杏吧原创

The latest images to be returned from the Cassini space probe reveal a mystery in Saturn鈥檚 rings. The unique close-up images show an unexplained clumping of material within the rings, which could help scientists understand how planets form.

Cassini entered into orbit around Saturn on 1 July, successfully negotiating a gap between the planet鈥檚 rings before returning its fist images later the same day.

One of the new images from Cassini is of the Encke gap, a 325-kilometre void in Saturn鈥檚 outermost main ring, known as the A ring. Scallops on the inner edge of the gap are thought to be caused by the gravity of the small moon Pan, which orbits inside the gap. The scallops leave a spiral wake behind them that spreads inwards from the edge.

鈥淭his is textbook ring physics,鈥� says Carolyn Porco, head of the imaging team. 鈥淚 thought my team was playing tricks on me and showing me a simulation of the rings rather than the rings themselves.鈥�

Gravitational influence

In another image, more waves cross the A ring, driven by the gravity of three more moons: Janus, Pandora and Prometheus. These 鈥渄ensity waves鈥� are generated when the orbital period of ice particles in the rings match that of one of the orbiting moons, so that the moon鈥檚 slight gravitational influence builds up.

But the graininess at the bottom left of the picture is harder to explain. 鈥淚t almost looks like straw. I don鈥檛 know what this is. I literally don鈥檛 have a clue,鈥� says Porco, who is an expert on Saturn鈥檚 rings. 鈥淚t may be brand new, something nobody鈥檚 predicted before. There may be processes going on that make the particles clump.鈥�

If so, it could be highly significant. Saturn鈥檚 rings are thought to be a pocket-sized version of the disk of ice and dust that once surrounded the Sun, from which the planets formed.

鈥淲e may be seeing some of the processes that aided the development of the planets,鈥� says Porco.