Scientists have long theorized that a remote moon in our solar system could exhibit weather patterns akin to those on Earth — featuring clouds and precipitation. Now, recent observations offer convincing evidence that Titan, Saturn’s largest moon, might indeed possess its own form of a climate cycle.

If validated, this would render Titan the only other known body in the solar system with a similar dynamic weather system as Earth. However, there’s a twist: rather than water, Titan’s precipitation consists of cold, viscous methane.

Employing the powerful James Webb Space Telescope alongside the Keck II telescope in Hawaii, astronomers detected clouds forming and ascending in Titan’s northern hemisphere — the area where most of the moon’s lakes and seas are situated. This represents the first instance of scientists observing such cloud activity in the northern region, occurring towards the conclusion of Titan’s summer season.

These results, detailed in Nature Astronomy, bolster the hypothesis that Titan’s lakes — some comparable in size to North America’s Great Lakes — are replenished by methane rain, similarly to how summer storms nourish Earth’s bodies of water.

“We were able to witness methane clouds evolving and shifting near Titan’s north pole over several days, in the zone where large seas and methane lakes were identified by the Cassini spacecraft,” said Conor Nixon, a NASA research scientist and the study’s primary author.

Titan presents a peculiar environment. With surface temperatures hovering around -300 degrees Fahrenheit and a dense, yellowish haze enveloping the moon, it starkly contrasts with Earth. Nonetheless, its nitrogen-rich atmosphere and the existence of organic molecules make it a focal point in the quest for extraterrestrial life.

Despite its extreme cold, Titan seems to possess the chemical building blocks essential for life as we understand it. This potential has driven NASA’s $3.35 billion Dragonfly mission — a rotorcraft lander set to study Titan’s surface in the 2030s. The mission recently achieved a significant design milestone, paving the way for engineers to start constructing the spacecraft.

The recent insights from Webb and Keck indicate that during Titan’s northern summer, clouds can ascend higher in the atmosphere, likely driven by solar heating — analogous to how storms develop on Earth. Although cloud activity had been previously documented on Titan, this is the first documentation of it occurring in the north, where the moon’s methane and ethane seas are mainly located. While these substances are gases on Earth, they exist as liquids on Titan — more similar to gasoline than water.

By examining light across various wavelengths, astronomers managed to ascertain the altitude of the clouds. On Earth, the troposphere — the lowest atmospheric layer where weather phenomena transpire — extends about 7.5 miles high. In Titan’s case, owing to its reduced gravity, this layer reaches up to 28 miles.

In addition to the cloud movements, Webb identified a transient molecule in Titan’s atmosphere known as the methyl radical. This ephemeral molecule indicates active chemical reactions and is linked to processes that may have contributed to life on Earth.

“It’s plausible that methane is being continually resupplied and bubbling up from the crust and interior over billions of years,” Nixon elaborated. “If not, it will eventually disappear, and Titan will transform into a largely airless realm of dust and dunes.”

While researchers did not directly observe rainfall during this study, the presence of ascending clouds strongly implies that precipitation is feasible. Scientists intend to persist in monitoring Titan’s weather, particularly following the recent equinox, to gain a deeper understanding of how its climate progresses over time.

If Titan’s methane is not being replenished from beneath, its atmosphere could ultimately evaporate, leading it to resemble a barren Mars rather than a vibrant, Earth-like body.

“For the first time we can see the chemical cake while it’s rising in the oven,” remarked coauthor Stefanie Milam. “Instead of only the initial ingredients of flour and sugar, and then the finished, iced cake.”