How are Planetary Rings Formed and Which Planets Have Them?
Most of us have seen the pictures of the lone planet out in space with a dusty looking flat ring orbiting all of the way around it. These rings seem both alien and intriguing – why is it that some planets have rings and our own Earth does not, and which planets in our solar system have such rings?
Planetary rings are actually complicated and somewhat mysterious phenomena that only occur on certain planets. They are most often associated with Saturn, which is often depicted with a bright, flat ring orbiting the entire planet. The appearance of this planetary ring characteristic is sometimes exaggerated depending on the source of image, but it is noticeable even in actual space photography.
The origin of the actual ring itself is a matter of debate with no clear-cut accepted theory, but it is currently most believed to be due to a couple specific factors. First, the planet on which a ring orbits must have a certain gravitational pull. Since the gravitational pull a planet has is dependent on its mass and overall size, only those planets that meet a certain ratio of mass and size will have the proper environment for ring formation.
Given that a planet meets the gravitational requirements for ring formation, the next factor that must be met is the availability of particulate matter that can form the actual ring. Some scientists believe that particles that would otherwise have formed large objects such as moons wound up forming rings due to the gravitational pull of the planet nearby, while other scientists believe the rings just formed roughly in tandem with the formation of certain planets. Planetary rings are generally believed to be made up of space dust and ice particles, but the material that makes up the rings of some planets is unknown.
As mentioned earlier, Saturn is the best and most common example of a planet with rings, but other planets in our solar system have rings as well. The others are Neptune, Jupiter, and Uranus. Below are pictures of them: