They analyzed all the Voyager images with the hope of finding an active geyser, but the search came up empty. The hopes of discovery were pinned on the next Jupiter mission known as Galileo. The Galileo spacecraft continues to orbit Jupiter since its arrival on December 7, 1995. It deployed a probe into Jupiter s atmosphere and went on to reveal the Galilean moons in detail as fine as 20 feet across. Since Europa is outside Jupiter's most intense radiation belt that could degrade or even destroy the delicate electronics aboard Galileo, several close flybys were allowed.
Photographs indicate that Europa has been resurfaced with water ice leaving very few craters.
The largest crater, Pwyll, has fresh white ice radiating hundreds of miles giving Europa an eerie resemblance to the Earth s Moon. Pwyll is nearly level with the surface indicating that it must have filled with something fluid from underneath. The central peak is considerably higher than the rim of the crater indicating that liquid water may have gushed upwards forming an icy hill and continued to ooze out and build it steadily skyward even after the crater collapsed and froze. Other images reveal very smooth, dark areas near the long cracks and are probably due to recent resurfacing from the ocean below. Further evidence for an ocean include the areas of upheaval and collapse in the icy crust that may be due to upwelling of warmer pockets of water below.