aesmael

Originally published at a denizen's entertainment. You can comment here or there.

In the past week I have been surprised by two pieces of news concerning Saturn and rings.

First, from the Planetary Society Blog: findings which might be evidence for a posited ring around Rhea. As described in that article, a series of equatorial spots on Rhea bright in ultaviolet light might be evidence of collisions from ring particles orbiting the moon. These particles, if they exist, would occupy a size and distribution which makes them particularly difficult to detect visually directly with the instruments we currently have available.

It seems the idea of rings around Rhea has been around longer than I have been aware of. Apparently they were originally proposed to explain a decreased electron flux in the vicinity of Rhea back in 2005, and I sure didn't realise there was this much evidence already. Would be very exciting indeed to get a direct and definite confirmation about this.

Sadly given how difficult these rings are proving to image, it is unlikely there will ever be beautiful views of the Rhean ringscape. We shall just have to comfort ourselves with the knowledge of something wonderful.

The other news is the discovery of a new ring around Saturn itself. This one, discovered by the Spitzer Space Telescope, is the largest and most diffuse planetary ring yet discovered. The details can be found in this press release. Basically it is very large and very faint, and only detected because of its cool infrared glow. I am concerned that the end of the release specifies this information was gathered before Spitzer ran out of coolant, and whether this means we won't be able to obtain further observations of the ring for a while. It might take us a long time to discover if this ring 'only' spans from six to twelve million kilometres from Saturn, or if that were merely its brightest, densest part.

Apart from the amazement of a whole new feature being discovered, this is particularly intriguing because Saturn's moon Phoebe orbits within this ring and is thought to be the source of its material (via dust knocked off from impacts, most likely). If so, and depending on what else is found, this ring could be a key part of one of astronomy's longer-standing mysteries: the two faces of Iapetus. Although it has long been suspected that material from Phoebe deposited on Iapetus is the reason that moon has one bright hemisphere and one dark (more or less), I think this ring is the first actual detection of a possible mechanism for the transfer of this material.

If that bears out I think I will finally have an answer to a mystery I have been intrigued by since I was a young child; for a long time Iapetus has been one of the solar system bodies I was most fascinated by.