Rings Like Seismographs Reveal the Heart of Saturn (Planetary Science)

Saturn’s core would not be the solid ball that scholars had hypothesized, but a soup of ice, rock and metallic fluids. This is suggested by a study, published in Nature Astronomy, conducted by Christopher Mankovich and Jim Fuller of Caltech, who analyzed the ripples of the rings through data from the Cassini spacecraft, obtaining valuable information on the interior of the planet.

The Cassini-Huygens mission for the study of Saturn and its system – the result of a collaboration between NASA, ESA and ASI – ended in 2017 after the orbiter disintegrated by diving into the gas giant’s atmosphere . Cassini’s gravitational and seismic measurements have now been used by two Caltech astronomers, Christopher Mankovich and Jim Fuller , to examine the planet’s oscillations and their reverberation on the rings. The findings were published this week in Nature Astronomy .

From the data acquired, it is more likely that Saturn’s core is a mixture of ice, rock and metallic fluids , and not a rock solid as some previous theories suggested. The analysis also reveals that the “fuzzy” core – fuzzy , as scientists have called it due to the absence of a well-defined stratification – extends for about 60 percent of the planet’s diameter, occupying a larger volume of as previously estimated. The mass of the core was found to be 55 times that of the Earth, with the equivalent of 17 Earth masses consisting of rock and ice and the rest of a fluid of hydrogen and helium.

The oscillations of Saturn create waves in its rings, a bit like the earthquakes, which make the planet “resonate”. The idea of ​​studying rings as if they were a seismograph is not new. In the early 1990s, the Voyager 1 spacecraft revealed peculiar ripples on Saturn’s C ring. Later, in 2013, a team of scientists, led by Matthew Hedman and Philip Nicholson of Cornell University, investigated the root cause of the phenomenon, and thanks to the data collected by Cassini it was discovered that the spiral ripples on the C ring were caused by fluctuations in the gravitational field generated by oscillations of matter inside the planet’s core.

“The planet’s surface moves about three feet every one or two hours, like a slowly rippling lake. Like a seismograph, the rings pick up the gravitational disturbances and the particles start moving, ”says Mankovich.

Now the two astronomers have used the wave pattern in the rings to study the movements of Saturn’s core. “For the planet’s gravitational field to oscillate with these particular frequencies,” Fuller explains, “the interior must be stable, and this is only possible if the fraction of ice and rock gradually increases as you get closer to the center of the planet” .

For the first time, the structure of a gas giant was probed through a seismological analysis, coming to the conclusion that the deep interior of Saturn may be composed of stable layers that formed after the heavier materials collapsed in the center of the planet and have stopped mixing with lighter materials on top of them.

The nucleus therefore does not have a uniform structure, but there would be a gradual distribution of heavy elements, which progressively increase towards the center. The results would agree with the recent evidence provided by Juno , the NASA probe that is exploring Jupiter. The two planets could have a very similar “diffuse” nucleus, which attracted the surrounding gas to itself from the beginning, that is, from when it was taking shape, refuting the theory that first the rocky core was formed and then the gas envelopes .

To know more:

Watch the video on MediaInaf Tv :

Featured image: The illustration shows the “muddled” core of Saturn. Credits: Caltech / R. Wound (Ipac)

Provided by INAF

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