Necessary AssumptionDiff: Medium
Logic Breakdown
Passage Summary: Scientists found methane on Mars, and since sunlight destroys methane quickly, they conclude that the gas must have been put there recently.
Conclusion: The methane detected in the Martian atmosphere must have been put there in the relatively recent past.
Reasoning: Methane is a fragile compound that is destroyed by ultraviolet radiation from sunlight, meaning it cannot persist in the atmosphere for long periods.
Analysis: The argument relies on a gap between the fragility of methane and the timing of its release. For the conclusion to be valid, there must not be some other factor protecting that methane from the UV radiation for a long time. Ask yourself: what if the methane was old but shielded from the sun? A necessary assumption would be that the methane was actually exposed to the radiation that destroys it, or that there isn't some other source of protection.
Conclusion: The methane detected in the Martian atmosphere must have been put there in the relatively recent past.
Reasoning: Methane is a fragile compound that is destroyed by ultraviolet radiation from sunlight, meaning it cannot persist in the atmosphere for long periods.
Analysis: The argument relies on a gap between the fragility of methane and the timing of its release. For the conclusion to be valid, there must not be some other factor protecting that methane from the UV radiation for a long time. Ask yourself: what if the methane was old but shielded from the sun? A necessary assumption would be that the methane was actually exposed to the radiation that destroys it, or that there isn't some other source of protection.
Passage Stimulus
Passage Redacted
Unlock Full Passage13.The argument relies on the assumption that
Correct Answer
B
B is necessary because if all methane in the Martian atmosphere is eventually exposed to sunlight, then old methane would have been broken down. Thus, any methane we observe must be recently released. Negating B (some methane is never exposed to sunlight) makes it possible for ancient methane to persist, undermining the conclusion. Reasoning gap: it assumes no atmospheric methane is permanently shielded from UV.
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