Saturn Moon Titan Offers Insights into Far-Off Planets
Scientists with the National Aeronautics and Space Administration's Saturn-orbiting Cassini mission have found how to study the atmospheres of exoplanets, or, planets in other solar systems, by using Saturn's own moon Titan.
According to a space agency news release, the smog-covered natural satellite serves as a good substitute for testing hypotheses about other worlds orbiting far-off stars.
"It turns out there's a lot you can learn from looking at a sunset," Tyler Robinson, a postdoctoral research fellow at NASA's Ames Research Center at Moffett Field, California, said in the release.
The findings from the new analysis, published May 26 in the Proceedings of the National Academy of Sciences, show how light from sunsets, as well as stars and other planets, can be separated into spectra -- or component colors, as prisms do when light passes through them.
Scientists in recent years have developed new techniques for detecting spectra of exoplanets: when one such world passes in front from Earth's perspective, some of the light from the star in question filters through the exoplanet's atmosphere, in ways that can be measured by telescopes here.
With the resulting data, researchers can then decipher atmospheric conditions on exoplanets, such as temperature, composition and structure, despite the fact such worlds are many light years from Earth.
Scientists assume many exoplanets are similarly blanketed in haze, as Titan is. Therefore, studying the happenings on Titan provide greater insights into how other plants are developing.
"Previously, it was unclear exactly how hazes were affecting observations of transiting exoplanets," said Robinson. "So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini."
The team's study used four observations made of Titan by Cassini's visual and infra-red scanning instruments between 2006 and 2011.
Based on those much-closer examples, Robinson and his colleagues found that hazes high above some exoplanets might drastically limit the spectra -- and resulting data -- seen by far-away observers.
The observations might be able to glean information only from a planet's upper atmosphere. On Titan, that corresponds to about 90 to 190 miles (150 to 300 kilometers) above the moon's surface, high above the bulk of its dense and complex atmosphere.
An additional finding from the study was that Titan's hazes affected light far differently than previous research had suggested, having a greater impact on shorter wavelengths, or bluer, colors of light.
"People had dreamed up rules for how planets would behave when seen in transit, but Titan didn't get the memo," said Mark Marley, a researcher from NASA Ames and a co-author of the study. "It looks nothing like some of the previous suggestions, and it's because of the haze."
"It's rewarding," said Cassini program scientist Curt Niebur, "to see that Cassini's study of the solar system is helping us to better understand other solar systems as well."
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