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CosmosUp | January 19, 2019

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Ice Crust In Europa Is Much Hotter Than We Thought

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Geoscientists from Brown and Columbia universities have run a set of experiments designed to understand how much heat is created when ice is deformed.

This experiments land some insight into how a moon like the Jovian moon Europa might behave under the strong tidal forces that undergoes as it orbits the giant planet. Europa is under a constant gravitational assault. As it orbits, Europa’ ice’ surface squeezed and stretched with due to Jupiter’s gravity creating enough heat, scientist think, to support a global ocean beneath the moon solid shell.

 These experiments suggest that this process, which is called tidal dissipation, could create far more heat in Europa’ ice than scientists had previously assumed.

The work ultimately will help researchers to estimate the thickness of the moon’ outer icy shell — an important factor in our search for extraterrestrial life. Astronomers could tell by looking at Europa from very early on that something was going on there, the surfaces were not remotely cold, dead places rather it was easy to see some sort of tectonic activity was occurring there.

[Scientists] had expected to see cold, dead places, but right away they were blown away by their striking surfaces,

said Christine McCarthy.

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.

So, to see how much ice is heated up as it was compressed-released, researchers put some ice in a compression device and subjected ice samples to repeated cyclical loads similar to what exists around Jupiter, therefore measuring how much deformation and heating are present.

People have been using simple mechanical models to describe the ice,

McCarthy said.

While those calculations suggested liquid water under Europa’s surface, they weren’t getting the kinds of heat fluxes that would create these tectonics. So we ran some experiments to try to understand this process better.

 The best way to imagine how the heat is formed is by comparing it to the heat which is generated when you bend a metal coat hanger back and forth till it breaks, as you keep bending, the wire gets hot… well the same thing happen on Europa, the more ‘you’ compress and decompress the ice is heats up.

What’s surprised everyone wasn’t the ice heated up but just how much is it, way more than they previously thought. The findings suggest that most of the heat actually comes from defects that form in the ice’s crystalline lattice as a result of deformation. Those defects create more heat than would be expected from the grain boundaries.

Christine discovered that, relative to the models the community has been using, ice appears to be an order of magnitude more dissipative than people had thought,

Reid Cooper said.

So, that mean that there may actually be more water under the icy surface of Europa than previously thought. The findings could ultimately help researchers to estimate the thickness of moon’s outer shell.

The beauty of this is that once we get the physics right, it becomes wonderfully extrapolative,

Cooper said.

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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