The Galilean Moons of Jupiter

There are far more moons in our solar system than we once thought and they are far more strange than the one we see orbiting our planet at night. Some planets, like our Earth have one, large moon. Others, like Mercury have none. Then there are planets that seem to operate as lords of their own realm, like the sun with its planetary satellites. Jupiter is one of those planets. It has a large, impressive system of moons and more are being found. Jupiter has both regular and irregular moons – some as large as planets, others as small as asteroids. Some of these moons have their own atmospheres and are active worlds in their own right. When it comes to planetary study, many of the outer planets are nearly impossible to study because of their hostile environments so we have to look at whether it is possible to explore them from their moons as a launching point. Let’s take a look at Jupiter’s major moons.

Regular moons are like earth’s moon. They tend to be large, stable with circular orbits. All of them move through a plane in space that is roughly equal to the planet’s equatorial plane and may have formed through collisions with other objects. Irregular moons tend to have retrograde orbits, are usually formed through accretion, are rarely round and tend to be very small. Jupiter seems to collect moons like some people collect stamps and it has four, regular moons: Io, Europa, Ganymede and Callisto. Landing on them to study Jupiter, and the moons too, may be a viable option in the future.

Io – Around the size of earth’s moon, it has spectacular volcanic convulsions and lava flows which was shocking for a moon. You don’t think of these kinds of active geological activity when you think of the word Moon. Jupiter is the force that is putting pressure on Io through tidal heating, which causes Io’s active vulcanism. It kneads and stretches Io’s surface and this is caused by being in an eccentric or an elliptical orbit. It must be noted that elliptical orbits elsewhere in the galaxy are actually normal. There are other star planetary systems where elliptical orbits are the norm and circular orbits are abnormal. So our solar system in unique in this aspect. The tidal heating not only creates the volcanoes on Io but they, in turn create the atmosphere that escapes into space to form a massive gas cloud around Jupiter. Although it would be fascinating to land on Io, it would be prohibitive because of the hostile atmosphere.

Europa – Europa is as cold as Io is hot but it is only cold on the surface. There’s heating beneath. There’s an underground ocean 10 – 15 miles below the surface. This water is in the form of ice oceans and icebergs. Where there’s water there could exist life. The surface is crisscrossed with “crop circles” and bands. Again, Jupiter’s mass might be the reason. Scientists believe that the icy cover may not reach all the way to the oceanic core but that the surface may really be a vast iceberg floating on top of an icy planetary ocean. The ocean wells up from beneath the surface through the long cracks in the surface and is smoothed over again.

Ganymede – It’s the largest moon in the jovial system. It is not as affected by Jupiter’s gravitational pull as the other regular moons because it is farther away. It is the only moon in the solar system with its own magnetic system and has the mildest of all jovial lunar atmospheres and environments. It may be the best moon to land on for exploration and research.

The other gas giants have weird and fascinating moons as well but Jupiter has gathered the lion’s share of moons so far in the solar system These are the regular moons of the jovial system and unlike their parent planet, it may be possible for explorers and scientists in the future to land on one of these moons for research purposes and even one day, colonization.