Second MPSE Workshop Warsaw, 3-5 June WROONA Group, Institute of Geological Sciences PAS, Wrocław, Poland 2 Space Research Centre PAS, Warsaw, Poland 3 Laboratoire de Planétologie et Géodynamique, Université de Nantes, France 4 Institute of Geological Sciences, University of Wrocław, Poland Joanna GURGUREWICZ 1,2, Daniel MEGE 1,3, Véronique CARRERE 3, Anne GAUDIN 3, Joanna KOSTYLEW 4, Yann MORIZET 3, Marta SKIŚCIM 1 Alteration on Mars: study of near-infrared spectra of terrestrial basalts altered in contrasted climate conditions

Second MPSE Workshop Alteration on Mars Gurgurewicz et al CLIMATE ON MARS Evolution of the Martian obliquity in the past 10 Myr. The main obliquity periodicity is about 120,000 earth years. Laskar et al Levrard et al. 2004

Mafic rocks are widespread at the surface of Mars: composition of Martian meteorites geomorphology orbital spectroscopic data sets in situ analyses MAFIC ROCKS ON MARS Second MPSE Workshop Alteration on Mars Gurgurewicz et al Total alkalis-silica diagram used for classification of volcanic rocks. Gusev RAT-ground and RAT- brushed compositions for the same rocks are connected by tie- lines. Analyses of Gusev rocks and soils, martian meteorites, and global GRS data (calculated on a volatile-free basis) indicate a crust dominated by basalts. TES- derived data and possibly the Mars Pathfinder rock composition may reflect alteration. McSween et al. 2009

Mustard et al., 2008 Mustard et al ALTERATION ON MARS Second MPSE Workshop Alteration on Mars Gurgurewicz et al Can information on the Martian environmental conditions prevailing during the alteration of its basaltic crust be inferred from data collected during space missions?

TERRESTRIAL ANALOGUES The studied basalts are located in the Udokan area of Siberia, and in the Ogaden region of southeast Ethiopia. Location of the Udokan volcanic field and Ogaden basalts. The dark patches are the volcanic exposures. The sampling sites are shown by circles: U – Udokan volcanic field; G – Gode; KD – Kebri Dehar; W – Werder. Photomicrographs of representative basalts samples from Udokan (a) and Ogaden (b). The phenocrysts include mainly plagioclase and iddingsitized olivine. Polarizing microscope, plane polarized light. Basaltic analogues used in this study are altered in arid cold and arid hot environments, as well as hot environments in which wet and arid climates occurred successively; any of these conditions may have been representative of the alteration conditions on Mars, present or past. They are alkali basalts, Ti-rich, and have the same mineralogical structure. Second MPSE Workshop Alteration on Mars Gurgurewicz et al

Polarizing microscope ASD FieldSpec® 3 Spectrometer X-ray diffractometer Siemens D5000/D5005 Scanning Electron Microscope JEOL 6400F Labram® Raman spectrometer METHODS Second MPSE Workshop Alteration on Mars Gurgurewicz et al

NEAR-INFRARED SPECTRA IRON-RICH PRIMARY MINERALS CLAYS

CARBONATES Second MPSE Workshop Alteration on Mars Gurgurewicz et al NEAR-INFRARED SPECTRA ZEOLITES IRON HYDROXIDES

Absorption band (µm) Secondary mineral phasesUdokan Ogaden RN01A/BRN02RN03RN04 K1.30K3.1W1.4W2.5 W3.2WS smectites, zeolites●●●● smectites, ferrihydrite, zeolites●●●● ●●●●●● 1.73zeolites●●●● 1.76ferrihydrite, zeolites, calcite●●●● 1.87smectites, zeolites, calcite●●●● ●●●●●● smectites, iddingsite, ferrihydrite, zeolites●●●● ●●●●●● 2.17calcite●●●● ­ 2.19beidellite, zeolites●●●● montmorillonite, zeolites●●●● ●●●●●● 2.30nontronite, zeolites●●●● ●●●●●● 2.34calcite● ● NEAR-INFRARED SPECTRA Absorption bands and corresponding mineral phases due to alteration identified in the Udokan and Ogaden basalt spectra Second MPSE Workshop Alteration on Mars Gurgurewicz et al

NEAR-INFRARED SPECTRA Second MPSE Workshop Alteration on Mars Gurgurewicz et al Reflectance spectra of the Ogaden and Udokan fresh or nearly fresh rock surfaces. The spectra are quite similar, apart from the missing ~1 μm absorption in two of the Udokan basalt spectra.

NEAR-INFRARED SPECTRA Second MPSE Workshop Alteration on Mars Gurgurewicz et al Reflectance spectra of the Ogaden and Udokan basalt alteration rind surfaces. Note the parallel spectra of the Udokan sample RN02 and Ogaden sample K1.30 in the range μm, and the nearly identical spectra of the Udokan sample RN01B and Ogaden sample K3.1 in the range μm. Water absorption band at 1.9 μm is almost always deeper in the Ogaden than in the Udokan basalt spectra, as detailed in the inset, where the band depth is calculated by subtracting from each spectrum a convex continuum hull between 1.88 and 2.13 μm, following the method presented by Morris et al. (1982).

NEAR-INFRARED SPECTRA Second MPSE Workshop Alteration on Mars Gurgurewicz et al Reflectance spectra of the Ogaden and Udokan basalt powders. Several spectral features, that are not apparent in bulk rock spectra, appear. The powder spectra of basalts altered in arid hot environment (Ogaden) show a first-order positive spectral slope in the range μm, whereas spectra of basalts altered in arid cold environment (Udokan) have a first-order negative spectral slope.

CONCLUSIONS & PERSPECTIVES The NIR spectra of the alteration rind surface and the internal part of the bulk samples from cold and hot environment are very similar, suggesting that the NIR spectra of Martian bulk rocks may be of limited help in identifying paleoenvironment conditions. Bulk rock spectra analysis reveals, however, that: (1) spectra of the least altered rocks display clear absorption bands of smectites; (2) the depth of the 1.9 μm water absorption band is not correlated with environmental humidity, possibly due to the weathering effect of groundwater, or to the hydration state of the secondary minerals. Additional compositional information can be retrieved from rock powder spectra: zeolites, which are identified in the Udokan basalt spectra, are indicators of ancient presence of groundwater or hydrothermal water. The presence of calcite and iddingsite is ascertained by other methods, but they are not apparent in bulk rock spectra and only weakly apparent in powder spectra. Although the alteration conditions of the two series of terrestrial basalt samples are very contrasted, analysis of near-infrared spectra could not unequivocally discriminate between them. Other techniques are required for characterization of alteration features in basalts that can accurately infer paleoclimate, and pottentially be used for in situ analysis on Mars. Second MPSE Workshop Alteration on Mars Gurgurewicz et al

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