Jupiter’s Moon Europa just got a boost for life - Global Times

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Wednesday, 6 December 2017

Jupiter’s Moon Europa just got a boost for life

The odd cracks, patches of dust and craters of Europa’s icy surface may conceal a liquid ocean beneath. Picture: NASA/JPL-Caltech/SETI InstituteSource:Supplied

Tectonic ice sheets may be ‘feeding’ Europa’s under-ice ocean with the seeds of life

THERE’S something odd going on inside Jupiter’s frozen moon Europa. And its presence could dramatically boost the chances there’s alien life under the ice.

Jupiter's ocean-harboring moon may have plate tectonics, a new study suggests. Credit: NASA/JPL-Caltech/SETI Institute
 
NUTRIENT BOOST

It’s tectonic activity. But not as we know it.

Europa spins about Jupiter on a slightly elliptical orbit. This means it swings close to the gas giant before looping somewhat further away.

The slight differences in gravity this produces flexes the moon’s core — creating the friction necessary to create a molten heart.

This warms the ice from below — likely creating a vast subsurface ocean of liquid water.

A possible body of water on the moon Europa that orbits planet Jupiter is believed by scientists to be the largest in our Solar System.Source:News Corp Australia

But is there any chance this ocean can harbour life, being some 100 kilometres under rock-hard ice and so far of our own warmth-giving Sun?

New simulations reported by the American Geophysical Union have just solved one of the many challenges such life would face.

A nutrient flow.

Essential minerals and compounds must circulate in a planet’s — or moon’s — ecosystem to maintain any cycle of life.

On Earth, that is done through tectonic activity.

MIXMASTERS

Here, tectonic plates of rock are constantly pushing against each other.

The result is often subduction — where the old Earth’s crust gradually slips into the molten mantle below. Elsewhere, new rock cools as it rises — taking the place of that which has been swallowed up.

It’s a process that refreshes the supply of vital nutrients on our planet’s surface. Otherwise, it would all be eroded — and consumed — away.

Turns out a similar process is likely to be happening on Europa.

Except the refreshing nutrients aren’t coming from below.

They’re coming from above.

Plate tectonic activity may be happening in Europa’s icy shell. Simulations show plates of rock-hard-ice could be grinding into each other, forcing the surface layer down to later melt in the liquid ocean below.

“We have this evidence of extension and spreading, so the question becomes where does that material go?” said Brandon Johnson, an assistant professor at Brown University’s Department of Earth, Environmental and Planetary Sciences.

“On Earth, the answer is subduction zones. What we show is that under reasonable assumptions for conditions on Europa, subduction could be happening there as well, which is really exciting.”

NASA image image projection showing the deep canyons and crevases which may link the icy surface of one of Jupiter's moons, called Europa, with a subsurface ocean.Source:Supplied

 INGREDIENTS FOR LIFE

As the ice is forced downward, it would carry dust and compounds that have been falling on Europa’s surface into the potentially life-giving liquid water.

This rich ‘seasoning’ of oxidants and other chemicals are the building blocks — and foods — of life.

“If indeed there’s life in that ocean, subduction offers a way to supply the nutrients it would need,” Professor Johnson says.

It all depends on the behaviour of Europa’s ice.

There is evidence Europa’s shell is made up of two layers of ice.

One is a thin outer casing that is intensely cold (and dirty, as the moon’s orange markings betray). This sits on a layer of slightly warmer, convecting ice.

The warmer ice is less dense than the crust, allowing the crust to sink until it cools to the temperature of the ice below.

But the new simulation shows that the presence of salts in Europa’s ice shell add enough difference in densities for it to subduct in the same manner as tectonic plates.

“Adding salt to an ice slab would be like adding little weights to it because salt is denser than ice,” Professor Johnson says. “So rather than temperature, we show that differences in the salt content of the ice could enable subduction to happen on Europa.”

This could all contribute to a cycle similar to that produced by the magma under Earth’s mantle. One such sign is cryovolcanism, where the salty contents of Europa’s ocean are sprayed out on its icy surface.
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