Density wave in Saturn’s A ring (at left). 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. This 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. Image via NASA
On January 30, 2017, NASA released some of the closest-ever images of the outer parts of planet Saturn’s main rings. The images were taken by the Cassini spacecraft on December 18, 2016. The spacecraft is now in its “ring-grazing” orbits phase – 20 orbits that dive past the outer edge of the main ring system. The new images resolve details as small as 0.3 mile (550 meters), which is on the scale of Earth’s tallest buildings.
According to a NASA statement:
Some of the structures seen in recent Cassini images have not been visible at this level of detail since the spacecraft arrived at Saturn in mid-2004. At that time, fine details like straw and propellers – which are caused by clumping ring particles and small, embedded moonlets, respectively – had never been seen before.
Propeller belts in Saturn’s A ring. This view shows a section of the A ring known to researchers for hosting belts of propellers – bright, narrow, propeller-shaped disturbances in the ring produced by the gravity of unseen embedded moonlets. Several small propellers are visible in this view. In this image, the level of detail is twice as high as this part of the rings has ever been seen before. The prominent feature at left is a density wave created by the ring’s gravitational interaction with the moon Prometheus. Density waves are spiral-shaped disturbances (similar to the spiral arms of galaxies) that propagate through the rings at certain distances from the planet. This view was obtained at a distance of approximately 33,000 miles (54,000 kilometers) from the rings and looks toward the unilluminated side of the rings. Image scale is about a quarter-mile (330 meters) per pixel. Image via NASA.
This image shows a region in Saturn’s outer B ring. NASA’s Cassini spacecraft viewed this area at a level of detail twice as high as it had ever been observed before. The view was obtained at a distance of approximately 32,000 miles (51,000 kilometers) from the rings, and looks toward the unilluminated side of the rings. Image scale is about a quarter-mile (360 meters) per pixel. Image via NASA
Straw in the B ring’s edge. The view here is of the outer edge of the B ring, at left, which is perturbed by the most powerful gravitational resonance in the rings: the “2:1 resonance” with the icy moon Mimas. This means that, for every single orbit of Mimas, the ring particles at this specific distance from Saturn orbit the planet twice. This results in a regular tugging force that perturbs the particles in this location. A lot of structure is visible in the zone near the edge on the left. This is likely due to some combination of the gravity of embedded objects too small to see, or temporary clumping triggered by the action of the resonance itself. Scientists informally refer to this type of structure as “straw.” The view was obtained at a distance of approximately 32,000 miles (52,000 kilometers) from the rings and looks toward the unilluminated side of the rings. Image scale is about a quarter-mile (360 meters) per pixel. Image via NASA
Cassini’s ring-grazing orbits began last November and will continue until late April 2017, when Cassini begins its grand finale. During the 22 finale orbits, Cassini will repeatedly plunge through the gap between the rings and Saturn. The first finale plunge is scheduled for April 26.
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Bottom line: Incredible new views from NASA’s Cassini spacecraft show Saturn’s rings in unprecedented detail.
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