Moons of the Solar System – answers and explanations
Here are the answers to all 15 questions in the Moons of the Solar System quiz, each with a short explanation. From Phobos to Titan: test your knowledge of the planets' satellites. Haven't played yet? Take the quiz first and compare your score.
Play the quiz · 15 questions1. Which Apollo mission first landed humans on the Moon, in July 1969?
Answer: Apollo 11
Apollo 11 made the first crewed Moon landing on July 20, 1969, when Neil Armstrong and Buzz Aldrin touched down in the Sea of Tranquility while Michael Collins orbited above. Apollo 8 only orbited the Moon, and Apollo 13's landing was aborted.
2. What are the names of the two moons of Mars?
Answer: Phobos and Deimos
Mars has two small, irregularly shaped moons, Phobos and Deimos, both discovered by American astronomer Asaph Hall in August 1877 and named after the Greek figures of fear and dread.
3. Which moon is the largest in the entire Solar System?
Answer: Ganymede
Jupiter's moon Ganymede is the largest moon in the Solar System at about 5,268 km across, making it bigger than the planet Mercury; it is also the only moon known to generate its own magnetic field.
4. Who discovered the four largest moons of Jupiter in 1610?
Answer: Galileo Galilei
Galileo Galilei spotted Io, Europa, Ganymede and Callisto with his telescope in January 1610, the first moons found orbiting another planet, which supported the idea that not everything circles Earth.
5. Which Saturn moon is the only one known to have a thick, hazy atmosphere?
Answer: Titan
Titan is the only moon known to have a dense, hazy atmosphere, mostly nitrogen with methane, and surface pressure about 1.5 times Earth's; the Huygens probe landed there in January 2005.
6. Which moon of Jupiter is the most volcanically active body in the Solar System?
Answer: Io
Io, the innermost Galilean moon of Jupiter, is the most volcanically active body in the Solar System, with roughly 400 volcanoes. Its eruptions are driven by tidal heating from Jupiter's gravity and the pull of Europa and Ganymede; Voyager spotted the activity in 1979.
7. What is the Moon phase called when its sunlit side faces away and it looks invisible?
Answer: New Moon
At new moon the Moon sits roughly between Earth and the Sun, so its sunlit half points away from us and it is essentially invisible. Solar eclipses can only happen at new moon, which recurs every 29.5 days.
8. Which American astronomer discovered Phobos and Deimos in 1877?
Answer: Asaph Hall
American astronomer Asaph Hall found both Martian moons in August 1877 at the U.S. Naval Observatory in Washington, D.C., using its 26-inch refractor: Deimos on 11-12 August and Phobos on 17-18 August.
9. Saturn's moon Mimas is nicknamed after what film object, thanks to its giant crater?
Answer: The Death Star
Saturn's moon Mimas is called the Death Star moon because the 130-km-wide Herschel crater covers about a third of its 396-km diameter. The resemblance is coincidental, as Voyager 1 revealed the crater in 1980, three years after Star Wars came out.
10. The Huygens probe parachuted onto the surface of which moon in 2005?
Answer: Titan
ESA's Huygens probe descended by parachute for about 2 hours 27 minutes and landed on Saturn's moon Titan on 14 January 2005, after being released by NASA's Cassini orbiter. It remains the most distant landing ever made from Earth.
11. Which Saturn moon sprays water-ice geysers from cracks near its south pole?
Answer: Enceladus
Cassini discovered in 2005 that Enceladus erupts plumes of water vapour and icy particles from four fractures nicknamed tiger stripes at its south pole, fed by a global salty subsurface ocean.
12. Which Apollo mission was the last to land astronauts on the Moon, in 1972?
Answer: Apollo 17
Apollo 17 landed in the Taurus-Littrow valley on 11 December 1972, the sixth and final crewed Moon landing; Gene Cernan and geologist Harrison Schmitt were the last people to walk on the lunar surface.
13. Which spacecraft is the only one to have flown past both Uranus and Neptune?
Answer: Voyager 2
Voyager 2, launched on 20 August 1977, remains the only spacecraft to have visited Uranus (closest approach 24 January 1986) and Neptune (25 August 1989), also flying past Triton and Miranda.
14. What word describes the Moon's lit part growing from new towards full?
Answer: Waxing
Waxing, from an Old English word meaning to grow, describes the roughly two weeks when the Moon's sunlit portion increases from new to full, passing through waxing crescent, first quarter and waxing gibbous.
15. Which is the largest moon of Neptune, famous for orbiting its planet backwards?
Answer: Triton
Triton is Neptune's largest moon and the only large moon in the Solar System with a retrograde orbit, suggesting it was captured from the Kuiper Belt. William Lassell discovered it on 10 October 1846, just 17 days after Neptune itself was found.