Saturn s rings reveal what s deep inside the planet

Saturn's rings vibrate like a bell, so researchers can indirectly look deep inside the planet itself.

Gravitational waves push seismic waves from the interior of Saturn directly into the planet's ring system, where the Cassini spacecraft was able to see their delicate tremors. According to the latest research, much of the planet's interior consists of clear layers.

All planets hide the construction of their interior under layers difficult to penetrate. Interiors of rocky objects such as the Earth or the Moon can be studied by analyzing seismic waves emitted by earthquakes, but gas giants do not have any solid surface on which to measure such waves. Instead, researchers must use other methods, e.g., studying the planet's magnetic field.

2004: Cassini enters the game

Shortly after the Cassini spacecraft reached Saturn in 2004, researchers realized that the planet's rings were strange oscillating. Instead of individual waves that perfectly explain existing theories, the probe spotted groups of small, local waves that can be explained by the presence of gravitational waves in the deepest regions of the planet's interior.

It is particularly interesting that the very fact of the existence of these gravitational waves means that at least part of the deep interior of the planet is relatively calm and stable, not convective - says Christopher Mankovich, a researcher at Caltech.

Earlier it was assumed that the hot, liquid interiors of gas giants push heat outside like a lava lamp. However, the presence of heavier components such as rocks or water ice under lighter hydrogen and helium can inhibit fluid movement and generate gravitational waves. In the case of Saturn, these waves make the planet vibrate like a bell.

Detection of gravitational waves inside Saturn through seismological ring research is one of the few hard evidence that a significant part of Saturn's interior is stable and layered, not just convective, "says Mankovich.

On rocky planets such as Earth, disturbances beneath the surface can travel like waves through the interior of the planet and its surface. As a result, the stronger ones can be recorded hundreds of kilometers from the epicenter of a strong earthquake. Over time, interference with other waves can create a standing wave that spans the entire planet.

Then the whole planet begins to tremble like a bell - he adds.

The same process occurs on Saturn surrounded by a system of numerous rings consisting of rocks and ice. Most of the time their orbit is orderly and calm, except for occasional collisions. Scientists have known for decades that the gravitational pull of 82 planet moons can affect the ring-forming grains. Although seismic testing of the rings was already proposed in the 1990s, it could actually be started only when the Cassini probe arrived in Saturn in 2004.

Cassini was able to identify over 20 different waves in Saturn's rings originating deep within the planet. Interactions are only visible in some parts of the rings, but their effects can be really strong. This does not change the fact that the waves are about one kilometer from peak to peak, while the entire ring system has a diameter of 300,000 km.

Of course, the waves are only visible when we look closely at the rings. If the Cassini spacecraft did not fly to Saturn and look at them closely, we would not be able to see them - adds Mankovich.

What's inside Saturn ?

Researchers are only now beginning to learn what is happening deep inside Saturn. According to Mankovich, ring tremor studies indicate that there is a dense, stable region within Saturn with a radius of 14,500 km (1/4 of the planet's radius) inside Saturn. This does not agree with the results of the study of the magnetic field of the planet, which speaks of a stable region with a radius of only 3000-6000 km. According to researchers, it is possible that the magnetic field of Saturn is generated in a different way than the magnetic field of even Jupiter.

It will be some really fascinating years when we will decipher all the data collected by the Cassini probe with various instruments. The fact that different instruments say different things means that we still have gaps in our knowledge, and this in turn is a great opportunity to discover something new that will allow us to fill these gaps - he concludes.

Saturn's rings reveal what's deep inside the planet