Interior-surface-atmosphere Interactions of Rocky Planets: Simulation of Volcanic Outgassing and Volatile Chemical Speciation in the C-O-H System PDF Download

Author: Gianluigi Ortenzi
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ISBN:
Category :
Languages : en
Pages :

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Author: Philippa Kate Liggins
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ISBN:
Category :
Languages : en
Pages : 0

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Author: Benjamin Hayworth
Publisher:
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Category :
Languages : en
Pages : 0

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Long-term atmospheric and climate evolution on terrestrial planets is primarily controlled by the silicate weathering feedback and evolution of the host-star. The former acts to regulate the climate of rocky planets by controlling the concentration of greenhouse gases in the atmosphere - shaping the habitability of said planet. In this dissertation, In Chapter 2, I explore how the silicate-weathering and ice-albedo feedbacks control the climate of early Mars when sufficient amounts of atmospheric H2 are present. This study can help us constrain the possible martian environments that allowed surface liquid water in its distant past. Explaining the evidence for surface liquid water on early Mars has been a challenge for climate modelers, as the sun was ~30% less luminous during the late-Noachian. I propose that the additional greenhouse forcing of CO2-H2 collision-induced absorption is capable of bringing the surface temperature above freezing and can put early Mars into a limit-cycling regime. Limit cycles occur when insolation is low and CO2 outgassing rates are unable to balance with the rapid drawdown of CO2 during warm weathering periods. Planets in this regime will alternate between global glaciation and transient warm climate phases. This mechanism is capable of explaining the geomorphological evidence for transient warm periods in the martian record. Previous work has shown that collision-induced absorption of CO2-H2 was capable of deglaciating early Mars, but only with high H2 outgassing rates (greater than ~600 Tmol/yr) and at high surface pressures (between 3 to 4 bars). I use new theoretically derived collision-induced absorption coefficients for CO2-H2 to reevaluate the climate limit cycling hypothesis for early Mars. The long-term habitability of a planet is often assumed to be controlled by its ability to cycle carbon between the solid planetary interior and atmosphere. This process allows the planet to respond to external forcings (i.e. changes in insolation, changes in volcanic outgassing rates, etc.) and regulate its surface temperature through negative feedbacks on atmospheric CO2 involved in silicate weathering. In Chapter 3, I explore how the different, non-linear dependencies on pCO2 between continental weathering and seafloor weathering rates can control how a habitable planet responds to external forcings. The evolution of a planet's host-star may not only impact its habitability, but its prebiotic environment. In Chapter 4, I explore what impact an active young Sun may have had on the young Earth's prebiotic environment at the dawn of life. Earth's Hadean atmosphere is thought to have been dominated by N2 and CO2 except in the aftermath of large impacts, when CO and CH4 may have become abundant. Here, I investigate the effect of high fluences of solar energetic particles (SEPs) from the more rapidly rotating, magnetically active young Sun. These particles would have penetrated deeply into Earth's atmosphere, ionizing and dissociating ambient gases as they did so. If the level of solar activity was very high, as it would have been if the Sun began its life as a rapid rotator, rapid dissociation of CO2 would have created an atmosphere rich in CO and O2. Such an atmosphere would have been too oxidized to be conducive to the origin of life in a surface environment. As the solar rotation rate slowed, the SEP fluence would have dropped off, causing O2 to disappear but allowing CO to remain abundant. Thermodynamic free energy from the 'water-gas shift' reaction, CO + H2O -> CO2 + H2, could have exceeded 50-60 kJ/mol -- more than enough to power nucleotide polymerization or ATP synthesis. Hence, charged particle bombardment could have played an important role in the origin of life. These same types of processes may operate on Earth-like planets orbiting other G-type stars, most of which are more magnetically active than the Sun.

Author: Aomawa L. Shields
Publisher:
ISBN:
Category :
Languages : en
Pages : 148

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The goal of the work presented here is to explore the unique interactions between a host star, an orbiting planet, and additional planets in a stellar system, and to develop and test methods that include both radiative and gravitational effects on planetary climate and habitability. These methods can then be used to identify and assess the possible climates of potentially habitable planets in observed planetary systems. In this work I explored key star-planet interactions using a hierarchy of models, which I modifed to incorporate the spectrum of stars of different spectral types. Using a 1-D energy-balance climate model, a 1-D line-by-line, radiative-transfer model, and a 3-D general circulation model, I simulated planets covered by ocean, land, and water ice of varying grain size, with incident radiation from stars of different spectral types. I find that terrestrial planets orbiting stars with higher near-UV radiation exhibit a stronger ice-albedo feedback. Ice extent is much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and ice-covered conditions occur on an F-dwarf planet with only a 2% reduction in instellation (incident stellar radiation) relative to the present instellation on Earth, assuming fixed CO2 (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance requires an 8% reduction in instellation, while a planet orbiting an M-dwarf star requires an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets, in addition to stronger absorption by water vapor, CO2, and clouds in their atmospheres, providing increased downwelling longwave radiation. The surface ice-albedo feedback effect becomes less important at the outer edge of the habitable zone, where atmospheric CO2 can be expected to be high. I show that ~3-10 bars of CO2 will entirely mask the climatic effect of ice and snow, leaving the traditional outer limit of the habitable zone unaffected by the spectral dependence of water ice and snow albedo. Simulations of the equilibrium climate response of a planet to increasing instellation from an F-, G-, or M-dwarf star indicate that the exit out of global ice cover is also sensitive to host star spectral energy distribution. Under fixed CO2 conditions, a planet orbiting an M-dwarf star exhibits a smaller resistance to melting out of a frozen state, requiring a smaller instellation to initiate deglaciation than planets orbiting hotter, brighter stars. This is due to the combined effects of surface ice and snow absorption of the large fraction of near-IR radiation emitted by M-dwarfs, and atmospheric near-IR absorption, which weakens the Hadley circulation, reducing the climate hysteresis (the range over which multiple stable equilibia are possible) of M-dwarf planets. Given their greater climatic stability, planets orbiting cooler, lower-mass stars may be the best candidates for long-term habitability and life beyond the Solar System. As lower-mass stars are likely candidates to host multiple rocky planets, it is important to consider whether gravitational interactions among planets may have significant effects on climate and habitability over long timescales. Using an n-body integrator with inputs from a method I developed to determine the locations of all planets in a given system at the same epoch using transit timing data, a specific case is explored- that of Kepler-62f (Borucki et al. 2013), a potentially habitable planet in a five-planet system orbiting a K-dwarf star. The maximum stable initial eccentricity possible for Kepler-62f is identified as e = 0.32. Simulations using a 3-D GCM indicate that Kepler-62f would have areas of the planet with surface temperatures above the freezing point of water with 1 bar or more of CO2 in its atmosphere. If it has an active carbon cycle, Kepler-62f could have ample amounts of greenhouse gases in its atmosphere to maintain atmospheric stability and habitable surface conditions while staying well below the maximum CO2 greenhouse limit. In a low-CO2 case (Earth-like levels), increases in planetary obliquity and orbital eccentricity coupled with an orbital configuration that places the summer solstice at or near pericenter generate regions of the planet with above-freezing surface temperatures, which may cause surface melting of an ice sheet formed during an annual cycle. If Kepler-62f is synchronously rotating and has an ocean, significant cloud cover could develop at the substellar point, increasing planetary albedo and reducing surface temperatures. The methods presented here serve as tested tools that can be used to assess the possible climates of potentially habitable planets in systems with a wide range of orbital architectures as they are discovered.

Author: Beth N. Orcutt
Publisher: Cambridge University Press
ISBN: 1108477496
Category : Nature
Languages : en
Pages : 687

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A comprehensive guide to carbon inside Earth - its quantities, movements, forms, origins, changes over time and impact on planetary processes. This title is also available as Open Access on Cambridge Core.

Author: Ryan S. Morgan
Publisher: ProQuest
ISBN: 9780549957997
Category : Io (Satellite)
Languages : en
Pages : 106

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Author: Stephen J. Mackwell
Publisher: University of Arizona Press
ISBN: 0816530599
Category : Science
Languages : en
Pages : 709

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"Through the contributions of more than sixty leading experts in the field, Comparative Climatology of Terrestrial Planets sets forth the foundations for this emerging new science and brings the reader to the forefront of our current understanding of atmospheric formation and climate evolution"--Provided by publisher.

Author: Bruce Fegley
Publisher: Academic Press
ISBN: 012251100X
Category : Science
Languages : en
Pages : 816

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-- Presents brief historical summaries and biographies of key thermodynamics scientists alongside the fundamentals they were responsible for.

Author: Zachary Sharp
Publisher: Prentice Hall
ISBN:
Category : Science
Languages : en
Pages : 368

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This is the first dedicated book to cover the basics of a wide range of stable isotope applications in a manner appropriate for someone entering the field. At the same time, it offers sufficient detail - and numerous references and examples - to direct research for further inquiry. Discusses diverse topics such as hydrology, carbon in plants, meteorites, carbonates, metamorphic rocks, etc. Explores the theory and principles of isotope fractionation. Offers unique, up-to-date discussion of meteorite (extraterrestrial) isotope data. Presents the subject in an interesting historical context, with the classic papers noted. A useful reference for students taking the course and professionals entering the field of Geochemistry.

Author: Heinrich D. Holland
Publisher: Princeton University Press
ISBN: 9780691023816
Category : Science
Languages : en
Pages : 604

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In this first full-scale attempt to reconstruct the chemical evolution of the Earth's atmosphere and oceans, Heinrich Holland assembles data from a wide spectrum of fields to trace the history of the ocean-atmosphere system. A pioneer in an increasingly important area of scholarship, he presents a comprehensive treatment of knowledge on this subject, provides an extensive bibliography, and outlines problems and approaches for further research. The first four chapters deal with the turbulent first half billion years of Earth history. The next four chapters, devoted largely to the Earth from 3.9 to 0.6 b.y.b.p., demonstrate that changes in the atmosphere and oceans during this period were not dramatic. The last chapter of the book deals with the Phanerozoic Eon; although the isotopic composition of sulfur and strontium in seawater varied greatly during this period of Earth history, the chemical composition of seawater did not.