viscous flow features on the surface of mars observations from high resolution mars orbiter camera moc images 10 5 10 7 years of the material our shear stress estimates of 10 1 5 10 2 5 mpa yield strain rates on the order of 10 11 10 16 s 1 which are within the superplastic flow regime of ice mean annual surface temperatures age constraints and strain estimates show that it is possible for a meters thick ice dust mixture to undergo viscous deformation under past or present surface conditions for ice grain sizes 10 mm the meters thick layer in which the viscous flow features formed is morphologically similar to a degraded meters thick ice dust surface deposit dissected mantle terrain locations of the viscous flow features dissected mantle terrain and recent gullies are concentrated in the midlatitude regions and all three show identical distributions as a function of latitude with the maximum frequency of occurrence at 40 n and s the strong association between these small scale flow features and the dissected mantle terrain large scale viscous flow features and recent gullies imply that deposition deformation and removal of ice rich materials has played an important role in the modification of the surface in the midlatitudes of mars during the amazonian and possibly longer index terms 5470 planetology solid surface planets surface materials and properties 5416 planetology solid surface planets glaciation 1863 hydrology snow and ice 1827 1823 hydrology frozen ground 8168 tectonophysics stresses general keywords viscous flow viscous creep dissected mantle terrain ice rich deposits mars climate recent gullies

hirise observations of fractured mounds possible martian pingos 1 early images from the high resolution imaging science experiment hirise camera have revealed small fractured mounds in the martian mid latitudes hirise resolves fractures on the mound surfaces indicating uplift and shows that the mound surface material resembles that of the surrounding landscape analysis of mars orbiter camera moc images shows that in utopia planitia the mounds lie almost exclusively between 35 45 n this range coincides with the peak abundance latitudes of several landforms attributed to ground water or ice including gullies and suggests a ground ice related origin the best terrestrial analogues for the observed mound morphology are pingos although some differences are noted the presence of uncollapsed pingos would indicate the presence of near surface ground ice in the martian mid latitudes at depths greater than the 1 meter sampled by orbital spectrometers pingo formation may require near surface liquid water which is consistent with a shallow groundwater model for the origin of gullies

young late amazonian near surface ground ice features near the equator athabasca valles mars abstract a suite of four feature types in a 20 km 2 area near 10 n 204 w in athabasca valles is interpreted to have resulted from near surface ground ice these features include mounds conical forms with rimmed summit depressions flatter irregularly shaped forms with raised rims and polygonal terrain based on morphology size and analogy to terrestrial ground ice forms these athabascan features are interpreted as pingos collapsing pingos pingo scars and thermal contraction polygons respectively thermal infrared mapping spectrometer themis data and geological features in the area are consistent with a sedimentary substrate underlying these features these observations lead us to favor a ground ice interpretation although we do not rule out volcanic and especially glaciofluvial hypotheses the hypothesized ground ice that formed the mounds and rimmed features may have been emplaced via the deposition of saturated sediment during flooding an alternative scenario invokes magmatically cycled groundwater the ground ice implicit in the hypothesized thermal contraction polygons may have derived either from this flooding ground water or from atmospheric water vapor the lack of obvious flood modification of the mounds and rimmed features indicates that they formed after the most recent flood inundated the area analogy with terrestrial pingos suggests that ground ice may be still extant within the positive relief mounds as the water that flooded down athabasca valles emerged via a volcanotectonic fissure from a deep aquifer any extant pingo ice may contain evidence of a deep subsurface biosphere

modification of the dichotomy boundary on mars by amazonian mid latitude regional glaciation 1 restoration of the dichotomy boundary to its original position to assess its origin requires a thorough knowledge of processes responsible for its degradation and retreat the unique fretted terrain located along the deuteronilus protonilus mensae northern mid latitude portion of the boundary has been long held to provide clues to dichotomy degradation processes we use new spacecraft data to show that fretted valleys display a multitude of characteristics typical of integrated valley glacial systems on earth multiple theater headed alcove like accumulation areas sharp arete like ridges typical of glacial erosion converging patterns of downslope valley flow valley lineation patterns typical of folding and shear wrap around features indicative of flow around obstacles and broad piedmont like lobes as the valley fill extends out into the northern lowlands the single integrated system containing these features covers about 30 000 km2 and is one of dozens of fretted valleys along the dichotomy boundary in this region these relationships suggest that the boundary area was subjected to very large scale regional glaciation during the amazonian recognition and documentation of this important late stage process provides information critical to reconstructing the original dichotomy boundary

pluto pits and mantles on uplands north and east of sputnik planitia abstract the highlands region north and east of sputnik planitia can be subdivided into seven terrain types based on their physiographic expression the northern rough uplands are characterized by jagged uplands and broad troughs and it may contain a deeply eroded ancient mantle dissected terrain has been interpreted to have been eroded by paleo glaciation the smooth uplands and pits terrain contains broad rolling uplands surrounding complexes of pits some of which contain smooth floors the uplands are mantled by smooth surfaced deposits possibly derived from adjacent pits through low power explosive cryovolcanism or through slow vapor condensation the eroded smooth uplands appear to have originally been smooth uplands and pits terrain modified by small scale sublimation pitting the bright pitted uplands features intricate texturing by reticulate ridges that may have originated by sublimation erosion volatile condensation or both the bladed terrain is characterized by parallel ridges oriented north south and is discussed in a separate paper the dark uplands are mantled with reddish deposits that may be atmospherically deposited tholins their presence has affected long term landform evolution widespread pit complexes occur on most of the terrain units most appear to be associated with tectonic lineations some pits are floored by broad expanses of ices whereas most feature deep conical depressions a few pit complexes are enclosed by elevated rims of uncertain origin

possible closed system pingo and ice wedge thermokarst complexes at the mid latitudes of utopia planitia mars abstract on earth hydrostatic or closed system pingos csps are perennial ice cored mounds formed by the freeze thaw cycling of water when or as thermokarst lakes lose their water by drainage or evaporation the mounds vary in shape from circular or sub circular to elongate are sub kilometre in their long axes and may reach decametres in height often the mounds show summit depressions radial fractures and single tiers or benches as the csps degrade small scale debris flows or slumps occur end stage degradation typically exhibits debris laden ramparts elevated metres above the surrounding terrain typically the csps originate and develop where deep and continuous permafrost is ice rich i e infused with excess ice as it is in the tuktoyaktuk coastlands of northern canada mid to northern alaska and northeast russia in these areas or regions the terrain often is populated by a thermokarst lakes and alases thermokarst lake basins absent of water b fields of small scale ice wedge polygons either low centred or high centred relative to the polygon margins and c melt water filled or emptied polygon margin troughs or corner pits individual troughs and pits connected by means of the local topographical gradient comprises beaded stream systems or networks here we report describe and discuss a suite of candidate csps at the mid latitudes of utopia planitia up 35 50 n 80 115 e the morphologies scale and height of the martian mounds as well as the surface textures and characteristics landscape features and spatially associated landforms are consistent with the csps observed in ice rich regions on earth the up mounds are nested in or reside adjacent to flat floored possibly thermokarstic depressions small scale polygons some of which exhibit low or high centres relative to their margins and connected polygon margin depressions or pits that mirror beaded stream systems in ice rich terrain on earth the size frequency distribution of craters in our study region precludes a surface younger than 100 ma thus the csp like mounds in up and the pre mound periglacial revisions of the landscape presented by us may be markers of freeze thaw cycling that occurred much earlier in the amazonian epoch than most of the current discussions about periglaciation in up suggest

searching for evidence of hydrothermal activity at apollinaris mons mars a multidisciplinary approach involving various remote sensing instruments is used to investigate apollinaris mons a prominent volcano on mars as well as the surrounding plains for signs of prolonged hydrologic and volcanic and possibly hydrothermal activity the main findings include 1 evidence from laser altimetry indicating the large thickness 1 5 2 km at some locations of the fan deposits draping the southern flank contrary to previous estimates coupled with possible layering which point to a significant emplacement phase at apollinaris mons 2 corroboration of robinson et al robinson m s mouginis mark p j zimbelman j r wu s s c ablin k k howington kraus a e 1993 icarus 104 301 323 hypothesis regarding the formation of incised valleys on the western flanks by density current erosion which would indicate magma water interaction or alternatively volatile rich magmas early in the volcano s history 3 mounds of diverse geometric shapes many of which display summit depressions and occur among faults and fractures possibly marking venting 4 strong indicators on the flanks of the volcano for lahar events and possibly a caldera lake 5 ubiquitous presence of impact craters displaying fluidized ejecta in both shield forming flank and caldera materials and materials that surround the volcano that are indicative of water rich target materials at the time of impact 6 long term complex association in time among shield forming materials and medusae fossae formation the findings point to a site of extensive volcanic and hydrologic activity with possibly a period of magma water interaction and hydrothermal activity finally we propose that the mound structures around apollinaris should be prime targets for further in situ exploration and search for possible exobiological signatures

stratigraphical and morphological evidence for pingo genesis in the cerberus plains rootless debris cones or pseudocraters occur in platy patterned ground throughout the cerberus plains of mars and are thought to represent the products of explosive magma ice interaction lanagan et al 2001 geophys res lett 28 2365 2368 fagents et al 2002 in smellie j l chapman m g eds volcano ice interaction on earth and mars in geol soc spec publ vol 202 pp 295 317 requiring lava and water interspersed they are central to theories of multiple magmatic and aqueous flood events burr et al 2002 icarus 159 53 73 berman d c hartmann w k 2002 icarus 159 1 17 and widespread sheet volcanism keszthelyi et al 2000 j geophys res 105 15027 15049 in the region during the late amazonian a region reported to have been occupied by water bodies ranging from lakes to oceans scott et al 1995 map of mars showing channels and possible paleolake basins usgs miscellaneous investigations series map i 2461 1 30 000 000 the nature of the platy substrate is the subject of debate with evidence given for lava keszthelyi et al 2000 j geophys res 105 15027 15049 plescia j b 2003 icarus 164 79 95 and ice brakenridge g r 1993 lunar planet sci xxiv part 1 175 176 rice et al 2002 lunar planet sci xxxiii abstract 2026 murray et al 2005 nature 434 352 355 the superposition relationships of cones and platy deposits in the channels of the athabasca valles precludes a magmatic origin indicating later formation as permafrost mounds or pingos with implications for geologically recent flood volcanism age constraints on young surfaces and recent climate change on mars

possible pingo fields in the utopia basin mars geological and climatical implications abstract the presence of pingos on mars has been hypothesized since the period of the viking mission in fact a diverse range of pingo like features has been found at various martian sites including elysium chryse and utopia planitiae in the northern lowlands due to the morphology and the geological setting some of those features were interpreted in different ways creating some controversies as happened in athabasca valles this reflects the complexity of interpreting these features by remote sensing and multiple plausible interpretations of the same feature with the objective of identifying new possible pingos or rootless cones on mars we selected a study area in utopia planitia 10 55 n 210 260 w where the presence of both features is possible due to its geological history volcanic and hydrological we analyzed more than 2100 mars orbiter camera moc narrow angle images in addition to viking thermal emission imaging system themis and high resolution stereo camera hrsc images together with mars orbiter laser altimeter mola derived digital elevation models dems with a geographic information system gis we found in 94 moc narrow angle images dome cone and ring shaped features we analyzed them from morphological and morphometrical points of view in order to compare them with relevant features on mars and earth we tested different possible origins for those features following the approach of multiple working hypotheses we conclude that the dome cone and ring shaped features could be pingos which is in agreement with their geological settings regarding the driving heat source for the formation of the purported pingos we propose the existence of a heat source possibly a magma chamber underneath the surface of the utopia basin together with possible climatic shifts the past activities of the heat source may have caused melting of ground ice the pingo growth due to freezing of the water would have occurred during the following cold climatic conditions

formation of martian gullies by the action of liquid water flowing under current martian environmental conditions 1 geomorphic evidence suggests that recent gullies on mars were formed by fluvial activity the martian gully features are significant because their existence implies the presence of liquid water near the surface on mars in geologically recent times irrespective of the ultimate source of the fluid carving the gullies we seek to understand the behavior of this fluid after it reaches the martian surface we find that contrary to popular belief the fluvially carved martian gullies are consistent with formation conditions such as now occur on mars outside of the temperature pressure stability regime of liquid water our model of the action of flowing pure liquid water produces the observed gully length distribution only at surface pressures and temperatures below the triple point where liquid water simultaneously boils and freezes and thus suggests that gullies were formed under conditions similar to present day mars our results suggest a typical flow rate of 30 m 3 s to carve the gully channels at least 0 15 km 3 has flowed across the surface of mars to carvethegullysystemsobservedtoday andthiswouldrequireanaquifer recharge rate of 10 13 10 12 m yr the absence of gullies on mars that are long enough to have been created above the triple point pressure argues that the atmospheric pressure has not been significantly larger than it is now since the origin of the gullies this result may imply that mars does not possess a significant reservoir of condensed co2

coastal geomorphology of the martian northern plains the paper considers the question of the formation of the outflow channels and valley networks discovered on the martian northern plains during the mariner 9 mission parker and saunders 1987 and parker et al 1987 1989 data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains it is suggested that of the geological processes capable of producing similar morphologies on earth lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on mars

the evolution of exposed ice in a fresh mid latitude crater on mars abstract recent observations of the surface of mars have shown several fresh mid latitude craters some of these craters show exposed ice byrne s et al 2009 science 325 1674 1676 in some craters albedo of ice slowly decreases while in others it remains nearly constant we attempt to determine influence of the regolith structure on the rate of sublimation of ice for this purpose we performed numerical simulations describing evolution of the exposed ice in model craters located at middle latitudes we consider a new model for the structure and evolution of the material at and beneath the crater floors in contrast to the previous study by dundas and byrne dundas c m byrne s 2010 icarus 206 716 728 we do not investigate sublimation of dirty ice and the related formation of a sublimation lag instead we consider sublimation of a pure ice layer on top of layered regolith in our model the observed reflectivity decreases due to the sublimation driven changes of the optical properties of thinning clean ice this offers an alternative to the deposition of the dust embedded in ice sublimation lag we have shown that in our model among many parameters affecting ice sublimation rate volumetric fraction of water ice in the subsurface beneath the crater has the strongest influence hence observed darkening of the ice patch on the crater floor might be sufficient to determine the content of water ice in the subsurface our calculations show that an albedo decrease of fresh ice patches in mid latitude craters can be explained by either strong dust sedimentation or if this is excluded by sublimation of a thin layer of water ice from the regolith with large thermal inertia this is consistent with a large volumetric fraction of water ice beneath the crater floor and contributes to evidence for an extended subsurface water reservoir on mars the overall conclusion of our work is that a thin post impact surface ice coating over ice rich ground beneath the crater floors is consistent with the observations

clastic patterned ground in lomonosov crater mars examining fracture controlled formation mechanisms the area surrounding lomonosov crater on mars has a high density of seemingly organised boulder patterns these form seemingly sorted polygons and stripes within kilometre scale blockfields patches of boulder strewn ground which are common across the martian high latitudes several hypotheses have been suggested to explain the formation of clastic patterned ground on mars it has been proposed that these structures could have formed through freeze thaw sorting or conversely by the interaction of boulders with underlying fracture polygons in this investigation a series of sites were examined to evaluate whether boulder patterns appear to be controlled by the distribution of underlying fractures and test the fracture control hypotheses for their formation it was decided to focus on this suite of mechanisms as they are characterised by a clear morphological relationship namely the presence of an underlying fracture network which can easily be evaluated over a large area it was found that in the majority of examples at these sites did not exhibit fracture control although fractures were present at many sites there were very few sites where the fracture network appeared to be controlling the boulder distribution in general these were not the sites with the best examples of organization suggesting that the fracture control mechanisms are not the dominant geomorphic process organising the boulders in this area

formation of recent martian gullies through melting of extensive water rich snow deposits the observation of gullies on mars indicates the presence of liquid water near the surface in recent times1 2 which is difficult to reconcile with the current cold climate gullies have been proposed to form through surface runoff from subsurface aquifers1 3 or through melting of near surface ice under warmer conditions4 but these gullies are observed to occur preferentially in cold mid latitudes2 where the presence of liquid water is less likely and on isolated surfaces where groundwater seepage would not be expected making both potential explanations unsatisfactory here i show that gullies can form by the melting of water rich snow that has been transported from the poles to mid latitudes during periods of high obliquity within the past 105 to 106 years refs 5 6 melting within this snow7 can generate sufficient water to erode gullies in about 5 000 years my proposed model for gully formation is consistent with the age and location of the gullies and it explains the occurrence of liquid water in the cold mid latitudes as well as on isolated surfaces remnants of the snowpacks are still present on mid latitude pole facing slopes and the recent or current occurrence of liquid water within them provides a potential abode for life

mars global surveyor observations of martian fretted terrain the martian fretted terrain between latitudes 30 and 50 n and between 315 and 360 w has been reexamined in light of new mars orbiter camera moc and mars orbiter laser altimeter mola data from mars global surveyor much of the terrain in the 30 50 latitude belt in both hemispheres has a characteristic stippled or pitted texture at moc 1 5 m scale the texture appears to result from partial removal of a formerly smooth thin deposit as a result of sublimation and deflation a complex history of deposition and exhumation is indicated by remnants of a former thicker cover of layered deposits in some hollows and on some slopes particularly those facing the pole are smooth textured deposits outlined by an outward facing escarpment throughout the study area are numerous escarpments with debris flows at their base the escarpments typically have slopes in the 20 30 range at the base of the escarpment is commonly a deposit with striae oriented at right angles to the escarpment outside this deposit is the main debris apron with a surface that typically slopes 2 3 and complex surface textures suggestive of compression sublimation and deflation the presence of undeformed impact craters indicates that the debris flows are no longer forming fretted valleys contain lineated fill and are poorly graded they likely form from fluvial valleys that were initially like those elsewhere on the planet but were subsequently widened and filled by the same mass wasting processes that formed the debris aprons slope reversals indicate that downvalley flow of the lineated fill is minor the ubiquitous presence of breaks in slope formed by mass wasting and the complex surface textures that result from mass wasting deflation and sublimation decreases the recognizability of the shorelines formerly proposed for this area

the various ages of occator crater ceres results of a comprehensive synthesis approach abstract the 90 5 km occator crater with its peculiar and unique bright spots is one of the most prominent and renowned feature on ceres occator attracted broad public attention in scientific media as it is proposed to exhibit signs of post impact cryovolcanic activity in order to understand the time sequence of deposition several attempts were made during dawn s primary mission by different research groups to date geomorphologic key units using superposed crater densities resulting absolute model formation ages for occator s ejecta and its interior lobate deposits range from 200 ma to 78 ma and about 100 ma to 6 9 ma but were based on different cratering chronology models measurements on image data at varying resolution and different statistical and methodological approaches here we present the results of a comprehensive approach of determining absolute model formation ages for occator this is achieved by using the best resolved framing camera image data by careful treatment of secondary crater admixture and the natural variability of crater detection and sizes by different crater analysts and by applying appropriate objective criteria for count area selection in this context we evaluate previously published model ages and explain why our results are likely to yield more consistent and robust information about the formation age of occator we also show that in contrast to previous publications csfds measured on occator s less competent ejecta blanket and its more competent cryovolcanic or impact melt related interior lobate deposits ilds are so similar to each other that the slight differences might rather be explained by different scaling parameters in different target materials or that the ilds have formed almost contemporaneously or only shortly after the occator forming impact

the central pit and dome at cerealia facula bright deposit and floor deposits in occator crater ceres morphology comparisons and formation abstract the prominent bright deposit cerealia facula ceres coincides with the central depression or central pit of the recently formed 92 km wide complex crater occator the central pit is 9 10 km wide and up to 1 km deep and is partially filled with a 700 m high 2 km wide dome the upper surface of the central dome is densely fractured but the flanks are not indicating that uplift of the dome surface occurred after the bright deposit was emplaced and primarily through uplift of the surface from below by laccolithic intrusion or volume expansion the pit is rimless except for two prominent massifs that flank it to the east and west this pit dome morphology bears a strong resemblance in morphology topography and dimensions to central pit craters observed on ganymede and callisto but is essentially absent on the similar sized ice rich moons of uranus saturn and pluto the lack of pit craters on midsize icy moons and the possible lack of central pit craters at the cold poles of ceres suggest that temperature is a significant controlling factor in central pit formation beyond the canonical inverse gravity scaling of complex crater transitions while renewed modeling will benefit from these new constraints the mapping of central pits on ceres including occator suggests that either the rheologically layered target model or more likely the melted central uplift model may be the most probable explanation for central pit formation on ceres lack of similar high resolution imaging on the galilean icy satellites precludes definitive evaluation of models there large volumes of lobate floor fill material at least 600 m thick in some places cover large areas of the southern and eastern floor of occator and small outcrops of this unit are found perched high on closed topographic depressions on the occator terrace zone and other higher areas of the crater floor the swirling and knobby surface textures of these lobate deposits are essentially indistinguishable from those on impact melt sheets on large lunar craters such as tycho these observations indicate that this unit is most likely an impact melt sheet formed from melted water ice admixed with unmelted particulate or dissolved phyllosilicates salts and or carbonates and large quantities of fragmented debris melt of ice phases within ceres crust is also supported by independent numerical models of impact at occator and would provide a ready source of fluids to promote hydrothermal deposition of the observed bright na carbonates on the surface of the central pit at occator if the deposit formed within a million years or so of impact the central dome finds analogs in salt domes on earth and pingos frost mounds on earth and mars which form by water and solute migration and freeze expansion later freezing of a central reservoir of volatiles beneath the central pit at occator or mobilization of ice or other phases during the cooling and refreezing process could explain the uplift of the central dome finally no changes were detected in the cerealia and vinalia facula bright deposits during the course of the prime dawn mapping mission placing additional constraints on their formation time and limits on ongoing activity

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

geomorphic analysis of lobate debris aprons on mars at mars orbiter camera scale evidence for ice sublimation initiated by fractures 1 lobate debris aprons known to be geomorphic landform indicators of the presence of ground ice are of special interest for future missions devoted to the research of water on mars lobate debris aprons in fretted terrains of deuteronilus and protonilus mensae 35 50 n show typical convex shapes interpreted to be the result of viscous deformation at the scale of mars orbiter camera moc high resolution images the surface of these debris aprons shows complex patterns with small pits and buttes these patterns can be explained by the mantling of dust the accumulation of interstitial ice and the subsequent removal of ice by sublimation the sublimation of the ground ice is especially initiated and accelerated by subsurface heterogeneities like fractures theoretical quantification of sublimation rates therefore minimizes sublimation which is not a homogeneous process at least over the landforms studied crater counts show that the sublimation occurred in the last tens of millions of years up to the recent past in the point of view of future searching of subsurface ice only surface layers are submitted to sublimation favoring the conservation of ground ice in deeper layers since the formation of the landform the geophysical survey of lobate debris aprons would give interesting insights into the subsurface distribution of ice and its seasonal variations especially in order to measure current sublimation of ground ice

bright carbonate surfaces on ceres as remnants of salt rich water fountains abstract vinalia and cerealia faculae are bright and salt rich localized areas in occator crater on ceres the predominance of the near infrared signature of sodium carbonate on these surfaces suggests their original material was a brine here we analyze dawn framing camera s images and characterize the surfaces as composed of a central structure either a possible depression vinalia or a central dome cerealia and a discontinuous mantling we consider three materials enabling the ascent and formation of the faculae ice ascent with sublimation and carbonate particle lofting pure gas emission entraining carbonate particles and brine extrusion we find that a mechanism explaining the entire range of morphologies topographies as well as the common composition of the deposits is brine fountaining this process consists of briny liquid extrusion followed by flash freezing of carbonate and ice particles particle fallback and sublimation subsequent increase in briny liquid viscosity leads to doming dawn observations did not detect currently active water plumes indicating the frequency of such extrusions is longer than years

comparison of geophysical investigations for detection of massive ground ice pingo ice 1 six different geophysical investigations 1 ground penetrating radar 2 dc resistivity sounding 3 seismic refraction 4 very low frequency vhf electromagnetic 5 helicopter borne electromagnetic hem and 6 transient electromagnetic tem techniques were employed to obtain information on the ice body properties of pingos near fairbanks alaska the surface nuclear magnetic resonance nmr data were also compared from similar sites near one of the study pingos the geophysical investigations were undertaken along with core sampling and permafrost drilling to enable measurement of the ground temperature regime drilling ground truthing results support field geophysical investigations and have led to the development of a technique for distinguishing massive ice and overburden material of the permafrost the two dimensional dc resistivity sounding tomography and ground penetrating radar profiling are useful for ice detection under heterogeneous conditions however the dc resistivity sounding investigation required high quality ground contact and less area coverage the active layer thickness and the homogeneous horizontal structure of the overburden material are important parameters influencing detection of massive ice in permafrost for most methods such as seismic tem or surface nmr

identification of volcanic rootless cones ice mounds and impact craters on earth and mars using spatial distribution as a remote sensing tool 1 this study aims to quantify the spatial distribution of terrestrial volcanic rootless cones and ice mounds for the purpose of identifying analogous martian features using a nearest neighbor nn methodology we use the statistics r ratio of the mean nn distance to that expected from a random distribution and c a measure of departure from randomness we interpret r as a measure of clustering and as a diagnostic for discriminating feature types all terrestrial groups of rootless cones and ice mounds are clustered r 0 51 0 94 relative to a random distribution applying this same methodology to martian feature fields of unknown origin similarly yields r of 0 57 0 93 indicating that their spatial distributions are consistent with both ice mound or rootless cone origins but not impact craters each martian impact crater group has r 1 00 i e the craters are spaced at least as far apart as expected at random similar degrees of clustering preclude discrimination between rootless cones and ice mounds based solely on r values however the distribution of pairwise nn distances in each feature field shows marked differences between these two feature types in skewness and kurtosis terrestrial ice mounds skewness 1 17 1 99 kurtosis 0 80 4 91 tend to have more skewed and leptokurtic distributions than those of rootless cones skewness 0 54 1 35 kurtosis 0 53 1 13 thus nn analysis can be a powerful tool for distinguishing geological features such as rootless cones ice mounds and impact craters particularly when degradation or modification precludes identification based on morphology alone

massive ice of the tuktoyaktuk area western arctic coast canada the extensive coastal exposure of massive underground ice at peninsula point southwest of tuktoyaktuk northwest territories is believed to be intrasedimental ice the ice grew beneath a frozen d

sub kilometre intra crater mounds in utopia planitia mars character occurrence and possible formation hypotheses abstract at the middle latitudes of utopia planitia 35 45 n 65 101 e hundreds of small sized mounds located in sub kilometre impact craters dot the landscape their shape varies from circular to crescentic and their height ranges from 10 to 50 m often metre to decametre pitting is observed as is metres thick banding or stratification mound albedo is relatively high i e 0 16 the plain s terrain in the region previously linked to the latitude dependent mantle ldm of ice dust displays pitting and albedo similar to the small intra crater mounds some workers have suggested that the mounds and the plain s terrain share a common ice dust origin if so then scrutinising the mounds could provide analogical insight on the key geological characteristics and spatial distribution of the ldm itself other workers have hypothesised that the mounds are eroded sedimentary landforms or periglacial mounds underlain by a perennial ice core closed system pingos in this article we develop and then discuss each of the three mound hypotheses in a much more substantial manner than has been done hitherto towards this end we use high resolution images present a detailed regional map of mound distribution and establish a regional platform of topographical analysis using mola data superposed on a large scale ctx mosaic although the ice dust hypothesis is consistent with some observations and measurements we find that a loess based sedimentary hypothesis shows greater plausibility of the three hypotheses evaluated the pingo or periglacial one is the weakest

radar sounding of temperate permafrost in alaska analogy to the martian midlatitude to high latitude ice rich terrains 1 radar detection of subsurface ice on mars has been widely debated in part because the dielectric signature of ice as deduced from the dielectric constant can be confused with dry silicate rich materials to identify the ice dielectric signature it is crucial to estimate the imaginary part of the dielectric permittivity inferred from the dielectric attenuation after removing the scattering loss unfortunately the latter remains poorly quantified at both mars advanced radar for subsurface and ionospheric sounding marsis and shallow subsurface radar sharad frequencies to address this ambiguity we conducted multiple frequency ground penetrating radar and resistivity investigations in well characterized temperate permafrost in fairbanks alaska the area shows several geomorphologic similarities to midlatitude and high latitude terrains on mars this approach allowed us to quantify the dielectric and scattering losses in temperate permafrost over the 10 to 1000 mhz frequency band at 20 mhz our results suggest an average dielectric loss rate of 0 25 0 03 db m whereas the corresponding average scattering loss rate is 0 94 0 37 db m the scattering loss was found to represent 69 of the total signal attenuation considering this result and the study by heggy et al 2006a in volcanic environments we revised the interpretation of the attenuation coefficient calculated from sharad data over the deuteronilus mensae region and amazonis planitia we then used the reevaluated dielectric loss to estimate the imaginary part of the dielectric permittivity our results suggest that even if deuteronilus mensae deposits and the vastitas borealis formation may have similar dielectric constants their imaginary parts are different this implies that the two regions have different bulk compositions with the former being ice rich sediments and the latter being nonconsolidated volcanic deposits

pitted cones and domes on mars observations in acidalia planitia and cydonia mensae using moc themis and tes data 1 domes and cones with summit pits located in acidalia planitia and cydonia mensae were studied using moc and themis images and a tes derived thermal inertia map north of 40 5 n latitude the features have a dome like morphology and south of that latitude the morphology is more cone like layering is apparent in the summit craters of fresher looking southern cones and asymmetric aprons were observed in some instances some of the northern domes also display layering in their summit craters but asymmetric aprons were not observed the northern domes can also display multiple summit pits or no summit pits at all and can occur in association with higher albedo pancake features the northern domes are higher in albedo but have apparent thermal inertias that are lower than the surrounding plains the apparent thermal inertia values of the southern cones range from values comparable to the surrounding plains to slightly lower from the tes thermal inertia map we infer that the thermal inertia values of the pitted cones are between those of basaltic fine dust and sand while those of the surrounding plains are closer to that of basaltic sand while a unique interpretation of the origin of the pitted cones is not possible with the available data we do not find compelling evidence to suggest an origin related to either basaltic volcanism or ground ice instead an origin for these features through some combination of mud volcanism and evaporite deposition around geysers and or springs is most consistent with the observations

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

ice flow and rock glaciers on mars several geologic features suggest the presence of rock glaciers on the surface of mars these features include lobate debris aprons concentric crater fill and lineated valley fill the lateral extent of these rock glaciers can range from 5 km to over 20 km a simple time marching model is developed and used here to demonstrate the ability of ice and ice rock mixtures to flow under martian conditions for temperatures lower than about 220 k even pure ice becomes too rigid to flow and a glacier 5 km long could not have formed results from this model indicate temperatures 20 to 40 k higher than present average midlatitude temperatures 210 k an ice content of no less than 80 and a net accumulation rate of at least 1 cm year 1 are required to produce rock glaciers of the size seen on mars

multi element soil prospection aiding geophysical and archaeological survey on an archaeological site in suburban sagalassos sw turkey in order to take full advantage of the archaeological information contained within buried archaeological sites it is important to apply an integrative approach combining complementary prospection methods in this study geochemical prospection data are combined with archaeological and geophysical survey results on an unexcavated site in suburban sagalassos sw turkey with the aim of obtaining better insights into the structural shapes and past functionalities of the area spatial and multivariate statistical analyses of the chemical data reveal anomalies of k p and zn on a location where archaeological and geophysical results suggest the presence of ceramic producing kilns these elemental enrichments are thought to result from burning wood or dung as fuel for the detected kilns in addition local anomalies of co cr fe mg mn and ni were found to reflect the working and storage of ophiolitic clays employed as a raw material for ceramic production radiocarbon dating of charcoal in a 2 5 m deep drill core in this zone provides ages between ad 120 and 350 at depths of 50 and 60 cm al as ba ca na sr ti and pb are considered geogenic elements in this study the present study supports the theory that geochemical prospection holds potential as a surveying technique as it was found that chemical data facilitate the interpretation of structures detected by geophysical and archaeological methods thereby creating an extra dimension to the interpretation of survey data the results further argue in favour of using strong acid extractions and the consideration of a large suite of elements when applying chemical soil survey as an archaeological prospection technique and highlight the importance of considering site lithology multivariate statistics proved to be invaluable in distinguishing anthropogenic from lithological soil patterns

fault terminations and barriers to fault growth abstract field observations of strike slip faults in jointed granitic rocks of the central sierra nevada california combined with a mechanical analysis of fault interaction provide insight into how fault terminations vary with scale we document here a strike slip fault system 2 3 km long clustered about the west end of the fault system are several dozen faults that parallel the three main fault zones in the system we interpret this cluster of small faults as a barrier that inhibited growth of fault zones in the fault system a two dimensional mechanical analysis shows that a cluster of small faults flanking the tip of a large fault zone will tend to diffuse the stress concentration near the fault zone tip an analogous effect in engineering is known as crack tip shielding near tip stress concentrations promote fault growth and processes that decrease these stress concentrations inhibit fault growth as faults lengthen and grow they interact with features at greater distances and over a broader area so the potential for tip shielding effects will increase as fault length increases this effect can account for why the mechanisms and character of fault terminations would tend to vary as a function of scale

combinations of processes responsible for martian impact crater layered ejecta structures emplacement 1 we utilized images and stereo derived topographic data acquired by the high resolution stereo camera hrsc and thermal emission imaging system themis images together with other data in order to study the geology of layered ejecta structures associated with relatively pristine martian impact craters the geomorphology and morphometric properties indicate their origin as complex combinations of a variety of impact processes the studied inner layered ejecta structures often exhibit ground hugging characteristics and many of them do not have topographic profiles expected from simple ballistic emplacement such profiles include ones that are plateau shaped or thickening outward we think that water rich fluidized flows driven by the momentum due to the impact and by gravity together with ballistic emplacement and vortex produced by the atmosphere ejecta curtain interaction were essential to the inner layered ejecta structure formation we hypothesize that the thinner outer layered ejecta structures were formed by various combinations of shockwave induced liquefaction of water rich near surface sediments ballistic emplacement of ejecta entraining water and strong winds expanding vapor vortex base surge related to the impact the contribution of each proposed layered ejecta structure formation mechanism should have been variable depending on the condition of the impact

sharad sounding radar on the mars reconnaissance orbiter 1 sharad shallow radar is a sounding radar provided by agenzia spaziale italiana asi as a facility instrument on the mars reconnaissance orbiter mission its 20 mhz center frequency and 10 mhz bandwidth complement the lower frequency relatively narrower bandwidth capability of the marsis sounding radar a joint italian u s team has guided the experiment development and is responsible for data analysis and interpretation the radar transmits signals at a 700 hz pulse repetition frequency prf and collects reflections from both the surface and near subsurface of mars vertical and horizontal resolutions are respectively 15 m free space and 3 6 km cross track by 0 3 1 km along track the scientific objective of sharad is to map in selected locales dielectric interfaces to at least several hundred meters depth in the martian subsurface and to interpret these results in terms of the occurrence and distribution of expected materials including competent rock soil water and ice a signal to noise ratio of 50 db for a specular surface return is achieved with 10 w of radiated power by using range and azimuth focusing in ground data processing preprocessed data as well as range and azimuth focused data will be formatted according to planetary data system pds standards and be made available from the asi science data center asdc and from the geosciences node of the planetary data system pds important targets for sharad include the polar layered deposits sedimentary stacks especially in terra meridiani buried channel systems buried impact craters volcanic complexes and shallow ice deposits in equilibrium with the atmosphere

pingo collapse and paleoclimatic reconstruction long term field studies of contemporary pingo growth collapse and rampart formation along the western arctic coast of canada provide criteria that may be helpful in the identification of pingo ramparts in nonpermafrost environments such criteria include the volume of the ramparts which should approximate that of the enclosed depressions from which the rampart materials were derived peripheral deposits associated with mass wasting streamflow and debris flow casts of dilation crack ice trending across the ramparts and high angle peripheral normal faults the conventional method of correlating the present mean annual air temperature with the present pingo distribution to establish warm side limiting temperatures for paleoclimatic reconstruction is unsound because most pingos in north america and the soviet union commenced growth hundreds to thousands of years ago under mean annual air temperatures that may have differed greatly from those of the present some other factors to be considered in paleo

athabasca valles mars a lava draped channel system athabasca valles is a young outflow channel system on mars that may have been carved by catastrophic water floods however images acquired by the high resolution imaging science experiment camera onboard the mars reconnaissance orbiter spacecraft reveal that athabasca valles is now entirely draped by a thin layer of solidified lava the remnant of a once swollen river of molten rock the lava erupted from a fissure inundated the channels and drained downstream in geologically recent times purported ice features in athabasca valles and its distal basin cerberus palus are actually composed of this lava similar volcanic processes may have operated in other ostensibly fluvial channels which could explain in part why the landers sent to investigate sites of ancient flooding on mars have predominantly found lava at the surface instead

a volcanic interpretation of gusev crater surface materials from thermophysical spectral and morphological evidence 1 gusev crater the mars exploration rover spirit landing site 160 km diameter 14 5 s 184 5 w has been identified in previous studies as a prime site of geological and exobiological interest on the basis of its potential for having hosted a fluviolacustrine environment such environment may have been favorable for the development of biological activity the origin and nature of the materials present at the surface of gusev crater are still being debated in previous studies based on geomorphological and thermophysical data surface materials in the crater have been interpreted as originating from fluviolacustrine volcanic or aeolian processes or combinations thereof we present results from the analysis of newly compiled thermophysical thermal emission spectrometer tes and thermal emission imaging system themis spectroscopic tes and visible themis and mars observer camera data for the gusev region these data were analyzed using a new mosaicking technique developed to match the values of contiguous scenes and to produce seamless mosaics apt for geological interpretation thermophysical spectroscopic and morphological evidence point to the presence of local outcrops of lava flows of basaltic composition materials consistent with a regolith developed from basaltic materials fine grained deposits of basaltic composition strongly modified by wind erosion and wind deposits according to these findings we conclude that most of the materials occupying the present surface of gusev have characteristics consistent with those of volcanic and aeolian deposits fluviolacustrine deposits proposed by other authors may exist under the volcanic materials and may be exposed in impact craters

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

observations of martian gullies and constraints on potential formation mechanisms ii the northern hemisphere abstract the formation process es responsible for creating the observed geologically recent gully features on mars has remained the subject of intense debate since their discovery we present new data and analysis of northern hemisphere gullies from mars global surveyor data which is used to test the various proposed mechanisms of gully formation we located 137 mars orbiter camera moc images in the northern hemisphere that contain clear evidence of gully landforms and analyzed these images in combination with mars orbiter laser altimeter mola and thermal emission spectrometer tes data to provide quantitative measurements of numerous gully characteristics parameters we measured include apparent source depth and distribution vertical and horizontal dimensions slopes orientations and present day characteristics that affect local ground temperatures northern hemisphere gullies are clustered in arcadia planitia tempe terra acidalia planitia and utopia planitia these gullies form in craters 84 knobby terrain 4 valleys 3 other unknown terrains 9 and are found on all slope orientations although the majority of gullies are equator facing most gullies 63 are associated with competent rock strata 26 are not associated with strata and 11 are ambiguous assuming thermal conductivities derived from tes measurements as well as modeled surface temperatures we find that 95 of the gully alcove bases with adequate data coverage lie at depths where subsurface temperatures are greater than 273 k and 5 of the alcove bases lie within the solid water regime the average alcove length is 470 m and the average channel length is 690 m based on a comparison of measured gully features with predictions from the various models of gully formation we find that models involving carbon dioxide melting ground ice in the upper few meters of the soil dry landslide and surface snowmelt are the least likely to describe the formation of the martian gullies although some discrepancies still exist between prediction and observation the shallow and deep aquifer models remain as the most plausible theories interior processes involving subsurface fluid sources are generally favored over exogenic processes such as wind and snowfall for explaining the origin of the martian gullies these findings gleaned from the northern hemisphere data are in general agreement with analyses of gullies in the southern hemisphere heldmann j l mellon m t 2004 icarus 168 285 304

assessment of pingo distribution and morphometry using an ifsar derived digital surface model western arctic coastal plain northern alaska abstract pingos are circular to elongate ice cored mounds that form by injection and freezing of pressurized water in near surface permafrost here we use a digital surface model dsm derived from an airborne interferometric synthetic aperture radar ifsar system to assess the distribution and morphometry of pingos within a 40 000 km2 area on the western arctic coastal plain of northern alaska we have identified 1247 pingo forms in the study region ranging in height from 2 to 21 m with a mean height of 4 6 m pingos in this region are of hydrostatic origin with 98 located within 995 drained lake basins most of which are underlain by thick eolian sand deposits the highest pingo density 0 18 km 2 occurs where streams have reworked these deposits morphometric analyses indicate that most pingos are small to medium in size

landscape evolution in martian mid latitude regions insights from analogous periglacial landforms in svalbard periglacial landforms on spitsbergen svalbard norway are morphologically similar to landforms on mars that are probably related to the past and or present existence of ice at or near the surface many of these landforms such as gullies debris flow fans polygonal terrain fractured mounds and rock glacier like features are observed in close spatial proximity in mid latitude craters on mars on svalbard analogous landforms occur in strikingly similar proximity which makes them useful study cases to infer the spatial and chronological evolution of martian coldclimate surface processes the analysis of the morphological inventory of analogous landforms on svalbard and mars allows the processes operating on mars to be constrained different qualitative scenarios of landscape evolution on mars help to better understand the action of periglacial processes on mars in the recent past

some mechanical aspects of pingo growth and failure western arctic coast canada many closed system pingos are underlain by sub pingo water lenses and the same is probably true of numerous open system pingos in the early growth stage the bending of the frozen overburden of a pingo by a sub pingo water lens can be compared to the bending of a thin elastic plate although the assumptions of elastic plate theory do not apply fully to a growing pingo because time dependent plastic and creep deformation are involved the application of elastic plate theory nevertheless helps to explain the peripheral normal faulting and spring flow of pingos summit failure the ease with which elongated pingos appear to collapse and the changing roles played by the radius and overburden thickness of pingos from early growth to the cessation of growth

radar evidence for ice in lobate debris aprons in the mid northern latitudes of mars 1 subsurface radar sounding data indicate that lobate debris aprons found in deuteronilus mensae in the mid northern latitudes of mars are composed predominantly of water ice the position in time delay and the relatively low amount of signal loss of the apparent basal reflectors below the debris aprons indicate that aprons contain only a minor component of lithic material the current presence of large ice masses at these latitudes has important implications for the climate evolution of mars and for future targets for in situ exploration

orientation and distribution of recent gullies in the southern hemisphere of mars observations from high resolution stereo camera mars express hrsc mex and mars orbiter camera mars global surveyor moc mgs data 1 geologically recent small gullies on mars display morphologies consistent with erosion by water or by debris flows suggested formation models are divided into two main categories 1 groundwater or 2 melting of near surface ice snow sourced from the atmosphere we have measured location and orientation and recorded the local contexts of gullies to constrain the likely models of gully formation more than 22 000 mars orbiter camera narrow angle moc na and 120 mars express high resolution stereo camera hrsc images in the southern hemisphere were searched for gullies discrete gullied slope sections with consistent orientation were recorded rather than individual gullies slope setting impact crater valley wall etc location and orientation were recorded for each slope section more than 750 moc images with gullies 900 distinct gullied slope sections and more than 40 hrsc images 380 distinct gullied slope sections were identified from both moc and hrsc gullies were found to be most common between 30 and 50 degrees latitude and to have an overall pole facing preference the preferred gully orientation for hrsc is southeast rather than south in moc owing to illumination effects that make gullies difficult to detect on south to southwest facing slopes in hrsc in both moc and hrsc surveys higher latitude gullies show less preference for pole facing than those at mid latitudes both data sets produced similar results demonstrating that our data are reliable we suggest that the observed latitudinal and orientation distributions of gullies show that insolation and atmospheric conditions play a key role in gully formation

an assessment of evidence for pingos on mars using hirise pingos are small hills with cores of ice formed by injection and freezing of pressurized water the possibility of pingos on mars is of particular interest because of the associated implications for liquid water we have systematically searched for candidate pingos using images from the high resolution imaging science experiment hirise camera since pingos are expected to develop surface fractures due to extension of the frozen ground over the ice core we have searched for fractured features and identified a variety of mounds these features are confined to the martian mid latitudes in the bands where gullies are also most common the observed fractured mounds have a variety of morphologies and are likely of multiple origins isolated fractured mounds found on the floors of gullied craters in the southern hemisphere match the general morphologic characteristics of terrestrial pingos and are the best candidates for martian pingos but there is currently no direct evidence for presence of ice cores and it is difficult to produce the necessary water volumes so these features should still be interpreted with caution other fractured mounds appear more likely to be erosional remnants of an unusual mantling layer or possibly thermokarst structures flat topped mounds in utopia have some characteristics fracture pattern and latitudinal distribution consistent with pingos but differ in other aspects such as shape and setting while we do not rule out a pingo origin we prefer an erosional model for these enigmatic features

possible frost mounds in an ancient martian lake bed abstract circular to elongated mounds are observed in gusev crater in the aeolis subquadrangle of mars they are arranged in a large cluster and show different stages of evolution from fresh to scar structures their morphology and morphometric ratios are comparable to those of terrestrial frost mounds this study shows how the paleolacustrine environment of the ma adim vallis gusev crater hydrogeologic system may have provided a suitable environment for the formation of frost mounds alternate hypotheses of formation including volcanism fluvial erosion and eolian erosion are discussed other features such as heavings curvilinear troughs hills ridges and depressions support the idea of a sediment ice interaction the typology of the mounds and plausible mechanisms for their formation are proposed their presence could support the model of a massive water body in gusev during the amazonian and provide indicators of paleoenvironmental conditions at the time of their formation

habitable periglacial landscapes in martian mid latitudes subsurface permafrost environments on mars are considered to be zones where extant life could have survived for the identification of possible habitats it is important to understand periglacial landscape evolution and related subsurface and environmental conditions many landforms that are interpreted to be related to ground ice are located in the martian mid latitudinal belts this paper summarizes the insights gained from studies of terrestrial analogs to permafrost landforms on mars the potential habitability of martian mid latitude periglacial landscapes is exemplarily deduced for one such landscape that of utopia planitia by a review and discussion of environmental conditions influencing periglacial landscape evolution based on recent calculations of the astronomical forcing of climate changes specific climate periods are identified within the last 10 ma when thaw processes and liquid water were probably important for the development of permafrost geomorphology no periods could be identified within the last 4 ma which met the suggested threshold criteria for liquid water and habitable conditions implications of past and present environmental conditions such as temperature variations ground ice conditions and liquid water activity are discussed with respect to the potential survival of highly specialized microorganisms known from terrestrial permafrost we conclude that possible habitable subsurface niches might have been developed in close relation to specific permafrost landform morphology on mars these would have probably been dominated by lithoautotrophic microorganisms i e methanogenic archaea

possible pingos and a periglacial landscape in northwest utopia planitia hydrostatic closed system pingos are small elongate to circular ice cored mounds that are perennial features of some periglacial landscapes the growth and development of hydrostatic pingos is contingent upon the presence of surface water freezing processes and of deep continuous ice cemented permafrost other cold climate landforms such as small sized polygonal patterned ground also may occur in the areas where pingos are found on mars landscapes comprising small elongate to circular mounds and other possible periglacial features have been identified in various areas including utopia planitia where water is thought to have played an important role in landscape evolution despite the importance of the martian mounds as possible markers of water most accounts of them in the planetary science literature have been brief and or based upon viking imagery we use a high resolution mars orbiter camera image eo300299 and superposed mars orbiter laser altimeter data tracks to describe and characterise a crater floor landscape in northwest utopia planitia 64 8 n 292 7 w the landscape comprises an assemblage of landforms that is consistent with the past presence of water and of periglacial processes this geomorphological assemblage may have formed as recently as the last episode of high obliquity a similar assemblage of landforms is found in the tuktoyaktuk peninsula of northern canada and other terrestrial cold climate landscapes we point to the similarity of the two assemblages and suggest that the small roughly circular mounds on the floor of the impact crater in northwest utopia planitia are hydrostatic pingos like the hydrostatic pingos of the tuktoyaktuk peninsula the origin of the crater floor mounds could be tied to the loss of ponded local water permafrost aggradation and the evolution of a sub surface ice core

evidence for recent climate change on mars from the identification of youthful near surface ground ice ground ice in the crust and soil may be one of the largest reservoirs of water on mars1 2 3 near surface ground ice is predicted to be stable at latitudes higher than 40 ref 4 where a number of geomorphologic features indicative of viscous creep and hence ground ice have been observed5 mid latitude soils have also been implicated as a water ice reservoir6 the capacity of which is predicted to vary on a 100 000 year timescale owing to orbitally driven variations in climate7 it is uncertain however whether near surface ground ice currently exists at these latitudes and how it is changing with time here we report observational evidence for a mid latitude reservoir of near surface water ice occupying the pore space of soils the thickness of the ice occupied soil reservoir 1 10 m and its distribution in the 30 to 60 latitude bands indicate a reservoir of 1 5 6 0 104 km3 equivalent to a global layer of water 10 40 cm thick we infer that the reservoir was created during the last phase of high orbital obliquity less than 100 000 years ago and is now being diminished

reinterpretation of pingos in antarctica abstract in 1983 pingos were reported in the vestfold hills antarctica the features form dome shaped hills up to 4 m high and 12 m in diameter and occur on an ice cored moraine their form structure and sedimentary processes observed on the surface of the moraine together with a consideration of the environmental requirements for pingo growth preclude their origin as pingos they appear to be residual landforms that have formed on the surface of the moraine as the ice core has been destroyed by ablation and thermal erosion the previous interpretation of the features has relied on the shape of the hills and their occurrence in a similar geologic setting to pingos in the northern hemisphere the interpretation appears to have misinterpreted tension cracks and coherent slumping of sediment as dilation cracks and as evidence for the extrusion of a central sediment plug pingos on supraglacial debris have not been described from any other locations and it seems that their formation is inconsistent with the ablation of the ice core of moraines

observations of martian gullies and constraints on potential formation mechanisms abstract the discovery of presumably geologically recent gully features on mars malin and edgett 2000 science 288 2330 2335 has spawned a wide variety of proposed theories of their origin including hypotheses of the type of erosive material to test the validity of gully formation mechanisms data from the mars global surveyor spacecraft has been analyzed to uncover trends in the dimensional and physical properties of the gullies and their surrounding terrain we located 106 mars orbiter camera moc images that contain clear evidence of gully landforms distributed in the southern mid and high latitudes and analyzed these images in combination with mars orbiter laser altimeter mola and thermal emission spectrometer tes data to provide quantitative measurements of numerous gully characteristics parameters we measured include apparent source depth and distribution vertical and horizontal dimensions slopes orientations and present day characteristics that affect local ground temperatures we find that the number of gully systems normalized to the number of moc images steadily declines as one moves poleward of 30 s reaches a minimum value between 60 63 s and then again rises poleward of 63 s all gully alcove heads occur within the upper one third of the slope encompassing the gully and the alcove bases occur within the upper two thirds of the slope also the gully alcove heads occur typically within the first 200 meters of the overlying ridge with the exception of gullies equatorward of 40 s where some alcove heads reach a maximum depth of 1000 meters while gullies exhibit complex slope orientation trends gullies are found on all slope orientations at all the latitudes studied assuming thermal conductivities derived from tes measurements as well as modeled surface temperatures we find that 79 of the gully alcove bases lie at depths where subsurface temperatures are greater than 273 k and 21 of the alcove bases lie within the solid water regime most of the gully alcoves lie outside the temperature pressure phase stability of liquid co2 based on a comparison of measured gully features with predictions from the various models of gully formation we find that models involving carbon dioxide melting ground ice in the upper few meters of the soil dry landslide and surface snowmelt are the least likely to describe the formation of the martian gullies although some discrepancies still exist between prediction and observation the shallow and deep aquifer models remain as the most plausible theories interior processes involving subsurface fluid sources are generally favored over exogenic processes such as wind and snowfall for explaining the origin of the martian gullies

radar sounding evidence for buried glaciers in the southern mid latitudes of mars lobate features abutting massifs and escarpments in the middle latitudes of mars have been recognized in images for decades but their true nature has been controversial with hypotheses of origin such as ice lubricated debris flows or glaciers covered by a layer of surface debris these models imply an ice content ranging from minor and interstitial to massive and relatively pure soundings of these deposits in the eastern hellas region by the shallow radar on the mars reconnaissance orbiter reveal radar properties entirely consistent with massive water ice supporting the debris covered glacier hypothesis the results imply that these glaciers formed in a previous climate conducive to glaciation at middle latitudes such features may collectively represent the most extensive nonpolar ice yet recognized on mars

mars observer camera the mars observer camera moc is a three component system one narrow angle and two wide angle cameras designed to take high spatial resolution pictures of the surface of mars and to obtain lower spatial resolution synoptic coverage of the planet s surface and atmosphere the cameras are based on the push broom technique that is they do not take frames but rather build pictures one line at a time as the spacecraft moves around the planet in its orbit moc is primarily a telescope for taking extremely high resolution pictures of selected locations on mars using the narrow angle camera areas ranging from 2 8 km 2 8 km to 2 8 km 25 2 km depending on available internal digital buffer memory can be photographed at about 1 4 m pixel additionally lower resolution pictures to a lowest resolution of about 11 m pixel can be acquired by pixel averaging these images can be much longer ranging up to 2 8 500 km at 11 m pixel high resolution data will be used to study sediments and sedimentary processes polar processes and deposits volcanism and other geologic geomorphic processes the moc wide angle cameras are capable of viewing mars from horizon to horizon and are designed for low resolution global and intermediate resolution regional studies low resolution observations can be made every orbit so that in a single 24 hour period a complete global picture of the planet can be assembled at a resolution of at least 7 5 km pixel regional areas covering hundreds of kilometers on a side may be photographed at a resolution of better than 250 m pixel at the nadir such images will be particularly useful in studying time variable features such as lee clouds the polar cap edge and wind streaks as well as acquiring stereoscopic coverage of areas of geological interest the limb can be imaged at a vertical and along track resolution of better than 1 5 km different color filters within the two wide angle cameras permit color images of the surface and atmosphere to be made to distinguish between clouds and the ground and between clouds of different composition

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

hydrovolcanic features on mars preliminary observations from the first mars year of hirise imaging abstract we provide an overview of features indicative of the interaction between water and lava and or magma on mars as seen by the high resolution imaging science experiment hirise camera during the primary science phase of the mars reconnaissance orbiter mro mission the ability to confidently resolve meter scale features from orbit has been extremely useful in the study of the most pristine examples in particular hirise has allowed the documentation of previously undescribed features associated with phreatovolcanic cones formed by the interaction of lava and groundwater on rapidly emplaced flood lavas these include moats and wakes that indicate that the lava crust was thin and mobile respectively jaeger w l keszthelyi l p mcewen a s dundas c m russel p s 2007 science 317 1709 1711 hirise has also discovered entablature style jointing in lavas that is indicative of water cooling milazzo m p keszthelyi l p jaeger w l rosiek m mattson s verba c beyer r a geissler p e mcewen a s and the hirise team 2009 geology 37 171 174 other observations strongly support the idea of extensive volcanic mudflows lahars evidence for other forms of hydrovolcanism including glaciovolcanic interactions is more equivocal this is largely because most older and high latitude terrains have been extensively modified masking any earlier 1 10 m scale features much like terrestrial fieldwork the prerequisite for making full use of hirise s capabilities is finding good outcrops