a young multilayered terrane of the northern mare imbrium revealed by chang e 3 mission china s chang e 3 ce 3 spacecraft touched down on the northern mare imbrium of the lunar nearside 340 49 e 44 12 n a region not directly sampled before we report preliminary results with data from the ce 3 lander descent camera and from the yutu rover s camera and penetrating radar after the landing at a young 450 meter crater rim the yutu rover drove 114 meters on the ejecta blanket and photographed the rough surface and the excavated boulders the boulder contains a substantial amount of crystals which are most likely plagioclase and or other mafic silicate mineral aggregates similar to terrestrial dolerite the lunar penetrating radar detection and integrated geological interpretation have identified more than nine subsurface layers suggesting that this region has experienced complex geological processes since the imbrian and is compositionally distinct from the apollo and luna landing sites

dust devil speeds directions of motion and general characteristics observed by the mars express high resolution stereo camera abstract a total of 205 dust devils were detected in 23 high resolution stereo camera hrsc images taken between january 2004 and july 2006 with the esa mars express orbiter in which average dust devil heights were 660 m and average diameters were 230 m for the first time dust devil velocities were directly measured from orbit and range from 1 to 59 m s the observed dust devil directions of motion are consistent with data derived from a general circulation model gcm in some respects hrsc dust devil properties agree favorably with data from the nasa mars exploration rover spirit dust devil analyses the spatial distribution of the active dust devils detected by hrsc supports the conjecture that the ascending branch of the hadley circulation is responsible for the increase in dust devil activity especially observed during southern summer between 50 and 60 s latitude combining the dust lifting rate of 19 kg km2 sol derived from the spirit observations with the fewer in number but larger in size dust devils from various other locations observed by hrsc we suggest that dust devils make a significant contribution to the dust entrainment into the atmosphere and to the martian dust cycle

identifying the behavioural characteristics of clay cliffs using intensive monitoring and geotechnical numerical modelling abstract coastal monitoring is routinely undertaken to provide an archival record of cliff line movement that can be used in the development and validation of predictive coast retreat and evolution models however coastal monitoring is often purely quantitative in nature and financial necessity requires deployment over extensive coastal sections as a result for local site conditions in particular only limited geomorphological data are available or included during the development of such predictive models this has resulted in many current models incorporating a simplistic or generalised representation of cliff behaviour an approach that progressively loses local credibility when deployed over extensive heterogeneous coastlines this study addresses this situation at a site of extreme coastline retreat holderness uk through the application of intensive monitoring of six representative cliff sections nested within a general geomorphological appraisal of the wider coastline as a whole the data from these surveys have been used to validate a finite difference based geotechnical modelling assessment of clay cliff stability once validated the geotechnical model was used to simulate a range of scenarios that were sufficient to represent the range of topographic hydrogeological geological and littoral conditions exhibited throughout the region our assessment identified that the cliff retreat occurs through the combined influence of direct marine erosion of the cliff with shallow structurally controlled failures or substantial mass failures critically the predisposition to any one of these failure mechanisms arises principally as a result of initial cliff height the results of the numerical modelling have been combined into an empirical slope model that derives the rate of landslide induced retreat that would arise from mass failures under various future scenarios results of this study can be used in the selection and development of retreat models at coastlines of similar physiographic setting to that found at holderness the results represent a key step in linking material deformation properties to the processes of cliff change and the subsequent range of landforms found on clay cliffs as such the results could also be used more generally to illustrate the likely cliff behaviour of other soft rock coastlines

the morphology of craters on mercury results from messenger flybys topographic data measured from the mercury laser altimeter mla and the mercury dual imaging system mdis aboard the messenger spacecraft were used for investigations of the relationship between depth and diameter for impact craters on mercury results using data from the messenger flybys of the innermost planet indicate that most of the craters measured with mla are shallower than those previously measured by using mariner 10 images mdis images of these same mla measured craters show that they have been modified the use of shadow measurement techniques which were found to be accurate relative to the mla results indicate that both small bowl shaped and large complex craters that are fresh possess depth to diameter ratios that are in good agreement with those measured from mariner 10 images the preliminary data also show that the depths of modified craters are shallower relative to fresh ones and might provide quantitative estimates of crater in filling by subsequent volcanic or impact processes the diameter that defines the transition from simple to complex craters on mercury based on messenger data is consistent with that reported from mariner 10 data

n view reconstruction a new method for morphological modelling and deformation measurement in volcanology abstract we present a method of reconstructing volcanic morphology using multiple digital views n view captured at different angles around an object this approach uses recent advances in the field of computer vision to provide accurate 3 d measurements of volcanic surfaces videogrammetry digital image reconstruction is used as it is best adapted to numerical processing the method is tested and now used in the laboratory on analogue volcanic cones the method begins with calibrating the camera and finding image positions using an accurate n view calibration method this is done by estimating internal and external parameters of the camera using several views of a specially constructed calibration target the n view reconstruction of the real object is then done by iteratively deforming an initial theoretical model of the surface laboratory tests show that reconstruction accuracy is about 10 4 m for a distance between the object and the camera of 0 5 m and is potentially several orders of magnitude higher for surfaces of finer texture and using higher precision sensors this is easily high enough to be useful for the accuracy required for morphological studies it is also sufficient for monitoring most types of volcano deformation the technique has the potential to detect morphology changes of the order of mm use of the method in the field requires a slightly different approach from that in the laboratory textures and lighting are more variable and the sensor and ground control point location and model calibration must be done differently we provide case studies from laboratory tests and qualitative image analysis for two field cases piton de la fournaise indian ocean and santaguito guatemala these illustrate the technique s potential and explore problems of field application using current sensors the method has the potential to provide sufficient precision for fine mm cm scale reconstruction and will represent a valuable simple and flexible tool when compared with classical stereophotogrammetry techniques

oblique photogrammetry with visible and thermal images of active lava flows digital images from hand held cameras are increasingly being acquired for scientific purposes particularly where non contact measurement is required however they frequently consist of oblique views with significant camera to object depth variations and occlusions that complicate quantitative analyses here we report the use of oblique photogrammetric techniques to determine ground based thermal camera orientations position and pointing direction and to generate scene information for lava flows at mount etna sicily multiple images from a consumer grade digital slr camera are used to construct a topographic model and reference associated ground based thermal imagery we present data collected during the 2004 2005 eruption and use the derived surface model to apply viewing distance corrections to account for atmospheric attenuation to the thermal images on a pixel by pixel basis for viewing distances of 100 to 400 m the corrections result in systematic changes in emissive power of up to 3 with respect to values calculated assuming a uniform average viewing distance across an image

growth of the lava dome and extrusion rates at soufriere hills volcano montserrat west indies 2005 2008 the third episode of lava dome growth at soufriere hills volcano began 1 august 2005 and ended 20 april 2007 volumes of the dome and talus produced were measured using a photo based method with a calibrated camera for increased accuracy the total dense rock equivalent dre volume of extruded andesite magma 306 51 mm3 was similar within error to that produced in the earlier episodes but the average extrusion rate was 5 6 0 9 m3s 1 dre higher than the previous episodes extrusion rates varied in a pulsatory manner from 0 5 m3s 1 to 20 m3s 1 on 18 may 2006 the lava dome had reached a volume of 85 mm3 dre and it was removed in its entirety during a massive dome collapse on 20 may 2006 extrusion began again almost immediately and built a dome of 170 mm3 dre with a summit height 1047 m above sea level by 4 april 2007 there were few moderate sized dome collapses 1 10 mm3 during this extrusive episode in contrast to the first episode of dome growth in 1995 8 when they were numerous the first and third episodes of dome growth showed a similar pattern of low 0 5 m3s 1 but increasing magma flux during the early stages with steady high flux after extrusion of 25 mm3

high precision photogrammetry for monitoring the evolution of the nw flank of stromboli volcano during and after the 2002 2003 eruption high precision aerial photogrammetry has been used in addition to other geophysical techniques such as bathymetric surveys geodetic measurements microseismicity recording etc for monitoring slope deformations and the volcanic activity of stromboli island aeolian arc italy during the last effusive eruption which started on december 28 2002 and soon after the major landslide tsunami event of december 30 qualitative and quantitative description of topographic and morphological changes of the sciara del fuoco were possible thanks to a recent pre eruption photogrammetric survey performed in 2001 the comparisons of 12 multi temporal digital terrain models carried out during the period january june 2003 were used to evaluate the displaced mass by the landslide the lava accumulation and the erosion processes of the sciara del fuoco after the end of the eruption four additional photogrammetric surveys were performed between july 2003 and october 2005 to monitor the evolution of the slope and detect potential instability phenomena the slope appeared significantly modified and continued to evolve showing marked erosion both on the lower part and toward the craters terrace over the same period the new lava flows showed progressive contraction of the thicker part of the lava pile caused by its cooling and compaction and the possible sliding along the shear surface of the december 2002 deep seated movement the present morphology seems to be far from equilibrium and the deformation processes are still ongoing justifying a continuous monitoring activity to understand the evolution of these instability phenomena

photogrammetric monitoring of lava dome growth during the 2009 eruption of redoubt volcano abstract the 2009 eruption of redoubt volcano alaska began with a phreatic explosion on 15 march followed by a series of at least 19 explosive events and growth and destruction of at least two and likely three lava domes between 22 march and 4 april on 4 april explosive activity gave way to continuous lava effusion within the summit crater we present an analysis of post 4 april lava dome growth using an oblique photogrammetry approach that provides a safe rapid and accurate means of measuring dome growth photogrammetric analyses of oblique digital images acquired during helicopter observation flights and fixed wing volcanic gas surveys produced a series of digital elevation models dems of the lava dome from 16 april to 23 september the dems were used to calculate estimates of volume and time averaged extrusion rates and to quantify morphological changes during dome growth effusion rates ranged from a maximum of 35 m 3 s 1 during the initial two weeks to a low of 2 2 m 3 s 1 in early summer 2009 the average effusion rate from april to july was 9 5 m 3 s 1 early rapid dome growth was characterized by extrusion of blocky lava that spread laterally within the summit crater in mid to late april the volume of the dome had reached 36 10 6 m 3 roughly half of the total volume and dome growth within the summit crater began to be limited by confining crater walls to the south east and west once the dome reached the steep north sloping gorge that breaches the crater growth decreased to the south but the dome continued to inflate and extend northward down the gorge effusion slowed during 16 april 1 may but in early may the rate increased again this rate increase was accompanied by a transition to exogenous dome growth from mid may to july the effusion rate consistently declined the decrease is consistent with observations of reduced seismicity gas emission and thermal anomalies as well as declining rates of geodetic deflation or inflation these trends suggest dome growth ceased by july 2009 the volume of the dome at the end of the 2009 eruption was about 72 10 6 m 3 more than twice the estimated volume of the largest dome extruded during the 1989 1990 eruption in total the 2009 dome extends over 400 m down the glacial gorge on the north end of the crater with a total length of 1 km width of 500 m and an average thickness of 200 m

an improved shadow measurement technique for constraining the morphometry of simple impact craters the lengths of the shadows cast within simple bowl shaped impact craters have been used to constrain their depths on a variety of planetary bodies this technique however only yields the true crater depth if the shadow transects the crater center where the floor is deepest in the past attempts have been made to circumvent this limitation by choosing only craters where the shadow tip lies very near the crater center but this approach may introduce serious artifacts that adversely affect the slope of the regressed depth vs diameter data and its variance here we introduce an improved method for deriving depth information from shadow measurements that considers three basic shape variations of simple craters paraboloidal conical and flat floored we show that the shape of the cast shadow can be used to constrain crater shape and we derive improved equations for finding the depths of these simple craters

morphometry of small recent impact craters on mars size and terrain dependence short term modification most recent studies of crater morphometry on mars have addressed large craters d 5 km using elevation models derived from laser altimetry in the present work we examine a global population of small 25 m d 5 km relatively well preserved simple impact craters using hirise stereo derived elevation models we find that scaling laws from prior studies of large simple craters generally overestimate the depth and volume at small diameters we show that crater rim curvature exhibits a strong diameter dependence that is well described by scaling laws for d 1 km above this diameter upper rim slopes begin to exceed typical repose angles and crater rims sharpen significantly this transition is likely the result of gravity driven collapse of the upper cavity walls during crater formation or short term modification in addition we identify a tendency for small craters d 500m to be more conical than large craters and we show that the average cavity cross section is well described by a power law with exponent 1 75 neither conical nor paraboloidal we also conduct a statistical comparison of crater subpopulations to illuminate trends with increasing modification and target strength these results have important implications for describing the initial condition of simple crater shape as a function of diameter and geological setting and for understanding how impact craters are modified on the martian surface over time

on the numerical simulation of dust devil like vortices in terrestrial and martian convective boundary layers 1 this paper presents an overview of the numerical simulation studies to date of vertical vortices or dust devil like vortices which arise in atmospheric convective boundary layers cbls the similarities and differences between these studies are highlighted in addition the accuracy of the simulated vortices as compared with observed physical characteristics is discussed it is notable that vertical vortices formed in all of the studies considered for both mars and earth simulations despite the fact that they have not often been pointed out in laboratory and numerical simulations of cbls a possible implication of this finding is that non visible vertical vortices may even be ubiquitous and thus may play an important role in boundary layer transports if this is so they may have implications for pollution and hazardous waste transports as well as on impacts on descent and landing of spacecraft on mars

investigation of the depth and diameter relationship of subkilometer diameter lunar craters abstract the depth and diameter relationship is one of the most important characteristics of craters however previous studies have focused mostly on large diameter craters because of the limitations of image resolution recently very high resolution images have been obtained that make it possible to expand this field of study to craters with diameters of

systematic morphometric characterization of volcanic edifices using digital elevation models abstract quantitative characterization of the size and shape of volcanic edifices is an essential step towards the understanding of factors controlling volcano growth and morphology the recent advent of digital elevation models dems with worldwide coverage offers the opportunity to systematically document the morphometry of all types of volcanoes using quantitative well formalized methodologies we present a methodology for the morphometric characterization of volcanic edifices after reviewing previous studies on volcano morphometry and the various existing dem sources we describe an integrated procedure that uses a dem and its derived products slope curvature to extract a coherent set of morphometric parameters for a given volcanic edifice edifice boundaries are manually defined by searching for breaks in slope around the base the parameters describe the overall size basal and summit region area and widths height volume planar shape ellipticity and irregularity index of elevation contours profile shape height width ratios and slope of the edifice similar parameters for relatively large depending on dem spatial resolution summit craters calderas are also computed slope values and ellipticity and irregularity indexes are extracted for successive height intervals providing detailed information of volcano shape as a function of height the number of secondary peaks is also estimated the method is tested on thirteen composite volcanoes in nicaragua using three dem datasets 90 m srtm 30 m aster g dem and an 80 m topographic map derived dem and the resulting parameters are evaluated in terms of boundary delineation and dem source finally the parameters obtained for the nicaraguan volcanoes are discussed as an illustrative example of the type of data and information that can be extracted systematically for volcanoes worldwide

lava channel roofing overflows breaches and switching insights from the 2008 2009 eruption of mt etna during long lived basaltic eruptions overflows from lava channels and breaching of channel levees are important processes in the development of extensive a lava flow fields short lived breaches result in inundation of areas adjacent to the main channel however if a breach remains open lava supply to the original flow front is significantly reduced and flow field widening is favoured over lengthening the development of channel breaches and overflows can therefore exert strong control over the overall flow field development but the processes that determine their location and frequency are currently poorly understood during the final month of the 2008 2009 eruption of mt etna sicily a remote time lapse camera was deployed to monitor events in a proximal region of a small ephemeral lava flow for over a period of 10 h the flow underwent changes in surface elevation and velocity repeated overflows of varying vigour and the construction of a channel roof a required prelude to lava tube formation quantitative interpretation of the image sequence was facilitated by a 3d model of the scene constructed using structure from motion computer vision techniques as surface activity waned during the roofing process overflow sites retreated up the flow towards the vent and eventually a new flow was initiated our observations and measurements indicate that flow surface stagnation and flow inflation propagated up flow at an effective rate of 6 m h 1 and that these processes rather than effusion rate variations were ultimately responsible for the most vigorous overflow events we discuss evidence for similar controls during levee breaching and channel switching events on much larger flows on etna such as during the 2001 eruption

a primary analysis of microwave brightness temperature of lunar surface from chang e 1 multi channel radiometer observation and inversion of regolith layer thickness abstract in china s first lunar exploration project chang e 1 ce 1 a multi channel microwave radiometer was aboard the satellite with the purpose of measuring microwave brightness temperature tb from lunar surface and surveying the global distribution of lunar regolith layer thickness in this paper the primary 621 tracks of swath data measured by ce 1 microwave radiometer from november 2007 to february 2008 are collected and analyzed using the nearest neighbor interpolation to collect the tb data under the same sun illumination global distributions of microwave brightness temperature from lunar surface at lunar daytime and nighttime are constructed based on the three layer media modeling the top dust soil regolith and underlying rock media for microwave thermal emission of lunar surface the ce 1 measured tb and its dependence upon latitude frequency and feo tio2 content etc are discussed the ce 1 tb data at apollo landing sites are especially chosen for validation and calibration on the basis of available ground measurements using the empirical dependence of physical temperature upon the latitude verified by the ce 1 multi channel tb data at apollo landing sites the global distribution of regolith layer thickness is further inverted from the ce 1 brightness temperature data at 3 ghz channel those inversions at apollo landing sites and the characteristics of regolith layer thickness for lunar maria are well compared with the apollo in situ measurements and the regolith thickness derived from the earth based radar data finally the statistical distribution of regolith thickness is analyzed and discussed

rain waves and short term evolution of composite seacliffs in southern california abstract a four year time series of nine airborne lidar surveys were used to assess the roles of wave attack and rainfall on the erosion of 42 km of southern california seacliffs nine continuous seacliff sections separated by coastal lagoon mouths all show maximum seacliff erosion in the rainiest time period when wave energy was not particularly elevated and in most sections the squared correlations between rainfall and erosion time series exceeded 0 8 although rain and associated subaerial mechanisms such as groundwater seepage triggered most of the observed seacliff failures wave attack accelerated seacliff erosion with erosion rates of cliffs exposed to wave attack five times higher than at adjacent cliffs not exposed to waves the results demonstrate the importance of both waves and rain in the erosion of southern california seacliffs and suggest that the combined influences of marine and subaerial processes accelerate the erosion rate through positive feedbacks

rapid low cost photogrammetry to monitor volcanic eruptions an example from mount st helens washington usa we describe a low cost application of digital photogrammetry using commercially available photogrammetric software and oblique photographs taken with an off the shelf digital camera to create sequential digital elevation models dems of a lava dome that grew during the 2004 2008 eruption of mount st helens msh volcano renewed activity at msh provided an opportunity to devise and test this method because it could be validated against other observations of this well monitored volcano the datasets consist of oblique aerial photographs snapshots taken from a helicopter using a digital single lens reflex camera twelve sets of overlapping digital images of the dome taken during 2004 2007 were used to produce dems and to calculate lava dome volumes and extrusion rates analyses of the digital images were carried out using photogrammetric software to produce three dimensional coordinates of points identified in multiple photos the evolving morphology of the dome was modeled by comparing successive dems results were validated by comparison to volume measurements derived from traditional vertical photogrammetric surveys by the us geological survey cascades volcano observatory our technique was significantly less expensive and required less time than traditional vertical photogrammetric techniques yet it consistently yielded volume estimates within 5 of the traditional method this technique provides an inexpensive rapid assessment tool for tracking lava dome growth or other topographic changes at restless volcanoes

impact cratering in and around the orientale basin results from recent high resolution remote sensing datasets abstract impact craters are the predominant geological features on the lunar surface data about the craters are crucial for inferring information about surface age the generation processes of the geological units and the sequences of geological events the higher resolution remote sensing datasets collected by recent lunar missions enable the investigation of impact craters of smaller size and provide more accurate information this paper presents an investigation of the distribution and population characteristics of impact craters in and around the orientale basin based on high resolution datasets first an update to the crater catalogue for the orientale basin and its surrounding area is provided including craters as small as 1 km in diameter based on the updated crater catalogue the crater densities and depth to diameter ratios in and around the orientale basin are investigated the inclusion of small craters enables a crater density map with higher resolution revealing a significantly higher crater density of the study area also the surface age of orientale basin is estimated from the size frequency distribution sfd using the new crater catalogue showing an age of 3 75 ga using the production function of neukum et al 2001 which is in good agreement with previous studies finally distribution patterns of secondary craters around the orientale basin are investigated indicating the orientale basin may be caused by an oblique impact with a downrange direction of about 235 260 and an offset strength towards the direction of about 305 350

the mars regional atmospheric modeling system model description and selected simulations the mars regional atmospheric modeling system mrams is introduced and selected model results are presented and compared with landed meteorological data when possible mrams is descended from a nonhydrostatic earth mesoscale and cloud scale model that is widely used for forecasting weather and simulating atmospheric systems over complex terrain mesoscale models such as mrams are ideal tools for making use of the high resolution data sets arriving from mars global surveyor experiments simulation of the mars pathfinder mpf landing site at lsd 142 using 1 2 degree mars orbiter laser altimeter mola derived topography and thermal emission spectrometer thermal inertia is shown to be in good agreement with observed near surface temperature pressure and wind direction simulations of topographically induced thermal circulations and mountain induced gravity waves are shown to be consistent with theory and earlier studies that tie large amplitude mountain waves to strong winds capable of producing dust streaks and local dust lifting events a large eddy simulation of the convective boundary layer provides estimates of vertical profiles of heat flux momentum flux turbulent kinetic energy and vertical velocity variance the model results suggest that the martian atmosphere is roughly two to three times more turbulent than the terrestrial atmosphere during the afternoon but fluxes are roughly an order of magnitude smaller due to the lower density dust devillike circulations are also predicted in the large eddy simulation finally a simulation that examines atmosphere surface interactions near big crater is discussed predicted surface wind stress patterns are consistent with aeolian processes inferred through mars orbiter camera imagery of big crater located near the mpf landing site c 2001 academic press

a new global database of mars impact craters 1 km 2 global crater properties and regional variations of the simple to complex transition diameter 1 we have generated a new 384 343 entry global crater database of mars statistically complete for craters with diameters d 1 km in this release the database contains detailed morphologic and morphometric data for craters d 3 km future releases will extend these to smaller diameters with detailed topographic data for the largest crater database to date we analyzed crater depth to diameter ratios for simple and complex morphologies across various terrains and for the planet as a whole and investigated the simple to complex morphology transition our results are similar to those in the published literature but we found a substantial terrain dependence of the simple to complex transition that occurs at 11 km diameter craters at high latitudes this suggests a model that requires melting of volatiles during high latitude crater formation that fill the crater during the modification phase but will still support the simple morphology to larger diameters we also use this database to reexamine previously observed distributions and patterns to show its fidelity and to further explore other global relationships of fresh craters those with central peaks pits and summit pits we present the global distribution of craters with different types of ejecta and morphometric properties overall this database is shown to be comparable to previous databases where there is overlap and to be useful in extending prior work into new regimes

temporal patterns and processes of retreat of drumlin coastal cliffs strangford lough northern ireland abstract monthly measurements of erosion pins at sixteen sites around the very low energy marine environment of strangford lough northern ireland were used to investigate temporal patterns and processes of retreat of low cliffs of glacial material erosion rates were extremely varied the mean was 76 49 03 mm a 1 erosion is strongly seasonal with 86 6 of the total erosion occurring during winter september to march periods this seasonal pattern was most exaggerated in some of the more rapidly eroding sites on the exposed eastern side of the lough preparatory processes heavy rainfall desiccation and frost action reduce the compressive strength of the cliff materials and act as important forcing of the erodibility of the cliffs direct wave attack on cliffs around the lough takes place when threshold conditions of wind speed and tidal heights are met tidal levels 1 50 m above o d with wind speed of 15 4 m s 1 30 knots maintaining for more than 4 h during the study period eighteen events exceeding the above criteria were identified extremely low atmospheric pressure has also been identified as important in raising water levels slumps falls topples and slides were the forms of cliff failure observed

determination of mars crater geometric data insights from high resolution digital elevation models we review the methods and data sets used to determine morphometric parameters related to the depth e g rim height and cavity depth and diameter of martian craters over the past 45 yr and discuss the limitations of shadow length measurements photoclinometry earth based radar and laser altimetry we demonstrate that substantial errors are introduced into crater depth and diameter measurements that are inherent in the use of 128th degree gridded mars orbiter laser altimeter mola topography we also show that even the use of the raw mola precision engineering data record pedr data can introduce errors in the measurement of craters a few kilometers in diameter these errors are related to the longitudinal spacing of the mola profiles the along track spacing of the individual laser shots and the mola spot size stereophotogrammetry provides an intrinsically more accurate method for measuring depth and diameter of craters on mars when applied to high resolution image pairs here we use 20 stereo context camera ctx image pairs to create digital elevation models dems for 25 craters in the diameter range 1 5 25 6 km and cover the latitude range of 25 s to 42 n these dems have a spatial scale of 24 m per pixel six additional craters 1 5 3 1 km in diameter were studied using publically available dems produced from high resolution imaging science experiment hirise image pairs depth diameter and rim height were determined for each crater as well as the azimuthal variation of crater rim height in 1 degree increments these data indicate that morphologically fresh martian craters at these diameters are significantly deeper for a given size than previously reported using viking and mola data most likely due to the improvement in spatial resolution provided by the ctx and hirise data

on the depths and shapes of the freshest kilometer scale simple craters on the lunar maria a new crater shape model recent work on the shapes of small simple impact craters on the moon has shown that the parabolic ideal does not well represent the vast majority of these craters they are hyperbolic in shape and usually resemble a cone more than a parabola a parabolic shape also does not fit the most commonly held archetype for simple craters in general linne which is also hyperbolic in addition linne itself may not be the best model for fresh simple craters in terms of cross sectional shape although shape data to compare it to have heretofore been lacking here the free shadowfront method for determining the shapes of simple craters is used to measure 64 fresh simple craters on five lunar maria to test both assumptions laser altimetry cross sections available for many of the craters measured herein are used to complement and spot check the shadow measurement results and thereby demonstrate the efficacy of the free shadowfront method a new shape model is established and two craters that better fit this model than linne are identified these are located at 24 45 n 328 12 e and 31 35 n 296 46 e and have diameters of 1 40 and 2 73 km respectively an apparent dichotomy between fresh simple craters smaller than 2 5 km and those larger than this is observed flat floors are found to be ubiquitous among the larger craters but rare and small in extent in smaller ones a slide in one crater which appears to be an incipient flat floor suggests a major mode of formation for these flat floors

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

relative depths of simple craters and the nature of the lunar regolith abstract we assessed the morphologies of more than 930 simple impact craters diameters 40 m 10 km on the moon using digital terrain models dtms of a variety of terrains in order to characterize the variability of fresh crater morphology as a function of crater diameter from lunar reconnaissance orbiter camera lroc narrow angle camera nac dtms we determined depth to diameter d d ratios for an extremely fresh set of these craters with diameters less than 400 m and found that their d d ratios range from 0 11 to 0 17 using both nac and kaguya terrain camera dtms we also determined the d d ratios for the set of fresh simple craters larger than 400 m in diameter the d d ratios of these larger craters are typically near 0 21 as expected of gravity dominated crater excavation fresh craters less than 400 m in diameter on the other hand exhibit significantly lower d d ratios various possible factors affect the morphologies and relative depths d d ratios of small strength dominated craters including impactor and target properties e g effective strength strength contrasts porosity pre existing weaknesses impact angle and velocity and degradation state while impact conditions resulting from secondary impacts can also affect crater morphologies we found that d d ratio alone was not a unique discriminator of small secondary craters to investigate the relative influences of degradation and target properties on the d d ratios of small strength dominated craters we examined a subset of fresh craters located on the geologically young rim deposits of tycho crater these craters are deeper and steeper than other craters of similar diameter and degradation state consistent with their relative freshness and formation in the relatively coherent melt rich deposits in this region the d d ratios of globally distributed small craters of similar degradation state and size range on the other hand are relatively shallow with lower average wall slopes consistent with crater excavation in a weak or poorly cohesive layer the widespread predominance of these small shallow craters is consistent with the pervasive poorly cohesive upper regolith

detecting the development of active lava flow fields with a very long range terrestrial laser scanner and thermal imagery regular topographic surveys of active lava flows could provide significant insight into the development of flow fields but data of sufficient accuracy spatial extent and repeat frequency to quantify the processes involved have yet to be acquired here we report results from the use of a new very long range terrestrial laser scanner tls on active lavas at mount etna sicily the scanner proved capable of providing useful topographic data from volcanic terrain at ranges up to 3500 m with laser returns from ash covered slopes as well as from lava despite very low effusion rates 1 m3s 1 topographic changes associated with the emplacement and inflation of new flows and the inflation of a tumulus were detected irregular data spacing resulting from oblique views makes the interpretation of laser derived digital elevation models alone difficult but fusing topographic data with thermal images allows active flow features to be clearly visualized

the variability of crater identification among expert and community crater analysts abstract the identification of impact craters on planetary surfaces provides important information about their geological history most studies have relied on individual analysts who map and identify craters and interpret crater statistics however little work has been done to determine how the counts vary as a function of technique terrain or between researchers furthermore several novel internet based projects ask volunteers with little to no training to identify craters and it was unclear how their results compare against the typical professional researcher to better understand the variation among experts and to compare with volunteers eight professional researchers have identified impact features in two separate regions of the moon small craters diameters ranging from 10 m to 500 m were measured on a lunar mare region and larger craters 100s m to a few km in diameter were measured on both lunar highlands and maria volunteer data were collected for the small craters on the mare our comparison shows that the level of agreement among experts depends on crater diameter number of craters per diameter bin and terrain type with differences of up to 45 we also found artifacts near the minimum crater diameter that was studied these results indicate that caution must be used in most cases when interpreting small variations in crater size frequency distributions and for craters 10 pixels across because of the natural variability found projects that emphasize many people identifying craters on the same area and using a consensus result are likely to yield the most consistent and robust information

straightforward reconstruction of 3d surfaces and topography with a camera accuracy and geoscience application topographic measurements for detailed studies of processes such as erosion or mass movement are usually acquired by expensive laser scanners or rigorous photogrammetry here we test and use an alternative technique based on freely available computer vision software which allows general geoscientists to easily create accurate 3d models from field photographs taken with a consumer grade camera the approach integrates structure from motion sfm and multi view stereo mvs algorithms and in contrast to traditional photogrammetry techniques it requires little expertise and few control measurements and processing is automated to assess the precision of the results we compare sfm mvs models spanning spatial scales of centimeters a hand sample to kilometers the summit craters of piton de la fournaise volcano with data acquired from laser scanning and formal close range photogrammetry the relative precision ratio achieved by sfm mvs measurement precision observation distance is limited by the straightforward camera calibration model used in the software but generally exceeds 1 1000 i e centimeter level precision over measurement distances of 10s of meters we apply sfm mvs at an intermediate scale to determine erosion rates along a 50 m long coastal cliff seven surveys carried out over a year indicate an average retreat rate of 0 70 0 05 m a 1 sequential erosion maps at 0 05 m grid resolution highlight the spatio temporal variability in the retreat with semivariogram analysis indicating a correlation between volume loss and length scale compared with a laser scanner survey of the same site sfm mvs produced comparable data and reduced data collection time by 80

the morphology of small fresh craters on mars and the moon the depth diameter ratio for new meter to decameter scale martian craters formed in the last 20 years averages 0 23 only slightly deeper than that expected for simple primary craters on rocky surfaces large variations in depth diameter d d between impact sites indicate that differences between the sites such as target material properties impact velocity angle and physical state of the bolide s are important in determining the depth of small craters in the strength regime on the moon the d d of random fresh small craters with similar diameters averages only 0 10 indicating that either the majority of them are unrecognized secondaries or some proportion are degraded primaries older craters such as these may be shallower due to erosional infilling which is probably not linear over time but more effective over recently disturbed and steeper surfaces processes that are not yet acting on the new martian craters brand new meter to decameter scale craters such as the martian ones studied here are statistically easily distinguishable as primaries but the origins of older craters of the same size such as the lunar ones in this study are ambiguous

a catalogue of impact craters larger than 200 m and surface age analysis in the chang e 5 landing area abstract chang e 5 ce 5 is the first sample return mission of china s lunar exploration and will be launched in 2020 the planned landing area is near mons rumker in oceanus procellarum it is important to have a detailed geological analysis of the landing area prior to the lunar sample collection the crater size frequency distribution curve combined with radioisotope dating of components of the returned sample by ce 5 may allow a refinement of the lunar chronology function based on a digital orthophoto map with a pixel size of 1 5 m generated from more than 700 lunar reconnaissance orbiter camera narrow angle camera images of the ce 5 landing area all impact craters larger than 200 m in diameter were extracted using the resultant crater catalogue of 32 277 craters a systematic analysis of the landing area including the crater distribution morphology characteristics and geologic model ages is conducted the results show that craters smaller than 1 000 m are denser in the east and the west parts of the region while those larger than 1 000 m tend to be more concentrated in the central part particularly within the range of 61 5 w 64 5 w within nine geologic units divided using the spectral characteristics the geologic unit of em1 eratosthenian aged mare em near the mons rumker is the youngest with a model age of 2 02 0 16 0 16 ga the three rumker plateau ir units are the oldest parts of the landing area with the largest model age of 3 49 0 12 0 073 ga the crater catalogue and the surface model age analysis results can contribute to the ce 5 mission as well as further scientific research

large eddy simulation of the convective atmospheric boundary layer abstract large eddy simulations of a free convective atmospheric boundary layer with an overlying capping inversion are considered attention is given to the dependence of the results upon the various factors influencing the simulation the subgrid model the domain size and the mesh resolution by providing artificial constraints upon the convection the results also provide extra insight into the underlying dynamics the gross features of the boundary layer such as the overall energy budget are not sensitive to the details of the simulations but a number of important factors are revealed it has been found that near the surface the subgrid diffusivity must be larger than is usually supposed in order for the vertical velocity skewness to have the correct sign this region of the flow has a significant subgrid scale heat flux and it seems that the subgrid model requires improvement in such cases a revised model which under statically unstable conditions allows the mixing length of the subgrid scale tu

crater formation and modification on the icy satellites of uranus and saturn depth diameter and central peak occurrence depth diameters d d for fresh craters on the intermediate sized icy satellites of uranus and saturn have been determined using photoclinometry and shadow lengths and are compared with similar measurements on the terrestrial planets simple bowl shaped craters on icy satellites including those on miranda for which the highest resolution data are available are systematically 20 40 shallower than on the terrestrial planets this pronounced difference between crater depths on icy and rocky surfaces indicates that differences in impact velocity or surface gravity are not as important as the differences in mechanical properties between ice and rock in controlling simple crater morphology experimental impact studies indicate that differences in material properties such as angle of internal friction can control crater depth alternatively breccia lenses may be thicker in icy satellite simple craters complex craters on the icy satellites become significantly deeper with increasing crater diameters unlike complex craters on terrestrial planets which are nearly constant in depth central peaks and hence floor rebound are also volumetrically and morphologically more prominent than wall slumping rim collapse on the icy satellites the magnitude of viscous relaxation of very large craters e g herschel and odysseus on the icy satellites can be estimated from extrapolation of the d d fits at smaller crater diameters the transition diameter from simple to complex morphology is inversely correlated with gravity as it is on the terrestrial planets but at significantly smaller diameters than would be expected from a simple extrapolation of the terrestrial trend thus crater modification especially floor rebound is easier to initiate on icy satellites estimated effective cohesions for shocked icy material are lower by a factor of 10 20 relative to rock although estimated effective viscosities are similar the distinct systematic differences between crater morphology on icy and rocky worlds indicate that gross material property differences between rock and ices play a key role in crater formation and modification but gravity is still the primary driving force

image based measurement of flux variation in distal regions of active lava flows 1 understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes here we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active a flows in order to investigate distal flow processes at mount etna sicily photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow fronts velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava significant variations of the magma flux were observed and pulses of increased flux arrived within the flow front region on timescales of several hours the pulses are believed to be the distal result of more frequent flux changes observed in the vent region hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short period variations in effusion rate in considering advance processes for the individual flow fronts it must be assumed that they were fed by a highly unsteady flux which was volumetrically at least an order of magnitude lower than that observed near the vent