PT151 S2 Q16 ExplanationScientist: An orbiting spacecraft detected

Answer choices, explained

1. A

   Correct66% picked this

   Conditions on Venus make it unlikely that any instrument targeting Venus would detect a

   Why this is right

   This is a fairly weak correct answer, but it gets at the author's move from "no direct evidence of active volcanoes, thus ... there probably aren't active volcanoes". This is saying that even if there are active volcanoes, we are unlikely to be able to directly perceive it. So a lack of direct evidence for active volcanoes isn't really conclusive in terms of whether or not there are active volcanoes there. It's almost like if the argument were, "Bruce's fingerprints weren't at the crime scene, so Bruce didn't commit the crime", and this answer is saying, "Well, given the conditions at the crime scene, we would have been very unlikely to find fingerprints no matter what instrument we used to hunt for them." (fwiw, Venus has an incredibly thick atmosphere. It creates a greenhouse effect that locks heat into Venus's surface, making Venus's surface temperatures higher than those of Mercury, which is much closer to the Sun. The thick atmosphere already has such a high concentration of noxious gases that it would hard for a volcanic eruption to be detectable as an anomaly. It'd be like trying to see whether a factory had polluted an already-brown river.)

   Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

   66%
2. B

   Opposite5% picked this

   Evidence suggests that there was a short-term spike in sulfur dioxide in Venus’s atmosphere

   This somewhat strengthens the author's hypothesis that sulfur dioxide spikes are cyclical variations.

   5%
3. C

   Out of Scope Comparison5% picked this

   Levels of sulfur dioxide have been higher in Venus’s atmosphere than in Earth’s atmosphere over

   We don't care how Venus's sulfur dioxide levels compare to Earth's. We're only interested in why Venus's current levels are higher than Venus's recent levels.

   5%
4. D

   No Impact23% picked this

   Traces of the sulfur dioxide from volcanic eruptions on Earth are detectable in the atmosphere years after

   This helps to establish some plausibility to the idea that volcanic activity can lead to sulfur dioxide in the atmosphere. But we actually already knew that. We were told in the paragraph that volcanoes are known to cause sulfur dioxide spikes in Earth's atmosphere, so this isn't telling us anything (relevant) that we didn't already know.

   23%
5. E

   No Impact / Opposite2% picked this

   Most instances of sulfur dioxide spikes in the Earth’s atmosphere are caused by the burning

   Since we don't think there are aliens on Venus who are burning fossil fuels, this has no real relevance to analyzing what's going on with Venus. However, if anything, it would suggest that the most common source of a sulfur dioxide spike is not volcanic activity, so that would support the author's conclusion.

   2%