The STEAM twins are back in a new adventure (Go Green!, 2015, etc.), this time competing against each other to win a chance to meet famous astronaut Cmdr. Kris Kornfield. As soon as she spies the poster announcing the contest, creative, artsy Sydney has her idea—a 3-D model of the moon—and for a change, she isn’t sharing it with her twin: she wants to win more than she wants to team with her brother. Simon is rather at loose ends on his own but makes observations and does research about the moon each night, educating readers about its phases and introducing solid science vocabulary. The mouse twins’ parents subtly try to point out the two are missing critical pieces, but it’s not until Ms. Fractalini introduces them to the work of Galileo that the twins see what’s missing. Now a team, they use a homemade telescope to make observations and the 3-D printer in the Makerspace Lab of their public library to print an accurate puzzle of the moon’s phases. Their classmates’ projects don’t all combine all the STEAM elements: there’s a poem, a crater model, a spaceship model, and a toothpick house that might someday be built on the moon. In this outing, the Reynoldses make Simon and Sydney a bit more kidlike than in prior outings, with their flaws and their enthusiasm. The learning readers will pick up about the moon is virtually painless, and Cmdr. Kornfield’s reveal is a nice touch. Another STEAM winner.