Mercury is very different from the other planets in our solar system. Scientists have a lot of questions about how this mysterious planet works. The closest planet to the sun, Mercury, is difficult for scientists to study! However, scientists have figured out ways to get up close to the mysterious Mercury. Young readers will discover why Mercury doesn't have moons and what we've learned from our missions to Mercury. With interesting facts, beautiful photographs, and more, readers will love learning more about this strange planet.