Death Star moon Mimas has a mysterious rotation happening with its orbit, scientists say in a recent study published in the journal Science. The orbital rotation of this smallest and closest Saturn moon is moving back and forth slightly like the way a pendulum swings. This swaying action is termed “libration” by scientists and is usually seen in moons affected by the gravity from planets nearby them. Mimas is one of Saturn’s eight moons with a crater covering a third of its surface and acquired its nickname Death Star because it looks very similar to the space station in the movie Star Wars.
The wobble itself does not surprise the scientists, since most known moons waver a bit as they orbit. But the mysterious rotation that is happening on Mimas is way too large for a moon that is approximately 250 miles in diameter. Cornell University research associate and planetary scientist Radwan Tajeddine explained, “We expected it would wobble by about three kilometers once every orbit, but it turned out to be twice that.”
Tajeddine looked at images of Mimas taken by the Cassini spacecraft probe that has been investigating Saturn’s system for the last decade. He discovered that the mysterious rotation of the Death Star moon has a much more pronounced liberation in one specific satellite area than he originally presumed. He assumes that the odd interior of Saturn’s icy moon may be the cause. The Cassini space probe has been accumulating data on Saturn, Mimas and the ringed planet’s other native satellites. Onboard the probe is a two-camera system called the Imaging Science Subsystem that acquires ultraviolet and infrared images of Saturn and its surrounding moon.
Tajeddine and his scientific research team analyzed five separate computer models on how the Death Star moon Mimas might look internally to determine if one of them could explain the mysterious rotation. The scientific team tried to see if the asteroid remnants under the large Herschel Crater making Midas bigger on one side were the reason behind the unusual rocking back and forth. However, Tajeddine ruled that out quickly saying the imbalance of Midas would have reoriented the planet permanently and the crater would face Saturn directly, which is not what has happened.
One theory that stood out is that Mimas has an enlarged oval-shape core that formed from the push and pull of the rings around Saturn. There is also a possibility of a subsurface ocean like the ones scientists believe are on Jupiter’s moons Europa, Ganymede, and Callisto. However, there has been no evidence yet of any liquid water found on Mimas. Any heat that escapes from the core and passes through the icy shell would make any subsurface ocean instantly freeze.
Tajeddine and his Cornell scientific team still remain unsure exactly why the Death Star moon Mimas has a mysterious rotation. All they know is that the moon is not acting the way the scientists think it should be. Tajeddine will not be able to know more until for a couple more years when the Cassini space probe will make its closest pass near the moon surface.
By Valerie Bordeau
Photo By: Flickr