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The nakhlite hydrothermal brine on Mars

Bridges, J. C. and Schwenzer, S. P. (2013). The nakhlite hydrothermal brine on Mars. In: The 3rd UK in Aurora Meeting: Advances in Mars Research, 8 Feb 2013, London, UK.

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Abstract

On the basis of ongoing mineralogical characterisation of the nakhlite secondary minerals (Changela and Bridges, 2010; Hicks et al. this meeting) by HR-TEM and X-ray Absorption Spectroscopy we apply thermochemical modelling to determine the fluid composition, temperature and redox conditions of the water. We show that the nakhlite parent rocks on Mars encountered a CO2-rich hydrothermal fluid at 150 ≤ T ≤ 200 °C, pH 6–8 with a water:rock ratio (W/R) ≤300 (Bridges and Schwenzer, 2012). Under these conditions, Fe-rich carbonate was precipitated within brittle fractures. As the fluid cooled to 50 °C, at pH 9 and W/R of 6, Fe-rich phyllosilicate precipitated, followed in turn by rapid precipitation of an amorphous gel. It was enriched in the most soluble species (e.g. K, Na), of alkaline pH, and similar to terrestrial, i.e. not seawater-influenced, dilute brines in basaltic terrains on Earth. Our results show that environments associated with this type of fluid were habitable, unlike those associated with acid-sulphate fluids. Considering the timing of the nakhlite alteration, the most likely cause is impact-generated hydrothermal alteration of the nakhlite pile at the margins of an impact crater. The martian subsurface fluid forming phyllosilicates provided habitable temperatures and many of the nutrients required for life.

Item Type: Conference or Workshop Item
Copyright Holders: 2013 The Authors
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Space
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Item ID: 37357
Depositing User: Susanne Schwenzer
Date Deposited: 10 Apr 2013 09:21
Last Modified: 07 Dec 2018 10:15
URI: http://oro.open.ac.uk/id/eprint/37357
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