When Galileo Galilei discovered Europa in 1610, he could only imagine
whether the Jovian satellite contained life. But recent scientific
discoveries suggest that Europa could possibly be an abode for life.
At one time, scientists believed that a solid layer of ice covered Europa's frigid surface. Later, photographs taken by the Galileo space probe, which is in orbit around Jupiter, revealed that the white, icy landscape is striated by spindly, rust-colored fissures, with relatively few crater impacts. The lack of craters and the surface ice cracks some of which are more than nine miles wide indicate that something is constantly fracturing and replacing the ice. Probably an ocean below.
Could an Europan ocean contain living things? Perhaps. For example, it is quite possible that the ocean, warmed by Europa's molten core, contains deep-sea vents like Earth's "black smokers." By dispatching a lander to melt a hole in the ice and dropping a submarine into the sea, scientists could search Europa's ocean for signs of life.
Europa was discovered on January 7, 1610 by Galileo Galilei.
Early spacecraft missions to Jupiter began in the 1970s with Pioneer 10 and Pioneer 11, which were sent to photograph Jupiter and its moon system. Scientists were unsure if the Pioneer spacecraft would survive the trip, but the successful missions yielded images of Jupiter and its satellites including some dark and blurry photos of Europa. Several years later, Europa came into focus when in 1979 the twin Voyager captured images of a pale-yellow sphere, covered in a thick layer of cracked ice. Improved technology aboard the Galileo spacecraft gave us a closer look at Europa, and close-up images indicated that Europa's huge fissures were being "repaired" in a sense by an upward flow of new material from below the surface.
Of Jupiter's 16 known satellites, Europa is sixth in proximity and is Jupiter's fourth largest slightly smaller than Earth's Moon.
Europa orbits Jupiter at an approximate 671,000 kilometer distance. Due to powerful push-and-pull gravitational forces, Europa's orbit is exceptionally oblong. This exaggerated ellipse is caused by a unique occurrence between Europa and its neighboring satellites Io and Ganymede. With nearly clock-like precision, Europa makes one trip around Jupiter while Europa's inner neighbor Io makes two trips around Jupiter. For every two trips Europa makes around Jupiter, Europa's outer neighbor Ganymede makes only one trip. This orbital phenomenon is called Laplace resonance, and causes a countering gravitational force that affects Europa's orbit.
Europa's extremely smooth surface is quite unique to the inner solar system. Only a few of Europa's landscape features reach above one hundred meters high and scientists have only located three craters larger than 5 kilometers. This smooth, craterless terrain suggests a very young, active surface similar to that of Earth.
Recent observations lead scientists to believe that below Europa's icy crust estimated to be only 5 kilometers deep a vast ocean may exist. Though Europa is far from the Sun, strong gravitational tides caused by Jupiter's powerful pull, could create the internal heat necessary for maintaining liquid water.
Europa does have an atmosphere, although tenuous. This atmosphere is composed solely of oxygen. Unlike our atmosphere, the oxygen in Europa's atmosphere is likely not produced biologically. Europa's atmosphere is maintained by charged particles that hit its cold surface and produce water vapor. The water vapor splits into oxygen and hydrogen; the hydrogen then escapes from the atmosphere leaving only oxygen behind.