Craters and Meteorites

Objective

In this science project, you will investigate how the size of a meteorite is related to the size of the crater it makes upon impact.

Introduction

Craters are round, bowl-shaped depressions surrounded by a ring. They are made when a meteorite collides with a planet or a moon. The craters are what make our moon look like Swiss cheese. Each round hole is the place where a meteorite impacted the surface of the moon, so craters are often called impact craters. Often, the meteorite that creates a crater explodes on impact, so the crater is an empty reminder of the collision.

This is a picture of the Barringer Crater in the desert of Arizona. (image from David Roddy, USGS)

All of the moons and planets have been impacted by meteorites since the formation of our solar system. On Earth, we only see a few of these craters because they have been changed by geological forces (like earthquakes and continental movements), or eroded away by atmospheric forces (like wind or rain). There is no atmosphere on the moon, which means there is no weather to erode away the craters. In fact, the footprints of the astronauts who landed on the moon over 30 years ago are still there, perfectly preserved!

Click here to watch a video of this investigation of craters, produced by DragonflyTV and presented by pbskidsgo.org.

Where can you find the few impact craters on the Earth? There are only about 150 designated impact craters on the Earth. Not all of them are obvious because most are eroded, covered by sediment, or under water. Each crater has to be identified using several different kinds of clues. First, geological clues are found by looking for pieces of the exploded iron-rich meteorite, or for glass that formed during the impact. Satellite imaging can be used to visualize crater formations that are beneath the Earth's surface or a body of water. Finally, chemical evidence is used to date the crater and find traces of elements that are more common in space than on our planet.

By piecing together this evidence, scientists can study craters on Earth and link them to different periods of Earth's history. This involves many different types of scientists, including astronomers, geologists, chemists, paleontologists, and meteorologists (who actually study weather, and not meteorites). This has led to an interesting hypothesis being proposed about the formation of a sea, the extinction of the dinosaurs, and even the origins of life!

The craters on both the Moon and Earth come in many sizes. And some are very deep, while others are shallow. Have you ever wondered why? Vanessa and Chris from DragonflyTV did, so they conducted a science project to figure out how meteorite impacts can create so many different-looking craters. They hypothesized that if meteorites hit with different speeds they’d create craters with different depths and sizes. Do you think they were right? Vanessa and Chris really used their marbles for this project—watch the video and find out!

Speed isn’t the only meteorite variable that could change the look of an impact crater. In this science project you will investigate whether or not the size of a crater depends upon the size of the meteorite. What types of clues will you look for in your investigation? How will studying an impact crater give you information about the collision, even if the meteorite is no longer there? Are there other clues of a meteorite impact that are important?

Terms, Concepts and Questions to Start Background Research

To do this science project you should know what the following terms mean. Have an adult help you search the Internet or take you to your local library to find out more.

• Crater
• Meteorite
• Planet
• Moon
• Impact

Questions

• How is the size of a crater related to the size of the meteorite?
• How is an impact crater formed?

Bibliography

• TPT. (2006). Moon Craters by Vanessa and Chris. DragonflyTV, Twin Cities Public Television. Retrieved May 14, 2008 from http://pbskids.org/dragonflytv/show/mooncraters.html
• Bray, Becky, et al. (2000). Meteor Impact Craters. Retrieved January 29, 2006 from
  http://liftoff.msfc.nasa.gov/Academy/SPACE/SolarSystem/Meteors/Craters.html
• The Cyrus Company. (1998). The Barringer Meteorite Crater. Retrieved January 20, 2006 from
  http://www.barringercrater.com/
• Assimov, Isaac. 1990. Library of the Universe: Projects in Astronomy. Milwaukee, WI: Gareth Steven's Inc.

Materials and Equipment

• Different-sized spherical objects, such as marbles, balls, beads, or fruit
• Ruler
• Lab notebook
• Cardboard box, should be larger than a shoebox and fairly deep, something like a small moving box would be perfect
• Flour (1-lb bag)
• Graph paper

Experimental Procedure

1. First choose a variety of different-sized, spherical-shaped objects to serve as "meteorites" in your experiment.
2. Using a ruler, measure the diameter of each object. The diameter is the distance across the middle of the sphere, from one side to the other. Write your measurements in a data table in your lab notebook, like the one below:

   Object	Diameter of Object (cm)	Diameter of Craters (cm)			Average Crater Diameter (cm)
   Marble
   Ball
   Apple
   Etc.

3. Prepare your meteorite landing area by slowly pouring a 1-lb bag of flour into the cardboard box. Shift the box from side to side to evenly distribute the flour. The flour should be a depth of at least 2 inches in your box. If there is not enough flour, you can either transfer the flour to a smaller box, or add another bag of flour.
4. Now drop one of your "meteorites" into the box by holding the object out at arm's length over the box and letting go. Remember to drop all of your meteorites the same way and from the same height for accurate results.
5. After the "meteorite" impacts the flour, carefully remove the object without disturbing the "crater" left behind.
6. Drop the same object two more times, each time in a different spot in the box. Carefully remove the object each time. You should have three craters to measure for the first object.
7. Measure the diameter of the first crater by measuring the distance across the center of the depression in the flour. Be very careful not to disturb the flour with your ruler, by breathing too hard, or by shaking the box. Write the diameter of the first crater in the data table.
8. Measure the other two craters, writing each measurement in the data table.
9. Calculate the average crater diameter by adding up the three measurements and then dividing your answer by three. Write the answer in your data table.
10. Prepare your box for the next "meteorite" by shaking it from side to side to even out the flour until it is smooth and level.
11. Repeat steps 4–10 for all of your objects, each time recording the diameter of the three craters and the averages in the data table.
12. Now make a graph of your data. On the left axis (y-axis), plot the average diameter of the crater, and on the bottom axis (x-axis), plot the diameter of the meteorite.
13. What size craters did the smallest objects make? What size craters did the biggest objects make? Do you notice any pattern between the size of the crater and the size of the meteorite?

Variations

• Meteorites are very dense, iron-rich materials. Even slight changes in size can result in large changes in overall weight of a meteorite. Do small meteorites and large meteorites make the same-sized craters? How is the impact of a crater affected by the weight of the meteorite? You can do an experiment by weighing the different objects to see if the weights of the objects are correlated to the size of craters they produce. The trick to this experiment is to find similarly sized, but differently weighted objects to use as meteorites.
• How does the impact of a crater change in different types of surface material? You can do an experiment using different types of material, like sand, cornmeal, clay, dirt, ash, salt, etc. How do impact craters form in different types of surface materials? What can this tell us about the geology of a crater? Can this information be used to predict the surface properties of other planets?
• Meteorites move at different speeds through space, depending upon many factors, like the origin, size, or composition of the meteorite. This means that meteorites impact the planet at different speeds. Can this change the way an impact crater is formed? How is the size of a crater related to the speed of a meteorite? You can do an experiment to investigate this by using a ladder to drop a "meteorite" from different heights above the landing pad. As you drop an object from a higher distance, the object will be moving faster when it hits the surface. Will the size of the crater change as you drop the object from a higher distance?

• For more science project ideas in this area of science, see Astronomy Project Ideas

Credits

Sara Agee, PhD, Science Buddies

Last edit date: 2008-06-18 20:00:00