The document summarizes key facts about the terrestrial planets Mercury, Venus, and Mars. Mercury is the innermost planet with cratered highlands and long scarps cutting across its surface. It has extreme temperature variations from -173°C to 427°C. Venus is similar in size to Earth but is covered in dense clouds and has a surface temperature of 475°C due to a intense greenhouse effect. Mars has the largest volcanoes in the solar system and evidence that water may have flowed on its surface recently, though the atmosphere is only 1% as dense as Earth's and temperatures range from -70°C to -100°C.

1. The Terrestrial Planets