geomorphic and geologic settings of the phoenix lander mission landing site 1 the phoenix lander touched down on the northern distal flank of the shield volcano alba patera in a 150 km wide valley underlain by the scandia region unit the geomorphology and geology of the landing site is dominated by the 0 6 ga 11 5 km wide bowl shaped impact crater heimdal and its areally extensive ejecta deposits the lander is located 20 km to the west of the crater and is sitting on a plains surface underlain by partially eroded heimdal ejecta deposits heimdal was produced by a hypervelocity impact into fine grained ice rich material and is inferred to have produced high velocity winds and a ground hugging ejecta emplacement mode that destroyed or buried preexisting surfaces and rock fields out to 10 crater radii patterned ground is ubiquitous with complex polygon patterns and rock rubble piles located on older plains 3 3 ga to the west of the ejecta deposits crater size frequency distributions are complex and represent equilibria between crater production and destruction processes e g aeolian infill cryoturbation relaxation of icy substrate rock abundances increase near craters for the older plains and rocks with their dark shadows explain the reason for the few percent lower albedo for these plains as opposed to the heimdal ejecta deposits many rocks at the landing site have been reworked by cryoturbation and moved to polygon troughs the evidence for cryoturbation and the lack of aeolian features imply that the soils sampled by phoenix are locally derived and mixed with a subordinate amount of windblown dust

tes premapping data slab ice and snow flurries in the martian north polar night in the 1970s mariner and viking spacecraft observations of the north polar region of mars revealed polar brightness temperatures that were significantly below the expected kinetic temperatures for co 2 sublimation for the past few decades the scientific community has speculated as to the nature of these martian polar cold spots thermal emission spectrometer tes thermal spectral data have shown these cold spots to result largely from fine grained co 2 and have constrained most of these cold spots to the surface or near surface cold spot formation is strongly dependent on topography forming preferentially near craters and on polar slopes tes data combined with mars orbiter laser altimeter mola cloud data suggest atmospheric condensates form a small fraction of the observed cold spots tes observations of spectra close to a blackbody indicate that another major component of the polar cap is slab co 2 ice these spectrally bland regions commonly have a low albedo the cause is uncertain but may result from most of the light being reflected toward the specular direction from the slab ice being intrinsically dark or from it being transparent regions of the cap where the difference between the brightness temperatures at 18 m t 18 and 25 m t 25 is less than 5 are taken to indicate deposits of slab ice slab ice is the dominant component of the polar cap at latitudes outside of the polar night

on the icy edge at louth and korolev craters abstract the modern climate of mars has been well characterized from over a decade of orbiting spacecraft in situ measurements via landers rovers and theoretical advances in climate modeling nonetheless important questions remain unanswered including the present day mass balance of the north polar residual cap and its icy outliers exposed water ice mounds are found in craters and extend as far equatorward as 70 2 n due to their southerly location these ice mounds are likely more sensitive to ongoing changes in climate we analyze high resolution images of the louth crater ice mound and employ a coupled 1 d thermal and atmospheric model to estimate annual mass balance of both louth and korolev water ice we incorporate the effects of shallowly sloping surfaces and seasonally dependent water ice albedo no clear trend in the advance or retreat of louth crater water ice is observed in over 4 mars years of repeat high resolution images secular changes are either sufficiently small as to not be detected or the ice is in equilibrium modeled mass balance ranges from 6 to 2 mm of water ice per mars year at both sites with nominal cases being in near equilibrium

martian seasonal co2 ice in polygonal troughs in southern polar region role of the distribution of subsurface h2o ice the mars orbiter camera onboard the mars global surveyor has obtained several images of polygonal features in the southern polar region in images taken during the end of the southern spring when the surrounding surface is free of the seasonal frost co2 ice still appears to be present within the polygonal troughs in earth s polar regions polygons such as these are indicative of water ice in the ground below we analyzed the seasonal evolution of the thermal state and the co2 content of these features our 2 d model includes condensation and sublimation of the co2 ice a self consistent treatment of the variations of the thermal properties of the regolith and the seasonal variations of the local atmospheric pressure which we take from the results of a general circulation model we find that the residence time of seasonal co2 ice in troughs depends not only on atmospheric opacity and albedo of the co2 ice but also and most significantly on the distribution of water ice in the regolith optical properties of the atmosphere and surface co2 ice can be independently obtained from observations to date this is not true about the distribution of water ice below the surface our analysis quantifies the dependence of the seasonal cycle of the co2 ice within the troughs on the assumed distribution of the water ice below the surface we show that presence of water ice in the ground at a depth smaller than the depth of the troughs reduces winter condensation rate of co2 ice this is due to higher heat flux conducted from the water ice rich regolith toward the facets of the troughs

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

seasonal defrosting of the phoenix landing site 1 the retreat of the seasonal polar cap at the phoenix landing site is analyzed through observations of high resolution images and thermal modeling of the co2 frost mass numerical simulations indicate that the onset of co2 frost formation occurs around ls 220 at 68 n however the polar hood prevented imaging of the surface during this time in the late winter early spring a continuous layer of frost coated the surface obscuring the underlying polygonal patterns however rocks are clearly evident indicating that the frost depth was relatively shallow rare dark fans originating from rocks are also observed in an image from early spring frost dissipated from the polygon centers first and lingered longer in polygon troughs polygon centers were first exposed on ls 13 9 and the polygon troughs were frost free by ls 57 frost distributions varied slightly between geologic units however in general global observations at similar latitudes are consistent with what is seen in the phoenix region a series of hypotheses is also explored to explain the preference for the co2 frost to linger in the troughs lower thermal inertia material in the troughs aeolian redistribution of frost burial of the ice table via aeolian redistribution of dust and shadowing each of these hypotheses has drawbacks to explaining this phenomenon as stand alone components shadows do play a role in keeping the co2 frost on the surface however this effect is small and cannot alone account for the observations

seasonal h2o and co2 ice cycles at the mars phoenix landing site 1 prelanding crism and hirise observations 1 the condensation evolution and sublimation of seasonal water and carbon dioxide ices were characterized at the mars phoenix landing site from martian northern midsummer to midspring ls 142 ls 60 for the year prior to the phoenix landing on 25 may 2008 ice relative abundances and grain sizes were estimated using data from the compact reconnaissance imaging spectrometer for mars and high resolution imaging science experiment aboard mars reconnaissance orbiter and a nonlinear mixing model water ice first appeared at the phoenix landing site during the afternoon in late summer ls 167 as an optically thin layer on top of soil co2 ice appeared after the fall equinox by late winter ls 344 the site was covered by relatively pure co2 ice 30 cm thick with a small amount of 100 m diameter water ice and soil as spring progressed co2 ice grain sizes gradually decreased a change interpreted to result from granulation during sublimation losses the combined effect of co2 sublimation and decreasing h2o ice grain sizes allowed h2o ice to dominate spectra during the spring and significantly brightened the surface co2 ice disappeared by early spring ls 34 and h2o ice by midspring ls 59 spring defrosting was not uniform and occurred more rapidly over the centers of polygons and geomorphic units with relatively higher thermal inertia values

periglacial landforms at the phoenix landing site and the northern plains of mars 1 we examine potentially periglacial landforms in mars orbiter camera moc and high resolution imaging science experiment hirise images at the phoenix landing site and compare them with numerical models of permafrost processes to better understand the origin nature and history of the permafrost and the surface of the northern plains of mars small scale 3 6 m polygonal patterned ground is ubiquitous throughout the phoenix landing site and northern plains larger scale 20 25 m polygonal patterns and regularly spaced 20 35 m rubble piles localized collections of rocks and boulders are also common rubble piles were previously identified as basketball terrain in moc images the small polygon networks exhibit well developed and relatively undegraded morphology and they overlay all other landforms comparison of the small polygons with a numerical model shows that their size is consistent with a thermal contraction origin on current day mars and are likely active in addition the observed polygon size is consistent with a subsurface rheology of ice cemented soil on depth scales of about 10 m the size and morphology of the larger polygonal patterns and rubble piles indicate a past episode of polygon formation and rock sorting in thermal contraction polygons while the ice table was about twice as deep as it is presently the pervasive nature of small and large polygons and the extensive sorting of surface rocks indicates that widespread overturning of the surface layer to depths of many meters has occurred in the recent geologic past this periglacial reworking has had a significant influence on the landscape at the phoenix landing site and over the martian northern plains

determining the amplitude and timing of streamflow discontinuities a cross wavelet analysis approach records of natural processes such as gradual streamflow fluctuations are commonly interrupted by long or short disruptions from natural non linear responses to gradual changes such as from river ice break ups freezing as a result of annual solar cycles or human causes such as flow blocking by dams and other means instrument calibrations and failure the resulting abrupt or gradual shifts and missing data are considered to be discontinuities with respect to the normal signal they differ from random noise as they do not follow any fixed distribution over time and hence cannot be eliminated by filtering the multi scale resolution features of continuous wavelet analysis and cross wavelet analysis were used in this study to determine the amplitude and timing of such streamflow discontinuities for specific wavebands the cross wavelet based method was able to detect the strength and timing of abrupt shifts to new streamflow levels gaps in data records longer than the waveband of interest and a sinusoidal discontinuity curve following an underlying modeled annual signal at 0 5 year uncertainty parameter testing of the time frequency resolution demonstrated that high temporal resolution using narrow analysis windows is favorable to high frequency resolution for detection of waveband related discontinuities discontinuity analysis on observed daily streamflow records from canadian rivers showed the following i that there is at least one discontinuity year related to the annual spring flood in each record studied and ii neighboring streamflows have similar discontinuity patterns in addition the discontinuity density of the canadian streamflows studied in this paper exhibit 11 year cycles that are inversely correlated with the solar intensity cycle this suggests that more streamflow discontinuities such as through fast freezing snowmelt or ice break up may occur during years with slightly lowered solar insolation copyright 2013 john wiley sons ltd

detection and interpretation of recent and historical streamflow alterations caused by river damming and hydropower production in the adige and inn river basins using continuous discrete and multiresolution wavelet analysis abstract in alpine catchments fluctuations of river discharge occur at multiple temporal scales due to natural e g snow and glacier melt and anthropogenic factors e g reservoir and hydropower operation in the last century several modifications of the natural flow regime have been observed originating in the complex interplay between construction of dams for hydropower production changes in water management policies and climate in this work we show that multiresolution analysis via discrete wavelet transform and continuous wavelet transform allow identifying both old breakpoints caused by dam and hydropower plant construction as well as more recent breakpoints caused by changes in hydropower plant operation according to the detected breakpoints we can differentiate a pre impact period natural flow regime post impact period characterized by river damming and hydropower facilities operation and a last period after the recent detected breakpoints caused by changes in water management moreover by analyzing streamflow time series and their log transform it is possible to highlight low flow alterations and distinguish the causes of the breakpoints since they affect different temporal scales the change point analysis is performed using different mother wavelets haar daubechies 2 db2 and daubechies 20 db20 considering the results obtained with the haar mother wavelet a total of 14 historical breakpoints in 13 streamflow time series belonging to the adige and inn catchments were identified and 93 correspond to metadata associated to river damming and hydropower production a total of 5 recent breakpoints were identified which correspond to metadata associated to river damming and hydropower production in case of the log transform of the streamflow 32 historical breakpoints were identified and 100 confirmed by metadata 20 recent breakpoints were detected and 83 correspond to metadata the uncertainty in the temporal location is investigated computing the mean difference between detected breakpoint temporal location and metadata and is generally smaller than 1 year this work shows that change point analysis performed using wavelet transform allows us to differentiate and correctly locate in time most of change points in streamflow variability that can be associated to river damming and hydropower production

rainfall runoff relations for karstic springs part ii continuous wavelet and discrete orthogonal multiresolution analyses abstract karstic watersheds appear as highly non linear and non stationary systems the main focus of this paper is a heuristic study of this non stationarity using a time scale localisation method called the wavelet transform first a mathematical overview of these analysis methods is given the wavelet transform methods used here can be divided into two main parts the continuous morlet wavelet transform and the multiresolution orthogonal analysis a statistical interpretation of the wavelet coefficients is also presented introducing wavelet spectrum analyses univariate and cross wavelet analyses these wavelet methods are applied to rainfall rates and runoffs measured at different sampling rates from daily to half hourly sampling rate the karstic springs under study are located in the pyrenees mountains ariege france and in the causses of larzac aveyron france they are first applied to a pumping and a naturally intermittent runoff process allowing the separation of different sub processes wavelet analyses of rainfall rates and runoffs and wavelet rainfall runoff cross analyses also give meaningful information on the temporal variability of the rainfall runoff relationship in particular this kind of analysis provides a simple interpretation of the distribution of energy between the different scales finally it is demonstrated that wavelet transforms make possible a physical explanation of the temporal structure of the basin response to rainfall allowing discrimination between a rapid response and recharge due to the karst drainage system and a slower one corresponding to infiltration response

in situ analysis of ice table depth variations in the vicinity of small rocks at the phoenix landing site 1 prior to the phoenix mission ice stability simulations predicted that surface rocks at the landing site would produce depressions in the ice table the boundary between dry and ice cemented soil if ground ice at the site were in diffusive equilibrium with atmospheric water vapor we use stereo images and digital elevation models to investigate variations in the depth of the ice table near two decimeter scale rocks at the phoenix landing site and compare the observed depth variations to ice stability simulations we find that ice table depth variations observed near rocks at the landing site are consistent with our theoretical predictions based on our results we conclude that 1 water transport in the near surface regolith occurs primarily via vapor diffusion 2 environmental conditions in which water transport is dominated by diffusion have been persistent at the landing site for 100s to 1000s of years or longer that is ground ice is in diffusive equilibrium with atmospheric water vapor and 3 in diffusive equilibrium thermal stability dictates the depth of the ice table on horizontal length scales as small as centimeters

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

results from the mars phoenix lander robotic arm experiment 1 the mars phoenix lander was equipped with a 2 4 m robotic arm ra with an icy soil acquisition device capable of excavating trenches in soil deposits grooming hard icy soil surfaces with a scraper blade and acquiring icy soil samples using a rasp tool a camera capable of imaging the scoop interior and a thermal and electrical conductivity probe were also included on the ra a dozen trench complexes were excavated at the northern plains landing site and 31 samples including water ice bearing soils were acquired for delivery to instruments on the lander during the 152 sol mission deliveries included sprinkling material from several centimeters height to break up cloddy soils on impact with instrument portals excavations were done on the side of the humpty dumpty and the top of the wonderland polygons and in nearby troughs resistive forces encountered during backhoe operations show that soils above the 3 5 cm deep icy soil interfaces are stronger with increasing depth further soils are similar in appearance and properties to the weakly cohesive crusty and cloddy soils imaged and excavated by the viking lander 2 which also landed on the northern plains adsorbed h2o is inferred to be responsible for the variable nature and cohesive strength of the soils backhoe blade chatter marks on excavated icy soil surfaces combined with rasp motor currents are consistent with laboratory experiments using grain supported icy soil deposits as is the relatively rapid decrease in icy soil strength over time as the ice sublimated on mars

geographic variations in the thermal and diffusive stability of ground ice on mars to investigate the stability of ground ice within the top several meters of the martian regolith time dependent models of the thermal and diffusive behavior of the regolith have been developed the geographic distribution of thermal inertia and albedo as well as the latitudinal variation in insolation have been included in calculations of surface and subsurface temperatures between 60 latitude ground ice was found to be stable where the annual mean surface and subsurface temperatures were below the atmospheric frost point this generally occurs poleward of the mid latitudes the latitude poleward of which ground ice is stable varies by about 20 to 30 from one longitude to another geographic variations in thermal inertia and albedo are the primary factors controlling regional variations in ice stability calculations of temperatures at high and low obliquity suggest that ground ice would be stable globally at high obliquity and would not be stable between 60 latitude at low obliquity thermally driven diffusion of atmospheric water vapor within the regolith was modeled accounting for both ordinary molecular and knudsen transport and equilibrium between ice vapor and adsorbed phases atmospheric water vapor was found to be able to supply the top few meters of the regolith with ice in regions where the annual mean surface temperature was below the atmospheric frost point ice was found to begin condensing in as short as 1000 martian years rapid accumulation of ice in the pore space of the upper layers of the regolith acted to choke transport to lower layers and slow the diffusion process even so after 105 martian years in some cases as much as 30 to 40 of the available pore space accumulated ice the total amount of subsurface ice ranged from a few to more than 25 g cm2 within the top few meters in regions of stability ground ice was found to form below a depth where the annual average vapor pressure over ice was equal to the annual average atmospheric vapor pressure near the surface atmospheric vapor was not found to accumulate as ice below a depth where the seasonal temperature oscillations gave way to the geothermal gradient the time scales for condensation of ground ice were found to be comparable to that of orbital oscillations suggesting that the present geographic distribution of ground ice may depend on the orbital history of mars

geomorphologic and mineralogic characterization of the northern plains of mars at the phoenix mission candidate landing sites 1 a suite of remote sensing data is used to evaluate both geomorphology and mineralogy of the candidate landing sites for the 2007 phoenix mission three candidate landing site boxes are situated in the northern plains of mars on the distal flank of alba patera in the region from 67 n to 72 n and from 230 e to 260 e geomorphology is mapped at subkilometer spatial scales using thermal emission imaging system themis visible and mars orbiter laser altimeter mola topographic data supplemented by images from the high resolution imaging science experiment hirise and context imager ctx mineralogy and spectral properties are examined using compact reconnaissance imaging spectrometer for mars crism visible and near infrared multispectral mapping and targeted hyperspectral data at 200 and 20 m pixel respectively geomorphic mapping supports the idea that terrains along the boundary between the amazonian scandia region and vastitas borealis marginal geologic units have undergone extensive modification intercrater plains are disrupted to form mesas and interlocking blocks while irregular depressions and knobby terrain are consistent with erosion subsidence and local deposition despite the varied morphology the present day surface is nearly homogeneous with spectral signatures dominated by nanophase iron oxides and basaltic sand and rocks similar to that of the gusev crater plains at the mars exploration rover mer landing site the compilation of geomorphic and spectral information for the candidate phoenix landing sites provides a framework for the mission s in situ observations to be extrapolated to the northern plains as a whole

recent advances in wavelet analyses part 2 amazon parana orinoco and congo discharges time scale variability this paper is devoted to illustrating new wavelet analysis methods in the field of hydrology new wavelet indicators are applied to long term hydrological and climatologic proxies they are first applied to four atlantic large river monthly discharges amazon parana orinoco and congo and then applied to two well known long term climatologic indexes the southern oscillation and the north atlantic oscillation this approach makes it possible to suggest physical explanations for time scale dependant relationships six month variability is present in all the rivers except in the parana in the congo river this signal is near stationary with strong entropy the strength of this scale coincides with higher discharge variability before 1920 and over the orinoco basin with higher discharge values between 1940 and 1955 an annual cycle is present in all the rivers but is much stronger along with the entropy in the rivers with a large tropical basin as in the amazon and the orinoco this annual signal is not permanent in the congo and much more intermittent in the parana where the annual recharge appears as very irregular a quasi biennial variability is apparent in all the equator ward rivers and a nearly permanent 2 year coherence is found between soi and the amazon discharge a 3 6 year oscillation typical of enso variability is observed in all the rivers it is intermittent observed before 1930 in all the rivers and after 1980 mostly in the amazon river these peaks of activity correspond to periods of major soi variability an 8 year variability is particularly strong in the parana river before 1940 and around 1970 and to a lesser extent in the orinoco river during the low nao index period between 1940 and 1970 the congo river exhibits that time scale around 1970 a 13 year variability common to soi nao and the south atlantic ocean circulation is observed in the parana and congo discharges in all the rivers the greatest entropy is observed at bi and multi decadal time scales with the greatest coherence with both nao and soi a near 20 year time scale is observed in most of the series around 1970 although it is strongest in amazon and parana discharges finally a 30 year time scale is observed between 1940 and 1970 it is to be noted that most of the time scale dominant activities in all the rivers may have been influenced by the interdecadal shifts that took place around 1940 and 1970 in the pacific and in the atlantic therefore in this contribution the application of new wavelet indicators combined continuous and multi resolution analysis wavelet entropy wavelet coherence wavelet cross correlation leads to several improvements in the analysis of these global hydrological signal fluctuations and of their mutual time varying relationships it is demonstrated that wavelets should be used more systematically in preference to the classical fourier analysis notably in hydrology

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

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

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

evolution of mars northern polar seasonal co2 deposits variations in surface brightness and bulk density small scale variations of seasonal ice are explored at different geomorphic units on the northern polar seasonal cap npsc we use seasonal rock shadow measurements combined with visible and thermal observations to calculate density over time the coupling of volume density and albedo allows us to determine the microphysical state of the seasonal co2 ice we find two distinct end members across the npsc 1 snow deposits may anneal to form an overlying slab layer that fractures these low density deposits maintain relatively constant densities over springtime 2 porous slab deposits likely anneal rapidly in early spring and fracture in late spring these high density deposits dramatically increase in density over time the end members appear to be correlated with latitude

hirise observations of gas sublimation driven activity in mars southern polar regions ii surficial deposits and their origins abstract the high resolution imaging science experiment hirise onboard mars reconnaissance orbiter mro has been used to monitor the seasonal evolution of several regions at high southern latitudes and in particular the jet like activity which may result from the process described by kieffer jgr 112 e08005 doi 10 1029 2006je002816 2007 involving translucent co 2 ice in this work we mostly concentrate on observations of the inca city 81 s 296 e and manhattan 86 s 99 e regions in the southern spring of 2007 two companion papers hansen et al this issue and portyankina et al this issue discuss the surface features in these regions and specific models of the behaviour of co 2 slab ice respectively the observations indicate rapid on set of activity in late winter initiating before hirise can obtain adequately illuminated images ls 2 titus et al 2007 agu abstract p41a 0188 these deposits originate from araneiform structures spiders boulders on ridges cracks on slopes and along linear cracks in the slab ice on flatter surfaces the type of activity observed can often be explained qualitatively by considering the local topography some dark fans are observed to shorten enormously in length on a timescale of 18 days we consider this to be strong evidence that outgassing was in progress at the time of hirise image acquisition and estimate a total particulate emission rate of 30 g s 1 from a single typical jet feature brighter deposits at inca city become increasingly hard to detect after ls 210 in the inca city region the orientations of surficial deposits are topographically controlled the deposition of dark material also appears to be influenced by local topography suggesting that the ejection from the vents is at low velocity 1 and that a ground hugging flow process a sort of cryo fumarole may be occurring the failure up to this point to obtain a clear detection of outgassing though stereo imaging is consistent with low level transport the downslope orientation of the deposits may result from the geometry of the vent or from catabatic winds at many sites more than one ejection event appears to have occurred suggesting re charging of the sources around ls 230 the brightness of the surface begins to drop rapidly on north facing slopes and the contrast between the dark deposits and the surrounding surface reduces this indicates that the co 2 ice slab is being lost completely in some areas at around this time by ls 280 at inca city the ice slab has effectively gone crism band ratios and themis brightness temperature measurements are consistent with this interpretation

a prelanding assessment of the ice table depth and ground ice characteristics in martian permafrost at the phoenix landing site 1 we review multiple estimates of the ice table depth at potential phoenix landing sites and consider the possible state and distribution of subsurface ice a two layer model of ice rich material overlain by ice free material is consistent with both the observational and theoretical lines of evidence results indicate ground ice to be shallow and ubiquitous 2 6 cm below the surface undulations in the ice table depth are expected because of the thermodynamic effects of rocks slopes and soil variations on the scale of the phoenix lander and within the digging area which can be advantageous for analysis of both dry surficial soils and buried ice rich materials the ground ice at the ice table to be sampled by the phoenix lander is expected to be geologically young because of recent climate oscillations however estimates of the ratio of soil to ice in the ice rich subsurface layer suggest that that the ice content exceeds the available pore space which is difficult to reconcile with existing ground ice stability and dynamics models these high concentrations of ice may be the result of either the burial of surface snow during times of higher obliquity initially high porosity soils or the migration of water along thin films measurement of the d h ratio within the ice at the ice table and of the soil to ice ratio as well as imaging ice soil textures will help determine if the ice is indeed young and if the models of the effects of climate change on the ground ice are reasonable

what drove late mesozoic extension of the northern china mongolia tract the northern china mongolia tract exhibited a tectonic transition from contractional to extensional deformation in late mesozoic time late middle to early late jurassic crustal shortening is widely thought to have resulted from collision of an amalgamated north china mongolia block and the siberian plate but widespread late late jurassic early cretaceous extension has not been satisfactorily explained by existing models some prominent features of the extensional tectonics of the northern china mongolia tract are 1 late jurassic voluminous volcanism prior to early cretaceous large magnitude rapid extension 2 overlapping in time of contractional deformation in the yinshan yanshan belt with development of extensionrelated basins in the interior of the northern china mongolia tract and 3 widespread occurrence of alkali granitic plutonism extensional basins and metamorphic core complexes in the early cretaceous a new explanation is advanced in this study for this sequence of events the collision of amalgamated north china mongolia with siberia led to crustal overthickening of the northern china mongolia tract and formation of a high standing plateau subsequent breakoff at depth of the north dipping mongol okhotsk oceanic slab is suggested as the main trigger for late mesozoic lithospheric extension of that tract slab breakoff resulted in mantle lithospheric stretching of the adjacent northern china mongolia tract with subsequent ascent of hot asthenosphere and magmatic underplating at the base of the crust collectively these phenomena triggered gravitational collapse of the previously thickened crust leading to late late jurassic early cretaceous crustal extension and importantly coeval contraction along the southern margin of the plateau in the yinshan yanshan belt the proposed model provides a framework for interpreting the spatial and temporal relationships of distinct processes and reconciling some seemingly contradictory phenomena such as the synchronous extension of northerly terranes during major contraction in the neighboring yanshan yinshan belt d 2003 elsevier b v all rights reserved

atmospheric dynamics at the phoenix landing site as seen by the surface stereo imager 1 the surface stereo imager has made observations of dust blowing aloft and clouds near the horizon at the phoenix landing site these subtle features are apparent because of the high signal to noise ratio of the camera which allows for the removal of a mean frame from multiple images captured in rapid succession and the ability to conduct simultaneous capture through different filters in each camera eye by examining the ratios between two filters it was possible to determine in a relative sense how the water ice content of the atmosphere changed over the mission and on a diurnal time scale the direction of travel and speed of features aloft near the zenith has been inferred and agree well with the diurnal pattern of near surface wind direction from the telltale direct observation of cumulus like cloud near the surface suggests convection of water vapor rich air but only until midday requiring a mechanism to inhibit cloud formation in the early afternoon the spectral ratios agree well with the observation of cloud and indicate a general increase in water ice toward the end of the mission as well as a strong diurnal pattern however even in periods of high water ice content there is still a great deal of variability and days when dense clouds are absent also different cloud layers are occasionally observed moving in different directions indicating occasional wind shear aloft features observed had estimated minimum optical depths up to 0 11

ground ice at the phoenix landing site stability state and origin 1 a primary objective of the phoenix mission was to examine the characteristics of high latitude ground ice on mars we report observations of ground ice its depth distribution and stability characteristics and examine its origins and history high latitude ground ice was explored through a dozen trench complexes and landing thruster pits over a range of polygon morphological provinces shallow ground ice was found to be abundant under a layer of relatively loose ice free soil with a mean depth of 4 6 cm which varied by more than 10x from trench to trench these variations can be attributed mainly to slope effects and thermal inertia variations in the overburden soil affecting ground temperatures the presence of ice at this depth is consistent with vapor diffusive equilibrium with respect to a mean atmospheric water content of 3 4 1019 m 3 consistent with the present day climate significant ice heterogeneity was observed with two major forms ice cemented soil and relatively pure light toned ice ice cemented soils which comprised about 90 of the icy material exposed by trenching are best explained as vapor deposited pore ice in a matrix supported porous soil light toned ice deposits represent a minority of the subsurface and are thought to consist of relatively thin near surface deposits the origin of these relatively pure ice deposits appears most consistent with the formation of excess ice by soil ice segregation such as would occur by thin film migration and the formation of ice lenses needle ice or similar ice structures

the periglacial landscape at the phoenix landing site 1 the mars scout mission phoenix landed in the northern high latitudes of mars in an area thought to be dominated by subsurface ground ice and has provided a unique detailed examination of periglacial morphology and topography that is not visible from orbit the landing site and surrounding terrain is dominated by polygonal patterned ground typical of the martian northern plains the polygons exhibit a gentle u shaped trough and rounded mound topography with an average trough depth of 17 cm and an average surface slopes of only 6 7 polygons an average 4 3 m across form a pattern superimposed on all other geologic landforms including larger 20 25 m polygons and kilometer long linear ridges the polygon morphology and the predominance of subsurface ice cemented soil are consistent with the formation of subsurface sand wedges in a permanently frozen arid climate small scale soil furrows and cracks into the ice cemented soil indicate that the thermal contraction process responsible for the formation of the polygons is active today rocks appear to be sorted within the polygon troughs indicating a process of cryoturbation within the permanently frozen polygons the complexity of the patterns crosscutting relations and rock distributions indicate advanced maturity of the polygon networks and shifting crack patterns possibly facilitated by crack and wedge annealing during times of low obliquity

the presence and stability of ground ice in the southern hemisphere of mars abstract we calculate new estimates of ground ice stability and the depth distribution of the ice table the depth boundary between ice free soil above and ice cemented soil below and compare these theoretical estimates of the distribution of ground ice with the observed distribution of leakage neutrons measured by the neutron spectrometer instrument of the mars odyssey spacecraft s gamma ray spectrometer instrument suite our calculated ground ice distribution contains improvements over previous work in that we include the effects of the high thermal conductivity of ice cemented soil at and below the ice table we include the surface elevation dependence of the near surface atmospheric humidity and we utilize new high resolution maps of thermal inertia albedo and elevation from mars global surveyor observations results indicate that ground ice should be about 5 times shallower than in previous predictions while results are dependent on the atmospheric humidity depths are generally between a few millimeters and a few meters with typical values of a few centimeters results are also geographically similar to previous predictions with differences due to the higher resolution of thermal inertia and the inclusion of elevation effects on humidity comparison with the measured epithermal neutron count rates in the southern hemisphere indicate that the geographic distribution of the count rate is best correlated with ground ice in equilibrium with 10 to 20 pr m precipitable micrometers column abundance of atmospheric water assuming a uniform distribution with co2 however given the uncertainties 5 to 30 pr m also may be viable this water abundance represents a longer term average over 100 to 1000 yr there is a high degree of correlation between the depth of the ice table and the epithermal count rate that agrees remarkably well with predicted count rates as a function of ice table depth these results indicate that ground ice in the upper meter of the martian soil is in diffusive equilibrium with the atmosphere since ground ice in this depth zone is expected to undergo saturation desiccation cycles with orbital variations this ice should be younger than about 500 kyr and was emplaced under similar cold and dry climate conditions of today remaining differences between the predicted depths of the ice table and those inferred from the neutron data are likely to be due to subpixel heterogeneity in the martian surface including the presence of rocks slopes and patches of soil with varying thermophysical properties

global distribution of neutrons from mars results from mars odyssey global distributions of thermal epithermal and fast neutron fluxes have been mapped during late southern summer northern winter using the mars odyssey neutron spectrometer these fluxes are selectively sensitive to the vertical and lateral spatial distributions of h and co 2 in the uppermost meter of the martian surface poleward of 60 latitude is terrain rich in hydrogen probably h 2 o ice buried beneath tens of centimeter thick hydrogen poor soil the central portion of the north polar cap is covered by a thick co 2 layer as is the residual south polar cap portions of the low to middle latitudes indicate subsurface deposits of chemically and or physically bound h 2 o and or oh