FLORIDA TODAY Space Online
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March 19, 1999
NASA team: Evidence of fossilized bacteria found in Mars meteorites
Copyright © 1999, The Associated Press. All rights reserved. This
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HOUSTON (AP) - A pair of Martian meteorites include features that resemble
bacteria, according to the same NASA researchers who three years claimed they
had evidence of "primitive life on early Mars."
The findings, made within the past six months, were from samples of
billion-year-old meteorite that fell to Earth in 1911 near Nakhla, Egypt and a
165 million-year-old meteorite that fell near Shergotty, India in 1865.
"My own opinion is that these will turn out to be true micro-fossils
said David S. McKay, a Johnson Space Center geologist.
"We're not counting on getting many converts," he said. "All we ask,
that people keep an open mind."
McKay's presentation at Houston's JSC for the Lunar and Planetary Science
Conference on Thursday was a cautious one, since more research is required and a
mission to get soil samples is planned in the next decade.
McKay, 62, was one of the researchers who in August 1996 announced the
of tiny fossilized structures in crevices of a 4 billion-year-old Mars meteorite
found in the Antarctic. The meteorite was recovered in 1984.
McKay said some of the Nakhla features resembled Earth bacteria in a
reproductive phase. He also referred to the remains of what could have been a
slimy "biofilm" useful in snaring mineral nutrients.
"It has to be very clear that I have found features which bear a striking
resemblance to known fossilized life, but we have not proven they are fossilized
bacteria, nor have we proven they are from Mars," he said. "We have to answer
those two questions."
Other experts have debated the significance of the NASA team's earlier
Independent analyses of the Mars rock known as Allan Hills 84001 have failed to
prove that the potato-sized chunk ever contained life.
The researchers said the Allan Hills meteorite contained organic molecules
called polycyclic aromatic hydrocarbons, or PAHs, that can be associated with
life processes. The scientists said they found shapes that resemble some forms
of fossilized bacteria.
In his latest presentation, McKay offered photographic comparisons of
fossil-like structures he observed in the Nakhla rock and those seen in similar
terrestrial formations. The remnants found in both meteorites bear a stronger
resemblance to bacteria on Earth than the structures in the Allan Hills
Finding water on Mars was a priority of the Mars Polar Lander launched
this year. Satellite imagery suggests traces of an ancient shoreline and NASA's
Viking probes of the late 1970s revealed major watersheds.
Scientists theorize that the existence of large amounts of surface water
enhance the prospects that bacteria once developed on Mars. McKay said if
bacteria once resided in the much younger Nakhla and Shergotty rocks, then life
may have persisted on Mars through a drastic and still unexplained climate
"If this proves out, we will have shown that life spanned almost the
history of Mars, and presumably today," he said. "Nothing has happened in the
last 165 million years that would kill off life on Mars.
"That is why (analysis of the Shergotty sample) is so important. If
what we see
there is borne out as signs of life, that pretty well predicts we will find life
when we go there."
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