29:52 Homework Set #2

Assigned:  September 23, 2004

Due: October 1, 2004

 

Confused? Ask for help and explanation from me. Even better, find some fellow students via the bulletin board and carry on a conversation there, or via the email facility. Be sure and check out the material in the Addenda to the lectures.  It is important for some of these problems.  

 

  1. Two asteroids (little planets; we’ll talk about them later in the semester) are in orbit around the Sun. Asteroid A has a period of 3 years, the while asteroid B has a period of 10 years.  Assume the eccentricity is small (close to zero) for both orbits.  Which one is further from the Sun?  Explain your reasoning,  and identify which astronomical principle you are using. 
  2.  An orbit is shown in the figure below.  What is the eccentricity of the orbit? 

 

  1. A radioisotope A decays to daughter isotope B (via Beta-decay, for example) with a half life of 1.5 billion years. You obtain a sample of a rock from the asteroid Vesta.  You analyse the rock and find that it has 10 atoms per cubic centimeter of  isotope A,  and 70 per cubic centimeter of  B.  You may assume that when the rock formed, it contained no atoms of isotope B,  in other words, all of B in the rock were produced by radioactive decay from isotope A.  How long ago did the rock form?  Show your calculations and explain what you are doing. 
  2. The semi-major axis of the orbit of Mars is 1.523 astronomical units, and the eccentricity is 0.093.  What is the closest Mars comes to the Sun (the so-called perihelion distance).  What is the furthest Mars is from the Sun (the aphelion distance).  Hint:  Think of how the eccentricity is defined (problem 2 should help in this regard.  Then think of what the semi-major axis means.  Finally, where is the Sun located? 
  3. You look up in the sky in daytime.  You see the Moon, about 45 degrees away from the Sun.  What phase is the Moon, i.e. new,  full, half, between half and full, etc. ?
  4. A spacecraft visits the planet Agrippina,  which has not previously had detailed observations of its surface.  The spacecraft returns the picture shown below.  Given what we have studied in this course,  specifically what we have studied about the geological history of the Moon,  what can you say about the geological history of this object? 
  5. Look at the Moon map linked to Lecture 7, topic 6.  If you could choose to land a spacecraft anywhere on the Moon,  where would you choose, and for what scientific reasons?  Use terms and concepts developed in this course. 
  6. This question is about the End-Permian Extinction Event.  Assume that you are describing this extinction event to a friend,  and you mention that a cosmic impact might have caused this extinction.  Your friend asks what kind of evidence one might look for to prove (or disprove)  this suggestion.  What do you say?  I only require that you use ideas, terms, and results presented in class,  but use of other sources would be great.