NASA’s James Webb Space Telescope has made history by discovering cloud convection in Titan’s northern hemisphere, a region of lakes and seas. The telescope, in collaboration with the Keck II telescope, also detected a key carbon-containing molecule that sheds light on the complex chemistry of Titan’s atmosphere.
Titan, Saturn’s largest moon, is an intriguing world shrouded in a yellowish haze. Its atmosphere is mostly nitrogen, similar to Earth’s, but its weather patterns are driven by methane instead of water. Methane evaporates from the surface and rises into the atmosphere, where it condenses to form clouds and, occasionally, chilly, oily rain.
The discovery was made possible by observations of Titan in November 2022 and July 2023 using both Webb and Keck telescopes. The team observed clouds rising to higher altitudes over time, a phenomenon previously seen only at southern latitudes. This is significant because most of Titan’s lakes and seas are located in its northern hemisphere.
The lower gravity on Titan allows the atmospheric layers to expand, extending up to 27 miles (45 kilometers) into the atmosphere, compared to Earth’s 7 miles (12 kilometers). The science team observed clouds that appeared to move to higher altitudes over a period of days but were not able to directly see any precipitation occurring.
Titan’s chemistry is of high astrobiological interest due to its complex organic molecules. Methane plays a crucial role in the chemical processes, getting split apart by sunlight or energetic electrons from Saturn’s magnetosphere and recombining with other molecules to form substances like ethane and more complex carbon-bearing molecules.
The James Webb Space Telescope provided a key missing piece for our understanding of Titan’s chemistry: a definitive detection of the methyl radical CH3. This molecule forms when methane is broken apart, allowing scientists to see chemistry in action on Titan for the first time.
The discovery has long-term implications for Titan’s atmosphere. Methane will be depleted over time unless it is replenished by some source. A similar process occurred on Mars, where water molecules were broken up and the resulting hydrogen lost to space, leaving a dry, desert planet behind.
Complementing the Dragonfly mission, which will land on Saturn’s moon in 2034, NASA’s Webb Space Telescope has provided a global perspective on Titan’s atmosphere. The discovery is a significant step towards understanding this enigmatic world and its place in our solar system.
Source: https://science.nasa.gov/missions/webb/webbs-titan-forecast-partly-cloudy-with-occasional-methane-showers