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05   Meteoroids and the Craters They Make

About this Activity
This activity investigates the formation of craters. You'll see how the size, angle, and speed of a meteorite's impact affects the properties of craters. In addition, your family will become familiar with the terms meteor, meteoroid, and meteorite.

Crater photo
Image of unnamed crater on the far side of the moon courtesy of NASA.

 What You'll Need
1 or 2 - shallow basins at least 1 square foot (30 centimeters), cat liter boxes work well

1 or 2 - bags of unbleached flour

1 - box of instant cocoa
Several pebbles, various sizes,
1/3 to 1 1/2 inches (1 to 4 centimeters)

1 - old newspaper
1 - ruler
1 - pen or pencil
1 - data sheet



Things to Talk About

Discuss these terms before beginning the activity.

A meteoroid is a particle or rock traveling through space. The size of a meteoroid can range from microscopic to many meters across.

meteorite photo
Image of Meteorite photo by Ron Hipschman, courtesy of California Academy of Science

A meteor is a streak of light seen in the night sky caused by a meteoroid entering the Earth's atmosphere and vaporizing in a flash of light. The light is produced by the heat of friction between the meteoroid and the atmosphere. The average size meteoroid, which causes the meteors that we see at night, is probably no larger than a grain of sand. Speeds can be as great as 50,000 miles per hour (80,000 kilometers-per-hour) or more.

A meteorite is a meteoroid that has struck the Earth. On impact, large meteoroids leave craters and may bury themselves deep underground. Meteorites of any size can be quite valuable.




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What to Do
To begin the activity, fill one of the basins with flour about 1 1/4 to 1 1/2 inches (3-4 centimeters) deep. Sprinkle a little cocoa on the surface. This will make the changes caused by the pebbles more visible. Gather the various pebbles; they will be the "meteoroids."


E X P E R I M E N T     1

Testing the Size of the Meteoroid
1 Pick out one of the smallest pebbles and have a family member volunteer to drop (not throw) the pebble from about eye level into the basin.
2 Describe what you observe, and try to predict the appearance of a crater formed by a larger pebble dropped from the same height.
3 Then have your volunteer drop a medium size pebble from about the same height. What is different about the crater?
4 Have the volunteer drop the largest pebble from the same height.

Record the results on your data sheets.

Meteor Crater
Meteor Crater near Winslow, Arizona was formed by an impact that happened 50,000 years ago. An explosive force greater than 20 million tons of TNT left a crater 700 feet deep (210 meters) and over 4,000 feet (1,200 meters) across.

E X P E R I M E N T     2

Testing the Speed of the Meteoroid
1 Pick out three or four pebbles of roughly the same (medium) size. Smooth over the flour and sprinkle on a little more cocoa. For a test comparison, have the smallest family member drop one of the pebbles from eye level.
2 Try to predict the appearance of a crater formed by a pebble of the same size dropped at a higher level.
3 Have the next person drop pebbles in at successively higher levels.
4 Have the tallest family member drop the pebble from as high of a distance as he/she can. Make sure that all trajectories are vertical for consistency in the test.

Record the results on your data sheets.


E X P E R I M E N T     3
Testing the Angle of Impact
1 Smooth the flour and sprinkle on more cocoa. Have someone throw a medium-sized pebble with moderate force vertically into the basin. Then try to predict the appearance of a crater if the meteoroid strikes the ground at an angle.
2 The next person should throw a similar sized pebble at about the same speed, but at a slight angle. Discuss the shape of the new crater and predict how the shape of the crater will change as the angle of impact increases.
3 Continue throwing pebbles into the basin, taking care to throw the same sized rocks at the same speed, but at varying angles. Discuss further the shape of the craters.
4 Record the results on your data sheets.

What's Going On
The results of this test are often very surprising. One would normally expect the crater to have an oblong shape on extremely wide-angle impacts. In fact, all craters that we have seen on the Moon and Earth are pretty much circular. The reason is that an explosion occurs on impact and the forces associated with an explosion are always spherically symmetrical.

Related Websites

This activity was derived and modified from "Experimenting with Craters," an activity in the Great Explorations in Math and Science (GEMS) teacher's guide, Moons of Jupiter, ©1993 UC Regents. GEMS is a series of more than 50 guides and handbooks developed at the Lawrence Hall of Science.

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