acid weathering of basalt and basaltic glass 2 effects of microscopic alteration textures on spectral properties 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 the natural sciences and 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

resonant forcing of mixed layer inertial motions by atmospheric easterly waves in the northeast tropical pacific abstract westward propagating atmospheric easterly waves contribute to much of the variability of the low level wind fields within the northeast tropical pacific with the dominant period of these waves 3 5 days close to the local inertial period 2 4 days at 12 n to 5 7 days at 5 n there is the expectation that the associated winds may resonantly force mixed layer inertial motions in this region the authors test this hypothesis using a simple slab model and roughly 4 yr of wind data from four noaa tropical atmosphere ocean eastern pacific investigation of climate processes tao epic buoys along 95 w at 12 10 8 and 5 n the degree of resonance is determined by comparing model simulations using observed wind stress with simulations forced with reversed rotation wind stress results strongly indicate that pacific easterly waves pews resonantly force inertial motions in the region this resonance shows both significant seasonality and latitudinal dependence that appears to be related to the me

upper ocean temperature structure inertial currents and richardson numbers observed during strong meteorological forcing abstract upper ocean currents and temperature in the northeastern pacific were measured during a 14 day period in november 1980 as part of strex velocities in the upper ocean are dominated by near inertial frequency oscillations thew oscillations are modified by wind stress variations associated with the passage of a strong cold front the change in the inertial currents both in the mixed layer and below is qualitatively consistent with linear internal wave dynamics if turbulent stresses during the storm are assumed to extend 10 20 m below the mixed layer the ratio of mean squared buoyancy frequency n2 and mean squared shear s2 computed over a 10 m interval defines an average richardson number r0 n2 s2 r0 is approximately 2 5 except in regions of high inertial shear in particular values as low as 0 7 are obtained in a 20 m thick region immediately below the base of the mixed layer the data are consistent with a model of the oecanic shear field consisting of a background shear corresponding to a va

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

characteristics distribution origin and significance of opaline silica observed by the spirit rover in gusev crater mars 1 the presence of outcrops and soil regolith rich in opaline silica 65 92 wt sio2 in association with volcanic materials adjacent to the home plate feature in gusev crater is evidence for hydrothermal conditions the spirit rover has supplied a diverse set of observations that are used here to better understand the formation of silica and the activity abundance and fate of water in the first hydrothermal system to be explored in situ on mars we apply spectral chemical morphological textural and stratigraphic observations to assess whether the silica was produced by acid sulfate leaching of precursor rocks by precipitation from silica rich solutions or by some combination the apparent lack of s enrichment and the relatively low oxidation state of the home plate silica rich materials appear inconsistent with the originally proposed hawaiian analog for fumarolic acid sulfate leaching the stratiform distribution of the silica rich outcrops and their porous and brecciated microtextures are consistent with sinter produced by silica precipitation there is no evidence for crystalline quartz phases among the silica occurrences an indication of the lack of diagenetic maturation following the production of the amorphous opaline phase

balances of heat and momentum at 33 5 n 127 w in the upper ocean during the mixed layer dynamics experiment the balances of momentum and heat were studied for an 18 day period in october november 1983 during the mixed layer dynamics experiment at a site 650 km off central california data were collected from a drifting platform from which surface winds air temperature and ocean currents from a string of vector measuring current meters were measured the position of the unattended drifter was determined by loran c on the platform currents in the surface layers were partially wind driven and partially coherent with low frequency currents at deeper levels the latter currents though coherent were sheared turned significantly with depth and were presumably nearly geostrophically balanced vertically differencing velocity in the mixed layer improved the balance between wind and current by removing a portion of the geostrophic flow the complex correlation coefficient between wind stress and current integrated to 38 m was 0 76 for current relative to 38 m yet only 0 36 for the undifferenced case surface heat flux magnitudes were not clearly reflected in the heat content of the near surface layers although variability was over the first 13 days of the experiment the correlation coefficient between daily averaged heat flux and heat content change was 0 89 but average net surface heating was 60 w m 2 while the average heat content change in the top 38 m was only 10 w m 2 heat balance must have been restored by advection vertical advection was rejected as an explanation because heat content changes in layers defined by isotherm depths showed similar imbalances with regard to surface heating horizontal advection was estimated by two methods 1 by using sparse thermistor chain tows around the current meter drifter to construct a history of horizontal temperature gradients and 2 by using current profiles at moderate depths to estimate pressure gradients essentially through geostrophy hence buoyancy gradients by the hydrostatic relation hence temperature gradients the two methods gave very different estimates though both tended to redress the imbalance between surface heat flux and local heat storage

internal swell generation the spatial distribution of energy flux from the wind to mixed layer near inertial motions the energy flux from the wind to inertial mixed layer motions is computed for all oceans from 50 8 st o 508n for the years 1996 99 the wind stress t is computed from 6 h 2 58 resolution ncep ncar global reanalysis surface winds the inertial mixed layer response ui and the energy flux p5 t ui are computed using a slab model the validity of the reanalysis winds and the slab model is demonstrated by direct comparison with wind and adcp velocity records from ndbc buoys at latitudes 508 the inertial response is too fast to be resolved by the reanalysis wind 6 h output interval midlatitude storms produce the greatest fluxes resulting in broad maxima near 40 8 latitude during each hemisphere s winter concentrated in the western portion of each basin northern hemisphere fluxes exceed those in the southern hemisphere by about 50 the global mean energy flux from 1996 to 1999 and 508 st o 508n is 0 98 6 0 08 3 1023 wm 22 for a total power of 0 29 tw 1 tw 5 1012 w this total is the same order of magnitude as recent estimates of the global power input to baroclinic m2 tidal motions suggesting that windgenerated near inertial waves may play an important role in the global energy balance

observations of strong inertial oscillations after the passage of tropical cyclone ofa one week after tropical cyclone ofa passed near samoa near inertial oscillations of almost 1 m s 1 in amplitude were observed with a shipboard acoustic doppler current profiler adcp the velocity was nearly uniform with depth in the upper 80 m the strongest currents in this layer were found about 300 km from ofa s track farther than expected from previous observations and models below 80 m was a layer 50 100 m thick in which the shear exceeded 0 01 s 1 strong near inertial oscillations with currents over 0 6 m s 1 from 130 to 200 m extended through the shear layer to at least 300 m the limit of the adcp measurements the phase of the oscillations propagated upward consistent with downward propagation of energy a simple slab model driven by an idealized wind field approximately matches the observed amplitude and phase of the oscillations in the surface layer within 150 km of ofa s track but not the stronger current 300 km from the track

velocity structure in the mixed layer during mildex abstract during october november 1983 a mixed layer dynamics experiment mildex took place off the coast of california as a part of mildex a number of sensors were deployed from the research platform flip in an effort to monitor the flow structure in the near surface mixed layer profiling current meters vmcms measured velocities down to 150 m on an hourly basis other vmvms were set at fixed depths depths of interest were examined using a package which measured three component velocities and displayed them in flip s laboratory in real time the current meters often observed sequences of downwind directed jets with maximum velocities exceeding 25 cm s 1 downwelling velocities of equal magnitude were also observed the strongest currents were found 10 to 35 m below the surface at mid depth in the mixed layer surface convergences associated with these jets were visualized by scattering tracers computer cards on the sea surface these features suggest langmuir circulation six doppler sonars wer

rock coatings in hawaii basaltic lava flows exposed to semiarid weathering on the island of hawaii develop hydrous silica coatings that thicken and incorporate detrital material with age the nearly pure silica coatings on the younger rocks are colorless but basaltic detritus and its weathering products incorporated into coatings on older flows produce colors ranging from brown to red age rate of supply of material and the mechanical stability of flow surfaces dictate the color and thickness of coatings fresh glassy pahoehoe surfaces support thin as much as 5 m clear silica coatings but break down in a few years to expose the vesicular underlying material at first coloring is concentrated in the open vesicles yielding a dark brown color a mixture of red vesicles and projections of black basalt with age thicker accumulations of silica incorporate layers of oxidized basaltic material the dark basaltic material in kilauea and mauna kea coatings is probably supplied by large explosive eruptions but at mauna loa and kohala the source could be locally derived basaltic weathering products the clear hydrous silica layers are probably the product of leaching of locally derived basaltic dust

thermal infrared analysis of weathered granitic rock compositions in the sacaton mountains arizona implications for petrologic classifications from thermal infrared remote sensing data 1 critical to spectral interpretations of geologic surfaces on the earth and mars is an understanding of the relationship between the composition of weathered rock surfaces and whole rock mineralogy in this study thermal infrared spectroscopic and remote sensing analyses were used to determine the composition of weathered granitoid rock surfaces in the sacaton mountains arizona a linear spectral deconvolution approach was employed to determine the mineralogies of naturally exposed weathered surfaces and artificially exposed fresh rock surfaces deconvolution results from fresh rock surfaces yield similar bulk mineralogy to results from point counting of rock slabs and thin sections deconvolution of weathered rock spectra indicate that compared to fresh samples weathered surfaces are deficient in plagioclase feldspar and are enriched in clay minerals the differential weathering of feldspar minerals impacts the interpretation of whole rock mineralogy and the spectral classification of bedrock geology which for plutonic rocks is dependent on the relative proportions of different feldspars deconvolutions of multispectral remote sensing or laboratory data show a deficiency of total feldspar in the weathered rock units but lack sufficient spectral resolution for the discrimination between different feldspars these results demonstrate that the differential breakdown and removal of primary minerals in rock surfaces due to weathering can affect the interpreted rock petrology from remote sensing studies the relationships observed in our granitic samples could be applied to any rock type and may be important to consider for remote sensing of mars

the energy flux from the wind to near inertial motions in the surface mixed layer abstract time series of wind stress computed from long term meteorological buoy data off north america are used to examine the forcing of surface inertial currents by the wind a simple damped slab model of the mixed layer is used to compute h the average flux of energy from the wind to mixed layer inertial currents in a mixed layer of fixed depth h the forcing of mixed layer inertial motions is highly intermittent most of the forcing occurs during the winter months with a few dozen events accounting for typically over half the total energy flux major forcing events are usually associated with translating cold fronts or small lows with scales of about 100 km the larger synoptic scale features have little energy at the inertial frequency and thus result in only weak forcing of inertial currents a strong seasonal signal exists in the inertial forcing at ows p 50 n 145 w 50 m is largest from october to february and is a factor of 12 above the june and july values if seasonally varying

structural dependence of crystalline silicate hydration during aqueous dissolution abstract by using mev ion beam analytical techniques which provide the depth profiles of incorporated hydrogen and major constituent elements we show that alike glasses crystalline silicates can form surficial hydrated layers upon aqueous dissolution at temperatures up to 200 c the occurrence of such layers depends on both crystal structure and chemical composition tridimensional network silicates containing easily exchangeable alkalis being the most suitable materials this phenomenon could have important implications for the geochemical cycle of certain trace elements since highly hydrolyzable ones tend to accumulate in such hydrated layers

fundamental processes controlling the first stage of alteration of a basalt glass by seawater an experimental study between 200 and 320 c the first stage of alteration of a basalt glass by seawater has been studied experimentally between 200 and 320 c under vapor pressure following both the chemical evolution of the reacting solutions during the experiments and the chemical and mineralogical transformations of the altered glass surface via microprobe scanning transmission electron microscope and resonant nuclear reactions the alteration is controlled by diffusion of dissolved species through an altered layer and not by surface chemical reaction selective removal of cations with respect to sio2 leads to the formation of a thick porous protonated surface layer enriched in sio2 aqueous diffusion of dissolved species from the reacting glass and from solution through the pores of this layer results in the formation of an amorphous silicate gel which is the precursor of normal crystalline clays saponites appearing in a later stage computer simulations of the alteration generated with the eq3 6 computer software package account for the chemical composition of the rim and the sequence of secondary minerals found in the experiments

the stratigraphic distribution of inertinite abstract the paper presents the results of an investigation into the stratigraphic distribution of inertinite in humic coals ranging from the silurian to the neogene periods this range equals the time span during which both land plants and atmospheric oxygen evolved the survey is based on a literature study of inertinite in coals covering a variety of depositional environments and climates in all continents the inertinite percentages listed in this paper have been arranged in stratigraphic order they are the mean values based on mineral free whole coal compilations maceral compositions listed in the literature for individual subsections have been averaged to represent complete coal seams beds although this might not have been always possible due to some ambiguity in the published record moreover not all of the published and unpublished information could be used because of poor sample description obscure geographic origin or insufficient stratigraphic information the results show that there have been times in the geological past e g during the late permian in which coals were particularly rich in inertinite compared with other times e g during much of the late tertiary in which many coals contained very little inertinite occasionally such primary global trends were modulated by a diffuse distribution of inertinite percentages that correspond to differences in climate depositional settings e g active orogenic margins versus tectonically inactive shelf margins and other local or regional variations although various mechanisms for the generation of inertinite have been proposed in the past the overall pattern in its stratigraphic distribution supports the notion of incomplete combustion as the main source of inertinite in coal this points to secular variations in the atmospheric oxygen content as an explanation for the global changes in the inertinite distribution while differential subsidence and climatically influenced reaction rates governed regional and local variations in inertinite percentages

basalt weathering rates on earth and the duration of liquid water on the plains of gusev crater mars where martian rocks have been exposed to liquid water chemistry versus depth profi les could elucidate both martian climate history and potential for life the persistence of primary minerals in weathered profi les constrains the exposure time to liquid water on earth mineral persistence times range from 10 k y olivine to 250 k y glass to 1 m y pyroxene to 5 m y plagioclase such persistence times suggest mineral persistence minima on mars however martian solutions may have been more acidic than on earth relative mineral weathering rates observed for basalt in svalbard norway and costa rica demonstrate that laboratory ph trends can be used to estimate exposure to liquid water both qualitatively mineral absence or presence and quantitatively using reactive transport models qualitatively if the martian solution ph 2 glass should persist longer than olivine therefore persistence of glass may be a ph indicator with evidence for the ph of weathering the reactive transport code crunchflow can quantitatively calculate the minimum duration of exposure to liquid water consistent with a chemical profi le for the profi le measured on the surface of the exposed martian rock known as humphrey in gusev crater the calculated exposure time is 22 k y which is a minimum due to physical erosion if correct this estimate is consistent with short term episodic alteration accompanied by ongoing surface erosion more of these depth profi les should be measured to illuminate the weathering history of mars

the relation of near inertial motions observed in the mixed layer during the jasin 1978 experiment to the local wind stress and to the quasi geostrophic flow field abstract oscillations with near inertial frequencies were an energetic component of the upper ocean velocity field observed at each of two moorings separated by 44 km during the joint air sea interaction jasin experiment during the late summer of 1978 at each mooring the amplitude of the inertial motion was highest in the mixed layer where it was nearly depth independent previous work pollard and millard 1970 pollard 1980 had found that the amplitude and phase of inertial motion in the mixed layer was related to the local wind stress in this case the loacal winds measured at each mooring were coherent but the time series of mixed layer near inertial motion at one mooring bore little resemblance to that at the other mooring during jasin 1978 the differences in the inertial response at the two moorings coincided with differences in the quasi geostrophic flow field in the vicinity of the two moorings inclusion of the horizontal gradients of the quasi geostrophic flow in model equations prov

timescales and mechanisms of formation of amorphous silica coatings on fresh basalts at kīlauea volcano hawai i young basalts from k lauea volcano hawai i frequently feature opaque surface coatings 1 80 m thick composed of amorphous silica and fe ti oxides these coatings are the product of interaction of the basaltic surface with volcanically derived acidic fluids previous workers have identified these coatings in a variety of contexts on hawai i but the timescales of coating development coating growth rates and factors controlling lateral coating heterogeneity were largely unconstrained we sampled and analyzed young lava flows of varying ages from hours to 40 years along k lauea s southwest and east rift zones to characterize variation in silica coating properties across the landscape coating thickness varies as a function of flow age flow surface type and proximity to acid sources like local fissure vents and regional plumes emitted from k lauea caldera and pu u silica coatings that form in immediate proximity to acid sources are more chemically pure than those forming in higher ph environments which contain significant al and fe incipient siliceous alteration was observed on basalt surfaces as young as 8 days old but periods of a year or more are required to develop contiguous coatings with obvious opaque coloration inferred coating growth rates vary with environmental conditions but were typically 1 5 m year coatings form preferentially on flow surfaces with glassy outer layers such as spatter ramparts volcanic bombs and dense pahoehoe breakouts due to glass strain weakening during cooling microtextural evidence suggests that the silica coatings form both by in situ dissolution reprecipitation and by deposition of silica mobilized in solution thin films of water acidified by contact with volcanic vapors dissolved near surface basalt then precipitated amorphous silica in place mobilizing more soluble cations additional silica was transported to and deposited on the surface by silica bearing altering fluids derived from the basalt interior

weathering rinds and rock coatings from an arctic alpine environment northern scandinavia coarse rock debris exposed in the subaerial environment of northern sweden displays the development of a wide variety of surface coatings these include weathering rinds as well as a great diversity of geochemical coatings including those dominated by ca fe si and al each of these types of rock coatings displays a high degree of geochemical complexity the weathering rinds exhibit both geochemical and morphologic changes to the parent rock cores including extensive dissolution oxidation and hydration as well as disaggregation fracturing and cementation by secondary geochemical coatings chemical breakdown of the rock to form weathering rinds includes loss of k si mg and ca and buildup of fe weathering rinds are fundamentally the result of dissolution as no clay minerals were identified in the rinds rock coatings are distinguished from rinds by their clear accretionary nature despite the distinction made between weathering rinds and rock coatings it is important to note that often the two are intimately related the presence of rock coatings as well as weathering rinds on rock surfaces amplifies the important role played by geochemical processes in the arctic alpine climate of northern sweden in particular as well as its significance in landscape evolution in such environments in general

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

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

silica coatings in the ka u desert hawaii a mars analog terrain a micromorphological spectral chemical and isotopic study high silica materials have been observed on mars both from orbit by the crism spectrometer and in situ by the spirit rover at gusev crater these observations potentially imply a wet geologically active martian surface to understand silica formation on mars it is useful to study analogous terrestrial silica deposits we studied silica coatings that occur on the 1974 kilauea flow in the ka u desert hawaii these coatings are typically composed of two layers a 10 m layer of amorphous silica capped by a 1 m layer of fe ti oxide the oxide coating is composed of 100 nm spherules suggesting formation by chemical deposition raman spectroscopy indicates altered silica glass as the dominant phase in the silica coating and anatase and rutile as dominant phases in the fe ti coating jarosite also occurs within the coatings oxygen isotopic contents of the coatings were determined by secondary ion mass spectrometry cameca 7f and nanosims the measured values 18 o fe ti 14 6 2 1 and 18 o silica 12 1 2 2 relative to smow are enriched in 18 o relative to the basalt substrate the observations presented are consistent with a residual formation mechanism for the silica coating acid sulfate solutions leached away divalent and trivalent cations leaving a silica enriched layer behind micrometer scale dissolution and reprecipitation may have also occurred within the coatings chemical similarities between the hawaiian samples and the high silica deposits at gusev suggest that the martian deposits are the product of extended periods of similar acid sulfate leaching

open ocean surface wave measurement using doppler sonar in october november 1983 doppler sonars mounted on the research platform flip were used to scatter 75 khz sound from the underside of the sea surface at low angle as well as from the interior of the mixed layer surface gravity waves were seen in velocity estimates from the surface scattering sonar even though the wave conditions were unusually calm valid measurements of sea surface motion were obtained over the range interval 600 to 1400 m from flip a second sonar which transmitted horizontally and scattered from the interior of the mixed layer also sensed surface waves although with amplitude reduced in proportion to the decay of the motions with depth wave number frequency spectra of the observed motions are consistent with linear theory the existence emergence of this technology enables the synthesis of kilometer long surface wave arrays in the open sea without the cost and logistical support usually associated with large aperture arrays in addition the doppler acoustic approach can provide information on lower frequency surface currents and on the spatial variations in these low frequency currents such as langmuir cells which might affect wave propagation

observations of near inertial surface currents off oregon decorrelation time and length scales 1 high resolution km in space and hourly in time surface currents observed by an array of high frequency radars off oregon are analyzed to quantify the decorrelation time and length scales of their near inertial motions the near inertial surface currents are dominantly clockwise with amplitudes of 9 12 cm s 1 however they appear asymmetric and elliptical as a result of counterclockwise inertial motions with magnitudes in a range of 2 5 cm s 1 the decorrelation time and length scales are computed from the decay slope of the near inertial peak and the spatial coherence in the near inertial frequency band respectively decorrelation time scales of clockwise near inertial motions increase from 2 days nearshore within 30 km from the coast to 6 days offshore and their length scales increase from 30 to 90 km seaward possibly due to coastal inhibition the local spatial coherence has an exponentially decaying structure for both clockwise and counterclockwise rotations and their phases propagate northwestward offshore for clockwise and northeastward onshore for counterclockwise rotations

interactions between near inertial mixed layer currents and the mesoscale the importance of spatial variabilities in the vorticity field abstract satellite tracked mixed layer drifter data from the 1987 ocean storms experiment in the northeast pacific are used to study the temporal and spatial variability in the near inertial currents of the surface mixed layer the data suggest that the near inertial currents interact with the mesoscale vorticity to explore the exact nature of this relationship an asymptotic analysis is extended to include the mesoscale and it is shown that not only gradients in the planetary vorticity but also the gradients in the mesoscale vorticity affect the generation and evolution of near inertial mixed layer currents while the effect is relevant for the large scale evolution of the near inertial currents the vorticity gradients of the mesoscale field determine the local behavior of near inertial currents using a three dimensional model it is shown that areas of large gradients in the mesoscale vorticity coincide with areas of low near inertial energy the smaller spatial scales in the near inertial energ

wind forced internal waves in the north pacific and sargasso sea abstract the three dimensional structure of the near inertial frequency internal wave field was measured at two open ocean sites using expendable velocity profilers both wave fields appear to be dominantly wind forced although their vertical structure and horizontal scales are quite different the hydro 79 data were taken in the sargasso sea in september 1979 the internal wave field is predominantly downward propagating and vertically uniform when wkb scaled in the upper 800 m of the ocean the energy density is roughly equal to munk s 1981 universal value the stkex data were taken during a period of strong storms in the northeastern pacific ocean in november 1980 in the upper few hundred meters the wave field is five times larger horizontally and five times more energetic when wkb scaled than the hydro 79 wave field measurements made after the passage of a strong cold front show an even more energetic and larger scale wave field extending to 500 m comparison with the simulations of price 198

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

near surface velocity variability at inertial and subinertial frequencies in the vicinity of the california current abstract observations of the horizontal velocity field in the upper 150 m made from the research platform flip as it drifted of the coast of baja california were used to examine the velocity of the velocity field and its relation to local wind forcing at subinertial frequencies a spatially varying flow field associated with the california current system was encountered in addition there was low frequency near surface flow to the right of the wind stress that decayed with depth at near inertial frequencies victory motion with an amplitude of up to 40 cm s 1 was observed most of the energy in the near inertial frequency band was associated with modes with vertical wavelengths large compared to the thickness of the mixed layer the local wind alone had neither the strength nor the variability needed to directly produce the observed inertial period variability it is suggested that flip encountered regions in which the shear of the quasi geostrophic flow resulted in localized intensifications of near i

combined use of visible reflected infrared and thermal infrared images for mapping hawaiian lava flows the weathering of hawaiian basalts is accompanied by chemical and physical changes of the surfaces these changes have been mapped using remote sensing data from the visible and reflected infrared and thermal infrared wavelength regions they are related to the physical breakdown of surface chill coats the development and erosion of silica coatings the oxidation of mafic minerals and the development of vegetation cover these effects show systematic behavior with age and can be mapped using the image data and related to relative ages of pahoehoe and aa flows the thermal data are sensitive to silica rind development and fine structure of the scene the reflectance data show the degree of oxidation and differentiate vegetation from aa and cinders together data from the two wavelength regions show more than either separately the combined data potentially provide a powerful tool for mapping basalt flows in arid to semiarid volcanic environments

relative dating of hawaiian lava flows using multispectral thermal infrared images a new tool for geologic mapping of young volcanic terranes the weathering of hawaiian basalts in arid and semiarid environments is accompanied by change in their thermal infrared emittance spectra the spectral differences can be measured and mapped with multispectral imaging systems the differences appear to be related to the degree of development preservation and alteration of glassy crusts the oxidation of iron and the accretion of silica rich surface veneers because the measurements are quantitative and in image format they are useful for estimating relative ages in geologic mapping of lava flows in hawaii this technique is most diagnostic for distinguishing among sparsely vegetated flows less than 1 5 ka in age

modulation of near inertial oscillations by low frequency current variations on the inner scotian shelf abstractnear inertial oscillations nios on the inner scotian shelf are studied using observations a simple slab model and two operational shelf circulation models high frequency radar and adcp

acidic volatiles and the mars soil large portions of mars surface are covered with deposits of fine homogeneous weathered dusty soil material nanophase iron oxides silicate mineraloids and salts prevail in the soil the mode of formation of this somewhat peculiar type of soil is still far from being clear one scenario suggests that weathering took place during early epochs when mars may have been warm and wet the properties of the soil are not easily reconciled with this scenario we propose another possible scenario that attributes in part the peculiar nature of the martian dust and soil to a relatively young weathering product formed during the last few hundreds of millions of years in a process that involves acidic volatiles we tested this hypothesis in an experimental study of the first step of acidolytic weathering of a partly palagonitized volcanic tephra of hawaiitic lava origin using sulfuric hydrochloric and nitric acids and their mixtures the tephra effectively neutralize the added acidity the protonic acidity added to the tephra attacks the primary minerals releasing fe al and mg which control the ph acting as lewis acid species of varying acid strengths the full amount of acidity added to the tephra is stored in it but only a very small fraction is preserved as the original protonic acidity the majority of the added sulfate and chloride were present as salts and easily solubilized minerals well crystallized sulfate salt minerals of aluminum and calcium were detected by powder x ray diffractometry whereas secondary magnesium and iron minerals were not detected due probably to lack of crystallinity the presence of gypsum caso4 2 h2o and alunogen al2 so4 3 17 h2o is probably responsible for the observed increased hygroscopicity of the acidified tephra and their tendency to form hardened crusts we suggest that if this mechanism is of importance on mars then the chemically weathered component of the martian soil consists of a salt rich mineral mixture containing the salts of the anionicligands so4 and cl resulting from volatiles emitted from volcanoes during more recent eruptions up to 109 years b p the lack of liquid water on mars surface during that time slowed or halted mineralogical evolution into highly crystallized minerals having large mineral grains the chemically weathered components are mixed with the products of physical weathering the recently formed soil may cover and coat more evolved hydrothermally modified mineral deposits formed in earlier epochs of mars

acid sulfate weathering of synthetic martian basalt the acid fog model revisited the acid fog model has received considerable attention as a model of soil formation on mars previous evaluations of this model have focused on experimental weathering of terrestrial basalt samples however these samples differ significantly from what now is thought to be typical of martian basalt the acid fog model is tested here using synthetic basaltic analogs derived from mars pathfinder soil and rock compositions reaction of synthetic basalt with various acidic solutions and subsequent evaporation has led to the formation of several putative secondary mineral phases many of these phases were not produced in prior experimental studies aimed at aqueous interactions on mars of these alteration phases mg fe ca and al sulfates were identified in addition secondary ferric oxide phases formed via rapid fe oxidation under relatively high ph levels buffered by basalt dissolution amorphous silica is a ubiquitous product in these experiments and has formed by precipitation from solution and by the dissolution of minerals and glasses leaving behind leached surface layers composed of residual silica the secondary products formed in these experiments demonstrate the importance of primary mineralogy when testing models of aqueous interactions on mars new constraints are placed on both the reactivity of primary basalt and the secondary mineralogy present at the martian surface copyright 2004 by the american geophysical union

the upper ocean internal wave field influence of the surface and mixed layer a model is developed to calculate the upper ocean internal wave spectrum as modified by the surface boundary and mixed layer the garrett munk spectrum is assumed to describe the deep ocean wave field the main effect of the surface and mixed layer is to align the vertical structure of the waves forming vertically standing waves locally this contrasts with the assumption of random alignment in the garrett munk model model spectra and coherences are calculated for idealized buoyancy frequency profiles and compared with the garrett munk model measurements in the upper 200 m from the mixed layer dynamics experiment in the northeast pacific in 1983 are also compared with the model results the most striking success of the model is predicting the observed high coherence and 180 phase difference across the mixed layer of horizontal velocity

widespread weathered glass on the surface of mars low albedo sediments cover 10 7 km 2 in the northern lowlands of mars but the composition and origin of these widespread deposits have remained ambiguous despite many previous investigations here we use near infrared spectra acquired by the mars express omega observatoire pour la mineralogie l9eau les glaces et l9activite imaging spectrometer to show that these sediments exhibit spectral characteristics that are consistent with both high abundances of iron bearing glass and silica enriched leached rinds on glass this interpretation is supported by observations of low albedo soil grains with possible rinds at the phoenix mars lander landing site in the northern lowlands by comparison with the extensive glass rich dune fields and sand sheets of iceland we propose an explosive volcanic origin for these glass rich sediments we also propose that the glassy remnant rinds on the sediments are the result of postdepositional alteration as these rinds are commonly formed in arid terrestrial volcanic environments during water limited moderately acidic leaching these weathered glass rich deposits in the northern lowlands are also colocated with the strongest concentrations of a major global compositional surface type previously identified in mid infrared spectra suggesting that they may be representative of global processes our results provide potential confirmation of models suggesting that explosive volcanism has been widespread on mars and also raise the possibilities that glass rich volcaniclastics are a major source of eolian sand on mars and that widespread surficial aqueous alteration has occurred under amazonian climatic conditions

inertial oscillations on the continental shelf of the gulf of lions observations and theory abstract observations in the gulf of lions northwestern mediterranean sea in summer have shown that gusts of wind lasting a few days generate transient upwellings and inertial motions oscillations at the inertial frequency were observed in current meter data near the shore and at a frequency 10 greater in the temperature data vertical coherences in current meter data show a strong baroclinic mode at frequencies greater than inertial frequency a simple one dimensional two layer transient model suggests that these motions are associated with two different physical processes the first process describes the local response of the ocean to meteorological forcing the second is associated with the propagation of long internal waves generated in the transient phase of the geostrophic adjustment process as suggested by the model the direction of propagation of the internal waves is computed from current and temperature data measured at one point and it is found that the shore is the source zone

on the behavior of internal waves in the wakes of storms abstract the rossby adjustment process in the wake of a storm is studied with a view to finding within the context of linear theory how wave dispersion in both the vertical and meridional directions spreads energy which is initially confined entirely to the mixed layer comparisons are made between three cases 1 a periodic storm on the f plane where dispersion is purely vertical 2 a bounded storm on the f plane and 3 a bounded storm centered 2700 km from the equator on an equatorial beta plane particular attention is paid to the initial rate of loss of energy from the mixed layer and some simple formulas which work very well in the cases studied are derived these show that the rate of loss goes up when the mixed layer depth is increased and also that the rate scales as the square of the wavenumber values of the rates are sufficient to provide a major source of energy for internal waves below the mixed layer the often observed tendency for phase lines to propagate upward is found in all case

thermal infrared spectral character of hawaiian basaltic glasses multispectral thermal infrared remote sensing of hawaiian basalts younger than a few hundred years old can be used to discriminate basalt lava flows that are difficult to map with visible and near infrared images laboratory thermal infrared reflectance spectra of the exposed surfaces of mauna loa and kilauea basalts show systematic changes with age fresh glass collected from active lava flows shows a broad reflectance feature between 8 and 12 m indicative of a strong degree of disorder after a few weeks of exposure to the environment the spectra of the top surfaces of samples begin to exhibit spectral features suggestive of ordering into silicate chainlike and sheetlike units with progressive aging features of apparent sheetlike structures become the preferred mode as soon as 3 years after emplacement a silica rich coating can begin to develop on the surfaces adding another spectral feature to the laboratory reflectance measurements the thermal infrared multispectral scanner tims with six channels between 8 and 12 m has been used to take advantage of these spectral differences in basalts to map flows in hawaii remote sensing instruments with increased spectral resolution in the thermal infrared would aid in further discrimination of basalts with more subtle differences in age quenching and weathering histories

influence of amorphous silica layer formation on the dissolution rate of olivine at 90 c and elevated pco2 for mitigating against rising levels of atmospheric co2 carbonation of m2 bearing silicates has been proposed as a possible option for sequestering co2 over long time spans due to its rapid far from equilibrium dissolution rate and its widespread occurrence in mafic and ultramafic rocks olivine has been suggested as a potentially good candidate for achieving this goal although the efficacy of the carbonation reaction still needs to be assessed with this as a goal the present study aims at measuring the carbonation rate of san carlos olivine in batch experiments at 90 c and pco2 of 20 and 25 mpa when the reaction was initiated in pure water the kinetics of olivine dissolution was controlled by the degree of saturation of the bulk solution with respect to amorphous silica this yet unrecognized effect for olivine was responsible for a decrease of the dissolution rate by over two orders of magnitude in long term 45 days carbonation experiments with a high surface area to solution volume ratio sa v 24 600 m 1 the final composition of the solution was close to equilibrium with respect to sio2 am independent of the initial concentration of dissolved salts nacl and naclo4 ranging between 0 and 1 m and with an aqueous mg si ratio close to that of olivine no secondary phase other than a ubiquitous thin 40 nm si rich amorphous layer was observed these results are at odds with classic kinetic modeling of the process due to experimental uncertainties it was not possible to determine precisely the dissolution rate of olivine after 45 days but the long term alteration of olivine was indirectly estimated to be at least 4 orders of magnitude slower than predicted taken together these results suggest that the formation of amorphous silica layers plays an important role in controlling the rate of olivine dissolution by passivating the surface of olivine an effect which has yet to be quantified and incorporated into standard reactive transport codes

incongruent and congruent dissolution of plagioclase feldspar effect of feldspar composition and ligand complexation abstract secondary ion mass spectrometry sims was used to characterize the surfaces of plagioclase feldspar two labradorite compositions and one anorthite leached in water ph 5 8 and in 10 4m hcl hf and oxalic acid all at the same ph 4 0 4 1 labradorite an54 and an60 leached at ph 4 for 72 days dissolved incongruently in hcl oxalic acid and hf yielding altered layers strongly depleted in al ca and sr and residually enriched in si the leached layers formed on the more calcic composition an60 were approximately 3 times thicker than those formed on the more sodic an54 composition the thinnest leached layers were produced by hcl up to 1000 a on an54 and up to 3000 a on an60 and the thickest leached layers by hf up to 1700 a on an54 and up to 5000 a on an60 because the h concentration was the same in each solution it was possible to clearly separate the relative importance of proton promoted dissolution in hcl and ligand promoted dissolution in oxalic acid and in hf for a given feldspar composition to do this the sims depth profiles obtained from an60 labradorite leached in oxalic acid and in hf were normalized to those produced in response to hcl this comparison clearly shows that the ligands oxalate and fluoride significantly increased the formation of leached layers compared to the effect of h alone in contrast anorthite an100 leached in the same solutions essentially dissolved congruently in response to hcl only very thin leached layers formed in which al and ca were only weakly depleted relative to si chemical analyses of the output solutions showed that the molar ratio of si to al in solution 1 1 to 1 is equal to the molar ratio of si to al in the fresh solid confirming that the anorthite dissolved congruently while the leached layers found on anorthite leached in oxalic acid and hf were thinner and less intensively depleted compared to the leached layers formed in response to hcl the concentrations of si and al in the output solutions were significantly greater than those in the hcl solutions while oxalate and fluoride again promoted the dissolution of the feldspar si and al were still released to solution in the same molar proportion as they are found in the solid congruent dissolution the early stages of feldspar dissolution therefore may be either incongruent or congruent depending upon the chemical composition of the feldspar

silica in a mars analog environment ka u desert kilauea volcano hawaii airborne visible near infrared imaging spectrometer aviris data acquired over the ka u desert are atmospherically corrected to ground reflectance and used to identify the mineralogic components of relatively young basaltic materials including 250 700 and 200 400 year old lava flows 1971 and 1974 flows ash deposits and solfatara incrustations to provide context a geologic surface units map is constructed verified with field observations and supported by laboratory analyses aviris spectral end members are identified in the visible 0 4 to 1 2 m and short wave infrared 2 0 to 2 5 m wavelength ranges nearly all the spectral variability is controlled by the presence of ferrous and ferric iron in such minerals as pyroxene olivine hematite goethite and poorly crystalline iron oxides or glass a broad nearly ubiquitous absorption feature centered at 2 25 m is attributed to opaline amorphous hydrated silica and is found to correlate spatially with mapped geologic surface units laboratory analyses show the silica to be consistently present as a deposited phase including incrustations downwind from solfatara vents cementing agent for ash duricrusts and thin coatings on the youngest lava flow surfaces a second ti rich upper coating on young flows also influences spectral behavior this study demonstrates that secondary silica is mobile in the ka u desert on a variety of time scales and spatial domains the investigation from remote field and laboratory perspectives also mimics exploration of mars using orbital and landed missions with important implications for spectral characterization of coated basalts and formation of opaline silica in arid acidic alteration environments

mechanism of leached layer formation during chemical weathering of silicate minerals the dissolution of most common multicomponent silicate minerals and glasses is typically incongruent as shown by the nonstoichiometric release of the solid phase components this results in the formation of so called surface leached layers due to the important effects these leached layers may have on mineral dissolution rates and secondary mineral formation they have attracted a great deal of research however the mechanism of leached layer formation is a matter of vigorous debate here we report on an in situ atomic force microscopy afm study of the dissolution of wollastonite casio 3 as an example of leached layer formation during dissolution our in situ afm results provide for the first time clear direct experimental evidence that leached layers are formed in a tight interface coupled two step process stoichiometric dissolution of the pristine mineral surfaces and subsequent precipitation of a secondary phase most likely amorphous silica from a supersaturated boundary layer of fluid in contact with the mineral surface this occurs despite the fact that the bulk solution is undersaturated with respect to the secondary phase our results differ significantly from the concept of preferential leaching of cations as postulated by most currently accepted incongruent dissolution models this interface coupled dissolution precipitation model has important implications in understanding and evaluating dissolution kinetics of major rock forming minerals

effects of chemical weathering on infrared spectra of columbia river basalt and spectral interpretations of martian alteration abstract we investigated the mineralogy of basalt weathering rinds and fresh basaltic rocks using visible near infrared vnir 0 4 2 5 m and thermal emission 6 30 m spectroscopy to 1 constrain the effects of chemical weathering on rock spectra and 2 further understand the context of infrared spectra of mars which may contain evidence for weathered rocks and particulates derived from them vnir spectra of weathered rock surfaces are generally redder and brighter than fresh surfaces thermal infrared spectra of weathered basalts show evidence for aluminous opal and clay minerals or clay precursor mineraloids in natural surfaces supporting vnir observations generally do not show the same evidence for neoformed clays or silica because of their textural occurrence as thin coatings and microfracture fill and possibly due to poor crystallinity of the aluminosilicate weathering products in this context spectral trends observed at mars such as the detection of low to moderate 10 25 abundances of silica and clay that are observed in the thermal infrared but not in the vnir are therefore consistent with trends observed for natural rock surfaces in the laboratory the combined use of thermal infrared and vnir suggest that vast areas of martian dark regions contain sandy rocky basaltic materials with weathering rinds and thin coatings that could have formed in conditions of relatively low water rock ratios

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

the surface of labradorite feldspar after acid hydrolysis abstract after reaction with a ph both the surface area of the reacted feldspar and the porosity increase with acid hydrolysis modeling of nitrogen sorption onto the surface suggests that the pores have a nominal radius of 20 80 a or less this distribution of pore sizes resembles other acid reacted silicate materials such as glass chrysotile and kaolinite although the mineral surface clearly becomes more porous during acid hydrolysis the increase in powder area also does not coincide with an increase in the flux of dissolved si from the powder we thus attribute most of this increase in area to spallation of the silica rich surface from the feldspar upon drying

inertial oscillations in the upper ocean during the mixed layer dynamics experiment mildex surface currents in the near inertial frequency band were analyzed from 18 day long measurements taken in october november 1983 as part of the mixed layer dynamics experiment the currents below two drifting platforms separated by 55 km were found to have differed in their inertial response to a frontal passage on november 1 by 10 cm s 1 wind records from the two platforms were used to compute the predicted inertial currents with a simple slab model of the wind driven flow the model currents reproduced most of the features of the observed inertial currents including the disparity between the two locations following the november 1 frontal passage the disparity was due to differences in the weak winds preceding the frontal passage which account for inertial currents of 5 cm s 1 in opposing directions at the two platforms at the time of the front these differences or small scale 50 km structure in the wind field were responsible for the disparity rather than the slight difference in the arrival time 2 hours of the front at the two locations

evaluation of directly wind coherent near inertial surface currents off oregon using a statistical parameterization and analytical and numerical models directly wind coherent near inertial surface currents off the oregon coast are investigated with a statistical parameterization of observations and outputs of a regional numerical ocean model and three one dimensional analytical models including the slab layer ekman and near surface averaged ekman models the transfer functions and response functions statistically estimated from observed wind stress at ndbc buoys and surface currents derived from shored based high frequency radars enable us to isolate the directly wind forced near inertial surface currents concurrent observations of the wind and currents are crucial to evaluate the directly wind forced currents thus the wind stress and surface current fields obtained from a regional ocean model which simulates variability of the wind and surface currents on scales comparable to those in observations are analyzed with the same statistical parameterization to derive the point by point transfer functions and response functions model and data comparisons show that the regional ocean model describes near inertial variability of surface currents qualitatively and quantitatively correctly the estimated response functions exhibit decay time scales in a range of 3 5 days and about 40 of the near inertial motions are explained by local wind stress among the one dimensional analytical models the near surface averaged ekman model explains the statistically derived wind current relationship better than other analytical models

wavenumber spectra of pacific winds measured by the seasat scatterometer abstract vector winds measured by the seasat a satellite scatterometer sass are analyzed to determine the spatial structure of oceanic surface winds over wavelengths from 200 to 2200 km the analysis is performed in four latitudinal bands in the pacific ocean sampling characteristics of sass preclude the possibility of determining full two dimensional spectra the analysis is therefore limited to one dimensional along the satellite ground track spectra of vector wind components and kinetic energy the salient features of the results are summarized as follows i for each of the four geographic regions the spectra of meridional and zonal wind components and of kinetic energy are consistent with a power law dependence on wavenumber for midlatitude regions in both the northern and southern hemispheres the wave number dependence of kinetic energy is k 2 2 while for tropical regions in both hemisphere it is k 1 9 ii for each individual region the spectral dependence on wavenumber is nearly the same

observations of near inertial waves in acoustic doppler current profiler measurements made during the mixed layer dynamics experiment measurements of upper ocean shear made during the mixed layer dynamics experiment mildex provide evidence of large horizontal scale motion at near inertial frequency the measurements consist of shipboard acoustic doppler current profiles four large scale spatial surveys of 2 4 days duration were made by the r v wecoma as a set of boxes approximately 60 km per side around a drifting current meter buoy velocity time series from the drifting buoy and from sonar measurements made from flip also indicated the presence of motions at near inertial frequency horizontal length and time scales of the motion are estimated from the phase of the shear vector measured during the spatial surveys estimates of the length scale of the waves range from 500 to 1000 km and the frequency is approximately 1 1f the behavior of the phase is found to be consistent with a model of narrow band inertial waves with vertical structure such that there is a zero crossing in velocity at the base of the mixed layer 40 60 m

coupled dissolution and precipitation at mineral fluid interfaces reactions occurring at mineral fluid interfaces are important in all geochemical processes and essential for the cycling of elements within the earth understanding the mechanism of the transformation of one solid phase to another and the role of fluids is fundamental to many natural and industrial processes problems such as the interaction of minerals with co2 saturated water the durability of nuclear waste materials the remediation of polluted water and mineral reactions that can destroy our stone based cultural heritage are related by the common feature that a mineral assemblage in contact with a fluid may be replaced by a more stable assemblage

the geology petrology palynology and geochemistry of permian coal basins in tanzania 2 songwe kiwira coalfield abstract this study provides coal quality petrological palynological and geochemical rock eval data on permian coal seams and associated shales and mudstones of the karoo supergroup of the songwe kiwira coalfield tanzania the coal seams which have a cumulative thickness of 6 80 m occur in the shale coal sandstone facies of the mchuchuma formation of artinskian to kungurian age coal quality data calorific values volatile matter contents and vitrinite reflectances indicate high volatile c bituminous to high volatile a bituminous coals having relatively high ash yields 22 49 wt and highly variable sulphur contents 0 17 9 2 wt they could be used to fuel small scale power generation units thereby providing electricity to nearby towns and villages also the coals could be used as a substitute for wood which is becoming increasingly scarce in rural tanzania charcoal is still the main energy source for cooking and wood is used extensively in brick kilns and for making roofing tiles petrological analysis indicated that the coals are dominated by dull to banded dull lithotypes with seams at the base of the mchuchuma formation enriched in inertinite macerals up to 83 vol whereas up section vitrinite contents increase palynological analyses indicated that the assemblage in the lower mchuchuma formation scheuringipollenites assemblage is dominated by trilete spores whereas in the remainder of the section non taeniate disaccates dominate scheuringipollenites protohaploxypinus assemblage facies critical macerals suggest for most seams a marsh wet forest swamp depositional setting which is consistent with the palynological data rock eval analyses indicate type ii iii kerogen with tmax c values ranging from 426 to 440 corresponding to the early stage of hydrocarbon generation thermal alteration indices 2 to 2 and vitrinite reflectance levels 0 60 0 83 ro support the rock eval maturity assessment and despite the predominance of terrestrial derived organic matter there is evidence of oil generation and expulsion in the form of cavity and fracture filling exsudatinite

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

internal wave observations from flip in mildex abstract during 0ctober november 1983 the research platform flip participated in the mixed layer dynamics experiment mildex off the coast of southern california included among the equipment on board was an array of six doppler sonars and a repeatedly profiling ctd the sonars operate at frequencies between 67 and 80 khz with peak transmitted power of order 2 kw each four of the sonars were directed downward 53 obtaining velocity profiles to depths in excess of 1100 m the ctd was profiled to a depth of 320 m every 3 minutes approximately 6000 ctd profiles were obtained during mildex the mildex internal wavefield is slightly less energetic than the garrett munk canonical standard except in the near inertial frequency band here very low energy levels are seen the semidiurnal baroclinic tide dominates the spectra of both horizontal and vertical velocity in this work slant velocity estimates from back to back sonar beam are combined to form estimates of horizontal velocity and its vertical der

mesoscale variability in marine winds at mid latitude wind data were collected by the national oceanic and atmospheric administration wp 3d aircraft on low level 50 and 90 m crosswind and along mean wind tracks of approximately 350 km during the storm transfer and response experiment in november and december 1980 observed mesoscale variations in the marine wind fields are characterized by the velocity correlation tensor for three atmospheric regimes cloud streets open and closed cellular convection and prefrontal warm air advection the dominant scale of mesoscale variation in the offshore wind field normal to the mean wind direction in the case of old continental air flowing over a warmer ocean producing cloud streets was 27 km for this case the standard deviation in momentum transfer which was calculated from 2 km subsets of the flight track by the bulk aerodynamic method assuming a constant drag coefficient was 13 of the synoptic scale 330km mean the dominant scale of mesoscale variation for open cellular convection was 62km and the dominant scale for closed cellular convection was 90 km the standard deviation of mesoscale momentum transfer scales greater than 2 km constant drag coefficient for a 345 km flight track containing both cell types was 26 of the synoptic scale mean the warm air advection case had no measurable mesoscale variability for each regime a model of the horizontal velocity correlation tensor which can be used to estimate a mesoscale variability is fitted to the observed velocity correlation tensor with velocity component and weather regime dependent coefficients this general model is consistent with an interpretation of the mesoscale wind field as an ensemble of coherent structures associated with cloud type in which the spatial variability of the wind field in each weather regime is associated with physically determined dominant length scales i e cells or rolls as contrasted with a continuum interpretation of two dimensional turbulence to accurately describe regional winds and fluxes at the sea surface wind speed and temperature data should be averaged over the dominant mesoscale length scale with either a suitable time average or a spatial average such as can be obtained by scatterometry or an estimate of the mesoscale variability should be explicitly stated it is also suggested that enhanced vertical flux in the oceanic mixed layer occurs at length scales of atmospheric boundary layer structures

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

laboratory simulated acid sulfate weathering of basaltic materials implications for formation of sulfates at meridiani planum and gusev crater mars 1 acid sulfate weathering of basaltic materials is a candidate formation process for the sulfate rich outcrops and rocks at the mer rover opportunity and spirit landing sites to determine the style of acid sulfate weathering on mars we weathered basaltic materials olivine rich glassy basaltic sand and plagioclase feldspar rich basaltic tephra in the laboratory under different oxidative acid sulfate conditions and characterized the alteration products we investigated alteration by 1 sulfuric acid vapor acid fog 2 three step hydrothermal leaching treatment approximating an open system and 3 single step hydrothermal batch treatment approximating a closed system in acid fog experiments a1 fe and ca sulfates and amorphous silica formed from plagioclase rich tephra and mg and ca sulfates and amorphous silica formed from the olivine rich sands in three step leaching experiments only amorphous si formed from the plagioclase rich basaltic tephra and jarosite mg and ca sulfates and amorphous silica formed from olivine rich basaltic sand amorphous silica formed under single step experiments for both starting materials on the basis of our experiments jarosite formation in meridiani outcrop is potential evidence for an open system acid sulfate weathering regime waters rich in sulfuric acid percolated through basaltic sediment dissolving basaltic phases e g olivine and forming jarosite other sulfates and iron oxides aqueous alteration of outcrops and rocks on the west spur of the columbia hills may have occurred when vapors rich in so 2 from volcanic sources reacted with basaltic materials soluble ions from the host rock e g olivine reacted with s to form ca mg and other sulfates along with iron oxides and oxyhydroxides