Book excerpt: People have been studying the solar system's inner planets for years. Mercury, Venus, and Mars are Earth's closest neighbors, and scientists are still learning new things about them all the time. This delightful book encourages readers to use critical thinking skills and explore many of the issues that astronauts and space scientists face when studying the inner planets. Bright images and high-interest material will attract even reluctant readers, and activity boxes will guide them to use their own problem-solving skills to address the issues at hand. Supporting STEM and NGSS curriculums, this book is sure to be a valuable addition to any library or classroom.