Leftover ice-rich planetesimals are called
(a) comets.
(b) asteroids.
(c) meteors.
The correct answer and explanation is :
The correct answer is (a) comets.
Explanation:
Leftover ice-rich planetesimals, often referred to as comets, are remnants from the early solar system that contain a mix of ice, dust, and rocky material. These bodies are remnants of the building blocks that formed the planets but did not coalesce into planets themselves. The distinction between comets, asteroids, and meteors lies primarily in their composition and location within the solar system.
Comets:
Comets are typically found in the outer regions of the solar system, especially in the Kuiper Belt and the Oort Cloud. These icy bodies are rich in volatile compounds such as water, methane, and ammonia. When a comet approaches the Sun, the heat causes the ice to sublimate (turn from solid to gas), releasing gas and dust that form the comet’s characteristic coma (a cloud of gas and dust) and tail. The icy components of comets suggest they are remnants from the solar system’s formation, representing some of the oldest materials.
Asteroids:
Asteroids are rocky or metallic bodies that are primarily found in the asteroid belt between Mars and Jupiter. Unlike comets, asteroids are largely devoid of significant amounts of ice and volatiles. These objects are made up mostly of metal, rock, and other minerals. They are the remnants of planetesimals that did not coalesce into planets due to the gravitational influence of Jupiter, which prevented the formation of a larger planetary body in the asteroid belt.
Meteors:
Meteors are the streaks of light produced when meteoroids (small fragments of comets or asteroids) enter the Earth’s atmosphere and burn up due to friction with the air. When these fragments survive their passage through the atmosphere and reach the ground, they are known as meteorites.
In summary, comets are ice-rich planetesimals that can be seen with a tail when they approach the Sun. They are primarily composed of water ice, frozen gases, and dust. This contrasts with asteroids, which are composed mostly of rock and metal, and meteors, which are the visible trails of meteoroids entering Earth’s atmosphere.