Mercury

Mercury is the smallest planet in our solar system and the one closest to the Sun, orbiting at a scorching distance that makes it the hottest planet despite Venus appearing hotter due to its thick atmosphere. This tiny, gray, cratered world is named after the Roman messenger god because of how quickly it zips across the sky, and it has virtually no atmosphere to protect its surface from extreme temperature swings between blazing day and freezing night. Scientists find Mercury fascinating because studying it helps us understand how planets form near stars and how extreme environments can exist right in our cosmic neighborhood.