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In early January, researchers at the California Institute of California (Caltech) created a computer model that reproduces Titan’s atmosphere and methane cycle, solving Titan’s weather phenomena that were once inexplicable.
Having a surface temperature of approximately -300°F (-183°C), Titan is one of Saturn’s largest moons. It has a thick atmosphere of methane, a gas deadly for humans. Titan, the only other planetary body in the solar system that has large bodies of liquid on the surface, contains lakes and precipitation of liquid methane. For nearly a decade, researchers at Caltech have noticed bizarre geographical settings and meteorological occurrences.
The first was noticed in 2009 by Odel Aharonson, leader of planetary science at Caltech. He noted that the lakes tended to cluster around Titan’s poles, more so in the northern pole than in the southern. This leaves areas around the equator very dry, lacking in clouds, precipitation, and bodies of liquid.
But in 2005, the space probe Huygens observed a presence of deep channels which look carved out by running liquid. Lastly, regions in the middle and around high altitudes contain clouds that cluster during Titan’s summer in the southern hemisphere.
Previously, scientists have created computer models to account for these meteorological mysteries, though none of them were successful. The newer model, which is three dimensional and simulates Titan’s atmosphere for the past 135 Titan years (equivalent to 3000 Earth years), manages to explain the phenomena by reproducing the distribution of clouds and lakes.
According to the newest model, more lakes exist in the northern hemisphere because Titan is farther from the Sun during the summer due to Saturn’s elliptical orbit, and since Titan is at the far end of Saturn’s orbit the, summer is longer in the northern pole. As Tapio Schneider explains in the Caltech press release, “Methane tends to collect in lakes around the poles because the sunlight there is weaker on average.”
Schneider is a co-author of the paper about the simulation’s findings published in the January 5th issue of Nature and is the Frank J. Gilloon Professor of Environmental Science and Engineering. Hence, without much heat from the Sun, the methane is unable to exist in the gaseous state at the north pole and remains in the liquid state.
To account for the second oddity, the model shows that Titan is closer to the Sun during the moon’s southern summer. Consequently, the rains are more intense here than in the northern hemisphere; however, the model further shows that more lakes exist in the north because storms occur more frequently than they do in the south.
This newer model also explains the presence of liquid-carved channels in the parched equator by producing a simulation that shows rain occurring during the vernal and autumnal equinoxes. Even though these rains are rare, they are quite intense: at the time of the equinoxes, Titan’s poles reverse, causing unstable weather patterns.
“The results for the first time give us a unified picture of how Titan’s methane cycle works,” Schneider tells Space.com. “What I find most satisfying is that many seemingly disparate observations – clouds, lakes, dry river beds – can be explained within one sparse and coherent framework.”
In addition to simulating its atmosphere and methane cycle, the model can also predict Titan’s weather several years in advance, similar to how we are able to predict Earth’s. For instance, the researchers have determined that lake levels will rise in the northern hemisphere for the next fifteen years, and over the next two years, more clouds will form at the north pole.
“This is just the beginning,” Scheinder adds. “We now have a tool to do new science with, and there’s a lot we can do and will do.”