Did the gas giant Saturn have another moon 100 to 200 million years ago? And does its destruction perhaps explain two of the planet’s peculiarities: the rings and the tilted axis of rotation? Jack Wisdom from the Massachusetts Institute of Technology in Cambridge and his team put forward this thesis in »Science«. According to the working group, simulations based on data from the Cassini space probe suggest that another satellite could have once existed between the moons Titan and Iapetus, the end of which had far-reaching consequences.
Saturn’s axis is tilted about 27 degrees from the orbital plane, and the tilt changes slowly over time through precession, a long-term and periodic change in direction of the axis of rotation. The speed of the precession is almost the same as that of Neptune’s orbit. Astronomers therefore assumed that the two could be connected, which is called resonance. According to this connection, it would be possible that Saturn’s largest moon, Titan, along with this resonance, could have tilted Saturn on its side.
According to the Cassini data, however, Saturn is just off resonance, which would indicate an event that was cosmologically relatively recent. In addition, based on Titan’s current motion, the planet should now have a tilt of about 36 degrees. However, the deviations could be explained by an additional satellite, the disappearance of which would have pushed Saturn out of resonance and raised its axis again somewhat.
This potential moon may have also formed the base of Saturn’s rings after being destroyed by strong tidal forces or a collision. Wisdom and Co therefore call it Chrysalis, derived from the protective cover in which butterflies pupate. As the insects hatch, breaking open the chrysalis, they unfurl their wings—similar to how the chunks of ice and dust spread out into the rings.