The entire icy surface of this moon might be floating on the ocean of salty liquid water and this ocean may contain more water than all the oceans on earth combined. Europa is the most intriguing moon in the solar system.
A bit of history
Discovered by Galileo Galilei on January 8, 1610, named after a lover of Zeus, the Greek counterpart of Jupiter. A total of 5 Spacecraft have visited the Jovian system, namely: Pioneer 10(1973), Pioneer 11(1974), Voyager 1(1979), Voyager 2(1979), and Galileo spacecraft. Most of the information that we have comes from Galileo spacecraft as it circled Jupiter 34 times with 11 flybys around Europa.
Place around Jupiter
Europa is the 6th closest moon of planet Jupiter at an average distance of 5.2 astronomical units from the Sun. It orbits Jupiter every 3.5 Earth days and only one side of Europa faces the planet due to gravitational lock.
The innermost 3 satellites of the Jovian system are in an orbital resonance. For every one orbit of Ganymede, Europa Orbits twice and Io orbits four times. This also means, sometimes all these moons align, with Io and Europa aligning most frequently.
Europa’s orbit is not exactly circular and hence, as Europa approaches closer to Jupiter, the gravitational attraction elongates the moon in the direction towards the planet and away from it. And as it reaches the farthest point from Jupiter, Europa relaxes back into a more spherical shape.
The Surface of Europa
The icy surface of Europa is filled with long and dark ridges and cracks known as ‘Lineae’. This is believed to occur due to the active glaciers sliding on the surface. These patterns and features of shifting Icy tectonic plates are a result of Jupiter’s Gravity tugging and pulling the Europa’s Surface causing friction and melting in the ice plates. Not all surface patterns are explained due to this phenomenon, some sections of the surface have rotated at certain angles as if the surface is floating above a liquid beneath.
A subsurface ocean? How?
Instruments onboard Galileo spacecraft during its mission, detected a magnetic field generated by Europa. This Magnetic field appeared to be shifted during subsequent flybys. Scientists explain this anomaly by understanding that the Europa behaves like a conductor with a special induced magnetic field around it. Which is believed to be caused by an electrically conductive fluid present between the crust and mantle (Salt Water).
Galileo spacecraft was also able to fly through the plumes of water-rich material ejected from Europa’s surface. Much like Saturn’s moons: Enceladus and Triton, further strengthening the hypothesis of the subsurface ocean.
Furthermore, scientists have also been pointing Hubble Space Telescope towards the moon. It has also detected the presence of water-rich plumes at the south pole of the Europa by taking ultraviolet images of Europa as it was passing in front of Jupiter.
Fun Facts
Europa is 5 times more reflective than our moon due to its surface of water ice.
Europa’s mass exceeds the combined mass of all the smaller moons in the Solar System.
Europa has the smoothest surface compared to any other known body in the solar system.
Radiation levels per day on the surface of Europa are 1800 times the average annual dose of a human here on Earth.
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