Dr. Henry Throop / University of Colorado
Astronomy 1110
July 6, 2000
Lecture 22: Planetary science and the Future (+ Pluto)

Announcements
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FCQ's
Final exam
Final grades -- posted outside my office Monday/Tuesday
Makeup assignments

Exam #2 -- multi-choice #1 - wrong!
  Io would be expected to be cold not because of its distance to Sun,
  but because of its small size.  It cools off fast.
  Io & moon are same size.  Moon is close to the sun, but it's still cold & dead.

Earth-Moon system
-----------------

Obs: Moon orbits over equator
Looks like Earth's crust
Looks same age as earth

Popped out from Ocean:  great, but Earth was spinning too fast
  (child)

Formed simultaneously: composition doesn't match
  (sister)

Capture: hard to do dynamically
  (stepchild)

Giant impact: works pretty well.  Violent.
  Most of system was probably already melted at the time.

Pluto
-----

Basics: 

  Dicovered 1930
  Orbits center of Mass
  Has a moon charon (1979)
  Has an atmosphere (1984?)
  Sizes (1100 km, 635 km)
  Icy
  Cratered?
  Atmosphere collapses, expands
  Want to send spacecraft before atmosphere collapses
  Never been visited by spacecraft
  Orbital resonance with neptune

Q: where does it fit in?
  r = 1200 km
  mass: 10x smaller than mercury
  Nothing like giant planets
  Nothing like terrestrial planets

For planet:
  Round (ie, not an asteroid)
  Closer than KBO's
  Large
  Historically a planet

For KBO:
  Largest of a continuum of sizes
  Wouldn't be called a planet today
  A lot smaller than it was `supposed' to be

For Comet:
  Has a tail sometimes
  Elliptical, tilted orbit
  Atmosphere collapses & expands, just like comet (or Mars polar caps)
  Icy

For weird:
  Double planet -- orbits center of mass
  Never been explored

For this being a silly Q:
  Why do we have to classify everything into one of 2 or three categories?
  A: because that's what scientists do: classify things!

History:
  3 yrs ago, L. Esposito started it
  1 yr ago, IAU had a _vote_.
  IAU = assigns names to asteroids, comets, impact craters, etc.
    e.g., craters on venus = women
  Made statement: Pluto is a planet

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Major Q's still in solar system

Some are fact-based (what does pluto's surface look like?)
Some are more complex (is there life on Mars?  Europa?)
Some require modeling (What will venus look like in next billion years?  Io?)
Some require major re-thinking (where is SS in context of other
  systems?  Is solar nebula model even right?  A lot of Jovian planets
  form closer to their stars -- why?)

  Are we alone -- 
    Earth-like planets out there?
    Life out there?
    Intelligence out there?

  Titan -- oceans?
  
  Pluto -- planet?  Is it just the largest of a big population of bodies?  What's on
  its surface -- volcanoes?

  Mars -- where did Valles Marinaris come from?

  Earth -- why is it so perfect?
 
  Venus -- how will it continue to evolve?

  Europa -- what causes its strange ridge patterns?  Will it be liquid ocean again?

  Uranus -- why is it tilted on its side?

  Neptune -- what causes its `ring arcs' -- blobby rings that don't spread out

  Saturn -- How long will the rings last for?  Is it just a temporary phase?

  Jupiter -- great red spot -- why, how long, is it really a hurricane, surface feature, etc?

Do:
  VG of major issues
  Pluto slides
  Pluto handouts
  Pluto song
  FCQ's
  B. Hall/ D. Rossi exams
  VCR