Two models are proposed to explain the heat source maintaining the liquid water ocean bene… — ACT

Two models are proposed to explain the heat source maintaining the liquid water ocean beneath the icy crust of Saturn's moon, Enceladus.

Tidal Heating Model
Orbital resonance with other moons causes gravitational tidal flexing of Enceladus's rocky core. This flexing generates significant frictional heat concentrated in the core, maintaining core temperatures above $1000^\circ\text{C}$ and driving high-temperature hydrothermal activity at the core-ocean boundary.

Radioactive Decay Model
The primary heat source is the decay of radioactive isotopes within the core. This decay produces a low-intensity, uniform heat flux. Because radioactive isotopes have decayed over billions of years, current core temperatures are predicted to be low, not exceeding $200^\circ\text{C}$ .

Spacecraft measurements detect silica ( $SiO_2$ ) nanoparticles in the plumes erupting from Enceladus's south polar fractures. Laboratory experiments demonstrate that these nanoparticles can only form when liquid water interacts with rock at temperatures of at least $800^\circ\text{C}$ .

Which of the following statements best describes how this finding relates to the two models?

It supports the Tidal Heating Model and contradicts the Radioactive Decay Model, because the required formation temperature for silica nanoparticles is within the range predicted by the Tidal Heating Model but exceeds the limit predicted by the Radioactive Decay Model.Answer
B
It contradicts the Tidal Heating Model and supports the Radioactive Decay Model, because the presence of silica nanoparticles indicates that Enceladus has a cold core below $200^\circ\text{C}$ .
C
It contradicts both models, because the formation temperature of $800^\circ\text{C}$ is incompatible with both the high temperatures of the Tidal Heating Model and the low temperatures of the Radioactive Decay Model.
D
It supports both models, because both tidal flexing and radioactive decay are expected to produce core temperatures high enough to facilitate the chemical reactions that form silica nanoparticles.

Answer

The finding supports the Tidal Heating Model and contradicts the Radioactive Decay Model, because the required formation temperature for silica nanoparticles is within the range predicted by the Tidal Heating Model but exceeds the limit predicted by the Radioactive Decay Model.

The space probe detected silica nanoparticles, which require temperatures of at least

800^\circ\text{C}

to form. The Tidal Heating Model predicts core temperatures above

1000^\circ\text{C}

, which can easily support the formation of these nanoparticles. The Radioactive Decay Model predicts that current core temperatures do not exceed

200^\circ\text{C}

, which directly contradicts the requirement of

800^\circ\text{C}

. Therefore, the finding supports the Tidal Heating Model and contradicts the Radioactive Decay Model.

Step-by-Step Solution

Identify the minimum temperature required to form the detected silica nanoparticles.

The nanoparticles require a water-rock interaction temperature of at least

800^\circ\text{C}

This sets the temperature constraint that the proposed models must satisfy to be supported by the new finding.

Compare this temperature constraint with the predictions of the Tidal Heating Model.

The Tidal Heating Model predicts core temperatures above

1000^\circ\text{C}

. Since

1000^\circ\text{C} > 800^\circ\text{C}

, the model supports the finding.

To determine whether the model is consistent with the temperature condition.

Compare the temperature constraint with the predictions of the Radioactive Decay Model.

The Radioactive Decay Model predicts core temperatures not exceeding

200^\circ\text{C}

. Since

200^\circ\text{C} < 800^\circ\text{C}

, the model contradicts the finding.

To evaluate the validity of the second model under the new experimental constraints.

Key Concept

Assessing Model Support and Contradiction

Estimated Time:1m 0s

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