Europa, only slightly smaller than the Earth’s Moon, is one of Jupiter’s four natural satellites discovered by Galileo in 1610. (Jupiter has 64 moons in all — more than any other planet). If life does exist elsewhere in the solar system, many scientists would put their money on Europa, though Saturn’s moon Titan is also a promising candidate.
|Surface of Jupiter’s moon Europa|
Europa’s surface is made of ice, which may have an ocean of water beneath it. Indeed, faint cracks visible on the surface are very much like the rifts in our own Arctic ice. (See the photo above.) Also like the Arctic, Europa may only be frozen on the top, with the ice layer just a few kilometers thick. The interior, especially near the bottom, is hotter than the surface. The interior flexes due to the gravitational forces of Jupiter and other neighboring moon lo, which is the hottest moon in our solar system. This produces heat in a process called tidal heating and keeps the bottom of Europa above freezing point. Studies of Earth’s deep oceans have discovered hot volcanic vents where bacteria and other primitive creatures live. It is possible that such life forms could exist on Europa as well.
Europa (moon) (Wikipedia)