How Old Are Saturn’s Rings?

Saturn acquired its glorious rings relatively late in life. Scientists think that something struck one of the gaseous planet’s moons -- a comet or an asteroid, maybe -- splashing hunks of rock and ice into orbit. Another theory is that the orbit of one of the planet’s many moons changed, and then that moon was ripped apart by Saturn’s gravitational forces. However the rings were formed, though, data from the Cassini spacecraft’s flybys indicates that they are not nearly as dense as previously thought. Their low mass suggests that the rings could have formed as recently as 100 million years ago.

From Galileo to Cassini:

• The Voyager mission in the 1980s suggested a similarly low mass, but researchers had doubted the result. Cassini was able to definitively determine the density of the planet’s B-ring by using the Doppler effect.
• Cassini performed 22 daring trips through the gap between Saturn and its rings before smashing into the planet in September 2017.
• Galileo Galilei discovered Saturn’s stunning rings about 400 years ago, and scientists have been making assumptions about them ever since.