I just can’t get enough of the Cassini probe photographs of the Saturn system. The thought that it might be shut down this year for budgetary reasons, with plenty of science and stunning imagery yet to beam us, is thoroughly depressing and I hope it doesn’t happen. Anyway, today’s Astronomy Photo of the Day (APOD) from NASA is a Cassini photograph of Saturn’s rings and its moon Tethys. The rings are about 250,000 kilometers wide, but they are remarkably thin and diffuse, so diffuse in fact that they are barely there. Their thickness varies from as little as 10 meters to as much as a kilometer and a half. Phil Nicholson, a planetary scientist at Cornell, called them “the most two-dimensional structure we know of in the universe.” As for the mass of the rings, they are less than the tiny moon Tethys in the upper right of the photograph. Just trying to help you get your New Year’s into perspective.