How Many Moons Does Saturn Have?

NASA's Hubble Space Telescope captured this image of Saturn July 4, 2020. Two of Saturn's icy moons are clearly visible in this exposure: Mimas at right and Enceladus at the bottom. This image is taken as part of the Outer Planets Atmospheres Legacy (OPAL) project.

By: Valerie Stimac | How Stuff Works

There’s a race happening in our solar system, but it has nothing to do with gravitational mechanics or velocity. Astronomers who study the gas giant planets of Saturn and Jupiter are in a close competition to see who can discover more moons — and it’s anybody’s game.

At this point, ringed Saturn has the most moons of any planet in the solar system, but exactly how many moons does Saturn have? And how does that compare to massive Jupiter’s count?

Counting Saturn’s Moons

In May 2023, Saturn’s moon count skyrocketed to 145 after the International Astronomical Union (IAU) officially recognized the ringed planet’s 62 new moons. These new findings mark significant milestones for the second-largest planet in the solar system, which has now surpassed Jupiter’s 95 recognized moons.

And on top of that, Saturn now has a record that even Jupiter can’t snatch up: It’s the first planet to have surpassed 100 confirmed moons in total.

All of the ringed planet’s newly discovered satellites belong to the category of irregular moons, believed to have been captured by Saturn in the distant past through a process known as gravitational capture. This occurs when a moon, which initially orbits the sun independently, comes too close to Saturn and gets caught in the planet’s gravitational pull.

As the moon enters Saturn’s gravitational field, the planet’s gravity gradually becomes dominant, altering the moon’s trajectory. Over time, the moon’s orbit becomes more circular and aligned with Saturn’s equatorial plane.

Capture & Absorb

During this capture process, the irregular moon loses energy, which causes it to slow down and transition to a stable orbit around Saturn. This captured moon becomes a part of Saturn’s moon system and can take on various roles, contributing to the dynamics of Saturn’s rings, participating in resonances with other moons or even influencing Saturn’s magnetic field.

These irregular moons stand out due to their large, elliptical and inclined orbits, unlike the more common regular moons. The count of recognized irregular moons around Saturn has more than doubled to 121, with 58 previously known before this search.

Irregular moons tend to group together based on their orbital tilt. Saturn’s system features three such groups named after various mythologies: Inuit, Gallic and Norse. Notably, all new moon discoveries fit within these groups, with the Norse group having the highest population among the newcomers. These groups likely originated from collisions, where existing moons within a group are remnants of earlier collisions involving originally captured moons.

A Proven Technique Leads to Big Breakthroughs

In 2023, the IAU announced 62 confirmed new moons orbiting the ringed planet, making it the new moon king of our solar system. Edward Ashton, a postdoctoral fellow at the Academia Sinica

Institute of Astronomy and Astrophysics, headed the team that discovered these fresh moons.

And it was all made possible by a tried-and-true technique known as “shift and stack,” which helped the team detect these smaller and dimmer satellites encircling Saturn.

Previously employed to find moons on Neptune and Uranus, “shift and stack” is a method used in astronomy to enhance the detection of faint and small objects, such as distant moons, within a series of images.

When searching for these dim objects, the technique involves aligning and superimposing multiple images of the same region of the sky, with each image slightly shifted to match the apparent movement of the object being sought. By combining these images, the faint object’s signal is boosted, making it more visible against the background.

This technique is particularly useful for discovering moons or other celestial bodies that might not be easily discernible in individual images due to their dimness. It allows astronomers to increase the signal-to-noise ratio and enhance the visibility of these faint objects, aiding in their identification and confirmation.

“Tracking these moons makes me recall playing the kid’s game Dot-to-Dot, because we have to connect the various appearances of these moons in our data with a viable orbit,” Ashton said in a statement. “But with about 100 different games on the same page, and you don’t know which dot belongs to which puzzle.”

What Does Space Smell Like?

NASA’s Cassini Mission

The Cassini mission, a landmark collaboration between NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI), unveiled the mysteries of Saturn and its moons. Launched in 1997, Cassini-Huygens entered Saturn’s orbit in 2004, providing unprecedented insights into the gas giant’s atmosphere, intricate ring system and diverse moons.

The Huygens probe, released by Cassini, descended through the atmosphere of Saturn’s largest moon, Titan, in 2005, revealing a world with lakes and rivers of liquid hydrocarbons. Over its 13-year mission, Cassini sent back captivating images, such as the stunning view of the hexagonal storm on Saturn’s North Pole.

Cassini’s final plunge on Sept. 15, 2017, was an intentional manoeuvre to ensure that the spacecraft would be destroyed in Saturn’s atmosphere. This decision was made to prevent any potential contamination of Saturn’s moons, especially the ones that might have conditions suitable for life.

During its final moments, Cassini continued to transmit data until its signal was lost, providing scientists with valuable insights into Saturn’s upper atmosphere and atmospheric composition.

Saturn’s Two Ocean Moons

While Jupiter is known for its four large Galilean moons (so named because they were observed by Galileo with his 17th century telescope), two of Saturn’s major satellites have drawn astronomers’ attention: Titan and Enceladus.

The Mighty Titan

Titan is an ocean moon, meaning it has subsurface oceans of liquid water. It’s the planet’s largest moon, known for its thick atmosphere and methane lakes. Titan is also the second largest moon in the solar system, bigger than the planet Mercury and Earth’s moon.

Thanks to NASA’s Cassini mission, we now know more about the unique features of this giant moon, which include an Earth-like landscape with dunes, rivers and a possible subsurface ocean, making it a prime target for future exploration.

Perhaps most notably, Titan is the only moon with a “substantial” atmosphere, which, like Earth’s, contains nitrogen. However, the similarities end there. Titan’s dense atmosphere has a pressure 147 times Earth’s, and its composition lacks oxygen.

Icy Enceladus

Enceladus is an icy moon known for spraying huge plumes of water up through its atmosphere into space. During the Cassini mission, astronomers were able to sample these geysers, and that’s how they discovered the ocean underneath its icy crust.

Enceladus displays a small, icy world with a smooth, bright surface. While predominantly covered in reflective ice, resulting in a brilliant white exterior, the moon also exhibits contrasting darker regions.

Notably, it features distinctive “tiger stripes,” which are linear fractures on its surface situated near its south pole. These unique features host active geysers, erupting icy particles and water vapour from beneath the icy crust. These geysers contribute not only to Saturn’s E-ring formation but also hint at a subsurface ocean’s presence.

Saturn’s Rings Have Moonlets

Saturn is most well-known for its big, beautiful rings, which are made of ice and rock. Some of these rocks and ice chunks are so large that they help shape the rings; NASA classifies these as “moonlets.” Some of the first moonlets discovered were as big as a football field and cause gravitational changes in the rings — that’s how astronomers discovered them.

Some moonlets were caused by collisions in Saturn’s rings, such as a larger moon breaking up at some point in Saturn’s past.

Now That’s Interesting

Saturn’s major moons have many names from cultures around the world. Some include Aegir (Norse), Bebhionn (Irish), Calypso (Greek), Ijiraq (Inuit) and Erriapus (Celtic). Saturn’s provisional, smaller moons don’t typically have names until they are confirmed; instead their names will comprise a string of letters and numbers that denote its discovery year and other details for astronomers.

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But water is ubiquitous in proto-planetary disks, and water’s origin may not be so mysterious after all.

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