Most comet nuclei are believed to be
A) chunks of rock or iron chipped from asteroids by impacts.
B) large carbon chondrite meteoroids that have been set on fire by the Sun and are trailing long smoke trails.
C) chunks of water and methane ice ejected from the surface of the icy satellites of the outer planets by asteroid impacts.
D) chunks of dirty ice left over from the formation of the solar system.

Question

Quizplus · Accepted Answer

Most comet nuclei are believed to be chunks of dirty ice left over from the formation of the solar system. These icy bodies are typically a few kilometers in size and are made of a mixture of water, methane, ammonia, and other volatile compounds, along with dust and rock. As comets approach the Sun and are heated, these volatile compounds sublimate away, creating the characteristic coma and tail.

Most Comet Nuclei Are Believed to Be