New analysis of Cassini spacecraft data reveals that particles from Saturn's rings extend hundreds of thousands of kilometers above and below the planet, forming a giant dusty doughnut. Scientists suggest micrometeorite impacts vaporize ring material, propelling it to these heights. This discovery challenges previous views of the rings as merely thin discs.
Saturn's iconic rings, celebrated for their flat, expansive appearance, harbor a more complex structure than previously understood. Data from NASA's Cassini mission, collected during its final 20 orbits in 2017, indicate that tiny rocky particles from the rings reach altitudes far beyond the main disc. The spacecraft's steep paths, starting up to three times Saturn's radius above the planet and sweeping below, allowed for unprecedented measurements.
The Cosmic Dust Analyzer on Cassini detected hundreds of these particles near the trajectory's peak, with a chemical composition matching the main ring's low-iron grains. "It’s a really distinct spectral type we never see anywhere else in the Saturnian system," explained Frank Postberg of the Free University of Berlin, lead author of the study. Postberg noted the surprise at finding such particles over 100,000 kilometers from the ring plane: "There’s much more stuff close to the ring plane, but it still is surprising that we see these ring particles that high, both above and below the ring plane."
The main rings span tens of thousands of kilometers outward but are only about 10 meters thick vertically, creating their striking view from Earth. Variations exist, like the puffier E ring influenced by Enceladus's icy plumes. To reach these distances, particles require speeds exceeding 25 kilometers per second to overcome Saturn's gravity and magnetic fields.
Researchers propose that micrometeorite collisions vaporize ring rock, generating high-velocity ejecta that later condenses into dust. This aligns with recent findings suggesting the rings are older than thought. Frank Spahn of the University of Potsdam, not involved in the study, called the distant dust surprising given the particles' small size and sticky nature, which leads to soft collisions.
Postberg suggests this mechanism could apply universally to icy rings on planets like Uranus, potentially creating similar dusty halos elsewhere in the solar system. The findings appear in the Planetary Science Journal.