This study, a sub-study of a National Science Foundation (NSF) funded research project, applies a modified strategy of the U[superscript 2]MC for an eight-week afterschool robotics curriculum to promote upper elementary students' computational thinking in the second grade. Twenty-one students in second grade participated in a Life on Mars project which lasted for ten days with one class hour per day. They participated in activities learning coding concepts, basics of robotics, as well as exploring life on Mars. Most notably, the study found a significant increase in participants' computational thinking skills. In addition, participants came to understand basic robotics, including operation, composites, and codes. Implications for future research and robotics curriculum design are discussed in the presentation.