Planetary scientists at the University of Arizona in Tucson have provided a model for how these features are created, providing perhaps the most convincing evidence yet for a global ocean on Europa, about the size of Earth s moon. They reported on it in the Sept. 17 issue of Science . Gregory V. Hoppa, B. Randall Tufts, Richard Greenberg and Paul E. Geissler of the UA Lunar and Planetary Laboratory theorize that cycloidal cracks form in Europa s solid-ice surface with the daily rise and fall of tides in the subsurface ocean.
New images show that cycloidal cracks and ridges are widely distributed over all of the moon.
Tidal stresses on Europa s ice-covered ocean ebb and flow as it orbits Jupiter, which is 300 times as massive as Earth. According to the UA researchers model, Europa s ocean tides rise and fall a distance of 30 meters. When Europa is farther, the tides fall because Jupiter s force falls. This causes Europa s ice shell to flex. A new collaboration between astronomers at the University of Arizona and the Australian National University will make it easier to spot and track asteroids headed towards Earth.