Question 31

A comet is most likely to be composed primarily of ice.

Comets are composed largely of ice, dust, and rocky material, making them distinct from other celestial bodies. This composition allows them to develop a glowing coma and tail when they approach the Sun, as the heat causes the ice to sublimate.

A) An asteroid

Asteroids are primarily composed of rock and metal, with very little ice present. They are typically found in the asteroid belt between Mars and Jupiter and do not exhibit the icy characteristics of comets. Therefore, asteroids cannot be considered as primarily composed of ice.

B) A red dwarf

Red dwarfs are small, cool stars that primarily consist of hydrogen and helium, with no significant presence of ice. Their composition is stellar, and they do not contain solid or icy materials like comets do. Thus, red dwarfs are not relevant to the question regarding ice composition.

C) A comet

Comets are indeed composed primarily of ice, along with dust and other materials. The icy nuclei of comets are often referred to as "dirty snowballs" due to their substantial ice content. When they approach the Sun, the heat causes the ice to vaporize, creating a visible tail, confirming their icy nature.

D) The planet Mercury

Mercury is a rocky planet with a surface composed mainly of metal and silicate materials. It lacks significant water ice, despite some deposits at its poles that may contain ice in shadowed craters. Overall, Mercury does not fit the description of a body primarily composed of ice.

Conclusion

Comets are the only option among those listed that are primarily composed of ice, making option C the correct answer. All other options—asteroids, red dwarfs, and Mercury—lack the significant ice content that characterizes comets, establishing their ineligibility in this context.