Category Archives: Cassini

Cresusa

Cassini took this image of the crater Creusa on the Saturn moon Dione on 26 November 2016 with a nice angle to show the crater nicely.

I changed the image a little to bring out some of the details, the original version can be seen here.

NASA’s caption:
When viewed from a distance with the sun directly behind Cassini, the larger, brighter craters really stand out on moons like Dione.

Among these larger craters, some leave bright ray patterns across the moon, calling attention to their existence and to the violence of their creation.

The rayed crater seen here on Dione (698 miles, or 1,123 kilometers across) is named Creusa. The rays are brighter material blasted out by the impact that formed the crater. Scientists can use the patterns of ejecta (like these rays), to help determine the order of geological events on a moon’s surface by examining which features lie on top of other features.

This view looks toward the Saturn-facing side of Dione. North on Dione is up and rotated 31 degrees to the right. The image was taken with the Cassini spacecraft narrow-angle camera on Nov. 26, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 727 nanometers.

The view was obtained at a distance of approximately 350,000 miles (560,000 kilometers) from Dione. Image scale is 1.8 miles (3 kilometers) per pixel.

Images: NASA/JPL-Caltech/Space Science Institute

Daphnis Making Waves

Daphnis making waves in the rings of Saturn,  yes we saw this image a little while ago, NASA added more images to show more of the waves caused the gravity of the moon – a lot more.

Daphnis, one of Saturn’s ring-embedded moons, is featured in this view, kicking up waves as it orbits within the Keeler gap. The mosaic combines several images to show more waves in the gap edges than seen in a previously released image, PIA21056.

Daphnis is a small moon at 5 miles (8 kilometers) across, but its gravity is powerful enough to disrupt the tiny particles of the A ring that form the Keeler gap’s edge. As the moon moves through the Keeler gap, wave-like features are created in both the horizontal and vertical plane. For more about these vertical structures see PIA11654 and PIA11547.

Images like this provide scientists with a close-up view of the complicated interactions between a moon and the rings, as well as the interactions between the ring particles themselves, in the wake of the moon’s passage. Three wave crests of diminishing sizes trail Daphnis here. In each subsequent crest, the shape of the wave evolves, as the ring particles within the crests collide with one another.

Close examination of Daphnis’ immediate vicinity also reveals a faint, thin strand of ring material that almost appears to have been directly ripped out of the A ring by Daphnis.

The images in this mosaic were taken in visible light, using the Cassini spacecraft narrow-angle camera at a distance of approximately 17,000 miles (28,000 kilometers) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 71 degrees. Image scale is 551 feet (168 meters) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Enceladus

A nice image of the Saturn moon Enceladus from Cassini. The thought of a global ocean with liquid water that far away is amazing.

From NASA:
Seen from outside, Enceladus appears to be like most of its sibling moons: cold, icy and inhospitable. But under that forbidding exterior may exist the very conditions needed for life.

Over the course of the Cassini mission, observations have shown that Enceladus (313 miles or 504 kilometers across) not only has watery jets sending icy grains into space; under its icy crust it also has a global ocean, and may have hydrothermal activity as well. Since scientists believe liquid water is a key ingredient for life, the implications for future missions searching for life elsewhere in our solar system could be significant.

This view looks toward the Saturn-facing hemisphere of Enceladus. North on Enceladus is up and rotated 6 degrees to the right. The image was taken in green light with the Cassini spacecraft narrow-angle camera on Nov. 27, 2016.

The view was obtained at a distance of approximately 81,000 miles (130,000 kilometers) from Enceladus. Image scale is 2,566 feet (782 meters) per pixel.

Saturn Straw

This Cassini image features a density wave in Saturn’s A ring (at left) that lies around 134,500 km from Saturn. Density waves are accumulations of particles at certain distances from the planet. This feature is filled with clumpy perturbations, which researchers informally refer to as “straw.” The wave itself is created by the gravity of the moons Janus and Epimetheus, which share the same orbit around Saturn. Elsewhere, the scene is dominated by “wakes” from a recent pass of the ring moon Pan.

Two versions of this image are available. This is a lightly processed version, with minimal enhancement, preserving all original details present in the image. The other version (Figure 1) has been processed to remove the small bright blemishes caused by cosmic rays and charged particle radiation near the planet — a more aesthetically pleasing image, but with a slight softening of the finest details.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on Dec. 18, 2016. The view was obtained at a distance of approximately 34,000 miles (56,000 kilometers) from the rings and looks toward the unilluminated side of the rings. Image scale is about a quarter-mile (340 meters) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

Credit: NASA/JPL-Caltech/Space Science Institute

Tethys and Odysseus

Each time we get a picture of a moon from Cassini it’s hard to know if it will be the last, especially one that has such a good angle on a magnificent landmark like the crater Odysseus.

Original caption from the Cassini team:

Tethys, one of Saturn’s larger icy moons, vaguely resembles an eyeball staring off into space in this view from NASA’s Cassini spacecraft. The resemblance is due to the enormous crater, Odysseus, and its complex of central peaks.

Like any solar system moon, Tethys (660 miles or 1,062 kilometers across) has suffered many impacts. These impacts are a prime shaper of the appearance of a moon’s surface , especially when the moon has no active geological processes. In this case, a large impact not only created a crater known as Odysseus, but the rebound of the impact caused the mountainous peaks, named Scheria Montes, to form in the center of the crater.

This view looks toward the leading side of Tethys. North on Tethys is up and rotated 1 degree to the left. The image was taken in green light with the Cassini spacecraft narrow-angle camera on Nov. 10, 2016.

The view was acquired at a distance of approximately 228,000 miles (367,000 kilometers) from Tethys. Image scale is 1.2 miles (2 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Daphnis

Probably one of our last views of Daphnis from Cassini. The moon appears to be traveling towards the right in this image.

From Cassini:

The wavemaker moon, Daphnis, is featured in this view, taken as NASA’s Cassini spacecraft made one of its ring-grazing passes over the outer edges of Saturn’s rings on Jan. 16, 2017. This is the closest view of the small moon obtained yet.

Daphnis (5 miles or 8 kilometers across) orbits within the 42-kilometer (26-mile) wide Keeler Gap. Cassini’s viewing angle causes the gap to appear narrower than it actually is, due to foreshortening.

The little moon’s gravity raises waves in the edges of the gap in both the horizontal and vertical directions. Cassini was able to observe the vertical structures in 2009, around the time of Saturn’s equinox (see PIA11654).

Like a couple of Saturn’s other small ring moons, Atlas and Pan, Daphnis appears to have a narrow ridge around its equator and a fairly smooth mantle of material on its surface — likely an accumulation of fine particles from the rings. A few craters are obvious at this resolution. An additional ridge can be seen further north that runs parallel to the equatorial band.

Fine details in the rings are also on display in this image. In particular, a grainy texture is seen in several wide lanes which hints at structures where particles are clumping together. In comparison to the otherwise sharp edges of the Keeler Gap, the wave peak in the gap edge at left has a softened appearance. This is possibly due to the movement of fine ring particles being spread out into the gap following Daphnis’ last close approach to that edge on a previous orbit.

A faint, narrow tendril of ring material follows just behind Daphnis (to its left). This may have resulted from a moment when Daphnis drew a packet of material out of the ring, and now that packet is spreading itself out.

The image was taken in visible (green) light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 17,000 miles (28,000 kilometers) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 71 degrees. Image scale is 551 feet (168 meters) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Mimas

mimas2

We need more missions like Cassini going to other as yet unexplored planets. Have a look at our Mimas page

The original caption:

Shadows cast across Mimas’ defining feature, Herschel Crater, provide an indication of the size of the crater’s towering walls and central peak.

Named after the icy moon’s discoverer, astronomer William Herschel, the crater stretches 86 miles (139 kilometers) wide — almost one-third of the diameter of Mimas (246 miles or 396 kilometers) itself.

Large impact craters often have peaks in their center — see Tethys’ large crater Odysseus in PIA08400. Herschel’s peak stands nearly as tall as Mount Everest on Earth.

This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 21 degrees to the left. The image was taken with the Cassini spacecraft narrow-angle camera on Oct. 22, 2016 using a combination of spectral filters which preferentially admits wavelengths of ultraviolet light centered at 338 nanometers.

The view was acquired at a distance of approximately 115,000 miles (185,000 kilometers) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 20 degrees. Image scale is 3,300 feet (1 kilometer) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Sunny Saturn

saturnsynnynorth

The sunny northern hemisphere on Saturn.

NASA:
Sunlight truly has come to Saturn’s north pole. The whole northern region is bathed in sunlight in this view from late 2016, feeble though the light may be at Saturn’s distant domain in the solar system.

The hexagon-shaped jet-stream is fully illuminated here. In this image, the planet appears darker in regions where the cloud deck is lower, such the region interior to the hexagon. Mission experts on Saturn’s atmosphere are taking advantage of the season and Cassini’s favorable viewing geometry to study this and other weather patterns as Saturn’s northern hemisphere approaches Summer solstice.

This view looks toward the sunlit side of the rings from about 51 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Sept. 9, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 728 nanometers.

The view was obtained at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn. Image scale is 46 miles (74 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Pandora

pandora

This is the Saturn moon Pandora like we’ve never seen before and likely not to see again for a long-long time once the Cassini mission comes to an end.

The details from the Cassini mission team:
This image from NASA’s Cassini spacecraft is one of the highest-resolution views ever taken of Saturn’s moon Pandora. Pandora (52 miles, 84 kilometers) across orbits Saturn just outside the narrow F ring.

The spacecraft captured the image during its closest-ever flyby of Pandora on Dec. 18, 2016, during the third of its grazing passes by the outer edges of Saturn’s main rings. (For Cassini’s closest view prior to this flyby, see PIA07632, which is also in color.)

The image was taken in green light with the Cassini spacecraft narrow-angle camera at a distance of approximately 25,200 miles (40,500 kilometers) from Pandora, or phase, angle of 29 degrees. Image scale is 787 feet (240 meters) per pixel.

Image: NASA/JPL-Caltech/Space Science Institute