Ch 27-Planets of Solar System

1. Ch 27-Planets of Solar System • Objectives • Nebular hypothesis of the origin of solar system • How planets formed • Formation of land, atmosphere, oceans of Earth • Models of universe developed by Ptolemy and Copernicus • Kepler’s laws of planetary motion • Describe how Newton explained Kepler’s laws of motion • Basic characteristics of inner planets • Compare the characteristics of inner planets • Summarize the features that allow Earth to sustain life • Basic characteristics of outer planets that make them different • Compare the characteristics of outer planets • Explain why Pluto is now considered a dwarf planet

2. Nebular Hypothesis • Solar system-sun and all of the planets and other bodies that travel around it • What is a planet? • Celestial body that orbits the sun, is round cause of its own gravity, and has cleared neighborhood around its orbital path • Nebular hypothesis-states that the sun and planets condensed at about the same time out of rotating cloud of gas and dust-nebula • Scientific calculations support hypothesis • Solar nebula-rotating cloud of gas and dust from which the sun and planets formed • About 99% of all matter contained in solar nebula now exists in sun

3. Formation of Planets • Planetesimal-small body from which planet originated in early stages of development of solar system • Protoplanets-larger bodies that were formed through collisions and through force of gravity • Moons-smaller bodies that orbit planets • Planets and moons are smaller and denser than protoplanets

4. Inner Planets • Features depended on distance between the protoplanet and developing sun • What are the inner planets? • Mercury, Venus, Earth, Mars • Contain large quantities of iron and nickel • Solid surfaces that smaller, rockier and denser than outer planets

5. Outer Planets • Jupiter, Saturn, Uranus, Neptune • Formed in colder regions of solar nebula • Retained their lighter elements-helium and hydrogen and ices-water ice, methane ice and ammonia ice • Gas giants-composed mostly of gases, low density and huge • Jupiter is 11 times Earth’s diameter • What about Pluto? • Dwarf planet, discovered in 1930’s, smaller than Earth’s moon • Ice ball made of frozen gases and rock

6. Earth • Early Earth-hot enough to melt iron • Differentiation-denser materials sank to center, less dense forced to outer layers • What did this cause? • Core, mantle, crust • Characteristics of present Earth • Cooled enough for solid rock to form

7. Earth’s Atmosphere • Why did the atmosphere form? • Differentiation caused hydrogen and helium to rise to surface • Atmosphere was to weak to hold hydrogen and helium-escaped becuz at the temp of the gases, the gravity was not strong enough to hold the gases • Outgassing-volcanic eruptions released large amounts of gases, water vapor, CO2, nitrogen, methane, sulfur dioxide, ammonia-formed new atmosphere • Gases interacted w/ radiation from sun, oxygen formed ozone layer • What is the ozone layer? • Molecule that contains 3 oxygen atoms, shields Earth from harmful ultraviolet radiation of sun

8. Formation of Earth’s Oceans • Part of water came from space • Icy bodies-comets collided w/ Earth, became part of atmosphere • Water cooled to become oceans • 1st ocean-freshwater • Flowed over land picking up dissolved solids-this is how the oceans became salty • Effects on atmosphere-affects temps in variety of ways • Dissolving CO2

9. Sec 2-Models of Solar System • Aristole-model in which Earth was center, everything revolved around Earth • Ptolemy-planets moved in small circles-epicycles, revolved around in larger circles around Earth • Copernicus-sun centered, planets revolved around sun in same direction but at different speeds and distances from sun

10. Kepler’s Laws • Law of ellipses-Each planet orbits the sun in a path called a ellipse, not a circle • Elliptical orbits can vary in shape • Eccentricity-degree of elongation of an elliptical orbit • Law of equal areas-objects travel at different speeds in their orbits • Mars travels fastest when closet to sun • Law of periods-describes the relationship between average distance between planet and sun and orbital period of planet • What is orbital period?

11. Newton • Hypothesized moving objects will keep moving and resist change in speed until acted upon by outside force • Inertia-tendency of an object to resist being moved or resist change in speed or direction until outside force acts on object • Newton’s Model of Orbits-gravity causes the orbit to curve • Gravity pulls object toward sun, inertia keeps object moving forward in straight line • Weaker gravitational pull further away from sun • Longer orbits=outer planets

12. Sec 3-Inner Planets • Terrestrial Planets • Mostly solid rock, metallic cores • Number of moons varies • Impact craters located on planets w/ bowl shaped depressions • What causes them?

13. Mercury • Closest to sun • Circles sun every 88 days, rotates on axis every 59 days • Heavily cratered, line of cliffs of km long, what caused this? • No atmosphere, slow rotation • 427 deg C during day, -173 deg C at night

14. Venus • 225 days orbital period, rotates once every 243 days • Same size, mass and density of Earth • Atmospheric pressure=90 times pressure on Earth • High concentration of CO2-atmosphere about 96% CO2 • Highest surface temp in solar system • Brightest object in night sky-evening star • Mts, volcanoes, lava plains and sand dunes • Maat Mons-highest volcano

15. Earth • What’s the orbital period? • How many rotations in a day? • How many moons? • Extreme active geologic history • What causes continue change to surface of Earth? • Liquid water • Only planet to support life • What’s needed to support life?

16. Mars • 228 million km from sun, 50% farther from sun than Earth • 687 days of orbit, rotates every 24 h and 37 min, seasons much like Earth’s • Geologically active in past • Covered by deep canyons • Valles Marineris-series of canyons, 4000 km • Olympus Mons-largest volcano in Tharsis Montes-volcanic region • No solid evidence for life yet

17. Outer Planets • Asteroid belt separates inner planets. What is the asteroid belt? • Gas giants • Deep massive atmospheres • What is Pluto considered? • More larger and massive than terrestrial planets • Less dense, huge amount of gravity-helped retain gases • What is the atmosphere made of? • All have ring systems-dust and icy debris • Where does it come from?

18. Jupiter • Largest planet, 300 times Earth • Orbital period=12 yrs, rotates every 9 hr and 50 min • 60 moons • Hydrogen and helium=92% of atmosphere • Orange, gray, blue, and white bands spread out parallel of equator • Severe storms and thunderstorms • Giant Red Spot-giant rotating storm, several hundred yrs

19. Saturn • Orbital period of 29.5 yrs • Very cold, average temp=-167 deg C • 47 moons-Titan largest moon=1/2 of Earth • Mostly hydrogen and helium w/ rocky iron core • Least dense planet in solar system • Rings of Saturn=2 times planet’s diameter • Rotates every 10 hr and 30 min

20. Uranus • 3rd largest, discovered in 1781 by Sir William Herschel • Difficult to study, images shows changes in atmosphere • 24 moons, 11 rings • Orbital period almost 84 yrs, rotates every 17 hrs • Blue green color indicates atmosphere contains significant amounts of methane

21. Neptune • Similar to Uranus in size and mass • Orbital period=164 yrs, rotates every 16 hr • 13 moons, 6 rings • John Couch Adams, Urbain Leverrier, Johann Galle • Hydrogen, helium, methane=atmosphere • Active weather system • Strongest winds in solar system • Great Dark Spot-storm size of Earth

22. Other Objects • Pluto-defined as dwarf planet in 2006 • 248 yr orbital period, but closer to sun than Neptune about 20 of those yrs • Smaller than Earth’s moon • Frozen methane, rock, and ice • Very thin nitrogen atmosphere • Kuiper-Belt Objects • Starts just beyond orbit of Neptune, contains dwarf planets and other small bodies made mostly of ice • Quaoar, Eris • What is a dwarf planet? • Any object that orbits sun, round cause of own gravity, not cleared its orbital pans • http://glencoe.com/sec/science/earthscience/2007/concept_motion/NGS/Visualizing_the_Kuiper_Belt_28.swf

23. Exoplanets • Circle stars other than Earth’s sun • Cannot be directly observed w/ telescopes or satellites • How is it detected then? • Gravity tugs on stars they orbit • Most identified are larger than Uranus • 2 discovered=Earth’s size