mineral biosignatures in evaporites presence of rosickyite in an endoevaporitic microbial community from death valley california rosickyite is a rare form of sulfur sulfur monoclinic symmetry that is not thermodynamically predicted to be stable at earth s surface temperatures instead it reverts to the more common sulfur form orthorhombic symmetry here we show for the first time that rosickyite exists and is stably maintained within an endoevaporitic microbial community from the salt pan of death valley california we hypothesize that this mineral is formed by a cycle of microbial dissolution of gypsum caso4 2h2o to sulfide and reoxidation of the sulfide to elemental sulfur rosickyite within a stable oxygen sulfide gradient maintained by the organisms furthermore we report a microstratigraphic layering of mineral types that correlates with layering of the microbial community knowledge of how microbial communities can affect the mineral assemblages of evaporite deposits on earth can help us to identify potential markers of the past or present existence of life on extraterrestrial bodies bearing evidence of ancient seas or lakes

transformations of mg and ca sulfate hydrates in mars regolith salt hydrates have an active role in regolith development on mars the mg sulfate system with highly variable values of n in the formula mgso 4 n h 2 o is particularly subject to transformations among several crystalline and amorphous forms the ca sulfate system caso 4 n h 2 o is likely to be associated with the mg sulfates in most occurrences but is less susceptible to transformations in n desiccation of mgso 4 n h 2 o occurs in exposed soils at the martian equator in summer where higher daytime temperatures at low relative humidity prevail against sluggish nighttime rehydration at high relative humidity desiccation and rehydration are both accelerated in the finest size fractions particularly in silt size aeolian particles subject to global redistribution by dust storms this redistribution and periodic excursions into long term episodes of high obliquity work to rehydrate desiccated mgso 4 n h 2 o to form epsomite mgso 4 7h 2 o at higher latitudes in the first case and more globally in the latter kieserite a monohydrate form of mgso 4 n h 2 o resistant to desiccation can survive equatorial summer conditions but not protracted high relative humidity preservation of kieserite at the surface may place limits on the equatorial distribution of ice during past episodes of high obliquity deeper horizons in equatorial regolith may preserve hydrated phases through repeated obliquity episodes raising the possibility of an ancient regolith archive of past hydration at shallower depths in the regolith in situ determination of the hydration states of the mg sulfates and possibly the ca sulfates may be used to constrain regolith dynamics if rates and modes of transitions in n can be fully characterized

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

measurement of outflow from a snowbank with basal ice by kathy l young and antoni g lewkowicz department of geography erindale college university of toronto mississauga ontario l5l i c6 canada abstract a technique is described for measuring melt water outflow from snowbanks that develop a basal ice layer the method involves excavation of channels across ice exposed at the lower edge of a snowbank in order to divert run off into a portable flume since discharges are measured before the water comes into contact with the soil sub surface flow and soil moisture changes do not have to be assessed outflow discharges recorded at a perennial snowbank site on melville island n w t canada compare favourably with energy balance calculations and measure ments of ablation introduction snow melt is regarded as the most significant hydrological input to non glacierized basins in alpine e g jordan 1983 sub arctic e g dunne and others 1976 low arctic e g landals and gill 1973 onesti and walti 1983 and high arctic environments e g lewkowicz and french 1982 woo 1983 woo and others 1983 consequently a thorough understanding of the relationship between snow melt and stream run off is essential for many aspects of resource development in these regions walker and lake 1973 colbeck 1977 the two main approaches used to determine run off resulting from snow melt are modelling and direct measurement vertical and horizontal movements of melt water in homogeneous and layered snow packs have been modelled extensively e g col beck 1971 1972 1973 1974 1977 and flow equations have been tested in alpine areas e g jordan 1979 and in the sub arctic dunne and others 1976 price 1977 more recently a simulation model has been developed which describes water movement through flow fingers the growth of ice lenses and wetting front advance in high arctic snow packs marsh and woo 1984b it also predicts basal ice growth and run off in spite of these advances more work is required before models can accurately describe melt water movement and quantify run off for snowbanks which are both non uniform in depth and heterogeneous in structure field measurements of run off from snow will continue to be necessary for the development and verification of such models direct measurement of snow melt and run off in northern areas has relied mainly on instrumented hill slope plots a review of researchers and their methods has been presented by steer and woo 1983 in most studies run off was measured on the ground surface down slope of the snow this increases the potential for error in estimating snow melt since evapotranspiration sub surface flow and ground storage changes all have to be considered e g dunne and black 1971 dunne and others 1976 lewkowicz and french 1982 steer and woo 1983 this paper describes a technique for the direct measurement of outflow from snow that has developed a basal ice layer the method can be used in snow of heterogeneous depth and structure and reduces the possibility of error in assessing melt since discharges are 358 measured before the water comes into contact with the substrate the technique could be employed to provide observed outflow values for comparison with predictions from snow melt models to determine snow melt inputs to experimental plots or to a drainage basin or to estimate the energy balance of ablating snow the method was tested at the site of a perennial snowbank on south east melville island northwest territories canada figs i and 2 in july and august 1986 the discharge data obtained compare favourably with independent measurements of the energy balance and snow ablation method the method can be used to monitor outflow from any snowbank that possesses a basal ice layer basal ice develops when negative ground temperatures are present beneath a melting snow pack and a sufficiently large soil thermal gradient exists for latent heat released by freezing to be conducted into the substrate woo and heron 1981 woo and others 1982 the basal ice layer has a low permeability and once formed beneath a snow pack is usually effective in preventing subsequent melt waves from

chromaticity of the martian sky as observed by the mars exploration rover pancam instruments 1 we have derived quantitative color estimates of the martian sky from data acquired by the panoramic cameras pancams on the mars exploration rovers spirit and opportunity we calculate the perceptual color of the sky directly from the absolute radiometric calibration of the cameras following similar approaches to those used in previous studies with viking lander and mars pathfinder data we further use these measurements to study changes in sky color throughout the mer missions and to compare these to changes in atmospheric opacity determined from direct solar imaging by the pancams we have derived a functional relationship between sky color and optical depth and discuss its possible uses and limitations finally we simulate changes in sky color as suspended dust is removed and present visual representations of these based on modeling results past studies and observed mer sky brightnesses the color of the martian sky as opacity decreases from 1 0 to 0 0 is estimated to change from dark yellowish brown at high opacity to bluish black or black if dust free

wetting front advance and freezing of meltwater within a snow cover 1 observations in the canadian arctic in a naturally stratified snow cover the movement of meltwater into dry snow is complicated by the interaction of the wetting front with stratigraphic horizons field observations showed that when the wetting front reached premelt stratigraphic horizons water ponded at the interface and then flow fingers developed and penetrated the lower stratum the flux in these fingers which was increased to about twice that of the surface flux was used to feed water to the impeding horizons where it froze to form ice layers these ice layers were the major source of latent heat released within the snow cover and they were responsible for the warming of the snow and the underlying soil these continuous ice layers grew only at stratigraphic boundaries because of this ice layer growth the wetting front advance was retarded and the arrival of meltwater at the snow cover base was significantly delayed owing to a cold substrate the strong heat flux from the snow into the soil delays the warming of the snow cover and limits runoff after the snow is isothermal at 0 c by the refreezing of soil infiltration and the development of a basal ice layer

is hydrology kinematic a wide range of phenomena natural as well as man made in physical chemical and biological hydrology exhibit characteristics similar to those of kinematic waves the question we ask is can these phenomena be described using the theory of kinematic waves since the range of phenomena is wide another question we ask is how prevalent are kinematic waves if they are widely pervasive does that mean hydrology is kinematic or close to it this paper addresses these issues which are perceived to be fundamental to advancing the state of the art of water science and engineering copyright 2002 john wiley sons ltd

aqueous alteration of the bali cv3 chondrite evidence from mineralogy mineral chemistry and oxygen isotopic compositions abstract a petrographic geochemical and oxygen isotopic study of the bali cv3 carbonaceous chondrite revealed that the meteorite has undergone extensive deformation and aqueous alteration on its parent body deformation textures are common and include flattened chondrules a well developed foliation and the presence of distinctive 100 planar defects in olivine the occurrence of alteration products associated with the planar defects indicates that the deformation features formed prior to the episode of aqueous alteration the secondary minerals produced during the alteration event include well crystallized mg rich saponite framboidal magnetite and ca phosphates the alteration products are not homogeneously distributed throughout the meteorite but occur in regions adjacent to relatively unaltered material such as veins of altered material following the foliation the alteration assemblage formed under oxidizing conditions at relatively low temperatures oxygen isotopic compositions for unaltered regions in bali fall within the field for other cv3 wholerocks however the oxygen isotopic compositions of the heavily altered material lie in the region for the cm and cr chondrites the heavy isotope enrichment of the altered regions in bali suggest alteration conditions similar to those for the petrographie type 2 carbonaceous chondrites

an evaluation of the hydrologic relevance of lateral flow in snow at hillslope and catchment scales lateral downslope flow in snow during snowmelt and rain on snow ros events is a well known phenomenon yet its relevance to water redistribution at hillslope and catchment scales is not well understood we used dye tracers geophysical methods and hydrometric measurements to describe the snow properties that promote lateral flow assess the relative velocities of lateral flow in snow and soil and estimate volumes of downslope flow results demonstrate that rain and melt water can travel tens of metres downslope along layers within the snowpack or at the snowpack base within tens of hours lateral flow within the snowpack becomes less likely as the snowpack becomes saturated and stratigraphic boundaries are destroyed flow along the base can be prevalent in all snowpack conditions the net result of lateral flow in snow can be the deposition of water on the soil surface in advanced downslope positions relative to its point of origin or direct discharge to a stream although both melt and ros events can redistribute water to downslope positions ros events produced the most significant volumes of downslope flow direct stream contributions through the snowpack during one ros event produced up to 12 of streamflow during the event this can help explain rapid delivery of water to streams during ros events as well as anomalously high contributions of event water during snowmelt hydrographs in catchments with a persistent snowpack lateral redistribution of water within the snowpack should be considered a relevant moisture redistribution mechanism

role of the supraglacial snowpack in mediating meltwater delivery to the glacier system as inferred from dye tracer investigations the supraglacial snowpack plays an important role in mediating the delivery of meltwater produced at the snowpack surface to the rest of the glacier system with potential implications for both proglacial hydrograph form and the timing and magnitude of glacier movement induced by changes in subglacial water pressure however there remain few field observations of the hydrological behaviour of supraglacial snowpacks and its seasonal evolution during the melt season data collected during the 2004 melt season at haut glacier d arolla valais switzerland uses both qualitative and quantitative dye tracing techniques to enhance our understanding of supraglacial snowpack hydrology observations of the movement of dye stained water show the complexity of flow patterns and the influence of ice layers and preferential flow zones in controlling percolation through the snowpack and fluorometric techniques yield average flow rates for percolation through the snowpack of between 0 13 and 0 49 m h the changing form of dye return curves and increasing percolation rates reflect an increase over the course of the melt season in the efficiency with whichthesnowpacktransmitsmeltwater snowpackpermeabilitywasfoundtobesignificantlylower 1 67x10 m on average than that assumed in previous modelling studies of glacial hydrology showing the need for improved information about snowpack hydrology if its importance in controlling runoff is to be fully appreciated

ancient impact and aqueous processes at endeavour crater mars the rover opportunity has investigated the rim of endeavour crater a large ancient impact crater on mars basaltic breccias produced by the impact form the rim deposits with stratigraphy similar to that observed at similar sized craters on earth highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits gypsum rich veins cut sedimentary rocks adjacent to the crater rim the gypsum was precipitated from low temperature aqueous fluids flowing upward from the ancient materials of the rim leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate rich sandstones of the meridiani region

meltwater movement in a deep snowpack 2 simulation model a numerical simulation model is developed describing the one dimensional flow of meltwater in a snowpack based on established methods of modeling unsaturated groundwater flow the results of field observations of snowmelt and meltwater flow are used to determine parameters describing the hydraulic properties of the snowpack and surface energy balance measurements are used as input to the model tests of the performance of the model show a high sensitivity to the saturated hydraulic conductivity of the snowpack and to liquid water content of the snow saturated hydraulic conductivity can be measured with acceptable precision by simple field methods however measurement of liquid water content is more difficult and constitutes the major limitation affecting calibration of the model the model is relatively insensitive to exponents in the power law equations relating conductivity capillary pressure and liquid water content meltwater wave speeds predicted by the model are somewhat slower than those observed in the field observations of snowpack layering and horizontal inhomogeneity of flow suggest that these features affect transient storage of meltwater and consequently cause meltwater wave speeds to differ from those predicted by a one dimensional model

mechanisms for the variation of sea ice extent in the northern hemisphere using daily sea ice data derived from satellite borne sensors and atmospheric data we examined processes controlling the variation of sea ice extent in the northern hemisphere the daily ice motion field was computed from imagery of the defense meteorological satellite program dmsp special sensor microwave imager ssm i for seven winters december to april from 1991 1992 to 1997 1998 by employing the maximum cross correlation method in order to examine mechanisms of the temporal variation of the ice extent we analyzed 50 specified lines across the daily ice edge although a high correlation between the ice motion and the geostrophic wind speed was observed in all the ice edge areas the degree for correlation between the speed of the ice edge displacement and the wind speed varied with region the degree for response of the ice edge speed to the wind speed largely depended upon that of the ice edge speed to the ice motion the following mechanisms controlling the variation of ice extent for regions in the northern hemisphere were anticipated in the barents sea bering sea and the sea of okhotsk the ice extent advances by wind driven ice advection and the daily scale variation of the ice extent were also controlled by the variation in wind speed in contrast the ice extent in the labrador sea and the greenland sea seemed to be considerably affected by oceanographic factors such as the location of the thermal front and was not related to the variation in wind speed the regional difference of the variation mechanism was also reflected in the interannual variation in maximum ice extent

correlation lengths of meltwater flow through ripe snowpacks colorado front range usa the flowpaths of meltwater through snow is known to be an inhomogeneous process the spatial distribution of meltwater flowing from the bottom of melting snowpacks is the result of horizontal and vertical flow paths within the snowpack the ability to characterize the spatial distribution of these meltwater flowpaths would be useful in developing models of snow melt runoff which could better characterize snow melt hydrographs we analyzed near infrared aerial photos of melting snow using a moving window analysis which can characterize correlation lengths in the reflectance of the snow surface near infrared is sensitive to snow grain size which in turn may indicate higher amounts of meltwater the grains grow faster if the liquid water content is higher correlation lengths were live to seven metres and the probability of finding such correlation lengths increased from 0 22 in may 1997 when the melt had just started to 0 68 by late june when melt was well established liquid water content at the snow surface was sampled with a dielectric sensor at 0 5 m intervals on 100 m 2 and 75 m 2 grids semi variograms showed a sill at five to six metres the liquid water measurements at the snow surface suggest that the correlation lengths derived from the infrared aerial photos represent surface expressions of higher flow density through the melting snowpack a circular array of 16 snow melt lysimeters each with areas of 0 2 m 2 was operated for two years at niwot ridge in the colorado front range variograms indicated that flows were correlated over a distance of five to seven metres these three independent methods all suggest a spatial organization of five to seven metres for flowpaths draining ripe snowpacks in the rocky mountains

vertical variations in bassanite distribution patterns in near surface sediments southern egypt abstract nile valley sediments of the el adaima area in southern egypt contain bassanite caso 4 0 5h 2 o associated with gypsum caso 4 2h 2 o in the upper 1 m of the deposits the presence of bassanite at this site formed by dehydration of gypsum is marked by variations in mode of occurrence with depth in the lowest bassanite bearing interval bassanite occurs mainly along the contact between gypsum crystals in pores which is related to the protection of bassanite from rehydration in those parts of the gypsum aggregates at a higher level bassanite occurs along the sides of lenticular gypsum crystals in the sediment matrix near the top of the studied sequence bassanite mainly appears as inclusions in gypsum crystals which represents a texture that developed by repeated dehydration and rehydration elsewhere in the upper part of the deposits bassanite occurs as aggregates of small crystals in pores without associated gypsum which was entirely dehydrated to bassanite in these parts these vertical variations in bassanite distribution patterns record differences in the diagenetic history of the deposits between depth intervals

meltwater movement in a deep snowpack 1 field observations the flow of meltwater through a snowpack can be described by darcy s law and by a set of equations relating conductivity capillary pressure and liquid water content which are similar to the equations governing unsaturated groundwater flow field observations were conducted which were designed to test the applicability of the unsaturated flow equations to the description of meltwater movement at the scale of a small watershed simple instrumentation was used to measure capillary pressure and meltwater flux rates this was supplemented with energy and water balance measurements for the study watershed observations of surface snowmelt meltwater flux and streamflow for the snowmelt period confirm the nature of meltwater flow as described by the unsaturated flow equations and illustrate the controlling influence of snowpack hydraulics on the streamflow hydrograph observed speeds of the meltwater wave front in the snowpack average about 0 22 m h 1 and capillary pressures and kinematic wave speeds observed are comparable to those reported in other deep snow environments the difficulty of obtaining reliable liquid water content measurements is identified as a major limitation in the determination of hydraulic properties of the snowpack

a habitable fluvio lacustrine environment at yellowknife bay gale crater mars the curiosity rover discovered fine grained sedimentary rocks which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy this aqueous environment was characterized by neutral ph low salinity and variable redox states of both iron and sulfur species carbon hydrogen oxygen sulfur nitrogen and phosphorus were measured directly as key biogenic elements by inference phosphorus is assumed to have been available the environment probably had a minimum duration of hundreds to tens of thousands of years these results highlight the biological viability of fluvial lacustrine environments in the post noachian history of 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

paleoclimate of mars as captured by the stratigraphic record in gale crater a kilometers thick sedimentary sequence in gale crater exhibits stratigraphic changes in lithology that are consistent with transitions in aqueous and climatic conditions purported to be global in scale the sequence is divided into two formations where the lower formation exhibits a net transition in mineralogy from clay sulfate to sulfate oxide assemblages and is separated from the overlying upper formation by an erosional unconformity superposition and crater counts suggest strata in the lower formation lie along the noachian hesperian time stratigraphic boundary whereas beds in the upper formation which lack signatures indicative of clay minerals or sulfates are thinner more regularly spaced and clearly younger the observed stratigraphic trends are consistent with the rocks at gale crater recording a global transition from a climate favorable to clay mineral formation to one more favorable to forming sulfates and other salts

beyond water on mars mars exploration has been guided by the search for water the more complex quest by mars science laboratory for habitable environments should illuminate the martian environmental history and possibly deliver insights into extraterrestrial life

silica rich deposits and hydrated minerals at gusev crater mars vis nir spectral characterization and regional mapping abstract the mars exploration rover mer spirit has discovered surprisingly high concentrations of amorphous silica in soil and nodular outcrops in the inner basin of the columbia hills in pancam multispectral observations we find that an absorption feature at the longest pancam wavelength 1009 nm appears to be characteristic of these silica rich materials however spectral analyses of amorphous silica suggest that the 1009 nm spectral feature is not a direct reflection of their silica rich nature based on comparisons with spectral databases we hypothesize that the presence of h 2 o or oh either free as water ice adsorbed or bound in a mineral structure is responsible for the spectral feature observed by pancam the gertrude weise soil which is nearly pure opaline silica may have adsorbed water cold trapped on mineral grains the origin of the 1009 nm pancam feature observed in the silica rich nodular outcrops may result from the presence of additional hydrated minerals specific sulfates halides chlorides sodium silicates carbonates or borates using the 1009 nm feature with other spectral parameters as a hydration signature we have mapped the occurrence of hydrated materials along the extent of spirit s traverse across the columbia hills from west spur to home plate sols 155 1696 we have also mapped this hydration signature across large panoramic images to understand the regional distribution of materials that are spectrally similar to the silica rich soil and nodular outcrops our results suggest that hydrated materials are common in the columbia hills

interannual seasonal and spatial patterns of meltwater and solute fluxes in a seasonal snowpack meltwater discharge and electrical conductivity were measured in eight 1 l m lysimeters and snow accumulation and electrical conductivity of melted samples were measured in snow pits during four snowmelt seasons at mammoth mountain california the peak snow water equivalent ranged from 0 57 to 2 92 m over the four melt seasons lysimeter discharges ranged from 20 to 205 of the mean flow however mean lysimeter flow was representative of snow ablation observed in snow pits the electrical conductivity in snow pit samples and meltwater averaged 2 3 s cm 1 peak meltwater electrical conductivity ranged from 6 to 14 times the bulk premelt snowpack electrical conductivity snow depth did not affect the magnitude of the ionic pulse and ion depletion as a function of snow ablation was similar from year to year despite interannual contrasts in melt rate and snow accumulation diel fluctuations in electrical conductivity were more pronounced in shallower snowpacks

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

elemental geochemistry of sedimentary rocks at yellowknife bay gale crater mars sedimentary rocks examined by the curiosity rover at yellowknife bay mars were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts no evidence of chemical weathering is preserved indicating arid possibly cold paleoclimates and rapid erosion and deposition the absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low temperature circumneutral ph rock dominated aqueous conditions analyses of diagenetic features including concretions raised ridges and fractures at high spatial resolution indicate that they are composed of iron and halogen rich components magnesium iron chlorine rich components and hydrated calcium sulfates respectively composition of a cross cutting dike like feature is consistent with sedimentary intrusion the geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of mars

kinematic wave modelling of vertical movement of snowmelt water through a snowpack vertical movement of snowmelt water through snowpacks is modelled by applying the kinematic wave theory analytical solutions are obtained for moisture flux particle velocity time history and velocity of meltwater front and total moisture content for a single melt event assuming that the melt rate is constant these solutions are extended to the case involving more than one event

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time