Inner Planets

1. Inner Planets Science Starter: An AU is the average distance between…a. Pluto & the Sun b. Pluto & Mercuryc. Earth & the Sun d. Earth & its MoonGet right side notes for ISN page 26 THE INNER PLANETS.

2. Review • Objects of the Solar System • Sun • inner planets • outer planets • moons • Asteroids & comets • Size of Planets • Pluto, Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn, Jupiter • Solar System formation:1. Nebula flattened into disk 2. Clumps of dust & frozen gas stuck together 3. Most of the mass fell to center of disk & formed Sun4. Large clumps of dust & frozen gases formed the planets

3. Terrestrial Planets • Layered • Rocky Crust • liquid outer core, solid dense inner core • Dense mantles • Hotter inside, cooler outside • planet radiates heat into space • outer crust cooled and hardened • center is hottest and has highest pressure • TERRESTRIAL PLANETS: Mercury, Venus, Mars, EarthROCKY SURFACETerra=Latin word for Earth

4. Planet Interiors (cont) • The inner planets have similar structure • although we don’t have a lot of data on other planets • Data on Earth’s interior comes from seismic readings of earthquakes

5. Four Main Processes • These processes shape the surfaces of planets • Tectonism • movement of pieces of the planet’s crust (plates) • Volcanism • flow of material (lava) from beneath the planet’s crust • Impact Cratering • meteors hitting a planet’s surface resulting in a crater • Weathering & Erosion • Wind, water, & heating move materials across surface of planet • The first 3 processes build up structure on the surface (mountains, valleys, etc) • The last process wears the surface down

6. Tectonics • Major movements of the planets crust • create mountain ranges, deep valleys • on Earth: tectonic plates rub against each other, move up and down/ side to side • other planets: not plates, but major cracking/shifting (fractures) • Mars is one solid plate that does not move

7. Volcanism • Earth: 95% of volcanoes are found on tectonic plates==cracks in crust so molten rock can rise; forms volcanoesRING OF FIRE • Mars: tall, wide volcanoes (but not steep)Olympic MonsVolcanoes form when molten rock pushes through Martian crust • Moon: lava formed the flat plains called maria • When the inside of a planet cools enough, no more molten rock reaches the surface.

8. Comparative Volcanism • Moon • mares are volcanic in nature and indicate the Moon once had a lot of lava flow • Mercury • some visual indications of lava flow, not enough known • Mars • largest mountains in the Solar System (up to 25 km high) caused by volcanism • Venus • evidence of a lot of complex volcanic activity • Earth • lots of current and previous volcanic activity (Pompeii, Hawaiian Islands, Mt. St. Helen’s)

9. Impact Cratering • The number of collisions between objects depends on how many objects there are • Early in the Solar System there were many more small planetesimals: more collisions • Number of craters can be used to “date” a planet • Craters can be erased by tectonism, volcanism and gradation • occurs on “active” planets (e.g. Earth) • on “dead” planets, craters remain (e.g. Moon) • Formation: • heats and compresses • material thrown outward • surface rebounds

10. Comparative Cratering • Moon • lots of craters in all sizes • Mars • craters with impact craters which indicate there might have been water on Mars once • Venus • dense atmosphere protects Venus • Earth • protected by atmosphere (many meteors burn up) • large oceans leave no impact crater • most craters erased by gradation

11. Weathering/ Erosion • Surface leveling • caused by blowing wind, flowing water and water/ice freezing/melting • Moon & Mercury • no atmosphere, possible ice, little gradation • Mars • large dust storms observed, evidence of water flow • Venus • evidence of blowing wind, no evidence of water • Earth • all processes present • e.g. dust/wind storms, rain, tides, glacier flow

12. Magnetic field • Inner planets all have some magnetic field • This magnetic field is not caused only by magnetized materials • At least partially caused by rotation of Earth • spinning electric charges in core create magnetic field • Facts: • Earth has a strong magnetic field • Earth’s magnetic field moves with time (magnetic north pole not the same as celestial north pole) • the Moon has no or very small magnetic field • Mercury has strong magnetic field • Venus and Mars have small magnetic field

13. Gases – Some Basics • Lighter gases rise • This is really because heavier gases sink and push the lighter gases upward • Temperature of a gas is really the speed of the molecules • Faster gases are hotter • Sunlight and heat from a planet’s interior provide energy to heat atmospheres • Sunlight can also break up molecules • Fast atoms/molecules in the outer atmosphere can escape the planet’s gravitational pull • Planets have a hard time hanging onto hydrogen and helium

14. Atmosphere • Formed from gases that poured out of volcanoes • If a planet’s gravity is strong it traps the gases, if it’s too weak the gases expand into outer space • Inner planets: carbon dioxide havy gashydrogen and helium lighter • Heat energy • Earth’s atmosphere mostly nitrogen, with some oxygen

15. Inner Planet Min-Project: Left Side ISN • Choices: Make trading cards, write song (type lyrics with picture), make a mini-book, power point, or come up with own idea! • Must include:Name of PlanetOrbit in Earth DaysRotationTectonicsVolcanismWeathering/ ErosionImpact Cratering2 Fascinating Facts • Use your science text pages 85-92 as primary resource!