A comet is primarily composed of what?

• A. A rocky body that orbits the Sun
• B. Ice and dust in space
• C. A gaseous body without a tail
• D. A metal-rich asteroid

Answer: (B)

Comets are made mostly of ice and dust, which is why they’re often described as dirty snowballs. Their nucleus contains frozen water, carbon dioxide, methane, and other ices mixed with rocky dust. When a comet gets close to the Sun, the heat causes these ices to sublimate into gas, creating a glowing coma around the nucleus and, with the solar wind, tails that stream away from the Sun. This combination of ice and dust best fits the idea of a comet’s composition. The other descriptions don’t match how comets are built or behave: a rocky body describes asteroids, a purely gaseous body without a tail isn’t typical once a comet nears the Sun, and a metal-rich asteroid isn’t what a comet is.