1. Solar System Formation – Earth & Moon

2. Asteroids

3. Asteroid Discovery First (and largest) Asteroid Ceres discovered New Year’s 1801 by G. Piazzi, fitting exactly into Bode’s law: a=2.8 A.U. Today more than 100,000 asteroids known Largest diameter 960 km, smallest: few km Most of them are named about 20 of them are visible with binoculars

4. Comets - Traveling Dirty Snowballs Small icy bodies, “dirty snowballs” Develops a “tail” as it approaches the Sun

5. Comet Anatomy Tail may be up to 1 A.U. long

6. Comet Tail Two kinds of tails: Dust Ion (charged particles)

7. Shapes Comet Giacobini- Zinner (1959) Ion tail 500,000 km long Coma: 70,000 km across Comet Hale-Bopp (1997) Tail 40° long as seen from earth

8. Halley’s Comet – a typical Comet

9. Halley’s Comet – Now and then Halley’s Comet in 1910 Top: May 10, 30° tail Bottom May 12, 40° tail Halley’s Comet in 1986 March 14, 1986

10. Meteor Showers – caused by comets RadiantDuration Quadrantids (QUA)Dec. 28-Jan. 7 Lyrids (LYR)Apr. 16-25 Eta AquaridsApr. 21-May 12 Beta TauridsJune 30 Delta Aquarids July 25-31 Perseids (PER) Aug. 10-14 Draconids Oct. 6-10 Orionids (ORI) Oct. 15-29 TauridsOct.12- Dec 2 Leonids (LEO) Nov. 14-20 Geminids (GEM)Dec. 6-19

11. Meteors, Meteroids and Meteorites A Meteor is a sudden strike of light in the night sky A Meteoroid is a small asteroid, less than 100 m in diameter A Meteorite is any piece of interplanetary matter that survives the passage through Earth’s atmosphere and lands on Earth’s surface

12. Meteors and Meteorites Small particles that strike the atmosphere Come from fragments of asteroids, Moon, Mars, comets Strike the earth all the time (“meteorites”) –High speed means lots of energy released on impact

13. Impact on Earth Most probably caused the extinction of the dinosaurs

14. Impact Craters Quebec's Manicouagan Reservoir. Large meteorite landed about 200 million years ago. The lake, 45 miles in diameter, now fills the ring. Barringer Crater, AZ 0.8 mi diameter, 200 yd deep; produced by impact about 25,000 years ago

15. Tunguska ~30 m body struck Siberia in 1908 Energy equal to that of a 10 Megaton bomb! Detonation above ground; several craters

16. 2013: Siberia Again! 1000 people injured as 20m rock strikes Explodes about 20km overhead 16 hours before known non-fatal asteroid encounter

17. Frequency of Impact Events

18. Formation of the Solar System Features to explain: –planets are far apart, not bunched together –orbits of planets are nearly circular –orbits of planets lie mostly in a single plane –directions of revolution of planets about Sun is the same, and is the same as the direction of the Sun's rotation –directions of rotation of planets about their axes is also mostly in the same direction as the Sun's (exceptions: Venus, Uranus, Pluto) –most moons revolve around their planets in the same direction as the rotation of the planets –differentiation between inner (terrestrial) and outer (Jovian) planets –existence and properties of the asteroids –existence and properties of the comets

19. Meteor Showers – caused by comets RadiantDuration Quadrantids (QUA)Dec. 28-Jan. 7 Lyrids (LYR)Apr. 16-25 Eta AquaridsApr. 21-May 12 Beta TauridsJune 30 Delta Aquarids July 25-31 Perseids (PER) Aug. 10-14 Draconids Oct. 6-10 Orionids (ORI) Oct. 15-29 TauridsOct.12- Dec 2 Leonids (LEO) Nov. 14-20 Geminids (GEM)Dec. 6-19

20. Meteors, Meteroids and Meteorites A Meteor is a sudden strike of light in the night sky A Meteoroid is a small asteroid, less than 100 m in diameter A Meteorite is any piece of interplanetary matter that survives the passage through Earth’s atmosphere and lands on Earth’s surface

21. Meteors and Meteorites Small particles that strike the atmosphere Come from fragments of asteroids, Moon, Mars, comets Strike the earth all the time (“meteorites”) –High speed means lots of energy released on impact

22. Impact on Earth Most probably caused the extinction of the dinosaurs

23. Impact Craters Quebec's Manicouagan Reservoir. Large meteorite landed about 200 million years ago. The lake, 45 miles in diameter, now fills the ring. Barringer Crater, AZ 0.8 mi diameter, 200 yd deep; produced by impact about 25,000 years ago

24. Tunguska ~30 m body struck Siberia in 1908 Energy equal to that of a 10 Megaton bomb! Detonation above ground; several craters

25. 2013: Siberia Again! 1000 people injured as 20m rock strikes Explodes about 20km overhead 16 hours before known non-fatal asteroid encounter

26. Frequency of Impact Events

27. Formation of the Solar System Features to explain: –planets are far apart, not bunched together –orbits of planets are nearly circular –orbits of planets lie mostly in a single plane –directions of revolution of planets about Sun is the same, and is the same as the direction of the Sun's rotation –directions of rotation of planets about their axes is also mostly in the same direction as the Sun's (exceptions: Venus, Uranus, Pluto) –most moons revolve around their planets in the same direction as the rotation of the planets –differentiation between inner (terrestrial) and outer (Jovian) planets –existence and properties of the asteroids –existence and properties of the comets

28. Formation of the Solar System Condenses from a rotating cloud of gas and dust –Conservation of angular momentum flattens it Dust helps cool the nebula and acts as seeds for the clumping of matter

29. Formation of Planets Orbiting dust – planitesimals Planitesimals collide Different elements form in different regions due to temperature Asteroids Remaining gas

30. Structure of the Planets explained Temperature and density of materials drop with distance to sun

31. Cleaning up the Solar System Small objects are forced out of the inner Solar System by gravitational pull of bigger planets Small planetesimals collide and form planets -- or are thrown out!

32. The Earth-Moon System Earth/Moon radius: ¼ Earth/Moon mass: 1/81 Earth-Moon distance: 384,000 km

33. Features of the Earth & Moon Mass: Earth: 6  10 24 kg Moon: 1/81 Earth’s Radius: Earth: 6400 kmMoon: 1/4 Earth’s ra Density: Earth: 5500 kg/m 3 Moon: 3300 kg/m 3 –5.5 times that of water –About 2 times that of a rock Gravity: Earth: 9.8 m/s 2 Moon: 1/6 Earth’s gravity (about the same as in water)

34. Moon: Large-Scale Features “Maria” –Dark areas resembling oceans –Plains of solidified lava –Part of the lunar mantle –About 3.2–3.9 billion years old Highlands (“Terrae”) –Light-colored, resemble continents –The lunar crust –More than 4 billion years old

35. The Moon – Far Side Can be seen by satellites only

36. The Mountains of the Moon Especially well visible near the terminator – the borderline between light and shadow

37. Structure of the Moon Also consists of crust, mantle and core No hydrosphere, magnetosphere or atmosphere Little seismic action

38. Tides Daily fluctuations in the ocean levels Two high and two low tides per day A result of the difference in gravitational pull from one side of the Earth to the other –F = G M m / R 2

39. Lunar Craters Old scars from meteoroid impacts Lots of them; all sizes –Copernicus ~ 90 km across –Reinhold ~ 40 km across –Also craters as small as 0.01 mm!

40. Ages of the Earth and Moon Determined by radioactive dating –Compare amount of radioactive material with amount of decay product –Useful isotopes: Uranium-238 (half-life 4.5 billion years) Uranium-235 (half-life 0.7 billion years) For shorter time scales, Carbon-14 (5730 years) Oldest surface rocks on Earth (Greenland, Labrador) about 3.9 billion years old –When rocks solidified Lunar highlands: 4.1–4.4 billion years old –Rocks from lunar maria slightly younger, more recently melted Meteorites: 4.5 billion years old –Date to origin of solar system