Solar System and Evolution of Earth: UPSC Previous Year Questions (Geography)
2 previous year UPSC Prelims questions on Solar System and Evolution of Earth (Geography). Choose an option to see the answer and explanation.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 1–2 of 2 questions
UPSC 2005Geography · Solar System and Evolution of Earth
Q1. Assertion (A): Existence of human life on Venus is highly improbable. Reason (R): Venus has extremely high level of carbon dioxide in its atmosphere.
Explanation
Assertion (a) is true: The conditions on Venus are extremely harsh for human life, and its atmosphere and surface are inhos-pitable for humans. Venus has an extremely high surface temperature, high atmospheric pressure, and a toxic atmosphere primarily composed of carbon dioxide (96.5%), with clouds of sulfuric acid. Reason (R) is true: The atmosphere of Venus is composed primarily of carbon dioxide (CO₂), with small amounts of nitrogen and trace gases. CO₂ constitutes about 96.5% of the atmosphere, and this contributes to a runaway greenhouse effect that traps heat and causes extreme surface temperatures around 465°C. Assertion A and Reason R are true and R correctly explains A as the inhospitability of Venus for humans is explained by the presence of carbon dioxide in the environment.
UPSC 2005Geography · Solar System and Evolution of Earth
Q2. Assertion (A): The same face of the moon is always presented to the earth. Reason (R): The moon rotates about its own axis in 23 and half days which is about the same time that it takes to orbit the earth.
Explanation
Assertion (A) is true: The Moon is tidally locked to the Earth, meaning that the same hemisphere of the Moon is always facing Earth. This occurs because the Moon’s rotational period (the time it takes to spin once on its axis) is equal to its orbital period (the time it takes to complete one revolution around the Earth). As a result, only about 59% of the Moon’s surface is ever visible from Earth due to lunar libration (a slight wobbling motion). The remaining 41% is permanently hidden from direct view from Earth and is called the far side of the Moon (often incorrectly referred to as the "dark side"). Reason (R) is false: The actual time the Moon takes to rotate on its own axis is 27.3 days, not 23.5 days. The Moon’s orbital period around the Earth is also 27.3 days (called the sidereal month) not 23 and a half days. Since these two periods are equal, the same face of the Moon always faces Earth, which is a result of synchronous rotation (tidal locking)
Answer key for these questions
Q
UPSC year
Correct answer
1
2005
(a) Both A and R are true and R is the correct explanation of A
2
2005
(c) A is true but R is false
Frequently asked questions
How many previous year UPSC questions are there on Solar System and Evolution of Earth?
This page covers 2 previous year UPSC Prelims GS Paper-I questions on Solar System and Evolution of Earth (Geography), asked from 1996 to 2025. Each has the correct answer and an explanation.
How should I use previous year UPSC questions for Prelims?
Attempt each question first, then open the answer and read the explanation for every option. Repeat by chapter, and track which statements UPSC reuses across years. Previous year questions show the exam pattern and difficulty level.
Which years are covered for Solar System and Evolution of Earth?
Questions on Solar System and Evolution of Earth (Geography) are available for 12 years, from 1996 to 2025. Use the Year filter to practise a single paper.
