15-Venus_Mars - Venus VenusandMars DeathbyFireor DeathbyIce...

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enus and Mars Venus and Mars Death by Fire or eath b Ice Death by Ice Biology 190A cture 15 Lecture 15
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The Outer Limits “Oort cloud” reaches ore than 100 000 AU of the lar System more than 100,000 AU from the Sun—and erhaps contains more Solar System perhaps contains more mass than the Earth e objects may have The objects may have formed near the giant planets and then were tossed outwards by gravitational encounters Passing stars or other gravitational influences nudge the comets into the inner Solar System
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Comet Nuclei few probes have visited comet nuclei They contain ices A few probes have visited comet nuclei. They contain ices and dust, venting gas where the Sun heats them. Since comets spend most of their lives in a remote deep freeze, they indicate the Solar System’s original composition. Comet Halley, visited by Giotto Comet Wild 2, visited by Stardust
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Comets s comet moves into the inner solar system it is As a comet moves into the inner solar system, it is warmed by the Sun. They may even have delivered ater to Earth in its early history water to Earth in its early history. Ices on the surface sublimate (go from solid to gas) d stream away from the comet nucleus also and stream away from the comet nucleus, also carrying away dust particles. he gas and dust are The gas and dust are pushed by the solar wind and radiation pressure, making “tails” that point away from the Sun.
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The Inner Solar stem System Bodies that look similar in many ways to Earth, but ith with distinct ifferences. differences.
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The Effects of a Planet’s Mass and Radius all planets cool quickly leading to little tectonic Small planets cool quickly, leading to little tectonic activity or outgasing from molten rock. tmospheres “leak away” to space faster if the surface Atmospheres leak away to space faster if the surface gravity is weaker. Without an atmosphere, the Moon and Mercury also have little erosion. Some features on Mercury and Mars’s volcanoes, imply me past geological activity perhaps until a few some past geological activity, perhaps until a few hundred million years ago on Mars.
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The Evolutionary Stages of Planets y g All of the terrestrial planets were more similar when born. Larger planets cool off more slowly, so even if born at the same time, they are generally in an earlier stage.
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Atmospheres of the Terrestrial Planets ll of the planets had comets impacting them and All of the planets had comets impacting them and
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This note was uploaded on 11/22/2011 for the course BIOLOGY 190a taught by Professor Staff during the Fall '11 term at UMass (Amherst).

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15-Venus_Mars - Venus VenusandMars DeathbyFireor DeathbyIce...

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