Shallow radar (SHARAD) sounding observations of the Medusae Fossae Formation, Mars

The SHARAD (shallow radar) sounding radar on the Mars Reconnaissance Orbiter detects subsurface reflections in the eastern and western parts of the Medusae Fossae Formation (MFF). The radar waves penetrate up to 580 m of the MFF and detect clear subsurface interfaces in two locations: west MFF between 150 and 155° E and east MFF between 209 and 213° E. Analysis of SHARAD radargrams suggests that the real part of the permittivity is ∼3.0, which falls within the range of permittivity values inferred from MARSIS data for thicker parts of the MFF. The SHARAD data cannot uniquely determine the composition of the MFF material, but the low permittivity implies that the upper few hundred meters of the MFF material has a high porosity. One possibility is that the MFF is comprised of low-density welded or interlocked pyroclastic deposits that are capable of sustaining the steep-sided yardangs and ridges seen in imagery. The SHARAD surface echo power across the MFF is low relative to typical martian plains, and completely disappears in parts of the east MFF that correspond to the radar-dark Stealth region. These areas are extremely rough at centimeter to meter scales, and the lack of echo power is most likely due to a combination of surface roughness and a low near-surface permittivity that reduces the echo strength from any locally flat regions. There is also no radar evidence for internal layering in any of the SHARAD data for the MFF, despite the fact that tens-of-meters scale layering is apparent in infrared and visible wavelength images of nearby areas. These interfaces may not be detected in SHARAD data if their permittivity contrasts are low, or if the layers are discontinuous. The lack of closely spaced internal radar reflectors suggests that the MFF is not an equatorial analog to the current martian polar deposits, which show clear evidence of multiple internal layers in SHARAD data.     

火星轨道器次表层探测雷达数据处理技术与现状研究

火星是人类重要的地外天体探测目标之一,对火星表面进行的探测和研究表明,火星表面曾经存在液态水,水是生命存在的基础,因此,在次表层寻找不同形式的水是目前火星探测的重要科学目标之一.近17年来,欧洲火星快车(Mars Express)上搭载的火星次表层和电离层探测先进雷达(Mars Advanced Radar for S...     

Integrating radar stratigraphy with high resolution visible stratigraphy of the north polar layered deposits,Mars

Shallow Radar (SHARAD) on board NASA’s Mars Reconnaissance Orbiter has successfully detected tens of reflectors in the subsurface of the north polar layered deposits (NPLD) of Mars. Radar reflections are hypothesized to originate from the same material interfaces that result in visible layering. As a first step towards verifying this assumption, this study uses signal analyses and geometric comparisons to quantitatively examine the relationship between reflectors and visible layers exposed in an NPLD outcrop. To understand subsurface structures and reflector geometry, reflector surfaces have been gridded in three dimensions, taking into account the influence of surface slopes to obtain accurate subsurface geometries. These geometries reveal reflector dips that are consistent with optical layer slopes. Distance–elevation profiling of subsurface reflectors and visible layer boundaries reveals that reflectors and layers demonstrate similar topography, verifying that reflectors represent paleosurfaces of the deposit. Statistical and frequency-domain analyses of the separation distances between successive layers and successive reflectors confirms the agreement of radar reflector spacing with characteristic spacing of certain visible layers. Direct elevation comparisons between individual reflectors and discrete optical layers, while necessary for a one-to-one correlation, are complicated by variations in subsurface structure that exist between the outcrop and the SHARAD observations, as inferred from subsurface mapping. Although these complications have prevented a unique correlation, a genetic link between radar reflectors and visible layers has been confirmed, validating the assumption that radar reflectors can be used as geometric proxies for visible stratigraphy. Furthermore, the techniques for conducting a stratigraphic integration have been generalized and improved so that the integration can be undertaken at additional locations.     

MARSIS radar sounder observations in the vicinity of Ma'adim Vallis, Mars

The MARSIS radar experiment aboard the ESA Mars Express satellite has recorded several unusual reflections in the Ma'adim Vallis region of Mars. These reflections display a wide variety of morphologies which are very different from those of reflections seen beneath the Polar Layered Deposits, Medusae Fossae Formation and Dorsa Argentea Formation. Their morphologies are sometimes very laterally extensive, parabolic or hyperbolic, and apparently deep, but they can also appear horizontal and shallow. Aided by a geological map of the Ma'adim Vallis region, the morphological, locational and temporal characteristics of the reflections have been studied individually in an attempt to constrain their origin. While some may be subsurface reflections based on their shallow morphologies and correlation with the Eridania Planitia basin network, all of the reflections are ambiguous to some degree, displaying characteristics that do not allow a definite subsurface- or possibly ionospheric-sourced mechanism to be proposed for their creation. Those with more exaggerated morphologies are regarded as being much more likely to result from ionospheric distortion rather than subsurface inhomogeneity.     

MARSIS surface reflectivity of the south residual cap of Mars

The south residual cap of Mars is commonly described as a thin and bright layer of CO₂-ice. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is a low-frequency radar on board Mars Express operating at the wavelength between 55 and 230 m in vacuum. The reflection of the radar wave on a stratified medium like the residual cap can generate interferences, causing weaker surface reflections compared to reflections from a pure water ice surface. In order to understand this anomalous low reflectivity, we propose a stratified medium model, which allows us to estimate both the thickness and the dielectric constant of the optically thin slab. First, we consider the residual cap as single unit and show that the decrease in the reflected echo strength is well explained by a mean thickness of 11 m and a mean dielectric constant of 2.2. This value of dielectric constant is close to the experimental value 2.12 for pure CO₂-ice. Second, we study the spatial variability of the radar surface reflectivity. We observe that the reflectivity is not homogeneous over the residual cap. This heterogeneity can be modeled either by variable thickness or variable dielectric constant. The surface reflectivity shows that two different units comprise the residual cap, one central unit with high reflectivity and surrounding, less reflective units.     

Investigation of biological, chemical and physical processes on and in planetary surfaces by laboratory simulation

The recently established Arkansas-Oklahoma Center for Space and Planetary Science has been given a large planetary simulation chamber by the Jet Propulsion Laboratory, Pasadena, California. When completely refurbished, the chamber will be dubbed Andromeda and it will enable conditions in space, on asteroids, on comet nuclei, and on Mars, to be reproduced on the meter-scale and surface and subsurface processes monitored using a range of analytical instruments. The following projects are currently planned for the facility. (1) Examination of the role of surface and subsurface processes on small bodies in the formation of meteorites. (2) Development of in situ sediment dating instrumentation for Mars. (3) Studies of the survivability of methanogenic microorganisms under conditions resembling the subsurface of Mars to test the feasibility of such species surviving on Mars and identify the characteristics of the species most likely to be present on Mars. (4) The nature of the biochemical “fingerprints” likely to have been left by live organisms on Mars from a study of degradation products of biologically related molecules. (5) Testing local resource utilization in spacecraft design. (6) Characterization of surface effects on reflectivity spectra for comparison with the data from spacecraft-borne instruments on Mars orbiters.     

A preparatory study on subsurface exploration on Mars using GPR and microwave tomography

The exploitation of ground penetrating radar in Mars subsurface exploration is becoming assessed in remote sensing observations and is of timely interest for high resolution in situ prospecting of the first meters of the underground.In this framework, we deal with a novel processing approach based on microwave tomography. Aiming to achieve accurate and reliable “images” of the investigated subsurface region in order to detect, localize and possibly determine the extent and the geometrical features of the embedded layers while reducing at the minimum possible the “interpretation” of the diagnostics result.The feasibility of the microwave tomographic approach has been tested in realistic cases dealing with conditions analogue to the Mars subsurface ones. In particular, we will present the tomographic reconstruction results achieved by experimental data collected in a field survey at Svalbard Islands (Norway) with a time-domain GPR.     

Development and testing of subsurface sampling devices for the Beagle 2 lander

For planetary landing missions, the capability to acquire samples of soil and rock is of high importance whenever complex analyses (e.g. isotopic studies) on these materials are to be carried out, or when samples are to be returned to Earth. Not only surface samples are of relevance, but in recent concepts at least for Mars landing missions also subsurface samples are required. Subsurface material on Mars is believed to have been protected from the inferred oxidants at the immediate surface while also being protected from the UV influx. Therefore, there is considerable hope that in subsurface soil samples on Mars, at least organic matter delivered by meteorites may be detected, and possibly also relics of earlier simple microbial life on the planet. Likewise, samples from the inside of Martian surface rocks promise to have been protected from weathering and for the same reason they are important for organic chemistry studies. In this paper, an overview is given of the development and science of two different subsurface sampling devices for the Beagle 2 lander of ESA's Mars Express mission, being a “Mole” subsurface soil sampler and a small rock coring and sampling mechanism. Besides their sampling function, both the Mole and the Corer/Grinder will provide data on physical properties of Martian soils and rock, respectively, through the way they interact with the sampled materials. Details of the Mole and Corer/Grinder design are presented, along with results of recent tests with prototypes in the laboratory on physically analogous sample materials.     

Radar absorption due to a corotating interaction region encounter with Mars detected by MARSIS

Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is a subsurface and topside ionosphere radar sounder aboard the European Space Agency spacecraft Mars Express, in orbit at Mars since 25 December 2003, and in operation since 17 June 2005. The ionospheric sounding mode of MARSIS is capable of detecting the reflection of the sounding wave from the martian surface. This ability has been used in previous work to show that the surface reflection is absorbed and disappears during periods when high fluxes of energetic particles are incident on the ionosphere of Mars. These absorption events are believed to be the result of increased collisional damping of the sounding wave, caused by increased electron density below the spacecraft, in turn caused by impact ionization from the impinging particles. In this work we identify two absorption events that were isolated during periods when the surface reflection is consistently visible and when Mars is nearly at opposition. The visibility of the surface reflection is viewed in conjunction with particle and photon measurements taken at both Mars and Earth. Both absorption events are found to coincide with Earth passing through solar wind speed and ion flux signatures indicative of a corotating interaction region (CIR). The two events are separated by an interval of approximately 27 days, corresponding to one solar rotation. The first of the two events coincides with abruptly enhanced particle fluxes seen in situ at Mars. Simultaneous with the particle enhancement there are an abrupt decrease in the intensity of electron oscillations, typically seen by the Mars Express particle instrument ASPERA-3 between the magnetic pileup boundary and the martian bow shock, and a sharp drop in the solar wind pressure, seen in the proxy quantity based on MGS magnetometer observations. The decrease in oscillation intensity is therefore the probable effect of a relaxation of the martian bow shock. The second absorption event does not show a particle enhancement and complete ASPERA-3 data during that time are unavailable. Other absorption events are the apparent result of solar X-ray and XUV enhancements. We conclude that surface reflection absorption events are sometimes caused by enhanced ionospheric ionization from high energy particles accelerated by the shocks associated with a CIR. A full statistical analysis of CIRs in relation to observed absorption events in conjunction with a quantitative analysis of the deposition of ionization during space weather events is needed for a complete understanding of this phenomenon. If such analyses can be carried out, radar sensing of the martian ionosphere might be useful as a space weather probe.     

Simulation of the Martian spectral radiance in the presence of atmospheric dust

The interest towards Mars is nowadays renewed as various satellites, already launched or foreseen for the future, will visit this planet, providing a new wealth of data. In particular, infrared spectroscopic observations need a parallel modelling effort for a proper interpretation of observations. The goal of our modelling is to evaluate the influence of a non negligible fraction of dust particles on intensity and profile of atmospheric Martian spectra. The joint effects of the atmosphere and the surface materials have been also accounted for. For the modelling, a version of the MODTRAN code, expressly modified for application to the Mars environment, has been used. As an example of the materials forming dust dispersed in the atmosphere and on the surface, we have considered andesite. Indices of refraction (n and k) of this material have been derived from laboratory measurements. The obtained results can have an important impact on the interpretation of infrared spectra that instruments such as TES (Thermal Emission Spectrometer), on board the Mars Global Surveyor, and PFS, in the Mars Express mission, will provide.     

Top layers charaterization of the Martian surface: Permittivity estimation based on geomorphology analysis

Mars Express spacecraft inserted successfully Martian orbit at the end of 2003. On board this probe, a radar instrument called MARSIS (for Mars Advanced Radar for Surface and Ionosphere Sounding) is looking for water inside the first kilometers of Martian crust. To support MARSIS planning and data inversion, Laboratoire de Planétologie de Grenoble developed a MARSIS signal simulator.We show in this paper that MARSIS can also characterize some surface features, in addition to subsurface water and ionosphere sounding. We study a Martian surface region of special interest: Nilokeras Mensae, inside Acidalia Planitia. We discuss the previous geological studies of this region, and show the geomorphologies analyze of this surface area could lead to a simple terrain model. Then, we present a possible data inversion scheme and applying the MARSIS simulator, we test a first radar data inversion.Finally, we will show that complete dielectric characteristics of surface top layers can be retrieved, at least as often Mars Express flies over some layered terrain (at wavelength scale).     

Geology of possible Martian methane source regions

Recent observations of methane on Mars suggest that spatially localized source regions are present. Here we discuss the surface morphology and mineralogy of these regions, focusing on features that may provide insights into mechanisms of methane production and/or release. Preliminary trends among methane source regions include old age, deep fractures, past or present subsurface water, and the presence of hydrated minerals, sometimes including serpentine. As the spatial and temporal coverage of Martian methane is expanded, geological observations of proposed source regions will be a powerful tool for understanding the methane cycle on modern Mars.     

Dielectric constant estimation of the uppermost Basal Unit layer in the martian Boreales Scopuli region

An electromagnetic inversion model has been applied to echoes from the subsurface sounding Shallow Radar (SHARAD) to retrieve the dielectric properties of the uppermost Basal Unit (BU) beneath the North Polar Layered Deposits of Mars. SHARAD data have been carefully selected to satisfy the assumption of the inversion model which requires a stratigraphy consisting of mostly plane parallel layers. The resulting values of the dielectric constant have been interpreted in terms of a variable percentage of dust in an ice–dust mixture through the use of a mixing model for dielectric properties. The resulting dust content exceeds 65%, reaching perhaps 95%, depending on the permittivity values assumed for the dust. Such a concentration is higher than that obtained by Selvans et al. (Selvans, M.M., Plaut, J.J., Aharonson, O. [2010]. J. Geophys. Res, 115, E09003). This discrepancy could be justified considering that our observations refer to the uppermost BU layer, whereas Selvans et al. (Selvans, M.M., Plaut, J.J., Aharonson, O. [2010]. J. Geophys. Res, 115, E09003) probed the BU full thickness. Moreover, if the BU is considered spatially inhomogeneous, with very different dust content and thickness (Tanaka, K.L., Skinner, J.A., Fortezzo, C.M., Herkenhoff, K.E., Rodriguez, J.A.P., Bourke, M.C., Kolb, E.J., Okubo, C.H. [2008]. Icarus, 196, 318–358), the discrepancy could be furtherly reconciled.     

Noble gas adsorption with and without mechanical stress: Not Martian signatures but fractionated air

Abstract– Sample preparation, involving physical and chemical methods, is an unavoidable step in geochemical analysis. From a noble gas perspective, the two important effects are loss of sample gas and/or incorporation of air, which are significant sources of analytical artifacts. This article reports on the effects of sample exposure to laboratory air without mechanical influence and during sample grinding. The experiments include pure adsorption on terrestrial analog materials (gibbsite and olivine) and grinding of Martian meteorites. A consistent observation is the presence of an elementally fractionated air component in the samples studied. This is a critical form of terrestrial contamination in meteorites as it often mimics the heavy noble gas signatures of known extra‐terrestrial end‐members that are the basis of important conclusions about the origin and evolution of a meteorite. Although the effects of such contamination can be minimized by avoiding elaborate sample preparation protocols, caution should be exercised in interpreting the elemental ratios (Ar/Xe, Kr/Xe), especially in the low‐temperature step extractions. The experiments can also be transferred to the investigation of Martian meteorites with long terrestrial residence times, and to Mars, where the Mars Science Laboratory mission will be able to measure noble gas signatures in the current atmosphere and in rocks and soils collected on the surface in Gale crater.     

Oxygenic photosynthesis and the oxidation state of Mars

The oxidation state of the Earth's surface is one of the most obvious indications of the effect of life on this planet. The surface of Mars is highly oxidized, as evidenced by its red color, but the connection to life is less apparent. Two possibilities can be considered. First, the oxidant may be photochemically produced in the atmosphere. In this case the fundamental source of O2 is the loss of H2 to space and the oxidant produced is H2O2. This oxidant would accumulate on the surface and thereby destroy any organic material and other reductants to some depth. Recent models suggest that diffusion limits this depth to a few meters. An alternative source of oxygen is biological oxygen production followed by sequestration of organic material in sediments--as on the Earth. In this case, the net oxidation of the surface was determined billions of years ago when Mars was a more habitable planet and oxidative conditions could persist to great depths, over 100 m. Below this must be a compensating layer of biogenic organic material. Insight into the nature of past sources of oxidation on Mars will require searching for organics in the Martian subsurface and sediments.     

Pluto—The ninth planet's golden year: A meeting held at New Mexico State University,Las Cruces,New Mexico

The simple-to-complex transition for impact craters on Mars occurs at diameters between about 3 and 8 km. Ballistically emplaced ejecta surround primarily those craters that have a simple interior morphology, whereas ejecta displaying features attributable to fluid flow are mostly restricted to complex craters. Size-dependent characteristics of 73 relatively fresh Martian craters, emphasizing the new depth/diameter (d/D) data of D. W. G. Arthur (1980, to be submitted for publication), test two hypotheses for the mode of formation of central peaks in complex craters. In particular, five features appear sequentially with increasing crater size: first flat floors (3–4 km), then central peaks and shallower depths (4–5 km), next scalloped rims (? km), and lastly terraced walls (～8 km). This relative order indicates that a shallow depth of excavation and an unspecified rebound mechanism, not centripetal collapse and deep sliding, have produced central peaks and in turn have facilitated failure of the rim. The mechanism of formation of a shallow crater remains elusive, but probably operates only at the excavation stage of impact. This interpretation is consistent with two separate and complementary lines of evidence. First, field data have documented only shallow subsurface deformation and a shallow transient cavity in complex terrestrial meteorite craters and in certain surface-burst explosion craters; thus the shallow transient cavities of complex craters never were geometrically similar to the deep cavities of simple craters. Second, the average depths of complex craters and the diameters marking the transition from simple to complex craters on Mars and on three other terrestrial planets vary inversely with gravitational acceleration at the planetary surface, g, a variable more important in the excavation of a crater than in any subsequent modification of its geometry. The new interpretation is summarized diagrammatically for complex craters on all planets.     

Studying methane and other trace species in the Mars atmosphere using a SOIR instrument

Solar Occultation in the InfraRed (SOIR) is one of three spectrometers of the SPICAV/SOIR instrument suite (Bertaux et al., 2007b) on board the Venus Express orbiter (VEX). VEX has been in orbit around Venus since April 2006 and to date SOIR has carried out over 674 measurements. Pre-launch and in-orbit performance analyses allow us to predict what SOIR would be capable of at Mars. SOIR spectra through the Martian atmosphere have been simulated with ASIMUT, a line-by-line (LBL) radiative transfer code also used for the retrieval of vertical profiles of atmospheric constituents of Venus (Vandaele et al., 2008, Bertaux et al., 2007a). The code takes into account the temperature and pressure vertical profiles as well as those of the atmospheric species, but also the instrument function and the overlapping of the diffraction orders of the echelle grating. We will show these spectra and the detection limits of species that could be studied using a SOIR spectrometer making solar occultation or nadir measurements in Mars orbit.     

Assimilation of thermal emission spectrometer atmospheric data during the Mars Global Surveyor aerobraking period

The Thermal Emission Spectrometer aboard the Mars Global Surveyor spacecraft has produced an extensive atmospheric data set, beginning during aerobraking and continuing throughout the extended scientific mapping phase. Temperature profiles for the atmosphere below about 40 km, surface temperatures and total dust and water ice opacities, can be retrieved from infrared spectra in nadir viewing mode. This paper describes assimilation of nadir retrievals from the spacecraft aerobraking period, L_S=190°–260°, northern hemisphere autumn to winter, into a Mars general circulation model. The assimilation scheme is able to combine information from temperature and dust optical depth retrievals, making use of a model forecast containing information from the assimilation of earlier observations, to obtain a global, time-dependent analysis. Given sufficient temperature retrievals, the assimilation procedure indicates errors in the a priori dust distribution assumptions even when lacking dust observations; in this case there are relatively cold regions above the poles compared to a model which assumes a horizontally-uniform dust distribution. One major reason for using assimilation techniques is in order to investigate the transient wave behavior on Mars. Whilst the data from the 2-h spacecraft mapping orbit phase is much more suitable for assimilation, even the longer (45–24 h) period aerobraking orbit data contain useful information about the three-dimensional synoptic-scale martian circulation which the assimilation procedure can reconstruct in a consistent way. Assimilations from the period of the Noachis regional dust storm demonstrate that the combined assimilation of temperature and dust retrievals has a beneficial impact on the atmospheric analysis.     

Does martian soil release reactive halogens to the atmosphere?

Detailed statistical examination of Cl, Br, and S distributions, in martian soil profiles at Gusev Crater and Meridiani Planum, indicates decreasing Br abundance and weakening Br–S association towards the surface. All three elements decrease towards the surface in the order Cl < S < Br. Furthermore, Br variability decouples from potential cations such as Mg at the surface relative to the subsurface. These observations support a relative loss of surficial Br compared to S and Cl, all highly mobile elements in aqueous environments. We propose that Br may have converted preferentially to gas phases (e.g., BrO), driven either by UV photolysis or by chemical oxidants. Such volatilization pathways may in turn impart a global signature on Mars by acting as controls on oxidants such as ozone and perchlorates. S/Cl mass ratios vary with depth (∼4–5 in the subsurface; 1.8–3.6 on the surface) as well, with a strong correlation of S and Cl near the surface but more variable at depth, consistent with differential vertical mobility, but not volatilization of Cl. Elevated S/Cl in subsurface soil also suggests that the ratio may be higher in bulk soil – a key repository of martian geologic and climatic records – than previously thought.     

Two geologic systems providing terrestrial analogues for the exploration of sulfate deposits on Mars: Initial spectral characterization

We present the Messinian evaporite suite (Mediterranean region) and the Solfatara hydrothermal system (Phlegraean Fields volcanic province, Italy), discuss their implications for understanding the origin of sulfates on Mars and show preliminary sets of VNIR laboratory and in situ reflectance spectra of rocks from these geologic systems. The choice was based on a number of evidence relative to Mars: (1) the chemistry of the Martian sulfates, suggesting fluid interactions with possibly alkali-basaltic rocks and/or regolith; (2) close range evidence of sulfates within sedimentary formations on Mars; (3) sulfate spectral signatures associated to large-scale layered patterns interpreted as thick depositional systems on Mars. The Messinian evaporites comprise three units: primary shallow-water sulfates (primary lower gypsum: PLG), shallow- to deep-water mixed sulfates and clastic terrigenous deposits (resedimented lower gypsum: RLG), and shallow-water associations of primary sulfates and clastic fluvio-deltaic deposits (upper evaporites: UE). The onset of the Messinian evaporites records the transition to negative hydrologic budget conditions associated with the Messinian Salinity Crisis, which affected the entire Mediterranean basin and lasted about 640 kyr. The Solfatara is a still evolving hydrothermal system that provides epithermal deposits precipitated from the interaction of fluids and trachybasaltic to phonolitic rocks. Thermal waters include alkali-chloride, alkali-carbonate and alkali-sulfate endmembers.The wide spectrum of sedimentary gypsum facies within the Messinian formation includes some of the depositional environments hitherto identified on Mars and others not found on Mars. The PLG unit includes facies associations correlated over long distances, that could be a possible analog of the stratified rock units exposed from Arabia Terra at least as far as Valles Marineris. The facies cycles within the UE unit can be compared to the sequences of strata observed in craters such as Holden and Eberswalden. The UE unit records paleoenvironmental changes which are ultimately controlled by terrestrial climatic variations. They can be considered as a reliable climatic proxy and may be useful for the reconstruction of climatic events on Mars. The intermediate Messinian RLG unit has not, at present, a well-defined depositional counterpart on Mars, although there are some similarities with the northern lowlands and Vastitas Borealis Formation. The dramatic variation of hydrologic budget conditions at the onset of the Messinian evaporites may provide criteria for the interpretation of similar variations on Mars.The volcanic rocks at the Solfatara bear some similarities with the “alkaline magmatic province” observed at the Gusev crater on Mars, and the assemblages of hydrothermal phases resulting from the Solfatara's parent rocks could be analogues for processes involving Gusev-type rocks.The Messinian sulfates have a prevalent Ca-sulfatic composition and wide textural variability. Preliminary laboratory reflectance spectra of rock samples in the VNIR region reveal the signature of sulfates and mixtures of several Fe-bearing phases. At the Solfatara, in situ reflectance measurements of epithermal minerals close to active fumaroles showed the presence of Fe-bearing sulfates, hematite, Al- and K-sulfates and abundant amorphous fraction. XRD analysis supported this interpretation.The range of depositional facies observed in the Messinian units and the variety of minerals detected in the Solfatara will be useful for the interpretation of close range data of Mars. The spectral characterization at various scales of the Messinian sedimentary facies and the Solfatara hydrothermal minerals will both help in the exploration of Mars from orbit and with close range inspection.