Which unit is used to measure the number of Martian days?

a. Sol

b. SoM

c. Solar Day

d. Sod

ANSWER: Sol

Explanation:

The term sol is used by planetary astronomers to refer to the duration of a solar day on Mars. A mean Martian solar day, or "sol", is 24 hours, 39 minutes, and 35.244 seconds.

Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its day is about the same length. Its year is almost twice as long as Earth's.