use of environmental magnetic measurements to validate the vertical extent of ice masses at the last glacial maximum analysis of soil samples from above and below trimlines representing the upper limit of glacial erosion at the last glacial maximum demonstrates that soils with prolonged weathering histories above such trimlines yield significantly different mineral magnetic signatures from soils below trimlines the nature of the contrast is conditioned by lithology basalt soils above the trimline yield significantly higher values of concentration dependent magnetic parameters arm irm3t soft irm and hard irm than those below the trimline due probably to transformation of non magnetic iron bearing minerals into magnetic forms conversely for sandstone soils most magnetic parameters yield significantly lower values for above trimline samples probably reflecting loss of ferrimagnetic minerals by dissolution and oxidation to aniferrimagnetic forms these significant contrasts represent a new approach to validating high level weathering limits as periglacial trimlines cut at the last glacial maximum copyright 2002 john wiley sons ltd

a vaporization model for iron silicate fractionation in the mercury protoplanet abstract a study has been carried out of the vaporization of a totally molten silicate magma of chondritic composition heated into the range 2500 3500 k the motivation for this was to determine the changes in the composition of the mantle that would occur in the mercury protoplanet should that body have been subjected to the high temperature phase in the evolution of the primitive solar nebula but the results are of more general interest we have used both ideal and nonideal descriptions of the magma chemistry an empirical model based on ideal mixing of complex components developed by hastie and co workers was used to describe the nonideal magma comparison of our results of the nonideal magma calculations with experimental work on vaporization of chondritic material shows generally good agreement we find that vaporization of about 70 80 of the original amount of silicate from a chondritic planet is required to produce an iron rich body with a mean uncompressed density equal to that deduced for mercury 5 3 g cm3 at this point the silicate is depleted in the alkalis feo and sio2 and enriched in cao mgo al2o3 and tio2 relative to chondritic material we also predict the production of unique trace element abundance patterns which are depleted in easily oxidized elements relative to other trace elements of similar volatilities

soil development of three chernozem like profiles from north bulgaria revealed by magnetic studies abstract a detailed magnetic study of three soil profiles of calcic chernozem luvic phaeozem and orthic luvisol described in the soil atlas of bulgaria was carried out in order to reveal the potential of magnetic methods for characterization of soil forming processes and properties of pedogenic iron oxides thermomagnetic analysis of susceptibility and sem edx observations revealed that the main pedogenic mineral in all three soils is fine grained superparamagnetic to single domain maghemite thermal stability of this pedogenic phase up to temperatures of 500 c is revealed by the partial thermomagnetic analyses of susceptibility depth variations of magnetic parameters and ratios point to the presence of stable single domain to pseudo single domain grains in humic horizons the quantity of which decreases sharply towards lower soil horizons these magnetic grain size changes are best expressed in orthic luvisol and reflect intensified processes of translocation of substances downward

mineral magnetic characteristics of podzolic soils developed on sand dunes in the lake gosciaz catchment central poland a number of samples from the a0 a2 b and c horizons have been collected from podzolic soils in the lake gosciaz catchment in central poland the catchment is very uniform consisting of 2 6 m high sand dunes with sparse stands of pine and a grass undervegetation radiocarbon dates of fossil soils covered by dune sand within the same type of environment as the lake gosciaz catchment indicate that the main dune forming phase is of older dryas age magnetic measurements have been carried out on bulk samples and on particle size fractions from the different soil horizons with respect to our mineral magnetic study it can be concluded that the soils are very uniform over the entire catchment relatively high concentrations of magnetic grains are found in the humus layer particularly in the 4 m size fraction as indicated by the highest x xfd sirm and hirm values the most likely mechanism for the magnetic enhancement in these podzolic top soils is continued burning processes low magnetic concentrations in the a2 horizon are due to eluviation and chelation local conditions can lead to a range of magnetic minerals precipitating in the b horizon

the effect of tides and an inner core on the forced longitudinal libration of mercury abstract mercury s longitudinal libration at a period of 88 days depends on the moment of inertia of the planet s silicate outer part and as such contains information on the interior structure and composition of mercury secondary effects on the libration may affect the interpretation of libration observations in terms of interior structure properties and may also provide further information on mercury s interior here we assess the importance of the effects of tides and the existence of a solid inner core on the librations of mercury with particular focus on the 88 days libration amplitude tides affect the librations of mercury by changing the gravitational torque exerted by the sun on mercury and by changing the polar moment of inertia we show that they slightly decrease the 88 days libration amplitude by about 1 2 m which is below the current and future expected observational precision we further demonstrate that the effect of an inner core on mercury s 88 days libration amplitude is also below the observational precision for small inner cores but could be observed if mercury s inner core is larger than at least 1000 km an inner core also changes considerably the free libration period by up to 25 if the inner core is very large besides giving information on the moment of inertia of the silicate shell observations of mercury s libration can therefore also yield information on the inner core

combined rock magnetic and geochemical characterization of angangueo mining district central mexico results of a combined rock magnetic and geochemical investigation carried out at angangueo mining district are presented the different thickness and color of layers observed in field are also sketched from the magnetic susceptibility vertical ground profile accomplished additionally an area with enhanced magnetic susceptibility values is clearly outlined from a radial survey on the top of one of the biggest tailing the internal differentiation of the tailing was also supported by a full set of laboratory rock magnetic and physical chemical parameters geochemical results of matched samples reveal a complex relationship along the profile between some heavy metal concentrations i e cu and pb and magnetic susceptibility never reported in mining wastes nor in environmental studies contrary to environmental investigations of topsoils magnetic susceptibility enhancements zones in a tailing do not correspond necessarily to more heavy metal contaminated zones these outcomes evidence the intricate nature of mining wastes and the need for a better and intensive investigation of these barely studied objects

magnetic mineralogy of the lower continental crust rocks that were once present in the deep continental crust can be found in surface exposure as xenoliths as parts of high grade metamorphic and plutonic terrains and as obducted lower crustal cross sections a review of magnetic and mineralogic studies of samples representing all such occurrences shows that magnetite is the only magnetic phase present in significant amounts in these rocks thermodynamic considerations indicate that tipoor magnetite is the expected magnetic oxide under equilibrium conditions that exist in the lower crust regardless of the primary magmatic composition of the spinel phase furthermore it seems unlikely that serpentinites with metal alloys contribute significantly to the magnetization of the lower crust or mantle thus magnetite in the deep crust is the most likely candidate for the source of the long wavelength magnetic anomalies observed in regional aeromagnetic and satellite magnetometer surveys if so the entire crust should be magnetic in most continental areas including shields in areas of high heat flow the bottom of the magnetic crust may lie considerably above the moho

ferrous oxide in mercury s crust and mantle mercury has widespread plains deposits proposed to be volcanic in origin in a mariner 10 color derived parameter image sensitive to feo and maturity these volcanic plains have a value equivalent to or slightly elevated above the hemispheric average thus implying feo equivalent to or slightly less than the hemispheric average 3 wt feo since feo has a solid liquid distribution coefficient 1 during partial melting we estimate the mantle of mercury to have an feo abundance equal to the lava flows this is consistent with models that predict mercury was assembled from planetesimals formed near the planet s current position this new estimate of mercury s bulk feo 3 wt is consistent with data for the other terrestrial planets that suggest there was a radial gradient in feo in the solar nebula

magnetization of lower crust and interpretation of regional magnetic anomalies example from lofoten and vesteralen norway the interpretation of regional magnetic anomalies commonly observed over continental crust in both satellite and near surface magnetic data has remained enigmatic in its requirement for laterally extensive thick highly magnetic and deep seated sources presented here are the results of a detailed field analytical and experimental study of the magnetic mineralogy and magnetic properties of rocks from lofoten and vesteralen norway a province of deep seated origin with associated regional magnetic and gravity anomalies these rocks have a bulk magnetic character of surprising uniformity with susceptibilities hysteresis and curie temperatures defined solely by coarse grained magnetite stable remanence is observed in samples from sw lofoten but is not of significant magnitude the thermal enhancement of magnetic susceptibility the hopkinson effect is not important rocks from the deepest part of the section have the largest average susceptibilities 6 10 2 si and magnitudes of natural remanent magnetization nrm 5 10 4 a m2 kg these values of susceptibility together with the oft observed viscous character of the nrm suggest that these granulite facies lithologies particularly those of sw lofoten are perfect examples of lower crustal sources of typical regional magnetic anomalies furthermore these intermediate pressure granulites define a unique magnetic petrology especially for mafic compositions at higher grades of metamorphism high pressure granulites and eclogites or lower grades greenschist and amphibolite facies such magnetite bearing assemblages will be unstable and their high or low grade equivalents will be only weakly magnetic this evidence and these conclusions may be used to constrain models of lower crustal sources of regional magnetic anomalies over stable cratons it portrays the lower crust as a highly magnetic unit defined by metamorphic grade with a curie isotherm of 575 c magnetite and magnetization parallel to the ambient geomagnetic field induced and viscous components

the moho as a magnetic boundary revisited we have re examined the question of whether it is generally true that in continental regions a relatively magnetic crust overlies a relatively non magnetic mantle whereas the original conclusion was based on limited data the present study is based on about 400 globally distributed xenolith samples while it is now clear that the moho represents a maximum velocity gradient in a complex transition from crust to mantle and while crustal magnetization is highly variable the original concept of a magnetic crust overlying a non magnetic mantle is strongly supported by the new data a large upper mantle xenolith suite of ultramafic composition is characterized by non magnetic chrome spinels and magnesian ilmenites such rocks are magnetic only where demonstrably altered the most significantly magnetic rocks within the crust are mafic types prograded to granulite grade or mafic melts of basaltic composition which crystallized deep in the crust at high pressure and temperature prograded rocks have characteristic magnetite curie points and are strongly magnetic especially the more mafic compositions while the mafic rocks formed by crystallization at depth have curie points between 400 570 c and are strongly magnetic induced magnetizations are commonly several a m and can readily account for long wavelength magnetic anomalies measured by satellite and aircraft thus there is no need to search for exotic sources for missing crustal magnetization no metal or other peculiar magnetic species have been observed by us in any of our unaltered samples mineral assemblages including magnetic components are consistent with oxidizing conditions close to the fmq buffer

depth of faulting on mercury implications for heat flux and crustal and effective elastic thickness 1 topographic profiles across a lobate fault scarp on mercury have been used to constrain the depth of faulting to 30 40 km here we use this depth to place constraints on the crustal thickness and heat flow into the base of the crust with no crustal heat production the mantle heat flux on mercury at the time of scarp formation was 30 50 mwm 2 however higher crustal heat production rates allow significantly lower mantle heat fluxes in all cases the mantle heat flux exceeds the likely radiogenic heat flux 4 gyr ago it is likely that secular cooling accounted for the remainder irrespective of crustal heat generation a crustal thickness of 140 km is required to satisfy both the faulting observations and the requirement that the base of the crust does not melt the effective elastic thickness of the lithosphere at the time of faulting is predicted to be 25 30 km

electrical investigation of metal olivine systems and application to the deep interior of mercury we report electrical conductivity measurements on metal olivine systems at about 5 and 6 gpa and up to 1 675 c in order to investigate the electrical properties of core mantle boundary cmb systems electrical experiments were conducted in the multianvil apparatus using the impedance spectroscopy technique the samples are composed of one metal layer fe fes fesi2 or fe ni s si and one polycrystalline olivine layer with the metal olivine ratio ranging from 1 0 7 to 1 9 2 for all samples we observe that the bulk electrical conductivity increases with temperature from 10 2 5 to 101 8 s m which is higher than the conductivity of polycrystalline olivine but lower than the conductivity of the pure metal phase at similar conditions in some experiments a conductivity jump is observed at the temperature corresponding to the melting temperature of the metallic phase both the metal olivine ratio and the metal phase geometry control the electrical conductivity of the two layer samples by combining electrical results textural analyses of the samples and previous studies of the structure and composition of mercury s interior we propose an electrical profile of the deep interior of the planet that accounts for a layered cmb outer core structure the electrical model agrees with existing conductivity estimates of mercury s lower mantle and cmb using magnetic observations and thermodynamic calculations and thus supports the hypothesis of a layered cmb outermost core structure in the present day interior of mercury we propose that the layered cmb outer core structure is possibly electrically insulating which may influence the planet s structure and cooling history

downward continuation of magsat lithospheric anomalies to the earth s surface summary the assumed lithospheric component of magsat data is downward continued to the earth s surface over continental sized areas using the depleted basis method with a regularizing constraint parker shure 1982 to make the problem numerically tractable and stable respectively the depleted basis is arranged to have a high density of points over the area of interest lower elsewhere all three components at satellite altitudes are used in the inversion for three orthogonal components at the earth s surface edge effects are seen if the depleted basis changes rapidly from a high to low spatial density which are eliminated by inserting a region of intermediate density basis points the downward continued field fits the data to within their probable uncertainties regularizing the solution produces a much smoother solution for very little increase in misfit some of the anomalies in the downward continued field over africa correlate with known tectonic features although the relationship between magnetic highs or lows and basins or cratons is not clear cut this magsat derived downward continued field can be used to control the longer wavelength component of the crustal magnetic field that is not defined by aeromagnetic surveys the method is illustrated on an aeromagnetic compilation of about 30 surveys from south africa however there is a mismatch in amplitudes between the aeromagnetic data and downward continued magsat data

the interior structure of mercury constrained by the low degree gravity field and the rotation of mercury abstract among all the planets of the solar system mercury stands out because it has a relatively high average density compared to its size to account for this high density mercury s core radius is thought to be larger than 3 4 of its radius here we use recent data about the second degree gravity field coefficients and measurements about mercury s rotation obliquity and 88 day libration amplitude to obtain constraints on mercury s interior structure by combining the gravity field data and the obliquity measurements the mean moment of inertia of mercury can be determined if the coupling between the core and the mantle is neglected then the gravity field data together with the libration amplitude provide an estimate of mercury s silicate shell moment of inertia however since the effect of core mantle coupling on the 88 day libration amplitude can be about as large as the libration amplitude s uncertainty van hoolst et al 2012 we use as data the mean moment of inertia and the 88 day libration amplitude to infer knowledge about mercury s interior structure we use two different interior modeling approaches the first one is based on rivoldini et al 2009 and uses a set of 5 mantle mineralogies a crust with a given thickness and density and two mantle temperatures in the second setting the density of the mantle the thickness and density of the crust and the temperature of the core mantle boundary are parameters of the model in both cases we assume that the core is made of iron and the light element sulfur and use the temperature pressure and the concentration of sulfur in the core together with the melting temperature of iron sulfur to determine the radius of the inner core our results show that the data provide a strong constraint on the radius of the core and on its average density or equivalently on the fraction of sulfur in the core if sulfur is the only light element in the core we find that mercury has a core radius of 2004 39 km an average core density of 7233 267 kg m 3 and a sulfur fraction of 4 5 1 8 wt the other parameters of the model in particular the density of the mantle are however only weakly constrained by the data the geodesy data can also not distinguish between a fully liquid core and the existence of an inner core

thermo chemical evolution and global contraction of mercury the very limited amount of global contraction observed on mercury s surface poses severe constraints on models of the planet s thermo chemical evolution and current models rely on a very refractory thorium rich composition to slow planetary cooling however a refractory composition appears to be incompatible with evidence for pyroclastic eruptions which require a substantial amount of volatiles to be present in the planetary interior furthermore volcanic activity appears to have been ongoing for a considerable part of the planet s history while current models predict an early cessation of crustal production to address these inconsistencies we have reinvestigated the thermo chemical evolution of mercury using a non refractory compositional model taking the presence of a thermally insulating regolith layer into account we find that models with a stiff mantle rheology satisfy the observational constraints if the regolith layer is at least 2 km thick in these models inefficient mantle convection and thermal insulation significantly slow planetary cooling and prolong the phase of crustal production to 2 5 gyr after core formation allowing the volume increase associated with mantle differentiation to offset some of the radial contraction caused by planetary cooling models furthermore predict substantial core sulfur contents above 6 wt average crustal thicknesses between 10 and 40 km and secular cooling rates of 30 k gyr

viscoelastic tides of mercury and the determination of its inner core size we computed interior structure models of mercury and analyzed their viscoelastic tidal response the models are consistent with mercury surface space environment geochemistry and ranging mission inferences of mean density mean moment of inertia moment of inertia of mantle and crust and tidal love number k2 based on these constraints we predict the tidal love number h2 to be in the range from 0 77 to 0 93 using an andrade rheology for the mantle the tidal phase lag is predicted to be 4 at maximum the corresponding tidal dissipation in mercury s silicate mantle induces a surface heat flux smaller than 0 16 mw m2 we show that independent of the adopted mantle rheological model the ratio of the tidal love numbers h2 and k2 provides a better constraint on the maximum inner core size with respect to other geodetic parameters e g libration amplitude or a single love number provided it responds elastically to the solar tide for inner cores larger than 700 km and with the expected determination of h2 from the upcoming bepicolombo mission it may be possible to constrain the size of the inner core the measurement of the tidal phase lag with an accuracy better than 0 5 would further allow constraining the temperature at the core mantle boundary for a given grain size and therefore improve our understanding of the physical structure of mercury s core

geodesy constraints on the interior structure and composition of mars abstract knowledge of the interior structure of mars is of fundamental importance to the understanding of its past and present state as well as its future evolution the most prominent interior structure properties are the state of the core solid or liquid its radius and its composition in terms of light elements the thickness of the mantle its composition the presence of a lower mantle and the density of the crust in the absence of seismic sounding only geodesy data allow reliably constraining the deep interior of mars those data are the mass moment of inertia and tides they are related to mars composition to its internal mass distribution and to its deformational response to principally the tidal forcing of the sun here we use the most recent estimates of the moment of inertia and tidal love number k2 in order to infer knowledge about the interior structure of the mars we have built precise models of the interior structure of mars that are parameterized by the crust density and thickness the volume fractions of upper mantle mineral phases the bulk mantle iron concentration and the size and the sulfur concentration of the core from the bulk mantle iron concentration and from the volume fractions of the upper mantle mineral phases the depth dependent mineralogy is deduced by using experimentally determined phase diagrams the thermoelastic properties at each depth inside the mantle are calculated by using equations of state since it is difficult to determine the temperature inside the mantle of mars we here use two end member temperature profiles that have been deduced from studies dedicated to the thermal evolution of mars we calculate the pressure and temperature dependent thermoelastic properties of the core constituents by using equations state and recent data about reference thermoelastic properties of liquid iron liquid iron sulfur and solid iron to determine the size of a possible inner core we use recent data on the melting temperature of iron sulfur within our model assumptions the geodesy data imply that mars has no solid inner core and that the liquid core contains a large fraction of sulfur the absence of a solid inner is in agreement with the absence of a global magnetic field we estimate the radius of the core to be 1794 65 km and its core sulfur concentration to be 16 2 wt we also show that it is possible for mars to have a thin layer of perovskite at the bottom of the mantle if it has a hot mantle temperature moreover a chondritic fe si ratio is shown to be consistent with the geodesy data although significantly different value are also possible our results demonstrate that geodesy data alone even if a mantle temperature is assumed can almost not constrain the mineralogy of the mantle and the crust in order to obtain stronger constraints on the mantle mineralogy bulk properties like a fixed fe si ratio have to be assumed

potential field power spectrum inversion for scaling geology we propose a method for inverting the power spectrum of gravity and magnetic data the method is demonstrated on aeromagnetic and bore well data from the german continental deep drilling project ktb density and susceptibility distributions in the earth s crust exhibit scaling behavior with power spectra proportional to f where f is the wavenumber and is the scaling exponent of the source distribution we model the sources of the potential field by a random function with scaling properties defined on a half space with its top at a specified depth beneath the observation plane comparing the theoretical power spectrum for this model with the power spectrum of the measured data we obtain the best values for the depth to source and the scaling exponent as a global minimum of the misfit function despite the simplicity of the model it offers a new understanding of the factors influencing the shape of the potential field power spectrum in particular the low wavenumber part of the power spectrum can be dominated by the scaling properties of the source distribution and not by the depth to some kind of basement the scaling exponent of the field varies with the type of surface geology the question of whether the scaling exponent can actually be used to identify different types of geology gives an interesting new aspect to power spectrum inversion

mineralogy of the martian interior up to core mantle boundary pressures in order to determine the mineralogy of the martian interior along a high temperature areotherm multianvil experiments have been performed with a model martian mantle composition up to 23 5 gpa the dreibus and wanke 19851 martian mantle composition yields an upper mantle that consists of olivine clinopyroxene orthopyroxene garnet at pressures up to 9 gpa above 9 gpa orthopyroxene is no longer present the transition zone is marked by the appearance of spinel at 13 5 gpa up to 15 gpa clinopyroxene and majorite coexists with phase and or spinel by 17 gpa clinopyroxene is entirely replaced by majorite and the modal abundance of spinel increases at the expense of phase the dominant assemblage throughout most of the transition zone is spinel majorite two experiments completed in the perovskite stability field indicate that the lower mantle consists of mg fe silicate perovskite magnesiowustite and majorite casio 3 perovskite is not present in these experiments both the presence of a martian lower mantle i e an mg fe silicate perovskite bearing zone and the phase assemblage stable in the martian lower mantle are very sensitive to the temperature profile of the interior a low temperature profile may stabilize stishovite in the lower mantle or it may lead to the absence of the lower mantle because of the higher transition pressure required for forming perovskite at lower temperatures regardless of the temperature profile assumed the martian upper mantle and transition zone will account for a larger proportion of the planet s interior than is the case for the earth s interior because of the smaller size of mars

in situ determination of fe fe3s phase diagram and liquid structural properties up to 65 gpa abstract lighter elements than iron such as sulphur are required in the earth s core to account of the core density deficit accurate determination of the evolution of the fe fes phase diagram at high pressure is essential to determine sulphur amount in the earth s core ab initio calculations predict extensive solubility of s in solid fe at core pressures of 330 gpa whereas multi anvil quench analysis exhibits deep eutectic system at moderate pressure of 21 gpa in this study we investigated the fe rich part of fe fes phase diagram up to 65 gpa and 2200 k using in situ angle dispersive x ray diffraction we report a uniform increase with pressure of the eutectic temperatures t eut of about 15 k gpa above 50 gpa we evidence a decrease of s content in eutectic liquid with increasing pressure extrapolating this trend to inner core boundary pressures suggests that s cannot account for the 10 wt outer core density deficit and that other light elements such as si and o are needed diffraction pattern recorded at 42 gpa and 2150 k was selected for structural investigations of the fe s liquid by applying liquid structure simulation based on gaussian distribution of atoms around crystalline positions a good agreement has been found with hcp fe model structure rather than with fe 3 s structure it suggests that s acts as an interstitial impurity in the liquid state therefore s could have a relatively minor effect on sound velocities in liquid outer core

the thermal evolution of mercury s fe si core abstract we have studied the thermal and magnetic field evolution of planet mercury with a core of fe si alloy to assess whether an fe si core matches its present day partially molten state mercury s magnetic field strength and the observed ancient crustal magnetization the main advantages of an fe si core opposed to a previously assumed fe s core are that a si bearing core is consistent with the highly reduced nature of mercury and that no compositional convection is generated upon core solidification in agreement with magnetic field indications of a stable layer at the top of mercury s core this study also present the first implementation of a conductive temperature profile in the core where heat fluxes are sub adiabatic in a global thermal evolution model we show that heat migrates from the deep core to the outer part of the core as soon as heat fluxes at the outer core become sub adiabatic as a result the deep core cools throughout mercury s evolution independent of the temperature evolution at the core mantle boundary causing an early start of inner core solidification and magnetic field generation the conductive layer at the outer core suppresses the rate of core growth after temperature differences between the deep and shallow core are relaxed such that a magnetic field can be generated until the present also the outer core and mantle operate at higher temperatures than previously thought which prolongs mantle melting and mantle convection the results indicate that s is not a necessary ingredient of mercury s core bringing bulk compositional models of mercury more in line with reduced meteorite analogues

internal structure of mercury implications of a molten core 1 mercury is unique among the terrestrial planets for its relatively low mass 3 302 1023 kg and high average density 5 427 g cm 3 that together imply an unusual iron rich bulk composition and thus provide an important constraint on planet formation and evolution and on compositional variations between the planets in light of the recent discovery of a partially or fully molten core of mercury we model plausible interior density structures of mercury using layered cores and the elastic properties of molten core materials we present constraints on mercury s decompressed density composition and interior structure including elucidation of assumptions and methodology we demonstrate the importance of molten and or layered cores to accurately model mercury s interior and to correctly interpret anticipated spacecraft geophysical observations the core radius and core mass fraction will be tightly constrained by earth based radar and anticipated spacecraft tracking observations but the bulk core sulfur content and extent of the molten core are less well constrained finally we discuss the implications of incorporating molten materials in modeled density structures on the hypotheses of mercury s iron enrichment and on anticipated spacecraft results

stochastic modeling of seafloor morphology inversion of sea beam data for second order statistics at scale lengths less than 100 km or so statistical descriptions of seafloor morphology can be usefully employed to characterize ridge crest processes off ridge tectonics and vulcanism sedimentation and postdepositional transport we seek to develop methods for the estimation of seafloor statistics that take into account the finite precision resolution and sampling obtained by actual echo sounding systems in this initial paper we restrict our attention to the problem of recovering second order statistics from data sets collected by multibeam devices such as sea beam the seafloor is modeled as a stationary zero mean gaussian random field completely specified by its two point covariance function we introduce an anisotropic two point covariance function that has five free parameters describing the amplitude orientation characteristic wave numbers and hausdorff fractal dimension of seafloor topography we formulate the general forward problem relating this model to the statistics of an ideal multibeam echo sounder in particular the along track autocovariance functions of individual beams and the cross covariance functions between beams of arbitrary separation using these second moments as data functionals we then pose the inverse problem of estimating the seafloor parameters from realistic noisy data sets with finite sampling and beamwidth and we solve this inverse problem by an iterative linearized least squares method the inversion method is applied to sea beam transit data from both the pacific and atlantic oceans sea beam system noise stands out as a sharp spike on the along track autocovariance function and can be modeled as a white noise process whose amplitude generally increases with beam angle the five parameters in our second order model can be estimated from the inversion of data sets comprising 100 200 km of track length in general the cross track wave number is the most poorly determined although uncertainties in the assumed sea beam response may bias the values of the fractal dimension using the assumed beamwidth the measured noise values and the seafloor parameters recovered from the inversion we generate sea beam synthetics whose statistical character can be directly compared with raw sea beam data for most of the track segments we have processed thus far the synthetics are similar to the data in the case of one atlantic profile however the comparison clearly indicates the necessity of incorporating higher order statistics the space domain procedures described in this paper can be extended for this purpose

topography of the northern hemisphere of mercury from messenger laser altimetry laser altimetry by the messenger spacecraft has yielded a topographic model of the northern hemisphere of mercury the dynamic range of elevations is considerably smaller than those of mars or the moon the most prominent feature is an extensive lowland at high northern latitudes that hosts the volcanic northern plains within this lowland is a broad topographic rise that experienced uplift after plains emplacement the interior of the 1500 km diameter caloris impact basin has been modified so that part of the basin floor now stands higher than the rim the elevated portion of the floor of caloris appears to be part of a quasi linear rise that extends for approximately half the planetary circumference at mid latitudes collectively these features imply that long wavelength changes to mercury s topography occurred after the earliest phases of the planet s geological history

no fes layer in mercury evidence from ti al measured by messenger abstract in this study we investigate the likeliness of the existence of an iron sulfide layer fes matte at the core mantle boundary cmb of mercury by comparing new chemical surface data obtained by the x ray spectrometer onboard the messenger spacecraft with geochemical models supported by high pressure experiments under reducing conditions we present a new data set consisting of 233 ti si measurements which combined with al si data show that mercury s surface has a slightly subchondritic ti al ratio of 0 035 0 008 multiphase equilibria experiments show that at the conditions of mercury s core formation ti is chalcophile but not siderophile making ti a useful tracer of sulfide melt formation we parameterize and use our partitioning data in a model to calculate the relative depletion of ti in the bulk silicate fraction of mercury as a function of a putative fes layer thickness by comparing the model results and surface elemental data we show that mercury most likely does not have a fes layer and in case it would have one it would only be a few kilometers thick 13 km we also show that mercury s metallic fe si core cannot contain more than 1 5 wt sulfur and that the formation of this core under reducing conditions is responsible for the slightly subchondritic ti al ratio of mercury s surface

curie temperature depth estimation using a self similar magnetization model summary the earth s crust is magnetized down to the curie temperature depth at about 10 to 50 km this limited depth extent of the crustal magnetization is discernible in the power spectra of magnetic maps of south africa and central asia at short wavelengths the power increases as rapidly towards longer wavelengths as expected for a self similar magnetized crust with unlimited depth extent above wavelengths of about 100 km the power starts increasing less rapidly indicating the absence of deep seated sources to quantify this effect we derive the theoretical power spectrum due to a slab carved out of a self similar magnetization distribution this model power spectrum matches the power spectra of south africa and central asia for a self similarity parameter of 4 and curie temperature depths of 15 to 20 km

gravity field and internal structure of mercury from messenger radio tracking of the messenger spacecraft has provided a model of mercury s gravity field in the northern hemisphere several large gravity anomalies including candidate mass concentrations mascons exceed 100 milli galileos mgal mercury s northern hemisphere crust is thicker at low latitudes and thinner in the polar region and shows evidence for thinning beneath some impact basins the low degree gravity field combined with planetary spin parameters yields the moment of inertia c mr2 0 353 0 017 where m and r are mercury s mass and radius and a ratio of the moment of inertia of mercury s solid outer shell to that of the planet of cm c 0 452 0 035 a model for mercury s radial density distribution consistent with these results includes a solid silicate crust and mantle overlying a solid iron sulfide layer and an iron rich liquid outer core and perhaps a solid inner core

mars high resolution gravity fields from mro mars seasonal gravity and other dynamical parameters abstract with 2 years of tracking data collection from the mro spacecraft there is noticeable improvement in the high frequency portion of the spherical harmonic mars gravity field the new jpl mars gravity fields mro110b and mro110b2 show resolution near degree 90 additional years of mgs and mars odyssey tracking data result in improvement for the seasonal j 3 gravity changes which compares well to global circulation models and odyssey neutron data and mars rotation and precession 7594 10 mas year once atmospheric dust is accounted for in the spacecraft solar pressure model solutions for mars solar tide are consistent between data sets and show slightly larger values k2 0 164 0 009 after correction for atmospheric tide compared to previous results further constraining core models an additional 4 years of mars range data improves the mars ephemeris determines 21 asteroid masses and bounds solar mass loss dgmsun dt

thermal evolution of mercury as constrained by messenger observations 1 orbital observations of mercury by the mercury surface space environment geochemistry and ranging messenger spacecraft provide new constraints on that planet s thermal and interior evolution specifically messenger observations have constrained the rate of radiogenic heat production via measurement of uranium thorium and potassium at the surface and identified a range of surface compositions consistent with high temperature high degree partial melts of the mantle additionally messenger data have placed new limits on the spatial and temporal variation in volcanic and tectonic activity and enabled determination that the planet s core is larger than previously estimated because mercury s mantle layer is also thinner than previously thought this result gives greater likelihood to the possibility that mantle convection is marginally supercritical or even that the mantle is not convecting we simulate mantle convection and magma generation within mercury s mantle under two dimensional axisymmetry and a broad range of conditions to understand the implications of messenger observations for the thermal evolution of the planet these models demonstrate that mantle convection can persist in such a thin mantle for a substantial portion of mercury s history and often to the present as long as the mantle is thicker than 300 km we also find that magma generation in mercury s convecting mantle is capable of producing widespread magmas by large degree partial melting consistent with messenger observations of the planet s surface chemistry and geology