There May Be Much More Heat on Europa's Icy Surface Than We Thought

Friday, 22 April 2016 - 1:08PM
Astrobiology
Alien Life
Europa
Friday, 22 April 2016 - 1:08PM
There May Be Much More Heat on Europa's Icy Surface Than We Thought
Jupiter's moon Europa has long considered to be a prime candidate for the discovery of extraterrestrial life, as scientists believe that it has a subsurface ocean lying under its icy shell. Now, researchers from Columbia and Brown University have discovered that Europa's surface may contain much more heat than we ever imagined, which would increase the chances of finding alien life.

For decades, scientists had assumed that Europa would be too cold to support life, since it's covered in ice. But when NASA first explored and took images of Europa back in the 1970s and 1990s, they were surprised to find that it was much warmer and more active than it had any right to be. 

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"[Scientists] had expected to see cold, dead places, but right away they were blown away by their striking surfaces," study leader Christine McCarthy, a geological sciences fellow at Columbia University, said in a statement. "There was clearly some sort of tectonic activity-things moving around and cracking. There were also places on Europa that look like melt-through or mushy ice."
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Researchers ultimately found that this activity is the result of a process called "tidal dissipation." Europa orbits Jupiter, and so its icy surface is constantly pulled back and forth by Jupiter's gravity. This causes friction between different surfaces, which in turn generates heat, which is then dissipated through tectonic activity. McCarthy compares the effect to bending a metal coat hanger.

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"If you bend it back and forth, you can feel it making heat at the junction," she said. "The way it does that is that internal defects within that metal are rubbing past each other, and it's a similar process to how energy would be dissipated in ice."
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Although we've known about tidal dissipation for years, the mechanics of the process weren't well-understood. In the new study published in Earth and Planetary Science Letters, McCarthy and her colleagues modeled the process by loading ice into a compression apparatus and simulating the cyclical pressure on Europa's surface ice. They then measured the lag time between the compression and deformation of the ice in order to estimate how much heat was produced. As a result, they found that ice is an order of magnitude more dissipative than the generally accepted model, or in other words, Europa's ice may produce far more heat than was previously assumed. And if that's true, then Europa is even more likely to support a liquid subsurface ocean than we thought.

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"The beauty of this is that once we get the physics right, it becomes wonderfully extrapolative," said co-author Reid Cooper, professor of Earth, environmental and planetary sciences at Brown. "Those physics are first order in understanding the thickness of Europa's shell. In turn, the thickness of the shell relative to the bulk chemistry of the moon is important in understanding the chemistry of that ocean. And if you're looking for life, then the chemistry of the ocean is a big deal."
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