Question 1

Which planet has the biggest moon relative to its own size? Not the biggest moon in terms of kilometers, but the biggest as a percentage of the size of the planet it orbits.

Accepted Answer

Pluto has the largest moon, Charon, relative to its own size. Charon is about half the size of Pluto, making this moon-planet ratio the largest among all known planets and dwarf planets in the solar system.

Question 2

The four large moons of Jupiter were first discovered by:

Accepted Answer

The four large moons of Jupiter (Io, Europa, Ganymede, and Callisto) were first discovered by Galileo Galilei in 1610 using his early telescope.

Question 3

What evidence can you give that shows the surface of Jupiter's moon Europa must be relatively young?

Accepted Answer

If Europa's surface were as old as the surfaces of Callisto and Ganymede, it would have a similar number of impact craters. However, Europa has very few craters, suggesting that its surface is relatively young. This is likely due to ongoing geological activity, such as the eruption of new material from beneath the icy crust.

Question 4

When astronomers say that Ganymede is a differentiated body, they mean that it:

Accepted Answer

When astronomers say that a body is "differentiated," it means that it has distinct layers of different materials. Ganymede is known to have a core made of rock and metal, surrounded by a mantle made of water ice, and then a crust made of solid ice. This is different from an undifferentiated body like a comet or some asteroids, which don't have different layers.

Question 5

The largest satellite (moon) in the solar system is:

Accepted Answer

Ganymede is the largest satellite in the solar system, with a diameter of 5,268 km. It is a moon of Jupiter and is even larger than the planet Mercury.

Question 6

The Galileo spacecraft measured that the moon Ganymede had a magnetic field, indicating that its interior was at least partly melted and warm. What do scientists think is the most likely reason for this?

Accepted Answer

Scientists believe that the most likely reason for the partially molten interior of Ganymede and the presence of its magnetic field is tidal heating caused by the gravitational pull of Jupiter. As Ganymede orbits Jupiter, its shape changes slightly due to the gravitational forces exerted on it, causing friction in its mantle and core and heating up its interior.

Question 7

The lakes found in the north polar region of Titan are filled with liquid

Accepted Answer

The lakes found in the north polar region of Titan are filled with liquid methane.

Question 8

Which of the jovian planets does NOT have any satellites?

Accepted Answer

All the Jovian planets (Jupiter, Saturn, Uranus, and Neptune) have satellites orbiting them, with varying numbers and sizes of moons.

Question 9

Callisto, the fourth moon of Jupiter's, takes 17 days to orbit Jupiter. If I stand on the surface of Callisto and see Jupiter high in the sky over my head, and then wait 8.5 Earth days in the same spot, where will I see Jupiter?

Accepted Answer

Since Callisto is tidally locked to Jupiter, it always shows the same face to the planet. This means that if you see Jupiter directly overhead, it will remain in that position relative to your location on Callisto's surface, regardless of how much time passes.

Question 10

Which of the following is NOT a way that the moon Titan probably resembles the Earth?

Accepted Answer

While all of the other answer choices describe ways that Titan is similar to Earth, option E is the only answer choice that describes a difference between Titan and Earth. At the surface of Titan, the temperature and pressure are not conducive to liquid water existing, so it cannot exist in all three phases like on Earth.

Question 11

The satellite which has the thickest atmosphere (so thick that it's quite a surprise for a satellite) is:

Accepted Answer

Titan, the largest moon of Saturn, has a thick atmosphere mainly composed of nitrogen and methane. Its atmosphere is about four times denser than Earth's atmosphere.

Question 12

The world in the solar system that is most active volcanically is:

Accepted Answer

Io, one of Jupiter's moons, is the most volcanically active world in the solar system. It has over 400 active volcanoes and constant volcanic eruptions due to the tidal forces from Jupiter and its neighboring moons.

Question 13

What do astronomers think is the origin of the many irregular moons around the outer planets (irregular meaning they are orbiting backwards and/or have eccentric orbits)?

Accepted Answer

Astronomers believe that the many irregular moons around the outer planets were likely formed elsewhere in the Solar System and were later captured by the gravitational pull of the giant planets. This theory is supported by the irregular moons' backwards and eccentric orbits, which suggest that they did not form in situ around the planets.

Question 14

Which element plays the same role on Titan as water does on Earth (existing as gas, liquid, and solid)?

Accepted Answer

Methane on Titan plays the same role as water on Earth, existing in its three states: gas, liquid, and solid. Methane makes up the lakes and rivers on Titan's surface, evaporates to form clouds, and falls as rain or snow.

Question 15

For a while, after the space age began, astronomers did not know what the surface of Titan looks like, but today they do. Which of the following was NOT a method by which astronomers have learned about the surface of Titan?

Accepted Answer

The Hubble Space Telescope has not taken a photo of the surface of Titan. It is not capable of doing so because it is an optical telescope and cannot penetrate the thick smog in Titan's atmosphere. The other four methods have all been used to learn about the surface of Titan.

Question 16

What features are abundant on Callisto and Ganymede and almost absent on Europa and Io?

Accepted Answer

Impact craters are abundant on Callisto and Ganymede, indicating older, less geologically active surfaces, while Europa and Io show fewer craters due to their more active surfaces.

Question 17

What is the cause of its many volcanic/geyser-like eruptions on the moon Io?

Accepted Answer

The gravitational stress of being so close to Jupiter and its other large moons causes tidal forces that heat Io's interior and create its many volcanic and geyser-like eruptions.

Question 18

The majority of the moons orbiting the outer (jovian) planets are:

Accepted Answer

The majority of the moons orbiting the outer (jovian) planets are small moons orbiting in a retrograde direction (opposite to the direction their planet turns and orbits).

Question 19

The satellite whose surface is characterized by a smooth icy crust with a complex network of cracks is:

Accepted Answer

Europa's surface has a smooth icy crust with a complex network of cracks, which is believed to be a result of the tidal forces exerted by Jupiter on the moon. Callisto has a heavily cratered surface with some areas of tectonic activity, Triton has a varied surface with features such as nitrogen geysers and icy volcanic pits, Io has a highly volcanic surface, and Ganymede has a mix of cratered and grooved terrain.

Question 20

Which of the following is NOT one of the largest moons in the Solar System?

Accepted Answer

While Atlas is a moon near Saturn, it is not one of the largest moons in the Solar System. The other choices (Titan, Triton, Ganymede, and Earth's Moon) are all among the largest moons in the Solar System.

Quiz 12: Rings, Moons, and Pluto