spectral mineralogical and geochemical variations across home plate gusev crater mars indicate high and low temperature alteration over the last 3 years in gusev crater mars the spirit rover observed coherent variations in color mineralogy and geochemistry across home plate an 80 m diameter outcrop of basaltic tephra observations of home plate from orbit and from the summit of husband hill reveal clear differences in visible near infrared vnir colors between its eastern and western regions that are consistent with mineralogical compositions indicated by mossbauer spectrometer mb and by miniature thermal emission spectrometer mini tes pyroxene and magnetite dominate the east side while olivine nanophase fe oxide npox and glass are more abundant on the western side alpha particle x ray spectrometer apxs observations reveal that eastern home plate has higher si mg al zn ni and k while cl and br are higher in the west we propose that these variations are the result of two distinct alteration regimes that may or may not be temporally related a localized higher temperature recrystallization and alteration of the east side of home plate and lower temperature alteration of the western side that produced npox

chemically striking regions on mars and stealth revisited 1 the mars odyssey gamma ray spectrometer suite has yielded global chemical information for mars in this work we establish regions of unusual chemical composition relative to average mars primarily on the basis of ca cl fe h k si and th using data from mars odyssey the mars exploration rovers the mars reconnaissance orbiter imaging and 3 5 cm and 1 35 cm radar observations from earth we examine a chemically striking 2 e6 km2 region and find it to overlap significantly with a radar stealth region on mars it is remarkably enriched in cl and depleted in fe and si along with minor variations in h k and th relative to average mars surface dust observed at the two rover sites mixed with and indurated by ca mg bearing sulfate salts would be a reasonable chemical and physical analog to meter scale depths we describe potential scenarios that may have contributed to the unique properties of this region the bulk dust component may be an air fall deposit of compositionally uniform dust as observed in situ hydrothermal acid fog reactions on the flanks of nearby volcanoes may have generated sulfates with subsequent deflation and transport alternatively sulfates may have been produced by low temperature regional scale activity of ground ice driven brine and or regional scale deposition of acidified h2o snowfall

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

chemistry and mineralogy of outcrops at meridiani planum analyses of outcrops created by the impact craters endurance fram and eagle reveal the broad lateral continuity of chemical sediments at the meridiani planum exploration site on mars approximately ten mineralogical components are implied in these salt rich silicic sediments from measurements by instruments on the opportunity rover compositional trends in an apparently intact vertical stratigraphic sequence at the karatepe west ingress point at endurance crater are consistent with non uniform deposition or with subsequent migration of mobile salt components dominated by sulfates of magnesium striking variations in cl and enrichments of br combined with diversity in sulfate species provide further evidence of episodes during which temperatures ph and water to rock ratios underwent significant change to first order the sedimentary sequence examined to date is consistent with a uniform reference composition modified by movement of major sulfates upward and of minor chlorides downward this reference composition has similarities to martian soils supplemented by sulfate anion and the alteration products of mafic igneous minerals lesser cementation in lower stratigraphic units is reflected in decreased energies for grinding with the rock abrasion tool survival of soluble salts in exposed outcrop is most easily explained by absence of episodes of liquid h2o in this region since the time of crater formation

rocks of the columbia hills 1 the mars exploration rover spirit has identified five distinct rock types in the columbia hills of gusev crater clovis class rock is a poorly sorted clastic rock that has undergone substantial aqueous alteration we interpret it to be aqueously altered ejecta deposits formed by impacts into basaltic materials wishstone class rock is also a poorly sorted clastic rock that has a distinctive chemical composition that is high in ti and p and low in cr wishstone class rock may be pyroclastic or impact in origin peace class rock is a sedimentary material composed of ultramafic sand grains cemented by significant quantities of mg and ca sulfates peace class rock may have formed when water briefly saturated the ultramafic sands and evaporated to allow precipitation of the sulfates watchtower class rocks are similar chemically to wishstone class rocks and have undergone widely varying degrees of near isochemical aqueous alteration they may also be ejecta deposits formed by impacts into wishstone rich materials and altered by small amounts of water backstay class rocks are basalt trachybasalt lavas that were emplaced in the columbia hills after the other rock classes were either as impact ejecta or by localized volcanic activity the geologic record preserved in the rocks of the columbia hills reveals a period very early in martian history in which volcanic materials were widespread impact was a dominant process and water was commonly present

phosphate removal by oceanic hydrothermal processes an update of the phosphorus budget in the oceans abstract we present a compilation of dissolved phosphate and solid phase p data from the oceanic crust to evaluate the effects of hydrothermal processes on the oceanic budget of p concentrations of phosphate in fluids that emanate from ridge axis hydrothermal systems are less than that in bottom seawater the extent of removal in these fluids is at least 30 and in some hydrothermal systems dissolved phosphate is removed completely from the circulating fluid evidence for the removal of phosphate in each of six ridge flank hydrothermal systems is based on systematic variations in porewater profiles of phosphate and speeds of porewater flow the extent of removal is 80 in these ridge flank systems these removal processes are recorded in the basaltic crust as an increase in p concentration that coincides with an increase in extent of alteration and content of ferric iron phosphate also is removed in hydrothermal plumes by coprecipitation with fe oxyhydroxide particles which eventually deposit on the seafloor each of these hydrothermal processes results in a flux of p into the oceanic crust bottom seawater flow through ridge axis hydrothermal systems removes at most 0 4 of the preindustrial dissolved riverine flux of p while ridge flanks remove at least 5 but less than 50 of the dissolved riverine flux consistent with p data from deep sea drilling project dsdp sites 417 and 418 removal of phosphate by coprecipitation with fe rich particles in hydrothermal plumes along ridge axes accounts for 18 33 of the dissolved riverine flux thus hydrothermal systems remove about 50 of the preindustrial dissolved riverine flux of phosphate we have included these new estimates in a revised budget for oceanic p

rock spectral classes observed by the spirit rover s pancam on the gusev crater plains and in the columbia hills 1 this paper examines the ferrous and ferric iron mineralogy of rocks inferred from 246 visible near infrared 430 1010 nm multispectral observations made by the mars exploration rover spirit s pancam on its traverse from its landing site to its second winter haven location principal component correspondence analyses and a sequential maximum angle convex cone technique were used to identify 14 candidate classes spectra from the west spur of husband hill and the watchtower area had the highest 535 and 601 nm band depths indicating that these areas were more oxidized differences in the depth and band center of a near infrared nir absorption feature were observed using 904 nm band depth and 803 904 nm ratio and parameters gauging the 754 864 and 754 1009 nm slopes spectra of rocks from the southern flank of husband hill had negative 754 1009 nm slopes and a broad nir absorption consistent with high olivine abundances rocks observed on the lower west spur at the cumberland ridge locale at the husband hill summit and at the haskin ridge locale had deep 904 nm band depths and steep 754 864 nm slopes consistent with greater pyroxene abundances these observations are consistent with results on iron bearing mineralogy from spirit s mossbauer spectrometer comparisons of these rock spectral classes with a set of terrestrial analog samples found similarities between the west spur and watchtower classes and red hematite bearing impact melts fewer similarities were found in comparisons of the columbia hills classes with basaltic hydrovolcanic tephras

on the origin of gypsum in the mars north polar region 1 we describe the distribution and concentration of the largest martian gypsum deposit discovered to date by the mars express omega observatoire pour le mineralogie l eau les glaces et l activite imaging spectrometer its relationship to the late amazonian aged north polar dunes in which it is found and its likely origin gypsum has not been discovered anywhere within the north polar region outside of the olympia undae dune sea in the areas of highest gypsum a concentration 35 pure gypsum grains of a few tens of micrometers in size mixed with 65 millimeter sized gypsum grains containing dark spectrally featureless inclusions best fit the omega observations the gypsum rich dunes contain no significant average albedo temperature or morphological anomalies we propose that water emanating from nearby channels carved during melting of the polar layered deposits infiltrated the eastern end of the polar dune sea percolating through the dunes deposits of gypsum resulted from a combination of direct in situ alteration of sulfide and high calcium pyroxene bearing dunes and from formation of evaporitic gypsum crystals in the pore spaces of these dunes this gypsum deposit formed in a unique local environment and is disconnected from sulfate forming events elsewhere on mars which are thought to have occurred much earlier during the late noachian and hesperian by various means sulfates have not been discovered in any other collection of dunes on mars

experimental constraints on the evaporation of partially oxidized acid sulfate waters at the martian surface abstract isothermal evaporation experiments were carried out on an acidic ph 2 partially oxidized fe2 fet 0 5 brine with a cation composition consistent with derivation from the chemical weathering of martian basalt during evaporation the brine composition evolved to a highly acidic un scaled ph 1 3 mg fe so4 cl brine depleted in ca al and k evaporite minerals identified throughout the course of the experiment include in order of crystallization gypsum mg rich voltaite mg0 7 fe 2 0 3 so4 7h2o and rhomboclase the solid solution compositions of voltaite and mg0 7 fe 2 0 3 so4 7h2o although uncommon in analogous environments on earth result from the distinct chemistry of evaporating martian surface fluids analysis of brine compositions with available thermodynamic models indicates that although gypsum and rhomboclase precipitate at equilibrium saturation kinetic controls on the precipitation of copiapite group minerals affect the subsequent sulfate mineralogy and evolving chemistry of the entire system in addition geochemical simulations of the experimental evaporation process suggest that the appearance of voltaite and rhomboclase indicate a metastable evaporation pathway for martian fluids whereby bilinite and copiapite group minerals did not form despite thermodynamic saturation comparison of the experimentally produced assemblage to available observations of saline minerals at the martian surface represents a step toward systematically characterizing evaporite mineralogy as a function of fe oxidation in the initially dilute fluid deconvolving the complexity of fe sulfate formation in martian environments ultimately will help to exploit the sensitivity of these minerals to ph and redox conditions present at the ancient martian surface

acid sulfate alteration of fluorapatite basaltic glass and olivine by hydrothermal vapors and fluids implications for fumarolic activity and secondary phosphate phases in sulfate rich paso robles soil at gusev crater mars 1 phosphate rich rocks and a nearby phosphate rich soil paso robles were analyzed in gusev crater mars by the mars exploration rover spirit and interpreted to be highly altered possibly by hydrothermal or fumarolic alteration of primary phosphate rich material to test mineral phases resulting from such alteration we performed hydrothermal acid vapor and acid fluid experiments on olivine ol fluorapatite ap and basaltic glass gl as single phases and a mixture of phases minerals formed include ca al fe and mg sulfates with different hydration states anhydrite bassanite gypsum alunogen hexahydrite and pentahydrite phosphate bearing minerals formed included monocalcium phosphate monohydrate mcp acid vapor and acid fluid alteration of fluorapatite only and ferrian giniite acid fluid alteration of the ol gl ap mixture mcp is likely present in paso robles if primary ca phosphate minerals reacted with sulfuric acid with little transport of phosphate under fluid rock ratios allowing transport of phosphate a ferric phosphate phase such as ferrian giniite might form instead mossbauer measurements of ferrian giniite bearing alteration products and synthetic ferrian giniite are consistent with spirit s mossbauer measurements of the ferric bearing phase in paso robes soil but are also consistent with ferric sulfate phases in the low p soil arad samra therefore mossbauer data alone do not constrain the fluid rock ratio however the excess iron hematite in paso robles soil which implies aqueous transport combined with our laboratory experiments suggest acid sulfate alteration in a hydrothermal fumarolic environment at fluid rock ratios sufficient to allow dissolution transport and precipitation of secondary chemical components including a ferric phosphate such as ferrian giniite

mineralogical constraints on the thermal history of martian regolith breccia northwest africa 8114 abstract martian meteorite northwest africa nwa 8114 a paired stone to nwa 7034 provides an opportunity to examine the thermal history of a martian regolith and study near surface processes and ancient environmental conditions near an impact crater on mars our study reports petrographic and alteration textures and focuses on pyroxene and iron oxide grains some of the pyroxene clasts show exsolution lamellae indicating a high temperature magmatic origin and slow cooling however transmission electron microscopy reveals that other predominantly pyroxene clasts are porous and have partially re crystallised to form magnetite and a k bearing feldspathic glassy material together with relict pyroxene this breakdown event was associated with oxidation with up to 25 fe3 fe in the relict pyroxene measured using fe k xanes by comparison with previous studies this breakdown and oxidation of pyroxene is most likely to be a result of impact shock heating being held at a temperature above 700 c for at least 7 days in an oxidising regolith environment we report an approximate 40ar 39ar maximum age of 1 13 1 25 ga for an individual separated augite clast the disturbed nature of the spectra precludes precise age determination in section this clast is porous and contains iron oxide grains this shows that it has undergone the high temperature partial breakdown seen in other relict pyroxene clasts and has up to 25 fe3 fe we infer that the age corresponds to the impact shock heating event that led to the high temperature breakdown of many of the pyroxenes after consolidation of the impact ejecta blanket high temperatures above 700 c may have been maintained for long enough to remobilise and congruently partially melt some of the alkali feldspar clasts to produce the feldspar veins and aureoles that crosscut and in some cases surround the oxidised pyroxene however the veins could alternatively be the result of a hydrothermal event in the impact regolith a simple fourier cooling model suggests that a regolith of at least five metres depth would be sufficient to maintain temperatures associated with the pyroxene breakdown for over seven days low temperature hydrous alteration took place forming goethite identified via xrd xanes and ftir comparing with previous studies the goethite is likely to be terrestrial alteration pseudomorphing martian pyrite

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

aqueous processes at gusev crater inferred from physical properties of rocks and soils along the spirit traverse 1 gusev crater was selected as the landing site for spirit on the basis of morphological evidence of long lasting water activity including possibly fluvial and lacustrine episodes from the columbia memorial station to the columbia hills spirit s traverse provides a journey back in time from relatively recent volcanic plains showing little evidence for aqueous processes up to the older hills where rock and soil composition are drastically different for the first 156 sols the only evidence of water action was weathering rinds vein fillings and soil crust cementation by salts the trenches of sols 112 145 marked the first significant findings of increased concentrations of sulfur and magnesium varying in parallel suggesting that they be paired as magnesium sulfate spirit s arrival at west spur coincided with a shift in rock and soil composition with observations hinting at substantial amounts of water in gusev s past we used the microscopic imager data up to sol 431 to analyze rock and soil properties and infer plausible types and magnitude of aqueous processes through time we show the role played early by topography and structure the morphology texture and deep alteration shown by the rocks in west spur and the columbia hills formation chf suggest conditions that are not met in present day mars and required a wetter environment which could have included transport of sulfur chlorine and bromine in water vapor in volcanic gases hydrothermal circulation or saturation in a briny fluid containing the same elements changing conditions that might have affected flow circulation are suggested by different textural and morphological characteristics between the rocks in the chf and those of the plains with higher porosity proxy higher void ratio and higher water storage potential in the chf soils were used to assess aqueous processes and water pathways in the top layers of modern soils we conclude that infiltration might have become more difficult with time

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

basalt weathering rates on earth and the duration of liquid water on the plains of gusev crater mars where martian rocks have been exposed to liquid water chemistry versus depth profi les could elucidate both martian climate history and potential for life the persistence of primary minerals in weathered profi les constrains the exposure time to liquid water on earth mineral persistence times range from 10 k y olivine to 250 k y glass to 1 m y pyroxene to 5 m y plagioclase such persistence times suggest mineral persistence minima on mars however martian solutions may have been more acidic than on earth relative mineral weathering rates observed for basalt in svalbard norway and costa rica demonstrate that laboratory ph trends can be used to estimate exposure to liquid water both qualitatively mineral absence or presence and quantitatively using reactive transport models qualitatively if the martian solution ph 2 glass should persist longer than olivine therefore persistence of glass may be a ph indicator with evidence for the ph of weathering the reactive transport code crunchflow can quantitatively calculate the minimum duration of exposure to liquid water consistent with a chemical profi le for the profi le measured on the surface of the exposed martian rock known as humphrey in gusev crater the calculated exposure time is 22 k y which is a minimum due to physical erosion if correct this estimate is consistent with short term episodic alteration accompanied by ongoing surface erosion more of these depth profi les should be measured to illuminate the weathering history of mars

fe oxidation processes at meridiani planum and implications for secondary fe mineralogy on mars fe oxidation processes may have occurred during groundwater mediated diagenesis in meridiani planum sediments to address this question melanterite oxidation experiments were conducted at epsomite saturation as a function of ph results show that schwertmannite is initially formed from acidic fe oxidation and that its formation and aging to mixtures of jarosite and nanocrystalline goethite is strongly controlled by ph over the range b 2 0 4 0 the ph is controlled in turn by fe oxidation and fe3 hydrolysis in one 77 d oxidation experiment nanocrystalline hematite was tentatively identified by mc6ssbauer spectroscopy accordingly aging experiments with synthetic nanocrystalline goethite were conducted 1 to further resolve the formation mechanisms of fe phases identified from oxidation experiments and 2 to test whether low water activity aw controls the thermodynamically favored goethite to hematite transition at low temperature mc6ssbauer spectroscopy and total x ray scattering show no observable changes after 4 months of aging and instead these results point to a jarosite precursor for the tentatively identified hematite on the basis of these results we suggest that the oxidation and maturation of initially formed fe2 bearing saline minerals may account in large part for the distribution of secondary fe minerals at the martian surface contributing to the association of fe oxides and mg ca sulfates observed from orbital surface analyses we hypothesize that oxidation of fe2 sulfates at low temperature could account for sustained diagenetic acidity in addition to much of the observed fe mineralogy in meridiani planum outcrop rocks the origin of the gray crystalline hematite at meridiani however is deserving of further experimental work to test this mechanism copyright 2008 by the american geophysical union

coordinated analyses of orbital and spirit rover data to characterize surface materials on the cratered plains of gusev crater mars 1 comparison of the mars exploration rover spirit s pancam 0 4 to 1 0 m and mars express observatoire pour la mineralogie l eau les glaces et l activite omega 0 4 to 2 5 m spectral reflectance data over spirit s traverses shows that gusev cratered plains are dominated by nanophase ferric oxide rich dust covering weakly altered basaltic sands this interpretation is also consistent with both observations from omega data covering plains beyond the traverse region and interpretations of data from the other payload instruments on the spirit rover omega observations of relatively low albedo regions where dust has presumably been stripped by dust devils show negative spectral reflectance slopes from 1 5 to 2 5 m and moderately masked spectral features which are indicative of olivine or pyroxene high albedo regions north and south of the spirit landing site have flat spectral reflectance slopes and few spectral features although all spectra have a nanophase ferric oxide absorption edge between 0 4 and 0 75 m comparison of themis derived thermal inertia values with omega derived spectral parameters shows that although the dust cover can be optically thick 0 4 to 2 5 m wavelength region in some areas it is not thick enough 1 cm to mask the thermal inertia of the underlying substrate for areas included in this study

hydrothermal activity recorded in post noachian aged impact craters on mars hydrothermal systems have previously been reported in ancient noachian and hesperian aged craters on mars using crism but not in amazonian aged impact craters however the nakhlite meteorites do provide evidence of amazonian hydrothermal activity this study uses crism data of 144 impact craters of 7 km diameter and 14 smaller craters 3 7 km diameter within terrain mapped as amazonian to search for minerals that may have formed as a result of impact induced hydrothermal alteration or show excavation of ancient altered crust no evidence indicating the presence of hydrated minerals was found in the 3 7 km impact craters hydrated minerals were identified in three complex impact craters located at 52 42 n 39 86 e in the ismenius lacus quadrangle at 8 93 n 141 28 e in elysium and within the previously studied stokes crater these three craters have diameters 20 km 62 km and 51 km the locations of the hydrated mineral outcrops and their associated morphology indicate that two of these three impact craters the unnamed ismenius lacus crater and stokes crater possibly hosted impact induced hydrothermal systems as they contain alteration assemblages on their central uplifts that are not apparent in their ejecta chlorite and fe serpentine are identified within alluvial fans in the central uplift and rim of the ismenius lacus crater whereas stokes crater contains a host of fe mg al phyllosilicates however excavation origin cannot be precluded our work suggests that impact induced hydrothermalism was rare in the amazonian and or that impact induced hydrothermal alteration was not sufficiently pervasive or spatially widespread for detection by crism

alpha particle x ray spectrometer apxs results from gusev crater and calibration report 1 the chemical composition of rocks and soils on mars analyzed during the mars exploration rover spirit mission was determined by x ray analyses with the alpha particle x ray spectrometer apxs details of the data analysis method and the instrument calibration are presented measurements performed on mars to address geometry effects and background contributions are shown cross calibration measurements among several instrument sensors and sources are discussed an unintentional swap of the two flight instruments is evaluated new concentration data acquired during the first 470 sols of rover spirit in gusev crater are presented there are two geological regions the gusev plains and the columbia hills the plains contain soils that are very similar to previous landing sites on mars a meteoritic component in the soil is identified rocks in the plains revealed thin weathering rinds the underlying abraded rock was classified as primitive basalt one of these rocks contained significant br that is probably associated with vein filling material of different composition one of the trenches showed large subsurface enrichments of mg s and br disturbed soils and rocks in the columbia hills revealed different elemental compositions these rocks are significantly weathered and enriched in mobile elements such as p s cl or br even abraded rock surfaces have high br concentrations thus in contrast to the rocks and soils in the gusev plains the columbia hills material shows more significant evidence of ancient aqueous alteration

identification of carbonate rich outcrops on mars by the spirit rover decades of speculation about a warmer wetter mars climate in the planet s first billion years postulate a denser co2 rich atmosphere than at present such an atmosphere should have led to the formation of outcrops rich in carbonate minerals for which evidence has been sparse using the mars exploration rover spirit we have now identified outcrops rich in magnesium iron carbonate 16 to 34 weight percent in the columbia hills of gusev crater its composition approximates the average composition of the carbonate globules in martian meteorite alh 84001 the gusev carbonate probably precipitated from carbonate bearing solutions under hydrothermal conditions at near neutral ph in association with volcanic activity during the noachian era

silica coatings in the ka u desert hawaii a mars analog terrain a micromorphological spectral chemical and isotopic study high silica materials have been observed on mars both from orbit by the crism spectrometer and in situ by the spirit rover at gusev crater these observations potentially imply a wet geologically active martian surface to understand silica formation on mars it is useful to study analogous terrestrial silica deposits we studied silica coatings that occur on the 1974 kilauea flow in the ka u desert hawaii these coatings are typically composed of two layers a 10 m layer of amorphous silica capped by a 1 m layer of fe ti oxide the oxide coating is composed of 100 nm spherules suggesting formation by chemical deposition raman spectroscopy indicates altered silica glass as the dominant phase in the silica coating and anatase and rutile as dominant phases in the fe ti coating jarosite also occurs within the coatings oxygen isotopic contents of the coatings were determined by secondary ion mass spectrometry cameca 7f and nanosims the measured values 18 o fe ti 14 6 2 1 and 18 o silica 12 1 2 2 relative to smow are enriched in 18 o relative to the basalt substrate the observations presented are consistent with a residual formation mechanism for the silica coating acid sulfate solutions leached away divalent and trivalent cations leaving a silica enriched layer behind micrometer scale dissolution and reprecipitation may have also occurred within the coatings chemical similarities between the hawaiian samples and the high silica deposits at gusev suggest that the martian deposits are the product of extended periods of similar acid sulfate leaching

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

diverse lithologies and alteration events on the rim of noachian aged endeavour crater meridiani planum mars in situ compositional evidence we report the results of geological studies by the opportunity mars rover on the endeavour crater rim four major units occur in the region oldest to youngest the matijevic shoemaker grasberg and burns formations the matijevic formation consisting of fine grained clastic sediments is the only pre endeavour impact unit and might be part of the noachian etched units of meridiani planum the shoemaker formation is a heterogeneous polymict impact breccia its lowermost member incorporates material eroded from the underlying matijevic formation the shoemaker formation is a close analog to the bunte breccia of the ries crater although the average clast sizes are substantially larger in the latter the grasberg formation is a thin fine grained homogeneous sediment unconformably overlying the shoemaker formation and likely formed as an airfall deposit of unknown areal extent the burns formation sandstone overlies the grasberg but compositions of the two units are distinct there is no evidence that the grasberg formation is a fine grained subfacies of the burns formation the rocks along the endeavour crater rim were affected by at least four episodes of alteration in the noachian and early hesperian i vein formation and alteration of preimpact matijevic formation rocks ii low water rock alteration along the disconformity between the matijevic and shoemaker formations iii alteration of the shoemaker formation along fracture zones and iv differential mobilization of fe and mn and caso 4 vein formation in the grasberg and shoemaker formations episodes ii and iii possibly occurred together but i and iv are distinct from either of these

overview of the spirit mars exploration rover mission to gusev crater landing site to backstay rock in the columbia hills spirit landed on the floor of gusev crater and conducted initial operations on soil covered rock strewn cratered plains underlain by olivine bearing basalts plains surface rocks are covered by wind blown dust and show evidence for surface enrichment of soluble species as vein and void filling materials and coatings the surface enrichment is the result of a minor amount of transport and deposition by aqueous processes layered granular deposits were discovered in the columbia hills with outcrops that tend to dip conformably with the topography the granular rocks are interpreted to be volcanic ash and or impact ejecta deposits that have been modified by aqueous fluids during and or after emplacement soils consist of basaltic deposits that are weakly cohesive relatively poorly sorted and covered by a veneer of wind blown dust the soils have been homogenized by wind transport over at least the several kilometer length scale traversed by the rover mobilization of soluble species has occurred within at least two soil deposits examined the presence of monolayers of coarse sand on wind blown bedforms together with even spacing of granule sized surface clasts suggests that some of the soil surfaces encountered by spirit have not been modified by wind for some time on the other hand dust deposits on the surface and rover deck have changed during the course of the mission detection of dust devils monitoring of the dust opacity and lower boundary layer and coordinated experiments with orbiters provided new insights into atmosphere surface dynamics

alkaline volcanic rocks from the columbia hills gusev crater mars 1 irvine backstay and wishstone are the type specimens for three classes of fine grained or fragmental relatively unaltered rocks with distinctive thermal emission spectra found as float on the flanks of the columbia hills chemical analyses indicate that these rocks are mildly alkaline basalt trachybasalt and tephrite respectively their mineralogy consists of na and k rich feldspar s low and high ca pyroxenes ferroan olivine fe ti and possibly cr oxides phosphate and possibly glass the texture of wishstone is consistent with a pyroclastic origin whereas irvine and backstay are lavas or possibly dike rocks chemical compositions of these rocks plot on or near liquid lines of descent for most elements calculated for adirondack class rocks olivine rich basalts from the gusev plains at various pressures from 0 1 to 1 0 gpa we infer that wishstone backstay and irvine class magmas may have formed by fractionation of primitive oxidized basaltic magma similar to adirondack class rocks the compositions of all these rocks reveal that the gusev magmatic province is alkaline distinct from the subalkaline volcanic rocks thought to dominate most of the planet s surface the fact that differentiated volcanic rocks were not encountered on the plains prior to ascending husband hill may suggest a local magma source for volcanism beneath gusev crater

acidic volatiles and the mars soil large portions of mars surface are covered with deposits of fine homogeneous weathered dusty soil material nanophase iron oxides silicate mineraloids and salts prevail in the soil the mode of formation of this somewhat peculiar type of soil is still far from being clear one scenario suggests that weathering took place during early epochs when mars may have been warm and wet the properties of the soil are not easily reconciled with this scenario we propose another possible scenario that attributes in part the peculiar nature of the martian dust and soil to a relatively young weathering product formed during the last few hundreds of millions of years in a process that involves acidic volatiles we tested this hypothesis in an experimental study of the first step of acidolytic weathering of a partly palagonitized volcanic tephra of hawaiitic lava origin using sulfuric hydrochloric and nitric acids and their mixtures the tephra effectively neutralize the added acidity the protonic acidity added to the tephra attacks the primary minerals releasing fe al and mg which control the ph acting as lewis acid species of varying acid strengths the full amount of acidity added to the tephra is stored in it but only a very small fraction is preserved as the original protonic acidity the majority of the added sulfate and chloride were present as salts and easily solubilized minerals well crystallized sulfate salt minerals of aluminum and calcium were detected by powder x ray diffractometry whereas secondary magnesium and iron minerals were not detected due probably to lack of crystallinity the presence of gypsum caso4 2 h2o and alunogen al2 so4 3 17 h2o is probably responsible for the observed increased hygroscopicity of the acidified tephra and their tendency to form hardened crusts we suggest that if this mechanism is of importance on mars then the chemically weathered component of the martian soil consists of a salt rich mineral mixture containing the salts of the anionicligands so4 and cl resulting from volatiles emitted from volcanoes during more recent eruptions up to 109 years b p the lack of liquid water on mars surface during that time slowed or halted mineralogical evolution into highly crystallized minerals having large mineral grains the chemically weathered components are mixed with the products of physical weathering the recently formed soil may cover and coat more evolved hydrothermally modified mineral deposits formed in earlier epochs of mars

athena mars rover science investigation 1 each mars exploration rover carries an integrated suite of scientific instruments and tools called the athena science payload the primary objective of the athena science investigation is to explore two sites on the martian surface where water may once have been present and to assess past environmental conditions at those sites and their suitability for life the remote sensing portion of the payload uses a mast called the pancam mast assembly pma that provides pointing for two instruments the panoramic camera pancam and the miniature thermal emission spectrometer mini tes pancam provides high resolution color stereo imaging while mini tes provides spectral cubes at mid infrared wavelengths for in situ study a five degree of freedom arm called the instrument deployment device idd carries four more tools a microscopic imager mi for close up imaging an alpha particle x ray spectrometer apxs for elemental chemistry a mossbauer spectrometer mb for the mineralogy of fe bearing materials and a rock abrasion tool rat for removing dusty and weathered surfaces and exposing fresh rock underneath the payload also includes magnets that allow the instruments to study the composition of magnetic martian materials all of the athena instruments have undergone extensive calibration both individually and using a set of geologic reference materials that are being measured with all the instruments using a mer like rover and payload in a number of field settings we have devised operations processes that will enable us to use the mer rovers to formulate and test scientific hypotheses concerning past environmental conditions and habitability at the landing sites

ancient groundwater flow in the valles marineris on mars inferred from fault trace ridges long linear ridges in the valles marineris region of mars most likely represent fault zones that have been cemented by water deposited minerals this implies that water in the martian crust could have traversed long distances via faults and fractures

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

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

magmatic complexity on early mars as seen through a combination of orbital in situ and meteorite data abstract until recently mars was considered a basalt covered world but this vision is evolving thanks to new orbital in situ and meteorite observations in particular of rocks of the ancient noachian period in this contribution we summarise newly recognised compositional and mineralogical differences between older and more recent rocks and explore the geodynamic implications of these new findings for example the msl rover has discovered abundant felsic rocks close to the landing site coming from the wall of gale crater ranging from alkali basalt to trachyte in addition the recently discovered martian regolith breccia nwa 7034 and paired samples contain many coarse grained noritic monzonitic clasts demonstrably noachian in age and even some clasts that plot in the mugearite field olivine is also conspicuously lacking in these ancient samples in contrast to later hesperian rocks the alkali suite requires low degree melting of the martian mantle at low pressure whereas the later hesperian magmatism would appear to be produced by higher mantle temperatures various scenarios are proposed to explain these observations including different styles of magmatic activity i e passive upwelling vs hotspots a second petrological suite of increasing interest involves quartzo feldspathic materials that were first inferred from orbit in local patches in the southern highlands and in the lower units of valles marineris however identification of felsic rocks from orbit is limited by the low detectability of feldspar in the near infrared on the other hand the msl rover has described the texture mineralogy and composition of felsic rocks in gale crater that are granodiorite like samples akin to terrestrial ttg tonalite trondhjemite granodiorite suites these observations and the low average density of the highlands crust suggest the early formation of continental crust on mars although the details of the geodynamic scenario and the importance of volatiles in their generation are aspects that require further work

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

olivine dissolution by acidic fluids in argyre planitia mars evidence for a widespread process compositional and morphological analyses of basin rim units in argyre planitia are con sistent with local olivine rich materials that become relatively olivine poor in the process of being transformed from rocky materials to fi particulate regolith where high thermal inertia rocky surfaces are observed the composition is more mafi c than the surrounding fi nes this relationship between rocks and soils appears to be common on mars as a similar pattern is observed in other locations such as gusev crater isidis planitia and nili fossae despite the lack of local detectable alteration products these trends may be an indication that most martian dark regions are not similar in composition to the primary igneous composition from which they are derived the martian crust may be signifi cantly more mafi c and alteration of these surfaces may be more pervasive than has been inferred from the bulk surface mineral ogy derived from orbital observations

a volcanic interpretation of gusev crater surface materials from thermophysical spectral and morphological evidence 1 gusev crater the mars exploration rover spirit landing site 160 km diameter 14 5 s 184 5 w has been identified in previous studies as a prime site of geological and exobiological interest on the basis of its potential for having hosted a fluviolacustrine environment such environment may have been favorable for the development of biological activity the origin and nature of the materials present at the surface of gusev crater are still being debated in previous studies based on geomorphological and thermophysical data surface materials in the crater have been interpreted as originating from fluviolacustrine volcanic or aeolian processes or combinations thereof we present results from the analysis of newly compiled thermophysical thermal emission spectrometer tes and thermal emission imaging system themis spectroscopic tes and visible themis and mars observer camera data for the gusev region these data were analyzed using a new mosaicking technique developed to match the values of contiguous scenes and to produce seamless mosaics apt for geological interpretation thermophysical spectroscopic and morphological evidence point to the presence of local outcrops of lava flows of basaltic composition materials consistent with a regolith developed from basaltic materials fine grained deposits of basaltic composition strongly modified by wind erosion and wind deposits according to these findings we conclude that most of the materials occupying the present surface of gusev have characteristics consistent with those of volcanic and aeolian deposits fluviolacustrine deposits proposed by other authors may exist under the volcanic materials and may be exposed in impact craters

mixing relationships and the effects of secondary alteration in the wishstone and watchtower classes of husband hill gusev crater mars 1 the wishstone and watchtower class rocks on husband hill preserve evidence for a geochemical relationship consistent with two component mixing between a high al 2 o 3 tio 2 cao na 2 o p 2 o 5 end member and a second end member enriched in the elements mgo zn s br and cl the first end member appears to be reasonably well represented by rocks of the wishstone class while the second end member is consistent with a chemical component not represented by any lithology encountered by spirit the watchtower class appears to be an intermediate in the mixture the concentration of the redox sensitive elements fe and mn display no systematic variation between rock classes and the fe redox state of the watchtower class is elevated relative to the wishstone class combined with evidence for two component mixing these observations suggest that the mixture was generated by interaction between an initially wishstone like deposit and a fluid phase enriched in the elements mgo zn s br and cl the fluid phase may have been weakly acidic ph 4 to basic ph 9 resulting in oxidation and immobilization offe and mn a number of secondary rock surface alteration processes which obscure the mixing relationship are also identified these include 1 removal of cao and p 2 o 5 from rock surfaces by dissolution of ca phosphate minerals under acidic low water to rock ratio conditions 2 addition of so 3 to rock surfaces via aeolian deposition of high so 3 soil and or precipitation of sulfate salts from solution and 3 homogenization of rock surface chemistry by soil contamination

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

ice rich terrain in gusev crater mars abstract the morphology of materials on the floor of gusev crater 14 s 175 w mars imply a history of volcanism and subsequent removal of an ice rich deposit fluid lava flows observed in the western portion of gusev crater paradoxically terminate in a steep thick 60 m flow front adjacent to hummocky terrain the hummocky terrain is morphologically similar to deglaciated terrain on earth generated when glacial debris are left behind after the glacier has retreated we propose the following scenario for the floor of gusev crater first ice rich material was deposited adjacent to thira crater second fluid lavas were emplaced and ponded against the ice rich deposits at some later time the ice within the deposit sublimated leaving hummocky terrain current age estimates for the gusev flows are hesperian suggesting that the ice removal occurred in the upper hesperian or more recently if this hypothesis is correct quench features glassy rinds columnar jointing should be observed at the lava flow margin the hummocky deposit should be poorly sorted angular debris

basaltic rocks analyzed by the spirit rover in gusev crater the spirit landing site in gusev crater on mars contains dark fine grained vesicular rocks interpreted as lavas pancam and mini thermal emission spectrometer mini tes spectra suggest that all of these rocks are similar but have variable coatings and dust mantles magnified images of brushed and abraded rock surfaces show alteration rinds and veins rock interiors contain 25 megacrysts chemical analyses of rocks by the alpha particle x ray spectrometer are consistent with picritic basalts containing normative olivine pyroxenes plagioclase and accessory feti oxides mossbauer pancam and mini tes spectra confirm the presence of olivine magnetite and probably pyroxene these basalts extend the known range of rock compositions composing the martian crust

alteration mineralogy of home plate and columbia hills formation conditions in context to impact volcanism and fluvial activity the mars exploration rover spirit investigated the igneous and alteration mineralogy and chemistry of home plate and its surrounding deposits here we focus on using thermochemical modeling to understand the secondary alteration mineralogy at the home plate outcrop and surrounding columbia hills region in gusev crater at high temperatures 300 c magnetite occurs at very high w r ratios but the alteration assemblage is dominated by chlorite and serpentine over most of the w r range quartz epidote and typical high t phases such as feldspar pyroxene and garnet occur at low w r at epithermal temperatures 150 c hematite occurs at very high w r a range of phyllosilicates including kaolinite nontronite chlorite and serpentine are precipitated at specific w r amphibole with garnet feldspar and pyroxene occur at low w r if the co2 content of the system is high the assemblage is dominated by carbonate with increasing amounts of an sio2 phase kaolinite carpholite and chlorite with lower w r at temperatures of hydrous weathering 13 c the oxide phase is goethite silicates are chlorite nontronite and talc plus an sio2 phase in the presence of co2 the mineral assemblage at high w r remains the same and only at low w r i e with increasing salinity carbonate precipitates the geochemical gradients observed at home plate are attributed to short lived initially high 300 c temperature but fast cooling events which are in agreement with our models and our interpretation of a multistage alteration scenario of home plate and gusev in general alteration at various temperatures and during different geological processes within gusev crater has two effects both of which increase the habitability of the local environment precipitation of hydrous sheet silicates and formation of a brine which might contain elements essential for life in diluted easily accessible form

the opportunity rover s athena science investigation at meridiani planum mars the mars exploration rover opportunity has investigated the landing site in eagle crater and the nearby plains within meridiani planum the soils consist of fine grained basaltic sand and a surface lag of hematite rich spherules spherule fragments and other granules wind ripples are common underlying the thin soil layer and exposed within small impact craters and troughs are flat lying sedimentary rocks these rocks are finely laminated are rich in sulfur and contain abundant sulfate salts small scale cross lamination in some locations provides evidence for deposition in flowing liquid water we interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water followed by evaporation exposure and desiccation hematite rich spherules are embedded in the rock and eroding from them we interpret these spherules to be concretions formed by postdepositional diagenesis again involving liquid water

sulfate deposition in subsurface regolith in gusev crater mars excavating into the shallow martian subsurface has the potential to expose stratigraphic layers and mature regolith which may hold a record of more ancient aqueous interactions than those expected under current martian surface conditions during the spirit rover s exploration of gusev crater rover wheels were used to dig three trenches into the subsurface regolith down to 6 11 cm depth road cut the big hole and the boroughs a high oxidation state of fe and high concentrations of mg s cl and br were found in the subsurface regolith within the two trenches on the plains between the bonneville crater and the foot of columbia hills data analyses on the basis of geochemistry and mineralogy observations suggest the deposition of sulfate minerals within the subsurface regolith mainly mg sulfates accompanied by minor ca sulfates and perhaps fe sulfates an increase of fe2o3 an excess of sio2 and a minor decrease in the olivine proportion relative to surface materials are also inferred three hypotheses are proposed to explain the geochemical trends observed in trenches 1 multiple episodes of acidic fluid infiltration accompanied by in situ interaction with igneous minerals and salt deposition 2 an open hydrologic system characterized by ion transportation in the fluid subsequent evaporation of the fluid and salt deposition and 3 emplacement and mixing of impact ejecta of variable composition while all three may have plausibly contributed to the current state of the subsurface regolith the geochemical data are most consistent with ion transportation by fluids and salt deposition as a result of open system hydrologic behavior although sulfates make up 20 wt of the regolith in the wall of the boroughs trench a higher hydrated sulfate than kieserite within the boroughs or a greater abundance of sulfates elsewhere than is seen in the boroughs wall regolith would be needed to hold the structural water indicated by the water equivalent hydrogen concentration observed by the gamma ray spectrometer on odyssey in the gusev region copyright 2006 by the american geophysical union

morphology and texture of particles along the spirit rover traverse from sol 450 to sol 745 1 we quantified and classified the shape roundness size and texture of 935 loose surface particles along the spirit rover traverse from sols 450 745 to assess origin transport and other alteration mechanisms that altered particles during and after formation variation in particle morphologic parameters along traverse is consistent with crossing mapped geologic unit boundaries texture is divided into four types vesicular smooth and flat faceted rough and flat faceted and very rough sphericity and roundness are intermediate and low respectively comparable to particles moved by high energy transport or to crushed particles this indicates intermittent high energy emplacement or modification of a single lithology rather than systematic continuous low energy abrasion or wear over time comparison with particle morphology at other mars landing sites is consistent with the hypothesis that no secondary systematic transport or wide scale chemical alteration was active at a significant enough level to alter macromorphology in particular particle morphology at the mars pathfinder site shows stronger evidence of abrasion than along the spirit traverse suggesting mars pathfinder particles have undergone abrasion processes that particles in this study area have not additionally morphology indices have correlation coefficients near zero indicating that a fluvial transport mechanism is likely not responsible for morphology morphology and texture are instead related to origin and composition rather than subsequent modification morphology and texture support a volcanic origin possibly without modification but most likely altered primarily by ballistic impact implying that the spirit landing site and traverse may be utilized in the future as a standard site for characterization of impact derived morphology

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

the spirit rover s athena science investigation at gusev crater mars the mars exploration rover spirit and its athena science payload have been used to investigate a landing site in gusev crater gusev is hypothesized to be the site of a former lake but no clear evidence for lacustrine sedimentation has been found to date instead the dominant lithology is basalt and the dominant geologic processes are impact events and eolian transport many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration any lacustrine sediments that may exist at this location within gusev apparently have been buried by lavas that have undergone subsequent impact disruption

iron and aluminum hydroxysulfates from acid sulfate waters acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite chalcopyrite pyrrhotite and marcasite in rocks soils sediments and industrial wastes this spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits the formation of acid sulfate soils and the mobilization and release of acidity and metals to surface and ground waters the purely natural process of acid rock drainage is often intensified by human activities related to mining mineral processing construction soil drainage and dredging geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water and to microbes that catalyze the reaction process large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation hydrolysis and neutralization the objective of this chapter is to describe the formation properties fate and environmental implications of the nano to microphase hydroxy sulfates of fe and al that are precipitated from acid sulfate waters these minerals are commonly of poor crystallinity and difficult to characterize much remains to be learned about their occurrence formation and properties mine drainage the best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited ash et al 1951 barton 1978 nordstrom 1982a rose and cravotta 1998 nordstrom and alpers 1999 there may be as many as 500 000 inactive or abandoned mine sites in the united states alone lyon et al 1993 although most of these pose no immediate water quality problem kleinmann 1989 estimated that about 19 300 km of streams and more than 72 000 ha of lakes and reservoirs have been

evolution of sulfide mineralization on mars the presence of komatiitic igneous rocks on marks based on geochemical evidence from snc meteorites and viking x ray fluorescence analyses of the regolith suggests that massive and disseminated iron sulfide mineralization occurs near the martian surface analogies are drawn between possible ultramafic fe ni sulfides on mars and terrestrial pyrrhotite pentlandite ore deposits associated with archean komatiites formed during early crustal development on earth partial melting of the mantle as a result of high radiogenic heat production then extrusion of turbulent high temperature ultramafic lavas segregation of immiscible fes melts during cooling gravitational settling and fractional crystallization of sulfide minerals in magma chambers or lava flows produced massive and disseminated sulfide mineralization associated with terrestrial komatiites comparable processes probably occurred on mars where on account of the inferred higher fe fe mg ratio of the x ray mantle estimated to contain approximately 4 5 wt s iron rich basaltic magmas were produced by partial melting at depths and temperatures exceeding 165 km and 1 400 degree c respectively adiabatic diapiric emplacement of these iron rich very low viscosity basaltic melts transported significant concentrations of dissolved sulfur as s sup 2 minus and hs sup minus from the mantle ensuing sulfide mineralization may have been either thinly disseminated within ultramafic lavas eruptingmore over large areas of mars or concentrated locally at the base of structural depressions cumulate ore deposits several meters thick may occur at the base of intrusions or in near surface magma chambers the evidence for insignificant plate tectonic activity on mars and minimal interactions of martian mantle with crust hydrosphere and atmosphere has restricted the evolution of sulfide ore deposits there less

mineralogy of the paso robles soils on mars visible near infrared thermal and mossbauer spectroscopic data from the exposed bright track soil at the paso robles site within gusev crater mars indicate the presence of fe3 sulfates and possibly fe3 phosphates admixed with the host soil when the spectroscopic analyses are combined with constraints imposed by chemical data the determined dominant fe3 sulfate component is hydrous and all of the spectroscopic methods suggest that it is probably ferricopiapite or some closely related structurally similar species possibly mixed with other fe3 sulfates such as butlerite or parabutlerite or perhaps para coquimbite fibroferrite or metahohmanite such an assemblage is consistent with formation in a highly oxidized relatively dehydrated environment with the bulk sulfate assemblage having oh oh 2so4 of 0 4 some fe3 is likely to be associated with phosphates in the soil in the form of ferristrunzite or strengite

soluble sulfate in the martian soil at the phoenix landing site 1 sulfur has been detected by x ray spectroscopy in martian soils at the viking pathfinder opportunity and spirit landing sites sulfates have been identified by omega and crism in valles marineris and by the spectrometers on the mer rovers at meridiani and gusev the ubiquitous presence of sulfur has been interpreted as a widely distributed sulfate mineralogy one goal of the wet chemistry laboratory wcl on nasa s phoenix mars lander was to determine soluble sulfate in the martian soil we report here the first in situ measurement of soluble sulfate equivalent to 1 3 0 5 wt as so 4 in the soil the results and models reveal so 4 predominately as mgso 4 with some caso 4 if the soil had been wet in the past epsomite and gypsum would be formed from evaporation the wcl derived salt composition indicates that if the soil at the phoenix site were to form an aqueous solution by natural means the water activity for a dilution of greater than 0 015 g h 2 o g soil would be in the habitable range of known terrestrial halophilic microbes

a new hypothesis for the origin and redistribution of sulfates in the equatorial region of western mars 1 the formation of sulfates on mars has been under debate since they were identified by several mars missions starting from the 1970s we propose that sulfates formed as evaporites in enclosed standing bodies of water in the valles marineris area following the early alteration of martian basaltic crust were then elevated by the tharsis uplift and transported together with rock materials to meridiani planum by periodic outbursts of water where they were deposited as sediments the proposed model comprehensively addresses all forms of sulfate occurrences near the equator in the western martian hemisphere and relates it to physiographic processes volcanic tectonic and sedimentary affecting the martian surface

mars science laboratory observations of chloride salts in gale crater mars the mars science laboratory curiosity rover is traversing a sequence of stratified sedimentary rocks in gale crater that contain varied aeolian fluviodeltaic and lake deposits with phyllosilicates iron oxides and sulfate salts here we report the chloride salt distribution along the rover traverse chlorine is detected at low levels 3 wt in soil and rock targets with multiple msl instruments isolated fine scale observations of high chlorine up to 15 wt cl detected using the chemcam instrument are associated with elevated na 2o and interpreted as halite grains or cements in bedrock halite is also interpreted at the margins of veins and in nodular altered textures we have not detected halite in obvious evaporitic layers instead its scattered distribution indicates that chlorides emplaced earlier in particular members of the murray formation were remobilized and reprecipitated by later groundwaters within murray formation mudstones and in diagenetic veins and nodules

martian cratering 8 isochron refinement and the chronology of mars abstract this paper reviews and refines the technique of dating martian surfaces by using impact crater isochrons defined as size distributions of impact craters on undisturbed martian surfaces of specified ages in the 1970s this system identified not only abundant ancient martian volcanic surfaces but also extensive lava plains with ages of a few 108 y old this dating was initially controversial but confirmed in the 1980s and 90s by martian meteorites the present update utilizes updated estimates of the mars moon cratering ratio the most important calibration factor improves treatment of gravity and impact velocity scaling effects combines aspects of the crater size distribution data from earlier work by both neukum and hartmann and for the first time applies a correction for loss of small meteoroids in the martian atmosphere from popova et al 2003 meteorit planet sci 38 905 925 the updated isochrons are not radically different from the previous 2002 iteration but fit observed data better and give somewhat older model ages for features dated from small craters diameter d 100 m crater counts from young lava flows in various areas give good fits to the new isochrons over as much as 3 orders of magnitude in d confirming the general isochron shape and giving crater retention ages in the range of some 106 to some 108 y interpreted as lava flow ages more complex older units are also discussed uncertainties are greatest if only small craters d 100 m are used suggestions by other workers of gross uncertainties due to local secondary craters and deposition exhumation are discussed they do not refute our conclusions of significant volcanic fluvial and other geologic activity in the last few percent of martian geologic time or the importance of cratering as a tool for studying processes such as exhumation indeed crater count data suggest certain very recent episodes of deposition exhumation and ice flow possibly associated with obliquity cycles of 10 7 y timescale evidence from ancient surfaces suggests higher rates of volcanism fluvial activity glaciation and other processes in noachian hesperian time than in amazonian time

in situ and experimental evidence for acidic weathering of rocks and soils on mars experimental data for alteration of synthetic martian basalts at ph 0 1 indicate that chemical fractionations at low ph are vastly different from those observed during terrestrial weathering rock surface analyses from gusev crater are well described by the relationships apparent from low ph experimental alteration data a model for rock surface alteration is developed which indicates that a leached alteration zone is present on rock surfaces at gusev this zone is not chemically fractionated to a large degree from the underlying rock interior indicating that the rock surface alteration process has occurred at low water to rock ratio the geochemistry of natural rock surfaces analyzed by apxs is consistent with a mixture between adhering soil dust and the leached alteration zone the chemistry of rock surfaces analyzed after brushing with the rat is largely representative of the leached alteration zone the chemistry of rock surfaces analyzed after grinding with the rat is largely representative of the interior of the rock relatively unaffected by the alteration process occurring at the rock surface elemental measurements from the spirit opportunity pathfinder and viking 1 landing sites indicate that soil chemistry from widely separated locations is consistent with the low ph low water to rock ratio alteration relationships developed for gusev rocks soils are affected principally by mobility of fe and mg consistent with alteration of olivine bearing basalt and subsequent precipitation of fe and mg bearing secondary minerals as the primary control on soil geochemistry copyright 2006 by the american geophysical union

sulfur bearing phases detected by evolved gas analysis of the rocknest aeolian deposit gale crater mars the sample analysis at mars sam instrument suite detected so2 h2s ocs and cs2 from 450 to 800 c during evolved gas analysis ega of materials from the rocknest aeolian deposit in gale crater mars this was the first detection of evolved sulfur species from a martian surface sample during in situ ega so2 3 22 mol is consistent with the thermal decomposition of fe sulfates or ca sulfites or evolution desorption from sulfur bearing amorphous phases reactions between reduced sulfur phases such as sulfides and evolved o2 or h2o in the sam oven are another candidate so2 source h2s 41 109 nmol is consistent with interactions of h2o h2 and or hcl with reduced sulfur phases and or so2 in the sam oven ocs 1 5 nmol and cs2 0 2 1 nmol are likely derived from reactions between carbon bearing compounds and reduced sulfur sulfates and sulfites indicate some aqueous interactions although not necessarily at the rocknest site fe sulfates imply interaction with acid solutions whereas ca sulfites can form from acidic to near neutral solutions sulfides in the rocknest materials suggest input from materials originally deposited in a reducing environment or from detrital sulfides from an igneous source the presence of sulfides also suggests that the materials have not been extensively altered by oxidative aqueous weathering the possibility of both reduced and oxidized sulfur compounds in the deposit indicates a nonequilibrium assemblage understanding the sulfur mineralogy in rocknest materials which exhibit chemical similarities to basaltic fines analyzed elsewhere on mars can provide insight in to the origin and alteration history of martian surface materials

soil sedimentology at gusev crater from columbia memorial station to winter haven 1 a total of 3140 individual particles were examined in 31 soils along spirit s traverse their size shape and texture were quantified and classified they represent a unique record of 3 years of sedimentologic exploration from landing to sol 1085 covering the plains unit to winter haven where spirit spent the martian winter of 2006 samples in the plains unit and columbia hills appear as reflecting contrasting textural domains one is heterogeneous with a continuum of angular to round particles of fine sand to pebble sizes that are generally dust covered and locally cemented in place the second shows the effect of a dominant and ongoing dynamic aeolian process that redistributes a uniform population of medium size sand the texture of particles observed in the samples at gusev crater results from volcanic aeolian impact and water related processes

isotopic and petrographic evidence for young martian basalts radiometric age data for shergottites yield ages of 4 0 ga and 180 575 ma the interpretation of these ages has been and remains a subject of debate here we present new 39 ar 40 ar laser probe data on lherzolitic shergottites allan hills alh 77005 and northwest africa nwa 1950 these two meteorites are genetically related but display very different degrees of shock damage on a plot of 40 ar 36 ar versus 39 ar 36 ar the more strongly shocked alh 77005 45 55 gpa does not yield an array of values indicating an isochron but the data are highly scattered with the shock melts yielding 40 ar 36 ar ratios of 1600 2026 apparent ages calculated from these extractions range from 374 8183 ma with 50 of the data particularly from the shock melts yielding impossibly old ages 4 567 ga on the same plot extractions from igneous minerals in the less shocked nwa 1950 30 44 gpa yield a fitted age of 382 36 ma argon extractions from the shock melts are well distinguished from minerals with the melts exhibiting the highest 40 ar 36 ar ratios 1260 1488 and the oldest apparent ages laser step heating was also performed on maskelynite separates from nwa 1950 yielding ages of 1000 ma at the lowest release temperatures and ages of 360 and 362 ma at higher temperature steps stepped heating data from previous studies have yielded ages of 500 and 700 ma to 1 7 ga for alh 77005 maskelynite separates if the ages obtained from igneous minerals represent undegassed argon from an ancient 4 0 ga rock then the ages are expected to anticorrelate with the degree of shock heating the data do not support this inference our data support young crystallization ages for minerals and martian atmosphere as the origin of excess 40 ar in the shock melts the shock features of shergottites are also reviewed in the context of what is known of the geologic history of the martian surface through remote observation the oldest most heavily cratered surfaces of mars are thought to be 4 0 ga we contend that ancient rocks from mars noachian 3 5 ga are likely to record multiple impact events reflecting megaregolith formation and the cumulative effects of erosion and aqueous alteration occurring during or since that era young rocks late amazonian 0 6 ga should record a relatively simple history of emplacement and ejection from the near surface we show that although shergottites are strongly shocked they are relatively pristine crystalline igneous rocks and not pervasively altered breccias the petrography of shergottites is at odds with an ancient age interpretation a model in which young coherent rocks are preferentially sampled by hypervelocity impact because of material strength is considered highly plausible

estimating rock compressive strength from rock abrasion tool rat grinds 1 each mars exploration rover carries a rock abrasion tool rat whose intended use was to abrade the outer surfaces of rocks to expose more pristine material motor currents drawn by the rat motors are related to the strength and hardness of rock surfaces undergoing abrasion and these data can be used to infer more about a target rock s physical properties however no calibration of the rat exists here we attempt to derive an empirical correlation using an assemblage of terrestrial rocks and apply this correlation to data returned by the rover spirit the results demonstrate a positive correlation between rock strength and rat grind energy for rocks with compressive strengths less than about 150 mpa a category that includes all but the strongest intact rocks applying this correlation to rocks abraded by spirit s rat the results indicate a large divide in strength between more competent basaltic rocks encountered in the plains of gusev crater adirondack class rocks and the weaker variety of rock types measured in the columbia hills adirondack class rocks have estimated compressive strengths in the range of 70 130 mpa and are significantly less strong than fresh terrestrial basalts this may be indicative of a degree of weathering induced weakening rock types in the columbia hills wishstone watchtower clovis and peace class all have compressive strengths 50 mpa and are consistent with impactites or volcanoclastic materials in general when considered alongside chemical spectral and rock textural data these inferred compressive strength results help inform our understanding of rock origins and modification history

comparisons of the four miller range nakhlites mil 03346 090030 090032 and 090136 textural and compositional observations of primary and secondary mineral assemblages abstract petrological and geochemical analyses of miller range mil 03346 indicate that this meteorite originated from the same augitic cumulate layer s as the nakhlite martian meteorites but underwent rapid cooling prior to complete crystallization as with the other nakhlites mil 03346 contains a secondary alteration assemblage in this case consisting of iddingsite like alteration veins in olivine phenocrysts fe oxide alteration veins associated with the mesostasis and ca and k fe sulfate veins we compared the textural and mineralogical compositions of mil 090030 090032 and 090136 with mil 03346 focusing on the composition and raman spectra of the alteration assemblages these observations indicate that the meteorites are paired and that the preterrestrial olivine bound alteration assemblages were produced by weakly acidic brine although these alteration assemblages resemble similar assemblages in nakhla the absence of siderite and halite in the miller range nakhlites indicates that the parental alteration brine was comparatively hco3 depleted and less concentrated than that which altered nakhla this indicates that the miller range nakhlite alteration brine experienced a separate evolutionary pathway to that which altered nakhla and therefore represents a separate branch of the lafayette nakhla evaporation sequence thin sections cut from the internal portions of these meteorites away from any fusion crust or terrestrially exposed edge contain little ca sulfate identified as gypsum and no jarosite whereas thin sections with terrestrially exposed edges have much higher sulfate abundances these observations suggest that at least the majority of sulfate within the miller range nakhlites is terrestrially derived

density specific surface area and correlation length of snow measured by high resolution penetrometry precise measurements of snow structural parameters are crucial to understand the formation of snowpacks by deposition and metamorphism and to characterize the stratigraphy for many applications and remote sensing in particular the area wide acquisition of structural parameters at high spatial resolution from state of the art methods is however still cumbersome since the time required for a single profile is a serious practical limitation as a remedy we have developed a statistical model to extract three major snow structural parameters density correlation length and specific surface area ssa solely from the snowmicropen smp a high resolution penetrometer which allows a meter profile to be measured with millimeter resolution in less than 1 min the model was calibrated by combining smp data with 3 d microstructural data from microcomputed tomography which was used to reconstruct full depth snow profiles from different snow climates alpine arctic and antarctic density correlation length and ssa were derived from the smp with a mean relative error of 10 6 16 4 and 23 1 respectively for validation we compared the density and ssa derived from the smp to traditional measurements and near infrared profiles we demonstrate the potential of our method by the retrieval of a two dimensional stratigraphy at kohnen station antarctica from a 46 m long smp transect the result clearly reveals past depositional and metamorphic events and our findings show that the smp can be used as an objective high resolution tool to retrieve essential snow structural parameters efficiently in the field

modeling aluminum silicon chemistries and application to australian acidic playa lakes as analogues for mars abstract recent mars missions have stimulated considerable thinking about the surficial geochemical evolution of mars among the major relevant findings are the presence in meridiani planum sediments of the mineral jarosite a ferric sulfate salt and related minerals that require formation from an acid salt brine and oxidizing environment similar mineralogies have been observed in acidic saline lake sediments in western australia wa and these lakes have been proposed as analogues for acidic sedimentary environments on mars the prior version of the equilibrium chemical thermodynamic frezchem model lacked al and si chemistries that are needed to appropriately model acidic aqueous geochemistries on earth and mars the objectives of this work were to 1 add al and si chemistries to the frezchem model 2 extend these chemistries to low temperatures frezchem is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the pitzer approach for the temperature range from 4 no 3 oh hco 3 co 3 co 2 o 2 ch 4 si h 2 o system that now contain 95 solid phases there were similarities differences and uncertainties between australian acidic saline playa lakes and waters that likely led to the burns formation salt accumulations on mars both systems are similar in that they are dominated by 1 acidic saline ground waters and sediments 2 ca and or mg sulfates and 3 iron precipitates such as jarosite and hematite differences include 1 the dominance of nacl in many wa lakes versus the dominance of fe mg ca so 4 in meridiani planum 2 excessively low k concentrations in meridiani planum due to jarosite precipitation 3 higher acid production in the presence of high iron concentrations in meridiani planum and probably lower rates of acid neutralization and hence higher acidities on mars owing to colder temperatures and 4 lateral salt patterns in wa lakes the wa playa lakes display significant lateral variations in mineralogy and water chemistry over short distances reflecting the interaction of acid ground waters with neutral to alkaline lake waters derived from ponded surface runoff meridiani planum observations indicate that such lateral variations are much less pronounced pointing to the dominant influence of ground water chemistry vertical ground water movements and aeolian processes on the martian surface mineralogy

overview of mars surface geochemical diversity through alpha particle x ray spectrometer data multidimensional analysis first attempt at modeling rock alteration 1 principal component analysis and a hierarchical clustering method have been employed to describe and quantify the compositional variability of martian rocks and soils measured by the alpha particle x ray spectrometers onboard the mars exploration rovers a robust classification of samples emerges which defines distinct rock classes and sheds light on the petrogenetic relationships between rocks this is particularly useful in the case of rocks from gusev crater where significant chemical diversity is observed this approach also highlights that compositional variability of rocks at meridiani is dominated by variations in sulfur content the relative proportions of other elements remaining approximately constant for soils variations in fe concentration dominate because of the presence of hematite rich berry bearing samples on the basis of this observation a simple geochemical model of acid fog alteration of martian basalts has been tested assuming either equivalent alteration of all phases or preferential alteration of certain phases thus taking into account kinetic considerations the results show that for certain ranges of so3 basalt many of the compositional and mineralogical features measured at both sites may be explained the secondary mineralogy and bulk rock compositions predicted by the model are broadly consistent with rock and soil compositions from gusev and meridiani especially if the role of brine circulation and evaporation are considered although agreement is not perfect comparison of observations and models argues in favor of variable interaction of the martian surface with sour gas explaining the high local abundance of sulfates for example

a review of the handheld x ray fluorescence spectrometer as a tool for field geologic investigations on earth and in planetary surface exploration x ray fluorescence xrf spectroscopy is a well established and commonly used technique in obtaining diagnostic compositional data on geological samples recently developments in x ray tube and detector technologies have resulted in miniaturized field portable instruments that enable new applications both in and out of standard laboratory settings these applications however have not been extensively applied to geologic field campaigns this study investigates the feasibility of using developing handheld xrf hxrf technology to enhance terrestrial field geology with potential applications in planetary surface exploration missions we demonstrate that the hxrf is quite stable providing reliable and accurate data continuously over a several year period additionally sample preparation is proved to have a marked effect on the strategy for collecting and assimilating hxrf data while the hxrf is capable of obtaining data that are comparable to laboratory xrf analysis for several geologically important elements such as si ca ti and k the instrument is unable to detect other elements such as mg and na reliably while this limits the use of the hxrf especially when compared to laboratory xrf techniques the hxrf is still capable of providing the field user with significantly improved contextual awareness of a field site and more work is needed to fully evaluate the potential of this instrument in more complex geologic environments

petrogenesis of high phosphorous wishstone class rocks in gusev crater mars 1 the spirit rover has analyzed a wide variety of alkaline volcanic rocks in gusev crater among them are wishstone class tephrites with unusually high p2o5 5 wt abundances to obtain the chemical compositions of rock interiors we extrapolated a trend defined by brushed and abraded surface compositions the extrapolation analysis suggests the high p2o5 tephrite signature is not attributable to secondary aqueous alteration but represents an igneous rock composition assessment of the compositional trend also suggests that merrillite is the phosphate mineral in wishstone class modified cipw norm calculations using merrillite instead of apatite show that wishstone class rocks are silica saturated hypersthene olivine normative and alkaline the high p2o5 whole rock compositions plot above solubility curves of merrillite in a diagram of p2o5 versus aluminosity suggesting that mechanical admixture of merrillite is required a source supplying merrillite cannot be a common silicate magma instead it could be a carbonatitic melt or a highly fractionated residual melt jotunite after anorthosite crystallization comparison with earth analogs suggests that the wishstone class is akin to alkaline basalts in the eastern snake river plain with regard to its chemistry texture and geologic context these alkaline basalts are interpreted to originate from mantle metasomatized by co2 fluids and highly alkaline melts in the wake of the yellowstone hot spot thus we propose that the wishstone class represents a silica saturated alkaline suite that has mechanically mixed xenocrystic merrillites probably during explosive volcanic eruption the merrillites crystallized from carbonate rich magma produced by melting of a co2 bearing martian mantle

iron sulfur mineralogy of mars magmatic evolution and chemical weathering products models for the evolution of sulfide minerals on mars and reaction pathways to their oxidative weathering products in martian regolith have been proposed based on petrogenetic associations between komatiitic rock types viking geochemical data snc meteorites and terrestrial fe ni sulfide deposits to test the weathering model komatiitic pyrrhotites and olivines were exposed to sulfuric acid solutions with and without dissolved ferric iron added to simulate deep weathering processes and the reaction products were identified by mossbauer spectroscopy secondary fes sub 2 pyrite or marcasite feooh goethite and possibly jarosite were formed from pyrrhotite while olivine was oxidized to nanophase goethite these results suggest that on mars acidic groundwater induced pyrrhotite yields fes sub 2 yields feooh jarosite oxidative weathering reactions particularly in the presence of dissolved fe sup 3 such gossaniferous materials occurring in martian regolith were derived mainly from fe ni sulfides associated with komatiitic basalts and not from sulfides occurring in calc alkaline porphyry copper deposits granitic hydrothermal veins sediment hosted pbs zns ores etc which presumably did not evolve on mars due to the virtual lack of plate tectonic activity there

hydrogen isotope analyses of alteration phases in the nakhlite martian meteorites abstract secondary alteration phases such as carbonates smectite clays and fe oxides are found within the martian meteorites if these meteorites were seen to fall the assumption can be reasonably made that the secondary phases have a martian origin however for martian meteorite finds this is not the case deuterium hydrogen d h ratio analysis can be used to distinguish between terrestrial and martian secondary alteration phases the martian atmosphere is currently five times enriched in deuterium compared to terrestrial seawater producing a deuterium enrichment in the martian alteration phases large enough to be detected with modern ion microprobe techniques we aimed to measure the d h ratio of the iddingsite like alteration veins in the nakhlite martian meteorites nakhla mil 03346 mil 090030 and y 000593 to help confirm the martian origin of this material and determine the relative amounts of terrestrial contamination in each meteorite as an observed fall nakhla is nominally uncontaminated by terrestrial alteration and shows elevated d values in its alteration veins however even the highest of these values is much below that of the martian atmosphere indicating that terrestrial contamination probably combined with fractionation effects between the martian atmosphere and the alteration material have reduced the d values of these veins the speed of hydrogen isotope exchange in the nakhlite iddingsite like alteration veins is demonstrated by the purely terrestrial d values in the veins of nakhla 110 a thin section exposed to the terrestrial atmosphere since its preparation in 1998 mineralogical heterogeneity also affects the hydrogen isotope exchange rate in these veins the wide variation in d within the veins of nakhla and y 000593 appears to be due to the heterogeneous nature of the vein material where some phases exchange hydrogen with the atmosphere at a faster rate than others

spectral variability among rocks in visible and near infrared multispectral pancam data collected at gusev crater examinations using spectral mixture analysis and related techniques 1 visible and near infrared vnir multispectral observations of rocks made by the mars exploration rover spirit s panoramic camera pancam have been analyzed using a spectral mixture analysis sma methodology scenes have been examined from the gusev crater plains into the columbia hills most scenes on the plains and in the columbia hills could be modeled as three end member mixtures of a bright material rock and shade scenes of rocks disturbed by the rover s rock abrasion tool rat required additional end members in the columbia hills there were a number of scenes in which additional rock end members were required the sma methodology identified relatively dust free areas on undisturbed rock surfaces as well as spectrally unique areas on rat abraded rocks spectral parameters from these areas were examined and six spectral classes were identified these classes are named after a type rock or area and are adirondack lower west spur clovis wishstone peace and watchtower these classes are discriminable based primarily on near infrared nir spectral parameters clovis and watchtower class rocks appear more oxidized than wishstone class rocks and adirondack basalts based on their having higher 535 nm band depths comparison of the spectral parameters of these gusev crater rocks to parameters of glass dominated basaltic tuffs indicates correspondence between measurements of clovis and watchtower classes but divergence for the wishstone class rocks which appear to have a higher fraction of crystalline ferrous iron bearing phases despite a high sulfur content the rock peace has nir properties resembling plains basalts

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

depositional environments and vegetation of aptian sequences affected by volcanism in patagonia abstract the continental deposits of the baquero group preserve one of the most abundant aptian floras on the southern margins of gondwana these floras represent an extinct biome that was subject to increasing regional volcanism in combination with the presence of shallow water bodies this biome provided suitable environments for the preservation of imprints and compressions of foliage together with permineralized trunks and palynofloras eight facies associations were identified in nine sections characterizing the evolution of lacustrine and fluvial environments under intense volcanic activity in addition three depositional sequences were defined with the purpose of establishing a chronostratigraphic framework to which the positions of the fossiliferous levels identified in the different sections can be referred a 206pb 238u age of 114 67 0 18 ma from the upper depositional sequence constrains the succession as no younger than the late aptian and probably represents an interval of 4 5 myr during which the vegetation was affected by increasing biotic stress conditions a qualitative analysis of the palynological assemblages and plant remains allowed a reconstruction of the dynamics of the vegetation developed during the deposition of the baquero group volcanic activity appears to have had relatively moderate effects on the biota at least at the order level nevertheless low species richness is observed toward the top of the baquero group reflecting an increase in adverse environmental conditions the possible interpretations of the assemblages identified as biozones or in contrast biofacies related to changeable environmental conditions are discussed herein

sands at gusev crater mars processes environments and the energy associated with the transport and deposition of sand at gusev crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the spirit rover as it crossed the plains and went into the columbia hills fine to medium sand is ubiquitous in ripples and wind drifts most distributions show excess fine material consistent with a predominance of wind erosion over the last 3 8 billion years negative skewness at west valley is explained by the removal of fine sand during active erosion or alternatively by excess accumulation of coarse sand from a local source the coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape their distribution display significant changes in their statistical moments within the 400 m that separate the columbia memorial station from bonneville crater results are consistent with aeolian and or impact deposition while the elongated and rounded shape of the grains forming the ripples as well as their direction of origin could point to ma adim vallis as a possible source for smaller particles on the traverse our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic e g ripples and plains soils and aerographic settings e g wind shadows

analysis of phyllosilicate deposits in the nili fossae region of mars comparison of tes and omega data abstract diverse phyllosilicate deposits discovered previously in the nili fossae region with near infrared reflectance data are a window into the complex history of aqueous alteration on mars in this work we used thermal infrared data from the thermal emission spectrometer tes in combination with near infrared data from the observatoire pour la mineralogie l eau les glaces et l activite omega to better constrain the mineralogy and geologic origin of these deposits we developed a tes spectral index for identification of clay minerals which correctly identifies the phyllosilicates in the nili fossae area and points to several other interesting deposits in the syrtis major region however detailed inspection of the tes spectral features of nili fossae phyllosilicates shows a feature at low wavenumbers 350 550 cm 1 that is not an exact match to any specific fe 3 al or mg rich phyllosilicate phase instead the feature is more similar to basaltic glass and may indicate that the phyllosilicates in this region are 1 rich in fe 2 based on similarity to trends seen in laboratory data of clay minerals 2 poorly crystalline extremely disordered and or 3 present within a matrix of actual basalt glass this feature is similar to spectral features seen in altered rocks in the columbia hills region of gusev crater by previous authors by calibrating measured spectral index values against mathematical spectral mixtures of typical martian dark surfaces and known abundances of alteration minerals we are able to estimate an enrichment in abundance of alteration minerals in the altered surfaces many dark noachian deposits in the nili fossae area are enriched phyllosilicates by 20 30 10 15 relative to dark volcanic surfaces in the same region the distribution and abundance of these phases indicates that alteration in the region was pervasive but did not completely erase the original mineralogy of what was likely an fe rich basalt protolith as a group the nili fossae phyllosilicate deposits are fundamentally different from those found in the mawrth vallis region nili fossae deposits have strong thermal infrared features related to admixed pyroxene plagioclase and occasionally olivine whereas the mawrth vallis deposits contain no mafic minerals comparison of tes and omega data also illustrates some more general differences between the datasets including the impact of physical character of the martian surface on detectability of minerals in each spectral range

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

themis characterization of the mer gusev crater landing site 1 gusev crater previously interpreted as the depocenter for the gusev ma adim vallis fluvio lacustrine system is a proposed landing site for one of the mars exploration rovers mer here we use new remote sensing data from the thermal emission imaging system themis supplemented by data from the thermal emission spectrometer tes mars orbiter camera moc and mars orbiter laser altimeter mola to characterize the geology of gusev crater thermal infrared data from themis and tes were used to map thermophysical units on the basis of relative albedos and diurnal temperature variations themis and moc visible images were used to map unit morphologies and to estimate crater density ages mola data were used to identify unit contacts and stratigraphic relationships various data were then combined to construct a new surface unit map and stratigraphy for units on the floor of gusev seven surface units were identified in gusev mostly hesperian in age but with two showing evidence of later modification and redistribution five or more surface units and layering are present within the mer a landing ellipse attesting to the geologic diversity of this site surface units show features that could be consistent with fluvio lacustrine aeolian and or volcanoclastic deposition but the spatial resolution of visible infrared data does not allow for the identification of unambiguous volcanic or fluvio lacustrine textures however a mer landing in gusev may provide the opportunity to analyze multiple units distinguish rock types examine stratigraphic relationships and shed light on the ancient depositional environment

geochemical properties of rocks and soils in gusev crater mars results of the alpha particle x ray spectrometer from cumberland ridge to home plate 1 geochemical diversity of rocks and soils has been discovered by the alpha particle x ray spectrometer apxs during spirit s journey over husband hill and down into the inner basin from sol 470 to 1368 the apxs continues to operate nominally with no changes in calibration or spectral degradation over the course of the mission germanium has been added to the spirit apxs data set with the confirmation that it occurs at elevated levels in many rocks and soils around home plate twelve new rock classes and two new soil classes have been identified at the spirit landing site since sol 470 on the basis of the diversity in apxs geochemistry the new rock classes are irvine alkaline basalt independence low fe outcrop descartes outcrop similar to independence with higher fe and mn algonquin mafic ultramafic igneous sequence barnhill volcaniclastic sediments enriched in zn cl and ge fuzzy smith high si and ti rock elizabeth mahon high si ni and zn outcrop and rock halley hematite rich outcrop and rock montalva high k hematite rich rock everett high mg magnetite rich rock good question high si low mn rock and torquas high k zn and ni magnetite rich rock new soil classes are gertrude weise very high si soil and eileen dean high mg magnetite rich soil aqueous processes have played a major role in the formation and alteration of rocks and soils on husband hill and in the inner basin

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

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

laboratory simulated acid sulfate weathering of basaltic materials implications for formation of sulfates at meridiani planum and gusev crater mars 1 acid sulfate weathering of basaltic materials is a candidate formation process for the sulfate rich outcrops and rocks at the mer rover opportunity and spirit landing sites to determine the style of acid sulfate weathering on mars we weathered basaltic materials olivine rich glassy basaltic sand and plagioclase feldspar rich basaltic tephra in the laboratory under different oxidative acid sulfate conditions and characterized the alteration products we investigated alteration by 1 sulfuric acid vapor acid fog 2 three step hydrothermal leaching treatment approximating an open system and 3 single step hydrothermal batch treatment approximating a closed system in acid fog experiments a1 fe and ca sulfates and amorphous silica formed from plagioclase rich tephra and mg and ca sulfates and amorphous silica formed from the olivine rich sands in three step leaching experiments only amorphous si formed from the plagioclase rich basaltic tephra and jarosite mg and ca sulfates and amorphous silica formed from olivine rich basaltic sand amorphous silica formed under single step experiments for both starting materials on the basis of our experiments jarosite formation in meridiani outcrop is potential evidence for an open system acid sulfate weathering regime waters rich in sulfuric acid percolated through basaltic sediment dissolving basaltic phases e g olivine and forming jarosite other sulfates and iron oxides aqueous alteration of outcrops and rocks on the west spur of the columbia hills may have occurred when vapors rich in so 2 from volcanic sources reacted with basaltic materials soluble ions from the host rock e g olivine reacted with s to form ca mg and other sulfates along with iron oxides and oxyhydroxides