Deck 9: Life on Jovian Moons

Question 1

The first Jovian moons were discovered by

A) Galileo
B) Tycho
C) Huygens
D) Cassini

Answer 1

Galileo

Question 2

Most of the smallest Jovian moons are most likely

A) captured asteroids and comets
B) captured objects from outside the solar system
C) small clumps of gas left over from the formation of the host planet
D) fragments of other moons

Answer 2

captured asteroids and comets

Question 3

The fact that the strength of gravity decreases with distance means the force of gravity exerted by one object on another (e.g., the Earth and Moon) is greater on the near side than the far side. This effect is commonly referred to as a

A) tidal force
B) differential force
C) distortive force
D) tractive force

Answer 3

tidal force

Question 4

The fact that many of the larger Jovian moons orbit nearly in the equatorial plane of their host world, moving in the same direction as their planet's spin, suggest that they

A) formed from a rotating disk of gas and dust like a miniature solar system
B) were spun out from the rapidly spinning host world as it formed
C) formed elsewhere in the solar system and were later captured
D) were formed from a giant impact between the host world and another body

Question 5

Like our own moon, many Jovian moons exhibit what is called synchronous rotation. This means that they rotate at the same rate

A) that their host planet rotates
B) as all other moons around the host planet
C) that the host planet orbits about the Sun
D) that they orbit their host planet

Question 6

What is the ratio of the tidal force in Newtons that Jupiter exerts on a 1 kg rock on Io to the force of the Io's own gravity on the same rock? (Useful data: M_Jupiter = 1.899 × 10²⁷ kilograms, r_Io = 3.642 × 10⁶ meters, the average Jupiter-Io distance is 4.216 × 10⁸ meters, and M_Io = 8.932 × 10²² kilograms)

A) 18.0
B) 32.5
C) 12.1
D) 99.6

Question 7

Which feature seen on Saturn's moon Iapetus suggests that its interior must have been warm at some time in the past?

A) the presence of several large impact features
B) the fact that one half is very bright while the other half is very dark
C) the observation of extinct volcanoes on its surface
D) the presence of a steep ridge running along its equator

Question 8

Jovian moons are typically made of

A) solid ice
B) ice and rock
C) rock and iron
D) solid rock

Question 9

If Ganymede orbits Jupiter every 7.16 days and the orbital periods of Ganymede, Europa, and Io are in a 1:2:4 resonance, what is the orbital period of Io?

A) 3.58 days
B) 1.79 days
C) 28.6 days
D) 14.3 days

Question 10

Compared to the moons of Jupiter, the moons of Saturn, Uranus, and Neptune

A) contain a higher proportion of rock
B) are made of pure ice
C) contain a higher proportion of ice
D) are made of pure rock

Question 11

Even though Jupiter's moon Io is similar in size to our geologically dead Moon, it is more geologically active than the Earth. How can this be?

A) because Io orbits very close to Jupiter, it still has a lot of heat trapped inside from its formation
B) Io is tidally heated by tidal forces exerted by the outer Galilean moons, which flex and distort its interior
C) Io has much more radioactive decay occurring inside it than does the Earth
D) Io is tidally heated due to its elliptical orbit, which causes the large tidal forces exerted by Jupiter to constantly change, flexing and distorting its interior

Question 12

Compared to the moons of Jupiter, the moons of Saturn, Uranus, and Neptune

A) contain not only water ice but also methane and other ices
B) are made of pure methane ice
C) contain less methane ice and more water ice
D) are made of pure rock

Question 13

Much of Europa's surface appears chaotic and clogged with huge iceberg-like blocks. This is consistent with

A) a thin icy crust that has been broken into pieces by tidal forces below which is a subsurface ocean of water
B) the surface thawing due to heat emitted by Jupiter
C) the breaking up of the surface due to plate tectonics
D) a giant impact that has recently shattered the crust into pieces

Question 14

The lack of large impact craters on the surface of Europa is consistent with

A) active volcanism that is constantly resurfacing the crust
B) the surface being covered with an ocean of liquid water
C) the crust being so thick and hard that impacts leave no marks on the surface
D) a subsurface ocean of water because large impacts will break the thin crust causing water and slushy ice below to flood out and resurface the crust

Question 15

Perhaps the MOST convincing piece of evidence suggesting that Europa has a subsurface ocean is the

A) fact that the magnetic field of Jupiter is able to induce a magnetic field in Europa consistent with a salty ocean beneath its crust
B) fact that calculations suggest that there is enough internal heat to keep the ice melted beneath the crust
C) lack of impact craters on its surface
D) observation of iceberg-like features on its surface

Question 16

The largest Jovian moon that appears to have been captured is

A) Titania, the moon of Uranus
B) Io, the moon of Jupiter
C) Triton, the moon of Neptune
D) Titan, the moon of Saturn

Question 17

Io experiences strong internal tidal heating because of

A) large amounts of radioactive decay occurring inside the moon
B) the large amount of internal heat left over from its formation
C) the strong tidal forces exerted by the outer Galilean moons, Europa, Ganymede, and Callisto
D) the strong tidal force from the massive Jupiter combined with its elliptical orbit which causes the strength and direction of the force to constantly change

Question 18

Which of the following best describes the internal structure of Europa?

A) thin icy crust, subsurface ocean of water, thick iron mantle, central rocky core
B) thin icy crust, subsurface ocean of water, thick rocky mantle, central iron core
C) thin icy crust, thick rocky mantle, central iron core
D) surface ocean of water, thick rocky mantle, central iron core

Question 19

The largest Jovian moon Ganymede and Titan are

A) larger than the Earth
B) larger than Mercury but smaller than the Earth
C) larger than the Moon but smaller than Mercury
D) about the same size as Mars

Question 20

Io has an elliptical orbit because

A) of its rapid rotation
B) of its synchronous rotation
C) of the strong gravitational influence of Jupiter
D) of orbital resonances with Europa and Ganymede

Question 21

Which of the following is the most convincing observation that suggests that like Europa, Ganymede may also have a subsurface ocean?

A) the detection of salts on the surface that may have been brought up from below the crust
B) the presence of young grooved terrain that may be the result of cryovolcanism
C) the fact that it is the largest moon in the solar system and, hence, should have plenty of internal heat to maintain liquid water beneath its surface
D) in addition to its internal magnetic field, Ganymede has a magnetic field induced by Jupiter which is consistent with a salty ocean beneath its crust

Question 22

In the subsurface ocean beneath Europa's icy crust, if life exists, it most likely originated

A) close to volcanic vents on its ocean floor
B) on the surface and then migrated down into the ocean
C) just below the surface of its thin icy crust where sunlight is still able to penetrate
D) via panspermia from impacts

Question 23

Life in the subsurface ocean of Europa will most likely consist of

A) creatures similar to seals and penguins which enter the ocean through holes in the icy crust
B) plants on the ocean floor
C) simple single-celled organisms
D) fish and other complex aquatic organisms

Question 24

The complexity of any life present in Europa's subsurface ocean is mainly limited by the

A) amount of water in the ocean
B) amount of available energy to sustain it
C) average temperature of the water
D) amount of organic material present

Question 25

What is believed to have been the main source of Titan's atmosphere?

A) outgassing from the interior
B) gas captured from the solar nebula
C) we have no idea
D) comet impacts

Question 26

Europa's subsurface ocean, if it indeed exists,

A) could be more than ten times deeper than the deepest ocean trenches on Earth
B) should be of similar depth to the deepest ocean trenches on Earth
C) should be of similar depth to the shallowest oceans on Earth
D) could be more than a hundred times deeper than the deepest ocean trenches on Earth

Question 27

How is Titan, the moon of Saturn, similar to the Earth?

A) like the Earth, Titan has an atmosphere made mostly of molecular nitrogen
B) Titan, like the Earth, has an internal magnetic field
C) like the Earth, Titan has oceans of liquid water on its surface
D) Titan is almost the same size as the Earth

Question 28

Titan is roughly the same size as Mercury, yet Titan has an atmosphere while Mercury does not. How can this be?

A) Although Titan is roughly the same size as Mercury, it is much denser, making its gravitational field stronger
B) Unlike Mercury, Titan is constantly being bombarded by icy comets that evaporate and maintain its atmosphere
C) On its surface, Titan has volcanism that is constantly replenishing its atmosphere while Mercury does not
D) Even though Titan's gravity is weak, it is much colder, allowing molecules to be trapped in its atmosphere

Question 29

Current models suggest that if Europa does indeed have a subsurface ocean, it

A) could contain roughly a hundred times as much water as all of Earth's oceans combined
B) could contain roughly twice as much water as all of Earth's oceans combined
C) should contain roughly half as much water as all of Earth's oceans combined
D) should contain much less water than all the Earth's oceans combined

Question 30

In addition to being the largest moon in the solar system, Ganymede, the Galilean moon of Jupiter, is

A) the only moon to have its own internal magnetic field
B) the only moon to have its own atmosphere
C) more geologically active than the Earth
D) the only moon to show evidence for a subsurface ocean of water

Question 31

What is the origin of the nitrogen in Titan's atmosphere?

A) gas captured from the solar nebula
B) breakdown of ammonia (NH₃) by ultraviolet light from the Sun
C) outgassing from Titan's interior
D) impacts from comets

Question 32

The probability of finding life in any subsurface ocean beneath the surface of Ganymede is much lower than for Europa because

A) its icy crust will be much thicker, making it much more difficult for nutrients to be transported from the surface
B) it does not have a rock/water boundary at its ocean bottom
C) there is less tidal heating
D) of all of these

Question 33

Which Galilean moons of Jupiter show evidence for subsurface oceans of water beneath their icy crusts?

A) Europa and Ganymede
B) all four show evidence for subsurface oceans
C) Europa
D) Europa, Ganymede, and Callisto

Question 34

During its descent into Titan's atmosphere, the Huygens probe found

A) large oceans of liquid methane covering the entire surface
B) small pools of liquids directly beneath its descent path
C) a completely smooth, frozen surface with no sign that any liquids had ever been present
D) no sign of flowing or pooled liquids currently on the surface although channels carved in the past by fluids were seen

Question 35

In addition to nitrogen, the other main components of Titan's atmosphere are

A) ammonia and water vapor
B) hydrogen and helium
C) oxygen and carbon dioxide
D) hydrocarbons like methane and ethane

Question 36

Life beneath the surface of Europa would most likely obtain energy from

A) the Sun
B) Jupiter
C) radioactivity
D) tidal heating

Question 37

Methane should be rapidly destroyed in Titan's atmosphere, yet it is still present in appreciable amounts. How can this be?

A) on the surface of Titan live cows that are constantly producing methane gas
B) larger hydrocarbons like ethane and propane are being broken down by ultraviolet light into methane
C) methane may be continually evaporating from the surface and the interior
D) comet impacts are constantly supplying the atmosphere with fresh methane

Question 38

A probe placed in orbit about Europa would be able to confirm the presence of a subsurface ocean using a

A) spectrometer to detect the spectral signature of liquid water at and beneath the surface
B) camera to observe the formation and breakup of icebergs on the surface
C) projectile to break the thin icy crust to reveal the water below
D) laser altimeter to detect the regular bulging of the thin icy crust on top of the ocean due to tidal forces

Question 39

In addition to being the second-largest moon in the solar system, Saturn's moon Titan, is

A) the only moon to have its own internal magnetic field
B) the only moon to have its own atmosphere
C) more geologically active than the Earth
D) the only moon to show evidence for a subsurface ocean of water

Question 40

Which of the four Galilean moons is least likely to harbor life beneath its surface?

A) Europa
B) Io
C) Callisto
D) Ganymede

Question 41

In chemistry, reduction occurs when a substance

A) accepts electrons
B) loses electrons
C) rearranges its electrons internally
D) breaks into its constituent atoms

Question 42

Neptune's moon Triton

A) rotates in the opposite direction to Neptune's rotation
B) orbits in the opposite direction to Neptune's rotation
C) orbits about Neptune's rotational axes
D) orbits in the same direction to Neptune's rotation

Question 43

Which of the following has the Cassini orbiter observed on the surface of Saturn's moon Titan?

A) no evidence for any liquid hydrocarbons at all
B) oceans of methane and ethane covering much of the surface
C) lakes of hydrocarbons in the north polar regions
D) small pools of hydrocarbons close to the equator

Question 44

Chemical disequilibrium inevitably exists near deep-sea volcanic vents, because

A) there are unequal concentrations of minerals and water
B) the high-temperature vent water causes water molecules to break down into hydrogen and oxygen
C) mixing between the high-temperature vent water and the surrounding low-temperature ocean water creates conditions in which minerals and water will undergo chemical reactions
D) the high pressures existing at the ocean floor cause chemical reactions between minerals and water

Question 45

Saturn's icy moon Enceladus

A) has an ancient, heavily cratered surface reminiscent of the Moon
B) is small and irregular in shape like an asteroid
C) has a smooth, icy surface criss-crossed with dark cracks
D) has fountains of ice particles and water vapor spraying out from its surface

Question 46

From a chemical energy standpoint, the basic requirement for life is a situation in which chemicals naturally exist in a state of

A) instability
B) disequilibrium
C) equilibrium
D) stability

Question 47

In chemistry, oxidation occurs when a substance

A) loses electrons
B) rearranges its electrons internally
C) accepts electrons
D) breaks into its constituent atoms

Question 48

Triton's source of internal heat is mostly associated with

A) tidal heat associated with its elliptical orbit around Neptune
B) tidal heat left over from it being captured into orbit around Neptune
C) radioactive decay
D) heat left over from its formation

Question 49

When the Huygens probe touched down on Titan, it landed

A) in a vast ocean of liquid methane
B) on a solid surface of frozen water and methane ices that resembled a streambed
C) in a shallow pool of liquid methane
D) on the slopes of an icy volcano covered with water and methane ice

Question 50

On Saturn's moon Enceladus, fountains of ice particles and water vapor are seen to be spraying out of

A) cryovolcanoes close to the equator
B) tiger stripe regions close to the south pole
C) tectonic plate boundaries
D) young impact craters near the north pole

Question 51

Most of the key energy-generating chemical reactions used by life on Earth are

A) rearrangement reactions
B) redox reactions
C) decomposition reactions
D) combination reactions

Question 52

If Triton has a subsurface ocean, it will most likely consist of

A) water mixed with ammonia, methane, or other melted ices
B) liquid nitrogen
C) liquid ammonia and methane
D) liquid water

Question 53

Even though Titan has liquid methane on its surface, some internal heat, and plenty of carbon-containing compounds, it is not a suitable place for life because

A) Titan orbits within Saturn's radiation belt so its surface is completely sterilized by high-energy particles
B) there is too much volcanic activity on the surface
C) it has no ozone layer to protect the surface from harmful UV rays from the Sun
D) it is far too cold, and methane is not a very good biological solvent

Question 54

Triton's retrograde orbit is consistent with it having

A) been spun out from a rapidly rotating Neptune
B) been captured by Neptune's gravity
C) undergone a massive impact
D) formed from a rotating disk of gas and dust around Neptune