Chemical divides and evaporite assemblages on Mars

N J Tosca, S M McLennan

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    109 Citations (Scopus)


    Assemblages of evaporite minerals record detailed physical and chemical characteristics of ancient surficial environments. Accordingly, newly discovered regions of saline minerals on Mars are high priority targets for exploration. The chemical divide concept of evaporite mineral formation is used successfully to predict evaporite mineralogy and brine evolution on Earth. However, basaltic weathering largely controls fluid compositions on Mars and the robust predictive capabilities of terrestrial chemical divides cannot be used to interpret Martian evaporites. Here we present a new chemical divide system that predicts evaporite assemblages identified in SNC-type meteorites, ancient evaporites discovered on Meridiani Planum by the Opportunity rover, and Mars Express OMEGA data. We suggest that a common fluid type that has been buffered to different pH levels by basaltic weathering controls the variability among Martian evaporite assemblages and that evaporite mineralogy and brine evolution is essentially established by the initial composition of the dilute evaporating fluid. (c) 2005 Elsevier B.V. All rights reserved.

    Original languageEnglish
    Pages (from-to)21-31
    Number of pages11
    JournalEarth and Planetary Science Letters
    Issue number1-2
    Publication statusPublished - 15 Jan 2006


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