Free Astronomy Magazine July-August 2025

50 JULY-AUGUST 2025 ASTRO PUBLISHING T he W. M. Keck Observatory is located at an elevation of 4,145 meters (13,600 feet) near the summit of Mauna Kea, Hawaii. The domes house twin telescopes with primary mirrors 10 meters (33 feet) in diame- ter. [W.M. Keck Observatory] chemical processes: a definitive de- tection of the methyl radical CH 3 . This molecule (called “radical” be- cause it has a “free” electron that is not in a chemical bond) forms when methane is broken apart. Detecting this substance means that scientists can see chemistry in action on Titan for the first time, rather than just the starting ingredients and the end products. “For the first time we can see the chemical cake while it’s rising in the oven, instead of just the starting in- gredients of flour and sugar, and then the final, iced cake,” said co- author Stefanie Milam of the God- dard Space Flight Center. This hydrocarbon chemistry has long-term implications for the fu- ture of Titan. When methane is bro- ken apart in the upper atmosphere, some of it recombines to make other molecules that eventually end up on Titan’s surface in one chemical form or another, while some hydrogen es- capes from the atmosphere. As a re- whose lower gravity allows the at- mospheric layers to expand, the tro- posphere extends up to about 27 miles (45 kilometers). Webb and Keck used different infrared filters to probe to different depths in Titan’s atmosphere, allowing as- tronomers to estimate the altitudes of the clouds. The science team ob- served clouds that appeared to move to higher altitudes over a pe- riod of days, although they were not able to directly see any precipitation occurring. Titan is an object of high astrobio- logical interest due to its complex organic (carbon-containing) chem- istry. Organic molecules form the basis of all life on Earth, and study- ing them on a world like Titan may help scientists understand the pro- cesses that led to the origin of life on Earth. The basic ingredient that drives much of Titan’s chemistry is meth- ane, or CH 4 . Methane in Titan’s at- mosphere gets split apart by sun- light or energetic electrons from Sat- urn’s magnetosphere, and then re- combines with other molecules to make substances like ethane (C 2 H 6 ) along with more complex carbon- bearing molecules. Webb’s data provided a key missing piece for our understanding of the sult, methane will be depleted over time, unless there is some source to replenish it. A similar process occurred on Mars, where water molecules were bro- ken up and the resulting hydrogen lost to space. The result was the dry, desert planet we see today. “On Titan, methane is a consum- able. It’s possible that it is being con- stantly resupplied and fizzing out of the crust and interior over billions of years. If not, eventually it will all be gone and Titan will become a mostly airless world of dust and dunes,” said Nixon. More of Titan’s mysteries will be probed by NASA’s Dragonfly mis- sion, a robotic rotorcraft scheduled to land on Saturn’s moon in 2034. Making multiple flights, Dragonfly will explore a variety of locations. Its in-depth investigations will comple- ment Webb’s global perspective. “By combining all of these resources, including Webb, NASA’s Hubble Space Telescope, and ground-based observatories, we maintain continu- ity between the former Cassini/Huy- gens mission to Saturn and the up- coming Dragonfly mission,” added Heidi Hammel, vice president of the Association of Universities for Re- search in Astronomy and a Webb In- terdisciplinary Scientist. !