Scientists think Europa’s ice shell is 10 to 15 miles (15 to 25 kilometers) thick, floating on an ocean 40 to 100 miles (60 to 150 kilometers) deep. Based on Europa's icy composition, scientists think the most likely material to create this magnetic signature is a global ocean of salty water. This measurement strongly implied that a special type of magnetic field is being created (induced) within Europa by a deep layer of some electrically conductive fluid beneath the surface. One of the most important discoveries made by Galileo showed how Jupiter's magnetic field was disrupted in the space around Europa. In all, the spacecraft made a total of 12 close flybys of the icy moon. The information about Europa that Galileo sent was so intriguing that the mission was extended for a two-year follow-on journey, known as the Galileo Europa mission. Galileo's primary mission included observations of each of the four Galilean moons during repeated flybys. The puzzling, fascinating surface of Jupiter's icy moon Europa looms large in this view made from images taken by NASA's Galileo spacecraft in the late 1990s. These cracks had separated, and dark, icy material appeared to have flowed into the opened gaps, suggesting that the surface had been active at some time in the past. In other words, Europa has a very smooth surface, relative to the other icy moons.Įven though the Voyagers did not pass extremely close to Europa, their images were of high enough quality that researchers noted some of the dark bands had opposite sides that matched each other extremely well, like pieces of a jigsaw puzzle. Images from the two Voyagers revealed a surface brighter than that of Earth's moon, crisscrossed with numerous bands and ridges, and with a surprising lack of large impact craters, tall cliffs, or mountains. The spacecraft snapped a full global image of Europa from a distance of about 1.2 million miles (2 million kilometers).Ī few months later, Voyager 2 had its closest encounter with Europa on July 9, 1979. Voyager 1's closest approach to Jupiter occurred on March 4, 1979. This picture of Europa was taken on March 4, 1979, from a distance of about 1.2 million miles (2 million kilometers) by NASA's Voyager 1.
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