December 20, 2013 - SAN FRANCISCO — Scientists may have spotted the first evidence for active plate tectonics on another world. Jupiter’s moon Europa is covered in an ice crust bearing scars that may reveal movement similar to that of Earth’s rocky plates.
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Europa was already considered to be among the most scientifically intriguing bodies in the solar system and one of the most promising places to hunt for life in the solar system because of the liquid ocean that resides beneath its crust. If the latest findings turn out to be true, it could be another point in favor of the moon’s potential habitability by providing a way to get nutrients from the surface down into the ocean.
“What’s exciting is that this would be the only other place outside of Earth where a plate-tectonic-style system is occurring,” said planetary scientist Alyssa Rhoden, a NASA postdoctoral program fellow who studies Europa, but was not involved in the new research.
Europa’s icy surface has been estimated to be between 40 million and 90 million years old, making it one of the youngest surfaces in the solar system, and far younger than the moon itself, which is more than 4 billion years old. This means that somehow the crust is being refreshed either by resurfacing or recycling of old crust.
Scientists believe new ice is being formed on Europa along linear features called dilational bands. There are thousands of kilometers of these bands on the planet, potentially creating significant amounts of new ice crust. The problem is that nobody knows where all the old crust is disappearing.
“Unless Europa has been expanding within the last 40 to 90 million years, there has to be some process on this icy moon that’s able to accommodate a large amount of new surface area being created at dilational bands,” planetary scientist Simon Kattenhorn of the University of Idaho said during a presentation about the new research Dec. 13 at the American Geophysical Union meeting.
On Earth new crust is created along seams on plates that underlie the oceans, known as mid-ocean ridges. Here, the two sides of the plate move away from each other as molten material rises from the mantle below the crust to fill the gap, cool and form new crust. A similar process is thought to create new ice along Europa’s dilational bands.
All the new crust formed on Earth is balanced out primarily by the destruction of older crust in a process known as subduction. When an oceanic plate runs into a plate bearing a continent, the ocean crust is usually pushed beneath the continent where it gradually melts and is recycled into the mantle.
Close-up of the surface of Europa.