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# Meteorites

By Janice VanCleave
Printed in Practical Homeschooling #62, 2005.

What happens when a meteor strikes the earth?

 Purpose. To determine what happens when a meteorite hits Earth. Materials. 6 to 8 cups (1.5 to 2 liters) of sand (corn meal will work), large shoe box or comparable size container, flat toothpick, 2 fine-point felt-tip pens (1 black, 1 red), walnut-size piece of modeling clay, ruler. Procedure. Pour the sand into the box, and shake the box so that the surface of the sand is as level as possible. Set the box of sand on the floor, then insert the toothpick vertically in the center of the sand. The tip of the toothpick should touch the bottom of the box. 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. Shape the clay into a ball. Stand next to the box and hold the clay ball waist high above the center of the sand in the container. Drop the ball. Carefully remove the ball from the sand so that you disturb the sand as little as possible. Insert the toothpick in the center of the hole in the sand formed by the ball. 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. Measure the difference between the two marks on the toothpick to determine the depth of the hole. Shake the box of sand to smooth its surface, and then repeat steps 5 to 9. Results. The depth of the holes in the sand will vary depending on the size and weight of the clay ball and height the balls falls. The author measured a hole of 1/2 inch (1.25 cm) deep. Why? "Crater" is from the Greek word meaning "cup" or "bowl." The surface of Earth has some craters due to meteorites slamming into it. But, due to its thin atmosphere, the Moon has many meteorite craters. The size of a crater is related to the energy of the meteorite forming it, which is determined by the size and mass of the object and its speed. In a real crater formation, the meteorite's energy of motion is transferred into shock waves and heat, which breaks the ground and causes the meteorite to vaporize. This super heated vapor results in an explosion, creating the cup-shaped hole in the ground called an impact crater. In this activity, only the meteorite striking the surface is demonstrated. There is no explosion to make the hole even larger than the one produced by the meteorite hitting the surface. This experiment was taken from Janice VanCleave's Help! My Science Project Is Due Tomorrow! and is used by permission of the publisher, John Wiley & Sons, Inc.
Q: Why don't large meteorites hit Earth?

A: Actually, large meteorites have struck Earth and others could in the future. But, generally these space rocks burn up when they travel through Earth's atmosphere. Any unburned part of the space rocks that reaches Earth is generally very small.

A meteorite is a piece of rock from space that strikes the Earth's surface. Meteoroids are space rocks in our solar system orbiting the Sun. If a meteoroid enters Earth's atmosphere, it becomes so hot due to the friction with air that it vaporizes (changes to a gas), or burns up, and light energy is produced. This streak of light is what you see when you see a shooting star. When the meteoroid enters the atmosphere, it is then referred to as a meteor. The streak of light is also called a meteor. If any part of the original meteoroid that entered the atmosphere reaches the surface of the Earth, it is then called a meteorite.

Each day as many as 4 billion meteoroids enter Earth's atmosphere. Most of these are very small and burn up before reaching the ground. Those that reach the ground generally range in size from a dust speck to slightly larger ones that strike Earth with no more energy than a falling hailstone.

A very large iron-nickel meteorite, estimated to be about 150 feet (45 meters) in diameter and weighing about 300,000 tons (272,727 metric tons), did strike Earth a long time ago. Its speed was about 40,000 miles per hour (25,000 km per hour). This huge space rock crashed into Earth, exploding with a force greater than 20 million tons (18.2 metric tons) of TNT. The crater produced by the impact was about 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.

With so many meteors zipping through the atmosphere, what are the odds of being struck? Slim to none. But it is possible. Records show that only a few people have been hit by a meteorite and no one has been killed. A confirmed hit was a Mrs. Ann Hodges in Sylacauga, Alabama. On November 30, 1954, Mrs. Hodges was napping in her living room when an 8.5 pound (3.9 kg) meteorite crashed through the roof and hit her thigh. She was only bruised.