hydrogen and carbon abundances and isotopic ratios in apatite from alkaline intrusive complexes with a focus on carbonatites we report h and c contents and d and 13 c values of apatites from 15 alkaline intrusive complexes ranging in age from 110 ma to 2 6 ga sampling focused on carbonatites but included silicate rocks as well heating at temperatures up to 1500 c is needed to extract fully h 2o and co 2 from these apatites apatites from carbonatite rich intrusive complexes contain 0 2 1 1 wt h 2o and 0 05 0 70 wt co 2 apatites from two silicate rich alkaline complexes with little or no carbonatite are generally poorer in both volatile components 0 1 0 2 h 2o and 0 01 0 11 co 2 d h ratios in apatites from these rocks are bimodally distributed group i d 51 to 74 and group ii d 88 to 104 we suggest that the d values of group i apatites represent primitive mantle derived values and that the group ii apatites crystallized from degassed magmas resulting in lower h 2o contents and d values although many factors influence the extent of degassing the depth of emplacement could represent a major control in contrast to h 2o contents and d values co 2 contents and 13 c values of gas released at high temperatures from multiple aliquots of these apatite samples are variable this suggests the presence of more than one c bearing component in these apatites one of which is proposed to be dissolved carbonate the other with 13 c 25 could be associated with hydrocarbons group i apatites have d values similar to those of primitive mantle derived basaltic magmas and overlap with but cover a narrower range than mantle derived mica amphibole and whole rocks 13 c values also overlap typical upper mantle these results suggest that igneous apatites can retain their primary d and 13 c values

assessment of shock effects on amphibole water contents and hydrogen isotope compositions 2 kaersutitic amphibole experiments to constrain the influence of impact shock on water and hydrogen isotope signatures of martian meteorite kaersutites we conducted shock recovery experiments on three terrestrial kaersutite crystals homogeneous impact shock to 32 gpa commensurate with shock levels experienced by martian meteorite kaersutites led to increases in kaersutite water contents h 2o 0 25 0 89 wt decreases in fe 3 fe 4 20 and enrichments in hydrogen isotope composition d 66 to 87 relative to pre shock values the latter values represent the largest shock induced hydrogen isotope fractionations measured to date these observations are explained most completely by a two step shock process first shock induced devolatilization led to hydrogen isotope enrichment through preferential loss of h relative to d second reaction of the kaersutite with the ambient atmosphere led to increased water contents and reduced fe fe reduction and water addition via the reaction fe 2 oh fe 3 o 2 h 2 explain the fe 3 fe data and some of the water data further water addition mechanisms irreversible adsorption shock implantation are necessary to fully explain the increased water contents addition of water from the terrestrial atmosphere which is isotopically light relative to the experimental kaersutite compositions means the measured hydrogen isotope enrichments are likely minima the measured minimum levels of hydrogen isotope enrichment are relevant to the hydrogen isotope variability within and among martian kaersutites but are minor relative to their absolute d values alternatively addition of water from the enriched martian atmosphere could explain both martian kaersutite hydrogen isotope variability and absolute d values however the low martian kaersutite water contents leave little room for significant water addition the importance of the ambient atmosphere to the outcome of the shock experiments makes it difficult to translate our results to mars given the unknown influence of its more tenuous atmosphere on the processes observed in the experiments our results suggest that shock is a feasible mechanism for influencing martian kaersutite water contents and hydrogen isotope compositions but that its complex signature precludes precise determination of that influence

hydrous melting of the martian mantle produced both depleted and enriched shergottites the search for water in our solar system is one of the primary driving forces for planetary science and exploration because water plays an important role in many geologic processes and is required for biologic processes as we currently understand them excluding earth mars is the most promising destination in the inner solar system to find water as it is undoubtedly responsible for shaping many geomorphologic features observed on the present day martian surface however the water content of the martian interior is currently unresolved much of our information about the martian interior comes from studies of the basaltic martian meteorites shergottites in this study we examined the water contents of magmatic apatites from a geochemically enriched shergottite the shergotty meteorite and a geochemically depleted shergottite the queen alexandria range 94201 meteorite from these data we determined that there was little difference in water contents between the geochemically depleted and enriched shergottite magmas the water contents of the apatite imply that shergottite parent magmas contained 730 2870 ppm h 2 o prior to degassing furthermore the martian mantle contains 73 290 ppm h 2 o and underwent hydrous melting as recently as 327 ma in the absence of plate tectonics the presence of water in the interior of mars requires planetary differentiation under hydrous conditions this is the first evidence of significant hydrogen storage in a planetary interior at the time of core formation and this process could support elevated h abundances in the interiors of other terrestrial bodies like the moon mercury venus large differentiated asteroids and earth

light lithophile elements in martian basalts evaluating the evidence for magmatic water degassing whether water has played a role in the petrogenesis of martian basalts remains a subject of significant debate estimates of pre eruptive water concentrations in martian magmas are impeded by the effects of degassing and shock however zoning trends of light lithophile elements lle in pyroxene have been interpreted as evidence for the degassing of magmatic water on the basis of the soluble behavior of these elements in hydrothermal fluids we provide ion microprobe analyses of lle in pyroxene in the zagami and shergotty martian basalts complemented by detailed electron microprobe analyses and major element x ray maps to independently verify the zoning of lle and its relationship to texture and major element variations our results corroborate previous results specifically that li concentrations are lower in rims than cores of shergotty and zagami pyroxene in contrast we see no evidence for a core to rim decrease in b in the absence of further data we interpret the decrease in li as reflecting either loss after crystallization of pyroxene cores consistent with magmatic degassing or the diffusive preferential loss of li from pyroxene rims possibly as a result of shock because the partitioning behavior of li between hydrous fluid minerals and melt under relevant conditions of pressure temperature and melt composition is unknown the viability of the water degassing hypothesis depends on experiments establishing the compatibility of li in hydrous fluid associated with martian basaltic melt and the incompatibility of li in pyroxene at elevated pressures

maskelynite hosted apatite in the chassigny meteorite insights into late stage magmatic volatile evolution in martian magmas apatite hosting maskelynite and alkali maskelynite within regions interstitial to cumulus olivine differ compositionally from that found within melt inclusions in the chassigny martian meteorite feldspar glass compositions within the interstitial regions evolve along a high temperature crystallization path within the melt inclusions feldspar glass shows evolution to low temperatures extending into the subsolidus regime coupled with these differences in maskelynite compositions are differences in volatile abundance in apatite included within the maskelynite apatite found within the large olivine hosted polyphase melt inclusions is uniformly fluorapatite whereas that interstitial to cumulus olivine is chlor fluorapatite we propose that the differences in maskelynite and apatite compositions within the melt inclusion and interstitial regions arose primarily from different crystallization conditions melt inclusion maskelynite and apatite are consistent with nearly closed system buildup of magmatic volatiles during crystallization within the melt inclusions exsolution of a cl bearing fluid phase and retention of this fluid phase within the melt inclusions into the hydrothermal regime for the interstitial regions however the higher solidus temperatures of the interstitial melts the early crystallization of feldspar with significant ternary component and the cl rich nature of the apatite all suggest open system fluid migration through the cumulus pile ingress of cl rich h2o poor brine from a hotter less evolved portion of the magma plumbing system and interaction of this cl rich fluid with melt prior to the crystallization of feldspar such processes of fluid migration through a cumulus pile have been suggested on earth in layered intrusions and apatite is the primary recorder of this process

hydrogen isotope evidence for loss of water from mars through time 1 the high d h of the martian atmosphere 5 6 terrestrial is considered strong evidence for the loss of martian water to space the timing and magnitude of the loss of water from mars can be constrained by measurements of d h in martian meteorites previous studies of martian meteorites have shown a large range in d h from terrestrial values to as high as the current martian atmosphere here we show that the ancient 4 ga mars meteorite alh84001 has a d h 4 terrestrial and that the young 0 17 ga shergotty meteorite has a d h 5 6 terrestrial we also find that the young los angeles shergottite has zoning in d h that can be correlated to igneous growth zoning strongly suggesting assimilation of d enriched water during igneous crystallization near the martian surface in contrast to previous studies we find higher and less variable d h ratios in these three meteorites our results suggest a two stage evolution for martian water a significant early loss of water to space prior to 3 9 ga followed by only modest loss to space in the last 4 billion years the current martian atmospheric d h has remained essentially unchanged for the last 165 ma

in situ study of the fractionation of hydrogen isotopes between aluminosilicate melts and coexisting aqueous fluids at high pressure and high temperature implications for the δd in magmatic processes abstract the hydrogen isotopic composition of melt inclusions trapped in phenocrysts during their crystallization and growth in a magma may contribute to a better understanding of the water cycle between the atmosphere the hydrosphere and the lithosphere such understanding relies on the knowledge of the hydrogen isotopic fractionation factors between aqueous fluids silicate melts and minerals at temperature and pressure conditions relevant to the earth s interior significant d h fractionation between silicate melts and aqueous fluids was reported at hundreds of mpa and c by using in situ measurements in hydrothermal diamond anvil cell hdac experiments mysen 2013a mysen 2013b am mineral 98 376 386 and 1754 1764 however the available dataset is focused on fluids and melts with d h ratios close to unity the relevance of such data for natural processes that involve per mil variations of d values may not always be clear to address such concerns the effect of the bulk d h ratio on hydrogen isotope partitioning between water saturated silicate melts and coexisting silicate saturated aqueous fluids has been determined in the na2o al2o3 sio2 h2o d2o system to this end in situ raman spectroscopic measurements were performed on fluids and melts with bulk d h ratios from 0 05 to 2 67 by using an externally heated diamond anvil cell in the 300 800 c and 200 1500 mpa temperature and pressure range respectively in these pressure temperature ranges the d h ratios of fluids in equilibrium with melt barely change with temperature in average h fluid 0 47 1 15 kj mol in contrast the d h ratios of coexisting melts display strong dependence on temperature average h melt 7 18 1 27 kj mol the temperature dependence of the d h fractionation factor between melt and fluid fluid melt d h fluid d h melt is comparable in all the experiments and can be written 1000 ln fluid melt 263 26 t 2 126 48 therefore the fluid melt is independent of the bulk d h ratio of the melt fluid system experimentally determined fluid melt using d enriched fluids therefore can be applied to natural systems it follows that for water saturated magma strong isotopic fractionation of d and h between water dissolved in magmas and deep aqueous fluids may occur the d values in melt inclusions in phenocrysts in such water saturated magma will reflect such fluid melt fractionation effects a likely result is underestimation of the d isotopic composition of slab fluids based on d values in melt inclusions the temperature dependent hydrogen isotope fractionation must be taken into account in the modeling of slab fluid magma interaction in the mantle wedge

sm nd chronology and petrogenesis of mesosiderites we have obtained sm nd data from four mesosiderite silicate clasts including three clasts with a variety of textures from the vaca muerta type 1a mesosiderite and one gabbroic clast from the mt padbury mesosiderite the gabbroic vaca muerta pebble 12 and basaltic pebble 16 yield identical 147 sm 143 nd ages of 4 48 0 19 ae and 4 48 0 09 ae respectively while the highly recrystallized pebble 5 gives an age of 4 42 0 02 ae mt padbury yields an age of 4 52 0 04 ae all clasts show a correlation of 142 nd 144 nd with 147 sm 144 nd and provide unequivocal evidence for the presence of live 146 sm at the time of their formation calculated initial 146 sm 144 sm values range from 0 004 pebble 5 to 0 006 pebbles 12 16 and mt padbury and are generally consistent with the 147 sm 143 nd ages however discordance of whole rock leach and residue data and some disagreement between 146 sm 142 nd relative ages and 147 sm 143 nd absolute ages indicate small but significant disturbances to the sm nd systematics the ranges of ages and initial 146 sm 144 sm and 143 nd 144 nd values suggest that each of these silicate clasts underwent a separate protracted evolution on its parent body prior to mixing with metal textural and trace element criteria indicate that individual clasts from the same mesosiderite often had very different igneous sources and thermal histories prior to their incorporation in the meteorite pebble 12 is extremely lree depleted probably a result of several melt extraction events whereas pebbles 5 and 16 and mt padbury have nearly chondritic sm nd with bulk ree concentrations higher than chondrites by factors of 5 to 15 in general the sm nd systematics of mesosiderite silicates require formation of the silicates on a parent planet which underwent relatively early and extreme differentiation preservation of diverse old ages and the presence of 146 sm imply that metal silicate mixing did not seriously alter the sm nd isotopic memories of these clasts we present a model for metal silicate mixing which combines the cooling history with isotopic reequilibration for the case of thermal blanketing we show that the total amount of isotopic reequilibration in a sample can be related to the initial temperature depth of burial grain size and diffusion parameters application of this model to the silicate clasts measured in this study indicates that if the metal and silicate were thermally equilibrated above the metal solidus temperature during mixing then the clasts must have been buried no deeper than 1 10 m in regolith during the initial high temperature cooling phase in order to prevent the sm nd systems from being extensively reset in order to reconcile these results with the slow cooling rates at lower temperatures determined from studies of exsolution in the metal phase we infer that heat was transferred rapidly from hot metal to cold silicate material during initial metal silicate mixing and that the deeply buried portions of the mixture then cooled slowly after reaching thermal equilibrium at 600 700 c the data from this study point to the following history for the mesosiderite parent body 1 differentiation of a silicate parent body within the first 50 m y of solar system history to form diverse parent magmas 2 emplacement of primitive and differentiated mafic magmas near the planetary surface and extensive differentiation in the near surface environment 3 formation and reworking of regolith breccias through impact gardening at the near surface of the body 4 mixing of molten fe ni metal with the regolith followed by rapid cooling 100 150 m y after the origin of the solar system 5 slow cooling from temperatures of 700 c to produce the observed nickel diffusion profiles in the iron phase 6 mild impact metamorphism and brecciation to obtain the much younger k ar ages and 7 recent collisions or perturbations sending mesosiderite fragments into earth crossing trajectories

the chlorine isotopic composition of martian meteorites 1 chlorine isotope composition of martian mantle and crustal reservoirs and their interactions the martian meteorites record a wide diversity of environments processes and ages much work has been done to decipher potential mantle sources for martian magmas and their interactions with crustal and surface environments chlorine isotopes provide a unique opportunity to assess interactions between martian mantle derived magmas and the crust we have measured the cl isotopic composition of 17 samples that span the range of known ages martian environments and mantle reservoirs the 37cl of the martian mantle as represented by the olivine phyric shergottites nwa 2737 chassignite and shergotty basaltic shergottite has a low value of approximately 3 8 this value is lower than that of all other planetary bodies measured thus far the martian crust as represented by regolith breccia nwa 7034 is variably enriched in the heavy isotope of cl this enrichment is reflective of preferential loss of 35cl to space most basaltic shergottites less shergotty nakhlites chassigny and allan hills 84001 lie on a continuum between the martian mantle and crust this intermediate range is explained by mechanical mixing through impact fluid interaction and assimilation fractional crystallization

martian magmas contained abundant chlorine but little water the martian water cycle a key for the habitability of mars largely relies on the abundance of water in martian magmas and their mantle sources yet martian snc shergottite nakhlite and chassigny classes meteorites contain minimal water however some experimental studies have suggested that martian parental magmas contained as much as 2 h2o here we integrate mineral chemical experimental and cosmochemical constraints to show that martian magmas contained little water but abundant chlorine apatite and amphibole in martian meteorites are chlorine rich and water poor this constrains the chlorine contents in their parental magmas to 0 3 wt and water contents to 0 3 wt our experimental work has shown that large amounts of water are not needed to explain the mineralogy of the martian meteorites because chlorine has effects similar to those of water on crystallization such chlorine rich water poor martian magmas are consistent with mars being chlorine rich 2 5 compared with the earth furthermore the bulk cl composition of martian meteorites shows that they have not preferentially lost cl by degassing of an h2o rich vapor together these results show that chlorine not water was the dominant volatile species in martian basalts and that these basalts contributed little h2o to mars surface environment

the explosive diversification of the diatom genus chaetoceros across the eocene oligocene and oligocene miocene boundaries in the norwegian sea abstract eocene to middle miocene stratigraphic changes in species richness abundance and valve size of chaetoceros resting spores in the norwegian sea dsdp site 338 were investigated in order to understand past productivity and paleoenvironmental changes in upwelling regions as a result drastic resting spore events were recognized in a 6 myr interval across the eocene oligocene boundary eo event the oligocene miocene boundary om event and in the early middle miocene emm event the eo event was characterized by explosive diversification at both the morpho generic and specific levels an increase in abundance and a decrease in valve size from the upper eocene through the lowest oligocene the om event was defined by a two fold increase in species richness during the emm event spore abundance decreased rapidly and species richness and valve size decreased gradually these changes may indicate changes in the nutrient supply especially in upwelling regions the increased species richness suggests a change from a stable water column with a constant nutrient supply in the eocene to an unstable one with a sporadic nutrient supply by increased vertical mixing in the oligocene based on evaluation of the ecologic differences between dinoflagellate cysts and chaetoceros resting spores the role of main primary producer might have switched from dinoflagellates and or nannoplankton in the eocene to diatoms especially chaetoceros in the oligocene in the norwegian sea increased resting spore species richness during the om event may show that environmental changes such as global cooling and nutrient mixing led to a diversification of the spore producing genus chaetoceros the emm event might have been affected by changes in paleoceanographic conditions perhaps a decrease in nutrient supply this study presents the first paleoceanographic analysis using not only the total resting spore abundance but also the abundances of individual species and establishes the value of spore taxonomy and diatom analysis including spores

volatiles in the martian crust and mantle clues from the nwa 6162 shergottite abstract martian meteorites of various petrogeneses retain a record of volatiles on mars from the hydrosphere crustal water to the mantle sputtering of the martian atmosphere by solar wind after the loss of mars magnetic field enriched it in deuterium which exchanged with martian crustal water recent studies show that the hydrogen isotopic composition of the martian crustal water reservoir varies from 3000 to 7000 but requires better constraints melt inclusion glasses maskelynite and fusion crust from the depleted olivine phyric shergotite nwa 6162 were analyzed using nanosims providing a unique insight into the hydrogen isotopic and volatile elemental content of both the martian crustal water reservoir and the mantle source the h2o s and cl contents of the melt inclusion glasses are 0 3137 14 239 and 16 967 ppm respectively d values vary from 560 to 6137 the water content positively correlates with the d values in both the melt inclusion glasses and maskelynite in a two end member mixing trend one end member is the magmatic water with a d value of 0 and the other end member is the martian crustal water with d ranging from 5000 to 6000 nwa 6162 a depleted olivine phyric shergottite originated from a different mantle source to the enriched lherzolitic shergottites however both types of shergottites exchanged with martian crustal water with the same d values indicating a homogeneous martian crustal water hydrogen isotopic composition 5000 6000 most melt inclusion glasses from nwa 6162 have low water content 0 234 ppm except for two enriched locations as micron sized bands and dendrites the low water content in most melt inclusion glasses the dendritic shaped water enriched areas in melt inclusions and the martian crustal water diffusion profile recorded in maskelynite collectively suggest short lived water rock interactions in the nwa 6162 parent rock that was probably induced by impact furthermore a great contribution up to 98 of surface cl accompanying d enriched water was recorded in the melt inclusions supported by the positive correlation between cl and h2o the presence of sulfide and s rich hot spots and low d end member of the magmatic water indicate that the degassing during post entrapment crystallization and ascent of the melt inclusion is negligible h2o s and cl contents of the martian mantle reservoir are estimated to be 0 1 3 0 5 15 and 0 5 4 ppm respectively after the correction of fractional crystallization of the melt inclusions and contribution from the martian surface reservoir the martian mantle reservoir estimated from nwa 6162 was water s and cl poorer than the earth s interior

a study of strontium diffusion in k feldspar na k feldspar and anorthite using rutherford backscattering spectroscopy abstract sr chemical diffusion has been measured in orthoclase anorthoclase and anorthite under dry 1 atm conditions a strontium oxide aluminosilicate powder mixture was used as the source material with rutherford backscattering spectroscopy rbs used to measure diffusion profiles over the temperature range 725 1075 c the following arrhenius relations were obtained orthoclase normal to 001 d 5 97 10 0 0060 0 0030exp 67900 1600rtcm 2 s 1 measurements of diffusion perpendicular to 010 and 100 indicate little diffusional anisotropy in orthoclase anorthoclase normal to 010 d 4 51 10 1 358 5 6exp 89100 4800rt cm 2 s 1 normal to 001 d 2 25 10 2 1615 31exp 89300 4600rt cm 2 s 1 anorthite normal to 010 d 3 85 10 2 0 380 0 0039 exp 78800 5400rt cm 2 s 1 the correlation of sr uptake with a reduction of k and ca in orthoclase and anorthite respectively indicates that sr is exchanging with these species nuclear reaction analysis nra measurements of al in orthoclase suggests that the coupled exchange sr 2 al 3 k 1 si 4 is taking place as expected sr closure temperatures for feldspars calculated with the above parameters are relatively high compared to those of some other minerals e g biotite muscovite apatite however closure temperatures of feldspars may be significantly depressed if they are exsolved or twinned leading to small effective diffusion lengths feldspar crystals of millimeter size should retain 87 sr 86 sr ratios except when subjected to thermal events of extreme temperature or duration

alteration assemblages in the nakhlites variation with depth on mars secondary mineral assemblages in the nakhlite meteorites lafayette governador valadares gv nakhla yamato y 000593 y 000749 have been studied using scanning electron microscopy transmission electron microscopy and electron probe micro analysis the different nakhlites have distinctive secondary assemblages in their olivine grains and mesostases showing compositional fractionation correlated with their relative depths below the martian surface fracture filled veins in lafayette at the bottom of the pile consist of a siderite phyllosilicate fe oxide hydrated silicate gel assemblage corresponding veins in nakhla and gv further up the pile are predominantly a siderite gel assemblage with additional evaporites including gypsum y 000593 y 000749 veins are dominated by gel the gel s mg mg fe ratio decreases from lafayette 0 37 to gv 0 32 nakhla 0 24 and y 000593 0 15 we suggest that hydrothermal fluid flowed up this depth profile initiated by melting of buried h2o co2 ice our results show a complex mix of fe rich phyllosilicate within the veins and mesostasis of lafayette with d spacings of 0 7 1 1 nm suggesting a mixture of smectite and serpentine the phyllosilicate formed at close to neutral ph 150 c we also suggest that water rock ratios w r of 1 10 occurred in lafayette with smaller values for the other nakhlites this is reflected in the volume of alteration minerals 10 of olivine in lafayette to 3 in nakhla textural evidence of rapid cooling together with the w r and likely fluid velocities suggest that the secondary assemblages formed quickly e g within months a model is proposed in which the secondary assemblages formed in an impact induced hydrothermal system terminated by precipitation of the gel and evaporation of soluble salts

evidence in tissint for recent subsurface water on mars we report unambiguous chemical evidence for subsurface water activity in the martian crust at 600 ma based on the data from tissint a fresh martian meteorite fall with minimal terrestrial weathering the impact melt pockets in tissint contain abundant volatiles h 2o co 2 f and cl and their concentrations are positively correlated with each other higher h 2o concentrations also accompany higher deuterium contents these correlations suggest mixing between two volatile sources the first source is h 2o in the precursor basalt inherited from martian magma magmatic h 2o in the basalt had low deuterium concentration and was likely stored in the nominally anhydrous minerals this source contributed little co 2 or halogens to the impact melts the second source is inferred to be aqueous alteration products introduced to the basalt by water activity after the basalt erupted these alteration materials contributed more volatiles to the impact melts than the magmatic source and had high deuterium abundance reflecting isotope equilibrium with recent martian atmosphere the water activities occurred beneath the martian surface after 600 ma crystallization age but before 1 ma ejection age the chemical and isotopic signatures of the alteration products in tissint resemble previously known martian samples associated with old water activities on mars which can be traced back to 4 2 billion years ago e g the mudstone at gale crater this similarity in chemistry and the wide age span indicate that such water activities were common on mars throughout its history which had the potential to form habitable environment however the rarity of the volatile rich zone in tissint suggests that martian crustal aqueous processes where they have occurred are generally limited in their extent of water rock reaction

a search for evidence of a fissionable nuclide in iron meteorites and implications on heat sources in planetary cores it is shown that nuclear fission could not have significantly contributed as a heat source to drive an early lunar core dynamo furthermore contributions of any fissionable nuclide to the energetics of the earth s core today are very unlikely in comparison to other sources of energy these conclusions are inferred from searches for records of fission events in the metal phase of ia and ivb meteorites we obtain strict upper limits for the concentration level of nd and sm in the canyon diablo ia pinon anom and santa clara ivb meteorites which are not distinguishable from the levels of the procedural blank and exhibit a normal isotopic composition no contribution from fission to the unshielded isotopes could be detected upper limits for contributions by fission are 10 8 atoms g 1 per isobar assuming a low fission yield of 10 4 we obtain 10 12 fission events g 1 it is reasonable to assume no losses of ree fission products due to late stage recrystallization or outgassing this limit would correspond to a maximum deposition of 30 j g 1 in the earth s core due to fission from earlier experiments on kr and xe in other ia iron meteorites upper limits for contributions by fission of 3 10 5 and 2 10 6 fission events g 1 per isobar can also be estimated for the unshielded isotopes recent studies on nuclear tracks in silicate inclusions of ia iron meteorites set upper limits of 10 9 10 10 fission events g 1 the detected tracks being most plausibly explained by spontaneous fission of 244 pu we can find no evidence in support of a fissionable siderophile superheavy element and all limits for fission events are too low to support fission as a heat source in planetary cores furthermore by nd and sm studies on two ivb iron meteorites we demonstrate that ag anomalies found earlier in meteorites of this class cannot have been produced by in situ fission of any known nuclide this further supports the interpretation that extinct 107 pd is the source of the 107 ag anomalies

strong water isotopic anomalies in the martian atmosphere probing current and ancient reservoirs we measured maps of atmospheric water h2o and its deuterated form hdo across the martian globe showing strong isotopic anomalies and a significant high deuterium hydrogen d h enrichment indicative of great water loss the maps sample the evolution of sublimation from the north polar cap revealing that the released water has a representative d h value enriched by a factor of about 7 relative to earth s ocean vienna standard mean ocean water vsmow certain basins and orographic depressions show even higher enrichment whereas high altitude regions show much lower values 1 to 3 vsmow our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 vsmow which would mean that early mars 4 5 billion years ago had a global equivalent water layer at least 137 meters deep

insights into martian water reservoirs from analyses of martian meteorite que94201 the martian atmospheric d h value of 5 2 times terrestrial is significantly higher than any found on earth and has been ascribed to preferential loss of h relative to d from the atmosphere through jeans escape over time here based on ion microprobe analyses of apatite grains from martian meteorite que94201 it is shown that the pre jeans escape martian water reservoir has a d h value twice that of terrestrial water rather than the terrestrial value that has been assumed in prior work the data support a two stage history for martian volatiles in which early hydrodynamic escape enriched martian water to 2x terrestrial d h values subsequent jeans escape to produce the current atmospheric values has thus been responsible for less d enrichment than previously thought a martian crust containing 2 3 times more water than previously proposed is implied by the results

evolution of water reservoirs on mars from d h ratios in the atmosphere and crust ancient fluvial networks on the surface of mars suggest that it was warm and wet over three billion years ago surface features resembling massive outflow channels provide evidence that even more recently the martian crust contained the equivalent of a planet wide reservoir of water several hundred metres deep but arguments based on the isotopic fraction and present day escape rate of hydrogen in the martian atmosphere require only 0 5 metres of crustal water today and about six metres in the past an additional constraint on the evolution of the isotopic composition of martian water has recently been obtained from measurements of the deuterium to hydrogen ratio of hydrous minerals in the snc meteorites meteorites that almost certainly originated on mars here i show that these new data require that the modern crustal reservoirs of martian water must be quite large at least several metres in global equivalent depth the deuterium enrichment of the present martian atmosphere then implies that the reservoir of crustal water on ancient mars was several hundred metres deep consistent with the geological evidence

the sources of water in martian meteorites clues from hydrogen isotopes abstract h isotope measurements of carbonate phosphate feldspathic and mafic glasses and post stishovite silica phase in the shergottites zagami shergotty sau 005 dag 476 alha 77005 and eeta 79001 as well as in chassigny and alh 84001 show that all these phases contain deuterium enriched water of extraterrestrial origin the minerals and glasses analyzed may contain an initial primary hydrogen component but their isotopic composition was modified to varying degrees by three different processes interaction with a fractionated exchangeable water reservoir on mars hydrogen devolatilization by impact melting and terrestrial contamination positive correlations between d and water abundance in feldspathic glass and post stishovite silica in zagami shergotty and sau 005 is indicative of mixing of a high d component 3000 4000 and a less abundant low d component 0 the high d component is primarily derived from the martian exchangable reservoir but may also have been influenced by isotopic fractionation associated with shock induced hydrogen loss the low d component is either a terrestrial contaminant or a primary magmatic component the negative correlation between d and water abundances in mafic and feldspathic glasses in alh 84001 alha 77005 and eeta 79001 is consistent with the addition of a low d terrestrial contaminant to a less abundant high deuterium martian component the low d of magmatic glass in melt inclusions suggests that the d of martian parent magma was low and that the initial h isotope signature of mars may be similar to that of earth

compositional differences between basaltic and gabbroic clasts in mesosiderites two gabbroic pebbles and one pebble with basaltic textural affinities from the vaca muerta mesosiderite were analyzed by instrumental neutron activation analysis and electron microprobe these analyses plus literature data reveal remarkable compositional differences between basaltic and gabbroic clasts in mesosiderites on average basaltic clasts have small 15 depletions in light relative to heavy rare earth elements rees and moderate positive eu anomalies i e h chondrite normalizedla lu 0 85 eu sm 1 30 the meanla lu andeu sm abundance ratios of gabbroic clasts are at least 3 3 smaller and 28 greater respectively intense meteoroid bombardment probably persisted until after the mesosiderite parent body had differentiated near surface mixtures of major amounts of basalt and lesser amounts of cumulate eucritic rocks were essentially totally melted and rapidly cooled accounting for the moderately fractionated ree patterns of most basaltic clasts at greater depths impact heating partially melted cumulate gabbros incompatible element rich eutectic liquids drained away creating large ree fractionations in the residual rocks these rocks cooled slowly and developed gabbroic textures

samarium neodymium evolution of meteorites we have obtained sm nd data on two differentiated meteorites ibitira a eucrite with distinct basaltic texture and with evidence of crystallization and morristown a group 3a mesosiderite as well as on acapulco an unclassified meteorite with chondritic chemical composition and a highly recrystallized texture we have demonstrated the presence of in situ decay of short lived 146 sm in these meteorites with initial abundance of 146 sm 144 sm from 0 009 to 0 007 for the different meteorites precisely defined 147 sm 143 nd internal isochrons were obtained yielding ages of 4 60 0 03 ae for acapulco 4 47 0 02 ae for morristown and 4 46 0 02 ae for ibitira the corresponding initial 143 nd 144 nd values obtained were 0 2 0 9 2 1 0 7 and 1 6 0 8 u epsilon units detailed consideration of the coupled 147 sm 143 nd and 146 sm 142 nd systematics and of the elevated initial 143 nd 144 nd values indicates the presence of inconsistencies in the data for the two sm nd parent daughter pairs in spite of the precise isochrons we present a model which provides an interpretation of the paired sm nd systematics in terms of an impulsive disturbance the abundance of phosphate with large concentrations of rees controls the ree economy plagioclase with low ree concentrations is assumed to be susceptible to exchange pyroxene is considered to be undisturbed because of the low diffusion coefficients of trace elements the experimental results can be reasonably explained by this model the results indicate that three meteorites studied some with very low ree concentrations including a mesosiderite are relatively ancient objects formed within the first 50 to 100 m y of the solar system by planetary differentiation and impact processes and were subjected to late metamorphism the time of late metamorphism is substantially younger than 4 4 ae and possibly as recent as 3 9 ae this metamorphism has resulted in partial very limited reequilibration between plagioclase and phosphate resulting in the observed shifts in initial 143 nd 144 nd sm nd model ages and the 142 nd 144 nd abundances but preserving the major temporal structures of early original formation and later disturbances these results show the need for care in the interpretation of the parent daughter systematics even when they appear well behaved and the mineral phases are viewed as highly resistant to mild metamorphism

magmatic water in the martian meteorite nakhla abstract mars does not recycle crustal materials via plate tectonics for this reason the magmatic water reservoir of the martian mantle has not been affected by surface processes and the deuterium hydrogen d h ratio of this water should represent the original primordial martian value following this logic hydrous primary igneous minerals on the martian surface should also carry this primordial d h ratio assuming no assimilation of martian atmospheric water during crystallization and no major hydrogen fractionation during melt degassing hydrous primary igneous minerals such as apatite and amphibole are present in martian meteorites here on earth providing these minerals have not been affected by terrestrial weathering martian atmospheric water or shock processes after crystallization they should contain a good approximation of the primordial martian d h ratio as nakhla was seen to fall in the egyptian desert in 1911 terrestrial contamination is minimized in this meteorite the nakhlites are also among the least shocked of the martian meteorites therefore apatite within nakhla could contain primordial martian hydrogen isotope ratios we produced in situ measurements of the d h ratios in nakhla apatite grains using a cameca ims 1280 ion microprobe our measurements produced d h values in nakhla apatite similar to terrestrial values despite strong evidence that our samples were not significantly contaminated by terrestrial hydrogen these results suggest that water trapped in the martian mantle has a similar d h to that of the earth therefore the water of these two planets may have originated from the same source material the d h ratios of the carbonaceous chondrite meteorites and the jupiter family comet 103p hartley 2 are similar to the d h of the two planets making both these primitive inner solar system materials strong candidates for the source of the terrestrial planets water these results support recent dynamical models of the formation of the solar system which suggest material in the inner solar system was homogenized by the migration of jupiter

mesosiderite clasts with the most extreme positive europium anomalies among solar system rocks pigeonite plagioclase gabbros that occur as clasts in mesosiderites brecciated stony iron meteorites show extreme fractionations of the rare earth elements rees with larger positive europium anomalies than any previously known for igneous rocks from the earth moon or meteorite parent bodies and greater depletions of light rees relative to heavy rees than known for comparable cumulate gabbros the ree pattern for merrillite in one of these clasts is depleted in light rees and has a large positive europium anomaly as a result of metamorphic equilibration with the silicates the extreme ree ratios exhibited by the mesosiderite clasts demonstrate that multistage igneous processes must have occurred on some asteroids in the early solar system melting of the crust by large scale impacts or electrical induction from an early t tauri phase sun may be responsible for these processes

the imprint of atmospheric evolution in the d h of hesperian clay minerals on mars the deuterium to hydrogen d h ratio in strongly bound water or hydroxyl groups in ancient martian clays retains the imprint of the water of formation of these minerals curiosity s sample analysis at mars sam experiment measured thermally evolved water and hydrogen gas released between 550 c and 950 c from samples of hesperian era gale crater smectite to determine this isotope ratio the d h value is 3 0 0 2 times the ratio in standard mean ocean water smow the d h ratio in this 3 billion year old mudstone that is half that of the present martian atmosphere but substantially higher than that expected in very early mars indicates an extended history of hydrogen escape and desiccation of the planet

volatile abundances of coexisting merrillite and apatite in the martian meteorite shergotty implications for merrillite in hydrous magmas whitlockite and merrillite are two ca phosphate minerals found in terrestrial and planetary igneous rocks sometimes coexisting with apatite whitlockite has essential structural hydrogen and merrillite is devoid of hydrogen whitlockite components have yet to be discovered in samples of extraterrestrial merrillite despite evidence for whitlockite merrillite solid solution in terrestrial systems the observation of merrillite in meteoritic and lunar samples has led many to conclude that the magmas from which the merrillite formed were very dry however the shergotty martian meteorite has been reported to contain both apatite and merrillite and recently the apatite has been shown to contain substantial oh abundances up to the equivalent of 8600 ppm h2o in the present study we determined the abundances of f cl h2o and s in merrillite from shergotty using secondary ion mass spectrometry sims we determined that the merrillite in shergotty was properly identified i e no discernible whitlockite component and it coexists with oh rich apatite the absence of a whitlockite component in shergotty merrillite and other planetary merrillites may be a consequence of the limited thermal stability of h in whitlockite stable only at t 1050 c which would prohibit merrillite whitlockite solid solution at high temperatures consequently the presence of merrillite should not be used as evidence of dry magmatism without a corresponding estimate of the t of crystallization in fact if a whitlockite component in extraterrestrial merrillite is discovered it may indicate formation by or equilibration with hydrothermal or aqueous fluids

deuterium and 37 chlorine rich fluids on the surface of mars evidence from the enriched basaltic shergottite northwest africa 8657 abstract apatite a major hydrous mineral in martian meteorites has the potential to reveal history of volatiles on mars here we report the h and cl isotopic systematics of apatite from the enriched basaltic shergottite nwa 8657 to better understand the processes influencing volatiles at or near the martian sub surface the apatite in nwa 8657 has the highest reported d value up to 6509 of any phosphates in martian meteorites the positive correlation between the h2o contents 72 2251 ppm and d values 3965 6509 as well as between the cl contents 1 28 6 17 wt and 37cl values 1 7 4 0 in nwa 8657 apatite are consistent with mixing between volatiles derived from the martian mantle and meteoric water fluid the d and 37cl enrichment of apatite in nwa 8657 implies isotopic exchange with sub surficial fluids during post crystallization hydrothermal event s plain language summary mars was probably a wet and warm world during its earliest geological history supported by many lines of evidence present day mars is cold and arid although recent remote sensing data support the existence of subsurface glaciers and seasonal fluid activities at some locations in this study our aim was to use ground truth about the potential water rock interaction on or near surface environments on recent mars via measuring the h and cl isotopic compositions of apatite from a geologically young meteorite from mars the enriched basaltic shergottite nwa 8657 the petrography and mineral chemistry of apatite and other associated phases e g merrillite maskelynite mesostasis and pyroxene were documented prior to in situ h and cl isotopes analysis the water contents of apatite merrillite maskelynite mesostasis and pyroxene are positively correlated with the d values all of the datasets can be reconciled in terms of mixing between two endmembers a d poor 0 mantle reservoir and a d rich 5920 500 near surface underground water reservoir moreover apatite in nwa 8657 displays 37cl enriched 1 1 in average characteristics these signatures are consistent with d and 37cl rich fluid assisted isotopic exchange in recent near surface environment on mars

high temperature chlorine rich fluid in the martian crust a precursor to habitability abstract we report scapolite in a melt inclusion in olivine in nakhla which is the first occurrence of cl scapolite found in a martian meteorite using terrestrial metamorphic experiments and modeling we constrain its origin cl rich scapolite in nakhla is consistent with formation from either a late stage cl rich water poor magma or magmatic cl rich hydrothermal brine at a minimum temperature of 700 c the temperature of hydrothermal activity recorded by the cl scapolite is significantly higher than the temperatures recorded by alteration minerals in nakhla and the fluid was cl rich not co 2 rich our results demonstrate that high temperature cl rich fluids were present within the martian crust and any potential biologic activity would have to survive in these high temperatures and saline fluids halophiles can thrive in nacl rich systems but at significantly lower temperatures than those recorded by the scapolite during cooling of the fluid the system could have reached a habitable state for halophiles importantly halophiles can survive the conditions of space if they are encased in salt crystals and therefore chlorine rich phases present an opportunity to investigate for extant life both on the surface of mars and in martian meteorites

rb and sr diffusion in alkali feldspars with implications for cooling histories of rocks volume diffusion of sr and rb have been measured in orthoclase feldspar as well as sr diffusion in albite using isotope exchange hydrothermal solutions and analysis by ion microprobe for water pressures of 1000 bars the kinetics of diffusion parallel to the c axis are given by the arrhenius relations strontium transport in the or is isotropic to within a factor of four the measurements use a new procedure in which only the elements in question are present in the starting fluid cooling rates of igneous rocks can now be determined from closure temperatures material balance and the rb sr dating method based on the departures of the mineral data from the whole rock isochron for cooling rates less than approximately 100 c my

experimental investigation of f cl and oh partitioning between apatite and fe rich basaltic melt at 1 0 1 2 gpa and 950 1000 c apatite melt partitioning experiments were conducted in a piston cylinder press at 1 0 1 2 gpa and 950 1000 c using an fe rich basaltic starting composition and an oxygen fugacity within the range of iw 1 to iw 2 each experiment had a unique f cl oh ratio to assess the partitioning as a function of the volatile content of apatite and melt the quenched melt and apatite were analyzed by electron probe microanalysis and secondary ion mass spectrometry techniques the mineral melt partition coefficients d values determined in this study are as follows d fap melt 4 4 19 d clap melt 1 1 5 d ohap melt 0 07 0 24 this large range in values indicates that a linear relationship does not exist between the concentrations of f cl or oh in apatite and f cl or oh in melt respectively this non nernstian behavior is a direct consequence of f cl and oh being essential structural constituents in apatite and minor to trace components in the melt therefore mineral melt d values for f cl and oh in apatite should not be used to directly determine the volatile abundances of coexisting silicate melts however the apatite melt d values for f cl and oh are necessarily interdependent given that f cl and oh all mix on the same crystallographic site in apatite consequently we examined the ratio of d values exchange coefficients for each volatile pair oh f cl f and oh cl and observed that they display much less variability k dcl fap melt 0 21 0 03 k doh fap melt 0 014 0 002 and k doh clap melt 0 06 0 02 however variations with apatite composition specifically when mole fractions of f in the apatite x site were low x f 0 18 were observed and warrant additional study to implement the exchange coefficient to determine the h2o content of a silicate melt at the time of apatite crystallization apatite based melt hygrometry the h2o abundance of the apatite an apatite melt exchange k d that includes oh either oh f or oh cl and the abundance of f or cl in the apatite and f or cl in the melt at the time of apatite crystallization are needed f if using the oh f k d and cl if using the oh cl k d to determine the h2o content of the parental melt the f or cl abundance of the parental melt is needed in place of the f or cl abundance of the melt at the time of apatite crystallization importantly however exchange coefficients may vary as a function of temperature pressure melt composition apatite composition and or oxygen fugacity so the combined effects of these parameters must be investigated further before exchange coefficients are applied broadly to determine volatile abundances of coexisting melt from apatite volatile abundances

unique meteorite from early amazonian mars water rich basaltic breccia northwest africa 7034 we report data on the martian meteorite northwest africa nwa 7034 which shares some petrologic and geochemical characteristics with known martian meteorites of the snc i e shergottite nakhlite and chassignite group but also has some unique characteristics that would exclude it from that group nwa 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent rover and orbiter missions it formed 2 089 0 081 billion years ago during the early amazonian epoch in mars9 geologic history nwa 7034 has an order of magnitude more indigenous water than most snc meteorites with up to 6000 parts per million extraterrestrial h2o released during stepped heating it also has bulk oxygen isotope values of 17o 0 58 0 05 per mil and a heat released water oxygen isotope average value of 17o 0 330 0 011 per mil suggesting the existence of multiple oxygen reservoirs on mars

meteoritic evidence for a previously unrecognized hydrogen reservoir on mars abstract fluvial landforms on mars suggest that it was once warm enough to maintain persistent liquid water on its surface the transition to the present cold and dry mars is closely linked to the history of surface water yet the evolution of surficial water is poorly constrained based on in situ hydrogen isotope d h analyses of quenched and impact glasses in martian meteorites we provide evidence for the existence of a distinct but ubiquitous water ice reservoir d h 2 3 times earth s ocean water that lasted from at least the time when the meteorites crystallized 173 472 million years ago to the time they were ejected by impacts 0 7 3 3 million years ago but possibly much longer the origin of this reservoir appears to predate the current martian atmospheric water d h 5 6 times earth s ocean water and is unlikely to be a simple mixture of atmospheric and primordial water retained in the martian mantle d h earth s ocean water this reservoir could represent hydrated crust and or ground ice interbedded within sediments our results corroborate the hypothesis that a buried cryosphere accounts for a large part of the initial water budget of mars

geochemical evidence for magmatic water within mars from pyroxenes in the shergotty meteorite observations of martian surface morphology have been used to argue that an ancient ocean once existed on mars1 it has been thought that significant quantities of such water could have been supplied to the martian surface through volcanic outgassing but this suggestion is contradicted by the low magmatic water content that is generally inferred from chemical analyses of igneous martian meteorites2 here however we report the distributions of trace elements within pyroxenes of the shergotty meteorite a basalt body ejected 175 million years ago from mars3 as well as hydrous and anhydrous crystallization experiments that together imply that water contents of pre eruptive magma on mars could have been up to 1 8 we found that in the shergotty meteorite the inner cores of pyroxene minerals which formed at depth in the martian crust are enriched in soluble trace elements when compared to the outer rims which crystallized on or near to the martian surface this implies that water was present in pyroxenes at depth but was largely lost as pyroxenes were carried to the surface during magma ascent we conclude that ascending magmas possibly delivered significant quantities of water to the martian surface in recent times reconciling geologic and petrologic constraints on the outgassing history of mars

hydrogen isotope ratios in lunar rocks indicate delivery of cometary water to the moon water has been found in many lunar rock samples but its sources are unknown isotopic analyses of apollo samples of lunar mare basalts and highlands rocks suggest that a significant volume of water was delivered to the moon by comets shortly after its formation by giant impact

hydrogen isotopic compositions in allan hills 84001 and the evolution of the martian atmosphere hydrogen isotopic compositions of carbonate and maskelynite in allan hills alh 84001 were measured by secondary ion mass spectrometry sims the delta d values of both minerals show considerable deviation the deviation seems to be caused by addition of varying amounts of terrestrial water in the case of carbonate in the case of maskelynite h is heterogeneously distributed and the deviation in delta d values seems to be due to mixing of this indigenous heavy h with isotopically normal h present in the sims chamber the indigenous delta d value in alh 84001 seems to be approximately 2000 carbonate rather than maskelynite seems to be the main carrier of h in alh 84001 because alh 84001 is approximately 4 ga old the h isotopic composition suggests that a large fraction of the initial martian atmosphere had already escaped by 4 ga

age of a eucrite clast from the bholghati howardite 39ar 40ar rb sr and sm nd investigations of the large eucrite clast 1 studied by the bholghati consortium show that it crystallized from a melt 4 51 ga ago the crystallization age is given most precisely by a sm nd internal isochron of 4 510 0 034 ga 2 error limits for 147sm 0 00654 ga 1 142nd144nd measurements show that the clast contained live 146sm at the time of crystallization a solar system initial 146sm144sm0 0 00431 0 0039 0 0026 at 4 555 ga ago can be calculated from a 146sm 142nd isochron and the age of the clast alternatively using 146sm144sm 0 0 0045 as previously reported in the literature a 146sm142nd formation interval of 0 05 0 12 0 08 ga can be calculated which is concordant with the 147sm 143nd isochron age and in agreement with pu u xe and pu nd xe formation intervals reported in a companion consortium paper the initial 143nd144nd ind of the clast was ind 0 505958 50 2 error limits normalized to 146nd 144nd 0 724140 and is consistent with the chur reference value for evolution in a source having chondritic relative ree abundances prior to magma generation however when interlaboratory bias is considered the data are also permissive of a lree depleted source as suggested in a companion consortium paper a primary rb sr isochron yields an age of 4 54 0 06 ga 2 error limits for 87rb 0 01402 ga 1 in agreement with the more precise sm nd age the initial 87sr86sr isr of the clast was isr 0 699006 21 and was the same within error limits as isr previously determined for a pristine eucrite clast from polymict eucrite y75011 compatible with a common parent body the 39ar 40ar data and some of the rb sr data show that bholghati was affected by a major thermal event 2 3 ga ago and also provide weak evidence for a minor thermal event 1 ga ago the age and isotopic systematics of the clast are consistent with those of other eucrites and support the widely held assumption of a common parent body for howardites and eucrites the isotopic investigations of polymict eucrites and howardites point to a prolonged cratering record on the howardite eucrite diogenite hed parent body and suggest that it survived the cataclysm affecting the moon 3 8 4 0 ga ago

effects of shock and martian alteration on tissint hydrogen isotope ratios and water content abstract the tissint meteorite a picritic shergottite fell to earth in morocco on the 18th of july 2011 and is only the fifth martian meteorite witnessed to fall hydrogen isotope ratios and water contents are variable within different minerals in tissint ringwoodite and shock melt pockets contain elevated d h ratios relative to terrestrial values d 761 4224 these high ratios in recrystallized phases indicate significant implantation of hydrogen from the d rich martian atmosphere during shock in contrast although olivine has detectable water abundances 230 485 ppm it exhibits much lower d h ratios d 88 to 150 suggesting this water was not implanted from the martian atmosphere the minimal terrestrial weathering experienced by tissint gives confidence that the olivine hosted water has a martian origin but its high concentration indicates direct inheritance from the parental melt is improbable especially given the low pressure of olivine crystallisation incorporation of a low d crustal fluid or deuteric alteration during crystallisation could explain the relatively high water contents and low d h ratios in tissint olivine

hydrogen isotopic composition of the martian mantle inferred from the newest martian meteorite fall tissint the hydrogen isotopic composition of planetary reservoirs can provide key constraints on the origin and history of water on planets the sources of water and the hydrological evolution of mars may be inferred from the hydrogen isotopic compositions of mineral phases in martian meteorites which are currently the only samples of mars available for earth based laboratory investigations previous studies have shown that d values in minerals in the martian meteorites span a large range of 250 to 6000 the highest hydrogen isotope ratios likely represent a martian atmospheric component either interaction with a reservoir in equilibrium with the martian atmosphere such as crustal water or direct incorporation of the martian atmosphere due to shock processes the lowest d values may represent those of the martian mantle but it has also been suggested that these values may represent terrestrial contamination in martian meteorites here we report the hydrogen isotopic compositions and water contents of a variety of phases merrillites maskelynites olivines and an olivine hosted melt inclusion in tissint the latest martian meteorite fall that was minimally exposed to the terrestrial environment we compared traditional sample preparation techniques with anhydrous sample preparation methods to evaluate their effects on hydrogen isotopes and find that for severely shocked meteorites like tissint the traditional sample preparation techniques increase water content and alter the d h ratios toward more terrestrial like values in the anhydrously prepared tissint sample we see a large range of d values most likely resulting from a combination of processes including magmatic degassing secondary alteration by crustal fluids shock related fractionation and implantation of martian atmosphere based on these data our best estimate of the d value for the martian depleted mantle is 116 94 which is the lowest value measured in a phase in the anhydrously prepared section of tissint this value is similar to that of the terrestrial upper mantle suggesting that water on mars and earth was derived from similar sources the water contents of phases in tissint are highly variable and have been affected by secondary processes considering the h2o abundances reported here in the driest phases most likely representing primary igneous compositions and appropriate partition coefficients we estimate the h2o content of the tissint parent magma to be 0 2 wt

igneous and shock processes affecting chassignite amphibole evaluated using chlorine water partitioning and hydrogen isotopes amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma but also shock and postshock processes we have analyzed amphibole and other phases from nwa 2737 melt inclusions and we evaluate these data along with published values to constrain the crystallization cl and h2o content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains using a model for the cl oh exchange between amphibole and melt we estimate primary crystallization oh contents of chassignite amphiboles sims analysis shows that amphibole from nwa 2737 currently has 0 15 wt h2o it has lost 0 6 wt h2o from an initial 0 7 0 8 wt h2o due to intense shock chassigny amphibole had on average 0 3 0 4 wt h2o and suffered little net loss of h2o due to shock nwa 2737 amphibole has d 3700 it absorbed martian atmosphere derived heavy h in the aftermath of shock chassigny amphibole with d 1900 incorporated less heavy h low h2o cl ratios are inferred for the primitive chassignite magma which had significant effects on melting and crystallization volatiles released by the degassing of martian magma were more cl rich than on earth resulting in the high cl content of martian surface materials

hydrogen isotope analyses of alteration phases in the nakhlite martian meteorites abstract secondary alteration phases such as carbonates smectite clays and fe oxides are found within the martian meteorites if these meteorites were seen to fall the assumption can be reasonably made that the secondary phases have a martian origin however for martian meteorite finds this is not the case deuterium hydrogen d h ratio analysis can be used to distinguish between terrestrial and martian secondary alteration phases the martian atmosphere is currently five times enriched in deuterium compared to terrestrial seawater producing a deuterium enrichment in the martian alteration phases large enough to be detected with modern ion microprobe techniques we aimed to measure the d h ratio of the iddingsite like alteration veins in the nakhlite martian meteorites nakhla mil 03346 mil 090030 and y 000593 to help confirm the martian origin of this material and determine the relative amounts of terrestrial contamination in each meteorite as an observed fall nakhla is nominally uncontaminated by terrestrial alteration and shows elevated d values in its alteration veins however even the highest of these values is much below that of the martian atmosphere indicating that terrestrial contamination probably combined with fractionation effects between the martian atmosphere and the alteration material have reduced the d values of these veins the speed of hydrogen isotope exchange in the nakhlite iddingsite like alteration veins is demonstrated by the purely terrestrial d values in the veins of nakhla 110 a thin section exposed to the terrestrial atmosphere since its preparation in 1998 mineralogical heterogeneity also affects the hydrogen isotope exchange rate in these veins the wide variation in d within the veins of nakhla and y 000593 appears to be due to the heterogeneous nature of the vein material where some phases exchange hydrogen with the atmosphere at a faster rate than others

distinct chlorine isotopic reservoirs on mars implications for character extent and relative timing of crustal interactions with mantle derived magmas evolution of the martian atmosphere and the building blocks of an early mars the style magnitude timing and mixing components involved in the interaction between mantle derived martian magmas and martian crust have long been a point of debate understanding this process is fundamental to deciphering the composition of the martian crust and its interaction with the atmosphere the compositional diversity and oxygen fugacity variations in the martian mantle the bulk composition of mars and the materials from which it accreted and the noble gas composition of mars and the sun recent studies of the chlorine isotopic composition of martian meteorites imply that although the variation in delta sup 37 cl is limited total range of approximately14 per mille there appears to be distinct signatures for the martian crust and mantle however there are potential issues with this interpretation new cl isotope data from the sam sample analysis at mars instrument on the mars science lab indicate a very wide range of cl isotopic compositions on the martian surface recent measurements by 10 duplicated the results of 7 8 but placed them within the context of sam surface data in addition martian meteorite chassigny contains trapped noble gases with isotopic ratios similar to solar abundance and has long been considered a pristine mantle derived sample however previous studies of apatite in chassigny indicate that crustal fluids have interacted with regions interstitial to the cumulus olivine the initial cl isotope measurements of apatite in chassigny suggest an addition of crustal component to this lithology apparently contradicting the rare gas data here we examine the cl isotopic composition of multiple generations and textures of apatite in chassigny to extricate the crustal and mantle components in this meteorite and to reveal the style and timing of the addition of crustal components to mantle derived magmas these data reveal distinct martian cl sources whose signatures have their origins linked to both the early solar system and the evolving martian atmosphere

oxygen escape from the earth during geomagnetic reversals implications to mass extinction abstract the evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field intensity oxygen can escape into interplanetary space as ions after gaining momentum from solar wind but earth s strong dipole field reduces the momentum transfer efficiency and the ion outflow rate except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes mars like in morphology the newest databases available for the phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of years we propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level which is known to be a cause of mass extinction we simulated the oxygen ion escape rate for the triassic jurassic event using a modified martian ion escape model with an input of quiet solar wind inferred from sun like stars the results show that geomagnetic reversal could enhance the oxygen escape rate by 3 4 orders only if the magnetic field was extremely weak even without consideration of space weather effects this suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass extinction therefore if this causal relation indeed exists it should be a many to one scenario rather the previously considered one to one and planetary magnetic field should be much more important than previously thought for planetary habitability

heterogeneous distribution of h2o in the martian interior implications for the abundance of h2o in depleted and enriched mantle sources we conducted a petrologic study of apatite within 12 martian meteorites including 11 shergottites and one basaltic regolith breccia these data were combined with previously published data to gain a better understanding of the abundance and distribution of volatiles in the martian interior apatites in individual martian meteorites span a wide range of compositions indicating they did not form by equilibrium crystallization in fact the intrasample variation in apatite is best described by either fractional crystallization or crustal contamination with a cl rich crustal component we determined that most martian meteorites investigated here have been affected by crustal contamination and hence cannot be used to estimate volatile abundances of the martian mantle using the subset of samples that did not exhibit crustal contamination we determined that the enriched shergottite source has 36 73 ppm h2o and the depleted source has 14 23 ppm h2o this result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the martian mantle we also estimated the h2o cl and f content of the martian crust using known crust mantle distributions for incompatible lithophile elements we determined that the bulk martian crust has 1410 ppm h2o 450 ppm cl and 106 ppm f and cl and h2o are preferentially distributed toward the martian surface the estimate of crustal h2o results in a global equivalent surface layer gel of 229 m which can account for at least some of the surface features on mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on mars surface

nanosims analyses of apatite and melt inclusions in the grv 020090 martian meteorite hydrogen isotope evidence for recent past underground hydrothermal activity on mars abstract we measured the hydrogen isotopes and water contents of melt inclusions and apatite that locate far from shock induced melt veins in the martian meteorite grv 020090 using nano scale secondary ion mass spectrometry nanosims the melt inclusions in olivine show hydration profiles with both the water contents and the d values increasing from the cores 2 170 7 ppm and 3386 126 to the rims 5337 200 ppm and 5519 65 the extremely high d values of the melt inclusions relative to a maximum of 4239 81 of apatite that crystallized from the last residual melt convincingly argue that the observed hydration postdated emplacement of the parent magma of grv 020090 this is also a robust line of evidence for past presence of liquid water on mars diffusion simulation of the hydration profiles of both water contents and d values constrains the duration of liquid water up to 130 000 250 000 years at 0 c or 700 1 500 years at 40 c all analyses of the melt inclusions including the hydration profiles show a logarithmic correlation between the water contents and the d values plotting within a two endmember mixing area the extremely d enriched endmember represents martian underground water with a d value of 6034 72 2 this is the highest d value reported in martian meteorites and it is consistent with the recent analyses of martian soils by the curiosity rover leshin et al 2013 suggestive of more water escaped from mars than previous estimates the analyses of apatite show a distinct positive correlation between the water contents 0 10 0 58 wt and the d values 737 4239 which can be explained by assimilation of d rich martian crustal materials and enhancement of water via fractional crystallization the observed correlation suggests that the water contents of martian mantle reservoirs might have been overestimated from d enriched apatite in previous studies our estimation based on the least contaminated apatite grains from grv 020090 turned out a low water content of the primordial parent magma 380 750 ppm which was likely derived from a relatively dry martian mantle reservoir of grv 020090 38 75 ppm h2o

chalcophile elements in martian meteorites indicate low sulfur content in the martian interior and a volatile element depleted late veneer abstract it is generally believed that the martian mantle and core are rich in sulfur and that shergottites originated from sulfide saturated magma however recent work suggests that the high feo contents would require very high s concentrations in shergottite parent magmas at sulfide saturation here we combine new and published data on chalcophile elements in shergottites nakhlites and alh84001 to constrain the sulfide saturation state of the parent magmas and the chalcophile element concentrations in their mantle sources regardless of the mgo content and the long term depletion history of incompatible lithophile elements as indicated by initial e143nd different groups of shergottites display limited variations in ratios of pt pd re cu s se and te the emplacement of most shergottites within the crust and limited variations of ratios of chalcophile elements with substantial differences in volatility during eruption e g cu s cu se and pt re indicate little degassing losses of s se te and re from shergottites limited variations in ratios of elements with very different sulfide silicate melt partition coefficients and negative correlations of chalcophile elements with mgo require a sulfide undersaturated evolution of the parent magmas from mantle source to emplacement in the crust consistent with the feo based argument sulfide petrography and the komatiite like fractionation of platinum group elements pge in shergottites also support this conclusion the absence of accumulated sulfides in the ancient martian cumulate alh84001 results in very low contents of pge re cu se and te in this meteorite hinting that sulfide undersaturated magmas may have occurred throughout the martian geological history the negative correlation of cu and mgo contents in shergottites suggests approximately 2 0 4 1 s g g cu in the martian mantle the ratios of cu s se and te indicate 360 120 g g 1s s 100 27 ng g 1s se and 0 50 0 25 ng g 1s te in the martian mantle at such low s concentrations all s in martian mantle sources may dissolve in basaltic melts that form at 5 partial melting assuming equilibrium metal silicate partitioning and provided that the compositional model of the martian mantle based on snc meteorites is correct martian mantle inventories of cu s and se were mostly established by core formation and the martian core should contain