clustered impacts experiments and implications impact by clusters of projectiles rather than a single projectile can result from several processes atmospheric breakup tidal breakup and ejecta from a large primary impact experiments have been performed in order to establish the characteristics of such events over a wide range of impact velocities 15 m s to 6 km s at very low impact velocities 15 200 m s clustered impacts were produced by launching a grouped projectiles of aluminum shot steel shot iron filings and sand at moderate to high velocities 0 8 6 km s pyrex spheres were shattered above the target during passage through aluminum foil or paper thereby forming a well defined cluster of fragments of overall radius rc the ratio of the overall radius rc of the cluster to the radius rs of a solid impactor of the same mass provides a measure of the cluster dispersion sand and compacted pumice targets were used in order to compare qualitatively the additional effect of slight differences in target strength the experiments reveal marked contrasts between impacts by clusters of projectiles and impacts by a single solid body tight clusters rc rs 20 displace a factor of 10 less mass this reduction in cratering efficiency is largely expressed as a shallow crater with an aspect ratio diameter depth as large as 30 for open clusters the size and velocity of the cluster as well as the density and strength contrast between the impactor and target can dramatically affect crater morphology open clusters impacting compacted pumice produce a flat hummocky floor with an incipient multiring pattern whereas a tight cluster impacting the same target produces a central floor mound oblique impacts by symmetrical clusters form a characteristic array of v shaped ridges pointing uprange the apex angle of the ridges depends on the cluster dispersion and impact angle inventories of postimpact projectile material reveal that the projectile is largely retained on the surface and spread downrange from the impact direction the amount of projectile material retained on the surfaces increases with decreasing impact angle from the horizontal and with increasing strength of the target relative to the projectile clustered impact craters and lunar secondary craters bear striking similarities over a broad range of morphologic features on this basis and on the basis of reasonable models of ejecta curtain structure we suggest that these experiments provide new clues for understanding ejecta emplacement around large lunar impact craters when the ejecta curtain around large impacts is viewed as a thick wall of debris and clustered impactors are viewed as a unit section of such a curtain then experimental results indicate that the continuous ejecta facies even for lunar craters larger than 100 km could contain as much as 90 primary material such a conclusion contrasts with many existing models that derive mixing ratios implicitly based on single noninteracting impact events beyond the continuous ejecta facies impacting clusters of ejecta provide a physical basis for understanding the wide variety of secondary morphologies and the large range in spectral signatures of primary material in crater rays

geology and petrology of enormous volumes of impact melt on the moon a case study of the orientale basin impact melt sea abstract lunar basin forming impacts produce enormous volumes 10 5 km 3 of impact melt all known basin forming impacts combined may produce 10 8 km 3 of impact melt 1 20th the volume of the lunar crust despite their volumetric importance the geology and petrology of massive deposits of impact melt on the moon have been little studied in part because most basin impact melt deposits are old and have been obscured or buried by subsequent impact cratering and mare infill we investigate the geology and model the petrology of fresh massive impact melt deposits in the relatively young 930 km diameter orientale basin models of impact melt production combined with geologic analyses based on new lola topographic data suggest that most of the impact melt 2 3 produced by the orientale forming impact occurs in a 15 km thick impact melt sheet better described as an impact melt sea 350 km in diameter with a volume of 10 6 km 3 we anticipate that the orientale melt sea has undergone large scale igneous differentiation since terrestrial impact melt sheets such as manicouagan sudbury and morokweng less than a tenth of the thickness and a hundredth of the volume of the orientale melt sea have differentiated we develop a model for the cumulate stratigraphy of the solidified orientale impact melt sea a modeled cumulate stratigraphy occurring below a quench crust and anorthositic fallback breccia with an 8 km thick layer of norite overlying a 4 km layer of pyroxenite and a basal 2 km thick layer of dunite produced by equilibrium crystallization of a homogenized melt sea consistent with vigorous convection in that melt sea is supported by remotely sensed norite excavated by the central peak of maunder crater from 4 km depth generally we predict that very large basin forming impacts including the south pole aitken spa basin forming impact produce melt seas with a cumulate stratigraphy similar to that of the orientale melt sea impact melt differentiation may explain apparently anomalous lithologies excavated in the spa basin interior we note that impact melt differentiates are slow cooled the orientale melt sea took on the order of 10 5 years to solidify and if meteoritic siderophiles fractionate into metal or sulfide layers may not be siderophile enriched therefore impact melt differentiates may pass for pristine highland plutonic rocks in the lunar sample suite these predictions can be tested with current and future mission data

is the martian crust also the martian elastic lithosphere 1 correlations between topography gravity and areoid on mars are used to constrain the crustal and lithospheric thicknesses on the planet assuming that the hellas basin is in isostatic equilibrium with airy compensation point correlations between areoid anomalies and topography are used to obtain the mean crustal density and the crustal thickness we find that the crustal thickness at the reference zero elevation is 90 10 km we also find that the mean crustal density is 2960 50 kg m 3 we have also used several approaches to constrain the thickness of the elastic lithosphere using the spherical harmonic coefficients of the gravity potential and topography as a function of degrees a relatively weak constraint on the globally averaged thickness of the elastic lithosphere is obtained an improved constraint is obtained using wavelet transform analyses of great circle tracks of gravity and topography the gravity topography admittance as a function of wavelet wavelength constrains the globally averaged thickness of the elastic lithosphere to be in the range 90 10 km the observation that the mean thicknesses of the crust and elastic lithosphere are likely to be equal suggests that a rheologically tougher crust is the elastic lithosphere

new views of lunar geoscience an introduction and overview beyond the earth the moon is the only planetary body for which we have samples from known locations the analysis of these samples gives us ground truth for numerous remote sensing studies of the physical and chemical properties of the moon and they are invaluable for our fundamental understanding of lunar origin and evolution prior to the return of the apollo 11 samples the moon was thought by many to be a primitive undifferentiated body e g urey 1966 a concept shattered by the data returned from the apollo and luna missions ever since new data have helped to address some of our questions but of course they also produced new questions in this chapter we provide a summary of knowledge about lunar geologic processes and we describe major scientific advancements of the last decade that are mainly related to the most recent lunar missions such as galileo clementine and lunar prospector 1 1 the moon in the planetary context compared to terrestrial planets the moon is unique in terms of its bulk density its size and its origin fig 1 1a c all of which have profound effects on its thermal evolution and the formation of a secondary crust fig 1 1d numerous planetary scientists considered the moon as an endmember among the planetary bodies in our solar system because its lithosphere has been relatively cool rigid and intact throughout most of geological time a one plate planet and its surface has not been affected by plate recycling an atmosphere water or life therefore the moon recorded and preserved evidence for geologic processes that were active over the last 4 4 5 b y and offers us the unique opportunity to look back into geologic times for which evidence on earth has long been erased fig 1 1c d impact cratering an exterior process is considered the most important surface process on the moon internal

influence of surrounding environment on subcritical crack growth in marble abstract understanding subcritical crack growth in rock is essential for determining appropriate measures to ensure the long term integrity of rock masses surrounding structures and for construction from rock material in this study subcritical crack growth in marble was investigated experimentally focusing on the influence of the surrounding environment on the relationship between the crack velocity and stress intensity factor the crack velocity increased with increasing temperature and or relative humidity in all cases the crack velocity increased with increasing stress intensity factor however for carrara marble cm in air we observed a region in which the crack velocity still increased with temperature but the increase in the crack velocity with increasing stress intensity factor was not significant this is similar to region ii of subcritical crack growth observed in glass in air region ii in glass is controlled by mass transport to the crack tip in the case of rock the transport of water to the crack tip is important in general region ii is not observed for subcritical crack growth in rock materials because rocks contain water because the porosity of cm is very low the amount of water contained in the marble is also very small therefore our results imply that we observed region ii in cm because the crack velocity increased in both water and air with increasing temperature and humidity we concluded that dry conditions at low temperature are desirable for the long term integrity of a carbonate rock mass additionally mass transport to the crack tip is an important process for subcritical crack growth in rock with low porosity

mars hellas planitia gravity analysis doppler radio tracking data from viking orbiter 1 has provided new detailed observations of gravity variations over hellas planitia line of sight bouguer gravity definitely indicates that isostatic adjustment has occurred two theoretical models were tested to obtain fits to the gravity data results for a surface deficit model and a model with a surface deficit and a mass excess at depth are displayed the mass at depth model produced very marked improvement in the data fit as compared to the surface deficit model the optimum depth for the mass excess is 130 km

subcritical crack growth and other time and environment dependent behavior in crustal rocks stable crack growth strongly influences both the fracture strength of brittle rocks and some of the phenomena precursory to catastrophic failure quantification of the time and environment dependence of fracture propagation is attempted with the use of a fracture mechanics technique we examine some of the difficulties encountered when applying techniques originally developed for simple synthetic materials to complex materials like rocks a picture of subcritical fracture propagation is developed that embraces the essential ingredients of the microstructure a microcrack process zone and the different roles that the environment plays to do this we examine the results of 1 fracture mechanics experiments on five rock types 2 optical and scanning electron microscopy 3 studies of microstructural aspects of fracture in ceramics and 4 exploratory tests examining the time dependent response of rock to the application of water

heterogeneities in the thickness of the elastic lithosphere of mars constraints on heat flow and internal dynamics derived values of the thickness of the effective elastic lithosphere on mars are converted to estimates of lithospheric thermal gradients and surface heat flow by finding the thickness of the elastic plastic plate having the same bending moment and curvature subject to assumed strain rates and temperature dependent flow laws for crustal and mantle material local thermal gradients and heat flow values so estimated were 10 14 k km 1 and 25 35 mw m 2 respectively at the time of formation of flexurally induced graben surrounding the tharsis montes and alba patera while gradients and heat flow values of less than 5 6 k km 1 and 17 24 mw m 2 respectively characterized the lithosphere beneath the isidis mascon and olympus mons at the time of emplacement of these loads on the basis of the mean global thickness of the elastic lithosphere inferred to support the tharsis rise and estimates of mantle heat production obtained from snc meteorites it is suggested that the present average global heat flux on mars is in the range 15 25 mw m 2 approximately 3 5 of this heat flux during the amazonian epoch has been contributed by excess conducted heat in the central regions of major volcanic provinces most likely this excess heat flux has been delivered to the base of the lithosphere by mantle plumes the fractional mantle heat transport contributed by plumes during the last 2 b y on mars is therefore similar to that at present on earth

a partially molten magma ocean model the properties of the lunar crust and upper mantle can be explained if the outer 300 400 km of the moon was initially only partially molten rather than fully molten the top of the partially molten region contained about 20 melt and decreased to 0 at 300 400 km depth nuclei of anorthositic crust formed over localized bodies of magma segregated from the partial melt then grew peripherally until they covered the moon throughout most of its growth period the anorthosite crust floated on a layer of magma a few km thick the thickness of this layer is regulated by the opposing forces of loss of material by fractional crystallization and addition of magma from the partial melt below concentrations of sr eu and sm in pristine ferroan anorthosites are found to be consistent with this model as are trends for the ferroan anorthosites and mg rich suites on a diagram of an in plagioclase vs mg in mafics clustering of eu sr and mg values found among pristine ferroan anorthosites are predicted by this model

scaling impact melting and crater dimensions implications for the lunar cratering record abstract the dimensions of large craters formed by impact are controlled to a large extent by gravity whereas the volume of impact melt created during the same event is essentially independent of gravity this differential scaling fosters size dependent changes in the dynamics of impact crater and basin formation as well as in the final morphologies of the resulting structures a variety of such effects can be observed in the lunar cratering record and some predictions can be made on the basis of calculations of impact melting and crater dimensions among them are the following 1 as event magnitude increases the volume of melt created relative to that of the crater will grow and more will be retained inside the rim of the crater or basin 2 the depth of melting will exceed the depth of excavation at diameters that essentially coincide with both the inflection in the depth diameter trend and the simple to complex transition 3 the volume of melt will exceed that of the transient cavity at a cavity diameter on the order of the diameter of the moon this would arguably correspond to a moon melting event 4 small lunar craters only rarely display exterior flows of impact melt because the relatively small volumes of melt created can become choked with clasts increasing the melt s viscosity and chilling it rapidly larger craters and basins should suffer little from such a process 5 deep melting near the projectile s axis of penetration during larger events will yield a progression in cen tral structure morphology with growing event magnitude this sequence should range from single peaks through multiple peaks to peak rings 6 the minimum depth of origin of central peak material should co incide with the maximum depth of melting the main central peak in a crater the size of tycho should have had a preimpact depth of close to 15 km

syrtis major and isidis basin contact morphological and topographic characteristics of syrtis major lava flows and material of the vastitas borealis formation received 18 october 2002 revised 10 march 2003 accepted 14 april 2003 published 28 june 2003 1 the floor of isidis basin is covered by materials of the vastitas borealis formation vbf that appear to be emplaced essentially as a single unit along its western boundary isidis basin is in contact with volcanic flows from syrtis major planum the contact between the isidis unit and volcanic flows from syrtis major is sharp to gradational and in places is characterized by a high 500 m scarp or by a network of faults that separate pieces of lava plains off the main plateau of syrtis clusters of knobs and mesas sometimes arranged in flow like features are also typical features of the transition zone several important characteristics of the transition from syrtis major to isidis basin are documented 1 the small scale surface texture seen in moc images appears to be the same for both the syrtis lava plateau and the knobs and mesas that characterize the transition 2 there is strong evidence for the breakup of the coherent surface of syrtis major where it is in contact with materials in isidis basin 3 the plateau breakup the knobby terrain occurs basinward after the major break of slope of syrtis major where it enters the isidis basin 4 there is no evidence for plateau breakup anywhere up on the slopes of syrtis major planum 5 the lavas of syrtis remain morphologically intact where they are in contact with other units such as the noachian cratered terrain or where lava flows are stacked within syrtis major itself these characteristic features of the transition zone from syrtis to isidis are readily explained if the zone of plateau breakup consists of relatively young lava flows that have been superimposed onto the surface of a volatile rich substratum such as the interior unit of isidis basin the vastitas borealis formation thus simple superposition of volcanic materials on top of volatile bearing sediments can explain the key geological and topographic aspects of the transition zone from syrtis major to isidis basin on the basis of our findings we outline the following scenario for the evolution of this region in the early hesperian volcanic plains are emplaced in syrtis major the lower part of the syrtis major formation and wrinkle ridges deform their surfaces soon thereafter concurrently volcanic plains are emplaced on the floor of the isidis basin and wrinkle ridges deform their surfaces soon thereafter the apparent simultaneity of these units may mean that syrtis major was the source of many of the flows in the isidis basin in the early part of the upper hesperian subsequent to the formation of most of the wrinkle ridges the vastitas borealis formation was emplaced in the isidis basin and elsewhere in the northern lowlands following the emplacement of the vastitas borealis formation the upper part of the syrtis major formation was emplaced erupting from the eastern margins of syrtis major planum and flowing down into the westernmost part of the isidis basin on top of the recently emplaced vastitas borealis formation modification of the superposed lavas by degradation and evolution of the vbf formed the scarps and unusual morphology of the marginal areas we found no compelling evidence for massive or sudden erosion from syrtis major to produce the plains currently on the surface of the floor of the isidis basin the vastitas borealis

the shallow structure of the martian lithosphere in the vicinity of the ridged plains wrinkle ridges in the smooth plains of the coprates and lunae planum regions of mars form linear or concentric patterns with a regular spacing of 25 50 km the authors test the hypothesis that the periodic development of deformation was a consequence of unstable horizontal compression that occurred prior to probable ridge related faulting of a strength stratified lithosphere which consists of a mechanically strong surface plains unit that successively overlies a weak megaregolith and a strong lithospheric basement results show that a range of models with both rigid and deformable megaregolith basement interface conditions yield solutions which can explain the ridge spacing within the constraint provided by the estimated thickness of the smooth plains materials in models that incorporate viscous and plastic rheologies uniform and exponentially varying vertical strength distributions and the presence or absence of interfacial slip at the base of the surface plains unit the ridge spacing is primarily controlled by the power law exponent of the lithosphere the megaregolith plains unit thickness ratio and the plains unit megaregolith strength contrast deformable basement models with a viscous rheology 1 le n approx le 3 can explain the ridge spacing if the megaregolith was thicker than and approximately 1 3 orders of magnitude weaker than themore plains unit similar models with a perfectly plastic n yields infinity rheology require plains unit thicknesses greater than 5 km which exceeds most observational estimates ridge spacing in the combined viscous and plastic models can be consistent with either a dry water rich or ice rich megaregolith at the time of ridge formation less

thickness of the martian crust improved constraints from geoid to topography ratios 1 the average crustal thickness of the southern highlands of mars was investigated by calculating geoid to topography ratios gtrs and interpreting these in terms of an airy compensation model appropriate for a spherical planet we show that 1 if gtrs were interpreted in terms of a cartesian model the recovered crustal thickness would be underestimated by a few tens of kilometers and 2 the global geoid and topography signals associated with the loading and flexure of the tharsis province must be removed before undertaking such a spatial analysis assuming a conservative range of crustal densities 2700 3100 kg m 3 we constrain the average thickness of the martian crust to lie between 33 and 81 km or 57 24 km when combined with complementary estimates based on crustal thickness modeling gravity topography admittance modeling viscous relaxation considerations and geochemical mass balance modeling we find that a crustal thickness between 38 and 62 km or 50 12 km is consistent with all studies isotopic investigations based on hf w and sm nd systematics suggest that mars underwent a major silicate differentiation event early in its evolution within the first 30 ma that gave rise to an enriched crust that has since remained isotopically isolated from the depleted mantle in comparing estimates of the thickness of this primordial crust with those obtained in this study we find that at least one third of the martian crust has an origin dating from the time of accretion and primary differentiation subsequent partial melting of the depleted mantle would have given rise to the remaining portion of the crust while we predict that a large portion of the crust should be composed of ancient enriched materials a representative sample of this primordial crust does not currently exist among the known martian meteorites index terms 6225 planetology solar system objects mars 5417 planetology solid surface planets gravitational fields 1227 5430 planetology solid surface planets interiors 8147 1227 geodesy and gravity planetary geodesy and gravity 5420 5714 6019 keywords mars crustal thickness crustal evolution geoid topography

density profile of an snc model martian interior and the moment of inertia factor of mars the density profile of an snc model martian interior is calculated from the results of previous experimental work that determined the modal mineralogy of the model mantle up to martian core mantle boundary pressures the moment of inertia factor of mars is calculated as a function of core composition and crustal thickness using the snc model mantle density profile as a constraint two sets of calculations are performed in the first the bulk composition of the planet is not constrained to a c1 chondrite composition assuming a martian crust density of 2 7 3 0 g cm3 a crust thickness of 25 150 km and the core composition proposed by dreibus and wanke fe 14 wt s the calculated moment of inertia factor ranges from 0 367 to 0 357 these models include a perovskite bearing zone in the martian interior considering core compositions ranging from pure fe to pure fes changes the moment of inertia factor by only 0 001 but at higher s abundances core size increases such that the depth of the core mantle boundary is shallower than the depth of perovskite stability in the second set of calculations the bulk composition of the planet is constrained to a c1 composition requiring a crust thickness of 180 320 km assuming a crust density of 2 7 3 0 g cm3 the calculated moment of inertia factor is 0 354 and a perovskite bearing layer is absent from the martian interior as it is unlikely that the thickness of the martian crust is greater than 100 km the bulk composition of mars cannot be constrained to a c1 chondrite composition as proposed by the dreibus and wanke model g dreibus h wanke meteoritics 20 1985 367 382 in order to determine if the martian mantle is more iron rich than the earth s mantle we may need not only an improved estimate of the moment of inertia factor of mars but also tighter constraints on martian crust thickness and density the absolute degree of iron enrichment however cannot be specified without also knowing the size of the martian core a moment of inertia factor of less than 0 342 is not geochemically feasible because it requires that the mantle of mars contains no iron

visible infrared spectral properties of iron bearing aluminate spinel under lunar like redox conditions remote sensing observations have identified aluminate spinel in the absence of measureable olivine and pyroxene as a globally distributed component of the lunar crust earlier remote sensing observations and returned samples did not indicate the presence of this component leaving its geologic significance unclear here we report visible to mid infrared v ir reflectance 300 25 000 nm and mossbauer spectra of aluminate spinels synthesized at lunar like oxygen fugacity o2 that vary systematically in fe abundance reflectance spectra of particulate 6 fe although the 2000 and 2800 nm bands are assigned to fe 2 iv electronic transitions spectra of aluminate spinels with excess al2o3 demonstrate that the strengths of the 1000 nm bands are related to the abundance of fe 2 vi the abundance of fe 2 vi depends on bulk fe content as well as factors that control the degree of structural order disorder such as cooling rate consequently the strength of the 1000 nm bands are useful for constraining the fe content and cooling rate of remotely sensed spinel controlling for cooling rate particle size and o2 we conclude that spinels with 12 fe 88 mg have observable 1000 nm bands under ambient lunar conditions and that only very mg rich spinels lack 1000 nm bands in their spectra this links remote observations of spinel anorthosite to mg suite magmatism the combined effects of fe oxidation state abundance of coexisting plagioclase and space weathering have not been explored here and may add additional constraints the relative strengths of the distinctive 1000 and 2000 nm bands of the spinels associated with pyroclastic deposits at sinus aestuum suggest fast cooling rates possibly in the absence of an extensive vapor cloud

unique spinel rich lithology in lunar meteorite alha 81005 origin and possible connection to m3 observations of the farside highlands 1 a new lunar rock type rich in mg fe al spinel and lacking abundant olivine and pyroxene was recently detected by near infrared reflectance spectroscopy by the m3 instrument on the chandrayaan 1 spacecraft no such material has been described from lunar rocks either returned samples or meteorites here we describe a fragment of rock containing 30 mg fe al spinel from the lunar meteorite alha 81005 although the fragment is not identical to the material detected by m3 it contains 20 olivine pyroxene both share the defining feature of an unusual enrichment in spinel the fragment 350 150 m is so fine grained that it reasonably could represent a larger rock body it is not spinel rich merely by chance incorporation of a few spinel grains the fragment is so rich in spinel and consequently in al2o3 that it could not have formed by melting a peridotitic mantle or a basaltic lunar crust the clast s small grain size and its apparent disequilibrium between spinel and pyroxene suggest fairly rapid crystallization at low pressure it could have formed as a spinel cumulate from an impact melt of troctolitic composition or from a picritic magma body that assimilated crustal anorthosite on its margins the latter mechanism is preferred because it not only explains the petrographic and chemical features of our clast but is also consistent with the regional setting of the moscoviense spinel deposit in that area m3 spectra have defined areas rich in olivine and in orthopyroxene these could represent igneous cumulate rocks formed during crystallization and differentiation of a picritic magma body and thus suggests a possible link between the analyzed clast and the observed spinels at moscoviense

a visible and near infrared photometric correction for moon mineralogy mapper m 3 observations of the moon obtained by the moon mineralogy mapper m 3 instrument were acquired at various local viewing geometries to compensate for this a visible near infrared photometric correction for the m 3 observations of the lunar surface has been derived images are corrected to the standard geometry of 30 phase angle with an incidence of 30 and an emission of 0 the photometric correction is optimized for highland materials but is also a good approximation for mare deposits the results are compared with ground based observations of the lunar surface to validate the absolute reflectance of the m 3 observations this photometric model has been used to produce the v1 0 level 2 delivery of the

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

projectile remnants in central peaks of lunar impact craters unusual minerals observed in lunar craters were thought to originate from beneath the moon s surface numerical simulations show that rather than being vaporized much of the impactor material can survive in the crater implying that the unusual minerals come from the impactor and may not be indigenous to the moon

hansteen alpha a volcanic construct in the lunar highlands 1 we have used data from the clementine and lunar prospector spacecraft in conjunction with near ir reflectance spectra collected with earth based telescopes to study the composition and origin of hansteen alpha an arrowhead shaped highlands feature located on the southern margin of oceanus procellarum hansteen alpha is a member of a class of lunar spectral anomalies red spots that are characterized by a relatively high albedo and a strong absorption in the uv it has been suggested that at least some of these spectral anomalies were produced by nonmare volcanism the stratigraphic relationships among the geologic and compositional units in the region show that hansteen alpha was emplaced by extrusive igneous processes the imbrian aged craters hansteen and billy emplaced relatively feo and tio2 rich ejecta hansteen alpha exhibits much lower feo and tio2 values if hansteen alpha was present prior to the billy and hansteen impact events it should have been covered with feo and tio2 rich ejecta because it is located within one crater diameter of the rim crest of each crater since it is not hansteen alpha was superposed on these ejecta units nonmare volcanism is the only viable process for the formation of hansteen alpha the morphology and surface texture of hansteen alpha is similar to many terrestrial features of dacitic and rhyolitic composition formed by extrusions of relatively viscous lavas such highly evolved compositions should be very enriched in th but hansteen alpha exhibits th abundances of 6 ppm hence hansteen alpha is not composed of a highly evolved highlands lithology

a new survey of multiring impact basins on mars multiring impact basins have profoundly influenced the geologic evolution of mars we compile and summarize the evidence for martian impact basins and suggest eight new examples multiring basins on mars define three morphologic subclasses with increasing basin size basins having diameters 300 3600 km have extremely shallow topographic profiles and numerous concentric structures expressed as scarps massifs and channels radial and concentric structures analogous to those associated with orientale are not apparent for basins of argyre size or larger these variations in basin morphology and structure may be associated with mechanical interactions between basin forming impacts relatively thin weak lithosphere and for the largest impacts spherical target geometry multiring basins are recognized on all parts of mars including tharsis elysium and the northern lowlands much of the subsequent resurfacing of cratered terrain such as lunae planum ridged plains is associated spatially with multiring basins nucleation of long lived volcanic complexes in tharsis and elysium was probably aided by early impact basins the planetary terrain dichotomy was probably established during the period of heavy meteoritic bombardment and subsequent processes in the northern plains region were not sufficiently vigorous to destroy or completely obscure the underlying multiring basin fabric the revised population of multiring basins is consistent with the size frequency distribution of craters 500 km in diameter on mars basins having diameters 500 d 1850 km are characterized by a cumulative frequency slope of 0 75 0 16 whereas the larger basins define a slope of 1 7 0 45 this change in slope occurs over the same diameter range as the significant change from orientale type basin morphology at smaller diameters to argyre and chryse type basin morphology the population of craters and basins on mars confirms that the relative crater densities on the terrestrial planets due to heavy bombardment are comparable perhaps suggesting a common source for the impacting objects

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

strength of martian lithosphere beneath large volcanoes this paper provides an estimate of the thermal state of martian lithosphere established since the formation of the shield volcanoes comparison of the spherical harmonic models of martian topography derived using harmonics truncated at degrees 10 11 12 and 14 shows that the volcanoes have almost no contribution from harmonic coefficients of the topography less than degree 11 therefore intermediate scale surface topography and gravity anomalies of mars specified by harmonics of degree 11 50 are considered in this study these harmonics are dominated by shield volcanoes alba patera and isidis basin the central part of valles marineris is also well defined by these harmonics the strong correlation of the topography and gravity anomalies over these harmonics and the positive bouguer anomalies of the volcanoes suggest significant excess masses beneath these surface features in addition to their topographic masses this indicates that the martian lithosphere has been strong enough to support both the topography and the internal excess masses we determine the rigidity of the lithosphere beneath a given surface feature the lithosphere is modeled by a thin elastic spherical shell that overlies an inviscid interior of higher density and is subjected to both surface and internal loads the thickness of the shell and the magnitude of the internal load are calculated such that the deformed structure resulting from the flexure of the shell under both surface and internal loads gives rise to the observed topography and gravity anomaly it is shown that the lithosphere beneath elysium mons alba patera and the central part of valles marineris can be modeled by elastic shells subjected to topographic loads alone whereas the lithosphere beneath olympus and tharsis montes cannot internal excess masses of at least 40 and more likely 50 of the topographic masses are required and the lithosphere beneath must have an elastic core of 100 80 km to support these volcanoes the mean thermal gradient beneath this region of tharsis is estimated to be 7 10 k km on the basis of the strength envelopes calculated using diabase rheology for the crust of 50 km thickness and olivine rheology for the underlying mantle

the evolution of elastic moduli with increasing crack damage during cyclic stressing of a basalt from mt etna volcano article i nfo volcanic edifices such as mt etna italy are commonly subject to repeated cycles of stress over time due to the combination of magma emplacement from deep reservoirs to shallow depths and superimposed tectonic stresses such repeated stress cycles lead to anisotropic deformation and an increase in the level of crack damage within the rocks of the edifice and hence changes to their elastic moduli which are a key parameter for reliable modelling of deformation sources we therefore report results of changes in elastic moduli measured during increasing amplitude cyclic stressing experiments on dry and water saturated samples of etna basalt in all experiments the young s modulus decreased by approximately 30 over the total sequence of loading cycles and the poisson s ratio increased by a factor of approximately 3 0 5 microseismicity in terms of acoustic emission ae output was also recorded throughout each experiment our results demonstrate that ae output only re commences during any loading cycle when the level of stress where ae ceased during the unloading portion of the previous cycle is exceeded a manifestation of the kaiser stress memory effect in cycles where no ae output was generated we also observed no change in elastic moduli this result holds for both mechanical and thermal stressing our results are interpreted in relation to measurements of volcano tectonic seismicity and deformation at mt etna volcano

estimates of martian crustal thickness from viscous relaxation of topography isostatically compensated crustal thickness variations and associated topographic contrasts at the surface of a planet result in lateral pressure gradients which may cause the lower crust to flow and reduce the relief areas of thicker crust are generally associated with more rapid relaxation of topography on mars topographic features such as impact basins and the hemispheric dichotomy have survived for 4 gyr we use a finite difference representation of depth dependent non newtonian lower crustal flow to investigate how topography decays with time for a dry diabase rheology total radiogenic concentrations 80 of terrestrial values and crustal radiogenic concentrations similar to terrestrial basalts we find that an upper bound on the mean planetary crustal thickness is 100 km in the probably unrealistic case where all the radiogenic elements are in the crust this maximum crustal thickness can be increased to 115 km the main uncertainty in these results is the total radiogenic abundances on mars comparing our results with the observed shape of the crustal dichotomy provides no evidence that this slope is primarily the result of lower crustal flow both hellas and the dichotomy are isostatically compensated if the mechanism is airy isostasy then the lower bound on mean crustal thickness is 30 km crustal thicknesses of 30 100 km on mars can be produced by mid ocean ridge spreading at potential temperatures of 1350 1600 c however for such crustal thicknesses the lithosphere is likely to be positively buoyant making subduction difficult

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

mechanisms controlling rupture shape during subcritical growth of joints in layered rocks during joint propagation the orientation of plume lines on joint faces allows for mapping the path taken by the crack tip line during rupture growth rupture shapes in layered clastic sediments of the devonian catskill delta finger lakes district new york indicate joint growth through three stages where velocity of the tip line v tl varies as a function of the crack tip stress intensity k i the initial stage of growth is characterized by a rupture of approximately circular or elliptical shape that expands from an initiation fl aw with a velocity v tl in some cases primary growth involves self correction where an elliptical rupture redistributes the crack tip stress so that the rupture returns to a more stable circular shape the crack tip line eventually propagates to a bedding interface where properties of either a plastic or a noncohesive bedding interface cause v tl 0 along a portion of the tip line the onset of secondary growth occurs when the rupture tip line intersects both bedding interfaces and splits into two discontinuous segments that propagate synchronously as a single coherent rupture nonuniform nonsystematic v tl eventually interferes with the rupture s ability to grow coherently and thus leads to the transition to tertiary growth characterized by the detachment of the coherent rupture into one or more independently propagating noncoherent tip lines throughout all three stages of rupture growth the k i dependent v tl points to subcritical propagation variation from a smooth to rough plume morphology is consistent with propagation through region i of the subcritical regime with a transition at v tl 10 5 m sec rupture velocity may enter region ii of the subcritical regime but such a broad range of k i must be crossed to reach region iii and quasistatic behavior at the critical stress intensity k ic that region ii acts as a barrier through which few joints pass thus greatly limiting the number of postcritical joints in the catskill delta if not in the crust of the earth

effects of relative humidity and temperature on subcritical crack growth in igneous rock abstract effects of relative humidity and temperature on subcritical crack growth in igneous rock have been investigated experimentally on samples of kumamoto andesite and oshima granite stress intensity factors and crack velocities were measured using the double torsion technique and all experiments were conducted in moist air our results show that in experiments conducted under the same relative humidity crack velocity increased with increasing temperature in agreement with previous studies our results also show that in experiments conducted at the same temperature crack velocity increased dramatically with increasing relative humidity a three to fourfold increase in relative humidity resulted in an increase in crack velocity of between one and four orders of magnitude such an increase is larger than that predicted by classical stress corrosion theory it is suggested that capillary condensation of water vapour close to crack tips of small aperture influences the rate of crack growth it is concluded that relative humidity needs to be controlled to avoid time dependent weakening and extend the lifetime of structures in a rock mass

elastic and fracture parameters of etna stromboli and vulcano lava rocks abstract the results of a series of experiments aimed at characterizing the elastic and failure parameters of lava specimens from mount etna vulcano and stromboli volcanos is presented the double torsion constant configuration load relaxation method has been employed to obtain the behavior of the stress intensity factor versus mode i subcritical crack velocity the experimental technique has been optimized in several respects first a very stiff machine expressly designed and built has been used second all samples have been carefully machined to low tolerance third the experimental conditions have been carefully controlled with temperature variations within 1 c and humidity within 10 fourth high resolution electronic measuring systems have been used together with a pulse stacking procedure fifth the length of the prefracture has been optically checked this optimization allowed us to measure the slope of the subcritical fracture propagation curve in the iii region which extends from velocities of 10 7 m s to catastrophic with a standard deviation around 20 suggesting that the results can be effectively used for modeling purposes as a by product we could measure the elastic parameters with an accuracy of a few percent

magnesian anorthositic granulites in lunar meteorites allan hills a81005 and dhofar 309 geochemistry and global significance abstract fragments of magnesian anorthositic granulite are found in the lunar highlands meteorites allan hills alh a81005 and dhofar dho 309 five analyzed clasts of meteoritic magnesian anorthositic granulite have mg molar mg mg fe 81 87 feo 5 wt al2o3 22 wt rare earth elements abundances 0 5 2 ci except eu 10 ci and low ni and co in a non chondritic ratio the clasts have nearly identical chemical compositions even though their host meteorites formed at different places on the moon these magnesian anorthositic granulites are distinct from other highlands materials in their unique combination of mineral proportions mg ree abundances and patterns ti sm ratio and sc sm ratio their mg is too high for a close relationship to ferroan anorthosites or to have formed as flotation cumulates from the lunar magma ocean compositions of these magnesian anorthositic granulites cannot be modeled as mixtures of or fractionates from known lunar rocks however compositions of lunar highlands meteorites can be represented as mixtures of magnesian anorthositic granulite ferroan anorthosite mare basalt and kreep meteoritic magnesian anorthositic granulite is a good candidate for the magnesian highlands component inferred from apollo highland impactites magnesian feldspathic and ree poor bulk compositions of meteorite magnesian anorthositic granulites are comparable to those inferred for parts of the lunar farside the feldspathic highlands terrane 4 5 wt feo 28 wt al2o3 and th 1 ppm thus magnesian anorthositic granulite may be a widespread and abundant component of the lunar highlands

mg spinel lithology a new rock type on the lunar farside 1 high resolution compositional data from moon mineralogy mapper m3 for the moscoviense region on the lunar farside reveal three unusual but distinctive rock types along the inner basin ring these are designated oos since they are dominated by high concentrations of orthopyroxene olivine and mg rich spinel respectively the oos occur as small areas each a few kilometers in size that are widely separated within the highly feldspathic setting of the basin rim although the abundance of plagioclase is not well constrained within the oos the mafic mineral content is exceptionally high and two of the rock types could approach pyroxenite and harzburgite in composition the third is a new rock type identified on the moon that is dominated by mg rich spinel with no other mafic minerals detectable 5 pyroxene olivine all oos surfaces are old and undisturbed since basin formation they are effectively invisible in image data and are only recognized by their distinctive composition identified spectroscopically the origin of these unusual lithologies appears to be linked to one or more magmatic intrusions into the lower crust perhaps near the crust mantle interface processes such as fractional crystallization and gravity settling within such intrusions may provide a mechanism for concentrating the mafic components within zones several kilometers in dimension the oos are embedded within highly anorthositic material from the lunar crust they may thus be near contemporaneous with crustal products from the cooling magma ocean

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

meteorite and asteroid reflectance spectroscopy clues to early solar system processes although earth has a magnetic shield that protects it from energetic ions and a cushioning atmosphere that catches the tons of small particles i mm that bombard it daily solid material from extraterrestrial sources nevertheless reaches the surface of earth many times a year dodd 1 98 1 when the largest of these bodies impact the surface with great velocity they release immense energy usually form a crater and often disrupt the terrestrial biosphere fortunately such events occur relatively infrequently although individual impacts are currently unpredictable beyond a statistical accounting shoemaker et al 1979 grieve 1 982 cosmic material between the size of small dust particles and the larger crater forming bodies is slowed by the terrestrial atmosphere upon entry the outermost portion of these objects is melted and ablated during passage forming a fusion crust which protects the interior and they land

sequence and mechanisms of deformation around the hellas and isidis impact basins on mars the distribution and age of early volcanic and tectonic features surrounding the itellas and isidis impact basins are shown to fit a four stage sequence first concentric canyons form outside the basin boundary scarp at or near the time of basin formation followed shortly thereafter by radial troughs extending beyond the boundary scarp after a hiatus concentric graben develop inside the basin within the massif ring finally soon after graben formation widespread volcanic plains are emplaced between the massif ring and the boundary scarp to one side of the basin three models of basin centered deformation are compared io hese observed deformation events elastic flexure due to loading elastic flexure due to uplift and impact fracture a central load of basin fill can account for concentric fractures by elastic flexure around the load formation of the distant concentric canyons however requires lithospheric thicknesses a factor of 5 greater than those indicated by planetary thermal history models and an increase in feature width by an order of magnitude relative to flexural graben identified elsewhere on mars and the moon although inclusion of loading by basin ejecta reduces the required lithospheric thickness to acceptable values flexure still fails to account for the large canyon widths observed impact fracture from a rapid inward flow of asthenosphere during transient cavity collapse however is consistent with the three key observational constraints for the distant canyons their age width and distance from the basin as the basin then undergoes isostatic uplift soon after impact elastic flexure induces a radial pattern of failure consistent with the observed extent and timing of the radial troughs later after a long period of basin infilling elastic failure due to loading of the central basin region can account for the ring grabens in the massif ring the localization of volcanism into a single ridged plains unit on the basin rim indicates a thermal source offset from the basin which is not included in these models and perhaps reflects an additional mechanism unique to mars

mars gravity data analysis of the crater antoniadi topography and gravity information for this 370 km crater are analyzed to determine a depth of compensation using an airy isostatic model a least squares fit to the gravity profile produces an estimate of 115 km for the depth of compensation

secondary earthquake fractures generated by a strike slip fault in the south iceland seismic zone most large earthquakes in the south iceland seismic zone occur on n s trending dextral strike slip faults the resulting rupture zones display complex en echelon patterns of secondary structures including nne trending arrays of mostly ne trending open fractures and hillocks three spatial scales characterize the surface faulting pattern the length of the main fault mf 104 m the arrays of fractures here interpreted as surface evidence of subordinate faults sf 102 m and the individual open fractures of 10 m in order to improve our understanding of the genetic relationship between the of and the mf we computed the stress field induced by slip on a buried mf using a dislocation model in a layered half space where the fault surface is assumed to be embedded in the basement rock topped by a softer tens of meters thick near surface layer the of were modeled as secondary fractures of either of the following types 1 pure mode i cracks opening in the near surface layer in the direction of the tensile principal stress or 2 mixed mode cracks slipping at depth as shear cracks and opening near the surface due to low confining pressure assuming that both types of secondary fractures occur in the sisz we can explain their first order characteristics by reasoning that they are the end product of a hierarchy of deformation produced by the main fault the coulomb failure function after the earthquake obtained by summing the mf stress change and the lithostatic stress suggests that subordinate faulting sf must be expected to occur in response to the main rupture below the upper soft layer extending to a depth of 100 m the total stress change induced by the mf and the sf is shown to yield quantitative explanations of the spatial extent the double en echelon arrangement and the orientation of surface fractures observed in the field in terms of a simple frictional model of rupture

compositional diversity at theophilus crater understanding the geological context of mg spinel bearing central peaks 1 analysis of high resolution moon mineralogy mapper m3 data reveals the presence of a prominent mg spinel rich lithology in the central peaks of theophilus crater on the lunar nearside other peak associated lithologies are comprised of plagioclase olivine and pyroxene bearing materials a consistent spatial association of mg spinel with mafic free anorthosite is recognized documentation of theophilus central peaks brings the global inventory of mg spinel rich lithology to two widely separated occurrences namely theophilus on the lunar nearside and moscoviense basin on the farside the theophilus crater target region lies on one of the inner rings of the nectaris basin indicating that the mg spinel bearing lithology source was deep in the lunar 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

detection of mg spinel bearing central peaks using m 3 images implications for the petrogenesis of mg spinel abstract mg spinel bearing lithologies lacking abundant mafic materials have been discovered with images acquired by the moon mineralogy mapper m3 aboard chandrayaan 1 we conducted a systematic screening of lunar crater central peaks for the presence of mg spinel to address its distribution and petrogenesis 38 mg spinel bearing crater central peaks were identified in this study out of 166 craters investigated the results suggest that mg spinel is common in the lunar crust and appears to be extensive in the middle part of the lunar crust underneath procellarum kreep terrane pkt mg spinel neither exclusively originated from deep layers 10 km nor necessarily coexist with the appearance of olivine or pyroxene 15 mg spinel bearing central peaks originated from depth less than 10 km nine investigated central peaks only contain mg spinel and plagioclase without any detectable mafic materials all those observations imply that the origin of mg spinel is possibly related to mg suite plutonism and assimilation between high mg magma with anorthositic crust the extensive distribution and mg suite related petrogenesis indicates that mg spinel bearing lithologies might represent a new member of mg suite rocks

an inversion of gravity and topography for mantle and crustal structure on mars analysis of the gravity and topography of mars presently provides our primary quantitative constraints on the internal structure of mars we present an inversion of the long wavelength harmonic degree 10 gravity and topography of mars for lateral variations of mantle temperature and crustal thickness our formulation incorporates both viscous mantle flow which most prior studies have neglected and isostatically compensated density anomalies in the crust and lithosphere our nominal model has a 150 km thick high viscosity surface layer over an isoviscous mantle with a core radius of 1840 km it predicts lateral temperature variations of up to a few hundred degrees kelvin relative to the mean mantle temperature with high temperature under tharsis and to a lesser extent under elysium and cool temperatures elsewhere surprisingly the model predicts crustal thinning beneath tharsis if correct this implies that thinning of the crust by mantle shear stresses dominates over thickening of the crust by volcanism the major impact basins hellas argyre isidis chryse and utopia are regions of crustal thinning as expected utopia is also predicted to be a region of hot mantle which is hard to reconcile with the surface geology an alternative model for utopia treats it as a mascon basin the utopia gravity anomaly is consistent with the presence of a 1 2 to 1 6 km thick layer of uncompensated basalt in good agreement with geologic arguments about the amount of volcanic fill in this area the mantle thermal structure is the dominant contributor to the observed geoid in our inversion the mantle also dominates the topography at the longest wavelengths but shorter wavelengths harmonic degrees 4 are dominated by the crustal structure because of the uncertainty about the appropriate numerical values for some of the model s input parameters we have examined the sensitivity of the model results to the planetary structural model core radius and core and mantle densities the mantle s viscosity stratification and the mean crustal thickness the model results are insensitive to the specific thickness or viscosity contrast of the high viscosity surface layer and to the mean crustal thickness in the range 25 to 100 km models with a large core radius or with an upper mantle low viscosity zone require implausibly large lateral variations in mantle temperature

thermal weakening of the carbonate basement under mt etna volcano italy implications for volcano instability abstract the physical integrity of a sub volcanic basement is crucial in controlling the stability of a volcanic edifice for many volcanoes this basement can comprise thick sequences of carbonates that are prone to significant thermally induced alteration these debilitating thermal reactions facilitated by heat from proximal magma storage volumes promote the weakening of the rock mass and likely therefore encourage edifice instability such instability can result in slow gravitational spreading and episodic to continuous slippage of unstable flanks and may also facilitate catastrophic flank collapse understanding the propensity of a particular sub volcanic basement to such instability requires a detailed understanding of the influence of high temperatures on the chemical physical and mechanical properties of the rocks involved the juxtaposition of a thick carbonate substratum and magmatic heat sources makes mt etna volcano an ideal candidate for our study we investigated experimentally the effect of temperature on two carbonate rocks that have been chosen to represent the deep heterogeneous sedimentary substratum under mt etna volcano this study has demonstrated that thermal stressing resulted in a progressive and significant change in the physical properties of the two rocks porosity wet i e water saturated dynamic poisson s ratio and wet vp vs ratio all increased whilst p and s wave velocities bulk sample density dynamic and static young s modulus dry vp vs ratio and dry dynamic poisson s ratio all decreased at temperatures of 800 c the carbonate in these rocks completely dissociated resulting in a total mass loss of about 45 and the release of about 44 wt of co 2 uniaxial deformation experiments showed that high in situ temperatures 500 c significantly reduced the strength of the carbonates and altered their deformation behaviour above 500 c the rocks deformed in a ductile manner and the output of acoustic emissions was greatly reduced we speculate that thermally induced weakening and the ductile behaviour of the carbonate substratum could be a key factor in explaining the large scale deformation observed at mt etna volcano our findings are consistent with several field observations at mt etna volcano and can quantitatively support the interpretation of 1 the irregularly low seismic velocity zones present within the sub volcanic sedimentary basement 2 the anomalously high co 2 degassing observed 3 the anomalously high vp vs ratios and the rapid migration of fluids and 4 the increasing instability of volcanic edifices in the lifespan of a magmatic system we speculate that carbonate sub volcanic basement may emerge as one of the decisive fundamentals in controlling volcanic stability