UPSC Prelims 2005 Q84: Science & Technology – Space Technology & Astronomy
Assertion (A): Existence of human life on Venus is highly improbable.
Reason (R): Venus has extremely high level of carbon dioxide in its atmosphere.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is not the correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (a) Both A and R are individually true and R is the correct explanation of A
Explanation
Venus and the improbability of life
| Part | Verdict |
|---|---|
| A. Human life on Venus is highly improbable | True |
| R. Venus has extremely high CO2 | True — about 96% of its atmosphere, giving a runaway greenhouse effect |
Both are true and R explains A: carbon dioxide causes a runaway greenhouse effect and a surface temperature of about 460 degrees Celsius, so human life is impossible.
Answer: (a) Both A and R are true and R explains A.
Why each option is right or wrong
- (a) CORRECT. A is true because the heat and CO2 atmosphere are hostile; R states that cause.
- (b) Incorrect. R does explain A, so this is wrong.
- (c) Incorrect. R is true, as CO2 is about 96% of Venus's air.
- (d) Incorrect. A is true, as human life there is impossible.
Key point
Venus: 96% CO2, about 460 C, crushing pressure, sulphuric acid clouds.
Remember
Venus is hotter than Mercury because of its CO2-rich atmosphere.
Common mistakes
- Thinking Venus is cold because it is bright.
- Not linking CO2 with the greenhouse effect.
- Treating the reason as unrelated to life.
Exam tip
Hottest planet is Venus, not Mercury.
Sources
- NCERT Class VIII Science — Stars and the Solar System
- NASA — Venus Fact Sheet (Goddard Space Flight Center, Planetary Fact Sheets)