Whipple's 'dirty snowball' theory describes which kind of celestial object?

• A. Asteroid
• B. Meteor
• C. Planet
• D. Comet

Answer: (D)

Whipple’s dirty snowball idea is describing what a comet is made of and how it behaves. He proposed that a comet’s nucleus is a loose mix of volatile ices (water, carbon dioxide, etc.) with dust grains—like a dirty snowball. When the comet travels toward the Sun, the heat causes the ices to sublimate, releasing gas and dragging dust with it. This outgassing creates the bright coma around the nucleus and often a tail that points away from the Sun. That icy, dusty composition and the resulting visible activity are what set comets apart from asteroids (rocky/metallic bodies with no outgassing), meteors (the streaks we see when debris burns up in the atmosphere), and planets (large bodies that don’t form comas or tails).