ponding draining and tilting of the cerberus plains a cryolacustrine origin for the sinuous ridge and channel networks in rahway vallis mars rahway vallis sits within a shallow basin the rahway basin in the cerberus plains of mars containing a branching network of channels converging on the basin floor using topographic cross profiles of the channels we have found that they are set within broader subtly expressed valleys these valleys are shallow around 15 m vertically compared to several kilometres in the horizontal and have convex to rectilinear slope profiles that are consistent in form across the whole rahway basin both channels and valleys descend and deepen consistently from west to east the channels typically widen down slope and increase in width at confluences the morphology and topology of this channel system are consistent with formation by contributory fluid flow generated from many distributed sources the transition between the older heavily cratered terrain and the floor of the rahway basin is bounded by near horizontal continuous topographic terraces plotting the elevation of the terraces shows that they conform to a plane with a height difference of around 100 m east to west for the 300 km width of the rahway basin we calculate that the volume of material needed to fill the topography up to the level of the plane best fit by the terraces is 1500 km3 bordering the channels are sinuous ridges typically several kilometres long 20 m across with heights on the order of 10 m they sometimes form branching networks leading into the channels but also occur individually and parallel to the channels the multiple tilted terraces the channel valley network with many fluvial like characteristics and the distributed source regions suggest that the landforms within the rahway basin are unlikely to have formed through purely volcanic processes rather the channels within the rahway basin are consistent with a genesis requiring the flow of liquid water and the sinuous ridges with melting of a static ice body that occupied the basin we suggest a hypothesis of rapid basin filling by fluvial flooding followed by lake drainage drainage could have occurred as a consequence of an ice or debris dam failure within or during the formation of the large nearby fluvial flood channel marte vallis if the lake was partly or largely frozen prior to drainage this offers a possible explanation for the sinuous ridge systems hence although the sinuous ridges provide some of the most compelling morphological analogues of terrestrial eskers yet observed we conclude that the contextual evidence for this interpretation in rahway vallis is not strong and instead they are better explained in the context of a frozen or partially frozen lake or cryolacustrine model

a successive steady state model for simulating freshwater discharges and saltwater wedge profiles at baffin bay texas submarine groundwater discharges sgd are an important source of freshwater to coastal bays and estuaries in arid and semi arid regions understanding groundwater flows to these ecologically sensitive bodies is important for coastal environmental sustainability a management oriented mathematical model capable of simulating the flow of groundwater into a coastal bay i e submarine groundwater discharge is developed here using the principles of quasi steady state flow and the existence of a sharp interface between the freshwater and the saltwater portions of the aquifer the model is applied to the baffin bay in south texas a hypersaline coastal body with no major river discharges two global sensitivity approaches the one at a time design oat and the grid based monte carlo sensitivity index are used to identify critical model inputs the sensitivity of the model inputs to the nash sutcliffe efficiency nse criterion is calculated making use of synoptic observed sgd measurements made over a period of one tidal cycle the results of the study indicate that global sensitivity analysis methods are particularly sensitive to the number of model realizations the ability of these techniques to screen out insensitive model inputs increased with increasing number of realizations the variability in the identified inputs was more prominent with the oat sensitivity methods than monte carlo based techniques in general the aquifer properties hydraulic conductivity and aquifer thickness as well as fluid properties seawater and fresh water densities along with the antecedent sgd was noted to be the most sensitive parameters this result indicates that the implementation of sharp front coastal aquifer models can be improved through better hydrogeologic characterization and measuring temperature and salinity data to improve density estimation the global sensitivity methods also help identify reasonable values for model inputs which can serve as a starting point for advanced calibrations the results however indicated that the model is likely over parameterized with different input sets yielding similar nse estimates based on these initial parameter estimates the model was able to capture the general trend in the observed sgd but could not capture the dynamic associated with high water levels in the bay pre calibration global sensitivity analysis is recommended in similar applications as it not only provides insights into future data collection efforts but can also help assess the likely success of model calibration however given the variability among the techniques it is suggested that multiple global sensitivity methods be utilized

eruption history of the elysium volcanic province mars abstract volcanism has played a significant role in shaping the surface of mars volatiles released during eruptions profoundly altered the composition and density of the martian atmosphere in the past quantifying the amounts of volcanic outgassing has been attempted regionally and globally however volume estimates of erupted volcanic material in time are still poorly constrained here we show the first eruption frequency record of a volcanic region the elysium volcanic province which is the second largest volcanic province on mars studied lava flows show model ages ranging from 3 4 ga to 60 ma together with observed resurfacing ages the visible record of volcanic activity extends back to 3 9 ga based on our 190 model ages continuous volcanic activity is apparent with a major peak at 2 2 ga in the last 1 gyr the activity rapidly waned although the majority of volcanic material including volatiles released to the atmosphere erupted within a short time span of less than 200 ma activity continued until the very recent past extrapolating the eruption record it appears likely that this region of mars is still volcanically active today our derivation of the eruption record has profound implications for global thermal and atmospheric modeling indicating sustained heat production melt generation and magma ascent at a single location over most of the planet s geological history

possible evidence for variation in magnitude for marsquakes from fallen boulder populations grjota valles mars following observations of mobilized boulder trail populations from cerberus fossae mars that have been interpreted as possible evidence of large magnitude marsquakes rupturing for distances of 207 km along exposed active faults additional boulder trail populations were measured along shorter faults within the region of grjota valles 50 150 km length to test the hypotheses that 1 these faults are also candidate locations for marsquakes and 2 that marsquake magnitude might be smaller limited by fault dimensions available for rupture for a region containing two en echelon graben boulder trail data define two anomalies with maxima in a boulder trails per kilometer and b maximum width of boulder trails one that is 116 km in length along strike and the other 70 km in length along strike values for the maxima are 45 trails per km and 5 m mean trail width for the 70 km long anomaly and 115 trails per km with 5 3 m mean trail width for the 116 km long anomaly above background values measured elsewhere along these faults of zero trails per kilometer with zero boulder trail widths if combined with published data from cerberus fossae with a 207 km long anomaly in boulder trails per km 125 trails per km maxima and maximum mean boulder trail width 8 5 m maximum trail width the 3 datasets suggest correlations between the a along strike length of boulder trail anomalies b boulder trails per km and c maximum boulder trail width if interpreted as due to single marsquakes and if the dimensions of these anomalies are a proxy for rupture length when combined one interpretation of this is that boulders have been mobilized by marsquakes and that the marsquake magnitude is proportional to the along strike length of the anomalies in other words the data suggest that marsquake magnitude if that is the cause of the anomalies is limited by fault length as expected for terrestrial seismically active faults such findings suggest that the martian surface may have been shaken in the very recent past by large magnitude marsquakes we discuss this in terms of the seismicity of mars

the morphologies of volcanic landforms at central elysium planitia evidence for recent and fluid lavas on mars abstract this paper focuses on physical parameters flow rates and rheological properties of lava flows observed in the central elysium planitia cep region of mars the flows are modeled as newtonian fluids using the jeffrey s equation and the concept of graetz number or alternatively as bingham fluids in addition to these approaches a theoretical model of the shape of shield volcanoes based on the solution for the porous flow of an unconfined aquifer is applied to 5 shields providing independent quantifications of rheological variations between the shields this analysis indicates that of the five volcanoes studied two are partially buried by lava postdating their formation a result which has been confirmed independently in one case by high resolution images our observations reveal that two types of lava flows may be found in the cep region the first group is composed of large lava flows with viscosities around 2 5 10 5 pa s or yield strengths ranging from 100 to 500 pa the second group includes small lava flows of the shield volcanoes and large leveed lava channels on the plains with viscosities below 103 pa s or yield strengths less than 200 pa when compared with other volcanic regions on mars investigated with similar approaches these latter values are at present the lowest inferred for martian lava flows several hypotheses for the formation of these lavas are discussed in the context of cep given that low viscosity can be the result of 1 high temperature 2 low crystal content 3 low si abundance of the liquid phase and or 4 the presence of dissolved volatiles two scenarios are considered in the first one it is demonstrated that low viscosity lavas of low silica content can be produced in the context proposed by schumacher and breuer schumacher s breuer d 2007 geophys res lett 34 l12202 for recent volcanism however geochemical maps derived from grs measurements do not provide support for anomalously low silica concentrations in this region in the second scenario a water rich magma is proposed although arguments in favor of a water rich mantle source below the cep are not available at the present time

stratigraphical and morphological evidence for pingo genesis in the cerberus plains rootless debris cones or pseudocraters occur in platy patterned ground throughout the cerberus plains of mars and are thought to represent the products of explosive magma ice interaction lanagan et al 2001 geophys res lett 28 2365 2368 fagents et al 2002 in smellie j l chapman m g eds volcano ice interaction on earth and mars in geol soc spec publ vol 202 pp 295 317 requiring lava and water interspersed they are central to theories of multiple magmatic and aqueous flood events burr et al 2002 icarus 159 53 73 berman d c hartmann w k 2002 icarus 159 1 17 and widespread sheet volcanism keszthelyi et al 2000 j geophys res 105 15027 15049 in the region during the late amazonian a region reported to have been occupied by water bodies ranging from lakes to oceans scott et al 1995 map of mars showing channels and possible paleolake basins usgs miscellaneous investigations series map i 2461 1 30 000 000 the nature of the platy substrate is the subject of debate with evidence given for lava keszthelyi et al 2000 j geophys res 105 15027 15049 plescia j b 2003 icarus 164 79 95 and ice brakenridge g r 1993 lunar planet sci xxiv part 1 175 176 rice et al 2002 lunar planet sci xxxiii abstract 2026 murray et al 2005 nature 434 352 355 the superposition relationships of cones and platy deposits in the channels of the athabasca valles precludes a magmatic origin indicating later formation as permafrost mounds or pingos with implications for geologically recent flood volcanism age constraints on young surfaces and recent climate change on mars

postdating of flow in athabasca valles by faulting of the cerberus fossae elysium planitia mars 1 mars orbiter laser altimeter mola topographic data high resolution imaging science experiment hirise thermal emission imaging system themis and mars orbiter camera moc images have been used to study the timing of the formation of athabasca valles relative to faulting of the southern cerberus fossae scf the topography of athabasca valles derived from mola elevation data appears as two troughs on the north and south footwalls of scf the same troughs can be identified on the floor of the fossae indicating that athabasca valles predates the accumulation of 500 m of vertical fault offset the topographic expression of athabasca valles is preserved on the graben floor because infill by sediment and lava since formation of the valles and fossae amounts to less than a few tens of meters we use this information to discuss the mode of formation of athabasca valles and cerberus fossae

sorted stone circles in elysium planitia mars implications for recent martian climate we have found sorted stone circles and polygons near the equator of mars using new 25 cm pixel nasa hirise high resolution imaging science experiment images the sorted circles occur in geologically recent catastrophic flood deposits in the equatorial elysium planitia region and are diagnostic of periglacial processes sorted polygons do not form from volcanic activity as has been suggested for non sorted polygons in this region these landforms indicate that i a long lived geologically recent active cryoturbation layer of ground ice was present in the regolith ii there was some degree of freeze thaw and thus iii there were sustained period s likely within the last 10 ma in which the martian climate was 40 to 60 k warmer than current models predict

origin of groundwater salinity and hydrochemical processes in an unconfined aquifer case of yang dai river basin in qinhuangdao china groundwater salinization has become a growing concern in yang dai river basin of qinhuangdao china where groundwater is commonly exploited for domestic industrial and agricultural uses in this study hydrochemical and physical parameters of groundwater were analyzed to identify the origin of groundwater salinity and the geochemical processes occurring in the unconfined aquifer groundwater types are ca mg hco3 so4 in the hills ca mg hco3 so4 in the piedmont plain and na cl in the coastal alluvial plain respectively electrical conductivity values varied between 322 and 3990 s cm chloride concentration attained to 942 mg l and the proportion of seawater intrusion in the coastal alluvial plain was 5 39 calculated by seawater fraction formal displaying the severe seawater intrusion cation exchange reactions and water rock interactions related to the dilution of halite gypsum dolomite and calcite occurred by ionic relationships during seawater intrusion high nitrate concentrations ranged from 35 6 to 686 5 mg l distributed in the hills and the south coastal alluvial plain where they are seriously polluted by the industrial wastewater agricultural fertilizers and domestic sewage seawater intrusion and nitrate contamination have common effects on the hydrochemical process in the south coastal alluvial plain therefore the origin of groundwater salinization was attributed not only to seawater intrusion but also to anthropogenic pollution in the study area this research provides useful information for groundwater salinization and water planning strategies in a coastal area

hydrochemical and isotopic characterisation of the bathonian and bajocian coastal aquifer of the caen area northern france abstract this paper describes the geochemical evolution of groundwater in the bathonian and bajocian aquifer along its flowpath since this aquifer represents one of the main sources of fresh water supply in the caen area and has been subjected to a holocene marine intrusion its management requires a sound knowledge of 1 the primary conditions and 2 the potential influence of either natural or anthropogenic pressures groundwater vertical sampling validity is discussed with the contribution of high resolution temperature logging the main processes of geochemical evolution along a groundwater flow line and the sea water intrusion characteristics are discussed using ionic concentrations br f and major elements and isotopes water 2 h and 18 o tdic 13 c and a 14 c sulphate 18 o and 34 s as the 13 c content of tdic is used as a tracer of water rock interaction it shows evidence of specific chemical and isotopic evolutions of groundwater within the aquifer both related to water rock interaction and mineral equilibria in groundwater all the above mentioned tracers evolve downflow cation concentrations are modified by exchange with clay minerals allowing a high f concentration in groundwater whereas br and so 2 4 concentrations appear to be redox condition dependant superimposed on these geochemical patterns 18 o and 2 h compositions indicate that aquifer recharge has varied significantly through time the chemical evolution of groundwater is locally affected by a salty water intrusion that is characterised by mixing between flandrian fresh water and sea water which has interacted with peat as evidenced by a high br cl ratio and so 2 4 reduction

mars mapping with delay doppler radar mars radar imaging results from arecibo 12 6 cm observations are presented the images were derived from delay doppler mapping using a coded long pulse technique to mitigate the effects of echo overspreading images of the depolarized echo are used to identify regions of high decimeter scale roughness some of the strongest echo features are located on the major shield volcanoes or on relatively young off shield flows such as the olympus and pavonis lava aprons the shields themselves have highly irregular radar signatures suggesting complex volcanic histories some mars radar features have twice the depolarized brightness of the roughest terrestrial lava flows apparently due to higher levels of multiple scattering from surfaces of spectacular roughness or from volume scattering low brightness smooth areas are associated with older surfaces such as fractured and highland terra as well as with terrain interpreted to be debris lobes ash flows and aureoles in particular a close connection was found between the 12 6 cm counterpart of the stealth feature and the medusae fossae formation postulated to be deep ignimbrite deposits marte valus is anomalous in being the only outflow channel showing strongly enhanced echoes which supports the idea that this channel and the elysium basin that it drained are filled with lava flows a weak radar feature was found for the south polar residual ice cap comparisons with goldstone 3 5 cm data show that the south polar enhancement is much weaker at 12 6 cm than at 3 5 cm indicating that the southern ice cap becomes optically thin at the longer wavelength a north polar enhancement has also been found which is comparable in strength to the 12 6 cm south polar feature

evidence from the mars express high resolution stereo camera for a frozen sea close to mars equator it is thought that the cerberus fossae fissures on mars were the source of both lava and water floods two to ten million years ago evidence for the resulting lava plains has been identified in eastern elysium but seas and lakes from these fissures and previous water flooding events were presumed to have evaporated and sublimed away here we present high resolution stereo camera images from the european space agency mars express spacecraft that indicate that such lakes may still exist we infer that the evidence is consistent with a frozen body of water with surface pack ice around 5 degrees north latitude and 150 degrees east longitude in southern elysium the frozen lake measures about 800 x 900 km in lateral extent and may be up to 45 metres deep similar in size and depth to the north sea from crater counts we determined its age to be 5 2 million years old if our interpretation is confirmed this is a place that might preserve evidence of primitive life if it has ever developed on mars

elysium planitia lava flows crater count chronology and geological implications mars global surveyor mgs and viking images allow analysis of chronological and geological relations among lava flows in southern elysium planitia based on crater populations mgs and viking images clearly show morphological features of lava flows with some extremely sparsely cratered young flow units atop somewhat older surfaces there is no evidence of substantial dust mantling on the young flows and hence we infer that the crater populations date not sediment accumulation but the lava flows themselves the youngest flows have some of the lowest crater densities that we have seen on mars some 1 of lunar mare values at crater diameters below about 180 to 500 m we infer that thin scattered volcanic flows some tens of meters thick have been emplaced atop stratigraphic units within the last 100 myr and possibly within the last 10 myr volcanism is thus a continuing process in the recent geologic history of mars and this must constrain geophysical models of the planet

recent flood lavas in the elysium region of mars abstract a vast area of smooth plains in southeastern elysium here referred to as the cerberus formation is interpreted to be of volcanic origin surface morphology lobate edges of the unit the identification of vents low shields and the embayment relation of the unit with adjacent older units all suggest a volcanic origin the plains were formed by the eruption of low viscosity lavas that filled a topographic depression in southeast elysium and then flowed into western amazonis planitia flow into western amazonis was facilitated by a series of channels carved by an earlier fluvial episode which were exploited by lavas as they moved down slope crater frequencies and stratigraphic relations indicate that the unit is very young upper amazonian the presence of such young flood lavas indicates 1 late in martian history large scale eruptions of low viscosity lava was still possible b sufficient heat remained in the mantle to mobilize large quantities of magma and c flood volcanism either continued or resumed in elysium after activity of the large central volcanoes had ceased each of these points are important considerations in understanding the martian thermal and volcanic history

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

eutectic brines on mars origin and possible relation to young seepage features abstract if the recently observed young gullies on mars represent seeps or outflows of aqueous fluid that fluid must be highly concentrated brine to be even moderately stable under current martian surface conditions such brines are to be expected in the megaregolith if an initial saline hydrosphere underwent evapoconcentration via water escape from the atmosphere evolved into subsurface cacl 2 enriched brines by chemical interaction with mafic rocks and then froze until eutectic compositions were reached although most such brines would tend to sink deep into the megaregolith they could be preserved locally at relatively high elevations as aquifers or frozen paleoaquifers perched between ground ice and crystalline salts

identification of volcanic rootless cones ice mounds and impact craters on earth and mars using spatial distribution as a remote sensing tool 1 this study aims to quantify the spatial distribution of terrestrial volcanic rootless cones and ice mounds for the purpose of identifying analogous martian features using a nearest neighbor nn methodology we use the statistics r ratio of the mean nn distance to that expected from a random distribution and c a measure of departure from randomness we interpret r as a measure of clustering and as a diagnostic for discriminating feature types all terrestrial groups of rootless cones and ice mounds are clustered r 0 51 0 94 relative to a random distribution applying this same methodology to martian feature fields of unknown origin similarly yields r of 0 57 0 93 indicating that their spatial distributions are consistent with both ice mound or rootless cone origins but not impact craters each martian impact crater group has r 1 00 i e the craters are spaced at least as far apart as expected at random similar degrees of clustering preclude discrimination between rootless cones and ice mounds based solely on r values however the distribution of pairwise nn distances in each feature field shows marked differences between these two feature types in skewness and kurtosis terrestrial ice mounds skewness 1 17 1 99 kurtosis 0 80 4 91 tend to have more skewed and leptokurtic distributions than those of rootless cones skewness 0 54 1 35 kurtosis 0 53 1 13 thus nn analysis can be a powerful tool for distinguishing geological features such as rootless cones ice mounds and impact craters particularly when degradation or modification precludes identification based on morphology alone

grjota valles and implications for flood sediment deposition on mars 1 grjota valles is one of mars four amazonian aged fissure headed catastrophic flood channels it originates at the northwestern most cerberus fossa and stretches several hundred kilometers eastward and southward moats around in channel knobs and various small scale mounds similar to mounds seen in athabasca valles are both attributed to flood related processes the floodwater sinks are ambiguous and the lack of recognizable flood deposits is attributed to two causes the first cause is the channel s high width to depth ratio which may have facilitated floodwater recession during flooding the second cause is the tendency of floodwater under lower gravity to move a higher percentage of material as washload as flood deposits are comprised of bedload and suspended load this tendency would result in fewer depositional bedforms our analysis of grjota valles supports the idea that formation of terrestrial style flood deposits is energetically unlikely on mars and that their presence indicates special paleohydraulic conditions

tectonic implications of mars crustal magnetism mars currently has no global magnetic field of internal origin but must have had one in the past when the crust acquired intense magnetization presumably by cooling in the presence of an earth like magnetic field thermoremanent magnetization a new map of the magnetic field of mars compiled by using measurements acquired at an 400 km mapping altitude by the mars global surveyor spacecraft is presented here the increased spatial resolution and sensitivity of this map provide new insight into the origin and evolution of the mars crust variations in the crustal magnetic field appear in association with major faults some previously identified in imagery and topography cerberus rupes and valles marineris two parallel great faults are identified in terra meridiani by offset magnetic field contours they appear similar to transform faults that occur in oceanic crust on earth and support the notion that the mars crust formed during an early era of plate tectonics

hydrovolcanic tuff rings and cones as indicators for phreatomagmatic explosive eruptions on mars hydrovolcanism is a common natural phenomenon on earth and should be common on mars too since its surface shows widespread evidence for volcanism and near surface water we investigate fields of pitted cones in the nephentes amenthes region at the southernmargin of the ancient impact basin utopia which were previously interpreted as mud volcanoes the cone fields contain pitted and breached cones with associated outgoing flow like landforms based on stratigraphic relations we determined ahesperian or youngermodel age we test the hypothesis of a hydro volcanic origin based on a detailed morphological and morphometrical analysis and an analysis of the regional context an igneous volcanic origin of these cones as hydrovolcanic edifices produced by phreatomagmatic eruptions is plausible several lines of evidence suggest the existence of subsurface water ice the pitted cones display well developed wide central craters with floor elevations below the preeruptive surface their morphometry and the overall appearance are analogous to terrestrial tuff cones and tuff rings mounds that are also observed in the same region resemble terrestrial lava domes the hydrovolcanic interaction between ascending magma and subsurface water and or water ice may explain the formation of the pitted cones although other scenarios such as mud volcanism cannot be ruled out together with the mounds the cones might represent effusive and explosive edifices of amonogenetic volcanic field composed of lava domes tuff rings tuff cones and possibly maars

arecibo radar imagery of mars the major volcanic provinces abstract we present earth based radar images of mars obtained with the upgraded arecibo s band 12 6 cm radar during the 2005 2012 oppositions the imaging was done using the same long code delay doppler technique as for the earlier pre upgrade imaging but at a much higher resolution 3 km and for some regions a more favorable sub earth latitude this has enabled us to make a more detailed and complete mapping of depolarized radar reflectivity a proxy for small scale surface roughness over the major volcanic provinces of tharsis elysium and amazonis we find that vast portions of these regions are covered by radar bright lava flows exhibiting circular polarization ratios close to unity a characteristic that is uncommon for terrestrial lavas and that is a likely indicator of multiple scattering from extremely blocky or otherwise highly disrupted flow surfaces all of the major volcanoes have radar bright features on their shields although the brightness distribution on olympus mons is very patchy and the summit plateau of pavonis mons is entirely radar dark the older minor shields paterae and tholi are largely or entirely radar dark which is consistent with mantling by dust or pyroclastic material other prominent radar dark features include the fan shaped deposits possibly glacial associated with the three major tharsis montes shields various units of the medusae fossae formation a region south and west of biblis patera where stealth deposits appear to obscure tharsis flows and a number of dark halo craters with radar absorbing ejecta blankets deposited atop surrounding bright flows several major bright features in tharsis are associated with off shield lava flows these include the olympus mons basal plains volcanic fields east and south of pavonis mons the daedalia planum flows south of arsia mons and a broad expanse of flows extending east from the tharsis montes to echus chasma the radar bright lava plains in elysium are concentrated mainly in cerberus and include the fluvio volcanic channels of athabasca valles grjota valles and marte valles as well as an enigmatic region at the southern tip of the cerberus basin some of the cerberus bright features correspond to the distinctive platy ridged flows identified in orbiter images the radar bright terrain in amazonis planitia comprises two distinct but contiguous sections a northern section formed of lavas and sediments debouched from marte valles and a southern section whose volcanics may derive in part from local sources this south amazonis region shows perhaps the most complex radar bright structure on mars and includes features that correspond to platy ridged flows similar to those in cerberus

1 d electrical conductivity structure beneath the philippine sea results from an ocean bottom magnetotelluric survey abstract eight months of observation using ocean bottom electro magnetometers obems have allowed us to estimate the regional electrical conductivity structure beneath the philippine sea six obems were deployed along a line crossing the philippine sea from nw to se and five of them recorded useful data the raw time series data were cleaned up before we estimated the magnetotelluric mt impedance tensor conductivity structure at five sites is estimated using 1 d occam s inversion to fit the determinant average of each mt impedance tensor after a correction for the effect of topography we examined effect from two dimensionalities on the 1 d conductivity structure and the robustness of solutions the results of the 1 d conductivity structural model are strongly related to tectonic setting and the crustal age beneath each site the structure beneath the spreading axis of the mariana trough shows a distinct low conductivity structure at depths of 50 150 km and it probably reflects the upwelling dynamics operating beneath the spreading axis these low values are comparable with that of olivine with low hydrogen content implying that 1 the melting process extracts water from minerals such as olivine and 2 the melt beginning depth in the mariana trough is deeper than that of the typical morb source region the off axis conductivity profiles infer the existence of a high conductivity peak or a conductivity gradient change at mid depth the depth level of the peak increases with crustal age suggesting that the conductivity structure is related to a geothermal structure and that these conductivity profiles are explained by the temperature gradient change possibly combined with the presence of partial melt our results suggest that further ocean bottom em study has high potential to investigate the temperature gradient change and amount of hydrogen water and melt in the upper mantle

icelandic pseudocraters as analogs to some volcanic cones on mars pseudocraters are rootless vents formed by the interaction of lava flows with surface or near surface water this interaction can produce mild explosions and the accumulation of scoria and spatter into small constructs pseudocraters in several localities in iceland were examined in the field and compared to similar appearing features observed on mars the icelandic pseudocrater cones in this study range in size from 6 to 70 m in diameter have summit craters which range from 2 to 28 m in diameter many cones lack craters entirely and have flanks that are either concave up or convex up the size and spacing of icelandic pseudocraters might be a function of the availability of water in which larger closely spaced features result from efficient lava water interaction as suggested by the environments in which the features formed possible martian pseudocrater cones in amazonis planitia range in diameter from 30 to 180 m and have craters 12 to 80 m in diameter a numerical model for volcanic explosions was adapted to study the formation of pseudocraters under terrestrial and martian conditions the results suggest that explosions forming martian cones require significantly less water calculated masses are less by a factor of 4 to 16 than those forming icelandic pseudocraters despite their larger sizes this is attributed to the low gravity and atmospheric pressure in the mars environment and is consistent with the likely lower abundance of water which might be present as interstitial ice at shallow depths in the regolith locations of potential pseudocraters on mars at latitudes as low as 8 n imply the presence of crustal ice stores at the time of their formation

faulting on the volcanic tableland owens valley california the volcanic tableland brittle surface of the 764 000 yr old bishop tuff documents extensive faulting in the northern owens valley california during the late quaternary the tableland surface is cut by at least 226 fault scarps with a total of 328 km of surface rupture scarps are lens shaped rips in the surface of the bishop tuff with vertical offsets of a few meters to 140 m and lengths up to several kilometers the scarps have an average trend of n10 20 w and dip steeply both to the east and west the tableland records at least 290 m of cross valley extension in the last 764 000 yrs at an average rate of at least 400 m m y and a cumulative seismic moment of at least 2 8 cdot 10 28 dyne cm the volcanic tableland lies astride what has been called the white mountain seismic gap of the eastern california central nevada seismic zone seismic moment recorded on the tableland can be used to estimate average recurrence interval of surface rupturing earthquakes on the floor of the owens valley

rift zone volcanism and associated cinder cone field in utopia planitia mars 1 we analyzed a small cone field in sw utopia planitia that shows striking similarities to volcanic rift zones on earth this is of particular interest as the study area lies off any of the volcanic centers of mars in the northern hemisphere lowlands and is surrounded by material of the amazonian aged vastitas borealis formation vbf we believe that the study area could be the first direct evidence for volcanic activity in utopia planitia prior to the resurfacing by vbf material the most striking characteristics that we observed are 1 a set of broad eruptive fissures showing signs of ongoing extension during cone formation 2 parallel dike swarms 3 magmatic intrusions and 4 a number of lava flows that have erupted from the fissures and pitted cones that surround a larger cone in the center of the study area and that are often associated with or aligned along the fissures and dikes cratering model ages indicate that the study area is of late noachian to early hesperian age and is thus distinctly older than the surrounding vbf falling into the time frame of the main phases of activity in the volcanic centers of syrtis major elysium planitia and the southern highlands

mars exploration rover candidate landing sites as viewed by themis the analysis of six landing sites that were candidates for the two nasa mars exploration rovers mer benefited from recently available image data from the thermal emission imaging spectrometer themis onboard the 2001 mars odyssey spacecraft the combination of daytime and nighttime thermal infrared images from themis supplemented by additional data sets has lead to new or expanded insights into the nature of each landing site in meridiani planum a layer of lighter toned higher thermal inertia material is observable just below the hematite bearing layer gusev crater displays a more complex stratigraphy than previously observed including an upper layer with lobate margins the highest inertia unit of southern isidis planitia is confined to topographic lows in the rim basin margin and does not appear to be due to highland material transported onto the basin floor the enigmatic ovoid blocky terrain on the floor of melas chasma displays higher thermal inertia than its surroundings an indication that it contains coarser or more indurated material than the adjacent aeolian bedforms the myriad channels of athabasca valles display distinctive thermal signatures despite the presence of a bright layer of dust covering the region the presence of alluvial fans produced from spur and gulley erosion of the walls of eos chasma demonstrates that mass movements have occurred following the canyon scouring floods

cerberus fossae elysium mars a source for lava and water cerberus fossae a long fracture system in the southeastern part of elysium has acted as a conduit for the release of both lava and water onto the surface the southeastern portion of the fracture system localized volcanic vents having varying morphology in addition low shields occur elsewhere on the cerberus plains three locations where the release of water has occurred have been identified along the northwest athabasca and grjota vallis and southeast rahway vallis portions of the fossae water was released both catastrophically and noncatastrophically from these locations a fluvial system that extends more than 2500 km has formed beginning at the lower flank of the elysium rise across the cerberus plains and out through marte vallis into amazonis planitia the timing of the events is late amazonian

dating martian climate change abstract geological evidence indicates that low latitude polygonally patterned grounds on mars generally thought to be the product of flood volcanism are periglacial in nature and record a complex signal of changing climate by studying the martian surface stratigraphically in terms of the geometrical relations between surface landforms and the substrate rather than genetically by form analogy with earth we have identified dynamic surfaces across one fifth of martian longitude new stratigraphical observations in the elysium amazonis plains have revealed a progressive surface polygonisation that is destructive of impact craters across the region this activity is comparable to the climatically driven degradation of periglacial landscapes on earth but because it affects impact craters the martian chronometer it can be dated here we show that it is possible to directly date this activity based on the fraction of impact craters affected by polygon formation nearly 100 of craters of all diameters are superposed by polygonal sculpture considering the few 100 ma age of the substrate this suggests that the process of polygon formation was active within the last few million years surface polygonisation in this region often considered to be one of the signs of young plains forming volcanism on mars is instead shown to postdate the majority of impact craters seen we therefore conclude that it is post depositional in origin and an artefact of thermal cycling of near surface ground ice stratigraphically controlled crater counts present the first way of dating climate change on a planet other than earth a record that may tell us something about climate change on our own planet parallel climate change on these two worlds an ice age mars coincident with earth s glacial quaternary period might suggest a coupled system linking both we have previously been unable to generalise about the causes of long term climate change based on a single terrestrial example with the beginnings of a chronology for climate change on our nearest planetary neighbour we can

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

sounding the subsurface of athabasca valles using marsis radar data exploring the volcanic and fluvial hypotheses for the origin of the rafted plate terrain 1 to test the volcanic and fluvial hypotheses for the origin of the rafted plate terrain observed in the vicinity of athabasca valles 5 n 150 e central elysium planitia we investigated the subsurface radar echo from the mars advanced radar for subsurface and ionosphere sounding marsis 5 mhz band data over this area the backscattered signal losses were compared to finite difference time domain fdtd simulations of those arising from three hypothetical geoelectrical subsurface models which differed in their assumed composition percentage basalt versus ice and assumed mode of origin fluvial discharge frozen sea mudflow and low viscosity lavas the dielectric values used in these models are derived from laboratory measurements of mars analog materials under mars like conditions fdtd simulations suggest that if the near surface environment is ice rich it will result in an average loss rate of 0 053 db m for massive ice having less than 1 of suspended particulates and 0 065 db m for a mudflow consisting of a 50 50 mixture of ice and basaltic dust whereas the losses associated with a lava flow model increase to 0 19 db m in comparison the actual signal losses experienced by marsis within this region were on the order of 0 18 db m within the first 160 m beneath the surface this suggests that propagation characteristics of athabasca s near subsurface are more consistent with a volcanic rather than a fluvial or mudflow origin of the rafted plate terrain although limitations on radar sounding depth in this region cannot rule out the possibility of more deeply buried massive ice deposits

an equatorial periglacial landscape on mars abstract we present evidence drawn from new 25 cm pixel hirise images of mars of landforms indicative of geologically recent thaw degradation of ice rich terrain near the martian equator we have focused our study on the head region of athabasca vallis a catastrophic flood carved outflow channel thought to have been active within the last 2 8 ma the geomorphology of the study area is characterised by a series of polygonally patterned surfaces that are bounded by erosional scarps the scarps are indented with cirque shaped niches that appear to be controlled in scale and form by the pre existing polygonal sculpture shallow basins defined by niche indented scarps are also seen and contain pitted mound and cone structures that are similar in form to terrestrial pingos associated with many of these scarps are dendritic channels and gullies blocky debris and hummocky terminal deposits together these correspond morphologically to terrestrial retrogressive thaw slumps which are landforms typical of thermokarst environments we have also observed an evolutionary sequence of morphologies beginning with subsidence of polygonised surfaces and ending with scarp bounded basins fed by inter polygon channels this is consistent with the former presence of surficial liquid water released by ground ice thaw and is again indicative of thermokarst moreover the observations of epigenetic polygons and channels and of polycyclic retrogressive thaw slumps suggest that thaw and standing water persisted for many seasonal cycles the assemblage of landforms the occurrence of polygons and pingo like forms within erosional basins and observations of fluvial like channels cross cutting pre existing surface features are consistent with a surface that has evolved significantly since it was originally emplaced this precludes this terrain being a volcanic i e primary landscape as has been suggested in the past the formation of this landform assemblage requires that there was thaw of ground ice and persistent liquid water at the surface given the geologically young flood deposits in which this assemblage occurs our observations point to a recent period in which mars climate supported thaw conditions in this region

discovery of columnar jointing on mars we report on the discovery of columnar jointing in marte valles mars these columnar lavas were discovered in the wall of a pristine 16 km diameter impact crater and exhibit the features of terrestrial columnar basalts there are discontinuous outcrops along the entire crater wall suggesting that the columnar rocks covered a surface area of at least 200 km 2 assuming that the rocks obliterated by the impact event were similarly jointed we also see columns in the walls of other fresh craters in the nearby volcanic plains of elysium planitia amazonis planitia which include marte vallis and in a well preserved crater in northeast hellas

rootless cones on mars indicating the presence of shallow equatorial ground ice in recent times high resolution mars orbiter camera moc images have revealed the existence of clusters of small cones in the cerberus plains marte valles and amazonis planitia mars these cones are similar in both morphology and planar dimensions to the larger of icelandic rootless cones which form due to explosive interactions between surficial lavas and near surface groundwater impact crater size frequency relationships indicate that surfaces upon which the cones sit are no older than 10 ma if martian cones form in the same manner as terrestrial rootless cones then equatorial ground ice or ground water must have been present near the surface in geologically recent times

geomorphic analysis of small rayed craters on mars examining primary versus secondary impacts 1 twenty confirmed impacts over a 7 year time period on mars were qualitatively and statistically compared to 287 secondary craters believed to originate from zunil an 500 ka 10 km diameter primary crater our goal was to establish criteria to distinguish secondaries from primaries in the general crater population on the basis of their horizontal planforms recent primary impacts have extensive air blast zones distal ray systems 100 crater radii r and ephemeral ejecta recent primaries formed clusters of craters from atmospheric fragmentation of the meteoroid body secondary craters have ejecta blankets with shorter rays that are consistent with emplacement by low impact velocities near 1 km s the mean extent of the continuous ejecta blankets was less distal for secondaries 5 38 1 57r versus primaries 18 07 7 01r though primary ejecta were less fractal fractal dimension index fdi 1 30 and more circular on average circularity ratio cr 0 55 0 25 versus 0 27 0 13 for secondaries crater rims were remarkably circular primaries cr 0 97 0 02 secondaries at 0 94 0 05 though secondaries have the lowest values cr 0 9 secondary crater rims were elongated toward or orthogonal to their primary of origin uprange source directions for most secondaries determined by ejecta planform and crater rim ellipticity point toward zunil although contamination from other primaries is considered in some areas ejecta blanket discrepancies between recent primaries and zunil secondaries are attributable to differences in impact velocity and retention age after removal of the ejecta blanket crater rims are generally not diagnostic for determining crater origin fragmentation of primaries may play some role in steepening the size frequency distribution of crater diameters in the 5 m d 30 m range

permeability changes during remediation of an aquifer affected by sea water intrusion a laboratory column study summary during flushing of a seawater affected aquifer with freshwater fine particles can be mobilized and can subsequently clog up pores thereby causing a reduction of permeability here we used packed columns 25 cm length to experimentally investigate the changes in permeability during such a remediation scenario we hypothesized that a gradual and abrupt change in salinity as well as the pressure boundary conditions along the column will affect the particle release and permeability changes we collected sediments from a coastal aquifer in china in which seawater had intruded the sediments were packed into laboratory columns the columns were oriented horizontally and instrumented with a series of piezometers to measure hydraulic heads along the column several sequences of displacements of seawater electrical conductivity ec 48 5 ms cm with freshwater ec 0 78 ms cm were passed through the columns permeability was determined from measured flow rates and hydraulic heads experiments were conducted both with constant head as well as with constant flux conditions column outflow was analyzed for suspended particles and electrical conductivity the results indicate that the permeability was reduced by up to 70 when seawater was displaced with freshwater under constant head conditions permeability reductions were more pronounced than under constant flux the critical salinity i e electrical conductivity associated with the critical salt concentration for particle release in the sediments was 7 ms cm when salinity was changed abruptly fine particles were eluted from the column however when the salinity change was gradual no fines were eluted in agreement with previous literature data we observed a more pronounced reduction of permeability under an abrupt than under a gradual salinity change permeability reduction was not uniform along the column with generally decreasing permeability with increasing distance from the column inlet

crater based dating of geological units on mars methods and application for the new global geological map abstract the new post viking generation of mars orbital imaging and topographical data provide significant higher resolution details of surface morphologies which induced a new effort to photo geologically map the surface of mars at 1 20 000 000 scale although from unit superposition relations a relative stratigraphical framework can be compiled it was the ambition of this mapping project to provide absolute unit age constraints through crater statistics in this study the crater counting method is described in detail starting with the selection of image data type locations both from the mapper s and crater counter s perspectives and the identification of impact craters we describe the criteria used to validate and analyse measured crater populations and to derive and interpret crater model ages we provide examples of how geological information about the unit s resurfacing history can be retrieved from crater size frequency distributions three cases illustrate short intermediate and long term resurfacing histories in addition we introduce an interpretation independent visualisation of the crater resurfacing history that uses the reduction of the crater population in a given size range relative to the expected population given the observed crater density at larger sizes from a set of potential type locations 48 areas from 22 globally mapped units were deemed suitable for crater counting because resurfacing ages were derived from crater statistics these secondary ages were used to define the unit age rather than the base age using the methods described herein we modelled ages that are consistent with the interpreted stratigraphy our derived model ages allow age assignments to be included in unit names we discuss the limitations of using the crater dating technique for global scale geological mapping finally we present recommendations for the documentation and presentation of crater statistics in publications

timing of basaltic volcanism along the mesa butte fault in the san francisco volcanic field arizona from 40ar 39ar dates implications for longevity of cinder cone alignments using high precision stepwise heating 40ar 39ar methods we dated volcanic products of at least 12 vents cropping out along the northern segment of the mesa butte fault in the san francisco volcanic field arizona where the relationship between fault and vent alignment is unambiguous the 40ar 39ar isochron dates indicate that the mesa butte fault hosted five episodes of volcanism over a 1 million year interval from 1400 to 300 ka the first episode occurred 1 km northwest of the trace of the mesa butte fault whereas the next two episodes were centered near the intersection of the mesa butte and cedar ranch faults the final two episodes produced red mountain 750 100 ka and shadow mountain 300 100 ka respectively ages of vents representing the third mesa butte episode of volcanism 760 50 ka to 900 80 ka indicate a systematic southwestward shift in the locus of volcanism along the mesa butte fault that contrasts sharply with overall eastward younging of volcanism within the field these data demonstrate that structures in basaltic volcanic fields are capable of hosting multiple episodes of volcanism over periods of time comparable to duration periods of composite volcanoes 106 years but at significantly lower recurrence intervals these results suggest that probability models of spatiotemporal recurrence of volcanism within basaltic volcanic fields should incorporate mapped structures particularly where these structures have either hosted previous volcanic activity or are proximal to population centers or sensitive installations such as nuclear power plants or waste repositories

explosive lava water interactions in elysium planitia mars geologic and thermodynamic constraints on the formation of the tartarus colles cone groups 1 volcanic rootless constructs vrcs are the products of explosive lava water interactions vrcs are significant because they imply the presence of active lava and an underlying aqueous phase e g groundwater or ice at the time of their formation combined mapping of vrc locations age dating of their host lava surfaces and thermodynamic modeling of lava substrate interactions can therefore constrain where and when water has been present in volcanic regions this information is valuable for identifying fossil hydrothermal systems and determining relationships between climate near surface water abundance and the potential development of habitable niches on mars we examined the western tartarus colles region 25 27 n 170 171 e in northeastern elysium planitia mars and identified 167 vrc groups with a total area of 2000 km2 these vrcs preferentially occur where lava is 60 m thick crater size frequency relationships suggest the vrcs formed during the late to middle amazonian modeling results suggest that at the time of vrc formation near surface substrate was partially desiccated but that the depth to the midlatitude ice table was 42 m this ground ice stability zone is consistent with climate models that predict intermediate obliquity 35 between 75 and 250 ma with obliquity excursions descending to 25 32 for lava thicknesses ranging from 30 to 60 m and ground ice fractions ranging from 0 1 to 0 3 an ice volume of 4 23 km3 could have been melted and or vaporized by the time the lava solidified and the associated hydrothermal systems could have retained temperatures 273 k for up to 1300 years

pathological martian craters evidence for a transient obliteration event we have detected three unusual low relief circular features 1 2 to 2 1 km in diameter in the northwest noachis highlands which may be craters that have undergone isostatic deformation they may shed light on the existence nature and timing of suspected widespread martian erosion obliteration events and offer clues to a type of martian terrain softening in the surrounding area we find an anomalous deficiency of craters in the 3 11 km diameter range and evidence that larger older craters have undergone relief softening and infill we discuss three different hypotheses to explain these features two of which involve martian ice this region may have undergone a transient event in which a near surface permafrost layer several hundred meters deep underwent partial melting or softening this would allow relaxation of kilometer scale craters and softening of larger craters crater data presented here suggest that this event happened some time in mid martian history whether the event was regional or related to global scale events is uncertain though it may represent a class of events that also happened in other martian areas

a simple approximation for a moving interface in a coastal aquifer an approximate analytical solution for a moving interface in a confined coastal aquifer is found by solving a nonlinear first order partial differential equation the solution which assumes that flow approaching the interface changes discontinuously with time from one constant value to another coincides with exact steady flow solutions obtained from the dupuit approximation at both t 0 and t a comparison with numerical solutions suggests that maximum errors of about ten percent occur in the toe location for intermediate values of time and that the approximate solution tends to overestimate both the rate of advance and retreat of the toe the approximation has a very simple form and in contrast to numerical solutions is easy to evaluate additional comparisons with numerical solutions also suggest that the analytical approximation can be applied with confidence to an unconfined flow only when the sudden change in approaching flow rate occurs at distances from the interface toe that are not too great this is because free surface storage effects slow the movement of the flow rate change before its effects are eventually felt downstream at the interface toe

investigating the volcanic versus aqueous origin of the surficial deposits in eastern elysium planitia mars abstract the elysium volcanic province consists of numerous overlapping flow units and may include the youngest lava flows on mars however it is possible that these volcanic units have been modified or overprinted by aqueous processes understanding the timing of the igneous and aqueous events in this region is therefore essential for constraining the geological and environmental history of mars during the amazonian period we investigate the geologic evolution of eastern elysium planitia to determine the relationship between major units with the support of a geological map and chronological constraints from crater size frequency distributions we also evaluate the hypothesized origin of these units via volcanic fluvial and or fluvioglacial processes using a detailed facies mapping approach the study area includes the eastern cerberus fossae rahway valles and marte vallis the surficial deposits in rahway valles were formerly interpreted to be modified by fluvial and fluvioglacial processes however our facies map reveals that the surface of eastern elysium planitia includes nineteen morphologically distinct regions i e facies which are interpreted to be the products of flood lava volcanism including a p hoehoe and transitional lava flow types in contrast to previous studies which determined that rahway valles and marte vallis consist of two distinct geologic units with middle to late amazonian ages the results of this work show that the region was resurfaced by at least two volcanic flows with much younger ages of 20 0 ma and 8 8 ma furthermore by coupling results of our geologic and facies mapping with chronological constraints as well as subsurface information provided by shallow radar reflectors we show that there is an erosional unconformity located between the two youngest lava flow units in marte vallis we interpret that this unconformity was generated by a catastrophic aqueous flooding event that occurred only 8 8 20 0 ma ago this implies alternating episodes of volcanism and aqueous flooding that have continued into the geologically recent past on mars and may again occur within elysium planitia

the search for active marsquakes using subpixel coregistration and correlation best practice and first results the state of seismic activity on mars is currently unknown on earth coseismic displacement has been observed using visible wavelength images and subpixel coregistration and correlation techniques we apply this method to mars with the cosi corr co registration of optically sensed images and correlation software package using high resolution imaging science experiment hirise images focusing on part of the cerberus fossae fault system we derive best practices for applying this method to the study of coseismic displacements on mars using a time series of eight overlapping hirise images we achieve pixel coregistration with a mean accuracy of about 1 50 of a pixel we see no clear evidence for coseismic displacement in this region during a time period of over 8 years one possible displacement signal 1 2 m of west east displacement over a length scale of about 50 m that has similarities to terrestrial coseismic deformation was dismissed as the result of incomplete correction of steep topography during the coregistration stage ancillary observations of recurring slope lineae rsl activity in the surrounding fault system offer no supporting evidence for the occurrence of coseismic displacement but do seem to suggest rsl activity that does not fit into previous seasonal timescales although it is unlikely that we have observed coseismic displacement in our study area during this time period the best practice method and the accuracy of our results offer encouragement for future studies hirise context camera and color and stereo surface imaging system images can be used to complement and independently verify in situ seismic observations by the insight interior exploration using seismic investigations geodesy and heat transport lander or source location changes from the exomars trace gas orbiter spacecraft

martian cratering vi crater count isochrons and evidence for recent volcanism from mars global surveyor this paper develops a methodology to establish absolute martian ages by deriving isochrons on a plot of martian impact crater density vs crater diameter calibrated by lunar crater age data the isochrons illustrated here are based on a mars moon cratering ratio of 1 6 at constant size but there is a factor of 2 to 4 uncertainty in this ratio and the consequent model ages martian crater diameter distributions are determined in several areas down to diameter d 16 45 m the shapes of the curves in young areas are found to be close to that of the predicted isochrons and close to the standard production function found by neukum the youngest areas studied here display the lunar like production function down to d 30 m where saturation equilibrium sets in model crater retention ages of several volcanic units are found to be a few hundred million years or less with estimated uncertainties ranging from a factor of 2 lower to a factor of 4 higher the results are consistent with martian meteorite ages volcanism on mars has probably persisted into the last 10 to 15 of the planet s history and is likely ongoing because surfaces as young as a few hundred million years have reached crater saturation equilibrium at d 60 to 100 m mars is likely to have widespread impact produced regoliths at least a few meters deep and this may contribute to the widespread mobile dust and boulder fields of mars

the snake river plain idaho representative of a new category of volcanism studies of the volcanic geology of the snake river plain idaho and comparison with other basaltic regions suggest a new category of volcanic activity termed basaltic plains volcanism typified by the snake river plain this style of volcanism is intermediate between basaltic flood or plateau eruptions and hawaiian volcanism characteristics that are common to both hawaiian and plains volcanism are multiple lava flow units which erupt primarily from point sources formation of low shields and frequent emplacement through lava tubes or channels characteristics that are common to both flood basalts and plains volcanism are high volume flows vents aligned along rift zones and planar surfaces the recognition of plains volcanism in other areas provides a means to interpret the style of eruption and volcanic history

cold springs in permafrost on earth and mars 1 perennial springs located on west central axel heiberg island in the canadian high arctic occur in a region with a mean annual air temperature of 15 c and flow through continuous permafrost 600 m thick the spring water is a low temperature up to 6 c brine that maintains constant discharge temperatures and flow rates throughout the year here we report on observations of temperature and discharge rate of these springs and develop a combined flow and thermal model of the subsurface flow using the measured geothermal gradient we also consider the implications these springs have for the search for similar environments past or present on mars

effect of natural recharge on sea water intrusion in coastal aquifers abstract parametric studies were carried out to investigate the effect of uniform recharge on sea water intrusion into coastal aquifers using a one dimensional finite element model for this purpose uniform recharge over the entire length of intrusion for a wide range of practical aquifers is considered useful relationships have been established between the interface motion and the intensity and duration of uniform recharge these relationships can be used to estimate the repulsion of sea water intrusion owing to rainfall this repulsion under favourable conditions is estimated to reach a maximum of about 5 the effect of uneven distribution of rainfall is demonstrated through an example movement of the interface is also tracked after the cessation of recharge

structural evolution of the northern cerberus fossae graben system elysium planitia mars to determine whether the structural evolution of the northern cerberus fossae ncf was dominated by cryospheric melting and collapse or fault related subsidence we used moc themis and hirise images and mola data to document spatial variations in vertical offset along strike the fossae are a series of fractures on the martian surface that cross cut noachian hesperian and in places very young late amazonian terrain serial cross sections across the fracture related topography from mola data show that vertical offsets are not greater where fractures traverse older terrain showing that offsets have accumulated since the formation of the amazonian terrain vertical offsets are greater in the central portions of the fracture system with the profile resembling that for a single fault system topographic features that pre date deformation are preserved on the graben floors suggesting little sediment infill so the mola elevation measurements constrain total vertical offsets since the fractures formed deficits in vertical offset occur where fractures have not linked and remain en echelon across relay zones or have linked leaving palaeo graben tips this indicates that the traces of the fractures propagate along strike at the surface and intersect over time periods that are likely to be in the range of 105 106 years rather than in a single collapse event deficits are also in places associated with collapse pits suggesting such collapse is the early stage of graben subsidence at propagating lateral graben tips we use these observations to argue that the primary mechanism causing subsidence is not cryospheric melting and collapse but faulting