As NASA’s Cassini soared above high northern latitudes on Saturn’s moon Dione, the spacecraft looked down at a region near the day-night boundary. Territory seen here is just east of a crater named Butes, near an unnamed tectonic structure around 65 degrees north latitude, 25 degrees west longitude. The broader view is from the spacecraft’s wide-angle camera (WAC) and includes an inset view from Cassini’s narrow-angle camera (NAC). The views were acquired in visible light at an altitude of 365 miles (588 kilometres) above Dione. The wide-angle camera image has an image scale of about 115 feet (35 metres) per pixel; the narrow-angle camera image has an image scale of about 12 feet (3.5 metres) per pixel. Image credit: NASA/JPL-Caltech/Space Science Institute.This was the fifth close encounter with Dione during NASA’s Cassini mission’s long tour at Saturn. The mission’s closest-ever flyby of Dione was in December 2011, at a distance of 60 miles (100 kilometres).
“I am moved, as I know everyone else is, looking at these exquisite images of Dione’s surface and crescent, and knowing that they are the last we will see of this far-off world for a very long time to come,” said Carolyn Porco, Cassini imaging team lead at the Space Science Institute, Boulder, Colorado. “Right down to the last, Cassini has faithfully delivered another extraordinary set of riches. How lucky we have been.”Saturn’s moon Dione hangs in front of Saturn’s rings in this view taken by NASA’s Cassini spacecraft during the inbound leg of its last close flyby of the icy moon. North on Dione is up. The image was acquired in visible light with the Cassini spacecraft narrow-angle camera on 17 August 2015. The view was acquired at a distance of approximately 98,000 miles (158,000 kilometres) from Dione and at a sun-Dione-spacecraft, or phase, angle of 35 degrees. Image scale is 3,100 feet (950 metres) per pixel. Image credit: NASA/JPL-Caltech/Space Science Institute.Processed images from the flyby are available by clicking here, while raw, unprocessed images from the flyby are available here.
The main scientific focus of this flyby was gravity science, not imaging. This made capturing the images tricky, as Cassini’s camera was not controlling where the spacecraft pointed.Five visible light (clear spectral filter), narrow-angle camera images from NASA’s Cassini spacecraft were combined to create this mosaic of Dione’s parting view. The scene is an orthographic projection centred on terrain at 0.4 degrees north latitude, 30.6 degrees west longitude on Dione. The view was acquired at distances ranging from approximately 37,000 miles (59,000 kilometres) to 47,000 miles (75,000 kilometres) from Dione and at a phase angle of 145 degrees. Image scale is about 1,300 feet (400 metres) per pixel. North on Dione is up and rotated 34 degrees to the right. Image credit: NASA/JPL-Caltech/Space Science Institute.“We had just enough time to snap a few images, giving us nice, high-resolution looks at the surface,” said Tilmann Denk, a Cassini participating scientist at Freie University in Berlin. “We were able to make use of reflected sunlight from Saturn as an additional light source, which revealed details in the shadows of some of the images.”
Cassini scientists will study data from the gravity science experiment and magnetosphere and plasma science instruments over the next few months as they look for clues about Dione’s interior structure and processes affecting its surface.This two-in-one view of Dione from NASA’s Cassini spacecraft includes the mission’s highest-resolution view of the Saturnian moon’s icy surface. The view, from the spacecraft’s wide-angle camera (WAC), includes an inset view, near centre left, from the narrow-angle camera (NAC). The NAC view shows features about 10 times smaller than the WAC view. The narrow-angle camera view has an image scale of about 10 feet (3 meters) per pixel. Sunlight illuminates the scene from top. North on Dione is down. The views were acquired in visible light at an altitude of 334 miles (537 kilometres) above Dione. Image credit: NASA/JPL-Caltech/Space Science Institute.Only a handful of close flybys of Saturn’s large, icy moons remain for Cassini. The spacecraft is scheduled to make three approaches to the geologically active moon Enceladus on 14 and 28 October, and 19 December. During the 28 October flyby, the spacecraft will come dizzyingly close to Enceladus, passing a mere 30 miles (49 kilometres) from the surface. Cassini will make its deepest-ever dive through the moon’s plume of icy spray at this time, collecting valuable data about what’s going on beneath the surface. The December Enceladus encounter will be Cassini’s final close pass by that moon, at an altitude of 3,106 miles (4,999 kilometres).This view from NASA’s Cassini spacecraft looks toward Saturn’s icy moon Dione, with giant Saturn and its rings in the background, just prior to the mission’s final close approach to the moon on 17 August 2015. At lower right is the large, multi-ringed impact basin named Evander, which is about 220 miles (350 kilometres) wide. The canyons of Padua Chasma, features that form part of Dione’s bright, wispy terrain, reach into the darkness at left. Image credit: NASA/JPL-Caltech/Space Science Institute.After December, and through the mission’s conclusion in late 2017, there are a handful of distant flybys planned for Saturn’s large, icy moons at ranges of less than about 30,000 miles (50,000 kilometres). Cassini will, however, make nearly two dozen passes by a menagerie of Saturn’s small, irregularly shaped moons — including Daphnis, Telesto, Epimetheus and Aegaeon — at similar distances during this time. These passes will provide some of Cassini’s best-ever views of the little moons.
During the mission’s final year — called its Grand Finale — Cassini will repeatedly dive through the space between Saturn and its rings.
The puzzling appearance of an ice cloud seemingly out of thin air in the stratosphere of Titan has prompted NASA scientists to suggest that a different process than previously thought — possibly similar to one seen over Earth’s poles — could be forming clouds in the giant Saturnian moon’s hazy, brownish-orange atmosphere.
Tethys appears to be peeking out from behind Rhea in this image from the Cassini probe. Scientists believe that Tethys’ surprisingly high albedo is due to the water ice jets emerging from its neighbour, Enceladus.
