While Earth’s one and only moon enthralls everyone on this planet, it can’t hold a candle to Saturn’s 274 moons, 128 of which were recently discovered and recognized by the International Astronomical Union. With this new surge in its moon count, Saturn prevails with the most moons out of any other planet in the Solar System.
Astronomers are now wondering, though, how this abundance of moons emerged in the first place.
Regular vs. Irregular Moons
Although Saturn boasts an impressive amount of moons, they aren’t quite like the one we’re used to seeing in our sky every night. The Earth’s moon falls under the category of regular moons, which are natural satellites that follow a mostly stable, circular orbit around a host planet.
The newly discovered moons of Saturn, on the other hand, have all been categorized as irregular (overall, 24 of Saturn’s moons are regular, while the other 250 are considered irregular).
Irregular moons typically follow distant and retrograde (backwards) orbits and have greater inclinations (related to the tilt of an orbit). Another difference is that while regular moons emerged as their host planet was forming, many irregular moons are believed to have been planetesimals (small, early-stage planets) captured by their host planet at the end of its formation.
Read More: Saturn’s Rings Will Disappear in 2025, but for How Long?
Split From Collisions
A large chunk of Saturn’s new irregular moons — 64 of them — were described in a recent paper submitted to the Planetary Science Journal, currently available on the arXiv preprint server.
In this paper, researchers propose that these small irregular moons likely originated early in Saturn’s history from multiple independent collisions, second-generation collisions between fragments of an initial collision, or a mixture of the two scenarios.
The moons, observed from 2019 to 2021 at the Canada-France-Hawaii Telescope, were placed into subgroups within two categories of Saturnian irregulars; the Inuit group contains the Kiviuq and Siarnaq subgroups, and the Norse group contains the Phoebe, Mundilfari, and Kari subgroups.
The researchers suggest that a recent collision, that may have occurred at least 100 million years ago, may have created the Mundilfari subgroup, a hypothesis that was previously advanced in a 2021 study. This collision would have involved a larger irregular moon that, when impacted, split into numerous fragments.
Read More: Saturn's Rings Formed Long After the Planet
The Outer Planets' Moons
Researchers are uncertain that any additional moons will be found orbiting Saturn in the future, although Jupiter might make up some ground — it currently has 95 recognized moons, and this number is expected to rise as more observations are made. However, Jupiter’s moons will likely not surpass Saturn’s moons according to researchers.
Back in 2024, astronomers announced one new moon for Uranus (S/2023 U1) and two new moons for Neptune (S/2002 N5 and S/2021 N1). The new moons, found using the Subaru Telescope at Mauna Kea, Hawaii, are the faintest to ever be observed with a ground-based telescope.
Similar to Saturn’s new moons, the irregular moons of Uranus and Neptune — exhibiting eccentric and distant orbits — were possibly part of larger parent moons that experienced collisions in the past, producing groupings of fragments. Astronomers believe there are smaller fragments in these groupings that have yet to be detected, but current ground-based telescopes cannot spot them.
More details on the outer planets' moons will require space missions to get a closer look. While all eyes are on Mars and the Earth's own moon, plans for missions that will explore the outer Solar System are fast-approaching; most notably, the Dragonfly spacecraft, the key piece to an upcoming mission headed by NASA, is planned to launch by 2028 for a 2034 landing on Titan, the largest moon of Saturn.
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
NASA. Moons: Facts
Cornell University. Retrograde predominance of small saturnian moons reiterates a recent retrograde collisional disruption
Carnegie Science. New moons of Uranus and Neptune announced
NASA. Dragonfly
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
