50 free Jupiter trivia questions with answers — science & nature quiz, new questions added Aug 2026.
This Jupiter trivia quiz is about the planet, the biggest thing in the Solar System after the Sun. It covers the numbers that make it a giant: 318 Earth masses, 11 Earth diameters, a ten-hour day that flattens it, a magnetic field that reaches nearly to Saturn, and a barycentre that lies outside the Sun. It then looks at the weather: the shrinking Great Red Spot, ammonia clouds, the polar cyclones Juno found and the Great Cold Spot, plus the metallic hydrogen and slow contraction that keep the planet radiating heat. The moons get their own section: Galileo's discovery and Marius's names, Ganymede bigger than Mercury, volcanic Io, ocean-bearing Europa, the Laplace resonance, Amalthea and the dusty rings. Then exploration and history: Pioneer 10, the Voyagers, the Galileo orbiter and its atmospheric probe, Juno's July 4 arrival, the crash of Comet Shoemaker–Levy 9, Rømer's speed of light, and finally the names, from Babylonian Marduk and the Chinese wood star to Guru, Phaethon, 'jovial' and the thunderbolt of the sky-father. Difficulty runs from easy to expert and is shown on each question, so it suits a classroom, a pub quiz or a space enthusiast. Every answer was checked against a reference page and each question carries its citation. Try our Planets and Solar System quizzes for more.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Where does Jupiter rank in distance from the Sun?
Fifth
It is the first of the giant planets beyond the asteroid belt.
Q 02Jupiter's mass is roughly how many times that of Earth?
318
That is nearly 2.5 times the mass of all the other planets combined, yet still less than a thousandth of the Sun.
Q 03Jupiter's diameter is about how many times Earth's?
11
It is also about a tenth the diameter of the Sun.
Q 04How long does Jupiter take to orbit the Sun?
About 11.9 years
The Chinese built their twelve-year cycle of earthly branches on this near-12-year orbit.
Q 05Roughly how long is a day on Jupiter?
About 10 hours
It is the fastest-spinning planet, which flattens it into an oblate spheroid 7% wider at the equator.
Q 06Jupiter's atmosphere is made mostly of which two gases?
Hydrogen and helium
About 76% hydrogen and 24% helium by mass, close to the primordial mix of the solar nebula.
Q 07What is the Great Red Spot?
A giant anticyclonic storm
It rotates anticlockwise about once every six days and rises some 8 km above the surrounding cloud tops.
Q 08Since when has the Great Red Spot been continuously observed?
1831
Robert Hooke and Cassini may have seen it in the 1660s, though that identification is disputed.
Q 09How does the Great Red Spot compare in size with our own planet?
It is larger than Earth
It has shrunk a lot: it was about 41,000 km across in the late 1800s and about 16,500 km by 2015.
Q 10Roughly how wide was the Great Red Spot in the late 1800s, before it began shrinking?
About 41,000 km
By 2015 it was down to about 16,500 by 10,940 km and losing roughly 930 km of length a year.
Q 11Jupiter's clouds are made mainly of crystals of what?
Ammonia
The orange and brown streaks come from compounds welling up and changing colour in sunlight.
Q 12Jupiter radiates more heat than it receives from the Sun. Which mechanism drives this?
Kelvin–Helmholtz contraction
The planet is still slowly shrinking, by about a millimetre a year.
Q 13Which planet has the strongest magnetic field in the Solar System?
Jupiter
Its magnetosphere stretches downwind almost to the orbit of Saturn.
What exotic material is thought to make up Jupiter's outer mantle and generate its magnetic field?
Q 21Which moon of Jupiter is the most volcanically active body in the Solar System?
Io
Over 400 active volcanoes are driven by tidal heating as Jupiter, Europa and Ganymede pull it about.
Q 22Which icy moon of Jupiter is a prime target in the search for life because of its subsurface ocean?
Europa
Hubble has detected water-vapour plumes, and NASA's Europa Clipper is on its way to investigate.
Q 23The three inner Galilean moons orbit in a 4:2:1 pattern known as what?
A Laplace resonance
Each moon gets an extra tug at the same point every orbit, keeping their orbits slightly elliptical and their interiors warm.
Fluid metallic hydrogen
Under enormous pressure hydrogen becomes an electrical conductor, like a liquid metal.
Q 15Jupiter is the only planet whose barycentre with the Sun lies where?
Outside the Sun's surface
The common centre of mass sits about 7% of a solar radius above the Sun's surface.
Q 16Jupiter is usually which brightest object in Earth's night sky?
Third, after the Moon and Venus
At opposition Mars can occasionally outshine it.
Q 17How many known moons does Jupiter have (as of the article)?
115
Only 16 of them are larger than 10 km across; most are captured asteroids.
Q 18Which four moons were discovered by telescope in 1610?
Io, Europa, Ganymede and Callisto
Simon Marius spotted them a day later and it was his names, taken from Zeus's lovers, that stuck.
Q 19Who gave the four big moons the names that stuck, taken from Zeus's lovers?
Simon Marius
Galileo had called them the Medicean Stars after his patrons.
Q 20Which moon of Jupiter is the largest moon in the Solar System, bigger than the planet Mercury?
Ganymede
It is also the only moon known to generate its own magnetic field.
Q 24Which moon, found by Barnard in 1892, was the last discovered by eye through a telescope?
Amalthea
Everything since has been found on photographs or by spacecraft.
Q 25Jupiter has faint rings. Unlike Saturn's, what are they mostly made of?
Dust
The main ring is thought to be debris knocked off the small moons Adrastea and Metis.
Q 26Which spacecraft discovered Jupiter's rings, in 1979?
Voyager
They also confirmed the Great Red Spot rotates anticlockwise.
Q 27Which was the first spacecraft to fly past Jupiter, in 1973?
Pioneer 10
It later became the first probe to leave the inner Solar System entirely.
Q 28Which was the first spacecraft to orbit Jupiter, arriving in December 1995?
Galileo
It stayed more than seven years and dropped a probe into the atmosphere, despite a jammed main antenna.
Q 29The 1995 atmospheric entry probe recorded winds of more than what speed before it was destroyed?
644 km/h
It parachuted through 150 km of atmosphere and found temperatures above 300 °C.
Q 30NASA's Juno spacecraft arrived at Jupiter on which US holiday in 2016?
July 4
It sent back the first-ever images of Jupiter's north pole and found clusters of polar cyclones.