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Nakhla

Being somewhat interested in Nakhla, I've just read the paper "Possible
bacteria in Nakhla" (D.S. McKay, S.W. Wentworth, K. Thomas-Keprta, F. Westall,
E.K. Gibson, Jr.) presented at yesterday's session of the Lunar and Planetary
Science Conference in Houston.  I'd like to (humbly) share my "Reader's
Digest" review of the paper and add a few observations for the members of this
list. 

Nakhla, along with most of the other Mars' meteorites shows evidence of
"aqueous alteration" by containing certain mineral byproducts.  If the water
dissolving the original mineral matrix is at certain favorable temperatures
(the range seems to expand as we explore the micro-niches of our own planet)
one could postulate that conditions for some life, some microbe or bacteria
are good.  That puts the focus of our efforts to find this evidence on the
Mars' meteorites (a lot of time has also been invested looking at the CI's) . 

In the newly released paper by McKay et al. they suggest that "the round and
ovoid     units ... represent the mineralized remains of bacterial cell
walls."  They measure these in sizes comparable to earth bacteria, believe to
see "cells attached to each other contiguously, reminiscent of dividing
bacteria," as having a surface texture typically complex of other
(known/earthly) mineralized bacteria cells, with a "fine filament attached to
the end of one ovoid... reminiscent of a bacterial fibril."  "The uneven
distribution ....of cells can be interpreted as an uneven distribution of
cells typical of colonies in confined spaces.  If the particles are inorganic
chemical precipitates, we might expect a more even distribution throughout the
smectite/alteration products."

The section entitled "Origin on Mars or Earth" especially caught my attention.
After citing evidence that the "alleged" bacteria (AKA embedded objects, AKA
round to ovoid objects)  "seem to be contemporaneous with the main mass of
alteration products" and "the products coat and follow the contours of
existing bumpy masses" they add, "the objects which appear to rest directly on
exposed surfaces of alteration products were clearly formed after most if not
all alteration product had stopped, which may even indicate terrestrial
formation shortly after fall or in the museum." (my italics)

They suggest the existence of two generations of bacteria, one Martian and one
from Earth adding "the close proximity of the two generations might be
explained if the organic Martian remains served as favorable attachment sites
for the terrestrial bacteria."

They conclude that "Nakhla contains variable concentrations of tiny round to
ovoid objects which can plausibly be interpreted as bacterial cells in various
stages of mineralzation.  Additional tests must confirm this interpretation
and distinguish between Martian and terrestrial bacteria."  They add that
Shergotty has the same objects in a similar concentration.

Some other background on this from data that's "out there" and from e-mail
I've gotten from Monica Grady (I don't think she'll mind me sharing this with
you).   Last year at about this time,  Monica Grady of the British Natural
History Museum "donated" material from their specimen catalogue #1913.25,
weighing 640.8 grams, and being 100% fusion crusted.  It was originally given
to them by the Egyptian government. The specimen was cut about in half at the
Johnson Space Center in Houston, of which about 300 grams was returned to the
BNHM and the rest distributed to 37 groups of investigators.  Monica felt that
after the controversy surrounding ALH84001, more could be gleaned by looking
at Nakhla. She hoped that by cutting into a 100% crusted specimen, assuming
that FC is a reasonably airtight seal, terrestrial contamination controversies
could be mitigated. 

Will we ever be able to separate the Mars' bacteria from the Earthly bacteria?
And if the Earthly bacteria found a "favorable attachment site on the Martian
organic remains", one must wonder why this affinity exists.  

I'm sure that further debate will surround these findings, and with other
distinguished researchers (she mentioned that Allan Treiman and Harry McSween
had applied for specimens) on the trail, we can look forward to more
intriguing findings as mankind searches for the historic, first evidence of
life on another planet. 

P.S. - Lafayette has even more alteration products than Nakhla (and is the
petrological kissin' cousin of Nakhla,  h--m-m-m, dare I say "paired"), but
should we take the saw blade to this most beautiful of oriented meteorites?

Best regards,

Kevin Kichinka   

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