FACTS ABOUT THE 8 PLANETS 1. Mercury Closest planet to the Sun. Smallest of the eight planets. Has no moons. Experiences extreme temperatures: scorching hot during the day and freezing at night. Its year is only 88 Earth days long. 2. Venus Hottest planet in the solar system due to its thick CO₂ atmosphere. Similar in size and structure to Earth (often called Earth’s “sister planet”). Rotates backwards (retrograde rotation). A Venus day is longer than its year. Covered in thick clouds of sulfuri