Saturn's Northern Hemisphere Storm, 6 March 2011

Like a swirl from a paintbrush being dipped in water, this image from the Cassini orbiter shows the progress of a massive storm on Saturn. The storm first developed in December 2010, and this mosaic captures how it appeared on 6 March 2011.

The head of the storm is towards the left of the image, where the most turbulent activity is shown in white, but towards the center you can also see the trace of a spinning vortex in the wake of the storm.

This image, centered at about 0º longitude and 35º N latitude, has had its colors enhanced to help reveal the complex processes in Saturn’s weather. The white corresponds to the highest cloud tops, but to the human eye the storm would appear more as a bright area against a yellow background.

Cassini also monitored the temperature of the storm, showing a rapid spike as energy was released into the atmosphere.

The storm grew so large that on Earth it would easily cover all of Europe. Atmospheric disturbances of this size can be expected once during each of Saturn’s orbits around the Sun, which takes 30 Earth years. However, this particular event surprised scientists by occurring during the northern hemisphere spring, rather than the more typically stormy Saturnian summer.

Image credit: NASA/JPL-Caltech/SSI/Hampton University

Saturn

The huge storm churning through the atmosphere in Saturn's northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA's Cassini spacecraft. This storm is the largest, most intense storm observed on Saturn and is still active today. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Northern Storm in Full Force

This mosaic of images from NASA's Cassini spacecraft shows the trail of a great northern storm on Saturn raging in full force. The contrast in the images has been enhanced to make the turbulent parts of the storm (in white) stand out without losing the details of the surrounding regions.

The head of the storm is the set of bright clouds near the left of the image. A clockwise-spinning vortex spawned by the storm shortly after it erupted in early December 2010 can be seen in the middle. The head of the storm moved very swiftly westward, while the vortex drifted more slowly westward.

Cassini's imaging camera obtained the images that went into this mosaic on March 6, 2011. The image is centered at about 0 degrees longitude and 35 degrees latitude.

In this image, scientists assigned red, green and blue channels to those visible-light colors. However, this view is not what a human eye would see at Saturn -- in enhancing the contrast, the natural color balance was not preserved. To human eyes, storm would have appeared more like a bright feature against a yellow background with less color variation, as is seen in PIA16724. In this color scheme, the brightness generally corresponds to the altitude of the cloud features. Bright white indicates highest cloud tops in the troposphere, and dark places indicate holes in the cloud layer. The subtle colors that become apparent in this enhanced-contrast view are probably produced by variation in the composition of clouds. However, the coloring agents responsible for producing these subtle hues remain unidentified.

Image credit: NASA/JPL-Caltech/SSI/Hampton University

First Chapter of the Northern Storm

This mosaic of false-color images from NASA's Cassini spacecraft shows what a giant storm in Saturn's northern hemisphere looked like about a month after it began. The bright head of the storm is on the left. The storm also spawned a clockwise-spinning vortex, seen as the light blue circular feature framed with a curl of bright clouds a little to the right of the storm head.

Cassini's imaging camera obtained the images that went into this mosaic on January 11, 2011. The storm erupted in early December 2010 and the head of the storm began moving rapidly westward. The vortex, spun off from the head of the storm in early December shortly after the storm began, drifted much more slowly. In August 2011, the head ran into the vortex, like a version of the mythical serpent that bites its own tail. By late August, the convective phase of the storm was over.

The colors indicate the altitudes of the clouds -- red is the lowest, green is an intermediate level and blue is the highest. White indicates thick clouds at a high altitude. Scientists assigned red to a wavelength of radiation that penetrates the atmosphere deep down to the top of the tropospheric cloud deck (750 nanometers). The troposphere is the part of the atmosphere where weather occurs. They assigned green to the 728-nanometer wavelength. Blue is a wavelength band that penetrates only to the top of tropospheric haze (890 nanometer).

Image credit: NASA/JPL-Caltech/SSI/Hampton University

Six Views of the Northern Hemisphere Vortex

A vortex that was part of a giant storm on Saturn slowly dissipates over time in this set of false color images from NASA's Cassini spacecraft. This clockwise vortex spun off the bright head of the storm shortly after the thunder-and-lightning storm erupted in early December 2010.

The top left image shows the vortex's most turbulent activity captured by Cassini's imaging cameras on January 11, 2011. It was centered around 54 degrees west longitude and 35 degrees north latitude. At the time, it was the largest vortex ever observed in Saturn's troposphere, which is the layer of the atmosphere where weather occurs. It measured up to 7,500 miles (12,000 kilometers) across. This is comparable in size to the giant storm on Jupiter known as Oval BA, though Oval BA and Jupiter's more famous storm -- the Great Red Spot -- are not thunder-and-lightning storms. Jupiter's vortices are known for their stability and longevity. Precursors to Oval BA formed in the 1930s, and evolved into what finally became Oval BA in the late 1990s. The Great Red Spot has been in existence at least since 1879, and possibly since 1664. Jupiter and Saturn are similar in many respects. However, why Jupiter's vortices are long-lived and why Saturnian ones are so short remain a mystery.

The image in the top middle was taken on March 17, 2011, when the center of the vortex had drifted west to around 6 degrees west longitude. The image on the top right was taken on April 25, 2011, when the vortex had moved to about 315 degrees west longitude.

The bright head of the storm was moving more quickly westward than the vortex and collided with the vortex by mid-June. The image at bottom left was obtained on July 12, 2011, after the head and vortex collided. The vortex here is less turbulent and is centered around 247 degrees west longitude. The bottom middle image was taken on August 24, 2011, about four days before the storm's thunder and lightning ceased completely. The vortex is swirling at about 218 degrees west longitude. The bottom right image was taken on October 6, 2011, when the vortex had nearly faded away. What is left of the vortex is centered around 248 degrees west longitude.The colors in these images denote the altitudes of the clouds – with red being the lowest, green being an intermediate level and blue being the highest. White indicates thick clouds at a high altitude. Scientists assigned the red color channel to a wavelength of radiation that penetrates the atmosphere deep down to the top of the tropospheric cloud deck (750 nanometers). They assigned blue to a wavelength that penetrates only to the top of tropospheric haze (890 nanometers). Green represents an intermediate wavelength above the troposphere (728 nanometers).

Image credit: NASA/JPL-Caltech/SSI/Hampton University

Note: For other images in this series, see PIA16722: Which Way the Wind Blows, PIA16723: Swirling Vortex, and PIA16724: Great Disturbances. Also, NASA's Cassini Watches Storm Choke on Its Own Tail.

Lightning Strike on Saturn

These false-color mosaics from NASA's Cassini spacecraft capture lightning striking within the huge storm that encircled Saturn's northern hemisphere for much of 2011.

The larger mosaic on the left of the panel shows the lightning flash, which appears as a blue dot. The smaller mosaic on the right is composed of images taken 30 minutes later, and the lightning is not flashing at that time.

See PIA14904 for a mosaic showing a wider view wrapping around the planet also in which some blue lightning is visible in the clouds.

The white arrow in the annotated version of this panel points to the location where the lightning occurred in the clouds. The optical energy of this and other flashes on Saturn is comparable to the strongest of the flashes on Earth. The flash is approximately 120 miles (200 kilometers) in diameter when it exits the tops of the clouds. From this, scientists deduce that the lightning bolts originate in the clouds deeper down in Saturn's atmosphere where water droplets freeze. This is analogous to where lightning is created on Earth.

This lightning flash appears only in the filter sensitive to blue visible light, and the images were enhanced to increase the visibility of the lightning.

Images taken using red, green and blue spectral filters are usually combined to create a natural color view. Because visible red-light images were not available, images taken using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers were used in place of red. Also, the blue filter image was enhanced to increase the visibility of the lightning. The result is a type of false color image.

The images were obtained with the Cassini spacecraft narrow-angle camera on March 6, 2011, at a distance of approximately 2 million miles (3.3 million kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 83 degrees. These mosaics are simple cylindrical map projections, defined such that a square pixel subtends equal intervals of latitude and longitude. At higher latitudes, the pixel size in the north-south direction remains the same, but the pixel size (in terms of physical extent on the planet) in the east-west direction becomes smaller. The pixel size is set at the equator, where the distances along the sides are equal. This map has a pixel size of 12 miles (20 kilometers) at the equator.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Note: For more information, see Cassini Spots Daytime Lightning on Saturn.

Saturn and Tethys

Even in a peaceful looking scene such as this one of Saturn and its moon Tethys, the Cassini spacecraft reveals clues about how Saturn is ever-changing.

Saturn's northern hemisphere still shows the scars of the huge storm that raged through much of 2011 (see PIA14905). And, day by day, the shadows cast by the rings on the planet's southern hemisphere are growing wider as the seasons progress toward northern summer. See PIA11667 and PIA09793 to learn about the changing seasons and the shadows cast by the rings.

Tethys (660 miles, or 1,062 kilometers across) appears above the rings to the left of the center of the image.

The image was taken with the Cassini spacecraft wide-angle camera on January 10, 2012 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.4 million miles (2.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 39 degrees. Image scale on Saturn is 84 miles (136 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Quieted Storm

The Cassini spacecraft examines Saturn and the planet's northern hemisphere, which was ravaged by a huge storm for much of 2011.

See PIA14905 and PIA14903 to learn more about the storm.

Four of Saturn's moons join the planet here. Two of these -- Janus and Epimetheus -- are almost lost in this view due to their small size. Mimas (246 miles, or 396 kilometers across) appears as a bright dot below the rings just to the right of the center of the image. Enceladus (313 miles, or 504 kilometers across) is visible below the rings on the far right of the image. Janus (111 miles, or 179 kilometers across) can just barely be discerned as a tiny speck past Enceladus on the right edge of the image. Epimetheus (70 miles, or 113 kilometers across) is likewise tiny, and can be detected on the extreme left of the image above the rings.

This view looks toward the southern, unilluminated side of the rings from just below the ringplane.

Relative to Saturn and other objects in this view, Janus and Epimetheus have been brightened by a factor 1.5 and 1.4 respectively.

The image was taken with the Cassini spacecraft wide-angle camera on February 11, 2012 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 1.7 million miles (2.8 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 60 degrees. Image scale on Saturn is 105 miles (170 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Close-Up of Saturn's Northern Hemisphere Storm

The biggest, most long-lasting Saturnian storm seen by either NASA's Cassini or Voyager spacecraft roils the atmosphere of the gas giant in this nearly true-color mosaic of Cassini images.

See PIA14903 and PIA14905 to learn more about the size and development of this storm. This mosaic shows the storm's effects encircling the planet and was created using 126 images taken in succession as different parts of Saturn's northern hemisphere rotated into Cassini's view.

Images taken using red, green and blue spectral filters are usually combined to create a natural color view. Because visible red light images were not available, images taken using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers were used in place of red. So the color is close to natural color, but is not exact.

A second version of this mosaic is also included here (Figure 1). This view uses these same nearly true color filters, but the images were contrast enhanced. The result is a view that increases the visibility of features.

The head of the storm is near the center of the mosaic, and a train of vortices appears as blue spots just to the south of the head. These blue spots are parts of the storm's tail that have already encircled the planet and are approaching from the west (left in the image). The blue color indicates they have some high, semi-transparent haze but no thick clouds underneath because there are no white- or yellow-colored clouds shown here.

This mosaic covers an area ranging from about 18 degrees north latitude to 47 degrees north latitude. The views stretch the whole longitude range, passing through 360/0 degrees west longitude near the far right of the mosaics.

The images were obtained with the Cassini spacecraft narrow-angle camera on March 6, 2011, over about 11 hours (about a Saturnian day) at a distance of approximately 2 million miles (3.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 83 degrees. These mosaics are simple cylindrical map projections, defined such that a square pixel subtends equal intervals of latitude and longitude. At higher latitudes, the pixel size in the north-south direction remains the same, but the pixel size (in terms of physical extent on the planet) in the east-west direction becomes smaller. The pixel size is set at the equator, where the distances along the sides are equal. This map has a pixel size of 28 miles (45 kilometers) at the equator.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Chronicling Saturn's Northern Storm

This series of images from NASA's Cassini spacecraft shows the development of the largest storm seen on the planet since 1990. These true-color and composite near-true-color views chronicle the storm from its start in late 2010 through mid-2011, showing how the distinct head of the storm quickly grew large but eventually became engulfed by the storm's tail.

The earliest image of the storm, taken December 5, 2010, is in the top left of the panel. The storm appears only as a small, white cloud on the terminator between the day side and night side of the planet. See PIA14905 for a magnified view of the storm at this time.

The next view, in the top middle of the panel and taken January 2, 2011, shows that the head quickly grew much larger and a tail began to trail a great distance eastward. Some of the clouds moved south and got caught up in a current that flows to the east (to the right) relative to the storm head. In the top right of the panel, this tail, which appears as slightly blue clouds south and now west (left) of the storm head, can be seen encountering the storm in the February 25 image.

The April 22 image, in the bottom left of the panel, is one of Cassini's last views of the storm when it still had a recognizable head. In this view, the tail is south of the head and is well established by this time.

The May 18 view, in the bottom middle, shows only the storm's tail. The head still existed at this time, but it is beyond the horizon and out of the field of view here.

Between the time of the May 18 image and the next image shown here (from August 12), the head of the storm was engulfed by the part of the storm's tail that spread eastward at the same latitude as the head. The August 12 image, in the bottom right, shows that the head has lost its distinct identity and is now just part of the jumble of the storm.

Also visible in these images are several of Saturn's moons and the shadows cast onto the planet by moons. For example, the planet's second largest moon, Rhea, can be seen in the February 25 view.

The February 25 and August 12 views are true color. Images taken using red, green and blue spectral filters were combined to create these natural-color views.

The December 5, January 2, April 22 and May 18 views are nearly true color. Because a visible red light image was not available, an image taken using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers was used in place of red. So the color is close to natural color, but it is not exact.

These views were acquired at distances ranges from approximately 1.4 million miles (2.2 million kilometers) to 1.9 million miles (3.0 million kilometers) from Saturn and at Sun-Saturn-spacecraft, or phase, angles of 41 degrees to 99 degrees. All the views are set to a scale of 101 miles (162 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Note: For other pictures in this series, see PIA14901: Eleven Hours Later and PIA14902: Birth of a Behemoth Storm.

Saturn's Northern Hemisphere Storm

Saturn's northern storm marches through the planet's atmosphere in the top right of this false-color mosaic from NASA's Cassini spacecraft.

See PIA14905 to learn more about this storm and watch its development over several months. Earlier in the Cassini mission, the spacecraft chronicled a smaller storm in the southern hemisphere, called the "Dragon Storm." See PIA06197 to learn more about that storm and to see a similar, false-color view.

Saturn's atmosphere and its rings are shown here in a false-color composite made from 12 images taken in near-infrared light through filters that are sensitive to varying degrees of methane absorption. Red and orange colors in this view indicate clouds that are deep in the atmosphere. Yellow and green colors, most noticeable along the top edge of the view, indicate intermediate clouds. White and blue indicate high clouds and haze. The rings appear as a thin horizontal line of bright blue because they are outside of the atmosphere and not affected by methane absorption.

This view looks toward the northern, sunlit side of the rings from just above the ring plane.

The images were taken with the Cassini spacecraft wide-angle camera using a combination of spectral filters sensitive to wavelengths of near-infrared light. The images filtered at 890 nanometers are projected as blue. The images filtered at 728 nanometers are projected as green, and images filtered at 752 nanometers are projected as red.

The images were taken on January 11, 2011, over about 50 minutes, at a distance of approximately 569,000 miles (915,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 45 degrees. The images were re-projected to the same viewing geometry, so that scale in this final mosaic is 63 miles (102 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Note: For similar images, see PIA12828: Storm Head in False Color and PIA12829: Storm Tail in False Color.