Titan's dense atmosphere could have resulted from the 'cooking' of organics in its interior

Atmosphere of Saturn's largest moon Titan is even thicker than the Earth's

A new study by scientists from the Southwest Research Institute (SwRI) suggests that the nitrogen-rich atmosphere on Saturn ' s moon Titan could be a result of the "cooking of organic material" in the interior of the moon.

Titan is the largest moon of Saturn, and is bigger than the planet Mercury. It is the only body in our Solar System, other than Earth, where huge quantities of liquid (hydrocarbons) on the surface are have been found. Like Earth, the atmosphere of Titan is comprised mostly of nitrogen, along with methane (five per cent), hydrogen and trace amounts of complex molecules.

Titan ' s atmosphere is extremely thick - even more dense (about 1.5 times) than the Earth ' s atmosphere. It is characterised by clouds and precipitation, which are not made of water, but liquid methane and ethane that evaporate from hydrocarbon lakes and seas near the poles.

"Because Titan is the only moon in our solar system with a substantial atmosphere, scientists have wondered for a long time what its source was," says Dr Kelly Miller, research scientist in SwRI ' s Space Science and Engineering Division and lead author of the study.

Scientists believe that some comets might have brought ammonia ice to Titan, which was converted - through impacts or photochemical reactions - into nitrogen to eventually create atmosphere on Titan.

Scientists also believe that there must also be some mechanism on Titan to continuously replenish the methane in the atmosphere, which reacts quickly to form organic compounds that gradually fall to the surface.

In the current study, Miller used data gathered by the European Space Agency ' s (ESA) Rosetta spacecraft about comet 67P/Churyumov-Gerasimenko. Rosetta mission was launched in March 2004 and finally arrived at the comet in August 2014.

The probe found that the comet 67P/Churyumov-Gerasimenko was made up of 50 per cent ice, 25 per cent organic material, and 25 per cent rock.

Comets like 67P/Churyumov-Gerasimenko are thought to be the leftover material from the early Solar System. There is a possibility that such several comets could have fused together to form a large body, like Titan, with organic-rich rocky material in the core.

Miller combined comet ' s organics data with thermal models of the Titan ' s interior to estimate the amount of gaseous material produced by the cooking of organic materials in the interior.

The results suggested that about half of the nitrogen and almost all the methane in Titan ' s atmosphere could be coming from the "cooking" of organic materials in the interior of this moon.

"Our model suggests that Titan's interior is likely warm, and that nitrogen from accreted organics may contribute on the order of 50 per cent of Titan's present-day nitrogen atmosphere," researchers state in their study paper.

The findings of the study are published in journal The Astrophysical Journal.