petrogenesis of the elephant moraine a79001 meteorite multiple magma pulses on the shergottite parent body abstract the eeta 79001 achondrite consists of two distinct igneous lithologies joined along a planar non brecciated contact both are basaltic rocks composed primarily of pigeonite augite and maskelynite but one contains zoned megacrysts of olivine orthopyroxene and chromite that represent disaggregated xenoliths of harzburzite both lithologies probably formed from successive volcanic flows or multiple injections of magma into a small shallow chamber many similarities between the two virtually synchronous magmas suggest that they are related possible mechanisms to explain their differences involve varying degrees of assimilation fractionation from similar parental magmas or partial melting of a similar source peridotite of these assimilation of the observed megacryst assemblage seems most plausible however some isotopic contamination may be required in any of these petrogenetic models the meteorite has suffered extensive shock metamorphism and localized melting during a large impact event that probably excavated and liberated it from its parent body both basaltic lithologies and the inferred ultramafic protolith of the megacryst assemblage are petrologically similar to other members of the shergottite group and all may have been derived from a volcanic plutonic complex on a planetary body

a global climatology of atmospheric fronts 1 atmospheric fronts in the lower troposphere often mark regions of significant weather and serve as an important conceptual tool that is frequently used and well understood by the public this study uses an objective method to identify fronts in the era 40 reanalysis and to compile a quantitative global climatology of their occurrence the climatology confirms the mid latitude storm tracks as the regions of highest front frequency and identifies slow moving frontal boundaries in the subtropics corresponding to major climate features such as the mei yu front the climatology also shows fronts to be common features of the south pacific convergence zone in the northern hemisphere fronts shift poleward in summer in the southern hemisphere this and other aspects of seasonal behavior are rather different

evidence for komatiite type lavas on mars from phobos ism data and other observations data from the phobos 2 imaging spectrometer for mars ism compiled by mustard et al 1993 and other observations support the existence of komatiitic lavas on mars mustard et al 1993 determined from ism data that the composition of the low albedo materials covering the syrtis major plateau originally consisted of augite bearing basalt containing both augite and pigeonite with no appreciable amount of olivine this description is consistent with a komatiitic basalt komatiite is significant for the earth because it contains a high amount of mgo implying generation under unique circumstances compared to more typical basaltic compositions and may be similarly important for mars

the dominance of cold and dry alteration processes on recent mars as revealed through pan spectral orbital analyses a b s t r a c t classic low albedo regions of the martian surface are investigated using combined reflectance and emission pan spectral data to constrain the types of alteration mineral phases that are present at spectrally significant abundances 10 15 the lack of hydrated mineral species observed using near infrared data suggests that anhydrous chemical alteration dominates at the regional scale spectral characteristics in the vnir and tir are consistent with those associated with weathering processes identified in the hyper arid hypo thermal and geologically stable mcmurdo dry valleys of antarctica where oxidative weathering processes dominate and significant aqueous alteration does not occur in addition the spectral trends associated with oxidative weathering processes are similar to regional trends in vnir spectral characteristics observed on mars and potentially complicate the spectral interpretation of basaltic terrains collectively these relationships suggest that the martian surface has been dominated by cold dry and stable conditions since the formation of these low albedo regions while significant at regional scales early in martian history aqueous alteration appears to be predominantly absent from large scale basaltic regions on mars

searching for the source regions of martian meteorites using mgs tes integrating martian meteorites into the global distribution of igneous materials on mars the objective of this study was to identify and map possible source regions for all 5 known martian meteorite lithologies basalt lherzolite clinopyroxenite orthopyroxenite and dunite using data from the mars global surveyor thermal emission spectrometer mgs tes we deconvolved the tes data set using laboratory spectra of 6 martian meteorites los angeles zagami alh a77005 nakhla alh 84001 and chassigny as end members along with atmospheric and surface spectra previously derived from tes data global maps 16 pixels degree of the distribution of each meteorite end member show that meteorite like compositions are not present at or above tes detectability limits over most of the planet s dust free regions however we have confidently identified local scale 100s1000s km2 concentrations of olivine and orthopyroxene bearing materials similar to alh a77005 chassigny and alh 84001 in nili fossae in and near ganges chasma in the argyre and hellas basin rims and in eos chasma nakhla like materials are identified near the detection limit throughout the eastern valles marineris region and portions of syrtis major basaltic shergottites were not detected in any spatially coherent areas at the scale of this study martian meteorite like lithologies represent only a minor portion of the dust free surface and thus are not representative of the bulk composition of the ancient crust meteorite like spectral signatures identified above tes detectability limits in more spatially restricted areas tens of km are targets of ongoing analysis

recognition of minor constituents in reflectance spectra of allan hills 84001 chips and the importance for remote sensing on mars reflectance spectra of splits 92 and 271 from the martian meteorite allan hills alh 84001 are presented and analyzed in this paper although the visible and infrared spectra of both chips show that the dominant mineralogy is low ca pyroxene the focus here is on identification of the minor constituents infrared spectra measured at multiple spots along the surface of chips 92 and 271 show subtle spectroscopic variations due to changes in the low ca pyroxene texture and composition and to the presence of secondary minerals absorption bands observed near 0 93 and 1 95 m are characteristic of low ca pyroxene strong mid infrared reststrahlen bands are observed near 9 and 19 5 m in all surface spectra and additional bands near 7 10 5 11 4 17 8 20 5 and 23 m are variable depending on the low ca pyroxene texture and the presence of secondary minerals selected spectra exhibit carbonate features near 4 6 4 7 1 and 11 3 m detailed analysis of these carbonate features indicates the presence of mg fe carbonate which is consistent with petrographic studies many of these spectra with strong carbonate features exhibit a magnetite feature near 17 9 m and a shoulder near 20 5 m that cannot be uniquely ascribed to one mineral spectroscopic identification of the minor carbonate and magnetite minerals in this probable piece of mars indicates that detection of small amounts of these minerals of possible biological significance will be possible using infrared hyperspectral analyses of the martian surface also of importance for remote sensing on mars is the result that mg fe and mg fe carbonates in a low ca pyroxene matrix should be distinguishable from one another in the spectral region measured by the thermal emmitance spectrometer tes

results from the ism experiment the imaging spectrometer ism operating in the near infrared is the first ever flown in space for planetary observation with a spectral range of 0 76 3 14 m its main goals were to obtain information on the mineralogical composition of the surfaces of mars and phobos and on the composition spatial and temporal variations of the martian atmosphere the infrared imaging spectrometer ism acquired 40 000 spectra of mars and phobos here we present the first results on the surface mineralogy of mars and phobos and the atmospheric composition of mars

mahli at the rocknest sand shadow science and science enabling activities 1 during martian solar days 57 100 the mars science laboratory curiosity rover acquired and processed a solid sediment sample and analyzed its mineralogy and geochemistry with the chemistry and mineralogy and sample analysis at mars instruments an aeolian deposit herein referred to as the rocknest sand shadow was inferred to represent a global average soil composition and selected for study to facilitate integration of analytical results with observations from earlier missions during first time activities the mars hand lens imager mahli was used to support both science and engineering activities related to sample assessment collection and delivery here we report on mahli activities that directly supported sample analysis and provide mahli observations regarding the grain scale characteristics of the rocknest sand shadow mahli imaging confirms that the rocknest sand shadow is one of a family of bimodal aeolian accumulations on mars similar to the coarse grained ripples interrogated by the mars exploration rovers spirit and opportunity in which a surface veneer of coarse grained sediment stabilizes predominantly fine grained sediment of the deposit interior the similarity in grain size distribution of these geographically disparate deposits support the widespread occurrence of bimodal aeolian transport on mars we suggest that preservation of bimodal aeolian deposits may be characteristic of regions of active deflation where winnowing of the fine sediment fraction results in a relatively low sediment load and a preferential increase in the coarse grained fraction of the sediment load the compositional similarity of martian aeolian deposits supports the potential for global redistribution of fine grained components combined with potential local contributions

using the modified gaussian model to extract quantitative data from lunar soils 1 the lunar soil characterization consortium lscc has examined and characterized a suite of lunar soils with a wide range of compositions and maturities the purpose of this study is to compare the vis nir spectral properties of these lunar soils with their petrologic and chemical compositions using the modified gaussian model mgm to obtain quantitative data about the character of relatively weak near infrared absorption bands useful compositional information can be extracted from high quality soil spectra using the mgm the model had some difficulty fitting absorption bands in the 2 mm region of the lunar spectrum but bands in the 1 and 1 2 mm regions provided physically realistic results the model was able to distinguish high ca and low ca pyroxenes in the lscc suite of lunar soils in the appropriate relative abundance in addition unexpected insights into the nature and causes of absorption bands in lunar soils were identified for example at least two distinct absorption bands are required in the 1 2 mm region of the spectrum and neither of these bands can be attributed to plagioclase or agglutinates but are found instead to be largely due to pyroxene

impact melts and glasses on mars 1 dark mobile materials on mars are widely considered to be volcanically derived windblown particulates such a conclusion is consistent with the large volcanic edifices on mars and the assumption that a volatile rich crust would not favor significant impact melt generation several post viking discoveries however provide new perspectives for reconsidering alternative origins not only for some of the mobile dark veneers but also certain materials at the pathfinder and viking landing sites first certain dark materials on mars do not exhibit the expected mafic absorption features in their reflectance spectra second the pathfinder mission revealed unexpected feldspathic compositions of vesicular blocks that lead to a preliminary conclusion that they represent andesites or basaltic andesites rather than basalts third recent discoveries of holocene to miocene impacts in argentine loessoid deposits provide new insights for the nature of melts generated from eolian sediments fourth global dispersal of impact melt products are now recognized in the terrestrial record throughout the cenozoic consequently the generation and preservation of impact glass on mars should be reconsidered possible occurrences include possible tektite like strewnfields downrange from recent oblique impacts dark avalanches emerging from backwasting cliffs of easily eroded unconformable deposits global dispersal of glassy ejecta from hesperian and amazonian craters of chicxulub scale and dark mobile veneers emerging from noachian craters we propose that the mobile dark materials comprising many of the named features of mars as well as some blocks at the pathfinder viking landing sites may represent impact melt products

the rocks of mars from far and near award of the meteoritical society 2001 h y mcsween jr the leonard medal address the rocks of mars from far and near

seeing through the dust martian crustal heterogeneity and links to the snc meteorites through the application of new analytical techniques to high spatial resolution imaging spectrometer data the ferrous mineralogy of major volcanic terrains on mars is shown to consist of significant fractions of both low and high calcium pyroxene changes in the relative abundances of these pyroxenes are observed for units of different age and morphology even in regions with higher degrees of alteration and contamination from dust volcanic rocks with these characteristics are uncommon on earth but are typical of the basaltic snc meteorites shergottites nakhlites and chassignites thought to be from mars thus it is possible to infer even through the veil of dust that the snc meteorites have mineralogic affinities to major volcanic provinces on mars and are therefore truly representative of the heterogeneity observed on the surface of the red planet

are oxidized shergottite like basalts an alternative to andesite on mars 1 we acquired new thermal emission spectra of oxidized synthetic martian meteorite like basalts for comparison to martian surface spectra acquired by the mars global surveyor thermal emission spectrometer mgs tes we find that true thermal emission spectra of the oxidized basalts do not provide good spectral matches to the martian spectra by contrast previous biconical reflectance spectra converted to emission spectra appeared to fit the mars observations well attempts to model the mineralogies of the oxidized basalts using a linear deconvolution algorithm and an end member set previously used to derive mineralogies for the martian surface were unsuccessful suggesting that the oxidized basalts contain altered phases not present in the end member set successful modeling of martian surface mineralogies using the end member set indicates that it sufficiently represents the phases present on the martian surface and does not require the altered phases needed to model the oxidized basalt mineralogies although oxidized martian meteorite like basalts may be viable analogues for some martian materials our results suggest that they cannot explain the two primary surface mineralogies measured by mgs tes

a systematic mapping procedure based on the modified gaussian model to characterize magmatic units from olivine pyroxenes mixtures application to the syrtis major volcanic shield on mars clenet et al 2011 have developed an adapted version of the modified gaussian model mgm the improvements allow the characterization of spectra of olivine pyroxene s mixtures addressing both modal composition and individual minerals chemical composition this version of mgm is fully automated and operational with large amounts of hyperspectral imaging data two natural cases are considered the first one is the sumail massif in the oman ophiolite earth based on our approach applied to hymap data two contrasted lithologic units are mapped the mantle which is harzburgite dominated and the crust made of gabbros and clinopyroxene rich cumulates with spectral variations interpreted in terms of pyroxenes chemical compositions once this new mgm mapping approach has been validated on a controlled natural situation we map the distribution of mafic assemblages across the syrtis major volcano on mars using a visible and near infrared vnir short wave infrared swir observatoire pour la mineralogie l eau les glaces et l activite omega mars express mex mosaic our results are in agreement with previous work but olivine appears to be more abundant than previously estimated in the central part of the volcanic edifice especially in ternary mafic assemblages augite olivine enstatite based on these results we propose a possible scenario for the igneous and thus thermal evolution of the syrtis major region surrounding terrains have formed first and local heterogeneity can be observed between northern and southern areas of the noachian crust we also observe variations in the mineral assemblages within syrtis major lavas which can be interpreted in terms of differentiation from a common parent melt and or of a progressive evolution of the mantle source composition and temperature key points mgm systematic mapping on syrtis major to characterize mafic minerals mixtures olivine and pyroxenes mixture is detected in the central lavas of the volcano pyroxenes have chemical compositions spanning the enstatite augite range

spectral reflectance of martian meteorites spectral signatures as a template for locating source region on mars we report the spectral reflectance of martian meteorites from 0 3 2 6 microns for the purpose of cataloguing spectra and the association of their spectral properties with mineralogy and petrology we fit the spectra to a series of overlapping modified gaussian absorptions using least squares fitting the results are validated against established relationships between photon interactions with mineral chemistry and the band parameters these resultant band parameters can be used to constrain interpretations of martian reflectance spectra in the search for the source region of meteorites from mars the limitations of the fitting method are discussed

acid sulfate weathering of synthetic martian basalt the acid fog model revisited the acid fog model has received considerable attention as a model of soil formation on mars previous evaluations of this model have focused on experimental weathering of terrestrial basalt samples however these samples differ significantly from what now is thought to be typical of martian basalt the acid fog model is tested here using synthetic basaltic analogs derived from mars pathfinder soil and rock compositions reaction of synthetic basalt with various acidic solutions and subsequent evaporation has led to the formation of several putative secondary mineral phases many of these phases were not produced in prior experimental studies aimed at aqueous interactions on mars of these alteration phases mg fe ca and al sulfates were identified in addition secondary ferric oxide phases formed via rapid fe oxidation under relatively high ph levels buffered by basalt dissolution amorphous silica is a ubiquitous product in these experiments and has formed by precipitation from solution and by the dissolution of minerals and glasses leaving behind leached surface layers composed of residual silica the secondary products formed in these experiments demonstrate the importance of primary mineralogy when testing models of aqueous interactions on mars new constraints are placed on both the reactivity of primary basalt and the secondary mineralogy present at the martian surface copyright 2004 by the american geophysical union

explosive volcanism as a cause for mass mortality of pteropods recently it has been proposed that anthropogenic co2 emissions may affect marine ecosystems by causing ocean acidification in particular it is suggested that within acidified waters calcifying organisms would be subject to malformation and enhanced dissolution here we present evidence suggesting that this process occurs naturally where explosive volcanism deposits ash directly into ocean surface waters sediment cores from around the island of montserrat lesser antilles volcanic arc contain distinct horizons of planktic fauna associated with recently deposited volcanic ash layers from the soufriere hills volcano within these layers are abundant thecosome pteropod shells that display evidence of partial dissolution and etching of their aragonitic shells and appear to have suffered mass mortality during large eruptions from the volcano laboratory studies show that the acids bound to ash surfaces from the 2003 volcanic dome collapse event of the soufriere hills volcano could have caused the upper 5 m of the water column to become undersaturated with respect to aragonite when combined with the large fluxes of acidic aerosols principally as so2 from the volcano during eruptions it is proposed that volcanogenic ocean acidification by marine ash falls is a significant contributing factor to these observed mass mortality events

chemical composition of martian fines of the 21 samples acquired for the viking x ray fluorescence spectrometer 17 were analyzed to high precision compared to typical terrestrial continental soils and lunar mare fines the martian fines are lower in al higher in fe and much higher in s and cl concentrations protected fines at the two lander sites are almost indistinguishable but concentration of the element s is somewhat higher at utopia duricrust fragments successfully acquired only at the chryse site invariably contained about 50 higher s than fines no elements correlate positively with s except cl and possibly mg a sympathetic variation is found among the triad si al ca positive correlation occurs between ti and fe sample variabilities are as great within a few meters as between lander locations 4500 km apart implying the existence of a universal martian regolith component of constant average composition the nature of the source materials for the regolith fines must be mafic to ultramafic

spectral identification of geological units on the surface of mars related to the presence of silicates from earth based near infrared telescopic charge coupled device imaging during the september 1988 mars opposition the authors obtained new high spatial 100 150 km and spectral delta lambda lambda 1 resolution near ir telescopic charge coupled device images of mars from pic du midi observatory these images allow the association of spectral units with morphologic surface units on mars especially within the dark regions which exhibit much greater variability than the bright regions mineralogical interpretation of the data leads to a global description of the surface state of alteration consistent with the spatial distribution of bright and dark regions with the bright regions being more altered than the dark within the less altered regions fe sup 2 crystal field absorption bands are detected indicative of the presence of mafic minerals opx cpx o1 in agreement with a likely crustal basaltic composition the most conspicuous fe sup 2 absorption features are clearly related to the volcanic regions of the syrtis major shield and hesperia planum unit the strongest observed absorptions due to olivine and clinopyroxene are spatially associated with the restricted central caldera complex of nili meroe paterae within syrtis major and the tyrrhena patera unit within hesperia planum and indicate an ultramafic composition

search for signs of ancient life on mars expectations from hydromagnesite microbialites salda lake turkey the 9white rock9 constituting a portion of what may be a lacustrine sedimentary sequence near the margin of a crater c 90 km across in sabaea terra mars measures 18 15 km 180 540 m high it is re interpreted as a lens of magnesium carbonate precipitated where ground waters seeped into an ancient evaporating crater lake were life to have emerged on mars as seems feasible then the 9white rock9 might be expected to comprise a complex of stromatolitic mounds salda golu lake in turkey is taken as an analogue this enclosed lake is nearly surrounded and underlain by partially serpentinized harzburgite hydromagnesite stromatolites microbialites up to 7 m high coalesce to form a group of small islands 200 m across the microbialites are seen to be growing near the mouth of the usually dry salda river in the southwestern sector smaller developments of hydromagnesite encircle the lake and image processing of satellite data reveals a second extensive zone beneath the lake surface over a delta in the southeast individual columns a few centimetres high constitute bulbous mounds which are about 2 m in diameter these columns terminate in domes a centimetre or so across the domes are often annulated and are covered with a green biofilm a few millimetres thick comprised of cyanobactrial filaments the columns consist of alternating fine and coarse hydromagnesite layers differentiated on a millimetric scale the coarser layers near the surface still contain traces of the biofilm fossil microbialites were also discovered in the friable hydromagnesite cliffs shoreward of the main developments though the structures of the individual microbes have not survived instead the vestiges of microbialites are easily recognized and delineated by their coarse grain size and high porosity annular structures on their upper surfaces can be seen in places the intervening and overlying material also comprised of hydromagnesite is a semi lithified mud bulbous megascopic structures separated by finer grained magnesium carbonate mudstone within strata in the 9white rock9 would be strong evidence of a photosynthetic microbial genesis another deposit of white rock on the western margin of juventae chasma could have a similar origin

mixing relationships in the martian regolith and the composition of globally homogeneous dust abstract comparison of the chemical compositions of martian soils reveals distinct mixing trends resulting from admixture of variable amounts of sulfate chloride cement at viking landing sites and of the local andesitic rock fragments at the mars pathfinder site these trends most easily visualized in plots of oxides versus so 3 intersect approximately at a common composition thought to represent a global dust that has been homogenized by pervasive aeolian activity the source rocks that were weathered to produce the global dust are inferred to have been basalts rather than felsic rocks based on the observation that the dust lies along well established chemical weathering trends for terrestrial basalts the basaltic protolith was chemically similar e g high fe mg low al 2 o 3 to basaltic shergottite meteorites chemical changes during the weathering of martian basaltic rocks are apparently not as drastic as in terrestrial weathering perhaps because of evaporation of hydrous fluids that leave soluble components behind in the residue comparison with chemical trends for previously proposed martian soil formation mechanisms suggests that palagonitization of basalts more readily explains the dust composition than do hydrothermal alteration at higher temperatures or reactions of rocks with an acid fog produced by volcanic exhalations local or temporal processing of dust into soil involves not only cementation by salts and mixing with rock fragments but also chemical fractionations of fe 2 o 3 tio 2 presumably resulting from aeolian sorting by grain size and density if the global dust represents a broad average of the martian surficial or upper crustal composition the planet s surface geology is dominated by basaltic volcanic rocks and evaporitic salts

chemical multispectral and textural constraints on the composition and origin of rocks at the mars pathfinder landing site rocks at the mars pathfinder site are probably locally derived textures on rock surfaces may indicate volcanic sedimentary or impact generated rocks but aeolian abration and dust coatings prevent unambiguous interpretation multispectral imaging has resolved four spectral classes of rocks gray and red which occur on different surfaces of the same rocks pink which is probably soil crusts and maroon which occurs as large boulders mostly in the far field rocks are assigned to two spectral trends based on the position of peak reflectance the primary spectral trend contains gray red and pink rocks maroon rocks constitute the secondary spectral trend the spatial pattern of spectral variations observed is oriented along the prevailing wind direction the primary spectral trend arises from thin ferric coatings of aeolian dust on darker rocks the secondary spectral trend is apparently due to coating by a different mineral probably maghemite or ferrihydrite a chronology based on rock spectra suggests that rounded maroon boulders constitute the oldest petrologic unit a flood deposit succeeded by smaller cobbles possibly deposited by impact and followed by aeolian erosion and deposition nearly linear chemical trends in alpha proton x ray spectrometer rock compositions are interpreted as mixing lines between rock and adhering dust a conclusion supported by a correlation between sulfur abundance and red blue spectral ratio extrapolations of regression lines to zero sulfur give the composition of a presumed igneous rock the chemistry and normative mineralogy of the sulfur free rock resemble common terrestrial volcanic rocks and its classification corresponds to andesite igneous rocks of this composition may occur with clastic sedimentary rocks or impact melts and breccias however the spectral mottling expected on conglomerates or breccias is not observed in any apxs analyzed rocks interpretation of the rocks as andesites is complicated by absence of a 1 m pyroxene absorption band plausible explanations include impact glass band masking by magnetite or presence of calcium and iron rich pyroxenes and olivine which push the absorption band minimum past the imager s spectral range the inferred andesitic composition is most similar to terrestrial anorogenic icelandites formed by fractionation of tholeiitic basaltic magmas early melting of a relatively primitive martian mantle could produce an appropriate parent magma supporting the ancient age of pathfinder rocks inferred from their incorporation in hesperian flood deposits although rocks of andesitic composition at the pathfinder site may represent samples of ancient martian crust inferences drawn about a necessary role for water or plate tectonics in their petrogenesis are probably unwarranted

the surface of syrtis major composition of the volcanic substrate and mixing with altered dust and soil syrtis major is an old low relief volcanic plateau near the equatorial regions of mars it is a persistent low albedo feature on the planet and is thought to contain a high abundance of exposed bedrock and or locally derived surface material and debris spatially resolved variations in surface spectral properties and therefore composition are investigated with data from the imaging spectrometer for mars ism instrument ism obtained 128 wavelength channel spectra from 0 76 to 3 16 m for contiguous pixels approximately 22 22 km in size across much of the plateau the value and spatial distribution of four primary spectral variables albedo continuum slope wavelength of the ferric ferrous band minimum area of the ferric ferrous absorption are mapped and coregistered to viking digital photomosaics analysis of these maps shows that although there is a high degree of overall spectral variability on the plateau the key indicators of mafic mineralogy are relatively homogeneous detailed examination of reflectance spectra from representative areas across the plateau indicate the volcanic surface is dominated by augite bearing basalts and the pyroxene composition in the basalts is estimated to be 0 275 0 075 ca ca fe mg and 0 3 0 1 fe fe ca mg additional mineral components may include olivine feldspar and glass most of the spectral variability on the plateau is interpreted to result from mixing of volcanic bedrock and or locally derived surface material and debris with highly altered dust and soil in western syrtis major the altered material is a transient component on the surface or occurs in large spatially coherent patches e g crater rims in eastern syrtis major it is apparent that the dust components are firmly fixed to the basaltic substrate as a stable oxide rind or coating

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

mineralogic and compositional properties of martian soil and dust results from mars pathfinder mars pathfinder obtained multispectral elemental magnetic and physical measurements of soil and dust at the sagan memorial station during the course of its 83 sol mission we describe initial results from these measurements concentrating on multispectral and elemental data and use these data along with previous viking snc meteorite and telescopic results to help constrain the origin and evolution of martian soil and dust we find that soils and dust can be divided into at least eight distinct spectral units based on parameterization of imager for mars pathfinder imp 400 to 1000 nm multispectral images the most distinctive spectral parameters for soils and dust are the reflectivity in the red the red blue reflectivity ratio the near ir spectral slope and the strength of the 800 to 1000 nm absorption feature most of the pathfinder spectra are consistent with the presence of poorly crystalline or nanophase ferric oxide s sometimes mixed with small but varying degrees of well crystalline ferric and ferrous phases darker soil units appear to be coarser grained compacted and or mixed with a larger amount of dark ferrous materials relative to bright soils nanophase goethite akaganeite schwertmannite and maghemite are leading candidates for the origin of the absorption centered near 900 nm in imp spectra the ferrous component in the soil cannot be well constrained based on imp data alpha proton x ray spectrometer apxs measurements of six soil units show little variability within the landing site and show remarkable overall similarity to the average viking derived soil elemental composition differences exist between viking and pathfinder soils however including significantly higher s and cl abundances and lower si abundances in viking soils and the lack of a correlation between ti and fe in pathfinder soils no significant linear correlations were observed between imp spectral properties and apxs elemental chemistry attempts at constraining the mineralogy of soils and dust using normative calculations involving mixtures of smectites and silicate and oxide minerals did not yield physically acceptable solutions we attempted to use the pathfinder results to constrain a number of putative soil and dust formation scenarios including palagonitization and acid fog weathering while the pathfinder soils cannot be chemically linked to the pathfinder rocks by palagonitization this study and mcsween et al 1999 suggest that palagonitic alteration of a martian basaltic rock plus mixture with a minor component of locally derived andesitic rock fragments could be consistent with the observed soil apxs and imp properties

mineralogy of volcanic rocks in gusev crater mars reconciling mossbauer alpha particle x ray spectrometer and miniature thermal emission spectrometer spectra 1 complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in gusev crater have been determined by modeling mossbauer subspectral areas as mineral weight percentages and combining those percentages with the proportions of iron free minerals not detected by mossbauer normative plagioclase apatite and chromite as calculated from alpha particle x ray spectrometer apxs chemical analyses comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured miniature thermal emission spectrometer mini tes spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic plagioclase compositions or unmodeled sulfate glass or pigeonite the normative compositions of olivine pyroxene and feldspar calculated from apxs data are consistent with spectroscopic constraints on mineral compositions systematic variations between olivine abundances in apxs norms which sample tens of micrometers depth and olivine proportions measured by mossbauer which sample hundreds of micrometers depth support the hypothesis that dissolution of olivine by acidic fluids has occurred on weathered rock surfaces

spectral signature of oxidized pyroxenes implications to remote sensing of terrestrial planets the fe2 ions in pyroxenes occurring in basalts on surfaces of terrestrial planets are vulnerable to oxidation particularly in magma in contact with the atmosphere this produces fe3 bearing assemblages that may mask spectral features of remnant fe2 in pyroxenes in telescopic reflectance spectra of oxidized planetary surfaces to assess such interferences reflectance spectra 0 3 2 6 urn were obtained for a variety of pyroxenes that had been heated in air at elevated temperatures mossbauer spectral measurements enabled the relative proportions of fe3 and fe2 ions and fe3 bearing phases to be determined in the reaction products nanophase hematite having particle diameters smaller than 10 nm obscures the pyroxene fe2 m2 site crystal field cf bands of oxidized enstatite and pigeonite intensification of fe2 fe3 intervalence charge transfer transitions in calcic clinopyroxenes mask pyroxene fe2 m1 site cf bands as well as the fe2 m2 site cf bands of augites and subcalcic hedenbergites the ferric iron derived from oxidation of fe2 ions may remain as structural fe3 ions in the oxidized calcic clinopyroxenes or exist as clusters of nanophase hematite particles having diameters of a few unit cells