Lenticulae terrain on the surface of Europa
March 15, 2014

Researchers Recreate Europa’s Crust In The Lab

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Astronomers believe that Europa, one of Jupiter's moons, has a huge ocean beneath its icy surface. They have theorized that water, salts and gasses that have dissolved into that ocean rise to the surface, generating the enigmatic geological formations associated with the red-tinged formations seen on the moon's surface. A group of researchers from the Centro de Astrobiologia (CAB) in Spain have confirmed this theory with a laboratory experiment using water, carbon dioxide and magnesium sulfate.

The idea of Europa's hidden reservoirs of liquid water — the essential element for life on Earth — emerged from information obtained on the Voyager and Galileo missions. These missions registered fractures and “chaotic” terrains, which are associated with the reddish materials. The red structures provide a stark contrast against the glacial white of the dominant water ice of the surface.

Observations made from various space missions suggest that these geological formations seem to be related to the rise of fluids coming from inside. The data also suggests that the red material is made up of hydrated salts - mainly magnesium sulfate (MgSO4) - and more volatile compounds like carbon dioxide (CO2), sulphur dioxide (SO2) and hydrogen peroxide (H2O2).

The research team used these theories and observations to develop an experiment that would explain how these fluids evolve in their way between the deep reservoirs and the moon's surface.

"Just like Earth's magma emerges to the surface, a similar phenomenon could occur in Europa. Although, in this case it would be a watery cryomagma that would evolve and emerge outwards from the interior of the icy moon," said Victoria Muñoz Iglesias.

The scientists simulated the extreme conditions of the fluid reservoirs in the crust in laboratory settings; especially the high pressure (reproducing up to 300 bars) and the low temperature (around -4 ºC). They then watched what happened to the aqueous solution with CO2 and MgSO4 from these conditions when it emerges from the surface and cools.

The results resemble a variety of processes similar to volcanism on Earth, but at temperatures well below zero. Depending on the fluid's evolution, three types of minerals are formed: water ice, clathrates of carbon dioxide and very hydrated magnesium sulfates, such as epsomite and meridianite.

"These crystallization processes are exothermic (they release energy); they also produce volume changes inside the crust, when the cryomagma solidifies," said Iglesias. "If in the final mineral assemblage the quantity of clathrates is less than that of hydrated salts, the volume increases causing positive topographical features and fracturation in the crust. However, if the proportion of clathrates is bigger than the rest of solids, or these phases are destroyed releasing the gas, volume decreases and the terrains above might collapse. Some of the chaotic terrains of Europa´s surface could have been produced in this way."

Iglesias suggests that the current theory behind the reddish color of these structures is that they are produced by the alteration of the salts due to the strong irradiation of Jupiter's charged particles. This process forms sulfurous compounds. Competing theories focus on the bombardment of sulphurous elements coming from volcanic emissions from the neighboring satellite Io.

"Either way, our experiments show that certain characteristics of Europa´s surface regarding its composition, morphology and topography might be explained if a saline aqueous medium is involved, which has important consequences for living beings on Earth," concluded the researcher.

Europa is considered one of the best candidates for life in our solar system. When President Obama presented NASA's budget for 2015, it included an item for 15 million dollars to search for signs of life on Europa in the next decade.

Plans are in the works for the European Space Agency (ESA) to launch the JUpiter ICy moons Explorer (JUICE) mission in 2022. When JUICE arrives among the icy moons of Jupiter in 2030, it will fly over Europa twice to measure the thickness of its mysterious crust and explore its habitability.

Findings of this research are described in a recent issue of Geochemica et Cosmochimica Acta.

Image 2 (below): The scientists have simulated in the laboratory the extreme conditions of the fluid reservoirs in the crust of Europa. Credit: CAB (INTA-CSIC)