Icy Surface of Jupiter’s Moon Flows Slowly
December 27, 2017
Is the ocean beneath the surface warm enough to support life?
Space.com – A new Ben-Gurion University study finds that ice on Jupiter’s moon Europa may drift across the satellite’s surface from the equator to the poles, or vice versa, at a glacial pace.
Potential future missions to Europa could analyze this ice flow to discover hints about whether the ocean, hidden under the ice’s surface, might be warm enough to support life, says Prof. Yosef Ashkenazy, the study’s lead author and BGU’s climate dynamicist at the Alexandre Yersin Department of Solar Energy and Environmental Physics of the Jacob Blaustein Institutes for Desert Research.
Europa is nearly the size of Earth’s moon. Under an icy shell up to more than 18 miles thick, Europa may possess an ocean perhaps about 100 miles deep, consisting of twice the amount of water found on Earth scientists have said.
Since there is life virtually wherever there is water on Earth, Europa may be one of the most likely places in the solar system to find extraterrestrial life, says Prof. Ashkenazy. The study was recently published in the journal Nature Astronomy.
Jupiter’s Ice Moon
Europa’s icy crust shields the moon’s ocean from view. Prior work suggested that this chaotic terrain, where ice has warped and broken into jumbled blocks, resulted from churning within the ice, causing blocks of it to rise vertically. Now, Prof. Ashkenazy and his colleagues have analyzed how this ice might also move horizontally across Europa’s surface.
The scientists developed a model of Europa’s shell composed of warm, soft ice flowing beneath a cold, brittle, rigid ice crust, a bit like how Earth’s crust possesses hot flowing rock underneath colder, even more brittle rock. Underneath Europa’s crust, the model also simulated an ocean heated by a warm core and by friction generated by Jupiter’s gravitational pull.
Ice on the Move
The model found that if Europa’s icy crust was thick enough, temperatures would vary enough within the underground ocean for a kind of churning known as convection to occur.
If convection occurred within Europa’s ocean, heat could flow from the equator to the poles, enough for the equator to become significantly cool compared to the poles, explains Prof. Ashekanazy. “In this scenario, ice would flow from the equator to the poles,” he says, because the ice at the equator could be miles thicker than at the poles.
However, if Europa’s crust is relatively thin and convection does not occur within its ocean, the poles would be much colder than the equator. “This would lead to warmer ice at the equator and thicker ice at the poles, and the pressure gradient would lead ice to flow from the poles to the equator,” says Prof. Ashkenazy.
The rate of ice flow would be very slow, on the order of about 0.4 inches per year, Prof. Ashkenazy says. Still, future missions to Europa could look for signs of this ice flow by measuring how thick Europa’s crust was at different points across the moon’s surface. Doing so “can help improve our understanding of what’s going on beneath Europa’s surface,” he adds.