[meteorite-list] Features In Martian Meteorite Found On Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:25:41 2004
Message-ID: <200305191534.IAA14578_at_zagami.jpl.nasa.gov>

http://news.bbc.co.uk/1/hi/sci/tech/3034165.stm

'Martian Features' Found On Earth
By Paul Rincon
BBC News
May 17, 2003

Features in a Martian meteorite believed by some to be the fossilised
remains of alien bacteria may have formed underwater, scientists claim.

Researchers have found a "striking" match between microscopic features on
underwater rocks and mineral deposits from Earth and microbe-like structures in
the famous Martian meteorite ALH84001.

The discovery could bring scientists closer to knowing whether the 3.9
billion-year-old meteorite contains fossilised alien life.

The evidence comes from volcanic rocks and underwater geological formations
called calcareous pinnacles found below the surface of Lake Van in Turkey, the
world's biggest alkaline lake.

Martian lakes

These rocks and pinnacles are dotted with globules of complex carbonates, very
similar to those found in ALH84001. They are also home to colonies of
photosynthetic cyanobacteria.

When examined under a scanning electron microscope, carbonates from Lake Van
were seen to be made up of tiny rod-like and ovoid structures - referred to as
"nano-bodies" by the researchers - of a similar size and texture to those famously
described in ALH84001.

The research was carried out by Professor Jozef Kazmierczak of the Polish Academy
of Sciences and Professor Stephan Kempe of the Technische Universität Darmstadt,
Germany.

Professor Kazmierczak said the Lake Van samples were the best match for the
structures in ALH84001.

"Physically and chemically, there is a strong indication that we are looking at
something similar," he told BBC News Online.

In the journal Naturwissenschaften, the authors argue that the globules in
ALH84001 may have formed in an alkaline lake on Mars.

Size limit

The findings support a growing body of evidence that lakes and shallow seas were
once commonplace on Mars.

They propose several possible origins for the Lake Van carbonates. One
possibility, say the scientists, is that they formed during the decomposition of
cyanobacteria by heterotrophs - bacteria that derive their energy from organic
compounds.

But the researchers also suggest the carbonates could have formed
spontaneously through precipitation. If this were shown to be true, it would cast
doubt on theories that ALH84001 contains remnants of Martian life.

Kazmierczak and Kempe draw no conclusions about the nature of the
nano-bodies. But other researchers have made claims for the existence of
ultra-small microbes called "nannobacteria".

The existence of nannobacteria is fiercely disputed by many scientists, who believe
in a lower size limit for life. One recurrent criticism against the Martian life
theory is that nano-bodies in ALH84001 are simply too small to be fossilised life
forms.

Sample return

Professor Hojatollah Vali, a planetary scientist from McGill University in Montreal,
Canada, who has worked on ALH84001, said there was no evidence for the
existence of nannobacteria.

Instead, he favours a non-biological origin for the Lake Van carbonates. Professor
Vali said the presence of magnetite and iron sulphide in ALH84001 similar to that
produced by certain bacteria on Earth was the best sign life once existed on Mars.

But Dr Kathie Thomas-Keprta of Lockheed-Martin Corporation in Houston,
Texas, who has also worked extensively on ALH84001, was intrigued by the Lake
Van samples.

"The similarity between the Lake Van and ALH84001 carbonates is striking, in that
the terrestrial carbonates are of varying composition and appear chemically complex,"
she told BBC News Online.

The controversy may only be solved once space missions return to Earth with
rocks from the Red Planet.
Received on Mon 19 May 2003 11:34:40 AM PDT