Scientists recreate Europa's red marks in laboratory experiment
Sen—Scientists have been simulating the geological processes believed to be taking place on Jupiter's moon Europa, creating an experiment that shows how water and salts could make their way from the moon's underground ocean to the surface.
Since observations by the Voyager and Galileo spacecraft, scientists have believed Europa has a salty subterranean sea. Further evidence supporting the existence of an ocean was captured by the Hubble Space Telescope which detected water vapor up to 201 km (125 miles) above Europa's south polar region in December 2012.
Europa's white icy surface is decorated with reddish lines, channels and marks, which previous research suggests are hydrated salts, mainly of magnesium sulfate (MgSO4). Volatile compounds like carbon dioxide (CO2), sulphur dioxide (SO2) and hydrogen peroxide (H2O2) have been also detected.
Researchers at Centro de Astrobiologia decided to create an experiment to show how liquids could make their way from the underground reservoirs to leave the reddish marks and lines on the surface.
In the laboratory the researchers simulated the extreme conditions of the sub-surface ocean, using an acqueous solution with CO2 and MgSO4 and observed what happened when it emerged and cooled on the 'surface'. The scientists describe the process as similar to Earth's volcanism but at temperatures below zero. The experiment showed three types of minerals were formed depending on the fluid’s evolution: water ice, clathrates of carbon dioxide and very hydrated magnesium sulfates (epsomite, meridianiite).
“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,” explained Victoria Muñoz Iglesias, one of authors of the research.
This image, compiled from data taken by NASA's Galileo spacecraft during two different orbits around Jupiter, shows reddish spots and shallow pits peppered across the ridged Europan surface. Image credit: NASA/JPL/University of Arizona/University of Colorado
“These crystallization processes are exothermic (they release energy); they also produce volume changes inside the crust, when the cryomagma solidifies,” said Victoria Muñoz-Iglesias in a statement on the research. “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”.
The reddish colour of the formations could be caused by the salts being altered due to the strong irradiation of Jupiter’s charged particles, forming sulfurous compounds, suggested the researchers. Another theory is that the sulphurous elements emanate from neighbouring moon Io which is known to be geologically active.
“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,” concludes the research.
Europa is one of the four Galilean moons discovered by Galileo Galilei in 1610. It is 3,140 km in diameter and lies 671,000 km from Jupiter, orbiting once every 3.55 days.
Europe is building a probe to study Europa, as well as two of the other Galilean moons, Callisto and Ganymede. The Juicy Icy Moons Explorer -- known as JUICE -- is due to launch in 2022 and arrive in orbit around Jupiter in 2030.
The research is published in the journal Geochimica et Cosmochimica Acta.