Lecture12 - Lecture#12 Earth Atmosphere and Climate Earth's...

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1 Lecture #12 • Earth: Atmosphere and Climate. Earth: Atmosphere and Climate. – Earth's atmosphere. Earth's atmosphere. – Weather and climate. Weather and climate. Astro 102/104 1 – The greenhouse effect. The greenhouse effect. – Cosmic influences on the biosphere. Cosmic influences on the biosphere. • Reading: Reading: – Chapters 10.1, 10.2, 10.6 Chapters 10.1, 10.2, 10.6 The Main Point The Earth has a relatively thin but di th t h t t h Astro 102/104 2 dynamic atmosphere that warms the surface via the greenhouse effect and makes life possible. Earth's Atmosphere Composition of the Earth’s Atmosphere Gas Symbol Percent PPM Permanent Nitrogen N 2 78.08 Oxygen O 2 20.95 Argon Ar 0.93 Astro 102/104 3 Neon Ne 0.0018 18 Helium He 0.0005 5 Hydrogen H 2 0.00006 0.6 Xenon Xe 0.000009 0.09 Variable Water Vapor H 2 0 0 to 4 Carbon Dioxide CO 2 .0364 364 Methane CH 4 .00018 1.8 Nitrous Oxide N 2 O .000031 0.31 Ozone (Troposphere) O 3 .000004 0.04 Ozone (Stratosphere) O 3 .0012 12 Particulates .000001 0.01 • Highly oxidizing atmosphere ("Non-Equilibrium"). • Surface pressure: 1 bar (~ 1 kg/cm 2 ). • 1 bar = 10 m of water. • Oceans equivalent to 300 bars! Origin of the Atmosphere • Three main possibilities: – (1) Primordial: Formed along with the rest of the Earth ~4.6 billion years ago. This hypothesis is hard to reconcile with our current understanding of planet formation. (2) I t l G l d b li ti th Astro 102/104 4 – (2) Internal: Gases released by volcanic outgassing over the history of the Earth. This is likely the main source of atmospheric gases for terrestrial planets. – (3) Extraterrestrial: Volatiles (materials that evaporate at relatively low temperatures ) delivered from impacts of icy comets and hydrated asteroids. Evaporation or sublimation of volatiles is another source of atmospheric gas.
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This note was uploaded on 03/04/2008 for the course ASTRO 1102 taught by Professor Squyres,s/margot,j during the Spring '07 term at Cornell.

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Lecture12 - Lecture#12 Earth Atmosphere and Climate Earth's...

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