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Sample records for accumulation rates mars

  1. Have graben wall scarps accumulated sand and dust on Mars?

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Davis, P. A.

    1991-01-01

    Grabens are linear fault bounded troughs that are extremely abundant on Mars (about 7000 cover the Western Hemisphere). Analysis of lunar and Martian grabens as well as analogous structures on Earth indicates that grabens form under extension when the crust is pulled apart. On Mars, topographic maps are not of sufficient resolution to measure graben wall slopes. Seismic shaking on Mars might be capable of reducing 60 deg fault scarps to an angle of repose. Some other process must be responsible for further reducing graben wall slopes. If the deposition of sand and dust along graben walls is responsible for their extremely low slopes, then a variety of implications are possible. Sand and/or dust movement and deposition is ubiquitous in grabens over most of Mars, as similar looking grabens are found over the entire Western Hemisphere and this requires a plentiful supply of sand or dust. If the material that accumulates is of low density and cohesion, attempts to traverse graben walls might be difficult. Rimless shallow depressions could be more effective sinks for sand and dust on Mars than has been realized.

  2. Deposition rates of oxidized iron on Mars

    NASA Technical Reports Server (NTRS)

    Burns, R. G.

    1993-01-01

    The reddened oxidized surface of Mars is indicative of temporal interactions between the Martian atmosphere and its surface. During the evolution of the Martian regolith, primary ferromagnesian silicate and sulfide minerals in basaltic rocks apparently have been oxidized to secondary ferric-bearing assemblages. To evaluate how and when such oxidized deposits were formed on Mars, information about the mechanisms and rates of chemical weathering of Fe(2+)-bearing minerals has been determined. In this paper, mechanisms and rates of deposition of ferric oxide phases on the Martian surface are discussed.

  3. Evaporation Rates of Brine on Mars

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    While Mars is now largely a dry and barren place, recent data have indicated that water has flowed at specific locations within the last approx. 10(exp 6) y. This had led to a resurgence of interest in theoretical and experimental work aimed at understanding the behavior of water on Mars. There are several means whereby the stability of liquid water on Mars could be increased, one being the presence solutes that would depress the freezing point. Salt water on Earth is about 0.5M NaCl, but laboratory experiments suggest that martian salt water is quite different. We recently began a program of laboratory measurements of the stability of liquid water, ice and ice-dust mixtures under martian conditions and here report measurements of the evaporation rate of 0.25M brine.

  4. Annual Greenland accumulation rates (2009-2012) from airborne Snow Radar

    NASA Astrophysics Data System (ADS)

    Koenig, L. S.; Ivanoff, A.; Alexander, P. M.; MacGregor, J. A.; Fettweis, X.; Panzer, B.; Paden, J. D.; Forster, R. R.; Das, I.; McConnell, J.; Tedesco, M.; Leuschen, C.; Gogineni, P.

    2015-12-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet (GrIS) through increasing surface melt, emphasizing the need to closely monitor surface mass balance (SMB) in order to improve sea-level rise predictions. Here, we quantify accumulation rates, the largest component of GrIS SMB, at a higher spatial resolution than currently available, using Snow Radar stratigraphy. We use a semi-automated method to derive annual-net accumulation rates from airborne Snow Radar data collected by NASA's Operation IceBridge from 2009 to 2012. An initial comparison of the accumulation rates from the Snow Radar and the outputs of a regional climate model (MAR) shows that, in general, the radar-derived accumulation matches closely with MAR in the interior of the ice sheet but MAR estimates are high over the southeast GrIS. Comparing the radar-derived accumulation with contemporaneous ice cores reveals that the radar captures the annual and long-term mean. The radar-derived accumulation rates resolve large-scale patterns across the GrIS with uncertainties of up to 11 %, attributed mostly to uncertainty in the snow/firn density profile.

  5. Accumulation and erosion of Mars' south polar layered deposits.

    PubMed

    Seu, Roberto; Phillips, Roger J; Alberti, Giovanni; Biccari, Daniela; Bonaventura, Francesco; Bortone, Marco; Calabrese, Diego; Campbell, Bruce A; Cartacci, Marco; Carter, Lynn M; Catallo, Claudio; Croce, Anna; Croci, Renato; Cutigni, Marco; Di Placido, Antonio; Dinardo, Salvatore; Federico, Costanzo; Flamini, Enrico; Fois, Franco; Frigeri, Alessandro; Fuga, Oreste; Giacomoni, Emanuele; Gim, Yonggyu; Guelfi, Mauro; Holt, John W; Kofman, Wlodek; Leuschen, Carlton J; Marinangeli, Lucia; Marras, Paolo; Masdea, Arturo; Mattei, Stefania; Mecozzi, Riccardo; Milkovich, Sarah M; Morlupi, Antonio; Mouginot, Jérémie; Orosei, Roberto; Papa, Claudio; Paternò, Tobia; Persi del Marmo, Paolo; Pettinelli, Elena; Pica, Giulia; Picardi, Giovanni; Plaut, Jeffrey J; Provenziani, Marco; Putzig, Nathaniel E; Russo, Federica; Safaeinili, Ali; Salzillo, Giuseppe; Santovito, Maria Rosaria; Smrekar, Suzanne E; Tattarletti, Barbara; Vicari, Danilo

    2007-09-21

    Mars' polar regions are covered with ice-rich layered deposits that potentially contain a record of climate variations. The sounding radar SHARAD on the Mars Reconnaissance Orbiter mapped detailed subsurface stratigraphy in the Promethei Lingula region of the south polar plateau, Planum Australe. Radar reflections interpreted as layers are correlated across adjacent orbits and are continuous for up to 150 kilometers along spacecraft orbital tracks. The reflectors are often separated into discrete reflector sequences, and strong echoes are seen as deep as 1 kilometer. In some cases, the sequences are dipping with respect to each other, suggesting an interdepositional period of erosion. In Australe Sulci, layers are exhumed, indicating recent erosion. PMID:17885128

  6. Climate Change on Mars Inferred from Erosion Rates at the Mars Pathfinder Landing Site

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Bridges, N. T.

    1999-01-01

    The observation that the Mars Pathfinder landing site probably looks very similar to when it was deposited by catastrophic floods some 1.8-3.5 Ga allows quantitative constraints to be placed on the rate of change at the landing site since that time. When combined with interpretations of data recently returned by the Mars Pathfinder and Global Surveyor missions and perspectives drawn from 20 years of analysis and interpretation of Viking data, these observations and inferences suggest an early warmer and wetter environment with vastly different erosion rates and a major climatic change on Mars. Additional information is contained in the original extended abstract.

  7. Annual Greenland accumulation rates (2009-2012) from airborne snow radar

    NASA Astrophysics Data System (ADS)

    Koenig, Lora S.; Ivanoff, Alvaro; Alexander, Patrick M.; MacGregor, Joseph A.; Fettweis, Xavier; Panzer, Ben; Paden, John D.; Forster, Richard R.; Das, Indrani; McConnell, Joesph R.; Tedesco, Marco; Leuschen, Carl; Gogineni, Prasad

    2016-08-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2-6.5 GHz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semiautomated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009-2012. The uncertainty in these radar-derived accumulation rates is on average 14 %. A comparison of the radar-derived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and long-term mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

  8. Annual Greenland Accumulation Rates (2009-2012) from Airborne Snow Radar

    NASA Technical Reports Server (NTRS)

    Koenig, Lora S.; Ivanoff, Alvaro; Alexander, Patrick M.; MacGregor, Joseph A.; Fettweis, Xavier; Panzer, Ben; Paden, John D.; Forster, Richard R.; Das, Indrani; McConnell, Joseph R.; Tedesco, Marco; Leuschen, Carl; Gogineni, Prasad

    2016-01-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2-6.5 gigahertz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semi-automated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009-2012. The uncertainty in these radar-derived accumulation rates is on average 14 percent. A comparison of the radarderived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and longterm mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR - Modele Atmospherique Regional for Greenland and vicinity) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

  9. Exploring PV on the Red Planet: Mars Array Technology Experiment and Dust Accumulation and Removal Technology

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Baraona, Cosmo; Brinker, David; Schelman, David

    2004-01-01

    The environment on the surface of Mars is different in several critical ways from the orbital environment in which space solar arrays normally operate. Some important differences are: 1) Low intensity, low temperature operation; 2) Spectrum modified by atmospheric dust, varies with time; 3) Indirect sunlight; 4) Possibility of dust atoms at some times of year; 5) Deposited dust; 6) Wind; 7) Peroxide-rich reactive soil. We are developing two experiments to test operation of solar arrays on the surface of Mars, to be flown on the 2001 Surveyor Lander mission. The Mars Array Technology Experiment (MATE) will test the operation of several types of solar cells under Mars conditions, and determine the direct and scattered solar spectrum at the surface. The Dust Accumulation and Removal Technology (DART) experiment will monitor the amount of dust deposition on a target solar cell, measure the characteristics of the dust, and test the feasibility of dust removal.

  10. Dust Accumulation and Solar Panel Array Performance on the Mars Exploration Rover (MER) Project

    NASA Technical Reports Server (NTRS)

    Turgay, Eren H.

    2004-01-01

    One of the most fundamental design considerations for any space vehicle is its power supply system. Many options exist, including batteries, fuel cells, nuclear reactors, radioisotopic thermal generators (RTGs), and solar panel arrays. Solar arrays have many advantages over other types of power generation. They are lightweight and relatively inexpensive, allowing more mass and funding to be allocated for other important devices, such as scientific instruments. For Mars applications, solar power is an excellent option, especially for long missions. One might think that dust storms would be a problem; however, while dust blocks some solar energy, it also scatters it, making it diffuse rather than beamed. Solar cells are still able to capture this diffuse energy and convert it into substantial electrical power. For these reasons, solar power was chosen to be used on the 1997 Mars Pathfinder mission. The success of this mission set a precedent, as NASA engineers have selected solar power as the energy system of choice for all future Mars missions, including the Mars Exploration Rover (MER) Project. Solar sells have their drawbacks, however. They are difficult to manufacture and are relatively fragile. In addition, solar cells are highly sensitive to different parts of the solar spectrum, and finding the correct balance is crucial to the success of space missions. Another drawback is that the power generated is not a constant with respect to time, but rather changes with the relative angle to the sun. On Mars, dust accumulation also becomes a factor. Over time, dust settles out of the atmosphere and onto solar panels. This dust blocks and shifts the frequency of the incoming light, degrading solar cell performance. My goal is to analyze solar panel telemetry data from the two MERs (Spirit and Opportunity) in an effort to accurately model the effect of dust accumulation on solar panels. This is no easy process due to the large number of factors involved. Changing solar

  11. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2002-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the areally Integrated snow accumulation and the net ice discharge of the ice sheet. Uncertainties in this calculation Include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken from isolated spots across the ice sheet. The sparse data associated with ice cores juxtaposed against the high spatial and temporal resolution provided by remote sensing , has motivated scientists to investigate relationships between accumulation rate and microwave observations as an option for obtaining spatially contiguous estimates. The objective of this PARCA continuation proposal was to complete an estimate of surface accumulation rate on the Greenland Ice Sheet derived from C-band radar backscatter data compiled in the ERS-1 SAR mosaic of data acquired during, September-November, 1992. An empirical equation, based on elevation and latitude, is used to determine the mean annual temperature. We examine the influence of accumulation rate, and mean annual temperature on C-band radar backscatter using a forward model, which incorporates snow metamorphosis and radar backscatter components. Our model is run over a range of accumulation and temperature conditions. Based on the model results, we generate a look-up table, which uniquely maps the measured radar backscatter, and mean annual temperature to accumulation rate. Our results compare favorably with in situ accumulation rate measurements falling within our study area.

  12. Rates of oxidative weathering on the surface of Mars

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.

    1992-01-01

    Implicit in the mnemonic 'MSATT' (Mars surface and atmosphere through time) is that rates of surface processes on Mars through time should be investigated, including studies of the kinetics and mechanism of oxidative weathering reactions occurring in the Martian regolith. Such measurements are described. Two major elements analyzed in the Viking Lander XRF experiment that are most vulnerable to atmospheric oxidation are iron and sulfur. Originally, they occurred as Fe(2+)-bearing silicate and sulfide minerals in basaltic rocks on the surface of Mars. However, chemical weathering reactions through time have produced ferric- and sulfate-bearing assemblages now visible in the Martian regolith. Such observations raise several question about: (1) when the oxidative weathering reactions took place on Mars; (2) whether or not the oxidized regolith is a fossilized remnant of past weathering processes; (3) deducting chemical interactions of the ancient Martian atmosphere with its surface from surviving phases; (4) possible weathering reactions still occurring in the frozen regolith; and (5) the kinetics and mechanism of past and present-day oxidative reactions on Mars. These questions may be addressed experimentally by studying reaction rates of dissolution and oxidation of basaltic minerals, and by identifying reaction products forming on the mineral surfaces. Results for the oxidation of pyrrhotite and dissolved ferrous iron are reported.

  13. Enhanced erosion rates on Mars during Amazonian glaciation

    NASA Astrophysics Data System (ADS)

    Levy, Joseph S.; Fassett, Caleb I.; Head, James W.

    2016-01-01

    Observations of Mars from the surface and from orbit suggest that erosion rates over the last ∼3 Gyr (the Amazonian) have been as slow as 10-5 m/Myr and have been dominated by aeolian processes, while ancient (Noachian) erosion rates may have been orders of magnitude higher due to impact bombardment and fluvial activity. Amazonian-aged glacial deposits are widespread on Mars, but rates of erosion responsible for contributing debris to these remnant glacial deposits have not been constrained. Here, we calculate erosion rates during Amazonian glaciations using a catalog of mid-latitude glacial landforms coupled with observational and theoretical constraints on the duration of glaciation. These calculations suggest that erosion rates for scarps that contributed debris to glacial landforms are 4-7 orders of magnitude higher than average Amazonian rates in non-glaciated, low-slope regions. These erosion rates are similar to terrestrial cold-based glacier erosion and entrainment rates, consistent with cold-based glacier modification of parts of Mars.

  14. Unprecedented last-glacial mass accumulation rates determined by luminescence dating of loess from western Nebraska

    USGS Publications Warehouse

    Roberts, H.M.; Muhs, D.R.; Wintle, A.G.; Duller, G.A.T.; Bettis, E. Arthur, III

    2003-01-01

    A high-resolution chronology for Peoria (last glacial period) Loess from three sites in Nebraska, midcontinental North America, is determined by applying optically stimulated luminescence (OSL) dating to 35-50 ??m quartz. At Bignell Hill, Nebraska, an OSL age of 25,000 yr near the contact of Peoria Loess with the underlying Gilman Canyon Formation shows that dust accumulation occurred early during the last glacial maximum (LGM), whereas at Devil's Den and Eustis, Nebraska, basal OSL ages are significantly younger (18,000 and 21,000 yr, respectively). At all three localities, dust accumulation ended at some time after 14,000 yr ago. Mass accumulation rates (MARs) for western Nebraska, calculated using the OSL ages, are extremely high from 18,000 to 14,000 yr-much higher than those calculated for any other pre-Holocene location worldwide. These unprecedented MARs coincide with the timing of a mismatch between paleoenvironmental evidence from central North America, and the paleoclimate simulations from atmospheric global circulation models (AGCMs). We infer that the high atmospheric dust loading implied by these MARs may have played an important role, through radiative forcing, in maintaining a colder-than-present climate over central North America for several thousand years after summer insolation exceeded present-day values. ?? 2003 Elsevier Science (USA). All rights reserved.

  15. Assessing hydrodynamic effects on jarosite dissolution rates, reaction products, and preservation on Mars

    NASA Astrophysics Data System (ADS)

    Dixon, Emily M.; Elwood Madden, Andrew S.; Hausrath, Elisabeth M.; Elwood Madden, Megan E.

    2015-04-01

    Jarosite flow-through dissolution experiments were conducted in ultrapure water (UPW), pH 2 sulfuric acid, and saturated NaCl and CaCl2 brines at 295-298 K to investigate how hydrologic variables may affect jarosite preservation and reaction products on Mars. K+-based dissolution rates in flowing UPW did not vary significantly with flow rate, indicating that mineral surface reactions control dissolution rates over the range of flow rates investigated. In all of the solutions tested, hydrologic variables do not significantly affect extent of jarosite alteration; therefore, jarosite is equally likely to be preserved in flowing or stagnant waters on Mars. However, increasing flow rate did affect the mineralogy and accumulation of secondary reaction products. Iron release rates in dilute solutions increased as the flow rate increased, likely due to nanoscale iron (hydr)oxide transport in flowing water. Anhydrite formed in CaCl2 brine flow-through experiments despite low temperatures, while metastable gypsum and bassanite were observed in batch experiments. Therefore, observations of the hydration state of calcium sulfate minerals on Mars may provide clues to unravel past salinity and hydrologic conditions as well as temperatures and vapor pressures.

  16. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2001-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the snow accumulation and the ice discharge of the ice sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken throughout the ice sheet. The sparse data associated with ice cores, coupled with the high spatial and temporal resolution provided by remote sensing, have motivated scientists to investigate relationships between accumulation rate and microwave observations.

  17. MAVEN Measurements of the Ion Escape Rate from Mars

    NASA Astrophysics Data System (ADS)

    Brain, Dave; Dong, Yaxue; Fortier, Kier; Fang, Xiaohua; McFadden, James; Halekas, Jasper; Connerney, Jack; Eparvier, Frank; Dong, Chuanfei; Bougher, Stephen; Ma, Yingjuan; Modolo, Ronan; Lillis, Rob; Luhmann, Janet; Curry, Shannon; Seki, Kanako; Jakosky, Bruce

    2015-04-01

    The loss of atmospheric particles (neutral atoms, neutral molecules, ions) to space is thought to have played a role in the evolution of Martian climate over the past ~4 billion years. Due to the lack of a global magnetic field on Mars, the solar wind has direct access to the upper layers of the Martian atmosphere, and can drive non-thermal escape of charged particles (ions) from the atmosphere. Two spacecraft (Phobos 2 and Mars Express) have previously measured escaping ions at Mars. The recently arrived MAVEN spacecraft is equipped with instruments to measure escaping ions with high time cadence and high energy and mass resolution, as well as instruments to provide contextual information about what controls the variation in escape rates. We report on the total escape rate of heavy planetary ions from the Martian atmosphere measured by MAVEN. Heavy ions are identified in data from the SupraThermal And Thermal Ion Composition (STATIC) instrument. Rudimentary estimates of ion escape rate are obtained by summing the measured ion fluxes over a surface downstream from Mars with respect to the solar wind flow. This estimate can then be refined to account for the limited field of view of the instrument (investigation of measured particle distributions) and the limited spatial coverage of the spacecraft orbit trajectory. Variability in measured escape rates can also be grouped according to upstream conditions and the orientation of Mars (and its crustal magnetic fields) with respect to the solar wind. Important upstream drivers include the solar Extreme Ultraviolet (EUV) flux, solar wind pressure, and the interplanetary magnetic field strength and direction. These drivers are measured directly by MAVEN's EUV, SWIA, and MAG instruments. We will provide an initial estimate of ion escape rates based on the first several months of MAVEN data. We will then report on progress to refine these estimates to correct for instrument field of view and spacecraft coverage effects, as

  18. Ages and Accumulation Rates of the Martian Polar Layered Deposits Estimated from Orbital Tuning

    NASA Astrophysics Data System (ADS)

    Sori, M.; Bailey, E. A.; Perron, J.; Huybers, P. J.; Aharonson, O.; Limaye, A.

    2013-12-01

    Layers of dusty water ice in the polar caps of Mars have been hypothesized to record climate changes driven by variation of the planet's orbit and spin axis, but the time interval over which the polar layered deposits (PLDs) formed is unknown, and an orbital influence has not been conclusively demonstrated. We performed orbital tuning of reconstructed PLD stratigraphic sequences in an attempt to constrain the accumulation interval and test for the presence of an orbital signal. Our procedure uses dynamic time warping (DTW) to search for a match between two time series - the polar insolation history and brightness or topographic information in the PLDs - and then assesses the significance of potential matches using a Monte Carlo procedure. We selected 30 images of the northern PLDs from the Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor spacecraft and used Mars Orbiter Laser Altimeter profiles to transform each image into a record of image brightness as a function of vertical depth. To constrain the PLD age and accumulation rate, we tuned each image record to Martian insolation records for varying time intervals. If a particular insolation interval produced the strongest match to an image, and if the match became weaker as the image was tuned to progressively longer or shorter intervals, we chose the best-fitting interval as an estimated accumulation time for that PLD sequence, and used the depth range to estimate a corresponding PLD accumulation rate. We also tuned the insolation records to synthetic records containing no orbital influence to test whether the image matches were spurious. Of the 30 MOC images analyzed, 16 produce insolation intervals that we consider strong matches. These images yield an average deposition rate of 0.5 × 0.2 mm/yr for the northern PLDs. The images represent only a fraction of the entire stratigraphy; extrapolating that deposition rate farther back in time yields an age of ~4 Ma for the entire PLD sequence present in the

  19. Rates of oxidative weathering on the surface of Mars

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.; Fisher, Duncan S.

    1993-01-01

    A model of acid weathering is proposed for the iron-rich basalts on Mars. Aqueous oxidation of iron sulfides released SO4(2-) and H(+) ions that initiated the dissolution of basaltic ferromagnesian silicates and released Fe(2+) ions. The Fe(2+) ions eventually underwent ferrolysis reactions and produced insoluble hydrous ferric oxide phases. Measurements of the time-dependence of acid weathering reactions show that pyrrhotite is rapidly converted to pyrite plus dissolved ferrous iron, the rate of pyrite formation decreasing with rising pH and lower temperatures. On Mars, oxidation rates of dissolved Fe(2+) ions in equatorial melt-waters in contact with the atmosphere are estimated to lie in the range 0.3-3.0 ppb Fe/yr over the pH range 2 to 6. Oxidation of Fe(2+) ions is estimated to be extremely slow in brine eutectic solutions that might be present on Mars and to be negligible in the frozen regolith.

  20. Rates of oxidative weathering on the surface of Mars

    NASA Astrophysics Data System (ADS)

    Burns, R. G.; Fisher, D. S.

    1993-02-01

    A model of acid weathering is proposed for the iron-rich basalts on Mars. Aqueous oxidation of iron sulfides released SO4(2-) and H(+) ions that initiated the dissolution of basaltic ferromagnesian silicates and released Fe(2+) ions. The Fe(2+) ions eventually underwent ferrolysis reactions and produced insoluble hydrous ferric oxide phases. Measurements of the time-dependence of acid weathering reactions show that pyrrhotite is rapidly converted to pyrite plus dissolved ferrous iron, the rate of pyrite formation decreasing with rising pH and lower temperatures. On Mars, oxidation rates of dissolved Fe(2+) ions in equatorial melt-waters in contact with the atmosphere are estimated to lie in the range 0.3-3.0 ppb Fe/yr over the pH range 2 to 6. Oxidation of Fe(2+) ions is estimated to be extremely slow in brine eutectic solutions that might be present on Mars and to be negligible in the frozen regolith.

  1. Effects of dust accumulation and removal on radiator surfaces on Mars

    SciTech Connect

    Gaier, J.R.; Perez-Davis, M.E.; Rutledge, S.K.; Hotes, D.; Olle, R.

    1991-01-01

    Tests were carried out to assess the impact of wind blown dust accumulation and abrasion on radiator surfaces on Mars. High emittance arc-textured copper (Cu) and niobium-1%-zirconium (Nb-1%Zr) samples were subjected to basaltic dust laden wind at Martian pressure (1000 Pa) at speeds varying from 19 to 97 m/s in the Martian Surface Wind Tunnel at NASA Ames Research Center. The effect of accumulated dust was also observed by pre-dusting some of the samples before the test. Radiator degradation was determined by measuring the change in the emittance after dust was deposited and/or removed. The principal mode of degradation was abrasion. Arc-textured Nb-1%Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion.

  2. Local late Amazonian boulder breakdown and denudation rate on Mars

    NASA Astrophysics Data System (ADS)

    Haas, Tjalling; Hauber, Ernst; Kleinhans, Maarten G.

    2013-07-01

    Inactive fan surfaces become smoother and develop desert pavement over time by weathering and erosion. We use this mechanism to estimate late Amazonian boulder breakdown and surface denudation rates on a young (˜1.25 Ma) (Schon et al., 2009) fan on Mars. This is done by comparing boulder size and surface relief between lobes of different ages. The boulder breakdown rate is 3.5 m/Myr, surface smoothing (denudation) rate is approximated as 0.89 m/Myr. These rates exceed previous estimates for the Amazonian by orders of magnitude. We attribute this to locality, high initial smoothing rates after morphological activity and obliquity and eccentricity-driven variation in the availability of (metastable) liquid water, which acts as a catalyst for weathering during these periods. The results have major implications for process interpretation of Martian landforms, as they imply that typical small-scale morphology may be subdued within <1 Myr.

  3. Dose rate effects during damage accumulation in silicon

    SciTech Connect

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-11-01

    The authors combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of silicon. They obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, the authors study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

  4. Dose rate effects during damage accumulation in silicon

    SciTech Connect

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-01-01

    We combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of Silicon. We obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, we study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

  5. Mass accumulation rates in Asia during the Cenozoic

    NASA Astrophysics Data System (ADS)

    Métivier, François; Gaudemer, Yves; Tapponnier, Paul; Klein, Michel

    1999-05-01

    This work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in Asia since the beginning of the Cenozoic, ~ 66 Ma. The estimates were derived from isopach maps, cross-sections and drill holes or stratigraphic columns assuming regional similarity of the strata. Average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods: Palaeocene ( ~ 66-58 Ma), Eocene ( ~ 58-37 Ma), Oligocene( ~ 37-30 and 30-24 Ma), Miocene ( ~ 24-17, 17-11 and 11-5 Ma), Pliocene ( ~ 5-2 Ma) and Quaternary ( ~ 2-0 Ma). These rates shed new light on the geological history of Asia since the onset of the collision of India with Asia ( ~ 50 Ma). The overall average accumulation rates curve for Asian sedimentary basins since the beginning of the Tertiary shows an exponential form with slow accumulation rates (less than 0.5 x 10^6 km^3 Myr^- 1) until the beginning of the Oligocene, more than 15 Myr after the onset of the collision. From the Oligocene onwards rates increase quickly in an exponential manner, reaching their maximum values in the Quaternary (more than 1.5 x 10^6 km^3 Myr^- 1). From these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the India-Eurasia collision history. At smaller scales one may distinguish between independent histories at the subcontinental and basin scales. This permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of Asia during the Cenozoic.

  6. Alunite dissolution rates: Dissolution mechanisms and implications for Mars

    NASA Astrophysics Data System (ADS)

    Miller, J. L.; Elwood Madden, A. S.; Phillips-Lander, C. M.; Pritchett, B. N.; Elwood Madden, M. E.

    2016-01-01

    Alunite (KAl3(SO4)2(OH)6) is a hydrated aluminous sulfate mineral associated with acidic, oxidizing aqueous environments on Earth. Additionally, orbiting spacecraft and rovers on Mars have reported spectral data that indicate a range of mono- and polyhydrated sulfate phases and hydroxysulfate phases, suggesting such conditions also existed on Mars in the past. This study examines alunite dissolution rates in aqueous systems with varying pH, temperature, and solution chemistry conditions. Alunite dissolution rates in dilute solutions are 2-3 orders of magnitude slower than jarosite dissolution rates measured under analogous conditions. Similar to jarosite, alunite dissolution rates vary as a function of activity of H+ and OH- following the rate law log r (mol m-2 s-1) = -0.133(±0.02)pH - 10.65(±0.07) at pH < 5 and log r = 0.194(±0.04)pH - 12.53(±0.26) at pH > 5. However, minimum alunite dissolution rates are shifted to higher pH (5-5.5), likely due to differences in Fe and Al speciation. Alunite and jarosite rates converge in saturated NaCl and CaCl2 brines as the activity of water decreases, suggesting that differences in water exchange rates with Fe3+ and Al3+ control dissolution rates in dilute solutions, while metal-Cl- complexation occurs at similar rates within the brines. Particle lifetimes based on measured dissolution rates in dilute solutions show that alunite particles are expected to be preserved two orders of magnitude longer than jarosite particles over a range of pH and temperature conditions. In particular, alunite is more likely to be preserved in neutral to moderately alkaline systems compared to jarosite, which is expected to be preserved in more acidic conditions. Alunite dissolution produced amorphous Al-rich alteration products at moderate to high pH. Unlike jarosite, alunite dissolution does not show a clear trend as a function of temperature; alunite dissolution rates do not increase with increasing temperature, likely due to lower

  7. Accumulation rates of airborne heavy metals in wetlands

    USGS Publications Warehouse

    Souch, C.J.; Filippelli, G.M.; Dollar, N.; Perkins, S.; Mastalerz, Maria

    2002-01-01

    Accumulation rates of heavy metals (Cd, Cr, Cu, Mn, Pb, and Zn) retained in wetland sediments in northwest Indiana-downwind of the Chicago-Gary-Hammond industrial area-are quantified to assess anthropogenic influences on atmospheric fluxes. Metal concentrations for 22 sediment cores are determined by ICP-AES after ashing and strong acid extraction. Relations between organic content and metal concentrations at depth are used to separate natural and anthropogenic sources. Accumulation rates over the lifetime of the wetlands (???4500 years) have averaged 0.2 (Cd), 1.4 (Cu), 1.7 (Cr), 13.4 (Mn), 4.8 (Pb), and 18.7 (Zn) mg m-2 y-1. Rates for the last 100 years have increased on average by factors of 6 (Cd), 8 (Cu), 10 (Mn), 15 (Pb), and 30 (Zn), remaining effectively constant for Cr. Where the wetlands have been drained, metals have been lost from the sediments, owing to changes in organic content and local hydrochemistry (exposure to acidic rainfall). Sediment-based accumulation rates at the undrained sites are higher, though generally consistent, with measured and modeled atmospheric fluxes documented by short-term studies conducted over the last three decades. The fraction of the total metals in the wetlands estimated to be of anthropogenic origin ranges from approximately 3% for Cr, up to approximately 35% for Pb, and 70% for Zn. This historic legacy of contamination must be considered in land management decisions, particularly when wetlands are drained.

  8. Duration and rates of discharge: Maja Valles, Mars

    NASA Technical Reports Server (NTRS)

    Dehon, R. A.; Pani, E. A.

    1992-01-01

    The 1600 km-long Maja Valles outflow system of Mars consists of three major divisions including the upper valley on Lunae Planum, the canyon section across Xanthe Terra, and the lower valley across western Chryse Planitia. Although water released from the source in Juventae Chasma could reach the terminus of the present day valley system in central Chryse Planitia within 44 hours, the original outflow did not traverse the Martian surface in a direct path. It ponded along its course on northern Lunae Planum and near the western edge of Chryse Planitia significantly prolonging the lifetime of surface flow. Calculation of pond volumes and discharge rates through various parts of the channel system indicates that water flowed through this system for nearly a (terrestrial) year. Discharge rates from the various basins along the Maja channels and the maximum flow rates within the various channels are calculated. With this data, it is possible to place reasonable estimates of the minimum length of time required to drain the various impoundments and the duration of flow in various parts of the channel system. The results of these calculations are discussed.

  9. Duration and rates of discharge - Maja Valles, Mars

    NASA Technical Reports Server (NTRS)

    De Hon, R. A.; Pani, E. A.

    1993-01-01

    The 1600 km-long Maja Valles outflow system of Mars consists of three major divisions including the upper valley on Lunae Planum, the canyon section across Xanthe Terra, and the lower valley across western Chryse Planitia. Although water released from the source in Juventae Chasma could reach the terminus of the present day valley system in central Chryse Planitia within 44 hours, the original outflow did not traverse the Martian surface in a direct path. It ponded along its course on northern Lunae Planum and near the western edge of Chryse Planitia significantly prolonging the lifetime of surface flow. Calculation of pond volumes and discharge rates through various parts of the channel system indicates that water flowed through this system for nearly a (terrestrial) year. Discharge rates from the various basins along the Maja channels and the maximum flow rates within the various channels are calculated. With this data, it is possible to place reasonable estimates of the minimum length of time required to drain the various impoundments and the duration of flow in various parts of the channel system. The results of these calculations are discussed.

  10. Sublimation rate of ice under simulated Mars conditions and the effect of layers of mock regolith JSC Mars-1

    NASA Astrophysics Data System (ADS)

    Chevrier, Vincent; Sears, Derek W. G.; Chittenden, Julie D.; Roe, Larry A.; Ulrich, Richard; Bryson, Kathryn; Billingsley, Lisa; Hanley, Jennifer

    2007-01-01

    We have studied the sublimation of ice buried beneath ≤200 mm of JSC Mars-1 model regolith under simulated Mars conditions. As expected, even thin layers of regolith cause large decreases in sublimation rate, up to one order of magnitude at 50 mm. When the depth of the regolith was 50 to 200 mm we detected water desorbing from the overlying layers for which we were able to determine a desorption coefficient of 1.45 ± 0.5 × 10-3 h-1. After allowing for the effect of desorption, we found that the diffusion coefficient for water vapor through our regolith is 1.74 ± 0.70 × 10-4 m2 s-1, in excellent agreement with theoretical values. We thus find that a 1-m thick layer of ice buried below a meter of regolith resembling JSC Mars-1 on Mars at 235 K would last ˜800 years.

  11. Death rates reflect accumulating brain damage in arthropods.

    PubMed

    Fonseca, Duane B; Brancato, Carolina L; Prior, Andrew E; Shelton, Peter M J; Sheehy, Matt R J

    2005-09-22

    We present the results of the first quantitative, whole-lifespan study of the relationship between age-specific neurolipofuscin concentration and natural mortality rate in any organism. In a convenient laboratory animal, the African migratory locust, Locusta migratoria, we find an unusual delayed-onset neurolipofuscin accumulation pattern that is highly correlated with exponentially accelerating age-specific Gompertz-Makeham death rates in both males (r=0.93, p=0.0064) and females (r=0.97, p=0.0052). We then test the conservation of this association by aggregating the locust results with available population-specific data for a range of other terrestrial, freshwater, marine, tropical and temperate arthropods whose longevities span three orders of magnitude. This synthesis shows that the strong association between neurolipofuscin deposition and natural mortality is a phylogenetically and environmentally widespread phenomenon (r=0.96, p < 0.0001). These results highlight neurolipofuscin as a unique and outstanding integral biomarker of ageing. They also offer compelling evidence for the proposal that, in vital organs like the brain, either the accumulation of toxic garbage in the form of lipofuscin itself, or the particular molecular reactions underlying lipofuscinogenesis, including free-radical damage, are the primary events in senescence. PMID:16191601

  12. A flight experiment to determine GPS photochemical contamination accumulation rates

    NASA Technical Reports Server (NTRS)

    Tribble, A. C.; Haffner, J. W.

    1990-01-01

    It was recently suggested that photochemically deposited contamination, originating from volatiles outgassed by a spacecraft, may be responsible for the anomalous degradation in power seen on the GPS Block 1 vehicles. In an attempt to confirm, or deny, the photochemical deposition rates predicted, a study was undertaken to design a flight experiment to be incorporated on the GPS vehicles currently in production. The objective was to develop an inexpensive, light weight instrument package that would give information on the contamination levels within a few months of launch. Three types of apparatus were studied, Quartz Crystal Microbalances, (QCM's), modified solar cells, and calorimeters. A calorimeter was selected due primarily to its impact on the production schedule of the GPS vehicles. An analysis of the sensitivity of the final design is compared to the predicted contamination accumulation rates in order to determine how long after launch it will take the experiment to show the effects of photochemical contamination.

  13. 210Pb mass accumulation rates in the depositional area of the Magra River (Mediterranean Sea, Italy)

    NASA Astrophysics Data System (ADS)

    Delbono, I.; Barsanti, M.; Schirone, A.; Conte, F.; Delfanti, R.

    2016-08-01

    Nine sediment cores were collected between 2009 and 2012 in the inner continental shelf (Mediterranean Sea, Italy) mainly influenced by the Magra River, at water depths ranging from 11 to 64 m. Mass Accumulation Rates (MARs) were calculated through 210Pb analysed by Gamma spectrometry. Three different dating models (single and two-layer CF-CS, CRS) were applied to clay normalised 210Pbxs profiles and 137Cs was used to validate the 210Pb geochronology. The maximum MAR values (>2 g cm-2 yr-1) were found in the region adjacent to the Magra River mouth and outside the Gulf of La Spezia (0.9±0.1 g cm-2 yr-1 at St. 3-C6 and 4-C4). Results from 137Cs/210Pbxs ratios calculated in Surface Mixed Layers (SMLs) evidenced the coastal boundaries of the Magra River depositional area, which is very limited towards south. Differently, in the north-west sector, fine sediments are generally driven by the Ligurian Current and move towards north-west: at the deepest and most distant station from the River mouth, the MAR value is the lowest one in the study area. Few major Magra River floods occurred during the sediment core sampling period. By using the short-lived radioisotope 7Be as a tracer of river floods, a clear 7Be signature of 2009 flood is present at St. 1-SA1C. Finally, by analyzing the clay normalised 210Pbxs profiles, a decrease of its activity dating the years 1999 and 2000 is observed in four cores, corresponding to two major Magra River floods occurring in those years.

  14. Lava Tube Flow Models at Alba Patera, Mars: Topographic Constraints on Eruption Rates

    NASA Technical Reports Server (NTRS)

    Riedel, S. J.; Sakimoto, S. E. H.; Bradley, B. A.; DeWet, A.

    2001-01-01

    Alba Patera has some of the longest lava tubes over some of the shallowest slopes on Mars. We use Mars Orbiter Laser Altimeter (MOLA) topography to model eruption rates for several Alba Patera lava tubes and compare them within Alba and with flows from other martian volcanic regions. Additional information is contained in the original extended abstract.

  15. Development and Validation of the User Version of the Mobile Application Rating Scale (uMARS)

    PubMed Central

    Stoyanov, Stoyan R; Kavanagh, David J; Wilson, Hollie

    2016-01-01

    Background The Mobile Application Rating Scale (MARS) provides a reliable method to assess the quality of mobile health (mHealth) apps. However, training and expertise in mHealth and the relevant health field is required to administer it. Objective This study describes the development and reliability testing of an end-user version of the MARS (uMARS). Methods The MARS was simplified and piloted with 13 young people to create the uMARS. The internal consistency and test-retest reliability of the uMARS was then examined in a second sample of 164 young people participating in a randomized controlled trial of a mHealth app. App ratings were collected using the uMARS at 1-, 3,- and 6-month follow up. Results The uMARS had excellent internal consistency (alpha = .90), with high individual alphas for all subscales. The total score and subscales had good test-retest reliability over both 1-2 months and 3 months. Conclusions The uMARS is a simple tool that can be reliably used by end-users to assess the quality of mHealth apps. PMID:27287964

  16. Rate of tree carbon accumulation increases continuously with tree size.

    PubMed

    Stephenson, N L; Das, A J; Condit, R; Russo, S E; Baker, P J; Beckman, N G; Coomes, D A; Lines, E R; Morris, W K; Rüger, N; Alvarez, E; Blundo, C; Bunyavejchewin, S; Chuyong, G; Davies, S J; Duque, A; Ewango, C N; Flores, O; Franklin, J F; Grau, H R; Hao, Z; Harmon, M E; Hubbell, S P; Kenfack, D; Lin, Y; Makana, J-R; Malizia, A; Malizia, L R; Pabst, R J; Pongpattananurak, N; Su, S-H; Sun, I-F; Tan, S; Thomas, D; van Mantgem, P J; Wang, X; Wiser, S K; Zavala, M A

    2014-03-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence. PMID:24429523

  17. Rate of tree carbon accumulation increases continuously with tree size

    USGS Publications Warehouse

    Stephenson, N.L.; Das, A.J.; Condit, R.; Russo, S.E.; Baker, P.J.; Beckman, N.G.; Coomes, D.A.; Lines, E.R.; Morris, W.K.; Rüger, N.; Álvarez, E.; Blundo, C.; Bunyavejchewin, S.; Chuyong, G.; Davies, S.J.; Duque, Á.; Ewango, C.N.; Flores, O.; Franklin, J.F.; Grau, H.R.; Hao, Z.; Harmon, M.E.; Hubbell, S.P.; Kenfack, D.; Lin, Y.; Makana, J.-R.; Malizia, A.; Malizia, L.R.; Pabst, R.J.; Pongpattananurak, N.; Su, S.-H.; Sun, I-F.; Tan, S.; Thomas, D.; van Mantgem, P.J.; Wang, X.; Wiser, S.K.; Zavala, M.A.

    2014-01-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage—increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to understand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  18. Rate of tree carbon accumulation increases continuously with tree size

    NASA Astrophysics Data System (ADS)

    Stephenson, N. L.; Das, A. J.; Condit, R.; Russo, S. E.; Baker, P. J.; Beckman, N. G.; Coomes, D. A.; Lines, E. R.; Morris, W. K.; Rüger, N.; Álvarez, E.; Blundo, C.; Bunyavejchewin, S.; Chuyong, G.; Davies, S. J.; Duque, Á.; Ewango, C. N.; Flores, O.; Franklin, J. F.; Grau, H. R.; Hao, Z.; Harmon, M. E.; Hubbell, S. P.; Kenfack, D.; Lin, Y.; Makana, J.-R.; Malizia, A.; Malizia, L. R.; Pabst, R. J.; Pongpattananurak, N.; Su, S.-H.; Sun, I.-F.; Tan, S.; Thomas, D.; van Mantgem, P. J.; Wang, X.; Wiser, S. K.; Zavala, M. A.

    2014-03-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  19. Mass accumulation rate changes in Chinese loess during MIS 2, and asynchrony with records from Greenland ice cores and North Pacific Ocean sediments during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Kang, Shugang; Roberts, Helen M.; Wang, Xulong; An, Zhisheng; Wang, Min

    2015-12-01

    Sensitivity-corrected quartz optically stimulated luminescence (OSL) dating methods have been widely accepted as a promising tool for the construction of late Pleistocene chronology and mass or dust accumulation rates (MARs or DARs) on the Chinese Loess Plateau (CLP). Many quartz OSL ages covering marine isotope stage (MIS) 2 (equal to L1-1 in Chinese loess) have been determined for individual sites within the CLP in the past decade. However, there is still a lack of detailed MAR or DAR reconstruction during MIS 2 across the whole of the CLP. Here, we present detailed MARs determined for eight sites with closely-spaced quartz OSL ages covering ∼MIS 2, and relative MARs suggested by a probability density analysis of 159 quartz OSL ages ranging from ∼30 to 10 ka ago, from 15 sites on the CLP. The results show enhanced dust accumulation during the Last Glacial Maximum (LGM), with particularly rapid dust accumulation from ∼23 to 19 ka ago (the late LGM). In contrast, MARs determined for the last deglaciation (from ∼19 to 12 ka ago) are low. The MAR changes during MIS 2 in Chinese loess are mainly controlled by the East Asian winter monsoon (EAWM) intensity, which is forced by Northern Hemisphere ice volume. The MAR changes also indicate that dust accumulation during MIS 2 is generally continuous at millennial time scales on the CLP. Comparison of Asian-sourced aeolian dust MARs in Chinese loess with those preserved in Greenland ice cores and North Pacific Ocean sediments indicates that rapid dust accumulation occurred from ∼26 to 23 ka ago (the early LGM) in Greenland ice cores and North Pacific Ocean sediments, suggesting a several kilo-year difference in timing when compared with the rapid dust accumulation during the late LGM in Chinese loess. This asynchronous timing in enhanced dust accumulation is probably related to both changes in the EAWM intensity and changes in the mean position of zone axis of the Westerly jet, both of which are greatly influenced

  20. Long-Term evolution of the erosion rates during Early Mars

    NASA Astrophysics Data System (ADS)

    Quantin-Nataf, C.; Craddock, R. A.; Dubuffet, F.; Lozac'h, L.; Martinot, M.

    2015-10-01

    Many Geologic features attest to the fact that liquid water was once stable on the Martian surface. The erosional processes necessary to create these features must have been supported by a climate that is much different than today. However, the evolution of these primitives conditions toward the current dry and cold Martian climate where the erosion processes are 2-3 orders in magnitude lower represents a major gap in our understanding of the evolution of Mars history. Here we document the time-dependence of the erosion rates on Mars during early Mars, period during which the erosion rates have decreased of at least one order in magnitude.

  1. Mars

    NASA Astrophysics Data System (ADS)

    McSween, H. Y., Jr.

    2003-12-01

    More than any other planet, Mars has captured our attention and fueled our speculations. Much of this interest relates to the possibility of martian life, as championed by Percival Lowell in the last century and subsequently in scientific papers and science fiction. Lowell's argument for life on Mars was based partly on geochemistry, in that his assessmentof the planet's hospitable climate was dependent on the identification of H2O ice rather than frozen CO2 in the polar caps. Although this reasoning was refuted by Alfred Wallace in 1907, widespread belief in extant martian life persisted within the scientific community until the mid-twentieth century (Zahnle, 2001). In 1965 the Mariner 4 spacecraft flyby suddenly chilled this climate, by demonstrating that the martian atmosphere was thin and the surface was a cratered moonscape devoid of canals. This view of Mars was overturned again in 1971, when the Mariner 9 spacecraft discovered towering volcanoes and dry riverbeds, implying a complex geologic history. The first geochemical measurements on Mars, made by two Viking landers in 1976, revealed soils enriched in salts suggesting exposure to water, but lacking organic compounds which virtually ended discussion of martian life.The suggestion that a small group of achondritic meteorites were martian samples (McSween and Stolper, 1979; Walker et al., 1979; Wasson and Wetherill, 1979) found widespread acceptance when trapped gases in them were demonstrated to be compositionally similar to the Mars atmosphere ( Bogard and Johnson, 1983; Becker and Pepin, 1984). The ability to perform laboratory measurements of elements and isotopes present in trace quantities in meteorites has invigorated the subject of martian geochemistry. Indeed, because of these samples, we now know more about the geochemistry of Mars than of any other planet beyond the Earth-Moon system. Some studies of martian meteorites have prompted a renewed search for extraterrestrial life using chemical

  2. Dynamic Dust Accumulation and Dust Removal Observed on the Mars Exploration Rover Magnets

    NASA Technical Reports Server (NTRS)

    Bertelsen, P.; Bell, J. F., III; Goetz, W.; Gunnlaugsson, H. P.; Herkenhoff, K. E.; Hviid, S. F.; Johnson, J. R.; Kinch, K. M.; Knudsen, J. M.; Madsen, M. B.

    2005-01-01

    The Mars Exploration Rovers each carry a set of Magnetic Properties Experiments designed to investigate the properties of the airborne dust in the Martian atmosphere. It is a preferred interpretation of previous experiments that the airborne dust in the Martian atmosphere is primarily composed by composite silicate particles containing one or more highly magnetic minerals as a minor constituent. The ultimate goal of the magnetic properties experiments on the Mars Exploration Rover mission is to provide some information/ constraints on whether the dust is formed by volcanic, meteoritic, aqueous, or other processes. The first problem is to identify the magnetic mineral(s) in the airborne dust on Mars. While the overall results of the magnetic properties experiments are presented in, this abstract will focus on dust deposition and dust removal on some of the magnets.

  3. A large-scale validation study of the Medication Adherence Rating Scale (MARS).

    PubMed

    Fialko, Laura; Garety, Philippa A; Kuipers, Elizabeth; Dunn, Graham; Bebbington, Paul E; Fowler, David; Freeman, Daniel

    2008-03-01

    Adherence to medication is an important predictor of illness course and outcome in psychosis. The Medication Adherence Rating Scale (MARS) is a ten-item self-report measure of medication adherence in psychosis [Thompson, K., Kulkarni, J., Sergejew, A.A., 2000. Reliability and validity of a new Medication Adherence Rating Scale (MARS) for the psychoses. Schizophrenia Research. 42. 241-247]. Although initial results suggested that the scale has good reliability and validity, the development sample was small. The current study aimed to establish the psychometric properties of the MARS in a sample over four times larger. The scale was administered to 277 individuals with psychosis, along with measures of insight and psychopathology. Medication adherence was independently rated by each individual's keyworker. Results showed the internal consistency of the MARS to be lower than in the original sample, though adequate. MARS total score correlated weakly with keyworker-rated adherence, hence concurrent validity of the scale appeared only moderate to weak. The three factor structure of the MARS was replicated. Examination of the factor scores suggested that the factor 1 total score, which corresponds to the Medication Adherence Questionnaire [Morisky,D.E., Green,L.W. and Levine,D.M., 1986. Concurrent and predictive validity of a self-reported measure of medication adherence. Medical Care. 24, 67-74] may be a preferable measure of medication adherence behaviour to the total scale score. PMID:18083007

  4. Solidification rate influence on orientation and mechanical properties of MAR-M-246+Hf

    NASA Technical Reports Server (NTRS)

    Hamilton, D.

    1983-01-01

    The influence of solidification rates on the orientation and mechanical properties of MAR-M-246+Hf was studied. The preferred orientation was found to be (001) for single crystals, with all samples with 45 degrees of (001). Tensile tests were performed at room temperature. The anisotropy of directionally solidified MAR-M-246+Hf was demonstrated by gage section deformation. Dendrite arm spacing and crystal growth were found to depend on solidification rates and source material conditions. The greatest strength occurred at lower solidification rates. Some single crystals were grown by control of growth rates without seeding.

  5. Forsterite dissolution rates in Mg-sulfate-rich Mars-analog brines and implications of the aqueous history of Mars

    NASA Astrophysics Data System (ADS)

    Albright Olsen, Amanda; Hausrath, Elisabeth M.; Rimstidt, J. Donald

    2015-03-01

    High salinity brines, although rare on Earth's surface, may have been important in the geologic history of Mars. Increasing evidence suggests the importance of liquid brines in multiple locations on Mars. In order to interpret the effect of high ionic strength brines on olivine dissolution, which is widely present on Mars, 47 new batch reactor experiments combined with 35 results from a previous study conducted at 25°C from 1 < pH < 4 in magnesium sulfate, sodium sulfate, magnesium nitrate, and potassium nitrate solutions with ionic strengths as high as 12 m show that very high ionic strength brines have an inhibitory effect of forsterite dissolution rates. Multiple linear regression analysis of the data suggests that the inhibition in dissolution rates is due to decreased water activity at high ionic strengths. Regression models also show that mMg up to 4 m and mSO4 up to 3 m have no effect on forsterite dissolution rates. The effect of decreasing dissolution rates with decreasing aH2O is consistent with the idea that water acts as a ligand that participates in the dissolution process. Less available water to participate in the dissolution reaction results in a slower dissolution rate. Multiple linear regression analysis of the data produces the rate equation log r = -6.81 - 0.52pH + 3.26log aH2O. Forsterite in dilute solutions with a water activity of one dissolves twice as fast as those in brines with a water activity of 0.8.

  6. Nickel accumulation by Streptanthus polygaloides (Brassicaceae) reduces floral visitation rate.

    PubMed

    Meindl, George A; Ashman, Tia-Lynn

    2014-02-01

    Hyperaccumulation is the phenomenon whereby plants take up and sequester in high concentrations elements that generally are excluded from above-ground tissues. It largely is unknown whether the metals taken up by these plants are transferred to floral rewards (i.e., nectar and pollen) and, if so, whether floral visitation is affected. We grew Streptanthus polygaloides, a nickel (Ni) hyperaccumulator, in short-term Ni supplemented soils and control soils to determine whether Ni is accumulated in floral rewards and whether floral visitation is affected by growth in Ni-rich soils. We found that while supplementation of soils with Ni did not alter floral morphology or reward quantity (i.e., anther size or nectar volume), Ni did accumulate in the nectar and pollen-filled anthers-providing the first demonstration that Ni is accumulated in pollinator rewards. Further, S. polygaloides grown in Ni-supplemented soils received fewer visits per flower per hour from both bees and flies (both naïve to Ni-rich floral resources in the study area) relative to plants grown in control soils, although the probability a plant was visited initially was unaffected by Ni treatment. Our findings show that while Ni-rich floral rewards decrease floral visitation, floral visitors are not completely deterred, so some floral visitors may collect and ingest potentially toxic resources from metal-hyperaccumulating plants. In addition to broadening our understanding of the effects of metal accumulation on ecological interactions in natural populations, these results have implications for the use of insect-pollinated plants in phytoremediation. PMID:24477333

  7. Oxygen ionization rates at Mars and Venus - Relative contributions of impact ionization and charge exchange

    NASA Technical Reports Server (NTRS)

    Zhang, M. H. G.; Luhmann, J. G.; Nagy, A. F.; Spreiter, J. R.; Stahara, S. S.

    1993-01-01

    Oxygen ion production rates above the ionopauses of Venus and Mars are calculated for photoionization, charge exchange, and solar wind electron impact ionization processes. The latter two require the use of the Spreiter and Stahara (1980) gas dynamic model to estimate magnetosheath velocities, densities, and temperatures. The results indicate that impact ionization is the dominant mechanism for the production of O(+) ions at both Venus and Mars. This finding might explain both the high ion escape rates measured by Phobos 2 and the greater mass loading rate inferred for Venus from the bow shock positions.

  8. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars

    USGS Publications Warehouse

    Head, J.W.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; Hoffmann, H.; Kreslavsky, M.; Werner, S.; Milkovich, S.; Van Gasselt, S.

    2005-01-01

    Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the base of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice-rich glacier-like viscous flow and sublimation. Together with new evidence for recent ice-rich rock glaciers at the base of the Olympus Mons scarp superposed on larger Late Amazonian debris-covered piedmont glaciers, we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid-latitude regions of Mars during periods of increased spin-axis obliquity when polar ice was mobilized and redeposited in microenvironments at lower latitudes. The data indicate that abundant residual ice probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration.

  9. Constraining mass accumulation rates across the Cretaceous-Paleogene boundary clay layer using extraterrestrial helium-3

    NASA Astrophysics Data System (ADS)

    Giron, M.; Sepulveda, J.; Mukhopadhyay, S.; Alegret, L.; Summons, R. E.

    2012-12-01

    The extended duration of the negative δ13C excursion observed in marine carbonates spanning the Cretaceous-Paleogene (K-Pg) mass extinction event has lead to two main hypothesized post-extinction models ("Strangelove" and "Living Ocean";[1, 2]) for the status of marine primary productivity and the global carbon cycle. However, these models are largely inconsistent with recent paleontological and geochemical evidence suggesting heterogeneous changes in marine productivity and carbon export [3, 4]. While the analysis of lipid biomarkers in the cosmopolitan boundary clay layer allows us to assess changes in primary production by non-calcifying organisms in the immediate aftermath of the mass extinction [4], our poor understanding of the deposition of the clay layer precludes a more detailed reconstruction of short-term variations in marine ecosystem resilience. Here, we present data on extraterrestrial 3He derived from interplanetary dust particles used as a constant flux proxy to constrain fluctuations in mass accumulation rates (MARs) [5] and the duration of the boundary clay deposition in three classic and expanded K-Pg boundary sections: El Kef (Tunisia), Caravaca (Spain), and Kulstirenden (Denmark). Our results from different depositional environments indicate average durations for the sedimentation of the clay layer that are comparable (~10 kyr) to other localities [5], thus confirming its globally brief deposition. Early Paleogene MARs vary among locations when compared to background Late Cretaceous values and do not strictly follow carbonate content as traditionally assumed, thus suggesting variable depositional conditions at different locations. Changes in sediment MARs across the K-Pg will be used to calculate MARs of algal- and bacterial-derived biomarkers, as well as benthic foraminifera, in order to assess the timing and global nature of the recovery of marine primary production and carbon export. 1. Hsu, K.J., He, Q., Mckenzie, J.A., Weissert, H

  10. MOLA Topographic Constraints on Lava Tube Effusion Rates for Alba Patera, Mars

    NASA Technical Reports Server (NTRS)

    Riedel, S. J.; Sakimoto, S. E. H.

    2002-01-01

    Using high resolution MOLA (Mars Orbiter Laser Altimeter) topographic data to accurately model flow rates, we find that Alba Patera tube-fed flows within the mid to lower flanks could accommodate flow rates between 10 Pa s to 1.308 x 10(exp 6) Pa s. Additional information is contained in the original extended abstract.

  11. Elevated rates of organic carbon, nitrogen, and phosphorus accumulation in a highly impacted mangrove wetland

    NASA Astrophysics Data System (ADS)

    Sanders, Christian J.; Eyre, Bradley D.; Santos, Isaac R.; Machado, Wilson; Luiz-Silva, Wanilson; Smoak, Joseph M.; Breithaupt, Joshua L.; Ketterer, Michael E.; Sanders, Luciana; Marotta, Humberto; Silva-Filho, Emmanoel

    2014-04-01

    The effect of nutrient enrichment on mangrove sediment accretion and carbon accumulation rates is poorly understood. Here we quantify sediment accretion through radionuclide tracers to determine organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) accumulation rates during the previous 60 years in both a nutrient-enriched and a pristine mangrove forest within the same geomorphological region of southeastern Brazil. The forest receiving high nutrient loads has accumulated OC, TN, and TP at rates that are fourfold, twofold, and eightfold respectively, higher than those from the undisturbed mangrove. Organic carbon and TN stable isotopes (δ13C and δ15N) reflect an increased presence of organic matter (OM) originating with either phytoplankton, benthic algae, or another allochthonous source within the more rapidly accumulated sediments of the impacted mangrove. This suggests that the accumulation rate of OM in eutrophic mangrove systems may be enhanced through the addition of autochthonous and allochthonous nonmangrove material.

  12. Spatial variation in rates of carbon and nitrogen accumulation in a boreal bog

    SciTech Connect

    Ohlson, M.; Oekland, R.H.

    1998-12-01

    Although previous studies hint at the occurrence of substantial spatial variation in the accumulation rates of C and N in bogs, the extent to which rates may vary on high-resolution spatial and temporal scales is not known. A main reason for the lack of knowledge is that it is problematic to determine the precise age of peat at a given depth. The authors determined rates of carbon and nitrogen accumulation in the uppermost decimeters of a bog ecosystem using the pine method, which enables accurate dating of surface peat layers. They combined accumulation data with numerical and geostatistical analyses of the recent vegetation to establish the relationship between bog vegetation and rate of peat accumulation. Use of a laser technique for spatial positioning of 151 age-determined peat cores within a 20 x 20 m plot made it possible to give the first tine-scaled account of spatial and temporal variation in rates of mass, carbon, and nitrogen accumulation during the last century. Rates of C and N accumulation were highly variable at all spatial scales studied. For example, after {approximately}125 yr of peat growth, C and N accumulation varied by factors of five and four, respectively, from 25 to 125 g/dm{sup 2} for C, and from 0.7 to 2.6 g/dm{sup 2} for N. It takes 40 yr of peat accumulation before significant amounts of C are lost through decay. Hummocks built up by Sphagnum fuscum and S. rubellum were able to maintain average rates of C accumulation that exceed 2 g{center_dot}dm{sup {minus}2}{center_dot} yr{sup {minus}1} during 50 yr of growth. The authors argue that data on spatial variation in rates of C accumulation are necessary to understand the role of boreal peatlands in the greenhouse effect and global climate.

  13. Discharge rates in Ma'adim Vallis, Mars

    NASA Astrophysics Data System (ADS)

    Thornhill, G. D.; Rothery, D. A.; Murray, J. B.; Day, T.; Cook, A. C.; Muller, J.-P.; Iliffe, J. C.

    1993-03-01

    A digital elevation model (DEM) of a small part of the Martian channel Ma'adim Vallis was produced using the Frankot and Chellappa shape-from-shading algorithm. Software developed by the Dept. of Photogrammetry and Surveying at University College London uses this technique to extract slope information from the grey levels of image pixels. This technique was applied to a Viking Orbiter image of part of Ma'adim Vallis, and measurements of the channel depth and bed-slope of a channel incised into the floor of Ma'adim Vallis were made. These results were used to calculate order of magnitude estimates for discharge rates through the channel. The maximum values calculated are three orders of magnitude less than those for N. Kasei Vallis and are similar to values cited for the Missoula floods. However, when more realistic values of the water depth are used, discharge rates comparable with those for the Mississippi River result.

  14. Discharge rates in Ma'adim Vallis, Mars

    NASA Technical Reports Server (NTRS)

    Thornhill, G. D.; Rothery, D. A.; Murray, J. B.; Day, T.; Cook, A. C.; Muller, J-P.; Iliffe, J. C.

    1993-01-01

    A digital elevation model (DEM) of a small part of the Martian channel Ma'adim Vallis was produced using the Frankot and Chellappa shape-from-shading algorithm. Software developed by the Dept. of Photogrammetry and Surveying at University College London uses this technique to extract slope information from the grey levels of image pixels. This technique was applied to a Viking Orbiter image of part of Ma'adim Vallis, and measurements of the channel depth and bed-slope of a channel incised into the floor of Ma'adim Vallis were made. These results were used to calculate order of magnitude estimates for discharge rates through the channel. The maximum values calculated are three orders of magnitude less than those for N. Kasei Vallis and are similar to values cited for the Missoula floods. However, when more realistic values of the water depth are used, discharge rates comparable with those for the Mississippi River result.

  15. Rates of fluvio-thermal erosion on Mars

    NASA Technical Reports Server (NTRS)

    Aguirre-Puente, J.; Costard, Francois M.; Posado-Cano, R.

    1993-01-01

    In order to get some ideas about the order of magnitude of fluvio-thermal recession rate, a mathematical thermal model for Martian outflow channels is proposed. This model corresponds to a system undergoing a permanent thermal regime where the surface temperature is constant and equal to the phase change temperature (due to the immediate removal of melted materials). This is an ablation model. For its application, estimations of the heat transfer coefficient h and thermal flux q are necessary. Determination of these coefficients needs the calculation of dimensionless numbers (Reynolds, Prandtl, and Nusselt), and the consideration of turbulent regime of the flow.

  16. The rate of aging: the rate of deficit accumulation does not change over the adult life span.

    PubMed

    Mitnitski, Arnold; Rockwood, Kenneth

    2016-02-01

    People age at different rates. We have proposed that rates of aging can be quantified by the rate at which individuals accumulate health deficits. Earlier estimates, using cross-sectional analyses suggested that deficits accumulated exponentially, at an annual rate of 3.5%. Here, we estimate the rate of deficit accumulation using longitudinal data from the Canadian National Population Health Survey. By analyzing age-specific trajectories of deficit accumulation in people aged 20 years and over (n = 13,668) followed biannually for 16 years, we found that the longitudinal average annual rate of deficit accumulation was 4.5% (±0.75%). This estimate was notably stable during the adult life span. The corresponding average doubling time in the number of deficits was 15.4 (95% CI 14.82-16.03) years, roughly 30% less than we had reported from the cross-sectional analysis. Earlier work also established that the average number of deficits accumulated by individuals (N), equals the product of the intensity of environmental stresses (λ) causing damage to the organism, by the average recovery time (W). At the individual level, changes in deficit accumulation can be attributed to both changes in environmental stresses and changes in recovery time. By contrast, at the population level, changes in the number of deficits are proportional to the changes in recovery time. In consequence, we propose here that the average recovery time, W doubles approximately every 15.4 years, independently of age. Such changes quantify the increase of vulnerability to stressors as people age that gives rise to increasing risk of frailty, disability and death. That deficit accumulation will, on average, double twice between ages 50 and 80 highlights the importance of health in middle age on late life outcomes. PMID:25972341

  17. A New Hypothesis for Relative High Rate of Volcanism in the Hesperian on Mars

    NASA Astrophysics Data System (ADS)

    Huang, J.; Li, M.; Xiao, L.; Wang, F.

    2013-12-01

    The rates of impact, weathering, erosion and valley formation on Mars all decreased greatly at the end of the Noachian. However, the average rate of volcanism stayed at a relatively high level throughout the Hesperian. The reason for extensive lava plains in the Hesperian is intriguing, since the rate of volcanism in the later time should have decreased dramatically than earlier time due to decreasing of internal thermal energy. Recent modeling results brought up 'cold and icy' against the prevalent 'warm and wet' for the early Mars, which showed tens to hundreds meters thick ice covered the Noachian highlands at a very limited total water inventory in 40 martian years. However, the thickness of ice could be much larger considering the enormous amount of water which created the channels and valleys on martian surface. In Iceland of Earth, both observation and numerical modeling results show that the great increase of rate of volcanism in the 1000-year time scale could be a result of ice sheet melting. Inspired from what has happened in Iceland, in this study, we are going to investigate the possibility of increasing the rates of volcanism by deglaciation in the Hesperian time. Our hypothesis is that the high rates of volcanism in Hesperian of Mars could also be the result of deglaciation.

  18. Estimates of Lava Eruption Rates at Alba Patera, Mars

    NASA Technical Reports Server (NTRS)

    Baloga, S. M.; Pieri, D. C.

    1985-01-01

    The Martian volcanic complex Alba Patera exhibits a suite of well-defined, long and relatively narrow lava flows qualitatively resembling those found in Hawaii. Even without any information on the duration of the Martian flows, eruption rates (total volume discharge/duration of the extrusion) estimates are implied by the physical dimensions of the flows and the likely conjecture that Stephan-Boltzmann radiation is the dominating thermal loss mechanism. The ten flows in this analysis emanate radially from the central vent and were recently measured in length, plan areas, and average thicknesses by shadow measurement techniques. The dimensions of interest are shown. Although perhaps morphologically congruent to certain Hawaiian flows, the dramatically expanded physical dimensions of the Martian flows argues for some markedly distinct differences in lava flow composition for eruption characteristics.

  19. Carbon and Nitrogen Accumulation Rates in Salt Marshes in Oregon, USA

    EPA Science Inventory

    Two important ecosystem services of wetlands are carbon sequestration and filtration of nutrients and particulates. We quantified the carbon and nitrogen accumulation rates in salt marshes at 135 plots distributed across eight estuaries located in Oregon, USA. Net carbon and ...

  20. The Measurement of Mars Rotation Rate and Pole Position with MGS

    NASA Technical Reports Server (NTRS)

    Smith, David E.; Zuber, Maria T.; Rowlands, David D.; Lemoine, Frank G.

    1999-01-01

    Laser altimeter data and microwave tracking of the MGS (Mars Global Surveyor) spacecraft have been used to estimate rotation parameters for Mars. With the recent development of new high resolution gravity models for Mars and the determination of the orbit of the MGS spacecraft to the few meter level it has become possible to obtain rotational information about the planet. Perturbations of the spacecraft orbit by the planet's gravity field permit the gravity field to be estimated from the tracking data. But the perturbations arising from the non-zonal components of the gravity field have a periodicity related to the rotation of Mars on its axis and these perturbations enable the rotation rate and direction of the rotation pole in inertial space to be measured with respect to the orbit of the spacecraft. It is the anomalies in the gravity field that permit these parameters to be obtained. Similarly, altimetry data are sensitive to errors in the orbital altitude at orbital cross-over locations and the locations themselves are a function of the rotation of the planet. Thus, altimetric measurements by MOLA provide a geometric constraint on the rotation of the planet through the timing of the orbital cross-over pattern as well as information that improves the orbit determination. For a few months in 1999 MGS tracking and altimetry data have been used in a preliminary experiment to estimate the rotation rate of Mars and the right ascension and declination of the pole from an orbiting spacecraft. These preliminary results appear to have sufficient accuracy to permit detection of seasonal changes in rotation rate and also precession of the pole thus leading to a possible eventual measurement of the moment of inertia.

  1. Using transplants to measure accumulation rates of epiphytic bryophytes in forests of western Oregon

    USGS Publications Warehouse

    Rosso, A.L.; Muir, Patricia S.; Rambo, T.

    2001-01-01

    We sought a simple and effective transplant method that could be used to measure biomass accumulation rates of epiphytic bryophytes. Trials were carried out in the Pseudotsuga menziesii-dominated forests of western Oregon. We tested multiple transplant methods over a 13-month period while comparing accumulation rates of Antitrichia curtipendula (Hedw.) Brid. and Isothecium myosuroides Brid. among an old-growth stand, a young stand, and a recent clearcut. In our study area, Antitrichia is considered to be an old-growth associate while Isothecium is a more ubiquitous species. Methods tested included containment in net bags, containment in hairnets, and directly tying mats to substrates. Three sizes of transplants were tested with both natural and inert artificial substrates. Transplants of approximately five g enclosed in plastic net bags and tied to either natural or artificial substrates worked well for our purposes. Only minor differences were found in mean accumulation rates between the old growth and young stand, though variation in accumulation rates was higher in the old growth. Neither species appeared capable of surviving in the clearcut. Antitrichia accumulated biomass 60% faster in the canopy than in the understory on average. Antitrichia also accumulated at a faster rate than Isothecium, with mean 13-month biomass increases of 11.8 and 3.7% respectively for 5 g transplants in the understory. Our results suggest that Antitrichia's association with old growth may be due more to dispersal or establishment limitations than to a decreased ability to grow in young stands.

  2. Topographic control and accumulation rate of some Holocene coral reefs: south Florida and Dry Tortugas

    USGS Publications Warehouse

    Shinn, E.A.; Hudson, J.H.; Halley, R.B.; Lidz, B.H.

    1977-01-01

    Core drilling and examination of underwater excavation on 6 reef sites in south Florida and Dry Tortugas revealed that underlying topography is the major factor controlling reef morphology. Carbon-14 dating on coral recovered from cores enables calculation of accumulation rates. Accumulation rates were found to range from 0.38 m/1000 years in thin Holocene reefs to as much as 4.85 m/1000 years in thicker buildups. Cementation and alteration of corals were found to be more pronounced in areas of low buildup rates than in areas of rapid accumulation rates. Acropora palmata, generally considered the major reef builder in Florida, was found to be absent in most reefs drilled. At Dry Tortugas, the more than 13-meter thick Holocene reef did not contain A. palmata. The principal reef builders in this outer reef are the same as those which built the Pleistocene Key Largo formation, long considered to be fossilized patch reef complex.

  3. Radiocarbon dating, chronologic framework, and changes in accumulation rates of holocene estuarine sediments from Chesapeake Bay

    USGS Publications Warehouse

    Colman, Steven M.; Baucom, P.C.; Bratton, J.F.; Cronin, T. M.; McGeehin, J.P.; Willard, D.; Zimmerman, A.R.; Vogt, P.R.

    2002-01-01

    Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelarator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210 Pb and 137 Cs data and pollen stratigraphy from the same sites. Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

  4. IMPACT OF PARTICLE AGGLOMERATION ON ACCUMULATION RATES IN THE GLASS DISCHARGE RISER OF HLW MELTER

    SciTech Connect

    Matyas, Josef; Jansik, Danielle P.; Owen, Antionette T.; Rodriguez, Carmen P.; Lang, Jesse B.; Kruger, Albert A.

    2013-08-05

    The major factor limiting waste loading in continuous high-level radioactive waste (HLW) melters is an accumulation of particles in the glass discharge riser during a frequent and periodic idling of more than 20 days. An excessive accumulation can produce robust layers a few centimeters thick, which may clog the riser, preventing molten glass from being poured into canisters. Since the accumulation rate is driven by the size of particles we investigated with X-ray microtomography, scanning electron microscopy, and image analysis the impact of spinel forming components, noble metals, and alumina on the size, concentration, and spatial distribution of particles, and on the accumulation rate. Increased concentrations of Fe and Ni in the baseline glass resulted in the formation of large agglomerates that grew over the time to an average size of ~185±155 µm, and produced >3 mm thick layer after 120 h at 850 °C. The noble metals decreased the particle size, and therefore significantly slowed down the accumulation rate. Addition of alumina resulted in the formation of a network of spinel dendrites which prevented accumulation of particles into compact layers.

  5. Impact Of Particle Agglomeration On Accumulation Rates In The Glass Discharge Riser Of HLW Melter

    SciTech Connect

    Kruger, A. A.; Rodriguez, C. A.; Matyas, J.; Owen, A. T.; Jansik, D. P.; Lang, J. B.

    2012-11-12

    The major factor limiting waste loading in continuous high-level radioactive waste (HLW) melters is an accumulation of particles in the glass discharge riser during a frequent and periodic idling of more than 20 days. An excessive accumulation can produce robust layers a few centimeters thick, which may clog the riser, preventing molten glass from being poured into canisters. Since the accumulation rate is driven by the size of particles we investigated with x-ray microtomography, scanning electron microscopy, and image analysis the impact of spinel forming components, noble metals, and alumina on the size, concentration, and spatial distribution of particles, and on the accumulation rate. Increased concentrations of Fe and Ni in the baseline glass resulted in the formation of large agglomerates that grew over the time to an average size of ~185+-155 {mu}m, and produced >3 mm thick layer after 120 h at 850 deg C. The noble metals decreased the particle size, and therefore significantly slowed down the accumulation rate. Addition of alumina resulted in the formation of a network of spinel dendrites which prevented accumulation of particles into compact layers.

  6. Effects of Atmospheric and Surface Dust on the Sublimation Rates of CO2 on Mars

    NASA Technical Reports Server (NTRS)

    Bonev, B. P.; James, P. B.; Bjorkman, J. E.; Hansen, G. B.; Wolff, M. J.

    2003-01-01

    We present an overview of our modeling work dedicated to study the effects of atmospheric dust on the sublimation of CO2 on Mars. The purpose of this study is to better understand the extent to which dust storm activity can be a root cause for interannual variability in the planetary CO2 seasonal cycle, through modifying the springtime regression rates of the south polar cap. We obtain calculations of the sublimation fluxes for various types of polar surfaces and different amounts of atmospheric dust. These calculations have been compared qualitatively with the regression patterns observed by Mars Global Surveyor (MGS) in both visible and infrared wavelengths, for two years of very different dust histories (1999, and 2001).

  7. Dynamical simulations of the impact rate, velocities, and angles of Mars-crossing asteroids

    NASA Astrophysics Data System (ADS)

    Avdellidou, C.; Price, M. C.; Kinnear, T.

    2014-07-01

    High-resolution spacecraft imagery has allowed us to obtain very accurate measurements of the sizes of impact craters on Mercury, the Moon, Mars, Vesta, and many of the Jovian and Saturnian satellites. In order to achieve a better understanding of the size distribution of craters on the terrestrial planets (and other minor bodies), knowledge of the range of asteroid impact energies and geometries is required. To begin to examine this, we used the population of Mars-crossing asteroids and ran dynamical simulations for 100 Myr forward in time. In total, ˜3,300 particles (with each particle representing a known asteroid) were integrated using the 'Hybrid' algorithm of the Mercury dynamical simulation package[1]. We report on the impact rate on the Martian surface along with a statistical estimation of the incident velocities and angles.

  8. Magma generation on Mars - Amounts, rates, and comparisons with earth, moon, and Venus

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Schneid, Byron D.

    1991-01-01

    Total extrusive and intrusive magma generated on Mars over the last approximately 3.8 billion years is estimated at 654 x 10 exp 6 cubic kilometers, or 0.17 cubic kilometers per year, substantially less than rates for earth (26 to 34 cu/km yr) and Venus (less than 20 cu/km yr) but much more than for the moon (0.025 cu/km yr). When scaled to earth's mass the Martian rate is much smaller than that for earth or Venus and slightly smaller than for the moon.

  9. Accumulation Rate of Microbial Biomass at Two Permeable Reactive Barrier Sites

    NASA Astrophysics Data System (ADS)

    Wilkin, R.; Sewell, G.; Puls, R.

    2001-12-01

    Accumulation of mineral precipitates and microbial biomass are key factors that impact the long term performance of in situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero valent iron reactivity and permeability. Results are presented from solid phase and groundwater monitoring studies conducted at two Permeable Reactive Barrier sites, U.S. Coast Guard Support Center (Elizabeth City, North Carolina) and the Denver Federal Center (Lakewood, Colorado). At both sites barrier installations have been in place for approximately five years. Over this period, consistent patterns of spatially heterogeneous microbial biomass accumulation are observed at these sites. The iron-aquifer interface witnesses the greatest accumulation of microbial biomass and mineral precipitates. There accumulation rates are a factor of 3 to 10 times greater than midwall or downgradient regions. Estimates of porosity loss due to mineral and biomass buildup range from about 1 to 5 percent per year of the initial available volume. Phospholipid fatty acid profiles indicate that the PRB biomass is dominated by biomarkers indicative of anaerobic sulfate reducing or iron reducing bacteria. This result is in agreement with acid volatile sulfide concentrations that strongly correlate with biomass concentrations. Upgradient groundwater chemistry and flow rate appear to be the main factors that control the rate (and type) of mineral precipitate formation as well as the rate of biomass accumulation. Notice, this is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

  10. Mars, Always Cold, Sometimes Wet: New Constraints on Mars Denudation Rates and Climate Evolution from Analog Studies at Haughton Crater, Devon Island, High Arctic

    NASA Technical Reports Server (NTRS)

    Lee, Pascal; Boucher, M.; Desportes, C.; Glass, B. J.; Lim, D.; McKay, C. P.; Osinski, G. R.; Parnell, J.; Schutt, J. W.

    2005-01-01

    Analysis of crater modification on Mars and at Haughton Crater, Devon Island, High Arctic, which was recently shown to be significantly older than previously believed (Eocene age instead of Miocene) [1], suggest that Mars may have never been climatically wet and warm for geological lengths of time during and since the Late Noachian. Impact structures offer particularly valuable records of the evolution of a planet s climate and landscape through time. The state of exposure and preservation of impact structures and their intracrater fill provide clues to the nature, timing, and intensity of the processes that have modified the craters since their formation. Modifying processes include weathering, erosion, mantling, and infilling. In this study, we compare the modification of Haughton through time with that of impact craters in the same size class on Mars. We derive upper limits for time-integrated denudation rates on Mars during and since the Late Noachian. These rates are significantly lower than previously published and provide important constraints for Mars climate evolution.

  11. Incorporation of radiometric tracers in peat and implications for estimating accumulation rates.

    PubMed

    Hansson, Sophia V; Kaste, James M; Olid, Carolina; Bindler, Richard

    2014-09-15

    Accurate dating of peat accumulation is essential for quantitatively reconstructing past changes in atmospheric metal deposition and carbon burial. By analyzing fallout radionuclides (210)Pb, (137)Cs, (241)Am, and (7)Be, and total Pb and Hg in 5 cores from two Swedish peatlands we addressed the consequence of estimating accumulation rates due to downwashing of atmospherically supplied elements within peat. The detection of (7)Be down to 18-20 cm for some cores, and the broad vertical distribution of (241)Am without a well-defined peak, suggest some downward transport by percolating rainwater and smearing of atmospherically deposited elements in the uppermost peat layers. Application of the CRS age-depth model leads to unrealistic peat mass accumulation rates (400-600 g m(-2) yr(-1)), and inaccurate estimates of past Pb and Hg deposition rates and trends, based on comparisons to deposition monitoring data (forest moss biomonitoring and wet deposition). After applying a newly proposed IP-CRS model that assumes a potential downward transport of (210)Pb through the uppermost peat layers, recent peat accumulation rates (200-300 g m(-2) yr(-1)) comparable to published values were obtained. Furthermore, the rates and temporal trends in Pb and Hg accumulation correspond more closely to monitoring data, although some off-set is still evident. We suggest that downwashing can be successfully traced using (7)Be, and if this information is incorporated into age-depth models, better calibration of peat records with monitoring data and better quantitative estimates of peat accumulation and past deposition are possible, although more work is needed to characterize how downwashing may vary between seasons or years. PMID:24946030

  12. Rates and environmental controls of aeolian dust accumulation, Athabasca River Valley, Canadian Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Hugenholtz, Chris H.; Wolfe, Stephen A.

    2010-09-01

    Despite an abundance of sedimentary archives of mineral dust (i.e. loess) accumulations from cold, humid environments, the absence of contemporary process investigations limits paleoenvironmental interpretations in these settings. Dust accumulations measured at Jasper Lake, a seasonally-filled reach of the glacially-fed Athabasca River in the Canadian Rocky Mountains, are some of the highest contemporary rates recorded to date. High deposition rates, including a maximum of 27,632 kg ha -1 month -1, occur during river low-flow periods, but even the lowest deposition rates, occurring during bankfull periods, exceed other contemporary rates of deposition. High rates of dust deposition may be attributed to geomorphic and climatic controls affecting sediment supply, availability and transport, and biologic factors affecting accumulation. Localized confinement of the Jasper River by tributary river alluvial fans has caused channel expansion upstream, and formation of the shallow depositional basin known as Jasper Lake. This localized sedimentary basin, coupled with large seasonal water level fluctuations and suitably high wind speeds, favors seasonal dust production. In addition, a dense source-proximal coniferous forest stand encourages high dust accumulation, via increased aerodynamic roughness and airflow deceleration. The forest stand also appears to act as an efficient dust filter, with the interception and storage of dust by the forest canopy playing a significant role with regards to secondary fallout and sediment accumulation. Overall, these results provide new insights on the environmental controls of dust entrainment and accumulation in cold, humid settings, and help clarify controls on the formation of Holocene river-sourced loess deposits.

  13. Surface Ages and Resurfacing Rates of the Polar Layered Deposits on Mars

    NASA Technical Reports Server (NTRS)

    Herkenhoff, K. E.; Plaut, J. J.

    1999-01-01

    The martian polar layered deposits (PLD) are probably the best source of information about the recent climate history of Mars, but their origin and the mechanisms of accumulation are still a mystery. The polar layers are sedimentary deposits that most planetary scientists believe are composed of water ice and varying amounts of wind-blown dust, but their composition is poorly constrained. Interpretation of the observed polar stratigraphy in terms of global climate changes is complicated by the significant difference in surface ages between the north and south PLD inferred from crater statistics. While no craters have been found in the north PLD, the surface of the south PLD appears to have been stable for many of the orbital/axial cycles that are thought to have induced global climate changes on Mars. Using medium-resolution Viking imagery, Plaut et al. found at least 15 impact craters in the southern layered deposits and concluded that their surface is 120 +/- 40 million years old. In contrast, Cutts et al. found no fresh impact craters larger than about 300 meters in summertime images of the north polar layered deposits. Additional information is contained in the original extended abstract.

  14. Spatial Accumulation-Rate Pattern Inferred from Radar Internal Layers and Point Measurements of Velocity and Accumulation near Taylor Mouth, Victoria Land

    NASA Astrophysics Data System (ADS)

    Waddington, E. D.; Neumann, T. A.; Morse, D. L.; Marshall, H.

    2002-12-01

    Internal layers in ice sheets, as measured by ice-penetrating radar, are most likely isochrones. The depth to a shallow internal layer is proportional to the local accumulation rate. However, low-frequency radars often do not record very shallow layers. High-frequency radars (GPR) record shallow layers, but cannot detect the deeper layers that reflect longer-term patterns of climate. Older, deeper layers are also influenced to an increasing degree by accumulated strain due to ice flow, and by the upstream accumulation rate. For this Geophysical Inverse Problem, our Forward Model is a steady-state ice-flow model with measured ice-sheet surface topography, ice thickness, and flowband width, which tracks particles to create modelled internal layers. Ice motion is driven by the input flux into the upper end of the flowband, and by the accumulation pattern along the flowband. To solve the Inverse Problem, our observations comprise depth of an internal layer, and point measurements of accumulation rate and surface velocity. Associated uncertainties are also required. We use Least-Squares or Singular-Value Decomposition to solve for model parameters (input ice flux, piece-wise linear accumulation-rate profile, and layer age) that minimize the mismatch between the data and the model estimates of the data. If the layer age and its uncertainty are known independently, they can also be used. Variable weights can be assigned to each type of data. The data-resolution matrix shows that, for shallow layers, we can resolve high-wavenumber variations in accumulation rate. For deeper layers, we resolve spatial averages of accumulation rates. We apply the model to a flowband at Taylor Mouth between Taylor Dome and Taylor Glacier. The model finds more variation in the inferred accumulation-rate profile than in the depth-profile of an internal layer. The new accumulation-rate profile produces an improved chronology for an ice core collected along the flowline.

  15. High Rates of Species Accumulation in Animals with Bioluminescent Courtship Displays.

    PubMed

    Ellis, Emily A; Oakley, Todd H

    2016-07-25

    One of the great mysteries of evolutionary biology is why closely related lineages accumulate species at different rates. Theory predicts that populations undergoing strong sexual selection will more quickly differentiate because of increased potential for genetic isolation [1-6]. Whether or not these population genetic processes translate to more species at macroevolutionary scales remains contentious [7]. Here we show that lineages with bioluminescent courtship, almost certainly a sexually selected trait, have more species and faster rates of species accumulation than their non-luminous relatives. In each of ten distantly related animal lineages from insects, crustaceans, annelid worms, and fishes, we find more species in lineages with bioluminescent courtship compared to their sister groups. Furthermore, we find under a Yule model that lineages with bioluminescent courtship displays have significantly higher rates of species accumulation compared to a larger clade that includes them plus non-luminous relatives. In contrast, we do not find more species or higher rates in lineages that use bioluminescence for defense, a function presumably not under sexual selection. These results document an association between the origin of bioluminescent courtship and increased accumulation of species, supporting theory predicting sexual selection increases rates of speciation at macroevolutionary scales to influence global patterns of biodiversity. PMID:27345160

  16. Holocene Carbon Accumulation Rates in the SPRUCE Bog Prior to Warming and Elevated CO2 Treatment

    NASA Astrophysics Data System (ADS)

    McFarlane, K. J.; Iversen, C. M.; Phillips, J. R.; Brice, D. J.; Hanson, P. J.

    2015-12-01

    In the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) experiment warming and elevated CO2 treatments are being applied to an ombrotrophic spruce bog: the S1 Bog (S1) at Marcell Experimental Forest in northern Minnesota. To provide a historical context for recent and expected experimentally-induced changes in the bog's belowground carbon balance, we reconstructed historical carbon accumulation rates in peat using radiocarbon from 19 peat cores collected from randomly distributed SPRUCE plots. This unusually high number of cores allows us to assess spatial variability in age-depth profiles and accumulation rates across the SPRUCE study area within S1. This data, along with recent C flux measurements, show that the bog has been accumulating carbon for at least 12,0000 years and has continued to be a sink for atmospheric carbon of approximately 150 g C m-2 yr-1 in recent decades. Early Holocene accumulation rates are similar to those reported for other northern peatlands (approximately 25 g C m-2 yr-1), but apparent carbon accumulation decreased substantially around 3,000 years ago (to 5-15 g C m-2 yr-1) and stayed low until the last century. This decrease is considerably larger than that reported for other peatlands and is therefore unlikely to result only from cooling during the Holocene or bog succession. Although no charcoal has been found in peat at this site, evidence from a neighboring bog indicates a considerable amount of peat formed during this period was consumed by fire and it is possible that smoldering fires consumed peat, resulting in low apparent accumulation rates. Past droughts may have also contributed to observed trends by lowering the acrotelm/catotelm boundary, allowing for enhanced aerobic peat decomposition. This work provides important background information on spatial variability and carbon biogeochemistry that will aid in interpretation of climate change simulation experiments at S1.

  17. Nutritive Value and Herbage Accumulation Rates of Pasture Sown to Grass, Legume, and Chicory

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Planting pastures to mixtures of forages may benefit herbage production; however, wide fluctuations in botanical composition could cause unstable nutritive value. A grazing study was conducted to examine how forage mixture complexity influenced nutritive value and accumulation rate during spring, su...

  18. Distinct mutation accumulation rates among tissues determine the variation in cancer risk

    PubMed Central

    Hao, Dapeng; Wang, Li; Di, Li-jun

    2016-01-01

    Cancer is believed to be a result of accumulated mutations. However, this concept has not been fully confirmed owing to the impossibility of tracking down the ancestral somatic cell. We sought to verify the concept by exploring the correlation between cancer risk and mutation accumulation among different tissues. We hypothesized that the detected mutations through bulk tumor sequencing are commonly shared in majority, if not all, of tumor cells and are therefore largely a reflection of the mutations accumulated in the ancestral cell that gives rise to tumor. We collected a comprehensive list of mutation frequencies revealed by bulk tumor sequencing, and investigated its correlation with cancer risk to mirror the correlation between mutation accumulation and cancer risk. This revealed an approximate 1:1 relationship between mutation frequency and cancer risk in 41 different cancer types based on the sequencing data of 5,542 patients. The correlation strongly suggests that variation in cancer risk among tissues is mainly attributable to distinct mutation accumulation rates. Moreover, the correlation establishes a baseline to evaluate the effect of non-mutagenic carcinogens on cancer risk. Finally, our mathematic modeling provides a reasonable explanation to reinforce that cancer risk is predominantly determined by the first rate-limiting mutation. PMID:26785814

  19. Distinct mutation accumulation rates among tissues determine the variation in cancer risk.

    PubMed

    Hao, Dapeng; Wang, Li; Di, Li-jun

    2016-01-01

    Cancer is believed to be a result of accumulated mutations. However, this concept has not been fully confirmed owing to the impossibility of tracking down the ancestral somatic cell. We sought to verify the concept by exploring the correlation between cancer risk and mutation accumulation among different tissues. We hypothesized that the detected mutations through bulk tumor sequencing are commonly shared in majority, if not all, of tumor cells and are therefore largely a reflection of the mutations accumulated in the ancestral cell that gives rise to tumor. We collected a comprehensive list of mutation frequencies revealed by bulk tumor sequencing, and investigated its correlation with cancer risk to mirror the correlation between mutation accumulation and cancer risk. This revealed an approximate 1:1 relationship between mutation frequency and cancer risk in 41 different cancer types based on the sequencing data of 5,542 patients. The correlation strongly suggests that variation in cancer risk among tissues is mainly attributable to distinct mutation accumulation rates. Moreover, the correlation establishes a baseline to evaluate the effect of non-mutagenic carcinogens on cancer risk. Finally, our mathematic modeling provides a reasonable explanation to reinforce that cancer risk is predominantly determined by the first rate-limiting mutation. PMID:26785814

  20. Accumulation-rate history at Siple Dome, West Antarctica, using bubble number-density

    NASA Astrophysics Data System (ADS)

    Spencer, M.; Dennison, A.; Alley, R. B.; Fitzpatrick, J. J.; Fegyveresi, J. M.

    2012-12-01

    Past allowable accumulation rate/temperature combinations at Siple Dome, West Antarctica, are estimated from the measured number-density of bubbles in ice core samples. Mass density increase and grain growth in polar firn both are controlled by temperature and accumulation rate, and their integrated effects are recorded in the number-density of bubbles as the firn changes to ice [1]. Accumulation-rate estimates from measured bubble number-density and additional constraints from numerical modeling of firn densification at Siple Dome are consistent with 1-D ice-flow model results that have little change in the thickness of the ice sheet in the central Ross Embayment of West Antarctica since the last glacial maximum [2]. Using methods developed to analyze late-Holocene bubble number-density samples from the West Antarctic Ice Sheet Divide Ice Core Project [3], Siple Dome bubble number-densities show an early-Holocene high in accumulation rate followed by an approximately 10% reduction in accumulation rate between 11.33 ka and 1.863 ka. [1] Spencer, M.K., R.B. Alley and J.J. Fitzpatrick. Developing a bubble number-density paleoclimatic indicator for glacier ice, J. Glaciol. 52(178), 358-364 (2006). [2] E.D. Waddington et al., Decoding the dipstick: thickness of Siple Dome, West Antarctica, at the last glacial maximum, Geology 33(4), 281-284 (2005). [3] J.M. Fegyveresi, et al., Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: bubble number-density estimates, J. Glaciol., 57(204) , 629 - 638 (2011).

  1. Cerberus Fossae and Elysium Planitia Lavas, Mars: Source Vents, Flow Rates, Edifice Styles and Water Interactions

    NASA Technical Reports Server (NTRS)

    Sakimoto, S. E. H.; Gregg, T. K. P.

    2004-01-01

    The Cerberus Fossae and Elysium Planitia regions have been suggested as some of the youngest martian surfaces since the Viking mission, although there was doubt whether the origins were predominantly volcanic or fluvial. The Mars Global Surveyor and Mars Odyssey Missions have shown that the region is certainly young in terms of the topographic preservation and the youthful crater counts (e.g. in the tens to a few hundred million yrs.). Numerous authors have shown that fluvial and volcanic features share common flow paths and vent systems, and that there is evidence for some interaction between the lava flows and underlying volatiles as well as the use by lavas and water of the same vent system. Given the youthful age and possible water-volcanism interaction environment, we'd like constraints on water and volcanic flux rates and interactions. Here, we model ranges of volcanic flow rates where we can well-constrain them, and consider the modest flow rate results results in context with local eruption styles, and track vent locations, edifice volumes, and flow sources and data.

  2. Rates of β-amyloid accumulation are independent of hippocampal neurodegeneration

    PubMed Central

    Wiste, Heather J.; Knopman, David S.; Vemuri, Prashanthi; Mielke, Michelle M.; Weigand, Stephen D.; Senjem, Matthew L.; Gunter, Jeffrey L.; Lowe, Val; Gregg, Brian E.; Pankratz, Vernon S.; Petersen, Ronald C.

    2014-01-01

    Objective: To test the hypotheses predicted in a hypothetical model of Alzheimer disease (AD) biomarkers that rates of β-amyloid (Aβ) accumulation on PET imaging are not related to hippocampal neurodegeneration whereas rates of neurodegenerative brain atrophy depend on the presence of both amyloid and neurodegeneration in a population-based sample. Methods: A total of 252 cognitively normal (CN) participants from the Mayo Clinic Study of Aging had 2 or more serial visits with both amyloid PET and MRI. Subjects were classified into 4 groups based on baseline positive/negative amyloid PET (A+ or A−) and baseline hippocampal volume (N+ or N−). We compared rates of amyloid accumulation and rates of brain atrophy among the 4 groups. Results: At baseline, 148 (59%) were amyloid negative and neurodegeneration negative (A−N−), 29 (12%) amyloid negative and neurodegeneration positive (A−N+), 56 (22%) amyloid positive and neurodegeneration negative (A+N−), and 19 (8%) amyloid positive and neurodegeneration positive (A+N+). High rates of Aβ accumulation were found in those with abnormal amyloid at baseline and were not influenced by hippocampal neurodegeneration at baseline. In contrast, rates of brain atrophy were greatest in A+N+. Conclusions: We describe a 2-feature biomarker approach to classifying elderly CN subjects that is complementary to the National Institute on Aging–Alzheimer's Association preclinical staging criteria. Our results support 2 key concepts in a model of the temporal evolution of AD biomarkers. First, the rate of Aβ accumulation is not influenced by neurodegeneration and thus may be a biologically independent process. Second, Aβ pathophysiology increases or catalyzes neurodegeneration. PMID:24706010

  3. Hydroacoustic and spatial analysis of sediment fluxes and accumulation rates in two Virginia reservoirs, USA.

    PubMed

    Clark, E V; Odhiambo, B K; Yoon, S; Pilati, L

    2015-06-01

    Watershed sediment fluxes and reservoir sediment accumulation rates were analyzed in two contrasting reservoir systems in central and western Virginia. Lake Pelham, located in the Piedmont geologic province, is a human-impacted reservoir with a watershed dominated by agricultural, residential and industrial land uses. Conversely, Lake Moomaw has a largely undeveloped watershed characterized by very steep slopes and forested land use located in the Valley and Ridge province. The Revised Universal Soil Loss Equation (RUSLE) and sediment delivery ratios (SDRs) were used to estimate soil losses in the two watersheds. Bathymetric and sediment accumulation surveys of the two reservoirs were also conducted using a multi-frequency hydroacoustic surveying system. The RUSLE/SDR erosion model estimates 2150 kg ha(-1) year(-1) for Lake Pelham and 2720 kg ha(-1) year(-1) for Lake Moomaw, a 410 and 13 % increase from assumed pristine (100 % forested) land use for the respective basins. Mean sediment accumulation rates of 1.51 and 0.60 cm year(-1) were estimated from the hydroacoustic survey of Lake Pelham and Lake Moomaw, respectively. Overall, Lake Moomaw has relatively low sediment accumulation rates; however, the reservoir is vulnerable to increases in sediment fluxes with further human development due to the steep slopes and highly erodible colluvial soils that characterize the basin. Higher erosion and sediment accumulation rates in Lake Pelham are most likely reflecting the impact of human development on sedimentation processes, where the loss of vegetal buffers and increase in impervious surfaces exacerbates both the surficial soil losses as well as intrinsic stream sediment production leading to the current annual reservoir capacity loss of 0.4 %. PMID:25563837

  4. Soil carbon stocks and their rates of accumulation and loss in a boreal forest landscape

    USGS Publications Warehouse

    Rapalee, G.; Trumbore, S.E.; Davidson, E.A.; Harden, J.W.; Veldhuis, H.

    1998-01-01

    Boreal forests and wetlands are thought to be significant carbon sinks, and they could become net C sources as the Earth warms. Most of the C of boreal forest ecosystems is stored in the moss layer and in the soil. The objective of this study was to estimate soil C stocks (including moss layers) and rates of accumulation and loss for a 733 km2 area of the BOReal Ecosystem-Atmosphere Study site in northern Manitoba, using data from smaller-scale intensive field studies. A simple process-based model developed from measurements of soil C inventories and radiocarbon was used to relate soil C storage and dynamics to soil drainage and forest stand age. Soil C stocks covary with soil drainage class, with the largest C stocks occurring in poorly drained sites. Estimated rates of soil C accumulation or loss are sensitive to the estimated decomposition constants for the large pool of deep soil C, and improved understanding of deep soil C decomposition is needed. While the upper moss layers regrow and accumulate C after fires, the deep C dynamics vary across the landscape, from a small net sink to a significant source. Estimated net soil C accumulation, averaged for the entire 733 km2 area, was 20 g C m-2 yr-1 (28 g C m-2 yr-1 accumulation in surface mosses offset by 8 g C m-2 yr-1 lost from deep C pools) in a year with no fire. Most of the C accumulated in poorly and very poorly drained soils (peatlands and wetlands). Burning of the moss layer in only 1% of uplands would offset the C stored in the remaining 99% of the area. Significant interannual variability in C storage is expected because of the irregular occurrence of fire in space and time. The effects of climate change and management on fire frequency and on decomposition of immense deep soil C stocks are key to understanding future C budgets in boreal forests.

  5. System Analysis Applied to Autonomy: Application to Human-Rated Lunar/Mars Landers

    NASA Technical Reports Server (NTRS)

    Young, Larry A.

    2006-01-01

    System analysis is an essential technical discipline for the modern design of spacecraft and their associated missions. Specifically, system analysis is a powerful aid in identifying and prioritizing the required technologies needed for mission and/or vehicle development efforts. Maturation of intelligent systems technologies, and their incorporation into spacecraft systems, are dictating the development of new analysis tools, and incorporation of such tools into existing system analysis methodologies, in order to fully capture the trade-offs of autonomy on vehicle and mission success. A "system analysis of autonomy" methodology will be outlined and applied to a set of notional human-rated lunar/Mars lander missions toward answering these questions: 1. what is the optimum level of vehicle autonomy and intelligence required? and 2. what are the specific attributes of an autonomous system implementation essential for a given surface lander mission/application in order to maximize mission success? Future human-rated lunar/Mars landers, though nominally under the control of their crew, will, nonetheless, be highly automated systems. These automated systems will range from mission/flight control functions, to vehicle health monitoring and prognostication, to life-support and other "housekeeping" functions. The optimum degree of autonomy afforded to these spacecraft systems/functions has profound implications from an exploration system architecture standpoint.

  6. Rate of production, dissolution and accumulation of biogenic solids in the ocean

    NASA Technical Reports Server (NTRS)

    Arrhenius, G.

    1988-01-01

    The equatorial current system, by its response to global circulation changes, provides a unique recording mechanism for long range climatic oscillations. A permanent record of the changes in rate of upwelling and organic production is generated in the equatorial deep sea sediments, particularly by such biogenic components which are unaffected by secondary dissolution. In order to determine the rates of accumulation of various sedimentary components, a reliable differential measurement of age of the strata must be obtained. Various approaches to this problem are reviewed, and sources of error discussed. Secondary dissolution of calcium carbonate introduces a substantial and variable difference between the dissolution-modified, and hence a priori unknown, rate of deposition on one hand and the rate of accumulation, derivable from the observed concentration, on the other. The cause and magnitude of these variations are of importance, particularly since some current dating schemes are based on assumed constancy in the rate of accumulation of this and, in some cases, also all other sedimentary components. The concepts used in rate evaluation are discussed with emphasis on the difference between the state of dissolution, an observable property of the sediment, and the rate of dissolution, a parameter that requires deduction of the carbonate fraction dissolved, and of the time differential. As a most likely cause of the enhanced state of dissolution of the interglacial carbonate sediments is proposed the lowered rates of biogenic production and deposition, which cause longer exposure of the carbonate microfossils to corrosion in the bioturbated surface layer of the sediment. Historical perspective is included in the discussion in view of the dedication of the Symposium to Hans Pettersson, the leader of the Swedish Deep Sea Expedition 1947-1948, an undertaking that opened a new era in deep sea research and planetary dynamics.

  7. The distribution of the heavy metal accumulation rate in the biomass of three Daphnia species

    SciTech Connect

    Gajula, V.K.; Hovorka, J.; Stuchlik, E.

    1995-12-31

    The difference in the accumulation rate of a mixture of heavy metals in aquatic organisms is of considerable interest because of its importance in the prediction of the effect of pollutants in aquatic systems. In this study the authors are making an effort to evaluate the accumulation patterns of pollutants in aquatic organisms by establishing a relation between the level of an accumulated mixture of heavy metals (Cd, Zn, Pb, As, Hg) in individuals of Daphnia magna, Daphnia pulicaria and Daphnia galeata and its dry weight with respect to the form of heavy metals in the aquatic environment. One age group of Daphnia species (10 day old) were exposed to 5 ppb, 10 ppb and 20 ppb of the mixture of heavy metals for 24 hours in three different experiments. In the first experiment the mixture of heavy metals was present exclusively in labelled algae (Scendesmus actus), in the second in an aquatic medium with non labelled algae, and in the third experiment the mixture of heavy metals was dissolved in the aquatic medium only without the addition of algae. The concentration of the heavy metal mixture in individuals of D.magna; D.pulicaria and D.galeata was determined using atomic absorption spectrometry. Results were statistically evaluated and the rate of accumulation and influence of various heavy metals in the biomass of three Daphnia species is discussed.

  8. Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Haider, S. A.; Kim, J.; Nagy, A. F.; Keller, C. N.; Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Szego, K.; Kiraly, P.

    1992-01-01

    The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

  9. Synthesis of passive microwave and radar altimeter data for estimating accumulation rates of polar snow

    NASA Technical Reports Server (NTRS)

    Davis, Curt H.

    1993-01-01

    In this paper, we compare dry-snow extinction coefficients derived from radar altimeter data with brightness temperature data from passive microwave measurements over a portion of the East Antarctic plateau. The comparison between the extinction coefficients and the brightness temperatures shows a strong negative correlation, where the correlation coefficients ranged from -0.87 to -0.95. The extinction coefficient of the dry polar snow decreases with increasing surface elevation, while the average brightness temperature increases with surface elevation. Our analysis shows that the observed trends are related to geographic variations in scattering coefficient of snow, which in turn are controlled by variations in surface temperature and snow accumulation rate. By combining information present in the extinction coefficient and brightness temperature data sets, we develop a model that can be used to obtain quantitative estimates of the accumulation rate of dry polar snow.

  10. Balancing sample accumulation and DNA degradation rates to optimize noninvasive genetic sampling of sympatric carnivores.

    PubMed

    Lonsinger, Robert C; Gese, Eric M; Dempsey, Steven J; Kluever, Bryan M; Johnson, Timothy R; Waits, Lisette P

    2015-07-01

    Noninvasive genetic sampling, or noninvasive DNA sampling (NDS), can be an effective monitoring approach for elusive, wide-ranging species at low densities. However, few studies have attempted to maximize sampling efficiency. We present a model for combining sample accumulation and DNA degradation to identify the most efficient (i.e. minimal cost per successful sample) NDS temporal design for capture-recapture analyses. We use scat accumulation and faecal DNA degradation rates for two sympatric carnivores, kit fox (Vulpes macrotis) and coyote (Canis latrans) across two seasons (summer and winter) in Utah, USA, to demonstrate implementation of this approach. We estimated scat accumulation rates by clearing and surveying transects for scats. We evaluated mitochondrial (mtDNA) and nuclear (nDNA) DNA amplification success for faecal DNA samples under natural field conditions for 20 fresh scats/species/season from <1-112 days. Mean accumulation rates were nearly three times greater for coyotes (0.076 scats/km/day) than foxes (0.029 scats/km/day) across seasons. Across species and seasons, mtDNA amplification success was ≥95% through day 21. Fox nDNA amplification success was ≥70% through day 21 across seasons. Coyote nDNA success was ≥70% through day 21 in winter, but declined to <50% by day 7 in summer. We identified a common temporal sampling frame of approximately 14 days that allowed species to be monitored simultaneously, further reducing time, survey effort and costs. Our results suggest that when conducting repeated surveys for capture-recapture analyses, overall cost-efficiency for NDS may be improved with a temporal design that balances field and laboratory costs along with deposition and degradation rates. PMID:25454561

  11. Trawling-induced alterations of deep-sea sediment accumulation rates during the Anthropocene

    NASA Astrophysics Data System (ADS)

    Puig, P.; Paradis, S.; Masque, P.; Martin, J.; Juan, X.; Palanques, A.

    2015-12-01

    Commercial bottom trawling causes direct physical disturbance of the marine sedimentary environments by scraping and ploughing the seabed, generating periodic resuspension of surface sediments. However, the quantification of the sediment that is removed by trawling and exported across the continental margin remains largely unaddressed, and the preservation of the signal of such impacts in the geological record have been mostly overlooked. The analysis of sediment cores collected along the Catalan margin (NW Mediterranean) has allowed evaluating the contribution of this anthropogenic activity to the present-day sediment dynamics. Sediment cores at intensively trawled sites are characterized by over-consolidated sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sedimentary deposits. In turn, combined 210Pb and 137Cs chronologies indicate a significant increase of sediment accumulation rates within submarine canyon environments since the 1970s, coincidently with a strong impulse in the industrialization of the trawling fleets of this region. Two sampling sites that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied 1-2 decades after the first studies and revealed a second and even larger increase of sediment accumulation rates (>2 cm/y) occurring at the beginning of the XXI century. This recent change has been attributed to a preferential displacement of the trawling fleet towards fishing grounds surrounding submarine canyons and, also, to technical improvements in trawling vessels, presumably related to financial subsidies provided to the fishing sector. The alteration of sediment accumulation rates described in this continental margin may occur in many regions of the World's oceans given the wide geographical distribution of this human activity, and therefore, it could represent a potential marker of the Anthropocene in deep-sea environments.

  12. Organic Carbon, Nitrogen and Phosphorus Accumulation Rates in the Soils of the Everglades Mangrove Ecotone

    NASA Astrophysics Data System (ADS)

    Smoak, J. M.; Breithaupt, J. L.; Sanders, C. J.

    2015-12-01

    One of the fundamental questions with regard to coastal ecotones relates to their role in the transformation, transport and storage of biogeochemically important constituents and how that role may be altered by climate change. Coastal wetlands provide a range of valuable ecosystem services including sequestering organic carbon (OC) and nutrients in their soils at rates greater than terrestrial ecosystems on a per area basis. As such the Everglades mangrove ecotone, the largest contiguous mangrove forest in North America, is a biogeochemical "hotspot" at the interface of freshwater marsh and the Gulf of Mexico. Over the last one hundred years this region has been impacted by a reduction in freshwater flow and a sea-level rise (SLR) of 2.3 mm/yr which combined to cause a landward shift in the ecotone. This creates an ideal setting to examine climate induced alterations in the mangrove-ecotone biogeochemical cycle. The ability of the Everglades mangrove forest to keep pace with SLR depends largely on the rate of organic matter accumulation as that accumulation is a key contributor to accretion. However, the basic threat from SLR can be exacerbated in some areas by accelerating organic matter mineralization due to increasing salinity. The increase in salinity supplies sulfate which functions as a terminal electron acceptor that soil microbes can utilize to enhance mineralization in the brackish ecotone regions of coastal wetlands. To investigate these processes, we measured mangrove forest soil accretion, OC, N and P accumulation rates over the most recent 10, 50 and 100 year periods (via 210Pb dating) from the Gulf of Mexico to the upper freshwater reaches of the mangrove forest within Everglades National Park. Lower organic carbon accumulation rates compared to the rest of the system were found in the ecotone region most susceptible to enhanced organic matter mineralization.

  13. Iunconsistencies in Accumulation Rates of Black Sea Sediments Inferred from Records of Laminae and 210Pb

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Anderson, R. F.

    1992-04-01

    Recently-published estimates for the age of the unit 1-unit 2 contact in Black Sea sediments based on accelerator mass spectrometry (AMS) 14C measurements [Jones, 1990; Calvert et al., 1991] appear to be older than those based on the previously published chronology based on lamina couplets [Degens et al., 1980; Hay, 1988] by a factor of 2 to 3. To help reconcile the differences, we compare sediment accumulation rates based on the 210Pb method with estimates based on lamina counts for two cores from the Black Sea abyssal plain. Accumulation rates estimated using the 210Pb technique have varied little over the last 150 years from the averages of 55 and 50 g m-2 yr-1 at stations in the western and eastern basins, respectively. These values are about a factor of 2 lower than accumulation rates derived by counting lamina couplets over the dated intervals. Close examination of the laminae suggests that the discrepancy exists both because it is difficult to count the very fine laminae and because a complete couplet is not deposited every year. In order to provide a useful stratigraphic horizon for future investigators studying sedimentary records of the Black Sea, we estimate the age of a distinct black marker horizon which can be easily identified across the entire abyssal plain to be 150±8 years (deposited in 1838±8 A.D.).

  14. Accumulation rates of Th-230, Pa-231, and some transition metals on the Bermuda Rise

    USGS Publications Warehouse

    Bacon, M.P.; Rosholt, J.N.

    1982-01-01

    Measurements of 238U, 234U, 230Th, 232Th, 231Pa, Mn, Fe, Co, Ni, Cu, and Zn were made on 23 samples from core GPC-5, a 29-m giant piston core from a water depth of 4583 m on the northeastern Bermuda Rise (33??41.2???N, 57??36.9???W). This area is characterized by rapid deposition of sediment transported by abyssal currents. Unsupported 230Th and 231Pa are present throughout the core but, because of large variations in the sedimentation rate, show marked departures from exponential decay with depth. The trend with depth of the 231Paex 230Thex ratio is consistent with the average accumulation rate of 36 cm/1000 y reported earlier on the basis of radiocarbon dating and CaCO3 stratigraphy. When expressed on a carbonate-free basis, concentrations of Mn, Co, Ni, Cu, Zn, 230Thex, and 231Paex all show cyclic variations positively correlated with those of CaCO3. The correlations can be explained by a model in which all of these constituents, including CaCO3, are supplied to the sediments from the water column at a constant rate. Concentration variations are controlled mainly by varying inputs of terrigenous detritus, with low inputs occurring during interglacials and high inputs during glacials. Relationships between the metal and 230Thex concentrations permit estimates of the rates at which the metals are removed to the sediment by scavenging from the water column. The results, in ??g/cm2-1000 y, are: 4300 ?? 1100 for Mn, 46 ?? 16 for Ni and 76 ?? 26 for Cu. These rates are somewhat larger than ocean-wide averages estimated by other methods, and the absolute rate of 230Th accumulation in GPC-5 averages about nine times higher than production in the overlying water column. This part of the Bermuda Rise and similar bottom-current deposits may act as important accumulators of elements scavenged from seawater. ?? 1982.

  15. Accumulation rate and mixing of shelf sediments in the Monterey Bay National Marine Sanctuary

    USGS Publications Warehouse

    Lewis, R.C.; Coale, K.H.; Edwards, B.D.; Marot, M.; Douglas, J.N.; Burton, E.J.

    2002-01-01

    The distribution of excess 210Pb in 31 sediment cores was used to determine modern (last 100 yr) mass accumulation rates and the depth of sediment mixing on the continental shelf between Pacifica and Monterey, California, USA. Apparent mass accumulation rates average 0.27 g cm-2 yr-1 and range from 0.42 g cm-2 yr-1 to 0.12 g cm-2 yr-1. Accumulation rates were highest at mid-shelf water depths (60-100 m) adjacent to major rivers and near the head of the Ascension submarine canyon. Cores from water depths of less than 65 m had low, uniform 210Pb activity profiles and sandy textures. The uppermost 5-13 cm of 15 cores had uniform 210Pb activity profiles above a region of steadily decreasing 210Pb activity. This phenomenon was attributed to sediment mixing. The thickness of this upper layer of uniform 210Pb activity decreased southward from 13 cm, west of Pacifica, to less than 5 cm, near Monterey Canyon. This southward decrease may be attributed to shallower bioturbation in the southern study area. Integrated excess 210Pb activities were generally higher where sedimentation rates were high. They were also higher with increasing distance from major rivers. Thus, sedimentation rate alone does not explain the distribution of integrated excess 210Pb in this study area. Excess 210Pb in the seafloor is controlled by other factors such as sediment texture, the atmospheric deposition rate of 210Pb, and the residence time of sediment particles in the water column. ?? 2002 Elsevier Science B.V. All rights reserved.

  16. Recent (Late Amazonian) enhanced backweathering rates on Mars: Paracratering evidence from gully alcoves

    NASA Astrophysics Data System (ADS)

    de Haas, Tjalling; Conway, Susan; Krautblatter, Michael

    2016-04-01

    Mars is believed to have been exposed to low planet-wide weathering and denudation since the Noachian period (˜4.1 - 3.7 Ga). However, the widespread occurrence of alcoves at the rim of pristine impact craters suggests locally enhanced recent backweathering rates. Here we derive Late Amazonian backweathering rates from the alcoves of 10 young equatorial and mid-latitude craters, ranging in age from 0.2 to 45 Ma. The enhanced Late Amazonian Martian backweathering rates (10‑4 - 10‑1 mm yr‑1) are approximately one order of magnitude higher than previously reported erosion rates, and are similar to terrestrial rates inferred from Meteor crater and various Arctic and Alpine rock faces, when corrected for age. Alcoves on initially highly fractured and oversteepened crater rims following impact show enhanced backweathering rates that decline over at least 101 - 102 Myr as the crater wall stabilizes. This 'paracratering' backweathering decline with time is analogous to the paraglacial effect observed in rock slopes after deglaciation, but the relaxation time scale of 101 - 102 Myr compared to 10 kyr of the Milankovitch-controlled interglacial duration questions whether a paraglacial steady state is reached on Earth. The backweathering rates on the gullied pole-facing alcoves of the studied mid-latitude craters are much higher (˜2 - 60 times) than those on slopes with other azimuths and those in equatorial craters. The enhanced backweathering rates on gullied crater slopes may result from liquid water acting as a catalyst for backweathering. The decrease in backweathering rates over time might explain the similar size of gullies in young (<1 Ma) and much older craters, as alcove growth and sediment supply decrease to low background rates over time.

  17. Recent (Late Amazonian) enhanced backweathering rates on Mars: Paracratering evidence from gully alcoves

    NASA Astrophysics Data System (ADS)

    Haas, Tjalling; Conway, Susan J.; Krautblatter, Michael

    2015-12-01

    Mars is believed to have been exposed to low planet-wide weathering and denudation since the Noachian. However, the widespread occurrence of alcoves at the rim of pristine impact craters suggests locally enhanced recent backweathering rates. Here we derive Late Amazonian backweathering rates from the alcoves of 10 young equatorial and midlatitude craters. The enhanced Late Amazonian Martian backweathering rates (10-4-10-1 mm yr-1) are approximately 1 order of magnitude higher than previously reported erosion rates and are similar to terrestrial rates inferred from Meteor crater and various Arctic and Alpine rock faces. Alcoves on initially highly fractured and oversteepened crater rims following impact show enhanced backweathering rates that decline over at least 101-102 Myr as the crater wall stabilizes. This "paracratering" backweathering decline with time is analogous to the paraglacial effect observed in rock slopes after deglaciation, but the relaxation timescale of 101-102 Myr compared to 10 kyr of the Milankovitch-controlled interglacial duration questions whether a paraglacial steady state is reached on Earth. The backweathering rates on the gullied pole-facing alcoves of the studied midlatitude craters are much higher (˜2-60 times) than those on slopes with other azimuths and those in equatorial craters. The enhanced backweathering rates on gullied crater slopes may result from liquid water acting as a catalyst for backweathering. The decrease in backweathering rates over time might explain the similar size of gullies in young (<1 Ma) and much older craters, as alcove growth and sediment supply decrease to low-background rates over time.

  18. Sediment mixing and accumulation rate effects on radionuclide depth profiles in Hudson estuary sediments

    SciTech Connect

    Olsen, C.R.; Simpson, H.J.; Peng, T.; Bopp, R.F.; Trier, R.M.

    1981-11-20

    Measured anthropogenic radionuclide profiles in sediment cores from the Hudson River estuary were compared with profiles computed by using known input histories of radionuclides to the estuary and mixing coefficients which decreased exponentially with depth in the sediment. Observed /sup 134/Cs sediment depth profiles were used in the mixing rate computation because reactor releases were the only significant source for this nuclide, whereas the inputs of /sup 137/Cs and /sup 239.240/Pu to the estuary were complicated by runoff or erosion in upstream areas, in addition to direct fallout from precipitation. Our estimates for the rates of surface sediment mixing in the low salinity reach of the estuary range from 0.25 to 1 cm/sup 2//yr, or less. In some areas of the harbor adjacent to New York City, were fine-particle accumulation rates are generally >3 cm/yr, and often as high as 10 to 20 cm/yr, sediment mixing rates as high as 10 cm/sup 2//yr would have little effect on radionuclide peak distributions. Consequently, anthropogenic radionuclide maximum activities in subsurface sediments of the Hudson appear to be useful as time-stratigraphic reference levels, which can be correlated with periods of maximum radionuclide inputs for estimating rates and patterns of sediment accumulation.

  19. Carbon accumulation rate of peatland in the High Arctic, Svalbard: Implications for carbon sequestration

    NASA Astrophysics Data System (ADS)

    Nakatsubo, Takayuki; Uchida, Masaki; Sasaki, Akiko; Kondo, Miyuki; Yoshitake, Shinpei; Kanda, Hiroshi

    2015-06-01

    Moss tundra that accumulates a thick peat layer is one of the most important ecosystems in the High Arctic, Svalbard. The importance of this ecosystem for carbon sequestration was estimated from the apparent rates of carbon accumulation based on the 14C age and amount of peat in the active layer. The study site at Stuphallet, Brøgger Peninsula, northwestern Svalbard was covered with a thick peat layer dominated by moss species such as Calliergon richardsonii, Paludella squarrosa, Tomenthypnum nitens, and Warnstorfia exannulata. The average thickness of the active layer (brown moss and peat) was approximately 28 cm in 1 August 2011. The calibrated (cal) age of peat from the bottom of the active layer (20-30 cm below the peatland surface) ranged from 81 to 701 cal yr BP (median value of 2σ range). Based on the total carbon (4.5-9.2 kg C m-2), the apparent rate of carbon accumulation in the active layer was 9.0-19.2 (g C m-2 yr-1), which is similar to or greater than the net ecosystem production or net primary production reported for other vegetation types in this area. Our data suggest that moss tundra plays an important role in carbon sequestration in this area.

  20. Systems Level Regulation of Rhythmic Growth Rate and Biomass Accumulation in Grasses

    SciTech Connect

    Kay, Steve A.

    2013-05-02

    Several breakthroughs have been recently made in our understanding of plant growth and biomass accumulation. It was found that plant growth is rhythmically controlled throughout the day by the circadian clock through a complex interplay of light and phytohormone signaling pathways. While plants such as the C4 energy crop sorghum (Sorghum bicolor (L.) Moench) and possibly the C3 grass (Brachypodium distachyon) also exhibit daily rhythms in growth rate, the molecular details of its regulation remain to be explored. A better understanding of diurnally regulated growth behavior in grasses may lead to species-specific mechanisms highly relevant to future strategies to optimize energy crop biomass yield. Here we propose to devise a systems approach to identify, in parallel, regulatory hubs associated with rhythmic growth in C3 and C4 plants. We propose to use rhythmicity in daily growth patterns to drive the discovery of regulatory network modules controlling biomass accumulation.

  1. The Sublimation Rate of CO2 Under Simulated Mars Conditions and the Possible Climatic Implications

    NASA Astrophysics Data System (ADS)

    Bryson, Kathryn; Chevrier, V.; Roe, L.; White, K.; Blackburn, D.

    2008-09-01

    In order to understand the behavior of CO2 on Mars, we have studied the sublimation of dry ice under simulated martian conditions. Our experiments resulted in an average sublimation rate for CO2 ice of 1.20 ± 0.27 mm h-1. These results are very close to those observed of the martian polar caps retreat, and suggest a common process for the sublimation mechanism on Mars and in our chamber. Based on these results we created a model where irradiance from the sun is the primary source of heat on the martian polar surface. Our model predicts a 32 cm offset between the amount of CO2 ice sublimated and deposited in the southern polar region. The eccentricity of the martian orbit causes the southern hemisphere to sublimate more then it deposits back during one martian year. We have compared MOC and HiRISE images from approximately the same season (Ls 285.57º and 289.5º, respectively) from three martian years apart. These images indicate an average sublimation rate of 0.43 ± 0.04 m y-1, very close to the 0.32 m y-1 predicted by our model. Due to the length of Mars’ precession cycle, 93,000 martian years, it will take an extensive amount of time for the equinoxes to change. Therefore, we predict that the CO2 of the south polar cap will migrate entirely to the northern polar cap before such changes could occur. If the CO2 ice is only a thin layer above a much thicker water ice layer, this could expose large amounts of water ice, having a drastic climactic affect.

  2. LATE CENOZOIC INCREASE IN ACCUMULATION RATES OF TERRESTRIAL SEDIMENT: How Might Climate Change Have Affected Erosion Rates?

    NASA Astrophysics Data System (ADS)

    Molnar, Peter

    2004-05-01

    Accumulation rates of terrestrial sediment have increased in the past few million years both on and adjacent to continents, although not everywhere. Apparently, erosion has increased in elevated terrain regardless of when last tectonically active or what the present-day climate. In many regions, sediment coarsened abruptly in late Pliocene time. Sparser data suggest increased sedimentation rates at 15 Ma, approximately when oxygen isotopes in benthic foraminifera imply high-latitude cooling. If climate change effected accelerated erosion, understanding how it did so remains the challenge. Some obvious candidates, such as lowered sea level leading to erosion of continental shelves or increased glaciation, account for increased sedimentation in some, but not all, areas. Perhaps stable climates that varied slowly allowed geomorphic processes to maintain a state of equilibrium with little erosion until 34 Ma, when large oscillations in climate with periods of 20,00040,000 years developed and denied the landscape the chance to reach equilibrium.

  3. Small crater modification on Meridiani Planum and implications for erosion rates and climate change on Mars

    USGS Publications Warehouse

    Golombek, M.P.; Warner, N.H.; Ganti, V.; Lamb, M.P.; Parker, T.J.; Fergason, Robin L.; Sullivan, R.

    2014-01-01

    A morphometric and morphologic catalog of ~100 small craters imaged by the Opportunity rover over the 33.5 km traverse between Eagle and Endeavour craters on Meridiani Planum shows craters in six stages of degradation that range from fresh and blocky to eroded and shallow depressions ringed by planed off rim blocks. The age of each morphologic class from <50–200 ka to ~20 Ma has been determined from the size-frequency distribution of craters in the catalog, the retention age of small craters on Meridiani Planum, and the age of the latest phase of ripple migration. The rate of degradation of the craters has been determined from crater depth, rim height, and ejecta removal over the class age. These rates show a rapid decrease from ~1 m/Myr for craters <1 Ma to ~ <0.1 m/Myr for craters 10–20 Ma, which can be explained by topographic diffusion with modeled diffusivities of ~10−6 m2/yr. In contrast to these relatively fast, short-term erosion rates, previously estimated average erosion rates on Mars over ~100 Myr and 3 Gyr timescales from the Amazonian and Hesperian are of order <0.01 m/Myr, which is 3–4 orders of magnitude slower than typical terrestrial rates. Erosion rates during the Middle-Late Noachian averaged over ~250 Myr, and ~700 Myr intervals are around 1 m/Myr, comparable to slow terrestrial erosion rates calculated over similar timescales. This argues for a wet climate before ~3 Ga in which liquid water was the erosional agent, followed by a dry environment dominated by slow eolian erosion.

  4. [Dynamics simulation on plant growth, N accumulation and utilization of processing tomato at different N fertilization rates].

    PubMed

    Wang, Xin; Ma, Fu-Yu; Diao, Ming; Fan, Huam; Cui, Jing; Jia, Biao; He, Hai-Bing; Liu, Qi

    2014-04-01

    Three field experiments were conducted to simulate the dynamics of aboveground biomass, N accumulation and utilization of drip-irrigated processing tomatoes at different N fertilization rates (0, 75, 150, 300, 450, or 600 kg x hm(-2)). The results showed that Logistic models best described the changes in aboveground biomass, N accumulation, and utilization of accumulated N efficiency with the physiological development time (PDT). Rapid accumulation of N began about 4-6 d (PDT) earlier than the rapid accumulation of aboveground biomass. The momentary utilization rate of N (NMUR) increased after emergence, reached a single peak, and then decreased. The N accumulation, aboveground biomass and yield were highest in the 300 kg x hm(-2) treatment. The quadratic model indicated that application rate of 349 to 382 kg N x hm(-2) was optimum for drip-irrigated processing tomatoes in northern Xinjiang. PMID:25011297

  5. An integral method to estimate the moment accumulation rate on the Creeping Section of the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Tong, Xiaopeng; Sandwell, David T.; Smith-Konter, Bridget

    2015-10-01

    Moment accumulation rate (also referred to as moment deficit rate) is a fundamental quantity for evaluating seismic hazard. The conventional approach for evaluating moment accumulation rate of creeping faults is to invert for the slip distribution from geodetic measurements, although even with perfect data these slip-rate inversions are non-unique. In this study, we show that the slip-rate versus depth inversion is not needed because moment accumulation rate can be estimated directly from surface geodetic data. We propose an integral approach that uses dense geodetic observations from Interferometric Synthetic Aperture Radar (InSAR) and the Global Positioning System (GPS) to constrain the moment accumulation rate. The moment accumulation rate is related to the integral of the product of the along-strike velocity and the distance from the fault. We demonstrate our methods by studying the Creeping Section of the San Andreas fault observed by GPS and radar interferometry onboard the ERS and ALOS satellites. Along-strike variation of the moment accumulation rate is derived in order to investigate the degree of partial locking of the Creeping Section. The central Creeping Segment has a moment accumulation rate of 0.25-3.1 × 1015 Nm yr-1 km-1. The upper and lower bounds of the moment accumulation rates are derived based on the statistics of the noise. Our best-fitting model indicates that the central portion of the Creeping Section is accumulating seismic moment at rates that are about 5 per cent to 23 per cent of the fully locked Carrizo segment that will eventually be released seismically. A cumulative moment budget calculation with the historical earthquake catalogue (M > 5.5) since 1857 shows that the net moment deficit at present is equivalent to a Mw 6.3 earthquake.

  6. Accumulation rates of biogenous silica and terrigenous detritus in late Miocene-early Pliocene Santa Maria basin, California

    SciTech Connect

    Ramiriz, P.C.

    1988-03-01

    The upper-Miocene-lower Pliocene laminated to massive diatomaceous strata of the Santa Maria basin encompass portions of the Monterey and overlying conformable to nonconformable Sisquoc Formations and record the continued accumulation of admixed siliceous (mostly diatoms) and terrigenous (silt and clay) components in a Neogene borderland basin. Lithologies, which vary from diatomite to diatomaceous mudstone, are the result of fluctuations in slope-accumulating silica and terrigenous debris. Bulk accumulation rates, as well as silica and terrigenous component accumulation rates, were calculated for four measured sections using accurate stratal thicknesses, absolute ages, rock compositions, and bulk densities. Bulk accumulation rates range from less than 20 to greater than 70 mg/cm/sup 2//year and are comparable to bulk accumulation rates in the present-day Santa Barbara basin and Gulf o f California. Silica accumulation rates (20-30 mg/cm/sup 2//year) suggest that sedimentation took place beneath productive waters and they exceed those encountered in other high-productivity oceanic areas, such as the Bering Sea and Peruvian coastal waters. Relatively high terrigenous accumulation rates (18-35 mg/cm/sup 2//year) reflect the dilution of these high-productivity waters by continentally derived detritus. Comparison of calculated accumulation rates with rates determined for similarly aged strata of the Santa Barbara basin reveals that silica and terrigenous debris were accumulating at higher rates within the Santa Maria basin. These differences are due to the complex interplay of tectonics and oceanographics and to the proximity of the basins relative to the strandline.

  7. Rapid Changes on Sediment Accumulation Rates within Submarine Canyons Caused By Bottom Trawling Activities

    NASA Astrophysics Data System (ADS)

    Puig, P.; Masque, P.; Martin, J.; Paradis, S.; Juan, X.; Toro, M.; Palanques, A.

    2014-12-01

    The physical disturbance of the marine sedimentary environments by commercial bottom trawling is a matter of concern. The direct physical effects of this fishing technique include scraping and ploughing of the seabed and increases of the near-bottom water turbidity by sediment resuspension. However, the quantification of the sediment that has been resuspended by this anthropogenic activity over years and has been ultimately exported across the margin remains largely unaddressed. The analysis of sediment accumulation rates from sediment cores collected along the axes of several submarine canyons in the Catalan margin (northwestern Mediterranean) has allowed to estimate the contribution of this anthropogenic activity to the present-day sediment dynamics. 210Pb chronologies, occasionally supported by 137Cs dating, indicate a rapid increase of sediment accumulation rates since the 1970s, in coincidence with a strong impulse in the industrialization of the trawling fleets of this region. Such increase has been associated to the enhanced delivery of sediment resuspended by trawlers from the shelves and upper slope regions towards the canyon's interior, and to the rapid technical development at that time, in terms of engine power and gear size. This change has been observed in La Fonera (or Palamós) Canyon at depths greater than 1700 m, while in other canyons it is restricted to shallower regions (~1000 m in depth) closer to fishing grounds. Two sampling sites from La Fonera and Foix submarine canyons that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied several years after the first chronological analyses. These two new cores reveal a second and more rapid increase of sediment accumulation rates in both canyons occurring circa 2002 and accounting for about 2 cm/y. This second change at the beginning of the XXI century has been attributed to a preferential displacement of the trawling fleet towards slope fishing grounds surrounding submarine

  8. Field studies using the oyster Crassostrea virginica to determine mercury accumulation and depuration rates

    SciTech Connect

    Palmer, S.J.; Presley, B.J.; Powell, E.N. ); Taylor, R.J. )

    1993-09-01

    Mercury as an environmental hazard, especially with regard to human health, has been of concern since the Minamata disaster. From 1966 to 1970 a chlor-alkali plant in Point Comfort, Texas released mercury-enriched wastewater (up to 29.9 kgHg/day) into Lavaca Bay (TWQB 1977). Since 1970 the Texas Department of Health (TDH) has periodically closed and then re-opened portions of Lavaca Bay to the harvesting of crabs and finfish based on their levels (<>0.5 ppm Hg wet weight) of mercury. A 1988 closure remains in effect as of this writing. Mercury contamination in Lavaca Bay organisms thus continues to be a problem 22 years after the chlor-alkali plant ceased releasing mercury into the bay. The goal of the following research was to better understand the behavior of mercury in Lavaca Bay. Oysters have been widely used as indicator species in metal pollution studies. Most such programs have focused on the concentrations of metals in oysters from different geographic areas. This study, however, investigated the rate and amount of mercury a [open quotes]clean[close quotes] oyster would accumulate when transplanted to a contaminated estuary and the rate of mercury depuration by contaminated oysters placed in a clean environment. The oysters were additionally analyzed for Ba, Cu, Fe, P, and Zn to test for the possible involvement of these metals in mercury accumulation and depuration. 17 refs., 3 figs., 2 tabs.

  9. Distributions and accumulation rates of polycyclic aromatic hydrocarbons in the northern Gulf of Mexico sediments.

    PubMed

    Adhikari, Puspa L; Maiti, Kanchan; Overton, Edward B; Rosenheim, Brad E; Marx, Brian D

    2016-05-01

    Sediment samples collected from shelf, slope and interior basin of the northern Gulf of Mexico during 2011-2013, 1-3 years after the Deepwater Horizon (DWH) oil spill, were utilized to characterize PAH pollution history, in this region. Results indicate that the concentrations of surface ΣPAH43 and their accumulation rates vary between 44 and 160 ng g(-1) and 6-55 ng cm(-2) y(-1), respectively. ΣPAH43 concentration profiles, accumulation rates and Δ(14)C values are significantly altered only for the sediments in the immediate vicinity of the DWH wellhead. This shows that the impact of DWH oil input on deep-sea sediments was generally limited to the area close to the spill site. Further, the PAHs source diagnostic analyses suggest a noticeable change in PAHs composition from higher to lower molecular weight dominance which reflects a change in source of PAHs in the past three years, back to the background composition. Results indicate low to moderate levels of PAH pollution in this region at present, which are unlikely to cause adverse effects on benthic communities. PMID:26895564

  10. A Spanish Version of the Short Mathematics Anxiety Rating Scale (sMARS)

    ERIC Educational Resources Information Center

    Nunez-Pena, M. Isabel; Suarez-Pellicioni, Macarena; Guilera, Georgina; Mercade-Carranza, Clara

    2013-01-01

    The aim of this study was to adapt and assess the psychometric properties of the Spanish version of the sMARS in terms of evidence of validity and reliability of scores. The sMARS was administered to 342 students and, in order to assess convergent and discriminant validity, several subsamples completed a series of related tests. The factorial…

  11. Measurements of the Coefficient of Restitution of Quartz Sand on Basalt: Implications for Abrasion Rates on Earth and Mars

    NASA Technical Reports Server (NTRS)

    Banks, M.; Bridges, N. T.; Benzit, M.

    2005-01-01

    Knowledge of the rates at which rocks abrade from the impact of saltating sand provides important input into estimating the age and degree of modification of arid surfaces on Earth and Mars. Previous work has relied on measuring mass loss rates in the field and the laboratory. The susceptibility of rocks and other natural materials has been quantified on a relative scale from laboratory studies.

  12. Complex Wind-Induced Variations of Surface Snow Accumulation Rates over East Antarctica

    NASA Astrophysics Data System (ADS)

    Das, I.; Scambos, T. A.; Koenig, L.; van den Broeke, M.; Lenaerts, J.

    2015-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. Using airborne radar, lidar and thresholds of surface slope, modeled surface mass balance (SMB) and wind fields, we have predicted continent-wide distribution of wind-scour zones over Antarctica. These zones are located over relatively steep ice surfaces formed by ice flow over bedrock topography. Near-surface winds accelerate over these steeper slopes and erode and sublimate the snow. This results in numerous localized regions (typically ≤ 200 km2) with reduced or negative surface accumulation. Although small zones of re-deposition occur at the base of the steeper slope areas, the redeposited mass is small relative to the ablation loss. Total losses from wind-scour and wind-glaze areas amounts to tens of gigatons annually. Near the coast, winds often blow significant amounts of surface snow from these zones into the ocean. Large uncertainties remain in SMB estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss or redistribution over the wind-scour zones. In this study, we also use Operation IceBridge's snow radar data to provide evidence for a gradual ablation of ~16-18 m of firn (~200 years of accumulation) from wind-scour zones over the upper Recovery Ice Stream catchment. The maximum ablation rates observed in this region are ~ -54 kg m-2 a-1 (-54 mm water equivalent a-1). Our airborne radio echo-sounding analysis show snow redeposition downslope of the wind-scour zones is <10% of the cumulative mass loss. Our study shows that the local mass loss is dominated by sublimation to water vapor rather than wind-transport of snow.

  13. Bounding the rate of moment deficit accumulation along the Tohoku segment using GEONET GPS data

    NASA Astrophysics Data System (ADS)

    Segall, P.; Johnson, K. M.; Miyazaki, S.

    2011-12-01

    Geodetic estimates of strain accumulation compared to the rate of past moment release provide important input to earthquake hazard forecasts. Prior to the March 2011 Tohoku earthquake a number of studies investigated plate coupling along the Japan Trench in NE Japan using GEONET GPS data. Most of these assumed an elastic back-slip framework, and regularized the underdetermined inverse problem by minimizing some norm of the back-slip rate. All studies apparently smoothed to zero coupling at the trench and therefore infer the highest coupling just offshore. In contrast, we estimate rigorous bounds on the maximum and minimum permissible rates of moment deficit (MDR) accumulation, not a ``favored'' model according to some ad hoc regularization, using methods of Johnson et al [1994] and Murray and Segall [2002]. Given a domain of interest (the Tohoku rupture segment) and Green's functions G relating slip to data, we solve the following optimization problem for back-slip rate m: {minimize}\\ || G m - d ||22 \\ {subject to} \\ A m = M0 \\ \\ {and} \\ \\ 0 ≤ mi ≤ vplate, where A = [1,1, ... 1], such that A m yields the (normalized) moment-rate. on the model domain. Preliminary results find that || G m - d ||22 exhibits a broad minimum over a factor of 2 in MDR. For the minimum MDR the locked zone is just offshore, while the plate-boundary near the trench slips at the plate rate. At the maximum MDR the locked zone is much larger, including the entire fault near the trench. This clearly demonstrates that the shallow fault is completely in the null-space for onshore data, and that there is at least a factor of two uncertainty in MDR. We will present results employing a bootstrap procedure that is independent of an assumed error distribution in the GPS data. We also extend the method to include viscoelastic earthquake cycle effects, including time-dependence due both to past earthquakes and steady backslip. In these models, fault locking near the trench induces flow which

  14. Verification of International Space Station Component Leak Rates by Helium Accumulation Method

    NASA Technical Reports Server (NTRS)

    Underwood, Steve D.; Smith, Sherry L.

    2003-01-01

    Discovery of leakage on several International Space Station U.S. Laboratory Module ammonia system quick disconnects (QDs) led to the need for a process to quantify total leakage without removing the QDs from the system. An innovative solution was proposed allowing quantitative leak rate measurement at ambient external pressure without QD removal. The method utilizes a helium mass spectrometer configured in the detector probe mode to determine helium leak rates inside a containment hood installed on the test component. The method was validated through extensive developmental testing. Test results showed the method was viable, accurate and repeatable for a wide range of leak rates. The accumulation method has been accepted by NASA and is currently being used by Boeing Huntsville, Boeing Kennedy Space Center and Boeing Johnson Space Center to test welds and valves and will be used by Alenia to test the Cupola. The method has been used in place of more expensive vacuum chamber testing which requires removing the test component from the system.

  15. Recent accumulation rates of an Alpine glacier derived from repeated airborne GPR and firn cores

    NASA Astrophysics Data System (ADS)

    Sold, Leo; Huss, Matthias; Eichler, Anja; Schwikowski, Margit; Hoelzle, Martin

    2014-05-01

    The topmost areas of glaciers contain a valuable record of their past accumulation rates. The water equivalent of annual firn layers can be used to initiate or extend existing time series of local mass balance and, ultimately, to consolidate the knowledge on the response of glaciers to changing climatic conditions. Measurements of the thickness and density of firn layers typically involve drilling in remote areas and core analysis and are thus expensive in terms of time and effort. Here, we discuss measurements from 2012 on Findelengletscher, Switzerland, a large Alpine valley glacier, using two in-situ firn cores and airborne Ground-Penetrating Radar (GPR). The firn cores were analysed regarding their density, major ions and deuterium concentration. The ammonium (NH4+) concentration is known to show seasonality due to a higher source activity and pronounced vertical transportation in the atmosphere in summer. The deuterium concentration serves as a proxy for air temperature during precipitation formation. Together, they provide depth and dating of annual summer surfaces. GPR has previously been used for a non-destructive assessment of internal layers in snow, firn and ice. Signal reflections indicate changes in the dielectric properties of the material, e.g. density changes at former summer surfaces. Airborne surveys allow measurements to be taken in remote and inaccessible areas. However, to transfer information from the GPR pulse travel time to the depth domain, the dielectric permittivity of the material is required, that changes with density of the firn. We observed a good agreement of the GPR signal with pronounced changes in the density profile, ice layers and peak contents of major ions. This underlines the high potential of GPR for detecting firn layers. However, not all peak-densities and thick ice layers represent a former glacier summer surface but can also be due to melting and refreezing during winter. We show that up to four years of annual

  16. Comparisons of 210Pb and pollen methods for determining rates of estuarine sediment accumulation

    USGS Publications Warehouse

    Brush, G.S.; Martin, E.A.; DeFries, R.S.; Rice, C.A.

    1982-01-01

    Comparisons of sedimentation rates obtained by 210Pb and pollen analyses of 1-m cores collected throughout the Potomac Estuary show good agreement in the majority of cores that can be analyzed by both methods. Most of the discrepancy between the methods can be explained by the analytical precision of the 210Pb method and by the exactness with which time horizons can be identified and dated for the pollen method. X-radiographs of the cores and the distinctness of the pollen horizons preclude significant displacement by reworking and/or mixing of sediments. Differences between the methods are greatest where uncertainties exist in assigning a rate by one or both methods (i.e., 210Pb trends and/or "possible" horizon assignments). Both methods show the same relative rates, with greater sediment accumulation more common in the upper and middle estuary and less toward the mouth. The results indicate that geochronologic studies of estuarine sediments should be preceded by careful observation of sedimentary structures, preferably by X-radiography, to evaluate the extent of mixing of the sediments. Time horizons, whether paleontologic or isotopic, are generally blurred where mixing has occurred, precluding precise identification. Whenever possible, two methods should be used for dating sediments because a rate, albeit erroneous, can be obtained isotopically in sediments that are mixed; accurate sedimentation rates are also difficult to determine where the time boundary is a zone rather than a horizon, where the historical record does not provide a precise date for the pollen horizon, or where scouring has removed some of the sediment above a dated pollen horizon. ?? 1982.

  17. Erosion rates at the Mars Exploration Rover landing sites and long-term climate change on Mars

    USGS Publications Warehouse

    Golombek, M.P.; Grant, J. A.; Crumpler, L.S.; Greeley, R.; Arvidson, R. E.; Bell, J.F., III; Weitz, C.M.; Sullivan, R.J.; Christensen, P.R.; Soderblom, L.A.; Squyres, S. W.

    2006-01-01

    Erosion rates derived from the Gusev cratered plains and the erosion of weak sulfates by saltating sand at Meridiani Planum are so slow that they argue that the present dry and desiccating environment has persisted since the Early Hesperian. In contrast, sedimentary rocks at Meridiani formed in the presence of groundwater and occasional surface water, and many Columbia Hills rocks at Gusev underwent aqueous alteration during the Late Noachian, approximately coeval with a wide variety of geomorphic indicators that indicate a wetter and likely warmer environment. Two-toned rocks, elevated ventifacts, and perched and undercut rocks indicate localized deflation of the Gusev plains and deposition of an equivalent amount of sediment into craters to form hollows, suggesting average erosion rates of ???0.03 nm/yr. Erosion of Hesperian craters, modification of Late Amazonian craters, and the concentration of hematite concretions in the soils of Meridiani yield slightly higher average erosion rates of 1-10 nm/yr in the Amazonian. These erosion rates are 2-5 orders of magnitude lower than the slowest continental denudation rates on Earth, indicating that liquid water was not an active erosional agent. Erosion rates for Meridiani just before deposition of the sulfate-rich sediments and other eroded Noachian areas are comparable with slow denudation rates on Earth that are dominated by liquid water. Available data suggest the climate change at the landing sites from wet and likely warm to dry and desiccating occurred sometime between the Late Noachian and the beginning of the Late Hesperian (3.7-3.5 Ga). Copyright 2006 by the American Geophysical Union.

  18. Erosion Rates at the Mars Exploration Rover Landing Sites and Long-Term Climate Change on Mars

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Grant, J. A.; Crumpler, L. S.; Greeley, R.; Arvidson, R. E.; Bell, J. F., III; Weitz, C. M.; Sullivan, R.; Christensen, P. R.; Soderblom, L. A.; Squyres, S. W.

    2006-01-01

    Erosion rates derived from the Gusev cratered plains and the erosion of weak sulfates by saltating sand at Meridiani Planum are so slow that they argue that the present dry and desiccating environment has persisted since the Early Hesperian. In contrast, sedimentary rocks at Meridiani formed in the presence of groundwater and occasional surface water, and many Columbia Hills rocks at Gusev underwent aqueous alteration during the Late Noachian, approximately coeval with a wide variety of geomorphic indicators that indicate a wetter and likely warmer environment. Two-toned rocks, elevated ventifacts, and perched and undercut rocks indicate localized deflation of the Gusev plains and deposition of an equivalent amount of sediment into craters to form hollows, suggesting average erosion rates of approx.0.03 nm/yr. Erosion of Hesperian craters, modification of Late Amazonian craters, and the concentration of hematite concretions in the soils of Meridiani yield slightly higher average erosion rates of 1-10 nm/yr in the Amazonian. These erosion rates are 2-5 orders of magnitude lower than the slowest continental denudation rates on Earth, indicating that liquid water was not an active erosional agent. Erosion rates for Meridiani just before deposition of the sulfate-rich sediments and other eroded Noachian areas are comparable with slow denudation rates on Earth that are dominated by liquid water. Available data suggest the climate change at the landing sites from wet and likely warm to dry and desiccating occurred sometime between the Late Noachian and the beginning of the Late Hesperian (3.7-3.5 Ga).

  19. Sexual difference in polychlorinated biphenyl accumulation rates of walleye (Stizostedion vitreum)

    USGS Publications Warehouse

    Madenjian, Charles P.; Noguchi, George E.; Haas, Robert C.; Schrouder, Kathrin S.

    1998-01-01

    Adult male walleye (Stizostedion vitreum) exhibited significantly higher polychlorinated biphenyl (PCB) concentrations than similarly aged female walleye from Saginaw Bay (Lake Huron). To explain this difference, we tested the following three hypotheses: (i) females showed a considerably greater reduction in PCB concentration immediately following spawning than males, (ii) females grew at a faster rate and therefore exhibited lower PCB concentrations than males, and (iii) males spent more time in the Saginaw River system than females, and therefore received a greater exposure to PCBs. The first hypothesis was tested by comparing PCB concentration in gonadal tissue with whole-body concentration, the second hypothesis was tested via bioenergetics modeling, and we used mark-recapture data from the Saginaw Bay walleye fishery to address the third hypothesis. The only plausible explanation for the observed difference in PCB accumulation rate was that males spent substantially more time in the highly contaminated Saginaw River system than females, and therefore were exposed to greater environmental concentrations of PCBs. Based on the results of our study, we strongly recommend a stratified random sampling design for monitoring PCB concentration in Saginaw Bay walleye, with fixed numbers of females and males sampled each year.

  20. Constraints on the Recent Rate of Lunar Regolith Accumulation from Diviner Observations

    NASA Technical Reports Server (NTRS)

    Ghent, R. R.; Hayne, P. O.; Bandfield, J. L.; Campbell, B. A.; Carter, L. M.

    2012-01-01

    Many large craters on the lunar nearside show radar CPR signatures consistent with the presence of blocky ejecta blankets, to distances pre dicted to be covered by continuous ejecta. However, most of these sur faces show limited enhancements in both derived rock abundance and rock-free regolith temperatures calculated from Diviner nighttime infrar ed observations. This indicates that the surface rocks are covered by a layer of thermally insulating regolith material. By matching the results of one-dimensional thermal models to Diviner nighttime temperat ures, we have constrained the thermophysical properties of the upper regolith, and the thickness of regolith overlying proximal ejecta. We find that for all of the regions surveyed (all in the nearside highla nds), the nighttime cooling curves are best fit by a density profile that varies exponentially with depth, consistent with a linear mixture of rocks and regolith fines, with increasing rock content with depth . Our results show significant spatial variations in the density e-folding depth, H, among young crater ejecta regions, indicating differen ces in the thickness of accumulated regolith. However, away from youn g craters, the average regional "equilibrium" value of H (Heq) is remarkably consistent, and is on the order of 5 cm. As expected, near-rim ejecta associated with young craters show lower values of H, indicating a high rock content in the shallow subsurface; for older craters, the average value of H approaches the regional value of Heq. Calculat ed H values for young craters show a clear correlation with published ages, providing the first observational constraint on the recent rate of lunar regolith accumulation. In addition, this result may help to resolve the apparent discrepancy between ages calculated from small crater counts on melt ponds versus counts on continuous ejecta (e.g., King crater; Ashley et al., 2011, LPSC 42, abstract 2437). This method could, in principle, be extended to other

  1. Target Selection Signals Influence Perceptual Decisions by Modulating the Onset and Rate of Evidence Accumulation.

    PubMed

    Loughnane, Gerard M; Newman, Daniel P; Bellgrove, Mark A; Lalor, Edmund C; Kelly, Simon P; O'Connell, Redmond G

    2016-02-22

    Computational and neurophysiological research has highlighted neural processes that accumulate sensory evidence for perceptual decisions [1]. These processes have been studied in the context of highly simplified perceptual discrimination paradigms in which the physical evidence appears at times and locations that are either entirely predictable or exogenously cued (e.g., by the onset of the stimulus itself). Yet, we are rarely afforded such certainty in everyday life. For example, when driving along a busy motorway, we must continually monitor the movements of surrounding vehicles for events that call for a lane change. In such scenarios, it is unknown which of the continuously present information sources will become relevant or when. Although it is well established that evidence integration provides an effective mechanism for countering the impact of noise [2], the question of how this mechanism is implemented in the face of uncertain evidence onsets has yet to be answered. Here, we show that when monitoring two potential sources of information for evidence occurring unpredictably in both time and space, the human brain employs discrete, early target selection signals that significantly modulate the onset and rate of neural evidence accumulation, and thereby the timing and accuracy of perceptual reports. These selection signals share many of the key characteristics of the N2pc component highlighted in the literature on visual search [3, 4] yet are present even in the absence of distractors and under situations of low temporal and spatial uncertainty. These data provide novel insights into how target selection supports decision making in uncertain environments. PMID:26853360

  2. The effects of temperature gradient and growth rate on the morphology and fatigue properties of MAR-M246(Hf)

    NASA Technical Reports Server (NTRS)

    Schmidt, D. D.; Alter, W. S.; Hamilton, W. D.; Parr, R. A.

    1989-01-01

    MAR-M246(Hf) is a nickel based superalloy used in the turbopump blades of the Space Shuttle main engines. The effects are considered of temperature gradient (G) and growth rate (R) on the microstructure and fatigue properties of this superalloy. The primary dendrite arm spacings were found to be inversely proportional to both temperature gradient and growth rate. Carbide and gamma - gamma prime morphology trends were related to G/R ratios. Weibull analysis of fatigue results shows the characteristic life to be larger by a factor of 10 for the low gradient/fast rate pairing of G and R, while the reliability (beta) was lower.

  3. Active Landslide Erosion of Mars' North Polar Cliffs: Current Rates, Causes, and Implications

    NASA Astrophysics Data System (ADS)

    Russell, P. S.; Byrne, S.; Pathare, A.

    2014-12-01

    While the North Polar Layered Deposits (NPLD) have long been considered Mars' best climate record, only recently have some of the processes governing the evolution of the NPLD to their current form been discovered and even directly observed. MOC revealed outcrops of an interbedded ice and dark-sand "basal unit" (BU) below steep NPLD scarps. Some bright markings on the BU were suggested to be talus deposits of mass-wasted NPLD ice, caused by undercutting via removal of easily erodible BU sand. In previous work with HiRISE images that confirmed the origin of these deposits, we: detailed their meter-scale morphology, constituent features, and variability; identified fractures of BU ice layers and NPLD scarps as additional mass-wasting facilitators; and, based on inter- and inter-annual monitoring, discovered that new deposits appear over time, thereby establishing mass wasting (of both BU and NPLD ice) as a currently active process. Here, we advance from qualitative descriptions of new, active processes to quantification of the rates at which they are occurring. From ~4 years of HiRISE observations, we cataloged the location, volume, source, and timing constraints of >160 landslide events along ~ 20 km of BU-NPLD scarp. Average rates are ~44 events/yr and ~2000 m3/yr, although 7 large events account for ~3/4 of the volume; this is a very geologically dynamic environment. BU events are more frequent and smaller than NPLD events, reflecting the relative thickness of ice source deposits but also perhaps differing proportions of two causal mechanisms: sand-removal undercutting and thermal-stress induced expansion, contraction, and fracturing. BU events prefer summer over spring; NPLD events strongly prefer fall-winter over spring-summer. We compare this observational data with 1) thermal stress models of the ice scarp to assess consistency in timing of activity, and 2) sublimation models of the ice scarp to assess the relative contributions to scarp retreat - our

  4. Tracing nitrogen accumulation in decaying wood and examining its impact on wood decomposition rate

    NASA Astrophysics Data System (ADS)

    Rinne, Katja T.; Rajala, Tiina; Peltoniemi, Krista; Chen, Janet; Smolander, Aino; Mäkipää, Raisa

    2016-04-01

    Decomposition of dead wood, which is controlled primarily by fungi is important for ecosystem carbon cycle and has potentially a significant role in nitrogen fixation via diazotrophs. Nitrogen content has been found to increase with advancing wood decay in several studies; however, the importance of this increase to decay rate and the sources of external nitrogen remain unclear. Improved knowledge of the temporal dynamics of wood decomposition rate and nitrogen accumulation in wood as well as the drivers of the two processes would be important for carbon and nitrogen models dealing with ecosystem responses to climate change. To tackle these questions we applied several analytical methods on Norway spruce logs from Lapinjärvi, Finland. We incubated wood samples (density classes from I to V, n=49) in different temperatures (from 8.5oC to 41oC, n=7). After a common seven day pre-incubation period at 14.5oC, the bottles were incubated six days in their designated temperature prior to CO2 flux measurements with GC to determine the decomposition rate. N2 fixation was measured with acetylene reduction assay after further 48 hour incubation. In addition, fungal DNA, (MiSeq Illumina) δ15N and N% composition of wood for samples incubated at 14.5oC were determined. Radiocarbon method was applied to obtain age distribution for the density classes. The asymbiotic N2 fixation rate was clearly dependent on the stage of wood decay and increased from stage I to stage IV but was substantially reduced in stage V. CO2 production was highest in the intermediate decay stage (classes II-IV). Both N2 fixation and CO2 production were highly temperature sensitive having optima in temperature 25oC and 31oC, respectively. We calculated the variation of annual levels of respiration and N2 fixation per hectare for the study site, and used the latter data together with the 14C results to determine the amount of N2 accumulated in wood in time. The proportion of total nitrogen in wood

  5. Calculation of Zonal Winds using Accelerometer and Rate Data from Mars Global Surveyor

    NASA Technical Reports Server (NTRS)

    Baird, Darren T.; Tolson, Robert; Bougher, Stephen; Steers, Brian

    2006-01-01

    The Mars Global Surveyor spacecraft was initially placed into a high eccentricity, nearly polar orbit about Mars with a 45-hour period. To accomplish the science objectives of the mission, a 2-hour, circular orbit was required. Using a method known as aerobraking, numerous passes through the upper atmosphere slowed the spacecraft, thereby reducing the orbital period and eccentricity. To successfully perform aerobraking, the spacecraft was designed to be longitudinally, aerodynamically stable in pitch and yaw. Since the orbit is nearly polar, the yaw orientation of the spacecraft was sensitive to disturbances caused by the zonal components of wind (east-to-west or west-to-east) acting on the spacecraft at aerobraking altitudes. Zonal wind velocities were computed by equating the aerodynamic and inertia-related torques acting on the spacecraft. Comparisons of calculated zonal winds with those computed from the Mars Thermospheric Global Circulation Model are discussed.

  6. Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the west of Ireland

    NASA Astrophysics Data System (ADS)

    Coggins, A. M.; Jennings, S. G.; Ebinghaus, R.

    The vertical distributions of three heavy metals: Hg, Pb and Cd were determined in 3 cores sampled from two ombrotrophic bogs in the west of Ireland, one at Knockroe Co. Mayo, and the second at Letterfrack National Park, Co. Galway. Core chronologies were established using 210Pb dating techniques and were checked with fallout radionuclides from weapons testing. Variations were found in metal concentrations and cumulative inventories of each of the metals within each site and between the two sites. Maximum accumulation rates of the anthropogenically derived elements Hg, Pb, and Cd, were found in peat sediments dated between 1950 and 1970s at both sites. Pb and Hg accumulation rates are slightly lower than those found in similar studies from remote sites in Europe. Hg accumulation rates are fairly similar to those found in peatlands in America. Unlike the Pb and Hg concentration profiles, the Cd concentration profiles at the Letterfrack site were dominated by a surface enrichment, thought to be due to biological cycling of Cd in the peat. However Cd accumulation rates calculated at the Knockroe site are lower than those observed in Eastern Europe. Local meteorological conditions at the sites chosen for this study may account for the lower concentrations profiles observed when compared with some of the European studies. The similarity between the timing of the increase in metal accumulation rates in peat bogs in Northern America and this study could indicate that long range transportation of trace metals from Northern America may be occurring. Lead accumulations in the surface peat sediments (1993-1996) were between 1.5-3.0 mg m -2 yr -1 and 4-5 mg m -2 yr -1 at Knockroe and Letterfrack, respectively. Mercury accumulation rates for the same period at Knockroe were found to be between 6-11 μg m -2 yr -1, and between 19-24 μg m -2 yr -1 at Letterfrack. A greater variation in surface Cd accumulation rates was observed at both sites, with surface layer accumulation

  7. Impacts of timber harvesting on historic sediment accumulation rates in the Coos Bay estuary, Oregon

    NASA Astrophysics Data System (ADS)

    Mathabane, N.; Roering, J. J.

    2014-12-01

    The expansion and development of human infrastructure along the coastline of the Pacific Northwest has profound consequences for the habitability and general ecological health of coastal ecosystems. Coos County, one of the most economically critical regions of the Oregon Coast, experienced vigorous timber harvest activity in the aftermath of WWII that declined in the last several decades. This period of extractive land use may have drastically altered the sediment supply in the major catchments of the Coos and Millicoma Rivers and lead to variations in sediment flux into the Coos Bay estuary. Accurate sediment flux histories are critical data for deciphering the relative importance of climate and land use factors such as logging and road construction on sediment production. Reduction of root reinforcement following timber harvest increases the likelihood of shallow landsliding and debris flows. In addition, forest roads increase sediment production due to overland flow and entrainment of fine sediments on hydrologically connected roads. Although these processes have been documented in small watersheds, their compounded effect on estuaries and coastal settings has not been well documented. We use Pb-210 activities derived from sediment cores taken at various locations in the Coos Bay estuary to establish temporal variations in sediment accumulation rates (SARs). Our cores will also be analyzed to assess dissolved oxygen and other proxies for ecosystem functioning. By correlating these SARs with quantitative metrics for timber extraction rate such as board feet per year and qualitative evaluations from historical photos, we propose to document the cumulative effect of historic forest practices. The temporal resolution provided by this technique should allow us to link changes in estuarine sedimentation to changes in land use as well as climatic triggers such as storms. The conclusions of this study will add valuable information regarding the ultimate impact of

  8. BIOACCUMULATION OF KEPONE BY SPOT ('LEIOSTOMUS XANTHURUS'): IMPORTANCE OF DIETARY ACCUMULATION AND INGESTION RATE

    EPA Science Inventory

    The relative extent of dietary accumulation and bioconcentration of Kepone by spot (Leiostomus xanthurus) was quantitatively evaluated at food rations of 4, 8, or 20% of the average wet weight of fish. 14C-Kepone was utilized to determine bioconcentration and dietary accumulation...

  9. Constraints on the recent rate of lunar regolith accumulation from Diviner observations

    NASA Astrophysics Data System (ADS)

    Ghent, R. R.; Hayne, P. O.; Bandfield, J. L.; Campbell, B. A.; Carter, L. M.; Allen, C.; Paige, D. A.

    2012-12-01

    Many large craters on the lunar nearside show radar CPR signatures consistent with the presence of blocky ejecta blankets, to distances predicted to be covered by continuous ejecta. However, most of these surfaces show limited enhancements in both derived rock abundance and rock-free regolith temperatures calculated from Diviner nighttime infrared observations. This indicates that the surface rocks are covered by a layer of thermally insulating regolith material. By matching the results of one-dimensional thermal models to Diviner nighttime temperatures, we have constrained the thermophysical properties of the upper regolith, and the thickness of regolith overlying proximal ejecta. We find that for all of the regions surveyed (all in the nearside highlands), the nighttime cooling curves are best fit by a density profile that varies exponentially with depth, consistent with a linear mixture of rocks and regolith fines, with increasing rock content with depth. Our results show significant spatial variations in the density e-folding depth, H, among young crater ejecta regions, indicating differences in the thickness of accumulated regolith. However, away from young craters, the average regional "equilibrium" value of H (Heq) is remarkably consistent, and is on the order of 5 cm. As expected, near-rim ejecta associated with young craters show lower values of H, indicating a high rock content in the shallow subsurface; for older craters, the average value of H approaches the regional value of Heq. Calculated H values for young craters (Giordano Bruno, Moore F, Byrgius A, Necho, Tycho, Jackson, King, and Copernicus) show a clear correlation with published ages, providing the first observational constraint on the recent rate of lunar regolith accumulation. In addition, this result may help to resolve the apparent discrepancy between ages calculated from small crater counts on melt ponds versus counts on continuous ejecta (e.g., King crater; Ashley et al., 2011, LPSC 42

  10. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative channel coding scheme called 'Accumulate Repeat Accumulate codes' (ARA). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes, thus belief propagation can be used for iterative decoding of ARA codes on a graph. The structure of encoder for this class can be viewed as precoded Repeat Accumulate (RA) code or as precoded Irregular Repeat Accumulate (IRA) code, where simply an accumulator is chosen as a precoder. Thus ARA codes have simple, and very fast encoder structure when they representing LDPC codes. Based on density evolution for LDPC codes through some examples for ARA codes, we show that for maximum variable node degree 5 a minimum bit SNR as low as 0.08 dB from channel capacity for rate 1/2 can be achieved as the block size goes to infinity. Thus based on fixed low maximum variable node degree, its threshold outperforms not only the RA and IRA codes but also the best known LDPC codes with the dame maximum node degree. Furthermore by puncturing the accumulators any desired high rate codes close to code rate 1 can be obtained with thresholds that stay close to the channel capacity thresholds uniformly. Iterative decoding simulation results are provided. The ARA codes also have projected graph or protograph representation that allows for high speed decoder implementation.

  11. Geographic variability in organic carbon stock and accumulation rate in sediments of East and Southeast Asian seagrass meadows

    NASA Astrophysics Data System (ADS)

    Miyajima, Toshihiro; Hori, Masakazu; Hamaguchi, Masami; Shimabukuro, Hiromori; Adachi, Hiroshi; Yamano, Hiroya; Nakaoka, Masahiro

    2015-04-01

    Organic carbon (OC) stored in the sediments of seagrass meadows has been considered a globally significant OC reservoir. However, the sparsity and regional bias of studies on long-term OC accumulation in coastal sediments have limited reliable estimation of the capacity of seagrass meadows as a global OC sink. We evaluated the amount and accumulation rate of OC in sediment of seagrass meadows and adjacent areas in East and Southeast Asia. In temperate sites, the average OC concentration in the top 30 cm of sediment was higher in seagrass meadows (780-1080 mmol g-1) than in sediments without seagrass cover (52-430 mmol g-1). The average OC in the top 30 cm of subtropical and tropical seagrass meadow sediments ranged from 140 to 440 mmol g-1. Carbon isotope mass balancing suggested that the contribution of seagrass-derived carbon to OC stored in sediments was often relatively minor (temperate: 10-40%; subtropical: 35-82%; tropical: 4-34%) and correlated to the habitat type, being particularly low in estuarine habitats. Stock of OC in the top meter of sediment of all the studied meadows ranged from 38 to 120 Mg ha-1. The sediment accumulation rates were estimated by radiocarbon dating of six selected cores (0.32-1.34 mm yr-1). The long-term OC accumulation rates calculated from the sediment accumulation rate and the top 30 cm average OC concentration for the seagrass meadows (24-101 kg ha-1 yr-1) were considerably lower than the OC accumulation rates previously reported for Mediterranean Posidonia oceanica meadows (580 kg ha-1 yr-1 on average). Current estimates for the global carbon sink capacity of seagrass meadows, which rely largely on Mediterranean studies, may be considerable overestimations.

  12. Small Rayed Crater Ejecta Retention Age Calculated from Current Crater Production Rates on Mars

    NASA Technical Reports Server (NTRS)

    Calef, F. J. III; Herrick, R. R.; Sharpton, V. L.

    2011-01-01

    Ejecta from impact craters, while extant, records erosive and depositional processes on their surfaces. Estimating ejecta retention age (Eret), the time span when ejecta remains recognizable around a crater, can be applied to estimate the timescale that surface processes operate on, thereby obtaining a history of geologic activity. However, the abundance of sub-kilometer diameter (D) craters identifiable in high resolution Mars imagery has led to questions of accuracy in absolute crater dating and hence ejecta retention ages (Eret). This research calculates the maximum Eret for small rayed impact craters (SRC) on Mars using estimates of the Martian impactor flux adjusted for meteorite ablation losses in the atmosphere. In addition, we utilize the diameter-distance relationship of secondary cratering to adjust crater counts in the vicinity of the large primary crater Zunil.

  13. Lineations on the ``White'' Accumulation Areas of the Residual Northern Ice Cap of Mars: Their Relation to the ``Accublation'' and Ice Flow Hypothesis

    NASA Astrophysics Data System (ADS)

    Fisher, David A.; Winebrenner, Dale P.; Stern, Harry

    2002-09-01

    Mars Orbiter Camera (MOC) images of the whiter areas of the residual North Polar Cap (P. C. Thomas et al. 2000, Nature404, 161-164) show a gentle hummocky pitted surface that has been popularly called "cottage cheese" terrain. The pits are 1 or 2 m deep and tens of meters across. They are typically joined in roughly linear strings or long depressions and these features are referred to here as "lineations." The lineations tend to have one or occasionally two preferred directions. We have examined the MOC imagery for the North Cap and using high-resolution images that have good wide-angle context images were able to determine the lineation angles for 31 sites scattered over most of the ice cap. We propose a process that will produce linear features in the white areas, then relate the orientation of the lineations over much of the North Cap to these processes and the inferred ice flow direction. There is first-order agreement between the measured sign of the lineation angles and those predicted assuming ice flow. Higher accumulations and velocities are predicted in the catchment for ice that flows into Chasma Boreale. This comes from the indications that katabatic winds are concentrated in this catchment.

  14. Marine debris accumulation in the Northwestern Hawaiian Islands: an examination of rates and processes.

    PubMed

    Dameron, Oliver J; Parke, Michael; Albins, Mark A; Brainard, Russell

    2007-04-01

    Large amounts of derelict fishing gear accumulate and cause damage to shallow coral reefs of the Northwestern Hawaiian Islands (NWHI). To facilitate maintenance of reefs cleaned during 1996-2005 removal efforts, we identify likely high-density debris areas by assessing reef characteristics (depth, benthic habitat type, and energy regime) that influence sub-regional debris accumulation. Previously cleaned backreef and lagoonal reefs at two NWHI locations were resurveyed for accumulated debris using two survey methods. Accumulated debris densities and weights were found to be greater in lagoonal reef areas. Sample weight-based debris densities are extrapolated to similar habitats throughout the NWHI using a spatial 'net habitat' dataset created by generalizing IKONOS satellite derivatives for depth and habitat classification. Prediction accuracy for this dataset is tested using historical debris point data. Annual NWHI debris accumulation is estimated to be 52.0 metric tonnes. For planning purposes, individual NWHI atolls/reefs are allotted a proportion of this total. PMID:17217968

  15. On determining ice accumulation rates in the past 40,000 years using in situ cosmogenic C-14

    NASA Technical Reports Server (NTRS)

    Lal, D.; Jull, A. J. T.

    1990-01-01

    Radiocarbon is produced in situ in ice by nuclear spallations of oxygen by cosmic ray neutrons. As the firn accumulates, it acquires a predictable concentration of in situ C-14, inversely proportional to the rate of accumulation. Most of this production occurs when the amount of overlying ice is less than (2-3) Lambda, where lambda is the absorption mean free path for cosmic radiation in ice, about 150 g/sq cm, i.e. within the top 10 m. In most accumulation areas, this is firn. In situ produced C-14 is added to the firn as it accumulates, and is not expected to be lost by diffusion. During the firn-ice transition, atmospheric CO2 is trapped, adding (C-14)02 to the ice. The signature of in situ C-14 is however not obliterated since about 60 percent of in situ C-14 is instantly oxidized to (C-14)O in the ice. The results available to date are discussed, and it is proposed that this in situ (C-14)O can be used to determine ice accumulation rates back to 40,000 yrs in the past.

  16. Recent rates of carbon accumulation in montane fens ofYosemite National Park, California, U.S.A.

    USGS Publications Warehouse

    Drexler, Judith; Fuller, Christopher C.; Orlando, James; Moore, Peggy E.

    2016-01-01

    Little is known about recent rates of carbon storage in montane peatlands, particularly in the western United States. Here we report on recent rates of carbon accumulation (past 50 to 100 years) in montane groundwater-fed peatlands (fens) of Yosemite National Park in central California, U.S.A. Peat cores were collected at three sites ranging in elevation from 2070 to 2500 m. Core sections were analyzed for bulk density, % organic carbon, and 210Pb activities for dating purposes. Organic carbon densities ranged from 0.026 to 0.065 g C cm-3. Mean vertical accretion rates estimated using210Pb over the 50-year period from ∼1960 to 2011 and the 100-year period from ∼1910 to 2011 were 0.28 (standard deviation = ±0.09) and 0.18 (±-0.04) cm yr-1, respectively. Mean carbon accumulation rates over the 50- and 100-year periods were 95.4 (±25.4) and 74.7 (±17.2) g C m-2 yr-1, respectively. Such rates are similar to recent rates of carbon accumulation in rich fens in western Canada, but more studies are needed to definitively establish both the similarities and differences in peat formation between boreal and temperate montane fens.

  17. Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Phillips, R.L.; Mullen, M.W.; Starratt, S.W.; Jones, Glenn A.; Naidu, A.S.; Finney, B.P.

    1996-01-01

    Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010??120 yr has consisted of a continuing rain of pelagic organic and ice-rafted elastic sediment with a net accumulation rate during the late Holocene of ???10 mm/1000 yr, and episodically emplaced turbidites 1-5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr. Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and ??13C values of -27 to - 25??? in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and ??13C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures. The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be

  18. ACCUMULATION RATE OF MICROBIAL BIOMASS AT TWO PERMEABLE REACTIVE BARRIER SITES

    EPA Science Inventory

    Accumulation of mineral precipitates and microbial biomass are key factors that impact the long-term performance of in-situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero-valent iron reactivity...

  19. Laboratory Determination of Molybdenum Accumulation Rates as a Measure of Hypoxic Conditions

    EPA Science Inventory

    Redox sensitive metals, such as molybdenum (Mo), are enriched in reducing sediments due to authigenic fixation in anoxic interstitial waters of sediments. This study tested whether the process of fixation and accumulation of Mo in sediments could provide a geochemical indicator o...

  20. Abundance of Cosmogenic Noble Gases as a Marker of the Organic Degradation by Cosmic Rays in the Surface Martian Rocks. Implications to MSL and Mars 2020

    NASA Astrophysics Data System (ADS)

    Pavlov, A. A.; Vasilyev, G. I.; Ostryakov, V. M.; Pavlov, A. K.; Mahaffy, P.

    2014-07-01

    We conducted a modeling study which links the rates of cosmogenic isotopes production with the radiation accumulation rates on Mars. We calculated the degradation level of the organic molecules at Cumberland based on the observed cosmogenic isotopes.

  1. Peat Accumulation in the Everglades (USA) during the Past 4000 Years: Rates, Drivers, and Sources of Error

    NASA Astrophysics Data System (ADS)

    Glaser, P. H.; Volin, J. C.; Givnish, T. J.; Hansen, B. C.; Stricker, C. A.

    2012-12-01

    Tropical and sub-tropical wetlands are considered to be globally important sources for greenhouse gases but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida, to assess these problems and determine the factors that could govern carbon accumulation in this large sub-tropical wetland. AMS-14C dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion ( 0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1 ) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands

  2. Carbon and sediment accumulation in the Everglades (USA) during the past 4000 years: Rates, drivers, and sources of error

    NASA Astrophysics Data System (ADS)

    Glaser, Paul H.; Volin, John C.; Givnish, Thomas J.; Hansen, Barbara C. S.; Stricker, Craig A.

    2012-09-01

    Tropical and subtropical wetlands are considered to be globally important sources of greenhouse gases, but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida in order to assess these problems and determine the factors that could govern carbon accumulation in this large subtropical wetland. Accelerator mass spectroscopy dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion (0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands.

  3. Carbon and sediment accumulation in the Everglades (USA) during the past 4000 years: rates, drivers, and sources of error

    USGS Publications Warehouse

    Glaser, Paul H.; Volin, John C.; Givnish, Thomas J.; Hansen, Barbara C. S.; Stricker, Craig A.

    2012-01-01

    Tropical and sub-tropical wetlands are considered to be globally important sources for greenhouse gases but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida, to assess these problems and determine the factors that could govern carbon accumulation in this large sub-tropical wetland. Accelerator mass spectroscopy dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion ( 0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1 ) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands.

  4. Amazonian mid- to high-latitude glaciation on Mars: Supply-limited ice sources, ice accumulation patterns, and concentric crater fill glacial flow and ice sequestration

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.

    2014-02-01

    Concentric crater fill (CCF) occurs in the interior of impact craters in mid- to high latitudes on Mars and is interpreted to have formed by glacial ice flow and debris covering. We use the characteristics and orientation of deposits comprising CCF, the thickness of pedestal deposits in mid- to high-latitude pedestal craters (Pd), the volumes of the current polar caps, and information about regional slopes and ice rheology to address questions about (1) the maximum thickness of regional ice deposits during the Late Amazonian, (2) the likelihood that these deposits flowed regionally, (3) the geological regions and features most likely to induce ice-flow, and (4) the locations and environments in which ice is likely to have been sequestered up to the present. We find that regional ice flow under Late Amazonian climate conditions requires ice thicknesses exceeding many hundreds of meters for slopes typical of the vast majority of the surface of Mars, a thickness for the mid-latitudes that is well in excess of the total volume available from polar ice reservoirs. This indicates that although conditions for mid- to high-latitude glaciation may have persisted for tens to hundreds of millions of years, the process is “supply limited”, with a steady state reached when the polar ice cap water ice supply becomes exhausted. Impact craters are by far the most abundant landform with associated slopes (interior wall and exterior rim) sufficiently high to induce glacial ice flow under Late Amazonian climate conditions, and topographic slope data show that Amazonian impact craters have been clearly modified, undergoing crater interior slope reduction and floor shallowing. We show that these trends are the predictable response of ice deposition and preferential accumulation and retention in mid- to high-latitude crater interiors during episodes of enhanced spin-axis obliquity. We demonstrate that flow from a single episode of an inter-crater terrain layer comparable to Pedestal

  5. T1 Relaxation Rate (R1) Indicates Nonlinear Mn Accumulation in Brain Tissue of Welders With Low-Level Exposure.

    PubMed

    Lee, Eun-Young; Flynn, Michael R; Du, Guangwei; Lewis, Mechelle M; Fry, Rebecca; Herring, Amy H; Van Buren, Eric; Van Buren, Scott; Smeester, Lisa; Kong, Lan; Yang, Qing; Mailman, Richard B; Huang, Xuemei

    2015-08-01

    Although the essential element manganese (Mn) is neurotoxic at high doses, the effects of lower exposure are unclear. MRI T1-weighted (TIW) imaging has been used to estimate brain Mn exposure via the pallidal index (PI), defined as the T1W intensity ratio in the globus pallidus (GP) versus frontal white matter (FWM). PI may not, however, be sensitive to Mn in GP because Mn also may accumulate in FWM. This study explored: (1) whether T1 relaxation rate (R1) could quantify brain Mn accumulation more sensitively; and (2) the dose-response relationship between estimated Mn exposure and T1 relaxation rate (R1). Thirty-five active welders and 30 controls were studied. Occupational questionnaires were used to estimate hours welding in the past 90 days (HrsW) and lifetime measures of Mn exposure. T1W imaging and T1-measurement were utilized to generate PI and R1 values in brain regions of interest (ROIs). PI did not show a significant association with any measure of Mn and/or welding-related exposure. Conversely, in several ROIs, R1 showed a nonlinear relationship to HrsW, with R1 signal increasing only after a critical exposure was reached. The GP had the greatest rate of Mn accumulation. Welders with higher exposure showed significantly higher R1 compared either with controls or with welders with lower exposure. Our data are additional evidence that Mn accumulation can be assessed more sensitively by R1 than by PI. Moreover, the nonlinear relationship between welding exposure and Mn brain accumulation should be considered in future studies and policies. PMID:25953701

  6. T1 Relaxation Rate (R1) Indicates Nonlinear Mn Accumulation in Brain Tissue of Welders With Low-Level Exposure

    PubMed Central

    Lee, Eun-Young; Flynn, Michael R.; Du, Guangwei; Lewis, Mechelle M.; Fry, Rebecca; Herring, Amy H.; Van Buren, Eric; Van Buren, Scott; Smeester, Lisa; Kong, Lan; Yang, Qing; Mailman, Richard B.; Huang, Xuemei

    2015-01-01

    Although the essential element manganese (Mn) is neurotoxic at high doses, the effects of lower exposure are unclear. MRI T1-weighted (TIW) imaging has been used to estimate brain Mn exposure via the pallidal index (PI), defined as the T1W intensity ratio in the globus pallidus (GP) versus frontal white matter (FWM). PI may not, however, be sensitive to Mn in GP because Mn also may accumulate in FWM. This study explored: (1) whether T1 relaxation rate (R1) could quantify brain Mn accumulation more sensitively; and (2) the dose-response relationship between estimated Mn exposure and T1 relaxation rate (R1). Thirty-five active welders and 30 controls were studied. Occupational questionnaires were used to estimate hours welding in the past 90 days (HrsW) and lifetime measures of Mn exposure. T1W imaging and T1-measurement were utilized to generate PI and R1 values in brain regions of interest (ROIs). PI did not show a significant association with any measure of Mn and/or welding-related exposure. Conversely, in several ROIs, R1 showed a nonlinear relationship to HrsW, with R1 signal increasing only after a critical exposure was reached. The GP had the greatest rate of Mn accumulation. Welders with higher exposure showed significantly higher R1 compared either with controls or with welders with lower exposure. Our data are additional evidence that Mn accumulation can be assessed more sensitively by R1 than by PI. Moreover, the nonlinear relationship between welding exposure and Mn brain accumulation should be considered in future studies and policies. PMID:25953701

  7. Viscous flow rates of icy topography on the north polar layered deposits of Mars

    NASA Astrophysics Data System (ADS)

    Sori, Michael M.; Byrne, Shane; Hamilton, Christopher W.; Landis, Margaret E.

    2016-01-01

    We investigate the importance of viscous flow in shaping topography at the north polar layered deposits (NPLD) of Mars by using finite element modeling to calculate the distribution of stresses and flow velocities. Present-day impact craters on the NPLD are too small and cold for viscous relaxation to have been an important mechanism in controlling their current dimensions; this effect may be ignored when analyzing crater size-frequency distributions. Scarps at the NPLD margins, where avalanches of dust and carbon dioxide frost occur, are sufficiently steep, high, and warm to experience significant viscous flow. We find flow velocities at the base of these steep scarps on the order of tens to hundreds of cm/yr, which are fast enough to significantly affect their slope over kiloyear timescales. Alternatively, the scarps could be close to steady state in which observed block falls provide a competing effect to viscous flow.

  8. Project Hotspot: Linear accumulation rates of late Cenozoic basalt at Kimama, Idaho, and implications for crustal strain and subsidence rates of the central Snake River Plain

    NASA Astrophysics Data System (ADS)

    Rodgers, D. W.; Potter, K. E.; Shervais, J. W.; Champion, D. E.; Duncan, R. A.

    2013-12-01

    Project Hotspot's Kimama drill hole on the Snake River Plain, Idaho recovered a 1912 m thick section of basalt core that ranges in age from ~700 ka to at least 6.14 Ma, based on five 40Ar/39Ar analyses and twenty paleomagnetic age assignments. Fifty-four flow groups comprising 510 individual flows were defined, yielding an average recurrence interval of ~11,400 years between flows. Age-depth analysis indicate that, over thicknesses >150 m and age spans >500 k.y., accumulation rates were constant at 30 m/100 k.y. The existence and persistence of this linear accumulation rate for greater than 5 m.y. documents an external tectonic control on eruption dynamics. One conceptual model relates accumulation rates to horizontal crustal strain, such that far-field extension rate controls the periodicity of dikes that feed basalt flows. In this model, each of the 54 flow groups would have a deep-seated, relatively wide (1-10m) dike that branches upward into a network of narrow (10-100 cm) dikes feeding individual lava flows. Assuming an east-west lateral lava flow extent of up to 50 km, the Kimama data record a steady-state crustal strain rate of 10-9 to 10-10 y-1. This rate is comparable to modern, decadal strain rates measured with GPS in the adjacent Basin & Range province, but exceeds decadal strain rates of zero measured in the eastern Snake River Plain. Linear accumulation rates also provide insight into basalt subsidence history. In this model, the middle-upper crust subsides due to the added weight of lava flows, the added weight of mid-crustal sills/dikes, and thermal contraction in the wake of the Yellowstone hot spot. Isostatic compensation would occur in the (nearly) molten lower crust. Assuming constant surface elevation and a basalt density of 2.6 g/cm3, the lava flow weight would account for 87% of the burial through time, yielding a steady-state "tectonic" subsidence rate of 4 m/100 k.y. attributed to the driving forces of mid-crustal injection and/or thermal

  9. Accumulation rates or percentages? How to quantify Sporormiella and other coprophilous fungal spores to detect late Quaternary megafaunal extinction events

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.

    2013-10-01

    Spores of coprophilous fungi, and in particular those of Sporormiella, are a routinely used proxy for detecting late Quaternary herbivore extinction events in sedimentary records. Spore abundance is typically quantified as a percentage of the total, or dryland, pollen sum. Although this is a quick method that does not require the development of site-specific age-depth models, it relies on stable pollen accumulation rates and is therefore highly sensitive to changes in vegetation. This may lead to incorrect placement of extinction events in sedimentary records, particularly when they occur contemporaneously with major climatic/vegetation transitions. We suggest that the preferred method of quantification should be accumulation rate, and that pollen abundance data should also be presented, particularly for periods of major vegetation change. This approach provides a more reliable record of past herbivore abundance independent of vegetation change, allowing extinction events to be more accurately placed in stratigraphic sequences.

  10. Basalt weathering rates on Earth and the duration of liquid water on the plains of Gusev Crater, Mars

    SciTech Connect

    Steefel, Carl; Hausrath, E.M.; Navarre-Sitchler, A.K.; Sak, P.B.; Steefel, C.; Brantley, S.L.

    2008-03-15

    Where Martian rocks have been exposed to liquid water, chemistry versus depth profiles could elucidate both Martian climate history and potential for life. The persistence of primary minerals in weathered profiles constrains the exposure time to liquid water: on Earth, mineral persistence times range from {approx}10 ka (olivine) to {approx}250 ka (glass) to {approx}1Ma (pyroxene) to {approx}5Ma (plagioclase). Such persistence times suggest mineral persistence minima on Mars. However, Martian solutions may have been more acidic than on Earth. Relative mineral weathering rates observed for basalt in Svalbard (Norway) and Costa Rica demonstrate that laboratory pH trends can be used to estimate exposure to liquid water both qualitatively (mineral absence or presence) and quantitatively (using reactive transport models). Qualitatively, if the Martian solution pH > {approx}2, glass should persist longer than olivine; therefore, persistence of glass may be a pH-indicator. With evidence for the pH of weathering, the reactive transport code CrunchFlow can quantitatively calculate the minimum duration of exposure to liquid water consistent with a chemical profile. For the profile measured on the surface of Humphrey in Gusev Crater, the minimum exposure time is 22 ka. If correct, this estimate is consistent with short-term, episodic alteration accompanied by ongoing surface erosion. More of these depth profiles should be measured to illuminate the weathering history of Mars.

  11. On the Effect of Ramp Rate in Damage Accumulation of the CPV Die-Attach: Preprint

    SciTech Connect

    Bosco, N. S.; Silverman, T. J.; Kurtz, S. R.

    2012-06-01

    It is commonly understood that thermal cycling at high temperature ramp rates may activate unrepresentative failure mechanisms. Increasing the temperature ramp rate of thermal cycling, however, could dramatically reduce the test time required to achieve an equivalent amount of thermal fatigue damage, thereby reducing overall test time. Therefore, the effect of temperature ramp rate on physical damage in the CPV die-attach is investigated. Finite Element Model (FEM) simulations of thermal fatigue and thermal cycling experiments are made to determine if the amount of damage calculated results in a corresponding amount of physical damage measured to the die-attach for a variety of fast temperature ramp rates. Preliminary experimental results are in good agreement with simulations and reinforce the potential of increasing temperature ramp rates. Characterization of the microstructure and resulting fatigue crack in the die-attach suggest a similar failure mechanism across all ramp rates tested.

  12. Accumulate-Repeat-Accumulate-Accumulate-Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Sam; Thorpe, Jeremy

    2004-01-01

    Inspired by recently proposed Accumulate-Repeat-Accumulate (ARA) codes [15], in this paper we propose a channel coding scheme called Accumulate-Repeat-Accumulate-Accumulate (ARAA) codes. These codes can be seen as serial turbo-like codes or as a subclass of Low Density Parity Check (LDPC) codes, and they have a projected graph or protograph representation; this allows for a high-speed iterative decoder implementation using belief propagation. An ARAA code can be viewed as a precoded Repeat-and-Accumulate (RA) code with puncturing in concatenation with another accumulator, where simply an accumulator is chosen as the precoder; thus ARAA codes have a very fast encoder structure. Using density evolution on their associated protographs, we find examples of rate-lJ2 ARAA codes with maximum variable node degree 4 for which a minimum bit-SNR as low as 0.21 dB from the channel capacity limit can be achieved as the block size goes to infinity. Such a low threshold cannot be achieved by RA or Irregular RA (IRA) or unstructured irregular LDPC codes with the same constraint on the maximum variable node degree. Furthermore by puncturing the accumulators we can construct families of higher rate ARAA codes with thresholds that stay close to their respective channel capacity thresholds uniformly. Iterative decoding simulation results show comparable performance with the best-known LDPC codes but with very low error floor even at moderate block sizes.

  13. Glaciation in the Late Noachian Icy Highlands: Ice accumulation, distribution, flow rates, basal melting, and top-down melting rates and patterns

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.

    2015-02-01

    Geological evidence for extensive non-polar ice deposits of Amazonian age indicates that the current cold and dry climate of Mars has persisted for several billion years. The geological record and climate history of the Noachian, the earliest period of Mars history, is less certain, but abundant evidence for fluvial channels (valley networks) and lacustrine environments (open-basin lakes) has been interpreted to represent warm and wet conditions, including rainfall and runoff. Alternatively, recent atmospheric modeling results predict a "cold and icy" Late Noachian Mars in which moderate atmospheric pressure accompanied by a full water cycle produce an atmosphere where temperature declines with elevation following an adiabatic lapse rate, in contrast to the current situation on Mars, where temperature is almost completely determined by latitude. These results are formulated in the Late Noachian Icy Highlands (LNIH) model, in which these cold and icy conditions lead to the preferential deposition of snow and ice at high elevations, such as the southern uplands. What is the fate of this snow and ice and the nature of glaciation in such an environment? What are the prospects of melting of these deposits contributing to the observed fluvial and lacustrine deposits? To address these questions, we report on a glacial flow-modeling analysis using a Mars-adapted ice sheet model with LNIH climate conditions. The total surface/near-surface water inventory is poorly known for the Late Noachian, so we explore the LNIH model in a "supply-limited" scenario for a range of available water abundances and a range of Late Noachian geothermal fluxes. Our results predict that the Late Noachian icy highlands (above an equilibrium line altitude of approximately +1 km) were characterized by extensive ice sheets of the order of hundreds of meters thick. Due to extremely cold conditions, the ice-flow velocities in general were very low, less than a few mm/yr, and the regional ice

  14. Slip rate of the Calico fault: Implications for anomalous geodetic strain accumulation across the Eastern California shear zone

    NASA Astrophysics Data System (ADS)

    Oskin, M.; Perg, L.; Blumentritt, D.; Mukhopadhyay, S.; Iriondo, A.

    2004-12-01

    Recent earthquake activity and high geodetically derived fault-slip rates across the Eastern California shear zone motivate comparisons with long-term geologic deformation rates to test for transient strain accumulation. We report new geologic slip-rate results from a transect at 34.8° N across the central Mojave Desert where six dextral faults (Helendale, Lenwood, Camp Rock, Calico, Pisgah-Bullion, and Ludlow) accommodate all late Quaternary right-lateral displacement. High-resolution LIDAR topography data have been successfully acquired across all six faults as part of a project to measure a complete budget of long-term geologic fault slip rates. Field investigations of the northern Rodman Mountains conducted with the aid of the new topography data identified several surfaces dextrally offset by the Calico fault. A preliminary slip rate of 1.3±0.3 mm/yr is calculated from an 800± 200 m offset of alluvial fan deposits containing clasts of the ca. 600 ka Pipkin basalt flow. Cosmogenic surface exposure age dating of offset geomorphic surfaces and refined Ar/Ar dating of the basalt flow, in progress, will provide multiple constraints of this fault slip rate. The slip rate of the Calico fault is more than twice that of the Blackwater fault, located on strike with the Calico fault in the northwest Mojave Desert. This discrepancy supports that strain is transferred away from the Calico fault and other adjacent northwest-striking dextral faults onto domino-style rotating blocks bounded by sinistral faults in the Fort Irwin region. A newly identified active thrust fault and fault-related fold bounding the northern Rodman mountains accommodates shortening east of the Calico fault that may be caused by space problems at the intersection of these conjugate fault systems. Overall, slip rate on the Calico fault, together with existing paleoseismic histories on adjacent faults, does not account for more than 5 mm/yr of strain accumulation across the Eastern California shear

  15. Processes and Rates of Sediment and Wood Accumulation in Headwater Streams of the Oregon Coast Range, U.S.A.

    NASA Astrophysics Data System (ADS)

    May, C. L.; Gresswell, R. E.

    2001-12-01

    Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low-order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was used to estimate the time since the previous debris flow in unlogged basins in the central Oregon Coast Range. Changes in sediment and wood storage were quantified for 13 streams that ranged from 4 to 135 years post-disturbance. The volume of wood in the channel was strongly correlated with the time since the previous debris flow, and the accumulation rate was linear. The pattern of sediment accumulation was non-linear and appeared to increase as the storage capacity of the channel increased through time. Wood recruited from the local hillslopes and riparian areas functioned to store the majority sediment in these steep headwater streams. In the absence of wood, channels that have been scoured to bedrock by a debris flow may lack the capacity to store sediment and could persist in a bedrock state for a longer period of time. With an adequate supply of wood, low-order channels have the potential for storing large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain.

  16. Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

    NASA Astrophysics Data System (ADS)

    Schwikowski, M.; Schläppi, M.; Santibañez, P.; Rivera, A.; Casassa, G.

    2012-12-01

    Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000 to 2006 from a 50 m (33.2 4 m weq) ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49°16´40´´ S, 73°21´14´´ W). Borehole temperatures indicate near temperate ice, but the average melt percent is only 16% ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4 to 7.1 water equivalent (m weq) with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.

  17. Optical communications and a comparison of optical technologies for a high data rate return link from Mars

    NASA Technical Reports Server (NTRS)

    Spence, Rodney L.

    1993-01-01

    The important principles of direct- and heterodyne-detection optical free-space communications are reviewed. Signal-to-noise-ratio (SNR) and bit-error-rate (BER) expressions are derived for both the direct-detection and heterodyne-detection optical receivers. For the heterodyne system, performance degradation resulting from received-signal and local oscillator-beam misalignment and laser phase noise is analyzed. Determination of interfering background power from local and extended background sources is discussed. The BER performance of direct- and heterodyne-detection optical links in the presence of Rayleigh-distributed random pointing and tracking errors is described. Finally, several optical systems employing Nd:YAG, GaAs, and CO2 laser sources are evaluated and compared to assess their feasibility in providing high-data-rate (10- to 1000-Mbps) Mars-to-Earth communications. It is shown that the root mean square (rms) pointing and tracking accuracy is a critical factor in defining the system transmitting laser-power requirements and telescope size and that, for a given rms error, there is an optimum telescope aperture size that minimizes the required power. The results of the analysis conducted indicate that, barring the achievement of extremely small rms pointing and tracking errors (less than 0.2 microrad), the two most promising types of optical systems are those that use an Nd:YAG laser (lambda = 1.064 microns) and high-order pulse position modulator (PPM) and direct detection, and those that use a CO2 laser (lambda = 10.6 microns) and phase shifting keying homodyne modulation and coherent detection. For example, for a PPM order of M = 64 and an rms pointing accuracy of 0.4 microrad, an Nd:YAG system can be used to implement a 100-Mbps Mars link with a 40-cm transmitting telescope, a 20-W laser, and a 10-m receiving photon bucket. Under the same conditions, a CO2 system would require 3-m transmitting and receiving telescopes and a 32-W laser to implement such

  18. Spatial and temporal variability of snow chemical composition and accumulation rate at Talos Dome site (East Antarctica).

    PubMed

    Caiazzo, Laura; Becagli, Silvia; Frosini, Daniele; Giardi, Fabio; Severi, Mirko; Traversi, Rita; Udisti, Roberto

    2016-04-15

    Five snow pits and five firn cores were sampled during the 2003-2004 Italian Antarctic Campaign at Talos Dome (East Antarctica), where a deep ice core (TALDICE, TALos Dome Ice CorE, 1650m depth) was drilled in 2005-2008 and analyzed for ionic content. Particular attention is spent in applying decontamination procedures to the firn cores, as core sections were stored for approximately 10years before analysis. By considering the snow pit samples to be unperturbed, the comparison with firn core samples from the same location shows that ammonium, nitrate and MSA are affected by storage post-depositional losses. All the other measured ions are confirmed to be irreversibly deposited in the snow layer. The removal of the most external layers (few centimeters) from the firn core sections is proved to be an effective decontamination procedure. High-resolution profiles of seasonal markers (nitrate, sulfate and MSA) allow a reliable stratigraphic dating and a seasonal characterization of the samples. The calculated mean accumulation-rate values range from 70 to 85mmw.e.year(-1), in the period 2003-1973 with small differences between two sectors: 70-74mmw.e.year(-1) in the NNE sector (spanning 2003-1996years) and 81-92mmw.e.year(-1) in the SSW sector (spanning 2003-1980years). This evidence is interpreted as a coupled effect of wind-driven redistribution processes in accumulation/ablation areas. Statistical treatment applied to the concentration values of the snow pits and firn cores samples collected in different points reveals a larger temporal variability than spatial one both in terms of concentration of chemical markers and annual accumulation. The low spatial variability of the accumulation rate and chemical composition measured in the five sites demonstrates that the TALDICE ice core paleo-environmental and paleo-climatic stratigraphies can be considered as reliably representative for the Talos Dome area. PMID:26849319

  19. Saltation transport on Mars.

    PubMed

    Parteli, Eric J R; Herrmann, Hans J

    2007-05-11

    We present the first calculation of saltation transport and dune formation on Mars and compare it to real dunes. We find that the rate at which grains are entrained into saltation on Mars is 1 order of magnitude higher than on Earth. With this fundamental novel ingredient, we reproduce the size and different shapes of Mars dunes, and give an estimate for the wind velocity on Mars. PMID:17677662

  20. Dust on Mars: Materials Adherence Experiment results from Mars Pathfinder

    SciTech Connect

    Landis, G.A.; Jenkins, P.P.

    1997-12-31

    Mars Pathfinder is the first solar-powered probe to operate on the surface of Mars. Pathfinder consists of a lander and a small, autonomous, six-wheel solar-powered rover, Sojourner. The Pathfinder spacecraft reflects NASA`s new philosophy of exploiting new technologies to reduce mission cost. The Materials Adherence Experiment on Pathfinder was designed to measure the degradation of solar arrays due to dust settling out of the atmosphere and blocking light to the solar array, lowering the array power output. The MAE measurements indicate steady dust accumulation at a rate of about 0.28% per day. This value is consistent with the performance of the solar arrays, which have decreased in power at an estimated rate of 0.29% per day.

  1. A closer look at the Neogene erosion and accumulation rate increase

    NASA Astrophysics Data System (ADS)

    Willenbring, J.; von Blanckenburg, F.

    2008-12-01

    Glacial erosion and Quaternary cold-stage warm-stage climate cycling have been cited as mechanisms to explain observations of increased Neogene marine sedimentation rates. Quantification of long-term glacial erosion rates from cosmogenic radionuclides from large areas mostly covered by cold-based ice during the Quaternary show very low erosion rates over several glacial cycles. In addition, isotope ratio proxies of dissolved metals in seawater, measured in chemical ocean sediments, lack clear evidence for an increase in terrigenous denudation. In particular, the stable isotope 9Be, derived from continental erosion, shows no change in its ratio to meteoric cosmogenic nuclide 10Be, derived from rain over the past 10 My. Radiogenic Pb and Nd isotopes, mainly show a change in the style of denudation from more chemical to more physical processes in the Quaternary. These data are at odds with a suggested increase in marine sedimentation rates during the late Cenozoic. In order to resolve this contradiction we have scrutinized these sedimentation rate calculations from ocean cores to identify whether they might show only apparent increases in the Neogene sections. Potential explanations are that in some cases, measured sediment thicknesses for different time intervals lack corrections for sediment compaction. Compaction of the lower portions of the cores drastically increases the apparent thickness of the more recent (Quaternary) sediment. In addition, sedimentation rates often only appear higher for recent sections in cores due to an artifact of an averaging timescale that decreases up-core. Such an averaging time scale decrease arises from better chronological resolution in recent times (Sadler et al., 1999). Cannibalization of older sediment might add to this effect. Together, these data question a clear, global-scale Quaternary climate-erosion connection that would be unique in Earth's history.

  2. Sediment accumulation rates in Conowingo Reservoir as determined by man-made and natural radionuclides

    SciTech Connect

    McLean, R.I.; Domotor, S.L. ); Summers, J.K.; Wilson, H. ); Olsen, C.R.; Larsen, I.L. )

    1991-05-01

    The Susquehanna River is the major contributor to sediment loadings in the Chesapeake Bay. Because many environmental contaminants are associated with suspended particulates, the degree of particle retention within the reservoirs of the lower Susquehanna River is an important consideration in evaluating contaminant loadings to the Chesapeake Bay. Profiles of weapons-test Cs-137, nuclear power plant-related Cs-134 and Cs-137, and naturally-derived Pb-210 were used to estimate rates of sediment accretion in the Conowingo Reservoir,an impoundmment of the Susquehanna River along the Maryland-Pennsylvania border. Net accretion rates ranged from about 2 cm yr{sup {minus}1} downstream of a nuclear power plant cooling discharge to a high of about 7 cm yr{sup {minus}1} at the mount of an incoming creek. Slight, but consistent, increases in the annual rate of accretion since the creation of the reservoir in 1928 are apparent. The current net average annual sediment load retained by the reservoir is estimated to be 0.4 {times} 10{sup 6} to 1.5 {times} 10{sup 6} metric tons yr{sup {minus}1}. The retained sediment load represents about 8-23% of the long-time average sediment input to the reservoir.

  3. An Investigation of the Validity and Reliability of the Adapted Mathematics Anxiety Rating Scale-Short Version (MARS-SV) among Turkish Students

    ERIC Educational Resources Information Center

    Baloglu, Mustafa

    2010-01-01

    This study adapted the Mathematics Anxiety Rating Scale-Short Version (MARS-SV) into Turkish and investigated the validity and reliability of the adapted instrument. Twenty-five bilingual experts agreed on the language validity, and 49 Turkish language experts agreed on the conformity and understandability of the scale's items. Thirty-two subject…

  4. Heart Rate and Blood Pressure Variability under Moon, Mars and Zero Gravity Conditions During Parabolic Flights

    NASA Astrophysics Data System (ADS)

    Aerts, Wouter; Joosen, Pieter; Widjaja, Devy; Varon, Carolina; Vandeput, Steven; Van Huffel, Sabine; Aubert, Andre E.

    2013-02-01

    Gravity changes during partial-G parabolic flights (0g -0.16g - 0.38g) lead to changes in modulation of the autonomic nervous system (ANS), studied via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were assessed via classical time and frequency domain measures. Mean systolic and diastolic blood pressure show both increasing trends towards higher gravity levels. The parasympathetic and sympathetic modulation show both an increasing trend with decreasing gravity, although the modulation is sympathetic predominant during reduced gravity. For the mean heart rate, a non-monotonic relation was found, which can be explained by the increased influence of stress on the heart rate. This study shows that there is a relation between changes in gravity and modulations in the ANS. With this in mind, countermeasures can be developed to reduce postflight orthostatic intolerance.

  5. Effect of self-alkalization on nitrite accumulation in a high-rate denitrification system: Performance, microflora and enzymatic activities.

    PubMed

    Li, Wei; Shan, Xiao-Yu; Wang, Zhi-Yao; Lin, Xiao-Yu; Li, Chen-Xu; Cai, Chao-Yang; Abbas, Ghulam; Zhang, Meng; Shen, Li-Dong; Hu, Zhi-Qiang; Zhao, He-Ping; Zheng, Ping

    2016-01-01

    The self-alkalization of denitrifying automatic circulation (DAC) reactor resulted in a large increase of pH up to 9.20 and caused a tremendous accumulation of nitrite up to 451.1 ± 49.0 mgN L(-1) at nitrate loading rate (NLR) from 35 kgN m(-3) d(-1) to 55 kgN m(-3) d(-1). The nitrite accumulation was greatly relieved even at the same NLR once the pH was maintained at 7.6 ± 0.2 in the system. Enzymatic assays indicated that the long-term bacterial exposure to high pH significantly inhibited the activity of copper type nitrite reductase (NirK) rather than the cytochrome cd1 type nitrite reductase (NirS). The terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that the dominant denitrifying bacteria shifted from the NirS-containing Thauear sp. 27 to the NirK-containing Hyphomicrobium nitrativorans strain NL23 during the self-alkalization. The significant nitrite accumulation in the high-rate denitrification system could be therefore, due to the inhibition of Cu-containing NirK by high pH from the self-alkalization. The results suggest that the NirK-containing H. nitrativorans strain NL23 could be an ideal functional bacterium for the conversion of nitrate to nitrite, i.e. denitritation, which could be combined with anaerobic ammonium oxidation (Anammox) to develop a new process for nitrogen removal from wastewater. PMID:26595097

  6. Rate of denitrification and the accumulation of intermediates in a denitrifying bioreactor

    NASA Astrophysics Data System (ADS)

    Parsignault, D. R.; Gursky, H.; Kellogg, E. M.; Matilsky, T.; Murray, S.; Schreier, E.; Tananbaum, H.; Giacconi, R.; Brinkman, A. C.

    2012-12-01

    Denitrifying bioreactors (DNBRs) are an emerging mechanism to mitigate the impact of excess reactive nitrogen by harnessing the activity of ubiquitous denitrifying soil microbes. DNBRs fundamentally consist of an organic carbon energy source sufficiently saturated to develop anaerobic conditions and support heterotrophic reduction of nitrate to dinitrogen. Although recent research has well established achievable nitrate removal in DNBRs upwards of 90%, few studies experimentally determine the fate of nitrogen in these systems. This study differentiates between denitrification to inert nitrogen gas, which permanently removes reactive nitrogen from an enriched ecosystem, and transformation of nitrate to another bioavailable form (such as N2O or NOX, powerful greenhouse gases). Previous research has failed to make this distinction and as both are perceived as a reduction in nitrate concentration at the outlet, the utility of DNBRs in reducing downstream reactive nitrogen has not been sufficiently established. In order to quantify the rate of nitrate removal and the products produced, dissolved gas samples are collected from the DNBR with passive diffusion gas samplers while the influent and effluent nitrate concentration and chemical oxygen demand are monitored in real time with spectrometer probes. Nitrate removal is compared with the denitrification rate and the ratio of dinitrogen to nitrous oxide is reported. Denitrification is quantified from the proportion of nitrogen gas products produced from the nitrate pool, indicated by the negative congruence of the regression of 15N enrichment in the nitrate pool and temporal depletion in the gaseous products. The proportion of nitrous oxide to dinitrogen is examined with respect to saturation and redox potential. This research informs the interpretation of previous studies as well as advises the focus of long-term system level monitoring that will provide further information on the design and application of DNBRs to

  7. Understanding the rates of nonpolar organic chemical accumulation into passive samplers deployed in the environment: Guidance for passive sampler deployments.

    PubMed

    Apell, Jennifer N; Tcaciuc, A Patricia; Gschwend, Philip M

    2016-07-01

    Polymeric passive samplers have become a common method for estimating freely dissolved concentrations in environmental media. However, this approach has not yet been adopted by investigators conducting remedial investigations of contaminated environmental sites. Successful adoption of this sampling methodology relies on an understanding of how passive samplers accumulate chemical mass as well as developing guidance for the design and deployment of passive samplers. Herein, we outline the development of a simple mathematical relationship of the environmental, polymer, and chemical properties that control the uptake rate. This relationship, called a timescale, is then used to illustrate how each property controls the rate of equilibration in samplers deployed in the water or in the sediment. Guidance is also given on how to use the timescales to select an appropriate polymer, deployment time, and suite of performance reference compounds. Integr Environ Assess Manag 2016;12:486-492. © 2015 SETAC. PMID:26426907

  8. Estimation of uptake rate constants for PCB congeners accumulated by semipermeable membrane devices and brown treat (Salmo trutta)

    USGS Publications Warehouse

    Meadows, J.C.; Echols, K.R.; Huckins, J.N.; Borsuk, F.A.; Carline, R.F.; Tillitt, D.E.

    1998-01-01

    The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMD to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB- contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and dissolved concentrations averaged 4.9 and 3.7 ??g/L, respectively, during the exposure. Total concentrations of PCBs in fish rose from 0.06 to 118.3 ??g/g during the 28-day exposure, while concentrations in the SPMD rose from 0.03 to 203.4 ??g/ g. Uptake rate constants (k1) estimated for SPMDs and brown trout were very similar, with k1 values for SPMDs ranging from one to two times those of the fish. The pattern of congener uptake by the fish and SPMDs was also similar. The rates of uptake generally increased or decreased with increasing K(ow), depending on the assumption of presence or absence of TOC.The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMB to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB-contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and

  9. Influences of sediment geochemistry on metal accumulation rates and toxicity in the aquatic oligochaete Tubifex tubifex.

    PubMed

    Méndez-Fernández, Leire; De Jonge, Maarten; Bervoets, Lieven

    2014-12-01

    Metal bioaccumulation and toxicity in the aquatic oligochaete Tubifex tubifex exposed to three metal-contaminated field-sediments was studied in order to assess whether sediment-geochemistry (AVS, TOC) plays a major role in influencing these parameters, and to assess if the biodynamic concept can be used to explain observed effects in T. tubifex tissue residues and/or toxicity. An active autotomy promotion was observed in three studied sediments at different time points and reproduction impairment could be inferred in T. tubifex exposed to two of the tested sites after 28 days. The present study showed that sediment metal concentration and tissue residues followed significant regression models for four essential metals (Cu, Co, Ni and Zn) and one non-essential metal (Pb). Organic content normalization for As also showed a significant relationship with As tissue residue. Porewater was also revealed to be an important source of metal uptake for essential metals (e.g. Cu, Ni and Zn) and for As, but AVS content was not relevant for metal uptake in T. tubifex in studied sediments. Under the biodynamic concept, it was shown that influx rate from food (IF, sediment ingestion) in T. tubifex, in a range of sediment geochemistry, was able to predict metal bioaccumulation, especially of the essential metals Cu, Ni and Zn, and for the non-essential metal Pb. Additionally, IF appeared to be a better predictor for metal bioaccumulation in T. tubifex compared to sediment geochemistry normalization. PMID:25456225

  10. Biogenic silica fluxes and accumulation rates in the Gulf of California

    SciTech Connect

    Thunell, R.C.; Pride, C.J.; Tappa, E. ); Muller-Karger, F.E. )

    1994-04-01

    The Gulf of California, though small in size, plays an important role in the global silica cycle. The seasonal pattern of biogenic silica flux in the gulf is closely related to that of phytoplankton biomass levels and is controlled by changes in weather and hydrographic conditions. The highest opal fluxes ([approximately] 0.35 g[center dot]m[sup [minus]2][center dot]d[sup [minus]1]) occur during winter and spring, and they are comparable to those measured in some of the most productive ecosystems of the world. Approximately 15%-25% of the biogenic silica produced in surface waters is preserved in gulf sediments, a figure significantly higher than the average global ocean preservation rate. However, the flux of opal at 500 m water depth is less than 25% of that being produced at the surface, suggesting that most of the recycling of biogenic silica in the Gulf of California occurs in the upper water column. 28 refs., 3 figs.

  11. Magma accumulation rates and thermal histories of plutons of the Sierra Nevada batholith, CA

    NASA Astrophysics Data System (ADS)

    Davis, Jesse W.; Coleman, Drew S.; Gracely, John T.; Gaschnig, Richard; Stearns, Michael

    2012-03-01

    Zircon U-Pb geochronology results indicate that the John Muir Intrusive Suite of the central Sierra Nevada batholith, California, was assembled over a period of at least 12 Ma between 96 and 84 Ma. Bulk mineral thermochronology (U-Pb zircon and titanite, 40Ar/39Ar hornblende and biotite) of rocks from multiple plutons comprising the Muir suite indicates rapid cooling through titanite and hornblende closure following intrusion and subsequent slow cooling through biotite closure. Assembly of intrusive suites in the Sierra Nevada and elsewhere over millions of years favors growth by incremental intrusion. Estimated long-term pluton assembly rates for the John Muir Intrusive Suite are on the order of 0.001 km3 a-1 which is inconsistent with the rapid magma fluxes that are necessary to form large-volume magma chambers capable of producing caldera-forming eruptions. If large shallow crustal magma chambers do not typically develop during assembly of large zoned intrusive suites, it is doubtful that the intrusive suites represent cumulates left behind following caldera-forming eruptions.

  12. Using Cyclic Variations Of Early Pliocene Diatom Assemblages To Determine Sediment Accumulation Rates In The ANDRILL AND-1B Core

    NASA Astrophysics Data System (ADS)

    Konfirst, M. A.; Scherer, R. P.; Monien, D.; Kuhn, G.; Winter, D.; Sjunneskog, C. M.

    2009-12-01

    In the 2006-2007 Antarctic field season, the ANDRILL MIS project recovered a 1,285m record of Miocene through Plio-Pleistocene sediments near Ross Island in the Ross Sea region of Antarctica. Diatom biostratigraphy, radiometric dating and magnetostratigraphy were used in conjunction with the evaluation of glacial surfaces of erosion (GSEs) to produce a well-constrained age model for the core. However, within the Plio-Pleistocene interval (the upper ~620m), the ANDRILL record also included 13 discrete intervals composed of nearly pure diatomite, the longest of which is over 80m thick. The lack of GSEs during periods of high diatom accumulation has created limitations in assigning ages to specific core depths within the diatomite intervals. In this study, data were collected on abundance of key diatom species present within 290 samples from the long Early Pliocene diatomite unit (DU XI- 363.37-459.24 mbsf) as well as ~15m of diatom-rich mudstone immediately overlying it. We analyzed diatom records at high resolution (as high as ca. 600 year sample interval, according to the chronostratigraphic correlations established by this study). This approximately 100m section was then subdivided into five units based on major diatom assemblage shifts and changes in both geochemical properties and clast abundance counts (Pompilio et al., 2007). Cyclic changes in relative diatom abundance were identified within each unit using characteristic species and matched to variations in the oxygen isotope record (Lisiecki & Raymo, 2005) using the chronostratigraphic framework established by Naish et al. (2007), which included the assignment of an oxygen isotope age to specific core depths. Additionally, the core ages provided by the correlation of diatom abundance with the isotope record allowed the calculation of sediment accumulation rates through the interval. The results presented here provide a further refinement to the ANDRILL age model and allow interpretation of the interaction

  13. Reliability and validity of a new Medication Adherence Rating Scale (MARS) for the psychoses.

    PubMed

    Thompson, K; Kulkarni, J; Sergejew, A A

    2000-05-01

    Medication compliance is one of the foremost problems affecting neuroleptic efficacy in psychiatric patients. To date, compliancy has most commonly been assessed with the Drug Attitude Inventory (DAI) developed by Hogan et al. (Hogan, T.P., Awad, A.G., Eastwood, R., 1983. A self-report scale predictive of drug compliance in schizophrenics: reliability and discriminative validity. Psychol. Med. 13, 177-183). The present study identified several deficiencies in the DAI. Using the partial credit version of the Item Response Theory measurement model, the DAI was refined with the aim of greater validity and clinical utility. The new inventory was administered to 66 patients, the majority of whom were diagnosed with schizophrenia. When available, lithium levels and carer ratings of compliance were also recorded and used to verify compliancy. The new inventory appears to be a valid and reliable measure of compliancy for psychoactive medications. PMID:10785582

  14. Biomass Accumulation Rates of Amazonian Secondary Forest and Biomass of Old-Growth Forests from Landsat Time Series and GLAS

    NASA Astrophysics Data System (ADS)

    Helmer, E.; Lefsky, M. A.; Roberts, D.

    2009-12-01

    We estimate the age of humid lowland tropical forests in Rondônia, Brazil, from a somewhat densely spaced time series of Landsat images (1975-2003) with an automated procedure, the Threshold Age Mapping Algorithm (TAMA), first described here. We then estimate a landscape-level rate of aboveground woody biomass accumulation of secondary forest by combining forest age mapping with biomass estimates from the Geoscience Laser Altimeter System (GLAS). Though highly variable, the estimated average biomass accumulation rate of 8.4 Mg ha-1 yr-1 agrees well with ground-based studies for young secondary forests in the region. In isolating the lowland forests, we map land cover and general types of old-growth forests with decision tree classification of Landsat imagery and elevation data. We then estimate aboveground live biomass for seven classes of old-growth forest. TAMA is simple, fast, and self-calibrating. By not using between-date band or index differences or trends, it requires neither image normalization nor atmospheric correction. In addition, it uses an approach to map forest cover for the self-calibrations that is novel to forest mapping with satellite imagery; it maps humid secondary forest that is difficult to distinguish from old-growth forest in single-date imagery; it does not assume that forest age equals time since disturbance; and it incorporates Landsat Multispectral Scanner (MSS) imagery. Variations on the work that we present here can be applied to other forested landscapes. Applications that use image time series will be helped by the free distribution of coregistered Landsat imagery, which began in December 2008, and of the Ice Cloud and land Elevation Satellite (ICESat) Vegetation Product, which simplifies the use of GLAS data. Finally, we demonstrate here for the first time how the optical imagery of fine spatial resolution that is viewable on Google Earth provides a new source of reference data for remote sensing applications related to land cover

  15. Accumulation of Cd by the marine sponge Halichondria panicea pallas: Effects upon filtration rate and its relevance for biomonitoring

    SciTech Connect

    Olesen, T.M.E.; Weeks, J.M. )

    1994-05-01

    The marine demosponge Halichondria panicea Pallas, is a cosmopolitan species occurring in coastal waters with varied conditions of light, current, salinity and turbidity. H. panicea has a leuconoid structure and is composed of siliceous spicules and spongin fibers. Sponges are important members of many shallow water marine benthic communities, but comparatively little is known of their trace metal biology. Sponge architecture is constructed around a system of water canals and the physiology of the sponge is largely dependent on the currents of water flowing through their bodies. The volume of water pumped by a sponge is remarkable, ca. 100-1200 ml h[sup [minus]1] g[sup [minus]1]. This large volume of water passing through the body of a sponge means that most cells are in direct contact with the external medium. Many sponges are able to accumulate trace metals and are highly tolerant of such pollutants. This has led to the proposal that a [open quotes]sponge watch[close quotes] program be initiated supplementary to the existing [open quotes]mussel watch[close quotes] program. In view of the large volume of water passing through the bodies of sponges such as H. panicea, the suitability of this species as a biomonitoring organism was further investigated. This study describes the accumulation strategy of the demosponge H. panicea exposed to dissolved cadmium (Cd) and the effect of Cd upon sponge filtration rate.

  16. Using beryllium-10 to test the validity of past accumulation rate reconstruction from water isotope records in East Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Landais, A.; Raisbeck, G. M.; Jouzel, J.; Bazin, L.; Kageyama, M.; Peterschmitt, J.-Y.; Werner, M.; Bard, E.; Aster Team

    2014-08-01

    Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 ka in Antarctica. Inferring the variations of past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high resolution beryllium-10 (10Be) as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high resolution 10Be record covering a full climatic cycle over the period 269 to 355 kyr BP from MIS 9 to MIS 10 (Marine Isotope Stages). After correcting 10Be for the estimated effect of the paleomagnetic field, we deduce that the classical estimation of accumulation rate variations from records of water isotopes agrees, with a possible underestimation of 16%, with the uncertainty on the temperature reconstruction from water isotopes in Antarctic ice cores. This is within their uncertainty of -10 to +30%. Finally, we show that the relationship between temperature and accumulation rate is comparable when using ice core data and results from several AGCM simulations run on glacial-interglacial conditions despite a larger spread in model outputs. These results indicate that the thermodynamic law linking moisture content in the air and temperature, as implemented in the different models, leads to realistic results even in polar regions, at the end of the water distillation trajectory.

  17. Belowground carbon balance and carbon accumulation rate in the successional series of monsoon evergreen broad-leaved forest

    USGS Publications Warehouse

    Zhou, G.; Liu, S.; Tang, X.; Ouyang, X.; Zhang, Dongxiao; Liu, J.; Yan, J.; Zhou, C.; Luo, Y.; Guan, L.; Liu, Yajing

    2006-01-01

    The balance, accumulation rate and temporal dynamics of belowground carbon in the successional series of monsoon evergreen broadleaved forest are obtained in this paper, based on long-term observations to the soil organic matter, input and standing biomass of litter and coarse woody debris, and dissolved organic carbon carried in the hydrological process of subtropical climax forest ecosystem - monsoon evergreen broad-leaved forest, and its two successional forests of natural restoration - coniferous and broad-leaved mixed forest and Pinus massoniana forest, as well as data of root biomass obtained once every five years and respiration measurement of soil, litter and coarse woody debris respiration for 1 year. The major results include: the belowground carbon pools of monsoon evergreen broad-leaved forest, coniferous and broad-leaved mixed forest, and Pinus massoniana forest are 23191 ?? 2538 g ?? m-2, 16889 ?? 1936 g ?? m-2 and 12680 ?? 1854 g ?? m-2, respectively, in 2002. Mean annual carbon accumulation rates of the three forest types during the 24a from 1978 to 2002 are 383 ?? 97 g ?? m-2 ?? a-1, 193 ?? 85 g ?? m-2 ?? a-1 and 213 ?? 86 g ?? m-2 ?? a-1, respectively. The belowground carbon pools in the three forest types keep increasing during the observation period, suggesting that belowground carbon pools are carbon sinks to the atmosphere. There are seasonal variations, namely, they are strong carbon sources from April to June, weak carbon sources from July to September; while they are strong carbon sinks from October to November, weak carbon sinks from December to March. ?? Science in China Press 2006.

  18. Hydrophobic Surfaces of Spacecraft Components Enhance the Aggregation of Microorganisms and May Lead to Higher Survival Rates on Mars

    NASA Technical Reports Server (NTRS)

    Schuerger, A. C.; Kern, R. G.

    2003-01-01

    In order to minimize the forward contamination of Mars, spacecraft are assembled under clean-room conditions that often require several procedures to clean and sterilize components. Surface characteristics of spacecraft materials may contribute to microbial survival by protecting spores from sterilizing agents, including UV irradiation on the surface of Mars. The primary objective of this study was to evaluate the effects of surface characteristics of several spacecraft materials on the survival of Bacillus subtilis spores under simulated Martian conditions.

  19. Long-term phenological trends, species accumulation rates, aphid traits and climate: five decades of change in migrating aphids.

    PubMed

    Bell, James R; Alderson, Lynda; Izera, Daniela; Kruger, Tracey; Parker, Sue; Pickup, Jon; Shortall, Chris R; Taylor, Mark S; Verrier, Paul; Harrington, Richard

    2015-01-01

    Aphids represent a significant challenge to food production. The Rothamsted Insect Survey (RIS) runs a network of 12·2-m suction-traps throughout the year to collect migrating aphids. In 2014, the RIS celebrated its 50th anniversary. This paper marks that achievement with an extensive spatiotemporal analysis and the provision of the first British annotated checklist of aphids since 1964. Our main aim was to elucidate mechanisms that advance aphid phenology under climate change and explain these using life-history traits. We then highlight emerging pests using accumulation patterns. Linear and nonlinear mixed-effect models estimated the average rate of change per annum and effects of climate on annual counts, first and last flights and length of flight season since 1965. Two climate drivers were used: the accumulated day degrees above 16 °C (ADD16) indicated the potential for migration during the aphid season; the North Atlantic Oscillation (NAO) signalled the severity of the winter before migration took place. All 55 species studied had earlier first flight trends at rate of β = -0·611 ± SE 0·015 days year(-1). Of these species, 49% had earlier last flights, but the average species effect appeared relatively stationary (β = -0·010 ± SE 0·022 days year(-1)). Most species (85%) showed increasing duration of their flight season (β = 0·336 ± SE 0·026 days year(-1)), even though only 54% increased their log annual count (β = 0·002 ± SE <0·001 year(-1)). The ADD16 and NAO were shown to drive patterns in aphid phenology in a spatiotemporal context. Early in the year when the first aphids were migrating, the effect of the winter NAO was highly significant. Further into the year, ADD16 was a strong predictor. Latitude had a near linear effect on first flights, whereas longitude produced a generally less-clear effect on all responses. Aphids that are anholocyclic (permanently parthenogenetic) or are monoecious (non

  20. Long-term phenological trends, species accumulation rates, aphid traits and climate: five decades of change in migrating aphids

    PubMed Central

    Bell, James R; Alderson, Lynda; Izera, Daniela; Kruger, Tracey; Parker, Sue; Pickup, Jon; Shortall, Chris R; Taylor, Mark S; Verrier, Paul; Harrington, Richard

    2015-01-01

    1. Aphids represent a significant challenge to food production. The Rothamsted Insect Survey (RIS) runs a network of 12·2-m suction-traps throughout the year to collect migrating aphids. In 2014, the RIS celebrated its 50th anniversary. This paper marks that achievement with an extensive spatiotemporal analysis and the provision of the first British annotated checklist of aphids since 1964. 2. Our main aim was to elucidate mechanisms that advance aphid phenology under climate change and explain these using life-history traits. We then highlight emerging pests using accumulation patterns. 3. Linear and nonlinear mixed-effect models estimated the average rate of change per annum and effects of climate on annual counts, first and last flights and length of flight season since 1965. Two climate drivers were used: the accumulated day degrees above 16 °C (ADD16) indicated the potential for migration during the aphid season; the North Atlantic Oscillation (NAO) signalled the severity of the winter before migration took place. 4. All 55 species studied had earlier first flight trends at rate of β = −0·611 ± SE 0·015 days year−1. Of these species, 49% had earlier last flights, but the average species effect appeared relatively stationary (β = −0·010 ± SE 0·022 days year−1). Most species (85%) showed increasing duration of their flight season (β = 0·336 ± SE 0·026 days year−1), even though only 54% increased their log annual count (β = 0·002 ± SE <0·001 year−1). 5. The ADD16 and NAO were shown to drive patterns in aphid phenology in a spatiotemporal context. Early in the year when the first aphids were migrating, the effect of the winter NAO was highly significant. Further into the year, ADD16 was a strong predictor. Latitude had a near linear effect on first flights, whereas longitude produced a generally less-clear effect on all responses. Aphids that are anholocyclic (permanently parthenogenetic) or are monoecious (non-host-alternating) were

  1. Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): Sediment accumulation rates, trawling and winnowing effects

    NASA Astrophysics Data System (ADS)

    Karageorgis, A. P.; Kaberi, H.; Price, N. B.; Muir, G. K. P.; Pates, J. M.; Lykousis, V.

    2005-12-01

    Four cores recovered within the framework of the INTERPOL Project have been analysed for their grain size and geochemistry; sediment accumulation rates (SARs) were also determined from 210Pb and 137Cs profiles. Two cores are representative of the Axios and Aliakmon Rivers depositional environment, whilst the third core represents the Pinios River province; the fourth core represents an environment of outer shelf relict sands. Apparent SARs ranged between 0.667 g cm -2 yr -1 (Axios and Aliakmon Rivers) and 0.414 g cm -2 yr -1 (Pinios River). Trawling activities and biomixing are critical processes that may be responsible for the mixing of the surface sediments, as observed from the excess 210Pb profiles. The thickness of the surface mixed layer was 4.5 cm in the vicinity of Axios and Aliakmon Rivers and in the area of Pinios River, 3.75 cm on the outer shelf and 1 cm in the area where no trawling was observed. Sediment accumulation appeared to be regulated by variations in the riverine discharge, shelf transport pathways and winnowing processes. Major element variations, such as Si, Al, Ti, V and Ni, were dominated by terrigenous supply as aluminosilicate minerals and quartz, whereas most Ca and Sr were biogenic. Si/Al and Ca/Al ratios have been used to express changes in sediment accumulation and winnowing. Redox processes were depicted by Mn, which showed an increase in the depth of its redoxcline, from ˜1 cm in inshore stations to ˜2 cm on the outer shelf. Si/Al ratios follow the Ca/Al ratios and can be used to assess percentage winnowing in the sediment. Increases in these ratios indicate a decrease in sediment input rates and are seen in the upper parts of most of the cores. Anthropogenic or 'excess' metal contents have been calculated from Zn/V and Pb/V ratios. Their distributions in the cores showed that by far the highest contamination is associated with the Axios River output, whilst sediments influenced by the Pinios River were relatively uncontaminated.

  2. Snow accumulation rate on Qomolangma (Mount Everest), Himalaya: synchroneity with sites across the Tibetan Plateau on 50-100 year timescales

    NASA Astrophysics Data System (ADS)

    Kaspari, Susan; Hooke, Roger Leb.; Mayewski, Paul Andrew; Kang, Shichang; Hou, Shugui; Qin, Dahe

    Annual-layer thickness data, spanning AD 1534-2001, from an ice core from East Rongbuk Col on Qomolangma (Mount Everest, Himalaya) yield an age-depth profile that deviates systematically from a constant accumulation-rate analytical model. The profile clearly shows that the mean accumulation rate has changed every 50-100 years. A numerical model was developed to determine the magnitude of these multi-decadal-scale rates. The model was used to obtain a time series of annual accumulation. The mean annual accumulation rate decreased from ˜0.8 m ice equivalent in the 1500s to ˜0.3 m in the mid-1800s. From ˜1880 to ˜1970 the rate increased. However, it has decreased since ˜1970. Comparison with six other records from the Himalaya and the Tibetan Plateau shows that the changes in accumulation in East Rongbuk Col are broadly consistent with a regional pattern over much of the Plateau. This suggests that there may be an overarching mechanism controlling precipitation and mass balance over this area. However, a record from Dasuopu, only 125 km northwest of Qomolangma and 700 m higher than East Rongbuk Col, shows a maximum in accumulation during the 1800s, a time during which the East Rongbuk Col and Tibetan Plateau ice-core and tree-ring records show a minimum. This asynchroneity may be due to altitudinal or seasonal differences in monsoon versus westerly moisture sources or complex mountain meteorology.

  3. Comparing past accumulation rate reconstructions in East Antarctic ice cores using 10Be, water isotopes and CMIP5-PMIP3 models

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Landais, A.; Raisbeck, G. M.; Jouzel, J.; Bazin, L.; Kageyama, M.; Peterschmitt, J.-Y.; Werner, M.; Bard, E.; Aster Team

    2015-03-01

    Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 kyr in Antarctica. Inferring the variations in past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic Plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such an assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high-resolution beryllium-10 (10Be) as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high-resolution 10Be record covering a full climatic cycle over the period 269 to 355 ka from Marine Isotope Stage (MIS) 9 to 10, including a period warmer than pre-industrial (MIS 9.3 optimum). After correcting 10Be for the estimated effect of the palaeomagnetic field, we deduce that the 10Be reconstruction is in reasonably good agreement with EDC3 values for the full cycle except for the period warmer than present. For the latter, the accumulation is up to 13% larger (4.46 cm ie yr-1 instead of 3.95). This result is in agreement with the studies suggesting an underestimation of the deuterium-based accumulation for the optimum of the Holocene (Parrenin et al. 2007a). Using the relationship between accumulation rate and surface temperature from the saturation vapour relationship, the 10Be-based accumulation rate reconstruction suggests that the temperature increase between the MIS 9.3 optimum and present day may be 2.4 K warmer than estimated by the water isotopes reconstruction. We compare these reconstructions to the available model results from CMIP5-PMIP3 for a glacial and an interglacial state, i

  4. Processes and rates of sediment and wood accumulation in headwater streams of the Oregon Coast Range, USA

    USGS Publications Warehouse

    May, Christine L.; Gresswell, Robert E.

    2003-01-01

    Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low-order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was used to estimate the time since the previous debris flow and the time since the last stand-replacement fire in unlogged basins in the central Coast Range of Oregon. Debris flow activity increased 42 per cent above the background rate in the decades immediately following the last wildfire. Changes in wood and sediment storage were quantified for 13 streams that ranged from 4 to 144 years since the previous debris flow. The volume of wood and sediment in the channel, and the length of channel with exposed bedrock, were strongly correlated with the time since the previous debris flow. Wood increased the storage capacity of the channel and trapped the majority of the sediment in these steep headwater streams. In the absence of wood, channels that have been scoured to bedrock by a debris flow may lack the capacity to store sediment and could persist in a bedrock state for an extended period of time. With an adequate supply of wood, low-order channels have the potential of storing large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain.

  5. Predicted detection rates of regional-scale meteorite impacts on Mars with the InSight short-period seismometer

    NASA Astrophysics Data System (ADS)

    Teanby, N. A.

    2015-08-01

    In 2016 NASA will launch the InSight discovery-class mission, which aims to study the detailed internal structure of Mars for the first time. Short- and long-period seismometers form a major component of InSight's payload and have the potential to detect seismic waves generated by meteorite impacts. Large globally detectable impact events producing craters with diameters of ∼ 100 m have been investigated previously and are likely to be rare (Teanby, N.A., Wookey, J. [2011]. Phys. Earth Planet. Int. 186, 70-80), but smaller impacts producing craters in the 0.5-20 m range are more numerous and potentially occur sufficiently often to be detectable on regional scales (≲1000 km). At these distances, seismic waves will have significant high frequency content and will be suited to detection with InSight's short-period seismometer SEIS-SP. In this paper I estimate the current martian crater production function from observations of new craters (Malin, M.C. et al. [2006]. Science 314, 1573-1577; Daubar, I.J. et al. [2013]. Icarus 225, 506-516), model results (Williams, J.P., Pathare, A.V., Aharonson, O. [2014]. Icarus 235, 23-36), and standard isochrons (Hartmann, W.K. [2005]. Icarus 174, 294-320). These impact rates are combined with an empirical relation between impact energy, source-receiver distance, and peak seismogram amplitude, derived from a compilation of seismic recordings of terrestrial and lunar impacts, chemical explosions, and nuclear tests. The resulting peak seismogram amplitude scaling law contains significant uncertainty, but can be used to predict impact detection rates. I estimate that for a short-period instrument, with a noise spectral density of 10-8 ms-2 Hz-1/2 in the 1-16 Hz frequency band, approximately 0.1-30 regional impacts per year should be detectable with a nominal value of 1-3 impacts per year. Therefore, small regional impacts are likely to be a viable source of seismic energy for probing Mars' crustal and upper mantle structure. This is

  6. Modern rates of glacial sediment accumulation along a 15° S-N transect in fjords from the Antarctic Peninsula to southern Chile

    NASA Astrophysics Data System (ADS)

    Boldt, Katherine V.; Nittrouer, Charles A.; Hallet, Bernard; Koppes, Michele N.; Forrest, Brittany K.; Wellner, Julia S.; Anderson, John B.

    2013-12-01

    of glacial erosion in temperate climates rank among the highest worldwide, and the sedimentary products of such erosion record climatic and tectonic signals in many glaciated settings, as well as temporal changes in glacier behavior. Glacial sediment yields are expected to decrease with increasing latitude because decreased temperature and meltwater production reduce glacial sliding, erosion, and sediment transfer; however, this expectation lacks a solid supportive database. Herein we present modern 210Pb-derived sediment accumulation rates on decadal to century time scales for 12 fjords spanning 15° of latitude from the Antarctic Peninsula to southern Chile and interpret the results in light of glacimarine sediment accumulation worldwide. 210Pb records from the Antarctic Peninsula show surprisingly steady sediment accumulation throughout the past century at rates of 1-7 mm yr-1, despite rapid warming and glacial retreat. Cores from the South Shetland Islands reveal accelerated sediment accumulation over the past few decades, likely due to changes in the thermal state of the glaciers in this region, which straddles the boundary between subpolar and temperate conditions. In Patagonia and Tierra del Fuego, sediment accumulates faster (11-24 mm yr-1), and previously collected seismic profiles show that rates reach meters per year close to the glacier termini. This increase in sediment accumulation rates with decreasing latitude reflects the gradient from subpolar to temperate climates and is consistent with glacial erosion being much faster in the temperate climate of southern Chile than in the polar climate of the Antarctic Peninsula.

  7. Lunar and Planetary Science XXXV: Mars Polar Science and Exploration

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session, "Mars Polar Science and Exploration" included the following reports: Evidence for Possible Exposed Water Ice Deposits in Martian Low Latitude Chasms and Chaos; Stability and Exchange of Subsurface Ice on Mars; Evaporation Rates for Liquid Water and Ice Under Current Martian Conditions; Seasonal Cycle of Carbon Dioxide and Atmospheric Circulation in Mars Southern Hemisphere as Observed by Neutron Spectroscopy; Imaging Polarimetry of Mars with Hubble Space Telescope in 2003 Opposition; GCM Simulations of Tropical Ice Accumulations: Implications for Cold-based Glaciers; Numerical Modeling of Glaciers in Martian Paleoclimates; Valley Glaciers on Mars: Calculation of Flow Rate and Thickness; Internal Structure of the Southern Polar Cap of Mars and Formation Implications; Sublimation at the Base of a Seasonal CO2 Slab on Mars; Impact Crater Abundance of the Martian South Polar Layered Deposits from THEMIS Visible Imaging; Recent Changes in South-Polar-Polygonal Terrain During One Martian Year: Implications for Subsurface Ice-Wedges; and An Historical Search for Unfrozen Water at the Phoenix Landing Site.

  8. Export Production Fluctuations in the Eastern Equatorial Pacific during the Pliocene-Pleistocene: Reconstruction Using Barite Accumulation Rates

    NASA Astrophysics Data System (ADS)

    Paytan, A.; Ma, Z.; Ravelo, A. C.; Liu, Z.

    2014-12-01

    Over the last 5 million years, Earth has experienced a transition from warmer climates to cooler climates. It is not clear how these changes affected export productivity in the Equatorial Pacific (EEP) and what are the potential feedbacks between ocean productivity and climate? To address these questions we use barite accumulation rates to reconstruct export productivity in the eastern equatorial Pacific (ODP Site 849) and compare the record to sea surface temperature (SST) fluctuations and other productivity proxies over the past 5.3 Ma. We find that export productivity fluctuated considerably on multiple time scales. During the Pliocene between 4.5 and 3 Ma, export productivity was on average higher (~50 g C m-2 yr-1) than during the Pleistocene (~ 35 g C m-2 yr-1). In the Pleistocene a trend of decreasing export production occurred between 3 Ma and 1 Ma (from ~60 to ~20 g C m-2 yr-1) followed by an increase over the last million years. Our record reveal decoupling between export productivity and SST on long (million year) time scales as previously suggested. Throughout this time interval shorter orbital-scale large amplitude fluctuations (between 10 and 100 g C m-2 yr-1) in export productivity are observed and export production was generally higher during cold periods or during transitions. Results from this study suggest that in the EEP mechanisms that affect carbon export on orbital time scales differed from those operating on longer time scales.

  9. Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe)

    NASA Astrophysics Data System (ADS)

    Zhou, Liangyong; Liu, Jian; Saito, Yoshiki; Gao, Maosheng; Diao, Shaobo; Qiu, Jiandong; Pei, Shaofeng

    2016-08-01

    Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river's course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5-18.6 cm year-1 on the delta front slope, 2 cm year-1 at the toe of the slope, and 1-2 cm year-1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year-1 in the delta front.

  10. Off-river waterbodies on tidal rivers: Human impact on rates of infilling and the accumulation of pollutants

    NASA Astrophysics Data System (ADS)

    Woodruff, Jonathan D.; Martini, Anna P.; Elzidani, Emhmed Z. H.; Naughton, Thomas J.; Kekacs, Daniel J.; MacDonald, Daniel G.

    2013-02-01

    Cut-off meanders, backwater ponds, and blocked valley coves are all common features along the tidal reaches of lowland rivers. While significant progress has been made to understand sediment dynamics in similar off-river environments above the head of tides, less is known about the processes driving transport and sedimentation within these systems when tidally influenced. To provide insight we combine sedimentological observations with flux analyses for a series of tidal off-river waterbodies along the Lower Connecticut River spanning the river's entire 100 km tidal reach. Sedimentation rates exhibit a clear seaward increase with growing tidal influence, and are an order of magnitude higher than accumulation rates obtained previously from neighboring marsh and subtidal environments. A simplified mass balance can relate time-series measurements of water level and suspended sediment concentration to observed trends in sedimentation, and support flood-dominated asymmetry in tidal sediment flux (i.e. tidal pumping) as the primary mechanism for enhanced trapping. Relatively steady rates of deposition are observed in off-river waterbodies over the last century, with little evidence of deposition dominated by extreme events. Suspended sediment concentrations rise significantly in the main tidal river with increasing river discharge, while tidal range is damped with rising freshwater flow. The net result is an optimal freshwater discharge for maximizing the tidal pumping of sediment from the main river into tidal off-river waterbodies, with more routine discharge events largely responsible for driving long-term trends in deposition. A sudden shift in lithology towards more inorganic, fluvial derived sediment is commonly observed towards the end of the 19th century, along with over an order of magnitude increase in the rate of deposition. The timing of the onset of rapid infilling occurs contemporaneous with the documented creation and/or deepening of tidal tie

  11. A novel method of determining accumulation rates during the last glacial period at Berkner Island, West Antarctica

    NASA Astrophysics Data System (ADS)

    Massam, Ashleigh; Sneed, Sharon; Mulvaney, Robert; Mayewski, Paul; Whitehouse, Pippa

    2015-04-01

    within the ice sheet - a particular issue in Antarctica where accumulation rates can be very low. In addition, this is the only study so far that is able to evaluate the empirical relationships used in modelled reconstructions of glacial conditions, by comparing modelled glaciological profiles with the profiles derived from the ultra-high resolution trace element analysis. The ultimate outcome of this research is the construction of a more robust age-depth profile which will enable better insight and comprehension of past climate conditions including palaeoaccumulation. The authors acknowledge funding from a NERC DTG studentship, with support from the Antarctic Science bursary, the WM Keck Foundation and the US National Science Foundation.

  12. Mauna Loa lava accumulation rates at the Hilo drill site: Formation of lava deltas during a period of declining overall volcanic growth

    USGS Publications Warehouse

    Lipman, P.W.; Moore, J.G.

    1996-01-01

    Accumulation rates for lava flows erupted from Mauna Loa, as sampled in the uppermost 280 m of the Hilo drill hole, vary widely for short time intervals (several thousand years), but overall are broadly similar to those documented elsewhere on this volcano since 100 ka. Thickness variations and accumulation rates for Mauna Loa lavas at the Hilo drill site have been strongly affected by local paleotopography, including funneling and ponding between Mauna Kea and Kilauea. In addition, gentle submerged slopes of Mauna Kea in Hilo Bay have permitted large shoreline displacements by Mauna Loa flows. Ages of eruptive intervals have been determined from published isotopic data and from eustatic sea level curves modified to include the isostatic subsidence of the island of Hawaii at 2.2-2.6 mm/yr. Prior to 10 ka, rates of Mauna Loa lava accumulation at the drill site varied from 0.6 to 4.3 mm/yr for dateable intervals, with an overall rate of 1.8 mm/yr. Major eruptive pulses at about 1.3 and 10 ka, each probably representing a single long-lived eruption based on lack of weathering between flow units, increase the overall accumulation rate to 2.4 mm/yr. The higher rate since 10 ka reflects construction of thick near-shoreline lava deltas as postglacial sea levels rose rapidly. Large lava deltas form only along coastal segments where initially subaerial slopes have been submerged by the combined effects of eustatic sea level rise, isostatic subsidence, or spreading of volcano flanks. Overall accumulation of 239 m of lava at the drill site since 100-120 ka closely balances submergence of the Hilo area, suggesting that processes of coastal lava deposition have been modulated by rise in sea level. The Hilo accumulation rate is slightly higher than average rates of 1-2 mm/yr determined elsewhere along the Mauna Loa coast, based on rates of shoreline coverage and dated sea cliff and fault scarp exposures. Low rates of coastal lava accumulation since 100 ka, near or below the rate

  13. Forest dynamics and tip-up pools drive pulses of high carbon accumulation rates in a tropical peat dome in Borneo (Southeast Asia)

    NASA Astrophysics Data System (ADS)

    Dommain, René; Cobb, Alexander R.; Joosten, Hans; Glaser, Paul H.; Chua, Amy F. L.; Gandois, Laure; Kai, Fuu-Ming; Noren, Anders; Salim, Kamariah A.; Su'ut, N. Salihah H.; Harvey, Charles F.

    2015-04-01

    Peatlands of Southeast Asia store large pools of carbon but the mechanisms of peat accumulation in tropical forests remain to be resolved. Patch dynamics and forest disturbance have seldom been considered as drivers that can amplify or dampen rates of peat accumulation. Here we used a modified piston corer, noninvasive geophysical measurements, and geochemical and paleobotanical techniques to establish the effect of tree fall on carbon accumulation rates in a peat swamp forest dominated by Shorea albida in Brunei (Borneo). Carbon initially accumulated in a mangrove forest at over 300 g C m-2 yr-1 but declined to less than 50 g C m-2 yr-1 with the establishment of a peat swamp forest. A rapid accumulation pulse of 720-960 g C m-2 yr-1 occurred around 1080 years ago as a tip-up pool infilled. Tip-up pools are common in the peatlands of northwest Borneo where windthrow and lightning strikes produce tree falls at a rate of 4 trees ha-1 every decade. A simulation model indicates that tip-up pools, which are formed across the entire forested peat dome, produce local discontinuities in the peat deposit, when peat is removed to create a pool that is rapidly filled with younger material. The resulting discontinuities in peat age at the base and sides of pool deposits obscure linkages between carbon accumulation rates and climate and require new approaches for paleoenvironmental reconstructions. Our results suggest that carbon accumulation in tropical peat swamps may be based on fundamentally different peat-forming processes than those of northern peatlands.

  14. Variation of Accumulation Rates Over the Last Eight Centuries on the East Antarctic Plateau Derived from Volcanic Signals in Ice Cores

    NASA Technical Reports Server (NTRS)

    Anschuetz, H.; Sinisalo, A.; Isaksson, E.; McConnell, J. R.; Hamran, S.-E.; Bisiaux, M. M.; Pasteris, D.; Neumann, T. A.; Winther, J.-G.

    2011-01-01

    Volcanic signatures in ice-core records provide an excellent means to date the cores and obtain information about accumulation rates. From several ice cores it is thus possible to extract a spatio-temporal accumulation pattern. We show records of electrical conductivity and sulfur from firn cores from the Norwegian-USA scientific traverse during the International Polar Year 2007-2009 (IPY) through East Antarctica. Major volcanic eruptions are identified and used to assess century-scale accumulation changes. The largest changes seem to occur in the most recent decades with accumulation over the period 1963- 2007/08 being up to 25 % different from the long-term record. There is no clear overall trend, some sites show an increase in accumulation over the period 1963 to present while others show a decrease. Almost all of the sites above 3200 m above sea level (asl) suggest a decrease. These sites also show a significantly lower accumulation value than large-scale assessments both for the period 1963 to present and for the long-term mean at the respective drill sites. The spatial accumulation distribution is influenced mainly by elevation and distance to the ocean (continentality), as expected. Ground-penetrating radar data around the drill sites show a spatial variability within 10-20 % over several tens of kilometers, indicating that our drill sites are well representative for the area around them. Our results are important for large-scale assessments of Antarctic mass balance and model validation.

  15. Stability of Mg-sulfates at-10C and the rates of dehydration/rehydration processes under conditions relevant to Mars

    USGS Publications Warehouse

    Wang, A.; Freeman, J.J.; Chou, I.-Ming; Jolliff, B.L.

    2011-01-01

    We report the results of low temperature (-10??C) experiments on the stability fields and phase transition pathways of five hydrous Mg-sulfates. A low temperature form of MgSO 47H 2O (LT-7w) was found to have a wide stability field that extends to low relative humidity (???13% RH at-10??C). Using information on the timing of phase transitions, we extracted information on the reaction rates of five important dehydration and rehydration processes. We found that the temperature dependencies of rate constants for dehydration processes differ from those of rehydration, which reflect differences in reaction mechanisms. By extrapolating these rate constants versus T correlations into the T range relevant to Mars, we can evaluate the possibility of occurrence of specific processes and the presence of common Mg-sulfate species present on Mars in different periods and locations. We anticipate in a moderate obliquity period, starkeyite and LH-MgSO 4H 2O should be two common Mg-sulfates at the surface, another polymorph MH-MgSO 4H 2O can exist at the locations where hydrothermal processes may have occurred. In polar regions or within the subsurface of other regions, meridianiite (coexisting with water ice, near 100% RH) and LT-7w (over a large RH range) are the stable phases. During a high obliquity period, meridianiite and LT-7w should exhibit widespread occurrence. The correlations of reaction rates versus temperature found in this study imply that dehydration and rehydration of hydrous Mg-sulfates would always be slower than the sublimation and crystallization of water ice, which would be supported by mission observations from Odyssey and by Mars Exploration Rovers. Copyright 2011 by the American Geophysical Union.

  16. Rates of post-fire vegetation recovery and fuel accumulation as a function of burn severity and time-since-burn in four western U.S. ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetation recovery and fuel accumulation rates following wildfire are useful measures of ecosystem resilience, yet few studies have quantified these variables over 10 years post-fire. Conventional wisdom is that recovery time to pre-fire condition will be slower as a function of burn severity, as i...

  17. A 9000 year perspective on carbon accumulation rates under changing hydro-climate and vegetation conditions in a mountain peatland, northern Carpathians, Romania

    NASA Astrophysics Data System (ADS)

    Feurdean, Angelica; Panait, Andrei; Gałka, Mariusz; Diaconu, Andrei; Hutchinson, Simon; Mulch, Andreas; Tantau, Ioan; Hickler, Thomas

    2016-04-01

    Peatlands, in particular ombrogenous bogs, which entirely depend on water from precipitation, are sensitive to changes in the balance between precipitation and evapotranspiration; and therefore highly suitable for hydro-climatological reconstruction. Peatlands also represent a large carbon pool in the terrestrial biosphere. However, little is known about the C sequestration processes in mountain peatlands under various competing drivers of change (climate, vegetation, fire). We applied a multi-proxy approach (bulk density, loss on ignition, total organic carbon, testate amoebae, δ13C in Sphagnum, plant macrofossils, pollen and charcoal) to a peat sequence from a mountain ombrogenous bog (Tǎul Muced) to explore how changes in hydro-climate conditions, peat plant composition and fire have affected long-term physical peat properties and the rate of carbon accumulation over the last 9000 years. Carbon accumulation at this site ranged from 7 to 105 g C cm2 yr1 (mean 23 ± 14 g C cm2 yr_1). We found that high moisture availability (P-E) as inferred from testate amoebae and δ13C values in Sphagnum increased the carbon sink capacity of peatland. The strength of the relationship between the rate of carbon accumulation and climate appears particularly evident over the last millennium when high C accumulation rates correlated with the warm and wet conditions of the Medieval Climate Anomaly and lower C accumulation rates with the dry conditions of the Little Ice Age. We also found a significant positive correlation between the rate of C accumulation and changes in vegetation; rates were lowest (17 g C cm2 yr_1), during periods of mixed Sphagnum (primarily S. magellanicum and S. angustifolium) and vascular plant (Cyperaceae, Eriophorum vaginatum) growth and increased (31 g C cm2 yr_1) during the accumulation of Sphagnum peat, regardless the dominant Sphagnum species. We did not find indication of peatland fire during the investigated interval. Our study represents one of the

  18. The Martian atmospheric ion escape rate dependence on solar wind and solar EUV conditions: 1. Seven years of Mars Express observations

    NASA Astrophysics Data System (ADS)

    Ramstad, Robin; Barabash, Stas; Futaana, Yoshifumi; Nilsson, Hans; Wang, Xiao-Dong; Holmström, Mats

    2015-07-01

    More than 7 years of ion flux measurements in the energy range 10 eV-15 keV have allowed the ASPERA-3/IMA (Analyzer of Space Plasmas and Energetic Ions/Ion Mass Analyzer) instrument on Mars Express to collect a large database of ion measurements in the Mars environment, over a wide range of upstream solar wind (density and velocity) and radiation (solar EUV intensity) conditions. We investigate the influence of these parameters on the Martian atmospheric ion escape rate by integrating IMA heavy ion flux measurements taken in the Martian tail at similar (binned) solar wind density (nsw), velocity (vsw), and solar EUV intensity (IEUV) conditions. For the same solar wind velocity and EUV intensity ranges (vsw and Is constrained), we find a statistically significant decrease of up to a factor of 3 in the atmospheric ion escape rate with increased average solar wind density (5.6 × 1024s-1 to 1.9 × 1024s-1 for 0.4 cm-3 and 1.4 cm-3, respectively). For low solar wind density (0.1-0.5 cm-3) and low EUV intensity, the escape rate increases with increasing solar wind velocity from 2.4 × 1024s-1 to 5.6 × 1024s-1. During high solar EUV intensities the escape fluxes are highly variable, leading to large uncertainties in the estimated escape rates; however, a statistically significant increase in the escape rate is found between low/high EUV for similar solar wind conditions. Empirical-analytical models for atmospheric escape are developed by fitting calculated escape rates to all sufficiently sampled upstream conditions.

  19. A Dust Characterization Experiment for Solar Cells Operating on Mars

    NASA Technical Reports Server (NTRS)

    Jenkins, Phillip; Landis, Geoffrey A.; Krasowski, Michael; Greer, Lawrence; Wilt, David; Baraona, Cosmo; Scheiman, David; Lekki, John

    2001-01-01

    During the Viking and Pathfinder missions to Mars, significant amounts of dust accumulated on the spacecrafts. In Pathfinder's case, the dust obscured the solar panels on the lander and the rover degrading their output current. The material adherence experiment aboard the Pathfinder rover quantified the rate of decrease in short circuit current at 0.28% per day. This rate is unacceptably high for long duration missions. In response, NASA has developed the Dust Accumulation and Removal Technology (DART) experiment. DART has three instruments for characterizing dust settling out of the atmosphere and tests two methods to keep dust from settling on solar cells.

  20. Elucidating effects of atmospheric deposition and peat decomposition processes on mercury accumulation rates in a northern Minnesota peatland over last 10,000 cal years

    NASA Astrophysics Data System (ADS)

    Nater, E. A.; Furman, O.; Toner, B. M.; Sebestyen, S. D.; Tfaily, M. M.; Chanton, J.; Fissore, C.; McFarlane, K. J.; Hanson, P. J.; Iversen, C. M.; Kolka, R. K.

    2014-12-01

    Climate change has the potential to affect mercury (Hg), sulfur (S) and carbon (C) stores and cycling in northern peatland ecosystems (NPEs). SPRUCE (Spruce and Peatland Responses Under Climate and Environmental change) is an interdisciplinary study of the effects of elevated temperature and CO2 enrichment on NPEs. Peat cores (0-3.0 m) were collected from 16 large plots located on the S1 peatland (an ombrotrophic bog treed with Picea mariana and Larix laricina) in August, 2012 for baseline characterization before the experiment begins. Peat samples were analyzed at depth increments for total Hg, bulk density, humification indices, and elemental composition. Net Hg accumulation rates over the last 10,000 years were derived from Hg concentrations and peat accumulation rates based on peat depth chronology established using 14C and 13C dating of peat cores. Historic Hg deposition rates are being modeled from pre-industrial deposition rates in S1 scaled by regional lake sediment records. Effects of peatland processes and factors (hydrology, decomposition, redox chemistry, vegetative changes, microtopography) on the biogeochemistry of Hg, S, and other elements are being assessed by comparing observed elemental depth profiles with accumulation profiles predicted solely from atmospheric deposition. We are using principal component analyses and cluster analyses to elucidate relationships between humification indices, peat physical properties, and inorganic and organic geochemistry data to interpret the main processes controlling net Hg accumulation and elemental concentrations in surface and subsurface peat layers. These findings are critical to predicting how climate change will affect future accumulation of Hg as well as existing Hg stores in NPE, and for providing reference baselines for SPRUCE future investigations.

  1. Variations in the accumulation, localization and rate of metabolization of selenium in mature Zea mays plants supplied with selenite or selenate.

    PubMed

    Longchamp, Mélanie; Castrec-Rouelle, Maryse; Biron, Philippe; Bariac, Thierry

    2015-09-01

    Quantification of selenium bioavailability from foods is a key challenge following the discovery of the antioxidant role of this micronutrient in human health. This study presents the uptake, accumulation and rate of metabolization in mature Zea mays plants grown in hydroponic solution supplemented with selenate or selenite. Selenium content was lower in plants supplemented with selenate and accumulated mainly in the leaves compared with selenite-treated plants where the selenium was retained in the roots. Selenite-treated grains accumulated more selenium. Selenate was metabolized less than selenite in whole plants, but in grains selenium was present exclusively as organic selenium compounds. For humans, the bioavailability of organic selenium was evaluated at 90% compared with only 50% for inorganic forms. Our results show that the potential for selenium bioavailability is increased with selenite treatment. PMID:25842318

  2. Mars Landscapes

    NASA Video Gallery

    Spacecraft have studied the Martian surface for decades, giving Earthlings insights into the history, climate and geology of our nearest neighbor, Mars. These images are from "Mars Landscapes," a v...

  3. Three hen strains fed photoisomerized trans,trans CLA-rich soy oil exhibit different yolk accumulation rates and source-specific isomer deposition.

    PubMed

    Shinn, Sara E; Gilley, Alex D; Proctor, Andrew; Anthony, Nicholas B

    2015-04-01

    Most CLA chicken feeding trials used cis,trans (c,t) and trans,cis (t,c) CLA isomers to produce CLA-rich eggs, while reports of trans,trans (t,t) CLA enrichment in egg yolks are limited. The CLA yolk fatty acid profile changes and the 10-12 days of feeding needed for maximum CLA are well documented, but there is no information describing CLA accumulation during initial feed administration. In addition, no information on CLA accumulation rates in different hen strains is available. The aim of this study was to determine a mathematical model that described yolk CLA accumulation and depletion in three hen strains by using t,t CLA-rich soybean oil produced by photoisomerization. Diets of 30-week Leghorns, broilers, and jungle fowl were supplemented with 15% CLA-rich soy oil for 16 days, and eggs were collected for 32 days. Yolk fatty acid profiles were measured by GC-FID. CLA accumulation and depletion was modeled by both quadratic and piecewise regression analysis. A strong quadratic model was proposed, but it was not as effective as piecewise regression in describing CLA accumulation and depletion. Broiler hen eggs contained the greatest concentration of CLA at 3.2 mol/100 g egg yolk, then jungle fowl at 2.9 mol CLA, and Leghorns at 2.3 mol CLA. The t,t CLA isomer levels remained at 55% of total yolk CLA during CLA feeding. However, t-10,c-12 (t,c) CLA concentration increased slightly during CLA accumulation and was significantly greater than c-9,t-11 CLA. Jungle fowl had the smallest increase in yolk saturated fat with CLA yolk accumulation. PMID:25771890

  4. OSL-based lateral progradation and aeolian sediment accumulation rates for the Apalachicola Barrier Island Complex, North Gulf of Mexico, Florida

    NASA Astrophysics Data System (ADS)

    Rink, W. J.; López, G. I.

    2010-11-01

    Vertical sediment cores in five separate beach ridge complexes along the north-east Gulf of Mexico Coast were recovered and dated using optically stimulated luminescence (OSL) dating of quartz: these are located on Cape San Blas (CSB), Little St. George Island (LSGI), Richardson's Hammock (RH), St. Joseph Peninsula (SJP) and Saint Vincent Island (SVI). All of these landforms are coastal barrier systems situated along a 100 km stretch of the Florida Panhandle, U.S.A. Two samples were collected for dating from each core. Ridge accumulation rates (RAR) associated with lateral progradation were calculated from the dated samples. We also determined average sediment accumulation rates (ASAR) for two intervals within each sediment core. All OSL ages within the sediment cores were found to be in stratigraphic order or in a few cases statistically indistinguishable. Moreover, all dated ridges were found to be in correct temporal sequence based on their geomorphic positions. Rapidly accreted sequences were found to be backed by St. Joseph Bay in the western region of the study area. More slowly accreted sequences were associated with the more eastern stretches of the study area backed by St. Vincent Sound and Apalachicola Bay. Our ASAR results are in accord with an Australian study of modern dune accumulation. Perhaps our most important finding is that in the barrier island environments of this north-eastern Gulf Coast region, aeolian sedimentation continues well after full vegetative cover develops and stranding of landward ridges takes place. This confirms our similar earlier observation on SVI (López and Rink, 2008). We find that up to approximately one order of magnitude lower sedimentation rates occur after an initial period of more rapid aeolian accumulation for the vertical intervals studied in foredune ridges. Lateral progradation rates of ridge sequences were highly variable within the study area, ranging from 92 to 848 m/100 years, but we did find agreement

  5. A comparison of conventional /sup 60/Co testing and low dose-accumulation-rate exposure of metal-gate CMOS IC'S

    SciTech Connect

    Roeske, S.B.; Edwards, W.H.; Gammill, P.E.; Puariea, J.W.; Zipay, J.W.

    1984-12-01

    Data are presented for the CD4000 family of Hi-Rel, rad-hard, metal-gate CMOS ICs which show a much greater tolerance to low dose-rate ionizing radiation than that observed with ''conventional rate'' (approximately 10/sup 6/ rad(Si)/hr) /sup 60/Co testing. Data obtained using conventional rate /sup 60/Co irradiations followed by either a 24-hour, high-temperature (100/sup 0/C) anneal or a 65-day, room temperature anneal are in good agreement with data obtained by exposing similar parts at a low dose-accumulation rate (daily 17second, 5000 rad(Si) exposures) for 200 consecutive days. Graphs of thresholds, output drive, and propagation delay for both low doseaccumulation rate and conventional rate exposures are included.

  6. Comparison of annual accumulation rates derived from in situ and ground penetrating radar methods across Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    McGrath, D.; Gusmeroli, A.; Oneel, S.; Sass, L. C.; Arendt, A. A.; Wolken, G. J.; Kienholz, C.; McNeil, C.

    2013-12-01

    Constraining annual snowfall accumulation in mountain glacier environments is essential for determining the annual mass balance of individual glaciers and predicting seasonal meltwater runoff to river and marine ecosystems. However, large spatial and elevation gradients, coupled with sparse point measurements preclude accurate quantification of this variable using traditional methods. Here, we report on an extensive field campaign conducted in March-May 2013 on key benchmark glaciers in Alaska, including Taku Glacier near Juneau, Scott Glacier near Cordova, both Eklutna and Wolverine Glacier near Anchorage and Gulkana Glacier in the interior Alaska Range. Over 50 km of 500 MHz common-offset ground penetrating radar (GPR) surveys were collected on each glacier, with an emphasis on capturing spatial variability in the accumulation zone. Frequent in situ observations were collected for comparison with the GPR, including probe depths, snow pits and shallow firn cores (~8 m). We report on spatial and elevation gradients across this suite of glaciers and across numerous climatic zones and discuss differences between GPR and in situ derived annual accumulation estimates. This comparison is an essential first step in order to effectively evaluate regional atmospheric re-analysis products.

  7. Sediment accumulation rates and high-resolution stratigraphy of recent fluvial suspension deposits in various fluvial settings, Morava River catchment area, Czech Republic

    NASA Astrophysics Data System (ADS)

    Sedláček, Jan; Bábek, Ondřej; Kielar, Ondřej

    2016-02-01

    We present a comprehensive study concerning sedimentary processes in fluvial sediment traps within the Morava River catchment area (Czech Republic) involving three dammed reservoirs, four meanders and oxbow lakes, and several natural floodplain sites. The objective of the study was to determine sediment accumulation rates (SAR), estimate erosion rates, calculating these using a combination of the 137Cs method and historical data. Another purpose of this study was to provide insight into changing erosion and accumulation rates over the last century. Extensive water course modifications were carried out in the Morava River catchment area during the twentieth century, which likely affected sedimentation rates along the river course. Other multiproxy stratigraphic methods (X-ray densitometry, magnetic susceptibility, and visible-light reflectance spectrometry) were applied to obtain additional information about sediment infill. Sediment stratigraphy revealed distinct distal-to-proximal patterns, especially in reservoirs. Granulometrically, silts and sandy silts prevailed in sediments. Oxbow lakes and meanders contained larger amounts of clay and organic matter, which is the main difference between them and reservoirs. Pronounced 137Cs peaks were recorded in all studied cores (maximum 377 Bq·kg- 1), thus indicating Chernobyl fallout from 1986 or older events. Calculated sediment accumulation rates were lowest in distal parts of reservoirs (0.13-0.58 cm/y) and floodplains (0.45-0.88 cm/y), moderately high rates were found in proximal parts of reservoirs and oxbow lakes (2.27-4.4 cm/y), and the highest rates in some oxbow lakes located near the river (6-8 cm/y). The frequency of the inundation still can be high in some natural areas as in the Litovelské Pomoraví protected area, whereas the decreasing frequency of the inundation in other modified parts can contribute to a lower sedimentation rate. The local effects such as difference between SARs in oxbow lakes and

  8. Increasing sediment accumulation rates in La Fonera (Palamós) submarine canyon axis and their relationship with bottom trawling activities

    NASA Astrophysics Data System (ADS)

    Puig, P.; Martín, J.; Masqué, P.; Palanques, A.

    2015-10-01

    Previous studies conducted in La Fonera (Palamós) submarine canyon (NW Mediterranean) found that trawling activities along the canyon flanks cause resuspension and transport of sediments toward the canyon axis. 210Pb chronology supported by 137Cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s, coincident with the rapid industrialization of the local trawling fleet. The same canyon area has been revisited a decade later, and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected, approaching ~2.4 cm yr-1 (compared to ~0.25 cm yr-1 pre-1970s). These results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins, eventually initiating the formation of anthropogenic depocenters in submarine canyon environments.

  9. Review and Analysis of Existing Mobile Phone Apps to Support Heart Failure Symptom Monitoring and Self-Care Management Using the Mobile Application Rating Scale (MARS)

    PubMed Central

    Maurer, Mathew S; Reading, Meghan; Hiraldo, Grenny; Hickey, Kathleen T; Iribarren, Sarah

    2016-01-01

    Background Heart failure is the most common cause of hospital readmissions among Medicare beneficiaries and these hospitalizations are often driven by exacerbations in common heart failure symptoms. Patient collaboration with health care providers and decision making is a core component of increasing symptom monitoring and decreasing hospital use. Mobile phone apps offer a potentially cost-effective solution for symptom monitoring and self-care management at the point of need. Objective The purpose of this review of commercially available apps was to identify and assess the functionalities of patient-facing mobile health apps targeted toward supporting heart failure symptom monitoring and self-care management. Methods We searched 3 Web-based mobile app stores using multiple terms and combinations (eg, “heart failure,” “cardiology,” “heart failure and self-management”). Apps meeting inclusion criteria were evaluated using the Mobile Application Rating Scale (MARS), IMS Institute for Healthcare Informatics functionality scores, and Heart Failure Society of America (HFSA) guidelines for nonpharmacologic management. Apps were downloaded and assessed independently by 2-4 reviewers, interclass correlations between reviewers were calculated, and consensus was met by discussion. Results Of 3636 potentially relevant apps searched, 34 met inclusion criteria. Most apps were excluded because they were unrelated to heart failure, not in English or Spanish, or were games. Interrater reliability between reviewers was high. AskMD app had the highest average MARS total (4.9/5). More than half of the apps (23/34, 68%) had acceptable MARS scores (>3.0). Heart Failure Health Storylines (4.6) and AskMD (4.5) had the highest scores for behavior change. Factoring MARS, functionality, and HFSA guideline scores, the highest performing apps included Heart Failure Health Storylines, Symple, ContinuousCare Health App, WebMD, and AskMD. Peer-reviewed publications were identified

  10. How Integrated Management Strategies Promote Protein Quality of Cotton Embryos: High Levels of Soil Available N, N Assimilation and Protein Accumulation Rate.

    PubMed

    Yang, HongKun; Meng, YaLi; Chen, BingLin; Zhang, XingYue; Wang, YouHua; Zhao, WenQing; Zhou, ZhiGuo

    2016-01-01

    Cottonseed is widely used as a source of ruminant feed and for industrial purposes. Therefore, there is a tremendous need to improve the nutritional value of cotton embryos. In this study, a conventional management (CM) and two integrated cotton management strategies (IMS1, IMS2) were performed at two soil fertility levels to study the relationships among soil N, N assimilation, embryonic protein accumulation and protein quality. The levels of proteins, essential amino acids, and semi-essential amino acids, especially those of glutamate, lysine, and methionine, were higher in IMS1 and IMS2 embryos than in CM embryos. These changes were significantly positively correlated with the soil-available N content, glutamine synthetase activity and peak value of protein accumulation rate and were negatively correlated with the free amino acid level. These results illustrated that integrated management strategies, especially the rates and timing of N application, raise the level of soil available N, which is beneficial for N assimilation in developing cotton embryos. The protein content was limited by the rate of protein accumulation rather than by the free amino acid content. The combination of target yield fertilization, a growth-driven N application schedule, a high plant density and the seedling raising with bio-organic fertilizer can substantially improve protein quality in cotton embryos, especially at a soil with low soil organic matter and total nitrogen. PMID:27532007

  11. How Integrated Management Strategies Promote Protein Quality of Cotton Embryos: High Levels of Soil Available N, N Assimilation and Protein Accumulation Rate

    PubMed Central

    Yang, HongKun; Meng, YaLi; Chen, BingLin; Zhang, XingYue; Wang, YouHua; Zhao, WenQing; Zhou, ZhiGuo

    2016-01-01

    Cottonseed is widely used as a source of ruminant feed and for industrial purposes. Therefore, there is a tremendous need to improve the nutritional value of cotton embryos. In this study, a conventional management (CM) and two integrated cotton management strategies (IMS1, IMS2) were performed at two soil fertility levels to study the relationships among soil N, N assimilation, embryonic protein accumulation and protein quality. The levels of proteins, essential amino acids, and semi-essential amino acids, especially those of glutamate, lysine, and methionine, were higher in IMS1 and IMS2 embryos than in CM embryos. These changes were significantly positively correlated with the soil-available N content, glutamine synthetase activity and peak value of protein accumulation rate and were negatively correlated with the free amino acid level. These results illustrated that integrated management strategies, especially the rates and timing of N application, raise the level of soil available N, which is beneficial for N assimilation in developing cotton embryos. The protein content was limited by the rate of protein accumulation rather than by the free amino acid content. The combination of target yield fertilization, a growth-driven N application schedule, a high plant density and the seedling raising with bio-organic fertilizer can substantially improve protein quality in cotton embryos, especially at a soil with low soil organic matter and total nitrogen. PMID:27532007

  12. In situ cosmogenic H-3, C-14, and Be-10 for determining the net accumulation and ablation rates of ice sheets

    NASA Technical Reports Server (NTRS)

    Lal, D.; Nishiizumi, K.; Arnold, J. R.

    1987-01-01

    The usefulness of the in situ cosmogenic H-3, C-14, and Be-10 produced by spallation of oxygen nuclei in ice, as tracers to determine net accumulation/ablation rates of ice sheets is explored. The application of the in situ H-3 and Be-10 is severely constrained because at deposition, ice contains appreciable amounts of these isotopes from the atmosphere. The case is much more favorable for C-14, which is not carried with wet precipitations; atmospheric C-14 gets mechanically trapped in the ice during deposition. It is pointed out that cosmogenic C-14 would probably exist as (C-14)O in ice. This seems to be supported by the published results of Fireman and Norris (1981). Considering their inherent amounts in the ice and the expected in situ production rates, conditions under which these isotopes can be used to study net accumulation and ablation rates are discussed. Available data on C-14 and Be-10 on polar ice from accumulation and ablation zones is also discussed. It is concluded that H-3 and C-14 should find wide applications in studying ice dynamics and Be-10 in very special circumstances.

  13. Shallow Sediment Trace Metal Concentrations and Short-Term Accumulation Rates in the Neponset River Estuary, Massachusetts, USA

    NASA Astrophysics Data System (ADS)

    Spencer, J. R.; Zhu, J.; Olsen, C. R.

    2010-12-01

    The Neponset River estuary is a small estuary that drains into the Boston Harbor on the east coast of the United States. It is also a highly urbanized estuary and has a long history of urban development over 450 years. In July 2006, six sediment cores were collected in the Neponset River estuary to examine particle dynamics and sediment accumulation via radionuclide (Beryllium-7) dating, and to determine sediment metal concentrations (As, Cu, Pb, and Zn) via ED-XRF measurements. Measured sediment Be-7 profiles indicate various sedimentation environments, where sediment accumulation, resuspension or redeposition is likely to occur. High metal concentrations were often corresponding to high Be-7 inventories in sediment cores. Possible sources of trace metal contaminants in the water column include: storm water run-off, Combined Sewer Overflows (CSOs), a well-documented industrial pollution event that occurred upstream in the early to mid twentieth century, and the resuspension of sediment. Existing and future data will provide baseline information for quantifying the effects of the proposed and pending environmental restoration project, which includes the removal of the Baker Dam. The combined pre- and post-Dam removal data may then be used in cost-benefit analyses for other similar estuarine restoration projects.

  14. Burst mode with ps- and fs-pulses: Influence on the removal rate, surface quality, and heat accumulation

    NASA Astrophysics Data System (ADS)

    Neuenschwander, B.; Kramer, Th.; Lauer, B.; Jaeggi, B.

    2015-03-01

    The burst mode for ps and fs pulses for steel and copper is investigated. It is found that the reduction of the energy in a single pulse (in the burst) represents the main factor for the often reported gain in the removal rate using the burst mode e.g. for steel no investigated burst sequence lead to a higher removal rate compared to single pulses at higher repetition rate. But for copper a situation was found where the burst mode leads to a real increase of the removal rate in the range of 20%. Further the burst mode offers the possibility to generate slightly melted flat surfaces with good optical properties in the case of steel. Temperature simulations indicate that the surface state during the burst mode could be responsible for the melting effect or the formation of cavities in clusters which reduces the surface quality.

  15. Accumulated occupational class and self-rated health. Can information on previous experience of class further our understanding of the social gradient in health?

    PubMed

    Kjellsson, Sara

    2013-03-01

    Previous research has shown a social gradient in health with better health for people in more advantaged positions in society. This research has mainly been on the relationship between current position and health, or social position in childhood and health, but less is known about the potential accumulative impact of positions held in adulthood. In this paper I use the economic activity histories from the Swedish Level of Living survey to examine the relationship between accumulated occupational class positions and health. Step-wise linear probability models are used to investigate how to best capture the potential association between class experience and self-rated health (SRH), and whether the effect of current class is modified when measures of accumulated class are included. I then further test the potentially lasting association between previous exposure to the health risk of working class by analysing only individuals currently in higher or intermediate level service class; the classes under least exposure. I find a positive association between accumulated experiences of working class and less than good SRH. Furthermore, even for employees currently in non-manual positions the risk for less than good SRH increases with each added year of previous experience within working class. This suggests that the social gradient can be both accumulative and lasting, and that more information on the mechanisms of health disparities can be found by taking detailed information on peoples' pasts into account. Although gender differences in health are not a focus in this paper, results also indicate that the influence of class experiences on health might differ between men and women. PMID:23422057

  16. Geologic ages and accumulation rates of basalt-flow groups and sedimentary interbeds in selected wells at the Idaho National Engineering Laboratory, Idaho

    SciTech Connect

    Anderson, S.R.; Liszewski, M.J.; Cecil, L.D.

    1997-01-01

    Geologic ages and accumulation rates, estimated from regressions, were used to evaluate measured ages and interpreted stratigraphic and structural relations of basalt and sediment in the unsaturated zone and the Snake River Plain aquifer at the Idaho National Engineering Laboratory (INEL) in eastern Idaho. Geologic ages and accumulation rates were estimated from standard linear regressions of 21 mean potassium-argon (K-Ar) ages, selected mean paleomagnetic ages, and cumulative depths of a composite stratigraphic section composed of complete intervals of basalt and sediment that were deposited in areas of past maximum subsidence. Accumulation rates also were estimated from regressions of stratigraphic intervals in three wells in and adjacent to an area of interpreted uplift at and near the Idaho Chemical Processing Plant (ICPP) and the Test Reactor Area (TRA) to allow a comparison of rates in areas of past uplift and subsidence. Estimated geologic ages range from about 200 thousand to 1.8 million years before present and are reasonable approximations for the interval of basalt and sediment above the effective base of the aquifer, based on reported uncertainties of corresponding measured ages. Estimated ages between 200 and 800 thousand years are within the range of reported uncertainties for all 15 K-Ar ages used in regressions and two out of three -argon ({sup 40}Ar/{sup 39}Ar) ages of duplicate argon samples. Two sets of estimated ages between 800 thousand and 1.8 million years are within the range of reported uncertainties for all seven K-Ar ages used in regressions, which include one shared age of about 800 thousand years. Two sets of ages were estimated for this interval because K-Ar ages make up two populations that agree with previous and revised ages of three paleomagnetic subchrons. The youngest set of ages is consistent with a K-Ar age from the effective base of the aquifer that agrees with previous ages of the Olduvai Normal-Polarity Subchron.

  17. The null hypothesis: steady rates of erosion, weathering and sediment accumulation during Late Cenozoic mountain uplift and glaciation

    NASA Astrophysics Data System (ADS)

    Willenbring, J. K.; Jerolmack, D. J.

    2015-12-01

    At the largest time and space scales, the pace of erosion and chemical weathering is determined by tectonic uplift rates. Deviations from this equilibrium condition arise from the transient response of landscape denudation to climatic and tectonic perturbations, and may be long lived. We posit that the constraint of mass balance, however, makes it unlikely that such disequilibrium persists at the global scale over millions of years, as has been proposed for late Cenozoic erosion. To support this contention, we synthesize existing data for weathering fluxes, global sedimentation rates, sediment yields and tectonic motions. The records show a remarkable constancy in the pace of Earth-surface evolution over the last 10 million years. These findings provide strong support for the null hypothesis; that global rates of landscape change have remained constant over the last ten million years, despite global climate change and massive mountain building events. Two important implications are: (1) global climate change may not change global denudation rates, because the nature and sign of landscape responses are varied; and (2) tectonic and climatic perturbations are accommodated in the long term by changes in landscape form. This work undermines the hypothesis that increased weathering due to late Cenozoic mountain building or climate change was the primary agent for a decrease in global temperatures.

  18. Effects of feeding and organism loading rate on PCB accumulation by Lumbriculus variegatus in sediment bioaccumulation testing

    EPA Science Inventory

    Sediment bioaccumulation test methods published by USEPA and ASTM in 2000 specify that the Lumbriculus variegatus, a freshwater oligochaete, should not be fed during the 28-day exposure and recommends an organism loading rate of total organic carbon in sediment to organism dry we...

  19. Post-bubble close-off fractionation of gases in polar firn and ice cores: effects of accumulation rate on permeation through overloading pressure

    NASA Astrophysics Data System (ADS)

    Kobashi, T.; Ikeda-Fukazawa, T.; Suwa, M.; Schwander, J.; Kameda, T.; Lundin, J.; Hori, A.; Motoyama, H.; Döring, M.; Leuenberger, M.

    2015-12-01

    Gases in ice cores are invaluable archives of past environmental changes (e.g., the past atmosphere). However, gas fractionation processes after bubble closure in the firn are poorly understood, although increasing evidence indicates preferential leakages of smaller molecules (e.g., neon, oxygen, and argon) from the closed bubbles through the ice matrix. These fractionation processes are believed to be responsible for the observed millennial δO2/N2 variations in ice cores, linking ice core chronologies with orbital parameters. In this study, we investigated high-resolution δAr/N2 of the GISP2 (Greenland Ice Sheet Project 2), NGRIP (North Greenland Ice Core Project), and Dome Fuji ice cores for the past few thousand years. We find that δAr/N2 at multidecadal resolution on the "gas-age scale" in the GISP2 ice core has a significant negative correlation with accumulation rate and a positive correlation with air contents over the past 6000 years, indicating that changes in overloading pressure induced δAr/N2 fractionation in the firn. Furthermore, the GISP2 temperature and accumulation rate for the last 4000 years have nearly equal effects on δAr/N2 with sensitivities of 0.72 ± 0.1 ‰ °C-1 and -0.58 ± 0.09 ‰ (0.01 m ice year-1)-1, respectively. To understand the fractionation processes, we applied a permeation model for two different processes of bubble pressure build-up in the firn, "pressure sensitive process" (e.g., microbubbles: 0.3-3 % of air contents) with a greater sensitivity to overloading pressures and "normal bubble process". The model indicates that δAr/N2 in the bubbles under the pressure sensitive process are negatively correlated with the accumulation rate due to changes in overloading pressure. On the other hand, the normal bubbles experience only limited depletion (< 0.5 ‰) in the firn. Colder temperatures in the firn induce more depletion in δAr/N2 through thicker firn. The pressure sensitive bubbles are so depleted in δAr/N2 at the

  20. Multihued Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken at JPL shows the panoramic camera used onboard both Mars Exploration Rovers. The panel to the lower right highlights the multicolored filter wheel that allows the camera to see a rainbow of colors, in addition to infrared bands of light. By seeing Mars in all its colors, scientists can gain insight into the different minerals that constitute its rocks and soil.

  1. Soil weathering and accumulation rates of oxalate-extractable phases derived from alpine chronosequences of up to 1 Ma in age

    NASA Astrophysics Data System (ADS)

    Dahms, Dennis; Favilli, Filippo; Krebs, Rolf; Egli, Markus

    2012-05-01

    In this study we compare newly-developed chemical weathering data with previously published data from soils developed along two chronosequences of glacial deposits in the European Alps and the Rocky Mountains (Wind River Range, USA). By combining these chronosequences, we are able to present a comprehensive dataset that represents a time period of > 1 Ma. We describe weathering trends of important elements using a number of weathering indices (e.g., K + Ca/Ti ratio, the weathering 'index B' of Kronberg and Nesbitt (1981) and the open mass transport function). Further, we describe the accumulation of Al, Fe, Si and Mn oxyhydroxides (including partially organic phases) as a function of time, and derive the corresponding accumulation rates. We calculated pedogenetically formed oxyhydroxides using an approach based on immobile elements. Our study represents one of only a few studies that describe rates of soil chemical weathering over a period as long as ~ 1 Ma. Results show that rates of chemical weathering clearly decrease along the chronosequences with increasing age of the soils. We find weathering rates are nearly four orders of magnitude lower in the 1 Ma-old soils than in the young soils. Our results suggest that the older soils may be reaching a steady state for these chemical properties in their present environments. A power function best explains the measured time-trends of the 'index B' and (K + Ca)/Ti) ratios in the soils. The best time-trend model for pedogenic weakly- to poorly crystalline phases and the relative losses/gains (based on the open-system mass transport function) were obtained with an exponential decay model function. In terms of the soil system, the decreases in the accumulation rate of the oxyhydroxides appears to be influenced not only by the factor of time but by climate as well (increased precipitation at higher altitudes slows the decrease in weathering rate over time). Thus, our ~ 1 Ma chronosequences also become pedogenic gradients

  2. The Mars Express - NASA Project at JPL

    NASA Technical Reports Server (NTRS)

    Thompson, Thomas W.; Horttor, Richard L.; Acton, C. H., Jr.; Zamani, P.; Johnson, W. T. K.; Plaut, J. J.; Holmes, D. P.; No, S.; Asmar, S. W.; Goltz, G.

    2006-01-01

    This viewgraph presentation gives a general overview of the Mars Express NASA Project at JPL. The contents include: 1) Mars Express/NASA Project Overview; 2) Experiment-Investigator Matrix; 3) Mars Express Support of NASA's Mars Exploration Objectives; 4) U.S./NASA Support of Mars Express; 5) Mars Express Schedule (2003-2007); 6) Mars Express Data Rates; 7) MARSIS Overview Results; 8) MARSIS with Antennas Deployed; 9) MARSIS Science Objectives; 10) Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) Experiment Overview; 11) Mars Express Orbit Evolution; 12) MARSIS Science - Subsurface Sounding; 13) MARSIS-North Polar Ice Cap; 14) MARSIS Data-Buried Basin; 15) MARSIS over a Crater Basin; 16) MARSIS-Buried Basin; 17) Ionogram - Orbit 2032 (example from Science paper); 18) Ionogram-Orbit 2018 (example from Science paper); and 19) Recent MARSIS Results ESA Press Releases.

  3. Urban rivers as conveyors of hydrocarbons to sediments of estuarine areas: source characterization, flow rates and mass accumulation.

    PubMed

    Mauad, Cristiane R; Wagener, Angela de L R; Massone, Carlos G; Aniceto, Mayara da S; Lazzari, Letícia; Carreira, Renato S; Farias, Cássia de O

    2015-02-15

    Aliphatic (n-C12-n-C40, unresolved complex mixture, resolved peaks) and aromatic hydrocarbons (46 PAH) were investigated in suspended particulate matter (SPM) sampled over eleven months in six of the major rivers and two channels of the Guanabara Bay Basin. PAH flow rates of the most contaminated rivers, the contribution to the PAH sediment load of the receiving bay, and the main sources of hydrocarbons were determined. PAH (38) ranged from 28 ng L(-1) to 11,514 ng L(-1). Hydrocarbon typology and statistical evaluation demonstrated contribution of distinct sources in different regions and allowed quantification of these contributions. Total flow rate for the five major rivers amounts to 3 t year(-1) and responds for 30% of the total PAH annual input into the northern area of the Guanabara Bay. For the first time PAH mass deposited in the bay sediments has been estimated and shall serve as base for decision making and source abatement. PMID:25434473

  4. Denudation rates determined from the accumulation of in situ-produced 10Be in the luquillo experimental forest, Puerto Rico

    USGS Publications Warehouse

    Brown, Erik Thorson; Stallard, Robert F.; Larsen, Matthew C.; Raisbeck, Grant M.; Yiou, Francoise

    1995-01-01

    We present a simple method for estimation of long-term mean denudation rates using in situ-produced cosmogenic 10Be in fluvial sediments. Procedures are discussed to account for the effects of soil bioturbation, mass wasting and attenuation of cosmic rays by biomass and by local topography. Our analyses of 10Be in quartz from bedrock outcrops, soils, mass-wasting sites and riverine sediment from the Icacos River basin in the Luquillo Experimental Forest, Puerto Rico, are used to characterize denudation for major landform elements in that basin. The 10Be concentration of a discharge-weighted average of size classes of river sediment corresponds to a long-term average denudation of ≈ 43 m Ma −1, consistent with mass balance results. 

  5. Myotubes from Severely Obese Type 2 Diabetic Subjects Accumulate Less Lipids and Show Higher Lipolytic Rate than Myotubes from Severely Obese Non-Diabetic Subjects

    PubMed Central

    Bakke, Siril S.; Kase, Eili T.; Moro, Cedric; Stensrud, Camilla; Damlien, Lisbeth; Ludahl, Marianne O.; Sandbu, Rune; Solheim, Brita Marie; Rustan, Arild C.; Hjelmesæth, Jøran; Thoresen, G. Hege; Aas, Vigdis

    2015-01-01

    About 80% of patients with type 2 diabetes are classified as overweight. However, only about 1/3 of severely obese subjects have type 2 diabetes. This indicates that several severely obese individuals may possess certain characteristics that protect them against type 2 diabetes. We therefore hypothesized that this apparent paradox could be related to fundamental differences in skeletal muscle lipid handling. Energy metabolism and metabolic flexibility were examined in human myotubes derived from severely obese subjects without (BMI 44±7 kg/m2) and with type 2 diabetes (BMI 43±6 kg/m2). Lower insulin sensitivity was observed in myotubes from severely obese subjects with type 2 diabetes. Lipolysis rate was higher, and oleic acid accumulation, triacylglycerol content, and fatty acid adaptability were lower in myotubes from severely obese subjects with type 2 diabetes compared to severely obese non-diabetic subjects. There were no differences in lipid distribution and mRNA and protein expression of the lipases HSL and ATGL, the lipase cofactor CGI-58, or the lipid droplet proteins PLIN2 and PLIN3. Glucose and oleic acid oxidation were also similar in cells from the two groups. In conclusion, myotubes established from severely obese donors with established type 2 diabetes had lower ability for lipid accumulation and higher lipolysis rate than myotubes from severely obese donors without diabetes. This indicates that a difference in intramyocellular lipid turnover might be fundamental in evolving type 2 diabetes. PMID:25790476

  6. Examination of sludge accumulation rates and sludge characteristics for a decentralized community wastewater treatment systems with individual primary clarifier tanks located in Wardsville (Ontario, Canada).

    PubMed

    Lossing, Heather; Champagne, Pascale; McLellan, P James

    2010-01-01

    In conventional septic systems, settling and partial treatment via anaerobic digestion occurs in the septic tank. One of the byproducts of solids separation in the septic tank is a semi-liquid material known as septage, which must be periodically pumped out. Septage includes the liquid portion within the tank, as well as the sludge that settles at the bottom of the tank and the scum that floats to the surface of the liquid layer. A number of factors can influence septage characteristics, as well as the sludge and scum accumulation rates within the tank. This paper presents the results of a 2007 field sampling study conducted in Wardsville (Ontario, Canada). The field study examined 29 individual residential two-chamber septic tanks in a community serviced by a decentralized wastewater treatment system in operation for approximately 7 years without septage removal. The field investigation provided a comprehensive data set that allowed for statistical analysis of the data to assess the more critical factors influencing solids accumulation rates within each of the clarifier chambers. With this data, a number of predictive models were developed using water usage data for each residence as an explanatory variable. PMID:21123926

  7. Intracellular accumulation of AMP as a cause for the decline in rate of ethanol production by Saccharomyces cerevisiae during batch fermentation

    SciTech Connect

    Dombek, K.M.; Ingram, L.O.

    1988-01-01

    A general hypothesis is presented for the decline in the rate of ethanol production (per unit of cell protein) during batch fermentation. Inhibition of ethanol production is proposed to result from the intracellular accumulation of AMP during the transition from growth to the stationary phase. AMP acts as a competitive inhibitor of hexokinase with respect to ATP. When assayed in vitro in the presence of ATP and AMP concentration equivalent to those within cells at different stages of fermentation, hexokinase activity declined in parallel with the in vivo decline in the rate of ethanol production. The coupling of glycolytic flux and fermentation to cell growth via degradation products of RNA may be of evolutionary advantage for Saccharomyces cerevisiae. Such a coupling would reduce the exposure of nongrowing cells to potentially harmful concentrations of waste products from metabolism and would conserve nutrients for future growth under more favorable conditions.

  8. Time scales of erosion and deposition recorded in the residual south polar cap of Mars

    NASA Astrophysics Data System (ADS)

    Thomas, P. C.; Calvin, W. M.; Gierasch, P.; Haberle, R.; James, P. B.; Sholes, S.

    2013-08-01

    The residual south polar cap (RSPC) of Mars has been subject to competing processes during recent Mars years of high resolution image coverage: continuing erosion of scarps while the maximum extent grows as well as shrinks (Piqueux, S., Christensen, P.R. [2008]. J. Geophys. Res. (Planets) 113, 2006; James, P.B., Thomas, P.C., Malin, M.C. [2010]. Icarus 208, 82-85). Additionally, the cap has a variety of morphologies and erosion (scarp retreat) rates (Thomas, P.C., James, P.B., Calvin, W.M., Haberle, R., Malin, M.C. [2009]. Icarus 203, 352-375). Do these different forms and competing processes indicate an aging and possibly disappearing cap, a growing cap, or a fluctuating cap, and is it possible to infer the timescales of the processes acting on the RSPC? Here we use the latest imaging data from Mars' southern summer in Mars year 30 (Calendar year 2011) to evaluate erosion rates of forms in the RSPC over 6 Mars years, and to map more fully features whose sizes can be used to predict deposit ages. Data through Mars year 30 show that scarp retreat rates in the RSPC have remained approximately the same for at least 6 Mars years and that these rates of erosion also apply approximately over the past 21 Mars years. The thicker units appear to have undergone changes in the locations of new pit formation about 30-50 Mars years ago. The thinner units have some areas that are possibly 80 Mars years old, with some younger materials having accumulated more than a meter in thickness since Mars year 9. Formation of the thicker units probably required over 100 Mars years. The upper surfaces of most areas, especially the thicker units, show little change at the few-cm level over the last 2 Mars years. This observation suggests that current conditions are substantially different from those when the thicker units were deposited. A prime characteristic of the evolution of the RSPC is that some changes are progressive, such as those involving scarp retreat, while others, such as the

  9. Experimental investigation of anaerobic nitrogen fixation rates with varying pressure, temperature and metal concentration with application to the atmospheric evolution of early Earth and Mars.

    NASA Astrophysics Data System (ADS)

    Gupta, Prateek

    2012-07-01

    The atmosphere of the early Earth is thought to have been significantly different than the modern composition of 21% O2 and 78% N2, yet the planet has been clearly established as hosting microbial life as far back as 3.8 billion years ago. As such, constraining the atmospheric composition of the early Earth is fundamental to establishing a database of habitable atmospheric compositions. A similar argument can be made for the planet Mars, where nitrates have been hypothesized to exist in the subsurface. During the early period on Mars when liquid water was likely more abundant, life may have developed to take advantage of available nitrates and a biologically-driven Martian nitrogen cycle could have evolved. Early Earth atmospheric composition has been investigated numerically, but only recently has the common assumption of a pN2 different than modern been investigated. Nonetheless, these latest attempts fail to take into account a key atmospheric parameter: life. On modern Earth, nitrogen is cycled vigorously by biology. The nitrogen cycle likely operated on the early Earth, but probably differed in the metabolic processes responsible, dominantly due to the lack of abundant oxygen which stabilizes oxidized forms of N that drive de-nitrification today. Recent advances in evolutionary genomics suggest that microbial pathways that are relatively uncommon today (i.e. vanadium and iron-based nitrogen fixation) probably played important roles in the early N cycle. We quantitatively investigate in the laboratory the effects of variable pressure, temperature and metal concentration on the rates of anoxic nitrogen fixation, as possible inputs for future models investigating atmospheric evolution, and better understand the evolution of the nitrogen cycle on Earth. A common anaerobic methanogenic archaeal species with i) a fully sequenced genome, ii) all three nitrogenases (molybdenum, vanadium and iron-based) and iii) the ability to be genetically manipulated will be used as

  10. Rippled Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    29 July 2004 Hundreds of large ripples or small dunes cover the landscape in the Terra Tyrrhena region of Mars in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. The winds responsible for these dunes blew from the north-northwest (top/upper left). This scene is located near 8.8oS, 252.8oW, and covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the terrain from the left.

  11. Accumulate-Repeat-Accumulate-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Samuel; Thorpe, Jeremy

    2007-01-01

    Accumulate-repeat-accumulate-accumulate (ARAA) codes have been proposed, inspired by the recently proposed accumulate-repeat-accumulate (ARA) codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. ARAA codes can be regarded as serial turbolike codes or as a subclass of low-density parity-check (LDPC) codes, and, like ARA codes they have projected graph or protograph representations; these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The objective in proposing ARAA codes as a subclass of ARA codes was to enhance the error-floor performance of ARA codes while maintaining simple encoding structures and low maximum variable node degree.

  12. Mars Underground News.

    NASA Astrophysics Data System (ADS)

    Edgett, K.

    Contents: Next entry to Mars (Mars Pathfinder and the microrover Sojourner). Hello, Mars, we're back! Mars Global Surveyor update. The Mars program - 2001 and beyond. Schedule of missions to Mars (as of June 11, 1997). Mars on the Web.

  13. Mars Bowling

    NASA Video Gallery

    More than 140 fourth and fifth graders from Kraft Elementary School in Hampton learned how Newton's laws of motion apply to bowling and the Mars Curiosity rover during "The Science of Bowling," an ...

  14. Mars Pathfinder

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    First of NASA's Discovery missions. Launched in December 1996 and arrived at Mars on 4 July 1997. Mainly intended as a technology demonstration mission. Used airbags to cushion the landing on Mars. The Carl Sagan Memorial station returned images of an ancient flood plain in Ares Vallis. The 10 kg Sojourner rover used an x-ray spectrometer to study the composition of rocks and travelled about 100 ...

  15. Mars resources

    NASA Technical Reports Server (NTRS)

    Duke, Michael B.

    1986-01-01

    The most important resources of Mars for the early exploration phase will be oxygen and water, derived from the Martian atmosphere and regolith, which will be used for propellant and life support. Rocks and soils may be used in unprocessed form as shielding materials for habitats, or in minimally processed form to expand habitable living and work space. Resources necessary to conduct manufacturing and agricultural projects are potentially available, but will await advanced stages of Mars habitation before they are utilized.

  16. Exploring Mars

    NASA Astrophysics Data System (ADS)

    Breuil, Stéphanie

    2016-04-01

    Mars is our neighbour planet and has always fascinated humans as it has been seen as a potential abode for life. Knowledge about Mars is huge and was constructed step by step through numerous missions. It could be difficult to describe these missions, the associated technology, the results, the questions they raise, that's why an activity is proposed, that directly interests students. Their production is presented in the poster. Step 1: The main Mars feature and the first Mars explorations using telescope are presented to students. It should be really interesting to present "Mars Canals" from Percival Lowell as it should also warn students against flawed interpretation. Moreover, this study has raised the big question about extra-terrestrial life on Mars for the first time. Using Google Mars is then a good way to show the huge knowledge we have on the planet and to introduce modern missions. Step 2: Students have to choose and describe one of the Mars mission from ESA and NASA. They should work in pairs. Web sites from ESA and NASA are available and the teacher makes sure the main missions will be studied. Step 3: Students have to collect different pieces of information about the mission - When? Which technology? What were the main results? What type of questions does it raise? They prepare an oral presentation in the form they want (role play, academic presentation, using a poster, PowerPoint). They also have to produce playing cards about the mission that could be put on a timeline. Step 4: As a conclusion, the different cards concerning different missions are mixed. Groups of students receive cards and they have to put them on a timeline as fast as possible. It is also possible to play the game "timeline".

  17. Role of heat accumulation in the multi-shot damage of silicon irradiated with femtosecond XUV pulses at a 1 MHz repetition rate.

    PubMed

    Sobierajski, Ryszard; Jacyna, Iwanna; Dłużewski, Piotr; Klepka, Marcin T; Klinger, Dorota; Pełka, Jerzy B; Burian, Tomáš; Hájková, Věra; Juha, Libor; Saksl, Karel; Vozda, Vojtěch; Makhotkin, Igor; Louis, Eric; Faatz, Bart; Tiedtke, Kai; Toleikis, Sven; Enkisch, Hartmut; Hermann, Martin; Strobel, Sebastian; Loch, Rolf A; Chalupsky, Jaromir

    2016-07-11

    The role played by heat accumulation in multi-shot damage of silicon was studied. Bulk silicon samples were exposed to intense XUV monochromatic radiation of a 13.5 nm wavelength in a series of 400 femtosecond pulses, repeated with a 1 MHz rate (pulse trains) at the FLASH facility in Hamburg. The observed surface morphological and structural modifications are formed as a result of sample surface melting. Modifications are threshold dependent on the mean fluence of the incident pulse train, with all threshold values in the range of approximately 36-40 mJ/cm2. Experimental data is supported by a theoretical model described by the heat diffusion equation. The threshold for reaching the melting temperature (45 mJ/cm2) and liquid state (54 mJ/cm2), estimated from this model, is in accordance with experimental values within measurement error. The model indicates a significant role of heat accumulation in surface modification processes. PMID:27410821

  18. Carbonic anhydrase activity and photosynthetic rate in the tree species Paulownia tomentosa Steud. Effect of dimethylsulfoxide treatment and zinc accumulation in leaves.

    PubMed

    Lazova, Galia N; Naidenova, Tsveta; Velinova, Katya

    2004-03-01

    The enzyme carbonic anhydrase (CA) (EC 4.2.1.1) catalyzes the reversible conversion of CO2 to HCO3- and has been shown to be involved in photosynthesis. The enzyme has been shown in animals, plants, eubacteria and viruses, but similar reports on the evidence for CA activity in tree plants does not be appear to be available. In the preliminary analyses of the work, the CA activity in leaf extracts from the tree species Paulownia tomentosa Steud. (introduced in Bulgaria) is described. A connection between CA activity and the rate of photosynthetic CO2 fixation is shown. In the second portion of the work, the effect of 10(-4) mol/L and 10(-2) mol/L dimethylsulfoxide (DMSO) on the zinc accumulation in leaves is demonstrated. It is suggested that CA activity is an indicator of the level of physiologically active zinc in leaves of P. tomentosa Steud. A connection between the process of zinc accumulation in leaves and the activity of the enzymes CA and glycolate oxidase (GO) (EC 1.1.3.1) is established. PMID:15077628

  19. Mars Exploration Program and Mars Technology Program

    NASA Technical Reports Server (NTRS)

    Whetsel, Charles W.

    2002-01-01

    The Mars Exploration Program and constituent Mars Technology Program are described. Current, ongoing and future NASA-led missions are presented, including discussions of scientific accomplishments and objectives as well as technology validations accomplished and technological enablers for future missions. The missions summarized include (in order of actual or planned launch): Mars Global Surveyor, Mars Pathfinder, 2001 Mars Odyssey, Mars Reconnaissance Orbiter, Mars 'Smart' Lander, Mars Scouts, Mars Sample Return. Key technology areas hdiscussed include: Navigation, Entry, Descent and Landing, Science and Surface Operations, Orbital Transport and Sample Return Technologies.

  20. The influence of structural features of marine humic substances on the accumulation rates of cadmium by a blue mussel Mytilus edulis

    SciTech Connect

    Pempkowiak, J.; Kozuch, J. ); Southon, T. )

    1994-01-01

    Laboratory experiments revealed that both concentration and origin of humic substances (HS) influence the accumulation rates of cadmium by the blue mussel Mytilus edulis. In the concentration of humic substances typical of seawater, the increase is about 60% and 100%, respectively, for aquatic and sedimentary humic substances. The phenomenon was attributed to the stimulation of cadmium uptake due to complexing properties of the substances toward cadmium. Complexing capacity of sedimentary humic substances was found to be 0.57 [mu]g/mg HS, that of aquatic substances 0.41 [mu]g/mg HS. Cross Polarization Magic Angle Spinning (CP/MAS) [sup 13]C NMR of the investigated humic substances revealed differences in the spectra at about 175, 100, 55 and 32 ppm. This was attributed to the varying content of oxygen containing functional groups involved in formation of complexes with metal ions. 8 refs., 4 figs., 3 tabs.

  1. Hydrophobic Surfaces of Spacecraft Components Enhance the Aggregation of Microorganisms and May Lead to Higher Survival Rates of Bacteria on Mars Landers

    NASA Technical Reports Server (NTRS)

    Schuerger, Andrew C.; Kern, Roger G.

    2004-01-01

    In order to minimize the forward contamination of Mars, spacecraft are assembled under cleanroom conditions that require several procedures to clean and sterilize components. Surface characteristics of spacecraft materials may contribute to microbial survival on the surface of Mars by protecting spores from sterilizing agents, including UV irradiation. The primary objective of this study was to evaluate the effects of surface characteristics of several spacecraft materials on the survival of Bacillus subtilis spores under simulated Martian conditions.

  2. Biomass accumulation rates of Amazonian secondary forest and biomass of old-growth forests from Landsat time series and the Geoscience Laser Altimeter System

    NASA Astrophysics Data System (ADS)

    Helmer, Eileen H.; Lefsky, Michael A.; Roberts, Dar A.

    2009-01-01

    We estimate the age of humid lowland tropical forests in Rondônia, Brazil, from a somewhat densely spaced time series of Landsat images (1975-2003) with an automated procedure, the Threshold Age Mapping Algorithm (TAMA), first described here. We then estimate a landscape-level rate of aboveground woody biomass accumulation of secondary forest by combining forest age mapping with biomass estimates from the Geoscience Laser Altimeter System (GLAS). Though highly variable, the estimated average biomass accumulation rate of 8.4 Mg ha-1 yr-1 agrees well with ground-based studies for young secondary forests in the region. In isolating the lowland forests, we map land cover and general types of old-growth forests with decision tree classification of Landsat imagery and elevation data. We then estimate aboveground live biomass for seven classes of old-growth forest. TAMA is simple, fast, and self-calibrating. By not using between-date band or index differences or trends, it requires neither image normalization nor atmospheric correction. In addition, it uses an approach to map forest cover for the self-calibrations that is novel to forest mapping with satellite imagery; it maps humid secondary forest that is difficult to distinguish from old-growth forest in single-date imagery; it does not assume that forest age equals time since disturbance; and it incorporates Landsat Multispectral Scanner imagery. Variations on the work that we present here can be applied to other forested landscapes. Applications that use image time series will be helped by the free distribution of coregistered Landsat imagery, which began in December 2008, and of the Ice Cloud and land Elevation Satellite Vegetation Product, which simplifies the use of GLAS data. Finally, we demonstrate here for the first time how the optical imagery of fine spatial resolution that is viewable on Google Earth provides a new source of reference data for remote sensing applications related to land cover.

  3. Biogeochemical cycling in an organic-rich coastal marine basin. 9. Sources and accumulation rates of vascular plant-derived organic material

    SciTech Connect

    Haddad, R.I.; Martens, C.S. )

    1987-11-01

    The sources, degradation and burial of vascular plant debris deposited over the past several decades in the lagoonal sediments of Cape Lookout Bight, North Carolina, are quantified using alkaline cupric oxide lignin oxidation product (LOP) analysis. Non-woody angiosperms, accounting for 92 {plus minus} 32% of the recognizable sedimentary vascular plant debris, are calculated to contribute 23 {plus minus} 17% of the total organic carbon buried over the past decade. When combined with a previously established sedimentary organic carbon budget for this site a vascular plant derived carbon burial rate of 26 {plus minus}20 mole C m{sup {minus}2} yr{sup {minus}1} is calculated for this same time interval. The refractory nature and invariant depth distributions of the lignin oxidation products (LOP), when coupled with evidence for constant degradation rates of metabolizable materials, indicate that sediment accumulation at this site has been a steady state process with respect to source and burial of organic carbon since its conversion from an inner-continental shelf to a lagoonal environment during the late 1960's. Thus systematic down-core decreases in labile organic matter result from early diagenetic processes rather than input rate variations.

  4. Autonomous Aerobraking at Mars

    NASA Technical Reports Server (NTRS)

    Hanna, Jill L.; Tolson, Robert; Cianciolo, Alicia Dwyer; Dec, John

    2002-01-01

    Aerobraking has become a proven approach for orbital missions at Mars. A launch of a 1000 kg class spacecraft on a Delta class booster saves 90% of the post-MOI fuel otherwise required to circularize the orbit. In 1997, Mars Global Surveyor demonstrated the feasibility and Mars 2001 Odyssey completed a nearly trouble free aerobraking phase in January 2002. In 2006, Mars Reconnaissance Orbiter will also utilize aerobraking. From the flight operations standpoint, however, aerobraking is labor intensive and high risk due to the large density variability in the Mars thermosphere. The maximum rate of aerobraking is typically limited by the maximum allowable temperature of the solar array which is the primary drag surface. Prior missions have used a surrogate variable, usually maximum free stream heat flux, as a basis for performing periapsis altitude corridor control maneuvers. This paper provides an adaptive sequential method for operationally relating measured temperatures to heat flux profile characteristics and performing maneuvers based directly on measured temperatures and atmospheric properties derived from the heat flux profiles. Simulations of autonomous aerobraking are performed using Odyssey mission data.

  5. Mars brine formation experiment

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Bullock, Mark A.; Stoker, Carol R.

    1992-01-01

    Evaporites, particularly carbonates, nitrates, and sulfates, may be major sinks of volatiles scavenged from the martian atmosphere. Mars is thought to have once had a denser, warmer atmosphere that permitted the presence of liquid surface water. The conversion of atmospheric CO2 into carbonate is hypothesized to have degraded the martian climate to its present state of a generally subfreezing, desiccated desert. The rate for such a conversion under martian conditions is poorly known, so the time scale of climate degradation by this process cannot be easily evaluated. If some models are correct, carbonate formation may have been fast at geological time scales. The experiments of Booth and Kieffer also imply fast (10(exp 6) - 10(exp 7) yr) removal of the missing CO2 inventory, estimated to be 1 - 5 bar, by means of carbonate formation. The timing of formation of many of the fluvial features observed on Mars is, in large part, dependent on when and how fast the atmosphere changed. A knowledge of the rate at which carbonates and nitrates formed is also essential for assessing the probability that life, or its chemical precursors, could have developed on Mars. No previous experiments have quantitatively evaluated the rate of solution for a suite of mobile anions and cations from unaltered minerals and atmospheric gases into liquid water under Mars-like conditions. Such experiments are the focus of this task.

  6. Surface characteristics of spacecraft components affect the aggregation of microorganisms and may lead to different survival rates of bacteria on Mars landers

    NASA Technical Reports Server (NTRS)

    Schuerger, Andrew C.; Richards, Jeffrey T.; Hintze, Paul E.; Kern, Roger G.

    2005-01-01

    Layers of dormant endospores of Bacillus subtilis HA101 were applied to eight different spacecraft materials and exposed to martian conditions of low pressure (8.5 mbar), low temperature (-10 degrees C), and high CO(2) gas composition and irradiated with a Mars-normal ultraviolet (UV-visible- near-infrared spectrum. Bacterial layers were exposed to either 1 min or 1 h of Mars-normal UV irradiation, which simulated clear-sky conditions on equatorial Mars (0.1 tau). When exposed to 1 min of Mars UV irradiation, the numbers of viable endospores of B. subtilis were reduced three to four orders of magnitude for two brands of aluminum (Al), stainless steel, chemfilm-treated Al, clear-anodized Al, and black-anodized Al coupons. In contrast, bacterial survival was reduced only one to two orders of magnitude for endospores on the non-metal materials astroquartz and graphite composite when bacterial endospores were exposed to 1 min of Mars UV irradiation. When bacterial monolayers were exposed to 1 h of Mars UV irradiation, no viable bacteria were recovered from the six metal coupons listed above. In contrast, bacterial survival was reduced only two to three orders of magnitude for spore layers on astroquartz and graphite composite exposed to 1 h of Mars UV irradiation. Scanning electron microscopy images of the bacterial monolayers on all eight spacecraft materials revealed that endospores of B. subtilis formed large aggregates of multilayered spores on astroquartz and graphite composite, but not on the other six spacecraft materials. It is likely that the formation of multilayered aggregates of endospores on astroquartz and graphite composite is responsible for the enhanced survival of bacterial cells on these materials.

  7. Surface Characteristics of Spacecraft Components Affect the Aggregation of Microorganisms and May Lead to Different Survival Rates of Bacteria on Mars Landers

    NASA Astrophysics Data System (ADS)

    Schuerger, Andrew W.; Richards, Jeffrey T.; Hintze, Paul E.; Kern, Roger G.

    2005-08-01

    Layers of dormant endospores of Bacillus subtilis HA101 were applied to eight different spacecraft materials and exposed to martian conditions of low pressure (8.5 mbar), low temperature (-10°C), and high CO2 gas composition and irradiated with a Mars-normal ultraviolet (UV-visible- near-infrared spectrum. Bacterial layers were exposed to either 1 min or 1 h of Mars-normal UV irradiation, which simulated clear-sky conditions on equatorial Mars (0.1 tau). When exposed to 1 min of Mars UV irradiation, the numbers of viable endospores of B. subtilis were reduced three to four orders of magnitude for two brands of aluminum (Al), stainless steel, chemfilm-treated Al, clear-anodized Al, and black-anodized Al coupons. In contrast, bacterial survival was reduced only one to two orders of magnitude for endospores on the non-metal materials astroquartz and graphite composite when bacterial endospores were exposed to 1 min of Mars UV irradiation. When bacterial monolayers were exposed to 1 h of Mars UV irradiation, no viable bacteria were recovered from the six metal coupons listed above. In contrast, bacterial survival was reduced only two to three orders of magnitude for spore layers on astroquartz and graphite composite exposed to 1 h of Mars UV irradiation. Scanning electron microscopy images of the bacterial monolayers on all eight spacecraft materials revealed that endospores of B. subtilis formed large aggregates of multilayered spores on astroquartz and graphite composite, but not on the other six spacecraft materials. It is likely that the formation of multilayered aggregates of endospores on astroquartz and graphite composite is responsible for the enhanced survival of bacterial cells on these materials.

  8. Aerothermodynamics of manned Mars missions

    NASA Technical Reports Server (NTRS)

    Park, Chul; Davies, Carol B.

    1989-01-01

    The aerothermodynamic problems associated with the aerobraking of the spacecraft proposed for the manned Mars mission are studied. The propulsive Delta V necessary at departure from earth and Mars and the velocities of the atmospheric entries into the two planets are deduced. It is shown that the propulsive Delta V can be reduced by increasing the entry velocities and that entry velocities up to about 15 km/sec are appropriate at both earth and Mars. L/D values of 0.8 and 2.0 are found to be necessary at earth and Mars, respectively. Density, pressure, and stagnation-point convective-heat-transfer rates are calculated for the typical aerobraking flights. Assuming the shock layer flow to be in equilibrium, the stagnation-point radiative-heat-transfer rates are calculated to be larger than the convective-heat-transfer rates. The possible impact of ablation, turbulence, and nonequilibrium are discussed.

  9. New constraints on Mars rotation determined from radiometric tracking of the Opportunity Mars Exploration Rover

    NASA Astrophysics Data System (ADS)

    Kuchynka, Petr; Folkner, William M.; Konopliv, Alex S.; Parker, Timothy J.; Park, Ryan S.; Le Maistre, Sebastien; Dehant, Veronique

    2014-02-01

    The Opportunity Mars Exploration Rover remained stationary between January and May 2012 in order to conserve solar energy for running its survival heaters during martian winter. While stationary, extra Doppler tracking was performed in order to allow an improved estimate of the martian precession rate. In this study, we determine Mars rotation by combining the new Opportunity tracking data with historic tracking data from the Viking and Pathfinder landers and tracking data from Mars orbiters (Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter). The estimated rotation parameters are stable in cross-validation tests and compare well with previously published values. In particular, the Mars precession rate is estimated to be -7606.1 ± 3.5 mas/yr. A representation of Mars rotation as a series expansion based on the determined rotation parameters is provided.

  10. Long-term reliability of single-crystal silicon thin films: the influence of environment on the fatigue damage accumulation rate

    NASA Astrophysics Data System (ADS)

    Pierron, Olivier N., II; Muhlstein, Christopher L.

    2004-12-01

    Single-crystal silicon thin films were forced to resonate at high frequency (~40 kHz) in different environments to study the long-term durability of this structural material used in microelectromechanical (MEMS) devices. The fatigue characterization structure consists of a notched cantilever beam attached to a plate shaped mass and is actuated at resonance, creating fully reversed, constant amplitude, sinusoidal stresses at the notch root. The dynamic behavior of the resonating structure has been meticulously quantified to allow accurate stress measurements from the knowledge of the driving voltage amplitude and the calculation of the quality factors in air and vacuum. In addition, the change in resonant frequency is periodically monitored for long-life specimens. Fatigue failure was observed for specimens tested in humid air and medium vacuum. In air, the stress-life (S-N) curve confirms the unique fatigue behavior already attributed to silicon thin films. In vacuum, the strength of the specimens appears to increase, and fatigue failure is delayed. Fracture surface examination reveals distinct features on the fracture surfaces of long-life fatigued specimens, not found in quasistatic failure, that are clear indications of initiation regions. The decrease rate in resonant frequency during cycling is demonstrated to be related to damage accumulation rate, and is strongly sensitive to both stress amplitude and humidity. The different currently proposed mechanisms are discussed in light of this new set of experimental evidence.

  11. Long-term reliability of single-crystal silicon thin films: the influence of environment on the fatigue damage accumulation rate

    NASA Astrophysics Data System (ADS)

    Pierron, Olivier N.; Muhlstein, Christopher L.

    2005-01-01

    Single-crystal silicon thin films were forced to resonate at high frequency (~40 kHz) in different environments to study the long-term durability of this structural material used in microelectromechanical (MEMS) devices. The fatigue characterization structure consists of a notched cantilever beam attached to a plate shaped mass and is actuated at resonance, creating fully reversed, constant amplitude, sinusoidal stresses at the notch root. The dynamic behavior of the resonating structure has been meticulously quantified to allow accurate stress measurements from the knowledge of the driving voltage amplitude and the calculation of the quality factors in air and vacuum. In addition, the change in resonant frequency is periodically monitored for long-life specimens. Fatigue failure was observed for specimens tested in humid air and medium vacuum. In air, the stress-life (S-N) curve confirms the unique fatigue behavior already attributed to silicon thin films. In vacuum, the strength of the specimens appears to increase, and fatigue failure is delayed. Fracture surface examination reveals distinct features on the fracture surfaces of long-life fatigued specimens, not found in quasistatic failure, that are clear indications of initiation regions. The decrease rate in resonant frequency during cycling is demonstrated to be related to damage accumulation rate, and is strongly sensitive to both stress amplitude and humidity. The different currently proposed mechanisms are discussed in light of this new set of experimental evidence.

  12. Late Quaternary sediment-accumulation rates within the inner basins of the California Continental Borderland in support of geologic hazard evaluation

    USGS Publications Warehouse

    Normark, W.R.; McGann, M.; Sliter, R.W.

    2009-01-01

    An evaluation of the geologic hazards of the inner California Borderland requires determination of the timing for faulting and mass-movement episodes during the Holocene. Our effort focused on basin slopes and turbidite systems on the basin floors for the area between Santa Barbara and San Diego, California. Dating condensed sections on slopes adjacent to fault zones provides better control on fault history where high-resolution, seismic-reflection data can be used to correlate sediment between the core site and the fault zones. This study reports and interprets 147 radiocarbon dates from 43 U.S. Geological Survey piston cores as well as 11 dates from Ocean Drilling Program Site 1015 on the floor of Santa Monica Basin. One hundred nineteen dates from 39 of the piston cores have not previously been published. Core locations were selected for hazard evaluation, but despite the nonuniform distribution of sample locations, the dates obtained for the late Quaternary deposits are useful for documenting changes in sediment-accumulation rates during the past 30 ka. Cores from basins receiving substantial sediment from rivers, i.e., Santa Monica Basin and the Gulf of Santa Catalina, show a decrease in sediment supply during the middle Holocene, but during the late Holocene after sea level had reached the current highstand condition, rates then increased partly in response to an increase in El Ni??o-Southern Oscillation events during the past 3.5 ka. ?? 2009 The Geological Society of America.

  13. Austere Human Missions to Mars

    NASA Technical Reports Server (NTRS)

    Price, Hoppy; Hawkins, Alisa M.; Tadcliffe, Torrey O.

    2009-01-01

    preposition a habitat, supplies, and exploration equipment. The next opportunity, two years later, would send to Mars orbit 1) a lander with a Mars Ascent Vehicle (MAV) and 2) a crewed Mars Transit Habitat with an Orion CEV for Earth return. The following opportunity, two years after the first crew, would go back to cargo-only launches. This alternation of cargo and crew opportunities results in a sustainable launch rate of six Ares V launches every two years. It is notable that four of the six launches per Mars opportunity are identical, build-to-print, Tran-Mars Injection stages. This type of production rate could lend itself well to a COTStype service provider, and would make it feasible to have a live spare in place in the event of a single launch failure.

  14. The Distribution of Non-Volatile Elements on Mars: Mars Odyssey GRS Results

    NASA Technical Reports Server (NTRS)

    Boynton, W.; Janes, D.; Kerry, K.; Kim, K.; Reedy, R.; Evans, L.; Starr, R.; Drake, D.; Taylor, J.; Waenke, H.

    2004-01-01

    The major scientific objective of the Gamma-Ray Spectrometer (GRS) on the 2001 Mars Odyssey Mission is to determine the distribution of elements in the near-surface of Mars. Mars Odyssey has been in its mapping orbit since February, 2002, and the GRS boom, which removes the instrument from the gamma-ray background of the spacecraft, was erected in June, 2002. In the 580 days since boom erection, we have accumulated 453 days of mapping data. The difference is due mostly to two times when Odyssey went into safe mode and the instrument warmed up forcing us to anneal out radiation damage that manifests itself after warming. Other data losses are due to simple transmitter data gaps and to intense solar particle events. The data from the GRS is statistical in nature. We have a very low count rate and a very low signal-to-noise ratio. With the exception of K, the most easily mapped elements have a signal/noise ratio on the order of 0.1 (0.5 for K) and the counting rates are on the order of 0.3 to 0.7 counts/min (4 cpm for K). In order to map the distribution of an element, we have to divide the total signal from Mars up into many cells that define the map s spatial resolution (unless the statistics are good enough that the intrinsic spatial resolution of the instrument, about 550 km diameter, dominates). The data for several elements have now achieved a statistical precision that permits us to make meaningful maps.

  15. Site selection for Mars exobiology

    NASA Technical Reports Server (NTRS)

    Farmer, J.; Des Marais, D.; Greeley, R.; Landheim, R.; Klein, H.

    1995-01-01

    The selection of sites on Mars that have a high priority for exobiological research is fundamental for planning future exploration. The most immediate need is to identify targets for high resolution orbital imaging during the Mars Observer and Mars '94/'96 missions that can be used to refined site priorities for surface exploration. We present an objective approach to site selection whereby individual sites are selected and scored, based on the presence of key geological features which indicate high priority environments. Prime sites are those that show evidence for the prolonged activity of liquid water and which have sedimentary deposits that are likely to have accumulated in environments favorable for life. High priority areas include fluvio-lacustrine (stream-fed lake systems), springs, and periglacial environments. Sites where mineralization may have occurred in the presence of organisms (e.g. springs) are given high priority in the search for a fossil record on Mars. A systematic review of Viking data for 83 sites in the Mars Landing Site Catalog (MLSC) resulted in the selection of 13 as being of exobiological interest. The descriptions of these sites were expanded to address exobiological concerns. An additional five sites were identified for inclusion in the second edition of the MLSC. We plan to broaden our site selection activities to include a systematic global reconnaissance of Mars using Viking data, and will continue to refine site priorities for exobiological research based on data from future missions in order to define strategies for surface exploration.

  16. Mars 2003

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-402, 25 June 2003

    The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) experiment consists of 3 different cameras: a narrow angle imager that provides the black-and-white high resolution views (up to 1.4 meters per pixel) of Mars, and 2 wide angle cameras, observing in red and blue wavelengths, from which color views of the entire planet are assembled each day. The wide angle cameras provide a daily record of changes in martian weather and surface frost as the seasons progress. MGS MOC has obtained a record of martian weather spanning a little over 2 martian years since it began systematic observations in March 1999.

    The view of Mars shown here was assembled from MOC daily global images obtained on May 12, 2003. At that time, the northern hemisphere was in early autumn, and the southern hemisphere in early spring. At the left/center of this view are the four large Tharsis volcanoes: Olympus Mons, Ascraeus Mons, Pavonis Mons, and Arsia Mons. Stretching across the center of the globe is the 5,000 kilometers (3,000 miles) long Valles Marineris trough system. The seasonal south polar carbon dioxide frost cap is visible at the bottom of this view. A dust storm sweeps across the plains of northern Acidalia at the upper right. North is up, east is right, sunlight illuminates the planet from the left.

  17. Corrigendum to "OSL-based lateral progradation and aeolian sediment accumulation rates for the Apalachicola Barrier Island Complex, North Gulf of Mexico, Florida" [Geomorphology 123 (2010) 330-342

    NASA Astrophysics Data System (ADS)

    Rink, W. J.; López, G. I.

    2015-07-01

    Correction: Sentence in Abstract. The correct version is: Lateral progradation rates of ridge sequences were highly variable within the study area, ranging from 92 to 691 m/100 years, but we did find an agreement between some of our slower ridge accumulation rates and these in other areas of Florida and around the world determined using OSL and 14C dating.

  18. Bird's Eye View of Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This artist's concept shows NASA's future Mars Reconnaissance Orbiter mission over the red planet.

    NASA plans to launch this multipurpose spacecraft in August 2005 to advance our understanding of Mars through detailed observation, to examine potential landing sites for future surface missions and to provide a high-data-rate communications relay for those missions.

    The orbiter's shallow radar experiment, one of six science instruments on board, is designed to probe the internal structure of Mars' polar ice caps, as well as to gather information planet-wide about underground layers of ice, rock and, perhaps, liquid water, which might be accessible from the surface.

  19. Estimated Radiation Dosage on Mars

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This global map of Mars shows the estimated radiation dosages from cosmic rays reaching the surface, a serious health concern for any future human exploration of the planet.

    The estimates are based on cosmic-radiation measurements by the Mars radiation environment experiment, an instrument on NASA's Mars 2000 Odyssey spacecraft, plus information about Mars' surface elevations from the laser altimeter instrument on NASA's Mars Global Surveyor. The areas of Mars expected to have the lowest levels of cosmic radiation are where the elevation is lowest, because those areas have more atmosphere above them to block out some of the radiation. Earth's thick atmosphere shields us from most cosmic radiation, but Mars has a much thinner atmosphere than we have on Earth.

    The colors in the map refer to the estimated annual dose equivalent in rems, a unit of radiation dose. The range is generally from 10 rems(color-coded dark blue) to 20 rems (color coded dark red). Radiation exposure for astronauts on the International Space Station in Earth orbit is typically equivalent to an annualized rate of 20 to 40 rems.

    NASA's Jet Propulsion Laboratory, Pasadena, Calif. manages the 2001 Mars Odyssey and Mars Global Surveyor missions for NASA's Office of Space Science, Washington D.C. The Mars radiation environment experiment was developed by NASA's Johnson Space Center, Houston. Lockheed Martin Astronautics, Denver, is the prime contractor for Odyssey, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  20. Seasonal variation of meteorological variables and recent surface ablation / accumulation rates on Davies Dome and Whisky Glacier, James Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Láska, K.; Nývlt, D.; Engel, Z.; Budík, L.

    2012-04-01

    In this study, surface mass balance data of two glaciers on James Ross Island, Antarctica, and its spatial and temporal variations are evaluated using snow ablation stakes, ground-penetrating radar, and dGPS measurements. The investigated glaciers are located on the Ulu Peninsula, northern part of James Ross Island. Davies Dome is an ice dome, which originates on the surface of a flat volcanic mesa at elevations >400 m a.s.l. and terminates with a single 700 m wide outlet in the Whisky Bay. Davies Dome has an area of ~6.5 km2 and lies in the altitude range of 0-514 m a.s.l. Whisky Glacier is a cold-based land-terminating valley glacier surrounded by an extensive moraine ridges made of debris-covered ice. The glacier has an area of ~2.4 km2 and lies in the altitude range of 215-520 m a.s.l. Within several summer austral summers, extensive field programme were carried out on both glaciers including the operation of two automatic weather stations, field mapping and mass balance measurements. Each station was equipped with albedometer CM7B (Kipp-Zonen, Netherlands), air temperature and humidity sensor EMS33 (EMS, Czech Republic), propeller anemometer 05103 (Young, USA), and snow depth sensors (Judd, USA). In the period 2009-2011, high seasonal and interdiurnal variability of incoming solar radiation and near-surface air temperature was found as a result of changes in the circulation patterns and synoptic-scale weather systems moving in the Circumpolar Trough. High ablation and accumulation rates were recorded mainly in the spring and summer seasons (October-February), while negligible changes were found in winter (May-September). The effects of positive degree-day temperatures on the surface ablation rates were examined using a linear regression model. In this approach, near-surface air temperature maps on the glacier surfaces were derived from digital elevation model according to actual temperature lapse rates. Mass balance investigations started in 2006 on Davies

  1. North polar region of Mars - Imaging results from Viking 2

    NASA Technical Reports Server (NTRS)

    Cutts, J. A.; Blasius, K. R.; Briggs, G. A.; Carr, M. H.; Masursky, H.; Greeley, R.

    1976-01-01

    During October 1976, the Viking 2 orbiter acquired approximately 700 high-resolution images of the north polar region of Mars. These images confirm the existence at the north pole of extensive layered deposits largely covered over with deposits of perennial ice. An unconformity within the layered deposits suggests a complex history of climate change during their time of deposition. A pole-girdling accumulation of dunes composed of very dark materials is revealed by the Viking cameras. The entire region is devoid of fresh impact craters. Rapid rates of erosion or deposition are implied. A scenario for polar geological evolution, involving two types of climate change, is proposed.

  2. Development of a solar-cell dust opacity measurement instrument for Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey; Jenkins, Phillip P.

    1996-01-01

    The atmosphere of Mars has a considerable load of suspended dust. Over time, this dust is deposited out of the atmosphere. The mechanism and the temporal and geographical variation of this deposition are not well characterized. Measurements of settling rates and dust properties are of considerable scientific interest. Atmospheric dust affects the atmospheric solar absorption and thus the heat balance of Mars, as well as serving as nucleation sites for water and CO2 frost. Knowledge of dust properties is of critical interest to design and prediction of the lifetime and power output of solar arrays, and also to design of mechanical mechanisms and radiators. An instrument has been designed and fabricated to measure the dust accumulation during the course of the Mars Pathfinder rover mission. The solar-cell coverglass transmission experiment will measure the change in optical opacity of a transparent coverglass as dust settles on the surface, and a quartz crystal monitor will measure the mass deposited.

  3. Accumulation Rate Variability and Winter Mass Balance Estimates using High Frequency Ground-Penetrating Radar and Snow Pit Stratigraphy on the Juneau Icefield, Alaska

    NASA Astrophysics Data System (ADS)

    Braddock, S. S.; Boucher, A. L.; Sandler, H. C.; McNeil, C.; Campbell, S. W.; Kreutz, K. J.

    2012-12-01

    In July 2012, 200 km of 400 MHz ground-penetrating radar (GPR) profiles were collected across the Juneau Icefield, Alaska. The goal was to determine if spatial accumulation rate variability and winter mass balance estimates could be improved by linking stratigraphic features between yearly-excavated snow pits through GPR. Profiles were collected along the centerline and cross sections of the main branch, northwest, and Southwest branch of the Taku Glacier as well as the Mathes, Llewellyn, and Demorest Glaciers. Over 650 km^2 of area and 1000 m of elevation range were covered during this pilot project linking sixteen snow pits with GPR data across the icefield. The field work was conducted as part of the Juneau Icefield Research Program (JIRP) with hopes of continuing this method in future years if first year results show promise. As an annually operated field research and education program, JIRP creates a unique opportunity to provide significant future contributions to Alaska mass balance records if the program is continued. Signal penetration reached ≤ 25 m with maximum depths reached at higher elevations of the icefield. Conversely, minimal penetration occurred in wetter regions at lower elevations, likely caused by volume scattering from free water within the firn and ice. Ice lenses and the annual layer located in mass balance snow pits correlated well with continuous stratigraphy imaged in GPR profiles suggesting that the lenses are relatively uninterrupted across the icefield and that GPR may be an appropriate tool for extrapolating point mass balance pit depths in this part of Alaska. The Northwest and Southwest Branches of the Taku Glacier show a strong stratigraphic thinning gradient, west to east; the main trunk of the Taku Glacier which originates from the Mathes-Llewellyn ice divide showed a similar thinning from the divide to the ELA. The thinning displayed by all three glacier systems matches a typical gradient from accumulation zone to ELA

  4. Mars habitat

    NASA Technical Reports Server (NTRS)

    Ayers, Dale; Barnes, Timothy; Bryant, Woody; Chowdhury, Parveen; Dillard, Joe; Gardner, Vernadette; Gregory, George; Harmon, Cheryl; Harrell, Brock; Hilton, Sherrill

    1991-01-01

    The objective of this study is to develop a conceptual design for a permanently manned, self-sustaining Martian facility, to accommodate a crew of 20 people. The goal is to incorporate the major functions required for long term habitation in the isolation of a barren planet into a thriving ecosystem. These functions include living, working, service, and medical facilities as well as a green house. The main design task was to focus on the internal layout while investigating the appropriate structure, materials, and construction techniques. The general concept was to create a comfortable, safe living environment for the crew members for a stay of six to twelve months on Mars. Two different concepts were investigated, a modular assembly reusable structure (MARS) designated Lavapolis, and a prefabricated space frame structure called Hexamars. Both models take into account factors such as future expansion, radiation shielding, and ease of assembly.

  5. Unsteady saltation on Mars

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Zheng, Xiaojing

    2015-11-01

    Saltation is an important process on Mars, as it contributes to dust raising, bedform dynamics, and aeolian abrasion. Lander measurements and mesoscale meteorological models suggest that winds in the Martian atmosphere rarely exceed the fluid threshold value that is necessary to aerodynamically initiate saltation, a fact in stark contrast to the existence of dunes and ripples on the planet, many of which are in an active state of migration. In an attempt to reconcile these observations, we perform an unsteady simulation with a simple turbulence model to calculate the saltation transport rate. Sinusoidal wind variations are imposed on the saltation layer. The numerical simulations verify that gusty transport is one of the main manifestations of Martian sediment transport events. A formula for the saltation transport rate is reported, Qm ∼(u∗ -u∗it) p , where u∗ and u∗it are the friction velocity and impact threshold friction velocity. The power p varies in the range of 0.7-1.8 on Mars and ∼1.5 on Earth, depending on the period and amplitude of the gusty inflow wind. Our results show that the law of Martian and terrestrial transport rate are not universal, and hence one should be cautious when trying to extrapolate existing terrestrial results to Mars.

  6. A record of barite accumulation rate for marine export productivity changes in the tropical Indian Ocean during the Mid-Pliocene--Early-Pleistocene transition

    NASA Astrophysics Data System (ADS)

    Zhou, Liping; Ma, Zhongwu; Ding, Xuan

    2016-04-01

    One of the most interesting features in the marine oxygen isotope records is the gradual shift towards heavier 18O from the Mid-Pliocene, which ends with the initiation of Northern Hemisphere glaciation (NHG) around 2.7 Ma. The lack of significant change in sea surface temperature in the tropical Indian Ocean as revealed in the previous studies does not rule out their possible contributions to this dramatic climate change during the Mid-Pliocene transition. Changing circulation systems in the region will control the supply of nutrients for the water masses which in turn determine the marine productivity. In the areas of high productivity, ocean export productivity may potentially provide a mechanism of CO2 draw-down into the deep ocean, through which contributing to the lowering of the global temperature. In this study, we present a record of barite accumulation rate (BAR) for DSDP Site 214 drilled on the Ninetyeast Ridge. Here we use the marine barite, which is formed during the decay of organism in the twilight zone, as a proxy for ocean export productivity. Our results show that the BAR of Site 214 varies between 0.25 and 1.25 mg/cm2/kyr during the period between 4 Ma and 2 Ma. Five intervals of increased BAR from 3.6 Ma to 2.4 Ma are identified with the most distinct peak centred around 3 Ma. The overall pattern does not follow either the oxygen isotope record for the Site or the sea surface temperature and subsurface temperature reconstructed with the Mg/Ca of foraminifera. This suggests that regional changes in ocean circulation and water masses may have played more important role than temperature in controlling the productivity change in the tropical Indian Ocean. The relative higher productivity around 3 Ma may imply a biogenetic process towards the intensification of NHGs.

  7. A revised surface age for the North Polar Layered Deposits of Mars

    NASA Astrophysics Data System (ADS)

    Landis, Margaret E.; Byrne, Shane; Daubar, Ingrid J.; Herkenhoff, Kenneth E.; Dundas, Colin M.

    2016-04-01

    The North Polar Layered Deposits (NPLD) of Mars contain a complex stratigraphy that has been suggested to retain a record of past eccentricity- and obliquity-forced climate changes. The surface accumulation rate in the current climate can be constrained by the crater retention age. We scale NPLD crater diameters to account for icy target strength and compare surface age using a new production function for recent small impacts on Mars to the previously used model of Hartmann (2005). Our results indicate that ice is accumulating in these craters several times faster than previously thought, with a 100 m diameter crater being completely infilled within centuries. Craters appear to have a diameter-dependent lifetime, but the data also permit a complete resurfacing of the NPLD at ~1.5 ka.

  8. NASA Mars Conference

    SciTech Connect

    Reiber, D.B.

    1988-01-01

    Papers about Mars and Mars exploration are presented, covering topics such as Martian history, geology, volcanism, channels, moons, atmosphere, meteorology, water on the planet, and the possibility of life. The unmanned exploration of Mars is discussed, including the Phobos Mission, the Mars Observer, the Mars Aeronomy Observer, the seismic network, Mars sample return missions, and the Mars Ball, an inflatable-sectored-tire rover concept. Issues dealing with manned exploration of Mars are examined, such as the reasons for exploring Mars, mission scenarios, a transportation system for routine visits, technologies for Mars expeditions, the human factors for Mars missions, life support systems, living and working on Mars, and the report of the National Commission on Space.

  9. Motor Brush Testing for Mars and Vacuum

    NASA Technical Reports Server (NTRS)

    Noon, Don E.

    1999-01-01

    Brush motors have been qualified and flown successfully on Mars missions, but upcoming missions require longer life and higher power. A test program was therefore undertaken to identify the best brush material for operation in the Mars atmosphere. Six different brush materials were used in 18 identical motors and operated under various load conditions for a period of four weeks in low-pressure CO2. All motors performed acceptably, with accumulated motor revolutions between 98 and 144 million revolutions, depending on load. A proprietary silver-graphite material from Superior Carbon (SG54-27) appears to be the best choice for long life, but even the stock copper-graphite brushes performed reliably with acceptable wear. The motors from the CO2 test were then cleaned and run in vacuum for 2 weeks. The difference in results was dramatic, with 5 motors failing catastrophically and wear rates increasing by orders of magnitude for the SG54-27 material. Three brush materials survived the test with no failures: SG54-27 with a proprietary Ball Aerospace impregnation, a silver-graphite-molybdenum disulfide material from Superior Carbon (SG59), and a copper sulfide-graphite material also from Superior Carbon (BG91).

  10. Radiation exposure for human Mars exploration.

    PubMed

    Simonsen, L C; Wilson, J W; Kim, M H; Cucinotta, F A

    2000-11-01

    One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human space flight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle events was of great concern. A new challenge appears in deep-space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays since the missions are of long duration, and accumulated exposures can be high. Because cancer induction rates increase behind low to moderate thicknesses of aluminum shielding, according to available biological data on mammalian exposures to galactic cosmic ray-like ions, aluminum shield requirements for a Mars mission may be prohibitively expensive in terms of mission launch costs. Alternative materials for vehicle construction are under investigation to provide lightweight habitat structures with enhanced shielding properties. In the present paper, updated estimates for astronaut exposures on a Mars mission are presented and shielding properties of alternative materials are compared with aluminum. PMID:11045525

  11. Mars @ ASDC

    NASA Astrophysics Data System (ADS)

    Carraro, Francesco

    "Mars @ ASDC" is a project born with the goal of using the new web technologies to assist researches involved in the study of Mars. This project employs Mars map and javascript APIs provided by Google to visualize data acquired by space missions on the planet. So far, visualization of tracks acquired by MARSIS and regions observed by VIRTIS-Rosetta has been implemented. The main reason for the creation of this kind of tool is the difficulty in handling hundreds or thousands of acquisitions, like the ones from MARSIS, and the consequent difficulty in finding observations related to a particular region. This led to the development of a tool which allows to search for acquisitions either by defining the region of interest through a set of geometrical parameters or by manually selecting the region on the map through a few mouse clicks The system allows the visualization of tracks (acquired by MARSIS) or regions (acquired by VIRTIS-Rosetta) which intersect the user defined region. MARSIS tracks can be visualized both in Mercator and polar projections while the regions observed by VIRTIS can presently be visualized only in Mercator projection. The Mercator projection is the standard map provided by Google. The polar projections are provided by NASA and have been developed to be used in combination with APIs provided by Google The whole project has been developed following the "open source" philosophy: the client-side code which handles the functioning of the web page is written in javascript; the server-side code which executes the searches for tracks or regions is written in PHP and the DB which undergoes the system is MySQL.

  12. Mars habitat

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The College of Engineering & Architecture at Prairie View A&M University has been participating in the NASA/USRA Advanced Design Program since 1986. The interdisciplinary nature of the program allowed the involvement of students and faculty throughout the College of Engineering & Architecture for the last five years. The research goal for the 1990-1991 year is to design a human habitat on Mars that can be used as a permanent base for 20 crew members. The research is being conducted by undergraduate students from the Department of Architecture.

  13. Mars Albedo

    NASA Technical Reports Server (NTRS)

    2001-01-01

    These two views of Mars are derived from the MGS Thermal Emission Spectrometer (TES) measurements of global broadband (0.3 - 3.0 microns) visible and near-infrared reflectance, also known as albedo. The range of colors are in dimensionless units. The values are the ratio of the amount of electromagnetic energy reflected by the surface to the amount of energy incident upon it from the sun (larger values are brighter surfaces).

    The TES instrument was built by Santa Barbara Remote Sensing and is operated by Philip R. Christensen, of Arizona State University, Tempe, AZ.

  14. Accumulate Repeat Accumulate Coded Modulation

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative coded modulation scheme called 'Accumulate Repeat Accumulate Coded Modulation' (ARA coded modulation). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes that are combined with high level modulation. Thus at the decoder belief propagation can be used for iterative decoding of ARA coded modulation on a graph, provided a demapper transforms the received in-phase and quadrature samples to reliability of the bits.

  15. Mars Exploration Program and Mars Technology Program

    NASA Technical Reports Server (NTRS)

    Whetsel, C. W.

    2002-01-01

    The Mars Exploration Program and constituent Mars Technology Program are described. Current ongoing and future NASA-led missions are presented, including discussions of scientific accomplishments and objectives as well as technology validations accomplished and technological enablers for future missions.

  16. Climate Change on Mars

    NASA Technical Reports Server (NTRS)

    Haberle, R. M.; Cuzzi, Jeffrey N. (Technical Monitor)

    1994-01-01

    Today, Mars is cold and dry. With a 7 mbar mean surface pressure, its thin predominantly CO2 atmosphere is not capable of raising global mean surface temperatures significantly above its 217K effective radiating temperature, and the amount of water vapor in the atmosphere is equivalent to a global ocean only 10 microns deep. Has Mars always been in such a deep freeze? There are several lines of evidence that suggest it has not. First, there are the valley networks which are found throughout the heavily cratered terrains. These features are old (3.8 Gyr) and appear to require liquid water to form. A warm climate early in Mars' history has often been invoked to explain them, but the precise conditions required to achieve this have yet to be determined. Second, some of the features seen in orbiter images of the surface have been interpreted in terms of glacial activity associated with an active hydrological cycle some several billion years ago. This interpretation is controversial as it requires the release of enormous quantities of ground water and enough greenhouse warming to raise temperatures to the melting point. Finally, there are the layered terrains that characterize both polar regions. These terrains are geologically young (10 Myr) and are believed to have formed by the slow and steady deposition of dust and water ice from the atmosphere. The individual layers result from the modulation of the deposition rate which is driven by changes in Mars' orbital parameters. The ongoing research into each of these areas of Martian climate change will be reviewed, and similarities to the Earth's climate system will be noted.

  17. Mars Exploration Rovers: 4 Years on Mars

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    2008-01-01

    This January, the Mars Exploration Rovers "Spirit" and "Opportunity" are starting their fifth year of exploring the surface of Mars, well over ten times their nominal 90-day design lifetime. This lecture discusses the Mars Exploration Rovers, presents the current mission status for the extended mission, some of the most results from the mission and how it is affecting our current view of Mars, and briefly presents the plans for the coming NASA missions to the surface of Mars and concepts for exploration with robots and humans into the next decade, and beyond.

  18. Mars Public Engagement Overview

    NASA Technical Reports Server (NTRS)

    Johnson, Christine

    2009-01-01

    This viewgraph presentation reviews the Mars public engagement goal to understand and protect our home planet, explore the Universe and search for life, and to inspire the next generation of explorers. Teacher workshops, robotics education, Mars student imaging and analysis programs, MARS Student Imaging Project (MSIP), Russian student participation, MARS museum visualization alliance, and commercialization concepts are all addressed in this project.

  19. 100 New Impact Crater Sites Found on Mars

    NASA Astrophysics Data System (ADS)

    Kennedy, M. R.; Malin, M. C.

    2009-12-01

    Recent observations constrain the formation of 100 new impact sites on Mars over the past decade; 19 of these were found using the Mars Global Surveyor Mars Orbiter Camera (MOC), and the other 81 have been identified since 2006 using the Mars Reconnaissance Orbiter Context Camera (CTX). Every 6 meter/pixel CTX image is examined upon receipt and, where they overlap images of 0.3-240 m/pixel scale acquired by the same or other Mars-orbiting spacecraft, we look for features that may have changed. New impact sites are initially identified by the presence of a new dark spot or cluster of dark spots in a CTX image. Such spots may be new impact craters, or result from the effect of impact blasts on the dusty surface. In some (generally rare) cases, the crater is sufficiently large to be resolved in the CTX image. In most cases, however, the crater(s) cannot be seen. These are tentatively designated as “candidate” new impact sites, and the CTX team then creates an opportunity for the MRO spacecraft to point its cameras off-nadir and requests that the High Resolution Imaging Science Experiment (HiRISE) team obtain an image of ~0.3 m/pixel to confirm whether a crater or crater cluster is present. It is clear even from cursory examination that the CTX observations are areographically biased to dusty, higher albedo areas on Mars. All but 3 of the 100 new impact sites occur on surfaces with Lambert albedo values in excess of 23.5%. Our initial study of MOC images greatly benefited from the initial global observations made in one month in 1999, creating a baseline date from which we could start counting new craters. The global coverage by MRO Mars Color Imager is more than a factor of 4 poorer in resolution than the MOC Wide Angle camera and does not offer the opportunity for global analysis. Instead, we must rely on partial global coverage and global coverage that has taken years to accumulate; thus we can only treat impact rates statistically. We subdivide the total data

  20. Mate and Dart: An Instrument Package for Characterizing Solar Energy and Atmospheric Dust on Mars

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Jenkins, Phillip; Scheiman, David; Baraona, Cosmo

    2000-01-01

    The MATE (Mars Array Technology Experiment) and DART (Dust Accumulation and Removal Test) instruments were developed to fly as part of the Mars ISPP Precursor (MIP) experiment on the (now postponed) Mars-2001 Surveyor Lander. MATE characterizes the solar energy reaching the surface of Mars, and measures the performance and degradation of solar cells under Martian conditions. DART characterizes the dust environment of Mars, measures the effect of settled dust on solar arrays, and investigates methods to mitigate power loss due to dust accumulation.

  1. A Martian Telecommunications Network: UHF Relay Support of the Mars Exploration Rovers by the Mars Global Surveyor, Mars Odyssey, and Mars Express Orbiters

    NASA Technical Reports Server (NTRS)

    Edwards, Charles D., Jr.; Barbieri, A.; Brower, E.; Estabrook, P.; Gibbs, R.; Horttor, R.; Ludwinski, J.; Mase, R.; McCarthy, C.; Schmidt, R.; Theisinger, P.; Thorpe, T.; Waggoner, B.

    2004-01-01

    NASA and ESA have established an international network of Mars orbiters, outfitted with relay communications payloads, to support robotic exploration of the red planet. Starting in January, 2004, this network has provided the Mars Exploration Rovers with telecommunications relay services, significantly increasing rover engineering and science data return while enhancing mission robustness and operability. Augmenting the data return capabilities of their X-band direct-to-Earth links, the rovers are equipped with UHF transceivers allowing data to be relayed at high rate to the Mars Global Surveyor (MGS), Mars Odyssey, and Mars Express orbiters. As of 21 July, 2004, over 50 Gbits of MER data have been obtained, with nearly 95% of that data returned via the MGS and Odyssey UHF relay paths, allowing a large increase in science return from the Martian surface relative to the X-band direct-to-Earth link. The MGS spacecraft also supported high-rate UHF communications of MER engineering telemetry during the critical period of entry, descent, and landing (EDL), augmenting the very low-rate EDL data collected on the X-band direct-to-Earth link. Through adoption of the new CCSDS Proximity-1 Link Protocol, NASA and ESA have achieved interoperability among these Mars assets, as validated by a successful relay demonstration between Spirit and Mars Express, enabling future interagency cross-support and establishing a truly international relay network at Mars.

  2. Constraints on the Interior Structure and Seasonal Mass Redistribution of Mars from Radio Tracking of Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    Preston, R. A.; Folkner, W. M.

    1997-01-01

    Doppler and range measurements to the Mars Pathfinder lander, made with its radio communications system, have been combined with similar measurements from the viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars's rotation rate.

  3. The Cratering Record of the South Polar Layered Deposits of Mars

    NASA Astrophysics Data System (ADS)

    Koutnik, M.; Byrne, S.; Murray, B.

    2001-11-01

    The Mars Orbiter Laser Altimeter (MOLA) and the Mars Orbiter Camera (MOC) instruments aboard the Mars Global Surveyor (MGS) were used in a detailed search of a selected part of the south polar layered deposits (SPLD) for impact craters. Impact craters were identified from the MOLA shaded relief map and validated using individual MOLA tracks and MOC narrow angle (NA) images. The resultant crater population is at least four times greater than the crater population previously recognized from Viking data [Plaut, et al., 1988]. The mean exposure age of the SPLD is estimated to be 30 to 100 Ma depending on the established production model isochrons used [Herkenhoff and Plaut, 2000; Hartmann, 1999]. All of the 0.8 to 5 km diameter craters are considerably shallower than other Martian craters in the same diameter range. The timescales postulated for layer formation modulated solely by deterministic astronomically driven climatic fluctuations of approximately 105 to 106 years [Ward, 1979] are much shorter than the high mean surface exposure age for the SPLD determined in this study. Thus the surface of the SPLD included in our study likely records some previously unrecognized event in polar history that marked the end of layer formation and erosion in that area. Hartmann, W.K., Martian Cratering VI: Crater count isochrons and evidence for recent volcanism from Mars Global Surveyor. Meteoritics & Planetary Science, 34, 167-177, 1999. Herkenhoff, K.E., and J.J. Plaut, Surface Ages and Resurfacing Rates of the Polar Layered Deposits on Mars, Icarus, 144, 243-253, 2000. Plaut, J.J., R. Kahn, E.A. Guiness, and R.E. Arvidson, Accumulation of Sedimentary Debris in the South Polar Region of Mars and Implications for Climate History, Icarus 75, 357-377, 1988. Ward, W.R., Present obliquity oscillations of Mars: Fourth-order accuracy in orbital e and I, J. Geophys. Res., 84, 237-241, 1979.

  4. Mars Observer Laser Altimeter

    NASA Technical Reports Server (NTRS)

    Zuber, Maria T.

    1997-01-01

    The objective of this study was to support the rebuild and implementation of the Mars Orbiter Laser Aftimeter (MOLA) investigation and to perform scientific analysis of current Mars data relevant to the future investigation. The instrument is part of the payload of the NASA Mars Global Surveyor (MGS) mission. The instrument is a rebuild of the Mars Observer Laser Altimeter that was originally flown on the ill-fated Mars Observer mission.

  5. Dust torus around Mars

    NASA Technical Reports Server (NTRS)

    Juhasz, Antal; Horanyi, Mihaly

    1995-01-01

    We investigate the orbital dynamics of small dust particles generated via the continuous micrometeoroid bombardment of the Martian moons. In addition to Mar's oblateness, we also consider the radiation pressure perturbation that is complicated by the planet's eccentric orbit and tilted rotational axis. Considering the production rates and the lifetimes of dust grains, we show that particles from Deimos with radii of about 15 micrometers are expected to dominate the population of a permanently present and tilted dust torus. This torus has an estimated peak number density of approximately equals 5 x 10(exp -12)/cu cm and an optical depth of approximately equals 4 x 10(exp -8).

  6. Surface chemistry and mineralogy. [of planet Mars

    NASA Technical Reports Server (NTRS)

    Banin, A.; Clark, B. C.; Waenke, H.

    1992-01-01

    The accumulated knowledge on the chemistry and mineralogy of Martian surface materials is reviewed. Pertinent information obtained by direct analyses of the soil on Mars by the Viking Landers, by remote sensing of Mars from flyby and orbiting spacecraft, by telescopic observations from earth, and through detailed analyses of the SNC meteorites presumed to be Martian rocks are summarized and analyzed. A compositional model for Mars soil, giving selected average elemental concentrations of major and trace elements, is suggested. It is proposed that the fine surface materials on Mars are a multicomponent mixture of weathered and nonweathered minerals. Smectite clays, silicate mineraloids similar to palagonite, and scapolite are suggested as possible major candidate components among the weathered minerals.

  7. Water on early Mars.

    PubMed

    Carr, M H

    1996-01-01

    Large flood channels, valley networks and a variety of features attributed to the action of ground ice indicate that Mars emerged from heavy bombardment 3.8 Ga ago, with an inventory of water at the surface equivalent to at least a few hundred metres spread over the whole planet, as compared with 3 km for the Earth. The mantle of Mars is much drier than that of the Earth, possibly as a result of global melting at the end of accretion and the lack of plate tectonics to subsequently reintroduce water into the interior. The surface water resided primarily in a porous, kilometres-thick megaregolith created by the high impact rates. Under today's climatic conditions groundwater is trapped below a thick permafrost zone. At the end of heavy bombardment any permafrost zone would have been much thinner because of the high heat flows, but climatic conditions may have been very different then, as suggested by erosion rates 1000 times higher than subsequent rates. Water trapped below the permafrost periodically erupted onto the surface to form large flood channels and lakes. Given abundant water at the surface and sustained volcanism, hydrothermal activity must have frequently occurred but we have yet to make the appropriate observations to detect the results of such activity. PMID:9243020

  8. Water on early Mars

    USGS Publications Warehouse

    Carr, M.H.

    1996-01-01

    Large flood channels, valley networks and a variety of features attributed to the action of ground ice indicate that Mars emerged from heavy bombardment 3.8 Ga ago, with an inventory of water at the surface equivalent to at least a few hundred metres spread over the whole planet, as compared with 3 km for the Earth. The mantle of Mars is much drier than that of the Earth, possibly as a result of global melting at the end of accretion and the lack of plate tectonics to subsequently reintroduce water into the interior. The surface water resided primarily in a porous, kilometres-thick megaregolith created by the high impact rates. Under today's climatic conditions groundwater is trapped below a thick permafrost zone. At the end of heavy bombardment any permafrost zone would have been much thinner because of the high heat flows, but climatic conditions may have been very different then, as suggested by erosion rates 1000 times higher than subsequent rates. Water trapped below the permafrost periodically erupted onto the surface to form large flood channels and lakes. Given abundant water at the surface and sustained volcanism, hydrothermal activity must have frequently occurred but we have yet to make the appropriate observations to detect the results of such activity.

  9. Mars Observer Lecture: Mars Orbit Insertion

    NASA Technical Reports Server (NTRS)

    Dodd, Suzanne R. (Personal Name)

    1993-01-01

    The Mars Observer mission spacecraft was primarily designed for exploring Mars and the Martian environment. The Mars Observer was launched on September 25, 1992. The spacecraft was lost in the vicinity of Mars on August 21, 1993 when the spacecraft began its maneuvering sequence for Martian orbital insertion. This videotape shows a lecture by Suzanne R. Dodd, the Mission Planning Team Chief for the Mars Observer Project. Ms Dodd begins with a brief overview of the mission and the timeline from the launch to orbital insertion. Ms Dodd then reviews slides showing the trajectory of the spacecraft on its trip to Mars. Slides of the spacecraft being constructed are also shown. She then discusses the Mars orbit insertion and the events that will occur to move the spacecraft from the capture orbit into a mapping orbit. During the trip to Mars, scientists at JPL had devised a new strategy, called Power In that would allow for an earlier insertion into the mapping orbit. The talk summarizes this strategy, showing on a slide the planned transition orbits. There are shots of the Martian moon, Phobos, taken from the Viking spacecraft, as Ms Dodd explains that the trajectory will allow the orbiter to make new observations of that moon. She also explains the required steps to prepare for mapping after the spacecraft has achieved the mapping orbit around Mars. The lecture ends with a picture of Mars from the Observer on its approach to the planet.

  10. Improved Mars Upper Atmosphere Climatology

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.

    2004-01-01

    The detailed characterization of the Mars upper atmosphere is important for future Mars aerobraking activities. Solar cycle, seasonal, and dust trends (climate) as well as planetary wave activity (weather) are crucial to quantify in order to improve our ability to reasonably depict the state of the Mars upper atmosphere over time. To date, our best information is found in the Mars Global Surveyor (MGS) Accelerometer (ACC) database collected during Phase 1 (Ls = 184 - 300; F10.7 = 70 - 90) and Phase 2 (Ls = 30 - 90; F10.7 = 90 - 150) of aerobraking. This database (100 - 170 km) consists of thermospheric densities, temperatures, and scale heights, providing our best constraints for exercising the coupled Mars General Circulation Model (MGCM) and the Mars Thermospheric General Circulation Model (MTGCM). The Planetary Data System (PDS) contains level 0 and 2 MGS Accelerometer data, corresponding to atmospheric densities along the orbit track. Level 3 products (densities, temperatures, and scale heights at constant altitudes) are also available in the PDS. These datasets provide the primary model constraints for the new MGCM-MTGCM simulations summarized in this report. Our strategy for improving the characterization of the Mars upper atmospheres using these models has been three-fold : (a) to conduct data-model comparisons using the latest MGS data covering limited climatic and weather conditions at Mars, (b) to upgrade the 15-micron cooling and near-IR heating rates in the MGCM and MTGCM codes for ad- dressing climatic variations (solar cycle and seasonal) important in linking the lower and upper atmospheres (including migrating tides), and (c) to exercise the detailed coupled MGCM and MTGCM codes to capture and diagnose the planetary wave (migrating plus non-migrating tidal) features throughout the Mars year. Products from this new suite of MGCM-MTGCM coupled simulations are being used to improve our predictions of the structure of the Mars upper atmosphere for the

  11. The H Corona of Mars

    NASA Astrophysics Data System (ADS)

    Chaffin, Michael Scott

    The atmosphere of every planet is surrounded by a tenuous cloud of hydrogen gas, referred to as a hydrogen corona. At Mars, a substantial fraction of the H present in the corona is moving fast enough to escape the planet's gravity, permanently removing H from the Martian atmosphere. Because this H is ultimately derived from lower atmospheric water, loss of H from Mars is capable of drying and oxidizing the planet over geologic time. Understanding the processes that supply the H corona and control its escape is therefore essential for a complete understanding of the climate history of Mars and for assessing its habitability. In this thesis, I present the most complete analysis of the H corona ever attempted, surveying eight years of data gathered by the ultraviolet spectrograph SPICAM on Mars Express. Using a coupled radiative transfer and physical density model, I interpret brightness measurements of the corona in terms of escape rates of H from the planet, uncovering an order-of-magnitude variability in the H escape rate never before detected. These variations are interpreted using a completely new photochemical model of the atmosphere, demonstrating that newly discovered high altitude water vapor layers are sufficient to produce the observed variation. Finally, I present first results of the SPICAM successor instrument IUVS, an imaging ultraviolet spectrograph carried by NASA's MAVEN spacecraft. IUVS measurements are producing the most complete dataset ever gathered for the Martian H corona, enabling supply and loss processes to be assessed in more complete detail than ever before. This dataset will allow present-day loss rates to be extrapolated into the past, determining the absolute amount of water Mars has lost to space over the course of its history. Planets the size of Mars may be common throughout the universe; the work of this thesis is one step toward assessing the habitability of such planets in general.

  12. Greenland annual accumulation along the EGIG line, 1959-2004, from ASIRAS airborne radar and neutron-probe density measurements

    NASA Astrophysics Data System (ADS)

    Overly, Thomas B.; Hawley, Robert L.; Helm, Veit; Morris, Elizabeth M.; Chaudhary, Rohan N.

    2016-08-01

    We report annual snow accumulation rates from 1959 to 2004 along a 250 km segment of the Expéditions Glaciologiques Internationales au Groenland (EGIG) line across central Greenland using Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) radar layers and high resolution neutron-probe (NP) density profiles. ASIRAS-NP-derived accumulation rates are not statistically different (95 % confidence interval) from in situ EGIG accumulation measurements from 1985 to 2004. ASIRAS-NP-derived accumulation increases by 20 % below 3000 m elevation, and increases by 13 % above 3000 m elevation for the period 1995 to 2004 compared to 1985 to 1994. Three Regional Climate Models (PolarMM5, RACMO2.3, MAR) underestimate snow accumulation below 3000 m by 16-20 % compared to ASIRAS-NP from 1985 to 2004. We test radar-derived accumulation rates sensitivity to density using modeled density profiles in place of NP densities. ASIRAS radar layers combined with Herron and Langway (1980) model density profiles (ASIRAS-HL) produce accumulation rates within 3.5 % of ASIRAS-NP estimates in the dry snow region. We suggest using Herron and Langway (1980) density profiles to calibrate radar layers detected in dry snow regions of ice sheets lacking detailed in situ density measurements, such as those observed by the Operation IceBridge campaign.

  13. Mars Radiator Characterization Experimental Program

    NASA Technical Reports Server (NTRS)

    Witte, Larry C.; Hollingsworth, D. Keith

    2004-01-01

    Radiators are an enabling technology for the human exploration and development of the moon and Mars. As standard components of the heat rejection subsystem of space vehicles, radiators are used to reject waste heat to space and/or a planetary environment. They are typically large components of the thermal control system for a space vehicle or human habitation facility, and in some cases safety factors are used to oversize them when the operating environment cannot be fully characterized. Over-sizing can impose significant weight and size penalties that might be prohibitive for future missions. Radiator performance depends on the size of the radiator surface, its emittance and absorptance, the radiator temperature, the effective sky temperature surrounding the radiator, solar radiation and atmospheric irradiation levels, convection to or from the atmosphere (on Mars), and other conditions that could affect the nature of the radiator surface, such as dust accumulation. Most particularly, dust is expected to be a major contributor to the local environmental conditions on either the lunar or Martian surface. This conclusion regarding Mars is supported by measurements of dust accumulation on the Mars Sojourner Rover solar array during the Pathfinder mission. This Final Report describes a study of the effect of Martian dust accumulation on radiator performance. It is comprised of quantitative measurements of effective emittance for a range of dust accumulation levels on surfaces of known emittance under clean conditions. The test radiator coatings were Z-93P, NS-43G, and Silver Teflon (10 mil) film. The Martian dust simulant was Carbondale Red Clay. Results were obtained under vacuum conditions sufficient to reduce convection effects virtually to zero. The experiments required the development of a calorimetric apparatus that allows simultaneous measurements of the effective emittance for all the coatings at each set of experimental conditions. A method of adding dust to

  14. Compartmentation Analysis of Paraquat Fluxes in Maize Roots as a Means of Estimating the Rate of Vacuolar Accumulation and Translocation to Shoots.

    PubMed Central

    DiTomaso, J. M.; Hart, J. J.; Kochian, L. V.

    1993-01-01

    Efflux analysis conducted after five loading periods of various lengths (2, 6, 12, 18, or 24 h) was used to investigate uptake, compartmentation, and translocation of [14C]paraquat in maize (Zea mays L.) seedlings. The time course for net paraquat uptake (paraquat concentration in uptake solution = 25[mu]M) into maize roots was linear (56.7 nmol g-1 root fresh weight h-1) for 24 h. Estimates of changes in paraquat content in the vacuole, cytoplasm, and cell wall after 2-, 6-, 12-, 18-, and 24-h loading periods indicated that the cell wall saturated rapidly, whereas accumulation of paraquat into the vacuole increased linearly (12.4 nmol g-1 root fresh weight h-1) over 24 h. In contrast to vacuolar accumulation, cytoplasmic paraquat content appeared to approach saturation. The half-time for paraquat efflux from the cell wall (16.6 min [plus or minus] 1.2 SD) and cytoplasm (58.8 min [plus or minus] 8.9 SD remained relatively constant regardless of the length of the loading period, whereas the half-time for efflux from the vacuole was considerably longer and increased linearly with increased loading time (6.1-18.7 h). The time course for paraquat translocation to the shoot was linear within a 24-h exposure to radiolabeled herbicide, but translocation did not begin until 5 h after initiation of treatment. The experimental approach used in these experiments provides a valuable method for examining the movement of paraquat in maize seedlings. Results indicate that the herbicide slowly accumulates in the vacuole of root cells but is also translocated to the shoot. PMID:12231834

  15. Paleohydrology of Eberswalde crater, Mars

    NASA Astrophysics Data System (ADS)

    Irwin, Rossman P.; Lewis, Kevin W.; Howard, Alan D.; Grant, John A.

    2015-07-01

    Eberswalde crater, Mars, contains a well-preserved fluvial distributary network in a likely deltaic setting. The meandering inverted paleochannels and closed drainage basin of this deposit support relatively well constrained estimates of channel-forming discharge (over an individual event flood timescale), runoff production (event and annual timescales), and longevity of deposition (geologic timescale) during the Late Hesperian to Early Amazonian Epochs. The width and meander dimensions of two inverted paleochannels reflect the channel-forming discharge from event floods (~ 200 to 400 m3/s), the deposit surface indicates the level (- 1400 to - 1350 m) and surface area (410 to 810 km2) of the likely paleolake, and the topography and mapped extent of tributaries constrain the watershed area (5000 to 17,000 km2). Based on these results and terrestrial empirical constraints on evaporation and sediment concentration, we evaluated three hypothetical water sources: meltwater liberated by the nearby Holden crater impact (continuous deposition over ~ 101-102 years), intermittent rainfall or snowmelt during finite periods controlled by orbital evolution (deposition over ~ 104-106 years), and highly infrequent runoff or melting of accumulated snowpacks following distant impacts or secular changes in orbital parameters. Local impact-generated runoff and highly infrequent rainfall or snowmelt require unreasonably high and low rates of evaporation, respectively, to maintain the paleolake level. The local impact hypothesis alternatively depends on one flooding episode with very high concentrations of fluvial sediment that are inconsistent with morphologic considerations. Multiple primary impact craters in the area postdate Holden ejecta but were later dissected, indicating fluvial erosion long after the Holden impact. Intermittent rainfall of ~ 1 cm/day and seasonal snowmelt are both consistent with our results over a deposition timescale totaling ~ 104-106 years.

  16. Lunar and Planetary Science XXXV: Mars Tectonism and Volcanism

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session "Mars Tectonism and Volcanism", included the following reports:Structural Attitudes of Large Scale Layering in Valles Marineris, Mars, Calculated from Mars Orbiter Laser Altimeter Data and Mars Orbiter Camera Imagery; Stratigraphy of Eastern Coprates Chasma, Mars; Temporal Variability in Tharsis Stress State Based on Wrinkle Ridges and Strike-Slip Faulting; State of Stress in the Martian Lithosphere; Displacement-Length Scaling of Faults on Earth, Mars, and Beyond; Topographic Analysis of Quasi-Circular Depressions Around the Utopia Basin, Mars; The Olympus Mons Aureole Deposits: New Evidence for a Flank-failure Origin; Cerberus Fossae and Elysium Planitia Lavas, Mars: Source Vents, Flow Rates, Edifice Styles and Water Interactions; and Topographic Evidence for Eruptive Style Changes and Magma Evolution of Small Plains.

  17. Electromagnetic braking for Mars spacecraft

    NASA Technical Reports Server (NTRS)

    Holt, A. C.

    1986-01-01

    Aerobraking concepts are being studied to improve performance and cost effectiveness of propulsion systems for Mars landers and Mars interplanetary spacecraft. Access to megawatt power levels (nuclear power coupled to high-storage inductive or capacitive devices) on a manned Mars interplanetary spacecraft may make feasible electromagnetic braking and lift modulation techniques which were previously impractical. Using pulsed microwave and magnetic field technology, potential plasmadynamic braking and hydromagnetic lift modulation techniques have been identified. Entry corridor modulation to reduce loads and heating, to reduce vertical descent rates, and to expand horizontal and lateral landing ranges are possible benefits. In-depth studies are needed to identify specific design concepts for feasibility assessments. Standing wave/plasma sheath interaction techniques appear to be promising. The techniques may require some tailoring of spacecraft external structures and materials. In addition, rapid response guidance and control systems may require the use of structurally embedded sensors coupled to expert systems or to artificial intelligence systems.

  18. Estimation of Potassium Recirculation in Tomato Plants by Comparison of the Rates of Potassium and Calcium Accumulation in the Tops with Their Fluxes in the Xylem Stream

    PubMed Central

    Armstrong, Michael J.; Kirkby, Ernest A.

    1979-01-01

    A procedure to estimate the extent of K recirculation in plants is proposed. This is based on the ratio of the upward fluxes of K to Ca in the xylem sap from root to shoot with the ratio of K to Ca accumulation in plant tops. In a preliminary investigation the factors influencing the K to Ca ratio in the xylem sap were considered. Tomato plants were grown at three levels of K nutrition and harvested at different times during the 24-hour day period. It was shown that the K to Ca ratio in xylem sap changed dramatically depending on the time of sap collection after decapitation, the values falling from over 2 to less than unity over the 4-hour period of collection. Diurnal effects on exudation were less marked but also of significance. The level of K nutrition was of little importance. It is suggested that a representative xylem sap from tomato plants can best be obtained from samples taken between 15 and 60 minutes after decapitation. In a second experiment K recirculation was estimated. At nine harvesting stages over a 24-hour period the K to Ca ratio in the xylem sap was invariably higher than the K to Ca ratio of accumulation in the tops over the same period. From this information it was calculated that about 20% of the upward flux of K in the xylem stream resulted from recirculated K. PMID:16660872

  19. Mars scouts: an overview

    NASA Technical Reports Server (NTRS)

    Matousek, S.

    2001-01-01

    The Mars program institutes the Mars Scout Missions in order to address science goals in the program not otherwise covered in the baseline Mars plan. Mars Scout Missions will be Principle-Investigator (PI) led science missions. Analogous to the Discovery Program, PI led investigations optimize the use of limited resources to accomplish the best focused science and allow the flexibility to quickly respond to discoveries at Mars. Scout missions also require unique investments in technology and reliance upon Mars-based infrastructure such as telecom relay orbiters.

  20. Mars Orbiter Laser Altimeter

    NASA Technical Reports Server (NTRS)

    Zuber, Maria T.

    1997-01-01

    The objective of this study was to support the rebuild and implementation of the Mars Orbiter Laser Altimeter (MOLA) investigation and to perform scientific analysis of current Mars data relevant to the investigation. The instrument is part of the payload of the NASA Mars Global Surveyor (MGS) mission. The instrument is a rebuild of the Mars Observer Laser Altimeter that was originally flown on the ill-fated Mars Observer mission. The instrument is currently in orbit around Mars and has so far returned remarkable data.

  1. Mars brine formation experiment

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Bullock, Mark A.; Stoker, Carol R.

    1993-01-01

    The presence of water-soluble cations and anions in the Martian regolith has been the subject of speculation for some time. Viking lander data provided evidence for salt-cemented crusts on the Martian surface. If the crusts observed at the two Viking landing sites are, in fact, cemented by salts, and these crusts are globally widespread, as IRTM-derived thermal inertia studies of the Martian surface seem to suggest, then evaporite deposits, probably at least in part derived from brines, are a major component of the Martian regolith. The composition of liquid brines in the subsurface, which not only may be major agents of physical weathering but may also presently constitute a major deep subsurface liquid reservoir, is currently unconstrained by experimental work. A knowledge of the chemical identity and rate of production of Martian brines is a critical first-order step toward understanding the nature of both these fluids and their precipitated evaporites. Laboratory experiments are being conducted to determine the identity and production rate of water-soluble ions that form in initially pure liquid water in contact with Mars-mixture gases and unaltered Mars-analog minerals.

  2. Mars integrated transportation system multistage Mars mission

    NASA Technical Reports Server (NTRS)

    1991-01-01

    In accordance with the objective of the Mars Integrated Transport System (MITS) program, the Multistage Mars Mission (MSMM) design team developed a profile for a manned mission to Mars. The purpose of the multistage mission is to send a crew of five astronauts to the martian surface by the year 2019. The mission continues man's eternal quest for exploration of new frontiers. This mission has a scheduled duration of 426 days that includes experimentation en route as well as surface exploration and experimentation. The MSMM is also designed as a foundation for a continuing program leading to the colonization of the planet Mars.

  3. Solar array development for the surface of Mars

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Dawson, S.; Rapp, D.; Sharps, Paul; Aiken, D.; Spence, B. R.; White, S. F.; King, R. P.; Edmonson, K.

    2003-01-01

    JPL's missions to Mars have revealed factors that have an adverse impact on the performance of Mars Surface Solar Arrays. These factors included a spectrum shift toward the red wavelengths, atmospheric scattering and absorption and an accumulation of Mars surface dust on the arrays. All of these factors will reduce the power generated from state of the art triple junction solar cells used by earth orbiting satellites. This paper will report the results of JPL supported work conducted by US solar array manufacturers to increase the performance of solar arrays for future Mars surface missions. JPL awarded four vendors contracts to evaluate methods of improving power generation on the surface of Mars. These four contracts cover the redesign of the existing triple junction solar cell, modifying solar simulator output to match the Mars surface spectrum and techniques to control or remove dust from the surface of the arrays. The methodology and results of this evaluation will be presented in this paper.

  4. Mars chronology: assessing techniques for quantifying surficial processes

    NASA Technical Reports Server (NTRS)

    Doran, Peter T.; Clifford, Stephen M.; Forman, Steven L.; Nyquist, Larry; Papanastassiou, Dimitri A.; Stewart, Brian W.; Sturchio, Neil C.; Swindle, Timothy D.; Cerling, Thure; Kargel, Jeff

    2004-01-01

    Currently, the absolute chronology of Martian rocks, deposits and events is based mainly on crater counting and remains highly imprecise with epoch boundary uncertainties in excess of 2 billion years. Answers to key questions concerning the comparative origin and evolution of Mars and Earth will not be forthcoming without a rigid Martian chronology, enabling the construction of a time scale comparable to Earth's. Priorities for exploration include calibration of the cratering rate, dating major volcanic and fluvial events and establishing chronology of the polar layered deposits. If extinct andor extant life is discovered, the chronology of the biosphere will be of paramount importance. Many radiometric and cosmogenic techniques applicable on Earth and the Moon will apply to Mars after certain baselines (e.g. composition of the atmosphere, trace species, chemical and physical characteristics of Martian dust) are established. The high radiation regime may pose a problem for dosimetry-based techniques (e.g. luminescence). The unique isotopic composition of nitrogen in the Martian atmosphere may permit a Mars-specific chronometer for tracing the time-evolution of the atmosphere and of lithic phases with trapped atmospheric gases. Other Mars-specific chronometers include measurement of gas fluxes and accumulation of platinum group elements (PGE) in the regolith. Putting collected samples into geologic context is deemed essential, as is using multiple techniques on multiple samples. If in situ measurements are restricted to a single technique it must be shown to give consistent results on multiple samples, but in all cases, using two or more techniques (e.g. on the same lander) will reduce error. While there is no question that returned samples will yield the best ages, in situ techniques have the potential to be flown on multiple missions providing a larger data set and broader context in which to place the more accurate dates.

  5. Mapping Mars with a Laser Altimeter

    NASA Technical Reports Server (NTRS)

    Smith, David E.

    2001-01-01

    In November 1996 the Mars Global Surveyor (MGS) spacecraft was launched to Mars. One of the instruments on the spacecraft was a laser altimeter, MOLA, for measuring the shape and topography of the planet. The altimeter has a diode pumped Q-switched ND:YAG laser at 1064nm, operating at 10Hz with an 8 nsec pulse width. The pulse energy is 48mJ, and the instrument has a 37cm ranging precision. The laser illuminates a spot on the surface of Mars approximately 160 meters in diameter and the instrument has accumulated over 600 million range measurements of the surface since arrival at Mars in September 1997. MOLA has operated continuously for over 2 years and has mapped the planet at a horizontal resolution of about 1 km and a radial accuracy of about a meter. MOLA has measured the shape of the planet, the heights of the volcanoes, the depths of the canyons, and the volumes of the polar icecaps. It has detected carbon dioxide clouds and measured the accumulation of seasonal CO2 on the polar icecaps. This new remote sensing tool has helped transform our understanding of Mars and its geological history, and opened a new door to planetary exploration.

  6. MAVEN's Trajectory to Mars

    NASA Video Gallery

    This movie shows the cruise trajectory of NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission, which was launched on Nov. 18, 2013. It will arrive at Mars on Sept. 21, 2014, to explore th...

  7. The Mars Chamber

    NASA Video Gallery

    The Mars chamber is a box about the size of a refrigerator that re-creates the temperatures, pressures, and atmosphere of the Martian surface, essentially creating a Mars environment on Earth! Scie...

  8. Europe is going to Mars

    NASA Astrophysics Data System (ADS)

    1999-06-01

    The Agency's Science Programme Committee (SPC) approved Mars Express after ESA's Council, meeting at ministerial level in Brussels on 11 and 12 May, had agreed the level of the science budget for the next 4 years, just enough to make the mission affordable. "Mars Express is a mission of opportunity and we felt we just had to jump in and do it. We are convinced it will produce first-rate science", says Hans Balsiger, SPC chairman. As well as being a first for Europe in Mars exploration, Mars Express will pioneer new, cheaper ways of doing space science missions. "With a total cost of just 150 million euros, Mars Express will be the cheapest Mars mission ever undertaken", says Roger Bonnet, ESA's Director of Science. Mars Express will be launched in June 2003. When it arrives at the red planet six months later, it will begin to search for water and life. Seven instruments, provided by space research institutes throughout Europe, will make observations from the main spacecraft as it orbits the planet. Just before the spacecraft arrives, it will release a small lander, provided by research institutes in the UK, that will journey on to the surface to look for signs of life. The lander is called Beagle 2 after the ship in which Charles Darwin sailed round the world in search of evidence supporting his theory of evolution. But just as Darwin had to raise the money for his trip, so the search is on for public and private finance for Beagle 2. "Beagle 2 is an extremely important element of the mission", says Bonnet. Europe's space scientists have envisaged a mission to Mars for over fifteen years. But limited funding has prevented previous proposals from going ahead. The positioning of the planets in 2003, however, offers a particularly favourable passage to the red planet - an opportunity not to be missed. Mars Express will be joined by an international flotilla of spacecraft that will also be using this opportunity to work together on scientific questions and pave the way

  9. Tectonic Evolution of Mars

    NASA Technical Reports Server (NTRS)

    Phillips, Roger J.

    1992-01-01

    The Final Technical Report on tectonic evolution of Mars is presented. Two papers and an abstract are included. Topics addressed include: scientific rationale and requirements for a global seismic network on Mars, permanent uplift in magmatic systems with application to the Tharsis Region of Mars, and the geophysical signal of the Martian global dichotomy.

  10. Rotorcraft as Mars Scouts

    NASA Technical Reports Server (NTRS)

    Young, L. A.; Aiken, E. W.; Gulick, V.; Mancinelli, R.; Briggs, G. A.; Rutkowski, Michael (Technical Monitor)

    2002-01-01

    A new approach for the robotic exploration of Mars is detailed in this paper: the use of small, ultralightweight, autonomous rotary-wing aerial platforms. Missions based on robotic rotorcraft could make excellent candidates for NASA Mars Scout program. The paper details the work to date and future planning required for the development of such 'Mars rotorcraft.'

  11. 1 Main Street, Mars

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Located outside StenniSphere, the visitor center at John C. Stennis Space Center, 1 Main Street Mars is a model of how a habitat on Mars might look. Complete with thermometers, scales and clocks set to Martian equivalents, this exhibit shows how very different life on Mars can be.

  12. Mars: The Viking Discoveries.

    ERIC Educational Resources Information Center

    French, Bevan M.

    This booklet describes the results of NASA's Viking spacecraft on Mars. It is intended to be useful for the teacher of basic courses in earth science, space science, astronomy, physics, or geology, but is also of interest to the well-informed layman. Topics include why we should study Mars, how the Viking spacecraft works, the winds of Mars, the…

  13. Mars: 2010 - 2020

    NASA Technical Reports Server (NTRS)

    Li, Fuk K.

    2006-01-01

    This slide presentation reviews the Mars Exploration program for the current decade and beyond. The potential items for procurements for the Mars Science Laboratory (MSL) are discussed, as well as future technology investments to enable to continued development of exploration of Mars by rovers and orbiters that are planned and envisioned for future missions.

  14. Instrumentation and Methodology Development for Mars Mission

    NASA Technical Reports Server (NTRS)

    Chen, Yuan-Liang Albert

    2002-01-01

    The Mars environment comprises a dry, cold and low air pressure atmosphere with low gravity (0.38g) and high resistivity soil. The global dust storms that cover a large portion of Mars were observed often from Earth. This environment provides an idea condition for triboelectric charging. The extremely dry conditions on the Martian surface have raised concerns that electrostatic charge buildup will not be dissipated easily. If triboelectrically generated charge cannot be dissipated or avoided, then dust will accumulate on charged surfaces and electrostatic discharge may cause hazards for future exploration missions. The low surface temperature on Mars helps to prolong the charge decay on the dust particles and soil. To better understand the physics of Martian charged dust particles is essential to future Mars missions. We research and design two sensors, velocity/charge sensor and PZT momentum sensors, to detect the velocity distribution, charge distribution and mass distribution of Martian charged dust particles. These sensors are fabricated at NASA Kenney Space Center, Electromagnetic Physics Testbed. The sensors will be tested and calibrated for simulated Mars atmosphere condition with JSC MARS-1 Martian Regolith simulant in this NASA laboratory.

  15. Accumulation and conversion of sugars by developing wheat grains. VII. Effect of changes in sieve tube and endosperm cavity sap concentrations on the grain filling rate. [Triticum aestivum

    SciTech Connect

    Fisher, D.B.; Gifford, R.M.

    1987-06-01

    The extent to which wheat grain growth is dependent on transport pool solute concentration was investigated by the use of illumination and partial grain removal to vary solute concentrations in the sieve tube and endosperm cavity saps of the wheat ear (Triticum aestivum L.). Short-term grain growth rates were estimated indirectly from the product of phloem area, sieve tube sap concentration, and /sup 32/P translocation velocity. On a per grain basis, calculated rates of mass transport through the peduncle were fairly constant over a substantial range in other transport parameters (i.e. velocity, concentration, phloem area, and grain number). The rates were about 40% higher than expected; this probably reflects some unavoidable bias on faster-moving tracer in the velocity estimates. Sieve tube sap concentration increased in all experiments (by 20 to 64%), with a concomitant decline in velocity (to as low as 8% of the initial value). Endosperm cavity sucrose concentration also increased in all experiments, but cavity sap osmolality and total amino acid concentration remained nearly constant. No evidence was found for an increase in the rate of mass transport per grain through the peduncle in response to the treatments. This apparent unresponsiveness of grain growth rate to increased cavity sap sucrose concentration conflicts with earlier in vitro endosperm studies showing that sucrose uptake increased with increasing external sucrose concentration up to 150 to 200 millimolar.

  16. Heavy metal and waste metabolite accumulation and their affect on rainbow trout performance in a replicated water reuse system operated at low or high system flushing rates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A six-month trial was conducted to compare the effects of high and low make-up water flushing rates on rainbow trout performance and water quality in replicated water reuse aquaculture systems (WRAS). Six identical 9.5 m3 WRAS, containing a single 5.3 m3 tank and operated at a total recirculating fl...

  17. Mars Drilling Status

    NASA Technical Reports Server (NTRS)

    Mandell, Humboldt, C., Jr.

    2002-01-01

    This slide presentation reviews the current status of work to explore Mars beneath the surface of planet. One of the objective of this work is to enable further exploration of Mars by humans. One of the requirements for this is to find water on Mars. The presences of water is critical for Human Exploration and a permanent presence on Mars. If water is present beneath the surface it is the best chance of finding life on Mars. The presentation includes a timeline showing the robotic missions, those that have already been on Mars, and planned missions, an explanation of why do we want to drill on Mars, and some of the challenges, Also include are reviews of a missions that would drill 200 and 4,000 to 6,000 meters into the Martian bedrock, and a overview description of the drill. There is a view of some places where we have hopes of finding water.

  18. Solar Power on Mars

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This chart illustrates the variation in available solar power for each of NASA's twin Mars Exploration Rovers over the course of approximately two Mars years. Two factors affect the amount of available power: the tilt of Mars' axis and the eccentricity of the Mars' orbit about the sun.

    The horizontal scale is the number of Martian days (sols) after the Jan. 4, 2004, (Universal Time) landing of Spirit at Mars' Gusev Crater. The vertical scale on the right indicates the amount of available solar power as a ratio of the amount available at the equator when Mars is closest to the sun (perihelion). The red line indicates power availability at Spirit's landing site (Gusev). The blue line indicates power availability at Opportunity's landing site (Meridiani).

    The vertical scale on the right applies to the dotted line, indicating the latitude north or south of Mars' equator where the noon sun is overhead at different times of the Martian year.

  19. Mars transportation system synthesis

    NASA Astrophysics Data System (ADS)

    Young, Archie C.; Mulqueen, John A.; Emrich, William J.

    Performance and requirements synthesized to support the manned Mars mission of the Space Exploration Initiative (SEI) are presented. Emphasis is placed on the Mars transportation system (MTS), which uses nuclear thermal rocket (NTR) propulsion technology associated with accomplishing the manned Mars mission. Data are also presented for a propulsion system options comparison of chemical/aerobrake and nuclear electric propulsion systems. Vehicle- and weight-scaling are used to determine the MTS mass, size, and performance range required for different Mars mission durations. The split sprint, opposition, and conjunction class mission modes are employed to determine the MTS requirements envelope. MTS sensitivity to Mars surface payload, crew size, Mars orbit payload, NTR engine thrust level, engine specific impulse, and NTR engine thrust-to-weight ratio are synthesized. A suggested NTR technology level to accomplish both cargo and piloted Mars missions is discussed.

  20. The Salmonella typhimurium mar locus: molecular and genetic analyses and assessment of its role in virulence.

    PubMed Central

    Sulavik, M C; Dazer, M; Miller, P F

    1997-01-01

    The marRAB operon is a regulatory locus that controls multiple drug resistance in Escherichia coli. marA encodes a positive regulator of the antibiotic resistance response, acting by altering the expression of unlinked genes. marR encodes a repressor of marRAB transcription and controls the production of MarA in response to environmental signals. A molecular and genetic study of the homologous operon in Salmonella typhimurium was undertaken, and the role of marA in virulence in a murine model was assessed. Expression of E. coli marA (marAEC) present on a multicopy plasmid in S. typhimurium resulted in a multiple antibiotic resistance (Mar) phenotype, suggesting that a similar regulon exists in this organism. A genomic plasmid library containing S. typhimurium chromosomal sequences was introduced into an E. coli strain that was deleted for the mar locus and contained a single-copy marR'-'lacZ translational fusion. Plasmid clones that contained both S. typhimurium marR (marRSt) and marA (marASt) genes were identified as those that were capable of repressing expression of the fusion and which resulted in a Mar phenotype. The predicted amino acid sequences of MarRSt, MarASt, and MarBSt were 91, 86, and 42% identical, respectively, to the same genes from E. coli, while the operator/promoter region of the operon was 86% identical to the same 98-nucleotide-upstream region in E. coli. The marRAB transcriptional start sites for both organisms were determined by primer extension, and a marRABSt transcript of approximately 1.1 kb was identified by Northern blot analysis. Its accumulation was shown to be inducible by sodium salicylate. Open reading frames flanking the marRAB operon were also conserved. An S. typhimurium marA disruption strain was constructed by an allelic exchange method and compared to the wild-type strain for virulence in a murine BALB/c infection model. No effect on virulence was noted. The endogenous S. typhimurium plasmid that is associated with virulence

  1. Four Finalist Landing Site Candidates for Mars Science Laboratory

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Out of more than 30 sites considered as possible landing targets for NASA's Mars Science Laboratory mission, by November 2008 four of the most intriguing places on Mars rose to the final round of the site-selection process.

    The four finalists are, alphabetically: Eberswalde, where an ancient river deposited a delta in a possible lake; Gale, with a mountain of stacked layers including clays and sulfates; Holden, a crater containing alluvial fans, flood deposits, possible lake beds and clay-rich deposits; and Mawrth, which shows exposed layers containing at least two types of clay.

    The locations of these four candidates are indicated here on a background map of color-coded topographical data from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor. Red is higher elevation; blue is lower elevation. In latitude, the map extends from 70 degrees (north) to minus 70 degrees (south). The east-west axis is labeled at the top in degrees of east longitude, with the zero meridian at the center.

    The Mars Science Laboratory mission's capabilities for landing more precisely and at higher elevation than ever before, for driving farther, and for generating electricity without reliance on sunshine have enabled consideration of a wider range of possible landing sites than for any previous Mars mission. During the past two years, multiple observations of dozens of candidate sites by NASA's Mars Reconnaissance Orbiter have augmented data from earlier orbiters for evaluating sites' scientific attractions and engineering risks.

    More than 100 Mars scientists have participated in a series of open workshops presenting and assessing data that the orbiters have provided about the candidate sites. The four sites rated highest by researchers at a September 2008 workshop were the same ones chosen by mission leaders after a subsequent round of safety evaluations and analysis of terrain for rover driving.

    As a clay-bearing site where a river once flowed

  2. An Improved Optical Model for the Non-LTE Problem for the CO2 Molecule in the Atmosphere of Mars: Nighttime Populations of Vibrational States and the Rate of Radiative Cooling of the Atmosphere

    NASA Astrophysics Data System (ADS)

    Ogibalov, V. P.; Shved, G. M.

    2003-01-01

    The estimates of the population of excited vibrational states of the CO2 molecule and of the rate of radiative cooling of the atmosphere in the 15-μm CO2 band are given for the nighttime mesosphere and thermosphere of Mars. For the first time, these estimates are made (1) with allowance for the overlap of lines in the 15-μm band; (2) for a wide set of vibrational states of seven isotopes of the CO2 molecule, which was used earlier in the solution of a similar terrestrial problem; and (3) using the rate constant for quenching of the CO2(0110) state in collisions with oxygen atoms, which has been recently measured for low temperatures by Khvorostovskaya et al. (2002). The main results are as follows. 1. The approximation of isolated lines provides a satisfactory accuracy of determining the radiative cooling rate and overestimates vibrational temperatures of the states of the ν2 mode by no more than 3 K for the 12C16O2 molecule and by no more than 2 K for low-abundant isotopes of the CO2 molecule. 2. A reasonably high accuracy of estimating the cooling rate can be achieved by taking into account only fundamental vibrational transitions in 12C16O2, 13C16O2, 16O12C18O, and 16O12C17O molecules and the hot transitions 2ν2 --> ν2 and 3ν2 --> 2ν2 in the 12C16O2 molecule. 3. The vertical profile of the total rate of radiative cooling displays two peaks. The maximum near a height of 130 km is very sensitive to temperature and to the ratio of the mixture for oxygen in the atmosphere.

  3. Mars: Cold, windy and occasionally unstable (Invited)

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Becerra, P.; Diniega, S.; Dundas, C. M.; Geissler, P.; Hansen, C. J.; McEwen, A. S.; Russell, P. S.; Thomas, N.

    2013-12-01

    observed to retreat from failure of sections up to 70m across. Avalanches on those scarps are so common in some seasons that several can be seen in progress in a single HiRISE image. New impact craters in the mid-latitudes expose sub-surface ice whose geographic extent implies that it is currently retreating, while infill of craters on the PLD confirm polar accumulation. This poleward transport of water ice is only the most recent chapter in PLD accumulation, but provides a link to this historical record. Wind is also a powerful agent of surface change. Migration of dunes and ripples is now monitored at many sites. Dark ejecta blankets of newly formed impact craters change over time as fallout of atmospheric dust gradually obscures them. Regional albedo boundaries shift episodically in response to dust storms while seasonal frost appears to reset surface albedo at high latitudes each year. The episodic nature and interannual variability of surface changes make extrapolation from short-term records perilous. Long-term monitoring increases the value of all datasets and is the means by which we can understand the nature and rates of many geologic processes on Mars today.

  4. Detection and characterization of oxidizing acids in the Atacama Desert using the Mars Oxidation Instrument

    NASA Astrophysics Data System (ADS)

    Quinn, R. C.; Zent, A. P.; Grunthaner, F. J.; Ehrenfreund, P.; Taylor, C. L.; Garry, J. R. C.

    2005-11-01

    We have performed field experiments to further develop and validate the Mars Oxidation Instrument (MOI) as well as measurement strategies for the in situ characterization of oxidation mechanisms, kinetics, and carbon cycling on Mars. Using the Atacama Desert as a test site for the current dry conditions on Mars, we characterized the chemical reactivity of surface and near-surface atmosphere in the dry core of the Atacama. MOI is a chemiresistor-based sensor array that measures the reaction rates of chemical films that are sensitive to particular types of oxidants or that mimic chemical characteristics of pre-biotic and biotic materials. With these sensors, the chemical reactivity of a planetary environment is characterized by monitoring the resistance of the film as a function of time. Our instrumental approach correlates reaction rates with dust abundance, UV flux, humidity, and temperature, allowing discrimination between competing hypotheses of oxidant formation and organic decomposition. The sensor responses in the Atacama are consistent with an oxidative attack by strong acids triggered by dust accumulation, followed by transient wetting due to an increase in relative humidity during the night. We conclude that in the Atacama Desert, and perhaps on Mars, low pH resulting from acid accumulation, combined with limited water availability and high oxidation potential, can result in oxidizing acid reactions on dust and soil surfaces during low-moisture transient wetting events (i.e. thin films of water). These soil acids are expected to play a significant role in the oxidizing nature of the soils, the formation of mineral surface coatings, and the chemical modification of organics in the surface material.

  5. Atmospheric engineering of Mars

    NASA Technical Reports Server (NTRS)

    Macelroy, R. D.; Averner, M. M.

    1976-01-01

    The feasibility of creating a breathable atmosphere on Mars was studied. Assuming that indigenous life is absent, and that human habitation will prove economically justifiable, several methods of introducing oxygen were considered. On the basis of energy requirements, photosynthetic oxygen production appears to be reasonable, assuming that the amounts of water, carbon dioxide, and mineral nutrients available on the Martian surface would be adequate for the growth of photosynthetic microorganisms. However, optimum rates of O2 formation could occur only after a significant increase in average temperature and in atmospheric mass. The generation of a runaway greenhouse/advective effect was considered. However, neither the energy requirement nor the time constant for initiation could be calculated. There appear to be no insuperable obstacles to the conversion of the Martian atmosphere to one containing oxygen, but the conversion would require many thousands of years.

  6. Solar-Panel Dust Accumulation and Cleanings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Air-fall dust accumulates on the solar panels of NASA's Mars Exploration Rovers, reducing the amount of sunlight reaching the solar arrays. Pre-launch models predicted steady dust accumulation. However, the rovers have been blessed with occasional wind events that clear significant amounts of dust from the solar panels.

    This graph shows the effects of those panel-cleaning events on the amount of electricity generated by Spirit's solar panels. The horizontal scale is the number of Martian days (sols) after Spirit's Jan. 4, 2005, (Universal Time) landing on Mars. The vertical scale indicates output from the rover's solar panels as a fraction of the amount produced when the clean panels first opened. Note that the gradual declines are interrupted by occasional sharp increases, such as a dust-cleaning event on sol 420.

  7. Mystery of the magnetic field of Mars

    NASA Astrophysics Data System (ADS)

    Mordovskaya, V.

    Research of interaction of the solar wind with bodies of Solar System is one of methods, which allows us to make the conclusion about substance of the bodies and about its magnetization. The investigation of the solar wind interaction with Mars and Phobos has been carried out using the data of the Soviet expedition "Phobos - 2" and the kinetic approach to study the data. It is shown, that the size of the Martian obstacle to the solar wind is actually the size of Mars, as a physical body. The weak ionosphere and crystal magnetic anomalies at Mars result in inelastic dispersion of particles of the solar wind on the Martian obstacle, which give additional accumulation of the plasma and magnetic field in front of the Martian obstacle. The more the density of the solar wind, the more will the pileup of the plasma in front of Mars. Mars has not magnetospheres, neither own, nor induced to give the additional size for the obstacle like the Earth. The tail inherent in the interaction of magnetized bodies with the solar wind plasma, practically, is absent at Mars. The magnetic topology of the Martian wake is a result of the flow by the warm plasma of the solar wind around Mars. The Phobos interaction with the solar wind has been investigated. Dependence of the pileup of the solar wind plasma ahead of Phobos from the ion skin-depth has been found, which shows the existence of an effective obstacle of Phobos with the sizes about 150-170 km. Source with equivalent magnetic moment as order 1015A m2 in Phobos leads to the development of such obstacle for the solar wind flow around Phobos. Thus the received results: absence of the intrinsic global magnetic field of Mars, the magnetization of the Martian moon of Phobos and so the crystal magnetic anomalies revealed by the MGS satellite on surface of Mars give the primal magnetic mystery of Mars. If we will understand it we may probably approach to the problem of lifelessness of Mars. It is necessary to remind that evidence of

  8. Growth, diffusion, and loss of subsurface ice on Mars : experiments and models

    NASA Astrophysics Data System (ADS)

    Hudson, Troy Lee

    Innovative experiments and models are used to explore the behavior of subsurface ice on Mars. Through communication with the atmosphere, the porous regolith of Mars hosts significant quantities of ice which grow, evolve, and are lost in response to climate changes. As a controlling property of rate of ice response to a changing equilibrium state, the diffusive properties of several regolith simulants are measured in Mars-like environments. Ice loss through a variety of particle sizes, particle size distributions, packing densities, and salt contents are examined and reveal that many unconsolidated media exhibit diffusion coefficients in the range of 2-6 cm^2 s^-1, indicating a response time on the order of several thousand years for ice within the upper meter of the regolith. Only high salt contents or mechanically packed micron-sized dust are observed to exhibit substantially lower coefficients, suggesting that strong diffusive barriers may not form as readily as previously invoked. The growth of ice directly from vapor under diffusive control is reproduced for Mars-like environmental conditions in the absence of the liquid phase. As predicted, ice deposits preferentially at grain contact points and the ice table interface is sharp and strongly controlled by near-surface temperature perturbations. The quantity of ice deposited as a function of depth and time accords well with new numerical models of vapor diffusion and ice deposition, though constriction of the pore space reduces the diffusion coefficient faster than originally expected. A numerical model incorporating a fast solution to subsurface ice growth predicts near-surface ice contents for the last 300,000 years of Mars' history at high latitude locations, including specifically the Phoenix landing site. Several parameterizations of constriction developed from laboratory observations of ice growth are employed and compared. The thickness of the ice-free layer above the ice table has the strongest effect on

  9. North polar region of Mars: imaging results from viking 2.

    PubMed

    Cutts, J A; Blasius, K R; Briggs, G A; Carr, M H; Greeley, R; Masursky, H

    1976-12-11

    During October 1976, the Viking 2 orbiter acquired approximately 700 high-resolution images of the north polar region of Mars. These images confirm the existence at the north pole of extensive layered deposits largely covered over with deposits of perennial ice. An unconformity within the layered deposits suggests a complex history of climate change during their time of deposition. A pole-girdling accumulation of dunes composed of very dark materials is revealed for the first time by the Viking cameras. The entire region is devoid of fresh impact craters. Rapid rates of erosion or deposition are implied. A scenario for polar geological evolution, involving two types of climate change, is proposed. PMID:17797095

  10. Mars Color Imager (MARCI) on the Mars Climate Orbiter

    USGS Publications Warehouse

    Malin, M.C.; Bell, J.F., III; Calvin, W.; Clancy, R.T.; Haberle, R.M.; James, P.B.; Lee, S.W.; Thomas, P.C.; Caplinger, M.A.

    2001-01-01

    The Mars Color Imager, or MARCI, experiment on the Mars Climate Orbiter (MCO) consists of two cameras with unique optics and identical focal plane assemblies (FPAs), Data Acquisition System (DAS) electronics, and power supplies. Each camera is characterized by small physical size and mass (???6 x 6 x 12 cm, including baffle; <500 g), low power requirements (<2.5 W, including power supply losses), and high science performance (1000 x 1000 pixel, low noise). The Wide Angle (WA) camera will have the capability to map Mars in five visible and two ultraviolet spectral bands at a resolution of better than 8 km/pixel under the worst case downlink data rate. Under better downlink conditions the WA will provide kilometer-scale global maps of atmospheric phenomena such as clouds, hazes, dust storms, and the polar hood. Limb observations will provide additional detail on atmospheric structure at 1/3 scale-height resolution. The Medium Angle (MA) camera is designed to study selected areas of Mars at regional scale. From 400 km altitude its 6?? FOV, which covers ???40 km at 40 m/pixel, will permit all locations on the planet except the poles to be accessible for image acquisitions every two mapping cycles (roughly 52 sols). Eight spectral channels between 425 and 1000 nm provide the ability to discriminate both atmospheric and surface features on the basis of composition. The primary science objectives of MARCI are to (1) observe Martian atmospheric processes at synoptic scales and mesoscales, (2) study details of the interaction of the atmosphere with the surface at a variety of scales in both space and time, and (3) examine surface features characteristic of the evolution of the Martian climate over time. MARCI will directly address two of the three high-level goals of the Mars Surveyor Program: Climate and Resources. Life, the third goal, will be addressed indirectly through the environmental factors associated with the other two goals. Copyright 2001 by the American

  11. An accumulation of two independent selection factors decreases the success rate of female students at the MUV (Medical University of Vienna).

    PubMed

    Mitterauer, Lukas; Haidinger, Gerald; Frischenschlager, Oskar

    2008-01-01

    Inspired by the implementation of a reformed medical curriculum at the Medical University of Vienna (Austria, MUV), we have investigated predictors for success in the decisive exam at the end of the first study-year (SIE). In four consecutive cohorts of freshmen, we have found that female students show significantly lower success rates (Odds Ratio, OR=1.67, 95%CI 1.44-1.97). By the introduction of a pre-selection of applicants ("aptitude test for medical studies", EMS) in 2006, a new and additional significant hindrance for female students emerged. Their OR for not being accepted into the second study-year increased to OR=2.14 (95%CI 1.68-2.72), compared to male students. PMID:18766317

  12. Mars Global Reference Atmospheric Model (Mars-GRAM) Version 3.8: Users Guide

    NASA Astrophysics Data System (ADS)

    Justus, C. G.; James, B. F.

    1999-05-01

    Mars Global Reference Atmospheric Model (Mars-GRAM) Version 3.8 is presented and its new features are discussed. Mars-GRAM uses new values of planetary reference ellipsoid radii, gravity term, and rotation rate (consistent with current JPL values) and includes centrifugal effects on gravity. The model now uses NASA Ames Global Circulation Model low resolution topography. Curvature corrections are applied to winds and limits based on speed of sound are applied. Altitude of the F1 ionization peak and density scale height, including effects of change of molecular weight with altitude are computed. A check is performed to disallow temperatures below CO2 sublimination. This memorandum includes instructions on obtaining Mars-GRAM source code and data files and running the program. Sample input and output are provided. An example of incorporating Mars-GRAM as an atmospheric subroutine in a trajectory code is also given.

  13. Mars Global Reference Atmospheric Model (Mars-GRAM) Version 3.8: Users Guide

    NASA Technical Reports Server (NTRS)

    Justus, C. G.; James, B. F.

    1999-01-01

    Mars Global Reference Atmospheric Model (Mars-GRAM) Version 3.8 is presented and its new features are discussed. Mars-GRAM uses new values of planetary reference ellipsoid radii, gravity term, and rotation rate (consistent with current JPL values) and includes centrifugal effects on gravity. The model now uses NASA Ames Global Circulation Model low resolution topography. Curvature corrections are applied to winds and limits based on speed of sound are applied. Altitude of the F1 ionization peak and density scale height, including effects of change of molecular weight with altitude are computed. A check is performed to disallow temperatures below CO2 sublimination. This memorandum includes instructions on obtaining Mars-GRAM source code and data files and running the program. Sample input and output are provided. An example of incorporating Mars-GRAM as an atmospheric subroutine in a trajectory code is also given.

  14. Lunar and Planetary Science XXXV: Mars: Gullies, Fluids, and Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session "Mars: Gullies, Fluids, and Rocks" included the following reports:Gullies on Mars and Constraints Imposed by Mars Global Surveyor Data; Gullies on Mars: Origin by Snow and Ice Melting and Potential for Life Based on Possible Analogs from Devon Island, High Arctic; Formation of Recent Martian Gullies by Avalanches of CO2 Frost; Martian Slope Streaks and Gullies: Origins as Dry Granular Flows; Depths and Geologic Setting of Northern Hemisphere Gullies (and Comparison to Their Southern Counterparts); Mars as a Salt-, Acid-, and Gas-Hydrate World; Composition of Simulated Martian Brines and Implications for the Origin of Martian Salts; Evaporation Rates of Brine on Mars; Hydrogeology of the Valles Marineris-Chaotic Terrain Transition Zone, Mars; Measured Fluid Flow in an Active H2O-CO2 Geothermal Well as an Analog to Fluid Flow in Fractures on Mars: Preliminary Report; Understanding Rock Breakdown on Earth and Mars: Geomorphological Concepts and Facet Mapping Methods; Classification and Distribution of Mars Pathfinder Rocks Using Quantitative Morphologic Indices; and Systematic Rock Classification in a Data-poor Environment: Application to Mars.

  15. Effects of Local Farming and Deforestation on Sediment Discharge Inferred From Sediment Accumulation Rates and Patterns in Lake Core Records From Coastal Lake Tanganyika, East Africa

    NASA Astrophysics Data System (ADS)

    Strickler, M. L.; Lezzar, K. E.; Soreghan, M.; Cohen, A. S.; Swarzenski, P. W.; Berke, M.; McHeni, M.; Gunderson, K.; Allen, K.; Palke, A.; Modesta, M.; Nkotagu, H.

    2006-12-01

    Lake Tanganyika is the oldest and largest of the East African rift lakes and vital to the economy of the surrounding villages and countries. Deforestation around the lake causes many negative effects from an increased sediment flux and has changed dramatically as a function of population. Increases in inorganic sediment flux from deforested watersheds and an associated decrease in organic sediment flux may negatively impact the viability of littoral habitats in the lake. This study examines the interrelationship between deforestation on streams that feed into Lake Tanganyika and sedimentation offshore. We mapped stream morphology of two distinct streams: Kalande (Gombe Stream National Park), and Ngelwa (deforested). An offshore core was collected from the lake bottom just offshore of the deforested Ngelwa stream at a water depth of 106m and dated using 14C and 210Pb geochronologic methods. In addition, multiple laboratory analyses were performed on the core and within the streams to help constrain sedimentation and deforestation effects. Three distinct units within the core correlate to reflect changes in sedimentation (higher rates as deforestation continues) in addition to a shift from dry, low lake level conditions to wet, high lake levels as evidenced by shifts in core lithologies, diatom taxonomy and content, magnetic susceptibility, and clastic particle size. Streambed and suspended sediment analyses reflect high levels of erosion in deforested watersheds coupled with changes in dissolved nutrients in the water (silica, orthophosphate), which may suggest an overall diminished level of ecosystem function in deforested and heavily farmed watersheds.

  16. Cars on Mars

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    2002-01-01

    Mars is one of the most fascinating planets in the solar system, featuring an atmosphere, water, and enormous volcanoes and canyons. The Mars Pathfinder, Global Surveyor, and Odyssey missions mark the first wave of the Planet Earth's coming invasion of the red planet, changing our views of the past and future of the planet and the possibilities of life. Scientist and science-fiction writer Geoffrey A. Landis will present experiences on the Pathfinder mission, the challenges of using solar power on the surface of Mars, and present future missions to Mars such as the upcoming Mars Twin Rovers, which will launch two highly-capable vehicles in 2003 to explore the surface of Mars.

  17. Sample Analysis At Mars

    NASA Technical Reports Server (NTRS)

    Brinckerhoff, W. B.; Mahaffy, P. R.; Cabane, M.; Atreya, S. K.; Coll, P.; Cornish, T. J.; Harpold, D. N.; Israel, G.; Niemann, H. B.; Owen, T.

    2003-01-01

    The next landed missions to Mars, such as the planned Mars Science Laboratory and ExoMars, will require sample analysis capabilities refined well beyond what has been flown to date. A key science objective driving this requirement is the determination of the carbon inventory of Mars, and particularly the detection of organic compounds. While the gas chromatograph mass spectrometers (GCMS) on the Viking landers did not detect any indigenous organics in near surface fines, it is possible that these measurements were not representative of Mars on the whole. That is, those compounds to which the GC/MS was sensitive would likely not have survived the strong oxidative decomposition in the regolith at the landing sites in question. The near surface fines could very well contain a significant quantity of refractory compounds that would not have been volatilized in the sample ovens on Viking. It is also possible that volatile organics exist on Mars in sedimentary, subsurface, or polar niches.

  18. Sample Analysis at Mars

    NASA Technical Reports Server (NTRS)

    Brinckerhoff, W. B.; Mahaffy, P. R.; Cabane, M.; Atreya, S. K.; Coll, P.; Cornish, T. J.; Harpold, D. N.; Israel, G.; Niemann, H. B.; Owen, T.

    2003-01-01

    The next landed missions to Mars, such as the planned Mars Science Laboratory and ExoMars, will require sample analysis capabilities refined well beyond what has been flown to date. A key science objective driving this requirement is the determination of the carbon inventory of Mars, and particularly the detection of organic compounds. While the gas chromatograph mass spectrometers (GC/MS) on the Viking landers did not detect any indigenous organics in near surface fines, it is possible that these measurements were not representative of Mars on the whole. That is, those compounds to which the GC/MS was sensitive would likely not have survived the strong oxidative decomposition in the regolith at the landing sites in question. The near surface fines could very well contain a significant quantity of refractory compounds that would not have been volatilized in the sample ovens on Viking. It is also possible that volatile organics exist on Mars in sedimentary, subsurface, or polar niches.

  19. Mars Surface Habitability Options

    NASA Technical Reports Server (NTRS)

    Howe, A. Scott; Simon, Matthew; Smitherman, David; Howard, Robert; Toups, Larry; Hoffman, Stephen J.

    2015-01-01

    This paper reports on current habitability concepts for an Evolvable Mars Campaign (EMC) prepared by the NASA Human Spaceflight Architecture Team (HAT). For many years NASA has investigated alternative human Mars missions, examining different mission objectives, trajectories, vehicles, and technologies; the combinations of which have been referred to as reference missions or architectures. At the highest levels, decisions regarding the timing and objectives for a human mission to Mars continue to evolve while at the lowest levels, applicable technologies continue to advance. This results in an on-going need for assessments of alternative system designs such as the habitat, a significant element in any human Mars mission scenario, to provide meaningful design sensitivity characterizations to assist decision-makers regarding timing, objectives, and technologies. As a subset of the Evolvable Mars Campaign activities, the habitability team builds upon results from past studies and recommends options for Mars surface habitability compatible with updated technologies.

  20. Mars Solar Power

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Kerslake, Thomas W.; Jenkins, Phillip P.; Scheiman, David A.

    2004-01-01

    NASA missions to Mars, both robotic and human, rely on solar arrays for the primary power system. Mars presents a number of challenges for solar power system operation, including a dusty atmosphere which modifies the spectrum and intensity of the incident solar illumination as a function of time of day, degradation of the array performance by dust deposition, and low temperature operation. The environmental challenges to Mars solar array operation will be discussed and test results of solar cell technology operating under Mars conditions will be presented, along with modeling of solar cell performance under Mars conditions. The design implications for advanced solar arrays for future Mars missions is discussed, and an example case, a Martian polar rover, are analyzed.

  1. Mars elevation distribution

    NASA Technical Reports Server (NTRS)

    Wu, Sherman S. C.; Howington-Kraus, Annie E.; Ablin, Karyn K.

    1991-01-01

    A Digital Terrain Model (DTM) of Mars was derived with both Mercator and Sinusoidal Equal-Area projections from the global topographic map of Mars (scale 1:15 million, contour interval 1 km). Elevations on the map are referred to Mars' topographic datum that is defined by the gravity field at a 6.1-millibar pressure surface with respect to the center of mass of Mars. The DTM has a resolution at the equator of 1/59.226 degrees (exactly 1 km) per pixel. By using the DTM, the volumetric distribution of Mars topography above and below the datum has previously been calculated. Three types of elevation distributions of Mars' topography were calculated from the same DTM: (1) the frequency distribution of elevations at the pixel resolution; (2) average elevations in increments of 6 degrees in both longitude and latitude; and (3) average elevations in 36 separate blocks, each covering 30 degrees of latitude and 60 degrees of longitude.

  2. Quick trips to Mars

    NASA Technical Reports Server (NTRS)

    Hornung, R.

    1991-01-01

    The design of a Mars Mission Vehicle that would have to be launched by two very heavy lift launch vehicles is described along with plans for a mission to Mars. The vehicle has three nuclear engine for rocket vehicle application (NERVA) boosters with a fourth in the center that acts as a dual mode system. The fourth generates electrical power while in route, but it also helps lift the vehicle out of earth orbit. A Mars Ascent Vehicle (MAV), a Mars transfer vehicle stage, and a Mars Excursion Vehicle (MEV) are located on the front end of this vehicle. Other aspects of this research including aerobraking, heat shielding, nuclear thermal rocket engines, a mars mission summary, closed Brayton cycle with and without regeneration, liquid hydrogen propellant storage, etc. are addressed.

  3. Mars: The Viking discoveries

    NASA Technical Reports Server (NTRS)

    French, B. M.

    1977-01-01

    An overview of the Viking Mars probe is presented. The Viking spacecraft is described and a brief history of the earlier observations and exploration of Mars is provided. A number of the Viking photographs of the Martian surface are presented and a discussion of the experiments Viking performed including a confirmation of the general theory of relativity are reported. Martian surface chemistry is discussed and experiments to study the weather on Mars are reported.

  4. Mars at Opposition

    ERIC Educational Resources Information Center

    Riddle, Bob

    2010-01-01

    On January 29, Mars will reach opposition, a point along its orbit around the Sun where Mars will be directly opposite from the Sun in a two-planet and Sun line-up with the Earth in between. At this opposition, the Earth and Mars will be separated by nearly 100 million km. An opposition is similar to a full Moon in that the planet at opposition…

  5. Fluvial processes on Mars: Erosion and sedimentation

    NASA Technical Reports Server (NTRS)

    Squyres, Steven W.

    1988-01-01

    One of the most important discoveries of the Mariner 9 and Viking missions to Mars was evidence of change of the Martian surface by the action of liquid water. From the standpoint of a Mars Rover/Sample Return Mission, fluvial activity on Mars is important in two ways: (1) channel formation has deeply eroded the Martian crust, providing access to relatively undisturbed subsurface units; and (2) much of the material eroded from channels may have been deposited in standing bodies of liquid water. The most striking fluvial erosion features on Mars are the outflow channels. A second type of channel apparently caused by flow of liquid water is the valley systems. These are similar to terrestial drainage systems. The sedimentary deposits of outflow channels are often difficult to identfy. No obvious deposits such as deltaic accumulations are visible in Viking images. Another set of deposits that may be water lain and that date approx. from the epoch of outflow channels are the layered deposits in the Valles Marineris. From the standpoint of a Mars Rover/Sample Return mission, the problem with all of these water-lain sediments is their age, or rather the lack of it.

  6. Gamma Radiation Dose Rate in Air due to Terrestrial Radionuclides in Southern Brazil: Synthesis by Geological Units and Lithotypes Covered by the Serra do Mar Sul Aero-Geophysical Project

    SciTech Connect

    Bastos, Rodrigo O.; Appoloni, Carlos R.

    2008-08-07

    The absorbed dose rates in air due to terrestrial radionuclides were estimated from aerial gamma spectrometric data for an area of 48,600 km{sup 2} in Southern Brazil. The source data was the Serra do Mar Sul Aero-Geophysical Project back-calibrated in a cooperative work among the Geological Survey of Brazil, the Geological Survey of Canada, and Paterson, Grant and Watson Ltd. The concentrations of eU (ppm), eTh (ppm) and K (%) were converted to dose rates in air (nGy{center_dot}h{sup -1}) by accounting for the contribution of each element's concentration. Regional variation was interpreted according to lithotypes and a synthesis was performed according to the basic geological units present in the area. Higher values of total dose were estimated for felsic igneous and metamorphic rocks, with average values varying up to 119{+-}24 nGy{center_dot}h{sup -1}, obtained by Anitapolis syenite body. Sedimentary, metasedimentary and metamafic rocks presented the lower dose levels, and some beach deposits reached the lowest average total dose, 18.5{+-}8.2 nGy{center_dot}h{sup -1}. Thorium gives the main average contribution in all geological units, the highest value being reached by the nebulitic gneisses of Atuba Complex, 71{+-}23 nGy{center_dot}h{sup -1}. Potassium presents the lowest average contribution to dose rate in 53 of the 72 units analyzed, the highest contribution being obtained by intrusive alkaline bodies (28{+-}12 nGy{center_dot}h{sup -1}). The general pattern of geographic dose distribution respects well the hypotheses on geo-physicochemical behavior of radioactive elements.

  7. The missing organic molecules on Mars

    PubMed Central

    Benner, Steven A.; Devine, Kevin G.; Matveeva, Lidia N.; Powell, David H.

    2000-01-01

    GC-MS on the Viking 1976 Mars missions did not detect organic molecules on the Martian surface, even those expected from meteorite bombardment. This result suggested that the Martian regolith might hold a potent oxidant that converts all organic molecules to carbon dioxide rapidly relative to the rate at which they arrive. This conclusion is influencing the design of Mars missions. We reexamine this conclusion in light of what is known about the oxidation of organic compounds generally and the nature of organics likely to come to Mars via meteorite. We conclude that nonvolatile salts of benzenecarboxylic acids, and perhaps oxalic and acetic acid, should be metastable intermediates of meteoritic organics under oxidizing conditions. Salts of these organic acids would have been largely invisible to GC-MS. Experiments show that one of these, benzenehexacarboxylic acid (mellitic acid), is generated by oxidation of organic matter known to come to Mars, is rather stable to further oxidation, and would not have been easily detected by the Viking experiments. Approximately 2 kg of meteorite-derived mellitic acid may have been generated per m2 of Martian surface over 3 billion years. How much remains depends on decomposition rates under Martian conditions. As available data do not require that the surface of Mars be very strongly oxidizing, some organic molecules might be found near the surface of Mars, perhaps in amounts sufficient to be a resource. Missions should seek these and recognize that these complicate the search for organics from entirely hypothetical Martian life. PMID:10706606

  8. The missing organic molecules on Mars

    NASA Technical Reports Server (NTRS)

    Benner, S. A.; Devine, K. G.; Matveeva, L. N.; Powell, D. H.

    2000-01-01

    GC-MS on the Viking 1976 Mars missions did not detect organic molecules on the Martian surface, even those expected from meteorite bombardment. This result suggested that the Martian regolith might hold a potent oxidant that converts all organic molecules to carbon dioxide rapidly relative to the rate at which they arrive. This conclusion is influencing the design of Mars missions. We reexamine this conclusion in light of what is known about the oxidation of organic compounds generally and the nature of organics likely to come to Mars via meteorite. We conclude that nonvolatile salts of benzenecarboxylic acids, and perhaps oxalic and acetic acid, should be metastable intermediates of meteoritic organics under oxidizing conditions. Salts of these organic acids would have been largely invisible to GC-MS. Experiments show that one of these, benzenehexacarboxylic acid (mellitic acid), is generated by oxidation of organic matter known to come to Mars, is rather stable to further oxidation, and would not have been easily detected by the Viking experiments. Approximately 2 kg of meteorite-derived mellitic acid may have been generated per m(2) of Martian surface over 3 billion years. How much remains depends on decomposition rates under Martian conditions. As available data do not require that the surface of Mars be very strongly oxidizing, some organic molecules might be found near the surface of Mars, perhaps in amounts sufficient to be a resource. Missions should seek these and recognize that these complicate the search for organics from entirely hypothetical Martian life.

  9. Options for Mars exploration

    NASA Technical Reports Server (NTRS)

    Pritchard, E. B.; Harrison, E. F.; Moore, J. W.

    1974-01-01

    The many possible post-Viking 1975 Mars mission options are explored. These include small atmospheric probe/landers (adaptations of the Venus Pioneer to Mars), repeat Vikings with and without science changes, long-life orbiters to provide coverage of both hemispheres for a full Martian year, small rovers deployed from the Viking lander with ranges of up to 1 km from it, large autonomous rovers, Mars sample-return missions and, finally, missions to the satellites of Mars, including sample return. The examination includes energy requirements and time frames.

  10. Mars Stratigraphy Mission

    NASA Technical Reports Server (NTRS)

    Budney, C. J.; Miller, S. L.; Cutts, J. A.

    2000-01-01

    The Mars Stratigraphy Mission lands a rover on the surface of Mars which descends down a cliff in Valles Marineris to study the stratigraphy. The rover carries a unique complement of instruments to analyze and age-date materials encountered during descent past 2 km of strata. The science objective for the Mars Stratigraphy Mission is to identify the geologic history of the layered deposits in the Valles Marineris region of Mars. This includes constraining the time interval for formation of these deposits by measuring the ages of various layers and determining the origin of the deposits (volcanic or sedimentary) by measuring their composition and imaging their morphology.

  11. Alluvial Fans on Mars

    NASA Technical Reports Server (NTRS)

    Kraal, E. R.; Moore, J. M.; Howard, A. D.; Asphaug, E. A.

    2005-01-01

    Moore and Howard [1] reported the discovery of large alluvial fans in craters on Mars. Their initial survey from 0-30 S found that these fans clustered in three distinct regions and occurred at around the +1 km MOLA defined Mars datum. However, due to incomplete image coverage, Moore and Howard [1]could not conduct a comprehensive survey. They also recognized, though did not quantitatively address, gravity scaling issues. Here, we briefly discuss the identification of alluvial fans on Mars, then consider the general equations governing the deposition of alluvial fans and hypothesize a method for learning about grain size in alluvial fans on Mars.

  12. Digital cartography of Mars

    NASA Technical Reports Server (NTRS)

    Batson, R. M.

    1987-01-01

    A medium-resolution Digital Image Model (DIM) of Mars is being compiled. A DIM is a mosaic of radiometrically corrected, photometrically modelled spacecraft images displaying accurate reflectance properties at uniform resolution, and geometrically tied to the best available control. The Mars medium-resolution DIM contains approximately 4700 Viking Orbiter image frames that were used to compile the recently completed 1:2,000,000-scale controlled photomosaic series of Mars. This DIM provides a planimetric control base to which all other Mars maps will be registered. A similar control base of topographic elevations (Digital Terrain Model, or DTM) is also being compiled. These products are scheduled for completion in 1989.

  13. A Mars base

    NASA Technical Reports Server (NTRS)

    Soule, Veronique

    1989-01-01

    This study was initiated to provide an approach to the development of a permanently manned Mars base. The objectives for a permanently manned Mars base are numerous. Primarily, human presence on Mars will allow utilization of new resources for the improvement of the quality of life on Earth, allowing for new discoveries in technologies, the solar system, and human physiology. Such a mission would also encourage interaction between different countries, increasing international cooperation and leading to a stronger unification of mankind. Surface studies of Mars, scientific experiments in the multiple fields, the research for new minerals, and natural resource production are more immediate goals of the Mars mission. Finally, in the future, colonization of Mars will ensure man's perpetual presence in the universe. Specific objectives of this study were: (1) to design a Mars habitat that minimizes the mass delivered to the Mars surface, provides long-stay capability for the base crew, and accommodates future expansion and modification; (2) to develop a scenario of the construction of a permanently manned Mars base; and (3) to incorporate new and envisioned technologies.

  14. Mass accumulation rate of detrital materials in Lake Suigetsu as a potential proxy for heavy precipitation: a comparison of the observational precipitation and sedimentary record

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshiaki; Tada, Ryuji; Yamada, Kazuyoshi; Irino, Tomohisa; Nagashima, Kana; Nakagawa, Takeshi; Omori, Takayuki

    2016-02-01

    In the densely populated region of East Asia, it is important to know the mechanism, scale, and frequency of heavy precipitation brought about during the monsoons and typhoons. However, observational data, which cover only several decades, are insufficient to examine the long-term trend of extreme precipitation and its background mechanism. In humid areas, the transport flux of a suspended detrital material through a river system is known to have an empirical power relationship with precipitation. Thus, the sedimentation flux of a fine detrital material could potentially be used as a proxy for reconstructing past heavy precipitation events. To test the idea that the sedimentation flux of detrital materials records past heavy precipitation events (e.g., typhoons), we focused on the detrital flux estimated from the annually laminated sediment of Lake Suigetsu, central Japan, which is capable of accurately correlating the age of detrital flux with the precipitation record. We first established a precise age model (error within ±1 year in average) beginning in 1920 A.D. on the basis of varve counting fine-tuned by correlation between event layers with historical floods. The flux of the detrital material (g/cm2/year) was estimated on the basis of Al2O3 content (wt%), dry bulk density (g/cm3), and sedimentation rate (cm/year) calculated from the age model. The detrital flux of background sedimentation showed a weak positive correlation with annual and monthly (June and September) precipitation excluding heavy precipitation that exceeded 100 mm/day. Furthermore, the thickness of instantaneous event layers, which corresponds to several maxima of detrital flux and is correlated with floods that occurred mainly during typhoons, showed a positive relationship with the total amount of precipitation that caused a flood event. This result suggests that the detrital flux maxima (deposition of event layers) record past extreme precipitation events that were likely associated with

  15. MARE: Mars Radioactivity Experiment

    NASA Astrophysics Data System (ADS)

    di Lellis, A. M.; Capria, M. T.; Espinasse, S.; Magni, G.; Orosei, R.; Piccioni, G.; Federico, C.; Minelli, G.; Pauselli, C.; Scarpa, G.

    1999-09-01

    MARE is an experiment for the measurement of the beta and gamma radioactivity in space and in the Martian soil, both at the surface and in the subsurface. This will be accomplished by means of a dosimeter and a spectrometer. The radiation dose rate to which crews will be exposed is one of the hazards that has to be quantified before the human exploration of Mars may begin. Data for evaluating radioactivity levels at Martian surface are of great interest for environmental studies related to life in general. The dosimeter will be able to measure the beta and gamma radiation dose received, with a responsivity which is very close to that of a living organism. The dosimeter is based on thermo-luminescence pills which emit an optical signal proportional to the absorbed dose when heated. Radioactive elements ((40) K, (235) U, (238) U and (232) Th) can be used as a mean of tracing the evolution of a terrestrial planet. These radioactive elements are the source of the internal heat, which drives convection in the mantle. They have been redistributed in this process and they are now concentrated in the crust where they are accessible for study. Their different behavior during the fractionation process can be used as a mean to investigate the geochemical characteristic of Mars. The spectrometer, a scintillation radiation absorber system for single event counting, is capable of detecting gamma photons with energies between 200 KeV and 10 MeV. The detected events will be processed in such a way to allow the recognition of the spectral signature of different decay processes, and thus the identification and the measurement of the concentrations of different radionuclides in the Martian soil.

  16. Exobiology and Future Mars Missions

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P. (Editor); Davis, Wanda, L. (Editor)

    1989-01-01

    Scientific questions associated with exobiology on Mars were considered and how these questions should be addressed on future Mars missions was determined. The mission that provided a focus for discussions was the Mars Rover/Sample Return Mission.

  17. Oxychlorine Detections on Mars: Implications for Cl Cycling

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Jackson, W. A.; Ming, D. W.; Archer, P. D.; Stern, J. C.; Mahaffy, P. R.; Gellert, R.

    2016-01-01

    The Sample Analysis at Mars (SAM) instrument has detected evolved O2 and HCl indicating the presence of perchlorate and/or chlorate (oxychlorine) in all 11 sediments analyzed to date. The hyperarid martian climate is believed to have allowed accumulation of oxychlorine and assumed chloride contents similar to those in hyperarid terrestrial settings. The linear correlation of oxychlorine and chloride of Gale Crater sediments is low (r (sup 2) equals 0.64). Correlations present in hyperarid Antarctica and the Atacama Desert are attributed to unaltered atmospheric source coupled with minimal redox cycling by biological activity. Terrestrial semi-arid to arid settings have low correlations similar to Gale Crater and are attributed to additional inputs of Cl minus from sea salt, dust, and/or proximal playa settings, and possible reduction of oxychlorine phases during wetter periods. While microbiological processes could contribute to low oxychlorine/chloride correlations on Mars, several abiotic mechanisms are more likely, such as changing oxychlorine production rates with time and/or post-depositional geochemical redox processes that altered the Gale Crater oxychlorine and chloride contents.

  18. Relays from Mars demonstrate international interplanetary networking

    NASA Astrophysics Data System (ADS)

    2004-08-01

    On 4 August at 14:24 CEST, as Mars Express flew over one of NASA’s Mars exploration rovers, Opportunity, it successfully received data previously collected and stored by the rover. The data, including 15 science images from the rover's nine cameras, were then downlinked to ESA’s European Space Operations Centre in Darmstadt (Germany) and immediately relayed to the Mars Exploration Rovers team based at the Jet Propulsion Laboratory in Pasadena, USA. NASA orbiters Mars Odyssey and Mars Global Surveyor have so far relayed most of the data produced by the rovers since they landed in January. Communication compatibility between Mars Express and the rovers had already been demonstrated in February, although at a low rate that did not convey much data. The 4 August session, at a transmit rate of 42.6 megabits in about six minutes, set a new mark for international networking around another planet. The success of this demonstration is the result of years of groundwork and was made possible because both Mars Express and the Mars rovers use the same communication protocol. This protocol, called Proximity-1, was developed by the international Consultative Committee for Space Data Systems, an international partnership for standardising techniques for handling space data. Mars Express was 1400 kilometres above the Martian surface during the 4 August session with Opportunity, with the goal of a reliable transfer of lots of data. Engineers for both agencies plan to repeat this display of international cooperation today, 10 August, with another set of Opportunity images. “We're delighted how well this has been working, and thankful to have Mars Express in orbit,” said Richard Horttor of NASA's Jet Propulsion Laboratory, Pasadena, California, project manager for NASA's role in Mars Express. JPL engineer Gary Noreen of the Mars Network Office said: “the capabilities that our international teamwork is advancing this month could be important in future exploration of Mars

  19. The physical volcanology of Mars

    NASA Technical Reports Server (NTRS)

    Mouginis-Mark, Peter J.; Wilson, Lionel; Zuber, Maria T.

    1992-01-01

    The physical volcanology of Mars is reviewed, with particular attention given to the diversity of volcanic landforms, the implied styles of eruption associated with the construction of these landforms, the inferred internal structure of the volcanoes, and the influence that the eruptions have had on the Martian environment (both local and global in scale). Volcanism in the central highlands appears to have been explosive in character, while most of the constructional activity in the northern plains was effusive. Highlands volcanism appears to be relatively old compared to that in the northern hemisphere. There is evidence for the existence of large magma chambers and very high effusion rate eruptions on Mars. Tectonic deformation associated with volcanic constructs is primarily a consequence of loading and magma transport, while deformation in the volcanic plains reflects stresses associated with Tharsis and major impact basins.

  20. Interior structure and seasonal mass redistribution of Mars from radio tracking of Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; Yoder, C. F.; Yuan, D. N.; Standish, E. M.; Preston, R. A.

    1997-01-01

    Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 +/- 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps.

  1. Interior structure and seasonal mass redistribution of Mars from radio tracking of Mars Pathfinder.

    PubMed

    Folkner, W M; Yoder, C F; Yuan, D N; Standish, E M; Preston, R A

    1997-12-01

    Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 +/- 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps. PMID:9388168

  2. Review of NASA's Planned Mars Program

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Contents include the following: Executive Summary; Introduction; Scientific Goals for the Exploration of Mars; Overview of Mars Surveyor and Others Mars Missions; Key Issues for NASA's Mars Exploration Program; and Assessment of the Scientific Potential of NASA's Mars Exploration Program.

  3. Evolution of Tethyan phosphogenesis along the northern edges of the Arabian--African shield during the Cretaceous--Eocene as deduced from temporal variations of Ca and Nd isotopes and rates of P accumulation

    NASA Astrophysics Data System (ADS)

    Soudry, D.; Glenn, C. R.; Nathan, Y.; Segal, I.; VonderHaar, D.

    2006-09-01

    The evolution of Tethyan phosphogenesis during the Cretaceous-Eocene is examined to try to explain fluctuations of phosphogenesis through time, and whether or not they reflect long-term changes in ocean circulation or in continental weathering. Twenty-seven time-stratigraphic phosphate levels in various Tethyan sites, covering a time span of about 90 Myr from the Hauterivian to the Eocene, were analyzed for 44Ca/ 42Ca and 143Nd/ 144Nd in their carbonate fluorapatite (CFA) fraction. P and Ca accumulation rates and bulk sedimentation rates were quantified throughout the Cretaceous-Eocene Negev sequence to examine how changes in 44Ca/ 42Ca and 143Nd/ 144Nd are reflected in the intensity of phosphogenesis. A clear-cut change occurs in ɛNd( T) and δ44Ca and in the rates of P and Ca accumulation and bulk sedimentation through the time analyzed. ɛNd( T) is much lower in the Hauterivian-Lower Cenomanian (- 12.8 to - 10.9) than in the Upper Cenomanian-Eocene (- 7.8 to - 5.9). Much lower δ44Ca values occur in the Hauterivian-Turonian (- 0.22 to + 0.02) than in the Coniacian-Eocene (+ 0.23 to + 0.40). P accumulation rates in the Negev steeply increase from < 200 μmol cm - 2 k yr - 1 in the Albian-Coniacian to ˜ 1500 μmol cm - 2 k yr - 1 in the Campanian, whereas a strong decrease is concomitantly recorded in the rates of Ca accumulation and bulk sedimentation. In addition, distinct ɛNd( T) values are shown by the phosphorites of the Negev (- 6.7 to - 6.4) and Egypt (- 9.1 to - 7.6) during the Campanian, and by those of the Negev (- 7.8 to - 6.3) and North Africa (- 10.1 to - 8.9) during the Maastrichtian-Eocene. The culmination of P accumulation rates in the Negev during the Campanian, occurring with a high in ɛNd( T) and δ44Ca and a low in sedimentation rates, indicates that paleoceanographic and paleogeographical factors mostly governed phosphorite accumulation in this area. The abrupt ɛNd( T) rise after the Cenomanian is attributed to increased incursion of

  4. Mars exploration planning

    NASA Technical Reports Server (NTRS)

    Eppler, Dean B.; Buoni, Corinne; Niehoff, John

    1993-01-01

    Mars exploration planning is discussed which is based on three scientific objectives: to understand Mars' geologic and geophysical evolution; to understand the present state and past evolution of Martian climate, and to determine the state of present biological activity and past life. The plan assumes a 25-year planning horizon, from 1995-2020, and includes both broad-scale and local exploration capabilities.

  5. Viking Mars encounter

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Various phases of planetary operations related to the Viking mission to Mars are described. Topics discussed include: approach phase, Mars orbit insertion, prelanding orbital activities, separation, descent and landing, surface operations, surface sampling and operations starting, orbiter science and radio science, Viking 2, Deep Space Network and data handling.

  6. Landing on Mars

    NASA Technical Reports Server (NTRS)

    Manning, Robert M.; Adler, Mark

    2005-01-01

    here have been five fully successful robotic landings on Mars. The systems used to deliver these robots to the surface have shown large design diversity and continue to evolve. How will future Mars landing systems evolve to eventually deliver precious human cargo? We do not yet know the answers, but current trends tell us an interesting and daunting tale.

  7. Plasma engineering for MARS

    SciTech Connect

    Carlson, G.A.; Baldwin, D.E.; Barr, W.L.

    1983-03-24

    The two-year Mirror Advanced Reactor Study (MARS) has resulted in the conceptual design of a commercial, electricity-producing fusion reactor based on tandem mirror confinement. The physics basis for the MARS reactor was developed through work in two highly coupled areas of plasma engineering: magnetics and plasma performance.

  8. Volatiles on Mars

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.

    1988-01-01

    The long-term evolution of both the atmosphere and the surface of Mars can be understood by examining the history of volatiles in the Mars atmosphere, their non-atmospheric reservoirs, and the processes of exchange between the two. Clearly, the present state of both the surface and the atmosphere can only be seen, so that any inferences about the evolution of the climate system are just that, inferences. The processes which control the atmosphere and surface on a seasonal basis, however, are the same processes which can act on longer timescales; only the specific solar and atmospheric forcing will differ. Once the ability of each process to affect the seasonal behavior is understood, the long-timescale forcing may be applied to the various processes in order to clearly identify the ability of the processes to act over the entire history of Mars. The areas of surface-atmospheric interaction of Mars are addressed in the ongoing research. The climate system on Mars is controlled by processes involving the exchange between the surface and atmosphere, so it is important to understand the current behavior of those processes. This is especially so in light of the current interest in understanding Mars; the upcoming Mars Observer mission, and the potential for a future sample-return or human-exploration mission will focus emphasis on this area of Mars science.

  9. Moessbauer on Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken at Meridiani Planum, Mars, by the panoramic camera on the Mars Exploration Rover Opportunity shows the rover's Moessbauer spectrometer (circular device in center), located on its instrument deployment device, or 'arm.' The image was acquired on the ninth martian day or sol of the rover's mission.

  10. Is Mars Red Hot?

    NASA Video Gallery

    What would it feel like if you could stand on Mars – toasty warm, or downright chilly? Find out more about the temperature on Mars in this 60-second video from NASA’s Jet Propulsion Laboratory.

  11. Mars transfer vehicle studies

    NASA Technical Reports Server (NTRS)

    Woodcock, Gordon

    1993-01-01

    Earth-to-Mars distances vary from 60 to 400 million kilometers over a 14-year cycle. This complicates Mars mission design as a function of calendar time. Stay times at Mars are also strongly driven by opportunities for a return flight path which are within the limits of delta-V associated with practical space vehicles. The biggest difference between Mars and lunar transfer missions is mission time, which grows from a few days for the moon, to as much as a few hundred days for Mars missions. As a result, modules for similarly sized crews must be much larger for Mars missions that for transfer to lunar orbit. Technology challenges for one Mars mission scenario analyzed by Boeing include aerobrakes, propulsion, and life support systems. Mission performance is very sensitive to aerobrake weight fraction and, as a result, there is an incentive to use high performance materials such as advanced composites and thermal protection systems. Lander aerobrake would be used twice (for both planetary capture and descent to the Mars surface), and it would need to survive temperatures up to 3500 degrees.

  12. Mars Exploratory Vehicles.

    ERIC Educational Resources Information Center

    Canizo, Thea L.; And Others

    1997-01-01

    Presents an activity in which students learn about the characteristics of the planet Mars. Challenges students to design and build a model of a robotic vehicle that can travel on the surface of Mars and accomplish an assigned task that will provide information useful for future manned trips to the planet. Outlines mission task cards and progress…

  13. Mars transfer vehicle studies

    NASA Astrophysics Data System (ADS)

    Woodcock, Gordon

    1993-02-01

    Earth-to-Mars distances vary from 60 to 400 million kilometers over a 14-year cycle. This complicates Mars mission design as a function of calendar time. Stay times at Mars are also strongly driven by opportunities for a return flight path which are within the limits of delta-V associated with practical space vehicles. The biggest difference between Mars and lunar transfer missions is mission time, which grows from a few days for the moon, to as much as a few hundred days for Mars missions. As a result, modules for similarly sized crews must be much larger for Mars missions that for transfer to lunar orbit. Technology challenges for one Mars mission scenario analyzed by Boeing include aerobrakes, propulsion, and life support systems. Mission performance is very sensitive to aerobrake weight fraction and, as a result, there is an incentive to use high performance materials such as advanced composites and thermal protection systems. Lander aerobrake would be used twice (for both planetary capture and descent to the Mars surface), and it would need to survive temperatures up to 3500 degrees.

  14. Microscope on Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken at Meridiani Planum, Mars by the panoramic camera on the Mars Exploration Rover Opportunity shows the rover's microscopic imager (circular device in center), located on its instrument deployment device, or 'arm.' The image was acquired on the ninth martian day or sol of the rover's mission.

  15. The Mars Millennium Project.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Washington, DC.

    The countdown to a new century provides a unique opportunity to engage America's youth in charting a course for the future. The Mars Millennium Project challenges students across the nation to design a community yet to be imagined for the planet Mars. This interdisciplinary learning project aims to encourage K-12 students in classrooms and youth…

  16. Rat on Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken on Mars by the panoramic camera on the Mars Exploration Rover Opportunity shows the rover's rock abrasion tool, also known as 'rat' (circular device in center), located on its instrument deployment device, or 'arm.' The image was acquired on the ninth martian day or sol of the rover's mission.

  17. Mars Underground News.

    NASA Astrophysics Data System (ADS)

    Edgett, K.

    Contents: Ten years Underground. Rover roundup (International Conference on Mobile Planetary Robots and Rover Roundup, Santa Monica, CA (USA), 29 Jan - 4 Feb 1997). Reaching the Red. Schedule of missions to Mars (as of April 1, 1997). Mars on the Web.

  18. The channels of Mars

    NASA Technical Reports Server (NTRS)

    Baker, Victor R.

    1988-01-01

    The geomorphology of Mars is discussed, focusing on the Martian channels. The great flood channels of Mars, the processes of channel erosion, and dendritic channel networks, are examined. The topography of the Channeled Scabland region of the northwestern U.S. is described and compared to the Martian channels. The importance of water in the evolution of the channel systems is considered.

  19. Mars Human Exploration Objectives

    NASA Technical Reports Server (NTRS)

    Briggs, Geoff

    1998-01-01

    This paper reviews the objectives and other considerations of Human exploration of Mars. The objectives of human exploration of Mars are: (1) to learn how Mars is similar to, and different from, Earth; (2) to explore possible life, past and present; (3) to discover what Mars is like now from the perspective of Geoscience and geologic history; and (4) how did Mars form and how did its formation differ from Earth. Considerations of human Martian exploration involve: (1) having a capable base laboratory; (2) having long range transportation; (3) having operational autonomy of the crew, and the requirement of the crew to possess a range of new cognitive processes along with easy communications with terrestrial colleagues; and finally (4) creating the human habitat along with human factors which involve more than just survivability.

  20. MEMOS - Mars Environment Monitoring Satellite

    NASA Astrophysics Data System (ADS)

    Ott, T.; Barabash, S.; von Schéele, F.; Clacey, E.; Pokrupa, N.

    2007-08-01

    The Swedish Institute of Space Physics (IRF) in cooperation with the Swedish Space Corporation (SSC) has conducted first studies on a Mars Environment Monitoring Satellite (MEMOS). The MEMOS microsatellite (mass < 20 kg) will accommodate four scientific instruments: solar EUV/UV monitor (SEM), solar wind monitor (SWIM), magnetometer (MAG) and radiation environment monitor (REM). The payload monitors the solar conditions at Mars and characterizes the Mars environment to support other missions and science investigations. Monitoring of the solar wind parameters (velocity, density, and field) is the key for any aeronomy and solar wind interaction mission at Mars. The solar EUV / UV (HeII 30.4 nm and HII 121.6 nm) flux monitoring is required for upper atmosphere / ionosphere studies. The radiation environment monitoring is needed to study space weather effects on the near-Mars environment as well as for the preparations for man-flights. MEMOS follows the design philosophy of a detached and autonomously flying instrument for achieving the mentioned objectives. It is intended to be carried "piggy-back" to Mars on a suitable mission. Potential missions are: ESA Mars orbiters within the NEXT or Cosmic Vision programs, NASA Mars orbiters, national / bilateral Mars missions. At Mars MEMOS is separated from its carrier (parent satellite) via the release mechanism implemented in the dual formation flight mission PRISMA. The separation will take place during the orbit insertion scenario of the parent satellite at Mars thus placing MEMOS in a highly elliptical orbit guarantying sufficient observation time in the solar wind. In orbit MEMOS will autonomously detumble and spin-up to ~1 rpm for reasons of stabilization and to fulfill instrument requirements. Such a low spin-rate is sufficient for a required inertial pointing accuracy of 2.5° because of the small external disturbance torques (< 10-7 Nm) predominant at Mars responsible for nutation and precession of the spin-axis. The

  1. Mars Exospheric studies with MENCA on a Mars Orbiter

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Anil; Menca Team

    2012-07-01

    The study of Martian exosphere is important for understanding the escape rate of Martian atmosphere and its impact on Mars' climate change. The neutral density distribution and the composition of Martian exosphere still remain largely unexplored. There are no in-situ measurements of the Martian exosphere; only a few remote sensing measurements have been made and some modelling studies are carried out. We proposed to fly a neutral mass spectrometer, namely "MENCA" (Mars Exospheric Neutral Composition Analyser) to explore the Martian exospheric neutral density and composition at an altitude of ~500 km and above from the surface of Mars, and to study its radial and diurnal variations. MENCA is based on the technique of quadrupole mass spectrometry and has the mass range of 1-300 amu with unit mass resolution. (*) MENCA Team includes: S.V. Mohankumar, T. P. Das, P. Sreelatha, P. Pradeepkumar, B. Sunder, Amarnath Nandi, Neha Naik, G. Supriya, Vipin K. Yadav, M. B. Dhanya, R. Satheesh Thampi, G. P. Padmanabhan

  2. Ionosphere of Mars observed by Mars Express.

    NASA Astrophysics Data System (ADS)

    Dubinin, Eduard; Fraenz, Markus; Andrews, Dave; Morgan, Dave

    2016-04-01

    The Martian ionosphere is studied at different solar zenith angles using the local electron number densities and total electron content (TEC) derived from the observations by MARSIS onboard Mars Express. The data are complemented by the ASPERA-3 observations which provide us with the information about upward/downward velocity of the low-energy ions and electron precipitation. We consider the Mars Express observations at different solar cycle intervals. Different factors which influence the ionosphere dynamics are analyzed. The focus is made on a role of the crustal magnetic field on the Martian ionosphere and its influence on ion escape.

  3. Formation and deposition of volcanic sulfate aerosols on Mars

    NASA Technical Reports Server (NTRS)

    Settle, M.

    1979-01-01

    The paper considers the formation and deposition of volcanic sulfate aerosols on Mars. The rate limiting step in sulfate aerosol formation on Mars is the gas phase oxidation of SO2 by chemical reactions with O, OH, and HO2; submicron aerosol particles would circuit Mars and then be removed from the atmosphere by gravitational forces, globally dispersed, and deposited over a range of equatorial and mid-latitudes. Volcanic sulfate aerosols on Mars consist of liquid droplets and slurries containing sulfuric acid; aerosol deposition on a global or hemispheric scale could account for the similar concentrations of sulfur within surficial soils at the two Viking lander sites.

  4. Age-related changes in amino acid pool sizes in the adult silkmoth, Bombyx mori, reared at low and high temperature; a biochemical examination of the rate-of-living theory and urea accumulation when reared at high temperature.

    PubMed

    Osanai, M; Yonezawa, Y

    1984-01-01

    To examine the rate-of-living theory, age-related changes in amino acid pool sizes were investigated in the adult silkmoth, Bombyx mori, reared at low and high temperature. At either temperature concentrations of free amino acids contained in silkmoths revealed a great sexual difference. Those in females were generally much higher than in males and the former changed much more dynamically than the latter. Major amino acids or ninhydrin-positive compounds inclusive of some essential amino acids such as Leu, Ile, Val, Thr, Arg, Phe, Met, Ala, Tyr, Gln, Aspn , Lan , Cysta , GABA and PEA accumulated in 4 degrees C-moths. However, the levels of these amino changed irregularly with advanced age. Inhibition of protein synthesis may occur generally at low temperature, while protein degradation may be promoted at high temperature. High concentrations of MSO and Tau in the moths reared at high temperature than in the normal moths suggested also catabolism of amino acids proceeding together with protein degradation at high temperature. Amino acid metabolism seems to be complicated under various temperature conditions. When reared at the optimal temperature of 25 degrees C, urea is not present in the body of the silkmoth except for a slight amount in the secreted meconium. In silkmoths reared at the higher temperature of 35 degrees C, however, an extraordinary accumulation of urea occurs accompanied by a reduction in lifespan by one half. Undoubtedly, urea is produced in this terrestrial insect, although the accumulation mechanism is not clear: in silkmoths reared at various temperatures, arginase is found, but urease is not detected. Arginase activity was found to be higher in male moths than in female moths regardless of the rearing temperature. High temperature rearing also did not induce activity and female activity never exceeded that in males at either 25 degrees C or 35 degrees C rearing. Protein degradation accelerated by rearing at high temperatures may result in

  5. Aeolian Slipface Processes on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Cornwall, Carin; Jackson, Derek; Bourke, Mary; Cooper, Andrew

    2016-04-01

    The surface of Mars is dominated by aeolian features and many locations show ripple and dune migration over the past decade with some sediment fluxes comparable to terrestrial dunes. One of the leading goals in investigating aeolian processes on Mars is to explore the boundary conditions of sediment transport, accumulation, and dune mor-phology in relation to wind regime as well as to quantify migration rates and sediment flux. We combine terrestrial field observations, 3D computational fluid dynamics (CFD) modeling and remote sensing data to investigate com-plex, small scale wind patterns and grainflow processes on terrestrial and martian dunes. We aim to constrain grain flow magnitudes and frequencies that occur on slipface slopes of dunes in order to improve estimates of martian dune field migration and sediment flux related to wind velocity and flow patterns. A series of ground-based, high resolution laser scans have been collected in the Maspalomas dune field in Gran Canaria, Spain to investigate grainflow frequency, morphology and slipface advancement. Analysis of these laser scans and simultaneous video recordings have revealed a variety of slipface activity. We identify 6 different grain-flow morphologies including, hourglass shape (classic alcove formation with deposit fan below), superficial flow (thin lenses), narrow trough (vertical lines cm in width), sheet, column (vertical alcove walls), and complex (combi-nation of morphologies triggered simultaneously in the same location). Hourglass grainflow morphologies were the most common and occurred regularly. The superficial and narrow trough morphologies were the second most com-mon and frequently occurred in between large grain flows. Sheet grainflows were rare and unpredictable. These flows involved large portions of the slipface (metres across) and mobilized a substantial amount of sediment in one event. We have compared these grainflow morphologies from Maspalomas to those in martian dune fields and

  6. Microcraters on Mars - Evidence for past climate variations

    NASA Astrophysics Data System (ADS)

    Vasavada, A. R.; Milavec, T. J.; Paige, D. A.

    1993-02-01

    Consideration is given to a simulation of the meteor bombardment of Mars which shows that during periods of the lowest theoretical atmospheric mass, the production rates of centimeter-sized hypervelocity impact craters are increased significantly. It is inferred that limited in situ observations of microcraters visible on Martian rock faces could validate major aspects of the astronomic theory for climate change on Mars.

  7. Plate Tectonism on Early Mars: Diverse Geological and Geophysical Evidence

    NASA Technical Reports Server (NTRS)

    Dohm, J. M.; Maruyama, S.; Baker, V. R.; Anderson, R. C.; Ferris, Justin C.; Hare, Trent M.

    2002-01-01

    Mars has been modified by endogenic and exogenic processes similar in many ways to Earth. However, evidence of Mars embryonic development is preserved because of low erosion rates and stagnant lid convective conditions since the Late Noachian. Early plate tectonism can explain such evidence. Additional information is contained in the original extended abstract.

  8. Tharsis block tectonics on Mars

    NASA Technical Reports Server (NTRS)

    Raitala, Jouko T.

    1988-01-01

    The concept of block tectonics provides a framework for understanding many aspects of Tharsis and adjoining structures. This Tharsis block tectonics on Mars is manifested partly by mantle-related doming and partly by response to loading by subsequent volcanic construction. Although the origin of the volcanism from beneath Tharsis is a subject of controversy explanations have to include inhomogeneities in Martian internal structure, energy distribution, magma accumulation and motion below the lithosphere. Thermal convection can be seen as a necessary consequence for transient initial phase of Martian cooling. This produced part of the elevated topography with tensional stresses and graben systems radial to the main bulge. The linear grabens, radial to the Tharsis center, can be interpreted to indicate rift zones that define the crustal block boundaries. The load-induced stresses may then have contributed on further graben and ridge formation over an extended period of time.

  9. Radar Stratigraphy of Ice on Earth and Mars: What are we Missing? An Evaluation of Multiple Radars and Processing Techniques.

    NASA Astrophysics Data System (ADS)

    Holt, J. W.; Blankenship, D. D.; Corr, H. F.; Plaut, J. J.; Safaeinili, A.

    2007-12-01

    Radar sounding has been used for decades on Earth to map sub-ice topography, yet we are only beginning to fully make use of the information contained within the radar-detected, ice-internal layering. This internal layering serves as a guide to estimate accumulation rates and flow reorganization, to detect geothermal anomalies and to extrapolate ice core results over large regions. Radar layering in snow and ice on Earth is generally caused by variations in acidity due to deposits from volcanic eruptions, changes in ice crystal fabric, or variations in density (near the surface). Radar studies in Antarctica have been undertaken by a variety of means, most commonly airborne systems operating at 60 or 150 MHz, typically with 10 - 15 MHz bandwidths, but also sled-mounted systems generally operating in the 1 - 10 MHz range. The stratigraphy of icy deposits on Mars is also thought to hold important information about past climatic variations there and radar sounding has started to reveal new stratigraphic information to complement optical and spectral studies. Two orbital radar sounders are currently operating at Mars. MARSIS on Mars Express operates at 2 - 5 MHz, while SHARAD on Mars Reconnaissance Orbiter operates in the 15 - 25 MHz band. This is a tremendous advance over our ability to probe the subsurface of Mars just a few years ago; however, we don't know how much information we may be missing due to limited over-ice data at these frequencies on Earth. We therefore examine the impact of different wavelengths, bandwidths, and pulse types on the reconstruction of ice stratigraphy on both Earth and Mars by comparing data obtained from different radar systems over the same locations. Simulated results are also compared, as are the effects of data reduction schemes such as unfocused and focused synthetic aperture radar (SAR) processing.

  10. ESA's Mars Program: European Plans for Mars Exploration

    NASA Technical Reports Server (NTRS)

    Forget, Francois

    2005-01-01

    A viewgraph presentation on the European Space Agency Mars Exploration Program is shown. The topics include: 1) History:Mars Exploration in Europe; 2) A few preliminary results from Mars Express; 3) A new instrument:Radar MARSIS; and 4) European Mars Exploration in the future?

  11. Warming early Earth and Mars

    SciTech Connect

    Kasting, J.F.

    1997-05-23

    Sagan and Chyba, in their article on page 1217 of this issue, have revived an old debate about how liquid water was maintained on early Earth and Mars despite a solar luminosity 25 to 30% lower than that at present. A theory that has been popular for some time is that greatly elevated concentrations of atmospheric COD produced by the action of the carbonate-silicate cycle, provided enough of a greenhouse effect to warm early Earth. However, Rye et al. have placed geochemical constraints on early atmospheric CO{sub 2} abundances that fall well below the levels needed to warm the surface. These constraints are based on the absence of siderite (FeCO{sub 3}) in ancient soil profiles-a negative and, hence, rather weak form of evidence- and apply to the time period 2.2 to 2.8 billion years ago, when Earth was already middle aged. Nonetheless, the soil data provide some indication that atmospheric CO{sub 2} levels may have been lower than previously thought. An even more serious problem arises if one tries to keep early Mars warm with CO{sub 2}. Model calculations predict that CO{sub 2} clouds would form on Mars in the upper troposphere, reducing the lapse rate and severely limiting the amount of surface warming. A suggestion that CO{sub 2} clouds may have warmed the planet radiatively has yet to be borne out by detailed calculations. 26 refs.

  12. Mars Science Laboratory Entry Guidance

    NASA Technical Reports Server (NTRS)

    Mendeck, Gavin F.

    2011-01-01

    The Mars Science Laboratory will be the first Mars mission to attempt a guided entry with the objective of safely delivering the entry vehicle to a survivable parachute deploy state within 12.5 km of the pre-designated parachute deploy coordinates. The Entry Terminal Point Controller guidance algorithm is derived from the final phase Apollo Command Module guidance and, like Apollo, modulates the bank angle to control range based on deviations in range, altitude rate, and drag acceleration from a reference trajectory. For application to Mars landers which must make use of the tenuous Martian atmosphere, it is critical to balance the lift of the vehicle to minimize the range while still ensuring a safe deploy altitude. An overview of the process to generate optimized guidance settings is presented, discussing improvements made over the last nine years. Performance tradeoffs between ellipse size and deploy altitude will be presented, along with imposed constraints of entry acceleration and heating. Performance sensitivities to the bank reversal deadbands, heading alignment, attitude initialization error, and entry delivery errors are presented.

  13. The Mars Orbiter Altimeter (MOLA) Investigation of the Shape and Topography of Mars

    NASA Technical Reports Server (NTRS)

    Smith, David E.; Zuber, Maria T.

    2001-01-01

    The Mars Orbiter Laser Altimeter (MOLA) is an instrument on the Mars Global Surveyor (MGS) spacecraft that has been orbiting Mars since September 1997. After some preliminary observations in Sept/Oct, 1997 and in the spring and summer of 1998, the MGS spacecraft entered its mapping orbit of 400 km above the surface of Mars in February 1999. MGS began a 2 year program of systematically mapping the planet with a camera (MOC), thermal emission spectrometer (TES), magnetometer (MAG), laser altimeter (MOLA), and a radio science investigation for gravity and radio occultations. MOLA has a 48mJ, 1064 nrn ND:YAG, diode pumped laser with a 8 nanosecond pulse width, a pulse rate of 10 Hz, and a range precision of less than 40 cm. MOLA has been operating almost continuously for over two years and obtained over 600 million measurements of the radius of Mars. Using very precise orbits for the MGS spacecraft derived from the Doppler and range tracking of MGS by the Deep Space Network a topographical map of Mars has been developed with an average radial accuracy of a meter and a horizontal accuracy of 100 meters. This topographical map has revealed a new Mars, a planet with some of the flattest areas in the solar system and one of the largest impact basins. MOLA has revealed clear evidence of the effect of past fluid action on the surface and found icecaps that contain as much water ice today as the icecap of Greenland.

  14. Obliquity-oblateness feedback on Mars

    NASA Astrophysics Data System (ADS)

    Bills, Bruce G.

    A simple model is presented for the coupled dynamics of the orbit-rotation-climate system of Mars. Changes in the orientation of the spin pole, relative to the orbit pole, influence the spatiotemporal pattern of incident radiation and thus drive climatic mass transport into and out of the polar regions on a variety of timescales. Changes in the mass distribution occur from direct climatic forcing and compensating viscous flow in the interior. The net change in mass distribution influences the rate of spin axis precession and thereby influences obliquity. The rate of secular obliquity drift depends on several poorly known parameters, including the magnitudes and response times of volatile inventories and viscosity structure within Mars. Even relatively modest secular obliquity drift can lead to trapping in nearby resonances. The dissipative nature of the coupled dynamical system makes reconstruction of past evolution much more difficult than for a purely inertial system. The long-term obliquity history of Mars is dominated by climate.

  15. An ice age recorded in the polar deposits of Mars.

    PubMed

    Smith, Isaac B; Putzig, Nathaniel E; Holt, John W; Phillips, Roger J

    2016-05-27

    Layered ice deposits at the poles of Mars record a detailed history of accumulation and erosion related to climate processes. Radar investigations measure these layers and provide evidence for climate changes such as ice advance and retreat. We present a detailed analysis of observational data showing that ~87,000 cubic kilometers of ice have accumulated at the poles since the end of the last ice age ~370,000 years ago; this volume is equivalent to a global layer of ~60 centimeters. The majority of the material accumulated at the north pole. These results provide both a means to understand the accumulation history of the polar deposits as related to orbital Milankovitch cycles and constraints for better determination of Mars' past and future climates. PMID:27230372

  16. Third International Colloquium on Mars

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Abstracts of papers concerning the geology and geophysics of Mars, volcanism on Mars, the Mars atmosphere, and the long term history of the atmosphere-cap-regolith volatile regime are presented. Formation of the Mars surface, climatology, gravity and magnetism, atmospheric boundary layers, and interpretation of Viking imagery and Earth-based observations are considered.

  17. The Environment of Early Mars

    NASA Astrophysics Data System (ADS)

    Matsubara, Yo

    A hydrologic routing model was applied to the Noachian cratered highlands to establish the climatic conditions required to maintain lakes and valley networks on early Mars. We used the ratio of precipitation and evaporation (the X-ratio) to express climatic conditions. Simulations were conducted using various X-ratios. The results from the lake analysis showed that many of the lakes that were not identified as overflowing probably overflowed as well. Because overflowing lakes can place constrain on possible climatic condition of early Mars, it is essential to identify as many overflowing craters as possible to understand the environment of early Mars. The multiple regression analyses indicate that incision depth is strongly influenced by gradient and weakly related to discharge. The factors determining incision depend partly on the type of channel bed. However, post-flow modification of the valleys precludes direct determination of bed morphology. We found through both lake and incision depth analysis that climatic conditions on early Mars were at least as moist as those that occurred in the Great Basin region during the Pleistocene (X ≤ 4). We also report on two studies motivated by the occurrence of sinuous paleochannels on Mars. Unconfined meanders require cohesive channel banks, which is obtained commonly by a vegetation cover coupled with high suspended sediment load. The Quinn River, Nevada is a sinuous channel that flows through lacustrine sediments resulting in the river having both bed and banks composed of sediment containing at least 40% mud. In addition, ion chromatography data and SEM images indicate the presence of high solute concentrations. In the absence of vegetation, bank cohesion is provided by mud with salts aiding flocculation and possibly providing additional cohesion through cementation. A 1D depth-averaged linearized meander evolution model was calibrated using the field data collected at the Quinn River. Both approaches gave similar

  18. Mars Equipment Transport System

    NASA Astrophysics Data System (ADS)

    Sorrells, Cindy; Geiger, Michelle; Ohanlon, Sean; Pieloch, Stuart; Brogan, Nick

    1993-12-01

    Mechanical Engineering Senior Design Project 1 (ME4182) is a part of the NASA/University Advanced Design Program. Under this program, NASA allocates money and resources to students to be used in design work for a specified topic. The current topic is the exploration and colonization of Mars. The specific area in which we are to work is the transportation of the modules in which astronauts will live while on Mars. NASA is concerned about the weight of the module transferring system, as the shipping cost to Mars is quite expensive. NASA has specified that the weight of the system is to be minimized in order to reduce the shipping costs.

  19. Mars Equipment Transport System

    NASA Technical Reports Server (NTRS)

    Sorrells, Cindy; Geiger, Michelle; Ohanlon, Sean; Pieloch, Stuart; Brogan, Nick

    1993-01-01

    Mechanical Engineering Senior Design Project 1 (ME4182) is a part of the NASA/University Advanced Design Program. Under this program, NASA allocates money and resources to students to be used in design work for a specified topic. The current topic is the exploration and colonization of Mars. The specific area in which we are to work is the transportation of the modules in which astronauts will live while on Mars. NASA is concerned about the weight of the module transferring system, as the shipping cost to Mars is quite expensive. NASA has specified that the weight of the system is to be minimized in order to reduce the shipping costs.

  20. Mars tectonics and volcanism

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1990-01-01

    The focus of this research was on three broad areas: (1) the relation between lithospheric stress in the vicinity of a growing volcano and the evolution of eruption characteristics and tectonic faulting; (2) the relation between elastic lithosphere thickness and thermal structure; and (3) a synthesis of constraints on heat flow and internal dynamics on Mars. The two reports presented are: (1) Heterogeneities in the Thickness of the Elastic Lithosphere of Mars--Constraints on Heat Flow and Internal Dynamics; and (2) State of Stress, Faulting, and Eruption Characteristics of Large Volcanoes on Mars.

  1. Mars Observer's costly solitude

    NASA Astrophysics Data System (ADS)

    Travis, John

    1993-09-01

    An evaluation is presented of the ramifications of the loss of contact with the Mars Observer spacecraft in August, 1993; the Observer constituted the first NASA mission to Mars in 17 years. It is noted that most, if not all of the scientists involved with the mission will have to find alternative employment within 6 months. The loss of the Observer will leave major questions concerning the geologic history of Mars, and its turbulent atmospheric circulation, unanswered. A detailed account of the discovery of the loss of communications, the unsuccessful steps taken to rectify the problem, and the financial losses incurred through the failure of the mission, are also given.

  2. Exobiology on Mars

    NASA Technical Reports Server (NTRS)

    Devincenzi, D. L. (Editor); Marshall, J. R. (Editor); Andersen, D. (Editor)

    1990-01-01

    Descriptions of several instrument concepts that were generated during a workshop entitled, Exobiology Instrument Concepts for a Soviet Mars 94/94 Mission, held at NASA Ames Research Center in 1989 are presented. The objective was to define and describe instrument concepts for exobiology and related science that would be compatible with the mission types under discussion for the 1994 and 1996 Soviet Mars missions. Experiments that use existing technology were emphasized. The concepts discussed could also be used on U.S. missions that follow Mars Observer.

  3. Solar radiation on Mars

    NASA Technical Reports Server (NTRS)

    Appelbaum, Joseph; Flood, Dennis J.

    1989-01-01

    Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. Presented here is a procedure and solar radiation related data from which the diurnally, hourly and daily variation of the global, direct beam and diffuse insolation on Mars are calculated. The radiation data are based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation.

  4. Spectroscopic observation of Mars

    NASA Technical Reports Server (NTRS)

    Singer, R. B.

    1985-01-01

    A review is given of what is known about the surface of Mars from reflectance spectroscopy, including some new results and providing an overview of the principles involved. While some form of bound water and/or OH has been known on Mars for many years, a new result presented is the identification of structural OH in a dilute or poorly crystalline magnesian clay. The detection of water ice in the residual north polar cap is noted. Also considered is the role that reflectance spectroscopy will play in the future, from earth and as an important part of the NASA Mars Geosciences/Climatology Orbiter mission.

  5. Mars Aerocapture Systems Study

    NASA Technical Reports Server (NTRS)

    Wright, Henry S.; Oh, David Y.; Westhelle, Carlos H.; Fisher, Jody L.; Dyke, R. Eric; Edquist, Karl T.; Brown, James L.; Justh, Hilary L.; Munk, Michelle M.

    2006-01-01

    Mars Aerocapture Systems Study (MASS) is a detailed study of the application of aerocapture to a large Mars robotic orbiter to assess and identify key technology gaps. This study addressed use of an Opposition class return segment for use in the Mars Sample Return architecture. Study addressed mission architecture issues as well as system design. Key trade studies focused on design of aerocapture aeroshell, spacecraft design and packaging, guidance, navigation and control with simulation, computational fluid dynamics, and thermal protection system sizing. Detailed master equipment lists are included as well as a cursory cost assessment.

  6. Airbag Tracks on Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The circular shapes seen on the martian surface in these images are 'footprints' left by the Mars Exploration Rover Opportunity's airbags during landing as the spacecraft gently rolled to a stop. Opportunity landed at approximately 9:05 p.m. PST on Saturday, Jan. 24, 2004, Earth-received time. The circular region of the flower-like feature on the right is about the size of a basketball. Scientists are studying the prints for more clues about the makeup of martian soil. The images were taken at Meridiani Planum, Mars, by the panoramic camera on the Mars Exploration Rover Opportunity.

  7. Solar radiation on Mars

    SciTech Connect

    Appelbaum, J.; Flood, D.J. )

    1990-01-01

    Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. In this paper the authors present a procedure and solar radiation related data from which the diurnally, hourly and daily variation of the global, direct beam and diffuse insolation on Mars are calculated. The radiation data are based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation.

  8. Human Exploration of Mars

    NASA Astrophysics Data System (ADS)

    Gwynne, Owen; McKay, Chris; Zubrin, Robert

    1991-06-01

    Novel approaches to the human exploration of Mars are considered with emphasis on a space suit design, extraterrestrial surface mobility, and water supply. A possible way of transporting personnel on the surface of Mars uses a suborbital rocket that will hop from one site to the next, refuelling each time it lands and giving the Martian explorers effective global mobility. Telepresence could be used to avoid limiting the people on Mars to a small exploration area as a result of a lack of transportation infrastructure. Drawings and photographs are included.

  9. Spectral properties of simulated impact glasses produced from martian soil analogue JSC Mars-1

    NASA Astrophysics Data System (ADS)

    Moroz, L. V.; Basilevsky, A. T.; Hiroi, T.; Rout, S. S.; Baither, D.; van der Bogert, C. H.; Yakovlev, O. I.; Fisenko, A. V.; Semjonova, L. F.; Rusakov, V. S.; Khramov, D. A.; Zinovieva, N. G.; Arnold, G.; Pieters, C. M.

    2009-07-01

    To simulate the formation of impact glasses on Mars, an analogue of martian bright soil (altered volcanic soil JSC Mars-1) was melted at relevant oxygen fugacities using a pulsed laser and a resistance furnace. Reduction of Fe3+ to Fe2+ and in some cases formation of nanophase Fe0 in the glasses were documented by Mössbauer spectroscopy and TEM studies. Reflectance spectra for several size fractions of the JSC Mars-1 sample and the glasses were acquired between 0.3 and 25 μm. The glasses produced from the JSC Mars-1 soil show significant spectral variability depending on the method of production and the cooling rate. In general, they are dark and less red in the visible compared to the original JSC Mars-1 soil. Their spectra do not have absorption bands due to bound water and structural OH, have positive spectral slopes in the near-infrared range, and show two broad bands centered near 1.05 and 1.9 μm, typical of glasses rich in ferrous iron. The latter bands and low albedo partly mimic the spectral properties of martian dark regions, and may easily be confused with mafic materials containing olivine and low-Ca pyroxene. Due to their disordered structures and vesicular textures, the glasses show relatively weak absorption features from the visible to the thermal infrared. These weak absorption bands may be masked by the stronger bands of mafic minerals. Positive near-infrared spectral slopes typical of fresh iron-bearing impact or volcanic glasses may be masked either by oxide/dust coatings or by aerosols in the Mars' atmosphere. As a result, impact glasses may be present on the surface of Mars in significant quantities that have been either misidentified as other phases or masked by phases with stronger infrared features. Spectrometers with sufficient spatial resolution and wavelength coverage may detect impact glasses at certain locations, e.g., in the vicinity of fresh impact craters. Such dark materials are usually interpreted as accumulations of mafic

  10. An examination of historic inorganic sedimentation and organic matter accumulation in several marsh types within the Mobile Bay and and Mobile-Tensaw River Delta region

    USGS Publications Warehouse

    Smith, Christopher G.; Osterman, Lisa E.; Poore, Richard Z.

    2013-01-01

    Mass accumulation rates (MAR; g cm-2 y-1), linear sedimentation rates (LSR; cm y-1), and core geochronology derived from excess lead-210 (210Pb) profiles and inventories measured in six sediment cores collected from marsh sites from the MobileTensaw River Delta and Mobile Bay region record the importance of both continuous and event-driven inorganic sedimentation over the last 120 years. MAR in freshwater marshes varied considerably between sites and through time (0.24 and 1.31 g cm-2 y-1). The highest MARs occurred in the 1950s and 1960s and correspond to record discharge events along the Mobile and Tensaw Rivers. In comparison, MAR at salt marsh sites increased almost threefold over the last 120 years (0.05 to 0.18 g cm-2 y-1 or 0.23 to 0.48 cm y-1). From 1880 to 1960, organic accumulation remained fairly constant (20%), while intermittent pulses of high inorganic sedimentation were observed following 1960. The pulses in inorganic sedimentation coincide with several major hurricanes (e.g., Hurricanes Camille, Fredric, Georges, and Ivan). The nearly threefold increase in MAR in salt marshes during the last 120 years would thus appear to be partially dependent on inorganic sedimentation from storm events. This study shows that while hurricanes, floods, and other natural hazards are well-known threats to human infrastructure and coastal ecosystems, these events also transport sediment to marshes that help abate other pressures such as sea-level rise (SLR) and subsidence.

  11. CO2 Condensation Models for Mars

    NASA Technical Reports Server (NTRS)

    Colaprete, A.; Haberle, R.

    2004-01-01

    During the polar night in both hemispheres of Mars, regions of low thermal emission, frequently referred to as "cold spots", have been observed by Mariner 9, Viking and Mars Global Surveyor (MGS) spacecraft. These cold spots vary in time and appear to be associated with topographic features suggesting that they are the result of a spectral-emission effect due to surface accumulation of fine-grained frost or snow. Presented here are simulations of the Martian polar night using the NASA Ames General Circulation Cloud Model. This cloud model incorporates all the microphysical processes of carbon dioxide cloud formation, including nucleation, condensation and sedimentation and is coupled to a surface frost scheme that includes both direct surface condensation and precipitation. Using this cloud model we simulate the Mars polar nights and compare model results to observations from the Thermal Emission Spectrometer (TES) and the Mars Orbiter Laser Altimeter (MOLA). Model predictions of "cold spots" compare well with TES observations of low emissivity regions, both spatially and as a function of season. The model predicted frequency of CO2 cloud formation also agrees well with MOLA observations of polar night cloud echoes. Together the simulations and observations in the North indicate a distinct shift in atmospheric state centered about Ls 270 which we believe may be associated with the strength of the polar vortex.

  12. Exploring Mars' Middle Atmosphere with the Extended NASA Ames Mars General Circulation Model

    NASA Astrophysics Data System (ADS)

    Brecht, A. S.; Hollingsworth, J. L.; Kahre, M. A.; Schaeffer, J.

    2013-12-01

    The NASA Ames Mars General Circulation Model (Mars GCM) upper boundary has been extended to ~120 km altitude (pT ~ 10-6 mbar). The extension of the Mars GCM upper boundary initiates the ability to understand the connection between the lower and upper atmosphere of Mars through the middle atmosphere. Moreover, it provides the opportunity to support missions (i.e. the 2013 MAVEN mission). A major factor in this extension is the incorporation of the Non-Local Thermodynamic Equilibrium (NLTE) heating (visible) and cooling (infrared). The calculated solar heating rates (LTE heating rates) within the Mars GCM are corrected for NLTE by applying factors from Table 1 in López-Valverde et al. (1998). The CO2 15-μm cooling parameterizations is adapted from Bougher et al. (2006). This modification to the radiative transfer forcing has been significantly tested in a 1D vertical column (i.e. RT code) and now has been ported to the full 3D Mars GCM. Initial results clearly show the effects of NLTE in the upper middle atmosphere. Diagnostic of seasonal mean fields and large-scale wave activity will be shown with insight into circulation patterns in the middle atmosphere. Furthermore, sensitivity tests with the resolution of the pressure and temperature grids, in which the k-coefficients are calculated upon, have been performed in the 1D RT code. Our progress on this research will be presented.

  13. Bassanite on Mars

    NASA Astrophysics Data System (ADS)

    Vaniman, D. T.; Bish, D. L.; Chipera, S. J.

    2009-03-01

    There are several ways to desiccate gypsum on Mars and form bassanite but rehydration in presence of ice at cold, dry conditions tends to form only bassanite or gypsum plus bassanite. This product may provide a paleoclimate or paleogeothermal marker.

  14. Mars Balance Challenge

    NASA Video Gallery

    The Challenge is to develop ideas for how NASA can turn available entry, descent, and landing balance mass on a future Mars mission into a scientific or technological payload. Proposed concepts sho...

  15. Mars planimetric mapping

    NASA Astrophysics Data System (ADS)

    Batson, R. M.; Bridges, P. M.; Lee, E. M.

    1985-04-01

    The 1:5,000,000 scale shaded relief maps of Mars originally compiled from Mariner 9 pictures are being upgraded by adding details visible on Viking Orbiter images. This work is done by modifying the original airbrush drawings; no attempt is made to reposition features according to the latest control nets. Thirteen of these maps have been published to date, two are in compilation, and two are in press. A hard cover atlas containing reduced scale versions of all Mars cartographic products will be published upon completion of the revisions of the 1:5,000,000 scale maps, the 1:2,000,000 scale photomosaics, and Mars color albedo mapping tasks. This atlas will supersede the existing Atlas of Mars prepared by Batson and others.

  16. Environment of Mars, 1988

    NASA Technical Reports Server (NTRS)

    Kaplan, David I. (Compiler)

    1988-01-01

    A compilation of scientific knowledge about the planet Mars is provided. Information is divided into three categories: atmospheric data, surface data, and astrodynamic data. The discussion of atmospheric data includes the presentation of nine different models of the Mars atmosphere. Also discussed are Martian atmospheric constituents, winds, clouds, and solar irradiance. The great dust storms of Mars are presented. The section on Mars surface data provides an in-depth examination of the physical and chemical properties observed at the two Viking landing sites. Bulk densities, dielectric constants, and thermal inertias across the planet are then described and related back to those specific features found at the Viking landing sites. The astrodynamic materials provide the astronomical constants, time scales, and reference coordinate frames necessary to perform flightpath analysis, navigation design, and science observation design.

  17. Mars Exploration Zones

    NASA Video Gallery

    This concept animation shows just one of many potential concepts for how the first human landing site on Mars might evolve throughout the course of multiple human expeditions to the Red Planet over...

  18. Walking on Mars

    NASA Astrophysics Data System (ADS)

    Cavagna, G. A.; Willems, P. A.; Heglund, N. C.

    1998-06-01

    Sometime in the near future humans may walk in the reduced gravity of Mars. Gravity plays an essential role in walking. On Earth, the body uses gravity to `fall forwards' at each step and then the forward speed is used to restore the initial height in a pendulum-like mechanism. When gravity is reduced, as on the Moon or Mars, the mechanism of walking must change. Here we investigate the mechanics of walking on Mars onboard an aircraft undergoing gravity-reducing flight profiles. The optimal walking speed on Mars will be 3.4 km h-1 (down from 5.5 km h-1 on Earth) and the work done per unit distance to move the centre of mass will be half that on Earth.

  19. Future Mars outpost architecture

    NASA Technical Reports Server (NTRS)

    Williams, T. D.; Owens, J.; Easter, R. W.; Mireles, O. R.; Ramsey, S. A.; Palko, C. W.

    2000-01-01

    This paper describes an outpost designed with the JPL Mars Long Range Planning Team's goals in mind. The design focuses on subsurface mapping and characterization, accomplished through seismic mapping and deep drilling.

  20. NASA's Mars Landings

    NASA Video Gallery

    This video shows the landing sites of all six NASA spacecraft to reachMars—Viking 1, Viking 2, Pathfinder, Spirit, Opportunity, Phoenix—and thetarget location where Curiosity will touch down ...

  1. Methane Plumes on Mars

    NASA Video Gallery

    Spectrometer instruments attached to several telescopes detect plumes of methane emitted from Mars during its summer and spring seasons. High levels of methane are indicated by warmer colors. The m...

  2. Mars Acoustic Anemometer

    NASA Astrophysics Data System (ADS)

    Banfield, D. J.

    2012-12-01

    We have developed a very high performance anemometer (wind gauge) for use at Mars. This instrument has great scientific as well as strategic reasons to be included on all future missions to the surface of Mars. We will discuss why we set out to develop this instrument, as well as why the previous wind sensors for Mars are insufficient to meet the scientific and strategic needs at Mars. We will also discuss how the instrument works, and how it differs from terrestrial counterparts. Additionally, we will discuss the current status of the instrument. Measuring winds at Mars is important to better understand the atmospheric circulation at Mars, as well as exchange between the surface and atmosphere. The main conduit of transport of water, and hence its current stability at any particular location on Mars is controlled by these atmospheric motions and the exchange between surface and atmosphere. Mars' large-scale winds are moderately well understood from orbital observations, but the interaction with the surface can only be addressed adequately in situ. Previous anemometers have been 2-D (with the exception of REMS on MSL) and slow response (typically <1Hz), and relatively low sensitivity/accuracy (>1 m/s). Our instrument is capable of fully 3-D measurements, with fast response (>20 Hz) and great sensitivity/accuracy (~3 cm/s). This significant step forward in performance is important for the surface-atmosphere exchanges of heat, momentum and volatiles. In particular, our instrument could directly measure the heat and momentum fluxes between surface and atmosphere using eddy-flux techniques proven terrestrially. When combined with a fast response volatile analysis instrument (e.g., a TLS) we can also measure eddy fluxes of volatile transport. Such a study would be nearly impossible to carry out with preceding anemometers sent to Mars with insufficient response time and sensitivity to adequately sample the turbulent eddies. Additionally, our instrument, using acoustics

  3. Mars Exploration Rover Mission

    NASA Technical Reports Server (NTRS)

    Cohen, Barbara A.

    2008-01-01

    This viewgraph presentation reviews the Mars Exploration Rover Mission. The design of the Rover along with the Athena science payload is also described. Photographs of the Gusev Crater and Meridiani rocks are also shown.

  4. Mars Express & Co

    NASA Astrophysics Data System (ADS)

    Borgeest, Ulf; Staude, Jakob; Kratzenber-Annies, Volker; Coradini, Marcello; Flury, Walter; Jaumann, Ralf; Neukum, Gerhard; Ongaro, Franco; Lemke, Dietrich; Althaus, Tilmann; Fuhrmeister, Birgit

    Contents: Europa und der übrige Kosmos. Der Weltraum und das öffentliche Interesse an ihm. Europa besucht Mars. INTEGRAL - Blick ins Herz der Galaxis. ISO - Von der Idee zum Instrument. Dienstreisen ins All. ENVISAT.

  5. Retrograde Motion of Mars.

    ERIC Educational Resources Information Center

    Knappenberger, Paul H.

    1979-01-01

    Presents an activity whereby students describe the path of Mars through a background starfield. Includes purpose, materials, pre-lab, and procedure. Also provides guidelines for making a dial-a-planet wheel. (MA)

  6. The conquest of Mars

    NASA Astrophysics Data System (ADS)

    David, L. W.

    1984-08-01

    Concepts for a manned mission to Mars have been examined as early as 1962. In 1969, NASA studies showed Apollo moon technology to be adequate for a 600-day flight with a proposed landing for 1982. However, financial drain, shifting economic priorities and a downgrading of the 'space race' in the late 1960s contributed to the downfall of the project. The successful Mariner and Viking missions of the 1970s have enhanced understanding of the planet, and in the wake of these flights, numerous studies have been made for future unmanned missions. Some suggested projects include a Mars Orbiter, sensor outposts, a mobile lander, A Mars' Air Force', and a return sample mission. Following a full unmanned reconnaissance of the planet, advances in space propulsion, refuelling and large scale construction, a manned voyage to Mars could be achieved.

  7. Environment of Mars, 1988

    SciTech Connect

    Kaplan, D.I.

    1988-10-01

    A compilation of scientific knowledge about the planet Mars is provided. Information is divided into three categories: atmospheric data, surface data, and astrodynamic data. The discussion of atmospheric data includes the presentation of nine different models of the Mars atmosphere. Also discussed are Martian atmospheric constituents, winds, clouds, and solar irradiance. The great dust storms of Mars are presented. The section on Mars surface data provides an in-depth examination of the physical and chemical properties observed at the two Viking landing sites. Bulk densities, dielectric constants, and thermal inertias across the planet are then described and related back to those specific features found at the Viking landing sites. The astrodynamic materials provide the astronomical constants, time scales, and reference coordinate frames necessary to perform flightpath analysis, navigation design, and science observation design.

  8. Mars' Inner Core

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This figure shows a cross-section of the planet Mars revealing an inner, high density core buried deep within the interior. Dipole magnetic field lines are drawn in blue, showing the global scale magnetic field that one associates with dynamo generation in the core. Mars must have one day had such a field, but today it is not evident. Perhaps the energy source that powered the early dynamo has shut down. The differentiation of the planet interior - heavy elements like iron sinking towards the center of the planet - can provide energy as can the formation of a solid core from the liquid.

    The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO. JPL is an operating division of California Institute of Technology (Caltech).

  9. Internal constitution of Mars.

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1972-01-01

    Models of the internal structure of Mars consistent with the mass, radius and moment of inertia of the planet are constructed. The models assume that the radius of the core is between 0.36 and 0.60 of the radius of the planet, that the zero-pressure density of the mantle is between 3.54 and 3.49 g/cu cm, and that the planet contains 25 to 28% iron. Meteorite models of Mars containing 25 wt % iron and 12 wt % core are also proposed. It is maintained that Mars in contrast to the earth is an incompletely differentiated planet with a core substantially richer in sulfur than the core of the earth. The absence of a magnetic field on Mars is possibly linked with lack of lunar precessional torque and the small size and high resistivity of the Martian core.

  10. Explore Mars With Curiosity

    NASA Video Gallery

    This animation shows the approximate true position of NASA’s Curiosityrover on Mars. A 3-D virtual model of Curiosity is shown inside GaleCrater, near Mount Sharp, Curiosity’s ultimate destin...

  11. The Cruise to Mars

    NASA Video Gallery

    The long journey to Mars through the harsh environment of spaceconfronts the Curiosity navigation team with a long list of challengesto get the spacecraft safely to its destination.› Mission site

  12. Dust deposition on the Mars Exploration Rover Panoramic Camera (Pancam) calibration targets

    USGS Publications Warehouse

    Kinch, K.M.; Sohl-Dickstein, J.; Bell, J.F., III; Johnson, J. R.; Goetz, W.; Landis, G.A.

    2007-01-01

    The Panoramic Camera (Pancam) on the Mars Exploration Rover mission has acquired in excess of 20,000 images of the Pancam calibration targets on the rovers. Analysis of this data set allows estimates of the rate of deposition and removal of aeolian dust on both rovers. During the first 150-170 sols there was gradual dust accumulation on the rovers but no evidence for dust removal. After that time there is ample evidence for both dust removal and dust deposition on both rover decks. We analyze data from early in both rover missions using a diffusive reflectance mixing model. Assuming a dust settling rate proportional to the atmospheric optical depth, we derive spectra of optically thick layers of airfall dust that are consistent with spectra from dusty regions on the Martian surface. Airfall dust reflectance at the Opportunity site appears greater than at the Spirit site, consistent with other observations. We estimate the optical depth of dust deposited on the Spirit calibration target by sol 150 to be 0.44 ?? 0.13. For Opportunity the value was 0.39 ?? 0.12. Assuming 80% pore space, we estimate that the dust layer grew at a rate of one grain diameter per ???100 sols on the Spirit calibration target. On Opportunity the rate was one grain diameter per ???125 sols. These numbers are consistent with dust deposition rates observed by Mars Pathfinder taking into account the lower atmospheric dust optical depth during the Mars Pathfinder mission. Copyright 2007 by the American Geophysical Union.

  13. Mars Express - Over 10 Years in Orbit Around Mars

    NASA Astrophysics Data System (ADS)

    Chicarro, Agustin; Svedhem, Hakan

    2014-05-01

    The ESA Mars Express mission was launched more than a decade ago, reaching its working orbit around Mars in January 2004. All the instruments and subsystems onboard the spacecraft are still in working order. As the first European planetary mission, Mars Express has been providing exciting new scientific results on all fields of Mars science, including the interior structure of the planet, its surface mineralogy and geological processes, its atmospheric dynamics and chemistry, the interaction of its upper atmosphere with the solar wind, as well as the geodesy of its satellite Phobos. Also, Mars Express has contributed to pave the way for future European Mars Exploration, including the Trace Gas Orbiter to be launched in 2016, the ExoMars rover in 2018 and further exploration in 2020 and beyond. Among the abundant Mars Express scientific results, the Top-10 scientific highlights of the mission will be presented, addressing all areas of Mars investigation from orbit.

  14. Status of MARS Code

    SciTech Connect

    N.V. Mokhov

    2003-04-09

    Status and recent developments of the MARS 14 Monte Carlo code system for simulation of hadronic and electromagnetic cascades in shielding, accelerator and detector components in the energy range from a fraction of an electronvolt up to 100 TeV are described. these include physics models both in strong and electromagnetic interaction sectors, variance reduction techniques, residual dose, geometry, tracking, histograming. MAD-MARS Beam Line Build and Graphical-User Interface.

  15. A Mars 1984 mission

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Mission objectives are developed for the next logical step in the investigation of the local physical and chemical environments and the search for organic compounds on Mars. The necessity of three vehicular elements: orbiter, penetrator, and rover for in situ investigations of atmospheric-lithospheric interactions is emphasized. A summary report and committee recommendations are included with the full report of the Mars Science Working Group.

  16. Mars Ice Age, Simulated

    NASA Technical Reports Server (NTRS)

    2003-01-01

    December 17, 2003

    This simulated view shows Mars as it might have appeared during the height of a possible ice age in geologically recent time.

    Of all Solar System planets, Mars has the climate most like that of Earth. Both are sensitive to small changes in orbit and tilt. During a period about 2.1 million to 400,000 years ago, increased tilt of Mars' rotational axis caused increased solar heating at the poles. A new study using observations from NASA's Mars Global Surveyor and Mars Odyssey orbiters concludes that this polar warming caused mobilization of water vapor and dust into the atmosphere, and buildup of a surface deposit of ice and dust down to about 30 degrees latitude in both hemispheres. That is the equivalent of the southern Unites States or Saudi Arabia on Earth. Mars has been in an interglacial period characterized by less axial tilt for about the last 300,000 years. The ice-rich surface deposit has been degrading in the latitude zone of 30 degrees to 60 degrees as water-ice returns to the poles.

    In this illustration prepared for the December 18, 2003, cover of the journal Nature, the simulated surface deposit is superposed on a topography map based on altitude measurements by Global Surveyor and images from NASA's Viking orbiters of the 1970s.

    Mars Global Surveyor and Mars Odyssey are managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, for the NASA Office of Space Science, Washington.

  17. 2001 Mars Odyssey Mission

    NASA Technical Reports Server (NTRS)

    Varghese, Philip

    2008-01-01

    This viewgraph presentation reviews the 2001 Mars Odyssey Mission. The contents include: 1) Mission Overview; 2) Current Scope of Work: 3) Facilities; 4) Critical Role of DSN; 5) Relay as Mission Supplement; 6) Current Mars Telecom Infrastructure; 7) PHX EDL Comm Overview; 8) EDL Geometry (Entry through Landing); 9) Phoenix Support; 10) Preparations for Phoenix; 11) EDL Support Timeline; 12) One Year Rolling Schedule; 13) E3 Rationale; and 14) Spacecraft Status.

  18. Mars Pathfinder [foldout].

    PubMed

    1997-12-01

    The following foldout present images and analysis from the Mars Pathfinder Mission that are discussed in seven subsequent Reports. The center is a four-page panorama of the surface of Mars around the lander (Plate 1). The back of the foldout contains surface images (Plate 7), a different perspective of the landing site (Plate 2), rover targets (Plate 3), locations of rocks and other features (Plate 6) and data analysis (Plates 4, 4, 8, 9, and 10). PMID:9411794

  19. Salt weathering on Mars

    NASA Technical Reports Server (NTRS)

    Malin, M. C.

    1974-01-01

    Mariner 9 photographs of Mars indicate that significant erosion has occurred on that planet. Although several possible erosion mechanisms have been proposed, most terrestrial weathering mechanisms cannot function in the present Martian environment. Salt weathering, believed to be active in the Antarctic dry valleys, is especially suited to Mars, given the presence of salts and small amounts of water. Volcanic salts are probably available, and the association of salts and water is likely from both thermodynamic and geologic considerations.

  20. Discovery concepts for Mars

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Russell, C. T.; Brace, L. H.; Nagy, A. F.; Jakosky, B. M.; Barth, C. A.; Waite, J. H.

    1992-01-01

    Two focused Mars missions that would fit within the guidelines for the proposed Discovery line are discussed. The first mission would deal with the issue of the escape of the atmosphere (Mars') to space. A complete understanding of this topic is crucial to deciphering the evolution of the atmosphere, climate change, and volatile inventories. The second mission concerns the investigation of remanent magnetization of the crust and its relationship to the ionosphere and the atmosphere.

  1. Optical Dust Characterization in Manned Mars Analogue Research Stations

    NASA Technical Reports Server (NTRS)

    Bos, B. J.; Krebs, Carolyn (Technical Monitor)

    2003-01-01

    Martian dust has been identified as a potentially serious hazard to any manned Mars landing mission. NASA and other organizations realize this risk and continue to support Martian dust research through the Matador project led by researchers at the University of Arizona. The Mars Society can contribute to this work by beginning a regimen of monitoring and measuring dust properties at its Mars analogue research stations. These research facilities offer the unique opportunity to study the transport and distribution of dust particles within a crewed habitat supporting active geologic exploration. Information regarding the amount, location and size of dust particles that may accumulate in a Mars habitat will be required to design a real Mars habitat and habitat equipment. Beginning such an effort does not require a large outlay of equipment and can be accomplished using crewmembers experienced with station operations. Various optical techniques, such as dark-field illumination, coupled with image processing algorithms enable the collection of dust grain relative size and frequency information. Such approaches can be applied in several different zones within the research stations to evaluate the various dust reduction and isolation procedures implemented during a particular crew rotation. As the stations simulation fidelity increases, the applicability of such data to a functional Mars lander will increase. This presentation describes the optical equipment and procedures for measuring dust properties in Mars analogue research stations that can be implemented during the next field season.

  2. Hydrogen Escape from early Earth and Mars

    NASA Astrophysics Data System (ADS)

    Zugger, M. E.; Ramirez, R. M.; Kasting, J. F.

    2012-12-01

    A controversy regarding hydrodynamic escape rates arose when Tian et al. (2005) published transonic escape rates for an atmosphere composed of pure H2. Tian et al. concluded that the hydrogen escape rate from early Earth would have been a factor of 20 or more slower than the diffusion limit, even if the solar EUV (extreme ultraviolet) flux was enhanced by a factor of 5 relative to today. This conclusion was challenged by Catling (2006), who pointed out that solar EUV fluxes could have been much higher than this so that plenty of energy should have been available to power escape. This controversy has remained unresolved to date. Hydrogen escape from early Mars is also of interest. As discussed in this session in a complementary paper by Ramirez et al., collision-induced absorption by molecular hydrogen could have helped to warm early Mars, perhaps explaining the formation of valleys and valley networks. Ramirez et al. have shown that a mixture of 90% CO2 and 10% H2 is capable raising early Mars' surface temperature above the freezing point of water, for surface pressures exceeding ~3 bar. However, we need to understand whether H2 mixing ratios of 10% are physically plausible. The H2 partial pressure in Mars' early atmosphere would have been determined by the balance between volcanic outgassing and escape to space. The 10% mixing ratio is high compared to the value of ~10-3 typically assumed for early Earth. But Mars' early atmosphere may have been more reduced than Earth's (Wadwha, 2001); if the hydrogen escape rate on Mars was also slower than on Earth, then additional increases in atmospheric hydrogen concentration are possible. To answer these questions about the early atmospheres of Earth and Mars, we have modified an existing model of hydrodynamic escape, developed by F. Tian, J. Kasting, and others, to converge for atmospheres with a wide range of hydrogen mixing ratios. The model finds subsonic solutions to the hydrodynamic equations; these can be shown to

  3. Normal faults geometry and morphometry on Mars

    NASA Astrophysics Data System (ADS)

    Vaz, D. A.; Spagnuolo, M. G.; Silvestro, S.

    2014-04-01

    In this report, we show how normal faults scarps geometry and degradation history can be accessed using high resolution imagery and topography. We show how the initial geometry of the faults can be inferred from faulted craters and we demonstrate how a comparative morphometric analysis of faults scarps can be used to study erosion rates through time on Mars.

  4. Why exobiology on Mars?

    NASA Astrophysics Data System (ADS)

    Brack, A.

    1996-11-01

    Processing of organic molecules by liquid water was probably an essential requirement towards the emergence of terrestrial primitive life. According to Oparin's hypothesis, organic building blocks required for early life were produced from simple organic molecules formed in a primitive reducing atmosphere. Geochemists favour now a less reducing atmosphere dominated by carbon dioxide. In such an atmosphere very few building blocks are formed. Import of extra-terrestrial organic molecules may represent an alternative supply. Experimental support for such an alternative scenario is examined in comets, meteorites and micrometeorites. The early histories of Mars and Earth clearly show similarities. Liquid water was once stable on the surface of Mars attesting the presence of an atmosphere capable of deccelerating C-rich micrometeorites. Therefore, primitive life may have developed on Mars as well. Liquid water disappeared from the surface of Mars very early, about 3.8 Ga ago. The Viking missions did not find, at the surface of the Martian soil, any organic molecules or clear-cut evidence for microbial activities such as photo-synthesis, respiration or nutrition. The results can be explained referring to an active photochemistry of Martian soil driven by the high influx of solar UV. These experiments do not exclude the existence of organic molecules and fossils of micro-organisms which developed on early Mars until liquid water disappeared. Mars may store below its surface some well preserved clues of a still hypothetical primitive life.

  5. Paleolakes on Mars

    NASA Technical Reports Server (NTRS)

    Wharton, R. A. Jr; Crosby, J. M.; McKay, C. P.; Rice, J. W. Jr; Wharton RA, ,. J. r. (Principal Investigator)

    1995-01-01

    Observational evidence such as outflow channels and valley networks suggest that in the past there was flowing water on Mars. The images of fluvial features on Mars logically suggest that there must exist downstream locations in which the water pooled and the sediment load deposited (i.e. lakes). Sediments and morphological features associated with the martian paleolakes are believed to occur in Valles Marineris, and several large basins including Amazonis, Chryse and Elysium planitia. As Mars became progressively colder over geological time, any lakes on its surface would have become seasonally, and eventually perennially ice-covered. We know from polar lakes on Earth that ice-covered lakes can persist even when the mean annual temperature falls below freezing. Thus, the most recent lacustrine sediments on Mars were probably deposited in ice-covered lakes. While life outside of the Earth's atmosphere has yet to be observed, there is a general consensus among exobiologists that the search for extraterrestrial life should be based upon liquid water. The inference that there was liquid water on Mars during an earlier epoch is the primary motivation for considering the possibility of life during this time. It would be of enormous interest from both an exobiological and paleolimnological perspective to discover lakes or the evidence of former lakes on another planet such as Mars. Limnology would then become an interplanetary science.

  6. The Mars Observer database

    NASA Technical Reports Server (NTRS)

    Albee, Arden L.

    1988-01-01

    Mars Observer will study the surface, atmosphere, and climate of Mars in a systematic way over an entire Martian year. The observations of the surface will provide a database that will be invaluable to the planning of a future Mars sample return mission. Mars Observer is planned for a September 1992 launch from the Space Shuttle, using an upper-stage. After the one year transit the spacecraft is injected into orbit about Mars and the orbit adjusted to a near-circular, sun-synchronous low-altitude, polar orbit. During the Martian year in this mapping orbit the instruments gather both geoscience data and climatological data by repetitive global mapping. The scientific objectives of the mission are to: (1) determine the global elemental and mineralogical character of the surface material; (2) define globally the topography and gravitational field; (3) establish the nature of the magnetic field; (4) determine the time and space distribution, abundance, sources, and sinks of volatile material and dust over a seasonal cycle; and (5) explore the structure and aspects of the circulation of the atmosphere. The science investigations and instruments for Mars Observer have been chosen with these objectives in mind. These instruments, the principal investigator or team leader and the objectives are discussed.

  7. Transportation: Destination Mars

    NASA Technical Reports Server (NTRS)

    Eoff, Bill

    1998-01-01

    As the agency space transportation lead center, Marshall Space Flight Center has been conducting transportation assessments for future robotic and human Mars missions to identify critical technologies. Five human Mars options are currently under assessment with each option including all transportation requirements from Earth to Mars and return. The primary difference for each option is the propulsion source from Earth to Mars. In case any of the options require heavy launch capability that is not currently projected as available, an in-house study has been initiated to determine the most cost effective means of providing such launch capability. This assessment is only considering launch architectures that support the overall human Mars mission cost goal of $25B. The guidelines for the launch capability study included delivery of 80 metric ton (176 KLB) payloads, 25 feet diameter x 92 feet long, to 220 nmi orbits at 28.5 degrees. The launch vehicle concept of the study was designated "Magnum" to differentiate from prior heavy launch vehicle assessments. This assessment along with the assessment of options for all transportation phases of a Mars mission are on-going.

  8. Life on Mars

    NASA Technical Reports Server (NTRS)

    McKay, Christopher P.; Cuzzi, Jeffrey (Technical Monitor)

    1996-01-01

    Although the Viking results may indicate that Mars has no life today, the possibility exists that Mars may hold the best record of the events that led to the origin of life. There is direct geomorphological evidence that in the past Mars had large amounts of liquid water on its surface. Atmospheric models would suggest that this early period of hydrological activity was due to the presence of a thick atmosphere and the resulting warmer temperatures. From a biological perspective the existence of liquid water, by itself motivates the question of the origin of life on Mars. From studies of the Earth's earliest biosphere we know that by 3.5 Gyr. ago, life had originated on Earth and reached a fair degree of biological sophistication. Surface activity and erosion on Earth make it difficult to trace the history of life before the 3.5 Gyr timeframe. If Mars did maintain a clement environment for longer than it took for life to originate on Earth, then the question of the origin of life on Mars follows naturally.

  9. Mars Rover RTG Study

    SciTech Connect

    Schock, Alfred

    1989-11-27

    This report summarizes the results of a Radioisotope Thermoelectric Generator (RTG) design study conducted by Fairchild Space Company at the direction of the U.S. Department of Energy's Office of Special Applications, in support of the Mars Rover and Sample Return mission under investigation at NASA's Jet Propulsion Laboratory. Presented at the 40th Congress of the IAF, Oct. 7-13, 1989 in Torremolinos, Malaga-Spain. The paper describes the design and analysis of Radioisotope Thermoelectric Generators (RTGs) for powering the Mars Rover vehicle, which is a critical element of the unmanned Mars Rover and Sample Return mission (MRSR). The RTG design study was conducted by Fairchild Space for the U.S. DOE in support of the JPL MRSR Project. The paper briefly describes a reference mission scenario, an illustrative Rover design and activity pattern on Mars, and its power system requirements and environmental constraints, including the RTG cooling requirements during transit to Mars. It summarizes the baseline RTG's mass breakdown, and presents a detailed description of its thermal, thermoelectric, and electrical analysis. The results presented show the RTG performance achievable with current technology, and the performance improvements that would be achievable with various technology developments. It provides a basis for selecting the optimum strategy for meeting the Mars Rover design goals with minimal programmatic risk and cost. Cross Reference CID #7135 dated 10/1989. There is a duplicate copy. This document is not relevant to the OSTI Library. Do not send.

  10. Time-variable and static gravity field of Mars from MGS, Mars Odyssey, and MRO

    NASA Astrophysics Data System (ADS)

    Genova, Antonio; Goossens, Sander; Lemoine, Frank G.; Mazarico, Erwan; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.

    2016-04-01

    The Mars Global Surveyor (MGS), Mars Odyssey (ODY), and Mars Reconnaissance Orbiter (MRO) missions have significantly contributed to the determination of global high-resolution global gravity fields of Mars for the last 16 years. All three spacecraft were located in sun-synchronous, near-circular polar mapping orbits for their primary mission phases at different altitudes and Local Solar Time (LST). X-Band tracking data have been acquired from the NASA Deep Space Network (DSN) providing information on the time-variable and static gravity field of Mars. MGS operated between 1999 and 2006 at 390 km altitude. ODY and MRO are still orbiting Mars with periapsis altitudes of 400 km and 255 km, respectively. Before entering these mapping phases, all three spacecraft collected radio tracking data at lower altitudes (˜170-200 km) that help improve the resolution of the gravity field of Mars in specific regions. We analyzed the entire MGS radio tracking data set, and ODY and MRO radio data until 2015. These observations were processed using a batch least-squares filter through the NASA GSFC GEODYN II software. We combined all 2- and 3-way range rate data to estimate the global gravity field of Mars to degree and order 120, the seasonal variations of gravity harmonic coefficients C20, C30, C40 and C50 and the Love number k2. The gravity contribution of Mars atmospheric pressures on the surface of the planet has been discerned from the time-varying and static gravity harmonic coefficients. Surface pressure grids computed using the Mars-GRAM 2010 atmospheric model, with 2.5° x2.5° spatial and 2-h resolution, are converted into gravity spherical harmonic coefficients. Consequently, the estimated gravity and tides provide direct information on the solid planet. We will present the new Goddard Mars Model (GMM-3) of Mars gravity field in spherical harmonics to degree and order 120. The solution includes the Love number k2 and the 3-frequencies (annual, semi-annual, and tri

  11. Computer processing of Mars Odyssey THEMIS IR imaging, MGS MOLA altimetry and Mars Express stereo imaging to locate Airy-0, the Mars prime meridian reference

    NASA Astrophysics Data System (ADS)

    Duxbury, Thomas; Neukum, Gerhard; Smith, David E.; Christensen, Philip; Neumann, Gregory; Albee, Arden; Caplinger, Michael; Seregina, N. V.; Kirk, Randolph L.

    The small crater Airy-0 was selected from Mariner 9 images to be the reference for the Mars prime meridian. Initial analyses were made in year 2000 to tie Viking Orbiter and Mars Orbiter Camera images of Airy-0 to the evolving Mars Orbiter Laser Altimeter global digital terrain model to improve the location accuracy of Airy-0. Based upon this tie and radiometric tracking of landers / rovers from earth, new expressions for the Mars spin axis direction, spin rate and prime meridian epoch value were produced to define the orientation of the Martian surface in inertial space over time. Now that the Mars Global Surveyor mission and the Mars Orbiter Laser Altimeter global digital terrain model are complete, a more exhaustive study has been performed to determine the location of Airy-0 relative to the global terrain grid. THEMIS IR image cubes of the Airy and Gale crater regions were tied to the global terrain grid using precision stereo photogrammetric image processing techniques. The Airy-0 location was determined to be within 50 meters of the currently defined IAU prime meridian, with this offset at the limiting absolute accuracy of the global terrain grid. Additional outputs of this study were a controlled multi-band photomosaic of Airy, precision alignment and geometric models of the ten THEMIS IR bands and a controlled multi-band photomosaic of Gale crater used to validate the Mars Surface Laboratory operational map products supporting their successful landing on Mars.

  12. The MARS2013 Mars analog mission.

    PubMed

    Groemer, Gernot; Soucek, Alexander; Frischauf, Norbert; Stumptner, Willibald; Ragonig, Christoph; Sams, Sebastian; Bartenstein, Thomas; Häuplik-Meusburger, Sandra; Petrova, Polina; Evetts, Simon; Sivenesan, Chan; Bothe, Claudia; Boyd, Andrea; Dinkelaker, Aline; Dissertori, Markus; Fasching, David; Fischer, Monika; Föger, Daniel; Foresta, Luca; Fritsch, Lukas; Fuchs, Harald; Gautsch, Christoph; Gerard, Stephan; Goetzloff, Linda; Gołebiowska, Izabella; Gorur, Paavan; Groemer, Gerhard; Groll, Petra; Haider, Christian; Haider, Olivia; Hauth, Eva; Hauth, Stefan; Hettrich, Sebastian; Jais, Wolfgang; Jones, Natalie; Taj-Eddine, Kamal; Karl, Alexander; Kauerhoff, Tilo; Khan, Muhammad Shadab; Kjeldsen, Andreas; Klauck, Jan; Losiak, Anna; Luger, Markus; Luger, Thomas; Luger, Ulrich; McArthur, Jane; Moser, Linda; Neuner, Julia; Orgel, Csilla; Ori, Gian Gabriele; Paternesi, Roberta; Peschier, Jarno; Pfeil, Isabella; Prock, Silvia; Radinger, Josef; Ramirez, Barbara; Ramo, Wissam; Rampey, Mike; Sams, Arnold; Sams, Elisabeth; Sandu, Oana; Sans, Alejandra; Sansone, Petra; Scheer, Daniela; Schildhammer, Daniel; Scornet, Quentin; Sejkora, Nina; Stadler, Andrea; Stummer, Florian; Taraba, Michael; Tlustos, Reinhard; Toferer, Ernst; Turetschek, Thomas; Winter, Egon; Zanella-Kux, Katja

    2014-05-01

    We report on the MARS2013 mission, a 4-week Mars analog field test in the northern Sahara. Nineteen experiments were conducted by a field crew in Morocco under simulated martian surface exploration conditions, supervised by a Mission Support Center in Innsbruck, Austria. A Remote Science Support team analyzed field data in near real time, providing planning input for the management of a complex system of field assets; two advanced space suit simulators, four robotic vehicles, an emergency shelter, and a stationary sensor platform in a realistic work flow were coordinated by a Flight Control Team. A dedicated flight planning group, external control centers for rover tele-operations, and a biomedical monitoring team supported the field operations. A 10 min satellite communication delay and other limitations pertinent to human planetary surface activities were introduced. The fields of research for the experiments were geology, human factors, astrobiology, robotics, tele-science, exploration, and operations research. This paper provides an overview of the geological context and environmental conditions of the test site and the mission architecture, in particular the communication infrastructure emulating the signal travel time between Earth and Mars. We report on the operational work flows and the experiments conducted, including a deployable shelter prototype for multiple-day extravehicular activities and contingency situations. PMID:24823799

  13. Mars Telecommunications Orbiter, Artist's Concept

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This illustration depicts a concept for NASA's Mars Telecommunications Orbiter in flight around Mars. The orbiter is in development to be the first spacecraft with a primary function of providing communication links while orbiting a foreign planet. The project's plans call for launch in September 2009, arrival at Mars in August 2010 and a mission of six to 10 years while in orbit. Mars Telecommunication Orbiter would serve as the Mars hub for an interplanetery Internet, greatly increasing the information payoff from other future Mars missions. The mission is designed to orbit Mars more than 10 times farther from the planet than orbiters dedicated primarily to science. The high-orbit design minimizes the time that Mars itself blocks the orbiter from communicating with Earth and maximizes the time that the orbiter is above the horizon -- thus capable of communications relay -- for rovers and stationary landers on Mars' surface.

  14. Mars - Pathway to the stars

    NASA Astrophysics Data System (ADS)

    Angelo, J. A., Jr.; Buden, D.

    Mars has and will continue to play a key role in our exploration and conquest of the Solar System. Within the context of the creation of humanity's extraterrestrial civilization, the major technical features of the following Mars programs are reviewed: the Mars Geoscience/Climatology Orbiter; the Mars Aeronomy Orbiter; the Mars airplane; the Mars Penetrator Network; Mars surface rovers and mobility systems; human exploration of Mars; and permanent Martian bases and settlements. Mars properly explored and utilized opens the way to the resources of the asteroid belt and the outer planets; supports the creation of smart machines for space exploration and exploitation; and encourages the creation of autonomous niches of intelligent life within heliocentric space. All of these developments, in turn, establish the technological pathway for the first interstellar missions.

  15. Examining Mars with SPICE

    NASA Technical Reports Server (NTRS)

    Acton, Charles H.; Bachman, Nathaniel J.; Bytof, Jeff A.; Semenov, Boris V.; Taber, William; Turner, F. Scott; Wright, Edward D.

    1999-01-01

    The International Mars Conference highlights the wealth of scientific data now and soon to be acquired from an international armada of Mars-bound robotic spacecraft. Underlying the planning and interpretation of these scientific observations around and upon Mars are ancillary data and associated software needed to deal with trajectories or locations, instrument pointing, timing and Mars cartographic models. The NASA planetary community has adopted the SPICE system of ancillary data standards and allied tools to fill the need for consistent, reliable access to these basic data and a near limitless range of derived parameters. After substantial rapid growth in its formative years, the SPICE system continues to evolve today to meet new needs and improve ease of use. Adaptations to handle landers and rovers were prototyped on the Mars pathfinder mission and will next be used on Mars '01-'05. Incorporation of new methods to readily handle non-inertial reference frames has vastly extended the capability and simplified many computations. A translation of the SPICE Toolkit software suite to the C language has just been announced. To further support cartographic calculations associated with Mars exploration the SPICE developers at JPL have recently been asked by NASA to work with cartographers to develop standards and allied software for storing and accessing control net and shape model data sets; these will be highly integrated with existing SPICE components. NASA specifically supports the widest possible utilization of SPICE capabilities throughout the international space science community. With NASA backing the Russian Space Agency and Russian Academy of Science adopted the SPICE standards for the Mars 96 mission. The SPICE ephemeris component will shortly become the international standard for agencies using the Deep Space Network. U.S. and European scientists hope that ESA will employ SPICE standards on the Mars Express mission. SPICE is an open set of standards, and

  16. Four Mars Years of South Polar Changes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year.

    Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera.

    Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year.

    Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar residual cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years.

    Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the

  17. Teleoperation from Mars Orbit: A proposal for Human Exploration

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    2004-01-01

    For a human expedition to Mars, a case can be made that the best strategy for initial exploration is not to actually land the humans on Mars, but to put the humans into Mars orbit and operate on the surface by the technology of teleoperation. This will provide the results of human exploration, but at greatly reduced risk and cost. Teleoperation of Mars surface robots from a Mars-orbital habitat will operation near real time operation with minimum time delay, giving a virtual presence on the surface. By use of teleoperation, it is possible to vastly simplify the surface exploration mission. We now have no need to develop a human-rated Mars Lander and Mars Ascent Vehicle, and we can send geologists & biologists on the mission; not VTOL pilots. It is a cheaper, simpler, and safer way to explore, and hence it will be a faster way to explore. It has the excitement of being there, at a fraction of the price. Tele-exploration from Mars orbit also allows human (virtual) presence at a wide variety of locations. With an orbital base controlling surface telerobotics, human explorers are not stuck with one base location, but can explore all over Mars. They can explore the polar caps and also near-equatorial canyon regions, from the same orbiting base. This frees the mission from landing site constraints. With no need to select a "grab bag" site that contains a large number of geologically diverse features at or near a single location; it is now possible go to all the best sites-- paleolake sites, river beds, volcanic calderas, lava tube sites, layered terrain, canyons, possible shoreline features, the North and South poles. A near-polar inclination 24-hr 39-minute period Mars orbit, for example, will put the orbital station in line-of-sight of a given region for about 8 hours per day-- one teleoperation shift. Since present day life could exist on Mars, planetary protection is also needed to preserve the (possible) fragile Mars biosphere from competition from ferocious Earth

  18. Volcanic recycling of carbonates on Mars

    NASA Technical Reports Server (NTRS)

    Schaefer, M. W.

    1993-01-01

    Thermal erosion of carbonate deposits by turbulently-flowing lava is investigated as a means of recycling carbon dioxide back into the atmosphere of Mars. Erosion rates of several meters/day are found, implying that up to hundreds of meters of carbonate could be removed over the lifetime of a flow. A large fraction of the northern plains and other parts of Mars were covered by lava during the Hesperian, and may have released the carbon dioxide trapped in carbonate deposits. This period of time, several times 10 exp 8 yrs, is comparable to that for the redeposition of such carbonate deposits. Therefore, there could have existed a relatively dense atmosphere, and enhanced weathering and erosion, after the Noachian era. This may help explain the apparent observational evidence for late fluvial and lacustrine activity on Mars.

  19. Effect of nontronite smectite clay on the chemical evolution of several organic molecules under simulated Mars surface UV radiation conditions

    NASA Astrophysics Data System (ADS)

    Poch, Olivier; Dequaire, Tristan; Stalport, Fabien; Jaber, Maguy; Lambert, Jean-François; Szopa, Cyril; Coll, Patrice

    2015-04-01

    The search for organic carbon-containing molecules at the surface of Mars, as clues of past habitability or remnants of life, is a major scientific goal for Mars exploration. Several lines of evidence, including the detection of phyllosilicates, suggest that early Mars offered favorable conditions for long-term sustaining of water. As a consequence, we can assume that in those days, endogenous chemical processes, or even primitive life, may have produced organic matter on Mars. Moreover, exogenous delivery from small bodies or dust particles is likely to have brought fresh organic molecules to the surface of Mars up today. Organic matter is therefore expected to be present at the surface/subsurface of the planet. But the current environmental conditions at the surface - UV radiation, oxidants and energetic particles - generate physico-chemical processes that may affect organic molecules. On the other hand, on Earth, phyllosilicates are known to accumulate and preserve organic matter. But are phyllosilicates efficient at preserving organic molecules under the current environmental conditions at the surface of Mars? We have monitored the qualitative and quantitative evolutions of glycine, urea and adenine interacting with the Fe3+-smectite clay nontronite, one of the most abundant phyllosilicates present at the surface of Mars, under simulated Martian surface ultraviolet light (190-400 nm), mean temperature (218 ± 2 K) and pressure (6 ± 1 mbar) in a laboratory simulation setup. We have tested organic-rich samples which may be representative of the evaporation of a warm little pond of liquid water having concentrated organics on Mars. For each molecule, we have observed how the nontronite influences the quantum efficiency of its photodecomposition and the nature of its solid evolution products. The results reveal a pronounced photoprotective effect of nontronite on the evolution of glycine and adenine: their efficiencies of photodecomposition are reduced by a factor

  20. Radiometry Measurements of Mars at 1064 nm Using the Mars Orbiter Laser Altimeter

    NASA Technical Reports Server (NTRS)

    Sun, Xiao-Li; Abshire, James B.; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E. (Technical Monitor)

    2001-01-01

    Measurements by the Mars Orbiter Laser Altimeter (MOLA) on board the Mars Global Surveyor (MGS) may be used to provides a radiometric measurement of Mars in addition to the topographic measurement. We will describe the principle of operation, a mathematical model, and the receiver calibration in this presentation. MOLA was designed primarily to measure Mars topography, surface roughness end the bidirectional reflectance to the laser beam. To achieve the highest sensitivity the receiver detection threshold is dynamically adjusted to be as low as possible while keeping a predetermined false alarm rate. The average false alarm rate 29 monitored in real time on board MOLA via a noise counter, whose output is fed to the threshold control loop. The false alarm rate at a given threshold is a function of the detector output noise which is the sum of the photo detector, shot noise due to the background light seen by the detector and the dark noise. A mathematical model has been developed that can be used to numerically solve for the optical background power given the MOLA threshold setting and the average noise count. The radiance of Mars can then be determined by dividing the optical power by the solid angle subtended by the MOLA receiver, the receiver optical band-width, end the Mars surface area within the receiver field of view. The phase angle which is the sun-Mars-MOLA angle is available from the MGS database. MOLA also measures simultaneously the bidirectional reflectance of Mars vie its 106-lum loser beam at nadir with nearly zero phase angle. The optical bandwidth of the MOLA receiver is 2um full width at half maximum (FWHM) and centered at 106-lum. The receiver field of view is 0.95mrad FWHM. The nominated spacecraft altitude is 100km and the ground track speed is about 3km/s. Under normal operation, the noise counter are read and the threshold levels are updated at 1Hz. The receiver sensitivity is limited by the detector dark noise to about 0.1nW, which

  1. Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory.

    PubMed

    Köhler, J; Ehresmann, B; Zeitlin, C; Wimmer-Schweingruber, R F; Hassler, D M; Reitz, G; Brinza, D E; Appel, J; Böttcher, S; Böhm, E; Burmeister, S; Guo, J; Lohf, H; Martin, C; Posner, A; Rafkin, S

    2015-04-01

    The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011. Although designed for measuring the radiation on the surface of Mars, the Radiation Assessment Detector (RAD) measured the radiation environment inside the spacecraft during most of the 253-day, 560-million-kilometer cruise to Mars. An important factor for determining the biological impact of the radiation environment inside the spacecraft is the specific contribution of neutrons with their high biological effectiveness. We apply an inversion method (based on a maximum-likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. The measured neutron spectrum (12-436 MeV) translates into a radiation dose rate of 3.8±1.2 μGy/day and a dose equivalent of 19±5 μSv/day. Extrapolating the measured spectrum (0.1-1000 MeV), we find that the total neutron-induced dose rate is 6±2 μGy/day and the dose equivalent rate is 30±10 μSv/day. For a 360 day round-trip from Earth to Mars with comparable shielding, this translates into a neutron induced dose equivalent of about 11±4 mSv. PMID:26177845

  2. Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory

    NASA Astrophysics Data System (ADS)

    Köhler, J.; Ehresmann, B.; Zeitlin, C.; Wimmer-Schweingruber, R. F.; Hassler, D. M.; Reitz, G.; Brinza, D. E.; Appel, J.; Böttcher, S.; Böhm, E.; Burmeister, S.; Guo, J.; Lohf, H.; Martin, C.; Posner, A.; Rafkin, S.

    2015-04-01

    The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011. Although designed for measuring the radiation on the surface of Mars, the Radiation Assessment Detector (RAD) measured the radiation environment inside the spacecraft during most of the 253-day, 560-million-kilometer cruise to Mars. An important factor for determining the biological impact of the radiation environment inside the spacecraft is the specific contribution of neutrons with their high biological effectiveness. We apply an inversion method (based on a maximum-likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. The measured neutron spectrum (12-436 MeV) translates into a radiation dose rate of 3.8 ± 1.2 μGy /day and a dose equivalent of 19 ± 5 μSv /day. Extrapolating the measured spectrum (0.1-1000 MeV), we find that the total neutron-induced dose rate is 6 ± 2 μGy /day and the dose equivalent rate is 30 ± 10 μSv /day. For a 360 day round-trip from Earth to Mars with comparable shielding, this translates into a neutron induced dose equivalent of about 11 ± 4 mSv.

  3. Use of Robotically Hollowed Out Moon of Mars as a Mars Space Station

    NASA Astrophysics Data System (ADS)

    Mardon, A.

    2002-01-01

    For long term manned exploration and colonization of Mars it is necessary to develop a space station as a way station to and from the Earth. The author proposes that one of the Moons of Mars could be converted into a permanent hollowed out space station. This could be done robotically before any manned mission to Mars arrives in orbit around Mars. In the construction industry there already exists small robotic tunneling devices that are used underground in urban settings. With excavated tunnels being completed by remotely controlled operators when a manned vehicle arrives from Earth with a crew all that would be needed to be done is seal the tunnels underneath the surface of one of the Moons of mars and then either erect tent like structures in the tunnels or seal up the actual surfaces of the tunnels so that it could be shirt sleeve rated. The hollowed out space station for Mars could be a permanent structure. Because the station would be inside the Moon the threat of micro-meteorites would be non-existent. If more space was needed then all that would be needed is to excavate more of the Moons. Also by using robots to tunnel the structure would be complete before the manned mission would arrive.

  4. Initial Mars Orbiter Laser Altimeter (MOLA) Measurements of the Mars Surface and Atmosphere

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Sun, Xiaoli; Afzal, Robert S.

    1998-01-01

    The Mars Orbiter Laser Altimeter (MOLA) has made an initial set of measurements of the Mars surface and atmosphere. As of this writing 27 orbital passes have been completed, starting Sept. 15, 1997 on orbit Pass 3 and orbits 20-36 and beginning again on March 27, 1998 for orbit passes 203 - 212. The lidar is working well in Mars orbit, and its data show contiguous measurement profiles of the Mars surface to its maximum range of 786 km, an average pulse detection rate of > 99% under clear atmospheric conditions, and < 1 m range resolution. MOLA has profiled the shape and heights of a variety of interesting Mars surface features, including Olympus Mons, the flat northern plains of Mars, Valles Marineris and the northern polar ice cap. It has also detected and profiled a series of cloud layers which occur near the edge of the polar cap and near 60-70 deg N latitude. This is the first time clouds around another planet have been measured using lidar.

  5. Initial Mars Orbiter Laser Altimeter (MOLA) Measurements of the Mars Surface and Atmosphere

    NASA Astrophysics Data System (ADS)

    Abshire, James B.; Sun, Xiaoli; Afzal, Robert S.

    1998-07-01

    The Mars Orbiter Laser Altimeter (MOLA) has made an initial set of measurements of the Mars surface and atmosphere. As of this writing 27 orbital passes have been completed, starting Sept. 15, 1997 on orbit Pass 3 and orbits 20-36 and beginning again on March 27, 1998 for orbit passes 203 - 212. The lidar is working well in Mars orbit, and its data show contiguous measurement profiles of the Mars surface to its maximum range of 786 km, an average pulse detection rate of > 99% under clear atmospheric conditions, and < 1 m range resolution. MOLA has profiled the shape and heights of a variety of interesting Mars surface features, including Olympus Mons, the flat northern plains of Mars, Valles Marineris and the northern polar ice cap. It has also detected and profiled a series of cloud layers which occur near the edge of the polar cap and near 60-70 deg N latitude. This is the first time clouds around another planet have been measured using lidar.

  6. Organic-Carbon Sequestration in Soil/Sediment of the Mississippi River Deltaic Plain - Data; Landscape Distribution, Storage, and Inventory; Accumulation Rates; and Recent Loss, Including a Post-Katrina Preliminary Analysis (Chapter B)

    USGS Publications Warehouse

    Markewich, Helaine W.; Buell, Gary R.; Britsch, Louis D.; McGeehin, John P.; Robbins, John A.; Wrenn, John H.; Dillon, Douglas L.; Fries, Terry L.; Morehead, Nancy R.

    2007-01-01

    Soil/sediment of the Mississippi River deltaic plain (MRDP) in southeastern Louisiana is rich in organic carbon (OC). The MRDP contains about 2 percent of all OC in the surface meter of soil/sediment in the Mississippi River Basin (MRB). Environments within the MRDP differ in soil/sediment organic carbon (SOC) accumulation rate, storage, and inventory. The focus of this study was twofold: (1) develop a database for OC and bulk density for MRDP soil/sediment; and (2) estimate SOC storage, inventory, and accumulation rates for the dominant environments (brackish, intermediate, and fresh marsh; natural levee; distributary; backswamp; and swamp) in the MRDP. Comparative studies were conducted to determine which field and laboratory methods result in the most accurate and reproducible bulk-density values for each marsh environment. Sampling methods included push-core, vibracore, peat borer, and Hargis1 sampler. Bulk-density data for cores taken by the 'short push-core method' proved to be more internally consistent than data for samples collected by other methods. Laboratory methods to estimate OC concentration and inorganic-constituent concentration included mass spectrometry, coulometry, and loss-on-ignition. For the sampled MRDP environments, these methods were comparable. SOC storage was calculated for each core with adequate OC and bulk-density data. SOC inventory was calculated using core-specific data from this study and available published and unpublished pedon data linked to SSURGO2 map units. Sample age was estimated using isotopic cesium (137Cs), lead (210Pb), and carbon (14C), elemental Pb, palynomorphs, other stratigraphic markers, and written history. SOC accumulation rates were estimated for each core with adequate age data. Cesium-137 profiles for marsh soil/sediment are the least ambiguous. Levee and distributary 137Cs profiles show the effects of intermittent allochthonous input and/or sediment resuspension. Cesium-137 and 210Pb data gave the most

  7. Telecommunications systems evolution for Mars Exploration

    NASA Technical Reports Server (NTRS)

    Noreen, Gary; De Paula, Ramon P.; Edwards, Charles D. Jr; Komarek, Thomas; Edwards, Bernard L.; Edwards, Bernard L.; Kerridge, Stuart J.; Diehl, Roger; Franklin, Stephen F.

    2003-01-01

    This paper describes the evolution of telecommunication systems at Mars. It reviews the telecommunications capabilities, technology and limiting factors of current and planned Mars orbiters from Mars Global Surveyor to the planned Mars Telecommunications Orbiter (MTO).

  8. Mars Rover RTG Study

    SciTech Connect

    Schock, Alfred

    1989-10-01

    Presented at the 40th Congress of the IAF, Oct. 7-13, 1989 in Torremolinos, Malaga-Spain. The paper describes the design and analysis of Radioisotope Thermoelectric Generators (RTGs) for powering the Mars Rover vehicle, which is a critical element of the unmanned Mars Rover and Sample Return mission (MRSR). The RTG design study was conducted by Fairchild Space for the U.S. DOE in support of the JPL MRSR Project. The paper briefly describes a reference mission scenario, an illustrative Rover design and activity pattern on Mars, and its power system requirements and environmental constraints, including the RTG cooling requirements during transit to Mars. It summarizes the baseline RTG's mass breakdown, and presents a detailed description of its thermal, thermoelectric, and electrical analysis. The results presented show the RTG performance achievable with current technology, and the performance improvements that would be achievable with various technology developments. It provides a basis for selecting the optimum strategy for meeting the Mars Rover design goals with minimal programmatic risk and cost. There is a duplicate copy and three copies in the file.

  9. Mars Climate Orbiter

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Mars Surveyor '98 Climate Orbiter is shown here during acoustic tests that simulate launch conditions. The orbiter was to conduct a two year primary mission to profile the Martian atmosphere and map the surface. To carry out these scientific objectives, the spacecraft carried a rebuilt version of the pressure modulated infrared radiometer, lost with the Mars Observer spacecraft, and a miniaturized dual camera system the size of a pair of binoculars, provided by Malin Space Science Systems, Inc., San Diego, California. During its primary mission, the orbiter was to monitor Mars atmosphere and surface globally on a daily basis for one Martian year (two Earth years), observing the appearance and movement of atmospheric dust and water vapor, as well as characterizing seasonal changes of the planet's surface. Imaging of the surface morphology would also provide important clues about the planet's climate in its early history. The mission was part of NASA's Mars Surveyor program, a sustained program of robotic exploration of the red planet, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. Lockheed Martin Astronautics was NASA's industrial partner in the mission. Unfortunately, Mars Climate Orbiter burned up in the Martian atmosphere on September 23, 1999, due to a metric conversion error that caused the spacecraft to be off course.

  10. Simulating "Mars on Earth"

    NASA Technical Reports Server (NTRS)

    Clancey, William J.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    By now, everyone who's heard of the Haughton-Mars Project knows that we travel to Devon Island to learn how people will live and work on Mars. But how do we learn about Mars operations from what happens in the Arctic? We must document our experience--traverses, life in the hab, instrument deployment, communications, and so on. Then we must analyze and formally model what happens. In short, while most scientists are studying the crater, other scientists must be studying the expedition itself. That's what I have done in the past four field seasons. I study field science, both as it naturally occurs at Haughton (unconstrained by a "Mars Sam") and as a constrained experiment using the Flashline Mars Arctic Research Station. During the second week of July 2001, I lived and worked in the hab as part of the Phase 2 crew of six. Besides participating in all activities, I took many photographs and time lapse video. The result of my work will be a computer simulation of how we lived and worked in the hab. It won't be a model of particular people or even my own phase per se, but a pastiche that demonstrates (a proof of concept) that we have appropriate tools for simulating the layout of the hab and daily routines followed by the group and individual scientists. Activities-how people spend their time-are the focus of my observations for building such a simulation model.

  11. Mars atmospheric water

    NASA Technical Reports Server (NTRS)

    Clancy, R. T.; Grossman, A. W.; Muhleman, D. O.

    1992-01-01

    We indicate the Dec. 3-4 spectrum averaged over the morning limb of Mars. Two synthetic spectra indicate the expected line emission for 3 precipitable microns of water with a uniform vertical distribution (dotted) and a vertical distribution in which water decreases rapidly above 20 km altitude if Mars atmospheric temperatures are approximately 20 K cooler than implied by the Viking Infrared Thermal Mapping (IRTM) and lander descent observations. Such cooler atmospheric temperatures have been argued on the basis of ground-based microwave observations of Mars atmospheric CO. Our 3 pr micron column abundance for water can be compared to the global value of approximately 6 pr microns, observation for the same season with the Viking MAWD experiment in 1977. We will investigate the latitude and diurnal variations when the data corresponding to the second day of observations are reduced. We also plan to compare these VLA water observations with a very complementary set of Hubble Space Telescope ozone observations. Ultraviolet (220-330 nm) spectra and imates of Mars were obtained on Dec. 13 1990 as part of a general Mars observing program with the Hubble Space Telescope.

  12. The Mars Technology Program

    NASA Technical Reports Server (NTRS)

    Hayati, Samad A.

    2002-01-01

    Future Mars missions require new capabilities that currently are not available. The Mars Technology Program (MTP) is an integral part of the Mars Exploration Program (MEP). Its sole purpose is to assure that required technologies are developed in time to enable the baselined and future missions. The MTP is a NASA-wide technology development program managed by JPL. It is divided into a Focused Program and a Base Program. The Focused Program is tightly tied to the proposed Mars Program mission milestones. It involves time-critical deliverables that must be developed in time for infusion into the proposed Mars 2005, and, 2009 missions. In addition a technology demonstration mission by AFRL will test a LIDAR as part of a joint NASNAFRL experiment. This program bridges the gap between technology and projects by vertically integrating the technology work with pre-project development in a project-like environment with critical dates for technology infusion. A Base Technology Program attacks higher riskhigher payoff technologies not in the critical path of missions.

  13. Mars digital terrain model

    NASA Technical Reports Server (NTRS)

    Wu, Sherman S. C.; Howington, Annie-Elpis

    1987-01-01

    The Mars Digital Terrain Model (DTM) is the result of a new project to: (1) digitize the series of 1:2,000,000-scale topographic maps of Mars, which are being derived photogrammetically under a separate project, and (2) reformat the digital contour information into rasters of elevation that can be readily registered with the Digital Image Model (DIM) of Mars. Derivation of DTM's involves interpolation of elevation values into 1/64-degree resolution and transformation of them to a sinusoidal equal-area projection. Digital data are produced in blocks corresponding with the coordinates of the original 1:2,000,000-scale maps, i.e., the dimensions of each block in the equatorial belt are 22.5 deg of longitude and 15 deg of latitude. This DTM is not only compatible with the DIM, but it can also be registered with other data such as geologic units or gravity. It will be the most comprehensive record of topographic information yet compiled for the Martian surface. Once the DTM's are established, any enhancement of Mars topographic information made with updated data, such as data from the planned Mars Observer Mission, will be by mathematical transformation of the DTM's, eliminating the need for recompilation.

  14. Relay Support for the Mars Science Laboratory Mission

    NASA Technical Reports Server (NTRS)

    Edwards, Charles D. Jr,; Bell, David J.; Gladden, Roy E.; Ilott, Peter A.; Jedrey, Thomas C.; Johnston, M. Daniel; Maxwell, Jennifer L.; Mendoza, Ricardo; McSmith, Gaylon W.; Potts, Christopher L.; Schratz, Brian C.; Shihabi, Mazen M.; Srinivasan, Jeffrey M.; Varghese, Phillip; Sanders, Stephen S.; Denis, Michel

    2013-01-01

    The Mars Science Laboratory (MSL) mission landed the Curiosity Rover on the surface of Mars on August 6, 2012, beginning a one-Martian-year primary science mission. An international network of Mars relay orbiters, including NASA's 2001 Mars Odyssey Orbiter (ODY) and Mars Reconnaissance Orbiter (MRO), and ESA's Mars Express Orbiter (MEX), were positioned to provide critical event coverage of MSL's Entry, Descent, and Landing (EDL). The EDL communication plan took advantage of unique and complementary capabilities of each orbiter to provide robust information capture during this critical event while also providing low-latency information during the landing. Once on the surface, ODY and MRO have provided effectively all of Curiosity's data return from the Martian surface. The link from Curiosity to MRO incorporates a number of new features enabled by the Electra and Electra-Lite software-defined radios on MRO and Curiosity, respectively. Specifically, the Curiosity-MRO link has for the first time on Mars relay links utilized frequency-agile operations, data rates up to 2.048 Mb/s, suppressed carrier modulation, and a new Adaptive Data Rate algorithm in which the return link data rate is optimally varied throughout the relay pass based on the actual observed link channel characteristics. In addition to the baseline surface relay support by ODY and MRO, the MEX relay service has been verified in several successful surface relay passes, and MEX now stands ready to provide backup relay support should NASA's orbiters become unavailable for some period of time.

  15. Basin Overflow Floods on Mars

    NASA Astrophysics Data System (ADS)

    Irwin, R. P.

    2006-12-01

    On Earth, the most intense recognized historical and paleofloods have been ice dambursts or overflows of large basins, often initiated by abundant runoff or meltwater from the contributing watersheds. Many impact craters and other basins also overflowed in the Martian cratered highlands, and some of their incised outlet valleys similarly record evidence of erosive floods. Otherwise, the commonly small, enclosed watersheds on Mars contain poorly developed valley networks and relatively simple depositional landforms, which record little evidence of intense (by terrestrial standards) meteorological floods. For these reasons, basin overflows may have been disproportionately important mechanisms for incision of large valleys on Mars. Many of the Martian outflow channels head in topographic settings that favored ponding, including large canyons, impact or intercrater basins, chaotic terrain basins, and grabens. This topography may have accumulated somewhat slower groundwater discharges from the subsurface to support peak channel discharges of 106-108 m3/s. To yield a discharge of 106, 107, and 108 m3/s from a dam failure with a width/depth ratio of 5, the model predicts that a breach of ~100, 250, and 640 m, respectively, must form rapidly with respect to the decline of lake level. Terrestrial damburst floods have not exceeded ~106 m3/s for earthen dams and ~107 m3/s for ice dams, but brecciation of the Martian surface by impact cratering may have allowed larger damburst failures, whereas solid bedrock was exposed at shallower depths in the terrestrial examples. Moreover, many of the Martian basins were much larger than enclosed continental basins on Earth, so long-lived overflows may have facilitated entrenchment of deeper channels. Some large, mid-latitude basins overflowed to carve Ma'adim Vallis and the Uzboi-Ladon-Margaritifer Valles system, which are similar in scale to the terrestrial Grand Canyon but record much larger formative discharges. Models of damburst

  16. Recent Surface Changes on Mars

    NASA Astrophysics Data System (ADS)

    Geissler, P. E.; Mukherjee, P.

    2010-12-01

    The MARCI camera on Mars Reconnaissance Orbiter has now been making global observations of the Martian surface for over two Martian years with better spatial resolution and better spectral definition than earlier visible imaging systems. These observations extend the record of continuous global monitoring of the planet's surface that dates from the arrival of Mars Global Surveyor (MGS) in 1999. The orbital images show a dynamic and rapidly changing pattern of bright and dark regions generated by erosion and deposition of sediments by the Martian winds. Previous analyses of the MGS MOC images (Geissler et al., AGU 2009) showed that the temporal behavior of surface albedo varied with geographic location on the planet, with some regions exhibiting gradual changes, while others showed episodic changes that typically took place during the perihelion season, and still other regions such as Solis that appeared to change on a quasi-continuous basis. These observations help to explain the significant changes observed on a decadal time scale between the era of the Viking Orbiters and the arrival of MGS (Geissler, 2005, 1029/2004JE2345). The MARCI data so far confirm many of the conclusions drawn from the MOC record up to the end of 2006. Over the most recent two Martian years, dramatic changes continued in the Solis Lacus region south of the Vallis Marineris. Another episodic wind event stripped away bright dust and darkened the area west of Syrtis Major. New dust accumulations were deposited in the southern mid-latitudes west of Hellas. Most interesting is the gradual advance of many albedo boundaries in the tropical latitudes of Mars. In several locations, dark terrain appears to be encroaching on formerly bright terrain as bright dust is stripped away from the region. MOC and MARCI observations show that these albedo boundaries are moving at speeds of up to tens of kilometers per Martian year. At sites such as Hyblaeus (west of Elysium), the Southern Tropical Dark Band

  17. Mars: New Determination of Impact Crater Production Function Size Distribution

    NASA Astrophysics Data System (ADS)

    Hartmann, William K.

    2006-12-01

    Several authors have questioned our knowledge of Martian impact crater production function size-frequency distribution (PFSFD), especially at small diameters D. Plescia (2005) questioned whether any area of Mars shows size distributions used for estimating crater retention ages on Mars. McEwen et al. (2005) and McEwen and Bierhaus (2006) suggested existing PFSFD’s are hopelessly confused by the presence of secondaries, and that my isochrons give primary crater densities off by factors of several thousand at small D. In 2005, I addressed some of these concerns, noting my curves do not estimate primary crater densities per se, but show total numbers of primaries + semi-randomly “distant secondaries” (negating many McEwen et al. critiques). In 2006 I have conducted new crater counts on a PFSFD test area suggested by Ken Tanaka. This area shows young lava flows of similar crater density, west of Olympus Mons (around 30 deg N, 100 deg W). Multiple crater counts were made on several adjacent Odyssey THEMIS images and MGS MOC images, giving the SFD over a range of 11mMars/moon cratering rate and in the accumulation rate of globally scattered background secondaries (Hartmann 2005). References: Hartmann, W.K., 2005, Icarus 174, 294-320. McEwen, A.S., Bierhaus, E.B., 2006, Ann. Rev. Earth. Planet. Sci. 34, 535-567. McEwen, A.S., 2005, Icarus 176, 351-381. Plescia, J.B. 2005, LPSC 36, 2171.

  18. Windblown sand on Mars: The effect of saltation threshold on drift potentials derived from Mars GCM

    NASA Technical Reports Server (NTRS)

    Xu, P.; Greeley, R.; Williams, S.; Pollack, J. B.

    1994-01-01

    The rate at which the wind can redistribute sedimentary material is an important part of any planet's sedimentologic cycle, particularly for Mars, where the competing effects of other gradational processes are less than on Earth. The aeolian drift potential (DP) is a measure of the amount of material capable of being moved through a unit length by the wind for a given period of time. DP is a useful measure of the potential redistribution rate of windblown material on regional scales. The Martian aeolian DP was calculated from laboratory studies of sand movement conducted at Martian atmospheric densities and from surface stress, temperature, and pressure values for that region as determined from the Mars General (Atmospheric) Circulation Model (GCM) developed at the NASA/Ames Research Center. In our simulations for Mars, DP changes in both magnitude (as expected) and direction if the saltation threshold is altered.

  19. Mars penetrator: Subsurface science mission

    NASA Technical Reports Server (NTRS)

    Lumpkin, C. K.

    1974-01-01

    A penetrator system to emplace subsurface science on the planet Mars is described. The need for subsurface science is discussed, and the technologies for achieving successful atmospheric entry, Mars penetration, and data retrieval are presented.

  20. Journey of a Lifetime -- Mars

    NASA Video Gallery

    NASA wants you to be part of the Journey to Mars. Today, NASA is pushing the boundaries of technology and innovation. NASA’s fleet of robotic scientific explorers at Mars are paving the way for hu...

  1. UBV photometry of Mars

    NASA Technical Reports Server (NTRS)

    Young, A. T.

    1974-01-01

    A critical analysis of selected high-quality photometric observations of Mars indicates that: (1) the phase function is concave upward out to at least 40-deg phase. No sudden brightening occurs at opposition, but the curvature increases at small phase; (2) large systematic differences (0.1-0.2 mag.) exist between different observers' data. However, the small random scatter attributable to Mars (0.01-0.02 mag.) in the better series suggests that these differences represent systematic errors in data reduction, not variations in the planet's brightness; (3) the disentangling of seasonal, diurnal, and phase effects leaves considerable ambiguity; more observations are needed, over a long time, with a stable instrumental system. However, even the present data are sufficient to expose substantial errors in published phase curves of Mars (and consequently, in interpretations based on them).

  2. Remanent magnetism at Mars

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Ness, N. F.

    1988-01-01

    It is shown that a strong case can be made for an intrinsic magnetic field of dynamo origin for Mars earlier in its history. The typical equatorial magnetic field intensity would have been equal to about 0.01-0.1 gauss. The earlier dynamo activity is no longer extant, but a significant remanent magnetic field may exist. A highly non-dipole magnetic field could result from the remanent magnetization of the surface. Remanent magnetization may thus play an important role in the Mars solar wind interactions, in contrast to Venus with its surface temperatures above the Curie point. The anomalous characteristics of Mars'solar wind interaction compared to that of Venus may be explicable on this basis.

  3. Spiders from Mars?

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-426, 19 July 2003

    No, this is not a picture of a giant, martian spider web. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a plethora of polygonal features on the floor of a northern hemisphere impact crater near 65.6oN, 327.7oW. The picture was acquired during spring, after the seasonal carbon dioxide frost cap had largely migrated through the region. At the time the picture was taken, remnants of seasonal frost remained on the crater rim and on the edges of the troughs that bound each of the polygons. Frost often provides a helpful hint as to where polygons and patterned ground occur. The polygons, if they were on Earth, would indicate the presence of freeze-thaw cycles in ground ice. Although uncertain, the same might be true of Mars. Sunlight illuminates the scene from the lower left.

  4. VR for Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    Blackmon, Theodore

    1998-01-01

    Virtual reality (VR) technology has played an integral role for Mars Pathfinder mission, operations Using an automated machine vision algorithm, the 3d topography of the Martian surface was rapidly recovered fro -a the stereo images captured. by the Tender camera to produce photo-realistic 3d models, An advanced, interface was developed for visualization and interaction with. the virtual environment of the Pathfinder landing site for mission scientists at the Space Flight Operations Facility of the Jet Propulsion Laboratory. The VR aspect of the display allowed mission scientists to navigate on Mars in Bud while remaining here on Earth, thus improving their spatial awareness of the rock field that surrounds the lenders Measurements of positions, distances and angles could be easily extracted from the topographic models, providing valuable information for science analysis and mission. planning. Moreover, the VR map of Mars has also been used to assist with the archiving and planning of activities for the Sojourner rover.

  5. Mars transportation system

    NASA Technical Reports Server (NTRS)

    Garrard, William; Vano, Andrew; Rutherford, Dave

    1992-01-01

    The University of Minnesota Advanced Space Design Program has developed a sample Mars exploration scenario. The purpose of the design project is to enhance NASA and university interaction, to provide fresh ideas to NASA, and to provide real world design problems to engineering students. The Mars Transportation System in this paper is designed to transport a crew of six astronauts to the Martian surface and return them to Low Earth Orbit (LEO) starting in the year 2016. The proposed vehicle features such advanced technologies as nuclear propulsion, nuclear power generation, and aerobraking. Three missions are planned. Orbital trajectories are of the conjunction class with an inbound Venus swingby providing a 60-day surface stay at Mars and an average total trip time of 520 days.

  6. Manned Mars mission

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Terrapin Technologies proposes a Manned Mars Mission design study. The purpose of the Manned Mars Mission is to transport ten people and a habitat with all required support systems and supplies from low Earth orbit (LEO) to the surface of Mars and, after an expedition of three months to return the personnel safely to LEO. The proposed hardware design is based on systems and components of demonstrated high capability and reliability. The mission design builds on past mission experience but incorporates innovative design approaches to achieve mission priorities. These priorities, in decreasing order of importance, are safety, reliability, minimum personnel transfer time, minimum weight, and minimum cost. The design demonstrates the feasibility and flexibility of a waverider transfer module. Information is given on how the plan meets the mission requirements.

  7. Mars Umbilical Technology Demonstrator

    NASA Technical Reports Server (NTRS)

    Houshangi, Nasser

    2000-01-01

    The objective of this project is to develop a autonomous umbilical mating for the mars umbilical technology demonstrator. The Mars Umbilical Technology Demonstrator (MUTD) shall provide electrical power and fiber optic data cable connections between two simulated mars vehicles. The Omnibot is used to provide the mobile base for the system. The mate to umbilical plate is mounted on a three axis Cartesian table, which is installed on the Omnibot mobile base. The Omnibot is controlled in a teleoperated mode. The operator using the vision system will guide the Omnibot to get close to the mate to plate. The information received from four ultrasonic sensors is used to identify the position of mate to plate and mate the umbilical plates autonomously. A successful experimentation verifies the approach.

  8. Mars Spark Source Prototype

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Lindamood, Glenn R.; Weiland, Karen J.; VanderWal, Randall L.

    1999-01-01

    The Mars Spark Source Prototype (MSSP) hardware has been developed as part of a proof of concept system for the detection of trace metals such as lead, cadmium, and arsenic in Martian dusts and soils. A spark discharge produces plasma from a soil sample and detectors measure the optical emission from metals in the plasma that will allow their identification and quantification. Trace metal measurements are vital for the assessment of the potential toxicity of the Martian environment for human exploration. The current method of X-ray fluorescence can yield concentrations only of major species. Other instruments are incompatible with the volume, weight, and power constraints for a Mars mission. The instrument will be developed primarily for use in the Martian environment, but would be adaptable for terrestrial use in environmental monitoring. This paper describes the Mars Spark Source Prototype hardware, the results of the characterization tests, and future plans for hardware development.

  9. Mars Rover Studies Soil on Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Both out on the plains of Gusev Crater and in the 'Columbia Hills,' NASA's Mars Exploration Rover Spirit has encountered a thin (approximately 1 millimeter or 0.04 inch thick), light-colored, fine-grained layer of material on top of a dark-colored, coarser layer of soil. In the hills, Spirit stopped to take a closer look at soil compacted by one of the rover's wheels. Spirit took this image with the front hazard-avoidance camera during the rover's 314th martian day, or sol (Nov. 19, 2004).

  10. Methane on Mars

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, V. A.

    Detection of methane on Mars has been claimed by Krasnopolsky Maillard Owen 2004 using FTS CFHT Formisano et al 2004 using PFS MEX and Mumma et al in preparation using CSHELL IRTF and Phoenix Gemini The measured abundances are 10 pm 3 ppb in Krasnopolsky et al 10 pm 5 ppb varying from 0 to 40 ppb in Formisano et al and 80 ppb varying from 30 to 300 ppb in Mumma et al The methane lifetime is sim 300 yr and its production loss is 300 tons yr -1 based on gas-phase chemistry Two basic questions are 1 why are the mean abundances so different and 2 how can methane vary if its lifetime is so long Variations of methane on Mars require a very effective heterogeneous loss of methane which is higher than that on Earth by a factor of ge 1000 although the expected efficiency on Earth is stronger than that on Mars because of the liquid ocean and the abundant oxygen Thermodynamic and kinetic data on the catalysis of methane do not also support variations of methane on Mars Production of methane on Mars by impacts of comets meteorites and interplanetary dust is sim 15 t yr -1 A probability that the observed methane on Mars came from impact of a single comet is 0 001 The lack of current volcanism hydrothermal activity hot spots and very low seepage of gases from the interior are not favorable for geologic methane Some weak points in the suggested geologic sources are discussed Though the geologic sources are not completely ruled out methanogenesis by living subterranean organisms is a plausible

  11. PERCIVAL mission to Mars

    NASA Technical Reports Server (NTRS)

    Reed, David W.; Lilley, Stewart; Sirman, Melinda; Bolton, Paul; Elliott, Susan; Hamilton, Doug; Nickelson, James; Shelton, Artemus

    1992-01-01

    With the downturn of the world economy, the priority of unmanned exploration of the solar system has been lowered. Instead of foregoing all missions to our neighbors in the solar system, a new philosophy of exploration mission design has evolved to insure the continued exploration of the solar system. The 'Discovery-class' design philosophy uses a low cost, limited mission, available technology spacecraft instead of the previous 'Voyager-class' design philosophy that uses a 'do-everything at any cost' spacecraft. The Percival Mission to Mars was proposed by Ares Industries as one of the new 'Discovery-class' of exploration missions. The spacecraft will be christened Percival in honor of American astronomer Percival Lowell who proposed the existence of life on Mars in the early twentieth century. The main purpose of the Percival mission to Mars is to collect and relay scientific data to Earth suitable for designing future manned and unmanned missions to Mars. The measurements and observations made by Percival will help future mission designers to choose among landing sites based on the feasibility and scientific interest of the sites. The primary measurements conducted by the Percival mission include gravity field determination, surface and atmospheric composition, sub-surface soil composition, sub-surface seismic activity, surface weather patterns, and surface imaging. These measurements will be taken from the orbiting Percival spacecraft and from surface penetrators deployed from Mars orbit. The design work for the Percival Mission to Mars was divided among four technical areas: Orbits and Propulsion System, Surface Penetrators, Gravity and Science Instruments, and Spacecraft Structure and Systems. The results for each of the technical areas is summarized and followed by a design cost analysis and recommendations for future analyses.

  12. Six Landing Sites on Mars

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The landing site chosen for NASA's Phoenix Mars Lander, at about 68 degrees north latitude, is much farther north than the sites where previous spacecraft have landed on Mars.

    Color coding on this map indicates relative elevations based on data from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor. Red is higher elevation; blue is lower elevation. In longitude, the map extends from 70 degrees (north) to minus 70 degrees (south).

  13. Mars Says 'hi'!

    NASA Technical Reports Server (NTRS)

    2004-01-01

    12 October 2004 Although one might argue that most of the 'i' is missing, and part of the 'h' has been eroded away, this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned sedimentary rock outcrops in northern Sinus Meridiani that almost seem to spell out the word, 'hi'. This natural graffiti is all that remains of a suite of sedimentary rock that once covered the area shown here. The 400 meter scale bar is about 437 yards long. The features are located near 1.8oN, 357.2oW. Sunlight illuminates the scene from the upper left.

  14. The stratigraphy of Mars

    NASA Technical Reports Server (NTRS)

    Tanaka, Kenneth L.

    1986-01-01

    A global stratigraphy of Mars was developed from a global geologic map series derived from Viking images; the stratigraphy is composed of three maps. A new chronostratigraphic classification system which consists of lower, middle, and upper Noachian, Hesperian, and Amazonian systems is described. The crater-density boundaries of the chronostratigraphic units and the absolute ages of the Martian epochs aer estimated. The relative ages of major geologic units and featues are calculated and analyzed. The geologic history of Mars is summarized on the maps in terms of epochs.

  15. Ferric sulfates on Mars

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.

    1987-01-01

    Evidence is presented for the possible existence of ferric sulfato complexes and hydroxo ferric sulfate minerals in the permafrost of Mars. A sequential combination of ten unique conditions during the cooling history of Mars is suggested which is believed to have generated an environment within Martian permafrost that has stabilized Fe(3+)-SO4(2-)-bearing species. It is argued that minerals belonging to the jarosite and copiapite groups could be present in Martian regolith analyzed in the Viking XRF measurements at Chryse and Utopia, and that maghemite suspected to be coating the Viking magnet arrays is a hydrolysate of dissolved ferric sulfato complexes from exposed Martian permafrost.

  16. Mars sample return - Science

    NASA Technical Reports Server (NTRS)

    Blanchard, Douglas P.

    1988-01-01

    The possible scientific goals of a Mars sample return mission are reviewed, including the value of samples and the selection of sampling sites. The fundamental questions about Mars which could be studied using samples are examined, including planetary formation, differentiation, volcanism and petrogenesis, weathering, and erosion. Scenarios are presented for sample acquisition and analysis. Possible sampling methods and tools are discussed, including drilling techniques, types of rovers, and processing instruments. In addition, the possibility of aerocapture out of elliptical or circular orbit is considered.

  17. Mars mission research center

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The Mars Mission Research Center is one of nine University Space Engineering Research Centers established by NASA to broaden the nation's engineering capability to meet the critical needs of the civilian space program. It has the goal of focusing on research and training technologies for planetary exploration with particular emphasis on Mars. The research combines: (1) composite materials and fabrication, (2) light weight structures and controls, and (3) hypersonic aerodynamics and propulsion in a cross disciplined program directed towards the development of the space transportation system for planetary travel.

  18. Iron Meteorite on Mars

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Mars Exploration Rover Opportunity has found an iron meteorite on Mars, the first meteorite of any type ever identified on another planet. The pitted, basketball-size object is mostly made of iron and nickel. Readings from spectrometers on the rover determined that composition. Opportunity used its panoramic camera to take the images used in this approximately true-color composite on the rover's 339th martian day, or sol (Jan. 6, 2005). This composite combines images taken through the panoramic camera's 600-nanometer (red), 530-nanometer (green), and 480-nanometer (blue) filters.

  19. Frost on Mars

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image shows bluish-white frost seen on the Martian surface near NASA's Phoenix Mars Lander. The image was taken by the lander's Surface Stereo Imager on the 131st Martian day, or sol, of the mission (Oct. 7, 2008). Frost is expected to continue to appear in images as fall, then winter approach Mars' northern plains.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  20. Gossans on Mars

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.

    1988-01-01

    The appearance of rusty iron-rich oxidized cappings over sulfide-bearing rocks on earth indicates that similar gossans may have formed on the surface of Mars. Electrochemical processes and thermodynamic relationships linking acidity to oxidation-reduction reactions between primary sulfide minerals and their oxidative weathering products present in the regolith of Mars are discussed. Remote-sensed visible spectra of the Martian surface are in keeping with the presence of poorly-crystalline FeOOH, jarosite, silica, and clay silicates found in gossans, while incompletely weathered pyrrhotite may represent the magnetic material observed in Martian regolith.