All you need to know about the moons of Saturn

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Saturn has 63 confirmed and named moons.
Only seven moons of the planet Saturn are visible.
Two of Saturn’s moons hold a certain potential for life in subsurface habitats.

A moon is essentially an astronomical body that describes an orbit around a planet, a dwarf planet, or an asteroid.

Earth has only one moon, but other planets have two or more moons or none at all. In the Solar System, Mercury and Venus do not have any moons, Mars has two small, close-orbiting moons called Phobos and Deimos, and Jupiter has as many as 80 moons.

In the case of Saturn, it has 63 confirmed and named moons, and another 20 are awaiting confirmation of discovery and official naming by the International Astronomical Union (IAU).

Major moons of Saturn.

Wikimedia Commons

How many Saturn moons are visible?

Only seven moons of the planet Saturn are visible. Titan is the easiest to see because it is the biggest and brightest.

With a diameter of 3,199.7 miles (about 5,150 kilometers), Titan can be spotted even in urban skies with a 60-millimeter (2-inch) telescope.

SPHERE image of Saturn’s moon Titan.

ESO/J.-L. Beuzit et al./SPHERE Consortium

It may look blurry, but that’s because its thick atmosphere is made of several layers.

Although Titan may look brownish from Earth, it actually has an orange haze due to the carbon-based compounds that are formed when the Sun breaks down methane and nitrogen particles in Titan’s atmosphere.

Other visible moons of Saturn are:

1. Rhea

Measuring 949 miles (1,500 kilometers) in diameter, Rhea is the second-largest moon of Saturn. It lies beyond the E ring, the second outermost Saturn ring. Rhea is made of water ice and rock (in a proportion of 75 percent and 25 percent, respectively); that is why it looks like a hard, dirty snowball full of craters.

Saturn’s icy moon Rhea.

NASA/JPL-Caltech/Space Science Institute

2. Dione

Dione is an icy moon with an icy crust of roughly 62 miles (100 kilometers) thick. Below it, there is a water ocean and a rocky core. Overall, Dione looks similar to Rhea, except for the fact that it is smaller (it has a diameter of just 696 miles or 1,120 kilometers) and is not as heavily cratered.

The surface of Dione.

NASA/JPL-Caltech/Space Science Institute

3. Tethys

Tethys is a mid-sized, icy moon of Saturn with high reflectivity. It is whiter in the northern hemisphere and darker near the Equator, where it is also not as cratered, except for the Odysseus Crater in the western hemisphere, which measures 250 miles (400 kilometers) in diameter. That is almost two-fifths of the moon itself.

Tethys, one of Saturn’s larger icy moons.

NASA/JPL-Caltech/Space Science Institute

4. Enceladus

Enceladus is a small icy moon that is also the whitest, most reflective body in the Solar System. It reflects almost 100 percent of the sunlight it receives, which is why it can be as cold as -330ºF (-201ºC). But that helps with visibility, especially in dark skies.

The surface of Enceladus.

NASA/JPL/Space Science Institute

5. Mimas

Mimas is the least visible Saturn moon for ground-based telescopes because it is the smallest and innermost of Saturn’s major moons. Made mostly of water ice, Mimas has an ovoid shape, and it’s full of impact craters. One of them, the Herschel Crater, covers one-third of the moon as it is about 80 miles (130 kilometers) wide. According to NASA, the impact that produced this crater almost shattered the moon in pieces.

Mimas.

NASA/JPL-Caltech/Space Science Institute

Are Saturn’s moons habitable?

Saturn and its natural satellites are outside the circumstellar habitable zone, but two of Saturn’s moons hold a certain potential for life in subsurface habitats.

Titan

Gravity measurements from NASA’s Cassini spacecraft and radio signals studied by ESA’s Huygens probe revealed the presence of an underground ocean of liquid water around 35 to 50 miles (55 to 80 kilometers) below Titan’s ice crust.

Apart from this, the Cassini spacecraft discovered hydrocarbon lakes and rivers that feed from hydrocarbon rains in the context of a complex weather system.

This way, Titan became the only celestial body known to have liquids on its surface apart from Earth. And while it doesn’t have liquid water on its surface, it does have liquid hydrocarbons like methane and ethane in those lakes and rivers.

Methane (CH4) and ethane (C₂H₆) are organic molecules that could constitute the prebiotic chemistry for new forms of life, such as organisms that “breathe” hydrogen instead of oxygen and react it with acetylene (C₂H₂) instead of glucose (C₆H₁₂O₆).

Titan’s atmosphere is also rich in elements that could form organic compounds (the atmosphere is 95 percent nitrogen and 5 percent methane) and could boost the formation of complex molecules needed for life.

However, the main threat to all life on Titan is the temperature. Because Titan is too far from the Sun, it can be as cold as -290º Fahrenheit (-179ºC) there.

Enceladus

Just like Titan, Enceladus has solid water in its ice crust and liquid water in an underground ocean. But unlike Titan, Enceladus has shown evidence of hydrothermal activity in this subsurface ocean, which is possibly an indicator of habitability.

Enceladus has, in fact, over 90 “geysers” that eject plumes of salty water vapor, ice particles, and organic compounds such as methane, propane, acetylene, and formaldehyde.

In 2015, the Cassini spacecraft detected molecular hydrogen in one of these plumes. Combined with carbon dioxide dissolved in the water, hydrogen could provide energy to alleged alien microbes.

Facts about Saturn’s Moons

About 70 percent of Rhea’s atmosphere consists of oxygen, but it is not breathable because Rhea’s atmosphere is estimated to be about 5 trillion times less dense than Earth’s.
Titan was discovered in 1655 by the Dutch astronomer Christiaan Huygens. All the other Saturn moons were discovered after that date.
Rhea was discovered in 1672 by Giovanni Cassini, the Italian astronomer, after which NASA’s Cassini probe was named. Another Saturn moon discovered by Cassini is Iapetus (in 1671).
According to NASA, Mimas likely formed from the same materials as found in Saturn’s rings. Other moons were possibly captured by Saturn’s powerful gravity or formed when Saturn’s gravity ripped other celestial bodies apart.