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Difficulty: EasyIdentifying Underlying Assumptions and Premises

Heat Source of Enceladus

Saturn's moon Enceladus has a liquid water ocean beneath its icy outer crust. Because Enceladus is far from the Sun, it receives very little solar energy. Two scientists discuss the primary source of the thermal energy that keeps this subsurface ocean liquid.

Scientist 1
The subsurface ocean is kept warm primarily by tidal heating. As Enceladus orbits Saturn in an elliptical path, the gravitational pull of Saturn and the neighboring moon Dione varies, causing Enceladus to repeatedly stretch and compress. This continuous deformation generates friction within the moon's interior, converting orbital energy into heat. This tidal heating is sufficient to prevent the ocean from freezing.

Scientist 2
The subsurface ocean is kept warm primarily by radiogenic heating (decay of radioactive elements). Enceladus's rocky core contains radioactive isotopes such as uranium, thorium, and potassium. The decay of these isotopes releases a steady supply of heat that warms the core and the ocean above it. Tidal forces are far too weak to generate the amount of heat required to maintain a liquid ocean over billions of years.

Both Scientist 1 and Scientist 2 share which of the following underlying assumptions?

  1. A
    Tidal forces are too weak to maintain a liquid ocean over billions of years.
  2. Enceladus must have an active internal source of heat to prevent its subsurface ocean from freezing.Answer
  3. C
    Radioactive isotopes are present in the core of all of Saturn's moons.
  4. D
    The surface temperature of Enceladus is warm enough to keep water liquid without internal heating.

Answer

Enceladus must have an active internal source of heat to prevent its subsurface ocean from freezing.
The correct answer is correct because both scientists are attempting to explain how a subsurface ocean remains liquid beneath an icy crust. They both assume that an internal thermal energy source is required to prevent the water from freezing in the cold environment of the outer solar system.

Step-by-Step Solution

1
Analyze the viewpoints of both scientists.
Scientist 1 attributes the liquid ocean to tidal heating. Scientist 2 attributes the liquid ocean to radiogenic heating.
To find a shared assumption, we must understand the core arguments proposed by both sides.
2
Identify what both viewpoints assume to be true implicitly.
Both scientists assume that without some form of internal heating (either tidal or radiogenic), the subsurface liquid ocean would freeze due to the lack of sufficient solar energy in the outer solar system.
An underlying assumption is an unstated premise required for the arguments to be logical and necessary.

Key Concept

Identifying shared underlying assumptions in scientific viewpoints.
Estimated Time:1m 0s
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Topics

Identifying Underlying Assumptions and Premises

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