It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth...
GMAT Critical Reasoning : (CR) Questions
It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth by a meteorite. However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time, and no two bacterial strains on Earth are different enough to have arisen on different planets. So, even if bacteria did arrive on Earth from Mars, they must have died out.
The argument is most vulnerable to which of the following criticisms?
Passage Analysis:
| Text from Passage | Analysis |
|---|---|
| It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth by a meteorite. |
|
| However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time |
|
| and no two bacterial strains on Earth are different enough to have arisen on different planets |
|
| So, even if bacteria did arrive on Earth from Mars, they must have died out. |
|
Argument Flow:
The author starts by acknowledging that Martian bacteria could have come to Earth, then establishes that different-planet bacteria should have major protein differences, shows that Earth bacteria don't have those differences, and concludes the Martian bacteria must be gone.
Main Conclusion:
Even if bacteria came from Mars to Earth, those Martian bacteria must have died out.
Logical Structure:
The argument relies on a key assumption: if bacteria from different planets should have major protein differences, and we don't see those differences on Earth, then any alien bacteria must be extinct. The logic chain is: different planets = different proteins → Earth bacteria are too similar → therefore no surviving alien bacteria.
Prethinking:
Question type:
Misc. - This is asking us to identify a flaw or vulnerability in the argument's reasoning
Precision of Claims
The argument makes definitive claims about protein differences persisting over time and about the similarity of Earth bacteria, then draws an absolute conclusion about Martian bacteria dying out
Strategy
Look for logical gaps, questionable assumptions, or alternative explanations that the argument fails to consider. Focus on ways the reasoning could be flawed even if we accept the stated facts
It fails to establish whether bacteria actually developed on Mars
'It fails to establish whether bacteria actually developed on Mars.' This isn't a vulnerability because the author explicitly states this is theoretical ('It is theoretically possible') and structures the argument as a conditional analysis. The author isn't trying to prove bacteria developed on Mars - they're examining what would follow IF it happened. The argument's logic doesn't depend on establishing this as fact.
it fails to establish how likely it is that Martian bacteria were transported to Earth
'It fails to establish how likely it is that Martian bacteria were transported to Earth.' This misses the point of the argument. The author is conducting a theoretical analysis assuming transport occurred. The probability of transport isn't relevant to the logical chain about protein differences and survival - the argument works by saying 'even if transport happened, here's what we can conclude.'
It fails to consider whether there were means other than meteorites by which Martian bacteria could have been carried to Earth.
'It fails to consider whether there were means other than meteorites by which Martian bacteria could have been carried to Earth.' The method of transport is irrelevant to the argument's core logic. Whether bacteria came via meteorite, spacecraft, or any other means doesn't affect the reasoning about protein differences and bacterial survival. The argument's conclusion would remain the same regardless of transport method.
It fails to consider whether all bacteria now on Earth could have arisen from transported Martian bacteria.
'It fails to consider whether all bacteria now on Earth could have arisen from transported Martian bacteria.' This exposes a critical flaw in the argument's reasoning. The author assumes that if Martian bacteria survived, we'd see them as distinct strains alongside Earth bacteria. But what if every bacterium on Earth today descended from those original Martian arrivals? In this scenario, there would be no 'original Earth bacteria' left to compare against, so we wouldn't expect to see the protein differences between Earth and Martian strains that the argument relies on. This alternative completely undermines the conclusion.
It fails to consider whether there could have been strains of bacteria that originated on Earth and later died out.
'It fails to consider whether there could have been strains of bacteria that originated on Earth and later died out.' This doesn't challenge the argument's logic. Even if some Earth bacteria went extinct, this wouldn't affect the reasoning about Martian bacteria survival. The argument only needs some Earth bacteria to exist for comparison - it doesn't require all original Earth strains to have survived.