Use of miniaturized Raman spectrometer for detection of sulfates of different hydration states – Significance for Mars studies Adam Culka, Filip Košek, Petr Drahota, Jan Jehlic ˇka ⇑ Charles University in Prague, Institute of Geochemistry, Mineralogy and Mineral Resources, Albertov 6, 12843 Prague, Czech Republic article info Article history: Received 5 March 2014 Revised 31 July 2014 Accepted 12 August 2014 Available online 23 August 2014 Keywords: Mars Mineralogy Spectroscopy abstract The presence of sulfates of different hydration states, specifically magnesium sulfates, has been firmly established on Mars from data acquired by both orbital and in-situ measurements. A lander mission typically involves a variety of instruments capable of performing a wide range of experiments from min- eralogical tasks to the search for traces of life. It is clear from ongoing research that Raman spectroscopy can cover all of these tasks, and it has already been decided that future mission to Mars will employ a miniature Raman spectrometer. In this paper we report and discuss the Raman spectra of various sulfate minerals, with an emphasis on the magnesium sulfates. These were acquired by a hand-held Raman instrument, using the presently uncommon 532 nm excitation, the wavelength that is planned for the ESA lander mission. A sufficient quality of spectra were obtained with reasonably low spectral acquisition times, and the characteristic shift of the sulfate m 1 band in the MgSO 4 n(H 2 O) minerals was confirmed. This was used for the unambiguous identification of magnesium sulfates of different hydration states. The present testing has confirmed the good performance of the handheld instrumentation for discrimi- nation of structurally similar sulfates of relevance for Mars studies. This step has been proposed as the basis for subsequent testing of this instrumentation under Earth-based but Mars-analogous conditions, even using currently existing miniaturized Raman prototypes. Ó 2014 Elsevier Inc. All rights reserved. 1. Introduction 1.1. Scientific background The chemical and mineralogical properties of the surface and subsurface of Mars have a major significance in any understanding of the processes of rock formation throughout the course of its geologic history. Sedimentary sequences can tell us about the sed- imentation environments, origins of these sedimentary materials, as well as about the potential presence and role of liquid water. The surface of Mars is mostly covered by aeolic layers of dust originating from different rocks. However, what are presumed to be non-aeolic sediments of different types have also been discov- ered on the martian surface (Squyres et al., 2004b); including clay rich layers (Poulet et al., 2005; Bibring et al., 2006) as well as zones of evaporites (Rieder et al., 2004), environments which are fre- quently thought to be formed through accumulation/precipitation in water basins. In a few places, along with sulfates, the presence of zeolites and clay minerals (such as illite and montmorillonite) have also been indicated (Ruff, 2004; Clark et al., 2007; Ehlmann et al., 2009), which will be summarized further in the text. Areas where these minerals and rocks occur are of major interest for deciphering of the paleoalteration processes, as well as for astrobiology. A detailed knowledge of the local mineralogy will permit a reconstruction of the geochemical as well as (potentially) of the biogeochemical processes in the past. This would include redox conditions, evolution over time, as well as basic climatic estimates. The detection and estimates of minerals containing OH and water molecules in the framework of the sedimentary sequences can be considered as the primary task, along with the potential detection of water in all of its different physical states. Several orbital remote-sensing techniques for mineral detection have been applied to obtain rough estimates of the surface distri- butions of minerals (Christensen et al., 2001; Bibring et al., 2004; Murchie et al., 2007). Further analytical tools were included in the rovers operating on the martian surface, or have been proposed for future missions (e.g. Squyres et al., 2003, 2004a). In 1976, the Viking landers discovered sulfur on the martian surface (Clark and Baird, 1977). Other minerals have been identified solely upon the basis of data obtained by the Mars Express (MEX) mission, spe- cifically by its OMEGA instrument (Langevin et al., 2005; Bibring et al., 2006). Additionally, the presence of jarosite was directly http://dx.doi.org/10.1016/j.icarus.2014.08.017 0019-1035/Ó 2014 Elsevier Inc. All rights reserved. ⇑ Corresponding author. E-mail address: jehlicka@natur.cuni.cz (J. Jehlic ˇka). Icarus 243 (2014) 440–453 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus