Current Events on Europa

Zonal flows in Europa-like ocean simulation. Credit: University of Texas Institute for Geophysics

Europa’s chaotic terrain may harbor materials from its heated ocean. The announcement, published this week in Nature Geophysics, sent a ripple of excitement through the astrobiology community. If proven, it raises the odds that any life harbored in the heated oceans of the sixth largest moon in the Solar System will be detected.

"Ocean water is being transformed into a new kind of ice, which is rising up from the interior and may be carrying ocean material with it," reported co-author Dr. Britney Schmidt, assistant professor at Georgia Tech.

This process, known as diapurism, would elevate elements of the liquid ocean higher into the ice shell at the more equatorial latitudes.

Current estimates of ice shell thickness range in the tens of kilometers. Penetrating such a depth to sample the ocean directly would be extremely challenging. In their article, “Ocean-driven heating of Europa’s icy shell at low latitudes”, Krista Soderland (UT Austin), Schmidt and colleagues describe how the lighter, newly made ice may be rising out of the heated oceans to create chaos terrains. These are features where the surface has been fractured into chunks of ice, both large and small, that are pushed up to a higher elevation than the matrix of ice that surrounds them.

When water from the ocean freezes and is pushed to the surface, any signs of life captured in the new ice would be more accessible to inspection.

Thera Macula (false color) is a region of likely active chaos production above a large liquid water lake in the icy shell of Europa. Color indicates topographic heights relative to background terrain. Purples and reds indicate the highest terrain. Image Credit: Paul Schenk/NASA

This paper not only suggests a location for future searches for life on the Galilean moon, but also describes the dynamics of Europa’s ocean currents.

"If you take models of planetary interiors," continues Schmidt, referring to models of atmospheric and oceanic circulation, "there is a fundamentally different behavior than what was assumed."

Gas giants Jupiter and Saturn demonstrate liquid dynamics driven by their rapid rotations. The liquid mixing on those planets occurs at the poles. Europa’s ocean follows a pattern found on ice giants Neptune and Uranus. These more slowly rotating planets experience mixing concentrated at the equator. Europa’s chaos terrains are found at +45 and -45 degrees latitude, and this is thought to reflect a concentration of circulation at the equator.

The new findings not only provide important information about life’s potential on Europa, but also improve our understanding of the dynamics of world-wide oceans on celestial bodies.

While rising plumes of heated water may be the best current explanation for the evolving appearance of Europe’s ice shell, the task of verifying this hypothesis will fall to future NASA missions such as the Europa Clipper. Using radar, magnetometers, infrared and thermal spectrometers, we may be able to detect the oceanic circulation at low latitudes predicted by this model. Sensitive recon cameras may one day close in on the chaos terrains and the compelling debris they have dredged up from the depths.