Nick Otten (left) and Grant LaMar, fourth-graders in Lisa Rehark’s class, work on their miniature “Mars rovers” Wednesday afternoon at Conger Elementary School in Delaware. Rehark said the students had to design their rovers, then build them and then rework their designs until they worked as intended. Rehark said activities like building the rovers is a great way to teach students about problem solving and scientific method. At the end of the projects, the distance traveled by the cars will be measured to see who designed the most efficient car.