an observational search for carbonates on mars a search for carbonates and other salts exposed on the surface of mars was undertaken by observing areas of the surface in the 2 6 m to 4 2 m spectral region using the university of hawaii 2 2 m telescope at the mauna kea observatory hawaii observations of four mars areas syrtis major hellas arabia and an area northeast of hellas were made on the night of september 19 1986 the reflectance spectra for two partially overlapping areas show a weak absorption band in the 3 8 m to 3 9 m region which is in the spectral region where carbonate absorptions appear 3 8 m to 4 0 m the mars area of overlap contains syrtis planum the spectral feature from about 3 76 m to 3 95 m is clearly shortward of and broader than the calcium carbonate band about 3 9 m to 4 0 m and is at a slightly shorter wavelength position than magnesium carbonate magnesite bands about 3 8 m to 3 96 m as measured in this study positive identification of this band cannot be made by us at this time measurements for two other mars areas show no evidence of carbonate or other bands if the band is due to absorptions in the mars surface material spectrum and if it is due to carbonates then the results imply about 3 to 5 wt of a carbonate such as magnesite on average in the upper few millimeters of the mars surface material over the two areas where the weak spectral feature appears we can place an upper limit of 3 to 5 wt calcium carbonate and about 5 wt magnesite for all areas observed the interpretations are based on laboratory measurements of the reflectance spectra of calcite and magnesite and their mixtures with palagonite effects of thermal emission on the detection of carbonates were also explored for a wide range of temperatures thermal effects are not sufficient to mask the presence of calcite in the 3 to 5 wt range theoretical reasoning strongly supporting the presence of carbonates as a component of the mars surface is reviewed these and earlier observations do not rule out carbonates below the surface in other locations as small outcrops or in concentrations of less than 3 to 5 of the areas observed

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

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

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

coordinated spectral and xrd analyses of magnesite nontronite forsterite mixtures and implications for carbonates on mars 1 mineral detection on mars largely relies on laboratory data of minerals and mineral mixtures the objective of this study is to provide reflectance spectra in the visible near infrared vnir and mid ir regions x ray diffraction xrd data and mossbauer spectra of a suite of carbonate phyllosilicate and olivine mixtures in order to facilitate identification and characterization of these minerals on mars remote sensing observations indicate that combinations of these minerals are present in ancient rocks on mars around the isidis basin and in gusev crater magnesite nontronite and forsterite size fractions 125 m were selected for this study results of the vnir reflectance analyses illustrate the complexity of vnir spectra of mixtures analyses of the nir band depths near 2 3 2 5 3 4 and 4 m showed clear trends with carbonate abundance although the data are not linear mixtures of magnesite and nontronite exhibited a band near 2 3 m much closer to that observed for nontronite than that for magnesite vnir analyses of the mixtures indicated that a small amount of forsterite in any of the mixtures contributed a large increase in the broad 1 m band and hence the red slope characteristic of fe2 bearing minerals mid ir mixture spectra were dominated by magnesite and forsterite and nontronite was much more difficult to detect by mid ir spectra in the mixtures this could be related to why phyllosilicates are detected in many locations on mars using data collected by the compact reconnaissance imaging spectrometer for mars but not detected using data collected by the thermal emission spectrometer mossbauer spectroscopy is well suited for analyses of fe2 and fe3 bearing minerals and modeling of the peak areas gave well correlated trends for nontronite and forsterite abundances where abundant fe was present xrd full pattern fitting analyses were performed on the magnesite forsterite series giving results within 6 wt of the actual values with a mean difference between actual and calculated values of 2 4 wt this study provides important laboratory data for characterizing the spectral and xrd properties of mineral mixtures that will facilitate mineral identification on mars carbonates in particular have been primarily observed at low abundances and in small outcrops and they are frequently found mixed with other minerals through analyses of mineral mixtures using multiple data sets this study seeks to provide ground truthing that will enable better coordination of carbonate detections in the dust and rocks of mars

the formation of martian river valleys by impacts we explore the role of large impacts in creating the martian valley networks recent dating shows that some large impact basins are contemporaneous with the valley networks the mass deposited and volatiles released by impacts is large and comparable with the mass from the tharsis volcanic construct steam atmospheres formed after large impacts can produce more than 600 m of rainfall followed by rainfall from water vapor greenhouse atmospheres and snowmelt the erosion rates from impacts that created the currently visible craters are somewhat less than the erosion rates suggested for the noachian 4 2 to 3 82 gya there are several possible explanations for this difference and it is possible that erosion rates are overestimated because the burial of small craters by global debris layers from impacts has not been considered rainfall after the noachian was low because the impact rate and co2 pressure declined we suggest tests of the hypothesis that impacts caused the river valleys

shock metamorphism of planetary silicate rocks and sediments proposal for an updated classification system we reevaluate the systematics and geologic setting of terrestrial lunar martian and asteroidal impactites resulting from single or multiple impacts for impactites derived from silicate rocks and sediments we propose a unified and updated system of progressive shock metamorphism shock metamorphosed rocks occur as lithic clasts or melt particles in proximal impactites at impact craters and rarely in distal impactites they represent a wide range of metamorphism typically ranging from unshocked to shock melted as the degree of shock metamorphism at a given shock pressure depends primarily on the mineralogical composition and the porosity of a rock or sediment sample different shock classification systems are required for different types of planetary rocks and sediments we define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments 1 crystalline rocks with classes f m a and u 2 chondritic rocks class c and 3 sedimentary rocks and sediments with classes sr se and re the abbreviations stand for felsic f mafic m anorthositic a ultramafic u sedimentary rocks sr unconsolidated sediments se and regoliths re in each class the progressive stages of shock metamorphism are denominated s1 to sx these progressive shock stages are introduced as s1 s7 for f s1 s7 for m s1 s6 for a s1 s7 for u s1 s7 for c s1 s7 for sr s1 s5 for se and s1 s6 for re s1 stands for unshocked and sx variable between s5 and s7 stands for whole rock melting we propose a sequence of symbols characterizing the degree of shock metamorphism of a sample i e f s1 to f s7 with the option to add the tabulated pressure ranges in gpa in parentheses

deep alteration between hellas and isidis basins abstract recent investigations of alteration of martian crustal outcrops suggest putative crustal hydrothermal systems which are favorable environments for the emergence of life in this study we perform an analysis of the crism targeted observations covering crustal outcrops in the region between the hellas and isidis basins with the goal of investigating the alteration phases over the wide studied region we detect the presence of possible serpentines chlorites smectites and carbonates these detections occur within ejecta blankets crater walls and central uplifts of impact craters we investigate the relation between the observed associations of minerals and the ages of the impact craters assessed by crater count no clear relation is observed we also investigate the relationship between the group of detected mineral and the pre impact depth of the studied outcrops assessed from the size of the impact craters this method allows us to reconstruct the pre impact cross section we suggest that alteration of the first 7 km of the crust between the hellas and isidis basins may have undergone alteration processes

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

co2 release due to impact devolatilization of carbonate results of shock experiments a study of pure single crystal calcite shocked to pressures from 9 0 to 60 8 gpa was conducted to address contradictory data for carbonate shock behavior the recovered materials were analyzed optically and by transmission electron microscopy tem as well as by thermogravimetry tga x ray diffraction xrd and raman spectroscopy in thin section progressive comminution of calcite is observed although grains remain birefringent to at least 60 8 gpa tga analysis reveals a positive correlation between percent of mass loss due to shock and increasing shock pressure r 0 77 and suggests that shock loading leads to the modest removal of structural volatiles in this pressure range xrd patterns of shocked iceland spar samples produce peaks that are qualitatively and quantitatively less intense more diffuse and shift to lower o2 however the regularity observed in these shocked powder patterns suggests that structures with very uniform unit cell separations persist to shock pressures as high as 60 8 gpa raman spectral analyses indicate no band asymmetry and no systematic peak shifting or broadening tem micrographs display progressively diminishing crystallite domain sizes selected area electron diffraction saed patterns reveal no signatures of amorphous material these data show that essentially intact calcite is recovered at shock pressures up to 60 8 gpa with only slight mass loss 7 this work suggests that the amount of co2 gas derived from shock devolatilization of carbonate by large meteorite impacts into carbonate targets has been substantially overestimated

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

extensive hydrated silica materials in western hellas basin mars abstract near infrared spectral data indicate the presence of hydrated poorly crystalline silica where high bulk silica contents have been previously identified in hellas basin no other aqueous phases are identified in these regions and the deposits may be nearly pure the silica bearing surfaces are sporadically exposed along a 650 km stretch of the western basin rim within a limited elevation range and display a variety of surface textures suggesting that the materials have been reworked but not transported large distances the high abundances and lack of associated aqueous phases indicate that high water to rock ratios were present in the region during the noachian period but without elevated temperatures or for durations necessary for quartz diagenesis the silica bearing materials may have formed via direct precipitation from silica saturated groundwater sources although other formation mechanisms are also plausible

mineralogy of the nili fossae region with omega mars express data 2 aqueous alteration of the crust 1 nili fossae is a region with fresh exposures of old material omega spectral data have revealed a strong diversity of minerals in the nili fossae region including mafic minerals and phyllosilicates phyllosilicates are found to be primarily fe rich smectites a type of clay minerals these phyllosilicates are observed only on the noachian crust in four types of locations three are without any signatures other than phyllosilicates on 1 smooth layered deposits 2 massive exhumed material and 3 crater ejecta and one type of location is associated with olivine 4 over an altered mafic unit this diversity suggests a widespread liquid water activity and a variety of alteration processes the formation of phyllosilicates underwent considerable reduction if not cessation by the time of formation of syrtis major lava flows in the hesperian period phyllosilicates are spatially and chronologically disconnected from the fluvial and depositional landforms observed in the nili fossae region observations suggest that these landforms formed after the extensive formation of phyllosilicates during short periods of time and or temperatures close to freezing

reproducing hydrogeochemical conditions triggering the formation of carbonate and phyllosilicate alteration mineral assemblages on mars nili fossae region 1 the cooccurrence of mg fe ca carbonate and stratigraphically lower phyllosilicate bearing rock units identified in the nili fossae region on mars may reveal a co2 driven aqueous alteration process on ancient mars we reproduce hydrogeochemical conditions for concurrent carbonate and phyllosilicate formation in rock columns by using hydrogeochemical one dimensional transport modeling which is based on chemical equilibrium thermodynamics our models assume the isochemical low temperature equilibration of ultramafic rocks with pure water at varying atmospheric co2 partial pressure water to rock ratio temperature and rock composition equilibration among 1 mineral assemblages of olivine rich rocks 18 28 wt mgo 2 pure water water to rock ratio 500 50 mol mol 1 3 co2 transferred from the atmosphere co2 partial pressure lower than 2 bars and higher than 0 01 bar at 278 k and 4 100 000 years of diffusive mass transport create hydrogeochemical conditions enabling the concurrent formation of mg rich mg fe ca solid solution carbonate and stratigraphically lower phyllosilicate rich alteration assemblages in rock columns the modeled composition of alteration mineral assemblages their depth distribution and carbonate composition are similar to the observations from the nili fossae region higher equilibration temperature 373 k results in the formation of ca dominated ca mg carbonate instead of mg rich mg fe ca carbonate and in an inverse stratification with phyllosilicate rich units overlying carbonate rich units modeling results suggest that rocks in the nili fossae region hosting the carbonate and phyllosilicate mineral assemblage have been exposed to a groundwater alteration process driven by atmospheric co2 partial pressures ranging between 2 bars and 0 01 bar at low temperature 278 k

surface and crater exposed lithologic units of the isidis basin as mapped by coanalysis of themis and tes derived data products 1 the stratigraphy and mineral heterogeneity of surface and crater exposed deposits in the southwestern portion of the isidis basin were investigated using spatial spectral visible and thermophysical data sets from both the mars global surveyor and odyssey missions four themis spectral surface units were identified progressing from the libya montes highlands to the inner lowland plains of isidis planitia lithologic determinations of these spectral units were made by linear deconvolution analysis of tes data olivine rich surface materials correlate with a well documented high thermal inertia unit based on spatial and stratigraphic relationships interpreted from both crater exposed and surface exposures the olivine rich unit was determined to have formed subsequent to the isidis basin forming event morphology occurrence and linear deconvolution of this unit suggests that it may represent noachian age to hesperian age picritic lavas that erupted as early stage lavas originating from sources such as syrtis major beneath isidis and as far as tyrrhena patera these lavas are suggested to have partially filled the basin based on crater exposed occurrences and were subsequently buried by further evolved olivine poor lavas later these lavas were exposed by erosion and subsequent impacts into the basin crater scaling suggests significant infilling of the basin by these lavas that may account for craters with very high d d ratios and the well developed positive mass anomaly associated with the basin this study also demonstrates that the remote sensing of impact craters in conjunction with surface mapping is a potent mapping tool for understanding stratigraphy and the petrogenesis of the martian crust

atmospheric conditions on early mars and the missing layered carbonates 1 widespread massive layered sediments studied by surface rovers and mars orbiting spectrometers are found to be rich in sulfates no similarly massive carbonates have been detected we present the results of coupled atmospheric and geochemical calculations of the formation of the sulfate rich meridiani sediments and offer an explanation for why extensive layered carbonates are not found there or elsewhere on mars large scale volcanism from the build up of tharsis during the late noachian would have injected large amounts of so2 into the atmosphere efficient photochemical conversion of so2 to h2so4 would have caused widespread sulfuric acid water clouds similar to those seen on venus today precipitation from these clouds and acidification of surface water would have sustained a thick warm co2 atmosphere via carbonate inhibition such an atmosphere could have been subjected to loss to space via impact erosion and sputtering once atmospheric so2 gas production dropped and waters become more alkaline the remaining co2 in the atmosphere collapsed to form poorly consolidated carbonate patinas on rock surfaces and in open fractures

petrographic and geochemical evidence for multiphase formation of carbonates in the martian orthopyroxenite allan hills 84001 martian meteorites can provide valuable information about past environmental conditions on mars allan hills 84001 formed more than 4 gyr ago and owing to its age and long exposure to the martian environment and this meteorite has features that may record early processes these features include a highly fractured texture gases trapped during one or more impact events or during formation of the rock and spherical fe mg ca carbonates in this study we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events the petrographic features and compositional properties of these carbonates indicate that at least two pulses of mg and fe rich solutions saturated the rock those two generations of carbonates can be distinguished by a very sharp change in compositions from being rich in mg and poor in fe and mn to being poor in mg and rich in fe and mn between these two generations of carbonate is evidence for fracturing and local corrosion

revised crism spectral parameters and summary products based on the currently detected mineral diversity on mars the investigation of hyperspectral data from the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism and the observatoire pour la mineralogie l eau les glaces et l activitie omega on mars express has revealed an increasingly diverse suite of minerals present on the martian surface a revised set of 60 spectral parameters derived from corrected spectral reflectance at key wavelengths in crism targeted observations and designed to capture the known diversity of surface mineralogy on mars is presented here as summary products some of the summary products have strong heritage to omega spectral parameter calculations this paper also presents newly derived parameters that highlight locations with more recently discovered spectral signatures type locations for the diversity of currently identified mineral spectral signatures have been compiled into a library presented in this work our analysis indicates that the revised set of summary products captures the known spectral diversity of the surface and successfully highlights and differentiates between locations with differing spectral signatures the revised spectral parameter calculations and related products provide a useful tool for scientific interpretation and for future mission landing site selection and operations

evidence for magma carbonate interaction beneath syrtis major mars 1 we used three methods spectral index mapping linear spectral mixture analysis and factor analysis and target transformation to determine if carbonate decomposition products including lime cao periclase mgo portlandite ca oh 2 and brucite mg oh 2 are present on the surface of mars using an expanded spectral library that includes decomposition products of calcite and magnesite we deconvolved a binned emissivity data set from the mars global surveyor thermal emission spectrometer mgs tes the deconvolution model indicates that anhydrous carbonates are not present at kilometer scales above the tes detection limit however carbonate decomposition products may be present at or above the tes detection limit in northeast syrtis major and several other small regions on mars the model results are supported by spectral index mapping and factor analysis and target transformation of tes data in this region the volcanic setting of the detections may indicate the interaction of syrtis major lavas with subsurface carbonates or alternatively the eruption of carbonate bearing lavas that were subsequently devolatilized by impacts or later lava flows

composition and structures of the subsurface in the vicinity of valles marineris as revealed by central uplifts of impact craters abstract despite recent efforts from space exploration to sound the martian subsurface with radar the structure of the martian subsurface is still unknown major geologic contacts or discontinuities inside the martian crust have not been revealed another way to analyze the subsurface is to study rocks that have been exhumed from depth by impact processes the last martian mission mro mars reconnaissance orbiter put forth a great deal of effort in targeting the central peaks of impact craters with both of its high resolution instruments crism compact reconnaissance imaging spectrometer for mars and hirise high resolution science experiment we analyzed the composition with crism and the physical characteristics on hirise of the rocks exhumed from depth from 31 impact craters in the vicinity of valles marineris our analyses revealed the presence at depth of two kinds of material massive light toned rocks and intact layers exhumed light toned massive rocks are enriched in low calcium pyroxenes and olivine hydrated phases such as smectites and putative serpentine are present and may provide evidence of hydrothermal processes some of the rocks may represent portions of the volatile rich pre noachian martian primitive crust in the second class of central peaks exhumed layers are deformed folded and fractured visible near infrared vnir spectra suggest that they are composed of a mixture of olivine and high calcium pyroxene associated with hydrated phases these layers may represent a noachian volcanic accumulation of up to 18 km due to tharsis activity the spatial distribution as well as the in depth distribution between the two groups of rocks exhumed are not random and reveal a major geologic discontinuity below the tharsis lava plateau the contact may be vertical over several kilometers depth suggesting the pre existence of a steep basin early giant impact or subsidence basin or sagduction processes

clay minerals in delta deposits and organic preservation potential on mars clay rich sedimentary deposits are often sites of organic matter preservation and have therefore been sought in mars exploration however regional deposits of hydrous minerals including phyllosilicates and sulphates are not typically associated with valley networks and layered sediments that provide geomorphic evidence of surface water transport on early mars the compact reconnaissance imaging spectrometer for mars crism has recently identified phyllosilicates within three lake basins with fans or deltas that indicate sustained sediment deposition eberswalde crater holden crater and jezero crater here we use high resolution data from the mars reconnaissance orbiter mro to identify clay rich fluvial lacustrine sediments within jezero crater which has a diameter of 45 km the crater is an open lake basin on mars with sedimentary deposits of hydrous minerals sourced from a smectite rich catchment in the nili fossae region we find that the two deltas and the lowest observed stratigraphic layer within the crater host iron magnesium smectite clay jezero crater holds sediments that record multiple episodes of aqueous activity on early mars we suggest that this depositional setting and the smectite mineralogy make these deltaic deposits well suited for the sequestration and preservation of organic material

study of phyllosilicates and carbonates from the capri chasma region of valles marineris on mars based on mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars mro crism observations abstract spectral reflectance data from the mro crism mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars of capri chasma a large canyon within valles marineris on mars have been studied results of this analysis reveal the presence of minerals such as phyllosilicates illite smectite montmorillonite and carbonates ankerite and manganocalcite these minerals hint of the aqueous history of noachian time on mars phyllosilicates are products of chemical weathering of igneous rocks whereas carbonates could have formed from local aqueous alteration of olivine and other igneous minerals four different locations within the capri chasma region were studied for spectral reflectance based mineral detection the study area also shows the spectral signatures of iron bearing minerals e g olivine with carbonate indicating partial weathering of parent rocks primarily rich in ferrous mineral the present study shows that the minerals of capri chasma are characterized by the presence of prominent spectral absorption features at 2 31 m 2 33 m 2 22 m 2 48 m and 2 52 m wavelength regions indicating the existence of hydrous minerals i e carbonates and phyllosilicates the occurrence of carbonates and phyllosilicates in the study area suggests the presence of alkaline environment during the period of their formation results of the study are important to understand the formation processes of these mineral assemblages on mars which may help in understanding the evolutionary history of the planet

a field guide to finding fossils on mars the martian surface is cold dry exposed to biologically harmful radiation and apparently barren today nevertheless there is clear geological evidence for warmer wetter intervals in the past that could have supported life at or near the surface this evidence has motivated national aeronautics and space administration and european space agency to prioritize the search for any remains or traces of organisms from early mars in forthcoming missions informed by 1 stratigraphic mineralogical and geochemical data collected by previous and current missions 2 earth s fossil record and 3 experimental studies of organic decay and preservation we here consider whether how and where fossils and isotopic biosignatures could have been preserved in the depositional environments and mineralizing media thought to have been present in habitable settings on early mars we conclude that noachian hesperian fe bearing clay rich fluvio lacustrine siliciclastic deposits especially where enriched in silica currently represent the most promising and best understood astropaleontological targets siliceous sinters would also be an excellent target but their presence on mars awaits confirmation more work is needed to improve our understanding of fossil preservation in the context of other environments specific to mars particularly within evaporative salts and pore fracture filling subsurface minerals

using the chemical composition of carbonate rocks on mars as a record of secondary interaction with liquid water in the search for habitable environments on mars sites that have been altered by liquid water represent an important target quickly dissolving and precipitating carbonates found in multiple locations on mars represent a key potential mineral indicator of locations with a history of aqueous alteration and therefore possible habitability recent liquid surface water on mars may differ significantly from the fluids either sedimentary hydrothermal or pedogenic that formed carbonate minerals on mars interactions of carbonate rocks with such recent surface water may therefore cause changes in chemistry and mineralogy with depth that form weathering profiles recording the conditions of alteration to test the prediction that martian carbonates may record a signature of aqueous alteration on mars we performed reactive transport modeling of putative carbonate outcrops on mars using the reactive transport code crunchflow model inputs included two parent rocks chosen based on the carbonate rich rock at gusev crater comanche one consisting of 60 magnesite 20 siderite and 20 porosity and one consisting of 50 magnesite 20 siderite 9 calcite 1 6 rhodochrosite and 20 porosity reacting solutions consisted of four scenarios acidic sulfate containing solutions perhaps resulting from an acid vapor scenario dilute solutions resulting from martian analog basalt dissolution concentrated solutions resulting from modeled evaporation of the dilute solutions and solutions based on the results of the phoenix lander modeling was performed under low oxidation and high oxidation conditions based on the modeling results a carbonate rock would become enriched in siderite upon interaction with acidic water under low oxidation conditions the same rock would become enriched in calcite after interaction with ca enriched solutions a carbonate rock reacting under more oxidizing conditions would preferentially dissolve siderite leaving a surface enriched in magnesite and ferric oxide therefore the mg rich carbonates on mars are consistent with possible interaction with liquid water under oxidizing conditions similar to those measured at the phoenix landing site future detailed chemical and mineralogical profiles through weathered rock into the unaltered interior of carbonate rocks may therefore allow the quantitative interpretation of the aqueous history and possible habitability of locations on mars

hydrous carbonates on mars evidence from mariner 6 7 infrared spectrometer and ground based telescopic spectra absorption features at 2 28 and 5 4 m identified in mariner 6 7 infrared spectrometer and terrestrial telescopic spectra are consistent with the spectra of hydrous magnesium carbonates such as hydromagnesite and artinite spectral characteristics of these hydrous carbonates are different from those of the anhydrous carbonates as the former do not have the strong spectral features typically associated with anhydrous carbonates such as calcite and siderite theoretical mixing indicates that depending on the type of hydrous carbonate 10 20 wt can be incorporated into the regolith without contradicting the spectral observations or the viking x ray fluorescence chemical analysis hydrous carbonates form as weathering products of mafic minerals in the presence of h2o and co2 even in the antarctic their formation as evaporite minerals from either original magmas or hydrothermally altered rocks is consistent with the martian environment provided liquid water is or has been at least transiently present on earth formation of hydrous mg carbonates is associated with the production of amorphous iron oxides which is consistent with both the environment and the inferred surface mineralogy of mars these minerals are about 60 wt h2o co3 and oh if they are abundant everywhere at the 10 level then about 6 of the surface weight could be volatiles bound in this type of mineral although the stability of hydrous carbonates in a martian environment is uncertain there may be kinetic factors inhibiting the dehydration of these minerals which may persist metastably in the current environment although the spectroscopic evidence for anhydrous carbonates is scant the possible presence of hydrous carbonates provides an appealing mechanism for the existence of carbonates on mars

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

a new terrestrial analogue site for mars research the qaidam basin tibetan plateau nw china abstract remote sensing observations and rover missions have documented the presence of playas salts and wind erosion landforms of lacustrine sediments on mars all of these observations suggest mars was aqueous in its early history however abundant questions remain how wet was the environment what were the properties of the liquids and the possibility of ancient habitability and what kinds of geological processes shaped the present landforms to explore these unknowns analogue studies can play a key role in this contribution we introduce the qaidam basin tibetan plateau northwestern china as a new and unique analogue site for studying the past aqueous and present arid environments of mars the qaidam basin the highest and one of the largest and driest deserts on earth is located in a dry cold and high uv environment similar to the surface of mars we demonstrate a variety of landforms and also their counterparts on mars which include aeolian dunes and yardangs polygons gullies valleys and fluvial fans in the qaidam basin various environmental regimes for the formation of linear and asymmetric barchans have been described saline lakes and playas representing different stages of lake evolution in arid environment are also present in the qaidam basin and provide promising cases for studying the habitability in mars like environments results for microorganism isolation suggest that halophiles are the most important fraction in the hypersaline sediments and this may shed light on studying present martian habitability moreover the remote but ready accessibility of the qaidam basin make it a potential site for engineering testing in regards to future martin exploration missions we propose that the variety of exogenic and endogenic geomorphic types lacustrine sediments evaporite mineral assemblages and mars like extreme environments collectively point to the qaidam basin as an optimal

weathering of olivine under co2 atmosphere a martian perspective abstract recent analyses from the curiosity rover at yellowknife bay gale crater mars show sedimentary rocks deposited in a lacustrine environment and containing smectite clays thought to derive from the alteration of olivine however little is known about the weathering processes of olivine under early martian conditions and about the stability of smectite clays in particular here we present a 3 month experiment investigating the weathering of forsteritic olivine powders fo 90 under a dense co 2 atmosphere and under present day terrestrial conditions for comparison the experiment also evaluates the potential effects of hydrogen peroxide h 2 o 2 as a representation of the highly oxidizing compounds produced by photochemical reactions throughout martian history the weathered samples were characterized by means of near infrared spectroscopy nir x ray diffraction xrd transmission electron microscopy with energy dispersive x ray spectrometry tem edx mossbauer spectroscopy and thermogravimetry the results show that a mg rich smectite phase formed from the weathering of olivine under co 2 conditions although in lower abundance than under terrestrial conditions the main secondary phase formed under co 2 turns out to be a silica rich phase possibly acting as a passivating layer with a non diagnostic near infrared spectral signature the use of h 2 o 2 highlights the critical importance of both the redox conditions and fe content of the initial olivine on the nature of the secondary phases

carbon sequestration on mars on earth carbon sequestration in geologic units plays an important role in the carbon cycle scrubbing co 2 from the atmosphere for long term storage while carbonate is identified in low abundances within the dust and soils of mars at 1 wt in select meteorites and in limited outcrops no massive carbonate rock reservoir on mars has been identified to date here we investigate the largest exposed carbonate bearing rock unit the nili fossae plains combining spectral thermophysical and morphological analyses to evaluate the timing and carbon sequestration potential of rocks on mars we find that the olivine enriched 20 25 basalts have been altered by low temperature in situ carbonation processes to at most 20 fe mg carbonate thus limiting carbon sequestration in the nili fossae region to 0 25 12 mbar of co 2 during the late noachian early hesperian before or concurrent with valley network formation while this is large compared to modern day co 2 reservoirs the lack of additional comparably sized post late noachian carbonate bearing deposits on mars indicates ineffective carbon sequestration in rock units over the past 3 7 b y this implies a thin atmosphere 500 mbar during valley network formation extensive post noachian atmospheric loss to space or diffuse deep sequestration by a yet to be understood process in stark contrast to earth s biologically mediated crust atmosphere carbon reservoir ratio of 10 4 10 5 mars ratio is a mere 10 10 3 even if buried pre noachian crust holds multiple bars

quantitative compositional analysis of sedimentary materials using thermal emission spectroscopy 2 application to compacted fine grained mineral mixtures and assessment of applicability of partial least squares methods fine grained sedimentary deposits on planetary surfaces require quantitative assessment of mineral abundances in order to better understand the environments in which they formed one way that planetary surface mineralogy is commonly assessed is through thermal emission 6 50 m spectroscopy to that end we characterized the tir spectral properties of compacted very fine grained mineral mixtures of oligoclase augite calcite montmorillonite and gypsum non negative linear least squares minimization nnls is used to assess the linearity of spectral combination a partial least squares pls method is also applied to emission spectra of fine grained synthetic mixtures and natural mudstones to assess its applicability to fine grained rocks the nnls modeled abundances for all five minerals investigated are within 10 of the known abundances for 39 of the mixtures showing the relationships between known and modeled abundance follow non linear curves the poor performance of nnls is due to photon transmission through small grains over portions of the wavelength range and multiple reflections in the volume the pls method was able to accurately recover the known abundances to within 10 for 78 90 of synthetic mixtures and for 85 of the mudstone samples chosen for this study the excellent agreement between known and modeled abundances is likely due to high absorption coefficients over portions of the thermal infrared tir spectral range and thus combinations are linear over portions of the range pls can be used to recover abundances from very fine grained rocks from tir measurements and could potentially be applied to landed or orbital tir observations

martian surface mineralogy from observatoire pour la mineralogie l eau les glaces et l activite on board the mars express spacecraft omega mex global mineral maps 1 after 2 years of operation the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer on board mars express has acquired data coverage of the martian surface with spatial resolution varying between 300 m and 4 8 km depending on the pericenter altitude of the spacecraft s elliptical orbit we report the global surface distributions of some minerals using the omega observations in the visible and near infrared vnir wavelength domains 0 35 2 5 m global maps of ferric phases mafic minerals pyroxenes and olivines and hydrated minerals have been derived from spectral parameters the limits of detection in terms of abundance for some minerals of different grain size distributions are given the distribution of pyroxenes is in general agreement with the mineral maps of previous telescopic and space observations the fe3 absorption feature in the visible wavelength region is present everywhere on the surface the spectra of the bright regions compare with anhydrous nanophase ferric oxides terrains with water bearing minerals cover a very small fraction of the martian surface olivine mg rich compositions is detected in more extensive regions of the pyroxene rich zones than previously reported olivine with higher iron content and or larger grain size 100 m is only detected in isolated areas the mineralogy of the northern low albedo regions is discussed in the light of these mineral maps chemical alteration or oxidation during extrusion producing a coating or varnish of anhydrous ferric phases over a dark basaltic surface best accounts for the vnir spectral properties of these regions although a glassy composition resulting from impact is also considered

orbital identification of carbonate bearing rocks on mars geochemical models for mars predict carbonate formation during aqueous alteration carbonate bearing rocks had not previously been detected on mars surface but mars reconnaissance orbiter mapping reveals a regional rock layer with near infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the nili fossae region the carbonate is closely associated with both phyllosilicate bearing and olivine rich rock units and probably formed during the noachian or early hesperian era from the alteration of olivine by either hydrothermal fluids or near surface water the presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering proposed to be characteristic of hesperian mars did not destroy these carbonates and thus did not dominate all aqueous environments

evidence for extensive olivine rich bedrock on mars color infrared observations of an area around the nili fossae acquired by the mars odyssey thermal emission imaging system have been used to map the regional distribution and geologic context of olivine rich materials that first were identified from mars global surveyor thermal emission spectrometer data spectral thermal geomorphic and topographic data demonstrate that the majority of olivine rich material is in the form of inplace layered rock covering an area roughly four times larger than previously recognized some high olivine concentrations are associated with spatially small areas dominated by sediments we favor olivine rich basalts as the origin of the observed olivine enrichment although several hypotheses are viable

an in situ record of major environmental transitions on early mars at northeast syrtis major the noachian hesperian transition on mars was a period marked by changes in volcanic processes and styles of aqueous alteration understanding the timing and nature of environmental change requires the exploration of units recording both sets of processes herein we report the compositional stratigraphy of distinctive noachian to hesperian units along the northeastern margin of the syrtis major volcanic flows a layered polyhydrated sulfate bearing unit with jarosite ridges has been discovered beneath the syrtis major lava flows and above the regionally extensive stratigraphy of noachian plains units reported previously sequential clay carbonate and sulfate bearing units formed in situ and record a transition from alkaline ph to acidic ph waters the sequence is chronologically bookended by the isidis impact and syrtis major flows and is one of the most temporally constrained and well preserved stratigraphic sections from early mars available for landed exploration

smectite formation in the presence of sulfuric acid implications for acidic smectite formation on early mars the excess of orbital detection of smectite deposits compared to carbonate deposits on the martian surface presents an enigma because smectite and carbonate formations are both favored alteration products of basalt under neutral to alkaline conditions we propose that mars experienced acidic events caused by sulfuric acid h2so4 that permitted phyllosilicate but inhibited carbonate formation to experimentally verify this hypothesis we report the first synthesis of smectite from mars analogue glass rich basalt simulant 66 wt glass 32 wt olivine 2 wt chromite in the presence of h2so4 under hydrothermal conditions 200 c smectites were analyzed by x ray diffraction mossbauer spectroscopy visible and near infrared reflectance spectroscopy and electron microprobe to characterize mineralogy and chemical composition solution chemistry was determined by inductively coupled plasma mass spectrometry basalt simulant suspensions in 11 42 mm h2so4 were acidic with ph 2 at the beginning of incubation and varied from acidic ph 1 8 to mildly alkaline ph 8 4 at the end of incubation alteration of glass phase during reaction of the basalt simulant with h2so4 led to formation of the dioctahedral smectite at final ph 3 and trioctahedral smectite saponite at final ph 4 and higher anhydrite and hematite formed in the final ph range from 1 8 to 8 4 while natroalunite was detected at ph 1 8 hematite was precipitated as a result of oxidative dissolution of olivine present in adirondack basalt simulant formation of secondary phases including smectite resulted in release of variable amounts of si mg na and ca while solubilization of al and fe was low comparison of mineralogical and solution chemistry data indicated that the type of smectite i e dioctahedral vs trioctahedral was likely controlled by mg leaching from altering basalt and substantial mg loss created favorable conditions for formation of dioctahedral smectite we present a model for global scale smectite formation on mars via acid sulfate conditions created by the volcanic outgassing of so2 in the noachian and early hesperian

a 3 5 ga record of water limited acidic weathering conditions on mars abstract the secondary mineral budget on earth is dominated by clay minerals al hydroxides and fe oxides which are formed under the moderate ph high water to rock ratio conditions typical of earth s near surface environment in contrast geochemical analyses of rocks and soils from landed missions to mars indicate that secondary mineralogy is dominated by mg fe ca sulfates and fe oxides this discrepancy can be explained as resulting from differences in the chemical weathering environment of earth and mars we suggest that chemical weathering processes on mars are dominated by 1 a low ph sulfuric acid rich environment in which the stoichiometric dissolution of labile mineral phases such as olivine and apatite fe ti oxides is promoted and 2 relatively low water to rock ratio such that other silicate phases with slower dissolution rates e g plagioclase pyroxene do not contribute substantially to the secondary mineral budget at the martian surface under these conditions al mobilization is limited and the formation of significant al bearing secondary phases e g clays al hydroxides al sulfates is inhibited the antiquity of rock samples analyzed in situ on mars suggest that water limited acidic weathering conditions have more than likely been the defining characteristic of the martian aqueous environment for billions of years

study of terrestrial fossils in phyllosilicate rich soils implication in the search for biosignatures on mars abstract the search for biosignatures in the soil of mars is a major objective of the planet exploration but the detection of such structures is not straightforward due to the degradation of the organic material in a previous work our group has analyzed the spectral reaction to thermal processing of biomineral carbonate samples including fresh and fossil shells we found that two terrestrial fossil shells collected from clay deposits preserve their biomineral characteristics much better than coeval fossils not embedded in clay layers in the present paper we extend our analysis to a set of fossils found in three different terrestrial clay deposits our results confirm that the level of degradation may be much lower than the standard values if fossils are surrounded by clay minerals as a result these fossils have a spectroscopic response to thermal treatment which make them much more distinguishable from their abiotic counterparts than coeval fossils not collected from clay deposits this result implies that the phyllosilicates regions recently discovered on mars may represent very interesting environments that can provide conditions favorable to preserve evidence of biomarkers and hence can be regarded as good candidate locations for their detection

thermal emission spectra of mars 5 4 10 5 μm evidence for sulfates carbonates and hydrates we have obtained spectra of the thermal emission from mars in the 5 4 10 5 m wavelength domain at a resolving power of about 60 from the kuiper airborne observatory spectra were obtained for several large spots on mars whose ground temperatures and air masses through the martian atmosphere differed significantly these data were taken at two times during the flight by taking the ratio of the spectral flux from one spot to that of a second spot we obtained results that were independent of uncertainties in the instrument s spectral response and the transmission of the earth s atmosphere these data as well as spectral fluxes of single spots based using the star tau as a calibration standard show a number of emission and absorption features they are present in sets of spectra taken at two different times some of the absorption features are due to gaseous co2 in the martian atmosphere the remainder of the absorption and emission features are due to minerals present in the airborne dust and on the surface comparison of the strength of features seen at similar times but with three different air masses and ground temperatures suggests that the emission features arise primarily from surface emissivity spectral variations and that the absorption features arise from components of the atmosphere based on comparisons of the observed features with laboratory data for a broad ensemble of minerals spectra of other solar system bodies and relevant compositional information about mars we have made the following tentative identifications of the observed features emission features at 7 8 and 9 7 m are attributed to surface silicates an emission feature at 6 1 m is attributed to a molecular water component of the surface material an absorption band at 8 7 m as well as possibly one at 9 8 m is ascribed to sulfate or bisulfate anions probably located in a distorted crystalline site and an absorption band at 6 7 m is attributed to carbonate or bicarbonate anions located in a distorted crystalline site although we cannot totally rule out a nitrate origin for this feature we have simulated these spectra with radiative transfer programs for the atmosphere and surface these simulations indicate that the sulfate and carbonate bearing minerals are contained in the same particles of the airborne dust as the dominant silicate minerals that the dust optical depth was about 0 6 at a reference wavelength of 0 3 m over the area of the observed spots and that sulfates and carbonates constitute about 10 15 and 1 3 by volume of the airborne dust respectively these results imply that minerals formed by weathering processes represent major reservoirs of volatile species on current mars

a chemical model for evaporites on early mars possible sedimentary tracers of the early climate and implications for exploration martian geomorphology seems to indicate extensive hydrological activity during the noachian era liquid water at the surface would require a large greenhouse effect that is widely hypothesized to have been caused by a high partial pressure of atmospheric carbon dioxide pco2 a sedimentation model driven by sequential evaporation is used to calculate the evaporite mineral sequence in a closed basin lake subject to high pco2 the initial fluid is derived from weathered igneous rock similar to martian meteorite basalts siderite feco3 is always the first major carbonate to precipitate thus siderite is predicted to be an important fades component in ancient martian sediments along with silica which is also an early precipitate these would form varves in lakes that undergo cycles of evaporation and water recharge after silica and siderite the sequence is magnesian calcite nearly pure hydromagnesite and gypsum followed by highly soluble salts like nacl the presence of siderite sediments generally requires an atmospheric pco2 level in excess of 0 1 bar otherwise iron silicates such as greenalite would form this may be used in exploration as an observational test on the past atmospheric composition of mars subject to consideration of the depositional environment at pco2 of approximately several bar gypsum precipitation could occur before calcite upon evaporation if the initial so42 ca2 ratio is high and there is no water recharge the predicted carbonate sequence upon evaporation is generally consistent with recent hypotheses suggesting traces of evaporite carbonates in some martian meteorites several mechanisms destroy or obscure carbonates at the martian surface consequently in situ analysis of the interior of ejecta from recent impact craters lying within sedimentary basins may offer the most practical approach to future exploration of ancient carbonate sediments

discovery of olivine in the nili fossae region of mars we have detected a 30 000 square kilometer area rich in olivine in the nili fossae region of mars nili fossae has been interpreted as a complex of grabens and fractures related to the formation of the isidis impact basin we propose that post impact faulting of this area has exposed subsurface layers rich in olivine linear mixture analysis of thermal emission spectrometer spectra shows surface exposures of 30 olivine where the composition of the olivine ranges from fo30 to fo70

magnetic effects of hydrothermal alteration in porphyry copper and iron oxide copper gold systems a review abstract magnetic anomaly patterns can be used as a tool for mapping lithology metamorphic zones and hydrothermal alteration systems as well as identifying structures that may control passage of magmas or hydrothermal fluids associated with mineralisation reliable geological interpretation of mineralised systems requires an understanding of the magmatic metamorphic and hydrothermal processes that create alter and destroy magnetic minerals in rocks predictive magnetic exploration models for porphyry copper and iron oxide copper gold iocg deposits can be derived from standard geological models by integrating magnetic petrological principles with petrophysical data deposit descriptions and modelling of observed magnetic signatures of these deposits even within a particular geological province the magnetic signatures of similar deposits may differ substantially due to differences in the local geological setting searching for look alike signatures of a known deposit is likely to be unrewarding unless pertinent geological factors are taken into account these factors include the tectonic setting and magma type composition and disposition of host rocks depth of emplacement and post emplacement erosion level depth of burial beneath younger cover post emplacement faulting and tilting remanence effects contingent on ages of intrusion and alteration and metamorphism because the effects of these factors on magnetic signatures are reasonably well understood theoretical magnetic signatures appropriate for the local geological environment can qualitatively guide exploration and make semiquantitative predictions of anomaly amplitudes and patterns the predictive models also allow detectability of deposit signatures to be assessed for example when deposits are buried beneath a considerable thickness of nonmagnetic overburden are covered by highly magnetic heterogeneous volcanic rocks or there is a strong regional magnetic gradient this paper reviews the effects of hydrothermal alteration on magnetic properties and magnetic signatures of porphyry copper and iron oxide copper gold systems and presents examples of predictive magnetic exploration models and their predicted signatures in various geological circumstances

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

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

palaeoproterozoic magnesite lithological and isotopic evidence for playa sabkha environments magnesite forms a series of 1 to 15 m thick beds within the 2ae 0g a palaeoproterozoic tulomozerskaya formation nw fennoscandian shield russia drillcore material together with natural exposures reveal that the 680m thick formation is composed of a stromatolite dolomite red bed sequence formed in a complex combination of shallow marine and non marine evaporitic environments dolomite collapse breccia stromatolitic and micritic dolostones and sparry allochemical dolostones are the principal rocks hosting the magnesite beds all dolomite lithologies are marked by d 13 c values from 7ae1 to 11ae6 v pdb and d 18 o ranging from 17ae4 to 26ae3 v smow magnesite occurs in different forms finely laminated micritic stromatolitic magnesite and structureless micritic crystalline and coarsely crystalline magnesite all varieties exhibit anomalously high d 13 c values ranging from 9ae0 to 11ae6 and d 18 o values of 20ae0 25ae7 laminated and structureless micritic magnesite forms as a secondary phase replacing dolomite during early diagenesis and replaced dolomite before the major phase of burial crystalline and coarsely crystalline magnesite replacing micritic magnesite formed late in the diagenetic metamorphic history magnesite apparently precipitated from sea water derived brine diluted by meteoric fluids magnesitization was accomplished under evaporitic conditions sabkha to playa lake environment proposed to be similar to the coorong or lake walyungup coastal playa magnesite magnesite and host dolostones formed in evaporative and partly restricted environments consequently extremely high d 13 c values reflect a combined contribution from both global and local carbon reservoirs a 13 c rich global carbon reservoir d 13 c at around 5 is related to the perturbation of the carbon cycle at 2ae0 ga whereas the local enhancement in 13 c up to 12 is associated with evaporative and restricted environments

nanosims analyses of apatite and melt inclusions in the grv 020090 martian meteorite hydrogen isotope evidence for recent past underground hydrothermal activity on mars abstract we measured the hydrogen isotopes and water contents of melt inclusions and apatite that locate far from shock induced melt veins in the martian meteorite grv 020090 using nano scale secondary ion mass spectrometry nanosims the melt inclusions in olivine show hydration profiles with both the water contents and the d values increasing from the cores 2 170 7 ppm and 3386 126 to the rims 5337 200 ppm and 5519 65 the extremely high d values of the melt inclusions relative to a maximum of 4239 81 of apatite that crystallized from the last residual melt convincingly argue that the observed hydration postdated emplacement of the parent magma of grv 020090 this is also a robust line of evidence for past presence of liquid water on mars diffusion simulation of the hydration profiles of both water contents and d values constrains the duration of liquid water up to 130 000 250 000 years at 0 c or 700 1 500 years at 40 c all analyses of the melt inclusions including the hydration profiles show a logarithmic correlation between the water contents and the d values plotting within a two endmember mixing area the extremely d enriched endmember represents martian underground water with a d value of 6034 72 2 this is the highest d value reported in martian meteorites and it is consistent with the recent analyses of martian soils by the curiosity rover leshin et al 2013 suggestive of more water escaped from mars than previous estimates the analyses of apatite show a distinct positive correlation between the water contents 0 10 0 58 wt and the d values 737 4239 which can be explained by assimilation of d rich martian crustal materials and enhancement of water via fractional crystallization the observed correlation suggests that the water contents of martian mantle reservoirs might have been overestimated from d enriched apatite in previous studies our estimation based on the least contaminated apatite grains from grv 020090 turned out a low water content of the primordial parent magma 380 750 ppm which was likely derived from a relatively dry martian mantle reservoir of grv 020090 38 75 ppm h2o

the high resolution imaging science experiment hirise during mro s primary science phase psp the high resolution imaging science experiment hirise on the mars reconnaissance orbiter mro acquired 8 terapixels of data in 9137 images of mars between october 2006 and december 2008 covering 0 55 of the surface images are typically 5 6 km wide with 3 color coverage over the central 20 of the swath and their scales usually range from 25 to 60 cm pixel nine hundred and sixty stereo pairs were acquired and more than 50 digital terrain models dtms completed these data have led to some of the most significant science results new methods to measure and correct distortions due to pointing jitter facilitate topographic and change detection studies at sub meter scales recent results address noachian bedrock stratigraphy fluvially deposited fans in craters and in or near valles marineris groundwater flow in fractures and porous media quasi periodic layering in polar and non polar deposits tectonic history of west candor chasma geometry of clay rich deposits near and within mawrth vallis dynamics of flood lavas in the cerberus palus region evidence for pyroclastic deposits columnar jointing in lava flows recent collapse pits evidence for water in well preserved impact craters newly discovered large rayed craters and glacial and periglacial processes of particular interest are ongoing processes such as those driven by the wind impact cratering avalanches of dust and or frost relatively bright deposits on steep gullied slopes and the dynamic seasonal processes over polar regions hirise has acquired hundreds of large images of past present and potential future landing sites and has contributed to scientific and engineering studies of those sites warming the focal plane electronics prior to imaging has mitigated an instrument anomaly that produces bad data under cold operating conditions

metamorphism in the martian crust compositions of basaltic and ultramafic rocks analyzed by mars rovers and occurring as martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions key minerals identified by remote sensing roughly constrain temperatures and pressures in the martian crust we use a traditional metamorphic approach phase diagrams to assess low grade hydrothermal equilibrium assemblages basaltic rocks should produce chlorite actinolite albite silica accompanied by laumontite pumpellyite prehnite or serpentine talc only prehnite bearing assemblages have been spectrally identified on mars although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates ultramafic rocks are predicted to produce serpentine talc and magnesite all of which have been detected spectrally on mars mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be h2o rich and co2 poor we confirm the hypothesis that low grade hydrothermal metamorphism affected the noachian crust on mars which has been excavated in large craters we estimate the geothermal gradient 20 c km 1 required to produce the observed assemblages this gradient is higher than that estimated from radiogenic heat producing elements in the crust suggesting extra heating by regional hydrothermal activity