Mars Rotates Toward the East and Takes About 24 1/2

Multiple Choice

Mars rotates toward the east and takes about 24 1/2 hours for one rotation. Phobos, the inner satellite of Mars, revolves around Mars toward the east and requires about 7 1/2 hours to circle the planet once. Viewed from the surface of Mars, how long does it take Phobos to traverse the 180° across the sky from rising to setting (in hours) ?

A) 17
B) 8 1/2
C) 7 1/2
D) 5 1/2