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When a large body strikes a planet or moon, material is ejected, there

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Re: When a large body strikes a planet or moon, material is ejected, there  [#permalink]

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New post 14 Sep 2018, 18:43
chippoochan wrote:
QZ wrote:
Skywalker18 wrote:
Took 4 mins 30 seconds to answer , including 2 mins 10 seconds to read
-The author explains how local deficits of mass are created on planets or on the moon
- The author then explains why certain multi ring impacts on the moon do not show properties they are expected to show

1."denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin"
Answer E

2.
"Scientists speculate that early in lunar history "....
"Thus today such gravitational compensation probably would not occur"
Answer A

3.
The author clearly wants to present an explanation on why the lunar surface does not exhibit certain expected properties. Hence option C is the best answer.



Can you explain using POE why option A is answer to Q2 (scientists speculate).


I can help you on this question.
Ok let's refer to our passage.

When a large body strikes a planet or moon, material is ejected, thereby creating a hole in the planet and a local deficit of mass. This deficit shows up as a gravity anomaly: the removal of material that has been ejected to make the hole results in an area in slightly lower gravity than surrounding areas. One would therefore expect that all of the large multi-ring impact basins on the surface of earth's moon would show such negative gravity anomalies, since they are, essentially, large holes in lunar surface. Yet data collected in 1994 by the Clementine spacecraft show that many of these Clementine basins have no anomalously low gravity and some even have anomalously high gravity. Scientists speculate that early in lunar history, when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin. Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such gravitational compensation probably would not occur: the outer layer of moon is too cold and stiff.

From Q2 The passage suggests that if the scientists mentioned in the highlighted text are correct in their speculations, the large multi-ring impact basins on the Moon with the most significant negative gravity anomalies probably?

So these scientists mentioned that in early time of the moon, when there is anything hit the moon really hard that that hit area should show gravity anomaly. But the moon was still elastic and its mantle rose up to compensate the gravity anomaly ---> No more gravity anomaly
If you keep reading the next sentence you will find that "Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete."
From these sentences, you can make a guess without reading any answer choices that these whatever basins caused negative gravity anomalies ---> No compensation effect ---> Must occured when there was no compensation thing
That's how I got my answer "A"

Or if you wanna to use POE, we can take a look at each answer choices
(A) were not formed early in the Moon's history ---> Sound good. keep it.
(B) were not formed by the massive ejection of crustal debris ---> I look back to the passage and don't think this is really relevant. Out
(C) are closely surrounded by other impact basins with anomalously low gravity ---> the passage doesn't mention that gravity will be affected by surrounded basins. Out
(D) were created by the impact of multiple large impactors ---> Idk can't find any reference in the passage. Out
(E) were formed when the moon was relatively elastic ---> opposite to what are we looking for! Out

With POE. Answer is also "A" but this approach takes longer time.


Hi,

I don't see how E is any different from A. The passage states that the moon is less elastic in later stages, resulting in the craters that you see.
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Re: When a large body strikes a planet or moon, material is ejected, there  [#permalink]

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New post 02 Nov 2018, 20:56
Quote:
1. According to the passage, the gravitational compensation referred to in the highlighted text is caused by which of the following?

(A) A deficit of mass resulting from the creation of hole in lunar surface
(B) The presence of material from the impactor in the debris created by its impact
(C) The gradual cooling and stiffening of the Moon's outer surface
(D) The ejection of massive amounts of debris from the moon's crust
(E) The rapid upwelling of material from the lunar mantle



Hi workout

Though I got that OA is E for Q1 but whats wrong in option D.
Can you please help here

Thanks!
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When a large body strikes a planet or moon, material is ejected, there  [#permalink]

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New post 02 Nov 2018, 22:48
1
gmat1393 wrote:
Quote:
1. According to the passage, the gravitational compensation referred to in the highlighted text is caused by which of the following?

(A) A deficit of mass resulting from the creation of hole in lunar surface
(B) The presence of material from the impactor in the debris created by its impact
(C) The gradual cooling and stiffening of the Moon's outer surface
(D) The ejection of massive amounts of debris from the moon's crust
(E) The rapid upwelling of material from the lunar mantle



Hi workout

Though I got that OA is E for Q1 but whats wrong in option D.
Can you please help here

Thanks!


gmat1393

Quote:
When a large body strikes a planet or moon, material is ejected, thereby creating a hole in the planet and a local deficit of mass. This deficit shows up as a gravity anomaly


As quoted above, the ejection of massive amount of debris, option D, is the reason for the gravitational anamoly.

Quote:
denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material


Again, as quoted above, the gravitational compensation is caused by the denser material from the moon's mantle that rose up which is option E.
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Re: When a large body strikes a planet or moon, material is ejected, there  [#permalink]

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New post 06 Nov 2018, 04:50
chippoochan wrote:
QZ wrote:
Skywalker18 wrote:
Took 4 mins 30 seconds to answer , including 2 mins 10 seconds to read
-The author explains how local deficits of mass are created on planets or on the moon
- The author then explains why certain multi ring impacts on the moon do not show properties they are expected to show

1."denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin"
Answer E

2.
"Scientists speculate that early in lunar history "....
"Thus today such gravitational compensation probably would not occur"
Answer A

3.
The author clearly wants to present an explanation on why the lunar surface does not exhibit certain expected properties. Hence option C is the best answer.



Can you explain using POE why option A is answer to Q2 (scientists speculate).


I can help you on this question.
Ok let's refer to our passage.

When a large body strikes a planet or moon, material is ejected, thereby creating a hole in the planet and a local deficit of mass. This deficit shows up as a gravity anomaly: the removal of material that has been ejected to make the hole results in an area in slightly lower gravity than surrounding areas. One would therefore expect that all of the large multi-ring impact basins on the surface of earth's moon would show such negative gravity anomalies, since they are, essentially, large holes in lunar surface. Yet data collected in 1994 by the Clementine spacecraft show that many of these Clementine basins have no anomalously low gravity and some even have anomalously high gravity. Scientists speculate that early in lunar history, when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin. Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such gravitational compensation probably would not occur: the outer layer of moon is too cold and stiff.

From Q2 The passage suggests that if the scientists mentioned in the highlighted text are correct in their speculations, the large multi-ring impact basins on the Moon with the most significant negative gravity anomalies probably?

So these scientists mentioned that in early time of the moon, when there is anything hit the moon really hard that that hit area should show gravity anomaly. But the moon was still elastic and its mantle rose up to compensate the gravity anomaly ---> No more gravity anomaly
If you keep reading the next sentence you will find that "Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete."
From these sentences, you can make a guess without reading any answer choices that these whatever basins caused negative gravity anomalies ---> No compensation effect ---> Must occured when there was no compensation thing
That's how I got my answer "A"

Or if you wanna to use POE, we can take a look at each answer choices
(A) were not formed early in the Moon's history ---> Sound good. keep it.
(B) were not formed by the massive ejection of crustal debris ---> I look back to the passage and don't think this is really relevant. Out
(C) are closely surrounded by other impact basins with anomalously low gravity ---> the passage doesn't mention that gravity will be affected by surrounded basins. Out
(D) were created by the impact of multiple large impactors ---> Idk can't find any reference in the passage. Out
(E) were formed when the moon was relatively elastic ---> opposite to what are we looking for! Out

With POE. Answer is also "A" but this approach takes longer time.


were not formed was clear to me. But I was not able to eliminate B
Quote:
(B) were not formed by the massive ejection of crustal debris

instead I eliminated A as it sounded broader.
Why is B is irrelevant?
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When a large body strikes a planet or moon, material is ejected, there  [#permalink]

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New post 06 Nov 2018, 05:51
1
idinuv wrote:
Source : GMATPrep Default Exam Pack

This passage was excerpted from material published in 1996.

When a large body strikes a planet or moon, material is ejected, thereby creating a hole in the planet and a local deficit of mass. This deficit shows up as a gravity anomaly: the removal of material that has been ejected to make the hole results in an area in slightly lower gravity than surrounding areas. One would therefore expect that all of the large multi-ring impact basins on the surface of earth's moon would show such negative gravity anomalies, since they are, essentially, large holes in lunar surface. Yet data collected in 1994 by the Clementine spacecraft show that many of these Clementine basins have no anomalously low gravity and some even have anomalously high gravity. Scientists speculate that early in lunar history, when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin. Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such gravitational compensation probably would not occur: the outer layer of moon is too cold and stiff.


1. According to the passage, the gravitational compensation referred to in the highlighted text is caused by which of the following?

(A) A deficit of mass resulting from the creation of hole in lunar surface
(B) The presence of material from the impactor in the debris created by its impact
(C) The gradual cooling and stiffening of the Moon's outer surface
(D) The ejection of massive amounts of debris from the moon's crust
(E) The rapid upwelling of material from the lunar mantle




2. The passage suggests that if the scientists mentioned in the highlighted text are correct in their speculations, the large multi-ring impact basins on the Moon with the most significant negative gravity anomalies probably

(A) were not formed early in the Moon's history
(B) were not formed by the massive ejection of crustal debris
(C) are closely surrounded by other impact basins with anomalously low gravity
(D) were created by the impact of multiple large impactors
(E) were formed when the moon was relatively elastic




3. The passage is primarily concerned with

(A) analyzing data from a 1994 exploration of lunar surface
(B) reconciling two opposing theories about the origin of lunar impact basins
(C) presenting a possible explanation of a puzzling finding about lunar impact basins
(D) discussing how impact basins on the Moon's surface are formed
(E) examining the claim that the moon's impact basins show negative gravity anomalies




Kindly provide explanations for 3rd Question. I selected E.


4 mins 46 seconds : including 2 min 10 sec reading

Divide passage in 2 paras


When a large body strikes a planet or moon, material is ejected, thereby creating a hole in the planet and a local deficit of mass. This deficit shows up as a gravity anomaly: the removal of material that has been ejected to make the hole results in an area in slightly lower gravity than surrounding areas. One would therefore expect that all of the large multi-ring impact basins on the surface of earth's moon would show such negative gravity anomalies, since they are, essentially, large holes in lunar surface. Yet data collected in 1994 by the Clementine spacecraft show that many of these Clementine basins have no anomalously low gravity and some even have anomalously high gravity.

(summary - An expected consequence of a phenomenon is challenged by recent findings.... prethinking - author may try to explain why such data was otained or he may try to put another thesis to explain the data obtained ...)


Scientists speculate that early in lunar history, when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin. Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such gravitational compensation probably would not occur: the outer layer of moon is too cold and stiff.

(summary - an explanation to the unexpected findings... )

TOPIC - Lunar deficit.
PURPOSE- to explain the unexpected finding about a phenomenon...
Main idea - There is a possibilty that the unexpected finding may be the result of upwelling of mass from moon.


1. According to the passage, the gravitational compensation referred to in the highlighted text is caused by which of the following?

According to the passage, the gravitational compensation referred to in the highlighted text is caused by which of the following?
Relevant text - when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin. Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such gravitational compensation probably would not occur
- When there is a hole ( deficit) , mantle rises up , and fills the void ..this phenomenon is COMPENSATION...
What causes the compensation?? - the rising of mantle...


(A) A deficit of mass resulting from the creation of hole in lunar surface
- this does not cause anything. This AC is telling about what happen when IMPACTORS collide...

(B) The presence of material from the impactor in the debris created by its impact
- The presence of material does not cause anything.. infact when the impactor makes an impact and the released debris has this material ...OOS

(C) The gradual cooling and stiffening of the Moon's outer surface
-This explains why compensation MAY not happen now

(D) The ejection of massive amounts of debris from the moon's crust
-ejection will result in debris in space... nothing else

(E) The rapid upwelling of material from the lunar mantle
- CORRECT ANSWER - rapid ( almost immediately - from passage) upwelling - see explanation...


2. The passage suggests that if the scientists mentioned in the highlighted text are correct in their speculations, the large multi-ringmpact basins on the Moon with the most significant negative gravity anomalies probably

The passage suggests that if the scientists mentioned in the highlighted text are correct in their speculations, the large multi-ring impact basins on the Moon with the most significant negative gravity anomalies probably
-relevant text - Scientists speculate that early in lunar history, when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin. Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such gravitational compensation probably would not occur: the outer layer of moon is too cold and stiff.

speculation - impact >> deficit (void) >> mantle rises up >> NO GRAVITATIONAL ANAMOLY ...
so if this process is true what will be true??


(A) were not formed early in the Moon's history- CORRECT
Look carefully at the end of 2nd passage ( Later, however, as moon grew cooler and less elastic, rebound from large impactors would have been only partial and incomplete. Thus today such gravitational compensation probably would not occur: the outer layer of moon is too cold and stiff.) .. so this means[color=#ff0000] NOW
MOON IS TOO STIFF AND COLD and hence gravitational compensation would not have happened .. if it would have happened it would be comoensated with mantle.. LOOK AT THE TIME PERIODS ... NOW - no compensation .. Earlier time - compensation possible... now the Q says there IS A LARGE DEFICIT ... so if there is a large deficit NOW then it wldnt have formed earlier , because if it did there would be compensation.. but now the moon is stiff and hence no compensation..[/color]

(B) were not formed by the massive ejection of crustal debris-
- There are many ways to form a deficit ... passage never says "only" impactors create

(C) are closely surrounded by other impact basins with anomalously low gravity- OOS
- NO IDEA

(D) were created by the impact of multiple large impactors
- There are many ways to form a deficit ... passage never says "only" impactors create

(E) were formed when the moon was relatively elastic
- MOST COMMON WRONG AC - why we fall for this AC?? because we read only the last part and think that now the moon is stiff and cold so deficits would not have formed but earlier, the moon was elastic so deficit was possible ... SO basically we just messed up the entire para .. the elasticity explanation is for GRAVITATIONAL COMPENSATION and not possible deficit.... the deficits can form all the time .. it is the compensation that cannot
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Re: When a large body strikes a planet or moon, material is ejected, there  [#permalink]

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New post 06 Nov 2018, 10:29
Trying to analyse Q2 .

If we read this part of the passage :
Yet data collected in 1994 by the Clementine spacecraft show that many of these Clementine basins have no anomalously low gravity and some even have anomalously high gravity. Scientists speculate that early in lunar history, when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin.

This says > basins with no low gravity i.e no negative gravity. Scientists speculate that something happened in early lunar history.

Now Q2 : talks of basins with negative gravity. So clearly this was not from early lunar history.

If these basins were from early lunar history, they wouldn't have negative gravity.

Point to note is that the basins mentioned in the Q2 and basins mentioned in the above mentioned part of the passage are different.
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Re: When a large body strikes a planet or moon, material is ejected, there  [#permalink]

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New post 06 Nov 2018, 22:23
BARUAH wrote:
Trying to analyse Q2 .

If we read this part of the passage :
Yet data collected in 1994 by the Clementine spacecraft show that many of these Clementine basins have no anomalously low gravity and some even have anomalously high gravity. Scientists speculate that early in lunar history, when large impactors struck the moon's surface, causing millions of cubic kilometers of crustal debris to be ejected, denser material from the moon's mantle rose up beneath the impactors almost immediately, compensating for the ejected material and thus leaving no gravity anomaly in the resulting basin.

This says > basins with no low gravity i.e no negative gravity. Scientists speculate that something happened in early lunar history.

Now Q2 : talks of basins with negative gravity. So clearly this was not from early lunar history.

If these basins were from early lunar history, they wouldn't have negative gravity.

Point to note is that the basins mentioned in the Q2 and basins mentioned in the above mentioned part of the passage are different.


Hi BARUAH,

Sometimes your kind of analysis though it looks trivial, it is indeed apt. I hope you have used the concept of complement of information along with limiting the scope of what is given and what is not? Sometimes narrowing down the scope too much makes me select the wrong choice especially in RC. In the Q2's case, how can one say if basins with no gravity occurred in the early lunar history, basins with anomalous gravity were not formed?
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Re: When a large body strikes a planet or moon, material is ejected, there &nbs [#permalink] 06 Nov 2018, 22:23

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