Europa has many unique features, including a warm, subterranean ocean covered in ice. As a result, astronomers have long wondered if such formations are the result of plate tectonics. That is because, if they were, it would make the Europa the only known place in the Solar System other than Earth to experience large, subduction-driven quakes. It would also make the moon more likely to support life.
In the new study, a group of scientists led by Brown University found that Europa can support such geological processes. They made that discovery by using computer models to demonstrate the feasibility of icy plates driving deep into Europa’s interior in processes similar to the mechanisms noted on Earth.
Europa has surface features that appear like Earth’s mid-ocean ridges. That suggests the moon could have geological processes that are similar to subduction zones, where tectonic plates slide underneath each other and sink deep into the Earth. Past studies have suggested Europa’s surface is composed of tectonic plates, and that occasionally a plate of ice will sink beneath the other into warmer layers below.
To look at that theory, the team in the studyused their simulations to theorize that Europa has two frozen layers: an outer lid of cold ice and a layer of slightly warmer convecting ice. Such a balance could create subduction, as long as the outer shell contains varying amounts of salt. That is because the mineral provides the necessary density differences for a slab to conduct.
“Adding salt to an ice slab would be like adding little weights to it because salt is denser than ice,” said lead authorBrandon Johnson, an assistant professor in Brown’s Department of Earth, Environmental and Planetary Sciences, in a statement. “So rather than temperature, we show that differences in the salt content of the ice could enable subduction to happen on Europa.”
While the team is not sure, they believe Europa does have such variability in salt content. In the past, researchers have observed water upwelling from the moon’s interior in a process that is similar to magma bubbling out of Earth’s mantle. That should then leave high salt content in the crust under which it rises.
“This supports the idea that something like plate tectonics is occurring on Europa and may tell us about the composition of Europa’s ice shell,” the authors, according to Gizmodo. “Our work also implies that the plates will sink all the way to Europa’s subsurface ocean. This is important because material from the surface of Europa could act as food for life that may exist in Europa’s ocean.”Astronomers will continue to monitor the surface to see what else they can find about the moon’smechanisms.