Puzzling Polar Vortex Of Saturn’s Largest Moon Titan Finally Explained By Scientists

Scientists finally have an explanation for the unexpected atmospheric behavior in one of Saturn’s natural satellites. The polar vortex on Titan, the planet’s largest moon, has been previously measured to be extremely cold, a behavior that runs counter to accepted model predictions.

Despite being categorized as one of Saturn’s moon, Titan is actually larger than earth’s own satellite. In fact, it is bigger than the planet Mercury and has its own atmosphere.

Before NASA’s Cassini satellite crashed into Saturn last September, it had long been observing Titan’s atmosphere and had noted the polar vortex start to develop in 2009, according to Science Daily. By 2012, however, the spot started behaving unexpectedly and became colder than previous estimates.

Just like the atmosphere of planets, scientists expected that Titan’s upper winter atmosphere to be warmer, an effect that happens due to compression as air starts sinking. This did not happen on Titan, however. In fact, 2015 measurements reveal that the upper part of the vortex plunged to as low as 120 degrees Kelvin, a behavior that had puzzled scientists since it was detected.

Thankfully, experts finally figured out why Titan’s atmosphere behaved differently. A study led an earth scientist from the University of Bristol concluded that it is the moon’s atmosphere composition that caused it to exhibit the unexpected cooling observed by Cassini.

As explained by earth scientist Dr. Nick Teanby, the cooling effect is actually dependent on the composition of a planet or a moon’s atmosphere. Dr. Teanby is the lead author of the study and is from the University of Bristol’s School of Earth Sciences.

“For Earth, Venus, and Mars, the main atmospheric cooling mechanism is infrared radiation emitted by the trace gas CO2 and because CO2 has a long atmospheric lifetime it is well mixed at all atmospheric levels and is hardly affected by atmospheric circulation,” Dr. Teanby explained. “However, on Titan, exotic photochemical reactions in the atmosphere produce hydrocarbons such as ethane and acetylene, and nitriles including hydrogen cyanide and cyanoacetylene, which provide the bulk of the cooling.”

Apparently, researchers failed to factor in the abundance of these radiatively active gases in the poles during winter. Thus, their past predictions based on previous atmospheric heating and cooling models did not hit the mark. However, it is not the scientists’ fault for failing to anticipate the significant cooling effect the trace gas enrichment has on the moon’s atmosphere. According to Dr. Teanby, it’s one of a kind in this solar system.

“This effect is so far unique in the solar system and is only possible because of Titan’s exotic atmospheric chemistry.”


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