Lecture Notes:

The final for this class has been canceled, and everyone is invited to a ride on the mother ship. Free pomegranate seeds will be served.
• OVERVIEW OF THE PLANETS [serious stuff]
  Collisions and catastrophes characterize many of the planets. Mercurys outer crust was torn away by a collision leaving it with a relatively large nickel-iron core and a small crust. Venus rotated in the backward direction (clockwise as viewed from the north) perhaps due to a glancing collision in the past which reversed it rotation. The earths moon was torn away from the earth.

  The great northern plains of Mars suggest a similar shearing away of its crust. Once great flash floods moved across its surface, similar in volume to the floods that caused the scablands of eastern Oregon or to 50 times the outflow of the Amazon at its delta. The asteroids could not settle down into a planet due to tidal deformation from Jupiter, and are constantly thrown into chaos due to resonance with Jupiter.

  Of the outer gas giants, Neptune may have lost one of its moons due to a near collision and that moon may now be the planet Pluto. The rotational axis of Uranus is tilted by 90 degrees, probably do to a collision in the distant past.

  The most remarkable planet of them all is Earth, a blue green jewel which constantly changes and which must delight alien observes with their eye stalks glued to their telescopes. Life may exist in primitive forms elsewhere in the solar system It perhaps was encouraged by the water and relatively benign conditions on Mars in the beginning but now any life on that planet must find it a tremendous struggle to keep going. Elsewhere, life may exist in the vast oceans of Europa, warmed by the tides of Jupiter.

  Since planets are probably debris nearly always left over after star formation, there may be billions and billions of planets in our galaxy. How many harbor life we can not say, but using the Drake equation (Snow 701) in an optimistic manner, we discover that there may be a billion planets containing intelligent life in our galaxy; the closest one may be no more than 30 light years away. But, are we intelligent?