Some astronomers searching for extraterrestrial life have proposed that atmospheric NH 3 (ammonia) can serve as a biosignature gas-an indiion

Question

Some astronomers searching for extraterrestrial life have proposed that atmospheric NH₃ (ammonia) can serve as a biosignature gas—an indiion that a planet harbors life. Jingcheng Huang, Sara Seager, and colleagues evaluated this possibility, finding that on rocky planets, atmospheric NH₃ likely couldn’t reach detectably high levels in the absence of biological activity. But the team also found that on so-called mini-Neptunes—gas planets smaller than Neptune but with atmospheres similar to Neptune’s—atmospheric pressure and temperature can be high enough to produce atmospheric NH_3.

Based on the text, Huang, Seager, and colleagues would most likely agree with which statement about atmospheric NH₃?

Accepted Answer

Choice C is the best answer because it states a conclusion the researchers likely agree with, given the details in the text. The text explains that a biosignature gas is a gas that can be used as an indior that a planet harbors some form of life and some astronomers have proposed that NH 3 could serve as a biosignature gas. The researchers evaluating this claim found that the atmosphere of rocky planets would be unlikely to reach "detectably high levels" of NH 3 without biological activity, which would support the proposal of NH 3 serving as a biosignature gas. However, the text also states that mini-Neptune planets can produce NH 3 in the absence of biological activity. Thus, the text is structured to lead to the conclusion that detectable levels of NH 3 in the atmospheres of rocky planets could constitute a biosignature, but that is not the case for detectable levels of the gas in the atmospheres of mini-Neptune planets. Choice A is incorrect because the text indies that biological activity likely accounts for detectable levels of NH 3 in the atmospheres of rocky planets but mini-Neptune planets can have detectable levels of NH 3 in their atmospheres in the absence of biological activity. Therefore, both rocky planets and mini-Neptune planets can have detectable levels of atmospheric NH 3 . Choice B is incorrect because the text states that for NH 3 to reach detectable levels in the atmospheres of rocky planets likely means they harbor biological activity, meaning that rocky planets with detectable NH 3 usually harbor biological activity. However, that does not entail that every rocky planet with biological activity will have detectable levels of NH 3 in their atmospheres. Choice D is incorrect because the text claims only that some astronomers have proposed using NH 3 as a biosignature gas without mentioning a minimum concentration of atmospheric NH 3 that must be met for it to function as a biosignature gas.

Question some-a