ponding draining and tilting of the cerberus plains a cryolacustrine origin for the sinuous ridge and channel networks in rahway vallis mars rahway vallis sits within a shallow basin the rahway basin in the cerberus plains of mars containing a branching network of channels converging on the basin floor using topographic cross profiles of the channels we have found that they are set within broader subtly expressed valleys these valleys are shallow around 15 m vertically compared to several kilometres in the horizontal and have convex to rectilinear slope profiles that are consistent in form across the whole rahway basin both channels and valleys descend and deepen consistently from west to east the channels typically widen down slope and increase in width at confluences the morphology and topology of this channel system are consistent with formation by contributory fluid flow generated from many distributed sources the transition between the older heavily cratered terrain and the floor of the rahway basin is bounded by near horizontal continuous topographic terraces plotting the elevation of the terraces shows that they conform to a plane with a height difference of around 100 m east to west for the 300 km width of the rahway basin we calculate that the volume of material needed to fill the topography up to the level of the plane best fit by the terraces is 1500 km3 bordering the channels are sinuous ridges typically several kilometres long 20 m across with heights on the order of 10 m they sometimes form branching networks leading into the channels but also occur individually and parallel to the channels the multiple tilted terraces the channel valley network with many fluvial like characteristics and the distributed source regions suggest that the landforms within the rahway basin are unlikely to have formed through purely volcanic processes rather the channels within the rahway basin are consistent with a genesis requiring the flow of liquid water and the sinuous ridges with melting of a static ice body that occupied the basin we suggest a hypothesis of rapid basin filling by fluvial flooding followed by lake drainage drainage could have occurred as a consequence of an ice or debris dam failure within or during the formation of the large nearby fluvial flood channel marte vallis if the lake was partly or largely frozen prior to drainage this offers a possible explanation for the sinuous ridge systems hence although the sinuous ridges provide some of the most compelling morphological analogues of terrestrial eskers yet observed we conclude that the contextual evidence for this interpretation in rahway vallis is not strong and instead they are better explained in the context of a frozen or partially frozen lake or cryolacustrine model

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

an ice rich flow origin for the banded terrain in the hellas basin mars the interior of hellas basin displays a complex landscape and a variety of geomorphological domains one of these domains the enigmatic banded terrain covers much of the northwestern part of the basin we use high resolution context camera and high resolution imaging science experiment digital terrain models to show that most of the complex viscous flowing behavior exhibited by the banded terrain is controlled by topography and flow like interactions between neighboring banded terrain furthermore the interior of the basin hosts several landforms suggestive of the presence of near surface ice which include polygonal patterns with elongated pits scalloped depressions isolated mounds and collapse structures we suggest that thermal contraction cracking and sublimation of near surface ice are responsible for the formation and the development of most of the ice related landforms documented in hellas the relatively pristine form lack of superposed craters and strong association with the banded terrain suggest an amazonian 3 ga age of formation for these landforms finally relatively high surface pressures above the triple point of water expected in hellas and summertime temperatures often exceeding the melting point of water ice suggest that the basin may have recorded relatively temperate climatic conditions compared to other places on mars therefore the potentially ice rich banded terrain may have deformed with lower viscosity and stresses compared to other locations on mars which may account for its unique morphology

seep carbonates in a thrust related anticline at the leading edge of an orogenic wedge the case of the middle late miocene salsomaggiore ridge northern apennines italy abstract seep carbonates are important indicators of submarine fluid expulsion and dewatering of sediments along convergent margins and accretionary prisms in the northern apennine compressional wedge seep carbonates usually occur in pelitic successions from different settings of the middle late miocene foreland basin system in serravallian foredeep deposits of the salsomaggiore area seep carbonates cemented and or encrusted coarse grained sandstones and conglomerates fluid expulsion strictly related to variable intensities in tectonic stresses generated seep carbonate facies and sediment instabilities depending on the position of the fluid pathway feeders within the salsomaggiore ridge a middle late miocene intra basinal high at the leading edge of the apenninic orogenic wedge this site provides a unique opportunity for analyzing depositional characters and the three dimensional distribution and evolution of a seepage system in a thrust related anticline the resulting evolutionary model shares common features with recent ridges in other accretionary wedges in this model a strict relationship between tectonics seepage and sediment instability during a major tectonic phase is outlined

lineated valley fill lvf and lobate debris aprons lda in the deuteronilus mensae northern dichotomy boundary region mars constraints on the extent age and episodicity of amazonian glacial events abstract in order to assess the nature degradational processes and history of the dichotomy boundary on mars we conducted a detailed morphological analysis of a 70 000 km 2 region of its northern portion north central deuteronilus mensae south of lyot in the vicinity of sinton crater this region is characterized by the distinctive sinuous 2 km high plateau scarp boundary outlying massifs to the north and extensive fretted valleys dissecting the plateau to the south these features represent the first order modification and retreat of the dichotomy boundary and are further modified by processes that form lineated valley fill lvf in the fretted valleys and lobate debris aprons lda along the dichotomy scarp and surrounding the outlying massifs we use new high resolution image and topography data to examine the nature and origin of lvf and lda and to investigate the climatic and accompanying degradational history of the escarpment on the basis of our analysis we conclude that 1 lvf and lda deposits within the study region are comprised of the same material show integrated flow patterns and originate as debris covered valley glaciers a significant amount of ice hundreds of meters is likely to remain today beneath a thin cover of sublimation till 2 there is depositional evidence to suggest glacial highstands at least 800 m above the present level implying previous conditions in which the distribution of ice was much more widespread this is supported by similar deposits within many other areas across the dichotomy boundary 3 the timing of the most recent large scale activity of the lda lvf in this area is about 100 500 million years ago similar to ages reported elsewhere along the dichotomy boundary 4 there is evidence for a secondary but significantly limited phase of glaciation the deposits of which are limited to the vicinity of the alcoves similar later phases have also been reported elsewhere along the dichotomy boundary 5 modification of the fretted valleys of the dichotomy boundary has been substantial locally but we find no evidence that the amazonian glacial epochs caused retreat of the dichotomy boundary of the scale of tens to hundreds of kilometers our findings support the results of an analysis just to the east of the study region and of studies carried out elsewhere along the dichotomy boundary that find further evidence for the remnants of debris covered glaciers and extensive valley glacial land systems

cold climate modification of martian landscapes a case study of a spatulate debris landform in the hellas montes region mars 1 we use spaceborne image and topographic data of mars for a geomorphological study of the origin development and postemplacement modification of a 30 km long spatulate landform in the hellas montes area east of hellas planitia the area is characterized by an abundance of lobate debris aprons all of which have been interpreted as a result of creep and viscous deformation of rock and ice mixtures that make the eastern hellas planitia assemblages a type location for possible martian rock glaciers the spatulate landform has been discussed controversially in the past explanations range from a rock glacier to a wet debris avalanche or debris flow origin this work scrutinizes arguments provided in earlier works and presents evidence that a landslide origin of the spatulate landform connected with a sector collapse of a volcanic construct is conceivable we also find extensive observational evidence that the landslide has recently undergone or is still undergoing significant postemplacement modifications which are characteristic of rock glaciers in periglacial environments creep deformation as well as disintegration of the original surface by thermokarstic degradation is considered to have obliterated impact craters and in consequence create a seemingly younger age similar processes are considered to be common on mars under current climatic conditions our results imply that the strong and possible long term modification of landforms on mars by cold climate processes often hinders the identification of their original nature and complicates the assessment of true ages

size and shape characteristics of drumlins derived from a large sample and associated scaling laws abstract ice sheets flowing across a sedimentary bed usually produce a landscape of blister like landforms streamlined in the direction of the ice flow and with each bump of the order of 102 to 103 m in length and 101 m in relief such landforms known as drumlins have mystified investigators for over a hundred years a satisfactory explanation for their formation and thus an appreciation of their glaciological significance has remained elusive a recent advance has been in numerical modelling of the land forming process in anticipation of future modelling endeavours this paper is motivated by the requirement for robust data on drumlin size and shape for model testing from a systematic programme of drumlin mapping from digital elevation models and satellite images of britain and ireland we used a geographic information system to compile a range of statistics on length l width w and elongation ratio e where e l w for a large sample mean l is found to be 629 m n 58 983 mean w is 209 m and mean e is 2 9 n 37 043 most drumlins are between 250 and 1000 metres in length between 120 and 300 metres in width and between 1 7 and 4 1 times as long as they are wide analysis of such data and plots of drumlin width against length reveals some new insights all frequency distributions are unimodal from which we infer that the geomorphological label of drumlin is fair in that this is a true single population of landforms rather than an amalgam of different landform types drumlin size shows a clear minimum bound of around 100 m horizontal maybe drumlins are generated at many scales and this is the minimum or this value may be an indication of the fundamental scale of bump generation proto drumlins prior to them growing and elongating a relationship between drumlin width and length is found with r2 0 48 and that is approximately w 7 l 1 2 when measured in metres a surprising and sharply defined line bounds the data cloud plotted in e w l space and records a scale dependent maximum elongation limit approximated by emax l1 3 when l measured in metres for a given length for some reason as yet unknown drumlins do not exceed the elongation ratio defined by this scaling law we also report and compare our statistics to an amalgamated sample 25 907 drumlins of measures derived from around 50 published investigations any theory must be able to explain the drumlin statistics and fundamental scaling properties reported herein and they thus provide powerful tests for drumlin modelling

the case against vast glaciation in valles marineris mars abstract the valles marineris of mars form the largest system of interconnected canyons in the solar system where morphological mineralogical and structural evidence of widespread glaciation has been recently reported however neither precipitation models nor global water budgets can account for such a colossal fill and the hypothesis has thus far remained unchallenged by additional scrutiny here we present the first thorough case against a valles marineris glaciation by describing new evidence that precludes the existence of a glacier most crucially we review high resolution imaging science experiment hirise images of chaos terrain in candor chasma previously interpreted as remnant glacial ice and identify layered boulder rich scarps bearing no similarity to scarps of massive ice in promethei terra or the north polar layered deposits we also find no significant differences in the structure morphology and composition of chaos terrain in candor and the chryse planitia region which suggests candor s chaos like chryse s is fractured highland terrain we also review several other key supports for the glacial hypothesis including the coincidence of an apparent glacial trimline with the water bearing mineral jarosite and the apparent presence of glacial features including kettle holes and sandur plains these too are found to have more plausible explanations with non glacial origins including tectonic reorganisation groundwater sapping and chaotic fracturing we conclude that the valles marineris glacial hypothesis is inconsistent with both observed morphology and our understanding of the ancient martian climate and we find no evidence to support its existence

the pliocene age stirone river hydrocarbon chemoherm complex northern apennines italy abstract the stirone river section in the italian northern apennines hosts a rare example of pliocene age hydrocarbon imprinted carbonates in the mediterranean basin associated with deep water hemipelagic lithologies these include meter sized dolomite cemented chimneys micritic brecciated limestones lucina mudstones and chemosymbiotic bivalve shells some such chimneys show 13 c values as low as 37 5 vpdb suggesting subsurface precipitation of authigenic dolomite induced by anaerobic oxidation of methane triggered by consortia of sulphate reducing bacteria these carbonates are interpreted as part of the plumbing system related to hydrocarbon expulsion onto the seafloor resulting from hydrocarbon enriched defluidization processes dated at an interval at 3 6 3 3 ma and associated with the thrust related salsomaggiore structure

unique chronostratigraphic marker in depositional fan stratigraphy on mars evidence for ca 1 25 ma gully activity and surficial meltwater origin the origin of gullies on mars is controversial e g catastrophic groundwater release debris flows dry granular flows or meltwater from surface ice and snow and their ages are difficult to determine due to their small size we describe a gully depositional fan that contains a unique chronostratigraphic marker secondary crater clusters between episodes of gully activity during fan development this marker can be traced to its source a 7 km diameter rayed crater that we have dated as ca 1 25 ma this age links gully activity to the emplacement of dust ice mantling deposits interpreted to represent recent ice ages on mars this association together with multiple episodes of depositional fan formation favors an origin for these gullies from top down melting of snow and ice during multiple favorable spin axis and orbital variations this melting mechanism is consistent with the occurrence of gullies in unique steep sloped poleward facing insolation microenvironments that favor the melting of small amounts of surficial snow and ice

comprehensive analysis of glaciated martian crater greg abstract the 66 km diameter martian crater greg east of hellas hosts various distinctive features including dendritic valleys filled with chevron textured masses south wall and lobate tongues a few kilometers long north wall we analyze these features by various quantitative techniques to illuminate martian geologic and climatic history crater retention model ages indicate that greg is at least 1 3 gy old but surface layers of mantles and glacial features are orders of magnitude younger properties of the dendritic valleys combined with climate models suggest that fluvial activity began under a thicker warmer atmosphere soon after the crater s formation the oldest exposed fluvial systems have surface crater retention ages of a few hundred my indicating runoff in recent geologic time much of greg is covered by ice rich mantle deposits for which we infer gradual accumulation and depths of order 30 85 m they mask pre existing landforms the lobate tongues are interpreted as glaciers with mean slope of 10 2 2 3 and average thickness of 33 19 m our calculations and data suggest that these glaciers were originally ice rich and that their surface layers have been depleted by volatile loss the glaciers probably formed when ice rich mantle deposits reached critical thickness and flowed downhill the top 5 10 m of the mantle and glaciers show crater survival times of order a few my to 15 my which remarkably is the time since the last 1 4 episodes of obliquity 45 global climate models affirm that greg lies in one of two non polar areas with extremes of ice deposition during high obliquity epochs this match with observations supports the use of such models in studies of planetary climate change

an analysis of sinuous ridges in the southern argyre planitia mars using hirise and ctx images and mola data 1 a suite of sinuous ridges with branching and braided morphologies forms an anastomosing network in southern argyre planitia mars several modes of origin have been proposed for the argyre ridges imagery from the high resolution imaging science experiment hirise and context camera ctx aboard mars reconnaissance orbiter mro and mars orbiter laser altimeter mola topographic data sets from mars global surveyor mgs are used to constrain processes involved in formation of the argyre ridges we find the characteristics of the ridges and associated layered deposits consistent with glaciofluvial lacustrine processes and conclude that the ridges are most likely eskers in particular variations in ridge height appear to be related to the surrounding surface slope ridge height increases with descending slopes and decreases with ascending slopes this characteristic is observed in terrestrial eskers and is related to subice flow processes the nature of some eroding beds in the ridges suggests induration if the argyre ridges are indeed eskers the southern argyre basin was once covered by the margin of a large thick stagnating or retreating ice deposit that extended for hundreds of kilometers or more during ridge formation water flowed on top within or beneath the ice deposit the continuity and preservation of the ridges suggests that flow was primarily at the base of the ice the dimensions up to hundreds of meters tall and several kilometers wide aspect ratio and extent hundreds of kilometers of the ridges as well as preliminary calculations of discharge suggest that a significant amount of water was available

ocean bottom seismometers in the northern north sea experience and preliminary results with the statfjord obs abstract the northern north sea is one of the most seismically active regions of northwest europe but offshore seismicity is difficult to study in detail because the severe environment places limits on options for deployment of near field ocean bottom seismometers obs the design of an obs system deployed on the statfjord oil field is presented together with some results amplitude density spectra of ambient noise from two obs installations are on average more than a factor of ten higher than the average of three onshore western norway network wnn seismic stations a theoretical detection threshold curve based on background noise levels is in close agreement with practical experience of detections at the statfjord obs and explains why only about 7 per cent of the events detected in the northern north sea by the wnn are also detected on the statfjord obs comparison of earthquake source spectra recorded on and off shore reveal no evidence for either high attenuation or amplification in the viking graben earthquake focal depths in the central northern north sea seem to be around 20 km

debris covered piedmont glaciers along the northwest flank of the olympus mons scarp evidence for low latitude ice accumulation during the late amazonian of mars we use viking and new mgs and odyssey data to characterize the lobate deposits superimposed on aureole deposits along the west and northwest flanks of olympus mons mars these features have previously been interpreted variously as landslide pyroclastic lava flow or glacial features on the basis of viking images the advent of multiple high resolution image and topography data sets from recent spacecraft missions allow us to revisit these features and assess their origins on the basis of these new data we interpret these features as glacial deposits and the remnants of cold based debris covered glaciers that underwent multiple episodes of advance and retreat occasionally interacting with extrusive volcanism from higher on the slopes of olympus mons we subdivide the deposits into fifteen distinctive lobes typical lobes begin at a theater like alcove in the escarpment at the base of olympus mons interpreted to be former ice accumulation zones and extend outward as a tongue shaped or fan shaped deposit the surface of a typical lobe contains moving outward from the basal escarpment a chaotic facies of disorganized hillocks interpreted as sublimation till in the accumulation zone arcuate ridged facies characterized by regular subparallel ridges and interpreted as the ridges of surface debris formed by the flow of underlying ice and marginal ridges interpreted as local terminal moraines several lobes also contain a hummocky facies toward their margins that is interpreted as a distinctive type of sublimation till shaped by structural dislocations and preferential loss of ice blocky units are found extending from the escarpment onto several lobes these units are interpreted as evidence of lava ice interaction and imply that ice was present at a time of eruptive volcanic activity higher on the slopes of olympus mons other than minor channel like features in association with lava ice interactions we find no evidence for the flow of liquid water in association with these lobate features that might suggest 1 near surface groundwater as a source for ice in the alcoves in the lobe source region at the base of the scarp or 2 basal melting and drainage emanating from the lobes that might indicate wet based glacial conditions instead the array of features is consistent with cold based glacial processes the glacial interpretations outlined here are consistent with recent geological evidence for lowlatitude ice rich features at similar positions on the tharsis montes as well as with orbital dynamic and climate models indicating extensive snow and ice accumulation associated with episodes of increased obliquity during the late amazonian period of the history of mars

time will tell temporal evolution of martian gullies and palaeoclimatic implications to understand martian palaeoclimatic conditions and the role of volatiles therein the spatiotemporal evolution of gullies must be deciphered while the spatial distribution of gullies has been extensively studied their temporal evolution is poorly understood we show that gully size is similar in very young and old craters gullies on the walls of very young impact craters less than a few myr typically cut into bedrock and are free of latitude dependent mantle ldm and glacial deposits while such deposits become increasingly evident in older craters these observations suggest that gullies go through obliquity driven degradation accumulation cycles over time controlled by 1 ldm emplacement and degradation and 2 glacial emplacement and removal in glacially influenced craters the distribution of gullies on crater walls coincides with the extent of glacial deposits which suggests that the melting of snow and ice played a role in the formation of these gullies yet present day activity is observed in some gullies on formerly glaciated crater walls moreover in very young craters extensive gullies have formed in the absence of ldm and glacial deposits showing that gully formation can also be unrelated to these deposits the martian climate varied substantially over time and the gully forming mechanisms are likely to have varied accordingly

martian hillside gullies and icelandic analogs abstract we report observations of icelandic hillside gully systems that are near duplicates of gullies observed on high latitude martian hillsides the best icelandic analogs involve basaltic talus slopes at the angle of repose with gully formation by debris flows initiated by ground water saturation and or by drainage of water from upslope cliffs we report not only the existence of mars analog gullies but also an erosional sequence of morphologic forms found both on mars and in iceland the observations support hypotheses calling for creation of martian gullies by aqueous processes issues remain whether the water in each case comes only from surficial sources such as melting of ground ice or snow or from underground sources such as aquifers that gain surface access in hillsides iceland has many examples of the former but the latter mechanism is not ruled out our observations are consistent with the martian debris flow mechanism of f costard et al 2001c science 295 110 113 except that classic debris flows begin at midslope more frequently than on mars from morphologic observations we suggest that some martian hillside gully systems not only involve significant evolution by extended erosive activity but gully formation may occur in episodes and the time interval since the last episode is considerably less than the time interval needed to erase the gully through normal martian obliteration processes

origin and evolution of a cold based tropical mountain glacier on mars the pavonis mons fan shaped deposit 1 each of the large tharsis montes volcanoes in the equatorial region of mars has an unusual amazonian aged fan shaped deposit on its west northwestern flank on the basis of viking orbiter data the origin of these deposits has been variously ascribed to volcanic mass wasting tectonic and glacial processes using new mgs and odyssey data combined with recent developments in the study of cold based glaciers we reassess the geology and mode of origin for these deposits with particular emphasis on pavonis mons the deposits share three characteristic facies including 1 a ridged facies consisting of tens to 100 parallel concentric ridges around the margins of the deposits 2 a knobby facies composed of irregular hills and hummocks and 3 a smooth facies of broad lobate plains that superposes all other units within the deposits on the basis of morphology topography superposition relationships and close terrestrial analogs in the dry valleys of antarctica we interpret the pavonis fan shaped deposit as the depositional remains of a cold based glacier that formed on the northwestern flank in recent martian history we interpret the ridged facies as drop moraines formed around the margins of a retreating cold based glacier the knobby facies as a sublimation till derived from in situ down wasting of cold based glacial ice and the smooth facies as extant debris covered glacial ice in addition to the three main facies the fan shaped deposit at pavonis mons contains several unique features including arcuate scarps high relief flow like features and radial ridges which suggest that volcanism played a role during its formation using recent results from mars general circulation model simulations we outline a model of glacier formation involving atmospheric deposition of water ice on the northwestern flanks of the tharsis montes during periods of high mean obliquity reconstructed ice sheet profiles for each of the tharsis montes glaciers suggest that the ice sheets attained average thicknesses of 1 6 2 4 km values that are consistent with a cold based glacial origin analysis of crater size frequency distributions using new data indicates that the age of the glaciation lies within the late amazonian 10 200 ma thus our results suggest that multiple phases of tropical mountain glaciation occurred on mars within the past few hundred myr and that significant amounts of near surface equatorial ice may remain within the deposit today

eskers in a complete wet based glacial system in the phlegra montes region mars although glacial landsystems produced under warm wet based conditions are very common on earth even here observations of subglacial landforms such as eskers emerging from extant glaciers are rare this paper describes a system of sinuous ridges emerging from the in situ but now degraded piedmont terminus of a late amazonian aged 150 ma glacier like form in the southern phlegra montes region of mars we believe this to be the first identification of martian eskers that can be directly linked to their parent glacier together with their contextual landform assemblage the eskers are indicative of significant glacial meltwater production and subglacial routing however although the eskers are evidence of a wet based regime the confinement of the glacial system to a well defined regionally significant graben and the absence of eskers elsewhere in the region is interpreted as evidence of sub glacial melting as a response to locally enhanced geothermal heat flux rather than climate induced warming these observations offer important new insights to the forcing of glacial dynamic and melting behaviour on mars by factors other than climate

recent basal melting of a mid latitude glacier on mars evidence for past basal melting of young late amazonian debris covered glaciers in mars mid latitudes is extremely rare thus it is widely thought that these viscous flow features vffs have been perennially frozen to their beds we identify an instance of recent localized wet based mid latitude glaciation evidenced by a candidate esker emerging from a vff in a tectonic rift in tempe terra eskers are sedimentary ridges deposited in ice walled meltwater conduits and are indicative of glacial melting we compare the candidate esker to terrestrial analogues present a geomorphic map of landforms in the rift and develop a landsystem model to explain their formation we propose that the candidate esker formed during a transient phase of wet based glaciation we then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid latitude vff both are within tectonic graben rifts proximal to volcanic provinces finally we calculate potential basal temperatures for a range of vff thicknesses driving stresses mean annual surface temperatures and geothermal heat fluxes which unlike previous studies include the possible role of internal strain heating strain heating can form an important additional heat source especially in flow convergence zones or where ice is warmer due to elevated surface temperatures or geothermal heat flux elevated geothermal heat flux within rifts perhaps combined with locally elevated strain heating may have permitted wet based glaciation during the late amazonian when cold climates precluded more extensive wet based glaciation on mars

martian gullies a comprehensive review of observations mechanisms and insights from earth analogues upon their discovery in 2000 martian gullies were hailed as the first proof of recent i e less than a few million years flowing liquid water on the surface of a dry desert planet many processes have been proposed to have formed martian gullies ranging from liquid water seepage from aquifers melting of snow ice and frost to dry granular flows potentially lubricated by co2 terrestrial analogues have played a pivotal role in the conception and validation of gully formation mechanisms comparison with the terrestrial landscape argues for gully formation by liquid water debris flows originating from surface melting however limited knowledge of sediment transport by sublimation is a critical factor in impeding progress on the co2 sublimation hypothesis we propose avenues towards resolving the debate a laboratory simulations targeting variables that can be measured from orbit b applications of landscape evolution models c incorporation of the concept of sediment connectivity d using 3d fluid dynamic models to link deposit morphology and flow rheology and e a more intense exchange of techniques between terrestrial and planetary geomorphology including quantitative and temporal approaches finally we emphasize that the present may not accurately represent the past and that martian gullies likely formed by a combination of processes

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

size shape and spatial arrangement of mega scale glacial lineations from a large and diverse dataset mega scale glacial lineations msgls are a characteristic landform on ice stream beds solving the puzzle of their formation is key to understanding how ice interacts with its bed and how this in turn influences the dynamics of ice streams however a comprehensive and detailed characterization of this landform s size shape and spatial arrangement which might serve to test and refine formational theories is largely lacking this paper presents a detailed morphometric analysis and comparison of 4043 msgls from eight palaeo ice stream settings three offshore norway and antarctica four onshore canada and one from under a modern ice stream in west antarctica the length of msgls is lower than previously suggested mode 1000 2000 m median 2892 m and they initiate and terminate at various locations on an ice stream bed their spatial arrangement reveals a pattern that is characterized by an exceptional parallel conformity 80 of all mapped msgls have an azimuth within 5 from the mean values and a fairly constant lateral spacing mode 200 300 m median 330 m which we interpret as an indication that msgls are a spatially self organized phenomenon results show that size shape and spatial arrangement of msgls are consistent both within and also generally between different ice stream beds we suggest this results from a common mechanism of formation which is largely insensitive to local factors although the elongation of msgls mode 6 8 median 12 2 is typically higher than features described as drumlins these values and those of their width mode 100 200 m median 268 m overlap which suggests the two landforms are part of a morphological continuum and may share a similar origin we compare their morphometry with explicit predictions made by the groove ploughing and rilling instability theories of msgl formation although the latter was most compatible neither is fully supported by observations 2014 the authors earth surface processes and landforms published by john wiley sons ltd

large scale ice moulding a discussion of genesis and glaciological significance abstract landsat images reveal a previously unsuspected large scale pattern of streamlining within drift which comprises a number of components drumlins and megaflutes form part of the pattern but in addition there are two previously undocumented ice moulded landform elements streamlined lineations of much greater proportions referred to as mega scale glacial lineations and a distinctive cross cutting topology within the grain consideration of the genesis and glaciological significance of such landforms leads to a number of conclusions it is suggested that mega scale glacial lineations were formed under conditions of fast ice flow and their presence may thus record former locations of ice streams or surge events many lineations of varying scales display a pattern that reveals that they were not formed in sub marginal positions extensive sets of lineations must have been formed approximately synchronously thus indicating that lineation generation occurs over a wide range of glaciodynamic conditions from sub marginal positions to interior portions of ice sheets subglacial deformation of tills has been widely invoked to account for rapid glacier motion criteria for identifying such tills are restricted to structures viewed in cross section and it is thus hard to assess how widespread the processes of deformation may have been lineations provide a surface marker of structure that records subsequent deformation from other ice flow events it is argued that the palaeo flow record including cross cutting patterns provides the surface or plan expression of subglacial deformation the degree of modification to pre existing lineations should permit the identification of zones favoured by deformation and thus assist in an assessment of how pervasive deforming bed processes were in influencing ice sheet dynamics

entrainment of glaciomarine sediments and formation of thrust block moraines at the margin of sorsdale glacier east antarctica the morphology sedimentology and structure of moraines at the margin of an outlet glacier in east antarctica are described and contemporary depositional processes in a marine inlet adjacent to the ice margin are examined results indicate that the principal moraines are thrust block moraines produced by basal freezing and deformation of glaciomarine sediment as the outlet glacier expands into a marine inlet preservation of detailed glaciomarine sedimentary structures and beds of marine shells suggests that the sediment was frozen during entrainment transportation and deposition the presence of low angle faults in the moraines show that the moraines consist of an en echelon arrangement of thrust plates the sedimentology structure thickness of the thrust plates and inferred entrainment processes are consistent with weertman s ice debris accretion hypothesis for debris entrainment at the edge of cold ice sheets a model of thrust block moraine development produced by this study provides a framework for the interpretation of radiocarbon dates from marine macrofossils in the moraines the model may also be useful in the interpretation of similar moraines in coastal east antarctic oases and other polar marginal marine environments 1997 by john wiley sons ltd

landform assemblage in isidis planitia mars evidence for a 3 ga old polythermal ice sheet abstract the floor of isidis planitia a giant impact basin located close to the martian equator exhibits a landform assemblage nicknamed thumbprint terrain made of arcuate ridges aligned cones isolated cones cone fields associated with a peripheral network of sinuous ridges linear depressions and mounds from a new comprehensive mapping initiative of these landforms and from comparisons with terrestrial analogues ribbed moraines dirt cones kettle holes eskers tunnel valleys and moraine plateaux we demonstrate that this distinctive assemblage is a glacial landsystem inherited from the presence of a massive polythermal ice sheet over the basin during the hesperian the flow of the ice sheet was controlled by its basal thermal regime wet based conditions led to the formation of arcuate ridges and aligned cones in most parts of the basin while a negative geothermal anomaly due to impact related crustal thinning was responsible for cold based conditions in its central part where only isolated cones and cones fields are present sinuous ridges linear depressions and mounds at the basin margins are interpreted as relicts of a radial network of subglacial channels which drained the glacial meltwater produced within the interior of the ice sheet across its cold based periphery

geomorphological evidence of cold based glacier activity in south victoria land antarctica cold based glaciers have long been recognized as capable of covering and protecting landscapes however recent studies of modern cold based glaciers in antarctica show that in some situations erosion deformation and deposition can occur recognizing the dual ability of cold based glaciers to protect and preserve surfaces on the one hand and erode and modify on the other is important for correctly interpreting the often subtle imprint of cold based glaciers on landscapes a range of geomorphological features related to cold based glacier activity has now been documented along with an improved understanding of cold based glacier structure processes and interaction with various substrates collectively this provides an enhanced ability to understand the impact of cold based glaciers on landscapes and reappraise the geomorphological record such insight allows recognition of previously unknown glacial events and better interpretations of the landscape exposure record this is particularly important at the margins of the antarctic ice sheets where past fluctuations in ice sheet volume and its contributions to post glacial sea level rise are poorly constrained this paper reviews the known geomorphological evidence associated with cold based glaciers in the south victoria land region of the transantarctic mountains it aims to provide progress towards a set of criteria for recognizing cold based glacier activity in other regions and to highlight the implications of cold based glacial activity for surface exposure studies and interpreting glacial history cold based glaciers are below pressure melting point throughout and are therefore frozen to the substrate and move primarily by internal deformation drewry 1986 this led to the long standing view that cold based glaciers cannot slide and are thus incapable of erosion and deposition and therefore protect the underlying surface while numerous studies have shown this to be true in many situations recent investigations of modern cold based glaciers have revealed that in some circumstances complex processes operate at subfreezing temperatures in the basal zone and that cold based glaciers can generate a variety of geomorphological features these studies have forced a reappraisal of the geomorphic effectiveness of cold based glaciers and have confirmed that they can both protect and modify landscapes e g fitzsimons 1996 atkins et al 2002 fitzsimons 2003 waller et al 2012 thus the debate has moved on and the challenge now is to understand the full range of processes and products associated with cold based glaciers and the implications for landscape development hambrey fitzsimons 2010 waller et al 2012 recognizing the often subtle features indicative of cold based glacial activity offers the potential to delineate and date previously unknown or poorly constrained glacial events this is particularly relevant for interpreting glacial history and modelling ice sheet reconstructions for example numerous surface exposure dating studies have been carried out on ice marginal landforms with the aim of constraining past variations in the ice sheet volume however many of these studies have produced inconsistent contradictory results including evidence of complex exposure histories suggesting episodes of burial and reworking by cold based ice e g strasky et al 2008 di nicola et al 2009 compared with warm based glaciers there are still relatively few studies of cold based glaciers and significant gaps in our understanding of the processes and products remains in addition lingering misconceptions regarding the geomorphic effectiveness of cold based glaciers and historic use of ambiguous terminology to describe cold based sediments and landforms mean that the evidence and implications of past cold based glacial events have yet to be fully appreciated by the wider geomorphological community this review provides a summary of known geomorphological features associated with cold based glaciers in the south victoria land region of antarctica it aims to provide a basis for recognizing similar features elsewhere and attempts to draw attention to the implications of cold based glacial geomorphology for the correct application of surface exposure dating studies and interpretation of cold based glacial history

amazonian modification of moreux crater record of recent and episodic glaciation in the protonilus mensae region of mars abstract morphologic characteristics of ice rich landforms in the martian mid latitudes record evidence for significant modification of the landscape in response to spin axis orbital parameter driven shifts in the late amazonian climate these landforms are spatially distributed across the mid latitudes and their co existing presence has so far not been observed from a single crater to infer how exactly a terrain has been modified while mars was undergoing major moderate minor shifts in its late amazonian climate we have therefore carried out an in depth investigation of moreux crater 135 km centered at 41 66 n 44 44 e in the protonilus mensae region for identification of features associated with recent and episodic glacial events and for emphasizing the role played by these glacial events in the modification of the crater evidence for extensive modification of the surfaces over crater rim wall and around central peak by emplacement of multiple scales of ice rich landforms that represents large history of glacial activities was found from our results we document phases of major moderate minor glacial activities within the crater as 1 piedmont lobes lobate debris aprons linear valley fills 1 ga 100 ma 2 viscous flow features 30 0 1 ma and 3 gullies thermal contraction crack polygons 2 1 0 4 ma the form and distribution of the random valleys observed within moreux suggests their formation by pressure induced melting and flow occurring beneath an extensive layer of ice we also suggest that central peak of moreux probably acted as the locus for accumulation of ice snow and the diversity of glacial periglacial features within the crater was possibly controlled by differences in the amount of accumulated ice snow and the rate at which the terrain responded to the shifts in climate during subsequent periods of obliquity changes taken together these ice rich deposits within moreux suggest that sequential modification of the crater surfaces over the rim wall and around central peak has occurred over the last tens of millions of years of martian history this new evidence thus adds another well documented case to rapidly accumulating evidences for widespread glacial activity in the middle latitudes of mars in recent martian history

geologically recent gully polygon relationships on mars insights from the antarctic dry valleys on the roles of permafrost microclimates and water sources for surface flow we describe the morphology and spatial relationships between composite wedge polygons and mars like gullies consisting of alcoves channels and fans in the hyper arid antarctic dry valleys adv as a basis for understanding possible origins for martian gullies that also occur in association with polygonally patterned ground gullies in the adv arise in part from the melting of atmospherically derived wind blown snow trapped in polygon troughs snowmelt that yields surface flow can occur during peak southern hemisphere summer daytime insolation conditions ice cemented permafrost provides an impermeable substrate over which meltwater flows but does not significantly contribute to meltwater generation relationships between contraction crack polygons and sedimentary fans at the distal ends of gullies show deposition of fan material in polygon troughs and dissection of fans by expanding polygon troughs these observations suggest the continuous presence of meters thick ice cemented permafrost beneath adv gullies we document strong morphological similarities between gullies and polygons on mars and those observed in the adv inland mixed microclimate zone on the basis of this morphological comparison we propose an analogous top down melting model for the initiation and evolution of martian gullies that occur on polygonally patterned mantled surfaces

u th dating and post depositional alteration of a cold seep carbonate chimney from the campos basin offshore brazil abstract dating authigenic cold seep carbonates allows determining the timing of active seepage of hydrocarbon rich fluids at continental margins and ultimately the detection of the geological factors affecting it u th dating has been selected in this study the method having been successfully used before however incorporation of initial thorium in substantial amounts of detrital material due to the precipitation of carbonates within the seabed and post depositional alteration potentially pose a major problem violating the basic assumptions of the method here we report results from several samples from the campos basin off the coast of brazil they are unusual in their high 13 c values mean of 10 0 vpdb high detrital contents and being dominantly dolomite elevated 230 th 238 u activity ratios indicate that most of the carbonates lost uranium during diagenesis isochrones are obtained from the unaffected samples yielding an age of 140 4 3 1 ka vertical growth of the chimney must have been short and rapid since results from the top and bottom parts of the chimney concur within analytical uncertainties furthermore profiles of u th radioisotope specific activity 234 u and 232 th specific activity on two quarter slices of a carbonate chimney reveal the occurrence of three distinct diagenetic processes u loss u exchange with seawater and th gain

small scale polygonal features on mars seasonal thermal contraction cracks in permafrost a time dependent viscoelastic model of thermal stress in martian ice rich permafrost is developed to test the hypothesis that small scale polygonal features observed from orbit and by the viking lander 2 are the result of thermal contraction cracking as commonly occurs in terrestrial permafrost results indicate that significant tensile stress occurs in martian ice rich permafrost as a result of seasonal cycles in the ground temperature using conservative rheological parameters appropriate for ice at low temperatures tensile stresses poleward of about 20 to 30 latitude easily exceed the tensile strength assumed to be 2 to 3 mpa and fractures should readily form in the equatorial regions special conditions may allow tensile stresses to approach the tensile strength these results support a thermal contraction origin of observed small scale polygonal features and emphasize the utility of these features as valuable morphological indicators of ground ice

volcanism induced local wet based glacial conditions recorded in the late amazonian arsia mons tropical mountain glacier deposits abstract the tropical mountain glacial fan shaped deposit fsd to the northwest of the arsia mons volcano on mars contains numerous glacial and volcanic landforms while most of the glacial landforms are interpreted to have formed by cold based glacial processes several glacial landforms near glaciovolcanic edifices are more consistent with localized wet based glacial processes these landforms include ribbed moraines which suggest local thermal transitions between wet and cold based ice thrust block moraines whose formation is typically assisted by the presence of subglacial water streamlined knobs that we interpret to have been sculpted by ice sliding along its base and a braided outflow channel the presence and association of these features together with evidence of both subglacial volcanic eruptions and local ice marginal advances favor polythermal glaciers with localized wet based conditions we propose that lava to ice heat transfer during the eruption of the glaciovolcanic edifices caused the arsia mons paleoglacier to melt at its base in some areas resulting in these locally wet based glacial conditions a polythermal glacier provides more potential microbial habitats and more connectivity between habitats than does a cold based glacier and we review glacial and glaciovolcanic habitats on earth that may provide insight into the likelihood of potential microbial habitats within the arsia mons fsd on mars

high latitude patterned grounds on mars classification distribution and climatic control patterned grounds such as polygonal features and slope stripes are the signature of the presence of ground ice and of temperature variations in cold regions on earth identifying similar features on mars is important to understand its past climate as well as the ground ice distribution in this study young patterned grounds are classed and mapped from the systematical analysis of mars observer camera high resolution images these features are located poleward of 55 latitude which fits the distribution of ground ice found by the neutron spectrometer onboard mars odyssey thermal contraction due to seasonal temperature variations is the predominant process of formation of polygons formed by cracks which sizes vary from 15 to 300 m the small 40 m widespread polygons are very recent and degraded by the desiccation of ground ice from the cracks which enhances the effect of ice sublimation the large polygons 50 to 300 m located only around the south co2 polar cap indicate the presence of ground ice and thus outline the limit of the co2 ice cap they could be due to the blanketing of water ice deposits by the advances and retreats of the residual co2 ice cap during the last thousand years large 50 250 m and homogeneous polygons similar to ice wedge polygons hillslope stripes and solifluction lobes may indicate that specific environments such as crater floors and hillslopes could have been submitted to freeze thaw cycles possibly related to higher summer temperatures in periods of obliquity higher than 35 these interpretations must be strengthened by higher resolution images such as those of the hirise mission of the mars reconnaissance orbiter because locations with past seasonal thaw could be of major interest as potential landing sites for the phoenix mission

ice dynamics and thermal regime of taylor glacier south victoria land antarctica les donnees glaciologiques recueillies sur le taylor glacier ont servi a reconstituer les principaux traits de la dynamique et du regime thermique du glacier les etudes du bilan de masse montrent que le glacier est proche de l equilibre les conditions thermiques de la glace basale sur une grande partie de la zone d ablation ont ete calculees a partir d estimation du flux de chaleur geothermique et de mesures des temperatures de la glace pres de la surface des vitesses et de l epaisseur de la glace on a trouve que jusqu a 50 de la zone d ablation la glace basale pouvait etre fondante

how do glaciers surge a review the quasi periodic oscillations between normal and fast motion exhibited by surge type glaciers provide the best observational opportunity to determine limiting conditions that allow fast motion the measurements from variegated glacier prove that its surge motion is caused by rapid sliding induced by high water pressure this arises from a major restructuring of the basal hydraulic system which impedes water discharge prior to and during surge although the evolving glacier geometry and stress distribution play a principal enabling role the seasonal timing of two distinct surge pulses each initiated in winter and terminated in summer indicates a major influence from variable external water inputs this influence is not considered in existing surge models and should promote caution in the use of data from temperate and subpolar surge type glaciers to deduce surge potential in polar ice masses the spatial spreading of surge motion from a zone of local initiation occurs by stress redistribution which may spread the surging zone rapidly upglacier or downglacier inside a region of active ice and by mass redistribution with compressional thickening at the surge front which enables down glacier propagation into less active ice the data from other surge type glaciers including the extensive data from medvezhiy glacier are not inconsistent with the above processes but are inadequate to establish whether completely different mechanisms operate in some surges the way by which water accumulates and produces fast sliding is not established in detail for any surge type glacier and may be different on different glaciers depending for example on the presence or absence of unconsolidated debris between the ice and rock

flow patterns of lobate debris aprons and lineated valley fill north of ismeniae fossae mars evidence for extensive mid latitude glaciation in the late amazonian a variety of late amazonian landforms on mars have been attributed to the dynamics of ice related processes evidence for large scale mid latitude glacial episodes existing within the last 100 million to 1 billion years on mars has been presented from analyses of lobate debris aprons lda and lineated valley fill lvf in the northern and southern mid latitudes we test the glacial hypothesis for lda and lvf along the dichotomy boundary in the northern mid latitudes by examining the morphological characteristics of lda and lvf surrounding two large plateaus proximal massifs and the dichotomy boundary escarpment north of ismeniae fossae centered at 45 3n and 39 2e lineations and flow directions within lda and lvf were mapped using images from the context ctx camera the thermal emission imaging spectrometer themis and the high resolution stereo camera hrsc flow directions were then compared to topographic contours derived from the mars orbiter laser altimeter mola to determine the down gradient components of lda and lvf flow observations indicate that flow patterns emerge from numerous alcoves within the plateau walls are integrated over distances of up to tens of kilometers and have down gradient flow directions smaller lobes confined within alcoves and superposed on the main lda and lvf represent a later less extensive glacial phase crater size frequency distributions of lda and lvf suggest a minimum youngest age of 100 ma the presence of ring mold crater morphologies is suggestive that lda and lvf are formed of near surface ice rich bodies from these observations we interpret lda and lvf within our study region to result from formerly active debris covered glacial flow consistent with similar observations in the northern mid latitudes of mars glacial flow was likely initiated from the accumulation and compaction of snow and ice on plateaus and in alcoves within the plateau walls as volatiles were mobilized to the mid latitudes during higher obliquity excursions together with similar analyses elsewhere along the dichotomy boundary these observations suggest that multiple glacial episodes occurred in the late amazonian and that lda and lvf represent significant reservoirs of non polar ice sequestered below a surface lag for hundreds of millions of years

extent and basal characteristics of the m clintock channel ice stream abstract the m clintock channel palaeo ice stream drained the northwestern margin victoria island arctic canada of the laurentide ice sheet functioning for 200 years prior to 10 ka bp from its bed imprint it is reconstructed as 720 140 km with a cross sectional area of 100 km2 comparable in size to the hudson strait ice stream it drained an estimated 80 000 km3 of ice enough to significantly affect the shrinking ice sheet and drive the keewatin ice divide south eastwards such discharges likely produced heinrich events and influenced the temperature and salinity of the western arctic ocean ice stream location was controlled by a topographic trough but glaciological regulation rather than properties of the bed controlled margin locations and hence ice stream width the ice stream eroded into pre existing unconsolidated sediments and left a pattern of subglacially produced landforms recording a snapshot view of the bed prior to shutdown frictional shutdown occurred once downcutting through sediments reached bedrock in places high sediment availability appears critical for ice stream functioning with a drift thickness of 50 m required to sustain its 200 year lifespan debris discharge was exceptionally high 73 000 m3 a 1 m 1 this ice stream demonstrates non steady response of ice sheets to climate change and their large impact on mass balance and stability of ice sheets

possible climate related signals in high resolution topography of lobate debris aprons in tempe terra mars lobate debris aprons are common features in the midlatitudes of mars that are assumed to be the result of the flow of ice rich material we produce high resolution digital elevation models of two of these features in the tempe terra region of mars using hirise stereo images we identify two main topographic features of different wavelength using a power spectrum analysis approach short wavelength features between approximately 10 and 20 m in length correspond to a polygonal surface texture present throughout our study area long wavelength features between approximately 700 and 1800 m in length correspond to broad ridges that are up to 20 m in amplitude we interpret both topographic signals to be the likely result of climate change affecting the debris contribution and or the flow regime of the lobate debris aprons the apparent surface age of about 300 ma could be evidence of an astronomical forcing mechanism recorded in these lobate debris aprons at this time in mars history citation grindrod p m and s a fawcett 2011 possible climate related signals in high resolution topography of lobate debris aprons in tempe terra mars geophys res lett 38 l19201 doi 10 1029 2011gl049295

fresh shallow valleys in the martian midlatitudes as features formed by meltwater flow beneath ice significant numbers of valleys have been identified in the martian midlatitudes 30 60 n s spatially associated with extant or recent ice accumulations many of these valleys date to the amazonian but their formation during these cold dry epochs is problematic in this study we look in detail at the form distribution and quantitative geomorphology of two suites of these valleys and their associated landforms in order to better constrain the processes of their formation since the valleys themselves are so young and thus well preserved uniquely we can constrain valley widths and courses and link these to the topography from the mars orbiter laser altimeter and high resolution stereo camera data we show that the valleys are both qualitatively and quantitatively very similar despite their being 5000 km apart in different hemispheres and around 7 km apart in elevation buffered crater counting indicates that the ages of these networks are statistically identical probably forming during the late amazonian 100 ma in both localities at least tens of valleys cross local drainage divides apparently flowing uphill we interpret these uphill reaches to be characteristic of flow occurring beneath a now absent relatively thin order 101 102 m regionally extensive ice cover ridges and mounds occasionally found at the foot of these valley systems are analogous to eskers and aufeis like refreezing features on the basis of their interaction with these aufeis like mounds we suggest that this suite of landforms may have formed in a single short episode perhaps order of days probably forced by global climate change

geomorphological characterisation and interpretation of a mid latitude glacier like form hellas planitia mars we describe and interpret the surface terrain types associated with a widely reported 4 km long midlatitude martian viscous flow feature vff the feature is located in the southern hemisphere on the poleward facing rim of a 60 km diameter crater in eastern hellas planitia high resolution imaging science experiment hirise images analysed in both 2d and 3d reveal that the upper margin of the feature is bounded by steep 30 headwalls typically some tens of metres high that are formed from unconsolidated material and characterised by a series of slope parallel linear incisions below these incised headwalls the feature flows at a general angle of 10 from a broad upper basin to a confined lower tongue that is bounded by a nested sequence of elongate raised ridges these characteristics are typical of several vffs in the region and are strikingly similar to moraine bounded valley glaciers on earth and we sub classify this feature as a glacier like form glf 1 the glf comprises five distinctive surface terrain types that contrast sharply with surface characteristics outside its bounding moraines four of these terrains scaly terrain polygonized terrain linear terrain and mound and tail terrain are located within the glf s innermost bounding moraine while the fifth rectilinear ridge terrain is located between its frontal moraines these terrains are mapped characterised and associated with possible mechanisms of formation to draw inferences about the glf s glaciology and glacial history this analysis suggests that the glf reached its maximal extent in the geologically recent past and that it may have been partially wetbased at that time subsequent to this phase the glf experienced an extended period of general recession that has been punctuated by several episodes of still stand or advance currently the glf s basin appears to be composed of a lower zone that is dominated by an exposed former glacier bed and an upper zone that may still contain a now degraded and dust mantled viscous mass similar to many partially glacierized basins on earth

global documentation of overlapping lobate deposits in martian gullies abstract martian gullies are landforms comprising an alcove channel and debris apron in some gullies lobate deposits have been observed implying a debris flow like process but uncertainty remains as to the importance of this process in the gully population and whether lobate deposits are related to a specific context we document evidence of overlapping lobate deposits on gully fan surfaces within craters emplaced between 30 75 in both hemispheres we have identified 26 craters in which lobate deposits occur in gullies of which 6 were previously reported this corresponds to 3 39 of the 765 gullied craters studied using 1004 hirise images we show that gullies with lobate deposits 1 do not show any location preference 2 are poleward facing 3 are found in craters with and without latitude dependent mantle ldm and or glacier like forms 4 are emplaced at average slopes of 22 and 15 at the foot of fans in the northern and southern hemispheres respectively and 5 form in craters of all ages we infer that preservation of lobate deposits in gullies is the main factor leading to their relative paucity within the gully population additionally we find that the size of the clasts embedded in the lobes does not seem to vary with host crater age and the presence of ldm and or glacial landforms further we observe morphological features associated with terrestrial wet debris flows including overlapping tongue shaped terminal lobes levees channel backfilling plug formation and avulsion we have not observed any significant present day changes in the morphology and topography of gullies and or lobes we conclude that a debris flow like process is likely responsible for the majority of sediment transport in gully landforms but whether the fluidising agent is or was liquid water or co2 ice sublimation remains unknown

early late pliocene biochronology and surface water temperature variations in the mediterranean a high resolution magnetobiostratigraphy is presented for the early late pliocene in sicily paleomagnetic measurements on samples from 100 stratigraphic levels provide an unprecedented high quality polarity sequence which extends from the upper reversed gilbert to the upper normal gauss subchron the resultant chronology for the early late pliocene provides ages for the following principal mediterranean bioevents 1 fodgloborotalia crassaformis at 3 40 ma 2 prolonged absence ofgloborotalia puncticulata between 3 38 and 3 16 ma 3 loduvigerina rutila at 3 16 ma 4 lodsphaeroidinellopsis seminulina at 3 07 ma 5 lodgloboquadrina altispira at 3 04 ma 6 lodcibicides italicus at 2 96 ma summer and winter surface water temperature estimates for the period 3 50 to 2 92 ma are based on the abundances ofglobigerinoides sacculifer andgloborotalia puncticulata in 111 samples with an average resolution of some 5000 years short term variations in temperature of the surface water and in colour and carbonate content of the sediment are primarily controlled by the equinoxal precession a higher seasonality during deposition of the grey coloured carbonate poor facies suggests that at that time the summer solstice occurred near perihelion whereas an inverse alignment occurred at the time of deposition of white coloured carbonate rich layers this phase relationship between the precession cycle and grey coloured layers is also valid for the sapropels which began to intercalate in the grey coloured layers at 2 94 ma long term changes in surface water temperatures include a warming between 3 38 and 3 18 ma followed by a cooling from 3 18 to 3 03 ma the warming of mediterranean surface waters at 3 38 ma is believed to be associated with the final closure of the isthmus of panama consequent strengthening of the gulf stream injected larger volumes of warm surface water into the north atlantic drift and eastern boundary current and this caused surface water temperatures in the mid to high latitude northeast atlantic and mediterranean to rise the subsequent climatic cooling at 3 18 ma is linked to a first stage of northern hemisphere continental ice growth

physical environment of drumlin formation review of published descriptions of drumlin fields suggests that the following conditions are important to drumlin growth 1 compressive longitudinal and possibly extending transverse strain rates in the ice 2 thin ice such as occurs near the glacier margin and 3 high pore water pressure in the subglacial sediments most drumlin fields display all of these and no fields of well developed drumlins were found that did not on the oilier hand the lithology of drumlin forming sediment appears not to be important in promoting drumlin growth since it varied widely nor are the lithology and large scale topography of the bed

evidence for subglacial ponding across taylor glacier dry valleys antarctica hubbard alun lawson w anderson b hubbard b p 2004 evidence for subglacial ponding across taylor glacier dry valleys antarctica annals of glaciology 39 1 79 84 rae2008

antarctic subglacial lakes abstract antarctic subglacial lakes were first identified by robin et al 1970 after airborne radio echo sounding res investigations of the ice sheet interior recently satellite altimetry was used to measure anomalous near flat regions on the ice sheet surface that represent a manifestation of the subglacial lake beneath using res and satellite altimetry the location and extent of antarctic subglacial lakes can be identified the largest subglacial lake exists beneath vostok station and is 14 000 km2 in area the combined area of additional subglacial lakes beneath dome c is 15 000 km2 and at least 15 000 km2 of lake surface lies beneath the remainder of the ice sheet the water depth of subglacial lakes can be estimated through seismic investigations although data exist only for lake vostok and consideration of the bedrock slopes that border subglacial lakes the depths of many subglacial lakes are of the order of 10 s 100 s of metres the total volume of water held beneath the ice sheet is estimated between 4000 and 12 000 km3 to date there are six known examples of radio echo reflections from the lake floors at a depth of no more than 20 m since e m attenuation through water is related to the salinity these data indicate that subglacial water is very pure and fresh some near flat surface regions that usually occur over lakes have been observed where no lakes exist such features are may be caused by water saturated basal sediments rather than subglacial lakes finally the spatial variation in geothermal heat flux around the central regions of antarctica can be established estimated by employing a simple thermal model of the ice sheet under an assumption that the basal ice temperature above subglacial lakes is equal to the pressure melting value calculations indicate that the geothermal heat flux varies spatially over the antarctic plate between 37 and 65 mw m 2

a new model of the petroleum system in the northern apennines italy a geochemical study on fluids from selected spontaneous seepages and drilled wells was carried out together with geologic investigation and deep cross sections reconstruction to examine the petroleum system in the western northern apennines foothills the hydrocarbons occurring in the miocene foredeep units that form the reservoirs are commonly interpreted as generated in a source reservoir system however the low total organic carbon its elevated dilution in the sediment pile and the limited amount of successions that entered in the oil window indicate a low potential for the hydrocarbons generation the structures deformation in the northern apennines foothills is mainly late miocene to pliocene in age and involves successions that are progressively younger towards southeast the earlier structure forms the salsomaggiore anticline in the western sector the comparison of the fluids from the wells and the mud volcanoes shows high geochemical and thermal history similarities saline waters originate from the connate pore water entrapped in the miocene reservoir rocks during their deposition the gaseous hydrocarbons are a mixture of secondary biogenic methane and primary and secondary thermogenic gases the associated oils show both early and late maturities these evidences account for different generation and migration steps depending on burial conditions and deformation time the various reservoirs appear confined by the thrust detachment at different depths and by the occurrence of reactivated lateral ramps these results suggest the occurrence of a common source rock deeper than the tertiary reservoir units which progressively entered in the oil window this source rock could have wide lateral extension at least comparable with the width of the studied area and represent a prime exploration target to evaluate the undiscovered oil and gas resources

formation of recent martian debris flows by melting of near surface ground ice at high obliquity the observation of small gullies associated with recent surface runoff on mars has renewed the question of liquid water stability at the surface of mars the gullies could be formed by groundwater seepage from underground aquifers however observations of gullies originating from isolated peaks and dune crests question this scenario we show that these landforms may result from the melting of water ice in the top few meters of the martian subsurface at high obliquity our conclusions are based on the analogy between the martian gullies and terrestrial debris flows observed in greenland and numerical simulations that show that above freezing temperatures can occur at high obliquities in the near surface of mars and that such temperatures are only predicted at latitudes and for slope orientations corresponding to where the gullies have been observed on mars

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

morphometric evidence of 3 6 ga glacial valleys and glacial cirques in martian highlands south of terra sabaea abstract the climate of early mars remains unclear and the debate is topical recently climatic models have suggested a cold climate during the noachian early hesperian on mars which goes against the wet and warm climate often put forward the purpose of this study is to seek geomorphologic evidence of this early cold climate to achieve this a step by step study of the geometry and morphology of several martian valleys has been done in the southern highlands the analysis highlights the morphometric properties which enable the identification of martian glacial landscapes we identified 100 cirques and 83 glacial valleys in two craters and on one mountain in the southern part of terra sabaea the studied morphologies have the same morphometric characteristics and trends as terrestrial and martian glacial valleys and glacial cirques in contrary these trends are very different from those observed in fluvial valleys on earth and on mars 1 the martian glacial valleys are u shaped with a large flat floor and a v index 0 20 while martian and terrestrial fluvial valleys are v shaped with a v index 1 while for fluvial valleys this ratio is 1 3 finally the cross sectional area and the elevation are higher for the glacial valleys compared to the fluvial ones these glacial valleys often originate with a topographic hollow which have the same properties than terrestrial glacial cirque the glacial landscapes identified in southern terra sabaea are restricted to elevations 1000 m and are dated by crater counting to be 3 6 ga this study strongly supports glacial processes as the origin of these valleys and cirques and is the first morphometric evidence of glacial valleys associated with glacial cirques in the southern highlands in agreement with the climatic models we propose that the martian climate during the late noachian early hesperian was characterized by glaciated highlands at elevations 1500 m and at lower elevations where fluvial valley network has been identified

northern mid latitude glaciation in the late amazonian period of mars criteria for the recognition of debris covered glacier and valley glacier landsystem deposits lobate debris aprons lda and lineated valley fill lvf have been known to characterize the mid latitude regions of mars since documented by viking their flow like character suggested that deposition of ice in talus pile pore space caused lubrication and flow during an earlier climatic regime a number of factors have remained uncertain however including the detailed structure and texture of lda lvf the relationships between them their direction of flow the origin and abundance of the lubricating agent and their exact mode of origin e g ice assisted rock creep ice rich landslides rock glaciers debris covered glaciers we use new high resolution stereo camera hrsc image and topography data in conjunction with a range of other post viking data sets and new insights provided by cold based terrestrial glacial analogs to assess the characteristics of lda lvf in the northern mid latitudes of mars we find evidence that the characteristics and flow patterns of the lda and lvf are most consistent with late amazonian debris covered glacial valley landsystems the broad distribution and integrated characteristics of the lda lvf systems suggest that earlier in the amazonian climatic conditions were such that significant snow and ice accumulated on mid latitude plateaus and in valleys producing integrated glacial landsystems the remnants of which are preserved today beneath residual sublimation till derived from adjacent valley walls atmospheric general circulation models suggest that these climatic conditions occurred when mars was at a spin axis obliquity of 35 and the atmosphere was relatively dusty glacial flow modeling under these conditions produces patterns similar to those documented in the lda lvf and sharad radar data suggests that significant amounts of ice remain sequestered below the sublimation lag today

former extent of glacier like forms on mars abstract mars mid latitude glacier like forms glfs have undergone substantial mass loss and recession since a hypothesised last martian glacial maximum lmgm stand to date there is a lack of knowledge of the nature and timing of the lmgm the subsequent mass loss and whether this mass loss has been spatially variable here we present the results of a population scale inventory of recessional glfs derived from analysis of 1293 glfs 3 identified within context camera ctx imagery to assess the distribution and controls on glf recession a total of 436 glfs were identified showing strong evidence of recession 197 in the northern hemisphere and 239 in the southern hemisphere relative to their parent populations recessional glfs are over represented in the low latitude belts between 25 and 40 and in areas of high relief suggesting that these zones exert some control over glf sensitivity and response to forcing this analysis is complemented by the reconstruction of the maximum extent and morphology of a specific glf for which high resolution imaging science experiment hirise derived digital elevation data are available using nye s nye j f 1951 proc roy soc lond ser a mat phys sci 207 554 572 perfect plastic approximation of ice flow applied to multiple flow lines under an optimum yield strength of 22 kpa we calculate that the reconstructed glf has lost an area of 6 86 km 2 with a corresponding volume loss of 0 31 km 3 since the lmgm assuming the loss reconstructed at this glf occurred at all mid latitude glfs yields a total planetary ice loss from mars glfs of 135 km 3 similar to the current ice volume in the european alps on earth

present day impact cratering rate and contemporary gully activity on mars the mars global surveyor mars orbiter camera has acquired data that establish the present day impact cratering rate and document new deposits formed by downslope movement of material in mid latitude gullies on mars twenty impacts created craters 2 to 150 meters in diameter within an area of 21 5 106 square kilometers between may 1999 and march 2006 the values predicted by models that scale the lunar cratering rate to mars are close to the observed rate implying that surfaces devoid of craters are truly young and that as yet unrecognized processes of denudation must be operating the new gully deposits formed since august 1999 are light toned and exhibit attributes expected from emplacement aided by a fluid with the properties of liquid water relatively long extended digitate distal and marginal branches diversion around obstacles and low relief the observations suggest that liquid water flowed on the surface of mars during the past decade

the formation and evolution of youthful gullies on mars gullies as the late stage phase of mars most recent ice age gullies are extremely young erosional depositional systems on mars that have been carved by an agent that was likely to have been comprised in part by liquid water malin m c edgett k s 2000 evidence for recent groundwater seepage and surface runoff on mars science 288 2330 2335 mcewen a s et al 2007 a closer look at water related geologic activity on mars science 317 1706 1709 the strong latitude and orientation dependencies that have been documented for gullies require 1 a volatile near the surface and 2 that insolation is an important factor for forming gullies these constraints have led to two categories of interpretations for the source of the volatiles 1 liquid water at depth beneath the melting isotherm that erupts suddenly groundwater and 2 ice at the surface or within the uppermost layer of soil that melts during optimal insolation conditions surface near surface melting in this contribution we synthesize global hemispheric regional and local studies of gullies across mars and outline the criteria that must be met by any successful explanation for the formation of gullies we further document trends in both hemispheres that emphasize the importance of top down melting of recent ice rich deposits and the cold trapping of atmospherically derived h 2o frost snow as important components in the formation of gullies this provides context for the incorporation of high resolution multi spectral and hyper spectral data from the mars reconnaissance orbiter that show that 1 cold trapping of seasonal h 2o frost occurs at the alcove channel level on contemporary mars 2 gullies are episodically active systems 3 gullies preferentially form in the presence of deposits plausibly interpreted as remnants of the late amazonian emplacement of ice rich material and 4 gully channels frequently emanate from the crest of alcoves instead of the base showing that alcove generation is not necessarily a product of undermining and collapse at these locations a prediction of the groundwater model we interpret these various lines of evidence to mean that the majority of gullies on mars are explained by the episodic melting of atmospherically emplaced snow ice under spin axis orbital conditions characteristic of the last several myr

an inventory and population scale analysis of martian glacier like forms abstract martian glacier like forms glfs indicate that water ice has undergone deformation on the planet within its recent geological past but the driving mechanisms behind the origin evolution and dynamics of these landforms remain poorly understood here we present the results of a comprehensive inventory of glfs derived from a database of 8058 context camera ctx images to describe the physical controls on glf concentration and morphometry the inventory identifies 1309 glfs 727 glfs in the northern hemisphere and 582 in the southern hemisphere clustered in the mid latitudes centred on a mean latitude of 39 3 in the north and 40 7 in the south and in areas of rough topography morphometric data show inter hemispheric similarity in glf length mean 4 66 km and width mean 1 27 km suggesting a common evolutionary history and a poleward orientation of glfs in both hemispheres indicating a sensitivity to climate and insolation on a local scale elevation is shown to be the most important control on glf location with most glfs occurring above an altitude threshold of 3000 m aod and in areas of moderate but not high relief we propose therefore that martian glfs may not exhibit accumulation or ablation areas as is the norm for terrestrial glacial systems but reflect ice motion in response to local relief within a widely distributed reservoir of ice deposited within prescribed latitudinal and elevational ranges

glacial and gully erosion on mars a terrestrial perspective the mid to high latitudes of mars host assemblages of landforms consistent with a receding glacial landscape on earth these landforms are postulated to have formed 5 ma under a different climate regime when mars orbital obliquity was on average 10 higher than today here we investigate the spatiotemporal relationship between gullies and glacial landforms both common in the mid latitudes gullies are kilometre scale landforms with a source alcove transportation channel and depositional apron the glacial landforms comprise 1 extant viscous flow features vff that extend from the base of crater walls into the interior of crater floors and are widely interpreted as debris covered glaciers containing extant ice and 2 landforms such as arcuate ridges at the base of crater walls that have been interpreted as relicts of more recent less extensive glacial advances focussed on crater walls we measure headwall retreat associated with glacial landforms and date their host craters to constrain minimum headwall retreat rates we record headwall retreat rates up to 102 m my 1 for the youngest suite of glacial landforms equivalent to erosion rates of wet based glaciers on earth and to headwall retreat rates associated with martian bedrock gully systems we find extensive evidence for a single erosional episode dating 5 10 ma which postdates emplacement of the majority of vff but seems to predate formation of the gullies we propose that the wet based glacial episode was associated with glaciation focussed on the crater walls rather than melting of the glacial ice deposits on the crater floors vff this is consistent with our observations of crater wall morphologies including the presence of arcuate ridges consistent with terrestrial glaciotectonic features that require liquid water to form textural alteration of the eroded bedrock surface consistent with ice segregation and frost shattering and the presence of downslope pasted on terrain tentatively interpreted here as glacial till deposits sourced from glacial erosion of the crater wall the pasted on terrain is usually interpreted as a thicker latitude dependant mantle located on sloping terrain formed from airfall of ice nucleated on dust but we suggest that it has been reworked by glaciation and is predominantly glacial in origin although our results cannot substantiate that gullies are produced by meltwater the discovery of this wet glacial event does provide evidence for widespread meltwater generation in mars recent history

martian cratering 8 isochron refinement and the chronology of mars abstract this paper reviews and refines the technique of dating martian surfaces by using impact crater isochrons defined as size distributions of impact craters on undisturbed martian surfaces of specified ages in the 1970s this system identified not only abundant ancient martian volcanic surfaces but also extensive lava plains with ages of a few 108 y old this dating was initially controversial but confirmed in the 1980s and 90s by martian meteorites the present update utilizes updated estimates of the mars moon cratering ratio the most important calibration factor improves treatment of gravity and impact velocity scaling effects combines aspects of the crater size distribution data from earlier work by both neukum and hartmann and for the first time applies a correction for loss of small meteoroids in the martian atmosphere from popova et al 2003 meteorit planet sci 38 905 925 the updated isochrons are not radically different from the previous 2002 iteration but fit observed data better and give somewhat older model ages for features dated from small craters diameter d 100 m crater counts from young lava flows in various areas give good fits to the new isochrons over as much as 3 orders of magnitude in d confirming the general isochron shape and giving crater retention ages in the range of some 106 to some 108 y interpreted as lava flow ages more complex older units are also discussed uncertainties are greatest if only small craters d 100 m are used suggestions by other workers of gross uncertainties due to local secondary craters and deposition exhumation are discussed they do not refute our conclusions of significant volcanic fluvial and other geologic activity in the last few percent of martian geologic time or the importance of cratering as a tool for studying processes such as exhumation indeed crater count data suggest certain very recent episodes of deposition exhumation and ice flow possibly associated with obliquity cycles of 10 7 y timescale evidence from ancient surfaces suggests higher rates of volcanism fluvial activity glaciation and other processes in noachian hesperian time than in amazonian time

formation of glaciers on mars by atmospheric precipitation at high obliquity surface conditions on mars are currently cold and dry with water ice unstable on the surface except near the poles however geologically recent glacierlike landforms have been identified in the tropics and the midlatitudes of mars the ice has been proposed to originate from either a subsurface reservoir or the atmosphere we present high resolution climate simulations performed with a model designed to simulate the present day mars water cycle but assuming a 45 obliquity as experienced by mars a few million years ago the model predicts ice accumulation in regions where glacier landforms are observed on the western flanks of the great volcanoes and in the eastern hellas region this agreement points to an atmospheric origin for the ice and reveals how precipitation could have formed glaciers on mars

mineralogy geochemistry and petrography of methane derived authigenic carbonates from enza river northern apennines italy abstract a remarkable exposure of carbonate pipe like and slab concretions occurs along the enza riverbanks on the northern apennines foothills italy based upon geochemical and field evidences their genesis has been attributed to microbial governed carbonate precipitation from hydrocarbon enriched fluids the pipe like concretions are thus interpreted as former conduits chimneys marking sites of methane ascent onto the seafloor the resulting enza river chimney field is arranged in a palisade fashion a rare example of such mineralogical and petrographic analyses of some chimneys and slabs document that the dominant cement is dolomite although the chimneys show a rather homogeneous texture a clear zonation is observed in the relative distribution of major and minor elements in their internal and external parts the occurrence of sulphide minerals in the stratigraphically upper samples indicates possible renewal of fluids leakage after a major erosive event

high resolution imaging science experiment hirise observations of glacial and periglacial morphologies in the circum argyre planitia highlands mars 1 the landscape of the argyre planitia and adjoining charitum and nereidum montes in the southern hemisphere of mars has been heavily modified since formation of the argyre impact basin this study examines morphologies in the argyre region revealed in images acquired by the high resolution imaging science experiment hirise camera and discusses the implications for glacial and periglacial processes distinctive features such as large grooves semicircular embayments in high topography and streamlined hills are interpreted as glacially eroded grooves cirques and whalebacks or roche moutonnee respectively large boulders scattered across the floor of a valley may be ground moraine deposited by ice ablation glacial interpretations are supported by the association of these features with other landforms typical of glaciated landscapes such as broad valleys with parabolic cross sections and stepped longitudinal profiles lobate debris aprons interpreted as remnant debris covered glaciers or rock glaciers and possible hanging valleys aligned boulders observed on slopes may also indicate glacial processes such as fluting alternatively boulders aligned on slopes and organized in clumps and polygonal patterns on flatter surfaces may indicate periglacial processes perhaps postglaciation that form patterned ground at least portions of the argyre region appear to have been modified by processes of ice accumulation glacial flow erosion sediment deposition ice stagnation and ablation and perhaps subsequent periglacial processes the type of bedrock erosion apparent in images suggests that glaciers were at times wet based the number of superposed craters is consistent with geologically recent glacial activity but may be due to subsequent modification

genesis of hummocky moraines by thrusting in glacier ice evidence from svalbard and britain irregular mounds of glacial debris commonly referred to as 9hummocky moraine9 until recently were linked to ice stagnation during rapid climatic amelioration however recent work in scotland has demonstrated that some hummocky moraine dating from the younger dryas event c 10 000 years bp was the product of deposition at active ice margins observations at modern high arctic glacier margins in svalbard 76 80 n indicate that some moraines of this type form under a dynamic glaciological regime mainly by thrusting in active polythermal ice undergoing strong longitudinal compression this situation is particularly common where there is a transition from warm based ice in the interior of a glacier to cold based ice at the margins or snout from their morphological similarity rectilinear slopes facing up glacier and irregular downglacier faces and apparent stacking of slabs of sediment of subglacial derivation it is concluded that some assemblages of british moraines are also the product of thrusting this process appears to be most dominant in polythermal glaciers rather than in temperate glaciers on this basis it is tentatively suggested that the younger dryas in britain was characterized by a climatic regime similar to that in svalbard today mean annual temperature 5 c 400 1000 mm precipitation and that the associated glaciers may have been of polythermal character

ultrahigh resolution topographic mapping of mars with mro hirise stereo images meter scale slopes of candidate phoenix landing sites 1 the objectives of this paper are twofold first to report our estimates of the meter to decameter scale topography and slopes of candidate landing sites for the phoenix mission based on analysis of mars global surveyor mgs mars orbiter camera moc images with a typical pixel scale of 3 m and mars reconnaissance orbiter mro high resolution imaging science experiment hirise images at 0 3 m pixel 1 and second to document in detail the geometric calibration software and procedures on which the photogrammetric analysis of hirise data is based a combination of optical design modeling laboratory observations star images and mars images form the basis for software in the u s geological survey integrated software for imagers and spectrometers isis 3 system that corrects the images for a variety of distortions with single pixel or subpixel accuracy corrected images are analyzed in the commercial photogrammetric software socet set bae systems yielding digital topographic models dtms with a grid spacing of 1 m 3 4 pixels that require minimal interactive editing photoclinometry yields dtms with single pixel grid spacing slopes from moc and hirise are comparable throughout the latitude zone of interest and compare favorably with those where past missions have landed successfully only the mars exploration rover mer b site in meridiani planum is smoother moc results at multiple locations have root mean square rms bidirectional slopes of 0 8 4 5 at baselines of 3 10 m hirise stereopairs one per final candidate site and one in the former site yield 1 8 2 8 slopes at 1 m baseline slopes at 1 m from photoclinometry are also in the range 2 3 after correction for image blur slopes exceeding the 16 phoenix safety limit are extremely rare

cold based mountain glaciers on mars western arsia mons surface environmental conditions on mars are currently extremely cold and hyperarid most equivalent to polar deserts on earth coupling newly acquired mars data with fieldbased observations regarding the flow surface morphology and depositional history of polar glaciers in antarctica we show that the multiple facies of an extensive fan shaped deposit on the western flanks of arsia mons volcano are consistent with deposition from cold based mountain glaciers an outer ridged facies that consists of multiple laterally extensive arcuate and parallel ridges resting without disturbance on both well preserved lava flows and an impact crater is interpreted as drop moraines formed at the margin of an ablating and predominantly receding cold based glacier a knobby facies that consists of equidimensional knobs each to several kilometers in diameter is inward of the ridges this facies is interpreted as a sublimation till derived from in situ downwasting of ashrich glacier ice a third facies comprising distinctive convex outward lobes with concentric parallel ridges and aspect ratios elongated downslope likely represents rock glacier deposits some of which may still be underlain by a core of glacier ice taken together these surficial deposits show that the western flank of arsia mons was occupied by an extensive mountain glacial system accumulating on and emerging from the upper slopes of the volcano and spreading downslope to form a piedmont like fan

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

sedimentary facies and landform genesis at a temperate outlet glacier soler glacier north patagonian icefield glasser n f hambrey m j 2002 sedimentary facies and landform genesis at a temperate outlet glacier soler glacier north patagonian icefield 49 1 43 64

controls on authigenic carbonate precipitation at cold seeps along the convergent margin off costa rica five sediment cores from cold seeps at the forearc off costa rica were used to explore the relationship between fluid advection dissolved ca concentrations in upward migrating fluids and authigenic caco3 precipitation a numerical transport reaction model was used to determine rates of anaerobic oxidation of methane aom caco3 precipitation and benthic fluxes of solutes production of carbonate alkalinity and formation of authigenic carbonates is most intense at intermediate flow rates 3 40 cm a 1 and reduced under low and high flux conditions 0 1 and 200 cm a 1 dissolved ca concentrations observed in the vent fluids off costa rica cover a wide range between 4 and 31 mm clearly exceeding seawater concentrations at two locations systematic model runs showed that high ca concentrations in ascending fluids enhance the rate of authigenic carbonate production at moderate flow rates leading to an almost quantitative fixation of deeply derived ca in authigenic carbonates hence caco3 precipitation is not only controlled by ca diffusing into the sediment from bottom water but also by the ca concentration in ascending fluids thus ca enriched fluids offer a reason for enhanced subsurface caco3 precipitation and the occurrence of carbonate caps on dewatering structures in the central american fore arc based on average precipitation rates deduced from the systematic model runs it is possible to give a rough estimate of the global ca fixation at cold seeps 2 1010 mol ca a 1 which suggests that cold seeps are most likely not of key importance with respect to ca cycling in the ocean

area and volume of mid latitude glacier like forms on mars abstract although a substantial ice cover has been identified within the mid latitudes of mars there is uncertainty regarding the formation current and former volume and dynamic evolution of these ice masses here we present the first comprehensive ice volume estimate of martian glacier like forms glfs from systematic population scale mapping and volumetric analysis the outlines of 1243 glfs were manually delineated from 6 m per pixel context camera ctx images and the volume of each determined using a volume area scaling approach our results show that glfs cover a surface area of 11344 393 km2 and have a total volume of 1744 441 km3 using two end member scenarios for ice concentration by volume of 30 pore ice and 90 debris covered glacier ice we calculate the volume of ice contained within glfs to be between 523 132 km3 480 121 gt and 1570 397 km3 1439 364 gt equivalent to a mean global water layer 3 to 10 mm thick we investigate the local topographic setting of each glf by reference to the mars orbiter laser altimeter mola digital elevation model our analysis reveals that globally glfs are on average larger in latitudes 36 and on slopes between 2 and 8 in the northern hemisphere glfs between 500 and 2500 m in elevation and in the southern hemisphere glfs with a northern aspect are also larger on average the observed spatial patterns of glf landform and volume distribution suggests that regional to local meteorological and topographical conditions play an important role in glf ice accumulation and or preservation assuming a net accumulation rate of 10 mm a 1 typical of climatic excursions with high obliquity we estimate a period of at least 13 ka is required to yield the average calculated glf ice thickness of 130 m such a period is well within the timeframe of a high obliquity cycle 20 40 ka suggesting that the current glf volume could have formed during a single climate excursion

calcarenite and sapropel deposition in the mediterranean pliocene shallow and deep water record of astronomically driven climatic events introductionsapropelformationinthemediterra nean basin during the pliocene andquaternary has been widely debated the time and phase relationship ofsapropels to astronomic cycles hasbeen established and a high reso lution sapropel based astronomictime scale has been reconstructedfor mediterranean neogene deposits e g hilgen 1991 lourens etal 1996 hilgenetal 1999 sapropels provide a deep water basin wide record of astronomicallydriven climatic events they occur asindividualcyclesthatcanbecorrelatedtoprecessionalminima 19 23kyr orassmall andlarge scaleclusters 100 400kyr withmoredevelopedindivid ualsapropels correspondingtoeccen tricity maxima obliquity 41kyr controls the thin thick pattern ofcyclicity e g lourens etal 1996 pliocene large scale sapropel clustersfollowmajorcoolingeventsreferredtoas the forerunners of the quaternarynorthern hemisphere glaciation keigwin 1987 raymo etal 1989 tiedemann etal 1994 rio et al 1997 these events dated at 3 1 2 7and 2 1ma are recorded in themediterranean basins by importantmicro and macrofaunal turnovers monegattiandra 2001 palaeoceanographic events relatedto sapropel formation have usuallybeen studied from a deep water per spective theirshallow waterrecordisless well known the stratigraphicarchitectureofplioceneshallow waterdepositsoftheapennine maghrebianbasins is frequently characterized bythe rhythmic alternation of coarse grained calcarenites and siliciclasticmudstones our observations suggestthat calcarenites are not randomlydistributed in the stratigraphic col umn but they occur in well de nedtimeslicesstartingfrom3 1ma theycanbetracedthroughdi erentgeody namicsettings suggestinganin uenceof climatic and or eustatic forcing individual calcarenites occur in clus tershavingthesameageaslong termsapropelclusters thiscorrelationsug gests that tightly linked factors con trolledtheformationofbothdeposits this paper documents the large scale 10

ancient glaciation on mars a large number of anomalous landforms on mars can be attributed to glaciation including the action of ice and meltwater glacial landscapes are concentrated south of lat 33 and in the northern plains suggesting vast austral and boreal ice sheets crater densities on the glaciated terrains indicate that the final glacial epoch occurred late in martian history thus mars may have had a relatively warm moist climate and dense atmosphere much later than previously believed

an alternative interpretation of late amazonian ice flow protonilus mensae mars abstract the morphological properties of glacial deposits located within a cirque like alcove in eastern protonilus mensae mars mars grid reference 54 55 lon 40 80 lat have been interpreted as indicative of an early phase of glaciation involving ice flowing out from the main glacierized valley and into a higher elevation box canyon or alcove this interpretation implies that the elevation of the glacial deposits currently located within the alcove mark a minimum former ice elevation in this catchment providing a regional datum for former ice thicknesses with implications for martian climate reconstruction here we raise the possibility of an alternative interpretation detailed geomorphological mapping and evaluation of the deposits remaining within the alcove suggest that they may have been formed by the more conventional mechanism of ice flowing out from the alcove and not into it both small scale and catchment scale morphologies allied to the site s location and orientation within an otherwise conventionally glacierized catchment are consistent with outbound flow this alternative hypothesis has important implications for ice thicknesses both in the local area and by extension regionally

grid mapping the northern plains of mars geomorphological radar and water equivalent hydrogen results from arcadia plantia a project of mapping ice related landforms was undertaken to understand the role of sub surface ice in the northern plains this work is the first continuous regional mapping from ctx context camera 6 m pixel malin et al 2007 imagery in arcadia planitia along a strip 300 km across stretching from 30 n to 80 n centred on the 170 west line of longitude the distribution and morphotypes of these landforms were used to understand the permafrost cryolithology the mantled and textured signatures occur almost ubiquitously between 35 n and 78 n and have a positive spatial correlation with inferred ice stability based on thermal modelling neutron spectroscopy and radar data the degradational features into the ldm latitude dependent mantle include pits scallops and 100 m polygons and provide supporting evidence for sub surface ice and volatile loss between 35 70 n in arcadia with the mantle between 70 78 n appearing much more intact pitted terrain appears to be much more pervasive in arcadia than in acidalia and utopia suggesting that the arcadia study area had more wide spread near surface sub surface ice and thus was more susceptible to pitting or that the ice was less well buried by sediments correlations with ice stability models suggest that lack of pits north of 65 70 n could indicate a relatively young age 1ma however this could also be explained through regional variations in degradation rates the deposition of the ldm is consistent with an airfall hypothesis however there appears to be substantial evidence for fluvial processes in southern arcadia with older underlying processes being equally dominant with the ldm and degradation thereof in shaping the landscape

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

martian flow features moraine like ridges and gullies terrestrial analogs and interrelationships ridges that resemble terrestrial moraines are commonly visible at the foot of many mid latitude crater walls in mars global surveyor mars orbiter camera images these moraine like ridges are often associated with hillside gullies mantling material and glacier like flows and are usually in contact with crater fill suggesting possible interrelationships we consider terrestrial glacier systems that may be analogs of martian moraine like ridges and glacier like flows and suggest that the formation of some gullies and crater fill is intimately tied to ice deposition ice flow and rock glacier processes upper limits on age suggest the possibility that many of these features formed during the last or last few high obliquity cycles

possible open system hydraulic pingos in and around the argyre impact region of mars abstract we report the observation of possible hydraulic open system pingos osps at the mid latitudes 37 s in and around the argyre impact basin osps are perennial water ice cored mounds they originate and evolve in periglacial and pro glacial landscapes on earth where intra or sub permafrost water under hydraulic artesian pressure uplifts localised sections of surface or near surface permafrost that then freezes in situ we invoke three lines of evidence in support of our analogue based interpretation 1 similarities of shape size and summit traits between terrestrial osps and the martian mounds 2 clustered distribution and the slope side location of the mounds consistent with terrestrial permafrost environments where osps are found and 3 spatially associated landforms putatively indicative of periglacial and glacial processes on mars that characterise osp landscapes on earth this article presents five osp candidate locations and nests these mound locations within a new geological map of the argyre impact basin and margins it also presents three periglacial hypotheses about the possible origin of the water required to develop the mounds alternative non periglacial formation hypotheses also are considered however we show that their robustness is not equal to that of the periglacial ones