Life on a Terrestrial Planet with Rings

I'm coming up with a setting of a terrestrial planet with a Saturn-like ring system to make it more exotic and fantastical, so how would these rings affect life on the planet? What would there significance be than just pure Scenery Porn?

Ring systems are mostly just debris whether failed/broken up moons during formation, captured asteroids or many other things.

About the only thing they'd do on a terrestrial environment is make space travel put a wee bit more thought into it.

On a related note, it's expected Mars will have rings in about 1-10 million years owing to its moon Phobos gradually drawing nearer, once Phobos crosses the Roche Limit it'll break apart and form a thin diffuse ring or set of rings around the Red Planet.

The only real effect I can think of is the rings are bright enough to be proper Scenery Porn they'd have effects on the day/night cycle and how animals and plants react but its wouldn't be hugely significant. Everything would be adapted to a certain minimum light level.

But yeah, ring systems don't tend to be physically substantial and at most would present a navigational hazard for early spaceflight.

I would imagine that the presence of a visible ring system around a planet like ours would give astronomy and astrophysics a jump start. The Moon played just such a role in our own society: our curiosity about it gave rise to a great deal of early science.

Would a molten core or a magnetosphere have any effect on the rings? I'm asking because as far as I know all planets with rings that we are aware of lack both of those.

Jupiter has the strongest magnetosphere in the Solar System short of the Sun and it has at least 4 rings. So I don't think magnetosphere plays that much a part especially considering at the distances involved (usually several hundred kilometers from the surface minimum) gravity is much much stronger a force than magnetism. On Earth at 200 km altitude, the magnetic field only has enough force to influence electromagnetic radiation and lone particles, it's why it deflects the solar wind but doesn't serve as a magnet for every last bit of ferrous materials in the Solar System.

Even at the surface, our magnetosphere doesn't rip steel out of our hands. It's quite tame as such things go. If the ring were made up of highly magnetic material, over time it would be influenced by the planet's magnetic field, with effects that I don't have enough information to predict. Otherwise it would mainly obey gravity.

Rings are inherently unstable and decay over time, so you'd only have a few tens of millions of years to enjoy them, but considering that all of human history occupies barely a thousandth of that span, I'd say you're good to treat them as permanent within your story.

Edited by Fighteer on Mar 2nd 2020 at 11:56:37 AM

The only thing that I can think of is the fact that once, maybe millions of years earlier, that planet had a sizable moon. By, in effect, distributing the mass of that moon around the planet, the tides and other lunar effects would change significantly. Some scientists believe that it was in the intertidal pools that life first began, so having the moon break up could conceivably affect the evolution of life there. The lunar tides also contribute to the energy available to ocean currents, which help distributes heat more evenly around the world. Other scientists believe that our moon helps stabilize the Earth's rotation, so the sudden loss of a moon could easily cause more wobbling and deviation from average temperatures, resulting in eras that were significantly hotter and colder than life on Earth had to deal with.

Bottom line is, a terrestrial world whose moon shattered at some point would have a more extreme and less stable climate than we have had. I think there are some opportunities there to create an interesting world to set stories in.

I have heard that there might not be quite as integral as previously believed, the tides would be weaker but still present thanks to gravitational pull from the sun and the axial wobble might not be as extreme as once thought and would still take millions of years.

I don't think much would change aside from greater challenges in space flight. It could be a way to explain why a race has never left their planet or to isolate them. They landed on the planet, and after several generations, the rings make it difficult to leave, and make them more isolate from the rest of civilized space.

I have something like this in my book—except the planet also has two relatively large moons, as well as various other shepherd moons. How would the gravity of the large moons affect the rings?

That's a very complicated question that is better addressed by someone with actual experience in orbital mechanics rather than a layman with a great deal of interest in the topic.

In very broad strokes, moons exert gravitational influence on a planet's rings that tends to lead to one of several outcomes:

• The ring material is dragged down until it deorbits and burns up in the planet's atmosphere.
• The ring material is thrown out of orbit and into interplanetary space.
• The ring material impacts other bodies in the planetary system, such as moons.
• Whatever is left over forms an orbital resonance with the moon(s) so that their gravitational influence is balanced. This will see them laid out in very specific and defined bands.

For example, the Mars-Jupiter asteroid belt in our own solar system is strongly influenced by Jupiter's gravity and has consolidated in an orbit that synchronizes with Jupiter's. Anything outside of that band has long since drifted out and into more eccentric orbits (or impacted other planets). There are asteroids in other parts of the solar system that hang out in stable gravitational zones, even inside the Earth's orbit. The rings of Jupiter and Saturn similarly form resonances with the moons of those planets.

Edited by Fighteer on Mar 3rd 2020 at 2:41:56 PM

The planet I have in mind for my setting is based on one I found in a program called Space Engine, becoming the main source of inspiration for what it could look like with a beautiful ring system.

Image here◊.

The rings of my planet, which I nicknamed "Eternal Garden" (no official name yet), are really significant to the plot. They're the shattered remains of an exotic moon that drifted too close to the planet and got ripped apart, and they're composed of crystals which are the Applied Phlebotinum of the story. Due to gravitational interactions with the other two moons, some of these crystal fragments fall to the planet to be discovered by humanity, which turn out to have energy properties akin to magic, and can have all sorts of uses, not unlike Quartz from the Trails Series.

The rings will be throwing a shadow on the surface of the planet, and I did read a long time ago that a ring-shaped ice cap could form underneath of rings were they exist around Earth & reasonably stable in their position.

Cool pic.

So in other words, uninhabitable. So too good to be true.

Huh? Earth is perfectly habitable despite the existence not one but two ice caps.

Alright then. I thought the rings would encase the whole planet in ice caps. Sorry for misreading your comment.

How would a ring system form ice caps under it? Are we talking something so unbelievably dense it blocks off nearly all solar radiation reaching that part of the surface?

And wide/tall enough to block off more than a couple degrees latitude at most? (If there's one truth to planetary rings, they are thin as paper almost.)

Even a small percentage of blocked sunlight could be enough to lower local ground temperatures, although I would find it very difficult to believe this could cause ice caps around the tropics were the rings oriented in that way.

Edited by Fighteer on May 21st 2020 at 8:48:35 AM

Wouldn't the planet have to be tidally locked to the sun in order for the shadow of the rings to stay on one spot continuously?

Tidal locking has no relevance here. The only thing needed is that the rings be wide and dense enough to cast long-lasting shadows; because of orbital mechanics they tend to align with the equator. This is the study I had in mind and this one.

Those are fascinating studies, but I see no reference to a "ring-shaped ice cap" forming in the shadow of the ring.