quantifying periglacial erosion in the nepal high himalaya abstract quantifying erosion rates in high mountain environments is challenging because the erosional processes are often stochastic and catastrophic distinguishing between periglacial and glacial rates is especially challenging in this study we focus on determining erosion rates from a glaciated alpine landscape where the bedrock sidewalls are eroding predominantly by blockfall we utilize a topographically well constrained debris covered glacier on the north slope of the annapurna range central nepal himalaya to quantify an average headwall retreat rate by measuring supraglacial debris depths from 0 1 to 2 4 m and average short term down valley transport rates of 17 m yr we calculate a yearly sediment flux of 5820 1990 m3 yr the supraglacial debris originates from the steep rocky headwall of the valley and we use the calculated flux with an estimated headwall contributing area to determine a slope perpendicular headwall retreat rate of 1 3 0 5 mm yr which corresponds to a vertical lowering rate of 0 42 0 16 mm yr and a horizontal retreat rate of 1 2 0 5 mm yr this rate is significantly greater than the steady state erosion rates that we determine for the valley ridge crests and sidewalls 0 08 0 03 mm yr and 0 20 0 05 mm yr respectively using concentrations of the in situ produced cosmogenic radionuclide 10be additionally 10be exposure ages of the lateral moraine crests and supraglacial debris suggest a glacial advance about 470 yr ago and a long term supraglacial transport rate of about 10 m yr using this long term transport rate reduces our inferred headwall retreat and suggests that the up glacial bedrock slopes are eroding at roughly the same rate while our results do not quantify the rate of glacial erosion the absence of a glacial gorge suggests that there may be a rough balance between glacial downcutting and the erosion of the valley sidewalls rates quantified here are almost an order of magnitude lower than fluvial incision rates of the upper marsyandi river that drains the study area suggesting that even glaciated catchments are not keeping pace with the rapidly down cutting rivers of the himalaya

chloride bearing materials in the southern highlands of mars chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing spectrally distinct surface deposits consistent with chloride bearing materials have been identified and mapped using data from the 2001 mars odyssey thermal emission imaging system these deposits are found throughout regions of low albedo in the southern highlands of mars geomorphologic evidence from orbiting imagery reveals these deposits to be light toned relative to their surroundings and to be polygonally fractured the deposits are small

chemically striking regions on mars and stealth revisited 1 the mars odyssey gamma ray spectrometer suite has yielded global chemical information for mars in this work we establish regions of unusual chemical composition relative to average mars primarily on the basis of ca cl fe h k si and th using data from mars odyssey the mars exploration rovers the mars reconnaissance orbiter imaging and 3 5 cm and 1 35 cm radar observations from earth we examine a chemically striking 2 e6 km2 region and find it to overlap significantly with a radar stealth region on mars it is remarkably enriched in cl and depleted in fe and si along with minor variations in h k and th relative to average mars surface dust observed at the two rover sites mixed with and indurated by ca mg bearing sulfate salts would be a reasonable chemical and physical analog to meter scale depths we describe potential scenarios that may have contributed to the unique properties of this region the bulk dust component may be an air fall deposit of compositionally uniform dust as observed in situ hydrothermal acid fog reactions on the flanks of nearby volcanoes may have generated sulfates with subsequent deflation and transport alternatively sulfates may have been produced by low temperature regional scale activity of ground ice driven brine and or regional scale deposition of acidified h2o snowfall

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

erosion by an alpine glacier assessing the impact of glaciation on earth s surface requires understanding glacial erosion processes developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice bedrock interface of contemporary glaciers we demonstrate that the glacial erosion rate is proportional to the ice sliding velocity squared by quantifying spatial variations in ice sliding velocity and the erosion rate of a fast flowing alpine glacier the nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation a nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast flowing glaciers it may also explain the wide range of observed glacial erosion rates and in part the impact of glaciation on mountainous landscapes during the past few million years

spectral and geological study of the sulfate rich region of west candor chasma mars sulfates have been discovered by the omega spectrometer in different locations of the planet mars they are strongly correlated to light toned layered deposits in the equatorial regions west candor chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates a detailed study coupling mineralogy derived from omega spectral data and geology derived from hrsc imager and other datasets leads to some straightforward issues the monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material it likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments or during hydrothermal alteration at depth because it is typically found on outcrops that are eroded and steep polyhydrated sulfates that match any ca na fe or mg sulfates with more than one water molecule are preferentially present on less eroded and darker outcrops than outcrops of kieserite these variations can be the result of a diversity in the composition and or of the rehydration of kieserite on surfaces with longer exposure the latter possibility of rehydration in the current or recent atmosphere suggests the low surface temperatures preserve sulfates from desiccation and also can rehydrate part of them strong signatures of iron oxides are present on sulfate rich scarps and at the base of layered deposits scarps they are correlated with tes gray hematite signature and might correspond to iron oxides present in the rock as sand size grains or possibly larger concretions that are eroded and transported down by gravity at the base of the scarp pyroxenes are present mainly on sand dunes in the low lying terrains pyroxene is strongly depleted or absent in the layered deposits when mixed with kieserite local observations favor a spatial mixing with dunes over layered deposits sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation either in an intermittent lacustrine environment or by hydrothermal fluid circulation both possibilities require the presence of sulfur rich groundwater to explain fluid circulation the elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2 5 km above datum only 1 km below the plateau surface

a 10be production rate calibration for the arctic we present a baffin bay 10 be production rate calibration derived from glacial deposits in western greenland and baffin island and test our results against published 10 be calibration datasets to develop an arctic 10 be production rate our calibration comprises i 10 be measurements from moraine boulders linked to a 14 c dated moraine at jakobshavn isfjord in western greenland ii an independent and previously published 10 be production rate at jakobshavn isfjord and iii re measured 10 be concentrations from a baffin island calibration site that is included in the north eastern north america dataset combined we calculate a sea level high latitude 10 be production rate for the baffin bay region of 3 96 0 07 atoms g 1 a 1 lal stone scaling model after testing the baffin bay rate against calibration sites in norway and north eastern north america we calculate a more conservative arctic production rate of 3 96 0 15 atoms g 1 a 1 the baffin bay and arctic 10 be production rates are indistinguishable from the north eastern north america 10 be production rate 3 91 0 19 atoms g 1 a 1 and yield overall uncertainties of 2 3 7 1s these production rates reduce systematic uncertainties in 10 be based chronologies of ice margin change and allow 10 be based chronologies to be more confidently compared with high resolution climate records such as those from greenland ice cores copyright 2013 john wiley sons ltd

field investigation of dried lakes in western united states as an analogue to desiccation fractures on mars potential desiccation polygons pdps tens to hundreds of meters in size have been observed in numerous regions on mars particularly in ancient 3 gyr old terrains of inferred paleolacustrine playa geologic setting and in association with hydrous minerals such as smectites therefore a better understanding of the conditions in which large desiccation polygons form could yield unique insight into the ancient climate on mars many dried lakebeds playas in western united states display large 50 m wide desiccation polygons which we consider to be analogues for pdps on mars therefore we have carried out fieldwork in seven of these dried lakes in san bernardino and the death valley national park regions complemented with laboratory and spectral analysis of collected samples our study shows that the investigated lacustrine playa sediments have a a soil matrix containing 40 75 clays and fine silt by volume where the clay minerals are dominated by illite muscovite followed by smectite b carbonaceous mineralogy with variable amounts of chloride and sulfate salts and significantly c roughly similar spectral signatures in the visible near infrared vis nir range we conclude that the development of large desiccation fractures is consistent with water table retreat in addition the comparison of the mineralogical to the spectral observations further suggests that remote sensing vis nir spectroscopy has its limitations for detailed characterization of lacustrine playa deposits finally our results imply that the widespread distribution of pdps on mars indicates global or regional climatic transitions from wet conditions to more arid ones making them important candidate sites for future in situ missions

antarctic dry valleys microclimate zonation variable geomorphic processes and implications for assessing climate change on mars the antarctic dry valleys adv are generally classified as a hyper arid cold polar desert the region has long been considered an important terrestrial analog for mars because of its generally cold and dry climate and because it contains a suite of landforms at macro meso and microscales that closely resemble those occurring on the martian surface the extreme hyperaridity of both mars and the adv has focused attention on the importance of salts and brines on soil development phase transitions from liquid water to water ice and ultimately on process geomorphology and landscape evolution at a range of scales on both planets the adv can be subdivided into three microclimate zones a coastal thaw zone an inland mixed zone and a stable upland zone zones are defined on the basis of summertime measurements of atmospheric temperature soil moisture and relative humidity subtle variations in these climate parameters result in considerable differences in the distribution and morphology of 1 macroscale features e g slopes and gullies 2 mesoscale features e g polygons including ice wedge sand wedge and sublimation type polygons as well as viscous flow features including solifluction lobes gelifluction lobes and debris covered glaciers and 3 microscale features e g rock weathering processes features including salt weathering wind erosion and surface pitting equilibrium landforms are those features that formed in balance with environmental conditions within fixed microclimate zones some equilibrium landforms such as sublimation polygons indicate the presence of extensive near surface ice identification of similar landforms on mars may also provide a basis for detecting the location of shallow ice landforms that today appear in disequilibrium with local microclimate conditions in the adv signify past and or ongoing shifts in climate zonation understanding these shifts is assisting in the documentation of the climate record for the adv a similar type of landform analysis can be applied to the surface of mars where analogous microclimates and equilibrium landforms occur 1 in a variety of local environments 2 in different latitudinal bands and 3 in units of different ages documenting the nature and evolution of the adv microclimate zones and their associated geomorphic processes is helping to provide a quantitative framework for assessing the evolution of climate on mars

the chemical composition of martian soil and rocks returned by the mobile alpha proton x ray spectrometer preliminary results from the x ray mode the alpha proton x ray spectrometer apxs on board the rover of the mars pathfinder mission measured the chemical composition of six soils and five rocks at the ares vallis landing site the soil analyses show similarity to those determined by the viking missions the analyzed rocks were partially covered by dust but otherwise compositionally similar to each other they are unexpectedly high in silica and potassium but low in magnesium compared to martian soils and martian meteorites the analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of earth s crust addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition

the use of ablation dominated medial moraines as samplers for 10be derived erosion rates of glacier valley walls kichatna mountains ak we use cosmogenic 10be concentrations in amalgamated rock samples from active ice cored medial moraines to constrain glacial valley sidewall backwearing rates in the kichatna mountains alaska range alaska this dramatic landscape is carved into a small 65 ma granitic pluton about 100 km west of denali where kilometer tall rock walls and cathedral spires tower over a radial array of over a dozen valley glaciers these supraglacial landforms erode primarily by rockfall but erosion rates are difficult to determine we use cosmogenic 10be to measure rockwall backwearing rates on timescales of 103 104 years with a straightforward sampling strategy that exploits ablation dominated medial moraines a medial moraine and its associated englacial debris serve as a conveyor system bringing supraglacial rockfall debris from accumulation zone valley walls to the moraine crest in the ablation zone we discuss quantitatively several factors that complicate interpretation of cosmogenic concentrations in this material including the complex scaling of production rates in very steep terrain the stochastic nature of the rockfall erosion process the unmixed nature of the moraine sediment and additional cosmogenic accumulation during transport of the sediment we sampled medial moraines on each of three glaciers of different sizes and topographic aspects all three moraines are sourced in areas with identical rock and similar sidewall relief of 1 km each sample was amalgamated from 25 to 35 clasts collected over a 1 km longitudinal transect of each moraine two of the glaciers yield similar 10be concentrations 1 6 2 2 104 at g and minimum sidewall slope normal erosion rates 0 5 0 7 mm yr the lowest 10be concentrations 8 103 at g and the highest erosion rates 1 3 mm yr come from the largest glacier in the range with the lowest late summer snowline these rates are reasonable in an alpine glacial setting and are much faster than long term exhumation rates of the western alaska range as determined by thermochronometric studies copyright 2010 john wiley sons ltd

observations of the south seasonal cap of mars during recession in 2004 2006 by the omega visible near infrared imaging spectrometer on board mars express 1 the omega visible near infrared imaging spectrometer on board mars express has observed the southern seasonal cap in late 2004 and 2005 and then in the summer of 2006 these observations extended from the period of maximum extension close to the southern winter solstice to the end of the recession at ls 325 the spectral range and spectral resolution of omega make it possible to monitor the extent and effective grain size of co2 ice and h2o ice on the ground the level of contamination of co2 ice and h2o ice by dust and the column density of m sized ice grains in the atmosphere the co2 seasonal cap is very clean and clear in early southern winter contamination by h2o ice spreads eastward from the hellas basin until the southern spring equinox during southern spring and summer there is a very complex evolution in terms of effective grain size of co2 ice and contamination by dust or h2o ice h2o ice does not play a significant role close to the southern summer solstice contamination of co2 ice by h2o ice is only observed close to the end of the recession as well as the few h2o ice patches already reported by bibring et al 2004a these observations have been compared to the results of a general circulation model with good qualitative agreement on the distribution of h2o ice on the surface and in the atmosphere resolving the remaining discrepancies will improve our understanding of the water cycle on mars

valleys paleolakes and possible shorelines at the libya montes isidis boundary implications for the hydrologic evolution of mars abstract we describe the results of our morphologic stratigraphic and mineralogic investigations of fluvial landforms paleolakes and possible shoreline morphologies at the libya montes isidis planitia boundary the landforms are indicative of aqueous activity and standing bodies of water including lakes seas and oceans that are attributed to a complex hydrologic cycle that may have once existed on mars in the noachian 3 7 ga and perhaps also in the hesperian 3 1 ga our observations of the libya montes isidis planitia boundary between 85 86 5 e and 1 8 5 n suggest that 1 the termination of valley networks between roughly 2500 and 2800 m coincide with lake size ponding in basins within the libya montes 2 an alluvial fan and a possible delta layered morphologies and associated al phyllosilicates identified within bright polygonally fractured material at the front of the delta deposits are interpreted to be the results of fluvial activity and discharge into a paleolake 3 the arabia shoreline appears as a series of possible coastal cliffs at about 3600 and 3700 m indicating two distinct still stands and wave cut action of a paleosea that temporarily filled the isidis basin the early hesperian and 4 the deuteronilus shoreline appears at 3800 m and is interpreted to be a result of the proposed sublimation residue of a frozen sea that might have filled the isidis basin similar to the vastitas borealis formation vbf identified in the northern lowlands we interpret the morphologic geologic setting and associated mineral assemblages of the libya montes isidis planitia boundary as results of fluvial activity lake size standing bodies of water and an environmental change over time toward decreasing water availability and a cold and dry climate

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

surface compositional properties of the malea planum region of the circum hellas volcanic province mars abstract we used thermal emission spectrometer tes thermal emission imaging system themis high resolution stereo camera hrsc and observatoire pour la mineralogie l eau les glaces et l activite omega data to assess the physical and compositional properties of the malea planum portion of the circum hellas volcanic province chvp our analysis of surface materials shows that the thermal inertia decreases from north to south and that there is greater dust cover on the flanks of the chvp volcanoes than in their putative calderas local variations in thermal inertia in malea planum are likely due to variations in surface material caused by aeolian and periglacial permafrost processes whereas regional variations are likely due to seasonal deposition and sublimation of ice at higher latitudes spectral analysis of omega data indicates the widespread presence of pyroxenes and or olivine particularly in the rims of craters that likely excavated volcanic materials dark materials occur throughout the chvp but are concentrated in topographic lows such as crater and caldera floors derivation of modal mineralogies from omega data show a variation in composition of dark materials across malea planum eastern dark deposits have higher olivine and low calcium pyroxene contents lower high calcium pyroxene contents and higher ratios of low calcium to total pyroxene relative to western dark deposits correlation with cratering model age estimates suggests that the western deposits are associated with older features 3 8 ga than the eastern deposits 3 6 ga but these age differences are within uncertainties nevertheless these results suggest a potential change in composition of volcanic materials in the malea planum portion of the chvp with space and possibly time

investigation of the near infrared spectral character of putative martian chloride deposits 1 putative chloride salt deposits observed throughout the southern highlands of mars by the compact reconnaissance imaging spectrometer for mars crism display featureless red slopes in near infrared ratio spectra it is hypothesized that the admixture of anhydrous chlorides or unoxidized sulfides with silicate rocks or minerals could imitate this spectral behavior three different sets of spectra were collected 1 simple mixtures of halite with labradorite and flood basalt at multiple concentrations 2 halite crusts formed on both labradorite and flood basalt and 3 simple mixtures of 25 and 50 wt acid washed pyrite with labradorite and flood basalt in all three instances multiple grain sizes were used to evaluate the effect of particle size on spectral results spectra of the mixtures and crusts were divided by pure labradorite and flood basalt spectra of the same grain size to produce ratio spectra comparable to the crism ratio spectra our study rules out pyrite as a possible component of these deposits whereas flood basalt mixtures with halite reproduced the observed red slope under some conditions this allows us to place some broad constraints on halite proportions and the effective grain sizes of these deposits

landform hierarchy and evolution in gorgonum and atlantis basins mars abstract this paper describes the evolution of landforms in atlantis and gorgonum basins using a geomorphologic approach which interprets landform distribution and hierarchy rather than looking at the distribution of large area 10 6 km 2 geologic sequences this study focuses on interpreting the local scale 3 km 2 cratered terrains tectono structural basins and local manifestation of exogenic processes specifically the evolution of fluvio lacustrine landforms is interpreted as being functionally subordinated to the evolution of the cratered terrains and to the tectono structural modifications of the landscape results show that three major phases of landscape evolution in atlantis and gorgonum basins can be identified a major impact cratering during the heavy bombardment period b tectonic displacements in response to volcano emplacement in the tharsis region and simultaneous landform creation by fluvial and lacustrine processes and c exogenic modification of the older landforms through weathering and eolian processes our results show that the smaller morphological features which form on the older geological units are not necessarily old themselves and can in fact be relatively recent e g amazonian the main implication of these results is that martian morphology did not form only during a period immediately following the heavy bombardment as commonly postulated but rather that landform evolution continued throughout the entire martian history

global mineral distributions on mars 1 determining the mineralogy of mars is an essential part of revealing the conditions of the surface and subsurface a deconvolution method was used to remove atmospheric components and determine surface mineralogy from thermal emission spectrometer data at 1 pixel per degree ppd minerals are grouped into categories on the basis of compositional and spectral similarity and global concentration maps are produced all binned pixels are fit well with rms errors of 0 005 in emissivity higher rms errors are attributed to short wavelength particle size effects on dust covered surfaces significant concentrations 0 10 of plagioclase high ca pyroxene sheet silicates high si glass and hematite are detected and display distributions consistent with previous studies elevated concentrations of plagioclase and high ca pyroxene are consistent with basaltic surfaces and are located in low albedo highlands regions north of 45 s significant concentrations of plagioclase and sheet silicates high si glass and low concentrations of high ca pyroxenes are consistent with andesitic surfaces and are concentrated in both southern and northern high latitude low albedo regions andesitic surfaces in the southern hemisphere have a lower spectral contrast than northern surfaces an isolated surface located in solis planum is spectrally distinct but compositionally similar to other surfaces interpreted to be andesitic in composition concentrations of olivine below the detection limit correctly identify its presence in two of three locations potassium feldspar low ca pyroxene basaltic glass olivine sulfate carbonate quartz and amphibole are not detected with confidence at 1 ppd the results presented here indicate a predominance of volcanic compositions within martian dust free surfaces

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

mineralogy of the nili fossae region with omega mars express data 2 aqueous alteration of the crust 1 nili fossae is a region with fresh exposures of old material omega spectral data have revealed a strong diversity of minerals in the nili fossae region including mafic minerals and phyllosilicates phyllosilicates are found to be primarily fe rich smectites a type of clay minerals these phyllosilicates are observed only on the noachian crust in four types of locations three are without any signatures other than phyllosilicates on 1 smooth layered deposits 2 massive exhumed material and 3 crater ejecta and one type of location is associated with olivine 4 over an altered mafic unit this diversity suggests a widespread liquid water activity and a variety of alteration processes the formation of phyllosilicates underwent considerable reduction if not cessation by the time of formation of syrtis major lava flows in the hesperian period phyllosilicates are spatially and chronologically disconnected from the fluvial and depositional landforms observed in the nili fossae region observations suggest that these landforms formed after the extensive formation of phyllosilicates during short periods of time and or temperatures close to freezing

a note of caution on the use of boulders for exposure dating of depositional surfaces abstract exposure dating of boulders has been widely applied to determine the age of depositional surfaces under the assumption that the pre depositional nuclide component in most boulders is negligible here we present a case study on fluvial terraces at the active mountain front of the eastern andes where this assumption is clearly invalid because sandstone boulders n 13 from terraces at two sites contain a highly variable inherited 10be component and have apparent 10be ages that exceed the age of the respective surface by up to 90 ka likewise boulders from active stream channels n 5 contain a substantial inherited 10be component equivalent to 5 48 ka of exposure the age of the fluvial terraces is well determined by two approaches that allow to correct for the pre depositional nuclide component 10be dating of amalgamated pebbles and 10be depth profiles on sand samples at site 1 three terraces have 10be ages of 3 5 ka t2 11 13 ka t3 and 16 20 ka t4 which are consistent with the terrace stratigraphy the age of terrace t3 is confirmed by a calibrated 14 c age of 12 61 0 20 ka bp obtained from a wood sample at site 2 terrace t3 has a 10be age of 13 16 ka the average inherited 10be concentration of sand grains determined from depth profiles and stream sediments is small and equivalent to 1 3 ka of exposure in contrast the mean inheritance of pebbles and boulders is higher and equivalent to exposure times of 10 ka and 30 ka respectively these differences in the pre depositional nuclide component are related to the different provenance and transport history of sand pebbles and boulders the sand is derived from rapidly eroding miocene sediments exposed near the mountain front whereas the pebbles and boulders originate from triassic sandstones in the internal part of the fold and thrust belt on their way to the mountain front boulders and pebbles were temporarily stored and irradiated in alluvial fans that are currently reworked as sediment deposition in intramontane basins and their subsequent excavation is common in the andes and other fold and thrust belts the presence of pre depositional nuclide components should be evaluated when applying exposure dating at active mountain fronts

exposure age chronology of the last glaciation in the eastern pyrenees abstract we present a chronology of ice recession in the eastern pyrenees based on in situ produced 10be data obtained from the tet paleoglacier complex the sampling strategy is based on the relative chronology provided by a detailed geomorphological map of glacial landforms results indicate that the last maximum ice advance occurred late i e during marine isotope stage 2 compared to the chronology currently established for the rest of the pyrenees despite debatable evidence for a glacial readvance during the oldest dryas stade ice cap melt out was rapid residual cirque glaciers having disappeared by the allerod interstade this is consistent both with north atlantic excursions established by the greenland ice cores and paleoenvironmental data for the region the rapid response of the east pyrenean ice cap to temperature variations is primarily linked to its small size compared to larger pyrenean ice fields to the dry mediterranean climate and to topography related nonlinearities in which a small vertical rise in equilibrium line altitude generates a large change in ice mass possible sources of age uncertainty are discussed in the context of sampling design for single nuclide 10be dating of landform sequences in formerly glaciated landscapes

opaline silica in young deposits on mars high spatial and spectral resolution reflectance data acquired by the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism instrument reveal the presence of h 2o and sioh bearing phases on the martian surface the spectra are most consistent with opaline silica and glass altered to various degrees confirming predictions based on geochernicall experiments and models that amorphous silica should be a common weathering product of the basaltic martian crust these materials are associated with hydrated fe sulfates including h 3o bearing jarosite and are found in finely stratified deposits exposed on the floor of and on the plains surrounding the valles marineris canyon system stratigraphic relationships place the formation age of these deposits in the late hesperian or possibly the amazonian implying that aqueous alteration continued to be an important and regionally extensive process on mars during that time

a large sedimentary basin in the terra sirenum region of the southern highlands of mars abstract different lines of evidence point to hydrological cycling in the martian past the extent duration and magnitude of this cycling remains unclear as well as the magnitude of aqueous processes on the surface here we provide geomorphic and mineralogic evidence of a large inter crater sedimentary basin located in the terra sirenum region which was once covered by a body of liquid water with an areal extent of at least 30 000 km 2 and a depth of approximately 200 m the topographic basin which is modified by a number of large impact craters is partly controlled by ancient impact and tectonic structures as a result of evaporation of the large body of water salt flats formed in the lowest topographic reaches of the basin hydrated phyllosilicates occur in close proximity to the salt flats and in the ejecta and rim materials of small impact craters with stratigraphic relations that suggest that they underlie the evaporite deposits crater statistics place the maximum age of aqueous activity during the late noachian epoch the relatively pristine mineral deposits in the basin have a high potential to yield information of the geochemistry and water activity during the ancient noachian period when conditions were seemingly more conducive to life

mars remote sensing analog studies in the badwater basin death valley california 1 the search for evaporites on mars has important implications for the role that liquid water has played in shaping the planet s geologic climatic and potential biologic history orbital investigations of surface mineralogy are crucial to this exploration effort with the exception of coarse grained gray hematite at a restricted number of sites and trace amounts of carbonate in globally distributed dust deposits the thermal emission spectrometer tes and thermal emission imaging system themis instruments have yet to find widespread mineralogical evidence of aqueously formed minerals this may reflect the coarse spatial resolution of tes 3 5 km pixel and low spectral resolution of themis 10 bands between 6 5 and 14 5 m spectral mapping in the badwater basin death valley california was conducted to better understand the capabilities of tes and themis in detecting evaporite minerals high resolution modis aster airborne simulator master data degraded to tes and themis spatial resolutions were used to evaluate the detection limits of sulfates and carbonates to assess the validity of this spectral remote sensing a quantitative ground truth analysis of surface mineralogy in the badwater basin was performed the analysis was based on thin section petrography x ray diffraction electron microprobe and laboratory and field thermal emission spectrometer analyses taken together the results of all five methods provided enough constraints for a robust interpretation that was in general agreement with the spectral remote sensing mapping study for 90 of the surface samples examined

a search for early to mid noachian chloride rich deposits on mars abstract chloride bearing deposits on mars that are recognizable in orbital infrared data are thought to date to the late noachian period 3 6 gyr ago during the last stages of surface water that persisted long enough over large regions to have emplaced aqueously formed minerals detectable from orbit we conducted an intensive regional search for older buried and exhumed chloride rich deposits and found none resolvable from orbit placing constraints on the upper age limit for this type of deposit

examination of surface exposure ages of antarctic moraines using in situ produced 10be and 26al concentrations of 10be t12 1 5 106 y and 26a1 t12 0 72 106 y have been determined by accelerator mass spectrometry ams in a suite of quartz samples taken from sandstone boulders in several moraines in arena valley a dry valley adjacent to the taylor glacier in the quatermain mountains southern victoria land east antarctica these isotopes are produced in surficial quartz by cosmic ray spallation of o and si the concentrations in these samples ranged from 6 1 105 to 3 0 107 at g 1 for 10be and from 9 4 106 to 1 2 108 at g 1 for 26a1 depending upon the extent of exposure at the surface analyses of 10be in several samples from a single moraine at altitudes ranging from 1300 to 1650 m permitted an estimation of the air attenuation pathlength of cosmic ray neutrons the value of 142 96 41 g cm 2 is consistent with other published values production rates of 17 6 4 at g 1 y 1 for 10be and 113 54 16 at g 1 y 1 for 26a1 at 1300 m and 87 s and a 26al 10be production ratio of 6 5 1 3 1 3 were calculated from the data these values correspond to sea level production rates at high geomagnetic latitude of 6 4 at g 1 y 1 and 41 7 at g 1 y 1 for 10be and 26a1 respectively consistent with determinations based on 11 ky glacially polished surfaces in the sierra nevada in california these production rates imply exposure ages for the various moraines ranging from 50 ky to 2 5 my in accordance with other geological evidence the 10be and 26al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of 3he examination of the 3he concentrations in conjunction with the present data set yields an estimate of 3he production of 230 8540 at g 1 y 1 corresponding to 85 31 15 at g 1 y 1 at sea level this is lower than previously reported values of 240 60 at g 1 y 1 and 190 at g 1 y 1 scaled to sea level and high geomagnetic latitude based respectively on volcanic flows less than 2000 years old at low latitude and samples collected from 14 400 year old volcanic flows this discrepancy is likely due to diffusive losses which may become significant up to 50 for surface exposure ages on the order of 2 0 my nevertheless the general correlations among the three isotopes suggest that 3he does not suffer gross losses through diffusion

spectral reflectance and morphologic correlations in eastern terra meridiani mars the mars express observatoire pour la mineralogie l9eau les glaces et l9activite omega hyperspectral image data covering eastern terra meridiani indicate the ubiquitous presence of molecular water in etched terrain materials that disconformably overlie heavily cratered terrains and underlie the hematite bearing plains explored by the opportunity rover identification of crystalline water in kieserite mgso4 h2o is linked to materials exposed in a valley and plateau to the north of hematite bearing plains the mineralogical similarities between the etched terrain deposits examined with omega data and the layered rocks examined by opportunity imply that the ancient aqueous environments inferred from analyses of the rover data extend over regional scales

palaeogeography and 10be exposure age chronology of middle and late pleistocene glacier systems in the northern pyrenees implications for reconstructing regional palaeoclimates abstract we present constraints on the chronology palaeogeography and palaeoclimatic implications for western europe of middle and late pleistocene glaciation in the ariege catchment north eastern pyrenees based on 37 cosmogenic 10 be exposure ages obtained from moraines and glacially scoured bedrock exposures we have dated six regional glacial stades the chronology emphasises several conclusions that are new to the region i in the pyrenees the global lgm occurred several thousands of years after the maximum ice extent of the wurmian glaciation ii almost full glacier extent occurred again during the global lgm but only in the eastern pyrenees iii valley glaciers such as in the ariege trunk valley attained lengths of 25 km during the oldest dryas stadial the cosmogenic exposure ages additionally provide the first direct evidence of 10 km scale fluctuations of ice front positions during the late pleistocene glacial cycle probably at the time of marine isotope stage 3 as well as rare insights into middle pleistocene ice margin positions compared with existing evidence of glacial palaeogeography in other catchments of the pyrenan range the data also reveal a sharp contrast in relative ice extent between the glacierized catchments of the eastern pyrenees ariege carol malniu tet where wurmian mie and lgm ice fronts reached similar positions and the rest of the range where ice fronts at the time of the mis 2 and global lgm palaeotemperature minima lagged far behind the wurmian mie terminal moraines we ascribe this non uniform behaviour among catchments to non uniform palaeoclimatic conditions along the strike of the pyrenees a range of palaeoenvironmental proxies reviewed in the literature highlight a sharp difference in sea surface temperatures between the warmer western mediterranean and the cooler bay of biscay the consequences of such an e w temperature gradient on weather patterns during the global lgm are compatible with a strengthening of mediterranean low pressure systems particularly the semi permanent balearic low generating greater precipitation over the eastern pyrenees compared to atlantic weather systems further west

analysis of polygonal cracking patterns in chloride bearing terrains on mars indicators of ancient playa settings the ancient southern highlands on mars 3 5 gyr old contain 600 regions that display spectral evidence in the infrared for the presence of chloride bearing materials many of these locations were previously reported to display polygonal cracking patterns we studied more than 80 of the chloride bearing terrains using high resolution 0 25 0 5 m pixel images as well as near infrared spectral data to characterize the surface textures and the associated cracking patterns and mineralogies our study indicates that 75 of the studied locations display polygonal cracks that resemble desiccation cracks while some resemble salt expansion thrust polygons furthermore we detect spectrally the presence of smectites in association with 30 of the studied fractured terrains we note that smectites are a special class of swelling clay minerals that can induce formation of large desiccation cracks as such we suggest that the cracking patterns are indicative of the presence of smectite phyllosilicates even in the absence of spectral confirmation our results suggest that many chloride bearing terrains have a lacustrine origin and a geologic setting similar to playas on earth such locations would have contained ephemeral lakes that may have undergone repeated cycles of desiccation and recharging by a near surface fluctuating water table in order to account for the salt phyllosilicates associations these results have notable implications for the ancient hydrology of mars we propose that the morphologies and sizes of the polygonal cracks can be used as paleoenvironmental as well as lithological indicators that could be helpful in planning future missions

water ice at low to midlatitudes on mars 1 in this paper we analyze water ice occurrences at the surface of mars using near infrared observations and we study their distribution with a climate model latitudes between 45 s and 50 n are considered data from the observatoire pour la mineralogie l eau les glaces et l actitite and the compact reconnaissance imaging spectrometer for mars are used to assess the presence of surface water ice as a function of location and season a modeling approach combining the 1 d and 3 d versions of the general circulation model of the laboratoire de meteorologie dynamique de jussieu is developed and successfully compared to observations ice deposits 2 200 m thick are observed during the day on pole facing slopes in local fall winter and early spring ice extends down to 13 latitude in the southern hemisphere but is restricted to latitudes higher than 32 in the north on a given slope the pattern of ice observations at the surface is mainly controlled by the global variability of atmospheric water precipitation and vapor with local ground properties playing a lower role only seasonal surface ice is observed no exposed patches of perennial ground ice have been detected surface seasonal ice is however sensitive to subsurface properties the results presented in this study are consistent with the recent discovery of low latitude subsurface ice obtained through the analysis of co 2 frost

control of geomorphic processes on 10be concentrations in individual clasts complexity of the exposure history in gobi altay range mongolia the dating of alluvial landforms by cosmogenic nuclides requires distinguishing the pre deposition inheritance from the post deposition history of the clasts in the studied marker moreover estimating catchment scale erosion rates from the concentrations of cosmogenic nuclides in active alluvia requires a good knowledge of the local regional relationships between rock exhumation and transport through space and time this is still poorly known for timescales of tens of thousand years in order to document the evolution of clast exhumation and transport rates through time we analyze in situ 10be concentrations in boulders and cobbles from hillslopes to outlet of an arid mountainous catchment located in gobi altay mongolia strongly affected by global climatic changes during the pleistocene holocene period samples were collected on bedrock abandoned alluvial deposits active colluvia and alluvia our results show a large 10be scattering in the active river bed consistent with a low and discontinuous catchment erosion rate dominated by mass wasting and fluvial incision on the contrary pre exposure signal within abandoned terraces is much more homogeneous consistent with climatic pulses responsible of strong erosional events on hillslopes and rapid fluvial transport these results show that exhumation transport processes at the catchment scale vary in style and intensity through time as a consequence of climatic oscillations the occurrence of abrupt climatic changes during short periods of time recorded by 10be concentrations in abandoned alluvia raise questions about the temporal applicability of catchment erosion rates derived from cosmogenic nuclide concentrations measured in sediments of active rivers on the other hand strong and short erosion events limit and homogenize the pre exposure 10be signal in associated deposits like debris flows making them particularly suitable markers for dating in active tectonic and paleoclimatic studies

an analysis of open basin lake deposits on mars evidence for the nature of associated lacustrine deposits and post lacustrine modification processes abstract a large number of candidate open basin lakes low lying regions with both inlet valleys and an outlet valley have been identified and mapped on mars and are fed by valley network systems that were active near the noachian hesperian boundary the nature of processes that modified the open basin lake interiors subsequent to lacustrine activity and how frequently sedimentary deposits related to lacustrine activity remain exposed has not been extensively examined an analysis of 226 open basin lakes was undertaken to identify evidence for 1 exposed deposits of possible lacustrine origin and 2 post lacustrine activity processes that may have modified or resurfaced open basin lakes spectroscopic data from the compact reconnaissance imaging spectrometer for mars crism instrument were analyzed over identified exposed open basin lake deposits to assess the mineralogy of these deposits particular attention was paid to the possible detection of any component of aqueous alteration minerals e g phyllosilicates hydrated silica zeolites or evaporites e g carbonates sulfates chlorides associated with these exposed deposits the aim of this paper is to act as a broad survey and cataloguing of the types of lacustrine and post lacustrine deposits that are present within these 226 paleolake basins results of the morphologic classification indicate that 79 open basin lakes 35 of the population contain exposed deposits of possible lacustrine origin identified on the basis of fan delta deposits layered deposits and or exposed floor material of apparent lacustrine origin additionally all 226 open basin lakes examined appear to have been at least partially resurfaced subsequent to their formation by several processes including volcanism glacial and periglacial activity impact cratering and aeolian activity results from the analysis of crism data show that only 10 29 of the 34 deposits with crism coverage of the exposed open basin lake deposits contain positively identified aqueous alteration minerals with one deposit also containing evaporites the identified hydrated and evaporite minerals include fe mg smectite kaolinite hydrated silica and carbonate with fe mg smectite the most commonly identified mineral these results indicate that hydrated and evaporite minerals are not as commonly associated with lacustrine deposits on mars as they are on earth this suggests in situ alteration and mineral precipitation a common source of such minerals in terrestrial lakes was not a major process occurring in these paleo lacustrine systems and that the observed minerals are likely to be present as transported material within the lacustrine deposits the lack of widespread in situ alteration also suggests that either the water chemistry in these paleolake systems was not conducive to aqueous alteration and mineral precipitation or that the open basin lake systems were relatively short lived

updated global map of martian valley networks and implications for climate and hydrologic processes 1 martian valley networks have long been viewed as some of the best evidence of prolonged surface water on mars analysis from viking data showed that valleys were primarily contained on the ancient crust drainage networks were immature and large undissected regions occurred in between individual systems these observations led many to propose that they formed primarily by groundwater processes and limited or no climate change from the present state was required using more recent and higher resolution data sets including visible infrared and topographic data we have manually remapped valleys on a global scale more than eight times as many valleys have been identified on the surface and calculated drainage densities are on average higher by a factor of 2 further regions previously thought to be undissected have significant incision by fluvial processes most of these systems seem to have formed around the noachian hesperian boundary 3 8 3 6 ga minor valley formation continued through the hesperian and into the early amazonian epoch approximately 2 8 ga ago the new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels terraces multiple periods of formation complex network morphology and correlation with other fluviosedimentary features and chloride salts on mars groundwater processes or a transient steam atmosphere generated by impacts played at most a minor role these new results imply that mars had a long lived period or periods of clement conditions toward the end of the noachian epoch that supported a hydrologic cycle and potentially a biosphere

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

two chloride sources in soils of the mcmurdo dry valleys antarctica 1 sulfate nitrate and chloride are major water soluble anions in soils of the mcmurdo dry valleys mdv antarctica we measured the chloride stable isotope composition of 40 soil samples from 16 different soil profiles the soil profiles come from three different microclimate zones in the mdv a coastal thaw zone which fosters a seasonally saturated active layer a stable upland zone in which air and soil temperatures are too cold to foster active layers and or significant snowmelt and an intermediate inland mixed zone results show that the total water soluble chloride content is low in both the coastal and the upland zones but highly variable in the inland mixed zone average 770 to 11520 ppm individual soil 37cl values range from 2 10 to 0 56 with profile average 37cl values broadly decreasing from the coast toward upland valleys vertically the 37cl increases with depth in soil profiles developed on basal tills but decreases on sublimation tills we propose that the spatial cl and 37cl patterns are the result of continuous influx and leaching of two major chloride sources an airborne sea salt chloride ssc with a 37cl value 0 0 and a secondary atmospheric chloride sac with a 37cl value 2 10 our model suggests that sublimation tills have their cl input from two boundaries a till atmosphere interface at the top and a buried ice till interface at the bottom differing distinctively from basal tills where there is no salt contribution from the bottom our model also suggests a higher influx of ssc relative to sac in the mdv in the past overall characterizing the sources budgets and spatial vertical patterns of chloride constitutes a first step toward unraveling climate tectonic and landscape changes archived in mdv soil profiles

towards successful osl sampling strategies in glacial environments deciphering the influence of depositional processes on bleaching of modern glacial sediments from jostedalen southern norway the optically stimulated luminescence osl signals of quartz and k feldspar are known to bleach poorly within some glacial settings and can present a major challenge to dating applications however because the osl signal is extremely sensitive to sunlight exposure history the residual luminescence signals of modern glacial sediments also encode information about transport and depositional processes through examination of the residual luminescence properties equivalent dose de and overdispersion values of a suite of modern glacial sediments from different depositional settings sandar proglacial delta and main meltwater channel this study provides insights not only into which sediments are likely to be fully bleached within glacial settings but also into how osl can be used to trace different depositional processes across sedimentary landforms improved understanding of the processes of sediment bleaching will enable better sample selection and may improve the accuracy and precision of osl dating of glacial sediments the luminescence signals of both coarse grained quartz and k feldspar with similar sediment sources are found to be sensitive to both depositional process and specific depositional setting whereas modern braid bar head deposits from the nigardsdalen ice proximal proglacial delta typically have ages of 3 ka similar depositional features from the fabergstolsgrandane sandur have residual ages of 26 ka exploration of changing residual luminescence signals across individual sandur and proglacial delta braid bar features shows that braid bar head deposits can retain large residual d e values while the partner braid bar tail deposits are almost completely bleached the quartz osl signal and k feldspar irsl50 and post ir irsl250 signals are shown to bleach at the same rate across the same bar feature and the irsl50 k feldspar signal is also shown to be completely bleached for bar tail deposits in nigardsdalen therefore the irsl50 k feldspar signal is suitable for dating some glacial deposits circumventing the challenges associated with dim quartz signals 2014 the authors published by elsevier ltd this is an open access article under the cc by license

distribution and formation of chlorides and phyllosilicates in terra sirenum mars 1 the terra sirenum region of mars located in the noachian southern highlands is mineralogically diverse providing unique insight into ancient aqueous processes analyses of remote sensing data over the region indicate the presence of both fe or mg rich phyllosilicates and a spectrally unique deposit interpreted to be rich in chloride salts the stratigraphic relationships indicate that the phyllosilicates are part of the ancient highland crust and that the salts were deposited at a later time in some instances there is clear morphological evidence that salts were mobilized and deposited by near surface waters

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

effects of surface roughness and graybody emissivity on martian thermal infrared spectra slopes are present in martian apparent surface emissivity observations collected by the thermal emission spectrometer tes and the thermal emission imaging system themis these slopes are attributed to misrepresenting the surface temperature either through incorrect assumptions about the maximum emissivity of surface materials or the presumption of a uniform surface temperature within the field of view these incorrect assumptions leave distinct characteristics in the resulting apparent emissivity data that can be used to gain a better understanding of the surface properties surfaces with steep slopes typically have a variable surface temperatures within the field of view that cause distinct and highly variable slopes in apparent emissivity spectra based on the observing conditions these properties are documented on the southwestern flank of apollinaris patera and can be reasonably approximated by modeled data this spectral behavior is associated with extremely rough martian surfaces and includes surfaces south of arsia mons and near warrego valles that also appear to have high slopes in high resolution images surfaces with low maximum values of emissivity have apparent emissivity spectra with more consistent spectral slopes that do not vary greatly based on observing conditions this spectral surface type is documented in terra serenum and is consistent with associated high resolution images that do not indicate the presence of a surface significantly rougher that the surrounding terrain

landscape preservation under fennoscandian ice sheets determined from in situ produced 10be and 26al some areas within ice sheet boundaries retain pre existing landforms and thus either remained as ice free islands nunataks during glaciation or were preserved under ice differentiating between these alternatives has significant implications for paleoenvironment ice sheet surface elevation and ice volume reconstructions in the northern swedish mountains in situ cosmogenic 10be and 26al concentrations from glacial erratics on relict surfaces as well as glacially eroded bedrock adjacent to these surfaces provide consistent last deglaciation exposure ages 8 13 kyr confirming ice sheet overriding as opposed to ice free conditions however these ages contrast with exposure ages of 34 61 kyr on bedrock surfaces in these same relict areas demonstrating that relict areas were preserved with little erosion through multiple glacial cycles based on the difference in radioactive decay between 26al and 10be the measured nuclide concentration in one of these bedrock surfaces suggests that it remained largely unmodified for a minimum period of 845 418 461 kyr these results indicate that relict areas need to be accounted for as frozen bed patches in basal boundary conditions for ice sheet models and in landscape development models subglacial preservation also implies that source areas for glacial sediments in ocean cores are considerably smaller than the total area covered by ice sheets these relict areas also have significance as potential long term subglacial biologic refugia

evolution of sulfide mineralization on mars the presence of komatiitic igneous rocks on marks based on geochemical evidence from snc meteorites and viking x ray fluorescence analyses of the regolith suggests that massive and disseminated iron sulfide mineralization occurs near the martian surface analogies are drawn between possible ultramafic fe ni sulfides on mars and terrestrial pyrrhotite pentlandite ore deposits associated with archean komatiites formed during early crustal development on earth partial melting of the mantle as a result of high radiogenic heat production then extrusion of turbulent high temperature ultramafic lavas segregation of immiscible fes melts during cooling gravitational settling and fractional crystallization of sulfide minerals in magma chambers or lava flows produced massive and disseminated sulfide mineralization associated with terrestrial komatiites comparable processes probably occurred on mars where on account of the inferred higher fe fe mg ratio of the x ray mantle estimated to contain approximately 4 5 wt s iron rich basaltic magmas were produced by partial melting at depths and temperatures exceeding 165 km and 1 400 degree c respectively adiabatic diapiric emplacement of these iron rich very low viscosity basaltic melts transported significant concentrations of dissolved sulfur as s sup 2 minus and hs sup minus from the mantle ensuing sulfide mineralization may have been either thinly disseminated within ultramafic lavas eruptingmore over large areas of mars or concentrated locally at the base of structural depressions cumulate ore deposits several meters thick may occur at the base of intrusions or in near surface magma chambers the evidence for insignificant plate tectonic activity on mars and minimal interactions of martian mantle with crust hydrosphere and atmosphere has restricted the evolution of sulfide ore deposits there less

contemporaneous deposition of phyllosilicates and sulfates using australian acidic saline lake deposits to describe geochemical variability on mars 1 studies of the origin of the martian sulfate and phyllosilicate deposits have led to the hypothesis that there was a marked global scale change in the mars environment from circum neutral ph aqueous alteration in the noachian to an acidic evaporitic system in the late noachian to hesperian however terrestrial studies suggest that two different geochemical systems need not be invoked to explain such geochemical variation western australian acidic playa lakes have large ph differences separated vertically and laterally by only a few tens of meters demonstrating how highly variable chemistries can coexist over short distances in natural environments we suggest diverse and variable martian aqueous environments where the coetaneous formation of phyllosilicates and sulfates at the australian sites are analogs for regions where phyllosilicates and sulfates coexist on mars in these systems fe and alkali earth phyllosilicates represent deep facies associated with upwelling neutral to alkaline groundwater whereas aluminous phyllosilicates and sulfates represent near surface evaporitic facies formed from more acidic brines

fluid evaporation records preserved in salt assemblages in meridiani rocks we studied the inter relationships between the major anions so sub 3 cl and br and cations feo cao and mgo using elemental abundances determined by apxs in salt assemblages of ratted abraded rocks at meridiani to characterize the behavior of fluids that infiltrated into this region on mars a plot of so sub 3 versus cl for the abraded rocks yielded an unusual pattern whereas the so sub 3 cl ratios versus cl for the same rocks showed a monotonically decreasing trend represented by a hyperbola the systematic behavior of the so sub 3 and cl data in the documented rocks at meridiani suggests that these anions behaved conservatively during fluid rock interactions these results further indicate that two kinds of fluids referred to as sol i and sol ii infiltrated into endurance eagle fram craters where they underwent progressive evaporative concentration sol i is a low ph fluid consisting of high so sub 3 and low cl and high br this fluid infiltrated all the way to the crater top region whereas sol ii fluid of high ph with low so sub 3 and high cl and low br reached only an intermediary level known as the whatanga contact at endurance based on the feo mgo as well as cao mgo versus so sub 3 cl diagram formore rocks above the whatanga contact the cation and anion relationships in this system suggest that the fe sup 2 so sub 4 and ca sup 2 so sub 4 ratios in sol i fluids at meridiani were 1 before the onset of evaporation based on the chemical divide considerations below the whatanga contact relatively dilute sol ii fluids seem to have infiltrated and dissolved flushed away the easily soluble mg sulfate chloride phases along with br without significantly altering the so sub 3 cl ratios in the residual salt assemblages further cl br versus br in rocks above the whatanga contact show a hyperbolic trend suggesting that cl and br behaved conservatively similar to so sub 3 and cl in the sol 1 fluids at meridiani our results are consistent with a scenario involving two episodes sol i and sol ii of groundwater recharge at meridiani planum less

martian surface mineralogy from observatoire pour la mineralogie l eau les glaces et l activite on board the mars express spacecraft omega mex global mineral maps 1 after 2 years of operation the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer on board mars express has acquired data coverage of the martian surface with spatial resolution varying between 300 m and 4 8 km depending on the pericenter altitude of the spacecraft s elliptical orbit we report the global surface distributions of some minerals using the omega observations in the visible and near infrared vnir wavelength domains 0 35 2 5 m global maps of ferric phases mafic minerals pyroxenes and olivines and hydrated minerals have been derived from spectral parameters the limits of detection in terms of abundance for some minerals of different grain size distributions are given the distribution of pyroxenes is in general agreement with the mineral maps of previous telescopic and space observations the fe3 absorption feature in the visible wavelength region is present everywhere on the surface the spectra of the bright regions compare with anhydrous nanophase ferric oxides terrains with water bearing minerals cover a very small fraction of the martian surface olivine mg rich compositions is detected in more extensive regions of the pyroxene rich zones than previously reported olivine with higher iron content and or larger grain size 100 m is only detected in isolated areas the mineralogy of the northern low albedo regions is discussed in the light of these mineral maps chemical alteration or oxidation during extrusion producing a coating or varnish of anhydrous ferric phases over a dark basaltic surface best accounts for the vnir spectral properties of these regions although a glassy composition resulting from impact is also considered

orbital identification of carbonate bearing rocks on mars geochemical models for mars predict carbonate formation during aqueous alteration carbonate bearing rocks had not previously been detected on mars surface but mars reconnaissance orbiter mapping reveals a regional rock layer with near infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the nili fossae region the carbonate is closely associated with both phyllosilicate bearing and olivine rich rock units and probably formed during the noachian or early hesperian era from the alteration of olivine by either hydrothermal fluids or near surface water the presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering proposed to be characteristic of hesperian mars did not destroy these carbonates and thus did not dominate all aqueous environments

global maps of anhydrous minerals at the surface of mars from omega mex 1 we here reassess the global distribution of several key mineral species using the entire omega mars express vis nir imaging spectrometer data set acquired from orbit insertion in january 2004 to august 2010 thirty two pixels per degree global maps of ferric oxides pyroxenes and olivines have been derived a significant filtering process was applied in order to exclude data acquired with unfavorable observation geometries or partial surface coverage with water and co2 frosts because of strong atmospheric variations over the 3 6 martian years of observations primarily due to the interannual variability of the aerosol opacity a new filter based on the atmospheric dust opacity calibrated by the mars exploration rovers measurements has also been implemented the fe3 absorption features are present everywhere on the surface with a variety of intensities indicating distinct formation processes the pyroxene bearing regions are localized in low albedo regions while the bright regions are spectrally comparable to anhydrous nanophase ferric oxides the expanded data set increases by a factor of about 2 the number of olivine detections reported in previous omega based studies olivine is mainly detected in three types of areas over the martian surface discontinuous patches on the terraces of the three main basins smooth inter crater plains and smooth crater floors throughout the southern highlands and crater sand dunes crater ejectas and extended bedrock exposures in the northern plains olivine is also detected in the low albedo pyroxene bearing dunes surrounding the northern polar cap

10be cosmic ray exposure dating of moraines and rock avalanches in the upper romanche valley french alps evidence of two glacial advances during the late glacial holocene transition abstract cosmic ray exposure cre dating of moraines allow glacier fluctuations and past climate change reconstructions in the french alps there is a lack of moraine dating for the late glacial holocene transition period here we present a chronology of glacier advances in the upper romanche valley french alps massif des ecrins based on 10 be cre dating cre ages of moraines of 13 0 1 1 ka and 12 4 1 5 ka provide evidence for two stages of glacial advance or standstill at the end of the late glacial the cre dating of a rock avalanche deposit at 12 2 1 5 ka is attributed to post glacial debuttressing and reveals rapid deglaciation at the end of the late glacial a cre age of 7 1 0 7 ka of a second mass wasting whose triggering factor is unidentified so far indicates that up to an altitude of 2300 m a s l the valley was ice free as of 7 kyr at the latest the re evaluation of 21 moraine 10 be cre ages from nine glacial valleys across the alps shows multiple glacial advances occurring at the late glacial holocene transition these results lead to a re evaluation of the importance of cooling events during the allerod and the younger dryas in the alps

the sedimentary history of the inner alpine inn valley austria extending the baumkirchen type section further back in time with new drilling the baumkirchen clay pit near innsbruck western austria is a well known site in alpine quaternary stratigraphy lacustrine sediments from the last glacial cycle from within the alps provide a unique opportunity to investigate the regional palaeoclimate recent drilling has extended the known sequence to a total length of at least 250 m consisting of almost entirely well laminated clayey silt luminescence dating identified two lake sequences separated by a hiatus of ca 7000 15 000 years lake phase 1 spans the period ca 77 55 ka i e from about marine isotope stage mis 5 4 to the mis 4 3 transition lake phase 2 extends from mid to late mis 3 between ca 45 and 33 ka down core x ray fluorescence core scanning confirmed the presence of the lake phases in the sediment composition suggesting different sediment sources and or transport mechanisms during these two intervals a unique section of exotic angular silt matrix supported gravel at the top of lake phase 1 is interpreted as ice rafted debris luminescence dating constrains this layer to ca 55 ka thus providing the first evidence of a late mis 4 or early mis 3 ice advance confined to the interior of the eastern alps a conceptual model of the sedimentary history of the valley is presented

experimental studies of mars analog brines evaporite deposits may represent significant sinks of mobile cations e g those of ca n mg and fe and anions e g those of c n s and cl among the materials composing the martian surface and upper crust carbon and nitrogen are especially interesting because of their role as atmospheric gases which can become incorporated into crustal rocks however the nature of evaporite precursor brines formed under martian conditions is poorly understood to date only a very limited number of laboratory investigations have been reported which have any bearing on a better understanding of various processes related to brine or evaporite formation on mars here we report on preliminary laboratory experiments that exposed igneous minerals analogous to those in martian shergottites nakhlites and chassigny snc group meteorites to a simulated martian atmosphere and pure deoxygenated water analysis of the water over intervals of time approaching 1 year showed that atmospheric gases dissolved to form carbonate and nitrate ions while minerals dissolved to form sulfate and chloride along with various cations on an annual basis ion formation gave a carbonate sulfate ratio that is comparable to the ratio found among salts in snc meteorites the sulfate chloride ratio of the experimental brines is higher than in snc meteorites but lower than in surface soils measured at the viking and pathfinder landing sites

diverse aqueous environments on ancient mars revealed in the southern highlands high resolution spectral images reveal many new exposures of hydrated minerals across the noachian southern highlands of mars several different phyllosilicates are observed with inferred accompanying phases ranging from zeolites to sulfates to chlorides each in distinct geologic settings hydrated sulfates are observed in several locations at mid latitudes and likely formed independently from the equatorial sulfates these assemblages suggest a greater diversity of aqueous environments on ancient mars than has previously been recognized and their distribution implies that alteration was widespread during the noachian period not restricted to a few locations

sulfates in the north polar region of mars detected by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer observed the northern circumpolar regions of mars at a resolution of a few kilometers an extended region at 240 e 85 n with an area of 60 kilometers by 200 kilometers exhibits absorptions at wavelengths of 1 45 1 75 1 94 2 22 2 26 and 2 48 micrometers these signatures can be unambiguously attributed to calcium rich sulfates most likely gypsum this region corresponds to the dark longitudinal dunes of olympia planitia these observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains

decadal centennial scale monsoon variations in the arabian sea during the early holocene 1 an essential prerequisite for the prediction of future climate change due to anthropogenic input is an understanding of the natural processes that control earth s climate on timescales comparable to human lifespan the early holocene period was chosen to study the natural climate variability in a warm interval when solar insolation was at its maximum the monsoonal system of the tropics is highly sensitive to seasonal variations in solar insolation and consequently marine sediments from the region are a potential monitor of past climate change here we show that during the early holocene period rapid 18o changes of the summer upwelling dwelling foraminifer g bulloides of up to 0 6 in core 905 from the arabian sea occurred on decadal centennial timescales this 18o change predominantly translates into summer temperature variations of roughly 2 3 c within the resolution of the ams14c dating the isotope changes occur in phase with precipitation induced 18o variations recorded in a stalagmite in the hoti cave in oman neff et al 2001 from this relationship we conclude that solar insolation affecting the monsoonal system not only induced the precipitation changes as recorded in oman in the sense of neff et al 2001 but also controlled temperature variations in the upwelled waters found off somalia the present study demonstrates that decadal scale climate records can be obtained from nonlaminated ocean sediment records and that coherent rapid high amplitude climate change is recorded in the arabian sea on a regional scale of 2000 km

early mars climate near the noachian hesperian boundary independent evidence for cold conditions from basal melting of the south polar ice sheet dorsa argentea formation and implications for valley network formation currently and throughout much of the amazonian the mean annual surface temperatures of mars are so cold that basal melting does not occur in ice sheets and glaciers and they are cold based the documented evidence for extensive and well developed eskers sediment filled former sub glacial meltwater channels in the south circumpolar dorsa argentea formation is an indication that basal melting and wet based glaciation occurred at the south pole near the noachian hesperian boundary we employ glacial accumulation and ice flow models to distinguish between basal melting from bottom up heat sources elevated geothermal fluxes and top down induced basal melting elevated atmospheric temperatures warming the ice we show that under mean annual south polar atmospheric temperatures 100 c simulated in typical amazonian climate experiments and typical noachian hesperian geothermal heat fluxes 45 65mw m 2 south polar ice accumulations remain cold based in order to produce significant basal melting with these typical geothermal heat fluxes the mean annual south polar atmospheric temperatures must be raised from today s temperature at the surface 100 c to the range of 50 to 75 c this mean annual polar surface atmospheric temperature range implies lower latitude mean annual temperatures that are likely to be below the melting point of water and thus does not favor a warm and wet early mars seasonal temperatures at lower latitudes however could range above the melting point of water perhaps explaining the concurrent development of valley networks and open basin lakes in these areas this treatment provides an independent estimate of the polar and non polar surface temperatures near the noachian hesperian boundary of mars history and implies a cold and relatively dry mars climate similar to the antarctic dry valleys where seasonal melting forms transient streams and permanent ice covered lakes in an otherwise hyperarid hypothermal climate 2012 elsevier inc

phyllosilicates in the mawrth vallis region of mars 1 omega mars express has discovered large outcrops rich in phyllosilicates in the region of mawrth vallis mars around 20 w 25 n the region is located in noachian highly cratered terrains close to the limit of the martian dichotomy where the outflow channel mawrth vallis cuts the highlands we have examined this region using omega spectra of the surface from 0 9 m to 2 6 m with spatial sampling from 500 m to 3 km offering a full coverage of the region omega spectra show two broad bands centered at 1 m and 2 2 m revealing the presence of clinopyroxene on dark surfaces phyllosilicates have been identified by absorption bands at 1 4 m 1 9 m and 2 2 or 2 3 m comparison with laboratory spectra reveals similarities with al oh smectites such as montmorillonites or fe or mg oh smectites such as nontronite a precise location of the phyllosilicate rich areas on visible hrsc images indicates that they are placed exclusively on bright outcrops mostly on the plateaus dated to the noachian period on hrsc and moc images the phyllosilicate rich outcrops reveal strong erosional features such as numerous residual buttes composed of layers a few meters thick the phyllosilicate rich unit corresponds to a geological unit more than 100 m thick over a horizontal extension approximately of 300 km 400 km this unit implies a large volume of altered rocks either in situ or after transport and deposition in noachian terrains revealing a different climatic and geologic environment from the present one

climatic reconstruction for the younger dryas early holocene transition and the little ice age based on paleo extents of argentiere glacier french alps abstract investigation of holocene extents of mountain glaciers along with the related naturally driven climate conditions helps improve our understanding of glacier sensitivity to ongoing climate change here we present the first holocene glacial chronology in the mont blanc massif argentiere glacier in the french alps based on 25 in situ produced cosmogenic 10be dates of moraines and glacial bedrocks the obtained ages from mapped sequences of moraines at three locations reveal that the glacier retreated from its lateglacial extent and oscillated several times between 11 7 ka and 10 4 ka i e during the younger dryas early holocene yd eh transition before substantially retreating at 10 4 ka climate conditions corresponding to the past extents of argentiere glacier during the yd eh transition 11 ka and the little ice age lia were modelled with two different approaches by determining summer temperature differences from reconstructed ela rises and by using a positive degree day pdd mass balance model the ela rise reconstructions yield a possible range of temperatures for the yd eh transition that were lower by between 3 0 and 4 8 c compared to the year 2008 depending on the choice of the ela sensitivity to temperature the results from the pdd model indicate temperatures lower by 3 6 5 5 c during the yd eh transition than during the 1979 2002 period for the lia our findings highlight the role of local precipitation changes superimposed on the dominant temperature signal in the detailed evolution of the glacier overall this study highlights the challenge that remains in accurately inferring paleoclimate conditions from past glacier extents

improved discrimination of subglacial and periglacial erosion using 10be concentration measurements in subglacial and supraglacial sediment load of the bossons glacier mont blanc massif france deciphering the complex interplays between climate uplift and erosion is not straightforward and estimating present day erosion rates can provide useful insights glaciers are thought to be powerful erosional agents but most published glacial erosion rates combine periglacial subglacial and proglacial erosion processes within a glaciated catchment sediments found in subglacial streams originate either from glacial erosion of substratum or from the rock walls above the glacier that contribute to the supraglacial load terrestrial cosmogenic nuclides tcn are produced by interactions between cosmic ray particles and element targets at the surface of the earth but their concentration becomes negligible under 15 m of ice measuring tcn concentrations in quartz sand sampled in subglacial streams and in supraglacial channels is statistically compliant with stochastic processes e g rockfalls and may be used to discriminate subglacial and periglacial erosion results for two subglacial streams of the bossons glacier mont blanc massif france show that the proportion of sediments originating from glacially eroded bedrock is not constant it varies from 50 to 90 n 6 the difference between the two streams is probably linked to the presence or absence of supraglacial channels and sinkholes which are common features of alpine glaciers therefore most of the published mean catchment glacial erosion rates should not be directly interpreted as subglacial erosion rates in the case of catchments with efficient periglacial erosion and particularly rockfalls the proportion of sediments in the subglacial stream originating from the supraglacial load could be considerable and the subglacial erosion rate overestimated here we estimate warm based subglacial and periglacial erosion rates to be of the same order of magnitude 0 39 0 33 and 0 29 0 17 mm a 1 respectively

compositional investigation of the proposed chloride bearing materials on mars using near infrared orbital data from omega mex 1 several hundred occurrences of chloride bearing salt deposits have been proposed in terrains within the southern highlands of mars on the basis ofthermal emission imaging system and thermal emission spectrometerinfrared observations the spectral identification of chloride salts by remote sensing is challenging because they are transparent over much of the thermal infrared portion of the spectrum further ambiguity arises from the diverse geologic settings in which the putative chloride bearing materials are found in order to better constrain the composition of these unique compositional units we perform a global survey of these materials in the near infrared nir domain with theobservatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer the spectral signatures of the deposits are consistent with although not specific of chlorides we do not observe olivine to be associated with the deposits which confirms that sulfides are an unlikely alternative candidate our systematic search reveals the global lack of association with hydrated minerals phyllosilicates sulfates hydrated silica except for a few deposits noteworthy in northwestern terra sirenum where a small fraction of chloride material overlaps fe mg rich clay bearing terrains even in these locations the morphology and crosscutting relationships of the deposits suggest two separate episodes of mineralization first phyllosilicates then chlorides followed by subsequent formation of sulfates our study shows that local groundwater upwelling seems to be the most frequent source for the water involved in the formation of chloride rather than surface runoff

mineralogy and fluvial history of the watersheds of gale knobel and sharp craters a regional context for the mars science laboratory curiosity s exploration a 500 km long network of valleys extends from herschel crater to gale knobel and sharp craters the mineralogy and timing of fluvial activity in these watersheds provide a regional framework for deciphering the origin of sediments of gale crater s mount sharp an exploration target for the curiosity rover olivine bearing bedrock is exposed throughout the region and its erosion contributed to widespread olivine bearing sand dunes fe mg phyllosilicates are found in both bedrock and sediments implying that materials deposited in gale crater may have inherited clay minerals transported from the watershed while some topographic lows of the sharp knobel watershed host chloride salts the only salts detected in the gale watershed are sulfates within mount sharp implying regional or temporal differences in water chemistry crater counts indicate progressively more spatially localized aqueous activity large scale valley network activity ceased by the early hesperian though later hesperian amazonian fluvial activity continued near gale and sharp craters

antarctic permafrost an analogue for water and diagenetic minerals on mars at high altitudes 1000 m throughout the dry valleys antarctica liquid water is rare yet ground ice which may be millions of years old is pervasive in glacial sediments and bedrock the origin of this ice is different from its arctic and alpine counterparts and may be similar to water on mars we present chemical and isotopic analyses of antarctic ground ice from cores of sirius group sediments at table mountain in the dry valleys these data together with the presence of diagenetic calcite and chabazite in the frozen sediments indicate that the ice and minerals accumulated over long periods of time from atmospheric water vapor and brine films formed on the surface of the ground this analogy indicates that ferric bearing minerals could precipitate under present conditions in the martian soil

the polygonal surface structures in the dalangtan playa qaidam basin nw china controlling factors for their formation and implications for analogous martian landforms