Making a splash on MARSKeith Piersol

Geochemistry

Article Article is “Making a splash on MARS” by Charles

W. Petit. Published July 2005 in National Geographic,

volume 208. Goes over the discoveries of the Spirit and

Opportunity landers.

Does not go deep into science but is never in error.

Very little context as to Mars paleoclimate or why Mars may have had water in the past.

Introduction Paleoclimate of Mars

› Major theory› Loss of atmosphere

Discoveries by Spirit and Opportunity› Hematite› Problems› Other proof of water

Conclusions

Paleoclimate Theorized to have had a much thicker atmosphere

in the past 4 billion years ago, primarily CO2.

May have been as thick as Earth’s atmosphere, allowing for the existence of large bodies of surface water.

Possibility of an oxygen rich atmosphere as indicated by comparisons of Martian meteorites and Martian surface rocks by Spirit and Opportunity.

Paleoclimate Lost atmosphere over the last 4 billion

years, current atmosphere is 1% of the pressure at earth sea level.

May have lost atmosphere and heat to:› Solar winds (gradual and plasmoids)› Large asteroid impact› Low gravity› High surface area relative to mass

Mars Today 95.9% CO2, pressure of only 7 millibars.

During winter 25% of atmospheric CO2 freezes at the poles as dry ice.

Frost forms at night during summer, as well as earth-like cirrus clouds.

Subsurface water discovered at north pole by Phoenix Mars mission.

Spirit and Opportunity

Purpose Finding evidence of past water on mars.

Equipped with:› Panoramic Camera› Miniature Thermal Emission

Spectrometer› Mossbauer spectrometer› Alpha particle X-ray

spectrometer› Microscopic Imager› Rock Abrasion tool.

Landings Spirit was landed at Gusev Crater

which had an apparent water channel flowing into it. Gusev Crater is 4 billion years old and 166 km in diameter.

Opportunity was landed on a flat equatorial plain called Meridiani Planum, where orbital satellites had detected infrared signatures of Gray Hematite.

Discoveries Found water-related minerals in thin

surface deposits, including a large deposit at Meridiani Planum, and also at Gusev Crater after a few months.

Gray Hematite Goethite Magnesium sulfate, chlorides,

bromides, other iron rich compounds.

Gray Hematite Fe2O3

Variant of red iron-oxide with sand-sized crystals.

Generally form in the presence of water through precipitation.

On Mars it was discovered in the form of round spheres geologists called “blueberries”.

Gray Hematite Gray hematite is not always a marker for the presence of

water. Arguments over how exactly was formed continue today.

The hematite could have formed through the following primary and secondary processes:

› Precipitation from cool iron rich waters.› Precipitation from warm iron rich hydrothermal systems› Thermal oxidation of volcanic deposits (No presence of water).

› Leaching from groundwater.› Hydrothermal modification to porous strata.› Hematite coatings caused by liquid and vaporous water.

Sedimentary Strata Crossbedding, festooning, and

ripples have been found all across Meridiani Planum, particularly at the Burn’s Cliffs.

Because of festooning the ripples are believed to not be caused by wind.

Ripples are estimated to have been created by shallow water at least 5 cm deep flowing between 10 cm and 50 cm per second.

Problems Beyond Gray Hematite and Goethite, rather exotic

evaporites minerals, there have been no common minerals to support a long-term presence of water.

No salts, gypsum, anhydrite, or carbonates have been detected.

Chemistry seems to have been a strongly acidic and weakly oxidizing and shallow body of water, either as individual bodies or one large body. Presence seems to have been ephemeral.

Conclusions Water seems to have been present on mars at one point, implying

an atmosphere and temperature that could support liquid water as well.

Presence of water seems to have been ephemeral and does not seem to have been present long enough to make deep deposits.

Deposits are all 3.7-4 bya, so water has not existed on the surface for a long time.

Theoretically there could be more water evaporite deposits beneath the surface, but that is unknown at this time.

As a side note, Opportunity is still functioning 3423 Martian days past it’s expected lifetime, or 9.6 Earth years.

Conclusions

Questions?

References http://science1.nasa.gov/media/mediali

brary/2001/03/22/ast28mar_1_resources/tes_hematite_sm.jpg

http://athena.cornell.edu/mars_facts/sb_hematite.html

http://paganpages.org/content/wp-content/uploads/2012/10/Goethite-171990.jpg

http://www.nasa.gov/vision/universe/solarsystem/mer-121304b.html

http://www.psrd.hawaii.edu/Mar03/Meridiani.html

References http://upload.wikimedia.org/wikipedia/c

ommons/d/d8/NASA_Mars_Rover.jpg http://science1.nasa.gov/science-news/

science-at-nasa/2008/21nov_plasmoids/

http://www.nasa.gov/vision/universe/solarsystem/Mars-more-water-clues.html

http://www.fas.org/irp/imint/docs/rst/Sect19/Sect19_13b.html