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Emily Lakdawalla • Sep 01, 2009

Cassini goodies: Telesto, Janus, Prometheus, Pandora, F ring

As I mentioned yesterday, the Cassini raw images website has been full of goodies lately. Here's a sample.

(First, a quick update on the Station fire: Mount Wilson is still unscathed, and firefighters predict today will be a better day. Concern is abating.)

My favorite recent set of images was targeted at Janus. Take a look at this animation and see if you can figure out what's going on before you read any further:

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Janus is the 10th largest moon of Saturn, 196 x 192 x 150 kilometers in diameter and orbits along with Epimetheus between the F and G rings.
Epimetheus from Voyager 1

NASA / JPL / animation by Emily Lakdawalla

Epimetheus from Voyager 1
On November 12, 1980, Voyager 1 captured a series of images of Epimetheus through different color filters. During the sequence, the shadow of the F ring crossed the moon.
Telesto

NASA / JPL / SSI / color composite by Gordan Ugarkovic

Telesto
Cassini captured this view of the leading hemisphere of Telesto on August 27, 2009. Telesto is a small moon, 34 x 28 x 36 kilometers in diameter, that occupies a Lagrange point behind Tethys in its orbit around Saturn. This is an approximately natural color view composed of raw images.
Saturn's moon Telesto

NASA / JPL / Space Science Institute

Saturn's moon Telesto
This raw image was captured by Cassini during its closest planned encounter with Telesto, on October 11, 2005.
Prometheus, Pandora, and the F ring

NASA / JPL / SSI / animation by Mike Malaska

Prometheus, Pandora, and the F ring
Cassini captured the images that compose this animation on August 20, 2009. At present, Prometheus (the inner shepherd of the F ring) and the F ring collide with every orbit of Prometheus around Saturn. Prometheus dips into the F ring, causing a gore and pulling out a streamer of material. On the next orbit, Prometheus dips into the F ring ahead of its previous position. The result is a series of gores that slowly get sheared out as a result of the differential rates that the ring particles orbit Saturn (objects closer to Saturn complete one orbit in a shorter period of time than objects farther from Saturn). Pandora, the outer shepherd of the F ring, is also visible in this animation. The moons are lit from below by the Sun and from above by Saturnshine.