New research suggests that nitrogen and methane seep from Titan's rocky core to the surface, helping to maintain its dense atmosphere. The findings could shed light on the internal chemistry of Saturn's largest moon and the possibility of life.
Understanding Titan's atmosphere
The Southwest Research Institute (SwRI) has teamed up with the Carnegie Institution for Science to conduct laboratory experiments that will reveal how Saturn's moon Titan maintains its unique, nitrogen-rich atmosphere.
Titan is the second largest moon in the solar system and the only one with a significant atmosphere.
"Although only 40% of Earth's diameter, Titan's atmosphere is 1.5 times denser than Earth's, despite its lower gravity," explained Dr. Kelly Miller of SwRI, lead author of a paper on these findings, published in the journal Geochimica et Cosmochimica Acta. "Walking on Titan would feel a bit like scuba diving."
Since its discovery in 1944, scientists have wondered about the origin, age, and evolution of Titan's atmosphere, which is composed of approximately 95% nitrogen and 5% methane.
To understand the dense, persistent atmosphere of Saturn’s largest moon, SwRI and the Carnegie Institution for Science lab created conditions that mimicked those in Titan’s rocky core. In these experiments, they heated and compressed test tubes containing organic materials, producing nitrogen and methane—gases that are essential for maintaining Titan’s atmosphere.
Credit: Southwest Research Institute
The critical role of methane
"The presence of methane is critical to the existence of Titan's atmosphere," Miller says. "The methane is removed by reactions triggered by sunlight and will disappear in about 30 million years, after which the atmosphere will freeze to the ground. Scientists believe that there must be an internal source that replenishes the methane supply, otherwise the geological lifespan of the atmosphere is short."
Miller was also the lead author of a 2019 paper in the Astrophysical Journal that proposed a theoretical model for how the atmosphere might have evolved and regenerated over time. The paper theorizes that large amounts of highly complex organic matter heat up inside Titan's rocky interior, releasing nitrogen and carbon-rich gases like methane. The gas seeps out to the surface, where it creates a dense atmosphere around it. This theory is supported by recent experiments that have heated organic matter to temperatures of 250 to 500 degrees Celsius at pressures of up to 10 kilobars, to simulate conditions inside Titan. The experiments have produced carbon-rich gases like carbon dioxide and methane in sufficient quantities to help replenish Titan's atmospheric reservoir.
Supporting evidence from experiments
The paper is based largely on data from the Cassini-Huygens spacecraft mission, which launched in 1997 and explored the Saturn system from 2004 to 2017. NASA plans to launch its next mission to the Saturn system, with a spacecraft called Dragonfly. It will include a quadcopter designed to scan Titan up close and investigate whether Titan's environments could ever support life. Miller's next assignment is with a global research team that will investigate the life-supporting potential of the subsurface liquid ocean.
Titan's Dense Atmosphere
More on this subject on the Hayadan Science News site:
