surficial deposits at gusev crater along spirit rover traverses the mars exploration rover spirit has traversed a fairly flat rock strewn terrain whose surface is shaped primarily by impact events although some of the landscape has been altered by eolian processes impacts ejected basaltic rocks that probably were part of locally formed lava flows from at least 10 meters depth some rocks have been textured and or partially buried by windblown sediments less than 2 millimeters in diameter that concentrate within shallow partially filled circular impact depressions referred to as hollows the terrain traversed during the 90 sol martian solar day nominal mission shows no evidence for an ancient lake in gusev crater

structure and stratigraphy of home plate from the spirit mars exploration rover home plate is a layered plateau observed by the mars exploration rover spirit in the columbia hills of gusev crater the structure is roughly 80 m in diameter and the raised margin exposes a stratigraphic section roughly 1 5 m in thickness previous work has proposed a pyroclastic surge possibly followed by aeolian reworking of the ash for the depositional origin for these beds we have performed a quantitative analysis of the structure stratigraphy and sedimentology at this location our results are consistent with an explosive volcaniclastic origin for the layered sediments analysis of bedding orientations over half of the circumference of home plate reveals a radially inward dipping structure consistent with deposition in the volcanic vent or topographic draping of a preexisting depression detailed observations of the sedimentology show that grain sorting varies significantly between outcrops on the east and west sides observations on the western side show a well sorted population of sand sized grains which comprise the bedrock while the eastern margin shows a wider range of grain sizes including some coarse granules these observations are consistent with primary deposition by a pyroclastic surge however aeolian reworking of the upper stratigraphic unit is not ruled out identification of explosive volcanic products on mars may implicate magma interaction with subsurface hydrologic reservoirs in the past

spade a rock crushing and sample handling system developed for mars missions 1 a novel system has been developed to access and analyze the interior of rocks on mars by crushing rocks a miniature rock crusher has been prototyped along with a method for distribution of the fines and fragments produced by the rock crusher to inspection and analysis instruments the science goals and advantages of this approach are substantial with respect to understanding the geologic and climate history of mars via the investigation of its mineralogy and petrology the system is described in detail and results of various performance metrics are reported engineering considerations constraints on functionality fault tolerance and its previously planned deployment on the 2009 mars science laboratory mission are described

the effects of sediment supply and concentrations on the formation timescale of martian deltas abstract we used a comprehensive 2 d and 3 d basin filling morphodynamical model to explore the effects of changing hydrologic and sedimentary conditions on delta formation under martian conditions spatial and temporal deposition of sediment into a body of standing water was simulated using event based time stepping e g seasons river and sediment discharge were calculated using the darcy weisbach equation for width and depth averaged flow velocity and well known and tested terrestrial sediment transport predictors modified for application to martian flows a range in sediment grain sizes was determined from both landers and orbiting spacecraft data in order to include grain sizes typical of mars and yet representative of the martian deltas several different scenarios of seasonal river discharge and sediment supply were explored to encompass a range of possible formation conditions with the ability to track sediment as it is transported throughout the basin it is apparent that non negligible amounts of material are moved beyond the delta forming region this loss of sediment increased with river discharge increasing the gap between the calculated and modeled formation timescales these results have important implications for the formation timescales of the deltas and the small number of identifiable deltas on mars today formation timescales that consider only the supply of sediment to the system and do not take into account factors affecting deposition and delta formation are underestimates of the actual amount of time needed to form the deposits the lack of identifiable deltas in many paleolakes is likely a result of significant sediment transport beyond the channel mouth causing the expected delta deposit to be draped throughout the basin

timescales of fluvial activity and intermittency in milna crater mars milna crater mars 23 4s 12 3w exhibits signs of fluvial modification early in mars history including a large multi lobed fan deposit cut by several sinuous valleys we describe the past hydrologic conditions in milna and the surrounding area including a potential lake with a volume of 50 km 3 we also introduce new methods i to calculate the timescale of sediment deposition by considering fluvial sediment input into the entire crater while accounting for non fluvial input and ii to place improved constraints on the channel dimensions through which sediment was delivered to milna by comparing to the dimensions of inner channels found in valleys in the region surrounding milna by calculating the flux of fluid and sediment into the crater we find that the crater cavity was flooded for at least months and that the time of active fluvial sediment transport without hiatus is on the order of decades to centuries with a preferred timescale of centuries we also calculate the total amount of water required to transport the volume of sediment we measure in milna and conclude that impacts alone are likely insufficient to deliver enough water to milna to allow the sedimentary fill we see combining the timescales of fluvial activity in the adjacent parana valles with estimates for global noachian erosion rates we calculate an intermittency factor for fluvial activity of 0 01 0 1 during 10 5 10 6 yr near the noachian hesperian boundary in the parana valles region these values are comparable to arid climates on earth where the majority of fluvial sedimentary transport takes place during floods with multi year to decadal recurrence intervals our calculations of intermittency help to quantitatively reconcile the divergent estimates of the short and long timescales of fluvial activity on mars reported in the literature

distribution and characteristics of adirondack class basalt as observed by mini tes in gusev crater mars and its possible volcanic source abstract we identified 104 unique rock targets belonging to the olivine rich adirondack class using mini tes data rare rocks on the west spur of the columbia hills and on the plains east of the hills also belong to this class we present evidence that adirondack class basaltic lavas may have had their origin at apollinaris tholus linear modeling of adirondack class rock spectra shows only minor variations in mineralogy and the primary phases identified are consistent with olivine basalt having an average olivine composition of fo 45 we used factor analysis and target transformation to identify variability within a single class of rocks for the first time and we find that olivine abundance varies independently of a basaltic matrix a spectral component previously attributed to downwelling radiance is proposed here to be attributable to optically thin dust on rocks which has a greater effect on mini tes spectra than previously recognized but can explain the sloping continuum observed in adirondack class rock spectra as well as the apparent distortion of an olivine absorption spectral mixing is not completely linear leading to the overestimation of sulfate and olivine fractions and the underestimation of plagioclase feldspar although linear mixing appears to successfully replicate the majority of the observed signal published tes spectra of low albedo low dust cover olivine bearing materials do not exhibit the spectral telltales of non linear behavior probably because orbital spectra represent mostly mobile regolith that has not accumulated a sufficient dust cover over 3 6 km areas

numerical modeling of martian gully sediment transport testing the fluvial hypothesis 1 using a stereo pair of hirise images of a pole facing crater slope at 38 s 218 e we measure topographic profiles along nine gullies typical slopes of the interior channel region above the depositional apron are 20 we test the hypothesis that sediment transport on gully slopes occurs via fluvial transport processes by developing a numerical sediment transport model based on steep flume experiments performed by smart 1984 at 20 slopes channels 1 m deep by 8 m wide and 0 1 m deep by 3 m wide transport a sediment volume equal to the alcove volume of 6 105 m3 in 10 h and 40 days respectively under constant flow conditions snowpack melting cannot produce the water discharge rates necessary for fluvial sediment transport unless long term kyr storage of the resulting meltwater occurs if these volumes of water are discharged as groundwater the required aquifer thicknesses and aquifer drawdown lengths would be unrealistically large for a single discharge event more plausibly the water volume required by the fluvial transport model could be discharged in 10 episodes for an aquifer 30 m thick with a recurrence interval similar to that of martian obliquity cycles 0 1 myr

erosion by flowing martian lava new insights for hecates tholus from mars express and mer data 1 we have used new compositional information on martian basaltic rocks from the mars exploration rover spirit and data from new stereo imaging by the high resolution stereo camera hrsc on the mars express orbiter to constrain an existing analytical numerical computer model to assess the potential of martian lavas to form lava channels by erosion of substrate the basaltic rocks studied in gusev crater by spirit have compositions consistent with lavas of higher liquidus temperature and lower dynamic viscosity than terrestrial tholeiitic basalts suggesting that they had a greater potential for turbulent flow and erosion of substrate during flow emplacement than terrestrial basalts more similar to lunar mare basalts we modeled a specific case to determine whether these lavas could have formed part of a 66 km long channel on the martian shield volcano hecates tholus this channel formed on relatively steep slopes 2 8 based on measurements from the hrsc digital terrain model our results suggest that erosion rates were of the order of tens to hundreds of centimeters day depending on flow rate and ice content of the substrate eruption durations required to erode the hecates channel 100 30 m deep over the first 20 km depth decreasing downstream range from weeks to months which are consistent with the known eruption durations of terrestrial basaltic lavas and the previous modeling of wilson and mouginis mark 2004 any hecates lava channels formed from erosion by lava could have served as conduits for later fluvial activity as recently described by fassett and head 2004 2005

initial results from the mini tes experiment in gusev crater from the spirit rover the miniature thermal emission spectrometer mini tes on spirit has studied the mineralogy and thermophysical properties at gusev crater undisturbed soil spectra show evidence for minor carbonates and bound water rocks are olivinerich basalts with varying degrees of dust and other coatings dark toned soils observed on disturbed surfaces may be derived from rocks and have derived mineralogy 5 to 10 of 45 pyroxene 20 ca rich pyroxene and 25 pigeonite 40 sodic to intermediate plagioclase and 15 olivine forsterite 45 5 to 10 two spectrally distinct coatings are observed on rocks a possible indicator of the interaction of water rock and airfall dust diurnal temperature data indicate particle sizes from 40 to 80 microm in hollows to approximately 0 5 to 3 mm in soils

gusev crater wind related features and processes observed by the mars exploration rover spirit 1 wind related features observed by the rover spirit in gusev crater mars include patches of soil on the surface some of which are organized into bed forms windblown grains include dust inferred to be 2 mm in diameter microscopic imager data show the sands and granules to be rounded and relatively spherical typical of grains transported long distances by the wind the interior of bed forms exposed by rover operations suggests the infiltration of dust among the grains indicating that these sands are not currently experiencing saltation orientations of 1520 features such as bed forms and ventifacts along spirit s traverse from the landing site the columbia memorial station to west spur in the columbia hills suggest primary formative winds from the north northwest which correlate with measurements of features seen in orbiter images and is consistent with afternoon winds predicted by atmospheric models a secondary wind from the southeast is also suggested which correlates with predictions for nighttime early morning winds wind abrasion is indicated by ventifacts in the form of facets and grooves cut into rocks the orientations of which also indicate prevailing winds from the north northwest orientations of many aeolian features in the west spur area however have more scatter than elsewhere along the traverse which is attributed to the influence of local topography on the patterns of wind active dust devils observed on the floor of gusev from the columbia hills demonstrate that dust is currently mobile sequential images of some dust devils show movement as rapid as 3 8 m s consistent with wind velocities predicted by atmospheric models for the afternoon when most of the dust devils were observed sands accumulated on the rover deck in the same period suggest that some sands in the columbia hills experience active saltation two toned rocks having a light band coating at their bases are considered to represent partial burial by soils and subsequent exposure while perched rocks could represent materials lowered onto other rocks by deflation of supporting soils measurements of the heights of the light bands and the perched rocks range from 1 cm to 27 cm indicating local deflation by as much as 27 cm

a case study of recurring slope lineae rsl at tivat crater implications for rsl origins abstract the origin or origins of recurring slope lineae rsl on mars are enigmatic these seasonally dark linear features correlate with temperatures appropriate for liquid water or brine they also progress slowly downslope and fade disappear when inactive similar to shallow subsurface groundwater flows that wick moisture to the surface if liquid water or brine does indeed flow so near the surface and is sufficiently dilute it could have profound implications for the modern habitability of mars we present the results of a case study at tivat crater in the southern midlatitudes that provide new insights into rsl including their potential origins at tivat these results include comprehensive maps of rsl extents in four mars years detailed rsl evolution across one growth season rockfall markings and dust devil tracks in two well constrained years rsl and rockfall markings which are more widely distributed than rsl fade at the same time suggesting a fading mechanism that acts across tivat based on relative albedo analyses rsl and rockfall markings at tivat fade because their host slopes darken which is most easily explained by the widespread removal of dust such a dry fading mechanism would favor a dry origin for rsl we also present a wide range of other rsl observations including highly variable growth pooling like behavior where slopes shallow to roughly 30 and total areal extents that decrease each year across a span of five years we discuss the implications of these observations for various rsl formation models including a new conceptual model that primarily mobilizes dust taken together our observations seem to favor a dry mass movement origin for rsl at tivat but significant challenges remain for each examined model

characterization and mapping of surface physical properties of mars from crism multi angular data application to gusev crater and meridiani planum the analysis of particle physical properties grain size shape and internal structure and its organization surface porosity roughness and grain size distribution provides information about the geological processes which formed and modified planetary surfaces crism compact reconnaissance imaging spectrometer for mars multi angular observations varied emission angles allow for the characterization of the surface scattering behavior which depends on the composition and on the material physical properties such as the grain size shape internal structure and the surface roughness after an atmospheric correction compensating mineral aerosol effects by the multi angle approach for retrieval of the surface reflectance from crism observations mars reco the surface reflectances at different geometries were analyzed by inverting the hapke photometric model depending on six parameters single scattering albedo 2 phase function terms macroscopic roughness and 2 opposition effects terms in this work surface photometric maps are created to observe the spatial variations of surface scattering properties as a function of geological units information regarding the single scattering albedo the particle phase function and the macroscopic roughness are provided at the crism spatial resolution 200 m pixel this article describes the application of this methodology to the data covering the mars exploration rover mer landing sites located at gusev crater and meridiani planum where orbital and in situ observations are available complementary orbital observations e g crism spectra thermal emission imaging system themis high resolution imaging science experiment hirise images were used for interpreting the modeled hapke photometric parameters in terms of physical properties which can be used to constrain the geological processes available mer in situ observations were used as ground truth to validate the interpretations of the hapke parameters varied scattering properties were observed within a crism observation 5 10 km suggesting that the surfaces are controlled by local geological processes e g volcanic resurfacing aeolian and impact processes rather than regional or global processes results are consistent with the in situ observations thus validating the approach and the use of photometry for the characterization of martian surface physical properties

aqueous processes at gusev crater inferred from physical properties of rocks and soils along the spirit traverse 1 gusev crater was selected as the landing site for spirit on the basis of morphological evidence of long lasting water activity including possibly fluvial and lacustrine episodes from the columbia memorial station to the columbia hills spirit s traverse provides a journey back in time from relatively recent volcanic plains showing little evidence for aqueous processes up to the older hills where rock and soil composition are drastically different for the first 156 sols the only evidence of water action was weathering rinds vein fillings and soil crust cementation by salts the trenches of sols 112 145 marked the first significant findings of increased concentrations of sulfur and magnesium varying in parallel suggesting that they be paired as magnesium sulfate spirit s arrival at west spur coincided with a shift in rock and soil composition with observations hinting at substantial amounts of water in gusev s past we used the microscopic imager data up to sol 431 to analyze rock and soil properties and infer plausible types and magnitude of aqueous processes through time we show the role played early by topography and structure the morphology texture and deep alteration shown by the rocks in west spur and the columbia hills formation chf suggest conditions that are not met in present day mars and required a wetter environment which could have included transport of sulfur chlorine and bromine in water vapor in volcanic gases hydrothermal circulation or saturation in a briny fluid containing the same elements changing conditions that might have affected flow circulation are suggested by different textural and morphological characteristics between the rocks in the chf and those of the plains with higher porosity proxy higher void ratio and higher water storage potential in the chf soils were used to assess aqueous processes and water pathways in the top layers of modern soils we conclude that infiltration might have become more difficult with time

geology of the gusev cratered plains from the spirit rover transverse 1 the cratered plains of gusev traversed by spirit are generally low relief rocky plains dominated by impact and eolian processes ubiquitous shallow soil filled circular depressions called hollows are modified impact craters rocks are dark fine grained basalts and the upper 10 m of the cratered plains appears to be an impact generated regolith developed over intact basalt flows systematic field observations across the cratered plains identified vesicular clasts and rare scoria similar to original lava flow tops consistent with an upper inflated surface of lava flows with adjacent collapse depressions crater and hollow morphometry are consistent with most being secondaries the size frequency distribution of rocks 0 1 m diameter generally follows exponential functions similar to other landing sites for total rock abundances of 5 35 systematic clast counts show that areas with higher rock abundance and more large rocks have higher thermal inertia plains with lower thermal inertia have fewer rocks and substantially more pebbles that are well sorted and evenly spaced similar to a desert pavement or lag eolian bed forms ripples and wind tails have coarse surface lags and many are dust covered and thus likely inactive deflation of the surface 5 25 cm likely exposed two toned rocks and elevated ventifacts and transported fines into craters creating the hollows this observed redistribution yields extremely slow average erosion rates of 0 03 nm yr and argues for very little long term net change of the surface and a dry and desiccating environment similar to today s since the hesperian or 3 ga

textures of the soils and rocks at gusev crater from spirit s microscopic imager the microscopic imager on the spirit rover analyzed the textures of the soil and rocks at gusev crater on mars at a resolution of 100 micrometers weakly bound agglomerates of dust are present in the soil near the columbia memorial station some of the brushed or abraded rock surfaces show igneous textures and evidence for alteration rinds coatings and veins consistent with secondary mineralization the rock textures are consistent with a volcanic origin and subsequent alteration and or weathering by impact events wind and possibly water

coordinated analyses of orbital and spirit rover data to characterize surface materials on the cratered plains of gusev crater mars 1 comparison of the mars exploration rover spirit s pancam 0 4 to 1 0 m and mars express observatoire pour la mineralogie l eau les glaces et l activite omega 0 4 to 2 5 m spectral reflectance data over spirit s traverses shows that gusev cratered plains are dominated by nanophase ferric oxide rich dust covering weakly altered basaltic sands this interpretation is also consistent with both observations from omega data covering plains beyond the traverse region and interpretations of data from the other payload instruments on the spirit rover omega observations of relatively low albedo regions where dust has presumably been stripped by dust devils show negative spectral reflectance slopes from 1 5 to 2 5 m and moderately masked spectral features which are indicative of olivine or pyroxene high albedo regions north and south of the spirit landing site have flat spectral reflectance slopes and few spectral features although all spectra have a nanophase ferric oxide absorption edge between 0 4 and 0 75 m comparison of themis derived thermal inertia values with omega derived spectral parameters shows that although the dust cover can be optically thick 0 4 to 2 5 m wavelength region in some areas it is not thick enough 1 cm to mask the thermal inertia of the underlying substrate for areas included in this study

geomorphological evidence for a dry dust avalanche origin of slope streaks on mars mars has several different types of slope feature that resemble aqueous flows however the current cold dry conditions are inimical to liquid water resulting in uncertainty about its role in modern surface processes dark slope streaks were among the first distinctive young slope features to be identified on mars and the first with activity seen in orbital images they form markings on steep slopes that can persist for decades and the role of water in their formation remains a matter of debate here i analyse the geomorphic features of new slope streaks using high resolution orbital images comparison of images before and after streak formation reveal how this process affects the surface and provides information about the cause these observations demonstrate that slope streaks erode and deposit material in some instances they also reveal that streaks can jump slopes and may be erosive very near their termini these observations support a formation model where dark slope streaks form as ground hugging low density avalanches of dry surface dust such streaks need not be treated as special regions for planetary protection patterns of erosion and deposition by some slope streaks on mars are consistent with a dry dust avalanche origin according to an analysis of orbital images before and after new streaks formed

athena microscopic imager investigation 1 the athena science payload on the mars exploration rovers mer includes the microscopic imager mi the mi is a fixed focus camera mounted on the end of an extendable instrument arm the instrument deployment device idd the mi was designed to acquire images at a spatial resolution of 30 microns pixel over a broad spectral range 400 700 nm the mi uses the same electronics design as the other mer cameras but has optics that yield a field of view of 31 31 mm across a 1024 1024 pixel ccd image the mi acquires images using only solar or skylight illumination of the target surface a contact sensor is used to place the mi slightly closer to the target surface than its best focus distance about 66 mm allowing concave surfaces to be imaged in good focus coarse focusing 2 mm precision is achieved by moving the idd away from a rock target after the contact sensor has been activated the mi optics are protected from the martian environment by a retractable dust cover the dust cover includes a kapton window that is tinted orange to restrict the spectral bandpass to 500 700 nm allowing color information to be obtained by taking images with the dust cover open and closed mi data will be used to place other mer instrument data in context and to aid in petrologic and geologic interpretations of rocks and soils on mars

evaluation of carbonate abundance in putative martian paleolake basins abstract carbonate deposits have not been found so far on mars although there appears to have been sufficient water to have supported their formation many hypotheses have been proposed in order to explain this in the present work we explore the possibility that the missed detection of carbonate deposits on the martian surface could be simply due to the fact that the concentration of carbonates when mixed with other materials present in the sedimentary deposits may be below the detection limit of the various instruments used so far in this search in the present study we consider 21 putative paleolacustrine basins and use a sediment transport model to estimate the abundance of carbonates which could be present in the sediments deposited on the basin floor in this way we find that for all the selected basins the estimated carbonate abundances are in general less than a few percent and such values are below or at best comparable to the detection limits of the spectrometers flown around mars during the recent space missions furthermore applying the sediment transport model to the well studied eberswalde crater we conclude that the fluvio lacustrine activity in this basin should have lasted for a period on the order of 10 3 10 4 years in good agreement with previous work our results suggest that a hydrological cycle able to move large volumes of water and to create relatively stable lakes could have been active intermittently on mars in the past producing carbonate deposits that could escape detection by the instruments that have flown to date

thermophysical properties of the mer and beagle ii landing site regions on mars 1 we analyzed remote sensing observations of the isidis basin gusev crater and meridiani planum landing sites for beagle ii mer a spirit and mer b opportunity spacecraft respectively we emphasized the thermophysical properties using daytime and nighttime radiance measurements from the mars global surveyor mgs thermal emission spectrometer and mars odyssey thermal emission imaging system themis and thermal inertias derived from nighttime data sets themis visible images mgs mars orbiter camera moc narrow angle images and mgs mars orbiter laser altimeter mola data are incorporated as well additionally the remote sensing data were compared with ground truth at the mer sites the isidis basin surface layer has been shaped by aeolian processes and erosion by slope winds coming off of the southern highlands and funneling through notches between massifs in the gusev region surface materials of contrasting thermophysical properties have been interpreted as rocks or bedrock duricrust and dust deposits these are consistent with a complex geological history dominated by volcanic and aeolian processes at meridiani planum the many layers having different thermophysical and erosional properties suggest periodic deposition of differing sedimentological facies possibly related to clast size grain orientation and packing or mineralogy

overview of the spirit mars exploration rover mission to gusev crater landing site to backstay rock in the columbia hills spirit landed on the floor of gusev crater and conducted initial operations on soil covered rock strewn cratered plains underlain by olivine bearing basalts plains surface rocks are covered by wind blown dust and show evidence for surface enrichment of soluble species as vein and void filling materials and coatings the surface enrichment is the result of a minor amount of transport and deposition by aqueous processes layered granular deposits were discovered in the columbia hills with outcrops that tend to dip conformably with the topography the granular rocks are interpreted to be volcanic ash and or impact ejecta deposits that have been modified by aqueous fluids during and or after emplacement soils consist of basaltic deposits that are weakly cohesive relatively poorly sorted and covered by a veneer of wind blown dust the soils have been homogenized by wind transport over at least the several kilometer length scale traversed by the rover mobilization of soluble species has occurred within at least two soil deposits examined the presence of monolayers of coarse sand on wind blown bedforms together with even spacing of granule sized surface clasts suggests that some of the soil surfaces encountered by spirit have not been modified by wind for some time on the other hand dust deposits on the surface and rover deck have changed during the course of the mission detection of dust devils monitoring of the dust opacity and lower boundary layer and coordinated experiments with orbiters provided new insights into atmosphere surface dynamics

pedogenic response to millennial summer monsoon enhancements on the tibetan plateau abstract the asian summer monsoons experienced both rapid episodic enhancement and long term evolution with the uplift of tibet the response of pedogenesis to those events on the tibetan plateau at mean elevations of 4000 5000 m is of great interest and significance in deciphering the history of asian and tibetan summer monsoons and in understanding soil development deterioration and management the over 22 m loess paleosol sequence at hezuo on the eastern tibetan plateau extending back through the last interglaciation and the thickest late pleistocene sequence identified thus far on the plateau provides a unique opportunity to tackle the above topics detailed chronology and soil development determined by field pedofeatures and soil proxies have revealed a millennial fluctuation of the asian and tibetan summer monsoons resembling the late pleistocene north atlantic climatic record the end of each heinrich event is closely followed by formation of a stronger paleosol and then some much weaker thin soil horizons weathered loess or loess the episodes of stronger soil development or paleosol events correspond without exception to strongest summer monsoon enhancement at the beginning or in the early part of each bond cycle recorded in the north atlantic the strongest pedogenesis and summer monsoon enhancement is observed to occur during 43 36 ka bp which is not observed in climatic records outside tibet probably indicating a coherent enhancement of asian and tibetan summer monsoons in the last mega interstadial mis3 increase of organic matter excluding decomposition and change of soil types from last interglacial calcic cambisols to holocene chernozems suggests an increase of relative humidity implying partially an increase of elevation due to late pleistocene rapid uplift of the tibetan plateau

understanding the signature of rock coatings in laser induced breakdown spectroscopy data surface compositional features on rocks such as coatings and weathering rinds provide important information about past aqueous environments and water rock interactions the search for these features represents an important aspect of the curiosity rover mission with its unique ability to do fine scale chemical depth profiling the chemcam laser induced breakdown spectroscopy instrument libs onboard curiosity can be used to both identify and analyze rock surface alteration features in this study we analyze a terrestrial manganese rich rock varnish coating on a basalt rock in the laboratory with the chemcam engineering model to determine the libs signature of a natural rock coating results show that there is a systematic decrease in peak heights for elements such as mn that are abundant in the coating but not the rock there is significant spatial variation in the relative abundance of coating elements detected by libs depending on where on the rock surface sampled this is due to the variability in thickness and spatial discontinuities in the coating similar trends have been identified in some martian rock targets in chemcam data suggesting that these rocks may have coatings or weathering rinds on their surfaces

crater gradation in gusev crater and meridiani planum mars 1 the mars exploration rovers investigated numerous craters in gusev crater and meridiani planum during the first 400 sols of their missions craters vary in size and preservation state but are mostly due to secondary impacts at gusev and primary impacts at meridiani craters at both locations are modified primarily by eolian erosion and infilling and lack evidence for modification by aqueous processes effects of gradation on crater form are dependent on size local lithology slopes and availability of mobile sediments at gusev impacts into basaltic rubble create shallow craters and ejecta composed of resistant rocks ejecta initially experience eolian stripping which becomes weathering limited as lags develop on ejecta surfaces and sediments are trapped within craters subsequent eolian gradation depends on the slow production of fines by weathering and impacts and is accompanied by minor mass wasting at meridiani the sulfate rich bedrock is more susceptible to eolian erosion and exposed crater rims walls and ejecta are eroded while lower interiors and low relief surfaces are increasingly infilled and buried by mostly basaltic sediments eolian processes outpace early mass wasting often produce meters of erosion and mantle some surfaces some small craters were likely completely eroded buried craters 100 m in diameter on the hesperian aged floor of gusev are generally more pristine than on the amazonian aged meridiani plains this conclusion contradicts interpretations from orbital views which do not readily distinguish crater gradation state at meridiani and reveal apparently subdued crater forms at gusev that may suggest more gradation than has occurred

assessment of mars exploration rover landing site predictions comprehensive analyses of remote sensing data during the three year effort to select the mars exploration rover landing sites at gusev crater and at meridiani planum correctly predicted the atmospheric density profile during entry and descent and the safe and trafficable surfaces explored by the two rovers the gusev crater site was correctly predicted to be a low relief surface that was less rocky than the viking landing sites but comparably dusty a dark low albedo flat plain composed of basaltic sand and haematite with very few rocks was expected and found at meridiani planum these results argue that future efforts to select safe landing sites based on existing and acquired remote sensing data will be successful in contrast geological interpretations of the sites based on remote sensing data were less certain and less successful which emphasizes the inherent ambiguities in understanding surface geology from remotely sensed data and the uncertainty in predicting exactly what materials will be available for study at a landing site

aeolian bedforms yardangs and indurated surfaces in the tharsis montes as seen by the hirise camera evidence for dust aggregates abstract hirise images of mars with ground sampling down to 25 cm pixel show that the dust rich mantle covering the surfaces of the tharsis montes is organized into ridges whose form and distribution are consistent with formation by aeolian saltation other dusty areas near the volcanoes and elsewhere on the planet exhibit a similar morphology the material composing these reticulate bedforms is constrained by their remote sensing properties and the threshold curve combined with the saltation suspension boundary both of which vary as a function of elevation atmospheric pressure particle size and particle composition considering all of these factors dust aggregates are the most likely material composing these bedforms we propose that airfall dust on and near the volcanoes aggregates in situ over time maybe due to electrostatic charging followed by cementation by salts the aggregates eventually reach a particle size at which saltation is possible aggregates on the flanks are transported downslope by katabatic winds and form linear and accordion morphologies materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds forming an interlinked honeycomb texture in many places on and near the volcanoes light toned low thermal inertia yardangs and indurated surfaces are present these may represent duststone formed when aggregates reach a particle size below the threshold curve such that they become stabilized and subsequently undergo cementation

pancam multispectral imaging results from the spirit rover at gusev crater panoramic camera images at gusev crater reveal a rock strewn surface interspersed with high to moderate albedo fine grained deposits occurring in part as drifts or in small circular swales or hollows optically thick coatings of fine grained ferric iron rich dust dominate most bright soil and rock surfaces spectra of some darker rock surfaces and rock regions exposed by brushing or grinding show near infrared spectral signatures consistent with the presence of mafic silicates such as pyroxene or olivine atmospheric observations show a steady decline in dust opacity during the mission and astronomical observations captured solar transits by the martian moons phobos and deimos as well as a view of earth from the martian surface

diffusion barriers at mars surface conditions salt crusts particle size mixtures and dust the diffusion coefficient of water vapor through porous media at mars like surface conditions is measured for a variety of complex particle size distributions and soil compositions micron sized dust simulants mixtures of sand and dust sized particles and salt encrusted sand are examined we find that while the value of the diffusion coefficient d can be reduced by up to a factor of 10 for heavily salt encrusted soils minimum observed d 0 4 0 04 cm 2 s 1 moderate amounts of salt only produce minor reductions in d mechanical packing of pure dust can lower d by a similar amount while mixtures of dust with sand sized particles produce at most a factor of 4 reduction we conclude that present day processes of aeolian redistribution moderate levels of salt encrustation and volatile loss from dirty ice would be inefficient at producing soil deposits and lags on mars that pose significant barriers to diffusion therefore subsurface ice deposits that are thermally unstable would not be protected against sublimative loss by such materials

a simple autocorrelation algorithm for determining grain size from digital images of sediment abstract autocorrelation between pixels in digital images of sediment can be used to measure average grain size of sediment on the bed grain size distribution of bed sediment and vertical profiles in grain size in a cross sectional image through a bed the technique is less sensitive than traditional laboratory analyses to tails of a grain size distribution but it offers substantial other advantages it is 100 times as fast it is ideal for sampling surficial sediment the part that interacts with a flow it can determine vertical profiles in grain size on a scale finer than can be sampled physically and it can be used in the field to provide almost real time grain size analysis the technique can be applied to digital images obtained using any source with sufficient resolution including digital cameras digital video or underwater digital microscopes for real time grain size mapping of the bed

experimental delta formation in crater lakes and implications for interpretation of martian deltas 1 the morphology of delta deposits in crater lakes on mars is indicative of upstream e g flow discharge and sediment properties and downstream e g basin characteristics parameters from which the hydrological conditions at the time of formation can be inferred to investigate the influences of these parameters on delta morphology we experimentally created deltas in crater shaped basins by feeding a range of constant flow discharges over a feeder channel of various sand textures we reproduced three categorically different types of deltas including most of the types that have been identified on mars our most striking observation is that water level behavior itself a unique function of flow discharge basin size and hypsometry and basin floor permeability can explain most delta morphologies observed on mars stepped retrograding deltas formed during water level rise prograding deltas formed during water level still stand and during water level fall deltas were partially destroyed by erosion on mars numerous retrograding and prograding deltas were preserved most of them without indications of channel incisions or other fluvial modification we conclude that the main difference between a single foreset prograding delta and a multiple foreset retrograding delta is the behavior of the water level in the basin these simple delta morphologies cannot be reconciled with long duration hydrological activity because that would imply crater lake fluctuations due to inherent complex water level histories along with complex sediment delivery histories our experiments and numerical verifications demonstrate that such deltas preferentially form during one aqueous event which parsimoniously argues for short duration hydrological activity

rock abrasion tool mars exploration rover mission 1 the rock abrasion tool rat is an integral part of the athena science payload serving primarily as the geologist s rock hammer the rat will expose fresh surfaces of martian rocks to other instruments on the payload the rat also brushes dust and debris from an excavated hole or unaltered rocks to accomplish these tasks autonomously the rat a sophisticated 3 axis precision controlled device was designed data products derived from rat telemetry enable the rat to also act as an important rock physical properties science instrument the returned rat grinding and penetration rate data will be inverted and compared to a rock library on the earth the design is also very compact and lightweight the rat is contained within a cylinder 128 mm long and 85 mm in diameter and has a mass of 687 g

basaltic rocks analyzed by the spirit rover in gusev crater the spirit landing site in gusev crater on mars contains dark fine grained vesicular rocks interpreted as lavas pancam and mini thermal emission spectrometer mini tes spectra suggest that all of these rocks are similar but have variable coatings and dust mantles magnified images of brushed and abraded rock surfaces show alteration rinds and veins rock interiors contain 25 megacrysts chemical analyses of rocks by the alpha particle x ray spectrometer are consistent with picritic basalts containing normative olivine pyroxenes plagioclase and accessory feti oxides mossbauer pancam and mini tes spectra confirm the presence of olivine magnetite and probably pyroxene these basalts extend the known range of rock compositions composing the martian crust

formation and erosion of layered materials geologic and dust cycle history of eastern arabia terra mars 1 eastern arabia terra is mantled in a layer of dust a few centimeters to a meter thick yet contains morphologic features that suggest a history of multiple events of deposition and consolidation of fine grained material and a significant amount of erosion early in martian history this region was affected by volcanic and fluvial activity but has since been dominated by aeolian processes five craters in this region contain interior mound material that ranges in height from 1600 to 2100 m above the crater floor the fluted erosional pattern and the thermal inertia are suggestive of a weakly indurated material and the extensive layering implies that these mounds were formed by a repeated process or processes although these materials primarily occur within craters there are materials outside craters that have similar erosional features and fine laminations suggesting a more extensive deposit the most likely process to form this material is the deposition and cementation of air fall dust and is potentially related to martian obliquity changes the significant amount of erosion of the intracrater mounds unit indicates a dramatic change from a depositional environment to an erosional regime over the past 106 108 years currently dust is accumulating in this region in years with planet encircling dust events but global circulation model results indicate that dust devils may be removing slight amounts of dust from arabia terra these observations suggest that the thickness of the dust mantle may not be currently increasing and may instead be in equilibrium

quantification of the dry history of the martian soil inferred from in situ microscopy 1 the particle size distribution psd of a martian soil sample a useful indicator of the underlying soil formation processes has been determined using optical and atomic force microscopy data acquired by the phoenix mars lander in particular the presence and fraction of clay sized particles in the psd reflects the extent of aqueous interaction with the soil two size populations have been identified for the martian sample larger mostly rounded grains and small reddish fines notably with a very low mass proportion in the clay size range below 2 m these fines reflect the smallest scale formation processes and indicate a single method of production for the particles up to 11 m a much larger value than that expected for the aqueous interaction of clay formation this suggests the fines are predominantly the product of global aeolian weathering under very dry conditions the proportion of clay sized soils can be used to estimate that there has been much less than 5 000 years exposure to liquid water over the history of the soil from the perspective of the psd lunar regolith rather than terrestrial soil is the best analog to martian soil a globally homogenous soil with such a psd would be an unlikely habitat for the propagation of life on mars

an aeolian grainflow model for martian recurring slope lineae abstract recurring slope lineae rsl on mars have been enigmatic since their discovery their behavior resembles a seeping liquid but sources of water remain puzzling this work demonstrates that the properties of rsl are consistent with observed behaviors of martian and terrestrial aeolian processes specifically rsl are well explained as flows of sand that remove a thin coating of dust observed rsl properties are supportive of or consistent with this model which requires no liquid water or other exotic processes but rather indicates seasonal aeolian behavior these settings and behaviors resemble features observed by rovers and also explain the occurrence of many slope lineae on mars that do not meet the strict definition of rsl this indicates that rsl can be explained simply as aeolian features other processes may add complexities just as they could modify the behavior of any sand dune

hapke mixture modeling applied to vnir spectra of mafic mineral mixtures and shergottites implications for quantitative analysis of satellite data 2018 the authors meteoritics planetary science published by wiley periodicals inc on behalf of the meteoritical society met this is an open access article under the terms of the creative commons attribution license which permits use distribution and reproduction in any medium provided the original work is properly cited

sulfate deposition in subsurface regolith in gusev crater mars excavating into the shallow martian subsurface has the potential to expose stratigraphic layers and mature regolith which may hold a record of more ancient aqueous interactions than those expected under current martian surface conditions during the spirit rover s exploration of gusev crater rover wheels were used to dig three trenches into the subsurface regolith down to 6 11 cm depth road cut the big hole and the boroughs a high oxidation state of fe and high concentrations of mg s cl and br were found in the subsurface regolith within the two trenches on the plains between the bonneville crater and the foot of columbia hills data analyses on the basis of geochemistry and mineralogy observations suggest the deposition of sulfate minerals within the subsurface regolith mainly mg sulfates accompanied by minor ca sulfates and perhaps fe sulfates an increase of fe2o3 an excess of sio2 and a minor decrease in the olivine proportion relative to surface materials are also inferred three hypotheses are proposed to explain the geochemical trends observed in trenches 1 multiple episodes of acidic fluid infiltration accompanied by in situ interaction with igneous minerals and salt deposition 2 an open hydrologic system characterized by ion transportation in the fluid subsequent evaporation of the fluid and salt deposition and 3 emplacement and mixing of impact ejecta of variable composition while all three may have plausibly contributed to the current state of the subsurface regolith the geochemical data are most consistent with ion transportation by fluids and salt deposition as a result of open system hydrologic behavior although sulfates make up 20 wt of the regolith in the wall of the boroughs trench a higher hydrated sulfate than kieserite within the boroughs or a greater abundance of sulfates elsewhere than is seen in the boroughs wall regolith would be needed to hold the structural water indicated by the water equivalent hydrogen concentration observed by the gamma ray spectrometer on odyssey in the gusev region copyright 2006 by the american geophysical union

mars exploration rover engineering cameras 1 nasa s mars exploration rover mer mission will place a total of 20 cameras 10 per rover onto the surface of mars in early 2004 fourteen of the 20 cameras are designated as engineering cameras and will support the operation of the vehicles on the martian surface images returned from the engineering cameras will also be of significant importance to the scientific community for investigative studies of rock and soil morphology the navigation cameras navcams two per rover are a mast mounted stereo pair each with a 45 square field of view fov and an angular resolution of 0 82 milliradians per pixel mrad pixel the hazard avoidance cameras hazcams four per rover are a body mounted front and rear facing set of stereo pairs each with a 124 square fov and an angular resolution of 2 1 mrad pixel the descent camera one per rover mounted to the lander has a 45 square fov and will return images with spatial resolutions of 4 m pixel all of the engineering cameras utilize broadband visible filters and 1024 1024 pixel detectors

the spirit rover s athena science investigation at gusev crater mars the mars exploration rover spirit and its athena science payload have been used to investigate a landing site in gusev crater gusev is hypothesized to be the site of a former lake but no clear evidence for lacustrine sedimentation has been found to date instead the dominant lithology is basalt and the dominant geologic processes are impact events and eolian transport many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration any lacustrine sediments that may exist at this location within gusev apparently have been buried by lavas that have undergone subsequent impact disruption

characterisation of the magnetic iron phases in clovis class rocks in gusev crater from the mer spirit mossbauer spectrometer abstract mossbauer backscattering spectra of eight martian rocks acquired by the mimos ii spectrometer of rover spirit mer a and containing goethite in addition to other iron minerals have been selected for in depth numerical analysis where feasible different temperature windows for a given rock were considered a novel calibration folding procedure exclusively based on the fitted positions of the eight prominent absorption lines in the transmission spectra of the reference target and not relying on the error signal of the mimos ii spectrometer has been developed it is demonstrated that this procedure yields reliable and reasonably accurate values for the adjusted mossbauer parameters of the respective spectra of the rock targets these spectra are all composed of magnetically split components arising from hematite magnetite and goethite phases in addition to a ferrous and a ferric doublet that can be ascribed to the presence of fe silicates possibly glasses it is argued that the fe 3 doublet has no significant contribution from superparamagnetic fe oxide particles the hematite components reflect the coexistence of antiferromagnetic and weakly ferromagnetic spin states in general the magnetite content in the selected rocks is low the goethite subspectra are very broad and asymmetric and need to be described by a model independent distribution of hyperfine fields the as such obtained parameter values indicate an average particle size of the order of 10 nm for all examined rock spectra the adjusted parameter values for the various fe oxides are completely in line with those known for terrestrial natural or synthetic species

wind driven particle mobility on mars insights from mars exploration rover observations at el dorado and surroundings at gusev crater 1 the ripple field known as el dorado was a unique stop on spirit s traverse where dust raising active mafic sand ripples and larger inactive coarse grained ripples interact illuminating several long standing issues of martian dust mobility sand mobility and the origin of transverse aeolian ridges strong regional wind events endured by spirit caused perceptible migration of ripple crests in deposits sse of el dorado erasure of tracks in sandy areas and changes to dust mantling the site localized thermal vortices swept across el dorado leaving paths of reduced dust but without perceptibly damaging nearly cohesionless sandy ripple crests from orbit winds responsible for frequently raising clay sized dust into the atmosphere do not seem to significantly affect dunes composed of more easily entrained sand sized particles a long standing paradox this disparity between dust mobilization and sand mobilization on mars is due largely to two factors 1 dust occurs on the surface as fragile low density sand sized aggregates that are easily entrained and disrupted compared with clay sized air fall particles and 2 induration of regolith is pervasive light toned bed forms investigated at gusev are coarse grained ripples an interpretation we propose for many of the smallest linear light toned bed forms of uncertain origin seen in high resolution orbital images across mars on earth wind can organize bimodal or poorly sorted loose sediment into coarse grained ripples coarse grained ripples could be relatively common on mars because development of durable well sorted sediments analogous to terrestrial aeolian quartz sand deposits is restricted by the lack of free quartz and limited hydraulic sediment processing

estimating rock compressive strength from rock abrasion tool rat grinds 1 each mars exploration rover carries a rock abrasion tool rat whose intended use was to abrade the outer surfaces of rocks to expose more pristine material motor currents drawn by the rat motors are related to the strength and hardness of rock surfaces undergoing abrasion and these data can be used to infer more about a target rock s physical properties however no calibration of the rat exists here we attempt to derive an empirical correlation using an assemblage of terrestrial rocks and apply this correlation to data returned by the rover spirit the results demonstrate a positive correlation between rock strength and rat grind energy for rocks with compressive strengths less than about 150 mpa a category that includes all but the strongest intact rocks applying this correlation to rocks abraded by spirit s rat the results indicate a large divide in strength between more competent basaltic rocks encountered in the plains of gusev crater adirondack class rocks and the weaker variety of rock types measured in the columbia hills adirondack class rocks have estimated compressive strengths in the range of 70 130 mpa and are significantly less strong than fresh terrestrial basalts this may be indicative of a degree of weathering induced weakening rock types in the columbia hills wishstone watchtower clovis and peace class all have compressive strengths 50 mpa and are consistent with impactites or volcanoclastic materials in general when considered alongside chemical spectral and rock textural data these inferred compressive strength results help inform our understanding of rock origins and modification history

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

soil sedimentology at gusev crater from columbia memorial station to winter haven 1 a total of 3140 individual particles were examined in 31 soils along spirit s traverse their size shape and texture were quantified and classified they represent a unique record of 3 years of sedimentologic exploration from landing to sol 1085 covering the plains unit to winter haven where spirit spent the martian winter of 2006 samples in the plains unit and columbia hills appear as reflecting contrasting textural domains one is heterogeneous with a continuum of angular to round particles of fine sand to pebble sizes that are generally dust covered and locally cemented in place the second shows the effect of a dominant and ongoing dynamic aeolian process that redistributes a uniform population of medium size sand the texture of particles observed in the samples at gusev crater results from volcanic aeolian impact and water related processes

bright dust devil tracks on earth implications for their formation on mars we report on the first observations of bright dust devil tracks bddts on earth observed in the turpan depression desert in northwestern china where raindrop impacts on sand surfaces form aggregates of sand silt and clay resulting in rough surface textures which are destroyed by passages of dust devils leading to smooth surface textures within the tracks the differences in photometric properties between the track and outside the tracks cause the albedo differences leading to the formation of bddts and similar processes might lead to bddts on mars in areas with thick dust covers

reconstructing the timescale of a catastrophic fan forming event on earth using a mars model the calculation of formation timescales of alluvial fans and deltas on mars is important as it has direct implications for understanding the planet s hydrologic history the robustness of sediment transport models is not in doubt but validation of the broad approach using a terrestrial example of similar scale and likely origin where hydraulic parameters and timescales are known is useful using a catastrophically formed terrestrial fan where abundant sedimentological information is available we find that the modeled hydraulic parameters and formation timescales are in very close agreement with the known values of the event this supports the general modeling approach as applied to mars fans but also highlights the added value of detailed sedimentary information when reconstructing hydraulics and timescales on earth and mars which cannot be confidently gleaned from the final snapshot of surface geomorphology alone

determination of the wind induced detachment threshold for granular material on mars using wind tunnel simulations experimental results are presented of wind induced grain detachment under mars simulation conditions a simple force balance equation is applied to quantify the wind shear stress required for removal of glass spheres from a sand bed the transport of fine grained martian dust is simulated by the detachment of hollow glass spheres which resemble low mass density dust aggregates observed to form during simulations when using mars analogue material the results agree well with observations of dust removal and wind speed measurements made by the nasa viking landers at the martian surface this work supports the suggestion that dust aggregate fragmentation allows wind induced dust entrainment at substantially lower wind shear than that of solid sand grains and has direct application to the study of global dust transport and martian climatology

modification of martian slope streaks by eolian processes recent images from the high resolution imaging science experiment hirise camera have shown that slope streaks have relief on the order of a meter or less this study presents observations of transverse bedforms and infill deposits within slope streak beds that were not previously identified or were uncommon from earlier analyses of hirise images transverse bedforms are linear to slightly arcuate features oriented transverse to the slope streak bed which may be analogous to terrestrial splash or coarse grained ripples based on their morphology wavelength and amplitude in addition to the bedforms there is also evidence that slope streak beds gradually shallow over time by infilling of material the presence of ripples within slope streaks implies that saltation capable material is available on the surface today and or was available in the recent past although airfall dust is not a capable saltation source material aggregates of electrostatically bound dust that are possibly later cemented by salts may serve as a source from the results of this study we hypothesize a sequence of events in a slope streak formation and modification cycle where grains saltate to form ripples along the bed of a slope streak airfall dust mantling causes gradual fading of the streak and infill material buries the ripples eventually reaching the pre avalanche surface that removes all traces of relief

wind related processes detected by the spirit rover at gusev crater mars wind abraded rocks ripples drifts and other deposits of windblown sediments are seen at the columbia memorial station where the spirit rover landed orientations of these features suggest formative winds from the north northwest consistent with predictions from atmospheric models of afternoon winds in gusev crater cuttings from the rover rock abrasion tool are asymmetrically distributed toward the south southeast suggesting active winds from the north northwest at the time midday of the abrasion operations characteristics of some rocks such as a two toned appearance suggest that they were possibly buried and exhumed on the order of 5 to 60 centimeters by wind deflation depending on location

transverse aeolian ridges on mars first results from hirise images abstract three images obtained by the high resolution imaging science experiment hirise were analyzed for the information they could provide regarding transverse aeolian ridges tars on mars tars from five locations in a hirise image of the floor of ius chasma show remarkably symmetric cross sectional profiles with average slopes for the entire feature of 15 these results apply to tars that span an order of magnitude in wavelength and a factor of 6 in height a hirise image of gamboa impact crater in the northern lowlands shows low albedo sand patches

sands at gusev crater mars processes environments and the energy associated with the transport and deposition of sand at gusev crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the spirit rover as it crossed the plains and went into the columbia hills fine to medium sand is ubiquitous in ripples and wind drifts most distributions show excess fine material consistent with a predominance of wind erosion over the last 3 8 billion years negative skewness at west valley is explained by the removal of fine sand during active erosion or alternatively by excess accumulation of coarse sand from a local source the coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape their distribution display significant changes in their statistical moments within the 400 m that separate the columbia memorial station from bonneville crater results are consistent with aeolian and or impact deposition while the elongated and rounded shape of the grains forming the ripples as well as their direction of origin could point to ma adim vallis as a possible source for smaller particles on the traverse our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic e g ripples and plains soils and aerographic settings e g wind shadows

an instrument system for monitoring and sampling suspended sediment in the benthic boundary layer abstract an instrument system has been constructed that can monitor and sample suspended sediment distributions in the benthic boundary layer it consists of miniature nephelometers and suspended sediment samplers placed within one meter of the seabed the system is capable of continuously monitoring suspended sediment profiles at eight levels between 14 and 100 cm above the seabed and collecting suspended sediment samples at four levels 20 50 70 and 100 cm at three times during a deployment period the suspended sediment system is designed to fit onto the instrumented tripod geoprobe which contains four electromagnetic current meters pressure sensor bottom stereo camera two temperature sensors transmissometer and a savonius rotor current meter sensor operation data recording and sediment sampling events are synchronized thus detailed measurements of the near bottom flow conditions are made concurrently with suspended sediment measurements the combined system has been used in sediment transporting environments within san francisco bay california and puget sound washington

origin of basaltic soils at gusev crater mars by aeolian modification of impact generated sediment 1 textural properties of soils including grain size sorting modality skewness shape quantified as sphericity and qualified as form roundness and grain size distribution have been measured and calculated from microscopic imager mi high resolution images from the mars exploration rover mer spirit in gusev crater soil targets were classified by grain size into five groups fine to medium sand dark soil medium sand to very fine pebble bed form armor and very fine to medium pebble lithic fragments a bimodal mixed soil and an excavated soil trench the abundance of submature very poorly sorted bimodal mixed soils indicates incomplete sorting by soil type probability distributions of excavated subsurface soil match crushed sediment analogs indicating impact comminution while all other soils show no direct evidence of an impact origin if soils were produced primarily by impacts then the evidence from probability distributions angular shapes and agglutinates have been reworked by postimpact surface activity soils in gusev crater are continuously modified reworked and sandblasted textures of surface sediments are disconnected from subsurface textures and only reflect modern surficial aeolian processes models to reconstruct physical and chemical soil formation properties should not assume a static three dimensional structure a three step model initiated by the formation of basaltic crust and its alteration followed by bolide impact and finally modification by aeolian reworking is envisioned for the formation of soils such a scenario accounts for the potential that surface sediments may be compositionally and texturally distinct from the subsurface

gusev photometric variability as seen from orbit by hrsc mars express minnaert and two term phase function hapke models are used to describe the photometric properties of the martian surface using hrsc high resolution stereo camera multi angular observations acquired along the ongoing mars express mission these observations can be pieced together to derive integrated phase functions over a wide range of phase angles the photometric diversity at 675 nm as seen from orbit of the martian surface properties across gusev is depicted with seven units three photometric units widespread across the flanks of apollinaris patera flank and the floor of gusev crater are identified as having high single scattering albedo with rather forward scattering properties low to intermediate macroscopic roughness and porous or not compacted powdered surface state as indicated by the opposition parameters another unit has the highest single scattering albedo the smoothest surface in terms of macroscopic roughness associated with an extremely forward scattering behavior the opposition parameters are consistent with the presence of transparent particles in the surface powder layer the distribution of this unit appears quite intermittent across the crater and does not seem to indicate any relationship with a given morphological structure it may correspond to sparse areas where the structure of the surface dust layer is the most preserved the most pronounced photometric changes are observed in three units associated with the low albedo features corresponding to dark wind streaks these units have a low single scattering albedo are the most backscattering surfaces across gusev have a high surface roughness and present variable surface states as shown by the opposition parameters estimates consistent with the occurrence of large grains organized in more or less packed layers clear differences are seen among these units in terms of opposition effect while one exhibits typical characteristics for the opposition effect another appears more unusual in terms of lobe width and the third suggests the occurrence of a packed compressed narrow size distribution powder surface the opposition effect thus appears to play a significant role suggesting that the surface state optical properties across gusev are strongly influenced by the porosity and packing characteristics or grain size distribution of the upper layer of the martian soil the mapping aspect of the investigation is quite useful to get a better sense of the meaning of the observed photometric variations indeed the hapke modeling suggests that surface organization surface roughness packing state is more important than the simple physical characterization of the intrinsic optical properties of the constitutive particles given the overall spatial patterns derived from the photometric analysis the variations at least for the western and central part of gusev crater are likely partly driven by the prevailing wind regimes considered to be oriented north northwest south southeast and disturbing the very upper surface layer the present photometric results agree with independent investigations based on thermal inertia reflectance spectroscopy in situ photometric and microscopic imaging and support the idea of a thin layer of fine grained dust being stripped off in the low albedo units to reveal a dark basaltic substrate comprising coarse grained materials

localization and physical properties experiments conducted by spirit at gusev crater the precise location and relative elevation of spirit during its traverses from the columbia memorial station to bonneville crater were determined with bundle adjusted retrievals from rover wheel turns suspension and tilt angles and overlapping images physical properties experiments show a decrease of 0 2 per mars solar day in solar cell output resulting from deposition of airborne dust cohesive soil like deposits in plains and hollows bright and dark rock coatings and relatively weak volcanic rocks of basaltic composition volcanic impact aeolian and water related processes produced the encountered landforms and materials

evidence from opportunity s microscopic imager for water on meridiani planum the microscopic imager on the opportunity rover analyzed textures of soils and rocks at meridiani planum at a scale of 31 micrometers per pixel the uppermost millimeter of some soils is weakly cemented whereas other soils show little evidence of cohesion rock outcrops are laminated on a millimeter scale image mosaics of cross stratification suggest that some sediments were deposited by flowing water vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis microscopic images support the hypothesis that hematite rich spherules observed in outcrops and soils also formed diagenetically as concretions

temperature dependent thermal inertia of homogeneous martian regolith 1 past studies of the thermophysical properties of the martian surface layer have assumed temperature independent thermal inertia which is a function of the material density specific heat and bulk conductivity in this paper we evaluate the temperature driven variations of these quantities for particulated and cemented material under martian conditions of atmospheric pressure and temperature temperature driven density variations are negligible the specific heat of a basaltic material is strongly influenced by the temperature 75 increase from 150 to 315 k inducing significant variations of the thermal inertia the thermal conductivity of uncemented martian regolith is weakly controlled by the solid phase conductivity and strongly controlled by the gaseous phase conductivity as a result the conductivity of the solid phase i e composition temperature is unimportant whereas medium to large variations 30 50 of the bulk conductivity are associated with temperature induced fluctuations of the pore filling gas conductivity overall the thermal inertia of uncemented martian soils is predicted to vary significantly 80 throughout the range of the observed surface temperatures in the case of cemented soils the contribution of the gas conductivity is generally small and the solid phase i e grains and cement conductivity i e composition temperature becomes more important consequently the magnitude of the thermal inertia change for cemented soils is variable and smaller than that predicted for uncemented materials 10 50 large diurnal and seasonal temperature variations only occur within the top material and most of the near surface regolith does not experience large thermal inertia variations the shapes of modeled diurnal temperature curves are not significantly modified e g the 0200 lt martian local time apparent thermal inertia of uncemented regolith is up to 15 lower than the average daily inertia of the top material thermally derived grain sizes are usually based on conductivity measurements operated at room temperature or above where the thermal inertia and specific heat are higher than on mars implying that grain size predictions for mars are currently underestimated however in situ observations by the mars exploration rovers and thermal conductivity modeling suggest that this underestimation is not significant

the effects of weathering on the strength and chemistry of columbia river basalts and their implications for mars exploration rover rock abrasion tool rat results abstract basalt physical properties such as compressive strength and density are directly linked to their chemistry and constitution as weathering progresses basalts gradually become weaker and transition from intact rock to saprolite and ultimately to soil here we quantify the degree of weathering experienced by the adirondack class basalts at the mars exploration rover spirit site by performing comparative analyses on the strength and chemistry of a series of progressively weathered columbia river basalt crb from western idaho and eastern washington crb samples were subjected to compressive strength tests rock abrasion tool grinds neutron activation analysis and inductively coupled plasma optical emission spectroscopy analyses of terrestrial basalts indicate linked strength chemical changes as expected weathering sufficient to induce the loss of more than 50 of some cations including 50 of mgo and mno as well as 38 of fe 2 o 3 and 34 of cao was observed to weaken these samples by as much as 50 of their original strength in comparison with the terrestrial samples adirondack class basalts are most similar to the weakest basalt samples measured in terms of compressive strength yet they do not exhibit a commensurate amount of chemical alteration since fluvial and lacustrine activity in gusev crater appears to have been limited after the emplacement of flood basalt lavas the observed weakness is likely attributable to thin film weathering on exposed displaced rocks in the gusev plains in addition to some likely shock effects the results indicate that adirondack class basalts may possess a several mm thick weak outer rind encasing an interior that is more pristine than otherwise indicated and also suggest that long rock residence times may be the norm