Using Earth as a model, the scientists theorize that hydrothermal vents could be the source of the CO2. Because the ice cap seals in the water, the CO2 would build up, much like soda in a shaken bottle, until it erupted through the ice onto the surface. Once exposed to the near vacuum on the surface, the water would dissolve and leave the salts behind. A briny ocean would explain the unusual magnetic readings that Galileo recorded. The surface of Europa displays a vast network of lines criss-crossing the fields of ice.
Planetary scientists believe that the fractures in the surface are caused by tectonic activity.
Others believe that the gravitational pull of Jupiter exerts a tidal force on the ice, causing the frozen surface to crack. The images sent from Galileo show images remarkably similar to those of Earth s polar ice floes. Large chunks of ice appear to have been broken apart and reassembled, perhaps by the action of water below. Galileo recorded that a crack appeared approximately every 3.5 days, or in sequence with the moon s rotation around Jupiter. It is conceivable that life could have existed on Europa at one point in time, if it does not still exist today.