Journey Through the Solar System – answers and explanations
Here are the answers to all 15 questions in the Journey Through the Solar System quiz, each with a short explanation. Test your knowledge of planets, moons and the missions that explored them. Haven't played yet? Take the quiz first and compare your score.
Play the quiz · 15 questions1. Which spacecraft is the most distant human-made object from Earth?
Answer: Voyager 1
Voyager 1, launched in 1977, is the most distant human-made object from Earth. It entered interstellar space in 2012 and is now more than 160 AU from the Sun.
2. Titan, a moon with a thick nitrogen-rich atmosphere, orbits which planet?
Answer: Saturn
Titan is Saturn's largest moon and has a thick nitrogen-rich atmosphere. It is the only moon in the Solar System with a dense atmosphere, and the Huygens probe landed on it in 2005.
3. Which NASA rover landed in Mars's Jezero Crater in February 2021?
Answer: Perseverance
NASA's Perseverance rover landed in Jezero Crater on 18 February 2021. The crater once held a lake and river delta, so it is a good place to look for signs of ancient life.
4. Which planet spins on its side, with an axial tilt of about 98 degrees?
Answer: Uranus
Uranus has an axial tilt of about 98 degrees, so it effectively orbits the Sun on its side. Venus is tilted about 177 degrees and rotates backwards, so it does not match.
5. What is the name of the larger of Mars's two moons?
Answer: Phobos
Phobos is the larger of Mars's two moons, with a mean diameter of about 22 km. Deimos is smaller, at about 12 km. Both moons were discovered by Asaph Hall in 1877.
6. Which moon of Jupiter is the most volcanically active body in the Solar System?
Answer: Io
Io is the most volcanically active body in the Solar System, with hundreds of active volcanoes. Its activity is driven by tidal heating from Jupiter and the neighbouring moons.
7. Which spacecraft ended its mission in 2017 by deliberately plunging into Saturn?
Answer: Cassini
Cassini ended its mission on 15 September 2017 by plunging into Saturn's atmosphere. The deliberate dive protected moons such as Enceladus and Titan from contamination by Earth microbes.
8. Olympus Mons, the tallest volcano in the Solar System, is found on which planet?
Answer: Mars
Olympus Mons on Mars is the tallest known volcano in the Solar System. It is a shield volcano about 22 km high, roughly two and a half times the height of Mount Everest above sea level.
9. Which NASA spacecraft made the first-ever flyby of Pluto in July 2015?
Answer: New Horizons
NASA's New Horizons made the first flyby of Pluto on 14 July 2015. It launched in 2006 and passed within about 12,500 km of the dwarf planet.
10. Triton, a large moon that orbits backwards, circles which planet?
Answer: Neptune
Triton orbits Neptune and has a retrograde orbit, moving opposite to the planet's rotation. This suggests it was captured from the Kuiper Belt rather than forming in place around Neptune.
11. Which planet takes longer to spin once on its axis than to orbit the Sun?
Answer: Venus
Venus rotates once every about 243 Earth days, which is longer than its 225-day orbit of the Sun. It also spins backwards (retrograde) compared with most planets.
12. Which planet has the shortest day, rotating once in under 10 hours?
Answer: Jupiter
Jupiter rotates once in about 9 hours 56 minutes, the fastest spin of any planet. Saturn is next at roughly 10.7 hours. Jupiter's quick rotation flattens it at the poles.
13. Which NASA mission brought samples from asteroid Bennu back to Earth in 2023?
Answer: OSIRIS-REx
NASA's OSIRIS-REx dropped its sample capsule over Utah on 24 September 2023, carrying material from asteroid Bennu. Japan's Hayabusa2 returned samples from Ryugu in 2020.
14. What is the largest moon in the Solar System, bigger than planet Mercury?
Answer: Ganymede
Ganymede, a moon of Jupiter, is the largest moon in the Solar System at about 5,268 km across. That is wider than Mercury, which is about 4,879 km, though Ganymede is less massive.
15. Which planet has the fastest winds in the Solar System, over 2,000 km/h?
Answer: Neptune
Neptune has the fastest winds of any planet in the Solar System, reaching about 2,000 km/h (1,200 mph). Its winds are supersonic and blow against the planet's rotation.