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# Splat!: What Happens When a Meteorite Strikes a Planet?

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Source:
Author: Janice VanCleave

### Problem

What happens when a meteorite strikes a planet?

### Materials

• 1 cup (250 ml) sand or cornmeal
• cereal bowl
• flat toothpick
• 2 fine-point felt-tip pens—l black, 1 red
• walnut-size piece of modeling clay
• ruler

### Procedure

1. Pour the sand into the bowl, and shake the bowl so that the surface of the sand is as level as possible.
2. Insert the toothpick vertically in the center of the sand. The tip of the toothpick should touch the bottom of the bowl.
3. Use the black pen to mark a line on the toothpick level with the surface of the sand. Remove the toothpick and set it aside.
4. Shape the clay into a ball.
5. With one hand, hold the ruler vertically next to the bowl. With your other hand, hold the clay ball over the center of the bowl in line with the 6-inch (l5-cm) mark on the ruler. Drop the ball.
6. Carefully remove the ball from the sand so that you disturb the sand as little as possible.
7. Insert the toothpick in the center of the hole in the sand made by the ball.
8. Use the red pen to mark a line on the toothpick level with the surface of the sand in the center of the hole. This mark should be on the same side of the toothpick as the first mark.
9. Measure the distance between the two marks on the toothpick to determine the depth of the hole.

### Results

The depth of the hole in the sand will vary depending on the size and weight of the clay ball. The author measured a hole 1/2 inch (1.25 cm) deep.

### Why?

If a meteoroid does not burn up in Earth's atmosphere and strikes the ground, it is called a meteorite. Meteorites made of material similar to Earth's outer rock layer are called stony meteorites. This experiment demonstrates the results of the impact of a stony meteorite in soft sand. On impact, the sand is pushed out of the way, creating an impact crater (a bowl-shaped depression caused by the impact of a solid body).

Most meteorites range from a dust speck to larger ones that strike Earth with no more energy than a falling hailstone. But about 50,000 years ago, a meteorite as large as a house hit Earth with the energy of a nuclear weapon. The crater produced was 3/4 mile (1.2 km) in diameter and 667 feet (200 m) deep. It is found in Arizona and is called the Barringer Meteorite Crater.

### Let's Explore

1. How would the composition of the meteorite affect the results of its impact? Iron meteorites contain about 90 percent iron and are almost three times as heavy as stony meteorites. Demonstrate the difference in the impact of a heavier meteorite by repeating the experiment, using an equal size but heavier piece of clay. The weight can be increased by wrapping clay around 3 to 4 metal washers. Use a different color pen to mark the toothpick. Compare the depth of the impact craters of the two types of meteorites. Science Fair Hint: Photograph the sand before and after impact. Display the photos to represent the results.
2. How does the composition of the surface of a celestial body affect the type of impact crater formed? Repeat the original experiment, using flour instead of sand.

### Show Time!

Impact cratering is the process by which objects from space form craters on surfaces of celestial bodies the objects strike. This has occurred on every terrestrial planet and nearly every satellite in the solar system. Prepare a poster, such as the one shown here, depicting the four basic steps of impact cratering.

For information about each step and suggestions for figures, see page 86 in Heather Couper and Nigel Henbest's How the Universe Works (New York: Reader's Digest, 1994).

### Check It Out!

Most meteorites are determined to be as old as the solar system itself, which is about 4.5 billion years. Find out more about meteorites. How do scientists date a meteorite? Are there any young meteorites? How can scientists determine that a meteorite came from Mars? For information, see pages 28-29 in Thomas R. Watters's Planets: A Smithsonian Guide (New York: Macmillan, 1995).