ASU Research E-Magazine: Pieces of Mars

Scientists have found microscopic bits of life buried miles beneath the surface of the Earth, near hot sea floor vents spewing in the deepest ocean recesses, and in the frozen rocks of Antarctica. Make the intuitive leap. If life ever existed on Mars, it is probably still there.

“If life was there it is still there,” says Carleton Moore, director of ASU’s Center for Meteorite Studies. “But it may have gone deep and evolved to survive.”

The United States launched space probes to Mars in November and December 1996. However, the probes will barely scratch the Martian surface and are unlikely to find any evidence for life.

Last August, scientists at the National Aeronautics and Space Administration announced that they had found circumstantial evidence for life on Mars. The evidence was contained in a Martian meteorite.

Everett K. Gibson Jr. was one of those NASA scientists. A former student of Moore’s, Gibson earned his doctorate in geochemistry from ASU in 1969.

Moore is a Regents Professor of Chemistry and Geology. He curates the 1,451 meteorites in ASU’s collection, the largest held by any university. Only London’s British Museum and the Smithsonian Institution in Washington, D.C., have more meteorites. The ASU collection includes five Martian meteorites.

Scientists have identified about 10,000 meteorites around the world. Twelve of those meteorites were blasted from Mars by an impacting comet or asteroid millions of years ago. Researchers informally refer to Martian meteorites as “snicks,” or SNCs, which is short for shergottites, nakhlites, and chassignites.

Most of the Martian meteorites were found in Antarctica. The five pieces in ASU’s collection are Chassigny, from France; Lafayette from Indiana; Nakhla from Egypt; Zagami from Nigeria; and Shergotty from India.

In 1985, an ASU graduate student conducted research that involved Earth rocks and meteorites, including some from Mars. The study revealed some facts that Moore found puzzling at first. Now it appears that the study provides indirect support for NASA’s recent Martian meteorite findings.

The student identified the non-metal minerals found in basalt, a type of volcanic rock. The analysis indicated that the Martian meteorites contained large amounts of chlorine. NASA’s Viking landers also found a high chlorine content on the Martian surface in 1976.

This might mean that chloride salt dissolved in water was carried down beneath the surface of the Red Planet. Perhaps simple life forms—if they existed—got swept underground in the same way.

The chlorine content of the Martian meteorites varied from 22 to 1,500 parts per million. That compares with less than 10 parts per million for Moon rocks and other non-Martian meteorites.

On the other hand, Earth rocks taken from the ocean floor measured chlorine in concentrations of more than 500 parts per million. Scientists say this indicates that water must be percolating into the upper crust.

“When we first got the data, we didn’t know what they meant,” Moore explains. “We didn’t think that surface material could wash a kilometer down into the crust of Mars. This is exciting stuff.”—Steve Koppes