SETI bioastro: Mystery surrounding Martian organic matter deepens

From: Larry Klaes (lklaes@bbn.com)
Date: Tue May 02 2000 - 13:38:46 PDT


http://www.spaceflightnow.com/news/n0005/02mars/index.html

Mystery surrounding Martian organic matter deepens

BY NEIL ENGLISH
ASTRONOMY NOW

Posted: May 2, 2000

In 1976, two superbly designed robotic emissaries from Earth
soft-landed on the rock-strewn surface of another world in
search of life. After conducting three biology experiments,
the American Viking missions to Mars concluded that they
could neither confirm nor refute the presence of biological
entities. Moreover, the instruments on board the spacecraft
failed to detect even the faintest presence of organic matter -
the stuff of life - in the Martian soil. But now, a quarter of
a century on, new research raises fresh doubts about a seminal
conclusion reached by these historic experiments.

For over a century, Mars has captured the imagination of the
general public as a likely abode for life beyond Earth. And
though astronomers' knowledge has come a long way from the
days of Percival Lowell's Canals, many scientists still entertain
hopes of finding some life on the Red planet. But when the Vikings
went to Mars over a quarter of a century ago, they dealt the
Martian life hypothesis a venomous blow.

Using a powerful scientific instrument called a gas
chromatograph-mass spectrometer (GC-MS), samples of Martian
soil were subjected to heating at temperatures between 200o C
and 500o C for 30 seconds, after which the vapourised molecules
were identified on the basis of their molecular mass and electrical
charge.

Though the Viking landers were positioned nearly 8,000
kilometres apart, neither detected any organic matter. But that
result was just plain weird. For one thing, the Red planet is dusted
with some 240 thousand kilograms of organic material each year
via meteorites - a concentration that could easily have been
detected by the Viking GC-MS experiments. The answer,
chemists soon realised, was that the Martian soil is highly oxidising,
more than capable of sundering even the most robust organic
species into smithereens. This result, above all others, was and
remains strong evidence against the possibility of life on Mars - at
least at the surface.

Now, in a paper published in March 14 edition of Proclamations
of the National Academy of Sciences, USA, a team of scientists
headed by Charles Benner at the University of Florida believe that
a sizeable store of organic material may have been undetectable
with the instruments placed on board Viking. In particular, they
have outlined an elaborate sequence of chemical reactions in which
organic molecules could have been modified by highly reactive
peroxides and radicals in the Martian regolith, rendering their
products difficult to detect using GC-MS. The failure of the Viking
experiments to find organics should not, they insist, be taken as a
strong argument against the presence of all organic matter on the
Red Planet. The mystery continues.



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