Martian Meteorites May Carry Micro-Fossils, Scientists Say
A pair of Martian meteorites include features that resemble Earth bacteria, according to the same NASA researchers who said three years ago that they had evidence of “primitive life on early Mars.”
The findings, made within the last six months, were from samples of a 1.3-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 from Mars,” said David S. McKay, a Johnson Space Center geologist.
“We’re not counting on getting many converts,” he said. “All we ask, though, is that people keep an open mind.”
McKay’s presentation Thursday in Houston at the Lunar and Planetary Science Conference was a cautious one because more research is required.
McKay, 62, was one of the researchers who in August 1996 announced the discovery 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 findings. 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 the 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 meteorite.
“If this proves out, we will have shown that life spanned almost the entire history of Mars, and presumably today,” McKay said. “Nothing has happened in the last 165 million years that would kill off life on Mars.”
