Glaciovolcanic hydrothermal environments in Iceland and implications for their detection on Mars

C.R Cousins,I.A Crawford,J.L Carrivick,M Gunn,J Harris,T.P Kee,M Karlsson,L Carmody,C Cockell,B Herschy,K.H Joy

doi:10.1016/j.jvolgeores.2013.02.009

Abstract

Volcanism has been a dominant process on Mars, along with a pervasive global cryosphere. Therefore, the interaction between these two is considered likely. Terrestrial glaciovolcanism produces distinctive lithologies and alteration terrains, as well as hydrothermal environments that can be inhabited by microorganisms. Here, we provide a framework for identifying evidence of such glaciovolcanic environments during future Mars exploration, and provide a descriptive reference for active hydrothermal environments to be utilised for future astrobiological studies. Remote sensing data were combined with field observations and sample analysis that included X-ray diffraction, Raman spectroscopy, thin section petrography, scanning electron microscopy, electron dispersive spectrometer analysis, and dissolved water chemistry to characterise samples from two areas of basaltic glaciovolcanism: Askja and Kverkfjöll volcanoes in Iceland. The glaciovolcanic terrain between these volcanoes is characterised by subglacially-erupted fissure swarm ridges, which have since been modified by multiple glacial outburst floods. Active hydrothermal environments at Kverkfjöll include hot springs, anoxic pools, glacial meltwater lakes, and sulphur- and iron-depositing fumaroles, all situated within ice-bound geothermal fields. Temperatures range from 0°C–94.4°C, and aqueous environments are acidic–neutral (pH2–7.5) and sulphate-dominated. Mineralogy of sediments, mineral crusts, and secondary deposits within basalts suggest two types of hydrothermal alteration: a low-temperature (<120°C) assemblage dominated by nanophase palagonite, sulphates (gypsum, jarosite), and iron oxides (goethite, hematite); and a high-temperature (>120°C) assemblage signified by zeolite (heulandite) and quartz. These mineral assemblages are consistent with those identified at the Martian surface. In-situ and laboratory VNIR (440–1000nm) reflectance spectra representative of Mars rover multispectral imaging show sediment spectral profiles to be influenced by Fe2+/3+-bearing minerals, regardless of their dominant bulk mineralogy. Characterising these terrestrial glaciovolcanic deposits can help identify similar processes on Mars, as well as identifying palaeoenvironments that may once have supported and preserved life.

Highlights

Hydrothermal environments driven by volcanism are prime targets for astrobiological exploration on Mars, and have many well-documented terrestrial analogues, e.g. Yellowstone National Park, USA (Bishop et al, 2004; Hellman and Ramsey, 2004; Marion et al, 2011), Cerro Negro volcano, Nicaragua (Hynek et al, 2011), and Iceland (Griffith and Shock, 1997; Nelson et al, 2005; Warner and Farmer, 2010)
This study provides an overview of Askja and Kverkfjöll and their volcanic environments, with a call for these localities to be used as test grounds for future Mars research, from exploring microbiological processes to field-testing Mars rover instrumentation
Field sites were characterised in situ through a combination of field photography, GPS, Visible - Near Infra-Red (VNIR) field spectroscopy, and pH, temperature, dissolved oxygen (DO), and conductivity measurements

Summary

Introduction

Hydrothermal environments driven by volcanism are prime targets for astrobiological exploration on Mars (for a review see Schulze-Makuch et al, 2007), and have many well-documented terrestrial analogues, e.g. Yellowstone National Park, USA (Bishop et al, 2004; Hellman and Ramsey, 2004; Marion et al, 2011), Cerro Negro volcano, Nicaragua (Hynek et al, 2011), and Iceland (Griffith and Shock, 1997; Nelson et al, 2005; Warner and Farmer, 2010). Despite the ubiquity of both volcanism and a widespread cryosphere on Mars, widespread glaciovolcanic terrains have yet to be definitively identified (Keszthelyi et al, 2010). If these two processes have both occurred concurrently, it is a challenge for future exploration to find unequivocal or diagnostic topographic, geomorphological, sedimentological and/or mineralogical evidence of glaciovolcanic interactions. It has been recently proposed that low-albedo sediments covering large areas (> 107 km2) of the northern lowlands of Mars are dominated by basaltic glass (Horgan and Bell, 2012), implying widespread explosive volcanism, such as that found during volcano – ice interaction (Horgan and Bell, 2012). One recent terrestrial example of this process is the 2010 Ejafjallajokull eruption in southern Iceland, which generated large volumes of ash as fine glass particles (Dellino et al, 2012)

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