stable carbon and oxygen isotopic evidence for late pleistocene to middle holocene climatic fluctuations in the interior of southern africa stable carbon and oxygen isotope analyses of ungulate grazers from four archaeolog ical sites located in different environs within the caledon river valley have provided a relatively well dated proxy palaeoenvironmental and palaeoclimatic sequence for the period between 16 000 and 6000 calendar cal yr bp within the overall trend towards hot mid holocene temperatures and a summer rainfall pattern stable carbon isotope results show that there were three periods when growth season temperatures were cool enough for c3 grasses to be present 16 000 14 000 10 200 9600 and 8400 8000 cal yr bp similar trends were recorded in stable oxygen isotope values reflecting shifts in either temperature or available moisture although having a similar pattern to that of the lower altitude site sites situated in foothills and montane portions of the valley consistently maintained lower temperatures until the mid holocene altithermal at this time growth season temperatures warmed sufficiently for a 100 c4 grassland to expand in altitude from the warmer low lying localities in relation to present understanding of synoptic and global climatic patterning these findings suggest that the early to middle holocene transition was not a gradual warming trend but rather it was marked by a series of climatic fluctuations of particular note is the possible global rather than regional occurrence of the 8200 cal yr bp event copyright 2002 john wiley sons ltd journal of quaternary science

the global martian volcanic evolutionary history abstract viking mission image data revealed the total spatial extent of preserved volcanic surface on mars one of the dominating surface expressions is olympus mons and the surrounding volcanic province tharsis earlier studies of the global volcanic sequence of events based on stratigraphic relationships and crater count statistics were limited to the image resolution of the viking orbiter camera here a global investigation based on high resolution image data gathered by the high resolution stereo camera hrsc during the first years of mars express orbiting around mars is presented additionally mars orbiter camera moc and thermal emission imaging system themis images were used for more detailed and complementary information the results reveal global volcanism during the noachian period 3 7 ga followed by more focused vent volcanism in three tharsis elysium and circum hellas and later two tharsis and elysium volcanic provinces finally the volcanic activity became localized to the tharsis region about 1 6 ga ago where volcanism was active until very recently 200 100 ma these age results were expected from radiometric dating of martian meteorites but now verified for extended geological units mainly found in the tharsis montes surroundings showing prolonged volcanism for more than 3 5 billions years the volcanic activity on mars appears episodic but decaying in intensity and localizing in space the spatial and temporal extent of martian volcanism based on crater count statistics now provides a much better database for modelling the thermodynamic evolution of mars

the age of the medusae fossae formation evidence of hesperian emplacement from crater morphology stratigraphy and ancient lava contacts abstract the medusae fossae formation mff covering about 2 1 10 6 km 2 with an estimated volume of 1 4 10 6 km 3 and straddling the equatorial region of mars east of tharsis has historically been mapped and dated as amazonian in age analysis of the mff using a range of new observations from recent mission data at multiple resolutions reveals evidence that the formation is older than previously hypothesized with parts of the mff having formed in the hesperian and parts having been reworked and reformed throughout the amazonian up to the present ancient outcroppings of the mff edged with jagged yardangs became a mold for embaying hesperian aged lavas the erosion of the mff left solidified lava casts in the embaying lava unit this lava edge morphology permits the identification of ancient contacts between the mff and hesperian aged lava terrain additionally the flanking fan of the hesperian aged apollinaris patera volcano embays the formation at its foot indicating that parts of the mff were formed in the hesperian erosion has erased and inverted many of the superposed craters in the region showing that very young amazonian ages derived from impact crater size frequency distributions are resurfacing ages and not emplacement ages we find abundant evidence that the formation is extremely mobile and continuously reworked we conclude that a significant part of the mff may have originally been emplaced in the hesperian these observations place new constraints on the mode of origin of the mff

outgassed water on mars constraints from melt inclusions in snc meteorites the snc shergottite nakhlite chassignite meteorites thought to be igneous rocks from mars contain melt inclusions trapped at depth in early formed crystals determination of the pre eruptive water contents of snc parental magmas from calculations of the solidification histories of these amphibole bearing inclusions indicates that martian magmas commonly contained 1 4 percent water by weight when combined with an estimate of the volume of igneous materials on mars this information suggests that the total amount of water outgassed since 3 9 billion years ago corresponds to global depths on the order of 200 meters this value is significantly higher than previous geochemical estimates but lower than estimates based on erosion by floods these results imply a wetter mars interior than has been previously thought and support suggestions of significant outgassing before formation of a stable crust or heterogeneous accretion of a veneer of cometary matter

concentration of h si cl k fe and th in the low and mid latitude regions of mars 1 we report maps of the concentrations of h si cl k fe and th as determined by the gamma ray spectrometer grs on board the 2001 mars odyssey mission for 45 latitudes the procedures by which the spectra are processed to yield quantitative concentrations are described in detail the concentrations of elements determined over the locations of the various mars landers generally agree well with the lander values except for fe although the mean of the grs fe data agrees well with that of martian meteorites the water equivalent concentration of hydrogen by mass varies from about 1 5 to 7 5 by mass with the most enriched areas being near apollinaris patera and arabia terra cl shows a distribution similar to h over the surface except that the cl content over medusae fossae is much greater than elsewhere the map of fe shows enrichment in the northern lowlands versus the southern highlands silicon shows only very modest variation over the surface with mass fractions ranging from 19 to 22 over most of the planet though a significant depletion in si is noted in a region west of tharsis montes and olympus mons where the si content is as low as 18 k and th show a very similar pattern with depletions associated with young volcanic deposits and enrichments associated with the tes surface type 2 material it is noted that there appears to be no evidence of significant globally distributed thick dust deposits of uniform composition

late quaternary paleotemperatures derived from a speleothem from cango caves cape province south africa abstract an oxygen isotope temperature record over a large part of the past 30 000 yr has been obtained for the southern cape province of south africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region results show that temperatures during the last glacial maximum were on average about 6 c lower than those today with peaks up to 7 c lower a detailed analysis of the past 5000 yr suggests multiple fluctuations with generally lower temperatures 1 2 c around 4500 and 3000 yr b p the carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late pleistocene and today and also during the second half of the holocene

late quaternary vegetation dynamics and hydro climate in the drakensberg south africa abstract a multi proxy study of a sediment sequence from braamhoek wetland covering the last c 16 000 years reveals a record of regional climate and vegetation dynamics in the drakensberg region south africa including signals from both the organic sediment fraction fossil pollen charcoal n alkane abundance n alkane 13c toc and the inorganic fraction mineral magnetic properties the reconstruction supported by a robust chronology indicates two major periods of increased regional wetness during the late pleistocene to early holocene phase c 13 800 12 600 cal yr bp c 10 200 8500 cal yr bp and one during the late holocene c 2000 cal yr bp to present drier conditions are recorded during the younger dryas c 12 600 11 300 cal yr bp and mid holocene c 7000 2000 cal yr bp a major decline in fynbos vegetation during the early holocene suggests a shift towards warmer temperatures and possibly towards less pronounced winter rains in eastern south africa from c 8500 cal yr bp comparison with records from interior of south africa show relatively high inter site variability however the braamhoek moisture proxies do co vary with the speleothem isotope records from makapansgat suggesting a similar hydro climate evolution in eastern and interior parts of the summer rainfall region during the studied period on multi millennial time scales an inverse hydro climatological pattern is evident between these two south african records and reconstructions from tropical locations in southeast africa such a rainfall dipole between eastern tropical and southern africa has previously been identified on shorter time scales i e on inter annual to millennial scales the braamhoek study suggests that a similar dipole pattern is acting also on a multi millennial perspective these long term precipitation anomalies are tentatively coupled to teleconnections from multi millennial changes in the dynamics of the indian ocean dipole iod and el nino southern oscillation enso

holocene climatic variability indicated by a multi proxy record from southern africa s highest wetland the eastern lesotho highlands experience climate patterns distinct from those of surrounding lower altitude regions representing a niche environment with a unique biodiversity leading to well adapted but restricted vegetation this study explores changes in the holocene composition of diatoms and pollen at southern africa s highest altitude wetland mafadi 3390 m a s l the palaeoenvironmental record for mafadi wetland indicates fluctuations between cold wet conditions prevalent between 8140 and 7580 cal yr bp and between 5500 and 1100 cal yr bp and warmer drier periods between 7520 and 6680 cal yr bp and between 6160 and 5700 cal yr bp marked climatic variability is noted from 1100 cal yr bp with colder conditions at 150 kyr bp notably the first of these cold periods occurs soon after the northern hemisphere 8 2 kyr event while a second period of notably cold conditions occurs around 1100 cal yr bp variability exists between the moisture reconstructions presented in this study and those from adjacent lower altitude sites which is hypothesised to reflect variations in the strength and extent of the westerlies throughout the holocene

topography of the shield volcano olympus mons on mars olympus mons one of the largest known shield volcanoes in the solar system covers an area of 3 2 105 km2and has a diameter of 600 km excluding its vast aureole deposits the structure is five times larger than the largest shield volcano on the earth it is situated on the north west flank of the tharsis volcanic region a broad topographic rise on the martian surface the volcano has three physical subdivisions the summit caldera the terraced upper flanks and the lower flanks which terminate in a scarp 2 10 km high that nearly surrounds the structure a large block of images of the tharsis region including olympus mons was obtained by the viking mission1 here we present a topographic map of olympus mons compiled using various combinations of stereo pairs of these images together with stereoscopic perspective views generated by image processing techniques

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

searching for evidence of hydrothermal activity at apollinaris mons mars a multidisciplinary approach involving various remote sensing instruments is used to investigate apollinaris mons a prominent volcano on mars as well as the surrounding plains for signs of prolonged hydrologic and volcanic and possibly hydrothermal activity the main findings include 1 evidence from laser altimetry indicating the large thickness 1 5 2 km at some locations of the fan deposits draping the southern flank contrary to previous estimates coupled with possible layering which point to a significant emplacement phase at apollinaris mons 2 corroboration of robinson et al robinson m s mouginis mark p j zimbelman j r wu s s c ablin k k howington kraus a e 1993 icarus 104 301 323 hypothesis regarding the formation of incised valleys on the western flanks by density current erosion which would indicate magma water interaction or alternatively volatile rich magmas early in the volcano s history 3 mounds of diverse geometric shapes many of which display summit depressions and occur among faults and fractures possibly marking venting 4 strong indicators on the flanks of the volcano for lahar events and possibly a caldera lake 5 ubiquitous presence of impact craters displaying fluidized ejecta in both shield forming flank and caldera materials and materials that surround the volcano that are indicative of water rich target materials at the time of impact 6 long term complex association in time among shield forming materials and medusae fossae formation the findings point to a site of extensive volcanic and hydrologic activity with possibly a period of magma water interaction and hydrothermal activity finally we propose that the mound structures around apollinaris should be prime targets for further in situ exploration and search for possible exobiological signatures

topography of martian central volcanoes abstract new topographic maps of six large central volcanoes on mars are presented and discussed these features are olympus mons elysium mons albor tholus ceraunius tholus uranius tholus and uranius patera olympus mons has the general form of a terrestrial basaltic shield constructed almost entirely from lava flows but with 20 to 23 km of relief it is far larger flank slopes average about 4 a nominal density calculated from the shield volume and the local free air gravity anomaly is so high that anomalously dense lithosphere probably underlies the shield uranius patera is a similar feature of much lower present relief about 2 km but its lower flanks have been buried by later lava flood deposits elysium mons has about 13 km of local relief and average slopes of 4 4 not significantly steeper than those of olympus mons its upper flank slopes are significantly steeper than those of olympus mons we suggest elysium mons is a shield volcano modified and steepened by a terminal phase of mixed volcanic activity alternatively the volcano may be a composite cone albor tholus is a partially buried 3 km tall shield like construct ceranius and uranius tholus are steeper cone like features with relief of about 6 and 2 km respectively slopes are within the normal range for terrestrial basaltic shields however and topographic and morphologic data indicate burial of lower flanks by plains forming lavas these cones may be lava shield constructs modified by a terminal stage of explosive activity which created striking radial patterns of flank channels differences among these six volcanoes in flank slopes and surface morphology may be primarily consequences of different terminal phases of volcanic activity which added little to the volume of any construct and burial of shallow lower flanks by later geologic events additional topographic data for olympus mons arsia mons and hadriaca patera are described the digital techniques used to extract topographiv data from viking orbiter stereo images are also described

shallow radar sharad sounding observations of the medusae fossae formation mars the sharad shallow radar sounding radar on the mars reconnaissance orbiter detects subsurface reflections in the eastern and western parts of the medusae fossae formation mff the radar waves penetrate up to 580 m of the mff and detect clear subsurface interfaces in two locations west mff between 150 and 155 e and east mff between 209 and 213 e analysis of sharad radargrams suggests that the real part of the permittivity is 3 0 which falls within the range of permittivity values inferred from marsis data for thicker parts of the mff the sharad data cannot uniquely determine the composition of the mff material but the low permittivity implies that the upper few hundred meters of the mff material has a high porosity one possibility is that the mff is comprised of low density welded or interlocked pyroclastic deposits that are capable of sustaining the steep sided yardangs and ridges seen in imagery the sharad surface echo power across the mff is low relative to typical martian plains and completely disappears in parts of the east mff that correspond to the radar dark stealth region these areas are extremely rough at centimeter to meter scales and the lack of echo power is most likely due to a combination of surface roughness and a low near surface permittivity that reduces the echo strength from any locally flat regions there is also no radar evidence for internal layering in any of the sharad data for the mff despite the fact that tens of meters scale layering is apparent in infrared and visible wavelength images of nearby areas these interfaces may not be detected in sharad data if their permittivity contrasts are low or if the layers are discontinuous the lack of closely spaced internal radar reflectors suggests that the mff is not an equatorial analog to the current martian polar deposits which show clear evidence of multiple internal layers in sharad data

a 16 ma record of paleodiet using carbon and oxygen isotopes in fossil teeth from pakistan abstract the siwalik sequence of northern pakistan contains a 16 ma record of paleosol carbonate and fossil teeth from which a record of paleovegetation can potentially be reconstructed and compared the carbon isotopic composition of paleosol carbonate and organic matter from siwalik strata reflects a major paleoecological change on the floodplains of major rivers beginning7 3 ma ago by 6 ma c 3 dominated plant communities probably composed of mostly trees and shrubs were displaced by nearly continuous c 4 grassland we find that the carbon isotopic ratios in herbivore tooth enamel reflect this dramatic ecologic shift carbonate in enamel older than 7 ma averages 11 in 13 c pdb consistent with a largely c 3 diet enamel from the plio pieistocene averages 1 9 in 13 c similar to the value displayed by modern c 4 grazers analysis of post burial carbonate cements and the concordance with isotopic evidence from paleosols argues strongly against major isotopic alteration of the enamel while coexisting bone may have been altered early in burial this study confirms that enamel apatite is useful for paleodietary reconstruction much further back in the geologic record than was previously thought

transitional morphology in west deuteronilus mensae mars implications for modification of the lowland upland boundary abstract west deuteronilus mensae which lies along the lowland upland boundary of mars at 45 latitude 345 longitude exhibits both gradational l a rossbacher 1985 in models in geomorphology woldenberg ed pp 343 372 allen unwin boston and fretted terrain r p sharp 1973 j geophys res 78 4073 4083 boundary types to the west the boundary is gradational and to the east it is defined by fretted terrain the two types of boundaries do not merge with one another within the west deuteronilus mensae region however the gradational boundary materials appear to overlap the fretted terrain by about 500 km contacts between units associated with the gradational boundary and the fretted terrain boundary can both be recognized in the region of overlap the fretted terrain can be identified as much as 300 km north of the gradational boundary in this region lowland units associated with the gradational boundary embay canyons of the fretted terrain in a topographically conformal fashion changes in the fretted terrain across the gradational boundary from uplands to lowlands include a reduction of canyon wall slopes and depths such that the fretted terrain north of the gradational boundary appears mantled but not obscured there are at least two major classes of processes which might explain the lateral overlap 1 erosion of stratified upland terrain and 2 deposition of plains materials onto the sloping upland margin and fretted terrain erosion of stratified upland terrain does not adequately explain the plainward decrease in crater densities across the gradational boundary nor is it consistent with evidence that lowland plains material appears to onlap the sloping upland margin in several places of the possible plains emplacement mechanisms eolian deposition would not produce the sharp apparently topographically conformal gradational unit contacts volcanics plains emplacement would not preserve the complex geometry of the underlying fretted terrain sediment deposition in either a liquid or ice covered sea could produce the draped appearance of the fretted terrain outflow channels along the lowland upland boundary particularly those of the circum chryse and west elysium regions may have flooded the northern lowlands to depths of tens to hundreds of meters the gradational unit contacts may represent the shorelines of such a sea the scale of characteristic morphologies along these contacts may require an unfrozen condition of sufficient duration to allow lacustrine style wave erosion and redistribution of material along the contacts our limited understanding of the martian paleoclimate and h 2 o inventories allows the possibility of clement periods in the past and other geological evidence e g small valley networks and outflow channels strongly suggests an extensive role of liquid water

volcanism on mars more than 15 years of planetary exploration of mars have given insight into the geologic processes that have shaped its surface the newly acquired viking data have shown that volcanism is one of the most important geologic processes operating on mars throughout its history in situ chemical analyses of martian soil by the viking lander spacecraft indicate mafic to ultramafic source rocks this is consistent both with available remote sensing data which indicate the presence of mafic minerals such as pyroxene and olivine and with petrologic modeling based on available geophysical data which suggest that martian lavas are probably iron rich and ultramafic these data strongly suggest that basaltic volcanism is widespread on mars and much of the photogeological data may be studied in this context photogeological analysis of the martian surface has shown two main types of volcanic morphologies the first type is central volcanoes which are volcanic landforms developed by continued and prolonged eruption from a point source vent this category includes 1 shields the classic low profile volcanic mountains of which olympus mons is the most spectacular example 2 domes steep sided constructs such as tharsis tholus that may represent lower rates of eruption than the shields or possibly more silicic lava compositions 3 highland patera radially textured low profile volcanoes that occur in the cratered terrain and are interpreted as ash shields 4 alba patera an apparently unique volcanic landform consisting of a vast volcanic center over 1500 km across with flank slopes of less than a tenth of a degree and 5 various small features such as cinder cones the second major category is volcanic plains which are units recognized by several criteria of which the presence of mare ridges and flow lobes are the most useful volcanic plains are subdivided into four main groups 1 simple flows broad smooth to rolling plains that contain numerous mare type ridges but no flow lobes interpreted as being composed of thick single cooling units 2 complex flows displaying multiple overlapping flow lobes interpreted to be indicative of thin multiple cooling units 3 undifierentiated flows plains that typically lack any morphologic identifying feature but are considered to be volcanic partly on the basis of their association with large volcanic centers and 4 questionable plains volcanic units heavily modified by other processes erosion tectonism etc so that their origins are uncertain when these categories of volcanic morphologies are combined with relative age data provided by crater statistics a volcanic history for mars can be derived as follows early heavy bombardment of mars was accompanied and followed by small scale fluvial channeling extensive flood volcanism the plateau plains and ash shield volcanism in the cratered terrain shortly after this time less extensive flood volcanism continued to resurface the planet during formation of the northern southern hemisphere dichotomy central volcanism became more prominent with the development of the alba patera center as well as the older shields and domes of the northern hemisphere early tharsis and elysium regions the development of the tharsis and elysium uplifts may have triggered the release of large scale catastrophic floods producing large channels continued uplift and lithospheric thinning concentrated volcanic activity in the tharsis region producing large shield volcanoes and extensive lava plains both central vent and plains volcanism have been active throughout martian history but the volumes of extrusion have gradually decreased with time this is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time gradually turning off the volcanism although many questions remain regarding martian volcanism the viking data have provided a remarkable detailed overview of the probable nature of the volcanic history of mars

mars radar mapping strong backscatter from the elysium basin and outflow channel abstract radar reflectivity maps of mars obtained at arecibo in 1990 using a modified delay doppler technique have revealed strong depolarized echoes coming from the elysium flood basin and outflow channel as well as from elysium mons this result is consistent with recent studies which show that much of the basin channel floor is covered with lava flows

isotopic analysis of equid teeth from wonderwerk cave northern cape province south africa abstract stable carbon and nitrogen isotope ratios have been determined from equid teeth from a well dated sequence of holocene deposits at wonderwerk cave situated in a summer rainfall area of the northern cape province of south africa stable carbon isotope ratios confirm the existence of a c 4 grassland habitat throughout the holocene nitrogen isotope ratios are assessed in relation to data from modern equid samples from southern africa temporal variability in both carbon and nitrogen isotope ratios of holocene equid samples from wonderwerk appears to be analogous to spatial variability of such ratios determined for faunal samples from modern environments relationships between isotope ratios and data from modern environments are used to obtain rainfall indices

a late quaternary pollen record from the transvaal bushveld south africa pollen spectra from cores of organic spring deposits from the transvaal provide evidence for the climatic evolution of the province during the last 35 000 yr b p or more the past climatic phases are derived from palynological reconstructions of past vegetation types by comparison of fossil pollen data with modern surface pollen spectra from various localities evidence is provided for an early moist cool phase with relatively mesic bushveld and expanded montane forest in the central transvaal followed by a drier period with drier bushveld which probably lasted until approximately 25 000 yr b p during the next phase which at the latest ended about 11 000 yr b p the temperatures were probably 5 6 c cooler than at present at that time bushveld vegetation in the central transvaal was replaced by open grassland with macchia elements climatic amelioration came and semiarid savanna returned to the plains at first gradually and then developing into a warm kalahari thornveld type vegetation after 6000 yr b p it apparently became slightly wetter and a more broad leafed bushveld developed about 4000 yr b p it again became cooler and slightly wetter and the bushveld vegetation on the central and northern plains was comparable to present open upland types after 2000 yr b p conditions gradually became warner until about 1000 yr b p when the modern climate of the central transvaal bushveld originated

transport reversals at taiwan strait during october and november 1999 1 the observed transport reversals at taiwan strait during october and november 1999 are examined by analytic solutions a numerical ocean model and the prediction from a real time north pacific ocean data assimilating model wind stress explains a majority of the transport reversals the reversals are forced by a combination of the local wind and the remote wind in the yellow and east china seas the connection between the yellow and east china seas wind stress and transport reversals at taiwan strait is provided by coastally trapped waves the waves are generated by the northerly winter wind bursts in the yellow sea and are enhanced in the east china sea by alongshore northerly wind

magnitude of a catastrophic flood event at kasei valles mars kasei valles compose an enormous outflow channel system on mars the upper part of the channel system is typically less than 1 km deep and descends from echus chasma about 1 km over a distance of 1000 km it then splits into north and south channels on the basis of a stereomodel of viking images we have measured the geometry of a steep constricted reach of the north channel that drops 900 m in only 100 km a late stage flood is hypothesized to have scoured the channel if we assume that channel striations indicate water levels then the flood had a minimum cross sectional area of 3 12 x 10 7 m 2 the putative flood had a width of 83 km an average depth of 374 m and maximum depth of 1280 m these channel measurements suggest that flood velocities ranged from 32 to 75 m s 1 and that discharge was greater than 1 km 3 s 1 values larger than those calculated for any other flood event on mars or earth the flood maintained supercritical flow and caused intense erosion in this area scouring a 350 m deep megapothole the source of the flood water may have been a temporary lake in echus chasma a deep canyon formed in association with tectonism at valles marineris

dissolved gas paleotemperatures and 18o variations derived from groundwater near uitenhage south africa abstract under the near ideal hydrologic conditions provided by the uitenhage artesian aquifer reliable estimates of paleotemperatures were obtained by measurement of the dissolved n2 and ar in groundwater confidently dated in the range 28 000 yr b p to the present using 14c the mean annual air temperature in this area during the last glaciation is calculated to have been on average 5 1 2 c lower than during the holocene the change in the 18 o 16 o ratio of the groundwater corrected for changes in ocean water amounted to 0 4 per c

soil carbon isotope evidence for holocene habitat change in the kenya rift valley in eastern africa the altitude of the boundary between montane forest and lowland savanna grassland changed substantially in response to climate change during the later holocene but this is not clearly reflected in regional pollen records the carbon 13 to carbon 12 ratios of tropical grasses are higher than those of most other plants and this difference is preserved in soil organic carbon stable isotope ratios soil organic matter 13 c 12 c ratios in profiles along an altitude transect in the central rift valley of kenya suggest that the forest savanna boundary advanced more than 300 meters in altitude this could have implications for understanding the effects of climate change on the configuration of floral zones prehistoric hunter gatherer land use patterns and the timing of the advent of neolithic food production

a multi proxy analysis of late quaternary palaeoenvironments sekhokong range eastern lesotho the eastern lesotho highlands host an array of periglacial and glacial geomorphic features their analysis has provided past climate interpretations predominantly for cold periods yet no multi proxy temporally continuous palaeoenvironmental records exist this study presents a palaeoenvironmental reconstruction based on sedimentary characteristics fossil pollen and diatoms from an alpine wetland located in the sekhokong mountain range the record commences in the late pleistocene with a wet period from 16 450 to 14 440 cal a bp interrupted by dry conditions from 16 350 to 15 870 cal a bp from 14 150 to 8560 cal a bp drier conditions are inferred slowly transitioning to warmer wetter conditions warmer dry conditions are inferred for 8560 7430 cal a bp followed by cold wet conditions from 7280 to 6560 cal a bp a dry warmer period occurs from 6560 to 3640 cal a bp indicated by pollen diatom and sedimentary records followed by cool wet conditions from 3400 to 1200 cal a bp the period from 1110 cal a bp to the present is characterized by progressive drying pronounced cold events are detected from the diatom record moisture records appear relatively specific to the topographic setting of sekhokong near the great escarpment edge probably driven by orographically constrained synoptic controls

3d structure of the gusev crater region abstract gusev crater lies within the aeolis quadrangle of mars at the boundary between the northern lowlands and southern highlands the ancient valley ma adim vallis dissects the highlands south of gusev crater and is thought to have fed the crater with sediments high resolution stereo camera data and digital elevation models were used to construct a geologic geomorphic map 173 5 178 5 e 10 18 s and cross sections complemented by data from mars orbiter camera mars orbiter laser altimeter and thermal emission imaging system three geologic domains are recognised the highlands in the south gusev crater and lowlands in the north twelve units are mapped with thicknesses ranging from hundred meters to several kilometres thicknesses of units and their bedding attitude are estimated combining the geologic map and topographic information relative ages are determined from crater counts ranging from early noachian for highland units to middle amazonian for units in gusev crater and in lowlands episodes of intense geologic activity deposition volcanism deformation occur at around 4 0 ga 3 7 ga and 3 5 ga comparing the geometry of the gusev crater with similar sized filled and un filled martian craters suggests that the columbia hills are relics of the original central peak of gusev crater

the dispersal of pyroclasts from ancient explosive volcanoes on mars implications for the friable layered deposits a number of voluminous fine grained friable deposits have been mapped on mars the modes of origin for these deposits are debated the feasibility for an origin by volcanic airfall for the friable deposits is tested using a global circulation model to simulate the dispersal of pyroclasts from candidate source volcanoes near each deposit it is concluded that the medusae fossae formation and electris deposits are easily formed through volcanic processes and that the hellas deposits and south polar pitted deposits could have some contribution from volcanic sources in specific atmospheric regimes the arabia and argyre deposits are not well replicated by modeled pyroclast dispersal suggesting that these deposits were most likely emplaced by other means

alteration of enamel carbonate environments during fossilization an understanding of enamel diagenesis is necessary to ensure sound isotopic palaeodietary and palaeoenvironmental reconstructions although carbon isotope signals of browsing and grazing herbivores remain distinct in enamel even after millions of years subtle alteration of isotopic signatures does occur to better understand this change we analysed modern and fossil enamel from a number of south african sites using fourier transform infra red spectroscopy our results indicate that while there is little evidence of increased crystallinity in fossil enamel there is a small but significant change in the proportion of carbonate ions occupying hydroxyl and phosphate sites this seems to occur early in the process of fossilization after which there is no noticeable change it is also important to note that the degree of alteration varies significantly within and between sites we suggest that this change results from one or some combination of three mechanisms exogenous carbonate incorporation endogenous carbonate loss and endogenous carbonate reorganization determining which mechanism s contribute to this alteration is important because all three are likely to affect biogenic carbon isotope ratios differently ftir spectroscopy promises to increase our knowledge of diagenesis and in so doing should improve our palaeodietary and palaeoenvironmental reconstructions

palaeoenvironmental conditions in south africa at the pleistocene holocene transition abstract palaeoenvironmental records which include the interval between 11 000 and 10 000 bp have been investigated for 15 sites in south africa less than half of them are well dated and have a resolution adequate for elucidating climatic conditions during the time of the younger dryas a sea surface temperature record from a marine mollusc sequence provides the only unequivocal evidence of cooling during this time none of the palynological sequences from the interior of the subcontinent suggest consistent deviations in temperature or moisture attributable to a younger dryas equivalent based on the available evidence therefore it seems that if global younger dryas conditions influenced the climate of south africa the effect was too small to register a spatially consistent pattern in the pollen sequences of the interior of the country

thermophysical properties of the mer and beagle ii landing site regions on mars 1 we analyzed remote sensing observations of the isidis basin gusev crater and meridiani planum landing sites for beagle ii mer a spirit and mer b opportunity spacecraft respectively we emphasized the thermophysical properties using daytime and nighttime radiance measurements from the mars global surveyor mgs thermal emission spectrometer and mars odyssey thermal emission imaging system themis and thermal inertias derived from nighttime data sets themis visible images mgs mars orbiter camera moc narrow angle images and mgs mars orbiter laser altimeter mola data are incorporated as well additionally the remote sensing data were compared with ground truth at the mer sites the isidis basin surface layer has been shaped by aeolian processes and erosion by slope winds coming off of the southern highlands and funneling through notches between massifs in the gusev region surface materials of contrasting thermophysical properties have been interpreted as rocks or bedrock duricrust and dust deposits these are consistent with a complex geological history dominated by volcanic and aeolian processes at meridiani planum the many layers having different thermophysical and erosional properties suggest periodic deposition of differing sedimentological facies possibly related to clast size grain orientation and packing or mineralogy

chronology eruption duration and atmospheric contribution of the martian volcano apollinaris patera geologic mapping thermal inertia measurements and an analysis of the color visual wavelengths of the martian volcano apollinaris patera indicate the existence of two different surface materials comprising an early easily eroded edifice and a more recent competent fan on the southern flank a chronology of six major events that is consistent with the present morphology of the volcano has been identified we propose that large scale explosive activity occurred during the formation of the main edifice and that the distinctive fan on the southern flank appears to have been formed by lavas of low eruptive rate similar to those that form compound pahoehoe flow fields on earth a basal escarpment typically 500 m in relief and morphologically similar to the one surrounding olympus mons was produced between the formation of the main edifice and the fan indicating multistage eruptions over a protracted period of time contact relations between the volcanic units and the adjacent chaotic material indicate that formation of the chaotic material occurred over an extended period of time and may be related to the volcanic activity that formed apollinaris patera stereophotogrammetric measurements permit the volume of the volcano to be estimated at 105 km3 from this volume measurement and an inferred eruption rate 1 5 10 2 km3 yr 1 we estimate the total eruption duration for the main edifice to be 107 yrs plausible estimates of the exsolved volatile content of the parent magma imply that greater than 1015 kg of water vapor was released into the atmosphere as a consequence of this activity this large amount of water vapor as well as other exsolved gases must have had a significant impact on local and possibly global climatic conditions

holocene pollen from swamp cave and hyrax dung deposits at blydefontein kikvorsberge karoo south africa abstract pollen analysis of material from a variety of sediment types including those from ponds streams a rock shelter and hyrax dung accumulations in the blydefontein basin 31 09 s 25 05 e fig 1b provide a record of vegetation change in the eastern karoo over the last 10 000 years the pollen composition fluctuated as a result of different taphonomic processes inherent in the various sampled deposits results further demonstrate that long term vegetation changes alternated between karoo shrub and grassland plant communities karoo shrubs suggesting relatively dry conditions were generally prominent in the early holocene until ca 5400 yr bp when more grassy vegetation began to flourish presumably in response to increased summer rain conditions pollen representation of the early holocene is not detailed enough to trace millennial scale variations during this period but more detailed middle to late holocene data show millennial or shorter scale shifts between grassland and drier karroid veld

geologic context of the mars radar stealth region in southwestern tharsis stealth is a region on mars that has no distinguishable radar return stealth was discovered in 1988 by muhleman et al 1991 in 3 5 cm earth based radar images and it was found to extend 2000 km along the martian equator west of arsia and pavonis montes stealth was proposed to be a deposit of unconsolidated granular material with a minimum thickness of several meters with the most likely explanation being that stealth is a volcanic tephra deposit muhleman et al 1991 1995 stealth overlies some of the youngest geologic units on mars including lava flows and a giant curvilinear ridged lobate unit on the west flank of arsia mons stealth also overlies part of a region of smooth and wind scoured materials called the medusae fossae formation examination of high resolution viking orbiter images suggests that stealth is the youngest of several discontinuous wind worked mantles of fine grained 1 cm sediment older deposits of fine sediment appear to be interbedded with lava flows and show evidence of aeolian deposition dunes and deposits in the lee of topographic obstacles and erosion yardangs and pedestal craters the geologic context supports a volcanic ash origin for stealth if stealth is composed of tephra then its extent and the nature of landforms in the region indicate that it resulted from multiple eruptions that occurred relatively late in martian history possible source vents include linear depressions flanked by constructive volcanic landforms that are located on the lower western slopes of arsia and pavonis montes

vegetation and seasonality shifts during the late quaternary deduced from 13c 12c ratios of grazers at equus cave south africa abstract season of rainfall can be a major influence on the relative proportions of c3 and c4 grasses in a landscape since their relative distribution is essentially constrained by temperatures during the growing season cool growing seasons favor c3 grasses whereas warm ones favor c4 grasses 13c 12c ratios in tooth enamel carbonate of grazers from the site of equus cave northern cape province south africa were used to determine vegetation and rainfall seasonality shifts during the late quaternary the results show shifts in the relative proportion of c3 and c4 grasses during the latter stages of the pleistocene and domination by c4 grasses in the holocene the data show that the northwestern cape did not fall within a winter rainfall zone during this period as has been postulated in recent climate models instead a more complex situation is suggested in which at least two periods of enhanced winter rainfall occurred within a predominantly summer rainfall regime

abrupt early to mid holocene climatic transition registered at the equator and the poles paleoclimatic records from equatorial east africa antarctica and greenland reveal that atmospheric circulation changed abruptly at the early to mid holocene transition to full postglacial conditions a climatic reorganization occurred at all three sites between 8200 and 7800 years ago that lasted 200 years or less and appears to have been related to abrupt transitions in both marine and terrestrial records around the world

a 3000 year high resolution stalagmitebased record of palaeoclimate for northeastern south africa high resolution stable isotope variations and growth structure analyses of the last three millennia of a 6600 year stalagmite record at cold air cave makapansgat valley south africa are presented growth layers which are measurable over the last 250 years are shown to be annual the correlation between the width of growth layers and precipitation is strongly positive changes in 18o and 13c are positively correlated and inversely correlated to changes in the colour of the growth layers in the stalagmite variations in colour are directly correlated with mean annual temperature dark colouration is the product of increased temperature and mobilization of organic matter from the soil and is associated with wetter summers and enhanced growth of c4 grasses darker colouring and enriched 18o and 13c reflect a warmer wetter environment whereas lighter colouring and depleted isotopic values are indicative of cooler drier conditions the dominant episode in the 3000 year record is the cool dry 500 year

the 8k event cause and consequences of a major holocene abrupt climate change abstract a prominent abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern hemisphere regions especially in wintertime in response to a very large outburst flood that freshened the north atlantic changes were much larger than typical climate variability before and after the event with anomalies up to many degrees contributing to major displacement of vegetative patterns this 8k event provides a clear case of cause and effect in the paleoclimatic realm and so offers an excellent opportunity for model testing the response to north atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following north atlantic freshening and so greatly strengthens the case that those older events also reflect north atlantic changes the north atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming caused ice melt and hydrologic cycle intensification at high latitudes lead to major changes in north atlantic circulation few model experiments have directly addressed the 8k event and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies so much work remains to be done

theoretical modeling of eruption plumes on mars under current and past climates we have used a combined conduit transport eruption column model to explore the evolution of volcanic eruption plumes on mars under different atmospheric conditions in the calculations we consider a volatile phase composed of h2o co2 and so2 and take into account that the magmatic water erupted at the vent may condense as the eruption column rises into the martian atmosphere as two end member models we explore the eruption of rhyolitic and basaltic melt compositions containing different amounts of volatiles as well as having different eruption temperatures under current martian atmospheric conditions eruption plumes are found to rise as high as 100 km for a mass eruption rate of 5 107 kg s 1 which is consistent with model calculations by wilson and head 1994 in contrast under a dense atmosphere 105 pa on the martian surface which may have existed earlier in martian history the same eruption plume reaches only about 25 km height all magmatic water released during the eruption is found to freeze as it rises in the eruption column which means that fallout from the plume will contain water ice which can be subsequently deposited in near surface layers this ice may then suddenly melt due to higher surface heat flow or shallow intrusions leading to rapid release of water on the flanks of volcanoes only if the atmosphere were hotter in the past could the water in the eruption plume condense and produce rain rather than ice furthermore the calculations show that smaller micron size particles would be distributed globally from eruption plumes under current martian conditions but would not have been as widely dispersed from plumes erupted into an earlier dense atmosphere

ignimbrite as a substrate for endolithic life in the hyper arid atacama desert implications for the search for life on mars the hyper arid core of the atacama desert in chile is considered the driest and most life limited place on earth with few habitats capable of sustaining an active microbial ecosystem as such it is one of the best terrestrial analogues of the extreme arid conditions on mars and an ideal environment to explore survival and biological adaptation strategies as the environment becomes increasingly dry here we show that weakly welded rhyolitic ignimbrites in this desert are abundantly colonized by endolithic cyanobacteria and associated heterotrophic bacteria we propose that the porous ignimbrite interior provides protection from damaging uv radiation and excessive levels of visible light rock porosity also favors cell hydration through water retention after scarce rainfall events even when the surrounding environment remains stubbornly dry this is the first known example of an endolithic microbial community colonizing ignimbrite rocks in an extremely dry environment the existence of a habitat capable of supporting abundant phototrophic and heterotrophic communities in an environment that precludes most life forms suggests that if similar deposits are found on mars these should be considered important targets in the search for life indeed ignimbrite rocks have been tentatively identified in gale crater the landing site of the mars science laboratory msl mission and could be directly analyzed by its rover curiosity

the geomorphology of planetary calderas abstract satellite derived observations of the geomorphology of calderas on earth mars and venus can be used to learn more about shield volcanoes examples of terrestrial basaltic volcanoes from the galapagos islands hawaii and the comoro islands show how these volcanoes contrast with examples found on mars and venus caldera structure degree of infilling and the location of vents on the flanks are used to interpret each volcano s recent history the geometry of the caldera floor can be used to infer some of the characteristics of the magma storage system and the orientation of the deep magma conduits the formation of benches within the caldera and the effects of the caldera on the distribution of flank eruptions are considered and it is evident that most calderas on the planets are were dynamic features presently deep calderas with evidence of overflowing lavas and ponded lavas high in the caldera wall show that these calderas were once shallow similarly shallow calderas filled with ponded lavas are evidence that they were once deeper it is probably a mistake therefore to place great significance on caldera depth with regard to the position shape or size of subsurface plumbing

aeolian dunes as evidence for explosive volcanism in the tharsis region of mars two transverse dune fields occur among late amazonian volcanic and aeolian landforms in southwestern tharsis mars the first is located 70 km northwest of biblis patera around 5 n 125 w the second is located about 500 km northwest of arsia mons at 2 s 130 w the latter is the largest dune field thus far documented to occur in the equatorial latitudes of mars unlike other dunes on the planet both dune fields in tharsis have low thermal inertias 2 7 10 3cal cm 2sec 0 5k 1 and high albedos 0 26 that are indistinct from their surrounding terrain both dune fields have superposed features such as impact craters lava flows smooth surfaced units and bright wind streaks the dune fields therefore appear to be inactive and mantled by fine grained material i e particles 60 m to form aeolian dunes require a supply of sand on earth most dune sands are supplied by fluvial and littoral processes but this is not the case in tharsis on mars because they are superposed on a late amazonian surface the climate is assumed to have been hyper arid throughout the time that the dunes have existed under these conditions the only plausible source for quantities of sediment sufficient to form transverse dune fields is explosive volcanism therefore the two dune fields in tharsis are evidence that explosive volcanism has occurred in this region in the late amazonian epoch

stable isotope evidence of late mis 3 to middle holocene palaeoenvironments from sehonghong rockshelter eastern lesotho evidence for human occupation of southern africa s high altitude maloti drakensberg mountains is surprisingly common in the last glacial yet the attraction of this relatively severe cold region for hunter foragers remains unclear sehonghong rockshelter 1870 m asl in the eastern lesotho highlands provides evidence for human occupation spanning marine isotope stage 3 through the late holocene excellent organic preservation provides opportunities for establishing multiple palaeoenvironmental proxy records to address this conundrum in high altitude zones the proportions of c3 and c4 plants archived in soil organic matter and faunal enamel provide sensitive indicators of past temperature shifts we first extended the radiocarbon chronology to ca 35 ka using abox sc radiocarbon dates of charcoals next we analysed stable isotopes in soil organic matter from the sedimentary sequence and in faunal tooth enamel from the newly dated lower strata the results suggest predictably that c3 vegetation and low temperatures prevailed until early warming at ca 15 ka with a series of sharp shifts thereafter low values for 13c and 18o in faunal enamel ca 33 ka suggest a negative temperature excursion at this time and potentially greater precipitation as snowfall in the highlands compared with lower altitudes

color and albedo of the south polar layered deposits on mars five color albedo units including polar frost have been recognized and mapped in the southern layered deposits on mars atmospheric dust scattering was measured in shadows and modeled in order to remove the component of brightness in mars images due to the atmosphere and quantify the albedo and color of the surface the layered deposits appear to be mantled by red dust except where eolian stripping has exposed the underlying bedrock frost and bare ground are mixed below the resolution of the images in many areas adjacent to the polar cap some of which appear to be younger than the surrounding layered terrain dark material has been deposited in topographic depressions in much of the south polar region including the layered deposits the available observational data suggest that the layered deposits are composed of bright dust ice and a small amount of dark material if the dark material is sand a periodic change in polar winds seems required in order to transport the sand poleward into the layered terrain in any case the observations are not consistent with the layered deposits being composed only of bright dust and ice the mars observer camera and infrared instruments should be particularly useful in this investigation

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

martian north polar hazes and surface ice results from the viking survey completion mission viking infrared observations of the martian north polar regions taken during the 1979 1980 viking survey completion mission have been used to determine the location and nature of the retreating polar cap edge and of an accompanying atmospheric ice haze the haze is composed of water ice and its visible opacity is approximately unity equivalent to 1 2 precipitable microns of water ice during the polar cap retreat aerocentric longitude ls 340 60 the haze is nearly always present and extends from at most a few degrees south of the polar cap edge to an undetermined distance over the cap interior the transition from ice free ground to a predominantly ice covered surface at the cap edge spans 5 10 of latitude the ability of the viking infrared observations to distinguish haze from surface condensate yields a more accurate seasonal regression for the polar cap than can be determined from visual images generally the infrared observations presented here yield a regression similar to those determined from earth based and or spacecraft visual data for the same and for previous northern springs however there are differences concerning details of the cap retreat the thermal data indicate that the martian seasonal polar cap did extend south of 60 n during this particular late winter and that the midspring resumption of the cap retreat occurs at ls 50

winter transport and sea level fluctuations in hecate strait british columbia observed winter transport and adjusted sea level fluctuations in hecate strait were investigated using empirical orthogonal function and coherence analyses the responses to large scale and local wind forcings were identified by the distinctive spatial patterns of their adjusted sea level responses at the resolved periods of 2 to 48 days the large scale and the local wind forcings were of roughly equal importance in driving transport fluctuations comparison of observations with a conceptual model indicates that the adjusted sea level in the northeast corner of the strait gives a good measure of response to both the local and large scale wind forcings this provides a physical explanation for the observed high correlation between the adjusted sea level at prince rupert and the winter transport fluctuations in hecate strait we also show that the transport fluctuations are associated with a particular spatial pattern of the velocity field which represents roughly 1 4 of the energy in the observed winter velocity fluctuations measured at an array of current meters this has implications for the use of surrogate transport series to hindcast oceanographic conditions in hecate strait

analysis of polygonal cracking patterns in chloride bearing terrains on mars indicators of ancient playa settings the ancient southern highlands on mars 3 5 gyr old contain 600 regions that display spectral evidence in the infrared for the presence of chloride bearing materials many of these locations were previously reported to display polygonal cracking patterns we studied more than 80 of the chloride bearing terrains using high resolution 0 25 0 5 m pixel images as well as near infrared spectral data to characterize the surface textures and the associated cracking patterns and mineralogies our study indicates that 75 of the studied locations display polygonal cracks that resemble desiccation cracks while some resemble salt expansion thrust polygons furthermore we detect spectrally the presence of smectites in association with 30 of the studied fractured terrains we note that smectites are a special class of swelling clay minerals that can induce formation of large desiccation cracks as such we suggest that the cracking patterns are indicative of the presence of smectite phyllosilicates even in the absence of spectral confirmation our results suggest that many chloride bearing terrains have a lacustrine origin and a geologic setting similar to playas on earth such locations would have contained ephemeral lakes that may have undergone repeated cycles of desiccation and recharging by a near surface fluctuating water table in order to account for the salt phyllosilicates associations these results have notable implications for the ancient hydrology of mars we propose that the morphologies and sizes of the polygonal cracks can be used as paleoenvironmental as well as lithological indicators that could be helpful in planning future missions

rift zone volcanism and associated cinder cone field in utopia planitia mars 1 we analyzed a small cone field in sw utopia planitia that shows striking similarities to volcanic rift zones on earth this is of particular interest as the study area lies off any of the volcanic centers of mars in the northern hemisphere lowlands and is surrounded by material of the amazonian aged vastitas borealis formation vbf we believe that the study area could be the first direct evidence for volcanic activity in utopia planitia prior to the resurfacing by vbf material the most striking characteristics that we observed are 1 a set of broad eruptive fissures showing signs of ongoing extension during cone formation 2 parallel dike swarms 3 magmatic intrusions and 4 a number of lava flows that have erupted from the fissures and pitted cones that surround a larger cone in the center of the study area and that are often associated with or aligned along the fissures and dikes cratering model ages indicate that the study area is of late noachian to early hesperian age and is thus distinctly older than the surrounding vbf falling into the time frame of the main phases of activity in the volcanic centers of syrtis major elysium planitia and the southern highlands

explosive volcanic eruptions on mars tephra and accretionary lapilli formation dispersal and recognition in the geologic record explosive volcanic eruptions potentially involving large amounts of magmatic and entrained water are thought to have been very important in the noachian and hesperian periods earlier in mars history and basaltic plinian eruptions are likely to have occurred throughout martian history previous treatments of explosive volcanic plumes on mars have simply extrapolated plume models for the earth s atmosphere to mars taking account of known limitations to the applicability of this approach which suggest that convective plumes may be capable of reaching only 20 km height on mars we introduce the concept of inertial plumes capable of carrying clasts to much greater heights and dropping them into the lower atmosphere over a wide area atmospheric circulation patterns guarantee wide dispersal and thick deposits of tephra resulting from both types of eruption the presence of large amounts of water in convecting explosive eruption plumes can also lead to condensation of water on small particles and the consequent accretion of other particles as the smaller particles fall through the plume producing accretionary lapilli formation of accretionary lapilli significantly alters the spatial distribution and grain sizes of pyroclastic fall deposits from those involving discrete juvenile clasts with negligible clast interactions we model the eruption and dispersal of tephra and the formation of accretionary lapilli on mars under current atmospheric conditions and explore the consequences of this for the geometry and grain size of deposits formed from explosive eruption plumes we show that explosive eruptions can produce thick widespread deposits of ash and lapilli similar to those thought to have produced mantling deposits in several regions of mars we develop a detailed example that shows that local hydrovolcanic explosive eruptions and solely magmatic eruptions originating from the nearby apollinaris patera could have emplaced tephra and accretionary lapilli in the columbia hills region of the mars exploration rover gusev site if the atmospheric pressure was higher early in mars history than now eruptions would have led to somewhat more extensive pyroclast dispersal than under current conditions

a volcanic interpretation of gusev crater surface materials from thermophysical spectral and morphological evidence 1 gusev crater the mars exploration rover spirit landing site 160 km diameter 14 5 s 184 5 w has been identified in previous studies as a prime site of geological and exobiological interest on the basis of its potential for having hosted a fluviolacustrine environment such environment may have been favorable for the development of biological activity the origin and nature of the materials present at the surface of gusev crater are still being debated in previous studies based on geomorphological and thermophysical data surface materials in the crater have been interpreted as originating from fluviolacustrine volcanic or aeolian processes or combinations thereof we present results from the analysis of newly compiled thermophysical thermal emission spectrometer tes and thermal emission imaging system themis spectroscopic tes and visible themis and mars observer camera data for the gusev region these data were analyzed using a new mosaicking technique developed to match the values of contiguous scenes and to produce seamless mosaics apt for geological interpretation thermophysical spectroscopic and morphological evidence point to the presence of local outcrops of lava flows of basaltic composition materials consistent with a regolith developed from basaltic materials fine grained deposits of basaltic composition strongly modified by wind erosion and wind deposits according to these findings we conclude that most of the materials occupying the present surface of gusev have characteristics consistent with those of volcanic and aeolian deposits fluviolacustrine deposits proposed by other authors may exist under the volcanic materials and may be exposed in impact craters

mars stratigraphy and gravimetry of olympus mons and its aureole olympus mons and its surroundings have been investigated using impact crater statistics crater retention ages of all major geological units show that their emplacement occurred during three time intervals the underlying fractured plains are part of the northern plains in general n 1 4 10 3 km 2 this time is followed by the time interval represented by crater retention ages n 1 8 10 4 to 3 10 3 km 2 some lava flows in the fractured plains the smooth plains and the aureole materials were emplaced during this time the aureole probably developed by some sort of collapse of the outer parts of an ancient volcano proto olympus mons underlying the present shield its remnants may show in the scarp and small parts of the shield not covered by younger lava flows the third interval covers crater retention ages n 1 5 10 5 to 3 10 4 km 2 this volcanic activity followed a period of dormancy a series of lava flows forming caldera and present shield surface and flooding a depression around the shield are distinguishable the regional stratigraphy is discussed as part of the global geological history the question of the genesis of the aureole material is addressed by gravity models the topographic mass of olympus mons contributes about 80 to the aureole gravity high northwest of the mountain the gravity high of the entire aureole can be explained by a density model consisting of the topographic masses of olympus mons and the aureole materials it does not require additional high density materials underneath the aureole thus aureole materials of an allochthonous origin by collapse are in agreement with the gravity data however the gravity data do not preclude an autochthonous and volcanic origin of the aureole materials in the latter case possible subsurface intrusions should have no density contrasts with the surroundings

evolution of the olympus mons caldera mars synoptic images of the martian volcano olympus mons are of a quality and quantity that are unique for mars and somewhat surprisingly are appreciably better than image data that exist for many volcanoes on earth useful information about the evolution of shield volcanoes on earth can thus be derived from the investigation of this extraterrestrial example we have used shadow length measurements and photoclinometrically derived profiles to supplement and refine the topographic map of the olympus mons caldera as much as 2 5 km of collapse took place within the 80 65 km diameter caldera and the elevation of the caldera rim varies by almost 2 0 km low around the oldest collapse events high around the youngest an eight stage evolutionary sequence for the caldera of olympus mons is identified which shows that caldera subsidence was a longterm process rather than the near instantaneous event that has been interpreted from comparable terrestrial examples tectonic features on the caldera floor indicate a transition from an extensional environment graben formation around the perimeter of the caldera to compression ridge formation towards the caldera center this transition from a compressional to extensional environment is surprisingly sudden occurs at a radial distance of 17 km from the caldera center and is import because it can be used to infer that the magma chamber was relatively shallow thought to be at a depth of 16 km beneath the caldera floor zuber and mouginis mark 1990 ample evidence is also found within the olympus mons caldera for solidified lava lakes more than 30 km in width and for the localzed overturning and or withdrawal of lava within these lakes

a regional 8200 cal yr bp cooling event in northwest europe induced by final stages of the laurentide ice sheet deglaciation the most notable change in 18o in greenland ice cores during the holocene occurs at 8200 cal yr bp here we present a new high resolution marine record from the northern north sea along with tree ring data from germany which contain evidence of a pronounced temperature drop 2 c contemporaneous with that of the greenland ice core records the synchronous timing of the cooling event in the greenland ice cores marine record and tree ring data from northwest europe reflects a regional influence on the north atlantic ocean atmospheric system suggesting a prominent role of the north atlantic thermohaline circulation the operation of the north atlantic ocean circulation is sensitive to variation in the freshwater budget implying that any change in freshwater flux is capable of altering the north atlantic circulation system we hypothesise minor but long term freshwater fluxes in the final stages of the deglaciation of the laurentide ice sheet as a forcing mechanism 1998 john wiley sons ltd

ice rich terrain in gusev crater mars abstract the morphology of materials on the floor of gusev crater 14 s 175 w mars imply a history of volcanism and subsequent removal of an ice rich deposit fluid lava flows observed in the western portion of gusev crater paradoxically terminate in a steep thick 60 m flow front adjacent to hummocky terrain the hummocky terrain is morphologically similar to deglaciated terrain on earth generated when glacial debris are left behind after the glacier has retreated we propose the following scenario for the floor of gusev crater first ice rich material was deposited adjacent to thira crater second fluid lavas were emplaced and ponded against the ice rich deposits at some later time the ice within the deposit sublimated leaving hummocky terrain current age estimates for the gusev flows are hesperian suggesting that the ice removal occurred in the upper hesperian or more recently if this hypothesis is correct quench features glassy rinds columnar jointing should be observed at the lava flow margin the hummocky deposit should be poorly sorted angular debris

examining the sediments and soils of gusev crater with the athena science payload 1 gusev crater has been proposed to contain lacustrine and or fluvial sediments however eolian or volcanic sediments global dust and locally produced soils may also be present this work describes the use of the athena instrument package to evaluate the environment in which sampled materials were deposited in gusev crater sedimentary or soil deposits can be sampled by examining materials that were 1 excavated by impact events 2 revealed by wind deflation or 3 exposed by spinning the rover wheels specific observations can be diagnostic of a depositional environment for instance pancam images of thin e g 5 cm planar layers of phyllosilicates and or evaporites as determined by mini tes would suggest lacustrine sediments layered sediments e g trough cross bed with rounded particles 4 mm would suggest fluvial activity eolian sediments may have planar or cross planar layers of well sorted grains 200 m parallel bed deposits consisting of glass observable by microscopic imager would indicate volcanic ash soil bulk chemistry reported by alpha particle x ray spectrometer that is similar to the viking and mars pathfinder soils would indicate global dust mini tes should only detect primary mineralogies in physically weathered soils whereas chemically weathered soils may contain carbonates sulfates and or phyllosilicates although some characteristics are unique to a sediment or soil deposit different deposit types can have similar characteristics e g planar layering determining the depositional history of material in gusev will require the integration of measurements from several instruments and careful geologic reasoning by the investigators

the long lava flows of elysium planita mars viking orbiter images are used to study the distribution and morphology of 59 lava flows in the elysium planitia region of mars average widths for these flows range from 3 to 16 km and many of the flows exceed 100 km in length the aspect ratio flow length to average width is highly variable 40 1 to 294 km from the summit of elysium mons an unusual attribute of five flows is their segmented nature with up to 13 individual segments on a single flow which each have a surface area from 25 to 250 km2 photoclinometry is used to derive an average thickness of 40 60 m for these flows indicating that individual flow volumes range from 17 7 to 68 1 km3 plausible values for the effusion rate 101 104 m3 s 1 suggest that individual eruptions could have lasted for a few months to several decades and could have injected between 1 36 and 2 04 1012 kg of water vapor into the atmosphere assuming a 1 wt water content for the parental magma a total volume for all 59 flows is estimated to be 817 1226 km3 which would have released 2 04 3 01 1013 kg of water vapor into the atmosphere or 0 2 of the amount previously calculated plescia 1993 as the amount released from the cerberus flows in se elysium planitia

stable carbon isotopic evidence for climate change across the late pleistocene to early holocene from lesotho southern africa although significant environmental and climatic changes are likely to have occurred across the pleistocene holocene transition in southern africa records are sparse with information regarding temperature change especially rare we thus know little about the conditions facing later stone age human populations at this time particularly those in the highland interior where temperature shifts would have had strong impacts on floral and faunal distributions in lesotho a well defined altitudinal distribution of c3 and c4 photosynthetic plant taxa and their remains in soil organic matter provides a means of estimating past temperature shifts we applied this principle to stratified sediments from two archaeological sequences in the lesotho lowlands c 1600 m a s l to produce a palaeotemperature record focusing on the period 14 000 9500 cal a bp the results show an overall trend from exclusively c3 vegetation at the last glacial maximum towards greater contributions of c4 taxa and thus warmer conditions during the holocene however large temperature fluctuations are evident within this trend with rapid changes of up to 4 c visible between 11 200 and 9500 cal a bp the continued presence of hunter gatherers during this time suggests that the region must have remained attractive to human populations despite significant climatic instability and cool episodes copyright 2013 john wiley sons ltd

extraterrestrial lava lakes abstract active lava lakes are rare on earth with only ten documented examples all formed by lavas of basaltic composition and housed inside summit craters or calderas the existence of lava lakes on other planetary bodies may imply similarities in either composition or volcano tectonic settings and so has important implications for understanding the link between melt production and volcanism we review lava lakes on earth and other planets particularly active caldera like features interpreted to be currently containing active lava lakes on jupiter s moon io and features interpreted as remnants of lava lakes on venus and mars mercury and the moon do not boast the major calderas or shield volcanoes of their larger rocky neighbors partly due to a horizontally compressive tectonic regime arising from global contraction that makes it difficult to move melts through the upper crust we discuss the evidence for active lava lakes on io and show how modeling based on terrestrial lava lakes can reveal how these phenomena differ on both bodies the superficial similarities do not necessarily imply that the plumbing is similar observations of the largest lava lake on io loki patera provide insight into the nature of ionian lava lakes in general which may be more similar to eruptive episodes on the east pacific rise on earth which lead to temporary lava lakes although temporal data for io s lava lake activity are scarce studies of temporal variability of lava lakes on earth are useful for providing ground truth for comparisons future studies of earth by remote sensing and field observations and of io by both ground based observations and future missions are needed to answer many questions including why lava lakes rare on earth appear to be common on io

origin and evolution of valleys on martian volcanoes morphological analyses of six martian volcanoes ceraunius tholus hecates tholus alba patera hadriaca patera apollinaris patera and tyrrhena patera indicate that fluvial processes were the dominant influence in the initiation and subsequent development of many dissecting valleys lava processes and possibly volcanic density flows were also important as valley forming processes fluvial valleys are especially well developed on alba patera ceraunius tholus and hecates tholus these valleys are inset into the surrounding landscape they formed in regions of subdued lava flow morphology contain tributaries and tend to widen slightly in the downstream direction lava channels on alba patera are located on the crest of lava flows and have a discontinuous irregular surface morphology and distributary patterns these channels sometimes narrow toward their termini possible volcanic density flow channels are located on the northern flank of ceraunius tholus valleys dissecting apollinaris patera hadriaca patera and tyrrhena patera appear to have a complex evolution probably a mixed fluvial and lava origin they are inset into a subdued possibly mantled surface lack tributaries and either have fairly constant widths or widen slightly downvalley valleys surrounding the caldera of apollinaris appear to have formed by fluvial and possibly by volcanic density flow processes while those on the apollinaris fan structure may have a mixed lava and fluvial origin valleys on tyrrhena have broad flat floors and theater heads which have been extensively enlarged probably by sapping hadriaca valleys have a trough shaped form like those on the fan structure on apollinaris but are more enlarged and have theater heads fluvial valleys on the martian volcanoes generally followed a two stage evolutionary sequence similar to that of the hawaiian volcano valleys including 1 initial formation by surface runoff and 2 subsequent enlargement by groundwater sapping because basalt is highly permeable valleys on hawaii island formed only in regions where lava flows were mantled by less permeable volcanic ash similarly fluvial valleys on the martian volcanoes particularly those on alba patera formed in regions where lava flow morphology is subdued probably by ash mantling thus the presence or absence of this mantling may explain why fluvial valleys are present on some martian volcanoes but not on others of the same age the formation of fluvial or fluvial modified valleys on the older volcanoes ceraunius hecates tyrrhena apollinaris and hadriaca implies that surface and near surface water activity was widespread during late noachian to early hesperian period of heavy bombardment however the presence of anomalously young fluvial valleys on alba patera indicates that fluvial valley activity did not entirely cease near the end of late heavy bombardment but rather persisted in isolated regions until mid to late amazonian

reconstruction of environmental and climate changes at braamhoek wetland eastern escarpment south africa during the last 16 000 years with emphasis on the pleistocene holocene transition abstract a paleo environmental record covering the last 16 ka 16 000 cal yrs bp from the eastern areas of the summer rainfall region in south africa is presented this area is until now sparsely investigated due to the lack of well preserved natural archives for this study we used a peat section from a wetland situated close to the drakensberg escarpment where the high annual rainfall amounts supported a continuous peat accumulation since c 16 ka one peat core was analysed in terms of fossil pollen composition carbon and nitrogen content isotope composition 13c 15n and microscopic charcoal concentration the greatest degree of temporal resolution was achieved from the late pleistocene and early holocene section where proxy records indicate relatively dry conditions between ca 16 13 7 ka 12 8 10 5 ka 9 5 8 2 ka and wet conditions between c 13 7 12 8 ka and 10 5 9 5 ka a weak moisture signal is also evident at c 8 2 7 5 ka the late pleistocene to early holocene period was relatively cool while conditions became generally warmer after 11 8 ka the interpretation of the mid and late holocene sequence is limited due to a slow accumulation and low sample resolution but the available data suggest relatively dry conditions until c 1 5 ka followed by more humid conditions until c 0 5 ka we suggest that the millennial scale variability within the record can be attributed to shifts in the circulation systems dominating the region i e the latitudinal movements of the inter tropical convergence zone itcz and the dynamics of the mid latitude low pressure belts

volcanic geology of hadriaca patera and the eastern hellas region of mars hadriaca patera is a low relief volcano in the southern highlands of mars northeast of the hellas basin layered friable deposits composing the extensive channeled flanks of the volcano surround a well defined summit caldera containing late stage eruptive products the morphologic characteristics of the channels suggest erosion by groundwater sapping and surface runoff the erosional morphology of the volcano the lack of lava flow features and the friable nature of the flank materials indicate that hadriaca patera consists predominantly of pyroclastic deposits gravity driven flow models demonstrate that the distribution of flank materials can be attributed to the emplacement of pyroclastic flows both magmatic and hydromagmatic eruption models are viable for the magmatic case the necessary mass eruption rates 107 108 kg s ejection velocities 400 m s and volatile contents 1 5 3 0 wt h2o are consistent with parameters derived for terrestrial plinian eruptions for the hydromagmatic case the required energy conversion efficiencies are comparable to those of laboratory experiments and the inferred permeability of the martian crust allows large amounts of groundwater to be transported rapidly at flow rates of 103 104 m3 s into the region models of cooling during emplacement indicate that welding of pyroclastic flows can occur at large distances hundreds of kilometers from a source vent on mars the layering within hadriaca patera could be attributed to welding of pyroclastic flows that would control its susceptibility to erosion morphologic similarities between hadriaca and tyrrhena paterae suggest a similar volcanic history with an early pyroclastic dominated shield building phase followed by effusive eruptions at their summit calderas and on the flank of tyrrhena patera the formation of the extensive ridged plains of hesperia planum following the formation of the highland paterae supports the interpretation of a transition from explosive to effusive volcanism in the eastern hellas region a progressive depletion of volatiles on mars is consistent with the morphologic properties of highland paterae and other central vent volcanoes a predominance of hydrovolcanic eruptions in the development of hadriaca and tyrrhena paterae would imply that the transition in volcanic eruption style can be attributed to a volatile depletion of the crust whereas magmatic eruptions at the paterae would be indicative of temporal changes in martian magmas

exploring gusev crater with spirit review of science objectives and testable hypotheses 1 gusev crater was selected as the landing site for the mars exploration rover mer spirit mission located at the outlet of ma adim vallis and 250 km south of the volcano apollinaris patera gusev is an outstanding site to achieve the goals of the mer mission the crater could have collected sediments from a variety of sources during its 3 9 ga history including fluvial lacustrine volcanic glacial impact regional and local aeolian and global air falls it is a unique site to investigate the past history of water on mars climate and geological changes and the potential habitability of the planet which are central science objectives of the mer mission because of its complex history and potential diversity gusev will allow the testing of a large spectrum of hypotheses with the complete suite of mer instruments evidence consistent with long lived lake episodes exist in the landing ellipse area they might offer a unique opportunity to study for the first time martian aqueous sediments and minerals formed in situ in their geological context we review the geological history and diversity of the landing site the science hypotheses that can be tested during the mer mission and the relevance of gusev to the mer mission objectives and payload

explosive volcanism on hecates tholus mars investigation of eruption conditions evidence is presented supporting the identification of a discrete well preserved air fall deposit generated by explosive volcanism on mars the deposit is located immediately to the west of the summit caldera of hecates tholus 32on 209ow the northernmost of the three volcanic constructs in the elysium planitia region the absence of superposed impact craters larger than the resolution limit of the viking images 40 m per pixel indicates a very young age for this eruption which evidently postdates even the most recent collapse episode of the olympus mons caldera 300 m y b p neukum and hiller 1981 from the distribution of craters smaller than 2 km in diameter it appears that the air fall material mantles an area about 50 x 75 km in extent to an estimated thickness of about 100 m by adapting numerical models for terrestrial volcanic eruptions to the martian environment these dimensions imply an eruption cloud height of about 70 km in order to attain such an altitude the mass eruption rate must have been 107 kg s and the volatile content either 1 wt for h20 or 2 wt for co2 although it is not possible to distinguish between silicic and basaltic volcanism on hecates were the volatile species co2 the depth of most recent storage prior to eruption of the magma would have to be 50 100 km due to the solubility of co2 in the melt if h20 were the driving volatile a minimum depth of storage would be 0 2 4 km thereby permitting the possibility of ground water assimilation by the magma

reexamining the relationship between apollinaris patera and the basalts of the gusev crater plains mars 1 a possible source of the gusev crater basalts analyzed by the spirit rover is apollinaris patera we test this hypothesis by identifying and analyzing potential lava flow paths using thermal emission imaging system mars orbiter camera high resolution imaging science experiment and mars orbiter laser altimeter data sets together with published geologic mapping image interpretation reveals three possible flow paths from apollinaris onto gusev crater floor via a breach in gusev s northwest rim an unnamed crater that must have postdated any potential flow along the paths currently blocks the breach after correcting for the unnamed crater topographic profiles constructed along possible flow paths demonstrate that elevation along each path increases from 80 to 430 m for two of the pathways this elevation change indicates that lavas could not have traversed through them the third profile though is less conclusive as the topography may reflect a broad flexural arch however on the basis of two of the topographic profiles together with the lack of obvious lava flow structures that indicate flow south through the breach we propose that apollinaris was not the direct source of the gusev basalts instead we argue that it seems more likely that the gusev basalts were sourced from below the crater itself the similar ages as derived from crater counts of apollinaris s south flank and the gusev plains lavas however suggest that the two volcanic regions may be part of a common magmatic feature

late stage intrusive activity at olympus mons mars summit inflation and giant dike formation by mapping the distribution of 351 lava flows at the summit area of olympus mons volcano on mars and correlating these flows with the current topography from the mars orbiter laser altimeter mola we have identified numerous flows which appear to have moved uphill this disparity is most clearly seen to the south of the caldera rim where the elevation increases by 200 m along the apparent path of the flow additional present day topographic anomalies have been identified including the tilting down towards the north of the floors of apollo and hermes paterae within the caldera and an elevation difference of 400 m between the northern and southern portions of the floor of zeus patera we conclude that inflation of the southern flank after the eruption of the youngest lava flows is the most plausible explanation which implies that intrusive activity at olympus mons continued towards the present beyond the age of the youngest paterae 200 300 myr neukum et al 2004 robbins et al 2011 we propose that intrusion of lateral dikes to radial distances 2 000 km is linked to the formation of the individual paterae at olympus mons two specific dikes to the se of the volcano are inferred to have volumes of 4 400 km3 and 6 100 km3 greater than the volumes of individual calderas and implying triggering of both caldera collapse and lateral dike injection by the arrival of large inputs of magma from the mantle a comparable disparity between lava flow direction and current topography together with a tilted part of the caldera floor has been identified at ascraeus mons

holocene palaeoenvironments inferred from a sedimentary sequence in the tsoaing river basin western lesotho abstract the paper presents a sedimentological palynological and phytolith record from a 13 m deep holocene sedimentary sequence located in the tsoaing river valley southwestern lesotho six conventional radiocarbon and two ams dates provide a relatively high resolution holocene record for the sedimentary sequence ranging from ca 12 000 to 4000 years bp pollen is absent in the upper section but present in the lower 2 m confirming terminal pleistocene holocene conditions reported in previous published pollen and charcoal records from the region the absence of pollen in the upper layers of ca 9000 years bp and younger suggests that conditions over southwestern lesotho throughout much of the holocene was typified by a seasonal climate that prevented long term preservation of plant remains although other plant material like robust spores microscopic charcoal and phytoliths withstood oxidation sedimentological and phytolith results suggest that the period from ca 8600 to 8450 years bp experienced rapid environmental change towards drier conditions phases of chemical disintegration with organic input including local swamp phytoliths are suggested at ca 7000 years bp and again after 4500 years bp

a spatially continuous magnetization model for mars 1 using a three component magnetic field data set at over 100 000 satellite points previously compiled for spherical harmonic analysis we have produced a continuously varying magnetization model for mars the magnetized layer was assumed to be 40 km thick an average value based on previous studies of the topography and gravity field the severe nonuniqueness in magnetization modeling is addressed by seeking the model with minimum root mean square rms magnetization for a given fit to the data with the trade off between rms magnetization and fit controlled by a damping parameter our preferred model has magnetization amplitudes up to 20 a m it is expressed as a linear combination of the green s functions relating each observation to magnetization at the point of interest within the crust leading to a linear system of equations of dimension the number of data points although this is impractically large for direct solution most of the matrix elements relating data to model parameters are negligibly small we therefore apply methods applicable to sparse systems allowing us to preserve the resolution of the original data set thus we produce more detailed models than any previously published although they share many similarities we find that tectonism in the valles marineris region has a magnetic signature and we show that volcanism south of the dichotomy boundary has both a magnetic and gravity signature the method can also be used to downward continue magnetic data and a comparison with other leveling techniques at mars surface is favorable

rootless cones on mars a consequence of lava ground ice interaction fields of small cratered cones on mars are interpreted to have formed by rootless eruptions due to explosive interaction of lava with ground ice contained within the regolith beneath the flow melting and vaporization of the ice and subsequent explosive expansion of the vapour act to excavate the lava and construct a rootless cone around the explosion site similar features are found in iceland where flowing lava encountered water saturated substrates the martian cones have basal diameters of c 30 1000 m and are located predominantly in the northern volcanic plains high resolution mars orbiter camera images offer significant improvements over viking data for interpretation of cone origins a new model of the dynamics of cone formation indicates that very modest amounts of water ice are required to initiate and sustain the explosive interactions that produced the observed features this is consistent with the likely low availability of water ice in the martian regolith the scarcity of impact craters on many of the host lava flows indicates very young ages suggesting that ground ice was present as recently as less than 10 l00 ma and may persist today rootless cones therefore act as a spatial and temporal probe of the distribution of ground ice on mars which is of key significance in understanding the evolution of the martian climate the location of water in liquid or solid form is of great importance to future robotic and human exploration strategies and to the search for extraterrestrial life

most mars minerals in a nutshell various alteration phases formed in a single environment in noctis labyrinthus 1 a closed depression in the noctis labyrinthus region of mars at 10 4 s 98 6 w believed to have formed in the late hesperian holds an inner pit partially filled with several hundred meters of stratified material compact reconnaissance imaging spectrometer for mars crism visible near infrared reflectance data reveal signatures of numerous hydrated minerals including halloysite kaolinite fe smectite si oh bearing phases and fe sulfates polyhydrated monohydrated and hydroxylated types including jarosite we use crism data high resolution imagery hirise and hrsc high resolution stereo camera derived elevation to analyze the morphology composition and stratigraphy of these materials we propose an alteration sequence including formation of acid sulfate solutions from groundwater and magmatic sulfur which then locally altered the basaltic bedrock and layered sediments mainly deposited from volcanic tephra forming fe smectite and fe sulfates the mineral variability can mostly be explained by local variations in the ph of the altering fluids with original acidity being buffered by dissolution of primary minerals and by variable fluid input and evaporation and or freezing rates resulting in various water rock ratios this site shows local formation of almost all classes of minerals identified thus far on mars without invoking global conditions processes related to local volcanic activity and associated hydrothermalism were able to produce during an era in which the climate is believed to have been cold a large variety of hydrated minerals this study highlights the importance of the geological setting of hydrated minerals in the understanding of mars geologic and climatic evolution

mars observer camera the mars observer camera moc is a three component system one narrow angle and two wide angle cameras designed to take high spatial resolution pictures of the surface of mars and to obtain lower spatial resolution synoptic coverage of the planet s surface and atmosphere the cameras are based on the push broom technique that is they do not take frames but rather build pictures one line at a time as the spacecraft moves around the planet in its orbit moc is primarily a telescope for taking extremely high resolution pictures of selected locations on mars using the narrow angle camera areas ranging from 2 8 km 2 8 km to 2 8 km 25 2 km depending on available internal digital buffer memory can be photographed at about 1 4 m pixel additionally lower resolution pictures to a lowest resolution of about 11 m pixel can be acquired by pixel averaging these images can be much longer ranging up to 2 8 500 km at 11 m pixel high resolution data will be used to study sediments and sedimentary processes polar processes and deposits volcanism and other geologic geomorphic processes the moc wide angle cameras are capable of viewing mars from horizon to horizon and are designed for low resolution global and intermediate resolution regional studies low resolution observations can be made every orbit so that in a single 24 hour period a complete global picture of the planet can be assembled at a resolution of at least 7 5 km pixel regional areas covering hundreds of kilometers on a side may be photographed at a resolution of better than 250 m pixel at the nadir such images will be particularly useful in studying time variable features such as lee clouds the polar cap edge and wind streaks as well as acquiring stereoscopic coverage of areas of geological interest the limb can be imaged at a vertical and along track resolution of better than 1 5 km different color filters within the two wide angle cameras permit color images of the surface and atmosphere to be made to distinguish between clouds and the ground and between clouds of different composition

snc meteorites clues to martian petrologic evolution the shergottites nakhlites and chassigny snc meteorites are apparently cumulate mafic and ultramafic rocks that crystallized at shallow levels in the crust of their parent body the mineralogy and chemistry of these meteorites are remarkably like equivalent terrestrial rocks although their ratios of fe fe mg and certain incompatible elements and their oxygen isotopic compositions are distinctive all have crystallization ages of 1 3 b y or younger and formed from magmas produced by partial melting of previously fractionated source regions isotope systematics suggest that the snc parent body had a complex and protracted thermal history spanning most of geologic time some meteorites have been severely shock metamorphosed and all were ejected from their parent body at relatively recent times possibly in several impact events late crystallization ages complex petrogenesis and possible evidence for a large gravitational field suggest that these meteorites are derived from a large planet trapped gases in shergottite shock melts have compositions similar to the composition measured in the martian atmosphere ejection of martian meteorites may have been accomplished by acceleration of near surface spalls or other mechanisms not fully understood if snc meteorites are of martian origin they provide important information on planetary composition and evolution the bulk composition and redox state of the martian mantle as constrained by shergottite phase equilibria must be more earthlike than most current models planetary thermal models should benefit from data on the abundances of radioactive heat sources the melting behavior of the mantle and the timing of planetary differentiation calculated depletion of chalcophile elements in source regions indicates a core dominated by sulfides and paleomagnetic measurements suggest the presence of a weak magnetic field within the last several hundred thousand years concentrations of volatile elements indicate that the snc parent body was not volatile depleted and trapped atmospheric components measured in shock melts may be useful in understanding planetary degassing by providing comparisons for spectral reflectance data and viking soil analyses these meteorites may also constrain surface mineralogy and weathering mechanisms