limnologic analysis of gusev crater paleolake mars abstract the survey of the hydrogeologic system formed by gusev crater and ma adim vallis aeolis subquadrangle of mars points out evidence for the existence of an ice covered lake in gusev crater a first lake was formed by the drainage of the aquifer in the region surrounding gusev before the entry of ma adim vallis in the crater the existence of a former lake in gusev is deduced from the morphology of the ma adim delta its comparison with terrestrial antarctic analogs argues for the presence of an ice covered lake in gusev at the time that the southern part of the crater s rampart was breached by ma adim first release and for a subice lacustrine construction of the valley s delta our survey shows that ma adim vallis may have entered gusev crater as late as late hesperian early amazonian as part of a second lake episode the relationship between the variation of the gusev lake water level the volume of the lake and the surface of the lake bed is established by our bathymetric model the elevation of the former lake is deduced from the elevation of the mesa like structures in the delta of ma adim vallis furthermore the correlation of the crater frequency of gusev rampart with mars stratigraphic age shows that lakes may have occupied gusev crater over a period of time covering 2 gyrs from the formation of the crater to the last episode of water release from ma adim vallis though it is most likely that the lake was episodical the recurrence of abundant water in gusev crater makes this site a high priority for missions either for martian resource exploration or for the search of life

valles marineris dune sediment provenance and pathways abstract although low albedo sand is a prevalent component of the martian surface sources and pathways of the sands are uncertain as one of the principal present day martian sediment sinks the valles marineris vm rift system hosts a diversity of dune field populations associated with a variety of landforms that serve as potential sediment sources including spur and gully walls interior layered deposits ilds and landslides here we test the hypothesis that vm dune fields are largely derived from a variety of local and regional intra rift sediment sources results show several dune fields are superposed on ancient wall massifs and ilds that are topographically isolated from extra rift sand sources spectral analysis of dune sand reveals compositional heterogeneity at the basinal dune field and dune scales arguing for discrete relatively unmixed sediment sources in coprates and melas chasmata mapping is consistent with the principle sand source for dunes being noachian aged upper and lower wall materials composed of primary igneous minerals and glasses some of which show evidence for alteration in contrast dune fields in capri juventae and ganges chasmata show evidence for partial sediment derivation from adjacent early hesperian aged hydrated sulfate bearing ild units this finding indicates that these ilds act as secondary sand sources dunes containing soft secondary minerals e g monohydrated sulfate are unlikely to have been derived from distant sources due to the physical weathering of sand grains during transport isolated extra rift dune fields sand sheets and sand patches are located on the plateaus surrounding vm and the adjoining areas but do not form interconnected networks of sand pathways into the rift if past wind regimes with respect to directionality and seasonality were consistent with more recent regimes inferred from morphological analysis i e dune slip faces wind streaks and were sufficient in strength and duration small dune populations within aurorae chaos and north of eastern vm might have resulted from extended sand pathways into vm however we favor local and regional derivation of dune sand from a variety of intra rift lithologic sources for most cases dune sand sources and the mechanism by which the sand is liberated are discussed in the context of findings described herein but are broadly applicable to analysis of sediment production elsewhere on mars

subsurface structure across the axis of the tongariro volcanic centre new zealand abstract the relationship between structure and volcanism in the tongariro volcanic centre new zealand is largely masked by a mantle of young volcanic deposits here we report the results of an integrated geophysical investigation using gravity multi level aeromagnetic and magnetotelluric methods of subsurface deposits and structures in the upper 1 2 km across the axis of the tongariro volcanic centre modelling of these data across the tama lakes saddle shows that the outcropping volcanic deposits are up to 800 m thick underlain by tertiary sediments of a few 10 s to a few 100 m in thickness and in turn lying above a basement of probable mesozoic greywacke basement faulting is shown to be concentrated in the centre of the rift which is 18 km wide at this location but no vertical offset is resolved at the rift axis vertical displacements on basement faults of 250 300 m are modelled giving a minimum total basement subsidence of 650 m a 5 km wide deep low resistivity zone occurs at the axis of the rift which is interpreted as either resulting from extensive fracturing and or hydrothermal alteration within the basement steep sided volcanic bodies with a high proportion of lavas dykes coincide with the waihi fault and the rift axis coincidence with the waihi fault suggests that this fault system may have provided magma pathways to the surface and a focus for dyke emplacement which could have contributed to rift extension the lack of offset at the rift axis may reflect the juvenile nature of faulting at this location which is consistent with the notion of a migration of faulting towards the centre of the graben alternatively rifting may have been entirely accommodated by dyke emplacement

the early environment and its evolution on mars implication for life there is considerable evidence that the early climate of mars was very different from the inhospitable conditions there today this early climate was characterized by liquid water on the surface and a dense atmosphere composed predominantly of co2 the duration of these warm initial conditions on the surface of mars is uncertain but theoretical models suggest that they could have persisted for hundreds of millions up to a billion years from studies of the earth s earliest biosphere we know that by 3 5 gyr ago life had originated on earth and reached a fair degree of biological sophistication surface activity and erosion on earth make it difficult to trace the history of life before the 3 5 gyr time frame if mars did maintain a clement environment for longer than it took for life to originate on earth then the question of the origin of life on mars follows naturally the fossil evidence of early life on earth provides clues as to what form fossils on mars might take of particular interest are stromatolites macroscopic layered structures that result from the anchoring of sediments by microorganisms living in the photic zone since over two thirds of the martian surface is more than 3 5 gyr old the possibility exists that mars may hold the best record of the events that led to the origin of life even though there may be no life there today

the evolution of andesite volcano structures new evidence from gravity studies in costa rica abstract published gravity data on active volcanoes generally reflect either the low density scoriaceous pumiceous deposits that are localized within ring fracture collapse depressions such as the calderas of mature silicic volcanoes or the high density frozen magma conduits that occur beneath basaltic shields and cones the intensive gravity surveys reported here over three complex andesite volcanoes reveal features of both types their multi component gravity fields have crater centred positive anomalies 1 2 km diameter surrounded by broader zones of negative gravity with similar amplitudes but greater width 5 10 km the former are thought to reflect sub crater magma pipes of normal density ca 2 5 2 6 mg m 3 surrounded by pyroclastic scoria ashes and occasional lava flows of much lower net density 1 8 2 4 mg m 3 which in turn account for the negative anomalous zones because the deeper more consolidated and older parts of these andesite volcano edifices have more normal densities 2 3 2 6 mg m 3 the low density materials are particularly interesting because they appear to have filled topographic depressions to depths of several hundred metres especially where old caldera like structures have been postulated from the steep gravity gradients over perimeter ring faults a model is developed whereby short periods of caldera collapse associated with intermittent large high level magma bodies are interspersed by normal crater like activity with narrow sub surface magma pipes dominantly pyroclastic activity from summit craters generates the materials that gradually fill earlier formed topographic depressions this study demonstrates the unique value of detailed gravity surveys combined with surface geological information for modelling and understanding the evolution of active volcano summit regions

three dimensional normal faulting models of the valles marineris mars and geodynamic implications inversion of martian topography using a three dimensional boundary element model permits revised estimates of fault dip angle depth of faulting paleogeothermal gradient and extensional strain in the valles marineris region the major normal faults dip at 40 55 to depths of 60 75 km with comparatively small footwall uplifts 500 m for throws to 10 km implying that paleogeothermal gradients during faulting were 10 k km 1 or less assuming relatively rapid strain rates appropriate to the extending martian crust accumulation of dip slip offsets along the main normal faults likely was associated with anticlinal flexure and deformation of preexisting strata within the troughs the magnitudes of the predicted vertical and horizontal displacements outside the troughs as well as extensional strains are spatially variable depending on both cross and along strike position relative to the troughs the predicted displacements and strains attain maximum values at the troughs and decay to background values at cross strike distances of 250 km corresponding to 3 4 times the depth of faulting with an average province wide strain of 4 15 by implication the aggregate strain field surrounding tharsis is a highly variable spatial and temporal composite of the inhomogeneous strain fields each associated and scaling in size with an individual graben from the smallest structures through the largest valles marineris troughs

spectral and geological study of the sulfate rich region of west candor chasma mars sulfates have been discovered by the omega spectrometer in different locations of the planet mars they are strongly correlated to light toned layered deposits in the equatorial regions west candor chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates a detailed study coupling mineralogy derived from omega spectral data and geology derived from hrsc imager and other datasets leads to some straightforward issues the monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material it likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments or during hydrothermal alteration at depth because it is typically found on outcrops that are eroded and steep polyhydrated sulfates that match any ca na fe or mg sulfates with more than one water molecule are preferentially present on less eroded and darker outcrops than outcrops of kieserite these variations can be the result of a diversity in the composition and or of the rehydration of kieserite on surfaces with longer exposure the latter possibility of rehydration in the current or recent atmosphere suggests the low surface temperatures preserve sulfates from desiccation and also can rehydrate part of them strong signatures of iron oxides are present on sulfate rich scarps and at the base of layered deposits scarps they are correlated with tes gray hematite signature and might correspond to iron oxides present in the rock as sand size grains or possibly larger concretions that are eroded and transported down by gravity at the base of the scarp pyroxenes are present mainly on sand dunes in the low lying terrains pyroxene is strongly depleted or absent in the layered deposits when mixed with kieserite local observations favor a spatial mixing with dunes over layered deposits sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation either in an intermittent lacustrine environment or by hydrothermal fluid circulation both possibilities require the presence of sulfur rich groundwater to explain fluid circulation the elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2 5 km above datum only 1 km below the plateau surface

early views of the martian surface from the mars orbiter camera of mars global surveyor high resolution images of the martian surface at scales of a few meters show ubiquitous erosional and depositional eolian landforms dunes sandsheets and drifts are prevalent and exhibit a range of morphology composition inferred from albedo and age as seen in occurrences of different dune orientations at the same location steep walls of topographic depressions such as canyons valleys and impact craters show the martian crust to be stratified at scales of a few tens of meters the south polar layered terrain and superposed permanent ice cap display diverse surface textures that may reflect the complex interplay of volatile and non volatile components low resolution regional views of the planet provide synoptic observations of polar cap retreat condensate clouds and the lifecycle of local and regional dust storms

a gravity study of the island of vulcano tyrrhenian sea italy a detailed gravity survey was carried out on the island of vulcano aeolian islands italy gravity was measured on 107 stations and the bouguer anomalies were computed by assuming geological densities

thermokarst landforms and processes in ares vallis mars abstract with a length of 1500 km ares vallis is one of the largest martian outflow channels and is inferred to have been formed by cataclysmic floods of water conveyed from source areas which are marked by chaotic terrain to chryse planitia near its downstream outlet 14 n 28 w the floor of ares widens to 100 km from its average 25 km width this area of widened channel floor is marked by a complex of irregular terraces elongated depressions linear ridges sinuous ridges and other indicators of highly irregular dissection of a formerly continuous surface thermokarst processes following either glacial or alluvial histories seem best to explain these relationships various indicators of fluctuating discharge for water and sediment ponding of debris and prolonged flow suggest the emplacement of ice rich debris in the anomalous reach of ares vallis post flood or post glacial thawing of the ice rich sediments would then generate the thermokarst landscape these processes which are consistent with other indicators of anomalously warm climatic conditions imply a profound change from the modern martian environment

morphology stratigraphy and mineralogical composition of a layered formation covering the plateaus around valles marineris mars implications for its geological history an extensive layered formation covers the high plateaus around valles marineris mapping based on hirise ctx and hrsc images reveals these layered deposits lds crop out north of tithonium chasma south of ius chasma around west candor chasma and southwest of juventae chasma and ganges chasma the estimated area covered by lds is not vert similar42 300 km2 they consist of a series of alternating light and dark beds a 100 m in total thickness that is covered by a dark unconsolidated mantle possibly resulting from their erosion their stratigraphic relationships with the plateaus and the valles marineris chasmata indicate that the lds were deposited during the early to late hesperian and possibly later depending on the region before the end of the backwasting of the walls near juventae chasma and probably before louros valles sapping near ius chasma their large spatial coverage and their location mainly on highly elevated plateaus lead us to conclude that lds correspond to airfall dust and or volcanic ash the surface of lds is characterized by various morphological features including lobate ejecta and pedestal craters polygonal fractures valleys and sinuous ridges and a pitted surface which are all consistent with liquid water and or water ice filling the pores of lds lds were episodically eroded by fluvial processes and were possibly modified by sublimation processes considering that lds correspond to dust and or ash possibly mixed with ice particles in the past lds may be compared to dissected mantle terrains currently observed in mid to high latitudes on mars which correspond to a mantle of mixed dust and ice that is partially or totally dissected by sublimation the analysis of crism and omega hyperspectral data indicates that the basal layer of lds near ganges chasma exhibits spectra with absorption bands at not vert similar1 4 m and not vert similar1 9 m and a large deep band between not vert similar2 21 and not vert similar2 26 m that are consistent with previous spectral analysis in other regions of lds we interpret these spectral characteristics as an enrichment of lds in opaline silica or by al phyllosilicate rich layers being overlain by hydroxylated ferric sulfate rich layers these alteration minerals are consistent with the aqueous alteration of lds at low temperatures

hematite bearing materials surrounding candor mensa in candor chasma mars implications for hematite origin and post emplacement modification abstract the valles marineris canyon system on mars is of enduring scientific interest in part due to the presence of interior mounds that contain extensive layering and water altered minerals such as crystalline gray hematite and hydrated sulfates the presence of hematite and hydrated sulfate minerals is important because their host rock lithologies provide information about past environments that may have supported liquid water and may have been habitable this work further defines the association and relationship between hematite bearing materials and low albedo presumably aeolian deposits and layered materials identifies physical characteristics that are strongly correlated with the presence of hematite and refines hypotheses for the origin and post emplacement modification including transport of these hematite bearing and associated materials there are only three regions surrounding candor mensa where hematite has been identified even though morphologic properties are similar throughout the entire mensa three possible explanations for why hematite is only exposed in these regions include 1 the topographic structure of the mensa walls concentrates hematite at the base of the layered deposits influencing the ability to detect hematite from orbit 2 the presence of differing amounts of dark mantling material and hematite free erosional sediment 3 the potential fracturing of the mensa and the influence of these structures on fluid flow and subsequent digenesis the observations of hematite bearing materials in this work support the hypothesis that hematite is eroding from a unit in the candor mensa interior layered deposits ild and is being concentrated as a lag deposit adjacent to the lower layers of candor mensa and at the base in the form of dark aeolian material due to the similar geologic context associated with hematite bearing and ild materials throughout the valles marineris canyon system the insight gained from studying these materials surrounding candor mensa can likely be applicable to similar layered deposits throughout valles marineris

new evidence for a magmatic influence on the origin of valles marineris mars in this paper we show that the complex geological evolution of valles marineris mars has been highly influenced by the manifestation of magmatism e g possible plume activity this is based on a diversity of evidence reported here for the central part melas chasma and nearby regions including uplift loss of huge volumes of material flexure volcanism and possible hydrothermal and endogenic induced outflow channel activity observations include 1 the identification of a new 50 km diameter caldera vent like feature on the southwest flank of melas which is spatially associated with a previously identified center of tectonic activity using viking data 2 a prominent topographic rise at the central part of valles marineris which includes melas chasma interpreted to mark an uplift consistent with faults that are radial and concentric about it 3 hirise identified landforms along the floor of the southeast part of melas chasma that are interpreted to reveal a volcanic field 4 crism identification of sulfate rich outcrops which could be indicative of hydrothermal deposits 5 grs k th signature interpreted as water magma interactions and or variations in rock composition and 6 geophysical evidence that may indicate partial compensation of the canyon and or higher density intrusives beneath it long term magma tectonic and water interactions late noachian into the amazonian albeit intermittent point to an elevated life potential and thus valles marineris is considered a prime target for future life detection missions

the large thaumasia graben on mars is it a rift 1 we investigate the morphology and topography of one of the largest fault bounded tectonic structures on mars a complex approximately n s trending system of troughs and scarps at the western border of the thaumasia plateau in the claritas region hereinafter referred to as thaumasia graben or tg it is located between 15 s and 38 s latitude and at 255 e longitude no detailed investigation of its morphotectonic setting has been performed yet the region is a complexly fractured area with a number of different fault sets including simple and complex graben the tg extends over more than 1000 km along its trend averaging 100 km in width and 1 6 km in depth crustal extension is accommodated by the formation of a system of asymmetric graben or halfgraben on the basis of fault orientation and trough depth the tg can be subdivided in a north south direction into three segments except for the northernmost segment the predominant master fault system is located along the eastern flank of the tg highlighting the overall asymmetric architecture fault length segments vary from 50 to 90 km with observable displacements of 1 3 2 2 km crustal extension inferred from gridded mola topography across scarp offsets varies along trend between 0 5 km and 4 km assuming a fault dip of 60 this is relatively moderate extension if compared to terrestrial continental rifts but consistent with extension measured across the tempe rift on mars we find that the thaumasia graben displays some characteristics which are common to terrestrial continental rifts whereas other properties are distinctively not rift like

microstructural evidence for seismic and aseismic slips along clay bearing carbonate faults in this multi methodological study microstructural observations of fault rocks are combined with micromechanical property analyses contact resonance atomic force microscopy cr afm and with rotary friction experiments shiva apparatus to find evidence of seismic to aseismic slip and understand the nanoscale rheology of clay bearing carbonate hosted faults fluidized structures truncated clasts pores and vesicles and phyllosilicate nano sized spherules and tubes suggest fast deformation events occurred during seismic slip whereas clay assisted pressure solution processes clumped clasts foliation surfaces and mantled clasts indicate slow deformation events occurred during postseismic interseismic periods cr afm measurements show that the occurrence of 5 wt of clay within the carbonate hosted gouges can significantly reduce the fault core stiffness at nanoscale in addition during high velocity friction experiments simulating seismic slip conditions the presence of ultra thin phyllosilicate bearing 3 wt layers within calcite gouges as those observed in the natural fault show faster dynamic weakening than that of pure calcite gouges the weak behavior of such layers could facilitate the upward propagation of seismic slip during earthquakes thus possibly enhancing surface faulting microstructural observations and experimental evidence fit some well known geophysical and geodetic observations on the short to long term mechanical behavior of faults such as post seismic interseismic aseismic creep interseismic fault locking and seismic slip propagation up to the earth s surface

potential field and bathymetric investigation of the monowai volcanic centre kermadec arc implications for caldera formation and volcanic evolution the dynamics of caldera formation are affected by internal factors such as magma chamber structure and properties and regional tectonic stresses understanding their interrelationship is important for assessing volcanic hazard and reconstructing the evolution of a volcano the monowai volcanic centre located at the tonga kermadec arc is a basaltic andesitic submarine stratovolcano and caldera recent surveys have shown that it is active but little is known about its structure and evolution here we present a combined analysis of swath bathymetry and potential field data from monowai acquired during cruise so215 on the r v sonne in 2011 april june the monowai caldera is associated with a 20 25 mgal bouguer gravity anomaly high and a broad positive magnetic anomaly short wavelength magnetic anomalies of up to 1400 and 800 nt are observed along the caldera rim and on the summit of monowai cone inversion of the bouguer gravity anomaly data shows that the caldera high is caused by a buried dense body with density contrast of up to 450 kg m 3 with respect to the surrounding arc crust the body has a volume of 250 km3 and is divided into a main unit extending from 3 to 6 km depth and a shallower ring structure that underlies the rim of monowai caldera we estimate the density of the body to be 2650 2850 kg m 3 suggesting a mafic composition the ring structure is interpreted as set of ring dykes and the main unit as a solidified or partly solidified magma chamber system the monowai pluton the observed magnetic anomalies are consistent with pluton intrusion within the bruhnes magnetic polarity analysis of the swath bathymetry data shows that monowai is located in a 20 km wide graben part of an en echelon left stepping horst and graben system that spans the length of the arc and backarc the monowai caldera is elongated perpendicular to the direction of rifting suggesting that it is affected by the regional stress regime geomorphological analysis suggests that the caldera was created by repeated collapse of a single caldera structure and that its complex shape and multiple ring faults can be attributed to prolonged activity and multiple cycles of inflation and collapse we propose a multiphase evolution of the monowai volcanic centre comprising initial magma emplacement and crustal inflation magma chamber evacuation and caldera collapse caldera resurgence and mass waisting southward migration of the eruptive vent and formation of monowai cone it remains unclear whether the current eruption at the monowai cone is fed directly from a small underlying magma chamber or laterally from the monowai pluton observation of radial fissure ridges on its flanks suggests that a shallow magma body may have been recently emplaced beneath the summit causing inflation and the formation of extensional cracks the summit appears unstable and may be prone to lateral or vertical collapse therefore the region remains a potential source of regional volcanic and tsunami hazard

the shallow structure of the martian lithosphere in the vicinity of the ridged plains wrinkle ridges in the smooth plains of the coprates and lunae planum regions of mars form linear or concentric patterns with a regular spacing of 25 50 km the authors test the hypothesis that the periodic development of deformation was a consequence of unstable horizontal compression that occurred prior to probable ridge related faulting of a strength stratified lithosphere which consists of a mechanically strong surface plains unit that successively overlies a weak megaregolith and a strong lithospheric basement results show that a range of models with both rigid and deformable megaregolith basement interface conditions yield solutions which can explain the ridge spacing within the constraint provided by the estimated thickness of the smooth plains materials in models that incorporate viscous and plastic rheologies uniform and exponentially varying vertical strength distributions and the presence or absence of interfacial slip at the base of the surface plains unit the ridge spacing is primarily controlled by the power law exponent of the lithosphere the megaregolith plains unit thickness ratio and the plains unit megaregolith strength contrast deformable basement models with a viscous rheology 1 le n approx le 3 can explain the ridge spacing if the megaregolith was thicker than and approximately 1 3 orders of magnitude weaker than themore plains unit similar models with a perfectly plastic n yields infinity rheology require plains unit thicknesses greater than 5 km which exceeds most observational estimates ridge spacing in the combined viscous and plastic models can be consistent with either a dry water rich or ice rich megaregolith at the time of ridge formation less

ignimbrites of amazonis planitia region of mars a series of postulated ignimbrite units is mapped in the amazonis memnonia and aeolis quadrangles of mars the units cover about 2 2 106 km2 within a broad but discontinuous and irregular belt trending east west along the highland lowland boundary the ignimbrites overlie parts of the western and southern aureole materials of olympus mons but are embayed in places by the lava plains of the lowlands stratigraphic relations between the basalt flows from the tharsis montes region and the ignimbrites are not clearly defined crater counts suggest that the younger ignimbrites postdate the lava flows crater counts per square kilometer for the ignimbrites range from 7 29 1 95 10 4 to 6 36 2 01 10 5 for craters larger than 1 km in diameter the ignimbrite materials form thick 100 m extensive relatively flat sheets that are smooth to grooved or gently undulating grooved surfaces appear to be yardangs and in most places are not alined with prevailing wind directions the seven mapped ignimbrite units are characterized by morphologic expression stratigraphic position and crater counts similarities to ignimbrites in the pancake range of central nevada include 1 rounded patches of smooth high albedo nonwelded material superposed on jointed low albedo welded material 2 local complementary joint sets in welded materials and 3 thick flow sheets of great areal extent that follow but subdue underlying topography four major eruptive centers occur in areas where units are thickest and where a dominant nnw sse structural trend is expressed locally by unit margins elongate collapse features and normal faulting a minimum volume of 3 85 106 km3 for the deposits has been calculated from thickness estimates based on shadow measurements and crater rim height relations

a comparison of volcanic eruption processes on earth moon mars io and venus the silicate planets and satellites display a wide range of physical chemical and atmospheric characteristics which may influence the nature of volcanism a major geological process common to the evolution of the surfaces of these bodies consideration of the process of magma ascent and eruption from first principles allows predictions to be made concerning volcanic eruption styles and expected landforms and deposits on each planetary body examination of actual land forms and deposits in light of these predictions leads to a better understanding of the nature of volcanic eruption processes and outlines outstanding problems

topography of valles marineris implications for erosional and structural history compilation of a simplified geologic geomorphic map onto digital terrain models of the valles marineris permitted an evaluation of elevations in the vicinity of the troughs and the calculation of depth of troughs below surrounding plateaus thickness of deposits inside the troughs volumes of void spaces above geologic geomorphic units and volumes of deposits the central troughs north ophir north and central candor and north melas chasmata lie as much as 11 km below the adjacent plateaus in ophir and candor chasmata interior layered deposits reach 8 km in elevation if the deposits are lacustrine and if all troughs were interconnected lake waters standing 8 km high would have spilled out of coprates chasma onto the surrounding plateaus having surface elevations of only 4 5 km in this case interior deposits above about 4 km in the central troughs would not be lacustrine they could be volcanic on the other hand the troughs may not have been interconnected at the time of interior deposit emplacement they may have formed isolated ancestral basins the existence of such basins is supported by independent structural and stratigraphic evidence the ancestral basins may have eventually merged perhaps through renewed faulting to form northern subsidiary troughs in ophir and candor chasmata and the coprates north melas ius graben system the peripheral troughs are only 2 5 km deep shallower than the central troughs they may have formed from a combination of erosional collapse and structural activity chaotic terrain is seen in the peripheral troughs near a common contour level of about 4 km on the adjacent plateaus which supports the idea of release of water under artesian pressure from confined aquifers the layered deposits in the peripheral troughs may have formed in isolated depressions that harbored lakes and predated the formation of the deep outflow channels if these layered deposits are of volcanic origin they may have been emplaced beneath ice in the manner of table mountains areal and volumetric computations show that erosion widened the troughs by about one third and that deposits occupy one sixth of the interior space even though the volume eroded is larger than the volume deposited topographic and geologic considerations imply that material eroded from trough walls was probably part of the interior layered deposits but not their sole source additional material may have come from subterranean piping from reworking of local disintegration products on the floors such as chaotic materials or from eolian influx but overall it is likely that the additional material is volcanic and that it forms mostly the upper more diversely bedded layers of the interior deposits

nanometre scale faulting in quartz under an atomic force microscope abstract we conducted nano indentation tests of quartz under a load of 294 mn at room temperature and ambient pressure using an atomic force microscope we performed topographic mapping of the indented surface immediately after the nano indentation test and again 46 h later differences in the contour patterns of the two surface topographies reveal that a new fault developed in the quartz specimen while it was secured on the specimen stage of the atomic force microscope between the two mapping times the fault length is 2 m and the maximum displacement on the fault plane is 20 nm when combined with existing displacement length data from natural faults the data suggest that a linear displacement length scaling relationship can be extrapolated to nanometre scale faulting

chryse basin channels low gradients and ponded flows gradients on the floors of the martian outflow channels that are derived from radar elevation profiles across lunae planum and the chryse basin have much lower values than those obtained from the u s geological survey s topographic map to arrive at this conclusion 26 radar elevation profiles clustered at four latitudinal channel crossings were analyzed and approximate longitudinal gradients of the channel floors were constructed whereas the gradients of maja and ares valles are similar to those of the catastrophic flood channels in the scablands of washington state and water or ice could have moved through them without difficulty the gradients of simud and tiu valles are essentially level and the movement of fluids to the north poses problems it is proposed that ponding from local runoff occurred before channel formation along the course of simud and tiu valles the ponding may have formed lakes in depressions associated with the valles marineris grabens ancient craters in the chaotic terrain area and possibly even the regional low where most chaotic terrains occur it is envisioned that lakes eventually overflowed drainages became integrated and headward erosion breached interfluves thus forming the present channel configurations when dams broke floods mudflows or mixtures of water sediments and ice were released catastrophically with a final gigantic flood from the valles marineris system of troughs this flood would have had sufficient head to move fluids across nearly level gradients through the simud and tiu channels the ponding and flooding probably occurred during a time when the climate was different from that at present permitting surface runoff of fluids and standing bodies of water

high resolution thermal inertia derived from the thermal emission imaging system themis thermal model and applications 1 thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the thermal emission imaging system themis on the mars odyssey spacecraft producing the highest resolution thermal inertia data set to date themis thermal inertia values have an overall accuracy of 20 a precision of 10 15 and are consistent with both thermal emission spectrometer orbital and miniature thermal emission spectrometer surface thermal inertia values this data set enables the improved quantification of fine scale surface details observed in high resolution visible images in the tharsis region surface textures and crater rims observed in visible images have no corresponding variation in the themis thermal inertia images indicating that the dust mantle is pervasive at themis scales and is a minimum of a few centimeters and up to 1 2 m thick the thermal inertia of bed form material indicates particle diameters expected for aeolian sediments and these materials are likely currently saltating variations in the thermal inertia within interior layered deposits in hebes chasma can be distinguished and the thermal inertia is too low to be consistent with bedrock or a lava flow thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation higher resolution themis thermal inertia enables the identification of exposed bedrock on the martian surface in nili patera and ares vallis bedrock material corresponds to distinct compositional and morphologic surfaces indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes

hydrated minerals in the deposits of aureum chaos abstract hydrated minerals have been detected in many martian chaos regions and chasmata playing a major role in its past aqueous activity based on short wave infrared data from crism imagery and elevation data we identified and mapped hydrated minerals in aureum chaos to shed light on their stratigraphy and geological context the interior layered deposits ilds display three stratigraphic units the lowest unit shows massive and also layered high albedo monohydrated sulfate mhs best matching kieserite 20 650 m thick with intercalated hydroxylated ferric sulfates hfss best matching jarosite and ferric oxides the overlying polyhydrated sulfate phs is commonly layered 20 40 m thick smooth to heavily fractured of lower albedo and partially contains ferric oxides spectrally neutral distinctly layered and bumpy cap rock 40 300 m thick forms the top we found spectral and morphological similarities to aram chaos phs mhs ferric oxides texture of ild and cap rock and juventae chasma hfs besides the phyllosilicate nontronite was found attributed to chaotic terrain as light toned fractured exposure and within dark smooth mantling the coexistence of sulfates and phyllosilicates indicates changes in the geochemistry of the aqueous environment since sulfates and phyllosilicates could be alteration products the observed mineralogy presumably is not the original conversions between phs and mhs mhs or phs into jarosite jarosite into iron oxides are considered due to its occurrence along mantling edges and on flat surfaces of mhs without textural differences it appears that phs is an alteration product of mhs e g due to surface exposure the facies and relative timing of sulfate formation remains undefined however two different formation models are considered the first implies contemporaneous ild and phs deposition and diagenetic sulfate conversion into mhs iron oxides due to overburden later on this model is less conclusive than groundwater evaporation the second model due to the lack of a sharp phs mhs boundary that would indicate a diagenetic formation alternatively the second model suggests subsequent sulfate formation groundwater would have penetrated into pre existing sulfate free ild the permeability and porosity of ild material would have defined the rate of water absorption and sulfate precipitation low in cap rock resulting in cementation of probably aeolian deposited ilds we think this model is more consistent and could explain ild stratigraphy with the potential anhydrous cap rock on top the surface age of chaotic terrain late hesperian and mantling deposits mid to late amazonian limit the ild age and possibly the emplacement of sulfates phyllosilicates in the mantling are presumably allochthonous limiting the timing of in situ phyllosilicates is more complicated they could be noachian excavated material following the phyllosian era or instead syn or post chaotic a close spatial and temporal association of sulfates and phyllosilicates in which nontronite represents the deep facies and sulfates the evaporitic facies is known from earth and is also possible and would combine groundwater alteration with the observed mineralogy the preservation of nontronite hfs and mhs probably reflects a relatively dry environment with intermittent aqueous activity since their emplacement

related magma ice interactions possible origins of chasmata chaos and surface materials in xanthe margaritifer and meridiani terrae mars abstract we examine here the close spatial and temporal associations among several unique features of xanthe and margaritifer terrae specifically the valles marineris troughs or chasmata and their interior deposits chaotic terrain the circum chryse outflow channels and the subdued cratered material that covers xanthe margaritifer and meridiani terrae though previous hypotheses have attempted to explain the origin of individual features or subsets of these we suggest that they may all be related all of these features taken together present a consistent scenario that includes the processes of sub ice volcanism and other magma ice interactions results of intrusive events during late noachian to early amazonian times

new martian paradigms several interrelated paradigms concerning the nature and the evolution of mars are discussed these include an impact origin of the northern lowland mars as a water rich planet former oceans in the northern lowlands a warm wet climate on early mars and the possibility of ancient life on mars locations on mars suggested for the search of possible ancient life include the heavily cratered terrain dissected by valley networks possible lacustrine deposits in valles marineris the oxidizing layer below the surface sites along the fringes of the hypothetical northern circumpolar ocean and in evaporite deposits

structural development of coprates chasma and western ophir planum valles marineris rift mars a portion of valles marineris was mapped in detail in order to clarify the dominant processes responsible for the formation of coprates chasma new crater counts indicate that the caprock on western ophir planum plateau has a late hesperian crater age whereas trough floor preserved in western coprates chasma has an early to late hesperian crater age caprock on western ophir planum correlates in relative age with the syria planum formation and the caprock may overlie lower hesperian ridged plains material the conspicuous absence of wrinkle ridges on ophir planum may reflect burial by this later material trough floor material in coprates chasma correlates in relative age with ridged plains material on the adjacent lunae planum and coprates plateaus and represents a structurally coherent block displaced downward by normal faulting the crater counts and detailed structural relationships demonstrate the commonly accepted view that coprates chasma occupies a graben the floor of this graben is only thinly mantled by intratrough deposits and is relatively intact the trough shows no evidence for a chaotically broken and jumbled floor as required by genesis models of collapse and subsurface drainage formation of coprates chasma by keystone collapse of locally elevated topography is not supported by available topographic data but a general association between the trough and volcanotectonic activity in the tharsis region is considered to be a likely explanation for the trough forming stresses subtle asymmetries in topography and boundary fault development across coprates chasma may imply a gentle down to the north half graben geometry for the trough normal faults that define the northern margin of western coprates chasma and those that deform the adjacent ophir planum plateau change trend systematically with position implying a 30 rotation of the local horizontal principal stresses in this region during trough growth faulting on ophir planum appears related to the faulting that created the coprates chasma trough the geology and structure of coprates chasma are comparable to those of other troughs such as melas ius and perhaps candor chasmata suggesting that these troughs may also have formed as grabens the revised crater age for western ophir planum indicates that the initiation of trough faulting and subsidence in the valles marineris system is early late hesperian and may have been synchronous across the system relative to the prevailing cratering rate

volcanomagnetic effects at vulcano island aeolian archipelago italy summary the installation of two continuously operating proton magnetometers 2 km apart and sampling simultaneously every 5 min on vulcano island from 1990 november to 1991 december allowed the detection of some transient anomalies thought to result from internal variations in the physical state of the volcano the diverence of mean values in the magnetic field at the two stations underwent a slow variation of 2 nt during the period of measurements the mean values in the total intensity at one station were inversely correlated to the diverence between the mean values of the two stations this suggests that the contribution to the signal generated by the transitory magnetic field may be broken down into two parts one of external origin which is identical for both stations and another of internal origin proportional to the former but dependent on the site following on from this simple description of the magnetic field a method of analysis was developed to distinguish between transients of volcanomagnetic origin and transients generated by strong variations in the external transitory magnetic field an accurate analysis which takes into account the correlation between the measurements at the two stations leads to the singling out of three magnetic anomalies on 1991 april 2 july 18 and december 23 comparison of the experimental data with the list of earthquakes occurring at vulcano during 1991 showed the close temporal correspondence between the magnetic anomalies and earthquakes the amplitude between 2 and 4 nt spatial extent approximately 2 km and polarity of anomalies point to the piezomagnetic evect as the primary physical mechanism driving these transient changes on the other hand the anomaly with respect to the regional field observed over one year is explicable in terms of a thermomagnetic evect detected at both stations the magnetic static anomaly produced by a completely demagnetized spherical source of 250 m radius located under the la fossa crater at a depth of 1300 m is in agreement with the slow changes observed at vulcano

gravity fields and the interpretation of volcanic structures geological discrimination and temporal evolution abstract a review of gravity data reflecting shallow concealed structures on volcanoes demonstrates that valuable information may be derived on the geological development of such structures and on the dynamic evolution of active volcanoes to a first approximation all recorded examples of anomalous gravity fields associated with volcanoes are concentric with and have sources that lie within the volcanic edifice positive anomalies with wavelengths less than 20 km and amplitudes up to ca 30 mgal characterise mainly basaltic volcanoes from various tectonic settings and are caused by a relatively dense intrusive complex magma body which contrasts with its surroundings either because the body is more mafic than average or more likely because near surface previously erupted materials are uncompacted negative anomalies with wavelengths up to 100 km and amplitudes up to ca 60 mgal occur over much larger volcanic calderas many of which have erupted highly silicic pyroclastic ash and pumice uncompacted silicic caldera infill with a possible contribution from low density magma bodies is responsible for the observed anomalies there is some evidence for a continuum of gravity anomaly types that corresponds to the geological evolution of volcanic systems generally from primitive rift or subduction related basaltic andesite to mature high level silicic calderas repeated microgravity observations over active volcanoes enable magma movements variations in magma input and changes in magma density to be monitored closely dynamic modelling of volcanic systems is providing new evidence on the behaviour of concealed magma bodies and could have considerable potential for predicting eruptive events

regional dust deposits on mars physical properties age and history major dust storms on mars play an important role in the deposition and removal of fine dust material thermal radar and visual remote sensing observations provide important constraints on the martian regolith which have been used to determine the location and physical properties of regional dust deposits these deposits are located in three northern equatorial regions tharsis 20 s to 50 n 60 to 190 w arabia 5 s to 30 n 300 to 360 w and elysium 10 to 30 n 210 to 225 w they are covered by fine 2 40 m bright albedo 0 27 particles with fewer exposed rocks and coarse deposits than found elsewhere dust is currently deposited uniformly throughout the equatorial region at a rate of 40 m global storm over geologic time the rate of accumulation may vary from 0 to 250 m yr due to changes in atmospheric conditions produced by orbital variations dust deposited during global storms is subsequently removed only from dark regions resulting in a net accumulation in the low inertia bright regions the thickness of these current dust deposits is 0 1 2 m the thermal inertia places a lower limit of 0 1 m on the thickness of these deposits while the sparse but ubiquitous presence of exposed rocks and the degree of visible mantling indicate that the thickness is less than 5 m dual polarization radar observations of a very rough texture in tharsis are consistent with this model with a 2 m thick dust layer burying most of the surface rocks but permitting radar sampling of the rough subsurface based on their thickness and rate of accumulation the age of these deposits is 105 106 years suggesting a cyclic process of deposition and removal one possible cause may be cyclic variations in the magnitude and location of maximum wind velocities related to variations in mars orbit at present perihelion and maximum wind velocities occur in the south whereas regional dust deposits occur in the north suggesting net transport from south to north orbital parameters oscillate with periods ranging from 5 104 to 106 years the agreement between these periods and the dust deposit age suggests a possible link at different stages in orbit evolution maximum wind velocities will occur in the north with subsequent erosion and redistribution of the accumulated fines based on this model much of the uppermost martian surface is very young and is being continually reworked

underlying structural control of small scale faults and fractures in west candor chasma mars 1 orientations of small scale faults and fractures within the interior layered deposits of west candor chasma were measured to investigate what information about the geologic history of valles marineris they can contribute deformational features were separated into six categories based on morphology and their orientations were analyzed the elevations at which the deformational features formed are recorded as a proxy for stratigraphic level deformational features occur over a continuous range of elevations and display regionally consistent preferred orientations indicating their formation was controlled by a regional stress regime the two most abundant preferred orientations of 35 and 110 are approximately parallel to the chasma walls and the inferred underlying normal faults the alignment of three populations of small faults at 140 consistent with the morphology of release faults indicates a large scale fault underlying the southeastern border of ceti mensa the preferred orientations imply these small scale deformational features formed from a continuation of the same imposed stresses responsible for the formation of valles marineris indicating these stresses existed past the formation of the interior layered deposits the origins of a fourth preferred orientation of 70 is less clear but suggests the study area has undergone at least two periods of deformation

valles marineris mars wet debris flows and ground ice abstract detailed study of the valles marineris equatorial troughs suggests that the landslides in that area contained water and probably were gigantic wet debris flows one landslide complex generated a channel that has several bends and extends for 250 km further support for water or ice in debris masses includes rounded flow lobes and transport of some slide masses in the direction of the local topographic slope differences in speed and emplacement efficiency between martian and terrestrial landslides can be attributed to the entrainment of volatiles on mars but they can also be explained by other mechanisms support that the wall rock contained water comes from the following observations 1 the water within the landslide debris must have been derived from wall rock 2 debris appears to have been transported through tributary canyons 3 locally channels emerged from the canyons 4 the wall rock apprarently disintegrated and flowed easily and 5 fault zones within the troughs are unusually resistant to erosion the study further suggests that in the equatorial region of mars material below depths of 400 800 m was not desiccated during the time of landslide activity within the last billion years of martian history therefore the martian ground water or groundice reservoir if not a relic from ancient times must have been replenished

composition and structures of the subsurface in the vicinity of valles marineris as revealed by central uplifts of impact craters abstract despite recent efforts from space exploration to sound the martian subsurface with radar the structure of the martian subsurface is still unknown major geologic contacts or discontinuities inside the martian crust have not been revealed another way to analyze the subsurface is to study rocks that have been exhumed from depth by impact processes the last martian mission mro mars reconnaissance orbiter put forth a great deal of effort in targeting the central peaks of impact craters with both of its high resolution instruments crism compact reconnaissance imaging spectrometer for mars and hirise high resolution science experiment we analyzed the composition with crism and the physical characteristics on hirise of the rocks exhumed from depth from 31 impact craters in the vicinity of valles marineris our analyses revealed the presence at depth of two kinds of material massive light toned rocks and intact layers exhumed light toned massive rocks are enriched in low calcium pyroxenes and olivine hydrated phases such as smectites and putative serpentine are present and may provide evidence of hydrothermal processes some of the rocks may represent portions of the volatile rich pre noachian martian primitive crust in the second class of central peaks exhumed layers are deformed folded and fractured visible near infrared vnir spectra suggest that they are composed of a mixture of olivine and high calcium pyroxene associated with hydrated phases these layers may represent a noachian volcanic accumulation of up to 18 km due to tharsis activity the spatial distribution as well as the in depth distribution between the two groups of rocks exhumed are not random and reveal a major geologic discontinuity below the tharsis lava plateau the contact may be vertical over several kilometers depth suggesting the pre existence of a steep basin early giant impact or subsidence basin or sagduction processes

interpretation of gravity and magnetic data in the phlegraean fields geothermal area naples italy abstract available gravity and magnetic data of the phlegraean fields geothermal area naples italy have been interpreted and the obtained structural models discussed in the light of the other available geological volcanological and geophysical data on the basis of the results of a previous seismic reflection survey in the gulf of naples and in the pozzuoli bay which delineated a basement characterized by a seismic velocity of 4 6 km s it has been possible to evaluate the gravity anomaly connected with the morphology of this horizon 2 7 g cm3 the residual anomaly map obtained after subtraction of the regional long wavelength components relative to mantle and deep crustal structures and the computed components relative to the above mentioned seismic basement shows up as a circular low with an amplitude of 10 mgal centred in the pozzuoli bay this gravity low has been interpreted as due to the occurrence in the centre of pozzuoli bay of light 0 2 g cm3 material with a maximum thickness of about 2 km however a contribution to the anomaly due to a narrow magmatic body intruded in the basement as suggested by volcanological and ground deformation data cannot be excluded the aeromagnetic map of the phlegraean fields is characterized by three main anomalies which have been fitted by superficial tridimensional parallelepipedic bodies schematically representing lava flows and domes their anomalies have been subsequently subtracted from the observed field obtaining as a residual a large anomaly centred in the southwestern area of the pozzuoli bay it has been interpreted as being due to a lowmagnetized body which taking into account the thermal state of the area should represent that part of the pyroclastic sequence which has lost part of its magnetization by thermo chemical alteration

geomorphic evidence for the distribution of ground ice on mars high resolution viking orbiter images show evidence for quasi viscous relaxation of topography the relaxation is believed to be due to creep deformation of ice in near surface materials the global distribution of the inferred ground ice shows a pronounced latitudinal dependence the equatorial regions of mars appear to be ice poor while the heavily cratered terrain poleward of 30 latitude appears to be ice rich the style of creep poleward of 30 varies with latitude possibly due to variations in ice rheology with temperature the distribution suggests that ice at low latitudes which is not in equilibrium with the present atmosphere has been lost via sublimation and diffusion through the regolith thereby causing a net poleward transport of ice over martian history

ages of valles marineris mars landslides and implications for canyon history the chronology of landslides of valles marineris the equatorial trough system of mars has been investigated by a crater population study valles marineris landslides have widespread debris aprons which offer a remarkable opportunity to study the crater population with high resolution images from mars orbiter camera moc and from mars odyssey thermal emission imaging system themis sixty six ages were determined within valles marineris including 56 landslide ages and 10 ages of the previous termcanyonnext term floor results reveal that landslides of valles marineris system of previous termcanyonsnext term occurred during a widespread period of time between 3 5 gy and 50 my in some locations the previous termcanyonnext term floor has an apparent age of 3 5 gy suggesting that at least locally within valles marineris no major refreshing processes have occurred for 3 5 gy the temporal repetitivity of landslides implies that the triggering mechanisms of the landslides are reproducible in time landslides have the same features whatever their age the dynamic of these landslides is probably the same either with intervention of water up to recently the last 100 my or without water since 3 5 gy

a geochemical model for the formation of hydrothermal carbonates on mars it is often argued that substantially more carbon dioxide and water were degassed from the martian interior than can be found at present in the atmosphere polar caps and regolith calculations have shown that atmospheric escape cannot account for all of the missing volatiles suggestions that carbon dioxide is stored as marine or lacustrine deposits are challenged by earth based and spacecraft remote sensing data moreover recent modelling of the martian atmosphere suggests that rainfall or open bodies of water are in any case unlikely to have persisted for extended periods of time hydrothermal carbonates therefore provide a possible solution to this dilemma using an accessible terrestrial system iceland as a guide to the underlying processes and a host rock composition inferred from the least altered martian meteorite we present a geochemical model for the formation of carbonates in possible martian hydrothermal systems our results suggest that an extensive reservoir of carbonate minerals equivalent to an atmospheric pressure of carbon dioxide of at least one bar could have been sequestered beneath the surface by widespread hydrothermal activity in the martian past

study of phyllosilicates and carbonates from the capri chasma region of valles marineris on mars based on mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars mro crism observations abstract spectral reflectance data from the mro crism mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars of capri chasma a large canyon within valles marineris on mars have been studied results of this analysis reveal the presence of minerals such as phyllosilicates illite smectite montmorillonite and carbonates ankerite and manganocalcite these minerals hint of the aqueous history of noachian time on mars phyllosilicates are products of chemical weathering of igneous rocks whereas carbonates could have formed from local aqueous alteration of olivine and other igneous minerals four different locations within the capri chasma region were studied for spectral reflectance based mineral detection the study area also shows the spectral signatures of iron bearing minerals e g olivine with carbonate indicating partial weathering of parent rocks primarily rich in ferrous mineral the present study shows that the minerals of capri chasma are characterized by the presence of prominent spectral absorption features at 2 31 m 2 33 m 2 22 m 2 48 m and 2 52 m wavelength regions indicating the existence of hydrous minerals i e carbonates and phyllosilicates the occurrence of carbonates and phyllosilicates in the study area suggests the presence of alkaline environment during the period of their formation results of the study are important to understand the formation processes of these mineral assemblages on mars which may help in understanding the evolutionary history of the planet

light toned layered deposits in juventae chasma mars abstract we examine hypotheses for the formation of light toned layered deposits in juventae chasma using a combination of data from mars global surveyor s mars orbiter camera moc mars orbiter laser altimeter mola and thermal emission spectrometer tes as well as mars odyssey s thermal emission imaging system themis we divide juventae chasma into geomorphic units of i chasm wall rock ii heavily cratered hummocky terrain iii a mobile and largely crater free sand sheet on the chasm floor iv light toned layered outcrop llo material and v chaotic terrain using surface temperatures derived from themis infrared data and slopes from mola we derive maps of thermal inertia which are consistent with the geomorphic units that we identify llo thermal inertias range from 400 to 850 j m 2 k 1 s 1 2 light toned layered outcrops are distributed over a remarkably wide elevation range 5 8 km from the chasm floor to the adjacent plateau surface geomorphic features the absence of small craters and high thermal inertia show that the llos are composed of sedimentary rock that is eroding relatively rapidly in the present epoch we also present evidence for exhumation of llo material from the west wall of the chasm within chaotic and hummocky terrains and within a small depression in the adjacent plateau the data imply that at least some of the llo material was deposited long before the adjacent hesperian plateau basalts and that juventae chasma underwent and may still be undergoing enlargement along its west wall due to wall rock collapse chaotic terrain evolution and exposure and removal of llo material the new data allow us to reassess possible origins of the llos gypsum one of the minerals reported elsewhere as found in juventae chasma llo material forms only at low temperatures 60 c and thus excludes a volcanic origin instead the data are consistent with either multiple occurrences of lacustrine or airfall deposition over an extended period of time prior to emplacement of hesperian lava flows on the plateau above the chasm

testing evidence of recent hydration state change in sulfates on mars the east candor interior layered deposit ild has signatures of mono and polyhydrated sulfate in alternating layers that give insight into the processes which formed these layered deposits and on the environmental conditions acting on them since then we use orbital data to explore multiple hypotheses for how these deposits formed 1 sulfate bearing ilds experience hydration changes on seasonal to a few years timescales under current mars environmental conditions 2 the deposits experience hydration under recent mars conditions but require the wetter climate of high obliquity and 3 the kieserite could be an original or diagenetic part of a complex evaporite mineral assemblage modeled climatology shows recent mars environmental conditions might pass between multiple sulfate fields however comparison of observatoire pour la mineralogie l eau les glaces et l activite omega and compact reconnaissance imaging spectrometer crism observations of the same ild do not show changes in hydration over 2 mars years low temperatures might slow the kinetics of that transition it is likely that more clement conditions during periods of high obliquity are needed to overcome mineral metastability and hydrate kieserite bearing deposits we find the alternate model that the deposit is a cyclic evaporite sequence of mono and polyhydrated sulfates also plausible but with an unexplained dearth of fe sulfates

morphology evolution and tectonics of valles marineris wallslopes mars abstract hillslopes up to 11 km in height can be found along the walls of the valles marineris troughs the widest and deepest troughs are grabens in which tectonics probably exerted the primary control on the wall morphology geographical variations in the wall morphology and profiles show that they result from complex persistent tectonic influences and that significant changes in erosional processes occurred during this evolution from late hesperian to late amazonian preliminary calculations suggest that about 85 95 of the fault controlled wall relief probably formed in an ancient stage prior to this transitional period a study of the volatile content of the wall rocks based upon the morphology and distribution of impact craters on the surrounding plateaus shows that extreme erosional widening of the central valles marineris troughs occurred during the ancient stage of high ground ice content during the subsequent recent stage of tectonic and morphological evolution the wall materials were partly desiccated

mars chronology assessing techniques for quantifying surficial processes abstract currently the absolute chronology of martian rocks deposits and events is based mainly on crater counting and remains highly imprecise with epoch boundary uncertainties in excess of 2 billion years answers to key questions concerning the comparative origin and evolution of mars and earth will not be forthcoming without a rigid martian chronology enabling the construction of a time scale comparable to earth s priorities for exploration include calibration of the cratering rate dating major volcanic and fluvial events and establishing chronology of the polar layered deposits if extinct and or extant life is discovered the chronology of the biosphere will be of paramount importance many radiometric and cosmogenic techniques applicable on earth and the moon will apply to mars after certain baselines e g composition of the atmosphere trace species chemical and physical characteristics of martian dust are established the high radiation regime may pose a problem for dosimetry based techniques e g luminescence the unique isotopic composition of nitrogen in the martian atmosphere may permit a mars specific chronometer for tracing the time evolution of the atmosphere and of lithic phases with trapped atmospheric gases other mars specific chronometers include measurement of gas fluxes and accumulation of platinum group elements pge in the regolith putting collected samples into geologic context is deemed essential as is using multiple techniques on multiple samples if in situ measurements are restricted to a single technique it must be shown to give consistent results on multiple samples but in all cases using two or more techniques e g on the same lander will reduce error while there is no question that returned samples will yield the best ages in situ techniques have the potential to be flown on multiple missions providing a larger data set and broader context in which to place the more accurate dates

estimates of strain due to brittle faulting sampling of fault populations abstract the geometry of sampling domains is a first order consideration in the characterization of brittle fault populations in most cases descriptions of fault size distributions based on map cross section traverse or borehole data systematically underestimate the number of small faults present in a volume the geometry of sampling domains may be accounted for using an empirical proportionality between fault displacement and trace length estimates of strain in which the sampling geometry is considered suggest that small faults accommodate a significant portion of the total strain due to the brittle faulting process

reconstructing the vulcano island evolution from 3d modeling of magnetic signatures abstract high resolution ground and marine magnetic data are exploited for a detailed definition of a 3d model of the vulcano island volcanic complex the resulting 3d magnetic imaging obtained by 3 d inverse modeling technique has delivered useful constraints both to reconstruct the vulcano island evolution and to be used as input data for volcanic hazard assessment models our results constrained the depth and geometry of the main geo structural features revealing more subsurface volcanic structures than exposed ones and allowing to elucidate the relationships between them the recognition of two different magnetization sectors approximatively coincident with the structural depressions of piano caldera in the southern half of the island and la fossa caldera at the north suggests a complex structural and volcanic evolution magnetic highs identified across the southern half of the island reflect the main crystallized feeding systems intrusions and buried vents whose nnw sse preferential alignment highlights the role of the nnw sse tindari letojanni regional system from the initial activity of the submarine edifice to the more recent activity of the vulcano complex the low magnetization area in the middle part of the island may result from hydrothermally altered rocks their presence not only in the central part of the volcano edifice but also in other peripheral areas is a sign of a more diffuse historical hydrothermal activity than in present days moreover the high magnetization heterogeneity within the upper flanks of la fossa cone edifice is an imprint of a composite distribution of unaltered and altered rocks with different mechanical properties which poses in this area a high risk level for failure processes especially during volcanic or hydrothermal crisis

relative age of interior layered deposits in southwest candor chasma based on high resolution structural mapping high resolution topography generated from stereo hirise high resolution imaging science experiment imagery reveals the meter scale structure of interior layered deposits ild in southwest candor chasma this study seeks to determine the age of the local ild relative to any normal faults that can be attributed to chasma formation the study area is located near the contact of these ild and the wall rock and is in an area where chasma forming normal faults have been proposed we find that while normal faults are found in the study area these faults are not sufficiently large nor appropriately located or oriented to accommodate the roughly northeast southwest extension that is required for normal faults that can be attributed to chasma formation additionally bedding exposed in the local ild generally dips toward the center of candor chasma consistent with sediment deposition in a preexisting basin further pit craters of tithonia catena presumed to predate or be contemporaneous with the formation of west candor chasma do not cut into the ild within the study area these independent lines of evidence support a postchasma age for the ild exposed within the study area chasma related normal faults may exist within these ild at depth but are not exposed at the surface approximately 2 km of conformable stratigraphy is exposed in the study area and therefore at least several kilometers of the local ild were deposited subsequent to any chasma related normal faulting that may have occurred in this part of candor chasma

stylolites a review abstract stylolites are ubiquitous geo patterns observed in rocks in the upper crust from geological reservoirs in sedimentary rocks to deformation zones in folds faults and shear zones these rough surfaces play a major role in the dissolution of rocks around stressed contacts the transport of dissolved material and the precipitation in surrounding pores consequently they play an active role in the evolution of rock microstructures and rheological properties in the earth s crust they are observed individually or in networks in proximity to fractures and joints and in numerous geological settings this review article deals with their geometrical and compositional characteristics and the factors leading to their genesis the main questions this review focuses on are the following how do they form how can they be used to measure strain and formation stress how do they control fluid flow in the upper crust geometrically stylolites have fractal roughness with fractal geometrical properties exhibiting typically three scaling regimes a self affine scaling with hurst exponent 1 1 0 1 at small scale up to tens or hundreds of microns another one with hurst exponent around 0 5 to 0 6 at intermediate scale up to millimeters or centimeters and in the case of sedimentary stylolites a flat scaling at large scale more complicated anisotropic scaling scaling laws depending of the direction of the profile considered is found in the case of tectonic stylolites we report models based on first principles from physical chemistry and statistical physics including a mechanical component for the free energy associated with stress concentrations and a precise tracking of the influence of grain scale heterogeneities and disorder on the resulting micro structures experimental efforts to reproduce stylolites in the laboratory are also reviewed we show that although micrometer size stylolite teeth are obtained in laboratory experiments teeth deforming numerous grains have not yet been obtained experimentally which is understandable given the very long formation time of such geometries finally the applications of stylolites as strain and stress markers to determine paleostress magnitude are reviewed we show that the scalings in stylolite heights and the crossover scale between these scalings can be used to determine the stress magnitude its scalar value perpendicular to the stylolite surface during the stylolite formation and that the stress anisotropy in the stylolite plane can be determined for the case of tectonic stylolites we also show that the crossover between medium millimetric scales and large pluricentimetric scales in the case of sedimentary stylolites provides a good marker for the total amount of dissolution which is still valid even when the largest teeth start to dissolve which leads to the loss of information since the total deformation is not anymore recorded in a single marker structure we discuss the impact of the stylolites on the evolution of the transport properties of the hosting rock and show that they promote a permeability increase parallel to the stylolites whereas their effect on the permeability transverse to the stylolite can be negligible or may reduce the permeability depending on the development of the stylolite

a new hematite formation mechanism for mars the origin of hematite detected in martian surface materials is commonly attributed to weathering processes or aqueous precipitation here we present a new hematite formation mechanism that requires neither water nor weathering glass rich basalts with martian meteorite like chemistry high feo low al2o3 oxidized at high 700 and 900 c temperatures in air and co2 respectively form thin 1 m hematite coatings on their outermost surfaces hematite is manifested macroscopically by development of magnetism and a gray metallic sheen on the glass surface and microscopically by fe enrichment at the glass surface observed in element maps visible and nearinfrared thermal infrared and raman spectroscopy confirm that the fe enrichment at the oxidized glass surfaces corresponds to hematite mineralization hematite formation on basaltic glass is enabled by a mechanism that induces migration of fe2 to the surface of an oxidizing glass and subsequent oxidation to form hematite a natural example of the hematite formation mechanism is provided by a hawaiian basalt hosting a gray metallic sheen that corresponds to a thin hematite coating hematite coating development on the hawaiian basalt demonstrates that martian meteorite like feo contents are not required for hematite coating formation on basalt glass and that such coatings form during initial extrusion of the glassy basalt flows if gray hematite originating as coatings on glassy basalt flows is an important source of martian hematite which is feasible given the predominance of igneous features on mars then the requirement of water as an agent of hematite formation is eliminated

imaging and modelling the subsurface structure of volcanic calderas with high resolution aeromagnetic data at vulcano aeolian islands italy in this paper we present a magnetic model of the subsurface structure of vulcano island based on high resolution aeromagnetic data three profiles across the most intense magnetic anomalies over the piano and fossa calderas were selected for the magnetic modelling which was constrained by structural and volcanological data previous geophysical models paleomagnetic data and borehole stratigraphy obtained from two deep wells the interpretation of the magnetic sources represents a significant contribution to the understanding of the piano and fossa calderas underlying structure providing us with evidence of the lateral discontinuity between them at depth we propose that the positive magnetic anomalies in the piano caldera area are caused by a the remnants of an early submarine volcano b an outcropping dyke swarm related to the feeding system of the primordial vulcano phase beneath mt saraceno and c the presence of a non outcropping dyke system intruded along a ne sw oriented intra caldera fault beneath the eastern part of the piano caldera offshore to the west the magnetic anomaly map suggests the presence of a submarine volcanic structure not revealed by bathymetric data which could represent the eruptive centre the presence of which has been indirectly deduced from the outcrop of eastern dipping lavas on the western seashore magnetic modelling of the fossa caldera points to the presence of a highly magnetized cone like body inside the fossa cone centred beneath the oldest crater rims we interpret this body as a pile of tephritic lavas emplaced in an early phase of activity of the fossa cone suggesting that the volume of mafic lavas that erupted at the beginning of the construction of the fossa edifice was more significant than has previously been deduced furthermore the presence of a magnetized body inside the fossa cone implies that high temperatures are contained in very limited spaces do not affect its bulk inner structure and are restricted to fumarolic conduits and vents in addition structures beneath the western and northern part of the fossa caldera are revealed to have null or low magnetization which can be ascribed to the presence of pyroclasts and hyaloclastites in this area as well as to a large volume of hydrothermally altered materials this suggests that the hydrothermal system with a very limited extension at present affected a larger area in the past especially beneath the western part of the caldera

spatiotemporal evolution mineralogical composition and transport mechanisms of long runout landslides in valles marineris mars abstract long runout landslides with transport distances of 50 km are ubiquitous in valles marineris vm yet the transport mechanisms remain poorly understood four decades of studies reveal significant variation in landslide morphology and emplacement age but how these variations are related to landslide transport mechanisms is not clear in this study we address this question by conducting systematic geological mapping and compositional analysis of vm long runout landslides using high resolution mars reconnaissance orbiter imagery and spectral data our work shows that 1 a two zone morphological division i e an inner zone characterized by rotated blocks and an outer zone expressed by a thin sheet with a nearly flat surface characterizes all major vm landslides 2 landslide mobility is broadly dependent on landslide mass and 3 the maximum width of the outer zone and its transport distance are inversely related to the basal friction that was estimated from the surface slope angle of the outer zone our comprehensive compact reconnaissance imaging spectrometer for mars crism compositional analysis indicates that hydrated silicates are common in landslide outer zones and nearby trough floor deposits furthermore outer zones containing hydrated minerals are sometimes associated with longer runout and increased lateral spreading compared to those without detectable hydrated minerals finally with one exception we find that hydrated minerals are absent in the inner zones of the investigated vm landslides these results as whole suggest that hydrated minerals may have contributed to the magnitude of lateral spreading and long distance forward transport of major vm landslides

sulfates and iron oxides in ophir chasma mars based on omega and crism observations abstract we investigate the sulfate and iron oxide deposits in ophir chasma mars based on short wave infrared data from the compact reconnaissance imaging spectrometer for mars crism and from the observatoire pour la mineralogie l eau les glaces et l activite omega sulfates are detected mainly in two locations in the valley between ophir mensa and the southern wall of ophir chasma kieserite is found both within the slope of ophir mensa and superposed on the basaltic wall of the chasm here kieserite is unconformably overlain by polyhydrated sulfate deposits and iron oxides locally jarosite and unidentified phases with absorptions at 2 21 m or 2 23 m are detected which could be mixtures of jarosite and amorphous silica or other poorly crystalline phases the second large sulfate rich outcrop is found on the floor of the central valley although the same minerals are found here polyhydrated sulfates kieserite iron oxides and locally a possibly jarosite bearing phase this deposit is very distinct it is not layered almost horizontal and located at a much lower elevation of below 4250 m kieserite superposes polyhydrated sulfate rich deposits and iron oxides form lags the facies of sulfate formation remains unclear and could be different for the two locations a formation in a lake playa or under a glacier is consistent with the mineralogy of the central valley and its flat low lying topography this is not conceivable for the kieserite deposits observed south of ophir mensa these deposits are observed over several thousands of meters of elevation which would require a standing body of water several thousands of meters deep this would have lead to much more pervasive sulfate deposits than observed these deposits are therefore more consistent with evaporation of groundwater infiltrating into previously sulfate free light toned deposits the overlying polyhydrated sulfates and other mineral phases are observed in outcrops on ridges along the slopes of the southern chasm wall which are too exposed to be reached by groundwater here a water supply from the atmosphere by rain snow fog or frost is more conceivable

explosive volcanism on hecates tholus mars investigation of eruption conditions evidence is presented supporting the identification of a discrete well preserved air fall deposit generated by explosive volcanism on mars the deposit is located immediately to the west of the summit caldera of hecates tholus 32on 209ow the northernmost of the three volcanic constructs in the elysium planitia region the absence of superposed impact craters larger than the resolution limit of the viking images 40 m per pixel indicates a very young age for this eruption which evidently postdates even the most recent collapse episode of the olympus mons caldera 300 m y b p neukum and hiller 1981 from the distribution of craters smaller than 2 km in diameter it appears that the air fall material mantles an area about 50 x 75 km in extent to an estimated thickness of about 100 m by adapting numerical models for terrestrial volcanic eruptions to the martian environment these dimensions imply an eruption cloud height of about 70 km in order to attain such an altitude the mass eruption rate must have been 107 kg s and the volatile content either 1 wt for h20 or 2 wt for co2 although it is not possible to distinguish between silicic and basaltic volcanism on hecates were the volatile species co2 the depth of most recent storage prior to eruption of the magma would have to be 50 100 km due to the solubility of co2 in the melt if h20 were the driving volatile a minimum depth of storage would be 0 2 4 km thereby permitting the possibility of ground water assimilation by the magma

phosphates and carbon on mars exobiological implications and sample return considerations much of the surface of mars may preserve chemical information contained in rocks from the noachian era with ages that overlap the correspondingly earliest archean geological history of the earth or from before around 3800 ma ma 1 106 years metabolically sophisticated life which utilized phosphate and carbon and was capable of fractionating carbon isotopes was apparently present already on earth by 3800 ma or within 600 ma after the formation of the planet an early appearance of life on earth opens the strong possibility for a similarly early and rapid emergence of life on planet mars this hypothesis remains within the realm of plausibility so long as it can be established that liquid water and energy sources were available there for inchoate life and that the life that emerged reached a level of complexity which could be recognized by its chemical and perhaps morphological remains hypotheses to be used in the search for an ancient martian biosphere from future sample return missions are testable by examining the record of life in ancient terrestrial sedimentary rocks including those that contain rare and recognizable physical microfossils morphofossils identified on the basis of their shape alone and stable authigenic biominerals which include carbonaceous matter having characteristically fractionated carbon isotope signatures here termed chemofossils prior to sample return these tests can be applied to the mineral associations of the snc meteorites a group of meteorites believed to have originated on mars recent claims of a biological origin for secondary minerals and their features as well as for trace organic compounds in the martian meteorite alh84001 are derived in part from the interpretation of putative nanofossil shapes and the nature of the associated mineral assemblage in small carbonate deposits of an igneous rock such igneous samples would not normally be the best candidate to search for evidence of past life even on earth investigations of these mineral occurrences in the martian meteorites and of the oldest geological records on earth provide a useful framework for 1 using mineral phase relationships 2 analytical data of stable carbon isotopic distributions and 3 the problematic task of morphofossil interpretations in the search for life via future sample return missions from the ancient surface of mars

surficial geologic surveys of gale crater and melas chasma mars integration of remote sensing data abstract remote sensing observations of gale crater and melas chasma are synthesized to better understand the present surface layer in these two scientifically interesting regions data sets analyzed include geologic maps mars orbiter laser altimeter mola elevation thermal emission spectrometer tes albedo tes thermal inertia mola residual pulse width tes rock abundance and viking and mars orbiter camera images using these data sets we constrain the properties of and processes acting on the present surface and create self consistent models for the surface layer surface properties within gale crater are variable and complex and interpreting the surface layer is not straightforward observations indicate that aeolian processes have shaped some of the intracrater surface but other areas do not comply with this model and have counterintuitive surface characteristics in contrast aeolian activity appears to have played a large role in shaping the present day physical structure of all surfaces in melas chasma and is reflected in the remote sensing data sets here we summarize our analysis and discuss the surface attributes as determined from these data sets

aeromagnetic data provide new insights on the volcanism and tectonics of vulcano island and offshore areas southern tyrrhenian sea italy 1 the active vulcano island southern tyrrhenian sea represents the southernmost portion of a nw se elongated volcanic ridge that includes also lipari and salina islands the ridge is affected by a regional nw se to n s striking fault system the elaboration and analysis of data from three high resolution aeromagnetic surveys carried out between 1999 and 2004 on vulcano and offshore allow us to recognize high intensity magnetic anomalies related to volcanic centers conduits or shallow intrusions previously unreported offshore submarine vents have been also recognized some of them may correspond with source areas of outcropping exotic pyroclastics on vulcano the spatial analysis of the recognized magnetic anomalies and volcanic structures shows that they are preferably aligned along the strikes of the main regional faults that affect the volcanic ridge submarine volcanic conduits revealed by the aeromagnetic survey might represent potential sources for future submarine effusive or explosive activity

present day mass wasting in sulfate rich sediments in the equatorial regions of mars abstract present day topographic changes are observed on steep slopes in equatorial regions of mars that are associated with sulfate rich sediments hydrated sulfates are known to be present in many sedimentary deposits on mars we document volume changes in the form of mass movements and gullies over these regions we have estimated erosion rates of 12 mm yr or 1 2 120 mm yr with uncertainties over steep slopes on sulfate rich mounds in ganges chasma much higher than mars average erosion rate near a few m yr at this rate the mounds would have shrunk in diameter by 18 000 km over 3 b y which greatly exceeds the width of the canyon supporting suggestions that these sediments once filled the canyons due to the soft nature of typical sulfate rich sediment it is susceptible to mass wasting and active eolian processes may remove loose material to maintain steep slopes the water in hydrated sulfates could potentially be extracted and used as a resource for future humans on mars and our results suggest that such deposits would be mechanically weak

an alternative model for the growth of faults conventional growth models suggest that faults become larger due to systematic increases in both maximum displacement and length we propose an alternative growth model where fault lengths are near constant from an early stage and growth is achieved mainly by increase in cumulative displacement the model reconciles the scaling properties of faults and earthquakes and predicts a progressive increase in fault displacement to length ratios as a fault system matures this growth scheme is directly applicable to reactivated fault systems in which fault lengths were inherited from underlying structure and established rapidly the model may also apply to some non reactivated fault systems near constant fault lengths during subsequent growth are attributed to retardation of lateral propagation by interaction between fault tips the model is validated using kinematic constraints from growth strata which are displaced by a system of reactivated normal faults in the timor sea nw australia

origin and evolution of the layered deposits in the valles marineris mars abstract thick sequences of layered deposits are found in the martian valles marineris they exhibit fine nearly horizontal layering and are present as isolated plateaus of what may have once been more extensive deposits individual sequences of layered deposits are as thick as 5 km the greatest total thicknesses of deposits are found in candor ophir and melas chasmata individual layer thicknesses range from about 70 to 300 m some tilting of sequences is observed but at the best image resolutions no angular unconformities are detectable in the layers the sequences of events in the canyons as deduced from morphologic and stratigraphic evidence was 1 graben formation in response to the tharsis uplift 2 canyon wall retreat and canyon enlargement roughly contemporaneous with formation of the layered deposits 3 deep erosion of the layered deposits 4 landsliding of the canyon walls and 5 eolian erosion of the layered deposits perhaps continuing up to the present we consider four hypotheses for the origin of the layered deposits they are eolian deposits they are remnants of the material that makes up the canyon walls they are deposits of explosive volcanic eruptions or they were deposited in standing bodies of water the rhythmic nature of the layers and their lateral continuity horizontality great thickness and stratigraphic relationships with other units in the canyons all appear most consistent with deposition in an aqueous environment if standing bodies of water existed in the valles marineris they were almost certainly ice covered there are three ways in which sediment could have entered an ice covered lake down through the ice cover up from the lake bottom or in from the lake margins layers of sediment could have been transported downward through an ice cover by foundering or rayleigh taylor instabilities but it is not clear whether there was a viable mechanism for repeatedly accumulating thick sediment layers on top of the ice cover subaqueous volcanic eruption on the lake bottom does not suffer from many of the morphologic arguments that make origin by subaerial volcanism seem improbable while this mechanism is attractive there are no eruptive centers observed and there is no other direct evidence to support it because canyon enlargement took place at roughly the same time as layer deposition debris from the canyon walls is an obvious and likely source for some of the material in the layered deposits however the volume of material removed from the canyon walls may be insufficient to account for all of the presently observed material we conclude that there are several geologically feasible but as yet unproven mechanisms that could have led to formation of thick deposits in ice covered paleolakes in the valles marineris present data are insufficient to choose conclusively among the various possibilities several types of data from the mars observer mission will be useful in further characterizing the deposits and clarifying the process of their origin the deposits should be considered important targets for a future mars sample return mission

vertical ground deformation on vulcano aeolian islands southern italy observations and interpretations 1976 1986 abstract vertical ground deformation studies have continued on vulcano southern italy since 1976 as part of a broader geophysical and geochemical program to monitor activity on the island following a magnitude 5 5 earthquake on 15th april 1978 located a few kilometers south of vulcano the northern part of the island was found to have subsided relative to its southern part two further episodes of displacement the first of inflation and the second of deflation were recorded before september 1981 these displacements have been interpreted using a model that considers the effect of pressure change at the point source located at a depth centered at 6 5 km in the northern part of the island such pressure change according to other geophysical and geochemical data is due to increasing and subsequent decreasing pressure connected with the migration of high temperature fluids through fractures and channels beneath the fossa area opened as a result of the april 15 earthquake subsequent measurements until november 1986 detected only one additional significant movement a small inflation between may 1984 and may 1985 this uplift appears to be related to the shallow seismicity recorded beneath the fossa in this period