Classroom Impact Crater

February 20, 2006


Provided by: Ben Laster, student
Summary authors & editors: Ben Laster; Jim Foster

The photo above shows an impact crater made in the classroom. My class and I made it using a tray filled with flour, which was then sprinkled with coco powder in order to make any ejecta rays more visible. A golf ball was then dropped from a prescribed height -- approximately eye level. The mass of the ball (45 grams) was sufficient to create a central uplift, formed when the surface stretches during the impact and then rebounds, much like when a rubber band is released. You may be able to observe the ejecta rays and ejecta blanket, as well as the central uplift on the photo. However, the ejecta features didn't photograph particularly well, but were visible in person. This crater was about 2 cm in depth, with a diameter of about 7 cm. Note the shadowing on the inside of the crater. We tried a number of different drops, and in one instance an ejecta ray was nearly 90 cm in length -- it actually extended beyond the edges of the tray and onto the grass. As expected, the greater the mass of the ball that was used, the greater the depth and diameter of the crater and the length of the ejecta rays. Try using plaster of paris (experiment with different viscosities) to make the ejecta rays more visible.

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