There are still many things in our solar system that our spacecraft have not yet gotten close to, and Saturn’s ring system is one of them. It’s the biggest of all the gas giants’ ring systems and to date we do not know how old it is or how it formed in the first place, or how it got so large compared to the rings of the other gas giants. It appears to be an outlier – and a lovely outlier at that.
The Cassini probe has been orbiting Saturn since 2004. It’s uncovered a lot since then, but there is still one central mystery left to discover. It’s apparent when you look at the rings themselves.
The estimated mass of the rings is equivalent to a small ice moon, such as Mimas. That leads some to believe that they were created by the breakup of said moon or many comets after passing through Saturn’s Roche limit. But these events are very rare and unlikely to have occurred within the last billion years.
Yet the rings look so young. Their pristine color is the result of >99% water ice. The slight reddish color comes from impurities which strongly absorb ultraviolet, as was found by Cassini’s UVIS instrument. They are thought to come from meteoritic infall, but if that really were the case, the rings should be much darker given their age.
That paradox can only be resolved by direct sampling of the ice particles within the rings, ranging from less than 1 cm to 10s of meters in size. Knowing what the impurities are will help us figure out what is causing the slight darkening, and why the rings hasn’t darkened that much.
This is the objective of the small spacecraft mission to Saturn in my master’s thesis. Stay tuned!