Campus: Cal Poly, San Luis Obispo -- November 20, 2001
Life on Mars Still Unproven, Cal Poly Professor and Colleagues Say in Journal Article
Life on Mars still remains in the realm of science fiction, not solid
science, according to Cal Poly Physics Professor Richard Frankel and his
co-authors in an article to be published Wednesday (Nov. 21) in The Proceedings
of the National Academy of Sciences.
Frankel and other members of his research team challenge NASA scientists'
much-publicized announcement in 1996 that a Martian meteorite found in
Antarctica contains evidence of fossil bacteria - and thus life on Mars
at some point in the planet's history.
That 1996 NASA announcement brought a storm of excitement, publicity and
controversy. In the five years since, other scientists have shown that
nonbacterial contamination could explain many of the "bacterium-shaped
objects" and supposedly organic chemicals found in the meteorite
and cited by NASA as evidence.
Now Frankel and the other members of his research team have assailed the
final NASA contention: that the magnetite crystals found in the Martian
meteorite have three-dimensional shapes identical to certain bacteria
here on Earth, and different from any of those produced by any inorganic
Frankel and team members argue that the assumed match between the Martian
meteorite's crystals and bacteria on Earth is at best ambiguous and at
In their paper, "Magnetite Morphology and Life on Mars," Frankel
and his co-authors argue that the evidence for bacterial magnetite crystals
on the Martian meteorite is inadequate, and they used comparisons with
bacterial magnetite crystals from Morro Bay to help explain why.
The magnetite crystals in the NASA Martian meteorite are tiny, even by
the standards of an electron microscope, Frankel explains. They are only
40 to 100 billionths of a meter wide.
"And there's the rub," says Frankel. "The technology necessary
to accurately describe the Cal Poly News three-dimensional shape of such
small crystals has become available only in the last few years."
The magnetite crystals in the Martian meteorite have not yet been subjected
to the new viewing techniques. So, Frankel says, "it's still too
early to say for sure what the exact shapes of the meteoritic crystals
are, let alone whether they match those in bacteria."
The only kind of microscope powerful enough to produce clear images of
the magnetite crystals found in the meteorite is a relatively new piece
of equipment called a transmission electron microscope, or TEM. By using
a beam of electrons rather than a beam of light to view the sample, a
TEM allows researchers to see objects smaller than one billionth of a
meter wide. But a TEM sees only in two dimensions. It generates a silhouette
image of a sample, but conveys little about its thickness, according to
An accurate description of the crystals contained in the Martian meteorite
and their complex three-dimensional shapes requires that they be examined
from a variety of perspectives, Frankel and his colleagues explain. Distinguishing
between the crystals' flat facets and tapered tips is a challenge. Only
by tilting each crystal at dozens of angles can scientists unequivocally
identify their three-dimensional shapes, according to Frankel and his
At the time of the NASA study, the tilting experiments could be done only
by hand, and with great difficulty. The NASA group used this approach
to create images of the magnetite crystals from both the meteorite and
from one strain of bacteria found on Earth.
Recently, scientists have coupled TEM technology with computer imaging
to make experiments more precise.
This new technology is available at Arizona State University and the University
of Cambridge in England. Frankel and his team of co-authors used it to
reexamine the evidence in the NASA study and contrast it with biological
magnetite crystals from Earth - some collected in Morro Bay.
Their results call into question whether the shapes of all crystals originating
in the Martian meteorite found in Antarctica are accurately known. In
their research, Frankel and his team demonstrate that the shapes of bacterial
magnetite grains found on Earth vary more than previously thought. According
to their research, the shapes and sizes differ among bacterial strains,
and even within individual bacteria. That expanded variety makes it more
likely that bacterial and meteoritic magnetite grains could match by simple
chance, Frankel's team concluded.
However, the team did not eliminate the possibility that the Martian crystals
could have a biological origin. With the advanced TEM technology now on
hand, Frankel and his team members plan more conclusive studies of the
magnetite crystals from the Martian meteor and several more strains of
Frankel's co-authors on the paper are Peter Busek and Martha McCartney
of Arizona State University; Rafal Dunin-Borkowski, Paul Midgley and Matthew
Weyland of Cambridge University; Bertrand Devouard of Blaise Pascal University
in France; and Mihalay Posfai of the University of Veszprem, Hungary.