The Solar System

1. Earth Science Ch. 23 The Solar System

2. 23.1 Overview of the Planets • 2 Groups of Planets • Terrestrial • Mercury, Venus, Earth, and Mars • Smaller, rocky, inner planets • Jovian • Jupiter, Saturn, Uranus, and Neptune • Huge gas giants, outer planets • Size is the most obvious difference between the terrestrial and jovian planets

3. Density • Terrestrial planets have higher densities • Jovian planets are less dense because much of their volume consists of gas and ice • Rate of Rotation • Jovian planets have faster rates of rotation

4. Interiors of Planets • The materials that make up the planets are divided into 3 groups: • Gases: hydrogen and helium • Rocks: silicate minerals and metallic iron • Ices: ammonia, methane, CO2, water

5. Terrestrial • Dense • Rocky and metallic substances • Minor amounts of gases and ices • Jovian • Less dense • Large amounts of gases and ices • Rocky and metallic materials found in the core

6. Atmospheres of Planets • Jovian • Very dense atmospheres of hydrogen, helium, methane, and ammonia • Maintain atmosphere due to large masses and colder temperatures which increase gravitational force • Terrestrial • Thin atmospheres due to warmer temperatures and smaller masses which decreases gravitational force

7. A gas molecule can escape from a planet if it reaches a speed known as escape velocity • Escape velocity depends on gravitational force • Larger gravitational force = larger escape velocity

8. Formation of the Solar System • Nebula • A cloud of gas and dust in space • A nebula often consists of 90% hydrogen, 9% helium, and a small percentage of heavier element

9. Nebular theory • The sun and planets formed from a rotating disk of dust and gases • Nebular material contracted due to gravity • Most of the material collected in the center • Remaining material formed a thick flattened rotating disk. • Within the disk the material cooled and formed grains and clumps of icy, rocky material

10. The growth of planets began as solid bits of matter collided and clumped together. This process is called accretion. • The accretion formed small irregular shaped bodies called planetesimals • The planetesimals grew larger as collisions and accretion continued • Once the planetesimals grew large enough to exert a gravitational pull they added more mass and became planets

11. The smaller inner planets formed because temperatures were so high that only metals and silicates could form solid grains. It was too hot for ices to form • The outer planets formed because it was cold enough for ices to form. Eventually the outer planets became so large that they could capture even the lightest of gases.

13. 23.2 Terrestrial Planets • Mercury • Orbital period: 88 days • Rotational period: 59 days • Planet closest to the sun • Slightly larger than Earth’s moon • Weak magnetic field which indicates a liquid core • Physical appearance is similar to the moon • Extremely hot because most solar energy is absorbed • No atmosphere to regulate temperatures • Greatest temperature extremes of any planet

14. Venus • Orbital period: 225 days • Period of rotation: 244 days • A day is longer than a year • Second planet from the sun • Second brightest natural object in the nighttime sky • Almost the same size as earth (earth’s twin) • Opposite rotation

15. Solid iron core and rocky crust similar to earth • Less craters than mercury but more than earth • Surface is shaped by basaltic volcanism and tectonic activity • Most of the surface is covered by volcanic flows • Densest atmosphere of the terrestrial planets • Extreme greenhouse effect • Most of the atmosphere is composed of CO2

16. Mars • Orbital period: 687 days • Period of rotation: 25 hours • 4th planet from the sun • Half the size of earth • 2 moons (Phobos and Deimos) • Very old surface features • Many large inactive volcanoes • Home to the largest volcano in the solar system – Olympus Mons

17. Very thin atmosphere composed mostly of CO2 • Contains polar ice caps • Very cold due to thin atmosphere • It is believed that Mars once had water at the surface. Most is underground now. • Evidence for surface water includes drainage patterns, evaporites, and geologic formations • The red color of Mars is due to the presence of iron oxide or rust

18. 23.3 The Outer Planets • Jupiter • Orbital Period: 12 years • Period of Rotation: 9 hrs. 50 min. (fastest) • Largest planet • Great pressure as you move toward the core which causes hydrogen gas to be changed into a liquid and then a metal. • Atmosphere contains hydrogen, helium, methane, ammonia, water, and sulfur compounds

19. Wind systems creates light and dark bands • Has a great red spot which is a giant wind storm • At least 69 natural satellites (53 have been named. • One of the moons of Jupiter, Io, is very volcanically active. • Volcanic activity is caused by gravitational energy • Has rings

20. The first 4 moons of Jupiter are the largest and were discovered by Galileo: • Io • Europa • Ganymede (largest) • Calisto

21. Saturn • Orbital period: 29 years • Period of Rotation: 10 hrs. 14 min. • Most prominent feature is the system of rings • At least 20 rings • Rings are composed of rock and ice particles • Very active atmosphere • Large storms • 61 natural satellites • Titan is the largest moon • Only natural satellite to have a dense atmosphere and liquid water at the surface

22. Uranus • Orbital period: 84 years • Period of rotation: 17 hrs • Rotates on its side • Axis of rotation lies parallel with the plane of the orbit • Atmosphere contains mostly hydrogen, helium, methane, water, and ammonia • 27 natural satellites • 9 ring belts

23. Neptune • Orbital period: 165 years • Period of rotation: 16 hrs • Outermost planet • Extreme winds. One of the windiest places in the solar system • Great dark spot that disappeared and reappeared may be a giant storm • Cirrus like clouds found in the atmosphere • Ring system • 13 moons • Triton is the largest and is the coldest body in the solar system

24. Pluto • Orbital period: 248 years • Rotational period: 6 days • Dwarf planet • Pluto met 2 of the 3 criteria to be a planet: • Orbits the sun • Sufficient mass for its gravity to produce a round shape • Pluto is not considered a planet because it has not cleared the neighborhood around its orbit

25. Pluto is a dwarf planet. A dwarf planet meets the 3 criteria above and is not the satellite of another planet • 3 satellites • Very elliptical orbit. At times during its orbit it is closer to the sun than Neptune • Largest moon is Charon

26. 23.4 Minor Members • Asteroids • Orbit the sun in a belt between Mars and Jupiter • Larger than 10 meters in diameter • Orbital period of 3 to 6 years • Many of the most recent impact craters on earth and the moon were probably caused by asteroids • Possibly formed by a pre-existing planet or collisions among large bodies in space

27. Comets • Composed of rocky and metallic materials • Held together by frozen water, ammonia, methane, CO2, and CO • Very elongated orbits that carry them beyond Pluto • Orbital periods can range from 100s to 1000s of years • The glowing head of a comet is called the coma • The coma is formed by solar energy

28. The tail of a comet always points away from the sun because of radiation pressure and solar winds • Comets originate in 2 regions of the outer solar system • Kuiper belt: beyond Neptune, short orbital periods • Oort clouds: long orbital periods, form a shell around the solar system • Comet Halley: most famous (76 years)

29. Meteoroids • Shooting stars occur when a meteoroid enters earth’s atmosphere • Small solid particles that travel through space • Formation: • Interplanetary debris • Asteroid belt material • Remains of a comet

30. Meteors • Meteoroids that enter earth’s atmosphere and burn up • Meteor showers are composed of materials lost by comets • Meteorites • meteoroids that reach the earth’s surface • Meteorites can be made of iron or silicates (stony) • Scientists have used evidence from meteoroids to estimate the age of the solar system (4.5 billion years)