Why  our solar system's moons have no  rings

Why  our solar system's moons have no  rings

Of the nearly 300 moons found to date in our solar system, not a single one is a ringed moon!

If giant planets in our Solar System have rings, and if centaurs (asteroids beyond Jupiter's orbit) and trans-Neptunian objects also have them, why don't moons in the Solar System have rings?

Because 'they can't exist'!

This is the explanation of the experts:

There is a lot of raw material from which rings could form around different moons in the Solar System. Some are covered in craters; dust ejected during impact could potentially form a ring. Others eject vapour or gas. So no problem there.

Expecting the gravitational influence of the moon, its host planet, and possibly other moons could be too powerful for rings to settle. Researchers designed and ran tests using N-body simulations.

The E ring of Saturn, created from material spewed out by ice moon Enceladus, seen embedded in the ring. 

For instance, Enceladus, a moon of Saturn with significant geological activity, ejects water vapor, ice particles, and gasses from geysers in its southern polar region. Instead of forming a ring around the moon, this material is transferred to the planet's orbit due to intense interactions with neighboring moons, feeding Saturn's E ring.

In other words, while moons generate part of the raw material for rings, the surrounding environment ensures that the more massive planet retains it, preventing the formation of rings around the moons themselves.

Researchers demonstrated in a research paper that isolated moons can have stable rings, but sceintists did not anticipate that moons in a hostile gravitational environment, with many other moons and planets disturbing their rings, would still maintain stability. The additional surprise came when they realized that these hostile environments, rather than destroying the rings, actually endowed them with great beauty by creating structures like gaps and waves, similar to those observed in Saturn's rings.

There are some features on Solar System moons that indicate the past existence of rings. The simulations support suggestions that debris found orbiting Saturn's moon Rhea could be the last remnants of what was once a full ring system. And Saturn's moon Iapetus has an equatorial ridge that could be the remains of a ring that fell onto the moon, just as Saturn's rings are slowly raining into the gas giant.

These findings suggest that the reason we see no moon rings in the Solar System is because we just weren't in the right place at the right time. Radiation pressure from the Sun, magnetic fields, internal heating, and magnetospheric plasma have all contributed to the loss of any moon rings that once existed, the researchers say.

 We human beings started observing the Universe during a period when these structures are no longer present. 

 Studies suggest that the only reason we see Saturn's rings is because we are in the right place at the right time. We only see the eclipses we do for the same reason; the Moon is moving away from Earth, and in time will be too far to completely block out the Sun.

Meanwhile, researchers are broadening their search, looking for ringed moons that might be orbiting alien worlds orbiting alien stars.

https://arxiv.org/abs/2408.10643