Next best thing to a real field trip, Leedy and her astrobiologist husband send a 22nd-century class on an excursion to Mars. Boarding a “spacejet” rather than a magic school bus, the children, while en route, report back in chatty email messages on the solar system in general. After landing, they send meaty observations on Martian climate, atmosphere and physical features as they visit the sites of various early missions, from Viking I to the Spirit Rover, and finally fetch up in the lush gardens beneath the dome of Marsbase Alpha. Around and within eye-filling, crisply reproduced color photos of the Martian surface, Leedy adds cartoon figures, labels, diagrams and insets for a full but never overcrowded look, and closes with a timeline, source URLs for the photos and a look at Martian mysteries that remain to be solved. Backed up by yet more information on her web site, this will please both casual and detail-hungry young readers, and makes a lively update for Franklyn Branley’s Mission To Mars (2002), illustrated by True Kelley. (Picture book/nonfiction. 7-9)