lunar surface magnetic fields and their interaction with the solar wind results from lunar prospector the magnetometer and electron reflectometer experiment on the lunar prospector spacecraft has obtained maps of lunar crustal magnetic fields and observed the interaction between the solar wind and regions of strong crustal magnetic fields at high selenographic latitude 30 s to 80 s and low 100 kilometers altitude electron reflection maps of the regions antipodal to the imbrium and serenitatis impact basins extending to 80 s latitude show that crustal magnetic fields fill most of the antipodal zones of those basins this finding provides further evidence for the hypothesis that basin forming impacts result in magnetization of the lunar crust at their antipodes the crustal magnetic fields of the imbrium antipode region are strong enough to deflect the solar wind and form a miniature 100 to several hundred kilometers across magnetosphere magnetosheath and bow shock system

magnetic study of large apollo samples possible evidence for an ancient centered dipolar field on the moon abstract we present new rock magnetic and paleomagnetic results obtained from seventeen apollo samples measurements of the magnetic properties of the samples confirm that the magnetic properties of lunar rocks are dominated by about 0 1 wt of multidomain feni grains the ferromagnetic mineral assemblage is to the first order the same in all lunar lithologies with higher concentration in basalts than in anorthosites some of which are diamagnetic impact processing leads to an increase of the ferromagnetic content out of the seventeen samples eleven show at least one stable component of natural remanent magnetization in some cases this magnetization may be a magnetic contamination however five basalt samples have a component of magnetization that may have recorded a lunar paleofield acquired on the moon for these samples plus two similar samples from a previous study using the rock magnetic fabric as a paleohorizontal proxy paleoinclinations can be estimated from the paleomagnetic data these paleoinclinations are best explained with a dipolar field and a magnetic paleopole located at 75 n therefore our results suggest the existence on the moon at least between 3 8 and 3 3 ga of a dipolar field whose axis is close to the present day rotation axis of the moon the estimated surface field intensities of several tens of t support previous result that the moon had a dynamo field in the past and the proposed paleofield geometry suggests that this dynamo was centered on the lunar present day rotation axis

slip rate estimate and past earthquakes on the doruneh fault eastern iran summary the doruneh fault with a length of 600 km is one of the longest and most prominent faults in iran it performs an important role in the regional tectonics but has no record of large earthquakes the geomorphology of the doruneh fault contains numerous indications of cumulative left lateral slip over various scales we describe three sites where late quaternary landforms are displaced by the fault a an incised alluvial fan near the village of uch palang is displaced by 800 850 m b the kuh e teagh ahmad fold is composed of folded quaternary gravels and is displaced by 200 400 m c a sequence of three terraces of the shesh taraz river are displaced left laterally by a maximum of 25 m infrared stimulated luminescence irsl dating of the uppermost shesh taraz river terrace gives a deposition age of 10 ka which correlates with changes in global climate 10 12 ka ago and provides a provisional slip rate estimate of 2 4 0 3 mm yr 1 no major recent or historical earthquakes are recorded on the doruneh fault relatively fresh scarps and partially infilled fractures appear to be the preserved surface ruptures from an earthquake event of unknown age a series of small streams showing left lateral displacements of 3 to 5 5 m with an average slip of 4 7 m record the possible magnitude of slip during this earthquake which from scaling relationships would have had an m w of 7 5 and ruptured the fault over a length of 100 km at the estimated slip rate of 2 5 mm yr 1 the average recurrence time between large magnitude earthquakes on the doruneh fault is 2000 yr

global spherical harmonic models of the internal magnetic field of the moon based on sequential and coestimation approaches 1 three new models of the global internal magnetic field of the moon based on lunar prospector lp fluxgate magnetometer observations are developed for use in understanding the origin of the moon s crustal magnetic field and for modeling its interaction with the solar wind the models are at spherical harmonic degree 170 corresponding to 64 km wavelength resolution from 30 km mean altitude lp observations coverage is complete except for a few areas near each pole original signal amplitudes are best preserved in the sequential approach map whereas feature recognition is superior in the coestimation and harmonic wave number correlation maps spherical harmonic degrees less than 15 corresponding to 666 km wavelength are largely absent from the moon s internal magnetic field we interpret this bound in terms of the moon s impact history a derived magnetization map suggests magnetizations may locally exceed 0 2 a m in the lunar crust at the survey resolution if the magnetic crust is as thick as 40 km

surface vector mapping of magnetic anomalies over the moon using kaguya and lunar prospector observations we have provided preliminary global maps of three components of the lunar magnetic anomaly on the surface applying the surface vector mapping svm method the data used in the present study consist of about 5 million observations of the lunar magnetic field at 10 45 km altitudes by kaguya and lunar prospector the lunar magnetic anomalies were mapped at 0 2 equi distance points on the surface by the svm method showing the highest intensity of 718 nt in the crisium antipodal region overall features on the svm maps indicate that elongating magnetic anomalies are likely to be dominant on the moon except for the young large basins with the impact demagnetization remarkable demagnetization features suggested by previous studies are also recognized at hertzsprung and kolorev craters on the farside these features indicate that demagnetized areas extend to about 1 2 radii of the basins craters there are well isolated central magnetic anomalies at four craters leibnitz aitken jules verne and grimaldi craters their magnetic poles through the dipole source approximation suggest occurrence of the polar wander prior to 3 3 3 5 ga when compared with high albedo markings at several magnetic anomalies such as the reiner gamma anomalies three dimensional structures of the magnetic field on near the surface are well correlated with high albedo areas these results indicate that the global svm maps are useful for the study of the lunar magnetic anomalies in comparison with various geological and geophysical data

magnetic properties of lunar materials meteorites luna and apollo returned samples abstract we present the first comprehensive study of the magnetic properties of lunar meteorites and compare them with measurements from apollo and luna returned samples 37 unpaired lunar meteorites were studied while new susceptibility measurements were performed on 88 luna soil and rock samples to complement published luna and apollo data new magnetic data were also obtained on 4 apollo mare basalt samples magnetic susceptibility and saturation remanence appear mainly controlled by the amount of metallic iron added by the regolith forming processes and meteoritic contamination as shown by a positive correlation with ni and ir content a decrease with depth in regolith core profiles and a decrease with increasing soil size fraction the three sources of lunar materials provide coherent range of magnetic properties although the much larger abundance of anorthositic highland samples in the meteorite collection allows one to better describe the properties of this major lunar lithology the observed range of saturation remanence implies that mare basalts cannot contribute significantly to the patchy lunar crustal magnetizations which must be attributed to superficial impact processed feldspathic or mafic lithologies

central magnetic anomalies of nectarian aged lunar impact basins probable evidence for an early core dynamo abstract a re examination of all available low altitude lp magnetometer data confirms that magnetic anomalies are present in at least four nectarian aged lunar basins moscoviense mendel rydberg humboldtianum and crisium in three of the four cases a single main anomaly is present near the basin center while in the case of crisium anomalies are distributed in a semi circular arc about the basin center these distributions together with a lack of other anomalies near the basins indicate that the sources of the anomalies are genetically associated with the respective basin forming events these central basin anomalies are difficult to attribute to shock remanent magnetization of a shocked central uplift and most probably imply thermoremanent magnetization of impact melt rocks in a steady magnetizing field iterative forward modeling of the single strongest and most isolated anomaly the northern crisium anomaly yields a paleomagnetic pole position at 81 19 n 143 31 e not far from the present rotational pole assuming no significant true polar wander since the crisium impact this position is consistent with that expected for a core dynamo magnetizing field further iterative forward modeling demonstrates that the remaining crisium anomalies can be approximately simulated assuming a multiple source model with a single magnetization direction equal to that inferred for the northernmost anomaly this result is most consistent with a steady large scale magnetizing field the inferred mean magnetization intensity within the strongest basin sources is 1 a m assuming a 1 km thickness for the source layer future low altitude orbital and surface magnetometer measurements will more strongly constrain the depth and or thicknesses of the sources

silica polymorphs in lunar granite implications for granite petrogenesis on the moon granitic lunar samples largely consist of granophyric intergrowths of silica and k feldspar the identification of the silica polymorph present in the granophyre can clarify the petrogenesis of the lunar granites the presence of tridymite or cristobalite would indicate rapid crystallization at high temperature quartz would indicate crystallization at low temperature or perhaps intrusive slow crystallization allowing for the orderly transformation from high temperature silica polymorphs tridymite or cristobalite we identify the silica polymorphs present in four granitic lunar samples from the apollo 12 regolith using laser raman spectroscopy typically lunar silica occurs with a hackle fracture pattern we did an initial density calculation on the hackle fracture pattern of quartz and determined that the volume of quartz and fracture space is consistent with a molar volume contraction from tridymite or cristobalite both of which are less dense than quartz moreover we analyzed the silica in the granitic fragments from apollo 12 by electron probe microanalysis and found it contains up to 0 7 wt tio2 consistent with initial formation as the high temperature silica polymorphs which have more open crystal structures that can more readily accommodate cations other than si the silica in apollo 12 granitic samples crystallized rapidly as tridymite or cristobalite consistent with extrusive volcanism the silica then inverted to quartz at a later time causing it to contract and fracture a hackle fracture pattern is common in silica occurring in extrusive lunar lithologies e g mare basalt the extrusive nature of these granitic samples makes them excellent candidates to be similar to the rocks that compose positive relief silicic features such as the gruithuisen domes

spherical earth gravity and magnetic anomaly analysis by equivalent point source inversion abstract to facilitate geologic interpretation of satellite elevation potential field data analysis techniques are developed and verified in the spherical domain that are commensurate with conventional flat earth methods of potential field interpretation a powerful approach to the spherical earth problem relates potential field anomalies to a distribution of equivalent point sources by least squares matrix inversion linear transformations of the equivalent source field lead to corresponding geoidal anomalies pseudo anomalies vector anomaly components spatial derivatives continuations and differential magnetic pole reductions a number of examples using 1 averaged surface free air gravity anomalies and pogo satellite magnetometer data for the united states mexico and central america illustrate the capabilities of the method

high resolution u pb ages of ca phosphates in apollo 14 breccias implications for the age of the imbrium impact abstract previous age estimates of the imbrium impact range from 3770 to 3920 ma with the latter being the most commonly accepted age of this basin forming event the occurrence of ca phosphates i

demagnetization signatures of lunar impact craters research at the university of california berkeley was supported by nasa through subcontract lri 99 101 from the lunar research institute

the lunar dynamo background it is unknown whether the moon has a fully differentiated and melted structure with a metallic core or retains a partially primordial unmelted interior the differentiation history of the moon is manifested by its record of past magnetism paleomagnetism although the moon today does not have a global magnetic field the discovery of remanent magnetization in lunar rocks and in the lunar crust demonstrated that there was a substantial lunar surface field billions of years ago however the origin intensity and lifetime of this field have been uncertain as a result it has been unclear whether this magnetization was produced by a dynamo in the moon s advecting metallic core or by fields generated externally to the moon establishing whether the moon formed a core dynamo would have major implications for understanding its interior structure thermal history and mechanism of formation as well for our understanding of the physics of planetary magnetic field generation the interior structure of the moon and the lunar dynamo new magnetic measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its advecting liquid metallic core innermost red shell this dynamo may have been driven by convection possibly powered by crystallization of the core innermost red sphere and or stirring from the solid mantle thick green shell the magnetic field was recorded as magnetization by rocks on the lunar surface image created by hernan canellas the interior structure of the moon and the lunar dynamo new magnetic measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its advecting liquid metallic core innermost red shell this dynamo may have been driven by convection possibly powered by crystallization of the core innermost red sphere and or stirring from the solid mantle thick green shell the magnetic field was recorded as magnetization by rocks on the lunar surface image created by hernan canellas advances a new generation of laboratory magnetic studies of lunar rocks and spacecraft measurements of lunar crustal magnetic fields have produced major advances in our understanding of the evolution of ancient magnetic fields on the moon it has now been established that a dynamo magnetic field likely existed on the moon from at least 4 5 billion to 3 56 billion years ago with an intensity similar to that at the surface of earth today the field then declined by at least an order of magnitude by 3 3 billion years ago the early epoch of high field intensities may require an exceptionally energetic power source such as mechanical stirring from mantle precession the extended history of the lunar dynamo appears to demand long lived power sources such as mantle precession and core crystallization outlook measurements of the intensity of the ancient lunar dynamo have shown that it was surprisingly intense and long lived the next phase of lunar magnetic exploration will be to obtain more accurate measurements of field paleointensities and to determine when the dynamo initiated and finally disappeared this will be coupled with the continued development of magnetohydrodynamic models for characterizing mechanical and other unusual dynamo mechanisms and further investigations into the thermal structural and geodynamical history of the lunar core and mantle the eventual availability of absolutely oriented samples and in situ spacecraft measurements of bedrock should enable the first measurements of the paleo orientation of lunar magnetic fields such directional data could determine the lunar field s geometry and reversal frequency as well as constrain ancient local and global scale tectonic events

early lunar magnetism it is uncertain whether the moon ever formed a metallic core or generated a core dynamo the lunar crust and returned samples are magnetized but the source of this magnetization could be meteoroid impacts rather than a dynamo here we report magnetic measurements and 40ar 39ar thermochronological calculations for the oldest known unshocked lunar rock troctolite 76535 these data imply that there was a long lived field on the moon of at least 1 microtesla approximately 4 2 billion years ago the early age substantial intensity and long lifetime of this field support the hypothesis of an ancient lunar core dynamo

osmium isotope and highly siderophile element constraints on ages and nature of meteoritic components in ancient lunar impact rocks abstract the concentrations of highly siderophile elements hse re os ir ru pt rh pd au and 187os 188os isotope compositions have been determined for 67 subsamples of six lunar impact rocks from the apollo 14 16 and 17 landing sites and the lunar meteorite dar al gani dag 400 using inductively coupled plasma mass spectrometry icp ms and negative thermal ionization mass spectrometry n tims we report the first re os isochron age on a lunar impact melt rock 187re 187os isotope systematics for apollo 16 sample 67935 define an isochron age of 4 21 0 13 ga mswd 1 5 which is interpreted to reflect localized partitioning processes between solid metal liquid metal as this rock melted the new age adds further constraints on the significance of pre 4 0 ga basin forming impacts on the moon and possible mixing of ancient impactor compositions in lunar impact rocks linear correlations displayed by subsamples of a given impact rock in plots of hse versus ir concentrations are explained by dilution processes through essentially hse free anorthositic lunar crustal target rocks or binary mixing between a high hse meteoritic end member and a low hse end member composition slope derived hse ratios and 187os 188os of the meteoritic component in granulitic impactites 67915 67955 and 79215 are similar to slightly volatile element depleted carbonaceous chondrites suprachondritic ratios of ru ir pt ir rh ir and pd ir for apollo 14 impact melt rock 14310 are similar to ratios observed for other apollo 14 samples and apollo 17 poikilitic impact melt rocks apollo 16 poikilitic and subophitic impact melt rocks 60315 and 67935 show slightly subchondritic os ir and suprachondritic ratios of 187os 188os ru ir pt ir rh ir pd ir and au ir their strongly fractionated hse compositions are similar to some members of the iva iron meteorite group and provide further evidence for an iron meteorite impactor component in apollo 16 impact melt rocks the range of chondritic to suprachondritic ratios of 187os 188os ru ir pt ir pd ir and chondritic to slightly subchondritic os ir of apollo 17 and 14 impact melt rocks may be explained by variable mixing of a carbonaceous chondrite like hse composition as in granulitic impactites with a suprachondritic iron meteorite like impactor composition as inferred from 67935 and 60315 and subsequent homogenization by younger impact events the inferred dispersal of these two components across the lunar nearside and their antiquity 4 2 ga suggest at least two basin forming impacts that predate the 3 9 3 8 ga basin forming era the hse composition of the silicate earth can be matched by a late veneer comprised of 80 volatile depleted carbonaceous chondrite like material and 20 differentiated meteoritic metal similar to what has been identified in ancient lunar impact rocks

initial mapping and interpretation of lunar crustal magnetic anomalies using lunar prospector magnetometer data maps of relatively strong crustal magnetic field anomalies detected at low altitudes with the magnetometer instrument on lunar prospector are presented on the lunar nearside relatively strong anomalies are mapped over the reiner gamma formation on western oceanus procellarum and over the rima sirsalis rille on the southwestern border of oceanus procellarum the main rima sirsalis anomaly does not correlate well with the rille itself but is centered over an imbrian aged smooth plains unit interpreted as primary or secondary basin ejecta the stronger reiner gamma anomalies correlate with the locations of both the main reiner gamma albedo marking and its northeastward extension both the rima sirsalis and the reiner gamma anomalies are extended in directions approximately radial to the center of the imbrium basin this alignment suggests that imbrium basin ejecta materials lying in many cases beneath the visible mare surface are the sources of the nearside anomalies if so then the albedo markings associated with the stronger refiner gamma anomalies may be consistent with a model involving magnetic shielding of freshly exposed mare materials from the solar wind ion bombardment two regions of extensive magnetic anomalies are mapped in regions centered on the ingenii basin on the south central farside and near the crater gerasimovic on the southeastern farside these regions are approximately antipodal to the imbrium and crisium basins respectively the imbrium antipode anomaly group is the most areally extensive on the moon while the largest anomaly in the crisium antipode group is the strongest detected by the lunar prospector magnetometer a consideration of the expected antipodal effects of basin forming impacts as well as a combination of sample data and orbital measurements on the nearside leads to the conclusion that the most probable sources of magnetic anomalies in these two regions are ejecta materials from the respective impacts in both regions the strongest individual anomalies correlate with swirl like albedo markings of the reiner gamma class visible on available orbital photography

magnetic fields of lunar multi ring impact basins we survey the magnetic fields of lunar multi ring impact basins using data from the electron reflectometer instrument on the lunar prospector spacecraft as for smaller lunar craters the primary signature is a magnetic low that extends to 1 5 2 basin radii suggesting shock demagnetization of relatively soft crustal magnetization a secondary signature as for large terrestrial basins is the presence of central magnetic anomalies which may be due to thermal remanence in impact melt rocks and or shock remanence in the central uplift the radial extent of the anomalies may argue for the former possibility but the latter or a combination of the two are also possible central anomaly fields are absent for the oldest pre nectarian basins increase to a peak in early nectarian basins and decrease to a low level for imbrian basins if basin associated anomalies provide a good indication of ambient magnetic fields when the basins formed this suggests the existence of a magnetic era possibly due to a lunar core dynamo similar to that implied by paleointensity results from returned lunar samples however the central basin anomalies suggest that the fields peaked in early nectarian times and were low in imbrian times while samples provide evidence for high fields in nectarian and early imbrian times

mapping of crustal magnetic anomalies on the lunar near side by the lunar prospector electron reflectometer lunar prospector lp electron reflectometer measurements show that surface fields are generally weak in the large mare basalt filled impact basins on the near side but are stronger over highland terranes especially those lying antipodal to young large impact basins between the imbrium and nectaris basins many anomalies correlate with the cayley and descartes formations statistical analyses show that the most strongly magnetic nearside terranes are cayley type light plains terra materials and pre imbrian craters light plains and terrae include basin impact ejecta as a major component suggesting that magnetization effects from basin forming impacts were involved in their formation the magnetization of pre imbrian craters however may be evidence of early thermal remanence relatively strong small scale magnetic anomalies are present over the reiner gamma feature on western oceanus procellarum and over the rima sirsalis rille on the southwestern border of procellarum both apollo subsatellite and lp data show that the latter anomaly is nearly aligned with the rille though lp magnetometer and reflectometer data show that the anomaly peak is actually centered over a light plains unit this anomaly and the reiner gamma anomaly are approximately radially aligned with the center of imbrium suggesting an association with ejecta from this basin

elemental mapping by dawn reveals exogenic h in vesta s regolith using dawn s gamma ray and neutron detector we tested models of vesta s evolution based on studies of howardite eucrite and diogenite hed meteorites global fe o and fe si ratios are consistent with hed compositions neutron measurements confirm that a thick diogenitic lower crust is exposed in the rheasilvia basin which is consistent with global magmatic differentiation vesta s regolith contains substantial amounts of hydrogen the highest hydrogen concentrations coincide with older low albedo regions near the equator where water ice is unstable the young rheasilvia basin contains the lowest concentrations these observations are consistent with gradual accumulation of hydrogen by infall of carbonaceous chondrites observed as clasts in some howardites and subsequent removal or burial of this material by large impacts

origin of strong lunar magnetic anomalies further mapping and examinations of lroc imagery in regions antipodal to young large impact basins work at the university of arizona was supported under grant nnx12aj03g from the nasa lunar advanced science and exploration research laser program

can the lunar crust be magnetized by shock experimental groundtruth abstract since the first evidence of magnetized lunar crust two mechanisms of magnetization have been suggested to account for lunar magnetism thermoremanent magnetization trm or shock remanent magnetization srm we present here the first experimental acquisition of shock remanence by lunar rocks in the 0 1 2 gpa range and discuss their implications for the interpretation of the paleomagnetic record of these rocks as well as for the distribution of magnetic anomalies revealed by orbital data laser shock experiments in controlled magnetic fields performed on lunar mare basalts demonstrated that in the presence of an ambient field these rocks can be magnetized significantly starting at low pressure 0 1 gpa hydrostatic loading experiments up to 1 8 gpa in controlled magnetic fields were used to impart piezo remanent magnetization an analogue for shock remanent magnetization to mare basalts and highland regolith breccias these experiments allow quantifying the shock remanence as a function of pressure and ambient field regarding the lunar antipodal magnetic anomaly model our results show that lunar soils regolith breccia and about 40 of lunar highland rocks comprising regolith and impact melt breccia in the upper crust can be magnetized by low pressure shocks for typical lunar rocks dominated by multidomain feni with low ni content the maximum remanent magnetization that can be acquired during a low pressure shock

topography of the moon from the clementine lidar range measurements from the lidar instrument carried aboard the clementine spacecraft have been used to produce an accurate global topographic model of the moon this paper discusses the function of the lidar the acquisition processing and filtering of observations to produce a global topographic model and the determination of parameters that define the fundamental shape of the moon our topographic model a 72nd degree and order spherical harmonic expansion of lunar radii is designated goddard lunar topography model 2 gltm 2 this topographic field has an absolute vertical accuracy of approximately 100 m and a spatial resolution of 2 5 the field shows that the moon can be described as a sphere with maximum positive and negative deviations of 8 km both occurring on the farside in the areas of the korolev and south pole aitken s p aitken basins the amplitude spectrum of the topography shows more power at longer wavelengths as compared to previous models owing to more complete sampling of the surface particularly the farside a comparison of elevations derived from the clementine lidar to control point elevations from the apollo laser altimeters indicates that measured relative topographic heights generally agree to within 200 m over the maria while the major axis of the lunar gravity field is aligned in the earth moon direction the major axis of topography is displaced from this line by approximately 10 to the east and intersects the farside 24 north of the equator the magnitude of impact basin topography is greater than the lunar flattening 2 km and equatorial ellipticity 800 m which imposes a significant challenge to interpreting the lunar figure the floors of mare basins are shown to lie close to an equipotential surface while the floors of unflooded large basins except for s p aitken lie above this equipotential the radii of basin floors are thus consistent with a hydrostatic mechanism for the absence of significant farside maria except for s p aitken whose depth and lack of mare require significant internal compositional and or thermal heterogeneity a macroscale surface roughness map shows that roughness at length scales of 10 1 10 2 km correlates with elevation and surface age

investigating sources of mercury s crustal magnetic field further mapping of messenger magnetometer data 106 low altitude passes of magnetometer data from the last two months of the messenger mission have been applied to produce a map of the crustal magnetic field at a constant altitude of 40 km covering latitudes of 35 75 n and longitudes of 270 90 e some anomalies correlate significantly with impact basins craters e g rustaveli and vyasa while other basins craters have no obvious anomalies a possible interpretation that is consistent with lunar evidence is that some impactors delivered more ferromagnetic fe ni metal to the interior subsurfaces and ejecta fields of the craters basins that they produced the amount of metallic iron that could plausibly be delivered is limited by the diameter and mass of an impactor that would yield a crater with observed diameters e g 200 km for rustaveli this in turn limits the maximum amplitude of anomalies that could be induced by impactor added iron in the present day mercury global field to relatively low values it is therefore concluded that if impactor added iron is the source of the observed crater associated anomalies then they must be almost entirely a consequence of ancient remanent magnetization a broad magnetic anomaly occurs over the northern rise a topographically high region with an associated strong free air gravity anomaly a possible interpretation of the latter anomaly is that an early major impact preconditioned the region for a later mantle uplift event

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

a new source of basaltic meteorites inferred from northwest africa 011 eucrites are a class of basaltic meteorites that share common mineralogical isotopic and chemical properties and are thought to have been derived from the same parent body possibly asteroid 4 vesta the texture mineralogy and noble gas data of the recently recovered meteorite northwest africa nwa 011 are similar to those of basaltic eucrites however the oxygen isotopic composition of nwa011 is different from that of other eucrites indicating that nwa011 may be derived from a different parent body the presence of basaltic meteorites with variable oxygen isotopic composition suggests the occurrence of multiple basaltic meteorite parent bodies perhaps similar to 4 vesta in the early solar system

decline of the lunar core dynamo abstract recent analyses of apollo samples have demonstrated that a core dynamo existed on the moon between at least 4 25 and 3 56 billion years ago ga with surface field intensities reaching 70 t however it is unknown when the moon s magnetic field declined determining the temporal evolution of the dynamo is important because it constrains secular changes in power at the lunar core mantle boundary and by implication the moon s thermal and orbital evolution and the field generation mechanism here we present paleomagnetic data from several younger mare basalts which demonstrate that the surface magnetic field had declined precipitously to 4 t by 3 19 ga it is currently unclear whether such a rapid decrease in field strength reflects either the cessation of the dynamo during this period or its persistence beyond 3 19 ga in a drastically weakened state

numerical modeling of lava regolith heat transfer on the moon and implications for the preservation of implanted volatiles 1 we have performed a series of numerical simulations of heat transfer between lunar lava flows and the underlying regolith with the goal of determining the depths in the substrate beneath which implanted extralunar volatiles would survive outgassing by the downward propagating heat pulse exogenous materials of interest include solar wind and solar flare particles and the cosmogenic products of galactic cosmic ray gcr particles emplaced in the lunar regolith early in solar system history extraction and analysis during future lunar missions would yield information about the evolution of the sun and inner solar system environment particles implanted in regolith deposits may be protected from gardening and saturation if buried by a lava flow but must be sufficiently deep in the regolith to survive the consequent heating our simulations include detailed treatments of lava and regolith thermophysical properties thermal conductivity specific heat capacity which vary widely over the temperature range relevant to lava flows in the lunar environment 200 to 1500 k simulations adopting temperature dependent properties together with a treatment of latent heat of lava crystallization indicate that implanted volatiles would be fully preserved at depths greater than 20 cm beneath 1 m thick lava flows 60 deeper than predicted by simulations employing constant properties these results highlight the necessity of appropriate prescription of material properties consideration of the range of lunar lava flow thicknesses allows us to determine the range of depths from which pristine samples may be recovered

the south african polymict eucrite macibini the polymict eucrite macibini is a fragmental breccia predominantly composed of eucritic materials with minor proportions maximum 2 vol of diogenitic material hence it is intermediate between the yamato 74159 type polymict eucrites which contain negligible amounts of magnesian orthopyroxene and the howardites the present study provides mineralogical and bulk compositional data for the meteorite breccia and for six clasts these clasts include both volcanic and igneous rocks and a variety of impact generated rocks a broad range of degrees of postcrystallization metamorphism affected these materials before the final aggregation of the breccia clast a is a fragment of unequilibrated eucrite with subophitic texture the edges of the zoned pyroxenes in this clast are composed of a host of fe rich augite containing vermicules blebs and lamellae composed of a mixture of fe rich olivine and silica similar features occur as fragments in lunar breccias and are attributed by some workers to the breakdown of pyroxferroite an fe rich pyroxenoid however textures and compositions of these augite olivine silica intergrowths in clast a suggest that in this case they are the result of decomposition in a series of steps of fe rich subcalcic augite among the fragments of impact generated material in macibini is clast 2 an earlier formed clastic breccia that was lithified before being broken apart and included in the meteorite breccia clast 3 is an impact melt breccia that is composed of rock and mineral fragments in a devitrified groundmass clast c is also an impact melt breccia that has a coarser grained hornfelsic groundmass that resulted from extensive metamorphism after formation

global mapping of lunar crustal magnetic fields by lunar prospector abstract the lunar prospector electron reflectometer has obtained the first global map of lunar crustal magnetic fields revealing that the effects of basin forming impacts dominate the large scale distribution of remanent magnetic fields on the moon the weakest surface magnetic fields 40 nt are diametrically opposite to these same basins this pattern is present though less pronounced for several other post nectarian impact basins larger than 500 km in diameter the reduced strength and clarity of the pattern for older basins may be attributed to 1 demagnetization from many smaller impacts which erases antipodal magnetic signatures over time 2 superposition effects from other large impacts and 3 variation in the strength of the ambient magnetizing field the absence of fringing fields stronger than 1 nt around the perimeter of the imbrium basin or associated with craters within the basin implies that any uniform magnetization of the impact melt must be weaker than 10 6 g cm3 g 1 this limits the strength of any steady ambient magnetic field to no more than 0 1 oe at the lunar surface while the basin cooled for tens of millions of years following the imbrium impact 3 8 billion years ago

ancient water on asteroid 4 vesta evidence from a quartz veinlet in the serra de mage eucrite meteorite abstract the meteorite serra de mage a eucrite inferred to be from the asteroid 4 vesta contains quartz veinlets they are identical to antitaxial or crack seal quartz veinlets in terrestrial rocks and are extraterrestrial and ancient because they pre date a 4 40 ga metamorphism the quartz was likely deposited from liquid water solutions as are terrestrial veins other potential solvents or transport mechanisms are inadequate or unlikely because there is no indication of internal magmatic water in the eucrite meteorites and thus in vesta the water from which the veinlet was deposited probably came from outside vesta by analogy with water ice deposits on the moon and mercury vesta and similar asteroids may have had or now have polar ice deposits possibly derived from comet impacts

using the sulfide replacement petrology in lunar breccia 67915 to construct a thermodynamic model of s bearing fluid in the lunar crust abstract in this work we investigate the compositions and origin of metasomatic fluids responsible for the formation of sulfide replacement textures in mg suite lithologies of lunar samples 67915 149 and 67915 150 we have constructed a quantitative thermodynamic model of the composition of the metasomatic fluid using f o 2 f s 2 and temperature constraints derived from a thermodynamic analysis of the metasomatic fluid mineral reactions and the measured compositions of the phases in the sulfide assemblages results from this modeling indicate that the metasomatic fluid responsible for the formation of the sulfide replacement textures was likely dominated by a combination of h 2 and ch 4 with minor abundances of h 2 o co and h 2 s the modeling indicates that h 2 s was by orders of magnitude the dominant s species present in the metasomatic fluid and s isotopes in the replacement sulfides suggest that the fluid experienced significant removal of h 2 s by sulfide precipitation the calculated h 2 and h 2 o contents of the metasomatic fluid are consistent with those that might be expected for the late stage degassing of shallowly emplaced intrusive magma bodies

thermal history of northwest africa 5073 a coarse grained stannern trend eucrite containing cm sized pyroxenes and large zircon grains we report on the bulk chemical composition petrology oxygen isotopic composition trace element composition of silicates and degree of self irradiation damage on zircon grains of the eucrite northwest africa nwa 5073 to constrain its formation and postcrystallization thermal history and to discuss their implications for the geologic history of its parent body this unequilibrated and unbrecciated meteorite is a new member of the rare stannern trend eucrites it is mainly composed of elongated zoned pyroxene phenocrysts up to 1 2 cm plagioclase laths up to 0 3 cm in length and is rich in mesostasis the latter contains zircon grains up to 30 m in diameter metal sulfide tridymite and ca phosphates textural observations and silicate compositions coupled with the occurrence of extraordinary fe rich olivine veins that are restricted to large pyroxene laths indicate that nwa 5073 underwent a complex thermal history this is also supported by the annealed state of zircon grains inferred from raman spectroscopic measurements along with u and th data obtained by electron probe microanalyses

a long lived lunar core dynamo paleomagnetic measurements indicate that a core dynamo probably existed on the moon 4 2 billion years ago however the subsequent history of the lunar core dynamo is unknown here we report paleomagnetic petrologic and 40ar 39ar thermochronometry measurements on the 3 7 billion year old mare basalt sample 10020 this sample contains a high coercivity magnetization acquired in a stable field of at least 12 microteslas these data extend the known lifetime of the lunar dynamo by 500 million years such a long lived lunar dynamo probably required a power source other than thermochemical convection from secular cooling of the lunar interior the inferred strong intensity of the lunar paleofield presents a challenge to current dynamo theory

initial mapping of mercury s crustal magnetic field relationship to the caloris impact basin seventy eight low altitude passes of mercury surface space environment geochemistry and ranging magnetometer data from august to september of 2014 have been applied to produce an approximate map of the crustal magnetic field at a constant altitude of 80 km covering latitudes of 50 80 n and longitudes of 160 330 e the strongest anomalies are located in the westernmost part of the mapped region just north and northeast of the caloris impact basin the strongest single anomaly group lies over a smooth plains unit that extends northward from caloris a second anomaly lies on the odin formation interpreted as primary caloris ejecta a third broad anomaly also lies over a smooth plains unit suisei planitia although many smooth plains on mercury may have a volcanic origin a subset of these plains is concentrated around caloris and could have a dominantly impact origin it is therefore proposed that many of the mercurian anomaly sources consist of impact basin ejecta materials

persistence and origin of the lunar core dynamo the lifetime of the ancient lunar core dynamo has implications for its power source and the mechanism of field generation here we report analyses of two 3 56 gy old mare basalts demonstrating that they were magnetized in a stable and surprisingly intense dynamo magnetic field of at least 13 t these data extend the known lifetime of the lunar dynamo by 160 my and indicate that the field was likely continuously active until well after the final large basin forming impact this likely excludes impact driven changes in rotation rate as the source of the dynamo at this time in lunar history rather our results require a persistent power source like precession of the lunar mantle or a compositional convection dynamo

magnetic anomalies in the imbrium and schrodinger impact basins orbital evidence for persistence of the lunar core dynamo into the imbrian epoch approximate maps of the lunar crustal magnetic field at low altitudes in the vicinities of the three imbrian aged impact basins orientale schrodinger and imbrium have been constructed using lunar prospector and kaguya orbital magnetometer data detectable anomalies are confirmed to be present well within the rims of imbrium and schrodinger anomalies in schrodinger are asymmetrically distributed about the basin center while a single isolated anomaly is most clearly detected within imbrium northwest of timocharis crater the subsurface within these basins was heated to high temperatures at the time of impact and required long time periods up to 1 myr to cool below the curie temperature for metallic iron remanence carriers 1043 k therefore consistent with laboratory analyses of returned samples a steady long lived magnetizing field i e a former core dynamo is inferred to have existed when these basins formed the asymmetrical distribution within schrodinger suggests partial demagnetization by later volcanic activity when the dynamo field was much weaker or nonexistent however it remains true that anomalies within imbrian aged basins are much weaker than those within most nectarian aged basins the virtual absence of anomalies within orientale where impact melt rocks the maunder formation are exposed at the surface is difficult to explain unless the dynamo field was much weaker during the imbrian period

geology and composition of the orientale basin impact melt sheet 1 the orientale basin is one of the largest 930 km diameter and youngest 3 8 ga impact craters on the moon as the basin is only partly flooded by mare lava its floor materials expose a major portion of the basin impact melt sheet which some previous work has suggested might have undergone igneous differentiation to test this idea we remapped the geology of the orientale basin using images and topography from the lunar reconnaissance orbiter mineralogical information from the chandrayaan 1 moon mineralogy mapper and elemental concentration maps from clementine multispectral imaging and lunar prospector gamma ray data the maunder formation impact melt sheet of the basin is uniform in chemical composition equivalent to anorthositic norite in at least the upper 2 km of the deposit the deepest sampling of the basin melt sheet maximum depths of 3 5 km by the crater maunder 55 km in diameter shows a variety of lithologies but these rock types anorthosite anorthositic norite melt rocks mare basalt and gabbro are not those predicted by the differentiation model we conclude that no differentiation of the orientale basin melt sheet has occurred and that such a process is not evident from new remote sensing data for the moon or in the apollo lunar samples

record of s rich vapors on asteroid 4 vesta sulfurization in the northwest africa 2339 eucrite in the northwest africa nwa 2339 eucrite a few high fe pigeonite fragments were partially replaced by fine grained troilite mg rich augite silica with minor ilmenite and mg rich ferrosilite the relict pigeonite has distinctly lower fe mn values 17 18 than those 30 of augite and mg rich ferrosilite in the fine grained replacement textures and other eucritic pyroxenes in nwa 2339 the few plagioclase grains associated with these fe rich pigeonite fragments contain high albite components ab17 31 similar replacement textures are also present in a lithic clast consisting of pyroxene and na rich plagioclase ab20 25 in this lithic clast high fe subcalcic augite was replaced by troilite mg rich hedenbergite silica and minor ilmenite whereas mg rich pigeonite remains intact troilite also occurs as tiny inclusions in porous regions of plagioclase moreover the porous regions of plagioclase are enriched in si and depleted in al ca and na compared to relict plagioclase these textures indicate that the formation of troilite rich mineral assemblages is related to the reaction between fesio3 component in pyroxene and s rich vapors whereas the formation of tiny troilite in porous regions of plagioclase is related to the reaction between fe2 in plagioclase and s rich vapors x ray mapping results reveal that during sulfurization of pyroxene and plagioclase lithophile elements mn al ca na and mg were removed to various extents very likely by the s rich vapors based on our observations the s rich vapors could be dry s o p vapors which most likely have been formed by volatilization of pre existing s p bearing materials due to impact heating on the surface of asteroid 4 vesta