Category Archives: Cassini

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

Prometheus

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Nice look at Prometheus from Cassini.

From Cassini/NASA:
Surface features are visible on Saturn’s moon Prometheus in this view from NASA’s Cassini spacecraft. Most of Cassini’s images of Prometheus are too distant to resolve individual craters, making views like this a rare treat.

Saturn’s narrow F ring, which makes a diagonal line beginning at top center, appears bright and bold in some Cassini views, but not here. Since the sun is nearly behind Cassini in this image, most of the light hitting the F ring is being scattered away from the camera, making it appear dim. Light-scattering behavior like this is typical of rings comprised of small particles, such as the F ring.

This view looks toward the unilluminated side of the rings from about 14 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 24, 2016..

The view was acquired at a distance of approximately 226,000 miles (364,000 kilometers) from Prometheus and at a sun-Prometheus-spacecraft, or phase, angle of 51 degrees. Image scale is 1.2 miles (2 kilometers) per pixel.

Image: NASA/JPL-Caltech/Space Science Institute

Rings in Detail

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A great look at the rings of Saturn from the Cassini spacecraft. Saturn is a treasure, I don’t think I have ever looked at it through even a small telescope and not thought “WOW”.

Check out Saturn.

From NASA and Cassini:
This view from NASA’s Cassini spacecraft showcases some of the amazingly detailed structure of Saturn’s rings.

The rings are made up of many smaller ringlets that blur together when seen from a distance. But when imaged up close, the rings’ structures display quite a bit of variation. Ring scientists are debating the nature of these features — whether they have always appeared this way or if their appearance has evolved over time.

This view looks toward the sunlit side of the rings from about 4 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Sept. 24, 2016.

The view was acquired at a distance of approximately 283,000 miles (456,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 32 degrees. Image scale is 17 miles (27 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Super Saturn

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Too good, this has to be one of Cassini’s best images of the Saturn globe.  Wonderful detail, click the image for a larger version (as is nearly always the case).

From NASA/JPL-Caltech/Space Science Institute
Saturn appears as a serene globe amid tranquil rings in this view from NASA’s Cassini spacecraft. In reality, the planet’s atmosphere is an ever-changing scene of high-speed winds and evolving weather patterns, punctuated by occasional large storms (see PIA14901). The rings, consist of countless icy particles, which are continually colliding. Such collisions play a key role in the rings’ numerous waves and wakes, which are the manifestation of the subtle influence of Saturn’s moons and, indeed, the planet itself.

The long duration of the Cassini mission has allowed scientists to study how the atmosphere and rings of Saturn change over time, providing much-needed insights into this active planetary system.

The view looks toward the sunlit side of the rings from about 41 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on July 16, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

The view was acquired at a distance of approximately 1 million miles (2 million kilometers) from Saturn. Image scale is 68 miles (110 kilometers) per pixel.

Summer Skies on Saturn

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Be sure the click the image to get the larger version.

The original caption:

These two natural color images from NASA’s Cassini spacecraft show the changing appearance of Saturn’s north polar region between 2012 and 2016.

Scientists are investigating potential causes for the change in color of the region inside the north-polar hexagon on Saturn. The color change is thought to be an effect of Saturn’s seasons. In particular, the change from a bluish color to a more golden hue may be due to the increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017.

Researchers think the hexagon, which is a six-sided jetstream, might act as a barrier that prevents haze particles produced outside it from entering. During the seven-year-long Saturnian winter, the polar atmosphere became clear of aerosols produced by photochemical reactions — reactions involving sunlight and the atmosphere. Since the planet experienced equinox in August 2009, the polar atmosphere has been basking in continuous sunshine, and aerosols are being produced inside of the hexagon, around the north pole, making the polar atmosphere appear hazy today.

Other effects, including changes in atmospheric circulation, could also be playing a role. Scientists think seasonally shifting patterns of solar heating probably influence the winds in the polar regions.

Both images were taken by the Cassini wide-angle camera.

Image Credit: NASA/JPL-Caltech/Space Science Institute/Hampton University

Light on the Nightside

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The shadow is getting shorter as Saturn nears the northern solstice. The moon is pretty easily seen at about 11:00.

NASA’s description:

NASA’s Cassini spacecraft looks down at the rings of Saturn from above the planet’s nightside. The darkened globe of Saturn is seen here at lower right, along with the shadow it casts across the rings.

The image shows that even on the planet’s night side, the rings remain in sunlight, apart from the portion that lies within Saturn’s shadow. The rings also reflect sunlight back onto the night side of the planet, making it appear brighter than it would otherwise appear.

Saturn’s small moon Prometheus (53 miles or 86 kilometers across) is faintly visible as a speck near upper left. The shadow of Saturn was once long enough to stretch to the orbit of Prometheus. But as northern summer solstice approaches, Saturn’s shadow no longer reaches that far (see PIA20498). So Prometheus will not move into the darkness of the planet’s shadow until the march of the seasons again causes the shadow to lengthen.

This view looks toward the sunlit side of the rings from about 41 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Aug. 14, 2016.

The view was obtained at a distance of approximately 870,000 miles (1.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 87 degrees. Image scale is 53 miles (86 kilometers) per pixel. Prometheus has been brightened by a factor of two to enhance its visibility.

Nearing the Summer Solstice

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The summer solstice on Saturn that is.  Superb!

The original caption:

Since NASA’s Cassini spacecraft arrived at Saturn in mid-2004, the planet’s appearance has changed greatly. The shifting angle of sunlight as the seasons march forward has illuminated the giant hexagon-shaped jet stream around the north polar region, and the subtle bluish hues seen earlier in the mission have continued to fade. Earlier views obtained in 2004 and 2009 (seePIA06077 and PIA11667) demonstrate how drastically the illumination has changed.

This view shows Saturn’s northern hemisphere in 2016, as that part of the planet nears its northern hemisphere summer solstice in May 2017. Saturn’s year is nearly 30 Earth years long, and during its long time there, Cassini has observed winter and spring in the north, and summer and fall in the south. The spacecraft will complete its mission just after northern summer solstice, having observed long-term changes in the planet’s winds, temperatures, clouds and chemistry.

Cassini scanned across the planet and its rings on April 25, 2016, capturing three sets of red, green and blue images to cover this entire scene showing the planet and the main rings. The images were obtained using Cassini’s wide-angle camera at a distance of approximately 1.9 million miles (3 million kilometers) from Saturn and at an elevation of about 30 degrees above the ring plane. The view looks toward the sunlit side of the rings from a sun-Saturn-spacecraft angle, or phase angle, of 55 degrees. Image scale on Saturn is about 111 miles (178 kilometers) per pixel.

The exposures used to make this mosaic were obtained just prior to the beginning of a 44-hour movie sequence (see PIA21047).

Image: NASA/JPL-Caltech/Space Science Institute