Studying for Exam II

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 78

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

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 its very
  big ? Jovian Planets
• Secondary atmosphere water, CO2, SO2,
• 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
• CO2 could not be absorbed by water, rocks
  because of higher temperatures
• ? run-away Greenhouse effect its hot, the
  greenhouse gases cant be be stored away, it gets
  hotter

10
Earths Atmospheric History

• Volcanic activity spews out water steam
• Temperature range allowed water to liquify
• CO2 dissolves in oceans, damping greenhouse
  effect
• More water condenses, more CO2 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, CO2 dissolves in liquid water
• But Mars is further away from the Sun
• ? temperature drops below freezing point ?
  inverse greenhouse effect
• permafrost forms with CO2 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 CO2 in the Atmosphere goes up
15
Correlation Temperatures rise when Carbon
Dioxide levels rise

• This is true since prehistoric times

16
The Jovian Planets
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Comparison

• Jovian
• far from the Sun
• widely spaced orbits
• large radii
• large masses
• predominantly gaseous
• low density
• no solid surface
• many moons
• many rings

• Terrestrial
• close to the Sun
• closely spaced orbits
• small radii
• small masses
• predominantly rocky
• high density
• solid surface
• few moons
• no rings

18
History

• Jupiter and Saturn known to the ancients
• Galileo observed 4 moons of Jupiter and Saturns
  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

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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
Jupiters Atmosphere

• Cloud bands parallel to equator
• Great Red Spot
• First observed in 1664 by Robert Hooke

23
Jupiters 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 eastwest 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
Saturns Atmosphere

• 92 Hydrogen 7 Helium some methane, water,
  ammonia
• Belt structure similar to Jupiters, but fainter
• Storms are rarer
• White spot seen, 1990 (Voyager)

27
Uranus and Neptunes Atmospheres
Neptunes Dark Spot

• Ammonia frozen out more methane
• Methane absorbs red light, leads to bluish color
• Almost no band structure on Uranus

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Magnetospheres

• Very strong Jupiter's extends past the orbit of
  Saturn!
• Indicate the presence of conducting cores

29
Rings
Saturn
Uranus
Neptune
Jupiter
30
Saturn

• Rings composed of small, icy fragments, orbiting
  in concentric circles
• Orbits obey Keplers laws (of course!)
• Inner rings move faster than outer ones

31
Visibility of Saturns Rings
2009
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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!