Space and Physics

Saturn’s Radiation Belts Are Unlike What We See On Earth


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockOct 31 2017, 17:34 UTC

In the shadow of Saturn. CYCLOPS/NASA/JPL/Space Science Institute

The magnetic field of our planet creates some interesting structures in space known as radiation belts, donut-shaped regions where particles from solar wind and cosmic rays get trapped. Saturn has similar radiation belts but, as reported in a new study, they are not created in the same way.


According to American and German researchers, the radiation belts of Saturn are influenced by the ringed planet's moons and by the ultraviolet radiation of the Sun. The radiation belts of Saturn are gigantic, extending for more than 285,000 kilometers (177,000 miles). Several moons orbit within them.

As reported in Nature Astronomy, the team monitored changes in the radiation belts and compared them to changes in the Sun. They noticed that while the solar wind didn’t play a significant role, the variation in extreme ultraviolet radiation (EUV) from our star matched with the movement of the radiation belts. The EUV light was heating up the planet’s ionosphere and pushing atoms into them.

"We observe that the intensity drop in the proton radiation belts of Saturn coincides exactly with strong changes in the EUV radiation from the Sun," co-author Dr Elias Roussos, from the Max Planck Institute for Solar System research, said in a statement.

The radiation belts of Saturn. MPS, Image of Saturn: NASA/JPL/Space Science Institute

The radiation belts of our planet, also known as Van Allen belts, extend up to 58,000 kilometers (36,000 miles) so our moon doesn’t affect them. But around Saturn, there are five major moons, including Enceladus, within the belts. Each moon ends up absorbing some of the protons, with Thetys acting as an outermost boundary.  


"Our analyses also remind us how strongly the properties of the radiation belts depend on the structure of the particular planet system, that is, the position and number of moons for the case of Saturn," Roussos explained.

These exciting results are a testament to the incredible Cassini mission. An analysis like this would not have been possible in a short amount of time as the Solar cycle takes 11 years to reset, and you need all those years to see the full picture. This is the most detailed analysis of radiation belts of any solar system object other than the Earth.

"If Cassini’s mission to the Saturn system had ended after four years, as initially planned, we would never have been able to achieve these results,” Roussos added.


Cassini was a collaborative mission between NASA, the European Space Agency, and the Italian Space Agency. It was purposely crashed into Saturn last month, to avoid potential contamination of Earthly microbes on its moons.

Space and Physics
  • Saturn,

  • cassini,

  • Enceladus,

  • cosmic rays,

  • Radiation Belts,

  • Van Allen Belts