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Difficulty: EasyIdentifying Underlying Assumptions and Premises

Scientist 1: The channels on Mars were formed by flowing liquid water. Liquid water requires a surface temperature above 0∘C0^\circ\text{C} and an atmospheric pressure high enough to prevent boiling. In Mars' early history, a thick carbon dioxide greenhouse atmosphere warmed the planet, allowing liquid water to exist on the surface and carve the channels.

Scientist 2: The channels on Mars were formed by flowing liquid carbon dioxide (CO2\text{CO}_2). Liquid CO2\text{CO}_2 can exist at temperatures well below 0∘C0^\circ\text{C} under moderate pressure. Early Mars was cold and dry, with a thin atmosphere. Under these cold conditions, subsurface liquid CO2\text{CO}_2 erupted and carved the channels before evaporating.

Based on the hypothesis of Scientist 1, which of the following is an underlying assumption regarding liquid water on early Mars?

  1. Liquid water has the physical capacity to erode surface material and carve channels.Answer
  2. B
    Liquid water can only exist on Mars if liquid carbon dioxide is also present on the surface.
  3. C
    Liquid water is incapable of boiling at temperatures below 0∘C0^\circ\text{C}.
  4. D
    Liquid water could only exist on Mars if the planet was closer to the Sun in the past.

Answer

Liquid water has the physical capacity to erode surface material and carve channels.
The correct option correctly identifies the foundational premise of Scientist 1's argument. Since Scientist 1 claims that flowing liquid water carved the channels, the scientist must assume that liquid water has the physical capacity to erode surface material and form these channels. Without this assumption, the hypothesis would not be viable.

Step-by-Step Solution

1
Identify the core claim of Scientist 1.
Scientist 1 claims that flowing liquid water carved the channels on Mars.
This establishes the causal agent (liquid water) for the observed geological features (channels).
2
Determine what must be implicitly true for this claim to hold.
In order for liquid water to carve channels, it must have the physical ability to erode the rock and soil on Mars' surface.
If water could not erode surface materials, it could not form channels, rendering the hypothesis impossible.

Key Concept

Identifying underlying assumptions behind a scientific hypothesis
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Topics

Identifying Underlying Assumptions and Premises

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