semi analytical solution for a slug test in partially penetrating wells including the effect of finite thickness skin this paper presents a new semi analytical solution for a slug test in a well partially penetrating a confined aquifer accounting for the skin effect this solution is developed based on the solution for a constant flux pumping test and a formula given by peres and co workers in 1989 the solution agrees with that of cooper and co workers and the kgs model when the well is fully penetrating the present solution can be applied to simulate the temporal and spatial head distributions in both the skin and formation zones it can also be used to demonstrate the influences of skin type or skin thickness on the well water level and to estimate the hydraulic parameters of the skin and formation zones using a least squares approach the results of this study indicate that the determination of hydraulic conductivity using a conventional slug test data analysis that neglects the presence of a skin zone will give an incorrect result if the aquifer has a skin zone

albedo matters understanding runaway albedo variations on pluto abstract the data returned from nasa s new horizons reconnaissance of the pluto system show striking albedo variations from polar to equatorial latitudes as well as sharp longitudinal boundaries pluto has a high obliquity currently 119 that varies by 23 over a period of less than 3 million years this variation combined with its regressing longitude of perihelion 360 over 3 7 million years creates epochs of super seasons where one pole is pointed at the sun at perihelion thereby experiencing a short relatively warm summer followed by its longest possible period of winter darkness in contrast the other pole experiences a much longer less intense summer and a short winter season we use a simple volatile sublimation and deposition model to explore the relationship between albedo variations latitude and volatile sublimation and deposition for the current epoch as well as historical epochs during which pluto experienced these super seasons our investigation quantitatively shows that pluto s geometry creates the potential for runaway albedo and volatile variations particularly in the equatorial region which can sustain stark longitudinal contrasts like the ones we see between tombaugh regio and the informally named cthulhu regio

obtaining the steady state drawdown solutions of constant head and constant flux tests the solutions of constant head and constant flux tests are commonly used to predict the temporal or spatial drawdown distribution or to determine aquifer parameters theis and thiem equations for instance are well known transient and steadystate drawdown solutions respectively of the constant flux test it is known that the theis equation is not applicable to the case where the aquifer has a finite boundary or the pumping time tends to infinity on the other hand the thiem equation does not apply to the case where the aquifer boundary is infinite however the issue of obtaining the thiem equation from the transient drawdown solution has not previously been addressed in this paper the drawdown solutions for constant head and constant flux tests conducted in finite or infinite confined aquifers with or without consideration of the effect of the well radius are examined comprehensively mathematical verification and physical interpretation of the solutions to these two tests converging or not converging to the thiem equation are presented the result shows that there are some finite domain solutions for these two tests that can converge to the thiem equation when the time becomes infinitely large in addition the time criteria to give a good approximation to the finite domain solution by the infinite domain solution and the thiem equation are investigated and presented copyright 2008 john wiley sons ltd

pluto pits and mantles on uplands north and east of sputnik planitia abstract the highlands region north and east of sputnik planitia can be subdivided into seven terrain types based on their physiographic expression the northern rough uplands are characterized by jagged uplands and broad troughs and it may contain a deeply eroded ancient mantle dissected terrain has been interpreted to have been eroded by paleo glaciation the smooth uplands and pits terrain contains broad rolling uplands surrounding complexes of pits some of which contain smooth floors the uplands are mantled by smooth surfaced deposits possibly derived from adjacent pits through low power explosive cryovolcanism or through slow vapor condensation the eroded smooth uplands appear to have originally been smooth uplands and pits terrain modified by small scale sublimation pitting the bright pitted uplands features intricate texturing by reticulate ridges that may have originated by sublimation erosion volatile condensation or both the bladed terrain is characterized by parallel ridges oriented north south and is discussed in a separate paper the dark uplands are mantled with reddish deposits that may be atmospherically deposited tholins their presence has affected long term landform evolution widespread pit complexes occur on most of the terrain units most appear to be associated with tectonic lineations some pits are floored by broad expanses of ices whereas most feature deep conical depressions a few pit complexes are enclosed by elevated rims of uncertain origin

analysis of well residual drawdown after a constant head test summary a recovery test measures the residual drawdown after an aquifer pumping test has ended and analyzes the recovery data to determine hydrogeological parameters such as transmissivity and storage coefficient to our knowledge the solution for the distribution of residual drawdown following a constanthead test has never been presented in this paper we first develop a mathematical model that describes the residual drawdown taking into consideration the wellbore storage effect and the drawdown distribution occurring at the end of a previous constant head test then the laplace domain solution of the model is developed using the laplace transforms and its time domain solution is obtained using the stehfest algorithm numerical results show that the distribution of residual drawdown depends on the boundary condition related to the well drawdown and the initial condition related to the aquifer drawdown the well residual drawdown i e the residual drawdown at wellbore during the early recovery period will be over estimated by the approximate residual drawdown solution based on the theis type solution and superposition principle due to the neglect of wellbore storage for a large recovery time the effect of wellbore storage is negligible and the approximate residual drawdown solution is therefore applicable

dunes on pluto the surface of pluto is more geologically diverse and dynamic than had been expected but the role of its tenuous atmosphere in shaping the landscape remains unclear we describe observations from the new horizons spacecraft of regularly spaced linear ridges whose morphology distribution and orientation are consistent with being transverse dunes these are located close to mountainous regions and are orthogonal to nearby wind streaks we demonstrate that the wavelength of the dunes 0 4 to 1 kilometer is best explained by the deposition of sand sized 200 to 300 micrometer particles of methane ice in moderate winds

transient solution for radial two zone flow in unconfined aquifers under constant head tests the constant head test cht is commonly employed to determine the aquifer parameters this test is also applied to many environmental problems such as recovering light nonaqueous phase liquids lnapl and controlling off site migration of contaminated groundwater in low transmissivity aquifers a well skin near the wellbore may be produced due to the well construction or development and its formation properties are significantly different from the original ones a more appropriate description for the skin effect on the aquifer system should treat the well skin as a different formation instead of using a skin factor thus the aquifer system becomes a two zone formation including the skin and formation zones this study presents a mathematical model developed for analyzing a two zone unconfined aquifer system and the associated solution for chts at partially penetrating wells under transient state the solution of the model may be used either to identify the in situ aquifer parameters or to investigate the effects of the wellbore storage and well skin on the head changes in unconfined aquifers under constant head pumping copyright 2010 john wiley sons ltd

three dimensional baroclinic eddies in the ocean evolution propagation overall structures and angular models abstractthe evolution and dynamics of an initially gaussian baroclinic vortex embedded in a resting stratification environment are investigated with a three dimensional primitive equation model th

bladed terrain on pluto possible origins and evolution abstract bladed terrain on pluto consists of deposits of massive ch 4 which are observed to occur within latitudes 30 of the equator and are found almost exclusively at the highest elevations 2 km above the mean radius our analysis indicates that these deposits of ch 4 preferentially precipitate at low latitudes where net annual solar energy input is lowest ch 4 and n 2 will both precipitate at low elevations however since there is much more n 2 in the atmosphere than ch 4 the n 2 ice will dominate at these low elevations at high elevations the atmosphere is too warm for n 2 to precipitate so only ch 4 can do so we conclude that following the time of massive ch 4 emplacement there have been sufficient excursions in pluto s climate to partially erode these deposits via sublimation into the blades we see today blades composed of massive ch 4 ice implies that the mechanical behavior of ch 4 can support at least several hundred meters of relief at pluto surface conditions bladed terrain deposits may be widespread in the low latitudes of the poorly seen sub charon hemisphere based on spectral observations if these locations are indeed bladed terrain deposits they may mark heretofore unrecognized regions of high elevation

initialization asymmetry and spindown of arctic eddies abstract initialization and development of cyclonic and anticyclonic eddies under the influence of a frictional surface as with arctic eddies under ice cover are examined both analytically and numerically using a three dimensional numerical model solutions of the linear rossby adjustment problem show that energy released from an initial density anomaly in the barotropic mode and the first few baroclinic modes destabilizes the numerical computation for small arctic eddies this result suggests the necessity of slow spinup to reduce energy release in these modes and sufficient vertical resolution to resolve higher baroclinic modes the numerical computation shows that in an initially stratified and motionless ocean a surface cyclone an anticyclone is produced by a localized salinity source sink in open waters the stable flow field consists of a vertically aligned pair of counterrotating eddies when dampened by surface friction an eddy pair produced by deep forcing has features dissimilar to the

the ch4 cycles on pluto over seasonal and astronomical timescales abstract pluto s surface is covered in numerous ch4 ice deposits that vary in texture and brightness as revealed by the new horizons spacecraft as it flew by pluto in july 2015 these observations suggest that ch4 on pluto has a complex history involving reservoirs of different composition thickness and stability controlled by volatile processes occurring on different timescales in order to interpret these observations we use a pluto volatile transport model able to simulate the cycles of n2 and ch4 ices over millions of years by assuming fixed solid mixing ratios we explore how changes in surface albedos emissivities and thermal inertias impact volatile transport this work is therefore a direct and natural continuation of the work by bertrand et al 2018 which only explored the n2 cycles results show that bright ch4 deposits can create cold traps for n2 ice outside sputnik planitia leading to a strong coupling between the n2 and ch4 cycles depending on the assumed albedo for ch4 ice the model predicts ch4 ice accumulation 1 at the same equatorial latitudes where the bladed terrain deposits are observed supporting the idea that these ch4 rich deposits are massive and perennial or 2 at mid latitudes 25 70 forming a thick mantle which is consistent with new horizons observations in our simulations both ch4 ice reservoirs are not in an equilibrium state and either one can dominate the other over long timescales depending on the assumptions made for the ch4 albedo this suggests that long term volatile transport exists between the observed reservoirs the model also reproduces the formation of n2 deposits at mid latitudes and in the equatorial depressions surrounding the bladed terrain deposits as observed by new horizons at the poles only seasonal ch4 and n2 deposits are obtained in pluto s current orbital configuration finally we show that pluto s atmosphere always contained over the last astronomical cycles enough gaseous ch4 to absorb most of the incoming lyman flux

winter and spring evolution of northern seasonal deposits on mars from omega on mars express the omega visible near infrared imaging spectrometer on mars express has observed the retreat of the northern seasonal deposits during martian year 27 28 from the period of maximum extension close to the northern winter solstice to the end of the retreat at l s 95 we present the temporal and spatial distributions of both co 2 and h 2o ices and propose a scenario that describes the winter and spring evolution of the northern seasonal deposits during winter the co 2 rich condensates are initially transparent and could be in slab form a water ice annulus surrounds the sublimating co 2 ice extending over 6 of latitude at l s 320 decreasing to 2 at l s 350 and gradually increasing to 4 5 at l s 50 this annulus first consists of thin frost as observed by the viking lander 2 and is then overlaid by h 2o grains trapped in the co 2 rich ice layer and released during co 2 sublimation by l s 50 h 2o ice spectrally dominates most of the deposits in order to hide the still several tens of centimeters thick co 2 ice layer in central areas of the cap we propose the buildup of an optically thick top layer of h 2o ice from ice grains previously embedded in the co 2 ice and by cold trapping of water vapor from the sublimating water ice annulus the co 2 ice signature locally reappears between l s 50 and 70 what emerges from our observations is a very active surface atmosphere water cycle these data provide additional constraints to the general circulation models simulating the martian climate copyright 2011 by the american geophysical union

an oceanic cyclonic eddy on the lee side of lanai island hawai i 1 a young cold core cyclonic eddy displaying a significant increase in surface chlorophyll was observed offshore lanai island hawai i where the marine optical buoy moby is located during one of its deployments moby broke free from its mooring in the course of its 3 day free drifting period moby followed a cyclonic eddy which is manifested by satellite remote sensing data chlorophyll data from moderate resolution imaging spectroradiometer and sea surface temperature sst from a geostationary operational environmental satellite the time series of the sst show that the cold core eddy was in a formative stage it existed as a stand alone eddy for about 9 days before it merged with cold water south of oahu island a high resolution numerical model simulation reproduces similar eddies in terms of location size and intensity an eddy detection algorithm is described and applied to locate and track the modeled eddies the results demonstrate that mesoscale and submesoscale eddies are frequently generated on and pass through the lee side of lanai island and the statistical analysis quantifies the general features of eddies in the area

laplace domain solutions for radial two zone flow equations under the conditions of constant head and partially penetrating well a mathematical model is presented for a constant head test performed in a partially penetrating well with a finite thickness skin the model uses a no flow boundary condition for the casing and a constant head boundary condition for the screen to represent the partially penetrating well the laplace domain solutions for the dimensionless flow rate at the wellbore and the hydraulic heads in the skin and formation zones are derived using the laplace and finite fourier cosine transforms the solutions of hydraulic heads have been shown to satisfy the governing equations related boundary conditions and continuity requirements for the pressure head and flow rate at the interface of the skin zone and undisturbed formation in addition an efficient algorithm for evaluating those solutions is also presented the dimensionless flow rates obtained from new solutions have been shown to be better than those of novakowski s solutions especially when the penetration ratio is large

pluto s global surface composition through pixel by pixel hapke modeling of new horizons ralph leisa data abstract on july 14th 2015 nasa s new horizons mission gave us an unprecedented detailed view of the pluto system the complex compositional diversity of pluto s encounter hemisphere was revealed by the ralph leisa infrared spectrometer on board of new horizons we present compositional maps of pluto defining the spatial distribution of the abundance and textural properties of the volatiles methane and nitrogen ices and non volatiles water ice and tholin these results are obtained by applying a pixel by pixel hapke radiative transfer model to the leisa scans our analysis focuses mainly on the large scale latitudinal variations of methane and nitrogen ices and aims at setting observational constraints to volatile transport models specifically we find three latitudinal bands the first enriched in methane extends from the pole to 55 n the second dominated by nitrogen continues south to 35 n and the third composed again mainly of methane reaches 20 n we demonstrate that the distribution of volatiles across these surface units can be explained by differences in insolation over the past few decades the latitudinal pattern is broken by sputnik planitia a large reservoir of volatiles with nitrogen playing the most important role the physical properties of methane and nitrogen in this region are suggestive of the presence of a cold trap or possible volatile stratification furthermore our modeling results point to a possible sublimation transport of nitrogen from the northwest edge of sputnik planitia toward the south

methane distribution on pluto as mapped by the new horizons ralph mvic instrument abstract the data returned from nasa s new horizons spacecraft have given us an unprecedented detailed look at the pluto system new horizons ralph mvic multispectral visible imaging camera is composed of 7 independent ccd arrays on a single substrate among these are a red channel 540 700 nm near infrared channel 780 975 nm and narrow band methane channel 860 910 nm by comparing the relative reflectance of these channels we are able to produce high resolution methane equivalent width based on the 890 nm absorption band and spectral slope maps of pluto s surface from these maps we can then quantitatively study the relationships between methane distribution redness and other parameters like latitude and elevation we find pluto s surface to show a great diversity of terrains particularly in the equatorial region between 30 n and 30 s latitude methane equivalent width also shows some dependence on elevation while spectral slope shows very little

on eddy scales in the eastern and northern north atlantic ocean as a function of latitude infrared satellite images and two ensembles of satellite tracked buoys have been used to analyze eddy scales in the central and eastern north atlantic between 35 n and 60 n both data sets yield eddy scales which decrease northward from the subtropical atlantic and can be closely related to the rossby radius of the first baroclinic mode

the interaction of a two layer isolated mesoscale eddy with bottom topography abstract the propagation of an isolated mesoscale eddy onto a western bounding topographic slope is examined through the use of a two layer primitive equation numerical model variable parameters in the study are sense of rotation cyclonic anticyclonic vertical structure baroclinic barotropic and layer thickness ratio h1 h2 eddy size and strength rotational velocity and frictional parameterization are fixed dispersion in the isolated eddy is induced by planetary and topographic beta effects giving the eddy an asymmetric distribution this asymmetric distribution allows for nonlinear self advective propagation tendencies these nonlinear tendencies play a key role in the direction of propagation of the eddy specifically in a quiescient background an anticyclone can have eastward propagation tendencies which can overcome planetary and topographic beta effects conversely cyclones can have westward propagation velocities which are augmented greater than maximum rossby wave phase speed b

physical state and distribution of materials at the surface of pluto from new horizons leisa imaging spectrometer abstract from earth based observations pluto is known to be the host of n2 ch4 and co ices and also a dark red material very limited spatial distribution information is available from rotational visible and near infrared spectral curves obtained from hemispheric measurements in july 2015 the new horizons spacecraft reached pluto and its satellite system and recorded a large set of data the leisa spectro imager of the ralph instruments are dedicated to the study of the composition and physical state of the materials composing the surface in this paper we report a study of the distribution and physical state of the ices and non ice materials on pluto s illuminated surface and their mode and degree of mixing principal component analysis as well as various specific spectral indicators and correlation plots are used on the first set of 2 high resolution spectro images from the leisa instrument covering the whole illuminated face of pluto at the time of the new horizons encounter qualitative distribution maps have been obtained for the 4 main condensed molecules n2 ch4 co h2o as well as for the visible dark red material based on specific spectral indicators using either the strength or the position of absorption bands these 4 molecules are found to indicate the presence of 3 different types of ices n2 rich ch4 co ices ch4 rich co n2 ices and h2o ice the mixing lines between these ices and with the dark red material are studied using scatter plots between the various spectral indicators ch4 is mixed at the molecular level with n2 most probably also with co thus forming a ternary molecular mixture that follows its phase diagram with low solubility limits the occurrence of a n2 rich ch4 rich ices mixing line associated with a progressive decrease of the co ch4 ratio tells us that a fractionation sublimation sequence transforms one type of ice to the other forming either a n2 rich ch4 rich binary mixture at the surface or an upper ch4 rich ice crust that may hide the n2 rich ice below the strong ch4 rich h2o mixing line witnesses the subsequent sublimation of the ch4 rich ice lag left behind by the n2 co sublimation n spring summer or a direct condensation of ch4 ice on the cold h2o ice s autumn the weak mixing line between ch4 containing ices and the dark red material and the very sharp spatial transitions between these ices and this non volatile material are probably due to thermal incompatibility finally the occurrence of a h2o ice red material mixing line advocates for a spatial mixing of the red material covering h2o ice with possibly a small amount intimately mixed in water ice from this analysis of the different materials distribution and their relative mixing lines h2o ice appears to be the substratum on which other ices condense or non volatile organic material is deposited from the atmosphere n2 rich ices seem to evolve to ch4 dominated ices possibly still containing traces of co and n2 as n2 and co sublimate away the spatial distribution of these materials is very complex the high spatial definition of all these composition maps as well as those at even higher resolution that will be soon available will allow us to compare them with pluto s geologic features observed by lorri panchromatic and mvic multispectral imagers to better understand the geophysical processes in action at the surface of this astonishingly active frozen world

basins fractures and volcanoes global cartography and topography of pluto from new horizons abstract the 2015 new horizons flyby has produced the first high resolution maps of morphology and topography of pluto and charon the most distant objects so mapped global integrated mosaics of pluto were produced using both lorri framing camera and mvic line scan camera data showing the best resolution data obtained for all areas of the illuminated surface 78 of the body a unique feature of the pluto imaging data set is the observation of terrains illuminated only by light scattered from atmospheric haze allowing us to map terrains in the southern hemisphere that would otherwise have been in darkness mvic 4 color data were combined with the panchromatic map to produce full color global maps digital elevation models dems over 42 of pluto were produced using combinations of mvic hemispheric scans and lorri mosaics from which slopes at scales of 1 km can be determined pluto can be divided into regions each with distinct topographic signatures corresponding with major physiographic terrain types large areas of pluto are comprised of low relief moderately cratered plains units deeply pitted and glaciated plains east of sputnik planitia are elevated 0 7 km the most dominant topographic feature on pluto is the 1200 by 2000 km wide depression enclosing the bright sputnik planitia ice sheet the surface of which is 2 5 to 3 5 km deep relative to the rim and 2 km deep relative to the mean radius the partial ring of steep sided massifs several of which are more than 5 km high along the western margins of sputnik planitia produce some of the locally highest and steepest relief on pluto with slopes of 40 50 the second major topographic feature is a complex eroded ridge trough system 300 400 km wide and at least 3200 km long extending north to south along the 155 meridian this enormous structure has several kilometers of relief it may predate the large impact event forming the basin though some post sputnik planitia deformation is evident the large depressed partially walled plain hyecho palus lies due southwest of sputnik planitia near the center of hyecho palus lie the circular constructional edifices wright and piccard montes wright mons rises 4 5 km above these plains with a central depression 4 5 km deep whereas piccard mons best observed in haze light rises 5 5 km above the plains but has a bowl shaped central depression 5 5 km below the plains for a total relief of up to 11 km the greatest observed on pluto both of these features are interpreted as constructional volcanic in nature additional prominent topographic features include a 2 3 km high and 600 km wide dome centered on the illuminated iau pole and the amoeboidal plateaus of bladed terrains in the equatorial region which rise 2 5 km above local terrains and are the highest standing geologic units on the encounter hemisphere the mean elevations in the integrated dem for the two radio occultation areas are consistent with the 5 6 km difference in elevation as determined independently by the radio experiment and a limb profile near the egress point confirms the presence of elevated bladed terrains in that area local relief of 3 5 km at massifs troughs and pits supports conclusions that the icy shell of pluto is relatively rigid numerous examples of topographic control of ice or frost deposition occur across pluto including the distinct coloration of the polar dome the elevated terrains of eastern tombaugh regio and along the ridge trough system where ridge tops and fossae rims are covered in different ices than at lower elevations the topographic hypsogram of pluto s encounter hemisphere is strongly bimodal due to the large sputnik planitia depression otherwise the topographic signature of pluto is controlled by deviations from the otherwise dominant low plains including elevated bladed terrain plateaus and the depressed volcanic province including wright and piccard montes

stream depletion rate and volume from groundwater pumping in wedge shape aquifers in river basins with several tributaries wells in alluvial valleys are often located near the wedge shaped confluence of two tributaries therefore stream depletion characteristics namely stream depletion rate sdr and stream depletion volume sdv induced by the pumping wells are distributed between two tributaries upstream from the confluence existing methods for the evaluation of stream depletion characteristics are applicable only for a wedge shaped aquifer with special or uncommon wedge angles or for steady state conditions in water resources management temporal stream depletion characteristics are important for the adjudication of water rights a new and practically important method for analytical evaluation of transient sdr and sdv is developed for a wedge shaped aquifer with arbitrary wedge angles results are obtained for each of two tributaries or the tributary segment lengths a simple expression for the sdr fraction that originates from each tributary is presented for long period of pumping after which 100 of the pumping rate is supplied by stream depletion the sensitivity analyses for different parameters are performed to examine their affects on the influence period of the total sdr and the results indicated that the sdr is sensitive to the angles of wedge shaped aquifer and the pumping well the results and sensitivity analysis presented in this study may provide useful information in the assessment of water balance or exploitation of river basins

modeling cryogenic mud volcanism on pluto abstract subsurface ice cryofluids and ice interactions with ammonia for cryovolcanic materials give the potential ingredients for the formation of mud volcanoes on pluto in order to constrain the possible morphology from images acquired by the new horizons spacecraft we have modeled the formation of mud volcanoes isostatic layers of ice overlain by denser material from a series of possible solid liquid mud compositions methane and ammonia as well as accounting for the full range of eruption variables e g mud viscosity conduit diameter and eruption duration we categorize them into nine specific scenarios based on the composition of the top ice layer and mud composition from these scenarios the maximum height of the potential mud volcano can be calculated we find that ammonia mud sources produce smaller edifice heights and wider flow profiles compared to methane dominant mud cryovolcanoes assuming certain preliminary parameters we also propose the evolution and development of the edifice of wright mons in as little as 3 8 million years given a 10 wt ammonia subsurface mud composition if characterized on pluto s surface mud volcanoes would provide an interesting insight on the subsurface dynamics of solids and cryofluids on pluto

the geology of pluto and charon through the eyes of new horizons nasa s new horizons spacecraft has revealed the complex geology of pluto and charon pluto s encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection with a crater retention age no greater than 10 million years surrounding terrains show active glacial flow apparent transport and rotation of large buoyant water ice crustal blocks and pitting the latter likely caused by sublimation erosion and or collapse more enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic and ridges with complex bladed textures pluto also has ancient cratered terrains up to 4 billion years old that are extensionally faulted and extensively mantled and perhaps eroded by glacial or other processes charon does not appear to be currently active but experienced major extensional tectonism and resurfacing probably cryovolcanic nearly 4 billion years ago impact crater populations on pluto and charon are not consistent with the steepest impactor size frequency distributions proposed for the kuiper belt

observed glacier and volatile distribution on pluto from atmosphere topography processes simulations of the levels of nitrogen methane and carbon monoxide over thousands of years confirm the existence of a nitrogen glacier in sputnik planitia pluto s deepest basin tanguy bertrand and francois forget have developed a model for volatile transport on pluto and use it to simulate the evolution of n2 ch4 and co on the dwarf plant over tens of thousands of earth years the model predicts n2 ice accumulation in the deepest low latitude basin and the threefold increase in atmospheric pressure that has been observed to occur since 1988 this points to atmospheric topographic processes as the origin of the prominent equatorial n2 glacier known as sputnik planitia formerly sputnik planum this is one of four papers on the geology of sputnik planitia in this issue of nature in news views amy barr puts these latest contributions into context pluto has a variety of surface frosts and landforms as well as a complex atmosphere1 there is ongoing geological activity related to the massive sputnik planitia glacier mostly made of nitrogen n2 ice mixed with solid carbon monoxide and methane2 covering the 4 kilometre deep 1 000 kilometre wide basin of sputnik planitia1 3 near the anti charon point the glacier has been suggested to arise from a source region connected to the deep interior or from a sink collecting the volatiles released planetwide1 thin deposits of n2 frost however were also detected at mid northern latitudes and methane ice was observed to cover most of pluto except for the darker frost free equatorial regions2 here we report numerical simulations of the evolution of n2 methane and carbon monoxide on pluto over thousands of years the model predicts n2 ice accumulation in the deepest low latitude basin and the threefold increase in atmospheric pressure that has been observed to occur since 19884 5 6 this points to atmospheric topographic processes as the origin of sputnik planitia s n2 glacier the same simulations also reproduce the observed quantities of volatiles in the atmosphere and show frosts of methane and sometimes n2 that seasonally cover the mid and high latitudes explaining the bright northern polar cap reported in the 1990s7 8 and the observed ice distribution in 20152 the model also predicts that most of these seasonal frosts should disappear in the next decade

the nitrogen cycles on pluto over seasonal and astronomical timescales abstract pluto s landscape is shaped by the endless condensation and sublimation cycles of the volatile ices covering its surface in particular the sputnik planitia ice sheet which is thought to be the main reservoir of nitrogen ice displays a large diversity of terrains with bright and dark plains small pits and troughs topographic depressions and evidences of recent and past glacial flows outside sputnik planitia new horizons also revealed numerous nitrogen ice deposits in the eastern side of tombaugh regio and at mid northern latitudes these observations suggest a complex history involving volatile and glacial processes occurring on different timescales we present numerical simulations of volatile transport on pluto performed with a model designed to simulate the nitrogen cycle over millions of years taking into account the changes of obliquity solar longitude of perihelion and eccentricity as experienced by pluto using this model we first explore how the volatile and glacial activity of nitrogen within sputnik planitia has been impacted by the diurnal seasonal and astronomical cycles of pluto results show that the obliquity dominates the n2 cycle and that over one obliquity cycle the latitudes of sputnik planitia between 25 s 30 n are dominated by n2 condensation while the northern regions between 30 n and 50 n are dominated by n2 sublimation we find that a net amount of 1 km of ice has sublimed at the northern edge of sputnik planitia during the last 2 millions of years it must have been compensated by a viscous flow of the thick ice sheet by comparing these results with the observed geology of sputnik planitia we can relate the formation of the small pits and the brightness of the ice at the center of sputnik planitia to the sublimation and condensation of ice occurring at the annual timescale while the glacial flows at its eastern edge and the erosion of the water ice mountains all around the ice sheet are instead related to the astronomical timescale we also perform simulations including a glacial flow scheme which shows that the sputnik planitia ice sheet is currently at its minimum extent at the northern and southern edges we also explore the stability of n2 ice deposits outside the latitudes and longitudes of the sputnik planitia basin results show that n2 ice is not stable at the poles but rather in the equatorial regions in particular in depressions where thick deposits may persist over tens of millions of years before being trapped in sputnik planitia finally another key result is that the minimum and maximum surface pressures obtained over the simulated millions of years remain in the range of milli pascals and pascals respectively this suggests that pluto never encountered conditions allowing liquid nitrogen to flow directly on its surface instead we suggest that the numerous geomorphological evidences of past liquid flow observed on pluto s surface are the result of liquid nitrogen that flowed at the base of thick ancient nitrogen glaciers which have since disappeared

color composition and thermal environment of kuiper belt object 486958 arrokoth introduction the new horizons spacecraft flew past 486958 arrokoth provisional designation 2014 mu69 on 1 january 2019 arrokoth is a member of the subclass of trans neptunian or kuiper belt objects kbos known as the cold classical kbos cckbos most kbos formed in a disk of planetesimals that extended to about 30 au from the sun neptune eventually disrupted that disk by migrating outward through it with the migration halted by the sparseness of the disk beyond 30 au that event eliminated most members of the planetesimal disk but a minority were emplaced into dynamically excited orbits in the present day kuiper belt cckbos differ from those objects in having formed well beyond the 30 au edge of the main planetesimal disk they remain approximately where they formed on low inclination near circular orbits between 42 and 47 au from the sun relicts of the early solar system their distributions of colors albedos sizes and binarity differ from those of the more excited kbos rationale initial results from the exploration of arrokoth were published previously more data have since been received from the spacecraft allowing a more detailed analysis we analyze a high spatial resolution color imaging observation near infrared spectral imaging and microwave radiometry of arrokoth the infrared spectral data have been processed to compensate for the changing range and scale during the observation our multiple scattering radiative transfer models provide compositional constraints from the infrared spectral imagery microwave thermal radiometry at 4 2 cm wavelength is combined with heat transport models that account for the bilobate shape of arrokoth and for self radiation results at visual wavelengths arrokoth s reflectance rises toward longer wavelengths this red coloration is typical of the broader cckbo population that has been studied using telescopic observations color differences across the surface of arrokoth correspond to geological features these color differences are subtle with deviations of just a few percent around the prevailing red coloration some of the color variations are associated with albedo markings such as the bright neck between the two lobes bright splotches associated with a large pit or crater on the smaller lobe and poorly resolved small bright spots methanol ice ch3oh and complex organic tholins dominate the near infrared reflectance spectrum with h2o ice contributing little or no detectable absorption at the 4 2 cm microwave wavelength of new horizons radio system arrokoth s winter night side glows with an average brightness temperature of 29 5 k this emission probably emerges from below the cold winter surface at depths where warmth from the previous summer lingers our models show that self radiation more than compensates for self shadowing in the neck region between the two lobes resulting in warmer temperatures in that region by up to a few kelvin conclusion the nearly uniform coloration across arrokoth is consistent with expectations for an object that accreted too quickly for the composition of the available nebular solids to have changed during the course of its accretion radiolysis and photolysis from long exposure to space radiation would be expected to result in a dark space weathered surface veneer that is distinct from the more pristine interior but there is little evidence for such a coating perhaps because radiolytically processed material is eroded away faster than it accumulates the abundance of ch3oh ice and apparent scarcity of h2o ice appear to be signatures of a distinct environment in the cold dust shaded midplane of the outer nebula during formation of the solar system in this region temperatures would have been low enough that volatile co and ch4 could freeze onto dust grains enabling production of ch3oh and perhaps also destruction of h2o when the nebular dust dissipated some time after arrokoth s formation exposure to sunlight would have raised its temperature rapidly driving off condensed co and ch4 the temperature has remained too cold to crystallize amorphous h2o volatile species may remain trapped in amorphous h2o ice within arrokoth s interior but the infrared spectrum shows little evidence for such ice at the surface although the neck region gets slightly warmer than the rest of arrokoth s surface this effect is small relative to the winter summer temperature contrast and is thus unlikely to account for the distinctly higher albedo and slightly less red material that is seen there a more plausible explanation for the neck s albedo and color contrasts involves texture changes induced by the merger of the two lobes or subsequent downslope movement of material there

solution for flow rates across the wellbore in a two zone confined aquifer a closed form solution for transient flow rates across the wellbore in a confined aquifer is derived from a two zone radial ground water flow equation subject to the boundary condition of keeping a constant head at the well radius an aquifer may be considered as a two zone system if the formation properties near the wellbore are significantly changed due to the well construction and or well development an efficient numerical approach is used to evaluate this newly derived solution values of the transient flow rate are provided in a tabular form and compared with those obtained by numerical inversion for the laplace domain solution the results show that the two solutions are in good agreement this newly derived solution can be used not only for predicting the transient flow rate across the wellbore but also for identifying the effects of a skin with a finite thickness on the estimation of transient flow rates in a ground water system with two different formation properties

westward motion of mesoscale eddies abstract since the pioneering work of nof the determination of the westward drift of mesoscale eddies under the planetary beta effect has been a recurrent theme in mesoscale oceanography and several different formulae have been proposed in the literature here recpatiulation is sought and within the confines of a single layer model a generalized formula is derived although it is similar to nof s the present formula is established from a modified definition and with fewer assumptions it also recaptiulates all other formulae for the one layer model and applies to a wide variety of situations including cases when the vortex develops a wake of rossby waves or undergoes axismmetrization following the derivation of the formula a physical interpretation clarifies the migration mechanism which can be divided between a self induced propulsion and a reaction from the displaced ambient fluid numerical simulations with primitive and geostrophic equations validate the formula for a variety of length sc

transient flow into a partially penetrating well during the constant head test in unconfined aquifers this study derives a semianalytical solution for drawdown distribution during a constant head test at a partially penetrating well in an unconfined aquifer the constant head condition is used to describe the boundary along the screen in addition a free surface condition is used to delineate the upper boundary of the unconfined aquifer the laplace domain solution is then derived using separation of variables and laplace transform this solution can be used to identify the aquifer parameters from the data of the constant head test when integrated with an optimization scheme or to investigate the effects of vertical flow caused by the partially penetrating well and free surface boundary in an unconfined aquifer

some aspects of vortex structure related to tropical cyclone motion abstract some effect of tropical cyclone structure on the vortex motion are examined in a nondivergent barotropic numerical model with no basic current as suggested earlier by demaria the initial maximum wind speed has little effect on the track vortex translation associated with the beta effect depends sensitively on the strength of the flow between 300 and 1000 km from the center if the flow in this annulus is made more cyclonic the track will turn cyclonically and move more toward the west in the northern hemisphere the dynamics of this beta drift is studied via a decomposition into symmetric and asymmetric circulations the symmetric flow experiences a slight weakening of the maximum wind speed and an anticyclonic circulation is induced beyond 600 km the asymmetric circulation is dominated by an azimuthal wavenumber one circulation with an anticyclonic gyre east of the center a cyclonic gyre to the west and a nearly uniform broad scale ventilation flow between the gyres the vortex translati

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

the pluto system initial results from its exploration by new horizons the pluto system was recently explored by nasa s new horizons spacecraft making closest approach on 14 july 2015 pluto s surface displays diverse landforms terrain ages albedos colors and composition gradients evidence is found for a water ice crust geologically young surface units surface ice convection wind streaks volatile transport and glacial flow pluto s atmosphere is highly extended with trace hydrocarbons a global haze layer and a surface pressure near 10 microbars pluto s diverse surface geology and long term activity raise fundamental questions about how small planets remain active many billions of years after formation pluto s large moon charon displays tectonics and evidence for a heterogeneous crustal composition its north pole displays puzzling dark terrain small satellites hydra and nix have higher albedos than expected

the evolution and propagation of quasigeostrophic ocean eddies abstractthe long term evolution of initially gaussian eddies is studied in a reduced gravity shallow water model using both linear and nonlinear quasigeostrophic theory in an attempt to understand westward propagating mesoscale eddies observed and tracked by satellite altimetry by examining both isolated eddies and a large basin seeded with eddies with statistical characteristics consistent with those of observed eddies it is shown that long term eddy coherence and the zonal wavenumber frequency power spectral density are best matched by the nonlinear model individual characteristics of the eddies including amplitude decay horizontal length scale decay and zonal and meridional propagation speed of a previously unrecognized quasi stable state are examined the results show that the meridional deflections from purely westward flow poleward for cyclones and equatorward for anticyclones are consistent with satellite observations examination of the fluid transport properties of the eddies shows that an

geological mapping of sputnik planitia on pluto abstract the geology and stratigraphy of the feature on pluto informally named sputnik planitia is documented through geologic mapping at 1 2 000 000 scale all units that have been mapped are presently being affected to some degree by the action of flowing n2 ice the n2 ice plains of sputnik planitia display no impact craters and are undergoing constant resurfacing via convection glacial flow and sublimation condensation of atmospheric n2 onto the surface to form a bright mantle has occurred across broad swathes of sputnik planitia and appears to be partly controlled by pluto s obliquity cycles the action of n2 ice has been instrumental in affecting uplands terrain surrounding sputnik planitia and has played a key role in the disruption of sputnik planitia s western margin to form chains of blocky mountain ranges as well in the extensive erosion by glacial flow of the uplands to the east of sputnik planitia

observed characteristics and vertical structure of mesoscale eddies in the southwest tropical pacific in the southwest pacific ocean waters transit from the subtropical gyre before being redistributed equatorward and poleward while the mean pathways are known the contribution to the mixing and transport of the water from mesoscale eddies has not been comprehensively investigated in this research satellite altimetry data combined with an eddy detection and tracking algorithm is used to investigate the distribution and surface characteristics of mesoscale eddies in this region of complex bathymetry 10 s 30 s 140 e 190 e detected eddies are then colocalized with in situ data from argo floats to determine their vertical structure and the effect of eddies on the water masses the numerous islands affect the eddy behavior as most eddies are formed in the lee of islands propagate westward and decay when encountering shallow bathymetry eddies are sparse and short lived in the tropical area north of fiji impacting only the top 200 meters of water they do not appear to be able to trap and transport waters in this region in the coral sea a region of lateral shear between currents transporting waters of different origins eddies are more numerous and energetic they affect the water properties down to at least 500 m depth and anticyclonic eddies trap water to 200 m contributing to the upper thermocline waters mixing and transport south of new caledonia mesoscale eddies are ubiquitous with typical lifetimes longer than 5 months they affect the temperature salinity and velocities down to 1 000 m depth and weakly contribute to the mixing of lower thermocline waters

pluto s haze as a surface material pluto s atmospheric haze settles out rapidly compared with geological timescales it needs to be accounted for as a surface material distinct from pluto s icy bedrock and from the volatile ices that migrate via sublimation and condensation on seasonal timescales this paper explores how a steady supply of atmospheric haze might affect three distinct provinces on pluto we pose the question of why they each look so different from one another if the same haze material is settling out onto all of them cthulhu is a more ancient region with comparatively little present day geological activity where the haze appears to simply accumulate over time sputnik planitia is a very active region where glacial convection as well as sublimation and condensation rapidly refresh the surface hiding recently deposited haze from view lowell regio is a region of intermediate age featuring very distinct coloration from the rest of pluto using a simple model haze particle as a colorant we are not able to match the colors in both lowell regio and cthulhu to account for their distinct colors we propose that after arrival at pluto s surface haze particles may be less inert than might be supposed from the low surface temperatures they must either interact with local materials and environments to produce distinct products in different regions or else the supply of haze must be non uniform in time and or location such that different products are delivered to different places

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent

constant head test in a leaky aquifer with a finite thickness skin summary constant head test is a commonly used aquifer testing method in groundwater hydrology a mathematical model for constant head test in a leaky aquifer with a finite thickness skin was developed in this study three different aquifer aquitard systems were considered and the laplace domain solutions were obtained and then inverted numerically with the stehfest method to yield the time domain solutions the well discharges for different cases were computed and a sensitivity analysis of the well discharge on different parameters was performed the results indicated that the dimensionless transmissivity of the aquitard had little effect on the well discharge at early times while a larger transmissivity of the aquitard leaded to a larger well discharge at late times the well discharge for the positive skin was smaller than that without the skin while the well discharge for the negative skin was larger than that without the skin where positive and negative skins refer to the cases in which the permeability values of the skin zones are less and greater than that of the formation zone respectively a thicker skin resulted in a smaller well discharge for the positive skin case but leaded to a larger well discharge for the negative skin case at late times we also found that the drawdown for the positive skin case was less than that for the negative skin case at the same time and a positive skin might result in delayed response of the aquifer to pumping the sensitivity analysis indicated that the well discharge was sensitive to the properties of the skin zone but not sensitive to the properties of the aquitards for the aquifer aquitard system presented in this study