midinfrared spectral features of rocks and their powders 1 we examined the thermal ir spectra of 35 rock samples and their fine powder equivalents to better understand the relationship between spectral features particle size and composition the christiansen features of solid crystalline rocks differ from those of their powdered samples and the magnitude of this difference changes systematically with rock type both the christiansen feature cf and the transparency feature tf in spectra of particulate igneous rocks are useful in rock type determination they correlate better with the scfm chemical index of rock type than with other numerical rock type indices that we considered major rock type divisions acidic intermediate basic and ultrabasic could be distinguished using both cf and tf but some overlap occurred if one or the other spectral feature was used alone spectral contrast decreases as rocks become more basic probably because of increasing opaque mineral content likewise metallic iron formed as a result of space weathering in an airless environment appears to be the most likely cause of reduced spectral contrast in mature lunar soils thus reststrahlen features should be difficult to detect in remote sensing measurements of such bodies as the moon and mercury moreover the vacuum environment of an airless planetary surface appears to enhance the cf but it may eliminate the tf depending critically on particle size the martian pressure and radiative environment on the other hand appears to enhance the tf which should be sought in spectra of finely particulate surface areas on mars additional environmental simulation spectral experiments are needed to more accurately define the roles of pressure particle size opacity and insolation angle on apparent emissivity

spectral mixture modeling a new analysis of rock and soil types at the viking lander 1 site a viking lander 1 image was modeled as mixtures of reflectance spectra of palagonite dust gray andesitelike rock and a coarse rocklike soil the rocks are covered to varying degrees by dust but otherwise appear unweathered rocklike soil occurs as lag deposits in deflation zones around stones and on top of a drift and as a layer in a trench dug by the lander this soil probably is derived from the rocks by wind abrasion and or spallation dust is the major component of the soil and covers most of the surface the dust is unrelated spectrally to the rock but is equivalent to the global scale dust observed telescopically a new method was developed to model a multispectral image as mixtures of end member spectra and to compare image spectra directly with laboratory reference spectra the method for the first time uses shade and secondary illumination effects as spectral end members thus the effects of topography and illumination on all scales can be isolated or removed the image was calibrated absolutely from the laboratory spectra in close agreement with direct calibrations the method has broad applications to interpreting multispectral images including satellite images

phyllosilicate poor palagonitic dust from mauna kea volcano hawaii a mineralogical analogue for magnetic martian dust the mineralogical and elemental composition of dust size fractions 2 and 5 m of eight samples of phyllosilicate poor palagonitic tephra from the upper slopes of mauna kea volcano hawaii were studied by x ray diffraction xrd x ray fluorescence xrf visible and near ir reflectance spectroscopy mossbauer spectroscopy magnetic properties methods and transmission electron microscopy tem the palagonitic dust samples are spectral analogues of martian bright regions at visible and near ir wavelengths the crystalline phases in the palagonitic dust are in variable proportions plagioclase feldspar ti containing magnetite minor pyroxene and trace hematite no basal reflections resulting from crystalline phyllosilicates were detected in xrd data weak broad xrd peaks corresponding to x ray amorphous phases allophane nanophase ferric oxide possibly ferrihydrite and for two samples hisingerite were detected as oxidative alteration products of the glass residual unaltered glass was also present mossbauer spectroscopy showed that the iron bearing phases are nanophase ferric oxide magnetite titanomagnetite hematite and minor glass and ferrous silicates direct observation by tem showed that the crystalline and x ray amorphous phases observed by xrd and mossbauer are normally present together in composite particles and not normally present as discrete single phase particles ti bearing magnetite occurs predominantly as 5 150 nm particles embedded in noncrystalline matrix material and most likely formed by crystallization from silicate liquids under conditions of rapid cooling during eruption and deposition of glassy tephra and prior to palagonitization of glass rare spheroidal halloysite was observed in the two samples that also had xrd evidence for hisingerite the saturation magnetization js and low field magnetic susceptibility for bulk dust range from 0 19 to 0 68 am2 kg and 3 4 10 6 to 15 5 10 6 m3 kg at 293 k respectively simulation of the mars pathfinder magnet array ma experiment was performed on mauna kea volcano in areas with phyllosilicate poor palagonitic dust and with copies of the pathfinder ma on the basis of the magnetic properties of dust collected by all five ma magnets and the observation that the pathfinder mas collected dust on the four strongest magnets the value for the saturation magnetization of martian dust collected in the ma experiments is revised downward from 4 2 am2 kg to 2 5 1 5 am2 kg the revised value corresponds to 2 7 1 6 wt magnetite if the magnetic mineral is magnetite using js 92 am2 kg for pure magnetite fe3o4 or to 5 0 3 0 to 3 4 2 0 wt maghemite if the magnetic mineral is pure maghemite using js 50 to 74 am2 kg for pure maghemite fe2o3 comparison of the magnetic properties of bulk mauna kea palagonitic dust to those for dust collected by ma magnets shows that the ma magnets extracted culled a subset 25 34 wt of composite magnetic particles from bulk dust the extent of culling of martian dust is not well constrained because the mauna kea palagonitic dust satisfies the essential constraints of the pathfinder magnetic properties experiment composite and magnetic particles capable of being collected by five ma magnets a working hypothesis for the strongly magnetic mineral present in martian dust and soil is magnetite possibly ti bearing formed by rapid crystallization from silicate liquids having volcanic and or impact origins subsequent palagonitization of the glass produces the nanophase ferric oxide phases that dominate the spectral properties of martian bright regions at visible and near ir wavelengths magnetic and phyllosilicate poor palagonitic dust from mauna kea volcano is thus a spectral and magnetic analogue for magnetic martian dust

a search for basaltic to intermediate glasses on mars assessing martian crustal mineralogy multiple datasets have demonstrated that the crust of mars is fundamentally basaltic however spectral libraries used to interrogate thermal infrared spectra of martian dark regions through spectral deconvolution have heretofore lacked mafic glasses despite the importance of amorphous phases or phases with amorphous like spectral signatures in martian mineralogy to establish the presence and importance of basaltic to intermediate glasses in martian lithologies we created five such glasses obtained their thermal infrared spectra and included the spectra in a library used to deconvolve nine regional thermal emission spectrometer spectra from mars we employed the nonnegative least squares nnls deconvolution method which yields deconvolved phase abundances and the uncertainties associated with those abundances the basaltic to intermediate glasses do not appear in the deconvolution solutions indicating they are not globally or regionally important phases because martian igneous or impact processes are capable of basaltic to intermediate glass formation the lack of such glasses in the deconvolved mineralogies suggests either the glasses did not form in detectable quantities or they or their signatures have been removed the masking or replacement of basaltic to intermediate glasses through alteration is supported by the appearance in the deconvolution solutions of amorphous phases e g silica rich glasses opal or phases with amorphous like spectral signatures e g clays zeolites that commonly form through aqueous alteration of mafic glasses the glasses may still be important to local scale thermal infrared studies given the basaltic nature of mars and the variety of local scale lithologies detected by various missions the regional mineralogies derived from the nnls deconvolution analysis divide into five statistically separable groups which provide insight into regional trends in mineralogy

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

distribution and characteristics of adirondack class basalt as observed by mini tes in gusev crater mars and its possible volcanic source abstract we identified 104 unique rock targets belonging to the olivine rich adirondack class using mini tes data rare rocks on the west spur of the columbia hills and on the plains east of the hills also belong to this class we present evidence that adirondack class basaltic lavas may have had their origin at apollinaris tholus linear modeling of adirondack class rock spectra shows only minor variations in mineralogy and the primary phases identified are consistent with olivine basalt having an average olivine composition of fo 45 we used factor analysis and target transformation to identify variability within a single class of rocks for the first time and we find that olivine abundance varies independently of a basaltic matrix a spectral component previously attributed to downwelling radiance is proposed here to be attributable to optically thin dust on rocks which has a greater effect on mini tes spectra than previously recognized but can explain the sloping continuum observed in adirondack class rock spectra as well as the apparent distortion of an olivine absorption spectral mixing is not completely linear leading to the overestimation of sulfate and olivine fractions and the underestimation of plagioclase feldspar although linear mixing appears to successfully replicate the majority of the observed signal published tes spectra of low albedo low dust cover olivine bearing materials do not exhibit the spectral telltales of non linear behavior probably because orbital spectra represent mostly mobile regolith that has not accumulated a sufficient dust cover over 3 6 km areas

basaltic andesite altered basalt and a tes based search for smectite clay minerals on mars 1 the global scale surface type 2 unit first identified with the mars global surveyor thermal emission spectrometer tes remains enigmatic competing hypotheses suggest that it represents either basaltic andesite or some form of altered basalt rich in dioctahedral smectite clay minerals and or spectrally similar amorphous silica phases common dioctahedral smectites contain a diagnostic feature in a portion of tes spectra that has been excluded in previous studies because of atmospheric co2 absorption we exploit the relative transparency of this spectral region to develop two indices that in tandem distinguish between certain smectites and amorphous phases smectites are not detected in northern lowlands type 2 settings consistent with other datasets but the case for primary or secondary amorphous silica phases is strengthened separately one index reveals an abundance of isolated type 2 occurrences in the southern high latitudes 50 associated with dunes the other shows olivine concentrations between 40 and 30

initial results from the mini tes experiment in gusev crater from the spirit rover the miniature thermal emission spectrometer mini tes on spirit has studied the mineralogy and thermophysical properties at gusev crater undisturbed soil spectra show evidence for minor carbonates and bound water rocks are olivinerich basalts with varying degrees of dust and other coatings dark toned soils observed on disturbed surfaces may be derived from rocks and have derived mineralogy 5 to 10 of 45 pyroxene 20 ca rich pyroxene and 25 pigeonite 40 sodic to intermediate plagioclase and 15 olivine forsterite 45 5 to 10 two spectrally distinct coatings are observed on rocks a possible indicator of the interaction of water rock and airfall dust diurnal temperature data indicate particle sizes from 40 to 80 microm in hollows to approximately 0 5 to 3 mm in soils

origins of marslike spectral and magnetic properties of a hawaiian palagonitic soil a palagonitic soil hwmk1 from mauna kea hawaii has marslike spectral and magnetic properties reflectivity spectra of 20 m size separates resemble spectra for martian bright regions and reflectivity spectra of coarser size separates have some spectral characteristics in common with spectra for martian dark regions the bulk soil is magnetic with a saturation magnetization of 0 98 a m2 kg of sample 10 a m2 kg of fe at 296 k petrographic observations show that the soil contains separate populations of black and orange tephra particles which are relatively unaltered fragments of tachylite merocrystalline basalt and extensively weathered palagonitized fragments of sideromelane clear brown basalt glass respectively although both types of particles contain plagioclase and olivine microphenocrysts their iron oxide mineralogies are substantially different as documented by mossbauer and static magnetic measurements a strongly magnetic opaque iron oxide titanomagnetite is associated with black particles and is responsible for the magnetic nature of the soil a relatively weakly magnetic superparamagnetic ferric oxide and minor hematite are associated with orange particles and are responsible for the color the more highly weathered state higher state of oxidation of orange particles is a consequence of the faster weathering palagonitization rate for their sideromelane precursors than for tachylite increasing state of oxidation decreasing saturation magnetization and increasing near ir reflectivity with decreasing particle diameter of bulk soil are manifestations of the increasing proportions of palagonitic material as particle diameter decreases

global distribution composition and abundance of olivine on the surface of mars from thermal infrared data 1 we used spectral indexing and linear deconvolution to compare thermal infrared emission spectra of fo91 fo68 fo53 fo39 fo18 and fo1 olivine samples to mars global surveyor thermal emission spectrometer tes data over low albedo regions of mars the fo91 fo68 fo53 and fo39 spectral end members were confidently identified on mars a range of compositions wider than inferred from martian meteorites small less than hundreds of square kilometers occurrences of the fo91 spectral end member are present in the rims of the argyre and hellas impact basins and may represent martian mantle materials the fo68 spectral end member is common throughout the highlands chasmata outflow channels and nili fossae region the fo53 spectral end member occurs in eastern syrtis major the nili fossae region and smooth floored craters of the highlands although less abundant than fo68 and fo53 the distribution of the fo39 spectral end member suggests that some olivine on mars is more fe rich than olivine in martian meteorites global maps of olivine show that 1 materials containing 10 20 of olivine are common in the southern highlands of mars 2 olivine is most common near the topographic dichotomy boundary and 3 olivine becomes uncommon near the poles suggesting that it may be influenced by topography and or latitude climate olivine is found in early noachian to amazonian terrains some of which may be coeval with phyllosilicate and sulfate deposits detected by omega implying that any early noachian wet period of mars climate history may have been globally inhomogeneous or insufficient to weather the olivine that remains today

mineralogy of three slightly palagonitized basaltic tephra samples from the summit of mauna kea hawaii certain palagonites from hawaii are considered to be among the best analogs for martian fines based upon similar spectral properties for this study three distinctly colored layers were sampled from slightly palagonitized basaltic tephra just below the summit of mauna kea at 4145 m elevation the mineralogy of size fractions of these samples was examined by diffuse reflectance visible and near ir and far ir spectroscopy optical microscopy x ray diffraction mossbauer spectroscopy magnetic analysis electron microprobe analysis empa and transmission and scanning electron microscopy for the 20 1000 m size fraction sample hwmk11 red is essentially completely oxidized and has a hematite ti hematite pigment dispersed throughout the silicate matrix the alteration is present throughout particle volumes and only a trace amount of glass is present no palagonitic rinds were detected in addition to ferric fe ti oxides other phases detected were plagioclase feldspar and a trace of olivine sample hwmk12 black has the lowest proportion of ferric bearing phases and is thus least weathered it consists mostly of unaltered glass with embedded plagioclase and minor amounts of pyroxene olivine and ti magnetite in some grains a thin palagonitic rind is visible indicating some surface alteration the mineralogy for sample hwmk13 yellow is the same as that for hwmk12 except that it has distinct well developed palagonitic rinds consisting of erionite and smectite for all samples the amount of glass and plagioclase decreases and the amount of smectite increases with decreasing particle size for size fractions 20 m for hwmk11 the amount of hematite is essentially constant and mica is present only in the coarse clay sized fraction smectites are low in structural fe for hwmk12 and hwmk13 the zeolite erionite is present along with smectites and nanophase ferric oxides np ox erionite abundance decreases and np ox abundance increases with decreasing particle size the smectite in both black and yellow samples contains some fe3 in octahedral layers there were only two mineral phases containing iron in the fine clay fraction namely smectites and iron oxides for hwmk11 relatively large iron oxide particles 0 1 to 0 4 m were dispersed on clay surfaces for hwmk12 and hwmk13 much finer np ox particles were present in lesser concentrations formation of the zeolite erionite is consistent with the arid climate zone where these samples were collected however transient hydrothermal processes that occurred during the eruption of mauna kea volcano under its permanent ice cap during the pleistocene may have resulted in minerals such as zeolites and smectites which may persist as relicts over a long period of time most of the iron released during weathering of basaltic tephra precipitated as poorly crystalline iron oxides and some of the fe has substituted for the octahedral cations in the structure of authigenic smectites the ti hematite in hwmk11 however is the result of high temperature oxidation of ti magnetite and exsolution from ironbearing silicate phases visible and near ir reflectivity spectra for the 20 m size fraction of hwmk11 is dominated by well crystalline ti hematite corresponding spectra for hwmk12 and hwmk13 whose ferric mineralogy is dominated by np ox particles are more similar to martian bright region spectra

spectroscopic examinations of hydro and glaciovolcanic basaltic tuffs modes of alteration and relevance for mars abstract hydro and glaciovolcanism are processes that have taken place on both earth and mars the amount of materials produced by these processes that are present in the martian surface layer is unknown but may be substantial we have used mars rover analogue analysis techniques to examine altered tuff samples collected from multiple hydrovolcanic features tuff rings and tuff cones in the american west and from glaciovolcanic hyaloclastite ridges in washington state and in iceland analysis methods include vnir swir reflectance mwir thermal emissivity thin section petrography xrd xrf and mossbauer spectroscopy we distinguish three main types of tuff that differ prominently in petrography and vnir swir reflectance minimally altered sideromelane tuff gray to brown colored smectite bearing tuff and highly palagonitized tuff differences are also observed between the tuffs associated with hydrovolcanic tuff rings and tuff cones and those forming glaciovolcanic hyaloclastite ridges for the locations sampled hydrovolcanic palagonite tuffs are more smectite and zeolite rich while the palagonitized hyaloclastites from the sampled glaciovolcanic sites are largely devoid of zeolites and relatively lacking in smectites as well the gray to brown colored tuffs are only observed in the hydrovolcanic deposits and appear to represent a distinct alteration pathway with formation of smectites without associated palagonite formation this is attributed to lower temperatures and possibly longer time scale alteration altered hydro or glaciovolcanic materials might be recognized on the surface of mars with rover based instrumentation based on the results of this study

distinct hematite populations from simultaneous fitting of mossbauer spectra from meridiani planum mars 1 at meridiani planum mars hematite occurs as a lag of 5 mm diameter spherules and their fragments and within the matrix of the sulfate rich outcrop as 30 m particles well crystalline and chemically pure bulk hematite undergoes a magnetic transition at 264 k morin transition that can be detected by mossbauer spectroscopy and is within the martian diurnal temperature range we analyzed outcrop and lag hematite mossbauer spectra obtained by the mars exploration rover mer opportunity as a function of temperature using a simultaneous fitting procedure to determine the morin temperature and the temperature interval over which it occurs mossbauer spectra for terrestrial hematite bearing samples were acquired for comparison at martian temperatures using a mer like spectrometer both outcrop and spherule hematites are characterized by two populations of hematite whose mossbauer sextets have different morin transition behavior compared to pure bulk hematite the morin temperature for martian hematite is lower or not present within the temperature measurement range 190 290 k and occurs over a wider temperature interval consistent with reduced crystallinity reduced particle or crystallite size and or chemical impurities e g al3 ti4 h2o and oh if the morin transition behavior for outcrop hematite results solely from particle size effects and the nonjarosite ferric doublet is interpreted as superparamagnetic hematite as a working hypothesis outcrop hematite is characterized by a size distribution of hematite particles ranging from superparamagnetic to possibly 30 m

pyroclastic activity at home plate in gusev crater mars home plate is a layered plateau in gusev crater on mars it is composed of clastic rocks of moderately altered alkali basalt composition enriched in some highly volatile elements a coarse grained lower unit lies under a finer grained upper unit textural observations indicate that the lower strata were emplaced in an explosive event and geochemical considerations favor an explosive volcanic origin over an impact origin the lower unit likely represents accumulation of pyroclastic materials whereas the upper unit may represent eolian reworking of the same pyroclastic materials

hematite pyroxene and phyllosilicates on mars implications from oxidized impact melt rocks from manicouagan crater quebec canada visible and near ir reflectivity mossbauer and x ray diffraction data were obtained on powders of impact melt rock from the manicouagan impact crater located in quebec canada the iron mineralogy is dominated by pyroxene for the least oxidized samples and by hematite for the most oxidized samples phyllosilicate smectite contents up to 15 wt were found in some heavily oxidized samples nanophase hematite and or paramagnetic ferric iron is observed in all samples no hydrous ferric oxides e g goethite lepidocrocite and ferrihydrite were detected which implies the alteration occurred above 250 c oxidative alteration is thought to have occurred predominantly during late stage crystallization and subsolidus cooling of the impact melt by invasion of oxidizing vapors and or solutions while the impact melt rocks were still hot the near ir band minimum correlated with the extent of aleration fe3 fetot and ranged from 1000 nm high ca pyroxene to 850 nm bulk well crystalline hematite for least and most oxidized samples respectively intermediate band positions 900 920 nm are attributed to low ca pyroxene and or a composite band from hematite pyroxene assemblages manicouagan data are consistent with previous assignments of hematite and pyroxene to the 850 and 1000 nm bands observed in martian reflectivity spectra manicouagan data also show that possible assignments for intermediate band positions 900 920 nm in martian spectra are pyroxene and or hematite pyroxene assemblages by analogy with impact melt sheets and in agreement with observables for mars oxidative alteration of martian impact melt sheets above 250 c and subsequent erosion could produce rocks and soils with variable proportions of hematite both bulk and nanophase pyroxene and phyllosilicates as iron bearing mineralogies if this process is dominant these phases on mars were formed rapidly at relatively high temperatures on a sporadic basis throughout the history of the planet the manicouagan samples also show that this mineralogical diversity can be accomplished at constant chemical composition which is also indicated for mars from analyses of soil at the two viking landing sites

spectral evidence for weathered basalt as an alternative to andesite in the northern lowlands of mars mineral abundances derived from the analysis of remotely sensed thermal emission data from mars have been interpreted to indicate that the surface is composed of basalt surface type 1 and andesite surface type 2 1 the global distribution of these rock types is divided roughly along the planetary dichotomy which separates ancient heavily cratered crust in the southern hemisphere basalt from younger lowland plains in the north andesite 1 but the existence of such a large volume of andesite is difficult to reconcile with our present understanding of the geological evolution of mars here we reinterpret martian surface rock lithologies using mineral abundances from previous work1 and new mineralogies derived from a spectral end member set representing minerals common in unaltered and low temperature aqueously altered basalts our results continue to indicate the dominance of unaltered basalt in the southern highlands but reveal that the northern lowlands can be interpreted as weathered basalt as an alternative to andesite the coincidence between locations of such altered basalt and a suggested northern ocean basin implies that lowland plains material may be composed of basalts weathered under submarine conditions or weathered basaltic sediments transported into this depocentre

mossbauer mineralogy of rock soil and dust at gusev crater mars spirit s journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the columbia hills 1 the mossbauer spectrometer on spirit measured the oxidation state of fe identified fe bearing phases and measured relative abundances of fe among those phases for surface materials on the plains and in the columbia hills of gusev crater eight fe bearing phases were identified olivine pyroxene ilmenite magnetite nanophase ferric oxide npox hematite goethite and a fe3 sulfate adirondack basaltic rocks on the plains are nearly unaltered fe3 fet px and minor npox and magnetite columbia hills basaltic rocks are nearly unaltered peace and backstay moderately altered woolypatch wishstone and keystone and pervasively altered e g clovis uchben watchtower keel and paros with fe3 fet 0 6 0 9 fe from pyroxene is greater than fe from olivine ol sometimes absent and fe2 from ol px is 40 49 and 9 24 for moderately and pervasively altered materials respectively ilmenite fe from ilm 3 6 is present in backstay wishstone keystone and related rocks along with magnetite fe from mt 10 15 remaining fe is present as npox hematite and goethite in variable proportions clovis has the highest goethite content fe from gt 40 goethite feooh is mineralogical evidence for aqueous processes because it has structural hydroxide and is formed under aqueous conditions relatively unaltered basaltic soils fe3 fet 0 3 occur throughout gusev crater 60 80 fe from ol px 10 30 from npox and 10 from mt pasorobles soil in the columbia hills has a unique occurrence of high concentrations of fe3 sulfate 65 of fe magnetite is identified as a strongly magnetic phase in martian soil and dust

spectral evidence for the mineralogy of high albedo soils and dust on mars because of the lack of direct mineralogic data available for mars spectral remote sensing techniques and in particular earth based reflectance spectroscopy remain the primary source of this information presented here are laboratory observations which further constrain the mineralogy and origin of the high albedo soils and dust earth based observations show the reflectance spectra of classical bright regions to be fairly uniform with a strong fe3 o2 charge transfer absorption edge extending from the near uv through the visible this absorption is relatively smooth unlike those observed for crystalline ferric oxides which have superimposed fe3 crystal field bands dilution of ferric oxide with a spectrally more neutral medium montmorillonite weakens the charge transfer and crystal field absorptions together and does not serve to make the ferric oxide spectrum more mars like smoother nontronite ferric iron bearing smectite clay was also investigated for spectral agreement with telescopic observations pure nontronite has fe3 absorptions analogous to but different from ferric oxides as in the previous case the absorptions are very distinct and inappropriate for mars admixture of neither montmorillonite nor ferric oxide serves to improve the nontronite spectrum the conclusion is that nontronite is not a major component of martian soils although the presence of other iron poor clays cannot be totally excluded based on currently available observational data the best spectral analogs known for high albedo soil and dust are a specific type of palagonite from hawaii x ray amorphous weathering products of mafic volcanic glass the indication is therefore that ferric iron on mars is likely to occur in poorly defined crystallo graphic sites such as found in these amorphous materials these materials form slowly under semiarid conditions at ambient temperature even low temperature hydrothermal alteration of glass might provide enough ion mobility to favor some formation of crystalline clays over amorphous gels and may therefore not be the primary mechanism responsible for soil formation on mars the amorphous hawaiian soils exist metastably for thousands of years on earth similar materials on mars would be expected to survive considerably longer under the present cold and dry climatic conditions

bulk mineralogy of the ne syrtis and jezero crater regions of mars derived through thermal infrared spectral analyses abstract we investigated the area to the northwest of the isidis impact basin hereby referred to as nw isidis using thermal infrared emission datasets to characterize and quantify bulk surface mineralogy throughout this region this area is home to jezero crater and the watershed associated with its two deltaic deposits in addition to ne syrtis and the strong and diverse visible near infrared spectral signatures observed in well exposed stratigraphic sections the spectral signatures throughout this region show a diversity of primary and secondary surface mineralogies including olivine pyroxene smectite clays sulfates and carbonates while previous thermal infrared investigations have sought to characterize individual mineral groups within this region none have systematically assessed bulk surface mineralogy and related these observations to visible near infrared studies we utilize an iterative spectral unmixing method to statistically evaluate our linear thermal infrared spectral unmixing models to derive surface mineralogy all relevant primary and secondary phases identified in visible near infrared studies are included in the unmixing models and their modeled spectral contributions are discussed in detail while the stratigraphy and compositional diversity observed in visible near infrared spectra are much better exposed and more diverse than most other regions of mars our thermal infrared analyses suggest the dominance of basaltic compositions with less observed variability in the amount and diversity of alteration phases these results help to constrain the mineralogical context of these previously reported visible near infrared spectral identifications the results are also discussed in the context of future in situ investigations as the nw isidis region has long been promoted as a region of paleoenvironmental interest on mars

thermal emission spectroscopy of the silica polymorphs and considerations for remote sensing of mars 1 the possible existence of silica rich rocks on mars requires consideration of all of the candidate forms of silica that might exist there we synthesized coesite and cristobalite and obtained natural samples of tridymite opal a and opal ct the thermal emission spectra of these silica phases were analyzed and related to their crystal structure and crystallinity structural differences between the polymorphs result in unique spectral character and the degree and type of crystal ordering in opal ct results in cristobalite or tridymite like spectral features these spectra will be useful for analysis of thermal emission spectrometer tes data from mars while silica polymorphs are not modeled in deconvolution of the two main tes surface type spectra this does not preclude the possible detection of local abundances of these minerals on mars spectral detection of silica phases on mars would have implications for the volcanic and alteration history of the planet

low temperature reflectivity spectra of red hematite and the color of mars reflectivity spectra visible and near ir were measured near 141 210 and 300 k for four red and well crystalline powders of hematite red hematite used as commercial pigments two samples of volcanic tephra from mauna kea volcano that contain red hematite as their dominant pigment three samples of palagonitic tephra from the same location that contain nanophase ferric oxide as their dominant pigment and two mixtures of the two types of pigmenting phases relative proportions of red hematite and nanophase ferric oxide were determined by mossbauer spectroscopy for samples containing red hematite as the dominant pigment the positions of the ferric electronic transitions near 430 500 630 and 860 nm are essentially independent of temperature but their widths decrease with decreasing temperature this decrease results in a well defined minimum for the band at 630 nm at low temperatures and in significant increases in reflectivity in spectral regions near 1050 and 600 nm for example the reflectivity ratios r 600 r 530 and r 600 r 860 both increase by a factor as large as l 4 between 300 and 140 k the spectral features from nanophase ferric oxide in samples of palagonitic tephra are nearly independent of temperature spectral data of martian bright regions that are characterized by a shallow band minimum near 860 nm a reflectivity maximum near 740 nm a distinct bend near 600 nm and a shallow absorption edge from 400 to 740 nm are attributed to the presence of nanophase ferric oxide plus subordinate amounts of red hematite the 600 740 and 860 nm features are associated with red hematite because the reflectivity of red hematite at 600 nm is strongly dependent on temperature and because this wavelength is in the red part of the visible spectrum the color of the martian surface may vary as a function of its temperature a conservative upper limit for the red hematite content of the optical surface of mars is 5

effects of pure silica coatings on thermal emission spectra of basaltic rocks considerations for martian surface mineralogy 1 on mars silica derived from chemical weathering could precipitate to coat rocks and particles we suggest that rock coatings of secondary amorphous silica may account for a widespread martian surface spectral unit previously modeled as andesite or weathered basalt in a laboratory study we investigated the effects of synthetic silica coatings on thermal infrared tir spectroscopic measurements secondary amorphous silica is spectrally similar to silicate glass and clay spectra used in previous spectroscopic models silica coating and substrate spectra combine nonlinearly to produce a composite spectrum of a coated rock silica coatings 10 m thick effectively mask the spectral contribution of a silicate substrate therefore the capability of volumetrically small amounts of silica present as thin coatings on rocks should be considered when seeking explanations for spectral variability of martian surface materials

hyperspectral reflectance mapping of cinder cones at the summit of mauna kea and implications for equivalent observations on mars 1 atmospherically corrected hyperspectral reflectance data 0 4 to 2 5 m derived from the airborne visible infrared imaging spectrometer aviris validated with field based traverses and laboratory analyses were used to map the distribution of ferric oxide sulfate and phyllosilicate minerals exposed on fresh and altered cones on the summit of mauna kea volcano hawaii spectra from 0 4 to 1 1 m exhibit charge transfer and electronic transition features related to hematite nanophase iron oxide and possibly jarosite whereas spectra from 2 0 to 2 5 m are characterized by cation oh features related to kaolinite montmorillonite and saponite unaltered cones exhibit concentric zoning of iron oxide signatures with crystalline hematite located near the summits and nanophase iron oxide signatures found at the base of cones and on flow surfaces altered cones puu poliahu and puu waiau have exposures of three phyllosilicate and possible jarosite units in some cases there is zoning with a core of saponite surrounded by montmorillonite kaolinite is only found in two exposures on puu poliahu with one exposure coinciding with a possible jarosite unit the relatively small spatial scale associated with alteration zones seen on mauna kea demonstrates the importance of obtaining high spatial resolution hyperspectral observations of mars

visible near infrared and middle infrared spectroscopy of altered basaltic tephras spectral signatures of phyllosilicates sulfates and other aqueous alteration products with application to the mineralogy of the columbia hills of gusev crater mars 1 we studied visible to near infrared vnir 0 35 2 5 m and middle infrared mir 1800 250 cm 1 also called thermal infrared and vibrational spectra of basaltic tephras from mauna kea volcano that were altered under ambient hydrothermal hydrolytic and acid sulfate and dry heat conditions although models of mir spectra of altered tephras generally produce fits whose quality is reduced compared to deconvolutions of primary lithologies they successfully identify major alteration phases cristobalite oxide phyllosilicate and sulfate except in palagonites mir spectra of the 1 in spectra of the 500 1000 m fraction only if phyllosilicates are present although mauna kea palagonitic tephra is considered a vnir analog to martian dust comparison of mir altered tephra spectra 45 m fraction to dust spectra retrieved from mars global surveyor and mars exploration rover instruments do not provide good spectral matches the best mir match is a tephra that has a strong plagioclase feldspar transparency feature and was altered under dry high temperature oxidizing conditions this sample is not a vnir analog and is not a process analog but it emphasizes the mineralogical importance of plagioclase feldspar in martian dust no single tephra is a good spectral analog across the vnir and mir we found no evidence for substantial sulfates or phyllosilicates in mini thermal emission spectrometer mini tes spectra from gusev crater

effect of precursor mineralogy on the thermal infrared emission spectra of hematite application to martian hematite mineralization 1 observations from the thermal emission spectrometer tes instrument aboard the mars global surveyor mgs spacecraft led to the discovery of two isolated deposits of gray crystalline hematite located in meridiani planum and aram chaos and several smaller deposits in valles marineris several pathways for formation of these hematite deposits have been proposed involving both aqueous and nonaqueous processes this work uses the precise shape and position of spectral features in the martian hematite thermal emission spectrum to constrain hematite formation pathways thermal infrared emission spectra x ray powder diffraction patterns mossbauer spectra and transmission electron microscope tem photomicrographs were obtained for synthetic and natural hematite samples derived by 1 dehydroxylation of fine grained goethite and 2 oxidation of magnetite collectively the instrumental analyses show that the mineralogical composition and crystal morphology of precursor samples and the time and temperature conditions under which decomposition to hematite occur determine the crystallinity and crystal morphology of the hematite product comparison of laboratory and mgs tes spectra shows that the martian hematite spectra correspond closely with a synthetic hematite sample derived by pseudomorphic and topotactic dehydroxylation of goethite at 300 c spectra of goethite precursor samples dehydroxylated at higher temperatures provide increasingly poor fits spectra of hematite samples derived by high temperature thermal oxidation of magnetite are also poorer fits to the martian hematite spectrum thermal emission spectra of goethites heated at lower temperatures are characterized by the spectral signatures of both hematite and goethite and are not consistent with the martian spectra the characteristic that distinguishes the synthetic hematite sample with the mars like spectral signature from the other synthetic hematite samples is the high proportion of crystal surfaces that are crystallographic 001 faces c faces for the former but not the latter the high proportion of 001 face area results because the largest surface of the lath shaped hematite particles is the 001 face as determined by tem thus a possible formation pathway for hematite in meridiani planum aram chaos and valles marineris is precipitation of goethite from aqueous solutions as lath shaped crystals possibly as a stain cement and or massive deposit followed by pseudomorphic and topotactic dehydroxylation to hematite at temperatures below 300 c

spectroscopic evidence for hydrous iron sulfate in the martian soil 1 despite in situ analyses by several landers the composition of the martian soil remains unclear recently constituent minerals in the soil have been proposed from thermal emissivity and mossbauer spectroscopic data from mars these data were interpreted to show spectral evidence for carbonate and an unspecified mineral containing bound water as well as olivine here we present an alternative interpretation suggesting that these spectral features can be satisfied by a single type of mineral namely hydrous iron sulfates acidic waters necessary for production of hydrous iron sulfates would preclude carbonate formation and indicate a dramatically different chemical environment on mars in which olivine would be highly unstable and unlikely to survive soil formation regardless of its presence in the rocks hydrous iron sulfates are efflorescent salts and may be crusting agents in the martian soils

mineral paragenesis on mars the roles of reactive surface area and diffusion geochemical models of secondary mineral precipitation on mars generally assume semiopen systems open to the atmosphere but closed at the water sediment interface and equilibrium conditions however in natural multicomponent systems the reactive surface area of primary minerals controls the dissolution rate and affects the precipitation sequences of secondary phases and simultaneously the transport of dissolved species may occur through the atmosphere water and water sediment interfaces here we present a suite of geochemical models designed to analyze the formation of secondary minerals in basaltic sediments on mars evaluating the role of i reactive surface areas and ii the transport of ions through a basalt sediment column we consider fully open conditions both to the atmosphere and to the sediment and a kinetic approach for mineral dissolution and precipitation our models consider a geochemical scenario constituted by a basin i e a shallow lake where supersaturation is generated by evaporation cooling and the starting point is a solution in equilibrium with basaltic sediments our results show that cation removal by diffusion along with the input of atmospheric volatiles and the influence of the reactive surface area of primary minerals plays a central role in the evolution of the secondary mineral sequences formed we conclude that precipitation of evaporites finds more restrictions in basaltic sediments of small grain size than in basaltic sediments of greater grain size

hematite spherules in basaltic tephra altered under aqueous acid sulfate conditions on mauna kea volcano hawaii possible clues for the occurrence of hematite rich spherules in the burns formation at meridiani planum mars abstract iron rich spherules 90 fe2o3 from electron microprobe analyses 10 100 m in diameter are found within sulfate rich rocks formed by aqueous acid sulfate alteration of basaltic tephra on mauna kea volcano hawaii although some spherules are nearly pure fe most have two concentric compositional zones with the core having a higher fe al ratio than the rim oxide totals less than 100 93 99 suggest structural h2o and or oh 1 the transmission mossbauer spectrum of a spherule rich separate is dominated by a hematite fe2o3 sextet whose peaks are skewed toward zero velocity skewing is consistent with al3 for fe3 substitution and structural h2o and or oh 1 the grey color of the spherules implies specular hematite whole rock powder x ray diffraction spectra are dominated by peaks from smectite and the hydroxy sulfate mineral natroalunite as alteration products and plagioclase feldspar that was present in the precursor basaltic tephra whether spherule formation proceeded directly from basaltic material in one event dissolution of basaltic material and precipitation of hematite spherules or whether spherule formation required more than one event formation of fe bearing sulfate rock and subsequent hydrolysis to hematite is not currently constrained by analogy a formation pathway for the hematite spherules in sulfate rich outcrops at meridiani planum on mars the burns formation is aqueous alteration of basaltic precursor material under acid sulfate conditions although hydrothermal conditions are present on mauna kea such conditions may not be required for spherule formation on mars if the time interval for hydrolysis at lower temperatures is sufficiently long

infrared reflectance spectroscopy of martian analogues one of the main goals of mars exploration is to determine the characteristics of surface materials to shed light on its geological evolution to this end infrared spectra acquired by ground based observations and by space borne remote sensing represent one of the most diagnostic tools in order to best interpret these data a careful comparison with laboratory spectra of martian surface analogues is needed in the present work we report the results of transmittance specular and diffuse biconical reflectance measurements of three materials potentially representative of bright regions on the surface of mars andesite palagonite and montmorillonite few spectroscopic data are available in the literature for andesite the palagonite from etna volcano exhibits important differences from hawaiian palagonite although montmorillonite has been already studied by various authors it was included here in order to build a self consistent set of data the infrared spectral range covered by our measurements 400 6000 cm 1 matches most of the mars radiance spectrum and the spectral resolution of 2 cm 1 has allowed us to perform an accurate band identification using the measurements we have computed the optical constants of the samples the chemical and morphological characterization of the analyzed samples has allowed us to perform a careful interpretation of the observed spectral features the dependence of the band intensities observed in diffuse reflectance on the particle size was used to identify fundamental and combination overtone bands this complex of laboratory data obtained by morphological chemical and spectroscopic analyses provides a reference for the martian mineral identification through interpretation of remote observations

alteration processes in volcanic soils and identification of exobiologically important weathering products on mars using remote sensing determining the mineralogy of the martian surface material provides information about the past and present environments on mars which are an integral aspect of whether or not mars was suitable for the origin of life mineral identification on mars will most likely be achieved through visible infrared remote sensing in combination with other analyses on landed missions therefore understanding the visible and infrared spectral properties of terrestrial samples formed via processes similar to those thought to have occurred on mars is essential to this effort and will facilitate site selection for future exobiology missions to mars visible to infrared reflectance spectra are presented here for the fine grained fractions of altered tephra lava from the haleakala summit basin on maui the tarawera volcanic complex on the northern island of new zealand and the greek santorini island group these samples exhibit a range of chemical and mineralogical compositions where the primary minerals typically include plagioclase pyroxene hematite and magnetite the kind and abundance of weathering products varied substantially for these three sites due in part to the climate and weathering environment the moist environments at santorini and tarawera are more consistent with postulated past environments on mars while the dry climate at the top of haleakala is more consistent with the current martian environment weathering of these tephra is evaluated by assessing changes in the leachable and immobile elements and through detection of phyllosilicates and iron oxide oxyhydroxide minerals identifying regions on mars where phyllosilicates and many kinds of iron oxides oxyhydroxides are present would imply the presence of water during alteration of the surface material tephra samples altered in the vicinity of cinder cones and steam vents contain higher abundances of phyllosilicates iron oxides and sulfates and may be interesting sites for exobiology

discrimination of glass and phyllosilicate minerals in thermal infrared data 1 thermal infrared spectra of glasses and phyllosilicates have similar shapes leading to a proposed ambiguity in deconvolution results we quantify the spectral separability of these two classes using discriminant analysis and linear deconvolution we apply the deconvolution technique to single spectra and two and four component mixtures missing end members result in quantifiable uncertainties between modeled abundances of glasses and phyllosilicates mixtures containing silica k2o glass are susceptible to overestimating phyllosilicates with minimal increases in root mean square error if the silica k2o glass spectrum is not present in the end member set missing phyllosilicate end members are likely to be modeled as combinations of other phyllosilicates rather than glasses with saponite nontronite and halloysite showing the highest uncertainties empirically 15 of the total glass plus phyllosilicate abundance incorporates all uncertainties in derived glass abundance if the glass in the mixture is in the end member set if the glass in the mixture is excluded from the end member set these uncertainties increase to 65 four component mixtures show that glasses and phyllosilicates act as a two component mixing system but can induce small uncertainties in other components applying the maximum derived uncertainties to deconvolutions of surface type 2 measured by the mars global surveyor thermal emission spectrometer we find that silica k2o glass abundance is above the instrument detection limit and a likely component of the surface pure silica glass a proposed amorphous weathering product is the least likely candidate for confusion with phyllosilicates and its noninclusion in models of martian spectra suggests it likely is not a component of the martian surface

estimating silicic lava vesicularity with thermal remote sensing a new technique for volcanic mapping and monitoring remote monitoring of active lava domes pro vides insights into the duration of continued lava extru sion and detection of potentially associated explosive activity on inactive flows variations in surface texture ranging from dense glass to highly vesicular pumice can be related to emplacement time volatile content and internal structure pumiceous surface textures also pro duce changes in thermal emission spectra that are clear ly distinguishable using remote sensing spectrally the textures describe a continuum consisting of two pure end members obsidian and vesicles the distinct spec tral features of obsidian are commonly muted in pu mice due to overprinting by the vesicles which mimic spectrally neutral blackbody emitters assuming that this energy combines linearly in direct proportion to the percentage of vesicles the surface vesicularity can be estimated by modeling the pumice spectrum as a lin ear combination of the glass and blackbody spectra based on this discovery a linear retrieval model using a least squares fitting approach was applied to airborne thermal infrared data of the little glass mountain and crater glass rhyolite flows at medicine lake volcano california as a case study the model produced a ve sicularity image of the flow with values from 0 to f70 which can be grouped into three broad textural classes dense obsidian finely vesicular pumice and coarsely vesicular pumice values extracted from the image compare well with those derived from sem anal ysis of collected samples as well as with previously re ported results this technique provides the means to accurately map the areal distributions of these textures resulting in significantly different values from those de rived using aerial photographs if applied to actively deforming domes this technique will provide volcano logists with an opportunity to monitor dome wide de gassing and eruptive potential in near real time in july 1999 such an effort will be possible for the first time when repetitive global multispectral thermal infrared data become available with the launch of the advanced spaceborne thermal emission and reflectance ra diometer aster instrument aboard the earth ob serving system satellite

weathering dynamics of large igneous provinces lips a case study from the lesotho highlands abstract basaltic terrains contribute a significant component to the global silicate weathering flux despite their limited areal coverage a strong correlation between chemical weathering flux and climatic factors such as temperature in volcanically inactive basaltic fields implies that weathering of basalt might have played an important role in maintaining the habitability of the earth and the balance of the geological carbon cycle however the low erosion rate of flood basalt provinces on tectonically quiescent cratons where the clear climate dependence of weathering rate has been observed implies a supply limited weathering regime so that weathering fluxes are expected to be controlled by physical erosion rather than climate this work tests the weathering dynamics of flood basalts by investigating the weathering flux of the karoo lip on the lesotho highlands where an extremely low rate of denudation has been recorded through terrestrial cosmogenic nuclide dating and sediment flux stream chemistry of the rivers from the lesotho highlands shows typical characteristics of basalt weathering with ca and mg as the dominant cations and hco 3 as the dominant anion strong spatial and seasonal variability of solute concentration possibly linked to a dilution effect is observed however the giant katse reservoir of the lesotho highlands water project lhwp effectively averages the spatial and seasonal variability of the solute concentration the average solution concentration and long term runoff of the katse reservoir give an average atmospheric co2 consumption rate of 0 26 0 02 106 mol km2 yr mean standard deviation the chemical weathering flux requires complete alteration of primary silicates and therefore a supply limited weathering regime is suggested given the low denudation rate nevertheless the chemical weathering rate of the lesotho highlands as well as other low eroding basaltic plateaus is still consistent with the global correlation between temperature and the rate of basalt weathering a production limited denudation rate modulated by temperature is suggested to reconcile the paradox between the observed temperature dependence of chemical weathering rates and supply limited weathering regimes

jarosite and hematite at meridiani planum from opportunity s mossbauer spectrometer mossbauer spectra measured by the opportunity rover revealed four mineralogical components in meridiani planum at eagle crater jarosite and hematite rich outcrop hematite rich soil olivine bearing basaltic soil and a pyroxene bearing basaltic rock bounce rock spherules interpreted to be concretions are hematite rich and dispersed throughout the outcrop hematitic soils both within and outside eagle crater are dominated by spherules and their fragments olivine bearing basaltic soil is present throughout the region bounce rock is probably an impact erratic because jarosite is a hydroxide sulfate mineral its presence at meridiani planum is mineralogical evidence for aqueous processes on mars probably under acid sulfate conditions

geochemical and mineralogical indicators for aqueous processes in the columbia hills of gusev crater mars 1 water played a major role in the formation and alteration of rocks and soils in the columbia hills the extent of alteration ranges from moderate to extensive five distinct rock compositional classes were identified the order for degree of alteration is watchtower clovis wishstone peace backstay the rover s wheels uncovered one unusual soil paso robles that is the most s rich material encountered clovis class rocks have compositions similar to gusev plains soil but with higher mg cl and br and lower ca and zn watchtower and wishstone classes have high al ti and p and low cr and ni peace has high mg and s and low al na and k backstay basalts have high na and k compared to plains adirondack basalts and paso robles soil has high s and p some rocks are corundum normative indicating that their primary compositions were changed by loss and or gain of rock forming elements clovis materials consist of magnetite nanophase ferric oxides npox hematite goethite ca phosphates ca and mg sulfates pyroxene and secondary aluminosilicates wishstone and watchtower rocks consist of fe oxides oxyhydroxides ilmenite ca phosphate pyroxene feldspar mg sulfates and secondary aluminosilicates peace consists of magnetite npox mg and ca sulfates pyroxene olivine feldspar apatite halides and secondary aluminosilicates paso robles consists of fe3 mg ca and other sulfates ca phosphates hematite halite allophane and amorphous silica columbia hills outcrops and rocks may have formed by the aqueous alteration of basaltic rocks volcaniclastic materials and or impact ejecta by solutions that were rich in acid volatile elements

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

the rocks of gusev crater as viewed by the mini tes instrument 1 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

evidence for montmorillonite or its compositional equivalent in columbia hills mars 1 during its exploration of the columbia hills the mars exploration rover spirit encountered several similar samples that are distinctly different from martian meteorites and known gusev crater soils rocks and sediments occurring in a variety of contexts and locations these independence class samples are rough textured iron poor equivalent feo 4 wt have high al si ratios and often contain unexpectedly high concentrations of one or more minor or trace elements including cr ni cu sr and y apart from accessory minerals the major component common to these samples has a compositional profile of major and minor elements which is similar to the smectite montmorillonite implicating this mineral or its compositional equivalent infrared thermal emission spectra do not indicate the presence of crystalline smectite one of these samples was found spatially associated with a ferric sulfate enriched soil horizon possibly indicating a genetic relationship between these disparate types of materials compared to the nearby wishstone and watchtower class rocks major aqueous alteration involving mineral dissolution and mobilization with consequent depletions of certain elements is implied for this setting and may be undetectable by remote sensing from orbit because of the small scale of the occurrences and obscuration by mantling with soil and dust

thermal infrared 2 5 13 5 μm spectroscopic remote sensing of igneous rock types on particulate planetary surfaces fundamental molecular vibration bands are significantly diminished by scattering thus such bands in spectra of fine particulate regoliths i e dominated by 5 m particles or regoliths displaying a similar scale of porosity are difficult to use for mineralogical or rock type identification consequently other spectral features have been sought that may be more useful in spectroscopic remote sensing of composition we find that mineralogical information is retained in overtones and combination tones of the fundamental molecular vibrations in the 3 0 to 7 0 m region but that relatively few minerals have a sufficiently distinctive band structure to be unambiguously identified with currently available techniques more significantly identification of general rock type as defined by the scfm chemical index scfm sio2 sio2 cao feo mgo is possible using spectral features associated with the principal christiansen frequency and with a region of relative transparency between the si o stretching and bending bands however environmental factors may affect the appearance and wavelengths of these features finally prominent absorption bands may result from the presence of relatively small amounts of water hydroxyl or carbonate because absorption bands exhibited by these materials in the 2 7 to 4 0 m region where silicate spectra are otherwise featureless increase strongly in spectral contrast with decreasing particle size such materials are thus detectable in very small amounts in a particulate regolith composed predominantly of silicate minerals

mossbauer mineralogy of rock soil and dust at meridiani planum mars opportunity s journey across sulfate rich outcrop basaltic sand and dust and hematite lag deposits additonal co authors p gutlich e kankeleit t mccoy dw mittlefehldt f renz me schmidt b zubkov sw squyres re arvidson

mapping the distribution of vesicular textures on silicic lavas using the thermal infrared multispectral scanner the thermal infrared multispectral scanner tims is a potentially powerful tool for mapping detailed chemical variations in silicic lava flows which in turn could expand knowledge of pre eruption compositional gradients and mixing processes in silicic magma bodies however thermal infrared image data may be greatly influenced by the range of vesicular textures which occur on silicic flows to investigate the effect of vesicularity on tims imagery independent of chemical variations we studied little glass mountain at the medicine lake volcano of northern california a large rhyolitic flow of uniform composition but textural heterogeneity the imagery was recalibrated so that the digital number values for a lake in the scene matched a calculated ideal spectrum for water tims spectra for the lava show useful differences in coarsely and finely vesicular pumice data particularly in tims bands 3 and 4 images generated by ratioing these bands accurately map out those areas known from field studies to be coarsely vesicular pumice these texture related emissivity variations are probably due to the larger vesicles being relatively deeper and separated by smaller septa leaving less smooth glass available to give the characteristic emission of the lava in studies of inaccessible lava flows as on mars areas of coarsely vesicular pumice must be identified and avoided before chemical variations can be interpreted remotely determined distributions of vesicular and glassy textures can also be related to the volatile contents and potential hazards associated with the emplacement of silicic lava flows on earth

evidence of phyllosilicates in wooly patch an altered rock encountered at west spur columbia hills by the spirit rover in gusev crater mars 1 on its traverse to columbia hills the mars exploration rover spirit investigated an outcrop designated wooly patch that exhibited morphological mineralogical and geochemical characteristics at the extreme ends of ranges observed among rocks studied at west spur a westward projecting salient near the foot of the columbia hills gusev crater the major element composition and fe mineralogy as determined by the alpha particle x ray spectrometer and mossbauer spectrometer are inconsistent with any reasonable assemblage of basaltic minerals in that there is an excess of si and al the combined data are best explained by the presence of 14 17 phyllosilicate minerals phyllosilicates that account for the composition and cation ratios include members of the kaolinite serpentine chlorite and septechlorite groups the potential existence of kaolinite type al rich phyllosilicates within the wooly patch outcrop suggests a mildly acidic environment ph 4 6 in the past and an open hydrologic system with good drainage conditions in the environment where these rocks were altered

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 2 application to martian surface spectra from the mars global surveyor thermal emission spectrometer atmospherically corrected thermal infrared spectra of large regions of the martian surface from the mars global surveyor thermal emission spectrometer mgs tes previously have been interpreted to represent two general spectral classes one class represents a basalt to basaltic andesite composition and the other class represents a basaltic andesite to andesite composition we have performed new linear deconvolutions of the two martian surface type spectra with an end member set tailored to represent volcanic rock types our preparatory study of laboratory spectra of terrestrial volcanic rocks acquired at 2 cm 21 sampling convolved to tes spectral sampling 10 cm 21 shows little degradation in deconvolution results when compared to results acquired using the higher spectral resolution data indicating that the deconvolution technique is valid for analyzing data at tes resolution our spectral fits to the martian data agree well with previous models and do not exhibit any notable deviations from the martian spectra that would indicate the absence of any significant end members in our model modal mineralogies obtained with these new spectral fits also compare favorably within the previously stated uncertainties to prior results the newly derived modal mineralogies are used with new and traditional classification schemes for volcanic igneous rocks introduced in a companion paper wyatt et al this issue to classify the martian compositions our results substantiate the previously proposed hypothesis that these two spectral classes on the martian surface represent volcanic compositions with distinguishable differences in silica content ranging from basalt to andesite

quantitative compositional analysis using thermal emission spectroscopy application to igneous and metamorphic rocks the mineral composition of a suite of igneous and metamorphic rocks was determined using the thermal infrared emission spectra of these rocks in a linear spectral deconvolution algorithm this algorithm assumes that the infrared spectrum of each rock is a linear mixture of the component mineral spectra weighted by volume abundance a diverse suite of 36 common rock forming and accessory minerals was used in the deconvolution the model was tested by comparing the mineralogy derived from the infrared spectrum with petrographically estimated abundances for 45 igneous and 51 metamorphic rock samples the mineral abundances derived from these two techniques agree to within 67 15 for the primary minerals feldspar pyroxene quartz and calcite dolomite and 69 17 for secondary minerals such as micas and amphiboles these differences are comparable to the error for traditional thin section mode estimates which are 65 15 for major minerals and 5 for minor minerals the detection limit for the primary and secondary minerals found in the rocks analyzed ranged from 5 to 10 each major rock type studied here was easily distinguished by its spectral characteristics the best results in both the qualitative determination of the rock type and dominant minerals and the quantitative reproduction of absorption features and mineral composition were obtained for igneous rock samples for metamorphic rocks pelite and quartzo feldspathic samples gave slightly better results than calcareous or mafic samples a controlled analysis in which the end member suite was reduced based on an initial estimate of the rock type only improved the results by several percent for most primary and secondary minerals the quality of the obtained results demonstrates that a linear deconvolution of infrared emission spectra provides an accurate rapid technique for determining the quantitative mineral composition of rock samples in a laboratory and has application to future in situ measurements

estimates of ocean macroturbulence structure function and spectral slope from argo profiling floats abstractthe argo profiling float network has repeatedly sampled much of the world ocean this study uses argo temperature and salinity data to form the tracer structure function of ocean variability at the macroscale 10 1000 km mesoscale and above here second order temperature and salinity structure functions over horizontal separations are calculated along either pressure or potential density surfaces which allows analysis of both active and passive tracer structure functions using argo data a map of global variance is created from the climatological average and each datum when turbulence is homogeneous the structure function slope from argo can be related to the wavenumber spectrum slope in ocean temperature or salinity variability this first application of structure function techniques to argo data gives physically meaningful results based on bootstrapped confidence intervals showing geographical dependence of the structure functions with slopes near on average independent of depth

hydrothermal precipitation of sanidine adularia having full al si structural disorder and specular hematite at maunakea volcano hawai i and at gale crater mars

emission spectroscopy of clay minerals and evidence for poorly crystalline aluminosilicates on mars from thermal emission spectrometer data 1 to understand the aqueous history of mars it is critical to constrain the alteration mineralogy of the martian surface previously published analyses of thermal infrared 6 25 m remote sensing data of mars suggest that dark regions have 15 20 clay minerals however near infrared 1 3 m spectral results generally do not identify widespread clay minerals thermal infrared detections of clays on mars are difficult to interpret owing in part to the relative paucity of published spectral analyses of clay minerals and clay bearing materials using similar spectra thermal infrared emission spectra in this study we present an analysis of the thermal emission spectral features 6 25 m or 400 1650 cm 1 of a suite of clay mineral reference materials and clay bearing rocks linking their spectral features to the crystal chemical properties of the clays on the basis of this context provided by the emission spectral analysis of clay minerals and clay bearing rocks we reconsider the evidence for clay minerals on mars from thermal emission spectrometer tes results we propose that global scale clay abundances determined from tes probably represent a geologically significant surface component though they may actually correspond to poorly crystalline aluminosilicates with similar si o ratios to clay minerals 0 3 0 4 rather than well crystalline clays if clay minerals or clay like materials on mars are poorly crystalline and or dessicated they may be detectable in the thermal infrared but not easily detected with near infrared data sets

mineralogy and chemistry of altered icelandic basalts application to clay mineral detection and understanding aqueous environments on mars we used a suite of techniques including those emulating compositional data sets obtained from mars orbit and obtainable at the mars surface to examine aqueous alteration of basaltic rocks from iceland as a mineralogic and geochemical analog for noachian environments on mars a sample suite was collected for laboratory measurement of 1 whole rock visible near infrared vnir reflectance and thermal infrared tir emission spectra 2 vnir and tir reflectance spectra of particle size separates derived from the bulk rock and from materials extracted from fractures vesicles 3 x ray diffraction xrd patterns for determination of quantitative modal mineralogy 4 major element chemistry using flux fusion of whole rock powders and 5 electron microprobe analyses of minerals in thin sections conclusions about aqueous alteration can be influenced by technique for these basalts whole rock chemical data showed scant evidence for chemical fractionation but tir vnir and xrd measurements identified distinctive assemblages of hydrous silicate minerals differing by sample xrd provided the most complete and accurate quantitative determination of sample mineralogy however vnir spectroscopy was the technique most useful for determining composition of low abundance smectite clays and tir spectroscopy was the most useful for recognizing hydrated silicates in thin surface coatings high spatial resolution mineralogical and chemical data sets were useful for understanding the texture and distribution of alteration products and variations in fluid chemistry no single approach provides a complete assessment of the environment of alteration demonstrating the importance of employing multiple synergistic mineralogical and geochemical techniques and instruments in exploration of rock strata from aqueous paleoenvironments on mars

microstructure mapping a new method for imaging deformation induced microstructural features of ice on the grain scale this work presents a method of mapping deformation related sublimation patterns formed on the surface of ice specimens at microscopic resolution 3 4 mm pixel 1 the method is based on the systematic sublimation of a microtomed piece of ice prepared either as a thick or a thin section the mapping system consists of an optical microscope a ccd video camera and a computer controlled xy stage about 1500 images are needed to build a high resolution mosaic map of a 4 5 9 cm section mosaics and single images are used to derive a variety of statistical data about air inclusions air bubbles and air clathrate hydrates texture grain size shape and orientation and deformation related features subgrain boundaries slip bands subgrain islands and loops pinned and bulged grain boundaries the most common sublimation patterns are described and their relevance for the deformation of polar ice is briefly discussed

evidence for platy hematite grains in sinus meridiani mars 1 midinfrared 1600 200 cm 1 spectral data received from the mars global surveyor thermal emission spectrometer mgs tes have provided evidence for a large hematite bearing fe2o3 deposit in sinus meridiani mars we report here the results of a laboratory spectroscopic investigation of 24 hematite samples including polycrystalline hand samples massive and schistose textures single crystal hand samples and particle size fractions single crystal and polycrystalline discrete particles laboratory midinfrared analyses of crystallographically oriented hematite samples suggest that the hematite emission in sinus meridiani sm is predominantly from the crystallographic c face of hematite this observation implies the presence of platy hematite particles with the plate face being the crystallographic c face the observations are consistent with a formational model where the platy gray hematite originated as an iron oxide chemically precipitated from fe rich aqueous and or hydrothermal solutions on early mars that was buried recrystallized to platy hematite and subsequently reexposed as lenses of schistose hematite in a friable consolidated stratigraphic unit unconsolidated platy hematite particles are also likely to be present as a physical weathering product of the schistose hematite lenses

mineralogy at meridiani planum from the mini tes experiment on the opportunity rover the miniature thermal emission spectrometer mini tes on opportunity investigated the mineral abundances and compositions of outcrops rocks and soils at meridiani planum coarse crystalline hematite and olivine rich basaltic sands were observed as predicted from orbital tes spectroscopy outcrops of aqueous origin are composed of 15 to 35 by volume magnesium and calcium sulfates a high silica component modeled as a combination of glass feldspar and sheet silicates 20 to 30 and hematite only minor jarosite is identified in mini tes spectra mini tes spectra show only a hematite signature in the millimeter sized spherules basaltic materials have more plagioclase than pyroxene contain olivine and are similar in inferred mineral composition to basalt mapped from orbit bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites bright wind streak material matches global dust waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering

photometric properties of mars soils analogs we have measured the bidirectional reflectance of analogs of dry wet and frozen martian soils over a wide range of phase angles in the visible spectral range all samples were produced from two geologic samples the standard jsc mars 1 soil simulant and hawaiian basaltic sand in a first step experiments were conducted with the dry samples to investigate the effects of surface texture comparisons with results independently obtained by different teams with similar samples showed a satisfying reproducibility of the photometric measurements as well as a noticeable influence of surface textures resulting from different sample preparation procedures in a second step water was introduced to produce wet and frozen samples and their photometry investigated optical microscope images of the samples provided information about their microtexture liquid water even in relatively low amount resulted in the disappearance of the backscattering peak and the appearance of a forward scattering peak whose intensity increases with the amount of water specular reflections only appeared when water was present in an amount large enough to allow water to form a film at the surface of the sample icy samples showed a wide variability of photometric properties depending on the physical properties of the water ice we discuss the implications of these measurements in terms of the expected photometric behavior of the martian surface from equatorial to circum polar regions in particular we propose some simple photometric criteria to improve the identification of wet and or icy soils from multiple observations under different geometries

thermally altered palagonitic tephra a spectral and process analog to the soil and dust of mars we studied six palagonitic soil samples ph 1 through ph 6 which were collected at 30 cm intervals from a lava slab on mauna kea hawaii the samples represent an alteration sequence caused by heating during emplacement of molten lava over a preexisting tephra cone they are both spectral and weathering alteration process analogs to the martian surface techniques employed included visible and near ir spectroscopy mossbauer spectroscopy and magnetic analysis the two samples collected from beyond 90 cm from the slab ph 5 and ph 6 did not see the transient heating event and are composed of coarse grained glassy basaltic hawaiitic particles some of which have been moderately palagonitized since formation of the cone in the late pleistocene the four samples closest to the slab ph 1 through ph 4 have been strongly altered in response to heating during its emplacement their iron oxide mineralogy is dominated by nanophase ferric oxide the sample adjacent to the slab ph 1 which would have seen the highest temperatures has a factor of 3 less h2o and contains crystalline hematite and magnetite in addition to nanophase ferric oxide lesser amounts of magnetite but not hematite are present in samples 30 cm ph 2 and 60 cm ph 3 from the slab the reflectivity spectra of samples ph 2 through ph 4 are similar to spectra of palagonites reported by other workers to be good mars visible to near ir spectral analogs the reflectivity spectrum of ph 1 is an even better spectral analog to mars in that it exhibits absorption features indicative of both nanophase and crystalline ferric oxides similar to several new martian telescopic data sets our sampling site may also be a process analog for mars in that heating episodes by volcanism and or impact cratering could produce crystalline ferric oxides from poorly crystalline palagonitic material thus localized thermal alteration events may provide a volumetrically important mechanism for the palagonitization of basaltic glass and the production of crystalline ferric oxides on mars

determination of martian meteorite lithologies and mineralogies using vibrational spectroscopy we have acquired thermal infrared emission spectra of four martian meteorite samples alh77005 nakhla zagami and eet79001 representing three major lithologies iherzolite clinopyroxenite and basalt the spectra of these meteorites are significantly different from each other and we can distinguish the three lithologies easily on the basis of their spectral morphologies using a linear deconvolution model the modal mineralogies of alh77005 nakhla and zagami were derived from their spectra to within 2 19 of the modes derived by optical methods for zagami and eet79001 the correct mineral types were identified as present using the linear method although an exact spectral match using available end member spectra was not obtained probably due to the lack of a pigeonite end member spectrum or shock effects in the meteorites the meteorite spectra we have acquired will be used for comparison with data to be returned by the thermal emission spectrometer tes on the mars global surveyor orbiter and would also be useful for comparing to future rover or lander based thermal ir spectra based on our results comparisons of mineral end member and meteorite spectra with tes spectra of coarse regolith and rocky regions should aid identification and mapping of martian surface lithologies and unit mineralogy

mineralogy composition and alteration of mars pathfinder rocks and soils evidence from multispectral elemental and magnetic data on terrestrial analogue snc meteorite and pathfinder samples major element multispectral and magnetic properties data were obtained at ares vallis during the mars pathfinder mission to understand the compositional mineralogical and process implications of these data we obtained major element mineralogical and magnetic data for well crystalline and nanophase ferric minerals terrestrial analogue samples with known geologic context and snc meteorites analogue samples include unaltered palagonitic and sulfatetic tephra from mauna kea volcano hydrolytic and acid sulfate alteration steam vent material from kilauea volcano hydrolytic alteration and impactites from meteor crater relithification salient results for mars pathfinder include 1 band depths bd530b and bd600 and the reflectivity ratio r800 r750 are consistent with the dominant ferric mineral being nanophase ferric oxide associated with an unknown amount of h2o and occurring in composite particles along with subordinate amounts of other ferric minerals hematite and hematite plus nanophase goethite are most consistent with the data but maghemite akaganeite schwertmannite and nanophase lepidocrocite are also possible interpretations ferric oxides that are consistently not favored by the data as sole alteration products are jarosites and well crystalline goethite and lepidocrocite 2 the strength of the ferric adsorption edge r750 r445 implies the fe3 fe2 values for pathfinder rock and soil are within the ranges 0 7 3 and 3 20 respectively 3 ferrous silicates are indicated for subsets of pathfinder rocks and soils one subset has a band minimum near 930 nm that can attributed to low ca pyroxene alternatively the band could be a second manifestation of certain ferric oxides including nanophase goethite maghemite akaganeite and schwertmannite another subset has a negative spectral slope from 800 to 1005 nm which could result from the high energy wing of a high ca pyroxene and or olivine band a mixture of bright and dark materials and for rocks thin coatings of bright dust on dark rocks 4 chemical data on pathfinder rocks and soils are consistent with two component mixtures between an andesitic rock with low mgo and so3 concentrations soil free rock and a global basaltic soil with high mgo and so3 concentrations rock free soil pathfinder rock free soil can be modeled as a chemical mixture of snc meteorites and the pathfinder soil free rock 5 pathfinder soil cannot be obtained by chemical alteration of pathfinder rocks by any of the hydrolytic and acid sulfate alteration processes we studied presumably global mixing has obscured and possibly erased the elemental signatures of chemical alteration 6 the strongly magnetic phase in palagonitic and sulfatetic tephra is titanomagnetite and possibly its oxidation product titanomaghemite fe ti spinels the saturation magnetization of the tephra samples 0 5 2 0 am2 kg is at or below the low end of the range inferred for martian dust 4 2 am2 kg implying that lithogenic fe ti spinels are a possible candidate for the martian strongly magnetic phase 7 the predominantly palagonitic spectral signature and magnetic nature of martian soil and dust are consistent with glassy precursors with imbedded fe ti spinel particles comparison with lunar glass production rates suggests that production of sufficient quantities of glassy materials on mars by volcanic and impact processes is sufficient to account for these observations

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 1 determination of mineralogy chemistry and classification strategies we have examined and applied existing classification schemes for volcanic rocks and developed new schemes using thermal emission spectra of terrestrial volcanic rocks laboratory thermal infrared spectra 5 25 m at 2 cm 1 spectral sampling deconvolved modal mineralogies and derived mineral and bulk rock chemistries were used to distinguish basalt basaltic andesite andesite and dacite modal mineralogies derived from linear deconvolution of terrestrial volcanic rocks were compared to modes measured by an electron microprobe phase mapping technique to determine the accuracy of linear deconvolution in modeling specific mineral abundances one standard deviations of the absolute differences between modeled and measured mineral abundances range from 2 4 to 12 2 vol with an average standard deviation of 4 8 vol being in agreement with average uncertainties calculated in previous studies weighted average compositions of feldspars in the deconvolution generally overlap the measured ranges of plagioclase compositions and the presence of low calcium and high calcium pyroxenes was correctly identified bulk chemistries of volcanic rocks were derived with a relatively high degree of accuracy 1 standard deviations ranging from 0 4 to 2 6 vol by combining the compositions of spectrally modeled phases in proportion to their relative abundances in a particular sample these data were collectively used to examine existing and develop new volcanic rock classification schemes however no single classification scheme was effective in accurately classifying all samples multiple steps of classification were required to distinguish volcanic rocks reflecting the mineralogic diversity and continuum of compositions that exists in volcanic rock types in a companion paper hamilton et al this issue these schemes are applied to the classification of martian surface compositions

iron isotopic and chemical tracing of basalt alteration and hematite spherule formation in hawaii a prospective study for mars abstract hematite spherules from mauna kea volcano hawaii resemble martian hematite spherules at meridiani planum in morphology mineralogy and geochemistry and they both formed in association with acid sulfate alteration of basalt to gain insights into the processes involved in the formation of these spherules we have measured the fe isotopic compositions of unaltered basalts and tephras as well as a variety of weathering alteration products including altered basalts hematite rich breccia and individual hematite spherules jarosite bearing tephras palagonitic tephras calcined tephras high t dry oxidation and steam vent tephras compared to other alteration processes that induce little fe mobility acid sulfate alteration produces large fe isotopic variations 56 fe values ranging from 0 15 to 0 94 we used rock slabs from a variably altered basaltic rock to constrain the fe isotope fractionation factor during acid sulfate alteration of basaltic rocks we found that the process followed a rayleigh distillation with an instantaneous fractionation factor of 0 24 between the fluid and the residue for 56 fe resulting in a heavy fe isotope enrichment in the alteration residue however the constant mn fe ratios of the slabs suggest that acid sulfate leaching does not significantly fractionate mn fe ratios in basalts which is consistent with the mobilization of iron as fe ii we also measured the fe isotopic compositions and mn fe ratios using nanosims of individual hematite spherules from a spherule rich breccia hwmk745r the spherules show heavy fe isotopic enrichments and low mn fe ratios compared to unaltered samples which is similar to the fractionations encountered in iron formations a rayleigh fractionation model suggests that both fe isotopic compositions and mn fe ratios of the spherules are consistent with 80 fe oxidation and precipitation from an acid sulfate fluid therefore direct fe precipitation from a fluid can readily explain the hematite spherule formation and a more complex scenario involving jarosite precipitation followed by conversion to hematite is not needed combined thermodynamic and kinetic constraints also suggest that precipitation of jarosite would be hindered the study presents a roadmap for studying future returned martian samples in the laboratory

surface mineralogy of martian low albedo regions from mgs tes data implications for upper crustal evolution and surface alteration 1 mars global surveyor thermal emission spectrometer mgs tes data are used to derive the modal mineralogy of spectrally distinct martian low albedo regions and to identify spatial trends in mineralogic assemblages results from this work are consistent with the major results of previous spectroscopic studies 1 plagioclase and clinopyroxene are the dominant minerals of most southern highlands regions 2 the northern plains exhibit the lowest pyroxene abundance within martian low albedo regions and 3 the highest concentrations of high silica phase s are found in the northern plains solis planum and a few southern high latitude regions low albedo regions may be classified into four units on the basis of relative abundances of plagioclase pyroxene and high silica phase s unit distributions between 45 latitude exhibit moderate correlation with distinct provinces e g syrtis major aonium sinus defined by large scale morphology elevation and to some extent surface age suggesting that the spectral and compositional differences between these units are more strongly controlled by original bedrock mineralogy than by surface atmosphere interactions and alteration syrtis major exhibits a difference in mineralogy from the surrounding highlands suggesting a differing degree of fractional crystallization assimilation or source region composition areas with thick crust near the tharsis plateau exhibit lower abundances of olivine and greater plagioclase pyroxene ratios than surrounding highland terrains suggesting that magmas in this region may have undergone increased olivine fractionation regions where surface alteration is more likely to be the primary control on observed spectral signatures are the high latitude areas 45 where globally surfaces dominated by high silica phase s are most commonly found

determining the modal mineralogy of mafic and ultramafic igneous rocks using thermal emission spectroscopy the modal mineralogies of 20 mafic and ultramafic igneous rocks were determined from their thermal infrared emission spectra using a linear deconvolution approach which uses a library of end member mineral spectra to model a bulk rock spectrum over 90 of the modes obtained from thermal emission spectra agree with modes obtained by traditional optical analyses to within the stated error of the optical analyses 5 15 vol library spectra of several compositions within a solid solution series e g plagioclase feldspars labradorite and bytownite were commonly used in each best fit model and are assumed to represent in combination a composition in the rock for which an identical mineral spectrum was unavailable in the library the accuracy of this assumption was evaluated by calculating a weighted average solid solution composition for plagioclase and or pyroxenes from the library minerals used in the model best fit of 14 rocks and comparing these compositions to the actual chemistries measured by electron microprobe or the optically estimated an the derived solid solution compositions are generally within 10 15 an or mg of the measured composition modal data derived from the spectra via the deconvolution were summed and converted to weight percent wt oxides for comparison to standard bulk chemistry data sio2 al2o3 and na2o k2o were generally slightly overestimated and feo and mgo were typically slightly underestimated modes and wt oxides were plotted on standard rock type classification diagrams and provide broadly accurate classifications demonstrating that the linear deconvolution technique is successful at deriving useful mineralogical information from thermal infrared emission spectra of bulk rock samples furthermore convolution of the laboratory data to spectral resolutions comparable to remote sensing instruments specifically the mars global surveyor thermal emission spectrometer demonstrates only a 5 vol increase in modal uncertainty for minerals present in abundances 10 vol this study thus provides a strong foundation for the application of this technique to mafic igneous sample spectra from both laboratory and remote sensing instruments

in situ evidence for an ancient aqueous environment at meridiani planum mars sedimentary rocks at eagle crater in meridiani planum are composed of fine grained siliciclastic materials derived from weathering of basaltic rocks sulfate minerals including magnesium sulfate and jarosite that constitute several tens of percent of the rock by weight and hematite cross stratification observed in rock outcrops indicates eolian and aqueous transport diagenetic features include hematite rich concretions and crystal mold vugs we interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history the environmental conditions that they record include episodic inundation by shallow surface water evaporation and desiccation the geologic record at meridiani planum suggests that conditions were suitable for biological activity for a period of time in martian history