Which of the following groups of planets is termed as ‘gas planets’ as they are composed primarily of lighter ices, liquids and gases?
- (a)Mars, Jupiter, Neptune, Uranus
- (b)Jupiter, Uranus, Neptune, Saturn
- (c)Saturn, Mars, Jupiter, Neptune
- (d)Neptune, Saturn, Mars, Uranus
Correct — B, Jupiter, Uranus, Neptune, Saturn. The four outer planets — Jupiter, Saturn, Uranus and Neptune — are the giant planets, and option (b) is the only one that names exactly those four and nothing else. Each of the other three options smuggles Mars into the group, and Mars is a small rocky world with a solid surface, one of the four terrestrial planets along with Mercury, Venus and Earth. The giants have no hard surface at all; they are deep envelopes of hydrogen, helium and heavier volatiles over a dense core, which is what the stem means by lighter ices, liquids and gases.
- (a)Mars, Jupiter, Neptune, Uranus — Mars is a terrestrial planet with a rocky crust, roughly half the diameter of Earth. Its presence disqualifies the set, and Saturn — a genuine giant — has been left out to make room for it.
- (c)Saturn, Mars, Jupiter, Neptune — The same defect. Mars is in and Uranus is out, so the set is wrong at both ends.
- (d)Neptune, Saturn, Mars, Uranus — Again Mars replaces Jupiter, which is the largest planet in the solar system and the least omissible member of any list of giants.
The eight planets divide cleanly at the asteroid belt. Inside it are the four terrestrial planets — Mercury, Venus, Earth and Mars — small, dense and rocky, with solid surfaces. Outside it are the four giants — Jupiter, Saturn, Uranus and Neptune — far larger, far less dense, without a solid surface, and all of them ringed and richly moon-bearing. The older textbooks call the whole outer group gas planets or Jovian planets; the composition of the outermost two is closer to water, ammonia and methane ices than to pure gas.
The item is easier than it looks, because it can be solved by elimination rather than by recall. Any option containing Mars is out, and three of the four contain Mars. That leaves only (b), which happens to list the four correctly, if in an unusual order. The one nuance worth carrying forward is that the four-planet grouping the stem uses has since been split. Present-day usage, including NASA's, keeps 'gas giants' for Jupiter and Saturn, which are overwhelmingly hydrogen and helium, and calls Uranus and Neptune 'ice giants', because a much larger share of their mass is water, ammonia and methane. The CDS stem's phrase 'lighter ices, liquids and gases' is the older, inclusive description, and on the paper's own terms all four belong together. Do not let the newer distinction talk you out of a four-planet answer when the stem defines the group that way.
- The four giant planets are Jupiter, Saturn, Uranus and Neptune; the four terrestrial planets are Mercury, Venus, Earth and Mars.
- The giants have no hard surface — swirling gases and fluids over a dense core — while the terrestrial planets have solid rocky surfaces.
- Present-day usage separates the gas giants, Jupiter and Saturn, from the ice giants, Uranus and Neptune.
- Jupiter is the largest planet in the solar system; Neptune is the farthest from the Sun since Pluto's reclassification as a dwarf planet in 2006.
- The asteroid belt lies between Mars and Jupiter and marks the division between the two families.
- Letting Mars slip into a list of giant planets because it is often discussed alongside them in mission news.
- Refusing a four-planet answer because modern usage separates gas giants from ice giants; the stem defines the group inclusively.
- Forgetting that Neptune, not Pluto, is now the outermost planet.
As a group-the-planets item, sometimes reversed into naming the terrestrial four, and sometimes as a single-planet superlative.
In order of their distances from the Sun, which of the following planets lie between Mars and Uranus?
- (a) Earth and Jupiter
- (b) Jupiter and Saturn
- (c) Saturn and Earth
- (d) Saturn and Neptune
Answer(b) Jupiter and Saturn
The same eight names, tested as an order instead of a grouping. Fixing the sequence outward from the Sun is what lets a candidate see instantly that any set containing Mars cannot be the set of giants.
CDS_GK_2020_II_Q632020The four planets closest to the Sun are called
- (a) terrestrial planets
- (b) giant planets
- (c) dwarf planets
- (d) gas planets
Answer(a) terrestrial planets
The mirror image of this question — the inner four instead of the outer four. Between them the two items cover the whole division, and its own wrong option 'gas planets' is precisely the label this question attaches to the other group.
Consider the following statements about some planets in the solar system: 1. Mercury has no atmosphere. 2. Venus has two moons. 3. There is no land on Jupiter. 4. Rings of Saturn are composed of lumps of ice and dust. Which of the statements given above are correct?
- (a) 1 and 2 only
- (b) 3 and 4 only
- (c) 1, 2 and 3
- (d) 1, 3 and 4
Answer(d) 1, 3 and 4
The planetary facts CDS tends to reuse, from the very next session. Its statements 3 and 4 are the giants' defining features — no land on Jupiter, and rings of ice and dust round Saturn — which is exactly what separates that family from the rocky inner planets.
- practice — not a real PYQ
Which of the following planets are described as ice giants?
- (a)Jupiter and Saturn
- (b)Uranus and Neptune
- (c)Earth and Mars
- (d)Mercury and Venus
Answer(b) Uranus and Neptune — water, ammonia and methane make up a much larger share of their mass than of Jupiter's or Saturn's.
- practice — not a real PYQ
The asteroid belt of the solar system lies between the orbits of
- (a)Earth and Mars
- (b)Mars and Jupiter
- (c)Jupiter and Saturn
- (d)Saturn and Uranus
Answer(b) Mars and Jupiter — it marks the boundary between the terrestrial planets and the giants.