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KNOXVILLE, Tenn. — The origin of minerals inside a Martian meteorite is a key factor in the

question of life on Mars, the head of the University of Tennessee geology department said Friday.

Dr. Harry McSween said tiny particles reported Wednesday as microfossil evidence of past life on

Mars were embedded in minerals called carbonates inside a Martian meteorite.

McSween said if the carbonates formed under extreme temperatures — and evidence allows the

possibility that they did — it is unlikely that life could have ever existed inside them.

A science team organized by NASA’s Johnson Space Center reported Wednesday that the meteorite

contained fossilized evidence that bacteria-sized organisms lived on Mars 3.6 billion years ago.

McSween and Dr. Ralph Harvey of Case Western University analyzed that same Martian meteorite

in a study of water on Mars.

Their analysis, published in last month’s issue of Nature and before this week’s NASA

announcement, suggests the carbonates inside the meteorite formed without water at temperatures

exceeding 1,200 degrees Fahrenheit, possibly as the result of an asteroid or meteorite striking the


However, if biological activity had occurred on Mars, that would allow another explanation for how

the carbonates formed, McSween said.

“On Earth, bacteria can apparently form carbonates, including those similar to the compositions we

found, but the process is uncommon,” McSween said.

“Understanding the origin of the carbonate containers for these possible microfossils is critical to

their validation. The scientific community will have to explore all these options.”

Contact: Dr. Harry McSween (423-974-2366)