Green Mineral Indicates Mars Is Dry

Contact: Heidi Koontz

303-202-4763
United States Geological Survey

Green mineral indicates red planet is dry

The presence of a common green mineral on Mars suggests that the red planet
could have been cold and dry since the mineral has been exposed, which may
be more than a billion years according to new research appearing in the Oct.
24 edition of Science.

Todd Hoefen, a U.S. Geological Survey (USGS) geophysicist, led a team of
researchers from USGS, Arizona State University and NASA, that found
abundant quantities of olivine on Mars. They based their conclusions on data
obtained from a Thermal Emission Spectrometer (TES) carried by the Mars
Global Surveyor (MGS).

Olivine, a transparent green-colored mineral found in many mafic rocks, is
susceptible to chemical weathering and readily alters to other minerals such
as iddingsite, goethite, serpentine, chlorite, smectite, maghemite and
hematite in the presence of water. Except for trace amounts of hematite,
which gives Mars its red color, none of these other weathering products have
been found.

The team detected a 30,000 square kilometer area rich in olivine, in the
Nili Fossae region of Mars. Nili Fossae has been interpreted as a complex of
grabens and fractures related to the formation of the Isidis impact basin,
where post-impact faulting exposed the abundant olivine. They have also
found smaller deposits of olivine all over the planet, all indicating a
surface dominated by volcanic processes.

The fact that so much olivine is exposed at the surface indicates that there
has been little to no weathering due to water, thus no liquid water-mineral
chemical reactions. The age of the surface is somewhat uncertain but is
probably over 3 billion years old.

It took approximately three years for the MGS spacecraft and the TES
instrument to gather the data for the analysis, and scientists another year
to analyze the results. The MGS spacecraft is healthy and continues to map
Mars.

###

The USGS serves the nation by providing reliable scientific information to
describe and understand the Earth; minimize loss of life and property from
natural disasters; manage water, biological, energy, and mineral resources;
and enhance and protect our quality of life.

(Ron Baalke) writes:

Contact: Heidi Koontz

303-202-4763
United States Geological Survey

Green mineral indicates red planet is dry

The presence of a common green mineral on Mars suggests that the red planet
could have been cold and dry since the mineral has been exposed, which may
be more than a billion years according to new research appearing in the Oct.
24 edition of Science.
[...]
The team detected a 30,000 square kilometer area rich in olivine, in the
Nili Fossae region of Mars. Nili Fossae has been interpreted as a complex of
grabens and fractures related to the formation of the Isidis impact basin,
where post-impact faulting exposed the abundant olivine. They have also
found smaller deposits of olivine all over the planet, all indicating a
surface dominated by volcanic processes.

The fact that so much olivine is exposed at the surface indicates that there
has been little to no weathering due to water, thus no liquid water-mineral
chemical reactions. The age of the surface is somewhat uncertain but is
probably over 3 billion years old.

It should be noted that Nili Fossae is a Martian "highland" region, and is
further above the martian "lowlands" than Mt. Everest is above terrestrial
sea level. One finds very little _liquid_ water on top of Mount Everest,
and therefore very little water-induced chemical weathering there. Olivine
outcrops on high mountaintops are not unusual.

Hence, and notwithstanding the slower decrease in atmospheric density
with altitude caused by the larger "scale height" of the Martian atmosphere,
even during a "warm wet phase," one would =NOT= expect to find liquid water
in the Martian "highlands," due to their higher relative altitude and Mars's
lower mean temperature. Even if the "lowalnd" pressure were a substantial
fraction of a bar, the Martian highland "climate" would still be a very cold,
very dry, near-vacuum. Therefore, IMO, this observation says NOTHING AT ALL
about the ancient martian lowland climate.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Gordon D. Pusch) wrote in message ...
(Ron Baalke) writes:

Green mineral indicates red planet is dry

The presence of a common green mineral on Mars suggests that the red planet
could have been cold and dry since the mineral has been exposed, which may
be more than a billion years according to new research appearing in the Oct.
24 edition of Science.
[...]

The fact that so much olivine is exposed at the surface indicates that there
has been little to no weathering due to water, thus no liquid water-mineral
chemical reactions. The age of the surface is somewhat uncertain but is
probably over 3 billion years old.

It should be noted that Nili Fossae is a Martian "highland" region, and is
further above the martian "lowlands" than Mt. Everest is above terrestrial
sea level.

ahhh - no. Nili Fossa is at about mean planetary radius - the floor
of the main valley is at about the same elevation as the MER landing
sites. It is right on the edge of Isidis after all - the Beagle's
target site. Christansen also reported olivine deep in the guts of
Vallis Marineris in March. It is a real problem - abundant evidence
for H2O as ice, and shaping the surface, but the weathering data goes
right against liquid water. The carbonate data seems pretty damning as
well.

Maybe you are thinking of Tharsis.

Hence, and notwithstanding the slower decrease in atmospheric density
with altitude caused by the larger "scale height" of the Martian atmosphere,
even during a "warm wet phase," one would =NOT= expect to find liquid water
in the Martian "highlands," due to their higher relative altitude and Mars's
lower mean temperature. Even if the "lowalnd" pressure were a substantial
fraction of a bar, the Martian highland "climate" would still be a very cold,
very dry, near-vacuum. Therefore, IMO, this observation says NOTHING AT ALL
about the ancient martian lowland climate.

The top of the south polar cap is +4 km higher than Nili Fossa. Ice
does not flow uphill. (And the latest thinking is that most of the SPC
is indeed water, not CO2 as previously thought).

We have a real paradox here. And this result *is* important regarding
water.

Cheers,
Duncan

-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'