Category Archives: Cassini

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

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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

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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

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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

Mimas

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NASA’s caption:
It may look as though Saturn’s moon Mimas is crashing through the rings in this image taken by NASA’s Cassini spacecraft, but Mimas is actually 28,000 miles (45,000 kilometers) away from the rings. There is a strong connection between the icy moon and Saturn’s rings, though. Gravity links them together and shapes the way they both move.

The gravitational pull of Mimas (246 miles or 396 kilometers across) creates waves in Saturn’s rings that are visible in some Cassini images. Mimas’ gravity also helps create the Cassini Division (not pictured here), which separates the A and B rings.

This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 15 degrees to the right. The image was taken in green light with the Cassini spacecraft narrow-angle camera on Oct. 23, 2016.

The view was acquired at a distance of approximately 114,000 miles (183,000 kilometers) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 29 degrees. Image scale is 3,300 feet (1 kilometer) per pixel.

Image: NASA/JPL-Caltech/Space Science Institute

New Views of Cassini

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If all goes as planned this is just the first of a new set of images the Cassini spacecraft will be returning in the new phase of its mission.

Click the image for a larger version.

From NASA:
This view from NASA’s Cassini spacecraft was obtained about half a day before its first close pass by the outer edges of Saturn’s main rings during its penultimate mission phase.

The view shows part of the giant, hexagon-shaped jet stream around the planet’s north pole. Each side of the hexagon is about as wide as Earth. A circular storm lies at the center, at the pole (see PIA14944).

The image was taken with the Cassini spacecraft wide-angle camera on Dec. 3, 2016, at a distance of about 240,000 miles (390,000 kilometers) from Saturn. Image scale is 14 miles (23 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Mimas and Saturn

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Be sure to check out our page on Mimas.

 

Saturn’s icy moon Mimas is dwarfed by the planet’s enormous rings.

Because Mimas (near lower left) appears tiny by comparison, it might seem that the rings would be far more massive, but this is not the case. Scientists think the rings are no more than a few times as massive as Mimas, or perhaps just a fraction of Mimas’ mass. Cassini is expected to determine the mass of Saturn’s rings to within just a few hundredths of Mimas’ mass as the mission winds down by tracking radio signals from the spacecraft as it flies close to the rings.

The rings, which are made of small, icy particles spread over a vast area, are extremely thin — generally no thicker than the height of a house. Thus, despite their giant proportions, the rings contain a surprisingly small amount of material.

Mimas is 246 miles (396 kilometers) wide.

This view looks toward the sunlit side of the rings from about 6 degrees above the ring plane. The image was taken in red light with the Cassini spacecraft wide-angle camera on July 21, 2016.

The view was obtained at a distance of approximately 564,000 miles (907,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 31 degrees. Image scale is 34 miles (54 kilometers) per pixel.

Image and caption: NASA/JPL-Caltech/Space Science Institute