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Researchers Dispute Claims Of 'Nanofossils' In Martian Meteorite

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Jane Sanders (404-894-2214) or (770-975-1014);
E-mail: jane.sanders@edi.gatech.edu.

TECHNICAL INFORMATION:
1. Dr. John Bradley, MVA Inc. (770-662-8509);
Email: jbradley@mvainc.com
2. Dr. Hap McSween, U. of Tenn.-Knoxville (423-974-9805);
Email: mcsween@utk.edu
3. Dr. Ralph Harvey, Case Western Reserve U. (216-368-3690);
Email: rph@po.cwru.edu

WRITER: Jane Sanders

For Immediate Release: July 6, 1998

CITING GROWTH PATTERNS, RESEARCHERS DISPUTE CLAIMS OF "NANOFOSSILS"
IN MARTIAN METEORITE

A team of researchers, including a Georgia Institute of Technology
adjunct professor, has fired a new volley in the continuing
scientific debate over claims that a meteorite found in Antarctica
contains evidence of life on Mars.

In a paper to be published in the July issue of the journal
Meteoritics and Planetary Science, the researchers report evidence
that crystals found in the meteorite were formed by epitaxial
processes at temperatures that were likely too  high for biological
organisms to exist. The findings cast new doubt on claims by NASA's
Johnson Space Center (JSC) researchers (led by David S. McKay) that
the so-called "Mars rock" contains forms consistent with nanofossils.

Using transmission electron microscopy, researchers discovered that
magnetite crystals in the meteorite, known as ALH84001, were
atomically intergrown with the surrounding carbonates by a rigorous
form of epitaxy. This process is an ordered growth of one mineral
on top of another. The resulting complementary orientation of
crystals means the magnetites and carbonates must have grown
simultaneously at temperatures much greater than 120 degrees
Celsius, researchers said.

Epitaxial formation rules out intracellular precipitation of the
magnetites by Martian organisms, a theory hypothesized by NASA
scientists who believe the meteorite contains nanofossils, the Tech
researchers said. And the implied high-temperature origin virtually
eliminates the possibility that fossilized Martian organisms exist
in this meteorite, they added.

This article is the third in a series of this research team's
technical papers that have disputed claims of biological life in
the meteorite. The other papers were published in the journals
Geochimica et Cosmochimica Acta (1996) and Nature (1997). NASA has
sponsored all of this research, as well as work by JSC scientists
who made the nanofossil claims.

"These three papers in combination basically invalidate much of
their (JSC's) evidence," said Dr. John Bradley, an adjunct
professor in the Georgia Tech School of Materials Science and
Engineering and executive director of MVA Inc., a microanalytic
company in Norcross, Ga. "Early skepticism has evolved into
international consensus among meteoriticists and planetary
scientists, with the exception of the JSC team, that this rock does
not contain Martian nanofossils. I do not know of a single other
individual who believes it at this point."

Bradley conducted the current and previous research with Drs. Hap
McSween of the University of Tennessee in Knoxville and Ralph
Harvey of Case Western Reserve University in Cleveland, Ohio. In
their first paper, the researchers used transmission electron
microscopy (TEM) to discover that elongated forms in the meteorite
contained crystallographic defects that look like a spiral
staircase, Bradley said. These defects, called screw dislocations,
typically form during high temperature vapor phase growth.

The JSC team, using field emission scanning electron microscopy, had
claimed that these worm-like, elongated forms were nanofossils. If
true, they should contain internal "daisy chains" of aligned
magnetite crystals called magnetosomes. Bradley's team found
elongated, rod-shaped magnetites called "whiskers" instead. But JSC
researchers countered that the differences resulted from scientists
using different microscopy techniques and thus seeing different
objects.

So Bradley's team duplicated the JSC researchers' scanning electron
microscopy (SEM) procedures at Georgia Tech using the same metal
coatings, gold and palladium, to make the specimen surfaces
conductive. With SEM, Bradley's team found the same worm-like
objects. Then, however, they rotated and tilted the meteorite
specimens to get a different microscopic angle. From that
perspective, the worm-like objects appeared to be inorganic mineral
lamellae or protruding ledges. Their worm-like segmented surface
structures were actually artifacts of the gold and palladium
coatings on the specimens. "They looked like the edge of a stack of
copy paper in which a few pages are sticking up on edge," Bradley
said.

In a rebuttal paper accompanying the Bradley team's 1997 article in
Nature, the NASA researchers conceded that these non-biological
worm-like structures are present in the meteorite, but that their
nanofossils are "different."

"It's like looking for worms in a plate of spaghetti," Bradley
said. "If the worms look like spaghetti noodles and they're not
wriggling around, how can you be sure they're worms and not
noodles?"

In the current paper, researchers focus on epitaxially grown
magnetite single crystals. They are key indicators of the
geochemical and thermal history of the carbonate-rich fracture
zones of the Martian rock, they said. Magnetite crystals,
apparently formed by several high temperature growth mechanisms,
are found in several distinct mineral settings in this meteorite.

With regard to whiskers, the researchers cite various evidence of
epitaxial crystal growth and high temperature origin of magnetites
in the meteorite. TEM techniques allowed researchers to view the
well-defined spatial orientation relationship between magnetite and
carbonate crystals. Epitaxy can occur if two similarly patterned
lattice planes of crystal structures are parallel. Previous studies
have shown the ideal lattice "misfit" between two crystal
structures should not exceed 15 percent. In this case, the lattice
"misfit" was only 11-13 percent, which is ideal for epitaxial
growth, Bradley said.

Furthermore, many of the epitaxially formed magnetite whiskers in
the meteorite appear to be free of internal defects, the
researchers said. Such is typically the case of crystals formed at
elevated temperatures, while those grown at lower temperatures tend
to have high densities of internal defects.

Also, researchers found epitaxially formed magnetite crystals in
mineral specimens from volcanoes in Indonesia and Alaska. These
crystals formed at temperatures in excess of 600 degrees Celsius,
researchers said. They compared these to the magnetites in the
meteorite because volcanoes also exist on Mars. The comparison
provided further evidence of a high temperature origin, Bradley
said.

Despite this paper and the other two Bradley team publications, the
debate over nanofossils in Martian meteorite ALH84001 will
continue, Bradley said.

"Unless the JSC team concedes, the debate will never die," Bradley
said. "When this news first became public, the debate was quickly
deflected into one about whether life exists or once existed on
Mars. But there are really two debates here -- whether there is
evidence of life in this meteorite and whether life exists on
Mars."

The first question is already answered in Bradley's estimation. The
second remains, and Bradley believes it is very unlikely that life
exists on the surface of Mars. "It may be down in the depths. We
now know that life thrives in very extreme conditions on Earth," he
said.

        ---------------------------------------------------

PHOTO CAPTION: [http://www.gtri.gatech.edu/res-news/MARS.html]
Dr. John Bradley presents electron microscope images of Martian
meteorite crystals that contain"nanofossils," according to some
scientists.


PHOTO COPYRIGHT INFORMATION: Photographs are copyrighted by the
Georgia Tech Research Corporation and may be freely used by the
news media with credit to the Georgia Institute of Technology. The
photographer is Stanley Leary, Georgia Tech Communications
Division.

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