Europa's variable plumes

Europa's variable plumes
Europa's variable plumes The Hubble Space Telescope has spotted a plume of water 200 kilometers above Europa's south polar region, but only at one position along its orbit, when the moon was at apoapsis. The bottom diagrams show a model for stresses across cracks in Europa's southern ice shell at different positions in its orbit. As the moon goes in its orbit around Jupiter, it gets squeezed pole-to-pole when close to Jupiter and returns to a more spherical shape when farther from Jupiter. Cracks near the moon's south pole are squeezed together when Europa is close to Jupiter and pulled apart when Europa is far from Jupiter. Roth et al. 2013