the global martian volcanic evolutionary history abstract viking mission image data revealed the total spatial extent of preserved volcanic surface on mars one of the dominating surface expressions is olympus mons and the surrounding volcanic province tharsis earlier studies of the global volcanic sequence of events based on stratigraphic relationships and crater count statistics were limited to the image resolution of the viking orbiter camera here a global investigation based on high resolution image data gathered by the high resolution stereo camera hrsc during the first years of mars express orbiting around mars is presented additionally mars orbiter camera moc and thermal emission imaging system themis images were used for more detailed and complementary information the results reveal global volcanism during the noachian period 3 7 ga followed by more focused vent volcanism in three tharsis elysium and circum hellas and later two tharsis and elysium volcanic provinces finally the volcanic activity became localized to the tharsis region about 1 6 ga ago where volcanism was active until very recently 200 100 ma these age results were expected from radiometric dating of martian meteorites but now verified for extended geological units mainly found in the tharsis montes surroundings showing prolonged volcanism for more than 3 5 billions years the volcanic activity on mars appears episodic but decaying in intensity and localizing in space the spatial and temporal extent of martian volcanism based on crater count statistics now provides a much better database for modelling the thermodynamic evolution of mars

lithospheric structure and tectonics at isidis planitia mars abstract we characterize the lithospheric structure of isidis planitia on mars by analyzing mars global surveyor and mars odyssey gravity and topography data using a flexural model of a thin elastic shell including bending and membrane stresses isidis planitia is a circular relatively flat plain formed near the end of the early noachian at the edge of the highlands lowlands boundary and the site of a large free air gravity anomaly features consistent with modification and filling of an impact basin our results suggest that the bulk density of the fill material inside isidis must be more than 2600 kg m 3 and higher densities are probable a comparison of the faulting observed at nili fossae to the predicted zone of extensional strain northwest of isidis constrains the thickness of the elastic lithosphere to be 100 180 km thick beneath the basin at the time of loading we also find that loads outside of the basin play a significant role in the interpretation of the tectonics simplified models tend to overestimate the lithospheric thickness we place relatively narrow bounds on the thermal gradient 3 4 6 5 k km 1 and heat flux 13 6 26 mw m 2 at isidis at the time of loading

composition morphology and stratigraphy of noachian crust around the isidis basin definitive exposures of pristine ancient crust on mars are rare and the finding that much of the ancient noachian terrain on mars exhibits evidence of phyllosilicate alteration adds further complexity we have analyzed high resolution data from the mars reconnaissance orbiter in the well exposed noachian crust surrounding the isidis basin we focus on data from the compact reconnaissance imaging spectrometer for mars as well as imaging data sets from high resolution imagine science experiment and context imager these data show the lowermost unit of noachian crust in this region is a complex brecciated unit of diverse compositions breccia blocks consisting of unaltered mafic rocks together with rocks showing signatures of fe mg phyllosilicates are commonly observed in regions of good exposure layered or banded phyllosilicate bearing breccia rocks are observed suggestive of pre isidis sedimentary deposits in places the phyllosilicate bearing material appears as a matrix surrounding mafic blocks and the mafic rocks show evidence of complex folded relationships possibly formed in the turbulent flow during emplacement of basin scale ejecta these materials likely include both pre isidis basement rocks as well as the brecciated products of the isidis basin forming event at 3 9 ga a banded olivine unit capped by a mafic unit covers a large topographic and geographic range from northwest of nili fossae to the southern edge of the isidis basin this olivine mafic cap combination superimposes the phyllosilicate bearing basement rocks and distinctly conforms to the underlying basement topography this may be due to draping of the topography by a fluid or tectonic deformation of a previously flatter lying morphology we interpret the draping superposed olivine mafic cap combination to be impact melt from the isidis basin forming event while some distinct post isidis alteration is evident carbonate kaolinite and serpentine the persistence of olivine from the time of isidis basin suggests that large scale aqueous alteration processes had ceased by the time this unit was emplaced

morphologic stratigraphic and morphometric investigations of valley networks in eastern libya montes mars implications for the noachian hesperian climate change dendritic valley networks and broad longitudinal valleys are widespread within the eastern libya montes region the morphologic characteristics of the studied dendritic valleys especially their occurrence at local summits provide evidence for the initial formation by surface runoff due to atmospheric precipitation whereas the longitudinal valley systems are thought to have been formed and modified by groundwater induced processes our crater counts and model ages show that the dendritic valley networks average age 4 0 ga formed earlier than the longitudinal valley systems average age 3 7 ga both fluvial forms indicate a temporal change of the erosive environment at the noachian hesperian transition at 3 8 ga our results suggest that the fluvial activity within our investigation area lasted for 800 my from 4 1 ga to 3 3 ga the dendritic valleys show valley densities between 0 12 km 1 and 0 57 km 1 indicative of highly mature and integrated valley systems that we interpret to be characteristic of warmer and wetter conditions on mars

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

the geological history of northeast syrtis major mars abstract as inferred from orbital spectroscopic data northeast syrtis major bears considerable mineral diversity that spans the noachian hesperian boundary despite its small geographic area in this study we use observations from the high resolution imaging science experiment supplemented with context camera imagery to characterize and map the lateral extent of geomorphic units in northeast syrtis major and constrain the geomorphic context of the orbital identified mineral signatures using recent observations we confirm previous mineralogy identified with the compact reconnaissance imaging spectrometer for mars and greatly extend the lateral extent of visible to near infrared investigation utilizing the greater coverage analysis of thermal emission imaging system observations reveals further physical properties and distribution of the geomorphic units the stratigraphy which spans the noachian hesperian boundary displays significant morphological heterogeneity at the decameter scale but it is unifiable under five distinct geomorphic units our paired morphological and mineralogical analysis allows us to construct a detailed geological history of northeast syrtis major several geological events that occurred in northeast syrtis major including the formation of the post isidis crust the emplacement of an olivine rich unit the formation of sulfate minerals and the emplacement of the syrtis major volcanics can be related to regional and global processes constraining the local chronology other mineralogical indicators particularly the formation of al phyllosilicates are difficult to place in the temporal sequence they are observed in isolated patches on the post isidis crust not as a distinct stratigraphic unit as observed elsewhere in nili fossae suggesting their formation via isolated leaching or through alteration of initial compositional heterogeneities within the crust exposures of an olivine rich unit are intermittently observed to form quasi circular landforms suggestive of emplacement in circular depressions which may indicate a period of cratering between the formation of the isidis basin and the deposition of the olivine rich unit we identify and discuss intriguing large linear features of the olivine rich unit reminiscent of dyke fed volcanism that have raised bounding ridges suggestive of contact metamorphism with the crust we compile review and discuss many of the outstanding questions and running hypotheses relevant to our mapping area a synthesis of our geomorphic mapping with recent literature reveals a well defined geological history with extensive aqueous activity at northeast syrtis major that is amassed in a stratigraphic sequence spanning a time likely greater than 250 million years of geological history our geomorphic and spectral analyses confirm that northeast syrtis major exhibits considerable geomorphic and mineralogic diversity within a relatively small geographic area that is representative of the geologic processes occurring throughout the broader nili fossae region during the noachian and hesperian northeast syrtis major adds to this sequence by exposing the diverse environmental history of this region as observed through the presence of alteration minerals not present in this fidelity or proximity elsewhere in nili fossae

transverse aeolian ridges tars on mars aeolian processes are probably the dominant ongoing surface modification process on mars as demonstrated by observations of dunes ripples yardangs ventifacts wind streaks dust devils and dust storms large dark dunes ldds are particularly common and were first recognized in the 1960 s from mariner data however another population of smaller often brighter ripple like aeolian bed forms that are morphologically distinct from ldds has been observed in recent higher resolution images calculations of saltation path length under martian conditions suggest these small bed forms could have formed as small barchanoid dunes or as mega ripples also known as granule ripples these features have therefore been called transverse aeolian ridges tars as this label has no genetic inference we have begun a study of tars that examines all high resolution mars orbiter camera data 1 5 to 8 m pixel resolution in a 45o longitude wide pole to pole swath we aim to determine the geographic distribution of tars assess whether they are active and to identify possible sediment sources we have already made some key observations first we present a new classification of tar deposits based on crest ridge morphology of individual forms and the size and degree of topographic control of the entire sediment mass second we present associations of tars with ldds slope streaks dust devils tracks and small impact craters that provide clues as to whether tars are currently active finally we present preliminary pole to pole survey results for the northern hemisphere that show clusters of tar deposits in the low latitudes suggesting possible unique sediment sources in these regions

dark aeolian sediments in martian craters composition and sources our research focuses on the mineralogical characteristics of dark sediment deposits in martian craters dunes dune fields and sand sheets and their local sediment sources carried out on the basis of 70 selected localities morphological analyses reveal dark layers exposed in a number of crater walls showing indications of material transport from the layers downwall to the intracrater deposits additional sites show dark sediment emerging from several craters floors suggesting a dark material source beneath the crater floor spectral analyses of omega and crism data showed for the first time that a direct mineralogical connection exists between the dark layers in the crater walls and the intracrater dune and sand sheet material based on these findings it is shown that these layers are the local sources for the dark aeolian sediment inside the craters spectral analyses further indicate that all deposits are nearly of the same mafic mineralogical composition hinting at a similar origin we conclude that the mineralogical composition points to a volcanic origin of the material the dark layers which we infer to be the material sources might represent layers of volcanic ash almost globally deposited in early noachian times and subsequently covered by regolith groundwater impact erosion and crustal movement led to the highly fragmented situation of the dark layers today however burial protected the layers of dark sediment from chemical alteration caused by surficial fluvial processes impact erosion after the wet periods on mars led to the exposure and mobilization of the material today

thermophysical properties of the isidis basin mars 1 we investigated the thermal properties of the isidis basin in order to understand the high values 450 j m 2 k 1 s 1 2 located in the southern region of the basin thermal inertia data were compared to a variety of complementary data sets including radar visible and results from mesoscale atmospheric simulations we considered four mechanisms for creating the high thermal inertia including 1 the thinning of a dust mantle 2 the presence of unconsolidated coarse grained material 3 high rock abundance and 4 a high degree of induration induration is the scenario most consistent with the data although we cannot rule out unconsolidated materials and it is likely that rocks contribute to values of thermal inertia to a lesser degree we also investigated three mechanisms for controlling the geographical distribution of the high thermal inertia values including 1 the influence of topography 2 the role of surface morphology and 3 present aeolian processes topography plays a significant role along the southern boundary of the basin but not within the basin itself themis data show a complex relationship between the thermal inertia and morphology the wind patterns modeled by the mars regional atmospheric modeling system mrams are not fully consistent with the wind directions implied by streaks in the thermal data but are consistent with a second group of streaks observed in the visible data this suggests that small scale tens of kilometers streaks observed in the thermal data did not form under present day nominal winds

coordinated spectral and xrd analyses of magnesite nontronite forsterite mixtures and implications for carbonates on mars 1 mineral detection on mars largely relies on laboratory data of minerals and mineral mixtures the objective of this study is to provide reflectance spectra in the visible near infrared vnir and mid ir regions x ray diffraction xrd data and mossbauer spectra of a suite of carbonate phyllosilicate and olivine mixtures in order to facilitate identification and characterization of these minerals on mars remote sensing observations indicate that combinations of these minerals are present in ancient rocks on mars around the isidis basin and in gusev crater magnesite nontronite and forsterite size fractions 125 m were selected for this study results of the vnir reflectance analyses illustrate the complexity of vnir spectra of mixtures analyses of the nir band depths near 2 3 2 5 3 4 and 4 m showed clear trends with carbonate abundance although the data are not linear mixtures of magnesite and nontronite exhibited a band near 2 3 m much closer to that observed for nontronite than that for magnesite vnir analyses of the mixtures indicated that a small amount of forsterite in any of the mixtures contributed a large increase in the broad 1 m band and hence the red slope characteristic of fe2 bearing minerals mid ir mixture spectra were dominated by magnesite and forsterite and nontronite was much more difficult to detect by mid ir spectra in the mixtures this could be related to why phyllosilicates are detected in many locations on mars using data collected by the compact reconnaissance imaging spectrometer for mars but not detected using data collected by the thermal emission spectrometer mossbauer spectroscopy is well suited for analyses of fe2 and fe3 bearing minerals and modeling of the peak areas gave well correlated trends for nontronite and forsterite abundances where abundant fe was present xrd full pattern fitting analyses were performed on the magnesite forsterite series giving results within 6 wt of the actual values with a mean difference between actual and calculated values of 2 4 wt this study provides important laboratory data for characterizing the spectral and xrd properties of mineral mixtures that will facilitate mineral identification on mars carbonates in particular have been primarily observed at low abundances and in small outcrops and they are frequently found mixed with other minerals through analyses of mineral mixtures using multiple data sets this study seeks to provide ground truthing that will enable better coordination of carbonate detections in the dust and rocks of mars

history of the clay rich unit at mawrth vallis mars high resolution mapping of a candidate landing site the mawrth vallis region is covered by some of the largest phyllosilicate rich outcrops on mars making it a unique window into the past history of mars in terms of water alteration potential habitability and the search for past life a landing ellipse had been proposed for the curiosity rover this area has been extensively observed by the high resolution imaging science experiment and the compact reconnaissance imaging spectrometer for mars offering the possibility to produce geologic structural and topographic maps at very high resolution these observations provide an unprecedented detailed context of the rocks at mawrth vallis in terms of deposition alteration erosion and mechanical constraints our analyses demonstrate the presence of a variety of alteration environments on the surface and readily accessible to a rover the presence of flowing water at the surface postdating the formation of the clay rich units and evidence for probable circulation of fluids in the rocks at different depths these rocks undergo continuous erosion creating fresh outcrops where potential biomarkers may have been preserved the diversity of aqueous environments over geological time coupled to excellent preservation properties make the area a very strong candidate for future robotic investigation on mars like the nasa mars 2020 mission

impact generated hydrothermal systems on earth and mars it has long been suggested that hydrothermal systems might have provided habitats for the origin and evolution of early life on earth and possibly other planets such as mars in this contribution we show that most impact events that result in the formation of complex impact craters i e 2 4 and 5 10 km diameter on earth and mars respectively are potentially capable of generating a hydrothermal system consideration of the impact cratering record on earth suggests that the presence of an impact crater lake is critical for determining the longevity and size of the hydrothermal system we show that there are six main locations within and around impact craters on earth where impact generated hydrothermal deposits can form 1 crater fill impact melt rocks and melt bearing breccias 2 interior of central uplifts 3 outer margin of central uplifts 4 impact ejecta deposits 5 crater rim region and 6 post impact crater lake sediments we suggest that these six locations are applicable to mars as well evidence for impact generated hydrothermal alteration ranges from discrete vugs and veins to pervasive alteration depending on the setting and nature of the system a variety of hydrothermal minerals have been documented in terrestrial impact structures and these can be grouped into three broad categories 1 hydrothermally altered target rock assemblages 2 primary hydrothermal minerals precipitated from solutions and 3 secondary assemblages formed by the alteration of primary hydrothermal minerals target lithology and the origin of the hydrothermal fluids strongly influences the hydrothermal mineral assemblages formed in these post impact hydrothermal systems there is a growing body of evidence for impact generated hydrothermal activity on mars although further detailed studies using high resolution imagery and multispectral information are required such studies have only been done in detail for a handful of martian craters the best example so far is from toro crater marzo g a davila a f tornabene l l dohm j m fairen a g gross c kneissl t bishop j l roush t l mckay c p 2010 icarus 208 667 683 we also present new evidence for impact generated hydrothermal deposits within an unnamed 32 km diameter crater 350 km away from toro and within the larger holden crater synthesizing observations of impact craters on earth and mars we suggest that if there was life on mars early in its history then hydrothermal deposits associated with impact craters may provide the best and most numerous opportunities for finding preserved evidence for life on mars moreover hydrothermally altered and precipitated rocks can provide nutrients and habitats for life long after hydrothermal activity has ceased

valleys paleolakes and possible shorelines at the libya montes isidis boundary implications for the hydrologic evolution of mars abstract we describe the results of our morphologic stratigraphic and mineralogic investigations of fluvial landforms paleolakes and possible shoreline morphologies at the libya montes isidis planitia boundary the landforms are indicative of aqueous activity and standing bodies of water including lakes seas and oceans that are attributed to a complex hydrologic cycle that may have once existed on mars in the noachian 3 7 ga and perhaps also in the hesperian 3 1 ga our observations of the libya montes isidis planitia boundary between 85 86 5 e and 1 8 5 n suggest that 1 the termination of valley networks between roughly 2500 and 2800 m coincide with lake size ponding in basins within the libya montes 2 an alluvial fan and a possible delta layered morphologies and associated al phyllosilicates identified within bright polygonally fractured material at the front of the delta deposits are interpreted to be the results of fluvial activity and discharge into a paleolake 3 the arabia shoreline appears as a series of possible coastal cliffs at about 3600 and 3700 m indicating two distinct still stands and wave cut action of a paleosea that temporarily filled the isidis basin the early hesperian and 4 the deuteronilus shoreline appears at 3800 m and is interpreted to be a result of the proposed sublimation residue of a frozen sea that might have filled the isidis basin similar to the vastitas borealis formation vbf identified in the northern lowlands we interpret the morphologic geologic setting and associated mineral assemblages of the libya montes isidis planitia boundary as results of fluvial activity lake size standing bodies of water and an environmental change over time toward decreasing water availability and a cold and dry climate

spectral and petrologic analyses of basaltic sands in ka u desert hawaii implications for the dark dunes on mars dark aeolian bedforms on mars are thought to consist of volcanic materials due to their mineral assemblages which are common to basalts however the sediment source is still debated and needs further affirmation basaltic dunes on earth are rare and can only be found in a few places including new zealand iceland the western usa peru and hawaii these dunes composed of volcaniclastic sediments are promising analogues for providing further insights into the assumed basaltic sand dunes on mars in our study we use basaltic dunes sands collected in hawaii s ka u desert which are especially interesting for addressing the source of martian dunes because of the co occurrence of active volcanic processes and dune development for these dunes we could prove that their material has been derived from airfall ashes from phreatomagmatic eruptions of kilaulea and reworked lava basaltic dunes sand from arizona builds a second set of terrestrial analogue samples in our study these sands have been collected from aeolian bedforms that are composed of reworked volcanic ash erupted from nearby sinter cones spectral analyses of the terrestrial samples show that the dune sands are enriched in pyroxene and olivine a basaltic composition similar to that of the martian dark dunes microprobe analyses show that the terrestrial sands are dominated by olivine pyroxene plagioclase and glasses resulting from the volcanic source of these aeolian sediments this result is consistent with modal mineralogy modeling of martian dunes sands these correlations prove the hypothesis of a similar origin of the martian and terrestrial dune sands consistent with reworked volcanic ash and lava

interaction of katabatic winds and near surface temperatures in the antarctic 1 a two dimensional mesoscale model was applied to simulate wintertime katabatic winds in the antarctic coastal region simulations were made for a constant slope angle with the slope height varying and for fixed slope heights with the slope angle varying thermal wind opposed the katabatic flow near the foot of the slope but enhanced it over the high plateau the steeper and higher the slope the stronger the effect on the plateau the 2 m potential temperature decreased down the slope toward sea ice because 1 the katabatic wind resulted in the accumulation of cold near surface air over the sea ice and the lower parts of the slope 2 over the flat sea ice zone the stratification was stronger and 3 the shallow slope was within the strong surface inversion from over the sea ice with a slope aspect ratio of 5 m km 1 and a slope height below 1000 m 2 m temperature t2m decreased down the slope but for slope heights of 1500 m and more t2m increased down the slope adiabatic warming and because of the stronger wind enhanced turbulent mixing of the warmer air from aloft contributed to the warming for slope angles ranging from 1 to 20 m km 1 with a small slope height of 500 m t2m decreased down the slope but not monotonically whereas with a slope height of 2000 m yielding stronger winds and larger adiabatic warming t2m increased monotonically down the slope the model results were supported by observations from several antarctic sites with different topographic conditions

the western libya montes valley system on mars evidence for episodic and multi genetic erosion events during the martian history a valley network in the western libya montes region extending from 80 e to 83 4 e and 1 2 s to 3 9 n exhibits significant detail about water release processes and duration of erosional activities the valley system originates at the southeastern offshoot of syrtis major and drains down to isidis planitia over a distance of about 300 km midstream the valley network splits into a shorter eastern and a longer western part for most of its length the valley exhibits an interior channel which allows constraining discharges ranging from 15 000 m3 s to 430 000 m3 s and yielding sediment volumes up to 250 tons s based on stratigraphic relations the valley system evolved during a period of about 2 8 billion years with major wet episodes in the noachian 4 1 ga the hesperian 3 6 to 3 0 ga and the amazonian 2 8 to 1 4 ga while precipitation dominated the fluvial activity during the noachian era as indicated by dendritic drainage pattern the close correlation of lava deposits and valley source regions suggests that volcanic processes such as ground ice melting and or hydrothermal water release might have played a major role during the hesperian and amazonian fluvial activities in addition multiple volcanic events in the hesperian and amazonian ages show that syrtis major was active at least locally until 1 4 ga ago discharge estimates demonstrate a significant increase from precipitation induced to volcanic triggered water release fluvial erosion rates discharges sediment transport rates and the lack of any widespread chemical alteration products such as sulphates and phyllosilicates that are indicative for large long lasting standing bodies of water suggest relatively short valley formation times of only a few thousands of years compared with the total age of the valley system short episodic water release events separated by long dry and inactive periods of some hundreds of millions of years at least in the hesperian and amazonian seem to be more realistic rather than a continuous flow the youngest channel segment dates back to less than 1 4 ga this indicates the presence of surface runoff at that time which required atmospheric conditions that support water to be stable on the surface even late in martian history in summary the western libya montes valley system demonstrates episodic and multi genetic erosion events over most of the martian history with a clear change in the erosion style from precipitation to volcanic triggered water release during the early hesperian

inverted channel deposits on the floor of miyamoto crater mars morphological features on the western floor of miyamoto crater in southwestern meridiani planum mars are suggestive of past fluvial activity imagery from the high resolution imaging science experiment hirise gives a detailed view of raised curvilinear features that appear to represent inverted paleochannel deposits the inverted terrain appears to be capped with a resistant dark toned deposit that is partially covered by unconsolidated surficial materials subsequent to deposition of the capping layer erosion of the surrounding material has left the capping materials perched on pedestals of uneroded basal unit material neither the capping material nor the surrounding terrains show any unambiguous morphological evidence of volcanism or glaciation the capping deposit may include unconsolidated or cemented stream deposits analogous to terrestrial inverted channels in the cedar mountain formation near green river utah in addition to this morphological evidence for fluvial activity phyllosilicates have been identified in the basal material on the floor of miyamoto crater by orbital spectroscopy providing mineralogical evidence of past aqueous activity based on both the morphological and mineralogical evidence miyamoto crater represents an excellent site for in situ examination and sampling of a potentially habitable environment

postmineralization faults in the beaufor gold deposit abitibi greenstone belt canada geometry origin and tectonic implications for the val d or mining district the beaufor mine is a mesothermal vein type gold deposit hosted by the bourlamaque pluton a synvolcanic intrusion crosscutting archean volcanic rocks of the abitibi greenstone belt in the val d or mining district the auriferous system is related to south dipping reverse shear zones and consists of up to 2 m wide sheared and extensional sulfide rich quartz veins the auriferous veins system is crosscut by two generations of faults east west trending south dipping 60 brittle ductile reverse faults e g the dike 01 central fault system and subvertical to steeply north dipping brittle faults e g the beaufor fault system the dike 01 central fault system presents structural fabrics kinematic and hydrothermal characteristics similar to those of auriferous shear zones both are interpreted as master faults and secondary structures respectively with the dike 01 central fault system acting as a channelway for the updip draining of ore fluids that were mainly trapped in low angle synthetic shear zones incremental deformation and progressive decrease of bulk fluid pressure led to strain localization and faulting of auriferous quartz veins by the dike 01 central fault system the beaufor fault system crosscuts all structures of the beaufor deposit it consists of a series of oblique reverse dextral faults that lack evidence for pervasive hydrothermal alteration the main structure of that system is the east west trending north dipping beaufor fault which is associated with northeast southwest trending synthetic i e west shear faults and north south trending antithetic faults i e post ore faults fault zones of the beaufor mine are reminiscent of large scale tectonics in the val d or mining camp auriferous quartz tourmaline vein deposits are commonly associated with east west trending high angle reverse shear zones and hydrothermal events coeval with or slightly postdating peak metamorphism and regional deformation several fault zones of the val d or area preserve evidence for both reverse shearing and dextral strike slip faulting structures recorded in the beaufor mine suggest that reverse and dextral trancurrent faulting is genetically unrelated and probably resulted from sequential faulting rather than transpression

mud volcanism and morphology of impact craters in utopia planitia on mars evidence for the ancient ocean abstract results of our detailed geological mapping and interpretation of the nature and relative and absolute model ages of units and structures in the sw portion of utopia planitia 20 45 n 100 120 e suggest the following 1 the size frequency distribution sfd of craters that both are buried by materials of the vastitas borealis units vb and superpose its surface indicate that the absolute model ages of terrain predating the emplacement of the vb is 3 7 ga 2 lack of craters that are partly embayed by materials of the vb in the sw portion of utopia planitia implies that the emplacement of the vb was faster than the rate of accumulation of impact craters and is consistent with the geologically short time of emplacement of the vb due to catastrophic release of water from outflow channels e g carr m h 1996 water on mars oxford university press new york p 229 3 the sfd of craters that superpose the surface of the vb indicates an absolute model age of 3 6 3 5 ga the absolute model ages of etched flows which represent the upper stratigraphic limit of the vb are estimated to be 3 5 ga 4 the majority of the larger i e 1 km impact craters show ejecta morphologies rampart and pancake like ejecta that are indicative of the presence of ice water in the target materials the distal portions of the pancake like ejecta are heavily degraded not due to embayment this suggests that these craters formed in targets that contained higher abundances of volatiles 5 the diameter ranges of the craters with either rampart or pancake like ejecta are overlapping from 2 to 60 km craters with pancake like ejecta are concentrated within the central portion of the utopia basin less than 1000 km from the basin center and rampart craters occur at the periphery of the basin this pattern of the crater spatial distribution suggests that materials within the center of utopia planitia contained more ice water 6 etched flows around the central portion of utopia planitia were erupted from beneath of the surface of the vb their morphology and pattern of degradation however are inconsistent with lava and instead indicate formation of the flows due to mud volcanism 7 etched flows are spatially associated with giant polygons and there is evidence that these features populated the center portion of utopia planitia before it was covered by the elysium derived units the outer southern edge of the zone of polygonal troughs and etched flows approximately corresponds to the transition from pancake like ejecta to rampart ejecta this suggest that the outer edge of the zone of the polygons and flows may outline the deeper portions of the large body 2000 km across of water ice that likely existed in the center of utopia planitia in late hesperian

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

hydrothermal formation of clay carbonate alteration assemblages in the nili fossae region of mars abstract the compact reconnaissance imaging spectrometer for mars crism has returned observations of the nili fossae region indicating the presence of mg carbonate in small

surface and crater exposed lithologic units of the isidis basin as mapped by coanalysis of themis and tes derived data products 1 the stratigraphy and mineral heterogeneity of surface and crater exposed deposits in the southwestern portion of the isidis basin were investigated using spatial spectral visible and thermophysical data sets from both the mars global surveyor and odyssey missions four themis spectral surface units were identified progressing from the libya montes highlands to the inner lowland plains of isidis planitia lithologic determinations of these spectral units were made by linear deconvolution analysis of tes data olivine rich surface materials correlate with a well documented high thermal inertia unit based on spatial and stratigraphic relationships interpreted from both crater exposed and surface exposures the olivine rich unit was determined to have formed subsequent to the isidis basin forming event morphology occurrence and linear deconvolution of this unit suggests that it may represent noachian age to hesperian age picritic lavas that erupted as early stage lavas originating from sources such as syrtis major beneath isidis and as far as tyrrhena patera these lavas are suggested to have partially filled the basin based on crater exposed occurrences and were subsequently buried by further evolved olivine poor lavas later these lavas were exposed by erosion and subsequent impacts into the basin crater scaling suggests significant infilling of the basin by these lavas that may account for craters with very high d d ratios and the well developed positive mass anomaly associated with the basin this study also demonstrates that the remote sensing of impact craters in conjunction with surface mapping is a potent mapping tool for understanding stratigraphy and the petrogenesis of the martian crust

extensive noachian fluvial systems in arabia terra implications for early martian climate valley networks are some of the strongest lines of evidence for extensive fluvial activity on early noachian 3 7 ga mars however their purported absence on certain ancient terrains such as arabia terra is at variance with patterns of precipitation as predicted by warm and wet climate models this disagreement has contributed to the development of an alternative icy highlands scenario whereby valley networks were formed by the melting of highland ice sheets here we show through regional mapping that arabia terra shows evidence for extensive networks of sinuous ridges we interpret these ridge features as inverted fluvial channels that formed in the noachian before being subject to burial and exhumation the inverted channels developed on extensive aggrading flood plains as the inverted channels are both sourced in and traverse across arabia terra their formation is inconsistent with discrete localized sources of water such as meltwater from highland ice sheets our results are instead more consistent with an early mars that supported widespread precipitation and runoff

the geological history of nili patera mars nili patera is a 50 km diameter caldera at the center of the syrtis major planum volcanic province the caldera is unique among martian volcanic terrains in hosting i evidence of both effusive and explosive volcanism ii hydrothermal silica and iii compositional diversity from olivine rich basalts to silica enriched units we have produced a new geological map using three mosaicked 18 m pixel context camera digital elevation models supplemented by compact remote imaging spectrometer for mars hyperspectral data the map contextualizes these discoveries formulating a stratigraphy in which nili patera formed by trapdoor collapse into a volcanotectonic depression the distinctive bright floor of nili patera formed either as part of a felsic pluton exposed during caldera formation or as remnants of welded ignimbrite s associated with caldera formation both scenarios deriving from melting in the noachian highland basement after caldera collapse there were five magmatic episodes 1 a basaltic unit in the caldera s north 2 a silica enriched unit and the associated nili tholus cone 3 an intrusive event forming a 300 m high elliptical dome 4 an extrusive basaltic unit emplaced from small cones in the east and 5 an extreme olivine bearing unit formed on the western caldera ring fault the mapping together with evidence for hydrated materials implies magmatic interaction with subsurface volatiles this in an area of elevated geothermal gradient presents a possible habitable environment sampled by the hydrothermal deposits additionally similarities to other highland volcanoes imply similar mechanisms and thus astrobiological potential within those edifices

occurrence of authigenic beidellite in the eocene transitional sandy sediments of the chu saryssu basin south central kazakhstan abstract this paper describes the petrographic properties and the clay mineralogy of eocene sandy sediments of the chu saryssu basin south central kazakhstan in which dioctahedral smectite formed during shallow burial diagenesis eogenesis evidence from petrography and clay mineralogy supports the successive occurrence of kaolinite and dioctahedral smectite during the eogenetic processes which may have resulted from a change from wet and humid to semi arid or arid climatic conditions an original result of this study is the predominantly beidellitic nature of the authigenic smectite which was determined via x ray diffraction xrd using the hofmann klemen test and fourier transform infrared spectroscopy ftir investigations and chemical microanalysis the crystal chemical investigations indicate a rather homogeneous chemical composition of the smectite at the regional scale and the following unit formula is proposed si4 3 65al3 0 35 al3 1 65fe3 0 21mg2 0 14 o10 oh 2na 0 10mg2 0 11ca2 0 04k 0 07 this type of smectite has been interpreted as representative of mixed layers of montmorillonite and beidellite the fact that the smectite that formed primarily in the unconsolidated sandy sediments is close to beidellite rather than montmorillonite may have a major impact on the rate of further illitization in the chu saryssu basin indeed the crystal chemistry of beidellite is more favorable to illitization and the presence of this mineral provides new insights concerning the different rates of illitization between sandstones and shale formations observed worldwide

widespread surface weathering on early mars a case for a warmer and wetter climate abstract early mars 3 ga underwent aqueous alteration as evidenced by fluvial lacustrine morphologies and the recent discovery of widespread hydrous clays despite compelling evidence for diverse and localized aqueous environments the possibility for sustained liquid water globally on the martian surface and over geological timescales is still highly debated instead a durably cold and dry mars scenario is often proposed by studying specific fe mg and al rich clay stratigraphies on mars by means of a planetary scale orbital investigation we present new evidence that mars experienced an early era 3 7 ga of widespread aqueous alteration consistent with surface weathering

elevated bulk silica exposures and evidence for multiple aqueous alteration episodes in nili fossae mars abstract the nili fossae region of mars contains some of the most mineralogically diverse bedrock on the planet previous studies have established three main stratigraphic units in the region a phyllosilicate bearing basement rock a variably altered olivine rich basalt and a capping rock here we present evidence for the localized alteration of the northeast nili fossae capping unit previously considered to be unaltered both near infrared and thermal infrared spectral datasets were analyzed including the application of a method for determining the relative abundance of bulk silica sio 2 over surfaces using thermal emission imaging system themis images elevated bulk silica exposures are present on surfaces previously defined as unaltered capping rock given the lack of spectral evidence for phyllosilicate hydrated silica or quartz phases coincident with the newly detected exposures the elevated bulk silica may have formed under a number of aqueous scenarios including as a product of the carbonation of the underlying olivine rich basalt under moderate water rock scenarios and temperatures regardless of formation mechanism the detection of elevated bulk silica exposures in the nili fossae capping unit extends the history of aqueous activity in the region to include all three of the main stratigraphic units

revised crism spectral parameters and summary products based on the currently detected mineral diversity on mars the investigation of hyperspectral data from the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism and the observatoire pour la mineralogie l eau les glaces et l activitie omega on mars express has revealed an increasingly diverse suite of minerals present on the martian surface a revised set of 60 spectral parameters derived from corrected spectral reflectance at key wavelengths in crism targeted observations and designed to capture the known diversity of surface mineralogy on mars is presented here as summary products some of the summary products have strong heritage to omega spectral parameter calculations this paper also presents newly derived parameters that highlight locations with more recently discovered spectral signatures type locations for the diversity of currently identified mineral spectral signatures have been compiled into a library presented in this work our analysis indicates that the revised set of summary products captures the known spectral diversity of the surface and successfully highlights and differentiates between locations with differing spectral signatures the revised spectral parameter calculations and related products provide a useful tool for scientific interpretation and for future mission landing site selection and operations

updated global map of martian valley networks and implications for climate and hydrologic processes 1 martian valley networks have long been viewed as some of the best evidence of prolonged surface water on mars analysis from viking data showed that valleys were primarily contained on the ancient crust drainage networks were immature and large undissected regions occurred in between individual systems these observations led many to propose that they formed primarily by groundwater processes and limited or no climate change from the present state was required using more recent and higher resolution data sets including visible infrared and topographic data we have manually remapped valleys on a global scale more than eight times as many valleys have been identified on the surface and calculated drainage densities are on average higher by a factor of 2 further regions previously thought to be undissected have significant incision by fluvial processes most of these systems seem to have formed around the noachian hesperian boundary 3 8 3 6 ga minor valley formation continued through the hesperian and into the early amazonian epoch approximately 2 8 ga ago the new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels terraces multiple periods of formation complex network morphology and correlation with other fluviosedimentary features and chloride salts on mars groundwater processes or a transient steam atmosphere generated by impacts played at most a minor role these new results imply that mars had a long lived period or periods of clement conditions toward the end of the noachian epoch that supported a hydrologic cycle and potentially a biosphere

geology of central libya montes mars aqueous alteration history from mineralogical and morphological mapping abstract we analyze the emplacement chronology and aqueous alteration history of distinctive mineral assemblages and related geomorphic units near hashir and bradbury impact craters located within the libya montes which are part of the southern rim of the isidis basin on mars we derive our results from a spectro morphological mapping project that combines spectral detections from crism near infrared imagery with geomorphology and topography from hrsc ctx and hirise imagery through this combination of data sets we were able to use the morphology associated with specific mineral detections to extrapolate the possible extent of the units hosting these compositions we characterize multiple units consistent with formation through volcanic impact hydrothermal lacustrine and evaporative processes altered pyroxene bearing basement rocks are unconformably overlain by an olivine rich unit which is in turn covered by a pyroxene bearing capping unit aqueously altered outcrops identified here include nontronite saponite beidellite opal and dolomite the diversity of mineral assemblages suggests that the nature of aqueous alteration at libya montes varied in space and time this mineralogy together with geologic features shows a transition from noachian aged impact induced hydrothermal alteration and the alteration of noachian bedrock by neutral to slightly basic waters via hesperian aged volcanic emplacements and evaporative processes in lacustrine environments followed by amazonian resurfacing in the form of aeolian erosion

redefinition of the crater density and absolute age boundaries for the chronostratigraphic system of mars abstract for the boundaries of each chronostratigraphic epoch on mars we present systematically derived crater size frequencies based on crater counts of geologic referent surfaces and three proposed standard crater size frequency production distributions as defined by a a simple 2 power law b neukum and ivanov c hartmann in turn these crater count values are converted to model absolute ages based on the inferred cratering rate histories we present a new boundary definition for the late hesperian early amazonian transition our fitting of crater size frequency distributions to the chronostratigraphic record of mars permits the assignment of cumulative counts of craters down to 100 m 1 km 2 km 5 km and 16 km diameters to martian epochs due to differences in the standard crater size frequency production distributions a generalized crater density based definition to the chronostratigraphic system cannot be provided for the diameter range used for the boundary definitions the resulting model absolute age fits vary within 1 5 for a given set of production function and chronology model ages crater distributions translated to absolute ages utilizing different curve descriptions can result in absolute age differences exceeding 10

mineralogy and morphology of geologic units at libya montes mars ancient aqueously derived outcrops mafic flows fluvial features and impacts 1 there is ample evidence of both ancient and long lasting fluvial activity and chemical alteration in the libya montes region south of isidis basin the region hosts noachian to amazonian aged surface rocks with extensive outcrops of olivine and pyroxene bearing material libya montes also features surface outcrops and or deposits hosting fe mg smectite fe mg smectite mixed with carbonate and or other fe mg rich phyllosilicates and al smectite these units likely formed through chemical alteration connected with hydrothermal activity resulting from the formation of the isidis basin and or the pervasive fluvial activity throughout this region the morphology and stratigraphy of the aqueous and mafic minerals are described using high resolution imaging science experiment and high resolution stereo camera derived digital terrain models analyses of the compact reconnaissance imaging spectrometer for mars spectra show variations in the chemistry of the fe mg smectite from nontronite like exposures with spectral features near 2 29 and 2 4 m more consistent with fe3 2oh groups in the mineral structure and saponite like outcrops with spectral features near 2 31 and 2 38 m characteristic of mg2 3oh groups these fe mg smectite bearing materials also have bands near 1 9 m due to h2o and near 2 5 m that could be due to the smectite other phyllosilicates and carbonates all regions exhibiting carbonate features near 3 4 3 5 m also have features consistent with the presence of olivine and fe mg smectite indicating that the carbonate signatures occur in rocks likely containing a mixture of these minerals the al smectite bearing rocks have bands near 1 41 1 91 and 2 19 m that are more consistent with beidellite than other al phyllosilicates indicating a higher temperature or diagenetically processed origin for this material our interpretation of the geologic history of this region is that ancient noachian basaltic crustal materials experienced extensive aqueous alteration at the time of the isidis impact during which the montes were also formed followed by emplacement of a rough olivine rich lava or melt and finally the smooth pyroxene bearing caprock unit

topography of mars from global mapping by hrsc high resolution digital terrain models and orthoimages characteristics and performance abstract we report on the results of the mars express high resolution stereo camera hrsc experiment pertaining to one of its major aims mapping the surface of mars by high resolution digital terrain models dtm up to 50 m grid spacing and orthoimages up to 12 5 m resolution we introduce the specifications and characteristics of these data products and give an overview of the procedures that have been developed and are applied for their derivation we also address the performance characteristics of the mapping project related to different aspects of internal accuracy accuracy with respect to the global reference system and regional aspects using adaptive processing techniques for terrain reconstruction and a revised approach to the improvement of orientation data a mean precision of the resulting 3d points of about 12 m is obtained exceeding the mean ground resolution of the stereo images using mars orbiter laser altimeter mola data the hrsc models are firmly tied to the global reference system at the scale of the hrsc dtm grid spacing in the lateral dimension and to within few meters vertically hrsc high resolution dtms are typically generated using a grid size of about 2 times the mean ground resolution but usually not larger than 3 times the mean ground resolution and not smaller than 3 times the precision of the integrated 3d points derived from stereo image analysis statistically every grid cell is based on at least one measured 3d point thus horizontal dtm resolution is well established with regard to the precision and density of the derived 3d points while the concurrent aim of a detailed terrain representation at maximum possible resolution is pursued comparison with the dtm derived from mola data allows us to identify specific advancements related to this updated view of martian topography we also address the mapping performance of hrsc in comparison to mola with respect to latitude and to different surface types and morphologies finally comparison with mola highlights typical complementarities of the two different approaches for mapping planetary surfaces

stratigraphy in the mawrth vallis region through omega hrsc color imagery and dtm abstract the mawrth vallis region contains an extensive at least 300 km 400 km and thick 300 m finely layered at meter scale clay rich unit detected by omega we use omega hrsc dtms derived from stereoscopic imagery hrsc color imagery and high resolution imagery such as moc ctx and hirise to characterize the geometry and the composition of the clay rich unit at the regional scale our results show that the clay bearing unit can be divided into sub units on the basis of differences in color and composition in false color visible imagery alternating white bluish and orange red colored units correspond to a compositional succession of respectively al and fe or mg phyllosilicate rich material geological cross sections are presented along the principal outcrops of the region in order to define the stratigraphy of these sub units this method shows that the dips of the sub units are frequently close to the slopes of the present topography except for scarps visible at the dichotomy boundary inside impact craters walls and outcrops inside mawrth vallis in addition to the al and fe or mg phyllosilicate rich sub units an altered surface is identified as the lower basement unit we propose two possible end member scenarios to explain the derived stratigraphy 1 alteration of volcaniclastic aeolian or aqueous layered deposits of various compositions by groundwater resulting in distinct altered rocks or 2 alteration coeval with the deposition of sediments under varying chemical conditions in wet pedodiagenetic environment

an impact origin for hydrated silicates on mars a synthesis 1 recent mars orbiting spectrometers continue to detect surface materials containing hydrated silicates particularly clays and amorphous phases e g silica glasses concentrated within the heavily cratered noachian highlands crust this paper provides a review summary and synthesis of observations from terrestrial impact structures with current martian data it is suggested that numerous and frequent impacts into the volatile rich silicate crust of mars through direct and indirect impact generated mechanisms represent a plausible hypothesis that can explain the widespread distribution of hydrated silicates in the surface and subsurface of the heavily cratered noachian highlands crust largely independent of climate in addition to impact generated hydrothermal activity devitrification autometamorphism and the voluminous production of impact damaged materials that are susceptible to alteration must be considered when taken together a drastically different early climate on mars in which water is stable at the surface for extended periods of time cannot be ruled out however it is noted here that these additional impact mechanisms can operate and thereby extend the range of possible alteration settings to include climate conditions that may have been predominately colder and drier such a climate would not be dissimilar to the conditions of today with the important exceptions of a higher geothermal gradient and punctuated thermal disturbance to the cryosphere and hydrosphere from igneous activity and an exponentially higher impact flux

orbital identification of carbonate bearing rocks on mars geochemical models for mars predict carbonate formation during aqueous alteration carbonate bearing rocks had not previously been detected on mars surface but mars reconnaissance orbiter mapping reveals a regional rock layer with near infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the nili fossae region the carbonate is closely associated with both phyllosilicate bearing and olivine rich rock units and probably formed during the noachian or early hesperian era from the alteration of olivine by either hydrothermal fluids or near surface water the presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering proposed to be characteristic of hesperian mars did not destroy these carbonates and thus did not dominate all aqueous environments

geology and mer target site characteristics along the southern rim of isidis planitia mars 1 the southern rim of the isidis basin contains one of the highest densities of valley networks several restricted paleolake basins and the stratigraphically lowest oldest terrain on mars geologic mapping in viking mgs moc and mola data odyssey themis data and other multispectral data products supports the presence of extensive fans of debris and sediments deposited along the inner rim of the isidis basin where large valleys enter the lowlands additional processes subsequent to the period of intense fluvial activity including mass flow analogous to some glacial processes have contributed to the materials accumulated on the margins of the isidis basin these have occurred along preexisting channels and valleys at the termini of major channels where they enter the plains along the highland lowland boundary if the abundant valley networks in highland terrains are the result of runoff accompanied by saturated groundwater flow as has been suggested in previous studies of ancient fluvial highland terrains then the extreme age and abundance of early valley networks in the libya montes highland rocks should have resulted in deposition of materials that record evidence for the long term presence of water in the form of aqueous alteration of polycrystalline constituents the material deposited along the basin margin is likely to consist of ancient altered highland rocks in several physical states weathered rounded and angular exposing both weathered and altered surfaces and exposures of alteration profiles in fractured faces and unweathered material from rock interiors debris fans shed off the southern rim of isidis planitia should contain materials that have experienced possible saturated groundwater flow residence within paleolake basins and derivative materials deposited during the most fluvially intensive part of martian geologic history many of these materials have also been reworked by ice related processes in situ measurements of the ancient crustal materials in the form of rocks within the debris fans and the weathered condition of the rocky material are potential sources for mineralogical evidence of climatic conditions in earliest martian geologic history the absence of alteration within rocks would on the other hand support the hypothesis that fluvial runoff during the earliest history of mars was geologically brief rather than long term and that long term saturated groundwater flow was not present determination of the presence or absence of alteration would have corresponding implications for hypotheses requiring the long term presence of aqueous solutions i e complex organic compounds and life a proposed mer site along the margin addresses realistic field science objectives of the mars exploration rover mission and the current goals of the mars exploration program in situ measurements may be important in deriving estimates of the longevity and intensity of past wetter climates

evidence for extensive olivine rich bedrock on mars color infrared observations of an area around the nili fossae acquired by the mars odyssey thermal emission imaging system have been used to map the regional distribution and geologic context of olivine rich materials that first were identified from mars global surveyor thermal emission spectrometer data spectral thermal geomorphic and topographic data demonstrate that the majority of olivine rich material is in the form of inplace layered rock covering an area roughly four times larger than previously recognized some high olivine concentrations are associated with spatially small areas dominated by sediments we favor olivine rich basalts as the origin of the observed olivine enrichment although several hypotheses are viable

an in situ record of major environmental transitions on early mars at northeast syrtis major the noachian hesperian transition on mars was a period marked by changes in volcanic processes and styles of aqueous alteration understanding the timing and nature of environmental change requires the exploration of units recording both sets of processes herein we report the compositional stratigraphy of distinctive noachian to hesperian units along the northeastern margin of the syrtis major volcanic flows a layered polyhydrated sulfate bearing unit with jarosite ridges has been discovered beneath the syrtis major lava flows and above the regionally extensive stratigraphy of noachian plains units reported previously sequential clay carbonate and sulfate bearing units formed in situ and record a transition from alkaline ph to acidic ph waters the sequence is chronologically bookended by the isidis impact and syrtis major flows and is one of the most temporally constrained and well preserved stratigraphic sections from early mars available for landed exploration

major episodes of geologic history of isidis planitia on mars abstract we have mapped the area of isidis planitia 1 27 n 75 103 e in order to assess the geologic history of this region using modern data sets such as mola topography and the high resolution images provided by the hrsc ctx and hirise cameras results of our mapping show that the geologic history of isidis planitia consists of three principal episodes 1 impact dominated episode noachian until 3 8 ga during this time the oldest materials in the study area were formed mostly by impact reworking and mass wasting other processes e g volcanism and fluvial glacial activity likely operated at this time but played a subordinate role 2 an episode related to volcanic and fluvial glacial activities late noachian early amazonian 3 8 2 8 ga volcanism appears as the most important process at the beginning of this episode 3 8 3 5 ga and was responsible for the formation of a large circum isidis volcanic province by the early hesperian epoch volcanic materials covered large portions of the isidis rim almost completely buried the previous crater record on the floor of the isidis basin and probably were the major contributors to the filling of the basin fluvial glacial processes prevailed closer to the end of the episode early hesperian early amazonian 3 5 2 8 ga and were responsible for widespread resurfacing in the isidis planitia region mostly at 3 1 3 4 ga glaciers and or ice sheets probably resulted in a massive glaciation of the rim and the floor of the isidis basin the total volume of material eroded from the isidis rim by glacial and fluvial activity is estimated to be about 35 000 50 000 km 3 which is equivalent to a composite layer about 40 60 m thick on entire floor of the basin more important however is that the eroded materials were likely saturated with ice water and could form wet deposits on the floor 3 wind dominated episode since early amazonian 2 8 ga wind activity dominated the later geologic history of isidis planitia but resulted only in minor modification of the surface

implications for early hydrothermal environments on mars through the spectral evidence for carbonation and chloritization reactions in the nili fossae region 1 previous identification of serpentine and magnesium carbonate in the eastern nili fossae region of mars indicates hydrothermal alteration of an olivine rich protolith here we characterize fe mg phyllosilicates associated with these units and present spectral evidence for the presence of a talc component distinguishable from saponite locations with magnesium carbonate are exclusively associated with talc related phyllosilicates in the westernmost portions of the nili fossae region where a mafic protolith dominates fe mg phyllosilicates display spectral evidence for a wide degree of chloritization we propose that noachian fe mg smectites were uniformly buried by hesperian lava flows that initiated hydrothermal alteration in the eastern nili fossae region the chloritization of smectites may have produced silica rich fluids necessary for the serpentinization of olivine temperature and depth constraints indicated by their distribution also suggest a hydrothermal system was present the subsequent carbonation of serpentine and or olivine in eastern nili fossae while requiring an additional co2 source provides an explanation for the limited occurrence of serpentine and the colocation of carbonate and talc bearing material throughout this area the consequence of the hypothesized carbonation reaction and the presence of serpentine provides geochemical constraints for the proportion of co2 present in the fluids that interacted with the protolith if this carbonation reaction was a widespread phenomenon it may have been an important process in the ancient martian carbon cycle and could have provided a sink for co2 in the past

compositional and structural constraints on the geologic history of eastern tharsis rise mars abstract identification and mapping of distinct compositional units using high resolution orbital imagery of the walls of valles marineris mars provide key structural and environmental constraints on the geologic history of the eastern tharsis rise our results corroborate an overall vertical structure of the upper crust consistent with that inferred from previous studies an upper unit spectrally consistent with basalt that has variable thickness is overlain on an early to possibly pre noachian substrate the pre early noachian material is heterogeneous dominated by low calcium pyroxene rich material but ranging locally from feldspathic to and olivine rich aqueous alteration of pre early noachian rock to dominantly fe mg smectite is widespread and observed along the chasma walls from 4 to 1 km however phyllosilicates outcrop discontinuously suggesting that they were emplaced via impact excavation of even older altered material or formed by non uniform alteration driven by impact or magma related hydrothermal activity a distinct higher temperature alteration assemblage identified by the presence of chlorite zeolite and associated carbonate serpentine occurs on both the north and south walls of eastern coprates chasma in a confined longitudinal band where the eastern margin of the thaumasia plateau intersects valles marineris these secondary minerals are concentrated within a heavily fractured band exposed at a regional tectonic boundary along the margin of the thaumasia plateau and likely record a regional zone of elevated crustal heat flow and fluid circulation the generally north south trending band exhibiting this distinct assemblage serves as a tracer for tectonic deformation its continuity across valles marineris is incongruous with previously suggested lateral slip along the margin of a megaslide and constrains left lateral transtensional faulting to less than 25 50 km mapping of compositionally distinct outcrops to the west also reveals localized uplift in western coprates chasma suggesting thrust faults underlying wrinkle ridges in western valles marineris the upper basalt layer thickens dramatically supporting either occurrence of a large infilled basin to the west or down dropping and volcanic burial of material near melas candor chasma the latter consistent with a constructional origin of the tharsis rise

primordial clays on mars formed beneath a steam or supercritical atmosphere on mars clay minerals are widespread in terrains that date back to the noachian period 4 1 billion to 3 7 billion years ago it is thought that the martian basaltic crust reacted with liquid water during this time to form hydrated clay minerals here we propose however that a substantial proportion of these clays was formed when mars primary crust reacted with a dense steam or supercritical atmosphere of water and carbon dioxide that was outgassed during magma ocean cooling we present experimental evidence that shows rapid clay formation under conditions that would have been present at the base of such an atmosphere and also deeper in the porous crust furthermore we explore the fate of a primordial clay rich layer with the help of a parameterized crustal evolution model we find that the primordial clay is locally disrupted by impacts and buried by impact ejected material and by erupted volcanic material but that it survives as a mostly coherent layer at depth with limited surface exposures these exposures are similar to those observed in remotely sensed orbital data from mars our results can explain the present distribution of many clays on mars and the anomalously low density of the martian crust in comparison with expectations

discovery of olivine in the nili fossae region of mars we have detected a 30 000 square kilometer area rich in olivine in the nili fossae region of mars nili fossae has been interpreted as a complex of grabens and fractures related to the formation of the isidis impact basin we propose that post impact faulting of this area has exposed subsurface layers rich in olivine linear mixture analysis of thermal emission spectrometer spectra shows surface exposures of 30 olivine where the composition of the olivine ranges from fo30 to fo70

ultrahigh resolution topographic mapping of mars with mro hirise stereo images meter scale slopes of candidate phoenix landing sites 1 the objectives of this paper are twofold first to report our estimates of the meter to decameter scale topography and slopes of candidate landing sites for the phoenix mission based on analysis of mars global surveyor mgs mars orbiter camera moc images with a typical pixel scale of 3 m and mars reconnaissance orbiter mro high resolution imaging science experiment hirise images at 0 3 m pixel 1 and second to document in detail the geometric calibration software and procedures on which the photogrammetric analysis of hirise data is based a combination of optical design modeling laboratory observations star images and mars images form the basis for software in the u s geological survey integrated software for imagers and spectrometers isis 3 system that corrects the images for a variety of distortions with single pixel or subpixel accuracy corrected images are analyzed in the commercial photogrammetric software socet set bae systems yielding digital topographic models dtms with a grid spacing of 1 m 3 4 pixels that require minimal interactive editing photoclinometry yields dtms with single pixel grid spacing slopes from moc and hirise are comparable throughout the latitude zone of interest and compare favorably with those where past missions have landed successfully only the mars exploration rover mer b site in meridiani planum is smoother moc results at multiple locations have root mean square rms bidirectional slopes of 0 8 4 5 at baselines of 3 10 m hirise stereopairs one per final candidate site and one in the former site yield 1 8 2 8 slopes at 1 m baseline slopes at 1 m from photoclinometry are also in the range 2 3 after correction for image blur slopes exceeding the 16 phoenix safety limit are extremely rare

inverted fluvial features in the aeolis zephyria plana region mars formation mechanism and initial paleodischarge estimates 1 a subset of the sinuous ridges srs in the aeolis zephyria plana azp region of mars has been previously hypothesized to be inverted fluvial features although the precise induration and erosion mechanisms were not specified morphological observations and thermal inertia data presented here support this hypothesis a variety of mechanisms can cause inversion and identification of the specific events that lead to fluvial sr formation can provide insights into the sedimentological geochemical and climatic processes of the region reconnaissance of two terrestrial lava capped ridges suggests some criteria that may be used to identify inverted fluvial features formed by lava infill on mars but these criteria are not satisfied by the majority of the azp fluvial srs armoring also appears inconsistent with terrestrial analogs layering and surface textures of fluvial srs indicate that the most likely induration mechanism was geochemical cementation of fluvial sediments and that the primary erosional mechanism that exposed the fluvial srs was aeolian abrasion this analysis of formation mechanism provides a foundation for estimating paleodischarge using an empirical form discharge approach to which we have applied scaling for martian gravity for those fluvial srs meeting a set of criteria for accurate paleodischarge estimates paleodischarge values generally range between 101 and 103 m3 s 1 the largest of these initial estimates are comparable to paleodischarge estimates for some late stage noachian fluvial channels on mars and provide a constraint on the atmospheric conditions at this equatorial location during the late hesperian to early amazonian time frame

halite cementation and carbonate diagenesis of intra salt reservoirs from the late neoproterozoic to early cambrian ara group south oman salt basin late neoproterozoic to early cambrian carbonates of the ara group form important intra salt stringer reservoirs in the south oman salt basin differential loading of thick continental clastics above the six carbonate to evaporite cycles of the ara group led to the formation of salt diapirs encasing a predominantly self charging hydrocarbon system within partly highly overpressured carbonate bodies stringers these carbonates underwent a complex diagenetic evolution with one stage of halite cementation in a shallow early and another in a deep late burial environment early and late halite cements are defined by their microstructural relationship with solid bitumen the early phase of halite cementation is post dated by solid reservoir bitumen this phase is most pervasive towards the top of carbonate stringers where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics bromine geochemistry revealed significantly higher bromine contents up to 280 p p m in the early halite compared with the late halite 173 p p m the distribution patterns and the high bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval later in burial history relatively small quantities of early halite were dissolved locally and re precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements late halite cement also seals fractures which show evidence for repeated reopening initially these fractures formed during a period of hydrothermal activity and were later reopened by a crack seal mechanism caused by high fluid overpressures porosity plugging by early halite cements affects the poroperm characteristics of the ara carbonates much more than the volumetrically less important late halite cement the formation mechanisms and distribution patterns of halite cementation processes in the south oman salt basin can be generalized to other petroliferous evaporite basins

phyllosilicates in the mawrth vallis region of mars 1 omega mars express has discovered large outcrops rich in phyllosilicates in the region of mawrth vallis mars around 20 w 25 n the region is located in noachian highly cratered terrains close to the limit of the martian dichotomy where the outflow channel mawrth vallis cuts the highlands we have examined this region using omega spectra of the surface from 0 9 m to 2 6 m with spatial sampling from 500 m to 3 km offering a full coverage of the region omega spectra show two broad bands centered at 1 m and 2 2 m revealing the presence of clinopyroxene on dark surfaces phyllosilicates have been identified by absorption bands at 1 4 m 1 9 m and 2 2 or 2 3 m comparison with laboratory spectra reveals similarities with al oh smectites such as montmorillonites or fe or mg oh smectites such as nontronite a precise location of the phyllosilicate rich areas on visible hrsc images indicates that they are placed exclusively on bright outcrops mostly on the plateaus dated to the noachian period on hrsc and moc images the phyllosilicate rich outcrops reveal strong erosional features such as numerous residual buttes composed of layers a few meters thick the phyllosilicate rich unit corresponds to a geological unit more than 100 m thick over a horizontal extension approximately of 300 km 400 km this unit implies a large volume of altered rocks either in situ or after transport and deposition in noachian terrains revealing a different climatic and geologic environment from the present one

geological and geophysical features of and controls on occurrence and accumulation of gas hydrates in the first offshore gas hydrate production test region in the shenhu area northern south china sea abstract integrated three dimensional seismic logging sediment cores and geochemical testing data were collected from guangzhou marine geological survey 3 and 4 hydrate drilling expeditions and used in this study for a comprehensive investigation of the geological and geophysical features and accumulation mechanism of hydrates in the first offshore gas hydrate production test region ghptr in the shenhu area of the south china sea seismic signatures indicative of disseminated hydrates and free gas include the bottom simulating reflector bsr gas chimney and mud diapir associated with enhanced seismic reflections acoustic blanking masking and chaotic appearance have been observed the acoustic travel time responses density and compensated neutron three porosity log analysis high precision grid tomography inversion analysis and constrained sparse spike inversion confirm the presence of free gas below the gas hydrate bearing zone ghbz free gas bearing zones have significantly different p wave impedances and low velocity anomalies than the overlying ghbz and surrounding strata these anomalous zones are controlled by the structural attitude of the reservoir strata which are characterized as inter bedded stratigraphic units variations in the type and geological characteristics of the hydrocarbon migration pathways were observed between sites w18 and w19 on the western ridge and sites w11 and w17 on the eastern ridge in the gmgs study area the efficiency of gas migration in the western ridge may be higher than that in the eastern ridge resulting in variations in hydrate gas types thickness of the ghbz and gas migration flux and accumulation except for site w11 hydrates were recovered below the structure i inferred bsr at sites w17 w18 and w19 the gas hydrate stability zone calculations reveal that the structure i hydrate stability zone differs from the bsr depth and is generally shallower than the base of the logging anomaly indicating the coexistence of structure i and ii hydrates the bsr is not indicative of the bghsz it is rather regarded as a transitional indicator of structure i and ii gas hydrates in the ghptr the appearance of free gas and hydrates below the structure i inferred bsr indicates that the shenhu area is characterized by a complex hydrate formation and accumulation system resulting from the supply of biogenic and thermogenic gases despite fine grained host sediments predominating the ghptr the coupling of favorable conditions including efficient hydrocarbon generation sufficient gas supply multiple pathways for gas migration and relatively high reservoir porosity have led to the development of highly saturated gas hydrate accumulations within relatively thick sedimentary sections which demonstrates a significant resource potential

evaluation of paleohydrologic models for terrestrial inverted channels implications for application to martian sinuous ridges abstract fluvial systems can be preserved in inverted relief on both earth and mars few studies have evaluated the applicability of various paleohydrological models to inverted fluvial systems the first phase of this investigation focused on an extensive spanning 12 km inverted paleochannel system that consists of four sandstone capped carbonate cemented sinuous ridges within the early cretaceous cedar mountain formation located southwest of green river utah morphologic and sedimentologic observations of the exhumed paleochannels were used to evaluate multiple numerical models for reconstructing paleofluvial hydrological parameters another objective of the study was to determine whether aerial or orbital observations yield model results that are consistent with those constrained by field data the models yield an envelope of plausible dominant discharge values 100 500 m 3 s reflecting the limitations of the approach and no single model can be used to reliably estimate paleodischarge on mars landforms with attributes consistent with inverted channels have been identified in spite of differences in the formation history between these martian landforms and the terrestrial analog described here including potential differences in cement composition and the erosional agent that was responsible for relief inversion these numerical models can be applied with modification to the martian landforms and yield an envelope of plausible values for dominant discharge

planetary surface dating from crater size frequency distribution measurements multiple resurfacing episodes and differential isochron fitting abstract the analysis of crater size frequency distributions and absolute densities forms the basis of current approaches for estimating the absolute and relative ages of planetary surfaces users of the neukum system of crater dating have conventionally used a cumulative presentation of the data but because of the recent proliferation of interest in identifying resurfacing ages it is worth emphasising the utility of the differential presentation of crater data in identifying resurfacing events and particularly in distinguishing the signature of short lived events such as volcanic flows from long acting processes such as aeolian erosion the work describes some additional considerations for making isochron fits to differentially plotted crater populations with respect to the removal of a binning bias for incrementally differentially plotted data the hartmann approach has not typically employed the fitting of isochrons but differential fitting would be a natural choice for this system and is implemented in the craterstats software a revised calculation of the martian epoch boundary times in both chronology systems is provided

compositional stratigraphy of clay bearing layered deposits at mawrth vallis mars phyllosilicates have previously been detected in layered outcrops in and around the martian outflow channel mawrth vallis crism spectra of these outcrops exhibit features diagnostic of kaolinite montmorillonite and fe mg rich smectites along with crystalline ferric oxide minerals such as hematite these minerals occur in distinct stratigraphic horizons implying changing environmental conditions and or a variable sediment source for these layered deposits similar stratigraphic sequences occur on both sides of the outflow channel and on its floor with al clay bearing layers typically overlying fe mg clay bearing layers this pattern combined with layer geometries measured using topographic data from hirise and hrsc suggests that the al clay bearing horizons at mawrth vallis postdate the outflow channel and may represent a later sedimentary or altered pyroclastic deposit that drapes the topography

the high resolution imaging science experiment hirise during mro s primary science phase psp the high resolution imaging science experiment hirise on the mars reconnaissance orbiter mro acquired 8 terapixels of data in 9137 images of mars between october 2006 and december 2008 covering 0 55 of the surface images are typically 5 6 km wide with 3 color coverage over the central 20 of the swath and their scales usually range from 25 to 60 cm pixel nine hundred and sixty stereo pairs were acquired and more than 50 digital terrain models dtms completed these data have led to some of the most significant science results new methods to measure and correct distortions due to pointing jitter facilitate topographic and change detection studies at sub meter scales recent results address noachian bedrock stratigraphy fluvially deposited fans in craters and in or near valles marineris groundwater flow in fractures and porous media quasi periodic layering in polar and non polar deposits tectonic history of west candor chasma geometry of clay rich deposits near and within mawrth vallis dynamics of flood lavas in the cerberus palus region evidence for pyroclastic deposits columnar jointing in lava flows recent collapse pits evidence for water in well preserved impact craters newly discovered large rayed craters and glacial and periglacial processes of particular interest are ongoing processes such as those driven by the wind impact cratering avalanches of dust and or frost relatively bright deposits on steep gullied slopes and the dynamic seasonal processes over polar regions hirise has acquired hundreds of large images of past present and potential future landing sites and has contributed to scientific and engineering studies of those sites warming the focal plane electronics prior to imaging has mitigated an instrument anomaly that produces bad data under cold operating conditions