NASA's Cassini mission finds evidence that an asteroid strike may have shifted the poles of Enceladus

NASA’s Cassini mission has found evidence that an ancient asteroid strike may have shifted the poles of Enceladus, one of the moons of Saturn.

The north pole of the moon is ancient and covered in craters. The south pole of the moon has striations that reach northwards, a feature known as “tiger stripes”. In 2005, Cassini spotted jets of water erupting from the tiger stripes, signs of geological activity deep within the surface. It is believed that before the event that changed the axis around which Enceladus spins, the north and south pole were more similar to each other.

The geological activity around the south pole is unlikely to have been caused because of internal forces, which has lead the scientists to speculate that an asteroid impact changed the way the moon spins. Radwan Tajeddine, from the Cassini imaging team said, “We found a chain of low areas, or basins, that trace a belt across the moon’s surface that we believe are the fossil remnants of an earlier, previous equator and poles.” The results have been published in Icarus .

The event that caused the tiger stripes and the axis of the moon to shift, is believed to have redistributed some of the mass of Enceladus. This lead to an irregular and wobbly spin, which stabilised over more than a million years. Cassini discovered moon of Saturn, and the fact that Enceladus has the ingredients necessary for harbouring life as we know it on Earth .