Miniature Thermal Research Articles

Temperature fluctuations and boundary layer turbulence as seen by Mars Exploration Rovers Miniature Thermal Emission Spectrometer

The Mini-TES spectrometer carried by Spirit and Opportunity is a unique instrument that enabled vertical temperature profiles to be retrieved at high frequency (every 2 s, or “ICK”). Observations obtained from this instrument provide information on boundary layer activity. As an extension of previous work, we have retrieved ICK-by-ICK vertical temperature profiles to characterize turbulent behavior at each rover site for up to two Mars Years. We have also retrieved ICK-by-ICK near-surface (1.1 m) atmospheric temperatures and surface temperatures from dedicated atmospheric observations as well as geologic observations that extend the coverage of near-surface observations. The extension and increased frequency of retrievals as well as the additional observations provide a more complete view of the vertical and temporal variation of temperature fluctuations within the PBL. Temperature fluctuations are assessed using detrended temperature time-series data. The results show fluctuations can be as large as 10 K at the surface and 8 K aloft with timescales on the order of minutes. We have calculated the peak-to-peak amplitudes of temperature fluctuations and the corresponding timescales over which they occur. Spirit and Opportunity temperature fluctuation amplitudes decrease in magnitude vertically, where higher atmospheric levels show smaller fluctuations in amplitudes than at the surface. The magnitude of temperature fluctuations changes with the difference in surface and air temperature. This difference varies little as a function of season at both rover sites. Fluctuations are observed to quickly decrease in the late afternoon reaching a minimum near 17:00 LTST followed by moderately increased activity near sunset caused by forced convection. There is no significant change in the observed convective activity as a function of dust optical depth during regional dust storms. The few large temperature fluctuations that are concurrent with dust events are likely the result of large-scale systems.

Wishstone to Watchtower: Amorphous alteration of plagioclase-rich rocks in Gusev crater, Mars

Previous observations by the Spirit rover in Gusev crater revealed a suite of rocks dubbed Wishstone and Watchtower Class in which the parent lithology and daughter products of a distinctive style of aqueous alteration are evident. Results from Spirit’s Miniature Thermal Emission Spectrometer (Mini-TES; ~2000–340 cm −1 ) were compromised by dust contamination of one of the instrument’s mirrors, for which a correction has since been developed. Now we have documented nearly 200 examples of rocks encompassing the span of alteration from Wishstone Class, which spectrally resemble minimally altered plagioclase-phyric basalt, to the most altered Watchtower Class. Among them is a rock dubbed Bruce that may be a previously unrecognized alteration spectral end-member. We employed factor analysis/target transformation and linear least-squares modeling to investigate the spectral characteristics and mineralogy of these rocks. Our results amplify those of a prior preliminary analysis showing that alteration produced a material resembling basaltic glass that masks the spectral features of plagioclase. The association of this amorphous silicate component with a ferric iron nanophase oxide phase identified via Spirit’s Mossbauer spectrometer is now clearly shown by our data, further characterizing the distinctive mineralogic expression of the alteration. These components and the absence of any recognizable secondary silicates or opaline silica may be an expression of alteration in the extreme aridity and cold of the martian environment. Similar mineralogic characteristics of soil measured with the CheMin X-ray diffraction instrument on the Curiosity rover in Gale crater may be an indication that this alteration process is widespread on Mars.

Characterizing the thermal infrared spectral effects of optically thin surface dust: Implications for remote-sensing and in situ measurements of the martian surface

A spectral contribution different from that observed for thick dust mantles has been identified in many of the in situ measurements of rocks and regolith acquired by the Miniature Thermal Emission Spectrometer (Mini-TES) instruments on the Mars Exploration Rovers (MER). This spectral contribution is thought to be caused by optically thin surface dust and if not corrected can greatly hinder the mineralogical interpretation of rock surfaces. The focus of this study is the characterization of key radiative processes that are necessary to understand the spectral contributions produced by optically thin surface dust. An understanding of these radiative processes is important to be able to reproduce, predict, and correct their contribution in thermal infrared (TIR; ∼200–2000cm−1; 5–50μm) datasets. By combining TIR spectroscopic laboratory measurements and radiative transfer (RT) modeling, we have reproduced and quantified the spectral contributions produced by optically thin surface dust in the TIR spectral range. TIR laboratory measurements were acquired of basaltic rocks and gold diffuse reflectors (GDR) mantled with varying amounts of optically thin dust. The spectral contributions of optically thin dust as observed by Mini-TES were not observed in the laboratory measurements of the dusty basaltic rocks, but were observed in the measurements of the dusty GDR’s. For the dust to contribute spectral features the dust must maintain a thermal contrast with the underlying surface. This thermal contrast was not achieved for the dusty basaltic rocks. Using our RT model, laboratory spectra of the dusty basaltic rocks and GDR’s were reproduced. Our RT model appears to reproduce the spectral features attributed to the dust in the laboratory measurements to first order and can quantify the relationship between dust coatings and measured radiance. After validating the RT model against the TIR laboratory measurements, it was then used in an initial application to reproduce measurements acquired by the Mini-TES. By characterizing the spectral behavior of the dust, including the potential for thermal contrast between the dust and the substrate, it is possible to better understand and interpret TIR spectra of dust mantled surfaces.

Investigation of Multiple Miniature Axial Fan Cooling Solutions and Thermal Modeling Approaches

This paper investigates the thermal and fluid dynamic characteristics due to multiple miniature axial fans with blade chord and span length scales less than 10 mm, impinging air onto finned surfaces. A coupled approach, utilizing both experimental and numerical techniques, has been devised to examine in detail the exit air flow interaction between cooling fans within an array. The findings demonstrate that fans positioned adjacently in an array can influence heat transfer performance both positively and negatively by up to 35% compared to an equivalent single fan—heat sink unit operating standalone. Numerical simulations have provided an insight into the flow fields generated by adjacent fans and also the air flow interaction with fixed fan motor support structures downstream. A novel experimental approach utilizing infrared thermography has been developed to locally assess the validity of the numerical models. In particular, an assessment on implementing compact lumped parameter fans and fans modeled with full geometric detail is shown for two configurations that are impinging air onto finned and flat surfaces. Overall, the study provides an insight into fan cooled heat sinks incorporating multiple miniature axial fans and general recommendations for improving current numerical modeling approaches.

The Martian surface: composition, mineralogy, and physical properties

Dedication Acknowledgements Foreword Part I. Introduction and Historical Perspective: 1. Exploration of the Martian surface: 1992-2007 2. Historical context: the pre-MGS view of Mars' surface composition Part II. Elemental Composition: Orbital and In Situ Surface Measurements: Part II. A. Results and Interpretations from New In Situ APXS Measurements: 3. Martian surface chemistry: APXS results from the Pathfinder landing site 4. Mars exploration rovers - chemical composition by the APXS Part II. B. Results and Interpretations from New Orbital Elemental Measurements: 5. Elemental abundances determined via the Mars Odyssey GRS 6. Volatiles on Mars: scientific results from the Mars Odyssey Neutron Spectrometer Part III. Mineralogy and Remote Sensing of Rocks, Soil, Dust, and Ices: Part III. A. Visible to Near-IR Telescopic and Orbital Measurements: 7. Mineralogy of the Martian surface from Mars Express OMEGA Observations 8. Visible to near-IR multispectral orbital observations Part III. B. Mid-IR and Magnetic Orbital Measurements: 9. Global mineralogy mapped from the Mars Global Surveyor Thermal Emission Spectrometer 10. The compositional diversity and physical properties mapped from the Mars Odyssey Thermal Emission Imaging System 11. Mars' crustal magnetization: a window into the past Part III. C. Observations from Surface Landers/Rovers: 12. Multispectral imaging from Mars Pathfinder 13. Mars Exploration Rover Pancam multispectral imaging of rocks, soil, and dust at Gusev Crater and Meridiani Planum 14. The mineralogy of Gusev Crater and Meridiani Planum derived from the Miniature Thermal Emission Spectrometers on the Spirit and Opportunity Rovers 15. Iron mineralogy and aqueous alteration on Mars from the MER Moessbauer Spectrometers 16. Magnetic properties results from surface landers and rovers Part III. D: 17. Martian meteorites as crustal samples Part IV. Physical Properties of Surface Materials: 18. The thermal inertia of the surface of Mars 19. Physical properties of the Martian surface from spectrophotometric observations 20. In-situ observations of the physical properties of the Martian surface 21. Martian surface properties from joint analyses of orbital, Earth-based, and surface observations Part V. Synthesis: 22. Implications of the observed primary lithologies 23. Aqueous alteration on Mars 24. The sedimentary rock cycle of Mars 25. Implications for Martian polar processes 26. Astrobiological implications of Mars surface composition and properties Part VI: 27. Summary, upcoming missions, and new measurement needs Acronyms Index.

Thermal structure of the atmospheric boundary layer on Mars based on Mini‐TES observations

AbstractThis paper presents and discusses the vertical profiles of the potential temperature in the Martian boundary layer. The profiles were remotely sensed from on‐board the Spirit Mars Exploration Rover during the first 702 sols of its operation in 2004–2005. The rover carried the Miniature Thermal Emission Spectrometer (Mini‐TES), which allowed it to retrieve temperature profiles up to a level 2 km above the ground surface. The data analysed here permit a reconstruction of the diurnal and seasonal structure of the lower part of the Martian convective boundary layer, an evaluation of the boundary layer depth, and a computation of the temperature heat flux. Copyright © 2009 Royal Meteorological Society

Simultaneous observations of the Martian atmosphere by Planetary Fourier Spectrometer on Mars Express and Miniature Thermal Emission Spectrometer on Mars Exploration Rover

In this study we present temperature profiles in the lower atmosphere of Mars from simultaneous observations performed by the Planetary Fourier Spectrometer (PFS) aboard the Mars Express spacecraft and the Miniature Thermal Emission Spectrometer (Mini‐TES) aboard the Mars Exploration Rovers. Thermal infrared spectra were collected in both the upward and downward looking geometries from the surface and from orbit, respectively. We used two sets of criteria to select PFS observations. These criteria took into account the location around the landing sites of the rovers, the local time (LT), and the solar longitude (Ls) corresponding to the Martian solar day (sol). The first set of criteria included PFS measurements carried out within ±1° in latitude and longitude, within 1 h in local time, and on the same sol. From the restricted set of measurements we conclude that the PFS data are consistent with the Mini‐TES data. The next set of criteria covered the area 5° × 5° around the landing sites, within 1 h in local time and within 9 sols. The latter criteria allow us to study the variation of parameters LT, distance, and Ls and their influence on changes of temperature profiles. This comparison for the group with relaxed criteria showed also that local time has strongest effect on temperature differences. The main purpose of this study is to confirm the validity of PFS temperature profiles close to the surface. Atmospheric temperatures below 5 km are retrieved from satellite measurements with a large uncertainty because of poor pieces of information in the wings of the CO2 absorption band at 667 cm−1. The Mini‐TES temperature profiles span atmospheric layers below 2 km. The good correspondence observed in a number of cases confirms the possibility of using PFS measurements to investigate the lower atmosphere.

Spectral, mineralogical, and geochemical variations across Home Plate, Gusev Crater, Mars indicate high and low temperature alteration

Over the last ~ 3 years in Gusev Crater, Mars, the Spirit rover observed coherent variations in color, mineralogy, and geochemistry across Home Plate, an ~ 80 m-diameter outcrop of basaltic tephra. Observations of Home Plate from orbit and from the summit of Husband Hill reveal clear differences in visible/near-infrared (VNIR) colors between its eastern and western regions that are consistent with mineralogical compositions indicated by Mössbauer spectrometer (MB) and by Miniature Thermal Emission Spectrometer (Mini-TES). Pyroxene and magnetite dominate the east side, while olivine, nanophase Fe oxide (npOx) and glass are more abundant on the western side. Alpha Particle X-Ray Spectrometer (APXS) observations reveal that eastern Home Plate has higher Si/Mg, Al, Zn, Ni, and K, while Cl and Br are higher in the west. We propose that these variations are the result of two distinct alteration regimes that may or may not be temporally related: a localized, higher temperature recrystallization and alteration of the east side of Home Plate and lower temperature alteration of the western side that produced npOx.

A new model to simulate the Martian mesoscale and microscale atmospheric circulation: Validation and first results

The Laboratoire de Météorologie Dynamique (LMD) Mesoscale Model is a new versatile simulator of the Martian atmosphere and environment at horizontal scales ranging from hundreds of kilometers to tens of meters. The model combines the National Centers for Environmental Prediction(NCEP)‐National Center for Atmospheric Research (NCAR) fully compressible nonhydrostatic Advanced Research Weather Research and Forecasting (ARW‐WRF) dynamical core, adapted to Mars, with the LMD‐general circulation model (GCM) comprehensive set of physical parameterizations for the Martian dust, CO2, water, and photochemistry cycles. Since LMD‐GCM large‐scale simulations are also used to drive the mesoscale model at the boundaries of the chosen domain of interest, a high level of downscaling consistency is reached. To define the initial state and the atmosphere at the domain boundaries, a specific “hybrid” vertical interpolation from the coarse‐resolution GCM fields to the high‐resolution mesoscale domain is used to ensure the stability and the physical relevancy of the simulations. Used in synoptic‐scale mode with a cyclic domain wrapped around the planet, the mesoscale model correctly replicates the main large‐scale thermal structure and the zonally propagating waves. The model diagnostics of the near‐surface pressure, wind, and temperature daily cycles in Chryse Planitia are in accordance with the Viking and Pathfinder measurements. Afternoon gustiness at the respective landing sites is adequately accounted for on the condition that convective adjustment is turned off in the mesoscale simulations. On the rims of Valles Marineris, intense daytime anabatic (∼30 m s−1) and nighttime katabatic (∼40 m s−1) winds are predicted. Within the canyon corridors, topographical channeling can amplify the wind a few kilometers above the ground, especially during the night. Through large‐eddy simulations in Gusev Crater, the model describes the mixing layer growth during the afternoon, and the associated dynamics: convective motions, overlying gravity waves, and dust devil–like vortices. Modeled temperature profiles are in satisfactory agreement with the Miniature Thermal Emission Spectrometer (Mini‐TES) measurements. The ability of the model to transport tracers at regional scales is exemplified by the model's prediction for the altitude of the Tharsis topographical water ice clouds in the afternoon. Finally, a nighttime “warm ring” at the base of Olympus Mons is identified in the simulations, resulting from adiabatic warming by the intense downslope winds along the flanks of the volcano. The surface temperature enhancement reaches +20 K throughout the night. Such a phenomenon may have adversely affected the thermal inertia derivations in the region.

Hydrothermal origin of halogens at Home Plate, Gusev Crater

In the Inner Basin of the Columbia Hills, Gusev Crater is Home Plate, an 80 m platform of layered clastic rocks of the Barnhill class with microscopic and macroscopic textures, including a bomb sag, suggestive of a phreatomagmatic origin. We present data acquired by the Spirit Mars Exploration Rover by Alpha Particle X‐Ray Spectrometer (APXS), Mössbauer Spectrometer, Miniature Thermal Emission Spectrometer (Mini‐TES), and Panoramic Camera (Pancam) for the Barnhill class rocks and nearby vesicular Irvine class basalts. In major element concentrations (e.g., SiO2, Al2O3, MgO, and FeO*), the two rock classes are similar, suggesting that they are derived from a similar magmatic source. The Barnhill class, however, has higher abundances of Cl, Br, Zn, and Ge with comparable SO3 to the Irvine basalts. Nanophase ferric oxide (np ox) and volcanic glass were detected in the Barnhill class rocks by Mössbauer and Mini‐TES, respectively, and imply greater alteration and cooling rates in the Barnhill than in the Irvine class rocks. The high volatile elements in the Barnhill class agree with volcanic textures that imply interaction with a briny groundwater during eruption and (or) by later alteration. Differences in composition between the Barnhill and Irvine classes allow the fingerprinting of a Na‐Mg‐Zn‐Ge‐Cl‐Br (±Fe ± Ca ± CO2) brine with low S. Nearby sulfate salt soils of fumarolic origin may reflect fractionation of an acidic S‐rich vapor during boiling of a hydrothermal brine at depth. Persistent groundwater was likely present during and after the formation of Home Plate.

Mineralogy of volcanic rocks in Gusev Crater, Mars: Reconciling Mössbauer, Alpha Particle X‐Ray Spectrometer, and Miniature Thermal Emission Spectrometer spectra

Complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in Gusev Crater have been determined by modeling Mössbauer subspectral areas as mineral weight percentages, and combining those percentages with the proportions of iron‐free minerals not detected by Mössbauer (normative plagioclase, apatite, and chromite, as calculated from Alpha Particle X‐Ray Spectrometer (APXS) chemical analyses). Comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured Miniature Thermal Emission Spectrometer (Mini‐TES) spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic plagioclase compositions or unmodeled sulfate, glass, or pigeonite. The normative compositions of olivine, pyroxene, and feldspar calculated from APXS data are consistent with spectroscopic constraints on mineral compositions. Systematic variations between olivine abundances in APXS norms (which sample tens of micrometers depth) and olivine proportions measured by Mössbauer (which sample hundreds of micrometers depth) support the hypothesis that dissolution of olivine by acidic fluids has occurred on weathered rock surfaces.

Mineralogical composition of sands in Meridiani Planum determined from Mars Exploration Rover data and comparison to orbital measurements

Constraints on the mineralogical composition of low‐albedo, low‐sulfur sands at Meridiani Planum are determined from Mars Exploration Rover (MER) Opportunity Miniature Thermal Emission Spectrometer (Mini‐TES), Mössbauer, and Alpha Proton X–Ray Spectrometer measurements. Results of this work show that the sand is olivine basaltic in composition, with minor amounts of sulfate and a high‐silica phase (glass or secondary amorphous silica). Measurements from all three instruments indicate that pyroxene is twice as abundant as olivine, and that the pyroxene composition is dominated by the low‐calcium variety. The volume abundance of olivine is constrained to be 10–15%. Results from detailed analyses of MER data are used to ground truth the spectral emissivity and mineral abundances derived from orbit with Mars Global Surveyor TES data. TES‐derived mineral abundances are within 5% of those derived from MER data, which is generally within the statistical errors associated with TES‐derived phase abundances. The agreement lends support to global‐ and regional‐scale variations in mineralogical composition determined from TES data in previous studies. An alternative method of least squares minimization is used for modeling the TES and Mini‐TES data; the benefits of this method are demonstrated by comparison with conventional least squares techniques previously used by TES data users.

High‐resolution thermal inertia derived from the Thermal Emission Imaging System (THEMIS): Thermal model and applications

Thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the Thermal Emission Imaging System (THEMIS) on the Mars Odyssey spacecraft, producing the highest‐resolution thermal inertia data set to date. THEMIS thermal inertia values have an overall accuracy of ∼20%, a precision of 10–15%, and are consistent with both Thermal Emission Spectrometer orbital and Miniature Thermal Emission Spectrometer surface thermal inertia values. This data set enables the improved quantification of fine‐scale surface details observed in high‐resolution visible images. In the Tharsis region, surface textures and crater rims observed in visible images have no corresponding variation in the THEMIS thermal inertia images, indicating that the dust mantle is pervasive at THEMIS scales and is a minimum of a few centimeters and up to 1–2 m thick. The thermal inertia of bed form material indicates particle diameters expected for aeolian sediments, and these materials are likely currently saltating. Variations in the thermal inertia within interior layered deposits in Hebes Chasma can be distinguished, and the thermal inertia is too low to be consistent with bedrock or a lava flow. Thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation. Higher‐resolution THEMIS thermal inertia enables the identification of exposed bedrock on the Martian surface. In Nili Patera and Ares Vallis, bedrock material corresponds to distinct compositional and morphologic surfaces, indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes.

One Martian year of atmospheric observations using MER Mini‐TES

The Spirit and Opportunity Mars Exploration Rovers (MER) landed on the surface of Mars in January 2004. Thermal infrared spectra taken by the Miniature Thermal Emission Spectrometer (Mini‐TES) instrument on board each rover, collected in both the upward‐looking and downward‐looking geometries, has allowed for the retrieval of atmospheric temperatures between 1 and 2000 m above the surface, the column optical depth of dust, and the column abundance of water vapor for more than one full Martian year. During this period, Mini‐TES has observed the annual cycle of temperature variations, the diurnal growth and decay of a near‐surface highly superadiabatic layer, and random temperature fluctuations on a timescale of less than a minute. Mini‐TES observations also record the timing, duration, and intensity of several local‐scale and regional‐scale dust storms and the annual variation of water vapor abundance at the two rover locations.

Constraints on dust aerosols from the Mars Exploration Rovers using MGS overflights and Mini‐TES

Overflights of the Mars Exploration Rovers (MER) by the Mars Global Surveyor (MGS) provide a unique opportunity to examine some of the basic properties of dust aerosols, starting with one of the most fundamental, the indices of refraction (m = n + ik) in the infrared. The upward‐viewing geometry of the Miniature Thermal Emission Spectrometer (Mini‐TES) and the combined contemporaneous observations from both MER and MGS are powerful tools. Their use allows atmospheric retrievals to directly determine n and k while offering constraints for the menagerie of other radiative transfer input parameters. We exploit these coordinated observing campaigns, along additional data sources, to carry out series of radiative transfer analyses that ultimately return the set of refractive indices. We apply the resulting m to a larger sample of Mini‐TES data to both further validate our approach and retrieve several other aerosol properties, including dust optical depth, dust size, and a measure of the vertical mixing profile. We find good agreement with the empirical approach of Smith et al. (2006), in terms of both the optical depths themselves and the frequency dependence of their extinction cross section and single scattering albedo. The retrieved dust sizes vary from near 1.3 μm to 1.8 μm within the selected sample, with a precision estimated to be ≃0.1–0.2 μm. The vertical mixing profile evolves from well‐mixed to appreciably confined by LS ∼ 30°. For Spirit (MER‐A), there is an abrupt transition back to a more well‐mixed vertical profile with the onset of regional dust activity at LS ∼ 140°. We discuss the lack of a definitive detection of water ice clouds in Mini‐TES observations and the potential effects of vertical gradients in particle size distribution. Finally, as part of coordinated overflight analyses, an atmospherically corrected TES Lambert albedo map is derived and presented in Appendix A.

The rocks of Gusev Crater as viewed by the Mini‐TES instrument

The Miniature Thermal Emission Spectrometer (Mini‐TES) on board the Mars Exploration Rover Spirit is part of a payload designed to investigate whether a lake once existed in Gusev Crater. Mini‐TES has observed hundreds of rocks along the rover's traverse into the Columbia Hills, yielding information on their distribution, bulk mineralogy, and the potential role of water at the site. Although dust in various forms produces contributions to the spectra, we have established techniques for dealing with it. All of the rocks encountered on the plains traverse from the lander to the base of the Columbia Hills share common spectral features consistent with an olivine‐rich basaltic rock known as Adirondack Class. Beginning at the base of the West Spur of the Columbia Hills and across its length, the rocks are spectrally distinct from the plains but can be grouped into a common type called Clovis Class. These rocks, some of which appear as in‐place outcrop, are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration. The northwest flank of Husband Hill is covered in float rocks known as Wishstone Class with spectral features that can be attributed uniquely to plagioclase feldspar, a phase that represents more than half of the bulk mineralogy. Rare exceptions are three classes of basaltic “exotics” found scattered across Husband Hill that may represent impact ejecta and/or float derived from local intrusions within the hills. The rare outcrops observed on Husband Hill display distinctive spectral characteristics. The outcrop called Peace shows a feature attributable to molecular bound water, and the outcrop that hosts the rock called Watchtower displays a dominant basaltic glass component. Despite evidence from the rover's payload for significant alteration of some of the rocks, no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by Mini‐TES. The mineralogical results supplied by Mini‐TES provide no clear evidence that a lake once existed in Gusev Crater.

Determination and interpretation of surface and atmospheric Miniature Thermal Emission Spectrometer spectral end‐members at the Meridiani Planum landing site

Factor analysis and target transformation techniques have been applied to Miniature Thermal Emission Spectrometer (Mini‐TES) spectra to isolate the end‐member surface and atmospheric component spectral shapes at Meridiani Planum. The surface spectral shapes recovered from the Mini‐TES data set include coarse, gray hematite, surface dust, basaltic sand, and the silica/sulfate‐rich outcrop. In addition, two atmospheric spectral shapes are identified, indicating the variable nature of the atmosphere over the course of the MER rover missions. Linear deconvolution of the basaltic spectral shape indicates that it is high in plagioclase and pyroxene, including pigeonite, with smaller amounts of glass/phyllosilicate and olivine. Linear deconvolution of the outcrop spectral shape indicates that it is composed primarily of amorphous silica/glass/phyllosilicates and Mg‐, Ca‐, and Fe‐bearing sulfates, with smaller amounts of plagioclase.

Mineralogy of the light‐toned outcrop at Meridiani Planum as seen by the Miniature Thermal Emission Spectrometer and implications for its formation

Analysis of Miniature Thermal Emission Spectrometer (Mini‐TES) data has led to the recovery of a pure end‐member spectral shape related to the light‐toned outcrop observed at Meridiani Planum. Data from the MER Mössbauer spectrometer, APXS, and previous Mini‐TES measurements were used to constrain a spectral library used to determine the mineralogy of the outcrop from this spectral shape. Linear deconvolution of the outcrop spectral shape suggests that it is composed primarily of Al‐rich opaline silica, Mg‐, Ca‐, and Fe‐bearing sulfates, plagioclase feldspar, nontronite, and hematite. Conversion of modeled mineralogy to chemistry shows good agreement with the chemical composition of the outcrops determined by APXS. Details of the analysis procedure and implications for the formation of the outcrop are discussed along with terrestrial analogs of the ancient environment at Meridiani.

Physical properties of the Mars Exploration Rover landing sites as inferred from Mini‐TES–derived thermal inertia

The Miniature Thermal Emission Spectrometer (Mini‐TES) on board the two Mars Exploration Rovers provides the first opportunity to observe thermal properties from the Martian surface, relate these properties to orbital data, and perform soil conductivity experiments under Martian conditions. The thermal inertias of soils, bedforms, and rock at each landing site were derived to quantify the physical properties of these features and understand geologic processes occurring at these localities. The thermal inertia for the Gusev plains rock target Bonneville Beacon (∼1200 J m−2 K−1 s−1/2) is consistent with a dense, basaltic rock, but the rocks at the Columbia Hills have a lower thermal inertia (∼620 J m−2 K−1 s−1/2), suggesting that they have a volcaniclasic origin. Bedforms on the floors of craters at both landing sites have thermal inertias of 200 J m−2 K−1 s−1/2, consistent with a particle diameter of ∼160 μm. This diameter is comparable to the most easily moved grain size in the current atmosphere on Mars, suggesting that these bedforms may have formed under current atmospheric conditions. Along the Meridiani plains, the thermal inertia is lower than that derived from TES and Thermal Emission Imaging System (THEMIS) orbital data. This discrepancy is not well understood. Mini‐TES–derived thermal inertias at Gusev along a ∼2.5 km traverse follow trends in thermal inertia measured from orbit with TES and THEMIS. However, along the traverse, there are variability and mixing of particle sizes that are not resolved in the orbital thermal inertia data due to meter‐scale processes that are not identifiable at larger scales.

Surface and near-surface atmospheric temperatures for the Mars Exploration Rover landing sites

Downward-looking spectra of the martian surface from the Miniature Thermal Emission spectrometer (Mini-TES), onboard each of the two Mars Exploration Rovers, are modeled in order to retrieve surface and near-surface atmospheric temperatures. By fitting the observed radiance in the vicinity of the 15-μm CO 2 absorption feature, the surface temperature and the near-surface atmospheric temperature, approximately 1.1 m above the surface, are determined. The temperatures from the first 180 sols (martian days) of each surface mission are used to characterize the diurnal dependence of temperatures. The near-surface atmospheric temperatures are consistently 20 K cooler than the surface temperatures in the warmest part of each sol, which is 1300–1400 LTST (local true solar time) depending on the location. Seasonal cooling trends are seen in the data by displaying the temperatures as a function of sol. Long ground stares, 8.5 min in duration, show as much as 8 K fluctuation in the near-surface atmospheric temperatures during the early afternoon hours when the near-surface atmosphere is unstable.