UPSC CSE Prelims 2011
Statement 1 is correct. Asteroids are predominantly small, rocky, and metallic bodies, considered remnants from the early solar system's formation. They are largely found in the asteroid belt located between the orbits of Mars and Jupiter. Comets, conversely, are composed primarily of frozen gases (water, methane, ammonia, carbon dioxide), dust, and rocky material, often described as "dirty snowballs."
Statement 3 is correct. When a comet approaches the Sun, solar radiation causes its volatile icy components to sublimate, forming a glowing coma (an atmosphere around the nucleus) and one or more tails that point away from the Sun due to solar wind and radiation pressure. Asteroids, being rocky and lacking significant volatile materials, do not exhibit such tails.
Statement 2 is incorrect. While asteroids are indeed found mostly between Mars and Jupiter, comets are not found mostly between Venus and Mercury. Comets originate in the outer reaches of the solar system, primarily from the Kuiper Belt (beyond Neptune's orbit) and the Oort Cloud (a vast spherical cloud far beyond the Kuiper Belt). Their orbits are highly elliptical, bringing them close to the Sun for a portion of their trajectory, but their primary reservoirs are in the distant solar system.
Option (a) is incorrect because Statement 2 is false.
Option (c) is incomplete as it correctly identifies Statement 3 but omits the correct Statement 1.
Option (d) is incorrect due to the inclusion of the false Statement 2.