Sol

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A sol is a day on mars which is slightly longer than a day on earth due to mars rotating a bit slower than earth. A sol is 24 hours, 39 minutes, 35 seconds long. A day on mars is similar to earth but a year isn't because a year on mars is around 668 sols which is equal to 687 earth days. The word sol is mainly used by NASA to measure the time of day on mars, mostly about the mars rovers.