Astronomy final exam question: Uranus vs. Neptune temperatures

Astronomy 210 Final Exam, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss evidence that supports the theory that the interior of Uranus is cooler than the interior of Neptune.

Solution and grading rubric:

• p = 20/20:
  Correct. The lack of belt-zone and cyclonic weather patterns on Uranus, which are generated by convection from core heat is evidence that the interior of Uranus is cooler than the interior of Neptune. The tilted axis of Uranus is evidence that may explain how a large impact may have caused a "Cooper Cooler(TM) Effect" (stirred fluids cool off faster than static fluids).
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Argues how the tilted axis may have been the result of a large impact that would have disrupted and stirred its interior, resulting cooling Uranus off faster than Neptune (which is a theory that explains why the interior of Uranus is cooler, not evidence that it is cooler).
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May appeal to the "Turkey/Cornish Hen Effect" (smaller objects cool off faster than larger objects), distance from the Sun (which would make Uranus warmer than Neptune), or some other plausible property of jovian planets.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. May involve properties of terrestrial planets, or stars.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
p: 10 students
r: 4 students
t: 7 students
v: 22 students
x: 5 students
y: 0 students
z: 0 students

A sample "p" response (from student 0301):

Another sample "p" response (from student 2823), appealing to the a "cream-in-coffee model:

Another sample "p" response (from student 3000):

A sample "r" response (from student 1000), at least recognizing the relevance of active versus sedate weather patterns in Neptune versus Uranus:

A sample "t" response (from student 1713), explaining the "Cooper Cooler(TM) effect":

Another sample "t" response (from student 8675), again putting theory before evidence:

A sample "v" response (from student 3834), considering distance as a factor:

Another sample "v" response (from student 5659), appealing to the megatherm "turkey/cornish hen" effect:

A sample "x" response (from student 6615):