Titan's weather patterns suggest liquid methane reservoirs below the surface near

Titan's poles.

E. Turtle et al. (2018) Geophys. Res. Lett., DOI:10.1029/2018GL078170

Cassini image, 10 July 2017

Clouds Lakes and seas

Clouds observed by Cassini areshown by black and grey lines,in comparison to modelprecipitation (clouds) in color.Fewer clouds are observed inNorthern summer than themodel predicts.

Methane Rain Clouds at TitanMore than 13 years of Cassini images of methane clouds on Titan show weather patterns from Titan's late southern summer to northern summer.

During southern summer, clouds and, on one occasion, rainfall were observed at Titan’s south pole.

Surprisingly, this weather pattern did not repeat at the north pole, and Cassini had clear views of the surface in northern summer (image at right).

By comparing cloud observations to atmospheric models, we can determine where the methane in the atmosphere comes from – models with liquid beneath the surface at the poles, in addition to the lakes and seas, best match the observations (inset graph).

Knowing there may be more liquid below Titan’s surface helps explain how methane is supplied to the atmosphere and how Titan’s methane cycle works (similar to Earth’s water cycle: evaporation, cloud formation, rain, and surface collection into rivers, lakes, and oceans).

NorthernWinter

NorthernSpring

NorthernSummer