Saturn vs Earth, side by side
About 764 Earths could fit inside Saturn by volume, and about 9.5 Earths would line up across its equator. Yet Saturn is only 95 times as massive as our planet, because it is made mostly of hydrogen and helium and is eight times less dense. Its day is less than half as long as ours, its year lasts 29.5 Earth years, and it receives about 1% of the sunlight Earth gets per square meter.
Contents
Comparison table
| Saturn | Earth | |
|---|---|---|
| Equatorial diameter | 120,536 km | 12,756 km |
| Polar diameter | 108,728 km | 12,714 km |
| Mass | 5.68 × 1026 kg | 5.97 × 1024 kg |
| Mean density | 0.687 g/cm³ | 5.51 g/cm³ |
| Surface or 1-bar gravity | 10.44 m/s² | 9.81 m/s² |
| Escape velocity | 35.5 km/s | 11.2 km/s |
| Rotation period (day) | 10 h 33 min | 23 h 56 min (sidereal) |
| Orbital period (year) | 29.46 years | 365.25 days |
| Mean distance from the Sun | 9.54 AU (1.43 billion km) | 1 AU (150 million km) |
| Axial tilt | 26.73° | 23.44° |
| Mean temperature | about -140 °C at 1 bar | about +15 °C at the surface |
| Main atmospheric gases | hydrogen, helium | nitrogen, oxygen |
| Solid surface | none | yes |
| Moons | 274 confirmed | 1 |
| Rings | yes, extensive | no |
| Magnetic field at the equator | about 0.2 gauss | about 0.3 gauss |
How many Earths fit inside Saturn?
By volume, Saturn equals about 764 Earths. That number assumes you could melt the Earths down and pour them in. If you packed solid Earth-sized balls, the gaps between spheres would reduce the total to roughly 500 to 560, depending on how tightly they are packed.
Across its equator, Saturn is about 9.45 Earths wide: 120,536 km against 12,756 km. The comparison is less extreme pole to pole, because Saturn is flattened by its fast rotation; its polar diameter is about 10% smaller than its equatorial one (see size and mass).
The rings add another dimension. The main rings stretch to about 140,000 km from Saturn's center, so the bright ring system spans roughly 280,000 km tip to tip, about three-quarters of the distance between Earth and the Moon, on a structure often only about ten meters thick.
Mass and density: big but light
Saturn's volume is 764 Earths, but its mass is only 95 Earths. Saturn's average density, 0.687 g/cm³, is lower than that of water, while Earth, at 5.51 g/cm³, is the densest planet in the solar system. Earth is built of rock around an iron core; Saturn is a ball of hydrogen and helium with a diffuse core of heavier material (see interior and density).
That combination explains a surprising fact: gravity at Saturn's cloud tops is only about 6.5% stronger than on Earth. Saturn's mass is huge, but the 1-bar level is so far from its center that the two effects nearly cancel. You can work out your own weight with the Saturn weight calculator.
Days, years and seasons
A day on Saturn lasts about 10 hours 33 minutes, a value only pinned down in 2019 using waves in the rings (see day length). A Saturn year lasts 29.46 Earth years: someone born on Earth when Saturn was in a given part of the sky will see it return there around their 29th or 30th birthday, which is the astronomy behind the astrological "Saturn return".
Because the two planets have similar axial tilts, 26.7° and 23.4°, their seasons work the same way. On Saturn, though, each season lasts about 7.4 years (see seasons).
Sunlight, temperature and weather
Saturn is on average 9.54 times farther from the Sun than Earth. Since sunlight weakens with the square of distance, Saturn receives about 1/91 of the sunlight per square meter that Earth does. Noon on Saturn's cloud tops would look roughly like a heavily overcast day on Earth, still far brighter than moonlight. Sunlight takes about 79 minutes to reach Saturn, against about 8 minutes 20 seconds for Earth.
The result is an atmosphere at about -140 °C at the 1-bar level (see temperature). Saturn's weather is far more violent than Earth's: equatorial winds reach about 1,800 km/h, compared with jet-stream winds of a few hundred km/h on Earth, and its storms can grow large enough to wrap around the planet.
Atmosphere and surface
Earth's atmosphere is 78% nitrogen and 21% oxygen above a rocky surface and liquid oceans. Saturn's is mostly hydrogen with a smaller share of helium, plus traces of methane, ammonia and water; it has no surface at all, just layers of gas becoming hotter and denser with depth until they turn into a fluid (see atmosphere). Standing on Saturn is impossible, as the page on whether we could live on Saturn explains.
Moons and rings
Earth has one large Moon, unusually big relative to its planet. Saturn has 274 confirmed moons, but none is as large relative to Saturn: even Titan, bigger than Mercury, has only about 1/4,200 of Saturn's mass, while our Moon has 1/81 of Earth's. Saturn's ring system has no equivalent on Earth.
Distance between Earth and Saturn
The distance between the two planets changes constantly as both orbit the Sun: from about 1.2 billion km at its closest, around opposition, to about 1.66 billion km at its farthest, when Saturn is behind the Sun. Radio signals take between about 67 and 92 minutes one way (see distance from Earth).
FAQ
How many Earths can fit inside Saturn?
About 764 by volume. If you packed whole Earth-sized spheres instead of filling the volume completely, the gaps would reduce the number to roughly 500 to 560.
How much bigger is Saturn than Earth?
Saturn's equatorial diameter is about 9.45 times Earth's, its volume about 764 times, and its mass about 95 times.
Is gravity on Saturn stronger than on Earth?
Slightly. At the 1-bar level near the equator it is about 1.065 times Earth's gravity, so a person weighing 70 kg on Earth would weigh about 74.6 kg.
How long is a day on Saturn compared with Earth?
A Saturn day lasts about 10 hours 33 minutes, less than half an Earth day. A Saturn year, however, lasts 29.46 Earth years.
Sources
- NASA Goddard: Saturn Fact Sheet
- NASA Goddard: Earth Fact Sheet
- NASA Science: Saturn facts
- Mankovich, C. et al. (2019), "Cassini ring seismology as a probe of Saturn's interior. I. Rigid rotation", The Astrophysical Journal