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Sample records for early terrestrial atmosphere

  1. Fractionation of the Early Terrestrial Atmospheres: Dynamical Escape

    NASA Technical Reports Server (NTRS)

    Hartle, Richard E.

    2002-01-01

    Hydrodynamic escape may have played a significant role in the early fractionation of the atmospheres of the terrestrial planets. This possibility has been demonstrated in the last two decades by numerous models that show radial, transonic flow of hydrogen can occur in the presence of sufficient solar EUV Hydrodynamic escape may have played a significant role in the early fractionation of the atmospheres of the terrestrial planets. This possibility has been demonstrated in the last two decades by numerous models that show radial, transonic flow of hydrogen can occur in the presence of sufficient solar EUV flux, thought to exist in the first 500 My. The models show that the larger the solar flux the greater the mass of the fractionating species, which are accelerated to escape speeds by the hydrogen wind through drag processes. As the atmospheres evolve and the solar EUV flux wanes, the maximum mass of flowing gas constituents decreases until all gases become static. We show that fractionation can continue beyond this point when non-radial flow and dynamically enhanced Jeans escape are considered. For example, the early terrestrial atmospheres are thought to have had large hydrogen contents, resulting in exobase altitudes of a planetary radius or more. In this case, rotational speeds at the exobases of Earth and Mars would be large enough so that light constituents would "spin" off and fractionate, especially at equatorial latitudes. Also, in the presence of transonic flow of hydrogen only, non-radial expansion throws heavier gases to high altitudes in the exosphere, accompanied by strong bulk speeds at the exobase, which results in enhanced thermal escape fluxes and fractionation. flux, thought to exist in the first 500 My. The models show that the larger the solar flux the greater the mass of the fractionating species, which are accelerated to escape speeds by the hydrogen wind through drag processes. As the atmospheres evolve and the solar EUV flux wanes, the

  2. Wind and Rotation Enhanced Escape from the Early Terrestrial Atmospheres

    NASA Technical Reports Server (NTRS)

    Hartle, Richard E.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    The earliest atmospheres of the terrestrial planets are thought to have been hotter, have stronger winds and rotate faster than atmospheres of today. Since these primitive atmospheres were weakly bound, they evolved rapidly because atmospheric escape was very strong, often referred to as "blowoff." Such escape has been treated as hydrodynamic, transonic flow; similar to solar wind flow dynamics. However, in many cases, although the outward flow is hydrodynamic at low altitudes, it becomes collisionless at higher altitudes, before sonic speeds are ever attained. Recent models dealing with the transition from fluid to kinetic flow have applied the Jeans escape flux at the exobase. This approach leads to escape rates that are too low, because thermospheric winds and planetary rotation are known to increase the escape flux above the corresponding Jeans flux. In particular, for a given density and temperature at the exobase, the escape flux increases as the wind speed and/or the rotation rate increase. Also, for a given wind speed and rotation rate, the escape flux enhancement over the Jeans flux increases as the mass of an escaping constituent increases, an important factor in isotope fractionation, especially the enrichment of deuterium on Mars. Accounting for a range of possible temperatures, thermospheric wind speeds and planetary rotation rates in the primitive atmospheres of the terrestrial planets, estimates are made of light constituent escape flux increases over the corresponding Jeans fluxes.

  3. Wind and Rotation Enhanced Escape From the Early Terrestrial Atmospheres

    NASA Astrophysics Data System (ADS)

    Hartle, R. E.

    2001-05-01

    The earliest atmospheres of the terrestrial planets are thought to have been hotter, have stronger winds and rotate faster than atmospheres of today. Since these primitive atmospheres were weakly bound, they evolved rapidly because atmospheric escape was very strong, often referred to as "blowoff." Such escape has been treated as hydrodynamic, transonic flow, similar to solar wind flow dynamics. However, in many cases the outward flow is hydrodynamic at low altitudes only to become collisionless at higher altitudes, well before sonic speeds are ever attained. Recent models dealing with such transition from fluid to kinetic flow have applied the Jeans escape flux at the exobase. This approach has lead to escape rates that are too low due to the fact that thermospheric winds and planetary rotation increase escape fluxes considerably over the corresponding Jeans fluxes (1). In particular, for a given density and temperature at the exobase, the escape flux increases as the wind speed and/or the rotation rate increase. Also, for a given wind speed and rotation rate, the escape flux enhancement over the Jeans flux increases as the mass of an escaping constituent increases, an important factor in isotope fractionation, especially the enrichment of deuterium on Mars. Accounting for a range of possible temperatures, thermospheric wind speeds and planetary rotation rates in the primitive atmospheres of the terrestrial planets, estimates are made of light constituent escape flux increases over the corresponding Jeans fluxes. (1) Hartle, R. E. and H. G. Mayr, J. Geophys. Res., 81, 1207, 1976.

  4. The persistent and pernicious myth of the early CO2-N2 atmospheres of terrestrial planets

    NASA Astrophysics Data System (ADS)

    Shaw, G. H.

    2009-12-01

    The accepted model for early atmospheres of terrestrial planets has settled on a CO2-N2 composition. Unfortunately, while it is largely based on a brilliant geological analysis by Rubey, there is no compelling evidence whatsoever for such a composition as the first “permanent” atmosphere for Earth or any other planet. In fact, geological discoveries of the past 50+ years reveal several problems with a CO2-N2 atmosphere, some of which Rubey recognized in his own analysis. He clearly addressed the problem of timing of degassing, concluding that early massive degassing of CO2 would produce readily observed and profound effects, which are not evident. Modeling and constraints on the timing of planetary accretion and core formation indicate massive early degassing. If early degassing emitted CO2-N2, the effects are concealed. Plate tectonic recycling is not a solution, as conditions would have persisted beyond the time of the earliest rocks, which do not show the effects. Attempts to return degassed CO2 to the mantle are not only ad hoc, but inconsistent with early thermal structure of the Earth. Second, production of prebiotic organic compounds from a CO2-N2 atmosphere has been a nagging problem. At best this has been addressed by invoking hydrogen production from the mantle to provide reducing capacity. While hydrogen may be emitted in volcanic eruptions, it is exceedingly difficult to imagine this process generating enough organics to yield high concentrations in a global ocean. The recent fashion of invoking organic synthesis at deep-sea vents suffers from the same problem: how to achieve sufficient concentrations of organics in a global ocean by abiotic synthesis when hydrothermal activity stirs the solution and carries the prebiotic products off to great dilution? Suggesting life began at deep-sea vents, and continues to carry on chemosynthesis there, begs the question. Unless you get high enough concentrations of prebiotics by abiotic processes, you simply

  5. On the relationship between early solar activity and the evolution of terrestrial planet atmospheres

    NASA Technical Reports Server (NTRS)

    Repin, Robert O.

    1989-01-01

    Mass fractionation during hydrodynamic escape of hydrogen-rich primordial atmospheres form Venus, earth, and Mars can account for most of the salient features of mass distributions in their present-day atmospheres. The principal assumptions and results of an escape-fractionation model for the evolution of terrestrial planet atmospheres from primary to final states are qualitatively described, with emphasis on the astrophysical conditions needed to enable the loss process. A substantial and rapidly declining flux of energetic solar radiation into atmospheric exospheres is required, initially (at solar ages of about 1-10 million years) two to three orders of magnitude more intense than that supplied by extreme-ultraviolet emission from the contemporary sun. The solar accretion disk must have dissipated if such radiation is to penetrate the system midplane to planetray distances. On both criteria, hydrodynamic escape from planets appears plausible in the astrophysical environment of the naked T-Tauri stars.

  6. The Atmospheres of the Terrestrial Planets:Clues to the Origins and Early Evolution of Venus, Earth, and Mars

    NASA Technical Reports Server (NTRS)

    Baines, Kevin H.; Atreya, Sushil K.; Bullock, Mark A.; Grinspoon, David H,; Mahaffy, Paul; Russell, Christopher T.; Schubert, Gerald; Zahnle, Kevin

    2015-01-01

    We review the current state of knowledge of the origin and early evolution of the three largest terrestrial planets - Venus, Earth, and Mars - setting the stage for the chapters on comparative climatological processes to follow. We summarize current models of planetary formation, as revealed by studies of solid materials from Earth and meteorites from Mars. For Venus, we emphasize the known differences and similarities in planetary bulk properties and composition with Earth and Mars, focusing on key properties indicative of planetary formation and early evolution, particularly of the atmospheres of all three planets. We review the need for future in situ measurements for improving our understanding of the origin and evolution of the atmospheres of our planetary neighbors and Earth, and suggest the accuracies required of such new in situ data. Finally, we discuss the role new measurements of Mars and Venus have in understanding the state and evolution of planets found in the habitable zones of other stars.

  7. Synthetic spectra of simulated terrestrial atmospheres containing possible biomarker gases

    NASA Technical Reports Server (NTRS)

    Schindler, T. L.; Kasting, J. F.

    2000-01-01

    NASA's proposed Terrestrial Planet Finder, a space-based interferometer, will eventually allow spectroscopic analyses of the atmospheres of extrasolar planets. Such analyses would provide information about the existence of life on these planets. One strategy in the search for life is to look for evidence of O3 (and hence O2) in a planet's atmosphere; another is to look for gases that might be present in an atmosphere analogous to that of the inhabited early Earth. In order to investigate these possibilities, we have calculated synthetic spectra for several hypothetical terrestrial-type atmospheres. The model atmospheres represent four different scenarios. The first two, representing inhabited terrestrial planets, are an Earth-like atmosphere containing variable amounts of oxygen and an early Earth-type atmosphere containing methane. In addition, two cases representing Mars-like and early Venus-like atmospheres were evaluated, to provide possible "false positive" spectra. The calculated spectra suggest that ozone could be detected by an instrument like Terrestrial Planet Finder if the O2 concentration in the planet's atmosphere is > or = 200 ppm, or 10(-3) times the present atmospheric level. Methane should be observable on an early-Earth type planet if it is present in concentrations of 100 ppm or more. Methane has both biogenic and abiogenic sources, but concentrations exceeding 1000 ppm, or 0.1% by volume, would be difficult to produce from abiogenic sources alone. High methane concentrations in a planet's atmosphere are therefore another potential indicator for extraterrestrial life.

  8. Fair weather terrestrial atmospheric electricity

    NASA Astrophysics Data System (ADS)

    Harrison, G.

    Atmospheric electricity is one of the oldest experimental topics in atmospheric science. The fair weather aspects, although having less dramatic effects than thunderstorm electrification, link the microscale behaviour of ion clusters to currents flowing on the global scale. This talk will include a survey of some past measurements and measurement methods, as atmospheric electrical data from a variety of sites and eras are now being used to understand changes in atmospheric composition. Potential Gradient data was the original source of information on the global atmospheric electrical circuit, and similar measurements can now be used to reconstruct past air pollution concentrations, and black carbon loading.

  9. Impact erosion of terrestrial planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Ahrens, Thomas J.

    1992-01-01

    I review current ideas about the nature of the planetesimals - composition, size distribution, and the planetary encounter velocity. Previous papers on accretion and erosion of planetary atmospheres as a result of multiple impacts are reviewed. Finally, the effects of blowing off a substantial fraction of the atmosphere from a terrestrial planet due to a single giant body impact are discussed.

  10. Nucleosynthesis in the terrestrial and solar atmospheres

    NASA Technical Reports Server (NTRS)

    Yu, C.; Zhou, R.; Zhan, S.

    1985-01-01

    Variations of Delta D, delta C-13, Delta C-14 and Delta O-18 with time were measured by a lot of experiments. Many abnormalities of isotope abundances in cosmic rays were found by balloons and satellites. It is suggested that these abnormalities are related to nuclearsynthesis in the terrestrial and solar atmospheres and are closely related to solar activities.

  11. Linkages between terrestrial ecosystems and the atmosphere

    NASA Technical Reports Server (NTRS)

    Bretherton, Francis; Dickinson, Robert E.; Fung, Inez; Moore, Berrien, III; Prather, Michael; Running, Steven W.; Tiessen, Holm

    1992-01-01

    The primary research issue in understanding the role of terrestrial ecosystems in global change is analyzing the coupling between processes with vastly differing rates of change, from photosynthesis to community change. Representing this coupling in models is the central challenge to modeling the terrestrial biosphere as part of the earth system. Terrestrial ecosystems participate in climate and in the biogeochemical cycles on several temporal scales. Some of the carbon fixed by photosynthesis is incorporated into plant tissue and is delayed from returning to the atmosphere until it is oxidized by decomposition or fire. This slower (i.e., days to months) carbon loop through the terrestrial component of the carbon cycle, which is matched by cycles of nutrients required by plants and decomposers, affects the increasing trend in atmospheric CO2 concentration and imposes a seasonal cycle on that trend. Moreover, this cycle includes key controls over biogenic trace gas production. The structure of terrestrial ecosystems, which responds on even longer time scales (annual to century), is the integrated response to the biogeochemical and environmental constraints that develop over the intermediate time scale. The loop is closed back to the climate system since it is the structure of ecosystems, including species composition, that sets the terrestrial boundary condition in the climate system through modification of surface roughness, albedo, and, to a great extent, latent heat exchange. These separate temporal scales contain explicit feedback loops which may modify ecosystem dynamics and linkages between ecosystems and the atmosphere. The long-term change in climate, resulting from increased atmospheric concentrations of greenhouse gases (e.g., CO2, CH4, and nitrous oxide (N2O)) will further modify the global environment and potentially induce further ecosystem change. Modeling these interactions requires coupling successional models to biogeochemical models to

  12. Solar-terrestrial relationships in atmospheric electricity

    SciTech Connect

    Roble, R.G.

    1985-06-30

    There are many suggested solar-terrestrial relationships in global atmospheric electricity. Of the various relationships, the downward mapping of ionospheric and magnetospheric electric fields, associated with the solar wind/magnetosphere and the ionosphere wind dynamos, is best understood theoretically and appears to be supported by the few available data. The solar cycle variations of ionospheric potential and air-earth current appear to be related to variations in galactic cosmic rays and perhaps to their effect on the current output from thunderstorms. The solar flare and solar magnetic sector boundary variations are not well understood but may be related to Forbush decreases in cosmic ray flux and/or effects resulting from energetic particle precipitation. The available data on auroral effects on atmospheric electricity are confusing and not understood at all. There is a clear need for further research to better define the physical mechanisms responsible for all of these solar-terrestrial relationships. The observed solar-terrestrial variations and the need for current closure in the global circuit suggest that the function of the equalization layer in the ''classical picture'' of atmospheric electricity should be revised to be consistent with our current knowledge of upper-atmospheric electrical processes.

  13. Early Formation of Terrestrial Crust

    NASA Astrophysics Data System (ADS)

    Harrison, T. M.; Schmitt, A. K.; McCulloch, M. T.; Lovera, O. M.

    2007-12-01

    Early (≥4.5 Ga) Formation of Terrestrial Crust T.M. Harrison1, A.K. Schmitt1, M.T. McCulloch2, and O.M. Lovera1 1Department of Earth and Space Sciences and IGPP, UCLA, Los Angeles, CA 90095, USA; 2Research School of Earth Sciences, Australian National University, Canberra, A.C.T. 2601 AUSTRALIA Large deviations in ǎrepsilonHf(T) from bulk silicate Earth seen in >4 Ga detrital zircons from Jack Hills, Western Australia, have been interpreted as reflecting a major differentiation of the silicate Earth at ca. 4.4 to 4.5 Ga. We have expanded the characterization of 176Hf/177Hf (Hf) in Hadean zircons by acquiring a further 116 laser ablation Lu-Hf measurements on 87 grains with ion microprobe 207Pb/206Pb ages up to 4.36 Ga. Most measurements employed concurrent Lu-Hf and 207Pb/206Pb analyses, permitting assessment of the use of ion microprobe data to characterize the age of the volumetrically larger domain sampled by laser drilling. Our new results confirm and extend the earlier observation of significant negative deviations in ǎrepsilonHf(T) throughout the Hadean, although no positive ǎrepsilonHf(T) values were documented in this study. These data yields an essentially uniform spectrum of single-stage model ages between 4.54 and 4.20 Ga for extraction of the zircons' protoliths from a chondritic reservoir. We derived the full error propagation expression for a parameter, ǎrepsilono, which measures the difference of a sample from solar system initial (Hf) (Hfo), and from this conclude that data plotting close to (Hfo), are statistically meaningful and consistent with silicate differentiation at 4.540±0.006 Ga. δ18O and Ti thermometry for these Hadean zircons show little obvious correlation with initial (Hf), consistent with their derivation through fusion of a broad suite of crustal rock types under near water-saturated conditions. Together with the inclusion assemblage and other isotopic and trace element data obtained from these ancient zircons, our results

  14. Solar-terrestrial coupling through atmospheric electricity

    NASA Technical Reports Server (NTRS)

    Roble, R. G.; Hays, P. B.

    1979-01-01

    There are a number of measurements of electrical variations that suggest a solar-terrestrial influence on the global atmospheric electrical circuit. The measurements show variations associated with solar flares, solar magnetic sector boundary crossings, geomagnetic activity, aurorae, differences between ground current and potential gradients at high and low latitudes, and solar cycle variations. The evidence for each variation is examined. Both the experimental evidence and the calculations made with a global model of atmospheric electricity indicate that there is solar-terrestrial coupling through atmospheric electricity which operates by altering the global electric current and field distribution. A global redistribution of currents and fields can be caused by large-scale changes in electrical conductivity, by alteration of the columnar resistance between thunderstorm cloud tops and the ionosphere, or by both. If the columnar resistance is altered above thunderstorms, more current will flow in the global circuit, changing the ionospheric potential and basic circuit variables such as current density and electric fields. The observed variations of currents and fields during solar-induced disturbances are generally less than 50% of mean values near the earth's surface.

  15. Atmospheric evolution of the terrestrial planets

    NASA Astrophysics Data System (ADS)

    Hunten, D. M.

    1993-02-01

    The major atmospheric gases on Earth, Venus, and Mars were probably CO2, H2O, and N2. Most of the Earth's CO2 is tied up in minerals such as limestone, and Venus has lost most of its H2O, leaving the CO2 in the atmosphere. Much of Mars' atmosphere may have been eroded in impacts by large meteoroids early in solar-system history. Noble gases are very underabundant everywhere, and must have been lost during an early period: they were probably dragged along during rapid loss of massive amounts of hydrogen. The tenuous atmospheres of Mercury and the moon have lifetimes of a few days or less and must be continuously replenished from internal or external sources.

  16. Were early pterosaurs inept terrestrial locomotors?

    PubMed Central

    2015-01-01

    Pterodactyloid pterosaurs are widely interpreted as terrestrially competent, erect-limbed quadrupeds, but the terrestrial capabilities of non-pterodactyloids are largely thought to have been poor. This is commonly justified by the absence of a non-pterodactyloid footprint record, suggestions that the expansive uropatagia common to early pterosaurs would restrict hindlimb motion in walking or running, and the presence of sprawling forelimbs in some species. Here, these arguments are re-visited and mostly found problematic. Restriction of limb mobility is not a problem faced by extant animals with extensive fight membranes, including species which routinely utilise terrestrial locomotion. The absence of non-pterodactyloid footprints is not necessarily tied to functional or biomechanical constraints. As with other fully terrestrial clades with poor ichnological records, biases in behaviour, preservation, sampling and interpretation likely contribute to the deficit of early pterosaur ichnites. Suggestions that non-pterodactyloids have slender, mechanically weak limbs are demonstrably countered by the proportionally long and robust limbs of many Triassic and Jurassic species. Novel assessments of pterosaur forelimb anatomies conflict with notions that all non-pterodactyloids were obligated to sprawling forelimb postures. Sprawling forelimbs seem appropriate for species with ventrally-restricted glenoid articulations (seemingly occurring in rhamphorhynchines and campylognathoidids). However, some early pterosaurs, such as Dimorphodon macronyx and wukongopterids, have glenoid arthrologies which are not ventrally restricted, and their distal humeri resemble those of pterodactyloids. It seems fully erect forelimb stances were possible in these pterosaurs, and may be probable given proposed correlation between pterodactyloid-like distal humeral morphology and forces incurred through erect forelimb postures. Further indications of terrestrial habits include antungual

  17. Sulfuric acid aerosols in the atmospheres of the terrestrial planets

    NASA Astrophysics Data System (ADS)

    McGouldrick, Kevin; Toon, Owen B.; Grinspoon, David H.

    2011-08-01

    Clouds and hazes composed of sulfuric acid are observed to exist or postulated to have once existed on each of the terrestrial planets with atmospheres in our solar system. Venus today maintains a global cover of clouds composed of a sulfuric acid/water solution that extends in altitude from roughly 50 km to roughly 80 km. Terrestrial polar stratospheric clouds (PSCs) form on stratospheric sulfuric acid aerosols, and both PSCs and stratospheric aerosols play a critical role in the formation of the ozone hole. Stratospheric aerosols can modify the climate when they are enhanced following volcanic eruptions, and are a current focus for geoengineering studies. Rain is made more acidic by sulfuric acid originating from sulfur dioxide generated by industry on Earth. Analysis of the sulfur content of Martian rocks has led to the hypothesis that an early Martian atmosphere, rich in SO 2 and H 2O, could support a sulfur-infused hydrological cycle. Here we consider the plausibility of frozen sulfuric acid in the upper clouds of Venus, which could lead to lightning generation, with implications for observations by the European Space Agency's Venus Express and the Japan Aerospace Exploration Agency's Venus Climate Orbiter (also known as Akatsuki). We also present simulations of a sulfur-rich early Martian atmosphere. We find that about 40 cm/yr of precipitation having a pH of about 2.0 could fall in an early Martian atmosphere, assuming a surface temperature of 273 K, and SO 2 generation rates consistent with the formation of Tharsis. This modeled acid rain is a powerful sink for SO 2, quickly removing it and preventing it from having a significant greenhouse effect.

  18. Ions in the Terrestrial Atmosphere and Other Solar System Atmospheres

    NASA Astrophysics Data System (ADS)

    Harrison, R. Giles; Tammet, Hannes

    Charged molecular clusters, traditionally called small ions, carry electric currents in atmospheres. Charged airborne particles, or aerosol ions, play an important role in generation and evolution of atmospheric aerosols. Growth of ions depends on the trace gas content, which is highly variable in the time and space. Even at sub-ppb concentrations, electrically active organic compounds (e.g. pyridine derivatives) can affect the ion composition and size. The size and mobility are closely related, although the form of the relationship varies depending on the critical diameter, which, at 273 K, is about 1.6 nm. For ions smaller than this the separation of quantum levels exceeds the average thermal energy, allowing use of a molecular aggregate model for the size-mobility relation. For larger ions the size-mobility relation approaches the Stokes-Cunningham-Millikan law. The lifetime of a cluster ion in the terrestrial lower atmosphere is about one minute, determined by the balance between ion production rate, ion-ion recombination, and ion-aerosol attachment.

  19. Ions in the Terrestrial Atmosphere and Other Solar System Atmospheres

    NASA Astrophysics Data System (ADS)

    Harrison, R. Giles; Tammet, Hannes

    2008-06-01

    Charged molecular clusters, traditionally called small ions, carry electric currents in atmospheres. Charged airborne particles, or aerosol ions, play an important role in generation and evolution of atmospheric aerosols. Growth of ions depends on the trace gas content, which is highly variable in the time and space. Even at sub-ppb concentrations, electrically active organic compounds ( e.g. pyridine derivatives) can affect the ion composition and size. The size and mobility are closely related, although the form of the relationship varies depending on the critical diameter, which, at 273 K, is about 1.6 nm. For ions smaller than this the separation of quantum levels exceeds the average thermal energy, allowing use of a molecular aggregate model for the size-mobility relation. For larger ions the size-mobility relation approaches the Stokes-Cunningham-Millikan law. The lifetime of a cluster ion in the terrestrial lower atmosphere is about one minute, determined by the balance between ion production rate, ion-ion recombination, and ion-aerosol attachment.

  20. Formation and Internal Structure of Terrestrial Planets, and Atmospheric Escape

    NASA Astrophysics Data System (ADS)

    Jin, S.

    2014-11-01

    As of 2014 April 21, over 1490 confirmed exoplanets and 3705 Kepler candidates have been detected. This implies that exoplanets may be ubiquitous in the universe. In this paper, we focus on the formation, evolution, and internal structure of terrestrial planets, and the atmospheric escape of close-in planets. In chapter 2, we investigate the dynamical evolution of planetary system after the protoplanetary disk has dissipated. We find that in the final assembly stage, the occurrence of terrestrial planets is quite common and in 40% of our simulations finally at least one planet is formed in the habitable zone. We also find that if there is a highly-inclined giant planet in the system, a great many bodies will be either driven out of the system, or collide with the giant planet or the central star. This will lead to the difficulty in planetary accretion. Moreover, our results show that planetary migration can lead to the formation of close-in planets. Besides migration, close-in terrestrial planets can also be formed by a collision-merger mechanism, which means that planetary embryos can kick terrestrial planets directly into orbits that are extremely close to their parent stars. In chapter 3, we construct numerically an internal structure model for terrestrial planets, and provide three kinds of possible internal structures of Europa (Jupiter's moon) based on this model. Then, we calculate the radii of low-mass exoplanets for various mass combinations of core and mantle, and find that some of them are inconsistent with the observed radius of rocky planets. This phenomenon can be explained only if there exists a large amount of water in the core, or they own gaseous envelopes. In chapter 4, we improve our planetary evolution codes using the semi-gray model of Guillot (2010), which includes the incident flux from the host star as a heating source in planetary atmosphere. The updated codes can solve the structure of the top radiative zone of intensely irradiated

  1. Synchronous negative carbon isotope shifts in marine and terrestrial biomarkers at the onset of the early Aptian oceanic anoxic event 1a: Evidence for the release of 13C-depleted carbon into the atmosphere

    NASA Astrophysics Data System (ADS)

    van Breugel, Yvonne; Schouten, Stefan; Tsikos, Harilaos; Erba, Elisabetta; Price, Gregory D.; Sinninghe Damsté, Jaap S.

    2007-03-01

    A common feature of records of the early Aptian oceanic anoxic event (OAE) 1a is the sharp negative δ13C excursion displayed in both carbonate and organic matter at the onset of this event. A synchronous negative δ13C excursion has also been noted for terrestrial organic matter. This negative excursion has been attributed to either an injection of 13C-depleted light carbon into the atmosphere or, in case of marine sediments, recycling of 13C-depleted CO2. However, most studies were done on separate cores, and no information on the relative timing of the negative spikes in terrestrial versus marine records has been obtained. Here we examine early Aptian core sections from two geographically distal sites (Italy and the mid-Pacific) to elucidate the causes and relative timing of this negative "spike." At both sites, increased organic carbon (Corg) and decreased bulk carbonate contents characterize the interval recording OAE 1a (variously referred to as the "Selli event"). The organic material within the "Selli level" is immature and of autochthonous origin. Measured δ13C values of marine and terrestrial biomarkers largely covary with those of bulk organic carbon, with lowest values recorded at the base of the organic-rich section. By contrast, sediments enveloping the "Selli level" exhibit very low Corg contents, and their extractable Corg is predominantly of allochthonous origin. Hydrous pyrolysis techniques used to obtain an autochthonous, pre-Selli δ13C value for algal-derived pristane from corresponding sample material yielded a negative δ13C shift of up to 4‰. A negative δ13C shift of similar magnitude was also measured for the terrigenous n-alkanes. The results are collectively best explained by means of a massive, syndepositional, rapid input of 13C-depleted carbon into the atmosphere and surface oceans, likely delivered either via methane produced from the dissociation of sedimentary clathrates or perhaps by widespread thermal metamorphism of Corg

  2. Rare earth element systematics of the chemically precipitated component in Early Precambrian iron formations and the evolution of the terrestrial atmosphere-hydrosphere-lithosphere system

    SciTech Connect

    Bau, M.; Moeller, P. )

    1993-05-01

    The chemically precipitated component in Early Precambrian (> 2.3 Ga) iron formations (IFs) displays (Sm/Yb)[sub CN] < 1 and (Eu/Sm)[sub SN] > 1 which reflects the corresponding ratios of contemporaneous seawater. In conjunction with [epsilon][sub Nd-IF] > [epsilon][sub Nd-shale] this rare earth element (REE) signature reveals that the REE distribution in Early Precambrian IFs must be explained by mixing between a marine bottom and a surface water component, and that the REEs (and by analogy the Fe) cannot be derived from weathering of a continental source. Mixing calculations reveal that (Sm/Yb)[sub CN] in Early Precambrian marine surface waters was significantly lower than it is today. To explain this difference, two mechanisms are discussed on the basis of higher P[sub CO[sub 2

  3. Chinguetti - terrestrial age and pre-atmospheric size

    SciTech Connect

    Welten, K C; Masarik, J; Bland, P A; Caffee, M W; Russell, S S; Grady, M M; Denyer, I; Lloyd, J

    2000-01-14

    Chinguetti is a 4.5 kg mesosiderite find recovered from the Adra region of Mauretania. In this paper the authors analyse a portion of the recovered sample for cosmogenic radionuclides to determine its terrestrial age, and to determine its pre-atmospheric radius. They determined the terrestrial age of Chinguetti to be < 30 ky. They constrain the pre-atmospheric radius to 50--80 cm and the shielding depths of 15--25 cm. These data indicate that Chinguetti is a comparatively recent fall.

  4. Transport of terrestrial atmospheric gases to the moon

    NASA Technical Reports Server (NTRS)

    Hills, H. K.; Freeman, J. W.

    1978-01-01

    The suprathermal Ion Detector Experiment instruments on the lunar surface have identified fluxes of ions which may be different from the solar wind both in elemental and in isotopic abundances. At present, only O/+/ is (tentatively) identified, but the mechanism operates to produce ions at the moon which have their origin in the earth's atmosphere. Consequently, the 'solar wind' component of the surface-correlated gases is effectively a combination of terrestrial atmospheric ions and the actual solar wind. The results differ from solar wind results if the terrestrial ion abundances strongly differ from those of the solar wind.

  5. Terrestrial nitrous oxide cycles and atmospheric effects

    NASA Technical Reports Server (NTRS)

    Whitten, R. C.; Lawless, J. G.; Banin, A.

    1984-01-01

    The basic processes that cause N2O emission from soils are briefly discussed, and the rate of the processes is shown to vary widely in space and time, depending on soil, climate, and agrotechnical conditions. Although significant amounts of N2O are indeed emitted from the land, the complexity of the soil processes involved and the wide variation of measured rates still prevents the quantitative evaluation, global budgeting, and reliable prediction of atmospheric N2O. Increased atmospheric N2O abundance increases the levels of odd-nitrogen in the stratosphere, which, in turn, decreases the stratospheric ozone density via a catalytic cycle. Using appropriate atmospheric models and current chemical kinetic data, it has been found that the dependence of ozone reduction on N2O increase is nearly linear; a simulated doubling of N2O leads to a predicted decrease of about 14 percent in total ozone column density. A 10 percent increase in N2O yields a predicted increase in nonmelanoma skin cancer of several percent, and a possible raising of surface temperature of 0.03 K.

  6. Space, Atmospheric, and Terrestrial Radiation Environments

    NASA Technical Reports Server (NTRS)

    Barth, Janet L.; Dyer, C. S.; Stassinopoulos, E. G.

    2003-01-01

    The progress on developing models of the radiation environment since the 1960s is reviewed with emphasis on models that can be applied to predicting the performance of microelectronics used in spacecraft and instruments. Space, atmospheric, and ground environments are included. It is shown that models must be adapted continually to account for increased understanding of the dynamics of the radiation environment and the changes in microelectronics technology. The IEEE Nuclear and Space Radiation Effects Conference is a vital forum to report model progress to the radiation effects research community.

  7. The Atmospheric and Terrestrial Mobile Laboratory (ATML).

    SciTech Connect

    Zak, Bernard Daniel; Rahn, Thom; Nitschke, Kim; Ivey, Mark D.; Mora, Claudia; McDowell, Nate; Love, Steve; Dubey, M.; Michelsen, Hope A.; Guilderson, Tom; Schubert, William Kent; Costigan, Keeley; Chylek, Petr; Bambha, Ray P.; Roskovensky, John K.

    2010-04-01

    The ionospheric disturbance dynamo signature in geomagnetic variations is investigated using the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model. The model results are tested against reference magnetically quiet time observations on 21 June 1993, and disturbance effects were observed on 11 June 1993. The model qualitatively reproduces the observed diurnal and latitude variations of the geomagnetic horizontal intensity and declination for the reference quiet day in midlatitude and low-latitude regions but underestimates their amplitudes. The patterns of the disturbance dynamo signature and its source 'anti-Sq' current system are well reproduced in the Northern Hemisphere. However, the model significantly underestimates the amplitude of disturbance dynamo effects when compared with observations. Furthermore, the largest simulated disturbances occur at different local times than the observations. The discrepancies suggest that the assumed high-latitude storm time energy inputs in the model were not quantitatively accurate for this storm.

  8. Solar Wind Ablation of Terrestrial Planet Atmospheres

    NASA Technical Reports Server (NTRS)

    Moore, Thomas Earle; Fok, Mei-Ching H.; Delcourt, Dominique C.

    2009-01-01

    Internal plasma sources usually arise in planetary magnetospheres as a product of stellar ablation processes. With the ignition of a new star and the onset of its ultraviolet and stellar wind emissions, much of the volatiles in the stellar system undergo a phase transition from gas to plasma. Condensation and accretion into a disk is replaced by radiation and stellar wind ablation of volatile materials from the system- Planets or smaller bodies that harbor intrinsic magnetic fields develop an apparent shield against direct stellar wind impact, but UV radiation still ionizes their gas phases, and the resulting internal plasmas serve to conduct currents to and from the central body along reconnected magnetic field linkages. Photoionization and thermalization of electrons warms the ionospheric topside, enhancing Jeans' escape of super-thermal particles, with ambipolar diffusion and acceleration. Moreover, observations and simulations of auroral processes at Earth indicate that solar wind energy dissipation is concentrated by the geomagnetic field by a factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Thus internal plasmas enable coupling with the plasma, neutral gas and by extension, the entire body. The stellar wind is locally loaded and slowed to develop the required power. The internal source plasma is accelerated and heated, inflating the magnetosphere as it seeks escape, and is ultimately blown away in the stellar wind. Bodies with little sensible atmosphere may still produce an exosphere of sputtered matter when exposed to direct solar wind impact. Bodies with a magnetosphere and internal sources of plasma interact more strongly with the stellar wind owing to the magnetic linkage between the two created by reconnection.

  9. Kinetics of Fast Atoms in the Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Kharchenko, Vasili A.; Dalgarno, A.; Mellott, Mary (Technical Monitor)

    2002-01-01

    This report summarizes our investigations performed under NASA Grant NAG5-8058. The three-year research supported by the Geospace Sciences SR&T program (Ionospheric, Thermospheric, and Mesospheric Physics) has been designed to investigate fluxes of energetic oxygen and nitrogen atoms in the terrestrial thermosphere. Fast atoms are produced due to absorption of the solar radiation and due to coupling between the ionosphere and the neutral thermospheric gas. We have investigated the impact of hot oxygen and nitrogen atoms on the thermal balance, chemistry and radiation properties of the terrestrial thermosphere. Our calculations have been focused on the accurate quantitative description of the thermalization of O and N energetic atoms in collisions with atom and molecules of the ambient neutral gas. Upward fluxes of oxygen and nitrogen atoms, the rate of atmospheric heating by hot oxygen atoms, and the energy input into translational and rotational-vibrational degrees of atmospheric molecules have been evaluated. Altitude profiles of hot oxygen and nitrogen atoms have been analyzed and compared with available observational data. Energetic oxygen atoms in the terrestrial atmosphere have been investigated for decades, but insufficient information on the kinetics of fast atmospheric atoms has been a main obstacle for the interpretation of observational data and modeling of the hot geocorona. The recent development of accurate computational methods of the collisional kinetics is seen as an important step in the quantitative description of hot atoms in the thermosphere. Modeling of relaxation processes in the terrestrial atmosphere has incorporated data of recent observations, and theoretical predictions have been tested by new laboratory measurements.

  10. Hydrogen and climate in primitive terrestrial and super-Earth atmospheres (Invited)

    NASA Astrophysics Data System (ADS)

    Wordsworth, R.

    2013-12-01

    For the three terrestrial planets with significant atmospheres in the Solar System (Earth, Venus and Mars), present-day conditions are oxidizing, with combinations of CO2, N2, O2 and H2O dominating by mass and in terms of the greenhouse effect. However, primitive terrestrial or ';super-Earth' exoplanet atmospheres may be much more reducing (i.e., hydrogen-rich), with major implications for climate, composition, and pre-biotic chemistry. Here I discuss recent work on the role of hydrogen in terrestrial planetary atmospheres, with a particular focus on the early Earth. I describe how collision-induced absorption (CIA) by hydrogen may have significantly warmed Earth's surface in the Archean and Hadean by blocking the critical water vapour absorption window at 800-1200 cm-1. This warming may have helped mitigate the faint young Sun effect early on. After the emergence of widespread methanogenesis, the consumption of H2 and CO2 should have led to a global shift in climate, with potentially observable consequences in the geological record. Because of variations in planetary mass, stellar XUV input and outgassing rates, hydrogen is also likely to be an important component of many super-Earth atmospheres. As I will discuss, this should have a significant effect on climate evolution and the carbon cycle on such planets, which should be considered in future predictions of atmospheric spectra and biosignatures.

  11. Terrestrial biogeochemical cycles - Global interactions with the atmosphere and hydrology

    NASA Technical Reports Server (NTRS)

    Schimel, David S.; Parton, William J.; Kittel, Timothy G. F.

    1991-01-01

    A review is presented of developments in ecosystem theory, remote sensing, and geographic information systems that support new endeavors in spatial modeling. A paradigm has emerged to predict ecosystem behavior based on understanding responses to multiple resources. Ecosystem models couple primary production to decomposition and nutrient availability utilizing this paradigm. It is indicated that coupling of transport and ecosystem processes alters the behavior of earth system components (terrestrial ecosystems, hydrology, and the atmosphere) from that of an uncoupled model.

  12. Energetic Metastable Oxygen and Nitrogen Atoms in the Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Kharchenko, Vasili

    2004-01-01

    We have investigated the impact of hot metastable oxygen atoms on the product yields and rate coefficients of atmospheric reactions involving O( (sup 1)D). The contribution of the metastable oxygen atoms to the thermal balance of the terrestrial atmosphere between 50 and 200 km has been determined. We found that the presence of hot O((sup l)D) atoms in the mesosphere and lower thermosphere significantly increases the production rate of the rotationally-vibrationally excited NO molecules. The computed yield of the NO molecules in N2O+ O((sup 1)D) atmospheric collisions, involving non-Maxwellian distributions of the metastable oxygen atoms, is more than two times larger than the NO-yield at a thermal equilibrium. The calculated non-equilibrium rate and yield functions are important for ozone and nitrous oxide modeling in the stratosphere, mesosphere and lower thermosphere.

  13. ABIOTIC OXYGEN-DOMINATED ATMOSPHERES ON TERRESTRIAL HABITABLE ZONE PLANETS

    SciTech Connect

    Wordsworth, Robin; Pierrehumbert, Raymond

    2014-04-20

    Detection of life on other planets requires identification of biosignatures, i.e., observable planetary properties that robustly indicate the presence of a biosphere. One of the most widely accepted biosignatures for an Earth-like planet is an atmosphere where oxygen is a major constituent. Here we show that lifeless habitable zone terrestrial planets around any star type may develop oxygen-dominated atmospheres as a result of water photolysis, because the cold trap mechanism that protects H{sub 2}O on Earth is ineffective when the atmospheric inventory of non-condensing gases (e.g., N{sub 2}, Ar) is low. Hence the spectral features of O{sub 2} and O{sub 3} alone cannot be regarded as robust signs of extraterrestrial life.

  14. Early terrestrial ecosystems: the animal evidence

    SciTech Connect

    Gray, J.

    1985-01-01

    Work on fossil spores indicates that plants at a level of vegetative organization comparable to bryophytes and vascular plants existed on land in the Early Silurian. Vascular plants, limnetic fishes, and probable Ascomycetes have Late Silurian records. Charophytes are known in the Late Silurian but may have been marine. The presence of microarthropods in the Ludlovian has been hypothesized from fungal masses in the Burgsvik Sandstone that closely resemble microarthropod frass. A number of microarthropods such as collembolans and mites are microphagous; these animals are among the earliest known from the Early Devonian. These fungal masses as animal traces have been given added credibility by the recovery of animal body fossils from basal Llandovery age fluvial deposits of the Central Appalachians that yield abundant plant spores but that lack marine invertebrates, phytoplankton or chitinozoans. The remains are abundant and sufficiently varied to suggest that they may represent a variety of organisms. Some are eurypterid-like, others grossly arthropod-like, although they may represent an unknown phylum or phyla. Many small invertebrates are associated with extant bryophytes, which have been viewed as stepping stones or halfway houses for them as they emerged from water onto land. The occurrence of these Early Silurian invertebrate remains with abundant spore tetrads, which Gray has hypothesized represent land plants at a bryophyte or hepatic grade of organization, is of great interest in trying to understand the early development of nonmarine ecosystems.

  15. Energetic Metastable Oxygen and Nitrogen Atoms in the Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Kharchenko, Vasili; Dalgarno, A.

    2005-01-01

    This report summarizes our research performed under NASA Grant NAG5-11857. The three-year grant have been supported by the Geospace Sciences SR&T program. We have investigated the energetic metastable oxygen and nitrogen atoms in the terrestrial stratosphere, mesosphere and thermosphere. Hot atoms in the atmosphere are produced by solar radiation, the solar wind and various ionic reactions. Nascent hot atoms arise in ground and excited electronic states, and their translational energies are larger by two - three orders of magnitude than the thermal energies of the ambient gas. The relaxation kinetics of hot atoms determines the rate of atmospheric heating, the intensities of aeronomic reactions, and the rate of atom escape from the planet. Modeling of the non-Maxwellian energy distributions of metastable oxygen and nitrogen atoms have been focused on the determination of their impact on the energetics and chemistry of the terrestrial atmosphere between 25 and 250 km . At this altitudes, we have calculated the energy distribution functions of metastable O and N atoms and computed non-equilibrium rates of important aeronomic reactions, such as destruction of the water molecules by O(1D) atoms and production of highly excited nitric oxide molecules. In the upper atmosphere, the metastable O(lD) and N(2D) play important role in formation of the upward atomic fluxes. We have computed the upward fluxes of the metastable and ground state oxygen atoms in the upper atmosphere above 250 km. The accurate distributions of the metastable atoms have been evaluated for the day and night-time conditions.

  16. Data Assimilation and Transport Modeling in Terrestrial and Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Houben, Howard C.; Young, Richard E. (Technical Monitor)

    2002-01-01

    Data assimilation is a blanket term used to describe a number of techniques for retrieving important physical parameters from observational data, subject to constraints imposed by prior knowledge (such as, in the case of meteorology, the primitive equations that govern atmospheric motion). Since these newly developed methods make efficient use of computational resources, they are of great importance in the interpretation of the voluminous datasets that are now produced by satellite missions. As proposed, these techniques have been applied to the study of the Martian and terrestrial atmospheres based on available satellite observations. In addition, a sophisticated hydrodynamic model (non-hydrostatic, and therefore applicable to the study of the interiors of the giant planets) has also been developed and successfully applied to the study of tidally induced motions in Jupiter.

  17. Terrestrial production vs. extraterrestrial delivery of prebiotic organics to the early Earth

    NASA Technical Reports Server (NTRS)

    Chyba, C. F.; Sagan, C.; Thomas, P. J.; Brookshaw, L.

    1991-01-01

    A comprehensive treatment of comet/asteroid interaction with the atmosphere, ensuring surface impact, and resulting organic pyrolysis is required to determine whether more than a negligible fraction of the organics in incident comets and asteroids actually survived collision with Earth. Results of such an investigation, using a smoothed particle hydrodynamic simulation of cometary and asteroidal impacts into both oceans and rock, demonstrate that organics will not survive impacts at velocities approx. greater than 10 km s(exp -1), and that even comets and asteroids as small as 100m in radius cannot be aerobraked to below this velocity in 1 bar atmospheres. However, for plausible dense (10 bar CO2) early atmospheres, there will be sufficient aerobraking during atmospheric passage for some organics to survive the ensuing impact. Combining these results with analytical fits to the lunar impact record shows that 4.5 Gyr ago Earth was accreting at least approx. 10(exp 6) kg yr(exp 1) of intact cometary organics, a flux which thereafter declined with a approx. 100 Myr half-life. The extent to which this influx was augmented by asteroid impacts, as well as the effect of more careful modelling of a variety of conservative approximations, is currently being quantified. These results may be placed in context by comparison with in situ organic production from a variety of terrestrial energy sources, as well as organic delivery by interplanetary dust. Which source dominated the early terrestrial prebiotic inventory is found to depend on the nature of the early terrestrial atmosphere. However, there is an intriguing symmetry: it is exactly those dense CO2 atmospheres where in situ atmospheric production of organic molecules should be the most difficult, in which intact cometary organics would be delivered in large amounts.

  18. Habitability of Terrestrial Planets in the Early Solar System

    NASA Astrophysics Data System (ADS)

    SLEEP, N. H.

    2001-12-01

    The Protoearth, Mars, Venus, and the Moon-forming impactor were potentially habitable in the early solar system. The interiors of larger asteroids had habitable circulating water. To see when the inner solar system became continuously habitable, one needs to consider the most dangerous events and the safest refugia from them. Early geochemical and accretionary processes set the subsequent silicate planet reservoirs and hence hydrospheric and atmospheric masses. The moon-forming impact made the Moon and the Earth sterile bodies. Following the impact, the Earth passed through a rock-vapor atmosphere on the scale of 1000s of years and an internally heated steam greenhouse on the scale of 2 m.y. Minerals bearing the principle volatiles (water, Cl, and CO2) were stable at the Earth's surface by the time it cooled to 800K. The mass of reactable shallow material was insufficient to contain the available water and CO2. Habitable conditions were established after CO2 could be deeply subducted into the mantle. Vast quantities of H2 were vented during accretion and after the moon-forming impact and eventually lost to space. It is unknown whether significant amounts of this gas were present when the Earth's surface cooled into the habitable range. The moon remained sterile because its interior is essentially devoid of water. The mantle of the Earth, in contrast, cannot hold the available water, leaving the excess to form oceans. Nitrogen may behave similarly with the excess going into the air. Impacts of large asteroids (and comets) were an ever-present danger on otherwise habitable planets. The safest niche on planets was kilometer or deeper crustal rocks habitable by thermophiles. It is inevitable that several objects, which would have left only thermophile survivors, struck the Earth. Such events were so infrequent that the conditions of such a bottleneck should not be confused with conditions for the origin of life. An alternative refugium involves ejection of life within

  19. Contribution of natural terrestrial sources to the atmospheric chloroform budget

    NASA Astrophysics Data System (ADS)

    Rhew, R. C.; Abel, T.; Pan, D.; Whelan, M.

    2008-12-01

    Chloroform (trichloromethane, CHCl3) is the second largest carrier of natural chlorine in the troposphere after methyl chloride, contributing to the reactive chlorine burden in the troposphere and to ozone destruction in the stratosphere. Our understanding of the biogeochemical cycling of atmospheric CHCl3 has undergone major adjustments recently, including the quantification of the total atmospheric burden of this compound, the estimated global source and sink strengths, and the relative contributions of anthropogenic versus natural contributions. Numerous natural terrestrial sources have been identified, including temperate peatlands, Arctic tundra, termite mounds, salt marshes, grasslands, forests and woodlands. However, the wide variability of fluxes within each ecosystem has complicated efforts to quantify the overall terrestrial source. In addition, the environmental and biogeochemical controls remain largely unknown. We shall present a comparison of recent CHCl3 flux measurements that cover a range of biome types and climatic conditions. To address within-biome variability, flux measurements from the Arctic tundra and temperate grasslands will be compared to common environmental parameters (e.g., temperature, soil moisture, solar insolation) and other trace gas fluxes (CH3Cl, CH4, CCl4). The generally poor correlations demonstrate that the variability of CHCl3 emissions may be affected by site-specific parameters that are not currently measured or by drastic changes in hydrologic conditions. Similar patterns are observed in laboratory incubations of tundra peat and grassland soils. We explore the possibility that the humification of plant material, which has been shown to produce organochlorine compounds through the chlorination of organic matter, may contribute to CHCl3 emissions. If this link exists, then CHCl3 production could potentially act as a proxy for organic matter degradation and carbon sequestration, essential biogeochemical and ecosystem

  20. Terrestrial atmospheric effects induced by counterstreaming dense interstellar cloud material

    NASA Astrophysics Data System (ADS)

    Yeghikyan, A.; Fahr, H.

    The Solar System during its life has encountered more than 10 times with dense interstellar clouds with particle concentrations about 10(8)-10(9) m(-3) and more suppressing the heliopause to dimensions smaller than 1 AU and bringing the Earth in immediate contact with the interstellar matter. For cloud's concentration greater than of 10(8) m(-3), the flow material at the Earth, completely shielded from solar wind protons would be only subject to solar photoionization processes. Previously published results were limited to consideration of processes outside of the accretion radius and have not been taken into account the photoionization. We have developed a 2D-2-fluid gasdynamical numerical code to describe the behavior of the incoming neutral matter near the Earth, taken into account both the photoionization and the gravity of the Sun. Increased neutral hydrogen fluxes ranging from 10(13) to 10(16) m(-2)s(-1) would cause an alteration of the terrestrial atmosphere. During immersion in the cloud the total incident flux of neutral hydrogen onto the terrestrial atmosphere in the steady state would be balanced by the upward escape flux of hydrogen and the downward flux of water, which is the product of hydrogen-oxygen chemistry via even-odd reaction schemes. In that case hydrogen acts as a catalyst for the destruction of oxygen atoms and causes the ozone concentration to diminish pronouncedly above 50 km from a factor of 1.5 at the stratopause to about a factor of 1000 and more at the mesopause. Thus, depending on the encounter parameters the large mixing ratio of hydrogen decreases the ozon concentration in the mesosphere and triggers an ice age of relatively long duration.

  1. Water loss from terrestrial planets with CO{sub 2}-rich atmospheres

    SciTech Connect

    Wordsworth, R. D.; Pierrehumbert, R. T.

    2013-12-01

    Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study the dependence of water loss rates from terrestrial planets on a range of atmospheric and external parameters. We show that CO{sub 2} can only cause significant water loss by increasing surface temperatures over a narrow range of conditions, with cooling of the middle and upper atmosphere acting as a bottleneck on escape in other circumstances. Around G-stars, efficient loss only occurs on planets with intermediate CO{sub 2} atmospheric partial pressures (0.1-1 bar) that receive a net flux close to the critical runaway greenhouse limit. Because G-star total luminosity increases with time but X-ray and ultraviolet/ultravoilet luminosity decreases, this places strong limits on water loss for planets like Earth. In contrast, for a CO{sub 2}-rich early Venus, diffusion limits on water loss are only important if clouds caused strong cooling, implying that scenarios where the planet never had surface liquid water are indeed plausible. Around M-stars, water loss is primarily a function of orbital distance, with planets that absorb less flux than ∼270 W m{sup –2} (global mean) unlikely to lose more than one Earth ocean of H{sub 2}O over their lifetimes unless they lose all their atmospheric N{sub 2}/CO{sub 2} early on. Because of the variability of H{sub 2}O delivery during accretion, our results suggest that many 'Earth-like' exoplanets in the habitable zone may have ocean-covered surfaces, stable CO{sub 2}/H{sub 2}O-rich atmospheres, and high mean surface temperatures.

  2. The early atmosphere - A new picture

    NASA Technical Reports Server (NTRS)

    Levine, Joel S.

    1986-01-01

    Over the last few years, discoveries in astronomy, geochemistry, and atmospheric chemistry have resulted in a new picture of how our planet and its atmosphere formed. The traditional view held that the early atmosphere was composed of methane, ammonia, and molecular hydrogen, but the actual composition may have been nitrogen, carbon dioxide, and water vapor. The history leading to the present understanding is discussed and topics covered include: chemical evolution, origin of the atmosphere, atmospheric evolution on earth, Venus, and Mars, and prebiological atmospheric oxygen and the early sun.

  3. Atmospheres on the terrestrial planets: Clues to origin and evolution

    NASA Astrophysics Data System (ADS)

    Pepin, Robert O.

    2006-11-01

    Earth, Venus and Mars reached their final sizes in the first 100 Myr or so of solar system history. For part of that time the growing planets and the materials forming them were immersed in the Sun-like gases of the solar nebula, and so one would expect that their early volatile inventories were acquired from the nebula. But the compositions of atmospheres presently on these planets are not solar, and therein lies a complex and fascinating story of physical and chemical evolution over the past 4.5 Ga. Records of physical processing survive most clearly in the chemically inert noble gases, and data on the elemental and isotopic abundances of these trace constituents, now from Mars and Venus as well as Earth, point to atmospheric histories punctuated by enormous inputs of energy from early astrophysical sources long since vanished. Observational and theoretical advances during the past 30 years underpin current evolutionary models in which primordial solar-like atmospheric gases are fractionated by gravitational escape, driven on Earth by a giant Moon-forming impact, on Mars by sputtering at high altitudes, and on all three planets by adsorption of intense ultraviolet radiation from the young Sun. Residual atmospheres left behind after these outflows to space are augmented by planetary degassing, including species generated in their interiors by radioactive decay. Interplay over time of these mechanisms for loss and gain of atmospheric gases can account for many of the details of contemporary noble gas distributions. These of course are just models. However they have predictive power for compositions as yet unmeasured, particularly on Venus, and the modeling assumptions are in principle testable by experiment or theory. The fundamental question of whether nature actually shaped the atmospheres in this way is still unanswered, but at least we have an outline of how it might have happened.

  4. Origin of the atmosphere and hydrosphere of the terrestrial planets

    NASA Technical Reports Server (NTRS)

    Matsui, T.; Abe, Y.

    1985-01-01

    An early thermal evolution of a planet growing by planetesimal impacts was studied. An evolution of an impact induced atmosphere was considered. It is known that the surface of a growing planet is heated due to the blanketing effect of the atmosphere and exceeds the melting temperature, which means that the surface of a growing planet was entirely covered by a magma ocean. The amount of water in a proto-atmosphere is influenced by the formation of a magma ocean. It is suggested the solubility of water in silicate melt controls the water content in a proto-atmsphere. It is noted that irrespective of difference in initial water content of planetesimals the final water content in the atmosphere becomes almost constant and is about 10 to the 21st power kg which is almost identical with the present amount of the ocean. It is also shown that the water in a proto-atmosphere can be liquid for the Earth and becomes to be an ocean but this does not happen on Venus.

  5. Processes Impacting Atmosphere-Surface Exchanges at Arctic Terrestrial Sites

    NASA Astrophysics Data System (ADS)

    Persson, Ola; Grachev, Andrey; Konopleva, Elena; Cox, Chris; Stone, Robert; Crepinsek, Sara; Shupe, Matthew; Uttal, Taneil

    2015-04-01

    Surface energy fluxes are key to the annual cycle of near-surface and soil temperature and biologic activity in the Arctic. While these energy fluxes are undoubtedly changing to produce the changes observed in the Arctic ecosystem over the last few decades, measurements have generally not been available to quantify what processes are regulating these fluxes and what is determining the characteristics of these annual cycles. The U.S. National Oceanic and Atmospheric Administration has established, or contributed to the establishment of, several terrestrial "supersites" around the perimeter of the Arctic Ocean at which detailed measurements of atmospheric structure, surface fluxes, and soil thermal properties are being made. These sites include Barrow, Alaska; Eureka and Alert, Canada; and Tiksi, Russia. Atmospheric structure measurements vary, but include radiosoundings at all sites and remote sensing of clouds at two sites. Additionally, fluxes of sensible heat and momentum are made at all of the sites, while fluxes of moisture and CO2 are made at two of the sites. Soil temperatures are also measured in the upper 120 cm at all sites, which is deep enough to define the soil active layer. The sites have been operating between 3 years (Tiksi) and 24 years (Barrow). While all sites are located north of 71° N, the summer vegetation range from lush tundra grasses to rocky soils with little vegetation. This presentation will illustrate some of the atmospheric processes that are key for determining the annual energy and temperature cycles at these sites, and some of the key characteristics that lead to differences in, for instance, the length of the summer soil active layer between the sites. Atmospheric features and processes such as cloud characteristics, snowfall, downslope wind events, and sea-breezes have impacts on the annual energy cycle. The presence of a "zero curtain" period, when autumn surface temperature remains approximately constant at the freezing point

  6. Terrestrial Effects of Nearby Supernovae in the Early Pleistocene

    NASA Astrophysics Data System (ADS)

    Thomas, B. C.; Engler, E. E.; Kachelrieß, M.; Melott, A. L.; Overholt, A. C.; Semikoz, D. V.

    2016-07-01

    Recent results have strongly confirmed that multiple supernovae happened at distances of ∼100 pc, consisting of two main events: one at 1.7–3.2 million years ago, and the other at 6.5–8.7 million years ago. These events are said to be responsible for excavating the Local Bubble in the interstellar medium and depositing 60Fe on Earth and the Moon. Other events are indicated by effects in the local cosmic ray (CR) spectrum. Given this updated and refined picture, we ask whether such supernovae are expected to have had substantial effects on the terrestrial atmosphere and biota. In a first look at the most probable cases, combining photon and CR effects, we find that a supernova at 100 pc can have only a small effect on terrestrial organisms from visible light and that chemical changes such as ozone depletion are weak. However, tropospheric ionization right down to the ground, due to the penetration of ≥TeV CRs, will increase by nearly an order of magnitude for thousands of years, and irradiation by muons on the ground and in the upper ocean will increase twentyfold, which will approximately triple the overall radiation load on terrestrial organisms. Such irradiation has been linked to possible changes in climate and increased cancer and mutation rates. This may be related to a minor mass extinction around the Pliocene-Pleistocene boundary, and further research on the effects is needed.

  7. Terrestrial Effects of Nearby Supernovae in the Early Pleistocene

    NASA Astrophysics Data System (ADS)

    Thomas, B. C.; Engler, E. E.; Kachelrieß, M.; Melott, A. L.; Overholt, A. C.; Semikoz, D. V.

    2016-07-01

    Recent results have strongly confirmed that multiple supernovae happened at distances of ˜100 pc, consisting of two main events: one at 1.7–3.2 million years ago, and the other at 6.5–8.7 million years ago. These events are said to be responsible for excavating the Local Bubble in the interstellar medium and depositing 60Fe on Earth and the Moon. Other events are indicated by effects in the local cosmic ray (CR) spectrum. Given this updated and refined picture, we ask whether such supernovae are expected to have had substantial effects on the terrestrial atmosphere and biota. In a first look at the most probable cases, combining photon and CR effects, we find that a supernova at 100 pc can have only a small effect on terrestrial organisms from visible light and that chemical changes such as ozone depletion are weak. However, tropospheric ionization right down to the ground, due to the penetration of ≥TeV CRs, will increase by nearly an order of magnitude for thousands of years, and irradiation by muons on the ground and in the upper ocean will increase twentyfold, which will approximately triple the overall radiation load on terrestrial organisms. Such irradiation has been linked to possible changes in climate and increased cancer and mutation rates. This may be related to a minor mass extinction around the Pliocene-Pleistocene boundary, and further research on the effects is needed.

  8. The Huygens Atmospheric Structure Instrument (HASI): Expected Results at Titan and Performance Verification in Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Ferri, F.; Fulchignoni, M.; Colombatti, G.; Stoppato, P. F. Lion; Zarnecki, J. C.; Harri, A. M.; Schwingenschuh, K.; Hamelin, M.; Flamini, E.; Bianchini, G.; Angrilli, F.

    2005-01-01

    The Huygens ASI is a multi-sensor package resulting from an international cooperation, it has been designed to measure the physical quantities characterizing Titan's atmosphere during the Huygens probe mission. On 14th January, 2005, HASI will measure acceleration, pressure, temperature and electrical properties all along the Huygens probe descent on Titan in order to study Titan s atmospheric structure, dynamics and electric properties. Monitoring axial and normal accelerations and providing direct pressure and temperature measurements during the descent, HASI will mainly contribute to the Huygens probe entry and trajectory reconstruction. In order to simulate the Huygens probe descent and verify HASI sensors performance in terrestrial environment, stratospheric balloon flight experiment campaigns have been performed, in collaboration with the Italian Space Agency (ASI). The results of flight experiments have allowed to determine the atmospheric vertical profiles and to obtain a set of data for the analysis of probe trajectory and attitude reconstruction.

  9. Evolution of an early Titan atmosphere

    NASA Astrophysics Data System (ADS)

    Johnson, R. E.; Tucker, O. J.; Volkov, A. N.

    2016-06-01

    Rapid escape from a proposed early CH4/NH3 atmosphere on Titan could, in principle, limit the amount of NH3 that is converted by photolysis into the present N2 atmosphere. Assuming that this conversion occurred, a recent estimate of escape driven by the surface temperature and pressure was used to constrain Titan's accretion temperature. Here we show that for the range of temperatures of interest, heating of the surface is not the primary driver for escape. Atmospheric loss from a thick Titan atmosphere is predominantly driven by heating of the upper atmosphere; therefore, the loss rate cannot be used to easily constrain the accretion temperature. We give an estimate of the solar driven escape rate from an early atmosphere on Titan, and then briefly discuss its relevance to the cooling rate, isotope ratios, and the time period suggested to convert NH3 to the present N2 atmosphere.

  10. Early Earth: Atmosphere's solar shock

    NASA Astrophysics Data System (ADS)

    Ramirez, Ramses

    2016-06-01

    Frequent storms on the young Sun would have ejected energetic particles and compressed Earth's magnetosphere. Simulations suggest that the particles penetrated the atmosphere and initiated reactions that warmed the planet and fertilized life.

  11. Early oxygenation of the terrestrial environment during the Mesoproterozoic.

    PubMed

    Parnell, John; Boyce, Adrian J; Mark, Darren; Bowden, Stephen; Spinks, Sam

    2010-11-11

    Geochemical data from ancient sedimentary successions provide evidence for the progressive evolution of Earth's atmosphere and oceans. Key stages in increasing oxygenation are postulated for the Palaeoproterozoic era (∼2.3 billion years ago, Gyr ago) and the late Proterozoic eon (about 0.8 Gyr ago), with the latter implicated in the subsequent metazoan evolutionary expansion. In support of this rise in oxygen concentrations, a large database shows a marked change in the bacterially mediated fractionation of seawater sulphate to sulphide of Δ(34)S < 25‰ before 1 Gyr to ≥50‰ after 0.64 Gyr. This change in Δ(34)S has been interpreted to represent the evolution from single-step bacterial sulphate reduction to a combination of bacterial sulphate reduction and sulphide oxidation, largely bacterially mediated. This evolution is seen as marking the rise in atmospheric oxygen concentrations and the evolution of non-photosynthetic sulphide-oxidizing bacteria. Here we report Δ(34)S values exceeding 50‰ from a terrestrial Mesoproterozoic (1.18 Gyr old) succession in Scotland, a time period that is at present poorly characterized. This level of fractionation implies disproportionation in the sulphur cycle, probably involving sulphide-oxidizing bacteria, that is not evident from Δ(34)S data in the marine record. Disproportionation in both red beds and lacustrine black shales at our study site suggests that the Mesoproterozoic terrestrial environment was sufficiently oxygenated to support a biota that was adapted to an oxygen-rich atmosphere, but had also penetrated into subsurface sediment. PMID:21068840

  12. Lichen metabolism identified in Early Devonian terrestrial organisms

    NASA Astrophysics Data System (ADS)

    Jahren, A. Hope; Porter, Steven; Kuglitsch, Jeffrey J.

    2003-02-01

    We used δ13C values to identify lichen metabolism in the globally distributed Early Devonian (409 386 Ma) macrofossil Spongiophyton minutissimum, which had been alternatively interpreted as a green plant of bryophyte grade or as a lichen, based on its morphology. Extant mosses and hornworts exhibited a range of δ13Ctissue values that was discrete from that of extant lichens. The δ13Ctissue values of 96 S. minutissimum specimens coincided with δ13Ctissue values of extant lichens. In contrast, S. minutissimum δ13Ctissue values showed no similarity to bryophyte carbon isotope values. The identification of large global populations of lichens during the Early Devonian may indicate that lichen-accelerated soil formation fostered the development of Paleozoic terrestrial ecosystems.

  13. North America's net terrestrial CO2 exchange with the atmosphere 1990-2009

    NASA Astrophysics Data System (ADS)

    King, A. W.; Andres, R. J.; Davis, K. J.; Hafer, M.; Hayes, D. J.; Huntzinger, D. N.; de Jong, B.; Kurz, W. A.; McGuire, A. D.; Vargas, R.; Wei, Y.; West, T. O.; Woodall, C. W.

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land-atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990-2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990-2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1.

  14. North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

    SciTech Connect

    King, Anthony W.; Andres, Robert; Davis, Kenneth J.; Hafer, M.; Hayes, Daniel J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, Werner; McGuire, A. David; Vargas, Rodrigo; Wei, Yaxing; West, Tristram O.; Woodall, Chris W.

    2015-01-21

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, \\"best\\" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the

  15. North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

    DOE PAGESBeta

    King, Anthony W.; Andres, Robert; Davis, Kenneth J.; Hafer, M.; Hayes, Daniel J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, Werner; McGuire, A. David; Vargas, Rodrigo; et al

    2015-01-21

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North Americanmore » land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, \\"best\\" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4

  16. North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

    USGS Publications Warehouse

    King, A.W.; Andres, R.J.; Davis, K.J.; Hafer, M.; Hayes, D.J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, W.A.; McGuire, Anthony; Vargas, Rodrigo I.; Wei, Y.; West, Tristram O.; Woodall, Christopher W.

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from −890 to −280 Tg C yr−1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are −472 ± 281 Tg C yr−1 based on the mean and standard deviation of the distribution and −360 Tg C yr−1 (with an interquartile range of −496 to −337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr−1 and assuming the estimate of −472 Tg C yr−1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was

  17. A massive early atmosphere on Triton

    NASA Technical Reports Server (NTRS)

    Lunine, Jonathan I.; Nolan, Michael C.

    1992-01-01

    The idea of an early greenhouse atmosphere for Triton is presented and the conditions under which it may have been sustained are quantified. The volatile content of primordial Triton is modeled, and tidal heating rates are assessed to set bounds on the available energy. The atmospheric model formalism is presented, and it is shown how a massive atmosphere could have been raised by modest tidal heating fluxes. The implications of the model atmospheres for the atmospheric escape rates, the chemical evolution, and the cratering record are addressed.

  18. Fungal decomposition of terrestrial organic matter accelerated Early Jurassic climate warming

    PubMed Central

    Pieńkowski, Grzegorz; Hodbod, Marta; Ullmann, Clemens V.

    2016-01-01

    Soils – constituting the largest terrestrial carbon pool - are vulnerable to climatic warming. Currently existing uncertainties regarding carbon fluxes within terrestrial systems can be addressed by studies of past carbon cycle dynamics and related climate change recorded in sedimentary successions. Here we show an example from the Early Jurassic (early Toarcian, c. 183 mya) marginal-marine strata from Poland, tracking the hinterland response to climatic changes through a super-greenhouse event. In contrast to anoxia-related enhanced carbon storage in coeval open marine environments, Total Organic Carbon (TOC) concentrations in the Polish successions are substantially reduced during this event. Increasing temperature favoured fungal-mediated decomposition of plant litter – specifically of normally resistant woody tissues. The associated injection of oxidized organic matter into the atmosphere corresponds to abrupt changes in standing vegetation and may have contributed significantly to the amplified greenhouse climate on Earth. The characteristic Toarcian signature of multiple warm pulses coinciding with rapidly decreasing carbon isotope ratios may in part be the result of a radical reduction of the terrestrial carbon pool as a response to climate change. PMID:27554210

  19. Fungal decomposition of terrestrial organic matter accelerated Early Jurassic climate warming.

    PubMed

    Pieńkowski, Grzegorz; Hodbod, Marta; Ullmann, Clemens V

    2016-01-01

    Soils - constituting the largest terrestrial carbon pool - are vulnerable to climatic warming. Currently existing uncertainties regarding carbon fluxes within terrestrial systems can be addressed by studies of past carbon cycle dynamics and related climate change recorded in sedimentary successions. Here we show an example from the Early Jurassic (early Toarcian, c. 183 mya) marginal-marine strata from Poland, tracking the hinterland response to climatic changes through a super-greenhouse event. In contrast to anoxia-related enhanced carbon storage in coeval open marine environments, Total Organic Carbon (TOC) concentrations in the Polish successions are substantially reduced during this event. Increasing temperature favoured fungal-mediated decomposition of plant litter - specifically of normally resistant woody tissues. The associated injection of oxidized organic matter into the atmosphere corresponds to abrupt changes in standing vegetation and may have contributed significantly to the amplified greenhouse climate on Earth. The characteristic Toarcian signature of multiple warm pulses coinciding with rapidly decreasing carbon isotope ratios may in part be the result of a radical reduction of the terrestrial carbon pool as a response to climate change. PMID:27554210

  20. A reduced atmosphere for early Mars?

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.

    1992-01-01

    One-dimensional, radiative-convective climate calculations indicate that the old model of a warm, dense, CO2 atmosphere on early Mars is no longer viable. The magnitude of the greenhouse effect in a CO2/H2O atmosphere is limited by condensation of CO2 clouds; this phenomenon is not important for Mars today, but has a pronounced cooling effect at the low solar luminosities thought to apply during early solar system history. The failure of this model indicates one of four things: (1) the new climate calculations are incorrect; (2) current solar evolution models are incorrect; (3) the idea that early Mars was warm and wet is incorrect; or (4) the atmosphere of early Mars contained other greenhouse gases (or particles) in addition to CO2 and H2O. Of these explanations, the most plausible is number (4) and the rest of the investigation is a further explanation of number (4).

  1. Origin of the atmospheres of the terrestrial planets

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.

    1983-01-01

    The monotonic decrease in the atmospheric abundance of per gram of planet in the sequence, Venus, earth, and Mars has been assumed to reflect some conditions in the primitive solar nebula at the time of formation of the planetary atmospheres, having to do either with the composition of the nebula itself or the composition of the trapped gases in small solid bodies in the nebula. Behind such hypotheses lies the assumption that planetary atmospheres steadily gain components. However, not only can gases enter atmospheres; they may also be lost from atmospheres both by adsorption into the planetary interior and by loss into space as a result of collisions with minor and major planetesimals. In this paper a necessarily qualitative discussion is given of the problem of collisions with minor planetesimals, a process called atmospheric cratering or atmospheric erosion, and a discussion is given of atmospheric loss accompanying collision of a planet with a major planetesimal, such as may have produced the earth's moon.

  2. Relating GRACE terrestrial water storage variations to global fields of atmospheric forcing

    NASA Astrophysics Data System (ADS)

    Humphrey, Vincent; Gudmundsson, Lukas; Isabelle Seneviratne, Sonia

    2015-04-01

    Synoptic, seasonal and inter-annual fluctuations in atmospheric dynamics all influence terrestrial water storage, with impacts on ecosystems functions, human activities and land-climate interactions. Here we explore to which degree atmospheric variables can explain GRACE estimates of terrestrial water storage on different time scales. Since 2012, the most recent GRACE gravity field solutions (Release 05) can be used to monitor global changes in terrestrial water storage with an unprecedented level of accuracy over more than a decade. In addition, the release of associated gridded and post-processed products facilitates comparisons with other global datasets such as land surface model outputs or satellite observations. We investigate how decadal trends, inter-annual fluctuations as well as monthly anomalies of the seasonal cycle of terrestrial water storage can be related to fields of atmospheric forcing, including e.g. precipitation and temperature as estimated in global reanalysis products using statistical techniques. In the majority of the locations with high signal to noise ratio, both short and long-term fluctuations of total terrestrial water storage can be reconstructed to a large degree based on available atmospheric forcing. However, in some locations atmospheric forcing alone is not sufficient to explain the total change in water storage, suggesting strong influence of other processes. Within that framework, the question of an amplification or attenuation of atmospheric forcing through land-surface feedbacks and changes in long term water storage is discussed, also with respect to uncertainties and potential systematic biases in the results.

  3. Photochemistry of methane in the earth's early atmosphere

    NASA Astrophysics Data System (ADS)

    Kasting, J. F.; Zahnle, K. J.; Walker, J. C. G.

    The photochemical behavior of methane in the early terrestrial atmosphere is investigated with a detailed model in order to determine how much CH4 might have been present and what types of higher hydroocarbons could have been formed. It is found that any primordial methane accumulated during the course of earth accretion would have been dissipated by photochemical reactions in the atmosphere in a geologically short period of time after the segregation of the core. Abiotic sources of methane are not likely to have been large enough to sustain CH4 mixing ratios as high as 10 to the -6th, the threshold for a possible methane greenhouse, with a CO-rich atmosphere being a possible exception. After the origin of life an increasing biogenic source of methane may have driven CH4 mixing ratios well above 10 to the 6th. The rise of atmospheric oxygen in the early Proterozoic may have led to a more rapid photochemical destruction of methane, lowering the mixing ratio to its present value.

  4. The Center for the Study of Terrestrial and Extraterrestrial Atmospheres (CSTEA)

    NASA Technical Reports Server (NTRS)

    Thorpe, Arthur N.; Morris, Vernon R.

    1997-01-01

    The Center for the Study of Terrestrial and Extraterrestrial Atmospheres (CSTEA) was established in 1992. The center began with 14 active Principal Investigators (PI's). The research of the Center's PIs has, for the most part, continued in the same four areas as presented in the original proposal: Remote Sensing, Atmospheric Chemistry, Sensors and Detectors, and Spacecraft Dynamics.

  5. Atmospheric transport of persistent pollutants governs uptake by holarctic terrestrial biota

    SciTech Connect

    Larsson, P.; Okla, L.; Woin, Per )

    1990-10-01

    The atmospheric deposition of PCBs, DDT, and lindane, governed uptake in terrestrial biota in the Scandinavian peninsula. Mammalian herbivores and predators as well as predatory insects contained higher levels of pollutants at locations where the fallout load was high than at stations where atmospheric deposition was lower, and the two variables were significantly correlated.

  6. Exploring Terrestrial Temperature Changes during the Early Eocene Hyperthermals

    NASA Astrophysics Data System (ADS)

    Snell, K. E.; Clyde, W. C.; Fricke, H. C.; Eiler, J. M.

    2012-12-01

    The Early Eocene is marked by a number of rapid global warming events called hyperthermals. These hyperthermals are associated with negative carbon isotope excursions (CIE) in both marine and terrestrial records. Multiple theories exist to explain the connection of these hyperthermals with the CIEs and each theory predicts different responses by the climate system. Characterizing the timing, duration and magnitude of temperature change that is associated with these hyperthermals is important for determining whether the hyperthermals are all driven by the same underlying climate dynamics or perhaps differ from one another in cause and climatic consequences. In the simplest case, all share a common underlying mechanism; this predicts that the associated temperature changes scale in a predictable way with the magnitude of the CIE (and perhaps exhibit other similarities, such as the relative amplitudes of marine and terrestrial temperature change). To our knowledge, however, the only hyperthermal with paleotemperature data from land is the Paleocene-Eocene Thermal Maximum (PETM). Here we present preliminary carbonate clumped isotope paleotemperature estimates for Early Eocene hyperthermal ETM2/H2 from paleosol carbonates from the Bighorn Basin in Wyoming, USA. We compare the results to existing clumped isotope paleotemperature estimates for the PETM in the Bighorn Basin. Temperatures recorded by paleosol carbonates (which likely reflect near-peak summer ground temperatures) prior to each CIE are ~30°C and increase to ~40-43°C during the apex of each CIE. Following both CIEs, temperatures drop back to pre-CIE values. In the case of ETM2/H2, temperatures begin to rise again immediately, possibly in association with a later hyperthermal, though further work needs to be done to establish this with certainty. These preliminary data suggest that both the absolute values and the magnitudes of temperature changes associated with the PETM and ETM2/H2 are similar; the

  7. On the (anticipated) diversity of terrestrial planet atmospheres

    NASA Astrophysics Data System (ADS)

    Leconte, Jérémy; Forget, François; Lammer, Helmut

    2015-12-01

    On our way toward the characterization of smaller and more temperate planets, missions dedicated to the spectroscopic observation of exoplanets will teach us about the wide diversity of classes of planetary atmospheres, many of them probably having no equivalent in the Solar System. But what kind of atmospheres can we expect? To start answering this question, many theoretical studies have tried to understand and model the various processes controlling the formation and evolution of planetary atmospheres, with some success in the Solar System. Here, we shortly review these processes and we try to give an idea of the various type of atmospheres that these processes can create. As will be made clear, current atmosphere evolution models have many shortcomings yet, and need heavy calibrations. With that in mind, we will thus discuss how observations with a mission similar to EChO would help us unravel the link between a planet's environment and its atmosphere.

  8. Proposed reference models for atomic oxygen in the terrestrial atmosphere

    NASA Technical Reports Server (NTRS)

    Llewellyn, E. J.; Mcdade, I. C.; Lockerbie, M. D.

    1989-01-01

    A provisional Atomic Oxygen Reference model was derived from average monthly ozone profiles and the MSIS-86 reference model atmosphere. The concentrations are presented in tabular form for the altitude range 40 to 130 km.

  9. Evaluation of terrestrial carbon cycle models with atmospheric CO2 measurements: Results from transient simulations considering increasing CO2, climate, and land-use effects

    USGS Publications Warehouse

    Dargaville, R.J.; Heimann, Martin; McGuire, A.D.; Prentice, I.C.; Kicklighter, D.W.; Joos, F.; Clein, J.S.; Esser, G.; Foley, J.; Kaplan, J.; Meier, R.A.; Melillo, J.M.; Moore, B., III; Ramankutty, N.; Reichenau, T.; Schloss, A.; Sitch, S.; Tian, H.; Williams, L.J.; Wittenberg, U.

    2002-01-01

    An atmospheric transport model and observations of atmospheric CO2 are used to evaluate the performance of four Terrestrial Carbon Models (TCMs) in simulating the seasonal dynamics and interannual variability of atmospheric CO2 between 1980 and 1991. The TCMs were forced with time varying atmospheric CO2 concentrations, climate, and land use to simulate the net exchange of carbon between the terrestrial biosphere and the atmosphere. The monthly surface CO2 fluxes from the TCMs were used to drive the Model of Atmospheric Transport and Chemistry and the simulated seasonal cycles and concentration anomalies are compared with observations from several stations in the CMDL network. The TCMs underestimate the amplitude of the seasonal cycle and tend to simulate too early an uptake of CO2 during the spring by approximately one to two months. The model fluxes show an increase in amplitude as a result of land-use change, but that pattern is not so evident in the simulated atmospheric amplitudes, and the different models suggest different causes for the amplitude increase (i.e., CO2 fertilization, climate variability or land use change). The comparison of the modeled concentration anomalies with the observed anomalies indicates that either the TCMs underestimate interannual variability in the exchange of CO2 between the terrestrial biosphere and the atmosphere, or that either the variability in the ocean fluxes or the atmospheric transport may be key factors in the atmospheric interannual variability.

  10. PHOTOCHEMISTRY IN TERRESTRIAL EXOPLANET ATMOSPHERES. I. PHOTOCHEMISTRY MODEL AND BENCHMARK CASES

    SciTech Connect

    Hu Renyu; Seager, Sara; Bains, William

    2012-12-20

    We present a comprehensive photochemistry model for exploration of the chemical composition of terrestrial exoplanet atmospheres. The photochemistry model is designed from the ground up to have the capacity to treat all types of terrestrial planet atmospheres, ranging from oxidizing through reducing, which makes the code suitable for applications for the wide range of anticipated terrestrial exoplanet compositions. The one-dimensional chemical transport model treats up to 800 chemical reactions, photochemical processes, dry and wet deposition, surface emission, and thermal escape of O, H, C, N, and S bearing species, as well as formation and deposition of elemental sulfur and sulfuric acid aerosols. We validate the model by computing the atmospheric composition of current Earth and Mars and find agreement with observations of major trace gases in Earth's and Mars' atmospheres. We simulate several plausible atmospheric scenarios of terrestrial exoplanets and choose three benchmark cases for atmospheres from reducing to oxidizing. The most interesting finding is that atomic hydrogen is always a more abundant reactive radical than the hydroxyl radical in anoxic atmospheres. Whether atomic hydrogen is the most important removal path for a molecule of interest also depends on the relevant reaction rates. We also find that volcanic carbon compounds (i.e., CH{sub 4} and CO{sub 2}) are chemically long-lived and tend to be well mixed in both reducing and oxidizing atmospheres, and their dry deposition velocities to the surface control the atmospheric oxidation states. Furthermore, we revisit whether photochemically produced oxygen can cause false positives for detecting oxygenic photosynthesis, and find that in 1 bar CO{sub 2}-rich atmospheres oxygen and ozone may build up to levels that have conventionally been accepted as signatures of life, if there is no surface emission of reducing gases. The atmospheric scenarios presented in this paper can serve as the benchmark

  11. Stability of ammonia in the primitive terrestrial atmosphere

    NASA Astrophysics Data System (ADS)

    Kasting, J. F.

    1982-04-01

    The rate at which ammonia would have been destroyed in the earth's atmosphere under assumed NH3 mixing ratio conditions of 10 to the -8th to 0.0001 is calculated by a one-dimensional photochemical model, and the destruction rates are compared with possible biotic and abiotic ammonia sources. It is found that, while the mixing ratio of 10 to the -8th needed for the evolution of life could have been maintained by abiotic sources, the value of 0.00001 needed for the production of significant greenhouse warming could not have been sustained abiotically. The increase of atmospheric ammonia due to biological activities during the Archean is also considered lower than the level required for the generation of measurable thermal effects.

  12. X-ray emission of the night terrestrial atmosphere (experiment

    NASA Astrophysics Data System (ADS)

    Pugacheva, Galina; Pankov, Vladislav; Prokhin, Vladimir; Gusev, Anatoly; Spjeldvik, Walther; Martin, Inacio; Pugacheva, Galina

    A spectrometer RPS-1 onboard the LEO "CORONAS-F" satellite monitored solar X-rays in the energy range 3-31.5 keV (31.07.2001 - 06.12.2005 years) using CdTe solid state detector with thermoelectric semiconductor micro cooler. The device registered X-ray emission of the upper atmosphere at shadowed branches of the orbit. When touching the inner radiation belt in the South Atlantic anomaly and at high latitudes the device registered signals produced by energetic trapped particles. Among the other factors determining the flux registered by the device there are solar activity, the Earth position relatively the Sun (seasonality), satellite position, the telescope orientation relatively nadir when entering and leaving the Earth's shadow. This paper presents global maps of the atmospheric X-ray emission in four energy intervals 3-5; 5-8, 8-16, and 16-31.5 keV during the total period from 23.03.2002 up to 23.03.2003 and periods of 23.03.2002-23.09.2002 and 23.09.2002-23.03/2003 corresponding "summer" and "winter" seasons in the Northern hemisphere. The energy of the registered emission does not exceed 8 keV out of the radiation belt. Comparison of the seasonal maps reveals a gap between the radiation belts at low altitudes ( 500km) in the summer of 2002 probably due to compression of the magnetosphere and/or the seasonal atmospheric temperature changesin time period close to the maximum of solar activity and the absence of the gap in summer of 2004 year near to solar activity minimum. A weak emission of 3-5 keV x-rays in the gap within radiation belts is produced by interaction of galactic cosmic rays with the atmosphere.

  13. The Martian atmospheric water cycle as viewed from a terrestrial perspective

    NASA Technical Reports Server (NTRS)

    Zurek, Richard W.

    1988-01-01

    It is noted that the conditions of temperature and pressure that characterize the atmosphere of Mars are similar to those found in the Earth's stratosphere. Of particular significance is the fact that liquid water is unstable in both environments. Thus, it is expected that terrestrial studies of the dynamical behavior of stratospheric water should benefit the understanding of water transport on Mars as well.

  14. Radiative transfer code SHARM for atmospheric and terrestrial applications

    NASA Astrophysics Data System (ADS)

    Lyapustin, A. I.

    2005-12-01

    An overview of the publicly available radiative transfer Spherical Harmonics code (SHARM) is presented. SHARM is a rigorous code, as accurate as the Discrete Ordinate Radiative Transfer (DISORT) code, yet faster. It performs simultaneous calculations for different solar zenith angles, view zenith angles, and view azimuths and allows the user to make multiwavelength calculations in one run. The Δ-M method is implemented for calculations with highly anisotropic phase functions. Rayleigh scattering is automatically included as a function of wavelength, surface elevation, and the selected vertical profile of one of the standard atmospheric models. The current version of the SHARM code does not explicitly include atmospheric gaseous absorption, which should be provided by the user. The SHARM code has several built-in models of the bidirectional reflectance of land and wind-ruffled water surfaces that are most widely used in research and satellite data processing. A modification of the SHARM code with the built-in Mie algorithm designed for calculations with spherical aerosols is also described.

  15. Carbon in the atmosphere and terrestrial biosphere in the 21st century.

    PubMed

    Malhi, Yadvinder

    2002-12-15

    The release of carbon dioxide from fossil-fuel combustion and land-use change has caused a significant perturbation in the natural cycling of carbon between land, atmosphere and oceans. Understanding and managing the effects of this disruption on atmospheric composition and global climate are likely to be amongst the most pressing issues of the 21st century. However, the present-day carbon cycle is still poorly understood. One remarkable feature is that an increasing amount of atmospheric carbon dioxide appears to be being absorbed by terrestrial vegetation. I review the recent evidence for the magnitude and spatial distribution of this 'terrestrial carbon sink', drawing on current research on the global atmospheric distribution and transport of carbon dioxide, oxygen and their isotopes; direct measurement of CO(2) fluxes above various biomes; and inventories of forest biomass and composition. I review the likely causes of these carbon sinks and sources and their implications for the ecology and stability of these biomes. Finally, I examine prospects and key issues over coming decades. Within a few years, satellite measurements of atmospheric CO(2) and forest biomass, coupled with 'real-time' biosphere-atmosphere models, will revolutionize our understanding of the terrestrial carbon cycle. Controlling deforestation and managing forests has the potential to play a significant but limited part in reaching the goal of stabilizing atmospheric CO(2) concentrations. However, there are likely to be limits to the amount of carbon storage possible in natural vegetation, and, in the long term, terrestrial carbon storage may be unstable, with the potential to accelerate rather than brake global warming. PMID:12626274

  16. The Evolution of Stellar Rotation and the Hydrogen Atmospheres of Habitable-zone Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Johnstone, C. P.; Güdel, M.; Stökl, A.; Lammer, H.; Tu, L.; Kislyakova, K. G.; Lüftinger, T.; Odert, P.; Erkaev, N. V.; Dorfi, E. A.

    2015-12-01

    Terrestrial planets formed within gaseous protoplanetary disks can accumulate significant hydrogen envelopes. The evolution of such an atmosphere due to XUV driven evaporation depends on the activity evolution of the host star, which itself depends sensitively on its rotational evolution, and therefore on its initial rotation rate. In this Letter, we derive an easily applicable method for calculating planetary atmosphere evaporation that combines models for a hydrostatic lower atmosphere and a hydrodynamic upper atmosphere. We show that the initial rotation rate of the central star is of critical importance for the evolution of planetary atmospheres and can determine if a planet keeps or loses its primordial hydrogen envelope. Our results highlight the need for a detailed treatment of stellar activity evolution when studying the evolution of planetary atmospheres.

  17. An impact-induced terrestrial atmosphere and iron-water reactions during accretion of the Earth

    NASA Technical Reports Server (NTRS)

    Lange, M. A.; Ahrens, T. J.

    1985-01-01

    Shock wave data and theoretical calculations were used to derive models of an impact-generated terrestrial atmosphere during accretion of the Earth. The models showed that impacts of infalling planetesimals not only provided the entire budget of terrestrial water but also led to a continuous depletion of near-surface layers of water-bearing minerals of their structural water. This resulted in a final atmospheric water reservoir comparable to the present day total water budget of the Earth. The interaction of metallic iron with free water at the surface of the accreting Earth is considered. We carried out model calcualtions simulating these processes during accretion. It is assumed that these processes are the prime source of the terrestrial FeO component of silicates and oxides. It is demonstrated that the iron-water reaction would result in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed. In order to obtain the necessary amount of terrestrial water, slightly heterogeneous accretion with initially 36 wt% iron planetesimals, as compared with a homogeneous value of 34 wt% is required.

  18. PHOTOCHEMISTRY IN TERRESTRIAL EXOPLANET ATMOSPHERES. II. H{sub 2}S AND SO{sub 2} PHOTOCHEMISTRY IN ANOXIC ATMOSPHERES

    SciTech Connect

    Hu Renyu; Seager, Sara; Bains, William

    2013-05-20

    Sulfur gases are common components in the volcanic and biological emission on Earth, and are expected to be important input gases for atmospheres on terrestrial exoplanets. We study the atmospheric composition and the spectra of terrestrial exoplanets with sulfur compounds (i.e., H{sub 2}S and SO{sub 2}) emitted from their surfaces. We use a comprehensive one-dimensional photochemistry model and radiative transfer model to investigate the sulfur chemistry in atmospheres ranging from reducing to oxidizing. The most important finding is that both H{sub 2}S and SO{sub 2} are chemically short-lived in virtually all types of atmospheres on terrestrial exoplanets, based on models of H{sub 2}, N{sub 2}, and CO{sub 2} atmospheres. This implies that direct detection of surface sulfur emission is unlikely, as their surface emission rates need to be extremely high (>1000 times Earth's volcanic sulfur emission) for these gases to build up to a detectable level. We also find that sulfur compounds emitted from the surface lead to photochemical formation of elemental sulfur and sulfuric acid in the atmosphere, which would condense to form aerosols if saturated. For terrestrial exoplanets in the habitable zone of Sun-like stars or M stars, Earth-like sulfur emission rates result in optically thick haze composed of elemental sulfur in reducing H{sub 2}-dominated atmospheres for a wide range of particle diameters (0.1-1 {mu}m), which is assumed as a free parameter in our simulations. In oxidized atmospheres composed of N{sub 2} and CO{sub 2}, optically thick haze, composed of elemental sulfur aerosols (S{sub 8}) or sulfuric acid aerosols (H{sub 2}SO{sub 4}), will form if the surface sulfur emission is two orders of magnitude more than the volcanic sulfur emission of Earth. Although direct detection of H{sub 2}S and SO{sub 2} by their spectral features is unlikely, their emission might be inferred by observing aerosol-related features in reflected light with future generation space

  19. New Data for Early Earth Atmospheric Modelling

    NASA Astrophysics Data System (ADS)

    Blackie, D.; Stark, G.; Lyons, J. R.; Pickering, J.; Smith, P. L.; Thorne, A.

    2010-12-01

    The timing of the oxygenation of the Earth’s atmosphere is a central issue in understanding the Earth’s paleoclimate. The discovery of mass-independent fractionation (MIF) of sulphur isotopes deposited within Archean and Paleoproterozoic rock samples (> 2.4 Gyrs) and the transition to mass-dependent fractionation found in younger samples, could provide a marker for the rise in oxygen concentrations in the Earth’s atmosphere [1]. Laboratory experiments [2; 3] suggest isotopic self shielding during gas phase photolysis of SO2 present at wavelengths shorter than 220 nm as the dominant mechanism for MIF. The UV absorption of SO2 is dominated by the C1B2-X1A1 electronic system which comprises strong vibrational bands extending from 170 - 230 nm. Within an atmosphere consisting of low O2 and O3 concentrations, such as that predicted for the early Earth, UV radiation would penetrate deep into the ancient Earth’s atmosphere in the 180 - 220 nm range driving the photolysis of SO2. We have conducted the first ever high resolution measurements of the photo absorption cross sections of several isotopologues of SO2, namely 32SO2, 33SO2, 34SO2 and 36SO2, using the Imperial College UV Fourier transform spectrometer [4] which is ideal for high resolution, broad-band, VIS/UV measurements. The cross sections are being measured at Imperial College at initial resolutions of 1.0 cm-1 which will be increased to resolutions < 0.5 cm-1 for inclusion in photochemical models of the early Earth’s atmosphere in order to more reliably interpret the sulphur isotope ratios found in ancient rock samples [5]. For discussion and interpretation of the photochemical models see the abstract by Lyons et al.(this meeting). References [1] J. Farquhar and B.A. Wing. Earth and Planetary Science Letters, 213:1-13, 2003. [2] J. Farquhar, J. Savarino, S. Airieau, and M.H Thiemens. Journal of Geophysical Research,106:32829-32839, 2001. [3] A. Pen and R. N. Clayton.Geochimica et Cosmochimica Acta

  20. Retention of an atmosphere on early Mars

    USGS Publications Warehouse

    Carr, M.H.

    1999-01-01

    The presence of valley networks and indications of high erosion rates in ancient terrains on Mars suggest that Mars was warm and wet during heavy bombardment. Various processes that could occur on early Mars were integrated into a self-consistent model to determine what circumstances might lead to warm temperatures during and at the end of heavy bombardment. Included were weathering and burial of CO2 as carbonates, impact erosion, sputtering, and recycling of CO2 back into the atmosphere by burial and heating. The models suggest that despite losses from the atmosphere by weathering and impact erosion, Mars could retain a 0.5 to 1 bar atmosphere at the end of heavy bombardment partly because weathering temporarily sequesters CO2 in the ground and protects it from impact erosion while the impact rate is declining and impact erosion is becoming less effective. Because of the low output of the early Sun, surface temperatures can be above freezing only for a very efficient greenhouse, such as that suggested by Forget and Pierrehumbert [1997]. With weak greenhouse models, temperatures are below freezing throughout heavy bombardment, and such a large amount of CO2 is left in the atmosphere at the end of heavy bombardment that it is difficult to eliminate subsequently to arrive at the present surface inventory. With strong greenhouse models, temperatures are well above freezing during heavy bombardment and drop to close to freezing at the end of heavy bombardment, at which time the atmosphere contains 0.5 to 1 bar of CO2. This can be largely eliminated subsequently by sputtering and low-temperature weathering. Such a model is consistent with the change in erosion rate and the declining rate of valley formation at the end of heavy bombardment. Conditions that favor warm temperatures at the end of heavy bombardment are an efficient greenhouse, low weathering rates, low impact erosion rates, and a smaller fraction of heat lost by conduction as opposed to transport of lava to

  1. Time-Dependent Simulations of the Formation and Evolution of Disk-Accreted Atmospheres Around Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Stoekl, Alexander; Dorfi, Ernst

    2014-05-01

    In the early, embedded phase of evolution of terrestrial planets, the planetary core accumulates gas from the circumstellar disk into a planetary envelope. This atmosphere is very significant for the further thermal evolution of the planet by forming an insulation around the rocky core. The disk-captured envelope is also the staring point for the atmospheric evolution where the atmosphere is modified by outgassing from the planetary core and atmospheric mass loss once the planet is exposed to the radiation field of the host star. The final amount of persistent atmosphere around the evolved planet very much characterizes the planet and is a key criterion for habitability. The established way to study disk accumulated atmospheres are hydrostatic models, even though in many cases the assumption of stationarity is unlikely to be fulfilled. We present, for the first time, time-dependent radiation hydrodynamics simulations of the accumulation process and the interaction between the disk-nebula gas and the planetary core. The calculations were performed with the TAPIR-Code (short for The adaptive, implicit RHD-Code) in spherical symmetry solving the equations of hydrodynamics, gray radiative transport, and convective energy transport. The models range from the surface of the solid core up to the Hill radius where the planetary envelope merges into the surrounding protoplanetary disk. Our results show that the time-scale of gas capturing and atmospheric growth strongly depends on the mass of the solid core. The amount of atmosphere accumulated during the lifetime of the protoplanetary disk (typically a few Myr) varies accordingly with the mass of the planet. Thus, a core with Mars-mass will end up with about 10 bar of atmosphere while for an Earth-mass core, the surface pressure reaches several 1000 bar. Even larger planets with several Earth masses quickly capture massive envelopes which in turn become gravitationally unstable leading to runaway accretion and the eventual

  2. Global and Regional Constraints on Exchanges of CO2 Between the Atmosphere and Terrestrial Biosphere

    NASA Astrophysics Data System (ADS)

    Piper, S. C.

    2001-12-01

    The vigorous atmospheric circulation rapidly mixes CO2 that is exchanged with the terrestrial biosphere and oceans. Therefore, at time scales greater than 1 year, the approximate interhemispheric exchange time of the atmosphere, an average of CO2 measurements from a network of surface stations can be used to accurately determine the global net change in atmospheric CO2. By subtracting CO2 produced by fossil fuel combustion, which is well characterized by national statistics, the global the sum of terrestrial biospheric and oceanic net fluxes, here termed the "nonfossil" CO2 flux, can also be accurately determined. The nonfossil CO2 flux averaged -2.1+/-0.3 PgC/yr and -3.2+/-0.4 PgC/yr in the 1980s and 1990s respectively (negative denotes out of the atmosphere), and varied in annual average from about 0 to -4 PgC/yr over these two decades. Two primary methods have been used to further partition the nonfossil CO2 flux between land and oceans: the O2 and 13C/12C methods, which rely, respectively, on measurements of atmospheric O2 (actually O2/N2 for technical reasons) and of the 13C/12C ratio of CO2. Burning of fossil fuel consumes atmospheric O2 and releases CO2 with a 13C/12C ratio lower than that of atmospheric CO2 whereas uptake of CO2 by terrestrial plants releases O2, and increases the atmospheric 13C/12C ratio owing to the preferential assimilation of 12CO2 relative to 13CO2. In contrast, the uptake of CO2 by the oceans has little effect on either the atmospheric O2 or 13C/12C ratio. Therefore, the net CO2 uptake or release from the terrestrial biosphere can be calculated in either method by subtracting the change owing to fossil fuel emissions from the measured change in the atmosphere, utilizing known stoichiometric ratios of O2 and CO2 in the O2 method, and isotopic fractionation factors in the 13C/12C method. Currently, the O2 method gives a net global terrestrial biospheric CO2 flux of -0.2+/-0.7 PgC/yr and -1.4+/-0.7 PgC/yr for the 1980s and the 1990s

  3. Exploring the control of land-atmospheric oscillations over terrestrial vegetation productivity

    NASA Astrophysics Data System (ADS)

    Depoorter, Mathieu; Green, Julia; Gentine, Pierre; Liu, Yi; van Eck, Christel; Regnier, Pierre; Dorigo, Wouter; Verhoest, Niko; Miralles, Diego

    2015-04-01

    Vegetation dynamics play an important role in the climate system due to their control on the carbon, energy and water cycles. The spatiotemporal variability of vegetation is regulated by internal climate variability as well as natural and anthropogenic forcing mechanisms, including fires, land use, volcano eruptions or greenhouse gas emissions. Ocean-atmospheric oscillations, affect the fluxes of heat and water over continents, leading to anomalies in radiation, precipitation or temperature at widely separated locations (i.e. teleconnections); an effect of ocean-atmospheric oscillations on terrestrial primary productivity can therefore be expected. While different studies have shown the general importance of internal climate variability for global vegetation dynamics, the control by particular teleconnections over the regional growth and decay of vegetation is still poorly understood. At continental to global scales, satellite remote sensing offers a feasible approach to enhance our understanding of the main drivers of vegetation variability. Traditional studies of the multi-decadal variability of global vegetation have been usually based on the normalized difference vegetation index (NDVI) derived from the Advanced Very High Resolution Radiometer (AVHRR), which extends back to the early '80s. There are, however, some limitations to NDVI observations; arguably the most important of these limitations is that from the plant physiology perspective the index does not have a well-defined meaning, appearing poorly correlated to vegetation productivity. On the other hand, recently developed records from other remotely-sensed properties of vegetation, like fluorescence or microwave vegetation optical depth, have proven a significantly better correspondence to above-ground biomass. To enhance our understanding of the controls of ocean-atmosphere oscillations over vegetation, we propose to explore the link between climate oscillation extremes and net primary productivity

  4. Carbon Fluxes Between the Atmosphere, Terrestrial, and River Systems Across a Glacier-Dominated Landscape in Southcentral Alaska

    NASA Astrophysics Data System (ADS)

    Zulueta, R. C.; Welker, J. M.; Tomco, P. L.

    2011-12-01

    The coastal Gulf of Alaska region is experiencing rapid and accelerating changes due to local and regional warming. Predicted high latitude warming may result in rapid recession of glaciers with subsequent changes in river discharge, nutrient fluxes into the rivers, shifts in landscape vegetation cover, and altered CO2 fluxes affecting the regional carbon balance. As glaciers recede an increase in glacier-dominated river discharge and a change in seasonality of the river discharge are expected. Recently deglaciated landscapes will, over time, be occupied by a succession of vegetation cover that are likely to alter the fluxes of carbon both between the atmosphere and terrestrial ecosystems, and between terrestrial ecosystems and stream and river systems. As the landscape evolves from deglaciated forelands it is expected that there is low to no CO2 fluxes between the atmosphere and the recently deglaciated landscape, as well as dissolved organic and inorganic carbon inputs into rivers and streams. These recently deglaciated landscapes will transition to early successional plant species and on towards mature spruce forests. Each transitional terrestrial ecosystem will have different carbon cycling between the atmosphere, terrestrial, and aquatic systems until the mature spruce forests which is expected to have high carbon uptake and sequestration as well as increased inputs of dissolved organic and inorganic carbon into the rivers and streams. A new research project was initiated in the summer of 2011 focusing on glacier-dominated landscapes within the Wrangell-St. Elias National Park and Preserve in southcentral Alaska with the objective to quantify how the transition from deglaciated forelands to mature spruce forests (a successional sequence) alters the patterns and magnitudes of CO2 exchange, the dissolved carbon inputs from terrestrial to aquatic systems and the extent to which these are manifested due to changes in glacier coverage. We seek to examine present

  5. The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of terrestrial ecosystems

    PubMed Central

    Kürschner, Wolfram M.; Kvaček, Zlatko; Dilcher, David L.

    2008-01-01

    The Miocene is characterized by a series of key climatic events that led to the founding of the late Cenozoic icehouse mode and the dawn of modern biota. The processes that caused these developments, and particularly the role of atmospheric CO2 as a forcing factor, are poorly understood. Here we present a CO2 record based on stomatal frequency data from multiple tree species. Our data show striking CO2 fluctuations of ≈600–300 parts per million by volume (ppmv). Periods of low CO2 are contemporaneous with major glaciations, whereas elevated CO2 of 500 ppmv coincides with the climatic optimum in the Miocene. Our data point to a long-term coupling between atmospheric CO2 and climate. Major changes in Miocene terrestrial ecosystems, such as the expansion of grasslands and radiations among terrestrial herbivores such as horses, can be linked to these marked fluctuations in CO2. PMID:18174330

  6. Preliminary experiment requirements document for Solar and Terrestrial Atmospheres Spectrometer (STAS)

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The principal scientific objective of the Solar and Terrestrial Atmospheres Spectrometer (STAS) project is the measurement of the absolute ultraviolet solar spectral irradiance with: (1) resolution of better than 15 mA, and (2) absolute irradiance uncertainty at the state of the art (less than or equal to 3%). High measurement accuracy coupled with high spectral resolution are necessary to identify the nature of the radiation, its variability, and to identify solar processes which may cause the changes. Solar radiation between 1200 and 3600 A dominates the photochemistry of the mesosphere and stratosphere. Some important minor species, such as NO, show very complex and fundamentally narrow structure in their photodestruction cross sections, especially in the region of the Schumann-Runge bands of O2. Understanding the photochemical processes in the terrestrial atmosphere requires knowledge of both the cross sections and of the solar spectrum with the highest possible resolution and accuracy.

  7. The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of terrestrial ecosystems.

    PubMed

    Kürschner, Wolfram M; Kvacek, Zlatko; Dilcher, David L

    2008-01-15

    The Miocene is characterized by a series of key climatic events that led to the founding of the late Cenozoic icehouse mode and the dawn of modern biota. The processes that caused these developments, and particularly the role of atmospheric CO2 as a forcing factor, are poorly understood. Here we present a CO2 record based on stomatal frequency data from multiple tree species. Our data show striking CO2 fluctuations of approximately 600-300 parts per million by volume (ppmv). Periods of low CO2 are contemporaneous with major glaciations, whereas elevated CO2 of 500 ppmv coincides with the climatic optimum in the Miocene. Our data point to a long-term coupling between atmospheric CO2 and climate. Major changes in Miocene terrestrial ecosystems, such as the expansion of grasslands and radiations among terrestrial herbivores such as horses, can be linked to these marked fluctuations in CO2. PMID:18174330

  8. Atmospheric circulation modeling of super Earths and terrestrial extrasolar planets using the SPARC/MITgcm

    NASA Astrophysics Data System (ADS)

    Kataria, T.; Showman, A. P.; Haberle, R. M.; Marley, M. S.; Fortney, J. J.; Freedman, R. S.

    2013-12-01

    The field of exoplanets continues to be a booming field of research in astronomy and planetary science, with numerous ground-based (e.g., SuperWASP, HARPS-N and S) and space-based surveys (e.g., Kepler) that detect and characterize planets ranging from hot Jupiters, Jovian-sized planets orbiting less than 0.1 AU from their star, to super Earths and terrestrial exoplanets, planets that have masses equal to or less than 10 times that of Earth with a range of orbital distances. Atmospheric circulation modeling plays an important role in the characterization of these planets, helping to constrain observations that probe their atmospheres. These models have proven successful in understanding observations of transiting exoplanets (when the planet passes in front of the star along our line of sight) particularly when the planet is passing through secondary eclipse (when the planet's dayside is visible). In modeling super Earths and terrestrial exoplanets, we must consider not only planets with thick fluid envelopes, but also traditional terrestrial planets with solid surfaces and thinner atmospheres. To that end, we present results from studies investigating the atmospheric circulation of these classes of planets using the SPARC/MITgcm, a state-of-the-art model which couples the MIT General Circulation Model with a plane-parallel, two-stream, non-gray radiative transfer model. We will present results from two studies, the first focusing on the circulation of GJ 1214b, a super-Earth detected by the MEarth ground-based survey, and a second study which explores the circulation of terrestrial exoplanets orbiting M-dwarfs.

  9. Relevance of O2 and O3 as biomarkers in terrestrial exoplanet atmospheres

    NASA Astrophysics Data System (ADS)

    Kieken, J.; Selsis, F.; Despois, D.; Billebaud, F.; Dobrijevic, M.; Parisot, J. P.; Bordeaux Observatory Team

    2001-11-01

    Darwin (ESA) and Terrestrial Planet Finder-TPF (NASA) are two projects of space interferometers aiming at the detection of extra-solar terrestrial planets and some of their atmospheric components. In particular, they will be sensitive to the 9.6 microns band of O3 which may be the signature of an O2-rich atmosphere produced by photosynthetic life forms. We point out that O2, and hence O3, can also be produced by photochemistry and investigate the risk of "false positive" detection of life incurred by these missions. We have developed a numerical model for the simulation of chemical and thermal evolution of terrestrial planet atmospheres, which also computes the thermal emission of the planet. Using this code for a large range of realistic atmospheres (including present and past Earth and Mars), we show that O2-rich atmospheres (up to 5 %) and IR absorbing O3 layers can build up without life from H2O and CO2 photolysis. However the two photochemical sources of O2 interfere with each other, and even when appreciable amounts of abiotic O2 are reached, the O3 feature is masked at CO2 pressure higher than 50 mbar, and the by-products of H2O photolysis destroy O3. As a result, whereas the unique detection of O2 remains ambiguous, the simultaneous infrared detection of O2, CO2 and H2O, provided by TPF and Darwin, is established to be a robust way to discriminate photochemical O2 production from biological photosynthesis: none of the atmospheres modelled exhibits this "triple signature" feature, even in the most extreme "high risk" cases.

  10. The molecular composition of impact-generated atmospheres on terrestrial planets during the post-accretion stage

    NASA Astrophysics Data System (ADS)

    Kuwahara, Hideharu; Sugita, Seiji

    2015-09-01

    Both geochemical measurements and theoretical calculations suggest that impact degassing from meteoritic materials after the completion of main phase of planetary accretion may have produced a large fraction of the early terrestrial atmospheres. However, the molecular compositions of such impact-generated atmospheres are not well constrained because the thermodynamic cooling path, which controls the chemical reactions in impact-induced vapor, has not been investigated extensively. In this study, we theoretically assess the chemical reactions within impact-induced vapor that cools adiabatically until the pressure equilibrates with the ambient atmosphere. The calculation results indicate that there are two primary controlling factors for the cooling path: impact entropy gain and atmospheric pressure. The former is mainly determined by both impact velocity and the presence/absence of an ocean. The degree of atmospheric effect depends on vapor plume size. For large impacts, atmospheric containment of vapor expansion is inefficient. However, the expansion of small vapor plumes is contained by the pre-existing atmosphere and their terminal molecular composition is controlled by this process. This is because whether a chemical reaction quenches during adiabatic cooling or during subsequent radiative cooling would depend on the cooling transition temperature, at which adiabatic expansion stops and radiative cooling takes over. For high atmospheric pressures and/or the vapor generated by high-velocity impacts, adiabatic expansion will cease at higher temperatures than typical quenching temperatures. Thus, the molecular composition of the vapor will not greatly depend on the impact velocity. The calculation results suggest that the molecular composition of the impact-induced vapor would vary widely (i.e., CH4/CO ratios) even if the compositions of the impactors are the same. More specifically, the impact-induced vapor generated by lower velocity impacts may be rich in CH4

  11. Evaluation of atmospheric aerosol and tropospheric ozone effects on global terrestrial ecosystem carbon dynamics

    NASA Astrophysics Data System (ADS)

    Chen, Min

    The increasing human activities have produced large amounts of air pollutants ejected into the atmosphere, in which atmospheric aerosols and tropospheric ozone are considered to be especially important because of their negative impacts on human health and their impacts on global climate through either their direct radiative effect or indirect effect on land-atmosphere CO2 exchange. This dissertation dedicates to quantifying and evaluating the aerosol and tropospheric ozone effects on global terrestrial ecosystem dynamics using a modeling approach. An ecosystem model, the integrated Terrestrial Ecosystem Model (iTem), is developed to simulate biophysical and biogeochemical processes in terrestrial ecosystems. A two-broad-band atmospheric radiative transfer model together with the Moderate-Resolution Imaging Spectroradiometer (MODIS) measured atmospheric parameters are used to well estimate global downward solar radiation and the direct and diffuse components in comparison with observations. The atmospheric radiative transfer modeling framework were used to quantify the aerosol direct radiative effect, showing that aerosol loadings cause 18.7 and 12.8 W m -2 decrease of direct-beam Photosynthetic Active Radiation (PAR) and Near Infrared Radiation (NIR) respectively, and 5.2 and 4.4 W m -2 increase of diffuse PAR and NIR, respectively, leading to a total 21.9 W m-2 decrease of total downward solar radiation over the global land surface during the period of 2003-2010. The results also suggested that the aerosol effect may be overwhelmed by clouds because of the stronger extinction and scattering ability of clouds. Applications of the iTem with solar radiation data and with or without considering the aerosol loadings shows that aerosol loading enhances the terrestrial productions [Gross Primary Production (GPP), Net Primary Production (NPP) and Net Ecosystem Production (NEP)] and carbon emissions through plant respiration (RA) in global terrestrial ecosystems over the

  12. XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part I: Atmospheric Expansion and Thermal Escape

    PubMed Central

    Lammer, Helmut; Odert, Petra; Kulikov, Yuri N.; Kislyakova, Kristina G.; Khodachenko, Maxim L.; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-01-01

    Abstract The recently discovered low-density “super-Earths” Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H2O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 REarth and a mass of 10 MEarth. We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general. Key Words: Stellar activity—Low-mass stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1011–1029. PMID:24251443

  13. Atmospheric Dispersal of Bioactive Streptomyces albidoflavus Strains Among Terrestrial and Marine Environments.

    PubMed

    Sarmiento-Vizcaíno, Aida; Braña, Alfredo F; González, Verónica; Nava, Herminio; Molina, Axayacatl; Llera, Eva; Fiedler, Hans-Peter; Rico, José M; García-Flórez, Lucía; Acuña, José L; García, Luis A; Blanco, Gloria

    2016-02-01

    Members of the Streptomyces albidoflavus clade, identified by 16S rRNA sequencing and phylogenetic analyses, are widespread among predominant terrestrial lichens (Flavoparmelia caperata and Xanthoria parietina) and diverse intertidal and subtidal marine macroalgae, brown red and green (Phylum Heterokontophyta, Rhodophyta, and Chlorophyta) from the Cantabrian Cornice. In addition to these terrestrial and coastal temperate habitats, similar strains were also found to colonize deep-sea ecosystems and were isolated mainly from gorgonian and solitary corals and other invertebrates (Phylum Cnidaria, Annelida, Echinodermata, Arthropoda, and Porifera) living up to 4700-m depth and at a temperature of 2-4 °C in the submarine Avilés Canyon. Similar strains have been also repeatedly isolated from atmospheric precipitations (rain drops, snow, and hailstone) collected in the same area throughout a year observation time. These ubiquitous strains were found to be halotolerant, psychrotolerant, and barotolerant. Bioactive compounds with diverse antibiotic and cytotoxic activities produced by these strains were identified by high-performance liquid chromatography (HPLC) and database comparison. These include antibacterials (paulomycins A and B), antifungals (maltophilins), antifungals displaying also cytotoxic activities (antimycins and 6-epialteramides), and the antitumor compound fredericamycin. A hypothetical dispersion model is here proposed to explain the biogeographical distribution of S. albidoflavus strains in terrestrial, marine, and atmospheric environments. PMID:26224165

  14. Nitrogen Fixation on Early Mars and Other Terrestrial Planets: Experimental Demonstration of Abiotic Fixation Reactions to Nitrite and Nitrate

    NASA Astrophysics Data System (ADS)

    Summers, David P.; Khare, Bishun

    2007-05-01

    Understanding the abiotic fixation of nitrogen is critical to understanding planetary evolution and the potential origin of life on terrestrial planets. Nitrogen, an essential biochemical element, is certainly necessary for life as we know it to arise. The loss of atmospheric nitrogen can result in an incapacity to sustain liquid water and impact planetary habitability and hydrological processes that shape the surface. However, our current understanding of how such fixation may occur is almost entirely theoretical. This work experimentally examines the chemistry, in both gas and aqueous phases, that would occur from the formation of NO and CO by the shock heating of a model carbon dioxide/nitrogen atmosphere such as is currently thought to exist on early terrestrial planets. The results show that two pathways exist for the abiotic fixation of nitrogen from the atmosphere into the crust: one via HNO and another via NO2. Fixation via HNO, which requires liquid water, could represent fixation on a planet with liquid water (and hence would also be a source of nitrogen for the origin of life). The pathway via NO2 does not require liquid water and shows that fixation could occur even when liquid water has been lost from a planet's surface (for example, continuing to remove nitrogen through NO2 reaction with ice, adsorbed water, etc.).

  15. Historical space psychology: Early terrestrial explorations as Mars analogues

    NASA Astrophysics Data System (ADS)

    Suedfeld, Peter

    2010-03-01

    The simulation and analogue environments used by psychologists to circumvent the difficulties of conducting research in space lack many of the unique characteristics of future explorations, especially the mission to Mars. This paper suggests that appropriate additional analogues would be the multi-year maritime and terrestrial explorations that mapped the surface of the Earth in previous centuries. These, like Mars, often involved a hazardous trek through unknown territory, flanked by extended, dangerous voyages to and from the exploration sites. Characteristic issues included interpersonal relationships under prolonged stress, stretches of boredom interspersed with intense work demands, the impossibility of rescue, resupply, or other help from home, chronic danger, physical discomfort and lack of privacy, and the crucial role of the leader. Illustrative examples of one important factor, leadership style, are discussed. The examination of such expeditions can help to identify the psychological stressors that are likely to be experienced by Mars explorers, and can also indicate countermeasures to reduce the damaging impact of those stressors.

  16. Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies.

    PubMed

    Behera, Sailesh N; Sharma, Mukesh; Aneja, Viney P; Balasubramanian, Rajasekhar

    2013-11-01

    Gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH3 emissions is agriculture, including animal husbandry and NH3-based fertilizer applications. Other sources of NH3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH3. Over the last two decades, a number of research papers have addressed pertinent issues related to NH3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH3 from the literature in a systematic manner, describes the environmental implications of unabated NH3 emissions and provides a scientific basis for developing effective control strategies for NH3. PMID:23982822

  17. Nested atmospheric inversion for the terrestrial carbon sources and sinks in China

    NASA Astrophysics Data System (ADS)

    Jiang, F.; Wang, H. W.; Chen, J. M.; Zhou, L. X.; Ju, W. M.; Ding, A. J.; Liu, L. X.; Peters, W.

    2013-08-01

    In this study, we establish a nested atmospheric inversion system with a focus on China using the Bayesian method. The global surface is separated into 43 regions based on the 22 TransCom large regions, with 13 small regions in China. Monthly CO2 concentrations from 130 GlobalView sites and 3 additional China sites are used in this system. The core component of this system is an atmospheric transport matrix, which is created using the TM5 model with a horizontal resolution of 3° × 2°. The net carbon fluxes over the 43 global land and ocean regions are inverted for the period from 2002 to 2008. The inverted global terrestrial carbon sinks mainly occur in boreal Asia, South and Southeast Asia, eastern America and southern South America. Most China areas appear to be carbon sinks, with strongest carbon sinks located in Northeast China. From 2002 to 2008, the global terrestrial carbon sink has an increasing trend, with the lowest carbon sink in 2002. The inter-annual variation (IAV) of the land sinks shows remarkable correlation with the El Niño Southern Oscillation (ENSO). The terrestrial carbon sinks in China also show an increasing trend. However, the IAV in China is not the same as that of the globe. There is relatively stronger land sink in 2002, lowest sink in 2006, and strongest sink in 2007 in China. This IAV could be reasonably explained with the IAVs of temperature and precipitation in China. The mean global and China terrestrial carbon sinks over the period 2002-2008 are -3.20 ± 0.63 and -0.28 ± 0.18 PgC yr-1, respectively. Considering the carbon emissions in the form of reactive biogenic volatile organic compounds (BVOCs) and from the import of wood and food, we further estimate that China's land sink is about -0.31 PgC yr-1.

  18. Prebiotic chemistry and atmospheric warming of early Earth by an active young Sun

    NASA Astrophysics Data System (ADS)

    Airapetian, V. S.; Glocer, A.; Gronoff, G.; Hébrard, E.; Danchi, W.

    2016-06-01

    Nitrogen is a critical ingredient of complex biological molecules. Molecular nitrogen, however, which was outgassed into the Earth’s early atmosphere, is relatively chemically inert and nitrogen fixation into more chemically reactive compounds requires high temperatures. Possible mechanisms of nitrogen fixation include lightning, atmospheric shock heating by meteorites, and solar ultraviolet radiation. Here we show that nitrogen fixation in the early terrestrial atmosphere can be explained by frequent and powerful coronal mass ejection events from the young Sun--so-called superflares. Using magnetohydrodynamic simulations constrained by Kepler Space Telescope observations, we find that successive superflare ejections produce shocks that accelerate energetic particles, which would have compressed the early Earth’s magnetosphere. The resulting extended polar cap openings provide pathways for energetic particles to penetrate into the atmosphere and, according to our atmospheric chemistry simulations, initiate reactions converting molecular nitrogen, carbon dioxide and methane to the potent greenhouse gas nitrous oxide as well as hydrogen cyanide, an essential compound for life. Furthermore, the destruction of N2, CO2 and CH4 suggests that these greenhouse gases cannot explain the stability of liquid water on the early Earth. Instead, we propose that the efficient formation of nitrous oxide could explain a warm early Earth.

  19. Atmospheric General Circulations of Synchronously Rotating Terrestrial Planets: Dependence on Planetary Rotation Rate

    NASA Astrophysics Data System (ADS)

    Noda, S.; Ishiwatari, M.; Nakajima, K.; Takahashi, Y. O.; Morikawa, Y.; Nishizawa, S.; Hayashi, Y.-Y.

    2012-04-01

    In order to investigate a variety of climates of synchronously rotating terrestrial planets, a parameter study on the dependence on planetary rotation rate Ω is performed by using a general circulation model (GCM) with simplified hydrologic and radiative processes. The planetary rotation rate is varied from zero to the Earth's value, and other parameters such as orbital parameters, planetary radius, solar constant are set to the Earth's values. The results show that there emerge four typical atmospheric states in ascending order of planetary rotation rate as follows: States in which dayside-nightside direct circulations dominate States in which weak super rotation emerges States in which strong super rotation emerges and meridionally asymmetric patterns oscillate States in which precipitation disturbances emerge in nightside midlatitudinal regions The atmospheric state is gradually accompanied by a qualitative circulation change from state (1) to state (3) with increasing Ω from zero, although Merlis and Schneider (2010) which performed similar GCM experiments lump together cases with small planetary rotation rates under the term "slowly rotating atmospheres". For cases for planetary rotation rate with the values of 0.75-0.85 times of the terrestrial value, multiple equilibrium solutions of state (3) and state (4) are obtained. It is shown that, in addition to dry atmosphere (Edson et al., 2011), moist atmospheres on synchronously rotating planet also have multiple equilibrium solutions. Although circulation patterns and amount of sensible/latent heat transport from the dayside to the nightside changes with the change of Ω, summation of sensible heat transport and latent heat transport almost remains unchanged, and the dependence of dayside to nightside temperature contrast on Ω is small.

  20. Flux of water vapor in the terrestrial stratosphere and in the Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Leovy, Conway; Hitchman, Matthew; Mccleese, Daniel J.

    1988-01-01

    A summary of the terrestrial satellite data is presented. The observations indicate that at equatorial latitudes, relatively dry air is introduced at the tropopause and carried to the upper stratosphere. At that altitude, any methane present in the ascending air mass is oxidized photochemically into water vapor. This vapor is eventually transported to high latitudes, where it is carried to the lower stratosphere by the descending leg of the diabatic circulation. The Pressure Modulator Infrared Radiometer instrument aboard the Mars Observer should provide a comparable picture of vapor transport in the martian atmosphere.

  1. Trophic network models explain instability of Early Triassic terrestrial communities

    PubMed Central

    Roopnarine, Peter D; Angielczyk, Kenneth D; Wang, Steve C; Hertog, Rachel

    2007-01-01

    Studies of the end-Permian mass extinction have emphasized potential abiotic causes and their direct biotic effects. Less attention has been devoted to secondary extinctions resulting from ecological crises and the effect of community structure on such extinctions. Here we use a trophic network model that combines topological and dynamic approaches to simulate disruptions of primary productivity in palaeocommunities. We apply the model to Permian and Triassic communities of the Karoo Basin, South Africa, and show that while Permian communities bear no evidence of being especially susceptible to extinction, Early Triassic communities appear to have been inherently less stable. Much of the instability results from the faster post-extinction diversification of amphibian guilds relative to amniotes. The resulting communities differed fundamentally in structure from their Permian predecessors. Additionally, our results imply that changing community structures over time may explain long-term trends like declining rates of Phanerozoic background extinction PMID:17609191

  2. Buildup of Abiotic Oxygen and Ozone in Atmospheres of Temperate Terrestrial Exoplanets

    NASA Astrophysics Data System (ADS)

    Kleinboehl, Armin; Willacy, Karen; Friedson, Andrew James; Swain, Mark R.

    2015-12-01

    The last two decades have seen a rapid increase in the detection and characterization of exoplanets. A focus of future missions will be on the subset of transiting, terrestrial, temperate exoplanets as they are the strongest candidates to harbor life as we know it.An important bioindicator for life as we know it is the existence of significant amounts of oxygen, and its photochemical byproduct ozone, in the exoplanet’s atmosphere. However, abiotic processes also produce oxygen and ozone, and the amount of oxygen abiotically produced in an atmosphere will largely depend on other atmospheric parameters. Constraining this parameter space will be essential to avoid ‘false positive’ detections of life, that is the interpretation of oxygen or ozone as a bioindicator despite being produced abiotically.Based on 1D radiative-convective model calculations, Wordsworth and Pierrehumbert (ApJL, 2014) recently pointed out that the formation and buildup of abiotic oxygen on water-rich planets largely depends on the amount of non-condensable gases in the atmosphere. The amount of non-condensable gases determines whether an atmosphere will develop a 'cold-trap' (similar to the tropopause on Earth) that contains most of the water in the lower atmosphere and dries out the upper atmosphere. If water vapor is a major constituent of the atmosphere, this cold-trapping is inhibited, leading to a much moister upper atmosphere. Water vapor in the upper atmosphere is photolyzed due to the availability of hard UV radiation, yielding oxygen.We use a photochemical model coupled to a 1D radiative-convective climate model to self-consistently study this effect in atmospheres with N2, CO2 and H2O as the main constituents. These are typical constituents for secondary, oxidized atmospheres, and they can exist in a wide range of ratios. We calculate the amounts of abiotically produced oxygen and ozone and determine the vertical structure of temperature and constituent mixing ratios for various

  3. Modeling the terrestrial hydrology for the global atmosphere - The future role of satellite data

    NASA Technical Reports Server (NTRS)

    Lin, J. D.; Bock, P.; Alfano, J. J.

    1981-01-01

    A global terrestrial hydrology model has been developed for the transport and storage of moisture and heat in the ground surface layer where the hydrological parameters react to diurnal and seasonal changes in the atmosphere. The spatial and temporal variability of land surface features is considered in the model by means of large scale parameterizations. The model can be either forced by the atmosphere using conventional meteorological data or coupled to an atmospheric general circulation model (GCM) for interactive studies. The global surface is divided into 4 deg longitude by 5 deg latitude cells while the ground is represented by a thin surface layer, a bulk layer (the root zone), and a deep layer (the ground water zone). Results are presented from a seven-day global experiment which was conducted utilizing the GLAS GCM (NASA Goddard Laboratory for Atmospheric Sciences). The model has demonstrated its capability to predict, over a large region, the overall soil moisture storage and major flux exchanges with the atmosphere above and the ground water below.

  4. Sulfur Chemistry in the Early and Present Atmosphere of Mars

    NASA Technical Reports Server (NTRS)

    Levine, Joel S.; Summers, M. E.

    2011-01-01

    Atmospheric sulfur species resulting from volcanic emissions impact the composition and chemistry of the atmosphere, impact the climate, and hence, the habitability of Mars and impact the mineralogy and composition of the surface of Mars. The geochemical/ photochemical cycling of sulfur species between the interior (via volcanism), the atmosphere (atmospheric photochemical and chemical processes) and the deposition of sulfuric acid on the surface of Mars is an important, but as yet poorly understood geochemical/ photochemical cycle on Mars. There is no observational evidence to indicate that Mars is volcanically active at the present time, however, there is strong evidence that volcanism was an important and widespread process on early Mars. The chemistry and photochemistry of sulfur species in the early and present atmosphere of Mars will be assessed using a one-dimensional photochemical model. Since it is generally assumed that the atmosphere of early Mars was significantly denser than the present 6-millibar atmosphere, photochemical calculations were performed for the present atmosphere and for the atmosphere of early Mars with assumed surface pressures of 60 and 350-millibars, where higher surface pressure resulted from enhanced atmospheric concentrations of carbon dioxide (CO2). The following sections include the results of earlier modeling studies, a summary of the one-dimensional photochemical model used in this study, a summary of the photochemistry and chemistry of sulfur species in the atmosphere of Mars and some of the results of the calculations.

  5. Global scale water isotope observations and the impact of the terrestrial biosphere on atmospheric hydrology

    NASA Astrophysics Data System (ADS)

    Noone, D. `; Brown, D.; Worden, J.

    2007-12-01

    Water isotope measurements are known to be extremely useful for identifying hydrologic exchange processes at both single site scales and at larger scales from networks of, for instance, precipitation. Recent advances in observational techniques have allowed the development of a global scale dataset of the HDO to H2O isotope ratio in lower troposphere from spacecraft. The HDO estimates are found though a spectroscopic retrieval based on high resolution and well calibrated infrared spectra obtained from the Tropospheric Emission Spectrometer (TES) on NASA's Aura spacecraft. With these global scale observations available almost every two days, the ability to use isotopes to understand the impact of the terrestrial biosphere on atmospheric hydrology has become a possibility at not just local scales but for large geographic regions. Simulating the isotope exchange in global climate models continues to advance, but now such models can for the first time be validated and tested with observations. Further, with models, the importance of the processes identified in the observational data can be assessed in detail. Of particular interest is identifying the terrestrial source of atmospheric water vapor, and specifically continental evapotransipration. Using a combination of the satellite observations and model simulations, we identify the terrestrial source of atmospheric water, and demonstrate its importance is larger than previously recognized. This can be deduced from the observations since the isotopic signature of transpired water reflects the isotopic composition of precipitation, while that of oceanic origin reflects the disequilibrium fractionation during evaporation from the ocean. Based on these results and guided by model simulations, we speculate that should the land use characteristics of the tropical continental regions change, and reflect more arid environments, the impacts on the atmospheric hydrology and climate is more than of just local in extent. The use

  6. The Heat-Pipe Hypothesis for Early Crustal Development of Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Webb, A. G.; Moore, W. B.; Simon, J. I.

    2014-12-01

    Crusts of the terrestrial planets other than Earth are dominated by mafic / ultramafic volcanics, with some contractional tectonics and minor extension. This description may also fit the early Earth. Therefore, a single process may have controlled early crustal development. Here we explore the hypothesis that heat-pipe cooling mode dominates early phases of terrestrial planet evolution. Volcanism is the hallmark of heat-pipe cooling: hot magma moves through the lithosphere in narrow channels, then is deposited and cools at the surface. A heat-pipe planet develops a thick, cold, downward-advecting lithosphere dominated by mafic/ultra-mafic flows. Contractional deformation occurs throughout the lithosphere as the surface is buried and forced toward smaller radii. Geologies of the Solar system's terrestrial planets are consistent with early heat-pipe cooling. Mercury's surface evolution is dominated by low-viscosity volcanism until ~4.1-4.0 Ga, with little activity other than global contraction since. Similar, younger features at Venus are commonly interpreted in terms of catastrophic resurfacing events with ~0.5 billion-year periodicity, but early support of high topography suggests a transition from heat-pipe to rigid-lid tectonics. Thick heat-pipe lithosphere may preserve the crustal dichotomy between Mars' northern and southern hemispheres, and explain the range in trace element abundances and isotopic compositions of Martian meteorites. At the Moon, global serial volcanism can explain refinement of ferroan anorthite rich rocks and coeval production of the "Mg-suite" rocks. The Moon's shape is out of hydrostatic equilibrium; it may represent a fossil preserved by thick early lithosphere. Active development of Jupiter's moon Io, which is warmed by tidal heating, is widely interpreted in terms of heat-pipe cooling. Given its potential ubiquity in the Solar system, heat-pipe cooling may be a universal process experienced by all terrestrial bodies of sufficient size.

  7. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.

    PubMed

    Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

    2010-11-23

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  8. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

    PubMed Central

    Shaheen, R.; Abramian, A.; Horn, J.; Dominguez, G.; Sullivan, R.; Thiemens, Mark H.

    2010-01-01

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4–3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O3 reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  9. The terrestrial biosphere as a net source of greenhouse gases to the atmosphere

    NASA Astrophysics Data System (ADS)

    Tian, Hanqin; Lu, Chaoqun; Ciais, Philippe; Michalak, Anna M.; Canadell, Josep G.; Saikawa, Eri; Huntzinger, Deborah N.; Gurney, Kevin R.; Sitch, Stephen; Zhang, Bowen; Yang, Jia; Bousquet, Philippe; Bruhwiler, Lori; Chen, Guangsheng; Dlugokencky, Edward; Friedlingstein, Pierre; Melillo, Jerry; Pan, Shufen; Poulter, Benjamin; Prinn, Ronald; Saunois, Marielle; Schwalm, Christopher R.; Wofsy, Steven C.

    2016-03-01

    The terrestrial biosphere can release or absorb the greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and therefore has an important role in regulating atmospheric composition and climate. Anthropogenic activities such as land-use change, agriculture and waste management have altered terrestrial biogenic greenhouse gas fluxes, and the resulting increases in methane and nitrous oxide emissions in particular can contribute to climate change. The terrestrial biogenic fluxes of individual greenhouse gases have been studied extensively, but the net biogenic greenhouse gas balance resulting from anthropogenic activities and its effect on the climate system remains uncertain. Here we use bottom-up (inventory, statistical extrapolation of local flux measurements, and process-based modelling) and top-down (atmospheric inversions) approaches to quantify the global net biogenic greenhouse gas balance between 1981 and 2010 resulting from anthropogenic activities and its effect on the climate system. We find that the cumulative warming capacity of concurrent biogenic methane and nitrous oxide emissions is a factor of about two larger than the cooling effect resulting from the global land carbon dioxide uptake from 2001 to 2010. This results in a net positive cumulative impact of the three greenhouse gases on the planetary energy budget, with a best estimate (in petagrams of CO2 equivalent per year) of 3.9 ± 3.8 (top down) and 5.4 ± 4.8 (bottom up) based on the GWP100 metric (global warming potential on a 100-year time horizon). Our findings suggest that a reduction in agricultural methane and nitrous oxide emissions, particularly in Southern Asia, may help mitigate climate change.

  10. The terrestrial biosphere as a net source of greenhouse gases to the atmosphere

    DOE PAGESBeta

    Tian, Hanqin; Lu, Chaoqun; Ciais, Philippe; Michalak, Anna M.; Canadell, Josep G.; Saikawa, Eri; Huntzinger, Deborah N.; Gurney, Kevin R; Sitch, Stephen; Zhang, Bowen; et al

    2016-03-09

    The terrestrial biosphere can release or absorb the greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and therefore has an important role in regulating atmospheric composition and climate1. Anthropogenic activities such as land-use change, agriculture and waste management have altered terrestrial biogenic greenhouse gas fluxes, and the resulting increases in methane and nitrous oxide emissions in particular can contribute to climate change2, 3. The terrestrial biogenic fluxes of individual greenhouse gases have been studied extensively4, 5, 6, but the net biogenic greenhouse gas balance resulting from anthropogenic activities and its effect on the climate system remains uncertain.more » Here we use bottom-up (inventory, statistical extrapolation of local flux measurements, and process-based modelling) and top-down (atmospheric inversions) approaches to quantify the global net biogenic greenhouse gas balance between 1981 and 2010 resulting from anthropogenic activities and its effect on the climate system. We find that the cumulative warming capacity of concurrent biogenic methane and nitrous oxide emissions is a factor of about two larger than the cooling effect resulting from the global land carbon dioxide uptake from 2001 to 2010. This results in a net positive cumulative impact of the three greenhouse gases on the planetary energy budget, with a best estimate (in petagrams of CO2 equivalent per year) of 3.9 ± 3.8 (top down) and 5.4 ± 4.8 (bottom up) based on the GWP100 metric (global warming potential on a 100-year time horizon). Lastly, our findings suggest that a reduction in agricultural methane and nitrous oxide emissions, particularly in Southern Asia, may help mitigate climate change.« less

  11. The terrestrial biosphere as a net source of greenhouse gases to the atmosphere.

    PubMed

    Tian, Hanqin; Lu, Chaoqun; Ciais, Philippe; Michalak, Anna M; Canadell, Josep G; Saikawa, Eri; Huntzinger, Deborah N; Gurney, Kevin R; Sitch, Stephen; Zhang, Bowen; Yang, Jia; Bousquet, Philippe; Bruhwiler, Lori; Chen, Guangsheng; Dlugokencky, Edward; Friedlingstein, Pierre; Melillo, Jerry; Pan, Shufen; Poulter, Benjamin; Prinn, Ronald; Saunois, Marielle; Schwalm, Christopher R; Wofsy, Steven C

    2016-03-10

    The terrestrial biosphere can release or absorb the greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and therefore has an important role in regulating atmospheric composition and climate. Anthropogenic activities such as land-use change, agriculture and waste management have altered terrestrial biogenic greenhouse gas fluxes, and the resulting increases in methane and nitrous oxide emissions in particular can contribute to climate change. The terrestrial biogenic fluxes of individual greenhouse gases have been studied extensively, but the net biogenic greenhouse gas balance resulting from anthropogenic activities and its effect on the climate system remains uncertain. Here we use bottom-up (inventory, statistical extrapolation of local flux measurements, and process-based modelling) and top-down (atmospheric inversions) approaches to quantify the global net biogenic greenhouse gas balance between 1981 and 2010 resulting from anthropogenic activities and its effect on the climate system. We find that the cumulative warming capacity of concurrent biogenic methane and nitrous oxide emissions is a factor of about two larger than the cooling effect resulting from the global land carbon dioxide uptake from 2001 to 2010. This results in a net positive cumulative impact of the three greenhouse gases on the planetary energy budget, with a best estimate (in petagrams of CO2 equivalent per year) of 3.9 ± 3.8 (top down) and 5.4 ± 4.8 (bottom up) based on the GWP100 metric (global warming potential on a 100-year time horizon). Our findings suggest that a reduction in agricultural methane and nitrous oxide emissions, particularly in Southern Asia, may help mitigate climate change. PMID:26961656

  12. Day-night Temperature Gradients and Atmospheric Collapse on Synchronously Rotating Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Koll, D. D. B.; Abbot, D. S.

    2015-12-01

    Terrestrial exoplanets orbiting small host stars are abundant and are also the most promising observational targets for finding life outside our Solar system. Due to their close-in orbits, these planets experience significant tidal interactions with their host stars and will tend to evolve towards spin-orbit resonances or synchronous rotation (=tidally locked). Synchronous rotation has a number of interesting implications for habitability, including the potential for atmospheric collapse on the night side if the surface temperature drops below the condensation point of the gases in the atmosphere. To understand the habitability of synchronously rotating planets, it is therefore important to work out a theory of their temperature and wind structure. Many of these planets will be rotating slowly enough that the well-known weak-temperature-gradient theory holds in the free atmosphere, but even for these planets this theory does not constrain the maximum surface temperature gradient, the planets' thermal phase curve signature, or the threshold for atmospheric collapse. Here we study tidally locked planets using theory and a large array of simulations in a global climate model (GCM) with grey radiative transfer and a full boundary layer scheme. We derive a theory for surface temperatures and atmospheric circulation on synchronously rotating planets that allows us to predict the night-side surface temperature and determine whether atmospheric collapse will occur. We find that atmospheric collapse is sensitive to both the ratio of the Rossby radius to the planetary radius and the ratio of the surface drag timescale to the radiative cooling timescale.

  13. Stability of CO2 Atmospheres on Terrestrial Exoplanets in the Proximity of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Gao, P.; Hu, R.; Yung, Y. L.

    2013-12-01

    M dwarfs are promising targets for the search and characterization of terrestrial exoplanets that might be habitable, as the habitable planets around M dwarfs are in much more close-in orbits compared to their counterparts around Sun-like stars. CO2, one of the most important greenhouse gases on our planet, is conventionally adopted as a major greenhouse gas in studying the habitability of terrestrial exoplanets around M dwarfs. However, the stability of CO2 in terrestrial atmospheres has been called into question due to the high FUV/NUV flux ratio of some M dwarfs in comparison to that of Sun-like stars. While CO2 is photolyzed into CO and O by photons in the FUV, with O2 forming from the O atoms through third body catalytic reactions, NUV photons are able to photolyze water, producing HOx radicals which go on to catalytically recombine the relatively stable CO and O2 molecules back into CO2. The comparatively low NUV flux of some M dwarfs leads to a significantly reduced efficiency of catalytic recombination of CO and O2 and the possible net destruction of CO2 and the build up of CO and O2. In this work we test the above hypothesis using a 1D photochemical kinetics model for a Mars-sized planet with an initial atmospheric composition similar to that of Mars and the incoming stellar flux of a weakly active M dwarf, assuming the exoplanet is 0.1 AU away from its parent star, in proximity of its habitable zone. We show that a CO2-dominated atmosphere can be converted into a CO2/CO/O2-dominated atmosphere in 10^3-10^4 years by CO2 photolysis. This process is kept from running away by a combination of O2 photolysis, three body reactions of O, O2, and another species to form O3, and reactions of CO with OH to form CO2 and H. However, such a large amount of O2 and CO, combined with some amount of H and H2, may be susceptible to spontaneous combustion or detonation, and thus could prove to be an especially unstable state in itself. Thus there could arise a situation

  14. Constraining terrestrial ecosystem CO2 fluxes by integrating models of biogeochemistry and atmospheric transport and data of surface carbon fluxes and atmospheric CO2 concentrations

    NASA Astrophysics Data System (ADS)

    Zhu, Q.; Zhuang, Q.; Henze, D.; Bowman, K.; Chen, M.; Liu, Y.; He, Y.; Matsueda, H.; Machida, T.; Sawa, Y.; Oechel, W.

    2014-09-01

    Regional net carbon fluxes of terrestrial ecosystems could be estimated with either biogeochemistry models by assimilating surface carbon flux measurements or atmospheric CO2 inversions by assimilating observations of atmospheric CO2 concentrations. Here we combine the ecosystem biogeochemistry modeling and atmospheric CO2 inverse modeling to investigate the magnitude and spatial distribution of the terrestrial ecosystem CO2 sources and sinks. First, we constrain a terrestrial ecosystem model (TEM) at site level by assimilating the observed net ecosystem production (NEP) for various plant functional types. We find that the uncertainties of model parameters are reduced up to 90% and model predictability is greatly improved for all the plant functional types (coefficients of determination are enhanced up to 0.73). We then extrapolate the model to a global scale at a 0.5° × 0.5° resolution to estimate the large-scale terrestrial ecosystem CO2 fluxes, which serve as prior for atmospheric CO2 inversion. Second, we constrain the large-scale terrestrial CO2 fluxes by assimilating the GLOBALVIEW-CO2 and mid-tropospheric CO2 retrievals from the Atmospheric Infrared Sounder (AIRS) into an atmospheric transport model (GEOS-Chem). The transport inversion estimates that: (1) the annual terrestrial ecosystem carbon sink in 2003 is -2.47 Pg C yr-1, which agrees reasonably well with the most recent inter-comparison studies of CO2 inversions (-2.82 Pg C yr-1); (2) North America temperate, Europe and Eurasia temperate regions act as major terrestrial carbon sinks; and (3) The posterior transport model is able to reasonably reproduce the atmospheric CO2 concentrations, which are validated against Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) CO2 concentration data. This study indicates that biogeochemistry modeling or atmospheric transport and inverse modeling alone might not be able to well quantify regional terrestrial carbon fluxes. However, combining

  15. CO2 greenhouse in the early martian atmosphere: SO2 inhibits condensation

    NASA Technical Reports Server (NTRS)

    Yung, Y. L.; Nair, H.; Gerstell, M. F.

    1997-01-01

    Many investigators of the early martian climate have suggested that a dense carbon dioxide atmosphere was present and warmed the surface above the melting point of water (J.B. Pollack, J.F. Kasting, S.M. Richardson, and K. Poliakoff 1987. Icarus 71, 203-224). However, J.F. Kasting (1991. Icarus 94, 1-13) pointed out that previous thermal models of the primitive martian atmosphere had not considered the condensation of CO2. When this effect was incorporated, Kasting found that CO2 by itself is inadequate to warm the surface. SO2 absorbs strongly in the near UV region of the solar spectrum. While a small amount of SO2 may have a negligible effect by itself on the surface temperature, it may have significantly warmed the middle atmosphere of early Mars, much as ozone warms the terrestrial stratosphere today. If this region is kept warm enough to inhibit the condensation of CO2, then CO2 remains a viable greenhouse gas. Our preliminary radiative modeling shows that the addition of 0.1 ppmv of SO2 in a 2 bar CO2 atmosphere raises the temperature of the middle atmosphere by approximately 10 degrees, so that the upper atmosphere in a 1 D model remains above the condensation temperature of CO2. In addition, this amount of SO2 in the atmosphere provides an effective UV shield for a hypothetical biosphere on the martian surface.

  16. The photochemistry of the early atmosphere

    NASA Technical Reports Server (NTRS)

    Levine, J. S.

    1985-01-01

    The composition of the earth's present atmosphere is described. The formation of the earth from the coalescence and accretion of the refractory elements of the solar nebula is examined. Two possible compositions of the prebiological paleoatmosphere, which are a reducing atmosphere of CH4, NH3, and H2 or a mildly reducing atmosphere of H2O, CO2, and N2, and their photochemistry are analyzed. General photochemical and chemical processes are reviewed. The use of the coupled continuity-transport equation to calculate the vertical distribution of each species is discussed. A study of the photochemical process of CH4 and NH3 reveals that the reducing atmosphere could not possibly exist. An analysis of the photochemistry and chemistry of the H2O, CO2, and N2 atmosphere reveals that the photodissociation of H2O and CO2 results in a prebiotic source of O2, H2CO, and HCN, which are the components for the evolution of photosynthetic organisms and a strongly oxidizing atmosphere. The reactions which produce O2 and H2CO from H2O and CO2, and the relation between H2O and CO2 concentrations and O2 levels are investigated. The formation of O3 photochemically from O2 is explained.

  17. Terrestrial microorganisms at an altitude of 20,000 m in Earth's atmosphere

    USGS Publications Warehouse

    Griffin, Dale W.

    2004-01-01

    A joint effort between the U.S. Geological Survey's (USGS) Global Desert Dust and NASA's Stratospheric and Cosmic Dust Programs identified culturable microbes from an air sample collected at an altitude of 20,000 m. A total of 4 fungal (Penicillium sp.) and 71 bacteria colonyforming units (70 colonies of Bacillus luciferensis believed to have originated from a single cell collected at altitude and one colony of Bacillus sphaericus) were enumerated, isolated and identified using a morphological key and 16S rDNA sequencing respectively. All of the isolates identified were sporeforming pigmented fungi or bacteria of terrestrial origin and demonstrate that the presence of viable microorganisms in Earth's upper atmosphere may not be uncommon.

  18. New Satellite Project Aerosol-UA: Remote Sensing of Aerosols in the Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Milinevsky, G.; Yatskiv, Ya.; Degtyaryov, O.; Syniavskyi, I.; Mishchenko, Michael I.; Rosenbush, V.; Ivanov, Yu.; Makarov, A.; Bovchaliuk, A.; Danylevsky, V.; Sosonkin, M.; Moskalov, S.; Bovchaliuk, V; Lukenyuk, A.; Shymkiv, A.

    2016-01-01

    We discuss the development of the Ukrainian space project Aerosol-UA which has the following three main objectives: (1) to monitor the spatial distribution of key characteristics of terrestrial tropospheric and stratospheric aerosols; (2) to provide a comprehensive observational database enabling accurate quantitative estimates of the aerosol contribution to the energy budget of the climate system; and (3) quantify the contribution of anthropogenic aerosols to climate and ecological processes. The remote sensing concept of the project is based on precise orbital measurements of the intensity and polarization of sunlight scattered by the atmosphere and the surface with a scanning polarimeter accompanied by a wide-angle multispectral imager-polarimeter. Preparations have already been made for the development of the instrument suite for the Aerosol-UA project, in particular, of the multi-channel scanning polarimeter (ScanPol) designed for remote sensing studies of the global distribution of aerosol and cloud properties (such as particle size, morphology, and composition) in the terrestrial atmosphere by polarimetric and spectrophotometric measurements of the scattered sunlight in a wide range of wavelengths and viewing directions from which a scene location is observed. ScanPol is accompanied by multispectral wide-angle imager-polarimeter (MSIP) that serves to collect information on cloud conditions and Earths surface image. Various components of the polarimeter ScanPol have been prototyped, including the opto-mechanical and electronic assemblies and the scanning mirror controller. Preliminary synthetic data simulations for the retrieval of aerosol parameters over land surfaces have been performed using the Generalized Retrieval of Aerosol and Surface Properties (GRASP) algorithm. Methods for the validation of satellite data using ground-based observations of aerosol properties are also discussed. We assume that designing, building, and launching into orbit a multi

  19. Exploring the Sensitivity of Terrestrial Ecosystems and Atmospheric Exchange of CO2 to Global Environmental Factors

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; Meiyappan, P.; Song, Y.; Barman, R.

    2011-12-01

    This presentation explores the sensitivity of terrestrial ecosystems and atmospheric exchange of carbon to global environmental factors to advance our understanding of uncertainty in CO2 projections. We use a land surface model, the Integrated Science Assessment Model (ISAM) recently coupled into the NCAR Community Earth System Model (CESM1) framework to evaluate ecosystem variability due to climatic and anthropogenic factors. The factors considered here include climate change, increasing ambient CO2 concentrations, anthropogenic nitrogen deposition, and land use change (LUC) activities such as clearing of land for agriculture, pasture, and wood harvest. Each factor has a potential to influence the net ecosystem exchange (NEE) of CO2. Using the ISAM-CESM modeling framework, we evaluate the individual and concurrent effects of all these environmental factors on the terrestrial NEE over the 20th century and the 21st century. The ISAM biogeochemical cycles consist of fully prognostic carbon and nitrogen dynamics associated with changes in land cover, litter decomposition, and soil organic matter. The ISAM biophysical model accounts for water and energy processes in the vegetation and soil column, integrated over a time step of 30 minutes. The newly available CRU-NCEP climate forcing data (1850-2010, 0.5ox0.5o spatial resolution) will be used for the historical period simulations. The 21st century simulations will be carried out using the Representative Concentration Pathway (RCP) storylines. This study will help quantify the importance of various environmental factors towards modeling land-atmosphere carbon exchange and better understand model related differences in CO2 estimates.

  20. New satellite project Aerosol-UA: Remote sensing of aerosols in the terrestrial atmosphere

    NASA Astrophysics Data System (ADS)

    Milinevsky, G.; Yatskiv, Ya.; Degtyaryov, O.; Syniavskyi, I.; Mishchenko, M.; Rosenbush, V.; Ivanov, Yu.; Makarov, A.; Bovchaliuk, A.; Danylevsky, V.; Sosonkin, M.; Moskalov, S.; Bovchaliuk, V.; Lukenyuk, A.; Shymkiv, A.; Udodov, E.

    2016-06-01

    We discuss the development of the Ukrainian space project Aerosol-UA which has the following three main objectives: (1) to monitor the spatial distribution of key characteristics of terrestrial tropospheric and stratospheric aerosols; (2) to provide a comprehensive observational database enabling accurate quantitative estimates of the aerosol contribution to the energy budget of the climate system; and (3) quantify the contribution of anthropogenic aerosols to climate and ecological processes. The remote sensing concept of the project is based on precise orbital measurements of the intensity and polarization of sunlight scattered by the atmosphere and the surface with a scanning polarimeter accompanied by a wide-angle multispectral imager-polarimeter. Preparations have already been made for the development of the instrument suite for the Aerosol-UA project, in particular, of the multi-channel scanning polarimeter (ScanPol) designed for remote sensing studies of the global distribution of aerosol and cloud properties (such as particle size, morphology, and composition) in the terrestrial atmosphere by polarimetric and spectrophotometric measurements of the scattered sunlight in a wide range of wavelengths and viewing directions from which a scene location is observed. ScanPol is accompanied by multispectral wide-angle imager-polarimeter (MSIP) that serves to collect information on cloud conditions and Earth's surface image. Various components of the polarimeter ScanPol have been prototyped, including the opto-mechanical and electronic assemblies and the scanning mirror controller. Preliminary synthetic data simulations for the retrieval of aerosol parameters over land surfaces have been performed using the Generalized Retrieval of Aerosol and Surface Properties (GRASP) algorithm. Methods for the validation of satellite data using ground-based observations of aerosol properties are also discussed. We assume that designing, building, and launching into orbit a multi

  1. The chemical composition and climatology of the earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Henderson-Sellers, A.

    1983-01-01

    The earth's climate as it relates to the evolution of life is discussed.. Seven fundamental characteristics of the early evolutionary environment are examined, including a carbon dioxide and water vapor atmosphere, atmospheric mass between 500 and 1000 mb, a global hydrosphere, lowered solar luminosity, hospitable average global temperatures, a convectively active atmosphere, and trace gases. The influence of the early earth's extensive hydrosphere on the origin of life is considered. The warming of that hydrosphere due to radiative fluxes and the greenhouse effect is examined, and the nature of the feedback between clouds and climate is addressed.

  2. A terrestrial biosphere model optimized to atmospheric CO2 concentration and above ground woody biomass

    NASA Astrophysics Data System (ADS)

    Saito, M.; Ito, A.; Maksyutov, S. S.

    2013-12-01

    This study documents an optimization of a prognostic biosphere model (VISIT; Vegetation Integrative Similator for Trace gases) to observations of atmospheric CO2 concentration and above ground woody biomass by using a Bayesian inversion method combined with an atmospheric tracer transport model (NIES-TM; National Institute for Environmental Studies / Frontier Research Center for Global Change (NIES/FRCGC) off-line global atmospheric tracer transport model). The assimilated observations include 74 station records of surface atmospheric CO2 concentration and aggregated grid data sets of above ground woody biomass (AGB) and net primary productivity (NPP) over the globe. Both the biosphere model and the atmospheric transport model are used at a horizontal resolution of 2.5 deg x 2.5 deg grid with temporal resolutions of a day and an hour, respectively. The atmospheric transport model simulates atmospheric CO2 concentration with nine vertical levels using daily net ecosystem CO2 exchange rate (NEE) from the biosphere model, oceanic CO2 flux, and fossil fuel emission inventory. The models are driven by meteorological data from JRA-25 (Japanese 25-year ReAnalysis) and JCDAS (JMA Climate Data Assimilation System). Statistically optimum physiological parameters in the biosphere model are found by iterative minimization of the corresponding Bayesian cost function. We select thirteen physiological parameter with high sensitivity to NEE, NPP, and AGB for the minimization. Given the optimized physiological parameters, the model shows error reductions in seasonal variation of the CO2 concentrations especially in the northern hemisphere due to abundant observation stations, while errors remain at a few stations that are located in coastal coastal area and stations in the southern hemisphere. The model also produces moderate estimates of the mean magnitudes and probability distributions in AGB and NPP for each biome. However, the model fails in the simulation of the terrestrial

  3. New Constraints on Terrestrial Surface-Atmosphere Fluxes of Gaseous Elemental Mercury Using a Global Database.

    PubMed

    Agnan, Yannick; Le Dantec, Théo; Moore, Christopher W; Edwards, Grant C; Obrist, Daniel

    2016-01-19

    Despite 30 years of study, gaseous elemental mercury (Hg(0)) exchange magnitude and controls between terrestrial surfaces and the atmosphere still remain uncertain. We compiled data from 132 studies, including 1290 reported fluxes from more than 200,000 individual measurements, into a database to statistically examine flux magnitudes and controls. We found that fluxes were unevenly distributed, both spatially and temporally, with strong biases toward Hg-enriched sites, daytime and summertime measurements. Fluxes at Hg-enriched sites were positively correlated with substrate concentrations, but this was absent at background sites. Median fluxes over litter- and snow-covered soils were lower than over bare soils, and chamber measurements showed higher emission compared to micrometeorological measurements. Due to low spatial extent, estimated emissions from Hg-enriched areas (217 Mg·a(-1)) were lower than previous estimates. Globally, areas with enhanced atmospheric Hg(0) levels (particularly East Asia) showed an emerging importance of Hg(0) emissions accounting for half of the total global emissions estimated at 607 Mg·a(-1), although with a large uncertainty range (-513 to 1353 Mg·a(-1) [range of 37.5th and 62.5th percentiles]). The largest uncertainties in Hg(0) fluxes stem from forests (-513 to 1353 Mg·a(-1) [range of 37.5th and 62.5th percentiles]), largely driven by a shortage of whole-ecosystem fluxes and uncertain contributions of leaf-atmosphere exchanges, questioning to what degree ecosystems are net sinks or sources of atmospheric Hg(0). PMID:26599393

  4. Do meteoroids of sedimentary origin survive terrestrial atmospheric entry? The ESA artificial meteorite experiment STONE

    NASA Astrophysics Data System (ADS)

    Brack, A.; Baglioni, P.; Borruat, G.; Brandstätter, F.; Demets, R.; Edwards, H. G. M.; Genge, M.; Kurat, G.; Miller, M. F.; Newton, E. M.; Pillinger, C. T.; Roten, C.-A.; Wäsch, E.

    2002-06-01

    The 18 SNC meteorites identified to date are all igneous rocks, being basalts or basaltic cumulates. The lack of sedimentary rocks in this inventory is therefore surprising, in view of the collisional history of Mars and the likelihood that Mars experienced warmer conditions, possibly with a significant hydrosphere, earlier in its history. To address the possibility that sedimentary rocks ejected by impact from the surface of Mars may have reached the Earth, but did not survive terrestrial atmospheric entry, an experiment was performed in which samples of dolomite, a simulated Martian regolith (consisting of basalt fragments in a gypsum matrix) and a basalt were fixed to the heat shield of a recoverable capsule and flown in low Earth orbit. Temperatures attained during re-entry were high enough to melt basalt and the silica fibres of the heat shield and were therefore comparable to those experienced by meteorites. The dolomite sample survived space flight and atmospheric re-entry, in part, as did fragments of the simulated Martian regolith, allowing detailed examinations of these 'artificial meteorites' to be conducted for chemical, mineralogical and isotopic modifications associated with atmospheric re-entry. Oxygen three-isotope measurements of the silica 'fusion crust' formed on the sample holder during atmospheric re-entry fit on a mixing line, with tropospheric O 2 and the interior of the sample holder as end members. Because much of the surface of Mars is covered by clastic sediments, meteorites of Martian provenance might be expected to be mostly sedimentary rocks rather than igneous ones. However, in the absence of a readily identifiable fusion crust, the extraterrestrial origin of such sedimentary rocks on Earth would most probably not be recognised without detailed petrological-geochemical examination and, ultimately, isotope measurements.

  5. Middle atmosphere electrodynamics: Report of the workshop on the Role of the Electrodynamics of the Middle Atmosphere on Solar Terrestrial Coupling

    NASA Technical Reports Server (NTRS)

    Maynard, N. C. (Editor)

    1979-01-01

    Significant deficiencies exist in the present understanding of the basic physical processes taking place within the middle atmosphere (the region between the tropopause and the mesopause), and in the knowledge of the variability of many of the primary parameters that regulate Middle Atmosphere Electrodynamics (MAE). Knowledge of the electrical properties, i.e., electric fields, plasma characteristics, conductivity and currents, and the physical processes that govern them is of fundamental importance to the physics of the region. Middle atmosphere electrodynamics may play a critical role in the electrodynamical aspects of solar-terrestrial relations. As a first step, the Workshop on the Role of the Electrodynamics of the Middle Atmosphere on Solar-Terrestrial Coupling was held to review the present status and define recommendations for future MAE research.

  6. Studies of volatiles and organic materials in early terrestrial and present-day outer solar system environments

    NASA Technical Reports Server (NTRS)

    Sagan, Carl; Thompson, W. Reid; Chyba, Christopher F.; Khare, B. N.

    1991-01-01

    A review and partial summary of projects within several areas of research generally involving the origin, distribution, chemistry, and spectral/dielectric properties of volatiles and organic materials in the outer solar system and early terrestrial environments are presented. The major topics covered include: (1) impact delivery of volatiles and organic compounds to the early terrestrial planets; (2) optical constants measurements; (3) spectral classification, chemical processes, and distribution of materials; and (4) radar properties of ice, hydrocarbons, and organic heteropolymers.

  7. Evidence for and implications of an Early Archean terrestrial impact record

    NASA Technical Reports Server (NTRS)

    Lowe, Donald R.; Byerly, Gary R.

    1988-01-01

    Early Archean, 3.5 to 3.2 Ga, greenstone sequences in South Africa and Western Australia contain a well-preserved record of early terrestrial meteorite impacts. The main impact-produced deposits are layers, 10 cm to over 1 m thick, composed largely of sand-sized spherules, 0.1 to 4 mm in diameter. The beds studied to date show an assemblage of features indicating formation by the fall of debris from impact-generated ejecta clouds. Some presented data effectively rule out normal magmatic or sedimentary processes in the origin of these units and provide substantial support for an origin by large impacts on the early earth. The presence of at least four, remarkably thick, nearly pure spherule layers suggests that smaller-scale impact deposits may be even more abundant in these sequences. The existence of a well-preserved Archean terrestrial impact record suggests that a direct source of evidence is available regarding a number of important aspects of early earth history.

  8. Remote sensing of aerosol in the terrestrial atmosphere from space: new missions

    NASA Astrophysics Data System (ADS)

    Milinevsky, G.; Yatskiv, Ya.; Degtyaryov, O.; Syniavskyi, I.; Ivanov, Yu.; Bovchaliuk, A.; Mishchenko, M.; Danylevsky, V.; Sosonkin, M.; Bovchaliuk, V.

    2015-09-01

    The distribution and properties of atmospheric aerosols on a global scale are not well known in terms of determination of their effects on climate. This mostly is due to extreme variability of aerosol concentrations, properties, sources, and types. Aerosol climate impact is comparable to the effect of greenhouse gases, but its influence is more difficult to measure, especially with respect to aerosol microphysical properties and the evaluation of anthropogenic aerosol effect. There are many satellite missions studying aerosol distribution in the terrestrial atmosphere, such as MISR/Terra, OMI/Aura, AVHHR, MODIS/Terra and Aqua, CALIOP/CALIPSO. To improve the quality of data and climate models, and to reduce aerosol climate forcing uncertainties, several new missions are planned. The gap in orbital instruments for studying aerosol microphysics has arisen after the Glory mission failed during launch in 2011. In this review paper, we describe several planned aerosol space missions, including the Ukrainian project Aerosol-UA that obtains data using a multi-channel scanning polarimeter and wide-angle polarimetric camera. The project is designed for remote sensing of the aerosol microphysics and cloud properties on a global scale.

  9. Remote sensing of aerosol in the terrestrial atmosphere from space: "AEROSOL-UA" mission

    NASA Astrophysics Data System (ADS)

    Yatskiv, Yaroslav; Milinevsky, Gennadi; Degtyarev, Alexander

    2016-07-01

    The distribution and properties of atmospheric aerosols on a global scale are not well known in terms of determination of their effects on climate. This mostly is due to extreme variability of aerosol concentrations, properties, sources, and types. Aerosol climate impact is comparable to the effect of greenhouse gases, but its influence is more difficult to measure, especially with respect to aerosol microphysical properties and the evaluation of anthropogenic aerosol effect. There are many satellite missions studying aerosol distribution in the terrestrial atmosphere, such as MISR/Terra, OMI/Aura, AVHHR, MODIS/Terra and Aqua, CALIOP/CALIPSO. To improve the quality of data and climate models, and to reduce aerosol climate forcing uncertainties, several new missions are planned. The gap in orbital instruments for studying aerosol microphysics has arisen after the Glory mission failed during launch in 2011. In this review paper, we describe several planned aerosol space missions, including the Ukrainian project AEROSOL-UA that will obtain the data using a multi-channel scanning polarimeter and wide-angle polarimetric camera. The mission is designed for remote sensing of the aerosol microphysics and cloud properties on a global scale.

  10. Remote Sensing of Aerosol in the Terrestrial Atmosphere from Space: New Missions

    NASA Technical Reports Server (NTRS)

    Milinevsky, G.; Yatskiv, Ya.; Degtyaryov, O.; Syniavskyi, I.; Ivanov, Yu.; Bovchaliuk, A.; Mishchenko, M.; Danylevsky, V.; Sosonkin, M.; Bovchaliuk, V.

    2015-01-01

    The distribution and properties of atmospheric aerosols on a global scale are not well known in terms of determination of their effects on climate. This mostly is due to extreme variability of aerosol concentrations, properties, sources, and types. Aerosol climate impact is comparable to the effect of greenhouse gases, but its influence is more difficult to measure, especially with respect to aerosol microphysical properties and the evaluation of anthropogenic aerosol effect. There are many satellite missions studying aerosol distribution in the terrestrial atmosphere, such as MISR/Terra, OMI/Aura, AVHHR, MODIS/Terra and Aqua, CALIOP/CALIPSO. To improve the quality of data and climate models, and to reduce aerosol climate forcing uncertainties, several new missions are planned. The gap in orbital instruments for studying aerosol microphysics has arisen after the Glory mission failed during launch in 2011. In this review paper, we describe several planned aerosol space missions, including the Ukrainian project Aerosol-UA that obtains data using a multi-channel scanning polarimeter and wide-angle polarimetric camera. The project is designed for remote sensing of the aerosol microphysics and cloud properties on a global scale.

  11. Using Dimers to Measure Biosignatures and Atmospheric Pressure for Terrestrial Exoplanets

    PubMed Central

    Meadows, Victoria; Claire, Mark; Crisp, Dave

    2014-01-01

    Abstract We present a new method to probe atmospheric pressure on Earth-like planets using (O2-O2) dimers in the near-infrared. We also show that dimer features could be the most readily detectable biosignatures for Earth-like atmospheres and may even be detectable in transit transmission with the James Webb Space Telescope (JWST). The absorption by dimers changes more rapidly with pressure and density than that of monomers and can therefore provide additional information about atmospheric pressures. By comparing the absorption strengths of rotational and vibrational features to the absorption strengths of dimer features, we show that in some cases it may be possible to estimate the pressure at the reflecting surface of a planet. This method is demonstrated by using the O2 A band and the 1.06 μm dimer feature, either in transmission or reflected spectra. It works best for planets around M dwarfs with atmospheric pressures between 0.1 and 10 bar and for O2 volume mixing ratios above 50% of Earth's present-day level. Furthermore, unlike observations of Rayleigh scattering, this method can be used at wavelengths longer than 0.6 μm and is therefore potentially applicable, although challenging, to near-term planet characterization missions such as JWST. We also performed detectability studies for JWST transit transmission spectroscopy and found that the 1.06 and 1.27 μm dimer features could be detectable (SNR>3) for an Earth analogue orbiting an M5V star at a distance of 5 pc. The detection of these features could provide a constraint on the atmospheric pressure of an exoplanet and serve as biosignatures for oxygenic photosynthesis. We calculated the required signal-to-noise ratios to detect and characterize O2 monomer and dimer features in direct imaging–reflected spectra and found that signal-to-noise ratios greater than 10 at a spectral resolving power of R=100 would be required. Key Words: Remote sensing—Extrasolar terrestrial planets

  12. A terrestrial vegetation turnover in the middle of the Early Triassic

    NASA Astrophysics Data System (ADS)

    Saito, Ryosuke; Kaiho, Kunio; Oba, Masahiro; Takahashi, Satoshi; Chen, Zhong-Qiang; Tong, Jinnan

    2013-06-01

    Land-plant productivity was greatly reduced after the end-Permian mass extinction, causing a pronounced "coal gap" worldwide during the Early Triassic. Newly obtained organic geochemistry data from the Chaohu area, south China, indicated an abrupt and profound terrestrial vegetation change over the middle part of the Early Triassic Smithian-Spathian (S-S) interval. Herbaceous lycopsids and/or bryophytes dominated terrestrial vegetation from Griesbachian to Smithian times. The terrestrial ecosystem underwent an abrupt change, and woody conifers became dominant over the S-S interval. Several important biomarkers, namely retene, simonellite, and dehydroabietane (with multiple sources: conifer, lycopsid, and/or herbaceous bryophyte), were relatively abundant during Griesbachian, Dienerian, and Smithian times. The relatively low C/N ratio values during the Griesbachian-Smithian interval indicate that these biomarkers were likely sourced from herbaceous lycopsids and/or bryophytes. The extremely abundant conifer-sourced pimanthrene, combined with relatively high C/N ratio values, suggested the recovery of woody conifers after the S-S boundary. The new data revealed that the switch from herbaceous vegetation to woody coniferous vegetation marked a terrestrial plant recovery, which occurred globally within 3 million years after the end-Permian crisis rather than at a later date estimated in previous studies. In Chaohu, the S-S terrestrial event was marked by a reappearance of woody vegetation, while the S-S marine event was marked by an increase in ichnodiversity, trace complexity, burrow size, infaunal tiering level, and bioturbation level, and a possible intense upwelling event indicated by the extended tricyclic terpane ratios (ETR). Coeval vegetation changes with comparable patterns have also been documented in Europe and Pakistan based on palynologic studies. The S-S boundaries in Asia and Europe are associated with a positive δ13C excursion, the rebound of woody

  13. Photochemical model for NH3 in an early Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Brown, L. L.; Kasting, J. F.

    1992-01-01

    A warm and wet climate scenario for early Mars has been explained by invoking a 5-bar CO2 atmosphere; however, Kasting has shown that CO2 will condense in the Martian atmosphere at these pressures. The formation of CO2 clouds will reduce the convection lapse rate and reduce the magnitude of the greenhouse effect. It is possible that additional greenhouse gases such as methane and ammonia were present in the early Mars atmosphere. We are using a one dimensional photochemical model to estimate the magnitude of the ammonia source required to maintain a given ammonia concentration in a dense CO2 atmosphere. Because CO2 is 2.5 times more efficient at Rayleigh scattering than Earth's N2 atmosphere, we anticipate increased scattering opacities and decreased photolytic destruction rates of ammonia on early Mars. The reduced gravity on Mars means that a 1 bar atmosphere will be approximately 3 times as thick as on Earth. It is possible that ammonia could have been shielded from photolysis by hydrocarbon aerosols which form as a product of methane photolysis.

  14. The sensitivity of terrestrial carbon storage to historical climate variability and atmospheric CO2 in the United States

    USGS Publications Warehouse

    Tian, H.; Melillo, J.M.; Kicklighter, D.W.; McGuire, A.D.; Helfrich, J.

    1999-01-01

    We use the Terrestrial Ecosystem Model (TEM, Version 4.1) and the land cover data set of the international geosphere-biosphere program to investigate how increasing atmospheric CO2 concentration and climate variability during 1900-1994 affect the carbon storage of terrestrial ecosystems in the conterminous USA, and how carbon storage has been affected by land-use change. The estimates of TEM indicate that over the past 95 years a combination of increasing atmospheric CO2 with historical temperature and precipitation variability causes a 4.2% (4.3 Pg C) decrease in total carbon storage of potential vegetation in the conterminous US, with vegetation carbon decreasing by 7.2% (3.2 Pg C) and soil organic carbon decreasing by 1.9% (1.1 Pg C). Several dry periods including the 1930s and 1950s are responsible for the loss of carbon storage. Our factorial experiments indicate that precipitation variability alone decreases total carbon storage by 9.5%. Temperature variability alone does not significantly affect carbon storage. The effect of CO2 fertilization alone increases total carbon storage by 4.4%. The effects of increasing atmospheric CO2 and climate variability are not additive. Interactions among CO2, temperature and precipitation increase total carbon storage by 1.1%. Our study also shows substantial year-to-year variations in net carbon exchange between the atmosphere and terrestrial ecosystems due to climate variability. Since the 1960s, we estimate these terrestrial ecosystems have acted primarily as a sink of atmospheric CO2 as a result of wetter weather and higher atmospheric CO2 concentrations. For the 1980s, we estimate the natural terrestrial ecosystems, excluding cropland and urban areas, of the conterminous US have accumulated 78.2 Tg C yr-1 because of the combined effect of increasing atmospheric CO2 and climate variability. For the conterminous US, we estimate that the conversion of natural ecosystems to cropland and urban areas has caused a 18.2% (17

  15. The rise of oxygen in Earth's early ocean and atmosphere.

    PubMed

    Lyons, Timothy W; Reinhard, Christopher T; Planavsky, Noah J

    2014-02-20

    The rapid increase of carbon dioxide concentration in Earth's modern atmosphere is a matter of major concern. But for the atmosphere of roughly two-and-half billion years ago, interest centres on a different gas: free oxygen (O2) spawned by early biological production. The initial increase of O2 in the atmosphere, its delayed build-up in the ocean, its increase to near-modern levels in the sea and air two billion years later, and its cause-and-effect relationship with life are among the most compelling stories in Earth's history. PMID:24553238

  16. Effects of atmospheric ammonia (NH3) on terrestrial vegetation: a review.

    PubMed

    Krupa, S V

    2003-01-01

    At the global scale, among all N (nitrogen) species in the atmosphere and their deposition on to terrestrial vegetation and other receptors, NH3 (ammonia) is considered to be the foremost. The major sources for atmospheric NH3 are agricultural activities and animal feedlot operations, followed by biomass burning (including forest fires) and to a lesser extent fossil fuel combustion. Close to its sources, acute exposures to NH3 can result in visible foliar injury on vegetation. NH3 is deposited rapidly within the first 4-5 km from its source. However, NH3 is also converted in the atmosphere to fine particle NH4+ (ammonium) aerosols that are a regional scale problem. Much of our current knowledge of the effects of NH3 on higher plants is predominantly derived from studies conducted in Europe. Adverse effects on vegetation occur when the rate of foliar uptake of NH3 is greater than the rate and capacity for in vivo detoxification by the plants. Most to least sensitive plant species to NH3 are native vegetation > forests > agricultural crops. There are also a number of studies on N deposition and lichens, mosses and green algae. Direct cause and effect relationships in most of those cases (exceptions being those locations very close to point sources) are confounded by other environmental factors, particularly changes in the ambient SO2 (sulfur dioxide) concentrations. In addition to direct foliar injury, adverse effects of NH3 on higher plants include alterations in: growth and productivity, tissue content of nutrients and toxic elements, drought and frost tolerance, responses to insect pests and disease causing microorganisms (pathogens), development of beneficial root symbiotic or mycorrhizal associations and inter species competition or biodiversity. In all these cases, the joint effects of NH3 with other air pollutants such as all-pervasive O3 or increasing CO2 concentrations are poorly understood. While NH3 uptake in higher plants occurs through the shoots, NH4

  17. 3D-radiative transfer in terrestrial atmosphere: An efficient parallel numerical procedure

    NASA Astrophysics Data System (ADS)

    Bass, L. P.; Germogenova, T. A.; Nikolaeva, O. V.; Kokhanovsky, A. A.; Kuznetsov, V. S.

    2003-04-01

    Light propagation and scattering in terrestrial atmosphere is usually studied in the framework of the 1D radiative transfer theory [1]. However, in reality particles (e.g., ice crystals, solid and liquid aerosols, cloud droplets) are randomly distributed in 3D space. In particular, their concentrations vary both in vertical and horizontal directions. Therefore, 3D effects influence modern cloud and aerosol retrieval procedures, which are currently based on the 1D radiative transfer theory. It should be pointed out that the standard radiative transfer equation allows to study these more complex situations as well [2]. In recent year the parallel version of the 2D and 3D RADUGA code has been developed. This version is successfully used in gammas and neutrons transport problems [3]. Applications of this code to radiative transfer in atmosphere problems are contained in [4]. Possibilities of code RADUGA are presented in [5]. The RADUGA code system is an universal solver of radiative transfer problems for complicated models, including 2D and 3D aerosol and cloud fields with arbitrary scattering anisotropy, light absorption, inhomogeneous underlying surface and topography. Both delta type and distributed light sources can be accounted for in the framework of the algorithm developed. The accurate numerical procedure is based on the new discrete ordinate SWDD scheme [6]. The algorithm is specifically designed for parallel supercomputers. The version RADUGA 5.1(P) can run on MBC1000M [7] (768 processors with 10 Gb of hard disc memory for each processor). The peak productivity is equal 1 Tfl. Corresponding scalar version RADUGA 5.1 is working on PC. As a first example of application of the algorithm developed, we have studied the shadowing effects of clouds on neighboring cloudless atmosphere, depending on the cloud optical thickness, surface albedo, and illumination conditions. This is of importance for modern satellite aerosol retrieval algorithms development. [1] Sobolev

  18. Effects of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Collilieux, X.; Dach, R.; Heflin, M. B.; Gross, R. S.; König, R.; Lemoine, F. G.; MacMillan, D. S.; Parker, J. W.; van Dam, T. M.; Wu, X.

    2013-12-01

    The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS global networks used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, the effect of non-tidal atmospheric loading (NTAL) corrections on the TRF is assessed adopting a Remove/Restore approach: (i) Focusing on the a-posteriori approach, the NTAL model derived from the National Center for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations. (ii) Adopting a Kalman-filter based approach, a linear TRF is estimated combining the 4 SG solutions free from NTAL displacements. (iii) Linear fits to the NTAL displacements removed at step (i) are restored to the linear reference frame estimated at (ii). The velocity fields of the (standard) linear reference frame in which the NTAL model has not been removed and the one in which the model has been removed/restored are compared and discussed.

  19. Dermal bone in early tetrapods: a palaeophysiological hypothesis of adaptation for terrestrial acidosis

    PubMed Central

    Janis, Christine M.; Devlin, Kelly; Warren, Daniel E.; Witzmann, Florian

    2012-01-01

    The dermal bone sculpture of early, basal tetrapods of the Permo-Carboniferous is unlike the bone surface of any living vertebrate, and its function has long been obscure. Drawing from physiological studies of extant tetrapods, where dermal bone or other calcified tissues aid in regulating acid–base balance relating to hypercapnia (excess blood carbon dioxide) and/or lactate acidosis, we propose a similar function for these sculptured dermal bones in early tetrapods. Unlike the condition in modern reptiles, which experience hypercapnia when submerged in water, these animals would have experienced hypercapnia on land, owing to likely inefficient means of eliminating carbon dioxide. The different patterns of dermal bone sculpture in these tetrapods largely correlates with levels of terrestriality: sculpture is reduced or lost in stem amniotes that likely had the more efficient lung ventilation mode of costal aspiration, and in small-sized stem amphibians that would have been able to use the skin for gas exchange. PMID:22535781

  20. Dermal bone in early tetrapods: a palaeophysiological hypothesis of adaptation for terrestrial acidosis.

    PubMed

    Janis, Christine M; Devlin, Kelly; Warren, Daniel E; Witzmann, Florian

    2012-08-01

    The dermal bone sculpture of early, basal tetrapods of the Permo-Carboniferous is unlike the bone surface of any living vertebrate, and its function has long been obscure. Drawing from physiological studies of extant tetrapods, where dermal bone or other calcified tissues aid in regulating acid-base balance relating to hypercapnia (excess blood carbon dioxide) and/or lactate acidosis, we propose a similar function for these sculptured dermal bones in early tetrapods. Unlike the condition in modern reptiles, which experience hypercapnia when submerged in water, these animals would have experienced hypercapnia on land, owing to likely inefficient means of eliminating carbon dioxide. The different patterns of dermal bone sculpture in these tetrapods largely correlates with levels of terrestriality: sculpture is reduced or lost in stem amniotes that likely had the more efficient lung ventilation mode of costal aspiration, and in small-sized stem amphibians that would have been able to use the skin for gas exchange. PMID:22535781

  1. Early tetrapod evolution and the progressive integration of Permo-Carboniferous terrestrial ecosystems

    SciTech Connect

    Beerbower, J.R. . Dept. of Geological Science); Olson, E.C. . Dept. of Biology); Hotton, N. III . Dept. of Paleobiology)

    1992-01-01

    Variation among Permo-Carboniferous tetrapod assemblages demonstrates major transformations in pathways and rates of energy and nutrient transfer, in integration of terrestrial ecosystems and in predominant ecologic modes. Early Carboniferous pathways were through plant detritus to aquatic and terrestrial detritivores and thence to arthropod and vertebrate meso-and macro-predators. Transfer rates (and efficiency) were low as was ecosystem integration; the principal ecologic mode was conservation. Late Carboniferous and Early Permian assemblages demonstrate an expansion in herbivory, primarily in utilization of low-fiber plant tissue by insects. But transfer rates, efficiency and integration were still limited because the larger portion of plant biomass, high-fiber tissues, still went into detrital pathways; high-fiber'' herbivores, i.e., tetrapods, were neither abundant or diverse, reflecting limited resources, intense predation and limited capabilities for processing fiber-rich food. The abundance and diversity of tetrapod herbivores in upper Permian assemblages suggests a considerable transfer of energy from high-fiber tissues through these animals to tetrapod predators and thus higher transfer rates and efficiencies. It also brought a shift in ecological mode toward acquisition and regulation and tightened ecosystem integration.

  2. Acyclic hydrocarbon environments ⩾ n-C 18 on the early terrestrial planets

    NASA Astrophysics Data System (ADS)

    Marcano, Vicente; Benitez, Pedro; Palacios-Prü, Ernesto

    2003-03-01

    The possible occurrence on the surface of the early Earth, Mars and Venus of hydrocarbon environments mainly composed by acyclic alkane molecules ⩾ n-C 18 has been revised. These hydrocarbons could be accumulated from the contribution of endogenous Fischer-Tropsh-type reactions and post-impact recombination reactions, as well as from exogenous sources such as comets, meteorites and dust particles. Such heavy alkane environments could offer protection for the synthesis and survival of biomolecules on the early terrestrial planets. Amounts of heavy n-alkanes delivered by large impactors, dust particles or produced by post-impact recombination on Venus would have been higher than those delivered or produced by the same sources on Earth and Mars before 3600 Myr ago. However, the high values of the total frequency of impacts by bolides >14-km in diameter estimated in this time period (viz. 3.9×10 3, Mars; 2.2×10 4, Earth, and 3.8×10 4 Venus) and the high surface temperatures generated by those impactors suggest the existence of very unstable conditions on the early terrestrial planets for the survival and long-term accumulation of acyclic hydrocarbons. Therefore, the most significant accumulation of n-alkanes could have occurred only during the longer intervals (10 5- 10 7 yr) between each impact through the contribution mainly of IDPs, and thereby a high decomposition rate would be expected for the accumulated n-alkanes by successive impacts. Amounts of n-alkanes accumulated from IDPs in these intervals have been estimated between 2.3×10 9 and 2.2×10 10 kg 3600- 3800 Myr ago. These processes are expected to occur on other planetary bodies or satellites belonging to our solar system and probably in analogs of the early solar system.

  3. Increased delivery of condensation nuclei during the Late Heavy Bombardment to the terrestrial and martian atmospheres

    NASA Astrophysics Data System (ADS)

    Losiak, Anna

    2014-05-01

    During the period of the Late Heavy Bombardment (LHB), between 4.1 and 3.8 Ga, the impact rate within the entire Solar System was up to a few thousand times higher than the current value (Ryder 2002, Bottke et al. 2012, Fassett and Minton 2013). Multiple basin-forming events on inner planets that occurred during this time had a strong but short-lasting (up to few thousands of years) effect on atmospheres of Earth and Mars (Sleep et al. 1989, Segura et al. 2002, 2012). However, the role of the continuous flux of smaller impactors has not been assessed so far. We calculated the amount of meteoric material in the 10^-3 kg to 106 kg size range delivered to Earth and Mars during the LHB based on the impact flux at the top of the Earth's atmosphere based on results from Bland and Artemieva (2006). Those values were recalculated for Mars based on Ivanov and Hartmann (2009) and then recalculated to the LHB peak based on estimates from Ryder (2002), Bottke et al. (2012), Fassett and Minton (2013). During the LHB, the amount of meteoritic material within this size range delivered to Earth was up to ~1.7*10^10 kg/year and 1.4*10^10 kg/year for Mars. The impactors that ablate and are disrupted during atmospheric entry can serve as cloud condensation nuclei (Rosen 1968, Hunten et al. 1980, Ogurtsov and Raspopov 2011). The amount of material delivered during LHB to the upper stratosphere and lower mezosphere (Hunten et al. 1980, Bland and Artemieva 2006) is comparable to the current terrestrial annual emission of mineral cloud condensation nuclei of 0.5-8*10^12 kg/year (Tegen 2003). On Mars, the availability of condensation nuclei is one of the main factors guiding water-ice cloud formation (Montmessin et al. 2004), which is in turn one of the main climatic factors influencing the hydrological cycle (Michaels et al. 2006) and radiative balance of the planet (Haberle et al. 1999, Wordsworth et al. 2013, Urata and Toon 2013). Increased delivery of condensation nuclei during the

  4. Simulation of atmospheric and terrestrial background signatures for detection and tracking scenarios

    NASA Astrophysics Data System (ADS)

    Schweitzer, Caroline; Stein, Karin

    2015-10-01

    In the fields of early warning, one is depending on reliable image exploitation: Only if the applied detection and tracking algorithms work efficiently, the threat approach alert can be given fast enough to ensure an automatic initiation of the countermeasure. In order to evaluate the performance of those algorithms for a certain electro-optical (EO) sensor system, test sequences need to be created as realistic and comprehensive as possible. Since both, background and target signature, depend on the environmental conditions, a detailed knowledge of the meteorology and climatology is necessary. Trials for measuring these environmental characteristics serve as a solid basis, but might only constitute the conditions during a rather short period of time. To represent the entire variation of meteorology and climatology that the future system will be exposed to, the application of comprehensive atmospheric modelling tools is essential. This paper gives an introduction of the atmospheric modelling tools that are currently used at Fraunhofer IOSB to simulate spectral background signatures in the infrared (IR) range. It is also demonstrated, how those signatures are affected by changing atmospheric and climatic conditions. In conclusion - and with a special focus on the modelling of different cloud types - sources of error and limits are discussed.

  5. Atmospheric pCO2 Reconstructed across the Early Eocene Hyperthermals

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Schubert, B.

    2015-12-01

    Negative carbon isotope excursions (CIEs) are commonly associated with extreme global warming. The Early Eocene is punctuated by five such CIEs, the Paleocene-Eocene thermal maximum (PETM, ca. 55.8 Ma), H1 (ca. 53.6 Ma), H2 (ca. 53.5 Ma), I1 (ca. 53.3 Ma), and I2 (ca. 53.2 Ma), each characterized by global warming. The negative CIEs are recognized in both marine and terrestrial substrates, but the terrestrial substrates exhibit a larger absolute magnitude CIE than the marine substrates. Here we reconcile the difference in CIE magnitude between the terrestrial and marine substrates for each of these events by accounting for the additional carbon isotope fractionation by C3 land plants in response to increased atmospheric pCO2. Our analysis yields background and peak pCO2 values for each of the events. Assuming a common mechanism for each event, we calculate that background pCO2 was not static across the Early Eocene, with the highest background pCO2 immediately prior to I2, the last of the five CIEs. Background pCO2 is dependent on the source used in our analysis with values ranging from 300 to 720 ppmv provided an injection of 13C-depleted carbon with δ13C value of -60‰ (e.g. biogenic methane). The peak pCO2 during each event scales according to the magnitude of CIE, and is therefore greatest during the PETM and smallest during H2. Both background and peak pCO2 are higher if we assume a mechanism of permafrost thawing (δ13C = -25‰). Our reconstruction of pCO2 across these events is consistent with trends in the δ18O value of deep-sea benthic foraminifera, suggesting a strong link between pCO2 and temperature during the Early Eocene.

  6. Early MAVEN results on the Mars Upper Atmosphere and Atmospheric Loss to Space

    NASA Astrophysics Data System (ADS)

    Jakosky, B. M.; Grebowsky, J. M.; Luhmann, J. G.

    2015-10-01

    The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft went into orbit around Mars on 21 September 2014. After a commissioning phase that included science observations of Mars and of Comet Siding Spring during its close approach, its primary science phase began on 16 November 2014 and will run for a full Earth year, until November 2015. Early results on structure, composition and dynamics of the upper atmosphere and on escape to space will be presented.

  7. Modelling the impact of atmospheric and terrestrial inputs on the Black Sea coastal dynamics

    NASA Astrophysics Data System (ADS)

    Kourafalou, V. H.; Stanev, E. V.

    2001-02-01

    The dynamics on the North Western Shelf area of the Black Sea are examined, with an emphasis on the circulation induced by buoyancy due to the land drained fresh waters and by the interaction with the atmosphere, notably wind stress. A three-dimensional, multi-layer hydrodynamic model is employed with realistic topography and parameterisation of river plume physics. We focus on the seasonal patterns of transport of the river induced low-salinity waters within the Coastal Low Salinity Band and the conditions that influence their removal toward the shelf interior. The numerical simulations show that coastal circulation is greatly influenced by river runoff and especially in the case of the Danube, which is excessively high with monthly aver-aged values ranging from 5000 to 10000 m3 /s. A significant contribution of runoff comes from the neighbouring rivers. At the same time, the North Western Shelf is quite broad, so that the coastal dynamics are largely sheltered from the conditions in the deeper sea. Buoyancy due to river runoff thus dominates, creating a southward coastal current that is the predominant pathway for the land-drained inputs. As in all shelf areas, wind stress is a major circulation forcing mechanism and it modifies the buoyancy induced flow. It is shown that the seasonal variability in river runoff and wind stress, in combination with the shelf topography, determines the different pathways for the terrestrial inputs. Implications on the overall basin circulation are drawn, as the availability of low-salinity waters of river origin affects the upper Black Sea layer. Consequently, the formation of distinct water masses (such as the Cold Intermediate Layer) and the properties of the outflow toward the Mediterranean are also influenced.

  8. Requirements for the early atmosphere of Mars from nitrogen isotope ratios

    NASA Technical Reports Server (NTRS)

    Fox, J. L.

    1993-01-01

    The N escape models of Fox and Dalgarno and Fox required the presence of a dense, early CO2 atmosphere to inhibit fractionation of the N isotopes N-15 and N-14. The computed photochemical escape fluxes are so large at the present that the isotope ratio measured by Viking (about 1.62x terrestrial) can be produced in about 1.5 b.y. This model was refined in several ways. It was updated to incorporate the variation of the escape fluxes with increases in the solar fluxes at earlier times according to the model of Zahnle and Walker. As expected, this exacerbates the problem with overfractionation, but not greatly. Most of the escape and fractionation of the N occurs in the last 1.5 b.y., when the solar flux was only slightly different from the present. The dense early atmosphere must persist only a bit longer in order to reproduce the measured isotope ratio. The model was also modified to take into account changes in the O mixing ratio with time in the past, assuming that the O abundance is proportional to the square root of the solar flux. Although the production rate of O from photodissociation of CO2 scales as the solar flux, the strength of the winds and other mixing processes also increases with the solar flux, resulting in possibly more effective transport of O to the lower atmosphere where it is destroyed by catalytic and three-body recombination mechanisms.

  9. A carbon dioxide/methane greenhouse atmosphere on early Mars

    NASA Technical Reports Server (NTRS)

    Brown, L. L.; Kasting, J. F.

    1993-01-01

    One explanation for the formation of fluvial surface features on early Mars is that the global average surface temperature was maintained at or above the freezing point of water by the greenhouse warming of a dense CO2 atmosphere; however, Kasting has shown that CO2 alone is insufficient because the formation of CO2 clouds reduces the magnitude of the greenhouse effect. It is possible that other gases, such as NH3 and CH4, were present in the early atmosphere of Mars and contributed to the greenhouse effect. Kasting et al. investigated the effect of NH3 in a CO2 atmosphere and calculated that an NH3 mixing ratio of approximately 5 x 10 (exp -4) by volume, combined with a CO2 partial pressure of 4-5 bar, could generate a global average surface temperature of 273 K near 3.8 b.y. ago when the fluvial features are believed to have formed. Atmospheric NH3 is photochemically converted to N2 by ultraviolet radiation at wavelengths shortward of 230 nm; maintenance of sufficient NH3 concentrations would therefore require a source of NH3 to balance the photolytic destruction. We have used a one-dimensional photochemical model to estimate the magnitude of the NH3 source required to maintain a given NH3 concentration in a dense CO2 atmosphere. We calculate that an NH3 mixing ratio of 10(exp -4) requires a flux of NH3 on the order of 10(exp 12) molecules /cm-s. This figure is several orders of magnitude greater than estimates of the NH3 flux on early Mars; thus it appears that NH3 with CO2 is not enough to keep early Mars warm.

  10. Heterogeneous Reactions of Polycyclic Aromatic Hydrocarbons on Atmospheric and Terrestrial Surfaces

    NASA Astrophysics Data System (ADS)

    Simonich, S. L.

    2014-12-01

    formation of 2-nitrofluoranthene or 2-nitropyrene, suggesting that heterogeneous reactions predominated. The importance of this research with respect to atmospheric long-range transport of PM-bound PAHs and heterogeneous reaction of PAHs on terrestrial surfaces will be discussed.

  11. The role of terrestrial plants in limiting atmospheric CO(2) decline over the past 24 million years.

    PubMed

    Pagani, Mark; Caldeira, Ken; Berner, Robert; Beerling, David J

    2009-07-01

    Environmental conditions during the past 24 million years are thought to have been favourable for enhanced rates of atmospheric carbon dioxide drawdown by silicate chemical weathering. Proxy records indicate, however, that the Earth's atmospheric carbon dioxide concentrations did not fall below about 200-250 parts per million during this period. The stabilization of atmospheric carbon dioxide concentrations near this minimum value suggests that strong negative feedback mechanisms inhibited further drawdown of atmospheric carbon dioxide by high rates of global silicate rock weathering. Here we investigate one possible negative feedback mechanism, occurring under relatively low carbon dioxide concentrations and in warm climates, that is related to terrestrial plant productivity and its role in the decomposition of silicate minerals. We use simulations of terrestrial and geochemical carbon cycles and available experimental evidence to show that vegetation activity in upland regions of active orogens was severely limited by near-starvation of carbon dioxide in combination with global warmth over this period. These conditions diminished biotic-driven silicate rock weathering and thereby attenuated an important long-term carbon dioxide sink. Although our modelling results are semi-quantitative and do not capture the full range of biogeochemical feedbacks that could influence the climate, our analysis indicates that the dynamic equilibrium between plants, climate and the geosphere probably buffered the minimum atmospheric carbon dioxide concentrations over the past 24 million years. PMID:19571882

  12. Land Use Effects on Atmospheric C-13 Imply a Sizable Terrestrial CO2 Sink in Tropical Latitudes

    NASA Technical Reports Server (NTRS)

    Townsend, Alan R.; Asner, Gregory P.; Tans, Pieter P.; White, James W. C.

    2000-01-01

    Records of atmospheric CO2 and 13-CO2, can be used to distinguish terrestrial vs. oceanic exchanges of CO2 with the atmosphere. However, this approach has proven difficult in the tropics, partly due to extensive land conversion from C-3 to C-4 vegetation. We estimated the effects of such conversion on biosphere-atmosphere C-13 exchange for 1991 through 1999, and then explored how this 'land-use disequilibrium' altered the partitioning of net atmospheric CO2 exchanges between ocean and land using NOAA-CMDL data and a 2D, zonally averaged atmospheric transport model. Our results show sizable CO2 uptake in C-3-dominated tropical regions in seven of the nine years; 1997 and 1998, which included a strong ENSO event, are near neutral. Since these fluxes include any deforestation source, our findings imply either that such sources are smaller than previously estimated, and/or the existence of a large terrestrial CO2 sink in equatorial latitudes.

  13. Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish.

    PubMed

    Dahl, Tais W; Hammarlund, Emma U; Anbar, Ariel D; Bond, David P G; Gill, Benjamin C; Gordon, Gwyneth W; Knoll, Andrew H; Nielsen, Arne T; Schovsbo, Niels H; Canfield, Donald E

    2010-10-19

    The evolution of Earth's biota is intimately linked to the oxygenation of the oceans and atmosphere. We use the isotopic composition and concentration of molybdenum (Mo) in sedimentary rocks to explore this relationship. Our results indicate two episodes of global ocean oxygenation. The first coincides with the emergence of the Ediacaran fauna, including large, motile bilaterian animals, ca. 550-560 million year ago (Ma), reinforcing previous geochemical indications that Earth surface oxygenation facilitated this radiation. The second, perhaps larger, oxygenation took place around 400 Ma, well after the initial rise of animals and, therefore, suggesting that early metazoans evolved in a relatively low oxygen environment. This later oxygenation correlates with the diversification of vascular plants, which likely contributed to increased oxygenation through the enhanced burial of organic carbon in sediments. It also correlates with a pronounced radiation of large predatory fish, animals with high oxygen demand. We thereby couple the redox history of the atmosphere and oceans to major events in animal evolution. PMID:20884852

  14. Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish

    PubMed Central

    Dahl, Tais W.; Hammarlund, Emma U.; Anbar, Ariel D.; Bond, David P. G.; Gill, Benjamin C.; Gordon, Gwyneth W.; Knoll, Andrew H.; Nielsen, Arne T.; Schovsbo, Niels H.; Canfield, Donald E.

    2010-01-01

    The evolution of Earth’s biota is intimately linked to the oxygenation of the oceans and atmosphere. We use the isotopic composition and concentration of molybdenum (Mo) in sedimentary rocks to explore this relationship. Our results indicate two episodes of global ocean oxygenation. The first coincides with the emergence of the Ediacaran fauna, including large, motile bilaterian animals, ca. 550–560 million year ago (Ma), reinforcing previous geochemical indications that Earth surface oxygenation facilitated this radiation. The second, perhaps larger, oxygenation took place around 400 Ma, well after the initial rise of animals and, therefore, suggesting that early metazoans evolved in a relatively low oxygen environment. This later oxygenation correlates with the diversification of vascular plants, which likely contributed to increased oxygenation through the enhanced burial of organic carbon in sediments. It also correlates with a pronounced radiation of large predatory fish, animals with high oxygen demand. We thereby couple the redox history of the atmosphere and oceans to major events in animal evolution. PMID:20884852

  15. Identification of Lichen Metabolism in an Early Devonian Terrestrial Fossil using Carbon Stable Isotope Signature

    NASA Astrophysics Data System (ADS)

    Porter, S.; Jahren, H.

    2002-05-01

    The fossil organismSpongiophyton minutissimum is commonly found in early terrestrial assemblages (Devonian age, 430-340 Ma). Suites of morphological descriptions of this fossil have been published, starting in 1954, and have led to two competing hypotheses: 1.) that this early colonizer of land was a primitive bryophyte, and therefore a precursor to modern plant organisms, and 2.) thatS. minutissimum was a lichen: a close association between an alga and a fungus. Because the ultimate mechanisms for carbon supply to the carboxylating enzyme in bryophytes and lichens differ fundamentally, we expect these two types of organisms to exhibit separate ranges of δ 13Ctissue value. In bryophytes, gaseous carbon dioxide diffuses through perforations in cuticle (resulting in δ 13Catmosphere - δ 13Cbryophyte = ~20 ‰ ). Within the lichen, carbon is supplied to the carboxylating enzyme of the photobiont as carbon dioxide dissolved in fungal cell fluids (resulting in δ 13Catmosphere - δ 13Clichen = ~15 ‰ ). By comparing the δ 13Ctissue value ofS. minutissimum (mean = -23 ‰ ;n = 75) with δ 13Ctissue values in twenty-five lichens, representative of the four different phylogenetic clades (mean = -23 ‰ ;n = 25) and thirty different genera of bryophytes including mosses, liverworts, and hornworts (mean = -28 ‰ ;n = 30), we conclude thatS. minutissimum was cycling carbon via processes that much more closely resembled those of lichens, and not bryophytes. We discuss the general strategies associated with lichen biology, such as the ability to withstand dessication during reproduction, and how they may have contributed to the successful colonization of terrestrial environments.

  16. Atmospheric composition and climate on the early Earth

    PubMed Central

    Kasting, James F; Howard, M. Tazewell

    2006-01-01

    Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85°C. We argue, following others, that this interpretation is incorrect—the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot. A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4 Ga were probably caused by the rise of atmospheric O2 and a concomitant decrease in greenhouse warming by CH4. Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9 Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere. PMID:17008214

  17. Atmospheric composition and climate on the early Earth.

    PubMed

    Kasting, James F; Howard, M Tazewell

    2006-10-29

    Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85 degrees C. We argue, following others, that this interpretation is incorrect-the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot.A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4Ga were probably caused by the rise of atmospheric O2 and a concomitant decrease in greenhouse warming by CH4. Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere. PMID:17008214

  18. The Role of Hydrogen in Determining the Stability of CO2 Atmospheres of Terrestrial Exoplanets Around M Dwarfs

    NASA Astrophysics Data System (ADS)

    Gao, Peter; Hu, Renyu; Robinson, Tyler D.; Yung, Yuk L.

    2014-11-01

    The recent discovery of terrestrial worlds in the Habitable Zones of M Dwarfs necessitates a more intensive investigation of the properties of these planets. One major feature of certain M Dwarfs is their high fluxes of EUV radiation, which photolyzes CO2, an important greenhouse gas that should be abundant on rocky worlds. This photolytic destruction of CO2 can be countered by HOx chemistry: photolysis of HOx species by NUV radiation generates OH, which reacts with CO to regenerate CO2. These processes are balanced around Sun-like stars such that Venus and Mars can maintain CO2-dominated atmospheres. However, M Dwarfs tend to have much lower NUV/EUV flux ratios, which could prevent the formation of significant CO2 atmospheres on any planets they may host. In this study, we evaluate the properties of CO2 atmospheres surrounding an Earth-massed, Earth-sized exoplanet in orbit of an M Dwarf using a 1D photochemical kinetics model. We consider an atmosphere similar in composition to that of Mars, but scaled to have a surface pressure of 1 bar. We choose to focus on Mars-like atmospheres rather than Earth-like ones, as Earth's atmosphere has been altered through biological sources and sinks and the presence of a large liquid water ocean, which are not necessarily present on terrestrial exoplanets. Our preliminary results show that the hydrogen content of the atmosphere is crucial in determining the ratio of CO2 to CO and O2. In particular, for a H2 mixing ratio identical to that of Mars 20-30 ppm), a steady state atmosphere is reached after 10 Gyr consisting of ~85% CO2, ~10% CO, and ~5% O2, with an ozone mixing ratio of ~0.01 ppm. In the extreme case where all hydrogen is lost to space, an atmosphere consisting of ~64% CO2, ~24% CO, and 12% O2 results, while ozone levels reach ~10 ppm. Finally, for H2 mixing ratios similar to that of Earth 0.5 ppm) and no atmospheric escape, a 49% CO2, 34% CO, 17% O2, and 0.1 ppm O3 atmosphere is possible. This not only points to the

  19. Simultaneous Assimilation of FAPAR and Atmospheric CO2 into a Terrestrial Vegetation Model

    NASA Astrophysics Data System (ADS)

    Kaminski, T.; Knorr, W.; Scholze, M.; Gobron, N.; Pinty, B.; Giering, R.; Mathieu, P. P.

    2012-04-01

    Tackling the possible severe impacts of climate change on the carbon cycle and land water resources requires further development of simulation models and monitoring capabilities. Carbon cycle impacts can lead to further climate change through releases of CO2, and impacts on water resources are critical for human survival. A rapidly increasing monitoring capability is Earth Observation (EO) by satellites. Usually, EO by its very nature focuses on diagnosing the current state of the planet. However, it is possible to use EO products in data assimilation systems to improve not only the diagnostics of the current state, but also the accuracy of future predictions. This study investigates the simultaneous assimilation of ground-based atmospheric CO2 concentration data and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) derived from measurements made by the MERIS sensor on-board ENVISAT and to what extent these data can be used to improve models of terrestrial ecosystems, carbon cycling and hydrology. Further development of the Carbon Cycle Data Assimilation System (CCDAS, see http://CCDAS.org) for the purpose of simultaneous assimilation of FAPAR and atmospheric carbon dioxide measurements showed that the design of the ecosystem model is critical for successful implementation of highly efficient variational data assimilation schemes. This is important, because each newly added data stream will typically require a separate observational operator. In the case of this study, it was the leaf development (phenology) sub-model that needed to be developed. As a variational data assimilation scheme, CCDAS relies on first and second derivatives of the underlying model for estimating process parameters with uncertainty ranges. In a subsequent step these parameter uncertainties are mapped forward onto uncertainty ranges for predicted carbon and water fluxes. We present assimilation experiments of MERIS FAPAR at the global scale together with in situ observations

  20. Spectral identification of abiotic O2 buildup from early runaways and rarefied atmospheres

    NASA Astrophysics Data System (ADS)

    Schwieterman, Edward; Meadows, Victoria; Domagal-Goldman, Shawn; Arney, Giada; Robinson, Tyler D.; Luger, Rodrigo; Barnes, Rory

    2016-01-01

    The spectral detection of oxygen (O2) in a planetary atmosphere has been considered a robust signature of life because O2 is highly reactive on planets with Earth-like redox buffers and because significant continuous abiotic sources were thought to be implausible. However, recent work has revealed the possibility that significant O2 may build-up in terrestrial atmospheres through (1) photochemical channels or (2) through the escape of hydrogen. We focus on the latter category here. Significant amounts of abiotic O2 could remain in the atmospheres of planets in the habitable zones of late type stars, where an early runaway greenhouse and massive hydrogen escape during the pre-main-sequence phase could have irreversibly oxidized the crust and mantle (Luger & Barnes 2015). Additionally, it has been hypothesized that O2 could accumulate in the atmospheres of planets with sufficiently low abundances of non-condensable gases such as N2 where water would not be cold trapped in the troposphere, leading to H-escape from UV photolysis in a wet stratosphere (Wordsworth & Pierrehumbert 2014). We self-consistently model the climate, photochemistry, and spectra of both rarefied and post-runaway, high-O2 atmospheres. Because an early runaway might not have lasted long enough for the entire water inventory to escape, we explore both completely desiccated scenarios and cases where a surface ocean remains. We find "habitable" surface conditions for a wide variety of oxygen abundances, atmospheric masses, and CO2 mixing ratios. If O2 builds up from massive or sustained H escape, the O2 abundance should be very high, and could be spectrally indicated by the presence of O2-O2 (O4) collisionally-induced absorption (CIA) features. We generate synthetic direct-imaging and transit transmission spectra of these atmospheres and calculate the strength of the UV/Visible and NIR O4 features. We find that while both the UV/Visible and NIR O4 features are strong in the radiance spectra of very

  1. Spectral identification of abiotic O2 buildup from early runaways and rarefied atmospheres

    NASA Astrophysics Data System (ADS)

    Schwieterman, Edward; Meadows, Victoria; Domagal-Goldman, Shawn; Arney, Giada; Luger, Rodrigo; Barnes, Rory

    2015-11-01

    The spectral detection of oxygen (O2) in a planetary atmosphere has been considered a robust signature of life because O2 is highly reactive on planets with Earth-like redox buffers and because significant continuous abiotic sources were thought to be implausible. However, recent work has revealed the possibility that significant O2 may build-up in terrestrial planet atmospheres through (1) photochemical channels or (2) through massive hydrogen escape. We focus on the latter category here. Significant amounts of abiotic O2 could remain in the atmospheres of planets in the habitable zones of late type stars, where an early runaway greenhouse and massive hydrogen escape during the pre-main-sequence phase could have irreversibly oxidized the crust and mantle (Luger & Barnes 2015). Additionally, it has been hypothesized that O2 could accumulate in the atmospheres of planets with sufficiently low abundances of noncondensable gases such as N2 where water would not be cold trapped in the troposphere, leading to H-escape from UV photolysis in a wet stratosphere (Wordsworth & Pierrehumbert 2014). We self-consistently model the climate, photochemistry, and spectra of both rarefied and post-runaway, high-O2 atmospheres. Because an early runaway might not have lasted long enough for the entire water inventory to have escaped, we explore both completely desiccated scenarios and cases where a surface ocean remains. We find “habitable” surface conditions for a wide variety of oxygen abundances, atmospheric masses, and CO2 mixing ratios. If O2 builds up from H escape, the O2 abundance should be very high, and could be spectrally indicated by the presence of O2 collisionally-induced absorption (CIA) features. We generate synthetic direct-imaging and transit transmission spectra of these atmospheres and calculate the strength of the UV/Visible and NIR O2 CIA features. We find that while both the UV/Visible and NIR O2 CIA features are strong in the direct-imaging spectra of very

  2. Loss of nutrients from terrestrial ecosystems to streams and the atmosphere following land use change in Amazonia

    NASA Astrophysics Data System (ADS)

    Davidson, Eric A.; Neill, Christopher; Krusche, Alex V.; Ballester, Victoria V. R.; Markewitz, Daniel; Figueiredo, Ricardo de O.

    Rates of deforestation in the Amazon region have been accelerating, but the quantity and timing of nutrient losses from forested and deforested ecosystems are poorly understood. This paper investigates the broad variation in soil properties of the Amazon Basin as they influence transfers of plant nutrients from the terrestrial biosphere to the atmosphere and the aquatic biosphere. The dominant lowland soils are highly weathered Oxisols and Ultisols, but significant areas of Alfisols also exist, resulting in a wide range of weatherable primary minerals. Despite this considerable variation among Amazonian soils, a common feature in most mature lowland Amazonian forests is a conservative P cycle and excess N availability. In cattle pastures and secondary forests, however, low rates of internal terrestrial N cycling, low N export to streams, and low gaseous N emissions from soils are common, due to significant previous losses of N through repeated fire. Export of P to streams may increase or remain nearly undetectable after forest-to-pasture conversion, depending on soil type. Oxisols exhibit very low P export, whereas increased P export to pasture streams has been observed in Ultisols of western Amazonia. Calcium is mostly retained in terrestrial ecosystems following deforestation, although increased inputs to streams can be detected when background fluxes are naturally low. Because soil mineralogy and soil texture are both variable and important, the effects of land-use change on nutrient export to aquatic ecosystems and to the atmosphere must be understood within the context of varying soil properties across the Amazon Basin.

  3. Using atmospheric observations to evaluate the spatiotemporal variability of CO2 fluxes simulated by terrestrial biospheric models

    NASA Astrophysics Data System (ADS)

    Fang, Y.; Michalak, A. M.; Shiga, Y. P.; Yadav, V.

    2014-12-01

    Terrestrial biospheric models (TBMs) are used to extrapolate local observations and process-level understanding of land-atmosphere carbon exchange to larger regions, and serve as predictive tools for examining carbon-climate interactions. Understanding the performance of TBMs is thus crucial to the carbon cycle and climate science communities. In this study, we present and assess an approach to evaluating the spatiotemporal patterns, rather than aggregated magnitudes, of net ecosystem exchange (NEE) simulated by TBMs using atmospheric CO2 measurements. The approach is based on statistical model selection implemented within a high-resolution atmospheric inverse model. Using synthetic data experiments, we find that current atmospheric observations are sensitive to the underlying spatiotemporal flux variability at sub-biome scales for a large portion of North America, and that atmospheric observations can therefore be used to evaluate simulated spatiotemporal flux patterns as well as to differentiate between multiple competing TBMs. Experiments using real atmospheric observations and four prototypical TBMs further confirm the applicability of the method, and demonstrate that the performance of TBMs in simulating the spatiotemporal patterns of NEE varies substantially across seasons, with best performance during the growing season and more limited skill during transition seasons. This result is consistent with previous work showing that the ability of TBMs to model flux magnitudes is also seasonally-dependent. Overall, the proposed approach provides a new avenue for evaluating TBM performance based on sub-biome-scale flux patterns, presenting an opportunity for assessing and informing model development using atmospheric observations.

  4. Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.

    PubMed

    Motani, Ryosuke; Jiang, Da-yong; Tintori, Andrea; Rieppel, Olivier; Chen, Guan-bao

    2014-01-01

    Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction. PMID:24533127

  5. Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils

    PubMed Central

    Motani, Ryosuke; Jiang, Da-yong; Tintori, Andrea; Rieppel, Olivier; Chen, Guan-bao

    2014-01-01

    Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction. PMID:24533127

  6. Photochemistry in terrestrial exoplanet atmospheres. III. Photochemistry and thermochemistry in thick atmospheres on super Earths and mini Neptunes

    SciTech Connect

    Hu, Renyu; Seager, Sara

    2014-03-20

    Some super Earths and mini Neptunes will likely have thick atmospheres that are not H{sub 2}-dominated. We have developed a photochemistry-thermochemistry kinetic-transport model for exploring the compositions of thick atmospheres on super Earths and mini Neptunes, applicable for both H{sub 2}-dominated atmospheres and non-H{sub 2}-dominated atmospheres. Using this model to study thick atmospheres for wide ranges of temperatures and elemental abundances, we classify them into hydrogen-rich atmospheres, water-rich atmospheres, oxygen-rich atmospheres, and hydrocarbon-rich atmospheres. We find that carbon has to be in the form of CO{sub 2} rather than CH{sub 4} or CO in a H{sub 2}-depleted water-dominated thick atmosphere and that the preferred loss of light elements from an oxygen-poor carbon-rich atmosphere leads to the formation of unsaturated hydrocarbons (C{sub 2}H{sub 2} and C{sub 2}H{sub 4}). We apply our self-consistent atmosphere models to compute spectra and diagnostic features for known transiting low-mass exoplanets GJ 1214 b, HD 97658 b, and 55 Cnc e. For GJ 1214 b, we find that (1) C{sub 2}H{sub 2} features at 1.0 and 1.5 μm in transmission and C{sub 2}H{sub 2} and C{sub 2}H{sub 4} features at 9-14 μm in thermal emission are diagnostic for hydrocarbon-rich atmospheres; (2) a detection of water-vapor features and a confirmation of the nonexistence of methane features would provide sufficient evidence for a water-dominated atmosphere. In general, our simulations show that chemical stability has to be taken into account when interpreting the spectrum of a super Earth/mini Neptune. Water-dominated atmospheres only exist for carbon to oxygen ratios much lower than the solar ratio, suggesting that this kind of atmospheres could be rare.

  7. Quantitative Hydraulic Models Of Early Land Plants Provide Insight Into Middle Paleozoic Terrestrial Paleoenvironmental Conditions

    NASA Astrophysics Data System (ADS)

    Wilson, J. P.; Fischer, W. W.

    2010-12-01

    humidity (<20%) combined with elevated temperatures (>25°C) could cause sufficient cavitation to reduce hydraulic conductivity by 50%. This suggests that the Early Devonian environments that supported the earliest vascular plants were not subject to prolonged midseason droughts, or, alternatively, that the growing season was short. This places minimum constraints on water availability (e.g., groundwater hydration, relative humidity) in locations where Asteroxylon fossils are found; these environments must have had high relative humidities, comparable to tropical riparian environments. Given these constraints, biome-scale paleovegetation models that place early vascular plants distal to water sources can be revised to account for reduced drought tolerance. Paleoclimate proxies that treat early terrestrial plants as functionally interchangeable can incorporate physiological differences in a quantitatively meaningful way. Application of hydraulic models to fossil plants provides an additional perspective on the 475 million-year history of terrestrial photosynthetic environments and has potential to corroborate other plant-based paleoclimate proxies.

  8. Mentors, networks, and resources for early career female atmospheric scientists

    NASA Astrophysics Data System (ADS)

    Hallar, A. G.; Avallone, L. M.; Edwards, L. M.; Thiry, H.; Ascent

    2011-12-01

    Atmospheric Science Collaborations and Enriching NeTworks (ASCENT) is a workshop series designed to bring together early career female scientists in the field of atmospheric science and related disciplines. ASCENT is a multi-faceted approach to retaining these junior scientists through the challenges in their research and teaching career paths. During the workshop, senior women scientists discuss their career and life paths. They also lead seminars on tools, resources and methods that can help early career scientists to be successful. Networking is a significant aspect of ASCENT, and many opportunities for both formal and informal interactions among the participants (of both personal and professional nature) are blended in the schedule. The workshops are held in Steamboat Springs, Colorado, home of a high-altitude atmospheric science laboratory - Storm Peak Laboratory, which also allows for nearby casual outings and a pleasant environment for participants. Near the conclusion of each workshop, junior and senior scientists are matched in mentee-mentor ratios of two junior scientists per senior scientist. An external evaluation of the three workshop cohorts concludes that the workshops have been successful in establishing and expanding personal and research-related networks, and that seminars have been useful in creating confidence and sharing resources for such things as preparing promotion and tenure packages, interviewing and negotiating job offers, and writing successful grant proposals.

  9. Heat flow vs. atmospheric greenhouse on early Mars

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Postawko, S. E.

    1991-01-01

    Researchers derived a quantitative relationship between the effectiveness of an atmospheric greenhouse and internal heat flow in producing the morphological differences between earlier and later Martian terrains. The derivation is based on relationships previously derived by other researchers. The reasoning may be stated as follows: the CO2 mean residence time in the Martian atmosphere is almost certainly much shorter than the total time span over which early climate differences are thought to have been sustained. Therefore, recycling of previously degassed CO2 quickly becomes more important than the ongoing supply of juvenile CO2. If so, then the atmospheric CO2 pressure, and thereby the surface temperature, may be approximated mathematically as a function of the total degassed CO2 in the atmosphere plus buried material and the ratio of the atmospheric and regolith mean residence times. The latter ratio can also be expressed as a function of heat flow. Hence, it follows that the surface temperature may be expressed as a function of heat flow and the total amount of available CO2. However, the depth to the water table can simultaneously be expressed as a function of heat flow and the surface temperature (the boundary condition). Therefore, for any given values of total available CO2 and regolith conductivity, there exist coupled independent equations which relate heat flow, surface temperature, and the depth to the water table. This means we can now derive simultaneous values of surface temperature and the depth of the water table for any value of the heat flow. The derived relationship is used to evaluate the relative importance of the atmospheric greenhouse effect and the internal regolith thermal gradient in producing morphological changes for any value of the heat flow, and to assess the absolute importance of each of the values of the heat flow which are thought to be reasonable on independent geophysical grounds.

  10. Responses of global terrestrial evapotranspiration to climate change and increasing atmospheric CO2 in the 21st century

    NASA Astrophysics Data System (ADS)

    Pan, Shufen; Tian, Hanqin; Dangal, Shree R. S.; Yang, Qichun; Yang, Jia; Lu, Chaoqun; Tao, Bo; Ren, Wei; Ouyang, Zhiyun

    2015-01-01

    Quantifying the spatial and temporal patterns of the water lost to the atmosphere through land surface evapotranspiration (ET) is essential for understanding the global hydrological cycle, but remains much uncertain. In this study, we use the Dynamic Land Ecosystem Model to estimate the global terrestrial ET during 2000-2009 and project its changes in response to climate change and increasing atmospheric CO2 under two IPCC SRES scenarios (A2 and B1) during 2010-2099. Modeled results show a mean annual global terrestrial ET of about 549 (545-552) mm yr-1 during 2000-2009. Relative to the 2000s, global terrestrial ET for the 2090s would increase by 30.7 mm yr-1 (5.6%) and 13.2 mm yr-1 (2.4%) under the A2 and B1 scenarios, respectively. About 60% of global land area would experience increasing ET at rates of over 9.5 mm decade-1 over the study period under the A2 scenario. The Arctic region would have the largest ET increase (16% compared with the 2000s level) due to larger increase in temperature than other regions. Decreased ET would mainly take place in regions like central and western Asia, northern Africa, Australia, eastern South America, and Greenland due to declines in soil moisture and changing rainfall patterns. Our results indicate that warming temperature and increasing precipitation would result in large increase in ET by the end of the 21st century, while increasing atmospheric CO2 would be responsible for decrease in ET, given the reduction of stomatal conductance under elevated CO2.

  11. Hf-W chronology of the accretion and early evolution of asteroids and terrestrial planets

    NASA Astrophysics Data System (ADS)

    Kleine, Thorsten; Touboul, Mathieu; Bourdon, Bernard; Nimmo, Francis; Mezger, Klaus; Palme, Herbert; Jacobsen, Stein B.; Yin, Qing-Zhu; Halliday, Alexander N.

    2009-09-01

    large collisions, and changes in the metal-silicate partition coefficients of W due to changing fO 2 in differentiating planetary bodies. Calculated core formation ages for Mars range from 0 to 20 Myr after CAI formation and currently cannot distinguish between scenarios where Mars formed by runaway growth and where its formation was more protracted. Tungsten model ages for core formation in Earth range from ˜30 Myr to >100 Myr after CAIs and hence do not provide a unique age for the formation of Earth. However, the identical 182W/ 184W ratios of the lunar and terrestrial mantles provide powerful evidence that the Moon-forming giant impact and the final stage of Earth's core formation occurred after extinction of 182Hf (i.e., more than ˜50 Myr after CAIs), unless the Hf/W ratios of the bulk silicate Moon and Earth are identical to within less than ˜10%. Furthermore, the identical 182W/ 184W of the lunar and terrestrial mantles is difficult to explain unless either the Moon consists predominantly of terrestrial material or the W in the proto-lunar magma disk isotopically equilibrated with the Earth's mantle. Hafnium-tungsten chronometry also provides constraints on the duration of magma ocean solidification in terrestrial planets. Variations in the 182W/ 184W ratios of martian meteorites reflect an early differentiation of the martian mantle during the effective lifetime of 182Hf. In contrast, no 182W variations exist in the lunar mantle, demonstrating magma ocean solidification later than ˜60 Myr, in agreement with 147Sm- 143Nd ages for ferroan anorthosites. The Moon-forming giant impact most likely erased any evidence of a prior differentiation of Earth's mantle, consistent with a 146Sm- 142Nd age of 50-200 Myr for the earliest differentiation of Earth's mantle. However, the Hf-W chronology of the formation of Earth's core and the Moon-forming impact is difficult to reconcile with the preservation of 146Sm- 142Nd evidence for an early (<30 Myr after CAIs

  12. The non-homogeneous accumulation model for terrestrial planet formation and the consequences for the atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Turekian, K. K.; Clark, S. P., Jr.

    1975-01-01

    The nonhomogeneous-accumulation model for the formation of the terrestrial planets is described, and its consequences for the formation of the Venusian atmosphere are assayed in the context of our knowledge of the composition of the earth and carbonaceous chondrites. The relative abundances of the low-temperature condensibles in the reservoirs at the earth's surface are applied to Venus. Although carbonaceous chondrites show similar properties for the chemically bound elements, they show large deficiencies for the rare gases. The major gases on Venus, by volume, are predicted to be 98.12% CO2, 1.86% N2 and 0.02% Ar-40.

  13. Multiple Tectonic Regimes and Diverging Geologic Histories of Terrestrial Planets: The Importance of the Early Years

    NASA Astrophysics Data System (ADS)

    Weller, M. B.; Lenardic, A.

    2013-12-01

    We use 3D mantle convection and planetary tectonics simulations to explore the links between tectonic regimes, the age of a planet, and its surface evolution. We demonstrate that the tectonic regime of a planet is dependant on its thermal and climatic evolution. A young planet with a high degree of internal heating has a strong susceptibility to climate-induced transitions in tectonic styles. The amplitude of a long lived surface temperature perturbation needed to initiate a transition from a mobile- to a stagnant-lid mode of tectonics decreases with increasing degrees of internal heating. As surface temperatures increase, episodic convection occurs over a larger range of lid strengths, suggesting that young and high temperature planetary bodies have a higher potential to exist in a long-lived mode of episodic tectonics. Once the system transitions into a stagnant-lid, the reverse transition is not attainable by a return to the original surface temperature, which indicates that the climate-tectonic system is bi-stable [multiple tectonic states are possible for the same parameter values]. As a planet ages, the system becomes increasingly insensitive to surface temperature induced transitions after ~30 - 50% of the original radiogenics decay. For a planet to transition from mobile- into episodic-, or stagnant-lid modes through the mechanism of increasing surface temperatures, the implication is that the change would have to occur early in its evolution, within the first 1-2 giga years. While the sensitivity to climatic perturbations decreases with the age of the planet, decreasing internal heat production can usher in a transition in tectonic regimes from a stagnant-lid state, into an episodic- and finally mobile-/sluggish-lid regimes. The implications are that terrestrial worlds can alternate between multiple tectonic states over giga-year timescales. The implications for the early Earth and Earth-Venus differences will be discussed.

  14. How do Early Impacts Modulate the Tectonic, Magnetic and Climatic Evolutions of Terrestrial Planets?

    NASA Astrophysics Data System (ADS)

    Jellinek, M.; Jackson, M. G.; Lenardic, A.; Weller, M. B.

    2015-12-01

    The landmark discovery showing that the 142Nd/144Nd ratio of the accessible modern terrestrial mantle is greater than ordinary-chondrites has remarkable implications for the formation, as well as the geodynamic, magnetic and climatic histories of Earth. If Earth is derived from ordinary chondrite precursors, mass balance requires that a missing reservoir with 142Nd/144Nd lower than ordinary chondrites was isolated from the accessible mantle within 20-30 Myr following accretion. Critically for Earth evolution, this reservoir hosts the equivalent of the modern continents' budget of radioactive heat-producing elements (U, Th and K). If this reservoir was lost to space through mechanical erosion by early impactors, the planet's radiogenic heat generation is 18-45% lower than chondrite-based compositional estimates. Recent geodynamic calculations suggest that this reduced heat production will favor the emergence of Earth-like plate tectonics. However, parameterized thermal history calculations favor a relatively recent transition from mostly Atlantic-sized plates to the current plate tectonic mode characterized predominantly by the subduction of Pacific-sized plates. Such a transition in the style of Earth's plate tectonics is also consistent with a delayed dynamo and an evolving rate of volcanic outgassing that ultimately favors Earth's long-term clement climate. By contrast, relatively enhanced radiogenic heat production related to a less early impact erosion reduces the likelihood of present day plate tectonics: A chondritic Earth has a stronger likelihood to evolve as a Venus-like planet characterized by potentially wild swings in tectonic and climatic regime. Indeed, differences in internal heat production related to varying extents of impact erosion may exert strong control over Earth's climate and explain aspects of the differences among the current climatic regimes of Earth, Venus and Mars.

  15. Consistent assimilation of MERIS FAPAR and atmospheric CO2 into a terrestrial vegetation model and interactive mission benefit analysis

    NASA Astrophysics Data System (ADS)

    Kaminski, T.; Knorr, W.; Scholze, M.; Gobron, N.; Pinty, B.; Giering, R.; Mathieu, P.-P.

    2012-08-01

    The terrestrial biosphere is currently a strong sink for anthropogenic CO2 emissions. Through the radiative properties of CO2, the strength of this sink has a direct influence on the radiative budget of the global climate system. The accurate assessment of this sink and its evolution under a changing climate is, hence, paramount for any efficient management strategies of the terrestrial carbon sink to avoid dangerous climate change. Unfortunately, simulations of carbon and water fluxes with terrestrial biosphere models exhibit large uncertainties. A considerable fraction of this uncertainty reflects uncertainty in the parameter values of the process formulations within the models. This paper describes the systematic calibration of the process parameters of a terrestrial biosphere model against two observational data streams: remotely sensed FAPAR (fraction of absorbed photosynthetically active radiation) provided by the MERIS (ESA's Medium Resolution Imaging Spectrometer) sensor and in situ measurements of atmospheric CO2 provided by the GLOBALVIEW flask sampling network. We use the Carbon Cycle Data Assimilation System (CCDAS) to systematically calibrate some 70 parameters of the terrestrial BETHY (Biosphere Energy Transfer Hydrology) model. The simultaneous assimilation of all observations provides parameter estimates and uncertainty ranges that are consistent with the observational information. In a subsequent step these parameter uncertainties are propagated through the model to uncertainty ranges for predicted carbon fluxes. We demonstrate the consistent assimilation at global scale, where the global MERIS FAPAR product and atmospheric CO2 are used simultaneously. The assimilation improves the match to independent observations. We quantify how MERIS data improve the accuracy of the current and future (net and gross) carbon flux estimates (within and beyond the assimilation period). We further demonstrate the use of an interactive mission benefit analysis tool

  16. The use of the terrestrial snails of the genera Megalobulimus and Thaumastus as representatives of the atmospheric carbon reservoir

    PubMed Central

    Macario, Kita D.; Alves, Eduardo Q.; Carvalho, Carla; Oliveira, Fabiana M.; Ramsey, Christopher Bronk; Chivall, David; Souza, Rosa; Simone, Luiz Ricardo L.; Cavallari, Daniel C.

    2016-01-01

    In Brazilian archaeological shellmounds, many species of land snails are found abundantly distributed throughout the occupational layers, forming a contextualized set of samples within the sites and offering a potential alternative to the use of charcoal for radiocarbon dating analyses. In order to confirm the effectiveness of this alternative, one needs to prove that the mollusk shells reflect the atmospheric carbon isotopic concentration in the same way charcoal does. In this study, 18 terrestrial mollusk shells with known collection dates from 1948 to 2004 AD, around the nuclear bombs period, were radiocarbon dated. The obtained dates fit the SH1-2 bomb curve within less than 15 years range, showing that certain species from the Thaumastus and Megalobulimus genera are reliable representatives of the atmospheric carbon isotopic ratio and can, therefore, be used to date archaeological sites in South America. PMID:27271349

  17. Changes in the terrestrial atmosphere-ionosphere-magnetosphere system due to ion propulsion for solar power satellite placement

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Grebowsky, J. M.

    1979-01-01

    Preliminary estimates of the effects massive Ar(+) injections on the ionosphere-plasmasphere system with specific emphasis on potential communications disruptions are given. The effects stem from direct Ar(+) precipitation into the atmosphere and from Ar(+) beam induced precipitation of MeV radiation belt protons. These injections result from the construction of Solar Power Satellites using earth-based materials in which sections of a satellite must be lifted from low earth to geosynchronous orbit by means of ion propulsion based on the relatively abundant terrestrial atmospheric component, Ar. The total amount of Ar(+) injected in transporting the components for each Solar Power Satellite is comparable to the total ion content of the ionosphere-plasmasphere system while the total energy injected is larger than that of this system. It is suggested that such effects may be largely eliminated by using lunar-based rather than earth-based satellite construction materials.

  18. The use of the terrestrial snails of the genera Megalobulimus and Thaumastus as representatives of the atmospheric carbon reservoir.

    PubMed

    Macario, Kita D; Alves, Eduardo Q; Carvalho, Carla; Oliveira, Fabiana M; Ramsey, Christopher Bronk; Chivall, David; Souza, Rosa; Simone, Luiz Ricardo L; Cavallari, Daniel C

    2016-01-01

    In Brazilian archaeological shellmounds, many species of land snails are found abundantly distributed throughout the occupational layers, forming a contextualized set of samples within the sites and offering a potential alternative to the use of charcoal for radiocarbon dating analyses. In order to confirm the effectiveness of this alternative, one needs to prove that the mollusk shells reflect the atmospheric carbon isotopic concentration in the same way charcoal does. In this study, 18 terrestrial mollusk shells with known collection dates from 1948 to 2004 AD, around the nuclear bombs period, were radiocarbon dated. The obtained dates fit the SH1-2 bomb curve within less than 15 years range, showing that certain species from the Thaumastus and Megalobulimus genera are reliable representatives of the atmospheric carbon isotopic ratio and can, therefore, be used to date archaeological sites in South America. PMID:27271349

  19. The use of the terrestrial snails of the genera Megalobulimus and Thaumastus as representatives of the atmospheric carbon reservoir

    NASA Astrophysics Data System (ADS)

    Macario, Kita D.; Alves, Eduardo Q.; Carvalho, Carla; Oliveira, Fabiana M.; Ramsey, Christopher Bronk; Chivall, David; Souza, Rosa; Simone, Luiz Ricardo L.; Cavallari, Daniel C.

    2016-06-01

    In Brazilian archaeological shellmounds, many species of land snails are found abundantly distributed throughout the occupational layers, forming a contextualized set of samples within the sites and offering a potential alternative to the use of charcoal for radiocarbon dating analyses. In order to confirm the effectiveness of this alternative, one needs to prove that the mollusk shells reflect the atmospheric carbon isotopic concentration in the same way charcoal does. In this study, 18 terrestrial mollusk shells with known collection dates from 1948 to 2004 AD, around the nuclear bombs period, were radiocarbon dated. The obtained dates fit the SH1-2 bomb curve within less than 15 years range, showing that certain species from the Thaumastus and Megalobulimus genera are reliable representatives of the atmospheric carbon isotopic ratio and can, therefore, be used to date archaeological sites in South America.

  20. Reducing Uncertainty in Terrestrial Biosphere Models with Satellite Observations of Atmospheric CO2: Comparing MsTMIP with GOSAT

    NASA Astrophysics Data System (ADS)

    Swetish, J. B.; Huntzinger, D. N.; Schwalm, C. R.; Fisher, J. B.; Liu, J.; Michalak, A. M.; Bowman, K. W.

    2014-12-01

    Global-scale terrestrial biosphere models (TBMs) vary in their underlying driving assumptions, inputs, and parameterizations. As a result, TBM estimates of carbon fluxes and pools vary greatly and the lack of direct observations of land-atmosphere carbon exchange at the same spatio-temporal resolution (e.g., 0.5° x 0.5° degree and sub-daily to monthly) of model estimates makes it difficult to assess TBM performance in terms of their ability to represent the terrestrial carbon cycle. Atmospheric CO2 measurements, however, may be a potentially powerful observational constraint for TBMs because they provide an integrated view of surface sources and sinks of carbon. The Greenhouse Gases Observing Satellite (GOSAT) measures atmospheric CO2 from space at spatio-temporal scales relatively consistent with model estimates. Using TBM estimates from the North American Carbon Program Multi-scale synthesis and Terrestrial Model Intercomparison Project (MsTMIP), together with estimates of fossil fuel emissions and air-sea fluxes, we translate surfaces fluxes into atmospheric CO2 concentrations using the GEOS-Chem atmospheric transport model. The performance of MsTMIP TBMs is evaluated by comparing the dry air column-averaged mole fractions of CO2 (ΧCO2) from transported surface fluxes to observations of ΧCO2 from GOSAT. While MsTMIP ΧCO2 signals are generally consistent with GOSAT ΧCO2 in the southern hemisphere, MsTMIP and GOSAT XCO2 show profound differences in the northern hemisphere (NH). In general, MsTMIP XCO2 tends to be higher than GOSAT XCO2 at northern latitudes, especially in the NH summer and fall. Looking specifically at regions in the NH, we compare each MsTMIP ΧCO2 to GOSAT ΧCO2 in terms of its ability to reproduce the spatial distribution, magnitude and timing of the GOSAT ΧCO2 seasonal cycle. We use the information derived from the comparison to link model performance with how certain processes are represented within the models themselves, thus aiding

  1. The "terminal Triassic catastrophic extinction event" in perspective: a review of carboniferous through Early Jurassic terrestrial vertebrate extinction patterns

    USGS Publications Warehouse

    Weems, R.E.

    1992-01-01

    A catastrophic terminal Triassic extinction event among terrestrial vertebrates is not supported by available evidence. The current model for such an extinction is based on at least eight weak or untenable assumptions: (1) a terminal Triassic extinction-inducing asteroid impact occurred, (2) a terminal Triassic synchronous mass extinction of terrestrial vertebrates occurred, (3) a concurrent terminal Triassic marine extinction occurred, (4) all terrestrial vertebrate families have similar diversities and ecologies, (5) changes in familial diversity can be gauged accurately from the known fossil record, (6) extinction of families can be compared through time without normalizing for changes in familial diversity through time, (7) extinction rates can be compared without normalizing for differing lengths of geologic stages, and (8) catastrophic mass extinctions do not select for small size. These assumptions have resulted in unsupportable and (or) erroneous conclusions. Carboniferous through Early Jurassic terrestrial vertebrate families mostly have evolution and extinction patterns unlike the vertebrate evolution and extinction patterns during the terminal Cretaceous event. Only the Serpukhovian (mid Carboniferous) extinction event shows strong analogy to the terminal Cretaceous event. Available data suggest no terminal Triassic extinction anomaly, but rather a prolonged and nearly steady decline in the global terrestrial vertebrate extinction rate throughout the Triassic and earliest Jurassic. ?? 1992.

  2. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: atmospheric expansion and thermal escape.

    PubMed

    Erkaev, Nikolai V; Lammer, Helmut; Odert, Petra; Kulikov, Yuri N; Kislyakova, Kristina G; Khodachenko, Maxim L; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-11-01

    The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H₂O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R(Earth) and a mass of 10 M(Earth). We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general. PMID:24251443

  3. Speciation of C-O-H volatiles in reduced magmas applicable to early terrestrial and planetary deep volatile cycles

    NASA Astrophysics Data System (ADS)

    Armstrong, Lora; Hirschmann, Marc

    2014-05-01

    The speciation and solubility of C-O-H volatiles in reduced magmas are of great importance for volatile behavior in the early Earth and other planets determining partitioning between Earth's earliest atmospheres, mantle, and cores, as well as influencing volcanogenic degassing on reduced planetary bodies such as Mars and the Moon. In mafic and ultramafic magmas, C is soluble chiefly as carbonate under oxidizing conditions, but when fO2 is below that required for graphite (or diamond) saturation, carbonate solubility diminishes severely. This has left the question as to what, if any, species may host dissolved C in magmas under reducing conditions. Initial results suggested that the principle species may be CH4 (Mysen et al. 2009), but experiments at well-defined thermodynamic conditions have shown that CH4 solubility is very small except under conditions of very high H2 fugacity (Ardia et al. 2012). More recent experiments (Wetzel et al. 2013; Stanley et al. 2014) have identified Fe-carbonyl-like species as possibly the most stable. To clarify the relative stability of these species, we have conducted additional high pressure experiments at 1.2 GPa and 1400°C with graphite-saturated martian and terrestrial (MORB) basalt compositions, over a range of oxygen fugacities, paying careful attention to the availability of H2O. FTIR and Raman analyses reveal a range of distinct species that predominate as a function of fO2 and availability of H2O. At comparatively oxidizing conditions, carbonate is the most abundant species but within 1 log unit of iron wustite (IW), carbonyl-like species predominate, provided that conditions are comparatively dry. At yet more reducing conditions, carbonyl is absent and instead N-H associated species (perhaps amides?) are more important. Methane is observed only when quenched glasses have appreciable H2O (approaching ~ 1 wt.%). In all cases, solubilities are small when conditions are reduced, with <100 ppm C at IW or below.

  4. Sea surface temperatures and terrestrial water storage provide early warning information about fire season severity in the Amazon

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Randerson, J. T.; Morton, D. C.; DeFries, R. S.; Collatz, G. J.; Kasibhatla, P. S.; Giglio, L.; Jin, Y.; Marlier, M. E.; Velicogna, I.; Famiglietti, J. S.

    2012-12-01

    Fires in South America cause forest degradation and contribute to carbon emissions associated with land use change. We investigated the relationship between year-to-year changes in satellite observations of active fires in South America and sea surface temperatures. We found that the Oceanic Niño Index was correlated with interannual fire activity in the eastern Amazon whereas the Atlantic Multidecadal Oscillation index was more closely linked with fires in the southern and southwestern Amazon. Combining these two climate indices, we developed an empirical model that predicted regional fire season severity with 3-5 month lead times. We further examined the hypothesis that year-to-year variations in soil water recharge during the wet season modifies atmospheric water vapor and fire behavior during the following dry season. We tested this hypothesis by analyzing terrestrial water storage (TWS) observations from the Gravity Recovery and Climate Experiment (GRACE), active fires from the Moderate Resolution Imaging Spectroradiometer (MODIS), and other satellite and climate data during 2002-2011. We found that TWS anomalies at the end of the wet season were negatively correlated with the number of active fires during the dry season for three regions across the southern Amazon. The most significant relationships (p < 0.02) were observed for TWS anomalies during April-August, several months before the peak month of burning (September). Analysis of other datasets provided evidence for a cascade of processes during drought events, with lower cumulative precipitation (and higher cumulative evapotranspiration) in the wet season substantially reducing TWS, and subsequently surface and column water vapor. Our results indicate that TWS from GRACE also has the potential to provide early warning information about fire season severity in the Amazon.

  5. A lookup table to compute high energy cosmic ray effects on terrestrial atmospheric chemistry

    NASA Astrophysics Data System (ADS)

    Atri, Dimitra

    A variety of events such as gamma-ray bursts and supernovae may expose the Earth to an increased flux of high-energy cosmic rays, with potentially important effects on the biosphere. Existing atmospheric chemistry software does not have the capability of incorporating the effects of substantial cosmic ray flux above 10 GeV . An atmospheric code, the NASA-Goddard Space Flight Center two-dimensional (latitude, altitude) time-dependent atmospheric model (NGSFC), is used to study atmospheric chemistry changes. We have created a table that, with the use of the NGSFC code, can be used to simulate the effects of high energy cosmic rays (10 GeV - 1 PeV ) ionizing the atmosphere. By interpolation, the table can be used to generate values for other uses which depend upon atmospheric energy deposition by ensembles of high-energy cosmic rays. We discuss the table, its use, weaknesses, and strengths.

  6. Hot atom populations in the terrestrial atmosphere. A comparison of the nonlinear and linearized Boltzmann equations

    NASA Astrophysics Data System (ADS)

    Sospedra-Alfonso, Reinel; Shizgal, Bernie D.

    2012-11-01

    We use a finite difference discretization method to solve the space homogeneous, isotropic nonlinear Boltzmann equation. We study the time evolution of the distribution function in relation to the solution of the linearized Boltzmann equation for three different initial conditions. The relaxation process is described in terms of the Laguerre moments and the spectral properties of the linearized collision operator. The motivation is the need to include self-collisions in the study of suprathermal oxygen atoms in the terrestrial exosphere.

  7. Multiple scattering of polarized light in planetary atmospheres. II - Sunlight reflected by terrestrial water clouds.

    NASA Technical Reports Server (NTRS)

    Hansen, J. E.

    1971-01-01

    The intensity and polarization of sunlight reflected by terrestrial water clouds are computed with the doubling method. The calculations illustrate that this method can be effectively used in problems involving strongly anisotropic phase matrices. The method can, therefore, be used to derive information about planetary clouds, including those of the earth, from polarimetric observations. The results of the computations indicate that the polarization is more sensitive than the intensity to cloud microstructure, such as particle size and shape.

  8. Increasing retention of early career female atmospheric scientists

    NASA Astrophysics Data System (ADS)

    Edwards, L. M.; Hallar, A. G.; Avallone, L. M.; Thiry, H.

    2010-12-01

    Atmospheric Science Collaborations and Enriching NeTworks (ASCENT) is a workshop series designed to bring together early career female scientists in the field of atmospheric science and related disciplines. ASCENT uses a multi-faceted approach to provide junior scientists with tools that will help them meet the challenges in their research and teaching career paths and will promote their retention in the field. During the workshop, senior women scientists discuss their career and life paths. They also lead seminars on tools, resources and methods that can help early career scientists to be successful and prepared to fill vacancies created by the “baby boomer” retirees. Networking is a significant aspect of ASCENT, and many opportunities for both formal and informal interactions among the participants (of both personal and professional nature) are blended in the schedule. The workshops are held in Steamboat Springs, Colorado, home of a high-altitude atmospheric science laboratory, Storm Peak Laboratory, which also allows for nearby casual outings and a pleasant environment for participants. Near the conclusion of each workshop, junior and senior scientists are matched in mentee-mentor ratios of two junior scientists per senior scientist. Post-workshop reunion events are held at national scientific meetings to maintain connectivity among each year’s participants, and for collaborating among participants of all workshops held to date. Evaluations of the two workshop cohorts thus far conclude that the workshops have been successful in achieving the goals of establishing and expanding personal and research-related networks, and that seminars have been useful in creating confidence and sharing resources for such things as preparing promotion and tenure packages, interviewing and negotiating job offers, and writing successful grant proposals.

  9. Reproducing Experiment in the Shock-Induced Removal of CO2 From the Atmosphere on the Early Mars

    NASA Astrophysics Data System (ADS)

    Ikeda, K.; Isobe, H.

    2005-12-01

    The evolution of the Mars is one of the most important problems on the environmental issues of terrestrial planets. The early Martian atmosphere was formed by degassing and it consisted thick CO2. Most of the CO2 must have been removed from the early Martian atmosphere in order to change to the present thin atmosphere. Heavy bombardment of planetesimals had been one of the important high energy processes on the primitive Mars. In this study, we experiment to reproduce the reaction between the early Martian atmosphere and the minerals in the high temperature condition caused by the shock-induced heating and discuss its effect of CO2 removal from the atmosphere. Reaction experiments were carried out with CO2 or CO2- H2O fluid at the pressure of 100MPa or 50MPa. A range of the temperature is 200-650°C and run duration is 7 days. Starting materials was the mixture of olivine, orthopyroxene, diopside, and plagioclase represented the main mineral phases of the early Mars. After the experiment, the reacted CO2 was weighed by CO2 mass remained in the experimental capsule. CO2 reactivity increased with decreasing temperature. If removed CO2 fixed as carbonate minerals in the run products, abundance of the carbonate minerals may be as much as 10% of the run products. Presence of H2O has no remarkable effect on CO2 reactivity. A Martian meteorite, ALH84001 includes approximately 1% of carbonate. Large-scale impact on the Martian surface brought shock-induced heating up to several hundred degrees C at several kilometers in depth. Accessory carbonate minerals in Martian rocks may be formed by reactions of CO2 atmosphere and brecciated rocks under craters. A layer of 1% carbonate-bearing rocks with 5km in thickness at Martian surface can settle 0.5MPa of CO2 (1MPa equivalent at the terrestrial gravity) from the Martian atmosphere. Carbonate formation by the shock-induced heating may have played a significant role in the evolution of the primitive Martian atmosphere.

  10. The coupled 182W-142Nd record of early terrestrial mantle differentiation

    NASA Astrophysics Data System (ADS)

    Puchtel, Igor S.; Blichert-Toft, Janne; Touboul, Mathieu; Horan, Mary F.; Walker, Richard J.

    2016-06-01

    New Sm-Nd, Lu-Hf, Hf-W, and Re-Os isotope data, in combination with highly siderophile element (HSE, including Re, Os, Ir, Ru, Pt, and Pd) and W abundances, are reported for the 3.55 Ga Schapenburg komatiites, South Africa. The Schapenburg komatiites define a Re-Os isochron with an age of 3550 ± 87 Ma and initial γ187Os = +3.7 ± 0.2 (2SD). The absolute HSE abundances in the mantle source of the Schapenburg komatiite system are estimated to be only 29 ± 5% of those in the present-day bulk silicate Earth (BSE). The komatiites were derived from mantle enriched in the decay products of the long-lived 147Sm and 176Lu nuclides (initial ɛ143Nd = +2.4 ± 0.1, ɛ176Hf = +5.7 ± 0.3, 2SD). By contrast, the komatiites are depleted, relative to the modern mantle, in 142Nd and 182W (μ182W = -8.4 ± 4.5, μ142Nd = -4.9 ± 2.8, 2SD). These results constitute the first observation in terrestrial rocks of coupled depletions in 142Nd and 182W. Such isotopic depletions require derivation of the komatiites from a mantle domain that formed within the first ˜30 Ma of Solar System history and was initially geochemically enriched in highly incompatible trace elements as a result of crystal-liquid fractionation in an early magma ocean. This mantle domain further must have experienced subsequent melt depletion, after 182Hf had gone extinct, to account for the observed initial excesses in 143Nd and 176Hf. The survival of early-formed 182W and 142Nd anomalies in the mantle until at least 3.55 Ga indicates that the products of early planetary differentiation survived both later planetary accretion and convective mantle mixing during the Hadean. This work moreover renders unlikely that variable late accretion, by itself, can account for all of the observed W isotope variations in Archean rocks.

  11. The Net Exchange Between Terrestrial Ecosystems and the Atmosphere as a Result of Changes in Land Use

    NASA Technical Reports Server (NTRS)

    Houghton, R. A.

    1998-01-01

    The general purpose of this research was to improve and update (to 1990) estimates of the net flux of carbon between the world's terrestrial ecosystems and the atmosphere from changes in land use (e.g., deforestation and reforestation). The estimates are important for understanding the global carbon cycle, and for predicting future concentrations of atmospheric CO2 that will result from emissions. The emphasis of the first year's research was on the northern temperate zone and boreal forests, where the greatest discrepancy exists between estimates of flux. Forest inventories suggest net sinks of 0.6 PgC/yr; inversion analyses based on atmospheric data and models suggest much larger sinks 2-3.6 PgC/yr (e.g., Tans et al. 1990, Ciais et al. 1995). The work carried out with this grant calculated the flux attributable to changes in land use. The estimated flux was somewhat smaller than the flux calculated from inventory data suggesting that environmental changes have led to a small accumulation of carbon in forests that exceeds the accumulation expected from past rates of harvest. Two publications have described these results (Houghton 1996, 1998). The large difference between these estimates and those obtained with atmospheric data and models remains unexplained. The recent estimate of a 1.7 PgC/yr sink in North America, alone (Fan et al. 1998), is particularly difficult to explain. That part of the sink attributable to land-use change, however, is defined as a result of this grant.

  12. Fractionation of terrestrial neon by hydrodynamic hydrogen escape from ancient steam atmospheres

    NASA Technical Reports Server (NTRS)

    Zahnle, K.

    1991-01-01

    Atmospheric neon is isotopically heavier than mantle neon. By contrast, nonradiogenic mantle Ar, Kr, and Xe are not known to differ from the atmosphere. These observations are most easily explained by selective neon loss to space; however, neon is much too massive to escape from the modern atmosphere. Steam atmospheres are a likely, if intermittent, feature of the accreting Earth. They occur because, on average, the energy liberated during accretion places Earth above the runaway greenhouse threshold, so that liquid water is not stable at the surface. It is found that steam atmospheres should have lasted some ten to fifty million years. Hydrogen escape would have been vigorous, but abundant heavy constituents would have been retained. There is no lack of plausible candidates; CO2, N2, or CO could all suffice. Neon can escape because it is less massive than any of the likely pollutants. Neon fractionation would have been a natural byproduct. Assuming that the initial Ne-20/Ne-22 ratio was solar, it was found that it would have taken some ten million years to effect the observed neon fractionation in a 30 bar steam atmosphere fouled with 10 bars of CO. Thicker atmospheres would have taken longer; less CO, shorter. This mechanism for fractionating neon has about the right level of efficiency. Because the lighter isotope escapes much more readily, total neon loss is pretty minimal; less than half of the initial neon endowment escapes.

  13. Early MAVEN Results on the Mars Upper Atmosphere and Atmospheric Loss to Space

    NASA Astrophysics Data System (ADS)

    Jakosky, Bruce; Grebowsky, Joseph; Luhmann, Janet

    2015-04-01

    , operations, and calibrations. We also expect to have sufficient data collected to allow us to reach preliminary conclusions about the state of the upper atmosphere, interactions with the solar wind, escape of atmospheric gas to space at the present epoch, and integrated escape to space over time. These early results will be presented.

  14. Early warning of atmospheric regime transitions using transfer operators

    NASA Astrophysics Data System (ADS)

    Tantet, Alexis; Dijkstra, Henk

    2015-04-01

    The existence of persistent midlatitude atmospheric regimes, such as blocking events, with time scales larger than 5-10 days and indications of preferred transition paths between them motivates the development of early-warning indicators of regime transitions. Here, we use a barotropic model of the northern midlatitudes winter flow to study such meta-stable regimes. We look at estimates of transfer operators acting on densities evolving on a reduced phase space spanned by the first Empirical Orthogonal Functions of the streamfunction and develop an early-warning indicator of zonal to blocked flow transition. The study of the spectra of transfer operators estimated for different lags reveals a multi-level structure in the flow as well as the effect of memory on the reduced dynamics due to past interactions between the resolved and unresolved variables. The slowest motions in the reduced phase space are thereby found to have time scales larger than 8 days and to behave as Markovian for larger lags. These motions are associated with meta-stable regimes and their transitions and can be detected as almost-invariant sets of the transfer operator. The early-warning indicator is based on the action on an initial density of products of the transfer operators estimated for sufficiently long lags, making use of the semi-group property of these operators and shows relatively good Peirce skill score. From the energy budget of the model, we are able to explain the meta-stability of the regimes and the existence of preferred transition paths as the manifestation of barotropic instability. Finally, even though the model is highly simplified, the skill of the early warning indicator is promising, suggesting that the transfer operator approach can be used in parallel to an operational deterministic model for stochastic prediction or to assess forecast uncertainty.

  15. Hydrogen and deuterium loss from the terrestrial atmosphere - A quantitative assessment of nonthermal escape fluxes

    NASA Technical Reports Server (NTRS)

    Yung, Yuk L.; Wen, Jun-Shan; Moses, Julianne I.; Landry, Bridget M.; Allen, Mark; Hsu, Kuang-Jung

    1989-01-01

    A comprehensive one-dimensional photochemical model extending from the middle atmosphere (50 km) to the exobase (432 km) has been used to study the escape of hydrogen and deuterium from the earth's atmosphere. The model incorporates recent advances in chemical kinetics as well as atmospheric observations by satellites, especially the Atmosphere Explorer C satellite. The results suggest that the escape fluxes of both H and D are limited by the upward transport of total hydrogen and total deuterium at the homopause. About one fourth of total hydrogen escape is thermal, the rest being nonthermal. It is shown that escape of D is nonthermal and that charge exchange and polar wind are important mechanisms for the nonthermal escape of H and D.

  16. On the Transport of Polarized Infrared Signals Through the Terrestrial Atmosphere

    NASA Astrophysics Data System (ADS)

    Pesses, Mark; Israel, Steven; Meyer, Rodney; Price, Michael J.

    2002-09-01

    Both the Mie scattering and polarimetric transport models indicate that, in the LWIR, the atmospheric effect on the transport of right-hand circularly polarized signals and left-hand circularly polarized signals is identical. In the LWIR, the observed normalized circular polarization anisotropy, S3/SO, of a signal should not require any atmospheric corrections. Because natural LWIR light in not circularly polarized, only an active system will be able to exploit this finding. Both the Mie scattering and polarimetric transport models indicate that, in the LWIR, the atmospheric effect on the transport of the two orthogonal components of linearly polarized signals should be significantly different. In the LWIR both the observed degree of lineal polarization and the observed normalized linear polarization anisotropy Si/SO of a signal should require atmospheric corrections.

  17. Dynamic oxygenation of the early atmosphere and oceans

    NASA Astrophysics Data System (ADS)

    Lyons, Timothy W.; Planavsky, Noah J.; Reinhard, Christopher T.

    2014-05-01

    The traditional view of the oxygenation of the early atmosphere and oceans depicts irreversibly rising abundances in two large steps: one at the Great Oxidation Event (GOE) ca. 2.3-2.4 billion years ago (Ga) and another near the end of the Neoproterozoic. This talk will explore how the latest data challenge this paradigm. Recent results reveal a far more dynamic history of early oxygenation, one with both rising and falling levels, long periods of sustained low concentrations even after the GOE, complex feedback relationships that likely coupled nutrients and ocean redox, and dramatic changes tied through still-emerging cause-and-effect relationships to first-order tectonic, climatic, and evolutionary events. In the face of increasing doubt about the robustness of organic biomarker records from the Archean, researchers are increasingly reliant on inorganic geochemical proxies for the earliest records of oxygenic photosynthesis. Proxy data now suggest oxygenesis at ca. 3.0 Ga with a likelihood of local oxygen build up in the surface ocean long before the GOE, as well as low (and perhaps transient) accumulation in the atmosphere against a backdrop of mostly less than ca. 0.001% of the present atmospheric concentration. By the GOE, the balance between oxygen sources and sinks shifted in favor of persistent accumulation, although sedimentary recycling of non-mass-dependent sulfur isotope signatures allows for the possibility of rising and falling atmospheric oxygen before the GOE as traditionally defined by the sulfur isotope record. Recycling may also hinder our ability to precisely date the transition to permanent oxygen accumulation beyond trace levels. Diverse data point to a dramatic increase in biospheric oxygen following the GOE, coincident with the largest positive carbon isotope excursion in Earth history, followed by an equally dramatic drop. This decline in Earth surface redox potential ushered in more than a billion years of dominantly low oxygen levels in

  18. Evolution and variation of atmospheric carbon dioxide concentration over terrestrial ecosystems as derived from eddy covariance measurements

    NASA Astrophysics Data System (ADS)

    Liu, Min; Wu, Jiabing; Zhu, Xudong; He, Honglin; Jia, Wenxiao; Xiang, Weining

    2015-08-01

    Carbon dioxide (CO2) is the most important anthropogenic greenhouse gas contributing to global climate change. Understanding the temporal and spatial variations of CO2 concentration over terrestrial ecosystems provides additional insight into global atmospheric variability of CO2 concentration. Using 355 site-years of CO2 concentration observations at 104 eddy-covariance flux tower sites in Northern Hemisphere, we presented a comprehensive analysis of evolution and variation of atmospheric CO2 concentration over terrestrial ecosystem (ACTE) for the period of 1997-2006. Our results showed that ACTE exhibited a strong seasonal variations, with an average seaonsal amplitude (peak-trough difference) of 14.8 ppm, which was approximately threefold that global mean CO2 observed in Mauna Loa in the United States (MLO). The seasonal variation of CO2 were mostly dominant by terrestrial carbon fluxes, i.e., net ecosystem procution (NEP) and gross primary produciton (GPP), with correlation coefficient(r) were -0.55 and -0.60 for NEP and GPP, respectively. However, the influence of carbon fluxes on CO2 were not significant at interannual scale, which implyed that the inter-annual changing trends of atmospheric CO2 in Northern Hemisphere were likely to depend more on anthropogenic CO2 emissions sources than on ecosystem change. It was estimated, by fitting a harmonic model to monthly-mean ACTE, that both annual mean and seasonal amplitude of ACTE increased over the 10-year period at rates of 2.04 and 0.60 ppm yr-1, respectively. The uptrend of annual ACTE could be attributed to the dramatic global increase of CO2 emissions during the study period, whereas the increasing amplitude could be related to the increases in Northern Hemisphere biospheric activity. This study also found that the annual CO2 concentration showed large variation among ecosystems, with the high value appeared in deciduous broadleaf forest, evergreen broadleaf forest and cropland. We attribute these

  19. Estimating Terrestrial Water Storage Changes in the Colorado River Basin: Atmospheric Data Analysis, Satellite Remote Sensing and Hydrologic Modeling

    NASA Astrophysics Data System (ADS)

    Troch, P. A.; Seneviratne, S.; Hirschi, M.; Hurkmans, R.; Hasan, S.; Durcik, M.

    2006-12-01

    The Colorado River basin covers about 637 000 km2 and spreads over the southwestern United States and a small portion of Mexico. Much of the basin is arid, and runoff derives from the high elevation snow pack over the Rocky Mountains, which contributes about 70% of the annual runoff. A secondary source of water for the basin is the summer monsoon precipitation. The Colorado River system is one of the most heavily regulated for providing water supply, irrigation, flood control, and hydropower to a large area of the U.S. Southwest. Estimating intra- and inter-annual variability of water storage in the basin is important for sustainable water management. In this paper, an overview is given on how terrestrial water storage changes can be estimated. Fifty (50) years (1955-2005) of re-analysis data from ECMWF (European Center for Medium Range Weather Forecasts) is used together with observed and natural stream flow to derive monthly atmospheric and terrestrial water balances (Seneviratne et al., 2004; Hirschi et al., 2006). The resulting water storage changes in the Colorado basin exhibit a strong annual and a weaker decadal cycle. Correlation with different climate variability indices (ENSO, PDO, AMO) is examined. We compare these water storage change estimates with those derived from the NARR (North-American Regional Re-analysis) time series (1979 to 2005). Three years (2002-2005) of GRACE (Gravity Recovery and Climate Experiment) satellite data are then used to estimate monthly terrestrial water storage changes from estimates of geoid anomalies over the area. We find a close relationship between both independent estimation procedures. Both the annual cycle and the amplitude agree very well, although a slight phase shift of about a month is observed. To further examine the water storage changes we apply a land surface hydrologic model (VIC: Variable Infiltration Capacity) forced with observations spanning the period between 1950 and 2000 and compiled by Maurer et al

  20. Assessing the impact of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Abbondanza, Claudio; Altamimi, Zuheir; Chin, Toshio; Collilieux, Xavier; Dach, Rolf; Gross, Richard; Heflin, Michael; König, Rolf; Lemoine, Frank; Macmillan, Dan; Parker, Jay; van Dam, Tonie; Wu, Xiaoping

    2014-05-01

    The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, we assess the impact of non-tidal atmospheric loading (NTAL) corrections on the TRF computation. Focusing on the a-posteriori approach, (i) the NTAL model derived from the National Centre for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations; (ii) adopting a Kalman-filter based approach, two distinct linear TRFs are estimated combining the 4 SG solutions with (corrected TRF solution) and without the NTAL displacements (standard TRF solution). Linear fits (offset and atmospheric velocity) of the NTAL displacements removed during step (i) are estimated accounting for the station position discontinuities introduced in the SG solutions and adopting different weighting strategies. The NTAL-derived (atmospheric) velocity fields are compared to those obtained from the TRF reductions during step (ii). The consistency between the atmospheric and the TRF-derived velocity fields is examined. We show how the presence of station position discontinuities in SG solutions degrades the agreement between the velocity fields and compare the effect of different weighting structure adopted while estimating the linear fits to the NTAL displacements. Finally, we evaluate the effect of restoring the atmospheric velocities determined through the linear fits of the NTAL displacements to the single-technique linear reference frames obtained by stacking the standard SG SINEX files

  1. Three-Dimensional Tracer Model Study of Atmospheric CO2 - Response to Seasonal Exchanges with the Terrestrial Biosphere

    NASA Technical Reports Server (NTRS)

    Fung, I.; Prentice, K.; Matthews, E.; Lerner, J.; Russell, G.

    1983-01-01

    A three-dimensional tracer transport model is used to investigate the annual cycle of atmospheric CO2 concentration produced by seasonal exchanges with the terrestrial biosphere. The tracer model uses winds generated by a global general circulation model to advect and convect CO2; no explicit diffusion coefficients are employed. A biospheric exchange function constructed from a map of net primary productivity, and Azevedo's (1982) seasonality of CO2 uptake and release closely simulates the annual cycles at coastal stations. The results show that zonal homogeneity in surface CO2 concentrations can never be achieved at mid-latitudes where the time scale for zonal mixing is longer than the time scale for biospheric exchange. Analysis of the zonal mean balance in the lower troposphere reveals that atmospheric transport processes may alter the CO2 response to local biospheric exchanges by 50% or more. Hence year-to-year variation of the annual CO2 cycle may result from the natural variability of the atmospheric circulation as well as from changes in the sources and sinks.

  2. Teaching about the Early Earth: Evolution of Tectonics, Life, and the Early Atmosphere

    NASA Astrophysics Data System (ADS)

    Mogk, D. W.; Manduca, C. A.; Kirk, K.; Williams, M. L.

    2007-12-01

    The early history of the Earth is the subject of some of the most exciting and innovative research in the geosciences, drawing evidence from virtually all fields of geoscience and using a variety of approaches that include field, analytical, experimental, and modeling studies. At the same time, the early Earth presents unique opportunities and challenges in geoscience education: how can we best teach "uncertain science" where the evidence is either incomplete or ambiguous? Teaching about early Earth provides a great opportunity to help students understand the nature of scientific evidence, testing, and understanding. To explore the intersection of research and teaching about this enigmatic period of Earth history, a national workshop was convened for experts in early Earth research and undergraduate geoscience education. The workshop was held in April, 2007 at the University of Massachusetts at Amherst as part of the On the Cutting Edge faculty professional development program. The workshop was organized around three scientific themes: evolution of global tectonics, life, and the early atmosphere. The "big scientific questions" at the forefront of current research about the early Earth were explored by keynote speakers and follow-up discussion groups: How did plate tectonics as we know it today evolve? Were there plates in the Hadean Eon? Was the early Earth molten? How rapidly did it cool? When and how did the atmosphere and hydrosphere evolve? How did life originate and evolve? How did all these components interact at the beginning of Earth's history and evolve toward the Earth system we know today? Similar "big questions" in geoscience education were addressed: how to best teach about "deep time;" how to help students make appropriate inferences when geologic evidence is incomplete; how to engage systems thinking and integrate multiple lines of evidence, across many scales of observation (temporal and spatial), and among many disciplines. Workshop participants

  3. A Carbon Flux Super Site. New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling

    SciTech Connect

    Leclerc, Monique Y.

    2014-11-17

    This final report presents the main activities and results of the project “A Carbon Flux Super Site: New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling” from 10/1/2006 to 9/30/2014. It describes the new AmeriFlux tower site (Aiken) at Savanna River Site (SC) and instrumentation, long term eddy-covariance, sodar, microbarograph, soil and other measurements at the site, and intensive field campaigns of tracer experiment at the Carbon Flux Super Site, SC, in 2009 and at ARM-CF site, Lamont, OK, and experiments in Plains, GA. The main results on tracer experiment and modeling, on low-level jet characteristics and their impact on fluxes, on gravity waves and their influence on eddy fluxes, and other results are briefly described in the report.

  4. Development of a model of atmospheric oxygen variations to estimate terrestrial carbon storage and release

    NASA Technical Reports Server (NTRS)

    Najjar, Raymond G.; Keeling, Ralph F.; Erickson, David J., III

    1995-01-01

    Two years of work has been completed towards the development of a model of atmospheric oxygen variations on seasonal to decadal timescales. During the first year we (1) constructed a preliminary monthly-mean climatology of surface ocean oxygen anomalies, (2) began modeling studies to assess the importance of short term variability on the monthly-mean oxygen flux, and (3) conducted preliminary simulations of the annual mean cycle of oxygen in the atmosphere. Most of the second year was devoted to improving the monthly mean climatology of oxygen in the surface ocean.

  5. Variability of projected terrestrial biosphere responses to elevated levels of atmospheric CO2 due to uncertainty in biological nitrogen fixation

    NASA Astrophysics Data System (ADS)

    Meyerholt, Johannes; Zaehle, Sönke; Smith, Matthew J.

    2016-03-01

    Including a terrestrial nitrogen (N) cycle in Earth system models has led to substantial attenuation of predicted biosphere-climate feedbacks. However, the magnitude of this attenuation remains uncertain. A particularly important but highly uncertain process is biological nitrogen fixation (BNF), which is the largest natural input of N to land ecosystems globally. In order to quantify this uncertainty and estimate likely effects on terrestrial biosphere dynamics, we applied six alternative formulations of BNF spanning the range of process formulations in current state-of-the-art biosphere models within a common framework, the O-CN model: a global map of static BNF rates, two empirical relationships between BNF and other ecosystem variables (net primary productivity and evapotranspiration), two process-oriented formulations based on plant N status, and an optimality-based approach. We examined the resulting differences in model predictions under ambient and elevated atmospheric [CO2] and found that the predicted global BNF rates and their spatial distribution for contemporary conditions were broadly comparable, ranging from 108 to 148 Tg N yr-1 (median: 128 Tg N yr-1), despite distinct regional patterns associated with the assumptions of each approach. Notwithstanding, model responses in BNF rates to elevated levels of atmospheric [CO2] (+200 ppm) ranged between -4 Tg N yr-1 (-3 %) and 56 Tg N yr-1 (+42 %) (median: 7 Tg N yr-1 (+8 %)). As a consequence, future projections of global ecosystem carbon (C) storage (+281 to +353 Pg C, or +13 to +16 %) as well as N2O emission (-1.6 to +0.5 Tg N yr-1, or -19 to +7 %) differed significantly across the different model formulations. Our results emphasize the importance of better understanding the nature and magnitude of BNF responses to change-induced perturbations, particularly through new empirical perturbation experiments and improved model representation.

  6. Variability of projected terrestrial biosphere responses to elevated levels of atmospheric CO2 due to uncertainty in biological nitrogen fixation

    NASA Astrophysics Data System (ADS)

    Meyerholt, J.; Zaehle, S.; Smith, M. J.

    2015-12-01

    Including a terrestrial nitrogen (N) cycle in Earth system models has led to substantial attenuation of predicted biosphere-climate feedbacks. However, the magnitude of this attenuation remains uncertain. A particularly important, but highly uncertain process is biological nitrogen fixation (BNF), which is the largest natural input of N to land ecosystems globally. In order to quantify this uncertainty, and estimate likely effects on terrestrial biosphere dynamics, we applied six alternative formulations of BNF spanning the range of process formulations in current state-of-the-art biosphere models within a common framework, the O-CN model: a global map of static BNF rates, two empirical relationships between BNF and other ecosystem variables (net primary productivity (NPP) and evapotranspiration), two process-oriented formulations based on plant N status, and an optimality-based approach. We examined the resulting differences in model predictions under ambient and elevated atmospheric [CO2] and found that the predicted global BNF rates and their spatial distribution for contemporary conditions were broadly comparable, ranging from 95 to 134 Tg N yr-1 (median 119 Tg N yr-1), despite distinct regional patterns associated with the assumptions of each approach. Notwithstanding, model responses in BNF rates to elevated levels of atmospheric [CO2] (+200 ppm) ranged between -4 Tg N yr-1 (-3 %) and 56 Tg N yr-1 (+42 %) (median 7 Tg N yr-1 (+8 %)). As a consequence, future projections of global ecosystem carbon storage (+281 to +353 Pg C, or +13 to +16 %), as well as N2O emission (-1.6 to +0.5 Tg N yr-1, or -19 to +7 %) differed significantly across the different model formulations. Our results emphasize the importance of better understanding the nature and magnitude of BNF responses to change-induced perturbations, particularly through new empirical perturbation experiments and improved model representation.

  7. Giant Impacts on Terrestrial Planets: A High-Resolution 3D Study of Magma Ocean Formation and Atmospheric Blowoff

    NASA Astrophysics Data System (ADS)

    Stewart-Mukhopadhyay, Sarah

    The end stages of terrestrial planet formation are dominated by giant impact events, which may significantly affect the final composition of a planet. The physical changes from giant impacts include formation of magma oceans and atmospheric blowoff. We propose to conduct unique numerical experiments to investigate the physics of giant impacts in order to determine their effect on the thermal state and volatile budget of terrestrial planets (0.1 to 10 Earth masses). Proposed work: High-resolution 3D giant impacts between differentiated silicate-iron and ice-silicate planets will be modeled with both the widely-used CTH shock physics code and a new second-order Godunov finite-volume hydrocode called AREPO. AREPO's powerful arbitrary Lagrangian-Eulerian grid and computational efficiency allows for unprecedented resolution of planetary structure (e.g., crust and ocean). Expected results: (1) We will calculate the amount of melt generated and fraction of atmosphere lost during different classes of giant impacts (merging, graze and merge, hit and run, and erosion/disruption). (2) We will derive general scaling laws to describe these complicated phenomena. (3) We will consider the effect of re-accretion of ejected material at late times on the total thermal input of giant impact events. (4) And we will test the giant impact hypothesis for the high bulk density of Mercury by conducting orbital integrations of ejected debris to determine the amount of re-accreted mantle material for different impact orientations. The science team has an established collaborative body of work in giant impact simulations and hydrocode development. As in previous studies, the simulation results will be generalized into sets of simple equations describing collision outcomes that are suitable for N-body planet formation models. The proposed work supports the goals of the Origins of Solar Systems program by conducting a fundamental theoretical investigation of a key stage of planet formation

  8. Atmospheric pressure as a natural climate regulator for a terrestrial planet with a biosphere

    PubMed Central

    Li, King-Fai; Pahlevan, Kaveh; Kirschvink, Joseph L.; Yung, Yuk L.

    2009-01-01

    Lovelock and Whitfield suggested in 1982 that, as the luminosity of the Sun increases over its life cycle, biologically enhanced silicate weathering is able to reduce the concentration of atmospheric carbon dioxide (CO2) so that the Earth's surface temperature is maintained within an inhabitable range. As this process continues, however, between 100 and 900 million years (Ma) from now the CO2 concentration will reach levels too low for C3 and C4 photosynthesis, signaling the end of the solar-powered biosphere. Here, we show that atmospheric pressure is another factor that adjusts the global temperature by broadening infrared absorption lines of greenhouse gases. A simple model including the reduction of atmospheric pressure suggests that the life span of the biosphere can be extended at least 2.3 Ga into the future, more than doubling previous estimates. This has important implications for seeking extraterrestrial life in the Universe. Space observations in the infrared region could test the hypothesis that atmospheric pressure regulates the surface temperature on extrasolar planets. PMID:19487662

  9. Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid

    PubMed Central

    Donaldson, Melissa A.; Bish, David L.; Raff, Jonathan D.

    2014-01-01

    Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day. PMID:25512517

  10. Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid.

    PubMed

    Donaldson, Melissa A; Bish, David L; Raff, Jonathan D

    2014-12-30

    Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼ 3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day. PMID:25512517

  11. Continental scale atmospheric and terrestrial water budget modeling and comparison to GRACE

    NASA Astrophysics Data System (ADS)

    Fersch, B.; Kunstmann, H.; Sneeuw, N.; Devaraju, B.

    2009-04-01

    Estimation of large scale water balances is still an unsolved challenge in hydrological sciences, particularly for data spare regions. The GRACE satellite mission (launched in 2002) provides a completely new opportunity to investigate seasonal large scale water mass changes based on measurements of gravitational acceleration differences. Our study aims at determining the potential of GRACE data for hydrological applications. Our approach assumes that vertically integrated atmospheric moisture convergence equals 1) precipitated minus evapotranspired water masses and therefore equals 2) aggregated surface runoff minus water storage changes. Using observed basin runoff, this interrelation allows us to compare GRACE derived water storage changes with modeled atmospheric moisture convergences. As regional atmospheric modeling is expected to yield more accurate meteorological fields than global model results, we use the WRF model for a dynamic downscaling of global atmospheric fields and hence derive high resolution fields of air pressure, horizontal moisture flux divergence, precipitation minus evapotranspiration, soil water storage, etc. Our study focuses on sensitivities and uncertainties of regionally modeled atmospheric mass and moisture fluxes due to specific model setup, origin of global driving data (NCEP vs. ECMWF) and spatial resolution. This is performed for four regions: Australia, Sahara, Siberia and the Amazon. The first three regions are characterized by a simplified hydrological mass balance, i.e. either evaporation or precipitation is close to zero. Central Australia represents a region with no outlet, meaning runoff is negligible. The Sahara also has zero runoff and for the dry periods evapotranspiration is close to zero. Siberia, comprising the catchments of Lena and Yenisei has negligible evapotranspiration for the winter months. The basin of the Amazon is representative for regions with high precipitation and evaporation terms. For the years 2003 to

  12. Verification of Atmospheric Signals Associated with Major Seismicity by Space and Terrestrial Observations

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick

    2008-01-01

    Observations from the last twenty years suggest the existence of electromagnetic (EM) phenomena during or preceding some earthquakes [Haykawa et a!, 2004; Pulinets at al, 1999,2004, 2006, Ouzounov et all 2007 and Liu et all 20041. Both our previous studies [Pulinets at al, 2005, 2006, Ouzounov et al, 2006, 20071 and the latest review by the Earthquake Remote Precursor Sensing panel [ERPS; 2003- 20051; have shown that there were precursory atmospheric TIR signals observed on the ground and in space associated with several recent earthquakes. [Tramutoli at al, 2005, 2006, Cervone et al, 2006, Ouzounov et all 2004,2006JT.o study these signals, we applied both multi parameter statistical analysis and data mining methods that require systematic measurements from an Integrated Sensor Web of observations of several physical and environmental parameters. These include long wave earth infra-red radiation, ionospheric electrical and magnetic parameters, temperature and humidity of the boundary layer, seismicity and may be associated with major earthquakes. Our goal is to verify the earthquake atmospheric correlation in two cases: (i) backward analysis - 2000-2008 hindcast monitoring of multi atmospheric parameters over the Kamchatka region, Russia ; and (ii) forward real-time alert analysis over different seismo-tectonic regions for California, Turkey, Taiwan and Japan. Our latest results, from several post-earthquake independent analyses of more then 100 major earthquakes, show that joint satellite and some ground measurements, using an integrated web, could provide a capability for observing pre-earthquake atmospheric signals by combining the information from multiple sensors into a common framework. Using our methodology, we evaluated and compared the observed signals preceding the latest M7.9 Sichuan earthquake (0511212008), M8.0 earthquake in Peru (0811512007), M7.6 Kashmir earthquake (1010812005) and M9.0 Sumatra earthquake (1212812004). We found evidence of the

  13. Modeling the atmospheric and terrestrial water and energy cycles in the ScaleX experiment through a fully-coupled atmosphere-hydrology model

    NASA Astrophysics Data System (ADS)

    Senatore, Alfonso; Benjamin, Fersch; Thomas, Rummler; Caroline, Brosy; Christian, Chwala; Junkermann, Wolfgang; Ingo, Völksch; Harald, Kunstmann

    2016-04-01

    The TERENO preAlpine Observatory, comprising a series of observatory sites along an altitudinal gradient within the Ammer catchment (southern Bavaria, Germany), has been designed as an international research platform, open for participation and integration, and has been provided with comprehensive technical infrastructure to allow joint analyses of water-, energy- and nutrient fluxes. In June and July 2015 the operational monitoring has been complemented by the ScaleX intensive measurement campaign, where additional precipitation and soil moisture measurements, remote sensing measurements of atmospheric wind, humidity and temperature profiles have been performed, complemented by micro-light aircraft- and UAV-based remote sensing for three-dimensional pattern information. The comprehensive observations serve as validation and evaluation basis for compartment-crossing modeling systems. Specifically, the fully two-way dynamically coupled atmosphere-hydrology modeling system WRF-Hydro has been used to investigate the interplay of energy and water cycles at the regional scale and across the compartments atmosphere, stream, vadose zone and groundwater during the ScaleX campaign and to assess the closure of the budgets involved. Here, several high-resolution modeled hydro-meteorological variables, such as precipitation, soil moisture, river discharge and air moisture and temperature along vertical profiles are compared with observations from multiple sources, such as rain gauges and soil moisture networks, rain radars, stream gauges, UAV and a micro-light aircraft. Results achieved contribute to the objective of addressing questions on energy- and water-cycling within the TERENO-Ammer region at a very high scale and degree of integration, and provides hints on how well can observations constrain uncertainties associated with the modeling of atmospheric and terrestrial water and energy balances.

  14. Global N/sub 2/O cycles - Terrestrial emissions, atmospheric accumulation and biospheric effects

    SciTech Connect

    Banin, A.; Lawless, J.G.; Whitten, R.C.; Oser, H.; Oro, J.; Macelroy, R.D.; Klein, H.P.; Devincenzi, D.L.; Young, R.S.

    1984-01-01

    Recent findings concerning the budget and cycles of nitrous oxide on earth are summarized, and the sources and sinks for N/sub 2/O on land, in the ocean, and in the atmosphere are examined in view of the N/sub 2/O concentration increase of 0.2-0.4 percent per year, observed over the period of 1975-1982. Possible atmospheric and biospheric consequences of the N/sub 2/O concentration increase are evaluated. N/sub 2/O emission values are given for several major ecosystem types, such as forest, desert, cultivated land; values from different sources are compared and discussed. Analysis shows an excess of documented sources over sinks by 0-51 Tg N/sub 2/O-N/yr. 63 references.

  15. Effects of long-period solar activity fluctuation on temperature and pressure of the terrestrial atmosphere

    NASA Technical Reports Server (NTRS)

    Rubashev, B. M.

    1978-01-01

    The present state of research on the influence of solar sunspot activity on tropospheric temperature and pressure is reviewed. The existence of an 11-year temperature cycle of 5 different types is affirmed. A cyclic change in atmospheric pressure, deducing characteristic changes between 11-year cycles is discussed. The existence of 80-year and 5-to-6-year cycles of temperature is established, and physical causes for birth are suggested.

  16. Observed and Modeled Tritium Concentrations in the Terrestrial Food Chain near a Continuous Atmospheric Source

    SciTech Connect

    Davis, P.A.; Kim, S.B.; Chouhan, S.L.; Workman, W.J.G.

    2005-07-15

    Tritium concentrations were measured in a large number of environmental and biological samples collected during 2002 at two dairy farms and a hobby farm near Pickering Nuclear Generating Station in Ontario, Canada. The data cover most compartments of the terrestrial food chain in an agricultural setting and include detailed information on the diets of the local farm animals. Ratios of plant OBT concentration to air moisture HTO varied between 0.12 and 0.56, and were generally higher for the forage crops collected at the dairy farms than for the garden vegetables sampled at the hobby farm. Animal OBT to air HTO ratios were more uniform, ranging from 0.18 to 0.45, and were generally higher for the milk and beef samples from the dairy farms than for the chicken products from the hobby farm. The observed OBT concentrations in plants and animals were compared with predictions of IMPACT, the model used by the Canadian nuclear industry to calculate annual average doses due to routine releases. The model performed well on average for the animal endpoints but overestimated concentrations in plants by a factor of 2.

  17. Using dimers to measure biosignatures and atmospheric pressure for terrestrial exoplanets.

    PubMed

    Misra, Amit; Meadows, Victoria; Claire, Mark; Crisp, Dave

    2014-02-01

    We present a new method to probe atmospheric pressure on Earth-like planets using (O2-O2) dimers in the near-infrared. We also show that dimer features could be the most readily detectable biosignatures for Earth-like atmospheres and may even be detectable in transit transmission with the James Webb Space Telescope (JWST). The absorption by dimers changes more rapidly with pressure and density than that of monomers and can therefore provide additional information about atmospheric pressures. By comparing the absorption strengths of rotational and vibrational features to the absorption strengths of dimer features, we show that in some cases it may be possible to estimate the pressure at the reflecting surface of a planet. This method is demonstrated by using the O2 A band and the 1.06 μm dimer feature, either in transmission or reflected spectra. It works best for planets around M dwarfs with atmospheric pressures between 0.1 and 10 bar and for O2 volume mixing ratios above 50% of Earth's present-day level. Furthermore, unlike observations of Rayleigh scattering, this method can be used at wavelengths longer than 0.6 μm and is therefore potentially applicable, although challenging, to near-term planet characterization missions such as JWST. We also performed detectability studies for JWST transit transmission spectroscopy and found that the 1.06 and 1.27 μm dimer features could be detectable (SNR>3) for an Earth analogue orbiting an M5V star at a distance of 5 pc. The detection of these features could provide a constraint on the atmospheric pressure of an exoplanet and serve as biosignatures for oxygenic photosynthesis. We calculated the required signal-to-noise ratios to detect and characterize O2 monomer and dimer features in direct imaging-reflected spectra and found that signal-to-noise ratios greater than 10 at a spectral resolving power of R=100 would be required. PMID:24432758

  18. Assessing the tolerance of the terrestrial moss Pseudoscleropodium purum to high levels of atmospheric heavy metals: a reciprocal transplant study.

    PubMed

    Boquete, M Teresa; Fernández, J Ángel; Carballeira, Alejo; Aboal, Jesús R

    2013-09-01

    We measured the concentrations of Cd, Cu, Hg, Pb and Zn in samples of the terrestrial moss Pseudoscleropodium purum reciprocally transplanted between an unpolluted and two polluted sampling sites. At the beginning of the experiment, the concentrations of all these elements differed significantly between mosses from the unpolluted site and mosses from the polluted sites. In general, the concentrations of the heavy metals in mosses from both polluted sites transplanted to the unpolluted site decreased until they reached the same levels as in autotransplants at this site (after 480-840 days). However, the concentrations of all heavy metals in mosses transplanted from the unpolluted site to both polluted sites increased to higher levels than in the autotransplants (except for Cu, Hg and Pb at one of the sampling sites). These results led us to conclude that mosses that have been continuously exposed to high atmospheric deposition of heavy metals undergo an adaptive response (probably genotypic) to such conditions. We therefore recommend active rather than passive biomonitoring of air quality in industrial environments because atmospheric deposition could be underestimated, and also recommend further investigation into the mechanisms involved in this response. PMID:23756214

  19. Bridging models for the terrestrial cryosphere and the atmosphere - The CryoMET project

    NASA Astrophysics Data System (ADS)

    Etzelmueller, Bernd; Westermann, Sebastian; Berntsen, Terje; Gisnås, Kjersti; Ove Hagen, Jon; Egill Kristjansson, Jon; Isaksen, Ketil; Schuler, Dagrun V.; Schuler, Thomas V.; Stordal, Frode; Aas, Kjetil S.

    2013-04-01

    Predictions of the future climate are generally based on atmospheric models operating on coarse spatial scales. However, the impact of a changing climate on most elements of the cryosphere becomes manifest on much smaller scales, which complicates sound predictions e.g. on glacier and permafrost development. CryoMET is a collaborative project between atmospheric modeling, glacier and permafrost research groups, seeking to bridge the scale gap between coarsely-resolved Earth System Models and the process and impact scales on the ground for the variables snow depth and snow water equivalent for sites in Norway and Svalbard. Snow is a crucial factor both for the thermal regime of permafrost and the mass balance on glaciers. However, the snow depth and properties can vary considerably on small scales due to wind redistribution, which for instance leads to distinctly different soil temperatures in permafrost areas on distances of tens of meters. CryoMET explores a seamless downscaling procedure to improve the representation in complex terrain: in a first step, we use the regional model PolarWRF to downscale atmospheric variables, including precipitation, air temperature and wind speed, to the so-called interface scale of 1 km to 3 km resolution, where these variables are constant to a good approximation. In a second step, we employ probabilistic downscaling of the average snow water equivalent at the interface scale (as delivered by PolarWRF) using snow redistribution models. With probability density functions of snow depth, the distribution of environmental parameters affected by snow, e.g. of permafrost temperatures, can be inferred for each grid cell at the interface scale. We present here first results demonstrating the capacity of the scheme in delivering the distribution of permafrost-relevant variables.

  20. Global N2O cycles--terrestrial emissions, atmospheric accumulation and biospheric effects.

    PubMed

    Banin, A; Lawless, J G; Whitten, R C

    1984-01-01

    Tropospheric nitrous oxide concentration has increased by 0.2-0.4% per year over the period 1975 to 1982, amounting to net addition to the atmosphere of 2.8-5.6 Tg N2O-N per year. This perturbation, if continued into the future, will affect stratospheric chemical cycles, and the thermal balance of the Earth. In turn it will have direct and indirect global effects on the biosphere. Though the budget and cycles of N2O on Earth are not yet fully resolved, accumulating information and recent modelling efforts enable a more complete evaluation and better definition of gaps in our knowledge. PMID:11537777

  1. Future NASA plans for the exploration of the terrestrial and planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Bauer, S.

    1974-01-01

    A brief outline of NASA's space exploration plans for the 1970s is given. Research of the upper atmosphere and near-earth space will slack off in comparison with that which was done in the past, although now missions with very specific tasks will be launched, instead of those intended to get a general picture of these regions. Space Shuttle and Spacelab will open up the possibility of using the ionosphere as a huge plasma laboratory without walls. Exploration of other planets will continue with the Mars Lander and Viking Lander, the Pioneer-Venus program, and flybys of Jupiter and Saturn.

  2. The National Ecological Observatory Network's Atmospheric and Terrestrial Instrumentation: Quality Control Approaches

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.; Luo, H.; Ayres, E.; Metzger, S. R.; Loescher, H. W.

    2012-12-01

    The National Ecological Observatory Network's Fundamental Instrument Unit (NEON-FIU) is responsible for making automated terrestrial observations at 60 different sites across the continent. FIU will provide data on key local physical, chemical, and climate forcing, as well as associated biotic responses (CO2, H2O, and energy exchanges). The sheer volume of data that will be generated far exceeds that of any other observatory network or agency, (i.e., > 45 Tb/year from 10's of thousands of remotely deployed sensors). We address the question of how to develop and implement a large ecological observatory that can accommodate such a large volume of data while maintaining high quality. Here, we describe our quality assurance and quality control (QA/QC) program to produce quality data while leveraging cyber infrastructure tools and optimizing technician time. Results focus on novel approaches that advance the quality control techniques that have been historically employed in other networks (DOE-ARM, AmeriFlux, USDA ARS, OK Mesonet) to new state-of-the-art functionality. These automated and semi-automated approaches are also used to inform automated problem tracking to efficiently deploy field staff. Ultimately, NEON will define its own standards for QA/QC and maintenance by building upon these existing frameworks. The overarching philosophy relies on attaining the highest levels of accuracy, precision, and operational time, while efficiently optimizing the effort needed to produce quality data products. Our preliminary results address the challenges associated with automated implementation of sensor command/control, plausibility testing, despiking, and data verification of FIU observations.

  3. On the emission of amines from terrestrial vegetation in the context of atmospheric new particle formation

    NASA Astrophysics Data System (ADS)

    Neftel, Albrecht; Sintermann, Jörg

    2015-04-01

    Airborne amines, specifically methylamines (MAs), play a key role in atmospheric new particle formation (NPF) by stabilising small molecule clusters. Agricultural emissions are assumed to constitute the most important MA source, but given the short atmospheric residence time of MAs, they can hardly have a direct impact on NFP events observed in remote regions. High MA contents as well as emissions by plants have already been described in the 19th century. Strong MA emissions predominantly occur during flowering as part of a pollination strategy. The behaviour is species specific, but examples of such species are common and widespread. In addition, vegetative plant tissue exhibiting high amounts of MAs might potentially lead to significant emissions, and the decomposition of organic material could constitute another source for airborne MAs. These mechanisms would provide sources, which could be crucial for the amine's role in NPF, especially in remote regions. Knowledge about vegetation-related amine emissions is, however, very limited and thus it is also an open question how Global Change and the intensified cycling of reactive nitrogen over the last 200 years have altered amine emissions from vegetation with a corresponding effect on NPF.

  4. The calculation of vibrational populations of O2 Herzberg states in the atmospheres of terrestrial planets

    NASA Astrophysics Data System (ADS)

    Kirillov, Andrey S.

    The calculated quenching rate constants of the c1, A'3, A3 states of O2 by molecules in [Kirillov, 2014, Chem. Phys. Lett., v.592, p.103] are applied in the simulation of vibrational populations of the Herzberg states in the nightglow of upper atmosphere of Venus and Mars where carbon dioxide is the main gas and in the mixture of molecular oxygen with CO2, CO, N2 gases for laboratory conditions. The results of the simulation show very important role of electronic-vibrational (EV) energy transfer processes in the redistribution of electronic excitation energy on vibrational levels of the states. The main aim of the simulation is an attempt to explain the high intensities of the Herzberg II band system observed in laboratory experiments with high CO2 concentrations [Lawrence et al., 1977, Science, v.195, p.573; Slanger, 1978, J. Chem. Phys., v.69, p.4779] and registered with spacecraft spectrometers in the nightglow of the Venus atmosphere [Krasnopolsky et al., 1977, Cosmic Res., v.14, p.687; Gerard et al., 2013, Icarus, v.223, p.602].

  5. Oxygen Isotopic Anomaly in Terrestrial Atmospheric Carbonates and its Implications to Understand the Role of Water on Mars

    NASA Astrophysics Data System (ADS)

    Thiemens, M. H.; Shaheen, R.

    2010-12-01

    Mineral aerosols produced from wind-blown soils are an important component of the earth system and comprise about 1000-3000 Tg.yr-1 compared to 400 Tg.yr-1 of secondary aerosols (e.g. carbonaceous substances, organics, sulfate and nitrates). Aerosols have important consequences for health, visibility and the hydrological cycle as they provide reactive surfaces for heterogeneous chemical transformation that may influence gas phase chemistry in the atmosphere. Tropospheric ozone produced in a cascade of chemical reactions involving NOx and VOC’s, can interact with aerosol surfaces to produce new compounds. Oxygen triple isotopic compositions of atmospheric carbonates have been used for the first time to track heterogeneous chemistry at the aerosol surfaces and to resolve a chemical mechanism that only occurs on particle surfaces. Fine and coarse aerosol samples were collected on filter papers in La Jolla, CA for one week. Aerosol samples were digested with phosphoric acid and released CO2 was purified chromatographically and analyzed for O isotopes after fluorination. Data indicated oxygen isotopic anomaly (Δ17O = δ17O - 0.524 δ18O) ranging from 0.9 to 3.9 per mill. Laboratory experiments revealed that adsorbed water on particle surfaces facilitates the interaction of the gaseous CO2 and O3 with formation of anomalous hydrogen peroxide and carbonates. This newly identified chemical reaction scenario provides a new explanation for production of the isotopically anomalous carbonates found in the SNC Martian meteorites and terrestrial atmospheric carbonates and it also amplifies understanding of water related processes on the surface of Mars. The formation of peroxide via this heterogeneous reaction on aerosols surface suggests a new oxidative process of utility in understanding ozone and oxygen chemistry both at Mars and Earth.

  6. Modeling coupled interactions of carbon, water, and ozone exchange between terrestrial ecosystems and the atmosphere. I: model description.

    PubMed

    Nikolov, Ned; Zeller, Karl F

    2003-01-01

    A new biophysical model (FORFLUX) is presented to study the simultaneous exchange of ozone, carbon dioxide, and water vapor between terrestrial ecosystems and the atmosphere. The model mechanistically couples all major processes controlling ecosystem flows trace gases and water implementing recent concepts in plant eco-physiology, micrometeorology, and soil hydrology. FORFLUX consists of four interconnected modules-a leaf photosynthesis model, a canopy flux model, a soil heat-, water- and CO2- transport model, and a snow pack model. Photosynthesis, water-vapor flux and ozone uptake at the leaf level are computed by the LEAFC3 sub-model. The canopy module scales leaf responses to a stand level by numerical integration of the LEAFC3model over canopy leaf area index (LAI). The integration takes into account (1) radiative transfer inside the canopy, (2) variation of foliage photosynthetic capacity with canopy depth, (3) wind speed attenuation throughout the canopy, and (4) rainfall interception by foliage elements. The soil module uses principles of the diffusion theory to predict temperature and moisture dynamics within the soil column, evaporation, and CO2 efflux from soil. The effect of soil heterogeneity on field-scale fluxes is simulated employing the Bresler-Dagan stochastic concept. The accumulation and melt of snow on the ground is predicted using an explicit energy balance approach. Ozone deposition is modeled as a sum of three fluxes- ozone uptake via plant stomata, deposition to non-transpiring plant surfaces, and ozone flux into the ground. All biophysical interactions are computed hourly while model projections are made at either hourly or daily time step. FORFLUX represents a comprehensive approach to studying ozone deposition and its link to carbon and water cycles in terrestrial ecosystems. PMID:12713923

  7. Intercomparison of atmospheric reanalysis data in the Arctic region: To derive site-specific forcing data for terrestrial models

    NASA Astrophysics Data System (ADS)

    Mori, J.; Saito, K.; Machiya, H.; Yabuki, H.; Ikawa, H.; Ohta, T.; Iijima, Y.; Kotani, A.; Suzuki, R.; Miyazaki, S.; Sato, A.; Hajima, T.; Sueyoshi, T.

    2015-12-01

    An intercomparison project for the Arctic terrestrial (physical and ecosystem) models, GTMIP, is conducted, targeting at improvements in the existing terrestrial schemes, as an activity of the Terrestrial Ecosystem research group in the Arctic of Japan GRENE Arctic Climate Change Research Project (GRENE-TEA). For site simulations for four GRENE-TEA sites (i.e., Fairbanks/AK, Kevo/Finland, Tiksi and Yakutsk/Siberia), we needed to prepare continuous, site-fit forcing data ready to drive the models. Due to scarcity of site observations in the region, however, it was difficult to make such data directly from the observations. Therefore, we decided to create a backbone dataset (Level 0 or Lv0) first by utilizing the reanalysis data to derive the site-specific data (Level 1 or Lv1). For selection of the best dataset for our purpose, we compared four atmospheric reanalysis datasets, i.e., ERA Interim, JRA-55, NCEP/NCAR Reanalysis 1, and NCEP-DOE Reanalysis 2, in terms of the climatic reproducibility (w.r.t. temperature at 2 m and precipitation) in the region north of 60°N. CRU for temperature and GPCP for precipitation were also used for monthly-mean ground-level climate. As we will show ERA-Interim showed the smallest bias for both the parameters in terms of RMSE. Especially, air temperature in the cold period was reproduced better in ERA-Interim than is in JRA-55 or other reanalysis products. Therefore, we created Lv0 from ERA-Interim. Comparison between the site observations and Lv0 showed good agreement except for wind speed at all sites and air temperature at Tiksi, a coastal site in the eastern Siberia. Air temperature of ERA-Interim showed significantly continental characteristics while the site observation more coastal. The 34-year-long, hourly, site-fit continuous data (Lv1) for each of the GRENE-TEA sites was then created from the Lv0 values at the grid point closest to the site, by merging with the observations.

  8. Transit Observations of Venus's Atmosphere in 2012 from Terrestrial and Space Telescopes as Exoplanet Analogs

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Penn, M. J.; Jaeggli, S. A.; Galayda, E.; Reardon, K. P.; Widemann, T.; Tanga, P.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.; Dantowitz, R.

    2013-06-01

    We extensively observed the 8 June 2012 transit of Venus from several sites on Earth; we provide this interim status report about this and about two subsequent ToVs observed from space. From Haleakala Obs., we observed the entire June transit over almost 7 h with a coronagraph of the Venus Twilight Experiment B filter) and with a RED Epic camera to compare with simultaneous data from ESA's Venus Express, to study the Cytherean mesosphere; from Kitt Peak, we have near-IR spectropolarimetry at 1.6 µm from the aureole and during the disk crossing that compare well with carbon dioxide spectral models; from Sac Peak/IBIS we have high-resolution imaging of the Cytherean aureole for 22 min, starting even before 1st contact; from Big Bear, we have high-resolution imaging of Venus's atmosphere and the black-drop effect through 2nd contact; and we had 8 other coronagraphs around the world. For the Sept 21 ToV as seen from Jupiter, we had 14 orbits of HST to use Jupiter's clouds as a reflecting surface to search for an 0.01% diminution in light and a differential drop that would result from Venus's atmosphere by observing in both IR/UV, for which we have 170 HST exposures. As of this writing, preliminary data reduction indicates that variations in Jovian clouds and the two periods of Jupiter's rotation will be too great to allow extraction of the transit signal. For the December 20 ToV as seen from Saturn, we had 22 hours of observing time with VIMS on Cassini, for which we are looking for a signal of the 10-hr transit in total solar irradiance and of Venus's atmosphere in IR as an exoplanet-transit analog. Our Maui & Sac Peak expedition was sponsored by National Geographic Society's Committee for Research and Exploration; HST data reduction by NASA: HST-GO-13067. Some of the funds for the carbon dioxide filter for Sac Peak provided by NASA through AAS's Small Research Grant Program. We thank Rob Ratkowski of Haleakala Amateur Astronomers; Rob Lucas, Aram Friedman, Eric

  9. The oxidation state of Hadean magmas and implications for early Earth's atmosphere.

    PubMed

    Trail, Dustin; Watson, E Bruce; Tailby, Nicholas D

    2011-12-01

    Magmatic outgassing of volatiles from Earth's interior probably played a critical part in determining the composition of the earliest atmosphere, more than 4,000 million years (Myr) ago. Given an elemental inventory of hydrogen, carbon, nitrogen, oxygen and sulphur, the identity of molecular species in gaseous volcanic emanations depends critically on the pressure (fugacity) of oxygen. Reduced melts having oxygen fugacities close to that defined by the iron-wüstite buffer would yield volatile species such as CH(4), H(2), H(2)S, NH(3) and CO, whereas melts close to the fayalite-magnetite-quartz buffer would be similar to present-day conditions and would be dominated by H(2)O, CO(2), SO(2) and N(2) (refs 1-4). Direct constraints on the oxidation state of terrestrial magmas before 3,850 Myr before present (that is, the Hadean eon) are tenuous because the rock record is sparse or absent. Samples from this earliest period of Earth's history are limited to igneous detrital zircons that pre-date the known rock record, with ages approaching ∼4,400 Myr (refs 5-8). Here we report a redox-sensitive calibration to determine the oxidation state of Hadean magmatic melts that is based on the incorporation of cerium into zircon crystals. We find that the melts have average oxygen fugacities that are consistent with an oxidation state defined by the fayalite-magnetite-quartz buffer, similar to present-day conditions. Moreover, selected Hadean zircons (having chemical characteristics consistent with crystallization specifically from mantle-derived melts) suggest oxygen fugacities similar to those of Archaean and present-day mantle-derived lavas as early as ∼4,350 Myr before present. These results suggest that outgassing of Earth's interior later than ∼200 Myr into the history of Solar System formation would not have resulted in a reducing atmosphere. PMID:22129728

  10. ATCOM: accelerated image processing for terrestrial long-range imaging through atmospheric effects

    NASA Astrophysics Data System (ADS)

    Curt, Petersen F.; Paolini, Aaron

    2013-05-01

    Long-range video surveillance performance is often severely diminished due to atmospheric turbulence. The larger apertures typically used for video-rate operation at long-range are particularly susceptible to scintillation and blurring effects that limit the overall diffraction efficiency and resolution. In this paper, we present research progress made toward a digital signal processing technique which aims to mitigate the effects of turbulence in real-time. Our previous work in this area focused on an embedded implementation for portable applications. Our more recent research has focused on functional enhancements to the same algorithm using general-purpose hardware. We present some techniques that were successfully employed to accelerate processing of high-definition color video streams and study performance under nonideal conditions involving moving objects and panning cameras. Finally, we compare the real-time performance of two implementations using a CPU and a GPU.

  11. Can we reconcile atmospheric estimates of the Northern terrestrial carbon sink with land-based accounting?

    SciTech Connect

    Ciais, Philippe; Luyssaert, Sebastiaan; Chevallier, Fredric; Poussi, Zegbeu; Peylin, Philippe; Breon, Francois-Marie; Canadell, J.G.; Shvidenko, Anatoly; Jonas, Matthias; King, Anthony Wayne; Schulze, E.-D.; Roedenbeck, Christian; Piao, Shilong; Peters, Wouter

    2010-10-01

    We estimatethenorthernhemisphere(NH)terrestrialcarbon sink bycomparingfourrecentatmosphericinversionswith land-based Caccountingdataforsixlargenorthernregions. The meanNHterrestrialCO2 sink fromtheinversionmodelsis 1.7 PgCyear1 over theperiod2000 2004. Theuncertaintyof this estimateisbasedonthetypicalindividual(1-sigma) precision ofoneinversion(0.9PgCyear1) andisconsistent with themin max rangeofthefourinversionmeanestimates (0.8 PgCyear1). Inversionsagreewithintheiruncertaintyfor the distributionoftheNHsinkofCO2 in longitude,withRussia being thelargestsink.Theland-basedaccountingestimateof NH carbonsinkis1.7PgCyear1 for thesumofthesixregions studied. The1-sigmauncertaintyoftheland-basedestimate (0.3 PgCyear1) issmallerthanthatofatmosphericinversions, but noindependentland-basedfluxestimateisavailableto derive a betweenaccountingmodel uncertainty. Encouragingly, thetop-downatmosphericandthebottom-up land-based methodsconvergetoconsistentmeanestimates within theirrespectiveerrors,increasingtheconfidenceinthe overall budget.Theseresultsalsoconfirmthecontinuedcritical role ofNHterrestrialecosystemsinslowingdownthe atmospheric accumulationofanthropogenicCO2

  12. Solar Terrestrial Influences on the D Region as Shown by the Level of Atmospheric Radio Noise

    NASA Technical Reports Server (NTRS)

    Satori, G.; Schaning, B.

    1984-01-01

    Measurements of the integrated atmospheric radio noise field strength at 27 kHz, used here, were made from 1965 to 1975 at Uppsala, Kuhlungsborn, and Prague-Panska Ves. The large scale meteorological situation was considered by comparing solar disturbed and undisturbed periods under similar weather situations. In order to show the effects of the precipitating high energy particle (HEP) flux and of the Forbush decrease on the noise level between pairs of stations were computed as deviations from the monthly median. Delta E (dB), day by day for all six periods was studied. The correlation coefficients for noon as well as for night values were computed. The correlation coefficients were compared with those for solar undisturbed periods.

  13. The production of trace gases by photochemistry and lightning in the early atmosphere

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Tennille, G. M.; Towe, K. M.; Khanna, R. K.

    1986-01-01

    Recent atmospheric calculation suggest that the prebiological atmosphere was most probably composed of nitrogen, carbon dioxide, and water vapor, resulting from volatile outgassing, as opposed to the older view of a strongly reducing early atmosphere composed of methane, ammonia, and hydrogen. Photochemical calculations indicate that methane would have been readily destroyed via reaction with the hydroxyl radical produced from water vapor and that ammonia would have been readily lost via photolysis and rainout. The rapid loss of methane and ammonia, coupled with the absence of a significant source of these gases, suggest that atmospheric methane and ammonia were very short lived, if they were present at all. An early atmosphere of N2, CO2, and H2O is stable and leads to the chemical production of a number of atmospheric species of biological significance, including oxygen, ozone, carbon monoxide, formaldehyde, and hydrogen cyanide. Using a photochemical model of the early atmosphere, the chemical productionof these species over a wide range of atmospheric parameters were investigated. These calculations indicate that early atmospheric levels of O3 were significantly below the levels needed to provide UV shielding. The fate of volcanically emitted sulfur species, e.g., sulfur dioxide and hydrogen sulfide, was investigated in the early atmosphere to assess their UV shielding properties. The photochemical calculations show that these species were of insufficient levels, due in part to their short photochemical lifetimes, to provide UV shielding.

  14. Effect of the shrinking dipole on solar-terrestrial energy input to the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    McPherron, R. L.

    2011-12-01

    The global average temperature of the Earth is rising rapidly. This rise is primarily attributed to the release of greenhouse gases as a result of human activity. However, it has been argued that changes in radiation from the Sun might play a role. Most energy input to the Earth is light in the visible spectrum. Our best measurements suggest this power input has been constant for the last 40 years (the space age) apart from a small 11-year variation due to the solar cycle of sunspot activity. Another possible energy input from the Sun is the solar wind. The supersonic solar wind carries the magnetic field of the Sun into the solar system. As it passes the Earth it can connect to the Earth's magnetic field whenever it is antiparallel t the Earth's field. This connection allows mass, momentum, and energy from the solar wind to enter the magnetosphere producing geomagnetic activity. Ultimately much of this energy is deposited at high latitudes in the form of particle precipitation (aurora) and heating by electrical currents. Although the energy input by this process is miniscule compared to that from visible radiation it might alter the absorption of visible radiation. Two other processes affected by the solar cycle are atmospheric entry of galactic cosmic rays (GCR) and solar energetic protons (SEP). A weak solar magnetic field at sunspot minimum facilitates GCR entry which has been implicated in creation of clouds. Large coronal mass ejections and solar flares create SEP at solar maximum. All of these alternative energy inputs and their effects depend on the strength of the Earth's magnetic field. Currently the Earth's field is decreasing rapidly and conceivably might reverse polarity in 1000 years. In this paper we describe the changes in the Earth's magnetic field and how this might affect GCR, SEP, electrical heating, aurora, and radio propagation. Whether these effects are important in global climate change can only be determined by detailed physical models.

  15. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2.

    PubMed

    Friend, Andrew D; Lucht, Wolfgang; Rademacher, Tim T; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B; Dankers, Rutger; Falloon, Pete D; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F Ian

    2014-03-01

    Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510-758 ppm of CO2), vegetation carbon increases by 52-477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended. PMID:24344265

  16. Terrestrial Vegetation Response to Climate Change Over North America from Increased Atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Ming, M.; Mao, H.; Talbot, R.

    2005-12-01

    We used a regional climate version of the MM5 mesoscale atmospheric modeling system that was asynchronically and simultaneously coupled with the biogeographical model BIOME to explore vegetation-climate interactions over North America. The impact of climate change due to increased greenhouse gases on potential ecosystem evolution was assessed, and a future scenario of vegetation distribution was explored. Doubled CO2 conditions induced strong high-latitude warming, while the southern U.S. became cooler in winter. Across almost all of the model domain precipitation tended to increase in all seasons with the highest intensification found over the Northeast, Southeast, and the Great Plains. In response to this future climate scenario, vegetation migrated northward systematically in the eastern United States. In particular, the sparsely vegetated area around Hudson Bay was predicted to be covered by cool conifer forests. Over the Great Plains and parts of the Midwest, the supply of water from precipitation was found to be a crucial factor affecting the natural evolution of vegetation; more precipitation under doubled CO2 led to temperate deciduous forests extending northward and to the northwest. Grasslands in the northern half of the Great Plains are expected to be replaced by cool conifer and mixed forests due to increased precipitation. Over the Cascade and Rocky Mountain ranges in the western U.S., no systematic changes in vegetation are predicted, due to the complex terrain and unsystematic changes in temperature and precipitation. Averaged over the whole model domain, 39% of areas are projected to have vegetation type changes under doubled CO2. The above results were obtained with model simulations using 108 km resolution, and they will be compared with runs using 50 km resolution to study the potential impact of model resolution on regional ecosystem response to climate change.

  17. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2

    PubMed Central

    Friend, Andrew D.; Lucht, Wolfgang; Rademacher, Tim T.; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B.; Dankers, Rutger; Falloon, Pete D.; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R.; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F. Ian

    2014-01-01

    Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510–758 ppm of CO2), vegetation carbon increases by 52–477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended. PMID:24344265

  18. The terrestrial plant and herbivore arms race -- A major control of Phanerozoic atmospheric CO[sub 2

    SciTech Connect

    Olsen, P.E. )

    1993-03-01

    Much recent work points to chemical weathering of continental silicates as the principal control of atmospheric CO[sub 2]. Presently, chemical weathering is mediated by plants. Vascular plants increase chemical weathering by drastically increasing acid leaching through respiration, decay, and microbial symbionts. Through the Phanerozoic the continuing evolution of terrestrial plant communities must have had a major effect on weathering rates. However, the efficacy of plant-induced-weathering is decreased by herbivory, which in turn decreases the invasion of soil by roots and leads to increased physical weathering. The author proposes that the major ice house--hot house cycles of the Devonian-Quaternary were caused by the lag between plant innovations and complete compensation by herbivore-detritivore response. In this way, it seems possible that: (1) the Carboniferous coals are a consequence of limited herbivory and soil litter decomposition and the Permo-Carboniferous glaciations were caused by dramatically increased chemical weathering caused by the previous global spread of vascular plants; (2) the Mesozoic hot house was brought on by massive increases in megaherbivores and litter decomposers; and (3) Cenozoic cooling and Quaternary glaciations resulted from the spread of herbaceous angiosperms and most recently grasslands. Earth's own superherbivory, if continued for tens of millions of years, will brings one back to mid-Mesozoic hot house conditions, not by the burning of fossil fuels, but rather by a global increase in physical over chemical weathering.

  19. Studies of Constraints from the Terrestrial Planets, Asteroid Belt and Giant Planet Obliquities on the Early Solar System Instability

    NASA Astrophysics Data System (ADS)

    Nesvorny, David

    The planetary instability has been invoked as a convenient way to explain several observables in the present Solar System. This theory, frequently referred to under a broad and somewhat ill-defined umbrella as the ‘Nice model’, postulates that at least one of the ice giants suffered scattering encounters with Jupiter and Saturn. This could explain several things, including the excitation of the proper eccentric mode in Jupiter's orbit, survival of the terrestrial planets during giant planet migration, and, if the instability was conveniently delayed, also the Late Heavy Bombardment of the Moon. These properties/events would be unexpected if the migration histories of the outer planets were ideally smooth (at least no comprehensive model has yet been fully developed to collectively explain them). Additional support for the planetary instability comes from the dynamical properties of the asteroid and Kuiper belts, Trojans, and planetary satellites. We created a large database of dynamical evolutions of the outer planets through and 100 Myr past the instability (Nesvorny and Morbidelli 2012. Many of these dynamical histories have been found to match constraints from the orbits of the outer planets themselves. We now propose to test these different scenarios using constraints from the terrestrial planets, asteroid belt and giant planet obliquities. As we explain in the proposal narrative, we will bring all these constraints together in an attempt to develop a comprehensive model of early Solar System's evolution. This will be a significant improvement over the past work, where different constraints were considered piecewise and in various approximations. Our work has the potential to generate support for the Nice-type instability, or to rule it out, which could help in sparking interest in developing better models. RELEVANCE The proposed research is fundamental to understanding the formation and early evolution of the Solar System. This is a central theme of NASA

  20. Biospheric-atmospheric coupling on the early Earth

    NASA Technical Reports Server (NTRS)

    Levine, J. S.

    1991-01-01

    Theoretical calculations performed with a one-dimensional photochemical model have been performed to assess the biospheric-atmospheric transfer of gases. Ozone reached levels to shield the Earth from biologically lethal solar ultraviolet radiation (220-300 nm) when atmospheric oxygen reached about 1/10 of its present atmospheric level. In the present atmosphere, about 90 percent of atmospheric nitrous oxide is destroyed via solar photolysis in the stratosphere with about 10 percent destroyed via reaction with excited oxygen atoms. The reaction between nitrous oxide and excited oxygen atoms leads to the production of nitric oxide in the stratosphere, which is responsible for about 70 percent of the global destruction of oxygen in the stratosphere. In the oxygen/ozone deficient atmosphere, solar photolysis destroyed about 100 percent of the atmospheric nitrous oxide, relegating the production of nitric oxide via reaction with excited oxygen to zero. Our laboratory and field measurements indicate that atmospheric oxygen promotes the biogenic production of N2O and NO via denitrification and the biogenic production of methane by methanogenesis.

  1. Impacts and atmospheric erosion on the early Earth

    NASA Technical Reports Server (NTRS)

    Vickery, A. M.

    1991-01-01

    It was suggested that heating and/or vaporization of accreting carbonaceous-chondrite-type planetestimals could result in the release of their volatile components. Modeling of this process strongly suggests that substantial atmospheres/hydrospheres could develop this way. During most of the accretionary process, impact velocities generally differed from the escape velocity of the growing proto-planet because most of the collisions were between bodies in nearly matching orbits. Toward the end of accretion, however, collisions were rarer but more energetic, involving large planetestimals and higher impact velocities. Such impacts result in a net loss of atmosphere from a planet, and the cumulative effect impacts during the period of heavy bombardment might have dramatically depleted the original atmospheres. Models developed to study atmospheric erosion by impacts on Mars and the interaction of the vapor plume produced by KT impactor on Earth are applied to the case of the evolution of Earth's atmosphere.

  2. Nonlinear Interactions between Climate and Atmospheric Carbon Dioxide Drivers of Terrestrial and Marine Carbon Cycle Changes from 1850 to 2300

    NASA Astrophysics Data System (ADS)

    Hoffman, F. M.; Randerson, J. T.; Moore, J. K.; Goulden, M.; Lindsay, K. T.; Munoz, E.; Fu, W.; Swann, A. L. S.; Koven, C. D.; Mahowald, N. M.; Bonan, G. B.

    2015-12-01

    Quantifying feedbacks between the global carbon cycle and Earth's climate system is important for predicting future atmospheric CO2 levels and informing carbon management and energy policies. We applied a feedback analysis framework to three sets of Historical (1850-2005), Representative Concentration Pathway 8.5 (2006-2100), and its extension (2101-2300) simulations from the Community Earth System Model version 1.0 (CESM1(BGC)) to quantify drivers of terrestrial and ocean responses of carbon uptake. In the biogeochemically coupled simulation (BGC), the effects of CO2 fertilization and nitrogen deposition influenced marine and terrestrial carbon cycling. In the radiatively coupled simulation (RAD), the effects of rising temperature and circulation changes due to radiative forcing from CO2, other greenhouse gases, and aerosols were the sole drivers of carbon cycle changes. In the third, fully coupled simulation (FC), both the biogeochemical and radiative coupling effects acted simultaneously. We found that climate-carbon sensitivities derived from RAD simulations produced a net ocean carbon storage climate sensitivity that was weaker and a net land carbon storage climate sensitivity that was stronger than those diagnosed from the FC and BGC simulations. For the ocean, this nonlinearity was associated with warming-induced weakening of ocean circulation and mixing that limited exchange of dissolved inorganic carbon between surface and deeper water masses. For the land, this nonlinearity was associated with strong gains in gross primary production in the FC simulation, driven by enhancements in the hydrological cycle and increased nutrient availability. We developed and applied a nonlinearity metric to rank model responses and driver variables. The climate-carbon cycle feedback gain at 2300 was 42% higher when estimated from climate-carbon sensitivities derived from the difference between FC and BGC than when derived from RAD. These differences are important to

  3. Early terrestrial impact events: Archean spherule layers in the Barberton Greenstone Belt, South Africa

    NASA Astrophysics Data System (ADS)

    Ozdemir, Seda; Koeberl, Christian; Schulz, Toni; Reimold, W. Uwe; Hofmann, Axel

    2015-04-01

    In addition to the oldest known impact structure on Earth, the 2.02-billion-year-old Vredefort Structure in South Africa, the evidence of Early Earth impact events are Archean spherule beds in South Africa and Australia. These spherules have been interpreted as condensation products from impact plumes and molten impact ejecta or/and impact ejecta that were melted during atmospheric re-entry [e.g., 1,2]. The 3.2-3.5 Ga spherule layers in the Barberton Greenstone Belt in South Africa currently represent the oldest known remnants of impact deposits on Earth. Aiming at identification of extraterrestrial components and to determine the diagenetic and metamorphic history of spherule layer intersections recently recovered in the CT3 drill core from the northeastern part of the Barberton Greenstone Belt, we have studied samples from these layers in terms of petrography and geochemistry. All samples, including spherule layer intersections and intercalating country rocks, were studied for mineral identification by optical and electron microscopy, as well as electron microprobe analysis (EPMA) at Natural History Museum Vienna and Museum für Naturkunde Berlin (MfN). Major and trace element compositions were determined via X-ray fluorescence spectrometry at MfN and instrumental neutron activation analysis (INAA) at University of Vienna. Os isotopes were measured by thermal ionization mass spectrometry (N-TIMS) at University of Vienna. Eighteen spherule beds are distributed over 150 meter drill core in CT3. Spherules are variably, deformed or undeformed. The high number of these layers may have been caused by tectonic duplication. Spherule beds are intercalated with shale, chert, carbonate, and/or sulfide deposits (country rocks). The size range of spherules is 0.5 to 2 mm, and some layers exhibit gradation. Shapes of spherules differ from spherical to ovoid, as well as teardrops, and spherules commonly show off-center vesicles, which have been interpreted as a primary

  4. A Study of the Abundance and 13C/12C Ratio of Atmospheric Carbon Dioxide to Advance the Scientific Understanding of Terrestrial Processes Regulating the Global Carbon Cycle

    SciTech Connect

    Stephen C. Piper

    2005-10-15

    The primary goal of our research program, consistent with the goals of the U.S. Climate Change Science Program and funded by the terrestrial carbon processes (TCP) program of DOE, has been to improve understanding of changes in the distribution and cycling of carbon among the active land, ocean and atmosphere reservoirs, with particular emphasis on terrestrial ecosystems. Our approach is to systematically measure atmospheric CO2 to produce time series data essential to reveal temporal and spatial patterns. Additional measurements of the 13C/12C isotopic ratio of CO2 provide a basis for distinguishing organic and inorganic processes. To pursue the significance of these patterns further, our research also involved interpretations of the observations by models, measurements of inorganic carbon in sea water, and of CO2 in air near growing land plants.

  5. Photochemistry of methane and the formation of hydrocyanic acid (HCN) in the earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Zahnle, K. J.

    1986-01-01

    A one-dimensional photochemical model is used to analyze the photochemistries of CH4 and HCN in the primitive terrestrial atmosphere. CH4, N2, and HCN photolysis are examined. The background atmosphere and boundary conditions applied in the analysis are described. The formation of HCN as a by-product of N2 and CH4 photolysis is investigated; the effects of photodissociation and rainfall on HCN is discussed. The low and high CH4 mixing ratios and radical densities are studied.

  6. Composition of early planetary atmospheres - I. Connecting disc astrochemistry to the formation of planetary atmospheres

    NASA Astrophysics Data System (ADS)

    Cridland, A. J.; Pudritz, R. E.; Alessi, M.

    2016-09-01

    We present a model of the early chemical composition and elemental abundances of planetary atmospheres based on the cumulative gaseous chemical species that are accreted on to planets forming by core accretion from evolving protoplanetary discs. The astrochemistry of the host disc is computed using an ionization-driven, non-equilibrium chemistry network within viscously evolving disc models. We accrete gas giant planets whose orbital evolution is controlled by planet traps using the standard core accretion model and track the chemical composition of the material that is accreted on to the protoplanet. We choose a fiducial disc model and evolve planets in three traps - water ice line, dead zone and heat transition. For a disc with a lifetime of 4.1 Myr, we produce two hot Jupiters (M = 1.43, 2.67 MJupiter, r = 0.15, 0.11 au) in the heat transition and ice line trap and one failed core (M = 0.003 MJupiter, r = 3.7 au) in the dead zone. These planets are found with mixing ratios for CO and H2O of 1.99 × 10-4 and 5.0 × 10-4, respectively, for both hot Jupiters. Additionally, for these planets we find CO2 and CH4, with mixing ratios of 1.8 × 10-6 → 9.8 × 10-10 and 1.1 × 10-8 → 2.3 × 10-10, respectively. These ranges correspond well with the mixing ratio ranges that have been inferred through the detection of emission spectra from hot Jupiters by multiple authors. We compute a carbon-to-oxygen ratio of 0.227 for the ice line planet and 0.279 for the heat transition planet. These planets accreted their gas inside the ice line, hence the sub-solar C/O.

  7. Seasonal exchange of carbon dioxide between the atmosphere and the terrestrial biosphere: extrapolation from site-specific models to regional models

    SciTech Connect

    King, A.W.

    1986-01-01

    Ecological models of the seasonal exchange of carbon dioxide (CO/sub 2/) between the atmosphere and the terrestrial biosphere are needed in the study of changes in atmospheric CO/sub 2/ concentration. In response to this need, a set of site-specific models of seasonal terrestrial carbon dynamics was assembled from open-literature sources. The collection was chosen as a base for the development of biome-level models for each of the earth's principal terrestrial biomes or vegetation complexes. The primary disadvantage of this approach is the problem of extrapolating the site-specific models across large regions having considerable biotic, climatic, and edaphic heterogeneity. Two methods of extrapolation were tested. The first approach was a simple extrapolation that assumed relative within-biome homogeneity, and generated CO/sub 2/ source functions that differed dramatically from published estimates of CO/sub 2/ exchange. The second extrapolation explicitly incorporated within-biome variability in the abiotic variables that drive seasonal biosphere-atmosphere CO/sub 2/ exchange.

  8. Removal of CO2 from the terrestrial atmosphere to curtail global warming: From methodology to laboratory prototype

    NASA Astrophysics Data System (ADS)

    Orton, Andrea E.

    This research has focused on the initial phase of required investigations in pursuit of a global scale methodology for reduction of CO 2 in terrestrial air for the purpose of curtailment of global warming. This methodology was initially presented by Agee, Orton, and Rogers (2013), and has provided the basis for pursuing this thesis research. The first objective of the research project was to design and build a laboratory prototype system, capable of depleting CO2 from terrestrial air at 1 bar of pressure through LN2 refrigeration. Design considerations included a 26.5L cylindrical Pyrex glass sequestration chamber, a container to hold a reservoir of LN2 and an interface between the two to allow for cooling and instrumentation ports for measurements inside the sequestration chamber. Further, consideration was given to the need for appropriate insulating material to enclose the assembled apparatus to help achieve efficient cooling and the threshold depositional temperature of 135 K. The Amy Facility in the Department of Chemistry provided critical expertise to machine the apparatus to specifications, especially the stainless steel interface plate. Research into available insulating materials resulted in the adaption of TRYMER RTM 2500 Polyisocyanurate, effective down to 90 K. The above described DAC prototype designed for CO2 sequestration accomplished two of the initial research objectives investigated: 1) conduct refrigeration experiments to achieve CO2 terrestrial deposition temperature of 135 K (uniformly) and 2) deplete CO2 from the chamber air at 1 bar of pressure, documented by appropriate measurements. It took approximately 5.5 hours for the chamber to be completely uniform in temperature of 135 K (and below) through the use of LN2 poured into the container sitting on an aluminum interface on top of the sequestration Pyrex chamber. As expected, Rayleigh-Taylor instability (more dense fluid over less dense fluid) was observed through the duration of the

  9. Climatic consequences of very high carbon dioxide levels in the earth's early atmosphere.

    PubMed

    Kasting, J F; Ackerman, T P

    1986-12-12

    The possible consequences of very high carbon dioxide concentrations in the earth's early atmosphere have been investigated with a radiative-convective climate model. The early atmosphere would apparently have been stable against the onset of a runaway greenhouse (that is, the complete evaporation of the oceans) for carbon dioxide pressures up to at least 100 bars. A 10- to 20-bar carbon dioxide atmosphere, such as may have existed during the first several hundred million years of the earth's history, would have had a surface temperature of approximately 85 degrees to 110 degrees C. The early stratosphere should have been dry, thereby precluding the possibility of an oxygenic prebiotic atmosphere caused by photodissociation of water vapor followed by escape of hydrogen to space. Earth's present atmosphere also appears to be stable against a carbon dioxide-induced runaway greenhouse. PMID:11539665

  10. Long-range atmospheric transport of terrestrial biomarkers by the Asian winter monsoon: Evidence from fresh snow from Sapporo, northern Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shinya; Kawamura, Kimitaka; Seki, Osamu

    2011-07-01

    Molecular distributions of terrestrial biomarkers were investigated in fresh snow samples from Sapporo, northern Japan, to better understand the long-range atmospheric transport of terrestrial organic matter by the Asian winter monsoon. Stable carbon (δ 13C) and hydrogen (δD) isotope ratios of C 22-C 28n-alkanoic acids were also measured to decipher their source regions. The snow samples are found to contain higher plant-derived n-alkanes, n-alkanols and n-alkanoic acids as major components. Relative abundances of these three biomarker classes suggest that they are likely derived from higher plants in the Asian continent. The C 27/C 31 ratios of terrestrial n-alkanes in the snow samples range from 1.3 to 5.5, being similar to those of the plants growing in the latitudes >40°N of East Asia. The δ 13C values of the n-alkanoic acids in the snow samples (-33.4 to -27.6‰) are similar to those of typical C 3 gymnosperm from Sapporo (-34.9 to -29.3‰). However, the δD values of the n-alkanoic acids (-208 to -148‰) are found to be significantly depleted with deuterium (by ˜72‰) than those of plant leaves from Sapporo. Such depletion can be most likely interpreted by the long-range atmospheric transport of the n-alkanoic acids from vegetation in the latitudes further north of Sapporo because the δD values of terrestrial higher plants tend to decrease northward in East Asia reflecting the δD of precipitation. Together with the results of backward trajectory analyses, this study suggests that the terrestrial biomarkers in the Sapporo snow samples are likely transported from Siberia, Russian Far East and northeast China to northern Japan by the Asian winter monsoon.