Q20. Which spacecraft was reported in March 2015 to have detected biologically useful nitrogen compounds on Mars?
[UPPSC Civil Services Prelims, 10 May 2015]
(A) Mangalyaan
(B) Mars Express
(C) Phoenix Mars Lander
(D) Curiosity Rover
Answer: (D) Curiosity Rover
Explanation: NASA’s Curiosity rover analysed Martian rocks and detected nitrogen-bearing compounds such as nitrates. Nitrogen is an important ingredient for life as known on Earth. Its detection strengthens evidence for potentially habitable chemistry, without proving the existence of Martian organisms.
Q19. Which spacecraft-purpose pairs are correct?
1. Cassini-Huygens — studying Venus
2. MESSENGER — investigating Mercury
3. Voyager 1 and 2 — exploring the outer Solar System.
[UPSC CSE Prelims 2014]
(A) 1 only
(B) 2 and 3 only
(C) 1 and 3 only
(D) All three
Answer: (B) 2 and 3 only
Explanation: Cassini-Huygens explored Saturn and Titan rather than Venus. NASA’s MESSENGER studied Mercury, while Voyager 1 and 2 investigated giant planets and their moons. Consequently, the second and third spacecraft-purpose pairs are the accurate ones.
Q18. Approximately how many times is the Sun’s diameter larger than Earth’s diameter?
[MPPSC State Service Prelims 2014]
(A) 124
(B) 100
(C) 109
(D) 115
Answer: (C) 109
Explanation: The Sun’s diameter is about 1.39 million kilometres, compared with Earth’s approximately 12,742 kilometres. Their ratio is close to 109. This comparison concerns linear diameter; the Sun’s volume is vastly greater, around 1.3 million Earth volumes.
Q17. ISRO and NASA discussed a bilateral working group in March 2013 for which areas?
1. Future Moon and Mars missions
2. Meteorology and space exploration
3. Heliophysics.
[UPPSC Civil Services Prelims 2013]
(A) Moon and Mars missions only
(B) Meteorology and space exploration only
(C) Heliophysics only
(D) All of the above
Answer: (D) All of the above
Explanation: ISRO–NASA cooperation encompasses planetary exploration, Earth observation and heliophysics. Joint technical discussions can address lunar and Martian missions, measurements of Earth’s atmosphere and investigations of the Sun and its influence on the space environment.
Q16. Which Indian satellite marked the country’s entry into the space age in 1975?
[RPSC RAS Prelims 2013]
(A) Bhaskara-I
(B) Aryabhata
(C) APPLE
(D) Agni
Answer: (B) Aryabhata
Explanation: Aryabhata was India’s first satellite, built domestically and launched in April 1975 using a Soviet rocket. It was named after the mathematician and astronomer Aryabhata. Bhaskara satellites and APPLE came later, while Agni denotes missile systems.
Q15. For which purpose was India’s GSAT-7 satellite primarily developed?
[RPSC RAS Prelims 2013]
(A) Weather forecasting
(B) Military communications
(C) Mars exploration
(D) Dedicated lunar coverage
Answer: (B) Military communications
Explanation: GSAT-7 is a multi-band communications satellite developed mainly for India’s defence services, especially the Indian Navy. Satellite communications can connect platforms separated by large ocean distances, strengthening secure operational coordination.
Q14. Which observations support the continuing expansion of the Universe?
1. Microwave background radiation
2. Cosmological redshift
3. Motion of asteroids
4. Supernova explosions.
[UPSC CSE Prelims 2012]
(A) 1 and 2 only
(B) 2 only
(C) 1, 3 and 4 only
(D) None of these
Answer: (A) 1 and 2 only
Explanation: The cosmic microwave background records relic radiation from the early universe, and the cosmological redshift of distant galaxies indicates the expansion of space. Ordinary asteroid movement is a local dynamical process and does not establish cosmic expansion.
Q13. Why does an artificial satellite in Earth orbit not simply fall vertically to the ground?
[UPSC CSE Prelims 2011]
(A) Earth’s gravity is absent
(B) The Moon cancels Earth’s gravity
(C) Gravity supplies steady speed
(D) Earth’s gravity provides the necessary centripetal acceleration
Answer: (D) Earth’s gravity provides the necessary centripetal acceleration
Explanation: An orbiting satellite is continuously falling under Earth’s gravity, but its forward velocity causes it to keep missing the surface. Gravitational acceleration continually bends the trajectory, supplying the centripetal acceleration needed for orbital motion.
Q12. Which statements distinguish asteroids and comets?
1. Asteroids are usually rocky; comets contain volatile ice.
2. Most comets occur between Mercury and Venus.
3. Comets can display a luminous tail, unlike most asteroids.
[UPSC CSE Prelims 2011]
(A) 1 and 2 only
(B) 1 and 3 only
(C) 3 only
(D) All three
Answer: (B) 1 and 3 only
Explanation: Many asteroids are rocky or metallic, whereas comets contain abundant ice and dust. Solar heating can release gas and dust from a comet, generating a coma and tail. Most comet reservoirs lie far beyond the inner planets.
Q11. A telecommunications satellite is geostationary if it has
1. A geosynchronous period
2. A circular orbit
3. An equatorial orbit
4. Altitude of 22,236 km.
Which conditions are correct?
[UPSC CSE Prelims 2011]
(A) 1, 2 and 3 only
(B) 1, 3 and 4 only
(C) 2 and 4 only
(D) All four
Answer: (A) 1, 2 and 3 only
Explanation: Geostationary satellites must orbit eastward in a circular equatorial orbit with a period equal to Earth’s sidereal rotation. Their actual altitude is approximately 35,786 kilometres, not the 22,236 kilometres given in the fourth statement.
