Despite the fact that Jupiter has a number of approximately 63 named satellites, only four of them are generally referred to as the planet's moons. These four celestial bodies, Io, Europa, Ganymede and Callisto, are also dubbed the Galilean Moons, in honor of the great Italian astronomer. Now, researchers have established that the four large moons that still exist today are roughly the fifth generation of natural satellites to form around the planet. In other words, more than 20 other similar bodies have been literally consumed by it in the early days of the solar system.
According to an international team of researchers, at the beginning of the solar system, when the new celestial body was still very young, moons started forming from the large amounts of dust that orbited it, and which would eventually become the dusty rings we see today. But because matter was still flying towards the planet from other parts of the solar system, the newly-formed moons were themselves “knocked off” their established orbits, and forced on a spiraling, descending course for the surface of Jupiter, which virtually “ate” them.
“There could have been five generations of moons. The current Galilean moons formed just as the inflow of material into the disc from the solar system choked off, so they escaped the fate of their unfortunate predecessors. All the other moons – and there could have been 20 or more – were devoured by the planet in the early days of the solar system,” Southwest Research Institute scientist Robin Canup, who works from Boulder, Colorado, explains.
“We think something similar happened around Saturn, where the last generation contained one giant moon – Titan,” he adds. Canup and colleague William Ward believe that this type of phenomenon may be characteristic to gas giants, given the fact that the moons of Saturn and Jupiter, as well as their rings, seem to share the same origin, or at least to have formed via the same basic process. They also say that the process of moon formation, once a former generation had disappeared, was swift, and that the speed of it could account for why it is only now that scientists have picked up its hints.
The two also emphasize the fact that, the first time it appeared, the solar system probably had a very different configuration than that it has today. The order of the planets was different, some hadn't even begun to form, others would still acquire mass, while the asteroid belts were still not well defined. It's possible, in these configurations, that the laws of planetary interactions, as we know them, be slightly bent.
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