Astronomers studying the remote exoplanet Kepler-186f have long debated its atmospheric composition. While early observations suggested a dense shroud of carbon dioxide, recent spectrographic data collected by a space telescope revealed high concentrations of methane and water vapor, alongside a complete absence of detectable carbon dioxide. Because methane is rapidly broken down by the radiation of the host star, Kepler-186, it must be continuously replenished by an active source on the planet’s surface. Which choice most logically completes the text?
- Athe active source on the surface of Kepler-186f is biological in origin.
- some process on the surface of Kepler-186f is actively replenishing the planet's atmospheric methane.Answer
- Cexoplanets orbiting stars like Kepler-186 generally cannot maintain stable atmospheric compositions.
- Dthe atmosphere of Kepler-186f contains more carbon dioxide than it does methane.
Answer
some process on the surface of Kepler-186f is actively replenishing the planet's atmospheric methane.
The correct answer is directly supported by the text. The passage states that because atmospheric methane is rapidly destroyed by radiation, it must be continuously replenished by an active source on the planet's surface. Therefore, it is logical to conclude that some process on the surface is actively replenishing the methane.
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Logical Inferences