Watching stellar impacts as they occur is a rare treat for astronomers. The famous Shoemaker-Levy 9 impact on Jupiter (which left water in the planet’s atmosphere), which happened only 20 years ago, was the first directly-seen extraterrestrial collision in the solar system.

This week, NASA revealed that Saturn has now been added to the short list of places in the Solar System where astronomers have been able to observe collisions occurring as they happen (Earth, the moon, and Jupiter are the others).

NASA’s Cassini probe has captured images of meteoroids hitting the debris that makes up Saturn’s rings. Researchers believe that studying the impact rate on Saturn can help them determine more precisely how the planets in the Solar System formed.

“These new results imply the current-day impact rates for small particles at Saturn are about the same as those at Earth – two very different neighborhoods in our solar system – and this is exciting to see,” said Linda Spilker, a Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL). “It took Saturn’s rings acting like a giant meteoroid detector – 100 times the surface area of the Earth – and Cassini’s long-term tour of the Saturn system to address this question.”

Cassini scientists studied data for years to find evidence of the tracks the small meteorites left behind. The research has been published in the latest issue of the journal Science.

“We knew these little impacts were constantly occurring, but we didn’t know how big or how frequent they might be, and we didn’t necessarily expect them to take the form of spectacular shearing clouds,” said Matt Tiscareno, lead author of the paper and a Cassini participating scientist at Cornell University. “The sunlight shining edge-on to the rings at the Saturnian equinox acted like an anti-cloaking device, so these usually invisible features became plain to see.”

(Image courtesy NASA/JPL-Caltech/Space Science Institute/Cornell)