What’s the News: Looking at images of odd undulations in the rings of Saturn and Jupiter, astronomers have discovered that comets are to blame. The finding means that a planet’s rings act as a historical record of passing comets, possibly leading to a better understanding of comet populations. “We now know that collisions into the rings are very common—a few times per decade for Jupiter and a few times per century for Saturn,” Mark Showalter, from the SETI Institute in Mountain View, California, told the Daily Mail. “Now scientists know that the rings record these impacts like grooves in a vinyl record, and we can play back their history later.”

How the Heck:

When a comet passes by the rings of a planet, its high-speed debris impacts the ring material and “changes the inclination of the particles’ orbits,” Bad Astronomer Phil Plait told me. “It’s like a cosmic shotgun blast.”
With the ring particles knocked out of alignment, they bob up and down as they orbit the planets—a phenomenon that looks in telescope images (see animation above) like ripples in a pond or corrugated metal.
The particles undulate up and down as they slowly gradually come back ...