Question

a subject of much speculation, distinctive sets of parallel ridges mark the icy crust of europa, jupiters smallest moon. researchers now claim that the ridges formation mechanism mirrors that of a strikingly similar pair on greenlands ice sheet. there, surface water seeped through fissures in the sheet and formed a water pocket that subsequently disrupted the overlying ice, forcing fragments of it upward and outward into peaks, as the pocket froze and expanded. although europa lacks liquid surface water, the same process could be driven by the moons subsurface ocean. which choice best states the main idea of the text? a researchers think that the ridges on europa and the ridges in greenland may have been formed by the same process even though europa, unlike greenland, doesnt have liquid water on its surface. b the primary difference between the ridges on europa and the ridges in greenland is that unlike the europa ridges, the greenland ridges are parallel. c the pair of ridges found on greenlands ice sheet appear to have formed long before the recently discovered sets of ridges on europa formed. d researchers dont understand why europa is marked by so many sets of ridges when the moon doesnt have any liquid water on its surface that could have collected and expanded under the icy crust.

Explanation:

The text discusses how researchers claim the ridge - formation mechanism on Europa's icy crust is similar to that on Greenland's ice sheet, despite Europa lacking liquid surface water. Option A captures this main idea. Option B is incorrect as both sets of ridges are parallel. Option C has no basis in the text regarding the time of formation. Option D is not the main idea as the text focuses on the similarity of formation processes, not the mystery of Europa's ridges.

Answer:

A. Researchers think that the ridges on Europa and the ridges in Greenland may have been formed by the same process even though Europa, unlike Greenland, doesn't have liquid water on its surface.