The average distance Europa is from Jupiter is 485,000,000 miles. This makes it the sixth moon of Jupiter’s 63 moons. The closest it comes to Jupiter is 664,862 kilometers and the farthest it gets from Jupiter is 676,938 kilometers. The moons that are closer to Jupiter than Europa are Metis, Adrastea, Amalthea, Theve, and Io in that order, starting with the closest.
It is about the same size as the moon and orbits Jupiter every 3.551181041 days. Europa has an iron core, rocky mantle, and an ocean composed of icy salty water. Europa’s erratic orbit causes high tides when it is close to Jupiter. This causes a “tidal warming” of the ocean. Because of the “tidal warming” and the fact that Europa has twice as much water as the Earth, astrobiologists believe that life could easily exist on Europa. It was discovered by Galileo Galilei in 1610. Much like Earth, Europa has a core that that is covered by silicate rock.
The Galilean moons (named after Galileo) are Europa, Io, Callisto, and Ganymede. Three of these moons have a symmetrical orbit. The moons are Europa, Ganymede, and Io. Ganymede orbits Jupiter one time per two orbits by Europa and four orbits by Io. This is an orbital resonance of 1:2:4. Each moon’s orbit also takes the same time to rotate on its axis that it does to orbit Jupiter, causing the moons to always have one side facing the moon much like Earth’s moon.
There were flybys of the moons of Jupiter by Pioneer 10 and Pioneer 11 in 1973 and 1974. In 1979, there were flybys by Voyager 1 and Voyager 2. The pictures taken were in vivid color. The Galileo satellite made flybys of the Galilean moons from 1995 to 2003. The satellite took many pictures after several orbits around Jupiter. It came within 162 miles of the Galilean moons. The pictures revealed much detail of Europa. Only a scattering of craters were found on Europa, evidence that there might be an ocean beneath its surface that contains more than twice the amount of water on all of the oceans of Earth combined.
Research indicates there might be enough oxygen on Europa for life more complex than microorganisms. Even without enough oxygen, life could exist in hot springs on the ocean floor based on sulphur and methane. Richard Greenberg of the University of Arizona did some research on whether or not enough oxygen exists for life. He found there could be enough oxygen for some life forms more complex than microorganisms.