Today I will start the section on Facts about the Solar System planets with the planet Mercury.
Mercury is a rocky planet, the closest to the Sun. It has a sidereal year of 88.0 Earth days and sidereal day 58.65 Earth days. This means that its rotation round its own axis is fairly slow. Mercury does not have an atmosphere, it has what is called an exosphere, which is made of atoms that the solar wind manages to remove from the planet's surface. Since it does not have an atmosphere, the temperature varies from -170 degrees Celsius at night to 420 degrees Celsius during the day.
Mercury is the smallest planet in the Solar System, its radius is 2439 km.It is smaller that Ganymede and Titan, satellites of Jupiter and Saturn.
Image of Mercury obtained from the public domain. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. Edited version of Image:Mercury in color - Prockter07.jpg by Papa Lima Whiskey., Public domain, via Wikimedia Commons
Image of Saturn obtained from the public domain. J.T. Trauger (JPL), J.T. Clarke (Univ. of Michigan), the WFPC2 science team, and NASA, Public domain, via Wikimedia Commons