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)