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Life on Mars

This topic has 1 expert reply and 4 member replies
Uva@90 Master | Next Rank: 500 Posts
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Life on Mars

Post 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.

_________________
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nathalie1107 Newbie | Next Rank: 10 Posts
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Posted:
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Post 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.

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Post 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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nathalie1107 Newbie | Next Rank: 10 Posts
Joined
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Posted:
1 messages
Post 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.

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Post 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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Post 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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