Humans have always wondered, “What is happening out there in the space?” For long, we could only tell based on our assumptions. Today, the tools such as rockets, space probes, satellites, and telescopes enable us to know what’s really cooking in our solar system. They have helped scientists to discover new things, see new stars being born, and observe numerous other occurrences every day. One of the interesting discoveries is the moons in our solar system. Also known as satellites, moons are solid bodies that come in various sizes, shapes, and types. Few of them have atmospheres. Some of them are large enough for their gravity to cause them to be spherical while smaller moons appear to be like asteroids.
Saturn, the sixth planet from the sun, is full of mysteries. NASA’s Cassini spacecraft, which helped us study and understand the ringed planet for nearly 13 years, took the closest images of its inner moons that left scientists amazed. The spacecraft revealed that unlike Earth’s perfectly spherical moon, the moons in proximity to Saturn had weird and irregular shapes. These odd shapes of the planet’s moons resemble objects such as ravioli, baguette, Kaiser roll, and potatoes. And scientists found out that the shapes of Saturn’s inner moons may be because of merging of tiny moonlets.
As the early days of the formation of our solar system were tumultuous, scientists have had many theories to prove the odd shapes of the planet’s moons. Nevertheless, none of them could explain the complete range of their strange structure or size. Martin Jutzi and Adrien Leleu, astrophysicists from the University of Bern in Switzerland, got involved in the task of explaining the formation and evolution of the moons over the years.
Initially, the researchers performed several tests and ruled out one of the popular theories explaining the formation of celestial bodies, i.e. gradual accretion of material around a core. The researchers say that Saturn’s mass is 95 times greater than that of Earth and the ringed planet’s inner moons orbit at a very close distance to the planet. Hence, at such a close distance, the strong gravitational pull from Saturn would have created tidal forces strong enough to pull the moons apart. This confirms that the moons couldn’t have formed with such shapes by the accumulation of materials. Instead, simulations focused on an alternative model known as the pyramidal regime formation scenario revealed that Saturn’s inner moons most likely formed by a series of collisions between same-sized tiny moonlets.
The simulations revealed that the collisions between the moonlets led to objects that resembled the inner moons. Direct head-on collisions resulted in the creation of flattened objects with large equatorial ridges similar to those in Atlas and Pan, while oblique moonlet impacts resulted in elongated objects such as Prometheus.
Martin Jutzi had previously found that collisions between comets could lead to bodies with the flattened shapes and equatorial ridges seen on Pan and Atlas.
Leleu said, “For bodies such as comets or asteroids, the impact configuration that would form these equatorial ridges have a very low probability of happening.” “But the small moons of Saturn are in a very specific environment – they are very close to Saturn and its rings, and on almost perfectly circular orbits, and almost all in the same plane.”
He also said, “We found that 20 to 50 percent of the small moons should display either an equatorial ridge or an elongated shape, while the rest should have more random potato-like shapes. And this is the case. Considering the six inner moons Pan, Atlas, Prometheus, Pandora, Janus and Epimetheus, the first three display these features, while the others – Pandora, Janus, and Epimetheus have random shapes.”
Apart from the inner moons of Saturn, there are various other moons with irregular shapes including Pluto’s Hydra, Neptune’s Laomedeia, and Jupiter’s Amalthea. And all have their different stories of formation.