the timing of martian valley network activity constraints from buffered crater counting abstract valley networks concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity have been cited as indicators that the climate of mars differed significantly in the past from the present hyperarid cold desert conditions some researchers suggest that the change in climate was abrupt while others favor a much more gradual transition thus the precise timing of valley network formation is critical to understanding the climate history on mars we examine thirty valley network incised regions on mars including both cratered upland valley networks and those outside the uplands and apply a buffered crater counting technique to directly constrain when valley network formation occurred the crater populations that we derive using this approach allow assessment of the timing of the last activity in a valley network independent of the mapping of specific geological units from these measurements we find that valley networks cluster into two subdivisions in terms characteristics and age 1 valley network activity in the cratered highlands has an average cessation age at the noachian hesperian boundary and all valleys that we crater counted are early hesperian or older no evidence is found for valley networks in the cratered uplands of late hesperian or amazonian age the timing of the cessation of cratered upland valley network activity at the noachian hesperian boundary also corresponds to a decline in the intensity of large crater formation and degradation and to the apparent end of phyllosilicate type weathering 2 a few valley network incised regions formed outside of the cratered uplands on volcanic edifices in association with younger impact craters and on the rim of valles marineris we applied our buffered crater counting technique to four such valleys on the volcanoes ceraunius tholus hecates tholus and alba patera and on the rim of echus chasma and find that each has distinctive and different late hesperian or early amazonian ages indicating that valley networks formed from time to time in the post noachian period unlike the cratered upland valley networks these isolated occurrences are very local and have been interpreted to represent local conditions e g snowpack melted during periods of intrusive volcanic activity in contrast to a gradual cessation in the formation of valley networks proposed by some workers our new buffered crater counting results indicate a relatively abrupt cessation in the formation of the widespread cratered upland valley networks at approximately the end of the noachian followed only by episodic and very localized valley network formation in later mars history very likely due to specific conditions e g local magmatic heating these valley network ages and correlations are thus consistent with a major change in the near surface aqueous environment on mars at approximately the noachian hesperian boundary the noachian environment supported surface running water and fluvial erosion across mars in the cratered uplands enhanced crater degradation and a weathering environment favoring the formation of phyllosilicates the hesperian amazonian environment was more similar to the hyperarid cold desert of today with valley networks forming only extremely rarely and confined to localized special conditions sources of water for these latter occurrences are likely to be related to periodic mobilization and equatorward migration of polar volatiles due to variations in spin axis orbital parameters and to periodic catastrophic emergence of groundwater

morphology and evolution of the ejecta of hale crater in argyre basin mars results from high resolution mapping we use various data sets including images from the high resolution imaging science experiment camera hirise to examine the ejecta of the generally fresh looking hale crater that occurs in the rugged mountain terrain of nereidum montes in the northern rim materials of the argyre impact structure on mars our investigation reveals that the distal parts of the hale crater ejecta and other basin deposits behave like viscous flows which we attribute to the secondary flow of ejecta mixed with water ice rich basin materials consistent with water enrichment of the basin materials our mapping further reveals occasionally deformed surfaces including highly conspicuous features such as mounds and fractured plateaus that we interpret to be a result of periglacial modification subsequent including possibly present day to the transient localized melting and fluvial erosion caused by hale impact generated heating in particular our morphometric analysis of a well defined valley system west of hale crater suggests that it may have been formed through hydrologic glacial activity prior to the hale impact with additional modification resulting from the impact and subsequent geologic and hydrologic phenomena including glacial and periglacial activity

a lake in uzboi vallis and implications for late noachian early hesperian climate on mars abstract uzboi vallis centered at 28 s 323 e is 400 km long and comprises the southernmost segment of the northward draining uzboi ladon morava ulm meso scale outflow system that emerges from argyre basin bond and holden craters blocked the valley to the south and north respectively forming a late noachian to hesperian paleolake basin that exceeded 4000 km 3 limited crism data suggest lake deposits in uzboi and underlying basin floor incorporate relatively more mg clays and more fe clays respectively the short lived lake overflowed and breached holden crater s rim at an elevation of 350 m and rapidly drained into the crater fan deltas in holden extend 25 km from the breach and incorporate meter sized blocks and longitudinal grooves along the uzboi basin floor are hundreds of meters long and average 60 m wide suggesting high discharge drainage of the lake precipitation derived runoff rather than regional groundwater or overflow from argyre dominated contributions to the uzboi lake although the failure of most tributaries to respond to a lowering of base level indicates their incision largely ended when the lake drained the uzboi lake may have coincided with alluvial and or lacustrine activity in holden eberswalde and other craters in southern margaritifer terra where fluvial lacustrine activity may have required widespread synoptic precipitation rain or snow perhaps associated with an ephemeral global hydrologic system during the late noachian into the hesperian on mars

translating the mineral systems approach into an effective exploration targeting system abstract holistic mineral systems approaches are being increasingly adopted in the study of ore deposits but application in industry has been suboptimal because of the lack of a conceptual framework to help translate the mineral system understanding to practical application a four step process is proposed for linking the conceptual mineral system with data available to support exploration targeting these steps include translation from 1 critical processes of the mineral system to 2 constituent processes of the mineral system to 3 targeting elements reflected in geology and 4 targeting criteria used to detect the targeting elements directly or by proxy this translation process is illustrated using examples from komatiite hosted ni cu pge and orogenic au mineral systems ranking of targets must be at the critical process level rather than the current practice of mixing processes elements and proxies the significance of targeting elements and their mappable criteria changes as a function of the scale at which the critical processes operate and the availability of relevant geoscience datasets this scale dependence is rarely recognised in current practice sources of uncertainty when translating the mineral system understanding into an effective exploration targeting system include 1 resolution of a mappable criterion in a dataset 2 how well the targeting criterion reflects the targeting element 3 how well the targeting element reflects the critical process and 4 whether the process being mapped is critical for the genesis of a mineral deposit the first three sources of uncertainty collectively are termed the representativeness of the targeting criteria i e how representative is a mappable criterion of the constituent process for which it is a proxy the last source of uncertainty reflects our lack of understanding of the processes that control mineralisation and highlights areas for further research

predictive modelling of prospectivity for pb zn deposits in the lawn hill region queensland australia a combination of geodynamic modelling mineral potential mapping and mineral deposit studies are commonly used to explore for mineral deposits this paper focuses on the mineral potential aspect exploring the interrelationship between a knowledge driven approach which uses subjective evidence based on expert knowledge and a data driven model based on bayesian probabilistic reasoning the limitations and strengths of these approaches provide an example of how blending human interpretation with computational models can be an effective way to aid exploration and ore genesis interpretation the study is focused on the lawn hill platform mount isa inlier situated in northwestern queensland australia the models are used to predict the mineral potential in the area focussing on sedex sedimentary exhalative deposits and vs vein style pb zn mineralisation the lawn hill region shows good mineral potential close to the termite range fault within areas marginal to known prospects and vein lode hosted deposits however there are lower favourability sites suggesting significant potential in the kamarga dome integration of the knowledge and data driven models is considered a potential way to more reliably assess the favourability of locating a century type system the use of this combined technique suggests that the highest favourability of locating a shale hosted mineralisation similar to century is close to this deposit along the termite range fault zone one particularly prospective site has been identified north of the edith cluster

paleohydrology of eberswalde crater mars abstract eberswalde crater mars contains a well preserved fluvial distributary network in a likely deltaic setting the meandering inverted paleochannels and closed drainage basin of this deposit support relatively well constrained estimates of channel forming discharge over an individual event flood timescale runoff production event and annual timescales and longevity of deposition geologic timescale during the late hesperian to early amazonian epochs the width and meander dimensions of two inverted paleochannels reflect the channel forming discharge from event floods 200 to 400 m 3 s the deposit surface indicates the level 1400 to 1350 m and surface area 410 to 810 km 2 of the likely paleolake and the topography and mapped extent of tributaries constrain the watershed area 5000 to 17 000 km 2 based on these results and terrestrial empirical constraints on evaporation and sediment concentration we evaluated three hypothetical water sources meltwater liberated by the nearby holden crater impact continuous deposition over 10 1 10 2 years intermittent rainfall or snowmelt during finite periods controlled by orbital evolution deposition over 10 4 10 6 years and highly infrequent runoff or melting of accumulated snowpacks following distant impacts or secular changes in orbital parameters local impact generated runoff and highly infrequent rainfall or snowmelt require unreasonably high and low rates of evaporation respectively to maintain the paleolake level the local impact hypothesis alternatively depends on one flooding episode with very high concentrations of fluvial sediment that are inconsistent with morphologic considerations multiple primary impact craters in the area postdate holden ejecta but were later dissected indicating fluvial erosion long after the holden impact intermittent rainfall of 1 cm day and seasonal snowmelt are both consistent with our results over a deposition timescale totaling 10 4 10 6 years

interior channels in martian valley networks discharge and runoff production the highland valley networks are perhaps the most compelling evidence for widespread fluvial activity on mars 3 5 ga however determining the hydrology of these features has been difficult owing to poor image resolution and the lack of available topographic data new orbital imaging reveals 21 late stage channels within valley networks which we use to estimate formative discharges and to evaluate water supply mechanisms we find that channel width and associated formative discharge are comparable to terrestrial valley networks of similar area and relief for 15 narrow channels in basin filling networks likely episodic runoff production rates up to centimeters per day and first order formative discharges of 300 3000 m 3 s are similar to terrestrial floods supplied by precipitation geothermal melting of ground ice would produce discharges 100 times smaller per unit area and would require pulsed outbursts to form the channels in four large valleys with few tributaries wider channels may represent large subsurface outflows or paleolake overflows as these four channels originate at breached basin divides and or near source regions for the catastrophic outflow channels

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

late alluvial fan formation in southern margaritifer terra mars 1 crater statistics indicate alluvial fans crater floor and fill mantling deposits within impact craters 50 km in diameter in southern margaritifer terra were likely emplaced during multiple epochs fans formed during the amazonian or near the amazonian hesperian boundary crater floor deposits are likely hesperian in age and most fill mantling deposits are amazonian the regional distribution of fans points to a late period of widespread water driven degradation two of the final candidate landing sites for the 2011 mars science laboratory mission would land on or near some of these fans which appear younger than previously considered

large alluvial fans on mars 1 several dozen distinct alluvial fans 10 to 40 km long downslope have been observed in highlands craters within a search region between 0 and 30 s alluvial fan containing craters were found only between 18 and 29 s and they all occur at around 1 km of the mola defined martian datum within the study area they are not randomly distributed but instead form three distinct clusters fans typically descend 1 km from where they disgorge from their alcoves longitudinal profiles show that their surfaces are very slightly concave with a mean slope of 2 many fans exhibit very long narrow low relief ridges radially oriented downslope often branching at their distal ends suggestive of distributaries morphometric data for 31 fans were derived from mola data and compared with terrestrial fans with high relief source areas terrestrial low gradient alluvial ramps in inactive tectonic settings and older martian alluvial ramps along crater floors the martian alluvial fans generally fall on the same trends as the terrestrial alluvial fans whereas the gentler martian crater floor ramps are similar in gradient to the low relief terrestrial alluvial surfaces for a given fan gradient martian alluvial fans generally have greater source basin relief than terrestrial fans in active tectonic settings this suggests that the terrestrial source basins either yield coarser debris or have higher sediment concentrations than their martian counterpoints martian fans and terrestrial basin and range fans have steeper gradients than the older martian alluvial ramps and terrestrial low relief alluvial surfaces which is consistent with the construction of martian fans from dominantly gravel sized sediment rather than sand and silt martian fans are relatively large and of low gradient similar to terrestrial fluvial fans rather than debris flow fans although gravity scaling uncertainties make the flow regime forming martian fans uncertain however evidence of bedforms accentuated by differential erosion such as scroll bars supports the contention that these are fluvially formed fans martian fans at least those in holden crater apparently formed around the time of the noachian hesperian boundary we infer that these fans formed during an episode of enhanced precipitation probably snow and runoff which exhibited both sudden onset and termination

translating expressions of intrusion related mineral systems into mappable spatial proxies for mineral potential mapping case studies from the southern new england orogen australia abstract an understanding of the modelled mineral system and high quality data that accurately map this system are prerequisites for producing geologically meaningful mineral potential maps critical to this is the translation of the targeted mineral system components into mappable targeting criteria and their spatial proxies this paper presents a workflow that illustrates this translation process also highlighting that if done well mineral potential mapping can produce statistically valid geologically meaningful and practically useful results that not only predict the location of known mineralisation but also identify new target areas an important ingredient of the workflow described herein is what we call a mineral systems atlas this compendium includes 1 a spatial data table detailing the translation of the modelled mineral system 2 the predictive maps that capture the mappable components of the targeted mineral system and 3 the final mineral potential maps a case study implementing and illustrating this workflow is presented for intrusion related au and sn w mineral systems in the southern new england orogen new south wales australia importantly the mineral potential maps generated as part of this study succeeded in identifying areas of known intrusion related au and sn w mineralisation and new areas with high potential for discovery

the geologic history of margaritifer basin mars in this study we investigate the fluvial sedimentary and volcanic history of margaritifer basin and the uzboi ladon morava outflow channel system this network of valleys and basins spans more than 8000 km in length linking the fluvially dissected southern highlands and argyre basin with the northern lowlands via ares vallis compositionally thermophysically and morphologically distinct geologic units are identified and are used to place critical relative stratigraphic constraints on the timing of geologic processes in margaritifer basin our analyses show that fluvial activity was separated in time by significant episodes of geologic activity including the widespread volcanic resurfacing of margaritifer basin and the formation of chaos terrain the most recent fluvial activity within margaritifer basin appears to terminate at a region of chaos terrain suggesting possible communication between surface and subsurface water reservoirs we conclude with a discussion of the implications of these observations on our current knowledge of martian hydrologic evolution in this important region

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

martian layered fluvial deposits implications for noachian climate scenarios 1 fluvial deposits in a basin north of holden crater exhibiting a sinuous anabranching pattern are of deltaic or fan origin channel width and meander wavelength indicate persistent flow magnitudes of about 700 m3 s if these flows were produced by quasi periodic climate episodes involving typical terrestrial style precipitation the deposit required thousands to millions of years to accumulate however a scenario of deposition during a few short episodes of constant heavy precipitation resulting from large impacts cannot be excluded

hesperian equatorial thermokarst lakes in ares vallis as evidence for transient warm conditions on mars on earth permafrost thawing is linked to climate warming similarly on mars permafrost degradation described from mid latitude and equatorial settings is likely linked to global or regional climate change putative thermokarst depressions identified on mars are widely considered to be the result of sublimation evaporation or thawing of an ice rich substrate the possibility that the depressions formed by melting of permafrost to create alas like lakes has been recently proposed but is controversial owing to the lack of primary evidence for liquid filling the depressions here we use high resolution mars reconnaissance orbiter context camera images and derived topographic data to characterize possible thermokarst terrain in ares vallis the terrain comprises subcircular to irregular flat floored rimless topographic depressions that occur at varying elevations we report the discovery of narrow channels connecting thermokarst like depressions that provide evidence for the previous presence of ponded liquid water crater counts on these surfaces indicate resurfacing that is likely related to flood deposition of water saturated sediments in ares vallis during the hesperian ca 3 6 3 0 ga we infer that thermokarst lakes formed after flooding by thawing of ice within the sediments during transient warm periods in the hesperian a time previously considered to be too cold to permit ice thaw

amazonian aged fluvial system and associated ice related features in terra cimmeria mars abstract the martian climate throughout the amazonian is widely believed to have been cold and hyper arid very similar to the current conditions however ubiquitous evidence of aqueous and glacial activity has been recently reported including channels that can be tens to hundreds of kilometres long alluvial and fluvial deposits ice rich mantles and glacial and periglacial landforms here we study a 340 km long fluvial system located in the terra cimmeria region in the southern mid latitudes of mars the fluvial system is composed of an upstream catchment system with narrow glaciofluvial valleys and remnants of ice rich deposits we observe depositional features including fan shaped deposits and erosional features such as scour marks and streamlined islands at the downstream section of this fluvial system is an outflow channel named k r n valles which displays a unique braided alluvial fan and terminates on the floor of the ariadnes colles basin our observations point to surface runoff of ice snow melt as the water source for this fluvial activity according to our crater size frequency distribution analysis the entire fluvial system formed during early to middle amazonian between 1 8 0 2 0 2 ga to 510 40 40 ma hydraulic modelling indicates that the k r n valles and consequently the alluvial fan formation took place in geologically short term event s we conclude that liquid water was present in terra cimmeria during the early to middle amazonian and that mars during that time may have undergone several episodic glacial related events

late hesperian to early amazonian midlatitude martian valleys evidence from newton and gorgonum basins 1 numerous shallowly incised valleys extend from the upper interior rims of newton and gorgonum basins across smooth interior basin deposits these valleys are a few meters to 300 m wide and may have experienced discharges over all or most of their width implying that they are in fact incised channels in newton crater these valleys extend up to 75 km to near the center of the basin floor in gorgonum basin the valleys terminate at what we interpret to be a former ice covered lake these valleys appear to be examples of scattered shallowly incised valleys found throughout the midlatitudes of mars superimposed upon the widespread mantling deposits within the region on the basis of crater count age dating the interior valleys in newton and gorgonum basins were formed at about the hesperian to amazonian transition the runoff through the valleys may have occurred due to episodic melting of snow and ice that had accumulated on the crater rims temperatures warm enough to cause extensive melting may have occurred during optimal orbital and obliquity configurations because of intensive volcanism releasing greenhouse gasses or as a result of a brief episode of warming from a large impact somewhere on mars the valleys were formed at about the same time as major outflow channels were active along the highlands lowlands boundary water delivered to the northern lowlands by the outflow channels may have been recycled as snow and ice deposits within the martian midlatitudes the episodic melting of such deposits may have formed the midlatitude valleys

amazonian aged fluvial valley systems in a climatic microenvironment on mars melting of ice deposits on the interior of lyot crater valley networks regional drainage patterns suggesting liquid water stability at the surface are confined to early in the history of mars the noachian hesperian boundary and before prior to a major climate transition to the hyperarid cold conditions of the amazonian several later fluvial valley systems have been documented in specific hesperian and early amazonian environments and are thought to have formed due to local conditions here we describe fluvial valley systems within lyot crater that have the youngest well constrained age reported to date middle or late amazonian for systems of this size tens of km these valleys are linked to melting of near surface ice rich units extend up to 50 km in length follow topographic gradients and deposit fans the interior of lyot crater is an optimal micro environment since its low elevation leads to high surface pressure and temperature conditions at its location in the northern mid latitudes are sufficient for melting during periods of high obliquity this micro environment in lyot apparently allowed melting of surface ice and the formation of the youngest fluvial valley systems of this scale yet observed on mars

recent aqueous environments in martian impact craters an astrobiological perspective the discovery of gullies and debris aprons raises the question of the existence of aqueous environments on mars in recent geological times and its astrobiological implications three cases of such environments are surveyed at moc high resolution in the e gorgonum chaos and newton and hale craters the regional setting of these craters suggests that the mechanisms of aquifer destabilization flow discharge and gully formation in these three cases result from local geological triggers that can include impact cratering and tectonic processes rather than climate or insolation factor we take as a working hypothesis that microbial life appeared on mars in ancient geological times probably in a geothermal environment but potentially evolving via infrared detection systems to give photosynthetic communities under the selective pressure of energetic solar radiation we hypothesize that some microbial communities could have survived underground in either dormant or active state or that their biomolecules could be preserved either frozen or desiccated in the subsurface beneath the upper oxidized zone we assess the known environmental constraints for life and what type of potential habitats are provided in these three craters by aquifer discharges using comparison with terrestrial analogues and their associated microbial communities these environments include 1 the release of water on a dry crater floor in e gorgonum and the possibility for microorganisms and preserved biomolecules to be flushed out and mixed in with the sediment exposed at the surface 2 the evidence of a recent lacustrine episode in the newton crater with analogy to antarctic dry valley lakes 3 the exposure on the floor of hale crater of material from a regional subsurface that is likely to have retained traces of one of the oldest martian bodies of water recognized to date parker et al 2000 in the argyre basin we show how the water in argyre 3 8 billion years ago gya was likely to have been alterated by hydrothermal processes and how the subsequent formation of the 150 km hale crater on the northern ring of argyre generated hydrothermal pumping this accounts for the anomalously high location of the springs on the crater crests today with respect to the rest of the regional subsurface distribution finally we envision current impact cratering as a factor for destabilizing aquifers on mars today thus creating new environments we analyze the implications of impacts for two geological types of rock units that could harbor traces of life as a result we compare the potential of astrobiological exploration of crater floors rims and ejecta on future missions to mars

fresh shallow valleys in the martian midlatitudes as features formed by meltwater flow beneath ice significant numbers of valleys have been identified in the martian midlatitudes 30 60 n s spatially associated with extant or recent ice accumulations many of these valleys date to the amazonian but their formation during these cold dry epochs is problematic in this study we look in detail at the form distribution and quantitative geomorphology of two suites of these valleys and their associated landforms in order to better constrain the processes of their formation since the valleys themselves are so young and thus well preserved uniquely we can constrain valley widths and courses and link these to the topography from the mars orbiter laser altimeter and high resolution stereo camera data we show that the valleys are both qualitatively and quantitatively very similar despite their being 5000 km apart in different hemispheres and around 7 km apart in elevation buffered crater counting indicates that the ages of these networks are statistically identical probably forming during the late amazonian 100 ma in both localities at least tens of valleys cross local drainage divides apparently flowing uphill we interpret these uphill reaches to be characteristic of flow occurring beneath a now absent relatively thin order 101 102 m regionally extensive ice cover ridges and mounds occasionally found at the foot of these valley systems are analogous to eskers and aufeis like refreezing features on the basis of their interaction with these aufeis like mounds we suggest that this suite of landforms may have formed in a single short episode perhaps order of days probably forced by global climate change

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

the structure and evolution of ancient impact basins on mars the number of martian impact basins once thought deficient owing to a low number of impactors has been significantly increased through the identification of structural imprints that remain even after nearly complete erasure of basin massifs five ancient multiringed impact basins were selected for detailed study and exhibit a systematic pattern of rejuvenation of the multiring plan through endogenic modification concentric zones of unstable terrain are believed to reflect deep seated impact related fractures that have localized regional igneous processes in a manner analogous with the basin controlled distribution of basalts on the moon most martian outflow channels were found to originate along the unstable ring zones hydrothermal melting and temporary confinement of channel source materials at sites analogous to lunar sinuous rille source regions are proposed to play an important role in the distribution of martian outflow channels ancient basins also can be delineated by the concentric pattern of topographically and structurally controlled narrow valley networks that are particularly abundant along the outer rings where basin ejecta deposits occur remnant massifs and scarps commonly exhibit extensive furrowing by narrow valley networks perhaps due to a different paleoclimate or sapping during a period of geothermal melting of trapped ices the systematic patterns of valley networks stable and unstable annuli scarps and massifs provide bases for interpreting impact structure in general and for recognizing multiringed structures elsewhere the chryse basin in particular is proposed to represent a major multiringed structure that controlled the formation and distribution of eastern valles marineris and the chaotic terrains of margaritifer sinus in response to volcanism tectonism related to tharsis we conclude that 1 mars is probably not deficient in large body impactors 2 the multiring patterns of basins represent deep seated fracture zones that can be reexposed through subsequent volcanism hydrothermal activity sapping and differential erosion 3 many martian terrains and features e g chaotic terrains and outflow channels are controlled by ancient basins and 4 the resurrection and destruction of impact basins reveal an important third dimension depth for interpreting impact basin formation

late noachian to hesperian climate change on mars evidence of episodic warming from transient crater lakes near ares vallis 1 the ares vallis region is surrounded by highland terrain containing both degraded and pristine large impact craters that suggest a change in climate during the late noachian early hesperian from warmer wetter conditions to colder dryer conditions however the regional occurrence of hesperian age crater outlet channels indicates that this period on mars was characterized by episodic climate fluctuations that caused transient warming facilitating the stability of liquid water at the surface an extensive survey of the morphology and topography of 75 impact basins in the region indicates that of the largest degraded craters 4 were identified with single outlet channels that suggest the former presence of water infill these basins lack inlets indicating that water influx was likely derived from sapping of groundwater a comparison of measured crater rim heights to modeled rim heights suggests that the bulk of the depth diameter reduction on these craters was the result of infilling possibly by sediments crater statistics indicate that crater degradation and infill occurred during a short 200 ma interval in the late noachian from 3 8 ga to 3 6 ga craters that formed after 3 6 ga exhibit a near pristine morphology our results support the hypothesis of rapid climate change at the end of the noachian period however geologic relationships between the crater outlet channels and ares vallis indicate that drainage occurred only after the period of intense crater modification during the hesperian 3 5 2 9 ga this suggests a delay between the time of infill of the craters and the time of drainage

absolute dune ages and implications for the time of formation of gullies in nirgal vallis mars 1 transverse dunes cover the valley floor of nirgal vallis a 670 km long valley network at 318 e and 29 s the dunes are superposed by small undeformed impact craters which implies that the dunes are inactive under present atmospheric conditions the last active phase of dune movement absolute age can be determined by crater size frequency distributions the derived absolute ages from high resolution mars global surveyor mars orbiter camera imagery range from approximately 300 000 years to 1 4 myr b p error of factor of 2 the dunes are also superposed by gully deposits aprons which implies a younger age of the gullies these superposition relationships show that the gullies in this midlatitude region are at the most 3 myr old but might be even younger than 300 000 years

geometric properties of martian impact craters preliminary results from the mars orbiter laser altimeter the mars orbiter laser altimeter mola acquired high spatial and vertical resolution topographic data for 18 tracks across the northern hemisphere of mars during the fall of 1997 it sampled 98 minimally degraded impact craters between the latitudes of 80 n and 12 s the best fitting depth d versus diameter d power law relationship for these craters is d 0 14 d0 90 for simple varieties and d 0 25 d0 49 for complex structures the simple to complex transition diameter is 8 km 0 5 km the cross sectional shape of the crater cavities was determined by fitting a power function to each profile variation in the exponent n suggest the craters flatten with increasing diameter and impact energy the ejecta thickness is skewed suggesting that use of existing empirical expressions for the expected radial decay of ejecta thickness is inappropriate for mars in most cases

mineral potential mapping in frontier regions a mongolian case study the quality of a mineral potential map is dependent on the quality of the input data used in the analysis in frontier regions or those with limited or no exploration history datasets are often of questionable quality and are generally incomplete with data missing either due to incomplete mapping or data not being made available to the public this study introduces a method for addressing these challenges in mineral potential mapping to derive exploration targets utilizing four established statistical measures an iterative weights of evidence method is employed to assess the strength of the relationship between known deposits and a set of geological feature layers this method acts as an indirect validation tool for assessing the quality of the data by allowing an expert user to determine whether the statistics conform to expected relationships taking data from mongolia this iterative weights of evidence method is used to produce a mineral potential map and to evaluate potential targets for orogenic gold mineralization the success of the method is determined by the ability of the mineral potential map to predict the location of the known mineralization

a geomorphic analysis of hale crater mars the effects of impact into ice rich crust abstract hale crater a 125 150 km impact crater located near the intersection of uzboi vallis and the northern rim of argyre basin at 35 7 s 323 6 e is surrounded by channels that radiate from incise and transport material within hale s ejecta the spatial and temporal relationship between the channels and hale s ejecta strongly suggests the impact event created or modified the channels and emplaced fluidized debris flow lobes over an extensive area 200 000 km2 we estimate 1010 m3 of liquid water was required to form some of hale s smaller channels a volume we propose was supplied by subsurface ice melted and mobilized by the hale forming impact if 10 of the subsurface volume was ice based on a conservative porosity estimate for the upper martian crust 1012 m3 of liquid water could have been present in the ejecta we determine a crater retention age of 1 ga inside the primary cavity providing a minimum age for hale and a time at which we propose the subsurface was volatile rich hale crater demonstrates the important role impacts may play in supplying liquid water to the martian surface they are capable of producing fluvially modified terrains that may be analogous to some landforms of noachian mars

extensive surface pedogenic alteration of the martian noachian crust suggested by plateau phyllosilicates around valles marineris 1 thousands of phyllosilicate rich outcrops mainly iron or magnesium rich are exposed on noachian terrains in the martian southern highlands we analyzed 90 crism observations and more than a hundred hirise images located on the plateaus surrounding valles marineris we mapped an extensive al and fe mg phyllosilicate rich formation covering at least 197 000 km2 for which we introduce the name plateau phyllosilicates tens of meters in thickness this light toned formation crops out at various elevations on top of the noachian units npl1 and npl2 as flat exposures on plateaus and along scarps such as valley walls chasma walls pit walls and impact crater rims the fe mg phyllosilicate rich lower member of the formation is composed of fe mg smectites nontronite saponite and vermiculite the al phyllosilicate rich upper member of the formation contains al smectites montmorillonite beidellite and locally kaolinite and or halloysite we suggest that the plateau phyllosilicates were mainly formed by pedogenesis related to the weathering of the noachian bedrock by percolation of meteoric water or melted snow under a temperate and subarid climate during the noachian epoch in an alkaline to neutral environment kaolinite and or halloysite may have formed in areas of more intense drainage at the surface under slightly acidic environments during the noachian and hesperian epochs fluvial activity and deuteric alteration may have locally contributed to the genesis of phyllosilicates this study suggests that the alteration of the noachian basement of the plateaus surrounding valles marineris was widespread during the noachian epoch and was still active during the hesperian epoch even though the water availability was limited

crater geometry and ejecta thickness of the martian impact crater tooting we use mars orbiter laser altimeter mola topographic data and thermal emission imaging system themis visible vis images to study the cavity and the ejecta blanket of a very fresh martian impact crater 29 km in diameter with the provisional international astronomical union iau name tooting crater this crater is very young as demonstrated by the large depth diameter ratio 0 065 impact melt preserved on the walls and floor an extensive secondary crater field and only 13 superposed impact craters all 54 to 234 meters in diameter on the 8120 km 2 ejecta blanket because the pre impact terrain was essentially flat we can measure the volume of the crater cavity and ejecta deposits tooting crater has a rim height that has 500 m variation around the rim crest and a very large central peak 1052 m high and 9 km wide crater cavity volume i e volume below the pre impact terrain is 380 km 3 and the volume of materials above the pre impact terrain is 425 km 3 the ejecta thickness is often very thin 20 m throughout much of the ejecta blanket there is a pronounced asymmetry in the ejecta blanket suggestive of an oblique impact which has resulted in up to 100 m of additional ejecta thickness being deposited down range compared to the up range value at the same radial distance from the rim crest distal ramparts are 60 to 125 m high comparable to the heights of ramparts measured at other multi layered ejecta craters tooting crater serves as a fresh end member for the large impact craters on mars formed in volcanic materials and as such may be useful for comparison to fresh craters in other target materials

evidential belief functions for data driven geologically constrained mapping of gold potential baguio district philippines abstract a data driven application of the theory of evidential belief to map mineral potential is demonstrated with a redefinition of procedures to estimate evidential belief functions the redefined estimates of evidential belief functions take into account not only the spatial relationship of an evidence with the target mineral deposit but also consider the relationships among the subsets of spatial evidences within a set of evidential data layer proximity of geological features to mineral deposits is translated into spatial evidence and evidential belief functions are estimated for the proposition that mineral deposits exist in a test area the integrated maps of degrees of belief for the proposition that mineral deposits exist in a test area is classified into a binary mineral potential map for the baguio district philippines the binary gold potential map delineates a about 74 of the training data i e locations of large scale gold deposits and b about 64 of the validation data i e locations of small scale gold deposits the results demonstrate the usefulness of a geologically constrained mineral potential mapping using data driven evidential belief functions to guide further surficial exploration work in the search for yet undiscovered gold deposits in the baguio district the results also indicate the usefulness of evidential belief functions for mapping uncertainties in the geologically constrained integrated predictive model of gold potential

mosaicking of global planetary image datasets 1 techniques and data processing for thermal emission imaging system themis multi spectral data 1 the mosaicking of global planetary data sets allows for the examination of local regional and global scale processes on all planetary bodies processing techniques that allow us and other users to crate mosaics of tens of thousands of images are documented along with the associated errors introduced by each image processing algorithm these techniques e g non uniformity correction running contrast stretches line and row correlated noise removal and random noise removal were originally developed for the 2001 mars odyssey thermal emission imaging system themis infrared multispectral imager data but can be adapted and applied to other data sets by the alteration of input parameters the techniques for mosaicking planetary image data sets e g image registration blending and normalization are also presented along with the generation of qualitative and quantitative products these techniques are then applied to generate themis daytime and nighttime infrared viking context imager ctx and mars orbiter camera moc visible mosaics using a variety of input and output types at a variety of scales by creating mosaics of the same area using different data sets such as those that illustrate compositional diversity thermophysical properties or small scale morphology it is possible to view the surface of the planet and geologic problems through many different perspectives in addition to the techniques used to create large scale seamless mosaics we also present the themis daytime and nighttime relative temperature global mosaics which are the highest resolution 100m pixel global scale data sets available for mars to date

geometric relationships of pristine martian complex impact craters and their implications to mars geologic history 1 based on the depths of pristine complex craters on mars we have estimated the final post modification phase depth dr to diameter d function of martian complex craters we suggest that the dr d function determined here holds globally for complex craters 12 km diameter the global nature of this function may be due to the stability of slopes in the highly fractured rock that makes up the steep interior walls of post modification phase craters the stability of such slopes should be controlled mainly by such factors as the nature of the fractures and not target strength this function is an essential benchmark for studies that utilize crater geometry as their basis for example the function can be used in gradation history of mars to predict the magnitude of degradation for instance an example 20 km diameter middle early noachian age crater that initially formed in the mid latitudes of mars with a depth of 1800 m instead of 1404 m as predicted by the fresh craters function has lost 1450 m of its depth over its history 350 m in the noachian 400 m during an intense episode of degradation at the end of the noachian and 700 m thereafter no evidence of the period of intense degradation is found in the high latitudes although those regions appear to have been affected by a process that reduced crater depth soon after they form

linking mineral deposit models to quantitative risk analysis and decision making in exploration this paper describes a methodology of translating mineral deposit models into flexible probabilistic structures based on 1 extraction of ore components fluids metals and ligands from crustal or mantle sources or both 2 fluid or melt assisted transport of ore components from source to trap zones 3 formation of trap zones i e effective melt or fluid channels that can focus melt or fluid migration and accommodate large amounts of metal and 4 operation of the physicochemical processes that promote and sustain the deposition of metal from fluids or melts passing through a particular trap site our approach integrates these critical mineralization processes and conditions with concepts of probability theory decision analysis and financial modeling the principal objective is to make mineral deposit models amenable to financial risk and value analysis and suitable for communication of value creating geologic concepts to financial stakeholders in economic terms a case study based on an actual porphyry copper project illustrates how the resulting probabilistic mineral systems model can generate a measure of the probability of ore occurrence as an input for exploration decision trees and simulations to calculate the expected value of an exploration project and the probability distribution of all possible surrounding net present values npvs within a minimum and maximum range formulation of the probabilistic model closely follows and combines principles of the well established petroleum and mineral systems approaches and makes use of excel based model templates with decision tree and simulation add in software packages

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

some aspects of the late tertiary geomagnetic field in iceland summary in 1972 78 the late n d watkins and others carried out ajoint field programme of geological mapping in the mio pliocene flood basalts of iceland including sampling for k ar dating and palaeomagnetic research the major part of the palaeomagnetic sampling is represented by 2462 lavas in five long composite sections through the lava pile this paper deals with various statistical properties of this data set it is concluded that geomagnetic reversals occur more frequently than is assumed in the current ocean floor polarity time scale there is no evidence for significant asymmetries between normal and reverse polarity states of the field neither as regards chron lengths secular variation or virtual dipole moment magnitude intensities of remanence in these lavas are shown to be well approximated in terms of a hyperbolic distribution the latitude distribution of virtual magnetic poles can be fitted with a bingham function having k 4 5 and low latitude poles do not occur preferentially in any particular longitude interval

catalogue of large alluvial fans in martian impact craters abstract we conducted a systematic global survey using thermal emission imaging system infrared themis ir coverage 100 m pixel to search for large alluvial fans in impact craters on mars our survey has focused on large fans apron areas greater than 40 km 2 usually located in craters greater than 20 km in diameter due to the resolution of the themis images and mars orbiter laser altimeter mola coverage we find that the host craters are found to have a distinctive diameter range from 30 150 km the fans generally cluster in three geographic areas southern margaritifer terra southwestern terra sabaea and southwestern tyrrhena terra however several outliers do exist the alluvial fans do not form in a particular orientation along the crater rim nor are they associated with the location of current high rim topography fan area magnitude and variability increase with crater diameter while fan concavity magnitude and variability increase with decreasing crater diameter smaller fan aprons in general have higher more variable concavity the source of the water forming these fans is uncertain given the challenges of accommodating the global distribution pattern and formation patterns within the craters

prospectivity for epithermal gold silver deposits in the deseado massif argentina previous prospectivity modelling for epithermal au ag deposits in the deseado massif southern argentina provided regional scale prospectivity maps that were of limited help in guiding exploration activities within districts or smaller areas because of their low level of detail because several districts in the deseado massif still need to be explored prospectivity maps produced with higher detail would be more helpful for exploration in this region we mapped prospectivity for low and intermediate sulfidation epithermal deposits liseds in the deseado massif at both regional and district scales producing two different prospectivity models one at regional scale and the other at district scale the models were obtained from two datasets of geological evidence layers by the weights of evidence wofe method we used more deposits than in previous studies and we applied the leave one out cross validation loocv method which allowed using all deposits for training and validating the models to ensure statistical robustness the regional and district scale models were selected amongst six combinations of geological evidence layers based on results from conditional independence tests the regional scale model 1000 m spatial resolution was generated with readily available data including a lithological layer with limited detail and accuracy a clay alteration layer derived from a landsat 5 7 band ratio and a map of proximity to regional scale structures the district scale model 100 m spatial resolution was generated from evidence layers that were more detailed accurate and diverse than the regional scale layers they were also more cumbersome to process and combine to cover large areas the evidence layers included clay alteration and silica abundance derived from aster data and a map of lineament densities the use of these evidence layers was restricted to areas of favourable lithologies which were derived from a geological map of higher detail and accuracy than the one used for the regional scale prospectivity mapping the two prospectivity models were compared and their suitability for prediction of the prospectivity in the district scale area was determined during the modelling process the spatial association of the different types of evidence and the mineral deposits were calculated based on these results the relative importance of the different evidence layers could be determined it could be inferred which type of geological evidence could potentially improve the modelling results by additional investigation and better representation we conclude that prospectivity mapping for liseds at regional and district scales were successfully carried out by using wofe and loocv methods our regional scale prospectivity model was better than previous prospectivity models of the deseado massif our district scale prospectivity model showed to be more effective reliable and useful than the regional scale model for mapping at district level this resulted from the use of higher resolution evidential layers higher detail and accuracy of the geological maps and the application of aster data instead of landsat etm data district scale prospectivity mapping could be further improved by a a more accurate determination of the age of mineralization relative to that of lithological units in the districts b more accurate and detailed mapping of the favourable units than what is currently available c a better understanding of the relationships between liseds and the geological evidence used in this research in particular the relationship with hydrothermal clay alteration and the method of detection of the clay minerals and d inclusion of other data layers such as geochemistry and geophysics that have not been used in this study

hirise imaging of impact megabreccia and sub meter aqueous strata in holden crater mars high resolution imaging science experiment hirise images of holden crater mars resolve impact megabreccia unconformably overlain by sediments deposited during two noachian age phases of aqueous activity a lighter toned lower unit exhibiting phyllosilicates was deposited in a long lived quiescent distal alluvial or lacustrine setting an overlying darker toned and often blocky upper unit drapes the sequence and was emplaced during later high magnitude flooding as an impounded uzboi vallis lake overtopped the crater rim the stratigraphy provides the first geologic context for phyllosilicate deposition during persistent wet and perhaps habitable conditions on early mars

porphyry epithermal and orogenic gold prospectivity of argentina this paper presents a review of the available information on the significant porphyry epithermal and orogenic gold districts in argentina including the tectonic geological and structural settings of large deposits or deposits that have been exploited in the past based on this review of the geology and mineralization targeting models are developed for epithermal and orogenic gold systems in order to produce gis based prospectivity models using publically available digital geoscience data weights of evidence and fuzzy logic prospectivity maps were generated for epithermal and orogenic gold mineralization in argentina the results of the prospectivity mapping highlight existing gold deposits within known mineralized districts throughout argentina as well as other highly prospective areas with no known deposits within these districts additionally areas within argentina that have no known gold mineralization based on publically available information were highlighted as being highly prospective based on the models used

the global topography of mars and implications for surface evolution elevations measured by the mars orbiter laser altimeter have yielded a high accuracy global map of the topography of mars dominant features include the low northern hemisphere the tharsis province and the hellas impact basin the northern hemisphere depression is primarily a long wavelength effect that has been shaped by an internal mechanism the topography of tharsis consists of two broad rises material excavated from hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary the present topography has three major drainage centers with the northern lowlands being the largest the two polar cap volumes yield an upper limit of the present surface water inventory of 3 2 to 4 7 million cubic kilometers