Planets Quiz

This volcano is about two and a half times as tall as Everest. On which planet does it stand?

• Mars
• Earth
• Mercury
• Venus

Answer: Mars. Olympus Mons on Mars rises about 22 km, roughly two and a half Everests.

This cloud-wrapped world is hotter than Mercury, though much farther from the Sun. Which planet is it?

• Venus
• Mercury
• Earth
• Mars

Answer: Venus. Venus is wrapped in thick carbon dioxide that traps heat like a greenhouse, so it beats Mercury.

This storm is wider than our whole Earth and has been watched since the 1830s. Which planet does it spin on?

• Saturn
• Jupiter
• Uranus
• Neptune

Answer: Jupiter. Jupiter's Great Red Spot is so big that Earth could fit inside it.

Neptune is farther from the Sun, yet its ice-giant neighbour holds the record for the coldest temperature measured on any planet, about minus 224°C. Which planet?

• Mars
• Saturn
• Uranus
• Jupiter

Answer: Uranus. Uranus. It gives off far less internal heat than Neptune, so its upper atmosphere gets colder.

Squeezed by the gravity of Jupiter and its neighbouring moons, this moon has hundreds of volcanoes, more volcanic activity than any other world in the solar system. Name it.

• Europa
• Io
• Callisto
• Triton

Answer: Io. Io. The constant tidal squeezing heats its interior, and some eruptions throw material hundreds of kilometres up.

All eight planets, their moons, the asteroids and the comets together make up only a tiny share of the solar system's mass. How much of it is in the Sun?

• About half
• About three quarters
• About 90%
• More than 99%

Answer: More than 99%. More than 99%: about 99.8%. Jupiter holds most of what is left.

This little world has a big heart-shaped plain. In 2006 astronomers moved it into which group?

• Moons of Neptune
• Comets
• Dwarf planets
• Gas giants

Answer: Dwarf planets. Dwarf planets. In 2006 the International Astronomical Union reclassified Pluto, leaving eight planets.

Saturn's largest moon is the only place besides Earth known to have lakes and seas on its surface. What are they filled with?

• Water
• Molten rock
• Liquid methane and ethane
• Liquid nitrogen

Answer: Liquid methane and ethane. Liquid methane and ethane. At about minus 180°C water is rock-hard, but these hydrocarbons flow, fall as rain and fill the lakes.

From Earth, Saturn's rings look like solid bands. What are they mostly made of?

• Water ice
• Iron dust
• Frozen carbon dioxide
• Volcanic ash

Answer: Water ice. Water ice, in pieces from smaller than a grain of sand to as big as a mountain. In most places the rings are only about 10 metres thick.

The red planet has a surprise at dusk. In 2015 NASA's Curiosity rover photographed a Martian sunset. What colour was the glow around the setting Sun?

• Blue
• Red
• Green
• Purple

Answer: Blue. Blue. Fine Martian dust lets blue light through slightly better and scatters it close to the Sun, while the rest of the sky looks yellow to orange.

Seven planets carry the names of Greek or Roman gods. Which is the only one that doesn't?

• Uranus
• Earth
• Neptune
• Mercury

Answer: Earth. Earth. NASA notes that its English name comes from Old English and Germanic words for the ground.

In 1846 astronomers found this planet almost exactly where a French mathematician's calculations said it would be. Which planet?

• Jupiter
• Uranus
• Pluto
• Neptune

Answer: Neptune. Neptune. Urbain Le Verrier worked out its position from the tug it had on Uranus, and Johann Galle spotted it within a degree of his prediction.

Named after the Romans' swift messenger god, this planet races once around the Sun in just 88 Earth days. Which is it?

• Venus
• Mars
• Saturn
• Mercury

Answer: Mercury. Mercury, the closest planet to the Sun, has the shortest year of any planet.

Mars has two small moons, named after the sons of Ares: Fear and Dread. What are they called?

• Io and Europa
• Phobos and Deimos
• Titan and Rhea
• Triton and Nereid

Answer: Phobos and Deimos. Phobos and Deimos. Asaph Hall found both in August 1877; phobos is the same Greek word that gives us "phobia".

In 1781 a musician-turned-astronomer in Bath spotted a new planet with his homemade telescope, and first took it for a comet. Who was he?

• Galileo Galilei
• Edmond Halley
• William Herschel
• Isaac Newton

Answer: William Herschel. William Herschel. His planet, Uranus, was the first ever discovered with a telescope.