evidence for perchlorates and the origin of chlorinated hydrocarbons detected by sam at the rocknest aeolian deposit in gale crater 1 a single scoop of the rocknest aeolian deposit was sieved 150 m and four separate sample portions each with a mass of 50mg were delivered to individual cups inside the sample analysis at mars sam instrument by the mars science laboratory rover ss ample acquisition system the samples were analyzed separately by the sam pyrolysis evolved gas and gas chromatograph mass spectrometer analysis modes several chlorinated hydrocarbons including chloromethane dichloromethane trichloromethane a chloromethylpropene and chlorobenzene were identified by sam above background levels with abundances of 0 01 to 2 3nmol the evolution of the chloromethanes observed during pyrolysis is coincident with the increase in o2 released from the rocknest sample and the decomposition of a product of n methyl n tert butyldimethylsilyl trifluoroacetamide mtbstfa a chemical whose vapors were released from a derivatization cup inside sam the best candidate for the oxychlorine compounds in rocknest is a hydrated calcium perchlorate ca clo4 2 nh2o based on the temperature release of o2 that correlates with the release of the chlorinated hydrocarbons measured by sam although other chlorine bearing phases are being considered laboratory analog experiments suggest that the reaction of martian chlorine from perchlorate decomposition with terrestrial organic carbon from mtbstfa during pyrolysis can explain the presence of three chloromethanes and a chloromethylpropene detected by sam chlorobenzene may be attributed to reactionsofmartian chlorine released during pyrolysiswith terrestrial benzene or toluene derived from 2 6 diphenylphenylene oxide tenax on the sam hydrocarbon trap at this time we do not have definitive evidence to support a nonterrestrial carbon source for these chlorinated hydrocarbons nor do we exclude the possibility that future sam analyses will reveal the presence of organic compounds native to the martian regolith

the dispersal of pyroclasts from apollinaris patera mars implications for the origin of the medusae fossae formation the medusae fossae formation mff has long been thought to be of amazonian age but recent studies propose that a significant part of its emplacement occurred in the hesperian and that many of the amazonian ages represent modification erosional and redepositional ages on the basis of the new formational age we assess the hypothesis that explosive eruptions from apollinaris patera might have been the source of the medusae fossae formation in order to assess the likelihood of this hypothesis we examine stratigraphic relationships between apollinaris patera and the mff and analyze the relief of the mff using topographic data we predict the areal distribution of tephra erupted from apollinaris patera using a mars global circulation model gcm combined with a semi analytical explosive eruption model for mars and compare this with the distribution of the mff we conclude that apollinaris patera could have been responsible for the emplacement of the medusae fossae formation

concentration of h si cl k fe and th in the low and mid latitude regions of mars 1 we report maps of the concentrations of h si cl k fe and th as determined by the gamma ray spectrometer grs on board the 2001 mars odyssey mission for 45 latitudes the procedures by which the spectra are processed to yield quantitative concentrations are described in detail the concentrations of elements determined over the locations of the various mars landers generally agree well with the lander values except for fe although the mean of the grs fe data agrees well with that of martian meteorites the water equivalent concentration of hydrogen by mass varies from about 1 5 to 7 5 by mass with the most enriched areas being near apollinaris patera and arabia terra cl shows a distribution similar to h over the surface except that the cl content over medusae fossae is much greater than elsewhere the map of fe shows enrichment in the northern lowlands versus the southern highlands silicon shows only very modest variation over the surface with mass fractions ranging from 19 to 22 over most of the planet though a significant depletion in si is noted in a region west of tharsis montes and olympus mons where the si content is as low as 18 k and th show a very similar pattern with depletions associated with young volcanic deposits and enrichments associated with the tes surface type 2 material it is noted that there appears to be no evidence of significant globally distributed thick dust deposits of uniform composition

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

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

the chlorine isotopic composition of martian meteorites 1 chlorine isotope composition of martian mantle and crustal reservoirs and their interactions the martian meteorites record a wide diversity of environments processes and ages much work has been done to decipher potential mantle sources for martian magmas and their interactions with crustal and surface environments chlorine isotopes provide a unique opportunity to assess interactions between martian mantle derived magmas and the crust we have measured the cl isotopic composition of 17 samples that span the range of known ages martian environments and mantle reservoirs the 37cl of the martian mantle as represented by the olivine phyric shergottites nwa 2737 chassignite and shergotty basaltic shergottite has a low value of approximately 3 8 this value is lower than that of all other planetary bodies measured thus far the martian crust as represented by regolith breccia nwa 7034 is variably enriched in the heavy isotope of cl this enrichment is reflective of preferential loss of 35cl to space most basaltic shergottites less shergotty nakhlites chassigny and allan hills 84001 lie on a continuum between the martian mantle and crust this intermediate range is explained by mechanical mixing through impact fluid interaction and assimilation fractional crystallization

searching for evidence of hydrothermal activity at apollinaris mons mars a multidisciplinary approach involving various remote sensing instruments is used to investigate apollinaris mons a prominent volcano on mars as well as the surrounding plains for signs of prolonged hydrologic and volcanic and possibly hydrothermal activity the main findings include 1 evidence from laser altimetry indicating the large thickness 1 5 2 km at some locations of the fan deposits draping the southern flank contrary to previous estimates coupled with possible layering which point to a significant emplacement phase at apollinaris mons 2 corroboration of robinson et al robinson m s mouginis mark p j zimbelman j r wu s s c ablin k k howington kraus a e 1993 icarus 104 301 323 hypothesis regarding the formation of incised valleys on the western flanks by density current erosion which would indicate magma water interaction or alternatively volatile rich magmas early in the volcano s history 3 mounds of diverse geometric shapes many of which display summit depressions and occur among faults and fractures possibly marking venting 4 strong indicators on the flanks of the volcano for lahar events and possibly a caldera lake 5 ubiquitous presence of impact craters displaying fluidized ejecta in both shield forming flank and caldera materials and materials that surround the volcano that are indicative of water rich target materials at the time of impact 6 long term complex association in time among shield forming materials and medusae fossae formation the findings point to a site of extensive volcanic and hydrologic activity with possibly a period of magma water interaction and hydrothermal activity finally we propose that the mound structures around apollinaris should be prime targets for further in situ exploration and search for possible exobiological signatures

halogen and cl isotopic systematics in martian phosphates implications for the cl cycle and surface halogen reservoirs on mars abstract the cl isotopic compositions and halogen cl f br and i abundances in phosphates from eight martian meteorites spanning most rock types and ages currently available have been measured in situ by secondary ion mass spectrometry sims likewise the distribution of halogens has been documented by x ray mapping halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in martian samples or on the martian surface and the inter element ratios are highly variable similarly cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks phosphates in ancient 4 ga meteorites orthopyroxenite alh 84001 and breccia nwa 7533 have positive 37 cl anomalies 1 1 to 2 5 these samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity in contrast the phosphates in the younger basaltic shergottite meteorites 37 cl anomalies 0 2 to 5 6 phosphates with the largest negative 37 cl anomalies display zonation in which the rims of the grains are enriched in all halogens and have significantly more negative 37 cl anomalies suggestive of interaction with the surface of mars during the latest stages of basalt crystallization the phosphates with no textural major element or halogen enrichment evidence for mixing with this surface reservoir have an average 37 cl of 0 6 supporting a similar initial cl isotope composition for mars the earth and the moon oxidation and reduction of chlorine are the only processes known to strongly fractionate cl isotopes both positively and negatively and perchlorate has been detected in weight percent concentrations on the martian surface the age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines which have been documented on the martian surface has been active throughout martian history

coastal geomorphology of the martian northern plains the paper considers the question of the formation of the outflow channels and valley networks discovered on the martian northern plains during the mariner 9 mission parker and saunders 1987 and parker et al 1987 1989 data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains it is suggested that of the geological processes capable of producing similar morphologies on earth lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on mars

refined data of alpha proton x ray spectrometer analyses of soils and rocks at the mars pathfinder site implications for surface chemistry 1 an extensive recalibration of the alpha proton x ray spectrometer apxs was performed to improve the data evaluation of the mars pathfinder mpf rock and soil in situ measurements many samples and geostandards were measured with an mpf identical spare apxs under simulated martian atmospheric pressure and low night temperature conditions precise calibration curves for major and minor elements were obtained using an improved spectral evaluation method for the original mpf spectra refined and new elemental compositions of the mpf rocks and soils were derived however all initial conclusions about soils and rocks remained valid the mpf soil composition revealed the mafic nature of the surface as inferred from the results of viking 1 and 2 data however the mpf rocks reflect a felsic composition for all samples linear correlations of sulphur with all other elements were noticed reflecting the fact that the rocks were covered with varying degrees of soil which compared to the rocks is rich in sulphur extrapolating to low sulphur abundance 0 3 the composition of a soil free rock was calculated the mpf rock composition is high in si and k and low in mg and fe compared to the soil using elemental data from mpf and martian meteorites a global estimation of the martian crust composition was derived the crust is of basaltic nature with a high abundance of incompatible elements k rb nd u th and volatile elements s cl while carbonates are lower or absent

ignimbrites of amazonis planitia region of mars a series of postulated ignimbrite units is mapped in the amazonis memnonia and aeolis quadrangles of mars the units cover about 2 2 106 km2 within a broad but discontinuous and irregular belt trending east west along the highland lowland boundary the ignimbrites overlie parts of the western and southern aureole materials of olympus mons but are embayed in places by the lava plains of the lowlands stratigraphic relations between the basalt flows from the tharsis montes region and the ignimbrites are not clearly defined crater counts suggest that the younger ignimbrites postdate the lava flows crater counts per square kilometer for the ignimbrites range from 7 29 1 95 10 4 to 6 36 2 01 10 5 for craters larger than 1 km in diameter the ignimbrite materials form thick 100 m extensive relatively flat sheets that are smooth to grooved or gently undulating grooved surfaces appear to be yardangs and in most places are not alined with prevailing wind directions the seven mapped ignimbrite units are characterized by morphologic expression stratigraphic position and crater counts similarities to ignimbrites in the pancake range of central nevada include 1 rounded patches of smooth high albedo nonwelded material superposed on jointed low albedo welded material 2 local complementary joint sets in welded materials and 3 thick flow sheets of great areal extent that follow but subdue underlying topography four major eruptive centers occur in areas where units are thickest and where a dominant nnw sse structural trend is expressed locally by unit margins elongate collapse features and normal faulting a minimum volume of 3 85 106 km3 for the deposits has been calculated from thickness estimates based on shadow measurements and crater rim height relations

baroclinic development within zonally varying flows previous idealized modelling studies have shown the importance of across jet barotropic shear to the resulting evolution of cyclones anticyclones surface based fronts and upper level fronts meanwhile many observational studies of cyclones have shown the importance of along jet variations in the horizontal wind speed i e confluence and diffluence this study investigates the importance of these along jet zonal for zonally oriented jets variations in the horizontal wind speed to the resulting structures and evolutions of baroclinic waves using idealized models of growing baroclinic waves an idealized primitive equation channel model is configured with growing baroclinic perturbations embedded within confluent and diffluent background flows when the baroclinic perturbations are placed in background confluence the lower tropospheric frontal structure and evolution initially resemble the shapiro keyser cyclone model with a zonally oriented cyclone strong warm front and bent back warm front later as the baroclinic wave is amplified in the stronger downstream baroclinicity the warm sector of the cyclone narrows becoming more reminiscent of the norwegian cyclone model the upper level frontal structure develops with a southwest northeast orientation and becomes strongest at the base of the trough where geostrophic cold advection is occurring in contrast when the baroclinic perturbations are placed in background diffluence the lower tropospheric frontal structure and evolution resemble the norwegian cyclone model with a meridionally oriented cyclone strong cold front and occluded front the upper level frontal structure is initially oriented northwest southeast on the western side of the trough before becoming zonally oriented weak geostrophic temperature advection occurs along its length these results are compared to those from previous observational and idealized modelling studies copyright 2007 royal meteorological society

jarosite dissolution rates and maximum lifetimes in high salinity brines implications for earth and mars abstract jarosite is a ferric sulfate salt k h na fe 3 so 4 2 oh 6 that forms in acidic oxidizing environments on earth and has also been observed in outcrops on mars high chloride concentrations within the outcrops at meridiani planum suggest that jarosite likely interacted with high salinity brines this study examines jarosite dissolution in h 2 o cacl 2 and h 2 o nacl brines activity of water a h 2 o 0 35 and 0 75 respectively to determine the effects of high salinity brines and a h 2 o on jarosite dissolution rates within brines with a h 2 o 0 75 and 0 35 initial k jarosite dissolution rates at 298 k decrease from log r 9 9 to 11 6 mol m 2 s 1 and na jarosite rates decrease from log r 10 6 to 11 2 mol m 2 s 1 respectively in addition k jarosite dissolution in nacl brine at 263 k yielded an average dissolution rate of log r 11 6 mol m 2 s 1 applying a shrinking sphere model to determine 1 mm jarosite particle lifetimes extends the maximum duration of fluid alteration from lifetimes of attack on residual fe 3 left on the surface of jarosite grains if brines on mars became highly concentrated in chlorine ions through sulfate precipitation the dissolution rate of jarosite and perhaps other minerals as well could accelerate with time shortening particle lifetimes and the inferred duration of aqueous diagenesis significantly

k and cl concentrations on the martian surface determined by the mars odyssey gamma ray spectrometer implications for bulk halogen abundances in mars 1 orbital gamma ray spectrometry shows that the martian surface has a mean cl k ratio of 1 3 0 2 indistinguishable from the ratio in ci chondrites 1 28 although cl and k fractionate by magma degassing and aqueous processing during igneous partial melting both elements are highly incompatible thus if the surface cl k reflects the bulk crustal value then the mantle hence primitive silicate mars also has a roughly ci ratio martian meteorite data indicate that cl br is also approximately chondritic suggesting that elements that condensed in the nebula between 1000 k k and cl to 500 k br are uniformly depleted in mars at about 0 6 ci chondrite concentrations mars clearly does not contain 0 6 ci levels of h2o which would be 6 wt indicating that mars was constructed by planetesimals rich in volatile elements but not in water

mixed hydrothermal fluids and the origin of the martian soil the martian soil consists mainly of weathered basaltic rock and a salt component enriched in volatile and mobile elements primarily sulfur chlorine sodium and potassium since the discovery of this mobile element component by the viking x ray fluorescence spectrometer volcanic aerosols have been considered a likely source for these enrichments alternative sources of the mobile element component are fluids supplied to the surface by hydrothermal processes related to impact craters and volcanism we show that a mixed hydrothermal fluid model can successfully explain the composition of the mobile element component of the soil this model is constructed using terrestrial analogs constrained by the viking and pathfinder measurements of the martian soil chemistry the potential hydrothermal fluid contributions to the soil are tightly constrained because the relative abundances of the mobile elements in hydrothermal fluids are nearly constant the two end member types of hydrothermal fluids considered in the model are the neutral chloride and the acid sulfate type the neutral chloride fluids have high cl and na contents and a significant amount of k but their s abundance relative to cl s cl ratio is too low to match the martian soil however acid sulfate hydrothermal systems characterized by substantial vapor transport and high s cl ratios are likely on mars due to the low abundance of water indeed as the availability of water declines in a hydrothermal system the neutral chloride system can evolve to a vapor dominated acid sulfate system a combination of the two types of fluids can quantitatively explain the s and cl abundance in the soil and provide reasonable abundances of other mobile elements including na k and br without predicting an excess of any element measured in the soil however the hydrothermal fluids are unlikely to be involved in the formation of the magnetic minerals in the soil because the fe contents of the fluids are too low although the acid sulfate fluids have fe concentrations a factor of 100 larger than the neutral chloride fluids the acid sulfate fluids would contribute less than 1 of the total fe in the soil the volcanic aerosol models are poorly constrained in contrast to the hydrothermal fluid models because in volcanic aerosols the relative abundances of the mobile elements are highly variable therefore while volcanic aerosols can explain the mobile element component of the soil significant contributions from other sources cannot be excluded determining the relative contributions of hydrothermal components compared to volcanic aerosols will require measurements in the martian soil of trace elements that provide signatures of the hydrothermal fluids such as high lithium contents that are associated with neutral chloride fluids

latent outflow activity for western tharsis mars significant flood record exposed observations permitted by the newly acquired mars observer laser altimeter data have revealed a system of gigantic valleys northwest of the huge martian shield volcano arsia mons in the western hemisphere of mars northwestern slope valleys nsvs these features which generally correspond spatially to gravity lows are obscured by veneers of materials including volcanic lava flows air fall deposits and eolian materials geologic investigations of the tharsis region suggest that the system of gigantic valleys predates the construction of arsia mons and its extensive associated lava flows of mainly late hesperian and amazonian age and coincides stratigraphically with the early development of the outflow channels that debouch into chryse planitia similar to the previously identified outflow channels which issued tremendous volumes of water into topographic lows such as chryse planitia the nsvs potentially represent flooding of immense magnitude and as such a source of water for a northern plains ocean

field reconnaissance geologic mapping of the columbia hills mars based on mars exploration rover spirit and mro hirise observations chemical mineralogic and lithologic ground truth was acquired for the first time on mars in terrain units mapped using orbital mars reconnaissance orbiter s high resolution imaging science experiment mro hirise image data examination of several dozen outcrops shows that mars is geologically complex at meter length scales the record of its geologic history is well exposed stratigraphic units may be identified and correlated across significant areas on the ground and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology despite their burial during the course of martian geologic time by widespread epiclastic materials mobile fines and fall deposits the selective exhumation of deep and well preserved geologic units has exposed undisturbed outcrops stratigraphic sections and structural information much as they are preserved and exposed on earth a rich geologic record awaits skilled future field investigators on mars the correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map most of the outcrops visited are interpreted to be pyroclastic impactite and epiclastic deposits overlying an unexposed substrate probably related to a modified gusev crater central peak fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit examination of the rocks exposed above and below the major unconformity between the plains lavas and the columbia hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of mars was a time of more intense deposition and modification of the surface although the availability of fluids and the chemical and mineral activity declined from this early period significant later volcanism and fluid convection enabled additional if localized chemical activity

evaluation of infilling and replenishment of river sand mining pits rivers are one of the main sources to supply sand and gravel for construction projects depending on river morphology and hydraulic characteristics its sediment transport capacity and mining operation method the extraction of river bed materials may affect its ecosystem through bank and bed erosion to advance the mechanisms of river pit infilling the effects of various parameters i e the distance between pits the pit plan shape the pit depth sediment size and approaching flow velocity on pit infilling volume are investigated in this research the results of this research show that infilling volume of upstream pit is insignificantly affected by the distance between the pits and it is completely refilled for different distances however the infilling volume of downstream pit decreases by increasing the distance between the pits in addition by reducing the ratio of pit length to its width pit shape extension in spanwise direction the pits can be excavated in a shorter distance from each other when this ratio decreases by 15 the infilling volume increases up to 30 subsequently as a cost effective option the pit distance can be reduced up to 50 in these conditions according to the obtained results although the sediment size has negligible effect on infilling volume in the studied range the infilling volume increases up to 20 by an increase of 8 in the approaching flow velocity increasing the ratio of pit length to its width pit shape extension in streamwise direction highlights the effectiveness of smaller depths so that the infilling volume increases up to 20 by a decrease of 20 in the pit depth in this regard it is recommended that the pit depth be restricted to 70 of the channel flow depth to have a complete pit refilling

global mineral distributions on mars 1 determining the mineralogy of mars is an essential part of revealing the conditions of the surface and subsurface a deconvolution method was used to remove atmospheric components and determine surface mineralogy from thermal emission spectrometer data at 1 pixel per degree ppd minerals are grouped into categories on the basis of compositional and spectral similarity and global concentration maps are produced all binned pixels are fit well with rms errors of 0 005 in emissivity higher rms errors are attributed to short wavelength particle size effects on dust covered surfaces significant concentrations 0 10 of plagioclase high ca pyroxene sheet silicates high si glass and hematite are detected and display distributions consistent with previous studies elevated concentrations of plagioclase and high ca pyroxene are consistent with basaltic surfaces and are located in low albedo highlands regions north of 45 s significant concentrations of plagioclase and sheet silicates high si glass and low concentrations of high ca pyroxenes are consistent with andesitic surfaces and are concentrated in both southern and northern high latitude low albedo regions andesitic surfaces in the southern hemisphere have a lower spectral contrast than northern surfaces an isolated surface located in solis planum is spectrally distinct but compositionally similar to other surfaces interpreted to be andesitic in composition concentrations of olivine below the detection limit correctly identify its presence in two of three locations potassium feldspar low ca pyroxene basaltic glass olivine sulfate carbonate quartz and amphibole are not detected with confidence at 1 ppd the results presented here indicate a predominance of volcanic compositions within martian dust free surfaces

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

clues to martian brines based on halogens in salts from nakhlites and mer samples 1 chlorine and br abundances in fracture filling secondary salts in nakhla veins determined in this study by synchrotron x ray microprobe br and electron microprobe cl techniques compare well to the halogens determined recently by apxs instruments in soils and rock rinds at the gusev and meridiani sites the salts in these mars rocks arise from martian brines that have undergone evaporative or freezing concentration the halogen abundances in these salts are corrected for dilution effect because of mixing with halogen poor phases to obtain their true abundances which seem to be close to the halogen abundances in terrestrial sea brines consistent with the petrographic evidence for evaporative salt deposition sequence of carbonate sulfate halite in nakhlite meteorites nakhla veins yield high br 250 ppm and low cl br ratios 10 50 suggesting possible salt deposition from concentrated brines whereas lafayette iddingsite with low br 11 ppm and high cl br ratios 250 300 indicates salt deposition from dilute brines on mars the low cl br ratios 20 to 80 in salts from gusev and meridiani rock rinds indicate that they presumably originate from concentrated subsurface martian brines the high cl br ratio 270 in salts deposited by dilute solutions in lafayette and adirondack is similar to the chondritic cl br ratio which seems to characterize the dilute brines on mars prior to halite precipitation including early mars waters noachian or earlier our results seem to be consistent with the burt knauth model involving density stratification during evaporation freezing of brine solutions in martian regolith

organic molecules in the sheepbed mudstone gale crater mars the sample analysis at mars sam instrument on board the mars science laboratory curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of mars at gale crater central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin diagenesis concentration and long term preservation this will guide the future search for biosignatures here we report the definitive identification of chlorobenzene 150 300 parts per billion by weight ppbw and c2 to c4 dichloroalkanes up to 70 ppbw with the sam gas chromatograph mass spectrometer gcms and detection of chlorobenzene in the direct evolved gas analysis ega mode in multiple portions of the fines from the cumberland drill hole in the sheepbed mudstone at yellowknife bay when combined with gcms and ega data from multiple scooped and drilled samples blank runs and supporting laboratory analog studies the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in sam we conclude that these chlorinated hydrocarbons are the reaction products of martian chlorine and organic carbon derived from martian sources e g igneous hydrothermal atmospheric or biological or exogenous sources such as meteorites comets or interplanetary dust particles

a potential vorticity diagnostic approach to upper level frontogenesis within a developing baroclinic wave the process of tropopause folding is studied in the context of the life cycle of baroclinic waves previous studies of upper level frontogenesis have emphasized the role of the vertical circulation in driving stratospheric air down into the midtroposphere here a potential vorticity based approach is adopted that focuses on the generation of a folded tropopause to facilitate comparison of the two approaches the diagnosis is applied to the upper level front previously simulated and studied by rotunno et al the potential vorticity approach clarifies the primary role played by the horizontal nondivergent wind in producing a fold and explains why folding should be a common aspect of baroclinic development between the trough and upstream ridge prolonged subsidence within a region of weak system relative flow generates a tropopause depression oriented at an angle to the large scale flow the large scale vertical shear then locally increases the slope of the tropopause eventually leading to a tropopause fold in contrast tropopause folding in the base of the trough is caused by the nondivergent cyclonic circulation associated with the surface thermal wave the winds associated with the thermal wave amplify the potential vorticity wave aloft and these winds which decrease with height rapidly generate a tropopause fold within the trough

geologic context of the mars radar stealth region in southwestern tharsis stealth is a region on mars that has no distinguishable radar return stealth was discovered in 1988 by muhleman et al 1991 in 3 5 cm earth based radar images and it was found to extend 2000 km along the martian equator west of arsia and pavonis montes stealth was proposed to be a deposit of unconsolidated granular material with a minimum thickness of several meters with the most likely explanation being that stealth is a volcanic tephra deposit muhleman et al 1991 1995 stealth overlies some of the youngest geologic units on mars including lava flows and a giant curvilinear ridged lobate unit on the west flank of arsia mons stealth also overlies part of a region of smooth and wind scoured materials called the medusae fossae formation examination of high resolution viking orbiter images suggests that stealth is the youngest of several discontinuous wind worked mantles of fine grained 1 cm sediment older deposits of fine sediment appear to be interbedded with lava flows and show evidence of aeolian deposition dunes and deposits in the lee of topographic obstacles and erosion yardangs and pedestal craters the geologic context supports a volcanic ash origin for stealth if stealth is composed of tephra then its extent and the nature of landforms in the region indicate that it resulted from multiple eruptions that occurred relatively late in martian history possible source vents include linear depressions flanked by constructive volcanic landforms that are located on the lower western slopes of arsia and pavonis montes

prodigious ash deposits near the summit of arsia mons volcano mars 1 mars orbiter camera images are used to identify widespread material interpreted to have formed via explosive volcanism on arsia mons volcano mars this material crops out in cliff sections associated with pit craters in layers 45 50 m thick the large range of elevations where the material is found 6 2 17 5 km suggests locally derived materials although extensive reworking has produced a wide variety of dune forms two possible styles of volcanism appear possible for generating this material 1 explosive volcanism associated with pit crater formation due to the release of magmatic gases or 2 the interaction between dikes and volatile rich substrates although the best examples occur on arsia mons pit craters on ascraeus mons also suggest explosive activity the absence of comparable features on olympus mons indicates that the eruptive histories of the larger tharsis shields were more diverse than has been inferred from viking orbiter images

high resolution thermal inertia mapping from the mars global surveyor thermal emission spectrometer abstract high resolution thermal inertia mapping results are presented derived from mars global surveyor mgs thermal emission spectrometer tes observations of the surface temperature of mars obtained during the early portion of the mgs mapping mission thermal inertia is the key property controlling the diurnal surface temperature variations and is dependent on the physical character of the top few centimeters of the surface it represents a complex combination of particle size rock abundance exposures of bedrock and degree of induration in this work we describe the derivation of thermal inertia from tes data present global scale analysis and place these results into context with earlier work a global map of nighttime thermal bolometer based thermal inertia is presented at 1 4 per pixel resolution with approximately 63 coverage between 50 s and 70 n latitude global analysis shows a similar pattern of high and low thermal inertia as seen in previous viking low resolution mapping significantly more detail is present in the high resolution tes thermal inertia this detail represents horizontal small scale variability in the nature of the surface correlation with albedo indicates the presence of a previously undiscovered surface unit of moderate to high thermal inertia and intermediate albedo this new unit has a modal peak thermal inertia of 180 250 j m 2 k 1 s 1 2 and a narrow range of albedo near 0 24 the unit covering a significant fraction of the surface typically surrounds the low thermal inertia regions and may comprise a deposit of indurated fine material local 3 km resolution maps are also presented as examples of eolian fluvial and volcanic geology some impact crater rims and intracrater dunes show higher thermal inertias than the surrounding terrain thermal inertia of aeolian deposits such as intracrater dunes may be related to average particle size outflow channels and valleys consistently show higher thermal inertias than the surrounding terrain generally correlations between spatial variations in thermal inertia and geologic features suggest a relationship between the hundred meter scale morphology and the centimeter scale surface layer

explosive volcanism in the tharsis region global evidence in the martian geologic record 1 a global equatorial set of layered deposits on mars has been reexamined with mars global surveyor data the stratigraphy morphology and erosional characteristics of units separated by thousands of kilometers are remarkably similar to each other and consistent with a widespread episodic subaerial source of fine grained material this study is the first to propose a genetic link between many units that have traditionally been considered on a local or regional level including the medusae fossae formation valles marineris interior deposits chaotic terrain terra meridiani and arabia materials mapping relationships suggest that all of these units are post noachian in age and formation may have continued until the recent past thinning of deposits with increasing distance from the tharsis rise suggests that much of these materials may be volcanic ash flows and air fall from explosive eruptions in the tharsis region analogous to those produced by terrestrial plinian eruptions contemporary martian winds would preferentially transport ash from an eruption plume near tharsis east or west along the equator depending on the season erosion has removed much of the original volcanic ash and only isolated layered stacks remain sometimes in topographic depressions that inhibit erosion modeling indicates that widespread dispersion of ash after an eruption is easily attainable in present or past atmospheric conditions consistent with the hypothesis that the far reaching deposits may be composed of ash from past explosive eruptions in the vicinity of tharsis

geochemistry of martian soil and bedrock in mantled and less mantled terrains with gamma ray data from mars odyssey 1 surficial materials including soil and dust are abundant in the upper tens of centimeters of the martian surface sensed by the mars odyssey gamma ray spectrometer grs seven large areas 14 of the martian surface that represent possible compositional end members were selected including three regions heavily mantled with surficial materials the selection process included mapping the ratio of exposed rocky terrain to surficial materials using high resolution imagery grs data for h cl fe si k and th were obtained for each area the areas are chemically homogeneous within each area given the spatial resolution and analytical uncertainty of the grs data however substantial chemical differences exist among the areas including the different mantled terrains contrary to earlier assumptions that surficial materials are globally homogeneous due to aeolian mixing the observed chemical differences among the areas may be due to variations in the protolith compositions extent of alteration of the protolith regions or post soil formation processes the abundances of cl k and th in rockier but still soil rich areas such as syrtis major planum can be explained by mixing between a soil with higher concentrations of cl k and th similar to the abundances in the mantled terrains and some of the landing sites and crustal rocks containing lower abundances of these elements similar to martian meteorites

gamma ray constraints on the chemical composition of the martian surface in the tharsis region a signature of partial melting of the mantle the gamma ray spectrometer grs on board mars odyssey is the first instrument to provide quantitative estimates of the composition of the martian surface at the global scale at the present time published concentration maps are available across a broad equatorial swath for ca cl fe h k si and th however it remains to be determined to what extent the observed chemical signatures are the result of primary magmatic processes or secondary alteration at the surface with this question in mind we have considered in detail the grs signature on the western part of the tharsis region including olympus mons this region was chosen as it is clearly of volcanic origin has had a prolonged magmatic history and is of spatial extent sufficiently large that potential contributions of surrounding regions to the grs signature are limited it also has a characteristic composition being notably low in silica relative to the average composition of the martian mid latitudes the major element chemistry of the surface in this region sio2 feo cao k2o is compared with predictions of thermodynamic calculations of liquids produced by partial melting of the martian mantle composition proposed by dreibus and wanke dreibus g wanke h 1985 mars a volatile rich planet meteoritics 20 no 2 267 381 over a range of pressures and temperatures for all four oxides the tharsis compositions are consistent with liquids produced at pressures from 15 to 20 kbar and degrees of partial melting between 3 and 10 this pressure of melting implies a magma source depth in the range 125 170 km consistent with current estimates of the thickness of the lithosphere in this region the idea that the surface chemistry in the tharsis region is dominated by the signature of primary magmatism would therefore appear to be a reasonable working hypothesis although as more data become available more stringent and detailed tests of this simple model will be possible

regional dust deposits on mars physical properties age and history major dust storms on mars play an important role in the deposition and removal of fine dust material thermal radar and visual remote sensing observations provide important constraints on the martian regolith which have been used to determine the location and physical properties of regional dust deposits these deposits are located in three northern equatorial regions tharsis 20 s to 50 n 60 to 190 w arabia 5 s to 30 n 300 to 360 w and elysium 10 to 30 n 210 to 225 w they are covered by fine 2 40 m bright albedo 0 27 particles with fewer exposed rocks and coarse deposits than found elsewhere dust is currently deposited uniformly throughout the equatorial region at a rate of 40 m global storm over geologic time the rate of accumulation may vary from 0 to 250 m yr due to changes in atmospheric conditions produced by orbital variations dust deposited during global storms is subsequently removed only from dark regions resulting in a net accumulation in the low inertia bright regions the thickness of these current dust deposits is 0 1 2 m the thermal inertia places a lower limit of 0 1 m on the thickness of these deposits while the sparse but ubiquitous presence of exposed rocks and the degree of visible mantling indicate that the thickness is less than 5 m dual polarization radar observations of a very rough texture in tharsis are consistent with this model with a 2 m thick dust layer burying most of the surface rocks but permitting radar sampling of the rough subsurface based on their thickness and rate of accumulation the age of these deposits is 105 106 years suggesting a cyclic process of deposition and removal one possible cause may be cyclic variations in the magnitude and location of maximum wind velocities related to variations in mars orbit at present perihelion and maximum wind velocities occur in the south whereas regional dust deposits occur in the north suggesting net transport from south to north orbital parameters oscillate with periods ranging from 5 104 to 106 years the agreement between these periods and the dust deposit age suggests a possible link at different stages in orbit evolution maximum wind velocities will occur in the north with subsequent erosion and redistribution of the accumulated fines based on this model much of the uppermost martian surface is very young and is being continually reworked

theoretical modeling of eruption plumes on mars under current and past climates we have used a combined conduit transport eruption column model to explore the evolution of volcanic eruption plumes on mars under different atmospheric conditions in the calculations we consider a volatile phase composed of h2o co2 and so2 and take into account that the magmatic water erupted at the vent may condense as the eruption column rises into the martian atmosphere as two end member models we explore the eruption of rhyolitic and basaltic melt compositions containing different amounts of volatiles as well as having different eruption temperatures under current martian atmospheric conditions eruption plumes are found to rise as high as 100 km for a mass eruption rate of 5 107 kg s 1 which is consistent with model calculations by wilson and head 1994 in contrast under a dense atmosphere 105 pa on the martian surface which may have existed earlier in martian history the same eruption plume reaches only about 25 km height all magmatic water released during the eruption is found to freeze as it rises in the eruption column which means that fallout from the plume will contain water ice which can be subsequently deposited in near surface layers this ice may then suddenly melt due to higher surface heat flow or shallow intrusions leading to rapid release of water on the flanks of volcanoes only if the atmosphere were hotter in the past could the water in the eruption plume condense and produce rain rather than ice furthermore the calculations show that smaller micron size particles would be distributed globally from eruption plumes under current martian conditions but would not have been as widely dispersed from plumes erupted into an earlier dense atmosphere

aeolian dunes as evidence for explosive volcanism in the tharsis region of mars two transverse dune fields occur among late amazonian volcanic and aeolian landforms in southwestern tharsis mars the first is located 70 km northwest of biblis patera around 5 n 125 w the second is located about 500 km northwest of arsia mons at 2 s 130 w the latter is the largest dune field thus far documented to occur in the equatorial latitudes of mars unlike other dunes on the planet both dune fields in tharsis have low thermal inertias 2 7 10 3cal cm 2sec 0 5k 1 and high albedos 0 26 that are indistinct from their surrounding terrain both dune fields have superposed features such as impact craters lava flows smooth surfaced units and bright wind streaks the dune fields therefore appear to be inactive and mantled by fine grained material i e particles 60 m to form aeolian dunes require a supply of sand on earth most dune sands are supplied by fluvial and littoral processes but this is not the case in tharsis on mars because they are superposed on a late amazonian surface the climate is assumed to have been hyper arid throughout the time that the dunes have existed under these conditions the only plausible source for quantities of sediment sufficient to form transverse dune fields is explosive volcanism therefore the two dune fields in tharsis are evidence that explosive volcanism has occurred in this region in the late amazonian epoch

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

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

an analysis of frontogenesis in numerical simulations of baroclinic waves abstract using a primitive equation pe model we revisit two canonical flows that were previously studied using a semigeostrophic equation sg model in a previous paper the authors showed that the pe and the sg models can have significantly different versions of the large scale dynamics here they report on the implications of this difference for frontogenesis the program for the study of frontogenesis developed by b j hoskins and collaborators is followed to show how in the pe version of the canonical cases the surface warm front develops before the cold front and why the upper level front is a long nearly continuous feature going from ridge to trough the frontogenesis experienced by an air parcel is computed following the parcel to illustrate better the mechanisms involved as the present calculations are carried out longer than most previous ones the relation of the upper frontogenesis to the formation of the upper level cutoff cyclone is also examined trajectory and three dimensional g

possible precipitation of ice at low latitudes of mars during periods of high obliquity most of the old cratered highlands of mars are dissected by branching river valleys that appear to have been cut by running water1 2 yet liquid water is unstable everywhere on the martian surface in the equatorial region where most of the valleys are observed even ice is unstable3 4 it has been suggested therefore that mars had an early denser atmosphere with sufficient greenhouse warming to allow the existence of liquid water5 here we suggest instead that during periods of very high obliquities ice could accumulate at low latitudes as a result of sustained sublimation of ice from the poles and transport of the water vapour equatorwards at low latitudes the water vapour would saturate the atmosphere and condense onto the surface where it would accumulate until lower obliquities prevailed the mechanism is efficient only at the very high obliquities that occurred before formation of tharsis very early in the planet s history but limited equatorial ice accumulation could also have occurred at the highest obliquities during the rest of the planet s history partial melting of the ice could have provided runoff to form the channels or replenish the groundwater system

the spatial distribution of rocks on mars abstract the spatial distribution of rocks exposed at the surface of mars has been mapped using viking infrared thermal mapper irtm observations overall there are no regions on the surface of mars at a scale of 1 1 in latitude and longitude that are rock free the modal value of rock abundance is 6 areal coverage with no areas having more than 30 35 rock cover the model developed to determine rock abundance relates the thermal emission in each of the four surface sensing irtm bands to temperature contrasts within the field of view non unit thermal emissivity due to absorption bands in the surface materials and the absorption and scattering of the outgoing energy by atmospheric dust and water ice each of these effects produce characteristic spectral and diurnal signatures allowing them to be separated the temperature contrasts provide a means to determine both the abundance of exposed rocks and the fine component thermal intertia rock abundance alone does not produce the observed variation in bulk thermal inertia of the surface low inertia fine bright surfaces have fewer rocks exposed than do high inertia coarse dark surfaces rock abundance does not correlate well with the rms slope nor reflectivity determined from delay doppler radar measurements there is however a possible correlation between rms slope determined from continuous wave radar observations dual polarization radar measurements which provide the best radar measure of small scale roughness indicate that the tharsis volcanic region is very rough whereas thermal measurements indicate very few rocks and a covering of dust together these observations suggest an approximately 1 m thick mantle of fines covering a very rough subsurface this fine material may be an aeolian deposit of dust storm fallout valles marineris together with several major channels and chaotic terrains have high rock abundances as does the acidalia planitia basin this observed distribution may reflect the initial deposition of coarse material associated with channel formation syrtis major is unique in having a high inertia but a very low rock abundance together with low radar roughness these observations are consistent with mantling of rocks by sand the observed distribution of rocks and fines indicates that aeolian processes both erosional and depositional play a dominant role in shaping the present martian surface

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

comments on the influence of rotational frontogenesis and its associated shearwise vertical motions on the development of an upper level front by a a lang and j e martin january a 2010 136 239 252 two previous studies by rotunno et al 1994 j atmos sci 51 3373 3398 and schultz and doswell 1999 q j r meteorol soc 125 2535 2562 offer conflicting views on the origin of geostrophic cold air advection that is sometimes present during upper level frontogenesis although lang and martin 2010 claim to reconcile these two studies this comment offers four reasons why reconciliation is not possible first the necessary calculations to compare the tilting frontogenesis term to the horizontal frontogenesis terms are not performed second the thermal advection tendency or isentrope orientation tendency in the region of the developing cold air advection is not calculated third previous studies showing that the vertical terms in these diagnostics are likely associated with warm air advection not cold air advection are not disproven this fact also may explain the predominance of relatively weak geostrophic thermal advection in climatologies of upper level fronts fourth concerns are raised about some of the statements made in lang and martin 2010 these comments also fix an error in eq 11 in schultz and doswell 1999 copyright 2012 royal meteorological society

episodic flood inundations of the northern plains of mars throughout the recorded history of mars liquid water has distinctly shaped its landscape including the prominent circum chryse and the northwestern slope valleys outflow channel systems and the extremely flat northern plains topography at the distal reaches of these outflow channel systems paleotopographic reconstructions of the tharsis magmatic complex reveal the existence of an europe sized noachian drainage basin and subsequent aquifer system in eastern tharsis this basin is proposed to have sourced outburst floodwaters that sculpted the outflow channels and ponded to form various hypothesized oceans seas and lakes episodically through time these floodwaters decreased in volume with time due to inadequate groundwater recharge of the tharsis aquifer system martian topography as observed from the mars orbiter laser altimeter corresponds well to these ancient flood inundations including the approximated shorelines that have been proposed for the northern plains stratigraphy geomorphology and topography record at least one great noachian early hesperian northern plains ocean a late hesperian sea inset within the margin of the high water marks of the previous ocean and a number of widely distributed minor lakes that may represent a reduced late hesperian sea or ponded waters in the deepest reaches of the northern plains related to minor tharsis and elysium induced amazonian flooding

sulfide petrology of four nakhlites northwest africa 817 northwest africa 998 nakhla and governador valadares the nakhlites martian meteorites contain small proportions of cu fe ni sulfide minerals we have studied these sulfides in northwest africa nwa 998 nakhla governador valadares and nwa 817 with optical microscopy scanning electron microscope and electron microprobe the meteorites studied are thought to derive from the bottom inner part and top of hypothetical nakhlite lava flow s respectively modal abundances of magmatic sulfides as estimated by image analysis on thin section are uniformly low 0 02 to 0 05 0 03 vol i e a factor 5 lower than in shergottites sulfides occur within the glassy mesostasis as composite two phase fe ti oxide sulfide grains intimately associated with interstitial grains or locally enclosed in postcumulus melt inclusions e g governador valadares in olivine they exhibit a uniform low ni monoclinic pyrrhotite composition chalcopyrite there is a gradation of sulfide grain sizes and textures across the nakhlites flow s droplets in nwa 817 resorbed blebs in governador valadares more massive true intercumulus blebs in nakhla and nwa 998 these nakhlites also show evidence for sulfide weathering hot desert finds e g nwa 998 and nwa 817 show a few percent fracture filling iron oxy hydroxides of likely terrestrial origin original sulfides are 50 altered in our nwa 998 section with iron oxy hydroxides at grain boundaries and as complete pseudomorphs the compositions of unaltered pyrrhotites are homogeneous close to that of the monoclinic endmember fe7s8 and are too sulfur rich to have been in chemical equilibrium with the late magmatic redox state fixed by the fayalite magnetite quartz buffer therefore the compositions of the pyrrhotites must have been altered during the later stages of magmatic crystallization by assimilation of s rich regolith and hydrothermal circulation

chemical compositions at mars landing sites subject to mars odyssey gamma ray spectrometer constraints 1 the mars odyssey gamma ray spectrometer grs is the first instrument suite to return elemental abundances throughout the midlatitudes of mars concentrations of cl fe h k si and th have been determined to tens of centimeter depths as mass fractions with reasonable confidence comparing such data with or normalizing them to in situ compositional data is difficult due to issues such as dramatic differences in spatial resolution difficulties in convolving densities abundances and compositions of different regolith components and a limited number of elements observed in common we address these concerns in the context of the grs using si at pathfinder to normalize remote data in addition we determine representative in situ compositions for spirit both with and without columbia hills rocks opportunity and viking 1 landing sites using grs derived h content to hydrate the soil component our estimate of the si mass fraction at pathfinder with 13 areal fraction of rocks is 21 the composition of major elements such as si and fe is similar across the four landing sites while minor elements show significant variability areal dominance of soil at all four landing sites causes representative compositions to be driven by the soil component while proportionally large uncertainties of bulk densities dominate the net uncertainties grs compositional determinations compare favorably with the in situ estimates for cl and k and for si by virtue of the normalization however the grs determined fe content at each landing site is consistently higher than the in situ value

conceptual models of upper level frontogenesis in south westerly and north westerly flow the conceptual model proposed by shapiro as it is applied to the evolution of an upper level frontal zone within a baroclinic wave is reviewed and its limitations are investigated through previous literature and two casestudies presented in this paper the early stages in the evolutions of these two cases are used to examine specific limitations of this conceptual model 1 upper level frontogenesis in south westerly flow that evolves from a state of equivalent barotropy to a state of cold advection along the front and 2 upper level frontogenesis in northwesterly flow with along front variation in the sign of the thermal advection such that warm advection occurs upstream of cold advection in the thermal trough vector frontogenesis diagnostics for the lagrangian rate of change of the magnitude and direction of the horizontal potential temperature gradient including tilting due to vertical motion are derived these diagnostics are applied to the two cases to examine the maintenance of the potential temperature gradient and the development of cold advection along each upper level front the upper level front in south westerly north westerly flow was maintained primarily by deformation tilting frontogenesis in agreement with previous research the increasing cold advection along the upper level front in both cases was related to an upstream vorticity maximum for the case in south westerly flow the pre existing vorticity maximum approached a downstream equivalent barotropic upper level front in a manner similar to an instant occlusion resulting in cold advection along the length of the upper level front for the case in north westerly flow an intensifying vorticity maximum concentrated the cold advection in the base of the thermal trough as warm advection developed upstream these two cases are compared to upper level fronts in previous literature and a climatology of upper level fronts associated with landfalling cyclones over the eastern north pacific ocean the results indicate that these two cases are typical of early evolutions of upper level fronts that can occur in south westerly and north westerly flow therefore a revised version of the shapiro conceptual model is presented that represents more accurately the early evolutions exhibited in the present and previous studies

sounding the subsurface of athabasca valles using marsis radar data exploring the volcanic and fluvial hypotheses for the origin of the rafted plate terrain 1 to test the volcanic and fluvial hypotheses for the origin of the rafted plate terrain observed in the vicinity of athabasca valles 5 n 150 e central elysium planitia we investigated the subsurface radar echo from the mars advanced radar for subsurface and ionosphere sounding marsis 5 mhz band data over this area the backscattered signal losses were compared to finite difference time domain fdtd simulations of those arising from three hypothetical geoelectrical subsurface models which differed in their assumed composition percentage basalt versus ice and assumed mode of origin fluvial discharge frozen sea mudflow and low viscosity lavas the dielectric values used in these models are derived from laboratory measurements of mars analog materials under mars like conditions fdtd simulations suggest that if the near surface environment is ice rich it will result in an average loss rate of 0 053 db m for massive ice having less than 1 of suspended particulates and 0 065 db m for a mudflow consisting of a 50 50 mixture of ice and basaltic dust whereas the losses associated with a lava flow model increase to 0 19 db m in comparison the actual signal losses experienced by marsis within this region were on the order of 0 18 db m within the first 160 m beneath the surface this suggests that propagation characteristics of athabasca s near subsurface are more consistent with a volcanic rather than a fluvial or mudflow origin of the rafted plate terrain although limitations on radar sounding depth in this region cannot rule out the possibility of more deeply buried massive ice deposits

context of ancient aqueous environments on mars from in situ geologic mapping at endeavour crater using the mars exploration rover opportunity we have compiled one of the first field geologic maps on mars while traversing the noachian terrain along the rim of the 22 km diameter endeavour crater latitude 2 16 33 longitude 5 10 51 in situ mapping of the petrographic elemental structural and stratigraphic characteristics of outcrops and rocks distinguishes four mappable bedrock lithologic units three of these rock units predate the surrounding burns formation sulfate rich sandstones and one the matijevic formation represents conditions on early mars predating the formation of endeavour crater the stratigraphy assembled from these observations includes several geologic unconformities the differences in lithologic units across these unconformities record changes in the character and intensity of the martian aqueous environment over geologic time water circulated through fractures in the oldest rocks over periods long enough that texturally and elementally significant alteration occurred in fracture walls these oldest pre endeavour rocks and their network of mineralized and altered fractures were preserved by burial beneath impact ejecta and were subsequently exhumed and exposed the alteration along joints in the oldest rocks and the mineralized veins and concentrations of trace metals in overlying lithologic units is direct evidence that copious volumes of mineralized and or hydrothermal fluids circulated through the early martian crust the wide range in intensity of structural and chemical modification from outcrop to outcrop along the crater rim shows that the ejecta of large 8 km in diameter impact craters is complex these results imply that geologic complexity is to be anticipated in other areas of mars where cratering has been a fundamental process in the local and regional geology and mineralogy

slope streaks on mars a new wet mechanism slope steaks are one of the most intriguing modern phenomena observed on mars they have been mostly interpreted as some specific type of granular flow we propose another mechanism for slope streak formation on mars it involves natural seasonal formation of a modest amount of highly concentrated chloride brines within a seasonal thermal skin and runaway propagation of percolation fronts given the current state of knowledge of temperature regimes and the composition and structure of the surface layer in the slope streak regions this mechanism is consistent with the observational constraints it requires an assumption that a significant part of the observed chlorine to be in form of calcium and ferric chloride and a small part of the observed hydrogen to be in form of water ice this wet mechanism has a number of appealing advantages in comparison to the widely accepted dry granular flow mechanism potential tests for the wet mechanism include better modeling of the temperature regime and observations of the seasonality of streak formation

the influence of rotational frontogenesis and its associated shearwise vertical motions on the development of an upper level front the total quasi geostrophic qg vertical motion is partitioned into transverse and shearwise couplets oriented parallel to and along the geostrophic vertical shear respectively in order to examine the role of rotational frontogenesis and its associated shearwise circulation in the life cycle of an upper front jet system in northwesterly flow in particular the analysis emphasizes two aspects of that role 1 the influence of shearwise on scalar frontogenesis and 2 the effect of rotational frontogenesis and its associated vertical circulation on the initiation of along flow cold air advection during upper frontogenesis the case study analysis reveals that shearwise subsidence persistently and significantly contributes to scalar frontogenesis throughout the life cycle the transverse subsidence contribution to scalar frontogenesis is initially weak but grows more substantial after the establishment of along flow cold air advection near the base of the thermal trough prior work has argued that the development of along flow cold air advection arises from a cyclonic rotation of promoted either by contributions from tilting or horizontal kinematics from the qg perspective adopted in the present study the tilting and kinematic rotations are seen as interconnected aspects of a single underlying dynamical process rotational frontogenesis in which the rotation of produced by vertical vorticity is accompanied by a discrete vertical circulation the shearwise circulation that provides the subsidence upshear of the vorticity maximum required to initiate along flow cold air advection it is further suggested that the characteristic distribution of the kinematic and tilting contributions to rotation of in the vicinity of an upper tropospheric vorticity maximum underlies the observed preference for the development of upper level fronts in northwesterly flow copyright 2010 royal meteorological society

primary centers and secondary concentrations of tectonic activity through time in the western hemisphere of mars five main stages of radial and concentric structures formed around tharsis from the noachian through the amazonian as determined by geologic mapping of 24 452 structures within the stratigraphic framework of mars and by testing their radial and concentric orientations tectonic activity peaked in the noachian stage 1 around the largest center claritas an elongate center extending more than 20 in latitude and defined by about half of the total grabens which are concentrated in the syria planum thaumasia and tempe terra regions during the late noachian and early hesperian stage 2 extensional structures formed along the length of present day valles marineris and in thaumasia with a secondary concentration near warrego vallis radial to a region just to the south of the central margin of valles marineris early hesperian stage 3 radial grabens in pavonis syria ulysses and tempe terra and somewhat concentric wrinkle ridges in lunae and solis plana and in thaumasia sirenum memnonia and amazonis are centered northwest of syria with secondary centers at thaumasia tempe terra ulysses fossae and western valles marineris late hesperian early amazonian stage 4 structures around alba patera the northeast trending alignment of tharsis montes and olympus mons appears centered on alba patera stage 5 structures middle late amazonian represent the last pulse of tharsis related activity and are found around the large shield volcanoes and are centered near pavonis mons tectonic activity around tharsis began in the noachian and generally decreased through geologic time to the amazonian statistically significant radial distributions of structures formed during each stage centered at different locations within the higher elevations of tharsis secondary centers of radial structures during many of the stages appear related to previously identified local magmatic centers that formed at different times and locations throughout tharsis

formation of glaciers on mars by atmospheric precipitation at high obliquity surface conditions on mars are currently cold and dry with water ice unstable on the surface except near the poles however geologically recent glacierlike landforms have been identified in the tropics and the midlatitudes of mars the ice has been proposed to originate from either a subsurface reservoir or the atmosphere we present high resolution climate simulations performed with a model designed to simulate the present day mars water cycle but assuming a 45 obliquity as experienced by mars a few million years ago the model predicts ice accumulation in regions where glacier landforms are observed on the western flanks of the great volcanoes and in the eastern hellas region this agreement points to an atmospheric origin for the ice and reveals how precipitation could have formed glaciers on mars

localization and physical property experiments conducted by opportunity at meridiani planum the location of the opportunity landing site was determined to better than 10 m absolute accuracy from analyses of radio tracking data we determined rover locations during traverses with an error as small as several centimeters using engineering telemetry and overlapping images topographic profiles generated from rover data show that the plains are very smooth from meter to centimeter length scales consistent with analyses of orbital observations solar cell output decreased because of the deposition of airborne dust on the panels the lack of dust covered surfaces on meridiani planum indicates that high velocity winds must remove this material on a continuing basis the low mechanical strength of the evaporitic rocks as determined from grinding experiments and the abundance of coarse grained surface particles argue for differential erosion of meridiani planum

mars odyssey gamma ray spectrometer elemental abundances and apparent relative surface age implications for martian crustal evolution 1 quantifying secular variations in the chemical composition of the martian crust provides unique insights into the processes that have guided the evolution of the martian crust mantle system using global abundances for a suite of elements determined by the gamma ray spectrometer grs on board the mars odyssey spacecraft and global mapping of apparent surface age adapted from existing geologic maps in the usgs martian geologic investigation series we report the average abundance of k th fe cl h and si for the major martian geologic epochs noachian hesperian and amazonian average grs determined k and th abundances generally decrease by 9 and 7 respectively between the hesperian and the amazonian possibly implying evolving magma chemistry throughout major resurfacing events although the effects of surficial alteration processes cannot be entirely discounted grs determined fe and cl averages increase by 12 and 19 respectively with younger apparent relative surface age suggesting the possible mobilization and transport of these elements through aqueous processes although an igneous origin for the variation in fe also cannot be excluded while h abundance does vary with surface age the relationship is likely not governed by geologic processes no statistically reliable apparent surface age relation was found for si

equatorial and midlatitude distribution of chlorine measured by mars odyssey grs 1 the 2001 mars odyssey gamma ray spectrometer grs has made the first measurement of the equatorial and midlatitude distribution of cl at the near surface of mars a mean concentration value of 0 49 wt cl has been determined from a grand sum of grs spectra collected over the planet excluding high latitude regions cl is significantly enriched within the upper few tens of centimeters of the surface relative to the martian meteorites and estimates for the bulk composition of the planet however cl is not homogeneously distributed and varies by a factor of 4 even after smoothing of data with a 10 arc radius filter several contiguous geographically large 20 regions of high and low cl concentrations are present in particular a region centered over the medusae fossae formation west of tharsis shows significantly elevated cl a large region north of syrtis major extending into utopia planitia in the northern hemisphere shows the lowest cl concentrations on the basis of hierarchical multivariate correlations cl is positively associated with h while negatively associated with si and thermal inertia we discuss four possible geologic mechanisms aeolian volcanic aqueous and hydrothermal that may have affected the cl distribution seen by grs while some of the distribution may be due to cl rich dust deposits transported by aeolian processes this mechanism does not appear to account for all of the observed variability we propose that reactions with volcanic exhalations may have been important for enriching cl in medusae fossae formation material

heterogeneous distribution of h2o in the martian interior implications for the abundance of h2o in depleted and enriched mantle sources we conducted a petrologic study of apatite within 12 martian meteorites including 11 shergottites and one basaltic regolith breccia these data were combined with previously published data to gain a better understanding of the abundance and distribution of volatiles in the martian interior apatites in individual martian meteorites span a wide range of compositions indicating they did not form by equilibrium crystallization in fact the intrasample variation in apatite is best described by either fractional crystallization or crustal contamination with a cl rich crustal component we determined that most martian meteorites investigated here have been affected by crustal contamination and hence cannot be used to estimate volatile abundances of the martian mantle using the subset of samples that did not exhibit crustal contamination we determined that the enriched shergottite source has 36 73 ppm h2o and the depleted source has 14 23 ppm h2o this result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the martian mantle we also estimated the h2o cl and f content of the martian crust using known crust mantle distributions for incompatible lithophile elements we determined that the bulk martian crust has 1410 ppm h2o 450 ppm cl and 106 ppm f and cl and h2o are preferentially distributed toward the martian surface the estimate of crustal h2o results in a global equivalent surface layer gel of 229 m which can account for at least some of the surface features on mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on mars surface

final chemical results from the mars pathfinder alpha proton x ray spectrometer 1 the calibrated pathfinder alpha proton x ray spectrometer apxs instrument is capable of measuring concentrations of all major and minor rock forming elements ranging from carbon through zirconium in atomic number therefore it is capable of constraining the petrology of the measured samples in particular the pathfinder data are the first in situ measurements of martian rocks and may be compared with previous remote sensing measurements as well as with the compositions of snc meteorites pathfinder soil and rock sample abundances from the alpha proton and x ray modes have been quantified the abundances suggest that 1 the rocks are covered with various amounts of soil 2 the soil free rocks on a volatile free basis have some element ratios similar to mars meteorites yet have different bulk chemistry indicative of more evolved rocks with higher silica abundances 3 the carbon and nitrogen contents are below detection limits and 4 the alpha mode oxygen reveals excess amounts of oxygen in some samples which is indicative of sample bound water contained within minerals or glasses in samples

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

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

the role of aqueous alteration in the formation of martian soils abstract martian equatorial dark regions are dominated by unweathered materials and it has often been assumed that they have not been significantly altered from their source lithology the suite of minerals present is consistent with a basaltic composition and there has been no need to invoke additional processes to explain the origin of these compositions we have begun to question this result based on detailed observations using a variety of datasets locally derived dark soils have a mineralogy distinct from that of adjacent rocky surfaces most notably a lower olivine content this pattern is common for many surfaces across the planet previous work using detailed measurements acquired within the gusev plains has shown that olivine dissolution via acidic weathering may explain chemical trends observed between rock rinds and interiors mineralogical trends obtained from rocks and soils within the gusev plains are more prominent than the elemental trends and support previous results that indicate that dissolution of olivine has occurred however clear differences are also present in elemental abundances that indicate a variety of inputs and processes are likely responsible for the formation of martian dark soils despite the potential complexity of source materials and processes it appears that most martian dark regions have likely experienced aqueous alteration and chemical weathering appears to be closely linked to the mechanical breakdown of materials regardless of the responsible mechanism there appears to be a general though not perfect correlation between elevated olivine abundance and high thermal inertia surfaces on mars

a small s mif signal in martian regolith pyrite implications for the atmosphere abstract the past martian atmosphere is often compared to the archean earth s as both were dominated by co2 rich and o2 poor chemistries archean earth rocks preserve mass independently fractionated sulfur isotopes s mif non zero 33s and 36s originating from photochemistry in an anoxic atmosphere thus martian crustal rocks might also be expected to preserve a s mif signature providing insights into past atmospheric chemistry we have used secondary ion mass spectrometry sims to investigate in situ the sulfur isotope systematics of nwa 8171 paired to nwa 7034 a martian polymict breccia containing pyrite that formed through hydrothermal sulfur addition in a near surface regolith setting in this meteorite pyrite grains have a weighted mean of 33s of 0 14 0 08 and 36s 0 70 0 40 2 s e m so the s mif signature is subtle sulfur isotope data for four additional shergottites yield 33s values that are not resolvable from zero as in previous studies of shergottites at first glance the result for the polymict breccia might seem surprising but no martian meteorite yet has yielded a s mif signature akin to the large deviations seen on earth we suggest that s mif bearing aerosols h2so4 and s8 were produced when volcanic activity pushed a typically oxidising martian atmosphere into a reduced state after rain out of these aerosols s8 would tend to be oxidised by chlorate dampening the s mif signal which might be somewhat retained in the more abundant photolytic sulfate then in the regolith mixing of aqueous surface derived sulfate with igneous sulfide the latter with zero mif to form the abundant pyrite seen in nwa 8171 would further dampen the s mif signal nonetheless the small negative 33s anomalies seen in martian meteorites imply that volcanic activity was sufficient to produce a reducing atmosphere at times this volcanically driven atmospheric evolution would tend to produce high levels of carbonyl sulfide ocs given that ocs is a relatively long lived strong greenhouse gas the s mif signal implies that volcanism periodically generated warmer conditions perhaps offering an evidence based solution to the young wet mars paradox

evidence for perchlorates and the origin of chlorinated hydrocarbons detected by sam at the rocknest aeolian deposit in gale crater evidence for perchlorates at rocknest

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

transient liquid water and water activity at gale crater on mars liquid water on equatorial mars is inconsistent with large scale climatic conditions humidity and temperature measurements by the curiosity rover support the formation of subsurface liquid brines by hydration of perchlorates during the night

martian magmas contained abundant chlorine but little water the martian water cycle a key for the habitability of mars largely relies on the abundance of water in martian magmas and their mantle sources yet martian snc shergottite nakhlite and chassigny classes meteorites contain minimal water however some experimental studies have suggested that martian parental magmas contained as much as 2 h2o here we integrate mineral chemical experimental and cosmochemical constraints to show that martian magmas contained little water but abundant chlorine apatite and amphibole in martian meteorites are chlorine rich and water poor this constrains the chlorine contents in their parental magmas to 0 3 wt and water contents to 0 3 wt our experimental work has shown that large amounts of water are not needed to explain the mineralogy of the martian meteorites because chlorine has effects similar to those of water on crystallization such chlorine rich water poor martian magmas are consistent with mars being chlorine rich 2 5 compared with the earth furthermore the bulk cl composition of martian meteorites shows that they have not preferentially lost cl by degassing of an h2o rich vapor together these results show that chlorine not water was the dominant volatile species in martian basalts and that these basalts contributed little h2o to mars surface environment