Explanation:
Mercury is the smallest planet in our Solar System. It has a diameter of about 4,879 kilometers, making it slightly larger than Earth's moon. Despite its small size, Mercury is dense and has a relatively large iron core, which contributes to its high density. Its small size also means that it has a weak gravitational pull, making it difficult for the planet to retain an atmosphere. Mercury is also the closest planet to the Sun, with an average distance of about 58 million kilometers.