For the first time, astronomers have observed cloud convection in the northern hemisphere of Titan, Saturn’s largest moon.
This groundbreaking discovery was made using the W. M. Keck Observatory in Hawaiʻi, offering new insights into the mysterious weather patterns of this distant world.
Titan is unique in our solar system because it has weather patterns that resemble those on Earth. However, while Earth’s weather is driven by water, Titan’s weather is powered by methane.
Titan’s thick atmosphere is mostly nitrogen, just like Earth’s, but it is covered in a smoggy haze. Methane on Titan behaves similarly to water on Earth: it evaporates from the surface, forms clouds, and sometimes falls back down as rain.
This methane cycle contributes to lakes and seas on Titan’s surface, primarily in its northern hemisphere. These large bodies of liquid methane were discovered by NASA’s Cassini spacecraft years ago.
Using the powerful Keck Observatory, researchers were able to watch methane clouds form and change over Titan’s northern pole for several days.
Conor Nixon, a research scientist at NASA Goddard Space Flight Center and the study’s lead author, explained that the advanced imaging capabilities of the Keck Observatory made it possible to see these clouds evolve.
This marks the first time scientists have been able to observe cloud convection—when clouds rise and fall in the atmosphere—in the northern region of Titan. Previous studies had only observed this phenomenon in the southern hemisphere.
Observations were made in November 2022 and July 2023, using both the Keck Observatory and the James Webb Space Telescope. These observations revealed clouds moving and rising in Titan’s atmosphere, a sign of convection.
This is important because most of Titan’s methane lakes and seas are located in the north. Understanding how clouds move and develop in this region may help scientists learn how methane evaporates from the lakes and replenishes the atmosphere.
One of the reasons Keck Observatory is so effective for observing Titan is its high altitude and stable atmosphere, along with its advanced near-infrared camera, NIRC2. This camera can capture detailed images that reveal different layers of Titan’s atmosphere.
During one of the observing nights, scientists saw the clouds moving to higher altitudes, much like convective cells that form in Earth’s atmosphere.
The troposphere, which is the lowest layer of the atmosphere where clouds form, is much taller on Titan than on Earth. On Earth, this layer extends about 7 miles (12 kilometers) up, while on Titan, it reaches nearly 27 miles (45 kilometers) due to Titan’s lower gravity.
By using different infrared filters, Keck and Webb were able to observe Titan’s clouds at various altitudes, showing how they change over time.
The Twilight Zone program at Keck Observatory made it possible for scientists to monitor Titan’s weather patterns consistently. This program is a collaborative effort involving the University of California, the California Institute of Technology, NASA, and Keck Observatory. Titan’s weather patterns are crucial to understanding its atmosphere and climate.
Methane evaporates from the lakes, rises into the atmosphere, forms clouds, and occasionally falls back down as rain. This process is similar to the water cycle on Earth, making Titan one of the most Earth-like worlds in our solar system.
Titan’s complex methane chemistry also plays a role in its atmosphere. NASA’s James Webb Space Telescope recently detected a key chemical called the methyl radical (CH3) on Titan for the first time. This discovery provides scientists with a new understanding of how methane is processed in Titan’s atmosphere.
Looking forward, scientists are eager to continue observing Titan, especially after its next equinox in May 2025, when dramatic weather changes are expected.
These new observations could offer even deeper insights into Titan’s methane cycle, its weather patterns, and its potential to support organic chemistry, a key component in the search for life.
