Asteroid 6478 Gault has experienced intermittent mass loss since at least 2013, but in contrast to some other asteroids with...
GMAT Craft and Structure : (Structure) Questions
Asteroid 6478 Gault has experienced intermittent mass loss since at least 2013, but in contrast to some other asteroids with repeated mass-loss episodes, 6478 Gault has not lost mass at its perihelion (the closest point of its orbit to the Sun), and thus the loss is not attributable to solar energy–driven ice vaporization. And as Jane X. Luu et al. point out, the singular nature of impact ejection makes it untenable as an account of multiple loss episodes of similar duration over several years. Instead, Luu et al. are likely correct that 6478 Gault is shedding mass due to rotational instability.
Which choice best describes the overall structure of the text?
It presents a scientific observation, describes a contrast between that observation and other observations, and then explains why those other observations should not be considered credible.
It describes an astronomical finding, discusses competing theories about that finding that the author regards as flawed, and then describes new evidence that supports an alternative theory.
It introduces a natural phenomenon, refutes two potential explanations for that phenomenon, and then presents a third explanation for that phenomenon that the author regards as plausible.
It discusses a physical process, evaluates possible causes of that process, and then states that a persuasive account of the process has yet to be put forward.
Step 1: Decode and Map the Passage
Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Asteroid 6478 Gault has experienced intermittent mass loss since at least 2013" |
|
| "but in contrast to some other asteroids with repeated mass-loss episodes, 6478 Gault has not lost mass at its perihelion (the closest point of its orbit to the Sun)" |
|
| "and thus the loss is not attributable to solar energy–driven ice vaporization" |
|
| "And as Jane X. Luu et al. point out, the singular nature of impact ejection makes it untenable as an account of multiple loss episodes of similar duration over several years." |
|
| "Instead, Luu et al. are likely correct that 6478 Gault is shedding mass due to rotational instability." |
|
Passage Architecture & Core Elements
Main Point: Asteroid 6478 Gault's mass loss is most likely caused by rotational instability rather than the typical explanations that apply to other asteroids.
Argument Flow: The passage introduces an unusual case of asteroid mass loss, distinguishes it from typical patterns, systematically eliminates two common explanations, and concludes with the most plausible alternative explanation supported by expert research.
Step 2: Interpret the Question Precisely
What's being asked? We need to identify how the text is organized - its overall structure and logical flow.
What type of answer do we need? A description of the passage's structural pattern - how the author builds the argument from beginning to end.
Any limiting keywords? None specified.
Step 3: Prethink the Answer
- The passage starts by introducing a specific phenomenon (asteroid mass loss)
- It systematically rules out two potential explanations (solar energy-driven vaporization and impact ejection)
- It ends by presenting a third explanation that the author views favorably (rotational instability)
- The structure follows a classic pattern of eliminating wrong explanations and presenting a better one
It presents a scientific observation, describes a contrast between that observation and other observations, and then explains why those other observations should not be considered credible.
✗ Incorrect
- Claims the passage explains why other observations should not be considered credible.
- The passage never questions the credibility of other observations - it simply shows they do not apply to this specific asteroid
It describes an astronomical finding, discusses competing theories about that finding that the author regards as flawed, and then describes new evidence that supports an alternative theory.
✗ Incorrect
- Says the passage describes new evidence that supports an alternative theory.
- The passage presents Luu et al.'s reasoning and conclusion, but does not introduce new evidence
It introduces a natural phenomenon, refutes two potential explanations for that phenomenon, and then presents a third explanation for that phenomenon that the author regards as plausible.
✓ Correct
- Perfectly captures the three-part structure: introduces phenomenon (mass loss), refutes two explanations (solar vaporization and impact ejection), presents third explanation as plausible (rotational instability).
- This matches our passage analysis exactly
It discusses a physical process, evaluates possible causes of that process, and then states that a persuasive account of the process has yet to be put forward.
✗ Incorrect
- Claims no persuasive account has been put forward yet.
- The passage actually endorses rotational instability as the likely correct explanation, contradicting this choice