Lesson Plan on Possible Collisions on Earth due to Asteroids and Comets

Objectives: Students will be able to

1. construct and interpret a geologic time line in order to understand the order of events since the Earth formed.
2. research and evaluate the theories that exist about the cause for the extinction of the dinosaurs.
3. explain the asteroid-impact theory relating to the extinction of the dinosaurs.
4. debate and defend their position on the issue of the extinction of the dinosaurs was caused by an asteroid hitting the Earth.

Grade Levels: 8-12

Background Information:

If the Earth would encounter an asteroid approximately 200 meters in diameter falling into the mid-Atlantic Ocean, a massive tidal wave would be produced. Astrophysicist Jack Hills of Los Alamos National Laboratory calculated that this sized object impacting the Atlantic Ocean would produce a tidal wave 185 meters high on the European and North American coasts. If a larger asteroid, about half a mile across, impacted the Earth's surface, it would rank as the greatest catastrophe in human history. The amount of dust that would be put up into the air would block sunlight from reaching the surface, and the ensuing darkness and cold would prevent crops from growing anywhere for at least one year.

The Earth would face its doom if an asteroid or comet larger than five kilometers in diameter would hit the Earth. For example, one of the most widely accepted theories for extinction of the dinosaurs is the asteroid-impact theory. This theory is that a comet or asteroid almost ten kilometers in diameter caused the extinction of the dinosaurs as well as approximately two-thirds of the species of life alive at that time. The suspected remnants of the resulting crater have recently been identified on the Yucatan coast of the Gulf of Mexico. If an object this size would currently land in the Gulf, it is estimated that a wave almost five kilometers high would be created from the impact. Nine hundred miles away the waves would still be able to reach to about 455 meters high. This would produce floods from the coast of the Gulf of Mexico to Kansas. So large an impact would penetrate the ocean to the rock below, lofting dust that would block the sunlight and make it impossible for agriculture to take place.

It has been noted that in the past 1000 years no human has been killed by a meteorite or the effects of its impact. A person's chance of being killed by a meteorite is extremely small. At this time, there is no known asteroid or comet on a collision course with the Earth, which makes the probability of a major collision anytime soon quite small. However, both the Earth and moon have impact craters ranging in age from just a few thousand years to billions of years. This history of impacts tells us that future collisions are a virtual certainty, even if they do not happen in our own lifetimes.

We were all reminded of the inevitability of such collisions during the summer of 1994 when the comet Shoemaker-Levy 9 impacted Jupiter. An earlier encounter with Jupiter had torn the comet into a line of fragments, earning it the nickname "string of pearls."

Shoemaker-Levy 9 before impact onto Jupiter
NASA, 7/16/69

Over a week in that July, the fragments of the comet successively impacted the planet, creating explosions comparable to that theorized to have killed the dinosaurs. The scars of the impacts in the planet's clouds seem small only because of Jupiter's enormous size, eleven times the diameter of earth.

Clouds of impact debris in Jupiter's atmosphere
NASA, 7/16/69

Hazards Due to Comets & Asteroids, "The Impact Hazard" 1994 by David Morrison, Clark R. Chapman, and Paul Slovic.

Activities:

No Frames Table of Contents

Contact Karen Krupinsky (kgurley@gsfc.nasa.gov) or Tammy Seergae (tseergae@umd.edu) for further information.