Finding of perchlorates on Mars may provide a

On Aug 12, 11:11 pm, (David Williams) wrote:
- However, having a source of oxygen is one thing. Using it for metabolism i
- another. There must be "food" for the organism to oxidize. What exists in
- Martian soil that an organism could use as food?

- How about hydro-carbons?
- Ken

Have they been detected in Martian soil?

dow


Methane which is a simple organic molecule has been detected in small
amounts from orbit. Methane consisting of carbon and hydrogen is a
hydrocarbon. So organics of some form do exist at the surface of
Mars. This is not proof of life though since methane being a simple
molecule can be produced in purely chemical ways.
Some microbes can survive on methane alone of course. It is also
interesting that some strains of the perchlorate-metabolizers are
autotrophic meaning they do not need to feed on organic compounds.
Some can feed on just CO2 from the atmosphere as their sole carbon
source.
Note though that if the microbes that did not require organic
molecules to feed on were found, autotrophs, then the organic
molecules in their makeup would be returned to the Martian soil when
they died so almost certainly there would exist other microbes that
feed on organics in their metabolism on Mars as well.
Most Mars scientists who have studied the Viking GCMS (gas
chromatography mass spectrometer) now realize that it could have
missed low amounts of organics on Mars. For instance the low numbers
of organics in the driest parts of Antarctica and the Atacama desert
were not detected in experiments using GCMS analog instruments. For
this reason most experts on the issue now say that more sensitive
organic detectors have to be sent to Mars to decide the question.
Here is one article discussing the issue:

The limitations on organic detection in Mars-like soils by thermal
volatilization-gas chromatography-MS and their implications for the
Viking results.
Proceedings of the National Academy of Sciences, October 31, 2006 vol.
103 no. 44 16089-16094
"The failure of Viking Lander thermal volatilization (TV) (without or
with
thermal degradation)-gas chromatography (GC)-MS experiments to detect
organics
suggests chemical rather than biological interpretations for the
reactivity of
the martian soil. Here, we report that TV-GC-MS may be blind to low
levels of
organics on Mars. A comparison between TV-GC-MS and total organics has
been
conducted for a variety of Mars analog soils. In the Antarctic Dry
Valleys and
the Atacama and Libyan Deserts we find 10-90 ìg of refractory or
graphitic carbon per gram of soil, which would have been undetectable
by the
Viking TV-GC-MS. In iron-containing soils (jarosites from Rio Tinto
and
Panoche Valley) and the Mars simulant (palogonite), oxidation of the
organic
material to carbon dioxide (CO2) by iron oxides and/or their salts
drastically
attenuates the detection of organics. The release of 50-700 ppm of CO2
by
TV-GC-MS in the Viking analysis may indicate that an oxidation of
organic
material took place. Therefore, the martian surface could have several
orders
of magnitude more organics than the stated Viking detection limit.
Because of
the simplicity of sample handling, TV-GC-MS is still considered the
standard
method for organic detection on future Mars missions. We suggest that
the
design of future organic instruments for Mars should include other
methods to
be able to detect extinct and/or extant life."
http://www.pnas.org/content/103/44/16089.full

Two things are very notable he first, that iron-containing
minerals of the type expected to be on Mars would have made the GCMS
sensitivity even worse, and second, rather surprisingly, the amounts
of CO2 released on heating in the Viking GCMS might actually have
indicated that organics *were* present.

Bob Clark