(Solved): Below are two images from Ganymede (A) and Europa (B). The smooth areas in both images are thought ...

Below are two images from Ganymede (A) and Europa (B). The smooth areas in both images are thought to be due to tectonic spreading and surface renewal (probably by water) from below. Which of the following best describes events in these images? The first thing to notice is that similar physical processes have occurred on both Ganymede and Europa. Both flat regions show lines running along the resurfaced areas suggesting that this was a spreading event, similar to the mid-Atlantic ridge on Earth. The spreading on Ganymede likely caused the tectonic crumpling of the older surface on the upper left. The lack of impact craters in the Europa image suggests that this feature occurred much more recently than the one on Ganymede. The fracture that stretches across the Europa smooth area is even younger, from cross-cutting relations and suggests that Europa was active much longer than Ganymede. It appears that the same type of processes occurred on Ganymede and Europa. The smooth areas on first inspection seem very similar. There are differences however. The surface to the left of the smooth area in image \( A \), suggest that expansion might have crumpled the surface as the expansion continued. In figure B it is clear that the fracture across the top formed first. It apparently allowed water to flow across the surface and make the smooth area. This seems to be the case because the smooth area is clearly younger than the fracture along the top. The higher crater density in the smooth area on Ganymede suggests that Europa has been active for much longer times than Ganymede. It appears that the same type of processes occurred on Ganymede and Europa. The smooth areas at first look seem very similar. There are differences however. The surface to the left of the smooth area in image \( A \), suggest that expansion might have crumpled the surface as the expansion continued. In figure \( B \) there are no impact craters at all. This suggests that the Ganymede surface is solidified water (ice) but Europa's smooth area is actually liquid water. It is a water channel. When impacts occur the splash quickly goes away and that is why there are no impact craters seen. It is not possible to say anything about relative age between Ganymede and Europa, because the liquid nature of Europa's smooth area erases impacts immediately. The first thing to notice is that similar physical processes have occurred on both Ganymede and Europa. Both flat regions show lines running along the resurfaced areas suggesting that this was a spreading event, similar to the mid-Atlantic ridge on Earth. The spreading on Ganymede likely caused the tectonic crumpling of the older surface on the left. The lack of impact craters on Europa seems to suggest that the surface is younger, however, Ganymede is a much larger moon and orbits outside of Europa's orbit. This allows Ganymede to shield Europa from impacts. The result is that Ganymede gets hit a lot and Europa hardly at all. So it could be the case that Ganymede's smooth surface is actually younger than Europa's.