In 1610, Simon Marius and Galileo Galilei were both responsible for the discovery of Jupiter's moons, Io, Europa, Ganymede, and Calisto. Ever since their discovery, the satellites of Jupiter have raised questions for astronomers. Many of these questions pertain to Jupiter's second moon, Europa. At a distance of 670,900 km from Jupiter and a size close to that of our own moon, Luna, Europa has earned much speculation and wonder. The U.S. sent two spacecraft to study Jupiter and Jupiter's moons in early 1970s, Pioneer 10 and 11, but they only produced blurry pictures of Europa. In 1979, Voyager flew by Jupiter and it's moons and gave us the first close-up view of Europa. However, much of the data on Europa was gathered from the recent Galileo mission. Europa is the sixth largest moon in the solar system and orbits around Jupiter every 3 ½ days in a synchronous rotation. Europa's average mean density is 2970kg/m. Although interestingf these aspects of Europa are not what makes it such an amazing place to study. Europa is so interesting because of its predicted global oceans, its thin molecular oxygen atmosphere, and the presence of a battery acid chemical on the surface. Not to mention that Europa has the smoothest surface of any of the moons with only a few visible impact craters.
This lack of craters is part of the evidence that led scientists to predict that Europa has a global ocean. "Robert Pappalardo, an assistant professor in the astrophysical and planetary sciences department and one of the world's foremost Europa experts, said the icy moon is believed to contain an ocean some 13 miles under its icy surface-(Spacedaily). Other evidence was collected by the Galileo spacecraft. "Data collected by Galileo's magnetic-field-detecting instruments when the spacecraft flew close to the icy moon, showed that there is an electrically charged layer of some substance stirring possibly as close as 4.