Geochemical models of secondary mineral precipitation on Mars generally assume semiopen systems (open to the atmosphere but closed at the water-sediment interface) and equilibrium conditions. However, in natural multicomponent systems, the reactive surface area of primary minerals controls the dissolution rate and affects the precipitation sequences of secondary phases, and simultaneously, the ...

The Lemoine tailings of Chibougamau, Quebec, Canada, were deposited as a pH-neutral mineral conglomerate consisting of aluminum-silicates, iron-aluminum-silicates, pyrite, chalcopyrite, and sphalerite. These tailings are colonized by an active population of Thiobacillus ferrooxidans which is localized to an acid zone occupying 40% of the tailings' surface. This population peaked at 7 x 10 most ...

The value of surface complexation modeling of radionuclide adsorption in supporting the selection of KI values should be given wider recognition within the performance assessment modeling process. Studies of uranium(Vl) adsorption by a weathered schist and specimen mineral phases that comprise the schist were conducted as a function of aqueous chemical conditions in laboratory experiments. The ...

AIM The aim of this study was to evaluate the surface/mineral changes on enamel before and after the application of acidulated phosphate fluoride (APF) gel, fluoride enhanced hydroxyapatite gel and propolis in conjunction with carbon-dioxide (CO2) laser. MATERIALS AND METHODS Crowns of 40 human maxillary central incisors were collected and were divided into four groups of 10 each: Topical flu...

Uranium (U) poses a significant contamination hazard to soils, sediments, and groundwater due to its extensive use for energy production. Despite advances in modeling the risks of this toxic and radioactive element, lack of information about the mechanisms controlling U transport hinders further improvements, particularly in reducing environments where U(IV) predominates. Here we establish that...

Introduction: Volcanic and hydrothermal supply of reducing gases to the early atmosphere of Mars likely surpassed the slow supply of oxidizing power from hydrogen escape to space, resulting in a neutral or mildly reducing atmosphere and in geochemical cycles that operated very differently than they do on the modern Earth. We have recently suggested that one such difference between the modern an...

There is no consensus as yet to account for the significant presence of water on the terrestrial planets, but suggested sources include direct hydrogen adsorption from the parent molecular cloud after the planets' formation, and delivery of hydrous material via comets or asteroids external to the zone of the terrestrial planets. Alternatively, a more recent idea is that water may have directly ...

Large quantities of clay minerals (and other micron-sized mineral powders) are used widely in materials science. Mineral fillers are major components, for example, of paints, rubber, plastics and paper and board. While the original object of such incorporation was to reduce costs, performance is now being "engineered" by design or choice of the relevant mineral particles. This paper concentrate...

Over the last decades, significant advances have been made in the study of adsorption processes at mineral–water interfaces. In particular, surface-enhanced infrared (IR) techniques, and, more recently, non-linear vibrational sum-frequency spectroscopy have provided novel insights into the structure and dynamics of these interfaces. The driving forces behind adsorption at mineral substrates are...

Introduction: In-depth analysis of evaporitic sediments at Meridiani Planum by the Opportunity Rover has highlighted the importance of fluid evaporation at the martian surface [1]. Previous work aimed at understanding the controls on evaporation and the resulting mineral assemblages has been largely theoretical [2]. Some recent experimental work has focused on evaporite minerals at the martian ...