The overall goal of this interrupted case study is for students to practice confirmation/disconfirmation reasoning while learning the basics of solar system and Moon formation. Students will compare predictions corresponding to various Moon formation scenarios with the measured composition of Moon rocks returned by the Apollo missions. Given five different formation scenarios, students will reason by process of elimination to identify the most likely scenario. An overview of solar system formation is given at the outset. A series of reflective questions at the end of the case connects the content with wider issues in planetary science involving other moons and other solar systems. The case, which is self-contained, is suitable for undergraduate lower-division students of any major, although it is ideally targeted at non-STEM majors who have had some introduction to the solar system.