Mars Shows Signs of Acid Fog: Study
Mars Shows Signs of Acid Fog: Study
A planetary scientist has pieced
together a compelling story
about how acidic vapours may have
eaten the rocks in a 100
-acre area on Husband Hill in the
Columbia Hills of Gusev
Crater on Mars.
Shoshanna Cole from the Cornell
University used data
gathered by multiple instruments
on the 2003 Mars
Exploration Rover Spirit to tease
out information from
exposures of the ancient bedrock.
The work focused on the
'Watchtower Class' outcrops
on Cumberland Ridge and the
Husband Hill summit.
By combining data from previous
studies of the area on Mars,
Cole saw some intriguing
patterns emerge.
Spirit examined "Watchtower
Class" rocks at a dozen
locationsspanning about 200
meters along Cumberland
Ridge and the Husband Hill
summit.
Across Cumberland Ridge the data
showed there was a
surprisingly wide range in the
proportion of oxidized iron to
total iron, as if something had
reacted with the iron in these
rocks to different degrees.
Meanwhile, further data showed
that the minerals within the
rocks changed and lost their
structure, becoming less
crystalline and more amorphous.
These trends match the size of
small bumps, which Cole calls agglomerations, seen in Pancam and Microscopic
Imager
pictures of the rocks.
"So we can see the
agglomerations progress in size from
west to east and the iron
changes in the same way," Cole
said. "It was super
cool."
But the fact that the rocks were
otherwise the same in
composition indicates that they
were originally identical.
"That makes us think that
they were made of the same stuff
when they started out. Then
something happened to make
them different from each
other," she noted.
Cole hypothesises that the rocks
were exposed to acidic
water vapour from volcanic
eruptions, similar to the corrosive
volcanic smog that poses health
hazards in Hawaii from the
eruptions of Kilauea.
When the Martian smog
landed on the surface of the rocks it
dissolved some minerals, forming
a gel.
Then the water evaporated,
leaving behind a cementing
agent that resulted in the
agglomerations.
She presented the
findings at the annual meeting of the
Geological Society of America in
Baltimore, Maryland, on
November 2.
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