PrepTest 138, Section 2, Question 3
Scientist: Venus contains a hot molten core, like(45 more words not shown)
Which one of the following,(14 more words not shown)
- ARock on the(14 more words not shown)
- BThe surface of(12 more words not shown)
- CThe interior of(11 more words not shown)
- DThough Venus lacks(14 more words not shown)
- EThe atmosphere of(8 more words not shown)
Reading the argument
Venus needs another way to get the heat out.
We're told that its core generates excess heat and that Venus must expel that heat. Earth releases its excess heat through active volcanoes and fissures created by separating tectonic plates. Venus lacks those outlets. That rules out Earth's explanation for Venus; it doesn't rule out every possible explanation.
What we’re looking for
The question asks us to resolve the apparent discrepancy. I want a different mechanism by which heat can escape from Venus. I don't know what that mechanism will be, and I don't need to guess the geology. I just need an answer that gets the internally generated heat out despite the absence of volcanoes and those fissures.
Working the answers
- A
A higher melting point tells us when surface rock would become liquid. It doesn't tell us how heat leaves the planet. The rock could remain solid while heat escaped, or remain solid while trapping it; A never supplies the needed connection.
- BCorrect
The heat can radiate through Venus's relatively thin surface and into space. That's the other route we needed. Venus can lack Earth's heat-releasing volcanoes and fissures and still expel its internally generated heat through its surface.
- C
Temperature fluctuations tell us that the interior becomes hotter and cooler. They don't explain how the heat escapes. Even if those fluctuations are greater than Earth's, we still need a route from the interior to the outside.
- D
Surface movement sounds promising because Earth's explanation also involves movement. But the important part isn't movement by itself; it's movement that creates an outlet for heat. D explicitly leaves Venus without the heat-diffusing fissures and never says that its other surface movement releases heat. We'd have to add that connection ourselves, while B supplies an escape mechanism directly.
- E
A hotter atmosphere isn't an explanation of how heat gets out of the core. We would still need to know how internally generated heat reaches the atmosphere or escapes beyond it. Comparing atmospheric temperatures leaves that missing step unanswered.
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