Science Education Standards: Standard D2:

Earth's History

• The Earth processes we see today, including erosion, movement of lithospheric plates, and changes in atmospheric composition, are similar to those that occurred in the past. Earth history is also influenced by occasional catastrophes, such as the impact of an asteroid or comet.

Standard D3:

Earth in the Solar System

• The Earth is the third planet from the sun in a system that includes the moon, the sun, seven other planets and their moons, and smaller objects, such as asteroids and comets. The sun, an average star, is the central and largest body in the solar system.

Short Description: Comets are an important class of objects found in the solar system. Created at the time of solar system formation, these "dirty snowballs" -- each the size of a city -- have remained virtually unchanged for billions of years in the cold outer reaches of the solar system. Their composition therefore provides clues as to how the solar system was
born, and comet impacts on the early Earth may have been the source of the molecules needed for the formation of life -- organic molecules. In the first activity, students explore the relative abundance of different atoms in the universe, and the molecules that are created from these atoms. In the second activity, students combine ingredients composed
of these molecules to build a good physical model of a comet. The model provides an understanding of cometary composition and structure, and how comets behave when some make a rare trip into the inner solar system and interact with the sun.