by events such as the shock of an impact can vaporize the volatile elements and destroy evidence of past events."
Further studies may help pinpoint the location of each of the regions, and could shed light on Mars' geological history, Lipschutz says.
His study was funded by the National Aeronautics and Space Administration's Cosmochemistry program.
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