GED Science Practice

What is a comet primarily composed of?

1. space object made of dust and rock particles mixed with frozen water

2. the preservation and careful management of the environment

3. a group of stars that form a pattern in the sky

4. transparent anterior portion of the outer covering of the eye

The correct answer is: space object made of dust and rock particles mixed with frozen water

A comet is primarily composed of a mixture of dust, rock particles, and frozen gases, including water vapor, carbon dioxide, and ammonia. This composition is sometimes described as "dirty ice," reflecting its structure. When a comet approaches the Sun, the heat causes the ice to vaporize and release gas and dust, which creates a glowing coma and often a tail that points away from the Sun. This characteristic is what distinguishes comets from other celestial objects like asteroids, which are primarily rocky and metallic. The other options represent different concepts: environmental preservation concerns the protection of natural resources, constellations refer to groups of stars forming identifiable patterns in the night sky, and the cornea is an essential part of the eye's anatomy. None of these describe the composition of a comet.