an ice rich flow origin for the banded terrain in the hellas basin mars the interior of hellas basin displays a complex landscape and a variety of geomorphological domains one of these domains the enigmatic banded terrain covers much of the northwestern part of the basin we use high resolution context camera and high resolution imaging science experiment digital terrain models to show that most of the complex viscous flowing behavior exhibited by the banded terrain is controlled by topography and flow like interactions between neighboring banded terrain furthermore the interior of the basin hosts several landforms suggestive of the presence of near surface ice which include polygonal patterns with elongated pits scalloped depressions isolated mounds and collapse structures we suggest that thermal contraction cracking and sublimation of near surface ice are responsible for the formation and the development of most of the ice related landforms documented in hellas the relatively pristine form lack of superposed craters and strong association with the banded terrain suggest an amazonian 3 ga age of formation for these landforms finally relatively high surface pressures above the triple point of water expected in hellas and summertime temperatures often exceeding the melting point of water ice suggest that the basin may have recorded relatively temperate climatic conditions compared to other places on mars therefore the potentially ice rich banded terrain may have deformed with lower viscosity and stresses compared to other locations on mars which may account for its unique morphology

searching at the right time of day evidence for aqueous minerals in columbus crater with tes and themis data the primary objective of the thermal emission imaging system themis experiment which has been in orbit at mars since early 2002 is to identify minerals associated with hydrothermal and subaqueous environments data from themis have supported the presence of clays silica rich deposits and chlorides but has not before provided definitive evidence for the presence of sulfates this is an especially puzzling result given that sulfates have been extensively identified with other instruments at mars if present sufficiently exposed and in high enough abundances such minerals should be detectable in orbital thermal infrared spectra at the resolution of themis the extended mission proposal for themis on mars odyssey suggests that the detection of all minerals may be enhanced by observing at an earlier time of day and thus at warmer temperatures therefore in 2009 odyssey moved to an earlier orbit time here we examine themis data collected when the earlier orbit time coincided with the martian local southern late summer ls 270 for columbus crater where compact reconnaissance imaging spectrometer for mars crism data have detected a number of aqueous minerals some of the warmest themis images show evidence for aqueous minerals although not in the same locations where crism finds the highest concentrations several factors contribute to this result including differences in the diurnal temperature curve and levels of induration and particle size for themis earlier time of day and proper seasonal observations combine to provide warm surface temperatures and ideal low atmospheric opacity that significantly increases the ability to definitively identify low spectral contrast aqueous minerals at the surface of mars

extensive aqueous deposits at the base of the dichotomy boundary in nilosyrtis mensae mars abstract thermal emission imaging system themis and compact reconnaissance imaging spectrometer for mars crism spectral datasets were used to identify high bulk sio 2 and hydrated compositions throughout the nilosyrtis mensae region four isolated locations were identified across the region showing short wavelength silicate absorptions within the 8 12 m spectral region indicating surfaces dominated by high si phases much more extensive exposures of hydrated compositions are present throughout the region indicated by a spectral absorption near 1 9 m in crism data although limited in spatial coverage detailed spectral observations indicate that the hydrated materials contain fe mg smectites and hydrated silica along with minor exposures of mg carbonates and an unidentified hydrated phase the high sio 2 and hydrated materials are present in layered sediments near the base of topographic scarps at the hemispheric dichotomy boundary typically near or within low albedo sand deposits the source of the high sio 2 and hydrated materials appears to be from groundwater discharge from nili fossae and syrtis major to the south where there is evidence for extensive aqueous alteration of the subsurface although discontinuous the exposures of high sio 2 and hydrated materials span a wide area and are present in a similar geomorphological context to previously identified deposits in western hellas basin these regional deposits may reflect aqueous conditions and alteration within the adjacent crust of the martian highlands

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

tertiary of the arabian gulf sedimentology and hydrocarbon potential abstract the paleogene neogene paleogeography of the arabian basin shows a change from the basic continuation of the mesozoic pattern during the paleogene to a new pattern of sedimentation established during the neogene and resulting from movements in the zagros the paleogene shallow water carbonate dominated lithologies in eastern arabia were replaced by deep water neogene carbonates near the zagros and mixed carbonate and clastics in the northern arabian gulf the hydrocarbon potential of these rocks except locally is low and the decreasing amplitude and frequency of faulted and folded structures away from the zagros front suggests that the discovery of fields in structures such as those in iraq iran is low this poverty may however suggest that the untapped potential of the mesozoic rocks may still be high

groundwater dynamics in fossil fractured carbonate aquifers in eastern arabian peninsula a preliminary investigation abstract eastern arabian peninsula represents the main natural groundwater discharge area of the arabian platform fossil aquifer system in such settings connections between aquifers could strongly affect the flow dynamics water quality and availability as well as karst formation and landscape evolution geological structures such as folds and faults are central to aquifer connectivity yet their role on groundwater flow is poorly understood herein we perform mapping of exposed and buried structural features in the qatar peninsula using landsat sentinel 2 and alos palsar scenes correlated with field gpr and isotopic data to assess their role in aquifer connections and groundwater dynamics our results suggest that ene wsw oriented fold related faults act as vertical conduits along which artesian upward leakages from the deep aruma aquifer take place into the shallower main aquifer unit i e umm er radhuma and rus in southern qatar peninsula on the other hand downward leakage from the freshwater lens in the dammam aquifer take place in northern qatar peninsula the deep brackish and gaseous rich waters ascending along faults in south qatar peninsula in addition to degrading the water quality in the main aquifer unit enhance dissolution of carbonates and evaporites leading to strong karstification that produces abundant collapse features our findings suggest that structure controls can add significant complexity to recharge mechanisms and groundwater dynamics in fossil aquifers future large scale radar subsurface mapping will be essential to resolve the variability of the water heads in such areas and its correlation to structural discontinuities

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

regional scale stratigraphy of surface units in tyrrhena and iapygia terrae mars insights into highland crustal evolution and alteration history 1 the compositional thermophysical and geologic characteristics of surface units in iapygia and tyrrhena terra 60 e 100 e 0 30 s provide new insights into the compositional stratigraphy of the region intercrater plains are dominated by two surface units the older unit unit 1 is deficient in olivine and more degraded and likely consists of a mixture of impact volcanic and sedimentary materials the younger unit unit 2 is enriched in olivine exhibits a resistant morphology and higher thermal inertia and likely represents volcanic infilling of plains units 1 and 2 bear a strong resemblance to those previously mapped in mare serpentis a section of highlands crust located northwest of hellas basin thus the two major intercrater plains units are even more widespread than previously thought and therefore likely constitute important components of mars highland stratigraphy many craters in the region contain high thermal inertia deposits unit 3 that are compositionally identical to unit 2 these may have formed via volcanic infilling or may represent sedimentary materials that have been eroded from crater walls and lithified less common units include olivine and or pyroxene rich massifs and crater central peaks these are primarily found within hellas basin rim units and may represent mantle materials brought toward the surface during the hellas impact putative chloride deposits are primarily associated with olivine deficient surfaces unit 1 that may be heavily degraded occurrences of unit 2 the observations raise a variety of questions related to martian crustal evolution and alteration that may have more widespread implications outside the study region

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

identification of quartzofeldspathic materials on mars 1 a unique spectral component has been identified near and on the central peaks of two 30 km diameter craters in northern syrtis major these exposures are clearly visible in thermal emission imaging system themis color radiance images as well as themis and thermal emission spectrometer tes surface emissivity data both tes and themis data indicate the presence of increased 1050 1250 cm 1 8 9 5 m absorption compared to the surrounding basaltic plains and tes data also display other absorptions at 400 470 and 800 cm 1 25 20 and 12 m consistent with the presence of quartz ratio and isolated central peak spectral unit spectra match laboratory emissivity spectra of granitoid rocks composed primarily of quartz and plagioclase feldspar deconvolution results also indicate that the surface contains quartz and feldspar in addition to a high si glass and or sheet silicate component because central peak materials are brought up from depth during the cratering event the association of the quartzofeldspathic mineralogy with the central peaks of the craters indicates that the quartz bearing material was excavated from depth the occurrence in the two adjacent craters may imply a granitoid pluton of considerable extent a plausible formation mechanism for this relatively silicic material may be similar to that of terrestrial trondhjemites which do not require plate tectonics the rarity of the exposures implies that the process that formed the granitoid composition was probably not widespread the presence of quartz bearing material on mars indicates that mechanisms that produce highly differentiated magmas have been present and extends the diversity of surface compositions identified

mars global surveyor observations of martian fretted terrain the martian fretted terrain between latitudes 30 and 50 n and between 315 and 360 w has been reexamined in light of new mars orbiter camera moc and mars orbiter laser altimeter mola data from mars global surveyor much of the terrain in the 30 50 latitude belt in both hemispheres has a characteristic stippled or pitted texture at moc 1 5 m scale the texture appears to result from partial removal of a formerly smooth thin deposit as a result of sublimation and deflation a complex history of deposition and exhumation is indicated by remnants of a former thicker cover of layered deposits in some hollows and on some slopes particularly those facing the pole are smooth textured deposits outlined by an outward facing escarpment throughout the study area are numerous escarpments with debris flows at their base the escarpments typically have slopes in the 20 30 range at the base of the escarpment is commonly a deposit with striae oriented at right angles to the escarpment outside this deposit is the main debris apron with a surface that typically slopes 2 3 and complex surface textures suggestive of compression sublimation and deflation the presence of undeformed impact craters indicates that the debris flows are no longer forming fretted valleys contain lineated fill and are poorly graded they likely form from fluvial valleys that were initially like those elsewhere on the planet but were subsequently widened and filled by the same mass wasting processes that formed the debris aprons slope reversals indicate that downvalley flow of the lineated fill is minor the ubiquitous presence of breaks in slope formed by mass wasting and the complex surface textures that result from mass wasting deflation and sublimation decreases the recognizability of the shorelines formerly proposed for this area

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

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

quantitative compositional analysis of sedimentary materials using thermal emission spectroscopy 1 application to sedimentary rocks thermal emission spectroscopy is used to determine the mineralogy of sandstone and mudstone rocks as part of an investigation of linear spectral mixing between sedimentary constituent phases with widespread occurrences of sedimentary rocks on the surface of mars critical examination of the accuracy associated with quantitative models of mineral abundances derived from thermal emission spectra of sedimentary materials is necessary although thermal emission spectroscopy has been previously proven to be a viable technique to obtain quantitative mineralogy from igneous and metamorphic materials sedimentary rocks with natural variation of composition compaction and grain size have yet to be examined in this work we present an analysis of the thermal emission spectral 270 1650 cm 1 characteristics of a suite of 13 sandstones and 14 mudstones x ray diffraction and traditional point counting procedures were all evaluated in comparison with thermal emission spectroscopy results from this work are consistent with previous thermal emission spectroscopy studies and indicate that bulk rock mineral abundances can be estimated within 11 2 for detrital grains i e quartz and feldspars and 14 8 for all other mineral phases present in both sandstones and mudstones in comparison to common in situ techniques used for determining bulk rock composition clay sized to fine silt sized grained phase identification is less accurate with differences from the known ranging from 5 to 24 on average nevertheless linear least squares modeling of thermal emission spectra is an advantageous technique for determining abundances of detrital grains and sedimentary matrix and for providing a rapid classification of clastic rocks

opal a in the nakhla meteorite a tracer of ephemeral liquid water in the amazonian crust of mars the nakhlite meteorites are clinopyroxenites that are derived from a 1300 million year old sill or lava flow on mars most members of the group contain veins of iddingsite whose main component is a fine grained and hydrous fe and mg rich silicate siderite is present in the majority of veins where it straddles or cross cuts the fe mg silicate this carbonate also contains patches of ferric oxy hydroxide despite 40 years of investigation the mineralogy and origins of the fe mg silicate is poorly understood as is the paragenesis of the iddingsite veins nanometer scale analysis of fe mg silicate in the nakhla meteorite by electron and x ray imaging and spectroscopy reveals that its principal constituents are nanoparticles of opal a this hydrous and amorphous phase precipitated from acidic solutions that had become supersaturated with respect to silica by dissolution of olivine each opal a nanoparticle is enclosed within a ferrihydrite shell that formed by oxidation of iron that had also been liberated from the olivine siderite crystallized subsequently and from solutions that were alkaline and reducing and replaced both the nanoparticles and olivine the fluids that formed both the opal a ferrihydrite and the siderite were sourced from one or more reservoirs in contact with the martian atmosphere the last event recorded by the veins was alteration of the carbonate to a ferric oxy hydroxide that probably took place on mars although a terrestrial origin remains possible these results support findings from orbiter and rover based spectroscopy that opaline silica was a common product of aqueous alteration of the martian crust

photogeologic mapping and the geologic history of the hellas basin floor mars abstract the hellas basin on mars is the second largest topographically well defined impact structure in the solar system and has repeatedly been interpreted as a major sink of volcanic glacio fluvial and eolian materials based on established guidelines for planetary mapping we compiled a comprehensive photogeological map of hellas planitia i e the hellas basin floor 1 2 000 000 1 8 106 km2 see supplementary online material using the thermal emission imaging system themis ir day time mosaic as basemap supplemented by several other datasets we identified 33 units which were categorized into a rim assemblage containing dissected units a layered rim sequence and other basin rim units as well as a floor assemblage containing the honeycomb formation an interior formation and a plains sequence relative dating of units was performed wherever contacts revealed stratigraphic relationships and was complemented by absolute model ages amas of all units that lend themselves to reliable crater size frequency distribution csfds measurements on the basis of our results as well as amas of circum hellas volcanic provinces by previous authors we compiled a chronostratigraphic model of the hellas basin floor the northern basin rim shows evidence vast layered hydrous mineral bearing deposits containing meandering channel like valleys that the early history of the basin until 3 8 ga ago experienced extended periods of low energy fluvial and possibly lacustrine activity superposing the layered rim sequence the majority of the hellas basin infill 1 5 1 7 106 km3 consists of volcanic material a lower and an upper wrinkle ridged plains unit which was shortened by a compressive stress field relatively soon after its emplacement based on their ages and stratigraphic considerations we identified malea patera and possibly also tyrrhena patera as a suitable source for the older lower plains 3 8 ga and hadriaca and or amphitrites paterae for the younger upper plains 3 7 ga shortly after these volcanic episodes the entire basin floor was covered by large amounts of deposits 106 km3 containing aqueously altered mafic materials we interpret the deposits to have originated from hesperia planum and the hesperia hellas trough where they might have been removed by glacio fluvial processes which also sculpted the hellas rim sections along northern promethei terra and malea planum around the same time such an apparent correlation between nearby volcanic activity and increased erosion deposition is in agreement with previous models which suggest outgassing by a maximum in global volcanism at that time caused warmer episodes enabling repeated subaerial water run off after the emplacement of these deposits intense erosion likely deflation along a rim parallel annulus began to exhume the outer parts of the wrinkle ridged plains again forming an interior formation of more elevated erosional remnants including the alpheus colles since 3 7 ga ago fluvial activity of dao niger and harmakhis valles dissected the eastern plains and emplaced pancake shaped deposits in the basin center later deflation and abrasion by katabatic winds moving through the hellas basin in a clock wise direction parallel to the basin floor outline carved out the northwestern hellas planitia trough called peneus palus possibly within a time span of few hundreds of ma or less within the amazonian being consistent with erosional patterns we observed within the basin circulation models predict such winds to be ongoing today and might thus have recently exhumed the so called honeycomb formation on parts of peneus palus this enigmatic unique terrain was possibly formed by ductile deformation of pre 3 8 ga material and appears to be partially covered by another unique landform the banded terrain although we cannot rule out that it is the surface expression of a thicker unit the banded terrain might represent flows of volatile rich airfall deposits emplaced along the edges of the hellas wind alley by turbulent marginal wind currents which currently recently prevail on both sides of the hellas planitia trough in summary our investigations enabled us to draw an updated comprehensive and self consistent picture of the geologic evolution of the hellas basin floor including volcanic peri glacial fluvial and eolian processes their possible interactions and the implications on the climatic and geologic development of the circum hellas region and the entire planet

geology of quartz and hydrated silica bearing deposits near antoniadi crater mars 1 the only area on mars where crystalline quartz has been identified from orbit is near antoniadi crater on the northern edge of the syrtis major shield volcano however the method of quartz formation has remained unknown in this study we use high resolution satellite imagery as well as thermal and near infrared spectroscopy to construct a geologic history of these deposits and their local context we find that the quartz bearing deposits are consistently co located with hydrated silica this spatial coherence suggests that the quartz formed as a diagenetic product of amorphous silica rather than as a primary igneous mineral diagenetic quartz is a mature alteration product of hydrated amorphous silica and indicates more persistent water and or higher temperatures at this site beneath the silica bearing rocks we also find spectral evidence for smectites in the lowermost exposed noachian aged breccia a similar stratigraphic sequence smectite bearing breccias beneath deposits containing minerals suggesting a greater degree of alteration has also been found at nearby exposures at nili fossae and toro crater suggesting a widespread sequence of alteration by merging the mineral detections of thermal infrared quartz feldspar and near infrared spectroscopy hydrated silica smectite clays we are able to construct a more complete geologic history from orbit

velocity porosity clay content systematics of poorly consolidated sandstones compressional velocities have been measured as a function of confining pressure for 14 west delta block louisiana sandstone cores the dry velocity data for these poorly consolidated sandstones at 10 mpa confining pressure plot on a linear velocity density trend with well consolidated sandstones but not loose sands the dry velocity data also show linear trends of decreasing velocity with increasing porosity along contours of constant clay content similar to those obtained at 40 mpa by tosaya and nur 1982 for saturated sandstones the spacing between clay contours indicates that a large portion of the velocity variation with clay content is due to microporosity which is not included in point counting within the clays the slope of the velocity porosity trends indicates that cementation increases with decreasing porosity

visible near infrared and mid infrared spectral characterization of hawaiian fumarolic alteration near kilauea s december 1974 flow implications for spectral discrimination of alteration environments on mars

elevated bulk silica exposures and evidence for multiple aqueous alteration episodes in nili fossae mars abstract the nili fossae region of mars contains some of the most mineralogically diverse bedrock on the planet previous studies have established three main stratigraphic units in the region a phyllosilicate bearing basement rock a variably altered olivine rich basalt and a capping rock here we present evidence for the localized alteration of the northeast nili fossae capping unit previously considered to be unaltered both near infrared and thermal infrared spectral datasets were analyzed including the application of a method for determining the relative abundance of bulk silica sio 2 over surfaces using thermal emission imaging system themis images elevated bulk silica exposures are present on surfaces previously defined as unaltered capping rock given the lack of spectral evidence for phyllosilicate hydrated silica or quartz phases coincident with the newly detected exposures the elevated bulk silica may have formed under a number of aqueous scenarios including as a product of the carbonation of the underlying olivine rich basalt under moderate water rock scenarios and temperatures regardless of formation mechanism the detection of elevated bulk silica exposures in the nili fossae capping unit extends the history of aqueous activity in the region to include all three of the main stratigraphic units

observational evidence of crystalline iron oxides on mars visible to near ir 0 4 1 0 mu m spectral reflectance observations of mars during the 1988 opposition were performed at mauna kea observatory using a circular variable filter spectrometer at a spectral resolution r lambda delta lambda approx 80 on august 13 and 14 1988 ut 41 regions 500 600 km in diameter were observed on mars the data have been reduced both to reflectance relative to solar analog mars 16 cyg b and to relative reflectance spot spot the spectra show the strong near uv reflectance dropoff characteristic of mars as well as absorptions at 0 62 0 72 mu m and 0 81 0 94 mu m both seen here clearly for the first time these absorption features are interpreted as fe sup 3 electronic transition bands that indicate the presence of crystalline ferric oxide or hydroxide minerals on the martian surface comparison of these data with laboratory spectra obtained by other workers supports the conclusion that a single iron oxide phase most likely hematite could account for all of the observed spectral behavior of the martian surface soils and airborne dust in the 0 4 1 0 mu m region this possibility must be reconciled with data from other possible spectral analogs and other wavelength regions as well as geochemical and mineral stability considerations to arrive at amore more complete understanding of the role of ferric minerals in martian surface mineralogy and weathering less

mineralogy of the light toned outcrop at meridiani planum as seen by the miniature thermal emission spectrometer and implications for its formation 1 analysis of miniature thermal emission spectrometer mini tes data has led to the recovery of a pure end member spectral shape related to the light toned outcrop observed at meridiani planum data from the mer mossbauer spectrometer apxs and previous mini tes measurements were used to constrain a spectral library used to determine the mineralogy of the outcrop from this spectral shape linear deconvolution of the outcrop spectral shape suggests that it is composed primarily of al rich opaline silica mg ca and fe bearing sulfates plagioclase feldspar nontronite and hematite conversion of modeled mineralogy to chemistry shows good agreement with the chemical composition of the outcrops determined by apxs details of the analysis procedure and implications for the formation of the outcrop are discussed along with terrestrial analogs of the ancient environment at meridiani

high silica deposits of an aqueous origin in western hellas basin mars 1 data from the thermal emission spectrometer and the thermal emission imaging system have been used to identify isolated high silica surfaces in western hellas basin deconvolution results indicate that the surfaces are composed of nearly 80 high silica phases amorphous silica phyllosilicates or zeolites the deposits may be derived from alcoves in the terrain immediately to the north the high silica deposits are an additional indicator of a variety of past aqueous processes on mars

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

in situ compositions of martian volcanics implications for the mantle the primary objective of this analysis is to determine the mineralogic composition of relatively pristine terrains exposed on the surface of mars this analysis is conducted using imaging spectrometer data acquired in 1989 by the imaging spectrometer for mars ism instrument that was onboard the phobos ii spacecraft the ism instrument acquired some of the highest spectral 64 channels between 0 77 and 3 14 m and spatial resolution 22 km pixel observations to date of mars focused on the equatorial region relatively unaltered surfaces were identified in these data on the basis of their spectral properties low albedo weak spectral slope absence of ferric absorptions and were found in volcanic terrains of syrtis major valles marineris ophir planum and sinus meridiani oxia palus spectra representative of the diversity among terrains were extracted for detailed analysis using the modified gaussian model to determine the primary mafic mineralogy it was determined that the mafic mineralogy of the regions investigated is dominated by low calcium and high calcium pyroxene lcp hcp and that there was homogeneity within a given region but some heterogeneity between regions in the relative abundance of lcp to hcp the two pyroxene mineralogy is consistent with the mineralogies of the basaltic snc meteorites believed to have originated on mars two pyroxene volcanic mineralogies are indicative of large degrees of partial melting e g komatiites or a mantle source depleted in aluminum integration of these findings with previous studies of mars and the snc meteorites indicates that 1 the snc mineralogies are representative of large volcanic regions of mars with surface ages as old as 2 3 ga 2 the martian mantle was depleted in aluminum at least as long ago as the oldest terrain analyzed ophir planum and 3 there has been little evolution in the composition of mantle source regions as the 180 ma snc mineralogies are comparable to those of the oldest terrains analyzed

lithostratigraphy of the middle eocene dammam formation in qatar arabian gulf effects of sea level fluctuations along a tidal environment abstract the middle eocene dammam formation dominates the surface exposure of qatar it consists of shales followed by limestone and is topped by dolomitic limestone it is subdivided from oldest to youngest into the midra shale dukhan umm bab and abaruq members three patterns of facies dominate the formation shale marl facies in the lower part mudstone wackestone packstone facies in the middle part and argillaceous dolomitic wackestone packstone facies in the upper part the main fauna of the dammam formation include nummulites alveolines linderines shark teeth molluscs and echinoderms the nummulites species are common particularly within the middle members dukhan and umm bab members coarsening upward parasequences reflect the cyclicity of the eocene dammam formation in qatar at least three short lived transgressive regressive cyclothems can be recognized in sediments of the formation these small scale cycles resulted from fluctuations in sea level a local hiatus is believed to separate these cycles in northeastern qatar a warm shallow marine environment was predominant as indicated by extensive dolomitization and the presence of alveolines linderines and nummulites with globular tests

effects of surface roughness and graybody emissivity on martian thermal infrared spectra slopes are present in martian apparent surface emissivity observations collected by the thermal emission spectrometer tes and the thermal emission imaging system themis these slopes are attributed to misrepresenting the surface temperature either through incorrect assumptions about the maximum emissivity of surface materials or the presumption of a uniform surface temperature within the field of view these incorrect assumptions leave distinct characteristics in the resulting apparent emissivity data that can be used to gain a better understanding of the surface properties surfaces with steep slopes typically have a variable surface temperatures within the field of view that cause distinct and highly variable slopes in apparent emissivity spectra based on the observing conditions these properties are documented on the southwestern flank of apollinaris patera and can be reasonably approximated by modeled data this spectral behavior is associated with extremely rough martian surfaces and includes surfaces south of arsia mons and near warrego valles that also appear to have high slopes in high resolution images surfaces with low maximum values of emissivity have apparent emissivity spectra with more consistent spectral slopes that do not vary greatly based on observing conditions this spectral surface type is documented in terra serenum and is consistent with associated high resolution images that do not indicate the presence of a surface significantly rougher that the surrounding terrain

the cenozoic kinematics of qatar evidence for high angle faulting along the dukhan anticline abstract new geological mapping and observations made across qatar favor a fault controlled model for the dukhan structure in the western part of the peninsula over previous fold related and regional erosion models regional stratigraphic relationships and sedimentology record significant fault localized accommodation development this miocene basin development may reflect far field extension in the foreland of coeval thrusting in oman the subsequent change in regional tectonics to convergence across the zagros front is interpreted to have led to basin inversion and the development of the present day topography and outcrop distribution

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

mosaicking of global planetary image datasets 1 techniques and data processing for thermal emission imaging system themis multi spectral data 1 the mosaicking of global planetary data sets allows for the examination of local regional and global scale processes on all planetary bodies processing techniques that allow us and other users to crate mosaics of tens of thousands of images are documented along with the associated errors introduced by each image processing algorithm these techniques e g non uniformity correction running contrast stretches line and row correlated noise removal and random noise removal were originally developed for the 2001 mars odyssey thermal emission imaging system themis infrared multispectral imager data but can be adapted and applied to other data sets by the alteration of input parameters the techniques for mosaicking planetary image data sets e g image registration blending and normalization are also presented along with the generation of qualitative and quantitative products these techniques are then applied to generate themis daytime and nighttime infrared viking context imager ctx and mars orbiter camera moc visible mosaics using a variety of input and output types at a variety of scales by creating mosaics of the same area using different data sets such as those that illustrate compositional diversity thermophysical properties or small scale morphology it is possible to view the surface of the planet and geologic problems through many different perspectives in addition to the techniques used to create large scale seamless mosaics we also present the themis daytime and nighttime relative temperature global mosaics which are the highest resolution 100m pixel global scale data sets available for mars to date

hydrous minerals on mars as seen by the crism and omega imaging spectrometers updated global view 1 the surface of mars has preserved the record of early environments in which its basaltic crust was altered by liquid water these aqueous environments have survived in the form of hydrological morphologies and alteration minerals including clays and hydrated salts because these minerals probe on earth aqueous environments compatible with biotic activity understanding their formation processes on mars is of great exobiological relevance and also offers insight into earth s now erased ancient water environments using remote sensing we conducted a large scale investigation of the distribution composition age and geomorphic settings of hydrous minerals on mars providing a sharpened global view of the early aqueous environments and their evolution with time aqueous alteration seems to have produced clays on a planetary scale but these are found to be restricted to the oldest observable terrains on mars 4 gyr however very diverse aqueous environments have also been found which suggest widespread complex aqueous settings from the surface to kilometric depths and spanning over 1 gyr by building a robust statistical sample of detections the global trends inferred here attempt to provide a broad view of our current understanding of hydrous minerals on mars and provide context for more localized in depth analyses collectively these trends suggest that at least transient conditions have existed on mars which may have been favorable for pre biotic to biotic activity

formation of silica by low temperature acid alteration of martian rocks physical chemical constraints 1 theoretical geochemical modeling has been used to evaluate the formation conditions of amorphous silica during aqueous alteration of typical martian igneous rocks at 0 c the models show that some silica can form during low temperature alteration of mafic to ultramafic rocks over a large range of ph and water rock ratios silica dominated deposits like those found at the columbia hills in gusev crater on mars could form at solution ph below 2 and water rock ratios of 102 104 high water rock conditions could represent acid flow through rocks solution discharge from an acid spring and or surface flow of released solutions low ph favors dissolution of silicates and saturation of solution with respect to relatively insoluble silica which then precipitates partial evaporation or freezing of released solutions would also cause precipitation of amorphous silica modeling shows that ti oxides are also present in silica rich deposits more soluble minerals e g ferric oxides phyllosilicates could precipitate downstream from partially neutralized evaporated or frozen solutions temperatures above 0 c are not required to form abundant silica through acid alteration of martian rocks

extended surface exposures of granitoid compositions in syrtis major mars 1 the number of quartz and feldspar rich surfaces identified in northwestern syrtis major has been extended beyond previously reported results to a region of about 230 by 125 km thermal emission imaging system infrared data were used to locate surfaces spectrally identical to previously reported central peak units in syrtis major these surfaces are indicative of the production of highly differentiated magmas though it is possible that the granitoid exposures add to the variety of igneous compositions associated with the syrtis major volcanic construct the geologic context of these exposures suggests a formation that predates syrtis major

crater floor polygons desiccation patterns of ancient lakes on mars 1 global mapping of intermediate size 100 200 m polygonal troughs occurring mainly in impact crater floors was carried out using high resolution images from spacecraft currently orbiting mars earlier works have classified these polygonal networks as periglacial features on account of their apparent occurrence at higher latitudes and morphological similarities to thermal contraction polygons tcps crater floor polygons cfps have diameters ranging from 15 to 350 m they morphologically resemble terrestrial tcps and desiccation cracks their size distribution however is significantly different from that of tcps that are ubiquitous in the high latitudes an analytical model based on fracture mechanics reveals that under current climatic conditions the maximum fracture spacing attainable by thermal stresses alone is 75 m at the most more reasonable values fall within 18 and 22 m which is the range for tcps on mars as a result we propose desiccation to be a dominant mechanism for the formation of cfps without ruling out thermal contraction as a possible contributor in some cases this implies that lakes or water rich sediments occupied the craters in the past many such aqueous environments have no apparent external source of water and thus hydrothermal processes occurring shortly after the impact event may be viable explanations for the observed evidence the association of features which correspond to terrestrial lakes such as sedimentary deposits mounds and shorelines corroborates lake formation and their eventual desiccation to form cfps the variation of cfp sizes with location can be indicative of different hydrologic environments

silica rich deposits and hydrated minerals at gusev crater mars vis nir spectral characterization and regional mapping abstract the mars exploration rover mer spirit has discovered surprisingly high concentrations of amorphous silica in soil and nodular outcrops in the inner basin of the columbia hills in pancam multispectral observations we find that an absorption feature at the longest pancam wavelength 1009 nm appears to be characteristic of these silica rich materials however spectral analyses of amorphous silica suggest that the 1009 nm spectral feature is not a direct reflection of their silica rich nature based on comparisons with spectral databases we hypothesize that the presence of h 2 o or oh either free as water ice adsorbed or bound in a mineral structure is responsible for the spectral feature observed by pancam the gertrude weise soil which is nearly pure opaline silica may have adsorbed water cold trapped on mineral grains the origin of the 1009 nm pancam feature observed in the silica rich nodular outcrops may result from the presence of additional hydrated minerals specific sulfates halides chlorides sodium silicates carbonates or borates using the 1009 nm feature with other spectral parameters as a hydration signature we have mapped the occurrence of hydrated materials along the extent of spirit s traverse across the columbia hills from west spur to home plate sols 155 1696 we have also mapped this hydration signature across large panoramic images to understand the regional distribution of materials that are spectrally similar to the silica rich soil and nodular outcrops our results suggest that hydrated materials are common in the columbia hills

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

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