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Difficulty: MediumComparing and Contrasting Models

### Models of the Formation of Saturn's Rings

Saturn's prominent ring system consists primarily of water ice (H2OH_2O) with trace amounts of rocky material and organic compounds. Geochemists and astrophysicists have proposed different models to explain the origin of these rings.

Model 1 (Tidal Disruption Model)
According to this model, about 100100 million years ago, a mid-sized, icy satellite (moon) with a rocky core migrated inward toward Saturn due to orbital resonances. As the satellite crossed Saturn's Roche limit (approximately 140,000 km140,000\text{ km} from the center of Saturn), Saturn's gravitational tidal forces overcame the satellite's self-gravity. The outer icy mantle of the satellite was stripped away and spread into a disk, while the denser rocky core spiraled into Saturn. This model predicts that the rings are relatively young (less than 100100 million years old) and consist of highly pure ice because the rocky core was segregated and lost.

Model 2 (Collisional Shattering Model)
According to this model, Saturn's rings are ancient structures formed over 44 billion years ago during the Late Heavy Bombardment. A population of large, organic-rich comets from the outer solar system was gravitationally pulled toward Saturn. Several of these comets collided at high velocities with pre-existing inner moons of Saturn. The energy of these impacts shattered both the comets and the moons, distributing the fragments into orbit. Because comets and ancient moons contain significant amounts of rocky silicates and complex organic compounds, the primordial ring material originally had a higher concentration of non-ice components, which have since been slowly eroded by micrometeorite bombardment.

Based on the models presented, match each physical description or formation scenario of Saturn's rings to the correct model or models.

  • The rings are relatively young, having formed approximately 100100 million years ago.Model 1 only
  • The ring material resulted from the destruction of at least one pre-existing satellite.Both Model 1 and Model 2
  • The initial ring material contained a high proportion of organic compounds and silicates.Model 2 only
  • The rings were formed by the direct gravitational capture of gas from the solar nebula.Neither Model 1 nor Model 2

Answer

The statement regarding the 100100 million-year age matches Model 1 only. The statement regarding the destruction of a satellite matches Both Model 1 and Model 2. The statement regarding initial organic and silicate content matches Model 2 only. The statement regarding gas capture from the solar nebula matches Neither Model 1 nor Model 2.
The correct matches are determined by carefully comparing the claims in each model: the young age (100100 million years) is unique to Model 1; the involvement of satellite destruction is shared by both models; the high initial concentration of organics and silicates is unique to Model 2; and the solar nebula gas capture theory is not supported by either model.

Step-by-Step Solution

1
Analyze the claims of Model 1 and Model 2 regarding the age of Saturn's rings.
Model 1 claims the rings are about 100100 million years old, while Model 2 claims they are over 44 billion years old. Therefore, the young age matches Model 1 only.
To associate the age statement with the correct model based on the text.
2
Analyze the mechanisms of satellite destruction in both models.
Model 1 describes tidal disruption of a satellite, while Model 2 describes collisional shattering of comets and pre-existing moons. Thus, both models involve the destruction of a pre-existing satellite.
To determine if satellite destruction is common to one, both, or neither model.
3
Examine the predicted initial composition of the ring material.
Model 1 predicts the rings consist of highly pure ice because the rocky core was lost. Model 2 states the initial material had a high concentration of organic compounds and silicates. Thus, the presence of organics and silicates matches Model 2 only.
To link the chemical composition to the correct model.
4
Evaluate the gas capture claim against both models.
Neither Model 1 nor Model 2 references gas capture from the solar nebula as a ring formation mechanism; both rely on solid body destruction. Thus, this matches Neither Model 1 nor Model 2.
To classify the remaining theoretical mechanism.

Key Concept

Comparing and Contrasting Models
Estimated Time:2m 0s
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Topics

Comparing and Contrasting Models

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