chloride bearing materials in the southern highlands of mars chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing spectrally distinct surface deposits consistent with chloride bearing materials have been identified and mapped using data from the 2001 mars odyssey thermal emission imaging system these deposits are found throughout regions of low albedo in the southern highlands of mars geomorphologic evidence from orbiting imagery reveals these deposits to be light toned relative to their surroundings and to be polygonally fractured the deposits are small

fluid lava flows in gusev crater mars 1 rocks on the floor of gusev crater are basaltic in composition as determined from measurements by the mars exploration rover spirit on the basis of compositional data models of the basaltic lavas at the time of their emplacement suggest viscosities of 2 3 to 50 pa s dependent on the number of phenocrysts and vesicles that were present which would be more fluid than terrestrial tholeiitic lavas and comparable to mare lavas on the moon or archean high mg basalts on earth morphological data and crater counts derived from the high resolution stereo camera on mars express and other orbiters suggest that the lavas flooded gusev crater at about 3 65 b y and postdate older floor materials such as putative sediments emplaced by ma adim vallis

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

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

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

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

mars aeolian sand regional variations among dark hued crater floor features different regions on mars appear to have low albedo intracrater deposits that have distinct regional thermophysical and or aeolian dune characteristics thermal inertia derived from a carefully selected set of viking infrared thermal mapper observations of the dark features obtained in 1977 1978 supports this conclusion the observed similarities and differences among dark intracrater features on mars is probably a function of the combined influences of sand availability and regional wind conditions

high resolution thermal inertia derived from the thermal emission imaging system themis thermal model and applications 1 thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the thermal emission imaging system themis on the mars odyssey spacecraft producing the highest resolution thermal inertia data set to date themis thermal inertia values have an overall accuracy of 20 a precision of 10 15 and are consistent with both thermal emission spectrometer orbital and miniature thermal emission spectrometer surface thermal inertia values this data set enables the improved quantification of fine scale surface details observed in high resolution visible images in the tharsis region surface textures and crater rims observed in visible images have no corresponding variation in the themis thermal inertia images indicating that the dust mantle is pervasive at themis scales and is a minimum of a few centimeters and up to 1 2 m thick the thermal inertia of bed form material indicates particle diameters expected for aeolian sediments and these materials are likely currently saltating variations in the thermal inertia within interior layered deposits in hebes chasma can be distinguished and the thermal inertia is too low to be consistent with bedrock or a lava flow thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation higher resolution themis thermal inertia enables the identification of exposed bedrock on the martian surface in nili patera and ares vallis bedrock material corresponds to distinct compositional and morphologic surfaces indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes

grain size evolution and fractionation trends in an experimental regolith the comminution of blocky planetary surfaces into fine grained regoliths was simulated by impacting a fragmental gabbro target 200 times with stainless steel projectiles diameter 6 35 mm mass 1 2g vi 1 35 km s initially the target fragments were 2 32 mm in size with a mean diameter of 15 2 mm which was reduced to 0 4 mm after 200 shots for the first 60 shots comminution was linear with cumulative kinetic energy and thus essentially linear with time the comminution efficiency however decreased at later stages this could be due to a change in fracture mechanism from predominantly intergranular to predominantly intragranular and or due to a change in partitioning of the projectile s kinetic energy from collisional fragmentation or large fragments at early times to cratering in a progressively finer grained medium at later stages mineral specific preferential comminution is abundantly observed in the modal make up of various grain size fractions plagioclase comminutes more readily than pyroxenes plagioclase initially present at 54 vol comprises typically 65 70 of the 125 250 m fraction pyroxenes initially at 33 are depleted to 20 25 this fractionation occurs in the earliest samples analyzed and is not a time dependent phenomenon bulk chemical analyses reveal a corresponding increase in al2o3 cao and na2o and a decrease in feo and mgo the finest grain sizes are generally the most severely affected by differential comminution similar if not exactly identical trends are abundantly documented for lunar soil samples these experimental findings illustrate that differential comminution is capable of producing fractionation in the finest grain sizes they diminish the need for prominent lateral and vertical transport of components otherwise foreign to a lunar soil sampling site as postulated by some workers on the basis of multivariate chemical mixing models

thermal emission spectroscopy of the silica polymorphs and considerations for remote sensing of mars 1 the possible existence of silica rich rocks on mars requires consideration of all of the candidate forms of silica that might exist there we synthesized coesite and cristobalite and obtained natural samples of tridymite opal a and opal ct the thermal emission spectra of these silica phases were analyzed and related to their crystal structure and crystallinity structural differences between the polymorphs result in unique spectral character and the degree and type of crystal ordering in opal ct results in cristobalite or tridymite like spectral features these spectra will be useful for analysis of thermal emission spectrometer tes data from mars while silica polymorphs are not modeled in deconvolution of the two main tes surface type spectra this does not preclude the possible detection of local abundances of these minerals on mars spectral detection of silica phases on mars would have implications for the volcanic and alteration history of the planet

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

related magma ice interactions possible origins of chasmata chaos and surface materials in xanthe margaritifer and meridiani terrae mars abstract we examine here the close spatial and temporal associations among several unique features of xanthe and margaritifer terrae specifically the valles marineris troughs or chasmata and their interior deposits chaotic terrain the circum chryse outflow channels and the subdued cratered material that covers xanthe margaritifer and meridiani terrae though previous hypotheses have attempted to explain the origin of individual features or subsets of these we suggest that they may all be related all of these features taken together present a consistent scenario that includes the processes of sub ice volcanism and other magma ice interactions results of intrusive events during late noachian to early amazonian times

geologic context of in situ rocky exposures in mare serpentis mars implications for crust and regolith evolution in the cratered highlands abstract global acquisition of infrared spectra and high resolution visible and infrared imagery has enabled the placement of compositional information within stratigraphic and geologic context mare serpentis a low albedo region located northwest of hellas basin is rich in spectral and thermophysical diversity and host to numerous isolated exposures of in situ rocky material most martian surfaces are dominated by fine grained particulate materials that bear an uncertain compositional and spatial relationship to their source thus location and characterization of in situ rock exposures is important for understanding the origin of highland materials and the processes which have modified those materials using spectral thermophysical and morphologic information we assess the local and regional stratigraphy of the mare serpentis surface in an effort to reconstruct the geologic history of the region the martian highlands in mare serpentis are dominated by two interspersed surface units which have distinct compositional and thermophysical properties 1 rock dominated surfaces relatively enriched in olivine and pyroxene and depleted in high silica phases and 2 sediment or indurated material depleted in olivine and pyroxene with relatively higher abundance of high silica phases this is a major previously unrecognized trend which appears to be pervasive in the mare serpentis region and possibly in other highland areas the detailed observations have led us to form two hypotheses for the relationship between these two units either 1 they are related through a widespread mechanical and or chemical alteration process where less mafic plains materials are derived from the mafic bedrock but have been compositionally altered in the process of regolith formation or 2 they are stratigraphically distinct units representing separate episodes of upper crust formation existing observations suggest that the second scenario is more likely in this scenario plains materials represent older degraded and possibly altered basement rock whereas the rocky exposures represent later additions to the crust and are probably volcanic in origin these hypotheses should be further testable with decimeter resolution imagery and meter resolution short wavelength infrared spectra

thermal infrared spectroscopy of experimentally shocked anorthosite and pyroxenite implications for remote sensing of mars 1 the feldspar and pyroxene mineralogies on mars revealed by the thermal emission spectrometer tes on mars global surveyor likely record a variety of shock effects as suggested by petrologic analyses of the martian meteorites and the abundance of impact craters on the planet s surface to study the effects of shock pressures on thermal infrared spectra of these minerals we performed shock recovery experiments on orthopyroxenite and anorthosite samples from the stillwater complex montana over peak pressures from 17 to 63 gpa we acquired emissivity and hemispherical reflectance spectra 350 1400 cm 1 7 29 mm of both coherent chips and fine grained powders of shocked and unshocked samples these spectra are more directly comparable to remotely sensed data of mars e g tes than previously acquired absorption or transmission spectra of shocked minerals the spectra of experimentally shocked feldspar show systematic changes with increasing pressure due to depolymerization of the silica tetrahedra for the spectra of chips this includes the disappearance of small bands in the 500 650 cm 1 region and a strong band at 1115 cm 1 and changes in positions of a strong band near 940 cm 1 and the christiansen feature near 1250 cm 1 spectra of the shocked powders show the gradual disappearance of a transparency feature near 830 cm 1 fewer changes are observed in the pyroxene spectra at pressures as high as 63 gpa spectra of experimentally shocked minerals will help identify more precisely the mineralogy of rocks and soils not only from tes but also from future mars instruments such as minites and themis index terms 3944 mineral physics shock wave experiments 3934 mineral physics optical infrared and raman spectroscopy 5420 planetology solid surface planets impact phenomena includes cratering 5460 planetology solid surface planets physical properties of materials keywords anorthosite pyroxenite shock spectra thermal infrared remote sensing mars

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

physical properties of the mars exploration rover landing sites as inferred from mini tes derived thermal inertia 1 the miniature thermal emission spectrometer mini tes on board the two mars exploration rovers provides the first opportunity to observe thermal properties from the martian surface relate these properties to orbital data and perform soil conductivity experiments under martian conditions the thermal inertias of soils bedforms and rock at each landing site were derived to quantify the physical properties of these features and understand geologic processes occurring at these localities the thermal inertia for the gusev plains rock target bonneville beacon 1200 j m 2 k 1 s 1 2 is consistent with a dense basaltic rock but the rocks at the columbia hills have a lower thermal inertia 620 j m 2 k 1 s 1 2 suggesting that they have a volcaniclasic origin bedforms on the floors of craters at both landing sites have thermal inertias of 200 j m 2 k 1 s 1 2 consistent with a particle diameter of 160 m this diameter is comparable to the most easily moved grain size in the current atmosphere on mars suggesting that these bedforms may have formed under current atmospheric conditions along the meridiani plains the thermal inertia is lower than that derived from tes and thermal emission imaging system themis orbital data this discrepancy is not well understood mini tes derived thermal inertias at gusev along a 2 5 km traverse follow trends in thermal inertia measured from orbit with tes and themis however along the traverse there are variability and mixing of particle sizes that are not resolved in the orbital thermal inertia data due to meter scale processes that are not identifiable at larger scales

the huygens hellas giant dike system on mars implications for late noachian early hesperian volcanic resurfacing and climatic evolution two narrow broadly arcuate low ridges extend for 600 700 km in western terra tyrrhena mars crosscut ancient noachian terrain and are associated with early hesperian plains which cover 30 of mars geological relationships suggest that the ridges represent near surface erosional remnants of subsurface dikes solidified magma filled cracks that were responsible for the volcanic emplacement of the plains ridge width and geometry are consistent with very high effusion rate flood basalt eruptions emplacement events that would form smooth featureless plains and input significant volcanic gas into the atmosphere geological relationships suggest that the ridges were exposed by erosion fluvial sublimation eolian and partial removal of a regional volatile rich dust layer

effect of precursor mineralogy on the thermal infrared emission spectra of hematite application to martian hematite mineralization 1 observations from the thermal emission spectrometer tes instrument aboard the mars global surveyor mgs spacecraft led to the discovery of two isolated deposits of gray crystalline hematite located in meridiani planum and aram chaos and several smaller deposits in valles marineris several pathways for formation of these hematite deposits have been proposed involving both aqueous and nonaqueous processes this work uses the precise shape and position of spectral features in the martian hematite thermal emission spectrum to constrain hematite formation pathways thermal infrared emission spectra x ray powder diffraction patterns mossbauer spectra and transmission electron microscope tem photomicrographs were obtained for synthetic and natural hematite samples derived by 1 dehydroxylation of fine grained goethite and 2 oxidation of magnetite collectively the instrumental analyses show that the mineralogical composition and crystal morphology of precursor samples and the time and temperature conditions under which decomposition to hematite occur determine the crystallinity and crystal morphology of the hematite product comparison of laboratory and mgs tes spectra shows that the martian hematite spectra correspond closely with a synthetic hematite sample derived by pseudomorphic and topotactic dehydroxylation of goethite at 300 c spectra of goethite precursor samples dehydroxylated at higher temperatures provide increasingly poor fits spectra of hematite samples derived by high temperature thermal oxidation of magnetite are also poorer fits to the martian hematite spectrum thermal emission spectra of goethites heated at lower temperatures are characterized by the spectral signatures of both hematite and goethite and are not consistent with the martian spectra the characteristic that distinguishes the synthetic hematite sample with the mars like spectral signature from the other synthetic hematite samples is the high proportion of crystal surfaces that are crystallographic 001 faces c faces for the former but not the latter the high proportion of 001 face area results because the largest surface of the lath shaped hematite particles is the 001 face as determined by tem thus a possible formation pathway for hematite in meridiani planum aram chaos and valles marineris is precipitation of goethite from aqueous solutions as lath shaped crystals possibly as a stain cement and or massive deposit followed by pseudomorphic and topotactic dehydroxylation to hematite at temperatures below 300 c

thermal inertia mapping of mars from 60 s to 60 n twenty micrometer brightness temperatures are used to derive the thermal inertia for 81 of the martian surface between latitudes 60 these data were acquired by the two viking infrared thermal mappers in 1977 and 1978 following the two global dust storms of 1977 the spatial resolution used is 2 in latitude by 2 in longitude and the total range in derived inertia is 1 to 15 10 3 cal cm 2 sec 12 k 1 the distribution of thermal inertia is strongly bimodal with all values of thermal inertia less than 4 10 3 cal cm 2 sec 12 k 1 being associated with three disjoint bright regions mostly in the northern hemisphere sufficient dust is raised in global storms to provide fine material adequate to produce these low inertia areas but the specific deposition mechanism has not been defined at the low resolution used no complete exposures of clean rock were found there is some tendency for darker material to be associated with higher thermal inertia although the trend is far from one to one the distribution of high and low inertia areas is sufficiently nonrandom to produce a variation in whole disk brightness temperature with central meridian longitude this variation and the change in surface kinetic temperature associated with dust storms are factors in establishing the whole disk brightness temperature at radio and infrared wavelengths and will be important for those who use mars as a calibration source

mineralogy and stratigraphy of the gale crater rim wall and floor units the curiosity rover has detected diverse lithologies in float rocks and sedimentary units on the gale crater floor interpreted to have been transported from the rim to understand their provenance we examine the mineralogy and geology of gale s rim walls and floor using high resolution imagery and infrared spectra while no significant differences in bedrock spectral properties were observed within most thermal emission imaging system and compact reconnaissance imaging spectrometer for mars crism scenes some crism scenes of rim and wall rocks showed olivine bearing bedrock accompanied by fe mg phyllosilicates hydrated materials with 2 48 m absorptions in gale s eastern walls are spectrally similar to the sulfate unit in mount sharp aeolis mons sedimentary strata on the gale floor southwest of the landing site likely coeval with the bradbury units explored by curiosity also are hydrated and or have fe mg phyllosilicates spectral properties of these phyllosilicates differ from the al substituted nontronite detected by crism in mount sharp suggesting formation by fluids of different composition geologic mapping of the crater floor shows that the hydrated or hydroxylated materials are typically overlain by spectrally undistinctive erosionally resistant cliff forming units additionally a 4 km impact crater exposes 250 m of the gale floor including finely layered units no basement rocks are exposed thus indicating sedimentary deposits 250 m beneath strata studied by curiosity collectively the data indicate substantial sedimentary infill of gale crater including some materials derived from the crater rim lowermost thin layers are consistent with deposition in a lacustrine environment interbedded hydrated hydroxylated units may signify changing environmental conditions perhaps in a drying or episodically dry lake bed

transformed eulerian mean theory part ii potential vorticity homogenization and the equilibrium of a wind and buoyancy driven zonal flow the equilibrium of a modeled wind and buoyancy driven baroclinically unstable flow is analyzed using the transformed eulerian mean tem approach described in part i within the near adiabatic interior of the flow ertel potential vorticity is homogenized along mean isopycnals a finding readily explained using tem theory given the geometry of the domain the equilibrium zonal mean buoyancy structure at the surface is determined entirely by a balance between imposed surface fluxes and residual mean and eddy buoyancy transport within a surface diabatic layer balance between these same processes and the wind stress determines the stratification and hence potential vorticity immediately below this layer ertel potential vorticity homogenization below then determines the mean buoyancy structure everywhere accordingly the equilibrium structure of this flow can be described and quantitatively reproduced from knowledge of the eddy mixing rates within the surface diabatic zone and the depth of this zone together with potential vorticity homogenization beneath these results emphasize the need to include near surface buoyancy transport as well as interior pv transport in eddy parameterization schemes they also imply that in more realistic models the surface buoyancy balances may be impacted by processes in remote locations that allow diapycnal flow

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

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

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

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

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

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

global distribution of bedrock exposures on mars using themis high resolution thermal inertia 1 we investigate high thermal inertia surfaces using the mars odyssey thermal emission imaging system themis nighttime temperature images 100 m pixel spatial sampling for this study we interpret any pixel in a themis image with a thermal inertia over 1200 j m 2 k 1 s 1 2 as bedrock which represents either in situ rock exposures or rock dominated surfaces three distinct morphologies ranked from most to least common are associated with these high thermal inertia surfaces 1 valley and crater walls associated with mass wasting and high surface slope angles 2 floors of craters with diameters 25 km and containing melt or volcanics associated with larger high energy impacts and 3 intercrater surfaces with compositions significantly more mafic than the surrounding regolith in general bedrock instances on mars occur as small exposures less than several square kilometers situated in lower albedo 350 j m 2 k 1 s 1 2 and relatively dust free dust cover index 0 95 regions however there are instances that do not follow these generalizations most instances are concentrated in the southern highlands with very few located at high latitudes poleward of 45 n and 58 s suggesting enhanced mechanical breakdown probably associated with permafrost overall mars has very little exposed bedrock with only 960 instances identified from 75 s to 75 n with likely 3500 km 2 exposed representing 1 ofthe total surface area these data indicate that mars has likely undergone large scale surface processing and reworking both chemically and mechanically either destroying or masking a majority of the bedrock exposures on the planet

experimental epithermal alteration of synthetic los angeles meteorite implications for the origin of martian soils and identification of hydrothermal sites on mars 1 the dissolution behavior and secondary minerals generated by experimental alteration of a synthetic los angeles basaltic shergottite la were evaluated at epithermal 75 c conditions starting ph values of 1 1 and 3 6 and water rock ratios ranging from 100 to 2000 were studied using flow through and batch reactor experimental apparatus dissolution of plagioclase dominates effluent solution chemistry under all experimental conditions little mg is released to solution because nearly 100 of the mg in unaltered la is contained in pyroxene m1 sites which are relatively resistant to dissolution secondary minerals generated include siliceous residue amorphous sio2 lepidocrocite and ferrihydrite anhydrite alunogen rhomboclase ferrinatrite halite and unidentified ca and na sulfates the dominance of alteration products of plagioclase suggests that la type basalts have not contributed significantly to the martian soils the search for hydrothermal sites by remote sensing may be hampered by the general similarity of the alteration products found in the near surface epithermal environment to those thought to exist in martian soils sulfates iron oxyhydroxides amorphous silica however the unique chemical composition of secondary products formed by la alteration may make detection of recent hydrothermal alteration of evolved basaltic rocks more straightforward in addition alteration in terrestrial epithermal environments associated with mafic to intermediate volcanic rocks generally produces abundant sulfides and kaolinite two potentially unique mineral phases which might also indicate the presence of active or extinct hydrothermal systems

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

emission spectroscopy of clay minerals and evidence for poorly crystalline aluminosilicates on mars from thermal emission spectrometer data 1 to understand the aqueous history of mars it is critical to constrain the alteration mineralogy of the martian surface previously published analyses of thermal infrared 6 25 m remote sensing data of mars suggest that dark regions have 15 20 clay minerals however near infrared 1 3 m spectral results generally do not identify widespread clay minerals thermal infrared detections of clays on mars are difficult to interpret owing in part to the relative paucity of published spectral analyses of clay minerals and clay bearing materials using similar spectra thermal infrared emission spectra in this study we present an analysis of the thermal emission spectral features 6 25 m or 400 1650 cm 1 of a suite of clay mineral reference materials and clay bearing rocks linking their spectral features to the crystal chemical properties of the clays on the basis of this context provided by the emission spectral analysis of clay minerals and clay bearing rocks we reconsider the evidence for clay minerals on mars from thermal emission spectrometer tes results we propose that global scale clay abundances determined from tes probably represent a geologically significant surface component though they may actually correspond to poorly crystalline aluminosilicates with similar si o ratios to clay minerals 0 3 0 4 rather than well crystalline clays if clay minerals or clay like materials on mars are poorly crystalline and or dessicated they may be detectable in the thermal infrared but not easily detected with near infrared data sets

global investigation of olivine on mars insights into crust and mantle compositions 1 we present the distribution of olivine on mars derived from spectral parameters based on the 1 m olivine absorption band the olivine can be defined with respect to two spectral end members type 1 corresponds to olivine with low iron content and or small grain size and or small abundance and type 2 which corresponds to olivine with higher iron content and or larger grain size and or larger abundance the spatial and statistical analysis of the global olivine distribution points out five major geological settings where olivine is detected 1 early hesperian olivine bearing smooth crater floors and flat intercrater plains throughout the southern highlands 2 olivine deposits around the three main basins argyre hellas and isidis 3 olivine in intercrater dunes crater ejecta or extended deposits in the northern plains 4 olivine associated with outcrops and sand in the floor of valles marineris and 5 olivine bearing butte outcrops in the vicinity of hellas the geological context the age and the composition of the olivine detections associated with these five major geological settings are detailed their origin and the implication of their occurrence on the composition of the martian mantle and crust as well as on the evolution of mars volcanism are discussed

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

mineralogical composition of sands in meridiani planum determined from mars exploration rover data and comparison to orbital measurements constraints on the mineralogical composition of low albedo low sulfur sands at meridiani planum are determined from mars exploration rover mer opportunity miniature thermal emission spectrometer mini tes mossbauer and alpha proton x ray spectrometer measurements results of this work show that the sand is olivine basaltic in composition with minor amounts of sulfate and a high silica phase glass or secondary amorphous silica measurements from all three instruments indicate that pyroxene is twice as abundant as olivine and that the pyroxene composition is dominated by the low calcium variety the volume abundance of olivine is constrained to be 10 15 results from detailed analyses of mer data are used to ground truth the spectral emissivity and mineral abundances derived from orbit with mars global surveyor tes data tes derived mineral abundances are within 5 of those derived from mer data which is generally within the statistical errors associated with tes derived phase abundances the agreement lends support to global and regional scale variations in mineralogical composition determined from tes data in previous studies an alternative method of least squares minimization is used for modeling the tes and mini tes data the benefits of this method are demonstrated by comparison with conventional least squares techniques previously used by tes data users

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

millochau crater mars infilling and erosion of an ancient highland impact crater the geology and stratigraphy of millochau crater 21 4 s 275 w located in the highlands of tyrrhena terra mars are documented through geomorphic analyses and geologic mapping crater size frequency distributions and superposition relationships are used to constrain relative ages of geologic units and determine the timing and duration of the geologic processes that modified millochau rim materials and emplaced deposits on millochau s floor crater size frequency distributions show a middle noachian age for rim materials and middle noachian to early hesperian ages for most of the interior deposits valley networks and gullies incised within millochau s rim materials and interior wall respectively indicate fluvial activity was an important erosional process millochau contains an interior plateau offset northeast of millochau s center which rises up to 400 m above the surrounding crater floor and slopes downward to the south and west layers exposed along the northern and eastern scarp boundaries of the plateau are tens to hundreds of meters thick and laterally continuous in moc images these layers suggest most materials within millochau were emplaced by sedimentary processes e g fluvial or eolian with the potential for lacustrine deposition in shallow transient bodies of water and contributions of volcanic airfall mass wasting may have also contributed significant quantities of material to millochau s interior especially to the deposits surrounding the plateau superposition relationships combined with impact crater statistics indicate that most deposition and erosion of millochau s interior deposits is ancient which implies that fluvial activity in this part of tyrrhena terra is much older than in the eastern hellas region eolian processes mobilized sediment to form complicated patterns of long and short wavelength dunes whose emplacement is controlled by local topography these deposits are some of the youngest within millochau amazonian and eolian modification may be ongoing

knobby terrain on ancient volcanoes as an indication of dominant early explosive volcanism on mars determining if the mechanically weak materials of the upper crust are products of early explosive volcanism or generated by modification of extensive effusive lava flows is important for understanding the geologic and thermal history of mars we examined 75 recently identified preserved ancient volcanoes whose eruption styles are representative of early volcanism we describe a unique knobby terrain that is associated with 17 of these volcanoes this newly identified terrain is characterized by a combination of high resolution images and thermophysical and thermal infrared hyperspectral data the morphology characteristics of these knobby terrains are similar to terrestrial eroded ignimbrites and the thermophysical properties indicate that they are composed of unconsolidated fine grained materials the spectral analysis indicates that they experienced some aqueous alteration we explain the knobby terrain associated with these ancient volcanoes as the products of an early explosive volcanic phase in martian history followed by subsequent modification of these deposits

the particle size of martian aeolian dunes the effective particle size of unconsolidated materials on the martian surface can be determined from thermal inertia due to a pore size dependence of thermal conductivity at martian atmospheric pressures because dunes consist of a narrow range of well sorted unconsolidated particles they provide for a test of the relationship between particle size and thermal inertia calculated from midinfrared emission data for the martian surface we use two independent approaches first thermal inertia data indicate that martian dunes have an average particle size of about 500 100 m or medium to coarse sand second we determine expected dune particle sizes from grain trajectory calculations and the particle size transition from suspension to saltation on earth the transition occurs for a grain when the ratio of the terminal fall velocity to the wind friction speed u t is near unity for grains at u t this occurs at about 52 m terrestrial dune sands have a mean of 250 m and are composed entirely of grains 52 m the corresponding martian transition grain size is about 210 m suggesting that martian dunes should be significantly coarser than terrestrial dunes grain saltation path length as a function of particle size also shows that under martian conditions larger grains than on earth will become suspended both approaches indicate that martian dune sand should be coarser than terrestrial dune sand thus while terrestrial dune grains are in the fine to medium sand range the average martian dune sediments are probably medium to coarse sands these results closely match the grain sizes determined from thermal inertia models providing the first direct test of the validity of these models for actual martian surface materials

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

evidence for episodic alluvial fan formation in far western terra tyrrhena mars a late noachian aged alluvial fan complex within harris crater in far western terra tyrrhena mars is comprised of two well defined source regions and associated discrete depositional lobes three fan units were recognized based on common morphological characteristics thermal properties and spectral signatures although the entire fan complex has been subjected to extensive erosional degradation the preserved morphologies record episodic fan formation and indicate the type of flow processes that occurred the bulk of the fan surface has morphology consistent with fluvial emplacement while one fan unit exhibits a rugged surface texture with boulders consistent with a debris flow this transition from fluvial to late stage debris flow s suggests a decline in available water and or change in sediment supply the thermal inertia values obtained for all three fan surface units mean values ranged from 318 to 344 j m 2 k

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 1 determination of mineralogy chemistry and classification strategies we have examined and applied existing classification schemes for volcanic rocks and developed new schemes using thermal emission spectra of terrestrial volcanic rocks laboratory thermal infrared spectra 5 25 m at 2 cm 1 spectral sampling deconvolved modal mineralogies and derived mineral and bulk rock chemistries were used to distinguish basalt basaltic andesite andesite and dacite modal mineralogies derived from linear deconvolution of terrestrial volcanic rocks were compared to modes measured by an electron microprobe phase mapping technique to determine the accuracy of linear deconvolution in modeling specific mineral abundances one standard deviations of the absolute differences between modeled and measured mineral abundances range from 2 4 to 12 2 vol with an average standard deviation of 4 8 vol being in agreement with average uncertainties calculated in previous studies weighted average compositions of feldspars in the deconvolution generally overlap the measured ranges of plagioclase compositions and the presence of low calcium and high calcium pyroxenes was correctly identified bulk chemistries of volcanic rocks were derived with a relatively high degree of accuracy 1 standard deviations ranging from 0 4 to 2 6 vol by combining the compositions of spectrally modeled phases in proportion to their relative abundances in a particular sample these data were collectively used to examine existing and develop new volcanic rock classification schemes however no single classification scheme was effective in accurately classifying all samples multiple steps of classification were required to distinguish volcanic rocks reflecting the mineralogic diversity and continuum of compositions that exists in volcanic rock types in a companion paper hamilton et al this issue these schemes are applied to the classification of martian surface compositions

dipping seismic reflectors electrically conductive zones and trapped water in the crust over a subducting plate the lithoprobe program across the northern cascadia subduction zone at vancouver island has obtained geophysical data that suggest a dipping zone of trapped free pore water in the overlying continental crust land and marine multichannel seismic reflection profiles show several bands of reflectors the primary one at a depth of about 30 km is about 5 km thick dips inland and appears to coincide with an electrically conductive layer defined by magnetotelluric data the downgoing oceanic crust is imaged as a thin reflector dipping at about 15 and 10 km deeper than the primary reflector a location that is consistent with seismicity and seismic refraction data both the reflectors and the conductor have been modeled by near horizontal lamellae with 1 4 saline water porosity detailed geothermal measurements defining heat flow that decreases inland indicate that the dipping bands are nearly isothermal at a temperature of 400 500 c it is suggested that free water generated by dehydration of the downgoing oceanic plate migrates upward until reduced temperature results in hydration reactions and mineral precipitation that forms an impermeable barrier low vertical permeability is required to keep the water from separating to the top of the layer this can be reconciled with the low electrical resistivity if pore interconnection is through thin grain boundary tubes as predicted by theoretical equilibrium pore geometry although very small effective grain size is necessary an abrupt transition from high permeability to very low permeability is predicted at a several percent porosity in agreement with the modeled porosity such pore geometry with low permeability may be restricted to temperatures above about 400 c i e in greenschist to amphibolite facies conditions where grains will deform to equilibrium geometry and cracks are annealed the region above the reflective and conductive band is estimated to be within blueschist conditions consistent with the inferred high seismic velocity from refraction data and high density from gravity data

geologic characteristics of relatively high thermal inertia intracrater deposits in southwestern margaritifer terra mars 1 twenty one craters in southwestern margaritifer terra exhibit unusually warm interior deposits in nighttime thermal emission imaging system themis infrared images these deposits exhibit nighttime temperatures as high as 223 k and are 5 18 warmer than the surrounding plain thermal inertia values derived from thermal emission spectrometer tes data are greater for the deposits than the plains with maximum values between 455 and 675 j m 2 k 1 s 1 2 analysis of themis thermal inertia data having nearly an order of magnitude better spatial resolution shows that the deposits can have a thermal inertia as high as 1060 j m 2 k 1 s 1 2 albedo and dust cover index values suggest that both the deposits and the surrounding region are generally dust free compositional analysis with tes and themis data show that though a small number of the deposits may have isolated compositional differences the majority of the deposits have a composition similar to that of the surrounding plains the geomorphology of the craters as viewed from mars orbiter camera moc images shows that the deposits are coherent units rather than sand deposits an observation that is consistent with the relatively high thermal inertia values if these deposits are coherent rock units as the results of our study suggest possible methods of formation include emplacement of primary igneous material or lithification of sediments from surrounding terrain

the global topography of mars and implications for surface evolution elevations measured by the mars orbiter laser altimeter have yielded a high accuracy global map of the topography of mars dominant features include the low northern hemisphere the tharsis province and the hellas impact basin the northern hemisphere depression is primarily a long wavelength effect that has been shaped by an internal mechanism the topography of tharsis consists of two broad rises material excavated from hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary the present topography has three major drainage centers with the northern lowlands being the largest the two polar cap volumes yield an upper limit of the present surface water inventory of 3 2 to 4 7 million cubic kilometers

aeolian processes in proctor crater on mars sedimentary history as analyzed from multiple data sets 1 proctor crater is a 150 km diameter crater in noachis terra within the southern highlands of mars the analysis leading to the sedimentary history incorporates several data sets including imagery elevation composition and thermal inertia mostly from the mars global surveyor mission the resulting stratigraphy reveals that the sedimentary history of proctor crater has involved a complex interaction of accumulating and eroding sedimentation aeolian features spanning much of the history of the crater interior dominate its surface including large erosional pits stratified beds of aeolian sediment sand dunes erosional and depositional streaks dust devil tracks and small bright bed forms that are probably granule ripples long ago up to 450 m of layered sediment filled the crater basin now exposed in eroded pits on the crater floor these sediments are probably part of an ancient deposit of aeolian volcaniclastic material since then some quantity of this material has been eroded from the top layers of the strata small bright dune forms lie stratigraphically beneath the large dark dune field relative to the large dark dunes the bright bed forms are immobile although in places their orientations are clearly influenced by the presence of the larger dunes their prevalence in the crater and their lack of compositional and thermal distinctiveness relative to the crater floor suggests that these features were produced locally from the eroding basin fill dust devil tracks form during the spring and summer following a west southwesterly wind early in the spring the dust devils are largely restricted to dark patches of sand as the summer approaches dust devil tracks become more plentiful and spread to the rest of the crater floor indicating that the entire region acquires an annual deposit of dust that is revealed by seasonal dust devils the dark dunes contain few dust devil tracks suggesting that accumulated dust is swept away directly by saltation rather than by the passage of dust devils spectral deconvolution indicates that the dark dunes have infrared spectra consistent with basalt like materials the average thermal inertia calculated from thermal emission spectrometer bolometric temperatures is 277 17 j m 2 s 0 5 k 1 leading to an effective grain size of 740 170 mm which is consistent with coarse sand and within the range expected for martian sand the coarse sand that composes the large dune field may have originated from outside the crater saltating in from the southwest most of the transport pathway that delivered this sand to the dune field has since been eroded away or buried the sand was transported to the east center of the crater floor where beneath the present day dunes a 50 m high mound of sand has accumulated dune slip faces indicate a wind regime consisting of three opposing winds some of these wind directions are correlated with the orientations of dust devil tracks and bright bed forms the combination of a tall mound of sand and three opposing winds is consistent with a convergent wind regime which produces the large reversing transverse and star dunes that dominate the dune field the dark dunes have both active slip faces and seemingly inactive slip faces suggesting that the dunes vary spatially in their relative activity nevertheless the aeolian activity that has dominated the history of proctor crater still continues today index terms 5415 planetology solid surface planets erosion and weathering 5470 planetology solid surface planets surface materials and properties 5410 planetology solid surface planets