UPSC Prelims 2009 Q66: Geography – Astronomy & Earth - Sun System

UPSC Prelims 2009, General Studies Paper I · Geography

Which one of the following planets has largest number of natural satellites or moons?

Answer: (a) Jupiter

Explanation

Which planet has the most moons

Among the solar system's planets, one gas giant hosts by far the largest number of known natural satellites.

Option	Verdict	Reason
(a) Jupiter	Correct	Jupiter, the solar system's largest planet, has the highest number of known moons, including the four large Galilean moons
(b) Mars	Incorrect	Mars has only two small moons (Phobos and Deimos)
(c) Saturn	Incorrect	Saturn has many moons too, but at the time of this question, Jupiter's count was recognized as higher
(d) Venus	Incorrect	Venus has no moons at all

Moon counts (approximate, at the time):

Planet	Moons
Jupiter	Largest number (including 4 large Galilean moons)
Mars	2 (Phobos, Deimos)
Venus	0

Answer: (a) Jupiter.

(a) CORRECT. Jupiter has the largest known number of natural satellites.
(b) Incorrect. Mars has only two small moons.
(c) Incorrect. Saturn's moon count, while large, was recognized as lower than Jupiter's at the time.
(d) Incorrect. Venus has no moons at all.

Jupiter has the largest number of known natural satellites (moons) among the planets listed, including its four large Galilean moons.

Jupiter has the largest number of natural satellites (moons) among the planets.

Confusing Jupiter's moon count with Saturn's, which is also large but was recognized as fewer at the time.
Not knowing Venus has zero moons.
Underestimating Mars's very small moon count (just 2).

Jupiter = largest number of moons among the planets, far more than Mars (2) or Venus (0).