It has been long thought that Mimas is one of the dullest moons of the mighty gas giant Saturn – apart from forthrightly worrying resemblance to the Death Star. But recently a new study revealed that, the humdrum space boulder could have hidden depths.
A team of astronomers have been studying the moon using the Cassini-Huygens spacecraft, which has been orbiting Saturn for the last ten years, and discovered Mimas’ orbit wobbles much more than theoretical models allow. The study is published in the ‘Science’ journal.
Radwan Tajeddine, Cornell research associate in astronomy and lead author of the study stated that, “After carefully examining Mimas, we discovered it librates — that is, it subtly wobbles — around the moon’s polar axis.”
He further stated that, “We are really excited about this measurement because it may specify much about the satellite’s insides. Nature is basically enabling us to do the same thing that a child does when she shakes a wrapped gift in hopes of figuring out what’s hidden inside.”
The team of astronomers used data collected from Cassini-Huygens spacecraft in order to create a 3D model of the moon’s orbit and found it wobbles twice as much as it ought. Such wobbles can be caused by the gravity of passing of planetary masses, but Mimas’ motion points to two other possibilities.
Firstly, there is the possibility that the moon’s rocky surface is hiding an ocean deep within the planet. With only 400kms in diameter Mimas won’t have enough mass to have a hot core, but tidal kneading caused by the close proximity of Saturn could provide enough heat for some of the moon’s innards to be liquids. On the basis of 3D modeling, we found that the ocean would have to be around 24 to 31kms beneath the surface of the moon’s crust to account for the wobble.
As per the second possibility, the Mimas’ birth left it somewhat abnormal. Mimas is believed to be the smallest body in the solar system to be rounded due to self-gravitation. It has enough mass to shape into a ball without being frayed apart.
According to the astronomers, Mimas core has been stretched out as it formed around Saturn. This would make the moon’s orbit more wobbly.
Eventually, we’re not going to know until mankind and/or our machinery get to the surface and discover but the team will be making more Mimonian measurements to refine their theory.