#19 - Spectroscopic analysis has revealed the existence of

[reop6780]

The correct answer is C while I chose A.

When the stimuli concludes, "the components of Pluto's atmosphere are nitrogen, carbon monoxide, and methane," does it imply that no other components make up Pluto's atmosphere?

Is C correct answer because it closes the possibility of any other components of Pluto's atmosphere other than those mentioned?

[KelseyWoods]

Hi reop6780!

You're missing one key component of the conclusion....the author concludes that Pluto's atmosphere consists of nitrogen, carbon monoxide, and methane, in order of decreasing abundance. That means the author is saying that there is more nitrogen than carbon monoxide, and more carbon monoxide than methane.

So, yes, by telling us that there is no frozen substance on Pluto that vaporizes at a rate between methane and carbon monoxide, answer choice (C) closes the possibility that there is another component of Pluto's atmosphere. If you apply the Assumption Negation Technique to answer choice (C) it would become: There IS a frozen substance on Pluto that vaporizes more readily than methane but less readily than carbon monoxide. That would attack the conclusion because it would mean there would have to be another component of Pluto's atmosphere, with an abundance between carbon monoxide and methane.

Hope this helps!

Best,
Kelsey

[LAM]

I thought the correct answer choice was wrong because according to the stimulus, doesn't it say that nitrogen essentially evaporates less readily than carbon monoxide. If the percentage in atmosphere is dependent on how readily the substances evaporate, then wouldn't it follow that given the order of abundance (carbon mon. being in the the middle) that nitrogen evaporates less readily than carbon monoxide?

[Francis O'Rourke]

The conclusion tells us that of the three chemicals listed, Nitrogen is the most abundant, followed by carbon monoxide, and then methane would be least abundant.

The premise also tells us that abundance in atmosphere directly correlates to rates of vaporization, the more quickly something vaporizes, the more of that chemical there will be in the atmosphere

Putting these together, of the three substances listed Nitrogen is the most abundant and vaporizes most readily, methane is the least abundant and vaporizes least readily, and carbon monoxide is in the middle.

The third sentence tells us that the rate of vaporization and amount in the atmosphere are directly proportional. It seems like you interpreted the stimulus as saying that the two levels were inversely proportional. To put it another way, what the stimulus is saying is that the more readily something turns into a gas, the more of it you will find in the atmosphere.

[wayouteast]

Not sure if I understand how to pick between the two competing answers on this one.
I was able to narrow it down to A/C, and I ultimately picked A, but I think I understand why C is the right answer based on the following:
1)Spec analysis has revealed x,y,z--> but stimulus doesn't state that these are the ONLY things on Pluto.
2)Proportion in atmosphere is based on how readily ice vaporizes- they have concluded x,y,z in decreasing abundance- but these are the ONLY items in the atmosphere.

So stimulus goes from talking about elemental ice (leaving the door open for other elements) to a more concise measurement in regards to gaseous x,y,z being the only items in the atmosphere. Based on this- can we pick C because there is in fact there is no other substance in vapor form found in the atmosphere? Meaning- the part in regards to rates of vaporization is simply an additional piece of information in C.

A: can be ruled out because we are unable to make assessments in regards to the sheer amount of Nitrogen on the planet- and even still the information in the stimulus states it's the most abundant and the proportion of gas is directly proportional to the vaporization rate.

Thanks!

[Francis O'Rourke]

Hi wayout,

It sounds like you understand this question. The most important point to focus on is that we don't have to assume that there is no more nitrogen on the surface than the other two elements. We don't know how much is left frozen; we only know that nitrogen vaporizes more readily.

If we apply the Assumption Negation Technique, choice (C) would tell us that the speaker's ordering of atmospheric abundance is incorrect.

Let me know if there is anything else that you want to address here

[MikeJones]

I think there's an important connection to be made from the stimulus to the correct answer (C).

In the second sentence of the stimulus, it states that if something vaporizes then it produces an atmosphere. As I read through this, I was thinking that "just because a frozen substance can vaporize, doesn't necessarily mean it will make up the atmosphere. maybe there are some substances that don't have this feature." But the stimulus clearly states that if it vaporizes, it produces an atmosphere.

So regardless of what the frozen substance is, in this case, if it evaporates, it becomes part of the atmosphere. Sounds simple but it's very easy to overlook and might cause some people to second guess the answer choice.

[Francis O'Rourke]

That's right, Mike!

It's easy to read statements like that in the way that we would commonly understand it. The LSAT is much more technical in how it expresses things. If the stimulus tells you that when something vaporizes, it produces an atmosphere, then it always does so. Keep this in mind on every stimulus you read, and you will be one step closer to really understanding the language used on this test

[jmramon]

Hi,

I understand why C is required for the conclusion to be valid. However, I’m trying to rule out D and was wondering if I could get feedback on whether my belief is correct as to why D is wrong. Is D a “must be true” answer based on the premises, but not an answer upon which the argument depends?

[Luke Haqq]

Hi jmramon!

Answer (D) looks close to a must be true answer choice, but it ultimately falls short. This stimulus is only focused on Pluto, whereas answer (D) states, "Nitrogen is found in the atmosphere of a planet only if nitrogen ice is found on the surface of that planet."

The fact that answer (D) is talking about planets generally--rather than just Pluto--would make (D) too strong to be a must be true answer, as it's beyond the scope of the information given. But even if we changed it to "Nitrogen is found in the atmosphere of [Pluto] only if nitrogen ice is found on the surface of [Pluto]," it still wouldn't necessarily be true. That is, the stimulus does state, "Such ices [like nitrogen] have a tendency to vaporize, producing an atmosphere," so it would be reasonable to think that nitrogen in the atmosphere of Pluto got there by way of this vaporization process. However, there's nothing in the stimulus that requires this to be true. It's consistent with the stimulus that at least some of the nitrogen found in the atmosphere of Pluto/other planets was not from ice on the surface (for example, maybe this nitrogen was absorbed into the atmosphere from a passing comet).

So, it's possible that nitrogen could be found in the atmosphere of a planet and not be found within ice on the planet's surface--which is why answer (D) couldn't work as a must-be-true answer.