In 1994, a team of scientists led by David McKay began studying the meteorite ALH84001, which had been discovered in...
GMAT Reading Comprehension : (RC) Questions
Source: Official Guide
...
...
Post a Query
In 1994, a team of scientists led by David McKay began studying the meteorite ALH84001, which had been discovered in Antarctica in 1984. Two years later, the McKay team announced that ALH84001, which scientists generally agree originated on Mars, contained compelling evidence that life once existed on Mars. This evidence includes the discovery of organic molecules in ALH84001, the first ever found in Martian rock. Organic molecules—complex, carbon-based compounds— form the basis for terrestrial life. The organic molecules found in ALH84001 are poly cyclic aromatic hydrocarbons, or PAHs. When microbes die, their organic material often decays into PAHs.
Skepticism about the McKay team's claim remains, however. For example, ALH84001 has been on Earth for 13,000 years, suggesting to some scientists that its PAHs might have resulted from terrestrial contamination. However, McKay's team has demonstrated that the concentration of PAHs increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination. The skeptics' strongest argument, however, is that processes unrelated to organic life can easily produce all the evidence found by McKay's team, including PAHs. For example, star formation produces PAHs. Moreover, PAHs frequently appear in other meteorites, and no one attributes their presence to life processes. Yet McKay's team notes that the particular combination of PAHs in ALH84001 is more similar to the combinations produced by decaying organisms than to those originating from non biological processes.
Ques. 1/6
The primary purpose of the passage is to:
Solution
1. Passage Analysis:
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| In 1994, a team of scientists led by David McKay began studying the meteorite ALH84001, which had been discovered in Antarctica in 1984. | What it says: A scientist named McKay and his team started studying a rock from space that was found in Antarctica 10 years earlier. What it does: Sets up the basic story - introduces the main characters (McKay's team) and the object of study (the meteorite) Source/Type: Historical fact Connection to Previous Sentences: This is our starting point - no previous information to connect to Visualization: Timeline: 1984 (meteorite found in Antarctica) → 1994 (McKay begins studying it) What We Know So Far: McKay's team, meteorite ALH84001, found in Antarctica What We Don't Know Yet: Why this meteorite matters, what they found Reading Strategy Insight: Simple setup - just getting oriented with who, what, when |
| Two years later, the McKay team announced that ALH84001, which scientists generally agree originated on Mars, contained compelling evidence that life once existed on Mars. | What it says: In 1996, McKay's team made a big announcement: this rock came from Mars and has strong evidence that life existed there. What it does: Reveals the major discovery and why it's significant Source/Type: McKay team's claim + scientific consensus about origin Connection to Previous Sentences: This builds directly on sentence 1 by telling us the result of McKay's study that began in 1994. The "two years later" creates a clear timeline. Visualization: 1984 (found) → 1994 (study begins) → 1996 (announcement: Mars rock contains evidence of life) What We Know So Far: McKay found evidence of past life on Mars in meteorite ALH84001 What We Don't Know Yet: What specific evidence they found Reading Strategy Insight: This is the main claim the passage will explore - everything else will relate back to this discovery |
| This evidence includes the discovery of organic molecules in ALH84001, the first ever found in Martian rock. | What it says: The evidence includes organic molecules, and this is the first time anyone has found organic molecules in a rock from Mars. What it does: Starts explaining what the "compelling evidence" actually is Source/Type: Factual description of the discovery Connection to Previous Sentences: This directly explains the "compelling evidence" mentioned in sentence 2. The author is helping us by breaking down the complex claim into specific details. Visualization: Evidence for life = Organic molecules (first ever found in Martian rock) What We Know So Far: McKay found organic molecules in Mars rock - this is unprecedented What We Don't Know Yet: What organic molecules are, why they suggest life Reading Strategy Insight: Feel confident here - the author is explaining, not adding complexity |
| Organic molecules—complex, carbon-based compounds— form the basis for terrestrial life. | What it says: Organic molecules are complicated carbon-based substances that are fundamental to life on Earth. What it does: Defines the technical term and explains why finding them matters Source/Type: Scientific definition/explanation Connection to Previous Sentences: This is pure simplification! Sentence 3 mentioned "organic molecules" and now the author is defining what they are and why they're important for life. Visualization: Organic molecules = carbon-based compounds = basis for Earth life Therefore: Finding them on Mars rock → suggests Mars life What We Know So Far: McKay found organic molecules (carbon-based life building blocks) in Mars rock What We Don't Know Yet: What specific type they found Reading Strategy Insight: Feel relieved here - this is simplification, not new complexity |
| The organic molecules found in ALH84001 are poly cyclic aromatic hydrocarbons, or PAHs. | What it says: The specific organic molecules they found are called PAHs (using the shorter name). What it does: Identifies the specific type of organic molecules Source/Type: Factual specification Connection to Previous Sentences: This continues the explanation from sentences 3-4. We went from "organic molecules" (sentence 3) to "what are organic molecules" (sentence 4) to "what specific type" (sentence 5). Visualization: Evidence chain: Mars rock → contains organic molecules → specifically PAHs What We Know So Far: McKay found PAHs (a type of organic molecule) in Mars rock What We Don't Know Yet: How PAHs relate to life Reading Strategy Insight: This is still explanation mode - the author is giving us a more specific name for what was already mentioned |
| When microbes die, their organic material often decays into PAHs. | What it says: When tiny living things die, they often break down into PAHs. What it does: Explains the connection between PAHs and life processes Source/Type: Scientific fact about biological processes Connection to Previous Sentences: This completes the logical chain! We learned that McKay found PAHs (sentence 5), and now we learn that PAHs come from dead life forms. This explains why finding PAHs suggests past life. Visualization: Life process: Microbes live → microbes die → decay into PAHs Mars discovery: Found PAHs in Mars rock → suggests microbes once lived and died on Mars What We Know So Far: Complete argument for life on Mars: PAHs found in Mars rock, PAHs come from dead microbes What We Don't Know Yet: What critics think about this evidence Reading Strategy Insight: The core argument is now complete and clear - everything made sense step by step |
Answer Choices Explained
A
describe new ways of studying the possibility that life once existed on Mars
Why It's Wrong:
- The passage focuses on interpreting evidence from ALH84001, not describing new research methods
- McKay's team used standard techniques to find PAHs - the novelty was what they found, not how they studied it
- The controversy is about the significance of the evidence, not about research methodology
B
revise a theory regarding the existence of life on Mars in light of new evidence
Why It's Wrong:
- The passage doesn't revise any existing theory - it presents a new claim and the debate around it
- McKay's discovery was the first evidence of organic molecules in Martian rock, so there wasn't an established theory to revise
- The passage shows ongoing disagreement, not a revision or update to accepted theory
C
reconcile conflicting viewpoints regarding the possibility that life once existed on Mars
Why It's Wrong:
- The passage presents conflicting viewpoints but doesn't reconcile them - the debate remains unresolved
- The passage ends with McKay's final argument, but doesn't indicate that skeptics accept it or that a compromise has been reached
- Both sides maintain their positions throughout; there's no synthesis or middle ground presented
D
evaluate a recently proposed argument concerning the origin of ALH84001
Why It's Wrong:
- The passage accepts that ALH84001 originated on Mars ("scientists generally agree originated on Mars") - there's no debate about its origin
- The controversy is about what the evidence inside ALH84001 means, not where the meteorite came from
- The passage doesn't evaluate arguments about the meteorite's origin, but rather about the significance of its contents
E
describe a controversy concerning the significance of evidence from ALH84001
Why It's Right:
- The entire passage structure supports this: McKay's claim → evidence explanation → skeptical challenges → McKay's responses
- The controversy centers specifically on interpreting the PAHs found in ALH84001 - do they indicate past life or not?
- The passage presents both sides of the debate about what the evidence means without resolving the controversy
Rate this Solution
Tell us what you think about this solution
Forum Discussions
Start a new discussion
Post
Load More