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Debate Over Evidence For Martian Life In Meteorite Rages On

Stanford University

5/29/97

CONTACT: David F. Salisbury, News Service (415) 725-1944;
e-mail: david.salisbury@stanford.edu

Debate over evidence for Martian life in meteorite rages on

Before it was published, Richard Zare suspected that the paper proposing
that a meteorite from Mars once hosted alien life would be a media
sensation. It was.

What Zare didn't expect was the course that the scientific debate has taken.
He thought that the resulting discourse would be skeptical and opinionated,
but also highly reasoned and dispassionate. But because of the high
stakes - nothing less than the first discovery of alien life - and the intensity
of the media spotlight, the scientific interchange has proven to be highly
emotional and highly disruptive, he said.

"Sometimes it is all too easy to forget that the object of this effort is
not to win a debate, but really to understand as much as we can about this
fascinating meteorite," said Zare, the Marguerite Blake Wilbur Professor of
Chemistry.

Since the initial study was published in Science magazine last summer, a
dozen or so scientific papers have been presented at meetings, circulated to
the media and published in scientific journals. A number have attacked
various aspects of the original study, but more have claimed to provide
additional support.

When they released their findings, Zare and his co-authors expected this
sort of give and take. They did not have direct evidence for Martian life,
so they wanted other scientists to examine their work and come to a
collective judgment about whether they were right or wrong. The quality of
much of the criticism and support, however, has not been terribly
impressive, according to Zare and graduate student Simon Clemett, who
took part in the study and has stayed on at Stanford to do additional research
in this area.

"I've become less sanguine about the possibility of a quick answer," Zare
said. "I would have thought by now that our hypothesis would have been
either shot down or accepted. But the situation has proven to be much more
complicated than I first realized."

That said, the two scientists have not seen anything yet that makes them
want to retract their hypothesis. In fact, they argue that the additional
supporting evidence that has been produced slightly outweighs the
criticisms. At the same time, they don't know of any research going on that
is likely to resolve the issue definitively.

The original paper by Zare and his co-authors - NASA scientists David McKay
and Everett Gibson Jr., Kathie Thomas-Keprta of Lockheed Martin, Christopher
Romanek from the University of Georgia and Hojatollah Vali from McGill
University plus Clemett and fellow graduate student Claude R. Maechling with
postdoctoral student Xavier Chillier -- contained four basic lines of
argument to support its pro-life hypothesis: (1) The meteorite, designated
ALH84001, that they examined came from Mars; (2) it contains a unique
pattern of organic compounds that could have been produced by the
fossilization of microorganisms; (3) it contains several unusual mineral
phases commonly produced by microbes; and (4) when examined by an
electron microscope, it reveals textures that appear to be the images of tiny
microfossils. In addition, the features suggestive of biological activity
all appear in the same locations with the rock.

Worm-like shapes

One of the major focal points of criticism has been the nature of the tiny
ovoid and worm-like shapes that the NASA scientists captured with their
high-powered electron microscope and suggested might be microfossils.