paleolakes and impact basins in southern arabia terra including meridiani planum implications for the formation of hematite deposits on mars 1 the hematite deposit in meridiani planum was selected for a mars exploration rover mer landing site because water could be involved in the formation of hematite and water is a key ingredient in the search for life our discovery of a chain of paleolake basins and channels along the southern margin of the hematite deposits in meridiani planum with the presence of the strongest hematite signature adjacent to a paleolake basin supports the possible role of water in the formation of the hematite and the deposition of other layered materials in the region the hematite may have formed by direct precipitation from lake water as coatings precipitated from groundwater or by oxidation of preexisting iron oxide minerals the paleolake basins were fed by an extensive channel system originating from an area larger than texas and located south of the schiaparelli impact basin on the basis of stratigraphic relationships the formation of channels in the region occurred over much of mars history from before the layered materials in meridiani planum were deposited until recently the location of the paleolake basins and channels is connected with the impact cratering history of the region the earliest structure identified in this study is an ancient circular multiringed basin 800 1600 km diameter that underlies the entire meridiani planum region the mer landing site is located on the buried northern rim of a later 150 km diameter crater this crater is partially filled with layered deposits that contained a paleolake in its southern portion

desiccation mechanism for formation of giant polygons on earth and intermediate sized polygons on mars results from a pre fracture model we present a pre fracture incrementally non linear elastic hydric model to constrain the models of formation of giant spacing of 20 300 m desiccation cracks on earth and possibly intermediate sized 80 to 350 m polygonal networks of cracks located in many impact craters on mars which have been interpreted to form by desiccation as opposed to thermal contraction el maarry et al 2010 the results of the model show that tensile stresses rise monotonically with desiccation however in soils with diffusivities below 10 4 m2 s it is not possible to generate high enough stresses to cause fracturing on the other hand intermediate values between 10 2 and 10 4 m2 s create optimum conditions for the formation of cracks at the time scales suggested for the formation of giant desiccation polygons on earth our model clearly shows that for typical diffusivity values of clayey soils with a considerable amount of smectites enough stress can build up to stimulate cracking of various spatial scales these results corroborate earlier assumptions that giant desiccation polygons on earth occur through lowering of the water table rather than surface evaporation extending the model to mars shows that soils would crack within similar diffusivity limits but in slightly longer periods of time owing to the lower gravity finally a model for formation of desiccation cracks on mars is presented that shows that two main conditions need to be fulfilled for desiccation cracks to occur under current martian climatic conditions namely that the thermal and soil diffusivity conditions 1 allow for the formation of an unsaturated zone with a considerable thickness while at the same time 2 limiting the growth of the permafrost downward which would disrupt the cracking process

boulder movement at high northern latitudes of mars 1 we examine a narrow latitudinal band 60 n 70 n on mars to place constraints on the seasonally averaged velocity q of boulder movements over patterned ground these latitudes comprise a region of the northern lowlands where patterned ground covers nearly every surface here boulders meters in diameter are consistently found to be concentrated at or near the cracks that define the polygonal networks indicating a mobilization process because impact craters are the source for many boulders we can use craters and their degradation to estimate the time scales for boulder movement we study and catalog 1018 degraded impact craters 100 m d 1 km in 55 high resolution imaging science experiment hirise images we find that crater degradation occurs on a time scale 1 ma which is too recent for melting related mechanisms in a past warmer epoch clustering of boulders occurs at a time scale of a few ma or shorter which means that boulders on 5 20 m diameter polygons move at seasonal velocities q 1 10 m yr or faster

revisiting the depositional environment of the neoproterozoic callanna group south australia abstract the callanna group was deposited around 800 million years ago ma during an interval in earth s history that saw a transition towards a more oxygenated atmosphere increasing biodiversity among eukaryotic microfossils and climatic perturbations culminating in low latitude glaciations previous researchers proposed that the callanna basin was lacustrine and highly alkaline which could provide important new insights into environmental cause effect relationships at this time to further interrogate these records we examined standard biogeochemical proxies including organic carbon and nitrogen isotopes iron speciation metal abundances and carbonate associated sulfate much of the primary information has been lost because the rocks of the callanna group have experienced extensive metamorphism up to amphibolite facies and are altered by modern weathering however relics of these proxies combined with sedimentological features preserve evidence of redox stratification within this basin furthermore our observations in particular weakly fractionated nitrogen isotopes and abundant gypsum pseudomorphs are incompatible with the interpretation of high alkalinity the high salt content and occurrences of tidal indicators are most parsimoniously explained by frequent incursions of seawater thus the callanna group cannot speak straightforwardly to environmental conditions in non marine habitats at this time lastly the absence of a large carbon isotope anomaly indicates that these rocks do not correlate with the bitter springs formation

compositional variability on the surface of 4 vesta revealed through grand measurements of high energy gamma rays measurements of the high energy gamma ray flux emanating from asteroid 4 vesta by the dawn gamma ray and neutron detector grand have revealed variability in the near surface elemental composition of the vestan surface these observations are consistent with the presence of large 8 104 km2 regions with distinct hed like elemental compositions the results agree broadly with other global measurements such as the macroscopic neutron absorption cross section and spectral reflectance derived mineralogic maps two distinct regions with eucrite like elemental compositions have been identified the first located primarily within the lucaria and marcia quadrangles and the second within oppia quadrangle the former region is collocated with some of the oldest most heavily cratered terrain on vesta the interior of the 500 km diameter rheasilvia impact basin is found to have a composition that is consistent with diogenite like material taken together these observations support the hypothesis that vesta s original crust was composed of basaltic outflows in the form of eucritic like material and that the rheasilvia basin forming impact exposed lower crustal diogenite like material these measurements also constrain the maximum amount of mesosiderite like material to 10 for each 15 15 surface element

testing polar spots of water rich permafrost on the moon lend observations onboard lro 1 results are presented for the lend instrument onboard lro for the detection of local spots of suppression and excess of epithermal neutron emission at the lunar poles twelve local neutron suppression regions nsrs and neutron excess regions ners are detected it is shown using the data from the lola and diviner instruments that six nsrs have the empirical property less local irradiation and lower temperature fewer local neutrons these nsrs may be identified with spots of water ice rich permafrost on the moon it is shown that detected nsrs are include in both permanently shadowed and illuminated areas and they are not coincident with permanently shadowed regions psrs at the bottom of polar craters as has been commonly expected before lend presented neutron data with high spatial resolution

setting and sedimentary facies of late proterozoic alkali lake playa deposits in the southern damara belt of namibia the late proterozoic damara belt of namibia has evolved from an elaborate system of continental rifts in which the basal portion nosib group of the damara sequence was deposited in the southern rift situated at the southern margin of the damara belt the nosib group is represented by coarse elastic sediments kamtsas formation and fine grained partly dolomitic deposits duruchaus formation both formations occur with interfingering relationships over nearly the total length of the rift in the geelkop dome area the pelitic dolomitic duruchaus formation includes in its upper part a sequence of sediments that are characterized by cyclical deposition high sodium contents abundant albite pseudomorphs after primary evaporite minerals and concordant solution and collapse breccias this 300 m thick sequence has been interpreted as deposits of an alkali lake or playa complex based on the playa lake models of eugster and hardie 1975 and rowlands et al 1980 four distinct facies have been distinguished in the upper part of the evaporitic duruchaus formation 1 the submergent lake facies represented by laminated shales containing layers of laminated siltstone 2 the submergent emergent mud flat facies represented by laminated siltstone and calcareous shale with layers of dolomitic mudstone calcareous shaly siltstone with scapolite and laminated sandy albitic dolomite with abundant pseudomorphs of albite after primary evaporite minerals e g shortite thermonatrite borax 3 the exposed saline crust facies characterized by solution breccias albitolite and albitolite breccias all originating from former salt crusts and 4 the elastic marginal facies represented by quartzites of fluviatile and partly aeolian origin from identified primary and diagenetic to metamorphic minerals and from the composition of several generations of fluid inclusions it is concluded that the brines of the alkali lake were of a na hco3 k b cl s type material creating the extremely alkaline environment was derived from eroded acid to basic magmatic basement rocks and from coeval alkali rich volcanism during tectogenesis the evaporite sequence was overridden by nappes approaching from the closing damara geosyncline saline crust horizons were thereby partly mobilized and the resulting mush of dolomite and crystal fragments was squeezed into the thrust planes of the nappes where they acted as lubricants which enhanced late orogenic thrusting along the southern margin of the damara belt

maps of subsurface hydrogen from the high energy neutron detector mars odyssey after 55 days of mapping by the high energy neutron detector onboard mars odyssey we found deficits of high energy neutrons in the southern highlands and northern lowlands of mars these deficits indicate that hydrogen is concentrated in the subsurface modeling suggests that water ice rich layers that are tens of centimeters in thickness provide one possible fit to the data

dielectric constant estimation of the uppermost basal unit layer in the martian boreales scopuli region abstract an electromagnetic inversion model has been applied to echoes from the subsurface sounding shallow radar sharad to retrieve the dielectric properties of the uppermost basal unit bu beneath the north polar layered deposits of mars sharad data have been carefully selected to satisfy the assumption of the inversion model which requires a stratigraphy consisting of mostly plane parallel layers the resulting values of the dielectric constant have been interpreted in terms of a variable percentage of dust in an ice dust mixture through the use of a mixing model for dielectric properties the resulting dust content exceeds 65 reaching perhaps 95 depending on the permittivity values assumed for the dust such a concentration is higher than that obtained by selvans et al selvans m m plaut j j aharonson o 2010 j geophys res 115 e09003 this discrepancy could be justified considering that our observations refer to the uppermost bu layer whereas selvans et al selvans m m plaut j j aharonson o 2010 j geophys res 115 e09003 probed the bu full thickness moreover if the bu is considered spatially inhomogeneous with very different dust content and thickness tanaka k l skinner j a fortezzo c m herkenhoff k e rodriguez j a p bourke m c kolb e j okubo c h 2008 icarus 196 318 358 the discrepancy could be furtherly reconciled

fluxes of fast and epithermal neutrons from lunar prospector evidence for water ice at the lunar poles maps of epithermal and fast neutron fluxes measured by lunar prospector were used to search for deposits enriched in hydrogen at both lunar poles depressions in epithermal fluxes were observed close to permanently shaded areas at both poles the peak depression at the north pole is 4 6 percent below the average epithermal flux intensity at lower latitudes and that at the south pole is 3 0 percent below the low latitude average no measurable depression in fast neutrons is seen at either pole these data are consistent with deposits of hydrogen in the form of water ice that are covered by as much as 40 centimeters of desiccated regolith within permanently shaded craters near both poles

major compositional units of the moon lunar prospector thermal and fast neutrons global maps of thermal and fast neutron fluxes from the moon suggest three end member compositional units a high thermal and low fast neutron flux unit correlates with the lunar highlands and is consistent with feldspathic rocks the south pole aitken basin and a strip that surrounds the nearside maria have intermediate thermal and fast neutron flux levels consistent with more mafic rocks there appears to be a smooth transition between the most mafic and feldspathic compositions which correspond to low and high surface altitudes respectively the maria show low thermal and high fast neutron fluxes consistent with basaltic rocks

chemical information content of lunar thermal and epithermal neutrons simulations of equilibrium thermal and epithermal neutron flux spectra for the moon have been studied to determine their chemical information content most of this information resides in a single parameter the ratio of macroscopic absorption to energy loss cross sections although this parameter cannot specify the chemistry of lunar soils uniquely it provides an index that can be used to quantitatively separate anorthositic from mafic chemistries hydrogen abundances can best be derived from measurements of the epithermal neutron flux which is strongly related to its macroscopic energy loss cross section the ratio of thermal to epithermal neutron flux measured by lunar prospector is shown to agree quantitatively with simulations this agreement is used to show that the highlands terrane on the farside of the moon is anorthositic containing high percentages of plagioclase and possibly a range of mg suite minerals with a high mg mg fe atomic ratio our best estimate of the abundance of feo is 2 with an upper limit of 5

stratigraphy and facies in the upper proterozoic damara orogen namibia based on a geodynamic model abstract the upper proterozoic damara orogen which forms a part of the pan african belt system contains a well developed geosynclinal sequence deposited 900 650 ma ago in the absence of sufficient biological and radiometric age data correlations of lithostratigraphic units across the orogen remain problematical this paper is an attempt to establish a unifying geodynamic model for the geosynclinal development of the damara orogen the model is based on the assumption that damaran geosynclinal history began with formation of continental rift structures the geosynclinal development started in the northern damara orogen with the formation of a continental rift 900 ma ago at the same time a rift dome or rift field existed in the southern part of the orogen the northern rift remained active for about 100 ma with three phases in increased differential subsidence during deposition of the nosib group the ugab subgroup and the chuos formation complex facies relationships including the ugab subgroup of the northern and the nosib group of the central orogen illustrate deposition in a shelf basin environment which had established itself after marine invasion of the northern rift subsequently the northern rift fell inactive and the northern to central orogen was affected by a phase of regional subsidence due to thermal relaxation of the stretched lithosphere the slowly subsiding region was covered by a carbonate platform karibib formation which eventually submerged giving way to the development of a wide basin in which the kuiseb formation was laid down the northern rift fell inactive when the rate of crustal stretching accompanied by rifting and differential subsidence significantly increased in the southern damara orogen 800 ma ago a trough khomas trough started to subside rapidly and was fed by turbidites from both the carbonate platform tinkas turbidites and the southern foreland of the orogen chausib turbidites only 20 30 ma later lithospheric stretching and thinning had proceeded far enough to allow crustal rupture and opening of a limited ocean matchless amphibolite this led to thermal relaxation of the lithosphere and to regional subsidence in the southern damara orogen the key for correlations across the orogen is the shift of the rifting activity from north to south this stage is marked by the development of the carbonate platform from whose southern edge the calcareous tinkas turbidites were transported into the subsiding khomas trough where pelites of the lower kuiseb formation were being laid down

martian north polar cap recession 2000 mars orbiter camera observations abstract the wide angle cameras of the mars orbiter camera moc on the mars global surveyor have recorded the 2000 recession of the seasonal co 2 cap in the north polar region from l s 330 to 90 in stark contrast to the asymmetric behavior of the south seasonal cap the seasonal north cap remains relatively circular and uniform until mid spring when the retreat reaches the circum polar dune field which is the one major nonuniformity in the cap the recession of cap edge latitude versus areocentric longitude l s is very well represented as a linear function until late spring there is no evidence for the plateau or standstill in the recession curve that has been observed in some prior years the lambert albedo of the seasonal frost deposits in the north polar region demonstrates the increase with insolation first observed by paige in 1985 increasing to approximately 0 57 at l s 40 the north polar cap near solstice visually appears smaller than that observed by moc at the start of mapping in 1999 but later images acquired in summer show the residual cap returning to its more usual shape the most likely explanation for these changes in albedo is precipitation and subsequent removal of dust on the cap as a result of frequent dust storms near the cap edge

geographic variations in the thermal and diffusive stability of ground ice on mars to investigate the stability of ground ice within the top several meters of the martian regolith time dependent models of the thermal and diffusive behavior of the regolith have been developed the geographic distribution of thermal inertia and albedo as well as the latitudinal variation in insolation have been included in calculations of surface and subsurface temperatures between 60 latitude ground ice was found to be stable where the annual mean surface and subsurface temperatures were below the atmospheric frost point this generally occurs poleward of the mid latitudes the latitude poleward of which ground ice is stable varies by about 20 to 30 from one longitude to another geographic variations in thermal inertia and albedo are the primary factors controlling regional variations in ice stability calculations of temperatures at high and low obliquity suggest that ground ice would be stable globally at high obliquity and would not be stable between 60 latitude at low obliquity thermally driven diffusion of atmospheric water vapor within the regolith was modeled accounting for both ordinary molecular and knudsen transport and equilibrium between ice vapor and adsorbed phases atmospheric water vapor was found to be able to supply the top few meters of the regolith with ice in regions where the annual mean surface temperature was below the atmospheric frost point ice was found to begin condensing in as short as 1000 martian years rapid accumulation of ice in the pore space of the upper layers of the regolith acted to choke transport to lower layers and slow the diffusion process even so after 105 martian years in some cases as much as 30 to 40 of the available pore space accumulated ice the total amount of subsurface ice ranged from a few to more than 25 g cm2 within the top few meters in regions of stability ground ice was found to form below a depth where the annual average vapor pressure over ice was equal to the annual average atmospheric vapor pressure near the surface atmospheric vapor was not found to accumulate as ice below a depth where the seasonal temperature oscillations gave way to the geothermal gradient the time scales for condensation of ground ice were found to be comparable to that of orbital oscillations suggesting that the present geographic distribution of ground ice may depend on the orbital history of mars

shock re equilibration of fluid inclusions in crystalline basement rocks from the ries crater germany this study examines the effects of shock metamorphism on fluid inclusions in crystalline basement target rocks from the ries crater germany the occurrence of two phase fluid inclusions decreases from shock stage 0 to shock stage 1 while single phase inclusions increase likely as a result of re equilibration in shock stages 2 and 3 both two phase and single phase inclusions decrease with increasing shock stage indicating that fluid inclusion vesicles are destroyed due to plastic deformation and phase changes in the host minerals however quartz clasts entrained in shock stage 4 melts contain both single phase and two phase inclusions demonstrating the rapid quenching of the melt and the heterogeneous nature of impact deformation inclusions in naturally shocked polycrystalline samples survive at higher shock pressures than those in single crystal shock experiments however fluid inclusions in both experimental and natural samples follow a similar trend in re equilibration at low to moderate shock pressures leading to destruction of inclusion vesicles in higher shock stages this suggests that shock processing may lead to the destruction of fluid inclusions in many planetary materials and likely contributed to shock devolatilization of early planetesimals

fluid inclusion systems in metaplaya deposits and their relationships to mineralization and tectonics abstract fluid inclusions have been analysed along traverses through the upper proterozoic damara orogen south west africa namibia two genetically different fluid systems of regional importance could be distinguished 1 a fluid system with 25 50 gross salinity nacl kcl cacl2 source continental evaporitic sequences and 2 another fluid system with 4 16 gross salinity nacl source metamorphic fluids derived from pelitic geosynclinal sediments further fluid systems of local importance are bound to numerous late tectonic granite and alaskite intrusions residual hypersaline solutions caused mineralization of stratiform cu deposits and numerous giant quartz reefs the two fluid systems have played an important role in the development of thrusts and nappes

the thermal stability of near surface ground ice on mars the existence of subsurface water ice on mars has been predicted in several theoretical studies1 5 but there are no definitive observations of its present distribution geomorphic features on the surface of mars have been widely interpreted as evidence for the presence of ground ice6 12 but many of these features are found at near equatorial latitudes where thermal models have predicted that near surface water ice should not be stable under present climate conditions3 13 14 here i present the results of thermal calculations which show that observed geographic variations in the thermal and reflectance properties of martian soils significantly affect subsurface temperatures my results indicate that in certain regions ground ice deposits could exist much closer to the surface and much closer to the equator than previously thought in the future these deposits could be a valuable resource for human exploration15

pan african rifting and orogenesis in southern to equatorial africa and eastern brazil abstract the upper proterozoic pan african belts of africa and brasiliano belts of south america are assumed to have evolved from an elaborate system of continental rifts which formed on the west gondwana continent 1100 1000 ma ago reviews of the damara belt kaoko belt gariep belt saldania belt west congolian belt lufilian arc and zambezi belt of southern and equatorial africa and the ribeira mantiqueira belt of brazil show the applicability of the continental rifting model to all these belts strict application of the rifting model describing the formation and further evolution of rift structures in the continental crust leads to the conclusion that the west congolian belt as traditionally described is incomplete and has to be supplemented by the mayumbian belt and a rift structure situated farther to the west the lufilian arc is assumed to have evolved from two rift structures separated from each other by the later domes region the golfe du katanga which branches off northeastwards from the lufilian arc is interpreted as an aulacogen shaba aulacogen the pan african brasiliano rift system is comparable to the mesozoic arctic north atlantic rift system with regard to size and distribution of rifts ocean floor spreading and opening of a proto south atlantic ocean most probably occurred along a main line of rifting situated between the west coast of africa and eastern brazil the wedge like ocean may have terminated at the sao francisco congo cratonic bridge between northeastern brazil and gabon cameroon there is no evidence of ocean floor spreading in the zambezi belt the lufilian arc and the traditional west congolian belt which are arranged along another major line of rifting closure of the pan african brasiliano rift system took place during two successive orogenic episodes the zambezi belt lufilian arc and west congolian belt underwent their main orogenic deformation with prevailing ene and wsw oriented tectonic transportation directions during the katangan episode at 900 750 ma the transcontinental sinistral mwembeshi shear zone adjusted opposite movement directions in the zambezi belt and lufilian arc and at its western prolongation concurrently supported opening of the khomas trough in the southern damara belt the proto south atlantic ocean still opening during the katangan episode was gradually closed during the damaran episode at 750 500 ma closure proceeded from north to south and was accompanied by northwest directed subduction underneath the brazilian plate and southeast directed tectonic transportation in the kaoko damara and gariep belts in the previously formed west congolian belt lufilian arc and zambezi belt a second deformation phase characterized by strike slip faulting and local emplacement of nappes occurred during this episode

formation and erosion of layered materials geologic and dust cycle history of eastern arabia terra mars 1 eastern arabia terra is mantled in a layer of dust a few centimeters to a meter thick yet contains morphologic features that suggest a history of multiple events of deposition and consolidation of fine grained material and a significant amount of erosion early in martian history this region was affected by volcanic and fluvial activity but has since been dominated by aeolian processes five craters in this region contain interior mound material that ranges in height from 1600 to 2100 m above the crater floor the fluted erosional pattern and the thermal inertia are suggestive of a weakly indurated material and the extensive layering implies that these mounds were formed by a repeated process or processes although these materials primarily occur within craters there are materials outside craters that have similar erosional features and fine laminations suggesting a more extensive deposit the most likely process to form this material is the deposition and cementation of air fall dust and is potentially related to martian obliquity changes the significant amount of erosion of the intracrater mounds unit indicates a dramatic change from a depositional environment to an erosional regime over the past 106 108 years currently dust is accumulating in this region in years with planet encircling dust events but global circulation model results indicate that dust devils may be removing slight amounts of dust from arabia terra these observations suggest that the thickness of the dust mantle may not be currently increasing and may instead be in equilibrium

what we know about mars from its impact craters martian impact craters provide insights into formation ages of terrain units nearsurface properties and the planet s degradational history crater size frequency distribution analyses allow determination of terrain unit relative ages and extrapolation of the lunar crater chronology can provide estimates of absolute ages for these units such analyses indicate that mars has been geologically active throughout its history but it also retains extensive regions dating back to ca 4 ga higher cratering rates during the late heavy bombardment lhb helped to create the martian regolith and formation of large impact basins helped to erode the initially denser martian atmosphere and may have created the hemispheric dichotomy low global degradation rates since the end of lhb ca 3 8 ga resulted in well preserved impact crater morphologies the presence of layered ejecta blankets and central pits associated with fresh to moderately eroded craters suggests a volatile rich crust impact crater depth diameter relationships allow estimation of the vertical extent of crustal volatiles to depths greater than those probed by current spacecraft instrumentation temporal changes in subsurface ice reservoir depths are revealed by differences in layered ejecta onset diameter as a function of crater age an understanding of the morphology and morphometry of pristine impact craters facilitates efforts to determine the amount and types of degradation and the periods over which they operated impact craters therefore play a major role in unraveling the climatic and geologic history of mars

boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites boron isotope ratios 11b 10b have been measured on 60 tourmaline separates from over 40 massive sulfide deposits and tourmalinites from a variety of geologic and tectonic settings the coverage of these localities is global 5 continents and includes the giant ore bodies at kidd creek and sullivan canada broken hill australia and ducktown usa overall the tourmalines display a wide range in 11b values from 22 8 to 18 3 possible controls over the boron isotopic composition of the tourmalines include 1 composition of the boron source 2 regional metamorphism 3 water rock ratios 4 seawater entrainment 5 temperature of formation and 6 secular variations in seawater 11b the most significant control appears to be the composition of the boron source particularly the nature of footwall lithologies variations in water rock ratios and seawater entrainment are of secondary importance the boron isotope values seem especially sensitive to the presence of evaporites marine and non marine and carbonates in source rocks to the massive sulfide deposits and tourmalinites

tectonic evolution of the lufilian arc central africa copper belt during neoproterozoic pan african orogenesis abstract the lufilian arc of central africa also called katangan belt or copperbelt is a zone of low to highgrade metasedimentary and subsidiary igneous rocks of neoproterozoic age hosting highgrade cucou and pbzn mineralizations the lufilian arc is located between the congo and kalahari cratons and defines a structure which is convex to the north three major phases of deformation characterize the construction of the lufilian arc the first phase d1 called the kolwezian phase developed folds and thrust sheets with a northward transport direction d1 deformation occurred in the lufilian arc between ca 800 and 710 ma with a peak in the range 790 750 ma it is here correlated with the main deformation in the zambezi belt southward verging folds with the same trends as the d 1 structures were previously linked to a second tectonic event named kundelunguian phase of the lufilian orogeny we show in this paper that they are backfolds developed during d1 along katangan ramps and especially along the kibaran foreland the second phase d2 of the lufilian orogeny is the monwezi phase including several large leftlateral strikeslip faults which have been activated successively during this deformation phase the eastern block of the belt rotated clockwise giving the present day nwse trend of d1 structures in this part of the lufilian arc and generating its convex geometry the mwembeshi dislocation the major transcurrent shear zone separating the zambezi and lufilian arc was mostly active during the d2 deformation phase d2 deformation occurred between ca 690 and 540 ma such a long time interval is attributed to the migration of strikeslip faults developed sequentially from south to north and probably to a slow convergence velocity during the collision between the congo and kalahari cratons the third phase d3 of the lufilian orogeny is a late event called the chilatembo phase marked by structures transverse to the trends of the lufilian arc this deformation and the post d 2 uppermost kundelungu sequence ks3 plateaux group are younger than 540 ma and probably early paleozoic

on developing thermal cave detection techniques for earth the moon and mars abstract the purpose of this study is to 1 demonstrate the viability of detecting terrestrial caves at thermal infrared wavelengths 2 improve our understanding of terrestrial cave thermal behavior 3 identify times of day when cave openings have the maximum thermal contrast with the surrounding surface regolith and 4 further our understanding of how to detect caves on earth the moon and mars we monitored the thermal behavior of two caves in the atacama desert of northern chile through this work we identified times when temperature contrasts between entrance and surface were greatest thus enabling us to suggest optimal overflight times the largest thermal contrast for both caves occurred during mid day one cave demonstrated thermal behavior at the entrance suggestive of cold trapping while the second cave demonstrated temperature shifts suggestive of airflow we also collected thermograms without knowing optimal detection times these images suggest both caves may also be detectable during off peak times we suggest cave detection using thermal remote sensing on earth and other planetary objects will be limited by 1 capturing imagery in the appropriate thermal wavelength 2 the size of cave entrance vs the sensor s spatial resolution 3 the viewing angle of the platform in relation to the slope trajectory of the cave entrance 4 the strength of the thermal signal associated with the cave entrance and 5 the time of day and season of thermal image capture through this and other studies we will begin to identify the range of conditions under which caves are detectable in the thermal infrared and thus improve our detection capabilities of these features on earth the moon and mars

sparse subsurface radar reflectors in hellas planitia mars abstract geomorphological features potentially related to subsurface ice such as scalloped depressions expanded craters pedestal craters and banded terrain are present in and around hellas planitia mars we present a radar survey of the region using the shallow radar sharad instrument on board the mars reconnaissance orbiter mro to identify candidate subsurface reflectors that may be due to the presence of potentially ice rich deposits we found that the majority of radar returns are likely from off nadir surface topography clutter arising from the rough topography of the region there is no widespread radar return from any subsurface interfaces however we identify a group of six reflectors adjacent to each other on a plateau in malea patera in which we have higher confidence landforms associated with a likely ice rich mantle are associated with the plateau but the thickness of this mantle does not correspond to the expected depth of the reflectors however layers beneath the mantle and marginal pitting at the edge of the plateau are similar to those associated with pedestal craters which may be ice rich and are a similar thickness to the expected depth of the reflectors malea patera has been interpreted to be a volcanic caldera so the reflectors may be associated with a volcanic deposit within the plateau although the evidence for this is inconclusive because this radar detection is localized and its origin ambiguous we cannot use it to make conclusions about the thickness of subsurface deposits in the hellas region as a whole the lack of widespread radar reflectors in this region as compared to the northern mid latitudes where extensive radar reflections have been mapped may be due in part to higher surface roughness which creates radar clutter that may obscure subsurface reflectors however on the southern rim of the basin and south of the basin the lack of reflectors may indicate that the possible ice rich deposits observed geomorphologically in this region are too thin to be resolved by sharad are dielectrically similar to the underlying unit or have a gradual vertical transition in ice content that is not reflective for the radar this would imply that recent climate processes may have favored widespread thick ice deposition or preservation in the northern hemisphere as compared to the southern hemisphere

constraints on the formation and properties of a martian lobate debris apron insights from high resolution topography sharad radar data and a numerical ice flow model

a coast parallel depression possibly caused by gas migration off western norway abstract during a recent pipeline route survey a depression 2 4 m deep and 100 220 m wide was found in layered soft clays 12 km ssw of utsira island off the west coast of norway the depression is at least 2 5 km in length and resembles iceberg ploughmarks which occur abundantly in the stiffer clays in shallower water to the east of the feature due to conspicious disturbances of the fine layers in the clays beneath the depression it is interpreted as having been formed not by icebergs but by escaping gas having lifted fine grained particles into suspension in much the same way as pockmarks are assumed to be formed the gas is believed to migrate along the westward dipping sedimentary units and forced to the surface parallel to the coast by the steeply dipping crystalline rocks thus forming the coast parallel depression

viscous relaxation of craters within the martian south polar layered deposits abstract the south polar layered deposits pld are of fundamental importance to martian climatology as they may comprise the largest reservoir of near surface water on mars the south pld exhibit relatively young crater retention surface ages which are widely attributed to recent resurfacing however we show that both constructional and destructional resurfacing mechanisms such as dust deposition and water ice sublimation respectively are inconsistent with the size depth and spatial distributions of south pld craters we demonstrate that another process viscous creep relaxation of dusty water ice is more compatible with the observed cratering of south pld surfaces the results of our finite element relaxation simulations suggest that despite their apparent youthfulness the pld have been stable for at least several hundred million and perhaps even over a billion years consequently our modeling implies that the time scales for the formation and preservation of the layers characteristic of the south and possibly north pld are much longer than generally assumed

possible pingos and a periglacial landscape in northwest utopia planitia hydrostatic closed system pingos are small elongate to circular ice cored mounds that are perennial features of some periglacial landscapes the growth and development of hydrostatic pingos is contingent upon the presence of surface water freezing processes and of deep continuous ice cemented permafrost other cold climate landforms such as small sized polygonal patterned ground also may occur in the areas where pingos are found on mars landscapes comprising small elongate to circular mounds and other possible periglacial features have been identified in various areas including utopia planitia where water is thought to have played an important role in landscape evolution despite the importance of the martian mounds as possible markers of water most accounts of them in the planetary science literature have been brief and or based upon viking imagery we use a high resolution mars orbiter camera image eo300299 and superposed mars orbiter laser altimeter data tracks to describe and characterise a crater floor landscape in northwest utopia planitia 64 8 n 292 7 w the landscape comprises an assemblage of landforms that is consistent with the past presence of water and of periglacial processes this geomorphological assemblage may have formed as recently as the last episode of high obliquity a similar assemblage of landforms is found in the tuktoyaktuk peninsula of northern canada and other terrestrial cold climate landscapes we point to the similarity of the two assemblages and suggest that the small roughly circular mounds on the floor of the impact crater in northwest utopia planitia are hydrostatic pingos like the hydrostatic pingos of the tuktoyaktuk peninsula the origin of the crater floor mounds could be tied to the loss of ponded local water permafrost aggradation and the evolution of a sub surface ice core

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