1. Studying for Exam II Same type of exam as first one Chapters covered: parts of Ch.1, Ch. 4-8. –Very little from Chapters 7&8

2. Mars Northern Hemisphere basically huge volcanic plains –Similar to lunar maria Valles Marineris – Martian “Grand Canyon” –4000 km long, up to 120 km across and 7 km deep –So large that it can be seen from Earth

3. Martian Volcanoes Olympus Mons –Largest known volcano in the solar system –700 km across at base –Peak ~25 km high (almost 3 times as tall as Mt. Everest!)

4. Martian Surface Iron gives the characteristic Mars color: rusty red! View of Viking 1 1 m rock Sojourner

5. Water on Mars? Mars Louisiana Outflow Channels Runoff channels

6. Life on Mars? Giovanni Schiaparelli (1877) – observed “canali” (channels) on Martian surface Interpreted by Percival Lowell (and others) as irrigation canals – a sign of intelligent life Lowell built a large observatory near Flagstaff, AZ (Incidentally, this enabled C. Tombaugh to find Pluto in 1930) Speculation became more and more fanciful –A desert world with a planet-wide irrigation system to carry water from the polar ice caps? –Lots of sci-fi, including H.G. Wells, Bradbury, … All an illusion! There are no canals…

7. Viking Lander Experiments (1976) Search for bacteria- like forms of life Results inconclusive at best

8. Atmospheric Histories Primary atmosphere: hydrogen, helium, methane, ammonia –Too light to “stick” to a planet unless it’s very big  Jovian Planets Secondary atmosphere: water, CO 2, SO 2, … –Outgassed from planet interiors, a result of volcanic activity

9. Atmospheric Histories - Venus Venus is closer to Sun than Earth  hotter surface Not a lot of liquid water on surface initially CO 2 could not be absorbed by water, rocks because of higher temperatures  run-away Greenhouse effect: it’s hot, the greenhouse gases can’t be be stored away, it gets hotter …

10. Earth’s Atmospheric History Volcanic activity spews out water steam Temperature range allowed water to liquify CO 2 dissolves in oceans, damping greenhouse effect More water condenses, more CO 2 is absorbed If too cold, ice forms  less cloud cover  more energy No oxygen at this point, since it would have been used up producing “rust” Tertiary atmosphere: early life contributes oxygen –1% 800 Myrs ago, 10% 400 Myrs ago

11. Mars – Freezing over Mars once had a denser atmosphere with liquid water on the surface As on Earth, CO 2 dissolves in liquid water But: Mars is further away from the Sun  temperature drops below freezing point  inverse greenhouse effect permafrost forms with CO 2 locked away Mars probably lost its atmosphere because its magnetic field collapsed, because Mars’ molten core cooled down

12. Greenhouse Effect Earth absorbs energy from the Sun and heats up Earth re-radiates the absorbed energy in the form of infrared radiation The infrared radiation is absorbed by carbon dioxide and water vapor in the atmosphere

13. Global Warming Excessively “politicized” topic Very complex problem scientifically Slow changes over long periods of time Sources of heating, sources of cooling themselves are temperature dependent

14. Man-made CO 2 in the Atmosphere goes up

15. Correlation: Temperatures rise when Carbon Dioxide levels rise This is true since prehistoric times

16. The Jovian Planets Jupiter Uranus Saturn Neptune

17. Comparison Terrestrial –close to the Sun –closely spaced orbits –small radii –small masses –predominantly rocky –high density –solid surface –few moons –no rings Jovian –far from the Sun –widely spaced orbits –large radii –large masses –predominantly gaseous –low density –no solid surface –many moons –many rings

18. History Jupiter and Saturn known to the ancients –Galileo observed 4 moons of Jupiter and Saturn’s rings Uranus –Discovered telescopically by William Herschel in 1781 (actually barely visible to naked eye) Neptune –Predicted from observed perturbations of Uranus’ orbit: Adams (1845) and Leverrier (1846) –Observed by Galle (1846) –Discovery great triumph for computational astronomy/physics

19. Grand Tour of Voyager 1 & 2 Used gravitational slingshot to get from planet to planet

20. Rotation About 10 hours for Jupiter and Saturn; about 17 hours for Uranus and Neptune Differential rotation: rotation speed varies from point to point on the “surfaces” –Gaseous bodies with no solid surfaces! –On Jupiter, the equatorial regions rotate 6 minutes slower than polar regions –On Saturn the equatorial region is about 26 minutes slower Tilt of rotation axes: –Jupiter: almost none – no seasons! –Saturn, Neptune: about like Earth –Uranus: weird

21. Uranus’ Strange Seasons

22. Jupiter’s Atmosphere Cloud bands parallel to equator Great Red Spot –First observed in 1664 by Robert Hooke

23. Jupiter’s Atmosphere 86% Hydrogen, 14% Helium; some methane, water, ammonia Several layers of clouds: ammonia, ammonium hydrosulfide, water Colors mostly due to compounds of sulfur and phosphorus

24. Jupiters’ Bands: Zones and Belts Belts: cool, dark, sinking Zones: warm, bright, rising Jovian weather mostly circles the planet due to high rotation rate Bands exhibit east–west flow  Great Red Spot lies between regions of opposite wind flow

25. Great Red Spot About twice the diameter of the Earth A hurricane that is hundreds of years old!

26. Saturn’s Atmosphere 92% Hydrogen 7% Helium; some methane, water, ammonia Belt structure similar to Jupiter’s, but fainter Storms are rarer White spot seen, 1990 (Voyager)

27. Uranus’ and Neptune’s Atmospheres Ammonia frozen out; more methane –Methane absorbs red light, leads to bluish color Almost no band structure on Uranus Neptune’s Dark Spot

28. Magnetospheres Very strong – Jupiter's extends past the orbit of Saturn! Indicate the presence of conducting cores

29. Rings Saturn Jupiter Uranus Neptune

30. Saturn Rings composed of small, icy fragments, orbiting in concentric circles Orbits obey Kepler’s laws (of course!) –Inner rings move faster than outer ones

31. Visibility of Saturn’s Rings 2009

32. How Do They Form? Miscellaneous debris Moons or other small bodies torn apart by tidal forces Roche limit – distance inside of which an object held together by gravity will be pulled apart

33. Ring Formation Rings may be short lived (on the time scale of solar system) Means that they must form fairly frequently A moon may pass too close to a planet (within the Roche limit) and be destroyed by tidal forces –This will probably happen to Triton (a moon of Neptune) within 100 million years!