December 4, 2013
Ocean Currents May Shape Europa’s Icy Shell
[ Watch the Video: Saturn's Moon Europa Has A Dynamic Subsurface Ocean ]
April Flowers for redOrbit.com - Your Universe Online
Researchers from The University of Texas at Austin's Institute for Geophysics (UTIG), the Georgia Institute of Technology, and the Max Planck Institute for Solar System Research have revealed that the subsurface ocean on Jupiter's moon Europa might have deep currents and circulation patterns. These currents and patterns have heat and energy transfers capable of sustaining life, a finding of relevance to the search for life in our solar system.
Europa is believed to be one of the most likely planetary bodies in our solar system to sustain life. Magnetometer readings from the Galileo spacecraft that detected signs of a salty, global ocean below the moon's icy shell reinforce this belief.
Scientists have to rely on magnetometer data and observations of the surface to account for oceanic conditions below the icy shell, due to a lack of direct measurements.
One of Europa's most prominent features is chaos terrains, or regions of disrupted ice on the surface. Krista Soderlund of UTIG explains that chaos terrains, which are concentrated in Europa’s equatorial region, could result from convection in Europa's ice shell, accelerated by heat from the ocean. Diapirs, or warm compositionally buoyant plumes of ice that rise through the shell, might be formed by the heat transfer and possible marine ice formation.
The research team created a numerical model of Europa's ocean circulation, finding that warm rising ocean currents near the equator and subsiding currents in latitudes closer to the poles could account for the location of chaos terrains and other features of Europa’s surface. Coupled with regionally more vigorous turbulence, such a pattern intensifies heat transfer near the equator. This could help initiate upwelling ice pulses that create features such as the chaos terrains.
“The processes we are modeling on Europa remind us of processes on Earth,” says Soderlund. A similar process has been observed in the patterns creating marine ice in parts of Antarctica, she noted.
The patterns observed on Jupiter and Saturn contrast with the current patterns modeled for Europa. On Jupiter and Saturn, bands of storms form because of the way their atmospheres rotate. Europa's ocean physics seem to have more in common with the oceans of the "ice giants," Uranus and Neptune. These oceans show signs of 3D convection.
“This tells us foundational aspects of ocean physics,” notes Britney Schmidt, assistant professor at the Georgia Institute of Technology. If the study's hypothesis is correct, says Schmidt, it reveals that Europa's oceans are very important as a controlling influence on the surface ice shell. This provides proof of the concept that ice-ocean interactions are important to Europa.
“That means more evidence that the ocean is there, that it’s active, and there are interesting interactions between the ocean and ice shell,” says Schmidt, “all of which makes us think about the possibility of life on Europa.”
Soderlund, who has studied icy satellites throughout her science career, is anticipating the opportunity to test her hypothesis through future missions to the Jovian system. The European Space Agency's (ESA) Jupiter Icy moons Explorer (JUICE) mission will provide tantalizing glimpses into the characteristics of the ocean and ice shell through two flyby observations. A concept under study at NASA, the Europa Clipper mission, would complement the view with global measurements.
Soderlund says she appreciates the chance “to make a prediction about Europa’s subsurface currents that we might know the answer to in our lifetimes — that’s pretty exciting.”
The findings of this study were published online in Nature Geoscience.
Image 2 (below): Zonal flows in Europa-like ocean simulation. Credit: University of Texas Institute for Geophysics