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

dalton wells geology and significance of debris flow hosted dinosaur bonebeds in the cedar mountain formation lower cretaceous of eastern utah usa the lower cretaceous dalton wells dinosaur locality north of moab utah consists of a 2 m thick stacked succession of four fossil rich bonebeds with an estimated collective lateral extent of more than 4000 m2 to date 215 m2 of the bonebeds have been excavated and more than 4200 vertebrate fossil field specimens have been collected the site occurs at the base of the yellow cat member of the cedar mountain formation and lies unconformably on upper jurassic strata of the morrison formation the age of the assemblage is tentatively accepted as barremian nine dinosaur taxa are recognized making dalton wells one of the richest abundance and diversity lower cretaceous dinosaur localities in the world the bonebeds are rare examples of fossiliferous subaerial debris flow deposits at least four flows originated an undetermined distance up slope from an early cretaceous site of dinosaur bone concentration and flowed through the site carrying bones short distances toward an adjacent area of lakes ponds and wetlands host sediments most likely accumulated on the eastward dipping slopes of a backbulge in a foreland basin the overall depositional setting was alluvial lacustrine in a warm to hot and seasonally wet and dry climate the consistent expression and location of lacustrine facies in both the brushy basin member of the morrison formation and the yellow cat member of the cedar mountain formation indicate that high rates of subsidence typified the dalton wells area both before and after the j k transition and further suggest that there was some form of long term to episodic and localized influence on subsidence the depositional slope required to generate debris flows may have been established by forebulge crustal flexure but could also have been established or amplified by the high rates of subsidence that maintained the lacustrine paleoenvironments in the field area concretionary deposits in the yellow cat member at dalton wells are diagenetic and apparently resulted from groundwater precipitation likely enhanced by the presence of organics bones and lacustrine carbonates the regional and cross facies expression of calcretes in the yellow cat member combined with the rarity of pedogenic indicators confirms that they are not paleosols mineral precipitation likely occurred as groundwater flow was established in response to foreland basin development it remains unknown under what specific circumstances animals died and carcasses accumulated prior to being reworked by debris flows however the stratigraphic association of seasonally wet and dry facies throughout the yellow cat member suggests that drought induced mortality events were probably common in a seasonally wet and dry environment debris flows may have been triggered by intense rainfall or seismic events

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

windblown trees as a palaeoclimate indicator the character and role of gusts abstract regional studies of the fall directions of windblown trees preserved in peats lignites and coals offer the possibility of widening knowledge of palaeowind fields beyond arid regions to areas where precipitation exceeded evaporation for the successful interpretation of tree fall directions however an improved understanding is required of tree wind interactions and of the sources of variance in regional patterns of fall the distribution of tree fall directions in a swathe created during the great storm of october 1987 in southeast england provides the first direct and detailed evidence for the structure and role in tree damage of canopy scale coherent vortices with a gust part in the atmospheric rough wall turbulent boundary layer the fall pattern appears to confirm the inference based so far on purely meteorological evidence that the vortices in which the strongest part is described as a gust combine features of townsend s double roller model of turbulence with theodorsen s concept of the horseshoe vortex the gust part as registered by the spread of tree fall directions in the swathe analysed appears to contribute 20 25 of the total variance of tree fall directions due to storms over a region in a geologically significant interval of time

alteration of hawaiian basalts under sulfur rich conditions applications to understanding surface atmosphere interactions on mars and venus a suite of hawaiian basalts that were variably altered in the presence of so 2 rich gases during the current summit eruptive episode at halemaumau crater kilauea were studied to determine their alteration phase assemblage and reactive pathways using electron microscopy mossbauer spectroscopy and x ray diffraction the alteration conditions represent an acid fog environment alteration rinds on the basalts vary in thickness from tens of micrometers to the entirety of the rock and are composed of amorphous silica rims 85 95 wt sio 2 overlain by sulfates sulfate mineralogy consisted of gypsum anhydrite and natroalunite jarosite no phyllosilicates were observed in any alteration assemblages phenocrysts and glass were both observed to be extensively reacted during alteration the halemaumau samples may provide good analogs for basalt alteration on other rocky planetary bodies i e mars venus and mercury where s is ubiquitous and low fluid rock ratios are common

experimental study of acid sulfate alteration of basalt and implications for sulfate deposits on mars 1 acid sulfate alteration of basalt by so2 bearing volcanic vapors has been proposed as one possible origin for sulfate rich deposits on mars to better define mineralogical signatures of acid sulfate alteration laboratory experiments were performed to investigate alteration pathways and geochemical processes during reaction of basalt with sulfuric acid pyroclastic cinders composed of phenocrysts including plagioclase olivine and augite embedded in glass were reacted with sulfuric acid at 145 c for up to 137 days at a range of fluid rock ratios during the experiments the phenocrysts reacted rapidly to form secondary products while the glass was unreactive major products included amorphous silica anhydrite and fe rich natroalunite along with minor iron oxides oxyhydroxides probably hematite and trace levels of other sulfates at the lowest fluid rock ratio hexahydrite and an unidentified fe silicate phase also occurred as major products reaction path models indicated that formation of the products required both slow dissolution of glass and kinetic inhibitions to precipitation of a number of minerals including phyllosilicates and other aluminosilicates as well as al and fe oxides oxyhydroxides similar models performed for martian basalt compositions predict that the initial stages of acid sulfate alteration of pyroclastic deposits on mars should result in formation of amorphous silica anhydrite fe bearing natroalunite and kieserite along with relict basaltic glass in addition analysis of the experimental products indicates that fe bearing natroalunite produces a mossbauer spectrum closely resembling that of jarosite suggesting that it should be considered an alternative to the component in sulfate rich bedrocks at meridiani planum that has previously been identified as jarosite

radar studies of long wavelength waves associated with mid latitude sporadic e layers the cornell university portable radar interferometer cupri a 50 mhz doppler radar system was operated during may and august september 1983 on the island of st croix 17 7 n 64 8 w to study the plasma instabilities associated with nighttime sporadic e layers two events on may 7 and august 22 show evidence of large amplitude waves with apparent horizontal wavelengths of 10 12 km and periods of 2 6 min these apparent wavelengths are upper limits for the true wavelengths the cupri beam was directed over arecibo puerto rico and on may 7 concurrent electron density profiles within the cupri scattering volume were measured by the arecibo observatory s 430 mhz radar during the stronger event of august 22 radar echoes were received from several altitudes up to 130 km large mean doppler velocities at times exceeding 250 m s were observed during this event and the power spectra closely resemble those obtained at the magnetic equator during type 1 conditions we believe 1 that the mid latitude large scale waves are generated by the same gradient drift instability mechanism responsible for equatorial large scale waves and 2 that the type 1 3 m waves can be generated at mid latitudes with drift velocities well below the sound speed because of the very sharp plasma density gradients associated with metallic ion sporadic e layers

spatial occurrence of decameter midlatitude e region backscatter this paper provides a statistical analysis of the spatial occurrence of midlatitude e region decameter backscatter measurements were made using the valensole hf high frequency radar located in southern france during the summer of 1995 when it operated simultaneously at four frequencies on the basis of the premise that e region scattering is fully magnetic aspect sensitive the spatial occurrence statistics show that the aspect sensitive region moves toward the radar southward with respect to line of sight propagation calculations with the lower frequency echoes being closer toward the radar than the higher frequency ones are in agreement with refraction theory predictions ray tracing inside nighttime midlatitude electron density profiles augmented with dense sporadic e s layers was used to calculate the expected echoing region and good agreement with the observed region was found another finding is the angular distribution of backscatter inside the wide azimuthal sector covered by the radar scan the spatial distribution of echo occurrence has its maximum at small azimuths at and about the geomagnetic north suggesting that statistically the meridional direction is strongly preferred for backscatter under the postulation that these are secondary decameter waves we concluded that the observed angular anisotropy in spatial occurrence is at odds with the concept of strong isotropic plasma turbulence sudan 1983 but in general agreement with the two step gradient drift instability theory of secondary wave generation proposed by sudan et al 1973

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

beyond maps patterns of formation processes at the middle pleistocene open air site of marathousa 1 megalopolis basin greece abstract recent excavations at the middle pleistocene open air site of marathousa 1 have unearthed in one of the two investigated areas area a a partial skeleton of a single individual of palaeoloxodon antiquus and other faunal remains in spatial and stratigraphic association with lithic artefacts in area b a much higher number of lithic artefacts was collected spatially and stratigraphically associated also with faunal remains the two areas are stratigraphically correlated the main fossiliferous layers representing an en mass depositional process in a lake margin context evidence of butchering cut marks has been identified on bones of the elephant skeleton as well on elephant and other mammal bones from area b however due to the secondary deposition of the main find bearing units it is of primary importance to evaluate the degree and reliability of the spatial association of the lithic artefacts with the faunal remains indeed spatial association does not necessarily imply causation since natural syn and post depositional processes may equally produce spatial association assessing the degree and extent of post depositional reworking processes is crucial to fully comprehend the archaeological record and therefore to reliably interpret past human behaviours the present study uses a comprehensive set of spatial statistics in order to disentangle the depositional processes behind the distribution of the archaeological and palaeontological record at marathousa 1 preliminary results of our analyses suggest that a high energy erosional process attributed to a hyperconcentrated flow deposited at the margin of a swamp reworked an autochthonous exposed or slightly buried scatter of lithic artefacts and faunal remains minor reworking and substantial spatial association of the lithic and faunal assemblages support the current interpretation of marathousa 1 as a butchering site

orientated plant fragments revealing tidal palaeocurrents in the fumanya mudflat maastrichtian southern pyrenees insights in palaeogeographic reconstructions abstract leafy axis fragments of frenelopsis sp leaves of sabalites longirhachis unger kvacek et herman and logs are common in the maastrichtian of the basal tremp formation in the vallcebre syncline southern pyrenees the largest plant remains i e leaves of s longirhachis and logs appear scattered and randomly orientated whereas the smallest plant remains i e frenelopsis sp are aligned in a clear east west trend this orientation based on 117 measurements is consistent with the basin palaeogeography which was an e w elongated foreland trough that confined tidal palaeoflow and deposits such as tidal bores in the absence of usual sedimentary indicators e g tractive structures and base marks the accurate study of fossil plant orientations can largely assist palaeoflow determinations in palaeogeographic reconstruction

the association of hydrogen with sulfur on mars across latitudes longitudes and compositional extremes nasa jet propulsion lab nasa mars data analysis program nnx07an96g nnx10aq23g mdap grants nnx12ag89g nnx13ai98g lsu s college of science and geology and geophysics

transformation of jarosite to hematite in simulated martian brines the presence of jarosite a hydrous iron sulfate at meridiani planum supports the past existence of water on mars surface thermodynamic calculations suggest that jarosite should transform to ferric oxyhydroxides in aqueous media here we show that jarosite can transform directly to hematite the iron oxide identified at meridiani planum in simulated martian brines our results are consistent with a short aqueous history but also indicate that jarosite can persist in highly saline martian brines the formation of goethite a common iron oxyhydroxide on earth is prevented by the low water activity and or high phosphate concentration of martian brines

acid sulfate alteration of fluorapatite basaltic glass and olivine by hydrothermal vapors and fluids implications for fumarolic activity and secondary phosphate phases in sulfate rich paso robles soil at gusev crater mars 1 phosphate rich rocks and a nearby phosphate rich soil paso robles were analyzed in gusev crater mars by the mars exploration rover spirit and interpreted to be highly altered possibly by hydrothermal or fumarolic alteration of primary phosphate rich material to test mineral phases resulting from such alteration we performed hydrothermal acid vapor and acid fluid experiments on olivine ol fluorapatite ap and basaltic glass gl as single phases and a mixture of phases minerals formed include ca al fe and mg sulfates with different hydration states anhydrite bassanite gypsum alunogen hexahydrite and pentahydrite phosphate bearing minerals formed included monocalcium phosphate monohydrate mcp acid vapor and acid fluid alteration of fluorapatite only and ferrian giniite acid fluid alteration of the ol gl ap mixture mcp is likely present in paso robles if primary ca phosphate minerals reacted with sulfuric acid with little transport of phosphate under fluid rock ratios allowing transport of phosphate a ferric phosphate phase such as ferrian giniite might form instead mossbauer measurements of ferrian giniite bearing alteration products and synthetic ferrian giniite are consistent with spirit s mossbauer measurements of the ferric bearing phase in paso robes soil but are also consistent with ferric sulfate phases in the low p soil arad samra therefore mossbauer data alone do not constrain the fluid rock ratio however the excess iron hematite in paso robles soil which implies aqueous transport combined with our laboratory experiments suggest acid sulfate alteration in a hydrothermal fumarolic environment at fluid rock ratios sufficient to allow dissolution transport and precipitation of secondary chemical components including a ferric phosphate such as ferrian giniite

reflectance spectroscopy and optical functions for hydrated fe sulfates visible and near infrared wavelength vnir 0 35 5 m laboratory diffuse reflectance spectra and corresponding optical functions real and imaginary refractive indices for several iron sulfates natural k and na jarosite szomolnokite rhomboclase are presented on mars jarosite has been identified in meridiani planum mawrth vallis melas chasma and eridania basin szomolnokite has been found as distinct layers at columbus crater and as outcrops at juventae chasma and rhomboclase has been identified at gusev crater constraining the mineralogy and chemistry fe vs mg rich of the sulfates on mars may contribute to our understanding of the environmental and aqueous conditions present on mars during their formation the data presented here will help to constrain the mineralogy abundance and distribution of sulfates on the martian surface which will lead to improvements in understanding the pressure temperature and humidity conditions and how active frost groundwater and atmospheric processes once were on mars

sedimentology and paleontology of a carboniferous log jam a localized sandstone split in the mary lee coal early pennsylvanian langsettian of the black warrior basin alabama has a channel form geometry and preserves a concentrated log and gravel pebbles cobbles and boulders assemblage at the top of the fill sequence gravel lithotypes within and amongst rooting structures of lycopsid cordaitean and calamitean trees are indicative of an appalachian orogenic provenance and support an allochthonous origin for some of the logs in addition a skolithos ichnological assemblage within the channel is indicative of opportunist colonization during channel fill a low sinuosity geometry characterizes the overall channel form belt exhibiting a general northwesterly trend paleocurrent measurements from the cross bedded sandstone at the margin of the channel belt indicate flow was to the northwest log orientations at these sites are subperpendicular to perpendicular to the overall sediment transport direction and are interpreted to represent an ancient log jam the genesis of the fluvial channel the introduction and emplacement of the concentrated log assemblage the effects of this floating log accumulation on sedimentation within the channel and the relationship between paleocurrent and log orientation are discussed the red river located in the southern united states is used as a modern analog for comparative purposes

observations of 50 and 12 mhz auroral coherent echoes at the antarctic syowa station data on 50 and 12 mhz e region coherent echoes from approximately the same directions and in a broad range of azimuths are available for 1995 1997 radar observations at the antarctic syowa station one event of such observations is considered to compare power and doppler velocity of echoes at these significantly different frequencies for the considered event doppler velocities of more than 600 ms 1 as recorded at both radar frequencies were observed we show that even though the 50 mhz echoes exhibit strong flow angle variation of the power the 12 mhz echoes do not apparent aspect angle power attenuation is found to be 10 and 2 5 dbdeg 1 at 50 and 12 mhz respectively measured doppler velocities along specific radar directions are found to be comparable in spite of the significant difference in radar frequencies with the velocity ratio v50mhz v12mhz being in between 1 6 and 0 9 for high velocities of more than 400 ms 1 the velocity ratio varies with slant range and azimuth of observations ionospheric propagation effects for radio waves and plasma physical effects for irregularities are considered in an attempt to explain several observed features for example the echo power and velocity ratio variations with slant range

superficial alteration mineralogy in active volcanic systems an example of poas volcano costa rica abstract the alteration mineralogy in the crater area of poas volcano costa rica has been studied to constrain acid fluid rock interaction processes and conditions relevant for the formation of sulphate bearing mineral assemblages found on the surface of mars individual sub environments which include the hyperacid lake laguna caliente ephemeral hot springs fumarole vents and areas affected by acid rain and or spray from the lake are marked by distinct secondary mineral associations with sulphates commonly as prevailing component the sulphates occur in a wide mineralogical diversity comprising gypsum anhydrite various polyhydrated al sulphates alunite jarosite group minerals halotrichite voltaite and copiapite group minerals epsomite and romerite depending on the sub environment they are variably associated with clay minerals kaolinite group and smectite group zeolites sio 2 polymorphs fe hydro oxides ti oxides native sulphur sulphides chlorides fluorides phosphates and carbonates geochemical modelling was performed to identify mechanisms responsible for the formation of the secondary minerals found in the field and to predict their possible stability under conditions not seen at the surface the results indicate that the appearance of amorphous silica hematite anhydrite gypsum pyrite anatase and kaolinite is relatively insensitive to the degree of acidity of the local aqueous system on the other hand alunite jarosite group minerals elemental sulphur and al oh so 4 only form under acidic conditions ph 2 sulphates is restricted to olivine bearing rocks exposed to acid rain or brine spray modelling suggests that their formation required a repetitive sequence of olivine dissolution and evaporation in an open system involving limited amounts of fluid the mineral variety in the crater of poas is remarkably similar to sulphate bearing assemblages considered to be the product of acid sulphate alteration on mars the analogy suggests that comparable fluid rock interaction controls operated in martian volcanic environments

phyllosilicate and hydrated silica detections in the knobby terrains of acidalia planitia northern plains mars here we report detections of fe mg phyllosilicates and hydrated silica in discrete stratigraphic units within the knobby terrains of acidalia planitia made using data acquired by compact reconnaissance imaging spectrometer for mars fe mg phyllosilicates are detected in knobs that were eroded during southward retreat of the dichotomy boundary a second later unit now eroded to steep sided platforms embaying the knobs contains hydrated silica which may have formed via localized vapor weathering thin film leaching or transient water that resulted in surface alteration these are then overlain by smooth plains with small cones hypothesized to be mud volcanoes which previous studies have shown to have no hydrated minerals in spite of acidalia s location within the putative northern ocean collectively the data record a history of aqueous processes much like that in the southern highlands with progressively less intensive aqueous chemical alteration from the noachian to amazonian

repeated flood events and fossil forests at curio bay middle jurassic new zealand during the middle jurassic the regional environment of curio bay southeast south island new zealand was a fluvial plain marginal to volcanic uplands intermittent flashy poorly confined flood events buried successive conifer forests with the termination of each flood soils developed and vegetation was reestablished in most cases this developed into coniferous forest in approximately 40 m of vertical section 10 fossil forest horizons can be distinguished highlighting a type of fluvial architecture which is poorly documented flood basin material is minimal but a short lived floodbasin lake is inferred to have developed within the interval of study paleocurrent indicators suggest enclosure of the basin on more than one side sedimentation style suggests a relatively dry less than humid but not arid climate with seasonal rainfall c 2001 elsevier science b v all rights reserved

ferric oxides in east candor chasma valles marineris mars inferred from analysis of omega mars express data identification and geological interpretation 1 the mineralogical composition of the martian surface is constrained by analyzing the data of the omega visible and near infrared imaging spectrometer onboard mars express ferric signatures had previously been reported in valles marineris margaritifer terra and terra meridiani here we use three independent data reduction methods spectral angle mapper a modified spectral mixture analysis and modified gaussian model to detect and map ferric oxides in east candor chasma a part of valles marineris ferric oxides in east candor chasma are concentrated in scattered formations mola altimetry indicates that the ferric oxides are preferentially located in topographic lows themis hrsc and moc images show that the ferric oxide spectral signatures are systematically correlated with superficial deposits of low albedo located at the foot of or resting on interior layered deposits ilds this spatial distribution suggests that ferric oxides are genetically linked to ilds gravity and wind driven remobilization of ferric oxides previously formed in the ilds can explain their accumulation around the ilds

orientation studies of waterlogged wood a paleocurrent indicator abstract fossil wood has been used extensively as a paleocurrent indicator and published evidence suggests that it may be aligned either parallel or perpendicular to a unidirectional current flume experiments on deposition of waterlogged wood show that most fragments are aligned parallel to the current for fragments with a high degree of symmetry however a perpendicular orientation is possible the dominant factors in controlling the orientation of wood fragments appear to be current velocity fragment shape and fragment size

selection of the mars exploration rover landing sites 1 the selection of meridiani planum and gusev crater as the mars exploration rover landing sites took over 2 years involved broad participation of the science community via four open workshops and narrowed an initial 155 potential sites 80 300 30 km to four finalists based on science and safety engineering constraints important to the selection included 1 latitude 10 n 15 s for maximum solar power 2 elevation less than 1 3 km for sufficient atmosphere to slow the lander 3 low horizontal winds shear and turbulence in the last few kilometers to minimize horizontal velocity 4 low 10 m scale slopes to reduce airbag spin up and bounce 5 moderate rock abundance to reduce abrasion or strokeout of the airbags and 6 a radar reflective load bearing and trafficable surface safe for landing and roving that is not dominated by fine grained dust the evaluation of sites utilized existing as well as targeted orbital information acquired from the mars global surveyor and mars odyssey three of the final four landing sites show strong evidence for surface processes involving water and appear capable of addressing the science objectives of the missions which are to determine the aqueous climatic and geologic history of sites on mars where conditions may have been favorable to the preservation of evidence of possible prebiotic or biotic processes the evaluation of science criteria placed meridiani and gusev as the highest priority sites the evaluation of the three most critical safety criteria 10 m scale slopes rocks and winds and landing simulation results indicated that meridiani and elysium planitia are the safest sites followed by gusev and isidis planitia

visible near infrared and mid infrared spectral characterization of hawaiian fumarolic alteration near kilauea s december 1974 flow implications for spectral discrimination of alteration environments on mars

orbital evidence for clay and acidic sulfate assemblages on mars based on mineralogical analogs from rio tinto spain outcrops of hydrated minerals are widespread across the surface of mars with clay minerals and sulfates being commonly identified phases orbitally based reflectance spectra are often used to classify these hydrated components in terms of a single mineralogy although most surfaces likely contain multiple minerals that have the potential to record local geochemical conditions and processes reflectance spectra for previously identified deposits in ius and melas chasma within the valles marineris mars exhibit an enigmatic feature with two distinct absorptions between 2 2 and 2 3 m this spectral doublet feature is proposed to result from a mixture of hydrated minerals although the identity of the minerals has remained ambiguous here we demonstrate that similar spectral doublet features are observed in airborne field and laboratory reflectance spectra of rock and sediment samples from rio tinto spain combined visible near infrared reflectance spectra and x ray diffraction measurements of these samples reveal that the doublet feature arises from a mixture of al phyllosilicate illite or muscovite and jarosite analyses of orbital data from the compact reconnaissance imaging spectrometer for mars crism shows that the martian spectral equivalents are also consistent with mixtures of al phyllosilicates and jarosite where the al phyllosilicate may also include kaolinite and or halloysite a case study for a region within ius chasma demonstrates that the relative proportions of the al phyllosilicate s and jarosite vary within one stratigraphic unit as well as between stratigraphic units the former observation suggests that the jarosite may be a diagenetic authigenic product and thus indicative of local ph and redox conditions whereas the latter observation may be consistent with variations in sediment flux and or fluid chemistry during sediment deposition

statistical study of midlatitude e region echoes observed by the hokkaido superdarn hf radar statistical characteristics of short range coherent echoes observed by the hokkaido super dual auroral radar network superdarn high frequency hf radar geographic geomagnetic latitude 43 5 n 37 3 n at midlatitudes are investigated we show that the echo occurrence is increased during nighttime and especially strongly during winter and summer during summer the occurrence rates are still large during morning prenoon hours for these periods strong sporadic e layers are observed by the wakkanai ionosonde geographic geomagnetic latitude 45 2 n 39 1 n located in the vicinity of the radar field of view echo occurrence rate does not increase with the planetary magnetic activity characterized by the kp and dst magnetic indices and seasonally anticorrelates with variations of the ap index with respect to the magnetic l shells echoes are seen more frequently in beams oriented almost perpendicular to l shells during summer in beams at intermediate angles during equinoxes and winter and sometimes in beams at the smallest available angles 45 during winter midlatitude echoes are of about the same power as at high latitudes but narrower by a factor of 5 power and spectral width of nighttime echoes increases with doppler velocity consistent with high latitude observations the doppler velocity shows a clear semidiurnal variation the local time of these maxima changes with season it is hypothesised that many hokkaido echoes are received at high magnetic aspect angles of several degrees and they are coming from the lower part of the e region where the irregularity phase velocity is affected by both e b plasma drifts and neutral winds

mantled and exhumed terrains in terra meridiani mars 1 hematite bearing deposits in the terra meridiani region of mars constitute the top stratum of a partially eroded layered complex that covers dissected noachian aged cratered terrain the hematite unit consists of dark plains and dunes covering a bright substrate this substrate is fully exposed beyond the borders of the hematite bearing deposit and consists of polygonal ground separated by ridges or valleys together with layered deposits that have been eroded into a variety of landforms the complex is partially covered by a regional scale aeolian mantle that thickens toward the north the hematite bearing stratum exhibits low albedoes pulse widths and intermediate thermal inertias whereas the underlying unit exhibits high values of these parameters both units have spectral emissivity signatures similar to those for the low albedo cratered terrain to the south with the addition of hematite for the top stratum the complex is interpreted to consist of extensive plains forming lava flows and tephra deposits emplaced during an extensional regime and at least partially buried by an aeolian mantle aeolian stripping of the mantle exposed much of the complex and differentially eroded the deposits to produce the landforms existent today exploration of the hematite bearing deposits by the 2003 mars exploration rover opportunity will allow testing of the hypotheses presented since this stratum has been locally reworked into dunes that only partially cover the underlying brighter portion of the complex in particular the rover based measurements will allow us to test the extent to which the unusual remote sensing properties of the units indicate aqueous alteration

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

modeling entrainment of waterlogged large wood in stream channels 1 research has led to an understanding of how floatable wood provides physical complexity and habitat in streams but little is known about large wood that does not float because it is waterlogged mineralized or naturally heavier than water to better understand the dynamics of this largely unrecognized component of streams i derived a theoretical model for predicting entrainment of waterlogged logs then constructed prototype logs to simulate waterlogged wood and used them to measure log friction and critical flow velocities at log entrainment in an alluvial creek i then modeled critical velocities under the same conditions entrainment was observed the model underpredicted critical velocities by an average of 24 with a range of error from 8 to 69 sensitivity analyses indicated that reducing lift and drag coefficients improved the average error but not the error range lack of unique drag coefficients for prototype logs winnowing of bed material from around prototype logs during entrainment tests error estimating friction for logs approaching neutral buoyancy and the variability of flow velocity common in streams were probable causes of error observed critical velocities that entrained prototype logs averaged 0 70 m s 1 critical velocities and log friction increased with branch length bed roughness and log density but only friction increased with log length friction coefficients averaged 0 62 and increased with branch length and bed roughness this model and existing equations for predicting movement of buoyant large wood can be used to compute budgets for logs with a range of attributes in streams

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

jarosite and hematite at meridiani planum from opportunity s mossbauer spectrometer mossbauer spectra measured by the opportunity rover revealed four mineralogical components in meridiani planum at eagle crater jarosite and hematite rich outcrop hematite rich soil olivine bearing basaltic soil and a pyroxene bearing basaltic rock bounce rock spherules interpreted to be concretions are hematite rich and dispersed throughout the outcrop hematitic soils both within and outside eagle crater are dominated by spherules and their fragments olivine bearing basaltic soil is present throughout the region bounce rock is probably an impact erratic because jarosite is a hydroxide sulfate mineral its presence at meridiani planum is mineralogical evidence for aqueous processes on mars probably under acid sulfate conditions

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

mid latitude e region field aligned irregularities observed with the mu radar fine structures e region field aligned irregularities were observed on june 24 25 1989 with the mu radar at shigaraki japan 34 9 n 136 1 e geomagnetic latitude 25 0 n the 3 2 m scale irregularities were observed with the mu radar in five main beam directions each of which was nearly perpendicular to the geomagnetic field at 100 km altitude doppler spectra were obtained every 20 s with a range resolution of 600 m field perpendicular echoes appeared from 2130 to 2330 lt and from 0400 to 1100 lt times that correspond to postsunset and postsunrise period in the e region a preliminary examination of the doppler spectra indicates spectral widths of 50 120 m s 1 and the mean doppler velocities are well below the ion acoustic speed these spectral characteristics are consistent with those obtained in the equatorial and auroral electrojets and have been attributed to the gradient drift instability the echoes observed during the postsunset and postsunrise periods showed quite different morphologies in the time height distribution for this reason they are classified into two types continuous and quasi periodic the appearance of the continuous echoes was mainly continuous in time and situated between 90 and 100 km altitude during the postsunrise period the appearance of the quasi periodic echoes was intermittent with periods of 5 10 min and situated above 100 km altitude during the postsunset period the quasi periodic echoes showed phase propagation toward the radar while the averaged mean doppler velocity was away from the radar by measuring the time delays in echo regions from five directions an apparent westward motion approximately 120 m s 1 of the irregularity regions was estimated

chemical composition of martian fines of the 21 samples acquired for the viking x ray fluorescence spectrometer 17 were analyzed to high precision compared to typical terrestrial continental soils and lunar mare fines the martian fines are lower in al higher in fe and much higher in s and cl concentrations protected fines at the two lander sites are almost indistinguishable but concentration of the element s is somewhat higher at utopia duricrust fragments successfully acquired only at the chryse site invariably contained about 50 higher s than fines no elements correlate positively with s except cl and possibly mg a sympathetic variation is found among the triad si al ca positive correlation occurs between ti and fe sample variabilities are as great within a few meters as between lander locations 4500 km apart implying the existence of a universal martian regolith component of constant average composition the nature of the source materials for the regolith fines must be mafic to ultramafic

using the chemical composition of carbonate rocks on mars as a record of secondary interaction with liquid water in the search for habitable environments on mars sites that have been altered by liquid water represent an important target quickly dissolving and precipitating carbonates found in multiple locations on mars represent a key potential mineral indicator of locations with a history of aqueous alteration and therefore possible habitability recent liquid surface water on mars may differ significantly from the fluids either sedimentary hydrothermal or pedogenic that formed carbonate minerals on mars interactions of carbonate rocks with such recent surface water may therefore cause changes in chemistry and mineralogy with depth that form weathering profiles recording the conditions of alteration to test the prediction that martian carbonates may record a signature of aqueous alteration on mars we performed reactive transport modeling of putative carbonate outcrops on mars using the reactive transport code crunchflow model inputs included two parent rocks chosen based on the carbonate rich rock at gusev crater comanche one consisting of 60 magnesite 20 siderite and 20 porosity and one consisting of 50 magnesite 20 siderite 9 calcite 1 6 rhodochrosite and 20 porosity reacting solutions consisted of four scenarios acidic sulfate containing solutions perhaps resulting from an acid vapor scenario dilute solutions resulting from martian analog basalt dissolution concentrated solutions resulting from modeled evaporation of the dilute solutions and solutions based on the results of the phoenix lander modeling was performed under low oxidation and high oxidation conditions based on the modeling results a carbonate rock would become enriched in siderite upon interaction with acidic water under low oxidation conditions the same rock would become enriched in calcite after interaction with ca enriched solutions a carbonate rock reacting under more oxidizing conditions would preferentially dissolve siderite leaving a surface enriched in magnesite and ferric oxide therefore the mg rich carbonates on mars are consistent with possible interaction with liquid water under oxidizing conditions similar to those measured at the phoenix landing site future detailed chemical and mineralogical profiles through weathered rock into the unaltered interior of carbonate rocks may therefore allow the quantitative interpretation of the aqueous history and possible habitability of locations on mars

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

basaltic rocks analyzed by the spirit rover in gusev crater the spirit landing site in gusev crater on mars contains dark fine grained vesicular rocks interpreted as lavas pancam and mini thermal emission spectrometer mini tes spectra suggest that all of these rocks are similar but have variable coatings and dust mantles magnified images of brushed and abraded rock surfaces show alteration rinds and veins rock interiors contain 25 megacrysts chemical analyses of rocks by the alpha particle x ray spectrometer are consistent with picritic basalts containing normative olivine pyroxenes plagioclase and accessory feti oxides mossbauer pancam and mini tes spectra confirm the presence of olivine magnetite and probably pyroxene these basalts extend the known range of rock compositions composing the martian crust

the rio tinto basin spain mineralogy sedimentary geobiology and implications for interpretation of outcrop rocks at meridiani planum mars abstract exploration by the nasa rover opportunity has revealed sulfate and hematite rich sedimentary rocks exposed in craters and other surface features of meridiani planum mars modern holocene and plio pleistocene deposits of the rio tinto southwestern spain provide at least a partial environmental analog to meridiani planum rocks facilitating our understanding of meridiani mineral precipitation and diagenesis while informing considerations of martian astrobiology oxidation thought to be biologically mediated of pyritic ore bodies by groundwaters in the source area of the rio tinto generates headwaters enriched in sulfuric acid and ferric iron seasonal evaporation of river water drives precipitation of hydronium jarosite and schwertmannite while mg al fe3 copiapite coquimbite gypsum and other sulfate minerals precipitate nearby as efflorescences where locally variable source waters are brought to the surface by capillary action during the wet season hydrolysis of sulfate salts results in the precipitation of nanophase goethite holocene and plio pleistocene terraces show increasing goethite crystallinity and then replacement of goethite with hematite through time hematite in meridiani spherules also formed during diagenesis although whether these replaced precursor goethite or precipitated directly from groundwaters is not known the retention of jarosite and other soluble sulfate salts suggests that water limited the diagenesis of meridiani rocks diverse prokaryotic and eukaryotic microorganisms inhabit acidic and seasonally dry rio tinto environments organic matter does not persist in rio tinto sediments but biosignatures imparted to sedimentary rocks as macroscopic textures of coated microbial streamers surface blisters formed by biogenic gas and microfossils preserved as casts and molds in iron oxides help to shape strategies for astrobiological investigation of meridiani outcrops

laboratory simulations of acid sulfate weathering under volcanic hydrothermal conditions implications for early mars we have completed laboratory experiments and thermochemical equilibrium models to investigate secondary mineral formation under conditions akin to volcanic hydrothermal acid sulfate weathering systems our research used the basaltic mineralogy at cerro negro volcano nicaragua characterized by plagioclase pyroxene olivine and volcanic glass these individual minerals and whole rock field samples were reacted in the laboratory with 1 molal sulfuric acid at varying temperatures 65 150 and 200 c fluid rock weight ratios 1 1 4 1 and 10 1 and durations 1 60 days thermochemical equilibrium models were developed using geochemist s workbench to understand the reaction products and fluids we employed scanning electron microscopy energy dispersive spectroscopy x ray diffraction and inductively coupled plasma atomic emission spectroscopy the results of our experiments and models yielded major alteration minerals that include anhydrite natroalunite minor iron oxide and amorphous al si gel we found that variations in experimental parameters did not drastically change the suite of minerals produced instead abundance size and crystallographic shape changed our results also suggest that it is essential to separate phases formed during experiments from those formed during fluid evaporation to fully understand the reaction processes our laboratory reacted and model predicted products are consistent with the mineralogy observed at places on mars however our results indicate that determination of the formation conditions requires microscopic imagery and regional context as well as a thorough understanding of contributions from both experiment precipitation and fluid evaporation minerals

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

the spirit rover s athena science investigation at gusev crater mars the mars exploration rover spirit and its athena science payload have been used to investigate a landing site in gusev crater gusev is hypothesized to be the site of a former lake but no clear evidence for lacustrine sedimentation has been found to date instead the dominant lithology is basalt and the dominant geologic processes are impact events and eolian transport many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration any lacustrine sediments that may exist at this location within gusev apparently have been buried by lavas that have undergone subsequent impact disruption

iron and aluminum hydroxysulfates from acid sulfate waters acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite chalcopyrite pyrrhotite and marcasite in rocks soils sediments and industrial wastes this spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits the formation of acid sulfate soils and the mobilization and release of acidity and metals to surface and ground waters the purely natural process of acid rock drainage is often intensified by human activities related to mining mineral processing construction soil drainage and dredging geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water and to microbes that catalyze the reaction process large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation hydrolysis and neutralization the objective of this chapter is to describe the formation properties fate and environmental implications of the nano to microphase hydroxy sulfates of fe and al that are precipitated from acid sulfate waters these minerals are commonly of poor crystallinity and difficult to characterize much remains to be learned about their occurrence formation and properties mine drainage the best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited ash et al 1951 barton 1978 nordstrom 1982a rose and cravotta 1998 nordstrom and alpers 1999 there may be as many as 500 000 inactive or abandoned mine sites in the united states alone lyon et al 1993 although most of these pose no immediate water quality problem kleinmann 1989 estimated that about 19 300 km of streams and more than 72 000 ha of lakes and reservoirs have been

inventory of h2o in the ancient martian regolith from northwest africa 7034 the important role of fe oxides water rich martian regolith breccia northwest africa nwa 7034 was analyzed by fourier transform infrared spectroscopy and transmission electron microscopy to determine the inventory and phase distribution of h2o used herein to refer to both molecular h2o and oh structural components in hydrous minerals hydrous fe oxide phases hydromaghemite and an unidentified nanocrystalline fe bearing oxide phase observed with hydromaghemite and phyllosilicates saponite were identified as the primary mineralogic hosts for h2o with a minor contribution from cl rich apatite based on mass balance calculations and modal abundances of minerals constrained by powder x ray diffraction and petrography we can account for the entire 6000 ppm h2o measured in bulk rock analyses of nwa 7034 this h2o is distributed evenly between hydrous fe rich oxides and phyllosilicates indicating that fe oxides could be as important as phyllosilicates for h2o storage in martian surface material

hydrothermal hexahydrite spherules erupted during the 2008 2010 summit eruption of kīlauea volcano hawai i small 1 3 mm hollow spherules of hexahydrite have been collected falling out of the magmatic gas plume downwind of k lauea s summit vent the spherules were observed on eight separate occasions during 2009 2010 when a lake of actively spattering lava was present 150 200 m below the rim of the vent the shells of the spherules have a fine bubbly foam structure less than 0 1 mm thick composed almost entirely of hexahydrite mgso4 6h2o small microspherules of lava 5 m across along with mineral and rock fragments from the magmatic plume adhered to the outside of the hexahydrite spherules phase relationships and the particulate matter in the magmatic plume indicate that the spherules originated as a bubbly solution injected into and mixed with the magmatic plume the most likely mechanism for production of hexahydrite spherules is boiling of mgso4 saturated meteoric water in the walls of the conduit above the surface of the lava lake solfataric sulfates may thus be recycled and reinjected into the plume creating particulates of sulfate minerals that can be distributed far from their original source

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

shallow marine sedimentation within an active margin basin james ross island antarctica abstract the santa marta formation exposed on northern james ross island antarctica represents shallow marine shelf sedimentation within an active margin basin the formation is approximately 1000 m thick is of uppermost santonian to campanian age and represents part of a 5000 6000 m thick sedimentary sequence forming the larsen basin the larsen basin represents either a back arc basin or a half graben basin developed on the extending margin of the weddell sea twelve sedimentary facies have been recognised which can be subdivided into two groups those which are controlled by shelf processes and those which are related to active arc volcanism background shelf processes include fair weather suspension sedimentation storm sands and rare tidal current reworking active arc processes include direct settling of airfall detritus and rapid resedimentation of volcaniclastic detritus by sandy debris flows and both high and low concentration turbidity currents in addition sheet conglomerates represent debris flows that evolved from syn sedimentary slumps two facies associations representing a mid to outer shelf and an inner shelf depositional setting respectively can be distinguished with an apparent regression in the mid to late campanian

plant material deposition in the tropical burdekin river australia implications for ancient fluvial sediments abstract in the deposits of the burdekin river north queensland australia plant material character and directional fabric together with the sedimentary facies character are generally diagnostic of depositional environment plant material is selectively entrained transported and deposited in all flow conditions ranging from dry season minimal flow

sand pseudomorphs of dinosaur bones implications for non preservation of tetrapod skeletal material in the hartford basin usa abstract early jurassic tetrapod tracks are common in the hartford and adjacent deerfield basins newark supergroup of connecticut and massachusetts usa but skeletal material is rare among the few examples is a set of several bones preserved as natural casts on the base of a slab of arkosic sandstone that probably derived from the portland formation of middletown connecticut this mode of preservation is otherwise unknown in the hartford basin and examination of this specimen suggests a complex taphonomic history the bones were fluvially transported and arranged in a v shaped pattern as they were deposited on a muddy substrate longitudinal cracks gouging breakage rounding and invertebrate boring indicate significant alteration prior to preservation as casts furthermore the boring represents the first record of osteophagy in the hartford basin details of the cast preservation such as sediment rims that wrapped up and over some of the bones suggest that the bones were dissolved in the subsurface prior to lithification of the overlying sand bed the decrease in ph that led to bone dissolution probably resulted from the infiltration of naturally acidic rainwater root respiration and the decomposition of plants under oxidative conditions may have contributed as well the depauperate skeletal fossil record of the hartford basin is attributable to dissolution under acidic and oxidative sediment conditions these natural casts offer a unique view of the actions of bone dissolution as a taphonomic process the lack of body fossils in similar aged deposits elsewhere may also be due to groundwater acidity

directional orientations of solitary rugose corals unattached solitary rugose corals lying parallel to bedding are common in many ordovician and younger paleozoic units but their directional orientations have seldom been examined interpretations based on occurrences in north american upper ordovician and lower silurian strata provide a foundation for such studies distinct directional patterns resulted from preferred orientation with respect to water motion they indicate transportation rather than biologic orientation if it can be shown that the corals were not preserved in life position or were abraded to a significant degree before burial transported slightly curved specimens having trochoid to ceratoid form were aligned parallel to currents with the apex pointing upstream and or were rolled nearly perpendicular to currents or almost parallel to crests of advancing waves with the apex facing either way but directed slightly upstream therefore unimodal orientation patterns bimodal patterns with equal peaks that are opposite one another but

azimuth time intensity striations of quasiperiodic radar echoes from the midlatitude e region ionosphere the valensole high frequency hf radar in the south of france is an ionospheric doppler sounder which can perform e region coherent backscatter measurements over an azimuthal sector of 86 from 26 e to 58 w with 2 angular resolution this large azimuthal coverage is taken advantage of in order to study quasiperiodic qp echoes in the zonal direction using azimuth time intensity ati analysis ati plots show sequential sloping striations of scatter reminiscent of those detected routinely in the range time intensity rti plots of midlatitude radars which view the medium at a fixed azimuth about the meridian it was found that ati striation periods range from a few minutes to less than 30 min whereas the striation slopes are systematically negative motions westward prior to local midnight and turn positive motions eastward in the post midnight hours the zonal rates dx dt computed from the striation slopes take values between 30 and 160 m s these are due to real motions of unstable plasma structures most likely sporadic e patches that drift along with the neutral wind that have zonal scale lengths of several tens of kilometers the present observations imply that the mechanism responsible for qp echoes is independent of azimuth and can basically operate effectively in any direction in the horizontal plane

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

modeling aluminum silicon chemistries and application to australian acidic playa lakes as analogues for mars abstract recent mars missions have stimulated considerable thinking about the surficial geochemical evolution of mars among the major relevant findings are the presence in meridiani planum sediments of the mineral jarosite a ferric sulfate salt and related minerals that require formation from an acid salt brine and oxidizing environment similar mineralogies have been observed in acidic saline lake sediments in western australia wa and these lakes have been proposed as analogues for acidic sedimentary environments on mars the prior version of the equilibrium chemical thermodynamic frezchem model lacked al and si chemistries that are needed to appropriately model acidic aqueous geochemistries on earth and mars the objectives of this work were to 1 add al and si chemistries to the frezchem model 2 extend these chemistries to low temperatures frezchem is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the pitzer approach for the temperature range from 4 no 3 oh hco 3 co 3 co 2 o 2 ch 4 si h 2 o system that now contain 95 solid phases there were similarities differences and uncertainties between australian acidic saline playa lakes and waters that likely led to the burns formation salt accumulations on mars both systems are similar in that they are dominated by 1 acidic saline ground waters and sediments 2 ca and or mg sulfates and 3 iron precipitates such as jarosite and hematite differences include 1 the dominance of nacl in many wa lakes versus the dominance of fe mg ca so 4 in meridiani planum 2 excessively low k concentrations in meridiani planum due to jarosite precipitation 3 higher acid production in the presence of high iron concentrations in meridiani planum and probably lower rates of acid neutralization and hence higher acidities on mars owing to colder temperatures and 4 lateral salt patterns in wa lakes the wa playa lakes display significant lateral variations in mineralogy and water chemistry over short distances reflecting the interaction of acid ground waters with neutral to alkaline lake waters derived from ponded surface runoff meridiani planum observations indicate that such lateral variations are much less pronounced pointing to the dominant influence of ground water chemistry vertical ground water movements and aeolian processes on the martian surface mineralogy

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

the seek sporadic e experiment over kyushu campaign the seek sporadic e experiment over kyushu campaign was conducted in late august 1996 from the southern region of kyushu japan to investigate the mechanism for the generation of quasi periodic qp radar backscatter from field aligned irregularities imbedded in nighttime sporadic e es layers seek was designed to determine in situ small scale electrodynamical properties using two sounding rockets and large scale dynamics and electrodynamics using ground based sensors which included a transportable radar and other radio and optical instruments deployed in the vicinity of the rocket range it was observed by this campaign that es layers existed in a convergent wind shear region where large electric fields were induced and when active atmospheric gravity waves existed in the mesosphere however there was little evidence which positively supported the hypothesis that es layers were deeply modulated in altitude

iron sulfur mineralogy of mars magmatic evolution and chemical weathering products models for the evolution of sulfide minerals on mars and reaction pathways to their oxidative weathering products in martian regolith have been proposed based on petrogenetic associations between komatiitic rock types viking geochemical data snc meteorites and terrestrial fe ni sulfide deposits to test the weathering model komatiitic pyrrhotites and olivines were exposed to sulfuric acid solutions with and without dissolved ferric iron added to simulate deep weathering processes and the reaction products were identified by mossbauer spectroscopy secondary fes sub 2 pyrite or marcasite feooh goethite and possibly jarosite were formed from pyrrhotite while olivine was oxidized to nanophase goethite these results suggest that on mars acidic groundwater induced pyrrhotite yields fes sub 2 yields feooh jarosite oxidative weathering reactions particularly in the presence of dissolved fe sup 3 such gossaniferous materials occurring in martian regolith were derived mainly from fe ni sulfides associated with komatiitic basalts and not from sulfides occurring in calc alkaline porphyry copper deposits granitic hydrothermal veins sediment hosted pbs zns ores etc which presumably did not evolve on mars due to the virtual lack of plate tectonic activity there

mineralogy composition and alteration of mars pathfinder rocks and soils evidence from multispectral elemental and magnetic data on terrestrial analogue snc meteorite and pathfinder samples major element multispectral and magnetic properties data were obtained at ares vallis during the mars pathfinder mission to understand the compositional mineralogical and process implications of these data we obtained major element mineralogical and magnetic data for well crystalline and nanophase ferric minerals terrestrial analogue samples with known geologic context and snc meteorites analogue samples include unaltered palagonitic and sulfatetic tephra from mauna kea volcano hydrolytic and acid sulfate alteration steam vent material from kilauea volcano hydrolytic alteration and impactites from meteor crater relithification salient results for mars pathfinder include 1 band depths bd530b and bd600 and the reflectivity ratio r800 r750 are consistent with the dominant ferric mineral being nanophase ferric oxide associated with an unknown amount of h2o and occurring in composite particles along with subordinate amounts of other ferric minerals hematite and hematite plus nanophase goethite are most consistent with the data but maghemite akaganeite schwertmannite and nanophase lepidocrocite are also possible interpretations ferric oxides that are consistently not favored by the data as sole alteration products are jarosites and well crystalline goethite and lepidocrocite 2 the strength of the ferric adsorption edge r750 r445 implies the fe3 fe2 values for pathfinder rock and soil are within the ranges 0 7 3 and 3 20 respectively 3 ferrous silicates are indicated for subsets of pathfinder rocks and soils one subset has a band minimum near 930 nm that can attributed to low ca pyroxene alternatively the band could be a second manifestation of certain ferric oxides including nanophase goethite maghemite akaganeite and schwertmannite another subset has a negative spectral slope from 800 to 1005 nm which could result from the high energy wing of a high ca pyroxene and or olivine band a mixture of bright and dark materials and for rocks thin coatings of bright dust on dark rocks 4 chemical data on pathfinder rocks and soils are consistent with two component mixtures between an andesitic rock with low mgo and so3 concentrations soil free rock and a global basaltic soil with high mgo and so3 concentrations rock free soil pathfinder rock free soil can be modeled as a chemical mixture of snc meteorites and the pathfinder soil free rock 5 pathfinder soil cannot be obtained by chemical alteration of pathfinder rocks by any of the hydrolytic and acid sulfate alteration processes we studied presumably global mixing has obscured and possibly erased the elemental signatures of chemical alteration 6 the strongly magnetic phase in palagonitic and sulfatetic tephra is titanomagnetite and possibly its oxidation product titanomaghemite fe ti spinels the saturation magnetization of the tephra samples 0 5 2 0 am2 kg is at or below the low end of the range inferred for martian dust 4 2 am2 kg implying that lithogenic fe ti spinels are a possible candidate for the martian strongly magnetic phase 7 the predominantly palagonitic spectral signature and magnetic nature of martian soil and dust are consistent with glassy precursors with imbedded fe ti spinel particles comparison with lunar glass production rates suggests that production of sufficient quantities of glassy materials on mars by volcanic and impact processes is sufficient to account for these observations

evidence from opportunity s microscopic imager for water on meridiani planum the microscopic imager on the opportunity rover analyzed textures of soils and rocks at meridiani planum at a scale of 31 micrometers per pixel the uppermost millimeter of some soils is weakly cemented whereas other soils show little evidence of cohesion rock outcrops are laminated on a millimeter scale image mosaics of cross stratification suggest that some sediments were deposited by flowing water vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis microscopic images support the hypothesis that hematite rich spherules observed in outcrops and soils also formed diagenetically as concretions

in situ evidence for an ancient aqueous environment at meridiani planum mars sedimentary rocks at eagle crater in meridiani planum are composed of fine grained siliciclastic materials derived from weathering of basaltic rocks sulfate minerals including magnesium sulfate and jarosite that constitute several tens of percent of the rock by weight and hematite cross stratification observed in rock outcrops indicates eolian and aqueous transport diagenetic features include hematite rich concretions and crystal mold vugs we interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history the environmental conditions that they record include episodic inundation by shallow surface water evaporation and desiccation the geologic record at meridiani planum suggests that conditions were suitable for biological activity for a period of time in martian history

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