[meteorite-list] Atacama Desert in Chile Is Amazingly Similar To Martian Surface
From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:16 2004
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Subject: Soil Surface In Chile Is Amazingly Similar To
Soil surface is amazingly similar to Martian dirt
by Douglas Fischer
of San Mateo County Times
on November 16, 2002
Sandwiched between the coastal hills and the Andes,
the Atacama runs some 600 miles down Chile's empty
northern spine. Years often pass between
rains in the most arid regions, and what does fall is
so thin Death Valley
looks dripping wet in comparison, McKay said.
Rainfall in the Mojave averages about 13 centimeters,
or five inches, every year. NASA's Atacama site gets a
two-millimeter rain -- the thickness of a dime -- once
every five or so years.
The surface at the site boasts a puffy crust of salts,
nitrates and gypsum that, researchers speculate, has
literally fallen from the sky. To walk in such soil is
to sink slightly, much the way Alan Shephard did en
route to his lunar tee-shot 31 years ago: Each step
compresses thousands of years of accumulated deposits.
Minerals fall out of the sky everywhere, said Ron
Amundson, a UC Berkeley soils science professor
studying the Atacama with McKay's team. But only
in the Atacama are they not washed away by rain or
digested by microbes.
Instead they migrate slowly through the soil,
accumulating in dense deposits of highly soluble
nitrates and gypsum found nowhere else on Earth.
And those deposits may offer the best chance of
finding life -- or its remains -- on Mars.
The Viking expeditions in the 1970s ran simple tests
given what scientists know now. But among the
discoveries, the landers found little carbon in
Martian soils. And what carbon was there was oxidized
-- "like someone has poured bleach on it," McKay said.
If there had been life at the surface, it had been
long ago blasted apart by the sun's rays, rather than
In October, scientists found hydrogen peroxide, an
oxidizing agent created as ultraviolet light hits
water vapor in the atmosphere, on the surface of
the Atacama. The levels were near the limits of
detection -- .03 parts per million -- and well below
the 1 part per million the Viking landers measured
But the find vitalized McKay and the team and
suggested that to find signs of life, they'd have to
As the desert's puffy crust gives way and salts
migrate downward, they gradually condense into a
hardpan layer that Amundson jokingly describes as
"softer than Sierran granite, but not by much."
In that hardpan, five feet below the surface,
Warren-Rhodes has found special bacteria that thrive
on salt. Below it, Brad Sutter, another NASA-Ames
researcher working with Amundson and UC Berkeley
graduate student Stephanie Ewing, found tiny
Water remains a problem, but to the NASA team, it's
further evidence that some of the best hopes for
finding life on Mars lies below the surface.
"There's not that much quartz on Mars," Warren-Rhodes
said. "But there are a lot of purported ancient lake
beds where there might be preserved organisms in salt.
"Deeper down, it might be similar."
For now, it's all speculation. The next surface rovers
won't arrive on Mars before 2004, and they are no more
than Pathfinder-like robots, capable of analyzing only
surface minerals and water samples.
It will be quite some time before anyone takes a core
sample. Still, scientists are thrilled to have
something at least to test theories against.
"Mars could be deceiving," Amundson said. "There could
be a lot more under (the surface) than we see.
"The Atacama is the closest thing on Earth that's gone
through 8 to 10 million years of climatic decline.
This gives us a way to test our ideas about how the
Earth works and biology adapts to climate."
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Received on Wed 20 Nov 2002 07:38:32 PM PST