Science.gov

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. Rate of wind abrasion on Mars

    NASA Technical Reports Server (NTRS)

    Greeley, R.; Leach, R. N.; Williams, S. H.; Krinsley, D. H.; Marshall, J. R.; White, B. R.; Pollack, J. B.

    1982-01-01

    A brief description is given of the experiments performed to obtain data on windblown particles and abrasion of rocks in a simulated Martian environment. Preliminary results are presented and combined with Viking meteorological data in estimating rates of wind abrasion at the VL-1 site on Mars. Attention is also given to the implications that the results have for Martian surface history. Calculations of the present rates of abrasion by windblown particles on Mars yield values ranging from 0.021 cm/yr to nearly zero, depending on the target, the agent of abrasion, and the availability of windblown particles.

  3. 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.

  4. 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.

  5. Amazonian chemical weathering rate derived from stony meteorite finds at Meridiani Planum on Mars

    NASA Astrophysics Data System (ADS)

    Schröder, Christian; Bland, Phil A.; Golombek, Matthew P.; Ashley, James W.; Warner, Nicholas H.; Grant, John A.

    2016-11-01

    Spacecraft exploring Mars such as the Mars Exploration Rovers Spirit and Opportunity, as well as the Mars Science Laboratory or Curiosity rover, have accumulated evidence for wet and habitable conditions on early Mars more than 3 billion years ago. Current conditions, by contrast, are cold, extremely arid and seemingly inhospitable. To evaluate exactly how dry today's environment is, it is important to understand the ongoing current weathering processes. Here we present chemical weathering rates determined for Mars. We use the oxidation of iron in stony meteorites investigated by the Mars Exploration Rover Opportunity at Meridiani Planum. Their maximum exposure age is constrained by the formation of Victoria crater and their minimum age by erosion of the meteorites. The chemical weathering rates thus derived are ~1 to 4 orders of magnitude slower than that of similar meteorites found in Antarctica where the slowest rates are observed on Earth.

  6. Amazonian chemical weathering rate derived from stony meteorite finds at Meridiani Planum on Mars

    PubMed Central

    Schröder, Christian; Bland, Phil A.; Golombek, Matthew P.; Ashley, James W.; Warner, Nicholas H.; Grant, John A.

    2016-01-01

    Spacecraft exploring Mars such as the Mars Exploration Rovers Spirit and Opportunity, as well as the Mars Science Laboratory or Curiosity rover, have accumulated evidence for wet and habitable conditions on early Mars more than 3 billion years ago. Current conditions, by contrast, are cold, extremely arid and seemingly inhospitable. To evaluate exactly how dry today's environment is, it is important to understand the ongoing current weathering processes. Here we present chemical weathering rates determined for Mars. We use the oxidation of iron in stony meteorites investigated by the Mars Exploration Rover Opportunity at Meridiani Planum. Their maximum exposure age is constrained by the formation of Victoria crater and their minimum age by erosion of the meteorites. The chemical weathering rates thus derived are ∼1 to 4 orders of magnitude slower than that of similar meteorites found in Antarctica where the slowest rates are observed on Earth. PMID:27834377

  7. Amazonian chemical weathering rate derived from stony meteorite finds at Meridiani Planum on Mars.

    PubMed

    Schröder, Christian; Bland, Phil A; Golombek, Matthew P; Ashley, James W; Warner, Nicholas H; Grant, John A

    2016-11-11

    Spacecraft exploring Mars such as the Mars Exploration Rovers Spirit and Opportunity, as well as the Mars Science Laboratory or Curiosity rover, have accumulated evidence for wet and habitable conditions on early Mars more than 3 billion years ago. Current conditions, by contrast, are cold, extremely arid and seemingly inhospitable. To evaluate exactly how dry today's environment is, it is important to understand the ongoing current weathering processes. Here we present chemical weathering rates determined for Mars. We use the oxidation of iron in stony meteorites investigated by the Mars Exploration Rover Opportunity at Meridiani Planum. Their maximum exposure age is constrained by the formation of Victoria crater and their minimum age by erosion of the meteorites. The chemical weathering rates thus derived are ∼1 to 4 orders of magnitude slower than that of similar meteorites found in Antarctica where the slowest rates are observed on Earth.

  8. Status of the Dust Accumulation and Removal Technology Experiment for the Mars 2001 Surveyor Lander

    NASA Technical Reports Server (NTRS)

    Jenkins, P. P.; Landis, G. L.; Krasowski, M. J.; Greer, L. C. , III; Lekki, J.; Baraona, C. R.; Scheiman, D. A.; Wilt, D. M.

    1999-01-01

    The Dust Accumulation and Removal Technology (DART) experiment is designed to quantify the nature of dust settling out of the Martian atmosphere. DART is part of the Mars in-situ propellant precursor (MIP) experiment which is a payload on the Mars 2001 Surveyor Lander. At the time of this writing, high fidelity development hardware has been integrated in to the MIP experiment and completed Mars environment testing. Additional information is contained in the original extended abstract.

  9. Tropical mountain glaciers on Mars: Altitude-dependence of ice accumulation, accumulation conditions, formation times, glacier dynamics, and implications for planetary spin-axis/orbital history

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.; Marchant, David R.; Forget, Francois

    2008-12-01

    Fan-shaped deposits up to ˜166,000 km in area are found on the northwest flanks of the huge Tharsis Montes volcanoes in the tropics of Mars. Recent spacecraft data have confirmed earlier hypotheses that these lobate deposits are glacial in origin. Increased knowledge of polar-latitude terrestrial glacial analogs in the Antarctic Dry Valleys has been used to show that the lobate deposits are the remnants of cold-based glaciers that formed in the extremely cold, hyper-arid climate of Mars. Mars atmospheric general circulation models (GCM) show that these glaciers could form during periods of high obliquity when upwelling and adiabatic cooling of moist air favor deposition of snow on the northwest flanks of the Tharsis Montes. We present a simulation of the Tharsis Montes ice sheets produced by a static accumulation pattern based on the GCM results and compare this with the nature and extent of the geologic deposits. We use the fundamental differences between the atmospheric snow accumulation environments (mass balance) on Earth and Mars, geological observations and ice-sheet models to show that two equilibrium lines should characterize ice-sheet mass balance on Mars, and that glacial accumulation should be favored on the flanks of large volcanoes, not on their summits as seen on Earth. Predicted accumulation rates from such a parameterization, together with sample spin-axis obliquity histories, are used to show that obliquity in excess of 45° and multiple 120,000 year obliquity cycles are necessary to produce the observed deposits. Our results indicate that the formation of these deposits required multiple successive stages of advance and retreat before their full extent could be reached, and thus imply that spin-axis obliquity remained at these high values for millions of years during the Late Amazonian period of Mars history. Spin-axis obliquity is one of the main factors in the distribution and intensity of solar insolation, and thus in determining the climate

  10. Tropical Mountain Glaciers on Mars: Altitude-Dependence of Ice Accumulation, Accumulation Conditions, Formation Times, Glacier Dynamics, and Implications for Planetary Spin- Axis/Orbital History

    NASA Astrophysics Data System (ADS)

    Fastook, J. L.; Head, J. W.; Marchant, D. R.

    2007-12-01

    Lobate deposits up to ~166,000 km2 in area are found on the northwest flanks of the huge Tharsis Montes volcanos in the tropics of Mars. Recent spacecraft data have confirmed earlier hypotheses that these lobate deposits are glacial in origin. Increased knowledge of polar-latitude terrestrial glacial analogs in the Antarctic Dry Valleys has been used to show that the lobate deposits are the remnants of cold-based glaciers that formed in the extremely cold, hyper-arid climate of Mars. Mars atmospheric general circulation models (GCM) show that these glaciers form during periods of high obliquity when upwelling and adiabatic cooling of moist polar air favor deposition of snow on the northwest flanks of the Tharsis Montes. We present a simulation of the Tharsis Montes ice sheets produced by a static accumulation pattern based on the GCM results and compare this with the nature and extent of the geologic deposits. We use the fundamental differences between the atmospheric snow accumulation environments (mass balance) on Earth and Mars, geological observations and ice sheet models to show that two equilibrium lines should characterize ice sheet mass balance on Mars, and that glacial accumulation should be favored on the flanks of large volcanos, not on their summits as seen on Earth. Predicted accumulation rates from such a parameterization, together with sample spin-axis obliquity histories, are used to show that mean obliquity in excess of 45 degrees and multiple 120,000 year obliquity cycles are necessary to produce the observed deposits. Our results indicate that the formation of these deposits required multiple successive stages of advance and retreat before their full extent could be reached, and thus imply that spin-axis obliquity remained at these high values for millions of years during the Late Amazonian period of Mars history. Spin-axis obliquity is one of the main factors in the distribution and intensity of solar insolation, and thus in determining the

  11. 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.

  12. 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.

  13. Variations of dose rate observed by MSL/RAD in transit to Mars

    NASA Astrophysics Data System (ADS)

    Guo, Jingnan; Zeitlin, Cary; Wimmer-Schweingruber, Robert F.; Hassler, Donald M.; Posner, Arik; Heber, Bernd; Köhler, Jan; Rafkin, Scot; Ehresmann, Bent; Appel, Jan K.; Böhm, Eckart; Böttcher, Stephan; Burmeister, Sönke; Brinza, David E.; Lohf, Henning; Martin, Cesar; Reitz, Günther

    2015-05-01

    Aims: To predict the cruise radiation environment related to future human missions to Mars, the correlation between solar modulation potential and the dose rate measured by the Radiation Assessment Detector (RAD) has been analyzed and empirical models have been employed to quantify this correlation. Methods: The instrument RAD, onboard Mars Science Laboratory's (MSL) rover Curiosity, measures a broad spectrum of energetic particles along with the radiation dose rate during the 253-day cruise phase as well as on the surface of Mars. With these first ever measurements inside a spacecraft from Earth to Mars, RAD observed the impulsive enhancement of dose rate during solar particle events as well as a gradual evolution of the galactic cosmic ray (GCR) induced radiation dose rate due to the modulation of the primary GCR flux by the solar magnetic field, which correlates with long-term solar activities and heliospheric rotation. Results: We analyzed the dependence of the dose rate measured by RAD on solar modulation potentials and estimated the dose rate and dose equivalent under different solar modulation conditions. These estimations help us to have approximate predictions of the cruise radiation environment, such as the accumulated dose equivalent associated with future human missions to Mars. Conclusions: The predicted dose equivalent rate during solar maximum conditions could be as low as one-fourth of the current RAD cruise measurement. However, future measurements during solar maximum and minimum periods are essential to validate our estimations.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. CO2 hydrate formation and dissociation rates: Application to Mars

    NASA Astrophysics Data System (ADS)

    Ambuehl, Dan; Elwood Madden, Megan

    2014-05-01

    CO2 clathrate hydrate is a crystalline material composed of water cages around a CO2 molecule. CO2 gas hydrates are naturally occurring on Earth and are a likely phase on Mars as well as other cold planetary bodies. CO2 hydrates have minor effects on terrestrial atmospheric composition, but may be a major reservoir for greenhouse gases on Mars. In this study, CO2 hydrate formation and dissociation rates were measured experimentally on ultrapure and CO2 infused water ice (ice containing previously trapped CO2 gas bubbles). Overall, increasing pressure and temperature increased CO2 consumption rates, indicating enhanced hydrate formation rates. CO2 consumption and release rates both increased significantly in infused ice experiments as did the overall amount of CO2 consumed. CO2 bubbles formed during freezing of the infused ice likely provided more surface area for hydrate nucleation, increasing the rate of formation. Higher dissociation rates in infused ice experiments compared to ultrapure ice may be due to the higher concentration of hydrate originally formed in the bubble-filled samples. These results suggest that CO2 hydrate formation in natural, gas-rich ice occurs significantly faster than previously assumed. In addition, formation rates would be maximized and dissociation rates minimized at Mars equatorial conditions, perhaps leading to long-term storage of atmospheric CO2 in localized clathrate reservoirs.

  19. 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.

  20. 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

    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.

  1. 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.

  2. 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.

  3. 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

  4. Temperature-dependence of biomass accumulation rates during secondary succession.

    PubMed

    Anderson, Kristina J; Allen, Andrew P; Gillooly, James F; Brown, James H

    2006-06-01

    Rates of ecosystem recovery following disturbance affect many ecological processes, including carbon cycling in the biosphere. Here, we present a model that predicts the temperature dependence of the biomass accumulation rate following disturbances in forests. Model predictions are derived based on allometric and biochemical principles that govern plant energetics and are tested using a global database of 91 studies of secondary succession compiled from the literature. The rate of biomass accumulation during secondary succession increases with average growing season temperature as predicted based on the biochemical kinetics of photosynthesis in chloroplasts. In addition, the rate of biomass accumulation is greater in angiosperm-dominated communities than in gymnosperm-dominated ones and greater in plantations than in naturally regenerating stands. By linking the temperature-dependence of photosynthesis to the rate of whole-ecosystem biomass accumulation during secondary succession, our model and results provide one example of how emergent, ecosystem-level rate processes can be predicted based on the kinetics of individual metabolic rate.

  5. 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.

  6. Effects of dust accumulation and removal on radiators surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Hotes, Deborah; Olle, Raymond M.

    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 and niobium-1 percent-zirconium 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. 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 principle mode of degradation was abrasion. Arc textured Nb-1 percent-Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion.

  7. Holocene and recent sediment accumulation rates in southern Lake Michigan

    USGS Publications Warehouse

    Colman, Steven M.; King, J.W.; Jones, Glenn A.; Reynolds, R.L.; Bothner, Michael H.

    2000-01-01

    Rates of sediment accumulation in Lake Michigan are a key component of its geologic history and provide important data related to societal concerns such as shoreline erosion and the fate of anthropogenic pollutants. Previous attempts to reconstruct Holocene rates of sediment accumulation in Lake Michigan, as well as in the other Laurentian Great Lakes, have been bedeviled by the effect of refractory terrestrial material on radiocarbon ages from total organic carbon samples of lake sediments. AMS radiocarbon ages on small samples of biogenic carbonate (ostracodes and mollusks) in Lake Michigan provide accurate Holocene ages. The present bicarbonate reservoir effect is estimated from shells of mollusks collected live before atmospheric nuclear testing to be 250 yr. From paired samples of biogenic carbonate and terrestrial macrofossils, the past reservoir effect is thought to be less than 500 yr. The radiocarbon ages indicate a distinct decrease in sediment accumulation rates throughout the southern basin of Lake Michigan at about 5 ka, about the time when lake level stabilized at the Nipissing level after rising rapidly for several thousand years. Average rates of sediment accumulation for the historic period (the last 150 yr) can be estimated from radioisotopes (210Pb and 137Cs), pollen stratigraphy, and changes in sediment properties associated with human activity. Multiple methods are necessary because at any given site, problems arise in the assumptions or applicability of one or more methods. In general, the mass accumulation calculations suggest that sediments were deposited 4 to 11 times faster in the historic period than before human settlement. The character of the sediment did not change in a dramatic way, but sediment magnetic properties suggest shifts in the sources of sediment. The data suggest that some of the changes in sources and (or) character of the sediment occurred just before human settlement and were probably related to climatic changes

  8. 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.

  9. The 216-bp marB gene of the marRAB operon in Escherichia coli encodes a periplasmic protein which reduces the transcription rate of marA.

    PubMed

    Vinué, Laura; McMurry, Laura M; Levy, Stuart B

    2013-08-01

    The marRAB operon is conserved in seven genera of enteric bacteria (Escherichia, Shigella, Klebsiella, Enterobacter, Salmonella, Cronobacter, and Citrobacter). MarA is a transcriptional regulator affecting many genes involved in resistance to stresses, and MarR is an autorepressor of the operon, but a role for the marB gene has been unclear. A recent work reported that deletion of marB causes resistance to certain stresses and increases the amount of marA transcript. We show here that the small (216 bp) marB gene encodes a protein, not an sRNA, because two different stop codons within the predicted open reading frame of marB prevented plasmid-borne marB from complementing ΔmarB::Kan. The ΔmarB::Kan mutation did not increase the stability of the marA transcript, suggesting that MarB does not destabilize the marA transcript but rather reduces its rate of transcription. Placing the putative signal sequence of MarB upstream of signal-sequence-less alkaline phosphatase guided the phosphatase to its normal periplasmic location. We conclude that MarB is a small periplasmic protein that represses the marRAB promoter by an indirect mechanism, possibly involving a signal to one of the cytoplasmic regulators of that promoter.

  10. 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.

  11. Present-day impact cratering rate and contemporary gully activity on Mars.

    PubMed

    Malin, Michael C; Edgett, Kenneth S; Posiolova, Liliya V; McColley, Shawn M; Dobrea, Eldar Z Noe

    2006-12-08

    The Mars Global Surveyor Mars Orbiter Camera has acquired data that establish the present-day impact cratering rate and document new deposits formed by downslope movement of material in mid-latitude gullies on Mars. Twenty impacts created craters 2 to 150 meters in diameter within an area of 21.5 x 10(6) square kilometers between May 1999 and March 2006. The values predicted by models that scale the lunar cratering rate to Mars are close to the observed rate, implying that surfaces devoid of craters are truly young and that as yet unrecognized processes of denudation must be operating. The new gully deposits, formed since August 1999, are light toned and exhibit attributes expected from emplacement aided by a fluid with the properties of liquid water: relatively long, extended, digitate distal and marginal branches, diversion around obstacles, and low relief. The observations suggest that liquid water flowed on the surface of Mars during the past decade.

  12. 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

  13. Equatorial Pacific Reactive Phosphorus Accumulation Rates across the Eocene/Oligocene Transition

    NASA Astrophysics Data System (ADS)

    Faul, K. L.; Stewart, K. L.

    2007-12-01

    Paired benthic foraminiferal stable isotope and trace metal records from ODP Site 1218 in the equatorial Pacific have shown that the Eocence/Oligocene (E/O) transition (~34 Ma) represents a major increase in Antarctic ice accumulation and a rapid deepening of the global calcite compensation depth (CCD) occurring in two steps [e.g., Lear et al., 2000; Lear et al., 2004; Coxall et al., 2005; Palike et al., 2006]. Simultaneous increases in biogenic mass accumulation rates (MARs) around Australia and in the Atlantic Ocean have been interpreted as representing increased productivity and/or organic carbon (C) burial possibly linked to cooling and ice sheet growth [Diester-Hass and Zahn, 2001; Anderson and Delaney, 2005]. Because the global CCD deepens across the transition, there is a need to distinguish organic C burial changes from CCD changes. We are determining reactive phosphorus (P, micromol P cm-2 kyr-1) MARs as an indicator of organic C burial for Site 1218 to help constrain the relative role of productivity during the E/O climatic transition. Reactive phosphorus (the sum of oxide associated, authigenic, and organic P; sequentially extracted from bulk sediment), delivered to the sediment water interface with organic C, is well preserved in oxygenated sediments. Preliminary results show an order of magnitude decrease in reactive P concentrations (from ~100 to ~10 micromol P g-1) across the E/O boundary. This may indicate that absolute organic C burial as well as the ratio of organic C burial to calcite burial may have decreased across the E/O transition in the equatorial Pacific upwelling zone.

  14. Progress of the Dust Accumulation and Removal Technology Experiment (DART) for the Mars 2001 Lander

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    Dust deposition could be a significant problem for photovoltaic array operation for long duration missions on the surface of Mars. Measurements made by Pathfinder showed 0.3 percent loss of solar array performance per day due to dust obscuration. We have designed an experiment package, "DART", which is part of the Mars ISPP Precursor (MIP) package, to fly on the Mars-2001 Surveyor Lander. This mission, to launch in April 2001, will arrive on Mars in January 2002. The DART experiment is designed to quantify dust deposition from the Mars atmosphere, measure the properties of settled dust, measure the effect of dust deposition on array performance, and test several methods of clearing dust from solar cells.

  15. Amazonian Chemical Weathering Rate Derived from Stony Meteorite Finds at Meridiani Planum on Mars

    NASA Astrophysics Data System (ADS)

    Schröder, C.; Bland, P. A.; Golombek, M. P.; Ashley, J. W.; Warner, N. H.; Grant, J. A.

    2016-08-01

    We used the ferric iron content in stony meteorite finds discovered with the MER Opportunity at Meridiani Planum and constrained their exposure age through related surface features to derive, we believe, the first chemical weathering rate for Mars.

  16. Inconsistencies between (14)C and short-lived radionuclides-based sediment accumulation rates: Effects of long-term remineralization.

    PubMed

    Baskaran, M; Bianchi, T S; Filley, T R

    2016-09-06

    (14)C is the most widely utilized geochronometer to investigate geological, geochemical and geophysical problems over the past 5 decades. Establishment of precise sedimentation rates is crucial for the reconstruction of paleo-climate, -ecological and - environmental studies when extrapolation of sedimentation rates is utilized for time scales beyond the dating range. However, agreement between short-term and long-term sedimentation rates in anthropogenically unperturbed sediment cores has not been shown. Here we show that the AMS (14)C-based long-term mass accumulation rate (MAR) of an organic-rich (>70%) sediment core from Mud Lake, Florida to be ∼5 times lower than the short-term MAR obtained using (239,240)Pu, (137)Cs and excess (210)Pb ((210)Pbxs). The measured sediment inventories of (210)Pbxs, (137)Cs and (239,240)Pu are comparable to the atmospheric fallout for the sampling site, indicating very little accelerated sediment erosion over the past several decades. Presence of sharp fallout peaks of (239,240)Pu indicates very little sediment mixing. The penetration depths of (137)Cs and (239,240)Pu were found to be much deeper than expected and this is attributed to their post-depositional mobility. MAR calculated using (14)C-ages in successive layers also indicated decreasing MARs with depth, and was reflective of progressive remineralization. Using first-order kinetics, the sediment remineralization rate was found to be 4.4 × 10(-4) y(-1) and propose that over the long-term, remineralization of organic-rich sediment affected the long-term MAR, but not the ratio of (14)C/(12)C. Thus, the MAR and linear sedimentation rate obtained using (14)C (and other isotope-based methods) could be erroneous, although (14)C ages may not be affected by such remineralization. Long-term remineralization rates of organic matter has a direct bearing on the biogeochemical cycling of elements in aqueous systems and mass balance of elements needs to be taken into consideration.

  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.

    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

    2014-03-06

    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. Mars

    NASA Technical Reports Server (NTRS)

    McKay, Christopher P.; Cuzzi, Jeffrey N. (Technical Monitor)

    1995-01-01

    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 associated with the presence of a thick atmosphere and warmer temperatures. It is possible that at some time in the future we might recreate a habitable climate on Mars, returning it to the life-bearing state it may have enjoyed early in its history. Our studies of Mars are still in a preliminary state but everything we have learned suggests that it may be possible to restore Mars to a habitable climate. Mars' current scientific value is indisputable but it is certainly true that extensive exploration followed by a careful and studied program of introducing life would yield an even greater scientific harvest. The scientific knowledge gained by studying the ways in which a biosphere could be introduced on Mars may inform us as to the preservation of the one on Earth.

  20. Recurrence Rate and Magma Effusion Rate for the Latest Volcanism on Arsia Mons, Mars

    NASA Technical Reports Server (NTRS)

    Richardson, Jacob A.; Wilson, James A.; Connor, Charles B.; Bleacher, Jacob E.; Kiyosugi, Koji

    2016-01-01

    Magmatism and volcanism have evolved the Martian lithosphere, surface, and climate throughout the history of Mars. Constraining the rates of magma generation and timing of volcanism on the surface clarifies the ways in which magma and volcanic activity have shaped these Martian systems. The ages of lava flows on other planets are often estimated using impact crater counts, assuming that the number and size-distribution of impact craters per unit area reflect the time the lava flow has been on the surface and exposed to potential impacts. Here we show that impact crater age model uncertainty is reduced by adding stratigraphic information observed at locations where neighboring lavas abut each other, and demonstrate the significance of this reduction in age uncertainty for understanding the history of a volcanic field comprising 29 vents in the 110-kilometer-diameter caldera of Arsia Mons, Mars. Each vent within this caldera produced lava flows several to tens of kilometers in length; these vents are likely among the youngest on Mars, since no impact craters in their lava flows are larger than 1 kilometer in diameter. First, we modeled the age of each vent with impact crater counts performed on their corresponding lava flows and found very large age uncertainties for the ages of individual vents, often spanning the estimated age for the entire volcanic field. The age model derived from impact crater counts alone is broad and unimodal, with estimated peak activity in the field around 130Ma (megaannum, 1 million years). Next we applied our volcano event age model (VEAM), which uses a directed graph of stratigraphic relationships and random sampling of the impact crater age determinations to create alternative age models. Monte Carlo simulation was used to create 10,000 possible vent age sets. The recurrence rate of volcanism is calculated for each possible age set, and these rates are combined to calculate the median recurrence rate of all simulations. Applying this

  1. Recurrence rate and magma effusion rate for the latest volcanism on Arsia Mons, Mars

    NASA Astrophysics Data System (ADS)

    Richardson, Jacob A.; Wilson, James A.; Connor, Charles B.; Bleacher, Jacob E.; Kiyosugi, Koji

    2017-01-01

    Magmatism and volcanism have evolved the Martian lithosphere, surface, and climate throughout the history of Mars. Constraining the rates of magma generation and timing of volcanism on the surface clarifies the ways in which magma and volcanic activity have shaped these Martian systems. The ages of lava flows on other planets are often estimated using impact crater counts, assuming that the number and size-distribution of impact craters per unit area reflect the time the lava flow has been on the surface and exposed to potential impacts. Here we show that impact crater age model uncertainty is reduced by adding stratigraphic information observed at locations where neighboring lavas abut each other, and demonstrate the significance of this reduction in age uncertainty for understanding the history of a volcanic field comprising 29 vents in the 110-km-diameter caldera of Arsia Mons, Mars. Each vent within this caldera produced lava flows several to tens of kilometers in length; these vents are likely among the youngest on Mars, since no impact craters in their lava flows are larger than 1 km in diameter. First, we modeled the age of each vent with impact crater counts performed on their corresponding lava flows and found very large age uncertainties for the ages of individual vents, often spanning the estimated age for the entire volcanic field. The age model derived from impact crater counts alone is broad and unimodal, with estimated peak activity in the field around 130 Ma. Next we applied our volcano event age model (VEAM), which uses a directed graph of stratigraphic relationships and random sampling of the impact crater age determinations to create alternative age models. Monte Carlo simulation was used to create 10,000 possible vent age sets. The recurrence rate of volcanism is calculated for each possible age set, and these rates are combined to calculate the median recurrence rate of all simulations. Applying this approach to the 29 volcanic vents, volcanism

  2. 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.

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  6. 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.

  7. 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.

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

    PubMed

    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

    2005-03-17

    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. Chemical weathering on Mars: Rate of oxidation of iron dissolved in brines

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.

    1993-01-01

    Salts believed to occur in Martian regolith imply that brines occur on Mars, which may have facilitated the oxidation of dissolved Fe(2+) ions after they were released during chemical weathering of basaltic ferromagnesian silicate and iron sulfide minerals. Calculations show that the rate of oxidation of Fe(2+) ions at -35 C in a 6M chloride-sulfate brine that might exist on Mars is about 10(exp 6) times slower that the oxidation rate of iron in ice-cold terrestrial seawater.

  11. Geomorphic signatures of glacial activity in the Alba Patera volcanic province: Implications for recent frost accumulation on Mars

    NASA Astrophysics Data System (ADS)

    Sinha, Rishitosh K.; Murty, Sripada V. S.

    2013-08-01

    landforms lying within impact craters on Mars have led to the identification of two mechanisms for their formation: (1) intermittent deposition of atmospherically emplaced snow/ice during past spin-axis/orbital conditions and (2) flow of debris-covered ice-rich deposits. The maximum presence of the young ice/snow-rich features (thermal contraction crack polygons, gullies, arcuate ridges, and lobate debris tongues) was observed on the pole-facing slope, indicating that this slope was the preferred site for ice/snow accumulation (during the last 10 Ma). In this study, we investigated 30 craters lying in the Alba Patera volcanic province in the latitudinal bands between 45°N and 32.4°N. Morphological comparison of the younger ice/snow-rich features in these craters led us to conclude that glacial/periglacial features in Alba Patera are mainly present within pole-facing slopes of craters lying within 45°N-39°N. The craters lying within 40.2°N-40°N did not show any glacial/periglacial features. We suggest that the formation of these young ice/snow-rich features follows the same orientation trends as those of other older (>10 Ma) glacial features (debris-covered ice/snow-rich large deposits at the base of the crater wall) in the region. The present work has revealed that the onset of physical processes that result in the formation of glacial/periglacial landforms is also dependent on the changes in elevation ranges of the investigated craters in Alba Patera. Our results confirm past inferences for accumulation of ice/snow on Mars and suggest that the period of ice/snow accumulation activity in Alba Patera occurred throughout the Amazonian and lasted until the recent past, i.e., 2.1-0.4 Ma.

  12. On laboratory simulation and the temperature dependence of the evaporation rate of brine on Mars

    NASA Astrophysics Data System (ADS)

    Sears, Derek W. G.; Chittenden, Julie D.

    2005-12-01

    We have determined the evaporation rate of brine under simulated martian conditions at temperatures from 0°C to -26.0°C as part of our efforts to better understand the stability of water on Mars. Correcting for the effect of water build-up in the atmosphere and the lower gravity on Mars relative to Earth we observed a factor of almost 30 decrease in evaporation, from 0.88 mm/h at ~0°C to 0.04 mm/h at -25.0°C. The results are in excellent agreement with the predictions of Ingersoll's (1970) theoretical treatment, lending support to the theory and our procedures. Thus brine formation will increase the stability of water on Mars not only by extending the liquid temperature range, but also by considerably decreasing the evaporation rate.

  13. Extinct isotope heterogeneities in the mantles of Earth and Mars: Implications for mantle stirring rates

    NASA Astrophysics Data System (ADS)

    Jacobsen, Stein B.; Yu, Gang

    2015-04-01

    Heterogeneities in terrestrial samples for 182W/183W and 142Nd/144Nd are only preserved in Hadean and Archean rocks while heterogeneities in 129Xe/130Xe and 136Xe/130Xe persist to very young mantle-derived rocks. In contrast, meteorites from Mars show that the Martian mantle preserves heterogeneities in 182W/183W and 142Nd/144Nd up to the present. As a consequence of the probable "deep magma ocean" core formation process, we assume that the Earth and Mars both had a very early two-mantle-reservoir structure with different initial extinct nuclide isotopic compositions (different 182W/183W, 142Nd/144Nd, 129Xe/130Xe, 136Xe/130Xe ratios). Based on this assumption, we developed a simple stochastic model to trace the evolution of a mantle with two initially distinct layers for the extinct isotopes and its development into a heterogeneous mantle by convective mixing and stretching of these two layers. Using the extinct isotope system 182Hf-182W, we find that the mantles of Earth and Mars exhibit substantially different mixing or stirring rates. This is consistent with Mars having cooled faster than the Earth due to its smaller size, resulting in less efficient mantle mixing for Mars. Moreover, the mantle stirring rate obtained for Earth using 182Hf-182W is consistent with the mantle stirring rate of ~500 Myr constrained by the long-lived isotope system, 87Rb-87Sr and 147Sm-143Nd. The apparent absence of 182W/183W isotopic heterogeneity in modern terrestrial rocks is attributed to very active mantle stirring which reduced the 182W/183W isotopic heterogeneity to a relatively small scale (~83 m for a mantle stirring rate of 500 Myr) compared to the common sampling scale of terrestrial basalts (~30 or 100 km). Our results also support the "deep magma ocean" core formation model as being applicable to both Mars and Earth.

  14. H Escape Rates Inferred from MAVEN/IUVS Observations of the Mars Hydrogen Corona

    NASA Astrophysics Data System (ADS)

    Chaffin, Michael S.; Chaufray, Jean-Yves; Deighan, Justin; Schneider, Nicholas M.; McClintock, William; Stewart, A. Ian F.; Thiemann, E. M.; Clarke, John T.; Holsclaw, Gregory; Jain, Sonal Kumar; Crismani, Matteo; Stiepen, Arnaud; Montmessin, Franck; Eparvier, Francis; Jakosky, Bruce

    2016-10-01

    H escape oxidizes and dessicates the Mars atmosphere and surface, providing a key control on the present-day chemistry and long-term evolution of the planet. Recently, large variations in the escape rate of H as a function of season have been reported by several studies, making continued observation of the variation a high priority. We present escape rates derived from Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging UltraViolet Spectrograph (IUVS) observations of the extended atmosphere of Mars at H Lyman alpha (121.6 nm), which must be interpreted with a coupled density/radiative transfer model owing to the optically thick nature of the emission and the small fraction of H present in the corona on escaping trajectories. We recover densities, temperatures, and escape rates under the assumption of spherical symmetry for multiple periods across MAVEN's mission so far, beginning in December 2014 (escape rates ~4e8/cm2/s). We describe the observed variation and compare it with previously observed seasonal variation in retrieved H escape rates, providing a necessary input for future photochemical modeling studies and estimates of water loss from Mars over its history.

  15. Accumulation rates from central North Greenland during the past 700 year

    NASA Astrophysics Data System (ADS)

    Karlsson, Nanna B.; Eisen, Olaf; Nielsen, Lisbeth T.; Kipfstuhl, Sepp; Freitag, Johannes; Paden, John D.; Dahl-Jensen, Dorthe; Winter, Anna; Wilhelms, Frank

    2016-04-01

    A key variable when interpreting the evolution and mass loss from polar ice sheets is the input from the surface mass balance. While ice core records contain information on past accumulation rates, they always only provide information for a single location. Here, we present spatially distributed accumulation rates from central northern Greenland, specifically the area between the NEEM (North Greenland Eemian Drilling) and NGRIP (North Greenland Ice Core Project) ice core drill sites. The accumulation rates have been reconstructed using ice-penetrating radar, firn core measurements and inverse methods, and we are able to retrieve both spatial and temporal changes in the accumulation over an area spanning 300 km by 300 km. We investigate the stability of the accumulation pattern over the past several hundred years, and we address the question of how well the measured accumulation rates at the ice core sites capture the regional variations in accumulation. We find that while the accumulation rates at NEEM have been stable for the past 700 years, the NGRIP site has experienced fluctuations in accumulation rate. We interpret this as an indication of shifts in the dominating weather pattern over the ice divide in central North Greenland.

  16. Solidification-Rate Effects In MAR-M-246+Hf Alloy

    NASA Technical Reports Server (NTRS)

    Hamilton, David

    1988-01-01

    Under slower solidification, primary-dendrite-arm spacing increases. Report discusses experiments on influence of solidification rates on crystallographic orientation and mechanical properties of superalloy MAR-M-246+Hf. Specimens grown in directional-solidification furnace, visually examined for microstructure, and stretched to failure in tensile-testing machine. Back-reflection Laue x-ray photographs taken to determine growth orientations.

  17. The measurement of mathematics anxiety: the Mathematics Anxiety Rating Scale for Adolescents--MARS-A.

    PubMed

    Suinn, R M; Edwards, R

    1982-07-01

    Describes the Mathematics Anxiety Rating Scale for Adolescents (MARS-A). Normative data on over 1,200 junior high and senior high students are reported. In addition, psychometric data that relate to reliability and construct validity for the MARS-A scale are discussed. Two factors were identified in the scale, a factor of numerical anxiety that appeared in 91% of the items and a factor of mathematics test anxiety that appeared in the remaining items. Results that show the association between high mathematics anxiety scale scores and low grade average in mathematics courses are reported on two samples of students.

  18. A 2000-year annual record of snow accumulation rates for Law Dome, East Antarctica

    NASA Astrophysics Data System (ADS)

    Roberts, J.; Plummer, C.; Vance, T.; van Ommen, T.; Moy, A.; Poynter, S.; Treverrow, A.; Curran, M.; George, S.

    2015-05-01

    Accurate high-resolution records of snow accumulation rates in Antarctica are crucial for estimating ice sheet mass balance and subsequent sea level change. Snowfall rates at Law Dome, East Antarctica, have been linked with regional atmospheric circulation to the mid-latitudes as well as regional Antarctic snowfall. Here, we extend the length of the Law Dome accumulation record from 750 years to 2035 years, using recent annual layer dating that extends to 22 BCE. Accumulation rates were calculated as the ratio of measured to modelled layer thicknesses, multiplied by the long-term mean accumulation rate. The modelled layer thicknesses were based on a power-law vertical strain rate profile fitted to observed annual layer thickness. The periods 380-442, 727-783 and 1970-2009 CE have above-average snow accumulation rates, while 663-704, 933-975 and 1429-1468 CE were below average, and decadal-scale snow accumulation anomalies were found to be relatively common (74 events in the 2035-year record). The calculated snow accumulation rates show good correlation with atmospheric reanalysis estimates, and significant spatial correlation over a wide expanse of East Antarctica, demonstrating that the Law Dome record captures larger-scale variability across a large region of East Antarctica well beyond the immediate vicinity of the Law Dome summit. Spectral analysis reveals periodicities in the snow accumulation record which may be related to El Niño-Southern Oscillation (ENSO) and Interdecadal Pacific Oscillation (IPO) frequencies.

  19. Metal accumulation rates in northwest Atlantic pelagic sediments

    NASA Astrophysics Data System (ADS)

    Thomson, J.; Carpenter, M. S. N.; Colley, S.; Wilson, T. R. S.; Elderfield, H.; Kennedy, H.

    1984-10-01

    Measurements of 230Th, 87Sr /86Sr and twenty-four metals were made on cores from the Nares Abyssal Plain. The sediment is characterized by slowly-accumulating (0.3-0.7 g/cm 2 10 3 yr) pelagic red clays and rapidly deposited grey clays transported by turbidity currents. Despite their colour differences and the enrichment of Mn, Fe, Cu, Co, Ni, Zn, V and, to a lesser degree, the rare earths in the red clays, Sr isotope evidence demonstrates that the clays have the same terrigenous origin. The excesses of metals in the red clays have been attributed to metal removal from the water column and a comparison with the grey clays has enabled the authigenic fluxes of metals to be estimated. The fluxes obtained are in the ranges 20-50 μmol/cm 2 10 3 yr for Mn and Fe, 0.1-0.4 μmol/cm 2 10 3 yr for Cu, Co, Ni, Zn, V, Sr and Ce, 10-20 nmol/cm 2 10 3 yr for La and Nd, and 0.5-3 nmol/cm 2 10 3 yr for Sm, Eu, Gd, Dy, Er and Yb. Authigenic fluxes of Y, Nb, Cr, Zr, Rb, U and Th were not resolvable. Fluxes appear to be near constant on the Plain but comparison with other areas shows that they are quite variable both between and within ocean basins. The chief factor controlling authigenic fluxes is the geochemical abundances of the elements but fractionation within both the transition element and rare earth series can be recognized from inter-element comparisons and from differences in fluxes between Atlantic and Pacific red clays corresponding to the oceanic reactivities of the elements.

  20. 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.

  1. 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.

  2. 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.

  3. Accumulator

    NASA Technical Reports Server (NTRS)

    Fenwick, J. R.; Karigan, G. H. (Inventor)

    1977-01-01

    An accumulator particularly adapted for use in controlling the pressure of a stream of fluid in its liquid phase utilizing the fluid in its gaseous phase was designed. The accumulator is characterized by a shell defining a pressure chamber having an entry throat for a liquid and adapted to be connected in contiguous relation with a selected conduit having a stream of fluid flowing through the conduit in its liquid phase. A pressure and volume stabilization tube, including an array of pressure relief perforations is projected into the chamber with the perforations disposed adjacent to the entry throat for accommodating a discharge of the fluid in either gaseous or liquid phases, while a gas inlet and liquid to gas conversion system is provided, the chamber is connected with a source of the fluid for continuously pressuring the chamber for controlling the pressure of the stream of liquid.

  4. Rates of biomass accumulation of North Carolina Piedmont forests

    SciTech Connect

    Peet, R.K.; Council, O.P.

    1980-01-01

    Recent work by Sharp et al. on the primary production of North Carolina vegetation has suggested that the average natural forest in North Carolina is unproductive relative to its potential as intensively managed forest, the difference being roughly 300%. This variation could be attributable to patterns of forest recovery after disturbance, to management practices, or even to species composition. These and other alternative hypotheses need to be tested in a careful and objective manner. The primary objectives of the present research project were twofold: (1) to use dimension analysis methods to develop a set of regression equations useful for evaluating the productivity (rate of solar energy fixation) and biomass (stored energy) of North Carolina piedmont forests; (2) to use the resulting equations to document patterns in and rates of change of forest production and biomass during forest recovery from disturbance. The first objective was divided into two component parts. First, the regression equations were developed. Second, the caloric content of trees was studied so as to allow conversion from biomass units (Kg/m/sup 2/) to energy units (Kcal/m/sup 2/). Section 2 of this report outlines the dimension analysis procedure, presents the resulting equations, and explains their use. The portion of the project assessing the caloric content of trees is presented in Section 3. The results of our second objective, the examination of changes in forest biomass and production, are presented in Section 4.

  5. 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.

  6. Estimates of lava eruption rates at Alba Patera, Mars

    NASA Astrophysics Data System (ADS)

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

    1985-04-01

    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.

  7. A two thousand year annual record of snow accumulation rates for Law Dome, East Antarctica

    NASA Astrophysics Data System (ADS)

    Roberts, J.; Plummer, C.; Vance, T.; van Ommen, T.; Moy, A.; Poynter, S.; Treverrow, A.; Curran, M.; George, S.

    2014-11-01

    Accurate high resolution records of snow accumulation rates in Antarctica are crucial for estimating ice sheet mass balance and subsequent sea level change. Snowfall rates at Law Dome, East Antarctica, have been linked with regional atmospheric circulation to mid-latitudes as well as regional Antarctic snowfall. Here, we extend the Law Dome accumulation record from 750 to 2035 years, using recent annual layer dating that extends to AD -22. Accumulation rates were calculated as the ratio of measured to modelled layer thicknesses, multiplied by the long term mean accumulation rate. The modelled layer thicknesses were based on a power law vertical strain rate profile fitted to observed annual layer thickness. The periods AD 380-442, AD 727-783 and AD 1970-2009 have above average snow accumulation rates, while AD 663-704, AD 933-975 and AD 1429-1468 were below average. The calculated snow accumulation rates show good correlation with atmospheric reanalysis estimates, and significant spatial correlation over a wide expanse of East Antarctica, demonstrating that the Law Dome record captures larger scale variability across a large region of East Antarctica well beyond the immediate vicinity of the Law Dome summit. Spectral analysis reveals periodicities in the snow accumulation record which may be related to ENSO and Interdecadal Pacific Oscillation frequencies.

  8. 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.

  9. Comparison of elemental accumulation rates between ferromanganese deposits and sediments in the South Pacific Ocean

    USGS Publications Warehouse

    Kraemer, T.; Schornick, J.C.

    1974-01-01

    Rates of accumulation of Fe and Mn, as well as Cu, Ni, Co, Pb, Zn, Hg, U and Th have been determined for five ferromanganese deposits from four localities in the South Pacific Ocean. Manganese is accumulating in nodules and crusts at a rate roughly equivalent to that found to be accumulating in sediments in the same area. Iron shows a deficiency in accumulation in nodules and crusts with respect to sediments, especially near the continents, but also in the central and south-central Pacific. Copper is accumulating in nodules and crusts at a rate one order of magnitude less than the surrounding sediments. This is interpreted as meaning that most of the Mn is supplied as an authigenic phase to both sediments and nodules while Fe is supplied mostly by ferromanganese micro-nodules and by detrital and adsorbed components of sediments; and Cu is enriched in sediments relative to nodules and crusts most probably through biological activity. ?? 1974.

  10. 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 ...

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

    USGS Publications Warehouse

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

    2000-01-01

    Interpretation of the polar stratigraphy of Mars in terms of global climate changes is complicated by the significant difference in surface ages between the north and south polar layered terrains inferred from crater statistics. We have reassessed the cratering record in both polar regions using Viking Orbiter and Mariner 9 images. No craters have been found in the north polar layered terrain, but the surface of most of the south polar layered deposits appears to have been stable for many of the orbital/axial cycles that are thought to have induced global climate changes on Mars. The inferred surface age of the south polar layered deposits (about 10 Ma) is two orders of magnitude greater than the surface age of the north polar layered deposits and residual cap (at most 100 ka). Similarly, modeled resurfacing rates are at least 20 times greater in the north than in the south. These results are consistent with the hypotheses that polar layered deposit resurfacing rates are highest in areas covered by perennial ice and that the differences in polar resurfacing rates result from the 6.4 km difference in elevation between the polar regions. Deposition on the portion of the south polar layered deposits that is not covered by the perennial ice cap may have ceased about 5 million years ago when the obliquity of Mars no longer exceeded 40??. ?? 2000 Academic Press.

  12. 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.

  13. 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.

  14. 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.; Taylor, D.L.

    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.

  15. Radiocarbon Dating, Chronologic Framework, and Changes in Accumulation Rates of Holocene Estuarine Sediments from Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Colman, Steven M.; Baucom, Pattie C.; Bratton, John F.; Cronin, Thomas M.; McGeehin, John P.; Willard, Debra; Zimmerman, Andrew R.; Vogt, Peter 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 accelerator 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 210Pb and 137Cs 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.

  16. 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.

  17. 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.

  18. 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.

  19. Radon exhalation rates from building materials using electret ion chamber radon monitors in accumulators.

    PubMed

    Kotrappa, Payasada; Stieff, Frederick

    2009-08-01

    An electret ion chamber (EIC) radon monitor in a sealed accumulator measures the integrated average radon concentration at the end of the accumulation duration. Theoretical equations have been derived to relate such radon concentrations (Bq m(-3) ) to the radon emanation rate (Bq d(-1)) from building materials enclosed in the accumulator. As an illustration, a 4-L sealable glass jar has been used as an accumulator to calculate the radon emanation rate from different granite samples. The radon emanation rate was converted into radon flux (Bq mm(-2) d(-1)) by dividing the emanation rate by surface area of the sample. Fluxes measured on typical, commercially available granites ranged from 20-30 Bq m(-2) d(-1). These results are similar to the results reported in the literature. The lower limit of detection for a 2-d measurement works out to be 7 Bq m(-2) d(-1). Equations derived can also be used for other sealable accumulators and other integrating detectors, such as alpha track detectors.

  20. Atmospheric Pb and Ti accumulation rates from Sphagnum moss: dependence upon plant productivity.

    PubMed

    Kempter, H; Krachler, M; Shotyk, W

    2010-07-15

    The accumulation rates of atmospheric Pb and Ti were obtained using the production rates of Sphagnum mosses collected in four ombrotrophic bogs from two regions of southern Germany: Upper Bavaria (Oberbayern, OB) and the Northern Black Forest (Nordschwarzwald, NBF). Surfaces of Sphagnum carpets were marked with plastic mesh and one year later the production of plant matter was harvested. Metal concentrations were determined in acid digests using sector field ICP-MS employing well established analytical procedures. Up to 12 samples (40 x 40 cm) were collected per site, and 6-10 sites were investigated per bog. Variations within a given sampling site were in the range 2.3-4x for Pb concentrations, 1.8-2.5x for Ti concentrations, 3-8.3x for Pb/Ti, 5.6-7.8x for Pb accumulation rates, and 2.3-6.4x for Ti accumulation rates. However, the median values of these parameters for the sites (6-10 per bog) were quite consistent. The mosses from the bogs in NBF exhibited significantly greater productivity (187-202 g m(-2) a(-1)) compared to the OB peat bogs (71-91 g m(-2) a(-1)), and these differences had a pronounced effect on the Pb and Ti accumulation rates. Highly productive mosses showed no indication of a "dilution effect" of Pb or Ti concentrations, suggesting that more productive plants were simply able to accumulate more particles from the air. The median rates of net Pb accumulation by the mosses are in excellent agreement with the fluxes obtained by direct atmospheric measurements at nearby monitoring stations in both regions (EMEP and MAPESI data).

  1. Large scale spatial variation of accumulation rate across ice promontory in coastal Dronning Maud Land, Antarctica.

    NASA Astrophysics Data System (ADS)

    Callens, Denis; Matsuoka, Kenichi; Drews, Reinhard; Pattyn, Frank

    2013-04-01

    Ice rises are known to play a key role on ice shelf dynamics. By buttressing the flow, they constrain the flow of ice from the continent toward the ocean. However, since they are small hills surrounded by extremely flat area, they also play a role on atmospheric circulation. However, this impact is relatively unknown. Here, we show evidence that ice rises play a significant role on the wind redistribution of the snow. We report observations of persistent features observed all around the coast of Dronning Maud Land (DML). By analyzing radio-echo sounding data, we identified internal reflection horizons assumed to be isochronous. These layers show a remarkable variability in layer depth at both sides of the ridge, pointing to variability in surface accumulation rates. We show that a strong gradient of accumulation rate exist across, at least, 5 different ice rises in DML : Halvfarryggen Ice Rise nearby Ekstromisen (7°W), 2 ice rises into the Fimbulisen (2°E) and 2 ice rises within the Roi Baudoin Ice Shelf (25°E, Derwael & FranKenny Ice Rise). We used deepness of radar reflector as a proxy of the accumulation rate as long as we removed the influence of ice dynamics. All collected data (both low and high frequency) all show the similar persistent gradient in accumulation rate. Comparison of accumulation rate distribution and meteorological data shows that accumulation rate is twice as high on the wind side of the ridge compared to the lee side, which makes ice rise topography playing a significant role in snow redistribution. This feature is important in term of ice coring and paleoclimatic reconstruction of on time scales of 2 to 20k years.

  2. 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.

  3. 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.

  4. 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.

  5. Effect of accumulation rate on water stable isotopes of near-surface snow in inland Antarctica

    NASA Astrophysics Data System (ADS)

    Hoshina, Yu; Fujita, Koji; Nakazawa, Fumio; Iizuka, Yoshinori; Miyake, Takayuki; Hirabayashi, Motohiro; Kuramoto, Takayuki; Fujita, Shuji; Motoyama, Hideaki

    2014-01-01

    changes in water stable isotopes in polar firn were investigated at three sites characterized by different accumulation rates along the East Antarctic ice divide near Dome Fuji. Water stable isotopes, major ion concentrations, and tritium contents of three 2-4 m deep pits were measured at high resolution (2 cm). Temporally, the snow pits cover the past 50 years with snow accumulation rates in the range of 29-41 kg m-2 a-1 around Dome Fuji. Oxygen isotopic profiles in the three pits do not show annual fluctuations, but instead exhibit multiyear cycles. These multiyear cycles are lower in frequency at Dome Fuji as compared with the other two sites. Peaks of water stable isotopes in the multiyear cycles correspond to some ion concentration minima in the pits, although such relationships are not observed in coastal regions. We propose that the extremely low accumulation environment keeps the snow layer at the near surface, which result in postdepositional modifications of isotopic signals by processes such as ventilation and vapor condensation-sublimation. We estimate that oxygen isotopic ratios could be modified by >10‰ and that the original seasonal cycle could be completely overprinted under the accumulation conditions at Dome Fuji. Moreover, stake measurements at Dome Fuji suggest that the large variability in snow accumulation rate is the cause of the multiyear cycles.

  6. 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.

  7. 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...

  8. 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.

  9. 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

  10. 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.

  11. 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 %.

  12. Greenland snow accumulation rates estimated by the retracking of percolation facies from airborne radar

    NASA Astrophysics Data System (ADS)

    de la Pena, S.; Howat, I. M.

    2012-12-01

    The margins of the Greenland Ice Sheet are experiencing substantial thinning due to warming in the arctic regions, and there is a growing concern about the effects that mass imbalance of the ice sheet could have on climate and sea level rise. Although volume changes of the ice sheet may be inferred by remote sensing methods, mass gain and accumulation fluctuations are not easily distinguished and are poorly resolved. Recent advances in airborne radar techniques have resulted in systems capable of resolving snow accumulation by retracking internal layers formed by refreezing of surface meltwater that percolates through the snowpack, a phenomenon increasingly common in Greenland. We present accumulation rates for the catchment areas of the Jakobshavn, Helheim, and Rusell glaciers derived from snow depth resolved by snow and Ku-band airborne radar, flown as part of NASA's Operation IceBridge.

  13. 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.

  14. Jarosite dissolution rates and maximum lifetimes in high salinity brines: Implications for Earth and Mars

    NASA Astrophysics Data System (ADS)

    Pritchett, B. N.; Elwood Madden, M. E.; Madden, A. S.

    2012-12-01

    Jarosite is a ferric sulfate salt ((K, H, Na)Fe3(SO4)2(OH)6) that forms in acidic, oxidizing environments on Earth and has also been observed in outcrops on Mars. High chloride concentrations within the outcrops at Meridiani Planum suggest that jarosite likely interacted with high salinity brines. This study examines jarosite dissolution in H2O-CaCl2, and H2O-NaCl brines (activity of water, aH2O=0.35 and 0.75 respectively) to determine the effects of high salinity brines and aH2O on jarosite dissolution rates. Within brines with aH2O=0.75 and 0.35, initial K-jarosite dissolution rates at 298 K decrease from log r=-9.9 to -11.6 mol m-2 s-1, and Na-jarosite rates decrease from log r=-10.6 to -11.2 mol m-2 s-1, respectively. In addition, K-jarosite dissolution in NaCl brine at 263 K yielded an average dissolution rate of log r=-11.6 mol m-2 s-1. Applying a shrinking sphere model to determine 1 mm jarosite particle lifetimes extends the maximum duration of fluid alteration from lifetimes of <500 years calculated for dilute solutions up to 30,000+ years in cold, high salinity conditions. While reduced activity of water in high salinity systems decreases the initial rate of jarosite dissolution, increased activity of chloride ions and water in solution due to sulfate precipitation effectively increased the jarosite dissolution rate over days to weeks. This suggests that jarosite dissolution rates increase with time within eutectic brines, perhaps due to Cl- attack on residual Fe3+ left on the surface of jarosite grains. If brines on Mars became highly concentrated in chlorine ions through sulfate precipitation, the dissolution rate of jarosite, and perhaps other minerals as well, could accelerate with time, shortening particle lifetimes and the inferred duration of aqueous diagenesis significantly.

  15. 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.

  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. 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.

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

    PubMed

    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.

  19. 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.

  20. Comparison of carbon emission and accumulation rates in sub-arctic lakes

    NASA Astrophysics Data System (ADS)

    Lundin, Erik; Bastviken, David; Klaminder, Jonatan; Olid Garcia, Carolina; Karlsson, Jan

    2013-04-01

    Lakes play an important role for the carbon cycling in the sub-arctic landscape by both storing carbon in sediments and by releasing carbon to the atmosphere. Still, our knowledge regarding the importance of carbon accumulation rates vs. carbon emissions in lakes is poor, restricting large scale assessment of source sink potential of lakes in the landscape. In this study we compare annual carbon accumulation rates and CO2 and CH4 emissions to the atmosphere for six Swedish subarctic lakes. We measured the partial pressure of CO2 (every second hour) during the ice free season. CH4 emissions were measured using floating chambers. Furthermore, we sampled sediment cores from each lake (one to three cores per lake depending on lakes sizes) and calculated the recent accumulation rate of carbon into sediments by dating each core, using 210Pb. Total annual carbon emissions (CO2 + CH4) ranged between 5 to 54 g C m-2 yr-1; hence, all lakes were atmospheric net sources of carbon. Carbon emissions were overall dominated by CO2 which made up to over 90 % of the total annual carbon emission in all lakes except one, having low CO2 emission, where CH4 counted for 40% of the annual carbon emission. Sediment carbon accumulation rates were of comparable magnitudes as the emissions, counting for rates of 30 to 60% of the total carbon emission to the atmosphere. This results stress the dual role of subarctic lakes as they are acting both as atmospheric sources of CO2 and CH4 and as significant storages of carbon in sediments.

  1. Daily accumulation rates of marine debris on sub-Antarctic island beaches.

    PubMed

    Eriksson, Cecilia; Burton, Harry; Fitch, Stuart; Schulz, Martin; van den Hoff, John

    2013-01-15

    The worlds' oceans contain a large but unknown amount of plastic debris. We made daily collections of marine debris stranded at two sub-Antarctic islands to establish (a) physical causes of strandings, and (b) a sampling protocol to better estimate the oceans' plastic loading. Accumulation rates at some beaches were dependent on tide and onshore winds. Most of the 6389 items collected were plastic (Macquarie 95%, Heard 94%) and discarded or lost fishing gear comprised 22% of those plastic items. Stalked barnacles (Lepas spp.) were a regular attachment on Macquarie debris but not at Heard Island. The daily accumulation rate of plastic debris on Macquarie Island was an order of magnitude higher than that estimated from monthly surveys during the same 4 months in the previous 5 years. This finding suggests that estimates of the oceans' plastic loading are an order of magnitude too low.

  2. Sedimentology of Southwestern Roads region, U.S. Virgin Islands: origin and rate of sediment accumulation

    USGS Publications Warehouse

    Kindinger, Jack G.; Miller, Ronald J.; Holmes, Charles W.

    1983-01-01

    Sand deposits on southern insular shelf of St. Thomas, U.S. Virgin Islands, were investigated to determine their origin, environmental processes and accumulation rates. Sea-floor samples show that the sand has been derived (in situ) mainly from calcareous algae and molluscs. Zonation of the dominant sand producers is related to the present environmental setting; water depth has the greatest influence. Carbon-14 data (bulk sample) of cores indicate accumulation rates of slightly less than 1 mm/year for the last 5,000 years. Faunal studies show that the climate has remained constant over the past 5,000 years. The only changes in environmental conditions appear to have been an increase in water depth, changes in the patterns of water movement, and an increase in water temperature.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. The amount and accumulation rate of plastic debris on marshes and beaches on the Georgia coast.

    PubMed

    Lee, Richard F; Sanders, Dorothea P

    2015-02-15

    The amount and accumulation rate of plastic debris at 20 sites along the Georgia coast were prepared using data reported by a number of volunteer organizations. The amount of plastic debris at highly visited barrier island beaches and estuarine marshes ranged from 300 to >1000 kg. Relatively large amount of plastics (180-500 kg) were found on less visited barrier island beaches, i.e. Blackbeard, Ossabaw and Cumberland Islands. A follow up monthly or quarterly collection study was carried out on two of the sites, a barrier beach and estuarine marsh, to determine accumulation rate in 8000 m(2) areas. Accumulation rates ranged from 0.18 to 1.28 kg/30 days-8000 m(2) on the barrier island beach and from 0.6 to 1.61 kg/30 days-8000 m(2) at the estuarine marsh site. The major type of plastics, e.g. bottles, food wrappers, plastic fragments, was highly variable at different seasons and sites. The authors recommend consideration of a standardization in reporting plastic debris, with respect to quantitation of debris and sample area.

  8. 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.

  9. 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.

  10. 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.

  11. Winter Insulation By Snow Accumulation in a Subarctic Treeline Ecosystem Increases Summer Carbon Cycling Rates

    NASA Astrophysics Data System (ADS)

    Parker, T.; Subke, J. A.; Wookey, P. A.

    2014-12-01

    The effect of snow accumulation on soil carbon and nutrient cycling is attracting substantial attention from researchers. We know that deeper snow accumulation caused by high stature vegetation increases winter microbial activity and therefore carbon and nitrogen flux rates. However, until now the effect of snow accumulation, by buffering winter soil temperature, on subsequent summer soil processes, has scarcely been considered. We carried out an experiment at an alpine treeline in subarctic Sweden in which soil monoliths, contained within PVC collars, were transplanted between forest (deep winter snow) and tundra heath (shallow winter snow). We measured soil CO2efflux over two growing seasons and quantified soil microbial biomass after the second winter. We showed that respiration rates of transplanted forest soil were significantly reduced compared with control collars (remaining in the forest) as a consequence of colder, but more variable, winter temperatures. We hypothesised that microbial biomass would be reduced in transplanted forests soils but found there was no difference compared to control. We therefore further hypothesised that the similarly sized microbial pool in the control is assembled differently to the transplant. We believe that the warmer winters in forests foster more active consortia of decomposer microbes as a result of different abiotic selection pressures. Using an ecosystem scale experimental approach, we have identified a mechanism that influences summer carbon cycling rates based solely on the amount of snow that accumulates the previous winter. We conclude that modification of snow depth as a consequence of changes in vegetation structure is an important mechanism influencing soil C stocks in ecosystems where snow persists for a major fraction of the year.

  12. 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.

  13. 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.

  14. Regulation of Activation-associated MicroRNA Accumulation Rates during Monocyte-to-macrophage Differentiation*

    PubMed Central

    Eigsti, Renee L.; Sudan, Bayan; Wilson, Mary E.; Graff, Joel W.

    2014-01-01

    Circulating monocytes recruited to tissues can differentiate into macrophages and adopt unique gene expression programs in response to environmental cues. We recently described the regulated expression of several microRNAs (miRNAs) in polarized human monocyte-derived macrophages (MDMs). Basal expression of these activation-associated miRNAs was low in monocytes relative to MDMs. As development occurs in the context of specific cellular environments, we hypothesized that the rate of miRNA accumulation would be modified in the presence of microbial or cellular products during monocyte-to-macrophage differentiation. Indeed, LPS treatment augmented the accumulation of miR-146a and miR-155, whereas IL-4 treatment augmented the accumulation of miR-193b and miR-222 during development. In contrast, some stimuli repressed accumulation of specific miRNAs including interferons (IFNs) (miR-27a, miR-125a-5p, and miR-222), IL-4 (miR-125a-5p), and LPS (miR-27a). RT-PCR-based expression profiling of monocytes differentiated with distinct methods showed that activation-associated miRNAs and markers of macrophage polarization were substantially altered in MDMs differentiated in the presence of non-monocytic peripheral blood mononuclear cells due in part to NF-κB and STAT1 pathway activation. Expression of several of these miRNAs was regulated at a preprocessing step because the expression of the primary miRNAs, but not Dicer, correlated with mature miRNA expression. We conclude that a set of miRNAs is regulated during MDM differentiation, and the rate is uniquely modified for each miRNA by environmental factors. The low basal expression of activation-associated miRNAs in monocytes and their dynamic rates of accumulation during MDM differentiation permit monocytes to tailor miRNA profiles in peripheral tissues during differentiation to macrophages. PMID:25148686

  15. 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…

  16. Moment accumulation rate on faults in California inferred from viscoelastic earthquake cycle models (Invited)

    NASA Astrophysics Data System (ADS)

    Johnson, K. M.

    2009-12-01

    Calculations of moment accumulation rates on active faults require knowledge of long-term fault slip rates and the area of the fault that is locked interseismically. These parameters are routinely estimated from geodetic data using elastic block models with back slip on dislocations in an elastic half-space. Yet, the elastic models are inconsistent with studies that infer postseismic viscous flow in the lower crust and mantle occurring for decades following large earthquakes. Viscous flow in the lower crust and mantle generates rapid, localized deformation early in the earthquake cycle and slower, more diffuse deformation later in the cycle. Elastic models which neglect this time-dependent flow process may lead to biased estimates of fault slip rates and locking distribution. To address this issue we have developed a three-dimensional earthquake cycle model consisting of fault-bounded blocks in an elastic crust overlying a viscoelastic lower crust and uppermost mantle. It is a kinematic model in which long-term motions of fault-bounded blocks is imposed. Interseismic locking of faults and associated deformation is modeled with steady back-slip on faults and imposed periodic earthquakes. Creep on unlocked portions of the faults occurs at constant stress and therefore the instantaneous creep rate is proportional to the instantaneous stressing rate on the fault. We compare geologic slip rate estimates in southern California with model estimates using GPS data and show that elastic block models underpredict slip rates on several faults that are late in the earthquake cycle and overpredict slip rates on faults that are early in the earthquake cycle. The viscoelastic cycle model, constrained by earthquake timing from the geologic record, predicts fault slip rates that are entirely consistent with geologic estimates for all major faults in southern California. For northern California, fault slip rate estimates using geodetic data appear not to be strongly dependent on

  17. Proton cyclotron waves occurrence rate upstream from Mars observed by MAVEN: Associated variability of the Martian upper atmosphere

    NASA Astrophysics Data System (ADS)

    Romanelli, N.; Mazelle, C.; Chaufray, J. Y.; Meziane, K.; Shan, L.; Ruhunusiri, S.; Connerney, J. E. P.; Espley, J. R.; Eparvier, F.; Thiemann, E.; Halekas, J. S.; Mitchell, D. L.; McFadden, J. P.; Brain, D.; Jakosky, B. M.

    2016-11-01

    Measurements provided by the Magnetometer and the Extreme Ultraviolet Monitor (EUVM) on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft together with atomic H exospheric densities derived from numerical simulations are studied for the time interval from October 2014 up to March 2016. We determine the proton cyclotron waves (PCWs) occurrence rate observed upstream from Mars at different times. We also study the relationship with temporal variabilities of the high-altitude Martian hydrogen exosphere and the solar EUV flux reaching the Martian environment. We find that the abundance of PCWs is higher when Mars is close to perihelion and decreases to lower and approximately constant values after the Martian Northern Spring Equinox. We also conclude that these variabilities cannot be associated with biases in MAVEN's spatial coverage or changes in the background magnetic field orientation. Higher H exospheric densities on the Martian dayside are also found when Mars is closer to perihelion, as a result of changes in the thermospheric response to variability in the ultraviolet flux reaching Mars at different orbital distances. A consistent behavior is also observed in the analyzed daily irradiances measured by the MAVEN EUVM. The latter trends point toward an increase in the planetary proton densities upstream from the Martian bow shock near perihelion. These results then suggest a method to indirectly monitor the variability of the H exosphere up to very high altitudes during large time intervals (compared to direct measurements of neutral particles), based on the observed abundance of PCWs.

  18. Accumulation rates during 1311-2011 CE in North Central Greenland derived from air-borne radar data

    NASA Astrophysics Data System (ADS)

    Karlsson, Nanna; Eisen, Olaf; Dahl-Jensen, Dorthe; Freitag, Johannes; Kipfstuhl, Sepp; Lewis, Cameron; Nielsen, Lisbeth; Paden, John; Winter, Anna; Wilhelms, Frank

    2016-11-01

    Radar-detected internal layering contains information on past accumulation rates and patterns. In this study, we assume that the radar layers are isochrones, and use the layer stratigraphy in combination with ice-core measurements and numerical methods to retrieve accumulation information for the northern part of central Greenland. Measurements of the dielectric properties of an ice core from the NEEM (North Greenland Eemian Ice Drilling) site, allow for correlation of the radar layers with volcanic horizons to obtain an accurate age of the layers. We obtain accumulation patterns averaged over 100 a for the period 1311-2011. Our results show a clear trend of high accumulation rates west of the ice divide and low accumulation rates east of the ice divide. At the NEEM site the accumulation pattern is persistent during our study period and only small temporal variations occur in the accumulation rate. However, from approximately 200 km south of the NEEM drill site, the accumulation rate shows temporal variations based on our centennial averages. We attribute this variation to shifts in the location of the high-low accumulation boundary that usually is aligned with the ice divide, but appears to have moved across the divide in the past.

  19. 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.

  20. Holocene sediment accumulation rates in fjords and bays of Chilean Patagonia and the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Wellner, J. S.; Anderson, J. B.; Milliken, K.; Fernandez, R.; Michalchuk, B.; Boyd, B.

    2007-12-01

    Beginning in 2005 and ending in May of 2007, we completed a series of four research cruises in the fjords and bays of Chilean Patagonia and the Antarctic Peninsula aimed, in part, at determining the style and rate of Holocene sediment accumulation in a range of glacial settings. Our original hypothesis stated that rates of glacial erosion are a function of sliding speed, and are therefore expected to diminish sharply as basal temperatures drop below the melting point. To test this hypothesis, we measured sediment accumulation in tidewater glacier fjords ranging from fast-moving temperate glaciers in Patagonia to slower moving polar glaciers on the Antarctic Peninsula. Four fjords were surveyed in Patagonia ranging from San Rafael fjord in the Northern Patagonia ice field to Marinelli fjord in Tierra del Fuego. The cruises to the Antarctic Peninsula included two SHALDRIL legs during which drill cores recovered 108 m and 80 m of Holocene sediment in Maxwell Bay, South Shetland Islands, and the Firth of Tay in the northwestern Weddell Sea, respectively. An additional nine fjords across the northern peninsula were surveyed with kasten and jumbo piston cores. To date, we have completed nearly 100 radiocarbon dates from fossil carbonate material, both shells and foraminifera, extracted from the sediment cores obtained in these fjords. Our initial results highlight the complexity of the controls on sediment yields and the extreme variability in sediment accumulation amongst fjords. While climate may be the first order control on glacier erosion rates and sediment transport to bays and fjords, several other factors must significantly influence these processes and may mask the broader signal. Our ongoing work with this newly acquired comprehensive dataset is examining additional controls including drainage basin size, precipitation gradient, altitude of the glaciers, and glacial substrate.

  1. 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

  2. A Survey of Sinuous Ridges and Inferred Fluvial Discharge Rates in Northwest Hellas, Mars

    NASA Astrophysics Data System (ADS)

    Anderson, R. B.; Herkenhoff, K. E.

    2012-12-01

    Sinuous ridges are a widespread class of geomorphic feature on Mars, and in many cases are interpreted to be inverted fluvial channels. Although negative-relief valley networks thought to be related to fluvial activity have been mapped in detail over the entire planet (e.g. Carr, 1995; Hynek et al., 2010), few regional- to global-scale surveys of sinuous ridges have been conducted (e.g. Williams, 2007; Jacobsen and Burr, 2012). With the availability of Context Camera (CTX ) images from the Mars Reconnaissance Orbiter (MRO) covering a significant fraction of the martian surface at 6 meters per pixel, such studies are now feasible. In addition, Williams et al. (2009) have demonstrated that paleodischarge can be calculated based on the width, meander wavelength, and meander radius of sinuous ridges interpreted to be inverted channels. This method has been used successfully on the sinuous ridges in the Aeolis/Zephyria plana region (Burr et al., 2010). We have begun a survey of sinuous ridges in the northwest Hellas region (-15 N to -45 N, 30 E to 75 E) using 1156 radiometrically calibrated and map projected CTX images. This region includes the northwestern portion of the Hellas basin floor and rim, as well as a significant expanse of the cratered highlands to the north and west of the basin. This region was chosen because it includes terrain of varying age (primarily Noachian to Hesperian; Leonard and Tanaka, 2001) and includes "raised curvilinear features" identified by Williams (2007) on the western basin floor, northern rim, and in the highlands northwest of Hellas . By mapping the distribution of sinuous ridges in terrain of varying age and estimating their paleodischarge rates, we will be able to determine how the discharge rate varied over martian history. Carr, M. H. (1995), J. Geophys. Res., 100, 7479-7507, doi:10.1029/95JE00260. Hynek, B. M., M. Beach, and M. R. T. Hoke (2010), J. Geophys. Res., 115, E09008, doi:10.1029/2009JE003548. Williams, R.M.E. (2007

  3. 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.

  4. Historical accumulation rates of mercury in four Scottish ombrotrophic peat bogs over the past 2000 years.

    PubMed

    Farmer, John G; Anderson, Peter; Cloy, Joanna M; Graham, Margaret C; MacKenzie, Angus B; Cook, Gordon T

    2009-10-15

    The historical accumulation rates of mercury resulting from atmospheric deposition to four Scottish ombrotrophic peat bogs, Turclossie Moss (northeast Scotland), Flanders Moss (west-central), Red Moss of Balerno (east-central) and Carsegowan Moss (southwest), were determined via analysis of (210)Pb- and (14)C-dated cores up to 2000 years old. Average pre-industrial rates of mercury accumulation of 4.5 and 3.7 microg m(-2) y(-1) were obtained for Flanders Moss (A.D. 1-1800) and Red Moss of Balerno (A.D. 800-1800), respectively. Thereafter, mercury accumulation rates increased to typical maximum values of 51, 61, 77 and 85 microg m(-2) y(-1), recorded at different times possibly reflecting local/regional influences during the first 70 years of the 20th century, at the four sites (TM, FM, RM, CM), before declining to a mean value of 27+/-15 microg m(-2) y(-1) during the late 1990s/early 2000s. Comparison of such trends for mercury with those for lead and arsenic in the cores and also with direct data for the declining UK emissions of these three elements since 1970 suggested that a substantial proportion of the mercury deposited at these sites over the past few decades originated from outwith the UK, with contributions to wet and dry deposition arising from long-range transport of mercury released by sources such as combustion of coal. Confidence in the chronological reliability of these core-derived trends in absolute and relative accumulation of mercury, at least since the 19th century, was provided by the excellent agreement between the corresponding detailed and characteristic temporal trends in the (206)Pb/(207)Pb isotopic ratio of lead in the (210)Pb-dated Turclossie Moss core and those in archival Scottish Sphagnum moss samples of known date of collection. The possibility of some longer-term loss of volatile mercury released from diagenetically altered older peat cannot, however, be excluded by the findings of this study.

  5. 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.

  6. 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.

  7. Accumulation of cAMP augments dynamic vagal control of heart rate.

    PubMed

    Nakahara, T; Kawada, T; Sugimachi, M; Miyano, H; Sato, T; Shishido, T; Yoshimura, R; Miyashita, H; Inagaki, M; Alexander, J; Sunagawa, K

    1998-08-01

    Recent investigations in our laboratory using a Gaussian white noise perturbation technique have shown that simultaneous sympathetic stimulation augmented the gain of the transfer function from vagal stimulation frequency to heart rate response. However, the mechanism of that augmentation remains to be elucidated. In this study, we examined in anesthetized rabbits how three pharmacological interventions known to cause intracellular accumulation of cAMP affected the transfer function. Isoproterenol (0.3 microg . kg-1 . min-1 iv) increased the dynamic gain of transfer function from 7.12 +/- 0.67 to 12.4 +/- 1.21 beats . min-1 . Hz-1 (P < 0.05) without changing the corner frequency or the lag time. Similar augmentations were observed when forskolin (5 microg . kg-1 . min-1 iv) or theophylline (20 mg/kg iv) was administered under conditions of beta-adrenergic blockade. These results suggest that the accumulation of cAMP at postjunctional effector sites contributes, at least in part, to the sympathetic augmentation of the dynamic vagal control of heart rate.

  8. Carbon accumulation rates and the origin of the Holocene sapropel in the Black Sea

    NASA Astrophysics Data System (ADS)

    Calvert, S. E.; Vogel, J. S.; Southon, J. R.

    1987-10-01

    A detailed radiocarbon chronology obtained by accelerator mass spectrometry together with organic carbon and carbonate measurements on two Black Sea cores has been used to compare and contrast the burial fluxes of organic carbon in the Holocene sapropel and the modern sediment. At both deep-water and eastern-slope sites, the sapropel is separated from the modern facies by a variable thickness of compositionally homogeneous sediment with low levels of organic carbon and anomalously old radiocarbon ages. This homogeneous unit probably represents deposition by slumping or mudflow. The age limits of the sapropel are 1600 6600 B.P. at the deep-water site and 4000 6000 B.P. (radiocarbon years before 1950 A.D.) at the shallow-water site. The carbon accumulation rate in the deep-water sapropel is higher than that in the modern deep-water facies by a factor of 2 and is approximately the same as that in the modern sediment in shallow water. The revised chronology of sapropel formation and the differences in the carbon accumulation rates probably indicate that the sapropel was formed by increased production during the transition from the premodern lake to the modern marine phases of the Black Sea. This conclusion is consistent with the clear marine carbon-isotope signal in the organic matter in the sapropel in both cores (results to be reported elsewhere), in contrast to the mixed source of carbon in the other facies.

  9. 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.

  10. 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

  11. 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.; 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.

  12. 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).

  13. Faster evolving Drosophila paralogs lose expression rate and ubiquity and accumulate more non-synonymous SNPs

    PubMed Central

    2014-01-01

    Background Duplicated genes can indefinately persist in genomes if either both copies retain the original function due to dosage benefit (gene conservation), or one of the copies assumes a novel function (neofunctionalization), or both copies become required to perform the function previously accomplished by a single copy (subfunctionalization), or through a combination of these mechanisms. Different models of duplication retention imply different predictions about substitution rates in the coding portion of paralogs and about asymmetry of these rates. Results We analyse sequence evolution asymmetry in paralogs present in 12 Drosophila genomes using the nearest non-duplicated orthologous outgroup as a reference. Those paralogs present in D. melanogaster are analysed in conjunction with the asymmetry of expression rate and ubiquity and of segregating non-synonymous polymorphisms in the same paralogs. Paralogs accumulate substitutions, on average, faster than their nearest singleton orthologs. The distribution of paralogs’ substitution rate asymmetry is overdispersed relative to that of orthologous clades, containing disproportionally more unusually symmetric and unusually asymmetric clades. We show that paralogs are more asymmetric in: a) clades orthologous to highly constrained singleton genes; b) genes with high expression level; c) genes with ubiquitous expression and d) non-tandem duplications. We further demonstrate that, in each asymmetrically evolving pair of paralogs, the faster evolving member of the pair tends to have lower average expression rate, lower expression uniformity and higher frequency of non-synonymous SNPs than its slower evolving counterpart. Conclusions Our findings are consistent with the hypothesis that many duplications in Drosophila are retained despite stabilising selection being more relaxed in one of the paralogs than in the other, suggesting a widespread unfinished pseudogenization. This phenomenon is likely to make detection of

  14. Investigation of the effect of dissolved salts, soil layers, and wind on the evaporation rate of water on Mars

    NASA Astrophysics Data System (ADS)

    Chittenden, Julie Diane

    2007-08-01

    Laboratory simulation experiments have been performed to study the stability of water under martian conditions. The first chapter of this thesis is a background introduction into the history of Mars and a description of the evidence for past and present water on Mars. The second chapter describes experiments that were performed on low concentration brine solutions, but were never published. The rest of the thesis is submitted in thesis by publication format. Chapters three and four were published in Geophysical Research Letters and chapter five has been submitted to Mars Polar Science Special Edition of Icarus . The experiments described in this thesis were performed in the planetary simulation chamber in the W.M. Keck Laboratory for Space Simulations at the Arkansas Center for Space and Planetary Sciences. By simulating the conditions on Mars, with the exception of the gravitational constant, we are able to accurately measure the evaporation and sublimation of water and water ice. We measured the evaporation rates of low concentrations of a sodium chloride brine solution, the effect of temperature on eutectic solutions of sodium chloride and calcium chloride brines, the effect of a soil layer on the sublimation rate of ice, and the effect of wind on the sublimation of ice. The results for the evaporation of brine solutions and the results for the sublimation of ice under a soil layer agree very well with theoretical calculations using Fick's Law of Diffusion, as put forth by A.P. Ingersoll and C.B. Farmer, respectively. In contrast, the sublimation rate of ice under varied wind velocities did not agree with previous theory. Therefore, a new theoretical model was developed in order to accurately describe the effect of increasing wind velocity on sublimation rates. The new theoretical model agreed extremely well with experimental data. In performing these experiments, we are better able to understand the behavior of water under martian condition and can be used to

  15. A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata).

    PubMed

    Weisrock, David W; Papenfuss, Theodore J; Macey, J Robert; Litvinchuk, Spartak N; Polymeni, Rosa; Ugurtas, Ismail H; Zhao, Ermi; Jowkar, Houman; Larson, Allan

    2006-11-01

    We examine phylogenetic relationships among salamanders of the family Salamandridae using approximately 2700 bases of new mtDNA sequence data (the tRNALeu, ND1, tRNAIle, tRNAGln, tRNAMet, ND2, tRNATrp, tRNAAla, tRNAAsn, tRNACys, tRNATyr, and COI genes and the origin for light-strand replication) collected from 96 individuals representing 61 of the 66 recognized salamandrid species and outgroups. Phylogenetic analyses using maximum parsimony and Bayesian analysis are performed on the new data alone and combined with previously reported sequences from other parts of the mitochondrial genome. The basal phylogenetic split is a polytomy of lineages ancestral to (1) the Italian newt Salamandrina terdigitata, (2) a strongly supported clade comprising the "true" salamanders (genera Chioglossa, Mertensiella, Lyciasalamandra, and Salamandra), and (3) a strongly supported clade comprising all newts except S. terdigitata. Strongly supported clades within the true salamanders include monophyly of each genus and grouping Chioglossa and Mertensiella as the sister taxon to a clade comprising Lyciasalamandra and Salamandra. Among newts, genera Echinotriton, Pleurodeles, and Tylototriton form a strongly supported clade whose sister taxon comprises the genera Calotriton, Cynops, Euproctus, Neurergus, Notophthalmus, Pachytriton, Paramesotriton, Taricha, and Triturus. Our results strongly support monophyly of all polytypic newt genera except Paramesotriton and Triturus, which appear paraphyletic, and Calotriton, for which only one of the two species is sampled. Other well-supported clades within newts include (1) Asian genera Cynops, Pachytriton, and Paramesotriton, (2) North American genera Notophthalmus and Taricha, (3) the Triturus vulgaris species group, and (4) the Triturus cristatus species group; some additional groupings appear strong in Bayesian but not parsimony analyses. Rates of lineage accumulation through time are evaluated using this nearly comprehensive sampling of

  16. 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.

  17. 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.

  18. 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

  19. Accumulation Rates of Trace Elements in the Cariaco Basin-A 20-kyr History of Seawater Chemistry and Global Climate

    NASA Astrophysics Data System (ADS)

    Piper, D. Z.; Dean, W. E.

    2002-12-01

    A sediment core from the Cariaco Basin on the Venezuelan continental shelf, which collected sediment as old as 20 kyr, was analyzed for its major-element-oxide and trace-element concen-trations. The elements can be partitioned between a siliciclastic, terrigenous-derived fraction and two seawater-derived fractions. The marine fractions are (1) a biogenic fraction represented by nutrient trace elements taken up mostly by phytoplankton in the photic zone, and (2) a hydroge-nous fraction derived from bottom water via adsorption and precipitation reactions. The present-day export of organic matter from the photic zone, redox conditions and advection of bottom water, and the flux of terrigenous debris into the basin are used to calculate current trace-element accu-mulation rates. The sums of calculated accumulation rates of Cd, Cu, Mo, Ni, V, and Zn show excellent agreement with their measured bulk rates of accumulation in the uppermost surface sediment. This agreement between current measured and calculated accumulation rates of trace elements supports a model of trace-element accumulation rates in the subsurface sediment that gives a 20-kyr history of upwelling into the photic zone, bottom-water advection, and sediment provenance. Extrema in the trace-element accumulation rates and interpreted hydrographic properties of the water column correspond to changes in eustatic sea level and global climate.

  20. 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.

  1. Debris-covered piedmont glaciers along the northwest flank of the Olympus Mons scarp: Evidence for low-latitude ice accumulation during the Late Amazonian of Mars

    NASA Astrophysics Data System (ADS)

    Milkovich, Sarah M.; Head, James W.; Marchant, David R.

    2006-04-01

    We use Viking and new MGS and Odyssey data to characterize the lobate deposits superimposed on aureole deposits along the west and northwest flanks of Olympus Mons, Mars. These features have previously been interpreted variously as landslide, pyroclastic, lava flow or glacial features on the basis of Viking images. The advent of multiple high-resolution image and topography data sets from recent spacecraft missions allow us to revisit these features and assess their origins. On the basis of these new data, we interpret these features as glacial deposits and the remnants of cold-based debris-covered glaciers that underwent multiple episodes of advance and retreat, occasionally interacting with extrusive volcanism from higher on the slopes of Olympus Mons. We subdivide the deposits into fifteen distinctive lobes. Typical lobes begin at a theater-like alcove in the escarpment at the base of Olympus Mons, interpreted to be former ice-accumulation zones, and extend outward as a tongue-shaped or fan-shaped deposit. The surface of a typical lobe contains (moving outward from the basal escarpment): a chaotic facies of disorganized hillocks, interpreted as sublimation till in the accumulation zone; arcuate-ridged facies characterized by regular, subparallel ridges and interpreted as the ridges of surface debris formed by the flow of underlying ice; and marginal ridges interpreted as local terminal moraines. Several lobes also contain a hummocky facies toward their margins that is interpreted as a distinctive type of sublimation till shaped by structural dislocations and preferential loss of ice. Blocky units are found extending from the escarpment onto several lobes; these units are interpreted as evidence of lava-ice interaction and imply that ice was present at a time of eruptive volcanic activity higher on the slopes of Olympus Mons. Other than minor channel-like features in association with lava-ice interactions, we find no evidence for the flow of liquid water in

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. Accumulation rates and predominant atmospheric sources of natural and anthropogenic Hg and Pb on the Faroe Islands

    NASA Astrophysics Data System (ADS)

    Shotyk, W.; Goodsite, M. E.; Roos-Barraclough, F.; Givelet, N.; Le Roux, G.; Weiss, D.; Cheburkin, A. K.; Knudsen, K.; Heinemeier, J.; van Der Knaap, W. O.; Norton, S. A.; Lohse, C.

    2005-01-01

    A monolith representing 5420 14C yr of peat accumulation was collected from a blanket bog at Myrarnar, Faroe Islands. The maximum Hg concentration (498 ng/g at a depth of 4.5 cm) coincides with the maximum concentration of anthropogenic Pb (111 μg/g). Age dating of recent peat accumulation using 210Pb (CRS model) shows that the maxima in Hg and Pb concentrations occur at AD 1954 ± 2. These results, combined with the isotopic composition of Pb in that sample ( 206Pb/ 207Pb = 1.1720 ± 0.0017), suggest that coal burning was the dominant source of both elements. From the onset of peat accumulation (ca. 4286 BC) until AD 1385, the ratios Hg/Br and Hg/Se were constant (2.2 ± 0.5 × 10 -4 and 8.5 ± 1.8 × 10 -3, respectively). Since then, Hg/Br and Hg/Se values have increased, also reaching their maxima in AD 1954. The age date of the maximum concentrations of anthropogenic Hg and Pb in the Faroe Islands is consistent with a previous study of peat cores from Greenland and Denmark (dated using the atmospheric bomb pulse curve of 14C), which showed maximum concentrations in AD 1953. The average rate of atmospheric Hg accumulation from 1520 BC to AD 1385 was 1.27 ± 0.38 μg/m 2/yr. The Br and Se concentrations and the background Hg/Br and Hg/Se ratios were used to calculate the average rate of natural Hg accumulation for the same period, 1.32 ± 0.36 μg/m 2/yr and 1.34 ± 0.29 μg/m 2/yr, respectively. These fluxes are similar to the preanthropogenic rates obtained using peat cores from Switzerland, southern Greenland, southern Ontario, Canada, and the northeastern United States. Episodic volcanic emissions and the continual supply of marine aerosols to the Faroe Islands, therefore, have not contributed significantly to the Hg inventory or the Hg accumulation rates, relative to these other areas. The maximum rate of Hg accumulation was 34 μg/m 2/yr. The greatest fluxes of anthropogenic Hg accumulation calculated using Br and Se, respectively, were 26 and 31 μg/m 2

  9. Radionuclide activities, geochemistry, and accumulation rates of sediments in the Gulf of Thailand

    NASA Astrophysics Data System (ADS)

    Srisuksawad, Kanitha; Porntepkasemsan, Boonsom; Nouchpramool, Sunun; Yamkate, Pathom; Carpenter, Roy; Peterson, Michael L.; Hamilton, Terry

    1997-07-01

    Downcore concentration profiles of 210Pb, U, and Th isotopes, Al, Fe, Ti, Mn and Sc were measured in sediment box cores collected at 22 stations (16-70 m water depth) covering most of the Thai zone of the Gulf of Thailand. Distributions of excess 210Pb and the detrital elements were used to study spatial variations in sedimentary processes, mineralogy, and geochemistry between different regions of the gulf. Steady-state depositional concentrations and fluxes of excess 210Pb are 3-10 times lower in Gulf of Thailand sediments than in sediments from mid-latitudes in the northern hemisphere, reflecting lower 210Pb inputs from atmospheric fallout at 6-13°N latitude and from lower production of 210Pb from 226Ra in the shallower waters of the Gulf. U and Th concentrations are approximately 2-3 times higher than those in shelf sediments from mid-latitudes of North America, consistent with a higher proportion of granitic source rocks in the Thai environment. Downcore variations in 228Th/ 232Th activity ratios and in U activities reveal that exchange of interstitial and overlying waters and their dissolved chemicals occurs down to 20 cm in 8 of 10 cores. This benthic exchange may be important in budgets of fluxes of other soluble chemicals in this shallow shelf sea. A net flux of U isotopes from overlying water into Gulf of Thailand sediments occurs, in contrast to their release from sediments of the tropical Amazon shelf. Detectable levels of 137Cs were found only in sediments near the mouth of the largest river, the Chao Phraya. The detrital elements 232Th, 230Th, Al, Ti, and Sc all show relatively uniform downcore concentration profiles. This supports a key assumption in calculations of sediment accumulation rates from downcore profiles of 210Pb activity, that steady-state depositional conditions exist and that basic sediment mineralogy and grain size does not change. 210Pb model derived mass accumulation rates vary between 270 and 490 mg/cm 2 per year in the upper Gulf

  10. 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.

  11. River sediment flux and shelf sediment accumulation rates on the Pacific Northwest margin

    NASA Astrophysics Data System (ADS)

    Wheatcroft, R. A.; Sommerfield, C. K.

    2005-02-01

    To test the generality of insight obtained from recent STRATAFORM studies of northern California's Eel margin, river sediment sources and continental shelf sinks were examined on the Pacific Northwest margin from 38° to 44.5°N. River discharge and sediment concentration data acquired by the US Geological Survey were used to update long-term annual suspended-sediment loads for 17 rivers that range in basin area from 635 to ˜22,000 km 2. Resulting annual load estimates vary over 3 orders of magnitude (0.065-18×10 9 kg/yr), with major suspended-sediment fluxes supplied by, in decreasing order, the Eel, Klamath/Trinity, Mad, Rogue, Umpqua and Russian rivers. Down-core profiles of excess 210Pb and 137Cs were used to estimate sediment accumulation rates (SARs) at prescribed depths (70 and 110 m) and distances (0-40-km north and south along-shelf) from each of the major rivers. SARs were found to vary much less than the river flux estimates, and are mostly in the range of 1.5 to 6 mm/yr. Most significantly, shelf SARs on the other Pacific Northwest margins are only slightly less than those observed on the Eel shelf, implying that much higher proportions of riverine sediment are retained on those shelves. Likely reasons that the Eel dispersal system exhibits greater off-shelf transport are (1) the narrower and steeper shelf geometry, and (2) the existence of a newly documented cross-isobath sediment transport mechanism that involves wave-modulated fluid mud flows. Testing whether the fluid mud flows are a consequence of the Eel River basin's high sediment yield, and are thus unique to the Eel, or are caused by intense wave energy during discharge events, and hence are operative on many other margins, awaits future bottom-boundary layer measurements.

  12. 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.

  13. 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.

  14. Carbon accumulation rates recorded in the last 150years in tropical high mountain peatlands of the Atlantic Rainforest, SE - Brazil.

    PubMed

    Lourençato, Lúcio F; Caldeira, Pedro P; Bernardes, Marcelo C; Buch, Andressa C; Teixeira, Daniel C; Silva-Filho, Emmanoel V

    2017-02-01

    Peatlands are environmental matrices that store large amounts of organic carbon (TOC) and work as records of environmental changes. Recent record of organic carbon accumulated were assessed in two Forest National Parks, Itatiaia and Serra dos Órgãos in the Southeastern of Brazil. Based on organic and inorganic characterization, the cores from peatlands presented a predominance of organic material in an advanced stage of decomposition and those soils were classified as typical Haplosaprists Histosols. The combination of favorable topographic and climatic conditions led to rapid C accumulation across coastal mountain in the tropical peatlands studied, presenting an average accumulation rate of C, in the last century, of 194gCm(-2)yr(-1) about 7 higher times than the rate found in boreal and subarctic peatlands, those higher values may be related to changes in the hydrological cycle occurred since 1950s.

  15. An excretory function for the Escherichia coli outer membrane pore TolC: upregulation of marA and soxS transcription and Rob activity due to metabolites accumulated in tolC mutants.

    PubMed

    Rosner, Judah L; Martin, Robert G

    2009-08-01

    Efflux pumps function to rid bacteria of xenobiotics, including antibiotics, bile salts, and organic solvents. TolC, which forms an outer membrane channel, is an essential component of several efflux pumps in Escherichia coli. We asked whether TolC has a role during growth in the absence of xenobiotics. Because tolC transcription is activated by three paralogous activators, MarA, SoxS, and Rob, we examined the regulation of these activators in tolC mutants. Using transcriptional fusions, we detected significant upregulation of marRAB and soxS transcription and Rob protein activity in tolC mutants. Three mechanisms could be distinguished: (i) activation of marRAB transcription was independent of marRAB, soxR, and rob functions; (ii) activation of soxS transcription required SoxR, a sensor of oxidants; and (iii) Rob protein was activated posttranscriptionally. This mechanism is similar to the mechanisms of upregulation of marRAB, soxS, and Rob by treatment with certain phenolics, superoxides, and bile salts, respectively. The transcription of other marA/soxS/rob regulon promoters, including tolC itself, was also elevated in tolC mutants. We propose that TolC is involved in the efflux of certain cellular metabolites, not only xenobiotics. As these metabolites accumulate during growth, they trigger the upregulation of MarA, SoxS, and Rob, which in turn upregulate tolC and help rid the bacteria of these metabolites, thereby restoring homeostasis.

  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 L.; 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. 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...

  19. 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...

  20. Highly anomalous accumulation rates of C and N recorded by a relic, free-floating peatland in Central Italy.

    PubMed

    Zaccone, Claudio; Lobianco, Daniela; Shotyk, William; Ciavatta, Claudio; Appleby, Peter G; Brugiapaglia, Elisabetta; Casella, Laura; Miano, Teodoro M; D'Orazio, Valeria

    2017-02-23

    Floating islands mysteriously moving around on lakes were described by several Latin authors almost two millennia ago. These fascinating ecosystems, known as free-floating mires, have been extensively investigated from ecological, hydrological and management points of view, but there have been no detailed studies of their rates of accumulation of organic matter (OM), organic carbon (OC) and total nitrogen (TN). We have collected a peat core 4 m long from the free-floating island of Posta Fibreno, a relic mire in Central Italy. This is the thickest accumulation of peat ever found in a free-floating mire, yet it has formed during the past seven centuries and represents the greatest accumulation rates, at both decadal and centennial timescale, of OM (0.63 vs. 0.37 kg/m(2)/yr), OC (0.28 vs. 0.18 kg/m(2)/yr) and TN (3.7 vs. 6.1 g/m(2)/yr) ever reported for coeval peatlands. The anomalously high accretion rates, obtained using (14)C age dating, were confirmed using (210)Pb and (137)Cs: these show that the top 2 m of Sphagnum-peat has accumulated in only ~100 years. As an environmental archive, Posta Fibreno offers a temporal resolution which is 10x greater than any terrestrial peat bog, and promises to provide new insight into environmental changes occurring during the Anthropocene.

  1. Highly anomalous accumulation rates of C and N recorded by a relic, free-floating peatland in Central Italy

    PubMed Central

    Zaccone, Claudio; Lobianco, Daniela; Shotyk, William; Ciavatta, Claudio; Appleby, Peter G.; Brugiapaglia, Elisabetta; Casella, Laura; Miano, Teodoro M.; D’Orazio, Valeria

    2017-01-01

    Floating islands mysteriously moving around on lakes were described by several Latin authors almost two millennia ago. These fascinating ecosystems, known as free-floating mires, have been extensively investigated from ecological, hydrological and management points of view, but there have been no detailed studies of their rates of accumulation of organic matter (OM), organic carbon (OC) and total nitrogen (TN). We have collected a peat core 4 m long from the free-floating island of Posta Fibreno, a relic mire in Central Italy. This is the thickest accumulation of peat ever found in a free-floating mire, yet it has formed during the past seven centuries and represents the greatest accumulation rates, at both decadal and centennial timescale, of OM (0.63 vs. 0.37 kg/m2/yr), OC (0.28 vs. 0.18 kg/m2/yr) and TN (3.7 vs. 6.1 g/m2/yr) ever reported for coeval peatlands. The anomalously high accretion rates, obtained using 14C age dating, were confirmed using 210Pb and 137Cs: these show that the top 2 m of Sphagnum-peat has accumulated in only ~100 years. As an environmental archive, Posta Fibreno offers a temporal resolution which is 10x greater than any terrestrial peat bog, and promises to provide new insight into environmental changes occurring during the Anthropocene. PMID:28230066

  2. [Estimating of decadal accumulation rates of heavy metals in surface rice soils in the Tai Lake region of China].

    PubMed

    Li, Lianqing; Pan, Genxing; Zhang, Pingjiu; Cheng, Jiemin; Zhu, Qiuhua; Qiu, Duosheng

    2002-05-01

    Estimation of decadal accumulation of some heavy metals in surface rice soils from the Tai Lake region, southern Jiangsu Province, China was made by means of calculating the monitoring data and/or analysis data of the archived soil samples. For the last decade, the estimated annual accumulation rate for Cu or Zn, Pb and Cd was 0.3-1 mg.(kg.a)-1, 0.2-1 mg.(kg.a)-1 and 0.3-3 micrograms.(kg.a)-1 respectively, the apparent pollution loading was, therefore, respectively 0.5-1 kg.(hm2.a)-1, 0.5-1.0 kg.(hm2.a)-1, 0.5-3.0 kg.(hm2.a)-1 [symbol: see text] 0.8-10 x 10(-3) kg.(hm2.a)-1. The accumulation rate for the content of available form was shown to be greater than that of total content. The non-point source pollution marked bigger contribution to the total annual loading for the Pb and Cd than the other source pollutions, while the Cd loading was prominently higher than those reported in Europe. These results may indicate that the food safety in this region may be constrained by the soil pollution of these heavy metals at high accumulation rates.

  3. 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

  4. 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.

  5. 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.

  6. Ice shelf snow accumulation rates from the Amundsen-Bellingshausen Sea sector of West Antarctica derived from airborne radar

    NASA Astrophysics Data System (ADS)

    Medley, B.; Kurtz, N. T.; Brunt, K. M.

    2015-12-01

    The large ice shelves surrounding the Antarctic continent buttress inland ice, limiting the grounded ice-sheet flow. Many, but not all, of the thick ice shelves located along the Amundsen-Bellingshausen Seas are experiencing rapid thinning due to enhanced basal melting driven by the intrusion of warm circumpolar deep water. Determination of their mass balance provides an indicator as to the future of the shelves buttressing capability; however, measurements of surface accumulation are few, limiting the precision of the mass balance estimates. Here, we present new radar-derived measurements of snow accumulation primarily over the Getz and Abbott Ice Shelves, as well as the Dotson and Crosson, which have been the focus of several of NASA's Operation IceBridge airborne surveys between 2009 and 2014. Specifically, we use the Center for Remote Sensing of Ice Sheets (CReSIS) snow radar to map the near-surface (< 30 m) internal stratigraphy to measure snow accumulation. Due to the complexities of the local topography (e.g., ice rises and rumples) and their relative proximity to the ocean, the spatial pattern of accumulation can be equally varied. Therefore, atmospheric models might not be able to reproduce these small-scale features because of their limited spatial resolution. To evaluate whether this is the case over these narrow shelves, we will compare the radar-derived accumulation rates with those from atmospheric models.

  7. 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

  8. Mutation accumulation in real branches: fitness assays for genomic deleterious mutation rate and effect in large-statured plants.

    PubMed

    Schultz, Stewart T; Scofield, Douglas G

    2009-08-01

    The genomic deleterious mutation rate and mean effect are central to the biology and evolution of all species. Large-statured plants, such as trees, are predicted to have high mutation rates due to mitotic mutation and the absence of a sheltered germ line, but their size and generation time has hindered genetic study. We develop and test approaches for estimating deleterious mutation rates and effects from viability comparisons within the canopy of large-statured plants. Our methods, inspired by E. J. Klekowski, are a modification of the classic Bateman-Mukai mutation-accumulation experiment. Within a canopy, cell lineages accumulate mitotic mutations independently. Gametes or zygotes produced at more distal points by these cell lineages contain more mitotic mutations than those at basal locations, and within-flower selfs contain more homozygous mutations than between-flower selfs. The resulting viability differences allow demonstration of lethal mutation with experiments similar in size to assays of genetic load and allow estimates of the rate and effect of new mutations with moderate precision and bias similar to that of classic mutation-accumulation experiments in small-statured organisms. These methods open up new possibilities with the potential to provide valuable new insights into the evolutionary genetics of plants.

  9. The accumulation rate of meteorite falls at the earth's surface - The view from Roosevelt County, New Mexico

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Wells, Gordon L.; Rendell, Helen M.

    1990-01-01

    The discovery of 154 meteorite fragments within an 11-sq km area of wind-excavated basins in Roosevelt County, New Mexico, permits a new calculation of the accumulation rate of meteorite falls at the earth's surface. Thermoluminescence dating of the coversand unit comprising the prime recovery surface suggests the maximum terrestrial age of the meteorites to be about 16.0 ka. The 68 meteorite fragments subjected to petrological analyses represent a minimum of 49 individual falls. Collection bias has largely excluded carbonaceous chondrites and achondrites, requiring the accumulation rate derived from the recovered samples to be increased by a factor of 1.25. Terrestrial weathering destroying ordinary chondrites can be modeled as a first-order decay process with an estimated half-life of 3.5 + or - 1.9 ka on the semiarid American High Plains. Having accounted for the age of the recovery surface, area of field searches, pairing of finds, collection bias and weathering half-life, an accumulation rate of 940 falls/a per 10 to the 6th sq km is calculated for falls greater than 10 g total mass. This figure exceeds the best-constrained previous estimate by more than an order of magnitude. One possible reason for this disparity may be the extraordinary length of the fall record preserved in the surficial geology of Roosevelt County. The high accumulation rate determined for the past 16 ka may point to the existence of periods when the meteorite fall rate was significantly greater than at present.

  10. Rates of Species Accumulation and Taxonomic Diversification during Phototrophic Biofilm Development Are Controlled by both Nutrient Supply and Current Velocity

    PubMed Central

    2013-01-01

    The accumulation of new and taxonomically diverse species is a marked feature of community development, but the role of the environment in this process is not well understood. To address this problem, we subjected periphyton in laboratory streams to low (10-cm · s−1), high (30-cm · s−1), and variable (9- to 32-cm · s−1) current velocity and low- versus high-nutrient inputs. We examined how current velocity and resource supply constrained (i) the rates of species accumulation, a measure of temporal beta-diversity, and (ii) the rates of diversification of higher taxonomic categories, defined here as the rate of higher taxon richness increase with the increase of species richness. Temporal biofilm dynamics were controlled by a strong nutrient-current interaction. Nutrients accelerated the rates of accumulation of new species, when flow velocity was not too stressful. Species were more taxonomically diverse under variable than under low-flow conditions, indicating that flow heterogeneity increased the niche diversity in the high-nutrient treatments. Conversely, the lower diversification rates under high- than under low-nutrient conditions at low velocity are explained with finer resource partitioning among species, belonging to a limited number of related genera. The overall low rates of diversification in high-current treatments suggest that the ability to withstand current stress was conserved within closely related species. Temporal heterogeneity of disturbance has been shown to promote species richness, but here we further demonstrate that it also affects two other components of biodiversity, i.e., temporal beta-diversity and diversification rate. Therefore, management efforts for preserving the inherent temporal heterogeneity of natural ecosystems will have detectable positive effects on biodiversity. PMID:23335757

  11. 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

  12. 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.

  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. Impact of Megadunes and Glaze Areas on Estimates of East Antarctic Mass Balance and Accumulation Rate Change

    NASA Astrophysics Data System (ADS)

    Scambos, T. A.; Fahnestock, M. A.; Shuman, C.; Haran, T. M.

    2006-12-01

    for megadunes, glaze regions, and undulations in East Antarctica (and elsewhere) may also impact estimates of changes in accumulation rate (changes in surface elevation due to accumulation increase or decrease) when those changes are made by satellite radar altimeters (e.g. Davis et al, 2005). Previous studies have demonstrated that the broad footprint of satellite radar altimeters interacts preferentially with local highs in the topography; however, local highs show an amplified accumulation signal relative to the regional net surface flux. Therefore, changes in the net surface flux would also be amplified at the local crests, and could cause satellite radar change detection values to be overestimated. We present a simple model of this effect based on the megadune field measurements.

  15. The impact of EDTA on the rate of accumulation and root/shoot partitioning of cadmium in mature dwarf sunflowers.

    PubMed

    Meighan, Michelle M; Fenus, Taressa; Karey, Emma; MacNeil, Joseph

    2011-06-01

    In addition to increasing the mobility of metal ions in the soil solution, chelating agents such as EDTA have been reported to alter both the total metal accumulated by plants and its distribution within the plant structures. Here, mature Mini-Sun Hybrid dwarf sunflowers exposed to 300 μM Cd(2+) in hydroponic solution had initial translocation rates of at least 0.12 mmol kg(-1)h(-1) and reached leaf saturation levels within a day when a 3-fold molar excess of EDTA was used. EDTA also promoted cadmium transfer from roots to the shoots. A threefold excess of EDTA increased the translocation factor (TF) 100-fold, resulting in cadmium levels in the leaves of 580 μg g(-1) and extracting 1400 μg plant(-1). When plants were exposed to dissolved cadmium without EDTA, the vast majority of the metal remained bound to the exterior of the root. The initial accumulation could be successfully modeled with a standard biosorption pseudo second-order kinetic equation. Initial accumulation rates ranged from 0.0359 to 0.262 mg g(-1)min(-1). The cadmium binding could be cycled, and did not show evidence of saturation under the experimental conditions employed, suggesting it might be a viable biosorbant for aqueous cadmium.

  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. 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.

  18. Early phase tumor accumulation of macromolecules: a great difference in clearance rate between tumor and normal tissues.

    PubMed

    Noguchi, Y; Wu, J; Duncan, R; Strohalm, J; Ulbrich, K; Akaike, T; Maeda, H

    1998-03-01

    The objective of this study was to investigate the molecular weight (MW) and time-dependence of the phenomenon termed "the enhanced permeability and retention" (EPR) effect in solid tumor, in particular to determine and define the early phase accumulation of macromolecules in tumor and normal tissues and the relationship between blood concentration and tissue clearance. As a model, radioiodinated N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers of MW ranging from 4.5 K to 800 K were administered i.v. to mice bearing sarcoma 180 tumor. Within 10 min all HPMA copolymers accumulated effectively in the tumor regardless of MW (1.0-1.5% of injected dose per g of tumor). However, higher MW copolymers (> 50 K) showed significantly increased tumor accumulation after 6 h, while the lower MW copolymers (< 40 K) were cleared rapidly from tumor tissue due to rapid diffusion back into the bloodstream. Blood clearance was also MW-dependent; the lower MW copolymers displayed rapid clearance, with kidney radioactivity of the copolymers of MW < 20 K representing 24% of injected dose per g kidney at 1 min after i.v. administration. Within 10 min these copolymers passed through the kidney and were excreted in the urine. Higher MW copolymers consistently showed kidney levels of 3-5% dose per g kidney in the early phase with no time-dependent accumulation in kidney. There was also no progressive accumulation in muscle or liver, regardless of polymer MW. These results suggest the "EPR effect" in solid tumor primarily arises from in the difference in clearance rate between the solid tumor and the normal tissues after initial penetration of the polymers into these tissues.

  19. A method to reconstruct past accumulation rates in alpine firn regions: A study on Fiescherhorn, Swiss Alps

    NASA Astrophysics Data System (ADS)

    Schwerzmann, Aurel; Funk, Martin; Blatter, Heinz; Lüthi, Martin; Schwikowski, Margit; Palmer, Anne

    2006-03-01

    Annual snow layers in the accumulation zone of glaciers become thinner by viscous deformation while moving to greater depth. The reconstruction of the accumulation rate history requires the correction of the thickness of annual layers. We apply a novel method to determine the vertical velocity by repeated survey with a caliper probe of grooves scratched into the wall of a borehole. With this information and the assumptions of steady state velocity and density fields, the correction of layer thicknesses can be determined without knowledge of the ice density profile and thus can be applied to boreholes without ice cores. The method is applied to a borehole on Fiescherhorn, Swiss Alps, resulting in a substantially larger correction than with the simpler method of Nye (1963).

  20. On laboratory simulation and the effect of small temperature oscillations about the freezing point and ice formation on the evaporation rate of water on Mars.

    PubMed

    Moore, Shauntae R; Sears, Derek W G

    2006-08-01

    We report measurements of the evaporation rate of water under Mars-like conditions (CO2 atmosphere at 7 mbar and approximately 0 degrees C) in which small temperature oscillations about the freezing point repeatedly formed and removed a thin layer of ice. We found that the average evaporation at 2.7 +/- 0.5 degrees C without an ice layer (corrected for the difference in gravity on Earth and on Mars) was 1.24 +/- 0.12 mm/h, while at -2.1 +/- 0.3 degrees C with an ice layer the average evaporation rate was 0.84 +/- 0.08 mm/h. These values are in good agreement with those calculated for the evaporation of liquid water and ice when it is assumed that evaporation only depends on diffusion and buoyancy. Our findings suggest that such differences in evaporation rates are entirely due to the temperature difference and that the ice layer has little effect on evaporation rate. We infer that the formation of thin layers of ice on pools of water on Mars does not significantly increase the stability of water on the surface of Mars.

  1. 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…

  2. Spatial and temporal variability of snow accumulation rate at East Antarctic ice sheet in 1993-2010

    NASA Astrophysics Data System (ADS)

    Motoyama, H.; Suzuki, K.; Yamanouchi, T.; Kawamura, K.

    2012-04-01

    Snow stakes along the traverse routes have been observed for long term monitoring program 'the variation of ice sheet surface mass balance' from the 1960's by the Japanese Antarctic Research Expedition in Shirase glacier drainage basin, East Antarctica. During the traverse route between coastal S16 point (69 02'S, 40 03'E, 580m a.s.l.) to inland Dome Fuji (77 22'S, 39 42'E, 3,810m a.s.l.), the snow stake observations every 2 km have been carried out from 1993. Latest stake heights were measured in January 2011 and February 2011. Yearly net snow accumulations from S16 to Dome Fuji were calculated. Heavy snow events were shown in 1998, 2004, 2005, 2008-2009 and 2010. Otherwise, in 1994, 1996, 1999, 2000, 2001, 2002 and 2006, light snow events were observed. They were different in way accumulating spatial pattern depending on places. The yearly accumulation rates were compared with seasonal change of AAO-index (SAM). As a result, yearly accumulation rate and AAO-index showed the positive correlation. We would indicate the spatial distributions of air parcel origins. So we calculate air transport by using the NITRAM trajectory model (Tomikawa and Sato, 2005) and ERA-Interim meteorological data set in 1990-2009. The time duration is 5 days and we suppose the origin of air parcel is the point of trajectory at 5 days ago. The starting points are distributed on 1 deg. x 1 deg. grids over Antarctica and its altitude is 1,300m above the surface. We indicate the spatial distributions of air parcel origins to Antarctica. If there were high ratios of sea origin atmosphere in the inland, there was much snow. It is indicated that the humid air from the sea is the main origin of snowfall. But such relations were not seen on the coast. We try to understand the cause of heavy snow and light snow event.

  3. Mercury accumulation in caged Corbicula: rate of uptake and seasonal variation.

    PubMed

    Neufeld, Douglas S G

    2010-09-01

    The uptake and seasonal fluctuations of total mercury were followed in caged and uncaged Asiatic clams, Corbicula fluminea, over a 1-year period in South River, Virginia. Mercury was rapidly accumulated in clams transplanted from a nominally uncontaminated site into cages on the contaminated South River, reaching 0.99 microg g(-1) dry mass within the first month. Resident clams moved to cages had higher mercury contents after the first month (2.04 microg g(-1) dry mass) and at all subsequent times in the study. Large monthly fluctuations in mercury were noted for both resident caged and transplant caged clams with a notable peak occurring in early spring (4.31 microg g(-1) dry mass in resident caged clams). Tissue mass of caged clams steadily increased through the winter and early spring. Adjustment of mercury concentrations for tissue mass changes indicated that the changes in mercury contents were primarily due to uptake/release rather than changes in tissue mass (concentration/dilution). The present study demonstrates the utility of using caged Corbicula as mercury biomonitors and illustrates the importance of accounting for large, short-term changes of mercury content in Corbicula when designing long-term biomonitoring studies.

  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. MarsSat: assured communication with Mars.

    PubMed

    Gangale, Thomas

    2005-12-01

    The author developed the MarsSat concept during the 1990s. For this task, he designed a class of orbits to solve the problem of communicating with crews on Mars when the planet is in solar conjunction as seen from Earth, a planetary configuration that occurs near the midpoint of a conjunction class mission to Mars. This type of orbit minimizes the distance between Mars and the communications satellite; thus, minimizing the size, weight, and power requirements, while providing a simultaneous line-of-sight to both Earth and Mars. The MarsSat orbits are solar orbits that have the same period as Mars, but are inclined a few degrees out of the plane of the Mars orbit and also differ in eccentricity from the orbit of Mars. These differences cause a spacecraft in this orbit to rise North of Mars, then fall behind Mars, then drop South of Mars, and then pull ahead of Mars, by some desired distance in each case-typically about 20 million kilometers-in order to maintain an angular separation of a couple of degrees as seen from a point in the orbit of Earth on the opposite side of the Sun. A satellite in this type of orbit would relay communications between Earth and Mars during the period of up to several weeks, when direct communication is blocked by the Sun. These orbits are far superior for this purpose when compared to stationing a satellite at one of the Sun-Mars equilateral Lagrangian points, L(4) or L(5), for two reasons. First, L(4) and L(5) are 228 million kilometers from Mars, about 10 times the distance of a spacecraft in one of the MarsSat orbits, and by virtue of the inverse-square law, all other things being equal, the signal strength received at L(4) or L(5) would be one percent of the signal strength received by a spacecraft in one of the MarsSat orbits. Thus, a relay satellite stationed at L(4) or L(5) would have to be that much more powerful to receive data at the same rate, with concomitant increases in spacecraft size and weight. Second, a number of

  6. Growth rate, protein accumulation, and catabolic enzyme activity of skeletal muscles of galliform birds.

    PubMed

    Shea, Russell E; Olson, John M; Ricklefs, Robert E

    2007-01-01

    We measured the mass and several potential indices of functional capacity of the leg and pectoral muscles through 21 d of age in chicks of three species of galliform birds and the domesticated turkey. The study was conducted to test the hypothesis that the growth rate of a tissue is inversely related to its capacity for mature function across species. We measured the proportion of protein and the activities of the catabolic enzymes citrate synthase (CS), pyruvate kinase (PK), and beta -hydroxy-acyl-CoA-dehydrogenase (HOAD) and estimated exponential growth rate (EGR) from growth increments. EGR was negatively related to proportion of protein, PK, and HOAD and positively related to CS activity. In a multiple regression, EGR was uniquely related only to proportion of protein; it was higher in pectoral muscles and increased in this order: wild turkeyrate. When the proportion of protein was normalized by its maximum value for each species and muscle type, the relationship between EGR and normalized protein did not differ significantly among species or muscle type. Thus, if we accept the proportion of protein relative to the mature level as an index of functional capacity--presumably representing the assembly of the contractile apparatus--then growth rate is consistently inversely related to a muscle's capacity for mature function, that is, force generation.

  7. 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.

  8. 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.

  9. 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

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

    PubMed

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

    2000-05-05

    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.

  11. Relationships between salinity and short-term soil carbon accumulation rates form marsh types across a landscape in the Mississippi River Delta

    USGS Publications Warehouse

    Baustian, Melissa M.; Stagg, Camille L.; Perry, Carey L; Moss, Leland C; Carruthers, Tim J.B.; Allison, Mead

    2017-01-01

    Salinity alterations will likely change the plant and environmental characteristics in coastal marshes thereby influencing soil carbon accumulation rates. Coastal Louisiana marshes have been historically classified as fresh, intermediate, brackish, or saline based on resident plant community and position along a salinity gradient. Short-term total carbon accumulation rates were assessed by collecting 10-cm deep soil cores at 24 sites located in marshes spanning the salinity gradient. Bulk density, total carbon content, and the short-term accretion rates obtained with feldspar horizon markers were measured to determine total carbon accumulation rates. Despite some significant differences in soil properties among marsh types, the mean total carbon accumulation rates among marsh types were not significantly different (mean ± std. err. of 190 ± 27 g TC m−2 year−1). However, regression analysis indicated that mean annual surface salinity had a significant negative relationship with total carbon accumulation rates. Based on both analyses, the coastal Louisiana total marsh area (1,433,700 ha) accumulates about 2.7 to 3.3 Tg C year−1. Changing salinities due to increasing relative sea level or resulting from restoration activities may alter carbon accumulation rates in the short term and significantly influence the global carbon cycle.

  12. 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.

  13. Mars sedimentary rock erosion rates constrained using crater counts, with applications to organic-matter preservation and to the global dust cycle

    NASA Astrophysics Data System (ADS)

    Kite, Edwin S.; Mayer, David P.

    2017-04-01

    Small-crater counts on Mars light-toned sedimentary rock are often inconsistent with any isochron; these data are usually plotted then ignored. We show (using an 18-HiRISE-image, > 104-crater dataset) that these non-isochron crater counts are often well-fit by a model where crater production is balanced by crater obliteration via steady exhumation. For these regions, we fit erosion rates. We infer that Mars light-toned sedimentary rocks typically erode at ∼102 nm/yr, when averaged over 10 km2 scales and 107-108 yr timescales. Crater-based erosion-rate determination is consistent with independent techniques, but can be applied to nearly all light-toned sedimentary rocks on Mars. Erosion is swift enough that radiolysis cannot destroy complex organic matter at some locations (e.g. paleolake deposits at SW Melas), but radiolysis is a severe problem at other locations (e.g. Oxia Planum). The data suggest that the relief of the Valles Marineris mounds is currently being reduced by wind erosion, and that dust production on Mars < 3 Gya greatly exceeds the modern reservoir of mobile dust.

  14. Variations in heavy metal accumulation, growth and yield of rice plants grown at different sewage sludge amendment rates.

    PubMed

    Singh, R P; Agrawal, M

    2010-05-01

    Use of sewage sludge in agriculture is an alternative disposal technique for this waste. The present field study was conducted to assess the suitability of sewage sludge amendment in soil for rice (Oryza sativa L. cv. Pusa sugandha 3) by evaluating the heavy metal accumulation, growth, biomass and yield responses of plants grown at 0, 3, 4.5, 6, 9, 12 kgm(-2) sewage sludge amendment (SSA) rate. Sewage sludge amendment modified the physico-chemical properties of soil, thus increasing the availability of heavy metals in soil and consequently with higher accumulation in plant parts. Root length decreased, whereas shoot length, number of leaves, leaf area and total biomass increased significantly when grown under various SSA rates. Yield of rice increased by 60%, 111%, 125%, 134% and 137% at 3, 4.5, 6, 9 and 12 kgm(-2) SSA, respectively, as compared to those grown in unamended soil. Sewage sludge amendment rates above 4.5 kgm(-2) though increased the yield of rice, but caused risk of food chain contamination as concentrations of Ni and Cd in rice grains were found to be above the Indian safe limits (1.5 mgkg(-1)) of human consumption above 4.5 kgm(-2) SSA and of Pb (2.5 mgkg(-1)) above 6 kgm(-2) SSA. Since aboveground parts of the rice also showed higher concentration than the permissible levels of Ni, Cd and Pb at 4.5 kgm(-2) SSA rate, it cannot be used as fodder. The rice husk may be used as bioresource for energy production. Efforts should be made to treat the effluents from small scale industries before discharge into the sewerage system.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Predicting the visitation of carcasses by carrion-related insects under different rates of degree-day accumulation.

    PubMed

    Michaud, Jean-Philippe; Moreau, Gaétan

    2009-03-10

    Common assumptions in forensic entomology are that insects visit and colonize carcasses following a predictable sequence, and that this succession varies among seasons. However, currently available evidence for insect succession on decomposing bodies is essentially descriptive and, to our knowledge, the fine-scale predictability of insect succession with respect to seasons has never been confirmed statistically. In this study, we test these assumptions through the sampling of carrion-related insects attracted to pig carcasses. The study was carried out during the summer and fall of 2006 in rural fields of New Brunswick, Canada. Of the five species of carrion-related insects with high enough occurrence on carcasses to allow modelling, three showed predictable occurrence with respect to degree-day accumulation and seasonal effects. This demonstrates that the occurrence probability of some carrion-related insects on carcasses can be estimated from meteorological records even across seasons with different rates of degree-day accumulation. As opposed to the prevailing idea that adult insects are not reliable for post-mortem interval estimation, the adults of some species exhibited a specific pattern of visitation that could be determined and used in forensic investigations. It is stressed, however, that the statistical predictability of species occurrence must be assessed before any species is considered as a post-mortem interval indicator.

  20. 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.

  1. 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

  2. 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.

  3. Drinking water boosts food intake rate, body mass increase and fat accumulation in migratory blackcaps (Sylvia atricapilla).

    PubMed

    Tsurim, Ido; Sapir, Nir; Belmaker, Jonathan; Shanni, Itai; Izhaki, Ido; Wojciechowski, Michał S; Karasov, William H; Pinshow, Berry

    2008-05-01

    Fat accumulation by blackcaps (Sylvia atricapilla) is a prerequisite for successful migratory flight in the autumn and has recently been determined to be constrained by availability of drinking water. Birds staging in a fruit-rich Pistacia atlantica plantation that had access to water increased their body mass and fat reserves both faster and to a greater extent than birds deprived of water. We conducted a series of laboratory experiments on birds captured during the autumn migration period in which we tested the hypotheses that drinking water increases food use by easing limitations on the birds' dietary choices and, consequently, feeding and food processing rates, and that the availability of drinking water leads to improved digestion and, therefore, to higher apparent metabolizable energy. Blackcaps were trapped in autumn in the Northern Negev Desert, Israel and transferred to individual cages in the laboratory. Birds were provided with P. atlantica fruit and mealworms, and had either free access to water (controls) or were water-deprived. In experiment 1, in which mealworm availability was restricted, water-deprived birds had a fourfold lower fruit and energy intake rates and, consequently, gained less fat and total mass than control birds. Water availability did not affect food metabolizability. In experiment 2, in which mealworms were provided ad libitum, water availability influenced the birds' diet: water-restricted birds ate more mealworms, while control birds consumed mainly P. atlantica fruit. Further, in experiment 2, fat and mass gain did not differ between the two treatment groups. We conclude that water availability may have important consequences for fat accumulation in migrating birds while they fatten at stopover sites, especially when water-rich food is scarce. Restricted water availability may also impede the blackcap's dietary shift from insectivory to frugivory, a shift probably necessary for successful pre-migratory fattening.

  4. Essentiality Is a Strong Determinant of Protein Rates of Evolution during Mutation Accumulation Experiments in Escherichia coli.

    PubMed

    Alvarez-Ponce, David; Sabater-Muñoz, Beatriz; Toft, Christina; Ruiz-González, Mario X; Fares, Mario A

    2016-09-26

    The Neutral Theory of Molecular Evolution is considered the most powerful theory to understand the evolutionary behavior of proteins. One of the main predictions of this theory is that essential proteins should evolve slower than dispensable ones owing to increased selective constraints. Comparison of genomes of different species, however, has revealed only small differences between the rates of evolution of essential and nonessential proteins. In some analyses, these differences vanish once confounding factors are controlled for, whereas in other cases essentiality seems to have an independent, albeit small, effect. It has been argued that comparing relatively distant genomes may entail a number of limitations. For instance, many of the genes that are dispensable in controlled lab conditions may be essential in some of the conditions faced in nature. Moreover, essentiality can change during evolution, and rates of protein evolution are simultaneously shaped by a variety of factors, whose individual effects are difficult to isolate. Here, we conducted two parallel mutation accumulation experiments in Escherichia coli, during 5,500-5,750 generations, and compared the genomes at different points of the experiments. Our approach (a short-term experiment, under highly controlled conditions) enabled us to overcome many of the limitations of previous studies. We observed that essential proteins evolved substantially slower than nonessential ones during our experiments. Strikingly, rates of protein evolution were only moderately affected by expression level and protein length.

  5. 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

  6. Effects of greenhouse warming and N-fertilization on carbon accumulation rates in a nutrient-poor boreal mire: decadal effects assessed using 210Pb

    NASA Astrophysics Data System (ADS)

    Olid, Carolina; Nilsson, Mats B.; Eriksson, Tobias; Klaminder, Jonatan

    2013-04-01

    Boreal peatlands represent a major long-term reservoir of atmospheric carbon (C) and play an important role in the global C cycle. How C accumulation in these peatlands responds to changing temperature and nutrient conditions is under debate. In this study, we assessed how peat and C accumulation rates have responded to increased annual nitrogen additions (30 kg ha-1 yr-1) and increased air temperatures (+3.6°C) in the longest ongoing boreal mire manipulation experiment. Accumulation rates for the uppermost 40 cm of peat in nitrogen and temperature treated plots (n=11) were assessed by 210Pb dating covering the last ~100yrs. A reference surface, installed in 1995 was used as independent validation of the dating model. An empirically based model of organic matter accumulation/degradation was applied to evaluate changes in both peat inputs and organic matter decay rates in response to the treatments. A significant increase in C-accumulation (15 g C m-2 yr-1) was observed in peat subjected to nitrogen additions, while greenhouse warming did not seem to significantly affect C-accumulation or decay rates. Based on our findings we argue that C-accumulation in nutrient poor boreal mires is mainly altered in near-surface peat layers (~15 cm) in response to nitrogen additions and that the uppermost peat layers (<40 cm) in nutrient poor boreal peatlands will continue to function as net C-sinks during the first decades of global warming.

  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. Glacio-chemical study spanning the past 2 kyr on three ice cores from Dronning Maud Land, Antarctica 1. Annually resolved accumulation rates

    NASA Astrophysics Data System (ADS)

    Sommer, S.; Appenzeller, C.; Röthlisberger, R.; Hutterli, M. A.; Stauffer, B.; Wagenbach, D.; Oerter, H.; Wilhelms, F.; Miller, H.; Mulvaney, R.

    2000-12-01

    For the first time, annually resolved accumulation rates have been determined in central Antarctica by means of counting seasonal signals of ammonium, calcium, and sodium. All records, obtained from three intermediate depth ice cores from Dronning Maud Land, East Antarctica, show rather constant accumulation rates throughout the last 9 centuries with mean values of 63, 61, and 44 mm H2Oyr-1 and a typical year-to-year variation of about 30%. For the last few decades, no trend was detected accounting for the high natural variability of all records. A significant weak intersite correlation is apparent only between two cores when the high-frequency part with periods less than 30 years is removed. By analyzing the records in the frequency domain, no persistent periods were found. This suggests that the snow accumulation in this area is mainly influenced by local deposition patterns and may be additionally masked by redistribution of snow due to wind. By comparing accumulation rates over the last 2 millennia a distinct change in the layer thickness in one of the three cores was found, which might be attributed either to an area upstream of the drilling site with lower accumulation rates, or to deposition processes influenced by surface undulations. The missing of a clear correlation between the accumulation rate histories at the three locations is also important for the interpretation of small, short time variations of past precipitation records obtained from deep ice cores.

  9. 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.

  10. Mars ice caps.

    PubMed

    Leovy, C

    1966-12-02

    Minimum atmospheric temperatures required to prevent CO(2) condensatio in the Mars polar caps are higher than those obtained in a computer experiment to simulate the general circulation of the Mars atmosphere. This observation supports the view that the polar caps are predominantly solid CO(2). However, thin clouds of H(2)0 ice could substantially reduce the surface condensation rate.

  11. 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.

  12. Recent peat accumulation rates in minerotrophic peatlands of the Bay James region, Eastern Canada, inferred by 210Pb and 137Cs radiometric techniques.

    PubMed

    Ali, Adam A; Ghaleb, Bassam; Garneau, Michelle; Asnong, Hans; Loisel, Julie

    2008-10-01

    (210)Pb and (137)Cs dating techniques are used to characterise recent peat accumulation rates of two minerotrophic peatlands located in the La Grande Rivière hydrological watershed, in the James Bay region (Canada). Several cores were collected during the summer 2005 in different parts of the two selected peatlands. These minerotrophic patterned peatlands are presently affected by erosion processes, expressed by progressive mechanical destruction of their pools borders. This erosion process is related to a water table rise induced by a regional increase of humidity since the last century. The main objective of the present paper is to (1) evaluate if (210)Pb and (137)Cs dating techniques can be applied to build accurate chronologies in these environments and (2) detect changes in the peat accumulation rates in regard to this amplification of humidity. In both sites, unsupported (210)Pb shows an exponential decreasing according to the depth. Chronologies inferred from (210)Pb allow to reconstruct peat accumulation rates since ca. 1855 AD. The (137)Cs data displayed evident mobility and diffusion, preventing the establishment of any sustained chronology based on these measurements. In the two sites, peat accumulation rates inferred from (210)Pb chronologies fluctuate between 0.005 and 0.038 g cm(-2) yr(-1). As a result, the rise of the water table during the last decade has not yet affected peat accumulation rates.

  13. Mars cratering chronology: new estimates

    NASA Astrophysics Data System (ADS)

    Ivanov, B.

    Many interpretations of Mars geologic evolution is making with the cratering chronology technique (e.g. Hartmann and Neukum, Space Sci. Rev. 96, 165-194, 2001). The core idea of the technique is that older planetary surfaces accumulate more impact craters of a given size than younger surfaces. Two issues are important for the cratering chronology: (i) the estimate of the Moon/Mars cratering ratio to transfer the absolute time scale form the Moon, studied with return sample missions, and (2) the relative importance of secondary impact craters in the interpretation of the available crater counts. In this presentation I describe a progress in both topics listed above. Modern impact rates on planets are defined by orbital evolution of small bodies under weak gravity and non-gravity forces, including resonances with large planets and effects of solar irradiation. In parallel with the celestial mechanics modeling we use the database of observed asteroids, converted into a planetary impact rate. The test of this technique is done for the Earth/moon cratering rate comparison with an independent verification with observed terrestrial atmospheric bursts of bolides and fireballs. For small craters (D<300 m) and young lunar surfaces (age < 100 Ma) the independent measurements of the lunar cratering rate and modern terrestrial bolide/fireball flux match pretty well, giving more confidence for the approach. However, for larger craters (300 m < D <3 km) one should assume the porous-like scaling law for lunar craters to match the astronomically estimated impact rate. This fact demands a reconsideration of Mars/moon cratering rate ratio, as the porosity of upper 1 km under Martian surface may be quite different from the lunar one due to larger Martian gravity and possible filling of porous space with ice/brine. The problem of secondary crater share among crater counts used for surface dating is analyzed by size-frequency distribution (SFD) of secondary and primary craters. The

  14. 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.

  15. Export production fluctuations in the eastern equatorial Pacific during the Pliocene-Pleistocene: Reconstruction using barite accumulation rates

    NASA Astrophysics Data System (ADS)

    Ma, Zhongwu; Ravelo, Ana Christina; Liu, Zhonghui; Zhou, Liping; Paytan, Adina

    2015-11-01

    Export production is an important component of the carbon cycle, modulating the climate system by transferring CO2 from the atmosphere to the deep ocean via the biological pump. Here we use barite accumulation rates to reconstruct export production in the eastern equatorial Pacific over the past 4.3 Ma. We find that export production fluctuated considerably on multiple time scales. Export production was on average higher (51 g C m-2 yr-1) during the Pliocene than the Pleistocene (40 g C m-2 yr-1), decreasing between 3 and 1 Ma (from more than 60 to 20 g C m-2 yr-1) followed by an increase over the last million years. These trends likely reflect basin-scale changes in nutrient inventory and ocean circulation. Our record reveals decoupling between export production and temperatures on these long (million years) time scale. On orbital time scales, export production was generally higher during cold periods (glacial maxima) between 4.3 and 1.1 Ma. This could be due to stronger wind stress and higher upwelling rates during glacial periods. A shift in the timing of maximum export production to deglaciations is seen in the last ~1.1 million years. Results from this study suggest that, in the eastern equatorial Pacific, mechanisms that affect nutrient supply and/or ecosystem structure and in turn carbon export on orbital time scales differ from those operating on longer time scales and that processes linking export production and climate-modulated oceanic conditions changed about 1.1 million years ago. These observations should be accounted for in climate models to ensure better predictions of future climate change.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. Influence of the rate of ethanol production and accumulation on the viability of Saccharomyces cerevisiae in "rapid fermentation".

    PubMed

    Nagodawithana, T W; Steinkraus, K H

    1976-02-01

    Whereas "rapid fermentation" of diluted clover honey (25 degrees Brix) fortified with yeast nutrients using 8 X 10(8) brewers' yeast cells per ml resulted in an ethanol content of 9.5% (wt/vol; 12% vol/vol) in 3 h at 30 C, death rate of the yeast cells during this period was essentially logarithmic. Whereas 6 h was required to reach the same ethanol content at 15 C, the yeast cells retained their viability. Using a lower cell population (6 X 10(7) cells/ml), a level at which the fermentation was no longer "rapid," the yeast cells also retained their viability at 30 C. Ethanol added to the medium was much less lethal than the same or less quantities of ethanol produced by the cell in "rapid fermentation." It was considered possible that ethanol was produced so rapidly at 30 C that it could not diffuse out of the cell as rapidly as it was formed. The hypothesis was postulated that ethanol accumulating in the cell was contributing to the high death rate at 30 C. It was found that the intracellular ethanol concentration reached a level of approximately 2 X 10(11) ethanol molecules/cell in the first 30 min of fermentation at 30 C. At 15 C, with the same cell count, intracellular ethanol concentration reached a level of approximately 4 X 10(10) ethanol molecules/cell and viability remained high. Also, at 30 C with a lower cell population (6 X 10(7) cells/ml), under which conditions fermentation was no longer "rapid," intracellular ethanol concentration reached a similar level (4 X 10(10) molecules ethanol/cell) and the cells retained their viability. Alcohol dehydrogenase (ADH) lost its activity in brewers' yeast under conditions of "rapid fermentation" at 30 C but retained its activity in cells under similar conditions at 15 C. ADH activity was also retained in fermentations at 30 C with cell populations of 6 X 10(7)/ml. It would appear that an intracellular level of about 5 X 10(10) ethanol molecules/cell is normal and that this level does not damage either cell

  1. Water filtration rate and infiltration/accumulation of low density lipoproteins in 3 different modes of endothelial/smooth muscle cell co-cultures.

    PubMed

    Ding, ZuFeng; Fan, YuBo; Deng, XiaoYan

    2009-11-01

    Using different endothelial/smooth muscle cell co-culture modes to simulate the intimal structure of blood vessels, the water filtration rate and the infiltration/accumulation of LDL of the cultured cell layers were studied. The three cell culture modes of the study were: (i) The endothelial cell monolayer (EC/Phi); (ii) endothelial cells directly co-cultured on the smooth muscle cell monolayer (EC-SMC); (iii) endothelial cells and smooth muscle cells cultured on different sides of a Millicell-CM membrane (EC/SMC). It was found that under the same condition, the water filtration rate was the lowest for the EC/SMC mode and the highest for the EC/Phi mode, while the infiltration/accumulation of DiI-LDLs was the lowest in the EC/Phi mode and the highest in the EC-SMC mode. It was also found that DiI-LDL infiltration/accumulation in the cultured cell layers increased with the increasing water filtration rate. The results from the in vitro model study therefore suggest that the infiltration/accumulation of the lipids within the arterial wall is positively correlated with concentration polarization of atherogenic lipids, and the integrity of the endothelium plays an important role in the penetration and accumulation of atherogenic lipids in blood vessel walls.

  2. Dust Accumulation and Cleaning of the MER Opportunity Solar Array

    NASA Astrophysics Data System (ADS)

    Herman, J.

    2015-12-01

    The solar array of the NASA Mars Exploration Rover (MER) Opportunity was expected to accumulate a sufficient quantity of dust after ninety Martian days (sols) such that it could no longer provide enough energy to guarantee continued surface operations. Instead, due in part to low dust accumulation rates and numerous dust cleaning events, Opportunity continues to operate on the Martian surface for over 4000 sols (over six Mars years). During this time period, the rover experienced six Martian winters and several dust storms. Because the sources of solar energy loss are known, the solar array energy output offers a method to scientifically estimate the loading and aeolian removal of dust from the solar array each sol. We will discuss the accumulation of dust on the solar panels as a proxy for dust movement at Meridiani Planum over the course of the entire mission to date.

  3. Dust Accumulation and Cleaning of the MER Spirit Solar Array

    NASA Astrophysics Data System (ADS)

    Herman, J. A.; Lemmon, M. T.; Johnson, J. R.; Cantor, B. A.; Stella, P. M.; Chin, K. B.; Wood, E. G.

    2012-12-01

    The solar array of the NASA Mars Exploration Rover (MER) Spirit was expected to accumulate so much dust after ninety Martian days (sols) that it could no longer provide enough energy to guarantee continued surface operations. Instead, due in part to low dust accumulation rates and numerous dust cleaning events, Spirit carried out surface operations for over 2200 sols (over three Mars years). During this time period, the rover experienced four Martian winters and several dust storms. Because the sources of solar energy loss are known, the solar array energy output offers a tool to quantitatively estimate the loading and aeolian removal of dust from the solar array each sol. We will discuss the accumulation of dust on the solar panels as a proxy for dust movement at Gusev Crater over the course of the entire mission.

  4. 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.

  5. 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...

  6. 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...

  7. 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.

  8. A sedimentary origin for intercrater plains north of the Hellas basin: Implications for climate conditions and erosion rates on early Mars

    NASA Astrophysics Data System (ADS)

    Salese, Francesco; Ansan, Veronique; Mangold, Nicolas; Carter, John; Ody, Anouck; Poulet, Francois; Ori, Gian Gabriele

    2016-11-01

    Understanding the origin (volcanic or sedimentary) and timing of intercrater plains is crucial for deciphering the geological evolution of Mars. We have produced a detailed geological map of the intercrater plains north of the Hellas basin, based on images from the Mars Express High-Resolution Stereo Camera, the Mars Reconnaissance High-Resolution Imaging Science Experiment, and Context. Erosional windows and fresh impact craters provide a way of studying the lithology of intercrater plain units. They are composed predominantly of light-toned sedimentary rocks with subhorizontal bedding over a broad extent (greater than tens of kilometers), showing cross-bedding stratifications locally. The broad extent, geometry, and flat topography of these sediments favor a formation by aqueous processes (alluvial and lacustrine) rather than airfall (eolian and volcaniclastic). The Late Noachian ( 3.7 Ga) sedimentary plains are locally covered by dark-toned, rough-textured lava flows of Late Hesperian age ( 3.3 Ga). Fe/Mg phyllosilicates were detected within sedimentary rocks, whereas volcanic rocks contain pyroxene and lack signatures of alteration, in agreement with interpretations made from texture and morphology. In erosional windows, the superimposition of sedimentary rocks by younger volcanic flows enables the estimation of an erosion rate of 1000 nm yr-1 during the Hesperian period (3.3-3.7 Ga). Thus, our study shows that an intense sedimentary cycle occurred on the northern rim of the Hellas basin before and during the Late Noachian, leading to the formation of widespread sedimentary plains, which were then eroded, in agreement with a gradual change in the climatic conditions in this period, and later covered by volcanic flows.

  9. 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

  10. 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.

  11. Predominant anthropogenic sources and rates of atmospheric mercury accumulation in southern Ontario recorded by peat cores from three bogs: comparison with natural "background" values (past 8000 years).

    PubMed

    Givelet, Nicolas; Roos-Barraclough, Fiona; Shotyk, William

    2003-12-01

    Peat cores from three bogs in southern Ontario provide a complete, quantitative record of net rates of atmospheric Hg accumulation since pre-industrial times. For comparison with modern values, a peat core extending back 8000 years was used to quantify the natural variations in Hg fluxes for this region, and their dependence on climatic change and land use history. The net mercury accumulation rates were separated into "natural" and "excess" components by comparing the Hg/Br ratios of modern samples with the long-term, pre-anthropogenic average Hg/Br. The average background mercury accumulation rate during the pre-anthropogenic period (from 5700 years BC to 1470 AD) was 1.4 +/- 1.0 microg m(-2) per year (n = 197). The beginning of Hg contamination from anthropogenic sources dates from AD 1475 at the Luther Bog, corresponding to biomass burning for agricultural activities by Native North Americans. During the late 17th and 18th centuries, deposition of anthropogenic Hg was at least equal to that of Hg from natural sources. Anthropogenic inputs of Hg to the bogs have dominated continuously since the beginning of the 19th century. The maximum Hg accumulation rates decrease in the order Sifton Bog, in the City of London, Ontario (141 microg Hg m(-2) per year), Luther Bog in an agricultural region (89 microg Hg m(-2) per year), and Spruce Bog which is in a comparatively remote, forested region (54 microg Hg m(-2) per year). Accurate age dating of recent peat samples using the bomb pulse curve of 14C shows that the maximum rate of atmospheric Hg accumulation occurred during AD 1956 and 1959 at all sites. In these (modern) samples, the Hg concentration profiles resemble those of Pb, an element which is known to be immobile in peat bogs. The correlation between these two metals, together with sulfur, suggests that the predominant anthropogenic source of Hg (and Pb) was coal burning. While Hg accumulation rates have gone into strong decline since the late 1950's, Hg

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Germline mutation rates and the long-term phenotypic effects of mutation accumulation in wild-type laboratory mice and mutator mice

    PubMed Central

    Uchimura, Arikuni; Higuchi, Mayumi; Minakuchi, Yohei; Ohno, Mizuki; Toyoda, Atsushi; Fujiyama, Asao; Miura, Ikuo; Wakana, Shigeharu; Nishino, Jo; Yagi, Takeshi

    2015-01-01

    The germline mutation rate is an important parameter that affects the amount of genetic variation and the rate of evolution. However, neither the rate of germline mutations in laboratory mice nor the biological significance of the mutation rate in mammalian populations is clear. Here we studied genome-wide mutation rates and the long-term effects of mutation accumulation on phenotype in more than 20 generations of wild-type C57BL/6 mice and mutator mice, which have high DNA replication error rates. We estimated the base-substitution mutation rate to be 5.4 × 10−9 (95% confidence interval = 4.6 × 10−9–6.5 × 10−9) per nucleotide per generation in C57BL/6 laboratory mice, about half the rate reported in humans. The mutation rate in mutator mice was 17 times that in wild-type mice. Abnormal phenotypes were 4.1-fold more frequent in the mutator lines than in the wild-type lines. After several generations, the mutator mice reproduced at substantially lower rates than the controls, exhibiting low pregnancy rates, lower survival rates, and smaller litter sizes, and many of the breeding lines died out. These results provide fundamental information about mouse genetics and reveal the impact of germline mutation rates on phenotypes in a mammalian population. PMID:26129709

  17. Germline mutation rates and the long-term phenotypic effects of mutation accumulation in wild-type laboratory mice and mutator mice.

    PubMed

    Uchimura, Arikuni; Higuchi, Mayumi; Minakuchi, Yohei; Ohno, Mizuki; Toyoda, Atsushi; Fujiyama, Asao; Miura, Ikuo; Wakana, Shigeharu; Nishino, Jo; Yagi, Takeshi

    2015-08-01

    The germline mutation rate is an important parameter that affects the amount of genetic variation and the rate of evolution. However, neither the rate of germline mutations in laboratory mice nor the biological significance of the mutation rate in mammalian populations is clear. Here we studied genome-wide mutation rates and the long-term effects of mutation accumulation on phenotype in more than 20 generations of wild-type C57BL/6 mice and mutator mice, which have high DNA replication error rates. We estimated the base-substitution mutation rate to be 5.4 × 10(-9) (95% confidence interval = 4.6 × 10(-9)-6.5 × 10(-9)) per nucleotide per generation in C57BL/6 laboratory mice, about half the rate reported in humans. The mutation rate in mutator mice was 17 times that in wild-type mice. Abnormal phenotypes were 4.1-fold more frequent in the mutator lines than in the wild-type lines. After several generations, the mutator mice reproduced at substantially lower rates than the controls, exhibiting low pregnancy rates, lower survival rates, and smaller litter sizes, and many of the breeding lines died out. These results provide fundamental information about mouse genetics and reveal the impact of germline mutation rates on phenotypes in a mammalian population.

  18. Significant relationships among frost tolerance and net photosynthetic rate, water use efficiency and dehydrin accumulation in cold-treated winter oilseed rapes.

    PubMed

    Urban, Milan Oldřich; Klíma, Miroslav; Vítámvás, Pavel; Vašek, Jakub; Hilgert-Delgado, Alois Albert; Kučera, Vratislav

    2013-12-15

    Five winter oilseed rape cultivars (Benefit, Californium, Cortes, Ladoga, Navajo) were subjected to 30 days of cold treatment (4 °C) to examine the effect of cold on acquired frost tolerance (FT), dehydrin (DHN) content, and photosynthesis-related parameters. The main aim of this study was to determine whether there are relationships between FT (expressed as LT50 values) and the other parameters measured in the cultivars. While the cultivar Benefit accumulated two types of DHNs (D45 and D35), the other cultivars accumulated three additional DHNs (D97, D47, and D37). The similar-sized DHNs (D45 and D47) were the most abundant; the others exhibited significantly lower accumulations. The highest correlations were detected between LT50 and DHN accumulation (r=-0.815), intrinsic water use efficiency (WUEi; r=-0.643), net photosynthetic rate (r=-0.628), stomatal conductance (r=0.511), and intracellular/intercellular CO2 concentration (r=0.505). Those cultivars that exhibited higher Pn rate in cold (and further a significant increase in WUEi) had higher levels of DHNs and also higher FT. No significant correlation was observed between LT50 and E, PRI, or NDVI. Overall, we have shown the selected physiological parameters to be able to distinguish different FT cultivars of winter oilseed rape.

  19. 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

  20. 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.

  1. Comprehensive modeling and investigation of the effect of iron on the growth rate and lipid accumulation of Chlorella vulgaris cultured in batch photobioreactors.

    PubMed

    Concas, Alessandro; Steriti, Alberto; Pisu, Massimo; Cao, Giacomo

    2014-02-01

    Recent works have shown that specific strains of microalgae are capable to simultaneously increase their growth rate and lipid content when cultured under suitable concentrations of iron. While these results are promising in view of the exploitation of microalgae for producing biofuels, to the best of our knowledge, no mathematical model capable to describe the effect of iron on lipid accumulation in microalgae, has been so far proposed. A comprehensive mathematical model describing the effect of iron on chlorophyll synthesis, nitrogen assimilation, growth rate and lipid accumulation in a freshwater strain of Chlorella vulgaris is then proposed in this work. Model results are successfully compared with experimental data which confirm the positive effect of growing iron concentrations on lipid productivity of C. vulgaris. Thus, the proposed model might represent a useful tool to optimize iron-based strategies to improve the lipid productivity of microalgal cultures.

  2. Preferential accumulation of sex and Bs chromosomes in biarmed karyotypes by meiotic drive and rates of chromosomal changes in fishes.

    PubMed

    Molina, Wagner F; Martinez, Pablo A; Bertollo, Luiz A C; Bidau, Claudio J

    2014-12-01

    Mechanisms of accumulation based on typical centromeric drive or of chromosomes carrying pericentric inversions are adjusted to the general karyotype differentiation in the principal Actinopterygii orders. Here, we show that meiotic drive in fish is also supported by preferential establishment of sex chromosome systems and B chromosomes in orders with predominantly bi-brachial chromosomes. The mosaic of trends acting at an infra-familiar level in fish could be explained as the interaction of the directional process of meiotic drive as background, modulated on a smaller scale by adaptive factors or specific karyotypic properties of each group, as proposed for the orthoselection model.

  3. 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

  4. 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.

  5. Combined effects of water flow and copper concentration on the feeding behavior, growth rate, and accumulation of copper in tissue of the infaunal polychaete Polydora cornuta.

    PubMed

    Colvin, Marienne A; Hentschel, Brian T; Deheyn, Dimitri D

    2016-12-01

    We performed an experiment in a laboratory flume to test the effects of water flow speed and the concentration of aqueaous copper on the feeding behavior, growth rate, and accumulation of copper in the tissues of juvenile polychaetes Polydora cornuta. The experiment included two flow speeds (6 or 15 cm/s) and two concentrations of added copper (0 or 85 μg/L). Worms grew significantly faster in the faster flow and in the lower copper concentration. In the slower flow, the total time worms spent feeding decreased significantly as copper concentration increased, but copper did not significantly affect the time worms spent feeding in the faster flow. Across all treatments, there was a significant, positive relationship between the time individuals spent feeding and their relative growth rate. Worms were observed suspension feeding significantly more often in the faster flow and deposit feeding significantly more often in the slower flow, but copper concentration did not affect the proportion of time spent in either feeding mode. The addition of 85 μg/L copper significantly increased copper accumulation in P. cornuta tissue, but the accumulation did not differ significantly due to flow speed. There was a significant interaction between copper and flow; the magnitude of the difference in copper accumulation between the 0 and 85 μg/L treatments was greater in the faster flow than in the slower flow. In slow flows that favor deposit feeding, worms grow slowly and accumulate less copper in their tissue than in faster flows that favor suspension feeding and faster growth.

  6. 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.

  7. Wind abrasion on Mars

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1991-01-01

    Aeolian activity was predicted for Mars from earth based observations of changing surface patterns that were interpreted as dust storms. Mariner 9 images showed conclusive evidence for aeolian processes in the form of active dust storms and various aeolian landforms including dunes and yardangs. Windspeeds to initiate particle movement are an order of magnitude higher on Mars than on Earth because of the low atmospheric density on Mars. In order to determine rates of abrasion by wind blown particles, knowledge of three factors is required: (1) particle parameters such as numbers and velocities of windblown grains as functions of windspeeds at various heights above the surface; (2) the susceptibility to abrasion of various rocks and minerals; and (3) wind frequencies and speeds. For estimates appropriate to Mars, data for the first two parameters can be determined through lab and wind tunnel tests; data for the last two factors are available directly from the Viking Lander meteorology experiments for the two landing sites.

  8. Accumulation Rates in the Dry Snow Zone of the Greenland Ice Sheet Inferred from L-band InSAR Data

    NASA Astrophysics Data System (ADS)

    Chen, A. C.; Zebker, H. A.

    2012-12-01

    The Greenland ice sheet contains about 2.9 million km3 of ice and would raise global sea levels by about 7.1 m if it melted completely. Two unusually large iceberg calving events at Petermann Glacier in the past several years, along with the unusually large extent of ice sheet melt this summer point to the relevance of understanding the mass balance of the Greenland ice sheet. In this study, we use data from the PALSAR instrument aboard the ALOS satellite to form L-band (23-centimeter carrier wavelength) InSAR images of the dry snow zone of the Greenland ice sheet. We form geocoded differential interferograms, using the ice sheet elevation model produced by Howat et.al. [1]. By applying phase and radiometric calibration, we can examine interferograms formed between any pair of transmit and receive polarization channels. In co-polarized interferograms, the InSAR correlation ranges from about 0.35 at the summit (38.7 deg W, 73.0 deg N) where accumulation is about 20 cm w.e./yr to about 0.70 at the north-eastern part of the dry snow zone (35.1 deg W, 77.1 deg N), where accumulation is about 11.7 cm w.e./yr. Cross-polarized interferograms show similar geographic variation with overall lower correlation. We compare our InSAR data with in-situ measurements published by Bales et.al. [2]. We examine the applicability of dense-medium radiative transfer electromagnetic scattering models for estimating accumulation rates from L-band InSAR data. The large number and broad coverage of ALOS scenes acquired between 2007 and 2009 with good InSAR coherence at 46-day repeat times and 21.5 degree incidence angles gives us the opportunity to examine the empirical relationship between in-situ accumulation rate observations and the polarimetric InSAR correlation and radar brightness at this particular imaging geometry. This helps us quantify the accuracy of accumulation rates estimated from InSAR data. In some regions, 46-day interferograms acquired in the winters of several consecutive

  9. Measuring water accumulation rates using GRACE data in areas experiencing glacial isostatic adjustment: The Nelson River basin

    NASA Astrophysics Data System (ADS)

    Lambert, A.; Huang, J.; Kamp, G.; Henton, J.; Mazzotti, S.; James, T. S.; Courtier, N.; Barr, A. G.

    2013-12-01

    Recovery and Climate Experiment (GRACE) satellite-derived total water storage can be obscured by glacial isostatic adjustment. In order to solve this problem for the Nelson River drainage basin in Canada, a gravity rate map from 110 months (June 2002 to October 2011) of GRACE gravity data was corrected for glacial isostatic adjustment using an independent gravity rate map derived from updated GPS vertical velocities. The GPS-based map was converted to equivalent gravity rate using a transfer function developed from GPS and absolute-g data at colocated sites. The corrected GRACE gravity rate map revealed a major positive anomaly within the drainage basin, which was independently shown by hydrological data to be due to changes in water storage. The anomaly represents a cumulative increase at its center of about 340 mm of water, reflecting a progression from extreme drought to extremely wet conditions.

  10. 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.

  11. Effect of altering the root-zone temperature on growth, translocation, carbon exchange rate, and leaf starch accumulation in the tomato.

    PubMed

    Hurewitz, J; Janes, H W

    1983-09-01

    Tomato seedlings (Lycopersicon esculentum Mill. cv Vendor) were grown hydroponically with their root systems maintained at a constant temperature for a 2-week period commencing with the appearance of the first true leaf. Based on fresh and dry weight and leaf area, the optimal root-zone temperature for seedling growth was 30 degrees C. The carbon exchange rate of the leaves was also found to increase with rising root-zone temperature up to 30 degrees C. However, a more complex relationship seems to exist between root-zone temperature and the accumulation of (14)C-labeled assimilates in the roots; inasmuch as there is no enhancement in this accumulation at the most growth promoting root-zone temperatures (22-30 degrees C).

  12. 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.

  13. Leaf senescence in rice due to magnesium deficiency mediated defect in transpiration rate before sugar accumulation and chlorosis.

    PubMed

    Kobayashi, Natsuko I; Saito, Takayuki; Iwata, Naoko; Ohmae, Yoshimi; Iwata, Ren; Tanoi, Keitaro; Nakanishi, Tomoko M

    2013-08-01

    Magnesium (Mg) is an essential macronutrient supporting various functions, including photosynthesis. However, the specific physiological responses to Mg deficiency remain elusive. In this study, 2-week-old rice seedlings (Oryza sativa. cv. Nipponbare) with three expanded leaves (L2-L4) were transferred to Mg-free nutrient solution for 8 days. In the absence of Mg, on day 8, L5 and L6 were completely developed, while L7 just emerged. We also studied several mineral deficiencies to identify specific responses to Mg deficiency. Each leaf was analyzed in terms of chlorophyll, starch, anthocyanin and carbohydrate metabolites, and only absence of Mg was found to cause irreversible senescence of L5. Resupply of Mg at various time points confirmed that the borderline of L5 death was between days 6 and 7 of Mg deficiency treatment. Decrease in chlorophyll concentration and starch accumulation occurred simultaneously in L5 and L6 blades on day 8. However, nutrient transport drastically decreased in L5 as early as day 6. These data suggest that the predominant response to Mg deficiency is a defect in transpiration flow. Furthermore, changes in myo-inositol and citrate concentrations were detected only in L5 when transpiration decreased, suggesting that they may constitute new biological markers of Mg deficiency.

  14. Estimating sediment accumulation rates in Manila Bay, a marine pollution hot spot in the Seas of East Asia.

    PubMed

    Sta Maria, E J; Siringan, F P; Bulos, A dM; Sombrito, E Z

    2009-01-01

    The GEF/UNDP/IMO/PEMSEA project identifies Manila Bay as among the marine pollution hot spots in the Seas of East Asia. (210)Pb dating of its sediment can provide a historical perspective of its pollution loading. However, the validity of (210)Pb dating in a complex dynamic coastal system of Manila Bay may come into question. Land-based sediment input can be high and physical and biological processes can possibly disturb the sediment layers. In this report, the (210)Pb profiles of sediment cores from different parts of the bay are presented. The linear sedimentation rates are shown to be higher in the recent past and are also variable across the bay. The largest change in sedimentation rate, coincided with the occurrence of a volcanic eruption in 1991 and is shown by applying a variant of the CIC model in sedimentation rate calculations. The data suggest that (210)Pb dating can be useful in estimating relative magnitudes of sedimentation rates, even in a complex dynamic coastal system like Manila Bay.

  15. 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...

  16. Sedimentation rates in eastern North America reveal strong links between regional climate, depositional environments, and sediment accumulation

    NASA Astrophysics Data System (ADS)

    Goring, S. J.; McLachlan, J. S.; Jackson, S. T.; Blaauw, M.; Christen, J.; Marlon, J.; Blois, J.; Williams, J. W.

    2011-12-01

    PalEON is a multidisciplinary project that combines paleo and modern ecological data with state-of-the-art statistical and modelling tools to examine the interactions between climate, fire and vegetation during the past two millennia in the northeastern United States. A fundamental challenge for PalEON (and paleo research more broadly) is to improve age modelling to yield more accurate sediment-core chronologies. To address this challenge, we assessed sedimentation rates and their controls for 218 lakes and mires in the northeastern U.S. Sedimentation rates (yr/cm) were calculated from age-depth models, which were obtained from the Neotoma database (www.neotomadb.org) and other contributed pollen records. The age models were recalibrated to IntCal09 and augmented in some cases using biostratigraphic markers (Picea decline, 16 kcal BP - 10.5 kcal BP; Quercus rise, 12 - 9.1 kcal BP; and Alnus decline, 11.5 - 10.6 kcal BP) as described in Blois et al. (2011). Relationships between sedimentation rates and sediment age, site longitude, and depositional environment (lacustrine or mire) are significant but weak. There are clear and significant links between variations in the NGRIP record of δ18O and sedimentation in mires across the PalEON region, but no links to lacustrine sedimentation rates. This result indicates that super-regional climatic control of primary productivity, and thus autochthonic sediment deposition, dominates in mires while deposition in lacustrine basins may be driven primarily by local and regional factors including watershed size, surficial materials,and regional vegetation. The shape of the gamma probability functions that best describe sedimentation rate distributions are calculated and presented here for use as priors in Bayesian age modelling applications such as BACON (Blaauw and Christen, in press). Future applications of this research are also discussed.

  17. Simulation of continental basin margin sedimentation in response to crustal movements, eustatic sea level change, and sediment accumulation rates

    SciTech Connect

    Helland-Hansen, W.; Kendall, C.G.St.C.; Lerche, I.; Nakayama, K.

    1988-10-01

    As eustasy, subsidence, and sediment accumulation vary, a 2D computer-based graphical simulation generates on-lapping and off-lapping geometries of both marine and near coastal alluvial deposits, reproducing timelines within sediment-bodies at basin margins. In the simulation, deposition is expressed by creation of new surfaces above previous ones. Thicknesses of layers are reduced by both erosion and compaction while their surfaces move vertically in response to tectonic change and loading. Simulation is divided into a series of equal time steps in which sediment is deposited as an array of en-echelon columns that mark the top of the previous depositional surface. The volume of sediment deposited in each time step is expressed as a 2D cross section and is derived from two right-angle triangles (sand and shale), whose areas are a 2D expression of the quantity of sediment deposited at that time step and whose length matches the width of the offshore sediment wedge seaward of the shoreline. Each column in the array is filled by both marine sediments up to sea level, and alluvial sediments to a surface determined by an alluvial angle that is projected landward from the shore to its intersection with the previous surface. Each time the area representing the sediment column is subtracted from the triangles, the triangle heights are reduced correspondingly. This process is repeated until the triangle heights match the position of sea level above the sediment surface, at which time the remaining area of the sediment triangle is deposited seaward as a single wedge of offshore sediments. This simulation is designed to aid interpretation of stratigraphic sequences. It can be used as a complement to seismic stratigraphy or can be used alone as an inexpensive test of stratigraphic models.

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. 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 ...

  5. 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. 

  6. 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.

  7. 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".

  8. 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 ...

  9. Human factors for Mars missions.

    NASA Astrophysics Data System (ADS)

    Nicogossian, A. E.

    A manned mission to Mars will challenge the human capacity to cope with extreme environments and solve new problems associated with them. Life support systems capable of preventing the accumulation of toxic chemicals will be necessary. Psychological issues may gain greater importance.

  10. Locomotor response to exercise in relation to plasma lactate accumulation and heart rate in Andalusian and Anglo-Arabian horses.

    PubMed

    Muñoz, A; Santisteban, R; Rubio, M D; Riber, C; Agüera, E I; Castejón, F M

    1999-10-01

    To establish the effect of the locomotor pattern on heart rate (HR) and plasma lactate (LA), 28 horses, 18 Andalusian (AN) and 10 Anglo-Arabian (AA), aged 3-4 years, were studied. After a warm-up period, the horses performed a four-step test at 5, 6, 7 and 8 m/s, covering 1000 m at each velocity. HR was monitored, LA was analysed at rest and after each workload, and images were filmed. The locomotor parameters determined were stride duration (SD), frequency (SF) and length (SL), step and bipedal support durations, stance (restraint and propulsion) and swing phase durations, and stride vertical component. The HR and LA were significantly higher in the AN horses from velocities of 5 m/s. Similarly, the stride vertical component was higher in the AN horses at the trot and in the leading forelimbs at the gallop. Conversely, at all the galloping velocities, swing phase duration and stride length were longer in the AA horses. Significant correlations between HR, LA and locomotor pattern were only found in the AN horses. It was concluded that the greater stride vertical component in the AN horses limits SL and the cranial advancement of the hoof, with the result that reaching a longer SL triggers an increase in HR and LA. AA horses reach a balance between SL and SF, improving the efficiency of the gait.

  11. Partitioning and accumulation rates of polycyclic aromatic hydrocarbons into polydimethylsiloxane thin films and black worms from aqueous samples.

    PubMed

    Qin, Zhipei; Mok, Sandra; Ouyang, Gangfeng; Dixon, D George; Pawliszyn, Janusz

    2010-05-14

    Partition equilibriums and extraction rates of polycyclic aromatic hydrocarbons (PAHs) were examined for live biomonitoring with oligochaetes (black worms, Lumbriculus variegatus) and for high surface area chemical passive samplers constructed from polydimethylsiloxane thin film. The goals were to better understand the principles of bioconcentration by aquatic organisms and to aid in the design of a convenient and simple chemical monitoring tool to replace the use of live animals. The worms and films were exposed simultaneously to the contaminated water stream. In the initial extraction stage, similar extracted amount per surface area indicated that thin-film samplers could mimic the behavior of worms for passive sampling. Equilibrium was reached faster by the thin films than by the worms. A good linear relationship between the bioconcentration factors and the film-water partition coefficients of PAHs was found, which demonstrated the feasibility of thin-film sampler for determining the bioavailability of PAHs in water. Compared to the lengthy and inconvenient process of liquid-liquid extraction in worm treatment, thin-film technique simplifies the sample pretreatment procedure by integrating sampling and sample preparation.

  12. Results From the Mars Odyssey THEMIS Experiment

    NASA Astrophysics Data System (ADS)

    Christensen, P. R.

    2003-05-01

    The Thermal Emission Imaging System (THEMIS) onboard Mars Odyssey began studying the surface and atmosphere of Mars in February 2002 using thermal infrared (IR) multi-spectral imaging between 6.5 and 15 μm, and visible/near-IR images from 450 to 850 nm. Regional-scale infrared mapping shows that Mars has both regional and local geologic units delineated by their thermophysical properties. In Meridiani Planum these units imply a complex history involving changes in the nature of volcanic units, the environment of deposition of sedimentary units, and/or the degree of lithification or cementation of initially unconsolidated units. Mars has km-scale exposures of bedrock, and rocky surfaces are commonly observed on slopes and scarps, demonstrating that the production or exposure rate of rock locally exceeds the rate of rock burial or breakdown. In places, thermally distinct ejecta deposits with a wide range of thermophysical properties are observed around craters of varying sizes. This variation in the preservation of the infrared signature of crater ejecta may be associated with crater age. Where large fields of sand dunes occur, the dunes are typically coarser-grained than the interdune surfaces, suggesting that finer-grained material is accumulating where active sand motion may be limited. Surfaces known to be mantled by air-fall dust, such as the Tharsis and Arabia provinces, also appear completely mantled at THEMIS 100-m per pixel resolution. THEMIS multi-spectral infrared observations show significant potential for compositional mapping at 100-m scales, as demonstrated by the identification of olivine-rich basaltic units on the floor of Ganges Chasma. Polar observations have confirmed the presence of CO2 slab ice and the presence of H2O exposed at the surface of the south polar summer cap. The visible imager also has obtained information on the color properties of the surface and of atmospheric aerosols at the highest spatial resolution yet obtained from Mars

  13. Effect of different tannery sludge compost amendment rates on growth, biomass accumulation and yield responses of Capsicum plants.

    PubMed

    Silva, Jayara D C; Leal, Tamara T B; Araújo, Ademir S F; Araujo, Raul M; Gomes, Regina L F; Melo, Wanderley J; Singh, Rajeev P

    2010-10-01

    Composting has been recognized as one of the most cost effective and environmentally sound alternatives for organic wastes recycling from long and composted wastes have a potential to substitute inorganic fertilizers. We investigated the potential of composted tannery sludge for ornamental purposes and to examine the effects of two different composts and concentrations on ornamental Capsicum growth. The two composts were produced with tannery sludge and the composition of each compost was: compost(1) of tannery sludge (C(1)TS) - tannery sludge+sugarcane straw and cattle manure mixed in the ratio 1:3:1 (v:v:v); compost(2) of tannery sludge (C(2)TS) - tannery sludge+"carnauba" straw and cattle manure in the ratio 1:3:1 (v:v:v). Each compost was amended with soil at rates (% v:v) of 0%, 25%, 50%, 75% and 100% (designation hereafter as T(1)-T(5), respectively). The number of leaves and fruits were counted, and the stem length was also measured. Chlorophyll content was recorded on three leaves of each harvested plant prior to harvest. Number of leaves and fruits, stem length, dry weight of shoot and roots did not vary significantly between the plants grown in two tannery composts. All the treatments with composted tannery sludge application (T(2)-T(5)) significantly increased the number of leaves and fruits, stem length and chlorophyll content compared with the control (T(1)). The chlorophyll content was higher in plants growing in the C(1)TS compared to C(2)TS. The results of the present study further suggest that Capsicum may be a good option to be grown on composted tannery amended soil.

  14. 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.

  15. 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.

  16. 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.

  17. Snow Accumulation and Spring Melt Rates of Bogs and Fens in the North Granny Creek Catchment Basin, Hudson Bay Lowlands, Ontario

    NASA Astrophysics Data System (ADS)

    Cook, C. F.; Price, J. S.

    2009-05-01

    The Hudson Bay Lowlands contain one of the most extensive, contiguous peatland complexes in the world. Interlinked patterned peatlands developed in this region because of the cool climate, low-gradient topography and an underlying layer of low conductivity marine sediments. There is currently little research regarding the mechanisms that control runoff and surface water connectivity in this region, especially the functions of different peatland types on runoff production and flow pathways. Runoff generation in these systems is dependent on several factors such as soil and pool storage capacity, snow accumulation and melt rates, and peatland morphometry. Snowmelt accounts for a major portion of total annual runoff in this region and the timing of the melt will determine effective runoff production from a peatland catchment. One of the objectives of this project is to identify the processes and mechanisms that generate spring snowmelt runoff in different peatland types (i.e. bogs and fens) and quantify the relative contribution of each type in a peatland-dominated catchment basin. This research is being conducted in a 30 km2 catchment basin located near the DeBeers Victor diamond mine, located 90 km west of Attawapiskat, Ontario. The North Granny Creek basin is located approximately 3 km from the mine pit and is comprised of several peatland types and forms. The surface hydrology of this area is expected to be affected by groundwater depressurization due to dewatering of the mine pit by deep groundwater pumping wells. Effects of this activity on surface hydrology could possibly include increased soil storage capacity due to drier conditions and decreased melt rates due to reduced inputs of warm groundwater. Surface water connectivity is usually at a maximum in the spring because of a relatively impermeable frost table and low soil storage capacity which reduces infiltration. These effects of melt will not be observed uniformly over the entire catchment because of the

  18. From Earth to Mars with micrometeorite volatiles

    NASA Astrophysics Data System (ADS)

    Maurette, M.; Duprat, J.; Engrand, C.; Kurat, G.

    2006-01-01

    The contribution of the accretion of "juvenile" micrometeorites to the volatile inventory of the Martian atmosphere had to mostly occur during the period of the late heavy bombardment of the inner solar system, prior to about 3.5 Ga ago, when the flux of micrometeorites was much higher than today. To assess this contribution, a micrometeorite accretion formula, developed and validated for the Earth, and based on the variation of lunar cratering rates with time, is extrapolated to Mars. This extrapolation suggests that the history of Martian volatiles was more complex than on the Earth. It is described with a two "shots" scenario involving the two last giant impacts on Mars separated by a time interval of about 500 Ma. The first one was triggered by the last planetary embryo that did merge to Mars thus closing its formation time interval and blowing up its complex pre-impact atmosphere. Thus, a new niche was formed for the accumulation of a dominant micrometeoritic atmosphere during the first 200 Ma of the post-merging period, when the partial pressures of H 2O, CO 2 and N 2 reached about 60, 34 and 0.3 bars, respectively (in water equivalent). This huge amount of water was probably not frozen because an early greenhouse effect was triggered during the simultaneous injection of huge amounts of three strong micrometeoritic greenhouse gases (SO 2, H 2O and CO 2) in the Martian atmosphere. Therefore, early microorganisms could have thrived on early Mars, because micrometeorites likely opened a surprising variety of reaction channels in the prebiotic chemistry of life. But they got likely extinguished a few 100 Ma later, when the last giant impactor, which was probably associated with the spike of bodies that invaded the inner solar system around 4 Ga ago, blew off the earlier massive micrometeoritic atmosphere of Mars and all ingredients of the early greenhouse effect. It thus produced the last "niche" that allowed the accumulation of the thin and sterile present day

  19. 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.

  20. 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.

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

    PubMed

    Schuerger, Andrew C; 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 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.

  2. 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.

  3. Cracky Mars

    NASA Technical Reports Server (NTRS)

    2006-01-01

    21 September 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows cracked, layered plains-forming material in the western part of Utopia Planitia, Mars. Investigators have speculated that ice might be -- or might once have been -- present in the ground, and changes in temperature and the amount of ice over time may have led to the formation of these cracks. But no one is certain just how these features formed.

    Location near: 45.0oN, 276.1oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

  4. Mars Topography

    NASA Technical Reports Server (NTRS)

    2001-01-01

    These maps are global false-color topographic views of Mars at different orientations from the Mars Orbiter Laser Altimeter (MOLA). The maps are orthographic projections that contain over 200,000,000 points and about 5,000,000 altimetric crossovers. The spatial resolution is about 15 kilometers at the equator and less at higher latitudes. The vertical accuracy is less than 5 meters. The right hand image view features the Hellas impact basin (in purple, with red annulus of high standing material). The left hand features the Tharsis topographic rise (in red and white). Note also the subtle textures associated with resurfacing of the northern hemisphere lowlands in the vicinity of the Utopia impact basin. These data were compiled by the Mars Orbiter Laser Altimeter (MOLA) Team led by David Smith at the Goddard Space Flight Center in Greenbelt, MD.

  5. 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.

  6. 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.

  7. Bouncing on Mars and the Moon-the role of gravity on neuromuscular control: correlation of muscle activity and rate of force development.

    PubMed

    Ritzmann, Ramona; Freyler, Kathrin; Krause, Anne; Gollhofer, Albert

    2016-11-01

    On our astronomical neighbors Mars and the Moon, bouncing movements are the preferred locomotor techniques. During bouncing, the stretch-shortening cycle describes the muscular activation pattern. This study aimed to identify gravity-dependent changes in kinematic and neuromuscular characteristics in the stretch-shortening cycle. Hence, neuromuscular control of limb muscles as well as correlations between the muscles' pre-activation, reflex components, and force output were assessed in lunar, Martian, and Earth gravity. During parabolic flights, peak force (Fmax), ground-contact-time, rate of force development (RFD), height, and impulse were measured. Electromyographic (EMG) activities in the m. soleus (SOL) and gastrocnemius medialis (GM) were assessed before (PRE) and during bounces for the reflex phases short-, medium-, and long-latency response (SLR, MLR, LLR). With gradually decreasing gravitation, Fmax, RFD, and impulse were reduced, whereas ground-contact time and height increased. Concomitantly, EMG_GM decreased for PRE, SLR, MLR, and LLR, and in EMG_SOL in SLR, MLR, and LLR. For SLR and MLR, Fmax and RFD were positively correlated to EMG_SOL. For PRE and LLR, RFD and Fmax were positively correlated to EMG_GM. Findings emphasize that biomechanically relevant kinematic adaptations in response to gravity variation were accompanied by muscle- and phase-specific modulations in neural control. Gravitational variation is anticipated and compensated for by gravity-adjusted muscle activities. Importantly, the pre-activation and reflex phases were differently affected: in SLR and MLR, SOL is assumed to contribute to the decline in force output with a decreasing load, and, complementary in PRE and LLR, GM seems to be of major importance for force generation.

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

    NASA Astrophysics Data System (ADS)

    Haddad, Robert I.; Martens, Christopher 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 ± 32% of the recognizable sedimentary vascular plant debris, are calculated to contribute 23 ± 17% of the total organic carbon buried over the past decade (upper meter of sediment column). When combined with a previously established sedimentary organic carbon budget for this site (Martens and Klump, 1984; Martens et al., 1987, in preparation) a vascular plant derived carbon burial rate of 26 ± 20 mole C m -2 yr -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.

  9. Site selection for Mars exobiology.

    PubMed

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

    1995-03-01

    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 refine 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 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.

  10. 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.

  11. Mars X: A Mars Mission Architecture with Lunar-Mars Synergy

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. E.

    2006-01-01

    A human mission to Mars, if it is to be cost effective, should take maximum advantage of previous efforts at the Moon, in terms of habitats, heavy lift boosters, and vehicles. It must also make use of nuclear site power for bases. However, to make such an effort sustainable over many administrations, it should not make use of nuclear propulsion. It is proposed in this architecture that high power Solar Electric Propulsion based around the MET (Microwave Electro-Thermal) thruster with water propellant, as an upper stage for a heavy lift booster, will allow a 46MT basic payload package to be sent to Mars. ISRU is utilized on Mars for production of RP1 and LOX to achieve Mars ascent and Mars Orbit rendezvous with an interplanetary stage. Two full tests of ISRU and Mars ascent are assumed for a human-rating of the system and to preposition water and RP1 in Mars orbit for abort to Earth from Mars orbit.

  12. 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.

  13. Mars exploration.

    PubMed

    Carr, M H; Garvin, J

    2001-07-12

    An international flotilla of spacecraft are to be sent to Mars over the next decade in an effort to understand the planet's geology and climate history, and to determine whether some form of life ever started there. At least two spacecraft will be sent at each launch opportunity, and at times up to four spacecraft may be operating simultaneously at the planet.

  14. 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.

  15. 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.

  16. Hydraulic conductance as well as nitrogen accumulation plays a role in the higher rate of leaf photosynthesis of the most productive variety of rice in Japan

    PubMed Central

    Taylaran, Renante D.; Adachi, Shunsuke; Ookawa, Taiichiro; Usuda, Hideaki; Hirasawa, Tadashi

    2011-01-01

    An indica variety Takanari is known as one of the most productive rice varieties in Japan and consistently produces 20–30% heavier dry matter during ripening than Japanese commercial varieties in the field. The higher rate of photosynthesis of individual leaves during ripening has been recognized in Takanari. By using pot-grown plants under conditions of minimal mutual shading, it was confirmed that the higher rate of leaf photosynthesis is responsible for the higher dry matter production after heading in Takanari as compared with a japonica variety, Koshihikari. The rate of leaf photosynthesis and shoot dry weight became larger in Takanari after the panicle formation and heading stages, respectively, than in Koshihikari. Roots grew rapidly in the panicle formation stage until heading in Takanari compared with Koshihikari. The higher rate of leaf photosynthesis in Takanari resulted not only from the higher content of leaf nitrogen, which was caused by its elevated capacity for nitrogen accumulation, but also from higher stomatal conductance. When measured under light-saturated conditions, stomatal conductance was already decreased due to the reduction in leaf water potential in Koshihikari even under conditions of a relatively small difference in leaf–air vapour pressure difference. In contrast, the higher stomatal conductance was supported by the maintenance of higher leaf water potential through the higher hydraulic conductance in Takanari with the larger area of root surface. However, no increase in root hydraulic conductivity was expected in Takanari. The larger root surface area of Takanari might be a target trait in future rice breeding for increasing dry matter production. PMID:21527630

  17. Hydraulic conductance as well as nitrogen accumulation plays a role in the higher rate of leaf photosynthesis of the most productive variety of rice in Japan.

    PubMed

    Taylaran, Renante D; Adachi, Shunsuke; Ookawa, Taiichiro; Usuda, Hideaki; Hirasawa, Tadashi

    2011-07-01

    An indica variety Takanari is known as one of the most productive rice varieties in Japan and consistently produces 20-30% heavier dry matter during ripening than Japanese commercial varieties in the field. The higher rate of photosynthesis of individual leaves during ripening has been recognized in Takanari. By using pot-grown plants under conditions of minimal mutual shading, it was confirmed that the higher rate of leaf photosynthesis is responsible for the higher dry matter production after heading in Takanari as compared with a japonica variety, Koshihikari. The rate of leaf photosynthesis and shoot dry weight became larger in Takanari after the panicle formation and heading stages, respectively, than in Koshihikari. Roots grew rapidly in the panicle formation stage until heading in Takanari compared with Koshihikari. The higher rate of leaf photosynthesis in Takanari resulted not only from the higher content of leaf nitrogen, which was caused by its elevated capacity for nitrogen accumulation, but also from higher stomatal conductance. When measured under light-saturated conditions, stomatal conductance was already decreased due to the reduction in leaf water potential in Koshihikari even under conditions of a relatively small difference in leaf-air vapour pressure difference. In contrast, the higher stomatal conductance was supported by the maintenance of higher leaf water potential through the higher hydraulic conductance in Takanari with the larger area of root surface. However, no increase in root hydraulic conductivity was expected in Takanari. The larger root surface area of Takanari might be a target trait in future rice breeding for increasing dry matter production.

  18. 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.

  19. 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.

  20. Mars mission

    NASA Astrophysics Data System (ADS)

    Katzoff, Judith A.

    To mark the 10th anniversary of the Apollo-Soyuz joint space mission, a recent conference examined the prospects for human exploration of Mars and for international cooperation in space. Most of the participants at the conference, which was jointly sponsored by the American Institute of Aeronautics and Astronautics and The Planetary Society, seemed to agree that some sort of collaboration like that between the United States and Soviet Union a decade ago would be desirable, and probably necessary, if humans are ever to reach Mars. Sen. Spark Matsunaga (D-Hawaii) extended the idea by saying that to gain the support of Congress, plans for future space exploration should be tied to international cooperation.

  1. 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.

  2. 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

  3. Carbon accumulation in a permafrost polygon peatland: steady long-term rates in spite of shifts between dry and wet conditions.

    PubMed

    Gao, Yang; Couwenberg, John

    2015-02-01

    Ice-wedge polygon peatlands contain a substantial part of the carbon stored in permafrost soils. However, little is known about their long-term carbon accumulation rates (CAR) in relation to shifts in vegetation and climate. We collected four peat profiles from one single polygon in NE Yakutia and cut them into contiguous 0.5 cm slices. Pollen density interpolation between AMS (14)C dated levels provided the time span contained in each of the sample slices, which--in combination with the volumetric carbon content--allowed for the reconstruction of CAR over decadal and centennial timescales. Vegetation representing dry palaeo-ridges and wet depressions was reconstructed with detailed micro- and macrofossil analysis. We found repeated shifts between wet and dry conditions during the past millennium. Dry ridges with associated permafrost growth originated during phases of (relatively) warm summer temperature and collapsed during relatively cold phases, illustrating the important role of vegetation and peat as intermediaries between ambient air temperature and the permafrost. The average long-term CAR across the four profiles was 10.6 ± 5.5 g C m(-2) yr(-1). Time-weighted mean CAR did not differ significantly between wet depression and dry ridge/hummock phases (10.6 ± 5.2 g C m(-2) yr(-1) and 10.3 ± 5.7 g C m(-2) yr(-1), respectively). Although we observed increased CAR in relation to warm shifts, we also found changes in the opposite direction and the highest CAR actually occurred during the Little Ice Age. In fact, CAR rather seems to be governed by strong internal feedback mechanisms and has roughly remained stable on centennial time scales. The absence of significant differences in CAR between dry ridge and wet depression phases suggests that recent warming and associated expansion of shrubs will not affect long-term rates of carbon burial in ice-wedge polygon peatlands.

  4. MARS15

    SciTech Connect

    Mokhov, Nikolai

    2016-07-15

    MARS is a Monte Carlo code for inclusive and exclusive simulation of three-dimensional hadronic and electromagnetic cascades, muon, heavy-ion and low-energy neutron transport in accelerator, detector, spacecraft and shielding components in the energy range from a fraction of an electronvolt up to 100 TeV. Recent developments in the MARS15 physical models of hadron, heavy-ion and lepton interactions with nuclei and atoms include a new nuclear cross section library, a model for soft pion production, the cascade-exciton model, the quark gluon string models, deuteron-nucleus and neutrino-nucleus interaction models, detailed description of negative hadron and muon absorption and a unified treatment of muon, charged hadron and heavy-ion electromagnetic interactions with matter. New algorithms are implemented into the code and thoroughly benchmarked against experimental data. The code capabilities to simulate cascades and generate a variety of results in complex media have been also enhanced. Other changes in the current version concern the improved photo- and electro-production of hadrons and muons, improved algorithms for the 3-body decays, particle tracking in magnetic fields, synchrotron radiation by electrons and muons, significantly extended histograming capabilities and material description, and improved computational performance. In addition to direct energy deposition calculations, a new set of fluence-to-dose conversion factors for all particles including neutrino are built into the code. The code includes new modules for calculation of Displacement-per-Atom and nuclide inventory. The powerful ROOT geometry and visualization model implemented in MARS15 provides a large set of geometrical elements with a possibility of producing composite shapes and assemblies and their 3D visualization along with a possible import/export of geometry descriptions created by other codes (via the GDML format) and CAD systems (via the STEP format). The built-in MARS-MAD Beamline

  5. 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.

  6. Radiation exposure for human Mars exploration

    NASA Technical Reports Server (NTRS)

    Simonsen, L. C.; Wilson, J. W.; Kim, M. H.; Cucinotta, F. A.; Dicello, J. F. (Principal Investigator)

    2000-01-01

    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.

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

    USGS Publications Warehouse

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

    2016-01-01

    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. 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.

  9. 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.

  10. Complex sediment deposition history on a wide continental shelf: Implications for the calculation of accumulation rates on the Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Lewis, Stephen E.; Olley, Jon; Furuichi, Takahisa; Sharma, Ashneel; Burton, Joanne

    2014-05-01

    Understanding the key processes controlling the delivery, deposition and fate of sediments on continental shelves is critical to appreciate the evolution of coasts and estuaries and to interpret geological sequences. This study presents radiocarbon and Optically Stimulated Luminescence (OSL) ages of sediment cores collected from key locations offshore from the Burdekin River, Australia, the largest single source of sediment delivered to the Great Barrier Reef (GBR) lagoon. The ages show variable sediment accumulation rates at the different locations that coincide with the Holocene avulsion history of the Burdekin River. Our data show that most fine sediment (<63 μm) delivered from the Burdekin River is retained within 50 km of the mouth, a finding that contrasts previous studies which postulated that fine sediments are advected northwards via longshore drift processes. The pairing of radiocarbon and OSL ages provides insights on resuspension regimes operating on the inner shelf of the GBR. It was thought that turbidity on inshore GBR coral reefs and seagrass meadows has increased as a result of increased erosion in the adjacent catchment from agricultural development. Our data show that the age of the sediments in Cleveland Bay (derived from the radiocarbon ages from shell and organic material) can be several thousand years older than when the sediment was last deposited (OSL ages). However, the increased turbidity could conceivably be caused from ‘new biologically-produced sediment’ (i.e. particulate organic matter) as a result of increased nutrient export to the GBR. We suggest that the composition of sediment in resuspension events before and after the wet season be analysed to examine whether newly delivered organic-rich sediment can affect coral reefs and seagrass meadows.

  11. 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.

  12. Mars vehicle TCS and aerobrake TPS

    NASA Technical Reports Server (NTRS)

    Comer, G.

    1986-01-01

    General design approach, some problems and technology needs for a Mars vehicle manned module Thermal Control System (TCS) and aerobrake Thermal Protection System (TPS) are discussed. The design approach of the TCS will be similar to that of the space station. Mars atmospheric dust storms are identified as an unknown that will impact the design of the Mars landing vehicle and base facility. New technology may be needed for thermal control surfaces to functionally survive the dust storms. The TPS for the Mars aerocapture vehicle will be subject to marginal stagnation heating rates for conjunction class missions and very high heating rates for opposition class missions. New technology TPS materials or an ablative heat shield will be required for the high stagnation heating rate trajectories. No significantly new technology is needed for the manned modules that do not descent to the Mars surface.

  13. Four Mars Years of Change

    NASA Technical Reports Server (NTRS)

    2005-01-01

    23 May 2005 These two Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images were acquired a little more than four Mars years apart. One Mars year is about 687 Earth days long. The two images show a portion of the south polar cap, which is composed of frozen, layered, carbon dioxide. Each Mars year since MGS has been observing the planet, the mesas and buttes composed of carbon dioxide have gotten a little bit smaller, and the pits and holes have become a little bit wider. The scarps formed in frozen carbon dioxide in the south polar region are retreating at an average rate of about 3 meters per Mars year. The example shown here includes an image obtained in August 1999, and a more recent picture from April 2005. Arrow '1' points to a dramatic example of the changes that have occurred; in this case a mesa shrank to a small butte in just four martian years. Arrow '2' indicates pits that developed in the cap layer of a carbon dioxide mesa that eroded during the same interval. Acquired during early southern spring, both images are illuminated by sunlight from the upper left.

  14. 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.

  15. 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.

  16. 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.

  17. Assessment of AOCS In-Orbit Performance for Mars Express and Rosetta

    NASA Astrophysics Data System (ADS)

    Lauer, M.; Kielbassa, S.; Herfort, U.

    ESA's interplanetary spacecraft (S/C) Mars Express and Rosetta were launched in June 2003 and March 2004, respectively. Mars Express was injected into Mars orbit end of 2003 with routine operations starting in spring this year. Rosetta is since launch in cruise towards the first Earth swingby in 2005, with spacecraft and payload commissioning activities being performed. Both spacecraft are three axes stabilised with a similar attitude and orbit control system (AOCS). The attitude is estimated on board using star and rate sensors and controlled using four reaction wheels. A bipropellant reaction control system with 10N thrusters serves for wheel off loadings and attitude control in safe mode. Mars Express has an additional 400N engine for the Mars orbit insertion. Nominal Earth communication is accomplished through a high gain antenna (HGA). The paper addresses several aspects of the AOCS performance relevant for successful spacecraft operations: • Star tracker performance Inertial attitude reference information to the AOCS is provided by a fully autonomous star tracker (STR). Up to 9 stars are identified and tracked. On ground the performance of the star tracker is assessed in terms of quality of the on board star catalogue, noise on star position measurements, measurement degradation due to Sun incidence, tracking probability of stars, ability of first attitude acquisition without a priori estimate. • Delta-V measurement accuracy Accumulated delta-v is estimated on board from accelerometer measurements to terminate orbit control manoeuvres. The bias of these sensors are regularly calibrated on ground. For Mars Express, this bias shows a strong dependency on the number of units that are switched on with a time constant of several hours. The finally measured delta-v's are consistent with radiometric data between some mm/s and some cm/s depending on the size of the manoeuvre. • Attitude estimation during solar flares During a solar flare in 2003, both Mars

  18. DR-induced escape of O and C from early Mars

    NASA Astrophysics Data System (ADS)

    Zhao, Jinjin; Tian, Feng; Ni, Yufang; Huang, Xiaomeng

    2017-03-01

    Energetic particles produced in Dissociative recombination (DR) reactions could escape planets with low gravity, such as Mars, if they could overcome collisions with the surrounding background gases. In this work, a 3-D Monte Carlo model is developed to study these photochemical escape processes on early Mars. Although the DR reaction rates of O2+, CO2+, and CO+ increase monotonically with solar soft X-ray and extreme ultraviolet (XUV) flux, the peak of the calculated DR-induced escape rates of O is near 3 × XUV, and the DR-induced escape rates of C increase with XUV until 10 × XUV. The non-monotonic behavior can be explained by the increased column densities of background species in high XUV conditions, which can deflect energetic particles through collisions more efficiently. At 20 × XUV, CO+ DR is the main source of escaping O and C, and the escape of secondary particles could contribute to 30∼40% and 10% of the total escape of O and C respectively. The time-integrated DR-induced escape of O and C is equivalent to 1 m of H2O and 20 mbar of CO2 escaping early Mars since 4.5 billion years ago. The accumulated CO2 loss is much lower than what's needed to explain the carbon isotopic ratios on Mars and much lower than the total CO2 needed to warm up early Mars. If more vigorous escape mechanisms were absent on early Mars, substantial inventories of volatiles have not been detected yet.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Missions to Mars

    NASA Astrophysics Data System (ADS)

    Chicarro, A. F.; Science Team

    2002-10-01

    This presentation started with a historical perspective of the astronomical discovery of Mars and followed by an overview of previous missions to Mars by the United States and the Soviet Union. Recently launched missions, such as Nozomi, Mars Global Surveyor and Mars Odyssey were addressed in more detailed, as well as a few other missions soon to be launched. Among these, Mars Express is particularly relevant as the first European mission towards the red planet, and the talk concentrated on it, including both the Mars Express orbiter spacecraft and the Beagle-2 lander to be launched in 2003.

  13. 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.

  14. 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.

  15. Mars chronology: Assessing techniques for quantifying surficial processes

    USGS Publications Warehouse

    Doran, P.T.; Clifford, S.M.; Forman, S.L.; Nyquist, L.; Papanastassiou, D.A.; Stewart, B.W.; Sturchio, N.C.; Swindle, T.D.; Cerling, T.; Kargel, J.; McDonald, G.; Nishiizumi, K.; Poreda, R.; Rice, J.W.; Tanaka, K.

    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 and/or 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. ?? 2004 Elsevier B.V. All rights

  16. 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.

  17. 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.

  18. 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

  19. Possibilities of Terraforming Mars

    NASA Astrophysics Data System (ADS)

    Shrivastava, M. K.

    2007-07-01

    Diminished internally produced energy of early Mars would have resulted in cold mantle, causing gradual submersion of surface water with dissolved gases. Therefore, to terraform or revive Mars, it is necessary to reactivate its diminished internally produced energy.

  20. 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...

  1. Mars Meteorolgical Network

    NASA Technical Reports Server (NTRS)

    Justh, H. L.; Spann, J. F.

    2012-01-01

    Exploring and ultimately establishing a permanent presence on the surface of Mars will necessitate an understanding the weather conditions and the ability to forecast its dynamic behavior. The meteorology of Mars will need to be developed. This abstract puts forth a concept for a Mars Meteorological Network that will be used to investigate the Mars atmosphere behavior, explore the surface environment, and prepare for operational activities. It is proposed that the long term and the dynamic nature of the lower atmosphere and surface of Mars be observed with a distributed global array of simple automated surface nodes. The data would be ingested into the Mars Global Reference Atmospheric Model (Mars-GRAM) and other research tools for analyses to gain a better understanding of the atmospheric conditions on Mars.

  2. 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...

  3. Mars - Water Ice Clouds

    NASA Technical Reports Server (NTRS)

    1997-01-01

    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.

  4. Rotorcrafts for Mars Exploration

    NASA Astrophysics Data System (ADS)

    Balaram, J.; Tokumaru, P. T.

    2014-06-01

    Rotorcraft mobility provides a number of useful capabilities to potential Mars missions. We present some recent results relating to the design and test of Mars rotorcraft mobility elements, and aspects of rotorcraft system and mission design.

  5. 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

  6. True Colors of Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken on Mars by the panoramic camera on the Mars Exploration Rover Spirit shows the rover's color calibration target, also known as the MarsDial. The target's mirror and the shadows cast on it by the Sun help scientists determine the degree to which dusty martian skies alter the panoramic camera's perception of color. By adjusting for this effect, Mars can be seen in all its true colors.

  7. 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

  8. 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.'

  9. 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.

  10. 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.

  11. Scale-Dependent Infrared Radiative Damping Rates on Mars and Their Role in the Deposition of Gravity-Wave Momentum Flux

    DTIC Science & Technology

    2010-01-01

    Maryland 27023, USA Abstract Using a Curtis matrix model of 15 µm CO2 radiative cooling rates for the Martian atmosphere, we have computed vertical...956;m CO2 radiative cooling rates for the Martian atmosphere, we have computed vertical scale-dependent IR radiative damping rates from 0-200 km...submitted to Icarus June 3, 2010 1. Introduction Being ∼95% CO2 by mixing ratio, the thermal balance of the Martian atmosphere is driven to a large

  12. 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.

  13. Bladder accumulated dose in image-guided high-dose-rate brachytherapy for locally advanced cervical cancer and its relation to urinary toxicity

    NASA Astrophysics Data System (ADS)

    Zakariaee, Roja; Hamarneh, Ghassan; Brown, Colin J.; Gaudet, Marc; Aquino-Parsons, Christina; Spadinger, Ingrid

    2016-12-01

    The purpose of this study was to estimate locally accumulated dose to the bladder in multi-fraction high-dose-date (HDR) image-guided intracavitary brachytherapy (IG-ICBT) for cervical cancer, and study the locally-accumulated dose parameters as predictors of late urinary toxicity. A retrospective study of 60 cervical cancer patients who received five HDR IG-ICBT sessions was performed. The bladder outer and inner surfaces were segmented for all sessions and a bladder-wall contour point-set was created in MATLAB. The bladder-wall point-sets for each patient were registered using a deformable point-set registration toolbox called coherent point drift (CPD), and the fraction doses were accumulated. Various dosimetric and volumetric parameters were calculated using the registered doses, including r{{\\text{D}}n \\text{c{{\\text{m}}\\text{3}}}} (minimum dose to the most exposed n-cm3 volume of bladder wall), r V n Gy (wall volume receiving at least m Gy), and r\\text{EQD}{{2}n \\text{c{{\\text{m}}\\text{3}}}} (minimum equivalent biologically weighted dose to the most exposed n-cm3 of bladder wall), where n  =  1/2/5/10 and m  =  3/5/10. Minimum dose to contiguous 1 and 2 cm3 hot-spot volumes was also calculated. The unregistered dose volume histogram (DVH)-summed equivalent of r{{\\text{D}}n \\text{c{{\\text{m}}3}}} and r\\text{EQD}{{2}n \\text{c{{\\text{m}}3}}} parameters (i.e. s{{\\text{D}}n \\text{c{{\\text{m}}\\text{3}}}} and s\\text{EQD}{{2}n \\text{c{{\\text{m}}3}}} ) were determined for comparison. Late urinary toxicity was assessed using the LENT-SOMA scale, with toxicity Grade 0-1 categorized as Controls and Grade 2-4 as Cases. A two-sample t-test was used to identify the differences between the means of Control and Case groups for all parameters. A binomial logistic regression was also performed between the registered dose parameters and toxicity grouping. Seventeen patients were in the Case and 43 patients in the Control group. Contiguous

  14. 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.

  15. 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.

  16. 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

  17. Relationship between plant traits and resistance to burial by marly sediment

    NASA Astrophysics Data System (ADS)

    Burylo, M.; Rey, F.; Dutoit, T.

    2009-04-01

    In marly lands of the French Southern Alps, harsh soil erosion results in sediment movements during intensive rainfall events. Plants can be submitted to sediment burial in their early stages of development and their protective function may be reduced. In a context of land restoration, it is important to know species resistance to environmental disturbances and to be able to predict it, in particular from plant traits (height, biomass, sugar and starch accumulation). However, few studies about woody species tolerance to burial by sediment have been carried out. Seedlings of five woody species were buried in marly sediment at three different depths in pot experiment during eight weeks: no burial (control), partial burial (50% stem height) and complete burial (100% stem height). Height through time, biomass and survival rates were measured to assess species resistance to burial. Results show that among the five species, only one (Acer campestre) survived complete burial. All plants survived partial burial, but there were significant differences in height and biomass between buried plants and control, and significant differences between species responses. Three different responses to disturbance were identified: negative (Hippophae rhamnoides, Ononis fruticosa), neutral (Robinia pseudo acacia, Pinus nigra) and positive (Acer campestre). Results finally suggest that species resistance to burial by marly sediment is related to sugar accumulation in plant stems.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. Replacement of the glucose phosphotransferase transport system by galactose permease reduces acetate accumulation and improves process performance of Escherichia coli for recombinant protein production without impairment of growth rate.

    PubMed

    De Anda, Ramón; Lara, Alvaro R; Hernández, Vanessa; Hernández-Montalvo, Verónica; Gosset, Guillermo; Bolívar, Francisco; Ramírez, Octavio T

    2006-05-01

    Acetate accumulation under aerobic conditions is a common problem in Escherichia coli cultures, as it causes a reduction in both growth rate and recombinant protein productivity. In this study, the effect of replacing the glucose phosphotransferase transport system (PTS) with an alternate glucose transport activity on growth kinetics, acetate accumulation and production of two model recombinant proteins, was determined. Strain VH32 is a W3110 derivative with an inactive PTS. The promoter region of the chromosomal galactose permease gene galP of VH32 was replaced by the strong trc promoter. The resulting strain, VH32GalP+ acquired the capacity to utilize glucose as a carbon source. Strains W3110 and VH32GalP+ were transformed for the production of recombinant TrpLE-proinsulin accumulated as inclusion bodies (W3110-PI and VH32GalP+-PI) and for production of soluble intracellular green fluorescent protein (W3110-pV21 and VH32GalP+-pV21). W3110-pV21 and VH32GalP+-pV21 were grown in batch cultures. Maximum recombinant protein concentration, as determined from fluorescence, was almost four-fold higher in VH32GalP+-pV21, relative to W3110-pV21. Maximum acetate concentration reached 2.8 g/L for W3110-pV21 cultures, whereas a maximum of 0.39 g/L accumulated in VH32GalP+-pV21. W3110-PI and VH32GalP+-PI were grown in batch and fed-batch cultures. Compared to W3110-PI, the engineered strain maintained similar production and growth rate capabilities while reducing acetate accumulation. Specific glucose consumption rate was lower and product yield on glucose was higher in VH32GalP+-PI fed-batch cultures. Altogether, strains with the engineered glucose uptake system showed improved process performance parameters for recombinant protein production over the wild-type strain.

  3. Space exploration, Mars, and the nervous system.

    PubMed

    Kalb, Robert; Solomon, David

    2007-04-01

    When human beings venture back to the moon and then on to Mars in the coming decade or so, we will be riding on the accumulated data and experience from approximately 50 years of manned space exploration. Virtually every organ system functions differently in the absence of gravity, and some of these changes are maladaptive. From a biologic perspective, long duration spaceflight beyond low Earth orbit presents many unique challenges. Astronauts traveling to Mars will live in the absence of gravity for more than 1 year en route and will have to transition between weightlessness and planetary gravitational forces at the beginning, middle, and end of the mission. We discuss some of what is known about the effects of spaceflight on nervous system function, with emphasis on the neuromuscular and vestibular systems because success of a Mars mission will depend on their proper functioning.

  4. Mars Color Imager (MARCI) on the Mars Climate Orbiter

    USGS Publications Warehouse

    Malin, M.C.; Bell, J.F.; 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

  5. 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.

  6. Modern accumulation rates and a budget of sediment off the Gaoping (Kaoping) River, SW Taiwan: A tidal and flood dominated depositional environment around a submarine canyon

    NASA Astrophysics Data System (ADS)

    Huh, Chih-An; Lin, Hui-Ling; Lin, Saulwood; Huang, Ya-Wen

    2009-03-01

    Ninety-two box cores collected during 2004-2006 from an area of ~ 3000 km 2 off the Gaoping (formerly spelled Kaoping) River, SW Taiwan, were analyzed for fallout radionuclides ( 210Pb, 137Cs and 7Be) to elucidate sedimentation rates and processes, and for the calculation of a sediment budget. The study area is located at an active collision margin with a narrow shelf and a submarine canyon extending essentially into the river's mouth. The results indicate fairly constant hemipelagic sedimentation in much of the open margin and for most of the time except in the inner shelf and along the axis of the canyon where sediment transport is more dynamic and is controlled by tidal current and wave activities constantly, and by fluvial floods or gravity-driven flows episodically. Sedimentation rates in the study area derived from 210Pb and constrained by 137Cs vary from 0.04 to 1.5 cm/yr, with the highest rates (> 1 cm/yr) flanking the Gaoping canyon over the upper slope (200-600 m) and the lowest rates (< 0.1 cm/yr) in the distal basin beyond the continental slope. The depocenter delineated from 210Pb-based sedimentation rates overlaps with the area covered by a flood layer resulting from super-typhoon Haitang in July 2005. Such correspondence supports the notion that the processes operating on event timescale have bearing on the formation of the sediment strata over centennial or longer timescales. From the distribution of sedimentation rates, sediment deposited in the study area annually is estimated to be 6.6 Mton/yr, accounting for less than 20% of Gaoping River's sediment load. The calculated budget, coupled with the presence of the short-lived 7Be and non-steady-state distribution of low levels of 210Pb in sediments along the canyon floor, suggests rapid transport of sediment from Gaoping River's mountainous watershed (the source) via the Gaoping (Kaoping) Submarine Canyon and adjacent channels (as the conduit and temporary sink) to the abyssal plain and the Manila

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Investigation of Mars Rotational Dynamics Using Earth-based Radio Tracking of Mars Landers

    NASA Technical Reports Server (NTRS)

    Edwards, C. D., Jr.; Folkner, W. M.; Kahn, R. D.; Preston, R. A.

    1993-01-01

    The development of space geodetic techniques over the past two decades has made it possible to measure the rotational dynamics of the Earth at the milliarcsecond level, improving our geophysical models of the Earth 's interior and the interactions between the solid Earth and its atmosphere. We have found that the rotational dynamics of Mars can be determined to nearly the same level of accuracy by acquiring Earth-based two-way radio tracking observations of three or more landers globally distributed on the surface of Mars. Our results indicate that the precession and long-term obliquity changes of the Mars pole direction can be determined to an angular accuracy corresponding to about 15 cm/yr at the planet's surface. In addition, periodic nutations of the pole and seasonal variations in the spin rate of the planet can be determined to 10 cm or less. Measuring the rotation of Mars at this accuracy would greatly improve the determination of the planet' s moment of inertia and would resolve the size of a planetary fluid core, providing a valuable constraint on Mars interior models. Detecting seasonal variations in the spin rate of Mars would provide global constraints on atmospheric angular momentum changes due to sublimation of the Mars CO2 polar ice caps. Finally, observation of quasisecular changes in Mars obliquity would have significant implications for understanding long-term climatic change. The key to achieving these accuracies is a globally distributed network of Mars landers with stable, phase-coherent radio transponders. By simultaneously acquiring coherent two-way carrier phase observations between a single Earth tracking station and multiple Mars landers, Earth media errors are essentially eliminated, providing an extremely sensitive measure of changes in the differential path lengths between the Earth tracking station and the Mars landers due to Mars rotation. Time variability of the instrumental phase delay through the radio transponder may represent

  13. 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…

  14. Instrumentation for Mars Environments

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    1997-01-01

    The main portion of the project was to support the "MAE" experiment on the Mars Pathfinder mission and to design instrumentation for future space missions to measure dust deposition on Mars and to characterize the properties of the dust. A second task was to analyze applications for photovoltaics in new space environments, and a final task was analysis of advanced applications for solar power, including planetary probes, photovoltaic system operation on Mars, and satellite solar power systems.

  15. 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.

  16. 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.

  17. 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.

  18. Simulations of Methane Hydrate Phenomena Over Geologic Timescales. Part I: Effect of Sediment Compaction Rates on Methans Hydrate and Free Gas Accumulation

    SciTech Connect

    Gering, Kevin Leslie

    2003-01-01

    The focus of this work is a model that describes migration and biogenic formation of methane under conditions representative of dynamic marine basins, and the conversion of soluble methane into either solid hydrate or exsolved gas. Incorporated into the overall model are an accurate phase equilibria model for seawater-methane, a methane source term based on biogenesis data, and a sediment compaction model based on porosity as a function of position, time, and the local volume fractions of hydrate solids and free gas. Simulations have shown that under some compaction scenarios, liquid overpressures reach the lithostatic limit due to permeability constraints, which can diminish the advective transfer of soluble methane within the porous sediment. As such, the formation of methane hydrate can be somewhat of a self-moderating process. The occurrence and magnitude of hydrate formation is directly tied to fundamental parameters such as the compaction/sedimentation rates, liquid advection rates, seafloor depth, geothermal gradient, etc. Results are shown for simulations covering 20 million years, wherein growth profiles for methane hydrate and free gas (neither exceeding 10 vol% at any location) are tracked within a vertical sediment column spanning over 3000 m. A case study is also presented for the Blake Ridge region (Ocean Drilling Program Leg 164, Sites 994, 995, and 997) based on simulations covering 6 Ma, wherein it is concluded that methane migration from compaction-driven advection may account for 15-30% of the total hydrate mass present in this region.

  19. 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.

  20. Mars - Destination and challenge

    NASA Astrophysics Data System (ADS)

    Aldrich, Arnold D.

    A general evaluation is conducted of the challenges associated with prospective Mars exploration efforts. The technical challenge posed stems from the unforgiving physical environment of space travel, and such peculiarities of Mars as its great orbital eccentricity and 15-year cyclic variation in transfer energy. Additional considerations arise from the 'architecture' of NASA's Space Exploration Initiative, encompassing the determination of a Mars exploration effort's purpose, scope, and schedule. Finally, numerous unresolved issues arise from the definition of detailed scientific experimentation that is to be done for the sake of the greatest long-term benefit to an understanding of Mars, and the rallying of political support behind a major new exploration initiative.

  1. Mars - Destination and challenge

    NASA Technical Reports Server (NTRS)

    Aldrich, Arnold D.

    1992-01-01

    A general evaluation is conducted of the challenges associated with prospective Mars exploration efforts. The technical challenge posed stems from the unforgiving physical environment of space travel, and such peculiarities of Mars as its great orbital eccentricity and 15-year cyclic variation in transfer energy. Additional considerations arise from the 'architecture' of NASA's Space Exploration Initiative, encompassing the determination of a Mars exploration effort's purpose, scope, and schedule. Finally, numerous unresolved issues arise from the definition of detailed scientific experimentation that is to be done for the sake of the greatest long-term benefit to an understanding of Mars, and the rallying of political support behind a major new exploration initiative.

  2. 2001 Mars Odyssey

    NASA Astrophysics Data System (ADS)

    Russell, C. T.

    2004-04-01

    Mars, the most habitable of our sister planets, holds a special place in our imaginations and in our space exploration program. Fully half of NASA's planetary exploration effort is now devoted to Mars. Key questions include: Has Mars ever harbored life? Is there life on Mars now? Will humans be able to survive on the Martian surface? Answers to these questions lie in determining the present location of water on Mars and its likely inventory in the past, and in determining the present radiation environment of Mars. The 2001 Mars Odyssey Mission contributes greatly these answers by detecting near-surface water through measurements of neutron flux, from the detection of carbonates, and the quantification of its radiation environment. This book captures the objectives, the design of the mission and the details of the instruments carried to Mars. It should be of interest to every scientist interested in participating in the on-going exploration of Mars from graduate students to senior scientists as it provides the background information essential to interpret the many exciting results now appearing from the mission. Link: http://www.wkap.nl/prod/b/1-4020-1696-4

  3. Mars Museum Visualization Alliance

    NASA Astrophysics Data System (ADS)

    Sohus, A. M.; Viotti, M. A.; de Jong, E. M.

    2004-11-01

    The Mars Museum Visualization Alliance is a collaborative effort funded by the Mars Public Engagement Office and supported by JPL's Informal Education staff and the Solar System Visualization Project to share the adventure of exploration and make Mars a real place. The effort started in 2002 with a small working group of museum professionals to learn how best to serve museum audiences through informal science educators. By the time the Mars Exploration Rovers landed on Mars in January 2004, over 100 organizations were partners in the Alliance, which has become a focused community of Mars educators. The Alliance provides guaranteed access to images, information, news, and resources for use by the informal science educators with their students, educators, and public audiences. Thousands of people have shared the adventure of exploring Mars and now see it as a real place through the efforts of the Mars Museum Visualization Alliance partners. The Alliance has been lauded for "providing just the right inside track for museums to do what they do best," be that webcasts, live presentations with the latest images and information, high-definition productions, planetarium shows, or hands-on educational activities. The Alliance is extending its mission component with Cassini, Genesis, Deep Impact, and Stardust. The Mars Exploration and Cassini Programs, as well as the Genesis, Deep Impact, and Stardust Projects, are managed for NASA by the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Deriving in vivo biotransformation rate constants and metabolite parent concentration factor/stable metabolite factor from bioaccumulation and bioconcentration experiments: An illustration with worm accumulation data.

    PubMed

    Kuo, Dave Ta Fu; Chen, Ciara Chun

    2016-12-01

    Growing concern for the biological fate of organic contaminants and their metabolites and the urge to connect in vitro and in vivo toxicokinetics have prompted researchers to characterize the biotransformation behavior of organic contaminants in biota. The whole body biotransformation rate constant (kM ) is currently determined by the difference approach, which has significant methodological limitations. A new approach for determining kM from the kinetic observations of the parent contaminant and its intermediate metabolites is proposed. In this method, kM can be determined by fitting kinetic data of the parent contaminant and the metabolites to analytical equations that depict the bioaccumulation kinetics. The application of the proposed method is illustrated using worm bioaccumulation-biotransformation data collected from the literature. Furthermore, a metabolite parent concentration factor (MPCF) is also proposed to characterize the persistence of the metabolite in biota. Because both the proposed kM method and MPCF build on the existing theoretical framework for bioaccumulation, they can be readily incorporated into standard experimental bioaccumulation protocols or risk assessment procedures or frameworks. Possible limitations, implications, and future directions are elaborated. Environ Toxicol Chem 2016;35:2903-2909. © 2016 SETAC.

  14. 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.

  15. 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.

  16. 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

    1997-12-05

    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.

  17. Micrometeoritic volatiles on Mars

    NASA Astrophysics Data System (ADS)

    Maurette, M.; Duprat, J.; Engrand, C.; Gounelle, M.; Kurat, G.

    rates, K(t), were ˜ 100 times higher than today. In the model, the integration of K(t) yield the total mass of micrometeorites accreted since t, i.e., about 4 Φ Norm. It is much easier to explain the constancy of the CO2/N2 ratio through time. But the reservoir of planetary embryos was exhausted. This last impactor was possibly belonging to the "burst" of impactors, which produced the largest impact basins of the Moon, around 3.9 Gyr ago. If a large amount of frozen water is still present on Mars today (equivalent to a ˜ 300 m thick global layer?), this water had to be fully frozen at the time of this last impact, as to be shielded from the cataclysmic blasting effect of this impact.

  18. Changes in growth rate and macroelement and trace element accumulation in Hydrocharis morsus-ranae L. during the growing season in relation to environmental contamination.

    PubMed

    Polechońska, Ludmiła; Samecka-Cymerman, Aleksandra; Dambiec, Małgorzata

    2017-02-01

    The temporal variations in plant chemistry connected with its life cycle may affect the cycling of elements in an ecosystem as well as determine the usefulness of the species in phytoremediation and bioindication. In this context, there is a gap in knowledge on the role of floating plants for elements cycling in aquatic reservoirs. The aim of the study was to determine if there are variations in Hydrocharis morsus-ranae (European frog-bit) bioaccumulation capacity and the growth rate of its population during the growing season and to test the impact of environmental pollution on these features. The content of macroelements (Ca, K, Mg, N, Na, P, S) and trace metals (Cd, Co, Cu, Cr, Hg, Fe, Mn, Ni, Pb, Zn) was determined in H. morsus-ranae collected monthly from June to October from habitats differing in environmental contamination. The results showed that the highest content of most trace metals (Co, Cr, Cu, Hg, Mn, Ni, Zn) and some nutrients (N, P) in plants as well as the greatest bioaccumulation efficiency occurred simultaneously in the beginning of the growing season. In the following months, a dilution effect (manifested by a decrease in content) related to the rapid growth was observed. Co, Mn, and Ni content in plant tissues reflected the level of environmental contamination throughout the growing season which makes H. morsus-ranae a potential biomonitor of pollution for these metals. Considering the great bioaccumulation ability, high sensitivity to contamination, and low biomass of European frog-bit in polluted systems, further investigation is required to assess the real phytoremediation capability of the species.

  19. 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.

  20. 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.

  1. 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.

  2. 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…

  3. 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…

  4. 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.

  5. 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.

  6. Mars' grand finale

    SciTech Connect

    Parker, D.C.; Beish, J.D.; Hernandez, C.E.

    1989-04-01

    Results are presented from observations of the 1988 Mars apparition. Consideration is given to observations of the Martian south polar cap, meteorological activity on the planet, and changes in the surface features of Mars during the apparition. Also, the Martian dust storms observed in November 1988 are described.

  7. 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.

  8. 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.

  9. 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

  10. New Mars vehicle concepts

    NASA Astrophysics Data System (ADS)

    Sherwood, Brent

    1993-02-01

    The paper briefly reviews the evolution of the Mars vehicle design concepts from 1952 to 1990, and the currently understood requirements, constraints, and options for manned Mars missions in the early decades of the 21st century. The most up-to-date integrated Mars vehicle concepts for crew-carrying transfer and excursion vehicles are presented together with the Mars descent-ascent mission phases. Particular attention is given to a reusable transfer ship, which is a modular vehicle launched to earth orbit on six 185 t-class boosters and assembled there robotically; it uses dual nuclear-thermal rocket engines and liquid hydrogen propellant. The lander concept is capable of supporting many kinds of surface missions anywhere on Mars.

  11. Mars Observer instrument complement

    NASA Astrophysics Data System (ADS)

    Komro, Fred G.; Hujber, Frank N.

    1991-10-01

    The mechanical and electrical characteristics and the functional designs of the eight scientific instruments of the Mars Observer's instrument complex are described, and their respective principal investigators and sponsoring institutions are listed. These instruments include a gamma-ray spectrometer, a magnetometer/electron reflectometer, the Mars balloon relay, the Mars Observer camera, the Mars Observer laser altimeter, a pressure modulator infrared radiometer, a thermal emission spectrometer, and an ultrastable oscillator. With these instruments, the Mars Observer will be able to determine the elemental and mineralogical character of Martial surface material; to define globally the topography and the gravitational field; to establish the nature of the magnetic field; to determine the spatial and temporal distribution abundances, sources, and sinks of volatile material and dust over a seasonal cycle; and to explore the structure and circulation of Martian atmosphere.

  12. 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.

  13. 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

  14. Lessons from Mars on exploring for giants

    SciTech Connect

    Woidneck, R.K.; Mutschler, J.C.; Kasten, R.K. )

    1996-01-01

    Mars field, located in Mississippi Canyon blocks 763 and 807, stands out as the largest known field in the deep water Gulf of Mexico. Discovered in 1989, Mars is currently in the early stages of development. Understanding the geologic controls on this giant oil field provides insights which can be applied to exploration. Characteristics that distinguish Mars as a giant oil field are the large number of high quality reservoirs within an effective trapping configuration, and the highly efficient hydrocarbon migration pathway. Reservoir deposition was strongly influenced by shallow salt sheets, which focused deep marine sediment gravity flows. Trapping is predominantly stratigraphic, with reservoir limits controlled by basin geometry during deposition. Surrounding salt canopies served to focus, rather than impede, hydrocarbon migration into the Mars basin. Mars field geology typifies that of a broader play fairway, providing a framework for evaluating further prospectivity. The play fairway is characterized by Miocene to lower Pliocene deep marine reservoirs, primary salt withdrawal basins, thin salt canopies, and a low Pleistocene sedimentation rate. Experience at Mars demonstrates the importance of considering a range of possible reserve outcomes during prospect evaluation, and the value of high quality 3-D seismic data for reducing uncertainty.

  15. Lessons from Mars on exploring for giants

    SciTech Connect

    Woidneck, R.K.; Mutschler, J.C.; Kasten, R.K.

    1996-12-31

    Mars field, located in Mississippi Canyon blocks 763 and 807, stands out as the largest known field in the deep water Gulf of Mexico. Discovered in 1989, Mars is currently in the early stages of development. Understanding the geologic controls on this giant oil field provides insights which can be applied to exploration. Characteristics that distinguish Mars as a giant oil field are the large number of high quality reservoirs within an effective trapping configuration, and the highly efficient hydrocarbon migration pathway. Reservoir deposition was strongly influenced by shallow salt sheets, which focused deep marine sediment gravity flows. Trapping is predominantly stratigraphic, with reservoir limits controlled by basin geometry during deposition. Surrounding salt canopies served to focus, rather than impede, hydrocarbon migration into the Mars basin. Mars field geology typifies that of a broader play fairway, providing a framework for evaluating further prospectivity. The play fairway is characterized by Miocene to lower Pliocene deep marine reservoirs, primary salt withdrawal basins, thin salt canopies, and a low Pleistocene sedimentation rate. Experience at Mars demonstrates the importance of considering a range of possible reserve outcomes during prospect evaluation, and the value of high quality 3-D seismic data for reducing uncertainty.

  16. Strain accumulation in quasicrystalline solids

    NASA Technical Reports Server (NTRS)

    Nori, Franco; Ronchetti, Marco; Elser, Veit

    1988-01-01

    The relaxation of two-dimensional quasicrystalline elastic networks when their constituent bonds are perturbed homogeneously is studied. Whereas ideal, quasi-periodic networks are stable against such perturbations, significant accumulations of strain in a class of disordered networks generated by a growth process are found. The grown networks are characterized by root mean square phason fluctuations which grow linearly with system size. The strain accumulation observed in these networks also grows linearly with system size. Finally, dependence of strain accumulation on cooling rate is found.

  17. 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

  18. 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.

  19. 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.

  20. The Mars Climate Sounder on the Mars Reconnaissance Orbiter

    NASA Astrophysics Data System (ADS)

    McCleese, D.; Taylor, F.; Schofield, J.; Calcutt, S.

    2003-04-01

    There remains a need for an intensive effort to obtain a climatology of the martian atmosphere. This objective was to have been accomplished with the Mars Observer and with the Mars Climatology Orbiter, both of which failed at Mars. In 2005, the Mars Reconnaissance Orbiter will carry the Mars Climate Sounder (MCS) to aquire the necessary measurements of the vertical profiles of atmospheric temperature, water vapor, dust and condensates. This paper describes the climate objectives and measurement approach of MCS.

  1. Mars Aerobot Validation Program

    NASA Technical Reports Server (NTRS)

    Kerzhanovich, V. V.; Cutts, J.; Bachelder, A.; Cameron, J.; Patzold, J.; Quadrelli, M.; Yavrouian, A.; Cantrell, J.; Lachenmeier, T.; Smith, M.

    1999-01-01

    The Mars Balloon Validation Program (MABVAP) was initiated in August 1997 to develop and validate key technologies needed for aerobot missions on Mars. The major elements of the program are the development of balloons for flight on Mars, robust techniques for deployment and inflation and modeling and simulation of balloon flight paths. selection, development and tests of available balloon materials, design and fabrication of balloons (both superpressure and solar- heated), design and fabrication of deployment and inflation systems for aerial deployment, design and fabrication of avionics to control deployment/inflation process and to get telemetry and video data. Modeling of main processes during deployment and actual flight is also a part of MABVAP. In order to validate deployment and inflation, MABVAP applies experience from previous Mars balloon development or study activities the Russian-French Mars Aerostat Project (1988-1995), Mars Aerial Platform Study (1994) and Mars Aerobot/Balloon Study (1996). The program includes laboratory, wind tunnel, vacuum chamber tests of the system components and a number of tropospheric and stratospheric flight tests of deployment and inflation of lightfilm balloons in a simulated Martian environment.

  2. Pebbles on Mars

    NASA Astrophysics Data System (ADS)

    Jerolmack, Douglas J.

    2013-05-01

    Mars is a cold, dry place. Yet there is abundant evidence that fluvial (river) processes have carved the planet's surface; witness deep canyons, streamlined islands, and drainage networks. Most of these features formed more than 3 billion years ago, and a long line of research has led to the "warm and wet early Mars" hypothesis. The idea is that early Mars had a thicker atmosphere with an enhanced greenhouse effect that allowed stable liquid water and a hydrologic cycle to exist. The search for life on Mars, or at least conditions suitable for life, is predicated on this idea. Until now, no observations have unambiguously identified and characterized river-lain sediments, although the Mars Exploration Rovers turned up some evidence of a watery past. As the first major finding from the Mars Science Laboratory mission and its car-sized rover, Curiosity, Williams et al. report on page 1068 of this issue the discovery of conglomerates on Mars - pebbles mixed with sand and turned to rock - resulting from ancient river deposits. The finding provides the clearest view yet on the nature of early martian rivers and should provide momentum for Curiosity's mission moving forward.

  3. ExoMars 2016 arrives at Mars

    NASA Astrophysics Data System (ADS)

    Svedhem, Hakan; Vago, Jorge L.; ExoMars Team

    2016-10-01

    The Trace Gas Orbiter (TGO) and the Schiaparelli Entry, descent and landing Demonstrator Model (EDM) will arrive at Mars on 19 October 2016. The TGO and the EDM are part of the first step of the ExoMars Programme. They will be followed by a Rover and a long lived Surface Platform to be launched in 2020.The EDM is attached to the TGO for the full duration of the cruise to Mars and will be separated three days before arrival at Mars. After separation the TGO will perform a deflection manoeuvre and, on 19 October (during the EDM landing), enter into a highly elliptical near equatorial orbit. TGO will remain in this parking orbit until January 2017, when the orbital plane inclination will be changed to 74 degrees and aerobraking to the final 400 km near circular orbit will start. The final operational orbit is expected to be reached at the end of 2017.The TGO scientific payload consists of four instruments. These are: ACS and NOMAD, both infrared spectrometers for atmospheric measurements in solar occultation mode and in nadir mode, CASSIS, a multichannel camera with stereo imaging capability, and FREND, an epithermal neutron detector for search of subsurface hydrogen. The mass of the TGO is 3700 kg, including fuel. The EDM, with a mass of 600 kg, is mounted on top of the TGO as seen in its launch configuration. The main objective of the EDM is to demonstrate the capability of performing a safe entry, descent and landing on the surface, but it does carry a descent camera and a small battery powered meteorological package that may operate for a few days on the surface.The ExoMars programme is a joint activity by the European Space Agency(ESA) and ROSCOSMOS, Russia. ESA is providing the TGO spacecraft and Schiaparelli (EDM) and two of the TGO instruments and ROSCOSMOS is providing the launcher and the other two TGO instruments. After the arrival of the ExoMars 2020 mission at the surface of Mars, the TGO will handle the communication between the Earth and the Rover and

  4. 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.

  5. The 1958-2008 Greenland ice sheet surface mass balance variability simulated by the regional climate model MAR

    NASA Astrophysics Data System (ADS)

    Fettweis, X.; Franco, B.

    2009-04-01

    Results made with the regional climate model MAR over 1958-2008 show a very high interannual variability of the Greenland ice sheet (GrIS) surface mass balance (SMB) modelled in average to be 330 ± 130 km3/yr. To a first approximation, the SMB variability is driven by the annual precipitation anomaly minus the meltwater run-off rate variability. Sensitivity experiments carried out by the MAR model evaluate the impacts on the surface melt of (i) the summer SST around the Greenland, (ii) the snow pack temperature at the beginning of the spring, (iii) the winter snow accumulation, (iv) the solid and liquid summer precipitations and (v) the summer atmospheric circulation. This last one, by forcing the summer air temperature above the ice sheet, explains mainly the surface melt anomalies.

  6. The Environment of Early Mars

    NASA Astrophysics Data System (ADS)

    Matsubara, Yo

    2013-12-01

    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

  7. 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.

  8. Mars surface transportation options

    NASA Technical Reports Server (NTRS)

    Leitner, Jeffrey M.; Alred, John W.

    1986-01-01

    As the number of scientific experiments for the surface of Mars grows, the need for effective surface transportation becomes critical. Because of the diversity of the experiments proposed, as well as the desire to explore Mars from the equator to the poles, the optimum surface vehicle configuration is not obvious. Five candidate vehicles are described, with an estimate of their size and performance. In order to maximize the success of a manned Mars mission, it appears that two vehicles should be designed for surface transportation: an advanced long-range rover, and a remotely-piloted airplane.

  9. Life on Mars

    NASA Technical Reports Server (NTRS)

    Soffen, G. A.

    1981-01-01

    The Viking biology experiments are examined. It is noted that the Viking missions did not find a terrestrial type of life at either of the two landing sites. This evidence may suggest that Mars is lifeless, but science demands a more rigorous proof; thus, it is still not known whether life exists on Mars. It is suggested that the Martian polar regions must be explored before a conclusive answer is possible; the permanent polar caps of Mars are frozen water and would act as a 'cold finger' of the planet to trap organic molecules.

  10. The Mars observer camera

    NASA Technical Reports Server (NTRS)

    Malin, M. C.; Danielson, G. E.; Ingersoll, A. P.; Masursky, H.; Veverka, J.; Soulanille, T.; Ravine, M.

    1987-01-01

    A camera designed to operate under the extreme constraints of the Mars Observer Mission was selected by NASA in April, 1986. Contingent upon final confirmation in mid-November, the Mars Observer Camera (MOC) will begin acquiring images of the surface and atmosphere of Mars in September-October 1991. The MOC incorporates both a wide angle system for low resolution global monitoring and intermediate resolution regional targeting, and a narrow angle system for high resolution selective surveys. Camera electronics provide control of image clocking and on-board, internal editing and buffering to match whatever spacecraft data system capabilities are allocated to the experiment. The objectives of the MOC experiment follow.

  11. 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.

  12. 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.

  13. Water on Mars

    NASA Technical Reports Server (NTRS)

    Waenke, H.; Dreibus, G.

    1987-01-01

    It is reported that the SNC meteorites are a factor of 2 richer in moderately volatile elements (Na, K, P, etc.) and some volatile elements (Cl, Br, I, S) compared to the Earth and Mars. It is proposed that Mars accreted homogeneously, with the result that all the water except trace amounts (on reaction with metallic Fe) was converted to H(sub 2) and escaped. This model predicts a total Mars H(sub 2)O inventory of 18 ppm (equivalent to an ocean 80 m deep on the planet), and a value for Earth of 300 ppm, close to the actual abundance.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Ion flux profiles observed at Mars

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Andersson, L.; Lundin, R. N.; Frahm, R. A.

    2012-12-01

    How Mars lost it's water and atmosphere is still an important question. Many studies have investigated high-energy ion fluxes (>10 eV) surrounding the planet and derived ion outflow rates in order to determine atmospheric loss. These rates suggest that the outflow from high-energy ions is not the dominant escape path for atmospheric loss. Over the years increasing evidence has indicated that the loss of low-energy ions are more important than the high-energy ion loss. In this presentation ion observations (down to the spacecraft potential) from the Mars Express (MEX) mission (2010/11), are used to describe the ion altitude distribution at Mars. The focus of this study is below the altitude of ~1000 km. Within the Mars environment, using the MEX electron observations different plasma regions was identified. Supported by electron identification, different altitude profiles of ion fluxes have been analyzed from the different plasma regions. One of the results from this study is that the altitude profile of the ion flux observed below the photoelectron boundary is different when comparing the northern and the southern hemispheres. The ion distributions, resulting altitude profile, the influence of the crustal magnetic field at Mars, and the implications relating to plasma outflow will be discussed in this presentation.

  20. Dust devils as observed by Mars Pathfinder

    NASA Astrophysics Data System (ADS)

    Ferri, Francesca; Smith, Peter H.; Lemmon, Mark; Rennó, Nilton O.

    2003-12-01

    Dust devils are localized meteorological phenomena frequently observed in terrestrial dry lands and desert landscapes as well as on Mars. They are low-pressure, warm core vortices that form at the bottom of convective plumes and loft dust from the surface. They move with the speed of the ambient wind and are tilted by wind shears. The Mars Pathfinder detected dust devils as dust plumes in the Imager for Mars Pathfinder images and as low-pressure convective vortices in the meteorological Mars Pathfinder Atmospheric Structure Investigation/Meteorology (ASI/MET) experiment data. The Pathfinder data have been analyzed in terms of dust devil size, spatial distribution, and frequency of occurrence. The results show that the Pathfinder imaging and MET observations are consistent with each other and with the observations made by the Viking 1 Orbiter and Mars Global Surveyor. The dust devil's ability to loft dust into the atmosphere has been investigated and a thermodynamic theory for dust devils has been used to calculate their physical parameters relevant to dust transport. The dust devils observed in an active day provide a pumping rate larger than the dust-settling rate derived from the optical obscuration of the Pathfinder rover solar panels. Therefore dust devils are a major factor in transporting dust from the surface to the atmosphere at the Pathfinder site.

  1. Radiation Environment at Mars and Earth

    NASA Technical Reports Server (NTRS)

    2003-01-01

    December 8, 2003

    This graphic shows the radiation dose equivalent as measured by Odyssey's martian radiation environment experiment at Mars and by instruments aboard the Earth-orbiting International Space Station (ISS), for the 18-month period from April 2002 through October 2003. The accumulated total in Mars orbit is just over two times larger than that aboard the Space Station. The bars where the Mars instrument's measurements are well above the average (as shown by the orange line) are months when there was significant solar activity, which increases the dose equivalent. Dose equivalent is expressed in units of milliSieverts per day.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington. The radiation experiment was provided by the Johnson Space Center, Houston, Texas. Lockheed Martin Space Systems, Denver, Colo., is the prime contractor for the project, 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.

  2. 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.

  3. 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.

  4. Selenium accumulation by plants

    PubMed Central

    White, Philip J.

    2016-01-01

    Background Selenium (Se) is an essential mineral element for animals and humans, which they acquire largely from plants. The Se concentration in edible plants is determined by the Se phytoavailability in soils. Selenium is not an essential element for plants, but excessive Se can be toxic. Thus, soil Se phytoavailability determines the ecology of plants. Most plants cannot grow on seleniferous soils. Most plants that grow on seleniferous soils accumulate <100 mg Se kg–1 dry matter and cannot tolerate greater tissue Se concentrations. However, some plant species have evolved tolerance to Se, and commonly accumulate tissue Se concentrations >100 mg Se kg–1 dry matter. These plants are considered to be Se accumulators. Some species can even accumulate Se concentrations of 1000–15 000 mg Se kg–1 dry matter and are called Se hyperaccumulators. Scope This article provides an overview of Se uptake, translocation and metabolism in plants and highlights the possible genetic basis of differences in these between and within plant species. The review focuses initially on adaptations allowing plants to tolerate large Se concentrations in their tissues and the evolutionary origin of species that hyperaccumulate Se. It then describes the variation in tissue Se concentrations between and within angiosperm species and identifies genes encoding enzymes limiting the rates of incorporation of Se into organic compounds and chromosomal loci that might enable the development of crops with greater Se concentrations in their edible portions. Finally, it discusses transgenic approaches enabling plants to tolerate greater Se concentrations in the rhizosphere and in their tissues. Conclusions The trait of Se hyperaccumulation has evolved several times in separate angiosperm clades. The ability to tolerate large tissue Se concentrations is primarily related to the ability to divert Se away from the accumulation of selenocysteine and selenomethionine, which might be incorporated

  5. 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 ...

  6. Bringing Life to Mars

    NASA Technical Reports Server (NTRS)

    McKay, C. P.

    1999-01-01

    A suitable long-term goal for human exploration of Mars is the determination of whether or not a self-sustainable bio-sphere could be constructed on Mars, a process called Terraforming. Preliminary considerations of the conditions on a habitable Mars suggest that there are two potentially habitable states: one -characterized by an atmosphere of 1-3 bars of CO2 - would be habitable for plants and microorganisms and another which would be habitable by humans. It may be possible to warm the planet by selective introduction of trace gases to enhance the greenhouse effect. Energy balance considerations suggest that warming Mars would take on the order of 100 years with a much longer time required to produce a breathable atmosphere.

  7. 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.

  8. 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.

  9. 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...

  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. Interactive Science on Mars

    NASA Astrophysics Data System (ADS)

    Mercer, C. R.; Landis, G. A.

    2017-02-01

    Swarms of small citizen-driven rovers can conduct Mars surface science missions. Transportation and communication technology needed for human exploration can enable this new interactive science mission architecture.

  12. 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...

  13. 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

  14. Mars Analytical Laboratory

    NASA Astrophysics Data System (ADS)

    Nagati, M. Gawad; Ale-Ibrahaim, Kordi; Bins, Llonda; Davis, Michael; Gamalo, Johnny; Johnson, Matt; May, Neal; Seneviratne, Waruna; Yurko, Aric; Yurko, Brenda

    1998-01-01

    As mankind continues to explore the solar system, planetary colonization may become an important goal. Permanently manned space stations, bases on the moon, and colonization of Mars will be important steps in this exploration. The colonization and exploration of Mars will be a particular challenge. As mankind one day attempts this colonization, knowledge of the Martian environment and human capacity to live there will become vitally important. The first scientific outposts on Mars will need research laboratories to make discoveries about how we can better live there and use the natural resources of the planet to sustain human life. The design of a laboratory for an existing Martian base is the purpose of this project. A laboratory on Mars would be very useful to the scientists we send.

  15. 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.

  16. 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...

  17. Airbag Deflates on Mars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image, taken by the navigation camera onboard the Mars Exploration Rover Spirit, shows the airbags used to protect the rover during landing. One bright, dust-covered bag is slightly puffed up against the lander.

  18. 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

  19. Mars exploration program

    NASA Technical Reports Server (NTRS)

    Weary, Dwayne

    1993-01-01

    An overview of the Mars Exploration Program is presented in outline and graphic form. Mission objectives, mission strategy, operations concept, transportation element, launch vehicle considerations and program schedule are addressed.

  20. Water on Mars

    USGS Publications Warehouse

    Carr, M.H.

    1987-01-01

    Estimates of the amount of water outgassed from Mars, based on the composition of the atmosphere, range from 6 to 160 m, as compared with 3 km for the Earth. In contrast, large flood features, valley networks, and several indicators of ground ice suggest that at least 500 m of water have outgassed. The two sets of estimates may be reconciled if early in its history, Mars lost part of its atmosphere by impact erosion and hydrodynamic escape. ?? 1987 Nature Publishing Group.

  1. 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.

  2. 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.

  3. Mars Gravity Anomoly Map

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This is a vertical gravity map of Mars color-coded in mgals based on radio tracking. Note correlations and lack of correlations with the Mars Orbiter Laser Altimeter (MOLA) global topography.

    This map was created using MGS data under the direction of Bill Sjogren, a member of the MGS Radio Science Team. The Radio Science Team is led by G. Leonard Tyler of Stanford University in Palo Alto, CA.

  4. 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.

  5. 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.

  6. 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.

  7. Clouds over Mars!

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This is the first color image ever taken from the surface of Mars of an overcast sky. Featured are pink stratus clouds coming from the northeast at about 15 miles per hour (6.7 meters/second) at an approximate height of ten miles (16 kilometers) above the surface. The clouds consist of water ice condensed on reddish dust particles suspended in the atmosphere. Clouds on Mars are sometimes localized and can sometimes cover entire regions, but have not yet been observed to cover the entire planet. The image was taken about an hour and forty minutes before sunrise by the Imager for Mars Pathfinder (IMP) on Sol 16 at about ten degrees up from the eastern Martian horizon.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages and Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  8. 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.

  9. 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.

  10. Modern myths of Mars

    NASA Astrophysics Data System (ADS)

    Levin, Gilbert V.

    2006-08-01

    July 30, 2006 was the 30 th anniversary of the Viking Mission's first Labeled Release (LR) life detection experiment on Mars. The strong response, together with supporting results from eight additional LR tests of Martian soil, established the presence of an active agent that was inhibited by heating. The data satisfied the pre-mission criteria for the detection of living microorganisms. However, the scientific community reacted cautiously, generally concluding that the activity in the soil was caused by chemistry or physics. Over the last three decades, investigation of Mars has greatly increased. Soil, rock and atmospheric analyses have been made. Multi-spectral observations have been made from Mars and Earth orbits and from Earth-based telescopes. Knowledge of extreme habitats and bizarre life forms that populate them on Earth has increased dramatically. However, this vast amount of new astrobiological information has yet to be integrated into an objective scientific evaluation of the LR results and the possibilities for life on Mars. Indeed, in part upon misinterpretations of the new findings, myths have been embedded into the scientific literature of Mars. Based on these myths as key ingredients, a false "standard model" of Martian life potential has been developed. It has been accepted by much of the astrobiological community, and, through its endorsement, the world at large. This paper attempts to bring the supportable facts together in calling for a revision of the current consensus regarding life on Mars. It recommends actions to facilitate the paradigm change.

  11. Paleolakes on Mars.

    PubMed

    Wharton, R A; Crosby, J M; McKay, C P; Rice, J W

    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.

  12. 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.

  13. Transportation: Destination Mars

    NASA Astrophysics Data System (ADS)

    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.

  14. Sexual selection and maintenance of sex: evidence from comparisons of rates of genomic accumulation of mutations and divergence of sex-related genes in sexual and hermaphroditic species of Caenorhabditis.

    PubMed

    Artieri, Carlo G; Haerty, Wilfried; Gupta, Bhagwati P; Singh, Rama S

    2008-05-01

    Several hypotheses have been proposed to explain the persistence of dioecy despite the reproductive advantages conferred to hermaphrodites, including greater efficiency at purging deleterious mutations in the former. Dioecy can benefit from both mutation purging and accelerated evolution by bringing together beneficial mutations in the same individual via recombination and shuffling of genotypes. In addition, mathematical treatment has shown that sexual selection is also capable of mitigating the cost of maintaining separate sexes by increasing the overall fitness of sexual populations, and genomic comparisons have shown that sexual selection can lead to accelerated evolution. Here, we examine the advantages of dioecy versus hermaphroditism by comparing the rate of evolution in sex-related genes and the rate of accumulation of deleterious mutations using a large number of orthologs (11,493) in the dioecious Caenorhabditis remanei and the hermaphroditic Caenorhabditis briggsae. We have used this data set to estimate the deleterious mutation rate per generation, U, in both species and find that although it is significantly higher in hermaphrodites, both species are at least 2 orders of magnitude lower than the value required to explain the persistence of sex by efficiency at purging deleterious mutations alone. We also find that genes expressed in sperm are evolving rapidly in both species; however, they show a greater increase in their rate of evolution relative to genes expressed in other tissues in C. remanei, suggesting stronger sexual selection pressure acting on these genes in dioecious species. Interestingly, the persistence of a signal of rapid evolution of sperm genes in C. briggsae suggests a recent evolutionary origin of hermaphrodism in this lineage. Our results provide empirical evidence of increased sexual selection pressure in dioecious animals, supporting the possibility that sexual selection may play an important role in the maintenance of sexual

  15. 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

  16. Dust deposition on the Mars Exploration Rover Panoramic Camera (Pancam) calibration targets

    USGS Publications Warehouse

    Kinch, K.M.; Sohl-Dickstein, J.; Bell, J.F.; 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.

  17. Real Time Mars Approach Navigation Aided by the Mars Network

    NASA Technical Reports Server (NTRS)

    Ely, Todd A.; Duncan, Courtney; Lightsey, E. Glenn; Mogensen, Andreas

    2006-01-01

    A NASA Mars technology project is described that is building a prototype embedded real time Mars approach navigation capability which can be hosted on the Mars Network's Electra transceiver. The paper motivates the reason for doing real time Mars approach navigation via a set of analyses demonstrating its utility for enabling Mars pin-point landing (less than 1-km landing error). The development approach, software design, and test results are discussed. Finally, the way forward towards a flight demonstration on the Mars Science Laboratory (MSL) is presented.

  18. Real Time Mars Approach Navigation Aided by the Mars Network

    NASA Technical Reports Server (NTRS)

    Ely, Todd A.; Duncan, Courtney; Lightsey, E. Glenn; Mogensen, Andreas

    2006-01-01

    A NASA Mars technology project is described that is building a prototype embedded real time Mars approach navigation capability which can be hosted on the Mars Network's Electra transceiver. The paper motivates the reason for doing real time Mars approach navigation via a set of analyses demonstrating its utility for enabling Mars pin-point landing (< 1-km landing error). The development approach, software design, and test results are discussed. Finally, the way forward towards a flight demonstration on the Mars Science Laboratory is presented.

  19. Mars at Ls 357o

    NASA Technical Reports Server (NTRS)

    2006-01-01

    31 January 2006 This picture is a composite of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) daily global images acquired at Ls 357o during a previous Mars year. This month, Mars looks similar, as Ls 357o occurred in mid-January 2006. The picture shows the south polar region of Mars. Over the course of the month, additional faces of Mars as it appears at this time of year are being posted for MOC Picture of the Day. Ls, solar longitude, is a measure of the time of year on Mars. Mars travels 360o around the Sun in 1 Mars year. The year begins at Ls 0o, the start of northern spring and southern autumn.

    Season: Northern Winter/Southern Summer

  20. Mars at Ls 324o

    NASA Technical Reports Server (NTRS)

    2005-01-01

    29 November 2005 This picture is a composite of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) daily global images acquired at Ls 324o during a previous Mars year. This month, Mars looks similar, as Ls 324o occurred in mid-November 2005. The picture shows the south polar region of Mars. Over the course of the month, additional faces of Mars as it appears at this time of year are being posted for MOC Picture of the Day. Ls, solar longitude, is a measure of the time of year on Mars. Mars travels 360o around the Sun in 1 Mars year. The year begins at Ls 0o, the start of northern spring and southern autumn.

    Season: Northern Winter/Southern Summer

  1. 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.

  2. 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 archi