Logical Reasoning

PT141 · S4 · Q13 In early 2003, scientists detected

A free, expert breakdown of this official LSAT Logical Reasoning question.

  • Save & drill this skill — build targeted practice sets from questions like this one

  • Video walkthroughs — watch every question solved step by step

  • 81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

In early 2003, scientists detected methane in the atmosphere of Mars.

Conclusion

Any methane in the Martian atmosphere must have been released relatively recently.

Evidence

Methane falls apart when it's hit by UV radiation from sunlight.

Evaluate

This argument makes sense, as long as UV radiation is constantly hitting the methane on Mars. Since UV breaks it apart into its constituent atoms, a methane compound's lifespan is only as long as it takes to get hit by UV radiation.

Missing Link: if Martian atmosphere → continually hit by UV

The whole argument is thinking 1. when you're in Martian atmosphere, you're continually hit by UV. 2. methane dies whenever its hit by UV. infer: methane in the Martian atmosphere is constantly dying. conc: any methane you find is near the beginning of its very short life span (cuz all this methane's gonna get zapped by UV in no time).

If a linking answer doesn't occur to us, we should be looking for an Objection.

GIVEN THAT methane falls apart whenever it's hit by the Sun's UV, HOW COULD WE ARGUE it's possible to find methane in Mars' atmosphere that was released a really long time ago?

We would just say, that old-ass Martian methane never got hit by the Sun's UV. Maybe this methane was released into some ridged crater that provided permanent shade from the sunlight.

Or maybe there's a "Dark Side of the Mars" that never faces the Sun.

Goal

Since our main way to object is to say, , we can say the author must assume

13.

The argument relies on the assumption that

  1. Mars had no methane in

    Too Strong: nothing prior to 2003

    The author isn't thinking that methane suddenly burst on the scene in 2003. He just thinks that as methane leaks out of Mars, it gets zapped by UV radiation shortly thereafter, which dissolves it into its constituent bits.

    13% picked this

  2. Correct

    all methane in the Martian

    Why this is right

    This actually does resemble our Missing Link: if Martian atmosphere → constantly hit by UV If we negated this, would it Weaken? Sure! "Hey, author, some methane in the Martian atmosphere is never exposed to sunlight. So we might discover methane in the Martian atmosphere that's a million years old. If it was never exposed to sunlight, then we have no reason to think that something made it fall apart."

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

    59% picked this

  3. methane cannot be detected until

    Too Strong: cannot be detected

    The conclusion and evidence are not really about "detection" at all, so there's no reason for the author to assume anything about detection. This answer also sort of offends common sense, like "I couldn't taste the soup until you spilled it on the floor". It should be easier to detect intact methane then crumbling methane, right?

    12% picked this

  4. the methane that scientists had

    Opposite

    Had the methane the scientists detected been exposed to UV, it wouldn't have been methane; it would have just been loose hydrogen and carbon atoms (the building blocks of methane). The author thinks that once methane is exposed to UV, it falls apart (its hydrogen and carbon atoms falls apart into disconnected atoms). So the author is assuming that the methane the scientists detected had not been exposed to UV.

    15% picked this

  5. methane in Earth's atmosphere does

    Trap

    Opposite, if anything Out of Scope: Earth's atmosphere The author would believe that anywhere in the solar system that methane gets hit by the UV radiation in sunlight is a place where methane will fall apart. If we negated this and objected, "Not in Earth's atmosphere, it doesn't!", we wouldn't be weakening this conclusion, which is exclusively about the Martian atmosphere.

    1% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill
LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free