What is the composition of a comet mainly made up of?

The composition of a comet is primarily made up of frozen dust and rock. Comets are often described as "dirty snowballs" because they contain a significant amount of ice, which can be made up of water, carbon dioxide, ammonia, and other volatile compounds, along with dust and rocky material. As comets approach the Sun, the heat causes the ice to sublimate, creating a glowing coma and a tail that extends away from the Sun. This unique combination of materials allows comets to have highly distinctive features and behaviors that are different from other celestial bodies, such as asteroids or planets.

The other options do not accurately reflect the main composition of comets. For instance, while gases are present in comets, they are not solely made up of liquid and gas; instead, the solid components play a significant role. Additionally, while stardust and cosmic rays are part of the broader universe, they do not specifically compose comets. Similarly, although iron and minerals can be found in some space objects, they do not represent the primary makeup of a comet. Thus, the correct answer highlights the essential elements that define a comet’s structure.