post impact alteration of surficial suevites in ries crater germany hydrothermal modification or weathering processes alteration of surficial suevites at ries crater germany was studied by means of x ray diffraction and scanning electron microscopy here we discuss the origin of hydrous silicate clay phases in these suevites that have been previously interpreted as resulting from post impact hydrothermal processes the results of this study indicate that the dominant alteration phases are dioctahedral al fe montmorillonite and halloysite which are typical low temperature clay minerals we suggest that the surficial suevites are not altered by hydrothermal processes and that alteration occurred by low temperature subsurface weathering processes if the surficial suevites were indeed hydrothermally modified during the early stages of post impact cooling then the alteration was of limited character and is completely masked by later weathering

on the enigma of day to day variability in equatorial spread f 1 we show that large scale wave structure lsws in plasma density in the bottomside f layer is a hitherto unheralded contributor to the long standing enigma of day to day variability in equatorial spread f esf little is known about lsws it seems to appear in altitude near a vertical shear in zonal plasma drift during the post sunset rise of the f layer and its growth via an interchange instability appears to predispose quasi periodically spaced regions to development of plasma bubbles first indications are that lsws development is necessary and sufficient for esf occurrence we suggest that variability in lsws development perhaps together with the shear in zonal drift may contribute to day to day esf variability a need revealed by this study is that a cluster of distributed sensors not isolated ones is necessary to pursue the problem of day to day variability

significant depletions of the ionospheric plasma density at middle latitudes a possible signature of equatorial spread f bubbles near the plasmapause 1 plasma density irregularities in the equatorial f region ionosphere are generally called equatorial spread f esf large scale plasma bubbles associated with esf processes are generated in the bottomside f region and penetrate the f peak to the topside f region it is still not fully understood how high esf bubbles can reach in this paper we present the measurements of deep depletions of the ionospheric plasma density at 840 km altitude with the defense meteorological satellite program dmsp satellites in the evening sector on 29 october 2003 the plasma depletions occurred after an interval of strong southward interplanetary magnetic field imf a prominent feature of the observations is that the plasma depletions occurred at very high magnetic latitudes mlat as well as at equatorial latitudes the equatorial depletions were identified as plasma bubbles the depletions at middle latitudes 20 46 mlat were separated from the conventional ionospheric midlatitude trough and identified as the extension of esf flux tubes into these latitudes it implies that the plasma bubble which caused the emptied flux tube at 46 mlat reached the altitude of 6800 km over the magnetic equator the observations may represent the highest altitude latitude of plasma bubbles that has ever been reported in the literature for the plasma depletions at even higher latitudes 47 49 mlat near the subauroral polarization stream saps midlatitude trough there are two candidate generation mechanisms one is the extension of esf flux tubes into these latitudes implying that the plasma bubbles reached the altitude of 8400 km over the magnetic equator because the saps midlatitude trough corresponds to the plasmapause at the plasmaspheric heights the observations suggest that esf plasma bubbles may have reached the plasmapause another mechanism is a field aligned low density structure between the plasmasphere and ionosphere and the plasma structure is generated through the strong electric field in the subauroral polarization stream region

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

hydrothermally altered impact melt rock and breccia contributions to the soil of mars samples of melt rock and breccia from 12 terrestrial impact craters were examined to identify alteration minerals and their conditions of formation the dominant assemblage in most cases is clay silica k feldspar zeolite indicating hydrothermal alteration at low pressures and temperatures of 100 300 c the clays are predominantly fe chlorites and smectites in most cases depleted in al and enriched in fe and mg relative to their source rocks alteration of impact glass is often complete while alteration of crystalling melt rock is limited to a few percent of the rock volume impact breccia is altered to only a small extent compared to the alteration of glass impact induced hydrothermal alteration is to be expected at martian impact sites if significant quantities of ground ice and or water are present the alteration products are likely to resemble the clays found at terrestrial craters al fe fractionation similar to that observed on earth is strongly suggested by the viking soil analyses the quantitative contribution of hydrothermal clays to the soil of mars is estimated based on a model which predicts the generation of the equivalent of a 61 m thick blanket of impact melt planet wide the inefficiency of melt production in small craters and the inefficiency of alteration in large craters limit the expected production of clay to a few percent of this figure clays produced by impact induced hydrothermal alteration may be expected to contribute to the fines on mars but this contribution is probably not dominant relative to other suggested sources

new evidence for persistent impact generated hydrothermal activity in the miocene ries impact structure germany the extent of impact generated hydrothermal activity in the 24 km sized ries impact structure has been controversially discussed to date mineralogical and isotopic investigations point to a restriction of hydrothermal activity to the impact melt bearing breccias specifically the crater fill suevite here we present new petrographic geochemical and isotopic data of postimpact carbonate deposits which indicate a hydrothermal activity more extended than previously assumed specifically carbonates of the erbisberg a spring mound located upon the inner crystalline ring of the crater show travertine facies types not seen in any of the previously investigated sublacustrine soda lake spring mounds of the ries basin in particular the streamer carbonates which result from the encrustation of microbial filaments in subaerial spring effluents between 60 and 70 c are characteristic of a hydrothermal origin while much of the primary geochemical and isotopic signatures in the mound carbonates have been obliterated by diagenesis a postimpact calcite vein from brecciated gneiss of the subsurface crater floor revealed a flat rare earth element pattern with a clear positive eu anomaly indicating a hydrothermal fluid convection in the crater basement finally the strontium isotope stratigraphic correlation of the travertine mound with the crater basin succession suggests a hydrothermal activity for about 250 000 yr after the impact which would be much longer than previously assumed

ordovician impact crater at kardla hiiumaa island estonia abstract the buried and well preserved kardla crater in estonia southern fennoscandia 58 59 22 40e with a diameter of approximately 4 km was discovered in 1967 the subsurface structure of the crater has been studied by gravity anomaly measurements aeromagnetics and by more than 300 boreholes in the crater on the rim ring wall and in the surrounding area recent boreholes reaching 800 m have revealed that the crater is 540 m deep and has 100 m high central peak barely visible in the present topography the crater is filled with palaeozoic and quaternary deposits and is mostly low marshy land surrounded by a low ridge along the ring wall quaternary landforms such as eskers and post glacial beach ridges also complicate the topography in the buried sub quaternary bedrock relief the crater occurs as a roundish depression bordered with two 10 30 m high horseshoe shaped elevations the bedrock topography was slightly drumlinized by glacial excavation the crater formed 455 ma in composite stratigraphy middle and lower ordovician 20 m and cambrian 120 m sedimentary rocks overlying crystalline basement on the bottom of a shallow nearshore sea the subsurface structure of the crater is well preserved in vertical section from the top are 1 post impact cover of ordovician sedimentary rocks 15 100 m thick 2 allochthonous breccias filling the lower part of the crater and beds of fall out breccias and conglomerates sandstones and sandy limestones consisting of debris of reworked fall out breccia and wall rocks surrounding the crater 3 a body of autochthonous and subautochthonous breccias forming the bottom and the central peak of the crater and also remnants of its rim shocked rocks and minerals from autochthonous and allochthonous breccias have been revealed by optical microscopy

stable isotope composition of bentonites from the swiss and bavarian freshwater molasse as a proxy for paleoprecipitation abstract the hydrogen and oxygen isotope compositions of bentonites and smectite rich tuffs from the north alpine foreland basin were measured for samples dated between 9 and 21 ma assuming clay mineral formation shortly after the deposition of the volcanic ash layers and at surface temperatures estimated from paleoclimatic studies the h and o isotope composition of water in equilibrium with the clay minerals can be calculated a comparison with values derived from other proxies of paleoprecipitation in the molasse basin such as pedogenic carbonates and mammal remains and 18 o values of carbonate in the bentonite beds suggests that the 18 o values of water estimated by this method are typical for foreland precipitation at this time and for this region therefore the 18 o value of smectite in bentonites and altered tuff layers can be a useful tool for studies of paleoclimate and topography there are however indications that the clay minerals did not retain their initial hydrogen isotopic composition but that a postformational exchange of h isotopes has occurred

the lappajarvi impact structure finland age duration of crater cooling and implications for early life abstract an in depth approach of 40 ar 39 ar dating of the 23 km lappajarvi impact structure finland was performed using carefully selected single grain aliquots of optically fresh clast poor impact melt rock and recrystallized k feldspar melt particles separated from impact metamorphosed granite pegmatite step heating analysis yielded a set of 13 statistically robust plateau ages obtained on six melt rock and seven k feldspar samples the melt rocks yielded fully concordant ages with a weighted mean of 76 37 0 46 ma dating of the k feldspar melt particles resulted in a series of younger plateau ages ranging from 75 11 0 36 to 76 11 0 35 ma the melt rock results combined with the oldest syn melt rock k feldspar age and including all sources of uncertainties yielded a weighted mean age of 76 20 0 29 ma 2 mswd 1 02 p 0 41 which is interpreted to represent the best estimate age of the lappajarvi impact the age spread of at least 1 1 0 5 ma between the crystallization of the impact melt rocks and the k feldspar melt particles warns against the use of single 40 ar 39 ar analysis to derive a meaningful impact age in turn the age offset monitors both rapid cooling of the lappajarvi melt sheet versus slow cooling and impact induced hydrothermal circulation within the crater basement most likely driven by long lasting heat flow from the hot central uplift of the impact structure this interpretation is in line with the grain size dependent argon diffusion parameters and apparent closure temperatures of 230 410 c determined for various domain sizes of k feldspars observed in this study our study shows that even in comparatively small impact craters post impact hydrothermal activity can be estimated to last between 600 ka and 1 6 ma and is technically resolved by means of the 40 ar 39 ar dating technique therefore the longevity of hydrothermal systems in medium sized impact craters might be an order of magnitude longer than previously estimated prolonged post impact heat flow in medium sized craters in analogy to lappajarvi might have played an important role in the emergence of life on early earth and possibly mars

effects of tidal forcing conductivity gradient and active seeding on the climatology of equatorial spread f over kwajalein plasma structure in nighttime equatorial f layer referred to as equatorial spread f esf displays climatology whose seasonal variation depends on longitude at longitudes where esf favors equinoxes times when maxima occur can be predicted in terms of the day of year when e region sunset is simultaneous in conjugate hemispheres i e sunset nodes aside from occurrences around equinoxes there are only three longitudes where esf also occurs during a solstice one is the central pacific region here esf activity is strong during the june solstice when solar activity is high to understand this puzzling behavior esf climatology over the kwajalein atoll was compared with properties of the postsunset rise pssr of the f layer and seeding activity in the troposphere the key findings are as follows 1 maxima in pssr velocity vpssr are better aligned with equinoxes than with sunset nodes hence seasonal pattern of vpssr not only sunset nodes should be included in interpretation of esf climatology 2 the source of vpssr during solstice appears to differ from that during equinoxes 3 equinoctial maxima in vpssr could be related to a semiannual variation in equatorial electrojet strength and its contribution to polarization of the f region dynamo current 4 enhanced vpssr during the june solstice is interpreted in terms of tidal forcing with a wave number of 2 5 displacements of maxima in esf climatology from maxima in vpssr are shown to be consistent with deep convective activity

distribution petrography and shock metamorphism of the ejecta of the ries crater in germany a review abstract the lithologies and distribution of the various ejecta formations from the ries crater germany are described they may be subdivided into 1 low shock level 10 gpa represented by polymict crystalline breccias fall out suevites crater suevite and tektites moldavites the ejecta from the mesozoic sedimentary column do not show effects of shock pressures exceeding 10 gpa and only basement gneisses were shock melted to yield suevite glasses it is therefore concluded that the maximum impact energy was transferred from the impactor to the target rocks at a depth of at least 1000 m below ground level where a complex of gneisses underlies shallower granitic intrusions the estimated depth of the transient crater was about 2700 m and its diameter was 12 13 km bunte breccia megablocks of sedimentary rocks and crystalline breccias and megablocks were ejected in ballistic trajectories and form the earliest ejecta deposits extending up to a radius of 22 km fall out suevites are understood to have been lofted from the transient crater by an expanding plume of vaporized rocks and deposited outside the crater as fluidized turbulent masses on top of the earlier ejecta in contrast the crater suevite never left the crater cavity it represents the main mass of suevite moldavites are understood to have been formed during the first encounter of the impactor with the ground by condensation from vaporized and ionizised tertiary sands covering the surface of the target area

the caco3 profile in a recent ionian sea core and the tree ring radiocarbon record over the last two millennia the calcium carbonate caco sub 3 profile of a recent sediment core drilled in the ionian sea in 1979 is studied the caco sub 3 content of the sediment has been measured at regularly spaced intervals of delta d 0 25 cm corresponding to delta t 3 87 yr from ad 170 to the present the caco sub 3 profile of the core closely resembles the radiocarbon time series as deduced from tree ring data the two records have a correlation coefficient of about 0 8 and show strikingly similar long term variations this result presumably follows from the fact that both systems take part in the carbon cycle the spectral analysis of the caco sub 3 time series reveals the presence of the well known periodicity with period ca 200 years characteristic of the delta sup 14 c record since the caco sub 3 content of sea sediments is governed by biological physical and chemical processes in surface sea waters which in turn are strongly influenced by climatic conditions and since the approx 200 yr delta sup 14 c wave is known to be governed by solar modulation of galactic cosmic rays the tuning of these two records on the same frequencies suggests a strong sun climate relationship

impact generated hydrothermal systems on earth and mars it has long been suggested that hydrothermal systems might have provided habitats for the origin and evolution of early life on earth and possibly other planets such as mars in this contribution we show that most impact events that result in the formation of complex impact craters i e 2 4 and 5 10 km diameter on earth and mars respectively are potentially capable of generating a hydrothermal system consideration of the impact cratering record on earth suggests that the presence of an impact crater lake is critical for determining the longevity and size of the hydrothermal system we show that there are six main locations within and around impact craters on earth where impact generated hydrothermal deposits can form 1 crater fill impact melt rocks and melt bearing breccias 2 interior of central uplifts 3 outer margin of central uplifts 4 impact ejecta deposits 5 crater rim region and 6 post impact crater lake sediments we suggest that these six locations are applicable to mars as well evidence for impact generated hydrothermal alteration ranges from discrete vugs and veins to pervasive alteration depending on the setting and nature of the system a variety of hydrothermal minerals have been documented in terrestrial impact structures and these can be grouped into three broad categories 1 hydrothermally altered target rock assemblages 2 primary hydrothermal minerals precipitated from solutions and 3 secondary assemblages formed by the alteration of primary hydrothermal minerals target lithology and the origin of the hydrothermal fluids strongly influences the hydrothermal mineral assemblages formed in these post impact hydrothermal systems there is a growing body of evidence for impact generated hydrothermal activity on mars although further detailed studies using high resolution imagery and multispectral information are required such studies have only been done in detail for a handful of martian craters the best example so far is from toro crater marzo g a davila a f tornabene l l dohm j m fairen a g gross c kneissl t bishop j l roush t l mckay c p 2010 icarus 208 667 683 we also present new evidence for impact generated hydrothermal deposits within an unnamed 32 km diameter crater 350 km away from toro and within the larger holden crater synthesizing observations of impact craters on earth and mars we suggest that if there was life on mars early in its history then hydrothermal deposits associated with impact craters may provide the best and most numerous opportunities for finding preserved evidence for life on mars moreover hydrothermally altered and precipitated rocks can provide nutrients and habitats for life long after hydrothermal activity has ceased

effects of solar and geomagnetic activities on the zonal drift of equatorial plasma bubbles equatorial plasma bubbles are mostly generated in the postsunset sector and then move in the zonal direction plasma bubbles can last for several hours and move over hundreds of kilometers even more than 1000 km in this study we use measurements of ion density by the communication navigation outage forecasting system satellite to determine the orbit averaged drift velocity of plasma bubbles the objective of the study is to identify the dependence of the bubble drift on the solar radio flux and geomagnetic activities in total 5463 drift velocities are derived over may 2008 to april 2014 and a statistical analysis is performed the average pattern of the bubble drift is in good agreement with the zonal drift of the equatorial f region plasma the zonal drift velocity of plasma bubbles increases with the solar radio flux however the increase shows different features at different local times geomagnetic activities cause a decrease of the eastward drift velocity of plasma bubbles equivalent to the occurrence of a westward drift through disturbance dynamo process in particular the decrease of the eastward drift velocity appears to become accelerated when the dst index is smaller than 60 nt or kp is larger than 4

evidence for a spatially extensive hydrothermal system at the ries impact structure germany the 15 ma 26 km diameter ries impact structure in south central germany was one of the first terrestrial impact structures where evidence of impact associated hydrothermal alteration was recognized previous studies suggested that pervasive high temperature hydrothermal activity was restricted to the area within the inner ring i e the crater fill impactite units here we present mineralogical evidence for localized hydrothermal activity in the ejecta beyond the crater rim in two previously unstudied settings a pervasively altered lens of suevite ejecta directly overlying the bunte breccia at the aumuhle quarry and suevite ejecta at depth overlain by 20 m of lacustrine sediments sampled by the wornitzostheim 1965 drill core a comprehensive set of x ray diffraction analyses indicates five distinct alteration regimes 1 surficial ambient weathering characterized by smectite and a minor illitic component 2 locally restricted hydrothermal activity characterized by an illitic component and minor smectite 3 hydrothermal activity at depth characterized by smectite a minor illitic component and calcite 4 hydrothermal activity at depth characterized by smectite a minor illitic component calcite zeolites and clinochlore and 5 pervasive hydrothermal activity at depth characterized by smectite a minor illitic component and minor clinochlore these data spatially extend the ries postimpact hydrothermal system suggesting a much more extensive complex and dynamic system than previously thought constraining the mineralogical alteration regimes at the ries impact structure may also further our understanding of impact associated phyllosilicate formation on mars with implications for climate models and habitability

hf zr and ree partition coefficients between ilmenite and liquid implications for lunar petrogenesis hf zr and ree partition coefficients between ilmenite and coexisting liquid were determined under near lunar conditions ilmenite was synthesized at 1125 c under low oxygen fugacity fo2 10 12 4 from glass of a high ti mare basalt composition doped with 50 100 g g of ree and hf and 500 1000 g g of zr the partition coefficients d of ilmenite for hf and zr obtained by isotope dilution analysis are 0 41 and 0 33 respectively these values are significantly lower than those of ilmenite 3 0 and 1 8 respectively from a kimberlite megacryst fujimaki et al 1984a dree for the synthesized ilmenite are slightly smaller than those of ilmenite from the kimberlite megacryst and the dlu is 0 056 these results suggest that ilmenite may have played an important role in the lu hf evolution of lunar mare basalts using newly determined dlu and dhf for ilmenite the lu hf evolution or lunar cumulates and the coexisting magma was examined for several different crystallization sequences by a model calculation the lu hf variation trend of most high ti mare basalts is well explained by a small degree less than 5 of partial melting of the cumulates however a higher degree of partial melting is required to explain the variation of very low ti basalts green glass and apollo 12 low ti basalts apollo 15 low ti basalts could not be produced by simple partial melting but may require chromite crystallization as well

the nature of the groundmass of surficial suevite from the ries impact structure germany and constraints on its origin surficial suevites from the ries impact structure have been investigated in the field and using optical and analytical scanning electron microscopy the groundmass of these suevites comprises calcite clay minerals impact melt glass crystallites plagioclase garnet and pyroxene francolite and ba phillipsite the latter zeolite is a secondary phase abundant textures have been observed intricate flow textures between the various groundmass phases globules of each phase in the other phases spheroids of pyrrhotite in calcite the budding off of clay globules into silicate glass and or calcite euhedral overgrowths of francolite on apatite clasts and quench textured crystallites in the groundmass groundmass forming calcite displays higher feo mno and sio2 contents than limestone target material the composition of suevite clay minerals is highly variable and not always consistent with montmorillonite three types of glasses are distinguished in the groundmass type 1 glasses are sio2 rich and are clearly derived from sandstones in the sedimentary cover while the protoliths of the other two glass types remains unclear analytical data and micro textures indicate that the calcite silicate glass francolite and clay minerals of the groundmass of the ries suevites represent a series of impact generated melts that were molten at the time of and after deposition on cooling plagioclase pyroxene and garnet crystallized from the groundmass these results are at variance with the current traditional descriptive definition of suevite given that ries is the original type occurrence of suevite some modification to the traditional definition may be in order as the results of this study are most consistent with the groundmass of ries surficial suevites representing a mix of several types of impact generated melts we suggest that a possible origin for these suevites is as some form of impact melt flow s that emanated from different regions of the evolving crater

oxygen and hydrogen isotope compositions in clay minerals a potential single mineral geothermometer the opposite slopes of the isotopic fractionation of hydrogen and oxygen in the clay water system and the well known relationship between d and 18o in meteoric waters allow the isotopic composition of clay minerals to be used as a single mineral geothermometer equations can be derived which are valid for continental systems where meteoric waters are common the following equation was derived for smectite 3 54 106t 2 18osm 0 125 dsm 8 95 0 150 this equation was used to determine the isotopic composition and temperature of the waters involved in the transformation of volcanic rock to bentonite at the cortijo de archidona southeastern spain site the values obtained 6 t 21 c i e environmental temperatures confirm the reliability of this equation

fluidization and hydrothermal alteration of the suevite deposit at the ries crater west germany and implications for mars the formation cooling and alteration of the impact ejecta deposits at the ries crater are an analog for impact processes and the formation of regoliths and soils on mars we have studied the suevite deposit an impact melt bearing breccia found outside of the crater rim this suevite contains large numbers of chimney like degassing pipes apparently formed by high gas pressures in the hot 500 c fluidized suevite immediately after deposition of the suevite the likely sources of the gas are volatiles from the melted and shocked basement inclusions the suevite outside of the crater rim contains about 15 wt clay indicating a large amount of alteration of the suevite the clay is an fe rich montmorillonite with less than 5 interstratified illite indicating that the temperature at which most of the alteration occurred was less than 100 130 c the duration of this low temperature period may have been extended by additional heating from the exothermal alteration reactions the surfaces of the degassing pipes are not altered to clays however but have a thin fe rich oxide or hydroxide coating the absence of alteration in the pipes suggests that the main alteration event outside the crater occurred under unsaturated conditions such that the walls of the pipes were dry suevite deposits are likely to exist on mars because of the presence of volatile rich target rock martian suevites may have also been fluidized and hydrothermally altered contributing significantly to the formation of the clay like phases inferred to exist in the martian soil

long term effect of the kardla crater hiiumaa estonia on late ordovician carbonate sedimentation abstract kardla impact crater 4 km in diameter was formed in the early caradoc late ordovician in the baltoscandian shelf sea a sediment starved temperate water carbonate basin the upper ordovician post impact sediments that cover the kardla crater are 15 275 m thick the crater rimwall is composed of three separate basement rises that formed islands or shoals in the late ordovician shelf sea and influenced the sedimentation in the surrounding area the rises provide the means to study the shallow water sedimentary environments and sea level history this may be one of the few cases where shore environments of the baltoscandian ordovician palaeobasin are preserved in the geological record lithofacies distribution was studied in the crater area from data of about 100 drillcores grain size distribution and composition of the non carbonate material were analyzed in six core sections in order to reconstruct the history of crater erosion the post impact marine deposits lie on a partly redeposited and mixed ejecta layer derived from the cambrian to lower ordovician silici clastic deposits in the target area beds of marine carbonate sediments of caradoc age wackestones and mudstones on lap on the slope of the crater rim a shift of sedimentation towards the crater rim during the caradoc is evidence of a relative sea level rise which was a combination of early caradoc eustatic rise crater area subsidence and compaction of pre impact and impact sediments the occurrences of coarse sand and gravel in specific stratigraphic intervals reflect the intensity of wave action and sea level changes in the area a detailed curve of sea level changes during late ordovician has been constructed and different post impact sedimentation models are presented for the crater area the sedimentation pattern changed during the caradoc as a result of sea level rise and climatic change the synchronous appearance of echinoderm bioclastic accumulations in shoal areas in estonian mainland and in the kardla rim dates the climatic change in the basin area as late keila middle caradoc time assuming that the caradoc lasted about 11 million years infilling of the kardla crater required about 7 million years and influence of the crater structure on sedimentation was obvious even 10 million years after the impact event the tectonic stability of the region the low rate of sedimentation and long lasting differential compaction of sediments in the crater area account for this extraordinary long influence of crater the kardla crater is an example of the astrobleme formed in ancient shelf sea which may be used to reconstruct basin history of post impact times

coherent and incoherent scatter radar study of the climatology and day to day variability of mean f region vertical drifts and equatorial spread f

40ar 39ar laser probe dating of the central european tektite producing impact event a new 40ar 39ar data set is presented for tektites from the central european strewn field moldavites this is the only strewn field that is entirely situated in a continental environment and still characterized by scattered ages 14 15 3 myr the main objectives of the study were to define more precisely the moldavite formation age and provide a good calibration for a glass standard proposed for fission track dating the laser total fusion ages obtained on chips from 7 individual specimens from the southern bohemian and moravian subfields are restricted to a narrow interval of time with an average of 14 34 0 08 myr relative to the 27 95 0 09 myr of the fish canyon tuff biotite this result gives a more precise age not only for the tektite field but also for its producing impact if the genetic link between the moldavites and the nordlinger ries impact crater is maintained then this new age has to be considered a reliable estimate for the ries crater also this new value places the formation of central european tektites within the lower serravallian period in the latest geologic timescales evidence of their impact products such as glass spherules or shocked minerals can therefore be sought in sedimentary marine formations in a more precisely defined age interval

hydrothermal alteration at the lonar lake impact structure india implications for impact cratering on mars the 50 000 year old 1 8 km diameter lonar crater is one of only two known terrestrial craters to be emplaced in basaltic target rock the 65 million year old deccan traps the composition of the lonar basalts is similar to martian basaltic meteorites which establishes lonar as an excellent analogue for similarly sized craters on the surface of mars samples from cores drilled into the lonar crater floor show that there are basaltic impact breccias that have been altered by post impact hydrothermal processes to produce an assemblage of secondary alteration minerals microprobe data and x ray diffraction analyses show that the alteration mineral assemblage consists primarily of saponite with minor celadonite and carbonate thermodynamic modeling and terrestrial volcanic analogues were used to demonstrate that these clay minerals formed at temperatures between 130 c and 200 c by comparing the lonar alteration assemblage with alteration at other terrestrial craters we conclude that the lonar crater represents a lower size limit for impact induced hydrothermal activity based on these results we suggest that similarly sized craters on mars have the potential to form hydrothermal systems as long as liquid water was present on or near the martian surface furthermore the fe rich alteration minerals produced by post impact hydrothermal processes could contribute to the minor iron enrichment associated with the formation of the martian soil

stable isotope composition of smectite in suevites at the ries crater germany implications for hydrous alteration of impactites abstract the 24 km diameter ries crater germany exhibits well preserved crater filling and surficial melt rich breccia deposits that are believed to have been altered by post impact hydrothermal fluids the alteration mineralogy of the crater filling breccias is characterized by clay smectite chlorite and a zeolite assemblage and secondary clay phases smectite minor halloysite in surficial melt bearing breccia deposits using stable isotope analysis of secondary smectitic clay fractions evidence of significant hydrous alteration of impactites at large water rock ratios was found the estimated fluid temperatures using data derived by 18 o and d fractionation suggest smectite precipitation in surficial breccias in equilibrium with meteoric fluids at temperatures 16 5 c in agreement with the long term variation of modern precipitation in the area the stable isotope composition of smectite in crater fill breccia however suggests a trend of monotonously increasing temperatures from 43 to 112 c with increasing depth through the breccia sequence this demonstrates a different origin of alteration and temperature distribution for the surficial and crater filling melt bearing impact breccias in the ries crater our results suggest that the inverted structure of hydrothermal systems observed in some terrestrial impact craters including the ries crater could indicate the initial configuration of a thermal anomaly in the crater filling sequence but which is replaced with a normal hydrothermal convection in crater proper during the course of post impact cooling

hydrothermal alteration in the core of the yaxcopoil 1 borehole chicxulub impact structure mexico petrographic electron microprobe and raman spectrometric analyses of yaxcopoil 1 core samples from the chicxulub crater indicate that the impact generated a hydrothermal system relative textural and vein crosscutting relations and systematic distribution of alteration products reveal a progression of the hydrothermal event in space and time and provide constraints on the nature of the fluids the earliest calcite halite and gaylussite suggest that the impactite sequence was initially permeated by a low temperature saline brine subsequent development of a higher temperature hydrothermal regime is indicated by thermal metamorphic diopside hedenbergite aeg3fs 18 33 en32 11wo 47 53 after primary augite and widespread na k for ca metasomatic alkali exchange in plagioclase hydrothermal sphene apatite magnetite bornite as well as early calcite combined 3 to 8 vol were introduced with metasomatic feldspar a lower temperature regime characterized by smectite after probable primary glass secondary chlorite and other pre existing mafic minerals as well as very abundant calcite veins and open space fillings extensively overprinted the early hydrothermal stage the composition of early and late hydrothermal minerals show that the solution was chlorine rich cl f 10 and that its fe mg ratio and oxidation state increased substantially 4 to 5 logo2 units as temperature decreased through time the most altered zone in the impactite sequence occurs 30 m above the impact melt the lack of mineralogical zoning about the impact melt and convective modeling constraints suggest that this unit was too thin at yaxcopoil 1 to provide the necessary heat to drive fluids and implies that the hydrothermal system resulted from the combined effects of a pre existing saline brine and heat that traveled to the yaxcopoil 1 site from adjacent areas where the melt sheet was thicker limonite after iron oxides is more common toward the top of the sequence and suggests that the impactite section was subjected to weathering before deposition of the tertiary marine cover in addition scarce latest anatase stringers chalcopyrite and barite in vugs francolite after apatite and recrystallized halite are the likely products of limited post ydrothermal ambient temperature diagenesis or ocean and or meteoric water circulation

compositional heterogeneity of impact melt rocks at the haughton impact structure canada implications for planetary processes and remote sensing connecting the surface expression of impact crater related lithologies to planetary or regional subsurface compositions requires an understanding of material transport during crater formation here we use imaging spectroscopy of 6 clast rich impact melt rock outcrops within the well preserved 23 5 ma 23 km diameter haughton impact structure canada to determine melt rock composition and spatial heterogeneity we compare results from outcrop to outcrop using clasts groundmass and integrated clast groundmass compositions as tracers of transport during crater fill melt rock formation and cooling supporting laboratory imaging spectroscopy analyses of 91 melt bearing breccia and clast samples and microscopic x ray fluorescence elemental mapping of cut samples paired with spectroscopy of identical surfaces validate outcrop scale lithological determinations results show different clast rich impact melt rock compositions at three sites kilometers apart and an inverse correlation between silica rich sandstone gneiss and phyllosilicate rich shales and gypsum rich rocks that suggests differences in source depth with location in the target stratigraphy gypsum is primarily sourced from 1 km depth while gneiss is from 1 8 km depth sandstone from 1 3 km and shales from 1 6 1 7 km observed heterogeneities likely result from different excavation depths coupled with rapid quenching of the melt due to high content of cool clasts results provide quantitative constraints for numerical models of impact structure formation and give new details on melt rock heterogeneity important in interpreting mission data and planning sample return of impactites particularly for bodies with impacts into sedimentary and volatile bearing targets e g mars and ceres

palaeoenvironment and palaeoclimate of the middle miocene lake in the steinheim basin sw germany a reconstruction from c o and sr isotopes of fossil remains a differentiated reconstruction of palaeolimnologic environmental and climatic conditions is presented for the middle miocene long term freshwater lake 14 3 to 13 5 ma of the steinheim basin on the basis of a combined c o and sr isotope study of sympatric skeletal fossils of aquatic and terrestrial organisms from the lake sediments the oxygen isotope composition for lake water of the steinheim basin 18oh2o 2 0 0 4 vsmow n 6 was reconstructed from measurements of 18opo4 of aquatic turtle bones the drinking water calculated from the enamel of large mammals proboscideans rhinocerotids equids cervids suids has 18oh2o values 18oh2o 5 9 1 7 vsmow n 31 typical for middle miocene meteoric water of the area this 18oh2o value corresponds to a mean annual air temperature mat of 18 8 3 8 c calculated using a modern day 18oh2o mat relation hence large mammals did not use the lake water as principal drinking water in contrast small mammals especially the then abundant pika prolagus oeningensis drank from 18o enriched water sources 18oh2o 2 7 2 3 vsmow n 7 such as the lake water differences in sr and o isotopic compositions between large and small mammal teeth indicate different home ranges and drinking behaviour and support migration of some large mammals between the swabian alb plateau and the nearby molasse basin while small mammals ingested their food and water locally changes in the lake level water chemistry and temperature were inferred using isotopic compositions of ostracod and gastropod shells from a composite lake sediment profile calcitic ostracod valves ilyocypris binocularis 18o 1 7 1 2 vpdb 13c 0 5 0 9 vpdb n 68 and aragonitic gastropod shells gyraulus spp 18o 2 0 1 3 vpdb 13c 1 1 1 3 vpdb n 89 have 18o and 13c values similar to or even higher than those of marine carbonates 13c values of the biogenic carbonates parallel lake level fluctuations while 18o values scatter around 2 2 and reflect the short term variability of meteoric water inflow vs longer term evaporation 87sr 86sr ratios of aragonitic gyraulus spp gastropod shells parallel the lake level fluctuations reflecting variable inputs of groundwater and surface waters using a water 18oh2o value of 2 0 vsmow water temperatures calculated from skeletal tissue 18o values of ostracods are 16 7 5 0 c gastropods 20 6 5 6 c otoliths 21 8 1 4 c and fish teeth 17 0 2 7 c the calculated mat 19 c lake water temperatures 17 to 22 c and the 18o enriched water compositions are indicative of warm temperate climatic conditions possibly with a high humidity during this period vegetation in the area surrounding the basin was largely of the c3 type as indicated by carbon isotopic compositions of tooth enamel from large mammals 13c 11 1 1 1 vpdb n 40

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

hornblende alteration and fluid inclusions in kardla impact crater estonia evidence for impact induced hydrothermal activity the well preserved krdla impact crater on hiiumaa island estonia is a 4 km diameter structure formed in a shallow ordovician sea about 455 ma ago into a target composed of thin 150 m unconsolidated sedimentary layer above a crystalline basement composed of migmatite granites amphibolites and gneisses the fractured and crushed amphibolites in the crater area are strongly altered and replaced with secondary chloritic minerals the most intensive chloritization is found in permeable breccias and heavily shattered basement around and above the central uplift alteration is believed to have resulted from convective flow of hydrothermal fluids through the central areas of the crater chloritic mineral associations suggest formation temperatures of 100 300 c in agreement with the most frequent quartz fluid inclusion homogenization temperatures of 150 300 c in allochthonous breccia the rather low salinity of fluids in krdla crater 13 wt nacleq suggests that the hydrothermal system was recharged either by infiltration of meteoric waters from the cater rim walls raised above sea level after the impact or by invasion of sea water through the disturbed sedimentary cover and fractured crystalline basement the well developed hydrothermal system in krdla crater shows that the thermal history of the shock heated and uplifted rocks in the central crater area rather than cooling of impact melt or suevite sheets controlled the distribution and intensity of the impact induced hydrothermal processes

the first coordinated ground and space based optical observations of equatorial plasma bubbles 1 we report on ionospheric optical emissions detected by the guvi instrument on the timed satellite as the satellite crosses the equatorial zone the bright appleton anomaly region is imaged often these bright zones are interrupted by regions slanted from west to east as the equator is approached forming a backwards c shape in the image to explain this feature we use simultaneous ground based observations looking equatorward from hawaii using the 777 4 nm emission we also compare these optical observations to inverted electron density maps as well as to those made by radar and to numerical simulations of the rayleigh taylor instability the characteristic shape is a result of a shear in the eastward plasma flow velocity which peaks near the f peak at the equator and decreases both above and below that height the ability to detect these unstable and usually turbulent ionospheric regions from orbit provides a powerful global remote sensing capability for an important space weather process

geology petrography shock petrography and geochemistry of impactites and target rocks from the kardla crater estonia the kardla crater is a 4 km wide impact structure of late ordovician age located on hiiumaa island estonia the 455 ma old buried crater was formed in shallow seawater in precambrian crystalline target rocks that were covered with sedimentary rocks basement and breccia samples from 13 drill cores were studied mineralogically petrographically and geochemically geochemical analyses of major and trace elements were performed on 90 samples from allochthonous breccias sub crater and surrounding basement rocks the breccia units do not include any melt rocks or suevites the remarkably poorly mixed sedimentary and crystalline rocks were deposited separately within the allochthonous breccia suites of the crater the most intensely shockmetamorphosed allochthonous granitoid crystalline derived breccia layers contain planar deformation features pdfs in quartz indicating shock pressures of 2035 gpa an apparent kenrichment and ca na depletion of feldspar and hornblende bearing rocks in the allochthonous breccia units and sub crater basement is interpreted to be the result of early stage alteration in an impact induced hydrothermal system the chemical composition of the breccias shows no definite sign of an extraterrestrial contamination by modeling of the different breccia units with hmxmixing the indigenous component was determined from the abundances of the siderophile elements cr co ni ir and au in the breccia samples no unambiguous evidence for the incorporation of a meteoritic component above about 0 1 wt chondrite equivalent was found

cooling of the kardla impact crater i the mineral paragenetic sequence observation the impact induced hydrothermal system in the well preserved 4 km diameter kardla impact crater on hiiumaa island western estonia was investigated by means of mineralogical chemical and stable c and o isotope studies the mineralization paragenetic sequence with gradually decreasing temperature reveals at least three evolutionary stages in the development of the post impact hydrothermal system 1 an early vapor dominated stage 300 c with precipitation of submicroscopic adularia type k feldspar 2 the main stage 300 to 150 100 c with the development of a two phase vapor to liquid zone leading to precipitation of chlorite corrensite idiomorphic euhedral k feldspar and quartz and 3 a late liquid dominated stage 100 c with calcite i dolomite quartz calcite ii chalcopyrite pyrite fe oxyhydrate and calcite iii precipitation

geothermal characteristics of the ries impact structure summary a new investigation of the thermal conductivity of the drill cores from the research drill hole nordlingen 1973 in the ries impact structure was conducted the 1206 m deep drill hole pen etrated 331 m of post impact lake formations then 275 m of suevitic impact formations with varying amounts of large crystalline basement blocks and then 600 m of fractured displaced basement blocks containing appreciable amounts of dyke breccias the main purpose of the measurements was to see the signature of the shock effects in the thermal properties of the impact formations the use of the new non contact optical scanning instrument allowed mea surements with a resolution of a few centimetres a complicated preparation of the samples was not required thermal conductivity values on dry and on water saturated drill cores and thermal inhomogeneity factors were obtained for samples with a spacing of about 2 m it could be shown that the thermal conductivity is extremely inhomogeneous on various scales and that there is a close relation with the degree of shock and thermal transformation of the target rocks an improved theoretical model for the thermal conductivity of rocks taking into account the form of grains pores and cracks and using measurements on dry and saturated cores yields information on the porous space of the rock samples correlations between the thermal con ductivity and other petrophysical properties determined from well logging data were found they allow other physical properties to be predicted from the conductivity values the new thermal conductivity data together with temperature logging data also gave the possibility of making new estimates of the undisturbed heat flow density in the crater area 90 95 mw m 2 with about 30 per cent higher values than previous estimates a significant increase of the heat flow density in the upper part of the structure indicates fluid migration from deeper parts the absence of thermal anisotropy in crystalline rocks increasing thermal conductivity with depth and increasing heat flow density may be characteristic features of impact structures

deep water formation and quaternary glaciations a large fraction of climatic varability on the quaternary time scale can be explained by nonlinear interactions between the radiation balance of the global atmosphere ocean system and the mass balance of northern hemisphere ice sheets recent analyses of paleoclimatic proxy data indicate a further important contribution to this variability from changes in deep water formation occurring in the north atlantic subpolar sea we study the effects of these changes on variations in global temperature and ice volume characteristic of the late quaternary the novel framework of boolean delay equations bdes is used to formulate a conceptual model of the climatic system under study and to analyze this formal model selfsustained oscillations in the intensity of the atlantic ocean s thermohaline circulation result from the interaction of sea ice formation with the waxing and waning of continental ice sheets the comparison of model results with paleoclimatic records suggests a considerable slowing down of the abyssal circulation during glacial episodes

the carbonate profile of two recent ionian sea cores evidence that the sedimentation rate is constant over the last millennia the authors confirm and extend the results previously reported on the carbonate profile of the gt14 ionian sea core cini castagnoli et al 1990 a second much longer core 2 81 meters named gt89 3 has been taken about 1 km apart from the previous one the carbonate profiles of the two cores are impressively similar the details of the caco sub 3 variations in the two sediments match on the scale of the sampling interval delta d 2 5 mm used for both cores the authors show that delta d corresponds to the mud deposited in a time interval delta t 3 87 plus minus 0 04 years a value which is constant throughout the entire length of the cores this precision is achieved by the tephroanalysis of the two cores in this approach the markers of well known historical eruptions in the vesuvius area are recognized pompei ad 79 pollena ad 472 ischia ad 1301 providing a precise dating which accurately tunes that obtained by the radiometric method the correlation between the carbonate profile of the gt14 core and the tree ring radiocarbon record has been discussed in cini castagnoli et al 1990 here the authors extend these results and show that the same correlation holds atmore least up to 1690 bc due to the longer length of the gt89 3 time series they also show that three periodic components at about 206 yr 228 yr and 179 yr may now be resolved in the carbonate series in close agreement with the results already found for the radiocarbon record less

stable isotope composition of impact glasses from the nordlinger ries impact crater germany abstract the ries impact which today is represented by a 24 km diameter complex crater occurred at 15 ma it is estimated that a projectile of about 1 km diameter formed a transient crater of 6 to 7 km radius and 2 8 km depth impact melt glasses investigated are found within the suevite the breccia that forms the uppermost layers of the ejecta blanket around the crater the glasses are considered to represent quenched melts produced as a result of the impact the oxygen isotope compositions of several glasses sampled from widely spaced localities are very homogeneous with 18 o values in the range of 6 7 to 7 4 and 17 o of 3 3 to 3 7 with increasing devitrification and alteration the 18 o values increase up to 15 8 17 o up to 8 1 water content also increases with devitrification from fresh glasses with about 1 3 wt to 3 8 wt in devitrified glass d values decrease with increasing water content from about 87 to 127 whole rock oxygen isotope compositions of the sedimentary cover sequence range from 17 to 27 and crystalline basement rocks range from 8 8 to 13 5 for granites and gneisses whereas amphibolites have 18 o values of 5 2 and 6 1 models suggesting that the glass in the suevite represents a mixed melt derived from all the rocks present in the suevite in proportion of their occurrence engelhardt 1997 do not agree with the oxygen isotope composition of the glass the simplest explanation for the homogeneous chemical and oxygen isotope composition is that the glass represents quenched melts from a few closely spaced lithologies only high fe and ni contents in the glass cr ni and cr co ratios and relatively low 18 o values indicate involvement of amphibolites during melting the balance of the melt was made up of spatially associated granites or gneisses as indicated by the major element and rare earth element geochemistry the best agreement between major element and oxygen isotope composition of the glass and model melts is obtained by mixtures of amphibolite and granite in proportions similar to their average occurrence in the fallout suevite

the characteristics and generation mechanism of small amplitude and large amplitude esf irregularities observed by the c nofs satellite it is well understood that equatorial plasma bubbles are initiated in the bottomside f region and grow into the topside f region producing equatorial spread f esf irregularities in both bottomside and topside f regions however it is not known whether small amplitude and large amplitude irregularities have the same occurrence pattern and how the generation of small amplitude and large amplitude irregularities is related to the postsunset vertical plasma drift and potential seeding processes in this study we use ion density and velocity data measured by the communications navigation outage forecasting system c nofs satellite during may 2008 july 2014 to derive the longitude month distributions of the occurrence probability of esf irregularities at different amplitudes it is found that the occurrence probability of large amplitude irregularities is well correlated with the postsunset vertical plasma drift and that small amplitude irregularities does not show a clear pattern at low solar activity but is anti correlated with that of large amplitude irregularities at moderate solar activity that is the months and longitudes with high occurrence probability of large amplitude irregularities are exactly those with low occurrence probability of small amplitude irregularities and vice versa esf irregularities are mostly limited below 500 km during low solar activity in 2008 2010 but large amplitude irregularities can reach 700 800 km in altitude during moderate solar activity in 2011 2014 the generation of large amplitude esf irregularities is controlled by the postsunset vertical plasma drift at both low and moderate solar activities in contrast small amplitude esf irregularities at moderate solar activity occur more frequently in the areas where the postsunset vertical plasma drift is small

impact crater lakes on mars the robotic search for life on mars centers on identifying accessible environments where the biological catalyst water has existed the formation of large impact craters on mars 65 km diameter may have resulted in the creation of ice covered impact crater lakes which would not freeze for thousands of years even under present climatic conditions water could be supplied from deep confined aquifers penetrated by the impact craters without the need for surface melt water freezing of the lakes is postponed owing to heat from impact generated melt bearing deposits from impact related uplift of hotter rocks from depth and from the latent heat of freezing of a deep crater lake abundant morphologic evidence for ancient crater lakes has not been found in viking images except for craters associated with outflow channels however ice covered crater lakes could have formed and further searches for evidence of these lakes are warranted the lake deposits from dissected impact craters may represent one of the best targets for future surface exobiology investigations or sample return missions from mars

global distribution of density irregularities in the equatorial ionosphere we analyzed measurements of ion number density made by the retarding potential analyzer aboard the atmosphere explorer e ae e satellite which was in an approximately circular orbit at an altitude near 300 km in 1977 and later at an altitude near 400 km large scale 60 km density measurements in the high altitude regions show large depletions of bubble like structures which are confined to narrow local time longitude and magnetic latitude ranges while those in the low altitude regions show relatively small depletions which are broadly distributed in space for this reason we considered the altitude regions below 300 km and above 350 km and investigated the global distribution of irregularities using the rms deviation n n over a path length of 18 km as an indicator of overall irregularity intensity seasonal variations of irregularity occurrence probability are significant in the pacific regions while the occurrence probability is always high in the atlantic african regions and is always low in the indian regions we find that the high occurrence probability in the pacific regions is associated with isolated bubble structures while that near 0 longitude is produced by large depletions with bubble structures which are superimposed on a large scale wave like background considerations of longitude variations due to seeding mechanisms and due to f region winds and drifts are necessary to adequately explain the observations at low and high altitudes seeding effects are most obvious near 0 longitude while the most easily observed effect of the f region is the suppression of irregularity growth by interhemispheric neutral winds

climatic implications of δ13c variations in a japanese cedar cryptomeria japonica during the last two millenia tree ring 13 c of both modern japanese cedars and of a giant japanese cedar growing throughout the last two millennia on yakushima island southern japan were studied 13 c of eleven modern trees from 320 m to 1700 m above mean sea level revealed a strong dependency on tree growth elevation and a decreasing trend from the late 19th century to the present changes in both climate and 13 c of atmospheric co2 appear to be important for these changes assuming temperature change to be a dominant factor influencing 13 c growth elevation relationship we have inferred a temperature dependency of 13 c 0 29 0 02 c 1 for japanese cedar applying this relationship to a decadal 13 c time series of a giant japanese cedar we reconstructed a high resolution climatic record for the last two millennia a maximum entropy spectral analysis of the tree ring 13 c time series revealed a resemblance of that of other climatic proxy and the presence of the well known periodicity ca 90 and near 200 years characteristic of tree ring 14 c governed by solar modulation of galactic cosmic rays supporting evidence for a sun climate relationship was presented

effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread f we use radar observations from the jicamarca observatory from 1968 to 1992 to study the effects of the f region vertical plasma drift velocity on the generation and evolution of equatorial spread f the dependence of these irregularities on season solar cycle and magnetic activity can be explained as resulting from the corresponding effects on the evening and nighttime vertical drifts in the early night sector the bottomside of the f layer is almost always unstable the evolution of the unstable layer is controlled by the history of the vertical drift velocity when the drift velocities are large enough the necessary seeding mechanisms for the generation of strong spread f always appear to be present the threshold drift velocity for the generation of strong early night irregularities increases linearly with solar flux the geomagnetic control on the generation of spread f is season solar cycle and longitude dependent these effects can be explained by the response of the equatorial vertical drift velocities to magnetospheric and ionospheric disturbance dynamo electric fields the occurrence of early night spread f decreases significantly during equinox solar maximum magnetically disturbed conditions due to disturbance dynamo electric fields which decrease the upward drift velocities near sunset the generation of late night spread f requires the reversal of the vertical velocity from downward to upward for periods longer than about half an hour these irregularities occur most often at 0400 local time when the prompt penetration and disturbance dynamo vertical drifts have largest amplitudes the occurrence of late night spread f is highest near solar minimum and decreases with increasing solar activity probably due to the large increase of the nighttime downward drifts with increasing solar flux

secular non random variations of cosmogenic carbon 14 in the terrestrial atmosphere abstract the time dependence of the14c content of bristlecone pine wood samples dated by their tree rings and grown during the last 8000 years was examined the14c values as measured by the la jolla radiocarbon laboratory were used for the investigation two different smoothing techniques were used for constructing values for equal time intervals in this manner the introduction of regularities that could have resulted from applied mathematical techniques could be excluded there is good evidence for non random features in the power spectrum in particular for a 200 year periodicity the regularities in the power spectrum are further indications supporting the assumption that the14c variations reflect a property of the sun

hydrothermal alteration associated with the chicxulub impact crater upper peak ring breccias abstract the 66 ma 180 km chicxulub impact structure in the northern yucatan peninsula and southern gulf of mexico is the best preserved large impact crater on earth with a well developed peak ring the most recent drilling campaign took place offshore during the joint international ocean discovery program international continental scientific drilling program iodp icdp expedition 364 at site m0077a 21 45 n 89 95 w and recovered 830 m of continuous core initial examination revealed that the peak ring comprises four main lithological units from the base upwards crystalline basement granitoid rocks unit 4 a thin layer of impact melt rocks units 3a and b melt bearing breccias units 2a c and post impact sedimentary rocks unit 1 preliminary analysis of the drill core indicated that hydrothermal alteration has affected all lithologies and is especially pervasive in the melt bearing breccias of unit 2 721 6 to 617 33 meters below sea floor mbsf here we present the first detailed investigation of hydrothermal alteration within the melt bearing breccias alteration phases are predominantly fe mg clay minerals zeolites alkali feldspars calcite and minor sulfides sulfates opal and fe ti oxides alteration is especially intense proximal to lithologic contacts particularly at the base of subunit 2b where there is an abrupt increase in host rock porosity 30 m above the impact melt rocks the pervasiveness of clay minerals and zeolites is attributed to the high amounts of devitrified silicate glass throughout unit 2 the phases preserved here are consistent with the findings of previous hydrothermal studies in other areas of the chicxulub structure and suggest an evolving water rock system that was alkaline saline comparable to seawater volcanic glass alteration

suevite breccia of the ries impact crater germany petrography chemistry and shock metamorphism of crystalline rock clasts clasts of deep seated crystalline basement rocks in suevites of the ries crater germany were catalogued lithologically and classified with regard to their degree of shock metamorphism the sample suite consisted of 806 clasts from 10 outcrops in fallout suevites and 447 clasts from drill cores encountering crater suevite in the crater interior these clasts can be grouped into seven types of metamorphic and nine types of igneous rocks one hundred forty three clasts representing these lithologies were analyzed for major element bulk composition the fallout suevite contains on average 4 vol of crystalline basement clasts 0 4 vol of sedimentary rocks 16 vol of glass bodies some of them aerodynamically shaped and 79 vol of groundmass on average 52 of all crystalline clasts are from metamorphic sources and 42 are of igneous origin using the shock classification of stoffler 1974 8 of all crystalline clasts appear unshocked 10 gpa and 34 30 and 27 of clasts are shocked to stages i 10 35 gpa ii 35 45 gpa and iii 45 60 gpa respectively the bulk composition of suevite glasses is consistent with the modal proportions of crystalline rock types observed in the clast populations this indicates that the glasses originate by shock fusion of a similarly composed basement the crater suevite contains the same crystalline rock types that occur in the fallout suevites the bore hole nordlingen 1973 yields an average of 62 vol metamorphic and 38 vol igneous rocks the crater suevite differs from fallout suevites by a higher clast glass ratio by preponderance 65 95 of clasts shocked to stage i only and by the absence of aerodynamically shaped glass bodies the source of crystalline clasts and melt particles of suevites is a volume of rocks located deep in the crystalline basement to which the projectile transmittted most of its energy so that only rocks of the basement were shocked by pressures exceeding 10 gpa deep burst impact model fallout suevites were ejected propelled by an expanding plume of vaporized rock and withdrew preferentially from this volume melt and highly shocked clasts leaving in the transient cavity the crater suevite with more clasts of modest shock levels and less melt

on monthly seasonal longitudinal variations of equatorial irregularity occurrences and their relationship with the postsunset vertical drift velocities 1 monthly variation of global equatorial density irregularity distribution has been obtained with the data taken by rocsat 1 at the 600 km topside ionosphere from march 1999 to june 2004 during high to moderate solar activity years this global distribution of monthly irregularity occurrence rate not only provides the best spatial temporal distribution in existence so far but also serves to fill the gap of irregularity distribution missing over some eastern pacific region where no ground observation is available the 5 1 2 year result of the monthly occurrence pattern indicates a smooth variation across the longitudes contrary to some beliefs that a drastic change in irregularity occurrence pattern has occurred across the eastern pacific longitudes excellent agreement is noted for the current results with aarons 1993 conjectured sketch of the global scintillation distribution furthermore the seasonal longitudinal s l variations of quiet time postsunset vertical drift velocities are found to track closely with the s l variations of irregularity occurrences linear regression analysis between the vertical drift velocity and the irregularity occurrence rate indicates that the vertical drift velocities at three different longitude zones of magnetic declination have good correlations with the irregularity occurrences for all seasons this implies that the averaged postsunset vertical drift velocity is a good indicator for the occurrences of equatorial density irregularities in a longitude region of similar magnetic declination the smooth variation of monthly seasonal longitudinal distributions of the vertical drift velocities that results in the smooth variation of topside density irregularity occurrences implies that the global occurrence pattern of either distribution is controlled by the smooth global variation of the postsunset ionospheric condition related to the magnetic declination effect and the seasonal variation of the ionospheric density level at the dip equator located with respect to the geographic equator there seems little need to include the global distribution of instability perturbation seeds from atmospheric disturbances to complete the global distribution of topside irregularity occurrences

the origin and timing of fluvial activity at eberswalde crater mars the fan deposit in eberswalde crater has been interpreted as strong evidence for sustained liquid water on early mars with a paleolake formed during the noachian period 3 7 gy this location became a key region for understanding the mars paleo environment eberswalde crater is located 50 km north of the rim of the 150 km diameter crater holden stratigraphic relationships and chronology obtained using recent mars express high resolution stereo camera and mars reconnaissance orbiter context camera images show that eberswalde fluvial activity crosscuts holden ejecta and thus postdates holden crater whose formation age is estimated from crater counts as late hesperian 3 5 gy depending on models fluvial modeling shows that short term activity over several years to hundreds of years involving dense flows with sediment water ratio between 0 01 and 0 3 may be as good an explanation of the fluvial landforms as dilute flow over longer durations modeling of the thermal effect of the holden impact in the eberswalde watershed is used to evaluate its potential role in aqueous activity the relative timing of the holden impact and eberswalde s fan is a constraint for future studies about the origin of these landforms holden ejecta form a weak and porous substrate which may be easy to erode by fluvial incision in a cold climate scenario impact heating could have produced runoff by melting snow or ground ice any attempt to model fluvial activity at eberswalde should take into account that it may have formed as late as in the late hesperian after the great majority of valley network formation and aqueous mineralization on mars this suggests that hypotheses for fan formation at eberswalde by transient and or localized processes i e impact volcanism unusual orbital forcing should be considered on a par with globally warmer climate

stable isotope records of hydrologic change and paleotemperature from smectite in cenozoic western north america abstract the oxygen and hydrogen isotopic composition of soil water 18ow and dw hereafter reflect the history of water through processes such as source evaporation precipitation and vapor recycling temperature humidity evaporation and post condensation processes can affect 18ow and dw as such isotope proxy records are often limited in their ability to constrain paleoclimate paleoecology or paleoelevation without independently corroborating data smectite preserves both the hydrogen and oxygen isotope signature of parent water and therefore provides critical insight into meteoric water line relationships and paleotemperature here we use in situ pedogenic smectite 18o and d records to characterize the evolution of the hydrologic cycle in cenozoic western north america we incorporate 192 samples 119 of which are previously unpublished from 11 cenozoic basins representing a range of environments in the basin and range rocky mountains and great plains our results indicate that the processes controlling smectite isotopic compositions vary both regionally and temporally in some localities such as oligocene to pleistocene western nebraska change in temperature is the primary control on smectite isotopic composition in other basins such as in miocene trapper creek id isotope values lie along the meteoric water line suggesting change in meteoric water composition is responsible for the variation in most basins especially those in the neogene basin and range smectite line slope suggests either evaporation of previously meteoric water or a combination of change in paleotemperature and meteoric water composition smectite geothermometry suggests mineral formation temperatures of 30 40 c in the middle miocene in the rocky mountains great plains and basin and range and a decrease of 10 15 c since the middle miocene climatic optimum consistent with clumped isotope and paleofloral temperature estimates

kardla hiiumaa island estonia the buried and well preserved ordovician marine impact structure abstract the kardla marine impact structure estonia 58 58 n 22 46 e was formed at 455 ma upper ordovician in a shallow epicontinental sea some tens of kilometres from the land and erosion area the iron rich projectile about 200 m in diameter approached from the west at an angle of 30 45 the impactor penetrated about 50 m thick water layer and the sedimentary cover and exploded in the uppermost part of the crystalline basement a complex crater 4 km wide and about 500 m deep with a central uplift rising 130 m from the crater floor was formed the highest point of the rimwall is 110 m above the target level the rimwall is cut by at least two resurge excavated gullies the variable height of the rimwall obviously results from the obliqueness of the impact outside the crater an elliptical area was revealed 12 15 km in diameter with deformed sedimentary rocks below the target level the elliptical shape of this area may also be due to the oblique impact because the crater and its surroundings were buried directly after the impact the whole complex of impact related sediments is preserved there they are recovered by 160 wells six of which penetrate the entire complex of impact breccias inside the crater

palaeoproterozoic age of the east baltic granulitic crust abstract the crust beneath the east european platform is one of the largest domains of precambrian crust in europe granulites of poorly defined ages make up a substantial part of this crust representative samples from the granulites in southern estonia are lree enriched and provide nd t dm model ages between 2 08 and 2 18 ga the equivalent nd for t 1 9 ga range from 0 2 to 2 0 these data are similar to those of the svecofennian crust in finland and sweden and suggest that the crustal material originated in the palaeoproterozoic rather than the archaean thus the known volume of juvenile palaeoproterozoic crust in europe is expanded considerably a new aspect is thereby introduced into the geodynamic interpretation of the ne european proterozoic orogenies

boron isotope composition of secondary smectite in suevites at the ries crater germany boron fractionation in weathering and hydrothermal processes abstract the 24 km diameter ries crater in germany is one of the best preserved terrestrial complex impact structure and clay minerals in the groundmass of the ries suevites have been recognized for several decades it is generally accepted that these clays were formed by post impact aqueous alteration of impact generated glasses and or finely comminuted crystalline basement material at temperatures above ambient conditions the ries impact structure provides a good opportunity to study the evolution of post impact development of impact craters here we present a study of boron isotopic compositions 11 b and b concentrations of the secondary smectite clay fraction in fall out and crater suevites from the ries crater germany these data were used to study the boron fractionation in clay mineral precipitation processes and to model using b isotope fractionation the characteristics ph temperature and salinity of fluids during fluid rock interaction at different positions within the crater the results of this study show that the boron isotopic composition of smectite in fall out suevites sampled from 4 different locations average 24 5 1 8 was significantly different from that of the smectite in crater suevites sampled from the nordlingen 1973 drill core at different depth intervals from 370 m to 525 m average 4 07 similarly the 11 b composition of the fluids responsible for the alteration calculated from smectite isotopic composition in the fall out suevites 7 5 1 6 differed from the alteration fluid composition in crater suevites 17 6 10 8 indicating a different origin of the fluids responsible for the alteration of the fall out and crater suevites in the ries crater our results suggest that the alteration in fall out suevites occurred at lower temperatures than the crater suevites and at a lower ph which is consistent with the smectite precipitation in equilibrium with meteoritic fluids the boron isotopic composition of smectite in the crater suevites suggests secondary clay formation at higher temperatures and or at elevated ph 8 9 low 11 b values of fixed boron in secondary smectite in fall out suevites suggests that b was incorporated into the mineral structure during the precipitation of authigenic smectite whereas the smectite precipitated in equilibrium with the boron and hydrogen isotopic composition in the meteoric water that percolated through the system our study provides new constraints on the origin and evolution of the geothermal fluids that were involved in the formation of altered minerals at the ries crater and suggests that boron isotope composition studies of the secondary clay phases associated with post impact cooling may have important implications for the changes in fluid flow and changes in geochemical signatures of the fluids and provide new constraints on fluid rock interaction and mass transport during the cooling of the impact crater

impact generated hydrothermal systems capable of forming phyllosilicates on noachian mars the early history of the terrestrial planets was punctuated by a period of heavy bombardment frequent large impacts condensed in a short 0 02 0 5 ga long time period resulted in heavily cratered planetary surfaces in volatile bearing planetary crusts each of these large impacts created a volume of hot rock and melt that drove vast subsurface hydrothermal systems in mars basaltic crust these systems produced a variety of alteration phases the nature of which we explored with thermochemical modeling using the computer code chiller we found a variety of oxides hydroxides and hydrous and water free silicates resulting from the hydrothermal alteration the main hydrous silicates are serpentine chlorite nontronite and other clay minerals some of the resulting assemblages contain up to 15 wt bound water our results constrain the temperature and water rock ratio at the time of alteration and compare well to the mineral assemblages found on mars by omega observatoire pour la mineralogie l eau les glaces et l activite and crism compact reconnaissance imaging spectrometer for mars and therefore provide an interpretative framework for analyzing martian mineralogy from orbital data our results also provide a geological template needed to select landing locations for future missions that search for water and energy sources associated with potential habitats on early mars

field aligned 777 4 nm composite airglow images of equatorial plasma depletions 1 we present a powerful tool to analyze two dimensional field aligned images of equatorial plasma depletions taken from mid latitudes by shifting each individual image by the sum of the longitudinal offsets obtained by performing a cross correlation between successive images a single composite image can be formed for the entire night it is shown that these field aligned composite images give information on the observation times of the depletions associated with spread f as they pass by hawaii in addition they can be used to estimate the formation time and location of the depletions to the west of the observing site this technique also yields estimates of the eastward velocity and velocity shear of the depletions we suggest that the information gained by using these images can be used to predict satellite scintillations at stations to the east of the observing station

suevite of the ries crater germany source rocks and implications for cratering mechanics suevites are impact breccias with a montmorillonitic matrix that contains shocked and unshocked mineral and rock fragments from the crystalline basement glass inclusions and a small amount of sedimentary clasts data are given of the modal composition of fall out suevites deposited at isolated points around the crater and crater suevite forming a layer below post impact lake sediments in the crater cavity fall out suevites contain aerodynamically shaped bombs which are absent in crater suevite taking into account not only large glass fragments and bombs but also the finer fractions the glass content of fall out and crater suevites amounts to 47 and 29 vol respectively crystalline clasts in suevites consist of all igneous and metamorphic rock types that constitute the local basement which consists of an upper layer of igneous rocks mainly granites and a lower series of gneisses and amphibolite based on a collection of 1 200 clasts from 13 suevite occurrences the average crystalline clast population of suevites was determined suevites contain on the average 46 igneous and 54 metamorphic clasts in constrast weakly shocked and unshocked crystalline ejecta of the ries structure consist of 82 igneous and 18 metamorphic rocks

ordovician oxygen isotopes and paleotemperatures abstract valid marine 18o proxies have been defined from three ordovician units and with previously estimated sea water 18o values we have calculated paleotemperatures for low latitude settings during a greenhouse climatic era valid marine proxies include marine equant bladed and translucent fibrous calcite these cements are interpreted to be valid marine proxies based on cathodoluminescence minor element content abundance of microdolomite and stable isotopic both altered marine and non marine calcite phases values valid marine proxies from the chickamauga alabama holston tennessee and kullsberg sweden formations have an overall range of 18o values in each unit that is confined to within 1 unlike altered marine cements which exhibit significantly wider ranges of 18o values we suggest a likely non glacial ordovician sea water value of 2 1 smow from which paleotemperatures can be calculated calculated paleotemperatures are broadly consistent with crowley and baum s 1995 late ordovician paleoclimatic model

the 206 year cycle in tree ring radiocarbon data and in the thermoluminescence profile of a recent sea sediment we study the secular variations observed 1 in the thermoluminescence tl profile of a recent sea sedimentary core 2 in the 14c time series from tree rings and 3 in the mean annual sunspot number rz we show that a regular oscillation with a period of approximately 206 years is present in the radiocarbon signal the comparison between the 14c secular oscillation and the 206 year tl modulation produced by the beats of two tl waves with close by decennial periods is considered the role of the 206 year radiocarbon wave and its possible relationships with the solar activity as represented by the annual sunspot number rz are finally discussed

impact glasses in fallout suevites from the ries impact structure germany an analytical sem study t impact generated glasses from fallout suevite deposits at the ries impact structure have been investigated using analytical scanning electron microscopy approximately 320 analyses of glass clasts were obtained four glass types are distinguished on the basis of composition and microtextures type 1 glasses correspond to the aerodynamically shaped glass bombs studied previously by many workers major oxide concentrations indicate the involvement of granitic rocks amphibolites and minor al rich gneisses during melting type 2 glasses are chemically heterogeneous even within individual clasts with variations of several wt in most of the major oxides e g 57 70 wt sio2 this suggests incomplete mixing of 1 mineral derived melts or 2 whole rock melts from a wide range of lithologies aluminium rich clinopyroxene and fe mg rich plagioclase quench crystals are present in type 1 and 2 glasses respectively type 3 glasses contain substantial amounts of h2o 12 17 wt low sio2 50 53 wt high al2o3 17 21 wt and high cao 5 7 wt contents this suggests an origin due to shock melting of part of the sedimentary cover type 4 glasses form a ubiquitous component of the suevites based on their high sio2 content 85 100 wt the only possible protolith are sandstones in the lowermost part of the sedimentary succession calcite forms globules within type 1 glasses with which it develops microtextures indicative of liquid immiscibility unequivocal evidence also exists for liquid immiscibility between what are now montmorillonite globules and type 1 2 and 4 glasses indicating that montmorillonite was originally an impact melt glass clearly the melt zone at the ries must have incorporated a substantial fraction of the sedimentary cover as well as the underlying crystalline basement rocks impact melts were derived from different target lithologies and these separate disaggregated melts did not substantially mix in most cases type 2 3 and 4 glasses and carbonate melts