spaceSpace and Physics

Daphnis Making Waves In Saturn’s Rings


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockJan 18 2017, 16:42 UTC

Daphnis moving through the Keeler Gap. NASA/JPL-Caltech/Space Science Institute

Spacecraft Cassini is currently performing a series of incredible ring-grazing orbits that will take it closer and closer to Saturn. Along the way, it has been continuously snapping images of the ringed planet.

Among the images available to the public, there’s a spectacular view of Daphnis – one of two tiny moons that orbit within Saturn’s main ring. The raw uncalibrated image was taken on January 16 and shows Daphnis inducing waves in the A ring.


The waves are three-dimensional, lifting material from the plane of the ring as Daphnis moves through the Keeler Gap. Daphnis, which is only 8 kilometers (5 miles) in diameter, is inclined with respect to the rings, bopping up and down by about 17 kilometers (10.5 miles).

The waves are one of the many effects that Daphnis has on the rings. The natural satellite is a shepherd moon, which means its gravity actually helps the rings to be stable. Daphnis and the other shepherd moons pick up and deflect the rock and ice particles that make up the rings, and by means of orbital resonance, they keep them in check.

The typical system of bands and gaps is due to the moons herding the rings. It should be noted that shepherd moons are not exclusive to Saturn, with the other three gas giant planets having them and even possibly the minor planets Chariklo and Chiron.

Cassini is a collaborative mission by NASA, the European Space Agency, and the Italian Space Agency. It has been studying the Saturnine system since its arrival in 2004 and it is now getting ready for its final bow.


In December, it began a series of 20 ring-grazing orbits that are bringing the probe closer and closer to the active rings. In April, it will have a final look at Titan, Saturn’s largest moon, before moving back towards the planet.

The final few months will see Cassini get nearer and nearer to Saturn, in preparation to take a plunge into the ringed giant on September 15.

spaceSpace and Physics
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