Scientists noticed plate tectonics on Jupiter's moon Europa, the finding marks the first sing surface-shifting geological features on a world other than our own Earth.
The team made their findings while looking at pictures taken by the Galileo orbiter in the early 2000s, the Jet Propulsion Laboratory reported. The researchers noticed clear evidence of the moon's icy crust expanding, but could not find areas where the old crust was being destroyed to make room for the new.
"We have been puzzled for years as to how all this new terrain could be formed, but we couldn't figure out how it was accommodated," said Louise Prockter, of the Johns Hopkins University Applied Physics Laboratory "We finally think we've found the answer."
Plate tectonics is a theory in which the Earth's outer layer is made up of "plates" that move, which is what causes mountains and volcanoes to form and triggers earthquakes. On Earth, new surface material forms at mid-ocean ridges while old material is destroyed at subduction zones. Researchers are not sure how Europa's surface is accommodating all of the new material.
Researchers rearranged the icy terrain in the image like a jigsaw puzzle and discovered nearly 12,000 square miles were missing in the moon's high northern latitudes. They also spotted ice volcanoes on the overriding plate, which could have been formed from the melting and absorption of slabs below the surface. The lack of mountains at the subduction zone implies material was forced into the interior rather than crumpled up when the two plates smashed together.
The team believes the subducted area was absorbed into Europa's 20-mile-thick ice shell instead of breaking into the ocean that lies below.
"Europa may be more Earth-like than we imagined, if it has a global plate tectonic system," Kattenhorn says. "Not only does this discovery make it one of the most geologically interesting bodies in the solar system, it also implies two-way communication between the exterior and interior -- a way to move material from the surface into the ocean -- a process which has significant implications for Europa's potential as a habitable world."
The findings were published in the Sunday edition of the journal Nature Geoscience.
