Rhea isn't as famous as some of Saturn's other moons. It doesn't shoot geysers like Enceladus, it doesn't have a thick atmosphere like Titan, and it doesn't look like the Death Star like Mimas.
But Rhea has its own quiet collection of interesting things: strange bright streaks across its surface that turned out to be giant cliffs hundreds of metres high; a wispy-thin oxygen atmosphere that nobody knew about until 2010; and one famous case where scientists briefly thought they'd found something amazing — the first moon in the solar system with its own ring system — and then, two years later, had to admit it wasn't there after all. Rhea is the steady, dependable big moon.
It's also a great example of how science actually works.
Rhea is named after a Greek goddess — and in this case, the name fits Saturn's family of moons better than almost any other.
Rhea is the second-largest of Saturn's many moons — about 1,528 km across, made mostly of water ice with a bit of rock mixed in. It was discovered in 1672 by the Italian astronomer Giovanni Cassini (the same Cassini the modern spacecraft is named after).
Rhea is heavily cratered, has a very thin oxygen-and-carbon-dioxide atmosphere, and shows giant fracture cliffs across some of its surface — bright lines that were first photographed by Voyager and later revealed by Cassini to be towering canyons hundreds of metres deep. In 2008, scientists briefly thought they had discovered a ring system around Rhea — which would have been the first moon ever found to have rings — but follow-up Cassini images in 2010 found no detectable rings around the moon.
Rhea is named after Rhea, the Greek goddess who was the mother of Zeus and the wife of Cronus (the Greek equivalent of the Roman god Saturn).
Quick Rhea facts
A pocket-sized list of the most-asked Rhea numbers.
| Type | An icy moon of Saturn — Saturn's 2nd-largest moon, after Titan. |
| Diameter | About 1,528 km (950 miles) — about two-fifths the size of Earth's Moon. |
| Made of | About three-quarters water ice and one-quarter rock, mixed throughout. |
| Density | About 1.236 g/cm³ — only slightly denser than water. |
| Orbital distance | About 527,000 km from Saturn — further out than Mimas, Enceladus, Tethys and Dione, closer than Titan. |
| Orbital period | About 4.5 Earth days. |
| Rotation | Tidally locked — the same face always points toward Saturn. |
| Surface temperature | About −174°C (very cold even for the outer solar system). |
| Discovered | 23 December 1672, by the Italian astronomer Giovanni Cassini. |
| Atmosphere | A very thin exosphere of oxygen and carbon dioxide, discovered by Cassini in 2010. |
| Most famous feature | Bright wispy lines — long streaks across the surface, revealed by Cassini in 2006 to be towering fracture cliffs hundreds of metres high. |
| Famous false alarm | In 2008, Cassini scientists thought they'd discovered a ring system around Rhea. In 2010, a careful follow-up search found no rings. |
| Named after | Rhea, a Titaness from Greek mythology — wife of Cronus and mother of Zeus, Hera, Poseidon, Hades, Hestia, and Demeter. |
What Rhea is actually like
Rhea is a fairly typical big moon for the outer solar system. It is a heavy ball of water ice (with a bit of rock mixed in throughout, rather than concentrated in a separate core like Earth has).
It is tidally locked, meaning it always shows the same face toward Saturn — just like our Moon does to Earth. It orbits Saturn once every 4.5 Earth days, far enough out that it sits beyond Mimas, Enceladus, Tethys, and Dione, but well inside Titan's orbit.
On the surface, Rhea looks like a heavily cratered snowball. Billions of years of impacts from passing rocks have left it covered in craters of every size, from kilometre-wide pits to massive basins.
Because Rhea is mostly water ice, those craters tend to look bright and sharp, with white walls and dark floors where dust has collected. The biggest craters on Rhea are named after creator-figures from different cultures — Tirawa from Pawnee mythology, Mamaldi from a creation story of the Selk'nam people, and Izanagi from Japanese myth, among others.
Walking across Rhea's surface, you would feel about 26 times lighter than on Earth — almost like floating.
Rhea has its own thin atmosphere — discovered by Cassini in 2010, decades after the moon was first studied up close. It is incredibly thin: about 5 trillion times less dense than Earth's atmosphere.
It is made of oxygen and carbon dioxide. The oxygen comes from a strange chemistry: when charged particles from Saturn's magnetic field hit Rhea's water-ice surface, they break some of the ice into hydrogen and oxygen, and the oxygen drifts up into the exosphere.
Nobody expected such a small cold moon to have any atmosphere at all.
The wispy lines — Voyager's mystery, Cassini's answer
In November 1980, NASA's Voyager 1 spacecraft flew through the Saturn system and sent back the first close-up photographs of Saturn's biggest moons. When the Rhea images came back, they showed something strange: long bright streaks running across one side of the moon. Astronomers called them 'wispy lines' or 'wispy terrain.' For 26 years, nobody knew what they actually were.
Then Cassini arrived. The Cassini-Huygens spacecraft, in orbit around Saturn from 2004 to 2017, took much higher-resolution images of Rhea than Voyager ever could.
When the close-ups of the wispy lines came back, the mystery was solved. The bright streaks weren't streaks at all — they were the bright walls of huge canyons.
Long, narrow cracks in Rhea's icy crust, hundreds of metres deep, with sheer cliffs on either side. Whenever dark dust from the moon's surface slipped down the cliff face, it exposed the bright fresh water ice underneath.
From a distance, that made the cliff edges look like a wispy white line.
Picture standing at the top of a brand-new cliff cut into ice. The cliff is several hundred metres high — taller than the tallest skyscrapers in most cities.
The walls are bright, fresh white ice, because every so often the dusty top layer slumps and slides down. Now picture that same cliff stretching in a thin, almost straight line across hundreds of kilometres of moon-surface.
That's what the wispy lines on Rhea really are. From Voyager's distance, they were a baffling streak of white.
From Cassini's distance, they're a cliff so long you'd never be able to see the end of it.
The fracture cliffs are interesting for a second reason too: they're a sign that Rhea was once tectonically active. Something deep inside the moon — probably tidal flexing from Saturn long ago — caused Rhea's crust to crack.
The cracks are still there, billions of years later, as a record of an ancient time when Rhea was a more dynamic world. Similar fracture systems exist on Saturn's other mid-sized moons Dione and Tethys, which suggests this kind of activity was once common across Saturn's icy family.
The wispy lines were first photographed by Voyager 1 in November 1980, then explained by the Cassini-Huygens mission in 2006.
The rings of Rhea — discovered, then un-discovered
Here is the most interesting thing that ever happened to Rhea, scientifically — and one of the cleanest examples in all of planetary science of how careful science actually works.
November 2005 — the strange charged-particle dip
In November 2005, the Cassini spacecraft made a close flyby of Rhea. As it passed near the moon, one of its instruments — designed to count electrons and other charged particles in Saturn's magnetic environment — noticed something odd.
On either side of Rhea, the count of energetic electrons dropped sharply, in a perfectly symmetrical pattern. Something was blocking the electrons before they reached Cassini, then doing it again on the other side.
If the moon itself was blocking the particles, the drop would have happened only right at Rhea — not on both sides, with a gap between them. So something else, spread out around Rhea on both sides, was getting in the way.
The best explanation scientists could think of was a thin disc of dust and small chunks of rock orbiting the moon. In other words: a ring system.
Around a moon.
March 2008 — the announcement
In March 2008, a team led by scientist Geraint Jones published a paper in the journal Science with that exact claim. Rhea, they said, appeared to have a ring system of its own — possibly several narrow dense bands embedded in a broader disc.
If true, this would be the first time anyone had ever found rings around a moon. Planets had rings.
Now a moon might, too. Major news outlets ran the story.
Diagrams of Rhea's possible ring system appeared in textbooks and kid science books.
If Rhea had really had rings, it would have been the only known moon in the entire solar system with its own ring system. Planets often have rings — Saturn, Jupiter, Uranus, and Neptune all do.
But moons, as far as anyone knows, do not. The 2008 announcement was genuinely exciting — and a little strange.
Why would Rhea, and only Rhea, have a ring? That was the question scientists set out to test.
2008-2009 — the careful follow-up
A different team of scientists, this one led by Matthew Tiscareno at Cornell University, decided to test the 2008 claim properly. If Rhea had rings, you should be able to see them with the right photograph.
Tiscareno's team carefully positioned the Cassini spacecraft so that the suspected rings would be edge-on to the camera — that is, viewed from the side, where any ring would look like a thin bright line. They took 65 separate images at different angles between 2008 and 2009.
Some of the images were taken with the Sun behind the camera, to catch sunlight reflecting off any larger ring chunks. Others were taken with the Sun in front, to catch tiny dust particles that diffract sunlight forward.
The team also added many short exposures together to reveal faint objects that wouldn't show up in a single frame. Whatever rings existed around Rhea, they should have left some trace in at least one of those 65 careful images.
July 2010 — the non-detection
They found nothing. No rings, no dust disc, no debris.
In July 2010, Tiscareno's team published their non-detection in the journal Geophysical Research Letters. The conclusion was clear: in 65 careful Cassini images taken at the angles that would best reveal any rings around Rhea, none were detected.
The 2008 hypothesis did not hold up.
That left a puzzle, of course. The charged-particle drop that Cassini measured in 2005 was real.
Something is causing it. But the careful 2010 imaging study found no detectable rings of physical material that could explain it.
What is actually causing the electron drop, nobody is completely sure. Several ideas exist — the local magnetic environment around Rhea might trap and channel charged particles in unusual ways, or there might be a very thin scattering of microscopic dust too faint to image but still enough to absorb some electrons.
The mystery isn't fully solved — but on current evidence, Rhea does not have a ring system anyone has been able to photograph.
This is exactly how science is supposed to work. A new finding gets reported.
Other scientists test it carefully. If the test confirms the finding, it becomes part of accepted knowledge.
If the test contradicts it, the original claim is retracted or revised. Sometimes the new answer is 'yes, you were right.' Sometimes it's 'no, we have to think again.' The point is that science is never about who said it first — it's about what holds up to careful checking.
The rings-of-Rhea story is a good example of that process working as it should.
Rhea the goddess — Saturn's wife and the mother of the gods
Of all the names given to Saturn's moons, Rhea's might be the one that fits most strongly with Saturn the planet itself. The reason is Greek and Roman mythology.
In Greek mythology, Rhea was a Titaness — one of the giant primordial gods who ruled before the Olympians. Rhea was married to Cronus, the leader of the Titans, and together they had six famous children: Zeus, Poseidon, Hades, Hera, Hestia, and Demeter.
Cronus, fearing a prophecy that one of his children would overthrow him, swallowed each baby as it was born. Rhea — broken-hearted — saved her youngest, Zeus, by hiding him in a cave on Crete and giving Cronus a stone wrapped in a baby's blanket to swallow instead.
When Zeus grew up, he came back and forced Cronus to release his swallowed siblings. The Olympians overthrew the Titans.
Zeus became king of the gods.
In Roman mythology, Cronus was renamed Saturn — and the Greek Rhea was often called Ops. The planet Saturn is named after Cronus/Saturn, the father.
The planet Jupiter is named after Zeus/Jupiter, the youngest son who overthrew him. And Rhea — the moon — is named after the mother who saved Jupiter and made the overthrow possible.
Picture the family tree. Saturn (the god) and Rhea (the goddess) are married.
Their six children include Jupiter (the god) and the other Olympians. Now look at the planets: Saturn (the planet) has dozens of moons named after Titans and Giants — and one of those moons is Rhea.
Even within the moon names, the family connection holds. Rhea-the-moon orbits Saturn-the-planet, exactly as Rhea-the-goddess was married to Saturn-the-god.
The mythology and the astronomy line up.
The moon was named after the goddess in 1847 by John Herschel, son of the William Herschel who discovered Mimas. John Herschel suggested that all of Saturn's moons should be named after Titans and Giants from Greek mythology, and Rhea (already known as the second-largest of the moons in the Saturn system) got the name of Cronus's wife.
It was the right call. The naming has stuck for nearly 180 years.
Read more about Saturn in mythology and where Rhea fits in the family tree.
Where Rhea sits in the family of Saturn's moons
Saturn has at least 285 known moons (as of May 2026, with the count still rising). Most are tiny — only a few are large enough to be round under their own gravity. Of the big round ones, Rhea is the second-largest, behind only Titan.
Here's how Rhea compares to the other named moons of Saturn that this Saturn collection has full pages on:
| Moon | Size (diameter) | Famous for | Where to read |
|---|---|---|---|
| Titan | 5,150 km — bigger than Mercury | Methane lakes, thick atmosphere, only moon with weather | Titan page |
| Rhea | 1,528 km — Saturn's #2 | Fracture cliffs, the rings-that-weren't | This page |
| Iapetus | 1,470 km — Saturn's #3 | Two-tone surface (one half bright, one half dark) | (Roadmap) |
| Dione | 1,123 km — Saturn's #4 | Bright icy cliffs and ancient cratering | (Roadmap) |
| Tethys | 1,062 km — Saturn's #5 | A huge canyon called Ithaca Chasma | (Roadmap) |
| Enceladus | 504 km — Saturn's #6 | Geysers, ancient global ocean, top target for life | Enceladus page |
| Mimas | 396 km — Saturn's #7 | Death Star look, young hidden ocean (2024) | Mimas page |
Rhea sits in a quiet middle position. It is much bigger than the famous small moons Enceladus and Mimas.
It is much smaller than the giant Titan. It doesn't have a single dramatic feature like Enceladus's geysers or Titan's lakes, but it has its own collection of interesting details — and a clean, memorable scientific story about how a piece of seemingly settled science can be tested and overturned.
Out of Saturn's many moons, Rhea is the one that has been studied carefully without ever quite stealing the show.
Why Rhea matters
Rhea is sometimes called 'the boring big moon' — the second-largest in Saturn's collection, but without a unique killer feature to make it instantly memorable. That is a little unfair.
Rhea has its towering fracture cliffs hundreds of metres high, telling the story of an ancient time when this small icy world was tectonically active. It has a wispy oxygen atmosphere that scientists didn't expect any small icy moon to have at all.
And it has the rings-of-Rhea story — a beautiful example of how scientific knowledge gets built, tested, and corrected over time.
Most of all, Rhea has its family connection. Of all the moons of Saturn, Rhea is the one whose name fits the planet most closely — because in mythology, Rhea was the goddess who actually married Saturn (Cronus).
The other moons are named after Titans and Giants from the same mythological family, but Rhea is the heart of it. Without her, there would be no Jupiter — no overthrow of the old gods — no Olympian gods at all.
The same family story that explains why Jupiter the planet is named the way it is also explains why Rhea the moon belongs exactly where it is.
- Rhea is the second-largest of Saturn's moons — about 1,528 km across, after Titan.
- It was discovered in 1672 by the Italian astronomer Giovanni Cassini.
- Rhea is made of about three-quarters water ice and one-quarter rock.
- It is tidally locked, always showing the same face to Saturn.
- Its surface is heavily cratered, with bright wispy lines that turned out to be towering fracture cliffs hundreds of metres high.
- Cassini discovered a very thin oxygen-and-carbon-dioxide atmosphere around Rhea in 2010.
- In 2008, scientists announced a ring system around Rhea — which would have been the first moon ever found to have rings.
- In 2010, careful follow-up Cassini images found no detectable rings around Rhea — the original claim was withdrawn.
- Rhea is named after the Greek Titaness Rhea, wife of Cronus (Saturn) and mother of Zeus (Jupiter), making the moon's name a tight fit with Saturn's family of mythological names.
Rhea — frequently asked questions
Quick answers to the most common questions.
What is Rhea?
Rhea is the second-largest moon of Saturn. It is about 1,528 km across, made mostly of water ice with a bit of rock mixed in. Rhea is tidally locked to Saturn — meaning the same face always points toward the planet — and it orbits Saturn every 4.5 Earth days. It is one of Saturn's 'classical' moons, named after a goddess from Greek mythology.
Who discovered Rhea?
Rhea was discovered on 23 December 1672 by the Italian-French astronomer Giovanni Cassini. This is the same Cassini that NASA's later Cassini-Huygens spacecraft was named after. Giovanni Cassini was working at the new Paris Observatory in France when he spotted Rhea, along with several other Saturn moons.
How big is Rhea?
Rhea is about 1,528 km (950 miles) wide. That makes it about two-fifths the size of Earth's Moon, and bigger than Pluto's biggest moon Charon. Among Saturn's many moons, only Titan is larger — Titan is about 3.4 times Rhea's diameter.
Does Rhea have rings?
No — though for a couple of years scientists thought it might. In March 2008, a Cassini team led by Geraint Jones published a paper in Science claiming Rhea might have its own ring system, which would have been the first moon ever found to have rings. But a follow-up Cassini imaging study published in 2010 by Matthew Tiscareno's team at Cornell found no rings in 65 careful pictures. So as of today, Rhea has no known rings.
What are the wispy lines on Rhea?
When Voyager 1 photographed Rhea in 1980, parts of its surface had long bright streaks across them — called the 'wispy lines.' For decades, nobody knew what they were. When Cassini took close-up images in 2006, the mystery was solved: the wispy lines are actually huge fracture cliffs, hundreds of metres high, with bright fresh water ice exposed on the cliff walls where darker dust has slipped off. From a distance, the cliff edges look like white streaks.
Does Rhea have an atmosphere?
Yes — but a very, very thin one. Cassini discovered Rhea's atmosphere in 2010. It is about 5 trillion times less dense than Earth's atmosphere, and is made of oxygen and carbon dioxide. The oxygen forms when charged particles from Saturn's magnetic field hit Rhea's icy surface and break some of the water ice into hydrogen and oxygen. Scientists didn't expect to find any atmosphere around such a small cold moon.
What is Rhea made of?
About three-quarters water ice and one-quarter rock. The rock is mixed throughout Rhea, not concentrated in a heavy core like Earth has. Because Rhea is mostly water ice, its density is only slightly higher than water — about 1.236 g/cm³.
How cold is Rhea?
Very cold. Rhea's surface temperature is about −174°C — colder than anywhere on Earth. The lowest temperature ever recorded on Earth is about −90°C (in Antarctica). Rhea is permanently more than 80 degrees colder than that, because it is so far from the Sun and has almost no atmosphere to hold any warmth.
What is Rhea named after?
Rhea was a Titaness in Greek mythology — one of the older generation of gods who ruled before the Olympians. She was married to Cronus, the leader of the Titans (called Saturn in Roman mythology). Their children included Zeus, Poseidon, Hades, Hera, Hestia, and Demeter. Zeus eventually overthrew Cronus and became king of the gods. The moon was given the name Rhea in 1847 by John Herschel.
Is there life on Rhea?
Almost certainly not. Rhea is far too cold for liquid water on its surface, and as far as scientists can tell, there is no hidden ocean inside it either (unlike Enceladus or Mimas). Without liquid water, life as we know it cannot start. Rhea is interesting for many reasons, but the search for life in the Saturn system is focused on Enceladus and Titan, not Rhea.
Has any spacecraft landed on Rhea?
No spacecraft has ever landed on Rhea. The Voyager 1 spacecraft flew past in 1980 and took the first close-up images. The Cassini-Huygens mission, in orbit around Saturn from 2004 to 2017, made several close flybys of Rhea — coming within just a few hundred kilometres on the closest passes — and took thousands of detailed photographs. But no probe has actually touched down. There are no current plans to send a lander to Rhea.
Mini quiz — test your Rhea knowledge
Try these without scrolling back up. (Answers below.)
- Roughly how big is Rhea across its diameter?
- Who discovered Rhea, and in what year?
- What is Rhea made of, mostly?
- True or false: Rhea has its own ring system.
- What did the wispy lines on Rhea turn out to be, when Cassini photographed them close-up?
- Rhea has a very thin atmosphere made of which two gases?
- In Greek mythology, who was Rhea married to, and who was her most famous son?
- Imagine you were on the team that published the 2008 rings-of-Rhea claim, and then in 2010 the follow-up showed you were wrong. What would you do next?
- Challenge: explain in your own words why the rings-of-Rhea story is a good example of how science is supposed to work.
1) About 1,528 km (950 miles) wide.
2) The Italian-French astronomer Giovanni Cassini, on 23 December 1672.
3) Mostly water ice (about three-quarters), with one-quarter rock mixed throughout.
4) False. In 2008 a team thought they had found rings, but a careful 2010 follow-up found no detectable rings in 65 Cassini images.
5) Towering fracture cliffs — huge canyons hundreds of metres high, with bright fresh ice exposed on the cliff walls where darker dust has slipped off.
6) Oxygen and carbon dioxide. The atmosphere is very thin — about 5 trillion times less dense than Earth's.
7) Rhea was married to Cronus (the Titan, called Saturn in Roman mythology). Her most famous son was Zeus, who later overthrew Cronus and became king of the gods.
8) Many good answers. The honest scientific thing to do is what the original team did: acknowledge the follow-up evidence, accept that the 2008 conclusion was wrong, and move on to the new mystery — what is actually causing the strange electron-drop pattern around Rhea? Science isn't about being right the first time; it's about following the evidence wherever it goes.
9) Several good answers. The 2008 claim was made in good faith based on the best evidence available at the time.
A different team tested it carefully and found a different answer. Both teams published their findings.
The community accepted the corrected answer based on the strength of the evidence — not on who made the claim or how famous they were. That's exactly how science is meant to self-correct: through careful, public, evidence-based testing.
Teacher and parent notes
Hooks for using this page in lessons or homework time.
Curriculum links:
- UK KS2 Year 5 — Earth and Space: moons of other planets, impact craters, scale of the solar system.
- UK KS3 Working Scientifically — how scientific knowledge is built, tested and revised; the role of peer review and follow-up studies.
- US NGSS MS-ESS1 — Earth's place in the solar system; MS-LS4 / NGSS Science and Engineering Practices — analysing and interpreting data, scientific arguments from evidence.
- Cross-curricular: science history (the 2008-2010 rings-of-Rhea cycle); language (the Greek-to-Roman name connection: Rhea → Ops, Cronus → Saturn, Zeus → Jupiter); maths (Rhea is about two-fifths the size of Earth's Moon — what fraction is that?).
Talking-point prompts:
- "In 2008 scientists thought Rhea had rings. In 2010 they found out it didn't. Is that a failure of science, or is that science working properly?"
- "The wispy lines on Rhea looked like simple bright streaks from Voyager's distance, but turned out to be huge cliffs from Cassini's close-up view. Why does the answer to a scientific question sometimes depend on how close you get?"
- "Rhea was the goddess who saved Zeus from being eaten by Cronus. The moon Rhea orbits the planet Saturn. The planet Jupiter is named after Zeus. Why do the planet names line up with the family tree so well?"
Activity suggestions:
- Greek-to-Roman name table: have students fill in pairs — Zeus / Jupiter, Cronus / Saturn, Rhea / Ops, Poseidon / Neptune, Hades / Pluto, Hera / Juno. Then connect each name to the planet or solar-system object it ended up labelling.
- Voyager vs Cassini: show a Voyager-era image of Rhea's wispy lines next to a Cassini close-up of the same fracture cliffs. Discuss how the answer changed when the resolution improved.
- Timeline of the rings: build a Rhea timeline showing 1672 (discovery), 1980 (Voyager wispy-lines images), 2005 (Cassini flyby and the electron-drop measurement), 2006 (wispy-lines explained as cliffs), 2008 (rings claim), 2010 (rings retraction; atmosphere discovered). Each date is a step in scientific understanding.
- Family tree drawing: have students draw the simple Greek family tree — Cronus (Saturn) + Rhea = six children including Zeus (Jupiter). Add notes for which name became a planet, which became a moon, etc.
More Saturn adventures
Pick what you want to explore next.
The other big moons
- Titan, Saturn's biggest moon — bigger than Mercury, with methane lakes and a thick atmosphere.
- Enceladus, the geyser moon — small but spectacular, with plumes shooting from its south pole.
- Mimas, the Death Star moon — and the hidden ocean discovered inside it in 2024.
The missions that studied Rhea
- Pioneer 11 and the Voyager flybys — Voyager 1 first photographed Rhea's wispy lines in 1980.
- The Cassini-Huygens mission — which revealed the wispy lines were giant cliffs and tested the rings claim.
The mythology connection
- Saturn in mythology — Cronus, Rhea, Zeus, and how the planets and moons got their names.
Back to the main Saturn page
- Saturn the planet itself — Rhea's home, with at least 285 confirmed moons.
Sources and last updated
This page is fact-checked against current sources from NASA, ESA, and peer-reviewed planetary science.
- NASA — Rhea overview page for basic data: 1,528 km diameter, composition, tidal locking, 4.5-day orbit.
- Jones, G. H. et al. (2008). 'The dust halo of Saturn's largest icy moon, Rhea.' Science, 7 March 2008 — the original rings-of-Rhea claim.
- Tiscareno, M. S. et al. (2010). 'Cassini imaging search rules out rings around Rhea.' Geophysical Research Letters, 29 July 2010 — the follow-up non-detection.
- Cornell University news release (29 July 2010) — 'No rings around Saturn's Rhea, astronomers find.'
- ESA Cassini-Huygens news (2008) — 'Saturn's moon Rhea may also have rings.'
- NASA Cassini — Rhea exosphere reports (2010) — the oxygen-and-carbon-dioxide atmosphere detected by the Cassini Plasma Spectrometer.
- Space.com — Rhea overview (January 2024) for composition (3/4 ice, 1/4 rock) and the 'rocky snowball' framing.
Last updated: May 2026. Rhea physical data (diameter ~1,528 km, density 1.236 g/cm³, orbital period 4.5 days, tidal locking) verified against NASA mission pages.
Discovery date (23 December 1672, Giovanni Cassini) verified against historical record. The 2008 rings-of-Rhea claim (Jones et al., Science) and the 2010 retraction (Tiscareno et al., Geophysical Research Letters) verified against the original papers and the Cornell University 2010 announcement.
Exosphere discovery (Cassini, 2010) verified against NASA reports.
Written and fact-checked by the Planets for Kids editorial team.
Explore the Rest of Saturn
- Saturn Facts for Kids — The Complete Guide
- Saturn's Rings
- Saturn's Hexagon Storm
- Saturn's Seasons & Ring Cycle
- Saturn's Atmosphere
- How Saturn Formed
- Titan
- Enceladus
- Mimas
- Rhea
- Iapetus
- Pan, Daphnis & the Shepherd Moons
- Why Saturn Has So Many Moons
- Pioneer 11 & the Voyager Flybys
- The Cassini-Huygens Mission
- The Huygens Probe on Titan
- Dragonfly — Titan Quadcopter
- How to Observe Saturn
- Could Humans Live on Saturn?
- Saturn in Mythology
- Saturn vs Jupiter
- Saturn vs Earth
- For Teachers & Parents