Backlit Saturn Infrared Images
October 18, 2013

NASA Releases New ‘Backlit’ Infrared Saturn Images

Brett Smith for - Your Universe Online

Without the sun to illuminate it, the ‘back’ of Saturn may not seem like much to look at. However, new images taken in the infrared spectrum that were released by NASA have revealed new details about the planet and its rings that are difficult to see from a sunlit view.

"Looking at the Saturn system when it is backlit by the sun gives scientists a kind of inside-out view of Saturn that we don't normally see," said Matt Hedman, a NASA scientist based at the University of Idaho. "The parts of Saturn's rings that are bright when you look at them from backyard telescopes on Earth are dark, and other parts that are typically dark glow brightly in this view."

According to NASA, getting a good view of Saturn’s faint outer F, E and G rings, or the indistinct inner ring, known as the D ring, can be difficult when sunlight is shining directly on them. This is because these rings are almost transparent and made up of small particles that do not readily reflect visible light.

In the newly released images, the faint rings are back-lit causing them to resemble “fog in the headlights of an oncoming vehicle,” according to a NASA statement.

The new images also clearly show the planet’s C ring. The ring appears brightly due to its makeup of mostly dirty, translucent water ice. Easily seen from Earth, the C ring was known as the "crepe ring" during the 18th and 19th centuries because it supposedly resembled crepe paper.

The B ring, also easily seen from Earth, appears dark in the new images because its thickness blocks almost all of the sunlight shining from behind it.

Infrared images were specifically calibrated to depict thermal radiation. While a visible-spectrum image taken from the same vantage point would only show a dimly-lit planet, Saturn glows brightly in the infrared spectrum because of heat being released from Saturn's interior.

NASA also released a second, tweaked version of the images that "stretched" or exaggerated the contrast of the data, teasing out subtleties not initially visible – most notably the wispy E ring.

"We're busy working on analyzing the infrared data from this special view of the Saturn system," said Phil Nicholson, a visual and infrared mapping spectrometer team member from Cornell University in upstate New York. "The infrared data should tell us more about the sizes of the particles which make up the D, E, F and G rings, and how these sizes vary with location in the rings, as well as providing clues as to their chemical composition."

The images were captured by NASA’s Cassini probe, which has been exploring the Saturn system for over nine years. Its instruments include visible-light cameras, ultraviolet and infrared spectrometers, as well as magnetic field and charged particle sensors.

"Cassini's long-term residency at the ringed planet means we've been able to observe change over nearly half a Saturn-year (one Saturn-year is equal to almost 30 Earth-years) with a host of different tools," said Linda Spilker, Cassini project scientist, based at NASA's Jet Propulsion Laboratory in California.

"Earth looks different from season to season and Saturn does, too. We can't wait to see how those seasonal changes affect the dance of icy particles as we continue to observe in Saturn's rings with all of Cassini's different 'eyes.'"