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Satellite of Jupiter discovered by Galileo in 1610. It has a diameter of 3138 km and a mass around 5‧1022 kg. The semi-major axis measuring 671,000 km, the orbital period of 3.55 days. The high value of its density suggests that it is mainly composed of rock, with no more than 10% of ice: because of its chemical composition, therefore, Europe would look like I do, but not the other two Galilean satellites of Jupiter (Ganymede and Callisto), which have a density of 1.9 g / cm3 and are constituted for approximately 50% of ice. Slightly smaller than the Moon, Europe is made mainly of silicates with a crust made up of ice water, probably in its interior there is an iron-nickel core and is surrounded externally by a tenuous atmosphere composed primarily of oxygen. Unlike Ganymede and Callisto, its surface is streaked and little cratered and is smoother than that of any known object in the solar system. The apparent youth and smoothness of its surface have led to hypothesize the existence of this ocean of water beneath the crust, which could be abode for extraterrestrial life. In this hypothesis it is proposed that Europe, heated internally by tidal forces caused by its proximity to Jupiter and the orbital resonance with the neighbors and I Ganymede, releases the heat necessary to maintain a liquid ocean beneath the surface and while stimulating activity geological similar to plate tectonics. On 8 September 2014, NASA reported finding evidence of plate tectonic activity on Europe, the first geological activities of this kind of a different world from the Earth. In December of 2013 NASA finds on the crust of Europa certain clay minerals, more precisely, phyllosilicates, which are often associated with organic material, moreover, the same NASA announced, based on observations made with the Hubble Space Telescope, which were detected of water vapor geysers similar to those of Enceladus, the satellite of Saturn.