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SOLAR SYSTEM CHAPTER 2 Copyright © 2011 by John Wiley & Sons Inc.

JUPITER vs. EARTH

Why would planets close to the Sun, such as Earth, have thin atmospheres and those far from the Sun, such as Jupiter, have thick atmospheres?

Earth’s Origin Is Described by the Solar Nebula Hypothesis. • The Sun is a star at the center of our Solar System -one of billions in the Milky Way Galaxy. • The Solar System formed ~ 4.6 bya. • The Sun and other objects originated from the collapse and rotation of a nebula Crab Nebula

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A Nebula is a cloud of gas and dust

Planetary nebula remaining mineral particles and gas after a star explodes!

• Stars release energy and build elements through nuclear fusion. • Nuclear fusion creates new elements. • Stars “burn” their hydrogen becoming brighter. • Eventually, stars become Red Giants and explode! Butterfly nebula 3800 light years away

NOVAS = exploding stars SUPERNOVAS = really big exploding stars

The Solar System began with the collapse and condensation of a Planetary Nebula.

Abundant carbon dioxide, methane, and ammonia. These are volatile gases most stable in outer region.

• Rocky particles and metallic compounds formed solids in the inner region (Terrestrial Planets). • Outer region (cooler) solids formed of hydrogen compounds, metals, and rocks (Gas Giants). • Transition zone between the two regions is known informally as the “frost line”. • Nuclear fusion triggered in core released Solar Wind and stopped contraction .

Planetesimal accretion rocky particles and gases coalesce into planets.

Approximately 5 bya, a swirling nebula began to collapse inward under the pull of gravity.

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The Solar System consists of • 8 classical planets. • 5 dwarf planets. • Small Solar System bodies. • 240 known satellites (moons). • Countless particles; and interplanetary space. Earth, the Sun, and other objects in the Solar System originated at the same time from the same source and have evolved in varying ways since then.

Our Sun: A Massive Hydrogen Bomb held together by gravity • Solar core is site of nuclear fusion. • H is converted to He, which has less mass. • Mass differential is expelled as energy (light and heat). • The Sun is getting “lighter” through time. • Enough fuel to last another 4 to 5 billion years.

MERCURY

VENUS

EARTH

MARS

Terrestrial planets are small and rocky, with thin atmospheres.

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• MERCURY Atmosphere: 42% O2, 28% Na, 22% H2, 6% He, 5% K Extreme daytime heat, extreme nighttime cold.

• VENUS Atmosphere: Carbon dioxide 96.5% CO2, 3.5% N2 Even hotter than Mercury due to high percentage of CO2.

• EARTH Atmosphere: 78.09% N2, 20.95% O2, 0.93% Ar, 0.39% CO2, variable H2O Hot, energy-providing core with surface cool enough for liquid H2O.

• MARS Atmosphere: 95.3% CO2, 2.7% N2, 1.6% Ar, 0.13% O2 Most Earthlike with dry river channels indicating water.

Gas Giants are massive planets with thick atmospheres.

Jupiter Neptune

Uranus Saturn

• JUPITER Atmosphere: (H2), 89.8% H2, 10.2% He Third-brightest object in the night sky after the Moon and Venus.

• SATURN Saturn’s Atmosphere: 96.3% H2, 3.25% He Oblate at the poles, due to a high rate of rotation.

• URANUS Atmosphere: 82.5% H2, 15.2% He, 2.3% CH4 The only planet that does not rotate perpendicular to the ecliptic.

• NEPTUNE Neptune’s Atmosphere: 80% H, 19% He, 1.5% CH4 Inner two-thirds are likely composed of a mixture of molten rock, water, liquid ammonia, and methane.

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Objects in the Solar System include Dwarf Planets Comets and Asteroids Comet exhibiting coma (tail)

Dwarf Planet “an object in the Solar System that orbits the Sun and is not a satellite of a planet or other celestial body. It must be spherical (or nearly so) in shape.”

The Five OFFICIALLY RECOGNIZED Dwarf Planets • HAUMEA, MAKEMAKE and PLUTO (with its moon, Charon) located in the Kuiper Belt Pluto’s Atmosphere: 98% N2, < 1% H2O, < 1% CH4, < 1% CO Pluto and Charon considered a “double-dwarf”.

• ERIS located in the scattered disk region

• CERES a large asteroid located in the asteroid belt

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Asteroids and Comets • Asteroids Rocky, metallic planetesimals.

Eros

• Comets Icy (water ice and other frozen liquids or gases) planetesimals.

Can you label it?

In time EARTH’S interior accumulated heat • New atmosphere created by volcanic

“Hadean Era”

outgassing and delivery of gases and water by ice-covered comets.

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Earth’s Geomagnetic Field Blown into a streamlined shape by the Solar Wind.

WHAT ABOUT THE MOON? Capture hypothesis: Earth’s gravity captured a passing planetesimal.

Double planet hypothesis Earth and the Moon were formed concurrently from a local cloud of gas and dust.

Fission hypothesis: Centrifugal force associated with Earth’s spin caused a bulge of material to separate from Earth. Impact hypothesis: Earth suffered a massive collision with a Mars-sized object ejecting parts of Earth’s mantle and core Into orbit.

IMPACT HYPOTHESIS Most widely accepted hypothesis of moon formation.

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