Examkin

Question

Difficulty: MediumComparing and Contrasting Models

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

Saturn possesses an extensive planetary ring system. Planetary scientists have proposed two models to explain the origin and chemical composition of these rings.

Model 1
Approximately 100 million100\text{ million} years ago, a large, icy moon of Saturn migrated too close to the planet, crossing Saturn's Roche limit. The intense tidal forces of Saturn pulled the moon apart. The silicate (rocky) core of the moon sank directly into Saturn's atmosphere, while the outer icy mantle was shattered into millions of fragments, forming the rings. Consequently, the rings are relatively young and consist of nearly 99%99\% pure water ice (H2OH_2O).

Model 2
Around 3.8 billion3.8\text{ billion} years ago, a giant, volatile-rich comet from the outer solar system was gravitationally captured and disrupted by Saturn's tidal forces. This tidal disruption occurred just outside Saturn's Roche limit. The comet was shredded into debris that spread out to form the planetary rings. Because comets contain significant amounts of rocky dust and organic compounds, the rings are ancient and contain a measurable fraction of silicate minerals and carbon-bearing dark matter mixed with water ice (H2OH_2O) throughout their structure.

Based on the descriptions of Model 1 and Model 2, which of the following statements represents a major point of disagreement between the two models regarding the age or composition of Saturn's rings?

  1. A
    Model 1 proposes that the rings formed from a disrupted comet, whereas Model 2 proposes that they formed from a shattered icy moon.
  2. B
    Model 1 proposes that the ring-forming event occurred 3.8 billion3.8\text{ billion} years ago, whereas Model 2 proposes that it occurred 100 million100\text{ million} years ago.
  3. Model 1 proposes that the rings are composed of almost pure water ice, whereas Model 2 proposes that they contain a mix of water ice, rocky minerals, and organic compounds.Answer
  4. D
    Model 1 proposes that the ring-forming material was disrupted outside Saturn's Roche limit, whereas Model 2 proposes that it was pulled apart inside the Roche limit.

Answer

Model 1 proposes that the rings are composed of almost pure water ice, whereas Model 2 proposes that they contain a mix of water ice, rocky minerals, and organic compounds.
The correct answer accurately describes the difference in ring composition between the two models: Model 1 proposes that the rings are nearly 99%99\% pure water ice, whereas Model 2 proposes that the rings contain a mixture of water ice, silicate (rocky) minerals, and organic compounds.

Step-by-Step Solution

1
Analyze Model 1's claims regarding composition.
Model 1 states that the rocky core sank and the outer icy mantle shattered, leaving the rings consisting of nearly 99%99\% pure water ice (H2OH_2O).
To establish the composition baseline for the first model.
2
Analyze Model 2's claims regarding composition.
Model 2 states that the source body was a comet containing rocky dust and organic compounds, resulting in rings that contain silicate minerals and carbon-bearing dark matter mixed with water ice.
To establish the composition baseline for the second model.
3
Compare the claims to identify the point of disagreement.
The two models disagree on whether the rings are almost entirely pure water ice (Model 1) or a mixture containing silicate minerals and organic compounds (Model 2).
To match the identified difference to the correct option.

Key Concept

Comparing and Contrasting Models
Rate this question

Topics

Comparing and Contrasting Models

More questions from this topic