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Saturday, October 16, 2021

Science of the Week: Saturn’s rings

The universe is a violent place. Not only did we start with an explosive Big Bang, but our solar system is continuously shaped by the desperate pull of gravity.

At a recent meeting of the American Astronomical Society, famed astrophysicist Robin Canup proposed that the picturesque rings of Saturn may have formed when an icy moon the size of the planet Mercury careened into the gas giant. For some perspective: Mercury is about one-third the size of Earth.

Astrophysicists have traditionally believed that the rings were formed when the planet’s gravitational pull ripped a small moon or comet into pieces. The moon Canup is picturing is much bigger.

A large moon with a combination of rock and ice could explain why Saturn’s rings are different from the rings of Jupiter, Uranus or Neptune. These other planets’ rings are made up of debris being blown off their moons by meteorites. Saturn’s rings are 90 to 95 percent ice, while these planets’ rings are merely dust.

Canup said tidal forces could have ripped off the moon’s outer, icy layers, and then the moon’s rocky core would have been blasted to smithereens when it hit the planet’s atmosphere. Some of the ice could also have formed a near-by moon. Canup believes Saturn’s moon Titan was far enough away not to be pulled down too.

According to observations by the NASA/ESA Cassini orbiter, the rings of Saturn are billions of years old. No human was around to see Saturn’s gravity take its toll.

If Canup’s hypothesis is correct, then for that doomed moon, resistance was futile.

– Madeline McCurry-Schmidt

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