seasonal thermal inertia variations at gale crater role of active surface deposition phenomena abstract thermal inertia has been found to play a significant role in planetary remote sensing applications forming the basis of potentially all major lithological discriminations of the planetary surface it has always been visualised to serve as a distinctive thermal property of the surface with its values remaining fairly constant at least for a short time period unless the surface undergoes extensive and rapid degradation thermal inertia for mars has been previously calculated from point spectrometer orbiter and rover measurements and they have been successfully used for surface geologic interpretations the present study computes surface thermal inertia over 12 sols along curiosity s traverse at gale crater using thermal infrared imaging system themis and rover environmental monitoring station rems observations and attempts to analyse the same on a seasonal timescale we find that surface thermal inertia at gale follows a seasonal sinusoidal behaviour with the surface exhibiting maximum and minimum thermal inertia values during southern autumn and spring respectively the difference between them of the order of 300 to 400 t i u we have attempted here to illustrate that the seasonal behaviour seen in surface thermal inertia may be the result of active surface deposition processes localised to gale in this regard we have also explored the potential role of seasonal dust and water ice deposition in contributing to these observed variations effectively concluding that seasonal dust deposition could be a highly likely cause to which these seasonal thermal inertia changes can be attributed to

an aerodynamic roughness length map derived from extended martian rock abundance data many boundary layer processes simulated within a mars general circulation model mgcm including the description of the processes controlling dust rising from the martian surface are highly sensitive to the aerodynamic roughness length z0 on the basis of rock size frequency distributions inferred from different martian landing sites and earth analog sites we have first established that lognormal modeled rock size frequency distributions are able to reproduce correctly the observed martian rock populations we have validated the hypothesis that the rock abundance of a given area could be estimated at a first order from its thermophysical properties namely its thermal inertia i and its albedo we have demonstrated the possibility of using rock abundance to estimate the roughness density on mars and to retrieve subsequently the aerodynamic roughness length by using semi empirical relationships based on terrestrial wind tunnel and field measurements by combining our methodology with remote sensing measurements of the thermal emission spectrometer aboard mars global surveyor we have derived a global map of the aeolian aerodynamic roughness length with a 1 8 1 8 resolution over the entire martian surface contrary to what is often assumed the martian aeolian aerodynamic roughness length is spatially highly heterogeneous at the fullest resolution the martian aerodynamic roughness length varies from 10 3 cm to 2 33 cm about 84 of the martian surface seems to be characterized by an aeolian aerodynamic roughness length value lower than 1 cm the spatially uniform value that most of the mgcms simulations have assumed recently since the aerodynamic roughness length z0 is a key parameter in deriving the erosion threshold wind velocities we anticipate a significant impact of our findings on the efficiencies for lifting dust in future mgcms

ice pumps and their rates an ice pump is a heat engine driven by the change of freezing point with pressure which will melt ice at depth in the ocean and deposit it at a shallower location it is self starting calculations of the maximum magnitude of this effect are made which show good agreement with field data available for sea and lake ice the discussion is applied to the general case of a moving pack ice sheet with a well mixed surface layer and to floating ice shelves the rate of melt from an 11 m deep pressure ridge keel due to ice pumping is estimated as 26 cm year and that from the front of the ross ice shelf at mcmurdo sound antarctica is estimated as 5 m year for the level of water movement noted in the authors field observations far from the ice front pumping between shelf areas of different thickness will still occur with tidal motion providing the necessary water exchange but its magnitude is now limited by the ability to remove the potentially stable layer of melt water out of the system it is important to realize that the pumping does not depend on the availability of sensible heat in the water column and its effects are additional to any melting caused by the advection of warmer water to the ice water interface

frazil ice formation in an ice shelf water plume 1 we present a model for the growth of frazil ice crystals and their accumulation as marine ice at the base of antarctic ice shelves the model describes the flow of buoyant water upward along the ice shelf base and includes the differential growth of a range of crystal sizes frazil ice formation starts when the rising plume becomes supercooled initially the majority of crystals have a radius of similar to0 3 mm and concentrations are below 0 1 g l depending on the ice shelf slope which controls the plume speed frazil crystals increase in size and number typically crystals up to 1 0 mm in radius are kept in suspension and concentrations reach a maximum of 0 4 g l the frazil ice in suspension decreases the plume density and thus increases the plume speed larger crystals precipitate upward onto the ice shelf base first with smaller crystals following as the plume slows down in this way marine ice is formed at rates of up to 4 m yr in some places consistent with areas of observed basal accumulation on filchner ronne ice shelf the plume continues below the ice shelf as long as it is buoyant if the plume reaches the ice front its rapid rise produces high supercooling and the ice crystals attain a radius of several millimeters before reaching the surface similar ice crystals have been trawled at depth north of antarctic ice shelves but otherwise no observations exist to verify these first predictions of ice crystal sizes and volumes

a boundary layer model for mars comparison with viking lander and entry data abstract a one dimensional boundary layer model for mars is described and its results are compared with viking data the model equations are similar to earth boundary layer models in that they include contributions from coriolis pressure gradient and frictional forces for momentum and radiation sensible heat flux convergence and advection for heat turbulent fluxes are computed from the level 2 second order closure theory of mellor and yamada with similarity relations employed for boundary conditions the pressure gradient force can be specified or computed from a simple slope model radiative heating is due to the absorption of solar and infrared radiation by co2 gas and suspended dust particles ground temperatures are computed by solving a surface heat budget using an accurate treatment of conduction into the martian soil the data used for comparison were obtained by the viking 1 and 2 landers for early northern summer at each site these data include a single profile of wind and temperature be

climbing and falling dunes in valles marineris mars 1 multiple occurrences of wall dunes are found several kilometers above the valles marineris canyon floor dune slip face orientation and bed form morphologies indicate transport direction and whether the wall dunes are climbing dunes or falling dunes on earth these types of dunes form in a unidirectional wind regime and are strongly controlled by the local topography newly acquired mars reconnaissance orbiter mro images and topography of the walls of valles marineris show similar sand dune morphologies as wind blown sediment has interacted with local and regional topography primarily found in melas and coprates chasmata these climbing and falling dunes are relevant for understanding aeolian sediment flux sediment sources and wind directions falling dunes show photogeologic and thermophysical evidence of their sand being provided by adjacent outcrops

mars express high resolution stereo camera spectrophotometric data characteristics and science analysis 1 the high resolution stereo camera hrsc on the mars express mex spacecraft in orbit about mars is delivering images of the mars surface and atmosphere from its high inclination elliptical orbit that are intended to cover most of the mars surface by the end of the mission these are acquired in four specific spectral passbands that sample the scene at different parts of the extended visual spectrum from near 0 4 m to about 1 m and in five additional channels four used for stereo and one nadir that use the same fifth spectral passband these channels view from different angles and can be used for photometric and spectral analysis the data allow a variety of studies of the surface and atmosphere of mars but these require detailed understanding of the data characteristics as there are several effects including of the observation geometry and the atmosphere that need to be treated this article is a report to the science community on the current understanding of the hrsc color data after an initial analysis and also a demonstration of their capabilities for study of mars which from this study appear to be considerable we first discuss the characteristics and calibration of the hrsc spectral data the atmospheric influence on the photometric appearance of the surface materials is explored and methods of compensating are considered reflectances are calculated for surface units by assuming the dark material is basalt and scaling the entire hrsc scene using a laboratory basalt spectrum for the selected dark material area the results and the correction factors for different orbits are compared we present several examples of what could become a large volume of future science results utilizing the hrsc spectrophotometric data in conjunction with photo interpretation for example we find relatively few but very important distinct spectral components at the hrsc resolution including what we interpret as iron oxide rich material unoxidized basalt and polar ice consistent with past works the major spectral components are distributed in ways that suggest compositional mixing and the need to revise the current geologic understanding of major regions

thermophysical properties along curiosity s traverse in gale crater mars derived from the rems ground temperature sensor abstract the rems instrument onboard the mars science laboratory rover curiosity has measured ground temperature nearly continuously at hourly intervals for two mars years coverage of the entire diurnal cycle at 1 hz is available every few martian days we compare these measurements with predictions of surface atmosphere thermal models to derive the apparent thermal inertia and thermally derived albedo along the rover s traverse after accounting for the radiative effects of atmospheric water ice during fall and winter as is necessary to match the measured seasonal trend the rems measurements can distinguish between active sand other loose materials mudstone and sandstone based on their thermophysical properties however the apparent thermal inertias of bedrock dominated surfaces 350 550 j m 2 k 1 s are lower than expected we use rover imagery and the detailed shape of the diurnal ground temperature curve to explore whether lateral or vertical heterogeneity in the surface materials within the sensor footprint might explain the low inertias we find that the bedrock component of the surface can have a thermal inertia as high as 650 1700 j m 2 k 1 s for mudstone sites and 700 j m 2 k 1 s for sandstone sites in models runs that include lateral and vertical mixing although the results of our forward modeling approach may be non unique they demonstrate the potential to extract information about lateral and vertical variations in thermophysical properties from temporally resolved measurements of ground temperature

morphology and composition of the surface of mars mars odyssey themis results the thermal emission imaging system themis on mars odyssey has produced infrared to visible wavelength images of the martian surface that show lithologically distinct layers with variable thickness implying temporal changes in the processes or environments during or after their formation kilometer scale exposures of bedrock are observed elsewhere airfall dust completely mantles the surface over thousands of square kilometers mars has compositional variations at 100 meter scales for example an exposure of olivine rich basalt in the walls of ganges chasma thermally distinct ejecta facies occur around some craters with variations associated with crater age polar observations have identified temporal patches of water frost in the north polar cap no thermal signatures associated with endogenic heat sources have been identified

structural evolution of connecting splay duplexes and their implications for critical taper an example based on geometry and kinematics of the canyon range culmination sevier belt central utah abstract critical taper in an evolving orogenic wedge can be maintained by structural thickening in the back of the wedge this is often achieved by folding and uplift of pre existing large internal thrust sheets by the continued growth and or reactivation of duplexes in the hinterland the growth of a blind imbricate complex off a lower thrust provides another mechanism for folding a higher thrust individual splays in a blind imbricate complex may have fault propagation folds and or fault bend folds associated with them if the splays reach the overlying thrust they serve as connecting splays between the lower thrust floor and the upper thrust roof thereby forming a connecting splay duplex csd this type of duplex geometry requires periodic reactivation of the pre existing roof thrust the canyon range thrust in central utah is an internal thrust that is folded into an overturned antiform synform pair and overrides its own synorogenic conglomerates the same conglomerates are infolded into the core of the synform and preserve critical timing information regarding the history of folding and thrust reactivation the folding is caused by the development of a footwall antiformal stack in the core of the canyon range antiformal culmination the geometry and timing relationships suggest that the structure grew as a csd regional timing relationships suggest that the growth of the csd and reactivation of the thrust took place during the later part of the evolution of the orogenic wedge and may have helped the wedge maintain critical taper during thrusting in the external fold and thrust belt

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

impact of antarctic ice shelf basal melting on sea ice and deep ocean properties 1 an approximation of antarctica s rocky and icy coastline normally forms the southern boundary in global climate models such a configuration neglects extensive ice shelf areas where ocean ice interaction initiates a net freshwater flux to the circumpolar continental shelf equal to 75 of the annual mean net precipitation in coastal seas the results of a numerical model for the southern ocean using two contrasting configurations with and without caverns beneath major antarctic ice shelves are compared they show that the freshwater flux due to deep basal melting significantly stabilizes the shelf water column in front of an ice shelf as well as downstream due to advection by the coastal current if the freshwater from the caverns is absent sea ice is thinner shelf waters are warmer and saltier and the southern ocean deep basins are flushed by denser waters

redox stratification of an ancient lake in gale crater mars introduction the primary goal of nasa s curiosity rover mission is to explore and quantitatively assess a local region on mars surface as a potential habitat for past or present life a necessary component of that assessment involves an investigation of the surface chemical conditions and paleoclimate of ancient mars gale crater was selected as the landing site for curiosity it hosts a 5 km tall mountain of layered sedimentary rock the rocks of mount sharp preserve a long duration record of martian environmental conditions geological reconstructions from curiosity rover data have revealed an ancient habitable lake environment that was sustained for tens of thousands to tens of millions of years by rivers draining into the crater rationale we seek to constrain the chemical environment within the lake in gale crater as well as short and long term climate variations in and around gale crater we focus on fine grained sedimentary rocks that carry information about sediment provenance the environment of deposition the conversion of sediment to rock during burial i e lithification and the chemical conditions of later modification i e diagenesis these were investigated during the first 1300 martian solar days sols of rover operations in gale crater using bulk geochemical and mineralogical analysis techniques combined with high resolution color imagery at a variety of scales results two mudstone units have been recognized both deposited in lakes the sheepbed member of the yellowknife bay formation an older set of strata defining the base of the stratigraphic section and the murray formation of relatively younger age and positioned higher in the stratigraphic section the chemical index of alteration cia paleoclimate proxy increases by up to 10 to 20 cia units expressed in from the sheepbed member to the murray formation on the basis of mineralogy geochemistry textural properties and stratigraphic relationships the murray formation can be subdivided into two sedimentary associations or facies the hematite phyllosilicate hp facies and the magnetite silica ms facies the hp facies is characterized by abundant fe 3 oxides accompanied by phyllosilicates as well as indications of mn oxidation and trace metal concentration these properties are consistent with deposition in an oxidizing environment the ms facies is recognized by a near complete absence of pure fe 3 minerals and high concentrations of silica accompanied by magnetite consistent with deposition in an anoxic environment both facies were affected by a saline overprint after burial and lithification conclusion the observed variations in cia are consistent with modest short term fluctuations in the ancient climate between cold dry conditions and relatively warmer wetter conditions these changes occurred during the deposition of lake bed mudstones in an environment that was conducive to the presence of a long lived lake in gale crater we propose that the distinct properties of the two murray facies were developed as a result of i fractionation of river borne detritus into coarser denser materials in shallow water close to shore and finer lower density materials offshore in deeper water as a result of deceleration of river flow as it entered the lake and ii redox stratification of the lake water body caused by depth dependent variations in the concentration of atmospheric oxidants and dissolved groundwater derived solutes resulting in oxidizing conditions in shallow water and anoxia in deeper water the addition of saline minerals during a later phase of brine migration through the section records longer term changes in martian climate at gale crater perhaps driven by global atmospheric escape processes the recognition of redox stratification in the lake in gale crater adds new detail to our understanding of ancient martian aquatic environments previously reported detections of organic carbon compounds nitrogen phosphate minerals and fe and s minerals in a variety of redox states combined with the evidence presented here for relatively stable climate conditions and gradients in fluid oxidation state provide compelling evidence that all of the physical chemical and energetic conditions necessary to establish a habitable environment were present on mars between 3 8 billion and 3 1 billion years ago

likely frost events at gale crater analysis from msl rems measurements abstract we provide indirect evidence for the formation of frost at the surface of gale crater by analyzing the highest confidence data from simultaneous measurements of relative humidity and ground temperature during the first 1000 sols of the mars science laboratory msl mission we find that except for sol 44 frost events could have occurred only between sols 400 and 710 corresponding to the most humid and coldest time of the year from early fall to late winter in particular measurements at dingo gap during sols 529 535 at an unnamed place during sols 554 560 at kimberley during sols 609 617 and at an unnamed place during sols 673 676 showed the largest likelihood of the occurrence of frost events at these four locations the terrain is composed of fine grained and loosely packed material with thermal inertia values of 200 si units much lower than the 365 50 si units value found at the landing ellipse this is important because terrains with exceptionally low thermal inertia favor the formation of frost by lowering minimum daily ground temperatures an order of magnitude calculation to determine the thickness of the frost layer at these four locations results in values of tenths of m while the precipitable water content is a few pr m therefore surface frost events can have important implications for the local water cycle at gale crater in addition frost is the most likely type of water that can be temporarily found in bulk amounts on the surface of mars at low latitudes and therefore can cause weathering influencing the geology of gale crater

high resolution thermal inertia mapping from the mars global surveyor thermal emission spectrometer abstract high resolution thermal inertia mapping results are presented derived from mars global surveyor mgs thermal emission spectrometer tes observations of the surface temperature of mars obtained during the early portion of the mgs mapping mission thermal inertia is the key property controlling the diurnal surface temperature variations and is dependent on the physical character of the top few centimeters of the surface it represents a complex combination of particle size rock abundance exposures of bedrock and degree of induration in this work we describe the derivation of thermal inertia from tes data present global scale analysis and place these results into context with earlier work a global map of nighttime thermal bolometer based thermal inertia is presented at 1 4 per pixel resolution with approximately 63 coverage between 50 s and 70 n latitude global analysis shows a similar pattern of high and low thermal inertia as seen in previous viking low resolution mapping significantly more detail is present in the high resolution tes thermal inertia this detail represents horizontal small scale variability in the nature of the surface correlation with albedo indicates the presence of a previously undiscovered surface unit of moderate to high thermal inertia and intermediate albedo this new unit has a modal peak thermal inertia of 180 250 j m 2 k 1 s 1 2 and a narrow range of albedo near 0 24 the unit covering a significant fraction of the surface typically surrounds the low thermal inertia regions and may comprise a deposit of indurated fine material local 3 km resolution maps are also presented as examples of eolian fluvial and volcanic geology some impact crater rims and intracrater dunes show higher thermal inertias than the surrounding terrain thermal inertia of aeolian deposits such as intracrater dunes may be related to average particle size outflow channels and valleys consistently show higher thermal inertias than the surrounding terrain generally correlations between spatial variations in thermal inertia and geologic features suggest a relationship between the hundred meter scale morphology and the centimeter scale surface layer

modeling the transport of passive tracers in sea ice 1 a model for the vertical transport of passive tracers in sea ice is presented two reynolds flux closure approximations are proposed for the tracer velocity dispersion term in the new ice tracer model icet the schemes enhanced molecular diffusion emd and mixing length diffusion mld are suggested parameterizations of gravity drainage the dominant mechanism of desalination in growing sea ice the performance of icet using each parameterization is tested against two experimental studies simulations i compare profiles of brine salinity with passive tracer concentrations during sea ice growth and melt and simulations ii compare bottom boundary salt and brine volume fluxes with passive tracer fluxes and bottom diffusivities icet behavior is evaluated under three salinity forcing prescriptions both schemes successfully reproduce expected tracer concentrations in simulations i when the salinity forcing evolves logarithmically however in simulations ii the mld scheme outperforms emd in two significant ways 1 growth rate trends in the mld diffusivity parallel measurements of brine volume flux while emd bottom diffusivities remain almost constant and 2 mld bottom tracer concentrations decrease with ice growth rate similar to excluded brine salinity while emd trends are contrary hence enhanced molecular diffusion is highly questionable for implementation in models of reactive passive tracers the icet mixing length diffusivity is a viable choice in sea ice biogeochemical modeling it remains a challenge to assess whether mld can provide quantitative estimates of desalination at each time step for use in forcing icet or for implementation in a model of sea ice salinity

observation and modeling of platelet ice fabric in mcmurdo sound antarctica 1 during the annual growth of landfast ice in mcmurdo sound antarctica an episodic flux of platelet ice crystals from the ocean contributes to the build up of a porous subice platelet layer which is steadily incorporated into the sea ice cover as it thickens over winter in november 2007 we examined the spatial variability of these processes by collecting sea ice cores with simultaneous oceanographic observations along an east west transect in the sound previously identified draped and bladed platelet ice types were observed in addition we identify resumed columnar growth which appears to be a result of geometric selection from the subice platelet layer after the arrival of new platelet crystals from the ocean has ceased a numerical model of mechanical platelet ice processes is developed that predicts crystal texture and c axis distributions producing virtual incorporated platelet ice with known growth history this model demonstrates how a disordered subice platelet layer arises from an initially flat interface and suggests that such a layer is more likely to form later in the growth season the model also suggests how the grain boundary density in incorporated platelet ice responds to changes in the flux of loose platelet crystals from the ocean application of this result to our 2007 platelet ice observations indicates that sea ice in western mcmurdo sound is subject to larger and more persistent platelet fluxes than the ice in the east this is consistent with the pattern of in situ supercooling just beneath the ocean surface

finite strain and strain variation analysis in the sheeprock thrust sheet an internal thrust sheet in the provo salient of the sevier fold and thrust belt central utah abstract the sheeprock thrust sheet in west central utah is an internal thrust sheet in the provo salient of the sevier fold and thrust belt we have measured finite strain in quartzites the dominant lithology sampled along a square grid within the thrust sheet using the modified normalized fry method mcnaught m a 1994 modifying the normalized fry method for aggregates of non elliptical grains journal of structural geology16 493 503 the x y and x z axial ratios from unsampled locations within the sample area were estimated using the spatial statistics approach the strain ellipsoids exhibit a variable three dimensional orientation pattern resulting from modification of the initial layer parallel shortening lps strain ellipsoid by fault parallel shear in conjunction with vertical flattening and or horizontal stretching indicating that the thrust sheet did not undergo plane strain deformation in the transport plane this suggests that the plane strain assumption used in drawing restorable balanced cross sections breaks down for internal thrust sheets with more than one penetrative strain producing deformation event the x z strain axial ratios decrease away from the thrust towards the middle of the sheet the x y strain axial ratios from interpolated image diagrams indicate transport parallel stretching at the front end of the sheet and strike parallel stretching at the back end of the sheet the footwall and hanging wall finite strain patterns are similar indicating that most of the strain in the sheeprock thrust sheet developed early in the deformation history of the thrust sheet before and perhaps during the growth of a large fault propagation fold pair

the influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern united states this paper reports systematic changes in mudrock composition through time on a single con tinental cmstal block the changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton the major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study major elements record sediment recycling processes as well as changing proportions of sedi mentary and first cycle source rocks with the exceptions of kzo which tends to increase and sioz and a o3 which show no trend most major oxides tend to decline in relative abundance in younger mud rocks patterns shown by the index of compositional variability fe03 kro naao cao mgo mno tiojialro and by k20 a1203 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material excursions from progressive trends marked by increases in mgo k20 and cao reflect episodes of large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift the chemistry of low solubility trace elements in contrast is not sensitive to recycling effects and reflects the composition of first cycle input incompatible elements are progressively enriched relative to compatible elements in younger mudrocks and values for chondrite normalised rare earth elements also increase in addition the eu anomaly becomes systematically more negative in younger samples these trends cmnot be explained by diagenetic or weathering processes and therefore indicate that the proportion of fnc tionated granitic first cycle detritus being added to the sedimentary system becomes greater with time these results confirm the importance of tectonic setting in controlling mudrock chemistry and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle

modeling brine and nutrient dynamics in antarctic sea ice the case of dissolved silica sea ice ecosystems are characterized by microalgae living in brine inclusions the growth rate of ice algae depends on light and nutrient supply here the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one dimensional model the model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component characterized by one nutrient namely dissolved silica dsi in the model dsi follows brine motion and is consumed by ice algae depending on physical ice characteristics the brine flow is either advective diffusive or turbulent the vertical profiles of ice salinity and dsi concentration are solutions of advection diffusion equations the model is configured to simulate the typical thermodynamic regimes of first year antarctic pack ice the simulated vertical profiles of salinity and dsi qualitatively reproduce observations analysis of results highlights the role of convection in the lowermost 5 10 cm of ice convection mixes saline nutrient poor brine with comparatively fresh nutrient rich seawater this implies a rejection of salt to the ocean and a flux of dsi to the ice in the presence of growing algae the simulated ocean to ice dsi flux increases by 0 115 compared to an abiotic situation in turn primary production and brine convection act in synergy to form a nutrient pump the other important processes are the flooding of the surface by seawater and the percolation of meltwater the former refills nutrients near the ice surface in spring the latter if present tends to expell nutrients from the ice in summer

simulation of the crystal growth of platelet sea ice with diffusive heat and mass transfer antarctic coastal sea ice often grows in water that has been supercooled by interaction with an ice shelf in these situations ice crystals can form at depth rise and deposit under the sea ice cover to form a porous layer that eventually consolidates near the base of the existing sea ice the least consolidated portion is called the sub ice platelet layer congelation growth eventually causes the sub ice platelet layer to become frozen into the sea ice cover as incorporated platelet ice in this study we simulate these processes in three dimensions using voronoi dynamics to govern crystal growth kinetics platelet deposition in situ growth and incorporation into the sea ice cover are integrated into the model heat and mass transfer are controlled by diffusion we extract and compare spatial temporal distributions of porosity salinity temperature and crystallographic c axes with observations from mcmurdo sound antarctica the model captures the crystallographic structure of incorporated platelet ice as well as the topology of the sub ice platelet layer the solid fraction which has previously been poorly constrained is simulated to be 0 22 in good agreement with an earlier estimate of 0 25 0 06 this property of the sub ice platelet layer is important for biological processes and for the freeboard thickness relationship around antarctica

evolution of a supercooled ice shelf water plume with an actively growing subice platelet matrix we use new observations in western mcmurdo sound combined with longitudinal hydrographic transects of the sound to identify a northward flowing ice shelf water isw plume exiting the cavity of the mcmurdo ross ice shelf we estimate the plume s net northward transport at 0 4 0 1 sv carving out a corridor approximately 35 km wide aligned with the victoria land coast basal topography of the mcmurdo ice shelf is such that the plume is delivered to the surface without mixing with overlying warmer water and is therefore able to remain below the surface freezing temperature at the point of observation beneath first year ice thus the upper ocean was supercooled by up to 50 mk at the surface due to pressure relief from recent rapid ascent of the steep basal slope the 70 m thick supercooled layer supports the growth and maintenance of a thick semirigid and porous matrix of platelet ice which is trapped by buoyancy at the ice ocean interface continued growth of individual platelets in supercooled water creates significant brine rejection at the top of the water column which resulted in convection over the upper 200 m thick homogeneous layer by examining the diffusive nature of the intermediate water between layers of isw and high salinity shelf water we conclude that the isw plume must have originated beneath the ross ice shelf and demonstrate that it is likely to expand eastward across mcmurdo sound with the progression of winter

influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the ross sea antarctica 1 satellite imagery shows that there was substantial variability in the sea ice extent in the ross sea during 2001 2003 much of this variability is thought to be due to several large icebergs that moved through the area during that period the effects of these changes in sea ice on circulation and water mass distributions are investigated with a numerical general circulation model it would be difficult to simulate the highly variable sea ice from 2001 to 2003 with a dynamic sea ice model since much of the variability was due to the floating icebergs here sea ice concentration is specified from satellite observations to examine the effects of changes in sea ice due to iceberg c 19 simulations were performed using either climatological ice concentrations or the observed ice for that period the heat balance around the ross sea polynya rsp shows that the dominant term in the surface heat budget is the net exchange with the atmosphere but advection of oceanic warm water is also important the area average annual basal melt rate beneath the ross ice shelf is reduced by 12 in the observed sea ice simulation the observed sea ice simulation also creates more high salinity shelf water another simulation was performed with observed sea ice and a fixed iceberg representing b 15a there is reduced advection of warm surface water during summer from the rsp into mcmurdo sound due to b 15a but a much stronger reduction is due to the late opening of the rsp in early 2003 because of c 19

apparent thermal inertia and the surface heterogeneity of mars abstract thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters consequently surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season to investigate these temporal variations we processed three mars years of mars global surveyor thermal emission spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia these maps show broad regions with diurnal and seasonal differences up to 200 j m 2 k 1 s 1 2 at mid latitudes 60 s to 60 n and 600 j m 2 k 1 s 1 2 or greater in the polar regions we compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5 resolution delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials the thermal behavior of most regions on mars appears to be dominated by layering with upper layers of higher thermal inertia e g duricrusts or desert pavements over fines prevailing in mid latitudes and upper layers of lower thermal inertia e g dust covered rock soils with an ice table at shallow depths prevailing in polar regions less common are regions dominated by horizontal mixtures such as those containing differing proportions of rocks sand dust and duricrust or surfaces with divergent local slopes other regions show thermal behavior that is more complex and not well represented by two component surface models these results have important implications for mars surface geology climate modeling landing site selection and other endeavors that employ thermal inertia as a tool for characterizing surface properties

observations of platelet ice growth and oceanographic conditions during the winter of 2003 in mcmurdo sound antarctica 1 platelet ice is the name given to ice crystals that nucleate in the ocean and grow either at depth or loosely attached to the ice water interface related to the proximity of ice shelves it is known to form in supercooled seawater this study details the conditions for its growth during the austral winter of 2003 in mcmurdo sound antarctica a key finding is that the presence of platelet ice in the sea ice cover is conclusively linked to the time history of the appearance of ice crystals in the water column monitored using the strength of the backscattered signal from an acoustic doppler current profiler as a proxy generally these crystals appeared from mid may as water near the interface became supercooled this near surface supercooling appears to be related to a simultaneous abrupt change in the structure of the upper 250 m of the water column from one that behaved dynamically and contained both the warmest and coolest measured temperatures to one in which the water was essentially isothermal near its surface freezing temperature near surface ocean temperature was also affected by tidal mixing and by an increase in the thickness and density over the course of winter of the surface mixed layer created by salt rejection during ice growth these processes allowed cold water trapped by buoyancy in a band at the base of the mixed layer in early winter to gain access to the ice water interface by midwinter this band of cold water probably had its origin beneath the mcmurdo ice shelf

water in the martian regolith from omega mars express here we discuss one of the current reservoirs of water on mars the regolith and rocks exposed at the surface this reservoir is characterized by the presence of h2o and oh bearing phases that produce a broad absorption at a wavelength of 3 m in near infrared nir reflectance spectra this absorption is present in every ice free spectrum of the martian surface obtained thus far by orbital nir spectrometers we present a quantitative analysis of the global distribution of the 3 m absorption using the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer that has been mapping the surface of mars at kilometer scale for more than 10 years based on laboratory reflectance spectra of a wide range of hydrous minerals and phases we estimate a model dependent water content of 4 1 wt in the equatorial and midlatitudes surface hydration increases with latitude with an asymmetry in water content between the northern and southern hemispheres the surface hydration is compared to various parameters albedo dust geological units time relative humidity atmospheric water pressure and in situ measurements performed by phoenix and curiosity to constrain the nature of the reservoir we conclude that the nature of the surface hydration of the martian low latitudes is not adsorbed water but rather more tightly bound water molecules and hydroxyl groups in the structure of the materials of the near top surface a frost related process best explains the implementation of water into and onto the first microns of the high latitude martian regolith

observations and preliminary science results from the first 100 sols of msl rover environmental monitoring station ground temperature sensor measurements at gale crater we describe preliminary results from the first 100 sols of ground temperature measurements along the mars science laboratory s traverse from bradbury landing to rocknest in gale the ground temperature data show long term increases in mean temperature that are consistent with seasonal evolution deviations from expected temperature trends within the diurnal cycle are observed and may be attributed to rover and environmental effects fits to measured diurnal temperature amplitudes using a thermal model suggest that the observed surfaces have thermal inertias in the range of 265 375 j m 2 k 1 s 1 2 which are within the range of values determined from orbital measurements and are consistent with the inertias predicted from the observed particle sizes on the uppermost surface near the rover ground temperatures at gale crater appear to warm earlier and cool later than predicted by the model suggesting that there are multiple unaccounted for physical conditions or processes in our models where the mars science laboratory msl descent engines removed a mobile layer of dust and fine sediments from over rockier material the diurnal temperature profile is closer to that expected for a homogeneous surface suggesting that the mobile materials on the uppermost surface may be partially responsible for the mismatch between observed temperatures and those predicted for materials having a single thermal inertia models of local stratigraphy also implicate thermophysical heterogeneity at the uppermost surface as a potential contributor to the observed diurnal temperature cycle

surface energy budget and thermal inertia at gale crater calculations from ground based measurements the analysis of the surface energy budget seb yields insights into soil atmosphere interactions and local climates while the analysis of the thermal inertia i of shallow subsurfaces provides context for evaluating geological features mars orbital data have been used to determine thermal inertias at horizontal scales of 104 m2 to 107 m2 here we use measurements of ground temperature and atmospheric variables by curiosity to calculate thermal inertias at gale crater at horizontal scales of 102 m2 we analyze three sols representing distinct environmental conditions and soil properties sol 82 at rocknest rck sol 112 at point lake pl and sol 139 at yellowknife bay ykb our results indicate that the largest thermal inertia i 452 j m 2 k 1 s 1 2 si units used throughout this article is found at ykb followed by pl with i 306 and rck with i 295 these values are consistent with the expected thermal inertias for the types of terrain imaged by mastcam and with previous satellite estimations at gale crater we also calculate the seb using data from measurements by curiosity s rover environmental monitoring station and dust opacity values derived from measurements by mastcam the knowledge of the seb and thermal inertia has the potential to enhance our understanding of the climate the geology and the habitability of mars

a magnetostratigraphic age constraint for the proximal synorogenic conglomerates of the late cretaceous cordilleran foreland basin northeast utah usa

surficial geologic surveys of gale crater and melas chasma mars integration of remote sensing data abstract remote sensing observations of gale crater and melas chasma are synthesized to better understand the present surface layer in these two scientifically interesting regions data sets analyzed include geologic maps mars orbiter laser altimeter mola elevation thermal emission spectrometer tes albedo tes thermal inertia mola residual pulse width tes rock abundance and viking and mars orbiter camera images using these data sets we constrain the properties of and processes acting on the present surface and create self consistent models for the surface layer surface properties within gale crater are variable and complex and interpreting the surface layer is not straightforward observations indicate that aeolian processes have shaped some of the intracrater surface but other areas do not comply with this model and have counterintuitive surface characteristics in contrast aeolian activity appears to have played a large role in shaping the present day physical structure of all surfaces in melas chasma and is reflected in the remote sensing data sets here we summarize our analysis and discuss the surface attributes as determined from these data sets