COLLIDE is an experiment that is being built at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado in Boulder. COLLIDE will fly on a future space shuttle mission. The experiment is easy to understand. Basically, we will be shooting small balls into trays of fine powder and videotaping the splash the ball makes in the powder. We are doing this in space, because we will be shooting the balls at the powder very slowly (between 1 and 100 centimeters per second). On the Earth, nothing much would happen at these low speeds of impact. In the microgravity environment of the space shuttle, however, the powder will be free to fly away from the impact, making a miniature crater. We are studying these gentle impacts because they are like the collisions that occur between planetary ring particles, and may have occurred in the early stages of planet formation.

One simple project that just about any class can try is to see what size crater is made in sand or fine powder (sifted flour is good for gentle impacts) depending on the speed of the impact. Younger students can relate the impact crater to the height from which an impactor (any kind of solid ball or marble will do), while middle or high school students can calculate the speed of impact based on the distance of the fall. How slow can you manage to get the marble to hit the sand? COLLIDE will be conducting experiments at very low velocities and in a microgravity environment. Ask your students to speculate on what the different gravity enironment will do to the results.

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