Europa

The Phoenician Princess

Europa [yur-ROH-pah] is the sixth of Jupiter's moons and the fourth largest. Europa is named after a Phoenician princess who was abducted by Zeus and taken to the island of Crete to be his lover. Zeus took the form of a white bull and coaxed Europa to climb on his back as he swam off to Crete. Europa was discovered by Galileo Galilei and Simon Marius in 1610 and is one of the Galilean satellites. As with the other moons of Jupiter, most of what we know about Europa was learned from the Voyager and Galileo missions.

Galileo false-color image of Europa surface features (NASA/JPL)		Galileo view of Europa showing dark spots known as lenticulae (NASA/JPL)		Galileo close-up of Europa's surface showing ice and dust (NASA/JPL)

A Frozen Ocean

Europa is very different from the other moons of Jupiter. Instead of a rocky, cratered surface like Callisto and Ganymede, it instead has a smooth outer surface of cracked ice. There are very few sign of craters on Europa. In fact, only three large craters have been found. This indicates that Europa's surface is very young and active. In photographs sent back by the Voyager and Galileo probes, the surface resembles sea ice on Earth. Astronomers believe that beneath this layer of ice may exist an ocean, kept liquid by the moon's internal heat. This liquid ocean could be as much as 30 miles deep. The existence of deep ocean vents on the ocean floor on Earth have led some scientists to speculate that there could be a possibility of life on Europa. Around these deep sea vents on Earth are life forms that do not need sunlight to survive. They instead feed on bacteria that get their nutrients from chemicals seeping up from the ocean floor. This process is known as chemosynthesis. Scientists believe that similar life forms could evolve on Europa if a liquid ocean does indeed exist beneath its frozen surface.

Features of Europa

The most apparent features on Europa are a series of dark streaks crisscrossing the entire surface of the moon. Astronomers believe that these marks may have been formed by a series of volcanic eruptions or geysers. Another theory is that tidal forces cause the frozen surface of Europa to crack. Water from the interior then flows through the cracks and refreezes. Like Ganymede, Europa was long thought to have no atmosphere. But recent observations with the Hubble space telescope indicate that a thin atmosphere of oxygen exists. It is believed to have been formed by sunlight and charged particles interacting with water particles on the surface. It is a process very similar to that which takes place on Ganymede. Recent data from the Galileo mission supports the theory of a liquid ocean beneath Europa's surface. If this can be proven, Europa will remain one of the prime candidates for extraterrestrial life in our solar system.