Spaceflight Insider

Cassini reveals Saturn’s rings in unprecedented detail

Density wave in Saturn's A ring (enhanced 40%)

This image (enhanced) from Cassini features a density wave in Saturn’s A ring (at left) that lies around 134,500 km from Saturn. 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. Image & Caption Credit: NASA / JPL-Caltech / Space Science Institute

Fresh images returned from NASA’s Cassini spacecraft are revealing fascinating new details of Saturn’s famous rings. Cassini is conducting a series of 22 ring-grazing orbits to study Saturn’s innermost rings and moons as it refines its trajectory before concluding its 20-year mission in September 2017. The recently released images were captured during a ring-grazing orbit on December 18, 2016.

The images reveal fine-scale details that are not visible in previous images of the rings, resolving details as small as 0.3 miles (550 meters), which is comparable in size to the tallest buildings on Earth. The high-resolution images are giving scientists their best look yet into features such as “straws” and “propellers” which until now have mostly been studied in images captured from more distant orbits.

'Straw' in the B Ring's Edge

This image shows an oblique view of Saturn’s outer B ring as Cassini crossed the planet’s ring plane. The outer edge of the B ring (at left) is perturbed by the most powerful gravitational resonance in the rings: the “2:1 resonance” with the icy moon Mimas. Therefore, 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. N.B: The view contains many small, bright blemishes due to cosmic rays and charged particle radiation near the planet. Image & Caption Credit: NASA / JPL-Caltech / Space Science Institute

Cassini did pass closer to Saturn and its rings during its orbital insertion in 2004, but due to the spacecraft’s speed and orientation, the images of the rings that it did capture are primarily backlit, underexposed, and noisy. By contrast, the images being acquired now are twice as detailed and are both backlit and sunlit. These conditions have allowed for greater flexibility in the type and volume of images being captured.

“As the person who planned those initial orbit-insertion ring images – which remained our most detailed views of the rings for the past 13 years – I am taken aback by how vastly improved are the details in this new collection,” said Cassini Imaging Team Lead Carolyn Porco, of Space Science Institute, Boulder, Colorado. “How fitting it is that we should go out with the best views of Saturn’s rings we’ve ever collected.”

Saturn's B Ring, Finer Than Ever

This image shows a region in Saturn’s outer B ring. Cassini is conducting a series of ring-grazing orbits and is capturing images at twice the detail of previous images. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Dec. 18, 2016. 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. N.B: The view contains many small, bright blemishes due to cosmic rays and charged particle radiation near the planet. Image & Caption Credit: NASA / JPL-Caltech / Space Science Institute

Among the details that scientists hope to tease out of the new images are how nearby moons and moonlets interact with the rings which lead to the formation of physical variations in the ring structure. These interactions induce features that include straws and propellers as well as density waves and wakes. In the case of the density waves, they represent accumulated particles that when clumped together result in the straw-like formations.

“These close views represent the opening of an entirely new window onto Saturn’s rings, and over the next few months we look forward to even more exciting data as we train our cameras on other parts of the rings closer to the planet,” said Matthew Tiscareno, a Cassini scientist who studies Saturn’s rings at the SETI Institute in Mountain View, California and helped to plan out the recent imaging campaign.

The Propeller Belts in Saturn's A Ring

This image (enhanced) 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. These are on the order of 10 times smaller than the large, bright propellers whose orbits scientists have routinely tracked (and which are given nicknames for famous aviators). N.B: The view contains many small, bright blemishes due to cosmic rays and charged particle radiation near the planet. Image & Caption Credit: NASA / JPL-Caltech / Space Science Institute

Cassini will be conducting near weekly ring-grazing orbits through April 26, after which it will transition into its finale phase. During the finale orbit, it will capture the highest-resolution images of the planet and its rings yet. Cassini will plunge through the gap between Saturn and its rings a total of 22 times before diving into the planet on September 15, 2017.



Paul is currently a graduate student in Space and Planetary Sciences at the University of Akransas in Fayetteville. He grew up in the Kansas City area and developed an interest in space at a young age at the start of the twin Mars Exploration Rover missions in 2003. He began his studies in aerospace engineering before switching over to geology at Wichita State University where he earned a Bachelor of Science in 2013. After working as an environmental geologist for a civil engineering firm, he began his graduate studies in 2016 and is actively working towards a PhD that will focus on the surficial processes of Mars. He also participated in a 2-week simluation at The Mars Society's Mars Desert Research Station in 2014 and remains involved in analogue mission studies today. Paul has been interested in science outreach and communication over the years which in the past included maintaining a personal blog on space exploration from high school through his undergraduate career and in recent years he has given talks at schools and other organizations over the topics of geology and space. He is excited to bring his experience as a geologist and scientist to the Spaceflight Insider team writing primarily on space science topics.

Reader Comments

The images have lots of short lines that are not parallel to ring structures. What are they?

The JPL article, The Propeller Belts in Saturn’s A Ring, states: “The view contains many small, bright blemishes due to cosmic rays and charged particle radiation near the planet.”

I’ve updated the captions of the images, accordingly.

– Ivan Simic, SFI copy-editor.

Not a lot you can say except AMAZING! What an achievement.

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