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Solar System Series

Saturn

The lord of the rings: young beauty with an expiration date

Author: Juan Carlos Euyoque Aguilera · October 7, 2026 · CC BY 4.0

Image of Saturn (NASA/JPL, public domain)
NASA/JPL illustration, public domain. Not to scale.
120,536 km
Diameter
-140 °C
Temperature
10.7 hours
Rotation
9.6 AU
Distance from the Sun

Saturn is the most photogenic planet in the solar system, but its rings hide a surprise: data from the Cassini mission indicate they are young and temporary. With 274 moons, 1,800 km/h winds, and a perfect hexagon at its north pole, Saturn is much more than a postcard.

Here we gather what Cassini and the Voyagers actually measured, we mark the myth of the eternal rings, and we leave open the questions not even NASA has closed.

Measured data [DATO]

DataValueStateSource
Diameter120,536 km[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Mass568 × 10²⁴ kg[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Mean density687 kg/m³[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Surface gravity9.0 m/s² (at the 1-bar level)[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Escape velocity35.5 km/s[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Mean distance from the Sun1,432 × 10⁶ km (9.6 AU)[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Orbital period10,747 days (29.4 years)[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Rotation period10.7 hours[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Mean temperature-140 °C (at the 1-bar level)[DATO] observedNASA Planetary Fact Sheet (NSSDCA)
Atmosphere / compositionHydrogen (~96%) and helium (~3%); traces of methane, ammonia, and other compounds[DATO] observedNASA NSSDC — Saturn Fact Sheet
Notable featureThe north-polar hexagon: a six-sided jet stream about 30,000 km wide with a central storm, seen by the Voyagers and studied by Cassini[DATO] observedNASA Science — Saturn Facts (misión Cassini)
RingsYes — the most spectacular ring system in the solar system: billions of chunks of ice and rock; it spans 282,000 km yet is only ~10 m thick in the main rings[DATO] observedNASA Science — Saturn Facts (misión Cassini)
Known moons285 (IAU Minor Planet Center / Edward Ashton's team (Academia Sinica), March 2026)
146 -> 274 on 11-Mar-2025 (128 new) -> 285 on 26-Mar-2026 (11 more: MPEC 2026-F14).		[DATO] observedIAU Minor Planet Center / Edward Ashton's team (Academia Sinica)

Truths [DATO]

  • [DATO] It is the only planet less dense than water (687 kg/m³): it would float in a big enough bathtub, as NASA itself puts it.
  • [DATO] It has 274 confirmed moons (March 2025), more than any other planet — including Titan, with lakes of liquid methane, and Enceladus, with water geysers at its south pole.
  • [DATO] Its rings span 282,000 km yet are only about 10 meters thick in the main rings: they are made of billions of chunks of ice and rock.
  • [DATO] Equatorial winds reach 500 m/s (1,800 km/h), and its north pole hosts a ~30,000 km hexagon discovered by the Voyagers.

Marked myths [MITO]

[MITO] Saturn's rings are eternal: they have existed since the planet formed, 4.5 billion years ago.

Cassini measured that the rings have very little mass (~0.4 times the mass of the moon Mimas) and are being darkened by micrometeorite dust, pointing to an age of 100 to 400 million years. They are also losing material as 'ring rain' at a rate that would deplete them in under 100 to 300 million years.

Fuente: Creencia clásica en textos antiguos; corregida por la NASA con datos de Cassini (estudio de James O'Donoghue, Icarus 2018)

Open questions [PREGUNTA]

  • [PREGUNTA] How were the rings born? Cassini data point to a shattered moon 100 to 400 million years ago, but the exact mechanism remains open.
  • [PREGUNTA] What keeps the north-pole hexagon stable for decades?
  • [PREGUNTA] Could there be life in Enceladus's subsurface ocean, which vents water into space through its geysers?

The chain in brief

  1. [DATA] 1. The planet that would float: Its density is 687 kg/m³, less than water: it is the only planet that would float in a big enough bathtub, as NASA itself puts it.
  2. [DATA] 2. 1,800 km/h winds and a hexagon: Equatorial winds reach 500 m/s, and its north pole hosts a ~30,000 km hexagon discovered by the Voyagers and studied by Cassini.
  3. [DATA] 3. Immense rings, almost no thickness: They span 282,000 km yet are only about 10 meters thick in the main rings: billions of chunks of ice and rock.
  4. [DISPUTED] 4. Young rings, not eternal: Cassini data point to a moon shattered 100 to 400 million years ago, but the exact mechanism remains open: the rings have not existed since the planet formed.
  5. [DATA] 5. A realm of moons: It has 274 confirmed moons (March 2025), more than any other planet — including Titan, with lakes of liquid methane, and Enceladus, with water geysers at its south pole.