seeking phyllosilicates in thermal infrared data a laboratory and martian data case study 1 previous analyses of thermal emission spectrometer tes data produce results that could suggest a widespread distribution of phyllosilicate minerals over the surface of mars whereas studies of visible to near infrared vnir data indicate a more limited distribution we use vnir detections of phyllosilicates in the vicinity of the nili fossae to determine the spectral characteristics of phyllosilicate bearing material in the thermal infrared tir by investigating areas of vnir phyllosilicate detection in more detail we find that the phyllosilicate bearing material corresponds to spectral variation in thermal emission imaging system decorrelation stretched tir images and differences in infrared spectral shape that are consistent with but not uniquely attributable to mixtures of phyllosilicates and basalt phyllosilicate phases are modeled from tes data at abundances that average 5 over the region and at abundances near the 10 15 detection limit in our specific regions of interest deconvolution of numerical mixtures of phyllosilicate and basalt spectra indicates that these low abundances of phyllosilicates likely are not influenced by uncertainties greater than the 10 15 uncertainty of the method tes spectra and modeled abundances vary between the phyllosilicate bearing material and the surrounding region but this difference in composition cannot be attributed solely to the presence of phyllosilicates we believe the inconsistencies in phyllosilicate occurrence between tes and vnir analyses may be explained by the inclusion of phyllosilicates in the models of tes data as substitutes for poorly crystalline phases e g allophane not currently available in public infrared spectral libraries

a search for basaltic to intermediate glasses on mars assessing martian crustal mineralogy multiple datasets have demonstrated that the crust of mars is fundamentally basaltic however spectral libraries used to interrogate thermal infrared spectra of martian dark regions through spectral deconvolution have heretofore lacked mafic glasses despite the importance of amorphous phases or phases with amorphous like spectral signatures in martian mineralogy to establish the presence and importance of basaltic to intermediate glasses in martian lithologies we created five such glasses obtained their thermal infrared spectra and included the spectra in a library used to deconvolve nine regional thermal emission spectrometer spectra from mars we employed the nonnegative least squares nnls deconvolution method which yields deconvolved phase abundances and the uncertainties associated with those abundances the basaltic to intermediate glasses do not appear in the deconvolution solutions indicating they are not globally or regionally important phases because martian igneous or impact processes are capable of basaltic to intermediate glass formation the lack of such glasses in the deconvolved mineralogies suggests either the glasses did not form in detectable quantities or they or their signatures have been removed the masking or replacement of basaltic to intermediate glasses through alteration is supported by the appearance in the deconvolution solutions of amorphous phases e g silica rich glasses opal or phases with amorphous like spectral signatures e g clays zeolites that commonly form through aqueous alteration of mafic glasses the glasses may still be important to local scale thermal infrared studies given the basaltic nature of mars and the variety of local scale lithologies detected by various missions the regional mineralogies derived from the nnls deconvolution analysis divide into five statistically separable groups which provide insight into regional trends in mineralogy

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

chemistry and mineralogy of outcrops at meridiani planum analyses of outcrops created by the impact craters endurance fram and eagle reveal the broad lateral continuity of chemical sediments at the meridiani planum exploration site on mars approximately ten mineralogical components are implied in these salt rich silicic sediments from measurements by instruments on the opportunity rover compositional trends in an apparently intact vertical stratigraphic sequence at the karatepe west ingress point at endurance crater are consistent with non uniform deposition or with subsequent migration of mobile salt components dominated by sulfates of magnesium striking variations in cl and enrichments of br combined with diversity in sulfate species provide further evidence of episodes during which temperatures ph and water to rock ratios underwent significant change to first order the sedimentary sequence examined to date is consistent with a uniform reference composition modified by movement of major sulfates upward and of minor chlorides downward this reference composition has similarities to martian soils supplemented by sulfate anion and the alteration products of mafic igneous minerals lesser cementation in lower stratigraphic units is reflected in decreased energies for grinding with the rock abrasion tool survival of soluble salts in exposed outcrop is most easily explained by absence of episodes of liquid h2o in this region since the time of crater formation

adjustment of the summertime marine atmospheric boundary layer to the western iberia coastal morphology during summer june july and august northerly winds driven by the azores anticyclone are prevalent over western iberia the quick scatterometer satellite 2000 to 2009 summertime estimates reveal a broad high wind speed 7 ms 1 area extending about 300 km from shore and along the entire iberian west coast nested in this large high speed region preferred maximum regions anchored in the iberian major capes finisterre roca and s vicente are found composite analyses of wind maxima were performed to diagnose the typical summertime synoptic scale pressure distribution associated with these smaller size high speed regions the flow low level structure was further studied with a mesoscale numerical prediction model for three northerly events characterized by typical summertime synoptic conditions a low level coastal jet setting the background conditions to the marine atmospheric boundary layer mabl response to topography was found in the three cases the causes for wind maximum downwind capes were investigated focusing on the hypothesis that western iberia mabl responds to hydraulic forcing for the three events supercritical and transcritical flow conditions were identified and expansion fan signatures were found downwind each cape aircraft measurements performed during one of the events gave additional evidence of the expansion fan leeward cape roca the importance of other forcing mechanisms was also assessed by considering the hypothesis of downslope wind acceleration and found to be in direct conflict with soundings and surface observations

impact of u s west coastline inhomogeneity and synoptic forcing on winds wind stress and wind stress curl during upwelling season 1 although buoy and aircraft measurements as well as numerical simulations have shown intense over shelf and slope dynamics of the west coast of the united states in the summer upwelling season satellite footprint limitations of approximately 25 km resolution have thus far precluded long term spatially extended monitoring of the near coastline dynamics however recent advancements in satellite data processing have allowed a finer footprint of approximately 12 km resolution to investigate further the properties of coastal winds and consequent upwelling this improved satellite data analysis has confirmed the intense coastal winds over the shelf and slope and revealed their spatial extensions and inhomogeneities on event and multiday scales the inhomogeneities are dominated by the along coast pressure gradient modulated by the synoptic effects and topographical forcing of the five major capes which also generate upwelling wind stress and curl pattern inhomogeneities synoptic forcing of the coastal flow was evidenced by high correlation coefficients in excess of 0 8 between the buoy measured pressure differences and wind speeds wind speeds greater than 11 m s 1 occurred only when the along coast pressure gradient was greater than 0 8 hpa 100 km based on bernoulli flow principles the observed upper limit of the wind speed on the downwind sides of the major capes is explained by using characteristic values of atmospheric marine layer parameters numerical simulations at a similar resolution 12 km as the new satellite data footprint for june 2001 completed as part of multiyear regional climate modeling efforts were able to reproduce the main characteristics of the flow

allophane detection on mars with thermal emission spectrometer data and implications for regional scale chemical weathering processes models of thermal emission spectrometer tes data suggest that poorly crystalline weathering products allophane and aluminosilicate gel occur in several low albedo regions of mars the presence of allophane in tes models indicates that the martian surface experienced low temperature chemical weathering at low water to rock ratios and mildly acidic to neutral ph on regional scales the allophane and gel may be ancient and preserved by a persistently dry martian climate alternatively evidence for recent ground ice in these regions suggests that pedogenic processes causing the formation of poorly crystalline aluminosilicates could be late amazonian in age and may be active today while previous models have suggested that global scale acidic weathering has occurred on mars for the past 3 5 billion years the presence of allophane indicates that acidic weathering was not occurring in these low albedo regions and that mildly acidic to neutral weathering has been an important regional scale weathering process on the martian surface

the dominance of cold and dry alteration processes on recent mars as revealed through pan spectral orbital analyses a b s t r a c t classic low albedo regions of the martian surface are investigated using combined reflectance and emission pan spectral data to constrain the types of alteration mineral phases that are present at spectrally significant abundances 10 15 the lack of hydrated mineral species observed using near infrared data suggests that anhydrous chemical alteration dominates at the regional scale spectral characteristics in the vnir and tir are consistent with those associated with weathering processes identified in the hyper arid hypo thermal and geologically stable mcmurdo dry valleys of antarctica where oxidative weathering processes dominate and significant aqueous alteration does not occur in addition the spectral trends associated with oxidative weathering processes are similar to regional trends in vnir spectral characteristics observed on mars and potentially complicate the spectral interpretation of basaltic terrains collectively these relationships suggest that the martian surface has been dominated by cold dry and stable conditions since the formation of these low albedo regions while significant at regional scales early in martian history aqueous alteration appears to be predominantly absent from large scale basaltic regions on mars

spectral evidence for weathered basalt as an alternative to andesite in the northern lowlands of mars mineral abundances derived from the analysis of remotely sensed thermal emission data from mars have been interpreted to indicate that the surface is composed of basalt surface type 1 and andesite surface type 2 1 the global distribution of these rock types is divided roughly along the planetary dichotomy which separates ancient heavily cratered crust in the southern hemisphere basalt from younger lowland plains in the north andesite 1 but the existence of such a large volume of andesite is difficult to reconcile with our present understanding of the geological evolution of mars here we reinterpret martian surface rock lithologies using mineral abundances from previous work1 and new mineralogies derived from a spectral end member set representing minerals common in unaltered and low temperature aqueously altered basalts our results continue to indicate the dominance of unaltered basalt in the southern highlands but reveal that the northern lowlands can be interpreted as weathered basalt as an alternative to andesite the coincidence between locations of such altered basalt and a suggested northern ocean basin implies that lowland plains material may be composed of basalts weathered under submarine conditions or weathered basaltic sediments transported into this depocentre

effects of pure silica coatings on thermal emission spectra of basaltic rocks considerations for martian surface mineralogy 1 on mars silica derived from chemical weathering could precipitate to coat rocks and particles we suggest that rock coatings of secondary amorphous silica may account for a widespread martian surface spectral unit previously modeled as andesite or weathered basalt in a laboratory study we investigated the effects of synthetic silica coatings on thermal infrared tir spectroscopic measurements secondary amorphous silica is spectrally similar to silicate glass and clay spectra used in previous spectroscopic models silica coating and substrate spectra combine nonlinearly to produce a composite spectrum of a coated rock silica coatings 10 m thick effectively mask the spectral contribution of a silicate substrate therefore the capability of volumetrically small amounts of silica present as thin coatings on rocks should be considered when seeking explanations for spectral variability of martian surface materials

mesoscale simulation of supercritical subcritical and transcritical flow along coastal topography abstract a mesoscale atmospheric model is used to address the characteristics of stratified flow bounded by a side wall along a varying coastline initial froude number values are varied through alteration of marine inversion strength permitting examination of supercritical subcritical and transcritical flow regimes encountering several coastal configurations consistent with shallow water models sharp drops in boundary layer depth and flow acceleration occur in flow rounding convex bends however significant flow response occurs in the stratified layer aloft which is unexplained by conventional shallow water theory the strongest flow acceleration occurs in the transcritical case while regardless of inversion strength the deformation of the isentropes aloft shows general structural similarity advection of horizontal momentum is an important component of the horizontal force balance a simulation having several coastline bends exhibits a detached oblique hydraulic jump upwind of a concave bend t

visible near infrared and middle infrared spectroscopy of altered basaltic tephras spectral signatures of phyllosilicates sulfates and other aqueous alteration products with application to the mineralogy of the columbia hills of gusev crater mars 1 we studied visible to near infrared vnir 0 35 2 5 m and middle infrared mir 1800 250 cm 1 also called thermal infrared and vibrational spectra of basaltic tephras from mauna kea volcano that were altered under ambient hydrothermal hydrolytic and acid sulfate and dry heat conditions although models of mir spectra of altered tephras generally produce fits whose quality is reduced compared to deconvolutions of primary lithologies they successfully identify major alteration phases cristobalite oxide phyllosilicate and sulfate except in palagonites mir spectra of the 1 in spectra of the 500 1000 m fraction only if phyllosilicates are present although mauna kea palagonitic tephra is considered a vnir analog to martian dust comparison of mir altered tephra spectra 45 m fraction to dust spectra retrieved from mars global surveyor and mars exploration rover instruments do not provide good spectral matches the best mir match is a tephra that has a strong plagioclase feldspar transparency feature and was altered under dry high temperature oxidizing conditions this sample is not a vnir analog and is not a process analog but it emphasizes the mineralogical importance of plagioclase feldspar in martian dust no single tephra is a good spectral analog across the vnir and mir we found no evidence for substantial sulfates or phyllosilicates in mini thermal emission spectrometer mini tes spectra from gusev crater

basalt weathering in an arctic mars analog site abstract the martian surface has undergone chemical and physical weathering in the past and these processes may continue intermittently today to explore whether martian rocks are likely to retain features indicative of weathering we investigated how basaltic material weathers on earth specifically we investigated weathering of a quaternary aged basaltic flow at the sverrefjell volcano in svalbard above the arctic circle this flow weathered since deglaciation under cold dry

tropical to mid latitude snow and ice accumulation flow and glaciation on mars images from the mars express hrsc high resolution stereo camera of debris aprons at the base of massifs in eastern hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice rich glacier like viscous flow and sublimation together with new evidence for recent ice rich rock glaciers at the base of the olympus mons scarp superposed on larger late amazonian debris covered piedmont glaciers we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid latitude regions of mars during periods of increased spin axis obliquity when polar ice was mobilized and redeposited in microenvironments at lower latitudes the data indicate that abundant residual ice probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration

mineralogy provenance and diagenesis of a potassic basaltic sandstone on mars chemin x ray diffraction of the windjana sample kimberley area gale crater the windjana drill sample a sandstone of the dillinger member kimberley formation gale crater mars was analyzed by chemin x ray diffraction xrd in the msl curiosity rover from rietveld refinements of its xrd pattern windjana contains the following sanidine 21 weight or95 augite 20 magnetite 12 pigeonite olivine plagioclase amorphous and smectitic material 25 and percent levels of others including ilmenite fluorapatite and bassanite from mass balance on the alpha proton x ray spectrometer apxs chemical analysis the amorphous material is fe rich with nearly no other cations like ferrihydrite the windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite from chemcam laser induced breakdown spectrometer libs chemical analyses windjana is representative of the dillinger and mount remarkable members of the kimberley formation libs data suggest that the kimberley sediments include at least three chemical components the most k rich targets have 5 6 k2o 1 8 times that of windjana implying a sediment component with 40 sanidine e g a trachyte a second component is rich in mafic minerals with little feldspar like a shergottite a third component is richer in plagioclase and in na2o and is likely to be basaltic the k rich sediment component is consistent with apxs and chemcam observations of k rich rocks elsewhere in gale crater the source of this sediment component was likely volcanic the presence of sediment from many igneous sources in concert with curiosity s identifications of other igneous materials e g mugearite implies that the northern rim of gale crater exposes a diverse igneous complex at least as diverse as that found in similar age terranes on earth

the marine atmospheric boundary layer jet in the coastal ocean dynamics experiment the vertical and horizontal structure of the atmospheric boundary layer near the northern california coast was investigated during spring upwelling conditions as part of the 1981 coastal ocean dynamics experiment two daytime aircraft flights were devised to measure mean and turbulent quantities for 25 km tracks along and across the continental shelf from 30 to 1200 m altitude the pacific high offshore and an inland thermal low characterized the synoptic situations and equatorward winds resulted which produced intense ocean upwelling the wind profile was found to be jet shaped maximum wind speeds were 25 m s 1 and 16 m s 1 at 400 and 100 m respectively in the two flights above and below the heights of the jet speed maxima the wind speed decreased rapidly sharp density inversions existed at the levels of the peak wind speeds in one flight the inversion also sloped down toward the coast turbulence was effectively confined below the inversions strong zonal temperature gradients above the inversion between the hot land and cool marine air caused a thermal wind for which the wind speed decreased with height below the inversion turbulent stress divergence was large and effective in transferring the horizontal momentum of the wind to the sea slowing the wind there was also a small thermal wind below the inversion but opposite to the one above owing to the well mixed air temperature following the sea surface temperature which was cold at the coast and relatively warmer offshore owing to the upwelling these effects explain the jet shaped wind profile the mean momentum equations show that an acceleration toward the coast can balance the pressure gradient coriolis and turbulent stress divergence forces and there were some observations to support this complete balance was not obtained for the turbulent kinetic energy budget inferred dissipation rates were too large

structural and spectroscopic changes to natural nontronite induced by experimental impacts between 10 and 40 gpa many phyllosilicate deposits remotely detected on mars occur within bombarded terrains shock metamorphism from meteor impacts alters mineral structures producing changed mineral spectra thus impacts have likely affected the spectra of remotely sensed martian phyllosilicates we present spectral analysis results for a natural nontronite sample before and after laboratory generated impacts over five peak pressures between 10 and 40 gpa we conducted a suite of spectroscopic analyses to characterize the sample s impact induced structural and spectral changes nontronite becomes increasingly disordered with increasing peak impact pressure every infrared spectroscopic technique used showed evidence of structural changes at shock pressures above 25 gpa reflectance spectroscopy in the visible near infrared region is primarily sensitive to the vibrations of metal oh and interlayer h2o groups in the nontronite octahedral sheet midinfrared mir spectroscopic techniques are sensitive to the vibrations of silicon and oxygen in the nontronite tetrahedral sheet because the tetrahedral and octahedral sheets of nontronite deform differently impact driven structural deformation may contribute to differences in phyllosilicate detection between remote sensing techniques sensitive to different parts of the nontronite structure observed spectroscopic changes also indicated that the sample s octahedral and tetrahedral sheets were structurally deformed but not completely dehydroxylated this finding is an important distinction from previous studies of thermally altered phyllosilicates in which dehydroxylation follows dehydration in a stepwise progression preceding structural deformation impact alteration may thus complicate mineral specific identifications based on the location of oh group bands in remotely detected spectra this is a key implication for martian remote sensing arising from our results

response of the summer marine layer flow to an extreme california coastal bend abstract a summer wind speed maximum extending more than 200 km occurs over water around point conception california the most extreme bend along the u s west coast the following several causes were investigated for this wind speed maximum 1 synoptic conditions 2 marine layer hydraulic flow effects 3 diurnal variations 4 mountain leeside downslope flow 5 sea surface temperature structure and 6 island influence synoptic conditions set the general wind speed around point conception and these winds are classified as strong moderate or weak the strong wind condition extends about point conception reaching well offshore toward the southwest and the highest speeds are within 20 km to the south moderate wind cases do not extend as far offshore and they have a moderate maximum wind speed that occurs over a smaller area in the western mouth of the santa barbara channel the weak wind speed case consists of light and variable winds about point conception each category occurs about one third

geochemical and mineralogical indicators for aqueous processes in the columbia hills of gusev crater mars 1 water played a major role in the formation and alteration of rocks and soils in the columbia hills the extent of alteration ranges from moderate to extensive five distinct rock compositional classes were identified the order for degree of alteration is watchtower clovis wishstone peace backstay the rover s wheels uncovered one unusual soil paso robles that is the most s rich material encountered clovis class rocks have compositions similar to gusev plains soil but with higher mg cl and br and lower ca and zn watchtower and wishstone classes have high al ti and p and low cr and ni peace has high mg and s and low al na and k backstay basalts have high na and k compared to plains adirondack basalts and paso robles soil has high s and p some rocks are corundum normative indicating that their primary compositions were changed by loss and or gain of rock forming elements clovis materials consist of magnetite nanophase ferric oxides npox hematite goethite ca phosphates ca and mg sulfates pyroxene and secondary aluminosilicates wishstone and watchtower rocks consist of fe oxides oxyhydroxides ilmenite ca phosphate pyroxene feldspar mg sulfates and secondary aluminosilicates peace consists of magnetite npox mg and ca sulfates pyroxene olivine feldspar apatite halides and secondary aluminosilicates paso robles consists of fe3 mg ca and other sulfates ca phosphates hematite halite allophane and amorphous silica columbia hills outcrops and rocks may have formed by the aqueous alteration of basaltic rocks volcaniclastic materials and or impact ejecta by solutions that were rich in acid volatile elements

the summertime low level jet and marine boundary layer structure along the california coast abstract this paper examines the strong summertime northerly low level jet llj that frequently exists along the california coast the persistent synoptic scale pressure distribution north pacific high to the west thermal low to the east and baroclinity created by the juxtaposition of the heated continent and the cool marine layer produce the mean structure of this llj strong diurnal thermal forcing coupled with topographic influences on the flow modulate the jet structure position and intensity a mesoscale model is used to examine many of the complex facets of the llj flow dynamics several sensitivity studies in addition to a control experiment aid in this investigation principal findings of this study include the following the pronounced east west slope of the marine planetary boundary layer mpbl is not due primarily to colder sst values along the coast dynamically forced low level coastal divergence coupled with synoptic scale divergence appears to be dominant in determining mpbl i

evidence for a changing martian climate from the mineralogy at mawrth vallis abstract layered outcrops in the mawrth vallis region of mars contain the greatest diversity of aqueous alteration products on the planet and these materials are used to infer past aqueous environments orbital investigations indicate al si rich clay bearing units overly an fe mg smectite rich unit many different secondary minerals have been identified in the upper al si rich clay units but the presence of poorly crystalline phases has not been previously investigated identification of 10 30 allophane and imogolite in the clay bearing units resolves previous mineralogical discrepancies between tes and crism of clay bearing units on mars we demonstrate here that the poorly crystalline aluminosilicates allophane and imogolite comprise a significant portion of the uppermost stratum of the al si clay rich units these phases are unique to immature soils derived from volcanic ash in well drained mildly acidic environments on earth and we hypothesize that the deposits discovered here originate from supervolcanic activity in nearby arabia terra the transition through time from smectite bearing units to the uppermost allophane imogolite unit in mawrth vallis signifies a change in climate from a warm and wet environment to one where water was sporadic and likely depleted rapidly

adjustment of the marine atmospheric boundary layer to the large scale bend in the california coast 1 observations of the surface wind field off the u s west coast were made from satellite by the sea surface microwave imager ssm i during june 1994 and june 1996 the coast bends inward 28 at 40 n latitude northerly wind speeds are high within a region that extends far south and offshore of this bend bounded on the east by the california coast on average the high speed wind zone extends 250 km from shore and 800 km alongcoast long coast perpendicular aircraft transects show that moving onshore the depth of the mabl decreases the northerly wind speed increases and the froude number increases a network of oceanographic buoys records the surface wind speed direction and pressure from six buoy pressure measurements the geostrophic wind vector was computed to represent the synoptic flow over the oregon northern california coastal waters the satellite surface wind fields were composited by the direction of the buoy geostrophic background wind the predominant direction is 210 180 a high speed region extends south of the bend for directions in the 0 180 range moving counterclockwise which corresponds to a downcoast component of the pressure gradient for directions between 180 and 0 flow splits at the bend and the region of highest winds is found to its north and offshore a high speed region south of the bend was present in 65 of the satellite wind maps as well as in the june averages the flow s response to coastal promontories such as point arena is nested within this broad zone of fast thin likely supercritical flow

adjustment of the summer marine boundary layer around point sur california an instrumented c 130 aircraft flew over water around point sur california on 17 june 1996 under strong northwest wind conditions and a strong marine inversion patterns were flown from 30 to 1200 m elevation and up to 120 km offshore nearshore marine air accelerated past point sur reaching a surface maximum of 17 ms 21 in the lee winds measured over water in and above the marine layer were alongshore with no significant cross shore flow sea level pressure 10 m air temperature and air temperature inversion base generally decreased toward the coast and were an absolute minimum just downcoast of the wind speed maximum the sea surface temperature also decreased toward the coast but was an absolute minimum directly off point sur the nearcoast air temperature inversion base height was 400 m north of point sur decreased to a minimum of 50 m in the lee of point sur then increased farther to the south wind speeds were at a maximum centered along the air temperature inversion base the fastest was 27 m s 21 in the lee of point sur using a froude number calculation that includes the lower half of the capping layer the marine layer in the area is determined to have been supercritical most of the marine layer had froude numbers between 1 0 and 2 0 with the extreme range of 0 8 2 8 temperatures in the air temperature inversion in the lee were substantially greater than elsewhere modifying the surface pressure gradient the overall structure was a hydraulic supercritical expansion fan in the lee of point sur under the influence of rotation and surface friction the naval research laboratory nonhydrostatic coupled ocean atmosphere mesoscale prediction system coamps indicated a broad supercritical marine boundary layer moving to the south along central california and point sur during the aircraft flight the marine boundary layer thinned and accelerated into the lee of point sur which was the site of the fastest sea level wind speed along central california isotherms dip and speeds decreased in the lee of point sur in the capping inversion well above the marine layer coamps forecasted a compression shock wave initiating off the upwind side of the topography behind point sur and other coastal points to the north evidence from the model and the aircraft supports the existence of an oblique hydraulic jump on the north side of point sur

the structure and variability of the marine atmosphere around the santa barbara channel the santa barbara channel is a region characterized by coupled interaction between the lower level atmosphere the underlying ocean and the elevated topography of the coastline the nature of these interactions and the resulting weather patterns vary between summer and winter during summer synoptic winds are largely controlled by the combined effect of the north pacific anticyclone and the thermal low located over the southwestern united states resulting in persistent northwesterly winds a well defined marine atmospheric boundary layer mabl with properties distinct from the free atmosphere above is a conspicuous feature during the summer the wind has different characteristics in each of three zones maximum winds occur in the area extending south and east from pt conception zone 1 where they initially increase as they turn to follow the coast then decrease farther east winds are usually weak in zone 2 located in the easternmost part of the channel offshore from the oxnard plain winds are also weak in zone 3 sometimes reversing to easterly at night in a narrow band located along the mainland coast summer air temperature at the surface follows the sst closely and varies significantly with location summer sea level pressure gradients are large with the lowest pressure occurring on the northeast end of the santa barbara channel diurnal variations are strongest in summer although the modulation is weakest in zone 1 the diurnal variation is parallel to the coast in all of zone 3 but the oxnard plain where it is perpendicular to the coast the height of the marine layer varies between 300 m in late afternoon and 350 m in late morning in winter synoptic conditions are driven by traveling cyclones and sometimes accompanied by fronts these are usually preceded by strong southeast winds and followed by strong northwest winds atmospheric parameters are distributed more uniformly than in summer and diurnal variations are greatly reduced sea level air temperature and pressure are more spatially uniform than in the summer spatial variations in the observed fields in the summer are consistent with a hydraulic model of the mabl as a transcritical expansion fan the summertime situation is governed by a coupled interaction between the atmosphere and the underlying water the ocean influences the density of the mabl to the extent that it behaves distinctly from the free atmosphere above resulting in strong winds polarized in the direction parallel to the coast in turn these winds provoke an upwelling response in the coastal ocean which in part determines the surface properties of the water

a 3 5 ga record of water limited acidic weathering conditions on mars abstract the secondary mineral budget on earth is dominated by clay minerals al hydroxides and fe oxides which are formed under the moderate ph high water to rock ratio conditions typical of earth s near surface environment in contrast geochemical analyses of rocks and soils from landed missions to mars indicate that secondary mineralogy is dominated by mg fe ca sulfates and fe oxides this discrepancy can be explained as resulting from differences in the chemical weathering environment of earth and mars we suggest that chemical weathering processes on mars are dominated by 1 a low ph sulfuric acid rich environment in which the stoichiometric dissolution of labile mineral phases such as olivine and apatite fe ti oxides is promoted and 2 relatively low water to rock ratio such that other silicate phases with slower dissolution rates e g plagioclase pyroxene do not contribute substantially to the secondary mineral budget at the martian surface under these conditions al mobilization is limited and the formation of significant al bearing secondary phases e g clays al hydroxides al sulfates is inhibited the antiquity of rock samples analyzed in situ on mars suggest that water limited acidic weathering conditions have more than likely been the defining characteristic of the martian aqueous environment for billions of years

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

water abundance of dunes in gale crater mars from active neutron experiments and implications for amorphous phases we report the water abundance of bagnold dune sand in gale crater mars by analyzing active neutron experiments using the dynamic albedo of neutrons instrument we report a bulk water equivalent hydrogen abundance of 0 68 0 15 wt which is similar to measurements several kilometers away and from those taken of the dune surface thus the dune is likely dehydrated throughout furthermore we use geochemical constraints including bulk water content to develop compositional models of the amorphous fraction for which little information is known we find the amorphous fraction contains 26 to 64 wt basaltic glass and up to 24 wt rhyolitic glass suggesting at least one volcanic source for the dune material we also find a range of hydrated phases may be present in appreciable abundances either from the incorporation of eroded aqueously altered sediments or the direct alteration of the dune sand

igneous and shock processes affecting chassignite amphibole evaluated using chlorine water partitioning and hydrogen isotopes amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma but also shock and postshock processes we have analyzed amphibole and other phases from nwa 2737 melt inclusions and we evaluate these data along with published values to constrain the crystallization cl and h2o content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains using a model for the cl oh exchange between amphibole and melt we estimate primary crystallization oh contents of chassignite amphiboles sims analysis shows that amphibole from nwa 2737 currently has 0 15 wt h2o it has lost 0 6 wt h2o from an initial 0 7 0 8 wt h2o due to intense shock chassigny amphibole had on average 0 3 0 4 wt h2o and suffered little net loss of h2o due to shock nwa 2737 amphibole has d 3700 it absorbed martian atmosphere derived heavy h in the aftermath of shock chassigny amphibole with d 1900 incorporated less heavy h low h2o cl ratios are inferred for the primitive chassignite magma which had significant effects on melting and crystallization volatiles released by the degassing of martian magma were more cl rich than on earth resulting in the high cl content of martian surface materials

coastal atmospheric circulation around an idealized cape during wind driven upwelling studied from a coupled ocean atmosphere model abstract the study analyzes atmospheric circulation around an idealized coastal cape during summertime upwelling favorable wind conditions simulated by a mesoscale coupled ocean atmosphere model the domain resembles an eastern ocean boundary with a single cape protruding into the ocean in the center of a coastline the model predicts the formation of an orographic wind intensification area on the lee side of the cape extending a few hundred kilometers downstream and seaward imposed initial conditions do not contain a low level temperature inversion which nevertheless forms on the lee side of the cape during the simulation and which is accompanied by high froude numbers diagnosed in that area suggesting the presence of the supercritical flow formation of such an inversion is likely caused by average easterly winds resulting on the lee side that bring warm air masses originating over land as well as by air warming during adiabatic descent on the lee side of the topographic obstacle mountain leeside

high resolution morpho bathymetric imaging of the messina strait southern italy new insights on the 1908 earthquake and tsunami the 28 december 1908 reggio calabria and messina earthquake named after the two most damaged cities on the coasts of messina strait was one of the strongest mw 7 1 ever to occur in italy and was also followed by a tsunami that severely impacted the coasts of the strait although there is general agreement that its epicentre is located offshore in the messina strait the source fault has never been detected a century long question is therefore pending on the source of both the 1908 earthquake and tsunami within the ongoing debate on this subject little attention has been given so far to morphological insights from high resolution bathymetric multibeam data particularly as regarding the evidence of faults affecting the seafloor and the question of whether a submarine landslide may had been the cause of the tsunami we aim to address this issue by presenting the results of a morpho bathymetric study in the messina strait and surroundings investigated by means of high resolution swath bathymetry the primary morpho structural feature in this area is the axial channel of the messina canyon towards which flow several tributary canyons that incise the steep continental slope on the calabrian and sicilian margins these canyons carve deeply into a very narrow almost lacking continental shelf and merge laterally forming a continuous erosional margin rimming the messina strait this giant composite canyon environment is the locus of intense erosional and depositional processes that superimpose on active tectonic deformation resulting in a complex geomorphology that hinders the distinction between tectonic and sedimentary features seafloor ruptures that may be linked to fault systems compatible with the source of the 1908 earthquake and tsunami could not be identified based from our morpho bathymetric analysis however we provide evidence of several geomorphic features indicative of tectonic deformation in the messina strait define the presence and distribution of submarine landslides and evaluate their possible role as tsunami sources

global spectral classification of martian low albedo regions with mars global surveyor thermal emission spectrometer mgs tes data 1 martian low albedo surfaces defined here as surfaces with mars global surveyor thermal emission spectrometer mgs tes albedo values 0 15 were reexamined for regional variations in spectral response low albedo regions exhibit spatially coherent variations in spectral character which in this work are grouped into 11 representative spectral shapes the use of these spectral shapes in modeling global surface emissivity results in refined distributions of previously determined global spectral unit types surface types 1 and 2 pure type 2 surfaces are less extensive than previously thought and are mostly confined to the northern lowlands regional scale spectral variations are present within areas previously mapped as surface type 1 or as a mixture of the two surface types suggesting variations in mineral abundance among basaltic units for example syrtis major which was the surface type 1 type locality is spectrally distinct from terrains that were also previously mapped as type 1 a spectral difference also exists between southern and northern acidalia planitia which may be due in part to a small amount of dust cover in southern acidalia groups of these spectral shapes can be averaged to produce spectra that are similar to surface types 1 and 2 indicating that the originally derived surface types are representative of the average of all low albedo regions

supercritical marine layer flow along a smoothly varying coastline abstract a model for hydraulically supercritical atmospheric marine layer flow along a smoothly varying coastline is formulated and solved numerically the model is motivated by a recent comparison of code observations to a simple hydraulic theory which suggested the presence of an expansion fan and a compression jump downstream of topographic features the marine layer is modeled as a homogeneous rotating fluid layer decelerated by surface friction and forced by imposed upper level pressure gradients the equations are solved by a characteristic based gridpoint scheme the results indicate that the expansion fan is a robust feature that persists under most conditions in the present more realistic model but is dramatically altered in structure by the presence of friction while the jump may weaken rapidly offshore due mainly to offshore variations of the layer height upstream of the jump the agreement between observations and model predictions is good enough to suggest that a first order description of

the iberian peninsula thermal low statistics of the thermal low above the iberian peninsula are presented for the period between 1979 and 1993 based on gridded data from the european centre for medium range weather forecasts reanalysis project the sample of days with a thermal low above the iberian peninsula was selected objectively using criteria applied to mean sea level pressure and 925 hpa geopotential fields the synoptic and regional scale horizontal structure is characterized by the climatology of the 500 hpa geopotential and mean sea level pressure distributions the diurnal evolution of the mean sea level pressure is portrayed by mean fields at 00 06 12 and 18 u tc the climatological vertical structure of the thermal low is shown by relation to meridional and zonal cross sections passing through the thermal low s centre the diurnal evolution of the divergence relative vorticity potential temperature and vertical velocity is investigated statistics are presented also for the monthly frequency geographical location vertical extent and intensity of the iberian thermal low copyright 2003 royal meteorological society

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

acidic weathering of basalt and basaltic glass 1 near infrared spectra thermal infrared spectra and implications for mars engineering research council of canada the canadian space agency the canada foundation for innovation the manitoba research innovations fund and the university of winnipeg for supporting the establishment and operation of the planetary spectrophotometer facility this work was funded in part by the nasa 2001 mars odyssey themis project jet propulsion laboratory contract 1228404 through arizona state university and by the arizona state university exploration postdoctoral fellowship