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

searching at the right time of day evidence for aqueous minerals in columbus crater with tes and themis data the primary objective of the thermal emission imaging system themis experiment which has been in orbit at mars since early 2002 is to identify minerals associated with hydrothermal and subaqueous environments data from themis have supported the presence of clays silica rich deposits and chlorides but has not before provided definitive evidence for the presence of sulfates this is an especially puzzling result given that sulfates have been extensively identified with other instruments at mars if present sufficiently exposed and in high enough abundances such minerals should be detectable in orbital thermal infrared spectra at the resolution of themis the extended mission proposal for themis on mars odyssey suggests that the detection of all minerals may be enhanced by observing at an earlier time of day and thus at warmer temperatures therefore in 2009 odyssey moved to an earlier orbit time here we examine themis data collected when the earlier orbit time coincided with the martian local southern late summer ls 270 for columbus crater where compact reconnaissance imaging spectrometer for mars crism data have detected a number of aqueous minerals some of the warmest themis images show evidence for aqueous minerals although not in the same locations where crism finds the highest concentrations several factors contribute to this result including differences in the diurnal temperature curve and levels of induration and particle size for themis earlier time of day and proper seasonal observations combine to provide warm surface temperatures and ideal low atmospheric opacity that significantly increases the ability to definitively identify low spectral contrast aqueous minerals at the surface of mars

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

the response of the southern greenland ice sheet to the holocene thermal maximum to determine the long term sensitivity of the greenland ice sheet to a warmer climate we explored how it responded to the holocene thermal maximum 8 5 cal kyr b p calibrated to calendar years before present i e a d 1950 when lake records show that local atmospheric temperatures in greenland were 2 4 c warmer than the present records from five new threshold lakes complemented with existing geological data from south of 70 n show that the ice margin was retracted behind its present day extent in all sectors for a limited period between ca 7 and 4 cal kyr b p and in most sectors from ca 1 5 to 1 cal kyr b p in response to higher atmospheric and ocean temperatures ice sheet simulations constrained by observations show good correlation with the timing of minimum ice volume indicated by the threshold lake observations the simulated volume reduction suggests a minimum contribution of 0 16 m sea level equivalent from the entire greenland ice sheet with a centennial ice loss rate of as much as 100 gt yr for several millennia during the holocene thermal maximum our results provide an estimate of the long term rates of volume loss that can be expected in the future as regional air and ocean temperatures approach those reconstructed for the holocene thermal maximum

mineralogy of the msl curiosity landing site in gale crater as observed by mro crism orbital data acquired by the compact reconnaissance imaging spectrometer for mars crism and high resolution imaging science experiment instruments on the mars reconnaissance orbiter mro provide a synoptic view of compositional stratigraphy on the floor of gale crater surrounding the area where the mars science laboratory msl curiosity landed fractured light toned material exhibits a 2 2 m absorption consistent with enrichment in hydroxylated silica this material may be distal sediment from the peace vallis fan with cement and fracture fill containing the silica this unit is overlain by more basaltic material which has 1 m and 2 m absorptions due to pyroxene that are typical of martian basaltic materials both materials are partially obscured by aeolian dust and basaltic sand dunes to the southeast exhibit differences in mafic mineral signatures with barchan dunes enhanced in olivine relative to pyroxene containing longitudinal dunes this compositional difference may be related to aeolian grain sorting

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

integration of modern and past pollen accumulation rate par records across the arctic tree line a method for more precise vegetation reconstructions abstract in order to assess the potential role of the boreal forest in the early to mid holocene global dynamics it is critical that the tree line reconstructions are based on precise palaeorecords pollen accumulation rate par calculations provide a technique for estimating past plant population densities independently for each species when considering tree lines an important concept is the threshold par value for the absence presence and dominance of the most common tree species such threshold values are often based on modern lake sediment core top par values in northern fennoscandia records obtained through pollen monitoring now add an important element to these studies as they allow more precise definitions of the temporal and spatial limits of par values here we compare modern par values based on pollen monitoring data with sediment core top data to evaluate the robustness of the threshold values for the major tree species of finnish lapland we apply these threshold values to two fossil par records from this tree line region and as an example of the potential of the approach map the vegetation patterns in the area at 7000 cal yr bp the results indicate that the extent of the mid holocene tree line advance in northern fennoscandia was substantially less than climate vegetation model simulations have predicted despite their value and potential in vegetation reconstructions the use of par values requires careful validation of the data we stress the importance of basin size of precise and reliable sediment dating age depth modelling and assessment of the sedimentary processes in each study basin as prerequisites for par based studies

lateglacial and early holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium line altitudes at northern folgefonna hardanger western norway northern folgefonna c 23 km 2 is a nearly circular maritime ice cap located on the folgefonna peninsula in hardanger western norway by combining the position of marginal mor aines with ams radiocarbon dated glacier meltwater induced sediments in proglacial lakes draining northern folgefonna a continuous high resolution record of variations in glacier size and equili brium line altitudes elas during the lateglacial and early holocene has been obtained after the termination of the younger dryas c 11 500 cal yr bp a short lived 100 150 years climatically induced glacier readvance termed the jondal event 1 occurred within the preboreal oscillation pbo c 11 100 cal yr bp bracketed to 10 550 10 450 cal yr bp a second glacier readvance is named the jondal event 2 a third readvance occurred about 10 000 cal yr bp and corresponds with the erdalen event 1 recorded at jostedalsbreen an exponential relationship between mean solid winter precipitation and ablation season temperature at the ela of norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ela and an indepen dent proxy for summer temperature compared to the present the younger dryas was much colder and drier the jondal event 1 pbo was colder and somewhat drier and the jondal event 2 was much wetter the erdalen event 1 started as rather dry and terminated as somewhat wetter varia tions in glacier magnitude elas and corresponding palaeoclimatic reconstructions at northern folge fonna suggest that low altitude cirque glaciers lowest altitude of marginal moraines 290 m in the area existed for the last time during the younger dryas these low altitude cirque glaciers of sug gested younger dryas age do not fit into the previous reconstructions of the younger dryas ice sheet in hardanger copyright 2005 john wiley sons ltd

conductivity and fluids in the oceanic upper mantle abstract three deep electromagnetic soundings in the north pacific ocean were re examined our inversion of existing data showed the presence of conductors below the three sites in very good agreement with previous results we showed that h 2 o rich fluids as well as partial melting account for the conductivities observed this led us to determine temperatures ranging firstly from 1050 to 1150 c when only h 2 o rich fluids were present and secondly from 1300 to 1350 c for partial melting only we suggest that the upper mantle below the two oldest sites 30 and 72 ma is characterized by about 1 of partial melting in the presence of about 1 of h 2 o rich fluids below the third site that nearest to the ridge zone 1 ma the degree of partial melting might reach 10 the presence of 1 of h 2 o rich fluids would reduce the effect of the asthenospheric outflows on the lithospheric magmatism this agrees with the principle of thermodynamic decoupling of the asthenosphere and lithosphere the weakening effect of fluids particularly water on upper mantle rheology is also discussed we suggest that the asthenosphere and lithosphere might be decoupled mechanically which if true would affect small scale convection below the oceanic lithosphere

electromagnetic induction in new zealand analogue model and field results abstract the behaviour of electric and magnetic variations over north island new zealand is studied with the aid of a laboratory analogue model the source field frequencies used in the analogue modelling simulate naturally occurring geomagnetic variations of 5 120 min periods in phase and quadrature magnetic and electric fields for a selection of traverses for the modelled region of north island are presented since north island is of a relatively narrow cross section the field responses even for inland locations are expected to show strongly the effects of the surrounding ocean the irregular coastlines as well as the strait between north and south islands lead to coastal and inland field anomalies due to induced currents being deflected and channelled to produce localized current densities the comparison of model results with field station measurements obtained earlier individually by ingham and by midha for sites in the northeastern central and southern near cook strait regions of north island demonstrates the large role the ocean has in the observed field responses differences in the model and field results at some sites are expected and should reflect the effects of the local geology and the conductive substructure related to the complex tectonics of the region not simulated in the model

regional scale stratigraphy of surface units in tyrrhena and iapygia terrae mars insights into highland crustal evolution and alteration history 1 the compositional thermophysical and geologic characteristics of surface units in iapygia and tyrrhena terra 60 e 100 e 0 30 s provide new insights into the compositional stratigraphy of the region intercrater plains are dominated by two surface units the older unit unit 1 is deficient in olivine and more degraded and likely consists of a mixture of impact volcanic and sedimentary materials the younger unit unit 2 is enriched in olivine exhibits a resistant morphology and higher thermal inertia and likely represents volcanic infilling of plains units 1 and 2 bear a strong resemblance to those previously mapped in mare serpentis a section of highlands crust located northwest of hellas basin thus the two major intercrater plains units are even more widespread than previously thought and therefore likely constitute important components of mars highland stratigraphy many craters in the region contain high thermal inertia deposits unit 3 that are compositionally identical to unit 2 these may have formed via volcanic infilling or may represent sedimentary materials that have been eroded from crater walls and lithified less common units include olivine and or pyroxene rich massifs and crater central peaks these are primarily found within hellas basin rim units and may represent mantle materials brought toward the surface during the hellas impact putative chloride deposits are primarily associated with olivine deficient surfaces unit 1 that may be heavily degraded occurrences of unit 2 the observations raise a variety of questions related to martian crustal evolution and alteration that may have more widespread implications outside the study region

identification of quartzofeldspathic materials on mars 1 a unique spectral component has been identified near and on the central peaks of two 30 km diameter craters in northern syrtis major these exposures are clearly visible in thermal emission imaging system themis color radiance images as well as themis and thermal emission spectrometer tes surface emissivity data both tes and themis data indicate the presence of increased 1050 1250 cm 1 8 9 5 m absorption compared to the surrounding basaltic plains and tes data also display other absorptions at 400 470 and 800 cm 1 25 20 and 12 m consistent with the presence of quartz ratio and isolated central peak spectral unit spectra match laboratory emissivity spectra of granitoid rocks composed primarily of quartz and plagioclase feldspar deconvolution results also indicate that the surface contains quartz and feldspar in addition to a high si glass and or sheet silicate component because central peak materials are brought up from depth during the cratering event the association of the quartzofeldspathic mineralogy with the central peaks of the craters indicates that the quartz bearing material was excavated from depth the occurrence in the two adjacent craters may imply a granitoid pluton of considerable extent a plausible formation mechanism for this relatively silicic material may be similar to that of terrestrial trondhjemites which do not require plate tectonics the rarity of the exposures implies that the process that formed the granitoid composition was probably not widespread the presence of quartz bearing material on mars indicates that mechanisms that produce highly differentiated magmas have been present and extends the diversity of surface compositions identified

observations of an aeolian landscape from surface to orbit in gale crater abstract landscapes derived solely from aeolian processes are rare on earth because of the dominance of subaqueous processes in contrast aeolian derived landscapes should typify mars because of the absence of liquid water the long exposure times of surfaces and the presence of wind as the default geomorphic agent using the full range of available orbital and mars science laboratory rover curiosity images wind formed features in gale crater were cataloged and analyzed in order to characterize the aeolian landscape and to derive the evolution of the crater wind regime over time inferred wind directions show a dominance of regional northerly winds over geologic time scales but a dominance of topography driven katabatic winds in modern times landscapes in gale crater show a preponderance of aeolian features at all spatial scales interpreted processes forming these features include first cycle aeolian abrasion of bedrock pervasive deflation organization of available sand into bedforms abundant cratering and gravity driven wasting all of which occur over a background of slow physical weathering the observed landscapes are proposed to represent a spectrum of progressive surface denudation from fractured bedrock to retreating bedrock capped mesas to remnant hills capped by bedrock rubble to desert pavement plains this model of landscape evolution provides the mechanism by which northerly winds acting over 3 ga excavated tens of thousands of cubic kilometers of material from the once sediment filled crater thus carving the intra crater moat and exhuming mount sharp aeolis mons the current crater surface is relatively sand starved indicating that potential sediment deflation from the crater is greater than sediment production and that most exhumation of mount sharp occurred in the ancient geologic past

laboratory electromagnetic modelling of the subducting juan de fuca plate abstract the effect of the depth of the dipping juan de fuca plate subducting the west coast of the vancouver island washington oregon region is studied using a scaled laboratory analogue model the subducting plate is modelled horizontal offshore then dipping at 10 under vancouver island and dipping further at 30 as it subducts the continent for the british columbia region and 45 under the washington oregon region the strike of the bending plate follows the general strike of the continental coastline with an abrupt 42 change in direction in the puget sound area the model results show that the coast effect described by the vertical to horizontal magnetic field ratio is highly dependent upon the period and the depth of the dipping substructure while the conducting boundaries of the subducting plate significantly reduce the apparent resistivities for coastal locations enhanced induction arrows exist for a large range inland owing to the steeply dipping subducting plate

dune morphology sand transport pathways and possible source areas in east thaumasia region mars an aeolian system located in aonia terra eastern thaumasia region consists of six dark dune fields the dune pattern suggests an organized extended sand transport system which is characterized by the presence of long sand corridors the latter connects the different ergs with potential sources the sand stored in the ergs is provided by layered materials exposed in pits and crater walls and by the ergs themselves most of the sand converges from the marginal dune fields into the central erg c the latter develops in an area of convergence of at least three different winds from the southwest the northeast and the northwest the northwesterly flows seem to postdate the other winds as suggested by the development of a complex dune pattern in the western portion of the erg c representing a successive episode of aeolian construction collectively such complex dune patterns show how dune fields could record major changes in the wind regimes of mars

comparison of the mineral composition of the sediment found in two mars dunefields ogygis undae and gale crater three distinct endmembers identified abstract the composition of two dune fields ogygis undae and the ne sw trending dune field in gale crater the bagnold dune field and western dune field were analyzed using thermal emission spectra from the mars global surveyor mgs thermal emission spectrometer tes and the mars odyssey thermal emission imaging system themis the gale crater dune field was used as a baseline as other orbital compositional analyses have been conducted and in situ sampling results will soon be available results from unmixing thermal emission spectra showed a spatial variation between feldspar mineral abundances and pyroxene mineral abundances in ogygis undae other datasets including nighttime thermal inertia values also showed variation throughout the dune field one explanation proposed for this variation is a bimodal distribution of two sand populations this distribution is seen in some terrestrial dune fields the two dune fields varied in both mineral types present and in uniformity of composition these differences point to different source lithologies and different distances travelled from source material examining these differences further will allow for a greater understanding of aeolian processes on mars

the coast effect response in geomagnetic field measurements abstract two dimensional 2d numerical models of electromagnetic em induction for anomalous conductors in continental and island coastal regions are studied to determine constraints on ocean conductor separation distances that would permit to within an acceptable approximation a simple vector subtraction of the coast effect response the anomalous conductors are in the form of an upwelling or a depression in the asthenospheric conductive substratum at depth the coast effect response range yr is arbitrarily taken to be the distance from the ocean at which the b z b y n coast effect response is reduced to a value of 0 2 the response ranges are determined and presented empirically as a function of period for a range of conductive substratum depths island widths and ocean depths the response ranges are tested in 2d numerical models that include an anomalous conductor in the form of either an upwelling or a depression in the conductive substratum under the ocean and host earth the induction arrows for the anomalous conductor are shown to be in good agreement with the difference arrows obtained by subtracting the responses of a model without the anomalous conductor from the responses of the model that includes the anomalous conductor as an application difference arrows obtained by subtracting three dimensional laboratory analogue model coast effect responses from field site responses are employed in the interpretation of induction arrow responses available for a number of sites in the bohai bay region of china and the kii peninsula region of japan

a laboratory electromagnetic model study of the juan de fuca plate region the behaviour of the magnetic field variations over the juan de fuca plate region is studied using a scaled laboratory analogue model the model includes a simulation of the complex juan de fuca plate subducting the vancouver island region the subducting plate is modelled with a profile of increasing inclination from east to west horizontal offshore dipping at 10 under vancouver island and bending further under georgia strait to subduct the continent at 30 for the b c region and 45 for the washington oregon region the strike of the bending plate follows the general strike of the continental coastline with an abrupt change in direction 42 in the puget sound area the model substructure simulates a subducting plate overplated by a sediment layer several kilometres thick and underlain by a 30 km thick highly conducting upper asthenosphere the model source frequencies used simulate periods 5 120 min in the geophysical scale in phase and quadrature hx hy and hz magnetic field measurements for the modelled region are presented for an approximately uniform overhead horizontal source field for e and h polarizations electric field of the source approximately parallel and perpendicular respectively to the west coast of vancouver island the fields for three regions of the model over vancouver island over the olympic peninsula and over a linear portion of the u s coastline are examined in detail the general conclusion is that the effect of the dipping subducting plates is to significantly attenuate at short periods the maxima in the anomalies at the coastlines underlain by the 10 dipping plate while leading to anomalous vertical and horizontal fields over ranges as large as 500 km inland over a wide period range anomalous fields are observed over the offshore and inland knee bends of the subducting plates at all periods for both e and h polarizations for locations on land the in phase induction arrows point seaward and perpendicular to the strikes of the dipping plates for all periods while the quadrature arrows at short periods point landward and rotate to point seaward for periods greater than 20 min

em induction in the vancouver island region 3d numerical analogue model and field site results electromagnetic induction in the vancouver island region for a uniform inducing source field for 300 s period is investigated with the aid of three dimensional 3 d numerical and analogue model results and field site measurements the thin sheet numerical model based on the subducting juan de fuca plate analogue model ofdossoet al consists of a 5km thick non uniform thin sheet comprising the lateral conductivity contrasts arising from the land the varying depth ocean and the sediment underlain by a four layer conductive structure the four layer conductive structure beneath the non uniform thin sheet simulates the effect of the juan de fuca plate subducting vancouver island to examine the effects of the ocean channel depth between vancouver island and the british columbia canada mainland numerical results were obtained for two channel depths 0 and 600 m the results indicate that the channel plays an important role in the geomagnetic response in the central and inner coastal regions of vancouver island the general agreement of the 3 d numerical model induction arrows with the analogue model and field site induction arrows for 300 s supports the premise of a layered conductive substructure dipping at a small angle at most beneath vancouver island

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

dust production by abrasion of eolian basalt sands analogue for martian dust dust is nearly ubiquitous on mars covering much of the planet s surface having been redistributed by dust storms analysis of dust via landed instrumentation indicates a basaltic composition for its protolith the same is interpreted for the dark dune sands encountered at rover field sites in this paper we used samples of aeolian sands derived from basaltic volcanoes in an experiment to simulate dust production from basalt dune sands within an abrasion chamber in addition we used samples from gypsum dunes because gypsum is found within dune fields on the northern plains of mars the results expressed as weight of sample reduced to dust show a remarkably broad range over four orders of magnitude aeolian abrasion of basalt sands can produce similar amounts of dust as is the case for some desert sands on earth some plausible mars analogue materials can produce large amounts of dust suggesting that aeolian movement of basaltic sand and volcanic sediments on the surface of mars is a potential source of fine grained sediment or dust

geologic context of in situ rocky exposures in mare serpentis mars implications for crust and regolith evolution in the cratered highlands abstract global acquisition of infrared spectra and high resolution visible and infrared imagery has enabled the placement of compositional information within stratigraphic and geologic context mare serpentis a low albedo region located northwest of hellas basin is rich in spectral and thermophysical diversity and host to numerous isolated exposures of in situ rocky material most martian surfaces are dominated by fine grained particulate materials that bear an uncertain compositional and spatial relationship to their source thus location and characterization of in situ rock exposures is important for understanding the origin of highland materials and the processes which have modified those materials using spectral thermophysical and morphologic information we assess the local and regional stratigraphy of the mare serpentis surface in an effort to reconstruct the geologic history of the region the martian highlands in mare serpentis are dominated by two interspersed surface units which have distinct compositional and thermophysical properties 1 rock dominated surfaces relatively enriched in olivine and pyroxene and depleted in high silica phases and 2 sediment or indurated material depleted in olivine and pyroxene with relatively higher abundance of high silica phases this is a major previously unrecognized trend which appears to be pervasive in the mare serpentis region and possibly in other highland areas the detailed observations have led us to form two hypotheses for the relationship between these two units either 1 they are related through a widespread mechanical and or chemical alteration process where less mafic plains materials are derived from the mafic bedrock but have been compositionally altered in the process of regolith formation or 2 they are stratigraphically distinct units representing separate episodes of upper crust formation existing observations suggest that the second scenario is more likely in this scenario plains materials represent older degraded and possibly altered basement rock whereas the rocky exposures represent later additions to the crust and are probably volcanic in origin these hypotheses should be further testable with decimeter resolution imagery and meter resolution short wavelength infrared spectra

lateglacial and early holocene climates of the atlantic margins of europe stable isotope mollusc and pollen records from orkney scotland the margins of mainland europe and especially those areas coming under the influence of north atlantic weather systems are ideally placed to record changing palaeoclimates cores from an infilled lake basin at crudale meadow in mainland orkney revealed basal deposits of calcareous mud marl beneath sedge peat stable isotope palynological and molluscan analyses allowed the establishment of palaeoenvironmental changes through the devensian lateglacial and the early holocene the 18omarl record exhibited the existence of possibly four climatic oscillations in the lateglacial one of which within event cf gi 1c is not often commented upon as well as the preboreal oscillation and other holocene perturbations the cold episodes succeeding the preboreal oscillation were demarcated conservatively and one of these event c5 11 0 ka may have previously been unremarked while the putative 9 3 and 8 2 ka events seem not to produce corresponding palynologically visible floristic changes the events at crudale meadow are consistent with those recorded at other sites from britain ireland and elsewhere and can be correlated with isotopic changes shown by the greenland ice cores the multi proxy approach enriches the environmental reconstructions from the site although the synchronicity of the response of the various proxies is sometimes equivocal depending upon the time period concerned taphonomy and the nature of the deposits the site may contain the most northerly lateglacial isotope record from northwest europe and it has yielded one of the best archives for the demonstration of abrupt early holocene events within britain

p wave velocity structure of the earth s crust beneath vancouver island refraction data were recorded from three shot points out to a maximum distance of 330 km as part of the 1980 vancouver island seismic project visp80 these vertical component data are partially reversed and so can be interpreted in terms of two dimensional structures by iterative modeling of p wave travel times and amplitudes the structure of the upper crust is the best constrained part of the model it consists generally of a gradually increasing velocity from 5 3 km s at the surface to 6 4 km s at 2 km depth to 6 75 km s at 15 5 km depth where the velocity increases sharply to 7 km s below 20 km depth the model becomes speculative because the data provide only indirect constraints on velocities at these depths an interpretation that fits the observed times and amplitudes has a low velocity zone in the lower crust and a moho at 37 km depth the only significant departure from this general structure is beneath the central part of vancouver island where the 15 5 km boundary in the model atta

mineralogical characterization of mars science laboratory candidate landing sites from themis and tes data abstract data from the mars global surveyor thermal emission spectrometer tes and the mars odyssey thermal emission imaging system themis instruments are used to assess the mineralogic and dust cover characteristics of landing regions proposed for the mars science laboratory msl mission candidate regions examined in this study are eberswalde crater gale crater holden crater mawrth vallis miyamoto crater nili fossae trough and south meridiani planum compositional units identified in each region from tes and themis data are distinguished by variations in hematite olivine pyroxene and high silica phase abundance whereas no units are distinguished by elevated phyllosilicate or sulfate abundance though phyllosilicate minerals have been identified in all sites using near infrared observations these minerals are not unambiguously detected using either tes spectral index or deconvolution analysis methods for some of the sites small phyllosilicate outcrop sizes relative to the tes field of view likely hinder phyllosilicate mineral detection porous texture and or small particle size 15 possibly up to 40 of a high silica phase such as amorphous silica or zeolite high silica phase abundance over phyllosilicate bearing surfaces in mawrth vallis is higher than that of surrounding surfaces by 10 15 with the exception of these high silica surfaces in mawrth vallis regions examined in this study exhibit similar bulk mineralogical compositions to that of most low albedo regions on mars the msl scientific payload will thus be able to provide important information on surface materials typical of low albedo regions in addition to investigating the origin of phyllosilicate and or sulfate deposits with the exception of gale crater all of the landing sites have relatively low dust cover compared to classic high albedo regions tharsis arabia and elysium and to previous landing sites in gusev crater utopia planitia and chryse planitia

a new method for the semiquantitative determination of major rock forming minerals with thermal infrared multispectral data application to themis infrared data 1 we have developed a new method least residual iterative spectral mixture analysis lrisma to semiquantitatively determine major rock forming minerals feldspar pyroxene olivine high silica phases and quartz with multispectral thermal infrared data sublibraries of minerals are generated from a master library of minerals based on prior knowledge to produce a suite of realistic mineral end member combinations to fit the target spectra mineral abundances that correspond to the least root mean square errors best fit generally agree best with previous petrographic studies of laboratory measured rock samples and thermal infrared hyperspectral analysis of materials on the surface of mars given the greatly reduced spectral range and resolution of thermal emission imaging system themis spectra the accuracy and reproducibility of lrisma is 4 16 and 5 20 respectively while the accuracy of petrographic and previous hyperspectral studies is 5 15 lrisma can be applied to semiquantitatively refine the bulk surface mineralogy of small scale 1 km2 geologic features with high quality themis spectral data high surface temperature 260 k low atmospheric opacity total ice 0 04 and total dust 0 15 with the ultimate goal of better understanding regional geologic processes

seismic reflection imaging of the subducting juan de fuca plate mckenzie and parker s early suggestion1 that the juan de fuca plate is underthrusting north america has since been confirmed by numerous studies evidence for plate convergence along this junction includes a sediment filled trench2 7 intense compressional deformation of the continental slope and shelf sediments2 7 seafloor magnetic anomalies that extend beneath the continental slope2 4 inland andesitic volcanoes8 paired low high heat flow and gravity anomalies9 10 active onshore deformation11 12 onshore crustal earthquakes with compressional axes parallel to the direction of plate convergence13 sinistral strike slip earthquakes along the nootka fault fig 1 14 and a well defined benioff wadati zone6 15 16 here we report the results of a seismic reflection survey that has delineated two slabs of oceanic lithosphere underlying vancouver island one that is currently being subducted and one that is underplated these findings lead us to speculate that successive underplating of oceanic lithosphere may be an important process in the evolution and growth of continents

mgs tes thermal inertia study of the arsia mons caldera 1 temperatures of the arsia mons caldera floor and two nearby control areas were obtained by the mars global surveyor mgs thermal emission spectrometer tes these observations revealed that the arsia mons caldera floor exhibits thermal behavior different from the surrounding tharsis region when compared with thermal models our technique compares modeled and observed data to determine best fit values of thermal inertia layer depth and albedo best fit modeled values are accurate in the two control regions but those in the arsia mons caldera are consistently either up to 15 k warmer than afternoon observations or have albedo values that are more than two standard deviations higher than the observed mean models of both homogeneous and layered such as dust over bedrock cases were compared with layered cases indicating a surface layer at least thick enough to insulate itself from diurnal effects of an underlying substrate material because best fit models of the caldera floor poorly match observations it is likely that the caldera floor experiences some physical process not incorporated into our thermal model even on mars arsia mons is an extreme environment where co2 condenses upon the caldera floor every night diurnal temperatures range each day by a factor of nearly 2 and annual average atmospheric pressure is only around one millibar here we explore several possibilities that may explain the poor modeled fits to caldera floor and conclude that temperature dependent thermal conductivity may cause thermal inertia to vary diurnally and this effect may be exaggerated by presence of water ice clouds which occur frequently above arsia mons

early to mid holocene forest line and climate dynamics in southern scandes mountains inferred from contrasting megafossil and pollen data the result of 344 radiocarbon dated megafossils is here presented and discussed this study aims at elucidating early to mid holocene forest line and climate dynamics in the southern scandes along

evidence for extensive olivine rich basalt bedrock outcrops in ganges and eos chasmas mars 1 several localized outcrops of olivine enriched bedrock have been previously identified in the ganges and eos chasma area on the eastern end of valles marineris with the thermal emission imaging system multispectral images these outcrops form a layer in the walls of ganges chasma and appear to be the remnants of a once continuous unit which was mapped over 100 km in this study we further characterize the composition forsterite content of 0 68 olivine abundance 10 to 15 thermal inertia 600 jk 1 m 2 s 1 2 consistent with in place rocky material vertical dimension 60 to 220 m extent 1100 km laterally volume 9 9 104 km3 dip 0 013 ne and continuity of this layer utilizing thermal emission spectrometer hyperspectral thermal emission imaging system multispectral and mars orbiter laser altimeter elevation data morphologic data from high resolution imagery display a relatively unmantled rough and pitted surface associated with the olivine enriched material consistent with thermal inertia data four possibilities for the origin of the olivine enriched unit are 1 volcanism associated with tectonic rifting of the valles marineris system 2 a volcaniclastic flow deposit 3 an intrusive mafic sill or 4 a discrete episode in martian history during which flood lavas were erupted onto the surface the most likely origin is an eruptive event consisting of compositionally uniform flood lavas originating from a primitive mantle source region possibly associated with the initiation of tharsis volcanism this unit is one of the largest continuous compositional units found on mars and is strikingly similar to other olivine enriched deposits identified in previous studies where compositional morphologic and thermophysical similarities are observed these similarities may indicate that there was a period in early martian history where compositionally uniform and extensive olivine enriched flood basalts were erupted on the martian surface

athena mars rover science investigation 1 each mars exploration rover carries an integrated suite of scientific instruments and tools called the athena science payload the primary objective of the athena science investigation is to explore two sites on the martian surface where water may once have been present and to assess past environmental conditions at those sites and their suitability for life the remote sensing portion of the payload uses a mast called the pancam mast assembly pma that provides pointing for two instruments the panoramic camera pancam and the miniature thermal emission spectrometer mini tes pancam provides high resolution color stereo imaging while mini tes provides spectral cubes at mid infrared wavelengths for in situ study a five degree of freedom arm called the instrument deployment device idd carries four more tools a microscopic imager mi for close up imaging an alpha particle x ray spectrometer apxs for elemental chemistry a mossbauer spectrometer mb for the mineralogy of fe bearing materials and a rock abrasion tool rat for removing dusty and weathered surfaces and exposing fresh rock underneath the payload also includes magnets that allow the instruments to study the composition of magnetic martian materials all of the athena instruments have undergone extensive calibration both individually and using a set of geologic reference materials that are being measured with all the instruments using a mer like rover and payload in a number of field settings we have devised operations processes that will enable us to use the mer rovers to formulate and test scientific hypotheses concerning past environmental conditions and habitability at the landing sites

extraordinary floods of 4100 4000 a bp recorded at the late neolithic ruins in the jinghe river gorges middle reach of the yellow river china abstract holocene palaeohydrological investigations were carried out in the middle reach of the jinghe river that drains the central part of the loess plateau a set of palaeoflood slackwater deposits was found interbedded in the holocene loess soil sequence within the cliff riverbanks both the sedimentary criteria and the analytical results show that this sediment was sourced from a suspended sediment load of floodwater the major cultural layer of a late neolithic settlement 4300 4000 a bp occurring at the same site is blanketed by this flood deposit directly slopewash with pottery shards charcoal and burnt earth occurs in between the palaeoflood slackwater deposit beds it indicates that each of the slackwater deposit beds has recorded one individual flood event and that these extraordinary floods occurred when the late neolithic people occupied the riverbank terrace land this pre historical settlement was abandoned after the floods eventually due presumably to repeated inundation by overbank floodwater the flood events were osl dated to between 4100 and 4000 a bp and checked by archaeological dating of the anthropogenic remains retrieved from the sequences peak discharges of the floods were estimated to between 19 500 and 22 000 m3 s 1 which is several times gauged maximum floods during the 4200 4000 a bp climatic event severe droughts were documented in china s monsoonal regions and great floods were known from an ancient legend this study provides a well dated sediment record of pre historical floods which occurred at the transition from the neolithic to the bronze age in the yellow river basin it shows that extraordinary floods were part of the abrupt climatic variability during the 4200 4000 a bp climatic event the highly variable unstable and catastrophic climate typified by both droughts and floods resulted in settlement abandonment and possibly the decline of the highly developed late neolithic civilizations in china s monsoonal regions

geomagnetic variation sounding of the asthenosphere beneath the juan de fuca ridge two ocean bottom magnetometers have been deployed at sites on either side of the juan de fuca ridge 20 and 40 km from the crest near latitude 47 n twelve days of data were recorded simultaneously at the two sites and these data have been used to determine the electrical conductivity structure beneath the region the vertical field variations at both stations are of very low amplitude in the period range 0 25 to 8 hours with no detectable phase reversal across the ridge electric fields in the ocean layer have been estimated from the attenuation of sea floor horizontal fields with respect to victoria and the resulting impedance spectra inverted to find resistivity as a function of depth using the technique of oldenburg 1979 resistivity models which fit the data within the specified bounds are characterized by a comparatively resistive crust and upper lithosphere overlying a low resistivity zone between depths of 55 and 75 km which in turn appears to be underlain by a higher resistivity section the average resistivities are used to estimate temperature and melt fraction on the basis of the effective medium theory of shankland and waff 1976 for a basalt melt fraction within an olivine matrix for the low resistivity zone and depending on the water content of the melt 0 to 10 the estimated temperature range is 1400 c to 1250 c and the corresponding melt fraction 0 05 to 0 09 the data suggest that the melt fraction decreases below 80 km the conductivity profile from magnetotelluric data on 72 ma ocean floor in the north central pacific filloux 1977 has similar characteristics to the 1 ma old conductivity structure near the juan de fuca ridge but with the low resistivity layer at depths of 140 to 220 km in both cases the resistivity minimum should be equated with the region of maximum partial melt within the asthenosphere rather than with the base of the lithosphere the increase in depth to this zone with increasing lithosphere age is in general agreement with plate tectonic concepts

olivine dissolution by acidic fluids in argyre planitia mars evidence for a widespread process compositional and morphological analyses of basin rim units in argyre planitia are con sistent with local olivine rich materials that become relatively olivine poor in the process of being transformed from rocky materials to fi particulate regolith where high thermal inertia rocky surfaces are observed the composition is more mafi c than the surrounding fi nes this relationship between rocks and soils appears to be common on mars as a similar pattern is observed in other locations such as gusev crater isidis planitia and nili fossae despite the lack of local detectable alteration products these trends may be an indication that most martian dark regions are not similar in composition to the primary igneous composition from which they are derived the martian crust may be signifi cantly more mafi c and alteration of these surfaces may be more pervasive than has been inferred from the bulk surface mineral ogy derived from orbital observations

lake store finnsjoen a key for understanding lateglacial early holocene vegetation and ice sheet dynamics in the central scandes mountains the lateglacial lg deglaciation and vegetation development in the scandes mountains has been debated for a century here we present new evidence from microfossils radiocarbon dated plant macrofossils and sedimentary ancient dna from laminated sediments in lake store finnsjoen 1260 m a s l at dovre central norway combined with previous results from three other dovre lakes this allows for new interpretations of events during and immediately after the lg deglaciation the finnsjoen sediments present the first uninterrupted record of local vegetation development in the scandes mountains from the late younger dryas yd ca 12 000 cal years bp to the early holocene around 9700 cal years bp the local vegetation in late yd early holocene was extremely sparse with pioneer herbs e g artemisia norvegica beckwithia campanula cf uniflora koenigia oxyria papaver saxifraga spp and dwarf shrubs betula nana salix including salix polaris from 11 300 cal years bp local vegetation rapidly closed with dominant dryas saxifraga spp and silene acaulis from ca 10 700 cal years bp open birch forests with juniper empetrum nigrum and other dwarf shrubs developed pine forests established within the area from 10 300 cal years bp we identified the cold preboreal oscillation pbo not earlier described from pollen data in south norway around 11 400 cal years bp by a regional pollen signal distinct local vegetation changes were not detected until the post pbo warming around 11 300 cal years bp apparently the earlier warming at the yd holocene transition at 11 650 cal years bp was too weak and short lived for vegetation closure at high altitudes at dovre for the first time we demonstrate a regional glacier readvance and local ice cap formations during the yd in the scandes mountains in two of the deep lakes with small catchments yd glaciation blocked sedimentation without removing old sediments and caused a hiatus separating sediments of the ice free lg interstadial lgi from those of the ice free holocene period both regional glaciers and local ice caps caused hiati ice free pre yd conditions at dovre followed by a yd readvance point to a scenario that is intermediate between the maximum ice model postulating a thick glacier during the entire lg and the minimum ice model postulating thin and multi domed early lg ice

megaripple migration on mars aeolian megaripples with 5 to 50 m spacing are abundant on the surface of mars these features were repeatedly targeted by high resolution orbital images but they have never been observed to move thus aeolian megaripples especially the bright toned ones often referred as transverse aeolian ridges tars have been interpreted as relict features of a past climate in this report we show evidence for the migration of bright toned megaripples spaced 1 to 35 m 5 m on average in two equatorial areas on mars indicating that megaripples and small tars can be active today the moving megaripples display sand fluxes that are 2 orders of magnitudes lower than the surrounding dunes on average and unlike similar bedforms on earth can migrate obliquely and longitudinally in addition the active megaripples in the two study areas of syrtis major and mawrth vallis show very similar flux distributions echoing the similarities between dune crest fluxes in the two study areas and suggesting the existence of a relationship between dune and megaripple fluxes that can be explored elsewhere active megaripples together with high sand flux dunes represent a key indicator of strong winds at the surface of mars a past climate with a denser atmosphere is not necessary to explain their accumulation and migration

reconstructing palaeoclimatic variables from fossil pollen using boosted regression trees comparison and synthesis with other quantitative reconstruction methods abstract we test and analyse a new calibration method boosted regression trees brts in palaeoclimatic reconstructions based on fossil pollen assemblages we apply brts to multiple holocene and lateglacial pollen sequences from northern europe and compare their performance with two commonly used calibration methods weighted averaging regression wa and the modern analogue technique mat using these calibration methods and fossil pollen data we present synthetic reconstructions of holocene summer temperature winter temperature and water balance changes in northern europe highly consistent trends are found for summer temperature with a distinct holocene thermal maximum at ca 8000 4000 cal a bp with a mean t jja anomaly of ca 0 7 c at 6 ka compared to 0 5 ka we were unable to reconstruct reliably winter temperature or water balance due to the confounding effects of summer temperature and the great between reconstruction variability we find brts to be a promising tool for quantitative reconstructions from palaeoenvironmental proxy data brts show good performance in cross validations compared with wa and mat can model a variety of taxon response types find relevant predictors and incorporate interactions between predictors and show some robustness with non analogue fossil assemblages

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

the formation of infilled craters on mars evidence for widespread impact induced decompression of the early martian mantle flat floored craters have long been recognized on mars with early work hypothesizing a sedimentary origin more recently high resolution thermal inertia measurements show that these craters contain some of the rockiest materials on the planet inconsistent with poorly consolidated sedimentary materials in this study the distribution physical properties morphology and thermal inertia and composition of these craters are thoroughly investigated over the entire planet the majority of the 2800 rocky crater floors identified are concentrated in the low albedo 0 1 0 17 cratered southern highlands these craters were infilled at 3 5 ga and are associated with the highest thermal inertia values and some of the most mafic materials identified on the planet although several processes may have led to the formation of the crater floors the most likely scenario is volcanic infilling through fractures created by the impact event the primitive magma source directly results from decompression melting of the martian mantle by the removal of the crustal material excavated by the impactor volcanic infilling of craters by decompression melting appears to only have occurred in early martian history when the lithosphere was still relatively thin and the thermal gradient was high this process was widespread and responsible for the eruption of significant volumes of primitive material inside and likely outside of craters impact induced decompression melting of the martian mantle accounts for the unusual infilling of martian craters and is a widespread planetary process that has gone previously undocumented

laboratory electromagnetic model results for the emslab region apparent resistivities and vertical to horizontal magnetic field ratios for the lincoln line traverse in the emslab project region are studied using a scaled laboratory analogue model the model includes a simulation of the juan de fuca plate subducting the canadian u s pacific northwest region in the model the subducting plate is taken to be horizontal offshore dipping at 10 beneath the coast then inland bending farther to dip at 45 in the washington oregon region and at 30 in the british columbia region the model results show that for inland sites the apparent resistivity for the telluric field component parallel to the coast and thus also parallel to the strike of the dipping conductive substructure depends strongly on period while the resistivity for the telluric field perpendicular to the coast is largely a galvanic effect and changes less with period the amplitude of the vertical to horizontal magnetic field ratio along the lincoln line shows a saddle shaped response with the coastal maximum followed by a second maximum inland due to the dipping substructure further rather than decreasing rapidly with distance inland as expected for a simple coast effect the field ratios retain significant values large distances inland for periods of 3 120 min model results for 120 min period are compared with one example of field results for the emslab project region

the vancouver island seismic project a co crust onshore offshore study of a convergent margin the seismic structure of the british columbia continental margin has been investigated using four reversed refraction profiles the profile across strike extended 350 km from the volcanic arc on the continent to the deep ocean of the juan de fuca plate the three profiles along strike were located on vancouver island on the continental shelf and in the deep ocean on the juan de fuca plate interpretation of the profile along vancouver island yields a well constrained model for the upper crust with velocity increasing from 5 3 km s at the surface to 6 4 km s at 2 km depth to 6 75 km s at 15 5 km depth where the velocity increases sharply to 7 km s the velocity structure of the deep crust and the crustal thickness are poorly constrained four possible velocity functions based on ambiguous first arrivals and or secondary phases interpreted as moho reflections are presented the preferred one includes a deep crustal low velocity zone with a crustal thickness of 37 km models with a constant 7 1 km

seismic reflections from subducting lithosphere data from two short reflection lines obtained using explosives and an airgun source together with offshore and onshore refraction profiles and a gravity interpretation provide evidence of coherent reflections between the subducting oceanic juan de fuca and overriding continental america plates

the mars global digital dune database mgd3 global patterns of mineral composition and bedform stability abstract we present an expansion to the mars global digital dune database mgd3 describing 1 bulk dune field composition determined by fitting a mineral spectral library to thermal emission spectra tes data and 2 a morphologic stability index that measures the degree of non aeolian modification that has eroded and stabilized each dune field this paper describes results for these two components providing insight into global patterns of dune sand sources postdepositional alteration and mineral maturity consistent with the work of others the main mineral components of each analyzed dune field are feldspar pyroxene and high silica phases with minor amounts of olivine and possibly sulfate minerals subtle global scale spatial variations in olivine and feldspar abundances correspond with previously observed trends in surface mineralogy suggesting that dune sand is reflective of its regional setting and thus that aeolian sand has typically not traveled far

conductivity structure of oceanic upper mantle beneath the pacific plate summary ocean bottom magnetotelluric responses from three ages on the pacific plate have been inverted to reveal the presence of a conductive zone whose depth is a function of lithospheric age the conductivity achieves its maximum value 0 1 sm 1 at depths near 70 120 and 180 km for lithospheric ages of 1 30 and 72 myr respectively the existence of this conductive structure has firmly been established by constructing a number of different acceptable models and also by obtaining unique averages over depth of the conductivity an explanation in terms of partial melting in the upper mantle has produced lower bounds for the volume fraction of melt which must exist in order to produce the high conductivity beneath jdf t 1 myr the lower bound lies in the range 0 04 0 12 beneath cal t 30 myr it lies in the range 0 02 0 10 and beneath ncp t 72 myr it lies in the range 0 008 0 02 the distributions of partial melt show that the major portion of melt beneath jdf lies between 40 and 90 km and that melting has ceased by depths of about 170 km at all three sites geotherms have been computed and they are qualitatively similar to those predicted from a convective system where the temperature increases rapidly through a boundary layer to achieve a maximum value and then possibly decreases with depth the depth at which the maximum temperature is reached is about 125 km for cal and about 175 km for ncp and the maximum temperatures are estimated to be 1400 1500 c lastly as an independent check upon the partial melt explanation the location and magnitude of the seismic low velocity zone has been correlated positively with the computed distribution of partial melt at all three ocean bottom sites

woody vegetation fuel and fire track the melting of the scandinavian ice sheet before 9500 cal yr bp abstract new studies indicate the presence of early holocene ice free areas far north in scandinavia post glacial fire and vegetation were investigated based on sedimentary charcoal and pollen from two small lakes in northern sweden accumulation of organic sediment started around 10 900 and 9200 cal yr bp showing that both lake valleys were ice free extremely early given their northerly location fire events started after 9600 cal yr bp and became less common around the 8 2 ka event woody vegetation provided fuel that contributed to fires the first vegetation in our pollen record consisted of hippophae dryas grasses and sedges subsequently broadleaved trees betula salix increased in abundance and later pinus alnus ferns and lycopodium characterized the vegetation pollen from larix picea and malus were also found the change in vegetation composition was synchronous with the decrease in lake water ph in the region indicating ecosystem scale processes this occurred during a period of net global and regional warming the changes in fire frequency and vegetation appear independent of regional trends in precipitation the reconstructed fire history and vegetation support the scenario of early ice free areas far north in scandinavia during early holocene warming creating favorable conditions for woody plants and wildfires

a magnetotelluric sounding across vancouver island detects the subducting juan de fuca plate magnetotelluric1 mt and geomagnetic2 depth sounding measurements have been made at 18 sites 7 with remote reference3 across vancouver island fig 1 beneath which the juan de fuca plate is underthrusting4 5 vancouver island is part of the old accretionary wrangellia terrane6 and is located in the central portion of a 350 km forearc region that extends from the sediment filled trench7 to the garibaldi volcanic belt8 gravity9 and seismic refraction studies10 suggest that the descending plate has a shallow northeasterly dip of 8 16 with perhaps higher dips beneath northeastern vancouver island a high resolution seismic reflection survey11 along lines 1 and 3 fig 1 located a zone of strong acoustic reflections the e horizon11 near the top of the subducting juan de fuca plate at depths of 23 34 km our model of the broad band mt data defines a sloping highly conducting zone also near the top of the subducting plate at the same depths as the seismic e horizon the high electrical conductivity in this zone the e conductor is the result of saline fluid within the pore spaces of sedimentary and mafic materials of the upper oceanic crust that have been subducted to those depths beneath vancouver island these are the first data which clearly define a dipping conductive layer associated with the boundary region between converging plates they have significant implications for thrust earthquakes and metamorphic reactions that occur in subduction zones

mosaicking of global planetary image datasets 1 techniques and data processing for thermal emission imaging system themis multi spectral data 1 the mosaicking of global planetary data sets allows for the examination of local regional and global scale processes on all planetary bodies processing techniques that allow us and other users to crate mosaics of tens of thousands of images are documented along with the associated errors introduced by each image processing algorithm these techniques e g non uniformity correction running contrast stretches line and row correlated noise removal and random noise removal were originally developed for the 2001 mars odyssey thermal emission imaging system themis infrared multispectral imager data but can be adapted and applied to other data sets by the alteration of input parameters the techniques for mosaicking planetary image data sets e g image registration blending and normalization are also presented along with the generation of qualitative and quantitative products these techniques are then applied to generate themis daytime and nighttime infrared viking context imager ctx and mars orbiter camera moc visible mosaics using a variety of input and output types at a variety of scales by creating mosaics of the same area using different data sets such as those that illustrate compositional diversity thermophysical properties or small scale morphology it is possible to view the surface of the planet and geologic problems through many different perspectives in addition to the techniques used to create large scale seamless mosaics we also present the themis daytime and nighttime relative temperature global mosaics which are the highest resolution 100m pixel global scale data sets available for mars to date

physical abrasion of mafic minerals and basalt grains application to martian aeolian deposits abstract sediment maturity or the mineralogical and physical characterization of sedimentary deposits has been used to identify sediment sources transport medium and distance weathering processes and paleoenvironments on earth mature terrestrial sands are dominated by quartz which is abundant in source lithologies on earth and is physically and chemically stable under a wide range of conditions immature sands such as those rich in feldspars or mafic minerals are composed of grains that are easily physically weathered and highly susceptible to chemical weathering on mars which is predominately mafic in composition terrestrial standards of sediment maturity are not applicable in addition the martian climate today is cold and dry and sediments are likely to be heavily influenced by physical weathering rather than chemical weathering due to these large differences in weathering processes and composition martian sediments require an alternate maturity index this paper reports the results of abrasion tests conducted on a variety of mafic materials and results suggest that mature martian sediments may be composed of well sorted well rounded spherical polycrystalline materials such as basalt volcanic glass is also likely to persist in a mechanical weathering environment while more fragile and chemically altered products are likely to be winnowed away a modified sediment maturity index is proposed that can be used in future studies to constrain sediment source paleoclimate mechanisms for sediment production and surface evolution this maturity index may also provide insights into erosional and sediment transport systems and preservation processes of layered deposits

the lateglacial and early holocene vegetation and environment in the dovre mountains central norway as signalled in two lateglacial nunatak lakes abstract by using heavy coring equipment in two high altitudinal lakes 1253 and 1316 m a s l at dovre central norway 1 1 5 m of unsorted coarsely minerogenic sediments were retrieved below the holocene organic sediments the minerogenic sequence contained well preserved pollen and chironomid remains revealing new and detailed palaeoenvironmental knowledge of the mountains in central norway during the last 5 6000 years of the lateglacial lg period however the lg chronology is based on biostratigraphical correlations and not on 14c dates due to low organic content in the minerogenic sediments the emerging lg nunataks probably indicating a thin and multi domed scandinavian ice sheet was rapidly inhabited by immigrating species which could explain the present centric distributions of certain arctic alpine plants the lg vegetation development included a pre interstadial dominated by mineral soil pioneers an interstadial dominated by shrubs and dwarf shrubs and the younger dryas cold period with recurring dominance of pioneers pollen and stomata of pinus and picea indicate their local lg presence at dovre lg climate oscillations are indicated by pollen stratigraphy and for the later part of lg also by chironomids these oscillations could correspond to heinrich event 1 gi 1d gi 1b and the younger dryas cold events the lg interstadial reached july mean temperatures of more than 7 8 c similar to the present chironomids colonized the lake already during the onset of the interstadial albeit at very low richness and abundances starting from yd there are sufficient chironomid head capsules to perform a temperature reconstruction the holocene warming of about 2 c initiated a vegetation closure from snow beds and dwarf shrub tundra to shrubs and forests birch forests established about 10 ka cal bp slightly earlier than pine forests alnus expanded ca 9 2 ka cal bp and a thinning of the local forests occurred from ca 7 ka cal bp two short lasting climate deteriorations found in the pollen record and the chironomid record may represent the preboreal oscillation and the 8 2 event the holocene thermal maximum is indicated around ca 7 8 7 3 ka cal bp showing a chironomid inferred july mean of at least 11 c this is ca 3 c warmer than today

the electrical conductivity of the oceanic upper mantle summary previous inversions of sea floor magnetotelluric mt sounding data have predicted upper mantle electrical conductivities which are more than an order of magnitude higher than laboratory measurements of the conductivity of olivine would suggest and controlled source field electromagnetic csem soundings require a lithospheric mantle conductivity of 3 x lop5 sm which is so low that the electromagnetic em coast effect would produce more anisotropy in mt soundings than is observed we address these issues by constructing an olivine mantle model for conductivity and examining the inversion of mt data from three sea floor sites and show that the incompatibilities can be largely resolved if the effects of oceans and coastlines are considered our mantle model is based on recent measurements of olivine conductivity the conductivity of tholeiite melt a thermal model for the upper mantle based on lithospheric cooling and the temperature of a a 3 olivine transition the pyrolite model of mantle petrology and conductivities derived from csem sounding we propose archie s law with exponent 2 and interconnected tubes as realistic lower and upper bounds for the effect of partial melt on rock conductivity and archie s law with exponent 1 5 as the preferred estimate the 1 d forward response of this model is not compatible with observed sea floor mt data three data sets presented by oldenburg 1981 pass a test for one dimensionality based on the size of the residuals when fit with parker s d algorithm but two of the three soundings fail a test for independence of residuals we also find that the presence of the upper mantle high conductivity zone previously inferred from these data is highly dependent on data misfit and not required when the misfit criterion is relaxed a reasonable amount re inversions of the mt data produce models which are incompatible with our petrological model of mantle conductivity however by adding an ocean with various coastlines of simple geometry to our petrological model and solving the forward 3 d problem using thin sheet analysis we predict mt responses which are distorted in a manner that is remarkably similar to the observed data

mineralogical composition of sands in meridiani planum determined from mars exploration rover data and comparison to orbital measurements constraints on the mineralogical composition of low albedo low sulfur sands at meridiani planum are determined from mars exploration rover mer opportunity miniature thermal emission spectrometer mini tes mossbauer and alpha proton x ray spectrometer measurements results of this work show that the sand is olivine basaltic in composition with minor amounts of sulfate and a high silica phase glass or secondary amorphous silica measurements from all three instruments indicate that pyroxene is twice as abundant as olivine and that the pyroxene composition is dominated by the low calcium variety the volume abundance of olivine is constrained to be 10 15 results from detailed analyses of mer data are used to ground truth the spectral emissivity and mineral abundances derived from orbit with mars global surveyor tes data tes derived mineral abundances are within 5 of those derived from mer data which is generally within the statistical errors associated with tes derived phase abundances the agreement lends support to global and regional scale variations in mineralogical composition determined from tes data in previous studies an alternative method of least squares minimization is used for modeling the tes and mini tes data the benefits of this method are demonstrated by comparison with conventional least squares techniques previously used by tes data users

mars global digital dune database and initial science results 1 a new mars global digital dune database mgd3 constructed using thermal emission imaging system themis infrared ir images provides a comprehensive and quantitative view of the geographic distribution of moderate to large size dune fields area 1 km2 that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of mars mgd3 extends from 65 n to 65 s latitude and includes 550 dune fields covering 70 000 km2 with an estimated total volume of 3 600 km3 this area when combined with polar dune estimates suggests moderate to large size dune field coverage on mars may total 800 000 km2 6 times less than the total areal estimate of 5 000 000 km2 for terrestrial dunes where availability and quality of themis visible vis or mars orbiter camera narrow angle moc na images allow we classify dunes and include dune slipface measurements which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification for dunes located within craters the azimuth from crater centroid to dune field centroid referred to as dune centroid azimuth is calculated and can provide an accurate method for tracking dune migration within smooth floored craters these indicators of wind direction are compared to output from a general circulation model gcm dune centroid azimuth values generally correlate to regional wind patterns slipface orientations are less well correlated suggesting that local topographic effects may play a larger role in dune orientation than regional winds

extended surface exposures of granitoid compositions in syrtis major mars 1 the number of quartz and feldspar rich surfaces identified in northwestern syrtis major has been extended beyond previously reported results to a region of about 230 by 125 km thermal emission imaging system infrared data were used to locate surfaces spectrally identical to previously reported central peak units in syrtis major these surfaces are indicative of the production of highly differentiated magmas though it is possible that the granitoid exposures add to the variety of igneous compositions associated with the syrtis major volcanic construct the geologic context of these exposures suggests a formation that predates syrtis major

insights into pollen source area transport and deposition from modern pollen accumulation rates in lake sediments abstract pollen accumulation rates par from late quaternary deposits can provide direct estimates of past plant abundance they are influenced by lake internal processes and therefore rarely used in between site comparisons although few studies from fennoscandia have applied them successfully this study aims to explore how pars from selected lakes from northeast germany reflect differences in plant abundance as a step towards quantitative vegetation reconstructions from pars short sediment cores were collected from 18 lakes of which 16 could be dated by 210pb pars were estimated for the youngest sediment representing approximately two years before sampling in 2009 and samples dated to around 1993 forest inventory data for the two time slices were obtained for 15 km around the sites and standing volume sv was estimated as a measure of above ground biomass pars were compared to the total sv within increasing areas around the lakes as well as to distance weighted sv using the prentice sugita model of pollen dispersal and deposition both assessments of the vegetation data yielded strong linear relationships with pars already over distances of tens of metres to a few kilometres documenting the importance of the local vegetation this indicates the importance of the often neglected trunk space component of pollen transport for small lakes results from the small number of large lakes suggest that these sites receive a larger absolute input of pollen from regional sources these observations indicate that small lakes may be somewhat sheltered from pollen transported above the canopy we demonstrate that pars of the major tree taxa obtained from lake sediments are linear related to the lake surrounding biomass this confirms that par can be used to infer past changes in plant biomass although absolute pollen deposition may also be determined by net primary productivity of the biomass

inversion of ocean bottom magnetotelluric data revisited three ocean bottom magnetotelluric data sets from sites on the pacific plate are reinterpreted the initial analysis found a correlation between the lithospheric age and the depth to a conductive zone beneath each site that work also suggested that the resistivity increased below the conductor this analysis which includes new methods for constructing one dimensional conductivity models shows that the postulated increase in resistivity is not demanded by the data it also reveals an unexpectedly large nonuniqueness inherent in the interpretation of these data the previously reported trends with lithospheric age still exist but they are not as strong as initially believed finally it is shown rigorously that the different age sites are distinct in that no one dimensional model can account for all three data sets

timing equilibrium line altitudes and climatic implications of two early holocene glacier readvances during the erdalen event at jostedalsbreen western norway following the younger dryas the e rst evidence of glacial activity in southern norway in response to climatic change occurred during the early holocene when terminal moraines from the erdalen event formed beyond the position of later little ice age moraines in front of present outlet glaciers on both sides of the jostedalsbreen ice cap sets of pre little ice age marginal moraines have been morphostratigraphicallycorre lated with the erdalen event the lithostratigraphyin a peat bog at hellemyrane in jostedalen western norway provides e rm evidence for a two phase erdalen event associated with two glacier readvances of nigardsbreen at the preboreal boreal transition radiocarbon dates from the peat bog give age estimates for the two phases the e rst erdalen event readvance took place between 10 100 and 10 050 cal bp while the second occurred close to 9700 cal bp the lowering of the equilibrium linealtitude ela during these readvances is estimated using the little ice age ratio lr approach to be about 230 m and 215 m respectively the e rst readvance is attributed to an increase in winter precipitation while the second readvance may have been primarily caused by a marked drop in summer temperature which reactivated already existing ice masses

reconstruction of holocene precipitation patterns in europe using pollen and lake level data abstract lake level data can be used to refine palaeoclimate reconstructions based on pollen data this approach is illustrated for the european holocene estimates of p pet precipitation minus potential evapotranspiration were first inferred from modern pollen analogues the pollen based estimates were then compared with the status of lakes within a 5 radius analogues with p pet anomalies inconsistent with the lake level changes were rejected the constrained sets of analogues were used to estimate continental scale patterns of annual mean temperature and annual precipitation at 3000 yr intervals estimated temperature anomalies differed only slightly from the unconstrained reconstructions estimated precipitation anomalies however showed improved spatial coherence and increased regional contrast and were occasionally reversed in sign the effect of the constraint was to impose a rational selection among almost equally similar modern pollen analogues with similar temperatures but widely varying moisture regimes the resulting maps showed clear spatially coherent patterns of change in precipitation as well as temperature suitable for comparison with climate model results further improvement of these maps will become possible as a more extensive coverage of lake level data is obtained

an analogue model study of em induction in the japan korea china region abstract electromagnetic induction in the coastal region of japan korea china is studied using a scaled laboratory analogue model the model includes a simulation of the known ocean bathymetry the complex coastlines and the deep conductive pacific trench model measurements of the electromagnetic field components are carried out for simulated periods of 15 180 min for two mutually perpendicular polarizations of a uniform horizontal inducing source field in phase and quadrature bx by and bz model measurements are examined in detail for a series of traverses over japan the korean peninsula and the coastal region of china and the u s s r large anomalous in phase model magnetic fields are observed over the korea japan strait for e polarization and over the bohai tsugaru and la perouse straits for b polarization owing to current channelling the significant responses observed at short periods over the peninsulas in the shallow coastal areas decrease with increasing period large gradients in the in phase b2 field are observed over japan for e polarization for both short and long periods owing to the effects of induced currents in the surrounding oceans thus induction arrow responses over all regions of japan are expected to show the dominant effects of the ocean a comparison of analogue model and field site induction arrows over the kii peninsula of japan indicates that the ocean effects alone cannot fully account for the observed responses the differences in the model and field results can be attributed to lateral inhomogeneities in the conductivity structure under japan

surface mineralogy of martian low albedo regions from mgs tes data implications for upper crustal evolution and surface alteration 1 mars global surveyor thermal emission spectrometer mgs tes data are used to derive the modal mineralogy of spectrally distinct martian low albedo regions and to identify spatial trends in mineralogic assemblages results from this work are consistent with the major results of previous spectroscopic studies 1 plagioclase and clinopyroxene are the dominant minerals of most southern highlands regions 2 the northern plains exhibit the lowest pyroxene abundance within martian low albedo regions and 3 the highest concentrations of high silica phase s are found in the northern plains solis planum and a few southern high latitude regions low albedo regions may be classified into four units on the basis of relative abundances of plagioclase pyroxene and high silica phase s unit distributions between 45 latitude exhibit moderate correlation with distinct provinces e g syrtis major aonium sinus defined by large scale morphology elevation and to some extent surface age suggesting that the spectral and compositional differences between these units are more strongly controlled by original bedrock mineralogy than by surface atmosphere interactions and alteration syrtis major exhibits a difference in mineralogy from the surrounding highlands suggesting a differing degree of fractional crystallization assimilation or source region composition areas with thick crust near the tharsis plateau exhibit lower abundances of olivine and greater plagioclase pyroxene ratios than surrounding highland terrains suggesting that magmas in this region may have undergone increased olivine fractionation regions where surface alteration is more likely to be the primary control on observed spectral signatures are the high latitude areas 45 where globally surfaces dominated by high silica phase s are most commonly found

determining olivine composition of basaltic dunes in gale crater mars from orbit awaiting ground truth from curiosity 1 the successful landing of the mars science laboratory curiosity rover in gale crater mars presents a rare opportunity for validation of a spectral index developed for determining olivine chemistry from orbital midinfrared remote sensing data here a spectral index is developed using laboratory emissivity data of 13 synthetic mg fe olivines utilizing this spectral index a prediction of olivine composition fo55 5 is made from orbital data for a ne sw trending dune field near the curiosity rover this dune field will be crossed during the mission as the rover travels toward a 5 km high sediment stack mount sharp that contains orbitally detected clays and sulfates curiosity can use its instrument suite chemmin alpha particle x ray spectrometer chemcam when it reaches the dunes to verify or refute the olivine chemistry prediction presented here the ability to validate the developed spectral index using the rover s ground truth instruments will strengthen olivine chemistry mapping across the martian surface using this spectral index

holocene tree line and climate change on the queen charlotte islands canada palynological study of two subalpine ponds on the queen charlotte islands reveals changes in tree line and climate during the holocene the findings agree with previous reconstructions from nearby louise pond on the queen charlotte islands that suggest a warmer than present climate and higher than present tree lines in the early holocene ca 9600 660014c yr b p basal ages at sc1 pond and shangri la bog indicate that the basins did not hold permanent water before 720014c yr b p consistent with a warmer and drier early holocene previously inferred from louise pond pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 9014c yr b p similar to the 5790 13014c yr b p age for cooling inferred from louise pond conditions similar to present were established at sc1 pond by 3460 10014c yr b p confirming the previous estimate of 340014c yr b p at louise pond this 340014c yr b p vegetation shift on the queen charlotte islands corresponds with the beginning of the tiedemann glacial advance in the south coastal mountains of british columbia ca 330014c yr b p the peyto and robson glacial advances between 3300 and 280014c yr b p in the rocky mountains and climatic cooling inferred from palynological studies throughout southern british columbia northern washington and southeast alaska these findings confirm that changes in regional climate influenced changes in vegetation in coastal british columbia

an integrated geochemical and palynological study of human impacts soil erosion and storminess from southern greenland since c ad 1000 abstract an integrated pollen analytical and geochemical study is presented from qinngua kangilleq southwest greenland this site was formerly one of the largest farms in the eastern settlement of norse greenland the study is the first to determine what link if any exists between norse landnam early settlement vegetation change soil erosion climate change and peat geochemistry the data suggest that fluxes in lithogenic elements supplied to a peat column by terrestrial sources and atmospheric deposition were coupled to the pattern of local norse settlement beginning cal ad 1020 a severe phase of soil erosion is indicated which is coincident with the landnam horizon this may represent proxy evidence for the stripping of turf for the construction of turf and stone buildings at the farm radiocarbon dates suggest the presence of a hiatus in the sediment column spanning cal ad 1380 1950 following the recommencement of sediment accumulation the geochemical data indicate a critical change in site conditions which may be consistent with the well known change in northern hemisphere atmospheric circulation that started between c ad 1400 and 1420 bromine br and chlorine cl concentrations are demonstrably higher in the sediments dating to the 20th century relative to the pre 15th century deposits rising halogen concentrations at qinngua appear to be correlated with increased levels of na sea salt sodium precipitation in the gisp2 ice core which earlier studies have interpreted as indicative of increased north atlantic storminess

comparison of analogue model and field station em responses on southern vancouver island abstract measurements of geomagnetic induction responses for a laboratory analogue model that includes a simulation of the subducting juan de fuca plate are compared with those obtained at three sites on vancouver island good agreement between model and field responses at the central vancouver island site is observed over the period range 3 60 min while at the east and west coastal sites good agreement is achieved only for periods greater than 20 min at shorter periods departures of the observed responses from those of the model are possibly the result of upper crust inhomogeneities not replicated in the simulation and the complex strait with its numerous small islands and its irregular coastlines inadequately simulated in the course model nevertheless the analogue model results are consistent with the premise of a juan de fuca plate underlain by the conductive asthenosphere subducting at a shallow depth beneath vancouver island