Formation of Berthierine in the Martian Meteorite Nakhla by Replacement Of Aluminosilicate Glass [abstract]

No abstract available

Glassy chondrule mesostasis in EET 96029: a CM3 component of a minimally altered CM2 carbonaceous chondrite

No abstract available

Martian Fluid Evolution Recorded in Smectite from the Northwest Africa (Nwa) 817 Nakhlite Meteorite [abstract]

No abstract available

Impact-generated hydrothermal circulation and metasomatism of the rochechouart astrobleme: mineralogy and major and trace element distribution

The energy released during a hypervelocity impact on Earth can generate high temperatures in the target rock. There are currently 170 known impact structures worldwide, of which over one-third contain fossil hydrothermal systems [1]. Results from the analysis of these hydrothermal systems have many implications for the study of the origin of life on Earth and potential thereof on Mars. Hypervelocity impacts are also of particular economic interest as they may produce, expose or concentrate high commodity resources such as hydrocarbons, precious metals and ore minerals

Impact fracturing and aqueous alteration of the CM carbonaceous chondrites

Aqueous alteration of the CM carbonaceous chondrites has produced a suite of secondary minerals, and differences between meteorites in their abundance defines a progressive alteration sequence [e.g. 1, 2]. The means by which this water gained access to the original anhydrous constituents of the meteorites is the subject of considerable debate. Studies of rock texture, mineralogy and bulk chemical composition have concluded that solutions were generated by the melting of water ice in situ, and remained essentially static as a consequence very low intergranular permeabilities [e.g. 3, 4]. By contrast, results of oxygen isotope work and modelling have suggested that the fluids moved considerable distances within the parent body [5, 6]. Given the intergranular permeability of the CMs, an extensive fracture network would be required to support such flow. Clues to how the two very different models for aqueous alteration of the CMs can be reconciled have been recently provided by Rubin [7]. He recognised a good correlation between the magnitude of impact-induced compaction of CM meteorites and their degree of aqueous processing, with the more highly deformed meteorites being more altered. Here we have asked whether compaction was accompanied by the development of fracture networks that could have provided the conduits for aqueous solutions that mediated all or some of the alteration

Fluid-rock interactions in the Martian meteorite North West Africa 817

No abstract available

Serpentinisation of Chondrules in the Murchison Cm Carbonaceous Chondrite by Centripetal Replacement and Cementation [abstract]

No abstract available

Polarization singularities in the clear sky

Ideas from singularity theory provide a simple account of the pattern of polarization directions in daylight. The singularities (two near the Sun and two near the anti-Sun) are points in the sky where the polarization line pattern has index +1/2 and the intensity of polarization is zero. The singularities are caused by multiple scattering that splits into two each of the unstable index +1 singularities at the Sun and anti-Sun, which occur in the single-dipole scattering (Rayleigh) theory. The polarization lines are contours of an elliptic integral. For the intensity of polarization (unnormalized degree), it is necessary to incorporate the strong depolarizing effect of multiple scattering near the horizon. Singularity theory is compared with new digital images of sky polarization, and gives an excellent description of the pattern of polarization directions. For the intensity of polarization, the theory can reproduce not only the zeros but also subtle variations in the polarization maxima