#13 - In early 2003, scientists detected methane in the

[Administrator]

Complete Question Explanation

Assumption—CE. The correct answer choice is (B)

In this stimulus, the author reaches a conclusion about the presence of methane in the Martian atmosphere. According to the stimulus, scientists found methane in the Martian atmosphere in early 2003, and we are told that methane is a fragile compound. In fact, methane falls apart when the ultraviolet radiation contained in sunlight strikes it. Based on this evidence, the author concludes that the methane found in the Martian atmosphere “must have been released into the atmosphere relatively recently.”

Note that the effect of the ultraviolet radiation hitting the methane means the methane disappears, or chemically speaking, it falls into separate component parts. For example, if this occurred with water (H2O), the water would "fall apart" into separate component parts of Hydrogen (H) and Oxygen (O). Thus, in this Assumption question we have a causal argument. The cause is the ultraviolet radiation, and the effect is decomposition of the methane in the atmosphere.

When the author concludes that the any methane found in the atmosphere “must have been released into the atmosphere relatively recently,” the author is implicitly stating that if the methane had been released longer ago than just recently, the scientists would not have found it because it would have fallen apart due to being hit by ultraviolet radiation. So, according to the author, the only way to have methane present is that it has to be relatively new (and that presumptively it hasn't been hit by sunlight yet or at least fully broken down).

Since the only reason apparent from the stimulus for the methane disappearing from the atmosphere is it having fallen apart after coming into contact with ultraviolet radiation in sunlight, our prephrase is that the correct answer choice will tell us that any methane in the Martian atmosphere will come into contact with the ultraviolet radiation in sunlight.

Answer choice (A): The presence or absence of methane in the atmosphere prior to 2003 is irrelevant to the conclusion, which concerns the methane found in early 2003.

Answer choice (B): This is the correct answer choice because it restates the author’s assumption that the cause of methane’s dissolution, ultraviolet radiation in sunlight, must impact the methane in Mars’ atmosphere. If it were not the case that the methane in Mars’ atmosphere is exposed to sunlight, then there would be no basis for the conclusion that the methane discovered in 2003 must have been released into the atmosphere recently.

Answer choice (C): The stimulus told us as a premise that the scientists detected methane, but did not tell us the state the methane was in at the time it was detected. The conclusion does not assume that the methane was in any particular state at the time it was detected, and we cannot conclude that the information in this answer choice must be the case.

Answer choice (D): This answer choice is attractive because it includes the cause from the stimulus, exposure to ultraviolet radiation in sunlight. However, the stimulus tells us that methane falls apart when hit by ultraviolet radiation. So, we have no reason to think that the methane must have been hit by radiation, and reason to think that it could not have been, given that the scientists were able to detect it.

Answer choice (E): Methane in Earth’s atmosphere is irrelevant to the conclusion, which deals only with the methane detected in Mars’ atmosphere.

[Jkjones3789]

Hello so in this assumption question I was a little confused and went with C could you please tell me why its B along with the proper assumption negation technique translation of the two answer choices. I hope I am not asking for too much.Thank you.

[Emily Haney-Caron]

Hi Jkjones,

The negation for B would be: NOT all methane in the Martian atmosphere is eventually exposed to sunlight.
The negation for C would be: Methane can be detected before it has started to fall apart.

B here, when negated, significantly weakens the conclusion. If not all methane is exposed to sunlight, then it could have been there far before 2003 without falling apart. Therefore, that is the correct answer.

[mokkyukkyu]

Hi,
I was not sure about A...what if there is no ultraviolet radiation at all for a long time?
Then it is not sure whether the methan is from the past or recently right?

[Adam Tyson]

This is an assumption question, so the question you have to ask yourself is whether Answer A must be something that the author believed when he made his claim that the methane that was detected in early 2003 must have been released recently. Did you try the negation technique on Answer A? What impact does it have if Mars had some methane in its atmosphere prior to 2003? Would that matter at all? We are only interested in the methane that was there in early 2003, so who cares if there had been some other methane there earlier? Couldn't it have been released, then hit by sunlight and broken down? That would be completely compatible with the conclusion, so it does not destroy the argument and cannot be the correct answer.

We are not trying to prove that one of these answers IS true, but only that the author must have BELIEVED (assumed) that it was true. He did not have to believe answer A to be true, so it is not an assumption of his argument.

[freddythepup]

Hi, can you please explain in more detail why C does not work? Thanks.

[Who Ray]

Hey Freddy!

When we apply the Negation Test, we should see an argument fall apart (or at least be hurt). Like Emily said, If we apply the negation test to answer choice B we get "Not all methane in the Martian atmosphere is exposed to sunlight."

How does that affect the argument? What if the scientists detected the methane that had been hiding in a cave and had never been exposed to sunlight? Could they assume that the cave methane was recently released into the atmosphere? No—the cave methane could be billions of years old for all they know. However, if ALL methane is eventually exposed to sunlight, then the argument holds.

You did not ask about AC B, but I wanted to illustrate how the negation test change an argument. If we do the negation test on AC C, we get "Methane can be detected before it has started to fall apart," again from Emily. This AC is a little more difficult to properly negate, because of the "until" but hopefully you can get to it!

How does this negation effect the argument? The scientists are able to detect methane before it falls apart. This seems to almost strengthen the argument, because the scientists have better data. Because the argument is not damaged by the AC after the negation test, it can not be the correct answer.

I hope this was helpful! If not, could you please elaborate on why you think that AC B was correct, so we can help clear things up in a more specific way.

Cheers,
Who Ray

[T.B.Justin]

In early 2003, say January 1st, methane was detected in the martian atmosphere.

When hit by UV rays from sunlight, methane decays.

Thus, some methane in the martian atmosphere must have been released into the atmosphere relatively recently.

Is methane undetectable when hit by UV rays from sunlight? The stimulus says it falls apart.

Can it only be detected if not hit by UV rays from sunlight?

Is there only a certain period of time that methane can be detected, from the moment it released into the martian atmosphere, until the moment UV rays from sunlight hit the methane in the martian atmosphere.


I thought mars must have had no methane in its atmosphere prior to 2003, but I think that is incorrect. I think the question is about the momentary period that methane can be detected after being released into the martian atmosphere, which the stimulus states occurred in early 2003.

[LSAT2018]

So is Answer (D) the opposite of what is said in the conclusion?

[T.B.Justin]

Is this a correct contrast between detection and dissolution?

The stimulus says that methane was detected (but not how)

UV from sunlight causes the dissolution of methane

Therefore, any methane must have been released relatively recently.

If the author is implying that, if the methane would have been released longer ago than just recently, the scientists would not have found (detected) it because of the UV rays from sunlight causing methanes dissolution.

So, the argument rests on the assumption that eventually methane that is released into the martian atmosphere must at some point come into contact with sunlight.

The conclusion is not causal so how is this a causal argument- when the causal claim is a premise?