### Titan's Sand Dunes Saturn's moon Titan has extensive fields of linear sand dunes. Scie… — ACT

### Titan's Sand Dunes

Saturn's moon Titan has extensive fields of linear sand dunes. Scientists debate the direction and speed of the winds responsible for forming and shaping these dunes.

Hypothesis 1
The dunes are formed by persistent, gentle easterly winds (blowing from east to west) that dominate Titan's daily global wind patterns. These weak winds, averaging less than $0.3\text{ m/s}$ , gradually transport fine organic sand grains over millions of years.

Hypothesis 2
The dunes are shaped by rare, high-velocity westerly winds (blowing from west to east). These strong winds, exceeding $1.0\text{ m/s}$ , occur only during seasonal equinox storms when methane clouds produce violent downdrafts. These brief but energetic storms are the primary drivers of sand movement.

New Evidence
A space probe analyzed the slope of dune crests across Titan's equatorial regions. The analysis revealed that the steeper slopes of the dunes uniformly face the east, indicating that sand is actively transported from west to east by winds averaging $1.2\text{ m/s}$ .

Based on the new evidence, which of the following statements best describes how Hypothesis 1 and Hypothesis 2 are affected?

It weakens Hypothesis 1 and supports Hypothesis 2.Answer
B
It supports Hypothesis 1 and weakens Hypothesis 2.
C
It supports both Hypothesis 1 and Hypothesis 2.
D
It weakens both Hypothesis 1 and Hypothesis 2.

Answer

The correct answer states that the new evidence weakens Hypothesis 1 and supports Hypothesis 2.

The correct answer is correct because the new evidence indicates that sand is transported from west to east (westerly winds) at an average speed of

1.2\text{ m/s}

. This contradicts Hypothesis 1, which posits wind blowing in the opposite direction (east to west) at a much slower speed (

<0.3\text{ m/s}

), thereby weakening it. Conversely, this supports Hypothesis 2, which predicts wind blowing from west to east at speeds exceeding

1.0\text{ m/s}

Step-by-Step Solution

Identify the key parameters of the new evidence.

The new evidence indicates that sand is transported from west to east by winds averaging

1.2\text{ m/s}

This establishes the factual basis of the new observation to compare against each hypothesis.

Compare the new evidence with Hypothesis 1.

The evidence contradicts and therefore weakens Hypothesis 1.

Hypothesis 1 asserts that winds are easterly (blowing from east to west) and weak (less than

0.3\text{ m/s}

), which is the opposite direction and much slower than the

1.2\text{ m/s}

westerly wind shown by the evidence.

Compare the new evidence with Hypothesis 2.

The evidence aligns with and therefore supports Hypothesis 2.

Hypothesis 2 asserts that winds are westerly (blowing from west to east) and exceed

1.0\text{ m/s}

. The evidence of a

1.2\text{ m/s}

westerly wind fits these criteria perfectly.

Key Concept

Evaluating how new experimental data or observations affect competing scientific hypotheses.

Estimated Time:1m 30s

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