Monday, December 2, 2013

Scientists Detect Hidden Ocean on Jupiter’s Moon

This rendering shows isosurfaces of warmer (red) and cooler (blue) temperatures in a simulation of Europa’s global ocean dynamics. More heat is delivered to the ice shell near the equator where convection is more vigorous, consistent with the distribution of chaos terrains on Europa. Credit: Model image created by J. Wicht with the image of Europa taken from NASA/JPL/University of Arizona


Liquid water may lurk beneath the frozen surfaces of Jupiter's moon Europa and other icy worlds. Extending ocean science beyond Earth, planetary oceanographers are linking Europa's ocean dynamics to its enigmatic surface geology. Although never directly observed, this hidden sea holds the key to Europa’s enigmatic surface geology, scientists believe. Any liquid water represents a potential habitat for life. A team of researchers at the University of Texas with assistance from a computer modeler at the Max Planck Institute in Germany has put together a computer model that might just explain the peculiar surface of Jupiter's moon Europa. In their paper published in the journal Nature Geoscience, the team suggests the odd surface terrain patterns likely come about due to convection. Jason Goodman of Wheaton College offers a perspective on the researchers' findings in a News & Views piece printed in the same journal.

Europa, the sixth-closest moon of Jupiter, is covered with icy chunks that have been cracked and crunched into chaotic patterns.

Scientists aren’t exactly sure what processes form and shape the patterns. But new computer simulations show turbulent global ocean currents that move Europa’s internal heat to the surface most effectively in regions closest to the moon’s equator.

Convective flow structures, zonal flows and temperature fields in planetary convection models. Credit: Nature Geoscience
Convective flow structures, zonal flows and temperature fields in planetary convection models. Credit: Nature Geoscience

That varied heat distribution pattern could allow more changes to the ice features and could explain the formation of the chaotic ice patterns at the moon’s lower latitudes, researchers report December 1 in Nature Geoscience.

It’s not yet clear whether the model, scaled up from laboratory experiments and simulations, fully captures the moon’s dynamics. But, without a space mission to Europa, the model provide scientists with the best understanding to date of the moon’s ice and ocean, according to a News & Views article accompanying the research.

This rendering shows the temperature field in a simulation of Europa’s global ocean dynamics, where hot plumes (red) rise from the seafloor and cool fluid (blue) sinks downward from the ice-ocean interface. More heat is delivered to the ice shell near the equator where convection is more vigorous, consistent with the distribution of chaos terrains on Europa. Credit: Model image created by K. M. Soderlund with the image of Europa taken from NASA/JPL/University of Arizona
This rendering shows the temperature field in a simulation of Europa’s global ocean dynamics, where hot plumes (red) rise from the seafloor and cool fluid (blue) sinks downward from the ice-ocean interface. More heat is delivered to the ice shell near the equator where convection is more vigorous, consistent with the distribution of chaos terrains on Europa. Credit: Model image created by K. M. Soderlund with the image of Europa taken from NASA/JPL/University of Arizona

The ice shell of Jupiter’s moon Europa is marked by regions of disrupted ice known as chaos terrains that cover up to 40% of the satellite’s surface, most commonly occurring within 40° of the equator. Concurrence with salt deposits implies a coupling between the geologically active ice shell and the underlying liquid water ocean at lower latitudes. Europa’s ocean dynamics have been assumed to adopt a two-dimensional pattern, which channels the moon’s internal heat to higher latitudes. 

Scientists present a numerical model of thermal convection in a thin, rotating spherical shell where small-scale convection instead adopts a three-dimensional structure and is more vigorous at lower latitudes. Global-scale currents are organized into three zonal jets and two equatorial Hadley-like circulation cells. The team finds that these convective motions transmit Europa’s internal heat towards the surface most effectively in equatorial regions, where they can directly influence the thermo-compositional state and structure of the ice shell.

They suggest that such heterogeneous heating promotes the formation of chaos features through increased melting of the ice shell and subsequent deposition of marine ice at low latitudes. Scientists conclude that Europa’s ocean dynamics can modulate the exchange of heat and materials between the surface and interior and explain the observed distribution of chaos terrains.

No comments:

Post a Comment