* Astronomy

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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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.


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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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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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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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