In the lab, students help create targets—mimicking the magnetic rock of an asteroid or forming that perfect mix of ice and rock to replicate the surface of Ganymede, Jupiter's frozen moon. They also help analyze the shape of the shock waves and the velocities of the impact debris. One thing they typically don't get to do is pull the trigger. "We have a lab tech who actually fires the gun," says Stewart. But students who stick around long enough, she says, "might earn that privilege."