Saturn has far more moons than Jupiter. However, if we consider only the largest ones—those comparable in size to planets—the situation is exactly the opposite. And recently, scientists have put forward a theory to explain why this happens.
Jupiter and Saturn. Source: phys.org
Moons of Jupiter and Saturn
A study by a group of astronomers from Japan and China on the formation of Jupiter’s and Saturn’s moons was recently published in the journal Nature Astronomy. They attempted to solve a long-standing mystery regarding the number of their moons and their formation.
In fact, Jupiter and Saturn aren’t just the largest planets in the Solar System. They also have more moons. Saturn, despite being smaller in size, is known to have 290 moons, while Jupiter has about 100.
However, the situation changes significantly if we consider not all moons, but only those with a radius greater than 1,000 km—that is, those that meet the criteria for being classified as planets. Jupiter has four moons: Io, Europa, Ganymede, and Callisto, while Saturn has only one—Titan.
That’s very strange, because it would be expected that where there are more moons overall, there should be more large ones. However, the reality is quite different, and scientists have long been trying to figure out why. However, this issue is part of the broader problem of the formation of large bodies from gas-dust disks.
Planet formation and magnetic fields
In general, the theory of planetary formation from gas and dust has, on the one hand, a fairly well-developed mathematical framework, but on the other hand, there is practically nothing to test it against. The Solar System is the only one we can study with sufficient accuracy. And that is precisely why scientists value the moons of Jupiter and Saturn so highly as miniature models of what happens around the Sun.
In general, the question of how similar the formation of the giant planets is to that of other planets remains open. However, scientists believe that they still have a few things in common. However, there are also differences, such as the interaction of Jupiter’s and Saturn’s magnetic fields with gas and dust, which could have led to the formation of large cavities. And inside them, not only small pebbles but also fairly large objects were forming.
The new model presented in the article focuses on the early evolution of giant planets during the period when they were merely clumps of matter—albeit extremely large ones. It establishes a link between the temperature of protoplanets and their magnetic fields. And these calculations show that Saturn’s was much weaker than Jupiter’s.
According to phys.org