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Re: Martian Life: A further look.
A recent article was published on the formation temperature of
carbonates in the ALH84001 Martian meteorite. Since the initial news
broke about the possibilty of life in a Martian meteorite found in these
carbonates, the temperature in which they formed became the center of
attention. If it was high(>500 degrees), than life most definatly was not
found, but if it were low(40-250 dgrees) than life may have had a foot
hold in the carbonate.
Scientists have used oxygen isotopes to determine the temperature
in which the carbonates formed. Certain oxygen isotopes are more abundant
at higher temps, than others. It is by counting the abundance of these
isotopes that a temperature can be constrained.
It was argued, at the end of last year, that, based on the oxygen
isotope data the carbonates formed at a high temperature. This then
negates the conclusion life may have existed in these carbonates. This
then leads to the conclusion that the biogenic structures are really
inorganic.
New data indicate that this may not be right. The reason for the
high temperature conclusion, is due to a trick played by mother nature.
Ground water here on Earth can penetrate a rock, and alter the minerals
of that rock. If the water is incorporated with the original minerals, it
would indicate a higher temperature of formation of the minerals. This is
due to the salinity, which has certain oxygen isotopes associated with it.
Perhaps the same thing happened on Mars. Groundwater may be
obscurring the true temperature of formation, thereby inhibiting the true
temperature of formation. When a method that is applied to Earth rocks to
remove the effects of ground water, is applied to the carbonates of
ALH84001, then the temperate is reduced to a temperature that does not
preclude the concurrent existence of life in the Martian meteorite.
It should be noted that, ground water dynamics are not well known
on Mars. This is due to lack of samples, and actual observations by
humans. Perhaps the method used can not be accurate do to some possible
anomalous charactor of the soil, water, or rock. The data do indicate
though, that, other factors do control what we see, and that we should
not jump to conclusions.
Frank Stroik
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