Rhea

The Moon with Rings

Saturn's second-largest moon may have its own ring system - the only moon with rings!

Orbital Period

4.52 days

Tidal Locking

Yes

Same face always visible

Planet Rotations

10.1×

per orbit

Atmosphere

Yes

Rare!

🌙 Mind-Blowing Fact

Rhea might have its own RINGS! In 2008, scientists found evidence of debris rings around Rhea, making it the only moon known to have rings. If confirmed, it would be rings around a moon around a planet with rings!

What is Time on Rhea?

Rhea is Saturn's second-largest moon and potentially the only moon in the solar system with its own rings. It's a world of ice, thin atmosphere, and possible ring debris.

The 4.5-Day Orbit

One orbit = 4.5 Earth days - A nice "week"!
Saturn fills 7.7° of sky - 15 full moons wide!
Ring view - Magnificent view of Saturn's rings edge-on
May have rings! - Debris ring evidence from 2008

The Oxygen Atmosphere

Rhea has a tenuous oxygen-rich atmosphere:

Created by radiolysis of surface ice
Extremely thin (100 trillion times thinner than Earth)
Not breathable, but scientifically fascinating
Only other moon with O2 is Europa

The Possible Rings

In 2008, Cassini detected possible rings:

Three narrow bands of debris
1,800-2,000 km from Rhea's center
Might be remnants of a shattered moonlet
If confirmed: Only ringed moon in solar system!

The Wispy Terrain

Rhea's surface features mysterious bright streaks:

Called "wispy terrain"
Actually fractures and cliffs
Bright because they're fresh ice
Result of ancient geological activity

A Day in the Life

Rings Within Rings

You hover in orbit around Rhea, gazing at Saturn beyond. The giant planet fills your view, its magnificent rings edge-on, creating a thin bright line across its equator.

"Look," your co-pilot says, pointing at Rhea below. "The debris ring. You can barely see it, but it's there."

Through the thin haze of particles, you see Rhea's gray surface below. The moon has rings. A moon with rings, orbiting a planet with rings, orbiting a star. Rings within rings.

"In 4.5 days, we'll complete this orbit," you say. "Saturn will have rotated 10 times by then. Time moves differently out here."

The pilot nods. "But the rings? The rings are eternal. Saturn's rings have been here for millions of years. Rhea's rings - if they're real - might be just as old. Or brand new from a recent collision. We don't know yet."

You watch Rhea rotate below, its icy surface scarred by impacts, decorated by bright wispy streaks. Somewhere in that thin debris ring, particles are slowly orbiting, marking time in their own way.

"Time and rings," you muse. "Both circular. Both eternal. Both measuring the passage of something we can barely comprehend."

Thought Experiments

If Rhea has rings, how would they look from the surface?

Unlike Saturn's spectacular rings, Rhea's rings would be very subtle from the surface. They're made of scattered boulders and rocks, not fine particles. You might see a slight arc or band of material overhead, perhaps brightening during certain times of day when the sun angle is right. They'd be more obvious from space than from the surface.

Could you breathe Rhea's oxygen atmosphere?

Absolutely not! While Rhea does have an oxygen-rich atmosphere, it's 100 trillion times thinner than Earth's. You'd need a spacesuit just as much as you would on the Moon. The oxygen is created by sunlight breaking apart water ice molecules, but there's so little of it that it doesn't provide any breathing capacity.