Doubts About ALH84001: The JSC Mars Meteorite Team Responds

Editor’s note: the following is a response provided to SpaceRef by the JSC Mars Meteorite Team (David McKay, Kathie Thomas-Keptra, and Everett Gibson) regarding a paper “Magnetite morphology and life on Mars” (and associated press releases) by Buseck et al. that appears in the 19 November 2001 issue of the Proceedings of the National Academy of Sciences (PNAS).

“Buseck et al. have “rediscovered “an anaytical method developed in 1947 by Dennis Gabor for defining the morphology of crystals using
electron microscopy. Unfortunately, the Buseck et al. paper adds nothing
to further the understanding of the issue of life on Mars. It demonstrates
that these authors fail to understand the work of Thomas-Keprta et al,
2001 who used a transmission electron microscope to image individual
microscopic particles at multiple angles and orientations. From this, the
3-D morphology of the particles could be reconstructed. The technique used
by Buseck et al. also uses a transmission electron microscope to image
microscopic particles at many different angles in order to reconstruct a
3-D image. These two techniques, for this particular application, are
essentially identical.

The Buseck et al. PNAS paper is interesting in that they do not
examine ALH84001’s population of likely biogenically produced magnetite
crystals or the reference MV-1 magnetite crystals; these magnetite
populations are the central issues in the debate and without studying
either population, at best, their conclusions are irrelevant to the
question of life on Mars. Buseck et al. describes the 3-D geometry of a
magnetite crystal from “an undescribed, uncultured magnetotactic coccus
collected from Sweet Springs Natural Reserve, Morro Bay, CA.” It is
unclear why they would describe just any magnetite from a previously
undescribed strain and compare the geometry of one crystal with one of the
best described terrestrial magnetite populations, that of strain MV-1.
Buseck et al. are trying to compare a quick study of “oranges (i.e., his
undescribed magnetites) with a well-defined study of “apples” (magnetites
from ALH84001 and MV-1).

Buseck et al. are trying to lay claim to
discovering an analytical method of defining morphology of nanocrystals.
Such work has been done for decades using conventional TEM techniques.
We see no scientific basis for the Buseck et al. comments “we argue
that the existing crystallographic and morphological evidence is
inadequate to support the inference of former life on Mars” when he has
not examined the magnetites in ALH84001 or MV-1.

The statement at the
conclusion of the Buseck et al. PNAS contribution is another example of
researchers trying to use data to refute a scientific hypothesis when the
data does not apply to the arguments. One must consider all the lines of
evidence used to reach the conclusions. Furthermore, Buseck et al. state
that three of the four lines of evidence proposed by McKay et al. 1996
have been refuted; that is incorrect. Gibson et al. 2001 (in Precambrian
Research) show additional evidence to support all the original lines of
evidence of possible biogenic activity within ALH84001 and its carbonate
globules are valid. Additional evidence for possible biogenic activity
was also described for two younger Martian meteorites-Nakhla (1.3 billion
years old) and Shergotty (165 million years old) in that same report
(Gibson et al. 2001).

The Buseck et al. paper appears to be little more than a poorly
disguised advertisement for the technique of electron tomography, an
attempt to capitalize on the intense debate surrounding the issue of life
on Mars to gain publicity. We have been looking forward to the scientific
results from Buseck et al. and were very disappointed.

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