Why Does Saturn Have Rings?
By: Jennifer R. Povey
Tags: Astronomy, Science, Space

Photo by Mishal Ibrahim on Unsplash

So, there are some amazing pictures of the Great Conjunction circulating, and some of them are taken with astronomical photography gear that shows Saturn’s rings.

A few years ago I had the privilege of a brief peek through the Lowell Telescope, located in Flagstaff, Arizona. The telescope, which was used to locate Pluto, is no longer used for science, but was recently restored and is open to the public (when the pandemic is over) and available to high school and undergrad students for projects.

The planet did not look real. It honestly looked like a painting. It was hard to believe I could just look at something that far away.

And the thing which makes Saturn is those rings. So, why does Saturn have rings? Why does Earth not have rings?

Read on.

Actually, it’s Not Just Saturn

First of all, Jupiter, Uranus and Neptune do have rings. They’re just a lot smaller. Saturn has rings that can be seen through a telescope from Earth.

The rings of the other gas giants are thinner, less bright, and not visible without very special gear.

This means it’s very likely that rings are a normal feature of gas giants, and probably exist around exoplanets too. Gas giants, because of their size, collect a lot of material around them, some of which coalesces into moons, and some of which forms rings.

Photo by David Menidrey on Unsplash

What are the Rings Made Of?

The rings are not solid. They are made up of, basically, space debris. Ice, rock, dust, etc. The composition varies; one of the reasons why Saturn’s rings are so bright is they contain a lot more ice, which reflects light better.

How are They Formed?

There are a few theories. These include the rings being the remains of a destroyed moon, or the rings being a moon that never quite came together.

The rings may also contain debris knocked off of moons by meteorites, bits of comets, etc.

Tidal forces prevent the rings from coming together into solid objects and interact with gravity to keep them “in line.”

As a note, Saturn has several rings…the three major A, B, and C rings and a couple of smaller ones. The E ring is particularly interesting; it appears to consist entirely of material outgassed from the moon Enceladus. (Does this give us an insight into ring formation?)

Photo by Richard Gatley on Unsplash

Why Doesn’t Earth have a Ring System?

There are a few reasons:

We’re too close to the sun for ice particles to stick around. Solar radiation sublimates them. The solar system has a frost line, and we’re well inside it. The only reason our water doesn’t wander off is, well, we have a magnetosphere. Mars doesn’t, so most of Mars’ water has, indeed, wandered off. The Earth is just too small to support a stable ring system. Everything coalesced into the moon. Thankfully, because a ring system around a small planet like ours? We’re talking a meteorite bombardment that would render the planet uninhabitable. Let’s keep the moon.

Ring systems are pretty and likely very common in the universe. Maybe one day we’ll observe the ring system of a large exoplanet and be absolutely sure they exist elsewhere.

Physics says they should.