1. The Planets & the Solar System Chapter 27 300

3. The Solar System The Inner Planets Ch. 27.1 What are the 2 “planetary neighborhoods”? –inner planets –outer planets What separates these 2 “neighborhoods?” –asteroid belt

4. What are the inner planets? –4 closest to sun Mercury Venus Earth Mars –What is another name for the inner planets? “terrestrial” planets –b/c earth-like characteristics »rocky crusts »dense mantle layers »very dense cores Distance Between Planets Visualization The Solar System

5. What are asteroids? –solid, rocklike masses that orbit the sun in same direction as planets Where are asteroids located? –between Mars & Jupiter in asteroid belt that separates inner planets from outer planets The Solar System

6. What are the outer planets? –remaining 4 planets Jupiter Saturn Uranus Neptune What is another name for the outer planets? –“Jovian” planets or Gas Giants How do they compare to the terrestrial planets? –considerably larger than Earth –gaseous –less dense –have ring systems The Solar System

7. What about Pluto??? –oddity of the solar system Not dense enough to be considered “terrestrial”. Too small to be “Jovian”. The Solar System

8. Inner Planets: Fun Facts Mercury –surface many craters –No atmosphere (due to weak gravity)… »So… no weather to erode craters smooth plains –formed by lava flowing from cracks in surface –extremely hot day temps (400+°C) & extremely cold night temps (-200°C) due to lack of atmosphere MESSENGER Orbits Mercury (AMNH Sci Bulletin)

9. Venus –“Earth’s twin/sister planet” similar diameter, mass, gravity –Unlike other planets rotates east to west (clockwise) –atmosphere = mostly carbon dioxide (CO 2 ) “runaway” greenhouse effect (~475°C) –yellow clouds = sulfuric acid Inner Planets: Fun Facts

10. Mars –Axis tilted at almost same angle & in same direction as Earth’s similar 4 seasons but ~2x as long (since year is ~2x longer than Earth’s) –largest volcano in the solar system = Olympus Mons –Valles Marineris canyon system (as long as U. S. is wide) Inner Planets: Fun Facts Curiosity: Searching for Carbon (AMNH Sci Bulletin)

11. Jupiter –More than 2x mass of all other planets combined –Colored zones & belts –“ Great Red Spot” May be calm area that rotates slowly in turbulent atmosphere Outer Planets: Fun Facts Ch. 27 Sec. 2

12. Saturn –less dense than water (1g/cm 3 ) would float –most visible ring system believed to be chunks of ice –colored zones & belts rising & sinking gases fewer than Jupiter Outer Planets: Fun Facts Saturn System Is Showing Its Age (AMNH Sci Bulletin) How Did Saturn Get Its Rings? (AMNH Sci Bulletin)

13. Uranus –inclination (tilt) of axis almost 90° So… rotates on its side –May have been tipped by collision early in history of solar system –blue tint from methane Outer Planets: Fun Facts

14. Neptune –occasionally outside Pluto’s orbit b/c Pluto’s orbit sometimes brings Pluto closer to the sun than Neptune –Astronomers predicted existence mathematically in 1846 Outer Planets: Fun Facts

15. Pluto –No longer “true” planet Now one of 40+ “dwarf” planets –Not dense enough to be “terrestrial” & too small to be “Jovian”. –Smaller than 7 moons in our solar system (including our moon) –New Horizons probe to Pluto launched Jan. 2006New Horizons probe will fly by Pluto & Charon ~2015 Outer Planets: Fun Facts Article on Why Pluto is No Longer Considered a Planet

16. Planetary Satellites Ch. 27 Sec. 3 What is a satellite? –an object that orbits a planet Example of natural satellites? –moons Example of artificial satellite? –TV satellite, GPS satellite, etc.

17. Earth  moon = only natural satellite Mars  2 tiny irregularly shaped moons –Phobos –Deimos Jupiter  at least 63 moons –4 largest Galilean satellites (in honor of discoverer Galileo) –Io –Europa –Ganymede –Callisto Planetary Satellites

18. Saturn  at least 61 moons –Titan only moon known to have substantial atmosphere Uranus  at least 27 moons –5 major moons Titania Oberon Umbriel Ariel Miranda Neptune  at least 13 moons –Triton Planetary Satellites Nile-Like River Found on Moon of Saturn (AMNH Sci Bulletin)

19. What are comets? –“dirty snowballs” dust particles trapped in mixture of frozen water, carbon dioxide, methane, & ammonia Where are comets usually found? –Most are Trans-Neptunian Objects (TNOs) spend most of their time beyond Neptune’s orbit –Including in Kuiper Belt & Oort Cloud Solar System Debris Ch. 27 Sec. 4

20. A few comets have highly elliptical orbits taking them closer to the sun –can become visible at night when icy surface is heated Forms coma (cloud of gas & dust that expands into space) –tail points away from sun due to solar wind –Halley’s Comet 76 years –Comet IsonComet Ison Solar System Debris http://news.discovery.com/space/astronomy/comet-ison-barely-survives- thanksgiving-solar-roast-131129.htm

21. What are asteroids? –solid, rocklike masses probably left over from formation of solar system How do asteroids orbit? –around sun in same direction as planets most have nearly circular orbits within asteroid belt between Mars & Jupiter Solar System Debris Protecting Earth from Asteroid Impacts (AMNH Sci Bulletin)

22. What are meteors, meteoroids, & meteorites? –rocky or icy fragments; smaller than asteroids meteoroid –traveling in space meteor –passing through Earth’s atmosphere »“shooting star” meteorites – hit Earth’s surface Solar System Debris

23. What are the 3 basic types of meteorites? –stony –iron –stony-iron Give info about: –how solar system evolved –possible effects of impacts Solar System Debris Willamette Meteorite Cape York Meteorite (Ahnighito)

24. What are impact craters? –bowl-shaped depressions that remain after meteor or other object hits Earth, other planet, moon ejecta (debris) rays radiate out from crater Solar System Debris Arizona’s Barringer Meteor Crater