HomeScienceThe rings of Saturn will eventually be as old as the solar...

The rings of Saturn will eventually be as old as the solar system

The age of the rings of Saturn causes debate between scientists. According to a new study, they would have formed at the same time as the solar system, while recent work estimated them much younger.

The mission of the Cassini spacecraft , which ended in September 2017, made it possible to collect a lot of data allowing, among other things, to estimate the evolution of the characteristic rings of the planet Saturn.

Last June, several scientists published works whose conclusions suggested that the rings of Saturn were relatively young , galactically, and would have formed 10 to 100 million years ago.

However, according to the recent work of French and American scientists, the processes that lead to the ejection of the dust and the material of the rings of Saturn could give them a look much younger than they actually are.


  • The rings of Saturn were discovered in 1610 by Galileo. It was however the Dutch astronomer Christiaan Huygens who, in 1656, understood first that the rings were separated from the body of the planet.
  • The International Astronomical Union identifies seven main rings designated by a capital letter in alphabetical order corresponding to the chronological order of their discovery. The last discovered rings are designated by a code name (year-planet-number of discovery) while waiting to receive a baptismal name.
  • The ring system is made up of millions of blocks of ice and icy rocks ranging in size from 1 centimeter to 10 meters. Some astronomers claim that these rings formed during a collision with a huge moon the size of Titan

A question of interpretation

French planetologist Aurélien Crida of the Côte d’Azur Observatory and American colleagues at the University of Colorado at Boulder took a closer look at the Cassini data that inspired the articles published in June and postponed today. in question the hypothesis of the relative youth of the rings.

According to them, this theory is based on assumptions and shortcuts that prove to be incorrect.

Estimating the age of the rings of Saturn is not a small task.

It can not be measured directly, as one would count the growth rings on the stump of a tree.

Aurélien Crida, Observatory of the Côte d’Azur

During the final dive of the probe to Saturn, measurements were made to estimate the mass of the rings, which are composed of more than 95% of water ice and less than 5% of rocks, organic materials and metals.

This estimate was then used to calculate how long the ice in the rings would be exposed to dust and micrometeorites to reach the level of contamination observed today.

This “contamination” has been estimated at a hundred million years only. An estimate that has also been presented as the age of the rings.

According to Aurélien Crida and his colleagues, this time would correspond to the age of ring formation only under three conditions:

  • That the flow of dust is constant;
  • That the mass of the rings be constant;
  • That any contamination received by the rings remains there.

However, nothing proves according to the Franco-American team that these three hypotheses are valid.

There is still a lot of uncertainty on all these points and, considering the other results of the Cassini mission, we believe there are good reasons to think that the rings are much, much older.

Aurélien Crida, Observatory of the Côte d’Azur

At the dawn of the solar system

The authors of this study, whose details are published in the journal Nature Astronomy (New Window ), argue that the mass measured during Cassini’s final descent is in agreement with the models of the dynamic evolution of rings going back to the primordial solar system, more than 4 billion years ago.

They now intend to assert their hypothesis to the community of planetologists.

According to our present understanding of the composition of the rings, the mass measured during Cassini’s final descent would be the product of several billion years of evolution.

Aurélien Crida, Observatory of the Côte d’Azur

Of course, nothing prevents the rings from being formed very recently with this precise mass and having barely changed since. However, it would be a coincidence! concludes Aurélien Crida.

Saturn is the sixth planet of the Solar System in order of distance from the Sun and the second planet after Jupiter both in size and mass. It is at a distance from the Earth ranging from 1.66 to 1.20 billion kilometers.

Launched in 1997, NASA’s Cassini-Huygens spacecraft arrived in the Saturn region in 2004 after a long journey through the solar system during which it flew over Venus, Earth and Jupiter. The mission was completed on September 15, 2017.



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