why is a day called a sol on mars
The average length of a Martian sidereal day is 24 h 37 m 22.663 s (88,642.66300 seconds based on SI units), and the length of its solar day (often called a sol) is 24 h 39 m 35.244147 s (88,775.244147 seconds). The corresponding values for Earth are 23 h 56 m 4.0916 s and 24h 00 m 00.002 s, respectively. This yields a conversion factor of 1.02749125170 days / sol. Thus Mars' solar day is only about 2.7% longer than Earth's.