Cassini mission scientists think the appearance of a cloud of dicyanoacetylene ice in Titan’s stratosphere is explained by “solid-state” chemistry taking place inside ice particles.
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While many were confused if this was the great news from NASA, on September 26, 2016, NASA has revealed that the ice cloud on Titan seemingly out of thin air could be similar to one seen over Earth’s poles.
Observations of this newer cloud, taken by the Cassini orbiter now exploring Saturn’s system, yielded similar results: The spacecraft saw a high-altitude cloud, but there was not enough raw material to make one. It is made of a carbon- and nitrogen based compound called dicyanoacetylene (C4N2), which is one of the elements that makes up Titan’s orange-colored haze. One cloud just like it was first seen by Voyager 1, which passed by Saturn in 1980.
Clouds aren’t unusual on Titan – they form when methane cools and condenses, just as clouds made of water form on Earth.
But Cassini has much more sensitive equipment and, when its composite infrared spectrometer (CIRS) instrument also saw a C4N2 cloud with no accompanying vapor in Titan’s troposphere, a new theory was called for. But when Cassini got the same result, that explanation was scrapped, researchers said in the NASA statement.
“For clouds that condense, this equilibrium is mandatory, like the law of gravity”, said study co-author Robert Samuelson, from NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The typical process for forming clouds involves condensation. The fact that Earth and Titan have similar processes in their upper atmosphere means that there might be other weather patterns the two have in common.
As per NASA, a different condensation process takes place in the stratosphere – the region above the troposphere – at Titan’s north and south winter poles. Circulation patterns push warm gas downward at the poles.
Cloud formation on Earth and other planets or moons involves a certain amount of vapor condensation. However, when clouds form in the stratosphere it is commonly the result of ice and vapor reaching a state of equilibrium. There should be at least 100 times more dicyanoacetylene vapor to form the ice cloud spotted by Cassini. “It is awesome to see how well the underlying physics of both atmospheres has led to analogous cloud chemistry”. Cyanoacetylene, which contains hydrogen, carbon and nitrogen, could become coated with hydrogen cyanide as it moved down an icy crystals into the stratosphere. Every so often, a photon of UV light gets inside the frozen shell and sets off chemical reactions in the ice. If the ultraviolet rays were to hit one of those dual-layer ice crystals, it could release a combination of dicyanoacetylene and hydrogen and create a cloud, The Washington Post reports. Chemical reactions then release the chlorine molecules into the air, which, in turn, destroy the ozone layer.
The team suggests that, on Titan, the reactions occur inside the ice particles, sequestered from the atmosphere.
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As stated on Zmescience, Michael Flasar, CIRS principal investigator at Goddard, said that “the composition of the polar stratospheres of Titan could not differ more, it is incredible to see how well the underlying physics of both atmospheres has led to analogous cloud chemistry”.
