Io and Europa, the inner two of Jupiter's four largest moons, are about the size of Earth's moon and are composed mostly or entirely of rock and metal. Ganymede and Callisto are larger and roughly half ice. Thus, these four moons are somewhat analogous to the planets of the solar system, in which the rock- and metal-rich inner planets are distinct from the much larger gas- and ice-rich outer planets. Jupiter's moons are, however, more "systematic": many of their properties vary continuously with distance from Jupiter. For example, Io is ice-free, Europa has a surface shell of ice, and while Ganymede and Callisto are both ice-rich, outermost Callisto has more.
This compositional gradient has geological parallels. Io is extremely geologically active, Europa seems to be active on a more modest scale, and Ganymede has undergone bouts of activity in its geological past. Only Callisto reveals no geological activity. In similar fashion, Callisto's surface is very heavily cratered from the impact of comets and asteroids; Ganymede, like Earth's moon, is heavily cratered in parts; Europa is very lightly cratered; and no craters have been detected on Io, even though Jupiter's gravity attracts comets and asteroids passing near it, substantially increasing the bombardment rate of the inner moons compared to that of the outer ones. But because of Io's high degree of geological activity, its surface undergoes more-or-less continuous volcanic resurfacing.EMPOWERgmat
This passage was retained in the OG 2016
: 1|+| Further -> Icier, resembles solar system, more systematicAnalysis
: The first paragraph is not just a report on the inner moons of Jupiter, but also an argument as to the similarity of Jupiter’s moons to that of the solar system itself. “Thus, these four moons are somewhat analogous to the planets of the solar system” That’s opinion. The rest is evidence supporting that opinion.Notes
: 2|+| Further -> Less geo activeAnalysis
: Here, the case is being made that the intensity of geological activity on the surface of the moons varies based on the distance from Jupiter. The further out, the less geologically active, and vice-versa.OG 2015 #11
OG 2016 #11
According to the passage, the difference in the amount of cratering on Callisto's and Io's respective surfaces can probably be explained by the difference between these two moons with respect to which of the following factors?
(B) Ice content
(C) The rate of bombardment by comets and asteroids
(D) The influence of Jupiter's other moons
(E) The level of geological activityDetail Question
Find the Facts: What causes the difference in cratering? Geologic activity. “because of Io's high degree of geological activity, its surface undergoes more-or-less continuous volcanic resurfacing” so the closer to Jupiter, the more active the volcanic activity, and the volcanoes essentially erase the craters off the surface more frequently, the closer the moon is to Jupiter. Which option says that? E. It’s not about the size, the ice content ,or the influence of Jupiter’s other moons. Those are the 3 easy outs. Option C is the runner up. We know it’s not C because the rate of bombardment intensifies the closer the moon is to Jupiter, but the closer the moon is to Jupiter, the fewer craters, so it can’t be about the bombardment. Again, at the end of paragraph 2, we’re told that the volcanic activity is what wipes the surface.OG 2015 #12
OG 2016 #12
Which of the following best describes the purpose of the second paragraph of the passage?
(A) To provide further evidence of the systematic variation in the characteristics of Jupiter's four largest moons
(B) To present a comprehensive theory to explain the systematic variation in the characteristics of Jupiter's four largest moons
(C) To explain the significance of the systematic variation in the characteristics of Jupiter's four largest moons
(D) To introduce facts that contradict conventional assumptions about Jupiter's four largest moons
(E) To contrast the characteristics of Jupiter's four largest moons with the characteristics of the planets of the solar systemPurpose Question
What’s The Purpose of Paragraph 2? Further proof of systematic relationship of the moons. The further the moon, the greater the catering. That is proof of a system in which the distance from Jupiter impacts the character of the moons. Which option says that? A) To provide further evidence of the systematic variation in the characteristics of Jupiter's four largest moons
B) Easy Out #1 Is this passage, let alone paragraph 2 actually presenting a COMPREHENSIVE theory? No. How would we know this is a comprehensive treatment. This option has the right flavor, but warps it by making it too extreme.
C) The runner up. Does this passage actually provide information as to how significant this systematic relationship is? No Just because the author is describing the systematic relationship doesn’t automatically make that issue a significant one. That distorts, or in other words warps what the answer should say.
D) Easy Out #2 Left field. Nothing in the passage indicates that these facts used to support this systematic theory counter the conventional thinking. For all we know, this passage might actually reinforce conventional assumptions, and beliefs about the moons.
E) Easy Out #3 Even though there is reference to the similarity of Jupiter’s moons to the planets in the solar system, that’s not automatically the goal if either paragraph. Instead, the author is really just drawing on the familiarity of the solar system to help illustrate what’s going on with Jupiter’s moons.OG 2015 #13
OG 2016 #13
The author's reference to Jupiter's gravity in line 25 serves primarily to
(A) indicate why the absence of craters on Io's surface is surprising
(B) explain the presence of craters on the surface of Jupiter's four largest moons
(C) provide an explanation for the lack of geological activity on Callisto
(D) contrast Jupiter's characteristics with the characteristics of its four largest moons
(E) illustrate the similarity between Jupiter's four largest moons and the planets of the solar systemPurpose Question
What’s the purpose of the reference to gravity in line 25? The passage points out that we’d expect more craters the closer we got to jupiter because of Jupiter’s gravity, but instead we see fewer craters. That seeming paradox is the point. Which option expresses that idea?
A) Yes! To point out that the absence of craters is not what we’d expect
B) A 180. We know for a fact that not all of the 4 moons have craters. Io is extremely volcanic, and the passage says that “its surface undergoes more-or-less continuous volcanic resurfacing.”
C) Is the entire purpose of the mention of Jupiter’s gravity to talk about the lack of activity on Callisto? No In fact Callisto is month the furthest out.
D) Easy Out #2 Is the purpose of sharing the information in paragraph 2 to contrast Jupiter’s characteristics to that of it’s moon? no.
E) Even though the passage does reference the similarity in P1, is that the purpose of referencing Jupiter’s gravity here? No. The reason why the author is referencing Jupiter’s gravity is to point out why it’s surprising these innermost moons don’t have more craters since they’re more likely to be bombarded.
"Students study. GMAT assassins train."
★★★★★ GMAT Club Verified Reviews for EMPOWERgmat & Special Discount
GMAT Club Verbal Advantage EMPOWERgmat Critical Reasoning Question Pack