A "sol" is a term used to describe a single day on the planet Mars. It is approximately 24 hours and 39 minutes long, making it slightly longer than an Earth day. The concept of a sol is important for scientists and researchers studying the Martian environment, as it helps them plan missions and experiments. The use of sols is particularly relevant for missions like NASA's Curiosity rover and Perseverance rover, which operate on the Martian surface. These missions track time in sols to coordinate activities and gather data, ensuring that they can effectively study the planet's geology and climate.