eolian controlled modification of the martian south polar layered deposits data from the mars orbiter laser altimeter mola and mars orbiter camera moc aboard the mars global surveyor mgs mission and the thermal emission imaging system themis aboard the mars odyssey mission have revealed unique surface features in a particular region of the south polar layered deposits spld the dominant morphology is large scale quasi parallel grooves that extend for hundreds of kilometers with only tens of meters of vertical relief that we have termed here the wire brush terrain the grooves are also transected by disjointed yet roughly continuous low relief sinuous ridges that cross roughly perpendicular to the trend direction of the large scale grooves and show only tens of meters of relief we interpret these ridges to be eroded remnants of folded layers at the northern end of the large scale grooves there are non symmetric mounds they are frequently preceded by a significant depression and or trailing grooves that are parallel to the wire brush trend we find that a two stage process involving winds that intermittently remove a low density crust exposing the underlying ice to ablation is the interpretation that best explains the multitude of features observed here these features appear to be currently inactive indicating higher winds in previous epochs

volcanology of arnus vallis mars abstract arnus vallis av is a 300 km long sinuous rille located on the northeastern flank of the syrtis major volcano on mars observational evidence presented here suggests that av formed as an open lava channel that was at least partly incised into the pre existing terrain the lava source area consists of a sub circular pit at the southwestern end of a 7 km long straight section of channel av trends down slope from this source with an average bottom slope of 0 26 or 0 14 width varies from 1 km at the source to 0 6 km near the distal end with a mean of 0 76 km depth decreases from 180 m at the source to 25 m near the distal end the av terminus is obscured by a large impact crater we suggest that the material that flowed in av must have been a relatively high temperature low viscosity lava dynamically and perhaps compositionally similar to terrestrial komatiite or some lunar basalt lavas if correct this finding has implications for the mode of construction of syrtis major

analysis of mola data for the mars exploration rover landing sites 1 we have used mars orbiter laser altimeter mola data to demonstrate that selected landing sites meet the mars exploration rover mer landing system topography and slope requirements at hectometer and kilometer scales to provide a comprehensive analysis we constrained slopes within each landing ellipse using four approaches 1 measurements of local slopes at 1 2 km length scales using both an adirectional maximum gradient method and a higher resolution bidirectional along track method 2 predictions of 100 m slopes using self affine statistics in conjunction with 3 calculations of both pulse width and slope corrected pulse width to constrain slopes at scales smaller than the mola spot size 180 m and 4 comparisons of simultaneously acquired mola data with mars orbiter camera data to identify the geomorphologic features associated with variations in observed slopes pulse width and for this analysis only reflectivity the results of the analysis indicate that the selected landing sites are consistent with the mer topography requirement of being below 1 3 km as well as having slopes less than 5 at length scales of 100 m and 2 at length scales of 1 2 km

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

monsoon reconstruction from radiocarbon dated tropical indian speleothems the potential of tropical speleothems as a climate proxy has been investigated amplitudes of 180 and 813c variations are found to be large and are likely to be primarily controlled by past rainfall contribution from past temperature variations seems to be relatively small the amount effect in rainfall has been observed and quantified by analysing rainwater samples collected during a monsoon season a tentative chronology to these speleothems is asssigned by the 14c radiometric dating method assuming that the variations in the 180 of cave carbonates are solely due to the past variations in rainfall a history of the latter has been reconstructed a high resolution rainfall reconstruction up to the last 3400 years is now available from gupteswar cave orissa subject to validation of dates by the u th method it is observed that in a tropical speleothem 513c is dominantly controlled by rainfall the study has shown that tropical indian speleothems faithfully record the annual monsoon rainfall in the

machine cataloging of impact craters on mars this study presents an automated system for cataloging impact craters using the mola 128 pixels degree digital elevation model of mars craters are detected by a two step algorithm that first identifies round and symmetric topographic depressions as crater candidates and then selects craters using a machine learning technique the system is robust with respect to surface types craters are identified with similar accuracy from all different types of martian surfaces without adjusting input parameters by using a large training set in its final selection step the system produces virtually no false detections finally the system provides a seamless integration of crater detection with its characterization of particular interest is the ability of our algorithm to calculate crater depths the system is described and its application is demonstrated on eight large sites representing all major types of martian surfaces an evaluation of its performance and prospects for its utilization for global surveys are given by means of detailed comparison of obtained results to the manually derived catalog of large martian impact craters we use the results from the test sites to construct local depth diameter relationships based on a large number of craters in general obtained relationships are in agreement with what was inferred on the basis of manual measurements however we have found that in terra cimmeria the depth diameter ratio has an abrupt decrease at 38 s regardless of crater size if shallowing of craters is attributed to presence of sub surface ice a sudden change in its spatial distribution is suggested by our findings

the geology of the viking lander 2 site revisited abstract reevaluating the geologic history of the prior mars landing sites provides important ground truth for recent and ongoing orbital missions at the viking 2 lander vl2 site topographic measurements of relict landforms indicate that at least 100 m of sedimentary mantle material has been stripped away the observed paucity of impact craters

medusae fossae formation new perspectives from mars global surveyor 1 the nature and origin of the medusae fossae formation mff on mars has been debated since the return of the first viking images the mff s young age distinctive surface texture and lack of obvious source have prompted multiple hypotheses for its origin this study uses data from the mars global surveyor mgs mission to examine the mff at all available scales we discuss and quantify observations from mars orbiter laser altimeter mola topography and mars orbiter camera moc images to better constrain the origin of the mff topographic grid estimates yield a present extent of 2 1 106 km2 and a volume of 1 4 106 km3 however remnant yardang deposits observed far from the thicker lobes of mff material suggest that it may have once covered up to 5 106 km2 we do not find compelling evidence for extensive fluvial reworking of the mff however in several regions buried channels are apparent in the mff because the formation is draped over underlying topography layering is apparent at all scales from submeter to hundreds of meters with variable resistance to weathering continuity of layers appears to be local to regional but not likely formation wide yardangs form both parallel and bidirectional patterns with resistant layers and jointing probably influencing their orientations a comparative study of mff regional topography and surface expression indicates that the mff is quantitatively dissimilar to martian polar layered deposits the material is most likely a friable and irregularly consolidated air fall deposit of probable volcanic origin

an improved solution of the gravity field of mars gmm 2b from mars global surveyor a spherical harmonic solution of the mars gravity field to degree and order 80 goddard mars model 2b gmm 2b has been developed using x band tracking data of mars global surveyor mgs from october 1997 to february 2000 and altimeter crossovers formed from the mars orbiter laser altimeter mola data between march and december 1999 during the mapping mission mgs was located in a near polar 92 9 inclination and near circular orbit at a mean altitude of 400 km the tracking data from this orbit provide a detailed global and high resolution view of the gravity field of mars mars gravity solutions are stable to 60 60 even without application of a kaula power law constraint the valles marineris is resolved distinctly with lows reaching 450 mgals olympus mons and its aureole are both separately resolved and the volcano has a peak anomaly of 2950 mgals the global correlation of the gmm 2b gravity coefficients with mola derived topography is 0 78 through degree 60 and the correlation remains above 0 6 through degree 62 the global gravity anomaly error predicted from the gmm 2b error covariance through 60 60 is 11 mgal the global geoid error from gmm 2b through 60 60 is 1 8 m mgs orbit quality using gmm 2b as measured by overlapping orbital arcs is 1 m in the radial direction and 10 m in total position

the plio pleistocene geologic and climatic record of the kashmir valley india a review and new data abstract the kashmir valley located in the northwestern himalayas provides an intermontane valley fill comprising unconsolidated fluvio lacustrine sediments of more than a km thickness datable at 4 myr these sediments have been investigated for the last 7 years under an interdisciplinary multi agency project using a variety of proxy climatic data techniques and other analyses to decipher climatic change as a result of this study a variety of proxy climatic data from a long continental record is available now from northernmost south asia in this paper we briefly review the lithostratigraphic and chronologic framework of the sediment profile and proxy climatic data based on flora fauna stable isotopes pedology mineral magnetics and sedimentology lastly the climatic events are put in an absolute time frame for comparison with the global climatic trends the chronology is based on 14c thermoluminescence tl palaeomagnetic and fission track techniques

modification of impact craters in the northern plains of mars implications for amazonian climate history we measured the depth wall steepness and ejecta roughness and surveyed the wall and floor morphology of all craters 10 25 km in diameter within the typical vastitas borealis formation in the northern lowlands of mars north of 52 n two of the 130 craters have unusually rough ejecta they are deep have steep walls and are apparently the youngest in the population icy mantles filling the local subkilometer scale topographic lows is the main contribution to ejecta smoothing which occurs at a time scale on the order of tens of myr wall degradation and crater shallowing generally occur at longer time scales comparable to the duration of the amazonian period many craters are shallow due to filling of the crater with specific ice rich material of uncertain origin we use our collected data to infer the nature of the past climate back through the amazonian a period prior to 10 20 myr ago when orbital parameter solutions are chaotic and one must rely on geological data to infer climate conditions we conclude that moderately high obliquity and wide obliquity variations were probable during the last 40 160 myr we tentatively conclude that high obliquity peaks 40 45 may have occurred episodically through the last 210 430 myr a sharp step in the frequency distribution of wall steepness at 20 may indicate a geologically long period prior to that time where obliquity never exceeded 40 45

internal structure of the martian south polar layered deposits 1 we investigate the three dimensional 3 d stratigraphic structure of the south polar layered deposits spld on mars prominent bench forming layers exposed on spld scarps were observed and mapped in three dimensions using high resolution topographic and imaging data sets using the 3 d location of exposures of one of these strata we can accurately describe the shape of that layer using simple mathematical functions analysis of these functions and the surface topography can be used to reliably predict where on other scarps this layer is exposed in general this bench forming layer and its surrounding strata is not flat and is well approximated as a parabolic dome near the center of the spld its curvature indicates that when deposited it was draped over a topographic dome similar in size to that of the present day the scarps in which this layer is exposed must have formed subsequently and have not been significantly modified by flow processes the basement topography exercises some control over the shape of the interior strata in extreme cases our successful layer fitting technique illustrates the regional uniformity in layer formation and the lack of major internal defects such as faulting within the spld we have mapped exposures of what appear to be this layer in scarps farther from the center of the deposits the position of these exposures can be used to modify the modeled parabolic shape at the periphery of the spld these peripheral elevations provide constraints on the role of flow in the overall shaping of the spld

comparing landslides to fluidized crater ejecta on mars 1 we use the mars global surveyor and viking data sets to compare and contrast the geomorphology of four large martian landslides located in valles marineris to fluidized ejecta of seven fresh martian craters located in lunae planum both mass movements have flowed over the martian surface and possess characteristics seen in terrestrial mass movements we combine these comparisons with simple flow models to determine how the planar geometry of landslides and the cylindrical geometry of ejecta can generate different topographic expressions for the same input constraints our purpose is to better understand the emplacement processes of both types of mass movements our geomorphic analyses are consistent with previous views that the large martian landslides resemble large terrestrial long run out flows the planar flow model supports this inference martian landslides probably flowed as a basal glide where motion is limited to a narrow interface at the base of the mass movement geomorphic investigations of fresh multilayered ejecta indicate that their inner portions with their subtle rampart probably flowed like their landslide counterparts as a basal glide distal pronounced contiguous ramparts however resemble features akin to terrestrial debris flows the cylindrical flow model shows that differences in geometry can mask the dynamics of flow emplacement this model suggests as expected a basal glide origin for the inner portions of the ejecta surprisingly basal glide also best explains the topography of the distal ejecta ramparts

north polar stratigraphy and the paleo erg of mars an accurate self consistent way of coregistering the imaging and topographic data sets of the mars global surveyor mission was developed and used to begin a stratigraphic analysis of the northern polar region a distinct change in the layering style exists at a definite stratigraphic horizon near the base of the north polar layered deposits occurrences of the contact between two distinct layered units can be mapped hundreds of kilometers apart at nearly the same mars orbiter laser altimeter mola elevation the lower layered unit has a consistent association with sand dunes leading to the conclusion that it is an eroding sand rich deposit that predates most of the overlying north polar layered deposits which exhibits the expected features of a dust ice mixture these results suggest that an areally extensive erg was in existence before the present ice cap and that the present circumpolar erg is likely composed of material reworked from this older deposit the volume of this lower unit is estimated to be on the order of 10 5 km 3 the presence of this deposit implies that there existed a period in mars history when there was no icy polar cap a dramatic climatic change leading to the deposition of the upper layered icy unit in the present day polar layered deposits represents a major event in mars history however owing to uncertainties in the mechanics of layered deposits formation such an event cannot be dated at this time

interior structure and seasonal mass redistribution of mars from radio tracking of mars pathfinder doppler and range measurements to the mars pathfinder lander made using its radio communications system have been combined with similar measurements from the viking landers to estimate improved values of the precession of mars pole of rotation and the variation in mars rotation rate the observed precession of 7576 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition the estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps

hemispheres apart the crustal dichotomy on mars the hemispheric dichotomy is a fundamental feature of mars expressed by a physiographic and geologic divide between the heavily cratered southern highlands and the relatively smooth plains of the northern lowlands the origin of the dichotomy which may have set the course for most of the subsequent geologic evolution of mars remains unclear internally driven models for the dichotomy form the lowlands by mantle convection plate tectonics or early mantle overturn externally driven models invoke one giant impact or multiple impacts areal densities of buried basins expressed by quasicircular depressions and subsurface echoes in radar sounding data suggest that the dichotomy formed early in the geologic evolution of mars tectonic features along the dichotomy boundary suggest late stage modification by flexure or relaxation of the highlands after volcanic resurfacing of the northern lowlands subsequent deposition and erosion by fluvial aeolian and glacial processes shaped the present day dichotomy boundary

estimates of fluvial erosion on titan from sinuosity of lake shorelines 1 titan has few impact craters suggesting that its surface is geologically young titan s surface also has abundant landforms interpreted to be fluvial networks here we evaluate whether fluvial erosion has caused significant resurfacing by estimating the cumulative erosion around the margins of polar lakes a scarcity of detailed topographic data makes it difficult to measure fluvial incision on titan but images of drowned fluvial features around the lake margins where elevated levels of hydrocarbon liquids appear to have partly flooded fluvial valleys offer a constraint on the topography we mapped the shorelines of several lakes to obtain topographic contours that trace the fluvially dissected topography we then used a numerical landscape evolution model to calibrate a relationship between contour sinuosity which reflects the extent of fluvial valley incision and cumulative erosion we confirmed this relationship by analyzing a partially dissected surface adjacent to the minnesota river usa comparison of the mapped titan contours with the sinuosity erosion relationship suggests that cumulative fluvial erosion around the margins of titan s polar lakes including ligeia mare kraken mare and punga mare in the north and ontario lacus in the south ranges from 4 to 31 of the initial relief additional model simulations show that this amount of fluvial erosion does not render craters invisible at the resolution of currently available imagery suggesting that fluvial erosion is not the only major resurfacing mechanism operating in titan s polar regions

detection of the lunar body tide by the lunar orbiter laser altimeter the lunar orbiter laser altimeter instrument onboard the lunar reconnaissance orbiter spacecraft collected more than 5 billion measurements in the nominal 50 km orbit over 10 000 orbits the data precision geodetic accuracy and spatial distribution enable two dimensional crossovers to be used to infer relative radial position corrections between tracks to better than 1 m we use nearly 500 000 altimetric crossovers to separate remaining high frequency spacecraft trajectory errors from the periodic radial surface tidal deformation the unusual sampling of the lunar body tide from polar lunar orbit limits the size of the typical differential signal expected at ground track intersections to 10 cm nevertheless we reliably detect the topographic tidal signal and estimate the associated love number h2 to be 0 0371 0 0033 which is consistent with but lower than recent results from lunar laser ranging

the mars pathfinder landing site and the viking control point network we recomputed the viking mars control point network and derived mars fixed three dimensional coordinates of 3739 selected globally distributed landmarks mars pathfinder and viking lander 1 coordinates as well as data from reanalyzed spacecraft occultation measurements are used as fixed control information in the analysis the network benefits greatly from recently restored viking orbiter trajectory data and new planet rotational parameters derived from pathfinder lander tracking in our attempt to predict the coordinates of the viking lander 1 site from given pathfinder coordinates we find an offset of 4 5 km of this lander location with respect to the previously reported data we suggest that this probably is explained by erroneous identification of this landing site in the images ninety percent of our landmark coordinates have positional errors of less than 1800 m this network thus removes previously noted severe offsets between mars fixed coordinates and cartographic products

climatic and topographic controls on the style and timing of late quaternary glaciation throughout tibet and the himalaya defined by 10be cosmogenic radionuclide surface exposure dating abstract temporal and spatial changes in glacier cover throughout the late quaternary in tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region and the lack of numerical dating to help reconstruct the timing and extent of glaciation throughout tibet and the bordering mountains we use geomorphic mapping and 10 be cosmogenic radionuclide crn surface dating in study areas in southeastern gonga shan southern karola pass and central western nyainqentanggulha shan and tanggula shan tibet and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands each of the study regions receives its precipitation mainly during the south asian summer monsoon when it falls as snow at high altitudes gonga shan receives the most precipitation 2000 mm a 1 while near the margins of monsoon influence the karola pass receives moderate amounts of precipitation 500 600 mm a 1 and in the interior of the plateau little precipitation falls on the western nyainqentanggulha shan 300 mm a 1 and the tanggula shan 400 700 mm a 1 the higher precipitation values for the tanggula shan are due to strong orographic effects in each region at least three sets of moraines and associated landforms are preserved providing evidence for multiple glaciations the 10 be crn surface exposure dating shows that the formation of moraines in gonga shan occurred during the early mid holocene neoglacial and little ice age on the karola pass during the lateglacial early holocene and neoglacial in the nyainqentanggulha shan date during the early part of the last glacial cycle global last glacial maximum and lateglacial and on the tanggula shan during the penultimate glacial cycle and the early part of the last glacial cycle the oldest moraine succession in each of these regions varies from the early holocene gonga shan lateglacial karola pass early last glacial western nyainqentanggulha shan and penultimate glacial cycle tanggula shan we believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south asian monsoon and in particular in regional precipitation gradients in zones of greater aridity the extent of glaciation has become increasingly restricted throughout the late quaternary leading to the preservation of old 100 ka glacial landforms in contrast in regions that are very strongly influenced by the monsoon 1600 mm a 1 the preservation potential of pre lateglacial moraine successions is generally extremely poor this is possibly because lateglacial and holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations furthermore the intense denudation mainly by fluvial and mass movement processes which characterize these wetter environments results in rapid erosion and re sedimentation of glacial and associated landforms which also contributes to their poor preservation potential

mars and mercury rotation variations from altimetry crossover data feasibility study 1 knowledge of the interior structure of terrestrial planets can be achieved by studying the changes of their rotation and orientation in time we simulate the use of time deviations of altimetry crossover positions to infer information on the nutations of mars and on the librations of mercury the analysis is based on the least squares estimator and uses simulated crossover points the simulations demonstrate that the use of crossover data improves the estimates of the observed libration amplitude and obliquity of mercury and allows detecting the nutations of mars

density structure of the upper thermosphere of mars from measurements of air drag on the mars global surveyor spacecraft we present measurements of the density of the martian atmosphere between 170 and 180 km altitude above the high northern latitudes over a 6 month period in 1998 when the solar cycle was beginning to rise out of its activity minimum these measurements were made from the observed orbital decay of the mars global surveyor mgs spacecraft during its science phasing orbits spo april to september 1998 using x band doppler tracking observations the densities that we retrieve are comparable to model values given by culp and stewart 1984 stewart 1987 mars gram 3 7 justus et al 1996 and recent mars thermospheric global circulation model mtgcm simulations bougher et al 2000 however the spo period can be divided into two time periods separated at ls 355 0 that are characterized by significantly different orbit to orbit variability that is not predicted by these earlier models the first time period corresponds to the time during which the mgs orbit perifocus moved toward the north pole while the local solar time was 1000 1100 during this period orbit to orbit variability is 50 70 and our average measured density at 175 km is 0 018 0 007 kg km 3 between 67 and 72 n and ls 315 to 320 the second time period corresponds to the time during which the orbit perifocus moved south from the north pole and the local time was 1700 1730 during this period orbit to orbit variability is 40 20 and our average measured density at 175 km is 0 024 0 004 kg km 3 between 62 and 69 n and ls 17 to 28 for both time periods the observed latitudinal gradient of density on a constant altitude surface exhibited a factor of 3 4 decrease between 60 and 90 n this gradient is comparable to that expected by the polar vortex high latitude wind effect modeled by the mtgcm for solar medium conditions at southern summer solstice bougher et al 2000 a southern hemisphere dust storm that the mgs thermal emission spectrometer tes observed at ls 309 is distinguishable in our data set as a 100 rise in density at 180 km above the 70 northern latitudes 7 days later ls 313

shape of the northern hemisphere of mars from the mars orbiter laser altimeter mola eighteen proles ofn s trending topography from the mars orbiter laser altimeter mola are used to analyze the shape of mars northern hemisphere mola observations show smaller northern hemisphere flattening than previously thought the hypsometric distribution is narrowly peaked with 20 of the surface lying within 200 m of the mean elevation low elevation correlates with low surface roughness but the elevation and roughness may re flect dierent mechanisms bouguer gravity indicates less variability in crustal thickness and or lateral density struc ture than previously expected the 3 1 km oset between centers of mass and gure along the polar axis results in a pole to equator slope at all longitudes the n s slope dis tribution also shows a subtle longitude dependent variation that may represent the antipodal eect of the formation of tharsis

small scale topography of 433 eros from laser altimetry and imaging abstract the near laser rangefinder nlr obtained more than 16 million range returns from asteroid 433 eros we present the first results from analyses of topographic profiles interpreted with the aid of simultaneous boresighted images obtained by the near multispectral imager msi the location of the nlr boresight relative to that of msi is determined by detailed correlations of ranging data and simultaneous images including cases where the laser boresight slewed off and on the limb of the asteroid and cases where the laser illuminated a boulder close to the time of an image in the data presented the precision of the range measurements is about 1 m with the minimum spot diameter under 5 m and successive spots are contiguous or overlapping elevation on the irregular object eros is given with respect to the gravitational and centrifugal potential landslides in craters are characterized possible crater benches are identified examples of infilled craters are presented these observations suggest a depth of unconsolidated regolith which is subject to sliding of typically a few tens of meters an example of structurally controlled cratering is presented examples of tectonic features are described surface roughness on eros is approximately self affine from scales of a few meters to hundreds of meters a comparison of fractal statistics shows that eros is extremely rough on observed scales when compared to terrestrial a a lava on submeter scales and undisturbed lunar regolith on subcentimeter scales

topography of the moon from the clementine lidar range measurements from the lidar instrument carried aboard the clementine spacecraft have been used to produce an accurate global topographic model of the moon this paper discusses the function of the lidar the acquisition processing and filtering of observations to produce a global topographic model and the determination of parameters that define the fundamental shape of the moon our topographic model a 72nd degree and order spherical harmonic expansion of lunar radii is designated goddard lunar topography model 2 gltm 2 this topographic field has an absolute vertical accuracy of approximately 100 m and a spatial resolution of 2 5 the field shows that the moon can be described as a sphere with maximum positive and negative deviations of 8 km both occurring on the farside in the areas of the korolev and south pole aitken s p aitken basins the amplitude spectrum of the topography shows more power at longer wavelengths as compared to previous models owing to more complete sampling of the surface particularly the farside a comparison of elevations derived from the clementine lidar to control point elevations from the apollo laser altimeters indicates that measured relative topographic heights generally agree to within 200 m over the maria while the major axis of the lunar gravity field is aligned in the earth moon direction the major axis of topography is displaced from this line by approximately 10 to the east and intersects the farside 24 north of the equator the magnitude of impact basin topography is greater than the lunar flattening 2 km and equatorial ellipticity 800 m which imposes a significant challenge to interpreting the lunar figure the floors of mare basins are shown to lie close to an equipotential surface while the floors of unflooded large basins except for s p aitken lie above this equipotential the radii of basin floors are thus consistent with a hydrostatic mechanism for the absence of significant farside maria except for s p aitken whose depth and lack of mare require significant internal compositional and or thermal heterogeneity a macroscale surface roughness map shows that roughness at length scales of 10 1 10 2 km correlates with elevation and surface age

the gravity field of mars results from mars global surveyor observations of the gravity field of mars reveal a planet that has responded differently in its northern and southern hemispheres to major impacts and volcanic processes the rough elevated southern hemisphere has a relatively featureless gravitational signature indicating a state of near isostatic compensation whereas the smooth low northern plains display a wider range of gravitational anomalies that indicates a thinner but stronger surface layer than in the south the northern hemisphere shows evidence for buried impact basins although none large enough to explain the hemispheric elevation difference the gravitational potential signature of tharsis is approximately axisymmetric and contains the tharsis montes but not the olympus mons or alba patera volcanoes the gravity signature of valles marineris extends into chryse and provides an estimate of material removed by early fluvial activity

crossover analysis of mars orbiter laser altimeter data in its first 15 months of continuous operation the mars orbiter laser altimeter mola instrument aboard mars global surveyor ranged to mars over 330 million times generating more than 5000 orbital profiles with a ranging precision of 0 4 m over smooth terrain the accuracy of the profiles depends on knowledge of the spacecraft position orientation and observation time which are subject to errors we model these errors via the analysis of over 24 million altimetric crossovers a quasiperiodic once per revolution adjustment of the ground tracks as a function of time in three locally orthogonal directions minimizes the altimetric residuals via least squares using a sparse matrix technique computational effort scales linearly with the number of crossovers and only marginally with the number of parameters orbital errors mainly result from poor modeling of spacecraft thrusting events in the absence of tracking seasonal effects likely due to changing thermal environment as well as residual miscalibrations are evident in the pointing solutions incorporating multiple parameters per revolution significantly improves crossover residuals and resolves pointing aberrations during orbital transitions from night to day altimetry from the adjusted tracks generates a topographic model whose accuracy is typically better than 1 m vertically with respect to the center of mass of mars the centroid position of each mola shot is typically accurate to 100 m horizontally terrain models from accurately located lidar data can be gradient shaded to illuminate geological structures with 1 in 1000 slopes that are invisible to cameras temporal changes in elevation e g frost deposition ablation at decimeter levels may also be assessed using crossovers but results must be interpreted with caution due to uncertainties in range walk correction

identification delineation and morphometric analysis of closed terrain depressions on mars abstract the purpose of this paper is to introduce an easy to use but powerful methodology that allows closed terrain depressions on the mars landscape to be correctly identified and delineated from digital elevation models closed terrain depressions have important implications for the geology and geomorphology of mars where they have been formed by the processes of impact subsidence collapse trickle down of unconsolidated material tensional tectonic forces dissolution and erosion the application of the procedure to six test sites covering a representative range of mars landscapes shows that closed depressions are ubiquitous on mars from the southern highlands where they cover 37 of the surface to the northern lowlands where they cover 26 of the surface the minimum coverage of 9 occurs on the tharsis dome around the three giant tharsis volcanoes a power law distribution which is directly related to the fractal dimension is shown to provide a very good fit to the size distribution of mars depressions in addition to the fractal dimension several other morphometric parameters are calculated to demonstrate the use of the methodology in planetary geology the work presented here uses digital elevation models provided by the mars orbiter laser altimeter mola the resolution of which limits the identification of terrain depressions to those that have diameters greater than around 460 m the methodology is however general and can be applied to smaller scale depressions that are available in detailed digital elevation models obtained from high resolution images such as the high resolution imaging science experiment hirise mounted on the mars reconnaissance orbiter this opens up a wide range of applications using the simple but powerful methodology described in this paper

an investigation of martian northern high latitude and polar impact crater interiors atypical interior topographic features and cavity wall slopes abstract we examine martian northern high latitude and polar impact craters npics to better understand the north polar materials and polar processes we examine topographic characteristics for 346 npics and compare them to global fit data e g garvin et al 2003 boyce and garbeil 2007 as well as to a small set n 92 of southern high latitude and polar impact craters spics we find that the npic population above 57 n is significantly shallower than the global crater population this suggests that the npics 1 were initially shallow due to target properties of polar geologic units 2 were once deeper but have been infilled due to polar processes or 3 a combination of both indeed many of the npics exhibit considerable noncentral peak interior topographic features ifts which may be indicative of infilling processes the npic ifts also appear to display trends in their preferential orientation within the crater cavity some spics display similar interior features but do not show a clear preference in their orientation within the crater cavity in addition the npic population displays cavity wall slope trends that seem to indicate steepening of slopes with increasing crater diameter in comparison to the global slope trend garvin et al 2003 these trends suggest that the npics are unique in their geometry when compared to the global data set as well as with the spics further indicating that the north polar region may exhibit target properties and polar processes not seen in the south polar region or elsewhere on mars

ranging performance of satellite laser altimeters topographic mapping of the earth moon and planets can be accomplished with high resolution and accuracy using satellite laser altimeters these systems employ nanosecond laser pulses and microradian beam divergences to achieve submetre vertical range resolution from orbital altitudes of several hundred kilometres in this paper the authors develop detailed expressions for the range and pulsewidth measurement accuracies and use the results to evaluate the ranging performances of several satellite laser altimeters currently under development by nasa for launch during the next decade the analysis includes the effects of the target surface characteristics spacecraft pointing jitter and waveform digitizer characteristics the results show that ranging accuracy is critically dependent on the pointing accuracy and stability of the altimeter especially over high relief terrain where surface slopes are large at typical orbital altitudes of several hundred kilometres single shot accuracies of a few centimetres can be achieved only when the pointing jitter is on the order of 10 mu rad or less

hydrological evolution during the last 15 kyr in the tso kar lake basin ladakh india derived from geomorphological sedimentological and palynological records abstract the tso kar lake basin in ladakh northwestern himalayas 33 18 n 78 e 4527 m a s l is located close to the modern boundary of effective moisture transport from the indian summer monsoon in order to reconstruct the possible monsoonal impact on the hydrology of the lake basin during the last 15 kyr we studied the geomorphology of the basin and combined the results with multi proxy records from tso kar lake sediments major analyses comprise geochemical data high resolution x ray fluorescence xrf mineral composition xrd aquatic pollen and non pollen palynomorphs npp although the chronological framework based on 41 14c ams dates remains speculative for the lateglacial and late holocene periods our results indicate major hydrological phases linked to regional climate variations and tectonic activity the maximum glacier advance falls within the period between the global lgm and ca 15 kyr bp while the basin remained open and may have drained along the paleo tso kar river tectonic pulses may have triggered terrace development and the closure of the lake the estimated mean vertical displacement rate accounts for 7 9 mm yr considerable summer monsoon moisture supply occurred for the periods around 12 5 kyr bp and between ca 11 5 and 8 6 kyr bp indicated by deposition of more profundal lake facies and the development of aquatic fauna and flora the lake level rise about 11 8 kyr bp was due to intensified glacier melt and summer monsoon effective moisture supply the lake reached its maximum level and extent between 8 5 and 7 kyr bp under warm moist climate conditions permafrost was absent from the basin summer monsoon influence weakened after 8 kyr bp with a short reverse trend at ca 5 6 kyr bp the lake shrank gradually after 7 kyr bp towards its lowest stand at about 4 2 kyr bp with return of permafrost activity subsequent terrace formation was probably amplified by tectonic movement the lake remained at a low level with minor fluctuations the results indicate that the orbitally driven regional climate variability is well reflected in the tso kar basin by hydrological variations considerable summer monsoon moisture seems to have influenced the area only during the early holocene the late quaternary evolution of the tso kar was controlled by the interplay of climate forces local morphodynamics and tectonic impact

quaternary geology tectonics and distribution of palaeo and present fluvio glacio lacustrine deposits in ladakh nw indian himalaya a study based on field observations abstract the ladakh region of the northwestern indian himalaya is rich in quaternary deposits but it has not received much attention previous quaternary research in the region has focused on the glacial sequences and only some scattered data of the lacustrine deposits are available this article addresses the reconstruction of the palaeo lacustrine deposits and the present day lakes and their distribution in the ladakh region the region was under the influence of tectonic activity and cold climate during the late quaternary times tectonic activity at 50 000 years bp 35 000 years bp and 25 000 years bp has been recorded we report the presence of three major lakes in the region in the late quaternary these formed due to the damming of the indus river and its tributaries by debris avalanches initiated mainly by tectonic activity along the indus suture shyok suture and the karakoram fault these are the spituk leh palaeolake formed 50 000 years bp the lamayuru palaeolake dated to 35 000 years bp in the indus valley and the khalsar palaeolake 60 km in length in the shyok valley vast exposures of the palaeolake deposits ranging from 25 to 150 m in thickness are reported spituk section 25 m lamayuru section 110 m and khalsar 150 m and hundri 100 m and which have a wide lateral extent a glacial lake basin at bhaktpur city north of baralacha la is now completely filled the tsokar lake has been subdivided into smaller units now and the water level is lowering other lakes in the region e g pangong tso tso morari the twin kyun tso lakes are confined to the western side of the study area limited chemical weathering rapid erosion and cold climatic conditions in late quaternary times are suggested by the stable illite values in the lamayuru section four levels of palaeoseismic structures convolute structures sand dykes intraformational folds micro faulting are present in the khalsar section and at three levels in the tirit section at shyok nubra confluence palaeoseismic activity was also prevalent after 25 000 years bp as is evident from the three levels of palaeoseismic structures in the younger sediments

high resolution topomapping of candidate mer landing sites with mars orbiter camera narrow angle images 1 we analyzed narrow angle mars orbiter camera moc na images to produce high resolution digital elevation models dems in order to provide topographic and slope information needed to assess the safety of candidate landing sites for the mars exploration rovers mer and to assess the accuracy of our results by a variety of tests the mapping techniques developed also support geoscientific studies and can be used with all present and planned mars orbiting scanner cameras photogrammetric analysis of moc stereopairs yields dems with 3 pixel typically 10 m horizontal resolution vertical precision consistent with 0 22 pixel matching errors typically a few meters and slope errors of 1 3 these dems are controlled to the mars orbiter laser altimeter mola global data set and consistent with it at the limits of resolution photoclinometry yields dems with single pixel typically 3 m horizontal resolution and submeter vertical precision where the surface albedo is uniform the dominant error is 10 20 relative uncertainty in the amplitude of topography and slopes after calibrating photoclinometry against a stereo dem to account for the influence of atmospheric haze we mapped portions of seven candidate mer sites and the mars pathfinder site safety of the final four sites elysium gusev isidis and meridiani was assessed by mission engineers by simulating landings on our dems of hazard units mapped in the sites with results weighted by the probability of landing on those units summary slope statistics show that most hazard units are smooth with only small areas of etched terrain in gusev crater posing a slope hazard

the effects of laterally varying icy shell structure on the tidal response of ganymede and europa we use a finite element model to solve for the response of ganymede and europa to tidal forcing from jupiter using various icy shell models with laterally variable 3 d structure in all cases the shell is assumed to be underlain by a liquid water ocean icy shells with laterally varying thickness are derived from a thermal conduction model three dimensional shear modulus profiles for the shell are built either from a conduction model or for europa by assuming a hemispherical difference in composition icy shell structures with a nonglobal ocean are built for ganymede using these shell structures to calculate the tidal response of ganymede and europa we conclude the following 1 the presence of lateral variations in thickness or in shear modulus would not degrade future attempts to use tidal observations to decide on the existence or absence of a liquid ocean and to determine the mean icy shell thickness 2 given accurate enough observations the presence of lateral variations in thickness or in shear modulus could be determined by searching for nondegree 2 components in the tidal response 3 in the absence of significant viscous convective flow in the shell the effects of a laterally varying shear modulus on the tidal response would be smaller than those of a laterally varying shell thickness 4 if the shell is partially grounded tidal observations of either gravity or uplift would be able to roughly differentiate regions where the ice is grounded from those where it is floating

timings and causes of glacial advances across the pep ii transect east asia to antarctica during the last glaciation cycle a comparison of glacial advances through the last glacial cycle between northern and southern hemispheres in the pep 2 transect east asia and australasia revealed 1 a relatively good synchrony of glacial advances during the lgm across the whole transect except antarctica 2 a rough synchrony in glacial advances in the karakorums himalayas japan and new zealand during marine isotope stages mis 3 and 4 although the age control is still poor and 1 a greater glacial extent in mis 3 and 4 than in mis 2 the lgm advances are driven by northern hemisphere temperature forcing but the mis 3 and or mis 4 advances appear to be dominantly controlled by the effects of moisture availability or lack of thereof in mainland australia and antarctica glaciers advanced only in the most humid phases in himalaya and karakorum where the moisture is supplied both by a summer monsoon and the westerlies timings of glacier advance coincide with both summer monsoon enhancement and westerly intensification in japan the glacier extent is controlled by monsoon changes sea surface temperatures ssts in the japan sea moisture source and by zonal shifts in westerly circulation in new zealand either insolalion changes or changes in the intensity of westerly circulation are invoked lis the main track of the westerlies did not change greatly during glacial times c 2003 elsevier ltd and inqua all rights reserved

igneous dikes on mars revealed by mars orbiter laser altimeter topography the origin of martian grabens has remained controversial for decades given the nonuniqueness of graben morphology and conflicting interpretations of dike induced or faultingbased formation processes we use measurements from the mars orbiter laser altimeter to identify the characteristic topographic signature at the surface of an igneous dike beneath a martian graben our results suggest that this subtle but diagnostic signature can be used to test competing interpretations of the formation of grabens and associated fissures and collapse depressions

mars reconnaissance orbiter radio science gravity investigation 1 the objectives of the mars reconnaissance orbiter mro radio science gravity investigation are to improve knowledge of the static structure and characterize the temporal variability of the martian gravitational field relevant to the planet s internal dynamics the structure and dynamics of the atmosphere and the orbital evolution of spacecraft at mars the investigation will utilize range rate and range measurements from x band and when available ka band tracking systems of the mro spacecraft mro will enable a considerable improvement in the spatial resolution and quality of mars global gravity field the low orbital periapsis of mro 255 km will yield gravity maps suitable for study of regional 102 km structure of the crust and lithosphere the addition of tracking data from the mars global surveyor and mars odyssey spacecraft also currently orbiting mars will be useful in decorrelating errors in spherical harmonic coefficients of the gravity field that will improve the quality of the static field studies of the low degree gravity field combined with measurements of rotational dynamics will permit insight about the structure of mars deep interior changes in the low degree spherical harmonic coefficients of the martian gravity field and in polar mass anomalies will be used to track the seasonal cycle of co2 exchange with the surface measurements of spacecraft drag will be used to estimate density variations in the atmosphere relevant to weather patterns and aerobraking of future spacecraft tracking observations will also be used to improve the ephemeris of mars and the masses of the martian moons

inverted fluvial features in the aeolis zephyria plana western medusae fossae formation mars evidence for post formation modification 1 the aeolis and zephyria plana contain the western most portion of the medusae fossae formation mff an enigmatic and extensive light toned deposit located in the martian equatorial region and dated from the hesperian to amazonian epochs this area hosts a large population of sinuous ridges srs interpreted as inverted fluvial features formed by precipitation indurated by chemical cementation buried by subsequent deposition and finally exhumed this interpretation of srs as uniformly fluvial represents a modification to an earlier hypothesis for one particular sr of possible glaciofluvial i e esker formation these srs provide a tool to investigate the degree and character of post fluvial modification processes in this region we combined digital terrain models made from context camera ctx and high resolution imaging science experiment hirise stereo image pairs with individual data points from the mars orbiter laser altimeter mola to estimate relief cross sectional profiles longitudinal profiles and slope directions of selected srs longitudinal profiles of several srs display undulations with amplitudes of up to order 100 m while some of the lower amplitude undulations may be due to differential erosion undulations having amplitudes in excess of sr relief require alternative explanations our combined morphologic and topographic analysis suggests that multiple post flow processes including compaction of the deposits and tectonic displacements have modified the original sr profiles specification of the type s and magnitudes of these modification processes will contribute to understanding both the potential of post flow modification of fluvial profiles elsewhere on mars as well as the nature and properties of the mff

late glacial and holocene vegetation indian monsoon and westerly circulation in the trans himalaya recorded in the lacustrine pollen sequence from tso kar ladakh nw india abstract palynological investigation of a 410 cm long core section from tso kar 33 10 n 78 00 e 4527 m a s l an alpine lake situated in the arid ladakh area of nw india at the limit of the present day indian summer monsoon was performed in order to reconstruct post glacial regional vegetation and climate dynamics the area was covered with alpine desert vegetation from ca 15 2 to 14 kyr bp 1 kyr 1000 cal years reflecting dry and cold conditions high influx values of long distance transported pinus sylvestris type pollen suggest prevailing air flow from the west and northwest the spread of alpine meadow communities and local aquatic vegetation is a weak sign of climate amelioration after ca 14 kyr bp pollen data e g influx values of pinus roxburghii type and quercus suggest that this was due to a strengthening of the summer monsoon and the reduced activity of westerly winds the further spread of artemisia and species rich meadows occurred in response to improved moisture conditions between ca 12 9 and 12 5 kyr bp the subsequent change towards drier desert steppe vegetation likely indicates more frequent westerly disturbances and associated snowfalls which favoured the persistence of alpine meadows on edaphically moist sites the spread of chenopodiaceae dominated vegetation associated with an extremely weak monsoon occurred at ca 12 2 11 8 kyr bp during the younger dryas interstadial a major increase in humidity is inferred from the development of artemisia dominated steppe and wet alpine meadows with gentianaceae after the late glacial early holocene transition in response to the strengthening of the summer monsoon monsoonal influence reached maximum activity in the tso kar region between ca 10 9 and 9 2 kyr bp the subsequent development of the alpine meadow steppe and desert steppe vegetation points to a moderate reduction in the moisture supply which can be linked to the weaker summer monsoon and the accompanying enhancement of the winter westerly flow from ca 9 2 to 4 8 kyr bp the highest water levels of tso kar around 8 kyr bp probably reflect combined effect of both monsoonal and westerly influence in the region an abrupt shift towards aridity in the tso kar region occurred after ca 4 8 kyr bp as evidenced by an expansion of chenopodiaceae dominated desert steppe low pollen influx values registered ca 2 8 1 3 kyr bp suggest scarce vegetation cover and unfavourable growing conditions likely associated with a further weakening of the indian monsoon

properties of a martian local dust storm in atlantis chaos from omega mex data abstract in this study we present the analysis of the dust properties of a local storm imaged in the atlantis chaos region on mars by the omega imaging spectrometer on march 2nd 2005 we use the radiative transfer model mitra to study the dust properties at solar wavelengths between 0 5 m and 2 5 m and infer the connection between the local storm dynamics and the topography we retrieve maps of effective grain radius reff optical depth at 9 3 m 9 3 and top altitude ta of the dust layer our results show that large particles reff 1 6 m are gathered in the centre of the storm lat 33 5 s lon 183 5 w where the optical depth is maximum 9 3 7 0 and the top altitude exceeds 18 km outside the storm we obtain 9 3 we speculate that a low thermal inertia region at the western border of atlantis chaos is a possible source of the dust storm moreover we find evidence that topography plays a role in confining the local storm in atlantis chaos the vertical wind component from the gcm does not provide any hint for the triggering of dust lifting on the other hand the combination of the horizontal and vertical wind profiles suggests that the dust once lifted is pushed eastward and then downward and gets confined within the north east ridge of atlantis chaos from our results the thickness of the dust layer collapsed on the surface ranges from about 1 m at the storm boundaries up to more than 100 m at its centre we verify that a layer of dust thicker than 1 m deposited on the surface can prevent the detection of mafic absorption features however such features are still present in omega data of atlantis chaos registered after the storm hence we deduce that once the storm is over the dust deposited on an area larger than the one where it has been observed

elastic dislocation modeling of wrinkle ridges on mars wrinkle ridges are one of the most common landforms on mars although it is generally agreed that they are compressional tectonic features formed by folding and thrust faulting there is no consensus on the number of faults involved the geometry of the faults or the maximum fault depth the topography of martian wrinkle ridges in solis planum and lunae planum has been studied using mola data as determined in previous studies the topography shows that most wrinkle ridges are a composite of two landforms a broad low relief arch and a superimposed ridge constrained by mola topographic profiles the geometry and parameters of the faults associated with wrinkle ridges have been modeled the best fits are obtained with a blind listric thrust fault that flattens into a decollement the listric fault geometry is approximated by a series of linear connecting segments with varying dips the major morphologic elements of wrinkle ridges can be matched by varying the displacement on the different fault segments modeling of large scale wrinkle ridges indicates that the maximum depth of faulting or depth to the decollement is about 4 5 km this may correspond to the depth of the contact between the ridged plains volcanic sequence and the underlying megabreccia the results suggest that wrinkle ridge thrust faults are shallow rooted and reflect thin skinned deformation

geochronology and geochemistry of granitoids related to the giant dahutang tungsten deposit middle yangtze river region china implications for petrogenesis geodynamic setting and mineralization abstract porphyry and skarn deposits in the middle yangtze valley within the northern yangtze craton have a combined tungsten resource of 3 million tonnes mt and represent one of the most important tungsten regions in the world the dahutang porphyry tungsten deposit with reserves of 1 mt is one of the largest deposits uranium pb analyses for the ore related granitoids yield ages of 147 4 0 58 ma 148 3 1 9 ma for porphyritic biotite granite 144 7 0 47 ma 146 1 0 64 ma for fine grained granite and 143 0 0 76 ma 143 1 1 2 ma for granite porphyry a progressive youngling of ages that is consistent with field observations geochemical data show that the three types of granite are characterized by enrichments in rb pb and u and depletion in ba nb p and ti with asi molar al 2 o 3 cao na 2 o k 2 o 1 1 that is characteristic of a peraluminous melt the p 2 o 5 contents of the granites are 0 13 0 37 and have a positive correlation with sio 2 and they are thus s type intrusions they exhibit initial 87 sr 86 sr of 0 721 to 0 731 and e nd t of 5 06 to 7 99 for porphyritic biotite granite 0 7196 to 0 7289 and 6 29 to 6 74 for fine grained granite and 0 7153 to 0 7365 and 5 09 to 7 64 for granite porphyry chondrite normalized rare earth element ree patterns for the granites are characterized by enrichment in the light ree and a strong negative eu anomaly indicating that they were derived from the proterozoic pelitic and psammitic basement strata and experienced strong fractional crystallization of plagioclase our ca 150 140 ma age for the dahutang s type magmatism and w mineralization is identical to that of the i type magmatism related to cu au mo fe bearing porphyry and skarn deposits along the middle to lower yangtze river valley we propose that the latest jurassic to earliest cretaceous granitoids and ores formed during a tearing of the subducting izanagi slab which caused the upwelling of asthenosphere and resulting mantle crust interaction the s type granitoids and related w ore systems resulted from the re melting of the proterozoic crust whereas the i type granitic rocks and related ores are attributed to the partial melting of the subducted slab

the last glacial maximum climate over europe and western siberia a pmip comparison between models and data under the framework of the palaeoclimate modelling intercomparison project pmip 17 climate models 16 of which are atmospheric general circulation models have been run to simulate the climate of the last glacial maximum 21 000 years ago using the same set of boundary conditions parallel to these numerical experiments new consistent data bases have been developed on a continental scale the present work compares the range of the model responses to the large perturbation corresponding to the conditions of the last glacial maximum with consistently derived climate reconstructions from pollen records over europe and western siberia it accounts for the differences in the model results due to the models themselves and directly compares this error bar due to the models to the uncertainties in the climate reconstructions from the pollen records overall the last glacial maximum climate simulated by the models over western europe is warmer especially in winter and wetter than the one depicted by the reconstructions this is the region where the reconstructed increase in temperature precipitation and moisture index from the last glacial maximum to the present conditions is largest the same disagreement but of smaller amplitude is found over central europe and the eastern mediterranean basin while models and data are in broad agreement over western siberia the numerous modelling results allow a study of the link between the changes in atmospheric circulation and those in temperature and an interpretation of the discrepancies in precipitation in terms of those in temperature

eridania basin an ancient paleolake floor as the next landing site for the mars 2020 rover abstract the search for traces of past martian life is directly connected to ancient paleolakes where ponding water or low energy water fluxes were present for long time intervals the eridania paleolakes system located along the 180 meridian is one of the largest lacustrine environments that were once present on mars morphological features suggest that it was constituted by connected depressions filled by water to maximum depths of 2400 m and a volume of at least 562 000 km3 we focused our attention on the northern side of the eridania basin where high albedo uneven patches of material characterized by the absence of dust are present based on omega and crism orbital imaging spectroscopy data a large clay bearing unit has been identified there in particular a set of aqueous minerals in present in the stratigraphy being visible through erosional windows in the first several tens of meters of the sedimentary sequence below this capping unit a thin al rich clay stratum attributable to al smectite and or kaolins is present this overlies a fe rich clay stratum attributable to the nontronite smectite at the base of the mineralogic sequence a stratum that could be either a zeolite or more likely a hydrated sulfate is present in addition small deposits of alunite a rare phase on mars and jarosite are here found at several locations such stratigraphy is interpreted as originating from a surface weathering process similar to terrestrial abiotic pedogenesis nonetheless possible exobiologic processes can be also invoked to explain it nasa s spirit rover landed on gusev crater in 2004 near the mouth of the ma adim vallis which connects this crater with the considered paleolakes system the eridania site provides the unique opportunity to complete the measurements obtained in gusev crater while investigating the exposed mineralogical sequence in its depositionary setting in addition the extremely favorable landing parameters such as elevation slope roughness rock distribution thermal inertia and dust coverage support this location as a possible landing site for the nasa mars 2020 rover

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

modeling the formation of bright slope deposits associated with gullies in hale crater mars implications for recent liquid water abstract our study investigates possible formation mechanisms of the very recent bright gully deposits bgds observed on mars in order to assess if liquid water was required we use two models in our assessment a one dimensional 1d kinematic model to model dry granular flows and a two dimensional 2d fluid dynamic model flo 2d o brien et al 1993 flo engineering to model water rich and wet sediment rich flows our modeling utilizes a high resolution topographic model generated from a pair of images acquired by the high resolution imaging science experiment hirise aboard the mars reconnaissance orbiter for the 1d kinematic modeling of dry granular flows we examine a range of particle sizes flow thicknesses initial velocities flow densities and upslope initiation points to examine how these parameters affect the flow run out distances of the center of mass of a flow our 1d modeling results show that multiple combinations of realistic parameters could produce dry granular flows that travel to within the observed deposits boundaries we run the 2d fluid dynamic model flo 2d to model both water rich and wet sediment rich flows we vary the inflow volume inflow location discharge rate water loss rate water rich models only and simulation time and examine the resulting maximum flow depths and velocities our 2d modeling results suggest that both wet sediment rich and water rich flows could produce the observed bright deposits our modeling shows that the bgds are not definitive evidence of recent liquid water on the surface of mars

statistics of mars topography from the mars orbiter laser altimeter slopes correlations and physical models data obtained recently by the mars orbiter laser altimeter mola were used to study the statistical properties of the topography and slopes on mars we find that the hemispheric dichotomy manifested as an elevation difference can be described by long baseline tilts but in places is expressed as steeper slopes the bimodal hypsometry of elevations on mars becomes unimodal when referenced to the center of figure contrary to the earth for which the bimodality is retained however ruling out a model in which the elevation difference is expressed in a narrow equatorial topographic step cannot be done by the hypsometry alone mars slope distribution is longer tailed than those of earth and venus indicating a lower efficiency of planation processes relative to relief building tectonics and volcanics we define and compute global maps of statistical estimators including the interquartile scale rms and median slope and characteristic decorrelation length of the surface a correspondence between these parameters and geologic units on mars is inferred surface smoothness is distinctive in the vast northern hemisphere plains where slopes are typically 0 5 amazonis planitia exhibits a variation in topography of 1 m over 35 km baselines the region of hematite mineralization in sinus meridiani is also smooth with median slopes lower than 0 4 but does not form a closed basin the shallower long wavelength portion of the lowlands topographic power spectrum relative to the highlands can be accounted for by a simple model of sedimentation such as might be expected at an ocean s floor the addition of another process such as cratering is necessary to explain the spectral slope in short wavelengths among their application these mola derived roughness measurements can help characterize sites for landing missions

investigating the volcanic versus aqueous origin of the surficial deposits in eastern elysium planitia mars abstract the elysium volcanic province consists of numerous overlapping flow units and may include the youngest lava flows on mars however it is possible that these volcanic units have been modified or overprinted by aqueous processes understanding the timing of the igneous and aqueous events in this region is therefore essential for constraining the geological and environmental history of mars during the amazonian period we investigate the geologic evolution of eastern elysium planitia to determine the relationship between major units with the support of a geological map and chronological constraints from crater size frequency distributions we also evaluate the hypothesized origin of these units via volcanic fluvial and or fluvioglacial processes using a detailed facies mapping approach the study area includes the eastern cerberus fossae rahway valles and marte vallis the surficial deposits in rahway valles were formerly interpreted to be modified by fluvial and fluvioglacial processes however our facies map reveals that the surface of eastern elysium planitia includes nineteen morphologically distinct regions i e facies which are interpreted to be the products of flood lava volcanism including a p hoehoe and transitional lava flow types in contrast to previous studies which determined that rahway valles and marte vallis consist of two distinct geologic units with middle to late amazonian ages the results of this work show that the region was resurfaced by at least two volcanic flows with much younger ages of 20 0 ma and 8 8 ma furthermore by coupling results of our geologic and facies mapping with chronological constraints as well as subsurface information provided by shallow radar reflectors we show that there is an erosional unconformity located between the two youngest lava flow units in marte vallis we interpret that this unconformity was generated by a catastrophic aqueous flooding event that occurred only 8 8 20 0 ma ago this implies alternating episodes of volcanism and aqueous flooding that have continued into the geologically recent past on mars and may again occur within elysium planitia

the location of airy 0 the mars prime meridian reference from stereo photogrammetric processing of themis ir imaging and digital elevation data the small crater airy 0 was selected from mariner 9 images to be the reference for the mars prime meridian initial analyses in the year 2000 tied viking orbiter and mars orbiter camera images of airy 0 to the evolving mars orbiter laser altimeter global digital terrain model to update the location of airy 0 based upon this tie and radiometric tracking of landers rovers from earth new expressions for the mars spin axis direction spin rate and prime meridian epoch value were produced to define the orientation of the martian surface in inertial space over time since the mars global surveyor mission and mars orbiter laser altimeter global digital terrain model were completed some time ago a more exhaustive study has been performed to determine the accuracy of the airy 0 location and orientation of mars at the standard epoch thermal emission imaging system themis ir image cubes of the airy and gale crater regions were tied to the global terrain grid using precision stereo photogrammetric image processing techniques the airy 0 location was determined to be about 0 001 east of its predicted location using the currently defined international astronomical union iau prime meridian location information on this new location and how it was derived will be provided to the nasa mars exploration program geodesy and cartography working group for their assessment this nasa group will make a recommendation to the iau working group on cartographic coordinates and rotational elements to update the expression for the mars spin axis direction spin rate and prime meridian location

channel slope reversal near the martian dichotomy boundary testing tectonic hypotheses abstract faults along the martian dichotomy boundary are evidence of tectonic activity which by analogy with terrestrial tectonism may cause changes in or even reversal of fluvial longitudinal profiles in the eastern hemisphere between 30 e and 150 e this tectonic activity has been hypothesized to result from lower crustal flow or from lithospheric flexure for which loading e g by material deposition of the northern lowlands is a possible cause watters 2003a nimmo 2005 the topographic slope changes resulting from these two different mechanisms are distinct and can provide a means for distinguishing between them although other processes may complicate interpretations of reversed longitudinal profiles two fan shaped networks of inverted channels are located near 150 e in the aeolis dorsa region just north of the dichotomy boundary their original flow directions inferred from planform morphology suggest flow to the northeast in contrast to their current longitudinal profiles sloping down to the southwest this contrast indicates slope reversal we investigate the lower crustal flow and flexure mechanisms for slope reversal by testing three different hypotheses 1 lower crustal flow 2 flexure caused by material erosion from the highlands and deposition in the lowlands and 3 flexure caused by highland erosion and deposition in the lowlands plus deposition of the medusae fossae formation in the lowlands we test these three hypotheses by comparing the inferred magnitudes of the slope reversals with predicted slope changes from geophysical models for these processes taking the possibility of non tectonic i e collapse processes into account our results suggest that among these three models the slope reversal is most consistent with the predicted tectonic response to erosion and deposition of highland material in conjunction with deposition of the medusae fossae formation contrary to previous findings our results do not support the mechanism of lateral crustal flow although they do not rule it out because lower crustal flow and erosion may both have been operating but on different time scales the result of this hypothesis testing provides insight into the evolution of the dichotomy boundary and martian crust in this location

thrust faults along the dichotomy boundary in the eastern hemisphere of mars 1 mars orbiter laser altimetry mola data have been used to characterize lobate scarps along the dichotomy boundary in the eastern hemisphere of mars these structures are the surface expression of thrust faulting of the southern highlands displacement on the thrust faults is generally less than 1 km except in the case of the amenthes rupes thrust fault where the maximum displacement is on the order of 3 km the ratio of maximum displacement to fault length of the population of thrust faults is 6 2 10 3 n 26 consistent with previous estimates for martian thrust faults based on photoclinometrically derived topography and other planetary thrust fault populations thrust faulting is roughly coincident with late noachian to early hesperian fracturing and normal faulting along the dichotomy boundary this suggests that the formation of the present day dichotomy boundary involved compressional and extensional deformation the long wavelength topography suggests that the dichotomy boundary in the eastern hemisphere may have been formed by flexure of the southern highlands lithosphere lithospheric flexure alone cannot account for the thrust faulting of the highlands along the dichotomy boundary a combination of stresses due to bending erosion and global contraction may have formed the lobate scarp thrust faults

sharp decrease in summer monsoon strength 4000 3500 cal yr b p in the central higher himalaya of india based on pollen evidence from alpine peat age constrained pollen data and magnetic susceptibility of an alpine peat profile from the garhwal higher himalaya display a continuous record of climate and monsoon trends for the past 7800 yr about 7800 cal yr b p dominance of evergreen oak quercus semecarpifolia alder alnus and grasses in the pollen record reflect a cold wet climate with moderate monsoon precipitation from 7800 to 5000 cal yr b p vegetation was progressively dominated by conifers indicating ameliorated climate with a stronger monsoon a warm humid climate with highest monsoon intensity from 6000 4500 cal yr b p represents the mid holocene climatic optimum between 4000 and 3500 cal yr b p the abundance of conifers sharply decreased with the greatest increase in evergreen oak this trend suggests progressive cooling with a decrease in the monsoon to its minimum about 3500 cal yr b p two relatively minor cold dry events at ca 3000 and 2000 cal yr b p marked step wise strengthening of the monsoon until ca 1000 cal yr b p after a cold dry episode that culminated ca 800 cal yr b p the monsoon again strengthened and continued until today a sharp decrease in temperature and rainfall at 4000 3500 cal yr b p represents the weakest monsoon event of the holocene record this cold dry event correlates with proxy data from other localities of the indian subcontinent arabian sea and western tibet

depth distribution and density of co2 deposition on mars observations by the mars orbiter laser altimeter have been used to detect subtle changes of the polar surface height during the course of seasonal cycles that correlate with the expected pattern of co2 deposition and sublimation using altimetric crossover residuals from the mars orbiter laser altimeter we show that while zonally averaged data capture the global behavior of co2 exchange there is a dependence of the pattern on longitude at the highest latitudes the surface height change is as high as 1 5 2 m peak to peak and it decreases equatorward decomposition of the signal into harmonics in time allows inspection of the spatial pattern and shows that the annual component is strongly correlated with the residual south polar cap deposits and to a lesser extent with the north polar cap in the north the second harmonic semiannual component correlates with the location of the ice deposits the phases of the annual cycles are in agreement with observations by the thermal emission spectrometer of the timing of the annual disappearance of co2 frost from the surface at the high latitudes at lower latitudes frost sublimation crocus date predates the mean depositional minima as expected these global scale volumetric measurements of the distribution of condensed co2 can be combined with measurements of the deposited column mass density derived from the neutron spectrometer on board mars odyssey to yield an estimate of the density of the seasonally exchanging material of 0 5 0 1 g cm 3 these constraints should be considered in models of the martian climate system and volatile cycles

new slope normalized global gully density and orientation maps for mars we reanalyse the global distribution of gullies in order to provide a set of observational constraints that models of gully formation must explain we validate our results derived from the global data with four detailed case studies we show that the availability of steep slopes is an essential factor to consider when assessing the spatial distribution and abundance of gullies when the availability of steep slopes is taken into account it reveals with a few exceptions that gullies are found almost uniformly across the whole 30 90 latitude band our analysis also reveals that massive ice deposits are anti correlated with gullies and that the undulations in the equatorwards limits of the gully distribution could be explained by longitudinal variations in maximum surface temperatures controlled by variations in surface properties including thermal inertia and albedo we find a sharp transition in both hemispheres between pole facing gullies which extend from 30 to 40 to a more mixed but dominantly equator facing orientation of gullies polewards of 40 we have no definitive explanation for this transition but based on previous studies we suggest it could be linked to the availability of near surface ice deposits

south polar layered deposits of mars the cratering record data from the mars orbiter laser altimeter mola and mars orbiter camera moc instruments aboard the mars global surveyor mgs were used in a detailed search of a selected part of the south polar layered deposits spld for impact craters impact craters with diameters from 0 8 to 5 km were identified from a mola derived shaded relief map and were primarily validated using individual mola tracks and in select cases moc narrow angle images the resultant crater population determined in this study is at least four times the density of the crater population previously recognized from these new statistics we estimate the mean apparent surface age of the spld to be 30 100 ma depending on the established production model isochrons used all of these craters are considerably shallower than other martian craters in the same diameter range we attribute this shallowness to be the cause of the lower detection rates of previous studies there is a correlation between crater depth and rim height which suggests that both erosion and infilling have affected the crater forms a similar study of the north polar layered deposits uncovered no craters in this diameter range a limited population of craters smaller than 800 m was uncovered in higher resolution moc narrow angle images these do not appear to have been degraded to the same degree this separate population implies a surface exposure age of only 100 000 years and perhaps indicates an event that erased all small craters and degraded and infilled the larger ones

topography of the northern hemisphere of mars from the mars orbiter laser altimeter the first 18 tracks of laser altimeter data across the northern hemisphere of mars from the mars global surveyor spacecraft show that the planet at latitudes north of 50 is exceptionally flat slopes and surface roughness increase toward the equator the polar layered terrain appears to be a thick ice rich formation with a non equilibrium planform indicative of ablation near the periphery slope relations suggest that the northern tharsis province was uplifted in the past a profile across ares vallis channel suggests that the discharge through the channel was much greater than previously estimated the martian atmosphere shows significant 1 micrometer atmospheric opacities particularly in low lying areas such as valles marineris

holocene environmental changes in bangong co basin western tibet part 2 the pollen record abstract a better knowledge of environmental variations in key regions such as the tibetan plateau which plays a fundamental role in the indian monsoon dynamics and thus on the whole northern hemisphere atmospheric circulation is of great importance we present here a detailed paleoenvironmental study based on pollen analyses of a sediment core from lake bangong results on the modern pollen rain are also discussed as they give valuable information for the interpretation of the fossil pollen data the pollen results of the bangong sequence and their paleoclimatic interpretation are integrated into a chronological framework on the basis of palynostratigraphical methods because of dead carbon in the lake system it has been difficult to establish a reliable chronology of the bangong sequence using a geochemical model for correcting measured 14c ages the pollen record from lake bangong compares well with the record from lake sumxi in western tibet lake bangong core provides a continuous holocene pollen record before 9600 yr b p the dominance of desertic elements in the pollen record reflects an arid environment at about 9600 yr b p an abrupt shift to steppe vegetation suggests the onset of moister conditions and from 9500 to 6200 yr b p proxy data indicate conditions warmer and wetter than today proxy data also indicate short term changes during this interval climate instability is suggested by the development of a local palustral flora which peaks at 7700 yr b p and is interpreted as a lake regression in phase with increase in the percentage of littoral and saline water diatom species between 8600 and 7700 yr b p the first humid pulse culminating at 9000 8500 yr b p is thus followed by drier conditions around 8000 7700 yr b p the interval between 7200 and 6500 yr b p regarded as optimal for vegetation growth from the pollen record corresponds to a second humid pulse a trend towards aridity is observed during the following period with dry events centered around 5500 3900 3200 and 700 yr b p

an assessment of surface matching for the automated co registration of mola hrsc and hirise dtms abstract martian topographic data has been collected by various exploration missions over the last decade these products provide detailed topographic information and are invaluable for scientists to interpret and understand the geological and climate evolution which has occurred on mars in order to fully utilise these multi sensor multi resolution and multi scale martian topographic products a co registration process has been developed which allows co registration of digital terrain models dtms to be performed to co align these multiple datasets surface matching is the core technique to implement this task and it is here assessed to determine the parameters of the most robust algorithm for dtm co registration once this task was finished the matching tool was developed accordingly with a decision algorithm this algorithm was then employed to align dtms derived from mars orbiter laser altimeter mola high resolution stereo camera hrsc and high resolution imaging science experiment hirise for mola and hrsc dtms the co registration was performed directly as the mola dtm acted as a reference surface within a bundle adjustment process dtms from different versions covering three hrsc orbital strips were used for the assessment process as a result the mean bias of the height differences of a preliminary version hrsc dtm was significantly reduced from 38 596 m to 2 233 m when compared against mola while the bias of a newer dtm was improved from 1 616 m to 0 161 m after matching regarding the co registration of hirise and mola dtms a hierarchical approach employing a hrsc dtm as an intermediate dataset was assessed the results demonstrated that the method is feasible and that the three dtms were co registered effectively due to the success highlighted in this paper a surface matching tool is recommended to be applied to dtms derived from multiple sources before these data are further used moreover surface matching can be considered as an additional step of any workflow for mars dtm creation

modification of secondary craters on the martian south polar layered deposits secondary crater fields are important stratigraphic markers that can shed light on resurfacing processes that have occurred since their formation we examine the morphologies of secondary craters formed from the ejection of material from two large impacts on the martian south polar layered deposits spld mcmurdo crater at 84 5 s 0 w and an unnamed impact at 80 8 s 284 w the morphologies of these secondary craters allow us to impose constraints on the modification history of the spld we have quantified crater morphologies using data sets from the mars global surveyor and mars odyssey missions we find a complete lack of secondary craters smaller than 300 m in diameter in both crater fields which implies that at least the upper 30 m of the deposits have been resurfaced since the time of these impacts secondary crater depth to diameter ratios are low average of 0 016 indicating that significant degradation has occurred since their emplacement we find that vertical resurfacing alone is not enough to explain the observed depth to diameter distribution and suggest that viscous relaxation of craters coupled with a small amount of vertical resurfacing best fits the data in the mcmurdo field high depth to diameter craters are found preferentially on steeper terrain associated with scarps cutting through the secondary field this observation suggests that crater modification exhibits a dependence on slope we comment on possible mechanisms that may explain this observation the morphologies of secondary craters on the spld point to modification processes without lunar parallel and not yet fully modeled for mars

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

evaluation of paleohydrologic models for terrestrial inverted channels implications for application to martian sinuous ridges abstract fluvial systems can be preserved in inverted relief on both earth and mars few studies have evaluated the applicability of various paleohydrological models to inverted fluvial systems the first phase of this investigation focused on an extensive spanning 12 km inverted paleochannel system that consists of four sandstone capped carbonate cemented sinuous ridges within the early cretaceous cedar mountain formation located southwest of green river utah morphologic and sedimentologic observations of the exhumed paleochannels were used to evaluate multiple numerical models for reconstructing paleofluvial hydrological parameters another objective of the study was to determine whether aerial or orbital observations yield model results that are consistent with those constrained by field data the models yield an envelope of plausible dominant discharge values 100 500 m 3 s reflecting the limitations of the approach and no single model can be used to reliably estimate paleodischarge on mars landforms with attributes consistent with inverted channels have been identified in spite of differences in the formation history between these martian landforms and the terrestrial analog described here including potential differences in cement composition and the erosional agent that was responsible for relief inversion these numerical models can be applied with modification to the martian landforms and yield an envelope of plausible values for dominant discharge

mer spirit rover localization comparison of ground image and orbital image based methods and science applications 1 during 6 years of continuous operations on the martian surface the mars exploration rover mer spirit has covered a traverse of approximately 7 km from the landing point to its current position at troy near home plate localization of spirit and opportunity has been performed using two different methods one that employs an incremental bundle adjustment iba using rover imagery and one that compares image features common to both a rover orthoimage and an orbital orthoimage the iba method continuously yields the desired 3 d rover positions at a very high level of accuracy and provides a simultaneous solution for high quality topographic mapping of neighborhoods surrounding the rover on the other hand high resolution orbital imagery can verify rover positions wherever the rover track is visible rapid rover localization on the orbital orthoimage is often achieved by comparing a rover orthoimage to the orbital orthoimage in this paper we present research results from a systematic comparison of these two localization methods over the entire length of the spirit traverse two orbital orthoimages were generated from high resolution imaging science experiment hirise imagery integration of mars orbiter laser altimeter mola data into the hirise digital elevation model dem and orthoimage generation was performed and proved to be effective in reducing large inconsistencies between mola and hirise data this study found an overall difference of 1 5 percent of the traversed distance between the two sets of traverse positions derived using the two different localization methods after a geometric transformation from one traverse to the other the remaining inconsistency then represents the local differences between them and can be reduced to a level of less than 0 15 percent discussions of error sources and the strength and weakness of the methods are given scientific applications of the localization data are also briefly introduced

mapping rays and secondary craters from the martian crater zunil 1 zunil a 10 1 km rayed crater in elysium planitia mars produced more than 7 107 secondary craters 15 m in diameter we mapped zunil s rays from thermal ir themis nighttime images up to 1700 km from the primary crater and mapped bright and dark ejecta craters candidate secondaries up to 3600 km range ray segments were mapped up to 450 km east of zunil and up to 1700 km to the west both rays and bright ejecta craters are best detected over terrains with moderate thermal inertia which are abundant west of but not east of zunil nevertheless our interpretation is that zunil was created by a moderately oblique impact from the east zunil secondaries are abundant over all terrain types except the medusae fossae formation mff given the likely age of zunil 100 ma parts of the mff must be eroding at 0 08 m ma the size frequency distribution of the secondaries in zunil s rays and probable distant secondaries 750 1700 km to the west of zunil have a cumulative power law exponent near 5 whereas secondaries between the major rays have an exponent near 3 4 we modeled the size velocity relationship for zunil s ejected fragments it is consistent with the predictions of melosh 1984 for spallation of a strong surface layer and demonstrates that the inverse size velocity correlation continues up to at least 2 km s

the use of laser altimetry in the orbit and attitude determination of mars global surveyor altimetry from the mars observer laser altimeter mola an instrument on board the mars global surveyor mgs spacecraft has been analyzed for the period of the mgs science phasing orbit 1 spo 1 mission phase altimeter ranges have been used to improve significantly the orbit and attitude knowledge of the spacecraft by the use of crossover constraint equations derived from short passes of the mola data these constraint equations differ from traditional crossover constraints and exploit the small footprint associated with laser altimetry the rationale for using this technique with laser altimetry over sloping terrain is laid out and evidence of the resulting benefit is presented

spirit rover localization and topographic mapping at the landing site of gusev crater mars 1 by sol 440 the spirit rover has traversed a distance of 3 76 km actual distance traveled instead of odometry localization of the lander and the rover along the traverse has been successfully performed at the gusev crater landing site we localized the lander in the gusev crater using two way doppler radio positioning and cartographic triangulations through landmarks visible in both orbital and ground images additional high resolution orbital images were used to verify the determined lander position visual odometry and bundle adjustment technologies were applied to compensate for wheel slippage azimuthal angle drift and other navigation errors which were as large as 10 5 in the husband hill area we generated topographic products including 72 ortho maps and three dimensional 3 d digital terrain models 11 horizontal and vertical traverse profiles and one 3 d crater model up to sol 440 also discussed in this paper are uses of the data for science operations planning geological traverse surveys surveys of wind related features and other science applications

north south topographic slope asymmetry on mars evidence for insolation related erosion at high obliquity 1 a map of north south subkilometer scale slope asymmetry on mars obtained from statistical analysis of along track mola topographic profiles reveals well defined zonal belts of north south slope asymmetry at 40 50 latitude in both hemispheres in these narrow anomalous belts the pole facing slopes are systematically gentler than equator facing slopes this asymmetry is especially pronounced for the steepest 20 slopes in which pole facing slopes are three times less frequent than 20 slopes facing the equator we interpret these belts to be related to insolation asymmetry specifically we suggest that summertime melting of ground ice on pole facing slopes occurred during periods of very high obliquity 45 in the past and favored downslope movement of material and reduction of steep pole facing slopes

constraints on the volatile distribution within shackleton crater at the lunar south pole shackleton crater is nearly coincident with the moon s south pole its interior receives almost no direct sunlight and is a perennial cold trap making shackleton a promising candidate location in which to seek sequestered volatiles however previous orbital and earth based radar mapping and orbital optical imaging have yielded conflicting interpretations about the existence of volatiles here we present observations from the lunar orbiter laser altimeter on board the lunar reconnaissance orbiter revealing shackleton to be an ancient unusually well preserved simple crater whose interior walls are fresher than its floor and rim shackleton floor deposits are nearly the same age as the rim suggesting that little floor deposition has occurred since the crater formed more than three billion years ago at a wavelength of 1 064 nanometres the floor of shackleton is brighter than the surrounding terrain and the interiors of nearby craters but not as bright as the interior walls the combined observations are explicable primarily by downslope movement of regolith on the walls exposing fresher underlying material the relatively brighter crater floor is most simply explained by decreased space weathering due to shadowing but a one micrometre thick layer containing about 20 per cent surficial ice is an alternative possibility

computer generated global map of valley networks on mars 1 the presence of valley networks vn on mars suggests that early mars was warmer and wetter than present however detailed geomorphic analyses of individual networks have not led to a consensus regarding their origin an additional line of evidence can be provided by the global pattern of dissection on mars but the currently available global map of vn compiled from viking images is incomplete and outdated we created an updated map of vn by using a computer algorithm that parses topographic data and recognizes valleys by their morphologic signature this computer generated map was visually inspected and edited to produce the final updated map of vn the new map shows an increase in total vn length by a factor of 2 3 a global map of dissection density d derived from the new vn map shows that the most highly dissected region forms a belt located between the equator and mid southern latitudes the most prominent regions of high values of d are the northern terra cimmeria and the margaritifer terra where d reaches the value of 0 12 km 1 over extended areas the average value of d is 0 062 km 1 only 2 6 times lower than the terrestrial value of d as measured in the same fashion these relatively high values of dissection density over extensive regions of the planet point toward precipitation fed runoff erosion as the primary mechanism of valley formation assuming a warm and wet early mars peculiarity of the global pattern of dissection is interpreted in the terms of climate controlling factors influenced by the topographic dichotomy

tides on europa and the thickness of europa s icy shell 1 it has been shown previously that measurements of tides on jupiter s moon europa can be used to determine whether there is a liquid ocean beneath this moon s icy outer shell in this paper we examine the further possibility of constraining the thickness of the icy shell in the case where a liquid ocean exists by combining measurements of tidal gravity obtained from tracking an orbiting spacecraft with measurements of vertical tidal surface displacements obtained from a precise onboard altimeter by simulating a 1 month europa mapping mission we demonstrate that this combination of tidal measurements would provide a much better estimate of ice thickness than could be obtained using either tracking or altimeter measurements alone the thickness value inferred from the combined data would also require an estimate of the shear modulus of europa s icy shell this introduces an additional uncertainty in the thickness estimate that is approximately proportional to the uncertainty in the inverse of the shear modulus