sedimentary challenge to snowball earth evidence from the magnetic field fossilized in sedimentary rocks suggests that more than 600 million years ago ice occupied tropical latitudes a popular explanation for these findings the snowball earth concept envisages a fully frozen earth for millions of years caused by a runaway ice albedo feedback a rapid catastrophic meltback at very high levels of atmospheric carbon dioxide is thought to have ended this extreme climatic state however sedimentary rocks deposited during these cold intervals indicate that dynamic glaciers and ice streams continued to deliver large amounts of sediment to open oceans throughout the glacial cycle the sedimentary evidence therefore indicates that despite the severity of glaciation some oceans must have remained ice free significant areas of open ocean have important implications for the survival and diversification of life and for the workings of the global carbon cycle the snowball earth concept envisages a fully frozen earth for millions of years several times during the neoproterzoic era between 1 000 and 542 million years ago however the sedimentary evidence suggests that despite the severity of glaciation some oceans must have remained ice free

spectrophotometric properties of materials observed by pancam on the mars exploration rovers 3 sols 500 1525 abstract the panoramic camera pancam on the mars exploration rovers spirit and opportunity acquired visible near infrared 432 1009 nm multispectral observations of soils and rocks under varying viewing and illumination geometries data retrieved from these images were modeled using radiative transfer theory to study the microphysical and surface scattering nature of materials at both sites nearly 57 000 individual measurements from 1900 images were collected of rock and soil units identified by their color and morphologic properties over a wide range of phase angles 0 150 images were acquired between sols 500 and 1525 in the columbia hills and regions around home plate in gusev crater and in the plains and craters between erebus and victoria craters in meridiani planum corrections for diffuse skylight incorporated sky models based on observations of atmospheric opacity throughout the mission disparity maps created from pancam stereo images allowed estimates of local facet orientations for spirit soils at lower elevations near home plate were modeled with lower single scattering albedo w values than those on the summit of husband hill but otherwise soils exhibited similar scattering properties to previous gusev soils dark ripple sands at the el dorado dunes were among the most forward scattering materials modeled silica rich soils and nodules near home plate were analyzed for the first time and exhibited increased forward scattering behavior with increasing wavelength consistent with microporosity inferred from previous high resolution images and thermal infrared spectroscopy for opportunity the opposition effect width parameter for sandstone outcrop rocks was modeled for the first time and demonstrated average values consistent with surfaces of intermediate porosity and or grain size distribution between those modeled for spherule rich soils and darker clast poor soils soils outside a wind streak emanating from the northern rim of victoria crater exhibited w values 16 higher than soils inside the streak overall w values and scattering properties for outcrop rocks spherule rich soils and rover tracks were similar to previous meridiani planum analyses emphasizing the homogeneity of these materials across nearly 12 km of rover odometry

visible near infrared spectral diversity from in situ observations of the bagnold dune field sands in gale crater mars as part of the bagnold dune campaign conducted by mars science laboratory rover curiosity visible near infrared reflectance spectra of dune sands were acquired using mast camera mastcam multispectral imaging 445 1013 nm and chemistry and camera chemcam passive point spectroscopy 400 840 nm by comparing spectra from pristine and rover disturbed ripple crests and troughs within the dune field and through analysis of sieved grain size fractions constraints on mineral segregation from grain sorting could be determined in general the dune areas exhibited low relative reflectance a weak 530 nm absorption band an absorption band near 620 nm and a spectral downturn after 685 nm consistent with olivine bearing sands the finest grain size fractions occurred within ripple troughs and in the subsurface and typically exhibited the strongest 530 nm bands highest relative reflectances and weakest red near infrared ratios consistent with a combination of crystalline and amorphous ferric materials coarser grained samples were the darkest and bluest and exhibited weaker 530 nm bands lower relative reflectances and stronger downturns in the near infrared consistent with greater proportions of mafic minerals such as olivine and pyroxene these grains were typically segregated along ripple crests and among the upper surfaces of grain flows in disturbed sands sieved dune sands exhibited progressive decreases in reflectance with increasing grain size as observed in laboratory spectra of olivine size separates the continuum of spectral features observed between the coarse and fine grained dune sands suggests that mafic grains ferric materials and air fall dust mix in variable proportions depending on aeolian activity and grain sorting

recurring slope lineae in equatorial regions of mars the presence of liquid water is a requirement of habitability on a planet possible indicators of liquid surface water on mars include intermittent flow like features observed on sloping terrains these recurring slope lineae are narrow dark markings on steep slopes that appear and incrementally lengthen during warm seasons on low albedo surfaces the lineae fade in cooler seasons and recur over multiple mars years recurring slope lineae were initially reported to appear and lengthen at mid latitudes in the late southern spring and summer and are more common on equator facing slopes where and when the peak surface temperatures are higher here we report extensive activity of recurring slope lineae in equatorial regions of mars particularly in the deep canyons of valles marineris from analysis of data acquired by the mars reconnaissance orbiter we observe the lineae to be most active in seasons when the slopes often face the sun expected peak temperatures suggest that activity may not depend solely on temperature although the origin of the recurring slope lineae remains an open question our observations are consistent with intermittent flow of briny water such an origin suggests surprisingly abundant liquid water in some near surface equatorial regions of mars dark streaks that appear on the surface of mars during warm seasons have been observed at the mid latitudes and tentatively attributed to the flow of briny water imagery from the mars reconnaissance orbiter over multiple mars years suggests that these seasonally active features are also present in equatorial regions where liquid surface water is not expected

mars aerosol studies with the mgs tes emission phase function observations optical depths particle sizes and ice cloud types versus latitude and solar longitude 1 emission phase function epf observations taken in 1999 2001 by mars global surveyor thermal emission spectrometer mgs tes support the broadest study of martian aerosol properties to date tes solar band and infrared ir spectral epf sequences are analyzed to obtain first time seasonal latitudinal distributions of visible optical depths particle sizes and single scattering phase functions this combined angular and wavelength coverage enables identification of two distinct ice cloud types over 45 s 45 n type 1 ice clouds exhibit small particle sizes reff 1 2 m and a distinctive backscattering increase they are most prevalent in the southern hemisphere during aphelion but also appear more widely distributed in season and latitude as topographic and high altitude 20 km ice hazes type 2 ice clouds exhibit larger particle sizes reff 3 4 m a distinct side scattering minimum at 90 100 phase angles characteristic of a change in particle shape relative to the type 1 and appear most prominently in the northern subtropical aphelion cloud belt the majority of retrieved dust visible to ir optical depth ratios are indicative of reff 1 5 0 1 m consistent with pathfinder and viking mariner 9 reanalyses however increased ratios 2 7 versus 1 7 appear frequently in the northern hemisphere over ls 50 200 indicating substantially smaller dust particles sizes reff 1 0 0 2 m at this time in addition larger reff 1 8 2 5 m dust particles were observed locally in the southern hemisphere during the peak of the 2001 global dust storm detailed spectral modeling of the tes visible band pass indicates agreement of epf derived dust single scattering albedos 0 92 0 94 with the spectrally resolved results from pathfinder observations

hypersaline wet patches in taylor valley antarctica 1 spatially isolated patches of soil located in taylor valley mcmurdo dry valleys antarctica are sites of elevated salt content and soil moisture during antarctic spring in the absence of snow melt visibly wet reduced albedo patches of soil are present at the surface the soil pore fluids are hypersaline and have average water activity of 0 74 the water activity of a solution determines the equilibrium vapor pressure of that solution and are an order of magnitude more saline than average soils in the dry valleys these salty soils are 3 5 times more water rich than average soils geochemical and meteorological analyses show that these wet patches are sites of direct vapor emplacement into soil pore fluids that may ultimately be sourced by the deliquescence of soil salts these wet patches represent a non precipitation non groundwater source for water into antarctic permafrost

a case study of recurring slope lineae rsl at tivat crater implications for rsl origins abstract the origin or origins of recurring slope lineae rsl on mars are enigmatic these seasonally dark linear features correlate with temperatures appropriate for liquid water or brine they also progress slowly downslope and fade disappear when inactive similar to shallow subsurface groundwater flows that wick moisture to the surface if liquid water or brine does indeed flow so near the surface and is sufficiently dilute it could have profound implications for the modern habitability of mars we present the results of a case study at tivat crater in the southern midlatitudes that provide new insights into rsl including their potential origins at tivat these results include comprehensive maps of rsl extents in four mars years detailed rsl evolution across one growth season rockfall markings and dust devil tracks in two well constrained years rsl and rockfall markings which are more widely distributed than rsl fade at the same time suggesting a fading mechanism that acts across tivat based on relative albedo analyses rsl and rockfall markings at tivat fade because their host slopes darken which is most easily explained by the widespread removal of dust such a dry fading mechanism would favor a dry origin for rsl we also present a wide range of other rsl observations including highly variable growth pooling like behavior where slopes shallow to roughly 30 and total areal extents that decrease each year across a span of five years we discuss the implications of these observations for various rsl formation models including a new conceptual model that primarily mobilizes dust taken together our observations seem to favor a dry mass movement origin for rsl at tivat but significant challenges remain for each examined model

seasonal slumps in juventae chasma mars dark topographic slumps several meters wide tens of meters in length and up to a meter in depth are observed on the slopes of juventae chasma jc valles marineris vm mars these slumps usually originate near the terminal points of recurring slope lineae rsl near their initiation points the slumps have topographic depressions due to the removal of materials near their lowermost reaches new materials are deposited in lobes over the course of three mars years ten active slumps have been observed in jc all of which formed in or near the same season areocentric longitude ls 0 120 mars color imager marci observations show low altitude atmospheric obscurations confined within the topography of the vm and jc in the seasons when the slumps form in one instance data from the compact reconnaissance imaging spectrometer for mars crism and marci show evidence of h2o ice in the atmospheric obscuration likely due to the formation of a low level afternoon cloud above a dust storm or mixing of condensate clouds with a diffuse dust cloud the presence of atmospheric obscurations with h2o ice near times when the slumps form is intriguing but no direct evidence currently exists to support that they aid in slump formation further monitoring of this site will help establish if rsl and or atmospheric events play a role in the creation of contemporary slumps

surface reflectance of mars observed by crism mro 1 multi angle approach for retrieval of surface reflectance from crism observations mars reco 1 this article addresses the correction for aerosol effects in near simultaneous multi angle observations acquired by the compact reconnaissance imaging spectrometer for mars crism aboard the mars reconnaissance orbiter in the targeted mode crism senses the surface of mars using 11 viewing angles which allow it to provide unique information on the scattering properties of surface materials in order to retrieve these data however appropriate strategies must be used to compensate the signal sensed by crism for aerosol contribution this correction is particularly challenging as the photometric curve of these suspended particles is often correlated with the also anisotropic photometric curve of materials at the surface this article puts forward an innovative radiative transfer based method named multi angle approach for retrieval of surface reflectance from crism observations mars reco the proposed method retrieves photometric curves of surface materials in reflectance units after removing aerosol contribution mars reco represents a substantial improvement regarding previous techniques as it takes into consideration the anisotropy of the surface thus providing more realistic surface products furthermore mars reco is fast and provides error bars on the retrieved surface reflectance the validity and accuracy of mars reco is explored in a sensitivity analysis based on realistic synthetic data according to experiments mars reco provides accurate results up to 10 reflectance error under favorable acquisition conditions in the companion article photometric properties of martian materials are retrieved using mars reco and validated using in situ measurements acquired during the mars exploration rovers mission

laboratory studies of perchlorate phase transitions support for metastable aqueous perchlorate solutions on mars abstract perchlorate salts recently discovered on mars are known to readily absorb water vapor from the atmosphere and deliquesce into the aqueous phase at room temperature here we study the deliquescence crystalline solid to liquid transition and efflorescence liquid to crystalline solid transition of perchlorate salts at low temperatures relevant to mars a raman microscope and environmental cell were used to determine the deliquescence relative humidity drh and efflorescence relative humidity erh of naclo 4 and mg clo 4 2 as a function of temperature and hydration state we find that the deliquescence of anhydrous naclo 4 is only slightly dependent on temperature and occurs at 38 rh the drh of naclo 4 h 2 o increases with decreasing temperature from 51 at 273 k to 64 at 228 k the drh of mg clo 4 2 6h 2 o also increases with decreasing temperature from 42 at 273 k to 64 at 223 k the efflorescence of both naclo 4 and mg clo 4 2 salt solutions occurs at a lower rh than deliquescence due to the kinetic inhibition of crystallization for all temperatures studied the erh values of naclo 4 and mg clo 4 2 are 13 and 19 respectively these results indicate perchlorate salts can exist as metastable supersaturated solutions over a wide range of rh and temperature conditions summer diurnal temperature and relative humidity cycles at low latitudes on mars could allow the surface salts to be aqueous for several hours per day

sea ice free conditions during the sturtian glaciation early cryogenian south australia in the neoproterozoic snowball earth hypothesis shutdown of the planet9s hydrological system has been attributed to a global ice cover during one or more extreme glaciations in the central flinders ranges south australia the yudnamutana subgroup of sturtian age includes diamictite sandstone and siltstone units of glaciomarine origin as much as 5000 m thick and is overlain by postglacial transgressive siltstone and shale of the tindelpina shale member tapley hill formation in the central flinders ranges the yudnamutana subgroup consists of 1 the pualco tillite gravity resedimented glacial deposits 2 the holowilena ironstone glacioturbidites 3 poorly stratified pebbly diamictite of the warcowie dolomite member lowermost wilyerpa formation gravity resedimented glacial deposits succeeded by 4 siltstones and sandstones with abundant hummocky cross stratification hcs storm deposits and 5 a lonestone bearing succession with cobble sized clasts in the upper wilyerpa formation ice rafted debris interpreted to record a glacial re advance in which hcs is absent because the action of oscillating waves is required to produce hcs on the seafloor its presence indicates an interval of significant meltback prior to glacial re advance given that the hcs occurs 2 km beneath the tindelpina shale member it signifies a major ice free interval during the sturtian glaciation

plume ridge interaction revisited evidence for melt mixing from he ne and ar isotope and abundance systematics abstract submarine volcanic glass he ne and ar data from the pacific antarctic rise at its intersection with the foundation seamount chain have been obtained to further elucidate one of the main outstanding problems in plume ridge interaction studies the physical state in which mantle flow and mixing occur in those settings mixing of plume mantle and mid ocean ridge basalt source material may either be in the form of two solids of solid melt or of two melt phases only the positive correlation of 4 he 40 ar with 206 pb 204 pb as well as the negative correlation of 4 he 40 ar with 40 ar and 4 he concentrations combined with a lack of correlation between 4 he 40 ar and ridge depth or mgo concentration indicate that the enriched mantle plume material has been extensively degassed prior to mixing with the mid ocean ridge source material degassing of the plume source and mid ocean ridge source material prior to mixing is also suggested by the he versus pb isotope systematics however the occurrence of degassing processes requires the existence of melts implying that mixing between the plume and the mid ocean ridge material occurs in the physical form of melts

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

preliminary results on photometric properties of materials at the sagan memorial station mars reflectance measurements of selected rocks and soils over a wide range of illumination geometries obtained by the imager for mars pathfinder imp camera provide constraints on interpretations of the physical and mineralogical nature of geologic materials at the landing site the data sets consist of 1 three small photometric spot subframed scenes covering phase angles from 20 to 150 2 two image strips composed of three subframed images each located along the antisunrise and antisunset lines photometric equator covering phase angles from 0 to 155 and 3 full image scenes of the rock yogi covering phase angles from 48 to 100 phase functions extracted from calibrated data exhibit a dominantly backscattering photometric function consistent with the results from the viking lander cameras however forward scattering behavior does appear at phase angles 140 particularly for the darker gray rock surfaces preliminary efforts using a hapke scattering model are useful in comparing surface properties of different rock and soil types but are not well constrained possibly due to the incomplete phase angle availability uncertainties related to the photometric function of the calibration targets and or the competing effects of diffuse and direct lighting preliminary interpretations of the derived hapke parameters suggest that 1 red rocks can be modeled as a mixture of gray rocks with a coating of bright and dark soil or dust and 2 gray rocks have macroscopically smoother surfaces composed of microscopically homogeneous clear materials with little internal scattering which may imply a glass like or varnished surface

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

earthquake induced soft sediment deformation structures in upper jurassic open marine microbialites neuquen basin argentina penecontemporaneous decimetre scale soft sediment deformation structures are reported from the basal part of the upper jurassic lower cretaceous vaca muerta formation in the malargue las lenas area of the back arc neuquen basin mendoza province central andes the deformed interval amarillas bed is only 0 3 to 0 9 m thick but occurs in a wide area larger than 1500 km2 its age determined by ammonite biostratigraphy is early tithonian the soft sediment deformation structures were generated in finely laminated partially consolidated organicrich carbonate microbialites that were deposited in open marine poorly oxygenated settings apparently devoid of any significant slope those structures include boudins of different sizes and complexity a variety of folds normal listric dm scale faults sub horizontal detachment surfaces and other features which are part of several larger scale complex slump structures deformation was dominantly plastic but near to the ductile brittle field transition on the basis of the observed soft deformation structures their geographic distribution their lateral homogeneity and the geodynamic framework of the basin in which it was generated the amarillas bed can be tentatively attributed to a large intermediate depth earthquake that occurred within the plate that subducted beneath the andean continental margin and the neuquen back arc basin

microbialites of the neoproterozoic beck spring dolomite southern california ancient microbialites reflect interactions between microbial communities and environmental conditions however evaluating the relative roles of microbial community processes and environmental influences on microbialite morphology and internal fabric in the rock record can be challenging the neoproterozoic beck spring dolomite preserves diverse microbialites and thus provides an opportunity to explore the factors that influenced microbialite development locally stromatolitic thrombolitic and composite microbialites are abundant in subtidal to upper intertidal carbonates in the beck spring dolomite thrombolitic and composite microbialites have not been recognized previously in this unit but compose much of the newly defined thrombolitic member stratigraphic relationships demonstrate that these three types of microbialites formed in close spatial and temporal association in subtidal to intertidal environments the relative proportions and distributions of stromatolitic and thrombolitic microbialites vary with depositional environment stromatolitic microbialites dominate in deeper intertidal to subtidal facies whereas thrombolitic textures are more abundant in upper intertidal facies composite microbialites composed of intermingled clotted and laminated textures formed in all environments but are most abundant in intertidal facies the broad environmental distribution of stromatolitic thrombolitic and composite microbialites and the intermingling of textures suggest that laminated and clotted textures reflect diverse microbial community morphologies rather than environmental variations furthermore the ca 750 ma age of thrombolitic microbialites in the beck spring dolomite requires that they formed without the influence of calcimicrobes or metazoans colonizing and grazing the microbial mat surface thus these thrombolites provide further evidence that the biostratigraphic distribution of thrombolites cannot be uniquely attributed to evolution of calcifying and grazing organisms in the earliest cambrian and that older microbial communities were capable of producing clotted textures

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

seismogenic deformation structures in microbialites and mudstones silurian lockport dolomite northwestern ohio u s a syndepositional deformation structures are present at two different stratigraphic levels in the silurian lockport dolomite at a quarry in maumee ohio such structures are absent in this unit at twelve other quarries in northwestern ohio the structures at maumee present within stromatolites thrombolites and variably bedded mudstones include convolute layers homogenization of bedding and breccia clasts clasts of stromatolites boudinage structures normal reverse and thrust faults and discordant and concordant breccias the distribution of deformation structures within beds suggests substantial control from substrate rheology possibly resulting from differences in degrees of lithification and from variations in water content the extensive variety of syndepositional deformation structures juxtaposed evidence for nearly synchronous compression and dilation proximity 4 5 km of the structures to the largest fault in northwestern ohio the bowling green fault and the restricted geographic distribution of the deformation structures suggest seismic shaking as a probable mode of genesis similarities between features produced by seismogenic deformation of siliciclastic sediments and deformation features in the lockport dolomite provide additional evidence that the latter features are seismogenic it is postulated that two earthquakes one with a magnitude 5 caused the formation of the syndepositional deformation structures present in the youngest facies in the lockport dolomite at maumee quarry the bowling green fault 4 5 km west of maumee was a growth fault during formation of the lockport dolomite and is considered to have been the source of earthquakes that created the syndepositonal deformation structures in this unit at maumee quarry evidence from the lockport dolomite in northwestern ohio suggests that seismogenic deformation structures created by two earthquakes along the bowling green fault with magnitudes of 5 did not form in this unit over large areas i e all of northwestern ohio this evidence challenges the suggestion that syndepositional seismogenic deformation structures are always formed over a large area

retrieving soil surface roughness with the hapke photometric model confrontation with the ground truth abstract surface roughness can be defined as the mean slope angle integrated over all scales from the grain size to the local topography it controls the energy balance of bare soils in particular the angular distribution of scattered and emitted radiation this provides clues to understand the intimate structure and evolution of planetary surfaces over ages in this article we investigate the capacity of the hapke photometric model the most widely used in planetary science to retrieve surface roughness from multiangular reflectance data its performance is still a question at issue and we lack validation experiments comparing model retrievals with ground measurements to address this issue and to show the potentials and limits of the hapke model we compare the mean slope angle determined from very high resolution digital elevation models of volcanic and sedimentary terrains sampled in the asal ghoubbet rift republic of djibouti to the photometric roughness estimated by model inversion on multiangular reflectance data measured on the ground chamelon field goniometer and from space pleiades images the agreement is good on moderately rough surfaces in the domain of validity of the hapke model and poor on others

concentrated perchlorate at the mars phoenix landing site evidence for thin film liquid water on mars 1 nasa s phoenix mission which landed on the northern plains of mars in 2008 returned evidence of the perchlorate anion distributed evenly throughout the soil column at the landing site here we use spectral data from phoenix s surface stereo imager to map the distribution of perchlorate salts at the phoenix landing site and find that perchlorate salt has been locally concentrated into subsurface patches similar to salt patches that result from aqueous dissolution and redistribution on earth we propose that thin films of liquid water are responsible for translocating perchlorate from the surface to the subsurface and for concentrating it in patches the thin films are interpreted to result from melting of minor ice covers related to seasonal and long term obliquity cycles

geologic context of recurring slope lineae in melas and coprates chasmata mars one of the major mars discoveries of recent years is the existence of recurring slope lineae rsl which suggests that liquid water occurs on or near the surface of mars today these dark and narrow features emerge from steep rocky exposures and incrementally grow fade and reform on a seasonal basis and are detected in images from the high resolution imaging science experiment camera rsl are known to occur at scattered midlatitude and equatorial sites with little spatial connection to one another one major exception is the steep low albedo slopes of melas and coprates chasmata in valles marineris where rsl are detected among diverse geologic surfaces e g bedrock and talus and landforms e g inselbergs and landslides new images show topographic changes including sediment deposition on active rsl slopes midwall locations in coprates and melas appear to have more areally extensively abundant rsl and related fans as compared with other rsl sites found on mars water budget estimates for regional rsl are on the order of 105 to 106 m3 of fluid for depths of 10 to 100 mm and suggest that a significant amount of near surface water might be present many rsl are concentrated near local topographic highs such as ridge crests or peaks which is challenging to explain via groundwater or ice without a recharge mechanism collectively results provide additional support for the notion that significant amounts of near surface water can be found on mars today and suggest that a widespread mechanism possibly related to the atmosphere is recharging rsl sources

experimental determination of the surface photometric contribution in the spectral reflectance deconvolution processes for a simulated martian crater like regolithic target we produce bidirectional reflectance experimental measurements in the visible and near infrared range of a macroscopic target simulating the case of a martian crater using hapke s equation of radiative transfer we compare the performance in terms of mineralogical abundance determination of different deconvolution processes on a multispectral image of the experimental target in particular we study the effects of the topography and the physical properties of natural rocky surfaces e g local variations of incidence and emergence angles grain size variations mixtures of materials on the data interpretation for this purpose we increase progressively the amount of quantitative knowledge available in terms of hapke parameters description textural properties and topography for the target we estimate the accuracy of results in comparison with the known ground truth as a function of the level of knowledge we have of the target and carry out a critical assessment on the relative applicability of the different processes this study shows that the more important parameters to take into account are in decreasing order 1 the textural roughness which is shown essential for the accurate determination of mineralogical abundances 2 the disparity of hapke parameters across the target 3 the topography dem that has a limited influence on the results these findings have obvious implications for interpreting planetary regolith reflectance properties in terms of photometry spectroscopy and mineralogy measured either from spaceborne e g io observations from galileo mars from mars express hrsc and omega or in situ mars pathfinder mer instruments

planetary regolith surface analogs optimized determination of hapke parameters using multi angular spectro imaging laboratory data this work presents a method for a determination of the global set of parameters involved in hapke s model for planetary surface analogs when dealing with a set of angular conditions representative of the usual range of observation in planetary exploration for spaceborne optical instruments the present approach is founded on a genetic algorithm the whole set of hapke parameters is treated simultaneously without any a priori assumptions it limits the risk of meeting a local extreme and the stability and repeatability of the determination are improved moreover it requires less computational time than a monte carlo routine as a demonstration using multi angular measurements acquired by a new laboratory wide field multispectral imaging facility parameter values for various grain sizes and material compositions of planetary regolith surface analogs are derived and their potential wavelength dependence is studied the results coherent with the literature validate all the steps in our methodology we focus our interest in the understanding of the physical meaning of hapke s parameters in particular of the parameter of the shadowing function for macroscopic roughness it appears that the features smaller than the centimeter scale contribute predominantly to the photometric effect related to the rocky aspect of planetary soil surfaces the parameter may thus be mainly considered as an integral of the roughness properties in the submillimetric centimetric range indeed the most representative case for describing natural regolith surface lies in texture classes in the millimeter range not involving necessarily a high macroscopic roughness with large surface slopes at hundreds of meters scale these findings strengthen the case that depends on both the grain size and the material geological properties

hydrological characteristics of recurrent slope lineae on mars evidence for liquid flow through regolith and comparisons with antarctic terrestrial analogs abstract on the basis of their morphology and seasonal thermal characteristics recurrent slope lineae rsl on mars have been inferred to be a possible result of the flow of a liquid likely a saline brine through the upper portions of the martian regolith in this note we analyze repeat hirise imaging of rsl to show that the downslope growth rate of recurrent slope lineae is well fit by an elementary groundwater flow model that also describes the downslope propagation of antarctic water tracks terrestrial analogs to rsl and that the apparent permeability of rsl bearing slopes is consistent with the observed sandy regolith substrate

an interglacial on snowball earth dynamic ice behaviour revealed in the chuos formation namibia the sturtian is the oldest ca 716 ma of three pan global glaciations in the cryogenian at omutirapo in northern namibia a 2 km wide 400 m deep palaeovalley is filled by glaciogenic strata of the chuos formation which represents the sturtian glacial record sedimentary logging of an exceptionally high quality exposure permits detailed stratigraphic descriptions and interpretations allowing two glacial cycles to be identified at the base of the exposed succession strong evidence supporting glaciation includes diamictites ice rafted dropstones and intensely sheared zones of interpreted subglacial origin these facies collectively represent ice proximal to ice rafted deposits upsection dropstone free mudstones in the middle of the succession and the absence of diamictites imply sedimentation free from glacial influence however the reappearance of glacial deposits above indicates a phase of sturtian glacial re advance comparison with age equivalent strata in south australia where evidence for sea ice free sedimentation has been established previously suggests that a sturtian interglacial may have been extensive implying global scale waxing and waning of ice sheets during a cryogenian glacial event

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

vis nir reflectance of water ice regolith analogue mixtures and implications for the detectability of ice mixed within planetary regoliths permanently shadowed regions at the poles of the moon and mercury have been pointed out as candidates for hosting water ice at their surface we have measured in the laboratory the visible and near infrared spectral range vis nir bidirectional reflectance of intimate mixtures of water ice and the jsc 1af lunar simulant for different ice concentrations particle sizes and measurement geometries the nonlinearity between the measured reflectance and the amount of ice in the mixture can be reproduced to some extent by the mixing formulas of standard reflectance models in particular those of hapke and hiroi which are tested here estimating ice concentrations from reflectance data without knowledge of the mixing coefficientsstrongly dependent on the size shape of the grainscan result in large errors according to our results it is possible that considerable amounts of water ice might be intimately mixed in the regolith of the moon and mercury without producing noticeable photometric signatures

formation of recurring slope lineae by liquid brines on present day mars 1 recurring slope lineae rsl are small scale seasonal flow features identified by mars reconnaissance orbiter that present several interesting characteristics such as an albedo contrast seasonal dependence and a strong preference for equator facing slopes all of these characteristics strongly suggest a thermally driven mechanism such as a liquid triggered or dominated flow here we investigate the possibility that these features are formed by melting of brines of various compositions via a combination of thermodynamic and kinetic numerical models results suggest that a solution with a freezing temperature of 223 k can best reproduce the observed seasonality relatively high surface evaporation rates at the rsl locations make the flows quickly disappear over a single season our model reproduces well the seasonality of rsl and can explain the preference for equator facing slopes suggesting that brine flows and therefore liquids are possible on a small time and space scale today on mars however if the rsl are indeed formed by brines it may indicate that a recharge mechanism is active in order to maintain a source of brine over even short geological timescales which would have important implications for the martian water cycle

observations of the northern seasonal polar cap on mars iii crism hirise observations of spring sublimation we analyze a series of targeted crism and hirise observations of seven regions of interest at high latitudes in the northern polar regions of mars these data allow us to investigate the temporal evolution of the composition of the seasonal ice cap during spring with a special emphasis on peculiar phenomena occurring in the dune fields and in the vicinity of the scarps of the north polar layered deposits nplds the strength of the spectral signature of co2 ice continuously decreases during spring whereas the one of h2o ice first shows a strong increase until ls 50 this evolution is consistent with a scenario previously established from analysis of omega data in which a thin layer of pure h2o ice progressively develops at the surface of the volatile layer during early spring ls 10 widespread jet activity is observed by hirise while strong spectral signatures of co2 ice are detected by crism later around ls 20 40 activity concentrates at the dune fields where crism also detects a spectral enrichment in co2 ice consistent with kieffer s model kieffer h h 2007 j geophys res 112 e08005 doi 10 1029 2006je002816 for jet activity effects of wind are prominent across the dune fields and seem to strongly influence the sublimation of the volatile layer strong winds blowing down the scarps could also be responsible for the significant spatial and temporal variability of the surface ice composition observed close to the npld

the cryogenian record of glaciation and deglaciation in south australia abstract this paper reviews the state of our current knowledge of the cryogenian glacial and deglacial sedimentary records of south australia two distinct glacial intervals are recognised within rocks of cryogenian 850 630 ma age separated by an interglacial succession that by definition lacks glacial facies the glacial successions were laid down during the sturt and elatina glaciations each of these glaciations is arguably of global extent under the snowball earth hypothesis hoffman and schrag 2002 evidence for glaciation has been known for over one hundred years from the sturt tillite howchin 1900 when compared like for like in a systematic facies analysis both glacial successions show some similarities notably the occurrence of diamictites representing glacial deposition and slope reflux and dropstone bearing intervals but also show some dramatic differences notably deposition of the sturt succession was strongly influenced by extensional tectonics for which evidence is provided by dramatic thickness variations either side of major faults and palaeocurrent data sub basins formed during regional extension contain diamictites 4 6000 m thick e g the yudnamutana and baratta troughs in the northern and central flinders ranges respectively deposition of the younger elatina glacial deposits was locally influenced by diapirism in the central flinders ranges but otherwise these younger deposits seem to maintain a relatively constant thickness of

testing the hapke photometric model improved inversion and the porosity correction abstract in conjunction with a companion paper shepard m k helfenstein p 2011 icarus submitted for publication we derive test and apply a detailed approach for visualizing the phase angle dependence of light scattering in particulate soils from both whole disk and disk resolved observations to reduce the number of model parameters and provide stronger constraints on model fits we combine hapke s hapke b 2008 icarus 195 918 926 recent correction for effects of porosity with his hapke b 1986 icarus 67 264 280 model of the shadow hiding opposition effect we further develop our method as a tool for least squares fitting of hapke s model to photometric data finally we present an improved method for estimating uncertainties in retrieved values of hapke model parameters we perform a preliminary test of the model on spectrogoniometric measurements from three selected laboratory samples from shepard and helfenstein shepard m k helfenstein p 2007 j geophys res 112 e03001 17 our preliminary suite of test samples is too small and selective to permit the drawing of general conclusions however our results suggest that hapke s porosity correction improves the fidelity of fits to samples composed of low and moderate albedo particles and may allow for more reliable retrieval of porosity estimates in these materials however we find preliminary evidence that in high albedo surfaces the effects of porosity may be difficult to detect

evolution of south seasonal cap during martian spring insights from high resolution observations by hirise and crism on mars reconnaissance orbiter 1 we use data from the high resolution imaging science experiment hirise camera and the compact reconnaissance imaging spectrometer for mars crism imaging spectrometer onboard the mars reconnaissance orbiter to follow the evolution of the appearance and composition of 12 regions of the south polar layered deposits from spring to summer time we distinguish three steps in the evolution of the volatile layer a decrease of both co2 band strength and albedo until ls 190 210 a significant increase in both until ls 240 260 and finally a rapid decrease until the complete defrosting of the ground in contrast the water ice band displays a more monotonic decrease analysis of hirise color images acquired simultaneously with crism data allows a plausible interpretation of this evolution in early springtime ls 200 intense jet activity results in deposition of fans of large mineral grains and a wide spatial distribution of fine grains the small scale topography controls the presence and location of the jets by allowing more solar energy to be collected on slopes grains from the dust fans warm and sink through the co2 layer resulting in a bluish color at the locations of the fans around ls 190 210 as the atmosphere warms up the surface of the ice layer sublimes and releases dust and water resulting in its brightening the last phase of the process consists in a progressive defrosting resulting in a patchwork of frozen and unfrozen areas

photometric properties of mars soils analogs we have measured the bidirectional reflectance of analogs of dry wet and frozen martian soils over a wide range of phase angles in the visible spectral range all samples were produced from two geologic samples the standard jsc mars 1 soil simulant and hawaiian basaltic sand in a first step experiments were conducted with the dry samples to investigate the effects of surface texture comparisons with results independently obtained by different teams with similar samples showed a satisfying reproducibility of the photometric measurements as well as a noticeable influence of surface textures resulting from different sample preparation procedures in a second step water was introduced to produce wet and frozen samples and their photometry investigated optical microscope images of the samples provided information about their microtexture liquid water even in relatively low amount resulted in the disappearance of the backscattering peak and the appearance of a forward scattering peak whose intensity increases with the amount of water specular reflections only appeared when water was present in an amount large enough to allow water to form a film at the surface of the sample icy samples showed a wide variability of photometric properties depending on the physical properties of the water ice we discuss the implications of these measurements in terms of the expected photometric behavior of the martian surface from equatorial to circum polar regions in particular we propose some simple photometric criteria to improve the identification of wet and or icy soils from multiple observations under different geometries

dielectric signatures of adsorbed and salty liquid water at the phoenix landing site mars 1 the real part of the dielectric permittivity of the martian regolith was measured by the thermal and electrical conductivity probe tecp on the phoenix lander we interpret these data using laboratory measurements of permittivity as a function of h2o and salt content soil type and temperature due to variability in sensor coupling we focus on data taken at one locality vestri three separate times spanning multiple sols a daytime increase in permittivity suggests progressive melting of a heterogeneous disconnected salty ice with a eutectic temperature of 239 k which is close to the eutectic temperatures of naclo4 or mgcl2 we found no evidence for mg clo4 2 naclo4 and mgcl2 are consistent with precipitation by freezing following a prior epoch of high obliquity the evaporation of diurnal briny meltwater is inhibited by surface tension in small pores an increase in permittivity occurred on the night of sol 70 that coincided with surface frost and measurement of a decrease in atmospheric water vapor the permittivity jump can be matched by an increase in adsorbed h2o from 1 monolayer to 3 monolayers in an analog soil with a viking like specific surface area 17 m2 g however the amount of adsorbed h2o is an order of magnitude larger than that inferred to have precipitated during the night we suggest that the electrical signature of adsorbed water on mars is stronger than we measured in the laboratory possibly due to radiation damage of the regolith

agglutinated tests in post sturtian cap carbonates of namibia and mongolia abstract paleomagnetic data suggest that the early cryogenian sturtian glaciation extended to sea level at low latitude the impact of this dramatic environmental change on biota and the composition of ecosystems in the immediate aftermath of the sturtian glaciation remain virtually unknown here we report the discovery of abundant agglutinated tests in organic rich carbonates directly overlying sturtian glacial deposits from two different paleocontinents the rasthof formation of the congo craton in northern namibia and the tsagaan oloom formation of the dzabkhan terrane in mongolia the most abundant tests preserve morphological and compositional characters consistent with those found in at least two different families of modern lobose testate amoebae amoebozoa a group of heterotrophic microbial eukaryotes the presence of spatially and compositionally variable clay minerals quartz and microcline on the test walls is a signature of widespread biological agglutination the post glacial fossil assemblages differ from the most common pre sturtian vase shaped fossil testate amoebae perhaps as a result of different preservational mechanisms or of the appearance of new forms after the glaciation the apparent local abundance of eukaryotic body fossils in the post sturtian carbonates suggests that the cryogenian limestones and dolostones may host a currently unexplored fossil record of modern eukaryotes

spectrogoniometry and modeling of martian and lunar analog samples and apollo soils abstract we present new visible near infrared multispectral reflectance measurements of seven lunar soil simulants two apollo soils and eight martian analog samples as functions of illumination and emission angles using the bloomsburg university goniometer by modeling these data with hapke theory we provide constraints on photometric parameters single scattering albedo phase function parameters macroscopic roughness and opposition effect parameters to provide additional ground truth photometric properties to assist analyses of spacecraft data a wide range of modeled photometric properties were variably related to albedo color grain size and surface texture finer grained samples here have high single scattering albedo values compared to their coarser grained counterparts as well as lower macroscopic roughness values the mars analog samples and apollo soils exhibit slightly lower opposition effect width parameter values than the lunar analogs whereas the opposition effect magnitude is not well constrained by the models the mars analog soils are typically relatively backscattering and consistent with fairly rough particles with a moderate density of internal scatterers similar to the in situ observations of some soils by the mars exploration rover mer spirit some lunar analog soil models result in moderately forward scattering behaviors as do the two apollo soils other fine grained and or glass rich lunar analog samples populate a narrowly forward scattering regime similar to model results from observations of some rover tracks observed by the mer opportunity rover and some dust poor gray rocks by the spirit rover an experiment to mimic the spherule rich soils observed by opportunity demonstrated a large decrease in single scattering albedo compared to spherule free soil surfaces as well as increased surface roughness narrow opposition effects and a significant increase in backscattering similar to some of the opportunity soils phase reddening effects are documented in many soils as an increase in near infrared visible ratios with phase angle some samples exhibit falloffs in these ratio phase curves at phase angles beyond 50 80 that are likely related to an increased importance of surface scattering at high phase angles none of the lunar analog soils perfectly match the modeled photometric parameters of the two apollo soils the phase reddening nature of the mare soil included an upturn in ratio values at phase angles

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

microbialite recovery in the aftermath of the sturtian glaciation insights from the rasthof formation namibia abstract ice sheet meltback in the aftermath of the sturtian mid cryogenian glaciation was accompanied or followed by deposition of thick carbonate successions in northern namibia the rasthof formation is a 200 400 m thick cap carbonate sequence divided into 1 a basal cap dolostone 2 a microbial member and 3 an epiclastic member this subdivision applies for 100 km along strike at the southern and western edges of the owambo basin in this paper we focus essentially on macrofacies of the cap dolostone and the microbial member cap dolostones are commonly interpreted as subtidal to deep water deposits with delicate mm thick laminae we describe well preserved ungraded hummocky cross stratification in the cap dolostone expected to occur no deeper than the offshore transition zone the overlying microbial member contains thickly laminated microbialites with folded and contorted intervals interpreted as soft sediment deformation structures the thickly laminated microbialites are followed by more thinly laminated microbialites with roll up structures and more unusual individual vertical stromatolite morphologies we interpret the vertical growths in the microbial member as a direct response to the changing environment the new observations and interpretations presented in this paper contrast with previous work on the rasthof formation we recognise a relatively shallower setting associated with a trend in the geometries of the microbial member

three decades of martian surface changes 1 the surface of mars has changed dramatically during the three decades spanned by spacecraft exploration comparisons of mars global surveyor images with viking and mariner 9 pictures suggest that more than one third of mars surface area has brightened or darkened by at least 10 such albedo changes could produce significant effects on solar heating and the global circulation of winds across the planet all of the major changes took place in areas of moderate to high thermal inertia and rock abundance consistent with burial of rocky surfaces by thin dust layers deposited during dust storms and subsequent exposure of the rocky surfaces by aeolian erosion several distinct mechanisms contribute to aeolian erosion on mars prevailing winds dominate erosion at low latitudes producing diffuse albedo boundaries and elongated wind streaks generally oriented in the direction of southern summer winds dust devils darken the mid to high latitudes from 45 to 70 degrees during the summer seasons forming irregular albedo patterns consisting of dark linear tracks dust storms produce regional albedo variations with distinct but irregular margins dark sand dunes in southern high latitudes appear to be associated with regional darkening that displays diffuse albedo boundaries no surface changes were observed to repeat regularly on an annual basis but many of the changes took place in areas that alternate episodically between high and low albedo states as thin mantles of dust are deposited and later stripped off hence the face of mars remains recognizable after a century of telescopic observations in spite of the enormous extent of alteration that has taken place during the era of spacecraft exploration

spectrophotometric properties of materials observed by pancam on the mars exploration rovers 2 opportunity 1 the panoramic camera pancam on the mars exploration rover opportunity acquired visible near infrared multispectral observations of soils and rocks under varying viewing and illumination geometries that were modeled using radiative transfer theory to improve interpretations of the microphysical and surface scattering nature of materials in meridiani planum nearly 25 000 individual measurements were collected of rock and soil units identified by their color and morphologic properties over a wide range of phase angles 0 150 at eagle crater in the surrounding plains in endurance crater and in the plains between endurance and erebus craters through sol 492 corrections for diffuse skylight incorporated sky models based on observations of atmospheric opacity throughout the mission disparity maps created from pancam stereo images allowed inclusion of local facet orientation estimates outcrop rocks overall exhibited the highest single scattering albedos 0 9 at 753 nm and most spherule rich soils exhibited the lowest 0 6 at 753 nm macroscopic roughness among outcrop rocks varied but was typically larger than spherule rich soils data sets with sufficient phase angle coverage resulting in well constrained hapke parameters suggested that models using single term and two term henyey greenstein phase functions exhibit a dominantly broad backscattering trend for most undisturbed spherule rich soils rover tracks and other compressed soils exhibited forward scattering while outcrop rocks were intermediate in their scattering behaviors some phase functions exhibited wavelength dependent trends that may result from variations in thin deposits of airfall dust that occurred during the mission

systematic variations in c o and sr isotopes and elemental concentrations in neoproterozoic carbonates in namibia implications for a glacial to interglacial transition abstract we analyzed c o and sr isotopic compositions of neoproterozoic cap carbonates overlying a glacial deposit in namibia to trace environmental changes following the glaciation the three isotopic records showed coherent and phased changes that corresponded to the stratigraphic variation a lower rhythmite unit had three intervals which were distinguished by isotopic variations and mineral type in the basal interval 13 c increased exponentially from a negative value 4 3 pee dee belemnite pdb 13 c values were relatively constant in the middle interval and increased again to positive values in the top interval indicating a phased removal of 13 c depleted carbon from the surface ocean the gradual increase to larger values 6 in the upper stromatolite unit was interpreted to reflect a change in seawater composition resulting from biological activity after environmental recovery from the glacial episode 18 o values and sr isotopic ratios decreased in the basal interval and approached stable values in the middle interval they increased in the upper interval and fluctuated in the stromatolite unit on the basis of geochemical screening criteria for detecting diagenetic alteration of sr isotopes the middle interval of the rhythmite unit with a minimum 87 sr 86 sr ratio of 0 70685 was interpreted to have retained the primary value or to have the least altered sr isotopic composition the basal interval which had ratios 0 718 at its base as high as those of old sialic rocks was interpreted as having altered sr isotopic ratios the high sr isotopic ratios at the base of this interval gradually decreased to near the minimum value at the top of the interval and other isotopic compositions and trace element concentrations showed systematic variations such systematic variations except for the variation in na concentration can be explained by a progressive diagenetic fluid rock interaction alternatively they might reflect a compositional transition from a local transport limited water following the glaciation to global well mixed seawater

surface reflectance of mars observed by crism mro 2 estimation of surface photometric properties in gusev crater and meridiani planum the present article proposes an approach to analyze the photometric properties of the surface materials from multi angle observations acquired by the compact reconnaissance imaging spectrometer for mars crism on board the mars reconnaissance orbiter we estimate photometric parameters using hapke s model in a bayesian inversion framework this work also represents a validation of the atmospheric correction provided by the multi angle approach for retrieval of surface reflectance from crism observations mars reco proposed in the companion article the latter algorithm retrieves photometric curves of surface materials in reflectance units after removing the aerosol contribution this validation is done by comparing the estimated photometric parameters to those obtained from in situ measurements by panoramic camera instrument at the mars exploration rover mer spirit and mer opportunity landing sites consistent photometric parameters with those from in situ measurements are found demonstrating that mars reco gives access to accurate surface reflectance moreover the assumption of a non lambertian surface as included in mars reco is shown to be significantly more precise to estimate surface photometric properties from space in comparison to methods based on a lambertian surface assumption in the future the presented method will allow us to map from orbit the surface bidirectional reflectance and the related photometric parameters in order to characterize the martian surface

characterization and mapping of surface physical properties of mars from crism multi angular data application to gusev crater and meridiani planum the analysis of particle physical properties grain size shape and internal structure and its organization surface porosity roughness and grain size distribution provides information about the geological processes which formed and modified planetary surfaces crism compact reconnaissance imaging spectrometer for mars multi angular observations varied emission angles allow for the characterization of the surface scattering behavior which depends on the composition and on the material physical properties such as the grain size shape internal structure and the surface roughness after an atmospheric correction compensating mineral aerosol effects by the multi angle approach for retrieval of the surface reflectance from crism observations mars reco the surface reflectances at different geometries were analyzed by inverting the hapke photometric model depending on six parameters single scattering albedo 2 phase function terms macroscopic roughness and 2 opposition effects terms in this work surface photometric maps are created to observe the spatial variations of surface scattering properties as a function of geological units information regarding the single scattering albedo the particle phase function and the macroscopic roughness are provided at the crism spatial resolution 200 m pixel this article describes the application of this methodology to the data covering the mars exploration rover mer landing sites located at gusev crater and meridiani planum where orbital and in situ observations are available complementary orbital observations e g crism spectra thermal emission imaging system themis high resolution imaging science experiment hirise images were used for interpreting the modeled hapke photometric parameters in terms of physical properties which can be used to constrain the geological processes available mer in situ observations were used as ground truth to validate the interpretations of the hapke parameters varied scattering properties were observed within a crism observation 5 10 km suggesting that the surfaces are controlled by local geological processes e g volcanic resurfacing aeolian and impact processes rather than regional or global processes results are consistent with the in situ observations thus validating the approach and the use of photometry for the characterization of martian surface physical properties

hummocky cross stratification like structures in deep sea turbidites upper cretaceous basque basins western pyrenees france hummocky cross stratification is a sedimentary structure which is widely interpreted as the sedimentary record of an oscillatory current generated by energetic storm waves remobilizing surface sediment on the continental shelf sedimentary structures named hummocky cross stratification like structures similar to true hummocky cross stratification have been observed in the turonian senonian basque flysch basin south west france the bathymetry 1000 to 1500 m suggests that the observed sedimentary structures do not result from a hydrodynamic process similar to those acting on a continental shelf the morphology of these three dimensional structures shares similarities with the morphology of hummocky cross stratification despite a smaller size the lateral extent of these structures ranges from a few decimetres to many decimetres they consist of convex up domes hummock and concave up swales with a non erosive base four types of hummocky cross stratification like geometries are described they occur in association with structures such as climbing current ripple lamination and synsedimentary deformations in the basque flysch hummocky cross stratification like structures are only found in the tc interval of the bouma sequence hummocky cross stratification like structures are sporadic in the stratigraphic series and observed only in few turbidite beds or bed packages this observation suggests that hummocky cross stratification like structures are linked genetically to the turbidity current but form under a very restricted range of parameters these structures sometimes show an up current upslope migration trend antidunes in the described examples they could result from standing waves forming at the upper flow interface because of kelvin helmholtz instability

testing models for post glacial cap dolostone deposition nuccaleena formation south australia sedimentologically and geochemically distinctive carbonate sequences consistently drape the glacial deposits associated with the younger cryogenian ice age the presence of ice rafted debris in the basal dolostone implies that at least the lower portion of the cap sequence records deglaciation an isochronous model proposes that cap dolostones were deposited synchronously around the world regardless of water depth whilst a diachronous model proposes that deposition tracked glacioeustatic flooding during deglaciation the nuccaleena formation of the adelaide rift complex arc south australia exhibits many of the unique sedimentary features observed in other younger cryogenian cap dolostones around the world some bedforms are the product of wind driven oscillatory flow thus constraining post glacial dolostone deposition to 400 m these sedimentary features are absent in the deepest basinal facies in the northern arc suggesting that this region was below storm wave base even at the glacial sea level lowstand in the north flinders ranges there is a distinct relationship between lateral facies variability in the pre syn and post glacial sediments and the axes of 50 km scale structural folds the northern fold limbs are characterised by basinal facies whilst the southern limbs are associated with upper slope facies we interpret the abrupt facies transitions to reflect lower slope to upper slope shelf breaks across a series of linked south facing half grabens the majority of cap dolostone carbon isotope records show monotonic declines in 13c of 2 with starting points between 0 5 and 3 5 an isochronous model implies a 3 0 lateral gradient from platform to lower slope that varies dramatically on a short spatial scale and non systematically with palaeobathymetry if pre and syn glacial facies are used to infer palaeobathymetry and cap dolostones are deposited diachronously as sea level rises during deglaciation then 13c values becomes progressively lighter with time implying that cap dolostone deposition tracked the glacioeustatic sea level rise over a series of half grabens that deepened to the north the carbon isotope dataset cannot rule out uniquely isochronous or diachronous models given the high frequency spatial variability of 13c values temperature cannot be the dominant control on the isotopic variability of the cap dolostone

distribution of mid latitude ground ice on mars from new impact craters new impact craters at five sites in the martian mid latitudes excavated material from depths of decimeters that has a brightness and color indicative of water ice near infrared spectra of the largest example confirm this composition and repeated imaging showed fading over several months as expected for sublimating ice thermal models of one site show that millimeters of sublimation occurred during this fading period indicating clean ice rather than ice in soil pores our derived ice table depths are consistent with models using higher long term average atmospheric water vapor content than present values craters at most of these sites may have excavated completely through this clean ice probing the ice table to previously unsampled depths of meters and revealing substantial heterogeneity in the vertical distribution of the ice itself

spectrophotometry from mars hand lens imager goniometer measurements kimberley region gale crater abstract the light scattering properties of surface materials on mars are typically modeled using in situ spectrophotometric imaging sequences taken at multiple times of day to provide sufficient phase coverage herein we report analyses of observations acquired at one time of day but under varying emission angles using the mars hand lens imager mahli on the robotic arm of the mars science laboratory msl rover as a goniometer a multiple viewpoint data set was acquired on sol 544 by manipulating the arm to provide mahli images from 20 arm positions all centered at the same location and from a near constant distance of 1 m from the surface permitting a phase angle coverage from 8 to 100 from these images we constructed a digital terrain model of the scene and used it in combination with atmospheric scattering models to remove the diffuse components of radiance from surface units radiative transfer models using hapke theory were conducted using the direct radiance components from specific rock and soil units despite the relatively limited number of observations our modeled hapke parameters were well constrained for terrain types such as soils and certain types of rocks that were common within the scene but the errors increased for rock types with fewer observations results from one term and two term henyey greenstein phase functions show the soil units to be more backscattering than rocks consistent with previous photometric studies of martian landing sites overall we find that the mahli goniometer sequences can produce reasonable and consistent photometric results providing a new and efficient means of acquiring spectrophotometric data by arm cameras on rovers such as msl