The moons of the giant outer planets have turned out to be stranger and more interesting than anyone had imagined. What do you know about the moons of Jupiter, Saturn, Uranus and Neptune? Try the quiz – then you can check your answers, and learn more about the moons.

Quiz: Solar System Discoveries

1. Astronomer who suggested a literary theme for naming the moons of Uranus: (A) William Herschel discoverer of Uranus; (B) William Lassell, who discovered two of the moons of Uranus; (C) John Herschel, William's son


2. A walnut-shaped moon, the most massive known body that is not spherical: (A) Mimas; (B) Rhea; (C) Iapetus


3. The only moon with an iron core and magnetic field: (A) Titan; (B) Ganymede; (C) Oberon


4. Moon that's a captured Kuiper Belt object: (A) Titan; (B) Triton; (C) Ariel.


5. The moons named for the king and queen of the fairies in Shakespeare's A Midsummer Night's Dream: (A) Oberon & Titania; (B) Umbriel & Miranda; (C) Prospero & Cressida


6. William Lassell discovered Triton in 1846, less than three weeks after the discovery of Neptune itself. How long did it take for a second moon of Neptune to be discovered?: (A) 15 years; (B) 55 years; (C) over 100 years


7. The moon with the oldest and most cratered surface in the Solar System: (A) Callisto; (B) Io; (C) Ganymede


8. Moon with a thick atmosphere that's 80% nitrogen: (A) Ganymede; (B) Titan; (C) Triton


9. Moon of Jupiter with a smooth icy surface that has a deep liquid ocean under it: (A) Enceladus; (B) Europa; (C) Callisto


10. Moon with a strange surface described as looking like “a giant smashed it apart and then put it back together blindfolded”: (A) Iapetus; (B) Io; (C) Miranda

Answers and notes

1. Astronomer who suggested a literary theme for naming the moons of Uranus: (C) John Herschel, William's son
William Herschel, who died in 1820, hadn't named the moons he discovered. When Lassell discovered two of the moons of Uranus in 1851, he asked his friend John Herschel to suggest names for the moons of the planet his father had discovered.

2. A walnut-shaped moon, the most massive known body that is not spherical: (C) Iapetus
Mimas is the least massive body known to be spherical. Rhea has also collapsed into a spherical body, but not Iapetus.

3. The only moon with an iron core and magnetic field: (B) Ganymede
Earth has a magnetic field maintained by its iron core, as does the planet Mercury, although it's much weaker. Ganymede is the only moon to do so.

4. Moon that's a captured Kuiper Belt object: (B) Triton
Titan formed in the same region as Saturn. Uranus's moon Ariel formed from a disk of material around the planet. It was either material left over from the formation of Uranus, or material thrown out from the collision that knocked the planet on its side. But Triton orbits in the opposite direction to Neptune's spin, which shows that it's a captured object. And captured from where? Triton's many similarities to Pluto strongly suggest that it came from the Kuiper Belt, a belt of small icy objects beyond Neptune.

5. The moons named for the king and queen of the fairies in Shakespeare's A Midsummer Night's Dream: (A) Oberon & Titania
Prospero and Miranda are characters in The Tempest. Umbriel and Ariel are spirits of the air in a work by 18th century poet Alexander Pope.

6. William Lassell discovered Triton in 1846, less than three weeks after the discovery of Neptune itself. How long did it take for a second Moon of Neptune to be discovered?: (C) over 100 years
Neptune is a very long way away, and except for Triton, its moons are small. Nereid, discovered by Gerard Kuiper in 1949, is about 350 km (220 mi) in diameter.

7. The moon with the oldest and most cratered surface in the Solar System: (A) Callisto;
Callisto, the third largest moon in the Solar System, shows no signs of internal geological activity. Its heavily cratered ancient surface is the result of a few billion years of impacts. Ganymede has cratered terrain, but its surface also shows various signs of internal activity. Io is the most volcanic body in the Solar System and is regularly resurfaced.

8. Moon with a thick atmosphere that's 80% nitrogen: (B) Titan
Ganymede has a tenuous oxygen atmosphere, and Triton a very thin nitrogen atmosphere. Titan's the only moon with a substantial atmosphere.

9. Moon of Jupiter with a smooth icy surface that has a deep liquid ocean under it: (B) Europa
The description almost fits Enceladus, but Enceladus is one of Saturn's moons. Callisto is a moon of Jupiter, but it doesn't have a smooth surface. (See Question 7.)

10. Moon with a strange surface described as looking as if “a giant smashed it apart and then put it back together blindfolded”: (C) Miranda
It's not a bad description of Miranda. Io definitely looks like a pizza. There's a link to an image of Iapetus in Question 2.

How did you do?
Did you get the answers right? If not, would you do better next time from what you've learned?