Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. The moons of Saturn may have large amounts of ammonia and methane ice, while those of Jupiter do not because (a) methane and ammonia come only from comets that exist in the Oort cloud; (b) Jupiter's strong magnetic field encourages water ice to form; (c) the greater cold at Saturn's distance from the Sun means that ices of ammonia and methane could condense there but not at Jupiter.

Short answer

The best answer is (c) because Saturn is farther from the Sun, allowing ammonia and methane ices to condense.

Step-by-step solution

Understanding the Problem

We need to determine why Saturn's moons contain ammonia and methane ice, whereas Jupiter's do not. The given options explore different reasons, such as comet origins, magnetic fields, and temperature differences.

Analyzing Option (a)

Option (a) suggests that methane and ammonia ice are only sourced from comets in the Oort cloud. However, comets can affect both Jupiter and Saturn; thus, this option does not adequately explain the difference between the moons of the two planets.

Analyzing Option (b)

Option (b) states that Jupiter's strong magnetic field encourages water ice formation. While it's true that Jupiter has a strong magnetic field, this doesn't negate the presence of other ices, like ammonia and methane. Therefore, it isn't sufficient to explain why these ices are absent on Jupiter's moons.

Analyzing Option (c)

Option (c) claims that the greater cold at Saturn's distance allows for the condensation of methane and ammonia ices. This is supported by the fact that further from the Sun, the environment is indeed colder, allowing for more volatile substances like ammonia and methane to condense as ices. This option directly addresses the difference between the moons of Saturn and Jupiter.

Choosing the Best Answer

Based on the analysis, the best explanation is provided by option (c). The colder environment around Saturn compared to Jupiter allows for ammonia and methane to condense and exist as ice on Saturn's moons, unlike on those of Jupiter.

Key concepts

Saturn's moons

Saturn is famous for its stunning rings, but it also boasts a multitude of fascinating moons. These moons vary greatly in size, composition, and characteristics. Titan, one of Saturn's largest moons, even has a dense atmosphere, mainly composed of nitrogen and a small amount of methane.
Saturn's moons are known to contain large amounts of ammonia and methane ice. This unique feature differentiates them from the moons of other planets, especially Jupiter.
These icy compositions play a crucial role in understanding the conditions and processes that form celestial bodies in the outer solar system. Many of Saturn’s moons are intensely studied because they provide clues about the solar system’s early conditions and progression.

Ammonia and methane ices

Ammonia and methane are volatile compounds, meaning they require cold conditions to transition into solid ice. In the cold environment of outer space, especially at great distances from the Sun, these substances can condense into ices.
On Saturn's moons, these ices form due to the lower temperatures compared to other regions of the solar system. The presence of ammonia and methane ices can influence many geological and atmospheric processes, raising questions about the potential for both past and present subsurface oceans.
It's intriguing to note that different moons have varying amounts of these ices, which can lead scientists to ask why some moons are more laden with these ices compared to others. These questions guide researchers in their quest to learn more about the diverse nature of celestial bodies' surfaces and atmospheres in our solar system.

Jupiter's magnetic field

Jupiter, the largest planet in our solar system, is encased by a powerful magnetic field. This field is generated by the rapid rotation of the planet and its metallic hydrogen core.
Jupiter's magnetic field is a prominent feature—it is so strong that it creates intense radiation belts and influences many aspects of the planet's environment and its moons. For example, it plays a role in trapping charged particles and forming spectacular auroras.
While the magnetic field is responsible for many phenomena around Jupiter, it does not specifically deter the presence of ammonia and methane ices on its moons. Instead, the strong magnetic influence is primarily linked to electromagnetic interactions rather than the chemical composition of the moons' surfaces.

Temperature differences in the solar system

The solar system is vast, and a wide range of temperatures can be observed depending on the distance from the Sun. Closer to the Sun, temperatures are higher and gradually decrease as we move outward towards the outer planets.
Temperature differences have a significant impact on the composition of moons and planets. In colder environments, like those around Saturn, volatile substances such as ammonia and methane can condense into ice. These conditions allow Saturn's moons to retain these ices, unlike the relatively warmer moons of Jupiter.
Understanding these temperature gradients allows scientists to hypothesize about the formation and evolution of celestial bodies. It’s clear that the solar system’s temperature profile is a deciding factor in the presence and type of substances found on any given planet or moon.