Phys 1810 Lecture 12:

1. (Image unknown origin) Phys 1810 Lecture 12: • Planets: Use material in lecture as a guide for topics to read about in text book on each planet. Upcoming topics: • Solar System Chapt 6 • Greenhouse effect P. 166-167, P. 231 • formation of the moon 8.8 • exoplanets Chapt 15 Topics include • scale, objects • terrestrial vs jovian • planetary system formation including (differentiation) • Mars • Earth – climate change • planetary system formation including differentiation

2. Please join us this week, and the first Thursday of every month, rain or shine. Friends and family are welcome too! October 2 at 7:30 pm Meet at Lockhart Planetarium (University College Room 394) Also this month: Oct 1-30:  An exhibit of astronomy images in Degrees Café. October 8:  total lunar eclipse! October 14: Astronomy in the restaurant – The Tallest Poppy at 7:30 PM.  A panel presentation & opportunity for the public to ask questions. Special guest Professor Ken Freeman (Australian National University). Topic: dark matter – The stuff that makes up 90% of the matter in the universe. October 23: partial solar eclipse!

3. Solar System Overview: What does the class already know about the classical planets? • For each planet: • revolve & rotate in the same direction as other planets? • primarily composed of rock or of gas? # Earth Masses, # Earth radii • small or large? (i.e. closer to Earth size or Jupiter size?) • in outer region or inner region of solar system? • hot or cold? surface T in Kelvin • Lots of moons? • Any other details are welcome  (eg. Does it have rings? B field?)

4. Solar System Overview • The density in kg/m • 1000 for water; if less than this, floats in water. • 2000-3000 for rocks; 8000 for iron • Note 2nd last column & density of Earth. • Ask yourself which planets have densities like rocks/iron? Float on water? 3

5. Tour of the Solar System

6. Mercury Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

7. Mercury Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington • NASA’s Messenger Mission • fly-bys until orbit in 2011

8. Mercury Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington • Colour-enhanced: • Yellow -> volcanic activity in the last billion years

9. Mercury Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington • Thin atmosphere called “exosphere” • Tail created by wind from sun  seasonal changes. • Several possible processes: • vaporization of rocks by impacts • evaporation by sunlight

10. Mercury Due to tidal pull of sun on Mercury we expect a synchronous orbit. P_rotation: P_orbit 3:2 resonance Mercury rotates 3 times for every 2 revolutions about sun. Why? Kepler’s Law about sweeping out equal areas.

11. Venus: Venus Express/European Space Agency Ultraviolet Image Slow, retrograde rotation. Venus Express/ESA

12. Tour of the Solar System: Venus Venus Express/ESA • Similar to Earth: R~0.95 * Earth_R, M~ 0.85 * Earth_M. • Atmosphere 90 *Earth’s; mostly CO2 bit of N, water vapour, sulfuric acid. • CO2 -- outgassing of volcanoes. • T~750K  hottest planet in Solar System.  Greenhouse effect.

13. A Day in the Life of Venus Express • Venus might have had plate tectonics, & even an ocean of water • ‘super-rotating’ atmosphere -- whips around Venus in just 4 Earth-days, much faster than 243 rotation about its axis.

14. Tour of the Solar System: Venus Venus Express/ESA Vortex at South Pole of Venus • A polar vortex is created by an area of low air pressure which sits at the rotation pole of a planet. This causes air to spiral down from higher in the atmosphere. • vortex at both poles.

15. Earth

16. Mars Mars Express/European Space Agency Hebes Chasma

17. Olympus Mons Rheasilvia Height of Olympus Mons on Mars: 25 km Height of Rheasilvia on Vesta (asteroid): 22 km

18. Jupiter

19. Jupiter’s Giant Red Spot

20. Jupiter New Horizons/NASA IR image.

21. Tour of the Solar System: Jupiter Cassini-Huygens/NASA/ESA • “mini”-sun: T higher than just due to sunlight at 5 AU • gravitational contraction when forming heated interior -- heat is now leaking outward Jupiter emits more energy than it receives from Sun NOT because of nuclear processes taking place within its core.

22. Tour of the Solar System: Jupiter Cassini-Huygens/NASA/ESA • Jupiter's moon Europa casting shadow (left).

23. Tour of the Solar System: Jupiter Cassini-Huygens/NASA/ESA • Red Spot is a storm that is at least 300 years old. Its diameter is about 2 Earth diameters.

24. Tour of the Solar System: Jupiter Voyager/NASA • limb (distorted by motion of spacecraft) • rings are orange lines.

25. Jupiter’s rings in IR

26. Tour of the Solar System: Jupiter’s North Pole Cassini-Huygens/NASA/ESA UV filter: Haze traces molecules called hydrocarbons (e.g. CH4 methane) • black area at the pole -- no presentable data • white circle marks 60 degrees latitude • region with a persistent aurora marked in blue. • Note a dark vortex forms.

27. Tour of the Solar System: Jupiter • Dark spot due to small comet or asteroid plunging into Jupiter. • Impact object size of several football fields. • “Bruise” - diameter of Canada. • Some of Jupiter’s moons --captured comets.

28. Tour of the Solar System: Jupiter’s Io Galileo/NASA • Volcanic activity due to tidal forces causing internal heat.

29. Tour of the Solar System: Jupiter’s Europa Galileo/NASA • Enhanced colour image. • Ocean under ice crust. • Cracks in ice crust may be sites for microbes.

30. Saturn Cassini/NASA

31. Saturn Cassini/NASA

32. Tour of the Solar System: Saturn Cassini-Huygens/NASA/ESA • About 10 AU • M ~ 95 * Earth mass • This is not an illustration but an image.

33. Tour of the Solar System: Saturn Cassini-Huygens/NASA/ESA Very thin optical ring system: • Outer radius of last optical ring ` 8 Saturn radii or 280,000 km. • Thickness typically a few 100 m (up to 1km)

34. Tour of the Solar System: Saturn Cassini-Huygens/NASA/ESA • How did the rings form? Two possibilities. • Similar to a planetary disk formation but on a smaller scale. (We’ll do planetary disk formation shortly.) • Tidal forces causing orbiting low density moons to fragment.

35. Saturn’s Moon Enceladus 3) Spewing ice plumes through (“blue”) tiger stripes  E ring • has an atmosphere • Other moon’s with atmospheres: • Enceladus • Triton • Io • Titan • Dione

36. Tour of the Solar System: Saturn Spitzer/NASA • Large Infra-red ring! (Moon Phoebe orbiting within this ring.) • diameter equivalent to 300 Saturns. • ~ 20 Saturns for its vertical height. • Too large for field of view of HST and too faint in visual range for optical telescopes.

37. Tour of Solar System: Saturn • South pole vortex.

38. Saturn’s North Pole Hexagonal Vortex • This can be created in the laboratory

39. Tour of Solar System: Saturn • South pole aurora.

40. Tour of Solar System: Saturn’s Moon Titan. Cassini-Huygens/NASA/ESA UV in false color • Atmosphere: Note upper layer of haze. • Thick enough to have polar vortex. • Seasonal changes due to tilt of spin axes.

41. Titan’s Atmosphere Sound of Huygens Mission descending • Huygens Mission Landing Site: the view from Huygens

42. Tour of Solar System: Saturn’s Moon Titan. Cassini-Huygens/NASA/ESA Ontario Lacus at South Pole Visible + IR • Ethane lake. Ethane created by sunlight breaking apart methane. • Only other solar system object known to have liquid on the surface.

43. Uranus Voyager2/NASA “True” Colour False Colour

44. Tour of the Solar System: Uranus Keck Observatory IR Weather • Rings

45. Neptune Voyager2/NASA

46. Tour of the Solar System: Neptune Visible +IR Voyager2/NASA • Rings. • Seasons due to inclination of rotation axis to orbital plane.

47. Moon of Neptune: Triton • Triton has an atmosphere. • possibly a Pluto-like object that Neptune pulled into orbit.