Astronomy Rough Notes – Brief Tour of our Planets
BRING:
PPT of planets
Video: Venus Unveiled
Video: Flying by the Planets
HANDOUTS:
"One Wonder of the Solar System”
General websites:
http://www.nineplanets.org
http://photojournal.jpl.nasa.gov/index.html
http://pds.jpl.nasa.gov/planets/welcome.htm
http://solarsystem.nasa.gov
http://www.jpl.nasa.gov/solar_system/
http://antwrp.gsfc.nasa.gov/apod/ and go to the Search button at the bottom
Mercury
Terrestrial Planets = Mercury, Venus, Earth, Mars
Few photos of Mercury (from http://pds.jpl.nasa.gov/planets/welcome.htm )
You don’t need to memorize the numbers in ( )
Size: A bit larger than our Moon
Density: (~5.5 times density of water)
Elliptical orbit (0.5 AU to 0.75 AU)
Atmosphere: None
Small planet  small mass  small gravity  small escape speed (Like our Moon )
Also atmospheric molecules have high speeds (it’s hot) so all escape
Surface temp: (800oF on sun side, -300oF on night side)
No atmosphere or oceans to moderate the temperature swings
Largest day/night temperature difference
Cratered surface
Crater counts give age of surface
Lots of craters implies old surface
Few craters implies new surface
No moons
Small if any magnetic field
Astronomy Rough Notes – Terrestrial Planets
Venus
Photos of Venus
See websites listed earlier plus
http://www2.jpl.nasa.gov/magellan/images.html
http://www.mentallandscape.com/V_DigitalImages.htm
Size: About Earth size
Density: like Mercury (~5 times density of water)
Surface T: ~900oF
Atmosphere:
Mostly CO2
Pressure: !!! (~90 X earth’s atmospheric pressure)
Clouds: Sulfuric acid
Video: “Venus Unveiled”
Craters evenly spread on surface
Implies entire surface is same age (about 500 million years old)
Implies Venus resurfaced itself 500 million years ago
Catastrophism vs Uniformitarianism
C: Processes happen catastrophically
U: Processes happen gradually
Greenhouse Effect (More next time)
What is it?
Astronomy Rough Notes – Terrestrial Planets
Mars
Photos of Mars
See http://mars.jpl.nasa.gov/
Most recent from http://marsrovers.jpl.nasa.gov/home/index.html
See also Mars Odyssey http://mars.jpl.nasa.gov/odyssey/
Mars Global Surveyor http://mars.jpl.nasa.gov/mgs
European space agency http://www.esa.int/export/SPECIALS/Mars_Express/
•
•
http://marsprogram.jpl.nasa.gov/
http://www.esa.int/esaCP/index.html
Size: Bigger than our moon and smaller than earth
Density: like Mercury, Venus, Earth (~4 times density of water)
Atmosphere: Thin, CO2, some greenhouse warming
Giant volcanoes due to small gravity
Large rift valley
Water
Flowed at one time
May be locked under the surface. Recent indications of permafrost melting on steep slopes.
Other evidence from Mars Rovers
Polar ice caps of frozen CO2 and water ice
Life? (See October 1996 Sky and Telescope)
Video: “Flying by the Planets” – “Mars: The Movie”
Astronomy Notes
Jovian planets
Jovian planets = Jupiter, Saturn, Uranus, Neptune
(Although better to classify as:
Gas giants = Jupiter, Saturn
Ice giants = Uranus, Neptune
For a summary of all four Jovian planets see the videos:
“To Boldly Go”
“And Then There Was Voyager”
Slides of Jupiter
Many photos on http://www2.jpl.nasa.gov/galileo
Large (about 10 Earth’s across)
Gaseous (H, He)
Density ~ 1.3 times density of water
No “surface”
Large magnetic fields
Many moons
Four Galilean moons
Io (http://science.nasa.gov/newhome/headlines/ast04oct99_1.htm )
Europa – water?
Rings http://science.nasa.gov/headlines/y2002/08nov_gossamer.htm?
Big storms like the Great Red Spot
Turbulent atmosphere, belt rotation (laminar flow)
Internal heat
(Side notes from Galileo probe (Dec 1995) (Students will not be tested on these)
1) Theory suggests that comets bombard early planets bringing organic compounds, noble gases,
atoms, and molecules. Therefore the planet’s chemistry should now differ from early solar nebula.
But probe found that Jupiter looks more like sun (C, O, S). This suggests we don’t fully
understand how planets evolve.
2) Measured 1/2 of sun’s He abundance
Maybe He drops rained down on Jupiter’s core (not reached by Galileo)
3) Probe entered a “dry” area (not as much water as expected)
4) Did not detect the three cloud layers
(Layers are: cloud tops of ammonia, then ammonium hydrosulfide, then water vapor)
5) Water measurements differ
About same as O indicated on sun
1/2 indicated by Voyager
1/10 expected after comet Shoemaker Levy 9
6) Winds blow stronger deeper (not at the cloud tops)
Means heat escaping from deep within Jupiter drives the weather (not the sun) )
Galileo probe has now been crashed into Jupiter – well done Galileo
Astronomy Notes
Saturn
Similar to Jupiter
Density ~ 0.7 times density of water
Atmosphere not as “vibrant” implies less internal heat
(Also a haze of methane)
Connection of moons and ring system
Titan: Atmosphere and oceans of ethane
Cassini probe at Saturn now
http://saturn.jpl.nasa.gov/home/index.cfm
Photo essay at http://www.jpl.nasa.gov/multimedia/cassini-essay/
Astronomy Notes
Uranus, Neptune
Uranus
Similar to other Jovian planets
Density a bit higher
Rocky core
Tilted
Magnetic field tilted to rotation
Center of magnetic field off center of planet
Miranda – moon, large scarps
Neptune
Similar to other Jovian planets
Windiest
Great Dark Spot (comes and goes)
Magnetic field way off center and tilted
Triton – moon, nitrogen geysers
Astronomy Notes
Pluto
Later
Beyond Pluto
http://science.nasa.gov/headlines/y2004/16mar_sedna.htm?list687798