UPSC Prelims 2011 · GS Paper I
Question 86: Science and Technology
What is the difference between asteroids and comets ?
- 1.Asteroids are small rocky planetoids, while comets are formed of frozen gases held together by rocky and metallic material.
- 2.Asteroids are found mostly between the orbits of Jupiter and Mars, while comets are found mostly between Venus and Mercury.
- 3.Comets show a perceptible glowing tail, while asteroids do not.
Which of the statements given above is/are correct ?
AnswerThe answer is (b).
Asteroids are small rocky bodies, mostly found in the belt between the orbits of Mars and Jupiter. Comets are icy bodies of frozen gases, dust and rock that come from the far outer solar system, the Kuiper belt and the Oort cloud. When a comet nears the Sun its ice vaporises and forms a glowing coma and tail, which asteroids lack. Comets are not found mainly between Venus and Mercury, so statement 2 is wrong.
- 1. Asteroids are rocky; comets are frozen gases held with rock and metal.
- 2. Comets come from the outer solar system, not from between Venus and Mercury.
- 3. Comets develop a glowing tail near the Sun; asteroids do not.
How you could have got this
- If you were sure statement 1 is correct, (c) goes: it leaves 1 out.
What you needed to know: Asteroids are rocky; comets are frozen gases held with rock and metal.
- Then, if you were sure statement 2 is not correct, (a) and (d) go: each of them includes 2.
What you needed to know: Comets come from the outer solar system, not from between Venus and Mercury.
Only (b) is left. You didn’t need statement 3.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Includes statement 2, which wrongly places comets between Venus and Mercury.
- (b) Right: composition differs, and only comets show a tail.
- (c) Statement 1 on composition is also correct.
- (d) Includes the wrong statement 2.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.