Sunsets on Saturn's giant moon Titan could reveal information about the atmosphere of alien worlds, says NASA.

Astronomers use a variety of techniques to measure information coming from planets, via light from the sun, reflected off planetary atmospheres. Additional data could be collected from light passing through these alien atmospheres, but those measurements could be difficult to interpret.

One of the challenges with such observations is the large number of complex interactions in the atmosphere that could affect readings. Astronomers typically simplify the effects, in order to save vast amounts of computing power.

The Cassini spacecraft was launched to Saturn in 1997, and has orbited that world since 2004, studying the moons and elaborate ring system of the giant planet. One of the targets of observation for the mission is Titan, the largest satellite orbiting Saturn. This planet-like world has a diameter 50 percent greater than our moon, and it is 80 percent more massive than our planetary companion.

Titan is the only moon in the known solar system to possess a significant atmosphere. Cassini has studied sunsets as seen through the haze of the body's atmosphere during the last decade, while orbiting the ringed planet.

Researchers believe that by studying how the sun is affected when it passes through Titan's atmosphere, they can hope to make measurements from around other worlds more accurate.

Spectrographic analysis takes light reflected off a body, or passing through an atmosphere and breaks it into a rainbow of colors or wavelengths. By studying light and dark bands created in these spectral readings, it is possible to determine the chemical makeup of alien atmospheres.

Tyler Robinson, a researcher at NASA's Ames Research Center in California, led a team studying data collected by Cassini, seeing how the atmosphere of Titan affected sunlight. This allowed the team to treat Titan as a test world for exo-planets, taking data from four observations made by the spacecraft between 2006 and 2011, including both visual and infrared data.

The team found that light from alien suns may only penetrate through the upper players of a world. For Titan, this limit was between the top 90 and 190 miles of its atmosphere. Shorter (bluer) wavelengths of light were also found to be more affected by haze than longer (redder) photons. Many astronomers believed such an atmosphere would affect all frequencies of light equally.

"Previously, it was unclear exactly how hazes were affecting observations of transiting exoplanets. So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini," Robinson said.

The technique they developed should work equally well on any world with an atmosphere.

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