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UPSC Prelims 1989 · World Geography · Earth in Space
Which one among the following is the smallest planet?
- (a) Mercury
- (b) Mars
- (c) Venus
- (d) Pluto
Show the answer and explanation
Answer: (d) Pluto
In 1989 Pluto counted as the smallest planet.
The idea
A size ranking must use a clearly defined group. In the 1989 nine-planet classification, Pluto belonged to that group. Its 2006 reclassification changed which objects were compared; Mercury became the smallest member of the eight-planet group without changing size.
Why the others are wrong
(a) Mercury is the smallest planet today.
The trap
Answer by the year: today it would be Mercury.
Also know
A dwarf planet can be round and have moons but still share its orbital region with many other bodies. Ceres is another dwarf planet, located between Mars and Jupiter. Do not confuse “smallest planet” with “nearest planet to the Sun”, even though Mercury fits both in the post-2006 eight-planet system.
🔒 Since 2006: Mercury smallest planet.
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