LSAT 21 | Section 2 | Logical Reasoning: Q19

LR Question 19 Explanation

QUESTION TEXT: Spectroscopic analysis has revealed the existence of…

QUESTION TYPE: Necessary Assumption

CONCLUSION: Pluto must have an atmosphere made up of nitrogen, carbon monoxide and methane.

REASONING: Pluto’s surface has ice made from nitrogen, carbon monoxide and methane. Ice vaporizes and the resulting gases form the atmosphere.

ANALYSIS: The astronomers haven’t ruled out the possibility that there are other ices on Pluto.

Spectroscopic analysis has found three types of ice. But there could be others we haven’t found.

The argument assumes there are no other frozen elements that can vaporize.

___________

1. The argument didn’t say how much of each type of ice was found on the surface. It shouldn’t matter; the astronomers’ conclusion was based on the fact that nitrogen vaporizes more quickly.
2. If this were false, then space probes could reach Pluto to analyze the atmosphere directly. How would more analysis hurt the argument?
3. CORRECT. If there is an element that vaporizes more easily than methane then methane won’t be the third most common element in the atmosphere.
4. The argument isn’t hurt if there are some other planets with nitrogen atmospheres but without nitrogen ice.
5. It doesn’t matter what the atmospheres of other planets are like. This argument is about Pluto.

Recap: The question begins with “Spectroscopic analysis has revealed the existence of”. It is a Necessary Assumption question. Learn how to master LSAT Necessary questions on the LSAT Logical Reasoning question types page.