Earhart Propeller in the A-Ring

Cassini scientists continue their quest to understand the origin and evolution of the newly discovered features observed in Saturn's A-ring which have become known as "propellers." In this image, the propeller which scientists have dubbed "Earhart" (at the lower left of the image) has been re-acquired.

Scientists hope to understand how the bodies which generate the features -- themselves too small to be seen, yet significantly larger than a typical ring particle -- move around the ring over time. It is hoped that these features may provide insights about how forming planets move around their solar systems. For more on Earhart, see PIA12790.

This view looks toward the sunlit side of the rings from about 48 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 11, 2013.

The view was acquired at a distance of approximately 250,000 miles (400,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 99 degrees. Image scale is 1 mile (2 kilometers) per pixel.

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

Bleriot Propeller

The Cassini spacecraft has been monitoring propeller features since their discovery. Here the propeller dubbed Bleriot is seen in a recent image. The bright dash-like features are regions where a small moonlet has caused ring particles to cluster together more densely than normal. Beyond the bright areas are fainter, longer dark linear features. These are believed to be extended regions where the same moonlet has caused particles to evacuate, leaving an under-dense (thus darker) area.

To learn more about propellers, see PIA07792 and PIA07791. For more of Bleriot, see PIA12789.

This view looks toward the sunlit side of the rings from about 33 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 3, 2013.

The view was acquired at a distance of approximately 301,000 miles (484,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 119 degrees. Image scale is 2 miles (3 kilometers) per pixel.

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

The Sikorsky Propeller

These three Cassini images show a propeller-shaped structure created by an unseen moon in Saturn's A ring. Propellers and other details of Saturn's rings are greeting scientists for the first time in two years, as Cassini's orbit took the spacecraft out of Saturn's equatorial plane in the spring of 2012, making face-on views of the rings possible again.

For years scientists have tracked this propeller, marked with red arrows here. These images are part of a growing catalog of "propeller" moons that, despite being too small to be seen, enhance their visibility by creating larger disturbances in the surrounding fabric of Saturn's rings.

This propeller, nicknamed "Sikorsky" after Russian-American aviator Igor Sikorsky, is about 30 miles (50 kilometers) long. See PIA12790, PIA12792 and PIA11672 to learn more about propellers.

In this most recent image, scientists knew they were observing a propeller they had seen before because Sikorsky was found close to the location predicted by a simple model of its motion. But its actual location did trail the predicted location by 6 degrees of longitude (8,000 miles, or 13,000 kilometers), underlining some of the changes known to occur in the orbits of propeller moons. These changes may occur because of interactions between the rings and the propeller moons. Scientists are eager to understand these interactions in Saturn's rings, as they may hold a key to similar systems such as solar systems forming from disks of matter.

In this most recent image, Sikorsky was found to trail its predicted position by 6 degrees of longitude (8,000 miles, or 13,000 kilometers), a discrepancy that underlines the changes that are known to occur in the orbits of propeller moons, possibly due to interactions between the rings and the embedded moons. Scientists are eager to understand these interactions in Saturn's rings, as they may hold a key to similar systems such as solar systems forming from disks of matter.

The Encke Gap of Saturn's A ring is on the right in the images. The A ring is the outermost of Saturn's main rings. This view looks toward the northern, sunlit side of the rings from about 12 degrees above the ringplane.

These images have not been cleaned of the effects of cosmic rays that struck the camera's sensor during exposure. These cosmic ray hits appear as small white specks or streaks on the images. These specks are not features in Saturn's rings. The image has been enhanced to aid visibility of compact objects like the propeller. The enhancement makes the edge of the Encke Gap appear dashed.

The images were taken in visible light with the Cassini spacecraft narrow-angle camera on June 5, 2012. The view was obtained at a distance of approximately 236,000 miles (380,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 24 degrees. Image scale is 1 mile (2 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/SSI/Cornell

Note: For more information, see Saturn's Rings are Back.

A-Ring Propeller

A propeller-shaped structure, created by an unseen moon, can be seen in Saturn's A ring.

The propeller, which looks like a small, dark line interrupting the bright surrounding ring material, is in the upper left of this image near the edge of the Keeler Gap. See PIA12790 to learn more about propellers.

This view looks toward the southern, unilluminated side of the rings from about 16 degrees below the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 3, 2010. The view was acquired at a distance of approximately 279,000 kilometers (173,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 16 degrees. Image scale is 1 kilometer (3,300 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Earhart Propeller in the A Ring

A propeller-shaped structure created by an unseen moon is brightly illuminated on the sunlit side of Saturn's rings in this image obtained by NASA's Cassini spacecraft.

The moon, which is too small to be seen, is at the center of the propeller structure visible in the upper left of the image, near the Encke Gap of the A ring. The A ring is the outermost of Saturn's main rings.

The moon is likely about a kilometer (half a mile) across. Disturbed ring material to the upper left and lower right of the moon reflects sunlight brightly and appears like a white airplane propeller. Several density waves are also visible in the ring. A spiral density wave is a spiral-shaped accumulation of particles that tightly winds many times around the planet. It is the result of gravitational tugs by individual moons whose orbits are in resonance with the particles' orbits at a specific distance from Saturn.

A propeller's appearance changes with viewing geometry, and this image shows the way a propeller looks when viewed from the sunlit side of the rings. Contrasts can reverse when the structure is observed on the dark side of the rings: for example, the bright structure of this propeller corresponds to the dark portion at the center of the propeller seen in PIA12791 which was imaged from the unilluminated side of the rings.

This image is part of a growing catalog of "propeller" moons that, despite being too small to be seen, enhance their visibility by creating larger disturbances in the surrounding fabric of Saturn's rings. Cassini scientists now have tracked several of these individual propeller moons embedded in Saturn's disk over several years.

These images are important because they represent the first time scientists have been able to track the orbits of objects in space that are embedded in a disk of material. Continued monitoring of these objects may lead to direct observations of the interaction between a disk of material and embedded moons. Such interactions help scientists understand fundamental principles of how solar systems formed from disks of matter. Indeed, Cassini scientists have seen changes in the orbits of these moons, although they don't yet know exactly what causes these changes.

Imaging scientists nicknamed the propeller shown here "Earhart" after the early American aviatrix Amelia Earhart. The propeller structure is 5 kilometers (3 miles) in the radial dimension (the dimension moving outward from Saturn which is far out of frame to the lower right of this image). It is 60 kilometers (35 miles) in the azimuthal (longitudinal) dimension.

This same propeller can be seen casting a shadow around the time of the planet's equinox in PIA11672. See PIA07791 and PIA07792 to learn more about propeller shapes and to see smaller propellers.

Scale in the original image was 2 kilometers (1 mile) per pixel. The image has been rotated and contrast-enhanced to aid visibility.

This view looks toward the southern, sunlit side of the rings from about 81 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 11, 2008. The view was obtained at a distance of approximately 364,000 kilometers (226,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 82 degrees.

Photo credit: NASA/JPL/Space Science Institute

Note: For other images in this series, see PIA12789: Tracking a Propeller, PIA12791: Propeller from Unlit Side (mentioned above), and PIA12792: Propeller Churns the A Ring, which features a short movie of the Propeller "Bleriot," named after the French aviator Louis Blériot.