Cassini finds straw and propellers in stunning new ring imagery
NASA has released some of the highest resolution images ever obtained of Saturn's A & B rings. The images, which were taken as Cassini made a close-proximity dive past Saturn's rings, display the icy matter of the gas giant's adornment manipulated by the gravity its moons.
Having weathered the space environment since its launch in 1997, NASA's veteran Cassini probe is finally nearing the end of its phenomenally successful mission. However, whilst the explorer may be limited in time, its scientific and inspirational potential is far from spent. Prior to initiating its "Grand Finale" on April 26, Cassini will perform a further 10 dives, seeing the probe pass only 6,800 miles (11,000 km) from the center of Saturn's F ring.
The only time the probe has passed closer than this was upon its arrival at Saturn in 2004. However, the quality of the images captured during this initial encounter were limited by the spacecraft's speed, which forced mission operators to limit the exposure time of Cassini's narrow angle camera. The resultant images were relatively dim and "noisy."
Cassini's remaining ring grazing orbits, and those which will be undertaken as part of the Grand Finale, will allow the probe to collect some of the most breathtakingly detailed views of Saturn, its rings, and its moons to date.
NASA's latest release stands as testament to this, and highlights the gravitational influence of the gas giant's moons over the icy particles that comprise the rings. The close proximity of Cassini during the pass allows a number of the new images to resolve features as small as 0.3 miles (0.5 km). The images were captured by Cassini on Dec. 18, 2016.
One of Cassini's images, which features Saturn's A ring, displays a number of large-scale accumulations of particles known as density waves, which were formed as a result of the gravitational influence of the Saturnian moons Janus and Epimetheus. Within these relatively dense, wide features, which are located on the left of the hero image, large groups of icy particles are observed to clump together to form perturbations that are informally referred to as "straw."
More subtle wakes can be seen in the ring matter to the right. These disturbances, which appear as perfect ocean waves in the icy material, were created by the passage of one of Saturn's smaller moons known as Pan that boasts a diameter of only 17 miles (28 km).
In another image (above), which was captured a mere 33,000 miles (54,000 km) from Saturn's A ring by the Cassini spacecraft's Wide Angle Camera, a large number of "propeller" features can be discerned disturbing the disk material. The image, which has a resolution of 330 meters (1,082 ft) per pixel, features dozens of bright propeller-shaped disturbances, which are created by the weak gravitational influence of tiny moonlets embedded within the ring.
Once more on the left of the image is another set of density waves, this time created by the Saturnian moon Prometheus. In an unprocessed image, these propellers are all but lost in the bright blemishes created by incredibly fast moving cosmic rays and charged particles. However, in the image above, the location of the propellers are highlighted in circles.