weathering and the mobility of phosphorus in the catchments and forefields of the rhone and oberaar glaciers central switzerland implications for the global phosphorus cycle on glacial interglacial timescales abstract in this study we evaluate the dynamics of the biophile element phosphorus p in the catchment and proglacial areas of the rhone and oberaar glaciers central switzerland we analysed erosion and dissolution rates of p containing minerals in the subglacial environment by sampling water and suspended sediment in glacier outlets during three ablation and two accumulation seasons we also quantified biogeochemical weathering rates of detrital p in proglacial sedimentary deposits using two chronosequences of samples of fresh suspended material obtained from the oberaar and rhone water outlets little ice age lia moraines and younger dryas yd tills in each catchment subglacial p weathering is mainly a physical process and detrital p represents more than 99 of the precipitation corrected total p denudation flux 234 and 540 kg km 2 yr 1 for the rhone and oberaar catchments respectively the calculated detrital p flux rates are three to almost five times higher than the world average flux the precipitation corrected soluble reactive p srp flux corresponds to 1 88 1 99 kg km 2 yr 1 rhone and 2 12 2 44 kg km 2 yr 1 oberaar respectively these fluxes are comparable to those of tropical rivers draining transport limited tectonically inactive weathering areas in order to evaluate the efficiency of detrital p weathering in the rhone and oberaar proglacial areas we systematically graded apatite grains extracted from the chronosequence in each catchment relative to weathering induced changes in their surface morphologies grades 1 4 fresh apatite grains are heavily indented and dissolution rounded grade 1 lia grains from two 0 10 cm deep moraine samples show extensive dissolution etching similar to surface grains from the yd profile mean grades 2 7 3 5 and 3 5 respectively in these proglacial deposits the weathering front deepens progressively as a function of time due to biocorrosion in the evolving acidic pedosphere with mechanical indentations on grains acting as sites of preferential dissolution we also measured iron bound organic and detrital p concentrations in the chronosequence and show that organic and iron bound p has almost completely replaced detrital p in the top layers of the yd profiles detrital p weathering rates are calculated as 310 and 280 kg km 2 yr 1 for lia moraines and 10 kg km 2 yr 1 for yd tills during the first 300 years of glacial sediment exposure p dissolution rates are shown to be approximately 70 times higher than the mean global dissolved p flux from ice free continents after 11 6 kyr the flux is 2 5 times the global mean these data strengthen the argument for substantial changes in the global dissolved p flux on glacial interglacial timescales a crude extrapolation from the data described here suggests that the global dissolved p flux may increase by 40 45 during the first few hundred years of a deglaciation phase

thermal properties of lobate ejecta in syrtis major mars implications for the mechanisms of formation 1 this paper reports an analysis of the thermal properties of ejecta layers of single and double lobe impact craters on mars first observations of thermal properties were made at low resolution from the phobos 88 mission and did not allow mapping of variations of thermal properties inside the ejecta layer the themis instrument on board the mars odyssey mission provides new high resolution thermal mapping of the surface of mars from these data we observe a systematic temperature increase at night at the edge of the ejecta we evaluate first the possible influences on the surface temperatures at night of postimpact modification processes given the topography of an impact crater and its ejecta we show that the observed thermal signature is more likely related to a particle size distribution inherited immediately after the impact event during the emplacement of ejecta we propose that the kinetic sieving process observed in experimental and natural granular flows like pyroclastic flows is responsible for the accumulation of larger particles at the ejecta flow front and thus is responsible for the temperature increase despite evidence of aeolian activity at syrtis major these craters offer an example of preserved surface physical properties resulting from geological processes which have occurred since the formation of the volcanic shield of syrtis major further studies are underway with the mars express ongoing observations produced by the hrsc and omega instruments in order to explore the interplay between the surface physical properties and the spectroscopic signatures seen at syrtis major

initial observations of lunar impact melts and ejecta flows with the mini rf radar 1 the mini rf radar on the lunar reconnaissance orbiter spacecraft has revealed a great variety of crater ejecta flow and impact melt deposits some of which were not observed in prior radar imaging the craters tycho and glushko have long melt flows that exhibit variations in radar backscatter and circular polarization ratio along the flow comparison with optical imaging reveals that these changes are caused by features commonly seen in terrestrial lava flows such as rafted plates pressure ridges and ponding small 20 km sized craters also show a large variety of deposits including melt flows and ponds two craters have flow features that may be ejecta flows caused by entrained debris flowing across the surface rather than by melted rock the circular polarization ratios cprs of the impact melt flows are typically very high even ponded areas have cpr values between 0 7 and 1 0 this high cpr suggests that deposits that appear smooth in optical imagery may be rough at centimeter and decimeter scales in some places ponds and flows are visible with no easily discernable source crater these melt deposits may have come from oblique impacts that are capable of ejecting melted material farther downrange they may also be associated with older nearby craters that no longer have a radar bright proximal ejecta blanket the observed morphology of the lunar crater flows has implications for similar features observed on venus in particular changes in backscatter along many of the ejecta flows are probably caused by features typical of lava flows

distribution of organic and inorganic phosphorus compounds in mrine and lacustrine sediments a31nmr study abstract solution 31 p nmr spectroscopy has been used for the characterization of different classes of organic and inorganic phosphorus compounds in a number of different marine and lacustrine sediment environments all samples contain orthophosphate mono and di esters of which the former is always the major constituent of possible orthophosphate mono ester candidates inositol phosphates may be of importance the amount of orthophosphate di esters is much higher in the reduced sediments from the baltic sea than in those areas with anoxic suboxic conditions indicating a more efficient decomposition of di esters in oxic environments the same situation was also observed in the lake sediment profiles pyro and polyphosphate are found in the oxic sediments from the lakes whereas no sign of such compounds could be seen in the baltic sea sediment samples redox variations lake samples and cation strength variations between the sea water and the lacustrine water will most likely be the main explanation for the observed distribution patterns of pyro and polyphosphate small but sharp peaks indicate the occurrence of phosphoric acids in a sediment from the southern baltic sea several other unidentified peaks were also observed some of which could be assigned to aromatic di and mono esters

how old are young lunar craters 1 the accurate definition of the lunar cratering chronology is important for deriving absolute model ages across the lunar surface and throughout the solar system images from the lunar reconnaissance orbiter narrow angle cameras and wide angle camera and the selene kaguya terrain camera provide new opportunities to investigate crater size frequency distributions csfds on individual geological units at lunar impact craters we report new csfd measurements for the copernican aged craters north ray tycho and copernicus which are crucial anchor points for the lunar cratering chronology we also discuss possible reasons for an age discrepancy observed between the impact melt and ejecta units our csfds for north ray and tycho crater ejecta deposits are consistent with earlier measurements however for copernicus crater and one of its rays we find significantly lower cumulative crater frequencies than previous studies our new results for copernicus crater fit the existing lunar absolute chronologies significantly better than the previous counts our derived model ages of the ejecta blankets of north ray tycho and copernicus agree well with radiometric and exposure ages of the apollo 16 17 and 12 landing sites respectively and are generally consistent with a constant impact rate over the last 3 ga however small variations of the impact rate cannot be resolved in our data and require further investigations

global distribution of lunar impact melt flows abstract in this study we analyzed the distribution and properties of 146 craters with impact melt deposits exterior to their rims many of these craters were only recently discovered due to their unusual radar properties in the near global mini rf data set we find that most craters with exterior deposits of impact melt are small 20 km and that the smallest craters have the longest melt flows relative to their size in addition exterior deposits of impact melt are more common in the highlands than the mare this may be the result of differing target properties in the highlands and mare the difference in titanium content or the greater variation of topography in the highlands we find that 80 of complex craters and 60 of simple craters have melt directions that are coincident or nearly coincident with the lowest point in their rim implying that pre existing topography plays a dominant role in melt emplacement this is likely due to movement during crater modification complex craters or breached crater rims simple craters we also find that impact melt flows have very high circular polarization ratios compared to other features on the moon this suggests that their surfaces are some of the roughest material on the moon at the centimeter to decimeter scale even though they appear smooth at the meter scale

unravelling the mystery of lunar anomalous craters using radar and infrared observations in miniature radio frequency mini rf radar images anomalous craters are those having a high circular polarization ratio cpr in their interior but not exterior to their rims previous studies found that most cpr anomalous craters contain permanently shadowed regions psrs and that their population is overabundant in the polar regions however there is considerable controversy in the interpretation of these signals both water ice deposits and rocks surface roughness have been proposed as the source of the elevated cpr values to resolve this controversy we have systematically analyzed 4000 impact craters with diameters between 2 5 and 24 km in the mini rf radar image and diviner rock abundance ra map we first constructed two controlled orthorectified global mosaics using 6818 tracks of mini rf raw data and then analyzed the correlations between radar cpr and surface slope rock abundance and depth diameter ratios of impact craters our results show that cpr anomalous craters are distributed relatively uniformly across the lunar surface with no apparent difference in cpr between the polar potentially icy and non polar not icy craters most cpr anomalous craters are relatively young with a large depth diameter ratio and they actually represent an intermediate stage of crater evolution comparison with a two component radar scattering model suggests that rocks and surface roughness are major contributors to the observed cpr values using craters of 4 7 22 km in diameter with known ages we find that craters spend up to 120 ma with a high exterior ra and 3 ga in the cpr anomalous phase

patterns in n dynamics and n isotopes during primary succession in glacier bay alaska abstract the primary successional sequence in glacier bay alaska represents a 230 year record of the development of nitrogen n dynamics because of low inputs of n in precipitation and the absence of initial soil n pools the pattern of n accumulation is strongly biologically controlled the simple successional sequence at glacier bay is dominated by two main species alnus sinuata and picea sitchensis thus the influence these species have on n dynamics is more easily deduced than in more complex systems along a successional sequence in glacier bay n mineralization rates foliage and soil c n and foliage and soil 15 n values in six sites ranging in age from 20 to 225 years old were examined it is concluded that 1 alnus sinuata and dryas drummondii derived most of their n through the fixation of atmospheric n 2 under conditions of high n availability differences among species in plant preference for ammonium or nitrate can be deduced from 15 n values 3 over time organic soil n separates into two isotopically distinct pools which differ in their turnover rate 4 the transition from an alder dominated to a spruce dominated system results in slower n cycling and 5 previous site conditions are an important factor in explaining patterns in 15 n values

lunar surface rock abundance and regolith fines temperatures derived from lro diviner radiometer data 1 surface temperatures derived from thermal infrared measurements provide a means of understanding the physical properties of the lunar surface the contrasting thermophysical properties between rocks and regolith fines cause multiple temperatures to be present within the field of view of nighttime multispectral data returned from the lunar reconnaissance orbiter lro diviner radiometer between 60 n s latitudes regolith temperatures are influenced by the presence of rocks in addition to factors such as the thermophysical properties of the regolith fines latitude and local slopes and radiative heating from adjacent crater walls preliminary comparisons of derived rock concentrations with lro camera images show both qualitative and quantitative agreement although comparisons of derived rock concentrations with circular polarization ratio radar data sets display general similarities there are clear differences between the two data sets in the relative magnitude and areal extent of rocky signatures several surface units can be distinguished based on their regolith temperature and rock concentration values and distributions including maria and highlands surfaces rocky impact craters rilles and wrinkle ridges dark mantled deposits and isolated cold surfaces rock concentrations are correlated with crater age and rocks are only preserved on the youngest surfaces or where steep slopes occur and mass wasting prevents mantling with fines the presence of rocky surfaces excavated by young impacts allows for the estimation of minimum regolith thickness from the size of the impact the derived rock concentrations confirm the presence of thicker regolith cover in the highlands and in locations of radar dark haloes

ages of large lunar impact craters and implications for bombardment during the moon s middle age abstract standard lunar chronologies based on combining lunar sample radiometric ages with impact crater densities of inferred associated units have lately been questioned about the robustness of their interpretations of the temporal dependance of the lunar impact flux in particular there has been increasing focus on the middle age of lunar bombardment from the end of the late heavy bombardment 3 8 ga until comparatively recent times 1 ga to gain a better understanding of impact flux in this time period we determined and analyzed the cratering ages of selected terrains on the moon we required distinct terrains with random locations and areas large enough to achieve good statistics for the small superposed crater size frequency distributions to be compiled therefore we selected 40 lunar craters with diameter 90 km and determined the model ages of their floors by measuring the density of superposed craters using the lunar reconnaissance orbiter wide angle camera mosaic absolute model ages were computed using the model production function of marchi et al marchi s mottola s cremonese g massironi m martellato e 2009 astron j 137 4936 4948 we find that a majority 36 of 40 of our superposed crater size frequency distributions are consistent with the model production function a histogram of the original crater floor model ages indicates the bombardment rate decreased gradually from 3 8 ga until 3 0 ga implying an extended tail to the late heavy bombardment for large craters it also preliminarily suggests that between 3 0 and 1 0 ga bombardment may be characterized by long periods 600 myr of relatively few impacts lulls broken by a short duration 200 myr of relatively more impacts spike while measuring superposed craters we also noted if they were part of a cluster or chain named obvious secondary and analyzed these craters separately interestingly we observe a wide variety of slopes to the differential size frequency power law which demonstrates that there can be considerable variation in individual secondary crater field size frequency distributions finally four of the small superposed crater size frequency distributions are found to be inconsistent with the model production function possible reasons are resurfacing has modified these distributions unrecognized secondary craters and or the model production function has incorrect inputs such as the scaling law for the target terrain the degraded appearance of the superposed craters and indications of resurfacing suggest that the first cause is the most likely

dynamic pedogenesis new views on some key soil concepts and a model for interpreting quaternary soils abstract inasmuch as soils are open systems and rarely if ever achieve equilibrium with their environments it is philosophically sound to view all soils as expressing varying levels of polygenesis as that term has been redefined soil genesis and resultant morphology may then be viewed in a comprehensive framework of soil evolution that consists of two linked pathways one developmental and the other regressive that reflect interactions of both exogenous and endogenous vectors vectors are factors processes and conditions of pedogenesis following this philosophy a model of pedogenesis is framed in an evolutional paradigm that emphasizes the integrated effects of dynamic and passive pedogenic vectors in directing pathways and in controlling rates of soil genesis through time the dynamic vectors include energy and mass fluxes frequencies of soil wetting and drying water table dynamics organisms feedback processes and pedoturbation the passive vectors include parent materials soil chemical environment stability of geomorphic surfaces and various evolved soil properties and conditions accessions both sets of vectors vary spatially and the dynamic vectors more so than passive vectors fluctuate through time the model is expressed as s f d p dd dt dd dt where s is the state of the soil or degree of profile evolution d is the set of dynamic vectors p is the set of passive vectors and dd dt and dp dt denote change through time t the model helps explain the apparent minimal development and regressed character of some old soils and the rapid and strong development of some young ones

the miniature radio frequency instrument s mini rf global observations of earth s moon abstract radar provides a unique means to analyze the surface and subsurface physical properties of geologic deposits including their wavelength scale roughness the relative depth of the deposits and some limited compositional information the nasa lunar reconnaissance orbiter s lro miniature radio frequency mini rf instrument has enabled these analyses on the moon at a global scale mini rf has accumulated 67 coverage of the lunar surface in s band 12 6 cm radar with a resolution of 30 m pixel here we present new mini rf global orthorectified uncontrolled s band maps of the moon and use them for analysis of lunar surface physical properties reported here are readily apparent global and regional scale differences in lunar surface physical properties that suggest three distinct terranes namely a 1 nearside radar dark region 2 orientale basin and continuous ejecta and the 3 highlands radar bright region integrating these observations with new data from lro s diviner radiometer rock abundance maps as well clementine and lunar prospector derived compositional values show multiple distinct lunar surface terranes and sub terranes based upon both physical and compositional surface properties previous geochemical investigations of the moon suggested its crust is best divided into three to four basic crustal provinces or terranes feldspathic highlands terrane an and outer procellarum kreep terrane and south pole aitken terrane that are distinct from one another however integration of these geochemical data sets with new geophysical data sets allows us to refine these terranes the result shows a more complex view of these same crustal provinces and provides valuable scientific and hazard perspectives for future targeted human and robotic exploration

constraints on the recent rate of lunar ejecta breakdown and implications for crater ages we present a new empirical constraint on the rate of breakdown of large ejecta blocks on the moon based on observations from the lunar reconnaissance orbiter lro diviner thermal radiometer we find that the rockiness of fresh crater ejecta can be quantified using the diviner derived rock abundance data set and we present a strong inverse correlation between the 95 th percentile value of the ejecta rock abundance ra 95 5 and crater age for nine craters with published model ages derived from crater counts on their continuous ejecta ra 95 5 decreases with crater age as age m y 0 46 this result implies shorter rock survival times than predicted based on downward extrapolation of 100 m crater size frequency distributions and represents a new empirical constraint on the rate of comminution of large rocks not previously analyzed experimentally or through direct observation in addition our result provides a new method for dating young lunar craters

a new look at the super outbreak of tornadoes on 3 4 april 1974 abstract the outbreak of tornadoes from the mississippi river to just east of the appalachian mountains on 2 5 april 1974 is analyzed using conventional techniques and the pennsylvania state university national center for atmospheric research fifth generation mesoscale model mm5 the mm5 was run for 48 h using the ncep ncar reanalysis dataset for initial conditions it is suggested that the first damaging squall line within the storm of 2 5 april 1974 herein referred to as the super outbreak storm was initiated by updrafts associated with an undular bore the bore resulted from the forward advance of a pacific cold front into a stable air mass the second major squall line within the super outbreak storm which produced the strongest and most numerous tornadoes was directly connected with the lifting associated with a cold front aloft this second squall line was located along the farthest forward protrusion of a pacific cold front as it occluded with a lee trough dryline an important factor in the

rock abundance on mars from the thermal emission spectrometer 1 nighttime infrared spectral observations returned from the mars global surveyor thermal emission spectrometer tes are well suited for determining the subpixel abundance of rocks on the surface of mars the algorithm used here determines both the areal fraction of rocky material and the thermal inertia of the fine grained nonrock component present on the surface rock is defined as any surface material that has a thermal inertia 1250 j m 2 k 1 s 1 2 this can be bedrock boulders indurated sediments or a combination of these on a surface mixed with finer grained materials over 4 9 million observations were compiled to produce the 8 pixels per degree global rock abundance and fine component inertia maps total coverage is 45 of the planet between latitudes 60 and 60 less than 1 of the planet has rock abundances greater than 50 and 7 of the mapped surface has greater than 30 rocks rocky regions on mars correspond primarily to the high inertia surfaces observed in thermal inertia data sets the fine component inertia data set is used to identify high inertia exposures that contain few rocks and more homogeneous materials

subsurface damage from oblique impacts into low impedance layers 1 layered planetary surfaces occur ubiquitously in the solar system where sedimentary sequences or icy layers overlay crystalline bedrock previous experimental studies investigated how the presence of weak layer overlying a strong basement affects crater morphology subsurface damage and soft sediment compression numerical studies generally focus on the final morphology as a function of thicknesses and burial depths of weak layers in field studies of impact craters the shock state of minerals is a key metric here we evaluate the effect of a surficial low impedance layer on peak pressure magnitudes and consequent damage extent in the competent substrate laboratory experiments coupled with 3d cth models of oblique 30 from horizontal hypervelocity impacts at laboratory and planetary scales show that surface layers with a thickness on the order of the projectile diameter shield the underlying surface and absorb scatter 70 of the impact energy numerical simulations reveal that surficial layers reduce peak pressure magnitudes within the subsurface by 60 70 while damage in the substrate is due to shear failure sedimentary layers are more efficient shields than icy layers but both reduce the extent of subsurface damage and the resulting shock levels recorded by minerals these results indicate that a thin surficial low impedance layer mitigates the expression of shocked minerals in the substrate even when a structural response is still observed

focused 70 cm wavelength radar mapping of the moon we describe new 70 cm wavelength radar images of the lunar near side and limb regions obtained via a synthetic aperture radar patch focusing reduction technique the data are obtained by transmitting a circularly polarized pulsed waveform from the arecibo telescope in puerto rico and receiving the echo in both senses of circular polarization with the robert c byrd green bank telescope in west virginia the resultant images in both polarizations have a spatial resolution as fine as 320 m 450 m near the lunar limb the patch focusing technique is a computationally efficient method for compensating for range migration and doppler azimuth smearing over long coherence times i e 983 s which is needed to achieve the required doppler resolution three to nine looks are averaged for speckle reduction and to improve the signal to noise ratio at this long wavelength the radar signal penetrates up to several tens of meters into the dry lunar surface materials thus revealing details of the bulk loss properties and decimeter scale rock abundance not evident in multispectral and other remote sensing data application of the new radar images to the analysis of basalt flow complexes in mare serenitatis shows that the long wavelength radar data are sensitive to differences in both flow age and composition and may be particularly useful for studies of smaller deposits that do not have robust crater statistics the new 70 cm lunar radar data are archived at the national aeronautics and space administration planetary data system

natural variations of δ30si ratios during progressive basalt weathering hawaiian islands abstract silicon stable isotopes can be used to trace the biogeochemical pathways of si as it moves from its continental sources to its sink in ocean sediments along the way si is incorporated into clay minerals taken up by plants where it forms plant opal and leached into rivers the major land to ocean conduit compared to igneous rocks the waters that drain continents are enriched in heavy si isotopes but the mechanisms that control fractionation have not been elucidated we studied si isotope fractionation along a 4 million yr basaltic soil chronosequence on the hawaiian islands using the natural context of these samples in combination with laboratory experiments we demonstrate that the isotopic composition of dissolved si in weathering systems is determined by the combined effects of rock disintegration clay mineral neosynthesis and si biocycling weathering preferentially releases 28si into solution whereas secondary mineral formation preferentially removes 28si from solution in humid environments leached soils have lost large amounts of this soluble si thus creating a net loss of 30si from the entire soil system as soils develop and greater fractions of si reside in neoformed clay minerals 30sibulk soil values change progressively toward more negative values basalt 30si values are about 0 5 but older soils have 30si values up to 2 5 the difference between the solid and solution 30si values remains more or less constant with progressive weathering and therefore soil water from older soils has a more negative 30si composition in the upper horizons of the hawaiian soils this weathering driven 30si shift is modified by the addition of unweathered primary minerals via dust carrying 30si values of about 0 5 and by biocycling of si via plants producing negative 30si values in phytoliths and positive 30si values in soil solutions derived from upper horizons due to the high concentrations of dissolved si in these near surface layers rivers have more positive 30si values than predicted based on the weathering status of the lower horizons when combined with published 30si values from large rivers worldwide we find that the results from hawaii point to weathering control of si isotopes delivered to the oceans and thus to an important continent ocean linkage that warrants further investigation

advances in holocene mountain geomorphology inspired by sediment budget methodology the sediment budget which links sediment sources to sediment sinks with hydroclimatic and weathering processes mediating the response is applied to the analysis of sediments in three alpine lakes in british columbia we provide two ways of using the sediment budget as an integrating device in the interpretation of mountain geomorphology these approaches differ in their resolution and ability to budget the major components of the fine sediment cascade in glaciated environments taken together they provide an integrated index of landscape change over the holocene the first example compares the hydroclimatic controls of lake sedimentation for the last 600 years a d 1370 1998 preserved in varved sediments from two of the lake basins this hydroclimatological approach incorporates contemporary monitoring air photo analysis and detailed stratigraphy of sedimentation events within a single varve to infer the timing sources and preferred pathways of fine grained sediments reaching the lake basins the results indicate that glaciers hillslope and channel instability within the major subbasins are the principal sediment sources to the lake basins transitory sediment storage of glacially derived sediments within the channels is believed to modulate the episodic and more frequent delivery of sediments from adjacent hillslope and fluvial storage sites and direct routing of glacial rock flour during years of prolonged glacial melt the second example relying on the phosphorus geochemistry of sediments in an alpine lake basin considers the evolution of phosphorus forms from mineral to occluded and organic fractions as a function of the soil development inherent slope instability and repeated cycles of glaciation and neoglaciation over the holocene this geochemical approach demonstrates that both neoglaciation and full glaciation have essentially zeroed the system in such a way that a high proportion of mineral phosphorus remains in the present lake sediments and the bioavailability of phosphorus a key to ecosystem development is low both examples illustrate the importance of variable sediment sources the seasonality frequency and magnitude of sediment transfers and the profound influence of ice cover over contemporary neoglacial and pleistocene time scales they also signal the value of including both clastic and dissolved components in the sediment budget d 2003 elsevier science b v all rights reserved

earth based 12 6 cm wavelength radar mapping of the moon new views of impact melt distribution and mare physical properties abstract we present results of a campaign to map much of the moon s near side using the 12 6 cm radar transmitter at arecibo observatory and receivers at the green bank telescope these data have a single look spatial resolution of about 40 m with final maps averaged to an 80 m four look product to reduce image speckle focused processing is used to obtain this high spatial resolution over the entire region illuminated by the arecibo beam the transmitted signal is circularly polarized and we receive reflections in both senses of circular polarization measurements of receiver thermal noise during periods with no lunar echoes allow well calibrated estimates of the circular polarization ratio cpr and the four element stokes vector radiometric calibration to values of the backscatter coefficient is ongoing radar backscatter data for the moon provide information on regolith dielectric and physical properties with particular sensitivity to ilmenite content and surface or buried rocks with diameter of about one tenth the radar wavelength and larger average 12 6 cm circular polarization ratio cpr values for low to moderate tio 2 mare basalt deposits are similar to those of rough terrestrial lava flows we attribute these high values to abundant few centimeter diameter rocks from small impacts and a significant component of subsurface volume scattering an outflow deposit inferred to be impact melt from glushko crater has cpr values near unity at 12 6 cm and 70 cm wavelengths and thus a very rugged near surface structure at the decimeter to meter scale this deposit does not show radar brightness variations consistent with levees or channels and appears to nearly overtop a massif suggesting very rapid emplacement deposits of similar morphology and or radar brightness are noted for craters such as pythagoras rutherfurd theophilus and aristillus images of the north pole show that despite recording the deposition of orientale material byrd and peary craters do not have dense patterns of radar bright ejecta from small craters on their floors such patterns in amundsen crater near the south pole were interpreted as diagnostic of abundant impact melt so the fraction of orientale derived melt in the north polar smooth plains 1000 km farther from the basin center is inferred to be much lower

lunar crater ejecta physical properties revealed by radar and thermal infrared observations abstract we investigate the physical properties and changes through time of lunar impact ejecta using radar and thermal infrared data we use data from two instruments on the lunar reconnaissance orbiter lro the diviner thermal radiometer and the miniature radio frequency mini rf radar instrument together with earth based radar observations we use this multiwavelength intercomparison to constrain block sizes and to distinguish surface from buried rocks in proximal ejecta deposits we find that radar detectable rocks buried within the upper meter of regolith can remain undisturbed by surface processes such as micrometeorite bombardment for 3 gyr we also investigate the thermophysical properties of radar dark haloes comprised of fine grained rock poor ejecta distal to the blocky proximal ejecta using diviner data we confirm that the halo material is depleted in surface rocks but show that it is otherwise thermophysically indistinct from background regolith we also find that radar dark haloes like the blocky ejecta remain visible in radar observations for craters with ages 3 ga indicating that regolith overturn processes cannot replenish their block populations on that timescale

ages and stratigraphy of lunar mare basalts in mare frigoris and other nearside maria based on crater size frequency distribution measurements 1 we report on ages derived from impact crater counts for exposed mare basalt units in the northern part of the lunar nearside hemisphere mare frigoris the eastern and northeastern part of the nearside hemisphere lacus temporis joliot hubble goddard mare marginis and mare smythii the central part of the nearside hemisphere palus putredinis mare vaporum and sinus medii and the southwestern part of the nearside hemisphere grimaldi cruger rocca a lacus aestatis and schickard in mare frigoris we dated 37 basalt units showing ages from 2 61 to 3 77 gyr with most units being formed in the late imbrian period between 3 4 and 3 8 gyr ago in mare vaporum we dated six spectrally homogeneous units that show model ages of 3 10 to 3 61 gyr our model ages of basalts in mare marginis range from 3 38 to 3 88 gyr and are mostly older than basalts in mare smythii 3 14 3 48 gyr the model ages of four units in sinus medii indicate that the basalts in this region formed 3 63 to 3 79 gyr ago we find an excellent agreement of our crater size frequency model ages of the palus putredinis area which contains the apollo 15 landing site with the radiometric ages of apollo 15 samples according to our crater counts basalts in palus putredinis are 3 34 gyr old and this compares favorably with the radiometric ages of 3 30 3 35 gyr of the olivine normative and quartz normative basalts of the apollo 15 landing site lacus aestatis is a small irregular shaped mare patch in the southwestern nearside and shows an imbrian age of 3 50 gyr basalts in lacus temporis in the northeastern nearside formed between 3 62 and 3 74 gyr ago and are therefore older than the basalts in lacus aestatis we found that basalts in craters of the southwestern nearside schickard grimaldi cruger and rocca a are also mostly younger than basalts in craters of the northeastern nearside hubble joliot and goddard while basalt ages vary between 3 16 and 3 75 gyr in the southwest basalts in the northeast are 3 60 3 79 gyr old these results confirm and extend the general distribution of ages of mare basalt volcanism and further underline the predominance of older mare basalt ages in the eastern and southern nearside and in patches of mare peripheral to the larger maria in contrast to the younger basalt ages on the western nearside oceanus procellarum

origin of discrepancies between crater size frequency distributions of coeval lunar geologic units via target property contrasts abstract recent work on dating copernican aged craters using lunar reconnaissance orbiter lro camera data re encountered a curious discrepancy in crater size frequency distribution csfd measurements that was observed but not understood during the apollo era for example at tycho copernicus and aristarchus craters csfds of impact melt deposits give significantly younger relative and absolute model ages amas than impact ejecta blankets although these two units formed during one impact event and would ideally yield coeval ages at the resolution of the csfd technique we investigated the effects of contrasting target properties on csfds and their resultant relative and absolute model ages for coeval lunar impact melt and ejecta units we counted craters with diameters through the transition from strength to gravity scaling on two large impact melt deposits at tycho and king craters and we used pi group scaling calculations to model the effects of differing target properties on final crater diameters for five different theoretical lunar targets the new csfd for the large king crater melt pond bridges the gap between the discrepant csfds within a single geologic unit thus the observed trends in the impact melt csfds support the occurrence of target property effects rather than self secondary and or field secondary contamination the csfds generated from the pi group scaling calculations show that targets with higher density and effective strength yield smaller crater diameters than weaker targets such that the relative ages of the former are lower relative to the latter consequently coeval impact melt and ejecta units will have discrepant apparent ages target property differences also affect the resulting slope of the csfd with stronger targets exhibiting shallower slopes so that the final crater diameters may differ more greatly at smaller diameters besides their application to age dating the csfds may provide additional information about the characteristics of the target for example the transition diameter from strength to gravity scaling could provide a tool for investigating the relative strengths of different geologic units the magnitude of the offset between the impact melt and ejecta isochrons may also provide information about the relative target properties and or exposure degradation ages of the two units robotic or human sampling of coeval units on the moon could provide a direct test of the importance and magnitude of target property effects on csfds

changes in erosion patterns during the holocene in a currently treeless subalpine catchment inferred from lake sediment geochemistry lake anterne 2063 m a s l nw french alps the role of climate and human activities a high resolution sedimentological and geochemical study was performed on a 20 m long core from the alpine lake anterne 2063 m a s l nw french alps spanning the last 10 ka sedimentation is mainly of minerogenic origin the organic matter quantity toc as well as its quality hydrogen hi and oxygen oi indices both indicate the progressive onset and subsequent stabilization of vegetation cover in the catchment from 9950 to 5550 cal bp during this phase the pedogenic process of carbonate dissolution is marked by a decrease in the calcium content in the sediment record between 7850 and 5550 cal bp very low manganese concentrations suggest anoxic conditions in the bottom water of lake anterne these are caused by a relatively high organic matter terrestrial and lacustrine content a low flood frequency and longer summer stratification triggered by warmer conditions from 5550 cal bp a decrease in toc stabilization of hi and higher sedimentation rates together reflect increased erosion rates of leptosols and developed soils probably due to a colder and wetter climate then three periods of important soil destabilization are marked by an increased frequency and thickness of flood deposits during the bronze age and by increases in topsoil erosion relative to leptosols hi increases during the late iron age roman period and the medieval periods these periods are also characterized by higher sedimentation rates according to palynological data human impact deforestation and or pasturing activity probably triggered these periods of increased soil erosion

lunar craters with radar bright ejecta abstract a small fraction of the lunar impact craters with diameters of 1 km and greater have extensive enhanced 3 8 cm radar echoes associated with their ejecta deposits the physical properties of these ejecta deposits and the ages of the central craters have been characterized via various infrared radar and optical signatures most of these ejecta deposits are radar bright at the 3 8 cm wavelength but are not radar bright at the 70 cm wavelength some ejecta have large infrared signatures others do not although most of these ejecta have bright albedos in full moon photographs a significant fraction of the bright albedo markings do not extend beyond the crater this mix of remote sensing signatures indicates that craters with 3 8 cm radar bright halos are young and have ejecta deposits containing an excess of surface or near surface rocks relative to the surrounding terrain abundant centimeter sized rocks are inferred from the high 3 8 cm radar and infrared signatures the low 70 cm radar signatures indicate that larger blocks are much less numerous the population of craters with 3 8 cm radar bright craters on the moon is much smaller than the population of craters in a similar size range on a young mare oceanus procellarum and has a different slope this population is interpreted as a steady state population reflecting a balance between the production of fresh craters and the destruction of the high infrared and radar signatures by small scale cratering the slope of difference between visual and radar craters is attributed to more rapid destruction of the radar signatures in smaller craters relative densities of 3 8 cm radar bright craters and mare craters are estimated to be 0 04 in 0 042 0 016 at a 4 km diameter and 0 100 0 07 0 007 at a 32 km diameter assigning ages on the basis of these relative densities raises the question of whether the 4 to 32 km diameter visual crater population is truly representative of a 3 3 by age if it is and if crater rates between 3 3 by and the present have been uniform than the 3 8 cm radar crater lifetimes are estimated to be 0 13 0 04 0 25 by and 0 03 0 13 0 23 by at diameters of 4 and 32 km respectively similarly lifetimes of the infrared signatures of 4 km diameter craters may be as short as 10 7 years however some data suggest that these estimates may be in error by a factor of 5 too small comminution of blocky ejecta material and the smoothing of slopes by lunar surface processes could account for the elimination of radar signatures on these time scales and the development of a steady state crater population an altenative interpretation which we do not fsvor is that the 3 8 cm radar bright crater population is formed by a subpopulation of primary bodies or by secondary cratering

the global surface temperatures of the moon as measured by the diviner lunar radiometer experiment abstract the diviner lunar radiometer experiment onboard the lunar reconnaissance orbiter lro has been acquiring solar reflectance and mid infrared radiance measurements nearly continuously since july of 2009 diviner is providing the most comprehensive view of how regoliths on airless bodies store and exchange thermal energy with the space environment approximately a quarter trillion calibrated radiance measurements of the moon acquired over 5 5 years by diviner have been compiled into a 0 5 resolution global dataset with a 0 25 h local time resolution maps generated with this dataset provide a global perspective of the surface energy balance of the moon and reveal the complex and extreme nature of the lunar surface thermal environment our achievable map resolution both spatially and temporally will continue to improve with further data acquisition daytime maximum temperatures are sensitive to the albedo of the surface and are 387 397 k at the equator dropping to 95 k just before sunrise though anomalously warm areas characterized by high rock abundances can be 50 k warmer than the zonal average nighttime temperatures an asymmetry is observed between the morning and afternoon temperatures due to the thermal inertia of the lunar regolith with the dusk terminator 30 k warmer than the dawn terminator at the equator an increase in albedo with incidence angle is required to explain the observed decrease in temperatures with latitude at incidence angles exceeding 40 topography and surface roughness influence temperatures resulting in increasing scatter in temperatures and anisothermality between diviner channels nighttime temperatures are sensitive to the thermophysical properties of the regolith high thermal inertia ti materials such as large rocks remain warmer during the long lunar night and result in anomalously warm nighttime temperatures and anisothermality in the diviner channels anomalous maximum and minimum temperatures are highlighted by subtracting the zonal mean temperatures from maps terrains can be characterized as low or high reflectance and low or high ti low maximum temperatures result from high reflectance surfaces while low minimum temperatures from low ti material conversely high maximum temperatures result from dark surface and high minimum temperatures from high ti materials impact craters are found to modify regolith properties over large distances the thermal signature of tycho is asymmetric consistent with an oblique impact coming from the west some prominent crater rays are visible in the thermal data and require material with a higher thermal inertial than nominal regolith the influence of the formation of the orientale basin on the regolith properties is observable over a substantial portion of the western hemisphere despite its age 3 8 gyr and may have contributed to mixing of highland and mare material on the southwest margin of oceanus procellarum where the gradient in radiative properties at the mare highland contact is broad 200 km

the formation of fluidized ejecta on mars by granular flows a simple granular flow model is used to investigate some of the conditions under which ejecta may flow as a granular media the purpose of this investigation is to provide some bounds as to when either volatiles or an atmosphere are required to explain the fluid like morphology of many martian ejecta deposits we consider the ejecta deposition process from when an ejecta curtain first strikes a target surface via ballistics and possibly flows thereafter a new finding is that either hard smooth surfaces or slightly erodible surfaces allow ejecta to flow readily as a granular medium neither volatiles nor an atmosphere are required to initiate flow a low friction coefficient between ejecta grains can also generate flow and would be analogous to adding volatiles to the ejecta the presence of either a rough or a densely packed erodible surface does not permit easy ejecta flow high friction coefficients between ejecta grain also prevent flow while changes in the coefficient of restitution a measure of how much energy is retained after collisions between particles plays a minor role in the flow dynamics of ejecta a hard smooth or a somewhat erodible surface could be generated by past fluvial activity on mars which can either indurate a surface erode and smooth a surface or generate sedimentary terrains that are fairly easy to erode no ramparts or layered ejecta morphologies are generated by our model but this may be because several simplifying assumptions are used in our model and should not be construed as proof that either volatiles or an atmosphere are required to form fluidized ejecta morphologies

earth based radar data reveal extended deposits of the moon s orientale basin we present new earth based radar observations of ejecta associated with the lunar orientale impact basin we can distinguish 1 a block poor ejecta facies composing a concentric halo of mantling material 10 m or greater in thickness that extends more than 1000 km from the basin center and 2 a melt rich deposit that forms a discontinuous but areally extensive stratigraphic marker across the southern highlands the melt rich component likely extends well into the south pole aitken basin a key target for future landed and sample return missions the observation of these two ejecta facies and their distribution across the southern nearside yields new insight into the types and distribution of material contributed by large basin forming impacts to the highlands megaregolith

xanes spectroscopy as a tool to trace phosphorus transformation during soil genesis and mountain ecosystem development from lake sediments the aim of this study is to investigate phosphorus p species modifications triggered by soil genesis and mountain ecosystem development after glacial retreat using a lake sediment archive lake anterne north french alps five lake sediment samples representative of different stages of soil and ecosystem development were selected for p speciation analyses furthermore a sequence of current soils from the catchment was analyzed to better constrain our interpretations of the lacustrine archive synchrotron techniques x ray fluorescence xrf mapping and p k edge x ray absorption near edge structure xanes spectroscopy were applied to lake sediments soils and standards mineral and organic to distinguish between different p species the results show that soil development during the first millennia of the holocene triggered increased p species diversity at the onset of the holocene p was present as apatite when rocks and leptosols dominated the catchment pedogenic processes then led to apatite dissolution and the formation of large amounts of p on metal clay organic complexes p geochemistry during the main step of soil genesis early leptosols dominated by apatite low weathered cambisols with p mainly adsorbed on iron oxides highly weathered podzols with large amounts of p on al fe clay organic complexes is thus clearly recorded in lake sediments p k edge xanes spectroscopy is particularly relevant as qualitative method to study p species in soils and lake sediments at high spatial resolution such resolution is needed to reveal the diversity of small p particles and like this better characterize the p cycle and improve our understanding of ecosystem evolution

ages of mare basalts on the lunar nearside the chronology of lunar volcanism is based on radiometric ages determined from apollo and luna landing site samples regional stratigraphic relationships and crater degradation and size frequency distribution data for units largely defined prior to the end of the apollo program here we report on new crater size frequency distribution data for 139 spectrally and morphologically defined basalt units which are exposed in six nearside impact basins australe tranquillitatis humboldtianum humorum serenitatis and imbrium crater size frequency distribution measurements are a statistically robust and accurate method to derive absolute model ages of unsampled regions of the moon compared to crater degradation ages crater size frequency ages performed on spectrally defined units offer significant improvements in accuracy our investigation showed that 1 in the investigated basins lunar volcanism was active for at least 1 5 2 0 b y starting at about 3 9 4 0 b y and ceasing at 2 0 b y 2 most basalts erupted during the late imbrian period at about 3 6 3 8 b y 3 significantly fewer basalts were emplaced during the eratosthenian period 4 basalts of copernican age were not found in any of the investigated basins 5 lunar basin filling volcanism probably started within 100 m y after the formation of the individual basins we also assessed the relationship between impact basin age and the history of mare basalt emplacement in these basins we found that 1 in all pre nectarian basins australe and tranquillitatis as well as in the humboldtianum basin which is of nectarian age the distribution of surface ages is clearly dominated by only a single peak in the number of erupted units at 3 6 3 8 b y 2 in the younger basins humorum serenitatis and imbrium a second peak at 3 3 3 5 b y is observed 3 basalt eruptions younger than 2 6 b y occur only intermittently and 4 in the youngest basins serenitatis and imbrium we see an extended period of active basin filling volcanism 1 5 1 6 b y which is 500 m y longer than in the australe and humorum and even 1 0 b y longer than in tranquillitatis and humboldtianum

biogenic silica a neglected component of the coupled global continental biogeochemical cycles of carbon and silicon on geological time scales 106 years the global geochemical cycles of carbon and silicon are coupled by the drawdown of atmospheric co2 through chemical weathering of ca and mg silicate minerals in continental rocks rivers transport the soluble products of weathering cations alkalinity and silicic acid to the oceans where they are utilized by marine ecosystems on decadal to glacial interglacial time scales however large biotic fluxes and storages of si within terrestrial and freshwater ecosystems need to be taken into account recent studies have emphasized the importance of si accumulating plants which deposit significant amounts of amorphous hydrated silica in their tissues as opal phytoliths these include grasses sedges palms some temperate deciduous trees and conifers and many tropical hardwoods landscapes dominated by accumulator plants such as tropical rainforests grasslands herbaceous wetlands and bamboo forests act as silica factories important silica bioengineers in freshwater ecosystems comprise diatoms sponges and chrysophytes this paper reviews the biological role of si in higher plants the impact of vegetation on rates of chemical weathering the fluxes of si through catchment ecosystems lakes and rivers and the potential contribution of new geochemical and isotopic tracers to si biogeochemistry multiproxy investigations of lake sediments will provide novel insights into past variations in si biocycling from terrestrial to aquatic realms on 10 106 year time scales copyright 2008 john wiley sons ltd

lunar cold spots granular flow features and extensive insulating materials surrounding young craters abstract systematic temperature mapping and high resolution images reveal a previously unrecognized class of small fresh lunar craters these craters are distinguished by near crater deposits with evidence for lateral ground hugging transport more distal highly insulating surfaces surround these craters and do not show evidence of either significant deposition of new material or erosion of the substrate the near crater deposits can be explained by a laterally propagating granular flow created by impact in the lunar vacuum environment further from the source crater at distances of 10 100 crater radii the upper few to 10s of centimeters of regolith appear to have been fluffed up without the accumulation of significant ejecta material these properties appear to be common to all impacts but quickly degrade in the lunar space weathering environment cratering in the vacuum environment involves a previously unrecognized set of processes that leave prominent but ephemeral features on the lunar surface

the development of the piedmont front and associated outbreak of severe weather on 13 march 1986 abstract an investigation was conducted of the mesoscale evolution of a quasi stationary front termed the piedmont front owing to its location through the central carolinas and an associated outbreak of severe weather on 13 march 1986 space time relationships between mesoscale processes associated with the evolution of the surface front and the initiation of severe thunderstorms were studied utilizing the enhanced surface and upper air observation networks deployed during the field phase of gale surface streamline patterns frontogenesis and moisture flux divergence were computed employing an objective analysis scheme following the arrival at the carolina coast of a coastal front the piedmont front rapidly developed along an axis of dilatation over the eastern margin of the piedmont while the coastal front gradually dissipated over the nearshore waters a differential cloud cover across the piedmont front resulted in enhanced solar insolation on the warm side of the front that strengthened frontog

organization and structure of clouds and precipitation on the mid atlantic coast of the united states part vii diagnosis of a nonconvective rainband associated with a cold front aloft abstract a numerical simulation using the pennsylvania state university national center for atmospheric research fifth generation mesoscale model mm5 was run on a rainband associated with a cold front aloft cfa in a warm occluded structure on the u s east coast the storm originally developed in the lee of the rocky mountains as a pacific cold front overtook a rocky mountain lee trough this formed a warm type occluded structure that was essentially maintained as the storm proceeded to the east coast the cfa was a thermal front and therefore dynamically active the prominence of the cfa in the equivalent potential temperature field was due primarily to the strong upward transport of water vapor from lower levels in the updraft associated with the cfa the baroclinic zone was characterized by a tipped forward lower region where the cfa coincided with a maximum in potential temperature and a tipped backward upper region where the cfa coincided with the leading warm side edge of a zone of enhance

earth based observations of radar dark crater haloes on the moon implications for regolith properties 1 earth based radar can be used in conjunction with other data sets collected remotely or in situ to characterize the physical and chemical properties of the lunar regolith we use previously existing and newly acquired earth based radar measurements at 70 cm wavelength to investigate the properties of distinctive low return haloes surrounding 39 nearside impact craters these haloes are distinct from the well known optically dark haloes associated with volcanic craters or with impacts into cryptomare deposits we examine two possible mechanisms for formation of radar dark haloes 1 excavation of high tio2 high loss tangent basalt and 2 deposition of a mantling layer produced in the impact process that is depleted in meter sized blocks comparison of the radar data with apollo and lunar orbiter images indicates a general spatial correspondence between radar dark crater haloes and radial ridged ejecta facies distal to the radar bright crater rims comparison with clementine uv vis multispectral data indicates no apparent spatial correlation between regions of enhanced tio2 content and radar dark haloes though variations in tio2 content may play a role for some mare craters they are insufficient to account for the observed offsets in radar echo power we conclude that the radar dark haloes result from a block poor ejecta deposit that disappears over time with meteoroid bombardment a more detailed and comprehensive analysis of ejecta degradation processes and rates following acquisition of additional high resolution radar data could lead to a refinement of the lunar geologic timescale

thermal fatigue as the origin of regolith on small asteroids space missions1 2 and thermal infrared observations3 have shown that small asteroids kilometre sized or smaller are covered by a layer of centimetre sized or smaller particles which constitute the regolith regolith generation has traditionally been attributed to the fall back of impact ejecta and by the break up of boulders by micrometeoroid impact4 5 laboratory experiments6 and impact models4 however show that crater ejecta velocities are typically greater than several tens of centimetres per second which corresponds to the gravitational escape velocity of kilometre sized asteroids therefore impact debris cannot be the main source of regolith on small asteroids4 here we report that thermal fatigue7 8 9 a mechanism of rock weathering and fragmentation with no subsequent ejection is the dominant process governing regolith generation on small asteroids we find that thermal fragmentation induced by the diurnal temperature variations breaks up rocks larger than a few centimetres more quickly than do micrometeoroid impacts because thermal fragmentation is independent of asteroid size this process can also contribute to regolith production on larger asteroids production of fresh regolith originating in thermal fatigue fragmentation may be an important process for the rejuvenation of the surfaces of near earth asteroids and may explain the observed lack of low perihelion carbonaceous near earth asteroids10

the production of small primary craters on mars and the moon abstract we model the primary crater production of small d d 10 20 cm well below the downturn observed in the distribution of fresh craters detected by the mars global surveyor mgs mars orbiter camera moc or the mars reconnaissance orbiter mro context camera ctx crater counts are conducted on the ejecta blanket of zunil crater and the interior of pangboche crater on mars and north ray and cone craters on the moon our model isochrons produce a similar slope and age estimate for the formation of zunil crater as the hartmann production function 1 ma we derive an age of 35 1 ma for pangboche when accounting for the higher elevation 20 km higher than zunil a factor 2 younger than estimated using the hartmann production function which assumes 6 mbar surface pressure we estimate ages of 52 3 ma and 23 9 ma for north ray and cone crater respectively consistent with cosmic ray exposure ages from apollo samples our results indicate that the average cratering rate has been constant on these bodies over these time periods since our monte carlo simulations demonstrate that the existing crater chronology systems can be applied to date young surfaces using small craters on the moon and mars we conclude that the signal from secondary craters in the isochrons must be relatively small at these locations as our monte carlo model only generates primary craters

phosphorus burial in sediments of the sulfidic deep black sea key roles for adsorption by calcium carbonate and apatite authigenesis abstract sedimentary burial of the essential nutrient phosphorus p under anoxic and sulfidic conditions is incompletely understood here we use chemical and micro scale spectroscopic methods to characterize sedimentary p burial along a water column redox transect six stations 78 2107 m water depth in the black sea from the shelf with its oxygenated waters to the anoxic and sulfidic deep basin organic p is an important p pool under all redox regimes accounting for up to 60 of p burial we find a general down core increase in the relative importance of organic p especially on the shelf where p bound to iron fe and manganese mn oxyhydr oxides is abundant in the uppermost sediment but rapidly declines in concentration with sediment depth our chemical and spectroscopic data indicate that the carbonate rich sediments unit i 3000 years 0 30 cm depth of the sulfidic deep black sea contain three major p pools calcium phosphate apatite organic p and p that is strongly associated with caco3 and possibly clay surfaces apatite concentrations increase from 5 to 25 of total p in the uppermost centimeters of the deep basin sediments highlighting the importance of apatite formation for long term p burial iron ii associated p ludlamite was detected with x ray absorption spectroscopy but was shown to be a minor p pool 5 indicating that lateral fe p transport from the shelf shuttling likely occurs but does not impact the p burial budget of the deep black sea the caco3 p pool was relatively constant throughout the unit i sediment interval and accounted for up to 55 of total p our results highlight that carbonate bound p can be an important sink for p in caco3 rich sediments of anoxic sulfidic basins and should also be considered as a potential p sink and p source in case of caco3 dissolution when reconstructing past ocean p dynamics from geological records

first plants cooled the ordovician the late ordovician period ending 444 million years ago was marked by the onset of glaciations the expansion of non vascular land plants accelerated chemical weathering and may have drawn down enough atmospheric carbon dioxide to trigger the growth of ice sheets

effects of climate and landscape development on the terrestrial phosphorus cycle past variations in the terrestrial cycle of phosphorus p a biolimiting nutrient are poorly understood detailed geochemical analysis of p in lake sediment cores spanning the late pleistocene to the present from the western appalachian plateau the coast mountains of british columbia and the san bernardino mountains of southern california reveal large changes in terrestrial p cycling p is transformed from a mineralized form to more bioavailable forms with increased soil development and landscape stability in the catchments this process occurs relatively rapidly i e within 3 000 5 000 yr and can be reset quickly the degree of transformation depends on local climate and the starting point of the soil system the release of solid phase p from these landscapes follows modeled patterns of high rates during the initial stages of soil development and low rates upon soil and landscape stabilization changes in weathering style were confirmed for the southern california catchment by analysis of ge si ratios of lake diatoms which revealed substantially higher values during an interval of high p release and low values at present these records point to significant variability in the terrestrial p mass balance on glacial time scales a feature that needs to be incorporated into models of nutrient andmore carbon cycling in the past less

alpine lake sediment records of the impact of glaciation and climate change on the biogeochemical cycling of soil nutrients lake sediment cores from the coast mountains of british columbia were analyzed using chemical sequential extractions to partition the dominant geochemical fractions of phosphorus p the p fractions include mineral p the original source of bioavailable p occluded p bound to soil oxides and organic p remains of organic matter by comparing p fractions of soil and recent lake sediment samples these fractions are shown to be a valid proxy for landscape scale nutrient status changes in soil development for an alpine watershed lower joffre lake are inferred from the p fractions in the basin s outlet lake sediments glacially sourced mineral p dominates at the base of the core but several rapid shifts in p geochemistry are evident in the first 3000 yr of the record the latter indicates an interval of early and rapid soil nutrient maturation from 9600 to 8500 cal yr bp and a significant influx of slope derived material into lower joffre lake a substantial increase in mineral p occurs at ca 8200 cal yr bp consistent with the cold event in the vicinity of the north atlantic at that time the more recent record reveals a continual increase in the proportion of mineral p from glacial sources to the lake indicating a trend toward cooler conditions in the coast mountains

formation age of the lunar crater giordano bruno using the terrain camera onboard the japanese lunar explorer selene kaguya we obtained new high resolution images of the 22 kilometer diameter lunar crater giordano bruno based on crater size frequency measurements of small craters 200 m in diameter superposed on its continuous ejecta the formation age of giordano bruno is estimated to be 1 to 10 ma this is constructive evidence against the craters medieval age formation hypothesis

biological fractionation of silicon isotopes in southern ocean surface waters 1 the fractionation of silicon isotopes by diatoms during silicification i e opaline cell wall formation provides a new tool for paleoceanographic studies of the silicon cycle here we examine the natural variations of the 30si 28si ratio in silicic acid si oh 4 and biogenic silica bsio2 in surface waters of the antarctic circumpolar current acc along 170 w the results provide direct evidence of biologically mediated fractionation of silicon isotopes with an enrichment factor of between 1 1 and 1 9 depending on the model employed comparison of the mass flux of bsio2 captured in sediment traps deployed in the study area with the silicon isotopic composition of that material establishes a direct linkage between diatom dynamics in surface waters and the isotopic signature of exported particles we calculated si oh 4 no3 utilization ratios from variations in silicon and nitrogen isotopic ratios in surface waters and sediment traps that agree well with direct observations of 4 1 in this region this work supports the use of variations in silicon isotopes in sedimentary opal as a proxy for relative si oh 4 utilization in surface waters

origin of the anomalously rocky appearance of tsiolkovskiy crater abstract rock abundance maps derived from the diviner lunar radiometer instrument on the lunar reconnaissance orbiter lro show tsiolkovskiy crater to have high surface rock abundance and relatively low regolith thickness the location of the enhanced rock abundance to the southeast of the crater is consistent with a massive well preserved impact melt deposit apparent in lro miniature radio frequency instrument circular polarization ratio data a new model crater age using lro lunar reconnaissance orbiter camera imagery suggests that while it originated in the late imbrian tsiolkovskiy may be the youngest lunar crater of its size 180 km diameter together these data show that tsiolkovskiy has a unique surface rock population and regolith properties for a crater of its size and age explanation of these observations requires mechanisms that produce more large blocks preserve boulders and large blocks from degradation to regolith and or uncover buried rocks these processes have important implications for formation of regolith on the moon

phosphorus burial and diagenesis in the central bering sea bowers ridge iodp site u1341 perspectives on the marine p cycle abstract to reconstruct the cycling of reactive phosphorus p in the bering sea a p speciation record covering the last 4 ma was generated from sediments recovered during integrated ocean drilling program iodp expedition 323 at site u1341 bowers ridge a chemical extraction procedure distinguishing between different operationally defined p fractions provides new insight into reactive p input burial and diagenetic transformations reactive p mass accumulation rates mars are 20 110 mol cm2 ka which is comparable to other open ocean locations but orders of magnitude lower than most upwelling settings we find that authigenic carbonate fluorapatite cfa and opal bound p are the dominant p fractions at site u1341 an overall increasing contribution of cfa to total p with sediment depth is consistent with a gradual sink switching from more labile p fractions fish remains fe oxides organic matter to stable authigenic cfa however the positive correlation of cfa with al content implies that a significant portion of the supposedly reactive cfa is non reactive detrital contamination by eolian and or riverine cfa in contrast to cfa opal bound p has rarely been studied in marine sediments we find for the first time that opal bound p directly correlates with excess silica contents this p fraction was apparently available to biosiliceous phytoplankton at the time of sediment deposition and is a long term sink for reactive p in the ocean despite the likelihood for diagenetic re mobilisation of this p at depth indicated by increasing ratios of excess silica to opal bound p average reactive p mars at site u1341 increase by 25 if opal bound p is accounted for but decrease by 25 if 50 of the extracted cfa fraction based on the lowest cfa value at site u1341 is assumed to be detrital combining our results with literature data we present a qualitative perspective of terrestrial cfa and opal bound p deposition in the modern ocean riverine cfa input has mostly been reported from continental shelves and margins draining p rich lithologies while eolian cfa input is found across wide ocean regions underlying the northern hemispheric dust belt opal bound p burial is important in the southern ocean north pacific and likely in upwelling areas shifts in detrital cfa and opal bound p deposition across ocean basins likely occurred over time responding to changing weathering patterns sea level and biogenic opal deposition

impact craters in the northern hemisphere of mars layered ejecta and central pit characteristics mars global surveyor mgs and mars odyssey data are being used to revise the catalog of large martian impact craters analysis of data in the revised catalog provides new details on the distribution and morphologic details of 6795 impact craters in the northern hemisphere of mars this report focuses on the ejecta morphologies and central pit characteristics of these craters the results indicate that single layer ejecta sle morphology is most consistent with impact into an ice rich target double layer ejecta dle and multiple layer ejecta mle craters also likely form in volatile rich materials but the interaction of the ejecta curtain and target produced vapor with the thin martian atmosphere may be responsible for the large runout distances of these ejecta pancake craters appear to be a modified form of double layer craters where the thin outer layer has been destroyed or is unobservable at present resolutions pedestal craters are proposed to form in an ice rich mantle deposited during high obliquity periods from which the ice has subsequently sublimated central pits likely form by the release of vapor produced by impact into ice soil mixed targets therefore results from the present study are consistent with target volatiles playing a dominant role in the formation of crater morphologies found in the martian northern hemisphere

terrestrial analogues for lunar impact melt flows abstract lunar impact melt deposits have unique physical properties they have among the highest observed radar returns at s band 12 6 cm wavelength implying that they are rough at the decimeter scale however they are also observed in high resolution optical imagery to be quite smooth at the meter scale these characteristics distinguish them from well studied terrestrial analogues such as hawaiian p hoehoe and a lava flows the morphology of impact melt deposits can be related to their emplacement conditions so understanding the origin of these unique surface properties will help to inform us as to the circumstances under which they were formed in this work we seek to find a terrestrial analogue for well preserved lunar impact melt flows by examining fresh lava flows on earth we compare the radar return and high resolution topographic variations of impact melt flows to terrestrial lava flows with a range of surface textures the lava flows examined in this work range from smooth hawaiian p hoehoe to transitional basaltic flows at craters of the moon cotm national monument and preserve in idaho to rubbly and spiny p hoehoe like flows at the recent eruption at holuhraun in iceland the physical properties of lunar impact melt flows appear to differ from those of all the terrestrial lava flows studied in this work this may be due to a differences in post emplacement modification processes or b fundamental differences in the surface texture of the melt flows due to the melts unique emplacement and or cooling environment information about the surface properties of lunar impact melt deposits will be critical for future landed missions that wish to sample these materials

terrestrial ecosystems and the global biogeochemical silica cycle 1 most research on the global si cycle has focused nearly exclusively on weathering or the oceanic si cycle and has not explored the complexity of the terrestrial biogeochemical cycle the global biogeochemical si cycle is of great interest because of its impact on global co2 concentrations through the combined processes of weathering of silicate minerals and transfer of co2 from the atmosphere to the lithosphere a sizable pool of si is contained as accumulations of amorphous silica or biogenic silica bsi in living tissues of growing plants known as phytoliths and after decomposition of organic material as remains in the soil the annual fixation of phytolith silica ranges from 60 200 tmol yr 1 and rivals that fixed in the oceanic biogeochemical cycle 240 tmol yr 1 internal recycling of the phytolith pool is intense with riverine fluxes of dissolved silicate to the oceans buffered by the terrestrial biogeochemical si cycle challenging the ability of weathering models to predict rates of weathering and consequently changes in global climate consideration must be given to the influence of the terrestrial bsi pool on variations in the global biogeochemical si cycle over geologic time and the influence man has had on modifying both the terrestrial and aquatic biogeochemical cycles

relative and absolute ages of individual craters and the rate of infalls on the moon in the post imbrium period abstract this paper contains a reasonably successful attempt to determine relative ages and then absolute ages of individual craters younger than imbrium and the rate of infalls onto the moon as a function of time after the tail of the massive premare bombardment became depleted before 3 aeons 1 aeon 109 years ago there was a period of minimal numbers of infalls the rate of infalls increased rather steadily from this minimum to the present the rate in the geologically recent past 0 3 aeon was about two times that found for the period immediately after the last of the major lave outpourings 3 2 aeons absolute ages were determined for large craters 8 km from crater counts on the surfaces within and on the rims of the large craters key dates were 0 and 0 3 aeon for terrestrial meteoritic craters 3 2 3 5 3 8 and 3 82 aeons for the various mare surfaces according to the determinations of d e wilhelms 1980 geologic history of the moon u s geol surv prof pap and 3 85 aeons from the formation of imbrium