Logical Reasoning

PT21 · S2 · Q19 Spectroscopic analysis has revealed

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Spectroscopic analysis has revealed the existence of frozen nitrogen, methane, and carbon monoxide on the surface of Pluto.

Conclusion (astronomers concluded)

The components of Pluto's atmosphere, in order of abundance, are 1. Nitrogen 2. CO2 3. Methane

Evidence (since)

We know that nitrogen, methane, and CO2 exist on Pluto in the form of ices. When those ices vaporize, it produces an atmosphere.

The proportion of these gases in Pluto's atmosphere depends directly on how readily the ice vaporizes.

Evaluate

Pretend I said,

What would we be assuming? We'd be assuming that of those three, Jesse is the best dancer, Tyler is 2nd, and Ferguson is 3rd.

Similarly, we were told that the prevalence of gases in Pluto's atmosphere will be based on "how readily the ice vaporizes".

Goal

So if the top 3 gases are concluded to be Nitrogen, CO2, and then methane, then we must be assuming that:

Nitrogen ice vaporizes more readily than CO2 ice, which vaporizes more readily than methane ice.

19.

The astronomers’ argument relies on which one of the following assumptions?

  1. There is no more frozen

    Out of Scope: surface amounts

    The author hasn't committed to any comparisons about the amounts of each element or molecule on the surface of Pluto. And if we negated this and said, "There is more frozen nitrogen ice than there is ice of the other two" that would only seem to strengthen the author's conclusion that nitrogen is the most prevalent.

    25% picked this

  2. Until space probes reach Pluto,

    Too Strong

    Too Strong: impossible Out of Scope: space probes This argument is only about the prevalence of difference gases in Pluto's atmosphere. It has nothing to do with whether we can or can't directly analyze the atmosphere. We can still reach solid conclusions about things even with indirect evidence. The author doesn't need to assume we need direct analysis, and she doesn't need to assume that space probes (which were not even mentioned) are necessary for that end.

    1% picked this

  3. Correct

    There is no frozen substance

    Why this is right

    This looks somewhat appealing, because we were anticipating an assumption about how readily nitrogen vs. CO2 vs. methane vaporize. It's a little unappealing for not mentioning nitrogen, but this is Necessary Assumption, not Sufficient. The answer doesn't have to prove the conclusion. If we negate this answer, would it weaken? Yes. If we said, "Hey, author, there is a frozen substance on Pluto that vaporizes more readily than methane but less readily than CO2", then the author's conclusion would be wrong in saying that methane is ranked #3 in terms of prevalence. This mystery substance would be our new #3, if it vaporizes more readily than methane but less readily than CO2. Since negating this answer weakens the argument, it's a correct answer. When Necessary Assumption answers are ruling out an idea with a word like "no" or "not", take the time to negate it. These answers often will not sound like any sort of idea we've predicted. We're usually only going to see their impact / relevance if we negate them (and they're the easiest type of claim to negate, because we just remove the negative word).

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

    52% picked this

  4. Nitrogen is found in the

    Too Strong: only if

    The author didn't need to assume that for every single planet in the universe, if we find nitrogen in the atmosphere, we find nitrogen ice on the surface. Just because that's true on Pluto doesn't mean the author is assuming it's true for all planets.

    18% picked this

  5. A mixture of nitrogen, carbon

    Out of Scope

    Out of Scope: how Solar System formed This argument isn't positing any claims about the relationship of Pluto's top 3 atmospheric gases to the component substances that formed the Solar System.

    3% picked this

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