Scientists using data and photos sent back from the Cassini Saturn probe are solidifying their ideas about how the tiny moons hovering in the planet's outer rings were formed. Naturally, the answer is that they were grown from moon-seeds.
These little moons have offered a bit of a puzzle over the years. It has been widely believed that these little satellites, like the rings themselves, were the remains of larger icy bodies, perhaps a bigger moon or moons destroyed by an impact, that dispersed and settled into the ring region.
The trouble was, many of these have very low density – lower than that of water ice – and shapes that indicated that they've been built up by the accumulation of ring material. Which is odd, given their location;
small particles in this area can't fuse together gravitationally to form bodies of this size.
Enter the seeds. Using the data and photographs from Cassini, and computer simulations, researchers have determined that these little moons likely started from relatively dense cores, and only then attracted the ring material over time. As long as the seed was initially as dense as water ice, material could accrete, creating a moon of about three times the size of the original core, they say.
The moon-seeds may well date back to the period that the original rings were formed. Says Derek
Richardson, astronomy professor at the University of Maryland:
So remember, readers. If you get your hands on some of these seeds, make sure you have plenty of space to grow them in. It'll take time to grow, but it'll beat even the biggest county-fair pumpkin all to hell.
Images of Saturn’s small moons tell the story of their origins[ESA press release]
(Image: Images of Saturn moons Atlas (right two) and Pan (left two), as seen by the Cassini probe. NASA/JPL/Space Science Institute.)
