The planet Saturn has over sixty moons making orbit around the gas giant. Even considering that Saturn is ten times the size of Earth, and has a mass 95 times that of our little blue planet, sixty moons is a staggering number. Saturn’s moons are widely different one from the other, including the huge moon Titan that is bigger than the planet Mercury, moons that actually orbit within Saturn’s rings, and moons that aren’t even spherical in shape. Of all of Saturn’s moons, the most unique just may be one of its smallest, Hyperion.
Hyperion was discovered circling Saturn in 1848. The moon is named after the mythical Greek god of watchfulness and observation. The three men credited with discovering Hyperion, William Cranch Bond, George Phillips Bond, and William Lassell, could not have known just how exceptional this moon was. It wasn’t until mankind started sending out satellite probes that we would get a good, close-up look.
Hyperion has what is classified as a highly irregular shape. Rather than having a typical spherical shape like many moons develop from gravitational and other natural forces, Hyperion is all irregular curves, giving it a shape not unlike a baked potato. Adding to its unusual appearance is a surface marked by many overlapping impact craters, the largest of which is about 120 kilometers across and ten kilometers deep. In 2005, the Cassini spacecraft sent back images taken of Hyperion that revealed for the first time an unusual, “spongy” appearance to its surface. Its shape, along with the evidence of multiple meteor strikes on the surface, indicate to many scientists that part of Hyperion was actually blasted away in some long ago cosmic collision.
The low density of Hyperion suggests that it is primarily composed of frozen water and only a small amount of rock. It is also porous, as its appearance would suggest, with nearly half of it made up of empty space. This type of composition allows for the craters on the surface to remain nearly unchanged over time. Cassini’s examination showed there was a dark, reddish substance filling the bottom of most craters containing long chains of carbon and hydrogen. Scientists remain curious as to what this substance is.
Hyperion does not have a stable orbit. Its eccentric orbit, along with its irregular shape, and the fact that it occupies a point over Saturn that is near to the moon Titan, combine to create a chaotic rotation. Hyperion’s axis wobbles so much that it has no true north or south poles, and which way it orients itself in space changes constantly. This is the only moon in our entire solar system known to do this.
Hyperion is an intriguing example of the complexity of our universe. Scientists plan to make further study of this moon to unlock the mysteries it presents to us. As with most of mankind’s discoveries in space, questions seem to be answered by questions. Perhaps one day, the opportunity will exist to go to Hyperion in person in our continuing quest to explore beyond our own tiny planet.