sedimentary resurfacing and fretted terrain development along the crustal dichotomy boundary aeolis mensae mars 1 the evolution of the martian crustal dichotomy boundary which separates the southern cratered highlands from the northern lowland plains by 1 3 km of elevation remains among the fundamental outstanding issues in mars research for a study area at aeolis mensae we show that fretted terrain formed exclusively in a 2 km thick late noachian 3 7 ga sedimentary deposit that overlies the base of an older cratered dichotomy boundary slope in this equatorial study area fretted terrain does not exhibit the debris aprons or lineated valley fills that are attributed to ground ice in otherwise similar midlatitude fretted terrain in arabia terra the massive deposit of fine sand or loess was probably transported from the north by wind and trapped against the precursor dichotomy slope producing a similar initial form to the younger medusae fossae layered materials that occur east of aeolis mensae contemporary with the latest noachian to early hesperian decline in fluvial erosion the fretting process likely initiated as the massive layer s indurated surface was compromised by fracture cratering or collapse into possible voids in these depressions grain impact or contact with water disaggregated the fine sedimentary materials which were then largely deflated by wind the fretting process largely ended when liquid water was no longer widely available for weathering during the early hesperian period although some degradation of the region by aeolian and slope processes has continued to the present

the age of the medusae fossae formation evidence of hesperian emplacement from crater morphology stratigraphy and ancient lava contacts abstract the medusae fossae formation mff covering about 2 1 10 6 km 2 with an estimated volume of 1 4 10 6 km 3 and straddling the equatorial region of mars east of tharsis has historically been mapped and dated as amazonian in age analysis of the mff using a range of new observations from recent mission data at multiple resolutions reveals evidence that the formation is older than previously hypothesized with parts of the mff having formed in the hesperian and parts having been reworked and reformed throughout the amazonian up to the present ancient outcroppings of the mff edged with jagged yardangs became a mold for embaying hesperian aged lavas the erosion of the mff left solidified lava casts in the embaying lava unit this lava edge morphology permits the identification of ancient contacts between the mff and hesperian aged lava terrain additionally the flanking fan of the hesperian aged apollinaris patera volcano embays the formation at its foot indicating that parts of the mff were formed in the hesperian erosion has erased and inverted many of the superposed craters in the region showing that very young amazonian ages derived from impact crater size frequency distributions are resurfacing ages and not emplacement ages we find abundant evidence that the formation is extremely mobile and continuously reworked we conclude that a significant part of the mff may have originally been emplaced in the hesperian these observations place new constraints on the mode of origin of the mff

deltaic deposits at aeolis dorsa sedimentary evidence for a standing body of water on the northern plains of mars a fundamental long standing question regarding mars history is whether the flat and low lying northern plains ever hosted an ocean the best opportunity to solve this problem is provided by stratigraphic observations of sedimentary deposits onlapping the crustal dichotomy here we use high resolution imagery and topography to analyze a branching network of inverted channel and channel lobe deposits in the aeolis dorsa region just north of the dichotomy boundary observations of stacked cross cutting channel bodies and stratal geometries indicate that these landforms represent exhumed distributary channel deposits observations of depositional trunk feeder channel bodies a lack of evidence for past topographic confinement channel avulsions at similar elevations and the presence of a strong break in dip slope between topset and foreset beds suggest that this distributary system was most likely a delta rather than an alluvial fan or submarine fan sediment transport calculations using both measured and derived channel geometries indicate a minimum delta deposition time on the order of 400 years the location of this delta within a thick and widespread clastic wedge abutting the crustal dichotomy boundary unconfined by any observable craters suggests a standing body of water potentially 105 km2 in extent or greater and is spatially consistent with hypotheses for a northern ocean

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

composition resolved size distributions of volcanic aerosols in the mt etna plumes 1 particle size distributions for soluble and insoluble species in mt etna s summit plumes were measured across an extended size range 10 nm d 100 m using a combination of techniques automated scanning electron microscopy qemscan was used to chemically analyze many thousands of insoluble particles collected on pumped filters allowing the relationships between particle size shape and composition to be investigated the size distribution of fine silicate particles d 10 m was found to be lognormal consistent with formation by bursting of gas bubbles at the surface of the magma the compositions of fine silicate particles were found to vary between magmatic and nearly pure silica this is consistent with depletion of metal ions by reactions in the acidic environment of the gas plume and vent measurements of the size shape and composition of fine silicate particles may potentially offer insights into preemission synemission and postemission processes the mass flux of fine silicate particles from mt etna released during noneruptive volcanic degassing in 2004 and 2005 was estimated to be 7000 kg d 1 analysis of particles in the range 0 1 d m 100 by ion chromatography shows that there are persistent differences in the size distributions of sulfate aerosols between the two main summit plumes analysis of particles in the range 0 01 m d 0 1 m by scanning transmission electron microscopy stem shows that there are significant levels of nanoparticles in the mt etna plumes although their compositions remain uncertain

transitional morphology in west deuteronilus mensae mars implications for modification of the lowland upland boundary abstract west deuteronilus mensae which lies along the lowland upland boundary of mars at 45 latitude 345 longitude exhibits both gradational l a rossbacher 1985 in models in geomorphology woldenberg ed pp 343 372 allen unwin boston and fretted terrain r p sharp 1973 j geophys res 78 4073 4083 boundary types to the west the boundary is gradational and to the east it is defined by fretted terrain the two types of boundaries do not merge with one another within the west deuteronilus mensae region however the gradational boundary materials appear to overlap the fretted terrain by about 500 km contacts between units associated with the gradational boundary and the fretted terrain boundary can both be recognized in the region of overlap the fretted terrain can be identified as much as 300 km north of the gradational boundary in this region lowland units associated with the gradational boundary embay canyons of the fretted terrain in a topographically conformal fashion changes in the fretted terrain across the gradational boundary from uplands to lowlands include a reduction of canyon wall slopes and depths such that the fretted terrain north of the gradational boundary appears mantled but not obscured there are at least two major classes of processes which might explain the lateral overlap 1 erosion of stratified upland terrain and 2 deposition of plains materials onto the sloping upland margin and fretted terrain erosion of stratified upland terrain does not adequately explain the plainward decrease in crater densities across the gradational boundary nor is it consistent with evidence that lowland plains material appears to onlap the sloping upland margin in several places of the possible plains emplacement mechanisms eolian deposition would not produce the sharp apparently topographically conformal gradational unit contacts volcanics plains emplacement would not preserve the complex geometry of the underlying fretted terrain sediment deposition in either a liquid or ice covered sea could produce the draped appearance of the fretted terrain outflow channels along the lowland upland boundary particularly those of the circum chryse and west elysium regions may have flooded the northern lowlands to depths of tens to hundreds of meters the gradational unit contacts may represent the shorelines of such a sea the scale of characteristic morphologies along these contacts may require an unfrozen condition of sufficient duration to allow lacustrine style wave erosion and redistribution of material along the contacts our limited understanding of the martian paleoclimate and h 2 o inventories allows the possibility of clement periods in the past and other geological evidence e g small valley networks and outflow channels strongly suggests an extensive role of liquid water

coastal geomorphology of the martian northern plains the paper considers the question of the formation of the outflow channels and valley networks discovered on the martian northern plains during the mariner 9 mission parker and saunders 1987 and parker et al 1987 1989 data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains it is suggested that of the geological processes capable of producing similar morphologies on earth lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on mars

sedimentology and climatic environment of alluvial fans in the martian saheki crater and a comparison with terrestrial fans in the atacama desert abstract the deflated surfaces of the alluvial fans in saheki crater reveal the most detailed record of fan stratigraphy and evolution found to date on mars during deposition of at least the uppermost 100 m of fan deposits discharges from the source basin consisted of channelized flows transporting sediment which we infer to be primarily sand and gravel sized as bedload coupled with extensive overbank mud rich flows depositing planar beds of sand sized or finer sediment flow events are inferred to have been of modest magnitude probably less than 60 m3 s of short duration and probably occupied only a few distributaries during any individual flow event occasional channel avulsions resulted in the distribution of sediment across the entire fan a comparison with fine grained alluvial fans in chile s atacama desert provides insights into the processes responsible for constructing the saheki crater fans sediment is deposited by channelized flows transporting sand through boulder sized material and overbank mudflows sand size and finer and wind erosion leaves channels expressed in inverted topographic relief the most likely source of water was snowmelt released after annual or epochal accumulation of snow in the headwater source basin on the interior crater rim during the hesperian to amazonian periods we infer the saheki fans to have been constructed by many hundreds of separate flow events and accumulation of the necessary snow and release of meltwater may have required favorable orbital configurations or transient global warming

oceans on mars an assessment of the observational evidence and possible fate the edges of the northern plains and interpreted to be shorelines remaining from these former standing bodies of water we examine the elevations and geologic relations along these contacts in detail and find little support for their interpretation as shorelines some contacts are clearly of volcanic origin and all have significant variations in elevation better support for the former presence of water over large parts of the northern plains is provided by the vastitas borealis formation vbf most of the post noachian fill within the northern basin is ridged plains of lower hesperian age interpreted to be volcanic in origin overlying the ridged plains is the vbf a thin veneer of material of upper hesperian age the vbf may have been deposited from large floods support for this interpretation is the similarity in age between the outflow channels and the vbf the presence of the vbf at the lower ends of the outflow channels and identification of numerous features in the outcrop areas of the vbf that are suggestive of basal melting of an ice sheet to cover all the area over which the vbf is exposed would require 2 3 10 7 km 3 of water spread over the entire surface of mars this volume is equal to a global layer global equivalent layer or gel 156 m deep we find no support for the larger estimates of ocean volumes that range up to 3 10 8 km 3 and which imply comparable amounts of water per unit area as are currently present on the surface of the earth under present climatic conditions on mars an ocean would freeze in a geologically short time period 10 4 years then would sublimate away at rates strongly dependent on the presence or absence of debris on the ice surface the present vbf is interpreted as a sublimation residue from the ponded outflow channel effluents the fate of a volume of water thought to have been emplaced by the outflow channels 2 3 10 7 km 3 is largely accounted for by the presence of other existing reservoirs on the planet an approximately 20 30 m gel of water is estimated to be in the present polar caps and a 50 m gel may have escaped to space since the hesperian leaving 80 m gel unaccounted for this amount may be partly trapped in other volatile rich deposits on the surface and a significant amount could have reentered the groundwater system by south polar basal melting and been progressively cold trapped at the base of a growing cryosphere on the basis of our assessment of the hesperian aged deposits we predict that testing of the clifford and parker 2001 hypothesis that a noachian aged ocean covered up to one third of the surface of mars will be made very difficult by the enhanced degradation rates in the noachian and subsequent geological events in the northern lowlands index terms 6225 planetology solar system objects mars 4267 oceanography general paleoceanography 5407 planetary sciences atmospheres evolution 5470 planetary sciences surface materials and properties 1635 global change oceans 4203 keywords mars oceans channels shorelines hesperian

the structure and composition of microspheres from the kilauea volcano hawaii microspheres from the plume of the kilauea volcano hawaii display previously unrecognized structural and compositional features indicating that the spheres are concentrically differentiated and at least partially crystalline the surfaces of some spheres display evenly spaced hexagonal sub micrometer grains whose compositions suggest that they may be spinels distinctive prismatic and dendritic structures on the surfaces of the microspheres are remarkably consistent through the population and indicate that the spheres have crystalline outer shells indications of chemical etching are present probably from exposure to hf in the volcanic plume the structures and compositions of the microspheres suggest that they differentiated and then solidified during rapid cooling as they passed through the gradients of temperature chemical composition and redox conditions established in the plume as air diluted the gaseous species evolved from magma

strong water isotopic anomalies in the martian atmosphere probing current and ancient reservoirs we measured maps of atmospheric water h2o and its deuterated form hdo across the martian globe showing strong isotopic anomalies and a significant high deuterium hydrogen d h enrichment indicative of great water loss the maps sample the evolution of sublimation from the north polar cap revealing that the released water has a representative d h value enriched by a factor of about 7 relative to earth s ocean vienna standard mean ocean water vsmow certain basins and orographic depressions show even higher enrichment whereas high altitude regions show much lower values 1 to 3 vsmow our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 vsmow which would mean that early mars 4 5 billion years ago had a global equivalent water layer at least 137 meters deep

gas and aerosol emissions from villarrica volcano chile here we report results from a multidisciplinary field campaign at villarrica volcano chile in march 2009 a range of direct sampling and remote sensing techniques was employed to assess gas and aerosol emissions from the volcano and extend the time series of measurements that have been made during recent years airborne traverses beneath the plume with an ultraviolet spectrometer yielded an average so2 flux of 3 7 kg s 1 this value is similar to previous measurements made at villarrica during periods of quiescent activity the composition of the plume was measured at the crater rim using electrochemical sensors and for the first time open path fourier transform infrared spectroscopy yielding a composition of 90 5 mol h2o 5 7 co2 2 6 so2 0 9 hcl 0 3 hf and 0 01 h2s comparison with previous gas measurements made between 2000 and 2004 shows a correlation between increased so2 hcl ratios and periods of increased activity base treated filter packs were also employed during our campaign yielding molar ratios of hbr so2 1 1 10 4 hi so2 1 4 10 5 and hno3 so2 1 1 10 3 in the gas phase our data represent the most comprehensive gas inventory at villarrica to date and the first evaluation of hbr and hi emissions from a south american volcano sun photometry of the plume showed the near source aerosol size distributions were bimodal with maxima at 0 1 and 1 m these findings are consistent with results from analyses in 2003 electron microscope analysis of particulate matter collected on filters showed an abundance of spherical micron sized particles that are rich in si mg and al non spherical s rich particles were also observed

differential subsidence and rebound in response to changes in water loading on mars possible effects on the geometry of ancient shorelines 1 if large liquid or solid water bodies existed in the past in martian basins such as argyre hellas and the northern lowland plains they would have represented massive surficial loads earth analogs suggest that the magnitudes of crustal displacements related to water loading and unloading would have varied spatially within and around affected basins it is likely that the effects of bathymetric irregularities on lithospheric flexure would have caused shoreline areas proximal to deep regions to be depressed and subsequently to rebound to a greater extent than shoreline areas located near shallow regions crustal and mantle inhomogeneities would have likely further contributed to spatial variation in water related subsidence and rebound simple two dimensional elastic flexure models suggest that martian shoreline features of common age and formed in association with a large ancient water body could vary in elevation today by hundreds of meters as a result of these differential effects examples of similar shoreline offsets on earth suggest that sets of martian strandline features will reflect the changing nature of loading through time

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

solid sulfur spherules near fumaroles of hakone volcano japan occurrence of sulfur spherules near subaerial fumaroles is relatively uncommon and their mineralogical characteristics and formation mechanisms are still incompletely understood yellow to greenish gray solid sulfur spherules were observed near a fumarole that was formed in the fumarolic area owakudani during the 2015 eruption of hakone volcano japan the yellow sulfur spherules up to 1 mm in diameter are composed entirely of sulfur and the greenish gray spherules up to 2 mm in diameter consist mainly of matrix forming sulfur with lesser amounts of pyrite amorphous silica pyrophyllite and rare marcasite based on the results of the field observations and the micro analyses of the samples these sulfur spherules were formed by rapid cooling of molten sulfur blobs ejected from a low viscosity molten sulfur pool 124 7 128 7 c in the bottom of the fumarole during vigorous fumarolic activity color difference between yellow and greenish gray sulfur spherules is explained by the presence of xenolithic altered mineral fragments in the greenish gray sulfur spherules our observations indicate significant fluctuations of the level of the molten sulfur forming inside the fumarolic vent and these fluctuations may imply the existence of other molten sulfur reservoirs beneath the fumarolic area presence of solid sulfur spherules in the fumarolic area may be an indicator of a molten sulfur pool within fumaroles or volcanic vents that are often difficult to directly observe

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

trace elements in the gas emissions from the erta ale volcano afar ethiopia high temperature 1084 c fumarolic emissions from a spatter cone at the erta ale north pit crater granted a rare opportunity to collect giggenbach bottles condensates and sublimates from the fumarolic gases of a rift plume volcano in the immediate proximity of degassing lava these results represent the highest temperature gases sampled directly for trace elements and the first high t fumarolic samples for a rift plume volcano sixty seven metals and metalloids were measured quantitatively by icp aes and icp ms in liquid gas condensates and solid sublimates the total amount of trace elements in the gas without si exceeded 170 ppm the ten most abundant elements transported in nonsilicate modes were na 61 ppm fe 41 ppm k 32 ppm br 12 4 ppm cd 3 0 ppm se 2 3 ppm cu 2 0 ppm zn 2 0 ppm te 1 7 ppm and as 1 2 ppm the gases contained 27 ppb re 1 5 ppb au 0 5 ppb pt and 0 27 ppb os rh and pd containing phases were observed in solid sublimates the only metal not detected by all analytical methods was ruthenium chalcophile elements cd cu zn se te as were transported primarily in the gaseous form alkali metals were emitted at least partially as liquid micron size sulfate droplets whereas alkali earths aluminum and ree had a high affinity to silicate aerosol in the form of basaltic microspheres the silicate aerosol content was evaluated at 59 ppm on average but varied within a 7 5 fold range during sampling because of the extremely high temperature refractory elements ca ba ta u and lree showed evidence of transport in the form of gaseous species the so2 flux in january 2011 was evaluated at 91 24 t d for the entire volcano including 31 t d from the north crater and 60 t d from the lava lake the daily output of trace elements from both erta ale craters without si was estimated at 53 kg d including 20 kg of na 13 5 kg of fe 10 5 kg of k 4 5 kg of chalcophile elements 9 g of re 0 5 g of au and 0 17 g of pt the trace element pattern of erta ale fumarolic gases do not possess any distinct geochemical specialization and resemble te patterns from fumarolic emissions of studied arc and plume volcanoes

geomorphology of ma adim vallis mars and associated paleolake basins 1 ma adim vallis one of the largest valleys in the martian highlands appears to have originated by catastrophic overflow of a large paleolake located south of the valley heads ma adim vallis debouched to gusev crater 900 km to the north the landing site for the spirit mars exploration rover support for the paleolake overflow hypothesis comes from the following characteristics 1 with a channel width of 3 km at its head ma adim vallis originates at two eastern and western gaps incised into the divide of the 1 1 m km2 enclosed eridania head basin which suggests a lake as the water source 2 the sinuous course of ma adim vallis is consistent with overland flow controlled by preexisting surface topography and structural control is not evident or required to explain the valley course 3 the nearly constant 5 km width of the inner channel through crater rim breaches the anastomosing course of the wide western tributary the migration of the inner channel to the outer margins of bends in the valley s lower reach a medial sedimentary bar 200 m in height and a step pool sequence are consistent with modeled flows of 1 5 106 m3 s peak discharges were likely higher but are poorly constrained by the relict channel geometry 4 small direct tributary valleys to ma adim vallis have convex up longitudinal profiles suggesting a hanging relationship to a valley that was incised quickly relative to the timescales of tributary development 5 the eridania basin had adequate volume between the initial divide and the incised gap elevations to carve ma adim vallis during a single flood 6 the eridania basin is composed of many overlapping highly degraded and deeply buried impact craters the floor materials of the six largest craters have an unusually high internal relief 1 km and slope 0 5 1 5 among degraded martian craters which are usually flat floored long term fluvial sediment transport appears to have been inhibited within these craters and the topography is inconsistent with basaltic infilling 7 fluvial valleys do not dissect the slopes of these deeper crater floor depressions unlike similar slopes that are dissected at higher levels in the watershed these characteristics 6 7 suggest that water mantled at least the lower parts of the eridania basin floor throughout the period of relatively intense erosion early in martian history the lake level increased and an overflow occurred near the close of the noachian age determined using 5 km crater counts initially the eridania basin debouched northward at two locations into the intermediate basin a highly degraded impact crater 500 km in diameter as this intermediate basin was temporarily filled with water erosion took place first along the lower northern reach of ma adim vallis debouching to gusev crater the western overflow point was later abandoned and erosion of the intermediate basin interior was concentrated along the eastern pathway subsequent air fall deposition impact gardening tectonism and limited fluvial erosion modified the eridania basin region so evidence for a paleolake is restricted to larger landforms that could survive post noachian degradation processes

possible ancient oceans on mars evidence from mars orbiter laser altimeter data high resolution altimetric data define the detailed topography of the northern lowlands of mars and a range of data is consistent with the hypothesis that a lowland encircling geologic contact represents the ancient shoreline of a large standing body of water present in middle mars history the contact altitude is close to an equipotential line the topography is smoother at all scales below the contact than above it the volume enclosed by this contact is within the range of estimates of available water on mars and a series of extensive terraces parallel the contact in many places

response of normal faults to glacial interglacial fluctuations of ice and water masses on earth s surface 1 changes in surface loads during glacial interglacial cycles and the associated flexure and rebound of the lithosphere alter the stress field in actively extending regions and may lead to slip rate variations on normal faults in particular loading may cause a period of seismic quiescence that is followed by temporal clustering of earthquakes during and after unloading here we present a suite of finite element experiments to evaluate how the magnitude distribution and temporal evolution of the load as well as rheological parameters of the lithosphere and asthenosphere influence the response of a normal fault the results show that the duration of the seismically quiet period during loading and the intensity of the slip rate increase during unloading are primarily controlled by the magnitude of the load the time lag between the changes in loading and the reaction of the fault is mainly determined by the viscosity of the asthenosphere parameters that play only a minor role for the fault s response include the rate of load removal fault strength and the thickness of the lithosphere our results imply that earthquake recurrence models derived from holocene slip histories may not be representative for the long term evolution of seismogenic faults

plume induced topography and geoid anomalies and their implications for the tharsis rise on mars the topography and geoid anomalies produced from an upwelling plume are sensitive to the depth of plume buoyancy d p and elastic lithospheric thickness t e both of which control the degree of compensation we formulated spherically axisymmetric convection models of mantle plumes with temperature and pressure dependent viscosity to dynamically determine d p and t e and the resulting topography and geoid anomalies from the plume from 10 cases with different rayleigh number activation energy and activation volume we determined te ranging from 100 km to 180 km and d p that is approximately twice t e the ratio of geoid to topography r g t from these plume models is either negative or slightly positive 0 03 at wavelengths that are most relevant to the tharsis rise low harmonics from degrees 2 to 4 the modeled r g t is significantly smaller than that observed for the tharsis rise suggesting that tharsis is unlikely to be dynamically supported

martian surface near surface water inventory sources sinks and changes with time today a 34 m global equivalent water layer gel lies in the martian polar layered deposits and shallow ground ice during the amazonian 3 m was outgassed and 31 m was lost to space and to the surface leaving 62 m at the end of hesperian during the hesperian volcanic outgassing added 5 m 7 m was lost and 40 m gel of groundwater was added to form outflow channels leaving 24 m carryover of surface water from the noachian into the hesperian the hesperian budget is incompatible with a northern ocean during this era these figures are for near surface water substantial amounts of water may have existed as deep ground ice and groundwater our estimate of approximately 24 m near surface water in the late noachian is insufficient to support an ocean at that time also and favors episodic melting of an icy highlands to produce the fluvial and lacustrine features

spherules with pure iron cores from myanmar jadeitite type i deep sea spherules abstract here we report spherules in myanmar jadeitite a rock forming from jadeitic fluids within mantle derived serpentinized rocks in subduction zones under high pressure conditions 1 0 gpa and rather low temperatures of about 250 370 c the spherules have off centre iron nuclei and dendritic wustite cortexes with tiny wustite crystals perpendicular to the surface of iron core within the spherules are vesicles occupied by calcite jadeite albite or mixtures of these phases and the cortexes contain about 10 wt sio 2 al 2 o 3 na 2 o filling materials within wustite the spherules are in direct contact with jadeite crystals contrasting patterns of some individual spherules are obvious between a front area with a crowd of hill like prominences and a rear zone with one or more rings on the surface such surface features and internal textures suggest that they experienced movement at high temperature and then rapid cooling chemical compositions of the nuclei are homogenous and consist of nearly pure iron with minor cr 56 fe and 57 fe in the core and cortex are 0 51and 0 78 respectively such features suggest that there is a very low possibility of origin associated with volcanic explosive eruption impact ejecta chemical reduction or oxidation of iron on seafloor since biological reduction processes are not significant under high p t condition in subduction zones this origin is excluded considering their low ni contents it is more likely that they belong to the minor type i deep sea cosmic spherules dusts of low isotope fractionation this discovery shows that such spherules could remain stable under low temperature and high pressure conditions during recycling processes and therefore could be found in rocks related to slab derived sediments within subduction zones this also suggests that subducted oceanic slab sediments contribute to the formation of jadeitite coupled with dehydration of sediments and altered oceanic crust

the origin and evolution of the peace vallis fan system that drains to the curiosity landing area gale crater mars the landing site for the curiosity rover is located at the distal end of the peace vallis fan in gale crater peace vallis fan covers 80 km2 and is fed by a 730 km2 catchment which drains an upland plains area through a 15 km wide gap in the crater rim valley incision into accumulated debris delivered sediment through a relatively low density valley network to a main stem channel to the fan an estimated total fan volume of 0 9 km3 matches the calculated volume of removal due to valley incision 0 8 km3 and indicates a mean thickness of 9 m the fan profile is weakly concave up with a mean slope of 1 5 for the lower portion numerous inverted channels outcrop on the western surface of the fan but on the eastern portion such channels are rare suggesting a change in process from distributary channel domination on the west to sheet flow on the eastern portion of the fan runoff discharge watershed area to produce the fan is estimated to be more than 600 m perhaps as much as 6000 m indicating a hydrologic cycle that likely lasted at least thousands of years atmospheric precipitation possibly snow not seepage produced the runoff based on topographic data peace vallis fan likely onlapped bradbury rise and spilled into a topographic low to the east of the rise this argues that the light toned fractured terrain within this topographic low corresponds to the distal deposits of peace vallis fan and in such a setting lacustrine deposits are expected

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

petrography and geochemistry of achnelithic tephra from las herrerias volcano calatrava volcanic field spain formation of nephelinitic achneliths and post depositional glass alteration abstract we present the results of a petrographic and geochemical study carried out on a layer of achnelithic tephra outcropping at the base of the volcanic cone of las herrerias miocene quaternary volcanic region of campo de calatrava spain the tephra with a composition of nephelinite and ash 3 of all major elements and notable increase in h 2 o content the elements liberated by this process formed smectite with an average structural formula comprised between those of beidellite and nontronite end terms na 0 01 k 0 03 ca 0 18 mg 0 22 fe 0 16 2 fe 0 48 al 1 02 3 ti 0 18 4 si 3 58 al 0 42 o 10 oh 2 the degree of palagonitization in each achnelith was likely related to the amount of water incorporated by individual clasts at the moment of their deposition in a volcanic maar lake afterwards there was no more water circulation through the achnelithic tephra which was sealed from water by overlying hydrovolcanic tuff deposits it was this isolation that made possible the preservation of glass to the present day

cryptoachneliths hidden glassy ash in composite spheroidal lapilli abstract cryptoachneliths perceptible by means of electron microscopy but unresolved under the optical microscope occur unnoticed inside spheroidal lapilli of ultrabasic composition of the cabezo segura volcano calatrava volcanic province spain the cryptoachneliths are glassy spherical particles that have compositions of al rich silicate with minor amounts of fe ca and other elements the smallest cryptoachneliths of 1 m microachneliths and homogeneous less regular masses of similar composition nano and microachneliths welded each other or to other types of volcanic particles crystals crystal fragments spinning droplets cognate lithic clasts etc to form spheroidal lapilli and even bomb size clasts within proximal fall deposits of the cabezo segura volcano the welding processes took place inside the eruptive column previous to the fall of the spheroidal lapilli on top of the volcanic cone the presence of the cryptoachneliths implies that lapilli and even bomb size tephra within deposits formed during explosive eruptions of low viscosity basic to ultrabasic magmas should be carefully examined in order to establish key parameters of eruption dynamics like size amount and distribution of juvenile fine particles

ancient ocean on mars supported by global distribution of deltas and valleys the climate of early mars could have supported a complex hydrological system analysis of ancient deltaic deposits and valley networks reveals the presence of a planet wide equipotential surface in the northern lowlands indicative of the existence of a vast ocean on mars 3 5 billion years ago

fan deltas and braid deltas varieties of coarse grained deltas two types of coarse grained deltas are recognized fan deltas and braid deltas fan deltas are gravel rich deltas formed where an alluvial fan is deposited directly into a standing body of water from an adjacent highland they occupy a space between the highland usually a fault bounded margin and the standing body of water in contrast braid deltas here introduced are gravel rich deltas that form where a braided fluvial system progrades into a standing body of water braid deltas have no necessary relationship with alluvial fans as exemplified by fluvioglacial braid deltas braid deltas have previously been classified as fan deltas even though the geomorphic and sedimentologic settings of the two systems can be vastly different braid deltas are a common present day geomorphic feature and are abundant in the geological record fan deltas and braid deltas can be distinguished in the rock record by distinctive subaerial components of these depositional systems the shoreline and subaqueous components of both are similar fan delta sequences have a subaerial component that is an alluvial fan facies comprising interbedded sheetflood debris flow and braided channel deposits fan deltas produce small a few tens of square kilometres wedge shaped bodies of sediment commonly displaying high variability in paleocurrent patterns and abrupt changes in facies the deposits are generally very coarse grained with large out sized clasts very poorly sorted matrix rich polymictic heterolithic partially cemented by penecontemporaneous carbonate and have low porosity and permeability braid deltas in contrast have a subaerial component consisting entirely of braided river or braidplain facies their deposits display better sorting roundness and clast orientation than do fan delta sediments they lack a muddy matrix they display size grading and bar migration they commonly have a sheet geometry with high lateral continuity tens to hundreds of square kilometres and they exhibit moderate to high porosity and permeability valuable paleogeographic and tectonic information concerning the proximity of highlands and major fault zones may be misinterpreted or lost if these two coarse grained deltaic systems are not differentiated

geomorphological evidence of water level changes in nepenthes mensae mars in the western sector of nepenthes mensae mars there are some geomorphological features that could be related to a standing water sheet in the area such as fluvial terraces deltas and shorelines a detailed analysis of these features reveals two variations in water level probably related to tectonic processes as suggested by the existence of a fissural volcano at this site

hydrothermal hexahydrite spherules erupted during the 2008 2010 summit eruption of kīlauea volcano hawai i small 1 3 mm hollow spherules of hexahydrite have been collected falling out of the magmatic gas plume downwind of k lauea s summit vent the spherules were observed on eight separate occasions during 2009 2010 when a lake of actively spattering lava was present 150 200 m below the rim of the vent the shells of the spherules have a fine bubbly foam structure less than 0 1 mm thick composed almost entirely of hexahydrite mgso4 6h2o small microspherules of lava 5 m across along with mineral and rock fragments from the magmatic plume adhered to the outside of the hexahydrite spherules phase relationships and the particulate matter in the magmatic plume indicate that the spherules originated as a bubbly solution injected into and mixed with the magmatic plume the most likely mechanism for production of hexahydrite spherules is boiling of mgso4 saturated meteoric water in the walls of the conduit above the surface of the lava lake solfataric sulfates may thus be recycled and reinjected into the plume creating particulates of sulfate minerals that can be distributed far from their original source

the evolution of lacustrine environments on mars is mars only hydrologically dormant abstract this study surveys the evolution of martian impact crater paleolakes through time by establishing their age comparing their locations and describing the formation of lacustrine sedimentary structures and features over time we explore their meaning in terms of global climate changes but also on local and regional scales we observe a co location between recent impact crater paleolakes and regions where gcm modeling shows that mars is currently experiencing days above triple point and below boiling point of water some source areas show morphologies that could be consistent with ancient glacier features in the argyre basin darwin crater region in locations that are also consistent with gcm models of past snow precipitation on mars we propose that at least for some paleolakes our results are best explained by recent and abundant aqueous activity on mars with some meteorological contribution these results are supported by other recent findings on martian meteorite ages by the analysis of new mgs data showing recent volcanic and fluvial activity and by climate modeling they point toward the possibility that mars currently is only hydrologically dormant and that there is a potential for hydrological activity to be generated again in the future following changes in the planet s orbital parameters

high resolution size distributions and emission fluxes of trace elements from masaya volcano nicaragua active volcanoes are significant natural sources of trace elements to the atmosphere yet the processes of emission and the impacts of deposition into terrestrial and aquatic environments remain poorly understood the varying contributions of volatile degassing and magma ejection i e spattering spraying extrusion and fragmentation to the emission of trace elements from masaya volcano nicaragua are investigated through measurement of high resolution trace element size distributions using cascade impactors in 2009 and 2010 the volatile elements e g as cd tl cu pb zn are strongly correlated across the size distribution and exist in the plume primarily as fine sulfate 0 6 m diameter with lesser amounts transported as coarse sulfates 3 5 m diameter and coarse chlorides 11 m diameter these results suggest that trace elements released from the magma as chlorides react rapidly with h2so4 in the plume to form sulfates in contrast the non volatile elements e g alkali earth and rare earth exist primarily as particles in the 1 10 m range and show no correlation with sulfate chloride or the volatile elements suggesting that they are emitted primarily by magma ejection trace element emission fluxes from masaya in 2010 were estimated using filter pack measurements with emissions of cu zn as tl rb and cd each in excess of 10 kg d 1 these emission fluxes are similar to those measured in 2000 2001 suggesting notable decadal stability in the emission of trace elements from masaya

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

pervasive aqueous paleoflow features in the aeolis zephyria plana region mars abstract a survey of themis visible wavelength images in the aeolis zephyria plana region over the two western lobes of the equatorial medusae fossae formation mff shows 150 sinuous ridges having a variety of morphologies and contexts to systematize investigation we use a classification scheme including both individual ridge and ridge network types as well as associations with impact craters and fan shaped features the morphology of the ridges their location downslope from higher topography e g crater rims and scarps and their association with fan shaped forms indicate that most sinuous ridges formed through overland aqueous flow analysis of observations by individual ridge type leads to interpretation of most of these sinuous ridges as inverted fluvial channels or floodplains and a few as possible eskers with the origin of the remaining ridges under continuing investigation about 15 of the sinuous ridges are associated with impact craters but data analysis does not support a genetic relationship between the craters and the sinuous ridges instead analysis of one sinuous ridge network associated with a crater indicates that the water source for the network was atmospheric in origin namely precipitation runoff the broad areal distribution of these 150 ridges and the network morphologies in particular the branched and subparallel types suggest that an atmospheric water source is generally applicable to the population of sinuous ridges as a whole this concentration of sinuous ridges is the largest single population of such landforms on mars and among the youngest these ridges are situated at a paleoscarp between cerberus palus and the aeolis highlands suggesting that the precipitation that formed them was orographic in origin the ages of the equatorial mff units in which this population of sinuous ridges is found imply that this orographic rain and or snow fell during some period from the late hesperian through the middle amazonian

silicate glass micro and nanospherules generated in explosive eruptions of ultrabasic magmas implications for the origin of pelletal lapilli abstract the genesis of spherical ash to lapilli sized clasts with a central phenocryst or lithic fragment mantled by a rim of fine grained juvenile material that includes abundant concentrically arranged prismatic crystals is interpreted as either i the result of the spinning of a magma bleb with a crystalline kernel in a fluidized system or ii the accretion of small melt droplets to a previously crystallized nucleus in a gas jet we demonstrate that the rims of pelletal lapilli within tephras of the cabezo segura volcano calatrava spain are clastic and were formed by the progressive welding of juvenile crystals and silicate glass droplets and to a lesser extent filaments both melt in origin around a large crystalline nucleus our results support the accretion hypothesis and offer explicit and new images of the melt droplets that were so far considered hypothetical particles these results indicate also that nanometre scale juvenile pyroclasts melt droplets and crystals can be generated in explosive eruptions of ultrabasic magmas those pyroclasts can be subsequently welded together inside a dense gas jet generating pelletal lapilli and ash

putative shorelines in northern arabia terra mars 1 three putative shorelines first proposed by parker et al 1989 are topographically and morphologically evaluated within a 700 000 km2 study area in northern arabia terra mars results are consistent with a shoreline interpretation for the arabia and deuteronilus contacts but do not support the proposed acidalia shoreline the arabia contact follows an equipotential surface with a mean elevation of 3707 m and a mean deviation of 13 m for deuteronilus results suggest that the originally proposed shoreline represents two distinct regional shorelines because two separate portions of the original deuteronilus contact approximate equipotential surfaces of 4200 m 5 m and 4000 m 6 m for both the deuteronilus and arabia contacts there is geomorphic evidence for erosion and some landforms are similar to analogous terrestrial coastal landforms these results permit but do not prove the past existence of an ocean ponded within the northern lowlands possibly as recently as the amazonian

magnetite spherules in pyroclastic iron ore at el laco chile the el laco iron deposits in northern chile consist of magnetite or martite and minor hematite pyroxene and apatite the orebodies are situated on a volcanic complex and resemble lavas and pyroclastic deposits but a magmatic origin is rejected by some geologists who regard the ores as products of hydrothermal replacement of volcanic rocks this study describes spherules of magnetite in the ore at laco sur and outlines a previously unrecognized crystallization process for the formation of spherical magnetite crystal aggregates during volcanic eruption mining at laco sur the second largest deposit at el laco shows that most of the ore is friable and resembles pyroclastic material hard ore with vesicle like cavities occurs subordinately the friable ore is a porous aggregate of 0 01 0 2 mm magnetite octahedra with only a local stratification defined by millimeter thin strata of apatite films of iron phosphate are common on magnetite crystals and vertical pipes called gas escape tubes are abundant in the ore a sem study reveals that magnetite spherules in the range 0 05 0 2 mm occur in most samples of friable ore from the central lower part of the deposit the proportion of spherules in a sample varies from high to nil but overall the spherule content is low in the ore the spherules are aggregates of octahedral crystals or single octahedra that have been rounded by stepwise subparallel growth of magnetite with a systematic slight shift in orientation of successive steps the shape of the spherules demonstrates that they formed unattached to any surface growth from hot magmatic gas saturated in iron in a volcanic plume and deposition as ash fall can account for the features of the spherule bearing friable ore

formation of composite pyroclasts by welding inside a lithic rich mafic eruption column los marteles caldera canary islands abstract the tuff ring of the los marteles phreatomagmatic maar gran canaria canary islands includes a particular unit that comprises abundant composite spheroidal clasts however these clasts differ from cored clasts elsewhere that consist of erupted lithic pyroclasts with an adhering rim of coherent chilled magma the composite clasts here studied range from lapilli to bombs and are cored or concentrically banded among the welded components several types of primary clasts are discerned that include i juvenile clasts resultant of the magma inertial fragmentation and ii cognate or accessory lithic clasts juvenile clasts include glass spheres nano and microachneliths and crystals lithic clasts include lava fragments scoriae and olivine xenocrysts primary clasts are interpreted to have been produced by the explosion of a partially crystallized mafic sio 2 50 55 magma that erupted into a maar filled up with scoriae plus lava fragments the explosion would have originated as a dense and turbulent gas thrust into which the repeated collisions of melt droplets with solid clasts generated droplet coated crystals lithic clasts and single glass spheres we interpret the cored and concentrically banded pyroclasts to be made of coalesced and or agglutinated particles coated with a melt rim to the rest of the components these composite clasts developed spheroidal shapes during transport within a violent strombolian eruption column due to spin effect and finally landed in solid state

minimum effective area for high resolution crater counting of martian terrains the acquisition of high resolution imagery for the surface of mars has enabled mapping of spatially limited order of 200 m on four type terrains using mars reconnaissance orbiter mro context camera ctx imagery that span the noachian hesperian and amazonian epochs the counts from each location include a region covering 10 000 km2 ten 1000 km2 subsets of that larger area and approximately one hundred 100 km2 samples the data demonstrate significant variation in the crater size frequency and derived model ages across a single terrain type for the 100 km2 samples the crater size frequency at this area scale varies across a single uniform geologic unit by up to a factor of 2 3 on the four different terrains at 1000 km2 the local pattern variations that are relevant at the 100 km2 scale become less important and the age variations are tighter in all four terrain cases the 10 000 km2 and 1000 km2 samples capture distinct crater populations km sized craters that formed before and after resurfacing event s however due to the relatively high mean distance between km sized craters the 100 km2 size area samples more commonly than not exclude a statistically significant sample at the kilometer size range masking important information about the pre resurfacing history of the terrain we therefore suggest that due to the effect of pattern variability in cratering over 100 km2 and the susceptibility of smaller craters to resurfacing crater counts derived from small area samples are suspect to major uncertainties

mineralogy and fluvial history of the watersheds of gale knobel and sharp craters a regional context for the mars science laboratory curiosity s exploration a 500 km long network of valleys extends from herschel crater to gale knobel and sharp craters the mineralogy and timing of fluvial activity in these watersheds provide a regional framework for deciphering the origin of sediments of gale crater s mount sharp an exploration target for the curiosity rover olivine bearing bedrock is exposed throughout the region and its erosion contributed to widespread olivine bearing sand dunes fe mg phyllosilicates are found in both bedrock and sediments implying that materials deposited in gale crater may have inherited clay minerals transported from the watershed while some topographic lows of the sharp knobel watershed host chloride salts the only salts detected in the gale watershed are sulfates within mount sharp implying regional or temporal differences in water chemistry crater counts indicate progressively more spatially localized aqueous activity large scale valley network activity ceased by the early hesperian though later hesperian amazonian fluvial activity continued near gale and sharp craters

inverted fluvial features in the aeolis zephyria plana western medusae fossae formation mars evidence for post formation modification 1 the aeolis and zephyria plana contain the western most portion of the medusae fossae formation mff an enigmatic and extensive light toned deposit located in the martian equatorial region and dated from the hesperian to amazonian epochs this area hosts a large population of sinuous ridges srs interpreted as inverted fluvial features formed by precipitation indurated by chemical cementation buried by subsequent deposition and finally exhumed this interpretation of srs as uniformly fluvial represents a modification to an earlier hypothesis for one particular sr of possible glaciofluvial i e esker formation these srs provide a tool to investigate the degree and character of post fluvial modification processes in this region we combined digital terrain models made from context camera ctx and high resolution imaging science experiment hirise stereo image pairs with individual data points from the mars orbiter laser altimeter mola to estimate relief cross sectional profiles longitudinal profiles and slope directions of selected srs longitudinal profiles of several srs display undulations with amplitudes of up to order 100 m while some of the lower amplitude undulations may be due to differential erosion undulations having amplitudes in excess of sr relief require alternative explanations our combined morphologic and topographic analysis suggests that multiple post flow processes including compaction of the deposits and tectonic displacements have modified the original sr profiles specification of the type s and magnitudes of these modification processes will contribute to understanding both the potential of post flow modification of fluvial profiles elsewhere on mars as well as the nature and properties of the mff