Astronomy quiz question: Mars low in the west at sunrise?

Astronomy 210 Quiz 2, fall semester 2016
Cuesta College, San Luis Obispo, CA

The locations of Mars and Jupiter are shown in the diagram below (not to scale, and orbits have been simplified as circles instead of ellipses).


Mars will be low above the west horizon at sunrise when Earth is located at:
(A) position (A).
(B) position (B).
(C) position (C).
(D) position (D).
(E) (None of the above choices.)

Correct answer (highlight to unhide): (D)

If a line is drawn from Earth to the sun, the observer at sunrise (6 AM) is located perpendicular to that line. Everything below that line would be below the horizon, such that it would not be visible at that time. Doing this for all possible positions of Earth shows that Mars would be visible above the west horizon at sunrise when Earth is at position (D).


(When Earth is at position (B), Mars would be visible above the east horizon at sunrise; Mars would not be visible at all at sunrise when Earth is at positions (A) or (C).)

Section 70160
Exam code: quiz02sr7Y
(A) : 4 students
(B) : 6 students
(C) : 4 students
(D) : 25 students
(E) : 2 students

Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.58