Lecture 05 202 Spring 2011

Lecture 05 202 Spring 2011 - Terrestrial Worlds Highlights:...

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Terrestrial Worlds Highlights: Mercury • Rotates three times for every two orbits • Appears to have shrunk early in its life • The most metal-rich planet • Has 3-month-long days and nights • Temperatures varying from extremely hot to extremely cold over the course of a full solar day • Has no atmosphere Venus • Spins backward compared to its orbit • Hottest surface temperature of any planet due to its extreme greenhouse effect • Has a dense atmosphere • Roughly the same size and mass as Earth Earth • Has a surprisingly large moon • Only planet with life (as far as we know) • Only planet with oxygen in the atmosphere Mars • Has two tiny moons that might have once been asteroids • Has volcanoes larger than any on Earth • Has a canyon that runs one-fifth of the way around the planet • Has polar ice caps • Shows signs of once having flowing water • May have once had life • Has a thin atmosphere • Most studied planet apart from Earth Geological Activity and Planetary Size Earth is the largest terrestrial planet o Active volcanoes, Earthquakes, Mountains, Erosion Venus is similar in size to Earth o “Recent” Volcanic activity Mars diameter is half of Earth
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o Volcanoes, Erosion in the past. Not much going on now Mercury only slightly larger than Moon o Cratered surfaces. Both geologically dead. Planetary Size and Internal Heat Most Geological activity driven by planet’s internal heat Sources of Internal heat o Accretion Heat due to collisions of planetesimals o Decay of radioactive material in the Interior of planet Planets cool down in space Once the heat is gone, most geological activity stops The amount of initial energy is related to the volume of the planets o Bigger planets will generate more heat The loss of heat is related to the surface of the planets o To cool down a hot potato, cut it in pieces to increase its total surface Small planets (Mercury, Moo) lost their internal heat early in their lives Large planets (Earth, Venus) still retain a substantial amount of heat. Internal Structure Differentiation: o Temperatures during accretion reached the point where rock and metal were able to flow Denser materials (metals) sank to the center of the planets Lighter materials (rock) floated towards the surface o Layered Internal structure Core: Highest density, mostly iron and nickel. Earth’s core is partially molten, generates magnetic field
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Mantle: rocky material rich in metal. Solid, but plastic, it flows over geological times
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This note was uploaded on 04/05/2011 for the course ECOLOGY 110 taught by Professor Young during the Spring '11 term at N. Colorado.

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Lecture 05 202 Spring 2011 - Terrestrial Worlds Highlights:...

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