Europa The next world we will explore also revolves, or circles the planet Jupiter. Europa is a cold smooth ice covered world. A long time ago in space there was a period of time when it was very common for asteroids, and comets to hit other worlds. This is called the Heavy Bombardment Period. During this time most worlds including Earth were scared with bowl shaped impressions called craters.
Most worlds remain scared today.
However some like the Earth have since recovered their surfaces with new rock lava, or ice, hiding these scars. Because Europa is smooth we know it too has recovered its surface since the Heavy Bombardment Period. This along with a few other clues has led scientists to believe that Beneath its icy outer shell lies a liquid water ocean heated by Europa's hot core. This makes Europa the most likely place for life to exist outside of the Earth. Our next stop is a large world that circles the planet Saturn.