Drumroll please… the little moon Telesto! (You like it, you really like it!) This image, captured by Cassini on Jan. 14, 2016, shows Saturn’s moon Telesto – a “leading trojan” of the much larger satellite Tethys.
A trojan moon is one that orbits a parent body within the same path as a more massive satellite, positioned at the Lagrangian points L4 and L5… usually at 60º ahead and behind within the orbit relative to the overall center (which, in the case of Tethys, is Saturn.)
The irregularly-shaped, 15-mile (24-km) -wide Telesto rides around Saturn ahead of Tethys, making it the moon’s “leading” trojan. Its slightly larger sister Calypso follows behind Tethys as the trailing trojan. All three orbit the ringed planet at a distance of over 183,000 miles (294,000 km).
After nearly eleven and a half years in orbit around Saturn the Cassini spacecraft has made its last-ever targeted flyby of Enceladus, the 320-mile-wide moon of Saturn that has intrigued scientists and the public alike with its active water ice geysers for more than a decade since their discovery. On Saturday Dec. 19, 2015, Cassini performed its E-22 flyby of Enceladus, coming within 3,106 miles (5,000 km) of the moon’s fractured and frozen surface as it sped by at over 21,000 mph. It captured some incredible images along the way, including the one above showing a crescent-lit Enceladus from its night side silhouetted against the hazy upper atmosphere of Saturn, 150,000 miles beyond.
Take a look through some more raw images from the E-22 flyby below.
On Nov. 11, 2015, NASA’s Cassini spacecraft passed relatively closely by Saturn’s moon Tethys, one of the ringed planet’s larger icy satellites. The animation above was made from 29 raw images acquired with Cassini’s narrow-angle camera as it passed by; you can see part of the incredibly cratered and ancient surface of this 662 mile (1,065 km) wide moon. Talk about flyover country!
On Wed. Oct. 28 Cassini performed its lowest-altitude dive yet through the icy plumes of Enceladus, coming just 30 miles from the moon’s surface — that’s only about 6 times higher than a commercial airliner at cruising altitude. But, traveling over 19,000 mph relative to Enceladus (which is 38 times faster than a jet plane!) the pass was over in just a few seconds. Still, Cassini managed to capture some images before, during, and after closest approach — and they’ve arrived on Earth today.
Here are some of the raw images from the E-21 flyby. These have not been validated or made into official releases by NASA or the Cassini imaging team yet, but they are a nice teaser of what we might expect once they are. (And, of course, the science performed during the flyby has yet to be revealed.) So pics only for now!
On Wednesday, Oct. 14 2015, Cassini performed its scheduled “E-20” close pass of Enceladus, a 320-mile-wide moon of Saturn that is now famous for the organics-laden ice geysers that fire from cracks in its southern crust. E-20 is the first of a series of three flybys to be performed before the end of 2015, specifically timed to give the spacecraft a good view of Enceladus’ north polar region now that Saturn is moving into its summer season.
The raw image data from E-20 has just arrived on Earth today (which, by the way, is the 18th anniversary of Cassini’s launch!) and I particularly liked the one above. Crescent-lit by the Sun, Enceladus’ night side is seen bathed in the dimmer glow of reflected light off Saturn and its rings. Dead-center is the 6.5-mile-wide crater Bahman, surrounded by a wrinkly field of cracks and troughs in the moon’s highly-reflective icy surface.
It’s been a while since I last made one of these: it’s an animation comprising 27 images acquired by Cassini in various color channels on October 11, 2015. It shows Saturn’s second-largest moon Rhea passing in front of the smaller and more distant* Dione, both partially illuminated by sunlight. I cleaned up some image artifacts from each frame and adjusted the levels to make the blacks black and not banded, like is often found in images like these. I also added a bit of a glow to the moons, to enhance the sense of light (and bring out some of the detail in the darker areas.)
There’s nothing particularly scientific here, just an enjoyment of the endless and ongoing dance of the spheres!
Check out an older moon animation of Rhea here.
*Dione is more distant from the Cassini spacecraft in these views; it’s actually closer to Saturn in its orbit than Rhea.