the new athena alpha particle x ray spectrometer for the mars exploration rovers 1 the new alpha particle x ray spectrometer apxs is part of the athena payload of the two mars exploration rovers mer the apxs sensor head is attached to the turret of the instrument deployment device idd of the rover the apxs is a very light weight instrument for determining the major and minor elemental composition of martian soils rocks and other geological materials at the mer landing sites the sensor head has simply to be docked by the idd on the surface of the selected sample x ray radiation excited by alpha particles and x rays of the radioactive sources is recorded by a high resolution x ray detector the x ray spectra show elements starting from sodium up to yttrium depending on their concentrations the backscattered alpha spectra measured by a ring of detectors provide additional data on carbon and oxygen by means of a proper calibration the elemental concentrations are derived together with data from the two other athena instruments mounted on the idd the samples under investigation can be fully characterized key apxs objectives are the determination of the chemistry of crustal rocks and soils and the examination of water related deposits sediments or evaporates using the rock abrasion tool attached to the idd issues of weathering can be addressed by measuring natural and abraded surfaces of rocks

fluid lava flows in gusev crater mars 1 rocks on the floor of gusev crater are basaltic in composition as determined from measurements by the mars exploration rover spirit on the basis of compositional data models of the basaltic lavas at the time of their emplacement suggest viscosities of 2 3 to 50 pa s dependent on the number of phenocrysts and vesicles that were present which would be more fluid than terrestrial tholeiitic lavas and comparable to mare lavas on the moon or archean high mg basalts on earth morphological data and crater counts derived from the high resolution stereo camera on mars express and other orbiters suggest that the lavas flooded gusev crater at about 3 65 b y and postdate older floor materials such as putative sediments emplaced by ma adim vallis

calcium sulfate veins characterized by chemcam curiosity at gale crater mars the curiosity rover has analyzed abundant light toned fracture fill material within the yellowknife bay sedimentary deposits the chemcam instrument coupled with mastcam and chemcam remote micro imager images was able to demonstrate that these fracture fills consist of calcium sulfate veins many of which appear to be hydrated at a level expected for gypsum and bassanite anhydrite is locally present and is found in a location characterized by a nodular texture an intricate assemblage of veins crosses the sediments which were likely formed by precipitation from fluids circulating through fractures the presence of veins throughout the entire similar to 5 m thick yellowknife bay sediments suggests that this process occurred well after sedimentation and cementation lithification of those sediments the sulfur rich fluids may have originated in previously precipitated sulfate rich layers either before the deposition of the sheepbed mudstones or from unrelated units such as the sulfates at the base of mount sharp the occurrence of these veins after the episodes of deposition of fluvial sediments at the surface suggests persistent aqueous activity in relatively nonacidic conditions

ries crater and suevite revisited observations and modeling part ii modeling we present the results of numerical modeling of the formation of the ries crater utilizing the two hydrocodes sova and isale these standard models allow us to reproduce crater shape size and morphology and composition and extension of the continuous ejecta blanket some of these results cannot however be readily reconciled with observations the impact plume above the crater consists mainly of molten and vaporized sedimentary rocks containing very little material in comparison with the ejecta curtain at the end of the modification stage the crater floor is covered by a thick layer of impact melt with a total volume of 6 11 km3 the thickness of true fallback material from the plume inside the crater does not exceed a couple of meters ejecta from all stratigraphic units of the target are transported ballistically no separation of sedimentary and crystalline rocks as observed between suevites and bunte breccia at ries is noted we also present numerical results quantifying the existing geological hypotheses of ries ejecta emplacement from an impact plume by melt flow or by a pyroclastic density current the results show that none of these mechanisms is consistent with physical constraints and or observations finally we suggest a new hypothesis of suevite formation and emplacement by postimpact interaction of hot impact melt with water or volatile rich sedimentary rocks

3d structure of the gusev crater region abstract gusev crater lies within the aeolis quadrangle of mars at the boundary between the northern lowlands and southern highlands the ancient valley ma adim vallis dissects the highlands south of gusev crater and is thought to have fed the crater with sediments high resolution stereo camera data and digital elevation models were used to construct a geologic geomorphic map 173 5 178 5 e 10 18 s and cross sections complemented by data from mars orbiter camera mars orbiter laser altimeter and thermal emission imaging system three geologic domains are recognised the highlands in the south gusev crater and lowlands in the north twelve units are mapped with thicknesses ranging from hundred meters to several kilometres thicknesses of units and their bedding attitude are estimated combining the geologic map and topographic information relative ages are determined from crater counts ranging from early noachian for highland units to middle amazonian for units in gusev crater and in lowlands episodes of intense geologic activity deposition volcanism deformation occur at around 4 0 ga 3 7 ga and 3 5 ga comparing the geometry of the gusev crater with similar sized filled and un filled martian craters suggests that the columbia hills are relics of the original central peak of gusev crater

alpha particle x ray spectrometer apxs results from gusev crater and calibration report 1 the chemical composition of rocks and soils on mars analyzed during the mars exploration rover spirit mission was determined by x ray analyses with the alpha particle x ray spectrometer apxs details of the data analysis method and the instrument calibration are presented measurements performed on mars to address geometry effects and background contributions are shown cross calibration measurements among several instrument sensors and sources are discussed an unintentional swap of the two flight instruments is evaluated new concentration data acquired during the first 470 sols of rover spirit in gusev crater are presented there are two geological regions the gusev plains and the columbia hills the plains contain soils that are very similar to previous landing sites on mars a meteoritic component in the soil is identified rocks in the plains revealed thin weathering rinds the underlying abraded rock was classified as primitive basalt one of these rocks contained significant br that is probably associated with vein filling material of different composition one of the trenches showed large subsurface enrichments of mg s and br disturbed soils and rocks in the columbia hills revealed different elemental compositions these rocks are significantly weathered and enriched in mobile elements such as p s cl or br even abraded rock surfaces have high br concentrations thus in contrast to the rocks and soils in the gusev plains the columbia hills material shows more significant evidence of ancient aqueous alteration

the nature of the groundmass of surficial suevite from the ries impact structure germany and constraints on its origin surficial suevites from the ries impact structure have been investigated in the field and using optical and analytical scanning electron microscopy the groundmass of these suevites comprises calcite clay minerals impact melt glass crystallites plagioclase garnet and pyroxene francolite and ba phillipsite the latter zeolite is a secondary phase abundant textures have been observed intricate flow textures between the various groundmass phases globules of each phase in the other phases spheroids of pyrrhotite in calcite the budding off of clay globules into silicate glass and or calcite euhedral overgrowths of francolite on apatite clasts and quench textured crystallites in the groundmass groundmass forming calcite displays higher feo mno and sio2 contents than limestone target material the composition of suevite clay minerals is highly variable and not always consistent with montmorillonite three types of glasses are distinguished in the groundmass type 1 glasses are sio2 rich and are clearly derived from sandstones in the sedimentary cover while the protoliths of the other two glass types remains unclear analytical data and micro textures indicate that the calcite silicate glass francolite and clay minerals of the groundmass of the ries suevites represent a series of impact generated melts that were molten at the time of and after deposition on cooling plagioclase pyroxene and garnet crystallized from the groundmass these results are at variance with the current traditional descriptive definition of suevite given that ries is the original type occurrence of suevite some modification to the traditional definition may be in order as the results of this study are most consistent with the groundmass of ries surficial suevites representing a mix of several types of impact generated melts we suggest that a possible origin for these suevites is as some form of impact melt flow s that emanated from different regions of the evolving crater

phase equilibrium investigations of the adirondack class basalts from the gusev plains gusev crater mars phase equilibrium experiments have been performed on a synthetic analog of the gusev plains basalt composition from the spirit landing site on mars near liquidus phase relations were determined over the pressure range of 0 1 to 1 5 gpa and at temperatures from 1125 to 1390 c in a piston cylinder apparatus and 1 atm gas mixing furnace the composition is multiply saturated with olivine orthopyroxene and spinel near its liquidus at 1320 c and 1 0 gpa or 85 km depth on mars placing an upper limit constraint on the thickness of the martian lithosphere at the time of eruption our experimental work suggests that the gusev basalts are anhydrous batch melts of a primitive martian mantle similar to the composition estimated by dreibus and wnke 1984 the temperature of multiple saturation indicates the persistence of high mantle potential temperatures on mars similar to those on the modern earth until at least the very latest noachian 3 7 ga these high mantle temperatures would be responsible for persistent basaltic volcanism throughout the southern highlands during the first billion years of mars s history the source for gusev basalts differs strongly from the source for shergottite meteorites reinforcing the idea of the absence of global mantle convection and mixing on mars the existence of a relatively primitive mantle reservoir requires that at least part of the mantle underwent little modification during early planetary differentiation

ries crater and suevite revisited observations and modeling part i observations we report results of an interdisciplinary project devoted to the 26 km diameter ries crater and to the genesis of suevite recent laboratory analyses of crater suevite occurring within the central crater basin and of outer suevite on top of the continuous ejecta blanket as well as data accumulated during the past 50 years are interpreted within the boundary conditions imposed by a comprehensive new effort to model the crater formation and its ejecta deposits by computer code calculations artemieva et al 2013 the properties of suevite are considered on all scales from megascopic to submicroscopic in the context of its geological setting in a new approach we reconstruct the minimum maximum volumes of all allochthonous impact formations 108 116 km3 of suevite 14 22 km3 and the total volume of impact melt 4 9 8 0 km3 produced by the ries impact event prior to erosion these volumes are reasonably compatible with corresponding values obtained by numerical modeling taking all data on modal composition texture chemistry and shock metamorphism of suevite and the results of modeling into account we arrive at a new empirical model implying five main consecutive phases of crater formation and ejecta emplacement numerical modeling indicates that only a very small fraction of suevite can be derived from the primary ejecta plume which is possibly represented by the fine grained basal layer of outer suevite the main mass of suevite was deposited from a secondary plume induced by an explosive reaction fuel coolant interaction of impact melt with water and volatile rich sedimentary rocks within a clast laden temporary melt pool both melt pool and plume appear to be heterogeneous in space and time outer suevite appears to be derived from an early formed melt rich and clast poor plume region rich in strongly shocked components melt clasts and originating from an upper more marginal zone of the melt pool crater suevite is obviously deposited from later formed clast rich and melt poor plumes dominated by unshocked and weakly shocked clasts and derived from a deeper central zone of the melt pool genetically we distinguish between primary suevite which includes dike suevite the lower sublayer of crater suevite and possibly a basal layer of outer suevite and secondary suevite represented by the massive upper sublayer of crater suevite and the main mass of outer suevite

diverse lithologies and alteration events on the rim of noachian aged endeavour crater meridiani planum mars in situ compositional evidence we report the results of geological studies by the opportunity mars rover on the endeavour crater rim four major units occur in the region oldest to youngest the matijevic shoemaker grasberg and burns formations the matijevic formation consisting of fine grained clastic sediments is the only pre endeavour impact unit and might be part of the noachian etched units of meridiani planum the shoemaker formation is a heterogeneous polymict impact breccia its lowermost member incorporates material eroded from the underlying matijevic formation the shoemaker formation is a close analog to the bunte breccia of the ries crater although the average clast sizes are substantially larger in the latter the grasberg formation is a thin fine grained homogeneous sediment unconformably overlying the shoemaker formation and likely formed as an airfall deposit of unknown areal extent the burns formation sandstone overlies the grasberg but compositions of the two units are distinct there is no evidence that the grasberg formation is a fine grained subfacies of the burns formation the rocks along the endeavour crater rim were affected by at least four episodes of alteration in the noachian and early hesperian i vein formation and alteration of preimpact matijevic formation rocks ii low water rock alteration along the disconformity between the matijevic and shoemaker formations iii alteration of the shoemaker formation along fracture zones and iv differential mobilization of fe and mn and caso 4 vein formation in the grasberg and shoemaker formations episodes ii and iii possibly occurred together but i and iv are distinct from either of these

the precambrian turbidite tempestite transition as displayed by the amphibolite facies puolankajarvi formation finland abstract the puolankajarvi formation pjf forms the lowermost unit of the progradational central puolanka group it is at least 2200 ma old metamorphosed to amphibolite facies displays polyphase deformation and is commonly near vertical or overturned the pjf is about 1500 2000 m thick and 30 km in strike length but grades into gneisses both below and at its northern extension thus the original sediments could have been much thicker and perhaps hundreds of kilometres long in strike length the lower part of the pjf consists of graded bedded mica schists and associated massive or graded arkosites at least 500 1000 m thick which represent metamorphosed turbidites deposited by low concentration and high concentration turbidite currents respectively the turbiditic unit is overlain and partly interfingers with semipelitic mica schists containing combined flow origin hummocky cross stratification and related structures indicating that these rocks about 100 200 m thick were originally fine sands and silty muds deposited by storm waves and other shelf processes large scale cross bedded quartzite interbeds at the top of the pjf indicate a progradational change into the overlying akanvaara formation of shallower water origin the pjf shows a change of relatively thin bedded turbidites to tempestites which is interpreted as representing either the distal and middle parts of a relatively steep shelf or the upper slope and the distal middle part of a narrow shelf

determination of planetary basalt parentage a simple technique using the electron microprobe many basaltic meteorites are being discovered in old and new meteorite suites including those from cold deserts e g antarctica and hot desert environments it is important to establish the specific planetary body source proven techniques for establishing planetary parentage include stable isotopic signatures especially oxygen certain elemental ratios in bulk samples and certain elemental ratios in specific minerals some of these techniques are expensive require considerable sample preparation and are adversely affected by weathering processes on the parent body or on earth we have been seeking key major and minor elemental ratios in pyroxene olivine and feldspar that can be measured by the electron microprobe on standard thin sections these ratios may be preserved in unweathered portions of mineral grains and thus see through weathering processes in addition if the sample is too small to provide a representative bulk composition it may still have key information recorded in individual minerals we have found that some of the most useful chemical parameters are fe mn atomic in olivine or pyroxene and the percent anorthite an in plagioclase solid solutions a plot of fe mn in pyroxene and or olivine verses an defines compositional fields that are significantly different for earth mars moon 4 vesta and the angrite parent body this method may be especially powerful when combined with oxygen isotope data

bounce rock a shergottite like basalt encountered at meridiani planum mars additional co authors thanasis economou steven p gorevan brian c hahn gostar klingelhofer timothy j mccoy harry y mcsween jr douglas w ming richard v morris daniel s rodionov steven w squyres heinrich wanke shawn p wright michael b wyatt albert s yen

sedimentary textures formed by aqueous processes erebus crater meridiani planum mars new observations at erebus crater olympia outcrop by the mars exploration rover opportunity between sols 671 and 735 a sol is a martian day indicate that a diverse suite of primary and penecontemporaneous sedimentary structures is preserved in sulfate rich bedrock centimeter scale trough festoon cross lamination is abundant and is better expressed and thicker than previously described examples postdepositional shrinkage cracks in the same outcrop are interpreted to have formed in response to desiccation considered collectively this suite of sedimentary structures provides strong support for the involvement of liquid water during accumulation of sedimentary rocks at meridiani planum

a three component borehole seismometer for earthquake seismology we have developed a three component borehole seismometer using 2 hz electromagnetic moving coil geophones as sensing elements the main achievement of our new borehole package is a compact internal device for leveling horizontal geophones horizontal moving coil geophones with a period longer than 0 5 sec need to be leveled to better than 1 5 to avoid nonlinear response and asymmetric clipping in boreholes where the axis of the package may well deviate from the vertical by more than 1 5 a special device is required for leveling the horizontal geophones a gimbal stage was adapted from the design of ocean bottom seismometers for leveling the two orthogonally oriented horizontal geophones the geophones can be leveled to better than 0 1 from an initial tilt of 10 5 the external package is 14 cm in diameter and approximately 40 cm long the gimbal stage uses free flex flexural pivots and during the leveling operation suspends a brass pendulum that houses the horizontal sensors in comparison with borehole seismometers that use electronic feedback principles the disadvantages of our system are a lack of response at long periods and because of coil contacting stops its inability to record strong motions nonetheless it has an inherently low noise level consumes no power is simple to build and is inexpensive it is therefore suitable for rapid deployment for aftershock studies and for low noise operation at remote sites such seismometers using mark products l 22d 2 hz geophones have been installed at several sites in california at the bottom of adjacent boreholes 150 and 300 m deep in granite at station knw near keenwild and at pinon flat of the anza digital seismic array and at the bottom of an 88 m deep borehole in hydrothermally altered serpentine in the marina district of san francisco the effects of cable impedance on the geophone output have been analyzed and found to be negligible for a cable length of 335 m consisting of four pairs of shielded 20 gauge wires azimuthal orientation of horizontal geophones can be determined using first p arrival particle motion generated by regional earthquakes earthquake data recorded by these borehole seismometers have been employed by several investigators for studies on the effects of near surface weathered rocks on the corner frequencies of earthquake spectra near anza california on the seismic shear wave polarization characteristics of seismograms recorded in the southern california batholith at 300 m depth and on site resonance amplification caused by sedimentary deposits overlying bedrock in the marina district of san francisco

hydrated minerals on endeavour crater s rim and interior and surrounding plains new insights from crism data 1 we have conducted a spectroscopic analysis of the rim and interior of endeavour crater using crism data in order to further constrain the mineralogical variability in the area and to identify targets of interest for in situanalysis by opportunity our analysis reveals that the spectral character of both the sulfates and the phyllosilicates in the area is more diverse than has been reported to date with phyllosilicates present on the rim and interior of endeavour crater as well as on the surrounding plains spectra of the sulfates adjacent to the rim and in the crater s interior mound exhibit features that are consistent with a component of ca sulfates the spectral character of the phyllosilicates is consistent with that of fe mg smectites but there are clear spectral differences between the rim and interior phyllosilicates specifically the phyllosilicates found inside the crater exhibit shallower more rounded fe mg oh bands a subtle 1 9 m hydration band and a strong 1 2 m spectral slope relative to the phyllosilicates on the rim suggesting that they have experienced modification relative to the rim phyllosilicates this modification may be attributed either to alteration via acidic leaching or to dehydration stratigraphically we find that these altered phyllosilicates unconformably overlie the sulfate bearing mound material suggesting that they were emplaced by the reworking of rim phyllosilicates after the interior mound had reached its present day form

hypotheses for the origin of fine grained sedimentary rocks at santa maria crater meridiani planum en route to endeavour crater the mars exploration rover opportunity embarked on a short but significant campaign at santa maria crater during sols 2450 2551 santa maria crater is a relatively young impact crater approximately 100 m in diameter and 11 17 m deep opportunity performed detailed analyses on several ejecta blocks and completed an extensive imaging campaign around the crater many of the ejecta blocks are composed of sandstone with abundant wind ripple laminations suggestive of eolian deposition however other ejecta blocks are massive fine grained and exhibit a nodular texture these rocks are interpreted to be the first rocks of a grain size smaller than the microscopic imager can resolve and may represent the first mudstones observed by the rover several depositional environments are considered for the origin of the fine grained rocks and the observations are best fit by a transient evaporitic lake if the inferred mudstones were deposited in a lacustrine setting then surface water may have been present in a broader range of surface environments than previously documented at meridiani planum

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

bunte breccia of the ries continuous deposits of large impact craters the ries crater an impact structure of 26 km diameter in south germany is the largest terrestrial crater where substantial amounts of ejecta are preserved on occasion 100 m deep further the target stratigraphy is well known and it is possible to relate specific clasts and breccia lithologies to initial target depth as a consequence the continuous deposits of the ries also known as bunte breccia may be studied with exceptional field control we report field observations and laboratory analyses obtained from 560 m core materials taken at nine different locations that range from 16 to 37 km in radial distance from the impact center the objective is to relate the ries observations to ejection and to emplacement processes of large scale planetary crater deposits the observations regarding the modal stratigraphic characteristics of the bunte breccia may be summarized as follows only 600 m some 0 7 is composed of triassic clasts originating from 300 to 600 m depths lower and middle jurassic horizons approximately 300 150 m constitute some 2 3 and upper jurassic 0 150 m makes up some 31 5 in addition the bunte breccia contains tertiary materials in the form of 1 cm clasts 29 1 and as highly comminuted fine grained matrix 10 gpa constitute 0 1 weight of the entire deposit which indicates that bunte breccia was emplaced at essentially ambient temperatures when possible the above observations are quantified via linear regressions throughout the text all of these observations are consistent with if not predicted by a ballistic emplacement scenario as postulated by oberbeck and co workers primary crater ejecta are expelled ballistically and will form secondary craters in the local substrate a mixture of primary and secondary ejecta results and combines into a highly turbulent ground hugging debris surge as the final phase of ejecta emplacement total emplacement time for the bunte breccia 200 km is estimated to be of the order of 5 min only these findings are compared with cratering theory relating to a number of ejecta thickness decay models and with the so called z model addressing material flow during various stages of crater formation qualitative to fair agreement of observations and predictions results an initial crater radius of 6 5 km an excavation depth of 1650 m an excavation volume of 136 km and an associated transient cavity volume of aproximately 230 km appear to be reasonable estimates approximately 170 km of material was involved in slumping and restoration of the transient cavity for the above radius and z 2 7 the modal composition of ries ejecta with regard to preimpact target stratigraphy indicates that materials contained in the continuous deposits of large complex planetary craters are predominantly derived from depths as small as one hundredth the apparent crater diameter a number of implications are addressed regarding remote sensing of planetary surfaces and investigation of lunar and meteoritic impact breccias

phyllosilicates and sulfates at endeavour crater meridiani planum mars 1 phyllosilicates have been identified on the martian surface from orbit and are hypothesized to have formed under wet non acidic conditions early in the planet s history exposures of these minerals have not yet been examined by a landed mission using mars reconnaissance orbiter data we report the detection of phyllosilicate bearing outcrops that may be accessible by the mars exploration rover opportunity currently exploring meridiani planum the phyllosilicates are associated with layered polygonally fractured rocks exposed in the rim of the 20 km diameter crater endeavour these rocks may have formed via regional or global scale processes of aqueous alteration that predated the period of acid sulfate formation recorded in the rocks that opportunity has studied to date detailed characterization by opportunity could better constrain the conditions under which these phyllosilicates formed hydrated sulfates are also detected from orbit in the plains adjacent to endeavour s rim providing the first opportunity for ground truth of these detections

the evolution of the onaping formation at the sudbury impact structure the 1 4 1 6 km thick onaping formation consists of a complex series of breccias and melt bodies lying above the sudbury igneous complex sic at the sudbury impact structure based on the presence of shocked lithic clasts and various glassy phases the onaping has been described as a suevitic breccia with an origin at least in part as fallback material recent mapping and a redefined stratigraphy have emphasized similarities and differences in its various vitric phases both as clast types and discrete intrusive bodies the nature of the onaping and that of other suevitic breccias overlying impact melt sheets is reviewed the relative thickness internal stratigraphic and lithological character and the relative chronology of depositional units indicate multiple processes were involved over some time in the formation of the onaping the sudbury structure formed in a foreland basin and water played an essential role in the evolution of the onaping as indicated by a major hydrothermal system generated during its formation taken together observations and interpretations of the onaping suggest a working hypothesis for the origin of the onaping that includes not only impact but also the interaction of sea water with the impact melt resulting in repeated explosive interactions involving proto sic materials and mixing with pre existing lithologies this is complicated by additional brecciation events due to the intrusion of proto sic materials into the evolving and thickening onaping fragmentation mechanisms changed as the system evolved and involved vesiculation in the formation of the upper two thirds of the onaping

thermodynamic and mass balance constraints on iron bearing phyllosilicate formation and alteration pathways on early mars 1 widespread occurrences of phyllosilicates predominantly nontronite and mg saponite in the noachian aged crust of mars place constraints on water availability and surface conditions however the noachian atmosphere likely lacked oxidants capable of forming nontronite from the basaltic crust and its origins are thus uncertain in this study scenarios for the formation of iron bearing phyllosilicates from the weathering and hydrothermal alteration of martian basalt were investigated using geochemical modeling to establish plausible pathways of nontronite generation and the effect of redox conditions on associated secondary phases hydrothermal alteration produced feii and mg saponite serpentine and zeolites at 100 c and chlorite prehnite and talc at 250 c consistent with phases observed in crater deposits on mars anoxic weathering produced primarily feii and mg saponite high water rock ratios produced al clays and amorphous silica and high pco2 conditions inhibited smectite formation because of carbonate precipitation oxic weathering produced primarily nontronite and mg saponite later oxidation of anoxic weathering products also formed nontronite mg saponite assemblages oxidation products of hydrothermal assemblages included nontronite mg saponite and either al smectites or residual zeolites or prehnite these calculations demonstrate that there are multiple plausible routes to form fe mg smectites on early mars and that an oxidizing atmosphere need not have existed in the noachian decoupling iron oxidation from initial clay formation raises the possibilities that mars transitioned to conditions favoring widespread iron oxidation after phyllosilicate formation ceased and that residual unoxidized ferrous iron phyllosilicates still exist today in the martian subsurface

the evolution of a heterogeneous martian mantle clues from k p ti cr and ni variations in gusev basalts and shergottite meteorites abstract martian basalts represent samples of the interior of the planet and their composition reflects their source at the time of extraction as well as later igneous processes that affected them to better understand the composition and evolution of mars we compare whole rock compositions of basaltic shergottitic meteorites and basaltic lavas examined by the spirit mars exploration rover in gusev crater concentrations range from k poor as low as 0 02 wt k 2 o in the shergottites to k rich up to 1 2 wt k 2 o in basalts from the columbia hills ch of gusev crater the adirondack basalts from the gusev plains have more intermediate concentrations of k 2 o 0 16 wt to below detection limit the compositional dataset for the gusev basalts is more limited than for the shergottites but it includes the minor elements k p ti cr and ni whose behavior during mantle melting varies from very incompatible prefers melt to very compatible remains in the residuum the range in partitioning behavior of these elements provides leverage on interpreting igneous processes models are presented that demonstrate how concentrations of these elements in gusev basaltic magmas would change by simple igneous processes fractional crystallization crustal contamination and mantle partial melting the gusev basalts may be related by two stage batch melting of a primitive k rich mantle source to first generate the k rich columbia hills basalts and second the lower k adirondack basalts leaving behind a k poor residuum the mantle source for the gusev basalts is separate from the more depleted k poorer source region of the shergottites this indicates that primitive k rich mantle persisted until the early hesperian during formation of the columbia hills basalts we suggest that separate mantle reservoirs developed by inhomogeneous partial melting at melt fractions greater than 0 05 to form the martian crust in the first 1 ga of the planet s history

overview of the opportunity mars exploration rover mission to meridiani planum eagle crater to purgatory ripple the mars exploration rover opportunity touched down at meridiani planum in january 2004 and since then has been conducting observations with the athena science payload the rover has traversed more than 5 km carrying out the first outcrop scale investigation of sedimentary rocks on mars the rocks of meridiani planum are sandstones formed by eolian and aqueous reworking of sand grains that are composed of mixed fine grained siliciclastics and sulfates the siliciclastic fraction was produced by chemical alteration of a precursor basalt the sulfates are dominantly mg sulfates and also include ca sulfates and jarosite the stratigraphic section observed to date is dominated by eolian bedforms with subaqueous current ripples exposed near the top of the section after deposition interaction with groundwater produced a range of diagenetic features notably the hematite rich concretions known as blueberries the bedrock at meridiani is highly friable and has undergone substantial erosion by wind transported basaltic sand this sand along with concretions and concretion fragments eroded from the rock makes up a soil cover that thinly and discontinuously buries the bedrock the soil surface exhibits both ancient and active wind ripples that record past and present wind directions loose rocks on the soil surface are rare and include both impact ejecta and meteorites while opportunity s results show that liquid water was once present at meridiani planum below and occasionally at the surface the environmental conditions recorded were dominantly arid acidic and oxidizing and would have posed some significant challenges to the origin of life copyright 2006 by the american geophysical union

mineralogy of volcanic rocks in gusev crater mars reconciling mossbauer alpha particle x ray spectrometer and miniature thermal emission spectrometer spectra 1 complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in gusev crater have been determined by modeling mossbauer subspectral areas as mineral weight percentages and combining those percentages with the proportions of iron free minerals not detected by mossbauer normative plagioclase apatite and chromite as calculated from alpha particle x ray spectrometer apxs chemical analyses comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured miniature thermal emission spectrometer mini tes spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic plagioclase compositions or unmodeled sulfate glass or pigeonite the normative compositions of olivine pyroxene and feldspar calculated from apxs data are consistent with spectroscopic constraints on mineral compositions systematic variations between olivine abundances in apxs norms which sample tens of micrometers depth and olivine proportions measured by mossbauer which sample hundreds of micrometers depth support the hypothesis that dissolution of olivine by acidic fluids has occurred on weathered rock surfaces

geochemical properties of rocks and soils in gusev crater mars results of the alpha particle x ray spectrometer from cumberland ridge to home plate 1 geochemical diversity of rocks and soils has been discovered by the alpha particle x ray spectrometer apxs during spirit s journey over husband hill and down into the inner basin from sol 470 to 1368 the apxs continues to operate nominally with no changes in calibration or spectral degradation over the course of the mission germanium has been added to the spirit apxs data set with the confirmation that it occurs at elevated levels in many rocks and soils around home plate twelve new rock classes and two new soil classes have been identified at the spirit landing site since sol 470 on the basis of the diversity in apxs geochemistry the new rock classes are irvine alkaline basalt independence low fe outcrop descartes outcrop similar to independence with higher fe and mn algonquin mafic ultramafic igneous sequence barnhill volcaniclastic sediments enriched in zn cl and ge fuzzy smith high si and ti rock elizabeth mahon high si ni and zn outcrop and rock halley hematite rich outcrop and rock montalva high k hematite rich rock everett high mg magnetite rich rock good question high si low mn rock and torquas high k zn and ni magnetite rich rock new soil classes are gertrude weise very high si soil and eileen dean high mg magnetite rich soil aqueous processes have played a major role in the formation and alteration of rocks and soils on husband hill and in the inner basin