Europa is the fourth-smallest moon of Jupiter. It is thought to have an underground icy ocean, one that may potentially sustain life. Europa has a diameter of about 3100 kilometers and an average density of 3.013 ± 0.005 grams per cubic centimeter, (making it smaller than Earth's moon) and is about 4.29 astronomical units away from the Earth. Europa is located in Sol, in the galaxy known as the Milky Way, within the Local Group, within the Virgo Supercluster.