ALL ABOUT OF JUPITER'S MOONS 

THE JUPITER'S MOON GALILEAN 

The smallest but perhaps most exciting of all the Galilean moons. Slightly smaller than our moon, it was known for decades to be very reflective, meaning its surface was probably loaded with water ice. But even so, the Voyager observation was shocking. 

They showed a surface completely lacking in craters, meaning something had resurfaced the moon like Io or Venus; but Europa has no volcanoes. Even more intriguing the surface was covered in long cracks, dark streaks all over the moon, as well as complex ridge. 

These or other features appeared to be due to material from the interior of Europa welling up and forming the new surface, kind of like Dev lava does on earth. But in this case, material is water. It's now thought that Europa has an entire ocean of water, sealed up under a solid crust of ice several kilometres thick. Water welling aap hand moving under The crust causes it to shift, creating all the various surface features. 

 The amount of water that may be locked up on Europa is staggering; easily more than all the water in all the oceans on earth. Like Ganymede and Io, the interior Europa is kept worn by the title fixing from the other moons, keeping the ice method. 

AMALTHEA THE MOON OF JUPIER 

The next biggest moon after the biggest 4 is way smaller; named Amalthea, it's an irregular lamp about 250 km across its longest dimension. It was discovered in 1892, and it's a red probably polluted by sulphur from Io. Its orbit just over 100,000 km from jupiter's cloud tops; if you stood on Amalthea's surface, Jupiter would fill half the sky.  

The moon gets smaller and more irregularly shaped from there, with hamelia and Thebe. Many of irregular, distant moons of Jupiter orbit the planet backward relative to the others, in what are called retrograde orbits. 

LOOKIGN AT THE SURFACE OF THE MOON

They may be captured asteroids from the nearby asteroid belt. Many of the Moon se have orbital characteristics that are very similar, too, which may indicate they were once a single object that broke up. Several such families of moon orbit Jupiter. 

The smallest moon as we have seen a rough t a kilometre across. If they were sitting on Earth Day might be hard to paidal up on a bicycle, but orbiting Jupiter they hardly rate as more than debris. There are probably thousands of moons the size of house circling the planet, and who knows, maybe milian the size of tennis ball.