deep crustal carbonate rocks exposed by meteor impact on mars mars may have once had a co2 rich atmosphere but carbonate rocks that could provide evidence for such conditions are sparse spectral analyses of rocks exposed from deep within an impact crater reveal that carbonate deposits may be extensive on mars but are buried under layers of younger volcanic rocks

effect of chemical composition of water on the oxygen 18 and carbon 13 signature preserved in cryogenic carbonates arctic canada implications in paleoclimatic studies abstract this study examines the 18o and 13c composition of cryogenic carbonate deposits in relation to the initial 18o 13cdic and chemical composition of the water from which it precipitated this study focuses on cryogenic calcites precipitated in relation to aufeis aggradation since it offers the possibility of examining the chemical and isotopic partitioning that occurs during freezing the studied aufeis are located in the western canadian arctic yt and nwt a region underlain mostly by limestone bedrock and southern baffin island nu an area of crystalline bedrock the results indicate that the 18o composition of cryogenic calcite from a carbonated environment are slightly depleted over that of the initial 18o of the parent water while those from a non carbonated environment are strongly depleted over the initial 18o of the parent water as a result of the lower calcite saturation state of the parent water this suggest that the 18o of cryogenic carbonates not only depends on the initial 18o composition of the parent water and the temperature at which the carbonate precipitated but also on the calcite saturation state of the parent water and kinetic inhibitions during calcite precipitation given that the aggradation of aufeis occurs under closed system freezing the residual water will become progressively depleted in 18o as a result of the removal of heavier isotopes in the ice in addition freezing imparts a concentration of solutes in the residual water which leads to an increase in calcite saturation index therefore carbonate precipitated in equilibrium from water that has a low calcite saturation index will have a highly depleted 18o composition over that of the initial 18o values of the parent water since the calcite saturation state will only be exceeded in the late stage of freezing by contrast solute and isotopic partitioning during freezing has little effect on the 13c of the cryogenic carbonates as it tends to reflect that of the initial 13cdic value of the parent water these findings have significant implications in the use of cryogenic carbonates in paleoclimate studies care must be taken when interpreting the 18o signature preserved in cryogenic carbonates since their signature might be modified by freezing prior to their precipitation which will lead to a lighter 18o composition of the cryogenic carbonates therefore it would be difficult to use the 18o composition of cryogenic carbonates as a direct proxy in paleoclimatic reconstruction unless details about the chemical composition of parent waters are known nevertheless the 13c composition of the cryogenic carbonates that precipitated under closed system conditions can allow insights into the different water sources contributing to carbonate precipitation

cryogenic cave calcite from several central european caves age carbon and oxygen isotopes and a genetic model abstract cryogenic cave calcite ccc formed by segregation of solutes during water freezing was found in three central european caves this calcite type forms accumulations of loose calcite grains on cave floor the calcite grains are of highly variable crystal morphology and of sizes ranging from less than 1 mm to over 1 cm the most typical feature is their accumulation as loose uncemented crystals u series dating indicates the formation of ccc in the studied caves during several climatic oscillations of the weichselian between 61 and 36 ka bp in the chelsiowa jama jaskinia jaworznicka cave system in poland between 34 and 26 ka bp in the buml cave in the czech republic and between 26 and 21 ka bp in the stratenska jasky a cave system slovakia at the time of ccc formation the studied caves were lying in a periglacial zone detailed c and o stable isotope study of ccc samples revealed that slow water freezing under isotope equilibrium was the dominant formational process in the studied polish and czech caves significantly higher 13 c values of ccc in the stratenska jasky a cave indicate either water freezing in a more opened system with continuous co 2 escape rayleigh fractional separation or participation of another co 2 source the model of slow water freezing under isotope equilibrium is supported by isolated character of the caves having limited ventilation in contrast modern cryogenic cave calcite powders sampled directly on the ice surface of two recently iced caves in slovakia with high ventilation showed much higher 18 o and 13 c data similar to cryogenic calcites obtained in experimental rapid water freezing

mineralogical and geochemical analyses of antarctic lake sediments a study of reflectance and mossbauer spectroscopy and c n and s isotopes with applications for remote sensing on mars abstract we analyzed lake bottom sediments from the dry valleys region of antarctica to study the influence of water chemistry on the mineralogy and geochemistry of these sediments as well as to evaluate techniques for remote spectral identification of potential biomarker minerals on mars lakes from the dry valleys region of antarctica have been investigated as possible analogs for extinct lake environments on early mars sediment cores were collected in the present study from perennially ice covered lake hoare in the taylor valley these sediments were taken from a core in an oxic region of the lake and another core in an anoxic zone differences between the two cores were observed in the sediment color fe ii fe iii ratio the presence of pyrite the abundance of fe s and some trace elements and the c n and s isotope fractionation patterns the results of visible infrared reflectance spectroscopy 0 3 25 m mossbauer spectroscopy 77 and 4 k and x ray diffraction are combined to determine the mineralogy and composition of these samples the sediments are dominated by plagioclase k feldspar quartz and pyroxene algal mats grow on the bottom of the lake and organic material has been found throughout the cores calcite is abundant in some layers of the sediment core from the shallow oxic region and pyrite is abundant in the upper sediment layers of the core from the deep anoxic region of lake hoare analysis of the spectroscopic features due to organics and carbonates with respect to the abundance of organic c and carbonate contents was performed in order to select optimal spectral bands for remote identification of these components in planetary regoliths carbonate bands near 4 and 6 8 m 2500 and 1500 cm 1 were detected for carbonate abundances as low as 0 1 wt co2 organic features at 3 38 3 42 and 3 51 m 2960 2925 and 2850 cm 1 were detected for organic c abundances as low as 0 06 wt c the 13c and 15n trends show a more complex organic history for the anoxic region sediments than for the oxic region sediments the biogenic pyrite found in the core from the anoxic zone is associated with depleted 34s values and high organic c levels and could be used as a potential biomarker mineral for paleolakes on mars

shear wave velocity in marine sediments on young oceanic crust constraints from dispersion analysis of scholte waves summary an experiment with a newly developed implosive source located about 1 m above the sea oor at 3665 m depth revealed a slow interface wave this wave is attributed to s waves in a soft sediment layer covering the hard rock sub bottom dispersion analysis by means of the multiple lter technique yields the group velocity as a function of frequency model calculations showed that the observed dispersion curve can be reproduced by considering a steep gradient of s velocity within the sediment layer nearly perfect agreement of experimental and model data could be achieved with a sediment layer thickness of 21 5 m an s speed of 225 m s 1 at the water sediment interface and an increase by 23 s 1 within the layer these values are relatively high compared to data from the literature however previous estimates of in situ s wave velocity have been obtained on old oceanic crust in the vicinity of continents or islands while our experiment was carried out on young paci c crust therefore we suggest two mechanisms which could support a relatively high s speed in sediments 1 the input of hydrothermally generated metalliferous sediments from the adjacent spreading axis and 2 post depositional diagenesis which has accelerated the induration of sediments

insights into the formation of fe and mg rich aqueous solutions on early mars provided by the alh 84001 carbonates abstract the chemical and isotopic pattern of the zoned carbonate globules in the alh 84001 meteorite reveals a unique aqueous environment on early mars if the evolution of the fluid composition was dictated primarily by carbonate precipitation the zoning pattern of the carbonates can constrain the fluid to have had an mg ca mole ratio 5 3 and a fe ca mole ratio 1 prior to the formation of the carbonates chemical equilibrium modeling of water rock interactions indicates that low temperatures and low ph favor the formation of an aqueous solution with elevated mg and fe concentrations the modeling shows that a sufficiently fe and mg rich fluid could have formed through low temperature 2 fugacity 0 1 1 bar formation of alh 84001 carbonates could have been driven by degassing of co 2 and corresponding ph increase in near surface environments during an upwelling of subsurface co 2 rich solutions this scenario is consistent with the unaltered nature of the alh 84001 rock and with chemical and isotopic composition of its carbonates

related magma ice interactions possible origins of chasmata chaos and surface materials in xanthe margaritifer and meridiani terrae mars abstract we examine here the close spatial and temporal associations among several unique features of xanthe and margaritifer terrae specifically the valles marineris troughs or chasmata and their interior deposits chaotic terrain the circum chryse outflow channels and the subdued cratered material that covers xanthe margaritifer and meridiani terrae though previous hypotheses have attempted to explain the origin of individual features or subsets of these we suggest that they may all be related all of these features taken together present a consistent scenario that includes the processes of sub ice volcanism and other magma ice interactions results of intrusive events during late noachian to early amazonian times

isotopic and geochemical investigation of two distinct mars analog environments using evolved gas techniques in svalbard norway the 2010 arctic mars analog svalbard expedition amase investigated two distinct geologic settings on svalbard using methodologies and techniques to be deployed on mars science laboratory msl amase related research comprises both analyses conducted during the expedition and further analyses of collected samples using laboratory facilities at a variety of institutions the sample analysis at mars sam instrument suite on msl includes pyrolysis ovens a gas processing manifold a quadrupole mass spectrometer qms several gas chromatography columns and a tunable laser spectrometer tls an integral part of sam development is the deployment of sam like instrumentation in the field during amase 2010 two parts of sam participated as stand alone instruments a hiden evolved gas analysis mass spectrometer ega qms system represented the ega qms component of sam and a picarro cavity ring down spectrometer ega crds represented the ega tls component of sam a field analog of chemin the xrd xrf on msl was also deployed as part of this field campaign carbon isotopic measurements of co2 evolved during thermal decomposition of carbonates were used together with ega qms geochemical data mineral composition information and contextual observations made during sample collection to distinguish carbonates formation associated with chemosynthetic activity at a fossil methane seep from abiotic processes forming carbonates associated with subglacial basaltic eruptions carbon and oxygen isotopes of the basalt hosted carbonates suggest cryogenic carbonate formation though more research is necessary to clarify the history of these rocks

microscale carbon isotope variability in alh84001 carbonates and a discussion of possible formation environments abstract the carbonates in martian meteorite alh84001 preserve a record of aqueous processes on mars at 3 9 ga and have been suggested to contain signatures of ancient martian life the conditions of the carbonate formation environment are critical for understanding possible evidence for life on mars the history of water on mars and the evolution of the martian atmosphere despite numerous studies of petrographic relationships microscale oxygen isotope compositions microscale chemical compositions and other minerals associated with the carbonates formation models remain relatively unconstrained microscale carbon isotope analyses of alh84001 carbonates reveal variable 13c values ranging from 27 to 64 the isotopic compositions are correlated with chemical composition and extent of crystallization such that the mg poor early formed carbonates are relatively 13c depleted and the mg rich later forming carbonates are 13c enriched these data are inconsistent with many of the previously proposed environments for carbonate formation and a new set of hypotheses are proposed specifically two new models that account for the data involve low temperature

a primitive alkali basaltic stratovolcano and associated eruptive centres northwestern spitsbergen volcanology and tectonic significance abstract three quaternary volcanic centres sverrefjell sigurdfjell and halvdanpiggen in northwestern spitsbergen formed by off ridge alkali basaltic volcanism associated with nearby ocean floor spreading and subsequent tectonism the sverrefjell volcano is a unique stratovolcano constructed of primitive alkali basaltic pyroclastics with subordinate lavas about 15 20 vol of this volcanic and the other centres comprises a wide variety of upper mantle and lower crustal xenoliths a new estimate of the age of the sverrefjell volcano places the time of formation at a minimum of 100 000 250 000 years ago earlier than previous estimates the occurrence of interbedded pillow lavas and pahoehoe flows at all levels of sverrefjell suggests that the volcano grew concurrently with the rise of the surrounding glaciers basaltic sequences occurring as nearby mountain cappings represent earlier volcanism 2 5 11 5 ma also probably a result of thermal disturbance related to nearby ocean floor spreading geothermobarometry calculations on xenoliths from the three quaternary localities define a very high geotherm consistent with their location near the yermak hot spot and provide a good datum point for the geothermal gradient adjacent to such a thermal anomaly

carbon isotope composition of organic compounds produced by abiotic synthesis under hydrothermal conditions although it is widely believed that production of organic compounds by fischer tropsch synthesis and related processes occurs in many geologic environments unambiguous identification of compounds with an abiotic origin in natural samples has been hampered by a lack of means to discriminate between abiotic compounds and organic matter from biological sources while isotopic compositions might provide a means to discriminate between biologic and non biologic sources of organic matter there are few data presently available to constrain the isotopic composition of compounds produced by abiotic processes in geologic systems here we report results of laboratory experiments conducted to evaluate the isotopic composition of organic compounds synthesized abiotically under hydrothermal conditions we find the organic products are depleted in 13c to a degree typically ascribed to biological processes indicating that carbon isotopic composition may not be a particularly effective diagnostic means to differentiate between biologic and non biologic sources furthermore our results suggest that the isotopic compositions of reduced carbon compounds found in many ancient rocks that have heretofore been attributed to biological sources could be consistent with an abiotic origin in a hydrothermal setting

carbon oxygen and nitrogen isotopic compositions of possible martian weathering products in eeta 79001 abstract carbon and oxygen isotopic analyses of carbonate rich white druse material isolated from a contact between lithologies a and c of the eeta 79001 shergottite indicate that this component is probably extraterrestrial in origin and not simply an antarctic weathering product the 13c 6 8 and 18o 21 1 values of the calcium carbonate predominantly calcite are unlike 13 c 18 o combinations of most common terrestrial carbonates whether biogenic or abiogenic however 13c and 18o of the carbonates in eeta 79001 are very similar to the corresponding values for carbonates analysed from nakhla a meteorite closely allied to shergottites it seems apparent that the carbonate minerals in these snc meteorites were formed on the meteorites parent body mars isotopic analysis of nitrogen liberated during combustion of a carbonate rich fraction of eeta 79001 does not give any clear evidence for the 15n enriched component isolated from eeta 79001 lithology c glass and postulated as trapped martian atmosphere however substantial amounts of nitrogen were present the origin of these components is unclear but the low temperature of release poses some constraints

hydrothermal origin for carbonate globules in martian meteorite alh84001 a terrestrial analogue from spitsbergen norway carbonate minerals in the ancient martian meteorite alh84001 are the only known solid phases that bear witness to the processing of volatile and biologically critical compounds co2 h2o on early mars similar carbonates have been found in xenoliths and their host basalts from quaternary volcanic centers in northern spitsbergen norway these carbonates were deposited by hot i e hydrothermal waters associated with the volcanic activity by analogy with the spitsbergen carbonates the alh84001 carbonates were probably also deposited by hot water hydrothermal activity was probably common and widespread on early mars which featured abundant basaltic rocks water as ice or liquid and heat from volcanos and asteroid impacts on earth descendants of the earliest life forms still prefer hydrothermal environments which are now shown to have been present on early mars

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

orbital identification of carbonate bearing rocks on mars geochemical models for mars predict carbonate formation during aqueous alteration carbonate bearing rocks had not previously been detected on mars surface but mars reconnaissance orbiter mapping reveals a regional rock layer with near infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the nili fossae region the carbonate is closely associated with both phyllosilicate bearing and olivine rich rock units and probably formed during the noachian or early hesperian era from the alteration of olivine by either hydrothermal fluids or near surface water the presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering proposed to be characteristic of hesperian mars did not destroy these carbonates and thus did not dominate all aqueous environments

depositional conditions of the bathonian to hauterivian janusfjellet subgroup spitsbergen abstract the janusfjellet subgroup was formed under shallow marine shelf conditions dominated by sedimentation of clay but silt and sand also accumulated in significant amounts the sand bodies recognized in the agardhfjellet formation bathonian b are redeposition of sediments originating from earlier deltaic coastal progradation the rurikfjellet formation berriasian hauterivian reveals an upwards increasing sand content reflecting built out of a delta system the prodeltaic material was partly reworked by storm currents the shales of the agardhfjellet formation were in part deposited under oxygen depleted conditions

transition of microbiological and sedimentological features associated with the geochemical gradient in a travertine mound in northern sumatra indonesia abstract modern travertines carbonate deposits in ca rich hydrothermal water with high pco2 often display a changing environment along the water path with corresponding variability in the microbial communities we investigated a travertine bearing hot spring at the blue pool in northern sumatra indonesia the thermal water of 62 c with high h2s 200 m and pco2 1 atm developed a travertine mound 70 m wide the concentrations of the gas components h2s and co2 decrease immediately after the water is discharged while the dissolved oxygen ph and aragonite saturation increase in the downstream direction responding to the geochemical gradient in the water the surface biofilms change color from white to pink light green dark green and brown as the water flows from the vent this corresponds to microbial communities characterized by chemolithoautotrophs halothiobacillaceae purple sulfur bacteria chromatiaceae anaerolineaceae and co occurrence of green non sulfur bacteria chloroflexales cyanobacteria and green sulfur bacteria chlorobiales respectively in an environment with a certain level of h2s 1 m sulfur digestion and anoxygenic photosynthesis can be more profitable than oxygenic photosynthesis by cyanobacteria the precipitated carbonate mineral consists of aragonite and calcite with the proportion of aragonite increasing downstream due to the larger mg2 ca2 ratio in the water or the development of thicker biofilm where the biofilm is well developed the aragonite travertines often exhibit laminated structures that were likely associated with the daily metabolism of these bacteria the microbiological and sedimentological features at the blue pool may be the modern analogs of geomicrobiological products in the early earth biofilm of anoxygenic photosynthetic bacteria had the potential to form ancient stromatolites that existed before the appearance of cyanobacteria

cretaceous cold seep communities and methane derived carbonates in the canadian arctic lower cretaceous cold seep fossil assemblages have been found in the canadian arctic archipelago serpulid worm tubes and bivalves are most abundant in these communities in contrast fossils are scarce in the surrounding strata the fossils are contained in an isotopically light delta 13 c 25 to 50 per mil carbonate rock groundmass that is interpreted to have formed from bacterial oxidation of methane the rocks were deposited at intermediate depth 400 meters in a cold marine environment nearby normal faults may have provided a conduit for seeping methane and hydrogen sulfide needed to fuel chemosynthetic bacteria and in turn the higher life forms

investigating the variations in carbon and nitrogen isotopes in carbonaceous chondrites the carbonaceous chondrites contain significant amounts of carbon and nitrogen bearing components the most abundant of which is organic matter stepped combustion data of whole rock and hf hcl residues of carbonaceous chondrites reveal that the organic material can be subdivided operationally into three components 1 free organic matter fom which is readily extractable from whole rock meteorites and is enriched in 13c and 15n 2 labile organic matter lom which has a macromolecular structure but is liberated by hydrous pyrolysis lom is the parent structure for some fom and is also enriched in 13c and 15n and 3 refractory organic matter rom which is also macromolecular but is virtually unaffected by hydrous pyrolysis and is relatively depleted in 13c and 15n the macromolecular entities lom and rom are by far the most abundant organic components present and as such the relative abundances of the 13c and 15n enriched lom and the 13c and 15n depleted rom will have a major influence on the overall isotopic composition of the whole rock meteorite laboratory experiments designed to simulate the effects of parent body aqueous alteration indicate that this form of processing removes lom from the macromolecular material allowing rom to exert a stronger influence on the overall isotopic compositions hence aqueous alteration of macromolecular materials on the meteorite parent body may have a significant control on the stable isotopic compositions of whole rock carbonaceous chondrites the enstatite chondrites are also carbon rich but have been subjected to high levels of thermal metamorphism on their parent body stepped combustion data of hf hcl residues of enstatite chondrites indicate that if they and carbonaceous chondrites inherited a common organic progenitor metamorphism under reducing conditions appears to incorporate and preserve some of the 13c enrichments in lom during graphitisation however when metamorphism is at its most extreme the 15n enrichments in lom are lost

distribution of mid latitude ground ice on mars from new impact craters new impact craters at five sites in the martian mid latitudes excavated material from depths of decimeters that has a brightness and color indicative of water ice near infrared spectra of the largest example confirm this composition and repeated imaging showed fading over several months as expected for sublimating ice thermal models of one site show that millimeters of sublimation occurred during this fading period indicating clean ice rather than ice in soil pores our derived ice table depths are consistent with models using higher long term average atmospheric water vapor content than present values craters at most of these sites may have excavated completely through this clean ice probing the ice table to previously unsampled depths of meters and revealing substantial heterogeneity in the vertical distribution of the ice itself

isotopic composition of carbonates in the snc meteorites allan hills 84001 and zagami we have measured the 13 c 12 c and 14 c 12 c ratios in co 2 released by acid etching of the meteorites zagami and allan hills 84001 we use the 14 c as a label to identify extraterrestrial carbonate phases as they will have a low 14 c 12 c ratio 4 modern terrestrial ratio compared to recent terrestrial material the new studies on allan hills 84001 confirm previous conclusions that the fe mg rich carbonate grains in this meteorite contain carbon with 13 c as high as 45 in contrast the carbon released from zagami is depleted in 13 c with 13 c as low as 20 we conclude that the isotopic composition of the carbon as carbonate released from acid etching of zagami is different from the carbonates observed in both allan hills 84001 and nakhla with the assumption that all of these meteorites sample the surface of mars we propose that the zagami carbonate samples a different carbon reservoir on this planet such as a magmatic source with this interpretation the high 13 c values of carbonate observed in allan hills 84001 and nakhla can be ascribed to a fractionated source compared with the originally light carbon a likely origin for this 13 c enriched component is an isotopically heavy martian atmosphere however given the possibility of biological activity involving allan hills carbonates we cannot exclude this as a source of the isotopic fractionation