How Can Titan Maintain its Atmosphere?

Saturn’s moon Titan is perhaps one of the most fascinating moons in the Solar System. It’s the second largest of all the moons in our planetary neighbourhood and is the only one with a significant atmosphere. It’s composed of 95% nitrogen and 5% methane and is 1.5 times as dense as the Earth’s atmosphere. The methane in the atmosphere of Titan is what puzzles scientists. It should have all be broken up within 30 million years causing the atmosphere to freeze but it hasn’t! There must be an internal process replenishing it, but what is it?

Titan is the largest moon of Saturn and second only in size to Ganymede, the largest moon of Jupiter. The surface of Titan is covered with dunes, icy mountains, and liquid hydrocarbon lakes—primarily composed of methane and ethane. Beneath its icy crust, scientists believe a vast subsurface ocean of water exists, raising the possibility of microbial life. NASA’s Cassini-Huygens mission provided detailed insights into Titan’s climate, seasonal changes, and its resemblance to early Earth, making it a target for future exploration.

Dr. Kelly Miller from the South West Research Institute and Lead author of a paper about Titan’s atmosphere said “While just 40% the diameter of the Earth, Titan has an atmosphere 1.5 times as dense as the Earth’s, even with a lower gravity, walking on the surface of Titan would feel a bit like scuba diving!” To try and understand the existence of methane in the atmosphere Southwest Research Institute joined forces with the Carnegie Institution for Science to conduct some experiments with interesting results. 

A model was proposed in 2019 that suggested just how the methane could be replenished over the years. It theorised that large amounts of organic materials are heated by the moon’s interior, releasing nitrogen and carbon based gas like methane. The gas seeps to the surface where it replenishes the atmosphere. The theory was developed off the back of data from NASA’s Cassini-Huygens spacecraft which arrived at the Saturnian system in 2004. It explored it for the next 13 years while the Huygens probe dropped onto the surface of Titan in 2005. 

The team led by Miller arranged experiments to heat up organic materials to temperatures up to 500 degrees Celsius at pressures up to 10 kilobars. This simulated the conditions found under the surface of Titan. The process generated sufficient quantities of methane that would enable Titan’s atmosphere to be replenished to the levels we observe today. 

To learn more about the atmosphere of Titan, NASA plans to launch another spacecraft to the Saturnian system in 2028. It’s been called Dragonfly and involves a quadcopter that will, like Ingenuity did on Mars, explore Titan’s atmosphere. The thick atmosphere and low surface gravity make it an ideal place to explore from the air. Not only will it help us to understand more about the atmospheric conditions but it will help to assess the moon’s habitability by analysing prebiotic molecules and searching for signs of past, or even present life! 

Source : SwRI-designed experiments corroborate theory about how Titan maintains its atmosphere

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