thermospheric circulation temperature and compositional structure of the southern hemisphere polar cap during october november 1981 thermospheric temperature composition and winds at f region heights over the southern hemisphere polar cap have been measured by the dynamics explorer 2 de 2 satellite during october november 1981 perigee of the de 2 satellite during this period was over the southern hemisphere polar cap and measurements made along 0900 2100 local time polar passes are used to determine the average universal time dependence of thermospheric properties for this local time slice the f region wind vector is derived from the meridional wind component measured by the fabry perot interferometer fpi and the zonal wind component measured by the wind and temperature spectrometer wats instruments on board de 2 the neutral gas temperature is derived from fpi and wats measurements and the compositional structure is determined from the neutral atmosphere composition spectrometer instrument the measured temperature composition and winds along the 0900 2100 local time polar passes all display a universal time dependence that is due to the displacement between geomagnetic and geographic poles the temperature and molecular nitrogen densities are enhanced and the atomic oxygen density is reduced in the magnetic polar cap in comparison with lower latitude regions the neutral wind pattern follows the pattern of ion drift associated with magnetospheric convection the national center for atmospheric research thermospheric general circulation model tgcm is used to calculate the temperature composition and winds over the southern hemisphere polar cap region for conditions similar to those of october 1981 the tgcm includes displaced geomagnetic poles the temperature composition and winds are determined along the de 2 satellite track for various universal times the calculated winds are in general agreement with the observed winds both having a two cell pattern of magnetospheric convection the calculated and observed composition patterns are also in general agreement with predictions made by the mass spectrometer and incoherent scatter radar 1983 empirical model when models and observations are normalized to the same constant pressure surface the calculated and observed maximum compositional variations in the magnetic polar cap occur near 0900 ut when the dawn sector of the auroral oval passes over the south geographic pole the overall pattern of the calculated temperature variation is similar to that observed except for the period between 1300 and 1500 ut better agreement with temperature in this time range is obtained with the inclusion of auroral particle precipitation within the magnetospheric cusp

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

the composition and evolution of the continental crust rare earth element evidence from sedimentary rocks the composition of the present day upper crust inferred from the uniformity of sedimentary rock r e e rare earth element patterns is close to that of granodiorite a revised andesite model is used to obtain total crustal composition the lower crust is the composition remaining assuming that the upper crust one third of the total is derived from intracrustal partial melting the upper crustal r e e pattern has pronounced eu depletion eu eu 0 64 the lower crustal pattern has eu enrichment eu eu 1 17 and the total crust has no eu anomaly relative to chondritic abundances the eu depletion in the upper crust is attributed to retention of eu in plagioclase in the lower crust because plagioclase is not stable below 40 km 10 kbar the anomaly is intracrustal in origin the archaean upper crust has a different r e e pattern to that of the present day upper crust being lower in total r e e and la yb ratios and lacking an eu anomaly these data are used to infer the archaean upper crustal composition which resembles that of the present day total crust except that ni and cr contents are higher the archaean crustal composition can be modelled by a mixture of tholeiites and tonalite trondhjemites the latter have steep light r e e enriched heavy r e e depleted patterns consistent with equilibration with garnet and hence probable mantle derivation there is little reason to suppose that the archaean lower crust was different in composition from the upper crust except locally where partial melting episodes occurred the r e e evidence is consistent with isotopic and geological evidence for a low continental growth rate in the early archaean a massive increase to about 70 of the total crust between about 3000 and 2500 ma b p and a slow increase until the present day the change from archaean to post archaean r e e patterns in the upper crust is not isochronous but is reflected in the sedimentary rock r e e patterns at differing times in different continents on the basis of a model composition for the mantle 36 of the potassium 30 of uranium 15 of lanthanum and 3 of ytterbium are concentrated in the present continental crust this enrichment is related to ionic size and valency differences from common mantle cations e g mg fe pre 3 9 ga b p crusts were obliterated by meteorite bombardment no geochemical evidence exists for primordial anorthositic sialic or mafic crusts

early views of the martian surface from the mars orbiter camera of mars global surveyor high resolution images of the martian surface at scales of a few meters show ubiquitous erosional and depositional eolian landforms dunes sandsheets and drifts are prevalent and exhibit a range of morphology composition inferred from albedo and age as seen in occurrences of different dune orientations at the same location steep walls of topographic depressions such as canyons valleys and impact craters show the martian crust to be stratified at scales of a few tens of meters the south polar layered terrain and superposed permanent ice cap display diverse surface textures that may reflect the complex interplay of volatile and non volatile components low resolution regional views of the planet provide synoptic observations of polar cap retreat condensate clouds and the lifecycle of local and regional dust storms

present day erosion of martian polar terrain by the seasonal co 2 jets abstract here we report on the detection of new dendritic troughs created by the seasonal co2 jet activity over several martian years according to kieffers hypothesis kieffer 2007 in martian polar areas seasonal co2 ice sublimation creates gas jets that deposit fans of mineral dust and sand on top of the co2 ice these jets and the related sub ice gas flows are believed to carve troughs in the underlying polar deposits which after multiple repetitions of this process throughout martian spring seasons create araneiform terrains the high resolution imaging science experiment hirise on the mars reconnaissance orbiter mro detected the new troughs during its campaign for seasonal monitoring of the polar areas the newly detected dendritic troughs are small shallow branching troughs 1 4 m wide similar to the seasonal furrows previously detected in the northern hemisphere bourke 2013 the essential difference between the new troughs and furrows lies in the fact that the troughs in the south are persistent while the northern furrows are erased each martian year by the sand movement due to summer winds from year to year the new southern troughs extend and develop new tributaries and their overall geometry turns from linear to dendritic a characteristic shared with araneiform terrains we believe that furrows have the same origin as the southern dendritic troughs but do not develop into dendritic shapes because of the high mobility of the dune material into which they are carved several locations where new dendritic troughs are observed lie in the vicinity of dunes this gives us an observational indication that presence of erosive sand material is an important factor in creating or at least starting erosive processes that lead to the formation of dendritic troughs by extrapolation the same mechanism should be acting to create the much larger araneiform terrains detection of the present day erosion working in polar areas and creating new topographical features is important for understanding of the processes that shape polar areas several years of hirise observations provide us with the information about the current rate of erosion and hence help estimate minimum ages of the araneiforms and the surface into which they are carved to be 1 3 103 martian years

trajectories of thermospheric air parcels flowing over alaska reconstructed from ground based wind measurements it is widely presumed that the convective stability and enormous kinematic viscosity of earth s upper thermosphere hinders development of both horizontal and vertical wind shears and other gradients any strong local structure over scale sizes of several hundreds of kilometers that might somehow form would be expected to dissipate rapidly air flow in such an atmosphere should be relatively simple and transport effects only slowly disperse and mix air masses however our observations show that wind fields in earth s thermosphere have much more local scale structure than usually predicated by current modeling techniques at least at auroral latitudes they complicate air parcel trajectories enormously relative to typical expectations for tracing air parcels we used wind measurements of an all sky scanning doppler fabry perot interferometer and reconstructed time resolved two dimensional maps of the horizontal vector wind field to infer forward and backward air parcel trajectories over time this is the first comprehensive study to visualize the complex motions of thermospheric air parcels carried through the actual observed local scale structures in the high latitude winds results show that thermospheric air parcel transport is a very difficult observational problem because the trajectories followed are very sensitive to the detailed features of the driving wind field to reconstruct the actual motion of a given air parcel requires wind measurements everywhere along the trajectory followed with spatial resolutions of 100 km or less and temporal resolutions of a few minutes or better understanding such transport is important for example in predicting the global scale impacts of aurorally generated composition perturbations

meridional neutral winds in the thermosphere at arecibo simultaneous incoherent scatter and airglow observations simultaneous measurements of ion and neutral wind velocities have been obtained at arecibo puerto rico on several nights in both the summer and winter seasons the diffusion velocity of o calculated in an analysis by using the accepted value for the ambipolar diffusion coefficient and the msis model atmosphere is found to be in fairly close agreement with the observations incoherent scatter radar data have also been used to derive height profiles of the meridional neutral wind velocity in the spring and summer months the meridional wind is strongest near 2100 ast with a southward velocity ranging from 50 100 m s 1 at about 0100 ast the midnight descent of the f layer occurs in association with a slackening or sometimes a reversal of the meridional wind in general the meridional wind is fairly constant with altitude however prior to midnight in the spring and summer months contours of constant velocity are often observed to slope downward with increasing time some degree of vertical wind shear is often observed between 0200 and 0500 ast as well in the winter months meridional wind velocities are lower and the nocturnal variation of the wind field is less pronounced than it is at other seasons

araneiform terrain formation in angustus labyrinthus mars abstract the south polar area of mars exhibits an abundance of distinctive and exotic landforms most of which occur within the region covered by the seasonal co2 cap araneiform terrain also referred to as terrain covered by spiders is one of these unusual geomorphic features resulting from co2 sublimation driven seasonal erosion the high resolution imaging science experiment hirise on board nasa s mars reconnaissance orbiter mro spacecraft has repeatedly imaged angustus labyrinthus informally known as the inca city region 81 s 296 e over a period of four martian years showing a variety of classic polar features associated with sublimation and deposition including spiders we mapped the spiders spatial distribution in the inca city region and classified them in view of their morphological and topographic characteristics into four types fat thin half and elongated spiders the latter two are reported for the first time in this work we find that the formation mechanisms of half and elongated spiders were substantially influenced by ridge boundaries topography and pre existing linear depressions respectively based on our observations we extend the conceptual model of spider erosion explaining new elements of the spider formation process we interpret the causes of deviating araneiform species from thin spiders i e half elongated and fat spiders in the context of the extended model we consider the migration of pressurized co2 through the porous substrate towards breaches in the ice cover and the influence of the substrate s cohesive strength on the development of spider legs analysis of the spatial distribution of a fat spider population revealed that the initiation locations of spiders are not random but more evenly spaced indicating the existence of an inhibited zone around a newly formed spider consistent with our interpretations of the formation mechanism our case study in the inca city region provides new understanding in the formation process of basal sublimation driven features and thus offers new insight into polar surface processes

observations of the south seasonal cap of mars during recession in 2004 2006 by the omega visible near infrared imaging spectrometer on board mars express 1 the omega visible near infrared imaging spectrometer on board mars express has observed the southern seasonal cap in late 2004 and 2005 and then in the summer of 2006 these observations extended from the period of maximum extension close to the southern winter solstice to the end of the recession at ls 325 the spectral range and spectral resolution of omega make it possible to monitor the extent and effective grain size of co2 ice and h2o ice on the ground the level of contamination of co2 ice and h2o ice by dust and the column density of m sized ice grains in the atmosphere the co2 seasonal cap is very clean and clear in early southern winter contamination by h2o ice spreads eastward from the hellas basin until the southern spring equinox during southern spring and summer there is a very complex evolution in terms of effective grain size of co2 ice and contamination by dust or h2o ice h2o ice does not play a significant role close to the southern summer solstice contamination of co2 ice by h2o ice is only observed close to the end of the recession as well as the few h2o ice patches already reported by bibring et al 2004a these observations have been compared to the results of a general circulation model with good qualitative agreement on the distribution of h2o ice on the surface and in the atmosphere resolving the remaining discrepancies will improve our understanding of the water cycle on mars

quantitative provenance analysis of sediments review and outlook provenance analysis of sediments is aimed at reconstructing the parent rock assemblages of sediments and the climaticphysiographic conditions under which sediments formed inferring sediment provenance from the final product a basin fill is anything but straightforward because the detrital spectrum evolves as the sediment is transported along the pathway from source to basin successful provenance analysis requires that the nature and extent of compositional and textural modifications to the detrital spectrum be recognised if not quantified the history of quantification in sediment provenance studies is summarised and illustrated by tracking two fundamental ideas the concept of the sediment petrological province or petrofacies and the relation between sandstone composition and plate tectonic environment progress in sedimentary provenance analysis has been closely linked with advancements in measurement technology a brief survey of modern data acquisition tools illustrates the possibilities and limitations of modern provenance research an operational definition of quantitative provenance analysis qpa is presented in which the central role of mass balance is acknowledged extension of this definition to include quantitative predictions obtained by forward modelling computer simulation of sediment production as well as methodological improvements in data acquisition and processing is needed to cover likely future developments in qpa the contributions to the special issue quantitative provenance analysis of sediments illustrate the intrinsic multidisciplinarity and rapid expansion of qpa d 2004 elsevier b v all rights reserved

mars south polar spring and summer behavior observed by tes seasonal cap evolution controlled by frost grain size thermal emission spectrometer tes observations of the recession phase of mars south polar cap are used to quantitatively map this recession in both thermal and visual appearance geographically nonuniform behavior interior to the cap is characterized by defining several small regions which exemplify the range of behavior for most of the cap while temperatures remain near the co2 frost point albedos slowly increase with the seasonal rise of the sun then drop rapidly as frost patches disappear over a period of 20 days a cryptic region remains dark and mottled throughout its cold period tes observations are compared with first order theoretical spectra of solid co2 frost with admixtures of dust and h2o the tes spectra indicate that the cryptic region has much larger grained solid co2 than the rest of the cap and that the solid co2 here may be in the form of a slab the mountains of mitchel remain cold and bright well after other areas at comparable latitude apparently as a result of unusually small size of the co2 frost grains we found little evidence for a significant presence of h2o although co2 grain size may be the major difference between these regions incorporated dust is also required to match the observations a self cleaning process carries away the smaller dust grains comparisons with viking observations indicate little difference in the seasonal cycle 12 martian years later the observed radiation balance indicates co2 sublimation budgets of up to 1250 kg m 2 regional atmospheric dust is common localized dust clouds are seen near the edge of the cap prior to the onset of a regional dust storm and interior to the cap during the storm

sublacustrine depositional fans in southwest melas chasma two depositional fan complexes have been identified on the floor of southwest melas chasma the western fan complex is located near the center of an enclosed basin in southwest melas chasma and is composed of multiple lobes with dendritic finger like terminations these fans are very flat and have a morphology unlike any other fan that has been previously identified on mars on the basis of the morphologic similarity of the western fan complex to the mississippi submarine fan complex we suggest that it may be a deep subaqueous fan depositional system there are numerous channels on the surface of the western fan complex and measurements of channel length width and sinuosity are consistent with channels observed on terrestrial submarine fans the eastern melas depositional fans are less well preserved and may be of deltaic or sublacustrine origin recognition of the fans supports earlier suggestions for the presence of a former lake in melas chasma and indicates that a significant body of water was present and stable at the surface of mars for at least 10 2 to 10 4 years

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

formation of martian araneiforms by gas driven erosion of granular material 1 sublimation at the lower surface of a seasonal sheet of translucent co2 ice at high southern latitudes during the martian spring and rapid outflow of the co2 gas generated in this manner through holes in the ice has been proposed as the origin of dendritic 100 m 1 km scale branched channels known as spiders or araneiforms and dark dust fans deposited on top of the ice we show that patterns very similar to araneiforms are formed in a hele shaw cell filled with an unconsolidated granular material by slowly deforming the upper wall upward and allowing it to return rapidly to its original position to drive air and entrained particles through a small hole in the upper wall straight braided and quasiperiodic oscillating channels unlike meandering channels on earth were also formed

compact reconnaissance imaging spectrometer for mars crism south polar mapping first mars year of observations 1 we report on mapping of the south polar region of mars using data from the compact reconnaissance imaging spectrometer for mars crism instrument our observations have led to the following discoveries 1 water ice is present in the form of pole circling clouds originating from the circum hellas region beginning prior to ls 162 and diminishing markedly at ls 200 204 2 it has previously been inferred by thermal infrared observations by titus et al 2003 and co2 h2o mixture spectral models by langevin et al 2007 that surface water ice was present in the cryptic region in the final stages of sublimation the high resolution of crism has revealed regions where only water ice is present not a co2 h2o ice mixture this water ice disappears completely by ls 252 and may be the source of water vapor observed by crism in southern latitudes between ls 240 260 by m smith et al 2009 3 we have estimated surface co2 ice grain size distributions for the south pole residual cap sprc and the seasonal co2 ice cap that covers it throughout summer spring and summer our analysis suggests that grain sizes peak at ls 191 199 with an apparent grain size of 7 1 cm by the end of the summer period our analysis demonstrates minimum apparent grain sizes of 5 1 mm predominate in the sprc 4 fine grained co2 ice condenses from ls 0 40 and extends symmetrically away from the geographic pole extending beyond 80 s by ls 4 10 no evidence for unusual co2 depositional processes in the cryptic region is observed up to ls 16

thermospheric dynamics at the south pole a self aligning fabry perot spectrometer has been installed at amundsen scott station antarctica geographic south pole and has been used to determine neutral upper thermosphere winds and temperatures obtained from the measurement of the doppler shift and doppler width of the line profiles of the oi 15 867 k 630 nm line emission during the austral winter of 1989 april 1989 to september 1989 these first ground based measurements of f region neutral dynamics at the south pole show a rich variety of dynamic phenomena and strong couplings with the ionospheric plasma data for two contrasting days in april 1989 are presented here the data of april 23 ut illustrate the diurnal variations of winds and temperatures during geomagnetic quiet to moderate conditions while the data of april 27 ut illustrate diurnal variations during geomagnetically disturbed periods these data are compared with the average pattern obtained at a similar geomagnetic latitude and conditions but in the northern hemisphere longyearbyen spitsbergen and with predictions of the average dynamics in the south pole region made by the ncar thermosphere ionosphere general circulation model tigcm the measured winds at the south pole have a stronger prevailing westward component in its diurnal cycle than is either observed at longyearbyen in the northern hemisphere or predicted at south pole by the tigcm

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

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

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

hirise observations of gas sublimation driven activity in mars southern polar regions iii models of processes involving translucent ice abstract enigmatic surface features known as spiders found at high southern martian latitudes are probably caused by sublimation driven erosion under the seasonal carbon dioxide ice cap the mars reconnaissance orbiter mro high resolution imaging science experiment hirise has imaged this terrain in unprecedented details throughout southern spring it has been postulated kieffer h h titus t n mullins k f christensen p r 2000 j geophys res 105 9653 9700 that translucent co 2 slab ice traps gas sublimating at the ice surface boundary wherever the pressure is released the escaping gas jet entrains loose surface material and carries it to the top of the ice where it is carried downslope and or downwind and deposited in a fan shape here we model two stages of this scenario first the cleaning of co 2 slab ice from dust and then the breaking of the slab ice plate under the pressure built below it by subliming ice our modeling results and analysis of hirise images support the gas jet hypothesis and show that outbursts happen very early in spring

opaline silica in young deposits on mars high spatial and spectral resolution reflectance data acquired by the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism instrument reveal the presence of h 2o and sioh bearing phases on the martian surface the spectra are most consistent with opaline silica and glass altered to various degrees confirming predictions based on geochernicall experiments and models that amorphous silica should be a common weathering product of the basaltic martian crust these materials are associated with hydrated fe sulfates including h 3o bearing jarosite and are found in finely stratified deposits exposed on the floor of and on the plains surrounding the valles marineris canyon system stratigraphic relationships place the formation age of these deposits in the late hesperian or possibly the amazonian implying that aqueous alteration continued to be an important and regionally extensive process on mars during that time

global features of the disturbance winds during storm time deduced from champ observations a wind driven disturbance dynamo has been postulated many decades ago but due to the sparseness of thermospheric wind measurements details of the phenomena could not be investigated in this study we use the champ zonal wind observations from 2001 to 2005 to investigate the global features of the disturbance winds during magnetically disturbed periods the disturbance zonal wind is mainly westward which increases with magnetic activity and latitude at subauroral region the westward zonal wind is strongly enhanced in the magnetic local time mlt sector from afternoon to midnight which we relate to the plasma drift within the subauroral polarization streams at middle and low latitudes the disturbance zonal wind is largely independent of season peak values of the disturbance zonal wind occur at different mlts for different latitudes that is around 1800 mlt at subauroal region with average values of about 200 m s around 2300 mlt at middle latitudes with average values of about 80 m s and around 0300 mlt at low latitudes with average values up to 50 m s the shift of the peak values of the westward disturbance zonal wind in local time at different latitudes could be considered as a response of the disturbance wind when it propagates from high to low latitudes further by applying for the first time a superposed epoch analysis we show that the disturbance zonal wind responds with a delay to the sudden changes of solar wind input which is different for the various latitudinal ranges the propagation time of disturbance wind from the auroral region to the equator is about 3 4 h this is consistent with the speed of traveling atmospheric disturbances based on champ observations we try to illustrate the whole chain of processes from the solar wind driving to the ionospheric effects at lower latitudes

mars remote sensing analog studies in the badwater basin death valley california 1 the search for evaporites on mars has important implications for the role that liquid water has played in shaping the planet s geologic climatic and potential biologic history orbital investigations of surface mineralogy are crucial to this exploration effort with the exception of coarse grained gray hematite at a restricted number of sites and trace amounts of carbonate in globally distributed dust deposits the thermal emission spectrometer tes and thermal emission imaging system themis instruments have yet to find widespread mineralogical evidence of aqueously formed minerals this may reflect the coarse spatial resolution of tes 3 5 km pixel and low spectral resolution of themis 10 bands between 6 5 and 14 5 m spectral mapping in the badwater basin death valley california was conducted to better understand the capabilities of tes and themis in detecting evaporite minerals high resolution modis aster airborne simulator master data degraded to tes and themis spatial resolutions were used to evaluate the detection limits of sulfates and carbonates to assess the validity of this spectral remote sensing a quantitative ground truth analysis of surface mineralogy in the badwater basin was performed the analysis was based on thin section petrography x ray diffraction electron microprobe and laboratory and field thermal emission spectrometer analyses taken together the results of all five methods provided enough constraints for a robust interpretation that was in general agreement with the spectral remote sensing mapping study for 90 of the surface samples examined

seasonal dependence of northern high latitude upper thermospheric winds a quiet time climatological study based on ground based and space based measurements this paper investigates the large scale seasonal dependence of geomagnetically quiet time northern high latitude f region thermospheric winds by combining extensive observations from eight ground based optical remote sensing and three space based optical remote sensing and in situ instruments to provide a comprehensive picture of the wind morphology data are assimilated into a seasonal empirical vector wind model as a function of season latitude and local time in magnetic coordinates the model accurately represents the behavior of the constituent data sets there is good general agreement among the various data sets but there are some major offsets between goce and the other data sets especially on the duskside the assimilated wind patterns exhibit a strong and large duskside anticyclonic circulation cell sharp latitudinal gradients in the duskside auroral zone strong antisunward winds in the polar cap and a weaker tendency toward a dawnside cyclonic circulation cell the high latitude wind system shows a progressive intensification of wind patterns from winter to equinox to summer the latitudinal extent of the duskside circulation cell does not depend strongly on season zonal winds show a mainly diurnal variation two extrema around polar and middle latitudes and semidiurnal variation four extrema at auroral latitudes meridional winds are primarily diurnal at all high latitudes the strength of zonal winds channeling through the auroral zone on the duskside is strongest in the summer season the vorticity of the wind pattern increases from winter to summer whereas divergence is maximum in equinox in all three seasons divergence is weaker than vorticity

martian layered fluvial deposits implications for noachian climate scenarios 1 fluvial deposits in a basin north of holden crater exhibiting a sinuous anabranching pattern are of deltaic or fan origin channel width and meander wavelength indicate persistent flow magnitudes of about 700 m3 s if these flows were produced by quasi periodic climate episodes involving typical terrestrial style precipitation the deposit required thousands to millions of years to accumulate however a scenario of deposition during a few short episodes of constant heavy precipitation resulting from large impacts cannot be excluded

planetary surface dating from crater size frequency distribution measurements spatial randomness and clustering we describe a quantitative procedure to measure the degree of clustering in an observed crater population relative to a series of randomly distributed populations we split the population by according to crater size to be able to identify clustering at different scales and find that a clustering analysis based on the mean 2nd closest neighbour distance measure more closely corresponds to visual interpretations of the spatial configuration than the mean closest neighbour distance standard deviation of adjacent area is found in certain cases to be an even more sensitive measure the technique is demonstrated for two sites on mars we were able to make use of a case where the spatial distribution was less clustered than random to reveal the transition between a crater population superimposed on a lava flow and that belonging to an underlying unit in general this type of analysis may give a better insight into the post formation modification of studied units enabling a more precise classification of which sizes of craters derive from the original accumulation population and which from areas resurfaced by later modification events consequentially improving the accuracy of dating resurfacing events clustering analysis is thus an additional tool for understanding the structure of a crater population and the effects causing an observed population to differ from an ideal one

cold jets in the martian polar caps 1 mars seasonal polar caps display dark ice local darker spots aligned elongate patches and radially dendritic forms that reverse albedo contrast the unexpected variety and sequence of these features are explained on the basis of processes involving co2 dust sand and h2o these processes are largely related to the atmosphere being near its saturation temperature and they have few terrestrial analogies in the simplest case the 1 m thick seasonal cap initially dusty cleans itself and becomes translucent after sunrise and is impermeable over extensive regions except for local vents the slab ice sublimates at the base and is levitated on high pressure gas causing humidity exchange with deeper layers subslab gas converging toward the vents erodes channels in the soil and ejects this material in high velocity jets recent spectral observations indicate great variety in the details

sublimation of mars s southern seasonal co2 ice cap and the formation of spiders 1 in this paper we define and describe morphological features that have colloquially been termed spiders and map their distribution in the south polar region of mars we show that these features go through a distinct seasonal evolution exhibiting dark plumes and associated fan shaped deposits during the local defrosting of the seasonal cap we have documented the seasonal evolution of the cryptic region and have found that spiders only occur within this terrain these observations are consistent with a geyser like model for spider formation association with the transparent cryptic portion of the seasonal cap is consistent with basal sublimation and the resulting venting of co2 gas also consistent with such venting is the observation of dark fan shaped deposits apparently emanating from spider centers spiders are additionally confined to the polar layered deposits presumably due to the poorly consolidated and easily eroded nature of their upper surface

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

mean neutral circulation in the winter polar f region direct measurements of the f region neutral wind field in the northern winter hemisphere during late november and december 1981 were obtained by using the dynamics explorer de 2 satellite and the network of ground based fabry perot interferometers sited in the north american and scandinavian sectors all available data for the study period have been collated and averaged according to universal time ut to provide a global scale experimental determination of the mean or average circulation in the northern hemisphere f region the data are organized into ut bins and are presented as a sequence of 12 climate maps depicting the neutral wind system at 2 hour ut intervals during a mean day in december 1981 the data set provides the most comprehensive experimental measure of the global scale high latitude thermospheric circulation yet reported the averaged measurements from the different instruments exhibit a satisfactory degree of internal consistency when viewed in terms of the global scale neutral flow a detailed comparison with the predictions of the ncar thermospheric general circulation model is discussed the model predictions are in good general agreement with the ut dependent mean circulation reproducing the basic control of the high latitude neutral wind system by ion drag forces modulated in ut as a result of the offset between the geomagnetic and geographic poles differences in flow directions and velocities between model predictions and experimental results are ascribed to natural variability in the thermosphere as well as to the use in the model of a less than fully realistic symmetric ion convection geometry and density distribution the two basic conclusions of this study are that 1 instrumentation deployed around the globe and on satellites can provide powerful composite data sets that can be used to monitor global scale mean thermospheric climatology and that 2 the mean thermospheric f region neutral circulation for the given geophysical situation solar maximum near solstice can be modeled reasonably well using a three dimensional time dependent model with appropriate parameterizations for the energy and momentum inputs

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

hirise observations of gas sublimation driven activity in mars southern polar regions i erosion of the surface the high resolution imaging science experiment hirise on the mars reconnaissance orbiter mro has imaged the sublimation of mars seasonal co2 polar cap with unprecedented detail for one complete martian southern spring in some areas of the surface beneath the conformal coating of seasonal ice radiallyorganized channels are connected in spidery patterns the process of formation of this terrain erosion by gas from subliming seasonal ice has no earthly analog the new capabilities high resolution color and stereo images of hirise enable detailed study of this enigmatic terrain two sites are analyzed in detail one within an area expected to have translucent seasonal co2 ice and the other site outside that region stereo anaglyphs show that some channels grow larger as they go uphill implicating gas rather than liquid as the erosive agent dark fans of material from the substrate are observed draped over the seasonal ice and this material collects in thin to thick layers in the channels possibly choking off gas flow in subsequent years resulting in inactive crisscrossing shallow channels in some areas there are very dense networks of channels with similar width and depth and fewer fans emerging later in the season are observed subtle variations in topography affect the channel morphology a new terminology is proposed for the wide variety of erosional features observed

goose bay radar observations of earth reflected atmospheric gravity waves in the high latitude ionosphere in the late fall and early winter the johns hopkins university hf radar at goose bay labrador observes the effects of atmospheric gravity waves on radar transmissions that are obliquely reflected from the ionosphere and subsequently backscattered from the earth s surface the waves exist under a wide variety of geomagnetic conditions however they are particularly noticeable under quiet conditions o le kp le 1 the clearest signatures of the waves are spatially localized enhancements in the backscattered power and quasi periodic fluctuations in the backscatter powers doppler velocities and reflection heights the waves are generally observed during daylight hours and propagate equatorward from regions of high latitude ionospheric backscatter that are located near the ionospheric convection reversal boundary the gravity waves appear to be generated just equatorward of the dayside flow reversal boundary in the vicinity of the auroral electrojet at altitudes of 115 to 135 km and propagate approximately perpendicular to the boundary along azimuths ranging from 156 degree to 180 degree the waves propagate obliquely downward through the lower atmosphere until they are reflected by the earth s surface back into the upper atmosphere the frequencies associated with these gravity waves cover the range of 0 3 to 0 6 mhz with wavelengths of 300more to 500 km and with average phase velocities of 110 to 180 m s the maximum phase speeds are 270 to 300 m s which is slightly less than the speed of sound in the lower atmosphere poleward propagating gravity waves are sometimes observed under disturbed conditions when the polar cap and convection reversal boundary have expanded equatorward less

interannual and seasonal changes in the south seasonal polar cap of mars observations from my 28 31 using marci the mars color imager marci camera on the mars reconnaissance orbiter provides daily synoptic coverage that allows monitoring of seasonal cap retreat and interannual changes that occur between mars years my and over the southern summer we present the first analysis of this data for the southern seasonal cap evolution observed in my 28 29 30 and 31 2 2007 to 07 2013 observation over multiple mars years allows us to compare changes between years as well as longer term evolution of the high albedo deposits at the poles seasonal cap retreat is similar in all years and to retreats observed in other years by both optical and thermal instruments the cryptic terrain has a fairly consistent boundary in each year but numerous small scale variations occur in each my observed additionally numerous small dark deposits are identified outside the classically identified cyptic region including inca city and other locations not previously noted the large water ice outlier is observed to retain seasonal frost the longest outside the polar dome and is also highly variable in each my the development of the cryptic anti cryptic hemispheres is inferred to occur due to albedo variations that develop after dust venting starts and may be caused by recondensation of co2 ice on the brightest and coldest regions controlled by topographic winds ground ice may play a role in which regions develop cryptic terrain as there is no elevation control on either cryptic terrain or the late season brightest deposits

the earth s thermospheric superrotation from dynamics explorer 2 neutral thermospheric zonal winds measured from the wind and temperature experiment on dynamics explorer 2 have been analyzed to provide a measure of the superrotation of the neutral thermosphere the data were averaged in local time in 10 degree bands from the equator to 40 degrees latitude the results show an average wind velocity on the order of 18 m s to the east at the equator and a westward wind of the same magnitude at mid latitudes within the range of altitudes of the data base 200 to 700 km no evidence of any significant altitude dependence was found averaging our data over the latitude bands studied indicates a net corotation of the thermosphere this result is not in agreement with the superrotation value reported by king hele and walker on the basis of satellite drag analysis

no signature of clear co2 ice from the cryptic regions in mars south seasonal polar cap the seasonal polar ice caps of mars are composed mainly of co2 ice a region of low 30 albedo has been observed within the south seasonal cap during early to mid spring the low temperature of this cryptic region has been attributed to a clear slab of nearly pure co2 ice with the low albedo resulting from absorption by the underlying surface here we report near infrared imaging spectroscopy of the south seasonal cap the deep and broad co2 absorption bands that are expected in the near infrared with a thick transparent slab of co2 ice are not observed models of the observed spectra indicate that the low albedo results from extensive dust contamination close to the surface of a co2 ice layer which could be linked to atmospheric circulation patterns the strength of the co2 absorption increases after mid spring so part of the dust is either carried away or buried more deeply in the ice layer during the co2 ice sublimation process

nighttime variation of thermospheric winds and temperatures over fritz peak observatory during the geomagnetic storm of march 2 1983 nighttime thermospheric winds and temperatures have been measured over fritz peak observatory colorado 39 9 n 105 5 w with a high resolution fabry perot spectrometer during the march 2 1983 geomagnetic storm the winds and temperatures are obtained from the doppler shifts and line profiles of the o i 15 867 k 630 nm line emission the planetary geomagnetic index kp increased abruptly from 4 to 7 during the beginning of the measuring period near 0000 ut on march 2 and remained at nearly that level throughout the night during the early evening hours near 1900 lt 0200 ut the zonal winds measured in both the east and west directions from fritz peak observatory were westward at a speed of about 100 m s 1 the westward winds increased in magnitude during the next 2 hours with the wind speed east of the station reaching 400 m s 1 and the winds to the west of the station reaching 300 m s 1 the westward winds remained at roughly these speeds until about local midnight 0700 ut when they gradually decreased to about 50 m s 1 in the east and the winds to the west of the station shifted to eastward at about 50 m s 1 the meridional winds measured in the early evening hours both to the north and south of the station were poleward at speeds ranging between 50 and 10 m s 1 near local midnight the wind measured north of the station gradually shifted to equatorward reaching a maximum speed of about 300 m s 1 near 0200 lt 0900 ut and then decreasing to about 100 m s 1 near dawn the wind measured south of the station remained poleward throughout the night at speeds ranging between 25 and 100 m s 1 the neutral gas temperature over fritz peak observatory increased throughout the night from about 1300 to 1600 k calculations made with the national center for atmospheric research thermospheric general circulation model suggest that the observed winds over fritz peak observatory l 3 are under the influence of an expanded magnetospheric convection pattern during the storm enhanced magnetospheric convection at mid latitudes characteristically produces westward winds during the early evening hours and a strong equatorward surge in the postmidnight winds

nighttime thermospheric winds over sondre stromfjord greenland observations of nighttime thermospheric neutral winds made at sondre stromfjord greenland with optical and radar instrumentation showed an occasional abatement in the equatorward meridional wind at a magnetic local time corresponding to the nighttime division between the evening and morning convection cells this abatement appeared primarily in the poleward observations in contrast however the characteristic midnight surge was usually seen in the equatorward set of observations the apparent acceleration of about 250 m s or greater within 4 6 latitude we attribute in part to a merging of neutral jet streams generated by polar cap ion drag adjacent to the auroral zone boundary and in part to the higher electron densities and plasma convection speeds adjacent to the auroral zone comparison of these results with those from ncar tgcm computations that assumed an analytical plasma convection model showed reasonable agreement except for the abatement feature

thermal and albedo mapping of the polar regions of mars using viking thermal mapper observations 1 north polar region we present the first maps of the apparent thermal inertia and albedo of the south polar region of mars the observations used to create these maps were acquired by the infrared thermal mapper irtm instruments on the two viking orbiters over a 30 day period in 1977 during the martian late southern summer season the maps cover the region from 60 s to the south pole at a spatial resolution of 1 of latitude thus completing the initial thermal mapping of the entire planet the analysis and interpretation of these maps is aided by the results of a one dimensional radiative convective model which is used to calculate diurnal variations in surface and atmospheric temperatures and brightness temperatures at the top of the atmosphere for a range of assumptions concerning dust optical properties and dust optical depths the maps show that apparent thermal inertias of bare ground regions decrease systematically from 60 s to the south pole in unfrosted regions close to the south pole apparent thermal inertias are among the lowest observed anywhere on the planet on the south residual cap apparent thermal inertias are very high due to the presence of co2 frost in most other regions of mars best fit apparent albedos based on thermal emission measurements are generally in good agreement with actual surface albedos based on broadband solar reflectance measurements however in the frost free region poleward of 75 s best fit apparent albedos are significantly higher than measured lambert albedos implying that measured brightness temperatures in this area are up to 15 k colder than would be expected for surfaces with the same measured albedos during this season the one dimensional atmospheric model calculations also predict anomalously cold brightness temperatures close to the pole during late summer and after considering a number of alternatives it is concluded that the net surface cooling due to atmospheric dust is the best explanation for this phenomenon the observed systematic decrease in apparent thermal inertia from 60 s to the south pole during this season is also consistent with the predictions of atmospheric model calculations the region of lowest apparent thermal inertia close to the pole which includes the south polar layered deposits is interpreted to be mantled by a continuous layer of aeolian material that must be at least a few millimeters thick the low thermal inertias mapped in the south polar region imply an absence of surface water ice deposits which is consistent with viking mars atmospheric water detector mawd measurements which show low atmospheric water vapor abundances throughout the summer season however these observations do not necessarily imply a complete absence of water thermal model calculations that can reproduce observed diurnal temperature variations in the south polar region show that annual maximum subsurface temperatures at depths ranging from 4 to 20 cm are cold enough to permit the stability of ground ice deposits even if they are in excellent diffusive contact with the atmosphere therefore the presence of near surface ground ice in the south polar region is not inconsistent with the viking irtm and mawd observations

the rocks of gusev crater as viewed by the mini tes instrument 1 the miniature thermal emission spectrometer mini tes on board the mars exploration rover spirit is part of a payload designed to investigate whether a lake once existed in gusev crater mini tes has observed hundreds of rocks along the rover s traverse into the columbia hills yielding information on their distribution bulk mineralogy and the potential role of water at the site although dust in various forms produces contributions to the spectra we have established techniques for dealing with it all of the rocks encountered on the plains traverse from the lander to the base of the columbia hills share common spectral features consistent with an olivine rich basaltic rock known as adirondack class beginning at the base of the west spur of the columbia hills and across its length the rocks are spectrally distinct from the plains but can be grouped into a common type called clovis class these rocks some of which appear as in place outcrop are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration the northwest flank of husband hill is covered in float rocks known as wishstone class with spectral features that can be attributed uniquely to plagioclase feldspar a phase that represents more than half of the bulk mineralogy rare exceptions are three classes of basaltic exotics found scattered across husband hill that may represent impact ejecta and or float derived from local intrusions within the hills the rare outcrops observed on husband hill display distinctive spectral characteristics the outcrop called peace shows a feature attributable to molecular bound water and the outcrop that hosts the rock called watchtower displays a dominant basaltic glass component despite evidence from the rover s payload for significant alteration of some of the rocks no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by mini tes the mineralogical results supplied by mini tes provide no clear evidence that a lake once existed in gusev crater

neutral winds in the high latitude winter f region coordinated observations from ground and space coordinated measurements of the f region neutral wind field in the northern winter polar cap are reported using instrumentation on board the dynamics explorer de 2 satellite and the ulster college ground based fabry perot interferometer sited at svalbard ufpi the satellite observations provide the full neutral wind vector along the track of the polar orbiting spacecraft with the meridional component measured by the fabry perot interferometer fpi and the zonal component measured by the wind and temperature spectrometer wats the ufpi observations provide a set of four horizontal wind components in the cardinal directions which may be merged to give two individual neutral wind vectors for each measurement cycle duration 30 minutes a comparison of data from the ground and spaceborne sensors for simultaneous near common volume observations indicates good agreement between the observational techniques simultaneous observations made when the svalbard observatory and de 2 were in different local time sectors of the northern polar cap provide a more detailed snap shot of the neutral circulation pattern than possible using either technique alone the measurements show the presence of a large scale anti cyclonic vortex system on the evening and day side sectors of the winter polar cap

a theoretical study of thermospheric composition perturbations during an impulsive geomagnetic storm the compositional response of the neutral thermosphere to an impulsive geomagnetic storm has been investigated using a numerical simulation made with the national center for atmospheric research thermospheric general circulation model ncar tgcm calculated time dependent changes in neutral thermospheric composition have been studied together with detailed neutral parcel trajectories and other diagnostic information from the model to gain a greater understanding of the physical mechanisms responsible for composition variability during geomagnetic storms and in particular to investigate the causes of the positive and negative ionospheric storm effects the following principal results were obtained from this study 1 calculated perturbations in thermospheric composition following the onset of an impulsive geomagnetic storm were found to be in good qualitative agreement with the previous experimental statistical study of storm time thermospheric morphology by prolss 1981 2 during the initial onset phase of the simulated storm upward vertical winds occurred in the auroral zone and downward winds occurred in the central magnetic polar cap 3 the largest perturbations in mass mixing ratio of nitrogen n2 at f region altitudes were found to be associated with parcels of neutral gas that travelled through the cusp region and with parcels that were trapped within the auroral zone for a long time 4 storm time enhancements in n2 were found to occur in the midnight and early morning sectors both within and equatorward of the auroral zone and these were determined to be associated with the advective effects of the large antisunward polar cap neutral winds the physical size of the region of enhanced n2 values was determined to be related to the time taken for individual parcels of air to corotate out of the large day to night thermospheric wind jet and thus to the magnitudes of the antisunward polar cap winds 5 decreases in n2 were found to occur in regions of downward vertical winds and in regions into which relatively nitrogen poor air was advected by the horizontal wind 6 calculated compositional perturbations following the onset of the storm were found to propagate to mid latitudes due to the advective effects of equatorward winds leading to the mid latitude positive ionospheric storm effects this last result is in disagreement with the earlier study of rishbeth et al 1985 who found the compositional disturbance to be largely restricted to the auroral zone on a constant pressure surface however it is consistent with the more recent study undertaken by fuller rowell et al 1991 who demonstrated that composition changes were seen well beyond the auroral oval

north and south subice gas flow and venting of the seasonal caps of mars a major geomorphological agent 1 dark polygons associated with fans and spots appear during the spring on the southern seasonal cap the basal sublimation of the translucent cap and the venting of the co2 gas are responsible for their formation as previously proposed for the spots and fans dark polygons appear when dark material emerges from elongated vents whereas spots and fans form from point sources a class of erosive features etched polygons is associated with depressions a few meters to tens of meters in diameters connected to a network of radiating troughs spiders spiders are shaped by the scouring action of the confined gas converging toward point sources whereas the etched polygons result from the forced migration of the co2 gas over longer distances the minimum age of the spiders is 104 years they result from one of the most efficient erosive processes on mars displacing 2 orders of magnitude more dust per year than a typical dust storm or than all the dust devils during the same time period in the north parts of the seasonal cap are translucent between ls 355 and ls 60 and are associated with spots fans dark polygons and possibly spiders suggesting that the basal sublimation and venting of the cap triggers a subice gas and dust flow that is modifying the morphology of the surface layer however perennial features are extremely uncommon on the north regolith indicating that the conditions for their formation or conservation are not met the reduced basal energy budget of the north cap compared to the south and the shorter seasonal life time of the north translucent ice may explain the relative scarcity of features in the north the polar layered deposits contain the stratigraphic record of climatic changes and catastrophic events both polar deposits may have been locally disrupted by the seasonal subice gas flow and the stratigraphic record may have been partially lost

planet four terrains discovery of araneiforms outside of the south polar layered deposits abstract we present the results of a systematic mapping of seasonally sculpted terrains on the south polar region of mars with the planet four terrains p4t online citizen science project p4t enlists members of the general public to visually identify features in the publicly released mars reconnaissance orbiter context camera ctx images in particular p4t volunteers are asked to identify 1 araneiforms including features with a central pit and radiating channels known as spiders 2 erosional depressions troughs mesas ridges and quasi circular pits characteristic of the south polar residual cap sprc which we collectively refer to as swiss cheese terrain and 3 craters in this work we present the distributions of our high confidence classic spider araneiforms and swiss cheese terrain identifications in 90 ctx images covering 11 of the south polar regions at latitudes 75 n we find no locations within our high confidence spider sample that also have confident swiss cheese terrain identifications previously spiders were reported as being confined to the south polar layered deposits spld our work has provided the first identification of spiders at locations outside of the spld confirmed with high resolution hirise high resolution imaging science experiment imaging we find araneiforms on the amazonian and hesperian polar units and the early noachian highland units with 75 of the identified araneiform locations in our high confidence sample residing on the spld with our current coverage we cannot confirm whether these are the only geologic units conducive to araneiform formation on the martian south polar region our results are consistent with the current co 2 jet formation scenario with the process exploiting weaknesses in the surface below the seasonal co 2 ice sheet to carve araneiform channels into the regolith over many seasons these new regions serve as additional probes of the conditions required for channel creation in the co 2 jet process

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

clay mineral formation and transformation in rocks and soils three mechanisms for clay mineral formation inheritance neoformation and transformation operating in three geological environments weathering sedimentary and diagenetic hydrothermal yield nine possibilities for the origin of clay minerals in nature several of these possibilities are discussed in terms of the rock cycle the mineralogy of clays neoformed in the weathering environment is a function of solution chemistry with the most dilute solutions favouring formation of the least soluble clays after erosion and transportation these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size clays undergo little reaction in the ocean except for ion exchange and the neoformation of smectite therefore most clays found on the ocean floor are inherited from adjacent continents upon burial and heating however dioctahedral smectite reacts in the diagenetic environment to yield mixed layer illite smectite and finally illite with uplift and weathering the cycle begins again

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

observations of the northern seasonal polar cap on mars i spring sublimation activity and processes abstract spring sublimation of the seasonal co2 northern polar cap is a dynamic process in the current mars climate phenomena include dark fans of dune material propelled out onto the seasonal ice layer polygonal cracks in the seasonal ice sand flow down slipfaces and outbreaks of gas and sand around the dune margins these phenomena are concentrated on the north polar erg that encircles the northern residual polar cap the mars reconnaissance orbiter has been in orbit for three mars years allowing us to observe three northern spring seasons activity is consistent with and well described by the kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer the crest of the dune the interface of the dune with the interdune substrate and through polygonal cracks in the ice pressurized gas flows through these vents and carries out material entrained from the dune furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially organized channels araneiform terrain albeit not permanent properties of the seasonal co2 ice layer are derived from timing of seasonal events such as when final sublimation occurs modification of dune morphology shows that landscape evolution is occurring on mars today driven by seasonal activity associated with sublimation of the seasonal co2 polar cap

mineralogy and chemistry of altered icelandic basalts application to clay mineral detection and understanding aqueous environments on mars we used a suite of techniques including those emulating compositional data sets obtained from mars orbit and obtainable at the mars surface to examine aqueous alteration of basaltic rocks from iceland as a mineralogic and geochemical analog for noachian environments on mars a sample suite was collected for laboratory measurement of 1 whole rock visible near infrared vnir reflectance and thermal infrared tir emission spectra 2 vnir and tir reflectance spectra of particle size separates derived from the bulk rock and from materials extracted from fractures vesicles 3 x ray diffraction xrd patterns for determination of quantitative modal mineralogy 4 major element chemistry using flux fusion of whole rock powders and 5 electron microprobe analyses of minerals in thin sections conclusions about aqueous alteration can be influenced by technique for these basalts whole rock chemical data showed scant evidence for chemical fractionation but tir vnir and xrd measurements identified distinctive assemblages of hydrous silicate minerals differing by sample xrd provided the most complete and accurate quantitative determination of sample mineralogy however vnir spectroscopy was the technique most useful for determining composition of low abundance smectite clays and tir spectroscopy was the most useful for recognizing hydrated silicates in thin surface coatings high spatial resolution mineralogical and chemical data sets were useful for understanding the texture and distribution of alteration products and variations in fluid chemistry no single approach provides a complete assessment of the environment of alteration demonstrating the importance of employing multiple synergistic mineralogical and geochemical techniques and instruments in exploration of rock strata from aqueous paleoenvironments on mars

the geomagnetic quiet nighttime thermospheric wind pattern over fritz peak observatory during solar cycle minimum and maximum nighttime thermospheric winds and temperatures at f region heights have been measured over fritz peak observatory colorado 39 9 n 105 5 w with a high resolution fabry perot spectrometer from about november 1972 to the present the winds and temperatures are obtained from the doppler shifts and line profiles of the o i 15 867 k 630 nm line emission the data obtained during geomagnetic quiet conditions ap 20 have been separated into two groups representing solar cycle minimum conditions 1972 1977 and solar cycle maximum conditions 1978 1979 the monthly variation of the nighttime zonal and meridional winds are presented for both groups the results show that during solar cycle minimum the zonal winds are predominantly eastward during the winter months at speeds of 50 75 m s 1 and westward during the summer months at speeds of 50 100 m s 1 the meridional winds measured to the north and south of fritz peak observatory are equatorward throughout most of the night at nearly the same speed the equatorward winds in the summer peak near midnight at about 100 150 m s 1 the equatorward winds in the winter also peak near midnight but with smaller speeds 50 75 m s 1 during solar cycle maximum the zonal winds are again predominantly eastward during the winter months reaching peak speeds of 60 75 m s 1 in the early evening hours and decreasing afterward in the summer the winds are eastward during the early evening hours shifting to westward near midnight and increasing to a maximum speed of 75 100 m s 1 in the early morning hours the meridional winds are poleward at 20 m s 1 in the early evening hours shifting to equatorward near 2100 lt and then increasing in magnitude with maximum speeds near or after midnight there is a considerable difference in the speed of the winds measured to the north and south of fritz peak observatory during the summer the equatorward winds measured to the north are 150 175 m s 1 whereas the equatorward winds measured to the south are 50 75 m s 1 during the winter the speeds are smaller 50 75 m s 1 and 25 30 m s 1 to the north and south of the station respectively calculations made with the national center for atmospheric research thermospheric general circulation model for different seasons are in reasonable agreement with the observations during both solar minimum and solar maximum during solar cycle maximum the observed and calculated meridional wind differences to the north and south of fritz peak observatory are attributed to enhanced auroral heating and ion drag associated with magnetospheric convection north of the observatory the equatorward driven winds slow south of fritz peak observatory owing to the diminishing influence of high latitude forcings

extensive hesperian aged south polar ice sheet on mars evidence for massive melting and retreat and lateral flow and ponding of meltwater local and regional mars orbiter laser altimeter mola topographic data support the presence of an extensive hesperian aged volatile rich south polar deposit the dorsa argentea formation hd and related units underlying the present amazonian aged polar cap api residual ice and apl layered terrain and covering a surface area that could be as large as 2 94 106 km2 about 2 of the surface of mars over twice the area of the present amazonian aged south polar deposits the deposit characteristics indicate that it contained significant quantities of water ice in amounts comparable to present day polar deposits several lines of evidence for melting indicate that the ice sheet deposits underwent melt back and liquid water drainage into surrounding lows including a large valley near the crater schmidt and the argyre basin narrow sinuous ridges lie in a broad linear depression extending from a high near the present polar cap continuously downslope to near the distal portion of hd the new topographic data support the interpretation of these ridges as eskers representing meltwater distribution networks at the base of the receding deposit extensive development of large pits and depressions cavi have previously been interpreted as eolian etching or basal melting of ice rich deposits analysis of mola topography supports the interpretation that they represent basal melting of ice rich deposits and shows that they have links to the esker systems volumetric considerations and topographic lineations suggest that some of the basal melting occurred beneath regions presently occupied by apl and that some of the liquid water formed ponds and lakes in the distal parts of hd the presence of pedestal craters is further evidence of the removal of extensive volatile rich deposits and contributes to the quantitative measure of the former deposit thickness where did the melt products go inspection of the margins of the dorsa argentea formation reveals several large channels that begin there and drain downslope for distances between 900 and 1600 km onto the floor of the argyre basin some 3 5 4 0 km below their origin these channels do not exhibit tributaries their broad lateral distribution supports other evidence that deposit melting was areally very widespread and volumetrically significant and that a large part of the meltwater entered the surface distribution system and was deposited on the floor of the argyre basin over 1000 km away estimates of the present deposit thicknesses together with amounts of the deposit removed by meltback suggest that the original volume could have been as much as 5 9 106 km3 equivalent to a global layer of water 20 m deep if the deposit consisted of 50 volatiles a portion of these volatiles migrated across the surface to pond in adjacent valleys and basins and into the groundwater system a significant portion of the volatiles remain in the deposit representing a net removal from the atmosphere and from the active hydrologic system in early to middle mars history and forming an accessible record of aqueous conditions and possible biological environments dating from that time

diverse aqueous environments on ancient mars revealed in the southern highlands high resolution spectral images reveal many new exposures of hydrated minerals across the noachian southern highlands of mars several different phyllosilicates are observed with inferred accompanying phases ranging from zeolites to sulfates to chlorides each in distinct geologic settings hydrated sulfates are observed in several locations at mid latitudes and likely formed independently from the equatorial sulfates these assemblages suggest a greater diversity of aqueous environments on ancient mars than has previously been recognized and their distribution implies that alteration was widespread during the noachian period not restricted to a few locations

evolution of south seasonal cap during martian spring insights from high resolution observations by hirise and crism on mars reconnaissance orbiter 1 we use data from the high resolution imaging science experiment hirise camera and the compact reconnaissance imaging spectrometer for mars crism imaging spectrometer onboard the mars reconnaissance orbiter to follow the evolution of the appearance and composition of 12 regions of the south polar layered deposits from spring to summer time we distinguish three steps in the evolution of the volatile layer a decrease of both co2 band strength and albedo until ls 190 210 a significant increase in both until ls 240 260 and finally a rapid decrease until the complete defrosting of the ground in contrast the water ice band displays a more monotonic decrease analysis of hirise color images acquired simultaneously with crism data allows a plausible interpretation of this evolution in early springtime ls 200 intense jet activity results in deposition of fans of large mineral grains and a wide spatial distribution of fine grains the small scale topography controls the presence and location of the jets by allowing more solar energy to be collected on slopes grains from the dust fans warm and sink through the co2 layer resulting in a bluish color at the locations of the fans around ls 190 210 as the atmosphere warms up the surface of the ice layer sublimes and releases dust and water resulting in its brightening the last phase of the process consists in a progressive defrosting resulting in a patchwork of frozen and unfrozen areas

dark spots and cold jets in the polar regions of mars new clues from a thermal model of surface co2 ice observations of the martian co2 ice cap in late winter and spring have revealed exotic phenomena unusual dark spots fans and blotches form as the south polar seasonal co2 ice cap retreats the formation mechanisms of these features are not clearly understood theoretical models suggest that photons could penetrate deep into the co2 ice down to the regolith leading to basal sublimation and gas and dust ejection we have developed a detailed thermal model able to simulate the temporal evolution of the regolith co2 ice layer atmosphere column it takes into account heat conduction radiative transfer within the ice and the atmosphere and latent heat exchange when there is a phase transition we found that a specific algorithm fully coupling these three components was needed to properly predict ice sublimation below the surface our model allows us to determine under what conditions basal sublimation is possible and thus when and where it can occur on mars our results show that basal sublimation is possible if we consider large pathlengths and very little dust content within the ice moreover the model can explain how dark spots can appear very early after the end of the polar night at high latitudes we also evaluate the importance of the different parameters in our simulations contrary to what was suggested by theoretical models the role of seasonal thermal waves is found to be limited solar radiation alone can initiate basal sublimation which therefore only depends on the co2 ice properties three main modes were identified one where condensation sublimation only occurs at the surface in the case of small grains and or high dust content one where basal sublimation is possible large pathlengths and very little dust content and an intermediate mode where sublimation within the ice may occur we suggest that these different modes could be keys to understanding many processes that occur at the surface of mars like the anticryptic area behavior or the recent reported activity in gullies

detection of hydrated silicates in crustal outcrops in the northern plains of mars the composition of the ancient martian crust is a key ingredient in deciphering the environment and evolution of early mars we present an analysis of the composition of large craters in the martian northern plains based on data from spaceborne imaging spectrometers nine of the craters have excavated assemblages of phyllosilicates from ancient noachian crust buried beneath the plains cover the phyllosilicates are indistinguishable from those exposed in widespread locations in the southern highlands demonstrating that liquid water once altered both hemispheres of mars

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time

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

comparison of the neutral wind seasonal variation from midlatitude conjugate observations the seasonal variation of f region neutral wind from the midlatitude conjugate fabry perot interferometer observations has been studied the meridional wind at palmer station 64 s 64 w has a significant local time dependence with strong equatorward wind at midnight and polarward wind at dawn and dusk the zonal wind switches from eastward to westward in the early morning section from the june solstice austral winter to equinox the maximum meridional wind increases from 90 m s to 130 m s and the zonal wind switches direction at an earlier local time the neutral winds from palmer have been compared with those from the geomagnetic conjugate location millstone hill mh at equinox the local time variation of neutral wind shows a very good conjugacy between these two locations but at june solstice the similarity in the zonal wind becomes less clear this seasonal dependence can be attributed to the seasonal variation of solar and geomagnetic forcings the annual variation of daily average neutral wind from palmer and mh has also been compared the meridional wind shows a clear offset of season and the magnitude at palmer is averagely 40 m s more equatorward than that at mh the zonal wind is dominantly westward at palmer and eastward at mh the annual variation of neutral wind especially the zonal component is much less symmetric between the two sites than the local time variation the empirical horizontal wind model shows a good agreement with the observations in both local time and annual variations

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

thermospheric winds at high latitudes from chemical release observations wind measurements from 39 chemical release rockets launched from auroral belt and polar cap sites between 1967 and 1979 are summarized and interpreted multipoint measurements between 200 and 320 km altitude were obtained from all flights by tracking the neutral strontium clouds produced as by products of ba cuo releases these releases producing ba clouds also provided the simultaneous measurements of ion drift that are needed for wind analysis trail releases of trimethylaluminum and lithium provided measurements between 90 and 200 km from 19 rockets the wind measurements at different local times and latitudes are disorganized when presented in geographic and solar local time coordinates an organized wind system at altitudes above 160 km emerges when wind vectors are presented in magnetic local time and invariant latitude coordinates the dominant role of electric field ion drag as a driving force and the inertial characteristics of the wind system are clearly illustrated when the wind vectors are superposed on model patterns of the global high latitude ion convection at altitudes above the 110 km shear region and below a transitional zone in the 140 160 km range relationships between the observed winds and the causative mechanisms become less apparent as a consequence of the slower response to changing ion drag conditions a notable exception occurs in the polar cap where high velocity winds are observed at all altitudes under the influence of continuous antisolar ion flow a key factor affecting the wind pattern is the formation of a pressure ridge along the interface zone between the polar cap and the auroral belt in the evening hours back pressures from this ridge suppress the coriolis forces in the adjacent regions and contribute to the development of a dusk to dawn component in the antisolar polar cap flow the observations clearly indicate that the antisolar polar cap wind loses momentum and deposits energy in the early morning auroral belt at high altitudes i e 160 320 km there is directional continuity but a velocity loss as the polar cap wind inertially penetrates the morning auroral region at lower altitudes i e 140 km the observations are less definitive but indicate that the wind is discontinuous along the morning auroral belt interface in general the observations do not reveal wind characteristics that can be attributed to pressure gradients from joule heating or heating by precipitating particles a possible but speculative exception is that the perturbing effects of heating may explain why observed velocities tend to be lower than velocities calculated for model ion drag conditions other wind effects from high latitude heating apparently have less influence than the time space variability of the electric field and are thus obscured by these variations the existence of the classical day night flow from dayside euv heating is demonstrated by measurements from three rockets launched at subauroral latitudes on the dayside the influence of this flow at higher latitudes is similarly not identifiable in the presence of the ion drag winds a number of the gross characteristics of the observed high latitude wind pattern are simulated reasonably well by fuller rowell and rees recent model