Multiple Aqueous Events in the Nakhlite Meteorite North West Africa (NWA)

Geological records suggest the past existence of abundant water flowing freely on Mars’ surface. Most of this aqueous activity appears to have been restricted to early Mars and although aqueous alteration by thin films of water or acid fog may still occur today, evidence suggests that liquid water has not existed at the surface for the last 3 Ga [1]. The Nakhlites, which are 1.3 Ga old Martian meteorites, contain mineralogical proof for the existence of liquid water within the shallow Martian crust duting the Amazonian [2]. To understand the nature of the water-rich fluids and conditions responsible for aqueous alteration on Mars, thorough characterization of chemical and mineralogical changes resulting from aqueous processes is essential.<p></p> The Nakhlite meteorite North West Africa (NWA) 817 was discovered in the Saharan desert (Morocco) as a single stone of 104g by meteorite hunters in 2000 [4]. In common with most other Nakhlite meteorites, NWA 817 presents mineralogical evidence of interactions with low temperature water-bearing fluids on Mars [5]. Here, we present a petrological and chemical reinvestigation of the alteration products of NWA 817. Our study reveals evidence for multiple fluid infiltrations in Mars subsurface during the Amazonian.<p></p&gt

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

No abstract available

Secondary Minerals in the Nakhlite Meteorite Yamato 000593: Distinguishing Martian from Terrestrial Alteration Products

The nakhlites are olivine-bearing clinopyroxenites that formed in a Martian lava flow or shallow intrusion 1.3 Ga ago [1, 2]. They are scientifically extremely valuable because they interacted with water-bearing fluids on Mars [3]. Fluid-rock interactions led to the precipitation of secondary minerals, many of which are hydrous. The secondary minerals consist in a mixture of poorly crystalline smectitic material and Fe-oxide, collectively called “iddingsite”, but also carbonate and sulphate [4]. The proportion, chemistry and habit of the secondary minerals vary between members of the Nakhlite group, which is thought to reflect compositional variation of the fluid within the Martian crust [5]. However, some secondary minerals are quite similar to terrestrial alteration products and thus the chemical and textural variations could also reflect terrestrial contamination (deposition or exchange). Identifying the origin of the secondary minerals is not straightforward but essential to unravel the Martian fluid chemistry and conditions.<p></p> Yamato 000593 (Y-000593) is a nakhlite meteorite that was discovered in Antarctica near the Yamato Mountains by the Japanesse Antarctic Research Expedition in 2000-2001 [6]. Most of the meteorite is covered by a black shiny fusion crust but it also has deep erosion features in its underside that probably formed by freeze- thaw cycles. As in most other Nakhlites, Y 000593 contains iddingsite-like alteration products believed to have been formed on Mars because they have devolatilization features at the vicinity of the fusion crust [7]. Additional evidence of Martian aqueous alteration is the presence of laihunite, a high temperature oxidative alteration product of fayalitic olivine [8].<p></p> The secondary minerals in Y-000593 can provide a powerful insight into the Martian hydrosphere from high to low temperature environments with implications for the origin, cycling, and availability of water on Mars. However, it is highly likely that some secondary minerals have formed on Earth which can biased our understanding of the Martian groundwater chemistry. With this in mind, we are trying to identify all the different secondary minerals and document their spatial and textural relations, their mineralogy and chemistry to better constrain their possible origin and the impact that terrestrial fluids may have had on the Martian alteration products.<p></p&gt

The nakhlite meteorites provide evidence for mineralization of martian CO2 by carbonation of silicates

Evidence from the Lafayette meteorite shows that carbon dioxide could have been sequestered very effectively from the martian atmosphere by mineral carbonation

Formation of iddingsite veins in the martian crust by centripetal replacement of olivine: evidence from the nakhlite meteorite Lafayette

The Lafayette meteorite is an olivine clinopyroxenite that crystallized on Mars ∼1300 million years ago within a lava flow or shallow sill. Liquid water entered this igneous rock ∼700 million years later to produce a suite of secondary minerals, collectively called ‘iddingsite’, that occur as veins within grains of augite and olivine. The deuterium/hydrogen ratio of water within these secondary minerals shows that the aqueous solutions were sourced from one or more near-surface reservoirs. Several petrographically distinct types of veins can be recognised by differences in their width, shape, and crystallographic orientation. Augite and olivine both contain veins of a very fine grained hydrous Fe- and Mg-rich silicate that are ∼1-2 micrometres in width and lack any preferred crystallographic orientation. These narrow veins formed by cementation of pore spaces that had been opened by fracturing and probably in response to shock. The subset of olivine-hosted veins whose axes lie parallel to (001) have serrated walls, and formed by widening of the narrow veins by interface coupled dissolution-precipitation. Widening started by replacement of the walls of the narrow precursor veins by Fe-Mg silicate, and a crystallographic control on the trajectory of the dissolution-precipitation front created micrometre-scale {111} serrations. The walls of many of the finely serrated veins were subsequently replaced by siderite, and the solutions responsible for carbonation of olivine also partially recrystallized the Fe-Mg silicate. Smectite was the last mineral to form and grew by replacement of siderite. This mineralization sequence shows that Lafayette was exposed to two discrete pulses of aqueous solutions, the first of which formed the Fe-Mg silicate, and the second mediated replacement of vein walls by siderite and smectite. The similarity in size, shape and crystallographic orientation of iddingsite veins in the Lafayette meteorite and in terrestrial basalts demonstrates a common microstructural control on water-mineral interaction between Mars and Earth, and indicates that prior shock deformation was not a prerequisite for aqueous alteration of the martian crust

Ephemeral Nebular Components in the Mildly Aqueously Altered CM Carbonaceous Chondrite LEW 85311

No abstract available

Cooling of the H Chondrite Parent Body: Examination and Assessment of 40Ar/39Ar Age Data

No abstract available

Shock Metamorphism in Impact Melt Rocks from the Gow Lake Impact Structure, Saskatchewan, Canada

Meteorite impact craters are the dominant surface feature on most terrestrial planetary bodies [1] and are gathering increased interest with the continued exploration of the Solar System. It is worth, then, taking a fresh look at impact craters on Earth, in particular those which have not yet been studied in great detail, like Gow Lake, in order to see if new techniques will shed light on some of the remaining questions about them

Evidence for Widespread Post-Hydration Heating of the CM Carbonaceous Chondrites

No abstract available