Tough RC- Moon

[dmitriyaleyev]

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 Clemenstine 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.

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

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

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

Source: GMAT PREP

Guys,
I feel the logic in the questions above, but cant quite explain....

For number 1, if moon is not elastic anymore, than how would basins form?
Please advise.
Thanks.[/img]

[raisethebar]

what makes you think that if surface is not elastic, the basin will not form after impact.

As per my understanding of the passage, the basin will form in both the cases only the negative gravity anomaly will not occour if the moon surface is elastic.

so for 1st IMO E
2. A
3. C
let me know OA

[Osirus@VeritasPrep]

I agree with the above poster

1 e
2 a
3 c

OA?

[dmitriyaleyev]

e
a
c

[dmitriyaleyev]

For number 2 I answered E, thinking that basins can only form when the moon is elastic...? where is the flaw in this logic?
Since later moon got colder and less elastic, as per text, basins must have been formed earlier in the history. no?

[Osirus@VeritasPrep]

Do you know what level question that was?

[tomada]

I agree with the two posters who said:

(1) E
(2) A
(3) C

I believe that the key statement for answering (2) is as follows:

"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"

Because the material rising up is denser, this would act to increase the gravity, which contradicts the otherwise negative gravitational anomaly. Thus, if the impact had occurred early in the moon's history, the negative gravitational anomaly would not have remained.

[dmitriyaleyev]

Do you know what level question that was?

looks like 650 +

I got 40 on V and that question was after a run of 10 right questions.

[vijay_venky]

For number 2 I answered E, thinking that basins can only form when the moon is elastic...? where is the flaw in this logic?
Since later moon got colder and less elastic, as per text, basins must have been formed earlier in the history. no?

As per the Passage, the gravitational compensation on the moon occurred because of the rapid expansion of the mantle and the relative elasticity of the moon.

Now the question asks us about the craters with negative gravity which is generally expected of a crater. What does that mean, to me it means that the crater which has a negative gravity (in other terms, gravitation anomaly) is not formed when the moon had the antidote of rapid expansion of the mantle and of course elasticity, (i.e, early in the moon's history).

So the answer is A

[pink_08]

Can you please explain why 3) is not A....

Any explanations for the correct choice C

[vijay_venky]

The purpose of the passage as a whole is the point in the question here. But the author discusses about the craters and particularly about the unusual behavior that was observed in the exploration. So analyzing the data becomes a too generic answer for this particular view.(after all we do not know whether the data collected is just about this particular behavior)

[missrochelle]

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

Can someone explain why E is incorrect? Is it because its too specific? The author is not JUST examining the claim, he's accepting the claim as true and also delving into how it has changed over the course of the moon's history. Hence C - which is a more general paraphrasing?

[frank1]

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

Can someone explain why E is incorrect? Is it because its too specific? The author is not JUST examining the claim, he's accepting the claim as true and also delving into how it has changed over the course of the moon's history. Hence C - which is a more general paraphrasing?

I think
E
A
C
5:40 seconds

I think for this one E is not correct because
There is no such specific CLAIM even if there were it is not examined(One word wrong)
It is only a part of larger story.See how the passage starts with larger scope.(Too specific).It would have been more clear if it were well formatted in paragraphs

[GmatKiss]

IMO:
[spoiler]E
A
C[/spoiler]

What is OA?

[AN24]

E
a
c