8aarcheanhist(1)

8aarcheanhist(1) - 2/22/12 Archean Eon and the Solar System...

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2/22/12 1 Archean Eon and the Solar System 87% of the Earth’s history is in the Precambrian! A little background before we get to the Earth • All of the planets were formed around the same time (~4.7bya). • They are formed from the same materials -but in differing percentages. • All planets move counterclockwise around the sun in elliptical orbits. more background • Each planet rotates in the same direction – except Venus and Uranus. • Most of the planets spin on an tilted axis. Solar nebular hypothesis • Nebula cools down and shrinks. • Forms a disk. • Concentrated in center –this becomes the Sun. • Protoplanets form. • Planets and star appear distinct.
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2/22/12 2 “our” planets Solar system The terrestrial “planets” • Venus • Mars • And of course, our Earth. Moon • Relatively small • BUT large compared to its planet! • No atmosphere, hydrosphere or biosphere. • Density of 3.3 g/cm3 • Rotation is similar to Earths orbit. • Each is covered with craters which record the birth of the solar system ~4.7bya. Mercury Innermost planet. Fastest in its orbit. Otherwise, similar to the Moon. Weak magnetic field. No tectonic history.
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8aarcheanhist(1) - 2/22/12 Archean Eon and the Solar System...

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