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TOPIC: Mars geology


L

Posts: 131433
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Tectonic signatures at Aeolis Mensae
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Tectonic transition zone, Aeolis Mensae
Tectonic transition zone, Aeolis Mensae

The High Resolution Stereo Camera (HRSC) on board Mars Express has provided snapshots of the Aeolis Mensae region. This area, well known for its wind-eroded features, lies on a tectonic transition zone, characterised by incised valleys and unexplained linear features.
Illuminated by the Sun from the west (right side in the image), the pictures are of a ground resolution of approximately 13 metres per pixel. The region, imaged on 26 and 29 March 2007, during Mars Express orbits 4136 and 4247, is located at approximately 6° South and 145° East.

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-- Edited by Blobrana at 12:24, 2007-07-01

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RE: Mars geology
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Oxidants from Pulverised Minerals
--- Laboratory measurements of hydrogen peroxide produced from crushed basaltic minerals immersed in water have important implications for Martian and lunar dust.
Joel Hurowitz (previously at State University of New York at Stony Brook and now at the Jet Propulsion Laboratory), Nick Tosca, Scott McLennan, and Martin Schoonen (SUNY at Stony Brook) studied the production of hydrogen peroxide (H2O2) from freshly pulverised minerals in solution. Their experiments focused on olivine, augite, and labradorite; silicate minerals of basaltic planetary surfaces, such as the Moon and Mars, that are exposed to the intense crushing and grinding of impact cratering processes. The H2O2 produced in the experiments was enough to adequately explain the oxidising nature of Martian regolith first determined by the Viking Landers and the results suggest, for the first time, that mechanically activated mineral surfaces may be an important part of the overall explanation for the Viking Lander biology experiment results. Hurowitz and coauthors further showed that when the pulverised minerals are heat-treated to high temperature under vacuum (to cause dehydroxylation) there is almost a 20 times increase in H2O2 production, a result which may be highly relevant to lunar dust. These careful studies demonstrate the importance of and concern about reactive dusts on planetary surfaces from two standpoints: the health of astronauts on surface manoeuvres who may inadvertently breath it and the viability of possible Martian organic species to survive in such a corrosive, antiseptic surface environment.

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Home Plate
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A plateau on Mars known as Home Plate shows evidence of long-past explosive volcanic activity, say scientists on NASA's Mars Exploration Rover mission. And data collected during the rover Spirit's initial pass across the 90-meter (295 feet) wide plateau also supports earlier findings indicating that water once existed at or beneath the planet's surface.

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NASA's Mars Exploration Rover Spirit has discovered evidence of an ancient volcanic explosion at "Home Plate," a plateau of layered bedrock approximately 2 metres high within the "Inner Basin" of Columbia Hills, at the rover's landing site in Gusev Crater. This is the first explosive volcanic deposit identified with a high degree of confidence by Spirit or its twin, Opportunity.
There is strong evidence that those layers are from a volcanic explosion, said Steve Squyres of Cornell University, Ithaca, N.Y. Squyres is principal investigator for the rovers' science instruments. The findings about volcanic activity are reported in a paper published in the May 4 issue of the journal Science.

homeplatebombsag
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The lower coarse-grained unit shows granular textures toward the bottom of the image and massive textures. Also shown in this false-colour view is a feature interpreted to be a "bomb sag," which is 4 centimetres across.
Image Credit: NASA/JPL-Caltech/USGS/Cornell

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RE: Mars geology
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Home Plate, a light-coloured feature in Mars's Gusev Crater, was likely formed by explosive volcanic eruptions, NASA's Spirit rover reveals. It is the first sign of such violent activity yet found on the planet.
Explosive volcanic events, known as pyroclastic eruptions, typically occur with a kind of lava that is high in silicates. But Mars appears to have only basaltic lava, which normally oozes relatively slowly.

"It's hard to get basaltic lava to explode.  The best way to get it to go boom on Earth is to have it come into contact with water" - Steve Squyres, rover chief scientist of Cornell University in New York, US.

Other evidence had already indicated that water was once present in the soil in Gusev. So it makes sense that lava may have come into contact with groundwater, which flashed into vapour and caused the explosive eruption.

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The impact of a giant asteroid could explain why Mars has two very different faces – but only if it struck the planet with a glancing blow, computer simulations suggest.
A longstanding puzzle about Mars is why its northern and southern hemispheres are so different. The northern hemisphere is much flatter and lies lower than the southern hemisphere, with a difference in elevation between the two of about 5 kilometres.
In the 1980s, scientists suggested a giant impact by an asteroid about 300 kilometres across in Mars's early history could have led to a permanent depression in the planet's northern hemisphere.
Now, two teams of scientists have created the first computer simulations testing whether such an impact could have produced the observed differences.

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dn11387_560
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Tooting Crater
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This fresh 29 kilometres wide Martian impact, called Tooting Crater, is located on a flat expanse of young lava flows west of Olympus Mons. The crater is named after a suburb in London.
Lava floods have not covered this craters indicating that the crater's age may be measured in only hundreds of thousands of years.
The crater has a two-level interior floor and a radial pattern of ejecta that is unexpectedly thin.

tootingcrater
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Credit NASA

This mosaic of the crater was taken at visible wavelengths by the Thermal Emission Imaging System (THEMIS), a multi-band camera on NASA's Mars Odyssey orbiter.

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L

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RE: Mars geology
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Mars is showing scientists its older, craggier face buried beneath the surface, thanks to a pioneering sounding radar co-sponsored by NASA aboard the European Space Agency's Mars Express orbiter.
Observations by the first project to explore a planet by sounding radar strongly suggest that ancient impact craters lie buried beneath the smooth, low plains of Mars' northern hemisphere. The technique uses echoes of waves that have penetrated below the surface.

"It's almost like having X-ray vision. Besides finding previously unknown impact basins, we've also confirmed that some of the subtle topographic depressions mapped previously in the lowlands are related to impact features" - Dr. Thomas R. Watters of the National Air and Space Museum's Centre for Earth and Planetary Studies, Washington.

Studies of how Mars evolved aid understanding of early Earth. Some signs of the forces at work a few billion years ago are more evident on Mars because, on Earth, many of them have been obliterated during Earth's more active resurfacing by tectonic activity.

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Layers on Mars are yielding history lessons revealed by instruments flying overhead and rolling across the surface.
Some of the first radar and imaging results from NASA's newest Mars spacecraft, the Mars Reconnaissance Orbiter, show details in layers of ice-rich deposits near the poles. Observed variations in the layers' thickness and composition will yield information about recent climate cycles on the red planet.
NASA's Mars Exploration Rover Opportunity has photographed patterns in the layering of crater-wall cliffs that are the clearest evidence of ancient sand dunes the rover has seen since arriving at Mars nearly three years ago. The science team for Opportunity's twin, Spirit, is using new orbital images of the rover's surroundings to interpret how some rocks with minerals altered by water fit into the area's complex layered structure.

"The combination of instruments on Mars Reconnaissance Orbiter is such a great advantage" - Dr. Jack Mustard of Brown University, Providence, R.I. He is deputy principal investigator for the Compact Reconnaissance Imaging Spectrometer for Mars, a mineral-identifying instrument on Mars Reconnaissance Orbiter.

Researchers are using mineral information from analyses of spectrometer observations, combined with images from the orbiter's High Resolution Imaging Science Experiment, to seek the source of the mineral gypsum in dunes near the Martian north pole and clay minerals elsewhere. Gypsum and clay minerals are indicators of formerly wet conditions.

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Martian soils
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Despite being separated by thousands of kilometres, Martian soils from Gusev Crater and Meridiani Planum have proved broadly similar in parts--rich in chlorine and sulphur. Recent high-precision measurements have shown that phosphorus--the critical energy carrier in all known forms of Earth life--is equally abundant in such patches of Martian dirt. And the only explanation for such similar soils in disparate locations is a large, acidic ocean, according to a new paper published today in the November issue of Geology.

Geologists James Greenwood of Wesleyan University and Ruth Blake of Yale University examined various explanations for the similar soils sampled by both Mars Rovers as well as at the two Viking and the Mars Pathfinder landing sites. Each contains at least some so-called bright dust or soil that has proved to contain much sulphur, chlorine and phosphorus along with the typical ferric oxide that gives Mars its red tinge. The researchers examined Martian meteorites here on Earth to determine that the sulphur and chlorine likely resulted from ancient volcanic explosions.

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