NASA Research: Europa’s Mystery Dark Material Could Be Sea Salt

NASA laboratory experiments suggest the dark material coating some geological features of Jupiter’s moon Europa is likely sea salt from a subsurface ocean, discolored by exposure to radiation. The presence of sea salt on Europa’s surface suggests the ocean is interacting with its rocky seafloor — an important consideration in determining whether the icy moon could support life. The study is accepted for publication in the journal Geophysical Research Letters and is available online.

“We have many questions about Europa, the most important and most difficult to answer being is there life? Research like this is important because it focuses on questions we can definitively answer, like whether or not Europa is inhabitable,” said Curt Niebur, Outer Planets Program scientist at NASA Headquarters in Washington. “Once we have those answers, we can tackle the bigger question about life in the ocean beneath Europa’s ice shell.”

For more than a decade, scientists have wondered about the nature of the dark material that coats long, linear fractures and other relatively young geological features on Europa’s surface. Its association with young terrains suggests the material has erupted from within Europa, but with limited data available, the material’s chemical composition has remained elusive.

“If it’s just salt from the ocean below, that would be a simple and elegant solution for what the dark, mysterious material is,” said research lead Kevin Hand, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

One certainty is that Europa is bathed in radiation created by Jupiter’s powerful magnetic field. Electrons and ions slam into the moon’s surface with the intensity of a particle accelerator. Theories proposed to explain the nature of the dark material include this radiation as a likely part of the process that creates it.

After tens of hours of exposure to Europa-like conditions, sodium chloride samples turned a yellowish-brown color. The color is spectrally similar to that of dark features on Europa imaged by NASA's Galileo spacecraft. Image credit: NASA/JPL-Caltech.

After tens of hours of exposure to Europa-like conditions, sodium chloride samples turned a yellowish-brown color. The color is spectrally similar to that of dark features on Europa imaged by NASA’s Galileo spacecraft. Image credit: NASA/JPL-Caltech.

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