Astronomy midterm question: NASA Asteroid Redirect Mission proposal

Astronomy 210 Midterm 2, spring semester 2015
Cuesta College, San Luis Obispo, CA

NASA's proposed Asteroid Redirect Mission[*] was recently described in the news:
NASA sends a spacecraft to an asteroid, plucks a boulder off its surface with a robotic claw, and brings [the boulder] back in orbit around the moon. Then, brave astronaut heroes go and study the [the boulder] up close.
Discuss whether or not the classification of Earth's moon would change by having a (small, irregularly-shaped) boulder in orbit around it, and how you know this. Explain using the International Astronomical Union classification scheme.

[*] Marcus Woo, "NASA's Plan to Give the Moon a Moon," March 25, 2015, wired.com/2015/03/nasas-plan-give-moon-moon/.

Solution and grading rubric:
  • p:
    Correct. Of the three IAU requirements for a planet (orbits the sun directly, has a rounded shape, cleared/dominates its orbit) Earth's moon does not meet the first question (orbits the sun directly), which immediately categorizes it as a moon. Placing a small, irregularly-shaped boulder in orbit around the moon does not affect its orbit around Earth, thus the moon will still fail to meet the first question, which does not affect its categorization as a moon.
  • r:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  • t:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors.
  • v:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion only tangentially related to the IAU classification scheme.
  • x:
    Implementation/application of ideas, but credit given for effort rather than merit. Discussion unrelated to the IAU classification scheme.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
Grading distribution:
Section 30674
Exam code: midterm02N4ra
p: 27 students
r: 0 students
t: 5 students
v: 2 students
x: 3 students
y: 0 students
z: 1 student

Section 30676
Exam code: midterm02s0Ju
p: 32 students
r: 8 students
t: 6 students
v: 3 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1234):

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