vertical sheets of dense plasma in the topside martian ionosphere 1 the low frequency radar mars advanced radar for subsurface and ionosphere sounding marsis on board the mars express spacecraft is used to sound electron densities in the topside martian ionosphere the radar records the delay times to echoes of reflected radio waves as a function of frequency yielding spectrograms with traces of radar echoes at times two traces are present in spectrograms of the martian ionosphere one of these traces corresponds to reflections from the direction to nadir the other trace originates in a localized reflector in the ionosphere the local reflectors can be associated with the cusplike regions of near vertical crustal magnetic fields the apparent nadir angle of reflection can occasionally increase to 90 this suggests that steep gradients of the altitude of the electron isodensity exist in the martian ionosphere and indicates rapid horizontal spatial variations of vertical diffusion of martian plasma such gradients may arise owing to preferential access of solar wind to the cusplike regions or to precipitation of energetic electrons from acceleration regions located on cusp magnetic field lines high above the ionosphere

automated detection of unstable glacier flow and a spectrum of speedup behavior in the alaska range surge type glaciers are loosely defined as glaciers that experience periodic alterations between slow and fast flow regimes glaciers from a variety of mountain ranges around the world have been classified as surge type yet consensus of what defines a glacier as surge type has not always been met a common source of dispute is the lack of a succinct and globally applicable delimiter between a surging and nonsurging glacier the attempt is often a boolean classification however glacier speedup events can vary significantly with respect to event magnitude duration and the fraction of the glacier that participates in the speedup for this study we first updated the inventory of glaciers that show flow instabilities in the alaska range and then quantified the spectrum of speedup behavior we developed a new method that automatically detects glaciers with flow instabilities our automated results show a 91 success rate when compared to direct observations of speedup events and glaciers that are suspected to display unstable flow based on surface features through a combination of observations from the landsat archive and previously published data our inventory now contains 36 glaciers that encompass at least one branch exhibiting unstable flow and we document 53 speedup events that occurred between 1936 and 2014 we then present a universal method for comparing glacier speedup events based on a normalized event magnitude metric this method provides a consistent way to include and quantify the full spectrum of speedup events and allows for comparisons with glaciers that exhibit clear surge characteristics yet have no observed surge event to date our results show a continuous spectrum of speedup magnitudes from steady flow to clearly surge type which suggests that qualitative classifications such as surge type or pulse type behavior might be too simplistic and should be accompanied by a standardized magnitude metric

greenland flow variability from ice sheet wide velocity mapping using radarsat synthetic aperture radar data we have mapped the flow velocity over much of the greenland ice sheet for the winters of 2000 01 and 2005 06 these maps provide a detailed view of the ice sheet flow including that of the hundreds of glaciers draining the interior the focused patterns of flow at the coast suggest a strong influence of bedrock topography differences between our two maps confirm numerous early observations of accelerated outlet glacier flow as well as revealing previously unrecognized changes the overall pattern is one of speed up accompanied by terminus retreat but there are also several instances of surge behavior and a few cases of glacier slowdown comprehensive mappings such as these at regular intervals provide an important new observational capability for understanding ice sheet variability

submarine landforms characteristic of glacier surges in two spitsbergen fjords abstract well preserved submarine landforms all less than 100 years old are imaged on high resolution swath bathymetry obtained from van keulenfjorden and rindersbukta inner van mijenfjorden spitsbergen svalbard several tidewater glaciers in these fjords have surged in the last few hundred years streamlined landforms found within the limits of known surges are interpreted as mega scale glacial lineations msgl formed subglacially beneath actively surging ice large transverse ridges are terminal moraines formed by thrusting at the maximum position of glacier surges sediment lobes at the distal margins of terminal moraines are interpreted as glacigenic debris flows formed either by failure of the frontal slopes of thrust moraines or from deforming sediment extruded from beneath the glacier sinuous ridges are eskers formed after surge termination by the sedimentary infilling of subglacial conduits concordant ridges parallel to former ice margins are interpreted as minor push moraines probably formed annually during winter glacier readvance discordant ridges oblique to former ice margins are interpreted as crevasse squeeze ridges forming when soft subglacial sediments are injected into basal crevasses these submarine landforms have been deposited in the following sequence based on cross cutting relationships between them linked to stages of the surge cycle 1 msgl 2a terminal moraines and 2b lobe shaped debris flows 3 isolated areas of crevasse fill ridges 4 eskers and 5 annual retreat ridges a descriptive landsystem model for tidewater surge type glaciers has been developed whose wider applicability is emphasised by comparison with two areas in isfjorden spitsbergen the model also has a number of features in common with landsystem models for terrestrial surge type glaciers but is likely to be more complete since submarine landforms are particularly well preserved the landforms discussed here may be produced and preserved in different proportions in the varied environmental settings where surging glaciers are found

marsis remote sounding of localized density structures in the dayside martian ionosphere a study of controlling parameters enhanced topside electron densities in the dayside martian ionosphere have been repetitively observed in areas of near radial crustal magnetic fields for periods of tens of days indicating their long term spatial and temporal stability despite changing solar wind conditions we perform a statistical study of these density structures using the ionospheric mode of the mars advanced radar for subsurface and ionosphere sounding marsis onboard mars express we estimate the apparent extents of these structures relative to the altitude of the surrounding ionosphere the apex of the density structures often lies higher than the surrounding ionosphere median vertical extent of 18 km which indicates upwellings these structures are much wider than they are high with latitudinal scales of several degrees the radar reflector regions are observed above both moderate and strong magnetic anomalies and their precise locations and latitudinal extents match quite well with the locations and latitudinal extents of magnetic structures of given magnetic polarity oblique to vertical fields which happen to be regions where the field lines are open part of the time the majority of the density structures occur in regions where ionospheric plasma is dominant indicating closed field regions shielded from shocked solar wind plasma

climatic and geometric controls on the global distribution of surge type glaciers implications for a unifying model of surging financial support was provided by the conocophillips lundin northern area program project crios

oblique reflections in the mars express marsis data set stable density structures in the martian ionosphere the mars advanced radar for subsurface and ionospheric sounding marsis onboard the european space agency s mars express mex spacecraft routinely detects evidence of localized plasma density structures in the martian dayside ionosphere such structures likely taking the form of spatially extended elevations in the plasma density at a given altitude give rise to oblique reflections in the active ionospheric sounder data these structures are likely related to the highly varied martian crustal magnetic field in this study we use the polar orbit of mex to investigate the repeatability of the ionospheric structures producing these anomalous reflections examining data taken in sequences of multiple orbits which pass over the same regions of the martian surface under similar solar illuminations within intervals lasting tens of days presenting three such examples or case studies we show for the first time that these oblique reflections are often incredibly stable indicating that the underlying ionospheric structures are reliably reformed in the same locations and with qualitatively similar parameters the visibility or lack thereof of a given oblique reflection on a single orbit can generally be attributed to variations in the crustal field within the ionosphere along the spacecraft trajectory we show that within these examples oblique reflections are generally detected whenever the spacecraft passes over regions of intense near radial crustal magnetic fields i e with a cusp like configuration the apparent stability of these structures is an important feature that must be accounted for in models of their origin

evidence for an acidic ocean on mars from phosphorus geochemistry of martian soils and rocks recent analyses of elemental concentrations and mineralogy of iron bearing compounds of martian soils and rocks by the mars exploration rovers at meridiani planum and gusev crater demonstrate that phosphorus concentration is correlated with sulfur and chlorine the positive correlation of these three elements with each other in soils at both sites argues for a globally homogeneous soil component sulfur and possibly chlorine in martian soils and meridiani planum outcrop rocks is likely derived from volcanic exhalations but phosphorus must be derived from the weathering of igneous rocks here we show that the similar concentration of phosphorus in soils at the two mars exploration rover sites coupled with positive correlations to chlorine and sulfur is best explained as resulting from mixing and homogenization of phosphate sulfate and chloride in a large acidic aqueous reservoir such as an acidic ocean acidic thin film or acid fog weathering cannot readily produce the similar p s and p cl ratios of soils measured on mars and more important cannot explain the high phosphorus content of ancient ca 3 4 ga sulfate rich rocks in outcrop at meridiani the existence of a global acidic hydrosphere or ocean at some time in early martian history can also explain the lack of extensive carbonate deposits on the martian surface

the duration of the active phase on surge type glaciers contrasts between svalbard and other regions many glaciers in svalbard and in other glacierized areas of the world are known to surge however the time series of observations required to assess the duration of fast motion is very restricted data on active phase duration in svalbard come from aerial photographs satellite imagery field surveys and airborne reconnaissance evidence on surge duration is available for eight svalbard ice masses varying from 3 to 1250 km 2 worldwide active phase duration is recorded for less than 50 glaciers few observations are available on high polar ice masses the duration of the active phase is significantly longer for svalbard glaciers than for surge type glaciers in other areas from which data are available in svalbard the active phase may last from 3 to 10 years by contrast a surge duration of 1 2 years is more typical of ice masses in northwest north america iceland and the pamirs ice velocities during the protracted active phase on svalbard glaciers are considerably lower than those for many surge type glaciers in these other regions mass is transferred down glacier more slowly but over a considerably longer period svalbard surge type glaciers do not exhibit the very abrupt termination of the active phase over periods of a few days observed for several alaskan glaciers the duration of the active phase in svalbard is not dependent on parameters related to glacier size the quiescent phase is also relatively long 50 500 years for svalbard ice masses detailed field monitoring of changing basal conditions through the surge cycle is required from surge type glaciers in svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago which may also typify other high polar ice masses the finding that surge behaviour in the form of active phase duration shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges

21st century evolution of greenland outlet glacier velocities earlier observations on several of greenland s outlet glaciers starting near the turn of the 21st century indicated rapid annual scale and large 100 increases in glacier velocity combining data from several satellites we produce a decade long 2000 to 2010 record documenting the ongoing velocity evolution of nearly all 200 of greenland s major outlet glaciers revealing complex spatial and temporal patterns changes on fast flow marine terminating glaciers contrast with steady velocities on ice shelf terminating glaciers and slow speeds on land terminating glaciers regionally glaciers in the northwest accelerated steadily with more variability in the southeast and relatively steady flow elsewhere intraregional variability shows a complex response to regional and local forcing observed acceleration indicates that sea level rise from greenland may fall well below proposed upper bounds

the influence of climate during and after a glacial surge a comparison of the last two surges of fridtjovbreen svalbard abstract glacial surges are periods of fast flow often limited in space and time and driven by internal conditions which are not fully explained the quantity and variety of documented case studies and settings demonstrate that the critical variables are difficult to isolate in an alternative approach two surges from the same basin were compared at fridtjovhamna one of the few known sites where this is possible fridtjovbreen is a polythermal glacier that has been through two recent surges the last event 1991 2002 occurred during an unusually warm period in the high arctic whereas the previous surge culminated in 1861 around the little ice age when many svalbard glaciers had their maximum holocene extent based on a multi disciplinary study processes and landforms from the two episodes were compared with respect to ice front movement rates formation and decay of ice cored moraines and glacial meltwater drainage patterns the study demonstrates that moraines and meltwater traces from the oldest surge locally well preserved provide excellent opportunities for reconstructing the behavior of the ice mass the last surge however took place during a period with ablation rates never seen at this latitude and 10 years after the maximum extent the deglaciated areas onshore hardly show traces from the event

shapes of magnetically controlled electron density structures in the dayside martian ionosphere nonhorizontal localized electron density structures associated with regions of near radial crustal magnetic fields are routinely detected via radar oblique echoes on the dayside of mars with the ionospheric sounding mode of the mars advanced radar for subsurface and ionospheric sounding marsis radar onboard mars express previous studies mostly investigated these structures at a fixed plasma frequency and assumed that the larger apparent altitude of the structures compared to the normal surrounding ionosphere implied that they are bulges however the signal is subjected to dispersion when it propagates through the plasma so interpretations based on the apparent altitude should be treated with caution we go further by investigating the frequency dependence i e the altitude dependence of the shape of 48 density structure events using time series of marsis electron density profiles corrected for signal dispersion four possible simplest shapes are detected in these time series which can give oblique echoes bulges dips downhill slopes and uphill slopes the altitude differences between the density structures and their edges are in absolute value larger at low frequency high altitude than at high frequency low altitude going from a few tens of kilometers to a few kilometers as frequency increases bulges dominate in numbers in most of the frequency range finally the geographical extension of the density structures covers a wide range of crustal magnetic fields orientations with near vertical fields toward their center and near horizontal fields toward their edges as expected transport processes are suggested to be a key driver for these density structures

arsenic in volcanic gases total arsenic contents were determined in volcanic gases by analysis of fumarolic condensates collected in the period 1984 1992 from different volcanoes around the world arsenic concentrations range from 0 006 to 30 g g the highest values 1 2 30 g g were found at vulcano aeolian islands southern italy the analytical data show that volcanic gases have a large variability of arsenic contents possibly related to both the different physicochemical features of magma source and rock properties within the volcanic system

glacier surge propagation by thermal evolution at the bed bakaninbreen southern svalbard began a prolonged surge during 1985 in 1986 an internal reflecting horizon on radio echo sounding data was interpreted to show that the position of the surge front coincided with a transition between areas of warm unfrozen and cold frozen bed ground penetrating radar lines run in 1996 and 1998 during early quiescence show that the basal region of the glacier is characterized by a strong reflection interpreted as the top of a thick layer of sediment rich basal ice down glacier of the present surge front features imaged beneath the basal reflection are interpreted as the bottom of the basal ice layer the base of a permafrost layer and local ice lenses this indicates that this region of the bed is cold up glacier of the surge front a scattering zone above the basal reflection is interpreted as warm ice there is no evidence for this warm zone down glacier of the surge front nor do we see basal permafrost up glacier of it thus as in early surge phase the location of the surge front is now at the transition between warm and cold ice at the glacier bed we suggest that the propagation of the front is associated with this basal thermal transition throughout the surge because propagation of the front occurs rapidly and generates only limited heat basal motion during fast flow must have been restricted to a thin layer at the bed and occurred by sliding or deformation localized at the ice bed interface

effects of magnetic anomalies discovered at mars on the structure of the martian ionosphere and solar wind interaction as follows from radio occultation experiments the slopes of the electron density profiles obtained by radio occultation experiments at mars revealed different variations with solar zenith angle in comparison with behavior of the electron density profiles in the magnetic field free ionosphere of venus the results obtained by the mars global surveyor mgs spacecraft show the existence of highly variable and very localized magnetic fields of crustal origin at mars addressing the difference between the ionosphere at venus and mars the scale heights of electron density profiles obtained by radio occultation methods onboard mariner 9 and viking 1 are analyzed at altitudes higher than the topside boundary of the photoequlibrium region in the magnetic field free ionosphere the local increase of the mean scale height in the altitude region 180 250 km is assumed to be either an effect of a nonhorizontal magnetic field associated with the magnetic anomalies or diffusive equilibrium in the magnetic field free ionosphere the areas where the scale height of electron density profile is increased in comparison with average one have been selected the angle between the magnetic field measured by mgs mag er at altitudes 120 250 km and local zenith direction is investigated throughout these selected areas

correlations of suspended sediment size with bedrock lithology and glacier dynamics the hypothesized link between glacier surging and bedrock geology motivates this study of the suspended sediment size distributions sssd from surge type and non surge type glaciers we analyze sssds from proglacial streams in 20 individual basins comprising various fractions of metasedimentary ms and felsic plutonic rocks we compare the size distributions by performing tests of significance on the distribution statistics and a principal component analysis on discrete grain sizes we find that surge type and non surge type glaciers underlain solely by ms rocks have significantly different sssds while surge type glaciers as a whole have remarkably similar sssds regardless of the underlying bedrock geology these observations hint at a relationship between sediment characteristics and glacier surging though causation in either direction cannot be established without additional data

hagen brae a surging glacier in north greenland 35 years of observations we use remotely sensed ice velocities in combination with observations of surface elevation and glacier area change to investigate the dynamics of hagen brae north greenland in high detail over the last 35 years from our data we can establish for the first time that hagen brae is a surge type glacier with characteristics of both alaskan and svalbard type surging glaciers we argue that the observed surge was preconditioned by the glacier geometry and triggered by englacially stored meltwater at present the glacier is in a transitional state between active and quiescence phases and is not building up to its pre surge geometry we suggest that the glacier is adjusting to the loss of its floating section general thinning and changes in fjord conditions that occurred over the study period which are unrelated to the surge behavior the high temporal resolution of the ice velocity data gives insight to the sub annual glacier flow

geometric evolution of the horcones inferior glacier mount aconcagua central andes during the 2002 2006 surge the central andes of chile and argentina 31 35 s contain a large number and variety of ice masses but only two surging glaciers have been studied in this region we analyzed the 2002 2006 surge of the horcones inferior glacier mount aconcagua argentina based on medium spatial resolution 15 30 m satellite images and digital elevation models during the buildup phase the glacier was stagnant with velocities lower than 0 1 m d in the active phase velocities reached 14 m d and the glacier front advanced 3 1 km at the peak of the active phase 2003 2004 the area averaged elevation change was 42 m in the reservoir zone 2 53 km2 and 30 m in the receiving zone 3 31 km2 the estimated ice flux through a cross section located at 4175 meter above sea level was 108 m3 during a period of 391 days a flux that suggests a mean glacier thickness at this location of 90 m the depletion phase showed a recovery of the reservoir zone elevation the down wasting of the receiving zone 17 m 2007 2014 and a return to quiescent velocities the short active phase the abrupt change in the velocities and the high level of the proglacial stream indicate a hydrological switch alaska type trigger the 2002 2006 and 1984 1990 surges of horcones inferior were synchronous with the surges of nearby grande del nevado glacier these events occurred after periods of positive mass balance so we hypothesize a climate driver

ionospheric characteristics above martian crustal magnetic anomalies 1 we studied several thousand electron density profiles from the mars global surveyor radio science experiment electron densities in some of these profiles change significantly over vertical distances as short as 1 2 km often causing localized bite outs these anomalous profiles are preferentially located above crustal magnetic anomalies anomalous features and their association with strong magnetic fields are also seen in profiles from mariner 9 the probability of a profile being anomalous depends on the orientation of the magnetic field suggesting localized electrodynamic effects upon otherwise global photochemical ionospheric processes on mars unlike most other planets the magnetic field has a short characteristic lengthscale so its effects on the ionosphere will vary over short horizontal distances we discuss possible ionospheric dynamo processes and encourage additional ionospheric observations over regions of strong crustal magnetic field

improved general circulation models of the martian atmosphere from the surface to above 80 km we describe a set of two new generation general circulation models of the martian atmosphere derived from the models we originally developed in the early 1990s the two new models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations the vertical resolution near the surface has been refined and the vertical domain has been extended to above 80 km these changes are accompanied by the inclusion of state of the art parameterizations to better simulate the dynamical and physical processes near the surface boundary layer scheme subgrid scale topography parameterization etc and at high altitude gravity wave drag in addition radiative transfer calculations and the representation of polar processes have been significantly improved we present some examples of zonal mean fields from simulations using the model at several seasons one relatively novel aspect previously introduced by wilson 1997 is that around northern winter solstice the strong pole to pole diabatic forcing creates a quasi global angular momentum conserving hadley cell which has no terrestrial equivalent within such a cell the coriolis forces accelerate the winter meridional flow toward the pole and induce a strong warming of the middle polar atmosphere down to 25 km this winter polar warming had been observed but not properly modeled until recently in fact thermal inversions are generally predicted above one and often both poles around 60 70 km however the mars middle atmosphere above 40 km is found to be very model sensitive and thus difficult to simulate accurately in the absence of observations

volatilization transport and sublimation of metallic and non metallic elements in high temperature gases at merapi volcano indonesia abstract condensates silica tube sublimates and incrustations were sampled from 500 800 c fumaroles and lava samples were collected at merapi volcano indonesia in jan feb 1984 with respect to the magma merapi gases are enriched by factors greater than 105 in se re bi and cd 104 105 in au br in pb and w 103 104 in mo cl cs s sn and ag 102 103 in as zn f and rb and 1 102 in cu k na sb ni ga v fe mn and li the fumaroles are transporting more than 106 grams day g d of s cl and f 104 106 g d of al br zn fe k and mg 103 104 g d of pb as mo mn v w and sr and less than 103 g d of ni cu cr ga sb bi cd li co and u with decreasing temperature 800 500 c there were five sublimate zones found in silica tubes 1 cristobalite and magnetite first deposition of si fe and al 2 k ca sulfate acmite halite sylvite and pyrite maximum deposition of cl na k si s fe mo br al rb cs mn w p ca re ag au and co 3 aphthitalite k na sulfate sphalerite galena and cs k sulfate maximum deposition of zn bi cd se and in higher deposition of pb and sn 4 pb k chloride and na k fe sulfate maximum deposition of pb sn and cu and 5 zn cu and k pb sulfates maximum deposition of pb sn ti as and sb the incrustations surrounding the fumaroles are also chemically zoned bi cd pb w mo zn cu k na v fe and mn are concentrated most in or very close to the vent as expected with cooling atmospheric contamination and dispersion the highly volatile elements br cl as and sb are transported primarily away from high temperature vents ba si p al ca and cr are derived from wall rock reactions incomplete degassing of shallow magma at 915 c is the origin of most of the elements in the merapi volcanic gas although it is partly contaminated by particles or wall rock reactions the metals are transported predominantly as chloride species as the gas cools in the fumarolic environment it becomes saturated with sublimate phases that fractionate from the gas in the order of their equilibrium saturation temperatures devolatilization of a cooling batholith could transport enough acids and metals to a hydrothermal system to play a significant role in forming an ore deposit however sublimation from a high temperature high velocity carrier gas is not efficient enough to form a large ore deposit re se cd and bi could be used as supporting evidence for magmatic fluid transport in an ore deposit

crystallization of apatite in natural magmas under high pressure hydrous conditions with particular reference to orogenic rock series two separate series of hydrous experiments involving 1 imposing apatite saturation on a series of igneous rock compositions from basanite to rhyolite and 2 crystallizing similar natural rock compositions progressively until apatite appears demonstrate a close dependence between apatite saturation and silica content of the magma and determine p2o5 levels at a given silica value and temperature at which that composition may be expected to crystallize apatite the effect of pressure on apatite solubility is not great and is most significant for silicic compositions

multi model photogrammetric analysis of the 1990s surge of sortebrae east greenland sortebrae is a surge type tidewater glacier complex draining southeastward from the geikie plateau east greenland sortebrae s main flow unit surged around 1950 and again between 1992 and 1995 the 1990s surge affected the lower 50 km of sorte brae over an area of approximately 335 km2 over a period of 5 km surge velocities in the order of kilometres per annum are about 100 fold the quiescent velocities multi model photogrammetric analysis shows a thinning of the reservoir zone of up to 219 m and thickening of the receiving zone of up to 74 m the surge transported approximately 18 6 km 3 of ice down glacier the total calving volume as a result of the surge amounted to 11 7 km 3 equivalent to a calving flux of 3 9 7 3 km a 1 the surge characteristics and environmental setting suggest that the surge mechanism involves a switch in the subglacial drainage this surge of sortebrae is more similar to the fast short alaskan type surges than to the sluggish long svalbard type surges

a case study of a density structure over a vertical magnetic field region in the martian ionosphere one of the discoveries made by the radar sounder on the mars express spacecraft is the existence of magnetically controlled structures in the ionosphere of mars which result in bulges in the ionospheric electron density contours these bulges lead in turn to oblique echoes which show up as hyperbola shaped features in the echograms a hyperbola shaped feature observed over an isolated region of strong crustal magnetic field is associated with a plasma cavity in the upper ionosphere and a corresponding density enhancement in the lower levels of the ionosphere we suggest that along open magnetic field lines the solar wind electrons are accelerated downward and the ionospheric ions are accelerated upward in a manner similar to the field line driven auroral acceleration at earth this heating due to precipitating electrons may cause an increase in the scale height and may drive a loss of ionospheric plasma at high altitudes

partition of arsenic and phosphorus between volcanic gases and rock part i analytical data and magmatic conditions of mt usu japan abstract in order to understand the behavior of arsenic and phosphorus in volcanic environments ejecta and volcanic gases collected at mt usu were analyzed and the differentiation of the two elements was investigated results of analyses show that phosphorus is depleted in the gas phase while it is abundant in the rock on the other hand arsenic is found to have a high volatility comparable to that of a major component of active volcanic gases like chloride the apparent partition coefficient as p gas as p rock is calculated to be in the range from 104 to 105 in order to examine the existing state of p and as in magmatic gases the fugacity ratios among chemical species of p and those of as are calculated it is suggested that p exists overwhelmingly as po2 while as exists as as4 under the usu magmatic conditions temp 1200 k fh2o 400 atm fo2 400 atm etc on the assumption that fpo2 is controlled by the equilibrium with the mineral assemblage ca3 po4 2 sio2 casio3 in orthopyroxene the calculated p content is 106 times less than that measured in the condensates several possible causes of this discrepancy are discussed the discrepancy may be due to 1 the admission of phosphorus from wall rock through interaction of ascending volcanic gases with wall rock if apatite is present in the magma and 2 the formation of po2 exclusively from po43 ion in the magma with the absence of apatite though thermodynamic estimation of fpo2 is not possible an absolute value of fas4 cannot yet be obtained because of the lack of thermodynamic data of arsenic bearing minerals the difference in the behavior of arsenic and phosphorus in volcanic environments seems to be closely related with the redox properties of the two elements

radar soundings of the ionosphere of mars we report the first radar soundings of the ionosphere of mars with the marsis mars advanced radar for subsurface and ionosphere sounding instrument on board the orbiting mars express spacecraft several types of ionospheric echoes are observed ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes the oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of mars echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength

high geothermal heat flow basal melt and the origin of rapid ice flow in central greenland age depth relations from internal layering reveal a large region of rapid basal melting in greenland melt is localized at the onset of rapid ice flow in the large ice stream that drains north off the summit dome and other areas in the northeast quadrant of the ice sheet locally high melt rates indicate geothermal fluxes 15 to 30 times continental background the southern limit of melt coincides with magnetic anomalies and topography that suggest a volcanic origin

characteristics of surge type glaciers glaciers can be divided into two classes according to their flow behavior normal relatively steady annually averaged flow rate and surge type pronounced cyclic flow variations having a typical periodicity of 10 100 years we have examined the population statistics of 2356 glaciers in the st elias mountains yukon territory canada and estimate that 151 6 4 of these glaciers are surge type to explore how various glacier attributes are associated with surging we compare the probability of surging associated with various subsets of the complete population to appropriate reference values in this way potential influences on surge tendency can be examined for the 55 drainage basins analyzed there is a pronounced spatial variation in the concentration of surge type glaciers but no obvious environmental control can be evinced within the study area the greatest concentration lies in the northern st elias mountains a region of high topographic elevation that is experiencing rapid tectonic uplift analysis of the influence of length on surge tendency reveals that long glaciers have a significantly greater probability of being surge type than short glaciers the surge probability increases monotonically from 0 61 for very short glaciers 0 1 km to 65 1 for long glaciers 10 75 km this result suggests that ice sheets and ice caps or at least portions of them should have a high probability of surging tributary glaciers have a greater tendency to surge than trunk glaciers presumably because they may themselves be surge type and may additionally participate in surges of the trunk glacier the nonrandom geographical distribution of surge type glaciers is not simply a consequence of the variation from basin to basin of the glacier length distribution surge type glaciers tend to have a higher overall elevation than normal glaciers the elevation of the highest point of the accumulation zone the elevation of the snow line and the elevation of the lowest point of the ablation zone on average exceed the corresponding elevations for normal glaciers there is no significant difference between the overall slopes of surge type and normal glaciers although there is a tendency for surge type glaciers to have greater slope in the accumulation zone and lesser slope in the ablation zone than normal glaciers although the prevalent flow direction for glaciers in the yukon data set is to the north surge type glaciers tend to flow to the east and southeast this orientation influence is probably explained by the fact that many of the longest glaciers also flow to the east and southeast

flow and structure in a dendritic glacier with bedrock steps sherpa romeo green journal open access article creative commons attribution 4 0 international cc by 4 0 applies

solar wind interaction with the ionosphere atmosphere and crustal magnetic fields at mars mars global surveyor magnetometer electron reflectometer radio science and accelerometer data 1 the solar wind sw mainly interacts with the martian ionosphere atmosphere however the intense crustal magnetization creates localized minimagnetospheres above the surface the interplanetary magnetic field imf can reconnect with these crustal fields and this allows sw and more energetic particles to precipitate into and heat the neutral atmosphere in localized regions especially in the southern hemisphere a study of 907 electron density profiles obtained by the mgs radio science rs experiment at latitudes from 63 to 77 and 219 profiles at latitudes 69 to 64 5 has been conducted the role of the magnetic field as a driving force of the cross terminator convection is discussed longitudinal variations of neutral atmosphere scale height hpeak derived from the mgs rs data have been analyzed ionospheric parameters are found to be more variable in the southern than in the northern hemisphere this correlates well with the variability of the magnetic field direction from local zenith the scale height of neutral atmosphere density hacc derived from the mgs accelerometer data is also found to be more variable in the southern than in the northern hemisphere

a field and reactive transport model study of arsenic in a basaltic rock aquifer abstract the use of geothermal energy as a source for electricity and district heating has increased over recent decades dissolved as can be an important constituent of the geothermal fluids brought to the earth s surface here the field application of laboratory measured adsorption coefficients of aqueous as species on basaltic glass surfaces is discussed the mobility of as species in the basaltic aquifer in the nesjavellir geothermal system iceland was modelled by the one dimensional 1d reactive transport model phreeqc ver 2 constrained by a long time series of field measurements with the chemical composition of geothermal effluent fluids ph eh and occasionally fe and as dissolved species measurements di tri and tetrathioarsenic species as oh s 2 2 ass 3 h 2 ass 3 3 and as sh 4 were the dominant form of dissolved as in geothermal waters exiting the power plant 2 556 m total as but converted to some extent to arsenite h 3 aso 3 and arsenate haso 4 2 oxyanions coinciding with rapid oxidation of s 2 to s 2 o 3 2 and finally to so 4 2 during surface runoff before feeding into a basaltic lava field with a total as concentration of 0 882 m following dilution with other surface waters a continuous 25 a data set monitoring groundwater chemistry along a cross section of warm springs on the lake thingvallavatn shoreline allowed calibration of the 1d model furthermore a series of ground water wells located in the basaltic lava field provided access along the line of flow of the geothermal effluent waters towards the lake the conservative ion cl moved through the basaltic lava field 4100 m in less than10 a but as was retarded considerably due to surface reactions and has entered a groundwater well 850 m down the flow path as arsenate in accordance to the prediction of the 1d model the 1d model predicted a complete breakthrough of arsenate in the year 2100 in a reduced system arsenite should be retained for about 1 ka

controls on the distribution of surge type glaciers in svalbard we analyzed the possible controls on the distribution of surge type glaciers in svalbard using multivariate logit models including 504 glaciers and a large number of glacial and geological attributes specifically we examined the potential effect of geological boundaries mass balance conditions and thermal regime on surging it was found that long glaciers with relatively steep slopes overlying young fine grained sedimentary lithologies with orientations in a broad arc clockwise from northwest to southeast are most likely to be of surge type no relation between lithological boundaries and surge potential could be established possible explanations for length being conducive to surging are transport distance related substrate properties distance related attenuation of longitudinal stresses and the possible relation between thermal regime and glacier size analysis of glaciers with recorded radioecho sounding reveals that a polythermal regime accumulation area ratios close to balance and a large elevation span increase the surge potential the logit models also enabled us to detect 19 new surge type glaciers to reclassify six glaciers as normal and to identify unusual surge type glaciers our model results suggest that a polythermal regime and fine grained potentially deformable beds are conducive to the surge potential of svalbard glaciers

magnetically controlled structures in the ionosphere of mars 1 the ionospheric sounding data obtained by the marsis mars advanced radar for subsurface and ionospheric sounding instrument on the mars express spacecraft show that the dayside ionosphere has considerable structure over regions of strong crustal magnetic fields this structure is typically seen as a hyperbola shaped trace in a display of echo intensity versus apparent altitude and time the hyperbola shapes are consistent with oblique reflections from regions of enhanced electron density that are fixed with respect to mars comparisons with the cain et al 2003 model for the crustal magnetic field of mars show that the apexes of the hyperbolas which identify the closest approach to the regions of enhanced electron density usually coincide with regions where the crustal magnetic field is strong and nearly vertical the electron density enhancements which extend as much as 50 km above the surrounding ionosphere are believed to arise from increases in the scale height of the ionosphere possibly due to heating of the ionosphere by solar wind electrons that reach the base of the ionosphere along the nearly vertical open magnetic field lines statistical analyses of the apparent altitudes of the apexes of the hyperbolas as well as analyses of repeated passes over the same region indicate that the electron density enhancements usually consist of horizontal cylinder like structures rather than isolated hemispherical structures in many cases the axes of the cylindrical density structures are aligned with the symmetry axes of adjacent cylindrical magnetic field structures with opposite polarity

rapid response of modern day ice sheets to external forcing abstract the great ice sheets covering antarctica and greenland were traditionally believed to take thousands of years to respond to external forcing recent observations suggest however that major changes in the dynamics of parts of the ice sheets are taking place over timescales of years these changes were not predicted by numerical models and the underlying cause s remains uncertain it has been suggested that regional oceanic and or atmospheric warming are responsible but separating the influence and importance of these two forcings has not been possible in most cases the role of atmospheric versus oceanic control remains uncertain here we review the observations of rapid change and discuss the possible mechanisms in the light of advances in numerical modelling and our understanding of the processes that may be responsible

threefold increase in marine terminating outlet glacier retreat rates across the atlantic arctic 1992 2010 accelerated discharge through marine terminating outlet glaciers has been a key component of the rapid mass loss from arctic glaciers since the 1990s however glacier retreat and its climatic controls have not been assessed at the pan arctic scale consequently the spatial and temporal variability in the magnitude of retreat and the possible drivers are uncertain here we use remotely sensed data acquired over 273 outlet glaciers located across the entire atlantic arctic i e areas potentially influenced by north atlantic climate and or ocean conditions specifically greenland novaya zemlya franz josef land and svalbard to demonstrate high magnitude accelerating and near ubiquitous retreat between 1992 and 2010 overall mean retreat rates increased by a factor of 3 5 between 1992 and 2000 30 5 m a 1 and 2000 10 105 8 m a 1 with 97 of the study glaciers retreating during the latter period the retreat was greatest in northern western and south eastern greenland and also increased substantially on the barents sea coast of novaya zemlya glacier retreat showed no significant or consistent relationship with summer air temperatures at decadal timescales the rate of frontal position change showed a significant but weak correlation with changes in sea ice concentrations we highlight large variations in retreat rates within regions and suggest that fjord topography plays an important role we conclude that marine terminating arctic outlet glaciers show a common response of rapid and accelerating retreat at decadal timescales

magnetically controlled density structures in the topside layer of the martian ionosphere magnetically controlled density structures in the main layer of the martian ionosphere are regularly detected by the mars advance radar for subsurface and ionospheric sounder marsis on board the mars express spacecraft when it passes over the regions of strong crustal magnetic fields these structures appear as oblique echoes in an ionogram and as hyperbola shaped feature in a radargram for the first time we observed such oblique echoes from the topside layer of the martian ionosphere comparison with a crustal magnetic field model suggests that these echoes mostly occur in regions close to magnetic field anomalies the marsis ionograms that show these oblique echoes are limited in number one reason for such limited occurrence is the fact that these echoes occur at the low frequency end of an ionogram where local plasma frequency lines and electron cyclotron lines make it difficult to discern these echoes in one case however we observed the topside layer with oblique echoes on several continuous ionograms and a hyperbola shaped feature on a radargram the apex of the hyperbola falls in the region of vertical magnetic fields unlike the main layer the recurrent occurrence of the topside layer at the same location is not common more importantly the oblique echoes from the topside layer are always associated with those from the main layer of the ionosphere but not vice versa the simultaneous observation of oblique echoes from the main and topside layers are explained by considering the formation of ionization bulges at the respective layer altitudes

arsenic in surface and up to 90 c ground waters in a basalt area n iceland processes controlling its mobility the concentrations of as in surface and up to 90 c ground waters in a tholeiite flood basalt area in n iceland lie in the range 0 5 g kg as the as content of ground waters increases on the whole with rising temperature arsenic is highly mobile in the basalt water environment of the study area an insignificant fraction of the as dissolved from the rock is taken up into secondary minerals arsenic is less mobile than b but considerably more mobile than na which has the highest mobility among the major aqueous components a significant fraction of the as in the basalt occurs in an easily soluble form the as hosted in the primary minerals is expected to be concentrated in the titano magnetite this mineral is stable in contact with both surface and ground waters and does not therefore supply as to the water explaining the difference in mobility between as and b aqueous as concentrations are a reflection of water rock ratios i e how much rock a given quantity of water has dissolved this ratio increases with increasing temperature and increasing residence time of the water in contact with the rock the distribution of as species has been calculated on the assumption of equilibrium at the redox potential retrieved from measurement of aqueous fe ii and fe iii concentrations these calculations indicate that pentavalent as is stable in surface waters and in ground waters with an in situ ph of 10 and would occur mostly as h 2 aso 4 and haso 2 4 in higher ph ground waters the concentrations of the arsenite species h 2 aso 3 is significant at equilibrium up to 65 of the total dissolved as

an altitude normalized magnetic map of mars and its interpretation techniques developed for the reduction and analysisofterrestrialsatellitemagneticelddataareusedto better understand the magnetic eld observations made by mars global surveyor a global distribution of radial br magnetic eld observations and associated uncertainties is invertedfor an equivalentsource magnetization distribution and then used to generate an altitude normalized map of br at 200 km the observations are well represented by a potential function of crustal origin consistent with a rema nent origin for the martian magnetic features the correla tion between the 40546 br observations andbr calculated from the magnetization solution at observation locations is 0 978 for a magnetization distribution connedto a 50 km layer calculatedmagnetizationsrangefrom 22to 17a m we see correlations with tectonics that were only hinted at in earlier maps magnetic features appear to be truncated against valles marineris and ganges chasma suggestive of a major change in crustal properties associated with fault ing

a 50 degree spherical harmonic model of the magnetic field of mars this paper presents a 50 degree and order spherical harmonic model of the magnetic field of mars derived at 120 km altitude using the three orthogonal components of the vector magnetic field data acquired by the mars global surveyor within the 80 to 200 km altitude range the downward continued vector magnetic field components to the surface of mars delineate details of the martian magnetic field the strong magnetic anomalies in the southern hemisphere do not show compelling evidence for magnetic lineations similar to those associated with the seafloor spreading on earth the anomalies are more or less equidimensional the magnetic signatures surrounding the impact basins hellas argyre and isidis show that the prominent magnetic anomalies are older than the impact events an average magnetization of 2 a m is estimated for the upper crust surrounding hellas basin four isolated magnetic anomalies are modeled by vertical prisms with circular cross sections of 170 to 190 km radius and 20 to 30 km thickness the magnetization of the model prisms is 5 a m more than that of the surroundings

magnetic field and plasma observations at mars initial results of the mars global surveyor mission the magnetometer and electron reflectometer investigation mag er on the mars global surveyor spacecraft has obtained magnetic field and plasma observations throughout the near mars environment from beyond the influence of mars to just above the surface at an altitude of 100 kilometers the solar wind interaction with mars is in many ways similar to that at venus and at an active comet that is primarily an ionospheric atmospheric interaction no significant planetary magnetic field of global scale has been detected to date 2 1021 gauss cubic centimeter but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of mars is reported

oblique reflections of mars express marsis radar signals from ionospheric density structures raytracing analysis mars advanced radar for subsurface and ionosphere sounding marsis radar sounder on board the mars express spacecraft revealed oblique reflections coming systematically from apparently stable dens

a general theory of glacier surges we present the first general theory of glacier surging that includes both temperate and polythermal glacier surges based on coupled mass and enthalpy budgets enthalpy in the form of thermal energy and water is gained at the glacier bed from geothermal heating plus frictional heating expenditure of potential energy as a consequence of ice flow enthalpy losses occur by conduction and loss of meltwater from the system because enthalpy directly impacts flow speeds mass and enthalpy budgets must simultaneously balance if a glacier is to maintain a steady flow if not glaciers undergo out of phase mass and enthalpy cycles manifest as quiescent and surge phases we illustrate the theory using a lumped element model which parameterizes key thermodynamic and hydrological processes including surface to bed drainage and distributed and channelized drainage systems model output exhibits many of the observed characteristics of polythermal and temperate glacier surges including the association of surging behaviour with particular combinations of climate precipitation temperature geometry length slope and bed properties hydraulic conductivity enthalpy balance theory explains a broad spectrum of observed surging behaviour in a single framework and offers an answer to the wider question of why the majority of glaciers do not surge

evaluation of gas data from high temperature fumaroles at mount st helens 1980 1982 abstract the mount st helens fumarole gases show linear composition trends during periods of noneruptive degassing between september 1980 and october 1981 the trends are characterized by increasing h2o and decreasing co2 and sulfur maximum fumarole temperatures also show a linear decrease during this period high temperature fumarole gases collected from the crater and dome between september 1980 and july 1982 are all h2o rich 90 with 1 10 co2 and small amounts of h2s so2 h2 co hc and hf trace amounts of cos and s2 are present and occasional observations of minor ch4 appear to result from contamination or low temperature reactions in sample vessels the o2 fugacities of the gases remain near ni nio during cooling the low sulfur content of the gases obviates the need for extensive gas rock oxygen exchange to maintain fo2 s near ni nio a detailed thermodynamic analysis of 50 gas samples collected between september 1980 and december 1981 led to improved compositions for 22 samples the gases were initially in a state of equilibrium but disequilibrium modifications from atmospheric oxidation of h2 and to a lesser extent co occurred within the upper portions of the fumarole vents the last temperatures of equilibrium for the fumarole gases range from 800 c to 650 c and are nearly always higher than the collection temperatures no evidence was found of disequilibrium admixture of surface waters if such modifications of the fumarole gases occurred the water must have been added at depth and have reequilibrated with the other gas species at magmatic or near magmatic temperatures the highest quality analytical data are obtained by field gas chromatograph measurements and from caustic soda bottle samples samples collected in evacuated bottles or by pumping through double stopcock tubes tend to be severely deficient in sulfur due to post collection reactions between h2s and so2 it is also necessary to infer the water content of the latter samples

the 2008 09 surge of central yulinchuan glacier northern tibetan plateau as monitored by remote sensing the 2008 09 surge of central yulinchuan glacier cyg on the northwestern slope of muztag mountain tibetan plateau is studied based on satellite remote sensing the widely used cross correlation feature tracking method was used to collect satellite image control points and validate their geometric accuracies as well as to derive glacier surface velocity changes in glacier length and area were also retrieved results show that the surge of cyg initiated in may 2008 and terminated in july 2009 two diffluent glacier termini advanced 590 26 m 5 1 0 2 of the 2004 length and 182 26 m 1 8 0 3 respectively and glacier area increased by similar to 1 41 0 11 km 2 4 6 0 4 of the 2004 area during this period the most significant surge period was october 2008 to march 2009 when most of the terminus advances and area increases occurred the glacier surface drastically crevassed during this time as much as 1657 297 m of horizontal surface displacements were produced by surge ice and maximum surface speed reached 13 1 5 m d 1 results of transverse and longitudinal velocity profiles revealed two surge waves during this surge of cyg

interpreting mars ionospheric anomalies over crustal magnetic field regions using a 2 d ionospheric model the spatially inhomogeneous small scale crustal magnetic fields of mars influence the escape of planetary atmospheric species and the interaction of the solar wind with the ionosphere understanding the plasma response to crustal magnetic field regions can therefore provide insight to ionospheric structure and dynamics to date several localized spatial structures in ionospheric properties that have been observed over regions of varying magnetic field at mars have yet to be explained in this study a two dimensional ionospheric model is used to simulate the effects of field aligned plasma transport in regions of strong crustal magnetic fields resulting spatial and diurnal plasma distributions are analyzed and found to agree with observations from several spacecraft and offer compelling interpretations for many of the anomalous ionospheric behaviors observed at or near regions of strong crustal magnetic fields on mars

identification and characteristics of surge type glaciers on novaya zemlya russian arctic we present a comprehensive new inventory of surge type glaciers on the novaya zemlya archipelago using high resolution up to 4 m satellite imagery from 1976 77 hexagon 1989 landsat tm 2001 landsat etm and 2006 aster a total of 692 glaciers and their forelands were observed for glaciological and geomorphological criteria indicative of glacier surging e g looped moraines heavy surface crevassing surface potholes thrust block moraines concertina eskers this enabled the identification of 32 potential surge type glaciers compared with four previously identified representing 4 6 of the total but 18 by glacier area we assess the characteristics of surge type glaciers surge type glaciers are statistically different from non surge type glaciers in terms of their area length surface slope minimum elevation mid range elevation and terminus type they are typically long median length 18 5 km large median area 106 8 km 2 outlet glaciers with relatively low overall surface slopes median slope 1 7 and tend to terminate in water marine or lacustrine they are predominantly directed towards and located in the more maritime western region of the russian arctic and we suggest that surge occurrence might be related to large and complex catchment areas that receive increased delivery of precipitation from the barents sea

subglacial drilling at black rapids glacier alaska u s a drilling method and sample descriptions we employed a commercial wireline drill rig to investigate the subglacial conditions of black rapids glacier a well studied surge type glacier in the central alaska range the four main goals were to assess the capabilities of the commercial drilling industry for sampling subglacial material to investigate the basal morphology to determine the subglacial geology and to emplace borehole instruments the drilling was done in an area where seasonal and secular variations in speed are large and where seismic studies suggested the presence of a till layer four holes were drilled at three locations to a maximum depth of 620 m three holes yielded samples of basal ice and till although recovery of the latter was generally poor bedrock was sampled in one or possibly two of the holes in the area sampled the glacier is underlain by a till layer some 4 7 m thick confirming the seismic interpretation it consists ofa sandy matrix at least 20 30 of which comprises larger clasts limited samples ofthe matrix indicate that near the top ofthe till the porosity is 40 and that some of the pore water is frozen geologic studies suggest that the drilling area lies to the north of the denali fault a major tectonic boundary followed by the glacier and that most of the till is locally derived with transport distances of 2 km

mapping tide water glacier dynamics in east greenland using landsat data landsat multispectral scanner and thematic mapper images were co registered for the kangerdlugssuaq fjord region in east greenland and were used to map glacier drainage basin areas changes in the positions of tide water glacier termini and to estimate surface velocities of the larger tide water glaciers statistics were compiled to document distance and area changes to glacier termini the methodologies developed in this study are broadly applicable to the investigation of tide water glaciers in other areas the number of images available for consecutive years and the accuracy with which images are co registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data three domains of glacier state were interpreted net increase in terminus area in the southern part of the study area net loss of terminus area for glaciers in upper kangerdlugssuaq fjord and a slight loss of glacier terminus area northward from ryberg fjord local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions ice surface velocity estimates were derived for several glaciers using automated image cross correlation techniques the velocity determined for kangerdlugssuaq gletscher is approximately 5 0 km a 1 and that for kong christian iv gletscher is 0 9 km a 1 the continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice front calving

glacier surge mechanism 1982 1983 surge of variegated glacier alaska the hundredfold speedup in glacier motion in a surge of the kind the kind that took place in variegated glacier in 1982 1983 is caused by the buildup of high water pressure in the basal passageway system which is made possible by a fundamental and pervasive change in the geometry and water transport characteristics of this system the behavior of the glacier in surge has many remarkable features which can provide clues to a detailed theory of the surging process the surge mechanism is akin to a proposed mechanism of overthrust faulting

estimation of the total electron content of the martian ionosphere using radar sounder surface echoes 1 the martian ionosphere s local total electron content tec and the neutral atmosphere scale height can be derived from radar echoes reflected from the surface of the planet we report the global distribution of the tec by analyzing more than 750 000 echoes of the mars advanced radar for subsurface and ionospheric sounding marsis this is the first direct measurement of the tec of the martian ionosphere the technique used in this paper is a novel transmission mode sounding of the ionosphere of mars in contrast to the active ionospheric sounding experiment ais on marsis which generally operates in the reflection mode this technique yields a global map of the tec for the martian ionosphere the radar transmits a wideband chirp signal that travels through the ionosphere before and after being reflected from the surface the received waves are attenuated delayed and dispersed depending on the electron density in the column directly below the spacecraft in the process of correcting the radar signal we are able to estimate the tec and its global distribution with an unprecedented resolution of about 0 1 deg in latitude 5 km footprint the mapping of the relative geographical variations in the estimated nightside tec data reveals an intricate web of high electron density regions that correspond to regions where crustal magnetic field lines are connected to the solar wind our data demonstrates that these regions are generally but not exclusively associated with areas that have magnetic field lines perpendicular to the surface of mars as a result the global tec map provides a high resolution view of where the martian crustal magnetic field is connected to the solar wind we also provide an estimate of the neutral atmospheric scale height near the ionospheric peak and observe temporal fluctuations in peak electron density related to solar activity

a coherent model of the crustal magnetic field of mars 1 the immense amount of the mapping phase mars global surveyor mgs magnetic data allows us to derive a highly accurate magnetic map of mars the data acquired at nighttimes within the first 3 years of the mapping phase are divided into two almost equal parts and each part is expressed in spherical harmonics of degree up to 90 the two models are almost identical over harmonics of degree up to 62 but show appreciable differences over higher degree harmonics indicating that the higher degree harmonic coefficients have appreciable noncrustal contribution the most repeatable components of the two models are combined to produce an accurate 62 degree harmonic model of the magnetic field of the martian crust it is further demonstrated that the altitude of mgs is the major limiting factor of the resolution of the mapping phase data the small scale features of the data with wavelengths shorter than 400 km have significant contribution from noncrustal sources they are not useful for delineating the details of the magnetic source bodies in the crust

radio science investigations with mars observer mars observer radio science investigations focus on two major areas of study the gravity field and the atmosphere of mars measurement accuracies expressed as an equivalent spacecraft velocity are expected to be of the order of 100 m s for both types of investigations from use of an improved radio transponder for two way spacecraft tracking and a highly stable on board oscillator for atmospheric occultation measurements planned gravity investigations include a combination of classical and modern elements a spherical harmonic or equivalent field model of degree and order in the range 30 50 will be obtained while interpretation will be in terms of internal stress and density models for the planet using the topography to be obtained from the mars observer laser altimeter atmospheric investigations will emphasize precision measurement of the thermal structure and dynamics in the polar regions which are regularly accessible as a result of the highly inclined orbit studies based on the measurements will include polar processes cycling of the atmosphere between the poles traveling baroclinic disturbances small scale waves and turbulence the planetary boundary layer and possibly the variability and altitude of the ionosphere as the radio occultation is insensitive to dust in the atmosphere per se and measures only the resulting change in thermal structure it is expected that the radio technique can contribute to understanding of dust storm phenomena mutual observations of the atmosphere by means of radio occultation and by the pressure modulator infrared radiometer and the thermal emission spectrometer are expected to strengthen the reliability and accuracy of all three investigations

radar soundings of the subsurface of mars the martian subsurface has been probed to kilometer depths by the mars advanced radar for subsurface and ionospheric sounding instrument aboard the mars express orbiter signals penetrate the polar layered deposits probably imaging the base of the deposits data from the northern lowlands of chryse planitia have revealed a shallowly buried quasi circular structure about 250 kilometers in diameter that is interpreted to be an impact basin in addition a planar reflector associated with the basin structure may indicate the presence of a low loss deposit that is more than 1 kilometer thick