Ch 17 (The Terrestrial Planets)-1

Ch 17 (The Terrestrial Planets)-1 - Comparative Planetology...

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Unformatted text preview: Comparative Planetology of the Terrestrial Planets Chapter 17: What are the main features of Earth when you view it as a planet? How does size affect a planet? How does distance from the sun affect a planet and its atmosphere? How does a planets atmosphere depend on the size of the planet? This chapter will answer the following questions. The moon and Mercury are small, Earth and Venus are large and about the same size and Mars is a medium sized world. Size is a critical factor in determining a worlds personality. Small worlds tend to be cold and dead, but larger worlds can be hot and active. 17-1: A Travel Guide to the Terrestrial Planets Five Worlds A Travel Guide to the Terrestrial Planets Core, Mantle and Crust All of the terrestrial worlds are made up of rock and metal. They all have dense, metallic cores and rocky, low density crusts. In between is the mantle, composed of dense rock. Core, Mantle, Crust, Atmosphere All terrestrial planets have a similar structure of A liquid core A mantle of molten lava A crust of solid, low- density rocks An atmosphere (large range of compositions and pressures) The planets generate heat in their interiors through the decay of radioactive elements. That heat, flowing up and outward through the crust, can make a world active with volcanoes and lava flows. The small worlds cooled fast and have little heat flowing outward now. Mercury and the moon are small and inactive. Earth and Venus , being larger, are geologically active. The moon and Mercury have no atmospheres. Venus has an atmosphere thicker than Earths. Mars, the medium sized terrestrial planet, has a medium atmosphere made up of thin gases. Atmospheres 17-2: Earth: Planet of Extremes Earths interior is molten i.e. hot enough to melt whatever it is made of and generates a strong magnetic field. This heat flows outward, causing volcanoes and earthquakes. The heat also breaks the crust into moving sections that bump into each other and push up mountains. Almost 75% of Earths surface is covered by liquid water and Earths atmosphere is an unusual mixture of nitrogen and oxygen. It is a complicated world! Celestial Profile, p.383 Four Stages of Planetary Development Stage 1: Differentiation Differentiation is the separation of material according to density. Earth has a dense metallic core, a thick rocky mantle, and a lower density crust. Stage 2: Cratering The heavy bombardment of the early solar system cratered Earth just as it did our moon. Stage 3: Flooding As the decay of radioactive elements heated Earths interior, rock melted in the upper mantle where the pressure was lower than in the deep interior, and some of the molten rock welled up through fissures in the crust and flooded the deeper basins. Later, as the atmosphere cooled, water fell as rain and flooded the basins to form the first oceans. Note: On Earth flooding includes both lava and water. Stage 4: Slow Surface Evolution Slow surface evolution has continued for the past...
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Ch 17 (The Terrestrial Planets)-1 - Comparative Planetology...

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