Click on the photos to see larger images and additional information.
When you look at the Moon, even without a telescope, you can see dark and light patches where the rocks are different colors. Long ago, people called the dark patches mare (MAR-ay), the Latin word for an ocean or sea, because they thought the dark areas were huge bodies of water. Now we know that these dark areas are large patches of lava that hardened long ago.
Some of the areas of lighter rock are craters. Craters are large "dents" on the surface of planets, moons, even asteroids and comets. The Moon is covered with impact craters caused when meteors, which are chunks of rock from space, hit the surface of the Moon. When large meteors hit, it causes a huge explosion so hot that it melts rocks. A rim of mountains usually forms around the edge of an impact crater, and sometimes streaks or rays of material called ejecta explode out beyond the crater.
Look at these and other pictures of the Moon. Do you see a man in the Moon? Can you see a rabbit, or other animals? Where are the mare? Can you see any craters?
Meteors also hit the Earth and cause craters like Barringer Crater in Arizona.
Craters on Earth are eventually covered by grass and trees, eroded by water, even hidden by oceans, so we cannot see old Earth craters. Why don't craters on the Moon get washed away? The Moon does not have a dense enough atmosphere for there to be any water on the surface of the planet, so there is no rain, no rivers, no oceans, and no plant or animal life to disturb the crater once it has formed.
In this experiment, students will create craters, measure them, and compare their shapes.
This can be messy, so cover the floor with newspaper or try this outside.
Fill the pans with 2 inches of flour or more. Sprinkle a thin layer of colored powder to evenly coat the flour. This will make the craters more visible. Drop (but do not throw) a rock into the pan. After filling the pan with craters, remove the rocks and smooth the surface with a spoon or ruler. Sprinkle more colored powder on top if necessary.
Take turns enjoying some free exploration, dropping different objects and observing the resulting craters. What observations can we make about the size, shape, or appearance of the craters, and the objects that created them?
Perform more controlled experiments by dropping different size objects from the same height, or the same size object from different heights. Measure the crater diameter and draw its shape and any rays of ejecta that might have formed.
We find craters on the surface of solid objects, but not on gaseous objects like the Sun or Jupiter. Why? Craters form when an objects hit gas planets or stars, but they are like the ripples when rocks are thrown into a pond -- they disappear quickly because the gas moves back in to fill the hole and smooth out the surface again.
Drop water droplets from your finger into a glass of water and watch the "craters" carefully. How are they similar to, or different from, the craters made in the flour?
http://eis.jpl.nasa.gov/eao/craters_i.html The Educator's Guide to Impact Craters by the Jet Propulsion Laboratory describes a crater-making exercise, with well-explained background information and vocabulary.
www.smv.org/jims/crater/crater2.htm Includes detailed instructions for a crater-making activity and helpful photographs of the process.
quest.arc.nasa.gov/mars/teachers/tg/program3/3.2ws.html Includes student worksheets on which to record all data and observations.
More Moon links are on the activity page Moon Phases and Eclipses.
© 2001 Challe Hudson
This web page was produced for Morehead Planetarium during a North Carolina State University astronomy class taken in pursuit of a Masters in Science Education.