One of the most important events for modern astronomy was the series o

Question

One of the most important events for modern astronomy was the series of collisions, during a single week in 1994, of more than a dozen large objects with Jupiter. The collision of these objects, which once formed most of the comet Shoemaker-Levy 9, resulted in formations that showed no signs of water. There was thus no water involved in the collisions, so we know that none of the comet’s fragments penetrated to Jupiter’s lower atmosphere and that the comet was composed of rock rather than ice.

Which one of the following is an assumption on which the argument depends?

(A) Comets tend to be composed largely of ice while asteroids are composed mainly of rock.

(B) If Jupiter’s lower atmosphere had been penetrated by the comet’s fragments, the resulting formations would show signs of water.

(C) A larger explosion would occur upon collision with Jupiter if Shoemaker-Levy 9 were composed of rock than if it were composed of ice.

(D) The post-collision analysis of Jupiter showed that the formations all had exactly the same composition.

(E) The deeper the explosion occurred in Jupiter’s atmosphere, the more difficult it would be to detect from Earth.

Sumi1010 · Answer

Ther argument says - 
There was thus no water involved in the collisions,  so  we know that none of the comet’s fragments penetrated to Jupiter’s lower atmosphere ...
Thus, 
If Jupiter’s lower atmosphere had been penetrated by the comet’s fragments, the resulting formations would show signs of water.
B is correct assumption.
Other options are easy to eliminate
(A) Comets tend to be composed largely of ice while asteroids are composed mainly of rock.
 No such info.

(C) A  larger explosion would occur  upon collision with Jupiter if Shoemaker-Levy 9 were composed of rock than if it were composed of ice.
 Can't infer it.

(D) The post-collision analysis of Jupiter showed that the formations all had  exactly the same composition. 
 Can't infer it.

(E) The deeper the explosion occurred in Jupiter’s atmosphere, the  more difficult  it would be to detect from Earth.
 No such info.

IMO  B

wali786 · Answer

A larger explosion would occur upon collision with Jupiter if Shoemaker-Levy 9 were composed of rock than if it were composed of ice. What does this double subjunctive mean "if Shoemaker-Levy 9 were composed of rock than if it were composed of ice".

RahulHGGmat · Answer

Hi  Sajjad1994 ,

Request you to please OE for this question.

Sajjad1994 · Answer

Explanation

Hello RahulHGGmat

I have no OE available with me, let me try to share my approach to the question.

First, read the stimulus and concentrate on the conclusion. When you have completed reading the stimulus pre-think the conclusion in your mind for a few seconds and lastly attack the answer choices.

One of the most important events for modern astronomy was the  series of collisions , during a single week in 1994, of more than a dozen  large objects  with Jupiter. The collision of these objects, which once  formed  most of the comet  Shoemaker-Levy 9,   resulted  in formations that showed  no signs of water.  There was thus  no water involved in the collisions,  so we know that none of the comet’s fragments penetrated to  Jupiter’s lower atmosphere  and that the comet was composed of rock rather than ice.

Conclusion:   If comet’s fragments penetrated to Jupiter’s lower atmosphere then it is composed of ice.

Let's read each answer choice.

(A) Comets tend to be composed largely of ice while asteroids are composed mainly of rock. 
(A) provides side information having no connection with the conclusion.

(B) If Jupiter’s  lower atmosphere  had been penetrated by the comet’s fragments, the resulting formations  would show signs of water.  
This is seemingly correct as it has a connection with the conclusion of the argument. Let's keep it.

(C) A larger explosion would occur upon collision with Jupiter if Shoemaker-Levy 9 were composed of rock than if it were composed of ice. 
This is out of context, we don't know the size of explosion. This option in inducting outside information.

(D) The post-collision analysis of Jupiter showed that the formations all had exactly the same composition. 
What if they had the same composition? This option makes no sense.

(E) The deeper the explosion occurred in Jupiter’s atmosphere, the more difficult it would be to detect from Earth. 
Same as C, out of context.

Answer: B

minalgambhir · Answer

CONCLUSION - None of the comet's fragments penetrated Jupiter's lower atmosphere and Comet was composed of rocks rather than ice

PRE THINKING -

IN WHAT SCENARIO - Comet's fragments entered Jupiter's lower atmosphere and Comet was composed of ice

GIVEN -

1) Series of collisions happened in 1994, >12 large objects with Jupiter
2) Collision showed no signs of water
3) No water was involved in the collisions

ANSWER CHOICE ANALYSIS -

A) Asteroids not talked of in the argument
B) CORRECT - Must be true in order for conclusion to hold true
C) Intensity of collision not mentioned in the argument
D) Whether the composition is same or different doesn't matter
E) Detection from earth not talked about

gmatBoy123456 · Answer

Hello Sajjad,

Here, isn't option B an answer to must be true question. How is the assumption regarding comet that penetrated lower atmosphere would have water helping a conclusion that if not lower atmosphere, then no water.

Posted from my mobile device

Sajjad1994 · Answer

Assumption and conclusion are closely inter-related but are in reverse order, Conclusion is made after setting up an assumption. Argument of this question contains conclusion and we have to find the assumption.

Pankaj0901 · Answer

There are two conditions that support that there was no water involved in the collisions:
1. none of the comet???s fragments penetrated to Jupiter???s lower atmosphere 
2. the comet was composed of rock rather than ice.

Option B covers ONLY the 1st point. Does B need to be NECESSARILY TRUE? What if B is not true and the second condition "the comet was composed of rock rather than ice" holds. We would not need option B as the assumption in that case.

Can someone please highlight what I am missing?

MartyTargetTestPrep · Answer

Hi Pankaj.

1 and 2 are not premises. They are conclusions that follow from the statements that precede them.

The statement "There was thus no water involved in the collisions," is an intermediate conclusion that follows from the facts first presented and support the two final conclusions.

So, (B) is an assumption required for the support of one of the final conclusions, "none of the comet’s fragments penetrated to Jupiter’s lower atmosphere."

We can see that this LSAT Assumption question works a bit differently from most GMAT Assumption questions.

Raman109 · Answer

Understanding the argument -
One of the most important events for modern astronomy was the series of collisions, during a single week in 1994, of more than a dozen large objects with Jupiter. Fact
The collision of these objects, which once formed most of the comet Shoemaker-Levy 9, resulted in formations that showed no signs of water. Fact
There was thus no water involved in the collisions, so we know that none of the comet’s fragments penetrated to Jupiter’s lower atmosphere and that the comet was composed of rock rather than ice. Let's break it.
- thus no water involved in the collisions - Intermediate conclusion.
- So two things
1. None of the comet’s fragments penetrated to Jupiter’s lower atmosphere
2. The comet was composed of rock rather than ice

Option Elimination - We need to find a minimum condition or a missing premise for the conclusion to hold true.

(A) Comets tend to be composed largely of ice while asteroids are composed mainly of rock. - at best, it's a weakener because, in the conclusion, we said the comet was composed of rock, while this option says that comets are composed mainly of ice. Opposite of what we need.

(B) If Jupiter’s lower atmosphere had been penetrated by the comet’s fragments, the resulting formations would show signs of water. - We need this for the conclusion to hold, which is "None of the comet’s fragments penetrated to Jupiter’s lower atmosphere" because had they penetrated the lower atmosphere, they would have shown signs of water (don't let your wild imaginations come into the picture as to how come Jupiter's lower atmosphere has water? That knowledge is outside the scope of this argument). And if we want to negate the option, we negate the main clause, "the resulting formations would show signs of water." So the negation will be "If Jupiter’s lower atmosphere had been penetrated by the comet’s fragments, the resulting formations would not show signs of water." Then, the conclusion is shattered.

(C) A larger explosion would occur upon collision with Jupiter if Shoemaker-Levy 9 were composed of rock than if it were composed of ice. - Do we know if the explosion in the argument was larger or smaller? We don't know. Even if we assume that the rock explosion would be larger then at best, this weakens.

(D) The post-collision analysis of Jupiter showed that the formations all had exactly the same composition. - We just wanted to know whether it had water or not. If the formations are of the same composition, i.e., the same hydrogen %age or the same X mineral %age, how does that matter to the conclusion? Out of scope.

(E) The deeper the explosion occurred in Jupiter’s atmosphere, the more difficult it would be to detect from Earth. - This raises doubts about whether our conclusion that it didn't penetrate the lower layers is proper. Maybe it was difficult to detect the deeper the explosion, so it is possible that it penetrated the lower atmosphere, but we couldn't detect it. So at best, it's a weakener.

VerbalBot · Answer

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One of the most important events for modern astronomy was the series o

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