Full Moon

Here’s an amazing portrait of Tethys, a 662-mile-wide, airless and  heavily-cratered moon of Saturn. The photo was taken by Cassini on October 14, 2009, with the moon fully lit by the sun. Its high reflectivity (albedo) indicate a large amount of ice in its composition. I adjusted the image to bring out the details in…

A Cratered Crescent Composition

The crescent of Saturn’s moon Tethys hovers serenely over a dimly-lit ringplane in this raw image, taken by the Cassini orbiter on October 11, 2009. Frigid, airless and heavily-cratered, Tethys is mostly composed of water ice and rock. It is 662 miles wide. Image: NASA/JPL/SSI

Worlds Great and Small

A wonderful raw image from the Cassini spacecraft showing a crescent-lit Saturn and one of its 61 known moons. Honestly I’m not sure which moon this is. Could be Tethys, could be Titan, it’s hard to make out in this wide-angle view. Also in crescent, its night side is dimly lit by reflected “Saturnshine”. Cassini…

Three Little Moons

A little family portrait from the house of Saturn. Enceladus, Tethys and Dione. Okay, they weren’t really all lined up like that….I combined three raw shots from Cassini, taken over the weekend, and lined them up nicely. Approximate sizes in relation to each other. Just for fun. Great images though! Tethys’ huge 250-mile-wide Odysseus crater…

Hail, Calypso

A lesser-known moon, Calypso orbits Saturn in the same path as Tethys and another miniature moon called Telesto. Known as the “Tethys Trojans”, these two oblong-shaped moons were discovered in 1980 by Earth-based telescopes and eventually photographed by Cassini. The moniker “trojan” in astronomy is reserved for satellites that orbit a planet in the same…

The Eye of Odysseus

  This is Tethys, a 662-mile-wide moon of Saturn captured by Cassini’s cameras in this raw image from May 14. Dominating its face is the huge Odysseus Crater, its rim gleaming in the sunlight. Much of Tethys is estimated to be water ice, due to its density and high albedo (reflectivity). That Tethys was able…

Shadow Facts

  A moon’s shadow falls upon ring after ring in this image, taken on April 29 by Cassini.  Varying brightnesses and compositions of ring segments scatter light differently, as shown above. With Saturn’s spring equinox (August 11) getting closer every day, the ringplane – and orbital plane of many of its moons – are approaching a perpendicular…

The Dark Side

  The dark side of Tethys is illuminated by reflected light from Saturn in this image from the Cassini orbiter. On the sunlit side, the giant Odysseus crater can be seen straddling the western edge. The crater is 280 miles across in its entirety, taking up a large portion of the 660-mile-wide moon’s icy surface….