Astronomy Picture of the Week – Small Wonders (Cassini’s Grand Finale)

(This is 30 minutes late because I was a couple days late with GGS.)

Still on the Grand Finale, and as I said when this started, I’ll be staying here until it’s over, because yes, I’m mourning the end of Cassini’s mission. It’s an image of three of Saturn’s smaller ring moons.

I hope you enjoy this one. As always, click on the image for the .tif download…

This montage of views from NASA's Cassini spacecraft shows three of Saturn's small ring moons: Atlas, Daphnis and Pan at the same scale for ease of comparison.

This montage of views from NASA’s Cassini spacecraft shows three of Saturn’s small ring moons: Atlas, Daphnis and Pan at the same scale for ease of comparison.

Two differences between Atlas and Pan are obvious in this montage. Pan’s equatorial band is much thinner and more sharply defined, and the central mass of Atlas (the part underneath the smooth equatorial band) appears to be smaller than that of Pan.

Images of Atlas and Pan taken using infrared, green and ultraviolet spectral filters were combined to create enhanced-color views (Figure A), which highlight subtle color differences across the moons’ surfaces at wavelengths not visible to human eyes. (The Daphnis image in figure A was colored using the same green filter image for all three color channels, adjusted to have a realistic appearance next to the other two moons.)


  1. StevoR says

    @ ^ Marcus Ranum : Same composition as Saturn’s rings really I expect -- mostly water ice although read somewhere (an astronomy magazine article) that actually ring particles have been found to be unexpectedly reddened by something. Shades of the dark side on Iapetus ( )

    The moonlets here have probably accreted from and broken up into Saturnian ring particles over their lives, perhaps repeatedly so.

  2. StevoR says

    ^ See :

    Plus :

    Two of Saturn’s small moons look eerily like flying saucers, new observations by the Cassini spacecraft reveal. The moons, which lie within the giant planet’s rings, may have come by their strange shape by gradually accumulating ring particles in a ridge around their equators.

    There’s also, as I think Isaac Asimov once noted, the unclear dividing line between what’s a ring particle and a moonlet or even small moon of Saturn with each ring particle technically being a natural satellite of Saturn’s. (tried tofind the quote but not been able to yet.)

Leave a Reply