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Register now and save up to $200 Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code ## Life on Mars This topic has 1 expert reply and 4 member replies Uva@90 Master | Next Rank: 500 Posts Joined 04 Jul 2013 Posted: 490 messages Followed by: 5 members Upvotes: 83 #### Life on Mars Fri May 08, 2015 7:47 pm Hi All, Could you help me with this one ? Because of the proximity and likeness of Mars to Earth, scientists have long speculated about the possibility of life on Mars. As early as the mid-17th century, astronomers observed polar ice caps on Mars, and by the mid-19th century, scientists discovered other similarities to Earth, including the length of day and axial tilt. But in 1965, photos taken by the Mariner 4 probe revealed a Mars without rivers, oceans or signs of life. And in the 1990s, it was discovered that Mars, unlike Earth, no longer possessed a substantial global magnetic field, allowing celestial radiation to reach the planet's surface and solar wind to eliminate much of Mars's atmosphere over the course of several billion years. More recent probes have focused on whether there was once water on Mars. Some scientists believe that this question is definitively answered by the presence of certain geological landforms. Others posit that different explanations, such as wind erosion or carbon dioxide oceans, may be responsible for these formations. Mars rovers Opportunity and Spirit, which have been exploring the surface of Mars since 2004, have both discovered geological evidence of past water activity. These findings substantially bolster claims that there was once life on Mars. 1) Each of the following discoveries is mentioned in the passage EXCEPT (A) Wind erosion and carbon dioxide oceans are responsible for certain geological landforms on Mars. (B) Mars does not have a substantial global magnetic field. (C) Mars does not currently have water activity. (D) The length of day on Mars is similar to that on Earth. (E) The axial tilt of Mars is similar to that of Earth. 2) Each of the following can be inferred from the passage EXCEPT (A) The presence of certain geological landforms is not definitive proof that there was once life on Mars. (B) It is likely that there were few significant discoveries related to the possibility of life on Mars prior to the mid-17th century. (C) The absence of a substantial global magnetic field on Mars suggests that it would be difficult to sustain life on Mars. (D) The presence of water activity on Mars is related to the possibility of life on Mars. (E) The claim that there was once water on Mars has only limited and indirect support from recent discoveries. OA 1: A 2: E Thanks in advance. Regards, Uva. _________________ Known is a drop Unknown is an Ocean Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums! nathalie1107 Newbie | Next Rank: 10 Posts Joined 11 Sep 2016 Posted: 1 messages Top Reply Fri Oct 21, 2016 8:04 am For question 1, I agree that A is the correct answer. However, I still wonder why C is mentioned in the passage. The passage shows that a probe reveals a Mars without rivers, oceans but water activity can be present under other form, such as ground water. The conclusion of a Mars without water activity cannot be stated directly without the assumption that "water activity includes rivers and oceans only." Hope someone can help me make clear on this matter. ### GMAT/MBA Expert DavidG@VeritasPrep Legendary Member Joined 14 Jan 2015 Posted: 2459 messages Followed by: 115 members Upvotes: 1153 GMAT Score: 770 Top Reply Fri Oct 21, 2016 8:34 am nathalie1107 wrote: For question 1, I agree that A is the correct answer. However, I still wonder why C is mentioned in the passage. The passage shows that a probe reveals a Mars without rivers, oceans but water activity can be present under other form, such as ground water. The conclusion of a Mars without water activity cannot be stated directly without the assumption that "water activity includes rivers and oceans only." Hope someone can help me make clear on this matter. Excellent question. You're right that the absence of rivers and oceans can't be taken as definitive proof that there's no active water anywhere on Mars. But consider the mention of no rivers or oceans in conjunction with the first line of paragraph 2: More recent probes have focused on whether there was once water on Mars. If researchers are trying to determine if there used to be water on Mars, it seems reasonable to conclude that they've determined that there's no water there now. Is it possible that they're wrong, and that there's water hidden somewhere and they just haven't found it? Sure. But given that it's close to impossible to prove a negative, it seems reasonable to conclude that 1) the researchers are confident that there's currently no active water on Mars and 2) they have evidence (if not proof) for this assertion. But I agree that this question would be tighter if C contained the prepositional modifier "on its surface." _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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nathalie1107 Newbie | Next Rank: 10 Posts
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Fri Oct 21, 2016 8:04 am
For question 1, I agree that A is the correct answer.
However, I still wonder why C is mentioned in the passage. The passage shows that a probe reveals a Mars without rivers, oceans but water activity can be present under other form, such as ground water. The conclusion of a Mars without water activity cannot be stated directly without the assumption that "water activity includes rivers and oceans only."

Hope someone can help me make clear on this matter.

### GMAT/MBA Expert

DavidG@VeritasPrep Legendary Member
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Fri Oct 21, 2016 8:34 am
nathalie1107 wrote:
For question 1, I agree that A is the correct answer.
However, I still wonder why C is mentioned in the passage. The passage shows that a probe reveals a Mars without rivers, oceans but water activity can be present under other form, such as ground water. The conclusion of a Mars without water activity cannot be stated directly without the assumption that "water activity includes rivers and oceans only."

Hope someone can help me make clear on this matter.
Excellent question. You're right that the absence of rivers and oceans can't be taken as definitive proof that there's no active water anywhere on Mars. But consider the mention of no rivers or oceans in conjunction with the first line of paragraph 2: More recent probes have focused on whether there was once water on Mars. If researchers are trying to determine if there used to be water on Mars, it seems reasonable to conclude that they've determined that there's no water there now. Is it possible that they're wrong, and that there's water hidden somewhere and they just haven't found it? Sure. But given that it's close to impossible to prove a negative, it seems reasonable to conclude that 1) the researchers are confident that there's currently no active water on Mars and 2) they have evidence (if not proof) for this assertion. But I agree that this question would be tighter if C contained the prepositional modifier "on its surface."

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Marty Murray Legendary Member
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Sun May 10, 2015 1:24 am
Answer A says that the presence of certain geological landforms is not definitive proof that there was once life on Mars.

Looking at the passage we see that there are competing theories as to how the landforms were created. Some theorize that the landforms were created by carbon dioxide oceans or wind erosion, neither of which are conducive to the existence of life. Further even if the landforms were created by water, evidence of water is described not as definitively proving that there was once life on Mars but rather as "substantially bolstering claims" that there was once life on Mars.

So from the passage one can infer that the presence of the landforms does not definitively prove that there was once life of Mars.

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