The role of water ice clouds in the Martian hydrologic cycle

Science.gov (United States)

James, Philip B.

1990-01-01

A one-dimensional model for the seasonal cycle of water on Mars has been used to investigate the direction of the net annual transport of water on the planet and to study the possible role of water ice clouds, which are included as an independent phase in addition to ground ice and water vapor, in the cycle. The calculated seasonal and spatial patterns of occurrence of water ice clouds are qualitatively similar to the observed polar hoods, suggesting that these polar clouds are, in fact, an important component of water cycle. A residual dry ice in the south acts as a cold trap which, in the absence of sources other than the caps, will ultimately attract the water ice from the north cap; however, in the presence of a source of water in northern midlatitudes during spring, it is possible that the observed distribution of vapor and ice can be in a steady state even if a residual CO2 cap is a permanent feature of the system.

Additions and corrections to the absorption coefficients of CO2 ice: Applications to the Martian south polar cap

International Nuclear Information System (INIS)

Calvin, W.M.

1990-01-01

Reflectance spectra of carbon dioxide frosts were calculated using the optical constants provided by Warren (1986) for the wavelength region 2-6 μm. In comparing these calculated spectra to spectra of frosts observed in the laboratory and on the surface of Mars, problems in the optical constants presented by Warren (1986) became apparent. Absorption coefficients for CO 2 ice have been derived using laboratory reflectance measurements and the Hapke (1981) model for calculating diffuse reflectance. This provides approximate values in regions where no data were previously available and indicates where corrections to the compilation by Warren (1986) are required. Using these coefficients to calculate the reflectance of CO 2 ice at varying grain sizes indicates that a typical Mariner polar cap spectrum is dominated by absorptions due to CO 2 frost or ice at grain sizes that are quite large, probably of the order of millimeters to centimeters. There are indications of contamination of water frost or dust, but confirmation will require more precise absorption coefficients for solid CO 2 than can be obtained from the method used here

Ice exposures and landscape evolution in the Martian mid-latitudes

Science.gov (United States)

Dundas, C. M.; Bramson, A. M.; Ojha, L.; Wray, J. J.; Mellon, M. T.; Byrne, S.; McEwen, A. S.; Putzig, N. E.; Viola, D.; Sutton, S.

2017-12-01

The large-scale geographic distribution of Martian shallow ground ice is now relatively well-known, but the vertical structure of the ice is not as well understood. Here we report on erosional scarps in kilometer-scale pits near ±55-60 degrees latitude that expose cross-sections through ice-rich mantling deposits covering much of the mid-latitudes. HiRISE images of the scarps reveal ice-rich deposits (i.e., not regolith-pore-filling ice) that are >100 m thick and occur within 1 m of the top of the scarps. CRISM spectra confirm the presence of water ice through late summer, implying exposed ground ice rather than seasonal frost. SHARAD sounding radar data show some candidate reflectors similar to those inferred to be from the base of excess ice deposits elsewhere on Mars, but no internal structure is resolved. Ice-exposing impacts and thermokarst landforms convey information about excess ice abundance in the upper few meters, but not its deeper structure. The overall structure of the ice table is simple, with massive ice (sometimes layered) under a relatively thin lithic mantle, plus a boulder-rich interior lens in one scarp. The latter may be partly ice-cemented. The ice is commonly fractured. These observations demonstrate how deep ice sheets link with the shallow ice table, at least locally. The likely origin of the ice is accumulation of snow with some admixed dust during a different climate. This snow accumulation could be related to 370 ka changes observed at the poles [1] but some ice sheets may be tens of Myr old [2]. the origin of superposed boulder-sized rocks is puzzling; possible explanations include glacial flow, impact gardening, or some form of frost heave or cryoturbation. Repeat HiRISE observations demonstrate that the scarps are actively retreating, as boulders have fallen from one scarp and there are albedo changes elsewhere. This activity demonstrates that local sublimation is contributing to present-day Martian landscape evolution and is an

The projected demise of Barnes Ice Cap: Evidence of an unusually warm 21st century Arctic

Science.gov (United States)

Gilbert, A.; Flowers, G. E.; Miller, G. H.; Refsnider, K. A.; Young, N. E.; Radić, V.

2017-03-01

As a remnant of the Laurentide Ice Sheet, Barnes Ice Cap owes its existence and present form in part to the climate of the last glacial period. The ice cap has been sustained in the present interglacial climate by its own topography through the mass balance-elevation feedback. A coupled mass balance and ice-flow model, forced by Coupled Model Intercomparison Project Phase 5 climate model output, projects that the current ice cap will likely disappear in the next 300 years. For greenhouse gas Representative Concentration Pathways of +2.6 to +8.5 Wm-2, the projected ice-cap survival times range from 150 to 530 years. Measured concentrations of cosmogenic radionuclides 10Be, 26Al, and 14C at sites exposed near the ice-cap margin suggest the pending disappearance of Barnes Ice Cap is very unusual in the last million years. The data and models together point to an exceptionally warm 21st century Arctic climate.

Clouds in the Martian Atmosphere

Science.gov (United States)

Määttänen, Anni; Montmessin, Franck

2018-01-01

Although resembling an extremely dry desert, planet Mars hosts clouds in its atmosphere. Every day somewhere on the planet a part of the tiny amount of water vapor held by the atmosphere can condense as ice crystals to form cirrus-type clouds. The existence of water ice clouds has been known for a long time, and they have been studied for decades, leading to the establishment of a well-known climatology and understanding of their formation and properties. Despite their thinness, they have a clear impact on the atmospheric temperatures, thus affecting the Martian climate. Another, more exotic type of clouds forms as well on Mars. The atmospheric temperatures can plunge to such frigid values that the major gaseous component of the atmosphere, CO2, condenses as ice crystals. These clouds form in the cold polar night where they also contribute to the formation of the CO2 ice polar cap, and also in the mesosphere at very high altitudes, near the edge of space, analogously to the noctilucent clouds on Earth. The mesospheric clouds are a fairly recent discovery and have put our understanding of the Martian atmosphere to a test. On Mars, cloud crystals form on ice nuclei, mostly provided by the omnipresent dust. Thus, the clouds link the three major climatic cycles: those of the two major volatiles, H2O and CO2; and that of dust, which is a major climatic agent itself.

Correlating Ice Cores from Quelccaya Ice Cap with Chronology from Little Ice Age Glacial Extents

Science.gov (United States)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.

2010-12-01

Proxy records indicate Southern Hemisphere climatic changes during the Little Ice Age (LIA; ~1300-1850 AD). In particular, records of change in and around the tropical latitudes require attention because these areas are sensitive to climatic change and record the dynamic interplay between hemispheres (Oerlemans, 2005). Despite this significance, relatively few records exist for the southern tropics. Here we present a reconstruction of glacial fluctuations of Quelccaya Ice Cap (QIC), Peruvian Andes, from pre-LIA up to the present day. In the Qori Kalis valley, extensive sets of moraines exist beginning with the 1963 AD ice margin (Thompson et al., 2006) and getting progressively older down valley. Several of these older moraines can be traced and are continuous with moraines in the Challpa Cocha valley. These moraines have been dated at chronology of past ice cap extents are correlated with ice core records from QIC which show an accumulation increase during ~1500-1700 AD and an accumulation decrease during ~1720-1860 AD (Thompson et al., 1985; 1986; 2006). In addition, other proxy records from Peru and the tropics are correlated with the records at QIC as a means to understand climate conditions during the LIA. This work forms the basis for future modeling of the glacial system during the LIA at QIC and for modeling of past temperature and precipitation regimes at high altitude in the tropics.

Landscape Evolution and the Reincarnation of the Southern Residual Ice Cap

Science.gov (United States)

Byrne, S.; Zuber, M. T.

2006-10-01

Given the present rate of erosion on the southern residual ice cap, it is unlikely that any part of the cap is older than a few centuries. Unless we're lucky, why is there a residual cap present today for us to observe? We propose a solution involving constant destruction and renewal of the cap.

Mars polar cap: a habitat for elementary life1

Science.gov (United States)

Wallis, M. K.; Wickramasinghe, N. C.

2009-04-01

Ices in the Martian polar caps are potential habitats for various species of microorganisms. Salts in the ice and biological anti-freeze polymers maintain liquid in cracks in the ices far below 0°C, possibly down to the mean 220-240 K. Sub-surface microbial life is shielded from ultraviolet (UV) radiation, but could potentially be activated on south-facing slopes under the midday, midsummer Sun. Such life would be limited by low levels of vapour, little transport of nutrients, low light levels below a protective dirt-crust, frost accumulation at night and in shadows, and little if any active translocation of organisms. As in the Antarctic and in permafrost, movement to new habitats depends on geo-climatic changes, which for Mars's north polar cap occur on a 50 000 year scale, except for rare meteorite impacts.

The Gregoriev Ice Cap length changes derived by 2-D ice flow line model for harmonic climate histories

OpenAIRE

Konovalov, Y. V.; Nagornov, O. V.

2009-01-01

Different ice thickness distributions along the flow line and the flow line length changes of the Gregoriev Ice Cap, Terskey Ala-Tau, Central Asia, were obtained for some surface mass balance histories which can be considered as possible surface mass balances in the future. The ice cap modeling was performed by solving of steady state hydrodynamic equations in the case of low Reynolds number in the form of the mechanical equilibrium equation in terms of stress deviator components coupled with...

Mass balance of Greenland and the Canadian Ice Caps from combined altimetry and GRACE inversion

DEFF Research Database (Denmark)

Forsberg, René; Simonsen, Sebastian Bjerregaard; Sørensen, Louise Sandberg

The combination of GRACE and altimetry data may yield a high resolution mass balance time series of the Greenlandice sheet, highlighting the varying individual mass loss behaviour of major glaciers. By including the Canadian arctic ice caps in the estimation, a more reliable estimate of the mass...... loss of both Greenlandand the Canadian ice caps may be obtained, minimizing the leakage errors otherwise unavoidable by GRACE. Actually, the absolute value of the Greenlandice sheet mass loss is highly dependent on methods and how the effects of Arctic Canadian ice caps are separated in the GRACE...... loss of the ice caps and ice sheet basins for the period 2003-15. This period shows a marked increase of ice sheet melt, especially in NW and NE Greenland, but also show large variability, with the melt anomaly year of 2012 showing a record mass loss, followed by 2013 with essentially no Greenland mass...

delta 18O variations in snow on the Devon Island ice cap, Northwest Territories, Canada

International Nuclear Information System (INIS)

Koerner, R.; Russel, R.D.

1979-01-01

A study of delta 18 O variations of snow samples taken on traverses across the Devon Island ice cap in June 1971, 1972, and 1973 has shown a difference between the accumulation conditions on the souteast and nortwest sides of the ice cap. On the souteast side there is an increasing depletion of 18 O in the snow with increasing elevation. This pattern is attibuted to the effect of orographic uplift of air masses moving over the ice cap from the southeast, which promotes condensation and precipitation due to adiabatic cooling. On the northwest side of the ice cap there is no evidence of any further depletion of 18 O in snow, neither with increasing distance from the possible moisture source in Baffin Bay to the southeast nor with increasing elevation if the air mass comes from the northwest. In this case condensation is due to isobaric cooling so that precipitation is generally from level cloud bases. The changes inferred for the isotopic composition of the water vapour as it rises up the southeast slope are found to be consistent with its depletion through precipitation under near-equilibrium conditions. It is calculated that approximately 30% of the moisture at sea level on the southeast side of the ice cap and 8% at the top of the ice cap are of local origin. Lower temporal and aerial variability of the delta values on the southeast side of the ice cap is attributed to dominance of the Baffin Bay low on that side Effecting consistency of storm conditions there. The delta values of ice in the ablation zone on the Sverdrup Glacier show the combined effect of ice movement from the accumulation to the ablation zone and climatic change during the period of movement from cold to warm and back to cold conditions again. (auth)

Using Airborne SAR Interferometry to Measure the Elevation of a Greenland Ice Cap

DEFF Research Database (Denmark)

Dall, Jørgen; Keller, K.; Madsen, S.N.

2000-01-01

A digital elevation model (DEM) of an ice cap in Greenland has been generated from airborne SAR interferometry data, calibrated with a new algorithm, and compared with airborne laser altimetry profiles and carrier-phase differential GPS measurements of radar reflectors deployed on the ice cap...... with GPS data and calibrated laser data....

Landscape Evolution and the Reincarnation of the Residual CO2 Ice Cap of Mars

Science.gov (United States)

Byrne, S.; Zuber, M.

2006-12-01

Observations of the southern residual CO2 cap of Mars reveal a wide range of landforms including flat-floored quasi-circular pits with steep walls (dubbed Swiss-cheese features). Interannual comparisons show that these depressions are expanding laterally at rates of ~2m/yr to ~4m/yr, prompting suggestions of climate change. The residual CO2 ice cap is up to 10m thick and underlain by an involatile basement, it also contains layers roughly 2m thick representing different accumulation episodes in the recent past. Changes in the appearance of the residual ice between the Mariner 9 and Viking missions indicate that the top-most layer was deposited in that time-frame, soon after the global dust storm of 1971. The spatial density of the Swiss-cheese features, and the rate at which they expand, mean that it is unlikely that any part of the residual ice cap is older than a few centuries. Given this, we may ask: how can there be a residual cap present today for us to observe? To answer this and other questions we have developed a model to examine the evolution of a CO2 ice landscape. This model reproduces the morphologies and expansion rates seen in the actual residual CO2 ice cap. Our model results indicate that the fate of CO2 ice surfaces is controlled by their surface roughness. Surface roughness always increases with time, which results in an unstable situation. When the surface roughness exceeds a critical point small pits can begin to develop. The walls of these pits rapidly steepen and begin retreating which enlarges and deepens the pit. This situation always occurs even if the surface of the CO2 slab has a high enough albedo to have a net mass gain each year. Once these pits begin expanding they quickly erode the entire ice slab. When the underlying non-CO2 material is exposed, it will not frost over again if Mars were to repeat like clockwork every year. We conclude that interannual climatic variability is actually a requirement for the continued existence of a

Mass balance of the Amitsulôq ice cap, West Greenland

DEFF Research Database (Denmark)

Ahlstrøm, Andreas P.; Bøggild, Carl Egede; Olesen, Ole B.

2007-01-01

We present detailed mass balance measurements from the Amitsulôq ice cap in West Greenland spanning from 1982 to 1990. The data includes summer and winter balances from 26 stake locations distributed over five transects covering the whole ice cap. The mass balance measurements are combined...... with a recent satellite-derived digital elevation model to calculate the specific balance, which is in turn compared to discharge data from the adjacent Tasersiaq basin. The correlation between specific summer balance and discharge is R2 = 0.93 indicating that the basin discharge is dominated by glacial...... meltwater, linking the hydropower potential of the basin closely to the fate of the adjoining Greenland ice-sheet margin....

Looking Through the Ice: Searching for Past and Present Habitable Zones in the Martian North Polar Region Using MOLA DEMs

Science.gov (United States)

Payne, M. C.; Farmer, J. D.

2002-12-01

Hydrothermal systems have been acknowledged as important gateways to accessing a potential subsurface biology (extant or extinct) on Mars. Groundwater circulation, sustained for up to one billion years by large plutonic bodies (as modeled by previous authors), might well be capable of tapping into a deep subsurface biosphere and subsequently carrying members of microbial communities to the surface. Hence, future robotic missions with near surface drilling capabilities may be able to unearth cryopreserved biosignatures, or perhaps extant organisms, in the midst of the hydrothermal system itself. Digital Elevation Models (DEMs) constructed from Mars Orbiter Laser Altimeter (MOLA) data have proved to be a valuable tool in the search for potential habitable zones for extant and extinct life, and the detection of possible hydrothermal systems on Mars. When formatted for use in a Geographical Information Systems (GIS) software package such as ESRI's ArcView, MOLA data can be used to compose DEMs. Those DEMs can, in turn, be used to create contour maps, to allow profiling through features of interest, and to generate hillshaded views, which provide an image-like perspective of a selected area. Furthermore, DEMs eliminate many problems associated with photographic images such as over-/underexposure, poor focus, and albedo values too high or low for optimal observations. During this study, DEMs were used in the analysis of several regions north of 70° N latitude, in the Martian north polar cap and polar cap margin. The regions were selected during a Viking image survey that concentrated on the location of surface expressions of potential magma-ice interactions, and hence past or present hydrothermal activity. Specific features sought included individual volcanoes and volcanic fields, as well as pseudocrater fields, subglacial volcanic constructs (such as tuyas and tindar ridges), fluvial channels and outwash plains (indicative of j”kulhlaup flooding events), possible

Erosion patterns produced by the paleo Haizishan ice cap, SE Tibetan Plateau

Science.gov (United States)

Fu, P.; Stroeven, A. P.; Harbor, J.; Hättestrand, C.; Heyman, J.; Caffee, M. W.

2017-12-01

Erosion is a primary driver of landscape evolution, topographic relief production, geochemical cycles, and climate change. Combining in situ 10Be and 26Al exposure age dating, geomorphological mapping, and field investigations, we examine glacial erosion patterns of the almost 4,000 km2 paleo Haizishan ice cap on the southeastern Tibetan Plateau. Our results show that ice caps on the low relief Haizishan Plateau produced a zonal pattern of landscape modification. In locations where apparent exposure ages on bedrock are consistent with the last deglaciation, complete resetting of the cosmogenic exposure age clock indicates glacial erosion of at least a few meters. However, older apparent exposure ages on bedrock in areas known to have been covered by the paleo ice cap during the Last Glacial Maximum indicate inheritance and thus limited glacial erosion. Inferred surface exposure ages from cosmogenic depth profiles through two saprolites vary from resetting and thus saprolite profile truncation to nuclide inheritance indicating limited erosion. Finally, significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate limited glacial erosion during the last glaciation. Hence, for the first time, our study shows clear evidence of preservation under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the paleo Haizishan ice cap during the LGM.

Barnes Ice Cap South Dome Trilateration Net Survey Data 1970-1984

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Barnes Ice Cap data set contains survey measurements of a network of 43 stakes along a 10 km flow line on the northeast flank of the south dome of the Barnes Ice...

Evidence From Hydrogen Isotopes in Meteorites for a Martian Permafrost

Science.gov (United States)

Usui, T.; Alexander, C. M. O'D.; Wang, J.; Simon, J. I.; Jones, J. H.

2014-01-01

Fluvial landforms on Mars suggest that it was once warm enough to maintain persistent liquid water on its surface. The transition to the present cold and dry Mars is closely linked to the history of surface water, yet the evolution of surficial water is poorly constrained. We have investigated the evolution of surface water/ ice and its interaction with the atmosphere by measurements of hydrogen isotope ratios (D/H: deuterium/ hydrogen) of martian meteorites. Hydrogen is a major component of water (H2O) and its isotopes fractionate significantly during hydrological cycling between the atmosphere, surface waters, ground ice, and polar cap ice. Based on in situ ion microprobe analyses of three geochemically different shergottites, we reported that there is a water/ice reservoir with an intermediate D/H ratio (delta D = 1,000?2500 %) on Mars. Here we present the possibility that this water/ice reservoir represents a ground-ice/permafrost that has existed relatively intact over geologic time.

Barnes Ice Cap South Dome Trilateration Net Survey Data 1970-1984, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — The Barnes Ice Cap data set contains survey measurements of a network of 43 stakes along a 10 km flow line on the northeast flank of the south dome of the Barnes Ice...

Eddy transport of water vapor in the Martian atmosphere

Science.gov (United States)

Murphy, J. R.; Haberle, Robert M.

1993-01-01

Viking orbiter measurements of the Martian atmosphere suggest that the residual north polar water-ice cap is the primary source of atmospheric water vapor, which appears at successively lower northern latitudes as the summer season progresses. Zonally symmetric studies of water vapor transport indicate that the zonal mean meridional circulation is incapable of transporting from north polar regions to low latitudes the quantity of water vapor observed. This result has been interpreted as implying the presence of nonpolar sources of water. Another possibility is the ability of atmospheric wave motions, which are not accounted for in a zonally symmetric framework, to efficiently accomplish the transport from a north polar source to the entirety of the Northern Hemisphere. The ability or inability of the full range of atmospheric motions to accomplish this transport has important implications regarding the questions of water sources and sinks on Mars: if the full spectrum of atmospheric motions proves to be incapable of accomplishing the transport, it strengthens arguments in favor of additional water sources. Preliminary results from a three dimensional atmospheric dynamical/water vapor transport numerical model are presented. The model accounts for the physics of a subliming water-ice cap, but does not yet incorporate recondensation of this sublimed water. Transport of vapor away from this water-ice cap in this three dimensional framework is compared with previously obtained zonally symmetric (two dimensional) results to quantify effects of water vapor transport by atmospheric eddies.

King George Island ice cap geometry updated with airborne GPR measurements

Directory of Open Access Journals (Sweden)

M. Rückamp

2012-07-01

Full Text Available Ice geometry is a mandatory requirement for numerical modelling purposes. In this paper we present a consistent data set for the ice thickness, the bedrock topography and the ice surface topography of the King George Island ice cap (Arctowski icefield and the adjacent central part. The new data set is composed of ground based and airborne ground penetrating radar (GPR and differential GPS (DGPS measurements, obtained during several field campaigns. Blindow et al. (2010 already provided a comprehensive overview of the ground based measurements carried out in the safely accessible area of the ice cap. The updated data set incorporates airborne measurements in the heavily crevassed coastal areas. Therefore, in this paper special attention is paid to the airborne measurements by addressing the instrument used, survey procedure, and data processing in more detail. In particular, the inclusion of airborne GPR measurements with the 30 MHz BGR-P30-System developed at the Institute of Geophysics (University of Münster completes the picture of the ice geometry substantially. The compiled digital elevation model of the bedrock shows a rough, highly variable topography with pronounced valleys, ridges, and troughs. Mean ice thickness is 240 ± 6 m, with a maximum value of 422 ± 10 m in the surveyed area. Noticeable are bounded areas in the bedrock topography below sea level where marine based ice exists. The provided data set is required as a basis for future monitoring attempts or as input for numerical modelling experiments. The data set is available from the PANGAEA database at http://dx.doi.org/10.1594/PANGAEA.770567.

Test of Newton's inverse-square law in the Greenland ice cap

International Nuclear Information System (INIS)

Ander, M.E.; Zumberge, M.A.; Lautzenhiser, T.

1989-01-01

An Airy-type geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 and 1673 m to test for possible violations of Newton's inverse-square law. An anomalous gravity gradient was observed. We cannot unambiguously attribute it to a breakdown of Newtonian gravity because we have shown that it might be due to unexpected geological features in the rock below the ice

Crustal movements due to Iceland's shrinking ice caps mimic magma inflow signal at Katla volcano.

Science.gov (United States)

Spaans, Karsten; Hreinsdóttir, Sigrún; Hooper, Andrew; Ófeigsson, Benedikt Gunnar

2015-05-20

Many volcanic systems around the world are located beneath, or in close proximity to, ice caps. Mass change of these ice caps causes surface movements, which are typically neglected when interpreting surface deformation measurements around these volcanoes. These movements can however be significant, and may closely resemble movements due to magma accumulation. Here we show such an example, from Katla volcano, Iceland. Horizontal movements observed by GPS on the flank of Katla have led to the inference of significant inflow of magma into a chamber beneath the caldera, starting in 2000, and continuing over several years. We use satellite radar interferometry and GPS data to show that between 2001 and 2010, the horizontal movements seen on the flank can be explained by the response to the long term shrinking of ice caps, and that erratic movements seen at stations within the caldera are also not likely to signify magma inflow. It is important that interpretations of geodetic measurements at volcanoes in glaciated areas consider the effect of ice mass change, and previous studies should be carefully reevaluated.

Thermal infrared properties of the Martian atmosphere 4. Predictions of the presence of dust and ice clouds from Viking IRTM spectral measurements

International Nuclear Information System (INIS)

Hunt, G.E.

1979-01-01

In this paper we investigate the response of the Martian atmosphere at the wavelengths measured by the Viking infrared thermal mapper instrument (IRTM) to the presence of varying amounts of dust and water ice clouds. A detailed radiative transfer study is represented to show that these IRTM measurements at channels centered at 7, 9, 11, and 20 μm may be used to differentiate between the presence of dust and water ice clouds in the Martian atmosphere. They show further that these measurements may also be used to provide some information on the structure of the lower atmosphere. The use of the IRTM measurements in the manner we describe can provide information associated with the thermal characteristics of Martian dust storms

Glaciological and chemical studies on ice cores from Hans Tausen ice cap, Greenland

DEFF Research Database (Denmark)

Clausen, H.B.; Stampe, Mia; Hammer, C.U.

2001-01-01

The paper presents studies of various chemical and isotopical parameters from ice cores drilled in the northernmost located ice cap, Hans Tausen Iskappe, Pearyland, Greenland (HT). The 346 m main core (MC95) was drilled to bedrock in 1995 as well as a 35 m shallow core (SC95). A 60 m shallow core...... (SC75) and a 51 m shallow core (SC76) was drilled at two different positions in 1975 and 1976, respectively. A 6 m shallow core (SC94) was drilled in 1994. Continuous stable isotope records exist for all of these cores, total b-activity only from SC75 and SC76. Continuous ECM inferred acidity records...... exist along the 1995 cores (MC95 and SC95) and finally detailed records of dust and water soluble ion concentrations exist on selected parts of MC95. To determine a time scale for the ice core is an important prerequisite for the interpretation of other records. The age scale is based on acid layers...

Holocene glacier and climate variations in Vestfirðir, Iceland, from the modeling of Drangajökull ice cap

Science.gov (United States)

Anderson, Leif S.; Flowers, Gwenn E.; Jarosch, Alexander H.; Aðalgeirsdóttir, Guðfinna Th; Geirsdóttir, Áslaug; Miller, Gifford H.; Harning, David J.; Thorsteinsson, Thorsteinn; Magnússon, Eyjólfur; Pálsson, Finnur

2018-06-01

Drangajökull is a maritime ice cap located in northwest (Vestfirðir) Iceland. Drangajökull's evolution is therefore closely linked to atmospheric and ocean variability. In order to better constrain the Holocene climate and glacier history of Vestfirðir we model the past evolution of Drangajökull ice cap. Simulations from 10 ka to present are forced by general circulation model output, ice-core-based temperature reconstructions, and sea-surface temperature reconstructions. Based on these 10-thousand year simulations, Drangajökull did not persist through the Holocene. We estimate that air temperatures were 2.5-3.0 °C higher during the Holocene Thermal Maximum than the local 1960-1990 average. Simulations support Drangajökull's late Holocene inception between 2 and 1 ka, though intermittent ice likely occupied cirques as early as 2.6 ka. Drangajökull is primarily a Little Ice Age ice cap: it expanded between 1300 and 1750 CE, with the most rapid growth occurring between 1600 and 1750 CE. The maximum Holocene extent of Drangajökull occurred between 1700 and 1925 CE, despite the lowest late Holocene temperatures, occurring between 1650 and 1720 CE. Between 1700 and 1925 CE temperatures were likely 0.6-0.8 °C lower than the 1950-2015 reference temperature. The modern equilibrium line altitude (ELA) is bracketed by topographic thresholds: a 1 °C temperature increase from the modern ELA would eliminate the ice cap's accumulation area, while a reduction of 0.5 °C would lead to the rapid expansion of the ice cap across Vestfirðir. The proximity of Drangajökull to topographic thresholds may explain its late inception and rapid expansion during the Little Ice Age.

Glaciers and ice caps outside Greenland

Science.gov (United States)

Sharp, Marin; Wolken, G.; Burgess, D.; Cogley, J.G.; Copland, L.; Thomson, L.; Arendt, A.; Wouters, B.; Kohler, J.; Andreassen, L.M.; O'Neel, Shad; Pelto, M.

2015-01-01

Mountain glaciers and ice caps cover an area of over 400 000 km2 in the Arctic, and are a major influence on global sea level (Gardner et al. 2011, 2013; Jacob et al. 2012). They gain mass by snow accumulation and lose mass by meltwater runoff. Where they terminate in water (ocean or lake), they also lose mass by iceberg calving. The climatic mass balance (Bclim, the difference between annual snow accumulation and annual meltwater runoff) is a widely used index of how glaciers respond to climate variability and change. The total mass balance (ΔM) is defined as the difference between annual snow accumulation and annual mass losses (by iceberg calving plus runoff).

The evolution of the englacial temperature distribution in the superimposed ice zone of a polar ice cap during a summer season

NARCIS (Netherlands)

Greuell, W.; Oerlemans, J.

1989-01-01

The aim of the present investigation was to provide more insight into the processes affecting the evolution of the englacial temperature distribution at a non-temperate location on a glacier. Measurements were made in the top 10 m of the ice at the summit of Laika Ice Cap (Canadian Arctic)

Variability of Seasonal CO2 Ice Caps on Mars for Mars Years 26 through 29

Science.gov (United States)

Feldman, W. C.; Maurice, S.; Prettyman, T. H.

2011-12-01

We have developed an improved thermal, epithermal, and fast neutron counting-rate time series data of the Mars Odyssey Neutron Spectrometer (MONS), optimized to greatly reduce both statistical and systematic uncertainties. This new data set was applied to study temporal and spatial distributions of the growth, decay, and maximum amount of precipitated CO2 ice during Martian years (MY) 26, 27, 28, and 29. For this study, we concentrate on the epithermal counting rate detected using the down-looking prism (P1) of MONS, and a combination of the epithermal and thermal counting rate detected by the forward-looking sensor (P2) of MONS. Although the energy range of neutrons detected by P2 covers both the thermal and epithermal range, it is heavily weighted to the thermal range. We find that the variance of the maximum epithermal counting rate is remarkably small over both north and south seasonal caps, varying by less than 3% over the four-year period. In contrast, although the maximum P2 counting rate over both poles is sensibly the same within error bars (about 2%) during the first three years, it drops by 18% over the north pole and 8% over the south pole during MY 29. The most-likely explanation of this drop is that abundances of the non-condensable gases N2 and Ar, are unusually enhanced during MY 29. Movies were also made of maps of the growth and decay of P2 counting rates summed over the first three years of these data. Careful inspection shows that both the growth and decay in the north were cylindrically symmetric, centered near the geographic north pole. In contrast, both the growth and decay of CO2 buildup in the south were skewed off the geographic pole to the center of the CO2 residual cap, and contained a small, but definitely distinct ring-like annular enhancement centered at a latitude of about 83.5° S spread over a longitude range that extends between about -35° and +35° E. This arc runs parallel to, and overlays, the very steep drop in altitude from

A Chronology of Late-Glacial and Holocene Advances of Quelccaya Ice Cap, Peru, Based on 10Be and Radiocarbon Dating

Science.gov (United States)

Kelly, M. A.; Lowell, T. V.; Schaefer, J. M.

2007-12-01

The Quelccaya Ice Cap region in the southeastern Peruvian Andes (~13-14°S latitude) is a key location for the development of late-glacial and Holocene terrestrial paleoclimate records in the tropics. We present a chronology of past extents of Quelccaya Ice Cap based on ~thirty internally consistent 10Be dates of boulders on moraines and bedrock as well as twenty radiocarbon dates of organic material associated with moraines. Based on results from both dating methods, we suggest that significant advances of Quelccaya Ice Cap occurred during late-glacial time, at ~12,700-11,400 yr BP, and during Late Holocene time ~400-300 yr BP. Radiocarbon dating of organic material associated with moraines provides maximum and minimum ages for ice advances and recessions, respectively, thus providing an independent check on 10Be dates of boulders on moraines. The opportunity to use both 10Be and radiocarbon dating makes the Quelccaya Ice Cap region a potentially important low-latitude calibration site for production rates of cosmogenic nuclides. Our radiocarbon chronology provides a tighter constraint on maximum ages of late-glacial and Late Holocene ice advances. Upcoming field research will obtain organic material for radiocarbon dating to improve minimum age constrains for late-glacial and Late Holocene ice recessions.

Possible significance of cubic water-ice, H2O-Ic, in the atmospheric water cycle of Mars

Science.gov (United States)

Gooding, James L.

1988-01-01

The possible formation and potential significance of the cubic ice polymorph on Mars is discussed. When water-ice crystallizes on Earth, the ambient conditions of temperature and pressure result in the formation of the hexagonal ice polymorph; however, on Mars, the much lower termperature and pressures may permit the crystallization of the cubic polymorph. Cubic ice has two properties of possible importance on Mars: it is an excellant nucleator of other volatiles (such as CO2), and it undergoes an exothermic transition to hexagonal ice at temperatures above 170 K. These properties may have significant implications for both martian cloud formation and the development of the seasonal polar caps.

High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution.

Science.gov (United States)

Lecavalier, Benoit S; Fisher, David A; Milne, Glenn A; Vinther, Bo M; Tarasov, Lev; Huybrechts, Philippe; Lacelle, Denis; Main, Brittany; Zheng, James; Bourgeois, Jocelyne; Dyke, Arthur S

2017-06-06

We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4-5 °C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800-7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland.

Calibrating a surface mass-balance model for Austfonna ice cap, Svalbard

Science.gov (United States)

Schuler, Thomas Vikhamar; Loe, Even; Taurisano, Andrea; Eiken, Trond; Hagen, Jon Ove; Kohler, Jack

2007-10-01

Austfonna (8120 km2) is by far the largest ice mass in the Svalbard archipelago. There is considerable uncertainty about its current state of balance and its possible response to climate change. Over the 2004/05 period, we collected continuous meteorological data series from the ice cap, performed mass-balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground-penetrating radar along several profile lines. These data are used to drive and test a model of the surface mass balance. The spatial accumulation pattern was derived from the snow depth profiles using regression techniques, and ablation was calculated using a temperature-index approach. Model parameters were calibrated using the available field data. Parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably. Testing model results against multiple criteria is an efficient method to cope with non-uniqueness. In doing so, a range of different data and observations was compared to several different aspects of the model results. We find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation, which suggests that refreezing processes play an important role. To represent these effects in the model, a simple PMAX approach was included in its formulation. Used as a diagnostic tool, the model suggests that the surface mass balance for the period 29 April 2004 to 23 April 2005 was negative (-318 mm w.e.).

Holocene fluctuations of Quelccaya Ice Cap, Peru based on lacustrine and surficial geologic archives

Science.gov (United States)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.

2013-12-01

Peru's Quelccaya Ice Cap (QIC; 13.9°S, 70.8°W, ~5200-5670 m asl) is an important site for understanding tropical paleoclimate, mainly because of annually layered ice cores that provide an ~1800 year long record of tropical paleoclimatic conditions (e.g., Thompson et al., 2013). Here, we present a detailed record of QIC fluctuations using surficial deposits and lake sediments that extend back to late glacial time. We compare the late Holocene records of QIC 10Be-dated moraines and ice core data with lake sediments from a nearby glacially fed lake to establish the framework we use to interpret a Holocene long sediment record from a glacially fed lake. We also examine sediments from a nearby non-glacial lake to constrain non-glacial clastic input. We collected two ~5 m-long sediment cores, one from Laguna Challpacocha, which is currently fed by QIC meltwater, and one from the Laguna Yanacocha, which has not received QIC meltwater since ~12.3 ka. Changes in magnetic susceptibility, loss on ignition, bulk density and X-ray fluorescence chemistry combined with 14C and 210Pb chronologies provide information about sediment transported to the lakes. Retreat from the late Holocene extent defined by the 10Be-dated moraine record (~0.52 ka) is contemporaneous with a sharp transition from organic to clastic sedimentation in the Challpacocha core at ~ 0.52 ka. This implies that glacially-sourced clastic sedimentation, as tracked by loss on ignition, Ti counts and bulk density, increased during ice cap recession. Based on these same proxy data, we suggest the following Holocene history of QIC: QIC receded from the Challpacocha basin by ~10.6 ka. Increased clastic sedimentation at 8.2 - 4.1, 3.6 - 2.7 ka and from 0.55 ka - present are interpreted as times of ice cap recession. The increased clastic sedimentation at ~8.2 - 4.1 ka is consistent with surficial deposits near the present-day ice margin that indicate that at ~7.0 - 4.6 ka QIC was smaller than at present (Buffen et al

Earth analogs for Martian life - Microbes in evaporites, a new model system for life on Mars

Science.gov (United States)

Rothschild, Lynn J.

1990-01-01

It is suggested that 'oases' in which life forms may persist on Mars could occur, by analogy with terrestrial cases, in (1) rocks, as known in endolithic microorganisms, (2) polar ice caps, as seen in snow and ice algae, and (3) volcanic regions, as witnessed in the chemoautotrophs which live in ocean-floor hydrothermal vents. Microorganisms, moreover, have been known to survive in salt crystals, and it has even been shown that organisms can metabolize while encrusted in evaporites. Evaporites which may occur on Mars would be able to attenuate UV light, while remaining more transparent to the 400-700 nm radiation useful in photosynthesis. Suggestions are made for the selection of Martian exobiological investigation sites.

Simulations of the general circulation of the Martian atmosphere. I - Polar processes

Science.gov (United States)

Pollack, James B.; Haberle, Robert M.; Schaeffer, James; Lee, Hilda

1990-01-01

Numerical simulations of the Martian atmosphere general circulation are carried out for 50 simulated days, using a three-dimensional model, based on the primitive equations of meteorology, which incorporated the radiative effects of atmospheric dust on solar and thermal radiation. A large number of numerical experiments were conducted for alternative choices of seasonal date and dust optical depth. It was found that, as the dust content of the winter polar region increased, the rate of atmospheric CO2 condensation increased sharply. It is shown that the strong seasonal variation in the atmospheric dust content observed might cause a number of hemispheric asymmetries. These asymmetries include the greater prevalence of polar hoods in the northern polar region during winter, the lower albedo of the northern polar cap during spring, and the total dissipation of the northern CO2 ice cap during the warmer seasons.

A new field experiment in the Greenland ice cap to test Newton's inverse square law

International Nuclear Information System (INIS)

Ander, M.E.; Nieto, M.M.; Zumberge, M.A.; Parker, R.L.; Lautzenhiser, T.; Aiken, C.L.V.; Ferguson, J.F.; McMechan, G.A.

1989-01-01

Recent experimental evidence suggests that Newton's law of gravity may not be precise. There are modern theories of quantum gravity that, in their attempts to unify gravity with other forces of nature, predict non-Newtonian gravitational forces that could have ranges on the order of 10 2 --10 5 m. If they exist, these forces would be apparent as violations of Newton's inverse square law. A geophysical experiment was carried out to search for possible finite-range, non-Newtonian gravity over depths of 213--1673 m in the glacial ice of the Greenland ice cap. The principal reason for this choice of experimental site is that a hole drilled through the ice cap already existed and the uniformity of the ice eliminates one of the major sources of uncertainty arising in the first of earlier studies, namely, the heterogeneity of the rocks through which a mine shaft or drill hole passes. This paper presents observations made in the summer of 1987 at Dye 3, Greenland, in the 2033-m-deep borehole, which reached the basement rock

Martian extratropical cyclones

Science.gov (United States)

Hunt, G. E.; James, P. B.

1979-01-01

Physical properties of summer-season baroclinic waves on Mars are discussed on the basis of vidicon images and infrared thermal mapping generated by Viking Orbiter 1. The two northern-hemisphere storm systems examined here appear to be similar to terrestrial mid-latitude cyclonic storms. The Martian storm clouds are probably composed of water ice, rather than dust or CO2 ice particles.

Sharply increased mass loss from glaciers and ice caps in the Canadian Arctic Archipelago.

Science.gov (United States)

Gardner, Alex S; Moholdt, Geir; Wouters, Bert; Wolken, Gabriel J; Burgess, David O; Sharp, Martin J; Cogley, J Graham; Braun, Carsten; Labine, Claude

2011-05-19

Mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond. The Canadian Arctic Archipelago, located off the northwestern shore of Greenland, contains one-third of the global volume of land ice outside the ice sheets, but its contribution to sea-level change remains largely unknown. Here we show that the Canadian Arctic Archipelago has recently lost 61 ± 7 gigatonnes per year (Gt yr(-1)) of ice, contributing 0.17 ± 0.02 mm yr(-1) to sea-level rise. Our estimates are of regional mass changes for the ice caps and glaciers of the Canadian Arctic Archipelago referring to the years 2004 to 2009 and are based on three independent approaches: surface mass-budget modelling plus an estimate of ice discharge (SMB+D), repeat satellite laser altimetry (ICESat) and repeat satellite gravimetry (GRACE). All three approaches show consistent and large mass-loss estimates. Between the periods 2004-2006 and 2007-2009, the rate of mass loss sharply increased from 31 ± 8 Gt yr(-1) to 92 ± 12 Gt yr(-1) in direct response to warmer summer temperatures, to which rates of ice loss are highly sensitive (64 ± 14 Gt yr(-1) per 1 K increase). The duration of the study is too short to establish a long-term trend, but for 2007-2009, the increase in the rate of mass loss makes the Canadian Arctic Archipelago the single largest contributor to eustatic sea-level rise outside Greenland and Antarctica.

Martian surface

International Nuclear Information System (INIS)

Carr, M.H.

1987-01-01

The surface of Mars is characterized on the basis of reformatted Viking remote-sensing data, summarizing results published during the period 1983-1986. Topics examined include impact craters, ridges and faults, volcanic studies (modeling of surface effects on volcanic activity, description and interpretation of volcanic features, and calculations on lava-ice interactions), the role of liquid water on Mars, evidence for abundant ground ice at high latitudes, water-cycle modeling, and the composition and dynamics of Martian dust

110 years of local glacier and ice cap changes in Central- and North East Greenland

Science.gov (United States)

Bjork, A. A.; Aagaard, S.; Kjaer, K. H.; Khan, S. A.; Box, J.

2014-12-01

The local glaciers and ice caps of Greenland are becoming more apparent players in global sea-level rise, and their contribution to future changes is significant. Very little information on their historical fluctuations exists as much of the focus has been on the Greenland Ice Sheet. Now, we can for the first time present historic data that spans 110 years for more than 200 of the local glaciers and ice caps covering this large and important region of the Arctic. The central- and north eastern part of Greenland is of particular interest as these areas are predicted to exhibit a more active behavior with higher mass loss in the future - simultaneously with an increase in precipitation. Our results show that the glaciers and ice caps in the region are responding very rapidly to changes in temperature and precipitation. The present retreat is the fastest observed within the last eight decades, only surpassed by the rapid post LIA retreat. The 1930s was the golden era for scientific exploration in Central- and North East Greenland as several large expeditions visited the area and photographed from land, sea and air. We use historic recordings from Danish and Norwegian aerial missions and terrestrial recordings from the renowned American Explorer Louise Boyd. These unique pictures from the early 1930s form the backbone of the study and are supplemented the more recent aerial photographs the 1940s and onwards and satellite imagery from the mid-1960s and up until present. From high resolution aerial photographs we are able to map the maximum extent of the glaciers during the LIA (Little Ice Age), from which retreat in this area is estimated to commence in 1900. Using a new SMB (Surface Mass Balance) model and its components covering the entire observational period along with high resolution DEMs and historic sea-ice records we are now able to extract valuable information on the past and present triggers of glacial change.

Constraints on the Within Season and Between Year Variability of the North Residual Cap from MGS-TES

Science.gov (United States)

Calvin, W. M.; Titus, T. N.; Mahoney, S. A.

2003-01-01

There is a long history of telescopic and spacecraft observations of the polar regions of Mars. The finely laminated ice deposits and surrounding layered terrains are commonly thought to contain a record of past climate conditions and change. Understanding the basic nature of the deposits and their mineral and ice constituents is a continued focus of current and future orbited missions. Unresolved issues in Martian polar science include a) the unusual nature of the CO2 ice deposits ("Swiss Cheese", "slab ice" etc.) b) the relationship of the ice deposits to underlying layered units (which differs from the north to the south), c) understanding the seasonal variations and their connections to the finely laminated units observed in high-resolution images and d) the relationship of dark materials in the wind-swept lanes and reentrant valleys to the surrounding dark dune and surface materials. Our work focuses on understanding these issues in relationship to the north residual ice cap. Recent work using Mars Global Surveyor (MGS) data sets have described evolution of the seasonal CO2 frost deposits. In addition, the north polar residual ice cap exhibits albedo variations between Mars years and within the summer season. The Thermal Emission Spectrometer (TES) data set can augment these observations providing additional constraints such as temperature evolution and spectral properties associated with ice and rocky materials. Exploration of these properties is the subject of our current study.

Environmental Effects on Volcanic Eruptions:From Deep Ocean to Deep Space. Chapter 3. Volcanism and Ice Interactions on Earth and Mars. Chapter 3

Science.gov (United States)

Chapman, Mary G.; Allen, Carlton C.; Gudmundsson, Magnus T.; Gulick, Virginia C.; Jakobsson, Sveinn P.; Lucchitta, Baerbel K.; Skilling, Ian P.; Waitt, Richard B.

2000-01-01

CONCLUSION Volcano/ice interactions produce meltwater. Meltwater can enter the groundwater cycle and under the influence of hydrothermal systems, it can be later discharged to form channels and valleys or cycled upward to melt permafrost. Water or ice-saturated ground can erupt into phreatic craters when covered by lava. Violent mixing of meltwater and volcanic material and rapid release can generate lahars or jokulhlaups, that have the ability to freight coarse material, great distances downslope from the vent. Eruption into meltwater generate unique appearing edifices, that are definitive indicators of volcano/ice interaction. These features are hyaloclastic ridges or mounds and if capped by lava, tuyas. On Earth, volcano/ice interactions are limited to alpine regions and ice-capped polar and temperate regions. On Mars, where precipitation may be an ancient phenomenon, these interactions may be limited to areas of ground ice accumulation or the northern lowlands where water may have ponded fairly late in martian history. The recognition of features caused by volcano/ice interactions could provide strong constraints for the history of volatiles on Mars.

Constraints on martian lobate debris apron evolution and rheology from numerical modeling of ice flow

Science.gov (United States)

Parsons, Reid A.; Nimmo, Francis; Miyamoto, Hideaki

2011-07-01

Radar observations in the Deuteronilus Mensae region by Mars Reconnaissance Orbiter have constrained the thickness and dust concentration found within mid-latitude ice deposits, providing an opportunity to more accurately estimate the rheology of ice responsible for the formation of lobate debris aprons based on their apparent age of ˜100 Myr. We developed a numerical model simulating ice flow under martian conditions using results from ice deformation experiments, theory of ice grain growth based on terrestrial ice cores, and observational constraints from radar profiles and laser altimetry. By varying the ice grain size, the ice temperature, the subsurface slope, and the initial ice volume we determine the combination of parameters that best reproduce the observed LDA lengths and thicknesses over a period of time comparable to the apparent ages of LDA surfaces (90-300 Myr). We find that an ice temperature of 205 K, an ice grain size of 5 mm, and a flat subsurface slope give reasonable ages for many LDAs in the northern mid-latitudes of Mars. Assuming that the ice grain size is limited by the grain boundary pinning effect of incorporated dust, these results limit the dust volume concentration to less than 4%. However, assuming all LDAs were emplaced by a single event, we find that there is no single combination of grain size, temperature, and subsurface slope which can give realistic ages for all LDAs, suggesting that some or all of these variables are spatially heterogeneous. Based on our model we conclude that the majority of northern mid-latitude LDAs are composed of clean (⩽4 vol%), coarse (⩾1 mm) grained ice, but regional differences in either the amount of dust mixed in with the ice, or in the presence of a basal slope below the LDA ice must be invoked. Alternatively, the ice temperature and/or timing of ice deposition may vary significantly between different mid-latitude regions. Either eventuality can be tested with future observations.

Formation of recent martian debris flows by melting of near-surface ground ice at high obliquity.

Science.gov (United States)

Costard, F; Forget, F; Mangold, N; Peulvast, J P

2002-01-04

The observation of small gullies associated with recent surface runoff on Mars has renewed the question of liquid water stability at the surface of Mars. The gullies could be formed by groundwater seepage from underground aquifers; however, observations of gullies originating from isolated peaks and dune crests question this scenario. We show that these landforms may result from the melting of water ice in the top few meters of the martian subsurface at high obliquity. Our conclusions are based on the analogy between the martian gullies and terrestrial debris flows observed in Greenland and numerical simulations that show that above-freezing temperatures can occur at high obliquities in the near surface of Mars, and that such temperatures are only predicted at latitudes and for slope orientations corresponding to where the gullies have been observed on Mars.

The Penetration of Solar Radiation Into Carbon Dioxide Ice

Science.gov (United States)

Chinnery, H. E.; Hagermann, A.; Kaufmann, E.; Lewis, S. R.

2018-04-01

Icy surfaces behave differently to rocky or regolith-covered surfaces in response to irradiation. A key factor is the ability of visible light to penetrate partially into the subsurface. This results in the solid-state greenhouse effect, as ices can be transparent or translucent to visible and shorter wavelengths, while opaque in the infrared. This can lead to significant differences in shallow subsurface temperature profiles when compared to rocky surfaces. Of particular significance for modeling the solid-state greenhouse effect is the e-folding scale, otherwise known as the absorption scale length, or penetration depth, of the ice. While there have been measurements for water ice and snow, pure and with mixtures, to date, there have been no such measurements published for carbon dioxide ice. After an extensive series of measurements we are able to constrain the e-folding scale of CO2 ice for the cumulative wavelength range 300 to 1,100 nm, which is a vital parameter in heat transfer models for the Martian surface, enabling us to better understand surface-atmosphere interactions at Mars' polar caps.

The Mars water cycle at other epochs: Recent history of the polar caps and layered terrain

Science.gov (United States)

Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

1992-01-01

The Martian polar caps and layered terrain presumably evolves by the deposition and removal of small amounts of water and dust each year, the current cap attributes therefore represent the incremental transport during a single year as integrated over long periods of time. The role was studied of condensation and sublimation of water ice in this process by examining the seasonal water cycle during the last 10(exp 7) yr. In the model, axial obliquity, eccentricity, and L sub s of perihelion vary according to dynamical models. At each epoch, the seasonal variations in temperature are calculated at the two poles, keeping track of the seasonal CO2 cap and the summertime sublimation of water vapor into the atmosphere; net exchange of water between the two caps is calculated based on the difference in the summertime sublimation between the two caps (or on the sublimation from one cap if the other is covered with CO2 frost all year). Results from the model can help to explain (1) the apparent inconsistency between the timescales inferred for layer formation and the much older crater retention age of the cap and (2) the difference in sizes of the two residual caps, with the south being smaller than the north.

High resolution spectroscopy of the Martian atmosphere - Study of seasonal variations of CO, O3, H2O, and T on the north polar cap and a search for SO2, H2O2, and H2CO

Science.gov (United States)

Krasnopolsky, V. A.; Chakrabarti, S.; Larson, H.; Sandel, B. R.

1992-01-01

An overview is presented of an observational campaign which will measure (1) the seasonal variations of the CO mixing ratio on the Martian polar cap due to accumulation and depletion of CO during the condensation and evaporation of CO2, as well as (2) the early spring ozone and water vapor of the Martian north polar cap, and (3) the presence of H2CO, H2O2, and SO2. The lines of these compounds will be measured by a combined 4-m telescope and Fourier-transform spectrometer 27097.

Recent mass balance of the Purogangri Ice Cap, central Tibetan Plateau, by means of differential X-band SAR interferometry

Directory of Open Access Journals (Sweden)

N. Neckel

2013-10-01

Full Text Available Due to their remoteness, altitude and harsh climatic conditions, little is known about the glaciological parameters of ice caps on the Tibetan Plateau. This study presents a geodetic mass balance estimate of the Purogangri Ice Cap, Tibet's largest ice field between 2000 and 2012. We utilized data from the actual TerraSAR-X mission and its add-on for digital elevation measurements and compared it with elevation data from the Shuttle Radar Topography Mission. The employed data sets are ideal for this approach as both data sets were acquired at X-band at nearly the same time of the year and are available at a fine grid spacing. In order to derive surface elevation changes we employed two different methods. The first method is based on differential synthetic radar interferometry while the second method uses common DEM differencing. Both approaches revealed a slightly negative mass budget of −44 ± 15 and −38 ± 23 mm w.eq. a−1 (millimeter water equivalent respectively. A slightly negative trend of −0.15 ± 0.01 km2 a−1 in glacier extent was found for the same time period employing a time series of Landsat data. Overall, our results show an almost balanced mass budget for the studied time period. Additionally, we detected one continuously advancing glacier tongue in the eastern part of the ice cap.

High Artic Glaciers and Ice Caps Ice Mass Change from GRACE, Regional Climate Model Output and Altimetry.

Science.gov (United States)

Ciraci, E.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.

2016-12-01

The Arctic hosts more than the 75% of the ice covered regions outside from Greenland and Antarctica. Available observations show that increased atmospheric temperatures during the last century have contributed to a substantial glaciers retreat in all these regions. We use satellite gravimetry by the NASA's Gravity Recovery and Climate Experiment (GRACE), and apply a least square fit mascon approach to calculate time series of ice mass change for the period 2002-2016. Our estimates show that arctic glaciers have constantly contributed to the sea level rise during the entire observation period with a mass change of -170+/-20 Gt/yr equivalent to the 80% of the total ice mass change from the world Glacier and Ice Caps (GIC) excluding the Ice sheet peripheral GIC, which we calculated to be -215+/-32 GT/yr, with an acceleration of 9+/-4 Gt/yr2. The Canadian Archipelago is the main contributor to the total mass depletion with an ice mass trend of -73+/-9 Gt/yr and a significant acceleration of -7+/-3 Gt/yr2. The increasing mass loss is mainly determined by melting glaciers located in the northern part of the archipelago.In order to investigate the physical processes driving the observed ice mass loss we employ satellite altimetry and surface mass balance (SMB) estimates from Regional climate model outputs available for the same time period covered by the gravimetry data. We use elevation data from the NASA ICESat (2003-2009) and ESA CryoSat-2 (2010-2016) missions to estimate ice elevation changes. We compare GRACE ice mass estimates with time series of surface mass balance from the Regional Climate Model (RACMO-2) and the Modèle Atmosphérique Régional (MAR) and determine the portion of the total mass change explained by the SMB signal. We find that in Iceland and in the and the Canadian Archipelago the SMB signal explains most of the observed mass changes, suggesting that ice discharge may play a secondary role here. In other region, e.g. in Svalbar, the SMB signal

Martian Radiative Transfer Modeling Using the Optimal Spectral Sampling Method

Science.gov (United States)

Eluszkiewicz, J.; Cady-Pereira, K.; Uymin, G.; Moncet, J.-L.

2005-01-01

The large volume of existing and planned infrared observations of Mars have prompted the development of a new martian radiative transfer model that could be used in the retrievals of atmospheric and surface properties. The model is based on the Optimal Spectral Sampling (OSS) method [1]. The method is a fast and accurate monochromatic technique applicable to a wide range of remote sensing platforms (from microwave to UV) and was originally developed for the real-time processing of infrared and microwave data acquired by instruments aboard the satellites forming part of the next-generation global weather satellite system NPOESS (National Polarorbiting Operational Satellite System) [2]. As part of our on-going research related to the radiative properties of the martian polar caps, we have begun the development of a martian OSS model with the goal of using it to perform self-consistent atmospheric corrections necessary to retrieve caps emissivity from the Thermal Emission Spectrometer (TES) spectra. While the caps will provide the initial focus area for applying the new model, it is hoped that the model will be of interest to the wider Mars remote sensing community.

Peruvian Tropical Glacier May Survive Longer Than Previously Thought: Landsat Image Analysis of Nevado Coropuna Ice Cap, Peru

Science.gov (United States)

Kochtitzky, W. H.; Edwards, B. R.; Marino, J.; Manrique, N.

2015-12-01

Nevado Coropuna is a large volcanic complex in southern Peru (15.56°S, 72.62°N; 6,425 m). The complex is approximately 12 km east-west and 8 km north-south with elevation from ~4,500 m at the base to over 6,000 m at the highest points. This ice cap is the largest hosted by a volcano in the tropics, and one of the ten biggest ice masses in the tropics. Previous workers have predicted that the Coropuna ice cap will completely melt by 2050. We present a new analysis of historic satellite imagery to test this hypothesis. In this study, ice and snow are classified based on unique spectral signatures including spectral band thresholds, Normalized Difference Snow Index, and Band 4/5 ratio. Landsat scenes (L2, 4, 5, 7, and 8) from 1975 to present in addition to one SPOT scene (2013) are used. Previous workers used images from June and July, which are peak snow periods in southern Peru, leading to overestimates of ice area. This study uses November and December images when snow is at an annual minimum. Annual equilibrium line altitudes are calculated for each end of year image (November/December). The glaciers of Nevado Coropuna were found to be shrinking at ~0.5 km2/yr, which is ~1/3 the rate previously published. In this study, SPOT (1.5 m resolution) and Landsat 7 ETM scenes from November 23 and 26, 2013 respectively were used to calibrate the spectral band threshold classification. While this study suggests that the ice cap of Coropuna will persist until 2100 given current rates, water quantity and security remains a concern for Peruvian agriculture. Coropuna is an active volcano, so it poses great risk to surrounding inhabitants from lahars, flooding, and debris avalanches. Our new data suggest that these will continue to be risks late into this century.

Ice core records of climate variability on the Third Pole with emphasis on the Guliya ice cap, western Kunlun Mountains

Science.gov (United States)

Thompson, Lonnie G.; Yao, Tandong; Davis, Mary E.; Mosley-Thompson, Ellen; Wu, Guangjian; Porter, Stacy E.; Xu, Baiqing; Lin, Ping-Nan; Wang, Ninglian; Beaudon, Emilie; Duan, Keqin; Sierra-Hernández, M. Roxana; Kenny, Donald V.

2018-05-01

Records of recent climate from ice cores drilled in 2015 on the Guliya ice cap in the western Kunlun Mountains of the Tibetan Plateau, which with the Himalaya comprises the Third Pole (TP), demonstrate that this region has become warmer and moister since at least the middle of the 19th century. Decadal-scale linkages are suggested between ice core temperature and snowfall proxies, North Atlantic oceanic and atmospheric processes, Arctic temperatures, and Indian summer monsoon intensity. Correlations between annual-scale oxygen isotopic ratios (δ18O) and tropical western Pacific and Indian Ocean sea surface temperatures are also demonstrated. Comparisons of climate records during the last millennium from ice cores acquired throughout the TP illustrate centennial-scale differences between monsoon and westerlies dominated regions. Among these records, Guliya shows the highest rate of warming since the end of the Little Ice Age, but δ18O data over the last millennium from TP ice cores support findings that elevation-dependent warming is most pronounced in the Himalaya. This, along with the decreasing precipitation rates in the Himalaya region, is having detrimental effects on the cryosphere. Although satellite monitoring of glaciers on the TP indicates changes in surface area, only a few have been directly monitored for mass balance and ablation from the surface. This type of ground-based study is essential to obtain a better understanding of the rate of ice shrinkage on the TP.

Water on Mars: Inventory, distribution, and possible sources of polar ice

Science.gov (United States)

Clifford, S. M.

1992-01-01

Theoretical considerations and various lines of morphologic evidence suggest that, in addition to the normal seasonal and climatic exchange of H2O that occurs between the Martian polar caps, atmosphere, and mid to high latitude regolith, large volumes of water have been introduced into the planet's long term hydrologic cycle by the sublimation of equatorial ground ice, impacts, catastrophic flooding, and volcanism. Under the climatic conditions that are thought to have prevailed on Mars throughout the past 3 to 4 b.y., much of this water is expected to have been cold trapped at the poles. The amount of polar ice contributed by each of the planet's potential crustal sources is discussed and estimated. The final analysis suggests that only 5 to 15 pct. of this potential inventory is now in residence at the poles.

Abnormal Winter Melting of the Arctic Sea Ice Cap Observed by the Spaceborne Passive Microwave Sensors

Directory of Open Access Journals (Sweden)

Seongsuk Lee

2016-12-01

Full Text Available The spatial size and variation of Arctic sea ice play an important role in Earth’s climate system. These are affected by conditions in the polar atmosphere and Arctic sea temperatures. The Arctic sea ice concentration is calculated from brightness temperature data derived from the Defense Meteorological Satellite program (DMSP F13 Special Sensor Microwave/Imagers (SSMI and the DMSP F17 Special Sensor Microwave Imager/Sounder (SSMIS sensors. Many previous studies point to significant reductions in sea ice and their causes. We investigated the variability of Arctic sea ice using the daily and monthly sea ice concentration data from passive microwave observations to identify the sea ice melting regions near the Arctic polar ice cap. We discovered the abnormal melting of the Arctic sea ice near the North Pole even during the summer and the winter. This phenomenon is hard to explain only surface air temperature or solar heating as suggested by recent studies. We propose a hypothesis explaining this phenomenon. The heat from the deep sea in Arctic Ocean ridges and/or the hydrothermal vents might be contributing to the melting of Arctic sea ice. This hypothesis could be verified by the observation of warm water column structure below the melting or thinning arctic sea ice through the project such as Coriolis dataset for reanalysis (CORA.

Temporal constraints on future accumulation-area loss of a major Arctic ice cap due to climate change (Vestfonna, Svalbard).

Science.gov (United States)

Möller, Marco; Schneider, Christoph

2015-01-28

Arctic glaciers and ice caps are major contributors to past, present and future sea-level fluctuations. Continued global warming may eventually lead to the equilibrium line altitudes of these ice masses rising above their highest points, triggering unstoppable downwasting. This may feed future sea-level rise considerably. We here present projections for the timing of equilibrium-line loss at the major Arctic ice cap Vestfonna, Svalbard. The projections are based on spatially distributed climatic mass balance modelling driven by the outputs of multiple climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) forced by the Representative Concentration Pathways (RCPs) 2.6, 4.5, 6.0 and 8.5. Results indicate strongly decreasing climatic mass balances over the 21(st) century for all RCPs considered. Glacier-wide mass-balance rates will drop down to -4 m a(-1) w.e. (water equivalent) at a maximum. The date at which the equilibrium line rises above the summit of Vestfonna (630 m above sea level) is calculated to range between 2040 and 2150, depending on scenario.

Remote Sensing Observations and Numerical Simulation for Martian Layered Ejecta Craters

Science.gov (United States)

Li, L.; Yue, Z.; Zhang, C.; Li, D.

2018-04-01

To understand past Martian climates, it is important to know the distribution and nature of water ice on Mars. Impact craters are widely used ubiquitous indicators for the presence of subsurface water or ice on Mars. Remote sensing observations and numerical simulation are powerful tools for investigating morphological and topographic features on planetary surfaces, and we can use the morphology of layered ejecta craters and hydrocode modeling to constrain possible layering and impact environments. The approach of this work consists of three stages. Firstly, the morphological characteristics of the Martian layered ejecta craters are performed based on Martian images and DEM data. Secondly, numerical modeling layered ejecta are performed through the hydrocode iSALE (impact-SALE). We present hydrocode modeling of impacts onto targets with a single icy layer within an otherwise uniform basalt crust to quantify the effects of subsurface H2O on observable layered ejecta morphologies. The model setup is based on a layered target made up of a regolithic layer (described by the basalt ANEOS), on top an ice layer (described by ANEOS equation of H2O ice), in turn on top of an underlying basaltic crust. The bolide is a 0.8 km diameter basaltic asteroid hitting the Martian surface vertically at a velocity of 12.8 km/s. Finally, the numerical results are compared with the MOLA DEM profile in order to analyze the formation mechanism of Martian layered ejecta craters. Our simulations suggest that the presence of an icy layer significantly modifies the cratering mechanics, and many of the unusual features of SLE craters may be explained by the presence of icy layers. Impact cratering on icy satellites is significantly affected by the presence of subsurface H2O.

Life on Mars: Evidence from Martian Meteorites

Science.gov (United States)

McKay, David S.; Thomas-Keptra, Katie L.; Clemett, Simon J.; Gibson, Everett K., Jr.; Spencer, Lauren; Wentworth, Susan J.

2009-01-01

New data on martian meteorite 84001 as well as new experimental studies show that thermal or shock decomposition of carbonate, the leading alternative non-biologic explanation for the unusual nanophase magnetite found in this meteorite, cannot explain the chemistry of the actual martian magnetites. This leaves the biogenic explanation as the only remaining viable hypothesis for the origin of these unique magnetites. Additional data from two other martian meteorites show a suite of biomorphs which are nearly identical between meteorites recovered from two widely different terrestrial environments (Egyptian Nile bottomlands and Antarctic ice sheets). This similarity argues against terrestrial processes as the cause of these biomorphs and supports an origin on Mars for these features.

Modelling the future of the arctic sea ice cover

OpenAIRE

Myklebust, Erik Bryhn

2017-01-01

Record lows in sea ice cover have recently sparked new interest in the small ice cap instability. The change in albedo when sea ice becomes open water introduces a nonlinearity called the ice-albedo feedback. Forcing a joint energy- balance and sea ice model can lead to unstable ice caps in certain parameter regimes. When the ice caps are unstable, a small perturbation will initiate a tipping point in the sea ice cover. For tipping points in general, a number of studies have pointed out that ...

The distribution of snow accumulation across the Austfonna ice cap, Svalbard: direct measurements and modelling

OpenAIRE

Taurisano, Andrea; Schuler, Thomas V.; Hagen, Jon Ove; Eiken, Trond; Loe, Even; Melvold, Kjetil; Kohler, Jack

2007-01-01

We present an analysis of the spatial variability in the snow accumulation on the Austfonna ice cap in Svalbard, Norway, based on the results of field investigations conducted in the spring of 1999, 2004 and 2005. During the campaigns ground penetrating radar measurements at 500 and 800 MHz were collected along profiles, along with additional manual snow sounding and pit stratigraphy work. The analysis of the data reveals a consistent pattern in the spatial distribution of the snow accumulati...

A Microphysically-based Approach to Inferring Porosity, Grain Size, and Dust Abundance in the Seasonal Caps from Atmospherically-corrected TES Spectra

Science.gov (United States)

Eluszkiewicz, J.; Titus, T. N.

2003-01-01

One of the highlights of the TES observations in the polar regions has been the identification of a "cryptic" region in the south where CO2 appears to be in the form of a solid slab rather than a fluffy frost. While the exact mechanism(s) by which the cryptic region is formed are still subject of some debate, it appears certain that a type of rapid metamorphism related to the high volatility of CO2 ice is involved. The high volatility of CO2 ice under martian conditions has several Solar System analogs (N2 on Triton and Pluto, SO2 on Io), thus making the martian cryptic region somewhat less cryptic and certainly non-unique among planetary objects. In an endmember scenario, both the formation and the spectral properties of the cryptic region (and of other areas in the seasonal caps) can be quantitatively modeled by considering sintering of an ensemble of quasi-spherical CO2 grains. This model includes the special case of instanteneous slab formation, which occurs when the grains are sufficiently small (in the submicron range) so that their sintering timescale is short relative to the deposition timescale (a situation analogous to the "sintering" of water droplets falling into a pond).

Salt or ice diapirism origin for the honeycomb terrain in Hellas basin, Mars?: Implications for the early martian climate

Science.gov (United States)

Weiss, David K.; Head, James W.

2017-03-01

The "honeycomb" terrain is a Noachian-aged cluster of ∼7 km wide linear cell-like depressions located on the northwestern floor of Hellas basin, Mars. A variety of origins have been proposed for the honeycomb terrain, including deformation rings of subglacial sediment, frozen convection cells from a Hellas impact melt sheet, a swarm of igneous batholiths, salt diapirism, and ice diapirism. Recent work has shown that the salt or ice diapirism scenarios appear to be most consistent with the morphology and morphometry of the honeycomb terrain. The salt and ice diapirism scenarios have different implications for the ancient martian climate and hydrological cycle, and so distinguishing between the two scenarios is critical. In this study, we specifically test whether the honeycomb terrain is consistent with a salt or ice diapir origin. We use thermal modeling to assess the stability limits on the thickness of an ice or salt diapir-forming layer at depth within the Hellas basin. We also apply analytical models for diapir formation to evaluate the predicted diapir wavelengths in order to compare with observations. Ice diapirism is generally predicted to reproduce the observed honeycomb wavelengths for ∼100 m to ∼1 km thick ice deposits. Gypsum and kieserite diapirism is generally predicted to reproduce the observed honeycomb wavelengths for ≥ 600-1000 m thick salt deposits, but only with a basaltic overburden. Halite diapirism generally requires approx. ≥ 1 km thick halite deposits in order to reproduce the observed honeycomb wavelengths. Hellas basin is a distinctive environment for diapirism on Mars due to its thin crust (which reduces surface heat flux), low elevation (which allows Hellas to act as a water/ice/sediment sink and increases the surface temperature), and location within the southern highlands (which may provide proximity to inflowing saline water or glacial ice). The plausibility of an ice diapir mechanism generally requires temperatures ≤ 250

Climate Changes Documented in Ice Core Records from Third Pole Glaciers, with Emphasis on the Guliya Ice Cap in the Western Kunlun Mountains over the Last 100 Years

Science.gov (United States)

Thompson, L. G.; Yao, T.; Beaudon, E.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.

2016-12-01

The Third Pole (TP) is a rapidly warming region containing 100,000 km2 of ice cover that collectively holds one of Earth's largest stores of freshwater that feeds Asia's largest rivers and helps sustain 1.5 billion people. Information on the accelerating warming in the region, its impact on the glaciers and subsequently on future water resources is urgently needed to guide mitigation and adaptation policies. Ice core histories collected over the last three decades across the TP demonstrate its climatic complexity and diversity. Here we present preliminary results from the flagship project of the Third Pole Environment Program, the 2015 Sino-American cooperative ice core drilling of the Guliya ice cap in the Kunlun Mountains in the western TP near the northern limit of the region influenced by the southwest monsoon. Three ice cores, each 51 meters in length, were recovered from the summit ( 6700 masl) while two deeper cores, one to bedrock ( 310 meters), were recovered from the plateau ( 6200 masl). Across the ice cap the net balance (accumulation) has increased annually by 2.3 cm of water equivalent from 1963-1992 to 1992-2015, and average oxygen isotopic ratios (δ18O) have enriched by 2‰. This contrasts with the recent ablation on the Naimona'nyi glacier located 540 km south of Guliya in the western Himalaya. Borehole temperatures in 2015 on the Guliya plateau have warmed substantially in the upper 30 meters of the ice compared to temperatures in 1992, when the first deep-drilling of the Guliya plateau was conducted. Compared with glaciers in the northern and western TP, the Himalayan ice fields are more sensitive to both fluctuations in the South Asian Monsoon and rising temperatures in the region. We examine the climatic changes of the last century preserved in ice core records from sites throughout the TP and compare them with those reconstructed for earlier warm epochs, such as the Medieval Climate Anomaly ( 950-1250 AD), the early Holocene "Hypsithermal

Sublimation and transport of water from the north residual polar cap on Mars

Science.gov (United States)

Haberle, Robert M.; Jakosky, Bruce M.

1990-01-01

The possible role of the north residual cap in the current Martian water cycle was examined using models to assess the ability of the cap to supply water to the atmosphere and the ability of the atmospheric circulation to transport it out of the polar regions to low northern latitudes. Results indicate that rather extreme circumstances would be required for the cap to provide all of the observed increase in atmospheric water, such as a combination of high surface winds, low cap emissivities, or substantial evaporation from dark material. But even if these conditions could be met, the high-latitude circulation is too localized in scale to move much water vapor out of the polar environment. Both the present calculations and the data from the Viking's Mars Atmospheric Water Detection Experiment show that about two thirds of the water appearing in the Martian northern hemisphere during summer must be supplied by other sources. It is suggested that the additional source is water desorbing from the nonpolar regolith.

Chlorine-containing salts as water ice nucleating particles on Mars

Science.gov (United States)

Santiago-Materese, D. L.; Iraci, L. T.; Clapham, M. E.; Chuang, P. Y.

2018-03-01

Water ice cloud formation on Mars largely is expected to occur on the most efficient ice nucleating particle available. Salts have been observed on the Martian surface and have been known to facilitate water cloud formation on Earth. We examined heterogeneous ice nucleation onto sodium chloride and sodium perchlorate substrates under Martian atmospheric conditions, in the range of 150 to 180 K and 10-7 to 10-5 Torr water partial pressure. Sub-155 K data for the critical saturation ratio (Scrit) suggests an exponential model best describes the temperature-dependence of nucleation onset of water ice for all substrates tested. While sodium chloride does not facilitate water ice nucleation more easily than bare silicon, sodium perchlorate does support depositional nucleation at lower saturation levels than other substrates shown and is comparable to smectite-rich clay in its ability to support cloud initiation. Perchlorates could nucleate water ice at partial pressures up to 40% lower than other substrates examined to date under Martian atmospheric conditions. These findings suggest air masses on Mars containing uplifted salts such as perchlorates could form water ice clouds at lower saturation ratios than in air masses absent similar particles.

Liquid Water in the Extremely Shallow Martian Subsurface

Science.gov (United States)

Pavlov, A.; Shivak, J. N.

2012-01-01

Availability of liquid water is one of the major constraints for the potential Martian biosphere. Although liquid water is unstable on the surface of Mars due to low atmospheric pressures, it has been suggested that liquid films of water could be present in the Martian soil. Here we explored a possibility of the liquid water formation in the extremely shallow (1-3 cm) subsurface layer under low atmospheric pressures (0.1-10 mbar) and low ("Martian") surface temperatures (approx.-50 C-0 C). We used a new Goddard Martian simulation chamber to demonstrate that even in the clean frozen soil with temperatures as low as -25C the amount of mobile water can reach several percents. We also showed that during brief periods of simulated daylight warming the shallow subsurface ice sublimates, the water vapor diffuses through porous surface layer of soil temporarily producing supersaturated conditions in the soil, which leads to the formation of additional liquid water. Our results suggest that despite cold temperatures and low atmospheric pressures, Martian soil just several cm below the surface can be habitable.

Differences in Bacterial Diversity and Communities Between Glacial Snow and Glacial Soil on the Chongce Ice Cap, West Kunlun Mountains.

Science.gov (United States)

Yang, Guang Li; Hou, Shu Gui; Le Baoge, Ri; Li, Zhi Guo; Xu, Hao; Liu, Ya Ping; Du, Wen Tao; Liu, Yong Qin

2016-11-04

A detailed understanding of microbial ecology in different supraglacial habitats is important due to the unprecedented speed of glacier retreat. Differences in bacterial diversity and community structure between glacial snow and glacial soil on the Chongce Ice Cap were assessed using 454 pyrosequencing. Based on rarefaction curves, Chao1, ACE, and Shannon indices, we found that bacterial diversity in glacial snow was lower than that in glacial soil. Principal coordinate analysis (PCoA) and heatmap analysis indicated that there were major differences in bacterial communities between glacial snow and glacial soil. Most bacteria were different between the two habitats; however, there were some common bacteria shared between glacial snow and glacial soil. Some rare or functional bacterial resources were also present in the Chongce Ice Cap. These findings provide a preliminary understanding of the shifts in bacterial diversity and communities from glacial snow to glacial soil after the melting and inflow of glacial snow into glacial soil.

Formation of martian araneiforms by gas-driven erosion of granular material

DEFF Research Database (Denmark)

de Villiers, S.; Nermoen, A.; Jamtveit, B.

2012-01-01

Sublimation at the lower surface of a seasonal sheet of translucent CO2 ice at high southern latitudes during the Martian spring, and rapid outflow of the CO2 gas generated in this manner through holes in the ice, has been proposed as the origin of dendritic 100 m–1 km scale branched channels known...

Evaporation Rates for Liquid Water and Ice Under Current Martian Conditions

Science.gov (United States)

Sears, D. W. G.; Moore, S. R.; Meier, A.; Chittenden, J.; Kareev, M.; Farmer, C. B.

2004-01-01

A number of studies have been concerned with the evaporation rates under martian conditions in order to place limits on the possible survival time of both liquid water and ice exposed on the surface of Mars. Such studies also aid in assessing the efficacy of an overlying layer of dust or loose regolith material in providing a barrier to free evaporation and thus prolong the lifetime of water in locations where its availability to putative living organisms would be significant. A better quantitative understanding of the effects of phase changes of water in the near surface environment would also aid the evaluation of the possible role of water in the formation of currently observed features, such as gullies in cliff walls and relatively short-term changes in the albedo of small surface areas ('dark stains'). Laboratory measurements aimed at refinement of our knowledge of these values are described here. The establishment of accurate values for evaporation rates and their dependence on the physical conditions of temperature, pressure and energy input, is an important benchmark for the further investigation of the efficacy of barriers to free evaporation in providing a prolonged period of survival of the water, particularly as a liquid.

Small Scale Polygons and the History of Ground Ice on Mars

Science.gov (United States)

Mellon, Michael T.

2003-01-01

Recent progress on polygon modeling has focused on the diameter and surface relief that we expect of thermal-contraction polygons in martian permafrost. With this in mind, we developed a finite-element model of thermal-contraction-crack behavior in permafrost in a martian climate. This model was generated from a finite element code by Jay Melosh (called TECTON) originally developed for terrestrial and planetary crustal-deformation studies. We adapted this model to martian permafrost by including time (and temperature) dependent rheologies, boundary conditions, and isotropic thermal-contraction, as well as several small adaptations to a martian environment. We tested our model extensively, including comparison to an analytic solution of pre-fracture stress. We recently published an analysis of two potential sources of water for forming the recent gullies. In this work we first evaluated the potential for near-surface ground ice (in the top meter or so of soil) to melt under conditions of solar heating on sloped surfaces at high obliquity, utilizing both thermal and diffusion-based ground-ice-stability models; our results suggested that the ground ice will sublimate, and the ice table will recede to greater depths before the melting temperature can be reached. An exception can occur only for extremely salt-rich ice, depressing the freezing point.

Response timescales for martian ice masses and implications for ice flow on Mars

DEFF Research Database (Denmark)

Koutnik, Michelle Rebecca; Waddington, E.D.; Winebrener, D.P.

2013-01-01

a predictable shape, which is a function of ice temperature, ice rheology, and surface mass-exchange rate. In addition, the time for surface-shape adjustment is shorter than the characteristic time for significant deformation or displacement of internal layers within a flowing ice mass; as a result, surface......On Earth and on Mars, ice masses experience changes in precipitation, temperature, and radiation. In a new climate state, flowing ice masses will adjust in length and in thickness, and this response toward a new steady state has a characteristic timescale. However, a flowing ice mass has...... topography is more diagnostic of flow than are internal-layer shapes. Because the shape of Gemina Lingula, North Polar Layered Deposits indicates that it flowed at some time in the past, we use its current topography to infer characteristics of those past ice conditions, or past climate conditions, in which...

Buried CO2 Ice traces in South Polar Layered Deposits of Mars detected by radar sounder

Science.gov (United States)

Castaldo, L.; Mège, D.; Orosei, R.; Séjourné, A.

2014-12-01

SHARAD (SHAllow RADar) is the subsurface sounding radar provided by the Italian Space Agency (ASI) as a facility instrument to NASA's 2005 Mars Reconnaissance Orbiter (MRO). The Reduced Data Record of SHARAD data covering the area of the South Polar Layered Deposits (SPLD), has been used. The elaboration and interpretation of the data, aimed to estimate electromagnetic properties of surface layers, has been performed in terms of permittivity. The theory of electromagnetic scattering from fractal surfaces, and the estimation of geometric parameters from topographic data by Mars Orbiter Laser Altimeter (MOLA) which was one of five instruments on board the Mars Global Surveyor (MGS) spacecraft, has been used. A deep analysis of inversion has been made on all Mars and extended to the South Polar Caps in order to extract the area with a permittivity constant of CO2 ice. Several corrections have been applied to the data, moreover the calibration of the signal requires the determination of a constant that takes into account the power gain due to the radar system and the surface in order to compensate the power losses due to the orbitographic phenomena. The determination of regions with high probability of buried CO2 ice in the first layer of the Martian surface, is obtained extracting the real part of the permittivity constant of the CO2 ice (~2), estimated by other means. The permittivity of CO2ice is extracted from the Global Permittivity Map of Mars using the global standard deviation of itself as following: ɛCO2ice=ɛCO2ice+ Σ (1)where Σ=±std(ɛMapMars)/2Figure 1(a) shows the south polar areas where the values of the permittivity point to the possibility of a CO2 ice layer. Figure 1(b) is the corresponding geologic map. The comparison between the two maps indicates that the area with probable buried CO2 overlaps Hesperian and Amazonian polar units (Hp, Hesperian plains-forming deposits marked by narrow sinuous, anabranching ridges and irregular depressions, and

The 20th century retreat of ice caps in Iceland derived from airborne SAR

DEFF Research Database (Denmark)

Magnússon, Eyjólfur; Björnsson, Helgi; Dall, Jørgen

2005-01-01

with the Danish airborne EMISAR radar system. Polarimetric and interferometric SAR data reveal the margins of the present ice caps as well as a series of terminal moraines in the fore field. These moraines date back to the maximum Neoglacial extent at the end of the 19th century and the outermost allow...... of the surges in W-Vatnajokull in the 20th century are observed in the SAR data including the most recent surges in the 1990s. Interestingly no push moraines were observed in front of the surge advance, but the moraines appear when the glaciers start retreating. We estimate that the collective decrease...

The Martian Water Cycle Based on 3-D Modeling

Science.gov (United States)

Houben, H.; Haberle, R. M.; Joshi, M. M.

1999-01-01

Understanding the distribution of Martian water is a major goal of the Mars Surveyor program. However, until the bulk of the data from the nominal missions of TES, PMIRR, GRS, MVACS, and the DS2 probes are available, we are bound to be in a state where much of our knowledge of the seasonal behavior of water is based on theoretical modeling. We therefore summarize the results of this modeling at the present time. The most complete calculations come from a somewhat simplified treatment of the Martian climate system which is capable of simulating many decades of weather. More elaborate meteorological models are now being applied to study of the problem. The results show a high degree of consistency with observations of aspects of the Martian water cycle made by Viking MAWD, a large number of ground-based measurements of atmospheric column water vapor, studies of Martian frosts, and the widespread occurrence of water ice clouds. Additional information is contained in the original extended abstract.

Vertical Distribution of Dust and Water Ice Aerosols from CRISM Limb-geometry Observations

Science.gov (United States)

Smith, Michael Doyle; Wolff, Michael J.; Clancy, Todd; Kleinbohl, Armin; Murchie, Scott L.

2013-01-01

[1] Near-infrared spectra taken in a limb-viewing geometry by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the Mars Reconnaissance Orbiter provide a useful tool for probing atmospheric structure. Specifically, the observed radiance as a function of wavelength and height above the limb enables the vertical distribution of both dust and water ice aerosols to be retrieved. More than a dozen sets of CRISM limb observations have been taken so far providing pole-to-pole cross sections, spanning more than a full Martian year. Radiative transfer modeling is used to model the observations taking into account multiple scattering from aerosols and the spherical geometry of the limb observations. Both dust and water ice vertical profiles often show a significant vertical structure for nearly all seasons and latitudes that is not consistent with the well-mixed or Conrath-v assumptions that have often been used in the past for describing aerosol vertical profiles for retrieval and modeling purposes. Significant variations are seen in the retrieved vertical profiles of dust and water ice aerosol as a function of season. Dust typically extends to higher altitudes (approx. 40-50km) during the perihelion season than during the aphelion season (water ice clouds are common, and water ice aerosols are observed to cap the dust layer in all seasons.

Ice thickness measurements and volume estimates for glaciers in Norway

Science.gov (United States)

Andreassen, Liss M.; Huss, Matthias; Melvold, Kjetil; Elvehøy, Hallgeir; Winsvold, Solveig H.

2014-05-01

Whereas glacier areas in many mountain regions around the world now are well surveyed using optical satellite sensors and available in digital inventories, measurements of ice thickness are sparse in comparison and a global dataset does not exist. Since the 1980s ice thickness measurements have been carried out by ground penetrating radar on many glaciers in Norway, often as part of contract work for hydropower companies with the aim to calculate hydrological divides of ice caps. Measurements have been conducted on numerous glaciers, covering the largest ice caps as well as a few smaller mountain glaciers. However, so far no ice volume estimate for Norway has been derived from these measurements. Here, we give an overview of ice thickness measurements in Norway, and use a distributed model to interpolate and extrapolate the data to provide an ice volume estimate of all glaciers in Norway. We also compare the results to various volume-area/thickness-scaling approaches using values from the literature as well as scaling constants we obtained from ice thickness measurements in Norway. Glacier outlines from a Landsat-derived inventory from 1999-2006 together with a national digital elevation model were used as input data for the ice volume calculations. The inventory covers all glaciers in mainland Norway and consists of 2534 glaciers (3143 glacier units) covering an area of 2692 km2 ± 81 km2. To calculate the ice thickness distribution of glaciers in Norway we used a distributed model which estimates surface mass balance distribution, calculates the volumetric balance flux and converts it into thickness using the flow law for ice. We calibrated this model with ice thickness data for Norway, mainly by adjusting the mass balance gradient. Model results generally agree well with the measured values, however, larger deviations were found for some glaciers. The total ice volume of Norway was estimated to be 275 km3 ± 30 km3. From the ice thickness data set we selected

Molecular Markers in the Quelccaya Ice Cap, Peru Describe 20th Century Biomass Burning Variability

Science.gov (United States)

Makou, M. C.; Thompson, L. G.; Eglinton, T. I.; Montluçon, D. B.

2007-12-01

Organic geochemical analytical methods were applied to Andean ice core samples, resulting in a multi- molecular biomass burning record spanning 1915 to 2001 AD. The Quelccaya Ice Cap in Peru is situated on the eastern flank of the Andes at 14°S and is well situated to receive aeolian inputs of organic matter derived from Amazonian forest fire events. Compounds of interest, which occur in trace quantities in ice, were recovered by stir bar sorptive extraction and analyzed by gas chromatography/time-of-flight mass spectrometry coupled with thermal desorption. These methods permitted identification and quantitation of numerous biomarkers in sample volumes of as little as 10 ml. At least one wet and dry season sample was analyzed for every year. Observed biomarkers that may be derived from vegetation fires include several polycyclic aromatic hydrocarbons (PAHs), atraric acid, 2-ethylhexyl p-methoxycinnamate, and a range of other aromatic compounds. Abrupt changes in compound abundances were superimposed on decadal variability. Systematic offsets between wet and dry season abundances were not observed, suggesting that the biomass burning signal is not biased by seasonal depositional effects, such as dust delivery. Inputs likely reflect a combination of sources from anthropogenic burning of the Amazon rainforest as well as natural fires related to aridity, and include both high and low elevation vegetation. These compounds and techniques can be applied to older ice in this and other core locations as an independent estimate of aridity.

Where to search for martian biota?

Science.gov (United States)

Tasch, Paul

1997-07-01

Martian Salt. Terrestrial halite containing negative crystals which entrapped drops of viscous fluid yielded viable bacteria. The fluid has a Br/Mg ratio which chemist W.T. Holser characterized as a `Permian bittern.' All relevant salt on Mars should be inspected for negative crystals and possible ancient bacterial tenants. Martian Water. Moist soil in the regolith, cooled hydrothermal fluids, sediments of recurrent oceanic water, and related to inferred strand lines, even limited water in future SNC-type meteorites, upper atmosphere liquid water or water vapor, and North Polar liquid water or ice--all liquid water in any form, wherever, should be collected for microbiological analysis. Vent Fauna. Living or fossil thermophiles as trace fossils, or fauna metallicized in relation to sulphide ores. Iron Bacteria. Limonitized magnetite ore (USSR) in thin section showed structures attributed to iron bacteria. Biogenic magnetite, produced by both aerobic and anaerobic bacteria and its significance. Carbonaceous chondrites (non martian) (Ivuna and Orgueil) yielded apparent life forms that could not be attributed to contamination during the given study. Are they extraterrestrial?

Basal friction evolution and crevasse distribution during the surge of Basin 3, Austfonna ice-cap - offline coupling between a continuum ice dynamic model and a discrete element model

Science.gov (United States)

Gong, Yongmei; Zwinger, Thomas; Åström, Jan; Gladstone, Rupert; Schellenberger, Thomas; Altena, Bas; Moore, John

2017-04-01

The outlet glacier at Basin 3, Austfonna ice-cap entered its active surge phase in autumn 2012. We assess the evolution of the basal friction during the surge through inverse modelling of basal friction coefficients using recent velocity observation from 2012 to 2014 in a continuum ice dynamic model Elmer/ice. The obtained basal friction coefficient distributions at different time instances are further used as a boundary condition in a discrete element model (HiDEM) that is capable of computing fracturing of ice. The inverted basal friction coefficient evolution shows a gradual 'unplugging' of the stagnant frontal area and northwards and inland expansion of the fast flowing region in the southern basin. The validation between the modeled crevasses distribution and the satellite observation in August 2013 shows a good agreement in shear zones inland and at the frontal area. Crevasse distributions of the summer before and after the glacier reached its maximum velocity in January 2013 (August 2012 and August 2014, respectively) are also evaluated. Previous studies suggest the triggering and development of the surge are linked to surface melt water penetrating through ice to form an efficient basal hydrology system thereby triggering a hydro- thermodynamic feedback. This preliminary offline coupling between a continuum ice dynamic model and a discrete element model will give a hint on future model development of linking supra-glacial to sub-glacial hydrology system.

IDENTIFYING SURFACE CHANGES ON HRSC IMAGES OF THE MARS SOUTH POLAR RESIDUAL CAP (SPRC

Directory of Open Access Journals (Sweden)

A. R. D. Putri

2016-06-01

Full Text Available The surface of Mars has been an object of interest for planetary research since the launch of Mariner 4 in 1964. Since then different cameras such as the Viking Visual Imaging Subsystem (VIS, Mars Global Surveyor (MGS Mars Orbiter Camera (MOC, and Mars Reconnaissance Orbiter (MRO Context Camera (CTX and High Resolution Imaging Science Experiment (HiRISE have been imaging its surface at ever higher resolution. The High Resolution Stereo Camera (HRSC on board of the European Space Agency (ESA Mars Express, has been imaging the Martian surface, since 25th December 2003 until the present-day. HRSC has covered 100 % of the surface of Mars, about 70 % of the surface with panchromatic images at 10-20 m/pixel, and about 98 % at better than 100 m/pixel (Neukum et. al., 2004, including the polar regions of Mars. The Mars polar regions have been studied intensively recently by analysing images taken by the Mars Express and MRO missions (Plaut et al., 2007. The South Polar Residual Cap (SPRC does not change very much in volume overall but there are numerous examples of dynamic phenomena associated with seasonal changes in the atmosphere. In particular, we can examine the time variation of layers of solid carbon dioxide and water ice with dust deposition (Bibring, 2004, spider-like channels (Piqueux et al., 2003 and so-called Swiss Cheese Terrain (Titus et al., 2004. Because of seasonal changes each Martian year, due to the sublimation and deposition of water and CO2 ice on the Martian south polar region, clearly identifiable surface changes occur in otherwise permanently icy region. In this research, good quality HRSC images of the Mars South Polar region are processed based on previous identification as the optimal coverage of clear surfaces (Campbell et al., 2015. HRSC images of the Martian South Pole are categorized in terms of quality, time, and location to find overlapping areas, processed into high quality Digital Terrain Models (DTMs and

Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

Science.gov (United States)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

2012-12-01

The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87�

Describing the Components of the Water Transport in the Martian Atmosphere

Science.gov (United States)

Montmessin, F.; Haberle, R. M.; forget, F.; Rannou, P.; Cabane, M.

2003-01-01

In this paper, we examine the meteorological components driving water transport in the Martian atmosphere. A particular emphasis is given to the role of residual mean circulation and water ice clouds in determining the geographical partitioning of water vapor and frost.

Martian sub-surface ionising radiation: biosignatures and geology

Directory of Open Access Journals (Sweden)

J. M. Ward

2007-07-01

Full Text Available The surface of Mars, unshielded by thick atmosphere or global magnetic field, is exposed to high levels of cosmic radiation. This ionising radiation field is deleterious to the survival of dormant cells or spores and the persistence of molecular biomarkers in the subsurface, and so its characterisation is of prime astrobiological interest. Here, we present modelling results of the absorbed radiation dose as a function of depth through the Martian subsurface, suitable for calculation of biomarker persistence. A second major implementation of this dose accumulation rate data is in application of the optically stimulated luminescence technique for dating Martian sediments.

We present calculations of the dose-depth profile in the Martian subsurface for various scenarios: variations of surface composition (dry regolith, ice, layered permafrost, solar minimum and maximum conditions, locations of different elevation (Olympus Mons, Hellas basin, datum altitude, and increasing atmospheric thickness over geological history. We also model the changing composition of the subsurface radiation field with depth compared between Martian locations with different shielding material, determine the relative dose contributions from primaries of different energies, and discuss particle deflection by the crustal magnetic fields.

Viking orbiter imaging observations of dust in the Martian atmosphere

International Nuclear Information System (INIS)

Briggs, G.A.; Baum, W.A.; Barnes, J.

1979-01-01

More than 20 local Martian dust clouds and two global dust storms were observed with the Viking orbiter camera. Sixteen of the local clouds were imaged in two colors or were observed with other instruments confirming their identification as dust clouds. These Viking results are compared with earth-based observations of Martian dust storms and with Mariner 9 data. Most of the dust activity seen by Viking occurred during southern hemisphere spring and early summer, when Mars was near perihelion and isolation was near maximum. About half the local clouds occurred near the edge of the southern polar cap, where winds are presumably enhanced by a strong regional temperature gradient. The other half occurred mainly in the southern hemisphere near regions where circulation models incorporating topography predict positive vertical velocities. Although dust clouds observed from earth show a similar partial correlation with models, some ambiguity exists concerning interpretation of regions near Hellespontus that have spawned the most spectacular Martian dust storms on record

Ice on Mars Utopia Planitia Again

Science.gov (United States)

1979-01-01

This high-resolution color photo of the surface of Mars was taken by Viking Lander 2 at its Utopia Planitia landing site on May 18, 1979, and relayed to Earth by Orbiter 1 on June 7. It shows a thin coating of water ice on the rocks and soil. The time the frost appeared corresponds almost exactly with the buildup of frost one Martian year (23 Earth months) ago. Then it remained on the surface for about 100 days. Scientists believe dust particles in the atmosphere pick up bits of solid water. That combination is not heavy enough to settle to the ground. But carbon dioxide, which makes up 95 percent of the Martian atmosphere, freezes and adheres to the particles and they become heavy enough to sink. Warmed by the Sun, the surface evaporates the carbon dioxide and returns it to the atmosphere, leaving behind the water and dust. The ice seen in this picture, like that which formed one Martian year ago, is extremely thin, perhaps no more than one-thousandth of an inch thick.

How accurate are estimates of glacier ice thickness? Results from ITMIX, the Ice Thickness Models Intercomparison eXperiment

DEFF Research Database (Denmark)

Farinotti, Daniel; Brinkerhoff, Douglas J.; Clarke, Garry K. C.

2017-01-01

Knowledge of the ice thickness distribution of glaciers and ice caps is an important prerequisite for many glaciological and hydrological investigations. A wealth of approaches has recently been presented for inferring ice thickness from characteristics of the surface. With the Ice Thickness Models...

Glacial Boundary Features Delineated Using Enhanced-resolution Passive-microwave Data to Determine Melt Season Variation of the Vatnajokull Ice Cap, Iceland

Science.gov (United States)

Marzillier, D. M.; Ramage, J. M.

2017-12-01

Temperate glaciers such as those seen in Iceland experience high annual mass flux, thereby responding to small scale changes in Earth's climate. Decadal changes in the glacial margins of Iceland's ice caps are observable in the Landsat record, however twice daily AMSR-E Calibrated Enhanced-Resolution Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature (CETB) Earth System Data Record (ESDR) allow for observation on a daily temporal scale and a 3.125 km spatial scale, which can in turn be connected to patterns seen over longer periods of time. Passive microwave data allow for careful observation of melt onset and duration in Iceland's glacial regions by recording changes in emissivity of the ice surface, known as brightness temperature (TB), which is sensitive to fluctuations in the liquid water content of snow and ice seen during melting in glaciated regions. Enhanced resolution of this data set allows for a determination of a threshold that defines the melting season. The XPGR snowmelt algorithm originally presented by Abdalati and Steffen (1995) is used as a comparison with the diurnal amplitude variation (DAV) values on Iceland's Vatnajokull ice cap located at 64.4N, -16.8W. Ground-based air temperature data in this region, digital elevation models (DEMs), and river discharge dominated by glacial runoff are used to confirm the glacial response to changes in global climate. Results show that Iceland glaciers have a bimodal distribution of brightness temperature delineating when the snow/ice is melting and refreezing. Ground based temperatures have increased on a decadal trend. Clear glacial boundaries are visible on the passive microwave delineating strong features, and we are working to understand their variability and contribution to glacier evolution. The passive microwave data set allows connections to be made between observations seen on a daily scale and the long term glacier changes observed by the Landsat satellite record that integrates the

Cryolitozone of Mars- as the climatic indicator of the Martian relict ocean

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Ozorovich, Y.; Fournier-Sicre, A.; Linkin, V.; Kosov, A.; Skulachev, D.; Gorbatov, S.; Ivanov, A.; Heggy, E.

2015-10-01

The existance of a large Martian cryolitozone consisting of different cryogenic formations both on the surface- polar caps ice and in subsurface layer (and probably overcooled salt solutions in lower horizons) is conditioned mostly by the planet's geological history and atmosphere evolution. The very structure of the cryolitozone with its strongly pronounced zone character owing to drying up of 0 to 200 m thick surface layer in the equatorial latitudes ranging from + 30 to - 300 was formed in the course of long-periodic climatic variations and at present is distincly heterogeneous both depthward and in latitudinal and longtudinal dimensions. The dryed up region of Martian frozen rocks is estimated to have been developing during more than 3.5 bln years, so the upper layer boundary of permafrost can serve as a sort of indicator reflecting the course of Martian climatic evolution. Since the emount of surface moisture and its distribition character are conditioned by the cryolitozone scale structure its investigation is considered to be an important aspect of the forthcoming Martian projects. In order to create Martian climate and atmosphere circulation models the whole complex information on surface provided by optical and infrared ranges observations, regional albedo surface measurements, ground layer thermal flow investigations, etc. must be carefully studed. The investigation of permafrost formation global distribution and their appearance in h ≤1 m thick subsurface layer may be provided successfully by using active-passive microwave remote sensing techniques [1]. Along with optical and infrared observations the method of orbital panoramic microwave radiometry in centi- and decimeter ranges would contribute to the mapping of the cryolitozone global surface distribution. This proposal discusses methodical and experimental possibilities of this global observation of Martian cryolitozone as the additional way for investigation subsurface of Mars. The main idea of

The effect of signal leakage and glacial isostatic rebound on GRACE-derived ice mass changes in Iceland

DEFF Research Database (Denmark)

Sørensen, Louise Sandberg; Jarosch, Alexander H.; Adalgeirsdottir, Gudfinna

2017-01-01

Monthly gravity field models from the GRACE satellite mission are widely used to determine ice mass changes of large ice sheets as well as smaller glaciers and ice caps. Here, we investigate in detail the ice mass changes of the Icelandic ice caps as derived from GRACE data. The small size...... of the Icelandic ice caps, their location close to other rapidly changing ice covered areas and the low viscosity of the mantle below Iceland make this especially challenging. The mass balance of the ice caps is well constrained by field mass balance measurements, making this area ideal for such investigations. We...... the Little Ice Age (∼ 1890 AD). To minimize the signal that leaks towards Iceland from Greenland, we employ an independent mass change estimate of the Greenland Ice Sheet derived from satellite laser altimetry. We also estimate the effect of post Little Ice Age glacial isostatic adjustment, from knowledge...

Inception of the Laurentide Ice Sheet using asynchronous coupling of a regional atmospheric model and an ice model

Science.gov (United States)

Birch, L.; Cronin, T.; Tziperman, E.

2017-12-01

The climate over the past 0.8 million years has been dominated by ice ages. Ice sheets have grown about every 100 kyrs, starting from warm interglacials, until they spanned continents. State-of-the-art global climate models (GCMs) have difficulty simulating glacial inception, or the transition of Earth's climate from an interglacial to a glacial state. It has been suggested that this failure may be related to their poorly resolved local mountain topography, due to their coarse spatial resolution. We examine this idea as well as the possible role of ice flow dynamics missing in GCMs. We investigate the growth of the Laurentide Ice Sheet at 115 kya by focusing on the mountain glaciers of Canada's Baffin Island, where geologic evidence indicates the last inception occurred. We use the Weather Research and Forecasting model (WRF) in a regional, cloud-resolving configuration with resolved mountain terrain to explore how quickly Baffin Island could become glaciated with the favorable yet realizable conditions of 115 kya insolation, cool summers, and wet winters. Using the model-derived mountain glacier mass balance, we force an ice sheet model based on the shallow-ice approximation, capturing the ice flow that may be critical to the spread of ice sheets away from mountain ice caps. The ice sheet model calculates the surface area newly covered by ice and the change in the ice surface elevation, which we then use to run WRF again. Through this type of iterated asynchronous coupling, we investigate how the regional climate responds to both larger areas of ice cover and changes in ice surface elevation. In addition, we use the NOAH-MP Land model to characterize the importance of land processes, like refreezing. We find that initial ice growth on the Penny Ice Cap causes regional cooling that increases the accumulation on the Barnes Ice Cap. We investigate how ice and topography changes on Baffin Island may impact both the regional climate and the large-scale circulation.

Martian Cryogenic Carbonate Formation: Stable Isotope Variations Observed in Laboratory Studies

Science.gov (United States)

Socki, Richard A.; Niles, Paul B.; Sun, Tao; Fu, Qi; Romanek, Christopher S.; Gibson, Everett K. Jr.

2014-01-01

The history of water on Mars is tied to the formation of carbonates through atmospheric CO2 and its control of the climate history of the planet. Carbonate mineral formation under modern martian atmospheric conditions could be a critical factor in controlling the martian climate in a means similar to the rock weathering cycle on Earth. The combination of evidence for liquid water on the martian surface and cold surface conditions suggest fluid freezing could be very common on the surface of Mars. Cryogenic calcite forms easily from freezing solutions when carbon dioxide degasses quickly from Ca-bicarbonate-rich water, a process that has been observed in some terrestrial settings such as arctic permafrost cave deposits, lake beds of the Dry Valleys of Antarctica, and in aufeis (river icings) from rivers of N.E. Alaska. A series of laboratory experiments were conducted that simulated cryogenic carbonate formation on Mars in order to understand their isotopic systematics. The results indicate that carbonates grown under martian conditions show variable enrichments from starting bicarbonate fluids in both carbon and oxygen isotopes beyond equilibrium values.

Experiments On Sublimating Carbon Dioxide Ice And Implications For Contemporary Surface Processes On Mars.

Science.gov (United States)

Mc Keown, L E; Bourke, M C; McElwaine, J N

2017-10-27

Carbon dioxide is Mars' primary atmospheric constituent and is an active driver of Martian surface evolution. CO 2 ice sublimation mechanisms have been proposed for a host of features that form in the contemporary Martian climate. However, there has been very little experimental work or quantitative modelling to test the validity of these hypotheses. Here we present the results of the first laboratory experiments undertaken to investigate if the interaction between sublimating CO 2 ice blocks and a warm, porous, mobile regolith can generate features similar in morphology to those forming on Martian dunes today. We find that CO 2 sublimation can mobilise grains to form (i) pits and (ii) furrows. We have documented new detached pits at the termini of linear gullies on Martian dunes. Based on their geomorphic similarity to the features observed in our laboratory experiments, and on scaling arguments, we propose a new hypothesis that detached pits are formed by the impact of granular jets generated by sublimating CO 2 . We also study the erosion patterns formed underneath a sublimating block of CO 2 ice and demonstrate that these resemble furrow patterns on Mars, suggesting similar formation mechanisms.

Atmospheric depositions of natural and anthropogenic trace elements on the Guliya ice cap (northwestern Tibetan Plateau) during the last 340 years

Science.gov (United States)

Sierra-Hernández, M. Roxana; Gabrielli, Paolo; Beaudon, Emilie; Wegner, Anna; Thompson, Lonnie G.

2018-03-01

A continuous record of 29 trace elements (TEs) has been constructed between 1650 and 1991 CE (Common Era) from an ice core retrieved in 1992 from the Guliya ice cap, on the northwestern Tibetan Plateau. Enrichments of Pb, Cd, Zn and Sb were detected during the second half of the 19th century and the first half of the 20th century (∼1850-1950) while enrichments of Sn (1965-1991), Cd and Pb (1975-1991) were detected during the second half of the 20th century. The EFs increased significantly by 20% for Cd and Sb, and by 10% for Pb and Zn during 1850-1950 relative to the pre-1850s. Comparisons of the Guliya TEs data with other ice core-derived and production/consumption data suggest that Northern Hemisphere coal combustion (primarily in Western Europe) is the likely source of Pb, Cd, Zn, and Sb during the 1850-1950 period. Coal combustion in Europe declined as oil replaced coal as the primary energy source. The European shift from coal to oil may have contributed to the observed Sn enrichment in ∼1965 (60% EF increase in 1975-1991), although regional fossil fuel combustion (coal and leaded gasoline) from western China, Central Asia, and South Asia (India, Nepal), as well as Sn mining/smelting in Central Asia, may also be possible sources. The post-1975 Cd and Pb enrichments (40% and 20% EF increase respectively in 1975-1991) may reflect emissions from phosphate fertilizers, fossil fuel combustion, and/or non-ferrous metal production, from western China, Central Asia, and/or South Asia. Leaded gasoline is likely to have also contributed to the post-1975 Pb enrichment observed in this record. The results strongly suggest that the Guliya ice cap has recorded long-distance emissions from coal combustion since the 1850s with more recent contributions from regional agriculture, mining, and/or fossil fuel combustion. This new Guliya ice core record of TEs fills a geographical gap in the reconstruction of the pollution history of this region that extends well beyond modern

Habitable periglacial landscapes in martian mid-latitudes

Science.gov (United States)

Ulrich, M.; Wagner, D.; Hauber, E.; de Vera, J.-P.; Schirrmeister, L.

2012-05-01

Subsurface permafrost environments on Mars are considered to be zones where extant life could have survived. For the identification of possible habitats it is important to understand periglacial landscape evolution and related subsurface and environmental conditions. Many landforms that are interpreted to be related to ground ice are located in the martian mid-latitudinal belts. This paper summarizes the insights gained from studies of terrestrial analogs to permafrost landforms on Mars. The potential habitability of martian mid-latitude periglacial landscapes is exemplarily deduced for one such landscape, that of Utopia Planitia, by a review and discussion of environmental conditions influencing periglacial landscape evolution. Based on recent calculations of the astronomical forcing of climate changes, specific climate periods are identified within the last 10 Ma when thaw processes and liquid water were probably important for the development of permafrost geomorphology. No periods could be identified within the last 4 Ma which met the suggested threshold criteria for liquid water and habitable conditions. Implications of past and present environmental conditions such as temperature variations, ground-ice conditions, and liquid water activity are discussed with respect to the potential survival of highly-specialized microorganisms known from terrestrial permafrost. We conclude that possible habitable subsurface niches might have been developed in close relation to specific permafrost landform morphology on Mars. These would have probably been dominated by lithoautotrophic microorganisms (i.e. methanogenic archaea).

North Polar Cap

Science.gov (United States)

2004-01-01

[figure removed for brevity, see original site] This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour. In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime. The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap. Image information: VIS instrument. Latitude 86.5, Longitude 64.5 East (295.5 West). 40 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen

The Mars water cycle at other epochs - Recent history of the polar caps and layered terrain

Science.gov (United States)

Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

1993-01-01

A numerical model is presented of the integrated role of seasonal water cycle on the evolution of polar deposits on Mars over the last 10 million years. From the model, it is concluded that the only major difference between the polar caps which affects their long-term behavior is ultimately the difference in their elevations. Because of that difference, there is a preference for CO2 frost to stay longer on the northern polar cap. The average difference in sublimation at the caps results in a net south-to-north transport of water ice over long time scales. Superimposed on any long-term behavior is a transfer of water ice between the caps on the 10 exp 5 - 10 exp 6 yr time scales. The amount of water exchanged is small compared to the total ice content of the polar deposits.

Volcano-ice interactions on Mars

International Nuclear Information System (INIS)

Allen, C.C.

1979-01-01

Central volcanic eruptions beneath terrestrial glaciers have built steep-sided, flat-topped mountains composed of pillow lava, glassy tuff, capping flows, and cones of basalt. Subglacial fissure eruptions produced ridges of similar compostion. In some places the products from a number of subglacial vents have combined to form widespread deposits. The morphologies of these subglacial volcanoes are distinctive enough to allow their recognition at the resolutions characteristic of Viking orbiter imagery. Analogs to terrestrial subglacial volcanoes have been identified on the northern plains and near the south polar cap of Mars. The polar feature provides probable evidence of volcanic eruptions beneath polar ice. A mixed unit of rock and ice is postulated to have overlain portions of the northern plains, with eruptions into this ground ice having produced mountains and ridges analogous to those in Iceland. Subsequent breakdown of this unit due to ice melting revealed the volcanic features. Estimated heights of these landforms indicate that the ice-rich unit once ranged from approximately 100 to 1200 m thick

Comparison of Mars Northern Cap Edge Advance and Recession Rates over the Last 6 Mars Years

Science.gov (United States)

Titus, T. N.; Cushing, G. E.; Langevin, Y.; Brown, A. J.; Themis Science Team; CRISM Science Team

2011-12-01

The most observable parameter that describes the Mars polar seasonal caps is their size, which has been measured since the days of Herschel. The advance and retreat of the polar cap from year to year may exhibit many clues to help elucidate little understood physical processes. For example, summertime heat storage in the regolith could delay the onset of seasonal CO2 cap formation. The evolution of the seasonal cap could also be directly affected by the thermal inertia of the near-surface regolith and place constraints on the depth of the ice table. Parameterizations of the seasonal cap edges provide useful constraints on atmospheric GCMs and mesoscale models. Longitudinally resolving the cap edges as they advance and retreat constrains the times when zonal means are appropriate and when longitudinal asymmetries make zonal means invalid. These same kinds of parameterizations can also be used when modeling other data that have low spatial resolutions, such as Gamma Ray Spectrometer (GRS )and Neutron Spectrometer (NS) data. By knowing where the cap edge should be, coarse spatial data can correct for subpixel mixing caused by large point-spread functions including both frosted and frost-free areas. The northern cap exhibits a near symmetric retreat, which has been well characterized at visible wavelengths by both telescopic and spacecraft observations. However, the advance of the cap has not been well characterized until the 21st century. Kieffer and Titus (2001) have used zonal means to observe surface temperature and visible bolometric albedo variations with season using MGS/TES. The TES thermal observations show an almost perfectly symmetrical advance; i.e., condensation at consistent latitude across all longitudes, with the most northern edge of the seasonal cap occurring between longitudes 245°E to 265°E and the most southern edge of the seasonal cap occurring between 280°E and 30°E. The advance of the northern cap typically leads the advance of the edge of

Atmospheric Modeling of the Martian Polar Regions: CRISM EPF Coverage During the South Polar Spring Recession

Science.gov (United States)

Brown, A. J.; McGuire, P.; Wolff, M. J.

2008-03-01

We describe efforts to model dust and ice aerosols content and soils and icy surface reflectance in the Martian southern polar region during spring recession (Ls = 152-320) using CRISM emission phase function (EPF) observations.

Response of Eyjafjallajökull, Torfajökull and Tindfjallajökull ice caps in Iceland to regional warming, deduced by remote sensing

Directory of Open Access Journals (Sweden)

Jørgen Dall

2011-07-01

Full Text Available We assess the volume change and mass balance of three ice caps in southern Iceland for two periods, 1979–1984 to 1998 and 1998 to 2004, by comparing digital elevation models (DEMs. The ice caps are Eyjafjallajökull (ca. 81 km2, Tindfjallajökull (ca. 15 km2 and Torfajökull (ca. 14 km2. The DEMs were compiled using aerial photographs from 1979 to 1984, airborne Synthetic Aperture Radar (SAR images obtained in 1998 and two image pairs from the SPOT 5 satellite's high-resolution stereoscopic (HRS instrument acquired in 2004. The ice-free part of the accurate DEM from 1998 was used as a reference map for co-registration and correction of the vertical offset of the other DEMs. The average specific mass balance was estimated from the mean elevation difference between glaciated areas of the DEMs. The glacier mass balance declined significantly between the two periods: from −0.2 to 0.2 m yr−1 w. eq. during the earlier period (1980s through 1998 to −1.8 to −1.5 m yr−1 w. eq. for the more recent period (1998–2004. The declining mass balance is consistent with increased temperature over the two periods. The low mass balance and the small accumulation area ratio of Tindfjallajökull and Torfajökull indicate that they will disappear if the present-day climate continues. The future lowering rate of Eyjafjallajökull will, however, be influenced by the 2010 subglacial eruption in the Eyjafjallajökull volcano.

The future sea-level rise contribution of Greenland’s glaciers and ice caps

DEFF Research Database (Denmark)

Machguth, H.; Rastner, P.; Bolch, T.

2013-01-01

We calculate the future sea-level rise contribution from the surface mass balance of all of Greenland's glaciers and ice caps (GICs, ~90 000 km2) using a simplified energy balance model which is driven by three future climate scenarios from the regional climate models HIRHAM5, RACMO2 and MAR...... experiments suggest that mass loss could be higher by 20–30% if a strong lowering of the surface albedo were to take place in the future. It is shown that the sea-level rise contribution from the north-easterly regions of Greenland is reduced by increasing precipitation while mass loss in the southern half...... feedback mechanisms are considered. The mass loss of all GICs by 2098 is calculated to be 2016 ± 129 Gt (HIRHAM5 forcing), 2584 ± 109 Gt (RACMO2) and 3907 ± 108 Gt (MAR). This corresponds to a total contribution to sea-level rise of 5.8 ± 0.4, 7.4 ± 0.3 and 11.2 ± 0.3 mm, respectively. Sensitivity...

10Be dating of late-glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap, Peru

Science.gov (United States)

Kelly, M. A.; Thompson, L. G.

2004-12-01

The surface exposure method, based on the measurement of cosmogenic 10Be produced in quartz, is applied to determine the age of deposition of glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap (about 13° S, 70° W) in southeastern Peru. These data are useful for examining the timing of past glaciation in the tropical Andes and for comparison with chronologies of glaciation at higher latitudes. The preliminary data set consists of more than ten surface exposure ages. Samples used for dating are from the surfaces of boulders on a set of prominent moraines about four kilometers away from the present ice margins. The age of the moraine set was previously bracketed by radiocarbon dating of peat associated with the glacial deposits. Based on radiocarbon ages, these moraines were formed during the late-glacial period, just prior to the last glacial-interglacial transition. The surface exposure dating method enables the direct dating of the moraines. Surface exposure dates are cross-checked with the previously existing radiocarbon dates and provide a means to improve the chronology of past glaciation in the tropical Andes.

Small-Scale Polygons and the History of Ground Ice on Mars

Science.gov (United States)

Mellon, Michael T.

2000-01-01

This research has laid a foundation for continued study of permafrost polygons on Mars using the models and understanding discussed here. Further study of polygonal patterns on Mars is proceeding (under new funding) which is expected to reveal more results about the origin of observed martian polygons and what information they contain regarding the recent history of tile martian climate and of water ice on Mars.

H2O grain size and the amount of dust in Mars' residual North polar cap

Science.gov (United States)

Kieffer, H.H.

1990-01-01

In Mars' north polar cap the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 ??m or more. Ice of this granularity containing 30% fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be "old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain. -Author

Multiple climate and sea ice states on a coupled Aquaplanet

Science.gov (United States)

Rose, B.; Ferreira, D.; Marshall, J.

2010-12-01

A fully coupled atmosphere-ocean-sea ice GCM is used to explore the climates of Earth-like planets with no continents and idealized ocean basin geometries. We find three qualitatively different stable equilibria under identical external forcing: an equable ice-free climate, a cold climate with ice caps extending into mid-latitudes, and a completely ice-covered "Snowball" state. These multiple states persist for millennia with no drift despite a full seasonal cycle and vigorous internal variability of the system on all time scales. The behavior of the coupled system is rationalized through an extension of the Budyko-Sellers model to include explicit ocean heat transport (OHT), and the insulation of the ice-covered sea surface. Sensitivity tests are also conducted with a slab ocean GCM with prescribed OHT. From these we conclude that albedo feedback and ocean circulation both play essential roles in the maintenance of the multiple states. OHT in the coupled system is dominated by a wind-driven subtropical cell carrying between 2 and 3 PW of thermal energy out of the deep tropics, most of which converges in the subtropics to lower mid-latitudes. This convergence pattern (similar to modern Earth) is robust to changes in the ocean basin geometry, and is directly responsible for the stabilization of the large ice cap. OHT also plays an essential but indirect role in the maintenance of the ice-free pole in the warm states, by driving an enhanced poleward atmospheric latent heat flux. The hysteresis loop for transitions between the warm and large ice cap states spans a much smaller range of parameter space (e.g. ±1.8% variations in solar constant) than the transitions in and out of the Snowball. Three qualitatively different climate states for the same external forcing in a coupled GCM: ice-free, large ice cap, and Snowball. SST and sea ice thickness are plotted. Similar results are found in a pure Aquaplanet (lower) and a "RidgeWorld" with a global-scale ocean basin

A prelanding assessment of the ice table depth and ground ice characteristics in Martian permafrost at the Phoenix landing site

Science.gov (United States)

Mellon, M.T.; Boynton, W.V.; Feldman, W.C.; Arvidson, R. E.; Titus, Joshua T.N.; Bandfield, L.; Putzig, N.E.; Sizemore, H.G.

2009-01-01

We review multiple estimates of the ice table depth at potential Phoenix landing sites and consider the possible state and distribution of subsurface ice. A two-layer model of ice-rich material overlain by ice-free material is consistent with both the observational and theoretical lines of evidence. Results indicate ground ice to be shallow and ubiquitous, 2-6 cm below the surface. Undulations in the ice table depth are expected because of the thermodynamic effects of rocks, slopes, and soil variations on the scale of the Phoenix Lander and within the digging area, which can be advantageous for analysis of both dry surficial soils and buried ice-rich materials. The ground ice at the ice table to be sampled by the Phoenix Lander is expected to be geologically young because of recent climate oscillations. However, estimates of the ratio of soil to ice in the ice-rich subsurface layer suggest that that the ice content exceeds the available pore space, which is difficult to reconcile with existing ground ice stability and dynamics models. These high concentrations of ice may be the result of either the burial of surface snow during times of higher obliquity, initially high-porosity soils, or the migration of water along thin films. Measurement of the D/H ratio within the ice at the ice table and of the soil-to-ice ratio, as well as imaging ice-soil textures, will help determine if the ice is indeed young and if the models of the effects of climate change on the ground ice are reasonable. Copyright 2008 by the American Geophysical Union.

Timing of Expansions of the Quelccaya Ice Cap, Peru, and Implications for Cosmogenic Nuclide Production Rate Calibration

Science.gov (United States)

Lowell, T. V.; Kelly, M. A.; Applegate, P. J.; Smith, C. A.; Phillips, F. M.; Hudson, A. M.

2010-12-01

We calibrate the production rate of the cosmogenic nuclide beryllium-10 (10Be) at a low-latitude, high-elevation site, using nuclide concentrations measured in moraine boulders and an independent chronology determined with bracketing radiocarbon dates. The measurement of terrestrial cosmogenic nuclide (TCN) concentrations in earth surface materials has been an important development for understanding a host of earth surface processes. Uncertainty in cosmogenic nuclide production rates has hampered application of this method. Here, we contribute to the estimation of 10Be production rates by reporting both preliminary 10Be concentrations and independent radiocarbon dates from a low latitude, high elevation site. Our study site in the southeastern Peruvian Andes (~13.9°S, 70.9°W, 4850 m asl) is centered on a moraine set, known as the Huancané II moraines, that represents a ~4 km expansion of Quelccaya Ice Cap during late glacial time. At this location, organic material situated both stratigraphically below and above moraines in two adjacent valleys provide material for radiocarbon dating. Based on geomorphic arguments, we correlate results from the two valleys. The timing of ice cap margin advance is bracketed by 13 radiocarbon ages on organic material within the outermost Huancané II moraines that range from 13.6 to 12.5 ka. Two stratigraphic sections upvalley from the moraines yield 6 radiocarbon ages from 11.3 to 12.4 ka, indicating the time of retreat . We computed the probability density function that lies between these two sets of dates, and assign an age of 12.4 ka (+/-???) for the formation of the Huancané II moraines. Calculating beryllium-10 exposure dates from the measured concentrations yield exposure dates that significantly underestimate the independently determined age of the moraine (~8-30%), if existing production rate estimates are used. We suggest that the radiocarbon age for the moraines can be used as a robust independent calibration for 10Be

Imaging the Antarctic Ice Sheet Subsurface with the HF GPR TAPIR

Science.gov (United States)

Le Gall, A.; Ciarletti, V.; Berthelier, J.; Reineix, A.; Ney, R.; Bonaimé, S.; Corbel, C.

2006-12-01

An HF impulse polarimetric Ground Penetrating Radar (GPR) operating at very low frequencies (ranging from ~2 to 8MHz) has been developed in the frame of the NetLander mission. This instrument, named TAPIR (Terrestrial And Planetary Investigation by Radar), was designed to probe the Martian subsurface down to kilometric depth and search for potential water reservoirs. Although the NetLander mission was cancelled in 2003, the interest on the exploration of Martian subsurface was recently enhanced by the promising observations of the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board of the ESA Mars Express orbiter. In particular, MARSIS detected the base of the North Polar Layered Deposits, penetrating up to ~1.8km the ice-rich upper layer of the underground. Such results suggest that TAPIR, which operates in the same frequency range as MARSIS and can performed a higher number of coherent integrations, is able to reach deeper structures. Yet, in contrast with classical GPRs, TAPIR can not move onto the surface and thus won't provide 2D or 3D scan of the subsurface. To retrieve, in spite of this NetLander restraint, the 3D distribution of the reflecting facets of the underground, the instrument was equipped with two electrical dipoles and a rotating magnetic sensor. These antennas allow to derive, from the measured values of 5 components of the wave field, the direction of arrival of the reflected waves hence the inclination of the buried reflectors. The first validation of this innovative concept was carried out during the RANETA (RAdar of NEtlander in Terre Adélie) campaign organized by the Institute Paul-Emile Victor in January-February 2004. This campaign took place on the Antarctic ice sheet close to the French-Italian Cap Prudhomme station. 8 soundings of the ice shelf were performed on various sites corresponding to different altitudes above the sea level (ranging from ~285m to ~1100m). We shall provide a detailed description of the

Troughs in Ice Sheets and Other Icy Deposits on Mars: Analysis of Their Radiative Balance

Science.gov (United States)

Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, H. J.

2000-01-01

It has long been known that groove-like structures in glaciers and ice sheets can trap more incoming solar radiation than is the case for a 'normal' flat, smooth surface. In this presentation, we shall describe the radiative regimes of typical scarps and troughs on icy surfaces of Mars, and suggest how these features originate and evolve through time. The basis of our analysis is the radiation balance model presented by Pfeffer and Bretherton. Their model considers the visible band radiation regime of a V-shaped groove on a terrestrial ice surface, and shows that absorbed energy can be enhanced by up to 50 percent for grooves with small opening angles and with typical polar values of the solar zenith angle. Our work extends this model by considering: (a) departures from V-shaped geometry, (b) both englacial and surficial dust and debris, and (c) the infrared spectrum. We apply the extended model to various features on the Martian surface, including the spiral-like scarps on the Northern and Southern ice sheets, the large-scale chasms (e.g., Chasm Borealis), and groove-like lineations on valley floors thought to be filled with mixtures of dust and icy substances. In conjunction with study of valley-closure experiments, we suggest that spiral-like scarps and chasms are stable features of the Martian climate regime. We also suggest that further study of scarps and chasms may shed light on the composition (i.e., relative proportions of water ice, carbon-dioxide ice and dust) of the Martian ice sheets and valley fills.

Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

Science.gov (United States)

Hudait, Arpa; Molinero, Valeria

2014-06-04

Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by

Palmer Quest: A Feasible Nuclear Fission "Vision Mission" to the Mars Polar Caps

Science.gov (United States)

Carsey, F. D.; Beegle, L. W.; Nakagawa, R.; Elliott, J. O.; Matthews, J. B.; Coleman, M. L.; Hecht, M. H.; Ivaniov, A. B.; Head, J. W.; Milkovich, S.

2005-01-01

We are engaged in a NASA Vision Mission study, called Palmer Quest after the American Antarctic explorer Nathaniel Palmer, to assess the presence of life and evaluate the habitability of the basal domain of the Mars polar caps. We address this goal through four objectives: 1. Determine the presence of amino acids, nutrients, and geochemical heterogeneity in the ice sheet. 2. Quantify and characterize the provenance of the amino acids in Mars ice. 3. Assess the stratification of outcropped units for indications of habitable zones. 4. Determine the accumulation of ice, mineralogic material, and amino acids in Mars ice caps over the present epoch. Because of the defined scientific goal for the vision mission, the Palmer Quest focus is astrobiological; however, the results of the study make us optimistic that aggressive multi-platform in-situ missions that address a wide range of objectives, such as climate change, can be supported by variations of the approach used on this mission. Mission Overview: The Palmer Quest baseline

STABLE ISOTOPE GEOCHEMISTRY OF MASSIVE ICE

Directory of Open Access Journals (Sweden)

Yurij K. Vasil’chuk

2016-01-01

Full Text Available The paper summarises stable-isotope research on massive ice in the Russian and North American Arctic, and includes the latest understanding of massive-ice formation. A new classification of massive-ice complexes is proposed, encompassing the range and variabilityof massive ice. It distinguishes two new categories of massive-ice complexes: homogeneousmassive-ice complexes have a similar structure, properties and genesis throughout, whereasheterogeneous massive-ice complexes vary spatially (in their structure and properties andgenetically within a locality and consist of two or more homogeneous massive-ice bodies.Analysis of pollen and spores in massive ice from Subarctic regions and from ice and snow cover of Arctic ice caps assists with interpretation of the origin of massive ice. Radiocarbon ages of massive ice and host sediments are considered together with isotope values of heavy oxygen and deuterium from massive ice plotted at a uniform scale in order to assist interpretation and correlation of the ice.

Rapid Access Ice Drill: A New Tool for Exploration of the Deep Antarctic Ice Sheets and Subglacial Geology

Science.gov (United States)

Goodge, J. W.; Severinghaus, J. P.

2014-12-01

The Rapid Access Ice Drill (RAID) will penetrate the Antarctic ice sheets in order to core through deep ice, the glacial bed, and into bedrock below. This new technology will provide a critical first look at the interface between major ice caps and their subglacial geology. Currently in construction, RAID is a mobile drilling system capable of making several long boreholes in a single field season in Antarctica. RAID is interdisciplinary and will allow access to polar paleoclimate records in ice >1 Ma, direct observation at the base of the ice sheets, and recovery of rock cores from the ice-covered East Antarctic craton. RAID uses a diamond rock-coring system as in mineral exploration. Threaded drill-pipe with hardened metal bits will cut through ice using reverse circulation of Estisol for pressure-compensation, maintenance of temperature, and removal of ice cuttings. Near the bottom of the ice sheet, a wireline bottom-hole assembly will enable diamond coring of ice, the glacial bed, and bedrock below. Once complete, boreholes will be kept open with fluid, capped, and made available for future down-hole measurement of thermal gradient, heat flow, ice chronology, and ice deformation. RAID will also sample for extremophile microorganisms. RAID is designed to penetrate up to 3,300 meters of ice and take sample cores in less than 200 hours. This rapid performance will allow completion of a borehole in about 10 days before moving to the next drilling site. RAID is unique because it can provide fast borehole access through thick ice; take short ice cores for paleoclimate study; sample the glacial bed to determine ice-flow conditions; take cores of subglacial bedrock for age dating and crustal history; and create boreholes for use as an observatory in the ice sheets. Together, the rapid drilling capability and mobility of the drilling system, along with ice-penetrating imaging methods, will provide a unique 3D picture of the interior Antarctic ice sheets.

Severnaya Zemlya, arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary

DEFF Research Database (Denmark)

Möller, Per; Lubinski, David J.; Ingólfsson, Ólafur

2006-01-01

Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from......-5e and MIS 5d-3. The MIS 6-5e event, associated with the high marine limit, implies ice-sheet thickness of >2000 m only 200 km from the deep Arctic Ocean, consistent with published evidence of ice grounding at ~1000 m water depth in the central Arctic Ocean. Till fabrics and glacial tectonics record...... repeated expansions of local ice caps exclusively, suggesting wet-based ice cap advance followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains, appear to have repeatedly fostered initiation...

The Martian Oasis Detector

Science.gov (United States)

Smith, P. H.; tomasko, M. G.; McEwen, A.; Rice, J.

2000-07-01

The next phase of unmanned Mars missions paves the way for astronauts to land on the surface of Mars. There are lessons to be learned from the unmanned precursor missions to the Moon and the Apollo lunar surface expeditions. These unmanned missions (Ranger, Lunar Orbiter, and Surveyor) provided the following valuable information, useful from both a scientific and engineering perspective, which was required to prepare the way for the manned exploration of the lunar surface: (1) high resolution imagery instrumental to Apollo landing site selection also tremendously advanced the state of Nearside and Farside regional geology; (2) demonstrated precision landing (less than two kilometers from target) and soft landing capability; (3) established that the surface had sufficient bearing strength to support a spacecraft; and (4) examination of the chemical composition and mechanical properties of the surface. The search for extinct or extant life on Mars will follow the water. However, geomorphic studies have shown that Mars has had liquid water on its surface throughout its geologic history. A cornucopia of potential landing sites with water histories (lakes, floodplains, oceans, deltas, hydrothermal regions) presently exist. How will we narrow down site selection and increase the likelihood of finding the signs of life? One way to do this is to identify 'Martian oases.' It is known that the Martian surface is often highly fractured and some areas have karst structures that support underground caves. Much of the water that formed the channels and valley networks is thought to be frozen underground. All that is needed to create the potential for liquid water is a near surface source of heat; recent lava flows and Martian meteorites attest to the potential for volcanic activity. If we can locate even one spot where fracturing, ice, and underground heat are co-located then we have the potential for an oasis. Such a discovery could truly excite the imaginations of both the

Marginal Ice Zone (MIZ) Program: Science and Experiment Plan

Science.gov (United States)

2012-10-01

MIZ ( Terra Nordica and Sir John Franklin, since renamed Amundsen) served largely to provide ground truth data. _______________________UNIVERSITY OF...ocean, and sea ice components. Currently under development is the incorporation of ice sheets, glaciers and ice caps, and dynamic vegetation . The...and dynamic vegetation to allow investigation of coupled physical processes responsible for decadal-scale climate change and variability in the

Evaluation of Composite-Hull Ships Operating in Arctic Ice

Science.gov (United States)

2016-06-01

COMPOSITE- HULL SHIPS OPERATING IN ARCTIC ICE by Ryan M. Tran June 2016 Thesis Advisor: Young W. Kwon Co-Advisor: Jarema M. Didoszak THIS...Master’s thesis 4. TITLE AND SUBTITLE EVALUATION OF COMPOSITE- HULL SHIPS OPERATING IN ARCTIC ICE 5. FUNDING NUMBERS 6. AUTHOR Ryan M. Tran 7...melting ice caps. Extensive research is thus being conducted to determine the interaction between ice and steel- hulls in anticipation of opening sea

Diversity of Holocene life forms in fossil glacier ice

DEFF Research Database (Denmark)

Willerslev, E.; Hansen, Anders J.; Christensen, B.

1999-01-01

Studies of biotic remains of polar ice caps have been limited to morphological identification of plant pollen and spores. By using sensitive molecular techniques, we now demonstrate a much greater range of detectable organisms; from 2000- and 4000-year-old ice-core samples, we obtained...

Very high elevation water ice clouds on Mars: Their morphology and temporal behavior

Science.gov (United States)

Jaquin, Fred

1988-01-01

Quantitative analysis of Viking images of the martian planetary limb has uncovered the existence and temporal behavior of water ice clouds that form between 50 and 90 km elevation. These clouds show a seasonal behavior that may be correlated with lower atmosphere dynamics. Enhanced vertical mixing of the atmosphere as Mars nears perihelion is hypothesized as the cause of the seasonal dependence, and the diurnal dependence is explained by the temporal behavior of the martian diurnal thermal tide. Viking images also provide a data set of the vertical distribution of aerosols in the martian atmosphere. The temporal and spatial distribution of aerosols are characterized.

The Mars water cycle at other epochs: History of the polar caps and layered terrain

Science.gov (United States)

Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

1992-01-01

The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasonally, but the water content of the atmosphere appears to be controlled by the polar caps. The net annual transport through the atmosphere, integrated over long timescales, must be the driving force behind the long-term evolution of the polar caps; clearly, this feeds back into the evolution of the layered terrain. We have investigated the behavior of the seasonal water cycle and the net integrated behavior at the pole for the last 10 exp 7 years. Our model of the water cycle includes the solar input, CO2 condensation and sublimation, and summertime water sublimation through the seasonal cycles, and incorporates the long-term variations in the orbital elements describing the Martian orbit.

Snowball Earth: Skating on Thin Ice?

Science.gov (United States)

Roberson, A. L.; Stout, A. M.; Pollard, D.; Kasting, J. F.

2011-12-01

There is evidence of at least two intervals of widespread glaciation during the late Neoproterozoic (600-800 Myr ago), which are commonly referred to as "Snowball Earth" episodes. The global nature of these events is indicated by the fact that glacial deposits are found at low paleolatitudes during this time. Models of a global glacial event have produced a variety of solutions at low latitudes: thick ice, thin ice, slushball, and open ocean . The latter two models are similar, except that the slushball model has its ice-line at higher latitudes. To be viable, a model has to be able to account for the survival of life through the glaciations and also explain the existence of cap carbonates and other glacial debris deposited at low latitudes. The "thick-ice" model is not viable because kilometers of ice prevent the penetration of light necessary for the photosynthetic biota below. The "slushball" model is also not viable as it does not allow the formation of cap carbonates. The "thin-ice" model has been discussed previously and can account for continuation of photosynthetic life and glacial deposits at low paleolatitudes. The recently proposed "open-ocean" or "Jormungand" model also satisfies these requirements. What is it, though, that causes some models to produce thin ice near the equator and others to have open water there? We examine this question using a zonally symmetric energy balance climate model (EBM) with flowing sea glaciers to determine what parameter ranges produce each type of solution.

Recent ice cap snowmelt in Russian High Arctic and anti-correlation with late summer sea ice extent

International Nuclear Information System (INIS)

Zhao, Meng; Ramage, Joan; Semmens, Kathryn; Obleitner, Friedrich

2014-01-01

Glacier surface melt dynamics throughout Novaya Zemlya (NovZ) and Severnaya Zemlya (SevZ) serve as a good indicator of ice mass ablation and regional climate change in the Russian High Arctic. Here we report trends of surface melt onset date (MOD) and total melt days (TMD) by combining multiple resolution-enhanced active and passive microwave satellite datasets and analyze the TMD correlations with local temperature and regional sea ice extent. The glacier surface snowpack on SevZ melted significantly earlier (−7.3 days/decade) from 1992 to 2012 and significantly longer (7.7 days/decade) from 1995 to 2011. NovZ experienced large interannual variability in MOD, but its annual mean TMD increased. The snowpack melt on NovZ is more sensitive to temperature fluctuations than SevZ in recent decades. After ruling out the regional temperature influence using partial correlation analysis, the TMD on both archipelagoes is statistically anti-correlated with regional late summer sea ice extent, linking land ice snowmelt dynamics to regional sea ice extent variations. (letter)

Geothermal Heating, Convective Flow and Ice Thickness on Mars

Science.gov (United States)

Rosenberg, N. D.; Travis, B. J.; Cuzzi, J.

2001-01-01

Our 3D calculations suggest that hydrothermal circulation may occur in the martian regolith and may significantly thin the surface ice layer on Mars at some locations due to the upwelling of warm convecting fluids driven solely by background geothermal heating. Additional information is contained in the original extended abstract.

Circum-Arctic Changes in the Flow of Glaciers and Ice Caps from Satellite SAR Data between the 1990s and 2017

Directory of Open Access Journals (Sweden)

Tazio Strozzi

2017-09-01

Full Text Available We computed circum-Arctic surface velocity maps of glaciers and ice caps over the Canadian Arctic, Svalbard and the Russian Arctic for at least two times between the 1990s and 2017 using satellite SAR data. Our analyses are mainly performed with offset-tracking of ALOS-1 PALSAR-1 (2007–2011 and Sentinel-1 (2015–2017 data. In certain cases JERS-1 SAR (1994–1998, TerraSAR-X (2008–2012, Radarsat-2 (2009–2016 and ALOS-2 PALSAR-2 (2015–2016 data were used to fill-in spatial or temporal gaps. Validation of the latest Sentinel-1 results was accomplished by means of SAR data at higher spatial resolution (Radarsat-2 Wide Ultra Fine and ground-based measurements. In general, we observe a deceleration of flow velocities for the major tidewater glaciers in the Canadian Arctic and an increase in frontal velocity along with a retreat of frontal positions over Svalbard and the Russian Arctic. However, all regions have strong accelerations for selected glaciers. The latter developments can be well traced based on the very high temporal sampling of Sentinel-1 acquisitions since 2015, revealing new insights in glacier dynamics. For example, surges on Spitsbergen (e.g., Negribreen, Nathorsbreen, Penckbreen and Strongbreen have a different characteristic and timing than those over Eastern Austfonna and Edgeoya (e.g., Basin 3, Basin 2 and Stonebreen. Events similar to those ongoing on Eastern Austofonna were also observed over the Vavilov Ice Cap on Severnaya Zemlya and possibly Simony Glacier on Franz-Josef Land. Collectively, there seems to be a recently increasing number of glaciers with frontal destabilization over Eastern Svalbard and the Russian Arctic compared to the 1990s.

Airborne observations of changes of ice sheet and sea ice in the Arctic using CryoVEx campaign data

DEFF Research Database (Denmark)

Hvidegaard, Sine Munk; Skourup, Henriette; Forsberg, René

measurements of ice sheet changes. The majority of the campaigns have been sponsored by the European Space Agency, ESA, as part of the CryoSat Validation Experiments – CryoVEx. These have been internationally coordinated efforts to collect coincident space‐borne, airborne, and in‐situ data for pre‐ and post...... cap (Svalbard), the EGIG line crossing the Greenland Ice Sheet, as well as the sea ice north of Alert and sea ice around Svalbard in the Fram Strait. Selected tracks were planned to match CryoSat‐2 passes and a few of them were flown in formation flight with the Alfred Wegener Institute (AWI) Polar‐5...

Ice Dragon: A Mission to Address Science and Human Exploration Objectives on Mars

Science.gov (United States)

Stoker, Carol R.; Davila, A.; Sanders, G.; Glass, Brian; Gonzales, A.; Heldmann, Jennifer; Karcz, J.; Lemke, L.; Sanders, G.

2012-01-01

We present a mission concept where a SpaceX Dragon capsule lands a payload on Mars that samples ground ice to search for evidence of life, assess hazards to future human missions, and demonstrate use of Martian resources.

Super-long Anabiosis of Ancient Microorganisms in Ice and Terrestrial Models for Development of Methods to Search for Life on Mars, Europa and other Planetary Bodies

Science.gov (United States)

Abyzov, S. S.; Duxbury, N. S.; Bobin, N. E.; Fukuchi, M.; Hoover, R. B.; Kanda, H.; Mitskevich, I. N.; Mulyukin, A. L.; Naganuma, T.; Poglazova, M. N.;

MASS BALANCE CHANGES AND ICE DYNAMICS OF GREENLAND AND ANTARCTIC ICE SHEETS FROM LASER ALTIMETRY

Directory of Open Access Journals (Sweden)

G. S. Babonis

2016-06-01

Full Text Available During the past few decades the Greenland and Antarctic ice sheets have lost ice at accelerating rates, caused by increasing surface temperature. The melting of the two big ice sheets has a big impact on global sea level rise. If the ice sheets would melt down entirely, the sea level would rise more than 60 m. Even a much smaller rise would cause dramatic damage along coastal regions. In this paper we report about a major upgrade of surface elevation changes derived from laser altimetry data, acquired by NASA’s Ice, Cloud and land Elevation Satellite mission (ICESat and airborne laser campaigns, such as Airborne Topographic Mapper (ATM and Land, Vegetation and Ice Sensor (LVIS. For detecting changes in ice sheet elevations we have developed the Surface Elevation Reconstruction And Change detection (SERAC method. It computes elevation changes of small surface patches by keeping the surface shape constant and considering the absolute values as surface elevations. We report about important upgrades of earlier results, for example the inclusion of local ice caps and the temporal extension from 1993 to 2014 for the Greenland Ice Sheet and for a comprehensive reconstruction of ice thickness and mass changes for the Antarctic Ice Sheets.

Life in Ice: Implications to Astrobiology

Science.gov (United States)

Hoover, Richard B.

2009-01-01

During the 2008 Tawani International Expedition Schirmacher Oasis/Lake Untersee Antarctica Expedition, living and instantly motile bacteria were found in freshly thawed meltwater from ice of the Schirmacher Oasis Lakes, the Anuchin Glacier ice and samples of the that perennial ice sheet above Lake Untersee. This phenomenon of living bacteria encased in ice had previously been observed in the 32,000 year old ice of the Fox Tunnel. The bacteria found in this ice included the strain FTR1T which was isolated and published as valid new species (Carnobacterium pleistocenium) the first validly published living Pleistocene organism still alive today. Living bacteria were also extracted from ancient ice cores from Vostok, Antarctica. The discovery that many strains of bacteria are able to survive and remain alive while frozen in ice sheets for long periods of time may have direct relevance to Astrobiology. The abundance of viable bacteria in the ice sheets of Antarctica suggests that the presence of live bacteria in ice is common, rather than an isolated phenomenon. This paper will discuss the results of recent studies at NSSTC of bacteria cryopreserved in ice. This paper advances the hypothesis that cryopreserved cells, and perhaps even viable bacterial cells, may exist today--frozen in the water-ice of lunar craters, the Polar Caps or craters of Mars; or in the permafrost of Mars; ice and rocks of comets or water bearing asteroids; or in the frozen crusts of the icy moons of Jupiter and Saturn. The existence of bacterial life in ice suggests that it may not be necessary to drill through a thick ice crust to reach liquid water seas deep beneath the icy crusts of Europa, Ganymede and Enceladus. The presence of viable bacteria in the ice of the Earth s Polar Caps suggests that the possibility that cryo-panspermia (i.e., the trans-planetary transfer of microbial life by impact ejection/spallation of bacteria-rich polar ice masses) deserves serious consideration and study as a

Sodium, Iodine and Bromine in Polar Ice Cores

DEFF Research Database (Denmark)

Maffezzoli, Niccolo

Abstract: This research focuses on sodium, bromine and iodine in polar ice cores, with the aim of reviewing and advancing their current understanding with additional measurements and records, and investigating the connections of these tracers with sea ice and their feasibility as sea ice indicators...... with a description of the main analytic al techniques used to measure ionic and elemental species in ice cores. Chapter 4 introduces sodium, bromine and iodine with a theoretical perspective and a particular focus on their connections with sea ice. Some of the physical and chemical properties that are believed...... back trajectory analyses of the past 17 years. The results identify the aerosol source area influencing the Renland ice cap, a result necessary for the interpretation of impurity records obtained from the ice core. Chapter 6 reviews the published ice/snow measurements of bromine and iodine at polar...

Using high resolution tritium profiles to quantify the effects of melt on two Spitsbergen ice cores

NARCIS (Netherlands)

van der Wel, L.G.; Streurman, H.J.; Isaksson, E.; Helsen, M.M.; van de Wal, R.S.W.; Martma, T.; Pohjola, V.A.; Moore, J.C.; Meijer, H.A.J.

2011-01-01

Ice cores from small ice caps provide valuable climatic information, additional to that of Greenland and Antarctica. However, their integrity is usually compromised by summer meltwater percolation. To determine to what extent this can affect such ice cores, we performed high-resolution tritium

Using high-resolution tritium profiles to quantify the effects of melt on two Spitsbergen ice cores

NARCIS (Netherlands)

Wel, L.G. van der; Streurman, H.J.; Isaksson, E.; Helsen, M.M.; Wal, R.S.W. van de; Martma, T.; Pohjola, V.A.; Moore, J.C.; Meijer, H.A.J.

2011-01-01

Ice cores from small ice caps provide valuable climatic information, additional to that of Greenland and Antarctica. However, their integrity is usually compromised by summer meltwater percolation. To determine to what extent this can affect such ice cores, we performed high-resolution tritium

Modeling of the Martian environment for radiation analysis

International Nuclear Information System (INIS)

De Angelis, G.; Wilson, J.W.; Clowdsley, M.S.; Qualls, G.D.; Singleterry, R.C.

2006-01-01

A model for the radiation environment to be found on the planet Mars due to Galactic Cosmic Rays (GCR) has been developed. Solar modulated primary particles rescaled for conditions at Mars are transported through the Martian atmosphere down to the surface, with altitude and backscattering patterns taken into account. The altitude to compute the atmospheric thickness profile has been determined by using a model for the topography based on the data provided by the Mars Orbiter Laser Altimeter (MOLA) instrument on board the Mars Global Surveyor (MGS) spacecraft. The Mars surface composition has been modeled based on averages over the measurements obtained from orbiting spacecraft and at various landing sites, taking into account the possible volatile inventory (e.g. CO 2 and H 2 O ices) along with its time variations throughout the Martian year. The Mars Radiation Environment Model has been made available worldwide through the Space Ionizing Radiation Effects and Shielding Tools (SIREST) website, a project of NASA Langley Research Center. This site has been developed to provide the scientific and engineering communities with an interactive site containing a variety of environmental models, shield evaluation codes, and radiation response models to allow a thorough assessment of ionizing radiation risk for current and future space missions

CO2 cycle

Science.gov (United States)

Titus, Timothy N.; Byrne, Shane; Colaprete, Anthony; Forget, Francois; Michaels, Timothy I.; Prettyman, Thomas H.

2017-01-01

This chapter discusses the use of models, observations, and laboratory experiments to understand the cycling of CO2 between the atmosphere and seasonal Martian polar caps. This cycle is primarily controlled by the polar heat budget, and thus the emphasis here is on its components, including solar and infrared radiation, the effect of clouds (water- and CO2-ice), atmospheric transport, and subsurface heat conduction. There is a discussion about cap properties including growth and regression rates, albedos and emissivities, grain sizes and dust and/or water-ice contamination, and curious features like cold gas jets and araneiform (spider-shaped) terrain. The nature of the residual south polar cap is discussed as well as its long-term stability and ability to buffer atmospheric pressures. There is also a discussion of the consequences of the CO2 cycle as revealed by the non-condensable gas enrichment observed by Odyssey and modeled by various groups.

Polarimetric SAR interferometry applied to land ice: modeling

DEFF Research Database (Denmark)

Dall, Jørgen; Papathanassiou, Konstantinos; Skriver, Henning

2004-01-01

This paper introduces a few simple scattering models intended for the application of polarimetric SAR interfer-ometry to land ice. The principal aim is to eliminate the penetration bias hampering ice sheet elevation maps generated with single-channel SAR interferometry. The polarimetric coherent...... scattering models are similar to the oriented-volume model and the random-volume-over-ground model used in vegetation studies, but the ice models are adapted to the different geometry of land ice. Also, due to compaction, land ice is not uniform; a fact that must be taken into account for large penetration...... depths. The validity of the scattering models is examined using L-band polarimetric interferometric SAR data acquired with the EMISAR system over an ice cap located in the percolation zone of the Greenland ice sheet. Radar reflectors were deployed on the ice surface prior to the data acquisition in order...

Extended survival of several organisms and amino acids under simulated martian surface conditions

Science.gov (United States)

Johnson, A. P.; Pratt, L. M.; Vishnivetskaya, T.; Pfiffner, S.; Bryan, R. A.; Dadachova, E.; Whyte, L.; Radtke, K.; Chan, E.; Tronick, S.; Borgonie, G.; Mancinelli, R. L.; Rothschild, L. J.; Rogoff, D. A.; Horikawa, D. D.; Onstott, T. C.

2011-02-01

Recent orbital and landed missions have provided substantial evidence for ancient liquid water on the martian surface as well as evidence of more recent sedimentary deposits formed by water and/or ice. These observations raise serious questions regarding an independent origin and evolution of life on Mars. Future missions seek to identify signs of extinct martian biota in the form of biomarkers or morphological characteristics, but the inherent danger of spacecraft-borne terrestrial life makes the possibility of forward contamination a serious threat not only to the life detection experiments, but also to any extant martian ecosystem. A variety of cold and desiccation-tolerant organisms were exposed to 40 days of simulated martian surface conditions while embedded within several centimeters of regolith simulant in order to ascertain the plausibility of such organisms' survival as a function of environmental parameters and burial depth. Relevant amino acid biomarkers associated with terrestrial life were also analyzed in order to understand the feasibility of detecting chemical evidence for previous biological activity. Results indicate that stresses due to desiccation and oxidation were the primary deterrent to organism survival, and that the effects of UV-associated damage, diurnal temperature variations, and reactive atmospheric species were minimal. Organisms with resistance to desiccation and radiation environments showed increased levels of survival after the experiment compared to organisms characterized as psychrotolerant. Amino acid analysis indicated the presence of an oxidation mechanism that migrated downward through the samples during the course of the experiment and likely represents the formation of various oxidizing species at mineral surfaces as water vapor diffused through the regolith. Current sterilization protocols may specifically select for organisms best adapted to survival at the martian surface, namely species that show tolerance to radical

Water ice clouds observations with PFS on Mars Express

Science.gov (United States)

Moroz, V. I.; Zasova, L. V.; Formisano, V.; Grassi, D.; Ignatiev, N. I.; Giuranna, M.; Maturilli, A.; Pfs Team

The water ice cloud observation is one of the scientific goals of PFS. Presence and properties of the ice particles are identified from absorption features, observed in both spectral ranges of PFS. Being in the near perihelion condition, the temperature of the Martian atmosphere is pretty high and ice clouds exist only in some places, for example, related to topography or at north high latitudes et etc. The ice clouds are observed often above the tops of the volcanoes. We have found the ice clouds above Olympus (orbit 37) and Ascraeus Mons (orbit 68). Effective radius of particles according to the thermal IR is preliminary estimated of 1 μ m, which leads to the visual opacity of 0.2 -0.3 above Olympus and of maximum of 0.6 above Ascraeus Mons. In the case of Ascraeus Mons the ice clouds are observed on the south slope near the top of the volcano. The maximum surface temperature, observed there, results in the upward flux of warm air, which, cooling, provides the condensation of H2O. We will present a detailed analysis of the ice clouds, observed over the planet in the IR spectral range.

Atmospheric Depositions of Natural and Anthropogenic Aerosols on the Guliya Ice Cap (Northwestern Tibetan Plateau) during the last 340 years

Science.gov (United States)

Sierra Hernandez, R.; Gabrielli, P.; Beaudon, E.; Thompson, L. G.; Wegner, A.

2017-12-01

Anthropogenic emissions (e.g., greenhouse gases, trace elements (TE) including toxic metals) to the atmosphere have dramatically increased since the Industrial Revolution in the 19th century. High temperature processes such as fossil fuel combustion and pyrometallurgy generate fumes and fine particles (industrial times. Thus, ice core records of TEs from mid- and low-latitudes are needed to assess the spatial and temporal extent and levels of pollution in the environment. Here we present records of 29 TEs spanning the period 1650-1991 CE from the Guliya ice cap in the western Kunlun Mountains, northwest Tibetan Plateau to assess their natural and anthropogenic sources. The Guliya TEs records show two distinct periods with only crustal contributions prior to the 1850s and non-crustal contributions (Pb, Cd, Sb, Zn, Sn) after the 1850s. Enrichments of Pb, Cd, Sb, and Zn in Guliya between 1850 and 1950 can be attributed primarily to coal combustion emissions from western countries (Europe) while regional emissions (fossil fuel combustion, mining/smelting, fertilizers) from Central Asia, and probably from Kashgar in western China, and South Asia (India, Nepal) could be the source of the TE enrichments (Cd, Pb, Sn) observed in Guliya after 1950. This information can be used by modelers to assess pollution transport at local, regional, and global scales and by policy makers to develop strategies and policies to reduce their emissions.

The future sea-level rise contribution of Greenland’s glaciers and ice caps

International Nuclear Information System (INIS)

Machguth, H; Rastner, P; Bolch, T; Mölg, N; Sørensen, L Sandberg; Aðalgeirsdottir, G; Van Angelen, J H; Van den Broeke, M R; Fettweis, X

2013-01-01

We calculate the future sea-level rise contribution from the surface mass balance of all of Greenland’s glaciers and ice caps (GICs, ∼90 000 km 2 ) using a simplified energy balance model which is driven by three future climate scenarios from the regional climate models HIRHAM5, RACMO2 and MAR. Glacier extent and surface elevation are modified during the mass balance model runs according to a glacier retreat parameterization. Mass balance and glacier surface change are both calculated on a 250 m resolution digital elevation model yielding a high level of detail and ensuring that important feedback mechanisms are considered. The mass loss of all GICs by 2098 is calculated to be 2016 ± 129 Gt (HIRHAM5 forcing), 2584 ± 109 Gt (RACMO2) and 3907 ± 108 Gt (MAR). This corresponds to a total contribution to sea-level rise of 5.8 ± 0.4, 7.4 ± 0.3 and 11.2 ± 0.3 mm, respectively. Sensitivity experiments suggest that mass loss could be higher by 20–30% if a strong lowering of the surface albedo were to take place in the future. It is shown that the sea-level rise contribution from the north-easterly regions of Greenland is reduced by increasing precipitation while mass loss in the southern half of Greenland is dominated by steadily decreasing summer mass balances. In addition we observe glaciers in the north-eastern part of Greenland changing their characteristics towards greater activity and mass turnover. (letter)

Simulating the roles of crevasse routing of surface water and basal friction on the surge evolution of Basin 3, Austfonna ice cap

Directory of Open Access Journals (Sweden)

Y. Gong

2018-05-01

Full Text Available The marine-terminating outlet in Basin 3, Austfonna ice cap, has been accelerating since the mid-1990s. Stepwise multi-annual acceleration associated with seasonal summer speed-up events was observed before the outlet entered the basin-wide surge in autumn 2012. We used multiple numerical models to explore hydrologic activation mechanisms for the surge behaviour. A continuum ice dynamic model was used to invert basal friction coefficient distributions using the control method and observed surface velocity data between April 2012 and July 2014. This has provided input to a discrete element model capable of simulating individual crevasses, with the aim of finding locations where meltwater entered the glacier during the summer and reached the bed. The possible flow paths of surface meltwater reaching the glacier bed as well as those of meltwater produced at the bed were calculated according to the gradient of the hydraulic potential.The inverted friction coefficients show the unplugging of the stagnant ice front and expansion of low-friction regions before the surge reached its peak velocity in January 2013. Crevasse distribution reflects the basal friction pattern to a high degree. The meltwater reaches the bed through the crevasses located above the margins of the subglacial valley and the basal melt that is generated mainly by frictional heating flows either to the fast-flowing units or potentially accumulates in an overdeepened region. Based on these results, the mechanisms facilitated by basal meltwater production, crevasse opening and the routing of meltwater to the bed are discussed for the surge in Basin 3.

Simulating the roles of crevasse routing of surface water and basal friction on the surge evolution of Basin 3, Austfonna ice cap

Science.gov (United States)

Gong, Yongmei; Zwinger, Thomas; Åström, Jan; Altena, Bas; Schellenberger, Thomas; Gladstone, Rupert; Moore, John C.

2018-05-01

The marine-terminating outlet in Basin 3, Austfonna ice cap, has been accelerating since the mid-1990s. Stepwise multi-annual acceleration associated with seasonal summer speed-up events was observed before the outlet entered the basin-wide surge in autumn 2012. We used multiple numerical models to explore hydrologic activation mechanisms for the surge behaviour. A continuum ice dynamic model was used to invert basal friction coefficient distributions using the control method and observed surface velocity data between April 2012 and July 2014. This has provided input to a discrete element model capable of simulating individual crevasses, with the aim of finding locations where meltwater entered the glacier during the summer and reached the bed. The possible flow paths of surface meltwater reaching the glacier bed as well as those of meltwater produced at the bed were calculated according to the gradient of the hydraulic potential. The inverted friction coefficients show the unplugging of the stagnant ice front and expansion of low-friction regions before the surge reached its peak velocity in January 2013. Crevasse distribution reflects the basal friction pattern to a high degree. The meltwater reaches the bed through the crevasses located above the margins of the subglacial valley and the basal melt that is generated mainly by frictional heating flows either to the fast-flowing units or potentially accumulates in an overdeepened region. Based on these results, the mechanisms facilitated by basal meltwater production, crevasse opening and the routing of meltwater to the bed are discussed for the surge in Basin 3.

Water Ice Clouds and Dust in the Martian Atmosphere Observed by Mars Climate Sounder

Science.gov (United States)

Benson, Jennifer L.; Kass, David; Heavens, Nicholas; Kleinbohl, Armin

2011-01-01

The water ice clouds are primarily controlled by the temperature structure and form at the water condensation level. Clouds in all regions presented show day/night differences. Cloud altitude varies between night and day in the SPH and tropics: (1) NPH water ice opacity is greater at night than day at some seasons (2) The diurnal thermal tide controls the daily variability. (3) Strong day/night changes indicate that the amount of gas in the atmosphere varies significantly. See significant mixtures of dust and ice at the same altitude planet-wide (1) Points to a complex radiative and thermal balance between dust heating (in the visible) and ice heating or cooling in the infrared. Aerosol layering: (1) Early seasons reveal a zonally banded spatial distribution (2) Some localized longitudinal structure of aerosol layers (3) Later seasons show no consistent large scale organization

Ice Lens Formation and Frost Heave at the Phoenix Landing Site

Science.gov (United States)

Zent, A. P.; Sizemore, H. G.; Remple, A. W.

2011-01-01

Several lines of evidence indicate that the volume of shallow ground ice in the martian high latitudes exceeds the pore volume of the host regolith. Boynton et al. found an optimal fit to the Mars Odyssey Gamma Ray Spectrometer (GRS) data at the Phoenix landing site by modeling a buried layer of 50-75% ice by mass (up to 90% ice by volume). Thermal and optical observations of recent impact craters in the northern hemisphere have revealed nearly pure ice. Ice deposits containing only 1-2% soil by volume were excavated by Phoenix. The leading hypothesis for the origin of this excess ice is that it developed in situ by a mechanism analogous to the formation of terrestrial ice lenses and needle ice. Problematically, terrestrial soil-ice segregation is driven by freeze/thaw cycling and the movement of bulk water, neither of which are expected to have occurred in the geologically recent past on Mars. If however ice lens formation is possible at temperatures less than 273 K, there are possible implications for the habitability of Mars permafrost, since the same thin films of unfrozen water that lead to ice segregation are used by terrestrial psychrophiles to metabolize and grow down to temperatures of at least 258 K.

Ice Thickness, Melting Rates and Styles of Activity in Ice-Volcano Interaction

Science.gov (United States)

Gudmundsson, M. T.

2005-12-01

In most cases when eruptions occur within glaciers they lead to rapid ice melting, jokulhlaups and/or lahars. Many parameters influence the style of activity and its impact on the environment. These include ice thickness (size of glacier), bedrock geometry, magma flow rate and magma composition. The eruptions that have been observed can roughly be divided into: (1) eruptions under several hundred meters thick ice on a relatively flat bedrock, (2) eruptions on flat or sloping bed through relatively thin ice, and (3) volcanism where effects are limitied to confinement of lava flows or melting of ice by pyroclastic flows or surges. This last category (ice-contact volcanism) need not cause much ice melting. Many of the deposits formed by Pleistocene volcanism in Iceland, British Columbia and Antarctica belong to the first category. An important difference between this type of activity and submarine activity (where pressure is hydrostatic) is that pressure at vents may in many cases be much lower than glaciostatic due to partial support of ice cover over vents by the surrounding glacier. Reduced pressure favours explosive activity. Thus the effusive/explosive transition may occur several hundred metres underneath the ice surface. Explosive fragmentation of magma leads to much higher rates of heat transfer than does effusive eruption of pillow lavas, and hence much higher melting rates. This effect of reduced pressure at vents will be less pronounced in a large ice sheet than in a smaller glacier or ice cap, since the hydraulic gradient that drives water away from an eruption site will be lower in the large glacier. This may have implications for form and type of eruption deposits and their relationship with ice thickness and glacier size.

Martian meteorites and Martian magnetic anomalies: a new perspective from NWA 7034 (Invited)

Science.gov (United States)

Gattacceca, J.; Rochette, P.; Scozelli, R. B.; Munayco, P.; Agee, C. B.; Quesnel, Y.; Cournede, C.; Geissman, J. W.

2013-12-01

The magnetic anomalies observed above the Martian Noachian crust [1] require strong crustal remanent magnetization in the 15-60 A/m range over a thickness of 20-50 km [2,3]. The Martian rocks available for study in the form of meteorites do contain magnetic minerals (magnetite and/or pyrrhotite) but in too small amount to account for such strong remanent magnetizations [4]. Even though this contradiction was easily explained by the fact that Martian meteorites (mostly nakhlites and shergottites) are not representative of the Noachian Martian crust, we were left with no satisfactory candidate lithology to account for the Martian magnetic anomalies. The discovery in the Sahara of a new type of Martian meteorite (NWA 7034 [5] and subsequent paired stones which are hydrothermalized volcanic breccia) shed a new light on this question as it contains a much larger amount of ferromagnetic minerals than any other Martian meteorite. We present here a study of the magnetic properties of NWA 7034, together with a review of the magnetic properties of thirty other Martian meteorites. Magnetic measurements (including high and low temperature behavior and Mössbauer spectroscopy) show that NWA 7034 contains about 15 wt.% of magnetite with various degrees of substitution and maghemitization up to pure maghemite, in the pseudo-single domain size range. Pyrrhotite, a common mineral in other Martian meteorites is not detected. Although it is superparamagnetic and cannot carry remanent magnetization, nanophase goethite is present in significant amounts confirming that NWA 7034 is the most oxidized Martian meteorite studied so far, as already indicated by the presence of maghemite (this study) and pyrite [5]. These magnetic properties show that a kilometric layer of a lithology similar to NWA 7034 magnetized in a dynamo field would be enough to account for the strongest Martian magnetic anomalies. Although the petrogenesis of NWA 7034 is still debated, as the brecciation could be either

Earth's Climate History from Glaciers and Ice Cores

Science.gov (United States)

Thompson, Lonnie

2013-03-01

Glaciers serve both as recorders and early indicators of climate change. Over the past 35 years our research team has recovered climatic and environmental histories from ice cores drilled in both Polar Regions and from low to mid-latitude, high-elevation ice fields. Those ice core -derived proxy records extending back 25,000 years have made it possible to compare glacial stage conditions in the Tropics with those in the Polar Regions. High-resolution records of δ18O (in part a temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although at many sites the early Holocene was warmer than today. Remarkable similarities between changes in the highland and coastal cultures of Peru and regional climate variability, especially precipitation, imply a strong connection between prehistoric human activities and regional climate. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions today are different from those under which these ice fields originated and have been sustained. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth's climate system is underway. Observations of glacier shrinkage during the 20th and 21st century girdle the globe from the South American Andes, the Himalayas, Kilimanjaro (Tanzania, Africa) and glaciers near Puncak Jaya, Indonesia (New Guinea). The history and fate of these ice caps, told through the adventure, beauty and the scientific evidence from some of world's most remote mountain tops, provide a global perspective for contemporary climate. NSF Paleoclimate Program

CALICE: Calibrating Plant Biodiversity in Glacier Ice

Science.gov (United States)

Festi, Daniela; Cristofori, Antonella; Vernesi, Cristiano; Zerbe, Stefan; Wellstein, Camilla; Maggi, Valter; Oeggl, Klaus

2017-04-01

The objective of the project is to reconstruct plant biodiversity and its trend archived in Alpine glacier ice by pollen and eDNA (environmental DNA) during the last five decades by analyzing a 40 m ice core. For our study we chose the Adamello glacier (Trentino - Südtirol, Lombardia) because of i) the good preservation conditions for pollen and eDNA in ice, ii) the thickness of the ice cap (270m) and iii) the expected high time resolution. The biodiversity estimates gained by pollen analysis and eDNA will be validated by historical biodiversity assessments mainly based on vegetation maps, aerial photos and vegetation surveys in the catchment area of the Adamello glacier for the last five decades. This historical reconstruction of biodiversity trends will be performed on a micro-, meso- and macro-scale (5, 20-50 and 50-100 Km radius, respectively). The results will serve as a calibration data set on biodiversity for future studies, such as the second step of the coring by the POLLiCE research consortium (pollice.fmach.it). In fact, arrangements are currently been made to drill the complete ice cap and retrieve a 270 m thick core which has the potential to cover a time span of minimum 400 years up to several millennia. This second stage will extend the time scale and enable the evaluation of dissimilarity/similarity of modern biodiversity in relation to Late Holocene trends. Finally, we believe this case study has the potential to be applied in other glaciated areas to evaluate biodiversity for large regions (e.g. central Asian mountain ranges, Tibet and Tian Shan or the Andes).

Origin of the outer layer of martian low-aspect ratio layered ejecta craters

Science.gov (United States)

Boyce, Joseph M.; Wilson, Lionel; Barlow, Nadine G.

2015-01-01

Low-aspect ratio layered ejecta (LARLE) craters are one of the most enigmatic types of martian layered ejecta craters. We propose that the extensive outer layer of these craters is produced through the same base surge mechanism as that which produced the base surge deposits generated by near-surface, buried nuclear and high-explosive detonations. However, the LARLE layers have higher aspect ratios compared with base surge deposits from explosion craters, a result of differences in thicknesses of these layers. This characteristics is probably caused by the addition of large amounts of small particles of dust and ice derived from climate-related mantles of snow, ice and dust in the areas where LARLE craters form. These deposits are likely to be quickly stabilized (order of a few days to a few years) from eolian erosion by formation of duricrust produced by diffusion of water vapor out of the deposits.

Revised estimates of Greenland ice sheet thinning histories based on ice-core records

DEFF Research Database (Denmark)

Lecavalier, B.S.; Milne, G.A.; Fisher, D.A.

2013-01-01

-based reconstructions and, to some extent, the estimated elevation histories. A key component of the ice core analysis involved removing the influence of vertical surface motion on the dO signal measured from the Agassiz and Renland ice caps. We re-visit the original analysis with the intent to determine if the use...... of more accurate land uplift curves can account for some of the above noted discrepancy. To improve on the original analysis, we apply a geophysical model of glacial isostatic adjustment calibrated to sea-level records from the Queen Elizabeth Islands and Greenland to calculate the influence of land...... in this selection is further complicated by the possible influence of Innuitian ice during the early Holocene (12-8 ka BP). Our results indicate that a more accurate treatment of the uplift correction leads to elevation histories that are, in general, shifted down relative to the original curves at GRIP, NGRIP, DYE...

Emission and absorption of CO2 during the sea ice formation and melting in the high Arctic

Directory of Open Access Journals (Sweden)

A. P. Nedashkovsky

2012-01-01

Full Text Available The carbonate system of the Arctic sea ice is considered. The observations were conducted in the Nansen Basin at the drifting station North Pole-35 in 2007–2008. It was found that total alkalinity – salinity ratio (TA/S and total inorganic carbon – salinity ratio (TC/S as well as TA/TC ratio in the ice column and seawater column are similar. The deviations from that pattern were observed in the upper thin layer of the young and first-year ice and in the ice snow cap. The TA/TC ratio (equals to ~2 in the ice snow cap was related with the calcium hydrocarbonate decay and CO₂ removal. It was shown that CO₂ removal was due to its emission into the atmosphere. The CO₂ flux was equal to ~0.02 mol/m² for season. The water formed during melting of the first-year ice was significantly under saturated of CO₂ and hence it may be a sink of 0.05 0.07 mol/m² of the atmospheric CO₂ per season.

Ma_MISS on ExoMars: Mineralogical Characterization of the Martian Subsurface

Science.gov (United States)

De Sanctis, Maria Cristina; Altieri, Francesca; Ammannito, Eleonora; Biondi, David; De Angelis, Simone; Meini, Marco; Mondello, Giuseppe; Novi, Samuele; Paolinetti, Riccardo; Soldani, Massimo; Mugnuolo, Raffaele; Pirrotta, Simone; Vago, Jorge L.; Ma_MISS Team

2017-07-01

The Ma_MISS (Mars Multispectral Imager for Subsurface Studies) experiment is the visible and near infrared (VNIR) miniaturized spectrometer hosted by the drill system of the ExoMars 2020 rover. Ma_MISS will perform IR spectral reflectance investigations in the 0.4-2.2 μm range to characterize the mineralogy of excavated borehole walls at different depths (between 0 and 2 m). The spectral sampling is about 20 nm, whereas the spatial resolution over the target is 120 μm. Making use of the drill's movement, the instrument slit can scan a ring and build up hyperspectral images of a borehole. The main goal of the Ma_MISS instrument is to study the martian subsurface environment. Access to the martian subsurface is crucial to our ability to constrain the nature, timing, and duration of alteration and sedimentation processes on Mars, as well as habitability conditions. Subsurface deposits likely host and preserve H2O ice and hydrated materials that will contribute to our understanding of the H2O geochemical environment (both in the liquid and in the solid state) at the ExoMars 2020 landing site. The Ma_MISS spectral range and sampling capabilities have been carefully selected to allow the study of minerals and ices in situ before the collection of samples. Ma_MISS will be implemented to accomplish the following scientific objectives: (1) determine the composition of subsurface materials, (2) map the distribution of subsurface H2O and volatiles, (3) characterize important optical and physical properties of materials (e.g., grain size), and (4) produce a stratigraphic column that will inform with regard to subsurface geological processes. The Ma_MISS findings will help to refine essential criteria that will aid in our selection of the most interesting subsurface formations from which to collect samples.

Atmospheric Modeling of the Martian Polar Regions: One Mars Year of CRISM EPF Observations of the South Pole

Science.gov (United States)

Brown, A. J.; Wolff, M. J.

2009-03-01

We have used CRISM Emission Phase Function gimballed observations to investigate atmospheric dust/ice opacity and surface albedo in the south polar region for the first Mars year of MRO operations. This covers the MY28 "dust event" and cap recession.

The seasonal cycle of snow cover, sea ice and surface albedo

Science.gov (United States)

Robock, A.

1980-01-01

The paper examines satellite data used to construct mean snow cover caps for the Northern Hemisphere. The zonally averaged snow cover from these maps is used to calculate the seasonal cycle of zonally averaged surface albedo. The effects of meltwater on the surface, solar zenith angle, and cloudiness are parameterized and included in the calculations of snow and ice albedo. The data allows a calculation of surface albedo for any land or ocean 10 deg latitude band as a function of surface temperature ice and snow cover; the correct determination of the ice boundary is more important than the snow boundary for accurately simulating the ice and snow albedo feedback.

Modelling the surface mass balance of the Greenland ice sheet and neighbouring ice caps : A dynamical and statistical downscaling approach

NARCIS (Netherlands)

Noël, B.P.Y.

2018-01-01

The Greenland ice sheet (GrIS) is the world’s second largest ice mass, storing about one tenth of the Earth’s freshwater. If totally melted, global sea level would rise by 7.4 m, affecting low-lying regions worldwide. Since the mid-1990s, increased atmospheric and oceanic temperatures have

Central Tibetan Plateau atmospheric trace metals contamination: a 500-year record from the Puruogangri ice core

Science.gov (United States)

Beaudon, E.; Gabrielli, P.; Sierra Hernandez, R.; Wegner, A.; Thompson, L. G.

2017-12-01

Since the 1980s, Asia has experienced enormous industrial development from rapid population growth, industrialization and consequent large-scale environmental changes. The inherent generated atmospheric pollution currently contributes to half of all Earth's anthropogenic trace metals emissions. Asian trace metal aerosols, when deposited on glaciers of the surrounding mountains of the Tibetan Plateau (TP), leave a characteristic chemical fingerprint. Interpreting trace element (TE) records from glaciers implies a thorough comprehension of their provenance and temporal variability. It is then essential to discriminate the TEs' natural background components from their anthropogenic components. Here we present 500-year TE records from the Puruogangri ice core (Tibet, China) that provide a highly resolved account of the impact of past atmospheric influences, environmental processes and human activities on the central TP. A decreasing aeolian dust input to the ice cap allowed the detection of an atmospheric pollution signal. The anthropogenic pollution contribution emerges in the record since the early 1900s and increases substantially after 1935. The metallurgy (Zn, Pb and steel smelting) emission products from the former Soviet Union and especially from central Asia likely enhanced the anthropogenic deposition to the Puruogangri ice cap between 1935 and 1980, suggesting that the westerlies served as a conveyor of atmospheric pollution to central Tibet. The impact of this industrial pollution cumulated with that of the hemispheric coal and gasoline combustion which are respectively traced by Sb and Pb enrichment in the ice. The Chinese steel production accompanying the Great Leap Forward (1958-1961) and the Chinese Cultural Revolution (1966-1976) is proposed as a secondary but proximal source of Pb pollution affecting the ice cap between 1958 and 1976. The most recent decade (1980-1992) of the enrichment time series suggests that Puruogangri ice cap recorded the early

Water-Searchers: A Reconfigurable and Self Sustaining Army of Subsurface Exploration Robots Searching for Water/Ice Using Multiple Sensors

Science.gov (United States)

Youk, G. U.; Whittaker, W. (Red); Volpe, R.

2000-01-01

Perhaps the most promising site for extant life on Mars today is where subsurface water has been maintained. Therefore, searching for underground water will provide a good chance to find evidence of life on Mars. The following are scientific/engineering questions that we want to answer using our approach: (1) Is there subsurface water/ice? How deep is it? How much is there? Is it frozen? (2) What kinds of underground layers exist in the Martian crust? (3) What is the density of Martian soil or regolith? Can we dig into it? Should we drill into it? (4) Can a sudden release of underground water occur if a big asteroid hits Mars? Our approach provides essential information to answer these questions. Moreover, dependence on the water content and depth in soil, not only resultant scientific conclusions but also proper digging/drilling methods, are suggested. 'How much water is in the Martian soil?' There can be several possibilities: (1) high water content that is enough to form permafrost; (2) low water content that is not enough to form permafrost; or (3) different layers with different moisture contents. 'How deep should a rover dig into soil to find water/ice?' The exact size-frequency distribution has not been measured for the soil particles. On-board sensors can provide not only the water content but also the density (or porosity) of Martian soil as a function of depth.

Comparison of ground-based and Viking Orbiter measurements of Martian water vapor - Variability of the seasonal cycle

Science.gov (United States)

Jakosky, B. M.; Barker, E. S.

1984-01-01

Earth-based observations of Mars atmospheric water vapor are presented for the 1975-1976, 1977-1978, and 1983 apparitions. Comparisons are made with near-simultaneous spacecraft measurements made from the Viking Orbiter Mars Atmospheric Water Detection experiment during 1976-1978 and with previous earth-based measurements. Differences occur between the behavior in the different years, and may be related to the Mars climate. Measurements during the southern summer in 1969 indicate a factor of three times as much water as is present at this same season in other years. This difference may have resulted from the sublimation of water from the south polar residual cap upon removal of most or all of the CO2 ice present; sublimation of all of the CO2 ice during some years could be a result of a greater thermal load being placed on the cap due to the presence of differing amounts of atmospheric dust.

Amazonis and Utopia Planitiae: Martian Lacustrine basins

Science.gov (United States)

Scott, David H.; Rice, James W., Jr.; Dohm, James M.; Chapman, Mary G.

1992-01-01

Amazonis and Utopia Planitiae are two large (greater than 10(exp 6) sq. km) basins on Mars having morphological features commonly associated with former lakes. The investigation of these areas is an extension of our previous paleolake studies in the Elysium basin. Using Viking images, we are searching for familiar geologic forms commonly associated with standing bodies of water on Earth. Like Elysium, the two basins exhibit terraces and lineations resembling shorelines, etched and infilled floors with channel-like sinuous markings in places, inflow channels along their borders, and other geomorphic indicators believed to be related to the presence of water and ice. In some areas these features are better displayed than in others where they may be very tenuous; their value as indicators can be justified only by their association with related features. Even though these postulated paleolakes are very young in the Martian stratigraphic sequence, their shoreline features are poorly preserved and they are probably much older than large Pleistocene lakes on Earth.

Seasonally-Active Water on Mars: Vapour, Ice, Adsorbate, and the Possibility of Liquid

Science.gov (United States)

Richardson, M. I.

2002-12-01

Seasonally-active water can be defined to include any water reservoir that communicates with other reservoirs on time scales of a year or shorter. It is the interaction of these water reservoirs, under the influence of varying solar radiation and in conjunction with surface and atmospheric temperatures, that determines the phase-stability field for water at the surface, and the distribution of water in various forms below, on, and above the surface. The atmosphere is the critical, dynamical link in this cycling system, and also (fortunately) one of the easiest to observe. Viking and Mars Global Surveyor observations paint a strongly asymmetric picture of the global seasonal water cycle, tied proximately to planetary eccentricity, and the existence of residual ice caps of different composition at the two poles. The northern summer experiences the largest water vapour columns, and is associated with sublimation from the northern residual water ice cap. The southern summer residual carbon dioxide ice cap is cold trap for water. Asymmetry in the water cycle is an unsolved problem. Possible solutions may involve the current timing of perihelion (the water cap resides at the pole experiencing the longer but cooler summer), the trapping of water ice in the northern hemisphere by tropical water ice clouds, and the bias in the annual-average, zonal-mean atmospheric circulation resulting from the zonal-mean difference in the elevation of the northern and southern hemispheres. Adsorbed and frozen water have proven harder to constrain. Recent Odyssey Gamma Ray Spectrometer results suggest substantial ground ice in the mid- and high-latitudes, but this water is likely below the seasonal skin depth for two reasons: the GRS results are best fit with such a model, and GCM models of the water cycle produce dramatically unrealistic atmospheric vapour distributions when such a very near surface, GRS-like distribution is initialized - ultimately removing the water to the northern and

Experimental Demonstration of the Formation of Liquid Brines under Martian Polar Conditions in the Michigan Mars Environmental Chamber

Science.gov (United States)

Fischer, Erik; Martinez, German; Elliott, Harvey; Borlina, Caue; Renno, Nilton

2014-05-01

Liquid water is one of the necessary ingredients for the development of life as we know it. The behavior of various liquid states of H2O such as liquid brine, undercooled liquid interfacial water, subsurface melt water and ground water [1] needs to be understood in order to address the potential habitability of Mars for microbes and future human exploration. It has been shown thermodynamically that liquid brines can exist under Martian polar conditions [2, 3]. We have developed the Michigan Mars Environmental Chamber (MMEC) to simulate the entire range of Martian surface and shallow subsurface conditions with respect to temperature, pressure, relative humidity, solar radiation and soil wetness at equatorial and polar latitudes. Our experiments in the MMEC show that deliquescence of NaClO4, Mg(ClO4)2 and Ca(ClO4)2 occurs diurnally under the environmental conditions of the Phoenix landing site when these salts get in contact with water ice. Since Phoenix detected these salts and water ice at the landing site, including frost formation, it is extremely likely that deliquescence occurs at the Phoenix landing site. By layering NaClO4, Mg(ClO4)2 or Ca(ClO4)2 on top of a pure water ice slab at 800 Pa and 190 K and raising the temperature stepwise across the eutectic temperature of the perchlorate salts, we observe distinct changes in the Raman spectra of the samples when deliquescence occurs. When crossing the eutectic temperatures of NaClO4 (236 K), Mg(ClO4)2 (205 K) and Ca(ClO4)2 (199 K) [4, 5], the perchlorate band of the Raman spectrum shows a clear shift from 953 cm-1 to 936 cm-1. Furthermore, the appearance of a broad O-H vibrational stretching spectrum between 3244 cm-1 and 3580 cm-1 is another indicator of deliquescence. This process of deliquescence occurs on the order of seconds when the perchlorate salt is in contact with water ice. On the contrary, when the perchlorate salt is only subjected to water vapor in the Martian atmosphere, deliquescence was not

Ice haze, snow, and the Mars water cycle

Science.gov (United States)

Kahn, Ralph

1990-01-01

Light curves and extinction profiles derived from Martian limb observations are used to constrain the atmospheric temperature structure in regions of the atmosphere with thin haze and to analyze the haze particle properties and atmospheric eddy mixing. Temperature between 170 and 190 K are obtained for three cases at levels in the atmosphere ranging from 20 to 50 km. Eddy diffusion coefficients around 100,000 sq cm/s, typical of a nonconvecting atmosphere, are derived in the haze regions at times when the atmosphere is relatively clear of dust. This parameter apparently changes by more than three orders of magnitude with season and local conditions. The derived particle size parameter varies systematically by more than an order of magnitude with condensation level, in such a way that the characteristic fall time is always about one Martian day. Ice hazes provide a mechanism for scavenging water vapor in the thin Mars atmosphere and may play a key role in the seasonal cycle of water on Mars.

Martian Environment Electrostatic Precipitator

Science.gov (United States)

McDougall, Michael Owen

2016-01-01

As part of the planned manned mission to Mars, NASA has noticed that shipping oxygen as a part of life support to keep the astronauts alive continuously is overly expensive, and impractical. As such, noting that the Martian atmosphere is 95.37% CO2, NASA chemists noted that one could obtain oxygen from the Martian atmosphere. The plan, as part of a larger ISRU (in-situ resource utilization) initiative, would extract water from the regolith, or the Martian soil which can be electrolyzed by solar panel produced voltage into hydrogen and oxygen. The hydrogen can then be used in the Sabatier reaction with carbon dioxide to produce methane and water producing a net reaction that does not lose water and outputs methane and oxygen for use as rocket fuel and breathing.

Possible occurrence and origin of massive ice in Utopia Planitia

Science.gov (United States)

Kargel, J. S.; Costard, F. M.

1993-01-01

F. M. Costard recently discovered a large field of possible thermokarst depressions near latitude 45 deg N, longitude 270 deg, in western Utopia Planitia. Oval to circular pits are typically 300-1000 m across and approximately 25 m deep; larger depressions, 3-5 km across, are compound and seem to have formed by coalescence of smaller pits. Small domical hills occur on the floors of two pits. These depressions characteristically have steep, scalloped edges and one or more inner benches. Truncation relations of the benches suggest a discontinuous, lenslike stratification of the material in which the pits are developed. Based on a close analogy in form and scale with coalesced thawlake basins (alases) on Earth, the Martian pits may have formed by thermophysical interactions of pooled water with ice-rich permafrost. This interpretation is not unique; sublimation of ice-rich permafrost or possibly even eolian processes acting on ice-free material might have formed the pits. However, the regional setting contains many other indications of massive ice. Some of these features are examined.

Relative chronology of Martian volcanoes

International Nuclear Information System (INIS)

Landheim, R.; Barlow, N.G.

1991-01-01

Impact cratering is one of the major geological processes that has affected the Martian surface throughout the planet's history. The frequency of craters within particular size ranges provides information about the formation ages and obliterative episodes of Martian geologic units. The Barlow chronology was extended by measuring small craters on the volcanoes and a number of standard terrain units. Inclusions of smaller craters in units previously analyzed by Barlow allowed for a more direct comparison between the size-frequency distribution data for volcanoes and established chronology. During this study, 11,486 craters were mapped and identified in the 1.5 to 8 km diameter range in selected regions of Mars. The results are summarized in this three page report and give a more precise estimate of the relative chronology of the Martian volcanoes. Also, the results of this study lend further support to the increasing evidence that volcanism has been a dominant geologic force throughout Martian history

A transient fully coupled climate-ice-sheet simulation of the last glacial inception

Science.gov (United States)

Lofverstrom, M.; Otto-Bliesner, B. L.; Lipscomb, W. H.; Fyke, J. G.; Marshall, S.; Sacks, B.; Brady, E. C.

2017-12-01

The last glacial inception occurred around 115 ka, following a relative minimum in the Northern Hemisphere summer insolation. It is believed that small and spatially separated ice caps initially formed in the high elevation regions of northern Canada, Scandinavia, and along the Siberian Arctic coast. These ice caps subsequently migrated down in the valleys where they coalesced and formed the initial seeds of the large coherent ice masses that covered the northern parts of the North American and Eurasian continents over most of the last glacial cycle. Sea level records show that the initial growth period lasted for about 10 kyrs, and the resulting ice sheets may have lowered the global sea level by as much as 30 to 50 meters. Here we examine the transient climate system evolution over the period between 118 and 110 ka, using the fully coupled Community Earth System Model, version 2 (CESM2). This model features a two-way coupled high-resolution (4x4 km) ice-sheet component (Community Ice Sheet model, version 2; CISM2) that simulates ice sheets as an interactive component of the climate system. We impose a transient forcing protocol where the greenhouse gas concentrations and the orbital parameters follow the nominal year in the simulation; the model topography is also dynamically evolving in order to reflect changes in ice elevation throughout the simulation. The analysis focuses on how the climate system evolves over this time interval, with a special focus on glacial inception in the high-latitude continents. Results will highlight how the evolving ice sheets compare to data and previous model based reconstructions.

Response of faults to climate-driven changes in ice and water volumes on Earth's surface.

Science.gov (United States)

Hampel, Andrea; Hetzel, Ralf; Maniatis, Georgios

2010-05-28

Numerical models including one or more faults in a rheologically stratified lithosphere show that climate-induced variations in ice and water volumes on Earth's surface considerably affect the slip evolution of both thrust and normal faults. In general, the slip rate and hence the seismicity of a fault decreases during loading and increases during unloading. Here, we present several case studies to show that a postglacial slip rate increase occurred on faults worldwide in regions where ice caps and lakes decayed at the end of the last glaciation. Of note is that the postglacial amplification of seismicity was not restricted to the areas beneath the large Laurentide and Fennoscandian ice sheets but also occurred in regions affected by smaller ice caps or lakes, e.g. the Basin-and-Range Province. Our results do not only have important consequences for the interpretation of palaeoseismological records from faults in these regions but also for the evaluation of the future seismicity in regions currently affected by deglaciation like Greenland and Antarctica: shrinkage of the modern ice sheets owing to global warming may ultimately lead to an increase in earthquake frequency in these regions.

Global Scale Analysis of Martian Landslide Mobility and Paleoenvironmental Clues

Science.gov (United States)

Crosta, Giovanni Battista; De Blasio, Fabio Vittorio; Frattini, Paolo

2018-04-01

The mobility of landslides on Mars is studied based on a database of 3,118 events. To establish the volume of the landslides for the whole data set based on the deposit area, a new volume-area relationship based on a representative data set of 222 landslides is used. By plotting the H/L ratio between fall height H and runout L versus volume, the landslide mobility is analyzed and compared with existing empirical relationships for Martian and terrestrial landslides. By analyzing the mobility in terms of normalized residuals, that is, the relative deviation of the H/L ratio from the data set best-fit line, mobility is found to depend on both the landslide location on Mars and the landslide typology. This allows us to identify four different types of high-mobility (hypermobile) landslides. Three classes of high-mobility landslides are associated respectively to meteoroid impact, the Olympus Mons aureoles, and landslides with Toreva-block failure style, and their mobility can be explained by the peculiar flow mechanics. The fourth class includes landslides associated with isolated craters, those in the regions wetted by the putative Oceanus Borealis, and the ones at high latitudes. We suggest that the common factor behind all the hypermobile landslides of this fourth kind is the presence of ice. This is confirmed by our data showing that landslides increase in mobility with latitude. The latitudinal trend mirrors the distribution of ice as detected by radar, neutron probes, and the presence of glacial and layered ejecta morphologies. Because the overall landslide distribution supports the presence of ice-lubricated conditions, two ice lubrication models are presented showing how ice melting within or underneath the landslides could enhance mobility. By proper analysis in terms of apparent friction residuals, we find that the mobility of landslides in Valles Marineris with the largest landslide concentration is lower than average. We explain this circumstance partly

Antarctic Martian Meteorites at Johnson Space Center

Science.gov (United States)

Funk, R. C.; Satterwhite, C. E.; Righter, K.; Harrington, R.

2018-01-01

This past year marked the 40th anniversary of the first Martian meteorite found in Antarctica by the ANSMET Antarctic Search for Meteorites) program, ALH 77005. Since then, an additional 14 Martian meteorites have been found by the ANSMET program making for a total of 15 Martian meteorites in the U. S. Antarctic meteorite collection at Johnson Space Center (JSC). Of the 15 meteorites, some have been paired so the 15 meteorites actually represent a total of approximately 9 separate samples. The first Martian meteorite found by ANSMET was ALH 77005 (482.500 g), a lherzolitic shergottite. When collected, this meteorite was split as a part of the joint expedition with the National Institute of Polar Research (NIPR) Japan. Originally classified as an "achondrite-unique", it was re-classified as a Martian lherzolitic shergottite in 1982. This meteorite has been allocated to 137 scientists for research and there are 180.934 g remaining at JSC. Two years later, one of the most significant Martian meteorites of the collection at JSC was found at Elephant Moraine, EET 79001 (7942.000 g), a shergottite. This meteorite is the largest in the Martian collection at JSC and was the largest stony meteorite sample collected during the 1979 season. In addition to its size, this meteorite is of particular interest because it contains a linear contact separating two different igneous lithologies, basaltic and olivine-phyric. EET 79001 has glass inclusions that contain noble gas and nitrogen compositions that are proportionally identical to the Martian atmosphere, as measured by the Viking spacecraft. This discovery helped scientists to identify where the "SNC" meteorite suite had originated, and that we actually possessed Martian samples. This meteorite has been allocated to 205 scientists for research and 5,298.435 g of sample is available.

Photovoltaic array for Martian surface power

Science.gov (United States)

Appelbaum, J.; Landis, G. A.

1992-01-01

Missions to Mars will require electric power. A leading candidate for providing power is solar power produced by photovoltaic arrays. To design such a power system, detailed information on solar-radiation availability on the Martian surface is necessary. The variation of the solar radiation on the Martian surface is governed by three factors: (1) variation in Mars-Sun distance; (2) variation in solar zenith angle due to Martian season and time of day; and (3) dust in the Martian atmosphere. A major concern is the dust storms, which occur on both local and global scales. However, there is still appreciable diffuse sunlight available even at high opacity, so that solar array operation is still possible. Typical results for tracking solar collectors are also shown and compared to the fixed collectors. During the Northern Hemisphere spring and summer the isolation is relatively high, 2-5 kW-hr/sq m-day, due to the low optical depth of the Martian atmosphere. These seasons, totalling a full terrestrial year, are the likely ones during which manned mission will be carried out.

Late Quaternary glaciation history of northernmost Greenland - Evidence of shelf-based ice

DEFF Research Database (Denmark)

Larsen, Nicolaj K.; Kjær, Kurt H.; Funder, Svend Visby

2010-01-01

We present the mapping of glacial landforms and sediments from northernmost Greenland bordering 100 km of the Arctic Ocean coast. One of the most important discoveries is that glacial landforms, sediments, including till fabric measurements, striae and stoss-lee boulders suggest eastward ice......-flow along the coastal plain. Volcanic erratic boulders document ice-transport from 80 to 100 km west of the study area. We argue that these findings are best explained by local outlet glaciers from the Greenland Ice Sheet and local ice caps that merged to form a shelf-based ice in the Arctic Ocean...... and possibly confirming an extensive ice shelf in the Lincoln Sea between Greenland and Ellesmere Island. It is speculated that the shelf-based ice was largely affected by the presence of thick multiyear sea ice in the Arctic Ocean that prevented it from breaking up and forced the outlet glaciers to flow...

Assessing lahars from ice-capped volcanoes using ASTER satellite data, the SRTM DTM and two different flow models: case study on Iztaccíhuatl (Central Mexico

Directory of Open Access Journals (Sweden)

D. Schneider

2008-06-01

Full Text Available Lahars frequently affect the slopes of ice-capped volcanoes. They can be triggered by volcano-ice interactions during eruptions but also by processes such as intense precipitation or by outbursts of glacial water bodies not directly related to eruptive activity. We use remote sensing, GIS and lahar models in combination with ground observations for an initial lahar hazard assessment on Iztaccíhuatl volcano (5230 m a.s.l., considering also possible future developments of the glaciers on the volcano. Observations of the glacial extent are important for estimations of future hazard scenarios, especially in a rapidly changing tropical glacial environment. In this study, analysis of the glaciers on Iztaccíhuatl shows a dramatic retreat during the last 150 years: the glaciated area in 2007 corresponds to only 4% of the one in 1850 AD and the glaciers are expected to survive no later than the year 2020. Most of the glacial retreat is considered to be related to climate change but in-situ observations suggest also that geo- and hydrothermal heat flow at the summit-crater area can not be ruled out, as emphasized by fumarolic activity documented in a former study. However, development of crater lakes and englacial water reservoirs are supposed to be a more realistic scenario for lahar generation than sudden ice melting by rigorous volcano-ice interaction. Model calculations show that possible outburst floods have to be larger than ~5×10⁵ m³ or to achieve an H/L ratio (Height/runout Length of 0.2 and lower in order to reach the populated lower flanks. This threshold volume equals 2.4% melted ice of Iztaccíhuatl's total ice volume in 2007, assuming 40% water and 60% volumetric debris content of a potential lahar. The model sensitivity analysis reveals important effects of the generic type of the Digital Terrain Model (DTM used on the results. As a consequence, the predicted affected areas can vary significantly. For such

Paloma-radon: atmospheric radon 222 as a geochemical probe for water in the martian subsoil

International Nuclear Information System (INIS)

Sabroux, J.Ch.; Michielsen, N.; Voisin, V.

2003-01-01

Radon exhalation from a porous soil is known to depend strongly on the soil moisture content: a minute amount of water, or water ice, in the pore space increases dramatically the possibility for radon to migrate far from its parent mineral. We propose to take advantage of this characteristic by using atmospheric radon 222 as a geochemical probe for water in the Martian soil, at least one order of magnitude deeper than the current Mars Odyssey neutron data. Strong thermal inversions during the Martian night will accumulate radon in the lowest atmospheric boundary layer, up to measurable levels despite the comparatively high environmental (cosmic and solar) background radiation and the assumed low uranium content of the upper crust of the planet. Preliminary studies and development of an instrument for the measurement of the Martian atmospheric alpha radioactivity is part of the CNES supported PALOMA experiment. Two test benches have been implemented, one of them allowing differential measurements of the diffusion of radon in the Martian soil simulant NASA JSC Mars-1, under relevant temperatures and pressures. The other, a 1 m3 radon-dedicated test bench, aims to characterize the instrument that will measure radon in the Mars environment (7 mb CO 2 ). Tests on several nuclear radiation detectors show that semiconductor alpha-particle detectors (PIPS) are the best option. In addition, the detection volume is left open in order to capitalize upon the long (ca. 4 m) alpha track at this low pressure. A stationary diffusion model was developed in order to assess the radon flux at the Mars soil surface. Diffusion of gas in Martian soil is governed by Knudsen diffusion. The radon Knudsen diffusion coefficient was estimated, depending on the soil moisture and relevant structural properties, leading to a radon diffusion length of the order of 20 m. The landed platform PALOMA-Radon instrument will consist of a set of alpha detectors connected to an electronic spectrometer, a

Paloma-radon: atmospheric radon 222 as a geochemical probe for water in the martian subsoil

Energy Technology Data Exchange (ETDEWEB)

Sabroux, J.Ch.; Michielsen, N.; Voisin, V

2003-07-01

Radon exhalation from a porous soil is known to depend strongly on the soil moisture content: a minute amount of water, or water ice, in the pore space increases dramatically the possibility for radon to migrate far from its parent mineral. We propose to take advantage of this characteristic by using atmospheric radon 222 as a geochemical probe for water in the Martian soil, at least one order of magnitude deeper than the current Mars Odyssey neutron data. Strong thermal inversions during the Martian night will accumulate radon in the lowest atmospheric boundary layer, up to measurable levels despite the comparatively high environmental (cosmic and solar) background radiation and the assumed low uranium content of the upper crust of the planet. Preliminary studies and development of an instrument for the measurement of the Martian atmospheric alpha radioactivity is part of the CNES supported PALOMA experiment. Two test benches have been implemented, one of them allowing differential measurements of the diffusion of radon in the Martian soil simulant NASA JSC Mars-1, under relevant temperatures and pressures. The other, a 1 m3 radon-dedicated test bench, aims to characterize the instrument that will measure radon in the Mars environment (7 mb CO{sub 2}). Tests on several nuclear radiation detectors show that semiconductor alpha-particle detectors (PIPS) are the best option. In addition, the detection volume is left open in order to capitalize upon the long (ca. 4 m) alpha track at this low pressure. A stationary diffusion model was developed in order to assess the radon flux at the Mars soil surface. Diffusion of gas in Martian soil is governed by Knudsen diffusion. The radon Knudsen diffusion coefficient was estimated, depending on the soil moisture and relevant structural properties, leading to a radon diffusion length of the order of 20 m. The landed platform PALOMA-Radon instrument will consist of a set of alpha detectors connected to an electronic spectrometer

Recession of the Northern polar cap from the PFS Mars Express observations

Science.gov (United States)

Zasova, L. V.; Formisano, V.; Moroz, V. I.; Giuranna, M.; Grassi, D.; Hansen, G.; Ignatiev, N. I.; Maturilli, A.; Pfs Team

Planetary Fourier Spectrometer (PFS) has two spectral channels, devoted to the thermal and solar reflected spectral range investigations. The first observations by PFS of the Northern hemisphere ,which includes the North pole, occurred at Ls= 342 (northern winter). Surface temperature alone the orbit shows that the CO2 ice polar cap, where the surface temperature is found around 150K and below, is extended down to about 62 N. The spectra at latitudes above 80 N are obtained at polar darkness and at latitudes below 80 at illumination by the low Sun. Retrieved temperature profiles of the atmosphere at darkness show that temperature of the atmosphere is low enough to allow the CO2 condensation up to about 25 km. Between 70 and 80 latitude the upper levels of the atmosphere are heated by the Sun, but condensation of the CO2 may occur in the near surface layer below 5 km. The water ice clouds exist at lower latitudes with maximum opacity at the edge of the polar cap. More detailed investigation of the data obtained in winter as well as of the measurements in the northern spring will be presented.

Cervical Cap

Science.gov (United States)

... Videos for Educators Search English Español The Cervical Cap KidsHealth / For Teens / The Cervical Cap What's in ... Call the Doctor? Print What Is a Cervical Cap? A cervical cap is a small cup made ...

Martian volcanism: A review

International Nuclear Information System (INIS)

Carr, M.H.

1987-01-01

Martian volcanism is reviewed. It is emphasized that lava plains constitute the major type of effusive flow, and can be differentiated by morphologic characteristics. Shield volcanoes, domes, and patera constitute the major constructional landforms, and recent work has suggested that explosive activity and resulting pyroclastic deposits may have been involved with formation of some of the small shields. Analysis of morphology, presumed composition, and spectroscopic data all indicate that Martian volcanism was dominantly basaltic in composition

An ice-binding and tandem beta-sandwich domain-containing protein in Shewanella frigidimarina is a potential new type of ice adhesin.

Science.gov (United States)

Vance, Tyler D R; Graham, Laurie A; Davies, Peter L

2018-04-01

Out of the dozen different ice-binding protein (IBP) structures known, the DUF3494 domain is the most widespread, having been passed many times between prokaryotic and eukaryotic microorganisms by horizontal gene transfer. This ~25-kDa β-solenoid domain with an adjacent parallel α-helix is most commonly associated with an N-terminal secretory signal peptide. However, examples of the DUF3494 domain preceded by tandem Bacterial Immunoglobulin-like (BIg) domains are sometimes found, though uncharacterized. Here, we present one such protein (SfIBP_1) from the Antarctic bacterium Shewanella frigidimarina. We have confirmed and characterized the ice-binding activity of its ice-binding domain using thermal hysteresis measurements, fluorescent ice plane affinity analysis, and ice recrystallization inhibition assays. X-ray crystallography was used to solve the structure of the SfIBP_1 ice-binding domain, to further characterize its ice-binding surface and unique method of stabilizing or 'capping' the ends of the solenoid structure. The latter is formed from the interaction of two loops mediated by a combination of tandem prolines and electrostatic interactions. Furthermore, given their domain architecture and membrane association, we propose that these BIg-containing DUF3494 IBPs serve as ice-binding adhesion proteins that are capable of adsorbing their host bacterium onto ice. Submitted new structure to the Protein Data Bank (PDB: 6BG8). © 2018 Federation of European Biochemical Societies.

Yamato 980459: Crystallization of Martian Magnesian Magma

Science.gov (United States)

Koizumi, E.; Mikouchi, T.; McKay, G.; Monkawa, A.; Chokai, J.; Miyamoto, M.

2004-01-01

Recently, several basaltic shergottites have been found that include magnesian olivines as a major minerals. These have been called olivinephyric shergottites. Yamato 980459, which is a new martian meteorite recovered from the Antarctica by the Japanese Antarctic expedition, is one of them. This meteorite is different from other olivine-phyric shergottites in several key features and will give us important clues to understand crystallization of martian meteorites and the evolution of Martian magma.

Mass budget of Queen Elizabeth Islands glaciers and ice caps, Canada, from 1992 to present

Science.gov (United States)

Millan, R.; Rignot, E. J.; Mouginot, J.

2015-12-01

Recent studies indicate to say that the Canadian Artic Archipelago's mass loss has increased in recent years. However the role of ice dynamics changes in this area is not well known. In this study, we present a comprehensive velocity mapping of the CAA using ALOS/PALSAR, RADARSAT-1, ERS1 and Landsat data between 1992 and 2015. Glaciers speed are calculated using a speckle and feature tracking algorithm.The results reveals that three large marine-terminating glaciers have accelerated significantly after 2010, while most others have slowed down or retreated to a sill to become similar to land-terminating glaciers. By combining the velocities of these glaciers with ice thickness measurements from NASA's Operation IceBridge, we calculate their ice discharge. The fluxes of these glaciers increased significantly since 2000 with a marked increase after 2011. The comparison of ice discharge with the surface mass balance from RACMO-2, shows that these glaciers came out of balance after 2011, which is also a time period where their discharge almost doubled. The analysis of RACMO-2 reveals an increase in runoff between 1970's and today and a precipitation with no significant trend. We digitalize the calving front positions of the glaciers and show an increasing rate retreat since 1976. We conclude that global pattern of velocity changes shows that the mass losses due to surface mass balance will likely going to raise in the coming years and that ice discharge will have a smaller part in the contribution of the CAA to sea level rise.

A new DEM of the Austfonna ice cap by combining differential SAR interferometry with ICESat laser altimetry

Directory of Open Access Journals (Sweden)

Geir Moholdt

2012-05-01

Full Text Available We present a new digital elevation model (DEM of the Austfonna ice cap in the Svalbard Archipelago, Norwegian Arctic. Previous DEMs derived from synthetic aperture radar (SAR and optical shape-from-shading have been tied to airborne radio echo-sounding surface profiles from 1983 which contain an elevation-dependent bias of up to several tens of metres compared with recent elevation data. The new and freely available DEM is constructed purely from spaceborne remote sensing data using differential SAR interferometry (DInSAR in combination with ICESat laser altimetry. Interferograms were generated from pairs of SAR scenes from the one-day repeat tandem phase of the European Remote Sensing Satellites 1/2 (ERS-1/2 in 1996. ICESat elevations from winter 2006–08 were used as ground control points to refine the interferometric baseline. The resulting DEM is validated against the same ground control points and independent surface elevation profiles from Global Navigation Satellite Systems (GNSS and airborne laser altimetry, yielding root mean square (RMS errors of about 10 m in all cases. This quality is sufficient for most glaciological applications, and the new DEM will be a baseline data set for ongoing and future research at Austfonna. The technique of combining satellite DInSAR with high-resolution satellite altimetry for DEM generation might also be a good solution in other glacier regions with similar characteristics, especially when data from TanDEM-X and CryoSat-2 become available.

Modeling ground thermal regime of an ancient buried ice body in Beacon Valley, Antarctica using a 1-D heat equation with latent heat effect

Science.gov (United States)

Liu, L.; Sletten, R. S.; Hallet, B.; Waddington, E. D.; Wood, S. E.

2013-12-01

An ancient massive ice body buried under several decimeters of debris in Beacon Valley, Antarctica is believed to be over one million years old, making it older than any known glacier or ice cap. It is fundamentally important as a reservoir of water, proxy for climatic information, and an expression of the periglacial landscape. It is also one of Earth's closest analog for widespread, near-surface ice found in Martian soils and ice-cored landforms. We are interested in understanding controls on how long this ice may persist since our physical model of sublimation suggests it should not be stable. In these models, the soil temperatures and the gradient are important because it determines the direction and magnitude of the vapor flux, and thus sublimation rates. To better understand the heat transfer processes and constrain the rates of processes governing ground ice stability, a model of the thermal behavior of the permafrost is applied to Beacon Valley, Antarctica. It calculates soil temperatures based on a 1-D thermal diffusion equation using a fully implicit finite volume method (FVM). This model is constrained by soil physical properties and boundary conditions of in-situ ground surface temperature measurements (with an average of -23.6oC, a maximum of 20.5oC and a minimum of -54.3oC) and ice-core temperature record at ~30 m. Model results are compared to in-situ temperature measurements at depths of 0.10 m, 0.20 m, 0.30 m, and 0.45 m to assess the model's ability to reproduce the temperature profile for given thermal properties of the debris cover and ice. The model's sensitivity to the thermal diffusivity of the permafrost and the overlaying debris is also examined. Furthermore, we incorporate the role of ice condensation/sublimation which is calculated using our vapor diffusion model in the 1-D thermal diffusion model to assess potential latent heat effects that in turn affect ground ice sublimation rates. In general, the model simulates the ground thermal

An Electrostatic Precipitator System for the Martian Environment

Science.gov (United States)

Calle, C. I.; Mackey, P. J.; Hogue, M. D.; Johansen, M. R.; Phillips, J. R., III; Clements, J. S.

2012-01-01

Human exploration missions to Mars will require the development of technologies for the utilization of the planet's own resources for the production of commodities. However, the Martian atmosphere contains large amounts of dust. The extraction of commodities from this atmosphere requires prior removal of this dust. We report on our development of an electrostatic precipitator able to collect Martian simulated dust particles in atmospheric conditions approaching those of Mars. Extensive experiments with an initial prototype in a simulated Martian atmosphere showed efficiencies of 99%. The design of a second prototype with aerosolized Martian simulated dust in a flow-through is described. Keywords: Space applications, electrostatic precipitator, particle control, particle charging

Martian Gullies: H2O or CO2 snow?

Science.gov (United States)

Yolanda, C.; Durand-Manterola, H. J.

2007-05-01

The theories proposed to try to explain the origin of the Martian gullies involve either liquid water, liquid carbon dioxide or flows of dry granular material. We propose another processes that can be favorable for the origin of the Martian gullies, with our model by gaseous fluidification of CO2. We propose that on the Martian slopes, CO2 snow and dust transported by winds, are accumulate. During the Martian spring, sublimation of carbonic snow starts because of heat and weigth of the frezze layer, causing that the material mixed its fluidifized and slide downslope by gravity. By experimental work with dry granular material, we simulated the development of the Martian gullies injecting air inside the granular material. We also present the characteristics of some terrestrial gullies forms at cold environment, sited at Nevado de Toluca Volcano near Toluca City, México. We compared them with some Martian gullies, to identify possible processes evolved in its formation. We measured the lengths of those Martian gullies and the range was from 24 meters to 1775 meters. Finally, we present results of our experimental work at laboratory with dry granular material and our field trip to Nevado de Toluca Volcano.

Hydrological and Climatic Significance of Martian Deltas

Science.gov (United States)

Di Achille, G.; Vaz, D. A.

2017-10-01

We a) review the geomorphology, sedimentology, and mineralogy of the martian deltas record and b) present the results of a quantitative study of the hydrology and sedimentology of martian deltas using modified version of terrestrial model Sedflux.

Cervical Cap

Science.gov (United States)

... giving birth vaginally, which means the cervical cap may not fit as well. Inconsistent or incorrect use of the cervical cap increases your risk of pregnancy. For example, you may get pregnant when using the cervical cap if: ...

Paloma-radon: Atmospheric radon-222 as a geochemical probe for water in the Martian subsoil.

Science.gov (United States)

Sabroux, J.-C.; Michielsen, N.; Voisin, V.; Ferry, C.; Richon, P.; Pineau, J.-F.; Le Roulley, J.-C.; Chassefière, E.

2003-04-01

Radon exhalation from a porous soil is known to depend strongly on the soil moisture content: a minute amount of water, or water ice, in the pore space increases dramatically the possibility for radon to migrate far from its parent mineral. We propose to take advantage of this characteristic by using atmospheric radon-222 as a geochemical probe for water in the Martian soil, at least one order of magnitude deeper than the current Mars Odyssey neutron data. Strong thermal inversions during the Martian night will accumulate radon in the lowest atmospheric boundary layer, up to measurable levels despite the comparatively high environmental (cosmic and solar) background radiation and the assumed low uranium content of the upper crust of the planet. Preliminary studies and development of an instrument for the measurement of the Martian atmospheric alpha radioactivity is part of the CNES-supported PALOMA experiment. Two test benches have been implemented, one of them allowing differential measurements of the diffusion of radon in the Martian soil simulant NASA JSC Mars-1, under relevant temperatures and pressures. The other, a 1 m^3 radon-dedicated test bench, aims to characterize the instrument that will measure radon in the Mars environment (7 mb CO_2). Tests on several nuclear radiation detectors show that semiconductor alpha-particle detectors (PIPS) are the best option (already on board the Mars Pathfinder Rover and other platforms). In addition, the detection volume is left open in order to capitalize upon the long (ca. 4 m) alpha track at this low pressure. A stationary diffusion model was developed in order to assess the radon flux at the Mars soil surface. Diffusion of gas in Martian soil is governed by Knudsen diffusion. The radon Knudsen diffusion coefficient was estimated, depending on the soil moisture and relevant structural properties, leading to a radon diffusion length of the order of 20 m. The landed platform PALOMA-Radon instrument will consist of a

Characterizing of a Mid-Latitude Ice-Rich Landing Site on Mars to Enable in Situ Habitability Studies

Science.gov (United States)

Heldmann, J.; Schurmeier, L. R.; Wilhelm, M.; Stoker, C.; McKay, C.; Davila, A.; Marinova, M.; Karcz, J.; Smith, H.

2012-01-01

We suggest an ice-rich landing site at 188.5E 46.16N within Amazonis Planitia as a candidate location to support a Mars lander mission equipped to study past habitability and regions capable of preserving the physical and chemical signs of life and organic matter. Studies of the ice-rich subsurface on Mars are critical for several reasons. The subsurface environment provides protection from radiation to shield organic and biologic compounds from destruction. The ice-rich substrate is also ideal for preserving organic and biologic molecules and provides a source of H2O for biologic activity. Examination of martian ground ice can test several hypotheses such as: 1) whether ground ice supports habitable conditions, 2) that ground ice can preserve and accumulate organic compounds, and 3) that ice contains biomolecules evident of past or present biological activity on Mars. This Amazonis site, located near the successful Viking Lander 2, shows indirect evidence of subsurface ice (ubiquitous defined polygonal ground, gamma ray spectrometer hydrogen signature, and numerical modeling of ice stability) and direct evidence of exposed subsurface ice. This site also provides surface conditions favorable to a safe landing including no boulders, low rock density, minimal rough topography, and few craters.

Carbon dioxide enhances fragility of ice crystals

International Nuclear Information System (INIS)

Qin Zhao; Buehler, Markus J

2012-01-01

Ice caps and glaciers cover 7% of the Earth, greater than the land area of Europe and North America combined, and play an important role in global climate. The small-scale failure mechanisms of ice fracture, however, remain largely elusive. In particular, little understanding exists about how the presence and concentration of carbon dioxide molecules, a significant component in the atmosphere, affects the propensity of ice to fracture. Here we use atomic simulations with the first-principles based ReaxFF force field capable of describing the details of chemical reactions at the tip of a crack, applied to investigate the effects of the presence of carbon dioxide molecules on ice fracture. Our result shows that increasing concentrations of carbon dioxide molecules significantly decrease the fracture toughness of the ice crystal, making it more fragile. Using enhanced molecular sampling with metadynamics we reconstruct the free energy landscape in varied chemical microenvironments and find that carbon dioxide molecules affect the bonds between water molecules at the crack tip and decrease their strength by altering the dissociation energy of hydrogen bonds. In the context of glacier dynamics our findings may provide a novel viewpoint that could aid in understanding the breakdown and melting of glaciers, suggesting that the chemical composition of the atmosphere can be critical to mediate the large-scale motion of large volumes of ice.

Reconstructing the last Irish Ice Sheet 2: a geomorphologically-driven model of ice sheet growth, retreat and dynamics

Science.gov (United States)

Greenwood, Sarah L.; Clark, Chris D.

2009-12-01

The ice sheet that once covered Ireland has a long history of investigation. Much prior work focussed on localised evidence-based reconstructions and ice-marginal dynamics and chronologies, with less attention paid to an ice sheet wide view of the first order properties of the ice sheet: centres of mass, ice divide structure, ice flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an ice sheet reconstruction yielding these fundamental ice sheet properties. We present a seven stage model of ice sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of ice from Scotland likely coalesced with local ice caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish Ice Sheet was then established during ice sheet growth, with a branching ice divide structure whose main axis migrated up to 140 km from the west coast towards the east. Ice stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. Ice cover is reconstructed as extending to the continental shelf break. The Irish Ice Sheet became autonomous (i.e. separate from the British Ice Sheet) during deglaciation and fragmented into multiple ice masses, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the ice sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the ice stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid

Interannual and seasonal changes in the south seasonal polar cap of Mars: Observations from MY 28-31 using MARCI

Science.gov (United States)

Calvin, W. M.; Cantor, B. A.; James, P. B.

2017-08-01

The Mars Color Imager (MARCI) camera on the Mars Reconnaissance Orbiter provides daily synoptic coverage that allows monitoring of seasonal cap retreat and interannual changes that occur between Mars Years (MY) and over the southern summer. We present the first analysis of this data for the southern seasonal cap evolution observed in MY 28, 29, 30 and 31 (2/2007 to 07/2013). Observation over multiple Mars years allows us to compare changes between years as well as longer-term evolution of the high albedo deposits at the poles. Seasonal cap retreat is similar in all years and to retreats observed in other years by both optical and thermal instruments. The cryptic terrain has a fairly consistent boundary in each year, but numerous small-scale variations occur in each MY observed. Additionally, numerous small dark deposits are identified outside the classically identified cyptic region, including Inca City and other locations not previously noted. The large water ice outlier is observed to retain seasonal frost the longest (outside the polar dome) and is also highly variable in each MY. The development of the cryptic/anti-cryptic hemispheres is inferred to occur due to albedo variations that develop after dust venting starts and may be caused by recondensation of CO2 ice on the brightest and coldest regions controlled by topographic winds. Ground ice may play a role in which regions develop cryptic terrain, as there is no elevation control on either cryptic terrain or the late season brightest deposits.

Can you play cricket on Mars? and other scientific questions answered

CERN Document Server

Moore, Sir Patrick

2011-01-01

All those nagging questions you have about the universe are answered here, like 'Is there a dark side to the moon? What happens when a comet hits the sun? Do the Martian canals have any water in them? Is the moon hot inside? What would happen if the sun were to collide with a black hole? Mars has polar ice caps: could polar bears live on Mars? if I could go back to the time of the dinosaurs, would the sky look the same as it does today?' and many more.

Anti-pp,. cap alpha cap alpha. and p. cap alpha. elastic scattering at high energies and Chou-Yang conjecture

Energy Technology Data Exchange (ETDEWEB)

Saleem, M.; Fazal-e-Aleem; Rifique, M.

1987-03-01

The recent experimental measurements for anti-pp and ..cap alpha cap alpha.. elastic scattering at high energies have shown that the Chou-Yang conjecture regarding the relationship between the electromagnetic and the hadronic form factor of a particle is only an approximation. A new ansatz has been proposed to obtain hadronic form factors of proton and the ..cap alpha..-particle. These form factors have been used to explain the various characteristics of anti-pp, ..cap alpha cap alpha.. and p..cap alpha.. elastic scattering at high energies.

The role of igneous sills in shaping the Martian uplands

Science.gov (United States)

Wilhelms, D. E.; Baldwin, R. J.

1989-01-01

Relations among geologic units and landforms suggest that igneous sills lie beneath much of the intercrater and intracrater terrain of the Martian uplands. The igneous rocks crop out along the upland-lowland front and in crater floors and other depressions that are low enough to intersect the sill's intrusion horizons. It is suggested that heat from the cooling sills melted some of the ice contained in overlying fragmental deposits, creating valley networks by subsurface flow of the meltwater. Terrains with undulatory, smooth surfaces and softened traces of valleys were created by more direct contact with the sills. Widespread subsidence following emplacement of the sills deformed both them and the nonvolcanic deposits that overlie them, accounting for the many structures that continue from ridged plains into the hilly uplands. Crater counts show that the deposit that became valleyed, softened, and ridged probably began to form (and to acquire interstitial ice) during or shortly after the Middle Noachian Epoch, and continued to form as late as the Early Hesperian Epoch. The upper layers of this deposit, many of the visible valleys, and the ridged plains and postulated sills all have similar Early Hesperian ages. Continued formation of valleys is indicated by their incision of fresh-appearing crater ejecta. The dependence of valley formation on internal processes implies that Mars did not necessarily have a dense early atmosphere or warm climate.

Nuclear thermal rockets using indigenous Martian propellants

International Nuclear Information System (INIS)

Zubrin, R.M.

1989-01-01

This paper considers a novel concept for a Martian descent and ascent vehicle, called NIMF (for nuclear rocket using indigenous Martian fuel), the propulsion for which will be provided by a nuclear thermal reactor which will heat an indigenous Martian propellant gas to form a high-thrust rocket exhaust. The performance of each of the candidate Martian propellants, which include CO2, H2O, CH4, N2, CO, and Ar, is assessed, and the methods of propellant acquisition are examined. Attention is also given to the issues of chemical compatibility between candidate propellants and reactor fuel and cladding materials, and the potential of winged Mars supersonic aircraft driven by this type of engine. It is shown that, by utilizing the nuclear landing craft in combination with a hydrogen-fueled nuclear thermal interplanetary vehicle and a heavy lift booster, it is possible to achieve a manned Mars mission in one launch. 6 refs

Architectural concepts of Martian bases built: of domes, around greenhouses and into slopes -the human aspect and the technology

Science.gov (United States)

Kozicki, Janek; Kozicka, Joanna

Human missions to Mars are a special kind of space missions due to their long duration. The human aspect of such missions becomes as important as the technological one. The need for a human friendly and comfortable habitat arises. Studies of human behavior in ICEs have shown that larger groups of people mean a lower occurrence of conflicts. However, for a larger crew a larger habitat has to be designed -a Martian base. The research deals with psychological, sociological and technological aspects influencing the architectural design of a Martian Base. Extreme conditions present on Mars demand a partic-ular approach to technological and architectural design. To reduce the cost of building a bigger habitat, low cost solutions have been inquired into. A series of analyses has been performed to identify the best architectural solutions for a Martian base. A review of existing technologies and extreme condition habitats (both terrestrial and extraterrestrial) has revealed solutions that are the most reliable and efficient ones. Additionally, innovative technologies have been analyzed in search of the best candidates for actual base construction. Low cost solutions have been prioritized in the process. An in-depth study of architectural problems inherent in the design of a Martian base has resulted in a number of guidelines for the architect. The main ones are introduced in this review. Based on them, several concepts have been drafted as examples of user-friendly and aesthetically pleasing habitats. They are discussed in the following order: habitats made of domes, those built around greenhouses and those situated in sloping terrain. One of them is presented in detail, including interior design.

Cradle Cap (For Parents)

Science.gov (United States)

... Safe Videos for Educators Search English Español Cradle Cap (Infantile Seborrheic Dermatitis) KidsHealth / For Parents / Cradle Cap ( ... many babies develop called cradle cap. About Cradle Cap Cradle cap is the common term for seborrheic ...

An extensive phase space for the potential martian biosphere.

Science.gov (United States)

Jones, Eriita G; Lineweaver, Charles H; Clarke, Jonathan D

2011-12-01

We present a comprehensive model of martian pressure-temperature (P-T) phase space and compare it with that of Earth. Martian P-T conditions compatible with liquid water extend to a depth of ∼310 km. We use our phase space model of Mars and of terrestrial life to estimate the depths and extent of the water on Mars that is habitable for terrestrial life. We find an extensive overlap between inhabited terrestrial phase space and martian phase space. The lower martian surface temperatures and shallower martian geotherm suggest that, if there is a hot deep biosphere on Mars, it could extend 7 times deeper than the ∼5 km depth of the hot deep terrestrial biosphere in the crust inhabited by hyperthermophilic chemolithotrophs. This corresponds to ∼3.2% of the volume of present-day Mars being potentially habitable for terrestrial-like life.

Magnesium Based Rockets for Martian Exploration, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — We propose to develop Mg rockets for Martian ascent vehicle applications. The propellant can be acquired in-situ from MgO in the Martian regolith (5.1% Mg by mass)...

Martian fluid and Martian weathering signatures identified in Nakhla, NWA 998 and MIL 03346 by halogen and noble gas analysis

Science.gov (United States)

Cartwright, J. A.; Gilmour, J. D.; Burgess, R.

2013-03-01

We report argon (Ar) noble gas, Ar-Ar ages and halogen abundances (Cl, Br, I) of Martian nakhlites Nakhla, NWA 998 and MIL 03346 to determine the presence of Martian hydrous fluids and weathering products. Neutron-irradiated samples were either crushed and step-heated (Nakhla only), or simply step-heated using a laser or furnace, and analysed for noble gases using an extension of the 40Ar-39Ar technique to determine halogen abundances. The data obtained provide the first isotopic evidence for a trapped fluid that is Cl-rich, has a strong correlation with 40ArXS (40ArXS = 40Armeasured - 40Arradiogenic) and displays 40ArXS/36Ar of ˜1000 - consistent with the Martian atmosphere. This component was released predominantly in the low temperature and crush experiments, which may suggest a fluid inclusion host. For the halogens, we observe similar Br/Cl and I/Cl ratios between the nakhlites and terrestrial reservoirs, which is surprising given the absence of crustal recycling, organic matter and frequent fluid activity on Mars. In particular, Br/Cl ratios in our Nakhla samples (especially olivine) are consistent with previously analysed Martian weathering products, and both low temperature and crush analyses show a similar trend to the evaporation of seawater. This may indicate that surface brines play an important role on Mars and on halogen assemblages within Martian meteorites and rocks. Elevated I/Cl ratios in the low temperature NWA 998 and MIL 03346 releases may relate to in situ terrestrial contamination, though we are unable to distinguish between low temperature terrestrial or Martian components. Whilst estimates of the amount of water present based on the 36Ar concentrations are too high to be explained by a fluid component alone, they are consistent with a mixed-phase inclusion (gas and fluid) or with shock-implanted Martian atmospheric argon. The observed fluid is dilute (low salinity, but high Br/Cl and I/Cl ratios), contains a Martian atmospheric component

Antarctic Mirabilite Mounds as Mars Analogs: The Lewis Cliffs Ice Tongue Revisited

Science.gov (United States)

Socki, Richard A.; Sun, Tao; Niles, Paul B.; Harvey, Ralph P.; Bish, David L.; Tonui, Eric

2012-01-01

It has been proposed, based on geomorphic and geochemical arguments, that subsurface water has played an important role in the history of water on the planet Mars [1]. Subsurface water, if present, could provide a protected and long lived environment for potential life. Discovery of gullies [2] and recurring slopes [3] on Mars suggest the potential for subsurface liquid water or brines. Recent attention has also focused on small (the mid to high latitudes on the surface of Mars which may be caused by eruptions of subsurface fluids [4, 5]. We have identified massive but highly localized Na-sulfate deposits (mirabilite mounds, Na2SO4 .10H2O) that may be derived from subsurface fluids and may provide insight into the processes associated with subsurface fluids on Mars. The mounds are found on the end moraine of the Lewis Cliffs Ice Tongue (LCIT) [6] in the Transantarctic Mountains, Antarctica, and are potential terrestrial analogs for mounds observed on the martian surface. The following characteristics distinguish LCIT evaporite mounds from other evaporite mounds found in Antarctic coastal environments and/or the McMurdo Dry Valleys: (1) much greater distance from the open ocean (approx.500 km); (2) higher elevation (approx.2200 meters); and (3) colder average annual temperature (average annual temperature = -30 C for LCIT [7] vs. 20 C at sea level in the McMurdo region [8]. Furthermore, the recent detection of subsurface water ice (inferred as debris-covered glacial ice) by the Mars Reconnaissance Orbiter [9] supports the use of an Antarctic glacial environment, particularly with respect to the mirabilite deposits described in this work, as an ideal terrestrial analog for understanding the geochemistry associated with near-surface martian processes. S and O isotopic compositions.

Ice Lens Formation, Frost Heave, Thin Films, and the Importance of the Polar H2O Reservoir at High Obliquity

Science.gov (United States)

Zent, A. P.; Sizemore, H. G.; Rempel, A. W.

2011-01-01

Several lines of evidence indicate that the volume of shallow ground ice in the martian high latitudes exceeds the pore volume of the host regolith. Boynton et al. found an optimal fit to the Mars Odyssey Gamma Ray Spectrometer (GRS) data at the Phoenix landing site by modeling a buried layer of 50-75% ice by mass (up to 90% ice by volume). Thermal and optical observations of recent impact craters in the northern hemisphere have revealed nearly pure ice. Ice deposits containing only 1-2% soil by volume were excavaged by Phoenix. One hypothesis for the origin of this excess ice is that it developed in situ by a mechanism analogous to the formation of terrestrial ice lenses and needle ice. Problematically, terrestrial soil-ice segregation is driven by freeze/thaw cycling and the movement of bulk water, neither of which are expected to have occurred in the geologically recent past on Mars. If however ice lens formation is possible at temperatures less than 273 K, there are possible implications for the habitability of Mars permafrost, since the same thin films of unfrozen water that lead to ice segregation are used by terrestrial psychrophiles to metaboluze and grow down to temperatures of at least 258 K.

MetNet Network Mission for Martian Atmospheric Investigations

Science.gov (United States)

Harri, A.-M.; Alexashkin, S.; Arrugeo, I.; Schmidt, W.; Vazquez, L.; Genzer, M.; Haukka, H.

2014-07-01

A new kind of planetary exploration mission for Mars called MetNet is being developed for martian atmospheric investigations. The eventual scope of the MetNet Mission is to deploy tens of small landers on the martian surface.

Long term ice sheet mass change rates and inter-annual variability from GRACE gravimetry.

Science.gov (United States)

Harig, C.

2017-12-01

The GRACE time series of gravimetry now stretches 15 years since its launch in 2002. Here we use Slepian functions to estimate the long term ice mass trends of Greenland, Antarctica, and several glaciated regions. The spatial representation shows multi-year to decadal regional shifts in accelerations, in agreement with increases in radar derived ice velocity. Interannual variations in ice mass are of particular interest since they can directly link changes in ice sheets to the drivers of change in the polar ocean and atmosphere. The spatial information retained in Slepian functions provides a tool to determine how this link varies in different regions within an ice sheet. We present GRACE observations of the 2013-2014 slowdown in mass loss of the Greenland ice sheet, which was concentrated in specific parts of the ice sheet and in certain months of the year. We also discuss estimating the relative importance of climate factors that control ice mass balance, as a function of location of the glacier/ice cap as well as the spatial variation within an ice sheet by comparing gravimetry with observations of surface air temperature, ocean temperature, etc. as well as model data from climate reanalysis products.

A model to calculate solar radiation fluxes on the Martian surface

Directory of Open Access Journals (Sweden)

Vicente-Retortillo Álvaro

2015-01-01

Full Text Available We present a new comprehensive radiative transfer model to study the solar irradiance that reaches the surface of Mars in the spectral range covered by MetSIS, a sensor aboard the Mars MetNet mission that will measure solar irradiance in several bands from the ultraviolet (UV to the near infrared (NIR. The model includes up-to-date wavelength-dependent radiative properties of dust, water ice clouds, and gas molecules. It enables the characterization of the radiative environment in different spectral regions under different scenarios. Comparisons between the model results and MetSIS observations will allow for the characterization of the temporal variability of atmospheric optical depth and dust size distribution, enhancing the scientific return of the mission. The radiative environment at the Martian surface has important implications for the habitability of Mars as well as a strong impact on its atmospheric dynamics and climate.

Do Martian Blueberries Have Pits? -- Artifacts of an Early Wet Mars

Science.gov (United States)

Lerman, L.

2005-03-01

Early Martian weather cycles would have supported organic chemical self-organization, the assumed predecessor to an independent "origin" of Martian life. Artifacts of these processes are discussed, including the possibility that Martian blueberries nucleated around organic cores.

The Development of 3d Sub-Surface Mapping Scheme and its Application to Martian Lobate Debris Aprons

Science.gov (United States)

Baik, H.; Kim, J.

2017-07-01

The Shallow Subsurface Radar (SHARAD), a sounding radar equipped on the Mars Reconnaissance Orbiter (MRO), has produced highly valuable information about the Martian subsurface. In particular, the complicated substructures of Mars such as polar deposit, pedestal crater and the other geomorphic features involving possible subsurface ice body has been successfully investigated by SHARAD. In this study, we established a 3D subsurface mapping strategy employing the multiple SHARAD profiles. A number of interpretation components of SHARAD signals were integrated into a subsurface mapping scheme using radargram information and topographic data, then applied over a few mid latitude Lobate Debris Aprons (LDAs). From the identified subsurface layers of LDA, and the GIS data base incorporating the other interpretation outcomes, we are expecting to trace the origin of LDAs. Also, the subsurface mapping scheme developed in this study will be further applied to other interesting Martian geological features such as inter crater structures, aeolian deposits and fluvial sediments. To achieve higher precision sub-surface mapping, the clutter simulation employing the high resolution topographic data and the upgraded clustering algorithms assuming multiple sub-surface layers will be also developed.

Luminescence Dating of Martian Polar Deposits: Concepts and Preliminary Measurements Using Martian Soil Analogs

Science.gov (United States)

Lepper, K.; Kuhns, C. K.; McKeever, S. W. S.; Sears, D. W. G.

2000-08-01

Martian polar deposits have the potential to reveal a wealth of information about the evolution of Mars' climate and surface environment. However, as pointed out by Clifford et al. in the summary of the First International Conference on Mars Polar Science and Exploration, 'The single greatest obstacle to unlocking and interpreting the geologic and climatic record preserved at the [martian] poles is the need for absolute dating.' At that same conference Lepper and McKeever proposed development of luminescence dating as a remote in-situ technique for absolute dating of silicate mineral grains incorporated in polar deposits. Clifford et al. have also acknowledged that luminescence dating is more practical from cost, engineering, and logistical perspectives than other isotope-based methods proposed for in-situ dating on Mars. We report here the results of ongoing experiments with terrestrial analogs of martian surface materials to establish a broad fundamental knowledge base from which robust dating procedures for robotic missions may be developed. This broad knowledge base will also be critical in determining the engineering requirements of remote in-situ luminescence dating equipment intended for use on Mars. Additional information can be found in the original extended abstract.

A New Look at Atmospheric Water on Mars

Science.gov (United States)

Yung, Y. L.; Kass, D. M.

1998-09-01

Water is a key component of the Martian climate, both at present and over the history of the planet. The current atmosphere averages ~ 10 pr-mu m of water. Its D/H ratio is enriched by a factor of five relative to terrestrial water, presumably due to water loss by escape. Based on H loss rates, H_2O loss is 10(-3) pr-mu m y(-1) . At this rate, the atmospheric reservoir would be depleted in 10(4) years, but there are several other reservoirs of water (the permanent northern polar cap, high latitude ground ice, and adsorbed water in the regolith) that should keep the atmospheric reservoir constant since its size climatologically controlled. Recently, Krasnopolsky et al. (1998) measured the D/H ratio in HD in the upper atmosphere. Their measurement implies that the fractionation factor, F (efficiency of D escape relative to H), is ~ 0.02. Mars has lost ~ 80 m of water via fractionating processes. This implies that Mars has an exchangeable reservoir equivalent to a ~ 13 m global layer, which represents a polar cap 2000 km in diameter (the Martian northern permanent cap is about 1200 km). Thus, while the northern permanent cap may be a significant water reservoir, it is probably not the only one. One of the major issues is the time-scale and mechanism for exchangeable reservoirs to buffer the atmosphere. During periods of high obliquity, high latitude water may be forced to migrate and equilibrate with the atmosphere in the process. But the low F value, combined with the rapid loss, implies that there has to be at least partial exchange on shorter time-scales to avoid extremely high D/H values. Over the last 4 x 10(5) years, since the last period of high obliquity, 40 pr-mu m of water have been lost. In order to keep this from causing more than a factor of 2 change in the atmospheric water D/H, at least 40 pr-mu m needs to have been involved in the hydrological cycle. This requires cycling through the atmosphere the equivalent of a 2 cm thick layer of ice covering the

The Martian climate and energy balance models with CO2/H2O atmospheres

Science.gov (United States)

Hoffert, M. I.

1986-01-01

The analysis begins with a seasonal energy balance model (EBM) for Mars. This is used to compute surface temperature versus x = sin(latitude) and time over the seasonal cycle. The core model also computes the evolving boundaries of the CO2 icecaps, net sublimational/condensation rates, and the resulting seasonal pressure wave. Model results are compared with surface temperature and pressure history data at Viking lander sites, indicating fairly good agreement when meridional heat transport is represented by a thermal diffusion coefficient D approx. 0.015 W/sq. m/K. Condensational wind distributions are also computed. An analytic model of Martian wind circulation is then proposed, as an extension of the EMB, which incorporates vertical wind profiles containing an x-dependent function evaluated by substitution in the equation defining the diffusion coefficient. This leads to a parameterization of D(x) and of the meridional circulation which recovers the high surface winds predicted by dynamic Mars atmosphere models (approx. 10 m/sec). Peak diffusion coefficients, D approx. 0.6 w/sq m/K, are found over strong Hadley zones - some 40 times larger than those of high-latitude baroclinic eddies. When the wind parameterization is used to find streamline patterns over Martian seasons, the resulting picture shows overturning hemispheric Hadley cells crossing the equator during solstices, and attaining peak intensities during the south summer dust storm season, while condensational winds are most important near the polar caps.

Frozen Martian lahars? Evaluation of morphology, degradation and geologic development in the Utopia-Elysium transition zone

Science.gov (United States)

Pedersen, G. B. M.

2013-09-01

Regional coverage of high-resolution data from the CTX camera has permitted new, detailed morphologic analysis of the enigmatic Utopia-Elysium flows which dominate the transition zone between Elysium volcanic province and Utopia Planitia. Based on topographic and morphologic analysis of the Galaxias region, this study supports the lahar hypothesis put forth by previous works and suggests that the center and the margins of the outflow deposits have very diverse morphologies that can be explained by varying degrees of water drainage and freezing. Regular channel and flood plain deposits are found in the central part of the outflow deposits, whereas the marginal deposits are interpreted to contain significant amount of ice because of their distinct morphological properties (smooth, lobate flow-fronts with upward convex snouts, unusual crater morphologies, raised rim fractures and localized flow fronts indicating rheomorphism). Thus, this study suggest that, unlike terrestrial lahars, lahar emplacement under Martian conditions only drain in the central parts, whereas the water in the margins of the outflow deposit (∼75% of the total outflow deposit in the Galaxias region) freezes up resulting in a double-layered deposit consisting of ice-rich core with an ice-poor surface layer. It is here furthermore suggested that continued intrusive volcanic activity was highly affected by the presence of the ice-rich lahar deposits, generating ground-ice-volcano interactions resulting in a secondary suite of morphologies. These morphologies include seventeen ridges that are interpreted to be möberg ridges (due to their NW-SE orientation, distinct ridge-crests and association with fractures and linear ridges) and depressions with nested faults interpreted to be similar to terrestrial ice-cauldrons, which form by enhanced subglacial geothermal activity including subglacial volcanic eruptions. These sub-lahar intrusions caused significant volatile loss in the ice-rich core of the

Solubility of C-O-H volatiles in graphite-saturated martian basalts and application to martian atmospheric evolution

Science.gov (United States)

Stanley, B. D.; Hirschmann, M. M.; Withers, A. C.

2012-12-01

The modern martian atmosphere is thin, leading to surface conditions too cold to support liquid water. Yet, there is evidence of liquid surface water early in martian history that is commonly thought to require a thick CO2 atmosphere. Our previous work follows the analysis developed by Holloway and co-workers (Holloway et al. 1992; Holloway 1998), which predicts a linear relationship between CO2 and oxygen fugacity (fO2) in graphite-saturated silicate melts. At low oxygen fugacity, the solubility of CO2 in silicate melts is therefore very low. Such low calculated solubilities under reducing conditions lead to small fluxes of CO2 associated with martian magmatism, and therefore production of a thick volcanogenic CO2 atmosphere could require a prohibitively large volume of mantle-derived magma. The key assumption in these previous calculations is that the carbonate ion is the chief soluble C-O-H species. The results of the calculations would not be affected appreciably if molecular CO2, rather than carbonate ion, were an important species, but could be entirely different if there were other appreciable C-species such as CO, carbonyl (C=O) complexes, carbide (Si-C), or CH4. Clearly, graphite-saturated experiments are required to explore how much volcanogenic C may be degassed by reduced martian lavas. A series of piston-cylinder experiments were performed on synthetic martian starting materials over a range of oxygen fugacities (IW+2.3 to IW-0.9), and at pressures of 1-3 GPa and temperatures of 1340-1600 °C in Pt-graphite double capsules. CO2 contents in experimental glasses were determined using Fourier transform infrared spectroscopy (FTIR) and range from 0.0026-0.50 wt%. CO2 solubilities change by one order of magnitude with an order of magnitude change in oxygen fugacity, as predicted by previous work. Secondary ion mass spectrometry (SIMS) determinations of C contents in glasses range from 0.0131-0.2626 wt%. C contents determined by SIMS are consistently higher

Cradle Cap: Treatment

Science.gov (United States)

Cradle cap Treatment Cradle cap usually doesn't require medical treatment. It clears up on its own within a few months. In the meantime, wash ... tips can help you control and manage cradle cap. Gently rub your baby's scalp with your fingers ...

Influence of carbon dioxide clouds on early martian climate.

Science.gov (United States)

Mischna, M A; Kasting, J F; Pavlov, A; Freedman, R

2000-06-01

Recent studies have shown that clouds made of carbon dioxide ice may have warmed the surface of early Mars by reflecting not only incoming solar radiation but upwelling IR radiation as well. However, these studies have not treated scattering self-consistently in the thermal IR. Our own calculations, which treat IR scattering properly, confirm these earlier calculations but show that CO2 clouds can also cool the surface, especially if they are low and optically thick. Estimating the actual effect of CO2 clouds on early martian climate will require three-dimensional models in which cloud location, height, and optical depth, as well as surface temperature and pressure, are determined self-consistently. Our calculations further confirm that CO2 clouds should extend the outer boundary of the habitable zone around a star but that there is still a finite limit beyond which above-freezing surface temperatures cannot be maintained by a CO2-H2O atmosphere. For our own Solar System, the absolute outer edge of the habitable zone is at approximately 2.4 AU.

Investigations of the form and flow of ice sheets and glaciers using radio-echo sounding

Energy Technology Data Exchange (ETDEWEB)

Dowdeswell, J A; Evans, S [Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER (United Kingdom)

2004-10-01

Radio-echo sounding (RES), utilizing a variety of radio frequencies, was developed to allow glaciologists to measure the thickness of ice sheets and glaciers. We review the nature of electromagnetic wave propagation in ice and snow, including the permittivity of ice, signal attenuation and volume scattering, along with reflection from rough and specular surfaces. The variety of instruments used in RES of polar ice sheets and temperate glaciers is discussed. The applications and insights that a knowledge of ice thickness, and the wider nature of the form and flow of ice sheets, provides are also considered. The thickest ice measured is 4.7 km in East Antarctica. The morphology of the Antarctic and Greenland ice sheets, and many of the smaller ice caps and glaciers of the polar regions, has been investigated using RES. These findings are being used in three-dimensional numerical models of the response of the cryosphere to environmental change. In addition, the distribution and character of internal and basal reflectors within ice sheets contains information on, for example, ice-sheet layering and its chrono-stratigraphic significance, and has enabled the discovery and investigation of large lakes beneath the Antarctic Ice Sheet. Today, RES from ground-based and airborne platforms remains the most effective tool for measuring ice thickness and internal character.

Laser-powered Martian rover

Science.gov (United States)

Harries, W. L.; Meador, W. E.; Miner, G. A.; Schuster, Gregory L.; Walker, G. H.; Williams, M. D.

1989-01-01

Two rover concepts were considered: an unpressurized skeleton vehicle having available 4.5 kW of electrical power and limited to a range of about 10 km from a temporary Martian base and a much larger surface exploration vehicle (SEV) operating on a maximum 75-kW power level and essentially unrestricted in range or mission. The only baseline reference system was a battery-operated skeleton vehicle with very limited mission capability and range and which would repeatedly return to its temporary base for battery recharging. It was quickly concluded that laser powering would be an uneconomical overkill for this concept. The SEV, on the other hand, is a new rover concept that is especially suited for powering by orbiting solar or electrically pumped lasers. Such vehicles are visualized as mobile habitats with full life-support systems onboard, having unlimited range over the Martian surface, and having extensive mission capability (e.g., core drilling and sampling, construction of shelters for protection from solar flares and dust storms, etc.). Laser power beaming to SEV's was shown to have the following advantages: (1) continuous energy supply by three orbiting lasers at 2000 km (no storage requirements as during Martian night with direct solar powering); (2) long-term supply without replacement; (3) very high power available (MW level possible); and (4) greatly enhanced mission enabling capability beyond anything currently conceived.

Martian Gullies: Formation by CO2 Fluidification

Science.gov (United States)

Cedillo-Flores, Y.; Durand-Manterola, H. J.

2006-12-01

Some of the geomorphological features in Mars are the gullies. Some theories developed tried explain its origin, either by liquid water, liquid carbon dioxide or flows of dry granular material. We made a comparative analysis of the Martian gullies with the terrestrial ones. We propose that the mechanism of formation of the gullies is as follows: In winter CO2 snow mixed with sand falls in the terrain. In spring the CO2 snow sublimate and gaseous CO2 make fluid the sand which flows like liquid eroding the terrain and forming the gullies. By experimental work with dry granular material, we simulated the development of the Martian gullies injecting air in the granular material. We present the characteristics of some terrestrial gullies forms at cold environment, sited at Nevado de Toluca Volcano near Toluca City, México. We compare them with Martian gullies choose from four different areas, to target goal recognize or to distinguish, (to identify) possible processes evolved in its formation. Also, we measured the lengths of those Martian gullies and the range was from 24 m to 1775 meters. Finally, we present results of our experimental work at laboratory with dry granular material.

Physical and chemical properties of the Martian soil: Review of resources

Science.gov (United States)

Stoker, C. R.; Gooding, James L.; Banin, A.; Clark, Benton C.; Roush, Ted

1991-01-01

The chemical and physical properties of Martian surface materials are reviewed from the perspective of using these resources to support human settlement. The resource potential of Martian sediments and soils can only be inferred from limited analyses performed by the Viking Landers (VL), from information derived from remote sensing, and from analysis of the SNC meteorites thought to be from Mars. Bulk elemental compositions by the VL inorganic chemical (x ray fluorescence) analysis experiments have been interpreted as evidence for clay minerals (possibly smectites) or mineraloids (palagonite) admixed with sulfate and chloride salts. The materials contained minerals bearing Fe, Ti, Al, Mg and Si. Martian surface materials may be used in many ways. Martian soil, with appropriate preconditioning, can probably be used as a plant growth medium, supplying mechanical support, nutrient elements, and water at optimal conditions to the plants. Loose Martian soils could be used to cover structures and provide radiation shielding for surface habitats. Martian soil could be wetted and formed into abode bricks used for construction. Duricrete bricks, with strength comparable to concrete, can probably be formed using compressed muds made from martian soil.

Evidence for methane in Martian meteorites.

Science.gov (United States)

Blamey, Nigel J F; Parnell, John; McMahon, Sean; Mark, Darren F; Tomkinson, Tim; Lee, Martin; Shivak, Jared; Izawa, Matthew R M; Banerjee, Neil R; Flemming, Roberta L

2015-06-16

The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity.

Evidence of martian perchlorate, chlorate, and nitrate in Mars meteorite EETA79001: Implications for oxidants and organics

Science.gov (United States)

Kounaves, Samuel P.; Carrier, Brandi L.; O'Neil, Glen D.; Stroble, Shannon T.; Claire, Mark W.

2014-02-01

The results from the Viking mission in the mid 1970s provided evidence that the martian surface contained oxidants responsible for destroying organic compounds. In 2008 the Phoenix Wet Chemistry Lab (WCL) found perchlorate (ClO4-) in three soil samples at concentrations from 0.5 to 0.7 wt%. The detection of chloromethane (CH3Cl) and dichloromethane (CH2Cl2) by the Viking pyrolysis gas chromatograph-mass spectrometer (GC-MS) may have been a result of ClO4- at that site oxidizing either terrestrial organic contaminates or, if present, indigenous organics. Recently, the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) Curiosity directly measured the presence of CH3Cl, CH2Cl2 and, along with measurements of HCl and oxygen, indirectly indicate the presence of ClO4-. However, except for Phoenix, no other direct measurement of the ClO4- anion in martian soil or rock has been made. We report here ion chromatographic (IC) and isotopic analyses of a unique sawdust portion of the martian meteorite EETA79001 that show the presence by mass of 0.6 ± 0.1 ppm ClO4-, 1.4 ± 0.1 ppm ClO3-, and 16 ± 0.2 ppm NO3- at a quantity and location within the meteorite that is difficult to reconcile with terrestrial contamination. The sawdust sample consists of basaltic material with a minor salt-rich inclusion in a mass ratio of ∼300:1, thus the salts may be 300 times more concentrated within the inclusion than the whole sample. The molar ratios of NO3-:ClO4- and Cl:ClO4-, are very different for EETA79001 at ∼40:1 and 15:1, respectively, than the Antarctic soils and ice near where the meteorite was recovered at ∼10,000:1 and 5000:1, respectively. In addition, the isotope ratios for EETA79001 with δ15N = -10.48 ± 0.32‰ and δ18O = +51.61 ± 0.74‰ are significantly different from that of the nearby Miller Range blue ice with δ15N = +102.80 ± 0.14‰ and δ18O = +43.11 ± 0.64‰. This difference is notable, because if the meteorite had been

Earth – Mars Similarity Criteria for Martian Vehicles

Directory of Open Access Journals (Sweden)

Octavian TRIFU

2010-09-01

Full Text Available In order to select the most efficient kind of a martian exploring vehicle, the similarity criteria are deduced from the equilibrium movement in the terrestrial and martian conditions. Different invariants have been obtained for the existing (entry capsules, parachutes and rovers and potential martian exploring vehicles (lighter-than-air vehicle, airplane, helicopter and Mars Jumper. These similarity criteria, as non dimensional numbers, allow to quickly compare if such a kind of vehicles can operate in the martian environment, the movement performances, the necessary geometrical dimensions and the power consumption. Following this way of study it was concluded what vehicle is most suitable for the near soil Mars exploration. “Mars Rover” has less power consumption on Mars, but due to the rugged terrain the performances are weak. A vacuumed rigid airship is possible to fly with high performances and endurance on Mars, versus the impossibility of such a machine on the Earth. Due to very low density and the low Reynolds numbers in the Mars atmosphere, the power consumption for the martian airplane or helicopter, is substantial higher. The most efficient vehicle for the Mars exploration it seems to be a machine using the in-situ non-chemical propellants: the 95% CO2 atmosphere and the weak solar radiation. A small compressor, electrically driven by photovoltaics, compresses the gas in a storage tank, in time. If the gas is expanded through a nozzle, sufficient lift and control forces are obtained for a VTOL flight of kilometers over the martian soil, in comparison with tens of meters of the actual Mars rovers.

Comparision of the Martian Gullies With Terrestrial Ones

Science.gov (United States)

Cedillo-Flores, Y.; Durand-Manterola, H. J.

2005-12-01

Some of the geomorphological features in Mars are the gullies. Some theories developed tried to explained its origin, either by liquid water, liquid carbon dioxide or flows of dry granular material. We made a comparative analysis of the Martian gullies with the terrestrial ones. We present the characteristics of some terrestrial gullies formed at cold enviroment, sited at the Nevado de Toluca volcanoe near Toluca City, Mexico. We compare them with Martian gullies, choisen from four different areas, to recognize possible processes evolved in its formation. Also, we measured the lenghts of those Martian gullies and their range was from 24 m 1775 m.

Survival of microorganisms in smectite clays: Implications for Martian exobiology

Science.gov (United States)

Moll, Deborah M.; Vestal, J. Robie

1992-08-01

Manned exploration of Mars may result in the contamination of that planet with terrestrial microbes, a situation requiring assessment of the survival potential of possible contaminating organisms. In this study, the survival of Bacillus subtilis, Azotobacter chroococcum, and the enteric bacteriophage MS2 was examined in clays representing terrestrial (Wyoming type montmorillonite) or Martian (Fe 3+-montmorillonite) soils exposed to terrestrial and Martian environmental conditions of temperature and atmospheric pressure and composition, but not to UV flux or oxidizing conditions. Survival of bacteria was determined by standard plate counts and biochemical and physiological measurements over 112 days. Extractable lipid phosphate was used to measure microbial biomass, and the rate of 14C-acetate incorporation into microbial lipids was used to determine physiological activity. MS2 survival was assayed by plaque counts. Both bacterial types survived terrestrial or Martian conditions in Wyoming montmorillonite better than Martian conditions in Fe 3+-montmorillonite. Decreased survival may have been caused by the lower pH of the Fe 3+-montmorillonite compared to Wyoming montmorillonite. MS2 survived simulated Mars conditions better than the terrestrial environment, likely due to stabilization of the virus caused by the cold and dry conditions of the simulated Martian environment. The survival of MS2 in the simulated Martian environment is the first published indication that viruses may be able to survive in Martian type soils. This work may have implications for planetary protection for future Mars missions.

Martian Mixed Layer during Pathfinder Mission

Science.gov (United States)

Martinez, G. M.; Valero, F.; Vazquez, L.

2008-09-01

In situ measurements of the Martian Planetary Boundary Layer (MPBL) encompass only the sur- face layer. Therefore, in order to fully address the MPBL, it becomes necessary to simulate somehow the behaviour of the martian mixed layer. The small-scale processes that happen in the MPBL cause GCM's ([1], [2]) to describe only partially the turbulent statistics, height, convective scales, etc, of the surface layer and the mixed layer. For this reason, 2D and 3D martian mesoscale models ([4], [5]), and large eddy simulations ([4], [6], [7], [8]) have been designed in the last years. Although they are expected to simulate more accurately the MPBL, they take an extremely expensive compu- tational time. Alternatively, we have derived the main turbu- lent characteristics of the martian mixed layer by using surface layer and mixed layer similarity ([9], [10]). From in situ temperature and wind speed measurements, together with quality-tested simu- lated ground temperature [11], we have character- ized the martian mixed layer during the convective hours of Pathfinder mission Sol 25. Mean mixed layer turbulent statistics like tem- perature variance , horizontal wind speed variance , vertical wind speed variance , viscous dissipation rate , and turbu- lent kinetic energy have been calculated, as well as the mixed layer height zi, and the convective scales of wind w? and temperature θ?. Our values, obtained with negligible time cost, match quite well with some previously obtained results via LES's ([4] and [8]). A comparisson between the above obtained mar- tian values and the typical Earth values are shown in Table 1. Convective velocity scale w doubles its counterpart terrestrial typical value, as it does the mean wind speed variances and . On the other hand, the temperature scale θ? and the mean temperature variance are virtually around one order higher on Mars. The limitations of these results concern the va- lidity of the convective mixed layer similarity. This theory

Magnesium isotope systematics in Martian meteorites

Science.gov (United States)

Magna, Tomáš; Hu, Yan; Teng, Fang-Zhen; Mezger, Klaus

2017-09-01

Magnesium isotope compositions are reported for a suite of Martian meteorites that span the range of petrological and geochemical types recognized to date for Mars, including crustal breccia Northwest Africa (NWA) 7034. The δ26Mg values (per mil units relative to DSM-3 reference material) range from -0.32 to -0.11‰; basaltic shergottites and nakhlites lie to the heavier end of the Mg isotope range whereas olivine-phyric, olivine-orthopyroxene-phyric and lherzolitic shergottites, and chassignites have slightly lighter Mg isotope compositions, attesting to modest correlation of Mg isotopes and petrology of the samples. Slightly heavier Mg isotope compositions found for surface-related materials (NWA 7034, black glass fraction of the Tissint shergottite fall; δ26Mg > -0.17‰) indicate measurable Mg isotope difference between the Martian mantle and crust but the true extent of Mg isotope fractionation for Martian surface materials remains unconstrained. The range of δ26Mg values from -0.19 to -0.11‰ in nakhlites is most likely due to accumulation of clinopyroxene during petrogenesis rather than garnet fractionation in the source or assimilation of surface material modified at low temperatures. The rather restricted range in Mg isotope compositions between spatially and temporally distinct mantle-derived samples supports the idea of inefficient/absent major tectonic cycles on Mars, which would include plate tectonics and large-scale recycling of isotopically fractionated surface materials back into the Martian mantle. The cumulative δ26Mg value of Martian samples, which are not influenced by late-stage alteration processes and/or crust-mantle interactions, is - 0.271 ± 0.040 ‰ (2SD) and is considered to reflect δ26Mg value of the Bulk Silicate Mars. This value is robust taking into account the range of lithologies involved in this estimate. It also attests to the lack of the Mg isotope variability reported for the inner Solar System bodies at current

Chemical evolution of the early Martian hydrosphere

International Nuclear Information System (INIS)

Schaefer, M.W.

1990-01-01

The chemical evolution of the early Martian hydrosphere is discussed. The early Martian ocean can be modeled as a body of relatively pure water in equilibrium with a dense carbon dioxide atmosphere. The chemical weathering of lavas, pyroclastic deposits, and impact melt sheets would have the effect of neutralizing the acidity of the juvenile water. As calcium and other cations are added to the water by chemical weathering, they are quickly removed by the precipitation of calcium carbonate and other minerals, forming a deposit of limestone beneath the surface of the ocean. As the atmospheric carbon dioxide pressure and the temperature decrease, the Martian ocean would be completely frozen. Given the scenario for the chemical evolution of the northern lowland plains of Mars, it should be possible to draw a few conclusions about the expected mineralogy and geomorphology of this regions

Curation of US Martian Meteorites Collected in Antarctica

Science.gov (United States)

Lindstrom, M.; Satterwhite, C.; Allton, J.; Stansbury, E.

1998-01-01

To date the ANSMET field team has collected five martian meteorites (see below) in Antarctica and returned them for curation at the Johnson Space Center (JSC) Meteorite Processing Laboratory (MPL). ne meteorites were collected with the clean procedures used by ANSMET in collecting all meteorites: They were handled with JSC-cleaned tools, packaged in clean bags, and shipped frozen to JSC. The five martian meteorites vary significantly in size (12-7942 g) and rock type (basalts, lherzolites, and orthopyroxenite). Detailed descriptions are provided in the Mars Meteorite compendium, which describes classification, curation and research results. A table gives the names, classifications and original and curatorial masses of the martian meteorites. The MPL and measures for contamination control are described.

Wind tunnel simulation of Martian sand storms

Science.gov (United States)

Greeley, R.

1980-01-01

The physics and geological relationships of particles driven by the wind under near Martian conditions were examined in the Martian Surface Wind Tunnel. Emphasis was placed on aeolian activity as a planetary process. Threshold speeds, rates of erosion, trajectories of windblown particles, and flow fields over various landforms were among the factors considered. Results of experiments on particles thresholds, rates of erosion, and the effects of electrostatics on particles in the aeolian environment are presented.

Electrodynamics of the Martian Ionosphere

Science.gov (United States)

Ledvina, S. A.; Brecht, S. H.

2017-12-01

The presence of the Martian crustal magnetic fields makes a significant modification to the interaction between the solar wind/IMF and the ionosphere of the planet. This paper presents the results of 3-D hybrid simulations of Martian solar wind interaction containing the Martian crustal fields., self-consistent ionospheric chemistry and planetary rotation. It has already been reported that the addition of the crustal fields and planetary rotation makes a significant modification of the ionospheric loss from Mars, Brecht et al., 2016. This paper focuses on two other aspects of the interaction, the electric fields and the current systems created by the solar wind interaction. The results of several simulations will be analyzed and compared. The electric fields around Mars due to its interaction with the solar wind will be examined. Special attention will be paid to the electric field constituents (∇ X B, ∇Pe, ηJ). Regions where the electric field is parallel to the magnetic field will be found and the implications of these regions will be discussed. Current systems for each ion species will be shown. Finally the effects on the electric fields and the current systems due to the rotation of Mars will be examined.

Water in Pyroxene and Olivine from Martian Meteorites

Science.gov (United States)

Peslier, A. H.

2012-01-01

Water in the interior of terrestrial planets can be dissolved in fluids or melts and hydrous phases, but can also be locked as protons attached to structural oxygen in lattice defects in nominally anhydrous minerals (NAM) like olivine, pyroxene, or feldspar [1-3]. Although these minerals contain only tens to hundreds of ppm H2O, this water can amount to at least one ocean in mass when added at planetary scales because of the modal dominance of NAM in the mantle and crust [4]. Moreover these trace amounts of water can have drastic effects on melting temperature, rheology, electrical and heat conductivity, and seismic wave attenuation [5]. There is presently a debate on how much water is present in the martian mantle. Secondary ionization mass spectrometry (SIMS) studies of NAM [6], amphiboles and glass in melt inclusions [7-10], and apatites [11, 12] from Martian meteorites report finding as much water as in the same phases from Earth's igneous rocks. Most martian hydrous minerals, however, generally have the relevant sites filled with Cl and F instead of H [13, 14], and experiments using Cl [15] in parent melts can reproduce Martian basalt compositions as well as those with water [16]. We are in the process of analyzing Martian meteorite minerals by Fourier transform infrared spectrometry (FTIR) in order to constrain the role of water in this planet s formation and magmatic evolution

The provenance, formation, and implications of reduced carbon phases in Martian meteorites

Science.gov (United States)

Steele, Andrew; McCubbin, Francis M.; Fries, Marc D.

2016-11-01

This review is intended to summarize the current observations of reduced carbon in Martian meteorites, differentiating between terrestrial contamination and carbon that is indigenous to Mars. Indeed, the identification of Martian organic matter is among the highest priority targets for robotic spacecraft missions in the next decade, including the Mars Science Laboratory and Mars 2020. Organic carbon compounds are essential building blocks of terrestrial life, so the occurrence and origin (biotic or abiotic) of organic compounds on Mars is of great significance; however, not all forms of reduced carbon are conducive to biological systems. This paper discusses the significance of reduced organic carbon (including methane) in Martian geological and astrobiological systems. Specifically, it summarizes current thinking on the nature, sources, and sinks of Martian organic carbon, a key component to Martian habitability. Based on this compilation, reduced organic carbon on Mars, including detections of methane in the Martian atmosphere, is best described through a combination of abiotic organic synthesis on Mars and infall of extraterrestrial carbonaceous material. Although conclusive signs of Martian life have yet to be revealed, we have developed a strategy for life detection on Mars that can be utilized in future life-detection studies.

The Ice Cap Zone: A Unique Habitable Zone for Ocean Worlds

Science.gov (United States)

Ramirez, Ramses M.; Levi, Amit

2018-03-01

Traditional definitions of the habitable zone assume that habitable planets contain a carbonate-silicate cycle that regulates CO2 between the atmosphere, surface, and the interior. Such theories have been used to cast doubt on the habitability of ocean worlds. However, Levi et al (2017) have recently proposed a mechanism by which CO2 is mobilized between the atmosphere and the interior of an ocean world. At high enough CO2 pressures, sea ice can become enriched in CO2 clathrates and sink after a threshold density is achieved. The presence of subpolar sea ice is of great importance for habitability in ocean worlds. It may moderate the climate and is fundamental in current theories of life formation in diluted environments. Here, we model the Levi et al. mechanism and use latitudinally-dependent non-grey energy balance and single-column radiative-convective models and find that this mechanism may be sustained on ocean worlds that rotate at least 3 times faster than the Earth. We calculate the circumstellar region in which this cycle may operate for G-M-stars (Teff = 2,600-5,800 K), extending from ˜1.23 - 1.65, 0.69 - 0.873, 0.38-0.528 AU, 0.219-0.308 AU, 0.146-0.206 AU, and 0.0428-0.0617 AU for G2, K3, M0, M3, M5, and M8 stars, respectively. However, unless planets are very young and not tidally-locked, our mechanism would be unlikely to apply to stars cooler than a ˜M3. We predict C/O ratios for our atmospheres (˜0.5) that can be verified by the JWST mission.

Some aspects of composition of the lower Martian atmosphere: input for MIRA

Science.gov (United States)

Moroz, V.; Korablev, O.; Krasnopolsky, V.; Rorin, A.

Recent spacecraft missions and high-resolution spectroscopic observations from the Earth-based, airborne and spaceborne observatories have justified the chemical contents of the Martian atmosphere at a new level of confidence. Both the lower and middle atmosphere of Mars reveal very limited chemical activity, while the variations of the abundance of minor constituents may be attributed to phase transitions of volatiles. Water vapor, which mixing ratio is controlled by complex hydrological cycle in the lower atmosphere and at the surface of the planet, affects seasonally varying depletion of ozone. Measured ratio of D/H can be explained with general models of the early evolution of the planet, though this estimate in the bulk atmosphere may not be ultimately representative due to altitude dependant fractionation of water isotopes. CO, as a chemically passive nonvolatile component, reveals increase of mixing ratio in the vicinity of winter polar caps during active condensation of the bulk CO2 atmosphere. No reliable evidence o any organicf matter in the atmosphere of Mars has been obtained.

Snow precipitation on Mars driven by cloud-induced night-time convection

Science.gov (United States)

Spiga, Aymeric; Hinson, David P.; Madeleine, Jean-Baptiste; Navarro, Thomas; Millour, Ehouarn; Forget, François; Montmessin, Franck

2017-09-01

Although it contains less water vapour than Earth's atmosphere, the Martian atmosphere hosts clouds. These clouds, composed of water-ice particles, influence the global transport of water vapour and the seasonal variations of ice deposits. However, the influence of water-ice clouds on local weather is unclear: it is thought that Martian clouds are devoid of moist convective motions, and snow precipitation occurs only by the slow sedimentation of individual particles. Here we present numerical simulations of the meteorology in Martian cloudy regions that demonstrate that localized convective snowstorms can occur on Mars. We show that such snowstorms--or ice microbursts--can explain deep night-time mixing layers detected from orbit and precipitation signatures detected below water-ice clouds by the Phoenix lander. In our simulations, convective snowstorms occur only during the Martian night, and result from atmospheric instability due to radiative cooling of water-ice cloud particles. This triggers strong convective plumes within and below clouds, with fast snow precipitation resulting from the vigorous descending currents. Night-time convection in Martian water-ice clouds and the associated snow precipitation lead to transport of water both above and below the mixing layers, and thus would affect Mars' water cycle past and present, especially under the high-obliquity conditions associated with a more intense water cycle.

Dione and Rhea seasonal exospheres revealed by Cassini CAPS and INMS

Science.gov (United States)

Teolis, B. D.; Waite, J. H.

2016-07-01

A Dione O2 and CO2 exosphere of similar composition and density to Rhea's is confirmed by Cassini spacecraft Ion Neutral Mass Spectrometer (INMS) flyby data. INMS results from three Dione and two Rhea flybys show exospheric spatial and temporal variability indicative of seasonal exospheres, modulated by winter polar gas adsorption and desorption at the equinoxes. Cassini Plasma Spectrometer (CAPS) pickup ion fluxes also show exospheric structure and evolution at Rhea consistent with INMS, after taking into consideration the anticipated charge exchange, electron impact, and photo-ionization rates. Data-model comparisons show the exospheric evolution to be consistent with polar frost diffusion into the surface regolith, which limits surface exposure and loss of the winter frost cap by sputtering. Implied O2 source rates of ∼45(7) × 1021 s-1 at Dione(Rhea) are ∼50(300) times less than expected from known O2 radiolysis yields from ion-irradiated pure water ice measured in the laboratory, ruling out secondary sputtering as a major exospheric contributor, and implying a nanometer scale surface refractory lag layer consisting of concentrated carbonaceous impurities. We estimate ∼30:1(2:1) relative O2:CO2 source rates at Dione(Rhea), consistent with a stoichiometric bulk composition below the lag layer of 0.01(0.13) C atoms per H2O molecule, deriving from endogenic constituents, implanted micrometeoritic organics, and (in particular at Dione) exogenous H2O delivery by E-ring grains. Impact deposition, gardening and vaporization may thereby control the global O2 source rates by fresh H2O ice exposure to surface radiolysis and trapped oxidant ejection.

Modelling large-scale ice-sheet–climate interactions following glacial inception

Directory of Open Access Journals (Sweden)

J. M. Gregory

2012-10-01

Full Text Available We have coupled the FAMOUS global AOGCM (atmosphere-ocean general circulation model to the Glimmer thermomechanical ice-sheet model in order to study the development of ice-sheets in north-east America (Laurentia and north-west Europe (Fennoscandia following glacial inception. This first use of a coupled AOGCM–ice-sheet model for a study of change on long palæoclimate timescales is made possible by the low computational cost of FAMOUS, despite its inclusion of physical parameterisations similar in complexity to higher-resolution AOGCMs. With the orbital forcing of 115 ka BP, FAMOUS–Glimmer produces ice caps on the Canadian Arctic islands, on the north-west coast of Hudson Bay and in southern Scandinavia, which grow to occupy the Keewatin region of the Canadian mainland and all of Fennoscandia over 50 ka. Their growth is eventually halted by increasing coastal ice discharge. The expansion of the ice-sheets influences the regional climate, which becomes cooler, reducing the ablation, and ice accumulates in places that initially do not have positive surface mass balance. The results suggest the possibility that the glaciation of north-east America could have begun on the Canadian Arctic islands, producing a regional climate change that caused or enhanced the growth of ice on the mainland. The increase in albedo (due to snow and ice cover is the dominant feedback on the area of the ice-sheets and acts rapidly, whereas the feedback of topography on SMB does not become significant for several centuries, but eventually has a large effect on the thickening of the ice-sheets. These two positive feedbacks are mutually reinforcing. In addition, the change in topography perturbs the tropospheric circulation, producing some reduction of cloud, and mitigating the local cooling along the margin of the Laurentide ice-sheet. Our experiments demonstrate the importance and complexity of the interactions between ice-sheets and local climate.

Iron Redox Systematics of Shergottites and Martian Magmas

Science.gov (United States)

Righter, Kevin; Danielson, L. R.; Martin, A. M.; Newville, M.; Choi, Y.

2010-01-01

Martian meteorites record a range of oxygen fugacities from near the IW buffer to above FMQ buffer [1]. In terrestrial magmas, Fe(3+)/ SigmaFe for this fO2 range are between 0 and 0.25 [2]. Such variation will affect the stability of oxides, pyroxenes, and how the melt equilibrates with volatile species. An understanding of the variation of Fe(3+)/SigmaFe for martian magmas is lacking, and previous work has been on FeO-poor and Al2O3-rich terrestrial basalts. We have initiated a study of the iron redox systematics of martian magmas to better understand FeO and Fe2O3 stability, the stability of magnetite, and the low Ca/high Ca pyroxene [3] ratios observed at the surface.

A nanobody targeting the F-actin capping protein CapG restrains breast cancer metastasis.

Science.gov (United States)

Van Impe, Katrien; Bethuyne, Jonas; Cool, Steven; Impens, Francis; Ruano-Gallego, David; De Wever, Olivier; Vanloo, Berlinda; Van Troys, Marleen; Lambein, Kathleen; Boucherie, Ciska; Martens, Evelien; Zwaenepoel, Olivier; Hassanzadeh-Ghassabeh, Gholamreza; Vandekerckhove, Joël; Gevaert, Kris; Fernández, Luis Ángel; Sanders, Niek N; Gettemans, Jan

2013-12-13

Aberrant turnover of the actin cytoskeleton is intimately associated with cancer cell migration and invasion. Frequently however, evidence is circumstantial, and a reliable assessment of the therapeutic significance of a gene product is offset by lack of inhibitors that target biologic properties of a protein, as most conventional drugs do, instead of the corresponding gene. Proteomic studies have demonstrated overexpression of CapG, a constituent of the actin cytoskeleton, in breast cancer. Indirect evidence suggests that CapG is involved in tumor cell dissemination and metastasis. In this study, we used llama-derived CapG single-domain antibodies or nanobodies in a breast cancer metastasis model to address whether inhibition of CapG activity holds therapeutic merit. We raised single-domain antibodies (nanobodies) against human CapG and used these as intrabodies (immunomodulation) after lentiviral transduction of breast cancer cells. Functional characterization of nanobodies was performed to identify which biochemical properties of CapG are perturbed. Orthotopic and tail vein in vivo models of metastasis in nude mice were used to assess cancer cell spreading. With G-actin and F-actin binding assays, we identified a CapG nanobody that binds with nanomolar affinity to the first CapG domain. Consequently, CapG interaction with actin monomers or actin filaments is blocked. Intracellular delocalization experiments demonstrated that the nanobody interacts with CapG in the cytoplasmic environment. Expression of the nanobody in breast cancer cells restrained cell migration and Matrigel invasion. Notably, the nanobody prevented formation of lung metastatic lesions in orthotopic xenograft and tail-vein models of metastasis in immunodeficient mice. We showed that CapG nanobodies can be delivered into cancer cells by using bacteria harboring a type III protein secretion system (T3SS). CapG inhibition strongly reduces breast cancer metastasis. A nanobody-based approach offers

Iron Redox Systematics of Martian Magmas

Science.gov (United States)

Righter, K.; Danielson, L.; Martin, A.; Pando, K.; Sutton, S.; Newville, M.

2011-01-01

Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite [1]. Morris et al. [1] propose that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks [2,3]. Magnetite stability in terrestrial magmas is well understood, as are the stability of FeO and Fe2O3 in terrestrial magmas [4,5]. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas we have undertaken an experimental study with two emphases. First we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition. Second, we determine the FeO and Fe2O3 contents of the same shergottite bulk composition at 1 bar and variable fO2 at 1250 C, and at variable pressure. These two goals will help define not only magnetite stability, but pyroxene-melt equilibria that are also dependent upon fO2.

Annually resolved ice core records of tropical climate variability over the past ~1800 years.

Science.gov (United States)

Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

2013-05-24

Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

Evidence for a Heterogeneous Distribution of Water in the Martian Interior

Science.gov (United States)

McCubbin, Francis; Boyce, Jeremy W.; Srinvasan, Poorna; Santos, Alison R.; Elardo, Stephen M.; Filiberto, Justin; Steele, Andrew; Shearer, Charles K.

2016-01-01

The abundance and distribution of H2O within the terrestrial planets, as well as its timing of delivery, is a topic of vital importance for understanding the chemical and physical evolution of planets and their potential for hosting habitable environments. Analysis of planetary materials from Mars, the Moon, and the eucrite parent body (i.e., asteroid 4Vesta) have confirmed the presence of H2O within their interiors. Moreover, H and N isotopic data from these planetary materials suggests H2O was delivered to the inner solar system very early from a common source, similar in composition to the carbonaceous chondrites. Despite the ubiquity of H2O in the inner Solar System, the only destination with any prospects for past or present habitable environments at this time, outside of the Earth, is Mars. Although the presence of H2O within the martian interior has been confirmed, very little is known regarding its abundance and distribution within the martian interior and how the martian water inventory has changed over time. By combining new analyses of martian apatites within a large number of martian meteorite types with previously published volatile data and recently determined mineral-melt partition coefficients for apatite, we report new insights into the abundance and distribution of volatiles in the martian crust and mantle. Using the subset of samples that did not exhibit crustal contamination, we determined that the enriched shergottite mantle source has 36-73 ppm H2O and the depleted shergottite mantle source has 14-23 ppm H2O. This result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the martian mantle. We also estimated the H2O content of the martian crust using the revised mantle H2O abundances and known crust-mantle distributions of incompatible lithophile elements. We determined that the bulk martian crust has

Terrestrial Permafrost Models of Martian Habitats and Inhabitants

Science.gov (United States)

Gilichinsky, D.

2011-12-01

The terrestrial permafrost is the only rich depository of viable ancient microorganisms on Earth, and can be used as a bridge to possible Martian life forms and shallow subsurface habitats where the probability of finding life is highest. Since there is a place for water, the requisite condition for life, the analogous models are more or less realistic. If life ever existed on Mars, traces might have been preserved and could be found at depth within permafrost. The age of the terrestrial isolates corresponds to the longevity of the frozen state of the embedding strata, with the oldest known dating back to the late Pliocene in Arctic and late Miocene in Antarctica. Permafrost on Earth and Mars vary in age, from a few million years on Earth to a few billion years on Mars. Such a difference in time scale would have a significant impact on the possibility of preserving life on Mars, which is why the longevity of life forms preserved within terrestrial permafrost can only be an approximate model for Mars. 1. A number of studies indicate that the Antarctic cryosphere began to develop on the Eocene-Oligocene boundary, after the isolation of the continent. Permafrost degradation is only possible if mean annual ground temperature, -28°C now, rise above freezing, i.e., a significant warming to above 25°C is required. There is no evidence of such sharp temperature increase, which indicates that the climate and geological history was favorable to persistence of pre-Pliocene permafrost. These oldest relics (~30Myr) are possibly to be found at high hypsometric levels of ice-free areas (Dry Valleys and nearby mountains). It is desirable to test the layers for the presence of viable cells. The limiting age, if one exists, within this ancient permafrost, where the viable organisms were no longer present, could be established as the limit for life preservation below 0oC. Positive results will extend the known temporal limits of life in permafrost. 2. Even in this case, the age of

Martian Ionospheric Observation and Modeling

Science.gov (United States)

González-Galindo, Francisco

2018-02-01

The Martian ionosphere is a plasma embedded within the neutral upper atmosphere of the planet. Its main source is the ionization of the CO2-dominated Martian mesosphere and thermosphere by the energetic EUV solar radiation. The ionosphere of Mars is subject to an important variability induced by changes in its forcing mechanisms (e.g., the UV solar flux) and by variations in the neutral atmosphere (e.g., the presence of global dust storms, atmospheric waves and tides, changes in atmospheric composition, etc.). Its vertical structure is dominated by a maximum in the electron concentration placed at about 120–140 km of altitude, coincident with the peak of the ionization rate. Below, a secondary peak produced by solar X-rays and photoelectron-impact ionization is observed. A sporadic third layer, possibly of meteoric origin, has been also detected below. The most abundant ion in the Martian ionosphere is O2+, although O+ can become more abundant in the upper ionospheric layers. While below about 180–200 km the Martian ionosphere is dominated by photochemical processes, above those altitudes the dynamics of the plasma become more important. The ionosphere is also an important source of escaping particles via processes such as dissociative recombination of ions or ion pickup. So, characterization of the ionosphere provides or can provide information about such disparate systems and processes as the solar radiation getting to the planet, the neutral atmosphere, the meteoric influx, the atmospheric escape to space, or the interaction of the planet with the solar wind. It is thus not surprising that the interest about this region dates from the beginning of the space era. From the first measurements provided by the Mariner 4 mission in the 1960s to the contemporaneous observations, still ongoing, by the Mars Express and MAVEN orbiters, our current knowledge of this atmospheric region is the consequence of the accumulation of more than 50 years of discontinuous

Laser induced breakdown spectroscopy library for the Martian environment

International Nuclear Information System (INIS)

Cousin, A.; Forni, O.; Maurice, S.; Gasnault, O.

2011-01-01

The NASA Mars Science Laboratory rover will carry the first Laser Induced Breakdown Spectroscopy experiment in space: ChemCam. We have developed a laboratory model which mimics ChemCam's main characteristics. We used a set of target samples relevant to Mars geochemistry, and we recorded individual spectra. We propose a data reduction scheme for Laser Induced Breakdown Spectroscopy data incorporating de-noising, continuum removal, and peak fitting. Known effects of the Martian atmosphere are confirmed with our experiment: better Signal-to-Noise Ratio on Mars compared to Earth, narrower peak width, and essentially no self-absorption. The wavelength shift of emission lines from air to Mars pressure is discussed. The National Institute of Standards and Technology vacuum database is used for wavelength calibration and to identify the elemental lines. Our Martian database contains 1336 lines for 32 elements: H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ar, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Rb, Sr, Cs, Ba, and Pb. It is a subset of the National Institute of Standards and Technology database to be used for Martian geochemistry. Finally, synthetic spectra can be built from the Martian database. Correlation calculations help to distinguish between elements in case of uncertainty. This work is used to create tools and support data for the interpretation of ChemCam results. - Highlights: ► Chemcam: first Laser Induced Breakdown Spectroscopy technique on Mars. ► Creation of a LIBS specific database to ChemCam on Mars. ► Data reduction scheme is proposed. ► Best signal under Martian conditions. ► LIBS emission lines database: subset of NIST database for Martian geochemistry.

/sup 58,60,62/Ni (. cap alpha. ,p) three--nucleon transfer reactions and. cap alpha. optical potential ambiguities

Energy Technology Data Exchange (ETDEWEB)

Yuanda, Wang; Xiuming, Bao; Zhiqiang, Mao; Rongfang, Yuan; Keling, Wen; Binyin, Huang; Zhifu, Wang; Shuming, Li; Jianan, Wang; Zuxun, Sun; others, and

1985-11-01

The differential cross sections are measured using 26.0 MeV ..cap alpha.. particle for /sup 58,62/Ni(..cap alpha.., ..cap alpha..) /sup 58,62/Ni and /sup 58,62/Ni(..cap alpha..,p) /sup 61,65/Cu reactions as well as 25.4 MeV ..cap alpha.. particle for /sup 60/Ni(..cap alpha.., ..cap alpha..)/sup 69/Ni and /sup 60/Ni(..cap alpha.., p)/sup 63/Cu reactions. Consistent calculations with optical model and ZR DWBA are made for (..cap alpha.., ..cap alpha..) and (..cap alpha.., p) reactions by using of single, two, three and four nucleon optical potential parameters. For elastic scattering due to the ..cap alpha.. optical potential ambiguities, all the above optical potential can reproduce the experimental angular distributions. However, the single, two and three nucleon potential, including the Baird's mass systematics and the Chang's energy systematics of ..cap alpha.. potentials, obviously can not provide a reasonable fitting with the (..cap alpha..,p) reaction experimental data. Only the results from the four nucleon potential is in good agreement with the (..cap alpha..,p) reaction experimental data. This reveals that in the ..cap alpha..-particle induced transfer reactions, the real depth of the ..cap alpha..-nucleus optical potential should be rather deep.

How does the antagonism between capping and anti-capping proteins affect actin network dynamics?

International Nuclear Information System (INIS)

Hu Longhua; Papoian, Garegin A

2011-01-01

Actin-based cell motility is essential to many biological processes. We built a simplified, three-dimensional computational model and subsequently performed stochastic simulations to study the growth dynamics of lamellipodia-like branched networks. In this work, we shed light on the antagonism between capping and anti-capping proteins in regulating actin dynamics in the filamentous network. We discuss detailed mechanisms by which capping and anti-capping proteins affect the protrusion speed of the actin network and the rate of nucleation of filaments. We computed a phase diagram showing the regimes of motility enhancement and inhibition by these proteins. Our work shows that the effects of capping and anti-capping proteins are mainly transmitted by modulation of the filamentous network density and local availability of monomeric actin. We discovered that the combination of the capping/anti-capping regulatory network with nucleation-promoting proteins introduces robustness and redundancy in cell motility machinery, allowing the cell to easily achieve maximal protrusion speeds under a broader set of conditions. Finally, we discuss distributions of filament lengths under various conditions and speculate on their potential implication for the emergence of filopodia from the lamellipodial network.

47 CFR 54.623 - Cap.

Science.gov (United States)

2010-10-01

... 47 Telecommunication 3 2010-10-01 2010-10-01 false Cap. 54.623 Section 54.623 Telecommunication... Universal Service Support for Health Care Providers § 54.623 Cap. (a) Amount of the annual cap. The annual cap on federal universal service support for health care providers shall be $400 million per funding...

47 CFR 54.507 - Cap.

Science.gov (United States)

2010-10-01

... 47 Telecommunication 3 2010-10-01 2010-10-01 false Cap. 54.507 Section 54.507 Telecommunication... Universal Service Support for Schools and Libraries § 54.507 Cap. (a) Amount of the annual cap. The annual funding cap on federal universal service support for schools and libraries shall be $2.25 billion per...

Implantation of Martian Materials in the Inner Solar System by a Mega Impact on Mars

Science.gov (United States)

Hyodo, Ryuki; Genda, Hidenori

2018-04-01

Observations and meteorites indicate that the Martian materials are enigmatically distributed within the inner solar system. A mega impact on Mars creating a Martian hemispheric dichotomy and the Martian moons can potentially eject Martian materials. A recent work has shown that the mega-impact-induced debris is potentially captured as the Martian Trojans and implanted in the asteroid belt. However, the amount, distribution, and composition of the debris has not been studied. Here, using hydrodynamic simulations, we report that a large amount of debris (∼1% of Mars’ mass), including Martian crust/mantle and the impactor’s materials (∼20:80), are ejected by a dichotomy-forming impact, and distributed between ∼0.5–3.0 au. Our result indicates that unmelted Martian mantle debris (∼0.02% of Mars’ mass) can be the source of Martian Trojans, olivine-rich asteroids in the Hungarian region and the main asteroid belt, and some even hit the early Earth. The evidence of a mega impact on Mars would be recorded as a spike of 40Ar–39Ar ages in meteorites. A mega impact can naturally implant Martian mantle materials within the inner solar system.

Nature of Reduced Carbon in Martian Meteorites

Science.gov (United States)

Gibson, Everett K., Jr.; McKay, D. S.; Thomas-Keprta, K. L.; Clemett, S. J.; White, L. M.

2012-01-01

Martian meteorites provide important information on the nature of reduced carbon components present on Mars throughout its history. The first in situ analyses for carbon on the surface of Mars by the Viking landers yielded disappointing results. With the recognition of Martian meteorites on Earth, investigations have shown carbon-bearing phases exist on Mars. Studies have yielded presence of reduced carbon, carbonates and inferred graphitic carbon phases. Samples ranging in age from the first approximately 4 Ga of Mars history [e.g. ALH84001] to nakhlites with a crystallization age of 1.3 Ga [e.g. Nakhla] with aqueous alteration processes occurring 0.5-0.7 Ga after crystallizaton. Shergottites demonstrate formation ages around 165-500 Ma with younger aqueous alterations events. Only a limited number of the Martian meteorites do not show evidence of significance terrestrial alterations. Selected areas within ALH84001, Nakhla, Yamato 000593 and possibly Tissint are suitable for study of their indigenous reduced carbon bearing phases. Nakhla possesses discrete, well-defined carbonaceous phases present within iddingsite alteration zones. Based upon both isotopic measurements and analysis of Nakhla's organic phases the presence of pre-terrestrial organics is now recognized. The reduced carbon-bearing phases appear to have been deposited during preterrestrial aqueous alteration events that produced clays. In addition, the microcrystalline layers of Nakhla's iddingsite have discrete units of salt crystals suggestive of evaporation processes. While we can only speculate on the origin of these unique carbonaceous structures, we note that the significance of such observations is that it may allow us to understand the role of Martian carbon as seen in the Martian meteorites with obvious implications for astrobiology and the pre-biotic evolution of Mars. In any case, our observations strongly suggest that reduced organic carbon exists as micrometer- size, discrete structures

Improved regional sea-level estimates from Ice Sheets, Glaciers and land water storage using GRACE time series and other data

Science.gov (United States)

He, Z.; Velicogna, I.; Hsu, C. W.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.; Fettweis, X.; van den Broeke, M. R.

2017-12-01

Changes in ice sheets, glaciers and ice caps (GIC) and land water mass cause regional sea level variations that differ significantly from a uniform re-distribution of mass over the ocean, with a decrease in sea level compared to the global mean sea level contribution (GMSL) near the sources of mass added to the ocean and an increase up to 30% larger than the GMSL in the far field. The corresponding sea level fingerprints (SLF) are difficult to separate from ocean dynamics on short time and spatial scales but as ice melt continues, the SLF signal will become increasingly dominant in the pattern of regional sea level rise. It has been anticipated that it will be another few decades before the land ice SLF could be identified in the pattern of regional sea level rise. Here, we combine 40 years of observations of ice sheet mass balance for Antarctica (1975-present) and Greenland (1978-present), along with surface mass balance reconstructions of glacier and ice caps mass balance (GIC) from 1970s to present to determine the contribution to the SLF from melting land ice (MAR and RACMO). We compare the results with observations from GRACE for the time period 2002 to present for evaluation of our approach. Land hydrology is constrained by GRACE data for the period 2002-present and by the GLDAS-NOAH land hydrology model for the longer time period. Over the long time period, we find that the contribution from land ice dominates. We quantify the contribution to the total SLF from Greenland and Antarctica in various parts of the world over the past 40 years. More important, we compare the cumulative signal from SLF with tide gauge records around the world, corrected for earth dynamics, to determine whether the land ice SLF can be detected in that record. Early results will be reported at the meeting. This work was performed at UC Irvine and at Caltech's Jet Propulsion Laboratory under a contract with NASA's Cryospheric Science Program.

Unusual Iron Redox Systematics of Martian Magmas

Science.gov (United States)

Danielson, L.; Righter, K.; Pando, K.; Morris, R. V.; Graff, T.; Agresti, D.; Martin, A.; Sutton, S.; Newville, M.; Lanzirotti, A.

2012-01-01

Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite. Morris et al. proposed that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks. Magnetite stability in terrestrial magmas is well understood, as are the stabilities of FeO and Fe2O3 in terrestrial magmas. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas, we have undertaken an experimental study with two emphases. First, we determine the FeO and Fe2O3 contents of super- and sub-liquidus glasses from a shergottite bulk composition at 1 bar to 4 GPa, and variable fO2. Second, we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition.

The pharmaceutical vial capping process: Container closure systems, capping equipment, regulatory framework, and seal quality tests.

Science.gov (United States)

Mathaes, Roman; Mahler, Hanns-Christian; Buettiker, Jean-Pierre; Roehl, Holger; Lam, Philippe; Brown, Helen; Luemkemann, Joerg; Adler, Michael; Huwyler, Joerg; Streubel, Alexander; Mohl, Silke

2016-02-01

Parenteral drug products are protected by appropriate primary packaging to protect against environmental factors, including potential microbial contamination during shelf life duration. The most commonly used CCS configuration for parenteral drug products is the glass vial, sealed with a rubber stopper and an aluminum crimp cap. In combination with an adequately designed and controlled aseptic fill/finish processes, a well-designed and characterized capping process is indispensable to ensure product quality and integrity and to minimize rejections during the manufacturing process. In this review, the health authority requirements and expectations related to container closure system quality and container closure integrity are summarized. The pharmaceutical vial, the rubber stopper, and the crimp cap are described. Different capping techniques are critically compared: The most common capping equipment with a rotating capping plate produces the lowest amount of particle. The strength and challenges of methods to control the capping process are discussed. The residual seal force method can characterize the capping process independent of the used capping equipment or CCS. We analyze the root causes of several cosmetic defects associated with the vial capping process. Copyright © 2015 Elsevier B.V. All rights reserved.

Martian regolith geochemistry and sampling techniques

Science.gov (United States)

Clark, B. C.

Laboratory study of samples of the intermediate and fine-grained regolith, including duricrust peds, is a fundamental prerequisite for understanding the types of physical and chemical weathering processes on Mars. The extraordinary importance of such samples is their relevance to understanding past changes in climate, availability (and possible physical state) of water, eolian forces, the thermal and chemical influences of volcanic and impact processes, and the inventory and fates of Martian volatiles. Fortunately, this regolith material appears to be ubiquitous over the Martian surface, and should be available at many different landing sites. Viking data has been interpreted to indicate a smectite-rich regolith material, implying extensive weathering involving aqueous activity and geochemical alteration. An all-igneous source of the Martian fines has also been proposed. The X-ray fluorescence measurement data set can now be fully explained in terms of a simple two-component model. The first component is silicate, having strong geochemical similarities with Shergottites, but not other SNC meteorites. The second component is salt. Variations in these components could produce silicate and salt-rich beds, the latter being of high potential importance for microenvironments in which liquid water (brines) could exist. It therefore would be desirable to scan the surface of the regolith for such prospects.

Martian regolith geochemistry and sampling techniques

Science.gov (United States)

Clark, B. C.

1988-01-01

Laboratory study of samples of the intermediate and fine-grained regolith, including duricrust peds, is a fundamental prerequisite for understanding the types of physical and chemical weathering processes on Mars. The extraordinary importance of such samples is their relevance to understanding past changes in climate, availability (and possible physical state) of water, eolian forces, the thermal and chemical influences of volcanic and impact processes, and the inventory and fates of Martian volatiles. Fortunately, this regolith material appears to be ubiquitous over the Martian surface, and should be available at many different landing sites. Viking data has been interpreted to indicate a smectite-rich regolith material, implying extensive weathering involving aqueous activity and geochemical alteration. An all-igneous source of the Martian fines has also been proposed. The X-ray fluorescence measurement data set can now be fully explained in terms of a simple two-component model. The first component is silicate, having strong geochemical similarities with Shergottites, but not other SNC meteorites. The second component is salt. Variations in these components could produce silicate and salt-rich beds, the latter being of high potential importance for microenvironments in which liquid water (brines) could exist. It therefore would be desirable to scan the surface of the regolith for such prospects.

SNC meteorites: Clues to martian petrologic evolution

International Nuclear Information System (INIS)

McSween, H.Y. Jr.

1985-01-01

The shergottites, nakhlites, and Chassigny (SNC meteorites) are apparently cumulate mafic and ultramafic rocks that crystallized at shallow levels in the crust of their parent body. The mineralogy and chemistry of these meteorites are remarkably like equivalent terrestrial rocks, although their ratios of Fe/(Fe+Mg) and certain incompatible elements and their oxygen isotopic compositions are distinctive. All have crystallization ages of 1.3 b.y. or younger and formed from magmas produced by partial melting of previously fractionated source regions. Isotope systematics suggest that the SNC parent body had a complex and protracted thermal history spanning most of geologic time. Some meteorites have been severely shock metamorphosed, and all were ejected from their parent body at relatively recent times, possibly in several impact events. Late crystallization ages, complex petrogenesis, and possible evidence for a large gravitational field suggest that these meteorites are derived from a large planet. Trapped gases in shergottite shock melts have compositions similar to the composition measured in the Martian atmosphere. Ejection of Martian meteorites may have been accomplished by acceleration of near-surface spalls or other mechanisms not fully understood. If SNC meteorites are of Martian origin, they provide important information on planetary composition and evolution. The bulk composition and redox state of the Martian mantle, as constrained by shergottite phase equilibria, must be more earthlike than most current models. Planetary thermal models should benefit from data on the abundances of radioactive heat sources, the melting behavior of the mantle, and the timing of planetary differentiation

Catastrophic antiphospholipid syndrome (CAPS): Descriptive analysis of 500 patients from the International CAPS Registry.

Science.gov (United States)

Rodríguez-Pintó, Ignasi; Moitinho, Marta; Santacreu, Irene; Shoenfeld, Yehuda; Erkan, Doruk; Espinosa, Gerard; Cervera, Ricard

2016-12-01

To analyze the clinical and immunologic manifestations of patients with catastrophic antiphospholipid syndrome (CAPS) from the "CAPS Registry". The demographic, clinical and serological features of 500 patients included in the website-based "CAPS Registry" were analyzed. Frequency distribution and measures of central tendency were used to describe the cohort. Comparison between groups regarding qualitative variables was undertaken by chi-square or Fisher exact test while T-test for independent variables was used to compare groups regarding continuous variables. 500 patients (female: 343 [69%]; mean age 38±17) accounting for 522 episodes of CAPS were included in the analysis. Forty percent of patients had an associated autoimmune disease, mainly systemic lupus erythematosus (SLE) (75%). The majority of CAPS episodes were triggered by a precipitating factor (65%), mostly infections (49%). Clinically, CAPS was characterized by several organ involvement affecting kidneys (73%), lungs (60%), brain (56%), heart (50%), and skin (47%). Lupus anticoagulant, IgG anticardiolipin and IgG anti-β2-glycprotein antibodies were the most often implicated antiphospholipid antibodies (83%, 81% and 78% respectively). Mortality accounted for 37% of episodes of CAPS. Several clinical differences could be observed based on the age of presentation and its association to SLE. Those cases triggered by a malignancy tended to occur in older patients, while CAPS episodes in young patients were associated with an infectious trigger and peripheral vessels involvement. Additionally, CAPS associated with SLE were more likely to have severe cardiac and brain involvement leading to a higher mortality (48%). Although the presentation of CAPS is characterized by multiorgan thrombosis and failure, clinical differences among patients exist based on age and underlying chronic diseases, e.g. malignancy and SLE. Copyright © 2016 Elsevier B.V. All rights reserved.

The land-ice contribution to 21st-century dynamic sea level rise

Science.gov (United States)

Howard, T.; Ridley, J.; Pardaens, A. K.; Hurkmans, R. T. W. L.; Payne, A. J.; Giesen, R. H.; Lowe, J. A.; Bamber, J. L.; Edwards, T. L.; Oerlemans, J.

2014-06-01

Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere-ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

Characterization of snow, ice and neve by image processing

International Nuclear Information System (INIS)

Gay, Michel

1999-01-01

It is now recognized that human activities, by the extent they have achieved since the industrial era, are likely to alter the Earth's climate (IPCC, 1996). Paleo climate and the climate change models show that the polar caps are particularly sensitive to global climate change. They are more likely to play an important role but unknown on the sea level. The positive term of mass balance of polar ice sheets is the accumulation of snow, whereas the negative term is formed by the flow of ice into the oceans. The size of the polar ice caps and their hostile environment limit the amount of available field data. Only satellite remote sensing is able to provide information on geographical scales as large as Antarctica or the Arctic and allows regular monitoring over time. But to be easily interpreted, in order to deduce the snowpack characteristics observed from space (size, shape of grains, surface roughness... ), satellite data should be validated and inverted using simplified parameters. Prior to the establishment of these relations, it is necessary to develop a snow reflectance model (thesis C. Leroux 1996) taking into account the physical and optical characteristics of the snow, and a microwave emissivity model (thesis Surdyck S. 1993) that provide volume information on the morphology of the snowpack. The snowpack is characterized by several physical parameters that depend on the depth: temperature, density, size and shape of grains mainly. It is therefore essential to establish a robust and simple parameterization of the size and shape of snow grains from their observation. Image processing allows to establish these relationships and allows automatic processing of a large number of data independent of the observer. Another glaciological problem of firn is the interpretation of data obtained from the analysis of trapped air bubbles in the gas. This study implies, in particular, the dating of the ice in the firn at the close off, is necessary to determine the age of

Physical properties of Martian meteorites: Porosity and density measurements

Science.gov (United States)

Coulson, Ian M.; Beech, Martin; Nie, Wenshuang

Martian meteorites are fragments of the Martian crust. These samples represent igneous rocks, much like basalt. As such, many laboratory techniques designed for the study of Earth materials have been applied to these meteorites. Despite numerous studies of Martian meteorites, little data exists on their basic structural characteristics, such as porosity or density, information that is important in interpreting their origin, shock modification, and cosmic ray exposure history. Analysis of these meteorites provides both insight into the various lithologies present as well as the impact history of the planet's surface. We present new data relating to the physical characteristics of twelve Martian meteorites. Porosity was determined via a combination of scanning electron microscope (SEM) imagery/image analysis and helium pycnometry, coupled with a modified Archimedean method for bulk density measurements. Our results show a range in porosity and density values and that porosity tends to increase toward the edge of the sample. Preliminary interpretation of the data demonstrates good agreement between porosity measured at 100× and 300× magnification for the shergottite group, while others exhibit more variability. In comparison with the limited existing data for Martian meteorites we find fairly good agreement, although our porosity values typically lie at the low end of published values. Surprisingly, despite the increased data set, there is little by way of correlation between either porosity or density with parameters such as shock effect or terrestrial residency. Further data collection on additional meteorite samples is required before more definitive statements can be made concerning the validity of these observations.

Black carbon aerosols and the third polar ice cap

Energy Technology Data Exchange (ETDEWEB)

Menon, Surabi; Koch, Dorothy; Beig, Gufran; Sahu, Saroj; Fasullo, John; Orlikowski, Daniel

2010-04-15

Recent thinning of glaciers over the Himalayas (sometimes referred to as the third polar region) have raised concern on future water supplies since these glaciers supply water to large river systems that support millions of people inhabiting the surrounding areas. Black carbon (BC) aerosols, released from incomplete combustion, have been increasingly implicated as causing large changes in the hydrology and radiative forcing over Asia and its deposition on snow is thought to increase snow melt. In India BC emissions from biofuel combustion is highly prevalent and compared to other regions, BC aerosol amounts are high. Here, we quantify the impact of BC aerosols on snow cover and precipitation from 1990 to 2010 over the Indian subcontinental region using two different BC emission inventories. New estimates indicate that Indian BC emissions from coal and biofuel are large and transport is expected to expand rapidly in coming years. We show that over the Himalayas, from 1990 to 2000, simulated snow/ice cover decreases by {approx}0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is {approx}36%, similar to that simulated for 2000 to 2010. Spatial patterns of modeled changes in snow cover and precipitation are similar to observations (from 1990 to 2000), and are mainly obtained with the newer BC estimates.

Development of A Microbalance System For Water and Dust Detection In Mars

Science.gov (United States)

Battaglia, R.; Palomba, E.; Palumbo, P.; Colangeli, L.

The cycle of dust on Mars is a key component of current climate, is relevant in the dynamic and thermodynamic evolution of atmosphere, and is directly involved in the water cloud formation. Furthermore, dust suspended in the atmosphere is a major driver of atmospheric motions at all scales and is suspected of having had great in- fluence on the morphological evolution of the Martian surface. The dust dispersed in the atmosphere thermally influences the behaviour of the lower atmosphere. Most of information on the nature of small particle on Mars is derived from Viking Lander data and Mars Pathfinder observations, even if the Viking orbiter IRTM instrument also was able to provide estimates of particle size distribution of Martian soil. On the other hand water is important as indicator of global climate changes on long time- scale. Seasonal variations in the column abundance are due to the combined effect of exchange of H2O between atmosphere and water reservoirs (e.g. polar caps, re- golith) and atmospheric transport. The Viking orbiters collected accurate information during the period 1976-1979 and much of what we know about water circulation in the Martian atmosphere derives from the observations by the Mars Atmospheric Wa- ter Detection experiments (MAWD). Despite the low absolute water content (0,03%), relative humidity can exceed 100%, leading to the formation of near surface fog and condensation clouds, thanks to low typical Mars temperatures. The typical value of 6.1 mbar (coincident with the triple point in the water phase diagram) of the surficial pressure, makes rather difficult the persistence of liquid water at the surface of Mars. This means that the water is present exclusively in a gaseous and (when the conditions are favourable) solid state. In this context, it is extremely important to study the role of the different contributions to the production of atmospheric water and to the forma- tion of water ice clouds by the three main reservoirs, i

The rebirth of the cervical cap.

Science.gov (United States)

Cappiello, J D; Grainger-Harrison, M

1981-01-01

In an effort to dispel myths surrounding the cervical cap, the historical and political factors affecting the cap's use in the U.S. are described. Clinical aspects of cap fitting are also included. The cervical cap has found only limited acceptance in the U.S. Skepticisms on the part of physicians may be the result of 2 factors: confusion of the cervical cap with intracervical devices used for artificial insemination and confusion with stem pessaries; and the lack of clinical research and statistical evaluation of efficacy rates. The latter factor prompted Tietze et al. to conduct the only U.S. statistical study of the cap in 1953. Of the 143 women studied, the pregnancy rate was 7.6/100 years of use. Of the 28 unplanned pregnancies, 6 were related to faulty technique or omission of a spermicide and 10 were instances of admittedly irregular use. When these failures are omitted, the theoretical effectiveness rate is about 98%. Some practitioners are concerned about an increased incidence of cervical erosion with cap use. Possibly currently conducted studies will show that cap and spermicide users have a lower incidence of cervical erosion than women using no contraceptive method. Study findings suggest that the cervical cap may afford protection without any spermicidal supplement, but the use of spermicides continues to be recommended to clients. Advantages of the cervical cap include the following: it can be left in place longer than a diaphragm without additional applications of spermicide in the vagina; and the insertion of the cap is unrelated to the time of intercourse. Despite research on toleration of the cap for 3 weeks at a time, it is recommended that the cap be worn for only a few days at a time. At this time there are no manufacturers of cervical caps for contraceptive use in the U.S. The cap is now being imported from England and it costs $6.00. A factor that has made the cap unpopular with many physicians is the lengthy time required for fitting. An

Volume changes of Vatnajökull ice cap, Iceland, due to surface mass balance, ice flow, and subglacial melting at geothermal areas

DEFF Research Database (Denmark)

Magnússon, Eyjólfur; Björnson, Helgi; Dall, Jørgen

2005-01-01

We present observed changes in the geometry of western Vatnajökull over a period of about ten years which are caused by the surface mass balance, ice flow (both during surges and quiescent periods), and basal melting due to geothermal and volcanic activity. Comparison of two digital elevation...

Possible evidence for non-Newtonian gravity in the Greenland ice gap

International Nuclear Information System (INIS)

Ander, M.E.

1988-01-01

An Airy-type geophysical experiment was conducted down a 2 km deep hole in the Greenland ice cap in order to test for possible violations of Newton's inverse square law by making gravity measurements over a range of 213 m to 1460 m. A significant departure from Newtonian gravity was observed. This result can be explained by the existence of an attractive non-Newtonian component of gravity with a strength of about 3.4% that of Newtonian gravity at a scale of 1460 m. Unfortunately, we cannot completely, unambiguously attribute it to a breakdown of Newtonian gravity because we have shown that lateral density variations in the bedrock beneath the ice can cause such apparent departures. If such variations existed, they would have to be rather unusual but certainly no impossible. 8 refs

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

Science.gov (United States)

Parsons, Reid; Holt, John

2016-03-01

Lobate debris aprons (LDAs) are midlatitude deposits of debris-covered ice formed during one or more periods of glaciation during the Amazonian period. However, little is known about the climate conditions that led to LDA formation. We explore a hypothesis in which a single, extended period of precipitation of ice on the steep slopes of Euripus Mons (45°S, 105°E—east of the Hellas Basin) produced a flowing ice deposit which was protected from subsequent ablation to produce the LDA found at this location. We test this hypothesis with a numerical ice flow model using an ice rheology based on low-temperature ice deformation experiments. The model simulates ice accumulation and flow for the northern and southern lobes of the Euripus Mons LDA using basal topography constrained by data from the Shallow Radar (SHARAD) and a range of ice viscosities (determined by ice temperature and ice grain size). Simulations for the northern lobe of the Euripus LDA produce good fits to the surface topography. Assuming an LDA age of ˜60 Myr and an expected temperature range of 200 to 204 K (for various obliquities) gives an ice grain size of ≈2 mm. Simulations of the southern section produce poor fits to surface topography and result in much faster flow timescales unless multiple ice deposition events or higher ice viscosities are considered.

Control parameters of the martian dune field positions at planetary scale: tests by the MCD

Science.gov (United States)

allemand, pascal

2016-04-01

The surface of Mars is occupied by more than 500 dunes fields mainly located inside impact craters of the south hemisphere and near the north polar cap. The questions of the activity of martian dunes and of the localization of the martian dune fields are not completely solved. It has been demonstrated recently by image observation and image correlation that some of these dune fields are clearly active. The sand flux of one of them has been even estimated. But there is no global view of the degree of activity of each the dune fields. (2)The topography of impact craters in which dune fields are localized is an important factor of their position. But there is no consensus of the effect of global atmospheric circulation on dune field localization. These two questions are addressed using the results of Mars Climate Database 5.2 (MCD) (Millour, 2015; Forget et al., 1999). The wind fields of the MCD have been first validated against the observations made on active dune fields. Using a classical transport law, the Drift Potential (DP) and the Relative Drift Potential (RDP) have been computed for each dune fields. A good correlation exists between the position of dune fields and specific values of these two parameters. The activity of each dune field is estimated from these parameters and tested on some examples by image observations. Finally a map of sand flow has been computed at the scale of the planet. This map shows that sand and dust is trapped in specific regions. These regions correspond to the area of dune field concentration.

Periglacial and glacial analogs for Martian landforms

Science.gov (United States)

Rossbacher, Lisa A.

1992-01-01

The list of useful terrestrial analogs for Martian landforms has been expanded to include: features developed by desiccation processes; catastrophic flood features associated with boulder-sized materials; and sorted ground developed at a density boundary. Quantitative analytical techniques developed for physical geography have been adapted and applied to planetary studies, including: quantification of the patterns of polygonally fractured ground to describe pattern randomness independent of pattern size, with possible correlation to the mechanism of origin and quantification of the relative area of a geomorphic feature or region in comparison to planetary scale. Information about Martian geomorphology studied in this project was presented at professional meetings world-wide, at seven colleges and universities, in two interactive televised courses, and as part of two books. Overall, this project has expanded the understanding of the range of terrestrial analogs for Martian landforms, including identifying several new analogs. The processes that created these terrestrial features are characterized by both cold temperatures and low humidity, and therefore both freeze-thaw and desiccation processes are important. All these results support the conclusion that water has played a significant role in the geomorphic history of Mars.

Microtubule's conformational cap

DEFF Research Database (Denmark)

Flyvbjerg, H.

1999-01-01

The molecular mechanisms that allow elongation of the unstable microtubule lattice remain unclear. It is usually thought that the GDP-liganded tubulin lattice is capped by a small layer of GTP- or GDP-P(i)-liganded molecules, the so called "GTP-cap". Here, we point-out that the elastic properties...

Sea surface temperature and sea ice variability in the subpolar North Atlantic from explosive volcanism of the late thirteenth century

DEFF Research Database (Denmark)

Sicre, M. -A.; Khodri, M.; Mignot, J.

2013-01-01

In this study, we use IP25 and alkenone biomarker proxies to document the subdecadal variations of sea ice and sea surface temperature in the subpolar North Atlantic induced by the decadally paced explosive tropical volcanic eruptions of the second half of the thirteenth century. The short-and long......-term evolutions of both variables were investigated by cross analysis with a simulation of the IPSL-CM5A LR model. Our results show short-term ocean cooling and sea ice expansion in response to each volcanic eruption. They also highlight that the long response time of the ocean leads to cumulative surface cooling...... and subsurface heat buildup due to sea ice capping. As volcanic forcing relaxes, the surface ocean rapidly warms, likely amplified by subsurface heat, and remains almost ice free for several decades....

75 FR 49527 - Caps Visual Communications, LLC; Black Dot Group; Formerly Known as Caps Group Acquisition, LLC...

Science.gov (United States)

2010-08-13

... DEPARTMENT OF LABOR Employment and Training Administration [TA-W-74,195] Caps Visual Communications, LLC; Black Dot Group; Formerly Known as Caps Group Acquisition, LLC Chicago, IL; Amended... of Caps Visual Communications, LLC, Black Dot Group, formerly known as Caps Group Acquisition, LLC...

Martian gullies: possible formation mechanism by dry granular material..

Science.gov (United States)

Cedillo-Flores, Y.; Durand-Manterola, H. J.

section Some of the geomorphological features in Mars are the gullies Some theories developed tried explain its origin either by liquid water liquid carbon dioxide or flows of dry granular material We made a comparative analysis of the Martian gullies with the terrestrial ones We propose that the mechanism of formation of the gullies is as follows In winter CO 2 snow mixed with sand falls in the terrain In spring the CO 2 snow sublimate and gaseous CO 2 make fluid the sand which flows like liquid eroding the terrain and forming the gullies By experimental work with dry granular material we simulated the development of the Martian gullies injecting air in the granular material section We present the characteristics of some terrestrial gullies forms at cold environment sited at Nevado de Toluca Volcano near Toluca City M e xico We compare them with Martian gullies choose from four different areas to target goal recognize or to distinguish to identify possible processes evolved in its formation Also we measured the lengths of those Martian gullies and the range was from 24 m to 1775 meters Finally we present results of our experimental work at laboratory with dry granular material

Iron snow in the Martian core?

Science.gov (United States)

Davies, Christopher J.; Pommier, Anne

2018-01-01

The decline of Mars' global magnetic field some 3.8-4.1 billion years ago is thought to reflect the demise of the dynamo that operated in its liquid core. The dynamo was probably powered by planetary cooling and so its termination is intimately tied to the thermochemical evolution and present-day physical state of the Martian core. Bottom-up growth of a solid inner core, the crystallization regime for Earth's core, has been found to produce a long-lived dynamo leading to the suggestion that the Martian core remains entirely liquid to this day. Motivated by the experimentally-determined increase in the Fe-S liquidus temperature with decreasing pressure at Martian core conditions, we investigate whether Mars' core could crystallize from the top down. We focus on the "iron snow" regime, where newly-formed solid consists of pure Fe and is therefore heavier than the liquid. We derive global energy and entropy equations that describe the long-timescale thermal and magnetic history of the core from a general theory for two-phase, two-component liquid mixtures, assuming that the snow zone is in phase equilibrium and that all solid falls out of the layer and remelts at each timestep. Formation of snow zones occurs for a wide range of interior and thermal properties and depends critically on the initial sulfur concentration, ξ0. Release of gravitational energy and latent heat during growth of the snow zone do not generate sufficient entropy to restart the dynamo unless the snow zone occupies at least 400 km of the core. Snow zones can be 1.5-2 Gyrs old, though thermal stratification of the uppermost core, not included in our model, likely delays onset. Models that match the available magnetic and geodetic constraints have ξ0 ≈ 10% and snow zones that occupy approximately the top 100 km of the present-day Martian core.

Pb evolution in the Martian mantle

Science.gov (United States)

Bellucci, J. J.; Nemchin, A. A.; Whitehouse, M. J.; Snape, J. F.; Bland, P.; Benedix, G. K.; Roszjar, J.

2018-03-01

The initial Pb compositions of one enriched shergottite, one intermediate shergottite, two depleted shergottites, and Nakhla have been measured by Secondary Ion Mass Spectrometry (SIMS). These values, in addition to data from previous studies using an identical analytical method performed on three enriched shergottites, ALH 84001, and Chassigny, are used to construct a unified and internally consistent model for the differentiation history of the Martian mantle and crystallization ages for Martian meteorites. The differentiation history of the shergottites and Nakhla/Chassigny are fundamentally different, which is in agreement with short-lived radiogenic isotope systematics. The initial Pb compositions of Nakhla/Chassigny are best explained by the late addition of a Pb-enriched component with a primitive, non-radiogenic composition. In contrast, the Pb isotopic compositions of the shergottite group indicate a relatively simple evolutionary history of the Martian mantle that can be modeled based on recent results from the Sm-Nd system. The shergottites have been linked to a single mantle differentiation event at 4504 Ma. Thus, the shergottite Pb isotopic model here reflects a two-stage history 1) pre-silicate differentiation (4504 Ma) and 2) post-silicate differentiation to the age of eruption (as determined by concordant radiogenic isochron ages). The μ-values (238U/204Pb) obtained for these two different stages of Pb growth are μ1 of 1.8 and a range of μ2 from 1.4-4.7, respectively. The μ1-value of 1.8 is in broad agreement with enstatite and ordinary chondrites and that proposed for proto Earth, suggesting this is the initial μ-value for inner Solar System bodies. When plotted against other source radiogenic isotopic variables (Sri, γ187Os, ε143Nd, and ε176Hf), the second stage mantle evolution range in observed mantle μ-values display excellent linear correlations (r2 > 0.85) and represent a spectrum of Martian mantle mixing-end members (depleted

Macrophage Capping Protein CapG Is a Putative Oncogene Involved in Migration and Invasiveness in Ovarian Carcinoma

Directory of Open Access Journals (Sweden)

J. Glaser

2014-01-01

Full Text Available The actin binding protein CapG modulates cell motility by interacting with the cytoskeleton. CapG is associated with tumor progression in different nongynecologic tumor entities and overexpression in breast cancer cell lines correlates with a more invasive phenotype in vitro. Here, we report a significant CapG overexpression in 18/47 (38% of ovarian carcinomas (OC analyzed by qRealTime-PCR analyses. Functional analyses in OC cell lines through siRNA mediated CapG knockdown and CapG overexpression showed CapG-dependent cell migration and invasiveness. A single nucleotide polymorphism rs6886 inside the CapG gene was identified, affecting a CapG phosphorylation site and thus potentially modifying CapG function. The minor allele frequency (MAF of SNP rs6886 (c.1004A/G was higher and the homozygous (A/A, His335 genotype was significantly more prevalent in patients with fallopian tube carcinomas (50% as in controls (10%. With OC being one of the most lethal cancer diseases, the detection of novel biomarkers such as CapG could reveal new diagnostic and therapeutic targets. Moreover, in-depth analyses of SNP rs6886 related to FTC and OC will contribute to a better understanding of carcinogenesis and progression of OC.

Chemical composition of Martian fines

Science.gov (United States)

Clark, B. C.; Baird, A. K.; Weldon, R. J.; Tsusaki, D. M.; Schnabel, L.; Candelaria, M. P.

1982-01-01

Of the 21 samples acquired for the Viking X-ray fluorescence spectrometer, 17 were analyzed to high precision. Compared to typical terrestrial continental soils and lunar mare fines, the Martian fines are lower in Al, higher in Fe, and much higher in S and Cl concentrations. Protected fines at the two lander sites are almost indistinguishable, but concentration of the element S is somewhat higher at Utopia. Duricrust fragments, successfully acquired only at the Chryse site, invariably contained about 50% higher S than fines. No elements correlate positively with S, except Cl and possibly Mg. A sympathetic variation is found among the triad Si, Al, Ca; positive correlation occurs between Ti and Fe. Sample variabilities are as great within a few meters as between lander locations (4500 km apart), implying the existence of a universal Martian regolith component of constant average composition. The nature of the source materials for the regolith fines must be mafic to ultramafic.

Life Detection and Characterization of Subsurface Ice and Brine in the McMurdo Dry Valleys Using an Ultrasonic Gopher: A NASA ASTEP Project

Science.gov (United States)

Doran, P. T.; Bar-Cohen, Y.; Fritsen, C.; Kenig, F.; McKay, C. P.; Murray, A.; Sherrit, S.

2003-01-01

Evidence for the presence of ice and fluids near the surface of Mars in both the distant and recent past is growing with each new mission to the Planet. One explanation for fluids forming springlike features on Mars is the discharge of subsurface brines. Brines offer potential refugia for extant Martian life, and near surface ice could preserve a record of past life on the planet. Proven techniques to get underground to sample these environments, and get below the disruptive influence of the surface oxidant and radiation regime, will be critical for future astrobiology missions to Mars. Our Astrobiology for Science and Technology for Exploring Planets (ASTEP) project has the goal to develop and test a novel ultrasonic corer in a Mars analog environment, the McMurdo Dry valleys, Antarctica, and to detect and describe life in a previously unstudied extreme ecosystem; Lake Vida (Fig. 1), an ice-sealed lake.

Distribution and Characteristics of Boulder Halos at High Latitudes on Mars: Ground Ice and Surface Processes Drive Surface Reworking

Science.gov (United States)

Levy, J. S.; Fassett, C. I.; Rader, L. X.; King, I. R.; Chaffey, P. M.; Wagoner, C. M.; Hanlon, A. E.; Watters, J. L.; Kreslavsky, M. A.; Holt, J. W.; Russell, A. T.; Dyar, M. D.

2018-02-01

Boulder halos are circular arrangements of clasts present at Martian middle to high latitudes. Boulder halos are thought to result from impacts into a boulder-poor surficial unit that is rich in ground ice and/or sediments and that is underlain by a competent substrate. In this model, boulders are excavated by impacts and remain at the surface as the crater degrades. To determine the distribution of boulder halos and to evaluate mechanisms for their formation, we searched for boulder halos over 4,188 High Resolution Imaging Science Experiment images located between 50-80° north and 50-80° south latitude. We evaluate geological and climatological parameters at halo sites. Boulder halos are about three times more common in the northern hemisphere than in the southern hemisphere (19% versus 6% of images) and have size-frequency distributions suggesting recent Amazonian formation (tens to hundreds of millions of years). In the north, boulder halo sites are characterized by abundant shallow subsurface ice and high thermal inertia. Spatial patterns of halo distribution indicate that excavation of boulders from beneath nonboulder-bearing substrates is necessary for the formation of boulder halos, but that alone is not sufficient. Rather, surface processes either promote boulder halo preservation in the north or destroy boulder halos in the south. Notably, boulder halos predate the most recent period of near-surface ice emplacement on Mars and persist at the surface atop mobile regolith. The lifetime of observed boulders at the Martian surface is greater than the lifetime of the craters that excavated them. Finally, larger minimum boulder halo sizes in the north indicate thicker icy soil layers on average throughout climate variations driven by spin/orbit changes during the last tens to hundreds of millions of years.

Towards Quantification of Glacier Dynamic Ice Loss through Passive Seismic Monitoring

Science.gov (United States)

Köhler, A.; Nuth, C.; Weidle, C.; Schweitzer, J.; Kohler, J.; Buscaino, G.

2015-12-01

Global glaciers and ice caps loose mass through calving, while existing models are currently not equipped to realistically predict dynamic ice loss. This is mainly because long-term continuous calving records, that would help to better understand fine scale processes and key climatic-dynamic feedbacks between calving, climate, terminus evolution and marine conditions, do not exist. Combined passive seismic/acoustic strategies are the only technique able to capture rapid calving events continuously, independent of daylight or meteorological conditions. We have produced such a continuous calving record for Kronebreen, a tidewater glacier in Svalbard, using data from permanent seismic stations between 2001 and 2014. However, currently no method has been established in cryo-seismology to quantify the calving ice loss directly from seismic data. Independent calibration data is required to derive 1) a realistic estimation of the dynamic ice loss unobserved due to seismic noise and 2) a robust scaling of seismic calving signals to ice volumes. Here, we analyze the seismic calving record at Kronebreen and independent calving data in a first attempt to quantify ice loss directly from seismic records. We make use of a) calving flux data with weekly to monthly resolution obtained from satellite remote sensing and GPS data between 2007 and 2013, and b) direct, visual calving observations in two weeks in 2009 and 2010. Furthermore, the magnitude-scaling property of seismic calving events is analyzed. We derive and discuss an empirical relation between seismic calving events and calving flux which for the first time allows to estimate a time series of calving volumes more than one decade back in time. Improving our model requires to incorporate more precise, high-resolution calibration data. A new field campaign will combine innovative, multi-disciplinary monitoring techniques to measure calving ice volumes and dynamic ice-ocean interactions simultaneously with terrestrial laser

Eddy intrusion of hot plasma into the polar cap and formation of polar-cap arcs

International Nuclear Information System (INIS)

Chiu, Y.T.; Gorney, D.J.

1983-01-01

We present plasma and electric field data obtained by the S3-3 satellite over the polar caps. We demonstrate that: (1) plasma signatures in the polar cap arc formation region near 5000 km altitude show clear intrusions of plasma sheet (approx.keV) and magneto sheath (approx.100 eV) plasma into a background of low-energy polar cap plasma; (2) the combined plasma and electric field signatures (electron inverted-V, ion beam and delxE<0) are exactly the same as in the evening discrete arc. We interpret this equivalence of polar cap and evening discrete arc signatures as indication that their formation processes are identical. The spatial structures of polar cap electric fields and the associated plasma signatures are consistent with the hypothesis that plasma intrusion into the polar cap takes the form of multiple cellular eddies. This hypothesis provides a unifying view of arc formation and arc configurations

Martian Neutron Energy Spectrometer (MANES)

Science.gov (United States)

Maurer, R. H.; Roth, D. R.; Kinnison, J. D.; Goldsten, J. O.; Fainchtein, R.; Badhwar, G.

2000-01-01

High energy charged particles of extragalactic, galactic, and solar origin collide with spacecraft structures and planetary atmospheres. These primaries create a number of secondary particles inside the structures or on the surfaces of planets to produce a significant radiation environment. This radiation is a threat to long term inhabitants and travelers for interplanetary missions and produces an increased risk of carcinogenesis, central nervous system (CNS) and DNA damage. Charged particles are readily detected; but, neutrons, being electrically neutral, are much more difficult to monitor. These secondary neutrons are reported to contribute 30-60% of the dose equivalent in the Shuttle and MIR station. The Martian atmosphere has an areal density of 37 g/sq cm primarily of carbon dioxide molecules. This shallow atmosphere presents fewer mean free paths to the bombarding cosmic rays and solar particles. The secondary neutrons present at the surface of Mars will have undergone fewer generations of collisions and have higher energies than at sea level on Earth. Albedo neutrons produced by collisions with the Martian surface material will also contribute to the radiation environment. The increased threat of radiation damage to humans on Mars occurs when neutrons of higher mean energy traverse the thin, dry Martian atmosphere and encounter water in the astronaut's body. Water, being hydrogeneous, efficiently moderates the high energy neutrons thereby slowing them as they penetrate deeply into the body. Consequently, greater radiation doses can be deposited in or near critical organs such as the liver or spleen than is the case on Earth. A second significant threat is the possibility of a high energy heavy ion or neutron causing a DNA double strand break in a single strike.

Designing Smart Charter School Caps

Science.gov (United States)

Dillon, Erin

2010-01-01

In 2007, Andrew J. Rotherham proposed a new approach to the contentious issue of charter school caps, the statutory limits on charter school growth in place in several states. Rotherham's proposal, termed "smart charter school caps," called for quality sensitive caps that allow the expansion of high-performing charter schools while also…

On the chemistry of the Martian surface

International Nuclear Information System (INIS)

Keil, K.

1978-01-01

Analyses of 13 smaples of Martian surface materials with the Viking X-ray fluorescence spectrometers show SiO 2 similar to that of terrestrial mafic rocks, whereas Fe 2 O 3 , Cl, and S are higher and Al 2 O 3 , K 2 O, Rb, Sr, Y, and Zr are lower. Low totals suggest presence of CO 2 , H 2 O, and Na 2 O. Duricrust fragments are higher in S than fines, but samples from both landing sites are surprisingly similar. We suggest that Martian surface materials are aeolian deposits of complex mixtures of weathering products of mafic-ultramafic rocks, possibly consisting of iron-rich clays, sulfates, iron oxides, carbonates, and chlorides. (orig.) 891 HK [de

On to Mars! chronicles of Martian simulations

CERN Document Server

PLETSER, Vladimir

2018-01-01

This book introduces the Martian simulations, one installed on Devon Island, an uninhabited island in the Canadian Arctic, well within the polar circle, and two in the desert of Utah, several hundreds of kilometers South of Salt Lake City. The book is based on the diaries during the simulations, held by Vladimir Pletser, a physicist-engineer, who was selected to attend these simulations. It relates the details of everyday life in these Martian habitats and of the scientific and exploratory work conducted in these extreme environments in preparation for future manned missions to Mars. Through the real experiences described in the book, readers will find space explorations and living on Mars more tangible. .

NATURE MANAGEMENT, LANDSCAPE AND THE CAP

OpenAIRE

Brouwer, Floor M.; Godeschalk, Frans E.

2004-01-01

The integration of nature management, landscape and environmental concerns into the Common Agricultural Policy (CAP) has gained momentum with the CAP reforms adopted in June 2003. The report explores instruments and approaches that contribute to the inte-gration of nature conservation and landscape concerns into the CAP. A broader use of the CAP instruments might help to achieve nature types in the Netherlands.

Local Dynamics of Baroclinic Waves in the Martian Atmosphere

KAUST Repository

Kavulich, Michael J.

2013-11-01

The paper investigates the processes that drive the spatiotemporal evolution of baroclinic transient waves in the Martian atmosphere by a simulation experiment with the Geophysical Fluid Dynamics Laboratory (GFDL) Mars general circulation model (GCM). The main diagnostic tool of the study is the (local) eddy kinetic energy equation. Results are shown for a prewinter season of the Northern Hemisphere, in which a deep baroclinic wave of zonal wavenumber 2 circles the planet at an eastward phase speed of about 70° Sol-1 (Sol is a Martian day). The regular structure of the wave gives the impression that the classical models of baroclinic instability, which describe the underlying process by a temporally unstable global wave (e.g., Eady model and Charney model), may have a direct relevance for the description of the Martian baroclinic waves. The results of the diagnostic calculations show, however, that while the Martian waves remain zonally global features at all times, there are large spatiotemporal changes in their amplitude. The most intense episodes of baroclinic energy conversion, which take place in the two great plain regions (Acidalia Planitia and Utopia Planitia), are strongly localized in both space and time. In addition, similar to the situation for terrestrial baroclinic waves, geopotential flux convergence plays an important role in the dynamics of the downstream-propagating unstable waves. © 2013 American Meteorological Society.

Local Dynamics of Baroclinic Waves in the Martian Atmosphere

KAUST Repository

Kavulich, Michael J.; Szunyogh, Istvan; Gyarmati, Gyorgyi; Wilson, R. John

2013-01-01

The paper investigates the processes that drive the spatiotemporal evolution of baroclinic transient waves in the Martian atmosphere by a simulation experiment with the Geophysical Fluid Dynamics Laboratory (GFDL) Mars general circulation model (GCM). The main diagnostic tool of the study is the (local) eddy kinetic energy equation. Results are shown for a prewinter season of the Northern Hemisphere, in which a deep baroclinic wave of zonal wavenumber 2 circles the planet at an eastward phase speed of about 70° Sol-1 (Sol is a Martian day). The regular structure of the wave gives the impression that the classical models of baroclinic instability, which describe the underlying process by a temporally unstable global wave (e.g., Eady model and Charney model), may have a direct relevance for the description of the Martian baroclinic waves. The results of the diagnostic calculations show, however, that while the Martian waves remain zonally global features at all times, there are large spatiotemporal changes in their amplitude. The most intense episodes of baroclinic energy conversion, which take place in the two great plain regions (Acidalia Planitia and Utopia Planitia), are strongly localized in both space and time. In addition, similar to the situation for terrestrial baroclinic waves, geopotential flux convergence plays an important role in the dynamics of the downstream-propagating unstable waves. © 2013 American Meteorological Society.

Martian Atmospheric Pressure Static Charge Elimination Tool

Science.gov (United States)

Johansen, Michael R.

2014-01-01

A Martian pressure static charge elimination tool is currently in development in the Electrostatics and Surface Physics Laboratory (ESPL) at NASA's Kennedy Space Center. In standard Earth atmosphere conditions, static charge can be neutralized from an insulating surface using air ionizers. These air ionizers generate ions through corona breakdown. The Martian atmosphere is 7 Torr of mostly carbon dioxide, which makes it inherently difficult to use similar methods as those used for standard atmosphere static elimination tools. An initial prototype has been developed to show feasibility of static charge elimination at low pressure, using corona discharge. A needle point and thin wire loop are used as the corona generating electrodes. A photo of the test apparatus is shown below. Positive and negative high voltage pulses are sent to the needle point. This creates positive and negative ions that can be used for static charge neutralization. In a preliminary test, a floating metal plate was charged to approximately 600 volts under Martian atmospheric conditions. The static elimination tool was enabled and the voltage on the metal plate dropped rapidly to -100 volts. This test data is displayed below. Optimization is necessary to improve the electrostatic balance of the static elimination tool.

Constraints on Lobate Debris Apron Evolution and Rheology from Numerical Modeling of Ice Flow

Science.gov (United States)

Parsons, R.; Nimmo, F.

2010-12-01

Recent radar observations of mid-latitude lobate debris aprons (LDAs) have confirmed the presence of ice within these deposits. Radar observations in Deuteronilus Mensae have constrained the concentration of dust found within the ice deposits to <30% by volume based on the strength of the returned signal. In addition to constraining the dust fraction, these radar observations can measure the ice thickness - providing an opportunity to more accurately estimate the flow behavior of ice responsible for the formation of LDAs. In order to further constrain the age and rheology of LDA ice, we developed a numerical model simulating ice flow under Martian conditions using results from ice deformation experiments, theory of ice grain growth based on terrestrial ice cores, and observational constraints from radar profiles and laser altimetry. This finite difference model calculates the LDA profile shape as it flows over time assuming no basal slip. In our model, the ice rheology is determined by the concentration of dust which influences the ice grain size by pinning the ice grain boundaries and halting ice grain growth. By varying the dust fraction (and therefore the ice grain size), the ice temperature, the subsurface slope, and the initial ice volume we are able to determine the combination of parameters that best reproduce the observed LDA lengths and thicknesses over a period of time comparable to crater age dates of LDA surfaces (90 - 300 My, see figure). Based on simulations using different combinations of ice temperature, ice grain size, and basal slope, we find that an ice temperature of 205 K, a dust volume fraction of 0.5% (resulting in an ice grain size of 5 mm), and a flat subsurface slope give reasonable model LDA ages for many LDAs in the northern mid-latitudes of Mars. However, we find that there is no single combination of dust fraction, temperature, and subsurface slope which can give realistic ages for all LDAs suggesting that all or some of these

CAPS Simulation Environment Development

Science.gov (United States)

Murphy, Douglas G.; Hoffman, James A.

2005-01-01

The final design for an effective Comet/Asteroid Protection System (CAPS) will likely come after a number of competing designs have been simulated and evaluated. Because of the large number of design parameters involved in a system capable of detecting an object, accurately determining its orbit, and diverting the impact threat, a comprehensive simulation environment will be an extremely valuable tool for the CAPS designers. A successful simulation/design tool will aid the user in identifying the critical parameters in the system and eventually allow for automatic optimization of the design once the relationships of the key parameters are understood. A CAPS configuration will consist of space-based detectors whose purpose is to scan the celestial sphere in search of objects likely to make a close approach to Earth and to determine with the greatest possible accuracy the orbits of those objects. Other components of a CAPS configuration may include systems for modifying the orbits of approaching objects, either for the purpose of preventing a collision or for positioning the object into an orbit where it can be studied or used as a mineral resource. The Synergistic Engineering Environment (SEE) is a space-systems design, evaluation, and visualization software tool being leveraged to simulate these aspects of the CAPS study. The long-term goal of the SEE is to provide capabilities to allow the user to build and compare various CAPS designs by running end-to-end simulations that encompass the scanning phase, the orbit determination phase, and the orbit modification phase of a given scenario. Herein, a brief description of the expected simulation phases is provided, the current status and available features of the SEE software system is reported, and examples are shown of how the system is used to build and evaluate a CAPS detection design. Conclusions and the roadmap for future development of the SEE are also presented.

The cervical cap (image)

Science.gov (United States)

The cervical cap is a flexible rubber cup-like device that is filled with spermicide and self-inserted over the cervix ... left in place several hours after intercourse. The cap is a prescribed device fitted by a health ...

Does uncertainty justify intensity emission caps?

International Nuclear Information System (INIS)

Quirion, Philippe

2005-01-01

Environmental policies often set 'relative' or 'intensity' emission caps, i.e. emission limits proportional to the polluting firm's output. One of the arguments put forth in favour of relative caps is based on the uncertainty on business-as-usual output: if the firm's production level is higher than expected, so will be business-as-usual emissions, hence reaching a given level of emissions will be more costly than expected. As a consequence, it is argued, a higher emission level should be allowed if the production level is more important than expected. We assess this argument with a stochastic analytical model featuring two random variables: the business-as-usual emission level, proportional to output, and the slope of the marginal abatement cost curve. We compare the relative cap to an absolute cap and to a price instrument, in terms of welfare impact. It turns out that in most plausible cases, either a price instrument or an absolute cap yields a higher expected welfare than a relative cap. Quantitatively, the difference in expected welfare is typically very small between the absolute and the relative cap but may be significant between the relative cap and the price instrument. (author)

The effect of sea ice loss on sea salt aerosol concentrations and the radiative balance in the Arctic

Directory of Open Access Journals (Sweden)

H. Struthers

2011-04-01

Full Text Available Understanding Arctic climate change requires knowledge of both the external and the local drivers of Arctic climate as well as local feedbacks within the system. An Arctic feedback mechanism relating changes in sea ice extent to an alteration of the emission of sea salt aerosol and the consequent change in radiative balance is examined. A set of idealized climate model simulations were performed to quantify the radiative effects of changes in sea salt aerosol emissions induced by prescribed changes in sea ice extent. The model was forced using sea ice concentrations consistent with present day conditions and projections of sea ice extent for 2100. Sea salt aerosol emissions increase in response to a decrease in sea ice, the model results showing an annual average increase in number emission over the polar cap (70–90° N of 86 × 10⁶ m⁻² s⁻¹ (mass emission increase of 23 μg m⁻² s⁻¹. This in turn leads to an increase in the natural aerosol optical depth of approximately 23%. In response to changes in aerosol optical depth, the natural component of the aerosol direct forcing over the Arctic polar cap is estimated to be between −0.2 and −0.4 W m⁻² for the summer months, which results in a negative feedback on the system. The model predicts that the change in first indirect aerosol effect (cloud albedo effect is approximately a factor of ten greater than the change in direct aerosol forcing although this result is highly uncertain due to the crude representation of Arctic clouds and aerosol-cloud interactions in the model. This study shows that both the natural aerosol direct and first indirect effects are strongly dependent on the surface albedo, highlighting the strong coupling between sea ice, aerosols, Arctic clouds and their radiative effects.

Cryopyrin-Associated Autoinflammatory Syndromes (CAPS) - Juvenile

Science.gov (United States)

... all ethnic groups can be affected. What are CAPS? Cryopyrin-associated autoinflammatory syndromes (CAPS) consist of three ... ears by magnetic resonance imaging (MRI). How is CAPS treated? Medications that target interleukin-1 are very ...

Modelling snow ice and superimposed ice on landfast sea ice in Kongsfjorden, Svalbard

Directory of Open Access Journals (Sweden)

Caixin Wang

2015-08-01

Full Text Available Snow ice and superimposed ice formation on landfast sea ice in a Svalbard fjord, Kongsfjorden, was investigated with a high-resolution thermodynamic snow and sea-ice model, applying meteorological weather station data as external forcing. The model shows that sea-ice formation occurs both at the ice bottom and at the snow/ice interface. Modelling results indicated that the total snow ice and superimposed ice, which formed at the snow/ice interface, was about 14 cm during the simulation period, accounting for about 15% of the total ice mass and 35% of the total ice growth. Introducing a time-dependent snow density improved the modelled results, and a time-dependent oceanic heat flux parameterization yielded reasonable ice growth at the ice bottom. Model results suggest that weather conditions, in particular air temperature and precipitation, as well as snow thermal properties and surface albedo are the most critical factors for the development of snow ice and superimposed ice in Kongsfjorden. While both warming air and higher precipitation led to increased snow ice and superimposed ice forming in Kongsfjorden in the model runs, the processes were more sensitive to precipitation than to air temperature.

Activity and stability of a complex bacterial soil community under simulated Martian conditions

Science.gov (United States)

Hansen, Aviaja Anna; Merrison, Jonathan; Nørnberg, Per; Aagaard Lomstein, Bente; Finster, Kai

2005-04-01

A simulation experiment with a complex bacterial soil community in a Mars simulation chamber was performed to determine the effect of Martian conditions on community activity, stability and survival. At three different depths in the soil core short-term effects of Martian conditions with and without ultraviolet (UV) exposure corresponding to 8 Martian Sol were compared. Community metabolic activities and functional diversity, measured as glucose respiration and versatility in substrate utilization, respectively, decreased after UV exposure, whereas they remained unaffected by Martian conditions without UV exposure. In contrast, the numbers of culturable bacteria and the genetic diversity were unaffected by the simulated Martian conditions both with and without UV exposure. The genetic diversity of the soil community and of the colonies grown on agar plates were evaluated by denaturant gradient gel electrophoresis (DGGE) on DNA extracts. Desiccation of the soil prior to experimentation affected the functional diversity by decreasing the versatility in substrate utilization. The natural dominance of endospores and Gram-positive bacteria in the investigated Mars-analogue soil may explain the limited effect of the Mars incubations on the survival and community structure. Our results suggest that UV radiation and desiccation are major selecting factors on bacterial functional diversity in terrestrial bacterial communities incubated under simulated Martian conditions. Furthermore, these results suggest that forward contamination of Mars is a matter of great concern in future space missions.

Curiosity analyzes Martian soil samples

Science.gov (United States)

Showstack, Randy; Balcerak, Ernie

2012-12-01

NASA's Mars Curiosity rover has conducted its first analysis of Martian soil samples using multiple instruments, the agency announced at a 3 December news briefing at the AGU Fall Meeting in San Francisco. "These results are an unprecedented look at the chemical diversity in the area," said NASA's Michael Meyer, program scientist for Curiosity.

The North Zealand CAP Monitor

DEFF Research Database (Denmark)

Nielsen, Minna; Ravn, Pernille; Notander Clausen, Lise

with CAP. We started with 34 audit variables. Through repeated cycles of testing, feedback and discussions, we reduced the number of indicators to 22 and time per audit from 20 to 10 minutes. Strategy for change To link the monitoring system with our patient pathway for CAP we established an improvement...... Designing a database Designing and testing a dashboard to present indicators in a balanced way Messages for others Auditing patients with a common disease as CAP is useful to identify areas for improvement for a large group of patients. The baseline audit can serve as a basis for a monitoring system......Contect We describe how we developed a monitoring system for community acquired pneumonia (CAP) at North Zealand Regional hospital. We serve 310.000 inhabitants and annually around 3200 patients with CAP are admitted. As part of a program of clinical pathways for common conditions, a pathway...

Spatial and temporal patterns of sea ice variations in Vilkitsky strait, Russian High Arctic

Science.gov (United States)

Ci, T.; Cheng, X.; Hui, F.

2013-12-01

The Arctic Ocean has been greatly affected by climate change. Future predications show an even more drastic reduction of the ice cap which will open new areas for the exploration of natural resources and maritime transportation.Shipping through the Arctic Ocean via the Northern Sea Route (NSR) could save about 40% of the sailing distance from Asia (Yokohama) to Europe (Rotterdam) compared to the traditional route via the Suez Canal. Vilkitsky strait is the narrowest and northest portion of the Northern Sea Route with heaviest traffic between the Taimyr Peninsular and the Severnaya Zemlya archipelago. The preliminary results of sea ice variations are presented by using moderate-resolution imaging spectro radiometer(MODIS) data with 250-m resolution in the Vilkitsky strait during 2009-2012. Temporally, the first rupture on sea ice in Vilkitsky strait usually comes up in April and sea ice completely break into pieces in early June. The strait would be ice-free between August and late September. The frequency of ice floes grows while temperature falls down in October. There are always one or two months suitable for transport. Spatially, Sea ice on Laptev sea side breaks earlier than that of Kara sea side while sea ice in central of strait breaks earlier than in shoreside. The phenomena are directly related with the direction of sea wind and ocean current. In summmary, study on Spatial and temporal patterns in this area is significant for the NSR. An additional research issue to be tackled is to seeking the trends of ice-free duration in the context of global warming. Envisat ASAR data will also be used in this study.

Origin of giant Martian polygons

Science.gov (United States)

Mcgill, George E.; Hills, L. S.

1992-01-01

Extensive areas of the Martian northern plains in Utopia and Acidalia planitiae are characterized by 'polygonal terrane'. Polygonal terrane consists of material cut by complex troughs defining a pattern resembling mudcracks, columnar joints, or frost-wedge polygons on earth. However, the Martian polygons are orders of magnitude larger than these potential earth analogues, leading to severe mechanical difficulties for genetic models based on simple analogy arguments. Plate-bending and finite element models indicate that shrinkage of desiccating sediment or cooling volcanics accompanied by differential compaction over buried topography can account for the stresses responsible for polygon troughs as well as the large size of the polygons. Although trough widths and depths relate primarily to shrinkage, the large scale of the polygonl pattern relates to the spacing between topographic elevations on the surface buried beneath polygonal terrane material. Geological relationships favor a sedimentary origin for polygonal terrane material, but our model is not dependent on the specific genesis. Our analysis also suggests that the polygons must have formed at a geologically rapid rate.

Martian Magmatic-Driven Hydrothermal Sites: Potential Sources of Energy, Water, and Life

Science.gov (United States)

Anderson, R. C.; Dohm, J. M.; Baker, V. R.; Ferris, J. C.; Hare, T. M.; Tanaka, K. L.; Klemaszewski, J. E.; Skinner, J. A.; Scott, D. H.

2000-01-01

Magmatic-driven processes and impact events dominate the geologic record of Mars. Such recorded geologic activity coupled with significant evidence of past and present-day water/ice, above and below the martian surface, indicate that hydrothermal environments certainly existed in the past and may exist today. The identification of such environments, especially long-lived magmatic-driven hydrothermal environments, provides NASA with significant target sites for future sample return missions, since they (1) could favor the development and sustenance of life, (2) may comprise a large variety of exotic mineral assemblages, and (3) could potentially contain water/ice reservoirs for future Mars-related human activities. If life developed on Mars, the fossil record would presumably be at its greatest concentration and diversity in environments where long-term energy sources and water coexisted such as at sites where long-lived, magmatic-driven hydrothermal activity occurred. These assertions are supported by terrestrial analogs. Small, single-celled creatures (prokaryotes) are vitally important in the evolution of the Earth; these prokaryotes are environmentally tough and tolerant of environmental extremes of pH, temperature, salinity, and anoxic conditions found around hydrothermal vents. In addition, there is a great ability for bacteria to survive long periods of geologic time in extreme conditions, including high temperature hydrogen sulfide and sulfur erupted from Mount St. Helens volcano. Our team of investigators is conducting a geological investigation using multiple mission-derived datasets (e.g., existing geologic map data, MOC imagery, MOLA, TES image data, geophysical data, etc.) to identify prime target sites of hydrothermal activity for future hydrological, mineralogical, and biological investigations. The identification of these sites will enhance the probability of success for future missions to Mars.

Chemical and Physical Interactions of Martian Surface Material

Science.gov (United States)

Bishop, J. L.

1999-09-01

A model of alteration and maturation of the Martian surface material is described involving both chemical and physical interactions. Physical processes involve distribution and mixing of the fine-grained soil particles across the surface and into the atmosphere. Chemical processes include reaction of sulfate, salt and oxidizing components of the soil particles; these agents in the soils deposited on rocks will chew through the rock minerals forming coatings and will bind surface soils together to form duricrust deposits. Formation of crystalline iron oxide/oxyhydroxide minerals through hydrothermal processes and of poorly crystalline and amorphous phases through palagonitic processes both contribute to formation of the soil particles. Chemical and physical alteration of these soil minerals and phases contribute to producing the chemical, magnetic and spectroscopic character of the Martian soil as observed by Mars Pathfinder and Mars Global Surveyor. Minerals such as maghemite/magnetite and jarosite/alunite have been observed in terrestrial volcanic soils near steam vents and may be important components of the Martian surface material. The spectroscopic properties of several terrestrial volcanic soils containing these minerals have been analyzed and evaluated in terms of the spectroscopic character of the surface material on Mars.

Electrical Activity in Martian Dust Storms

Science.gov (United States)

Majid, W.; Arabshahi, S.; Kocz, J.

2016-12-01

Dust storms on Mars are predicted to be capable of producing electrostatic fields and discharges, even larger than those in dust storms on Earth. Such electrical activity poses serious risks to any Human exploration of the planet and the lack of sufficient data to characterize any such activity has been identified by NASA's MEPAG as a key human safety knowledge gap. There are three key elements in the characterization of Martian electrostatic discharges: dependence on Martian environmental conditions, frequency of occurrence, and the strength of the generated electric fields. We will describe a recently deployed detection engine using NASA's Deep Space Network (DSN) to carry out a long term monitoring campaign to search for and characterize the entire Mars hemisphere for powerful discharges during routine tracking of spacecraft at Mars on an entirely non-interfering basis. The resulting knowledge of Mars electrical activity would allow NASA to plan risk mitigation measures to ensure human safety during Mars exploration. In addition, these measurements will also allow us to place limits on presence of oxidants such as H2O2 that may be produced by such discharges, providing another measurement point for models describing Martian atmospheric chemistry and habitability. Because of the continuous Mars telecommunication needs of NASA's Mars-based assets, the DSN is the only instrument in the world that combines long term, high cadence, observing opportunities with large sensitive telescopes, making it a unique asset worldwide in searching for and characterizing electrostatic activity at Mars from the ground.

Remote Sensing Studies Of The Current Martian Climate

Science.gov (United States)

Taylor, F. W.; McCleese, D. J.; Schofield, J. T.; Calcutt, S. B.; Moroz, V. I.

A systematic and detailed experimental study of the Martian atmosphere remains to be carried out, despite many decades of intense interest in the nature of the Martian climate system, its interactions, variability and long-term stability. Such a study is planned by the 2005 Mars Reconnaissance Orbiter, using limb-scanning infrared radiometric techniques similar to those used to study trace species in the terrestrial stratosphere. For Mars, the objectives are temperature, humidity, dust and condensate abundances with high vertical resolution and global coverage in the 0 to 80 km height range. The paper will discuss the experiment and its methodology and expectations for the results.

Estimated release from the saltstone landfill effect of landfill caps and landfill-cap/monolith-liner combinations

International Nuclear Information System (INIS)

Wilhite, E.L.

1985-01-01

The effect of capping the entire saltstone landfill is dependent on the effectiveness of the clay cap in preventing infiltration. A cap that is 99% effective will reduce releases from the saltstone landfill by a factor of 7.7. Several combinations of landfill design alterations will result in meeting ground water standards

Assessment of the Relationship between Andean Ice Core Precipitation Indicators and Amazon River Discharge

Science.gov (United States)

Johnson, N.; Alsdorf, D.; Thompson, L.; Mosley-Thompson, E.; Melack, J.

2006-12-01

Prior to the last 100 years, there is a significant lack of hydrologic knowledge for the Amazon Basin. A 100- year record of discharge from the city of Manaus, located at the confluence of the Solimoes and Negro rivers, is the most complete record for the basin. Inundated wetlands play a key role in carbon out-gassing to the atmosphere whereas discharge from the Amazon River contributes about 20% of the total freshwater flux delivered to the world's oceans. As discharge (Q) and inundation are directly related to precipitation, we are developing a method to extend our understanding of Q and inundation into the 19^{th} century. Using proxy data preserved in Andean glaciers and ice caps and recovered from ice cores, annually resolved histories of δ^{18)O and mass accumulation are available. The latter is a proxy for local precipitation amount whereas δ18O is influenced by continental scale processes (i.e., evaporation, convection) as well as by temperature and hence, by varying climate regimes. We have correlated the accumulation and δ18O records from Core 1 drilled on the Quelccaya ice-cap in the southern Andes of Peru with the Manaus discharge data. As ice core annual layers correspond to the thermal year (in Peru, July to June of the following year) and the discharge records are kept daily (January to December), we averaged 365 days of Q data seeking the optimal correlation for each start and end date. The best statistical relationship between δ18O and Q (r = -0.41, p = < 0.001) is attained when Q is averaged from March 16 to March 15 of the following year. We also correlated 23 years of ENSO events, which are linked to both Amazon River discharge and ice core δ18O (r = -0.60, p = < 0.001). These linear relationships are used to create Amazon discharge for the 20^{th} century and to extrapolate Q into the 19^{th} century. Previously developed relationships between Q and mainstem inundated area are then used to estimate inundated area along the main Amazon

Post-Viking view of Martian geologic evolution

International Nuclear Information System (INIS)

Arvidson, R.E.; Goettel, K.A.; Hohenberg, C.M.

1980-01-01

The mean density, 3.393 g/cm 3 , and the estimated moment of inertia factor constrain the density distribution within Mars but do not define it uniquely. For plausible core density, core radii can range from approx. 1350 to approx. 2200 km, with the core constituting from approx. 13 to approx. 35% of the planet's mass. Possible extremes for the zero-pressure density of the Martian mantle could be as high as 3.6 g/cm 3 or as low as 3.3 g/cm 3 . The Martian mantle is probably denser than the terrestrial mantle. The dominant Martian lavas are probably mafic or ultramafic. Martian surface materials probably consist of variable proportions of mafic igneous minerals and weathering products, the latter primarily oxides and carbonates. A major geologic dichotomy exists between the complex northern plains and the ancient southern cratered terrain. The Tharsis plateau, which dominates the low-degree harmonics of the gravity field, appears to be only partially compensated; Olympus Mons appears to be completely uncompensated. Substantial stresses must be supported, either statically by a thick, rigid lithosphere, or dynamically. Mean crustal thicknesses from 23 to 40 km have been obtained from modeling of Bouguer gravity data. Lithospheric thicknesses from 25 to 50 km under volcanoes in the Tharsis and Elysium provinces to >150 km under olympus Mons have been obtained from consideration of the effects of mass loading by volcanic constructs. Many of the compressional and extensional features on Mars have orientations consistent with formation by fracturing in response to loading by the Tharsis plateau. The deficiency of small craters within cratered terrain is attributed to obliteration by volcanism. The maximum resurfacing rate due to volcanism occurred between 1.0 and 1.5 b.y. ago if a constant cratering flux is assumed and between 3.5 and 4.0 b.y. ago if the lunar cratering flux (scaled to Mars) is assumed

Permeability Barrier Generation in the Martian Lithosphere

Science.gov (United States)

Schools, Joe; Montési, Laurent

2015-11-01

Permeability barriers develop when a magma produced in the interior of a planet rises into the cooler lithosphere and crystallizes more rapidly than the lithosphere can deform (Sparks and Parmentier, 1991). Crystallization products may then clog the porous network in which melt is propagating, reducing the permeability to almost zero, i.e., forming a permeability barrier. Subsequent melts cannot cross the barrier. Permeability barriers have been useful to explain variations in crustal thickness at mid-ocean ridges on Earth (Magde et al., 1997; Hebert and Montési, 2011; Montési et al., 2011). We explore here under what conditions permeability barriers may form on Mars.We use the MELTS thermodynamic calculator (Ghiorso and Sack, 1995; Ghiorso et al., 2002; Asimow et al., 2004) in conjunction with estimated Martian mantle compositions (Morgan and Anders, 1979; Wänke and Dreibus, 1994; Lodders and Fegley, 1997; Sanloup et al., 1999; Taylor 2013) to model the formation of permeability barriers in the lithosphere of Mars. In order to represent potential past and present conditions of Mars, we vary the lithospheric thickness, mantle potential temperature (heat flux), oxygen fugacity, and water content.Our results show that permeability layers can develop in the thermal boundary layer of the simulated Martian lithosphere if the mantle potential temperature is higher than ~1500°C. The various Martian mantle compositions yield barriers in the same locations, under matching variable conditions. There is no significant difference in barrier location over the range of accepted Martian oxygen fugacity values. Water content is the most significant influence on barrier development as it reduces the temperature of crystallization, allowing melt to rise further into the lithosphere. Our lower temperature and thicker lithosphere model runs, which are likely the most similar to modern Mars, show no permeability barrier generation. Losing the possibility of having a permeability

Ice, Ice, Baby!

Science.gov (United States)

Hamilton, C.

2008-12-01

The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an outreach program based on hands-on activities called "Ice, Ice, Baby". These lessons are designed to teach the science principles of displacement, forces of motion, density, and states of matter. These properties are easily taught through the interesting topics of glaciers, icebergs, and sea level rise in K-8 classrooms. The activities are fun, engaging, and simple enough to be used at science fairs and family science nights. Students who have participated in "Ice, Ice, Baby" have successfully taught these to adults and students at informal events. The lessons are based on education standards which are available on our website www.cresis.ku.edu. This presentation will provide information on the activities, survey results from teachers who have used the material, and other suggested material that can be used before and after the activities.

Thermo-chemical Ice Penetrator for Icy Moons

Science.gov (United States)

Arenberg, J. W.; Lee, G.; Harpole, G.; Zamel, J.; Sen, B.; Ross, F.; Retherford, K. D.

2016-12-01

The ability to place sensors or to take samples below the ice surface enables a wide variety of potential scientific investigations. Penetrating an ice cap can be accomplished via a mechanical drill, laser drill, kinetic impactor, or heated penetrator. This poster reports on the development of technology for the latter most option, namely a self-heated probe driven by an exothermic chemical reaction: a Thermo-chemical ice penetrator (TChIP). Our penetrator design employs a eutectic mix of alkali metals that produce an exothermic reaction upon contact with an icy surface. This reaction increases once the ice starts melting, so no external power is required. This technology is inspired by a classified Cold-War era program developed at Northrop Grumman for the US Navy. Terrestrial demonstration of this technology took place in the Arctic; however, this device cannot be considered high TRL for application at the icy moons of the solar system due to the environmental differences between Earth's Arctic and the icy moons. These differences demand a TChIP design specific to these cold, low mass, airless worlds. It is expected that this model of TChIP performance will be complex, incorporating all of the forces on the penetrator, gravity, the thermo-chemistry at the interface between penetrator and ice, and multi-phase heat and mass transport, and hydrodynamics. Our initial efforts are aimed at the development of a validated set of tools and simulations to predict the performance of the penetrator for both the environment found on these icy moons and for a terrestrial environment. The purpose of the inclusion of the terrestrial environment is to aid in model validation. Once developed and validated, our models will allow us to design penetrators for a specific scientific application on a specific body. This poster discusses the range of scientific investigations that are enabled by TChIP. We also introduce the development plan to advance TChIP to the point where it can be

Alteration of Sedimentary Clasts in Martian Meteorite Northwest Africa 7034

Science.gov (United States)

McCubbin, F. M.; Tartese, R.; Santos, A. R.; Domokos, G.; Muttik, N.; Szabo, T.; Vazquez, J.; Boyce, J. W.; Keller, L. P.; Jerolmack, D. J.;

ATLAS electromagnetic end-cap detector

CERN Multimedia

Maximilien Brice

2003-01-01

After the insertion of the first end-cap into this cryostat, the team proceed to the wiring operations. Millions of wires are connected to the electromagnetic calorimeter on this end-cap, whch must be carefully fed out from the detector so that data can be read out. The energy of photons, electrons and positrons will be measured as they pass through the end-cap having been created along the line of the beams in the proton-proton collisions.

ATLAS end-cap detector

CERN Multimedia

Maximilien Brice

2003-01-01

Three scientists from the Institute of Nuclear Phyiscs at Novossibirsk with one of the end-caps of the ATLAS detector. The end-caps will be used to detect particles produced in the proton-proton collisions at the heart of the ATLAS experiment that are travelling close to the axis of the two beams.

Microwave Palaeointensity Experiments On Terrestrial and Martian Material

Science.gov (United States)

Shaw, J.; Hill, M.; Gratton, M.

The microwave palaeointensity technique was developed in Liverpool University (Walton et al 1996) and has successfully been applied to archaeological ceramics and recent lavas (Shaw et al 1996, 1999.; Hill et al 1999,2000). These published results show that microwave analysis provides accurate palaeointensity determinations com- bined with a very high success rate. Most recently the technique has been successfully applied to Martian material (Shaw et al, 2001) to look for the existence of an internal Martian dynamo early in Martian history. New experiments have been carried out us- ing microwaves to demagnetise synthetic muti-component TRM's and new palaeoin- tensity experiments providing a comparison between microwave analysis of laboratory TRM's and conventional thermal Thellier analysis of microwave generated mTRM's. These experiments demonstrate the equivalence of microwave and thermally gener- ated TRM's. D. Walton, S Snape, T.C. Rolph, J. Shaw and J.A. Share, Application of ferromagnetic resonance heating to palaeointensity determinations.1996, Phys Earth Planet Int,94, 183-186. J. Shaw, D. Walton, S Yang, T.C.Rolph, and J.A. Share. Microwave Archaeointensities from Peruvian Ceramics. 1996, Geophys. J. Int,124,241-244 J. Shaw, S. Yang, T. C. Rolph, and F. Y. Sun. A comparison of archaeointensity results from Chinese ceramics using Microwave and conventional ThellierSs and ShawSs methods.,1999, G J Int.136, 714-718 M. Hill, and J. Shaw, 1999, Palaeointensity results for Historic Lavas from Mt. Etna using microwave demagnetisation/remagnetisation in a modified Thellier type exper- iment. G. J. Int, 139, 583-590 M. J. Hill, and J. Shaw, 2000. Magnetic field intensity study of the 1960 Kilauea lava flow, Hawaii, using the microwave palaeointensity technique, Geophys. J. Int., 142, 487-504. J. Shaw, M. Hill, and S. J. Openshaw, 2001, Investigating the ancient Martian magnetic field using microwaves, Earth and Planetary Science Letters 190 (2001) 103-109

Sea ice - Multiyear cycles and white ice

Science.gov (United States)

Ledley, T. S.

1985-01-01

The multiyear thickness cycles represent one of the interesting features of the sea ice studies performed by Semtner (1976) and Washington et al. (1976) with simple thermodynamic models of sea ice. In the present article, a description is given of results which show that the insulating effect of snow on the surface of the sea ice is important in producing these multiyear cycles given the physics included in the model. However, when the formation of white ice is included, the cycles almost disappear. White ice is the ice which forms at the snow-ice interface when the snow layer becomes thick enough to depress the ice below the water level. Water infiltrates the snow by coming through the ice at leads and generally freezes there, forming white ice.

Impact of Dust on Mars Surface Albedo and Energy Flux with LMD General Circulation Model

Science.gov (United States)

Singh, D.; Flanner, M.; Millour, E.; Martinez, G.

2015-12-01

Mars, just like Earth experience different seasons because of its axial tilt (about 25°). This causes growth and retreat of snow cover (primarily CO2) in Martian Polar regions. The perennial caps are the only place on the planet where condensed H2O is available at surface. On Mars, as much as 30% atmospheric CO2 deposits in each hemisphere depending upon the season. This leads to a significant variation on planet's surface albedo and hence effecting the amount of solar flux absorbed or reflected at the surface. General Circulation Model (GCM) of Laboratoire de Météorologie Dynamique (LMD) currently uses observationally derived surface albedo from Thermal Emission Spectrometer (TES) instrument for the polar caps. These TES albedo values do not have any inter-annual variability, and are independent of presence of any dust/impurity on surface. Presence of dust or other surface impurities can significantly reduce the surface albedo especially during and right after a dust storm. This change will also be evident in the surface energy flux interactions. Our work focuses on combining earth based Snow, Ice, and Aerosol Radiation (SNICAR) model with current state of GCM to incorporate the impact of dust on Martian surface albedo, and hence the energy flux. Inter-annual variability of surface albedo and planet's top of atmosphere (TOA) energy budget along with their correlation with currently available mission data will be presented.

Radio Emissions from Electrical Activity in Martian Dust Storms

Science.gov (United States)

Majid, W.; Arabshahi, S.; Kocz, J.; Schulter, T.; White, L.

2017-12-01

Dust storms on Mars are predicted to be capable of producing electrostatic fields and discharges, even larger than those in dust storms on Earth. There are three key elements in the characterization of Martian electrostatic discharges: dependence on Martian environmental conditions, event rate, and the strength of the generated electric fields. The detection and characterization of electric activity in Martian dust storms has important implications for habitability, and preparations for human exploration of the red planet. Furthermore, electrostatic discharges may be linked to local chemistry and plays an important role in the predicted global electrical circuit. Because of the continuous Mars telecommunication needs of NASA's Mars-based assets, the Deep Space Network (DSN) is the only facility in the world that combines long term, high cadence, observing opportunities with large sensitive telescopes, making it a unique asset worldwide in searching for and characterizing electrostatic activity from large scale convective dust storms at Mars. We will describe a newly inaugurated program at NASA's Madrid Deep Space Communication Complex to carry out a long-term monitoring campaign to search for and characterize the entire Mars hemisphere for powerful discharges during routine tracking of spacecraft at Mars on an entirely non-interfering basis. The ground-based detections will also have important implications for the design of a future instrument that could make similar in-situ measurements from orbit or from the surface of Mars, with far greater sensitivity and duty cycle, opening up a new window in our understanding of the Martian environment.

21 CFR 884.5250 - Cervical cap.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cervical cap. 884.5250 Section 884.5250 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... cap. (a) Identification. A cervical cap is a flexible cuplike receptacle that fits over the cervix to...

21 CFR 888.3000 - Bone cap.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Bone cap. 888.3000 Section 888.3000 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3000 Bone cap. (a) Identification. A bone cap is a mushroom...

Genetic ablation of root cap cells in Arabidopsis

OpenAIRE

Tsugeki, Ryuji; Fedoroff, Nina V.

1999-01-01

The root cap is increasingly appreciated as a complex and dynamic plant organ. Root caps sense and transmit environmental signals, synthesize and secrete small molecules and macromolecules, and in some species shed metabolically active cells. However, it is not known whether root caps are essential for normal shoot and root development. We report the identification of a root cap-specific promoter and describe its use to genetically ablate root caps by directing root cap-specific expression of...

Martian Bow Shock and Magnetic Pile-Up Barrier Formation Due to the Exosphere Ion Mass-Loading

Directory of Open Access Journals (Sweden)

Eojin Kim

2011-03-01

Full Text Available Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.

CENTRIFUGE END CAP

Science.gov (United States)

Beams, J.W.; Snoddy, L.B.

1960-08-01

An end cap for ultra-gas centrifuges is designed to impart or remove angular momentum to or from the gas and to bring the entering gas to the temperature of the gas inside the centrifuge. The end cap is provided with slots or fins for adjusting the temperature and the angular momentum of the entering gas to the temperature and momentum of the gas in the centrifuge and is constructed to introduce both the inner and the peripheral stream into the centrifuge.

High Ice Water Concentrations in the 19 August 2015 Coastal Mesoconvective System

Science.gov (United States)

Proctor, Fred H.; Harrah, Steven; Switzer, George F.; Strickland, Justin K.; Hunt, Patricia J.

2017-01-01

During August 2015, NASA's DC-8 research aircraft was flown into High Ice Water Content (HIWC) events as part of a three-week campaign to collect airborne radar data and to obtain measurements from microphysical probes. Goals for this flight campaign included improved characterization of HIWC events, especially from an airborne radar perspective. This paper focuses on one of the flight days, in which a coastal mesoscale convective system (MCS) was investigated for HIWC conditions. The system appears to have been maintained by bands of convection flowing in from the Gulf of Mexico. These convective bands were capped by a large cloud canopy, which masks the underlying structure if viewed from an infrared sensing satellite. The DC-8 was equipped with an IsoKinetic Probe that measured ice concentrations of up to 2.3 g m(exp -3) within the cloud canopy of this system. Sustained measurements of ice crystals with concentrations exceeding 1 g m(exp -3) were encountered for up to ten minutes of flight time. Airborne Radar reflectivity factors were found to be weak within these regions of high ice water concentrations, suggesting that Radar detection of HIWC would be a challenging endeavor. This case is then investigated using a three-dimensional numerical cloud model. Profiles of ice water concentrations and radar reflectivity factor demonstrate similar magnitudes and scales between the flight measurements and model simulation. Also discussed are recent modifications to the numerical model's ice-microphysics that are based on measurements during the flight campaign. The numerical model and its updated ice-microphysics are further validated with a simulation of a well-known case of a supercell hailstorm measured during the Cooperative Convective Precipitation Experiment. Differences in HIWC between the continental supercell and the coastal MCS are discussed.

THE TURN OF THE MONTH EFFECT CONTINUED: A COMPARISON OF SMALL CAP STOCKS AND LARGE CAP STOCKS

OpenAIRE

Ramsundhar, Shamman

2010-01-01

The purpose of this paper is to investigate whether the turn of the month effect occurs in small cap and large cap stocks and if it occurs in both categories, to determine whether there is a difference in the magnitude. My research, for the period of 1963-2008, based on the CRSP value weighted index, shows that there is a significant turn of the month effect in small and large cap stocks, however the effect is larger in small cap stocks. Furthermore, this effect is not limited to a short time...

Optical properties of dust and the opacity of the Martian atmosphere

Science.gov (United States)

Korablev, O.; Moroz, V. I.; Petrova, E. V.; Rodin, A. V.

Particulate component of the Mars atmosphere composed by micron-sized products of soil weathering and water ice clouds strongly affects the current climate of the planet. In the absence of a dust storm so-called permanent dust haze with τ ≈ 0.2 in the atmosphere of Mars determines its thermal structure. Dust loading varies substantially with the season and geographic location, and only the data of mapping instruments are adequate to characterize it, such as TES/MGS and IRTM/Viking. In spite of vast domain of collected data, no model is now capable to explain all observed spectral features of dust aerosol. Several mineralogical and microphysical models of the atmospheric dust have been proposed but they cannot explain the pronounced systematic differences between the IR data (τ = 0.05-0.2) and measurements from the surface (Viking landers, Pathfinder) which give the typical “clear” optical depth of τ ≈ 0.5 from one side, and ground-based observations in the UV-visible range showing much more transparent atmosphere, on the other side. Also the relationship between τ9 and the visible optical depth is not well constrained experimentally so far. Future focused measurements are therefore necessary to study Martian aerosol.

Effect of chitosan-carvacrol coating on the quality of Pacific white shrimp during iced storage as affected by caprylic acid.

Science.gov (United States)

Wang, Qianyun; Lei, Jun; Ma, Junjie; Yuan, Gaofeng; Sun, Haiyan

2018-01-01

This study aimed to investigate the effect of chitosan-carvacrol coating with or without caprylic acid (CAP) on the quality of Pacific white shrimp (Litopenaeus vannamei) during 10days of iced storage. The result showed that chitosan-carvacrol coating significantly inhibited the increase in total aerobic plate count (TPC), pH and total volatile basic nitrogen content (TVB-N) of shrimp in comparison with the control. Chitosan-carvacrol coating also delayed the melanosis formation and changes of ΔE values, and improved the texture and sensory properties of shrimp. Moreover, incorporation of CAP potentiated the efficacy of chitosan-carvacrol coating in retarding the increase of TPC and TVB-N. Incorporation of CAP into chitosan-carvacrol coating also enabled the texture characteristics of shrimp to be retained greater degrees. These results suggested that chitosan-carvacrol coating may be promising to be used as active packaging for extending the shelf life, and incorporation of CAP may enhance the efficacy of the coating. Copyright © 2017 Elsevier B.V. All rights reserved.

Morphogenesis of Antarctic Paleosols: Martian Analogue

Science.gov (United States)

Mahaney, W. C.; Dohm, J. M.; Baker, V. R.; Newsom, Horton E.; Malloch, D.; Hancock, R. G. V.; Campbell, Iain; Sheppard, D.; Milner, M. W.

2001-11-01

Samples of horizons in paleosols from the Quartermain Mountains of the Antarctic Dry Valleys (Aztec and New Mountain areas) were analyzed for their physical characteristics, mineralogy, chemical composition, and microbiology to determine the accumulation and movement of salts and other soluble constituents and the presence/absence of microbial populations. Salt concentrations are of special interest because they are considered to be a function of age, derived over time, in part from nearby oceanic and high-altitude atmospheric sources. The chemical composition of ancient Miocene-age paleosols in these areas is the direct result of the deposition and weathering of airborne-influxed salts and other materials, as well as the weathering of till derived principally from local dolerite and sandstone outcrops. Paleosols nearer the coast have greater contents of Cl, whereas near the inland ice sheet, nitrogen tends to increase on a relative basis. The accumulation and vertical distribution of salts and other soluble chemical elements indicate relative amounts of movement in the profile over long periods of time, in the order of several million years. Four of the six selected subsamples from paleosol horizons in two ancient soil profiles contained nil concentrations of bacteria and fungi. However, two horizons at depths of between 3 and 8 cm, in two profiles, yielded several colonies of the fungi Beauveria bassiana and Penicillium brevicompactum, indicating very minor input of organic carbon. Beauveria bassiana is often reported in association with insects and is used commercially for the biological control of some insect pests. Penicillium species are commonly isolated from Arctic, temperate, and tropical soils and are known to utilize a wide variety of organic carbon and nitrogen compounds. The cold, dry soils of the Antarctic bear a close resemblance to various present and past martian environments where similar weathering could occur and possible microbial populations

Ice and ocean velocity in the Arctic marginal ice zone: Ice roughness and momentum transfer

Directory of Open Access Journals (Sweden)

Sylvia T. Cole

2017-09-01

Full Text Available The interplay between sea ice concentration, sea ice roughness, ocean stratification, and momentum transfer to the ice and ocean is subject to seasonal and decadal variations that are crucial to understanding the present and future air-ice-ocean system in the Arctic. In this study, continuous observations in the Canada Basin from March through December 2014 were used to investigate spatial differences and temporal changes in under-ice roughness and momentum transfer as the ice cover evolved seasonally. Observations of wind, ice, and ocean properties from four clusters of drifting instrument systems were complemented by direct drill-hole measurements and instrumented overhead flights by NASA operation IceBridge in March, as well as satellite remote sensing imagery about the instrument clusters. Spatially, directly estimated ice-ocean drag coefficients varied by a factor of three with rougher ice associated with smaller multi-year ice floe sizes embedded within the first-year-ice/multi-year-ice conglomerate. Temporal differences in the ice-ocean drag coefficient of 20–30% were observed prior to the mixed layer shoaling in summer and were associated with ice concentrations falling below 100%. The ice-ocean drag coefficient parameterization was found to be invalid in September with low ice concentrations and small ice floe sizes. Maximum momentum transfer to the ice occurred for moderate ice concentrations, and transfer to the ocean for the lowest ice concentrations and shallowest stratification. Wind work and ocean work on the ice were the dominant terms in the kinetic energy budget of the ice throughout the melt season, consistent with free drift conditions. Overall, ice topography, ice concentration, and the shallow summer mixed layer all influenced mixed layer currents and the transfer of momentum within the air-ice-ocean system. The observed changes in momentum transfer show that care must be taken to determine appropriate parameterizations

Instability of water-ice interface under turbulent flow

Science.gov (United States)

Izumi, Norihiro; Naito, Kensuke; Yokokawa, Miwa

2015-04-01

It is known that plane water-ice interface becomes unstable to evolve into a train of waves. The underside of ice formed on the water surface of rivers are often observed to be covered with ice ripples. Relatively steep channels which discharge melting water from glaciers are characterized by beds covered with a series of steps. Though the flowing agent inducing instability is not water but gas including water vapor, a similar train of steps have been recently observed on the Polar Ice Caps on Mars (Spiral Troughs). They are expected to be caused by the instability of water-ice interface induced by flowing fluid on ice. There have been some studies on this instability in terms of linear stability analysis. Recently, Caporeale and Ridolfi (2012) have proposed a complete linear stability analysis in the case of laminar flow, and found that plane water-ice interface is unstable in the range of sufficiently large Reynolds numbers, and that the important parameters are the Reynolds number, the slope angle, and the water surface temperature. However, the flow inducing instability on water-ice interface in the field should be in the turbulent regime. Extension of the analysis to the case of fully developed turbulent flow with larger Reynolds numbers is needed. We have performed a linear stability analysis on the instability of water-ice interface under turbulent flow conditions with the use of the Reynolds-averaged Navier-Stokes equations with the mixing length turbulent model, the continuity equation of flow, the diffusion/dispersion equation of heat, and the Stefan equation. In order to reproduce the accurate velocity distribution and the heat transfer in the vicinity of smooth walls with the use of the mixing length model, it is important to take into account of the rapid decrease in the mixing length in the viscous sublayer. We employ the Driest model (1956) to the formulation. In addition, as the thermal boundary condition at the water surface, we describe the

The chemical reactivity of the Martian soil and implications for future missions

Science.gov (United States)

Zent, Aaron P.; Mckay, Christopher P.

1994-01-01

Possible interpretations of the results of the Viking Biology Experiments suggest that greater than 1 ppm of a thermally labile oxidant, perhaps H2O2, and about 10 ppm of a thermally stable oxidant are present in the martian soil. We reexamine these results and discuss implications for future missions, the search for organics on Mars, and the possible health and engineering effects for human exploration. We conclude that further characterization of the reactivity of the martian regolith materials is warrented-although if our present understanding is correct the oxidant does not pose a hazard to humans. There are difficulties in explaining the reactivity of the Martian soil by oxidants. Most bulk phase compounds that are capable of oxidizing H2O to O2 per the Gas Exchange Experiment (GEx) are thermally labile or unstable against reduction by atmospheric CO2. Models invoking trapped O2 or peroxynitrates (NOO2(-)) require an unlikely geologic history for the Viking Lander 2 site. Most suggested oxidants, including H2O2, are expected to decompose rapidly under martian UV. Nonetheless, we conclude that the best model for the martian soil contains oxidants produced by heterogeneous chemical reactions with a photochemically produced atmospheric oxidant. The GEx results may be due to catalytic decomposition of an unstable oxidizing material by H2O. We show that interfacial reaction sites covering less than 1% of the available soil surfaces could explain the Viking Biology Experiments results.

Spatial and temporal distributions of Martian north polar cold spots before, during, and after the global dust storm of 2001

Science.gov (United States)

Cornwall, C.; Titus, T.N.

2009-01-01

In the 1970s, Mariner and Viking observed features in the Mars northern polar region that were a few hundred kilometers in diameter with 20 fj,m brightness temperatures as low as 130 K (considerably below C02 ice sublimation temperatures). Over the past decade, studies have shown that these areas (commonly called "cold spots") are usually due to emissivity effects of frost deposits and occasionally to active C02 snowstorms. Three Mars years of Mars Global Surveyor Thermal Emission Spectrometer data were used to observe autumn and wintertime cold spot activity within the polar regions. Many cold spots formed on or near scarps of the perennial cap, probably induced by adiabatic cooling due to orographic lifting. These topographically associated cold spots were often smaller than those that were not associated with topography. We determined that initial grain sizes within the cold spots were on the order of a few millimeters, assuming the snow was uncontaminated by dust or water ice. On average, the half-life of the cold spots was 5 Julian days. The Mars global dust storm in 2001 significantly affected cold spot activity in the north polar region. Though overall perennial cap cold spot activity seemed unaffected, the distribution of cold spots did change by a decrease in the number of topographically associated cold spots and an increase in those not associated with topography. We propose that the global dust storm affected the processes that form cold spots and discuss how the global dust storm may have affected these processes. ?? 2009 by the American Geophysical Union.

Ice cream structure modification by ice-binding proteins.

Science.gov (United States)

Kaleda, Aleksei; Tsanev, Robert; Klesment, Tiina; Vilu, Raivo; Laos, Katrin

2018-04-25

Ice-binding proteins (IBPs), also known as antifreeze proteins, were added to ice cream to investigate their effect on structure and texture. Ice recrystallization inhibition was assessed in the ice cream mixes using a novel accelerated microscope assay and the ice cream microstructure was studied using an ice crystal dispersion method. It was found that adding recombinantly produced fish type III IBPs at a concentration 3 mg·L -1 made ice cream hard and crystalline with improved shape preservation during melting. Ice creams made with IBPs (both from winter rye, and type III IBP) had aggregates of ice crystals that entrapped pockets of the ice cream mixture in a rigid network. Larger individual ice crystals and no entrapment in control ice creams was observed. Based on these results a model of ice crystals aggregates formation in the presence of IBPs was proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ice Sheets & Ice Cores

DEFF Research Database (Denmark)

Mikkelsen, Troels Bøgeholm

Since the discovery of the Ice Ages it has been evident that Earth’s climate is liable to undergo dramatic changes. The previous climatic period known as the Last Glacial saw large oscillations in the extent of ice sheets covering the Northern hemisphere. Understanding these oscillations known....... The first part concerns time series analysis of ice core data obtained from the Greenland Ice Sheet. We analyze parts of the time series where DO-events occur using the so-called transfer operator and compare the results with time series from a simple model capable of switching by either undergoing...

Eulerian Method for Ice Crystal Icing

NARCIS (Netherlands)

Norde, Ellen; van der Weide, Edwin Theodorus Antonius; Hoeijmakers, Hendrik Willem Marie

In this study, an ice accretion method aimed at ice crystal icing in turbofan engines is developed and demonstrated for glaciated as well as mixed-phase icing conditions. The particle trajectories are computed by an Eulerian trajectory method. The effects of heat transfer and phase change on the

Loss of Water to Space from Mars: Processes and Implications

Science.gov (United States)

Kass, D. M.

2001-12-01

most of the water on Mars is likely to be in the form of ice, it is presumably further fractionated by ~ 0.8 due to ice/water vapor interactions. This yields an effective D/H enrichment of ~ 7 for reservoirs in equilibrium with the atmosphere. From a loss to space point of view, Martian water can be divided into three reservoirs. The first is the thin, 10 pr-\\micron, atmospheric water. The second is a global exchangeable reservoir in long term isotopic equilibrium with the atmosphere. This probably encompasses the polar caps, ice in polar layered deposits and any other near surface ice or adsorbed water. The third, more speculative, reservoir is a non-exchanging reservoir (a deep sub-surface cryosphere). In addition, due to the small size of the atmospheric reservoir, difficulty in isotopically equilibrating it with the entire exchangeable reservoir, and the relatively rapid H2 loss rate, there is also an intermediate exchangeable reservoir of ~ 4~mm. This is probably either a surface layer on the polar caps or near surface ice deposits. By assuming an initial terrestrial D/H ratio for Martian water (based on condritic meteorites) and a loss to space of ~ 50~m (based on the total O loss), the size of the exchangeable reservoir can be estimated. Two conceptual models are possible, depending on whether or not the non-exchangeable reservoir replenishes the exchangeable one. Quantitatively, the two models yield almost identical reservoir sizes, ~ 9~m (about the size of the northern polar cap). If, due to slow rate of isotopic diffusion in ice, the exchangeable reservoir actually has the same isotopic enrichment as the atmosphere, it would contain ~ 12~m of water.

Periglacial complexes in Utopia Planitia: rimless, tiered depressions, (clastically) sorted and unsorted polygonised terrain and an ice-rich mantle

Science.gov (United States)

Soare, Richard; Conway, Susan; Gallagher, Colman; Dohm, James; Clifford, Stephen M.; Williams, Jean-pierre

2016-10-01

We report the spatial and possible genetic-relationship at the mid-latitudes of Utopia Planitia (45-500N 115-1200E), Mars, of: (a) metre to decametre deep, rimless, tiered depressions; terrain that exhibits (b) (clastically) sorted and (c) unsorted (small-sized) polygons; and, (d) a very youthful, ice-rich mantle. We show that these individual landscape features are separated stratigraphically, this being presented to the Mars community for the first time, and suggest that the stratigraphical separation of these features could be the result of boundary conditions and formation processes that have varied much more widely than has been thought hitherto. In cold-climate and non-glacial regions such as the Yamal Peninsula of eastern Russia and the Tuktoyaktuk Coastlands of northern Canada, landscape assemblages comprised of similar features are referenced as "ice complexes" and are indicative of periglacialism on two fronts: first, the presence of "ice-rich" permafrost or permafrost comprised of "excess ice", i.e. "permafrost" whose pore space is exceeded by the "water ice" within that body of sediment; and, second, antecedently or currently active freeze-thaw cycling, minimally, to the full depth of the "ice-complex" depressions. In the Dry Valleys of the Antarctic, where the atmospheric aridity and cold-temperatures approach those of Mars, ice-vapour diffusion and adsorption cycles are cited as the means by which the near-surface, permafrost, i.e. ≤1m deep, has become ice-cemented. However, the metre to decametre depths of the "ice-complex" depressions on Earth and the morphologically-similar ones on Mars lie beyond the vertical reach of the Antarctic diffusion and adsorption cycles, both empirically and theoretically. By deduction, this points to the freeze-thaw cycling of water to depth, fostered either by exogenic or endogenic means, perhaps playing a more important role in the formation of the possible Martian "ice complexes" than might be expected were

Experimental provocation of 'ice-cream headache' by ice cubes and ice water.

Science.gov (United States)

Mages, Stephan; Hensel, Ole; Zierz, Antonia Maria; Kraya, Torsten; Zierz, Stephan

2017-04-01

Background There are various studies on experimentally provoked 'ice-cream headache' or 'headache attributed to ingestion or inhalation of a cold stimulus' (HICS) using different provocation protocols. The aim of this study was to compare two provocation protocols. Methods Ice cubes pressed to the palate and fast ingestion of ice water were used to provoke HICS and clinical features were compared. Results The ice-water stimulus provoked HICS significantly more often than the ice-cube stimulus (9/77 vs. 39/77). Ice-water-provoked HICS had a significantly shorter latency (median 15 s, range 4-97 s vs. median 68 s, range 27-96 s). There was no difference in pain localisation. Character after ice-cube stimulation was predominantly described as pressing and after ice-water stimulation as stabbing. A second HICS followed in 10/39 (26%) of the headaches provoked by ice water. Lacrimation occurred significantly more often in volunteers with than in those without HICS. Discussion HICS provoked by ice water was more frequent, had a shorter latency, different pain character and higher pain intensity than HICS provoked by ice cubes. The finding of two subsequent HICS attacks in the same volunteers supports the notion that two types of HICS exist. Lacrimation during HICS indicates involvement of the trigeminal-autonomic reflex.

Mars Gardens in the University - Red Thumbs: Growing Vegetables in Martian regolith simulant.

Science.gov (United States)

Guinan, Edward Francis

2018-01-01

Over the next few decades NASA and private enterprise missions plan to send manned missions to Mars with the ultimate aim to establish a permanent human presence on this planet. For a self-sustaining colony on Mars it will be necessary to provide food by growing plants in sheltered greenhouses on the Martian surface. As part of an undergraduate student project in Astrobiology at Villanova University, experiments are being carried out, testing how various plants grow in Martian regolith. A wide sample of plants are being grown and tested in Mars regolith simulant commercially available from The Martian Garden (TheMartian Garden.com). This Mars regolith simulant is based on Mojave Mars Simulant (MMS) developed by NASA and JPL for the Mars Phoenix mission. The MMS is based on the Mojave Saddleback basalt similar that used by JPL/NASA. Additional reagents were added to this iron rich basalt to bring the chemical content close to actual Mars regolith. The MMS used is an approximately 90% similar to regolith found on the surface of Mars - excluding poisonous perchlorates commonly found on actual Mars surface.The students have selected various vegetables and herbs to grow and test. These include carrots, spinach, dandelions, kale, soy beans, peas, onions, garlic and of course potatoes and sweet potatoes. Plants were tested in various growing conditions, using different fertilizers, and varying light conditions and compared with identical “control plants” grown in Earth soil / humus. The results of the project will be discussed from an education view point as well as from usefulness for fundamental research.We thank The Martian Garden for providing Martian regolith simulant at education discounted prices.

Potential Antifreeze Compounds in Present-Day Martian Seepage Groundwater

Directory of Open Access Journals (Sweden)

Jiin-Shuh Jean

2008-01-01

Full Text Available Is the recently found seepage groundwater on Mars pure H2O, or mixed with salts and other antifreeze compounds? Given the surface conditions of Mars, it is unlikely that pure water could either exist in its liquid state or have shaped Mars¡¦ fluid erosional landforms (gullies, channels, and valley networks. More likely is that Mars¡¦ seepage groundwater contains antifreeze and salt compounds that resist freezing and suppress evaporation. This model better accounts for Mars¡¦ enigmatic surface erosion. This paper suggests 17 antifreeze compounds potentially present in Martian seepage groundwater. Given their liquid state and physical properties, triethylene glycol, diethylene glycol, ethylene glycol, and 1,3-propylene glycol are advanced as the most likely candidate compounds. This paper also explores how a mixing of glycol or glycerol with salts in the Martian seepage groundwater may have lowered water¡¦s freezing point and raised its boiling point, with consequences that created fluid gully and channel erosion. Ethylene glycol and related hydrocarbon compounds have been identified in Martian and other interstellar meteorites. We suggest that these compounds and their proportions to water be included for detection in future explorations.

Effects of rooting and tree growth of selected woodland species on cap integrity in a mineral capped landfill site.

Science.gov (United States)

Hutchings, T R; Moffat, A J; Kemp, R A

2001-06-01

The above and below ground growth of three tree species (Alnus glutinosa, Pinus nigra var. maritima and Acer pseudoplatanus) was studied on a containment landfill site at Waterford, Hertfordshire, UK. Tree root architecture was studied using soil inspection pits excavated next to 12 trees of each species and mapped in detail. Tree height was related to soil thickness over the compacted mineral cap. No roots entered the cap where soil thickness was 1.3 m, but a few roots, especially of alder, were observed within it when the soil cover was 1.0 m or less. Micromorphological analysis of undisturbed samples of the mineral cap suggested that roots exploited weaknesses in the cap rather than actively causing penetration into it. Alder roots were more tolerant of anaerobic conditions within the cap than the other species examined. The results confirm that mineral caps should be covered by 1.5 m of soil or soil-forming material if tree establishment is intended over a restored landfill site, unless protected by other parts of a composite capping system.

Ice flow Modelling of the Greenland Ice Sheet

DEFF Research Database (Denmark)

Nielsen, Lisbeth Tangaa

Models of ice flow have a range of application in glaciology, including investigating the large-scale response of ice sheets to changes in climate, assimilating data to estimate unknown conditions beneath the ice sheet, and in interpreting proxy records obtained from ice cores, among others. In t...... a steady state with respect to the reference climate at the end of the simulation and that the mass balance of the ice sheet at this time was more sensitive to recent climate fluctuations than the temperature forcing in the early or mid-Holocene.......Models of ice flow have a range of application in glaciology, including investigating the large-scale response of ice sheets to changes in climate, assimilating data to estimate unknown conditions beneath the ice sheet, and in interpreting proxy records obtained from ice cores, among others....... In this PhD project, the use of ice flow models for the interpretation of the age-structure of the Greenland ice sheet, i.e. the depth within the ice, at which ice deposited at given times are found at present day. Two different observational data sets of this archive were investigated. Further, paleo...

Arctic sea-ice ridges—Safe heavens for sea-ice fauna during periods of extreme ice melt?

Science.gov (United States)

Gradinger, Rolf; Bluhm, Bodil; Iken, Katrin

2010-01-01

The abundances and distribution of metazoan within-ice meiofauna (13 stations) and under-ice fauna (12 stations) were investigated in level sea ice and sea-ice ridges in the Chukchi/Beaufort Seas and Canada Basin in June/July 2005 using a combination of ice coring and SCUBA diving. Ice meiofauna abundance was estimated based on live counts in the bottom 30 cm of level sea ice based on triplicate ice core sampling at each location, and in individual ice chunks from ridges at four locations. Under-ice amphipods were counted in situ in replicate ( N=24-65 per station) 0.25 m 2 quadrats using SCUBA to a maximum water depth of 12 m. In level sea ice, the most abundant ice meiofauna groups were Turbellaria (46%), Nematoda (35%), and Harpacticoida (19%), with overall low abundances per station that ranged from 0.0 to 10.9 ind l -1 (median 0.8 ind l -1). In level ice, low ice algal pigment concentrations (Turbellaria, Nematoda and Harpacticoida also were observed in pressure ridges (0-200 ind l -1, median 40 ind l -1), although values were highly variable and only medians of Turbellaria were significantly higher in ridge ice than in level ice. Median abundances of under-ice amphipods at all ice types (level ice, various ice ridge structures) ranged from 8 to 114 ind m -2 per station and mainly consisted of Apherusa glacialis (87%), Onisimus spp. (7%) and Gammarus wilkitzkii (6%). Highest amphipod abundances were observed in pressure ridges at depths >3 m where abundances were up to 42-fold higher compared with level ice. We propose that the summer ice melt impacted meiofauna and under-ice amphipod abundance and distribution through (a) flushing, and (b) enhanced salinity stress at thinner level sea ice (less than 3 m thickness). We further suggest that pressure ridges, which extend into deeper, high-salinity water, become accumulation regions for ice meiofauna and under-ice amphipods in summer. Pressure ridges thus might be crucial for faunal survival during periods of

Early Holocene climate oscillations recorded in three Greenland ice cores

DEFF Research Database (Denmark)

Rasmussen, Sune Olander; Vinther, Bo Møllesøe; Clausen, Henrik Brink

2007-01-01

around 9.3 ka before present, and the Preboreal Oscillation during the first centuries of the Holocene. For each of these sections, we present a d18O anomaly curve and a common accumulation signal that represents regional changes in the accumulation rate over the Greenland ice cap....... and accumulation anomalies that are common to the three cores in the Early Holocene (7.9–11.7 ka before present). Three time periods with significant and synchronous anomalies in the d18O and accumulation signals stand out: the well-known 8.2 ka event, an event of shorter duration but of almost similar amplitude...

Organic and inorganic interpretations of the martian UV-IR reflectance spectrum

Energy Technology Data Exchange (ETDEWEB)

Pang, K D; Ajello, J M [Jet Propulsion Lab., Pasadena, CA (USA); Chun, S F.S. [California Univ., San Francisco (USA). School of Medicine; Nansheng, Z [Beijing Planetarium (China); Minji, L [Beijing Glass Institute (China)

1982-01-07

The Viking gas chromatography-mass spectrometer analysis of martian soil samples are discussed, in particular why no organic molecules were detected at the landing sites, whether the sterility of the two sites is representative of the entire planet and if there are locations on Mars more conducive to the formation and preservation of organics. The destruction of organic compounds has been simulated in Mars-like laboratory conditions and the possible planetwide destructive mechanism considered. The UV and IR reflectance spectra of Mars has been re-examined for any evidence of organic molecules and an upper limit on the organic carbon content of average martian soil has been set. The results reveal that the average martian soil is organic-poor, makes an unfavourable habitat for life forms based on carbon chemistry, and there is no reason to believe that organic molecules are preferentially preserved anywhere on the planet.

Organic and inorganic interpretations of the martian UV-IR reflectance spectrum

International Nuclear Information System (INIS)

Pang, K.D.; Ajello, J.M.; Chun, S.F.S.; Minji, L.

1982-01-01

The Viking gas chromatography-mass spectrometer analysis of martian soil samples are discussed, in particular why no organic molecules were detected at the landing sites, whether the sterility of the two sites is representative of the entire planet and if there are locations on Mars more conducive to the formation and preservation of organics. The destruction of organic compounds has been simulated in Mars-like laboratory conditions and the possible planetwide destructive mechanism considered. The UV and IR reflectance spectra of Mars has been re-examined for any evidence of organic molecules and an upper limit on the organic carbon content of average martian soil has been set. The results reveal that the average martian soil is organic-poor, makes an unfavourable habitat for life forms based on carbon chemistry, and there is no reason to believe that organic molecules are preferentially preserved anywhere on the planet. (U.K.)

Analyses of hydraulic performance of velocity caps

DEFF Research Database (Denmark)

Christensen, Erik Damgaard; Degn Eskesen, Mark Chr.; Buhrkall, Jeppe

2014-01-01

The hydraulic performance of a velocity cap has been investigated. Velocity caps are often used in connection with offshore intakes. CFD (computational fluid dynamics) examined the flow through the cap openings and further down into the intake pipes. This was combined with dimension analyses...

Constraining the Timing of Lobate Debris Apron Emplacement at Martian Mid-Latitudes Using a Numerical Model of Ice Flow

Science.gov (United States)

Parsons, R. A.; Nimmo, F.

2010-03-01

SHARAD observations constrain the thickness and dust content of lobate debris aprons (LDAs). Simulations of dust-free ice-sheet flow over a flat surface at 205 K for 10-100 m.y. give LDA lengths and thicknesses that are consistent with observations.

49 CFR 230.41 - Flexible staybolts with caps.

Science.gov (United States)

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Flexible staybolts with caps. 230.41 Section 230... Appurtenances Staybolts § 230.41 Flexible staybolts with caps. (a) General. Flexible staybolts with caps shall have their caps removed during every 5th annual inspection for the purpose of inspecting the bolts for...

Polygons in Martian Frost

Science.gov (United States)

2003-01-01

MGS MOC Release No. MOC2-428, 21 July 2003This June 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polygonal pattern developed in seasonal carbon dioxide frost in the martian southern hemisphere. The frost accumulated during the recent southern winter; it is now spring, and the carbon dioxide frost is subliming away. This image is located near 80.4oS, 200.2oW; it is illuminated by sunlight from the upper left, and covers an area 3 km (1.9 mi) across.

Characterization of cap binding proteins associated with the nucleus

International Nuclear Information System (INIS)

Patzelt, E.

1986-04-01

Eucaryotic mRNAs a carry 7-methylguanosine triphosphate residue (called cap structure) at their 5' terminus. The cap plays an important role in RNA recognition. Cap binding proteins (CBP) of HeLa cells were identified by photoaffinity labelling using the cap analogue γ-( 32 P)-(4-(benzoyl-phenyl)methylamido)-7-methylguanosine-5'-triphosphate (BP-m 7 GTP). Photoreaction of this cap analogue with HeLa cell initiation factors resulted in specific labelling of two polypeptides of Msub(r) 37000 and 26000. The latter was also labelled in crude initiation factors prepared from reticulocytes and is identical to the cap binding protein CBP I previously identified. These cap binding proteins were also affinity labelled in poliovirus infected cell extracts. Photoaffinity reaction with BP-m 7 GTP of whole HeLa cell homogenate showed three additional polypeptides with Msub(r) 120000, 89000 and 80000. These cap binding proteins were found to be associated with the nucleus and are therefore referred to as nuclear cap binding proteins, i.e. NCBP 1, NCBP 2 and NCBP 3. They were also present in splicing extracts. Photoaffinity labelling in these nuclear extracts was differentially inhibited by various cap analogues and capped mRNAs. Affinity chromatography on immobilized globin mRNA led to a partial separation of the three nuclear cap binding proteins. Chromatography on m 7 GTP-Sepharose resulted in a specific binding of NCBP 3. The different behaviour of the cap binding proteins suggests that they are functionally distinct and that they might be involved in different processes requiring cap recognition. (Author)

Martian Methane From a Cometary Source: A Hypothesis

Science.gov (United States)

Fries, M.; Christou, A.; Archer, D.; Conrad, P.; Cooke, W.; Eigenbrode, J.; ten Kate, I. L.; Matney, M.; Niles, P.; Sykes, M.;

Theoretical model of polar cap auroral arcs

International Nuclear Information System (INIS)

Kan, J.R.; Burke, W.J.; USAF, Bedford, MA)

1985-01-01

A theory of the polar cap auroral arcs is proposed under the assumption that the magnetic field reconnection occurs in the cusp region on tail field lines during northward interplanetary magnetic field (IMF) conditions. Requirements of a convection model during northward IMF are enumerated based on observations and fundamental theoretical considerations. The theta aurora can be expected to occur on the closed field lines convecting sunward in the central polar cap, while the less intense regular polar cap arcs can occur either on closed or open field lines. The dynamo region for the polar cap arcs is required to be on closed field lines convecting tailward in the plasma sheet which is magnetically connected to the sunward convection in the central polar cap. 43 references

Following the south polar cap recession as viewed by OMEGA/MEX using automatic detection of H2O and CO2 ices.

Science.gov (United States)

Schmidt, F.; Doute, S.; Schmitt, B.

In order to understand Mars' current climate it is necessary to detect, characterize and monitor CO2 and H2O at the surface (permanent and seasonal icy deposits) and in the atmosphere (vapor and clouds). Here we will focus on the South Seasonal Polar Cap (SSPC) whose recession was previously observed with different techniques : from earth in the visible range with HST [James 1996], or from MGS spacecraft with MOC images [Benson 2005], in the thermal IR range by the TES [Kieffer 2000], in the near infrared by OMEGA/MEX [Langevin submitted]. The time and space evolutions of the SSPC is a major annual climatic signal both at the global and the regional scales. In particular the measurement of the temporal and spatial distributions of CO2 constrains exchange processes between both surface and atmosphere. This exchange may involve preponderant species : H2O, CO2 and dust. In this work we will apply a new detection technique : "wavanglet" in order to follow the recession of the SSPC thanks to OMEGA/MEX observations. This method was especially developed in the goal to classify a huge dataset, such OMEGA ones. We propose to use "wavanglet" as a supervised automatic classification method that identifies spectral features and classifies the image in spectrally homogeneous units. Additionally we will evaluate quantitative detection limits of "wavanglet" based on synthetic dataset simulating OMEGA spectra in typical situation of the SSPC. This detection limit will be discussed in terms of abundance for H2O and CO2 ices in order to improve the interpretation of the classification. Finally we will present the recession of the SSPC using "wavanglet" and we will compare the results with those of earlier investigation. An interpretation of the similarities and disagreements between those maps will be done.

Rate of ice accumulation during ice storms

Energy Technology Data Exchange (ETDEWEB)

Feknous, N. [SNC-Lavalin, Montreal, PQ (Canada); Chouinard, L. [McGill Univ., Montreal, PQ (Canada); Sabourin, G. [Hydro-Quebec, Montreal, PQ (Canada)

2005-07-01

The rate of glaze ice accumulation is the result of a complex process dependent on numerous meteorological and physical factors. The aim of this paper was to estimate the distribution rate of glaze ice accumulation on conductors in southern Quebec for use in the design of mechanical and electrical de-icing devices. The analysis was based on direct observations of ice accumulation collected on passive ice meters. The historical database of Hydro-Quebec, which contains observations at over 140 stations over period of 25 years, was used to compute accumulation rates. Data was processed so that each glaze ice event was numbered in a chronological sequence. Each event consisted of the time series of ice accumulations on each of the 8 cylinders of the ice meters, as well as on 5 of its surfaces. Observed rates were converted to represent the average ice on a 30 mm diameter conductor at 30 m above ground with a span of 300 m. Observations were corrected to account for the water content of the glaze ice as evidenced by the presence of icicles. Results indicated that despite significant spatial variations in the expected severity of ice storms as a function of location, the distribution function for rates of accumulation were fairly similar and could be assumed to be independent of location. It was concluded that the observations from several sites could be combined in order to obtain better estimates of the distribution of hourly rates of ice accumulation. However, the rates were highly variable. For de-icing strategies, it was suggested that average accumulation rates over 12 hour periods were preferable, and that analyses should be performed for other time intervals to account for the variability in ice accumulation rates over time. In addition, accumulation rates did not appear to be highly correlated with average wind speed for maximum hourly accumulation rates. 3 refs., 2 tabs., 10 figs.

Diagnostic criteria for cryopyrin-associated periodic syndrome (CAPS).

Science.gov (United States)

Kuemmerle-Deschner, Jasmin B; Ozen, Seza; Tyrrell, Pascal N; Kone-Paut, Isabelle; Goldbach-Mansky, Raphaela; Lachmann, Helen; Blank, Norbert; Hoffman, Hal M; Weissbarth-Riedel, Elisabeth; Hugle, Boris; Kallinich, Tilmann; Gattorno, Marco; Gul, Ahmet; Ter Haar, Nienke; Oswald, Marlen; Dedeoglu, Fatma; Cantarini, Luca; Benseler, Susanne M

2017-06-01

Cryopyrin-associated periodic syndrome (CAPS) is a rare, heterogeneous disease entity associated with NLRP3 gene mutations and increased interleukin-1 (IL-1) secretion. Early diagnosis and rapid initiation of IL-1 inhibition prevent organ damage. The aim of the study was to develop and validate diagnostic criteria for CAPS. An innovative process was followed including interdisciplinary team building, item generation: review of CAPS registries, systematic literature review, expert surveys, consensus conferences for item refinement, item reduction and weighting using 1000Minds decision software. Resulting CAPS criteria were tested in large cohorts of CAPS cases and controls using correspondence analysis. Diagnostic models were explored using sensitivity analyses. The international team included 16 experts. Systematic literature and registry review identified 33 CAPS-typical items; the consensus conferences reduced these to 14. 1000Minds exercises ranked variables based on importance for the diagnosis. Correspondence analysis determined variables consistently associated with the diagnosis of CAPS using 284 cases and 837 controls. Seven variables were significantly associated with CAPS (pCAPS-typical symptoms: urticaria-like rash, cold-triggered episodes, sensorineural hearing loss, musculoskeletal symptoms, chronic aseptic meningitis and skeletal abnormalities. Sensitivity was 81%, specificity 94%. It performed well for all CAPS subtypes and regardless of NLRP3 mutation. The novel approach integrated traditional methods of evidence synthesis with expert consensus, web-based decision tools and innovative statistical methods and may serve as model for other rare diseases. These criteria will enable a rapid diagnosis for children and adults with CAPS. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

A massive hydrogen-rich Martian greenhouse recorded in D/H

Science.gov (United States)

Pahlevan, K.; Schaefer, L. K.; Desch, S. J.; Elkins-Tanton, L. T.

2017-12-01

The deuterium-to-hydrogen (D/H) ratio in Martian atmospheric water ( 6x standard mean ocean water, SMOW) [1,2] is higher than that of known sources [3,4] alluding to a planetary enrichment process. A recent measurement by the Curiosity rover of Hesperian clays yields a D/H value 3x higher than SMOW [5], demonstrating that most enrichment occurred early in planetary history, buttressing the conclusions of Martian meteorite studies [6,7]. Extant models of the isotopic evolution of the Martian hydrosphere have not incorporated primordial H2, despite its likely abundance on early Mars. Here, we report the first 1D climate calculations with an atmospheric composition determined via degassing from a reducing magma ocean to study Martian climate during an early water ocean stage. A reducing Martian magma ocean is expected based on experimental petrology [8], the degassing of which gives rise to an H2-rich steam atmosphere [9] with strong attendant greenhouse warming [10,11] even after the removal of steam via condensation. At the pressures and temperatures prevailing in such a degassed greenhouse, we find that isotopic exchange in the fluid envelope is rapid, strongly concentrating deuterium in water molecules over molecular hydrogen [12]. The subsequent loss of the isotopically light H2-rich atmosphere results in a 2x D/H enrichment in the oceans via isotopic equilibration alone. These calculations suggest that most of the D/H enrichment observed in the first billion years of Martian history is produced by the evolution of a massive ( 100 bar) H2-rich greenhouse in the aftermath of magma ocean crystallization. The proposed link between early planetary process and modern isotopic observable opens a new window into the earliest history of Mars. [1] Owen, T. et al. Science 240, 1767-1770 (1988). [2] Webster, C. R. et al. Science 341, 260-263 (2013). [3] Lunine, J. I. et al. Icarus 165, 1-8, (2003). [4] Marty, B. et al. EPSL 441, 91-102, (2016). [5] Mahaffy, P. et al

Enzymatic synthesis of RNAs capped with nucleotide analogues reveals the molecular basis for substrate selectivity of RNA capping enzyme: impacts on RNA metabolism.

Directory of Open Access Journals (Sweden)

Moheshwarnath Issur

Full Text Available RNA cap binding proteins have evolved to specifically bind to the N7-methyl guanosine cap structure found at the 5' ends of eukaryotic mRNAs. The specificity of RNA capping enzymes towards GTP for the synthesis of this structure is therefore crucial for mRNA metabolism. The fact that ribavirin triphosphate was described as a substrate of a viral RNA capping enzyme, raised the possibility that RNAs capped with nucleotide analogues could be generated in cellulo. Owing to the fact that this prospect potentially has wide pharmacological implications, we decided to investigate whether the active site of the model Paramecium bursaria Chlorella virus-1 RNA capping enzyme was flexible enough to accommodate various purine analogues. Using this approach, we identified several key structural determinants at each step of the RNA capping reaction and generated RNAs harboring various different cap analogues. Moreover, we monitored the binding affinity of these novel capped RNAs to the eIF4E protein and evaluated their translational properties in cellulo. Overall, this study establishes a molecular rationale for the specific selection of GTP over other NTPs by RNA capping enzyme It also demonstrates that RNAs can be enzymatically capped with certain purine nucleotide analogs, and it also describes the impacts of modified RNA caps on specific steps involved in mRNA metabolism. For instance, our results indicate that the N7-methyl group of the classical N7-methyl guanosine cap is not always indispensable for binding to eIF4E and subsequently for translation when compensatory modifications are present on the capped residue. Overall, these findings have important implications for our understanding of the molecular determinants involved in both RNA capping and RNA metabolism.

Synthesis of tritium or deuterium labelled 19-nor-3. cap alpha. -hydroxy-5. cap alpha. -androstan-17-one from nortestosterone

Energy Technology Data Exchange (ETDEWEB)

Protiva, J; Klinotova, E [Karlova Univ., Prague (Czechoslovakia). Prirodovedecka Fakulta; Filip, J [Ustav pro Vyzkum, Vyrobu a Vyuziti Radioisotopu, Prague (Czechoslovakia); Hampl, R [Research Inst. of Endocrinology, Praha (Czechoslovakia)

1982-10-20

Tritium and/or deuterium (5-H) labelled 19-nor-3..cap alpha..-hydroxy-5..cap alpha..-androstan-17-one (norandrosterone) was prepared from nortestosterone in view to use it as a radioligand for radioimmunoassay of the main nortestosterone metabolites. Based upon model experiments using testosterone and deuterium labelling, the following four step procedure was established: nortestosterone was oxidized with pyridine chlorochromate and the resulting 19-nor-4-androsten-3,17-dione was tritiated with tritium gas under catalysis with tris(triphenylphosphine)rhodium chloride to give (4,5..cap alpha..-/sup 3/H)19-nor-5..cap alpha..-androstan-3,17-dione. A selective reduction of the latter compound yielded (5-/sup 3/H)19-nor-3..cap alpha..-hydroxy-5..cap alpha..-androstan-17-one of the molar radioactivity 0.3 TBq (8.15 Ci)/mmol.

Enrichment of Inorganic Martian Dust Simulant with Carbon Component can Provoke Neurotoxicity

Science.gov (United States)

Pozdnyakova, Natalia; Pastukhov, Artem; Dudarenko, Marina; Borysov, Arsenii; Krisanova, Natalia; Nazarova, Anastasia; Borisova, Tatiana

2017-02-01

Carbon is the most abundant dust-forming element in the interstellar medium. Tremendous amount of meteorites containing plentiful carbon and carbon-enriched dust particles have reached the Earth daily. National Institute of Health panel accumulates evidences that nano-sized air pollution components may have a significant impact on the central nervous system (CNS) in health and disease. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the CNS. Based on above facts, here we present the study, the aims of which were: 1) to upgrade inorganic Martian dust simulant derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, nanodiamonds and carbon dots; 2) to analyse acute effects of upgraded simulant on key characteristics of synaptic neurotransmission; and 3) to compare above effects with those of inorganic dust and carbon components per se. Acute administration of carbon-containing Martian dust analogues resulted in a significant decrease in transporter-mediated uptake of L-[14C]glutamate (the major excitatory neurotransmitter) and [3H]GABA (the main inhibitory neurotransmitter) by isolated rat brain nerve terminals. The extracellular level of both neurotransmitters increased in the presence of carbon-containing Martian dust analogues. These effects were associated with action of carbon components of upgraded Martian dust simulant, but not with its inorganic constituent. This fact indicates that carbon component of native Martian dust can have deleterious effects on extracellular glutamate and GABA homeostasis in the CNS, and so glutamate- and GABA-ergic neurotransmission disballansing exitation and inhibition.

Methylated silicates may explain the release of chlorinated methane from Martian soil

Science.gov (United States)

Bak, Ebbe N.; Jensen, Svend J. Knak; Nørnberg, Per; Finster, Kai

2016-01-01

The only organic compounds that have been detected in the Martian soil are simple chlorinated compounds released from heated surface material. However, the sources of the organic carbon are in dispute. Wind abraded silicates, which are widespread on the Martian surface, can sequester atmospheric methane which generates methylated silicates and thus could provide a mechanism for accumulation of reduced carbon in the surface soil. In this study we show that thermal volatilization of methylated silicates in the presence of perchlorate leads to the production of chlorinated methane. Thus, methylated silicates could be a source of the organic carbon released as chlorinated methane upon thermal volatilization of Martian soil samples. Further, our experiments show that the ratio of the different chlorinated compounds produced is dependent on the mass ratio of perchlorate to organic carbon in the soil.

7 CFR 1714.7 - Interest rate cap.

Science.gov (United States)

2010-01-01

... 7 Agriculture 11 2010-01-01 2010-01-01 false Interest rate cap. 1714.7 Section 1714.7 Agriculture... PRE-LOAN POLICIES AND PROCEDURES FOR INSURED ELECTRIC LOANS General § 1714.7 Interest rate cap. Except... section, or both the rate disparity test for the interest rate cap and the consumer income test set forth...

20 CFR 606.22 - Application for cap.

Science.gov (United States)

2010-04-01

... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Application for cap. 606.22 Section 606.22... Reduction § 606.22 Application for cap. (a) Application. (1) The Governor of the State shall make... a State requests a cap on tax credit reduction. The Governor is required to notify the Department on...

A late Holocene metal record of Andean climate and anthropogenic activity in lake sediments near Quelccaya Ice Cap, Peru

Science.gov (United States)

Beal, S. A.; Kelly, M. A.; Jackson, B. P.; Stroup, J. S.; Osterberg, E. C.

2011-12-01

The tropical hypothesis maintains that major changes in global climate are motivated by phenomena based at tropical latitudes. Evidence for this hypothesis lies in: modern-day observations of El Niño Southern Oscillation (ENSO); East African lake sediment records of Intertropical Convergence Zone (ITCZ) position that precede high-latitude changes; and the potential for ITCZ shifts to cause major CO2 degassing from the Southern Ocean. In order to improve the understanding of these phenomena we present an ~1800 year record of atmospheric metal deposition in a lake sediment core near Quelccaya Ice Cap, Peru (13.9 °S). In June, 2010 we collected a 1.45 meter-long core from Yanacocha - a small, closed-basin tarn that has been isolated from glacial input since ~11,200 BP. The chronology for the core is based on 4 of 6 AMS 14C dates on aquatic macrofossils and one sharp Zr/Ti anomaly at 36 cm, likely derived from the 350 BP eruption of Huaynaputina. We completely digested organic-rich core samples at 1 cm resolution using HNO3, HCl, and HF in a closed-vessel microwave system, and then analyzed the digestates for 67 metals by inductively coupled plasma mass spectrometry. Here we show fluxes of lithogenic metals (Fe, Nb, Ti, and Zr) that reflect changes in wind strength and aridity, fluxes of lithogenic metal isotopes (REEs and Pb) that reflect wind direction, and enrichment factors (EFs) of metals (Ag, As, Cd, Cu, Hg, and Pb) that reflect anthropogenic activity. Five episodic peaks in lithogenic metal fluxes, centered around 1800, 1300, 900, 600, and 100 yrs BP, are thought to result from either drier or windier conditions, potentially caused by a northern ITCZ position or a more persistent El Niño state. The provenance of atmospheric deposition, evidenced by REE ratios (light REEs / heavy REEs), suggest that high lithogenic fluxes are associated with a change in wind direction, possibly caused by a change in the ENSO state, which will be explored with forthcoming Pb

IAA transport in corn roots includes the root cap

International Nuclear Information System (INIS)

Hasenstein, K.H.

1989-01-01

In earlier reports we concluded that auxin is the growth regulator that controls gravicurvature in roots and that the redistribution of auxin occurs within the root cap. Since other reports did not detect auxin in the root cap, we attempted to confirm the IAA does move through the cap. Agar blocks containing 3 H-IAA were applied to the cut surface of 5 mm long apical segments of primary roots of corn (mo17xB73). After 30 to 120 min radioactivity (RA) of the cap and root tissue was determined. While segments suspended in water-saturated air accumulated very little RA in the cap, application of 0.5 μ1 of dist. water to the cap (=controls) increased RA of the cap dramatically. Application to the cap of 0.5 μ1 of sorbitol or the Ca 2+ chelator EGTA reduced cap RA to 46% and 70% respectively compared to water, without affecting uptake. Control root segments gravireacted faster than non-treated or osmoticum or EGTA treated segments. The data indicate that both the degree of hydration and calcium control the amount of auxin moving through the cap

A Martian origin for the Mars Trojan asteroids

Science.gov (United States)

Polishook, D.; Jacobson, S. A.; Morbidelli, A.; Aharonson, O.

2017-08-01

Seven of the nine known Mars Trojan asteroids belong to an orbital cluster1,2 named after its largest member, (5261) Eureka. Eureka is probably the progenitor of the whole cluster, which formed at least 1 Gyr ago3. It has been suggested3 that the thermal YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect spun up Eureka, resulting in fragments being ejected by the rotational-fission mechanism. Eureka's spectrum exhibits a broad and deep absorption band around 1 μm, indicating an olivine-rich composition4. Here we show evidence that the Trojan Eureka cluster progenitor could have originated as impact debris excavated from the Martian mantle. We present new near-infrared observations of two Trojans ((311999) 2007 NS2 and (385250) 2001 DH47) and find that both exhibit an olivine-rich reflectance spectrum similar to Eureka's. These measurements confirm that the progenitor of the cluster has an achondritic composition4. Olivine-rich reflectance spectra are rare amongst asteroids5 but are seen around the largest basins on Mars6. They are also consistent with some Martian meteorites (for example, Chassigny7) and with the material comprising much of the Martian mantle8,9. Using numerical simulations, we show that the Mars Trojans are more likely to be impact ejecta from Mars than captured olivine-rich asteroids transported from the main belt. This result directly links specific asteroids to debris from the forming planets.

Correlations Between Surficial Sulfur and a REE Crustal Assimilation Signature in Martian Shergottites

Science.gov (United States)

Jones, J. H.; Franz, H. B.

2015-01-01

Compared to terrestrial basalts, the Martian shergottite meteorites have an extraordinary range of Sr and Nd isotopic signatures. In addition, the S isotopic compositions of many shergottites show evidence of interaction with the Martian surface/ atmosphere through mass-independent isotopic fractionations (MIF, positive, non-zero delta(exp 33)S) that must have originated in the Martian atmosphere, yet ultimately were incorporated into igneous sulfides (AVS - acid-volatile sulfur). These positive delta(exp 33)S signatures are thought to be governed by solar UV photochemical processes. And to the extent that S is bound to Mars and not lost to space from the upper atmosphere, a positive delta(exp 33)S reservoir must be mass balanced by a complementary negative reservoir.

Characterization of an IceTop tank for the IceCube surface extension IceVeto

Energy Technology Data Exchange (ETDEWEB)

Kemp, Julian; Auffenberg, Jan; Hansmann, Bengt; Rongen, Martin; Stahlberg, Martin; Wiebusch, Christopher [III. Physikalisches Institut B, RWTH Aachen University (Germany); Collaboration: IceCube-Collaboration

2015-07-01

IceTop is an air-shower detector located at the South Pole on the surface above the IceCube detector. It consists of 81 detector stations with two Cherenkov tanks each. The tanks are filled with clear ice and instrumented with two photomultipliers. IceTop detects cosmic-ray induced air-showers above an energy threshold of ∝300 TeV. Muons and neutrinos from these air-showers are the main background for astrophysical neutrino searches with IceCube. The usage of IceTop to veto air-showers largely reduces this background in the field of view. To enlarge the field of view an extension of the surface detector, IceVeto, is planned. Therefore, we investigate the properties of an original IceTop tank as a laboratory reference for the development of new detection module designs. First results of these measurements are presented.

Open questions on optical properties of dust and the opacity of the Martian atmosphere

Science.gov (United States)

Korablev, O.; Moroz, V.; Petrova, E.; Rodin, A.

Particulate component of the atmosphere composed by micron-sized products of soil weathering and water ice clouds that strongly affect the current climate of the planet. In the absence of a dust storm so-called permanent dust haze with0.2 in the atmosphere of Mars determines its thermal structure. Dust loading varies substantially with the season and geographic location, and only the data of mapping instruments are adequate to characterize it, such as TES/MGS and IRTM/Viking. In spite of vast domain of collected data, no model is now capable to explain all observed spectral features of dust aerosol. Several mineralogical and microphysical models of the atmospheric dust have been proposed but they cannot explain the pronounced systematic differences between the IR data and measurem ents from the surface (Viking landers, Pathfinder) which give in the quiet seasons the typical optical depth of? 0.5 from one side, and ground-based observations in the UV-visible range that frequently infer <0.2, on the other side. Also the relationship between9 and the visible optical depth is not well established experimentally so far. Future focused measurements are therefore necessary to study Martian aerosol.

Biological life support systems for martian missions: some problems and prospects

Science.gov (United States)

Tikhomirov, A. A.; Ushakova, S. A.; Kovaleva, N. P.; Lasseur, C.

Taking into account the experience of scientific researches obtained during experiments in the BIOS - 3 of the Institute of Biophysics of Siberian Branch of Russian Academy of Science (IBP SB RAS) and the MELISSA program (ESA), approaches in creation biological life support systems for a flight period and a fixed-site base of Martian mission are considered. Various alternate variants of designing of elements of BLSS based on use of Chlorella and/or Spirulina, and also greenhouses with higher plants for the flight period of Martian mission are analyzed. For this purpose construction of BLSS ensuring full closure of matter turnover according to gas exchange and water and partial closure on the human's exometabolites is supposed. For the fixed site Martian station BLSS based on use of higher plants with a various degree of closure of internal mass exchange are suggested. Various versions of BLSS configuration and degree of closure of mass exchange depending on duration of Martian mission, the diet type of a crew and some other conditions are considered. Special attention is given to problems of reliability and tolerance of matter turnover processes in BLSS which maintenance is connected, in particular, with additional oxygen reproduction inside a system. Technologies for realization of BLSS of various configurations are offered and justified. The auxiliary role of the physicochemical methods in BLSS functioning both for the flight period and for the crew stay on Mars is justified.

Mars analog minerals' spectral reflectance characteristics under Martian surface conditions

Science.gov (United States)

Poitras, J. T.; Cloutis, E. A.; Salvatore, M. R.; Mertzman, S. A.; Applin, D. M.; Mann, P.

2018-05-01

We investigated the spectral reflectance properties of minerals under a simulated Martian environment. Twenty-eight different hydrated or hydroxylated phases of carbonates, sulfates, and silica minerals were selected based on past detection on Mars through spectral remote sensing data. Samples were ground and dry sieved to <45 μm grain size and characterized by XRD before and after 133 days inside a simulated Martian surface environment (pressure 5 Torr and CO2 fed). Reflectance spectra from 0.35 to 4 μm were taken periodically through a sapphire (0.35-2.5 μm) and zinc selenide (2.5-4 μm) window over a 133-day period. Mineral stability on the Martian surface was assessed through changes in spectral characteristics. Results indicate that the hydrated carbonates studied would be stable on the surface of Mars, only losing adsorbed H2O while maintaining their diagnostic spectral features. Sulfates were less stable, often with shifts in the band position of the SO, Fe, and OH absorption features. Silicas displayed spectral shifts related to SiOH and hydration state of the mineral surface, while diagnostic bands for quartz were stable. Previous detection of carbonate minerals based on 2.3-2.5 μm and 3.4-3.9 μm features appears to be consistent with our results. Sulfate mineral detection is more questionable since there can be shifts in band position related to SO4. The loss of the 0.43 μm Fe3+ band in many of the sulfates indicate that there are fewer potential candidates for Fe3+ sulfates to permanently exist on the Martian surface based on this band. The gypsum sample changed phase to basanite during desiccation as demonstrated by both reflectance and XRD. Silica on Mars has been detected using band depth ratio at 1.91 and 1.96 μm and band minimum position of the 1.4 μm feature, and the properties are also used to determine their age. This technique continues to be useful for positive silica identifications, however, silica age appears to be less consistent

Mapping the northern plains of Mars: origins, evolution and response to climate change - a new overview of the recent ice-related landforms in Utopia Planitia

Science.gov (United States)

Costard, Francois; Sejourne, Antoine; Losiak, Ania; Swirad, Zusanna; Balm, Matthew; Conway, Susan; Gallagher, Colman; van-Gassel, Stephan; Hauber, Ernst; Johnsson, Andreas; Kereszturi, Akos; Platz, Thomas; Ramsdale, Jason; Reiss, Dennis; Skinner, James

2015-04-01

An ISSI (International Space Science Institute) international team has been convened to study the Northern Plain of Mars. The northern plains of Mars are extensive, geologically young, low-lying areas that contrast in age and relief to Mars' older, heavily cratered, southern highlands. Mars' northern plains are characterised by a wealth of landforms and landscapes that have been inferred to be related to the presence of ice or ice-rich material. Such landforms include 'scalloped' pits and depressions, polygonally-patterned grounds, and viscous flow features similar in form to terrestrial glacial or ice-sheet landforms. Furthermore, new (within the last few years) impact craters have exposed ice in the northern plains, and spectral data from orbiting instruments have revealed the presence of tens of percent by weight of water within the upper most ~50 cm of the martian surface at high latitudes. The western Utopia Planitia contains numerous relatively young ice-related landforms (Utopia Planitia along a long strip from ~30N to ~80N latitude and about 250km wide. The goals are to: (i) map the geographical distribution of the ice-related landforms; (ii) identify their association with subtly-expressed geological units and; (iii) discuss the climatic modifications of the ice-rich permafrost in UP. Our work combines a study with CTX (5-6 m/pixel) and HRSC (~12.5-50 m/pixel) images, supported by higher resolution HiRISE (25 cm/pixel) and MOC (~2 m/pixel) and a comparison with analogous landforms on Earth.

Assessment of the turbulence parameterization schemes for the Martian mesoscale simulations

Science.gov (United States)

Temel, Orkun; Karatekin, Ozgur; Van Beeck, Jeroen

2016-07-01

Turbulent transport within the Martian atmospheric boundary layer (ABL) is one of the most important physical processes in the Martian atmosphere due to the very thin structure of Martian atmosphere and super-adiabatic conditions during the diurnal cycle [1]. The realistic modeling of turbulent fluxes within the Martian ABL has a crucial effect on the many physical phenomena including dust devils [2], methane dispersion [3] and nocturnal jets [4]. Moreover, the surface heat and mass fluxes, which are related with the mass transport within the sub-surface of Mars, are being computed by the turbulence parameterization schemes. Therefore, in addition to the possible applications within the Martian boundary layer, parameterization of turbulence has an important effect on the biological research on Mars including the investigation of water cycle or sub-surface modeling. In terms of the turbulence modeling approaches being employed for the Martian ABL, the "planetary boundary layer (PBL) schemes" have been applied not only for the global circulation modeling but also for the mesoscale simulations [5]. The PBL schemes being used for Mars are the variants of the PBL schemes which had been developed for the Earth and these schemes are either based on the empirical determination of turbulent fluxes [6] or based on solving a one dimensional turbulent kinetic energy equation [7]. Even though, the Large Eddy Simulation techniques had also been applied with the regional models for Mars, it must be noted that these advanced models also use the features of these traditional PBL schemes for sub-grid modeling [8]. Therefore, assessment of these PBL schemes is vital for a better understanding the atmospheric processes of Mars. In this framework, this present study is devoted to the validation of different turbulence modeling approaches for the Martian ABL in comparison to Viking Lander [9] and MSL [10] datasets. The GCM/Mesoscale code being used is the PlanetWRF, the extended version

Increased 5. cap alpha. -reductase activity in idiopathic hirsutism

Energy Technology Data Exchange (ETDEWEB)

Serafini, P.; Lobo, R.A.

1985-01-01

In vitro, genital skin 5..cap alpha..-reductase activity (5..cap alpha..-RA) was measured in ten hirsute women with normal androgen levels (idiopathic hirsutism (IH)) and in ten hirsute women with elevated androgen levels (polycystic ovary syndrome (PCO)) in order to determine the influence of secreted androgens on 5..cap alpha..-RA. In vitro 5..cap alpha..-RA was assessed by incubations of skin with /sup 14/C-testosterone (T) for 2 hours, after which steroids were separated and the radioactivity of dihydrotestosterone (DHT) and 5..cap alpha..-androstane 3..cap alpha..-17..beta..-estradiol (3..cap alpha..-diol) in specific eluates were determined. All androgens were normal in IH with the exception of higher levels of 3..cap alpha..-diol glucuronide which were similar to the levels of PCO. The conversion ratio (CR) of T to DHT in IH and PCO were similar, yet significantly greater than the CR of control subjects. The CR of T to 3..cap alpha..-diol in IH and PCO were similar, yet higher than in control subjects. Serum androgens showed no correlation with 5..cap alpha..-RA, while the CR of T to DHT showed a significant positive correlation with the Ferriman and Gallwey score. The increased 5..cap alpha..-RA in IH appears to be independent of serum androgen levels and is, therefore, an inherent abnormality. The term idiopathic is a misnomer, because hirsutism in these patients may be explained on the basis of increased skin 5..cap alpha..-RA.

Production of reactive oxygen species from abraded silicates. Implications for the reactivity of the Martian soil

Science.gov (United States)

Bak, Ebbe N.; Zafirov, Kaloyan; Merrison, Jonathan P.; Jensen, Svend J. Knak; Nørnberg, Per; Gunnlaugsson, Haraldur P.; Finster, Kai

2017-09-01

The results of the Labeled Release and the Gas Exchange experiments conducted on Mars by the Viking Landers show that compounds in the Martian soil can cause oxidation of organics and a release of oxygen in the presence of water. Several sources have been proposed for the oxidizing compounds, but none has been validated in situ and the cause of the observed oxidation has not been resolved. In this study, laboratory simulations of saltation were conducted to examine if and under which conditions wind abrasion of silicates, a process that is common on the Martian surface, can give rise to oxidants in the form of hydrogen peroxide (H2O2) and hydroxyl radicals (ṡOH). We found that silicate samples abraded in simulated Martian atmospheres gave rise to a significant production of H2O2 and ṡOH upon contact with water. Our experiments demonstrated that abraded silicates could lead to a production of H2O2 facilitated by atmospheric O2 and inhibited by carbon dioxide. Furthermore, during simulated saltation the silicate particles became triboelectrically charged and at pressures similar to the Martian surface pressure we observed glow discharges. Electrical discharges can cause dissociation of CO2 and through subsequent reactions lead to a production of H2O2. These results indicate that the reactions linked to electrical discharges are the dominant source of H2O2 during saltation of silicates in a simulated Martian atmosphere, given the low pressure and the relatively high concentration of CO2. Our experiments provide evidence that wind driven abrasion could enhance the reactivity of the Martian soil and thereby could have contributed to the oxidation of organic compounds and the O2 release observed in the Labeled Release and the Gas Exchange experiments. Furthermore, the release of H2O2 and ṡOH from abraded silicates could have a negative effect on the persistence of organic compounds in the Martian soil and the habitability of the Martian surface.

Flank tectonics of Martian volcanoes

International Nuclear Information System (INIS)

Thomas, P.J.; Squyres, S.W.; Carr, M.H.

1990-01-01

On the flanks of Olympus Mons is a series of terraces, concentrically distributed around the caldera. Their morphology and location suggest that they could be thrust faults caused by compressional failure of the cone. In an attempt to understand the mechanism of faulting and the possible influences of the interior structure of Olympus Mons, the authors have constructed a numerical model for elastic stresses within a Martian volcano. In the absence of internal pressurization, the middle slopes of the cone are subjected to compressional stress, appropriate to the formation of thrust faults. These stresses for Olympus Mons are ∼250 MPa. If a vacant magma chamber is contained within the cone, the region of maximum compressional stress is extended toward the base of the cone. If the magma chamber is pressurized, extensional stresses occur at the summit and on the upper slopes of the cone. For a filled but unpressurized magma chamber, the observed positions of the faults agree well with the calculated region of high compressional stress. Three other volcanoes on Mars, Ascraeus Mons, Arsia Mons, and Pavonis Mons, possess similar terraces. Extending the analysis to other Martian volcanoes, they find that only these three and Olympus Mons have flank stresses that exceed the compressional failure strength of basalt, lending support to the view that the terraces on all four are thrust faults

Lava Tubes as Martian Analog sites on Hawaii Island

Science.gov (United States)

Andersen, Christian; Hamilton, J. C.; Adams, M.

2013-10-01

The existence of geologic features similar to skylights seen in Mars Reconnaissance Orbiter HIRISE imagery suggest Martian lava tube networks. Along with pit craters, these features are evidence of a past era of vulcanism. If these were contemporary with the wet Mars eras, then it is suggestive that any Martian life may have retreated into these subsurface oases. Hawaii island has numerous lava tubes of differing ages, humidity, lengths and sizes that make ideal analog test environments for future Mars exploration. PISCES has surveyed multiple candidate sites during the past summer with a team of University of Hawaii at Hilo student interns. It should be noted that Lunar features have also been similarly discovered via Lunar Reconnaissance Orbiter LROC imagery.

Survival of microorganisms in smectite clays - Implications for Martian exobiology

Science.gov (United States)

Moll, Deborah M.; Vestal, J. R.

1992-01-01

The survival of Baccillus subtilis, Azotobacter chroococcum, and the enteric bacteriophage MS2 has been examined in clays representing terrestrial (Wyoming type montmorillonite) and Martian (Fe3+ montmorillonite) soils exposed to terrestrial and Martian environmental conditions of temperature and atmospheric composition and pressure. An important finding is that MS2 survived simulated Mars conditions better than the terrestrial environment, probably owing to stabilization of the virus caused by the cold and dry conditions of the simulated Mars environment. This finding, the first published indication that viruses may be able to survive in Mars-type soils, may have important implications for future missions to Mars.

Crater size-frequency distributions and a revised Martian relative chronology

International Nuclear Information System (INIS)

Barlow, N.G.

1988-01-01

A relative plotting technique is applied to Viking 1:2M photomosaics of 25,826 Martian craters of diameter greater than 8 km and age younger than that of the Martian surface. The size-frequency distribution curves are calculated and analyzed in detail, and the results are presented in extensive tables and maps. It is found that about 60 percent of the crater-containing lithologic units, including many small volcanoes and the ridged planes, were formed during the heavy-bombardment period (HBP), while 40 percent arose after the HBP. Wide region-to-region variation in the crater density is noted, and localized age estimates are provided. 42 references

The IceProd (IceCube Production) Framework

International Nuclear Information System (INIS)

Díaz-Vélez, J C

2014-01-01

IceProd is a data processing and management framework developed by the IceCube Neutrino Observatory for processing of Monte Carlo simulations and data. IceProd runs as a separate layer on top of middleware or cluster job schedulers and can take advantage of a variety of computing resources including grids such as EGI, OSG, and NorduGrid as well as local clusters running batch systems like HT Condor, PBS, and SGE. This is accomplished by a set of dedicated daemons which process job submission in a coordinated fashion through the use of middleware plug-ins that serve to abstract the details of job submission and job management. IceProd can also manage complex workflow DAGs across distributed computing grids in order to optimize usage of resources. We describe several aspects of IceProd's design and it's applications in collaborative computing environments. We also briefly discuss design aspects of a second generation IceProd, currently being tested in IceCube.

Ice recrystallization inhibition in ice cream as affected by ice structuring proteins from winter wheat grass.

Science.gov (United States)

Regand, A; Goff, H D

2006-01-01

Ice recrystallization in quiescently frozen sucrose solutions that contained some of the ingredients commonly found in ice cream and in ice cream manufactured under commercial conditions, with or without ice structuring proteins (ISP) from cold-acclimated winter wheat grass extract (AWWE), was assessed by bright field microscopy. In sucrose solutions, critical differences in moisture content, viscosity, ionic strength, and other properties derived from the presence of other ingredients (skim milk powder, corn syrup solids, locust bean gum) caused a reduction in ice crystal growth. Significant ISP activity in retarding ice crystal growth was observed in all solutions (44% for the most complex mix) containing 0.13% total protein from AWWE. In heat-shocked ice cream, ice recrystallization rates were significantly reduced 40 and 46% with the addition of 0.0025 and 0.0037% total protein from AWWE. The ISP activity in ice cream was not hindered by its inclusion in mix prior to pasteurization. A synergistic effect between ISP and stabilizer was observed, as ISP activity was reduced in the absence of stabilizer in ice cream formulations. A remarkably smoother texture for ice creams containing ISP after heat-shock storage was evident by sensory evaluation. The efficiency of ISP from AWWE in controlling ice crystal growth in ice cream has been demonstrated.

Strategies for Distinguishing Abiotic Chemistry from Martian Biochemistry in Samples Returned from Mars

Science.gov (United States)

Glavin, D. P.; Burton, A. S.; Callahan, M. P.; Elsila, J. E.; Stern, J. C.; Dworkin, J. P.

2012-01-01

A key goal in the search for evidence of extinct or extant life on Mars will be the identification of chemical biosignatures including complex organic molecules common to all life on Earth. These include amino acids, the monomer building blocks of proteins and enzymes, and nucleobases, which serve as the structural basis of information storage in DNA and RNA. However, many of these organic compounds can also be formed abiotically as demonstrated by their prevalence in carbonaceous meteorites [1]. Therefore, an important challenge in the search for evidence of life on Mars will be distinguishing between abiotic chemistry of either meteoritic or martian origin from any chemical biosignatures from an extinct or extant martian biota. Although current robotic missions to Mars, including the 2011 Mars Science Laboratory (MSL) and the planned 2018 ExoMars rovers, will have the analytical capability needed to identify these key classes of organic molecules if present [2,3], return of a diverse suite of martian samples to Earth would allow for much more intensive laboratory studies using a broad array of extraction protocols and state-of-theart analytical techniques for bulk and spatially resolved characterization, molecular detection, and isotopic and enantiomeric compositions that may be required for unambiguous confirmation of martian life. Here we will describe current state-of-the-art laboratory analytical techniques that have been used to characterize the abundance and distribution of amino acids and nucleobases in meteorites, Apollo samples, and comet- exposed materials returned by the Stardust mission with an emphasis on their molecular characteristics that can be used to distinguish abiotic chemistry from biochemistry as we know it. The study of organic compounds in carbonaceous meteorites is highly relevant to Mars sample return analysis, since exogenous organic matter should have accumulated in the martian regolith over the last several billion years and the

The investigation of active Martian dune fields using very high resolution photogrammetric measurements

Science.gov (United States)

Kim, Jungrack; Kim, Younghwi; Park, Minseong

2016-10-01

At the present time, arguments continue regarding the migration speeds of Martian dune fields and their correlation with atmospheric circulation. However, precisely measuring the spatial translation of Martian dunes has succeeded only a very few times—for example, in the Nili Patera study (Bridges et al. 2012) using change-detection algorithms and orbital imagery. Therefore, in this study, we developed a generic procedure to precisely measure the migration of dune fields with recently introduced 25-cm resolution orbital imagery specifically using a high-accuracy photogrammetric processor. The processor was designed to trace estimated dune migration, albeit slight, over the Martian surface by 1) the introduction of very high resolution ortho images and stereo analysis based on hierarchical geodetic control for better initial point settings; 2) positioning error removal throughout the sensor model refinement with a non-rigorous bundle block adjustment, which makes possible the co-alignment of all images in a time series; and 3) improved sub-pixel co-registration algorithms using optical flow with a refinement stage conducted on a pyramidal grid processor and a blunder classifier. Moreover, volumetric changes of Martian dunes were additionally traced by means of stereo analysis and photoclinometry. The established algorithms have been tested using high-resolution HIRISE time-series images over several Martian dune fields. Dune migrations were iteratively processed both spatially and volumetrically, and the results were integrated to be compared to the Martian climate model. Migrations over well-known crater dune fields appeared to be almost static for the considerable temporal periods and were weakly correlated with wind directions estimated by the Mars Climate Database (Millour et al. 2015). As a result, a number of measurements over dune fields in the Mars Global Dune Database (Hayward et al. 2014) covering polar areas and mid-latitude will be demonstrated

Plasma and wave properties downstream of Martian bow shock: Hybrid simulations and MAVEN observations

Science.gov (United States)

Dong, Chuanfei; Winske, Dan; Cowee, Misa; Bougher, Stephen W.; Andersson, Laila; Connerney, Jack; Epley, Jared; Ergun, Robert; McFadden, James P.; Ma, Yingjuan; Toth, Gabor; Curry, Shannon; Nagy, Andrew; Jakosky, Bruce

2015-04-01

Two-dimensional hybrid simulation codes are employed to investigate the kinetic properties of plasmas and waves downstream of the Martian bow shock. The simulations are two-dimensional in space but three dimensional in field and velocity components. Simulations show that ion cyclotron waves are generated by temperature anisotropy resulting from the reflected protons around the Martian bow shock. These proton cyclotron waves could propagate downward into the Martian ionosphere and are expected to heat the O+ layer peaked from 250 to 300 km due to the wave-particle interaction. The proton cyclotron wave heating is anticipated to be a significant source of energy into the thermosphere, which impacts atmospheric escape rates. The simulation results show that the specific dayside heating altitude depends on the Martian crustal field orientations, solar cycles and seasonal variations since both the cyclotron resonance condition and the non/sub-resonant stochastic heating threshold depend on the ambient magnetic field strength. The dayside magnetic field profiles for different crustal field orientation, solar cycle and seasonal variations are adopted from the BATS-R-US Mars multi-fluid MHD model. The simulation results, however, show that the heating of O+ via proton cyclotron wave resonant interaction is not likely in the relatively weak crustal field region, based on our simplified model. This indicates that either the drift motion resulted from the transport of ionospheric O+, or the non/sub-resonant stochastic heating mechanism are important to explain the heating of Martian O+ layer. We will investigate this further by comparing the simulation results with the available MAVEN data. These simulated ion cyclotron waves are important to explain the heating of Martian O+ layer and have significant implications for future observations.

Clean conditions for the determination of ultra-low levels of mercury in ice and snow samples

International Nuclear Information System (INIS)

Ferrari, C.P.; Moreau, A.L.; Boutron, C.F.; Univ. Joseph Fourier de Grenoble

2000-01-01

Laboratory facilities and methods are presented for the determination of ultra-low levels of mercury (Hg) in ice and snow samples originating from polar ice caps or temperate regions. Special emphasis will be given to the presentation of the clean laboratory and the cleaning procedures. The laboratory is pressurized with air filtered through high efficiency particle filters. This first filtration is not enough to get rid of contamination by Hg in air. Experiments are conducted in a clean bench, especially built for Hg analysis, equipped with both particle filter and activated charcoal filter. It allows to obtain very low levels of atmospheric Hg contamination. Ultrapure water is produced for cleaning all the plastic containers that will be used for ice and snow samples and also for the dilution of the standards. Hg content in laboratory water is about 0.08 ± 0.02 pg/g. A Teflon system has been developed for the determination of Hg in ice and snow samples based on Hg(II) reduction to Hg(0) with a SnCl 2 /HNO 3 solution followed by the measurement of gaseous Hg(0) with a Hg analyzer GARDIS 1A+ based on the Cold Vapor Atomic Absorption Spectroscopy method. Blank determination is discussed. (orig.)

The comparison of CAP88-PC version 2.0 versus CAP88-PC version 1.0

International Nuclear Information System (INIS)

Yakubovich, B.A.; Klee, K.O.; Palmer, C.R.; Spotts, P.B.

1997-12-01

40 CFR Part 61 (Subpart H of the NESHAP) requires DOE facilities to use approved sampling procedures, computer models, or other approved procedures when calculating Effective Dose Equivalent (EDE) values to members of the public. Currently version 1.0 of the approved computer model CAP88-PC is used to calculate EDE values. The DOE has upgraded the CAP88-PC software to version 2.0. This version provides simplified data entry, better printing characteristics, the use of a mouse, and other features. The DOE has developed and released version 2.0 for testing and comment. This new software is a WINDOWS based application that offers a new graphical user interface with new utilities for preparing and managing population and weather data, and several new decay chains. The program also allows the user to view results before printing. This document describes a test that confirmed CAP88-PC version 2.0 generates results comparable to the original version of the CAP88-PC program

Cap-independent translation of plant viral RNAs.

Science.gov (United States)

Kneller, Elizabeth L Pettit; Rakotondrafara, Aurélie M; Miller, W Allen

2006-07-01

The RNAs of many plant viruses lack a 5' cap and must be translated by a cap-independent mechanism. Here, we discuss the remarkably diverse cap-independent translation elements that have been identified in members of the Potyviridae, Luteoviridae, and Tombusviridae families, and genus Tobamovirus. Many other plant viruses have uncapped RNAs but their translation control elements are uncharacterized. Cap-independent translation elements of plant viruses differ strikingly from those of animal viruses: they are smaller (translation factors, and speculate on their mechanism of action and their roles in the virus replication cycle. Much remains to be learned about how these elements enable plant viruses to usurp the host translational machinery.

Characterization of a mimivirus RNA cap guanine-N2 methyltransferase.

Science.gov (United States)

Benarroch, Delphine; Qiu, Zhicheng R; Schwer, Beate; Shuman, Stewart

2009-04-01

A 2,2,7-trimethylguanosine (TMG) cap is a signature feature of eukaryal snRNAs, telomerase RNAs, and trans-spliced nematode mRNAs. TMG and 2,7-dimethylguanosine (DMG) caps are also present on mRNAs of two species of alphaviruses (positive strand RNA viruses of the Togaviridae family). It is presently not known how viral mRNAs might acquire a hypermethylated cap. Mimivirus, a giant DNA virus that infects amoeba, encodes many putative enzymes and proteins implicated in RNA transactions, including the synthesis and capping of viral mRNAs and the promotion of cap-dependent translation. Here we report the identification, purification, and characterization of a mimivirus cap-specific guanine-N2 methyltransferase (MimiTgs), a monomeric enzyme that catalyzes a single round of methyl transfer from AdoMet to an m(7)G cap substrate to form a DMG cap product. MimiTgs, is apparently unable to convert a DMG cap to a TMG cap, and is thereby distinguished from the structurally homologous yeast and human Tgs1 enzymes. Nonetheless, we show genetically that MimiTgs is a true ortholog of Saccharomyces cerevisiae Tgs1. Our results hint that DMG caps can satisfy many of the functions of TMG caps in vivo. We speculate that DMG capping of mimivirus mRNAs might favor viral protein synthesis in the infected host.

Thermal behavior and ice-table depth within the north polar erg of Mars

Science.gov (United States)

Putzig, Nathaniel E.; Mellon, Michael T.; Herkenhoff, Kenneth E.; Phillips, Roger J.; Davis, Brian J.; Ewer, Kenneth J.; Bowers, Lauren M.

2014-01-01

We fully resolve a long-standing thermal discrepancy concerning the north polar erg of Mars. Several recent studies have shown that the erg’s thermal properties are consistent with normal basaltic sand overlying shallow ground ice or ice-cemented sand. Our findings bolster that conclusion by thoroughly characterizing the thermal behavior of the erg, demonstrating that other likely forms of physical heterogeneity play only a minor role, and obviating the need to invoke exotic materials. Thermal inertia as calculated from orbital temperature observations of the dunes has previously been found to be more consistent with dust-sized materials than with sand. Since theory and laboratory data show that dunes will only form out of sand-sized particles, exotic sand-sized agglomerations of dust have been invoked to explain the low values of thermal inertia. However, the polar dunes exhibit the same darker appearance and color as that of dunes found elsewhere on the planet that have thermal inertia consistent with normal sand-sized basaltic grains, whereas Martian dust deposits are generally lighter and redder. The alternative explanation for the discrepancy as a thermal effect of a shallow ice table is supported by our analysis of observations from the Mars Global Surveyor Thermal Emission Spectrometer and the Mars Odyssey Thermal Emission Imaging System and by forward modeling of physical heterogeneity. In addition, our results exclude a uniform composition of dark dust-sized materials, and they show that the thermal effects of the dune slopes and bright interdune materials evident in high-resolution images cannot account for the erg’s thermal behavior.

Thermal behavior and ice-table depth within the north polar erg of Mars

Science.gov (United States)

Putzig, Nathaniel E.; Mellon, Michael T.; Herkenhoff, Kenneth E.; Phillips, Roger J.; Davis, Brian J.; Ewer, Kenneth J.; Bowers, Lauren M.

2014-02-01

We fully resolve a long-standing thermal discrepancy concerning the north polar erg of Mars. Several recent studies have shown that the erg's thermal properties are consistent with normal basaltic sand overlying shallow ground ice or ice-cemented sand. Our findings bolster that conclusion by thoroughly characterizing the thermal behavior of the erg, demonstrating that other likely forms of physical heterogeneity play only a minor role, and obviating the need to invoke exotic materials. Thermal inertia as calculated from orbital temperature observations of the dunes has previously been found to be more consistent with dust-sized materials than with sand. Since theory and laboratory data show that dunes will only form out of sand-sized particles, exotic sand-sized agglomerations of dust have been invoked to explain the low values of thermal inertia. However, the polar dunes exhibit the same darker appearance and color as that of dunes found elsewhere on the planet that have thermal inertia consistent with normal sand-sized basaltic grains, whereas Martian dust deposits are generally lighter and redder. The alternative explanation for the discrepancy as a thermal effect of a shallow ice table is supported by our analysis of observations from the Mars Global Surveyor Thermal Emission Spectrometer and the Mars Odyssey Thermal Emission Imaging System and by forward modeling of physical heterogeneity. In addition, our results exclude a uniform composition of dark dust-sized materials, and they show that the thermal effects of the dune slopes and bright interdune materials evident in high-resolution images cannot account for the erg's thermal behavior.

Death cap

DEFF Research Database (Denmark)

Rudbæk, Torsten R; Kofoed, Pernille Bouteloup; Bove, Jeppe

2014-01-01

Death cap (Amanita phalloides) is commonly found and is one of the five most toxic fungi in Denmark. Toxicity is due to amatoxin, and poisoning is a serious medical condition, causing organ failure with potential fatal outcome. Acknowledgement and clarification of exposure, symptomatic and focused...

Martian crustal dichotomy: product of accretion and not a specific event?

International Nuclear Information System (INIS)

Frey, H.; Schultz, R.A.; Maxwell, T.A.

1987-01-01

Attempts to explain the fundamental crustal dichotomy on Mars range from purely endogenic to extreme exogenic processes, but to date no satisfactory theory has evolved. What is accepted is: (1) the dichotomy is an ancient feature of the Martian crust, and (2) the boundary between the cratered highlands and northern plains which marks the dichotomy in parts of Mars has undergone significant and variable modification during the observable parts of Martian history. Some ascribe it to a single mega-impact event, essentially an instantaneous rearrangement of the crustal structures (topography and lithospheric thickness). Others prefer an internal mechanism: a period of vigorous convection subcrustally erodes the northern one third of Mars, causing foundering and isostatic lowering of that part of Mars. The evidence for each theory is reviewed, with the conclusion that there is little to recommend either. An alternative is suggested: the formation of the crustal dichotomy on Mars was not a specific tectonic event but a byproduct of the accretionary process and therefore a primordial characteristic of the Martian crust, predating the oldest recognizable landforms

Orbital evolution and origin of the Martian satellites

International Nuclear Information System (INIS)

Szeto, A.M.K.

1983-01-01

The orbital evolution of the Martian satellites is considered from a dynamical point of view. Celestial mechanics relevant to the calculation of satellite orbital evolution is introduced and the physical parameters to be incorporated in the modeling of tidal dissipation are discussed. Results of extrapolating the satellite orbits backward and forward in time are presented and compared with those of other published work. Collision probability calculations and results for the Martian satellite system are presented and discussed. The implications of these calculations for the origin scenarios of the satellites are assessed. It is concluded that Deimos in its present form could not have been captured, for if it had been, it would have collided with Phobos at some point. An accretion model is therefore preferred over capture, although such a model consistent with the likely carbonaceous chondritic composition of the satellites has yet to be established. 91 references

Alteration of the Carbon and Nitrogen Isotopic Composition in the Martian Surface Rocks Due to Cosmic Ray Exposure

Science.gov (United States)

Pavlov, A. A.; Pavlov, A. K.; Ostryakov, V. M.; Vasilyev, G. I.; Mahaffy, P.; Steele, A.

2014-01-01

C-13/C-12 and N-15/N-14 isotopic ratios are pivotal for our understanding of the Martian carbon cycle, history of the Martian atmospheric escape, and origin of the organic compounds on Mars. Here we demonstrate that the carbon and nitrogen isotopic composition of the surface rocks on Mars can be significantly altered by the continuous exposure of Martian surface to cosmic rays. Cosmic rays can effectively produce C-13 and N-15 isotopes via spallation nuclear reactions on oxygen atoms in various Martian rocks. We calculate that in the top meter of the Martian rocks, the rates of production of both C-13 and N-15 due to galactic cosmic rays (GCRs) exposure can vary within 1.5-6 atoms/cm3/s depending on rocks' depth and chemical composition. We also find that the average solar cosmic rays can produce carbon and nitrogen isotopes at a rate comparable to GCRs in the top 5-10 cm of the Martian rocks. We demonstrate that if the total carbon content in a surface Martian rock is <10 ppm, then the "light," potentially "biological" C-13/C-12 ratio would be effectively erased by cosmic rays over 3.5 billion years of exposure. We found that for the rocks with relatively short exposure ages (e.g., 100 million years), cosmogenic changes in N-15/N-14 ratio are still very significant. We also show that a short exposure to cosmic rays of Allan Hills 84001 while on Mars can explain its high-temperature heavy nitrogen isotopic composition (N-15/N-14). Applications to Martian meteorites and the current Mars Science Laboratory mission are discussed.

Enhancement of device performance by using quaternary capping over ternary capping in strain-coupled InAs/GaAs quantum dot infrared photodetectors

International Nuclear Information System (INIS)

Tongbram, B.; Shetty, S.; Ghadi, H.; Adhikary, S.; Chakrabarti, S.

2015-01-01

We investigate and compare the performance of 30 layers strain-coupled quantum dot (SCQD) infrared photodetectors capped with one of two different layers: a quaternary (In 0.21 Al 0.21 Ga 0.58 As) or ternary (In 0.15 Ga 0.85 As) alloy of 30 Aa and a GaAs layer with a thickness of 120-150 Aa. Measurements of optical properties, spectral responsivity, and cross-sectional transmission electron microscopy were conducted. Results showed that quaternary capping yielded more superior multilayer QD infrared photodetectors than ternary capping. Quaternary capping resulted in enhanced dot size, order, and uniformity of the QD array. The presence of Al in the capped layer helped in the reduction in dark current density and spectral linewidth as well as led to higher electron confinement of the QDs and enhanced device detectivity. The vertically ordered SCQD system with quaternary capping exhibited higher peak detectivity (∝10 10 cm Hz 1/2 /W) than that with ternary capping (∝10 7 cm Hz 1/2 /W). In addition, a very low noise current density of ∝10 -16 A/cm 2 Hz 1/2 at 77 K was achieved with quaternary-capped QDs. (orig.)

Plasma Extraction of Oxygen from Martian Atmosphere, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Plasma techniques are proposed for the extraction of oxygen from the abundant carbon dioxide contained in the Martian atmosphere (96 % CO2). In this process, CO2 is...

Saltation under Martian gravity and its influence on the global dust distribution

Science.gov (United States)

Musiolik, Grzegorz; Kruss, Maximilian; Demirci, Tunahan; Schrinski, Björn; Teiser, Jens; Daerden, Frank; Smith, Michael D.; Neary, Lori; Wurm, Gerhard

2018-05-01

Dust and sand motion are a common sight on Mars. Understanding the interaction of atmosphere and Martian soil is fundamental to describe the planet's weather, climate and surface morphology. We set up a wind tunnel to study the lift of a mixture between very fine sand and dust in a Mars simulant soil. The experiments were carried out under Martian gravity in a parabolic flight. The reduced gravity was provided by a centrifuge under external microgravity. The onset of saltation was measured for a fluid threshold shear velocity of 0.82 ± 0.04 m/s. This is considerably lower than found under Earth gravity. In addition to a reduction in weight, this low threshold can be attributed to gravity dependent cohesive forces within the sand bed, which drop by 2/3 under Martian gravity. The new threshold for saltation leads to a simulation of the annual dust cycle with a Mars GCM that is in agreement with observations.

Apical cap

International Nuclear Information System (INIS)

McLoud, T.C.; Isler, R.J.; Novelline, R.A.; Putman, C.E.; Simeone, J.; Stark, P.

1981-01-01

Apical caps, either unilateral or bilateral, are a common feature of advancing age and are usually the result of subpleural scarring unassociated with other diseases. Pancoast (superior sulcus) tumors are a well recognized cause of unilateral asymmetric apical density. Other lesions arising in the lung, pleura, or extrapleural space may produce unilateral or bilateral apical caps. These include: (1) inflammatory: tuberculosis and extrapleural abscesses extending from the neck; (2) post radiation fibrosis after mantle therapy for Hodgkin disease or supraclavicular radiation in the treatment of breast carcinoma; (3) neoplasm: lymphoma extending from the neck or mediastinum, superior sulcus bronchogenic carcinoma, and metastases; (4) traumatic: extrapleural dissection of blood from a ruptured aorta, fractures of the ribs or spine, or hemorrhage due to subclavian line placement; (5) vascular: coarctation of the aorta with dilated collaterals over the apex, fistula between the subclavian artery and vein; and (6) miscellaneous: mediastinal lipomatosis with subcostal fat extending over the apices

A nucleation theory of cell surface capping

International Nuclear Information System (INIS)

Coutsias, E.A.; Wester, M.J.; Perelson, A.S.

1997-01-01

We propose a new theory of cell surface capping based on the principles of nucleation. When antibody interacts with cell surface molecules, the molecules initially form small aggregates called patches that later coalesce into a large aggregate called a cap. While a cap can form by patches being pulled together by action of the cell''s cytoskeleton, in the case of some molecules, disruption of the cytoskeleton does not prevent cap formation. Diffusion of large aggregates on a cell surface is slow, and thus we propose that a cap can form solely through the diffusion of small aggregates containing just one or a few cell surface molecules. Here we consider the extreme case in which single molecules are mobile, but aggregates of all larger sizes are immobile. We show that a set of patches in equilibrium with a open-quotes seaclose quotes of free cell surface molecules can undergo a nucleation-type phase transition in which the largest patch will bind free cell surface molecules, deplete the concentration of such molecules in the open-quotes seaclose quotes and thus cause the other patches to shrink in size. We therefore show that a cap can form without patches having to move, collide with each other, and aggregate

Perturbation and melting of snow and ice by the 13 November 1985 eruption of Nevado del Ruiz, Colombia, and consequent mobilization, flow and deposition of lahars

Science.gov (United States)

Pierson, T.C.; Janda, R.J.; Thouret, J.-C.; Borrero, C.A.

1990-01-01

A complex sequence of pyroclastic flows and surges erupted by Nevado del Ruiz volcano on 13 November 1985 interacted with snow and ice on the summit ice cap to trigger catastrophic lahars (volcanic debris flows), which killed more than 23,000 people living at or beyond the base of the volcano. The rapid transfer of heat from the hot eruptive products to about 10 km2 of the snowpack, combined with seismic shaking, produced large volumes of meltwater that flowed downslope, liquefied some of the new volcanic deposits, and generated avalanches of saturated snow, ice and rock debris within minutes of the 21:08 (local time) eruption. About 2 ?? 107 m3 of water was discharged into the upper reaches of the Molinos, Nereidas, Guali, Azufrado and Lagunillas valleys, where rapid entrainment of valley-fill sediment transformed the dilute flows and avalanches to debris flows. Computed mean velocities of the lahars at peak flow ranged up to 17 m s-1. Flows were rapid in the steep, narrow upper canyons and slowed with distance away from the volcano as flow depth and channel slope diminished. Computed peak discharges ranged up to 48,000 m3 s-1 and were greatest in reaches 10 to 20 km downstream from the summit. A total of about 9 ?? 107 m3 of lahar slurry was transported to depositional areas up to 104 km from the source area. Initial volumes of individual lahars increased up to 4 times with distance away from the summit. The sedimentology and stratigraphy of the lahar deposits provide compelling evidence that: (1) multiple initial meltwater pulses tended to coalesce into single flood waves; (2) lahars remained fully developed debris flows until they reached confluences with major rivers; and (3) debris-flow slurry composition and rheology varied to produce gradationally density-stratified flows. Key lessons and reminders from the 1985 Nevado del Ruiz volcanic eruption are: (1) catastrophic lahars can be generated on ice- and snow-capped volcanoes by relatively small eruptions; (2

47 CFR 61.41 - Price cap requirements generally.

Science.gov (United States)

2010-10-01

... 47 Telecommunication 3 2010-10-01 2010-10-01 false Price cap requirements generally. 61.41 Section... (CONTINUED) TARIFFS General Rules for Dominant Carriers § 61.41 Price cap requirements generally. (a... companies shall not bar a carrier from electing price cap regulation provided the carrier is otherwise...

Late Holocene spatio-temporal variability of the south Greenland Ice Sheet and adjacent mountain glaciers

Science.gov (United States)

Sinclair, G.; Carlson, A. E.; Rood, D. H.; Axford, Y.

2017-12-01

The late Holocene, with its spatially complex pattern of centennial-scale climate variation, is an ideal time period to test the response of the cryosphere to atmospheric and oceanic temperature changes. The south Greenland Ice Sheet (sGrIS), with its proximity to areas of North Atlantic Deep Water formation and a large spectrum of glaciological regimes over a relatively small area, provides an excellent location to examine the spatial heterogeneity of ice-sheet and glacier responses to climate change. Here, we will present 50 Be-10 surface exposure ages from eight moraines in six locations around the margin of the sGrIS. These moraines are located just outboard of historical moraines, and will therefore allow us to constrain the timing of the most extensive prehistoric late-Holocene advance and retreat of ice margins draining the sGrIS and independent valley glaciers. The dataset includes both marine- and land-terminating glaciers draining the sGrIS, the low-altitude Qassimiut lobe, the high-altitude alpine Julianhåb ice cap and isolated valley glaciers. This diverse dataset will allow us to determine to what extent late-Holocene centennial-scale behavior of the ice-sheet and glacier margins were synchronous, perhaps in response to an external climate forcing, or more stochastic, governed instead by local factors such as basal thermal regime, bedrock topography, or microclimates. This has implications for understanding the forcings and responses of cryospheric changes at timescales relevant to human society. In addition to providing context for paleoclimatic and glacial geologic investigations, this work will inform future sea-level projections by providing targets for validating high-resolution ice-sheet and glacier models.

Using ice melting and ice rolling technologies to remove ice from sub-transmission and transmission lines at Manitoba Hydro

International Nuclear Information System (INIS)

Farias, A. R.

1999-01-01

Development of an of an Ice Storm Management program by Manitoba Hydro to reduce ice storm damage to its 8 kV feeders to 115 kV transmission lines, is discussed. The program consists of the de-icing of overhead lines, either by ice melting, or ice rolling. Ice melting involves the placement of a three-phase short at a calculated point. The term ice rolling denotes a process of mechanically stripping the ice from conductors. The most recent major ice storm experienced by Manitoba Hydro was in the winter of 1997/1998. During the period from February 6 to February 17, 1998, a total of 83 'ice melt' procedures were performed to melt the ice from 2,628 km of overhead line (7,883 km of conductor), in addition to 'ice rolling'. This paper describes Manitoba Hydro's 25-years' experience with ice melting and it also describes the advantages and disadvantages of both ice melting and ice rolling. Although not a panacea to combat the effects of ice storms, ice melting was found to be the most effective way of removing ice from overhead transmission and sub-transmission lines. Ice rolling was also found to be effective. Other tools that have been found to be useful by various utilities in combating ice storm damage include improved structure and line design, system design that provide more redundancies and emergency sources, and standby generators at critical load points