Tuesday, January 17, 2012

"Earth's Twin" May Be in Our Solar System: Saturn's Moon, Titan --Hosts a Layered Atmosphere


Saturn's moon Titan may be more similar to an Earth-like world than previously thought, possessing a layered atmosphere just like our planet. Titan has long held interest for scientists because of its promise, as the only known moon in the solar system that has a dense atmosphere, there has been hope that it might host some form of life. Information provided by three separate spacecraft missions sent to the area has created more speculation about the moon, which is roughly twice the size of our own (which, quite inexplicably, still has no name) but is nine times farther away from the sun and a freezzing -180°C.

The first mission was Voyager 1, which flew by in 1981, followed by Cassini in 2004, and the next year by the Huygens probe, which actually landed on its surface. Despite the massive amounts of data collected by all three vehicles and the dense athmosphere, scientists have still not been able to get conclusive evidence on what is going on with Titan’s atmosphere.

To clear up some of the mystery, the two researchers --Benjamin Charnay, a planetary scientist at France's National Center of Scientific Research and colleague, S├ębastien Lebonnois-- put together a three dimensional computer model that incorporates information collected from all three space vehicles that includes among other things, chemical compositions, dune movement and measurements of wind and cloud formations and were able to conclude that Titan’s atmosphere very clearly has at least one boundary, which is the part of an atmosphere that is impacted by the surface (friction, heat, etc.) and vice-versa.

But they also found evidence that there appears to be a second boundary as well that is likely caused by changes in seasonal air circulation. The lowest layer is most influenced by a planet or moon's surface, and has greatest influence on the surface with clouds and winds, as well as by sculpting dunes found on Titan.

Earth's boundary layer, which is between 1,650 feet and 1.8 miles (500 meters and 3 kilometers) thick, is controlled mostly by solar heat warming the planet's surface. Since Titan is more distnat from the sun, its boundary layer might behave quite differently. Titan's atmosphere is thick and opaque, obscuring our knowledge about its lower layers. "This layer is very important for the climate and weather — we live in the terrestrial boundary layer," said Charnay.

Their simulations revealed the lower atmosphere of Titan appears separated into two layers that are both distinct from the upper atmosphere in terms of temperature. The lowermost boundary layer is shallow, only about 2,600 feet (800 meters) deep and, like Earth's, changes on a daily basis. The layer above, which is 1.2 miles (2 kilometers) deep, changes seasonally.

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