Viking Landers - There was a high proportion of Fe and S,...

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Viking Landers The Viking Landers gave us our first detailed view of the surface. Viking 1 landed in volcanic terrain in the Chryse region. It was broken and blocky terrain with signs of faulting and impacts, with weathering by formation of a Ferric Oxide stain and iron- bearing clays. There were drifts of fine grain dust over much of the landscape. Viking 2 landed near the crater Mie in Utopia Planitia in the outskirts of the ejecta debris. The area was flat and rich in wind-transported sediments. There was a moderately dense and uniform coating of boulders of about 1m in width. Most rocks were vesiculated (i.e. filled with voids) which could be due to gas bubbles in volcanic extruded lava or solvent extraction of water- soluble components. There were clods of dust, loosely cemented, and thin sheets of apparent "duricrust" held together by a chemical sediment such as calcium sulphate (whicih also forms a cement in terrestrial deserts).
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Unformatted text preview: There was a high proportion of Fe and S, the latter some 10-100 times that found in terrestrial rocks. There was some Ca, Al and Si with small amounts of Ti. There was a high Ca:K. There was a high Ca:K ratio. The overal suggestion was of 80% iron-rich clays, 10% Mg 2 SO 4 and 5% each of calcite and higher oxides of iron like haemetite, goethite and maghemite. The material was not dissimilar to what was seen in CI chondrites. The water content was unresolved, but the presence of Goethite is interesting as it is unstable on the surface at daytime and undergoes the reaction 2 FeOOH => Fe 2 O 3 + H 2 O, i.e. it turns into haemetite. Infra-red spectroscopy of the surface suggests the presence of limonite, a mixture of goethite and haemetite, and it has been suggested that this what gives Mars its red colour. There may only be a fraction of this in the surface material, though....
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