How did Hubble find evidence of an ocean under Ganymede's ice?

By watching how its auroras shifted

Who was Ganymede in Greek myth?

A Trojan youth who became cupbearer to the gods

What two types of terrain cover Ganymede?

Dark old regions and lighter grooved areas

Ganymede Quiz: The Moon With Its Own Magnetic Field

Auroras glowing on Jupiter's largest moon helped Hubble reveal a hidden saltwater ocean in 2015, and this Ganymede quiz explains what makes the moon so unusual. Play an interactive set of 10 questions on Galileo's 1610 discovery, its size, its magnetic field, grooved terrain, the Juno flyby, ESA's JUICE mission and orbital resonance with Io and Europa.

Start Ganymede Quiz

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

Size
Which is larger, Ganymede or the planet Mercury?
Field
What makes Ganymede unique among moons?
Discovery
Who discovered Ganymede in 1610?
Ocean
How did Hubble find evidence of an ocean under Ganymede's ice?
Name
Who was Ganymede in Greek myth?
JUICE
Which mission will orbit Ganymede?
Juno
Which NASA spacecraft flew close to Ganymede in 2021?
Terrain
What two types of terrain cover Ganymede?
Resonance
Ganymede is in a 1:2:4 orbital resonance with which moons?
Lock
Which side of Ganymede faces Jupiter?

Explanations: answer key for all 10 questions

Q1: Which is larger, Ganymede or the planet Mercury?
Answer: Ganymede
Ganymede's diameter of about 5,268 km makes it the largest moon in the solar system.
Q2: What makes Ganymede unique among moons?
Answer: It has its own magnetic field
The Galileo spacecraft detected the field in 1996.
Q3: Who discovered Ganymede in 1610?
Answer: Galileo Galilei
It is one of the four Galilean moons.
Q4: How did Hubble find evidence of an ocean under Ganymede's ice?
Answer: By watching how its auroras shifted
A salty ocean dampens the auroras' rocking motion.
Q5: Who was Ganymede in Greek myth?
Answer: A Trojan youth who became cupbearer to the gods
Zeus carried him to Olympus.
Q6: Which mission will orbit Ganymede?
Answer: ESA's JUICE
JUICE launched in 2023 and should enter orbit around Ganymede in the 2030s.
Q7: Which NASA spacecraft flew close to Ganymede in 2021?
Answer: Juno
Juno took detailed images during a flyby.
Q8: What two types of terrain cover Ganymede?
Answer: Dark old regions and lighter grooved areas
Grooved terrain formed as the icy crust cracked and shifted.
Q9: Ganymede is in a 1:2:4 orbital resonance with which moons?
Answer: Io and Europa
For every orbit of Ganymede, Europa orbits twice and Io four times.
Q10: Which side of Ganymede faces Jupiter?
Answer: Always the same side
Like Earth's Moon, Ganymede is tidally locked.

Ganymede Quiz – Jupiter's Giant Moon

Ganymede, discovered by Galileo Galilei in 1610, is the largest moon in the solar system, larger than the planet Mercury. Its surface mixes dark, ancient regions with lighter, grooved terrain formed as the icy crust cracked.

It is the only moon known to have its own magnetic field, detected by the Galileo spacecraft in 1996. In 2015 Hubble observations of its auroras pointed to a salty ocean beneath the ice, possibly holding more water than Earth's oceans.

Ganymede is in a 1:2:4 orbital resonance with Io and Europa. NASA's Juno flew past in 2021, and ESA's JUICE mission, launched in 2023, is set to orbit Ganymede in the 2030s.

What This Quiz Teaches

Space fans and students will enjoy these questions.

How big Ganymede is
What its magnetic field means
How its ocean was detected
Which missions study it
How it relates to other moons

Did You Know?

Ganymede has a very thin oxygen atmosphere.
Its ice crust may be about 150 km thick.
The Galilean moons can be seen with binoculars.
Ganymede orbits Jupiter in about seven days.
Gilgamesh is a large impact basin on Ganymede.