Mercury is the smallest planet in our solar system and the closest to the Sun. It has a rocky surface covered with craters, similar to the Moon. Due to its proximity to the Sun, temperatures on Mercury can vary dramatically, reaching up to 800 degrees Fahrenheit (427 degrees Celsius) during the day and dropping to -330 degrees Fahrenheit (-201 degrees Celsius) at night. Mercury has a very thin atmosphere, which means it cannot retain heat. The planet has no moons and completes an orbit around the Sun in just 88 Earth days. Its unique features and extreme conditions make it a fascinating subject for scientists studying planetary formation and evolution.