On February 13, 2010, NASA’s Cassini probe encountered a mysterious object (“Death Star”) orbiting Saturn during its mission to uncover the planet’s secrets. The object, known as Mimas, is one of Saturn’s many moons, and it’s only about 250 miles across, made mostly of rock and water ice. But what sets Mimas apart is its striking resemblance to the Death Star from Star Wars, thanks to a massive crater on its surface.
In 2014, during a second pass around Mimas, Cassini picked up strange readings indicating that the tiny rock was vibrating as it traveled through space.
The moon also had an unusual wobble that puzzled scientists, who couldn’t explain why it was happening. Some even speculated that Mimas might be the real Death Star.
To investigate this strange phenomenon, Cassini mission researchers focused on the Herschel Creator, the most recognizable feature on Mimas’ surface. This gigantic crater, compared in size to Australia, was created by an object that should have smashed the moon apart.
Researchers were surprised that Mimas had survived the impact, but Brad Want to Jetton developed a theory that the impact had compacted Mimas’ rocks, creating an unbalanced moon that produced a “mass anomaly.”
However, the math didn’t add up. The mass anomaly wasn’t big enough to explain the wobble, which was twice as large as expected from computer simulations.
To account for this unnatural vibration, scientists turned to another of Saturn’s moons, Enceladus, which also had a puzzling wobble.
In 2015, scientists discovered that Enceladus had a massive subterranean ocean that sloshed around, creating a wobble.
Could Mimas have a hidden ocean, too? If there was a subsurface ocean 15 to 18 miles underneath the surface of Mimas, it could account for its unusual motion.
However, the examination of the moon’s surface reveals no trace of activity that could produce enough heat to melt the ice, and its orbit doesn’t fit the ocean theory.
Mimas is a spherical moon with an elliptical orbit that wobbles, making it a cold, frozen, and dead world that remains a mystery to scientists.