If you were in any doubt about the similarities between Earth and Titan, several observations snapped by NASA’s Cassini Saturn orbiter last year should convince you otherwise.
As Cassini approached Saturn’s largest moon during its July flyby, the mission watched clouds develop and dissipate over Titan’s large methane-rich sea Ligeia Mare. Over the course of two days, Cassini watched the clouds blow over the sea at a speed of 7 to 10 miles per hour (3-4.5 meters per second).
Cloud formation in Titan’s atmosphere has fascinated planetary scientists for some time. Since arriving in Saturn orbit in 2004, Cassini observed Titan’s clouds on several occasions as the moon’s south pole was experiencing late summer. As Titan’s northern hemisphere experienced spring, clouds were observed there too. Then, when a huge storm spread throughout Titan’s lower latitudes in 2010, few clouds have been spotted — puzzling many scientists. Are Titan’s clouds a seasonal phenomenon? As yet, they’re not really sure.
“We’re eager to find out if the clouds’ appearance signals the beginning of summer weather patterns, or if it is an isolated occurrence,” said Elizabeth Turtle, a Cassini imaging team associate at the Johns Hopkins University Applied Physics Lab in Laurel, Md. “Also, how are the clouds related to the seas? Did Cassini just happen catch them over the seas, or do they form there preferentially?”
Like Earth’s water cycle — where water from the oceans evaporate, condense in the atmosphere, falls as precipitation and flows back into the oceans — Titan is thought to have a complex methane and ethane cycle, where the chemicals are chilled into a liquid state, forming large lakes or seas on the moon’s surface.