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Decades of speculation about a warmer, wetter Mars climate in the planet's first billion years postulate a denser C[O.sub.2]-rich atmosphere than at present. Such an atmosphere should have led to the formation of outcrops rich in carbonate minerals, for which evidence has been sparse. Using the Mars Exploration Rover Spirit, we have now identified outcrops rich in magnesium-iron carbonate (16 to 34 weight percent) in the Columbia Hills of Gusev crater. Its composition approximates the average composition of the carbonate globules in martian meteorite ALH 84001. The Gusev carbonate probably precipitated from carbonate-bearing solutions under hydrothermal conditions at near-neutral pH in association with volcanic activity during the Noachian era. 10.1126/science.1189667

Author(s): Walter Goetz (corresponding author) [1]; Preben Bertelsen [2]; Charlotte S. Binau [2]; Haraldur P. Gunnlaugsson [3]; Stubbe F. Hviid [1]; Kjartan M. Kinch [3]; Daniel E. Madsen [2]; Morten [...]

Author(s): Larry A. Haskin [1, 18]; Alian Wang (corresponding author) [1]; Bradley L. Jolliff [1]; Harry Y. McSween [2]; Benton C. Clark [3]; David J. Des Marais [4]; Scott M. [...]

Author(s): Albert S. Yen (corresponding author) [1]; Ralf Gellert [2]; Christian Schröder [3]; Richard V. Morris [4]; James F. Bell, III [5]; Amy T. Knudson [6]; Benton C. Clark [7]; [...]

Calculating magnetic hysteresis loops by means of classical spin dynamic methods is a computationally challenging task. To reduce the computing time, we have developed a method that divides the complete hysteresis cycle into intervals. These intervals can be calculated in parallel leading to a significant speedup. We have applied our method to two different examples: first, the switchable exchange bias system Co/ $\alpha $ -Cr2O3 with perpendicular magnetization and second, a single layer CoFe(B) as part of a magnetic spin valve system. However, our approach can be applied to other spin systems, even with finite temperatures. [ABSTRACT FROM AUTHOR]

Magnetoresistive sensor devices can be developed in the form of magnetic multilayer systems or on the basis of magnetic nanoparticles or beads that are immersed in a nonmagnetic matrix. Using a conductive gel matrix with a liquid–solid transition, printable low-cost sensor systems can be developed. While in the liquid state of the gel, the magnetoresistive properties can be adjusted by structuring the magnetic particles by means of an external magnetic field. Then, the optimized properties are preserved in the solid state of the gel. In order to design sensor devices, numerical investigation is an essential tool. Here, we present a hybrid approach that involves classical spin dynamics and molecular dynamics simulations. By this means, detailed information about the structuring process of interacting magnetic particles can be obtained. Furthermore, it can be concluded with the magnetoresistive properties from the resulting magnetization curves. [ABSTRACT FROM AUTHOR]

Author(s): Albert S. Yen; Ralf Gellert; Christian Schröder; Richard V. Morris; James F. Bell, III; Amy T. Knudson; Benton C. Clark; Douglas W. Ming; Joy A. Crisp; Raymond E. Arvidson; [...]

Editors' notes: [ABSTRACT FROM AUTHOR]

Sedimentary rocks exposed in the Meridiani Planum region of Mars record aqueous and eolian deposition in ancient dune and interdune playa-like environments that were arid, acidic, and oxidizing. On Earth, microbial populations have repeatedly adapted to low pH and both episodic and chronic water limitation, suggesting that, to a first approximation, the Meridiani plain may have been habitable during at least part of the interval when deposition and early diagenesis took place. On the other hand, the environmental conditions inferred for Meridiani deposition would have posed a challenge for prebiotic chemical reactions thought to have played a role in the origin of life on Earth. Orbital observations suggest that the combination of sulfate minerals and hematite found in Meridiani rocks may be unusual on the martian surface; however, there is reason to believe that acidity, aridity, and oxidizing conditions were broadly distributed on ancient Mars. When these conditions were established and how much environmental heterogeneity existed on early Mars remain to be determined. Because sulfates and iron oxides can preserve detailed geochemical records of environmental history as well as chemical, textural and microfossil signatures of biological activity, Meridiani Planum is an attractive candidate for Mars sample return., Organismic and Evolutionary Biology