# Cassini's Discovery: Saturn's Mysterious Two-Faced Moon Iapetus
Published: December 26, 2025
Duration: 1:54
# This is your Astronomy Tonight podcast.
Good evening, stargazers! Today we're celebrating December 26th, and oh, do we have a cosmic celebration to talk about!
On December 26th, 1672, the Italian astronomer Gian Domenico Cassini made one of the most thrilling discoveries in the history of planetary science: **he discovered Iapetus, one of Saturn's moons!**
Now, here's where it gets absolutely fascinating. Iapetus is no ordinary moon—it's basically the cosmic Yin-Yang of our solar system! One hemisphere is bright and shiny, while the other side is dark as coal. For centuries, astronomers were baffled. Ho...
Good evening, stargazers! Today we're celebrating December 26th, and oh, do we have a cosmic celebration to talk about!
On December 26th, 1672, the Italian astronomer Gian Domenico Cassini made one of the most thrilling discoveries in the history of planetary science: **he discovered Iapetus, one of Saturn's moons!**
Now, here's where it gets absolutely fascinating. Iapetus is no ordinary moon—it's basically the cosmic Yin-Yang of our solar system! One hemisphere is bright and shiny, while the other side is dark as coal. For centuries, astronomers were baffled. Ho...