The Mars Exploration Rover Spirit ended its mission in Gusev crater on sol 2210 after it had become stuck in a deposit of fined-grained and sulfate rich soil with dust covered solar panels unfavorably pointed toward the sun. Final analysis of remaining data from Spirit's Moessbauer spectrometer (Fe redox and mineralogy) for sols 1529 through 2071 is now complete. We focus here on chemical (APXS) and MB data for targets having high-SiO2 or high-SO3 and process link the targets through mixing and geochemical modelling to an acid-sulfate system centered at Home Plate, which is considered to be a hydrovolcanic complex.

Instruments for surface missions to extraterrestrial bodies should be cross-calibrated using a common suite of relevant materials. Such work is necessary to improve instrument performance and aids in the interpretation of in-situ measurements. At the CNRS campus in Orléans, the Observatoire des Sciences de l'Univers en région Centre (OSUC) has created a collection of well-characterised rocks and minerals for testing and calibrating instruments to be flown in space missions. The characteristics of the analogue materials are documented in an accompanying online database. In view of the recent and upcoming rover missions to Mars (NASA's 2011 Mars Science Laboratory (MSL) and ESA/Roscosmos' 2018 ExoMars), we are concentrating initially on materials of direct relevance to the red planet. The initial collection consists of 15 well-studied rock and mineral samples, including a variety of basalts (ultramafic, weathered, silicified, primitive), sediments (volcanic sands, chert, and a banded iron formation –BIF-), and the phyllosilicate nontronite (a clay). All the samples were characterised petrographically, petrologically, and geochemically using the types of analyses likely to be performed during in-situ missions, in particular ExoMars: hand specimen description; optical microscopy; mineralogical analysis by XRD, Raman and IR spectrometry; iron phase analysis by Mössbauer spectroscopy (MBS), elemental analysis by Energy-Dispersive X-ray spectroscopy (EDX), microprobe, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) and Mass Spectrometry (ICP-MS); and reduced carbon analysis by Raman spectrometry.

In order to prepare the next in situ space missions we have created a collection of analogue rocks for calibrating and testing present and future space flight instruments. This collection is called the International Space Analogue Rockstore (ISAR) and is hosted at the CNRS and the Observatoire des Sciences de l’Univers en Region Centre (OSUC), in Orleans, France. In the context of the present MSL mission and to the future ExoMars-2018 mission, the first samples where chosen for their relevance to Mars. These samples are available for calibrating and testing space instrumentation and are now being used by several instruments on ExoMars and MSL. Use of the same suite of samples to calibrate all the instruments of a single mission will greatly increase their complementarity and thus to improve the interpretation of the analyses carried out in situ.

The miniaturized Mössbauer spectrometer MIMOS II was developed for the exploration of planetary surfaces. Two MIMOS II instruments were successfully deployed on the martian surface as payload elements of the NASA Mars Exploration Rover (MER) mission and have returned data since landing in January 2004. Mössbauer spectroscopy has made significant contributions to the success of the MER mission, in particular identification of iron-bearing minerals formed through aqueous weathering processes. As a field-portable instrument and with backscattering geometry, MIMOS II provides an opportunity for non-destructive in-situ investigations for a range of applications. For example, the instrument has been used for analyses of archaeological artifacts, for air pollution studies and for in-field monitoring of green rust formation. A MER-type MIMOS II instrument is part of the payload of the Russian Phobos-Grunt mission, scheduled for launch in November 2011, with the aim of exploring the composition of the martian moon Phobos. An advanced version of the instrument, MIMOS IIA, that incorporates capability for elemental analyses, is currently under development.

AbstractRecently reported results from latest Mars Orbiters and Rovers missions are transforming our opinion about the red planet. That dry and inhospitable planet reported in the past is becoming a wetter planet with high probabilities of water existence in the past. Nowadays, some results seem to indicate the presence of water beneath the Mars surface. But also mineralogy studies by NASA Opportunity Rover report iron oxides and hydroxides precipitates on Endurance Crater. Sedimentary deposits have been identified at Meridiani Planum. These deposits must have generated in a dune aqueous acidic and oxidizing environment. Similarities appear when we study Rio Tinto, and acidic river under the control of iron.The discovery of extremophiles on Earth widened the window of possibilities for life to develop in the Universe, and as a consequence on Mars and other planetary bodies with astrobiological interest. The compilation of data produced by the ongoing missions offers an interested view for life possibilities to exist: signs of an early wet Mars and rather recent volcanic activity as well as ground morphological characteristics that seem to be promoted by liquid water. The discovery of important accumulations of sulfates and the existence of iron minerals such as jarosite in rocks of sedimentary origin has allowed specific terrestrial models to come into focus. Río Tinto (Southwestern Spain, Iberian Pyritic Belt) is an extreme acidic environment, product of the chemolithotrophic activity of micro-organisms that thrive in the massive pyrite-rich deposits of the Iberian Pyritic Belt. Some particular protective environments should house the organic molecules and bacterial life forms in harsh environments such as Mars surface supporting microniches inside precipitated minerals or inside rocks. Terrestrial analogues could help us to afford the comprehension of habitability (on other planetary bodies).We are reporting here the multidisciplinary study of some endolithic niches inside salt deposits used by phototrophs for taking advantage of sheltering particular light wavelengths. These acidic salts deposits located in Río Tinto shelter life forms that are difficult to visualize by eye. This interdisciplinary field analogue campaign was conducted in the framework of the CAREX FP7 EC programme.

Introduction: The NASA Mars Exploration Rovers (MER) Spirit and Opportunity landed on Mars in 2004, Spirit at site A (Gusev Crater) and Opportunity at site B (Meridiani Planum), 180 degrees apart. They have now been working for more than 6 and 7 terrestrial years, respectively. Numerous soils were investigated by the two rovers along their 7 and 25 kilometers long traverses, respectively. In-situ measurements were made on undisturbed soils (SU) and soils disturbed by rover wheels (SD) using the Alpha Particle X-ray Spectrometer (APXS) to determine their chemical composition [1] and the Mössbauer Spectrometer (MB) to provide data on their iron mineralogy [2]. The Microscopic Imager (MI) provided information on the texture of the soils. These and images by the Panoramic Camera and data from the Mini-TES are reported elsewhere. The martian soils are surficial deposits that are formed by a variety of geological processes, such as impacts, weathering, volcanic activities, aeolian and subsurface processes [3, 4]. Data: The Mg/Si versus Al/Si ratios of most of the soil samples fall in a relatively small field except for a few samples (Fig. 1) indicating similar chemical compositions of the soils at both landing sites. The B soils have somewhat lower ratios than the A soils (see blue oval). Some SD soils deviate very much from the “parent cluster”, which are those soils that were modified by special aqueous processes in the subsurface [1] and, hence, show strong enrichments of one or more of the elements Mg, Si, P, S, or Cl (not shown here). In general, site B soils have higher Fe concentrations compared to site A ones. The compositions of the SU and SD soils are mainly a product of weathering of rocks, formation of grains, and subsequent transportation of dust. Saltation of sand is an effective means for raising dust into the atmosphere under wind speeds, which would otherwise be too low for grain transport [5]. Thus, large areas can be the source of saltating sand, which gradually averages the soil composition of a whole region. Interestingly enough, regional averaging of site A and B produces similar soil compositions in spite the fact that they are located on opposite sides of the martian globe. APXS and Mössbauer data revealed the occurrence of iron-rich spherules, also called blueberries [1, 6]. Iron/Mn concentration ratios act as planetary fingerprints as long as Fe is dominantly Fe. In Fig. 2, Fe/Mn ratios are compared with hematite contents determined at different Meridiani locations, such as outcrops, soils, and rocks. The mean of shergottites and normal Gusev soils may indicate the global variation of Fe/Mn ratios varying between 40 and 50. Samples with many spherules in the field of view of APXS and MB have high Fe/Mn ratios (enrichment of Fe, only) and high hematite contents. However, in Meridiani outcrop samples the Fe/Mn ratios are comparable to the global mean value, while their hematite contents are elevated (though no spherules in the field of view). This points to the fact that formation of the hematite in the outcrops did not involve differential movement of Fe and Mn ions, except for formation of spherules.

Meridiani Planum is the first officially recognized meteorite find on the surface of Mars. It was discovered at and named after the landing site of the Mars Exploration Rover Opportunity. Based on its composition, it was classified as a IAB complex iron meteorite. Mossbauer spectra obtained by Opportunity are dominated by kamacite (alpha-Fe-Ni) and exhibit a small contribution of ferric oxide. Several small features in the spectra have been neglected to date. To shed more light on these features, five iron meteorite specimens were investigated as analogs to Meridiani Planum with a laboratory Mossbauer setup. Measurements were performed on (1) their metallic bulk, (2) troilite (FeS) inclusions, (3) cohenite ((Fe,Ni,Co)(3)C) and schreibersite ((Fe,Ni)(3)P), and (4) corroded rims. In addition to these room-temperature measurements, a specimen from the Mundrabilla IAB-ungrouped meteorite was measured at Mars-equivalent temperatures. Based on these measurements, the features in Meridiani Planum spectra can be explained with the presence of small amounts of schreibersite and/or cohenite and iron oxides. The iron oxides can be attributed to a previously reported coating on Meridiani Planum. Their presence indicates weathering through the interaction of the meteorite with small amounts of water.

IRON METEORITES FOUND BY THE OPPORTUNITY ROVER AND THEIR IMPLICATIONS FOR MARTIAN WEATHERING PROCESSES J.W. Ashley, M.P. Golombek, P.R. Christensen, S.W. Squyres, T.J. McCoy, C. Schroder, I. Fleischer, J.R. Johnson, K.E. Herkenhoff, T.J. Parker. Mars Space Flight Facility, Arizona State University. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. Department of Astronomy, Cornell University, Ithaca, NY, USA. Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA. Center for Applied Geoscience, Eberhard Karls University, Tubingen, Germany. Institut fur Anorganische und Analytische Chemie, Johannes Gutenberg-Universitat, Mainz, Germany. Astrogeology Science Center, U. S. Geological Survey, Flagstaff, AZ, USA. E-mail: james.ashley@ser.asu.edu.

Iron occurs naturally as Fe2+, Fe3+, and, to a lesser extent, as Fe-0. Many fundamental (bio)geochemical processes are based on redox cycling between these oxidation states. Mossbauer spectroscopy provides quantitative information about the distribution of Fe among its oxidation states, identification of Fe-bearing phases, and relative distribution of Fe among those phases. Portable, miniaturised Mossbauer spectrometers were developed for NASA's Mars Exploration Rovers (in operation since 2004) and provide a means for non-destructive, in-situ field investigations. On Mars, these instruments provided evidence for aqueous activity with implications for habitability, were applied in geological mapping of the landing sites, and helped to identify meteorites, for example. On Earth, they were used in field studies of green rust, the identification of air pollution sources, or the study of archaeological artefacts. Their application to in-situ resource utilisation (ISRU) on the Moon has been demonstrated in a recent NASA field test of hardware for oxygen production. A new detector system in an advanced version of these instruments is based on Si Drift Detectors and permits the simultaneous acquisition of X-ray fluorescence spectra to determine elemental compositions.

Opportunity has been traversing the Meridiani plains since 25 January 2004 (sol 1), acquiring numerous observations of the atmosphere, soils, and rocks. This paper provides an overview of key discoveries between sols 511 and 2300, complementing earlier papers covering results from the initial phases of the mission. Key new results include (1) atmospheric argon measurements that demonstrate the importance of atmospheric transport to and from the winter carbon dioxide polar ice caps; (2) observations showing that aeolian ripples covering the plains were generated by easterly winds during an epoch with enhanced Hadley cell circulation; (3) the discovery and characterization of cobbles and boulders that include iron and stony-iron meteorites and Martian impact ejecta; (4) measurements of wall rock strata within Erebus and Victoria craters that provide compelling evidence of formation by aeolian sand deposition, with local reworking within ephemeral lakes; (5) determination that the stratigraphy exposed in the walls of Victoria and Endurance craters show an enrichment of chlorine and depletion of magnesium and sulfur with increasing depth. This result implies that regional-scale aqueous alteration took place before formation of these craters. Most recently, Opportunity has been traversing toward the ancient Endeavour crater. Orbital data show that clay minerals are exposed on its rim. Hydrated sulfate minerals are exposed in plains rocks adjacent to the rim, unlike the surfaces of plains outcrops observed thus far by Opportunity. With continued mechanical health, Opportunity will reach terrains on and around Endeavour's rim that will be markedly different from anything examined to date.

Novel Fe3C-based nanostructures with an inner layered structure have been synthesized by a simple medium-temperature (T = 700 °C) process based on carbothermal reduction. In this process, the iron precursor reacts with a selected nitrogen rich carbon source (namely, 4,5-dicyanoimidazole) to form wrapped nano-sheets of Fe3C@C(N). The nanosheets are composed of 5 nm crystalline Fe3C nanoparticles, which are integrated into a nitrogen-doped carbon phase giving rise to the wrapped morphology. By variation of reaction parameters (such as initial concentration, temperature, reaction time), the typical accompanying side products of iron carbide such as metallic iron and amorphous carbon can be kept very low or even avoided. Contrary to simple expectations, those nanostructures are surprisingly robust against oxidation in air and could have potential applications in nanomagnetism and catalysis.

The weathering of meteorites found on Mars involves chemical and physical processes that can provide clues to climate conditions at the location of their discovery. Beginning on sol 1961, the Opportunity rover encountered three large iron meteorites within a few hundred meters of each other. In order of discovery, these rocks have been assigned the unofficial names Block Island, Shelter Island, and Mackinac Island. Each rock presents a unique but complimentary set of features that increase our understanding of weathering processes at Meridiani Planum. Significant morphologic characteristics interpretable as weathering features include (1) a large pit in Block Island, lined with delicate iron protrusions suggestive of inclusion removal by corrosive interaction; (2) differentially eroded kamacite and taenite lamellae in Block Island and Shelter Island, providing relative timing through crosscutting relationships with deposition of (3) an iron oxide-rich dark coating; (4) regmaglypted surfaces testifying to regions of minimal surface modification, with other regions in the same meteorites exhibiting (5) large-scale, cavernous weathering (in Shelter Island and Mackinac Island). We conclude that the current size of the rocks is approximate to their original postfall contours. Their morphology thus likely results from a combination of atmospheric interaction and postfall weathering effects. Among our specific findings is evidence supporting (1) at least one possible episode of aqueous acidic exposure for Block Island; (2) ripple migration over portions of the meteorites; (3) a minimum of two separate episodes of wind abrasion; alternating with (4) at least one episode of coating-forming chemical alteration, most likely at subzero temperatures.

The Mars Exploration Rover Opportunity investigated four rocks, informally dubbed Barberton, Santa Catarina, Santorini, and Kasos, that are possible stony meteorites. Their chemical and mineralogical composition is similar to the howardite, eucrite, and diogenite group but with additional metal, similar to mesosiderite silicate clasts. Because of their virtually identical composition and because they appear to represent a relatively rare group of meteorites, they are probably paired. The four rocks were investigated serendipitously several kilometers apart, suggesting that Opportunity is driving across a larger population of similar rock fragments, maybe a meteorite strewn field. Small amounts of ferric Fe are a result of weathering. We did not observe evidence for fusion crusts. Four iron meteorites were found across the same area. Although mesosiderites are stony irons, a genetic link to these irons is unlikely. The stony meteorites probably fell later than the irons. The current atmosphere is sufficiently dense to land such meteorites at shallow entry angles, and it would disperse fragments over several kilometers upon atmospheric breakup. Alternatively, dispersion by spallation from an impacting meteoroid may have occurred. Santa Catarina and a large accumulation of similar rocks were found at the rim of Victoria crater. It is possible that they are associated with the impactor that created Victoria crater, but our limited knowledge about their distribution cannot exclude mere coincidence.

Numerous loose rocks with dimensions of a few centimeters to tens of centimeters and with no obvious physical relationship to outcrop rocks have been observed along the traverse of the Mars Exploration Rover Opportunity. To date, about a dozen of these rocks have been analyzed with Opportunity's contact instruments, providing information about elemental chemistry (Alpha Particle X‐ray Spectrometer), iron mineralogy and oxidation states (Mössbauer Spectrometer) and texture (Microscopic Imager). These “cobbles” appear to be impact related, and three distinct groups can be identified on the basis of chemistry and mineralogy. The first group comprises bright fragments of the sulfate‐rich bedrock that are compositionally and texturally indistinguishable from outcrop rocks. All other cobbles are dark and are divided into two groups, referred to as the “Barberton group” and the “Arkansas group,” after the first specimen of each that was encountered by Opportunity. Barberton group cobbles are interpreted as meteorites with an overall chemistry and mineralogy consistent with a mesosiderite silicate clast composition. Arkansas group cobbles appear to be related to Meridiani outcrop and contain an additional basaltic component. They have brecciated textures, pointing to an impact‐related origin during which local bedrock and basaltic material were mixed.

We have used visible and near‐infrared Panoramic Camera (Pancam) spectral data acquired by the Opportunity rover to analyze 15 rock fragments at the Meridiani Planum landing site. These spectral results were then compared to geochemistry measurements made by the in situ instruments Mössbauer (MB) and Alpha Particle X‐ray Spectrometer (APXS) to determine the feasibility of mineralogic characterization from Pancam data. Our results suggest that dust and alteration rinds coat many rock fragments, which limits our ability to adequately measure the mineralogy of some rocks from Pancam spectra relative to the different field of view and penetration depths of MB and APXS. Viewing and lighting geometry, along with sampling size, also complicate the spectral characterization of the rocks. Rock fragments with the same geochemistry of sulfate‐rich outcrops have similar spectra, although the sulfate‐rich composition cannot be ascertained based upon Pancam spectra alone. FeNi meteorites have spectral characteristics, particularly ferric oxide coatings, that generally differentiate them from other rocks at the landing site. Stony meteorites and impact fragments with unknown compositions have a diverse range of spectral properties and are not well constrained nor diagnostic in Pancam data. Bounce Rock, with its unique basalt composition, is easily differentiated in the Pancam data from all other rock types at Meridiani Planum. Our Pancam analyses of small pebbles adjacent to these 15 rock fragments suggests that other rock types may exist at the landing site but have not yet been geochemically measured.

Decades of speculation about a warmer, wetter Mars climate in the planet’s first billion years postulate a denser CO 2 -rich atmosphere than at present. Such an atmosphere should have led to the formation of outcrops rich in carbonate minerals, for which evidence has been sparse. Using the Mars Exploration Rover Spirit, we have now identified outcrops rich in magnesium-iron carbonate (16 to 34 weight percent) in the Columbia Hills of Gusev crater. Its composition approximates the average composition of the carbonate globules in martian meteorite ALH 84001. The Gusev carbonate probably precipitated from carbonate-bearing solutions under hydrothermal conditions at near-neutral pH in association with volcanic activity during the Noachian era.

The Rio Tinto, located in southwest Spain, exhibits a nearly constant, acidic pH-value along its course. Due to the formation of sulfate minerals, Rio Tinto is considered a potential analogue site for sulfate-rich regions on Mars, in particular at the landing site of the Mars Exploration Rover Opportunity, where the ferric sulfate mineral jarosite was identified with Opportunity's Mossbauer spectrometer. Primary and secondary mineralogy was investigated in situ with portable Raman and Mossbauer spectrometers at four different Rio Tinto sampling sites. The two techniques analyse different sample portions due to their specific field of view and sampling depth and provide complementary mineralogical information.