boulder movement at high northern latitudes of mars 1 we examine a narrow latitudinal band 60 n 70 n on mars to place constraints on the seasonally averaged velocity q of boulder movements over patterned ground these latitudes comprise a region of the northern lowlands where patterned ground covers nearly every surface here boulders meters in diameter are consistently found to be concentrated at or near the cracks that define the polygonal networks indicating a mobilization process because impact craters are the source for many boulders we can use craters and their degradation to estimate the time scales for boulder movement we study and catalog 1018 degraded impact craters 100 m d 1 km in 55 high resolution imaging science experiment hirise images we find that crater degradation occurs on a time scale 1 ma which is too recent for melting related mechanisms in a past warmer epoch clustering of boulders occurs at a time scale of a few ma or shorter which means that boulders on 5 20 m diameter polygons move at seasonal velocities q 1 10 m yr or faster

formation of patterned ground and sublimation till over miocene glacier ice in beacon valley southern victoria land antarctica a thin glacial diamicton informally termed granite drift occupies the floor of central beacon valley in southern victoria land antarctica this drift is 40 ar 39 ar analyses of presumed in situ ash fall deposits that occur within granite drift at odds with the great age of this ice are high centered polygons that cut granite drift if polygon development has reworked and retransported ash fall deposits then they are untenable as chronostratigraphic markers and cannot be used to place a minimum age on the underlying glacier ice our results show that the surface of granite drift is stable at polygon centers and that enclosed ash fall deposits can be used to define the age of underlying glacier ice in our model for patterned ground development active regions lie only above polygon troughs where enhanced sublimation of underlying ice outlines high centered polygons the rate of sublimation is influenced by the development of porous gravel and cobble lag deposits that form above thermal contraction cracks in the underlying ice a negative feedback associated with the development of secondary ice lenses at the base of polygon troughs prevents runaway ice loss secondary ice lenses contrast markedly with glacial ice by lying on a d versus 18 o slope of 5 rather than a precipitation slope of 8 and by possessing a strongly negative deuterium excess the latter indicates that secondary ice lenses likely formed by melting downward percolation and subsequent refreezing of snow trapped preferentially in deep polygon troughs the internal stratigraphy of granite drift is related to the formation of surface polygons and surrounding troughs the drift is composed of two facies a nonweathered matrix supported diamicton that contains 25 striated clasts in the 16 mm fraction and a weathered clast supported diamicton with varnished and wind faceted gravels and cobbles the weathered facies is a coarse grained lag of granite drift that occurs at the base of polygon troughs and in lenses within the nonweathered facies the concentration of cosmogenic 3 he in dolerite cobbles from two profiles through the nonweathered drift facies exhibits steadily decreasing values and shows the drift to have formed by sublimation of underlying ice these profile patterns and the 3 he surface exposure ages of 1 18 0 08 ma and 0 18 0 01 ma atop these profiles indicate that churning of clasts by cryoturbation has not occurred at these sites in at least the past 10 5 and 10 6 yr although granite drift is stable at polygon centers low frequency slump events occur at the margin of active polygons slumping together with weathering of surface clasts creates the large range of cosmogenic nuclide surface exposure ages observed for granite drift maximum rates of sublimation near active thermal contraction cracks calculated by using the two 3 he depth profiles range from 5 m m y to 90 m m y sublimation rates are likely highest immediately following major slump events and decrease thereafter to values well below our maximum estimates nevertheless these rates are orders of magnitude lower than those computed on theoretical grounds during eruptions of the nearby mcmurdo group volcanic centers ash fall debris collects at the surface of granite drift either in open thermal contraction cracks or in deep troughs that lie above contraction cracks these deposits subsequently lower passively as the underlying glacier ice sublimes the fact that some regions of granite drift have escaped modification by patterned ground for at least 8 1 ma indicates long term geomorphic stability of individual polygons once established polygon toughs likely persist for as long as 10 5 10 6 yr our model of patterned ground formation which applies to the hyperarid cold desert polar climate of antarctica may also apply to similar sized polygons on mars that occur over buried ice in utopia planitia

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

martian gullies in the southern mid latitudes of mars evidence for climate controlled formation of young fluvial features based upon local and global topography a new survey of mars orbiter camera moc narrow angle images of gullies in the 30 45 s latitude band includes their distribution morphology local topographic setting orientation elevation and slopes these new data show that gully formation is favored over a specific range of conditions elevation 5000 to 3000 m slope 10 and orientation 83 8 on pole facing slopes these data and the frequent occurrence of gullies on isolated topographic highs lead us to support the conclusion that climatic related processes of volatile accumulation and melting driven by orbital variations are the most likely candidate for processes responsible for the geologically recent formation of martian gullies

hydraulic modeling of the tributary and the outlet of a martian paleolake located in the memnonia quadrangle we present a steady state hydraulic model of the tributary and the outlet of a martian paleolake located in the memnonia quadrangle between 167 0 0 w and 167 30 0 w longitude and between 9 25 0 s and 9 45 0 s latitude the mars express high resolution stereo camera hrsc digital elevation model h31850000da4 with a spatial resolution of 75 m is used to describe the geometrical features of the hydraulic system a steady state hydraulic model through a monte carlo procedure is adopted to investigate the assumption that the tributary lake outlet hydraulic system was acting simultaneously during its last water related evolutionary phase through our analysis we infer the roughness coefficient and the discharge of both the tributary and the outlet channels geomorphic evidence such as river terraces were used to constrain the water discharge and the manning s roughness coefficient thereby obtaining estimates of the water level in the lake during the last evolutionary phase of the system our analysis of the outlet reveals a median paleodischarge of 7135 m3 s 1 and a median manning s roughness coefficient of 0 067 m 1 3 s tributary analysis provides a median flow and a median roughness coefficient of 6405 m3 s 1 and 0 123 m 1 3 s respectively moreover the hydraulic analysis suggests that the paleolake water surface level was 1397 m median value hrsc elevation which is consistent with the observed paleoshoreline the results imply that the tributary the lake and the outlet were hydraulically synchronized therefore confirming the presence of a connected water system this study demonstrates that hydraulic analysis can provide valuable information regarding ancient martian water fluxes

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

distribution of polygon characteristic scale in martian patterned ground terrain in the northern hemisphere using the fourier transform 1 permafrost patterned ground forms on the surface of nearly all landscapes between 50 n and 70 n on mars this landform appears in satellite imagery as an interconnected network of polygonal shapes previous studies used geomorphologic observations to characterize patterned ground terrains on mars these classification systems prove useful but suffer from somewhat subjective methods we find objective analysis of the polygons comprising patterned ground terrains on the surface of mars feasible using high resolution imaging science experiment imagery acquired from orbit we perform a two dimensional fourier transform on 124 images of patterned surfaces to characterize the spatial scale pertinent to scenes and analyze the distribution of these properties on the surface of mars between 50 n and 70 n we find two distinct sets of polygons large polygons which form below 60 n and small polygons primarily above 60 n with exception for sites within acidalia planitia our findings show similar trends to those found in previous studies but also fundamental differences in the populations of polygons above and below 60 n the polygons within 60 n 70 n share roughly the same polygonal scale implying that seasonal temperature change is not the only factor forcing polygon development as previous models found in some cases our method indicates the presence of multiple scales of polygons although it cannot quantify the larger scale this method in conjunction with observational analysis improves our ability to characterize surfaces and examine patterned ground terrains on mars

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

orbital change experiments with a mars general circulation model abstract we use a mars general circulation model to examine the effect of orbital changes on the planet s general circulation and climate system experiments are performed for obliquities ranging from 0 to 60 for two different longitudes of perihelion each experiment simulates a full mars year assuming a fixed atmospheric dust distribution and fixed amount of co 2 in the atmosphere cap system we find that global mean surface temperatures and pressures decline with increasing obliquity due to the increasing extent of the winter polar caps the seasonal co 2 cycle and intensity of the solstice circulation amplify considerably with increasing obliquity such that global dust storms are likely at both solstices the most significant feature of the high obliquity solstice circulations is the development of an intense low level jet associated with the return branch of the hadley circulation model surface stresses are used to map regions of preferred dust lifting which are defined in terms of an annual deflation potential for the present obliquity the model predicted regions of high deflation potential are in good agreement with cantor et al s 2001 j geophys res 106 23653 23688 observations which gives us some confidence in the model s ability to predict where lifting might occur when mars orbit parameters are different than they are today in general we find that the dust lifting potential increases sharply with obliquity and is greatest at times of high obliquity when perihelion coincides with northern summer solstice over an obliquity cycle the model global annual deflation potential ranges from several tenths of a millimeter at 0 obliquity to almost 15 mm at 60 obliquity much higher values are possible when the atmosphere is very dusty we find a strong correlation between the deflation potential and surface thermal inertia regions of high deflation potential correspond to regions of high thermal inertia high rock abundance and regions of low deflation potential correspond to regions of low thermal inertia high dust sand abundance furthermore while the regions of preferred lifting high deflation potential expand somewhat with increasing obliquity and dust loading the central parts of tharsis arabia and elysium show no tendency for significant lifting at any obliquity or longitude of perihelion these regions may therefore be very old and represent net long term sinks for atmospheric dust it is the topography of the planet through its influence on surface pressure and wind systems which ultimately determines where dust accumulates finally as was found by fenton and richardson 2001 j geophys res 106 32885 32909 we find no tendency for the development of east southeasterly winds at the pathfinder site for any of our orbital change experiments this suggests that the ancient wind regime discussed by greeley et al 2000 j geophys res 105 1829 1840 was produced by other factors such as polar wander

sorted stone circles in elysium planitia mars implications for recent martian climate we have found sorted stone circles and polygons near the equator of mars using new 25 cm pixel nasa hirise high resolution imaging science experiment images the sorted circles occur in geologically recent catastrophic flood deposits in the equatorial elysium planitia region and are diagnostic of periglacial processes sorted polygons do not form from volcanic activity as has been suggested for non sorted polygons in this region these landforms indicate that i a long lived geologically recent active cryoturbation layer of ground ice was present in the regolith ii there was some degree of freeze thaw and thus iii there were sustained period s likely within the last 10 ma in which the martian climate was 40 to 60 k warmer than current models predict

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

sorted clastic polygons in the argyre region mars and possible evidence of pre and post glacial periglaciation in the late amazonian epoch abstract the argyre basin and associated rim materials in the southern highlands of mars are ancient having been formed by the impact of a large body 3 9 gya despite its age the regional landscape exhibits a wide range of geological geomorphological modifications and or features e g fluvial lacustrine aeolian glacial and periglacial collectively this bears witness to the dynamic evolution of the argyre region from the deep past through to perhaps the present day here we present three principal findings that point to at least two distinct episodes of periglaciation separated by a possible glacial interval during the very late amazonian epoch in eastern aonia terra at i e on the western flank of the argyre basin these findings are the product of our circum argyre study of all hirise images 35 65 s and 290 350 e 1 a the first periglacial episode involves the development of small sized 15 25 m in diam and clastically sorted polygons sps the sps are observed at eighteen locations within eastern at hitherto the presence of sps in this region has been reported at one location alone no other observations of sps in the southern hemisphere of mars have been documented morphologically similar landforms develop in cold climate permafrost landscapes on earth by means of periglacial processes i e freeze thaw cycling segregated ice formation cryoturbation and frost heave b we ascribe a periglacial origin to the sps in eastern at on the basis of this similarity of form and no less importantly on the close spatial association of the sps with blockfields whose weathered clastic products are the building blocks of periglacial sorting on earth gelifluction like lobes and possible wet gullies where similar assemblages occur in terrestrial permafrost landscapes the presence of liquid water and of boundary conditions tolerant of freeze thaw cycling are observed or inferred c fifteen of the eighteen sp locations are clustered longitudinally 44 4 57 5 s 289 9 302 4 e this is inconsistent with the latitudinal and obliquity driven dependency of freeze thaw cycling in the late amazonian epoch hypothesised by many workers in the discipline 2 the second periglacial episode is highlighted by the development of small sized and clastically non sorted polygons nsps these polygons could have formed by means of a dry cryotic process i e thermal contraction cracking 3 the nsps incise and thus postdate a light toned mantle thought by numerous workers to comprise an ice dust admixture at some of the locations where the putatively icy mantle has undergone apparent ablation underlying sps are observed this suggests that the sps predate the mantle and derivatively the nsps as well the proposed geochronology of wet based sp icy mantle dry based nsp periods and interval is entirely new to the community moreover it underlines the possibility that periglacial and glacial boundary conditions at least in our study area may have oscillated much more substantially in the very late amazonian epoch than many workers have thought possible

evidence from the mars express high resolution stereo camera for a frozen sea close to mars equator it is thought that the cerberus fossae fissures on mars were the source of both lava and water floods two to ten million years ago evidence for the resulting lava plains has been identified in eastern elysium but seas and lakes from these fissures and previous water flooding events were presumed to have evaporated and sublimed away here we present high resolution stereo camera images from the european space agency mars express spacecraft that indicate that such lakes may still exist we infer that the evidence is consistent with a frozen body of water with surface pack ice around 5 degrees north latitude and 150 degrees east longitude in southern elysium the frozen lake measures about 800 x 900 km in lateral extent and may be up to 45 metres deep similar in size and depth to the north sea from crater counts we determined its age to be 5 2 million years old if our interpretation is confirmed this is a place that might preserve evidence of primitive life if it has ever developed on mars

recent flood lavas in the elysium region of mars abstract a vast area of smooth plains in southeastern elysium here referred to as the cerberus formation is interpreted to be of volcanic origin surface morphology lobate edges of the unit the identification of vents low shields and the embayment relation of the unit with adjacent older units all suggest a volcanic origin the plains were formed by the eruption of low viscosity lavas that filled a topographic depression in southeast elysium and then flowed into western amazonis planitia flow into western amazonis was facilitated by a series of channels carved by an earlier fluvial episode which were exploited by lavas as they moved down slope crater frequencies and stratigraphic relations indicate that the unit is very young upper amazonian the presence of such young flood lavas indicates 1 late in martian history large scale eruptions of low viscosity lava was still possible b sufficient heat remained in the mantle to mobilize large quantities of magma and c flood volcanism either continued or resumed in elysium after activity of the large central volcanoes had ceased each of these points are important considerations in understanding the martian thermal and volcanic history

formation of gullies on mars link to recent climate history and insolation microenvironments implicate surface water flow origin features seen in portions of a typical midlatitude martian impact crater show that gully formation follows a geologically recent period of midlatitude glaciation geological evidence indicates that in the relatively recent past sufficient snow and ice accumulated on the pole facing crater wall to cause glacial flow and filling of the crater floor with debris covered glaciers as glaciation waned debris covered glaciers ceased flowing accumulation zones lost ice and newly exposed wall alcoves continued as the location for limited snow frost deposition entrapment and preservation analysis of the insolation geometry of this pole facing crater wall and similar occurrences in other craters at these latitudes on mars shows that they are uniquely favored for accumulation of snow and ice and a relatively more rapid exposure to warmer summer temperatures we show that after the last glaciation melting of residual snow and ice in alcoves could have formed the fluvial channels and sedimentary fans of the gullies recent modeling shows that top down melting can occur in these microenvironments under conditions similar to those currently observed on mars if small amounts of snow or frost accumulate in alcoves and channels accumulation and melting is even more favored in the somewhat wetter relatively recent geological past of mars after the period of active glaciation

black limestones used in antiquity the petrographic isotopic and epr database for provenance determination abstract we compiled a database of some of the most important black limestone quarries used in roman times to be able to determine the provenance of ancient artifacts for this purpose we adopted a multimethod approach using the techniques commonly applied to study the provenance of white marbles petrographic observations carbon and oxygen isotope composition electron paramagnetic resonance epr spectra characteristics few black limestones were quarried and traded in ancient times indeed the importance of most of these quarries was restricted to the areas in which they were located in this work we selected a limited number of quarries that produced material believed to have been exported and used throughout the mediterranean area most of the quarries selected are found in northern tunisia i e the roman proconsular africa djebel oust djebel azeiz ain al ksir and presumably thala the nero chiota limestone quarried on the aegean island of chios greece was also included in the database the petrographic and physicochemical parameters used to distinguish between the different provenances of the black limestones we selected proved to be very effective the isotope and epr numerical data processed by means of discriminant analysis proved to be almost decisive in determining the provenance of unknown artifacts however the combination of these parameters with the petrographic data definitely provides a more organic characterization

the distribution of putative periglacial landforms on the martian northern plains in this investigation hirise images were surveyed across three regions of the northern plains of mars acidalia arcadia and utopia planitiae a sample of hirise images within each of these areas was examined the aim of the investigation was to determine the distribution of three varieties of landform clastic patterned ground lobate hill slope features and scalloped depressions these features are of importance as they are morphologically similar to terrestrial periglacial features examples of these landforms were found across the study areas scalloped depressions are common at mid latitudes in each of the three regions sorted patterned ground was not as widespread some examples of sorted patterned ground were found in all three study areas but the main concentration occurs in the north western region of acidalia planitia lobate hill slope features were the least common of the three landform types despite occurring infrequently several possible examples of lobate features were found to occur in proximity to other putative periglacial features it was found that lobate hill slope features and clastic patterns occurred further south than expected beyond the southern extent of many previous studies these features and by extension the processes that form them could thus occur more widely than previously thought it also appears that although putative periglacial features are often found in crater interiors they are not limited to these environments extensive areas of patterned ground were found on the inter crater plains lobate features and sorted stripes were often found on crater walls which would support the hypothesis that they are analogous to hill slope features on earth scalloped depressions were most often found in crater interiors or on crater ejecta although examples on the inter crater plains were not uncommon

thermokarst lakes and ponds on mars in the very recent late amazonian past the history of water is fundamental to understanding the geological evolution of mars and to questions concerning the possible development of life on the red planet today mars is cold and dry it

fifty years of coastal erosion and retrogressive thaw slump activity on herschel island southern beaufort sea yukon territory canada abstract patterns of coastal erosion in the arctic differ dramatically from those coasts in more temperate environments thick sea ice and shore fast ice limit wave based erosional processes to a brief open water season however despite this permafrost coasts containing massive ice ice wedges and ice bonded sediments tend to experience high rates of erosion these high rates of erosion reflect the combined thermal mechanical processes of thawing permafrost melting ground ice and wave action climate change in the arctic is expected to result in increased rates of coastal erosion due to warming permafrost increasing active layer depths and thermokarst rising sea levels reduction in sea ice extent and duration and increasing storm impacts with the most ice rich permafrost in the canadian arctic the southern beaufort sea coast between the tuktoyaktuk peninsula and the alaskan border is subject to high rates of erosion and retrogressive thaw slump activity under many climate change scenarios this area is also predicted to experience the greatest warming in the canadian arctic this paper presents results of a remote sensing study on the long term patterns of coastal erosion and retrogressive thaw slump activity for herschel island in the northern yukon territory using orthorectified airphotos from 1952 and 1970 and an ikonos image from 2000 corrected with control points collected by kinematic differential global positioning system and processed using softcopy photogrammetric tools mean coastal retreat rates of 0 61 m yr and 0 45 m yr were calculated for the periods 1952 1970 and 1970 2000 respectively the highest coastal retreat rates are on north west facing shorelines which correspond to the main direction of storm related wave attack during the period 1970 2000 coastal retreat rates for south to south east facing shorelines displayed a distinct increase even though these are the most sheltered orientations however south to south east facing shorelines correspond to the orientations where the highest densities of retrogressive thaw slumps are observed differences in rates of headwall retreat of retrogressive thaw slumps and coastal erosion results in the formation of larger thermokarst scars and the development of polycyclic thaw slumps on south to south east exposures the number and the total area of retrogressive thaw slumps increased by 125 and 160 respectively between 1952 and 2000 as well the proportion of active retrogressive thaw slumps increased dramatically polycyclic retrogressive thaw slumps appear to develop in a periodic fashion related to retrogressive thaw slump stage and maximum inland extent

determining the provenance of black limestone artifacts using petrography isotopes and epr techniques the case of the monument of bocco abstract this paper investigates the provenance of the black limestone of the monument known as bocco named after the king of mauretania who presented silla with this work as a sign of his submission to the power of rome a multi method approach comprising petrographic observations carbon and oxygen isotope composition and electron paramagnetic resonance epr spectra characteristics was used for this purpose the monument is part of a reconstruction of a rectangular base approx 8 2 m which is likely to have served as the base for a bronze statuary group and is currently composed of six blocks of limestone whose exterior is engraved with a fine frieze the results of the different analyses were compared with the data of a published database of the most important black limestone quarries exploited during roman times in the mediterranean area the petrographic and physico chemical parameters did not prove to be very effective in determining the provenance of the black limestone of bocco the isotopes result even raised some uncertainty as to whether all six blocks came from the same quarry though this doubt was dispelled by the epr data and above all by the evident petrographic similarity between them differences in the isotopic composition of the various blocks may be due to an in situ rock alteration process caused by interaction with an aqueous fluid it was however impossible to determine with certainty the origin of the material of the stone artifact using the database available it is possible that the black limestone of bocco came from an ancient quarry that is likely to be located in north western africa but has not yet been uncovered an alternative hypothesis according to which the limestone used for the monument of bocco came from the ancient quarry of ain el ksir one of the tunisian quarries present in the database is also discussed

archaeological carved slabs of the langobard art in churches of peligna valley and spoleto italy provenance of the stones abstract in this study we investigate the provenance of the limestone and marble used to made carved slabs today placed in three churches located in raiano and vittorito peligna valley abruzzo italy and in spoleto umbria italy the slabs representative examples of the langobard art middle ages are dated approximately from 8th to 9th centuries a d and have the same pattern in terms of decoration suggesting a progressive expansion of langobards in central and southern italy after the foundation of the pavia kingdom a multi analytical approach including petrographic characterization chemical carbon and oxygen isotope composition was used for the complete characterization of these stones the comparison of the results of the limestone slabs with those of the geological units outcropping in the area proves a local quarrying from the calcari cristallini formation conversely the carved marble slab has petrographic and isotopic signatures comparable to those of carrara marble and presumable was imported from this famous locality

an enhanced model of the contemporary and long term 200 ka sublimation of the massive subsurface ice in beacon valley antarctica a massive ice body buried under several decimeters of dry regolith in beacon valley antarctica is believed to be more than 1 ma old and perhaps over 8 1 ma however vapor diffusion models suggest that subsurface ice in this region is not stable under current climate conditions to better understand the controls on sublimation rates and stability of this massive ice we have modeled vapor diffusion using 12 years of climate and soil temperature data from 1999 to 2011 including field measurements of episodic snow cover and snowmelt events that have not been represented in previous models of ground ice sublimation the model is then extended to reconstruct the sublimation history over the last 200 ka using paleotemperatures estimated from ice core data from nearby taylor dome and a relationship between atmospheric temperature and humidity derived from our meteorological records the model quantifies the impact of episodic snow events they account for a nearly 30 reduction in the massive ice loss the sublimation rate of ground ice averages 0 11 mm a 1 between 1999 and 2011 in beacon valley parameterized with past environmental conditions and assuming the same regolith thickness the modeled sublimation rate of ground ice in beacon valley averages 0 09 mm a 1 for the last 200 ka comparable to the long term average rate estimated independently from various studies based on cosmogenic isotopes this study provides a realistic estimate of the long term sublimation history and supports the inference that the buried ice in beacon valley is older than 1 ma

metastability of liquid water on mars abstract a simple model of local heat transport on mars demonstrates that transient melting of ice may occur in depressions and gullies nearly anywhere on the planet where thin ice is illuminated by normal incidence insolation an experiment has been performed to confirm the model of evaporation rate at low pressure reduction of radiative cooling due to gully geometry is shown to be important since appropriate meteorological topographic and optical conditions may occur on slopes nearly anywhere on the planet hydrological features such as gullies would likely form only where such ice might accumulate notably in sheltered locations at high latitudes it is suggested that cold trapping of winter condensation could concentrate a sufficient amount of ice to allow seasonal melting in gullies

modeling and observational occurrences of near surface drainage in utopia planitia mars during the past 15 years evidence for an ice rich planet mars has rapidly mounted become increasingly varied in terms of types of deposits and types of observational data and has become more widespread across the surface the mid latitudes of mars especially utopia planitia show many types of interesting landforms similar to those in periglacial landscapes on earth that suggest the presence of ice rich permafrost these include thermal contraction polygonal networks scalloped terrains similar to thermokarst pits debris flows small mounds like pingos and rock glaciers here we address questions concerning the influence of meltwater in the utopia planitia up landscape using analogs of near surface melting and drainage along ice wedge troughs on bylot island northern canada in utopia planitia based on the identification of sinuous channel like pits within polygonal networks we suggest that episodic underground melting was possible under severe periglacial climate conditions in up the collapse pattern and morphology of unconnected sinuous elongated pits that follow the polygon crack are similar to underground melting in bylot island nunavut canada based on this terrestrial analogue we develop a thermal model that consists of a thick insulating dusty layer over ice saturated dust during a period of slight climatic warming relative to today s climate in the model the melting point is reached at depths down to 150 m we suggest that small scale melting could have occurred below ground within ground ice polygonal fractures and pooled in underground cavities then the water may have been released episodically causing mechanical erosion as well as undermining and collapse after melting the dry surface dusty layer might have been blown away thus exposing the degraded terrain of the substrate layer

petrophysical properties composition and deterioration of the calatorao biogenic stone case of the sculptures masonry of the valley of the fallen madrid spain the huge sculptures placed outdoors in the valley of the fallen memorial park el escorial madrid made with blocks of black limestone from calatorao zaragoza spain blcz and disposed on a concrete core exhibit weathering traces flaking saline efflorescence and falling fragments currently represent a danger for visitors frost action is important in the valley of the fallen by the large number of freeze thaw cycles produced during sculptures live under a temperate mediterranean climate with severe seasonality the formation of fissures facilitates the water transport within the rock and the salt and ice induced deterioration temperate climates with frequent freezing and thawing cycles can be the most effective drivers of the visible physical weathering in order to propose a suitable weathering model collected black limestones from sculptures and calatorao quarries were analyzed by optical microscopy environmental scanning electron microscopy with energy dispersive spectrometry esem eds inductively coupled mass spectrometry icp ms and x ray diffraction mercury intrusion porosimetry mip nitrogen absorption and helium pycnometry techniques were used for pore analyses of the blcz micro blocks 10 10 10 cm described in terms of pore size distribution pore volume and specific surface area the appreciable amount of organic matter was isolated by solvent extraction acid treatment flotation and perborate degradation followed by gas chromatography mass spectrometry gc ms analytical pyrolysis py gc ms fourier transformed infrared spectroscopy and raman techniques both weathered and fresh blcz samples contained more than 90 calcite shells with circa 10 of pyrite fresh samples or iron hydroxides weathered samples quartz grains claystone and fossil organic matter consisting of a condensed matrix with polyalkyl chains and polycyclic methoxyl lacking aromatic structures the petrophysical analyses revealed volumes of pores sized 0 025 m obtained by n2 adsorption of 3 18 10 3 cm3 g 1 while the measured porosity by mip in the pore range from 0 005 to 200 m was 3 30 10 3 cm3 g 1 these data could be explained by the existence of clay minerals and organic matter in the pore system less than 50 nm of diameter concerning blcz deterioration it was found that the porous framework of blcz was filled with sulphates formed from artificial cement observed in the sculptures inside trough a testing hole and from its intrinsic pyrite the results suggested that although biological processes were not major agents in rock deterioration there was also weak compatibility between sculptures constituents limestone concrete and oxidized iron clamps which under continental mediterranean conditions were continuously releasing weathering compounds accelerating disruption of the cut stone sculptures

numerical modeling of percolating flow path in a caprock formation during aquifer pressurization and its implication for co2 sequestration spatial distribution of sand bodies in caprock is important to its sealing potential in the evaluation of a potential waste disposal site a numerical investigation was conducted to investigate the roles of sand bodies in caprock integrity and a new leaking mechanism associated with the embedded sand bodies has been identified for the first time this numerical model is characterized by a low proportion of sand bodies in caprock formation and stochastic permeability assignments to the shale facies with a consideration of stress sensitive permeability the research revealed that sand bodies in caprock even initially unconnected due to their low concentration represent the foundation for creating a percolating flow path if certain conditions are met these conditions include a relatively high pore pressure gradient across the caprock which may occur during fluid injection and a favorable geometric configuration of these sand bodies sand bodies of different shapes play different roles in forming a percolating flow path sand bars dykes can lead pore pressure front to cover a considerable vertical thickness quickly while thin sand sheets tend to transfer the pore pressure front across a large horizontal range and thus increase the possibility of involving other local sand bodies in the evolution of percolating flow paths on the other hand the presence of percolating flow path in caprock can limit the pore pressure increase in the aquifer formation during fluid injection the more active the flow paths the less increase the pore pressure that occurs in the aquifer stress dependent permeability can facilitate the formation of percolating flow path but evaluating how much impact it may have remains a question for future research the modeling results indicate that the underlying geologically based discrete structure of permeable domains even when masked by a low permeable rock matrix exerts a significant influence on the location and magnitude of fluid flow within the system during fluid injection

headwall retreat of ground ice slumps banks island northwest territories the relationship between ice face ablation and headwall retreat is described for three ground ice slumps in the sand hills moraine southwest banks island retreat exceeds ablation by a geometric factor that depends on the slope of the ice and the gradient of the surrounding terrain amounts of retreat predicted from ice ablation calculations compare favourably with field measurements except at the start of thermokarst activity in the spring or when the ground ice remains covered by debris for long periods long term headwall retreat for slumps in southern banks island with different orientations and ice contents can be estimated using a model based on meteorological information the model predicts headwall recession of 11 m a for a ground ice slump facing south and 8 8 9 3 m a for one facing north with inputs of a 35 ice face a ground slope of 5 and a volumetric latent heat of 270 mj m3 these predictions are close to the maximum rates of retreat over a 10 year period as measured from air photographs

the indication of martian gully formation processes by slope area analysis the formation process of recent gullies on mars is currently under debate this study aims to discriminate between the proposed formation processes pure water flow debris flow and dry mass wasting through the application of geomorphological indices commonly used in terrestrial geomorphology high resolution digital elevation models dems of earth and mars were used to evaluate the drainage characteristics of small slope sections data from earth were used to validate the hillslope debris flow and alluvial process domains previously found for large fluvial catchments on earth and these domains were applied to gullied and ungullied slopes on mars in accordance with other studies our results indicate that debris flow is one of the main processes forming the martian gullies that were being examined the source of the water is predominantly distributed surface melting not an underground aquifer evidence is also presented indicating that other processes may have shaped martian crater slopes such as ice assisted creep and solifluction in agreement with the proposed recent martian glacial and periglacial climate our results suggest that within impact craters different processes are acting on differently oriented slopes but further work is needed to investigate the potential link between these observations and changes in martian climate

hydraulic modeling of a distributary channel of athabasca valles mars using a high resolution digital terrain model 1 estimating magnitudes of flow rates in outflow channels has a central role in developing understanding of the paleohydrology of mars the typical approach to flow estimation is to identify geomorphic features which indicate bankfull levels and then use a hydraulic model to convert these levels into flow rates data constraints have meant that important assumptions about model equations boundary conditions and parameter values have been necessary in this paper we use a high resolution digital terrain model derived from nasa s mars reconnaissance orbiter context camera stereopair imagery to develop a finer resolution step backwater hydraulic model than previously attempted furthermore the data facilitate a more critical more formal and broader assessment of this type of model than has previously been attempted a distributary channel of athabasca valles is used as a case study the median bankfull flow estimate was 39 000 m3 s 1 although estimates range up to 140 000 m3 s 1 depending on the assumptions employed the principal uncertainties stem from assumptions about bankfull levels and downstream boundary conditions and assumptions about the friction coefficient criticality of flow expansion and contraction losses and geometric details of the channel are also important under certain conditions examination of additional dtms further downstream would permit the analysis to be extended to hydraulic control sections that provide better known boundary conditions hence improving flow estimates it is concluded that new generation dtm data provide opportunity for deeper insight into the challenges and opportunities for modeling the paleohydrology of mars although further work is needed to achieve satisfactory levels of confidence

observational evidence for an active surface reservoir of solid carbon dioxide on mars high resolution images of the south polar residual cap of mars acquired in 1999 and 2001 show changes in the configuration of pits intervening ridges and isolated mounds escarpments have retreated 1 to 3 meters in 1 martian year changes that are an order of magnitude larger than can be explained by the sublimation of water ice but close to what is expected for sublimation of carbon dioxide ice these observations support a 35 year old conjecture that mars has a large surface reservoir of solid carbon dioxide the erosion implies that this reservoir is not in equilibrium with the present environment and that global climate change is occurring on mars

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

cerberus fossae elysium mars a source for lava and water cerberus fossae a long fracture system in the southeastern part of elysium has acted as a conduit for the release of both lava and water onto the surface the southeastern portion of the fracture system localized volcanic vents having varying morphology in addition low shields occur elsewhere on the cerberus plains three locations where the release of water has occurred have been identified along the northwest athabasca and grjota vallis and southeast rahway vallis portions of the fossae water was released both catastrophically and noncatastrophically from these locations a fluvial system that extends more than 2500 km has formed beginning at the lower flank of the elysium rise across the cerberus plains and out through marte vallis into amazonis planitia the timing of the events is late amazonian

absolute dune ages and implications for the time of formation of gullies in nirgal vallis mars 1 transverse dunes cover the valley floor of nirgal vallis a 670 km long valley network at 318 e and 29 s the dunes are superposed by small undeformed impact craters which implies that the dunes are inactive under present atmospheric conditions the last active phase of dune movement absolute age can be determined by crater size frequency distributions the derived absolute ages from high resolution mars global surveyor mars orbiter camera imagery range from approximately 300 000 years to 1 4 myr b p error of factor of 2 the dunes are also superposed by gully deposits aprons which implies a younger age of the gullies these superposition relationships show that the gullies in this midlatitude region are at the most 3 myr old but might be even younger than 300 000 years

an equatorial periglacial landscape on mars abstract we present evidence drawn from new 25 cm pixel hirise images of mars of landforms indicative of geologically recent thaw degradation of ice rich terrain near the martian equator we have focused our study on the head region of athabasca vallis a catastrophic flood carved outflow channel thought to have been active within the last 2 8 ma the geomorphology of the study area is characterised by a series of polygonally patterned surfaces that are bounded by erosional scarps the scarps are indented with cirque shaped niches that appear to be controlled in scale and form by the pre existing polygonal sculpture shallow basins defined by niche indented scarps are also seen and contain pitted mound and cone structures that are similar in form to terrestrial pingos associated with many of these scarps are dendritic channels and gullies blocky debris and hummocky terminal deposits together these correspond morphologically to terrestrial retrogressive thaw slumps which are landforms typical of thermokarst environments we have also observed an evolutionary sequence of morphologies beginning with subsidence of polygonised surfaces and ending with scarp bounded basins fed by inter polygon channels this is consistent with the former presence of surficial liquid water released by ground ice thaw and is again indicative of thermokarst moreover the observations of epigenetic polygons and channels and of polycyclic retrogressive thaw slumps suggest that thaw and standing water persisted for many seasonal cycles the assemblage of landforms the occurrence of polygons and pingo like forms within erosional basins and observations of fluvial like channels cross cutting pre existing surface features are consistent with a surface that has evolved significantly since it was originally emplaced this precludes this terrain being a volcanic i e primary landscape as has been suggested in the past the formation of this landform assemblage requires that there was thaw of ground ice and persistent liquid water at the surface given the geologically young flood deposits in which this assemblage occurs our observations point to a recent period in which mars climate supported thaw conditions in this region

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

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

rootless cones on mars indicating the presence of shallow equatorial ground ice in recent times high resolution mars orbiter camera moc images have revealed the existence of clusters of small cones in the cerberus plains marte valles and amazonis planitia mars these cones are similar in both morphology and planar dimensions to the larger of icelandic rootless cones which form due to explosive interactions between surficial lavas and near surface groundwater impact crater size frequency relationships indicate that surfaces upon which the cones sit are no older than 10 ma if martian cones form in the same manner as terrestrial rootless cones then equatorial ground ice or ground water must have been present near the surface in geologically recent times

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

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

periglacial mass wasting landforms on mars suggestive of transient liquid water in the recent past insights from solifluction lobes on svalbard abstract on earth periglacial solifluction is a slow mass wasting process related to freeze thaw activity we compare the morphology of small scale lobate features on mars to solifluction lobes in svalbard to constrain their processes of formation the analysis is based on high resolution satellite imagery of mars hirise 25 cm pxl aerial images of svalbard with a similar spatial resolution hrsc ax 20 cm pxl acquired through an air campaign in summer 2008 and ground truth obtained during two summer expeditions in 2009 and 2011 on svalbard we present a detailed study of two crater environments on mars displaying two types of lobate forms characterized as sorted clast banked and non sorted lobes on both svalbard and mars such lobes typically occur as clusters of overlapping risers lobe fronts pointing to differential velocities in the soil the martian small scale lobes have well defined arcuate risers and lobe treads surface lobe widths range between 14 and 127 m and tread lengths between 13 and 105 m riser height is estimated to be approximately 1 5 m the lobes on mars share the plan view morphology of solifluction lobes on svalbard and their morphometry is within the range of values of terrestrial solifluction lobes the lobes are distinct from permafrost creep landforms such as rock glaciers we show the results of a survey of 53 hirise images covering latitudes between 59 n and 81 n similar to svalbard the studied lobate features on mars occur in close spatial proximity to gullies and thermal contraction polygons the widespread distribution of the lobate forms in the northern hemisphere and their close association to ground ice and gullies are best explained by mass wasting processes related to frost creep gelifluction and or plug like flow this suggests a protracted process thousand to several thousands of years of freeze thaw activity at the northern high latitudes on mars age constraints on lobe deposits and superposition relationships with gullies and polygons imply a process involving liquid water within the last few million years

coils and polygonal crust in the athabasca valles region mars as evidence for a volcanic history athabasca valles is a near equatorial martian outflow channel that contains many well preserved features whose formation and composition have been a point of contention large plates of terrain that have clearly fractured and drifted may have once been ice rafts or the rocky solidification crust of a large lava flow we have identified 269 spiral coils ranging from 5 to 30 meters wide on the polygonally patterned interplate terrain that are morphologically consistent with terrestrial lava coils that form in zones of flow shear this patterned terrain also exhibits signs of fracture and drift indicating that it is platelike as well the coils in the athabasca region are inconsistent with ice rheology and the plates spirals and polygons are interpreted to be of volcanic origin

new perspectives on ancient mars mars was most active during its first billion years the core mantle and crust formed within 50 million years of solar system formation a magnetic dynamo in a convecting fluid core magnetized the crust and the global field shielded a more massive early atmosphere against solar wind stripping the tharsis province became a focus for volcanism deformation and outgassing of water and carbon dioxide in quantities possibly sufficient to induce episodes of climate warming surficial and near surface water contributed to regionally extensive erosion sediment transport and chemical alteration deep hydrothermal circulation accelerated crustal cooling preserved variations in crustal thickness and modified patterns of crustal magnetization

crystal molds on mars melting of a possible new mineral species to create martian chaotic terrain images sent back by the mars exploration rover opportunity from the meridiani planum show sulfate rich rocks containing plate shaped voids with tapered edges that are interpreted as crystal molds formed after a late stage evaporite mineral has been removed experimental studies of the mgso4 h2o system at low temperatures reveal that the triclinic phase mgso4 11h2o exhibits a crystal morphology that matches the shapes of these molds mgso4 11h2o melts incongruently above 2 c to a mixture of 70 epsomite mgso4 7h2o and 30 h2o by volume when this occurs while crystals are encased in sediment plate shaped voids remain the existence of ice low surface temperatures and the high sulfate content of surface rocks and soil on mars makes mgso4 11h2o a possible mineral species near the surface at high latitudes or elsewhere in the subsurface if an evaporite layer contained a significant amount of this phase incongruent melting would result in a rapid release of a large volume of water and could explain some of the landform features on mars that are interpreted as outflow channels mgso4 11h2o would not survive a sample return mission unless extraordinary precautions were taken