chloride bearing materials in the southern highlands of mars chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing spectrally distinct surface deposits consistent with chloride bearing materials have been identified and mapped using data from the 2001 mars odyssey thermal emission imaging system these deposits are found throughout regions of low albedo in the southern highlands of mars geomorphologic evidence from orbiting imagery reveals these deposits to be light toned relative to their surroundings and to be polygonally fractured the deposits are small

initial pb sr nd isotopic heterogeneity in a single allanite epidote crystal implications of reaction history for the dating of minerals with low parent to daughter ratios we analyzed 17 fragments from a zoned allanite epidote crystal ca 2 2 mm 4 0 mm which had formed during different prograde and retrograde stages of ultra high pressure uhp and amphibolite facies metamorphism 240 230 ma sulu belt e china for the isotopic composition of pb nd and sr and contents of pb u and th sr and rb and nd and sm since most fragments had 238u 204pb and 232th 204pb values less than 1 corrections for in situ pb growth are small and uncertainties in the recalculation of the pb isotopic compositions to 240 ma are insignificant the recalculated pb falls on a linear trend in the 206pb 204pb vs 207pb 204pb diagram with the allanite defining the low 206pb 204pb end 17 07 of this trend and the epidote defining its high 206pb 204pb end 17 56 the recalculated data scatter in the 206pb 204pb vs 208pb 204pb diagram which implies that the initial pb isotopic variation reflects the involvement of at least three different pb sources the low 87rb 86sr values account for a change in 87sr 86sr by in situ 87sr growth of less than 0 0007 which implies that the isotopic heterogeneity of 87sr 86sr 0 70601 0 7200 is a primary feature the pb and sr isotope data unequivocally demonstrate that contributions from different precursor minerals result in initial isotopic heterogeneity in the metamorphic reaction product it is likely that such an initial isotopic heterogeneity also exists for nd but it could not be resolved in the present study initially heterogeneous pb and sr isotope compositions imply that age differences between core and rim of large crystals may result in the determination of highly arbitrary geological rates especially for minerals with relatively low parent to daughter ratios

chemistry and mineralogy of outcrops at meridiani planum analyses of outcrops created by the impact craters endurance fram and eagle reveal the broad lateral continuity of chemical sediments at the meridiani planum exploration site on mars approximately ten mineralogical components are implied in these salt rich silicic sediments from measurements by instruments on the opportunity rover compositional trends in an apparently intact vertical stratigraphic sequence at the karatepe west ingress point at endurance crater are consistent with non uniform deposition or with subsequent migration of mobile salt components dominated by sulfates of magnesium striking variations in cl and enrichments of br combined with diversity in sulfate species provide further evidence of episodes during which temperatures ph and water to rock ratios underwent significant change to first order the sedimentary sequence examined to date is consistent with a uniform reference composition modified by movement of major sulfates upward and of minor chlorides downward this reference composition has similarities to martian soils supplemented by sulfate anion and the alteration products of mafic igneous minerals lesser cementation in lower stratigraphic units is reflected in decreased energies for grinding with the rock abrasion tool survival of soluble salts in exposed outcrop is most easily explained by absence of episodes of liquid h2o in this region since the time of crater formation

ash layers from iceland in the greenland grip ice core correlated with oceanic and land sediments four previously known ash layers ash zones i and ii saksunarvatn and the settlement layer all originating in iceland have been identified in the central greenland ice core grip this correlation of the ash between the different environments is achieved by comparison of the chemical composition of glass shards from the ash this establishes and confirms detailed correlations between the different types of depositional records and the absolute dating of the younger part of the ice core by counting annual layers dates the eruptions accurately a precise connection with dates obtained by14c beyond the range of dendrochronology is established which provides an excellent confirmation of230th 234u dates from corals four additional icelandic ash layers have also been identified in the core but not yet correlated with known ash deposits

stratigraphic evidence for a high marine shore line during the late weichselian deglaciation on the kullen peninsula southern sweden mineral magnetic properties and the carbon content of a sediment sequence in lake kullatorpssjon on the kullen peninsula in northwest scania southern sweden were investigated diatom and ostracod analyses were undertaken for palaeoecological reconstruction and a chronology was constructed from accelerator mass spectrometry ams radiocarbon dating of terrestrial plant remains and mosses five stratigraphical units were identified units 1 5 from oldest to youngest the two lowermost units consist of clay the lowest clay unit 1 is strikingly black 2 m thick and has magnetic properties dominated by high concentrations of authigenic greigite fe3s4 in contrast the overlying clay unit 2 is grey 1 18 m thick and has magnetic properties dominated by low concentrations of detrital magnetite fe3o4 a major palaeoecological change is reflected in the diatom flora and ostracod fauna at the transition from unit 1 to unit 2 the sediment stratigraphy geochemical mineral magnetic and palaeoecological analyses also point to a significant change in depositional environment at this transition which is proposed to represent the isolation of lake kullatorpssjon from the kattegat sea earlier investigations have determined the marine limit to ca 65 m a s l on the kullen peninsula the separate independent lines of evidence presented here however suggest that the late weichselian marine limit developed at 85 90 m a s l at the deglaciation ca 17 200 cal yr bp ca 14 500 yr bp this limit is ca 25 m higher than assumed previously lake kullatorpssjon formed ca 1000 cal yr later when the basin became isolated from the kattegat sea copyright c 1999 john wiley sons ltd less

laboratory studies of perchlorate phase transitions support for metastable aqueous perchlorate solutions on mars abstract perchlorate salts recently discovered on mars are known to readily absorb water vapor from the atmosphere and deliquesce into the aqueous phase at room temperature here we study the deliquescence crystalline solid to liquid transition and efflorescence liquid to crystalline solid transition of perchlorate salts at low temperatures relevant to mars a raman microscope and environmental cell were used to determine the deliquescence relative humidity drh and efflorescence relative humidity erh of naclo 4 and mg clo 4 2 as a function of temperature and hydration state we find that the deliquescence of anhydrous naclo 4 is only slightly dependent on temperature and occurs at 38 rh the drh of naclo 4 h 2 o increases with decreasing temperature from 51 at 273 k to 64 at 228 k the drh of mg clo 4 2 6h 2 o also increases with decreasing temperature from 42 at 273 k to 64 at 223 k the efflorescence of both naclo 4 and mg clo 4 2 salt solutions occurs at a lower rh than deliquescence due to the kinetic inhibition of crystallization for all temperatures studied the erh values of naclo 4 and mg clo 4 2 are 13 and 19 respectively these results indicate perchlorate salts can exist as metastable supersaturated solutions over a wide range of rh and temperature conditions summer diurnal temperature and relative humidity cycles at low latitudes on mars could allow the surface salts to be aqueous for several hours per day

a calendar age estimate of the younger dryas holocene boundary at krakenes western norway the younger dryas holocene transition yd h in the sediments of krakenes lake western norway is well marked both lithologically and palaeobiologically at 756 5 cm in the investigated core a ser

evidence for the occurrence of vedde ash in sweden radiocarbon and calendar age estimates a tephra layer of rhyolitic composition has been recorded in sediments from lake madtjarn southwestern sweden geochemical analyses have shown that the tephra is identical to the rhyolitic component of the middle younger dryas vedde ash a series of ams radiocarbon measurements places the radiocarbon age of the tephra within a 14c plateau at 10 400 10 300 14c y bp based on a linear younger dryas sedimentation rate and assumptions about the apparent synchroneity of changes in lake sediments tree rings and ice core records the calendar year age of the tephra concentrations is estimated at 12 045 11 975 yr bp which accords well with the age of the equivalent tephra in the grip core 1998 john wiley sons ltd

holocene history of the baltic sea as a background for assessing records of human impact in the sediments of the gotland basin sediment cores from the gotland basin were studied for their siliceous microfossil assemblages and organic carbon content to compare recent environmental changes in the baltic sea with its natural

perennial water ice identified in the south polar cap of mars the inventory of water and carbon dioxide reservoirs on mars are important clues for understanding the geological climatic and potentially exobiological evolution of the planet1 from the early mapping observation of the permanent ice caps on the martian poles2 3 the northern cap was believed to be mainly composed of water ice whereas the southern cap was thought to be constituted of carbon dioxide ice however recent missions nasa missions mars global surveyor and odyssey have revealed surface structures4 altimetry profiles5 underlying buried hydrogen6 and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide7 here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes at a resolution of 2 km during the local summer when the extent of the polar ice is at its minimum we observe that this south polar cap contains perennial water ice in extended areas as a small admixture to carbon dioxide in the bright regions associated with dust without carbon dioxide at the edges of this bright cap and unexpectedly in large areas tens of kilometres away from the bright cap

extending the limits of the borrobol tephra to scandinavia and detection of new early holocene tephras analyses of two infilled lakes in blekinge southeast sweden indicate the presence of at least three tephra horizons of termination 1 and early holocene age geochemical analyses confirm the presence of the borrobol tephra the askja tephra 10 000 14c yr b p and one previously unreported tephra of icelandic origin extending the limits of the borrobol tephra to scandinavia illustrates that this ash is far more widespread than previously realized and is therefore an important marker horizon for determining the rate and timing of the initial warming at the start of greenland interstade 1 gi 1 within europe the relatively unknown askja tephra and the newly discovered hasseldalen tephra are stratigraphically placed at the younger dryas preboreal transition this paper demonstrates the suitability and success associated with the extraction techniques for tracing microtephra horizons in areas distal to volcanic sources

an event stratigraphy for the last glacial holocene transition in eastern middle sweden results from investigations of varved clay and terrestrial sequences this paper presents an event stratigraphy for the last glacial holocene transition in eastern middle sweden the event stratigraphy for eastern middle sweden comprises ten events and covers the tim

synchronized terrestrial atmospheric deglacial records around the north atlantic on the basis of synchronization of three carbon 14 c 14 dated lacustrine sequences from sweden with tree ring and ice core records the absolute age of the younger dryas preboreal climatic shift was determined to be 11 450 to 11 390 80 years before the present a 150 year long cooling in the early preboreal associated with rising delta 14 c values is evident in all records and indicates an ocean ventilation change this cooling is similar to earlier deglacial coolings and box model calculations suggest that they all may have been the result of increased freshwater forcing that inhibited the strength of the north atlantic heat conveyor although the younger dryas may have begun as an anomalous meltwater event

the use of microtephra horizons to correlate late glacial lake sediment successions in scotland evidence is presented to show that two measurable concentrations of microtephra particles can be detected in deposits of late devensian late glacial age in three sites in scotland one layer is attributed to the vedde ash a marker horizon within the younger dryas chronozone the second is a new tephra reported for the first time which we name the borrobol tephra this occurs consistently near the base of the late glacial interstadial organic sediments at each site and is thought to date to around 12 5 14c ka bp geochemical determinations using an electron microprobe confirm the identification of the vedde ash suggest the borrobol tephra to have an icelandic origin and demonstrate the consistency of the geochemical signals at all three sites 1997 john wiley sons ltd

high resolution analyses of an early holocene climate event may imply decreased solar forcing as an important climate trigger early holocene lacustrine tree ring ice core and marine records reveal that the northern hemisphere underwent a short cooling event at 10 300 calendar yr b p 9100 14 c yr b p the records were compared on a common high resolution time scale and show that the event lasted less than 200 yr with a cooling peak of 50 yr and the event coincides with a distinct holocene thermohaline disturbance recognized in the north atlantic ocean in spite of wellknown freshwater forcings at the time of the event the negligible difference between the modeled d 14 c record based on the gisp2 greenland ice sheet project 2 10 be data and the measured values does not allow for detectable d 14 c changes related to global ocean ventilation we can however show that the onset of the cooling coincides with the onset of one of the largest holocene 10 be flux peaks this finding may imply that the climate system is more

exposed water ice discovered near the south pole of mars the mars odyssey thermal emission imaging system themis has discovered water ice exposed near the edge of mars southern perennial polar cap the surface h2o ice was first observed by themis as a region that was cooler than expected for dry soil at that latitude during the summer season diurnal and seasonal temperature trends derived from mars global surveyor thermal emission spectrometer observations indicate that there is h2o ice at the surface viking observations and the few other relevant themis observations indicate that surface h2o ice may be widespread around and under the perennial co2 cap

extending the known distribution of the younger dryas vedde ash into northwestern russia the known distribution of wind blown vedde ash ca 10 3 ka bp has been extended to the karelian isthmus in northwestern russia this has been possible as the result of a density separation technique that separates the rhyolitic vedde ash shards from the minerogenic host sediment the vedde ash occurs in the middle of a pollen zone with high percentages of for example artemisia and chenopodiaceae suggesting that the younger dryas or gs i in the grip ice core event stratigraphy was cold and dry throughout its duration this is in agreement with sites in south sweden where the vedde ash also occurs in the middle of a pollen zone dominated by artemisia chenopodiaceae and cyperaceae copyright 2000 john wiley sons ltd

martian hydrogeology sustained by thermally insulating gas and salt hydrates numerical simulations and geologic studies suggest that high thermal anomalies beneath within and above thermally insulating layers of buried hydrated salts and gas hydrates could have triggered and sustained hydrologic processes on mars producing or modifying chaotic terrains debris flows gullies and ice creep features these simulations and geologic examples suggest that thick hydrate deposits may sustain such geothermal anomalies shallow ground water tables and hydrogeologic activity for eons the proposed mechanism may operate and be self reinforcing even in today9s cold martian climate without elevated heat flux

a younger dryas ash bed in western norway and its possible correlations with tephra in cores from the norwegian sea and the north atlantic abstract a bed of volcanic ash up to 23 cm thick is found in lacustrine and marine sediments in western norway it is formally mamed the vedde ash bed and its age is approximately 10 600 yr b p i e mid younger dryas the bed consits of pure glass having a bimodal basaltic and rhyolitic somposition the geochemistry of the glass shards suggests an icelandic source by means of stratigraphic position and geochemistry the ash is correlated with ash zones found in cores from the continental shelf the norwegian sea and the north atlatic

salinity changes in the central baltic sea nw europe over the last 10 000 years a comment on emeis struk blanz kohly voβ we question the effort to date the lower part of a core from the baltic sea with a combination of tephra layers and stratigraphical markers no geochemical data is presented for the two tephra layers believed to be the saksunarvatn ash and vedde ash furthermore the age used for one of the stratigraphical markers is erroneous we present two alternative age models of which the second gives a plausible sediment accumulation rate but excludes the identification of the vedde ash

effect of evaporation and freezing on the salt paragenesis and habitability of brines at the phoenix landing site abstract the wcl wet chemistry lab instrument on board the phoenix lander identified the soluble ionic composition of the soil at the landing site however few studies have been conducted to understand the parent salts of these soluble ions here we studied the possible salt assemblages at the phoenix landing site using two different thermodynamic models frezchem and geochemist s workbench gwb two precipitation pathways were used evaporation t 0 c using both frezchem and gwb and freezing t 0 c using only frezchem through applying three different models of initial ionic concentrations from sulfate to chlorate perchlorate dominated we calculated the resulting precipitated minerals the results through both freezing and evaporation showed some common minerals that precipitated regardless of the ionic initial concentration these ubiquitous minerals are magnesium chlorate hexahydrate mg clo 3 2 6h 2 o potassium perchlorate kclo 4 and gypsum caso 4 2h 2 o other minerals evidence specific precipitation pathway precipitation of highly hydrated salts such as meridianiite mgso 4 11h 2 o and mgcl 2 12h 2 o indicate freezing pathway while precipitation of the low hydrated salts anhydrite kieserite and epsomite indicate evaporation the present hydration states of the precipitated hydrated minerals probably reflect the ongoing thermal processing and recent seasonally varying humidity conditions at the landing site but these hydration states might not reflect the original depositional conditions the simulations also showed the absence of ca perchlorate in all models mainly because of the formation of two main salts kclo 4 and gypsum which are major sinks for clo 4 and ca 2 respectively finally in consideration to the martian life it might survive at the very low temperatures and low water activities of the liquids formed however besides the big and widely recognized challenges to life posed by those extreme environmental parameters especially low water activity another main challenge for any form of life in such an environment is to maintain contact with the small droplets of the stable liquids in the regolith and to interact with life in other isolated droplets

sulfates and iron oxides in ophir chasma mars based on omega and crism observations abstract we investigate the sulfate and iron oxide deposits in ophir chasma mars based on short wave infrared data from the compact reconnaissance imaging spectrometer for mars crism and from the observatoire pour la mineralogie l eau les glaces et l activite omega sulfates are detected mainly in two locations in the valley between ophir mensa and the southern wall of ophir chasma kieserite is found both within the slope of ophir mensa and superposed on the basaltic wall of the chasm here kieserite is unconformably overlain by polyhydrated sulfate deposits and iron oxides locally jarosite and unidentified phases with absorptions at 2 21 m or 2 23 m are detected which could be mixtures of jarosite and amorphous silica or other poorly crystalline phases the second large sulfate rich outcrop is found on the floor of the central valley although the same minerals are found here polyhydrated sulfates kieserite iron oxides and locally a possibly jarosite bearing phase this deposit is very distinct it is not layered almost horizontal and located at a much lower elevation of below 4250 m kieserite superposes polyhydrated sulfate rich deposits and iron oxides form lags the facies of sulfate formation remains unclear and could be different for the two locations a formation in a lake playa or under a glacier is consistent with the mineralogy of the central valley and its flat low lying topography this is not conceivable for the kieserite deposits observed south of ophir mensa these deposits are observed over several thousands of meters of elevation which would require a standing body of water several thousands of meters deep this would have lead to much more pervasive sulfate deposits than observed these deposits are therefore more consistent with evaporation of groundwater infiltrating into previously sulfate free light toned deposits the overlying polyhydrated sulfates and other mineral phases are observed in outcrops on ridges along the slopes of the southern chasm wall which are too exposed to be reached by groundwater here a water supply from the atmosphere by rain snow fog or frost is more conceivable

facilitation of endolithic microbial survival in the hyperarid core of the atacama desert by mineral deliquescence 1 the hyperarid core of the atacama desert is considered the dry limit for life on earth soils in this region have very low abundance of heterotrophic bacteria and are practically barren of photosynthetic microorganisms because of the extreme dry conditions 2 mm a 1 rainfall however relatively abundant endolithic communities of cyanobacteria chroococcidiopsis occur within halite crusts in paleolake evaporitic deposits by means of continuous monitoring of the microclimate conditions temperature relative humidity water vapor density wetness and photosynthetically active radiation inside and around the halite crusts we demonstrate here that water vapor condenses within the pore space of the halite at relative humidity rh levels that otherwise hinder the occurrence of liquid water in the surrounding environment water condensation occurs at rh 75 which corresponds to the deliquescence point of halite we have estimated a total of 57 deliquescence events i e water condensation within the halite crusts as opposed to only 1 liquid water event outside these wet events resulted in a total of 213 8 h of potential photosynthetic activity for the endolithic microorganisms versus only 6 h for organisms outside the halite crusts halite crusts may therefore represent the last available niche for photosynthetic activity in extreme arid environments on earth

stability of liquid saline water on present day mars 1 perchlorate salts mostly magnesium and sodium perchlorate have been detected on mars arctic soil by the phoenix lander furthermore chloride salts have been found on the meridiani and gusev sites and on widespread deposits on the southern martian hemisphere the presence of these salts on the surface is not only relevant because of their ability to lower the freezing point of water but also because they can absorb water vapor and form a liquid solution deliquesce we show experimentally that small amounts of sodium perchlorate 1 mg at mars atmospheric conditions spontaneously absorb moisture and melt into a liquid solution growing into 1 mm liquid spheroids at temperatures as low as 225 k also mixtures of water ice and sodium perchlorate melt into a liquid at this temperature our results indicate that salty environments make liquid water to be locally and sporadically stable on present day mars

salinity changes in the central baltic sea nw europe over the last 10 000 years a reply to wastegard and andren while it is acknowledged that an incorrect age datum was used to construct the depth age relationship for the lower part of the core in question the conclusions of the paper which related to salinity changes of the last 10 000 years are unaffected

correction to stability of perchlorate hydrates and their liquid solutions at the phoenix landing site mars 1 in the paper stability of perchlorate hydrates and their liquid solutions at the phoenix landing site mars by vincent f chevrier et al geophysical research letters 36 l10202 doi 10 1029 2009gl037497 2009 there is an error in figure 3b of the published paper the curve describing the gcm global circulation model results for humidity at the phoenix landing site is wrong the new figure gives the right humidity variations from the gcm the legend is the same as for the original figure 3b this error does not affect subsequent calculations and all the conclusions of the paper remain valid since they were based on the measured humidity data by the phoenix thermal and electrical conductivity prove tecp instrument rather than on the gcm model results 2 the description of the gcm results in the paper page 5 end of the first paragraph should be modified accordingly the gcm results on water vapor pressure show a similar trend than the tecp data with high daytime values up to 7 pa and low nighttime value down to 3 5 10 3 pa however the amplitude of pressure variations calculated form the gcm is higher than the tecp data which range from 2 10 3 to 2 pa this suggests some form of interaction of water vapor with the regolith compared to pure atmospheric processes

mars the regolith atmosphere cap system and climate change abstract a new model for predicting the behavior of the martian regolith atmosphere cap co 2 regime and describing its role in climate change is derived the model describes the time temperature histories of 90 regolith chunks on a latitude depth grid accounting for co 2 exchange by means of laboratory derived expressions relating temperature co 2 pressure p co 2 and adsorbed co 2 mass co 2 polar cap formation and sublimation is accounted for subject to the constraint of constant total co 2 in the atmosphere regolith cap system the influence of differences in regolith adsorption laws for basalt and clay and the influence of variations in regolith depth with latitude regolith thermal diffusivity and total exchangeable co 2 inventory on predicted variations in atmospheric pressure and cap mass are examined the following results are indicated 1 the atmosphere acts as a low capacity conduit through which flows between 10 and 100 times the current atmospheric mass of co 2 between two reservoirs a regolith ocean of adsorbed co 2 and a polar cap cryosphere 2 exchange between these reservoirs is driven by variations of obliquity with the polar cap the dominant co 2 sink at low and the regolith dominating at high atmospheric pressure ranges between 0 1 low and 15 mbar high pressures of up to 25 mbar could result from pre tharsis variations pressure up to 40 mbarare achieved only in models which also call for a huge quasi permanent present co 2 cap which is not apparent 3 at high the atmospheric pressure is buffered by the regolith and satisfies adsorption equilibrium for the 90 chunks as well as conservation of co 2 mass at low a potetially large co 2 cap appears and the atmospheric pressure is buffered by the cap not the regolith 4 the periodic reservoir flushing can account for the observation of simultaneous nonenrichment of 18 o and enrichment of 13 n 5 mars climate history may be divided into three parts a post tharsis formation history as described above b pre tharsis formation with qualitatively similar processes but larger oscillations between reservoirs and larger atmospheric pressure and cap mass variation and c the very early period of channel formation 6 the nature of the response of the three part regolith atmosphere polar cap martian climate system to surface insolation variations may be analogous to that of earth s ocean atmosphere cryosphere system

salinity changes in the central baltic sea nw europe over the last 10000 years we attempt a reconstruction of salinity levels of the central baltic sea based on diatom assemblages the isotopic composition of organic matter and sedimentological expression of anoxia over the last 10 000 years we use the data to investigate the dependence of salinity levels on climate evolution and isostasy changes in salinity of surface and deep waters were most pronounced from 8400 to approximately 5000 cal bp density stratification between salty deep and fresher surface waters caused the frequent development of anoxic conditions and deposition of laminated sediments on large parts of the sea floor in the central baltic sea and dramatic changes in organic carbon accumulation rates from 5000 to 3100 cal bp the salinity of the basin decreased oxygenation of deep sea floors was improved and fertility of the sea surface was significantly reduced this is reflected by low accumulation rates of organic carbon in bioturbated sediments since 2800 cal bp salinity rose again and anoxic periods were more common even though the major steps in environmental evolution in the baltic sea coincide with known patterns of climatic change of the north atlantic realm over the last 10 000 years we find no conclusive evidence for synchronous changes or linear responses on submillennial timescales however we note that major variations in our salinity records agree with temporal patterns of reconstructed summer warmth and winter precipitation in southern scandinavia both types of record suggest that climate in the mid holocene was far from stable our data also confirm that climate evolution over the late holocene had significant impact on environmental conditions in the baltic sea

tephrochronology of last termination sequences in europe a protocol for improved analytical precision and robust correlation procedures a joint scotav intimate proposal the precise sequence of events during the last termination 18 000 9000 ka 14 cy r bp and the extent to which major environmental changes were synchronous are difficult to estab lish using the radiocarbon method alone because of serious distortions of the radiocarbon time scale as well as the influences of site specific errors that can affect the materials dated attention has there fore turned to other methods that can provide independent tests of the chronology and correlation of events during the last termination with emphasis on european sequences we summarise here the potential of tephrostratigraphy and tephrochronology to fulfil this role recent advances in the detection and analysis of hidden tephra layers cryptotephra indicate that some tephras of last termination age are much more widespread in europe than appreciated hitherto and a number of new tephra deposits have also been identified there is much potential for developing an integrated tephrochronological framework for europe which can help to underpin the overall chronology of events during the last termination for that potential to be realised however there needs to be a more systematic and robust analysis of tephra layers than has been the practice in the past we pro pose a protocol for improving analytical and reporting procedures as well as the establishment of a centralised data base of the results which will provide an important geochronological tool to support a diverse range of stratigraphical studies including opportunities to reassess volcanic hazards although aimed primarily at europe the protocol proposed here is of equal relevance to other regions and periods of interest copyright 2004 john wiley sons ltd

global distribution of neutrons from mars results from mars odyssey global distributions of thermal epithermal and fast neutron fluxes have been mapped during late southern summer northern winter using the mars odyssey neutron spectrometer these fluxes are selectively sensitive to the vertical and lateral spatial distributions of h and co 2 in the uppermost meter of the martian surface poleward of 60 latitude is terrain rich in hydrogen probably h 2 o ice buried beneath tens of centimeter thick hydrogen poor soil the central portion of the north polar cap is covered by a thick co 2 layer as is the residual south polar cap portions of the low to middle latitudes indicate subsurface deposits of chemically and or physically bound h 2 o and or oh