Saturn's moon Titan has a serene environment with calm lakes of liquid methane and waves reaching only about a centimetre high – potentially making it easier for future probes to make a smooth landing on its surface, scientists say.

Titan is the largest moon of Saturn and one of the locations in the solar system that is thought to possess the ingredients for life.

In photos taken by the Cassini orbiter, a NASA probe, it appears as a smooth brown orb because of its thick atmosphere clouded with gaseous nitrogen and hydrocarbons.

However, radar images from the same probe show that it has a surface crust made of water ice and drenched in liquid hydrocarbons.

On Titan, methane and ethane fall from the sky as rain, fill deep lakes that dot the surface, and are possibly spewed into the air by icy volcanoes called cryovolcanoes.

“There's a lot of interest in one day sending probes to the lakes, and when that's done, you want to have a safe landing, and you don't want a lot of wind,” said Cyril Grima, a research associate at the University of Texas Institute for Geophysics (UTIG) in the US.

“Our study shows that because the waves aren't very high, the winds are likely low,” said Grima, lead author of the research published in the journal Earth and Planetary Science Letters.

“The atmosphere of Titan is very complex, and it does synthesise complex organic molecules – the bricks of life,” Grima said.

“It may act as a laboratory of sorts, where you can see how basic molecules can be transformed into more complex molecules that could eventually lead to life,” she said.

Researchers developed a technique for measuring surface roughness in minute detail from radar data, called radar statistical reconnaissance, and used it to measure Titan's waves.

They zeroed in on the three largest lakes in Titan's northern hemisphere: Kraken Mare, Ligeia Mare and Punga Mare.
Kraken Mare, the largest of the three, is estimated to be larger than the Caspian Sea.

By analysing radar data collected by Cassini during Titan's early summer season, researchers found that waves across these lakes are diminutive, reaching only about one centimetre high and 20 centimetres long.

“Cyril's work is an independent measure of sea roughness and helps to constrain the size and nature of any wind waves,” said Alex Hayes, an assistant professor of astronomy at Cornell University in the US.

“From the results, it looks like we are right near the threshold for wave generation, where patches of the sea are smooth and patches are rough,” Hayes said.

Information on Titan's climate is essential for sending a probe safely to the surface. Although there are no formal plans for a mission, Grima said that there are plenty of concepts being developed by researchers around the world.
The study indicates that if a future mission lands in early summer, there's a good chance that it is in for a smooth landing.